Oocyte recovery and fertilization rates in women at various times after the administration of hCG

Volunteer women requesting laparoscopic sterilization were subjected to a fixed schedule of ovulation induction and oocyte recovery. Follicle aspiration was carried out in four groups: those to whom hCG was not administered and 12, 24 or 36 h respectively after the administration of hCG. For each group oocytes were cultured in vitro for 42 h, 30 h, 18 h and 6 h respectively, before insemination with donor spermatozoa. Oocyte recovery rates improved with longer hCG-to-recovery intervals (36% with no hCG to 81% 36 h after hCG). Although there was a slight reduction in fertilization rates when oocytes were not exposed to hCG in the follicle, normal cleavage was noted in more than 50% of oocytes in all four groups. It therefore appears that the final maturation stages of the human oocyte are not dependent on the midcycle gonadotrophin surge, provided the oocyte is matured in vitro before insemination. However, it was also evident that the fertilization rates were reduced when oocytes were removed from less mature follicles, as reflected by high androstenedione/oestradiol ratios.     

Effects of a high-voltage direct-current transmission line on beef cattle production

Two herds of beef cattle were maintained beneath a +/- 500 kV direct-current transmission line during a 30-month period, and were compared with two similar herds maintained away from the transmission line. Exposures of animals under the line were five to 30 times greater than those of control animals, depending on the parameter of interest, with average exposure magnitudes of 5.6 kV/m, 4.1 nA/m2, and 13 k ions/cm3, respectively, for electric field, ion current, and density of ions. Productivity and health status of cows and calves were similar between lines and control treatments. Mean body mass of cows increased with maturity, from 438 kg in 1985 to 496 kg in 1987. Calf gain averaged 0.93 kg per head per day. No unusual sources of mortality were observed. Based on this confinement study, beef cattle permitted to graze in the vicinity of a high-voltage, direct-current transmission lines are not expected to experience any decrease in frequency of conception, calving, growth rate, or survival.     

Localisation of luciferase in luminous marine bacteria by gold immunocytochemical labelling

Abstract Bioluminescent bacteria are able to produce light by an oxidative reaction involving the enzyme luciferase. The biochemistry of the reaction has been well documented. It has been postulated from the reaction pathway that the enzyme luciferase is membrane bound. Two species of luminous bacteria, Vibrio fischeri and V. harveyi , were isolated from sea water, fixed and embedded in resin for transmission electron microscopy. A commercially available V. fischeri bacterial luciferase was used to immunise rats for production of an antibody against luciferase. This antibody was coupled with a protein A gold probe and used to immunolabel the sections of bacteria. It was shown that the luciferase was associated with the inner membrane, and to a lesser extent present in the cytoplasm. Our results confirm that the luciferase is predominantly membrane bound.     

Development time mediates the effect of larval diet on ageing and mating success of male antler flies in the wild

High-quality developmental environments often improve individual performance into adulthood, but allocating toward early life traits, such as growth, development rate and reproduction, may lead to trade-offs with late-life performance. It is, therefore, uncertain how a rich developmental environment will affect the ageing process (senescence), particularly in wild insects. To investigate the effects of early life environmental quality on insect life-history traits, including senescence, we reared larval antler flies (Protopiophila litigata) on four diets of varying nutrient concentration, then recorded survival and mating success of adult males released in the wild. Declining diet quality was associated with slower development, but had no effect on other life-history traits once development time was accounted for. Fast-developing males were larger and lived longer, but experienced more rapid senescence in survival and lower average mating rate compared to slow developers. Ultimately, larval diet, development time and body size did not predict lifetime mating success. Thus, a rich environment led to a mixture of apparent benefits and costs, mediated by development time. Our results indicate that ‘silver spoon'' effects can be complex and that development time mediates the response of adult life-history traits to early life environmental quality.     

Seasonal habitat use indicates that depth may mediate the potential for invasive round goby impacts in inland lakes

1. The round goby (Neogobius melanostomus) is among the fastest-spreading introduced aquatic species in North America and is radiating inland from the Great Lakes into freshwater ecosystems across the landscape. Predicting and managing the impacts of round gobies requires information on the factors influencing their distribution in habitats along the invasion front, yet this information is not available for many recently invaded ecosystems. We evaluated the seasonal habitat use and biomass of round gobies in an inland temperate lake to define the spatiotemporal scope of biological interactions at the leading edge of the round goby invasion.
2. Using novel statistical approaches, we combined hierarchical models that control for imperfect species detection with flexible smooth terms to describe non-linear relationships between round goby abundance and environmental gradients. Subsequently, we generated accurate detection-corrected estimates of the standing stock biomass of round gobies.
3. Our results show seasonally differentiated habitat niches, where suitable round goby habitat in summer months is restricted to shallow depths (<18.4 m) with a mixture of vegetative and mussel cover. We found high round goby biomass of 122 kg/ha in occupied habitats during the summer, with a total lake-wide biomass of 766,000 kg. In winter, round gobies migrate to deep offshore habitats and disperse, dramatically altering their scope for biological interactions with resident aquatic species across summer and winter seasons.
4. The results of this study indicate that the scope of biological interactions in inland lakes may be seasonally variable, with potential for high round goby biomass in shallow lakes or at the periphery of deep lakes in the summer months. Such shallow-water habitats may therefore present higher risk of ecological impacts from round gobies in invaded lentic ecosystems. As round gobies expand inland, consideration of seasonal habitat use will be an important factor in predicting the impacts of this pervasive invader.