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Human tissue samples are often mixtures of heterogeneous cell types, which can confound the analyses of gene expression data derived from such tissues. The cell type composition of a tissue sample may itself be of interest and is needed for proper analysis of differential gene expression. A variety of computational methods have been developed to estimate cell type proportions using gene-level expression data. However, RNA isoforms can also be differentially expressed across cell types, and isoform-level expression could be equally or more informative for determining cell type origin than gene-level expression. We propose a new computational method, IsoDeconvMM, which estimates cell type fractions using isoform-level gene expression data. A novel and useful feature of IsoDeconvMM is that it can estimate cell type proportions using only a single gene, though in practice we recommend aggregating estimates of a few dozen genes to obtain more accurate results. We demonstrate the performance of IsoDeconvMM using a unique data set with cell type-specific RNA-seq data across more than 135 individuals. This data set allows us to evaluate different methods given the biological variation of cell type-specific gene expression data across individuals. We further complement this analysis with additional simulations.

Immunotherapies have attracted lots of research interests recently. The need to understand the underlying mechanisms of immunotherapies and to develop precision immunotherapy regimens has spurred great interest in characterizing immune cell composition within the tumor microenvironment. Several methods have been developed to estimate immune cell composition using gene expression data from bulk tumor samples. However, these methods are not flexible enough to handle aberrant patterns of gene expression data, e.g., inconsistent cell type-specific gene expression between purified reference samples and tumor samples. We propose a novel statistical method for expression deconvolution called ICeD-T (Immune Cell Deconvolution in Tumor tissues). ICeD-T automatically identifies aberrant genes whose expression are inconsistent with the deconvolution model and down-weights their contributions to cell type abundance estimates. We evaluated the performance of ICeD-T versus existing methods in simulation studies and several real data analyses. ICeD-T displayed comparable or superior performance to these competing methods. Applying these methods to assess the relationship between immunotherapy response and immune cell composition, ICeD-T is able to identify significant associations that are missed by its competitors.

The study of gene expression quantitative trait loci (eQTL) is an effective approach to illuminate the functional roles of genetic variants. Computational methods have been developed for eQTL mapping using gene expression data from microarray or RNA-seq technology. Application of these methods for eQTL mapping in tumor tissues is problematic because tumor tissues are composed of both tumor and infiltrating normal cells (e.g. immune cells) and eQTL effects may vary between tumor and infiltrating normal cells. To address this challenge, we have developed a new method for eQTL mapping using RNA-seq data from tumor samples. Our method separately estimates the eQTL effects in tumor and infiltrating normal cells using both total expression and allele-specific expression (ASE). We demonstrate that our method controls type I error rate and has higher power than some alternative approaches. We applied our method to study RNA-seq data from The Cancer Genome Atlas and illustrated the similarities and differences of eQTL effects in tumor and normal cells.

Immunotherapies have achieved phenomenal success in the treatment of cancer and promise even more breakthroughs in the near future. The need to understand the underlying mechanisms of immunotherapies and to develop precision immunotherapy regimens has spurred great interest in characterizing immune cell composition within the tumor microenvironment. Several methods have been developed to estimate immune cell composition using gene expression data from bulk tumor samples. However, these methods are not flexible enough to handle aberrant patterns of gene expression data, e.g., inconsistent cell type-specific gene expression between purified reference samples and this cell type in tumor samples. In this paper, we present a novel statistical model for expression deconvolution called ICeD-T (Immune Cell Deconvolution in Tumor tissues), which models gene expression by a log-normal distribution that is appropriate for both microarray and RNA-seq data. ICeD-T automatically identifies aberrant genes whose expressions are inconsistent with the deconvolution model and down-weights their contributions to cell type abundance estimates. We evaluated the performance of ICeD-T versus existing methods in simulation studies and several real data analyses. ICeD-T displayed comparable or superior performance to these competing methods. Applying these methods to assess the relationship between immunotherapy response and immune cell composition, ICeD-T is able to identify significant associations that are missed by its competitors.

Abstract 2102 Background: Despite the abundant laboratory evidence of platelet activation and inflammation in sickle cell disease (SCD), the contribution of these changes to the pathogenesis of SCD remains uncertain. Patients with SCD exhibit increased platelet activation in the non-crisis, “steady state,” and further increases with acute pain episodes. In addition, levels of the inflammatory mediator, CD40 ligand (CD40L) are increased in the plasma and significantly reduced in the platelets of SCD patients compared to healthy individuals. CD40L may contribute to the pathogenesis of acute pain episodes. Despite an improved understanding of the pathophysiology of SCD, the treatment of acute pain episodes is supportive. We performed a randomized, placebo-controlled study to evaluate the safety and efficacy of eptifibatide, a synthetic peptide inhibitor of the glycoprotein (GP) IIb/IIIa receptor, in patients with SCD during acute painful episodes. Methods: In this single site placebo-controlled trial, eligible patients admitted for acute painful episodes received eptifibatide (two 180 mg/kg boluses 10 minutes apart, followed by a continuous infusion at 2 mg/kg/min for 6 hours) or placebo at a ratio of 2:1. The Post-Treatment Phase lasted for up to 7 days or until resolution of the crisis, whichever was shorter, but no less than 24 hours after discontinuation of infusion. The Follow-up Phase included safety evaluations obtained 14 to 17 days and 28 to 35 days after discontinuation of infusion. The primary outcomes were major bleeding episodes and the largest observed decrease in platelet count during the study. We also evaluated the effect of eptifibatide on the duration of acute pain episodes, pain intensity, duration of hospitalization, total opioid use and acute chest syndrome. Results: Thirteen patients (SS - 10, Sb0 - 2, SC - 1) were randomized to receive either eptifibatide (N=9; 6 females; median age - 25 years) or placebo (N=4; 3 females; median age - 31 years). One patient in the eptifibatide arm withdrew consent following completion of study drug infusion and 1 patient in the placebo arm was withdrawn early because she did not meet eligibility criteria. In the intent-to-treat analysis, there were no major bleeding episodes in either group (point estimate of difference in eptifibatide vs. placebo proportion: 0.0, 95% CI; −0.60, 0.37).There was one minor bleeding episode in a patient on the eptifibatide arm (point estimate of difference in eptifibatide vs. placebo proportion: 0.11, 95% CI: −0.502, 0.494). There was a trend for the largest decrease in platelet count to be greater in the eptifibatide arm compared to the placebo arm, although the difference was not statistically significant (Hodges-Lehman estimate of location shift for eptifibatide vs. placebo: −82, 95% CI; −281, 54). There was no significant difference in the proportion of patients with thrombocytopenia between the treatment groups (point estimate of difference in eptifibatide vs. placebo proportion: 0.11, 95% CI: −0.587, 0.495). The median time to discharge and the median time to crisis resolution were 3.0 days for both treatment arms. The median total opioid use was 400.2 morphine equivalents (ME) for the eptifibatide group and 1471 ME for the placebo group (Hodges-Lehman estimate of location shift for eptifibatide vs. placebo: −65.8, 95% CI: −2519, 1700). There was one episode of acute chest syndrome in each treatment arm. Conclusions: In this small study of SCD patients hospitalized with acute painful episodes, eptifibatide appeared to be safe, but did not improve the times to crisis resolution or hospital discharge. Eptifibatide was associated with a reduced requirement for opioid analgesics, although the difference was not statistically significant. Clinicaltrials.gov Identifier: NCT00834899. Disclosures: Parise: BD: Consultancy; Biogen-Idec: Consultancy; NIH: Research Funding; AHA: Research Funding; SCDAC-NIH: Membership on an entity's Board of Directors or advisory committees; BRI Milwaukee: Membership on an entity's Board of Directors or advisory committees. Ataga:Pfizer: Consultancy; HemaQuest Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adventrx Pharmaceuticals: Consultancy. Off Label Use: Eptifibatide, a glycoprotein IIb/IIIa inhibitor, was evaluated as treatment for acute pain episodes in patients with sickle cell disease.

