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Background: Coroners in Australia, Canada, New Zealand and other countries in the Commonwealth hold inquests into deaths in two situations. Mandatory inquests are held when statutory rules dictate they must be; discretionary inquests are held based on the decisions of individual coroners. Little is known as to how and why coroners select particular deaths for discretionary inquests.Methods: We analyzed the deaths investigated by Australian coroners for a period of seven and one-half years in five jurisdictions. We classified inquests as mandatory or discretionary. After excluding mandatory inquests, we used logistic regression analysis to identify the factors associated with coroners' decisions to hold discretionary inquests.Results: Of 20 379 reported deaths due to external causes, 1252 (6.1%) proceeded to inquest. Of these inquests, 490 (39.1%) were mandatory and 696 (55.6%) were discretionary. In unadjusted analyses, the rates of discretionary inquests varied widely in terms of age of the decedent and cause of death. In adjusted analyses, the odds of discretionary inquests declined with the age of the decedent; the odds were highest for children (odds ratio [OR] 2.17, 95% confidence interval [CI] 1.54-3.06) and lowest for people aged 65 years and older (OR 0.38, 95% CI 0.28-0.51). Using poisoning as a reference cause of death, the odds of discretionary inquests were highest for fatal complications of medical care (OR 12.83, 95% CI 8.65-19.04) and lowest for suicides (OR 0.44, 95% CI 0.30-0.65).Interpretation: Deaths that coroners choose to take to inquest differ systematically from those they do not. Although this vetting process is invisible, it may influence the public's understanding of safety risks, fatal injury and death. [ABSTRACT FROM AUTHOR]

Background: Recent government inquiries in several countries have identified the length of time it takes coroners to investigate deaths due to injury and other unnatural causes as a major problem. Delays undermine the integrity of vital statistics and adversely affect the deceased's family and others with interests in coroners' findings. Little is publicly known about the extent, nature and causes of these delays., Methods: We used Kaplan-Meier estimates and multivariable regression analysis to decompose the timelines of nearly all inquest cases (n=5096) closed in coroners' courts in Australia between 1 January 2007 and 31 December 2013., Results: The cases had a median closure period of 19.0 months (95% CI 18.4 to 19.6). Overall, 70% of cases were open at 1 year, 40% at 2 years and 22% at 3 years, but there was substantial variation by jurisdiction. Adjusted analyses showed a difference of 22 months in the average closure time between the fastest and slowest jurisdictions. Cases involving deaths due to assault (+12.2 months, 95% CI 7.8 to 17.0) and complications of medical care (+9.0 months, 95% CI 5.5 to 12.3) had significantly longer closure periods than other types of death. Cases that produced public health recommendations also had relatively long closure periods (+8.9 months, 95% CI 7.6 to 10.3)., Conclusions: Nearly a quarter of inquests in Australia run for more than 3 years. The size of this caseload tail varies dramatically by jurisdiction and case characteristics. Interventions to reduce timelines should be tried and carefully evaluated., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

Background: Most countries have detailed lists of traffic rules and elaborate legal regimes for penalizing drivers who break them. Previous research has suggested that drivers tend to drive more safely after receiving penalties for traffic infringements., Methods: We linked driver-level data on infringements and crashes in Queensland, Australia (1995-2010) with information on the licence histories of all drivers in the state. We used a case-crossover design to examine drivers' risk of crashing in the month following an infringement penalty. We also examined whether changes in crash risk following infringement penalties varied according to driver age and gender, type of infringement and whether the offender was at fault in a subsequent crash., Results: Drivers had higher risks of crashes following infringement penalties [odds ratio (OR) 1.32; 95% confidence interval (CI) 1.29-1.36], especially crashes in which the offender was at fault (1.41; 1.36-1.46). Crash risk relative to a comparable period was particularly high for teenage drivers (1.55; 1.34-1.78) and among drivers penalized for dangerous driving (3.19; 2.52-4.03) or driving under the influence of alcohol (1.99; 1.67-2.37). The risk remained relatively high for more than 6 months after the penalty, but declined steadily over this period., Conclusions: Crash risk among drivers in Queensland was higher, not lower, following receipt of penalties for traffic infringements. Penalties themselves are unlikely to increase crash risk. A more likely explanation is that penalties (or the corresponding infringements) mark episodes of risky driving. Our findings suggest that such episodes trounce any deterrent effect penalties may produce.

