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Sperm competition is an important fitness component in many animal groups. Drosophila melanogaster males exhibit substantial genetic variation for sperm competitive ability and females show considerable genetic variation for first versus second male sperm use. Currently, the forces responsible for maintaining genetic variation in sperm competition related phenotypes are receiving much attention. While several candidate genes contributing to the variation seen in male competitive ability are known, genes involved in female sperm use remain largely undiscovered. Without knowledge of the underlying genes, it will be difficult to distinguish between different models of sexual selection such as cryptic female choice and sexual conflict. We used quantitative trait locus (QTL) mapping to identify regions of the genome contributing to female propensity to use first or second male sperm, female refractoriness to re-mating, and early-life fertility. The most well supported markers influencing the phenotypes include 33F/34A (P2), 57B (refractoriness) and 23F/24A (fertility). Between 10% and 15% of the phenotypic variance observed in these recombinant inbred lines was explained by these individual QTLs. More detailed investigation of the regions detected in this experiment may lead to the identification of genes responsible for the QTLs identified here.

In this study, we examined the long-term development of the overall structural morphology and community composition of a biofilm formed in a model drinking water distribution system with biofilms from 1 day to 3 years old. Visualization and subsequent quantification showed how the biofilm developed from an initial attachment of single cells through the formation of independent microcolonies reaching 30 μm in thickness to a final looser structure with an average thickness of 14.1 μm and covering 76% of the surface. An analysis of the community composition by use of terminal restriction fragment length polymorphisms showed a correlation between the population profile and the age of the sample, separating the samples into young (1 to 94 days) and old (571 to 1,093 days) biofilms, whereas a limited spatial variation in the biofilm was observed. A more detailed analysis with cloning and sequencing of 16S rRNA fragments illustrated how a wide variety of cells recruited from the bulk water initially attached and resulted in a species richness comparable to that in the water phase. This step was followed by the growth of a bacterium which was related to Nitrospira, which constituted 78% of the community by day 256, and which resulted in a reduction in the overall richness. After 500 days, the biofilm entered a stable population state, which was characterized by a greater richness of bacteria, includingNitrospira, Planctomyces, Acidobacterium, and Pseudomonas. The combination of different techniques illustrated the successional formation of a biofilm during a 3-year period in this model drinking water distribution system.

Agrin is an extracellular matrix protein involved in the formation of the postsynaptic apparatus of the neuromuscular junction. In addition to spinal motor neurons, agrin is expressed by many other neuronal populations throughout the nervous system. Agrin's role outside of the neuromuscular junction, however, is poorly understood. Here we use the polymerase chain reaction to examine expression and alternative splicing of agrin in mouse somatosensory cortex during early postnatal development in vivo and in dissociated cell culture. Peak levels of agrin gene expression in developing cortex coincide with ingrowth of thalamic afferent fibres and formation of thalamocortical and intracortical synapses. Analysis of alternatively spliced agrin messenger RNA variants shows that greater than 95% of all agrin in developing and adult somatosensory cortex originates in neurons, including isoforms that have little or no activity in acetylcholine receptor aggregation assays. The levels of expression of "active" and "inactive" isoforms, however, are regulated during development. A similar pattern of agrin gene expression is also observed during a period when new synapses are being formed between somatosensory neurons growing in dissociated cell culture. Changes in agrin gene expression, observed both in vivo and in vitro, are consistent with a role for agrin in synapse formation in the central nervous system.

HBV A1762T/G1764A double nucleotide substitution (also called TA mutation) is relatively common in liver diseases. Hepatocyte nuclear factor 4 (HNF4) is one of liver-enriched transcription factors, and TA mutation is located in the binding region of HNF4 and HBV and plays an important regulatory role in HBV gene transcription and replication. Several studies have pointed out that TA mutation may aggravate liver diseases after HBV infection and increase the risk of chronic liver failure and liver cancer; however, it is still unclear how TA mutation can aggravate liver disease after HBV infection, and more studies are needed for clarification in the future. This article reviews the association between HBV A1762T/G1764A double nucleotide substitution and liver diseases. [ABSTRACT FROM AUTHOR]