The impact of diet and environmental factors on genes concerned with epigenetic inheritance and the mechanism of evolution has grown significantly beyond the Modern Synthesis period. Epigenetic inheritance is the passing of phenotypic change to subsequent generations in ways that are outside the genetic code of DNA. Recently, polymorphisms of the human Delta-5 (fatty acid desaturase, FADS1) and Delta-6 (FADS2) desaturase genes have been described as being associated with the level of several long-chain n-3 and n-6 polyunsaturated fatty acids (PUFAs) in serum phospholipids. Increased consumption of refined starches and sugar increases the generation of superoxide anion in the tissues and free fatty acids (FFA) in the blood. There is an increased amount and activity of nuclear factor-κB (NF-κB), a transcriptional factor regulating the activity of at least 125 genes, most of which are pro-inflammatory. The consumption of glucose may be associated with an increase in 2 other pro-inflammatory transcription factors: activating protein-1 (AP-1), and early growth response protein-1 (Egr-1). AP-1 regulates the transcription of matrix metallo-proteinases and Egr-1 modulates the transcription of tissue factor and plasminogen activator inhibitor-1. It is possible that a complex set of factors, including nutritional factors, come into play during epigenetic inheritance.

This article assesses the partnership functioning of Families First Edmonton, a multisectored collaborative effort formed to determine the best health and recreation service delivery model for families with low income. Partners’ evaluations of the collaborative process are examined across the formation, implementation, and maintenance stages of development. Statistical analyses of questionnaire data reveal a significant decrease in the partnership’s capacity to maximize synergy—a main indicator of a successful collaborative process—in the implementation stage of the partnership. Implications for partnership practice are addressed.

Continuous ambulatory peritoneal dialysis (CAPD) has been initiated on 51 patients: 27 females (mean age — 43.9 years) and 24 males (mean age — 46.4 years). This group has been observed for a total of 1420 patient weeks of treatment (27.3 patient years). Thirty-six episodes of peritonitis have been noted among 19 patients. The overall incidence was one episode per 39.4 patient weeks. Recurrent episodes of peritonitis resulted in discontinuation of CAPD in five (9.8%) of the patients. Three (5.9%) of the patients were unable to continue with CAPD because of its inability to control extracellular fluid balance. In the patients who transferred from intermittent peritoneal dialysis to CAPD, there was a 4.5 mg/dl drop in serum creatinine and a 34 mg/dl drop in mean BUN values. There was a rise of approximately 2 gm in the hemoglobin levels of this group of patients. If the problem of peritonitis can be solved, CAPD will become the dialytic treatment of choice for the majority of patients with end-stage renal disease.

In May 2003 all university faculties of medicine, health sciences, nursing, business, and public administration in Canada were surveyed to document whether their promotion practices gave equal treatment to researchers with traditional disciplinary-based scholarly outputs versus those with nontraditional outputs flowing from an applied interest in interdisciplinary research, collaboration with nonacademics, and knowledge transfer. Forty-seven deans (response rate = 67 percent) and thirty-two promotion committee members (response rate = 51 percent) consistently rated research as more important than teaching and community service in promotion proceedings. Furthermore, in their considerations of research they accorded significantly more value in promotion to traditional than to nontraditional scholarly outputs. Among the deans, for example, the top ten ranked activities included seven traditional research outputs, two teaching-related outputs, and only one nontraditional research output. Scholars with nontraditional outputs were slightly less disadvantaged in health-related faculties compared to the nonhealth faculties. Despite broader acceptance of an evolving research landscape in Canadian universities, current reward structures may create barriers for academics interested in conducting nontraditional research characteristic of the emerging paradigm of applied scholarship.

Background: Teamwork and collaborative practice are acknowledged as key to strengthening primary health care. This study assessed Canadian family physicians/ general practitioners’ (FPs/GPs) interest and involvement in interdisciplinary collaborative practice. Methods: From nine focus groups conducted with 46 FPs/GPs in the Capital Health region (Edmonton, Alberta) concerning the quality and capacity of services in family practice, the discussions related to collaborative practice and practice teams were extracted and qualitatively analysed. Based on this analysis, one section of a mail survey assessed FPs/GPs levels of interest and current involvement with 11 other types of health professionals. Results: In focus groups, FPs/GPs identified seven categories of issues related to interdisciplinary collaborative practice: quality and capacity of care, quality of work life, affordability, availability/accessibility of other health professionals, team-building processes, responsibility/accountability, and system resources. Survey responses from 300 of 583 FPs/GPs in the region (51%) showed substantial interest in working with other health professionals, but strikingly less frequent current working relationships. Conclusions: The large gap between the interest and willingness of FPs/GPs to collaborate and their current involvement in teamwork must be addressed if collaborative practice is to increase in line with the goals of primary care reform in Canada.

The article addresses the question of the value of the virtual visiting seminar compared to the verbatim seminar in a Clinical Pastoral Education (CPE) Unit. A Virtual Visit occurs when a volunteer allows a CPE student to engage them in a pastoral visit with the expressed purpose of providing feedback to the student The effectiveness of the virtual visiting seminar was monitored by a Site Review Team, two independent expert witnesses, by students who have experienced both learning tools, and the Education Sub Committee of the Pastoral Care Advisory Committee. The results point to advantages of the virtual visiting seminar over the verbatim seminar.

Objectives: The purpose was to develop and test a framework for assessing the overall effectiveness of health promotion in one Canadian province.

A patient undergoing management of heroin dependency with high dosages of the long-acting methadone derivative, levomethadyl acetate HCl (LAAM; ORLAAM) developed a prolonged QTc interval and polymorphic QRS complexes on EKG consistent with torsades de pointes (TdP). The patient was taking other drugs known to prolong the QTc interval (fluoxetine and IV cocaine), and those known to antagonize the activity of the P450 enzymes responsible for the metabolism of LAAM and its active metabolite (fluoxetine, cocaine and marijuana). No previous reports have appeared in the literature attributing this adverse event to LAAM therapy; however, five similar cases have been reported to the manufacturer. Animal studies indicate that LAAM and metabolites prolong the action potential duration of myocardial cells. We propose that predisposed patients on high doses of LAAM may be at risk for developing TdP. Patients being treated with LAAM should receive dosages consistent with guidelines and be evaluated for concomitant diseases, interacting drug therapies, and EKG abnormalities.

We retrospectively reviewed 255 consecutive scleral buckling and vitrectomy operations dividing the patients into two groups. One group was managed traditionally with general anesthesia and postoperative hospitalization. The second group was managed with local anesthesia and with no hospitalization or abbreviated hospitalization whenever possible. There was no difference in the technical or functional success rates achieved in the two groups. We conclude that vitreoretinal surgery may be performed safely and effectively on an outpatient basis in selected cases.

While there has been much discussion concerning the sustainability and improvement of Canada's health system, the perspectives of front-line practitioners in primary care have not been the focus of reported research. There have been no published reports of the extent to which their views have been identified and/or adopted in the reform process. Recent Canadian national and provincial commissions have highlighted primary care reform (National Forum on Health 1997; Mazankowski 2001; Fyke 2001; Romanow 2002). It has been suggested that there are underlying factors both motivating and inhibiting health system changes (Tuohy 1999). Progress with primary care reform has been notably slow (Hutchison et al. 2001) and without the benefit of needed infrastructure investment (Hutchison 2007). An international survey of primary care physicians in seven countries indicated the inadequate current status of Canada's primary care system in comparison to other nations (Schoen et al. 2006). Understanding the realities of primary care service provision and identifying the enhancing and inhibiting policies and processes of Canada's health system could help to guide change. Perspectives of practising physicians could inform policy makers and planners who have an interest in health system efficiency, effectiveness and productivity. While Canada has benefited from national and provincial professional groups reporting on the challenges faced by healthcare practitioners and on potential solutions, the degree to which these suggestions address the realities of working in community primary care practice is questionable. Thomson et al. (2001) have complained about the inadequacy of physician input to such reports. Although changes in policy and practice related to primary care have been proceeding, there has been a paucity of empirical data to support or direct these changes. With the background of a prior qualitative investigation, this study utilized a survey conducted in an urban health region to determine FP/GP perspectives on the quality and capacity of the services these physicians provide and the system in which they work. The survey also assessed FP/GP attitudes to potential changes and elicited their suggestions to enhance the quality and capacity of primary care services.