Objective: To determine whether Olympic medallists live longer than the general population., Design: Retrospective cohort study, with passive follow-up and conditional survival analysis to account for unidentified loss to follow-up., Setting and Participants: 15 174 Olympic athletes from nine country groups (United States, Germany, Nordic countries, Russia, United Kingdom, France, Italy, Canada, and Australia and New Zealand) who won medals in the Olympic Games held in 1896-2010. Medallists were compared with matched cohorts in the general population (by country, age, sex, and year of birth)., Main Outcome Measures: Relative conditional survival., Results: More medallists than matched controls in the general population were alive 30 years after winning (relative conditional survival 1.08,95% confidence interval 1.07 to1.10). Medallists lived an average of2.8 years longer than controls. Medallists in eight of the nine country groups had a significant survival advantage compared with controls. Gold, silver, and bronze medallists each enjoyed similar sized survival advantages. Medallists in endurance sports and mixed sports had a larger survival advantage over controls at 30 years (1.13, 1.09 to 1.17; 1.11,1.09 to 1.13) than that of medallists in power sports (1.05,1.01 to 1.08)., Conclusions: Olympic medallists live longer than the general population, irrespective of country, medal, or sport. This study was not designed to explain this effect, but possible explanations include genetic factors, physical activity, healthy lifestyle, and the wealth and status that come with international sporting glory., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Objective: To investigate whether the Victorian mandatory personal flotation device wearing regulations that came into effect on 1 December 2005 reduced drowning deaths among recreational boaters in Victoria, Australia., Design: A retrospective population-based 'before and after' study using Victorian coronial data on drowning deaths of occupants of recreational vessels operating in Victorian waters., Methods: The annual numbers of deaths in the 5 years after the transition year of the regulations (2005) was compared with the annual numbers of deaths in the 6 years prior to the transition year, using the Mann-Whitney U test., Results: There were 59 recreational boating drowning deaths in the 6-year preintervention period (1 December 1998 to 30 November 2004) compared with 16 in the 5-year postintervention period (1 December 2005 to 30 November 2010). The analysis showed a significant decrease in drowning deaths among all recreational boaters (U=30.0, p=0.01) and among these strata: vessel occupants aged 0-29 years (U=28.0, p=0.02) and 30-59 years (U=27.5, p=0.02), vessel occupants engaged in pleasure cruising (U=29.0, p=0.01) and in 'other' boating activities (U=25.0, p=0.04), boaters on small powerboats ≤4.8 m in length (U=29.5; p=0.01), boaters on motorised (U=29.5; p=0.01) and sail-powered vessels (U=26.0; p=0.04), and occupants of vessels operating in inland waterways (U=30.0; p=0.01)., Conclusions: These findings provide further support for the adoption of a regulatory approach to personal flotation device wearing to reduce drowning among recreational boaters., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Objectives: To determine the nature and extent of governance activities by health service boards in relation to quality and safety of care and to gauge the expertise and perspectives of board members in this area., Methods: This study used an online and postal survey of the Board Chair, Quality Committee Chair and two randomly selected members from the boards of all 85 health services in Victoria. Seventy percent (233/332) of members surveyed responded and 96% (82/85) of boards had at least one member respond., Results: Most boards had quality performance as a standing item on meeting agendas (79%) and reviewed data on medication errors and hospital-acquired infections at least quarterly (77%). Fewer boards benchmarked their service's quality performance against external comparators (50%) or offered board members formal training on quality (53%). Eighty-two percent of board members identified quality as a top priority for board oversight, yet members generally considered their boards to be a relatively minor force in shaping the quality of care. There was a positive correlation between the size of health services (total budget, inpatient separations) and their board's level of engagement in quality-related activities. Ninety percent of board members indicated that additional training in quality and safety would be 'moderately useful' or 'very useful'. Almost every respondent believed the overall quality of care their service delivered was as good as, or better than, the typical Victorian health service., Conclusions: Collectively, health service boards are engaged in an impressive range of clinical governance activities. However, the extent of engagement is uneven across boards, certain knowledge deficits are evident and there was wide agreement among board members that further training in quality-related issues would be useful.

Objective: To determine whether Olympic medallists live longer than the general population., Design: Retrospective cohort study, with passive follow-up and conditional survival analysis to account for unidentified loss to follow-up., Setting and Participants: 15,174 Olympic athletes from nine country groups (United States, Germany, Nordic countries, Russia, United Kingdom, France, Italy, Canada, and Australia and New Zealand) who won medals in the Olympic Games held in 1896-2010. Medallists were compared with matched cohorts in the general population (by country, age, sex, and year of birth)., Main Outcome Measures: Relative conditional survival., Results: More medallists than matched controls in the general population were alive 30 years after winning (relative conditional survival 1.08, 95% confidence interval 1.07 to 1.10). Medallists lived an average of 2.8 years longer than controls. Medallists in eight of the nine country groups had a significant survival advantage compared with controls. Gold, silver, and bronze medallists each enjoyed similar sized survival advantages. Medallists in endurance sports and mixed sports had a larger survival advantage over controls at 30 years (1.13, 1.09 to 1.17; 1.11, 1.09 to 1.13) than that of medallists in power sports (1.05, 1.01 to 1.08)., Conclusions: Olympic medallists live longer than the general population, irrespective of country, medal, or sport. This study was not designed to explain this effect, but possible explanations include genetic factors, physical activity, healthy lifestyle, and the wealth and status that come with international sporting glory.

This paper examines the relationship between the remoteness of locations in which deaths occur and coroners' decisions to hold inquests. We analysed 16,242 deaths investigated by coroners in three Australian states over 7.5 yrs. We used a choropleth map to show inquest rates in each remoteness locality (excluding deaths for which inquests were mandated by statute). We then used adjusted logistic regression to assess the association between the remoteness of a death's location and the odds coroners would select it for investigation by inquest. We found the remoteness of a death's location strongly and positively predicts the chance that an inquest will be held. Like analogous findings in the delivery of health services, this small-area variation in legal decision making raises questions of appropriateness., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: Although it is known that moderate-to-high doses of the neurohypophysial hormones oxytocin and vasopressin are natriuretic, doubts remain over the identity of the receptors responsible. To address this issue, we have used highly selective antagonists of oxytocin and vasopressin receptors in animals with elevated endogenous circulating levels of the 2 hormones., Methods: Rats were anaesthetised and prepared surgically for clearance studies, thereby raising plasma oxytocin and vasopressin concentrations. Sodium excretion, glomerular filtration rate and lithium clearance (an index of end-proximal fluid delivery) were measured: first during a control period, then after administration of the selective oxytocin receptor antagonist desGly-NH(2),d(CH(2))(5)[D-Trp(2),Thr(4),Dap(5)]OVT, the selective vasopressin V(1a) receptor antagonist d(CH(2))(5)[Tyr(Me)(2),Dab(5)]AVP, or vehicle alone., Results: Absolute and fractional sodium excretion fell in rats given the oxytocin antagonist (by 32 and 27%, respectively, compared with corresponding values in vehicle-infused rats), but not in those given the V(1a) antagonist or vehicle. Antinatriuresis was associated with a small reduction in the ratio of sodium clearance to lithium clearance (an index of the fraction of distally delivered sodium that escapes reabsorption in the distal nephron)., Conclusions: These results corroborate previous studies showing that activation of oxytocin receptors increases sodium excretion and imply that the natriuretic effect of elevated plasma vasopressin concentrations results from stimulation of oxytocin receptors., (Copyright © 2010 S. Karger AG, Basel.)

Ischemic damage plays an important role in post-transplant organ failure. Activation of the apoptotic cascade is crucially involved in post-ischemic inflammation resulting in tissue damage and organ dysfunction. Here we investigate the initiation of the apoptotic cascade during normothermic ischemia in human kidneys using a model for normothermic ischemia with kidneys nephrectomized because of renal cell carcinoma. Ex vivo, kidneys were stored at 37 degrees C, and consecutive biopsies were taken from disease-free tissue. Pro- and anti-apoptotic proteins were assessed by Western blotting and immunofluorescence. During normothermic ischemia the pro-apoptotic proteins Bax and activated caspase-9 increased with ischemia time, whereas caspase-8 was not activated. The anti-apoptotic proteins Bcl-2 and cFLIP decreased in time. Data on Bcl-2 and Bax were supported by immunofluorescence for Bcl-2 and activated Bax. However, activation of the central effector caspase-3, essential for execution of the apoptotic process, was not detected. In conclusion, during normothermic ischemia the apoptotic cascade in the human kidney is initiated, but not fulfilled. Our data show that the duration of ischemia significantly correlates with activation of the apoptotic cascade. These findings provide insight in the initiation of apoptotic cell-death during warm ischemia and may be useful in the assessment of ischemic injury.