El propósito de esta investigación persigue evaluar por medio de la disección de cadáveres, las variantes arteriales de las ramas de la aorta descendente abdominal. El trabajo prospectivo, se realizó en el laboratorio de anatomía de la facultad. La accesibilidad proporcionada por la disección, posibilitó el alcance del conocimiento práctico y teórico de una gama de ramas aberrantes, más frecuentes en riñón e hígado. Concluimos que los hallazgos, servirán para mejorar la formación de los estudiantes y, de los futuros especialistas en cirugía vascular. Los hallazgos encontrados deben tenerse en cuenta para futuras investigaciones y, por ahora integrarlos a la cátedra de anatomía.The aim of our anatomic cadaver dissection study was to evaluate the variants of the arterial branches of the descending abdominal aorta. It is a prospective study performed at the school of medicine´s anatomy laboratory. The dissection approach provides theoretical and practical knowledge on a wide range of aberrant anatomic variants, which appear most frequent in the liver and kidney. Our findings contribute to the improvement of the teaching of medical students and of future general and vascular surgeons. These findings should be considered in future anatomic studies, and as of now be incorporated in the anatomy course.

En uno de los cadáveres disecados durante el primer semestre de 2006 en el anfiteatro del Departamento de Morfología de la Universidad del Valle en Cali (Colombia), se encontró una variación anatómica poco descrita en la literatura científica mundial. Se trata de la desembocadura aberrante del conducto torácico. Normalmente, este conducto linfático asciende en el tórax y se desvía hacia el lado izquierdo del cuello para desembocar en el confluente venoso yúgulo-subclavio izquierdo. En este cadáver masculino de etnia mestiza, el conducto se desvió hacia el lado derecho del cuello y desembocaba en la vena yugular interna derecha. El trabajo describe el origen embrionario del conducto torácico y ofrece una posible explicación para la anomalía encontrada.

Introducción. Giardia intestinalis es un parásito protozoario que causa la infección gastrointestinal conocida como giardiosis, la cual se transmite principalmente a través de la contaminación fecal-oral. Estudios genéticos de aislamientos de Giardia cultivados axénicamente han identificado dos grupos genéticos principales distribuidos en el mundo. En el presente estudio se analizaron 24 cepas nativas del parásito por medio de la técnica RAPD (ADN polimórfico amplificado aleatoriamente). Objetivo. Determinar el nivel de polimorfismo y la complejidad de las cepas circulantes en áreas específicas de Colombia. Materiales y métodos. Se utilizó el método RAPD debido a que permite obtener un análisis rápido, sencillo y confiable, que no requiere conocimiento previo de la genética del parásito. El análisis RAPD se realizó en cultivos continuos de aislamientos nativos recolectados en Colombia entre 1997 y 2001. Se evaluaron separadamente diversos iniciadores con el objeto de incrementar la capacidad de discriminación del método. Resultados. De las 24 cepas incluidas en el estudio, 22 se agruparon en clusters independientes. Las cepas que provenían de la misma zona geográfica, y que fueron recolectadas aproximadamente al mismo tiempo, generalmente presentaron patrones RAPD sumamente similares pero distinguibles entre sí. Se analizaron así mismo los clones aislados de una misma cepa y fue posible diferenciarlos molecularmente. Conclusión. Los resultados de las cepas estudiadas indicaron que éstas corresponden al genotipo A, y sugieren que consisten en una mezcla heterogénea de poblaciones strechamente relacionadas.

Copy number variations (CNVs) can serve as significant disease susceptibility markers in many disorders. The availability of a large number of chromosomal copy number profiles in both malignant and normal tissues in cancer patients presents an opportunity to characterize not only somatic alterations but also germline CNVs, which may confer increased risk for cancer. The determination methods of CNVs mainly includes the gene chip technology, high throughput sequencing, real-time quantitative PCR and FISH, etc. The most important method is the gene chip technology. At present the study of CNVs in gynecologic malignant tumor is relatively limited. The article focus on researching that CNVs is closely related to some tumor disease of gynaecology, such as ovarian cancer, cervical cancer, endometrial cancer. Comprehensive mining of copy number variations and bioinformatics analysis, understanding of the progress of the gynecological malignant tumors, degradation mechanism, and provide new ideas and methods for tumor prevention, diagnosis and treatment. [ABSTRACT FROM AUTHOR]

