Chromosomal and histological changes in the reproductive organs of infertile men

Summary The chromosomal changes in the process of spermatogenesis in 27 infertile men have been examined. Normal chromosomal meiotic activity was found in 44% of cases, various chromosomal anomalies were seen in 18%, and no cells in meiosis were detected in 37% of cases.     

Effect of cannabinoids on progesterone production by ovarian granulosa cells of pig and rat

Various cannabinoids inhibited both basal and FSH-stimulated progesterone synthesis by pig and rat granulosa cells $\text{in vitro}$ in a dose- (0.09 – 16 μM) and time- (4 – 24 h) dependent manner. The data present further evidence for a possible direct interference of cannabinoids with ovarian functions.     

Characterization of gluconeogenesis in hepatocytes isolated from the American eel,Anguilla rostrata LeSueur,

Summary Isolated hepatocyte preparations from fed immature American eels,Anguilla rostrata Le Sueur, were used to study gluconeogenic, lipogenic, glycogenic and oxidative rates of radioactively labelled lactate, glycerol, alanine and aspartate. Eel hepatocytes maintain membrane integrity and energy charge during a 2 h incubation period and are considered a viable preparation for studying fish liver metabolism.Incubating eel hepatocytes with 10 mM substrates, the following results were obtained: glycerol, alanine and lactate, in that order, were effective gluconeogenic substrates; these three substrates reduced glucose release from glycogen stores, while aspartate had no such effect; lactate, alanine and aspartate led to high rates of glycerol production, with subsequent incorporation into lipid; incorporation into glycogen was low from all substrates; and, alanine oxidation was seven times higher than that observed with other substrates.When eel hepatocytes were incubated with low or physiological substrate concentrations gluconeogenic rates from lactate were twice those from alanine; rates from aspartate were very low. Glucagon stimulated lactate gluconeogenesis, but not amino acid gluconeogenesis, and had no significant effect on glycogenolysis. Cortisol increased gluconeogenic rates from 1 mM lactate.Thus, in the presence of adequate substrate, eel liver gluconeogenesis is preferentially stimulated relative to glycogenolysis to produce plasma glucose. These data support three important roles for gluconeogenesis: the recycling of muscle lactate, the synthesis of glucose from dietary amino acids to supplement glucose levels, and the production of glycerol for lipogenesis.This work was supported from operating grants to TWM from the National Research Council of Canada (A6944)     

Studies onSargassum

Summary Cytological comparisons of homologous tissues in blades and stipes by stereological analysis have shown differences exist between blade and stipe organs inSargassum. Based on measurements of total thylakoid and cristae membrane surface areas in these organs blades were found to contain 61% more thylakoid membrane surface and 65% more cristae membrane than stipes on a per unit volume basis. Assuming photosynthesis and respiration are directly related to the surface area of the internal membranes in the respective organelles it is possible to predict that blades will have a 61% greater photosynthetic and a 65% greater respiratory potential. Photosynthetic and respiratory rates for blades and stipes were determined manometrically and show a 62% greater photosynthetic and 59% greater respiratory rates for the blade tissues agreeing very well with predicted values.Present evidence indicates that photosynthetic and respiratory rate differences observed in the blades and stipes inSargassum are the result of increased membrane surface areas in the larger cells of the tissues which make up the blade. The basic cell structure,i.e., the percent volume of cell cytoplasm occupied by each organelle, is similar in homologous tissues of both organs regardless of cell size. Therefore physiological differences between the two organs are primarily due to changes in cell size and not in basic cell construction. This provides an interesting mechanism for producing physiological differences without changing basic cell structure in the organs of this plant.     

Fine structure and metabolism of multiply innervated fast muscle fibres in teleost fish

Summary Both the fast and slow muscle fibres of advanced teleost fish are multiply innervated. The fraction of slow-fibre volume occupied by mitochondria is 31.3%, 25.5% and 24.6%, respectively, for the myotomal muscles of brook trout (Salvelinus fontinalis), crucian carp (Carassius carassius), and plaice (Pleuronectes platessa), respectively. The corresponding figures for the fast muscles of these species are 9.3%, 4.6% and 2.0%, respectively. Cytochrome-oxidase and citrate-synthetase activities in the fast muscles of 9 species of teleost range from 0.20–0.93 moles substrate utilised, g wet weight muscle^-1 min^-1 (at 15° C) or around 4–17% of that of the corresponding slow fibres. Ultrastructural analyses reveal a marked heterogeneity within the fast-fibre population. For example, the fraction of fibres with <1% or >10% mitochondria is 0,4,42% and 36, 12 and 0%, respectively, for trout, carp and plaice. In general, small fibres (<500 m²) have the highest and large fibres (>1,500 m²) the lowest mitochondrial densities. The complexity of mitochondrial cristae is reduced in fast compared to slow fibres.Hexokinase activities range from 0.4–2.5 in slow and from 0.08–0.7 moles, g wet weight^-1 min^-1 in fast muscles, indicating a wide variation in their capacity for aerobic glucose utilisation. Phosphofructokinase activities are 1.2 to 3.6 times higher in fast than slow muscles indicating a greater glycolytic potential. Lactate dehydrogenase activities are not correlated with either the predicted anaerobic scopes for activity or the anoxic tolerances of the species studied. The results indicate a considerable variation in the aerobic capacities and principal fuels supporting activity among the fast muscles of different species. Brook trout and crucian carp are known to recruit fast fibres at low swimming speeds. For these species the aerobic potential of the fast muscle is probably sufficient to meet the energy requirements of slow swimming.     