Background Childhood injury is the leading cause of mortality, morbidity and permanent disability in children in the developed world. This research examines relationships between socio-economic status (SES), demographics, and types of childhood injury in the province of Alberta, Canada. Methods Secondary analysis was performed using administrative health care data provided by Alberta Health and Wellness on all children, aged 0 to 17 years, who had injuries treated by a physician, either in a physician's office, outpatient department, emergency room and/or as a hospital inpatient, between April 1st. 1995 to March 31st. 1996. Thirteen types of childhood injury were assessed with respect to age, gender and urban/rural location using ICD9 codes, and were related to SES as determined by an individual level SES indicator, the payment status of the Alberta provincial health insurance plan. The relationships between gender, SES, rural/urban status and injury type were determined using logistic regression. Results Twenty-four percent of Alberta children had an injury treated by physician during the one year period. Peak injury rates occurred about ages 2 and 13–17 years. All injury types except poisoning were more common in males. Injuries were more frequent in urban Alberta and in urban children with lower SES (receiving health care premium assistance). Among the four most common types of injury (78.6% of the total), superficial wounds and open wounds were more common among children with lower SES, while fractures and dislocations/sprains/strains were more common among children receiving no premium assistance. Conclusion These results show that childhood injury in Alberta is a major health concern especially among males, children living in urban centres, and those living on welfare or have Treaty status. Most types of injury were more frequent in children of lower SES. Analysis of the three types of the healthcare premium subsidy allowed a more comprehensive picture of childhood injury with children whose families are on welfare and those of Treaty status presenting more frequently for an injury-related physician's consultation than other children. This report also demonstrates that administrative health care data can be usefully employed to describe injury patterns in children.

This study investigated the use of health-related services by low-income Canadians living in two large cities, Edmonton and Toronto. Interview data collected from low-income people, service providers and managers, advocacy group representatives, and senior-level public servants were analyzed using thematic content analysis. Findings indicate that, in addition to health care policies and programs, a broad range of policies, programs, and services relating to income security, recreation, and housing influence the ability of low-income Canadians to attain, maintain, and enhance their health. Furthermore, the manner in which health-related services are delivered plays a key role in low-income people’s service-use decisions. We conclude the paper with a discussion of the health and social policy implications of the findings, which are particularly relevant within the context of recent health care reform discussions in Canada. © 2005 Elsevier Ireland Ltd. All rights reserved.

Objective: To determine the incidence of maternal cell contamination (MCC) in the open-needle amniocentesis sampling technique compared with the trocar-in-place technique. Methods: A retrospective analysis was conducted on 2,498 mid-trimester amniocenteses performed in two tertiary care centres in Canada. The University of Alberta centre used the open-needle (without the trocar) technique and the University of British Columbia centre used the standard (with the trocar in place) technique. Data were gathered regarding the nature of the amniotic fluid, number of needle passes, amniocentesis results, and the occurrence of maternal cell contamination. The statistical analysis used logistic regression, and controlled for the potential confounders of bloody fluid taps and requirement for more than one needle insertion. Results: The incidence of maternal cell contamination was 1.16% with the open-needle technique and 0.78% with the standard trocar-in-place technique (p Conclusion: The data suggested there is no significant increase in maternal cell contamination with the open-needle versus trocar-in-place techniques of amniocentesis. However, the small sample size, combined with the low prevalence of the outcome of interest (MCC), provides insufficient power to draw firm conclusions about the difference in MCC between the two techniques.

Schools are faced with the challenging mandate of addressing the learning needs of students while simultaneously managing a gamut of behavior and health problems. School health policies have been successfully used for many health-related issues. Although asthma is the most common chronic disease among children, schools receive only a small amount of support to manage asthma issues. This article describes our experiences in developing an asthma policy in schools. The problem of asthma in schools was assessed as part of a comprehensive community-based asthma intervention, and a plan was established to develop a school asthma policy. The goal of the policy was to facilitate a physical and social environment that enabled students with asthma to control optimally their condition, have a good quality of life, and learn effectively. Specific objectives included enhancing environmental control, educating staff, clarifying medication protocols, and responding appropriately to symptoms. Strategies in developing the policy included strengthening collaboration and networks among health, school, and community sectors; defining the role of the school and health sectors; designing the policy; refining the policy based on stakeholder feedback; and developing an evaluation plan.

Objective: Maternal cell contamination (MCC) is rare in cultured amniotic fluid samples, but it poses a serious potential source of prenatal misdiagnosis. Our goal was to determine whether the amniocentesis sampling technique influences the incidence of maternal cell contamination. Study design: A retrospective study was performed on 2,498 amniocentesis results in two tertiary care centers in Canada. The University of Alberta used the open-needle technique, and the University of British Columbia used a technique with the trocar in place. We reviewed midtrimester amniocenteses performed by perinatologists on singleton male fetuses. We excluded all transplacental insertions. Data were gathered regarding the nature of the amniotic fluid, number of needle passes, amniocentesis results, and the occurrence of maternal cell contamination. Results: The incidence of MCC was similar at the two study centers: 1.16% and 0.78% at the University of Alberta and the University of British Columbia, respectively. The odds ratio for MCC with the open versus the trocar-in-place technique with use of logistic regression was 1.48 (95% CI, 0.3–3.3) with a P value less than 0.315, which is not significant. Bloody fluid taps and the number of needle insertions were both controlled for in the statistical analysis. Conclusion: The data indicate that there is no significant increase in maternal cell contamination with the open-needle technique of amniocentesis. We believe that open-needle amniocentesis has advantages for the patient and the physician and that it is a safe and reliable technique for amniocentesis.

In the late distal and cortical collecting tubule, which is the principal regulatory site for potassium (K) excretion, vasopressin stimulates, and epinephrine via β-adrenergic action, inhibits K secretion. In the inner medullary collecting duct (IMCD) we have shown that vasopressin also stimulates K secretion. The present experiments were designed to determine whether the β-adrenergic agonist, isoproterenol, would induce K reabsorption in the IMCD, and (or) prevent a secretory response to acute KCl infusion. Two groups of rats, with or without isoproterenol administration (3 μg/h), were subjected to retrograde microcatheterization of the IMCD before and during infusion of 0.83 mol/h KCl. Isoproterenol reduced plasma K concentration and urinary K excretion, but the response to acute KCl infusion was qualitatively similar to control. Isoproterenol decreased delivery of potassium, chloride, and fluid to the IMCD, there was no net transport of K along the duct in either group, and KCl infusion did not result in K secretion in either group. The results indicate that isoproterenol may inhibit K secretion in the late distal or cortical collecting tubule. However, there was no statistically significant difference in K transport along the IMCD between isoproterenol and control groups. Reduced sodium excretion, which was found during isoproterenol administration both before and after KCl infusion, was associated with no change in sodium delivery but with increased sodium reabsorption in the IMCD. This increased sodium reabsorption may be a direct effect of isoproterenol, or may be due to reflex cardiovascular adjustments associated with systemic actions of the drug.Key words: rat, KCl infusion, potassium transport, fluid reabsorption, sodium reabsorption, chloride reabsorption, catecholamines.