The duplex collecting system, a malformation of duplex renal pelvis and ureter, is a disease of congenital anomalies of the kidney and urinary tract (CAKUT). The morbidity of this disease is about 0.07%. There is a broad spectrum of forms, or it may accompany with many anomalies of other organs, such as hypospadia, cryptorchidism, vas deferens absence, and hypoplasia of testis and penis. Some of patients may feel no discomfort all through their life, meanwhile others may get irreversible impairment of renal function due to secondary hydronephrosis and calculi. The family history of the duplex collecting system is the most frequent within all CAKUT. Owing to its incomplete penetrance and the undefined pathogenesis, the genetic research of this disease is a challenge. It was found that this disease is related to gene mutations, copy number variants, and interaction between heredity and environment and some other factors. Some pathogenic factors found in human have also been confirmed in animal models, while others could be found either in animal models or human. We herein reviewed the research progress of the pathogenic factors of duplex collecting system. [ABSTRACT FROM AUTHOR]

Introducción. Plasmodium falciparum es un parásito altamente polimórfico, lo cual le permite evadir la respuesta inmune del hospedero, diseminar la resistencia a medicamentos y favorecer la transmisión. Objetivos. Analizar la diversidad genética de las poblaciones de P. falciparum en muestras de cuatro zonas endémicas de malaria en Colombia. Materiales y métodos. Se incluyeron muestras de sangre recolectadas en papel de filtro de 123 pacientes con malaria no complicada por P. falciparum durante los años 2002 a 2004; la genotipificación se realizó mediante reacción en cadena de la polimerasa con iniciadores específicos para los marcadores moleculares de la región polimórfica del bloque 2 del gen msp1 y del codón 108 de dhfr. Resultados. En el bloque 2 del gen msp1 se detectó MAD20 en 95,9% (118/123; IC 95%: 90,8 a 98,7), K1 en 6,5% (8/123; IC 95%: 2,8 a 12,4) y RO33 en 2,4% (3/123; IC 95%: 0,5 a 6,9) de las muestras. Para el gen dhfr, el alotipo mutante N108 se detectó en todas las muestras analizadas y el alotipo T108 en 3,2% (4/123; IC 95%: 0,9 a 8,1); el alotipo silvestre S108 se encontró en 34,1% (42/123; IC 95%: 25,8 a 43,2). Al combinar los resultados de ambos genes, el 61,8% (76/123; IC 95%: 52,6 a 70,4) de las muestras correspondieron a infecciones simples y el 38,2% (47/123; IC 95%: 29,6 a 47,4) a infecciones mixtas, siendo MAD20/N108-S108 la combinación más frecuente entre estas últimas (30,1%). Conclusiones. Las infecciones simples, o sea, la presencia de un solo alelo en cada uno de los genes, predominaron en las muestras estudiadas; las poblaciones de parásitos analizadas fueron muy homogéneas en su composición genética.

Objective To amplify and determine the hepatitis B virus (HBV) reverse transcrptase (RT) sequences of 153 Chinese patients with chronic HBV infection and investigate the drag resistance mutations related to nucleos(t)ide analogues, and to analyze if there are drug resistance mutations which might lead to tenofovir resistance. Methods A total of 153 patients with chronic HBV infection were divided into two groups : 78 HBV carriers who had never used nucleos(t)ide analoges (NAs) and 75 patents with chronic hepatitis B who had been treated with NAs. Their serum samples were used for HBV DNA extraction and RT gene amplification by PCR, and the RT sequences were analyzed to identify the known drug resistance mutations related to NAs and detect the drug resistance mutations related to tenofovir. The obtained data were statistically analyzed using SPSS 19.0; the Student 'st test was used for normally distributed data, and the Wilcoxon' s rank sum test for non - normally distributed data. Results Drug resistance mutations related to NAs were detected in 7 cases (8.97% ) of the untreated group, but there was no drug resistance mu-tation related to tenofovir. Drug resistance mutations were detected in 16 cases (21. 33% ) of the treated group, with rtA181T + rtN236T mutations in one case, which might be related to tenofovir resistance. Conclusion The drug resistance mutation detection rate in untreated group was 8. 97%. The drug resiitance mutation detection rate was not significantly correlated with HBV genotype and patient' s sex and age in either group. The rtA181T + rtN236T mutations were detected in only one case of the tteated group, which indicates a very low rate of pre - existence of tenofovir - related drug resistance mutations in Chinese patients with chronic HBV infection. [ABSTRACT FROM AUTHOR]