The production of 6-aminopenicillanic acid by a multistage tubular reactor packed with immobilized penicillin amidase

A theoretical model equation was derived to find the correlation between the conversion and the amount of immobilized penicillin amidase in column. The theoretical values of the conversion were predicted form this correlation and compared with experimental results. It was observed in a column reactor that the pH drop along the column path was linear versus the enzyme loading and that the enzyme activity was also linearly dependent on pH up to 8.0. In order to diminish the effect of pH drop, a continuous two-stage plug-flow reactor (PFR) with pH adjustment between the two columns was used was used in the experiments, and two- and three-stage PFRs were simulated by computer. In the case of the two-stage PFR, the maximum productivity was demonstrated experimentally and theoretically as well. when an equal amount of the immobilized enzyme was packed in both columns. It was also predicted in the tree-stage PFR system that the optimal distributions of enzyme loading in three columns were found to be 1:1:1. It was demonstrated that the increased number of reactors in series could enhance the level of the maximum productivity with a given amount of enzyme loading.     

Karyotaxonomical studies in theJuncus bufonius aggregate in Slovakia

Karyotaxonomical investigations into theJuncus bufonius aggregate in Slovakia revealed the existence of three cytodemes, namely 2n=34, 2n=c. 72, 2n=c. 100–110.     

Mutants of initiator tRNA that function both as initiators and elongators

We describe the effect of mutations in the acceptor stem of Escherichia coli initiator tRNA on its function in vivo. The acceptor stem mutations were coupled to mutations in the anticodon sequence from CAU----CUA to allow functional studies on the mutant tRNAs in initiation and in elongation in vivo. We show that, with one exception, there is a good correlation between the kinetic parameters for formylation of the mutant tRNAs in vitro (preceding paper, Lee, C.P., Seong, B. L., and RajBhandary, U.L. (1991) J. Biol. Chem. 266, 18012-18017) and their activity in initiation in vivo. These results suggest an important role for formylation of initiator tRNA in its function in initiation, at least when it is aminoacylated with glutamine as is the case with the mutant tRNAs used here. Mutant tRNAs that have a base pair between nucleotides 1 and 72 at the top of the acceptor stem function as elongators, as analyzed by their ability to suppress an amber mutation in the E. coli beta-galactosidase gene. One of these mutants is also quite active in initiation. Thus, activities of a tRNA in initiation and elongation steps of protein synthesis are not mutually exclusive. Using a mRNA with two in frame UAG codons, we show that this mutant tRNA can both initiate protein synthesis from the upstream UAG and suppress the down-stream UAG. We discuss the potential use of tRNAs with such "dual" functions in tightly regulated expression of genes for proteins in E. coli.     

牛病毒性腹泻病毒RNA的cDNA合成及其分子杂交的研究

BVDV(牛病毒性腹泻病毒)是一类有重要经济价值的病毒,其核酸为单链RNA。该病毒提纯以后.用苯酚-氯仿-异戊醇提取RNA.在提取的BVDy RNA中所含的DNA杂质用DNase I降解除去,然后进一步用oligo dT纤维素拄亲和层析,琼脂糖凝胶电泳等方法纯化。纯化的BVDV RNA在E.coli,poly A聚合酶的催化作用下,在3’羟基末端聚腺化。cDNA在逆向转录酶的作用下,用polyA接尾的BVDV RNA作模板,oligodT_12—18作引物合成。琼脂糖凝胶电泳结果说明它与BVDV RNA相似。该cDNA的探针用斑点杂交方法与BVDV RNA,HCV RNA和酵母tRNA杂交,BVDV RNA和HCVRNA显阳性反应,酵母tRNA显阴性反应,结果说明合成的cDNA为BVDV RNA的cDNA。BVDV和HCV同为披盖科疫病毒属成员,它们具有部分相同的抗原,因此编码病毒蛋白的RNA序列具有同源序列,本研究证实了这种假设。