Influence of age,weaning, season and body weight on the levels of progesterone,oestradiol-17β and luteinizing hormone in growing buffalo heifers (Bubalus bubalis)

The influence of age, weaning, season of the year and body weight on the peripheral levels of progesterone, oestradiol-17β and luteinizing hormone (LH) were studied during neonatal, perinatal and peripubertal periods in buffalo heifers. The buffalo heifers exhibited oestrus only after 30 months of age and had higher levels of LH and oestradiol-17β and a lower level of progesterone on the day of oestrus. The progesterone concentration was affected significantly (P < 0.01) by different seasons, by weaning (P < 0.05) and varied between pubertal and neonatal periods (P < 0.01), whereas the oestradiol-17β level was affected significantly (P < 0.01) by weaning and varied at different seasons and with body weight. However, the LH concentration was greater during the neonatal period than the pre- and peripubertal periods and changed significantly (P < 0.01) between groups of ages and body weights. The results suggest that increases in the levels of oestradiol-17β and progesterone after 30 months of age are probably indicative of the onset of puberty in buffalo heifers. However, a further increase in oestradiol-17β, LH, and a decrease in progesterone are essential for oestrus and cyclicity to be exhibited in buffalo heifers.     

Volume and density changes of biological fluids with temperature

High-precision (10(-5) g/ml) mass density measurements on human blood, plasma, plasma ultrafiltrate (using PM-10 membranes), and erythrocyte concentrate samples were performed with the mechanical oscillator technique. Measurement temperatures varied between 4 and 48 degrees C and were accurate to +/- 1 X 10(-2) K. The coefficient of thermal expansion (beta), defined as relative volume change with temperature, was calculated. It was shown that beta increases with temperature in these fluid samples over the entire temperature range investigated; the magnitude of this increase declines with increasing temperature; beta increases with density at temperatures below 40 degrees C but is independent of density above 40 degrees C; and the beta of the intracellular fluid has about twice the value of the beta for extracellular fluid at low (4-10 degrees C) temperatures but is equal for both fluids at greater than or equal to 40 degrees C. The mechanical oscillator technique provides data with an accuracy sufficient to perform precise (10(-5) K) calculations of beta of small volumes of biological fluids.     

Alteration of domain architecture of chicken erythrocyte chromatin

The higher-order organisation of chromatin in chicken erythrocyte nuclei as a function of the ionic strength of the nuclear suspension buffer and also of the time of incubation in this buffer prior to nuclease digestion has been investigated. This organisation is described in terms of a physical parameter called the domain length. The 45-kbp-long domains of control nuclei were unravelled to give rise to domains of length 150 kbp on overnight equilibration at 0 degree C of the nuclei in standard isolation buffer containing 0.135 M NaCl prior to nuclease digestion. However, transition to the equilibrium state was preceded by a metastable and irregular domain architecture when the nuclei were incubated for only 1 h. In contrast, the domain length remained unchanged when nuclei were incubated in the isolation buffer alone for identical periods of time. The proteins dissociated at the higher ionic strength were characterised and their role in stabilising the domain structure is discussed.     

Propagation of Zea mays L. by Shoot Tip Culture: A Feasibility Study

A procedure for the stimulation of axillary bud developmentfrom young shoots of maize, their subculture to root-inducingmedia and transfer as rooted plants to soil is described. Axillarybud development was enhanced by the addition of kinetin andauxin to the culture medium. Root initiation on explanted axillarybuds, while successful with some cultivars, was variable. Anumber of mature plants with normal tassels and ears were producedfrom the lowermost buds of an original stem explant. Buds fromhigher positions on the explant exhibited different potentialitieswith some, those normally from cob producing nodes, producingshort-stalked plants with terminal female influorescences. Agradient of bud potentiality along the stem appears to be establishedextremely early after each is initiated. Zea mays., corn, maize, shoot tip culture, clone, vegetative propagation     

Catches in pitfall traps in relation to mean densities of carabid beetles

Summary Based on continuous pitfall catches summed over the whole activity period for the carabid beetles Pterostichus versicolor Sturm and Calathus melanocephalus L., a satisfactorily linear relationship is presented between the mean densities in several habitats and in different years and the numbers of beetles trapped. This means that with the help of continuous pitfall sampling a reliable relative measure of the sizes of carabid populations can be obtained.Simulation experiments show that for individuals of P. versicolor the distances covered each day should be represented by strips of some width instead of by lines to obtain numbers trapped that equal the field data. The influence on numbers trapped of the high mobility of beetles in unfavorable habitats is probably not significant. Simulation experiments with C. melanocephalus indicate that a much lower capture efficiency than for P. versicolor has to be programmed to fit the simulation results with the field data.The catch from different types of pitfalls is not always proportional to trap perimeter due to different vegetation cover of the immediate trap surroundings and to different kinds of roofs placed over the pitfalls. For the same species the capture efficiency of a pitfall can also change throughout the season.Simulation experiments show that the number and shape of the pitfalls need not influence the catches, provided that the traps keep the same total perimeter and are broadly spaced.Remodelling of some data from the literature reveals that the linear relationship between mean densities and year-catches in pitfalls is probably a general one among carabid species. This leads to the hypothesis that carabid beetles have to work through a fixed reproductive program each year by means of an almost constant total amount of locomotory activity which is realized step by step during spells of suitable weather.Some recommendations are given for intraspecific and interspecific comparisons of pitfall catches between sites and years.Communication no. 196 of the Biological Station of the Agricultural University (Wageningen), Wijster (Drenthe), The Netherlands