The frequency of gonadotropin-releasing hormone secretion regulates expression of alpha and luteinizing hormone beta-subunit messenger ribonucleic acids in male rats

The influence of GnRH pulse frequency on LH subunit mRNA concentrations was examined in castrate, testosterone-replaced male rats. GnRH pulses (25 ng/pulse) or saline to controls, were given via a carotid cannula at intervals of 7.5-240 min for 48 h. alpha and LH beta mRNA concentrations were 109 +/- 23 and 30 +/- 5 pg cDNA bound/100 micrograms pituitary DNA, respectively, in saline controls. GnRH pulse intervals of 15, 30, and 60 min resulted in elevated alpha and LH beta mRNAs (P less than 0.01) and maximum responses (4-fold, alpha; 3-fold, LH beta) were seen after the 30-min pulses. Acute LH release to the last GnRH pulse was seen after the 15-, 30-, and 60-min pulse intervals. In contrast, LH subunit mRNAs were not increased and acute LH release was markedly impaired after the rapid (7.5 min) or slower (120 and 240 min) pulse intervals. Equalization of total GnRH dose/48 h using the 7.5- and 240-min intervals did not increase LH subunit mRNAs to levels produced by the optimal 30-min interval. These data indicate that the frequency of the pulsatile GnRH stimulus regulates expression of alpha and LH beta mRNAs in male rats. Further, GnRH pulse frequencies that increase subunit mRNA concentrations are associated with continuing LH responsiveness to GnRH.     

Protein concentration of cerebrospinal fluid by precipitation with Pyrogallol Red prior to sodium dodecyl sulphate-polyacrylamide gel electrophoresis

The Pyrogallol Red Molybdate (PRM) and Coomassie Brilliant Blue (CBB) protein dye-binding assays have been applied to samples of cerebrospinal fluid (CSF) to investigate protein concentration by dye precipitation prior to sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The protein concentration values of the CSF samples (N=62) showed good agreement between the PRM and CBB assays as indicated by linear regression analysis (y(PRM)=1.033x(CBB)+1.004 in units of mg/l, r=0.99) but the PRM assay was optimal for protein concentration as the PRM protein-dye complex was less soluble allowing protein recovery over a wider working range. Dye precipitation using PRM is recommended as a simple, rapid and economic method for protein concentration of samples of CSF prior to SDS-PAGE.     

A hybrid protein of urokinase growth-factor domain and plasminogen-activator inhibitor type 2 inhibits urokinase activity and binds to the urokinase receptor.

The binding of urokinase-type plasminogen activator (uPA) to its specific cell-surface receptor (uPAR) localises the proteolytic cascade initiated by uPA to the pericellular environment. Inhibition of uPA activity or prevention of uPA binding to uPAR might have a beneficial effect on disease states wherein this activity is deregulated, e.g. cancer and some inflammatory diseases. To this end, a bifunctional hybrid molecule consisting of the uPAR-binding growth-factor domain of uPA (amino acids 1-47; GFuPA) at the N-terminus of plasminogen-activator inhibitor type 2 (PAI-2) was produced in Saccharomyces cerevisiae. The purified protein inhibited uPA with kinetics similar to placental or recombinant PAI-2 and was also found to bind to U937 cells and to FL amnion cells. GFuPA-PAI-2 competed with uPA, the N-terminal fragment of uPA and a proteolytic fragment of uPA (amino acids 4-43) in cell binding experiments, indicating that the molecule bound to the cells via uPAR. Hence, both the uPA-inhibitory and uPAR-binding domains of the hybrid molecule were functional, demonstrating the feasibility of the novel concept of introducing an unrelated, functional domain onto a member of the serine-protease-inhibitor superfamily.     

Determinants of child mortality in south-west Uganda.