Ischemia-reperfusion (I/R) is an important cause of acute renal failure (ARF). The complement system appears to be essentially involved in I/R injury. However, via which pathway the complement system is activated and in particular whether the mannose-binding lectin (MBL)-pathway is activated is unclear. This tempted us to study the activation and regulation of the MBL-pathway in the course of experimental renal I/R injury and in clinical post-transplant ARF. Mice subjected to renal I/R displayed evident renal MBL-depositions, depending on the duration of warm ischemia, in the early reperfusion phase. Renal deposition of C3, C6 and C9 was observed in the later reperfusion phase. The deposition of MBL-A and -C completely co-localized with the late complement factor C6, showing that MBL is involved in complement activation in the course of renal I/R injury. Moreover, the degree of early MBL-deposition correlated with complement activation, neutrophil-influx, and organ-failure observed in the later reperfusion phase. In serum of mice subjected to renal I/R MBL-A, levels increased in contrast to MBL-C levels, which dropped evidently. In line, liver mRNA levels for MBL-A increased, whereas MBL-C levels decreased. Renal MBL mRNA levels rapidly dropped in the course of renal I/R. Finally, in human biopsies, MBL-depositions were observed early after transplantation of ischemically injured kidneys. In line with our experimental data, in ischemically injured grafts displaying post-transplant organ-failure extensive MBL depositions were observed in peritubular capillaries and tubular epithelial cells. In conclusion, in experimental renal I/R injury and clinical post-transplant ARF the MBL-pathway is activated, followed by activation of the complement system. These data indicate that the MBL-pathway is involved in ischemia-induced complement activation.

Background: Although ischemia-reperfusion (I/R) injury represents a major problem in posttransplant organ failure, effective treatment is not available. The acute phase protein alpha-1-acid glycoprotein (AGP) has been shown to be protective against experimental I/R injury. The effects of AGP are thought to be mediated by fucose groups expressed on the AGP protein inhibiting neutrophil infiltration. However, the precise mechanism of protection remains to be established. We therefore studied the effects of exogenous human AGP (hAGP) in a mouse model of ischemic acute renal failure., Methods: Mice were subjected to renal I/R and treated with hAGP, fucose-depleted hAGP, or control treated. Also, transgenic mice over-expressing rat AGP or wild-type controls were subjected to renal I/R., Results: Treatment was with hAGP as well as fucose-depleted hAGP protected mice against I/R-induced acute renal failure. Surprisingly, AGP-over-expressing mice were not protected against I/R injury. Both natural and fucose-depleted hAGP inhibited the activation of the complement system, as determined by renal C3 deposition and influx of neutrophils measured by immunohistochemistry and myeloperoxidase-enzyme-linked immunoadsorbent assay. Tubular epithelial cell structure (actin cytoskeleton) and cell-cell interaction (tight-junction architecture) were completely preserved in AGP-treated mice. Also, epithelial caspase activation and apoptotic DNA cleavage were prevented by AGP treatment., Conclusions: Both natural and fucose-depleted hAGP protect against renal I/R injury by preservation of tubular epithelial structure and inhibition of apoptosis and subsequent inflammation. Therefore, hAGP can be regarded as a potential new therapeutic intervention in the treatment of acute renal failure, as seen after transplantation of ischemically injured kidneys.

Uncertainties exist over the glomerular filtration of aluminium and virtually nothing is known about its segmental handling along the nephron. The present study has used micropuncture, combined with electrothermal atomic absorption spectroscopy, to determine directly the aluminium content of glomerular filtrate and of late PCTs (proximal convoluted tubules) and early distal tubules in anaesthetized Munich-Wistar rats infused with three different doses of aluminium citrate (plasma aluminium concentrations, 2.9+/-0.1, 5.2+/-0.4 and 10.0+/-0.9 microg.ml(-1) respectively). Aluminium filtration into Bowman's space was found to be considerably greater than that predicted by an in vitro filtration system: in all three groups it was essentially filtered freely. No significant aluminium reabsorption took place along the PCT, but with every dose the FD(Al) (fractional delivery of aluminium; tubular fluid:plasma aluminium/inulin concentration ratio) was lower at the early distal site than at the late PCT (P<0.001 in each case), indicating net aluminium reabsorption in the loop of Henle. This reabsorption amounted to 19-26% of the filtered aluminium load. In the low- and medium-dose groups, there was no significant difference between FD(Al) at the early distal site and that in the final urine; however, in the high-dose group, FD(Al) in the urine (1.02+/-0.06) exceeded that at the early distal tubule (0.75+/-0.04; P<0.001), suggesting aluminium secretion in the distal nephron. The results indicate that aluminium loads, when complexed with citrate, are excreted efficiently owing to a combination of glomerular filtration and minimal reabsorption.

Background: Warm ischemia-reperfusion (I/R) injury plays an important role in posttransplant organ failure. In particular, organs from marginal donors suffer I/R injury. Although iron has been implicated in the pathophysiology of renal I/R injury, the mechanism of iron-mediated injury remains to be established. The authors therefore investigated the role of circulating redox-active iron in an experimental model for renal I/R injury., Methods: Male Swiss mice were subjected to unilateral renal ischemia for 45 min, followed by contralateral nephrectomy and reperfusion. To investigate the role of circulating iron, mice were treated with apotransferrin, an endogenous iron-binding protein, or iron-saturated apotransferrin (holotransferrin)., Results: Renal ischemia induced a significant increase in circulating redox-active iron levels during reperfusion. Apotransferrin, in contrast to holotransferrin, reduced the amount of circulating redox-active iron and abrogated renal superoxide formation. Apotransferrin treatment did not affect I/R-induced renal apoptosis, whereas holotransferrin aggravated apoptotic cell death. Apotransferrin, in contrast to holotransferrin, inhibited the influx of neutrophils. Both apo- and holotransferrin reduced I/R-induced complement deposition, indicating that the effects of transferrin are differentially mediated by its iron and protein moiety. Finally, apotransferrin, in contrast to holotransferrin, dose-dependently inhibited the loss of renal function induced by ischemia., Conclusions: Redox-active iron is released into the circulation in the course of renal I/R. Reducing the amount of circulating redox-active iron by treatment with apotransferrin protects against renal I/R injury, inhibiting oxidative stress, inflammation, and loss of function. Apotransferrin could be used in the treatment of acute renal failure, as seen after transplantation of ischemically damaged organs.

