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S Irving

Publications and source records attributed to S Irving.

15 recordsLinked to original sources
PubMed2001

Complex epistasis and the genetic basis of hybrid sterility in the Drosophila pseudoobscura Bogota-USA hybridization.

We analyzed the genetic basis of postzygotic isolation between the Bogota and USA subspecies of Drosophila pseudoobscura. These subspecies diverged very recently (perhaps as recently as 155,000 to 230,000 years ago) and are partially reproductively isolated: Bogota and USA show very little prezygotic isolation but form sterile F1 males in one direction of the hybridization. We dissected the basis of this hybrid sterility and reached four main conclusions. First, postzygotic isolation appears to involve a modest number of genes: we found large chromosome regions that have no effect on hybrid fertility. Second, although apparently few in number, the factors causing hybrid sterility show a remarkably complex pattern of epistatic interaction. Hybrids suffer no hybrid sterility until they carry the "right" allele (Bogota vs. USA) at at least four loci. We describe the complete pattern of interactions between all chromosome regions known to affect hybrid fertility. Third, hybrid sterility is caused mainly by X-autosomal incompatibilities. Fourth, hybrid sterility does not involve a maternal effect, despite earlier claims to the contrary. In general, our results suggest that fewer genes are required for the appearance of hybrid sterility than implied by previous studies of older pairs of Drosophila species. Indeed, a maximum likelihood analysis suggests that roughly 15 hybrid male steriles separate the Bogota and USA subspecies. Only a subset of these would act in F1 hybrids.

Animals↗
PubMed2001

Urban stress and mental health among African-American youth: assessing the link between exposure to violence, problem behavior, and coping strategies.

This project examines gender differences in exposure to violence, coping strategies and problem behavior among 306 African-American middle and high school students in the state of Virginia. Gender differences in problem behaviors among youth exposed to violence as either victims or witnesses are examined in addition to variations in coping strategies. Relying on recent research examining violent behavior and victimization events, the study focuses on the internalizing and externalizing behavioral characteristics (i.e., academic achievement, anxiety, depression, negative self-esteem, and delinquency) of urban students exposed to violence and the extent to which coping strategies differ. Results show specific gender differences with regard to problem behavior and coping strategy among African-American youth exposed to violence. For adolescent males, exposure to violence and victimization is strongly associated with externalizing problem behaviors such as delinquency, while adolescent females exposed to violence and victimization are more likely to exhibit internalizing symptoms indicative of post-traumatic stress disorder. Among students exposed to violence and victimization, females are more likely to use problem-focused coping (i.e., social support) as an adaptive strategy in comparison to males. Implications for intervention and future research are discussed.

Adaptation, Psychological↗
PubMed2000

Genetic analysis of the hybrid male rescue locus of Drosophila.

Several hybrid rescue mutations-alleles that restore the viability of normally lethal hybrids-have been discovered in Drosophila melanogaster and its relatives. Here we analyze one of these genes, Hybrid male rescue (Hmr), asking two questions about its role in hybrid inviability. (1) Does the wild-type allele from D. melanogaster (Hmr(mel)) cause hybrid embryonic inviability? (2) Does Hmr(mel) cause hybrid larval inviability? Our results show that the wild-type product of Hmr is neither necessary nor sufficient for hybrid embryonic inviability. Hmr(mel) does, however, appear to lower the viability of hybrid larvae. The data further suggest (though do not prove) that Hmr(mel) acts as a gain-of-function poison in hybrids. These findings support previous claims that hybrid embryonic and larval lethalities are genetically distinct and suggest that Hmr(mel) is at least one of the proximate causes of hybrid larval inviability.

Animals↗
PubMed1999

Scrotal trauma: a cause of testicular atrophy.

Scrotal trauma is often mentioned as a cause of testicular atrophy yet there have been few studies documenting the effect of scrotal trauma on testicular size months or years following injury. We performed clinical and sonographic examinations in 10 patients who had suffered blunt scrotal trauma. A significant reduction in volume of the injured testis was observed in 5/10 cases at follow-up sonography. In two cases the affected testis was heterogeneous and colour flow Doppler examination showed reduced flow. In three cases the testis was homogeneous but reduced in volume and in the remaining five cases the affected testis appeared normal. We conclude that testicular atrophy is a sequel of scrotal trauma and occurred in 50% of patients in this study.

Adolescent↗
PubMed1998

Association of alcohol consumption to morality in middle-aged U.S. and Russian men and women.