Anthropometric and sociodemographic variables were taken from 4320 children in a baseline survey carried out in March-April 1988 in the district of Mbarara, south-west Uganda. After 12 months a follow-up survey assessed the mortality of the children during the preceding year. Lack of ownership of cattle, recent arrival in the village, using candles for lighting, being of birth order higher than 5 and having a father with less than 8 years of schooling were significantly associated with child mortality. The addition of mid-upper arm circumference significantly improved the logistic model of socioeconomic variables and mortality and did not diminish the predictive power of socioeconomic variables in relation to increased mortality. This suggests that nutritional status and specific socioeconomic factors are both, independently, important predictors of child mortality.     

Wetland plant growth under contrasting water regimes associated with river regulation and drought: implications for environmental water management

An important characteristic of many wetland plants in semi-arid regions is their capacity to withstand fluctuations between extended dry phases and floods. However, anthropogenic river regulation can reduce natural flow variability in riverine wetlands, causing a decline in the frequency and duration of deep flooding as well as extended droughts, and an increase in shallow flooding and soil saturation. Our aim in this paper was to use an experimental approach to examine whether reductions in flooding and drought disadvantage species adapted to both these extremes, and favours those with water requirements that match the new regime of frequent low-level flooding. We compared the growth characteristics and biomass allocation of three native Australian aquatic macrophytes (Pseudoraphis spinescens, Juncus ingens and Typha domingensis), which co-occur at Barmah Forest, south-eastern Australia, under three water treatments: drought, soil saturation and deep flooding. The responses of species to the treatments largely reflected changes in their relative abundance at Barmah Forest since river regulation. Typha domingensis, which has remained uncommon, performed relatively poorly in all treatments, while J. ingens, which has increased its range, exhibited more vigorous growth under soil saturation. Pseudoraphis spinescens, which was once widespread but has declined markedly in its distribution, grew strongly under all water treatments. These findings suggest that a return to more natural, variable river flow regimes can potentially be an important conservation and restoration strategy in ecosystems characterised by species that have adaptations to extreme hydrological growing conditions.     

The relationship between offspring size and performance in the sea

The historical focus on offspring size has been to explain variation among populations, but there have been few attempts to determine whether variation is greatest at population scale. Offspring size variation is typically viewed as an adaptive response to changes in the relationship between offspring size and performance, yet direct tests remain elusive. We partitioned natural variation in offspring size for a marine invertebrate, Watersipora subtorquata, at a range of spatial and temporal scales across southeastern Australia, and we estimated the relationship between offspring size and performance at each population and time. There was significant variation in offspring size among populations, but regional differences explained only approximately 25% of the observed variation, suggesting that there should be a greater focus on small-scale variation in offspring size. We used our data to parameterize an optimality model to generate predictions of offspring size among different populations and times. Differences in the relationship between offspring size and postmetamorphic performance (and therefore changes in size of offspring that were predicted to maximize maternal fitness) among populations and times were associated with differences in offspring sizes among those populations and times. We suggest that interpopulation variation in offspring size can be an adaptive response to local conditions, but the optimal offspring size is surprisingly dynamic.     

The biology of Bracon celer as a parasitoid of the olive fruit fly

A series of laboratory experiments was conducted on a colony of Bracon celer Szépligeti (Hymenoptera: Braconidae) reared on the olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae). Female B. celer preferentially probe and oviposit into olives containing late third-instar fly larvae. The parasitoid develops as a solitary, ectoparasitic idiobiont. Mean development time (oviposition to adult eclosion) at 22 °C was, for females, 36±1 (SE) days, and for males, 34±1 days. The mean longevity of adult female wasps when provided honey and water was significantly greater than when they were provided water alone, or nothing. The females produced an average of 9.7±7.2 progeny during their lifetimes, but production levels in the insectary colony suggested that this level of fecundity was artificially low and could be improved. The discrepancy may be a consequence of constraints on oviposition behavior imposed by the experimental design. The results are discussed with respect to insectary production methods and the potential use of B. celer as a biological control agent for olive fly in California.