In order to assess the intrarenal mechanisms responsible for the natriuretic action of caffeine, the renal clearances of (51)Cr-EDTA [used as a measure of glomerular filtration rate (GFR)] and lithium (used as an index of end-proximal fluid delivery) were measured in eight healthy males before (control period) and immediately after (experimental period) a 400 mg oral dose of caffeine (given over 90 min) or placebo. In caffeine-treated subjects, the fractional excretion of sodium rose from 1.00+/-0.25% in the control period to 1.47+/-0.18% in the experimental period, while corresponding values on the placebo day were 1.04+/-0.16% and 0.70+/-0.07% respectively. GFR was unchanged following either caffeine or placebo. When compared with the placebo day, caffeine caused increases in lithium clearance (experimental period values: caffeine, 37+/-1 ml/min; placebo, 28+/-2 ml/min; P <0.001), the fractional excretion of lithium (caffeine, 34+/-1%; placebo, 26+/-2%; P <0.001) and the sodium/lithium clearance ratio (used as an index of the fraction of sodium delivered to the distal nephron that escapes reabsorption therein: caffeine, 4.4+/-0.3%; placebo, 2.8+/-0.2%; P <0.001). These results suggest that reduced fractional sodium reabsorption in both the proximal tubule and the distal nephron contributes to the acute natriuretic effect of caffeine. The data also confirm the importance of controlling caffeine intake when investigating renal function using lithium clearance.

Inhibition of sodium reabsorption in the loop of Henle (LOH) contributes to the natriuretic effect of systemically administered glibenclamide. Although it has been suggested that the underlying mechanism involves inhibition of low-conductance potassium channels in the apical membrane of the thick ascending limb, these channels are relatively insensitive to glibenclamide ( K(i) ~200 micro M). In the present study we used capillary electrophoresis techniques to determine plasma and tubular fluid concentrations of glibenclamide in anaesthetised, glibenclamide-infused rats during maximal natriuresis. The plasma glibenclamide concentration was 158+/-29 micro M, whereas that in the tubular fluid entering the LOH was below detectable limits (10 micro M). In additional experiments, rats were infused intravenously with either glibenclamide or vehicle alone, while the LOH was perfused with a standard, glibenclamide-free solution. Loop sodium reabsorption ( J(Na)) was significantly reduced in the rats receiving the drug (vehicle: J(Na) 1.65+/-0.05 nmol/min, n=23; glibenclamide: J(Na) 1.34+/-0.07 nmol/min, n=36; P<0.01). In a further group of rats, glibenclamide was introduced directly into the LOH at a concentration known to inhibit the low-conductance potassium channel in vitro (250 micro M). However, J(Na) was unaffected. These data confirm that systemic glibenclamide inhibits sodium reabsorption in the LOH but argue strongly that it does not act from the luminal site.

In vitro evidence suggests that the 'recycling' of K(+) ions through luminal K(+) channels in the thick ascending limb of the loop of Henle (TALH) is essential for the normal operation of the luminal Na(+)-K(+)-2Cl(-) co-transporter. In the present study these channels were investigated in vivo by perfusing superficial loops of Henle in anaesthetised rats with and without the K(+) channel blocker barium. Using a standard perfusate, intraluminal barium (5 mmol l(-1)) reduced sodium reabsorption (J(Na)) from 1887 +/- 50 to 1319 +/- 53 pmol min(-1) (P < 0.001). When the experiment was repeated using a low-Na(+) perfusate, designed to inhibit reabsorption in the pars recta (the initial segment of the loop of Henle), a similar reduction in J(Na) was observed (from 698 +/- 47 to 149 +/- 23 pmol min(-1), P < 0.001), strongly suggesting that the effect of barium is localised to the TALH. The magnitude of the reduction in J(Na) during blockade of K(+) channels confirms the importance of K(+) recycling in facilitating Na(+) reabsorption in the TALH in vivo. However, the reduction in J(Na) was not associated with a fall in the K(+) concentration of the fluid collected at the early distal tubule. When bumetanide, an inhibitor of the Na(+)-K(+)-2Cl(-) co-transporter, was included in the low-Na(+) perfusate, net K(+) secretion was observed. Addition of barium to this perfusate reduced, but did not abolish, the secretion, suggesting that bumetanide-induced K(+) secretion results partly from paracellular transport. Experimental Physiology (2001) 86.4, 469-474.

In order to clarify the effects on sodium reabsorption in the loop of Henle of methazolamide (a carbonic anhydrase inhibitor), chlorothiazide and the loop diuretics frusemide and bumetanide, superficial loops were perfused in vivo in anaesthetized rats and the individual diuretics were included in the perfusate. Differentiation between effects in the pars recta and in the thick ascending limb of Henle (TALH) was achieved by comparing responses to the diuretics when using a standard perfusate, designed to mimic native late proximal tubular fluid, and a low-sodium perfusate, designed to block net sodium reabsorption in the pars recta. With the standard perfusate, methazolamide caused decreases in sodium reabsorption (J(Na)) and water reabsorption (J(V)); with the low-sodium perfusate, a modest effect on J(Na) persisted, suggesting that carbonic anhydrase inhibition reduces sodium reabsorption in both the pars recta and the TALH. The effects of chlorothiazide were very similar to those of methazolamide with both the standard and low-sodium perfusates, suggesting that chlorothiazide also inhibits sodium reabsorption in the pars recta and TALH, perhaps through inhibition of carbonic anhydrase. With the standard perfusate, both frusemide and bumetanide produced the expected large decreases in J(Na), but J(V) was also lowered. With the low-sodium perfusate, the inhibitory effects of the loop diuretics, particularly those of frusemide, were substantially reduced, while net potassium secretion was found. These observations indicate that a significant component of the effect of frusemide (and possibly of bumetanide) on overall sodium reabsorption is located in the pars recta, and that loop diuretics induce potassium secretion in the TALH.