A method is described that allows perfusion of the inner medullary collecting duct (IMCD) of the rat kidney in situ and in vivo. Fine polyethylene catheters connected to a microperfusion pump were inserted into collecting ducts via the openings at the exposed papilla tip. Perfusate contained 22Na as well as [3H]inulin. During perfusion at 30 nl/min, urine was simultaneously collected. A decrease in the Na-to-inulin concentration ratio in the urinary sample, compared with the perfusate, was taken as indicating unidirectional efflux of Na from the perfused duct system. The effects of luminal amiloride (2 X 10(-4) M) or atrial natriuretic factor (ANF, 10(-8) M) were studied. Compared with control perfusions, both agonists reduced Na efflux from the IMCD to approximately 50%, indicating luminal sites of action. Combination of amiloride and ANF at their respective concentrations had no further effect. The lack of statistically significant additivity suggests, but does not prove, that ANF, administered from the luminal side, is able to block amiloride-sensitive Na channels in the apical membrane of IMCD cells.

The role of the medullary collecting duct in pressure natriuresis has not been established. In vivo microcatheterization was used to study the effect of an acute increase in blood pressure induced by bilateral carotid artery and vagal nerve ligation on medullary collecting duct function in anaesthetized rats. Increased fluid and electrolyte excretion during pressure natriuresis were accompanied by increased delivery of water, sodium, chloride, and potassium to the beginning of the medullary collecting duct, a change that was significantly greater than in a second series of time-control animals. These increases in delivery were within the range for which constant fractional NaCl reabsorption had been found previously. However, during increased perfusion pressure, reabsorption of both sodium and chloride in the medullary collecting duct as a fraction of delivered load were reduced from 81 ± 4.1 to 51 ± 9.3% (p

Many myopic people, expressing dissatisfaction with traditional methods of optical correction, are interested in a permanent correction of their refractive error which would alleviate dependence on corrective lenses. Although much effort has been put forth in the last century, there is still no method of correcting myopia which is broadly acceptable as safe and effective. The nonsurgical procedures of orthokeratology and the topical use of cycloplegics have not been well proven. Surgical measures are the current vectors of hope. Surgical procedures on parts of the eye other than the cornea have proven to be difficult. Surgery which alters the refractive power of the cornea (refractive keratoplasty) has been used frequently in the past decade. These procedures include keratomileusis, epikeratophakia and radial keratotomy. The latter is currently the most often performed method for the correction of myopia. This paper critiques the major methods, explains their historical development and basic procedures, lists major published studies and discusses their problems and promise for their future.

To investigate the interaction of cyclosporine nephrotoxicity and renal ischemia, an animal model in rats with bilateral renal artery clamping was used. Rats given cyclosporine had a lower rate of recovery from ischemia. However, the percentages of reduction in glomerular filtration rate in vehicle and cyclosporine groups were the same in sham-operated or ischemically treated group. This suggests a superimposition of cyclosporine nephrotoxicity on the recovering kidneys rather than synergistic potentiation between ischemia and cyclosporine nephrotoxicity.

Lithium-induced impairment of urine acidifcation. The purpose of this study was to clarify the means by which lithium induced a disorder of urine acidification. Rats infused with hydrochloric acid (1 mEq/kg) developed acute metabolic acidosis (blood pH=7.32; bicarbonate, 18 mEq/liter) with a urine pH of approximately 5.85. The addition of lithium chloride (4 mEq/kg i.p.) caused an increase in the urine pH (6.38) and a further decrease in blood bicarbonate (11.0 mEq/liter). During bicarbonate loading, lithium caused the urine Pco 2 to fall significantly (urine minus blood Pco 2 decreased from 25.3 ± 2.8 to 14.4 ± 2.3 mm Hg). These changes were not seen following equimolar i.p. administration of sodium chloride. Similarly, lithium administration depressed bicarbonate reabsorption by 11.1% (from 30.6 to 27.2 µEq/ml of GFR) during alkali infusion, while saline caused only a 5% decrease (30.0 to 28.3 µEq/ml of GFR). The combination of an increase in urine pH and bicarbonate excretion during acidosis and a decrease in urine Pco 2 in alkaline urine indicates that lithium produced a defect in distal nephron hydrogen ion secretion. The fall in bicarbonate reabsorption following lithium administration could be due to a mild hydrogen ion secretory defect located in the proximal tubule or a severe defect in the distal nephron.

Medullary collecting duct function was studied using the in vivo microcatheterization technique in three groups of rats receiving amiloride, hydrochlorothiazide, or both diuretics. In each group of animals, atrial natriuretic factor (ANF 99–126) was given in the second phase of the experiment. The combination of amiloride and hydrochlorothiazide resulted in a more marked natriuresis than either diuretic given as a single agent. Sodium reabsorption in the medullary collecting duct, as a fraction of the delivered load, was reduced from 64% (amiloride) and 69% (hydrochlorothiazide) to 29% (amiloride and hydrochlorothiazide). Atrial natriuretic factor reduced collecting duct sodium reabsorption when added to amiloride or hydrochlorothiazide to 23% and to 41%, respectively, but had no additional effect when given with amiloride and hydrochlorothiazide. Potassium excretion with amiloride and hydrochlorothiazide was intermediate between amiloride or hydrochlorothiazide given as single agents. With the diuretic combination, potassium transport showed no significant reabsorption or secretion along the medullary collecting duct, amiloride was associated with potassium reabsorption, and hydrochlorothiazide was associated with potassium secretion in the duct. The results confirm the importance of the medullary collecting duct as a site of diuretic action. The known additive effects of amiloride and hydrochlorothiazide on sodium excretion and the opposing effects of these agents on potassium excretion occur, to a major degree, in the medullary collecting duct. Furthermore, the additive effects of amiloride and ANF indicate that blocking of amiloride-sensitive sodium channels is not the only mechanism of action of ANF on duct salt transport in vivo.

Microcatheterization was used to study the effect of renal arterial infusion of acetylcholine or secretin on medullary collecting duct function in anaesthetized rats. Acetylcholine infusion was associated with natriuresis and increased sodium delivery to, and decreased reabsorption in, the collecting duct. No changes from control function were found with secretin. Renal blood flow was increased with acetylcholine (+82%, p

The influence of volume expansion on renal function after relief of unilateral chronic ureteral obstruction. Postobstructive diuresis was not observed after the relief of chronic partial ureteral obstruction in hydropenic rats with an intact contralateral kidney. However, when such animals were volume-expanded with hypotonic saline solution after relief of obstruction, urine flow from the hydronephrotic kidney was double that of the contralateral kidney, while urine osmolality was lower and fractional sodium excretion and free water clearance were higher from the postobstructive kidney. These differences were partly related to blunted diuresis from the contralateral normal kidney. Micropuncture measurements during volume expansion in normal and hydronephrotic kidneys showed no significant differences in surface nephron glomerular filtration rate (GFR) or proximal reabsorption, but there was a significant decrease in fractional water reabsorption in the distal nephron of hydronephrotic kidneys. Surface nephron GFR was increased in comparison to whole kidney GFR in both normal and hydronephrotic kidneys during volume expansion, suggesting that a change in distribution of nephron filtration rates was not responsible for the greater diuresis from the postobstructive kidney. Volume expansion could be an important factor in postobstructive diuresis by exaggerating a defect in water reabsorption in the distal nephron and/or in the deep nephrons or collecting ducts of the hydronephrotic kidney. Influence de l'expansion extracellulaire sur la fonction renale apres la levee d'une obstruction unilaterale chronique. La diurese post obstructive n'a pas ete observee apres la levee d'une occlusion ureterale partielle chez des rats hydropeniques dont le rein controlateral est intact. Cependant, quand ces animaux recoivent du solute sale hypotonique apres la levee de l'obstruction, le debit urinaire du rein hydronephrotique est le double de celui du rein controlateral alors que l'osmolalite urinaire est inferieure et l'excretion fractionnelle du sodium et la clearance de l'eau libre sont superieures du cote hydronephrotique. Ces differences sont en partie liees a la diurese attenuee du rein normal controlateral. Les determinations dans des echantillons de microponction obtenus pendant l'expansion extracellulaire dans les reins normaux et hydronephrotiques ne montrent pas de difference significative en ce qui concerne le debit de filtration glomerulaire des nephrons superficiels et leur reabsorption proximale. Par contre une diminution significative de la reabsorption fractionnelle d'eau est observee dans les tubes distaux des reins hydronephrotiques. Le debit de filtration glomerulaire des nephrons superficiels est augmente par rapport au debit de filtration du rein entier aussi bien dans les reins normaux qu'hydronephrotiques, ce qui suggere qu'une modification de la distribution des debits de filtration ne peut pas etre la cause de la plus grande diurese observee dans le rein ayant subi l'occlusion. L'expansion pourrait etre un facteur important dans la diurese post obstructive en exagerant un deficit de la reabsorption de l'eau par le tube distal et/ou les nephrons profonds et les canaux collecteurs de rein hydronephrotique.

