Effect of number of motile sperms inseminated on reproductive performance of rabbit does

The relationship between the number of motile sperms inseminated and fertility rate and litter size at birth in rabbits was investigated. A total of 651 artificial inseminations on multiparous rabbit does in different physiological states (lactating or not; sexually receptive or not) were inseminated with a number of motile cells/dose varying from about 1-20 x 10(6). The statistical model computed the following traits: maximum expected value (a), rate of approach to this value (b) and number of motile spermatozoa/dose needed to obtain threshold level (95% of the maximum). The physiological condition of the doe affected the reproductive performance. The sexual receptivity had significant effect during lactation: non-receptive does had the lowest fertility (a: 43.70%; P < 0.05) while no significant differences were found in non-lactating ones (73.80 vs. 89.11%). Also the rate of approach to this maximum was different: non-receptive does showed a higher dependence on spermatozoa number than receptive females (b: 0.69 and 0.58, respectively, in lactating and non-lactating does) and consequently more spermatozoa (13.1 and 11.1 x 10(6) motile/dose) were needed to reach the threshold value. The physiological state of the does did not affect litter size and only 4.1 x 10(6) of motile spermatozoa/dose are needed to reach the threshold value.     

The orientation of the sandhopper <Emphasis Type="Italic">Talitrus saltator</Emphasis> during a partial solar eclipse

To acquire more information about the identification and use of the sun and other celestial cues in the sea–land orientation of the sandhopper Talitrus saltator, we carried out releases in a confined environment during a partial solar eclipse and at sunset. The sandhoppers were unable to identify the sun (86% covered) during the eclipse nor to use other celestial compass factors of orientation. This was probably due to the low level of light intensity (close to the minimum level for orientation recorded at sunset) and to the variations in intensity and pattern of skylight polarization.     

Digestive constraints on an aquatic carnivore: effects of feeding frequency and prey composition on harbor seals

We hypothesized that increased feeding frequency in captive harbor seals would increase nutrient loads and thus reduce retention time and the digestive efficiency of natural prey. We measured daily feed intake and excretion during 6 feeding trials and fed herring (49% lipid), pollock (22% lipid) or an equal mix of each diet over 24 months. Animals were accustomed to feeding at either high or low frequency. Body mass and intake did not vary with season. Although mean retention times were similar between diets and feeding frequencies, solute and particulate digesta markers separated at high feeding frequency. Consistent dry matter digestibility resulted in greater gut fill from pollock than from herring. Digestible energy intakes from pollock were approximately 25% greater than from either herring or the mixed diet. Lipid digestibility of herring declined from 90% to 50% when lipid intake exceeded 60 g kg^–0.75 day^–1. Our hypothesis of a trade-off between intake and digestion was not supported for protein but was supported for lipid. Results of this study imply that a flexible digestive system for harbor seals can compensate for ingesting prey of lower energy density by increasing gut fill and enhancing protein and lipid assimilation, to sustain digestible energy intake.Abbreviations DM dry matter - DEI digestible energy intake - DIT diet-induced thermogenesis - FF feeding frequency - MRT mean retention time Communicated by: G. Heldmaier     

Role of rabbit prostate granules on sperm viability and acrosome reaction evaluated with different methods

In the present study, the role of rabbit seminal granules was observed. Their influence on motility, capacitation and acrosome reaction, as well as the presence of apoptosis and the morphology of rabbit sperm, were compared in different conditions. Ejaculated sperm from five mature New Zealand White rabbit bucks during three series of collections were studied, comparing raw semen, Percoll-selected sperm and Percoll-selected sperm plus prostate granules. We observed sperm motility kinetic traits by computer-assisted sperm analyzer (CASA) analysis in each sample. Acrosome status was evaluated by FITC-labeled Pisum sativum Agglutinin staining and chlortetracycline fluorescence assay, phosphatidylserine translocation was determined by AnnexinV/Propidium iodide assay and sperm morphology was studied using transmission electron microscopy (TEM). All traits were observed after 30 min incubation at 37 °C in 5% CO₂. Data showed that sperm motility and viability markedly improved in the presence of prostate granules, whereas capacitation, acrosome reaction and phosphatidylserine translocation were lowered. TEM confirmed these results. In conclusion, the role of granules was confirmed in synchronizing sperm capacitation and acrosome reaction with egg availability; indeed, rabbit ovulation occurs only 6 to 10 h after mating.     

Oxidative stress indicators and trace elements in the blue shark (Prionace glauca) off the east coast of the Mexican Pacific Ocean

Trace element concentrations and oxidative stress indicators (including production of reactive oxygen species (ROS), antioxidant enzyme activities and oxidative damage) were measured in muscle of blue sharks collected along the west coast of Baja California Sur to determine potential differences by sex and maturity cohorts. Mercury (Hg) concentration in muscle samples from larger sharks (>200 cm LT) exceeded the permissible limit (>1 ppm wet weight) for human consumption set by numerous international agencies. Significant differences were found in Hg concentrations (mature>immature; males>females), and in protein carbonyl concentrations (male>female); however, except for carbonyl protein levels, no significant differences by sex or maturity stage were found in the oxidative stress indicators. Differences between sexes and maturity stages in trace element concentration and carbonyl protein levels in blue shark muscle may be related to variations in diet within different cohorts.     