In the present study, we have investigated the effects of dietary potassium depletion on the activity and distribution of the H+-ATPase in the distal nephron of the Sprague-Dawley rat. H+-ATPase activity was assessed from the change in transepithelial potential difference (Vte) in response to bafilomycin A1 during perfusion of the late distal tubule in vivo, with solutions containing inhibitors of known ion channels. Bafilomycin A1 caused a negative deflection in Vte in control animals, an effect that was significantly enhanced during potassium depletion (P < 0.01). The distribution of H+-ATPase within the population of intercalated cells was assessed using a specific monoclonal antibody (E11). Hypokalemia was associated with a highly significant redistribution of the staining pattern (P < 0. 001), with an increase in the percentage of cells displaying immunoreactivity in the apical membrane. These results indicate that dietary potassium depletion increases electrogenic H+-ATPase activity in the rat distal tubule; this may be associated with increased insertion of pumps into the apical membrane.

1. In order to examine the electrochemical gradient for potassium reabsorption across the S2 segment of the proximal convoluted tubule, transepithelial potential differences and transepithelial potassium concentrations were measured in anaesthetized potassium-replete and potassium-depleted rats. 2. Potassium-depleted rats were markedly hypokalaemic (plasma potassium, 1.4 +/- 0.1 vs. 4.1 +/- 0.1 mmol l-1 in potassium-replete rats) and had a significantly reduced muscle potassium content. In confirmation of previous reports, glomerular filtration rate was slightly reduced, while fractional reabsorption in the proximal convoluted tubule was enhanced. 3. In potassium-replete animals, the transepithelial potential difference (PD) at the late proximal convoluted tubule was +2.1 +/- 0.3 mV (lumen positive) and the tubular fluid to plasma ultrafiltrate concentration ratio for potassium (TFK/UFK) at the same site was 1. 03 +/- 0.01. In potassium-depleted rats, there was a striking reversal of the transepithelial PD (to -4.0 +/- 0.4 mV), while the TFK/UFK was increased to 1.19 +/- 0.03. 4. The data from both potassium-replete and potassium-depleted animals are consistent with accumulating evidence that potassium reabsorption in the proximal convoluted tubule is passive in nature and depends partly on diffusion down an electrochemical gradient.

1. The contribution of apical Na+-H+ exchange to sodium reabsorption in the thick ascending limb of the loop of Henle (TALH) in vivo was examined in anaesthetized rats by perfusing loops of Henle of superficial nephrons with solutions containing the Na+-H+ exchange inhibitor, ethyl isopropyl amiloride (EIPA). 2. Using a standard perfusate, no statistically significant effect of EIPA on net sodium reabsorption (JNa) was detected. However, when sodium reabsorption in the pars recta of the proximal tubule was minimized by using a low-sodium perfusate, EIPA reduced JNa from 828 +/- 41 to 726 +/- 37 pmol min-1 (P < 0.05), indicating that apical Na+-H+ exchange can make a small contribution to net sodium reabsorption in the TALH in vivo. This contribution appears to be dependent on the bicarbonate load, since an increase in the latter led to an enhancement of EIPA-sensitive sodium transport. 3. Addition of the Na+-K+-2Cl- cotransport inhibitor, bumetanide, to the low-sodium perfusate reduced baseline JNa to 86 +/- 27 pmol min-1. In this setting, EIPA reduced JNa further, to -24 +/- 18 pmol min-1 (P < 0.05), an effect similar to that seen in the absence of bumetanide. This finding argues against previous suggestions (based on in vitro evidence) that inhibition of the Na+-K+-2Cl- cotransporter leads to an increase in apical Na+-H+ exchange in the TALH.

The renal effects of glibenclamide were investigated using free flow micropuncture techniques in anesthetized Sprague-Dawley rats. Intravenous infusion of the drug (3 mg/hr) evoked a natriuresis and diuresis; potassium excretion remained unchanged. Fractional reabsorption in the proximal convoluted tubule in glibenclamide-infused rats did not differ significantly from that in control animals, although the late proximal tubular fluid to plasma concentration ratio for potassium was reduced. Fractional sodium delivery to the early distal tubule was elevated, while the fractional deliveries of water and potassium to this nephron site were unaffected. We conclude that glibenclamide impairs sodium reabsorption in one or more of the nephron segments that comprise the loop of Henle. These results are consistent with the hypothesis that the natriuresis resulting from glibenclamide administration is a consequence of blockade of potassium channels in the apical membrane of the thick ascending limb of Henle's loop. The data suggest that glibenclamide may additionally inhibit a small secretory potassium flux in the proximal tubule.

1. In order to identify the tubular sites responsible for the reduced fractional excretion of lithium (FELi) during potassium depletion, free-flow micropuncture was performed in anaesthetized rats that had been fed a low potassium (low-K+) diet or a control diet for 5-6 days. FELi in low-K+ rats was 0.09 +/- 0.02, compared with 0.25 +/- 0.01 in control animals. 2. Fractional water reabsorption in proximal convoluted tubules was enhanced in potassium-depleted rats. However, fractional lithium reabsorption was not. Consequently, the tubular fluid-to-plasma lithium concentration ratio at the late proximal convoluted tubule was raised in the low-K+ animals (1.50 +/- 0.03 vs. 1.18 +/- 0.02; P < 0.001). 3. Fractional lithium delivery to the early distal tubule in low-K+ rats (0.31 +/- 0.01) was similar to that in control animals (0.30 +/- 0.02). However, whereas in control rats there was no significant difference between early and late distal tubular deliveries of lithium, late distal fractional lithium delivery in the low-K+ group was reduced markedly (to 0.10 +/- 0.01). 4. Treatment of potassium-depleted rats with amiloride had no effect on lithium reabsorption in the proximal convoluted tubule or loop of Henle. However, fractional lithium delivery to the end of the distal tubule was increased slightly (to 0.15 +/- 0.02; P < 0.05) and FELi was increased substantially (to 0.22 +/- 0.01; P < 0.001). 5. It is concluded that two factors contribute to the reduced FELi seen in potassium-depleted rats: lithium reabsorption in the superficial distal tubules and amiloride-sensitive lithium reabsorption in the collecting ducts. The data also suggest heterogeneity with respect to lithium handling between superficial and deep nephrons during potassium depletion.

