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Biomedical subjects

A Robertson

Publications and source records attributed to A Robertson.

At least 91 records · Page 5Linked to original sources
PubMed1999

Effect of inbreeding avoidance on Hardy-Weinberg expectations: examples of neutral and selected loci.

Although all human populations avoid close inbreeding, the effect of inbreeding avoidance on genotype proportions has not been formally considered. This paper examines the expected proportions of genotype frequencies after adjusting the Hardy-Weinberg model for close inbreeding avoidance in an inbred population. This corrected model was used to evaluate genotype distributions for HLA haplotypes and haplotypes created from three microsatellite loci on human chromosome 13 in a sample of 315 married Hutterites. In this sample, there were five individuals who were homozygous for an HLA haplotype and 15 individuals who were homozygous for a chromosome 13 haplotype. The expected numbers of homozygotes were 21 for HLA and 26 for chromosome 13 haplotypes using a model adjusted for overall inbreeding (P = 0.00031 for HLA and P = 0.019 for chromosome 13) and 18 for HLA and 22 chromosome 13 haplotypes using a model adjusted for both overall inbreeding and close inbreeding avoidance (P = 0. 0016 for HLA and P = 0.099 for chromosome 13). The model that takes into account both overall inbreeding and inbreeding avoidance provided a better fit to the observed genotype distributions for chromosome 13 haplotypes (P = 0.099), suggesting that nonrandom aspects of Hutterite mating structure, other than inbreeding and inbreeding avoidance, have small effects on genotype distributions in the population. The fact that significant deficiencies of HLA homozygotes persist after taking into account inbreeding avoidance further suggests that factors related to the HLA haplotype per se influence the genotype proportions at HLA loci in the Hutterites.

Adult↗
PubMed1999

Clozapine as a drug of dependence.

RATIONALE: In schizophrenics, clozapine has been reported to induce various withdrawal signs and rapid onset relapse to psychosis on cessation of chronic treatment. OBJECTIVE: The study was designed to develop an animal model of one aspect of clozapine tolerance and withdrawal using core body temperature measures. METHODS: Two groups of 15 female Wistar rats were treated chronically (b.i.d.) with clozapine at 6 or 12 mg/kg per injection for 21 days prior to cessation of drug treatment, withdrawal being studied over 4 consecutive days. Body temperatures were assessed daily throughout the study. RESULTS: Acutely, clozapine induced dose-related hypothermia, to which complete tolerance developed in both groups, the development of tolerance being more rapid in the group treated with 6 mg/kg per injection of clozapine. During withdrawal only the group treated chronically with 12 mg/kg per injection of clozapine showed rapid onset significant hyperthermia. This dissipated progressively over days, and was completely absent after 4 days of withdrawal. CONCLUSIONS: Clozapine induced a clear somatic withdrawal sign after chronic treatment. It is suggested that, in future research in both humans and animals, it is important to attempt to differentiate between clozapine withdrawal and clozapine withdrawal-induced relapse to psychosis. It is also important to characterise the clozapine withdrawal syndrome fully in animals; to establish the neurochemical mechanisms involved in such withdrawal; and to determine which novel antipsychotics are most efficacious in inducing clozapine-like withdrawal effects, in suppressing clozapine withdrawal, and in preventing relapse to psychosis in patients being transferred from clozapine to novel atypical antipsychotic drugs.

Animals↗
PubMed1999

Impaired brachial artery endothelial function is not predicted by elevated triglycerides.

OBJECTIVES: The purpose of this study was to determine if patients with modest hyperlipidemia, and no other risk factors for coronary artery disease (CAD), have impaired endothelium-dependent (ED) vasoactivity. BACKGROUND: Hypercholesterolemia impairs ED vasodilation, but the impact of elevated triglycerides on endothelial function is not as well established. METHODS: High-resolution ultrasound was used to determine flow-mediated dilation (FMD) in the brachial artery (BA) after a 5-min arterial occlusion (endothelium-dependent stimulus) and nitroglycerin-induced dilation (endothelium-independent stimulus). We studied 40 healthy controls (Group 1), 38 patients with elevated low-density lipoprotein (LDL) cholesterol (Group 2) and 35 patients with elevated triglycerides (Group 3). Patients were excluded if they had known CAD or other risk factors for CAD, or if they were receiving lipid-lowering or vasoactive medications. RESULTS: Control patients (Group 1) had normal LDL cholesterol (2.6+/-0.8 mmol/liter) and triglyceride levels (1.0+/-0.5 mmol/liter) compared with Group 2 (5.2+/-1.2 mmol/liter, 1.8+/-0.6 mmol/liter) and Group 3 (3.5+/-0.9 mmol/liter, 4.2+/-2.5 mmol/liter) subjects (p < 0.001). Baseline BA diameters were the same across the three groups. There was no significant attenuation of flow-mediated vasodilation (FMD) in either of the hyperlipidemic groups (Group 1: 10.9+/-5.0% vs. Group 2: 8.6+/-6.1% vs. Group 3: 9.4+/-3.9%; p = 0.14). However, nitroglycerin-induced vasodilation was mildly reduced (Group 1: 21.0+/-5.0% vs. 16.9+/-7.6% vs. 17.3+/-7.7%; p = 0.01). By multivariate analysis, after controlling for baseline diameters, only the ratio of LDL/high-density lipoprotein predicted a minor impairment in FMD. CONCLUSIONS: In patients free from other cardiac risk factors, modest elevations of triglycerides or LDL cholesterol do not significantly attenuate BA endothelial-dependent vasodilation. Synergism with other cardiac risk factors may be required to significantly impair endothelial function in these patients.

Adult↗
PubMed1999

Recommended permissible noise criteria for occupied, newly constructed or renovated hospital nurseries. The Sound Study Group of the National Resource Center.