Involvement of nuclear factor-kappa B in bcl-xL-induced interleukin 8 expression in glioblastoma

We recently reported that bcl-xL regulates interleukin 8 (CXCL8) protein expression and promoter activity in glioblastoma cells. In this paper we demonstrate that CXCL8 induction by bcl-xL is mediated through a nuclear factor-kappa B (NF-kB)-dependent mechanism. Mutational studies on the CXCL8 promoter showed that NF-kB binding site was required for bcl-xL-induced promoter activity and an enhanced nuclear expression of NF-kB subunits p65 and p50 was observed after bcl-xL over-expression. Electrophoretic mobility shift assay showed an increased DNA-binding activity of NF-kB in bcl-xL over-expressing cells and the use of specific antibodies confirmed the involvement of p65 and p50 in NF-kB activity on CXCL8 promoter sequence. NF-kB activity regulation by bcl-xL involved IkBalpha and IKK complex signaling pathway. In fact, bcl-xL over-expression induced a decrease of cytoplasmic expression of the IkBalpha protein, paralleled by an increase in the phosphorylation of the same IkBalpha and IKKalpha/beta. Moreover, the down-regulation of the ectopic or endogenous bcl-xL expression through RNA interference confirmed the ability of bcl-xL to modulate NF-kB pathway, and the transient expression of a degradation-resistant form of the cytoplasmic NF-kB inhibitor IkBalpha in bcl-xL transfectants confirmed the involvement of that inhibitor in bcl-xL-induced CXCL8 expression and promoter activity. In conclusion, our results demonstrate the role of NF-kB as the mediator of bcl-xL-induced CXCL8 up-regulation in glioblastoma cells.     

Adaptations to pressure in the RBC metabolism of diving mammals

Marine mammals are known to dive up to 2000 m and, therefore, tolerate as much as 200 atm. of hydrostatic pressure. To examine possible metabolic adaptations to these elevated pressures, fresh blood samples from marine and terrestrial mammals were incubated for 2 h at 37 degrees C under 136 atm (2000 psi) of hydrostatic pressure. The consumption of plasma glucose and the production of lactate over the 2-h period were used to assess glycolytic flux in the red cells. The results indicate that glycolytic flux as measured by lactate production under pressure can be significantly depressed in most terrestrial mammals and either not altered or accelerated in marine mammals. The data also suggest that there is a significant shift in the ratio of lactate produced to glucose consumed under pressure. Interestingly, human and dolphin blood do not react to pressure. These combined data imply a metabolic adaptation to pressure in marine mammal RBC that may not be necessary in human or dolphin cells due to their unique patterns of glucose metabolism.     

Mental Health Problems in Adolescence and the Interpretation of Unambiguous Threat

Aberrant threat perception has been linked to paranoia, anxiety and other mental health problems, and is widely considered to be a core, transdiagnostic feature of psychopathology. However, to date there has been only limited investigation of whether mental health problems are associated with a biased interpretation of stimuli that have explicit (as opposed to ambiguous) connotations of threat. In the present study, 41 adolescents diagnosed with a mental illness and 45 demographically matched controls were asked to provide danger ratings of stimuli normatively rated as being either low or high in potential threat. All participants were also asked to complete background measures of cognitive function, mental health and wellbeing. The results indicated that the two groups did not differ in their capacity to discriminate between low and high threat stimuli, nor did they differ in the absolute level of threat that they attributed to these stimuli. However, for the control group, the overall level of threat perceived in facial stimuli was correlated with two important indices of mental health (depression and anxiety). No associations emerged in the clinical group. These data are discussed in relation to their potential implications for the role of aberrant threat perception in transdiagnostic models of mental health.     

Artificial light and sun compass orientation in the sandhopper Talitrus saltator (Crustacea, Amphipoda)

Experiments on compass orientation under artificial light were conducted with adult individuals of Talitrus saltator. The aim was to reproduce in the laboratory an orientation based on the sun compass corresponding to that recorded in conditions of the true sun and sky. This was obtained by the creation within an opaque Plexiglas dome of a scenario that permitted variation of the brightness of the artificial sky and sun. The results show that it is possible to obtain sun compass orientation corresponding to the natural situation even in an artificial environment. It can be concluded that sandhoppers identify an artificial light source as the sun if the artificial sky is also illuminated and if the intensities of the artificial sun and sky exceed certain threshold values (1.13 and 10 μW cm⁻², respectively). The results of other experiments under the natural blue sky with an artificial sun and with the real sun attenuated are discussed. Accepted: 23 May 1997