The influence of volume status on the effect of physiological doses of vasopressin on sodium excretion was assessed in anaesthetized Brattleboro rats. Following a 1 h control period, animals were divided into four groups. Group 1 (control) rats were kept in water balance throughout (by adjustment of the rate of i.v. glucose infusion) and received no vasopressin. In group 2 rats, vasopressin (20 microU/min) was infused i.v. for 2 h, then withdrawn during the following 2 h; the vasopressin-induced antidiuresis and subsequent return to water diuresis were matched by appropriate changes in the i.v. infusion, thus maintaining water balance. In this group, vasopressin had no effect on sodium excretion. Group 3 rats received the same dose of vasopressin, but the infusion rate of the glucose solution was not reduced; consequently these rats became water-loaded. In this group, sodium excretion increased significantly during vasopressin infusion, and rapidly returned to baseline values when the vasopressin was discontinued. Group 4 rats were treated in the same way as group 3 animals except that the vasopressin infusion was maintained (but without additional water loading) for a further 2 h; this did not prevent the fall in sodium excretion during the final 2 h of the experiment. We conclude that the natriuretic effect of physiological levels of vasopressin reported elsewhere may be dependent on an accompanying acute volume expansion during infusion of the hormone.

1. The nephron sites involved in the blunted natriuretic response to frusemide during sodium depletion were investigated using micropuncture techniques in anaesthetized rats. 2. Glomerular filtration rate was lower, and fractional sodium reabsorption in the proximal convoluted tubule higher, in sodium-depleted than in sodium-replete rats. Consequently, sodium delivery to the loop of Henle was reduced (by approximately 35%) in the sodium-depleted animals. Intravenous frusemide (2.5 mg h-1 kg-1; urinary water and electrolyte losses replaced) had no effect on glomerular filtration rate or proximal tubular sodium reabsorption in either group. 3. The inhibitory effect of intravenous frusemide on fractional sodium reabsorption in the nephron segments constituting the loop of Henle (measured by free-flow micropuncture) was attenuated during sodium depletion. However, when loops of Henle were microperfused at identical rates with artificial late proximal tubular fluid, no difference in the responses of sodium-depleted and sodium-replete rats to intraluminal frusemide (10(-5) mol/l) could be detected. 4. In sodium-replete animals, the increased load of sodium delivered from the loop of Henle during frusemide administration resulted in a lowering of fractional sodium reabsorption in the distal tubule. In contrast, in sodium-depleted rats given frusemide, fractional distal sodium reabsorption tended to increase, so that values in the two groups of frusemide-treated animals were markedly different (0.30 +/- 0.04 versus 0.51 +/- 0.03). 5. It is concluded that the blunted natriuretic response to frusemide during sodium depletion results from at least three factors: a reduced sodium delivery to the loop of Henle; a reduced inhibitory effect of frusemide on fractional sodium reabsorption in the loop of Henle, which may be a consequence of the reduced sodium load; and enhanced fractional reabsorption of sodium in the distal tubule, which partially buffers the diuretic-induced increase in sodium delivery from the loop.

Micropuncture techniques were used to investigate the nephron site(s) responsible for the vasopressin-induced reductions in lithium clearance and fractional lithium excretion (FELi) in anesthetized Brattleboro rats lacking endogenous vasopressin. In rats treated intravenously with the vasopressin analogue 1-desamino-8-D-arginine vasopressin (DDAVP; 40 pg/min), FELi was significantly lower than in untreated animals (0.23 +/- 0.01 vs. 0.28 +/- 0.02, P < 0.05). Free-flow micropuncture showed that fractional lithium delivery (FDLi) to late proximal convolutions was identical in the two groups, whereas at the early distal tubule both FDLi (0.28 +/- 0.02 vs. 0.33 +/- 0.01, P < 0.05) and the tubular fluid-to-plasma lithium concentration ratio (1.18 +/- 0.04 vs. 1.36 +/- 0.06, P < 0.05) were lower in the DDAVP-treated group. No differences between the groups with respect to lithium handling beyond the early distal tubule were observed. In rats subjected to in vivo microperfusion of loops of Henle, intravenous infusion of DDAVP (40 pg/min) increased fractional lithium reabsorption in the loop from 0.56 +/- 0.03 to 0.66 +/- 0.04 (P < 0.05) and from 0.39 +/- 0.02 to 0.45 +/- 0.02 (P < 0.05) at perfusion rates of 10 and 15 nl/min, respectively. We conclude that DDAVP stimulates lithium reabsorption in the loop of Henle and suggest that this results from an increased transepithelial potential difference in the thick ascending limb.

The possible role of the proximal tubule in the natriuresis which follows the administration of small doses of lithium, as used in lithium clearance studies, was investigated in 12 healthy males on a fixed sodium intake. Subjects were given placebo tablets, or 100 mg or 600 mg of lithium carbonate; renal function was assessed 3-6 h later. The 600-mg dose of lithium carbonate caused a 50-60% increase in sodium excretion, whereas the 100-mg dose was without effect. Creatinine clearance, used as an index of glomerular filtration rate, was unaffected by either dose. Three indices of end-proximal fluid delivery were used simultaneously: urine flow rate during suppression of vasopressin secretion (Vmax), phosphate clearance and lithium clearance (the latter only on the days on which lithium was administered). No effect of either dose of lithium on Vmax or phosphate clearance was evident; nor was there a difference between values for lithium clearance following the two doses. We conclude that administration of the standard 600-mg test dose of lithium carbonate does not affect proximal tubular function.