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Inosine 5′-monophosphate dehydrogenase 2 is required for purine synthesis in activated lymphocytes. Variants in the IMPDH2 gene may account for the large inter-individual variability in baseline enzyme activity, immunosuppressive efficacy and side effects in transplant recipients receiving mycophenolic acid. Therefore, the objective of this study was to identify and functionally characterize IMPDH2 variants.DNA samples from 152 solid organ transplant patients were screened at exons and exon/intron junctions of the IMPDH2 genes by PCR amplification followed by bidirectional direct DNA sequencing. Genetic variant was constructed by site-directed mutagenesis and transformed to an inosine 5′-monophosphate dehydrogenase-deficient strain of Escherichia coli h712. Proteins were purified to homogeneity and the enzymatic activity was measured by reduced nicotinamide adenine dinucleotide production.Nine genetic variants were identified in the IMPDH2 gene, with frequencies of the rarer alleles ranging from 0.5 to 10.2%. A novel nonsynonymous variant L263F was identified, and the kinetic assay demonstrated that the inosine 5′-monophosphate dehydrogenase activity of L263F variant was decreased to 10% of the wild-type. The Ki for mycophenolic acid inhibition of the L263F variant was comparable with the wild-type, and the variant Km for inosine 5′-monophosphate and nicotinamide adenine dinucleotide did not change significantly.IMPDH2 has low genetic diversity, but the nonsynonymous variant L263F has a significant impact on inosine 5′-monophosphate dehydrogenase activity. This novel functional variant may be one of the factors contributing to the inter-individual difference of baseline inosine 5′-monophosphate dehydrogenase activity as well as drug efficacy and adverse events in transplant patients. [ABSTRACT FROM AUTHOR]

Abstract: Clinical gene sequencing is growing in importance and cost-effectiveness. In the past two years, the number of genes associated with disease has grown by roughly 25%. Knowledge of genetic variations will soon guide drug selection and dosages, predict risks from toxin exposures, and inform nutritional needs. Despite the significance of sequencing, methods for reporting results are problematic. Frequent use of paper and infrequent use of naming standards impede data exchange and make incorporation into the electronic medical record difficult. Reports often describe only variations found, rather than all data (all patient bases sequenced). Also, reports frequently do not describe reference data used to define variations. These practices create risks for loss of both data and information. Standardized electronic reporting of all data (all bases sequenced and all reference data) and electronic record systems capable of storing these results would both prevent data loss and simplify the preservation of information those data provide. [Copyright &y& Elsevier]

Aims: An association between paternal age and type 1 diabetes (IDDM) among their offspring was recently reported as well as transgenerational responses in humans. This paper aims to assess the association of markers for prenatal exposures with IDDM. Methods: We analysed data from two birth cohorts in Great Britain on 5214 cohort members from the National Child Development Study (NCDS) and 6068 members of the 1970 British Birth Cohort Study (BCS70) with full information on IDDM and explanatory variables using multivariate logistic regression. Results: IDDM prevalence was 0.7% (95% CI 0.5–1.0%; n=38) in the NCDS and 0.4% (95% CI 0.3–0.6%; n=27) in the BCS70 cohort. Paternal age was not associated with IDDM possibly due to lack of sample power. Unexpectedly, a lowered prevalence of IDDM was observed among offspring of smoking fathers in both cohorts, with a combined odds ratio of 0.44 (95% CI 0.25–0.75). This association could not be explained by maternal smoking prior to, during or after pregnancy, number of siblings, parental social class, maternal and paternal age, or cohort. Maternal smoking in pregnancy did not alter the IDDM prevalence among offspring. Conclusions: This unexpected finding may be explained by germ-line mutations or other mechanisms associated with paternal smoking. This phenomenon should be investigated and these results should not be used as a justification for smoking. Paternal exposures may be important in determining IDDM risk. [ABSTRACT FROM AUTHOR]