PURPOSE: The purpose of this paper is to assess the relationships of alcohol consumption to total and cardiovascular disease mortality in U.S. and Russian men and women after adjustment for several covariates. A secondary objective is to determine how this relationship varies by country and gender. METHODS: Men aged 40-59 and women aged 40-69 screened in Russia and the U.S. between 1972 and 1982 were followed for mortality for 13 years as part of the Lipid Research Clinics Prevalence and Follow-up Studies. Alcohol consumption was based on a 7-day recall of drinks of beer, wine, mixed drinks, and liquors. Drinkers of alcohol were classified into four levels based on amount consumed during the recall period. RESULTS: Age-adjusted mortality rates were higher for non-drinkers than lower level drinkers in both genders and countries, and there was an indication that mortality rates for high level drinkers, especially in men, approached those of non-drinkers. When mortality rates were adjusted for other risk factors they remained higher for non-drinkers in U.S. men and women, but in Russia, with one exception, there was no difference in mortality rates between drinkers and non-drinkers. Relative risks for cardiovascular disease mortality rates were similar to those of total mortality. CONCLUSIONS: Beneficial association of alcohol consumption and mortality may be limited depending upon the prevalence of other risk factors in the studied population.

Adult↗
PubMed1997

Changes over time in blood lipids and their correlates in Polish rural and urban populations: the Poland-United States Collaborative Study in cardiopulmonary disease epidemiology.

PURPOSE: The purpose of this manuscript is to examine changes in blood lipid levels and related factors between 1983 and 1987 in two selected Polish populations, to evaluate these changes and their association with other coronary heart disease (CHD) risk factors, and to examine the nutrient intake changes for consistency with observed lipid changes. METHODS: Men and women, aged 35-64 were screened from Warsaw and rural Tarnobrzeg province, Poland-the Pol-MONICA screening sites. An independent random sample of 5132 screened in 1983-84 and a second independent random sample of 2596 screened in 1987-88 were compared. A 25% cohort of the 1983-84 sample was also rescreened in 1987-88 (n = 1236) and 24-hour dietary recall information on this cohort was used to evaluate nutrient intake changes and their relationship to the lipid changes. RESULTS: For the random samples, the total cholesterol increased by 5.1 mg/dL (rural) and by 7.9 mg/dL (urban) for women; there were no significant changes among men. Low-density lipoprotein cholesterol (LDL-C) increased for all site and gender subgroups by 5.4-8.7 mg/dL. Among rural men and women, high-density lipoprotein cholesterol (HDL-C) decreased by 3.4 and 3.3 mg/dL, respectively, whereas it increased by 3.3 mg/dL among urban women and did not change among urban men. Total triglycerides (TG) increased by 9.5 mg/dL for rural men, with no significant change for rural women. For urban men and women, TG decreased by 29.5 and 21.8 mg/dL respectively. In the cohort, changes in dietary intake (decreases in energy from fat, Keys index and increases in the polyunsaturated to saturated fats ratio) were related to a decrease in TC at both sites and to a decrease or smaller increase in LDL-C for rural men. CONCLUSIONS: The observed changes were generally unfavorable, with a decrease in the proportion of persons with desirable lipid levels. At both sites nutritional changes were favorable, including a drop in total energy intake. Less pronounced were changes in percentages of total energy from fats, where the only significant decrease was for rural women; however, improvements in dietary fat composition and declines in cholesterol consumption were found. These favorable changes in diet were not strong enough or were not in effect long enough to counter the unfavorable changes in blood lipids.

Adult↗
PubMed1994

Body mass, fat distribution and cardiovascular risk factors in a lean population of south China.

The associations of body mass index and abdominal adiposity, represented by an elevated waist/hip circumference ratio, with cardiovascular risk factors were examined in men and women, aged 28-69 years, from urban and rural areas of Guangzhou, China. Mean body mass index ranged from 20.1 to 21.9 kg/m2 across the four sex- and area-groups. Mean waist/hip ratio was 0.84 in men and 0.80 in women. After accounting for age and body mass index, waist/hip ratio was associated negatively (p < 0.05) with fasting serum HDL cholesterol (both sexes), and positively with serum triglycerides (both sexes), total and LDL cholesterol (men only), uric acid (both sexes), glucose (women only), and mean systolic blood pressure (women only). Body mass index was associated in a similar direction with most of these risk factors. These data confirm that abdominal adiposity is independently associated with cardiovascular disease risk factors, even in a lean Asian population.