1. The marked reduction in fractional lithium excretion (FELi) which accompanies chronic sodium depletion was investigated using free-flow micropuncture in anaesthetized rats which had been maintained in a sodium-depleted state for 8-10 days. 2. Compared with previous values in sodium-replete rats, sodium depletion was associated with small reductions in total and superficial nephron glomerular filtration rate and enhanced fractional reabsorption of water, sodium and lithium in the proximal convoluted tubule. 3. In untreated (sodium-depleted) rats, fractional deliveries of lithium (FDLi) to the late proximal convoluted tubule, early distal tubule and late distal tubule were 0.41 +/- 0.02, 0.20 +/- 0.01 and 0.18 +/- 0.02 (means +/- S.E.M.), respectively. Fractional lithium excretion (0.08 +/- 0.01) was significantly lower than late distal FDLi (P < 0.001). 4. Treatment with amiloride did not affect segmental lithium handling up to the late distal tubule. Frusemide had no effect on lithium reabsorption in the proximal convoluted tubule, but early distal FDLi (0.30 +/- 0.01) was raised compared with the untreated group (P < 0.001). Both diuretics eliminated the difference between late distal FDLi and FELi, respective values being 0.17 +/- 0.02 and 0.15 +/- 0.01 (amiloride-treated rats) and 0.31 +/- 0.02 and 0.34 +/- 0.02 (frusemide-treated rats). 5. These data indicate that part of the reduction in FELi in chronic sodium depletion is due to enhanced fractional fluid (and lithium) reabsorption in the proximal convoluted tubule. In addition, however, they provide direct evidence for amiloride-sensitive lithium reabsorption in the collecting ducts.(ABSTRACT TRUNCATED AT 250 WORDS)

We present a method based on dynamical systems theory which can be used to filter time series in a way which is superior to classical Fourier decomposition. This method is applied to three data-sets, taken from respiratory measurements of two children in quiet and REM sleep. Our purpose is to filter the several different oscillatory mechanisms which operate, in order to provide clearer signals on which further analysis and diagnosis can be based.

The contribution of the loop segments to lithium reabsorption in sodium-replete, anesthetized Sprague-Dawley rats was examined by perfusing superficial loops of Henle between late proximal convolutions and early distal tubules. Preliminary experiments in which lithium was initially present only inside or outside the perfused loop confirmed substantial permeability of one or more of the loop segments to lithium. In subsequent experiments, in which lithium was infused intravenously and included in the perfusate so that the perfusate-to-plasma lithium concentration ratio was close to that found in late proximal tubules during lithium clearance studies, lithium reabsorption was inversely related to the perfusion rate: values for fractional lithium reabsorption (FRLi) at perfusion rates of 10, 20, and 30 nl/min were 58 +/- 3, 17 +/- 2, and 2 +/- 2%, respectively. Bumetanide (10(-6) M) markedly inhibited FRLi but also reduced water reabsorption, suggesting an effect on the pars recta at this dose; 10(-7) M bumetanide, which was without effect on water reabsorption, had only a small effect on FRLi at a perfusion rate of 10 nl/min but reduced FRLi by approximately 70% at 20 nl/min. We argue that the remarkable flow dependency of lithium reabsorption, together with its bumetanide sensitivity, provides evidence for significant voltage-driven lithium reabsorption in the thick ascending limb of Henle.

Although the renal clearance of lithium is widely used as an index of sodium and water delivery to the end of the proximal tubule, micropuncture studies of superficial nephrons suggest that lithium may be reabsorbed additionally in the loop of Henle. In order to examine the possibility of lithium transport in the thin loop segments of deep nephrons, we conducted a computer simulation study using a modification of the mathematical model reported previously. The data for the model were obtained from measurements of osmolality and electrolyte concentrations in systemic plasma and renal papillary interstitial fluid of control and furosemide-treated rats. Papillary interstitium/plasma Li+ concentration ratios were 3.23 and 1.48 in the control and the furosemide group, respectively. Assuming that solute concentration in the renal medulla increases as an exponential function, and applying phenomenological coefficients obtained from hamsters, the transport profiles of Li+ along the thin loop segments were calculated to be very similar to those of Na+. In the control group, about 82% of delivered Li+ was reabsorbed along the entire thin loop segments, with all segments contributing equally. This value may represent the highest possible capacity of the thin loop segments. In the furosemide group, Li+ reabsorption in the thin loop was reduced to 31% of delivered Li+. From these analyses, we conclude that an appreciable amount of lithium may be reabsorbed in the thin loop segments of long-looped nephrons by passive mechanisms. Furosemide inhibits Li+ reabsorption by dissipating the osmotic concentration gradient in the renal medulla.(ABSTRACT TRUNCATED AT 250 WORDS)

The validity of the lithium clearance technique as a measure of end-proximal fluid delivery was assessed using micropuncture in sodium-replete, Inactin-anesthetized Sprague-Dawley rats. Three groups of animals were used: controls, amiloride treated, and furosemide treated. Diuretic-induced salt and water losses were replaced. Fractional lithium excretion (FELi) was 0.23 +/- 0.01, 0.24 +/- 0.02, and 0.40 +/- 0.03 in the control, amiloride, and furosemide groups, respectively. In each group, the tubular fluid-to-plasma lithium concentration ratio at the end of the proximal convoluted tubule (PCT) was significantly greater than unity (control, 1.16 +/- 0.03; amiloride, 1.16 +/- 0.02; furosemide, 1.17 +/- 0.02). In the control group, fractional lithium delivery (FDLi) at the late PCT was 0.50 +/- 0.02, while FDLi at the early distal tubule was 0.25 +/- 0.01; the latter did not differ significantly from FDLi at the late distal tubule or from FELi. Values in amiloride-treated rats were almost identical. Furosemide had no effect on FDLi at the late PCT, but raised that at the early distal tubule to 0.37 +/- 0.03. We conclude that 1) lithium reabsorption in the PCT lags slightly behind that of water, 2) substantial furosemide-sensitive lithium reabsorption occurs beyond the PCT, and 3) no significant lithium reabsorption occurs in nephron segments beyond the loop. These findings call into question the use of lithium clearance as a quantitative measure of end-proximal fluid delivery in sodium-replete animals.

Free-flow micropuncture was used to assess proximal and distal tubular function in rats immediately (2 to 5 hours), five days and 30 days after uninephrectomy (UN); results were compared with those in sham-operated littermates. Excretion rates of water, sodium and potassium were approximately doubled in the remaining kidney of UN rats. Two to five hours after UN there were small increases in glomerular filtration rate (GFR) and single nephron GFR which at this stage were not accompanied by an increase in absolute proximal reabsorption; that is, fractional proximal reabsorption fell. After five days, GFR and single nephron GFR had increased further; at this stage absolute proximal reabsorption was also significantly elevated. After 30 days, kidney weight, GFR, single nephron GFR and absolute proximal reabsorption had all increased by approximately 40%, and glomerulotubular balance in the proximal tubule had been fully restored. Data derived from distal tubular collections indicated that at every stage after UN: (a) fluid delivery to both early and late distal puncture sites was increased; (b) in contrast, there was no increase in sodium delivery to the late distal tubule, suggesting that the natriuresis resulted from reduced sodium reabsorption beyond the distal tubule and/or increased delivery of sodium from deep nephrons; and (c) there was a marked increase in potassium secretion into the accessible portion of the distal tubule which was more than adequate to explain the observed kaliuresis.