Abstract: In most of the Western world, age-related macular degeneration (AMD) remains the largest single cause of severe visual impairment, and its prevalence continues to increase. It is considered to be a complex disease, in which multiple genes and environment play a role in pathogenesis. Several environmental insults are implicated with smoking, serum cholesterol, hypertension, sunlight exposure, and many other factors being variously associated with disease pathogenesis. Until recently, there have been relatively few breakthroughs to further our understanding of the genetics of AMD, despite remarkable progress in molecular genetic techniques over the last 20 years, and the fact that many rare inherited macular diseases have had their causative genes mapped. Development of new tools such as high-density single-nucleotide polymorphism chips and microarrays have changed the face of genetic research, but have yet to directly translate into improved clinical outcomes in ophthalmology. However with the recent finding of the Tyr402His polymorphism in the complement factor H gene being implicated in AMD, we are about to witness a new wave of research in this disease. Not only does the identification of a biologically plausible gene identify a new pathway, but it also identifies new biological mechanisms for disease, avenues to pursue treatment, and a better understanding of how the environment interacts with the genetic background to create disease. This article aims to review the process of gene discovery in complex disease, why the search for genes remains difficult, how to translate laboratory findings to a clinical setting, and how these findings will impact on disease treatment and public health issues. [Copyright &y& Elsevier]

Context Early-onset antisocial behavior accompanied by attention-deficit/hyperactivity disorder is a clinically severe variant of antisocial behavior that is associated with a particularly poor outcome. Identifying early predictors is thus important. Genetic and prenatal environmental risk factors and prefrontal cortical function are thought to contribute. Recent evidence suggests that prefrontal cortical function is influenced by a valine/methionine variant in the catechol O-methyltransferase (COMT) gene. Objective To test the a priori hypothesis that this genetic variant predicts early-onset antisocial behavior in a high-risk sample and further examine the effects of birth weight, an environmentally influenced index of prenatal adversity previously linked to childhood disruptive behaviors and genotype × birth weight interaction. Design, Setting, and Participants A family-based genetic study was undertaken between 1997 and 2003. Participants were prospectively recruited from child and adolescent psychiatry and child health clinics in the United Kingdom and included 240 clinic children who met diagnostic criteria for attention-deficit/hyperactivity disorder or hyperkinetic disorder. Participants underwent comprehensive standardized assessments including measures of antisocial behavior and IQ. Main Outcome Measure DSM-IV symptoms of childhood-onset conduct disorder rated by trained interviewers using a standard diagnostic interview. Results The results show main effects of the COMT gene variant (P = .002), birth weight (P = .002), and a significant gene × environment (COMT × birth weight) interaction (P = .006). Conclusions Early-onset antisocial behavior in a high-risk clinical group is predicted by a specific COMT gene variant previously linked with prefrontal cortical function and birth weight, and those possessing the val/val genotype are more susceptible to the adverse effects of prenatal risk as indexed by lower birth weight. [ABSTRACT FROM AUTHOR]

Aedes aegypti is the responsible vector for transmission of dengue fever virus, and its geographical distribution has been widely broadened, mainly because of human intervention. Objectives: To analyze the mosquito genetic variability comparing the Second Internal Trascribed Spacer (ITS-2) from the ribosomal DNA (rDNA). Materials and Methods: Samples from seven Peruvian sites (Jaen, Tingo Maria, Iquitos, Lambayeque, Rimac district in Lima, Sullana, and Zarumilla) and one site from Ecuador (Huaquillas Province) were assessed. Variability analysis was determined using the SSCP (Single-Stranded Conformational Polymorphism) technique. Results: The study shows that there are genetic variability between the analyzed populations, mainly between the samples from the Peruvian northern and central coast (Zarumilla, Sullana, and Rímac) as well as in the Ecuador sample (Huaquillas) and the samples from the northeastern region in Peru (Tingo Maria, Iquitos, Jaen, and Lambayeque). Conclusions: Two genetic variants were determined for Aedes aegypti populations: Coastal and northeastern, which probably come from different lineages, and whose common ancestor became isolated because of the distance. It was observed that there is no relationship between genetic distances and geographical distances, indicating that the migration of the mosquito populations is a consequence of human intervention disseminating the vector and not because of active mosquito migration. We propose that there is a role for the Andes Mountains with respect to Aedes populations migration and separation. [ABSTRACT FROM AUTHOR]