Abdomen↗
PubMed1992

A high proportion of early response genes are constitutively activated in T cells by HTLV-I.

Immortalization of T cells by HTLV-I is mediated by the X region of the virus and probably involves transactivation of cellular genes. We show that T cells transformed by HTLV-I constitutively express a high proportion of early response genes that are normally transiently induced following antigenic or mitogenic activation of T cells. Thus, HTLV-I-infected T cells display an 'early activation' phenotype that is distinct from the gene expression pattern of continuously dividing T cells. Ten early response genes representing a diverse array of functional categories were assayed. Four DNA-binding proteins/transcription factors including the p50 subunit of NF-kappa B were evaluated. A protein(s) encoded by the X region of HTLV-I appeared to contribute to up-regulated expression of most, if not all, of the early response genes. For those genes that could be assayed, increased transcriptional rates, but not substantial changes in mRNA half-life, were demonstrated in the presence of pX-encoded proteins, suggesting that the transcriptional transactivator, Tax, affects the induction or maintenance of transcription for these mitogen-inducible genes. Therefore, Tax may mimic or interact with a component(s) of the signal transduction pathway activated by antigen or mitogen treatment. These data demonstrate that early response genes, some of which probably play roles in initiating or maintaining cellular proliferation, are frequent targets of HTLV-I activation.

Blotting, Northern↗
PubMed1991

Effects of prenatal antiandrogen treatment on masculinization and defeminization of guinea pigs.

Gonadectomized (gdx) guinea pigs which had received the antiandrogen flutamide prenatally were tested for female-typical and male-typical sexual behavior in adulthood. In tests for lordosis behavior, gdx males and females were injected with estradiol benzoate and progesterone. Prenatally flutamide-treated females showed a longer mean lordosis response than control females. This was true whether they were given either a high or a low dose of EB. No male ever showed a lordosis response. In tests for male-typical sexual behavior, gdx adult males were treated with testosterone propionate and tested with stimulus females. The prenatally flutamide-treated males showed significantly decreased levels of ejaculation, a lower intromission rate and a decreased percentage of mounts which included pelvic thrusts, when compared to control males. Mount rate and rate of pericopulatory behavior did not differ between the flutamide and control males. The fact that prenatal administration of flutamide increased female-typical behavior in adult females suggests that the female guinea pig is normally partially defeminized by androgens in utero. The male guinea pig appears to be resilient to attempts to block defeminization with prenatal antiandrogens. However, some aspects of masculinization can be blocked.

Androgen Antagonists↗
PubMed1990

A controlled model of moist wound healing: comparison between semi-permeable film, antiseptics and sugar paste.

An established wound model in the pig has been modified using a Stomahesive ring to enable study of the effects of fluids used in wound care. Full thickness wounds (up to 9 mm deep) were treated with the substances under test. Each application was held in place with a Stomahesive flange, the inner part of which had been excised as far as the hard plastic ring. All dressings were then covered with OpSite which allowed gaseous exchange whilst retaining treatment fluids and secretions. Wounds were treated immediately and at 2 and 4 days. The experiment was terminated after 7 days and the whole wound, with dressing, was excised for histological examination. The wounds covered with OpSite alone and those treated with sugar paste under Opsite were found to be infilled with granulation tissue over which epidermal migration was taking place. Those wounds which had been packed with gauze, to which had been added one of the following: chlorhexidine gluconate 0.2%, Irgasan 0.2%, povidone iodine 0.8% or EUSOL half-strength, showed delayed healing in that less infilling had taken place over the same time period. This delay could be attributed to the nature of the chemicals used and/or the influence of gauze packing. This delay in the healing of wounds treated with chemical agents was least with EUSOL half-strength and greatest with chlorhexidine. No toxic effects were observed with sugar paste which may be preferable to antiseptics for the management of dirty or infected wounds.

Aerosols↗
PubMed1984

Heterotransplantation of experimentally induced sheep lung adenomatosis into nude mice.

Male ICR nude mice inoculated subcutaneously with minced tissue obtained from pulmonary adenomatosis of sheep which was induced by RNA type-C retrovirus developed a transplant which contained cysts lined by a proliferative epithelium. These cysts showed several characteristics of the epithelial tumour cells of origin, such as high glycogen content and secretion of mucin. Microinvasion of epithelial cells from the adenomatous cysts into the stroma was observed. The stromal tissue demonstrated islets of cartilage. It was concluded that virus-induced pulmonary carcinoma of sheep can be transplanted and grown in nude mice.

Animals↗