Cultivation of trematodes in chick embryos

The chick embryo can be used as a substitute for adult animals in the cultivation of a variety of parasites. Bernard Fried describes its use in cultivating trematodes, and suggests that the system might be useful as a preliminary chemotherapeutic screen.     

The heat generated by yeast cultures with a mixed metabolism in the transition between respiration and fermentation

The heat generated by both batch and continuous cultures of the yeast K. fragilis was studied using a modified Bench Scale Calorimeter. Batch cultures were used to measure the heat dissipation rates and the heat yields during fully aerobic and completely anaerobic growth, whereas continuous cultures enabled, in addition, a quantitative study of heat dissipation rates during growth on mixed metabolism. In this case, the extent of fermentation versus respiration could be specified and controlled by varying the degree of oxygen limitation. The heat dissipated per unit biomass formed was highest for fully respirative catabolism and fell continuously to a much lower value typical of anaerobic cultures as the catabolism was shifted increasingly to the fermentative mode. The heat generated per mole of oxygen taken up stayed quite close to the fully aerobic value of 506 kJ mol(-1) even when a sizable fraction of the substrate available to catabolism was fermented. If the fraction of respiration in the metabolism is lowered beyond a certain threshold, the ratio of the heat generation to oxygen consumption starts to increase dramatically and finally tends to infinity for fully anaerobic growth. All experimental results were quantitatively analyzed and explained on the basis of a simple model which formally describes the cultures in terms of two parallel "chemical" reactions. In simple cases such as the one presented here, the model enables calculation of the whole stoichiometry of the culture from a single measured heat yield.     

南斯拉夫的洞穴生物学

洞穴生物生活在地下。地下栖息场所最主要的特点是永远处于黑暗中,无自养生物,食物的种类和数量非常贫乏。当然,栖息地的大小以及其他非生物特征各有不同。来自地表食物极少的碎石间的空隙,也属于地下栖息地。但最主要的是喀斯特洞穴,尤其是在石灰岩地区形成的洞穴。溶岩流中的溶岩隧道是一类特殊     

The flea ovary: ultrastructure and analysis of cell clusters

Panoistic ovarioles are found in the order of fleas (Siphonaptera). Only in some species of the Hystrichopsylloidea do polytrophic meroistic ovaries occur. No stem cells and no dividing cystocytes are found in female imagines of Hystrichopsylla talpae. However, each germ cell cluster consists of 32 cells which are generated by five mitotic cycles during the pupal stage. One of the cells containing five intercellular bridges becomes the oocyte, the others serve as nurse cells. Thus, germ cell cluster formation follows the 2(n)-rule. However, no polyfusome is found and nurse cells do not form a rosette. Furthermore, nurse cells remain small and show the same ultrastructural characters as the oocytes, which became distinguishable from nurse cells only by their enhanced growth during pre-vitellogenesis. The first phase of pre-vitellogenesis is dominated by the production of an unknown cytoplasmatic component, consisting of spherical particles, clearly distinguishable from ribosomes by diameter and contrast. The next phase is characterized by a tremendous increase in the production of ribosomes. During this second phase another cytoplasmic component consisting of ball-like structures becomes prominent. During pre-vitellogenesis, germ cell nuclei undergo a pronounced structural change in which, finally, numerous extranucleolar particles predominate. Thus, H. talpae has a polytrophic meroistic ovary, but its oocyte genomes behave panoistically.     

Eye muscles of the pike (Esox lucius) fiber types and their actomyosin ATPase and SDH activity

The eye muscles of the pike are organized in two distinct populations of fibers arranged in semicircular layers. The distal layer, consisting of small diameter muscle fibers, is mainly made up of type I and tonic (slow) fibers. The central and proximal (facing the eyeball) parts of the eye muscles are occupied by IIB and IIC (fast) fibers. As a main criterion for identification of muscle fiber types, the reaction for actomyosin ATPase activity has been used: metabolic characterization of these fibers has been carried out on the basis of SDH activity.     

Ovarian function and pregnancy rates in reindeer calves (Rangifer tarandus ) in Southern Norway

Reindeer calves (n = 632) were slaughtered in November/December (n = 476) or in January (n = 156). Dressed weights and amount of perirenal fat were recorded, and the reproductive organs were collected. A separate group of 130 reindeer calves were weighed at 7 months of age and were followed up with repeated weighings and pregnancy examinations up to 21 months. The onset of puberty and the pregnancy rate were significantly influenced by body weight and the amount of perirenal fat. Approximately 60 g of perirenal fat and 22 kg dressed weight were found at the lower limits for pregnancy. A total of 222 (35%) animals had reached puberty and 126 (20%) were pregnant when examined after slaughter. Animals which conceived during their first autumn showed only a moderate weight gain the following year, and the calf mortality rate in these animals was 47.4%. It was concluded that calf pregnancies are common among the reindeer of Southern Norway and that measures need to be taken to prevent them.     

The production of cellulase in a spouted bed fermentor using cells immobilized in biomass support particles

Continuous cellulase production by Trichoderma viride QM 9123, immobilized in 6 mm diameter, spherical, stainless steel biomass support particles, has been achieved using a medium containing glucose as the main carbon source. Experiments were carried out in a 10-L spouted bed fermentor. In this type of reactor-recycled broth is used to create a jet at the base of a bed of particles, causing the particles to spout and circulate. During the circulation, particles pass through a region of high shear near the jet inlet. This effectively prevents a buildup of excess biomass and thus enables steady-state conditions to be achieved during continuous operation. Continuous production of cellulase was achieved at significantly higher yield and productivity than in conventional systems. At a dilution rate of 0.15 h(-1) (nominal washout rate for freely suspended cells is 0.012 h(-1)), the yield of cellulase on glucose was 31% higher than that measured during batch operation, while the volumetric productivity (31.5 FPA U/L. h) was 53% greater than in the batch system. The specific cellulase productivity of the immobilized cells was more than 3 times that of freely suspended cells, showing that diffusional limitations can be beneficial. This offers significant opportunity for the further development of biomass support particles and associated bioreactors.