OBJECTIVE: To base permissible noise criteria for occupied, new nurseries on research findings. STUDY DESIGN: An interdisciplinary group of clinicians reviewed the literature regarding the effect of sound on the fetus, newborn, and preterm infant and based recommended criteria on the best evidence. An external panel subsequently reviewed the criteria. RESULTS: The recommended criteria: Patient bed areas and the spaces opening onto them shall be designed to produce minimal ambient noise and to contain and absorb much of the transient noise that arises within the nursery. The overall, continuous sound in any bed space or patient care area shall not exceed: (1) an hourly Leq of 50 dB and (2) an hourly L10 of 55 dB, both A-weighted, slow response. The 1-second duration Lmax shall not exceed 70 dB, A-weighted, slow response. CONCLUSION: The permissible noise criteria will protect sleep, support stable vital signs, and improve speech intelligibility for many infants most of the time.

Female↗
PubMed1999

Male reproductive success in a promiscuous mammal: behavioural estimates compared with genetic paternity.

Molecular techniques have enabled behavioural ecologists to reassess mating systems from a genetic perspective. Studies of paternity frequently reveal that mating behaviour does not always reflect parentage, and may bring to light alternative mating tactics. Here we present a comparison of behavioural and genetic measures of male reproductive success in a mammalian mating system in which both sexes are highly promiscuous. Rather than having a stable harem social structure, Soay rams (Ovis aries) on the island of Hirta, St Kilda, UK usually consort with individual oestrous ewes sequentially. Not all matings occur between consort pairs, however, and ewes have been seen to mate with up to 10 different rams on the same day. Using locus-specific polymorphism at five protein and 10 microsatellite DNA loci, we determined paternity for 236 lambs born into three cohorts, and compared paternity with estimates of mating success derived from more than one census of rutting behaviour. The correlation between the number of ewes with which each ram was witnessed in consort and the number of paternities assigned was positive and statistically significant, and rams that were observed in consort with a ewe were 18 times more likely to have sired her offspring than other candidate rams. However, most lambs (73%) were not sired by a ram seen in consort with the oestrous mother. Many juveniles, yearlings and some adult rams were rarely seen in consort with ewes, yet were assigned a significant number of paternities. These results suggest that mating tactics differ between age groups, and that alternative mating strategies among adults that do not involve forming consorts with many females also confer mating success. For these reasons, census-based observations of consort associations between individuals cannot be used to accurately estimate individual male reproductive success in this population.

Animals↗
PubMed1999

Patterns of smoking in the Baltic Republics.

BACKGROUND: Tobacco is a leading cause of avoidable death in the Baltic Republics but there is, as yet, relatively little information in the public domain on who is smoking and how this is changing. This information is important for those seeking to develop effective policies to tackle this issue. OBJECTIVE: To determine the pattern of smoking in Estonia, Latvia, and Lithuania. METHODS: Analysis of data on patterns of tobacco consumption from representative surveys of approximately 3000 adults aged under 65 in each country undertaken in 1997. RESULTS: The prevalence of smoking among men is 53.9%, 56.0%, and 53.2% respectively in Estonia, Latvia, and Lithuania. The corresponding figures for women are 24.1%, 10.9%, and 7.6%. For both sexes, current smoking rates are consistently lowest in the age group 50 to 64 and highest in the age group 35 to 49. Education and income are determinants of smoking rates among men but much less so among women. Russian men are more likely to smoke than are men from the majority group in each country. Smoking rates among women are much lower in rural than in urban areas of Latvia and Lithuania but this is not so in Estonia. CONCLUSIONS: Smoking rates among men in the Baltic Republics are already very high. Among women, they still vary considerably. Each country has implemented some measures to reduce smoking. These seem to have been especially effective in Lithuania but, overall, much more action is needed.

Adult↗
PubMed1999

Lost ear wicks.

Explore the source record for details and available documents.

Bandages↗
PubMed1999

Directly inherited partial trisomy of chromosome 6p identified in a father and daughter by chromosome microdissection.

Cytogenetic analysis of a 4 year old girl with developmental delay and dysmorphic features showed extra chromosomal material of unknown origin on 20p (46,XX,add(20)(p13)). Familial chromosome studies showed direct inheritance of add(20)(p13) from the father, who had a similar, albeit milder, phenotype. Fibroblast chromosome studies of the father showed no karyotype mosaicism. The additional material could not be identified on the basis of the G banding pattern owing to its small size and ambiguous banding pattern. Chromosome microdissection of the unknown material was performed, the DNA was amplified and labelled using degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) and reverse painted to the proband's cells to show the karyotype 46,XX,der(20)t(6;20) (p23;p13), conferring partial trisomy 6p and presumed partial monosomy for 20p. Chromosome microdissection has made possible the first reported case of directly inherited partial trisomy 6p.

Child, Preschool↗
PubMed1999

AIDS knowledge, condom attitudes, and risk-taking sexual behavior of substance-abusing juvenile offenders on probation or parole.

AIDS knowledge, condom attitudes, and sexual behavior were examined in a sample of 193 substance-abusing juvenile offenders on probation or parole. The majority of these youths reported being sexually active, and many admitted to early onset of sexual activity as well as unsafe sexual practices. Potential predictors of condom use by these juveniles were examined including age, condom use at first sexual experience, number of sexual partners in the last 6 months, locus of control, AIDS knowledge, condom attitudes, perceived risk for AIDS, self-efficacy for avoiding HIV, condom use by peers, delinquency risk, race, and gender. General attitudes toward condoms and the reported use of a condom at first sexual intercourse experience were the only statistically significant predictors of subsequent condom use. The relevance of these findings to the development of AIDS prevention programs for juvenile offenders is discussed.

Acquired Immunodeficiency Syndrome↗