pH dependence of hormonal regulation of gluconeogenesis and urea synthesis from glutamine in suspensions of hepatocytes

Hepatocytes from rats deprived of food for 48 h synthesized glucose and urea from glutamine at a rate which, at pH 7.3, was markedly stimulated (175-250%) by dibutyryl cAMP, phenylephrine, and norepinephrine, in agreement with previous investigators. These effectors also stimulated respiration, elevating ATP production by the amount required for the increase in glucose and urea synthesis. Both the basal and stimulated rates were strongly pH dependent with maxima in the region of pH 7.2-7.6 (urea synthesis) and 7.2-7.5 (glucose synthesis) and declined rapidly on either side of these pH values. The inhibitions at acid and alkaline pH were neither due to lack of energy nor to limitation in glutamine uptake. The intracellular concentrations of aspartate, glutamate, and glutamine were lower at pH 6.7 than at pH 7.3 and were differently affected by dibutyryl cAMP and phenylephrine at the two pH values investigated. When calcium was omitted from the suspending medium, the basal rates of glucose and urea production were decreased as was stimulation by the effectors, phenylephrine completely, and the others partially. The stimulations by phenylephrine and dibutyryl cAMP were additive under all conditions tested. The pattern of metabolite changes indicates that although both effectors stimulated glutaminase and increased supply of aspartate to the argininosuccinate synthetase, dibutyryl cAMP gave greater activation of glutaminase whereas the adrenergic agonists gave greater stimulation of later steps on the biosynthetic pathways. It may be physiologically important than at acid pH both ureagenesis and gluconeogenesis are severely suppressed and cannot be effectively stimulated by the major hormonal regulators of these pathways.     

The influence of proteases on the activity of glucoamylase from Aspergillus niger C

Summary Two proteases from Aspergillus niger C post-culture medium were isolated by fractionation on a DEAE-sepharose column and ultrafiltration. The four fractions of glucoamylase activity (GA1, GA2, GA3 and GA4) present in the medium showed different susceptibility to the influence of proteases. The effects of proteases on the different glucoamylase fractions during the growth of the fungus are demonstrated. The activity was found to decrease at the beginning of the culture, but by its end there was a stimulation of GA4 glucoamylase. After treating GA2 and GA3 with protease II, a new additional fraction of glucoamylase was detected.     

Crosslinking of chromosomal antigen common in human tumors to DNA by cis-diamminedichloroplatinum (II)

The antisera specific for dehistonized Hela cell chromatin were obtained by injecting rabbits or goats. Treatment of chromatin with cis-DDP crosslinked the active proteins to DNA thus preventing dissociation of the proteins in a high salt environment.Immunochemical staining of electrophoretically separated chromosomal proteins transferred to nitrocellulose sheets revealed that cis-DDP among others crosslinked the protein with m.w. of about 81 000. This protein is the only major protein antigen presented in several human tumors and absent in normal human tissues.     

Effect of dexamethasone and hydrocortisone on the course of superovulation in cattle

The effect of hydrocortisone and dexamethasone on superovulation was examined in 12 cows. On the day PMSG was given, each animal received either the first of five daily doses of 250 mg succinate hydrocortisone or one injection of 30 mg dexamethasone. In the 48-hr interval between the injection of PMSG and PGF(2)alpha, the concentration of progesterone rose from 6.97 to 10.22 ng/ml in the experimental groups and only to about 2.8 ng/ml in the control group. In the following days progesterone increased even more, from 15.7 to 26.0 ng/ml seven days after estrus in the experimental group and to 19.25 ng/ml in the control group. The group which received dexamethasone had an average of 4.7 corpora lutea and one embryo flushed per animal. The hydrocortisone group had an average of 2.5 corpora lutea and one cow had two embryos. The control group had 6.2 corpora lutea and 5.2 embryos per animal.     

Lignocellulose biotransformation with immobilized cellulase,d-glucose oxidase and fungal peroxidases

Three enzymes, cellulase [see 1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4], d-glucose oxidase (β-d-glucose: oxygen 1-oxidoreductase, EC 1.1.3.4) and peroxidase (donor:hydrogen peroxide oxidoreductase, EC 1.11.1.7) immobilized on glass beads, have been incubated with lignocellulose. Fungal peroxidases from Trametes versicolor and Inonotus radiatus when mixed with cellulase and d-glucose oxidase were able to liberate phenolic compounds and d-glucose from lignocellulose. Three lignin monomers were identified. When the immobilized enzymes were incubated individually with lignocellulose they did not degrade lignin.     