Thiazide diuretic effect on medullary collecting duct function in the rat. The distal convoluted tubule is thought to be the principal site of action of thiazide diuretics, but, to our knowledge, there are no studies of their possible effects on collecting duct transport. Microcatheterization of the inner medullary collecting duct (IMCD) was carried out in rats undergoing a modest diuresis, natriuresis, and chloriuresis from hydrochlorothiazide (2 mg/kg/hr) and in normal controls. Delivery of fluid, sodium, and chloride to the beginning of the IMCD was increased, but not significantly, while the load remaining at the papillary tip (end) of the duct was increased markedly by hydrochlorothiazide. Chloride reabsorption in the IMCD was affected most markedly; the chloride reabsorption between the beginning and end of the duct, as a fraction of the delivered load, was reduced from 70.4 ± 5.4% in controls to insignificant amounts with hydrochlorothiazide (8.2 ± 11.5%, P < 0.001). The fraction of delivered sodium reabsorbed along the collecting duct was decreased from 78.5 ± 4.9% in controls to 37.2 ± 12.4% (P < 0.005) in thiazide-treated rats and fluid reabsorption was decreased from 59.4 ± 4.0% in controls to 31.9 ± 5.1% (P < 0.005). Small but significant potassium secretion into the IMCD occurred with hydrochlorothiazide, probably secondary to the marked increase in potassium delivery to the duct. Increased potassium excretion could account for a maximum of 50% of chloriuresis with hydrochlorothiazide. The observation that thiazide diuretics decrease chloride, sodium, and fluid reabsorption in the medullary collecting duct, like the recently demonstrated inhibitory effect of furosemide on this nephron segment, has significant implications for the rationale for diuretic use.Effet des diurétiques thiazidiques sur la fonction du canal collecteur médullaire chez le rat. Le tubule contourné distal est considéré comme étant le site principal d'action des diurétiques thiazidiques, mais, à notre connaissance, il n'existe aucune étude de leurs effets éventuels sur les transports dans le canal collecteur. Des microcathétérisations du canal collecteur médullaire interne (IMCD) ont été effectuées chez des rats ayant une diurèse, une natriurèse, et une chlorurèse modestes par l'hydrochlorothiazide (2 mg/kg/hr) et chez des rats contrôles. Le débit de liquide, de sodium, et de chlore au début de l'IMCD était augmenté, mais non significativement, tandis que la charge délivrée à l'extrémité (fin) papillaire du canal était augmentée de façon marquée par l'hydrochlorothiazide. La réabsorption de chlore dans l'IMCD était affectée de façon très marquée; la réabsorption de chlore entre le début et la fin du canal, sous forme de fraction de la charge délivrée, était réduite de 70,4 ± 5,4% chez les rats contrôles à des quantités insignifiantes par l'hydrochlorothiazide (8,2 ± 11,5%, P < 0,001). La fraction de sodium délivrée réabsorbée le long du canal collecteur était diminuée de 78,5 ± 4,9% chez les contrôles à 37,2 ± 12,4% (P < 0,005) chez les rats traités par le thiazide, et la réabsorption de liquide était diminuée de 59,4 ± 4,0% chez les contrôles à 31,9 ± 5,1% (P < 0,005). Une sécrétion faible mais significative de potassium dans l'IMCD est apparue avec l'hydrochlorothiazide, probablement secondaire à une augmentation marquée du potassium délivré au canal. L'augmentation de l'excrétion de potassium pourrait représenter au maximum 50% de la chlorurèse avec l'hydrochlorothiazide. L'observation que les diurétiques thiazidiques diminuent la réabsorption de chlore, de sodium et d'eau dans le canal collecteur médullaire, comme l'effet inhibiteur du furosémide récemment démontré dans ce segment néphronique, a des applications significatives pour l'utilisation rationnelle du diurétique.

Characteristics of sodium transport in the inner medullary collecting duct were determined in anesthetized rats before and during intravenous infusion of synthetic atrial natriuretic factor (atriopeptin II). Infusion of the factor was associated with increased sodium delivery and reduced fractional reabsorption in the duct. Increasing delivery to the same extent by KCl infusion had no effect on fractional reabsorption. The results demonstrate that atrial natriuretic factor has a specific inhibitory effect on net sodium transport in this part of the nephron. The mechanism of this inhibition may involve induction of sodium permeability and consequent backflux into the tubular lumen.

Ammonia addition into the medullary collecting duct of the rat. The purpose of these studies was to determine if ammonia is added directly to the medullary collecting duct of the rat, and if so, to estimate its quantitative contribution to ammonium excretion. Samples of fluid were obtained along the length of the medullary collecting duct by retrograde microcatheterization. To document net addition of ammonium, we measured the ammonium concentration in tubular fluid by an enzymatic isotope technique, and we calculated the degree of fluid reabsorption from the ratio of the inulin concentration in tubular fluid and plasma. The ammonium concentration corrected for water reabsorption ([NH 4 + ]/[TF/P] In ) rose progressively from the beginning to the end of the medullary collecting duct, indicating net ammonia addition to this nephron segment. By calculation, it appears that about 40% of the excreted ammonium reached the urine by direct addition of ammonia to the duct fluid. Addition d'ammoniaque dans le canal collecteur medullaire du rat. Le but de ce travail a ete de detecter une addition directe d'ammoniaque dans le canal medullaire collecteur du rat et, dans ce cas, d'estimer sa contribution quantitative a l'excretion d'ammoniaque. Des echantillons de liquide ont ete preleves le long du canal collecteur medullaire par micro-catheterisation. Afin d'evaluer une addition nette d'ammonium, la concentration d'ammoniaque dans le liquide tubulaire a ete mesuree par une technique radio-enzymatique et la reabsorption de fluide a ete evaluee au moyen du rapport de concentration de l'inuline (tubule/plasma). La concentration d'ammonium corrigee pour la reabsorption d'eau ([NH 4 + ]/[TF/P]In) augmente progressivement du debut a la fin du canal collecteur medullaire ce qui indique une addition nette d'ammonium dans ce segment du nephron. Le calcul montre qu'environ 40% de l'ammonium excrete provient d'addition directe au canal collecteur.