The US measles epidemics of 1989-1991 included a series of outbreaks resulting from vaccine failure. A series of studies was launched aimed at elucidating the mechanisms of this vaccine failure. A meta-analysis of the literature examining epidemics in vaccinated populations was conducted, which showed that the secondary vaccine failure rate (development of the disease despite an initial or primary vaccine success) is no more than 0.2%. The overwhelming proportion of measles vaccine failure was due to primary vaccine failure (failure to ever generate antibody from antigenic stimulation). This comparison of two geographically distinct communities revealed that 10% of children previously vaccinated against measles lacked antibody on follow-up and that these vaccine failures clustered in families. A study of monozygotic and dizygotic twins revealed a high degree of heritability of measles vaccine antibody level. Subsequent studies found associations with both class I and class II alleles in these population-based studies. In the future, detection of the specific peptides that interact with human leukocyte antigen (HLA) molecules may serve as the basis for improved vaccines and address vaccine failure that results from coldchain problems, immaturity of the immune system, malnutrition and maternal immunity. [ABSTRACT FROM AUTHOR]

Population-based studies have used DNA typing of Mycobacterium tuberculosis organisms to estimate the extent of ongoing tuberculosis transmission in various communities and to characterize associated risk factors. The finding of matched DNA “fingerprints” among isolates from an immigrant subgroup may reflect transmission in the adopted country but could also reflect limited diversity among M. tuberculosis organisms within that immigrant community. The authors sought to determine which hypothesis is more likely to explain the high frequency of matched isolates among Haitian-born tuberculosis patients in Montreal, Quebec, Canada. The authors determined the number of different bacterial genotypes in this community as compared with other foreign-born tuberculosis patients and applied a recently described measure of genetic similarity between M. tuberculosis organisms (“genetic distance”). Among 76 Haitian-born tuberculosis patients diagnosed during 1996–1998, the authors identified 47 distinct genotypes on the basis of standard IS6110 DNA typing and categorical analysis. In genetic distance analysis, these 47 genotypes showed as great a genetic diversity as that observed among the 191 distinct genotypes identified in 216 other foreign-born tuberculosis patients. A mycobacterial “founder effect” is unlikely to account for the high proportion of shared isolates among Haitian-born Montrealers. Recent transmission remains the most likely explanation. [ABSTRACT FROM AUTHOR]

Mucopolysaccharidosis type IIID (MPS IIID; Sanfilippo syndrome type D; MIM 252940) is caused by deficiency of the activity of N-acetylglucosamine-6-sulfatase (GNS), which is normally required for degradation of heparan sulfate. The clinical features of MPS IIID include progressive neurodegeneration, with relatively mild somatic symptoms. Biochemical features include accumulation of heparan sulfate and N-acetylglucosamine-6-sulfate in the brain and viscera. To date, diagnosis required a specific lysosomal enzyme assay for GNS activity. From genomic DNA of a subject with MPS IIID, we amplified and sequenced the promoter and 14 exons of GNS. We found a homozygous nonsense mutation in exon 9 (1063C → T), which predicted premature termination of translation (R355X). We also identified two common synonymous coding single-nucleotide polymorphisms and genotyped these in samples from four ethnic groups. This first report of a mutation in GNS resulting in MPS IIID indicates the potential utility of molecular diagnosis for this rare condition. [Copyright &y& Elsevier]