1. In order to investigate the lithiuretic effect of frusemide, simultaneous measurements of fractional lithium excretion (FELi) and fractional fluid delivery to the end of the proximal convoluted tubules were made in Inactin-anaesthetized rats, first during a control period, then during intravenous infusion of frusemide at either 0.8 or 8.0 mg kg-1 h-1. Fluid balance was maintained by infusion of NaCl-KCl solution adjusted to match urinary excretion rates; measurements were made after urine flow had stabilized. 2. In time-control animals, which did not receive frusemide, no significant changes were observed in either FELi or fractional fluid delivery to the end of the proximal convoluted tubules (determined as the plasma/tubular fluid inulin concentration ratio, P/TFIn). 3. In animals given the high dose of frusemide, FELi increased from 0.22 +/- 0.02 (mean +/- S.E.M.) during the control period to 0.45 +/- 0.03 during frusemide infusion (P less than 0.001); this was accompanied by a modest increase in P/TFIn, from 0.43 +/- 0.02 to 0.51 +/- 0.02 (P less than 0.01). 4. In animals given the lower dose of frusemide, FELi increased from 0.21 +/- 0.01 to 0.37 +/- 0.01 (P less than 0.001). In this group, however, there was no discernible change in P/TFIn (0.43 +/- 0.02 vs. 0.44 +/- 0.01, not significant). 5. These results suggest that under control conditions a significant component of lithium reabsorption may occur beyond the proximal tubule, most likely in the loop of Henle.

Renal function was examined in unrestrained conscious rats maintained on either a control diet or a low-potassium diet, then re-examined in the same animals after thiobutabarbital (Inactin) anaesthesia and preparation for micropuncture studies. In conscious rats, insulin clearance (CIn) was not significantly different in the two groups (control 1012 +/- 43, low-K 904 +/- 58 microliters/min per 100g body wt; mean +/- SE), but lithium clearance (CLi; used as an estimate of end-proximal fluid delivery) and fractional lithium excretion (FELi) were substantially reduced in the low-K group (CLi: 246 +/- 11 vs 126 +/- 8 microliters/min per 100g body wt, P less than 0.001; FELi: 0.245 +/- 0.009 vs 0.143 +/- 0.008, P less than 0.001). Following anaesthesia and preparation for micropuncture, there were significant reductions in urine flow rate and sodium excretion in the control group, but not in the low-K rats. Potassium excretion increased in both groups, but values in the potassium-depleted animals remained extremely low. In neither group of rats was preparation for micropuncture associated with significant changes in CIn, CLi or FELi. Thus, differences in tubular function between control and potassium-depleted rats were still apparent. The results suggest that preparation for micropuncture disturbs the function of the distal nephron, but that rates of glomerular filtration and proximal tubular reabsorption remain similar to values in conscious animals.

Hydrochlorothiazide was administered at two doses to Long-Evans rats for 7-10 days. Both doses resulted in an initial natriuresis and diuresis. After 1 day of treatment the natriuresis abated, but the diuresis persisted. The mechanisms responsible for these chronic effects were investigated by performing clearance and micropuncture studies on all animals; collections were made from late proximal tubules and from early and late regions of distal tubules. Values for total glomerular filtration rate and single-nephron filtration rate in thiazide-treated rats were not significantly different from those in control animals. The delivery of sodium to the end of the proximal convoluted tubule was considerably reduced in each group of thiazide-treated rats. Although sodium delivery to the early distal tubule was also significantly lower than in control animals, the difference had disappeared by the late distal tubule. It is concluded that the return of sodium excretion to control levels during chronic hydrochlorothiazide administration is a consequence of increased fractional reabsorption by the proximal tubules, secondary to a thiazide-induced sodium depletion. This results in less sodium being delivered to the nephron site at which thiazides exert their major inhibitory effect. Fluid delivery to the end of the proximal convoluted tubule and to the early distal tubule was significantly reduced in thiazide-treated rats; in animals given the higher dose of diuretic it was also significantly reduced at the end of the distal tubule. Nevertheless, in both thiazide-treated groups urine flow rate was elevated, suggesting that reabsorption of water from the collecting ducts is reduced during chronic thiazide administration.

To test whether factor VII activation correlated with the generation of thrombin activity when plasma was exposed to a glass surface and reduced temperature, an association was sought between the changes in factor VII clotting activity (VIIc) and fibrinopeptide A concentration (an index of thrombin activity) in platelet-poor citrated plasma from 42 healthy adults. The Spearman rank correlation (rs) between responses was 0.82 (P less than 0.001). The VIIc assay response to surface/cold exposure was unaffected when thrombin was suppressed by hirudin. An assay for factor VII activity based upon its activation of tritiated factor X revealed an association between the increase in fibrinopeptide A concentration and reduction in functional factor VII concentration during activation of a subset of 22 plasma samples (rs = -0.62; P = 0.003). This loss of functional factor VII was probably due to conversion of active factor VII to its non-functional end-product by factor Xa. The results suggest that VIIc is an index of flux within the coagulation system and support the hypothesis that a high VIIc is an indicator of a hypercoagulable state.

Sectioning of the two major outflows from the superior cervical ganglia in two week mice results in a marked drop in the number of neurons within one week of operation and a smaller drop over the following two weeks. In animals receiving daily injections of nerve growth factor (NGF), the effect of axotomy is modified. One week after axotomy, the number of neurons in the axotomized ganglia is approximately the same in NGF treated animals as in the control, sham operated ganglia. Over the next two weeks, however, the cell death that results from axotomy is no longer prevented by treatment with NGF. The normal, hyperplastic response to NGF appears to occur independently of the cell reaction caused by axotomy.

Experiments are described that confirm the presence of gamma-globulin in standard preparations of mouse nerve growth factor (7-S complex and beta subunit) and show that antibodies to this protein are present in horse antisera to the growth factor. These antibodies may be partially removed by adsorption with soluble antigen and totally removed by affinity chromatography on columns of insolubilised antigen. These procedures do not affect the potency of the antiserum in vitro or in vivo. Contaminating globulin may be removed from samples of the isolated beta subunit by gel filtration to give an immunochemically pure preparation which will permit more meaningful studies on nerve growth factor and its antiserum.