Mitochondrial calcium accumulation and respiration in ischemic acute renal failure in the rat. Changes in mitochondrial (Mito) calcium (Ca++) and Mito respiration have been demonstrated 24hr after a renal ischemic insult. The Ca++ accumulation has been suggested to contribute to impaired Mito function; alternatively, the Mito Ca++ accumulation could be a late event resulting from cell death. The present aim was, therefore, to determine the sequence of changes in Mito function in ischemic acute renal failure (ARF) induced by 45 min of bilateral renal pedicle clamping in the rat. Animals were studied at the end of clamping, 1, 4, and 24 hr after reflow. By 24 hr, the serum creatinine level had risen progressively to almost ten times control values and fractional excretion of sodium and water were increased. Mito respiration (state 3, adenosine diphosphate-stimulated; acceptor control ratio, state 3/state 4; and uncoupled, FCCP) was severely depressed immediately after 45 min of clamping but improved significantly at 1 and 4 hr after reflow although remaining below sham-operated controls. At 24 hr, when ischemic ARF was established, Mito respiration was again severely depressed. Mito Ca++ was increased slightly but significantly at the end of clamping and increased progressively at 1, 4, and 24 hr after reflow. The Mito Ca++ accumulation was not only demonstrated to occur very early after the ischemic insult, but was relatively selective since it was not associated with Mito Mg++ accumulation. Moreover, the increased Mito Ca++ during reperfusion (1, 4, and 24 hr) demonstrated a significant correlation with the decreased state 3 respiration and the rising serum creatinine level (P < 0.001). The results therefore suggest that an early and progressive increase in Mito Ca++ may be important in the pathogenesis of ischemic ARF. Alternatively, or in addition, Mito Ca++ may be an indication of other cellular dysfunction such as cellular membrane damage and associated increased permeability.Accumulation mitochondriale de calcium et respiration lors de l'insuffisance rénale aiguë ischémique chez le rat. Des modifications du calcium (Ca++) mitochondrial (Mito) et de la respiration Mito ont été démontrées 24 heures après une ischémie rénale. Il a été suggéré que l'accumulation de Ca++ contribue à l'anomalie de fonction Mito; par ailleurs, l'accumulation de Ca++ Mito pourrait être un évènement tardif découlant de la mort cellulaire. C'est pourquoi ce projet a été de déterminer la séquence des modifications de la fonction Mito dans l'insuffisance rénale aiguë (ARF) ischémique induite par une obstruction de 45 minutes bilatérale du pédicule rénal chez le rat. Les animaux ont été étudiés à la fin de l'obstruction, 1, 4, et 24 heures après la reperméabilisation. Au bout de 24 heures, le niveau de créatinine sérique s'est élevé progressivement à presque dix fois les valeurs contrôles et l'excrétion fractionnelle de sodium et d'eau était augmentée. La respiration Mito (stade 3, stimulée par l'adenosine diphosphate; rapport accepteur contrôle, stade 3/stade 4, et découplée FCCP) était sévèrement déprimée immédiatement après 45 minutes de clampage, mais s'est améliorée significativement à 1 et 4 heures après la reperméabilisation, bien que restant plus bas que les contrôles ayant subi un simulacre d'opération. A 24 heures, quand l'ARF ischémique était installée, la respiration Mito était à nouveau sévèrement déprimée. Le Ca++ Mito était augmenté légèrement mais significativement à la fin du clampage, et s'élevait progressivement à 1, 4, et 24 heures après la reperméabilisation. L'accumulation de Ca++ Mito ne survenait pas seulement très précocément après la lésion ischémique, mais était aussi relativement sélective, puisqu'elle n'était pas associée avec l'accumulation de Mg++ Mito. En outre, l'augmentation du Ca++ Mito pendant la reperfusion (1, 4, et 24 heures) démontrait une corrélation significative avec la diminution de la respiration de stade 3, et l'augmentation du niveau de créatinine sérique (P < 0.001). Ces résultats suggèrent donc qu'une augmentation précoce et progressive du Ca++ Mito pourrait être importante dans la pathogénie de l'ARF ischémique. D'un autre côté, en plus, le Ca++ Mito pourrait constituer une indication d'autres dysfonctionnements cellulaires, comme une anomalie de la membrane cellulaire, et une augmentation associée de la perméabilité.

Using the technique of short interval sequential tetracycline labeling, it was documented that the apposition of mineralized bone matrix in adult male Sprague-Dawley rats was inhibited by hydrocortisone. The inhibition occurred as early as six days after the onset of the treatment and was dose dependent over a dose range of 0.62 to 20 mg per kg body weight per day. Vitamin D2 supplements by injection protected bone from this hydrocortisone action. 64 I. U. of vitamin D2 injected daily was able to prevent the inhibition of bone apposition by 20 mg per kg body weight per day of hydrocortisone. The results imply that vitamin D or its metabolites may compete with hydrocortisone in some cellular mechanisms and support the usefulness of vitamin D supplements in the treatment and the prevention of steroid-induced osteoporosis.

The effect of furosemide on inner medullary collecting duct chloride reabsorption has not been determined, and the blunting of furosemide action by drugs that inhibit prostaglandin synthesis, while known to occur, has not been examined in detail. The effect of indomethacin and meclofenamate on furosemide diuresis was studied in the rat using clearance and collecting duct microcatheterization methods. Furosemide-treated control animals showed complete inhibition of chloride, sodium, and water reabsorption in the inner medullary collecting duct. Rats given indomethacin or meclofenamate before and during furosemide administration showed marked reduction of the chloriuresis, natriuresis, and diuresis. Reduced delivery of sodium and chloride to the beginning of the inner medullary collecting duct, associated with a decrease in glomerular filtration rate and increased reabsorption in more proximal nephron segments, was largely responsible for the reduced natriuresis and chloriuresis during inhibition of prostaglandin synthesis. In addition, indomethacin increased collecting duct NaCl reabsorption toward normal, but meclofenamate showed no such effect. The results indicate that furosemide inhibits medullary collecting duct reabsorption of chloride, sodium, and water in the rat. The blunting of diuretic action seen with inhibition of prostaglandin synthesis is largely, although not entirely, due to effects of indomethacin and meclofenamate on furosemide action at nephron sites proximal to the collecting duct.

Nephron functional heterogeneity in the postobstructive kidney. The purpose of this study was to determine the distribution of nephron filtration rates between superficial and juxtamedullary nephrons (S/J ratio) in kidneys studied immediately after relief of 24-hr total obstruction (acute) and after relief of prolonged partial obstruction (chronic). Injection of 14 C-ferrocyanide and microdissection (modified Hanssen's technique) was used to provide an index of superficial and deep nephron glomerular filtration rate (GFR), and standard clearance determinations were done. In normal kidneys S/J ratio of 14 C content (nephron GFR) was 0.73 ± 0.03, a value similar to those obtained by other workers. After relief of acute obstruction, nephron GFR was too low for accurate measurement in 22% of superficial and 13% of deep nephrons. The mean S/J ratio of 14 C content was similar to control, being 0.67 ± 0.07, with only three of seven kidneys showing loss of the normal S/J ratio. Since redistribution of nephron GFR was an inconsistent finding, while marked diuresis and natriuresis occurred in all rats, it appears that redistribution of nephron GFR is not an important factor in the phenomenon of postobstructive diuresis. After relief of chronic obstruction, diuresis and natriuresis were less marked but the mean S/J ratio of 14 C content was 0.95 ± 0.11, and in the majority of kidneys (six of eight), there was loss of distinction between superficial and deep nephron GFR. This redistribution of nephron function after relief of chronic, rather than acute, obstruction may be due to the more severe structural damage to the renal medulla of such kidneys and, although not responsible for postobstructive diuresis, it may be important in the diminished capacity of the chronically hydronephrotic kidney to conserve salt and water. Heterogenite fonctionnelle des nephrons du rein ayant subi une obstruction. Le but de ce travail est de determiner la distribution des debits de filtration des nephrons superficiels et juxta-medullaires (rapport S/J) dans les reins etudies immediatement apres l'ablation d'une occlusion ureterale totale de 24 heures (aigue) ou d'une occlusion partielle prolongee (chronique). L'injection de ferrocyanure 14 C et la microdissection (technique de Hanssen modifiee) ont ete employees pour obtenir un index des debits de filtration des nephrons superficiels et profonds et le debit de filtration global a ete mesure. Dans les reins normaux le rapport S/J du contenu en 14 C (egal au rapport des filtrations) est de 0,73 ± 0,03, valeur semblable a celles d'autres auteurs. Apres l'ablation d'un obstacle aigu, la filtration est trop faible pour permettre une mesure precise dans 22% des nephrons superficiels et 13% des nephrons profonds. Le rapport S/J du contenu en 14 C est semblable a celui des controles: 0,67 ± 0,07. Trois reins sur sept seulement ont une diminution du rapport S/J. Du fait que la redistribution de la filtration n'est pas constante, alors qu'une diurese et une natriurese nettes sont survenues chez tous les rats, il apparait que la redistribution des filtrations n'est pas un facteur important dans le phenomene de diurese post-obstructive. Apres la levee d'un obstacle chronique, la diurese et la natriurese sont moins nettes mais le rapport S/J moyen du contenu en 14 C est 0,95 ± 0,11 et dans la majorite des reins (six sur huit) il y a une perte de la difference entre les filtrations des nephrons superficiels et profounds. Cette redistribution de la fonction des nephrons apres la levee d'un obstacle chronique, a la difference de l'obstacle aigu, peut etre due a des lesions plus severes de la medullaire renale dans ces reins et elle peut jouer un role important dans la diminution de la capacite du rein en hydronephrose chronique a conserver l'eau et le sel encore qu'elle ne soit pas responsable de la diurese post-obstruction.

