Sex skewed kleptoparasitic exploitation of kestrel Falco tinnunculus was studied on foraging areas in south-east Poland. All kestrel prey subject to kleptoparasitism attempts were small mammals caught by kestrels hunting by hovering.. Kleptoparasites attacked male kestrels more frequently than females. Males did not defend their prey as vigorously as females but males were more efficient at capturing further prey following loss of prey. Males also seemed to select habitats that facilitated more effective foraging which reduced costs of lost prey. Kleptoparasitism on kestrels was more successful by groups than by individual attackers.
The sex steroid hormones (SSHs) such as testosterone, estradiol, progesterone, and their metabolites have important organizational and activational impacts on the brain during critical periods of brain development and in adulthood. A variety of slow and rapid mechanisms mediate both organizational and activational processes via intracellular or membrane receptors for SSHs. Physiological concentrations and distribution of SSHs in the brain result in normal brain development. Nevertheless, dysregulation of hormonal equilibrium may result in several mood disorders, including depressive disorders, later in adolescence or adulthood. Gender differences in cognitive abilities, emotions as well as the 2-3 times higher prevalence of depressive disorders in females, were already described. This implies that SSHs may play a role in the development of depressive disorders. In this review, we discuss preclinical and clinical studies linked to SSHs and development of depressive disorders. Our secondary aim includes a review of up-to-date knowledge about molecular mechanisms in the pathogenesis of depressive disorders. Understanding these molecular mechanisms might lead to significant treatment adjustments for patients with depressive disorders and to an amelioration of clinical outcomes for these patients. Nevertheless, the impact of SSHs on the brain in the context of the development of depressive disorders, progression, and treatment responsiveness is complex in nature, and depends upon several factors in concert such as gender, age, comorbidities, and general health conditions.
The morphology and proliferation of vascular smooth muscle cells (VSMC) were studied in cultures prepared from the aorta of newborn male and female Wistar rats. The doubling times (DT) of the male-derived population were 16.4 ±0.7 h and 30.0 ±2.2 h in the exponential and post-exponential growth phases, respectively. In the female donor cells, the corresponding DT values were significantly longer, i.e. 21.9 ± 1.8 h and 38.0 ±2.2 h. In addition, the period of growth was shorter in the female-derived cultures. The percentage of 3H-thymidine labelled cells in male cultures was 61.0±3.1, 92.8± 1.9 and 98.7±0.6 % at 2, 27 and 52 h, respectively. In the female-derived populations, only 24.6 ±4.4, 66.1 ±3.8 and 82.8 ±2.0 % of cells were labelled at the corresponding incubation intervals. As a consequence, the final population density in male cultures was 5.6 times higher. In addition, the male-derived VSMC were mainly spindle-shaped and bulgy in appearance while those from female donors were flat and polygonal which means that the cells were adhering to the growth support to a different extent. The study revealed early determination and long-term persistence of lower adhesiveness as well as higher growth potential of male VSMC, i.e. properties which may be of importance for explaining the higher incidence of vascular wall disorders in males.
The growth capacity of cultured vascular smooth muscle cells (VSMC) obtained from the thoracic aorta of 8-week-old male and female spontaneously hypertensive rats (SHR) was compared. Explants from the intima- media complex were cultured in Dulbecco minimum essential medium supplemented with fetal calf serum (10 %). The migration of VSMC out of the explants started on day 2 in both sexes but on day 18 the number of explants with VSMC migration was 100 ±32 explants/flask in male VSMC and only 24 ±5 explants/flask in female ones. The doubling time at the early exponential phase of growth was shorter (13.5 ±0.5 h) and the p H]-thymidine Labelling Index was higher (34.0±2.3 %) in male VSMC than in those from females (19.9±0.6 h and 23.9±1.9 %, p<0.01, respectively). The difference in the doubling time became even more apparent in the late exponential phase of growth (male VSMC: 51.8±2.0 h, female VSMC: 91.5±5.8 h, p<0.001). Moreover, at the end of the exponential growth phase, the male VSMC reached significantly higher (pcO.OOl) maximum population density than VSMC from females. Our data provide evidence of different growth characteristics of cultured VSMC isolated from male and female SHR aortas.
Spring spawning migrations of paddlefish Polyodon spathula into the River Missouri above Fort Peck Reservoir, Montana were investigated with radio-telemetry during 2006-2009. Selected migration characteristics (total movement, rate of movement, maximum upriver ascent, duration of the migration, upriver residence time and spawning periodicity) were compared between sexes and among years. Paddlefish exhibited sexual dimorphisms in selected measures of migratory behavior. Females typically moved at a faster rate (mean, 13.4 km/ day for females versus 10.1 km/day for males) and remained in the river a shorter time (mean, 40 days) than did males (mean, 45 days). Females and males exhibited similar total movements, upriver residence times and mean maximum ascents. Spawning periodicity was shorter for males (mean, 1.5 years) than females (mean, 2.3 years). Total movement, movement rate, mean duration of the spawning migration and upriver residence time of both sexes differed among years. Results from this study indicate that certain analyses of paddlefish migrations and migratory behavior should be undertaken separately for female and male fish.