Biomedical subjects

Daniel Levin

Publications and source records attributed to Daniel Levin.

4 recordsLinked to original sources

PubMed2004

Constraints on evolution and postcopulatory sexual selection: trade-offs among ejaculate characteristics.

Ejaculates function as an integrated unit to ensure male fertility and paternity, can have a complex structure, and can experience multiple episodes of selection. Current studies on the evolution of ejaculates typically focus on phenotypic variation in sperm number, size, or related traits such as testes size as adaptations to postcopulatory male-male competition. However, the evolution of the integrated nature of ejaculate structure and function depends on genetic variation in and covariation between the component parts. Here we report a quantitative genetic study of the components of the ejaculate of the cockroach Nauphoeta cinerea, including those we know to experience postcopulatory sexual selection, in the context of functional integration of ejaculate characters. We use the patterns of genetic variation and covariation to infer how the integration of the functions of the ejaculate constrain and shape its evolution. Ejaculate components were highly variable, showed significant additive genetic variance, and moderate to high evolvability. The level of genetic variation in these characters, despite strong directional or truncating selection, may reflect the integration of multiple episodes of selection that occur in N. cinerea. There were few significant phenotypic correlations, but all the genetic correlations among ejaculate characters were significantly different from zero. The patterns of genetic variation and covariation suggest that there are important trade-offs among individual traits of the ejaculate and that evolution of ejaculate characteristics will not proceed unconstrained. Fully describing the genetic relationships among traits that perform as an integrated unit helps us understand how functional relationships constrain or facilitate the evolution of the complex structure that is the ejaculate.

Analysis of Variance↗

PubMed2004

The "nation's conscience:" assessing bioethics commissions as public forums.

As the fifth national bioethics commission has concluded its work and a sixth is currently underway, it is time to step back and consider appropriate measures of success. This paper argues that standard measures of commissions' influence fail to fully assess their role as public forums. From the perspective of democratic theory, a critical dimension of this role is public engagement: the ability of a commission to address the concerns of the general public, to learn how average citizens resolve moral issues in healthcare, and to monitor public opinion on the topics addressed in the commission. Such a public forum role is supported by the critical literature within bioethics, which has deemed some commissions successful, supported more generally by the history of bioethics as a reform discourse that has brought socially important values into the medical domain, and supported more generally still by the example of the great social issues commissions of the 1960s.

Advisory Committees↗

PubMed2003

Vaginitis in a gynecologic practice in Israel: causes and risk factors.

BACKGROUND: Vaginal symptoms are a leading reason for a patient to visit her gynecologist. Little is known about the prevalence of the different causes of vaginitis and the risk factors for this entity in Israel. OBJECTIVE: To determine the prevalence of the main forms of vaginitis: vulvovaginal candidiasis, bacterial vaginosis, and trichomoniasis, in a gynecologic practice in Israel. METHODS: We evaluated 208 patients presenting with vaginal symptoms to a gynecologic clinic; 100 asymptomatic women who attended the clinic for routine check-up served as controls. Demographic, medical and gynecologic histories were obtained, and a pelvic examination was performed in all patients. Vaginal specimens were tested for pH and amine reaction, smeared for Gram-staining and cultured for yeasts and Trichomonas vaginalis. Bacterial vaginitis was diagnosed using the Nugent scoring system. Candida infection was diagnosed by microscopic examination and by culture. RESULTS: Candida spp. was the most common pathogen, documented by microscopy and culture in 35.5% of symptomatic women and 15% of asymptomatic controls (P < 0.001). Detection by culture only (negative microscopy) was documented in 18.7% of symptomatic patients and 15% of controls (P = 0.5). Bacterial vaginosis (Nugent score > or = 7) was diagnosed in 23.5% of patients and 13% of controls (P = 0.04). Trichomoniasis was present in 8.1% of symptomatic women and 4% of controls (P = 0.1). The main risk factors were antibiotic use for candidiasis and lack of use of oral contraception and condom use for trichomoniasis. CONCLUSION: Candida was by far the most common pathogen detected in our population. A statistically significant difference between patients and controls was noted for the prevalence of microscopically diagnosed candidiasis and bacterial vaginosis.

Adult↗

PubMed2002

The effects of enoxaparin on the reparative processes in experimental osteonecrosis of the femoral head of the rat.

The blood supply of one femoral head of 6-month-old rats was severed by incising the periosteum of the neck and cutting the ligamentum teres. The rats were killed on the 30th postoperative day and the femoral bones were obtained for semiquantification of the reparative processes in the necrotic heads. Fourteen rats were treated with enoxaparin and 14 untreated animals served as controls. Statistically, the amounts of necrotic bone in the epiphysis were less, the extent of remodeling of the femoral heads was milder, and the articular cartilage degeneration was slighter in the enoxaparin-treated than untreated rats. There was no significant difference in the quantities of newly formed bone in femoral heads of treated and untreated rats. These findings are in agreement with the known effects of unfractionated and low-molecular-weight heparins which enhance osteoclastic bone resorption and angiogenesis and decrease osteoblastic bone formation. The former activities, operative in minimizing the structural distortion of the femoral head, oppose the crucial event in the pathogenesis of post-osteonecrotic osteoarthritis.

Animals↗