Microcatheterization was used to study the effect of cis-platinum nephrotoxicity on inner medullary collecting duct function in anaesthetized rats. Osmolality of collecting duct fluid increased from the beginning to the end (papillary tip) of the collecting duct by only 69 ± 11 mosmol/kg in cis-platinum treated rats (at 5–6 days) compared with 306 ± 75 mosmol/kg in sham controls (p

Medullary collecting duct function in the remnant kidney before and after volume expansion. The role of the medullary collecting ducts (CD) in the regulation of water and electrolyte excretion by the remnant kidney has not been determined. Medullary CD function was therefore studied by the microcathetenzation technique during hydropenia and after volume expansion with an isotonic saline load in rats with sham-operated normal kidney (stage I), remnant kidney (stage II), remnant kidney after contralateral nephrectomy (stage III), and sham-operated normal kidney after contralateral nephrectomy (stage-III control). Sodium, potassium, water, and solute reabsorption along the medullary CD were not altered in stage II during hydropenia when compared to normal control (stage I), but water reabsorption proximal to the medullary CD was decreased. In stage III, where the uremia was mild (BUN, 41 mg/dl), the fractions of the filtered load of sodium (72%) and water (62%) which were reabsorbed along the medullary CD were reduced in comparison to stage II (94% and 83%, respectively), stage I, or stage-III control. The fraction of filtered potassium entering the medullary CD was increased to 53% in stage III, compared to 16% in stage II, and 10 or 11% in stage I or stage-III control. No change in the fraction of filtered potassium remaining along the collecting ducts was observed. After volume expansion, there was no significant change in the fraction of filtered sodium and water remaining along the medullary CD in stage I, II, or III. The greater fractional excretion in stage III resulted from decreased reabsorption in more proximal nephron segments. The results indicate that (a) during hydropenia, fractional reabsorption of sodium and water is decreased along the medullary CD of the stage-III remnant kidney in the presence of mild uremia, (b) the increased fractional excretion of potassium in the remnant kidney with uremia is not determined by altered potassium handling in the medullary CD but occurs proximal to this nephron segment, and (c) extracellular fluid volume expansion with isotonic saline results in similar inhibition of fractional sodium and water reabsorption in the collecting ducts of both remnant and normal kidneys. Fonction du canal collecteur medullaire du rein reduit avant et apres expansion extra-cellulaire. Le role des canaux collecteurs (CD) medullaires dans la regulation de l'excretion de l'eau et des electrolytes par le rein reduit n'a pas encore ete precise. La fonction des CD medullaires a donc ete etudiee par microcatheterisation au cours de l'antidiurese et apres expansion au moyen de solute sale isotonique chez des rats dans les situations suivantes: rein intact ayant subi un simulacre de reduction (stade I), rein reduit (stade II), rein reduit et nephrectomie controlaterale (stade III), rein ayant subi un simulacre de reduction et nephrectomie controlaterale (temoin pour le stade III). La reabsorption d'eau, de sodium, de potassium, et d'autres substances dissoutes n'est pas modifiee, au cours de l'antidiurese, le long du CD medullaire des reins reduits de stade II par rapport aux controles normaux du stade I. Cependant la reabsorption d'eau en amont du CD medullaire est diminuee. Au stade III, ou l'uremie est moyenne (azote ureique, 41 mg/dl), les fractions des charges filtrees de sodium (72%) et d'eau (62%) qui sont reabsorbees le long du CD medullaire sont diminuees par rapport au stade II (94% et 83%, respectivement), ou par rapport aux stades I ou III-controle. La fraction du potassium filtre qui entre dans le CD medullaire est augmentee a 53% dans le stade III alors qu'elle represente 16% au stade II, 10 et 11% aux stades I et III-controle. Il n'a pas ete observe de modification de la fraction de potassium filtre encore presente dans les canaux collecteurs. Apres l'expansion il n'y a pas de modification significative de la fraction du sodium et de l'eau filtres presente le long des CD medullaires dans les stades I, II, et III. L'augmentation de l'excretion fractionnelle au stade III resulte d'une diminution de la reabsorption dans les segments plus proximaux du nephron. Les resultats indiquent que: (a) au cours de l'antidiurese la reabsorption fractionnelle du sodium et de l'eau est diminuee le long du CD medullaire du rein reduit au stade III en presence d'une uremie moyenne, (b) l'augmentation de l'excretion fractionnelle de potassium par le rein reduit au cours de l'uremie n'est pas liee a une modification du comportement du CD medullaire vis a vis du potassium mais survient en amont de ce segment, et (c) l'expansion determine une inhibition des reabsorptions fractionnelles de sodium et d'eau comparables dans les CD des reins reduits et des reins normaux.

Tubuloglomerular feedback and interstitial pressure in obstructive nephropathy. The possible role of the tubuloglomerular feedback (TGF) mechanism in the altered glomerular hemodynamics and tubular reabsorption which occur with prolonged (24-hr) ureteral obstruction and the changes in renal interstitial hydrostatic and oncotic pressure which may modulate TGF sensitivity were examined. The proximal tubule stop-flow pressure (PSF) response to increased distal tubular flow rates (TGF activity) was determined in rats with sham operation, 24-hr unilateral ureteral obstruction (UUO), or 24-hr bilateral ureteral obstruction (BUO), both before and for 2 hr after relief of obstruction. Subcapsular hydrostatic pressure, lymph flow and oncotic pressure, clearance and excretory data were measured in the second series of animals. During and after release of UUO, TGF sensitivity was increased, as indicated by the marked decrease in the loop perfusion rate at which 50% of the maximum decrease in PSF occurred (the turning point of TGF activation). Interstitial oncotic pressure but not hydrostatic pressure was significantly increased in UUO kidneys. In BUO rats, the turning point for TGF activation was slightly higher than the controls and the change in PSF with maximum loop perfusion rates was reduced, indicating a blunting of the TGF response before and particularly during postobstructive diuresis after release of BUO. Interstitial hydrostatic and oncotic pressures were both slightly increased resulting in no changes in net interstitial Starling forces. We conclude that enhanced TGF sensitivity after release of prolonged UUO, associated with increased interstitial oncotic pressure, may play a role in preventing postobstructive diuresis, while the blunting of TGF sensitivity after BUO may contribute to this phenomenon.Rétrocontrôle glomérulo-tubulaire et pression interstitielle au cours de la néphropathie obstructive. Le rôle possible du mécanisme de rétrocontrôle glomérulo-tubulaire (TGF) dans l'altération de l'hémadynamique glomérulaire et la réabsorption tubulaire qui se produisent lors d'une obstruction urétérale prolongée (24 heures) et les modifications des pressions hydrostatiques et oncotiques interstitielles rénales qui pourraient moduler la sensibilité TGF ont été étudiés. La réponse de pression en flux interrompu (PSF) du tubule proximal à une augmentation des débits tubulaires distaux a été déterminée chez des rats ayant subi un simulacre d'intervention, lors d'une obstruction urétérale unilatérale de 24 heures (UUO) ou lors d'une obstruction urétérale bilatérale de 24 heures (BUO), avant et 2 heures après la levée de l'obstruction. La pression hydrostatique sous-capsulaire, le flux et la pression oncotique lymphatiques, les paramètres de clearance et d'excrétion ont été mesurés chez une deuxième série d'animaux. Pendant et après levée de l'UUO, la sensibilité TGF a augmenté, comme le montrait la diminution marquée du débit de perfusion de l'anse pour lequel 50% de la chute maximale de PSF se produisait (le point d'inflexion de l'activation TGF). La pression oncotique mais non la pression hydrostatique interstitielle était significativement accrue dans les reins UUO. Chez les rats BUO, le point d'inflexion de l'activation TGF était légèrement plus élevé que chez les contrôles, et la modification de PSF aux débits de perfusion de l'anse maxima était diminuée, indiquant une altération de la réponse TGF avant et surtout pendant la diurèse post-obstructive, après levée de la BUO. Les pressions interstitielles hydrostatiques et oncotiques légèrement augmentées, d'où l'absence de modification des forces de Starling interstitielles nettes. Nous concluons que l'augmentation de la sensibilité TGF après levée d'une UUO prolongée associée à une élévation de la pression oncotique interstitielle, pourrait jouer un rôle pour prévenir la diurèse post-obstructive, alors que l'altération de la sensibilité TGF après BUO pourrait contribuer à ce phénomène.