The respiration and calcium content of heart mitochondria from rats with vitamin D-induced cardionecrosis.

Mitochondria were isolated from the heart and skeletal muscle of rats treated with three consecutive daily doses of 100 000 i.u. of calciol (cholecalciferol; 'vitamin D3'). On the fourth day after the last dose, cardiac necrosis developed. At that time mitochondria isolated from heart displayed a 10-fold higher Ca2+ content and a 6-fold lower respiratory rate with pyruvate-plus-malate as substrate as well as with other NAD-dependent substrates. No decrease in respiratory rate with succinate as substrate was observed. EDTA (5 mM) added to the medium during the isolation procedure restored both the high respiratory rate with pyruvate + malate and the low Ca2+ content of the heart mitochondria. The addition of 1 mM-CaCl2 to the medium in which a healthy (control) rat heart had been homogenized caused the same impairment of the mitochondria as did calciol treatment of the animals. No changes of mitochondria isolated from skeletal muscle were observed in rats treated with calciol. It is concluded that the heart mitochondria in vivo fail to accumulate Ca2+ from the cardiac cell overloaded with Ca2+ as the consequence of calciol treatment. Mitochondrial Ca2+ accumulation occurs during the isolation procedure unless an appropriate amount of chelating agent is added to the homogenization medium. The implication of these findings for the biochemical sequence of events in the calciol-induced cardiac necrosis is discussed.     

Non-histone chromatin protein fractions associated with ‘active’ chromatin in embryonic chicken liver

Non-histone chromatin proteins synthesized during chicken embryonic liver development were labeled with [3H]tryptophan and [3H]methionine and characterized by electrophoresis. During embryonic development protein/DNA ratio in chromatin was low (1.30-1.62) but synthesis of non-histone protein was high. Especially one characteristic fraction K (MW 18 000), tightly bound with DNA was preferentially associated with DNAase II sensitive, active transcribed sequences. In 7-day old and adult chicken synthesis of all non-histone proteins was low, fraction K was absent or synthesized only in small amounts in association with non-active sequences, however protein/DNA ratio in chromatin was high (2.30-2.33).     

Differentiation and frequency distributions of body weights in plants and animals

The basic and simplest system that one can consider in ecology is a group of individuals of equal age and representing one species, that is, a cohort. This paper is an attempt to show that analysis of such a system may be of great importance to understanding basic ecological problems, such as, intraspecific competition and the dynamics of a single population. It is easy to observe that in even-aged populations individuals differ in weights. A close look can show that weight distributions in even-aged populations may have different skewness. Most common are distributions with coefficients of skewness greater than zero. Sometimes weight distributions are symmetrical or with skewness coefficients less than zero. In a cohort of growing individuals the coefficient of skewness changes with time: most often starting from zero (symmetrical distribution), it increases in time; sometimes after an initial increase it can decrease in the final stage of growth, which is related to an increased mortality of individuals. The rate of change in skewness, and the skewness itself depend on the density of individuals in a cohort and on food conditions. They are greater at higher densities and increase with deteriorating food conditions. Weight distributions are symmetrical at low densities and optimal food conditions. The differences in individual weights measured by variance of weight distributions or coefficient of variation follow the same pattern, but observed changes with time, density and food conditions are not so clear. These conclusions rest upon the review of numerous papers concerning both plants and animals, which is presented in this paper. In the past, the properties of weight distributions in even-aged populations were explained not by interactions between individuals, but rather as a natural outcome of the growth process of non-interacting individuals. The exponential equation of growth, with relative growth rate having a normal distribution in populations, was used to support this hypothesis. Obtained weight distributions were of positive skewness; however, this model, which in fact is able to describe the growth process only in its initial stage, cannot explain the changes of skewness of weight distributions with density and food conditions. A model has been developed which includes competitive interactions among members of even-aged populations to explain observed properties of weight distributions in them. The basic assumption is that intraspecific competition leads to uneven partitioning of resources, which are the object of competition. Functions describing resource partitioning among individuals are included into the model.(ABSTRACT TRUNCATED AT 400 WORDS)