Neutrophils and alveolar macrophages are essential defence mechanisms against bacterial infection of the lung. The purpose of this study was to evaluate the variability of a panel of neutrophil and alveolar macrophage function assays in swine, and to determine if the function of these leukocytes differed at various stages of production. Measured neutrophil functions included chemotaxis, phagocytosis, oxidative burst, and degranulation. Phagocytosis and oxidative burst were measured in alveolar macrophages isolated from bronchoalveolar lavage fluid (BALF). Both neutrophil and alveolar macrophage functions were highly variable from day-to-day and between pigs. Individual pigs did not have consistently high or low neutrophil and macrophage responses over time when compared to their cohorts. Older grower–finisher pigs had significantly greater neutrophil oxidative burst responses than younger suckling and weaner pigs (P<0.001). Similarly, alveolar macrophages from suckling and early weaner pigs less than 40 days of age had significantly lower oxidative burst responses than those from older pigs (P=0.02). Age-related variation in phagocytosis, chemotaxis, or granule secretion were not detected. These results establish baseline data for individual and age-related variation in swine leukocyte function, and form a basis for further evaluation of the contribution of non-infectious factors to development of the porcine respiratory disease complex. [Copyright &y& Elsevier]

In a previous cross-sectional study of twins, the authors found evidence of a substantial genetic influence on functional abilities among elderly women. It has been suggested that rate of change in functional abilities over time could underlie such findings and that rate-of-change phenotypes may have an even larger genetic component than “level” phenotypes (e.g., functional abilities per se). If so, rate-of-change phenotypes could be more powerful than level phenotypes in studies aimed at identifying specific polymorphisms of importance for aging. In 1995, the authors assessed a population-based sample of 2,401 Danish twins aged 75 years or more. The survivors were recontacted after 2 years and again after 4 years. Consistent mean-level declines, high within-person correlations over time, and substantial heritability in the female sample were observed for functional abilities. Nonetheless, structural-equation analyses revealed only a very modest and nonsignificant heritability for rate of change in functional abilities: 16% (95% confidence interval: 0, 35) for women and 9% (95% confidence interval: 0, 44) for men. This study had a large initial sample size, high participation rates, and a valid and reliable measure of rate of change in a phenotype that had previously shown substantial heritability in cross-sectional analyses in the same twin population. Still, the present study revealed only a modest and nonsignificant genetic influence on rate of change, which suggests that detection of polymorphisms influencing rate of change in functional abilities among the elderly may prove to be difficult. [ABSTRACT FROM PUBLISHER]

Lean mass and areal bone mineral density at the lumbar spine, femoral neck, and total forearm were measured in 215 volunteer female twin pairs (122 monozygotic, 93 dizygotic), aged 10–26 years, using dual energy X-ray absorptiometry. The study was conducted in Melbourne from 1990 to 1994. Under the classic twin model, there was evidence for a genetic component of variation in bone mineral density, adjusted for age or for age and lean mass, at all sites. Adjusting for lean mass almost halved the genetic variances in the adolescent years of peak growth, during which genetic variances peaked. Genetic variances were reduced in the late teenage years and increased in early adulthood. The latter may reflect gene-environment interactions or covariation. Importantly, there was evidence for environmental effects shared by twins on lumbar spine and femoral neck bone mineral density, even when adjusted for lean mass as well as age. These were greatest during the late teenage years, abated over the years when pairs started to live apart, and appear to be independent of lean mass during adolescence but not in early adulthood. In summary, the genetic and environmental etiology of bone mineral density is more complex than previously thought. [ABSTRACT FROM AUTHOR]

In Os/+ mice of the XVIII strain, nephron number was reduced by 80% and GFR by 50%. Plots of (U/P) against percentage filtered solute load excreted showed that the consequent osmotic diuresis per nephron was a sufficient explanation for the mild concentrating defect in XVIII Os/+ mice. This conclusion was confirmed by the fact that subtotal nephrectomy mimicked the effect of the Os gene in this strain. However the same experiments demonstrated that there was an additional qualitative impairment of the renal concentrating mechanism in mice of the DI strain having oligosyndactyly (DI Os/+). Observations on a genetically segregating backcross generation showed that a reduction in mean length of short loops of Henle, but not the absence of a pars recta of the proximal tubule, was probably responsible for the severe concentrating defect in DI Os/+ mice. The usefulness and specific limitations of genetic variation in physiological investigations are discussed. [ABSTRACT FROM AUTHOR]