Micropuncture study of chronic obstructive nephropathy before and after release of obstruction. The nature of the intrinsic renal defect in chronic obstructive nephropathy was studied in rats with unilateral partial ureteral ligation. In the surface nephrons of chronically hydronephrotic kidneys, proximal intratubular pressure was slightly increased when compared to sham-operated control animals. Tubular fluid flow rate was reduced by 35%, fractional reabsorption was increased by 8% and single nephron filtration rate was 76% of control values. There was no post-obstructive diuresis in rats with a normal contralateral kidney studied 2 to 6 hrs after relief of chronic obstruction and there was no evidence of hyperfiltration or decreased fractional reabsorption in the proximal tubule of surface nephrons in the post-obstructive kidney. A disproportionately high surface nephron to whole kidney glomerular filtration rate (GFR) was present in most animals studied before or after relief of obstruction. It is concluded that the increased fractional excretion of sodium and diminished urine osmolality observed in chronic obstructive nephropathy result from decreased reabsorption in the distal nephron and/or impaired function of the deep nephrons and renal medulla. The results also indicate that these intrarenal functional defects are not solely responsible for the phenomenon of post-obstructive diuresis; it must also depend on other factors such as superimposed volume expansion or further reduction in functioning nephron mass.

Sites of ammonia addition to tubular fluid in rats with chronic metabolic acidosis. The purpose of this investigation was to determine in which nephron segments ammonia was added to or removed from the lumenal fluid of the rat. Ammonium was measured in proximal and distal tubular fluid samples obtained by micropuncture and in collecting duct fluid samples obtained by microcatheterization. Water abstraction was assessed by examining the tubular fluid-to-plasma inulin concentration, (TF/P) In . In normal or acidotic rats, the vast bulk of the final urine ammonium appeared in the proximal tubular fluid samples. Most of this ammonia was lost, however, in transit from the proximal to the distal tubule so that only 20 to 30% of the excreted ammonium was present at the distal site. Ammonia reentered the lumenal fluid primarily in the cortical collecting duct in acidotic rats and in the medullary collecting duct in normal rats. Although the pattern was qualitatively similar in both groups of rats, the absolute quantity of ammonium in each nephron segment of normal rats was about 10 to 20% of that in acidotic animals. Sites de l'addition d'ammoniaque au liquide tubulaire chez les rats en acidose metabolique chronique. Le but de cette etude a ete d'identifier les segments du nephron ou l'ammoniaque est ajoute ou soustrait du liquide tubulaire chez le rat. L'ammoniaque a ete mesure dans les echantillons de liquide proximal et distal obtenus par microponction et dans les echantillons de liquide du canal collecteur obtenus par micro-catheterisation. La soustraction d'eau a ete evaluee par le rapport liquide tubulaire/plasma de l'inuline. Chez les rats normaux et en acidose la majorite de l'ammoniaque de l'urine definitive apparait deja dans les echantillons tubulaires proximaux. La plupart de cet ammoniaque cependant est perdu entre le tube proximal et le tube distal si bien que 20 a 30% seulement de l'ammoniaque excrete est present au site distal. L'ammoniaque entre a nouveau dans la lumiere tubulaire principalement dans le canal collecteur medullaire chez les rats noir-maux. Bien que les modalites soient qualitativement semblables dans les deux groupes de rats la quatite absolue d'ammoniaque dans chaque segment tubulaire des rats normaux est environ 10 a 20% de celle des animaux en acidose.

The effects of urinary-tract obstruction on renal function have been clarified using modern physiologic techniques in animal models. These effects are obviously dependent on the severity and duration of obstruction, together with the presence or absence of extrarenal factors, particularly uremia, as exemplified by the differences in renal function between bilateral and unilateral obstruction. The beneficial effects on the unilateral postobstructive kidney of volume expansion (5) and the importance of azotemia in determining POD (20, 21) have possible clinical applications. Further experimental work is required to understand the mechanism responsible for the altered renal hemodynamics and decreased GFR, as well as the abnormalities in medullary function resulting from obstruction. Improvement in the management of this common clinical problem may then be forthcoming.

Recurrent calcium-containing renal calculi are a common and poorly understood problem. Thiazide diuretics decrease urinary calcium excretion but their effect on other parameters of calcium metabolism is not established. The purpose of this study was to determine the effect of chronic administration of thiazide diuretics on intestinal calcium absorption, skeletal calcium turnover, and urinary calcium excretion, and to use this information to attempt to clarify the pathogenesis of idiopathic hypercalciuria. Forty-one patients with recurrent calcium-containing renal calculi were studied; 73% had hypercalciuria, 44% had increased intestinal absorption, and 7% had increased bone turnover. Thiazide diuretics given to 22 patients for 3–16 mo resulted in a consistent reduction in urinary calcium excretion, while calcium absorption was unchanged (

The association between heavy consumption of analgesics and nephropathy was first described in Canada in 1961 [1]. Thirty-seven such patients were reported in 1968 [2, 3], and an additional 314 were reported in 1972 from a survey of Canadian nephrologists [4], which provides a baseline from which an evaluation of the effect of removal of phenacetin can be made.

Blood supply and drainage of the outer medulla of the rat kidney were studied by scanning electron microscopy of vascular casts, using both arterial (n = 10) and venous (n = 10) injections of resin. Both outer and inner stripes of the outer medulla were supplied through different arterial capillary networks arising from efferent arterioles and arterial (descending) vasa recta. In contrast to previous studies using silicone rubber and light microscopy, a rich arterial capillary network supplying the outer stripe was demonstrated. Capillaries in the outer stripe and outer part of the inner stripe drained into venous vasa recta between vascular bundles, while capillaries in the inner part of the inner stripe drained into venous vasa recta within the bundles. The results indicate that each zone in the outer medulla is supplied through separate capillary networks. The demonstration of a rich capillary network in the outer stripe of the outer medulla suggests that the predilection of this zone for tubular necrosis with ischemic or toxic injury is not related to a sparse capillary blood supply.

The pathogenesis of zinc deficiency and its relationship to hypogeusia were studied in three chronic dialysis units in Toronto. The difference between low plasma zinc levels at two of the hospitals compared to the normal levels in the third hospital was significantly related to levels of dietary zinc intake which in turn was due to the levels of dietary protein intake. Thus one cause of zinc deficiency in chronic uremia is dietary protein deprivation. In addition, in the hospital with normal plasma levels there was a small but significant rise in plasma zinc postdialysis in contrast to the other two hospitals where there was no change. Thus slight leaching of zinc from dialysis equipment could help prevent zinc deficiency in such patients. Hypogeusia was more common in zinc-deficient patients. Am. I Clin. Nutr. 34: 2658-2661, 1981.