Activation of mitochondrial glycerol 3-phosphate dehydrogenase by cadmium ions

Mitochondrial glycerol 3-phosphate dehydrogenase (EC 1.1.2.1.) requires Ca2+ ions for its activity. Cadmium ions also have activatory effect on the enzyme. They activate the glycerol 3-phosphate dehydrogenase in a very narrow concentration range (1-2 mmol/l). As contrasted with calcium, strong inhibitory effect occurred at higher concentrations (3-4 mmol/l). The inhibition induced by cadmium ions was completely reversible by washing of the mitochondria.     

Relation of coenzyme F420 to the activity of methanogenic microorganisms

Summary The relationship between the coenzyme F₄₂₀ content and the activity of methanogenic microorganisms was investigated under different cultivation conditions in anaerobic reactors. The coenzyme F₄₂₀ concentration depends on the substrate used and the cultivation conditions. Coenzyme F₄₂₀ appears not to be a measure of the total methanogenic activity but rather a measure of the amount of methanogenic microorganisms in mixed anaerobic cultures.     

Entrainment of split circadian activity rhythms in hamsters

Hamsters that showed splitting of their circadian rhythms of wheel-running activity following long-term exposure to constant illumination (LL) were exposed to light-dark (LD) cycles with 2-hr dark segments, and with periods of 24.00, 24.23 or 24.72 hr. For comparison, hamsters showing nonsplit rhythms were also studied. In all cases of split rhythms, at least one of the two split components entrained to the LD cycles. In some animals, the second component continued to free-run until it merged with the entrained component, while in others, the second component also entrained to the LD cycle but maintained a stable phase angle of 6-14.5 hr relative to dark onset. These results were obtained in cases where the period of the LD cycle was shorter than that of the split rhythms and in cases where it was longer, implying that split components can be phase-advanced as well as phase-delayed by 2 hr of darkness. Three hamsters that showed stable entrainment of split rhythms were allowed to free-run in LL. The LD cycles were then reinstated, but instead of overlapping with the first component, as it did before, the dark segment was timed to overlap with the second. The entrainment patterns that ensued were similar to the ones obtained during the first LD exposure, indicating that the two split components respond to darkness in a qualitatively similar fashion. These results are further evidence that the pacemaker system underlying split circadian activity rhythms in hamsters is composed of two mutually coupled populations of oscillators that have similar properties, including a bidirectional phase response curve. Such a dual-oscillator organization may also underlie normal, or nonsplit, activity rhythms, as suggested by Pittendrigh and Daan (1976c), but the data are also compatible with the alternative view that the circadian pacemaker consists of a large number of coupled oscillators, which only dissociate into two separate populations in some animals under conditions of moderate LL intensity.     

Effects of fructose on human fibroblast metabolism: the application of DNA measurements as a basis for interpretation

Summary A fluorometric procedure for measuring DNA was used to study growth and metabolic responses of eight cell strains of human foreskin fibroblasts. In preliminary studies this procedure gave more precise specific activity changes inN-acetyl-β-d-glucosaminidase (NAG) than did a protein activity basis, when changes in this enzyme's specific activity were investigated as a function of experimental cell manipulation. When fibroblast growth in eight cell strains was compared in 134 mM d-fructose vs. 13.4 mM glucose-supplemented minimum essential media, a significant increase in cellular DNA (50%) and protein (45%) occurred over an 11-d period. No significant differences in media pH change, lactate production, or carbohydrate uptake occurred on a DNA basis when cell metabolism was compared over the last 24 h of culture in the two media. Cells grown in fructose-containing media tended to show a reduction in NAG specific activity when compared with those grown in glucose-containing media.     

Kinetic Effects of Terbium Ions on Muscarinic Acetylcholine Receptors of Murine Neuroblastoma Cells

Preincubation of murine neuroblastoma cells (clone N1E-115) with terbium chloride resulted in a significant potentiation of carbachol-mediated increase in cyclic GMP formation. This effect was accompanied by a shift of the peak response from 30 s to 120 s and a 6-fold decrease in carbachol concentration producing half-maximal responses, in addition to a significant increase in the Hill coefficient. Terbium ions also caused a significant decrease in the affinity and an increase in the maximum binding of [3H]quinuclidinyl benzilate to muscarinic receptors, the change in affinity being mainly due to a decrease in the association rate. Preincubation of cells with 1 mM carbachol for 4 h (the desensitized state of the muscarinic receptor) resulted in a decrease in the ability of terbium to alter [3H]quinuclidinyl benzilate binding. The effects of terbium reported here might be due to its affecting muscarinic receptor-effector coupling, which is considered to be lost upon receptor desensitization.     

Viability of the R, S and M variants of Mycobacterium lacticolum under various preservation conditions

The survival rate of Mycobacterium lacticolum and the proportion between its R, S and M variants were studied in the course of 12 months under different conditions of storage (freeze-drying, under vaseline oil, in 0.85% NaCl solution and in distilled water). A high survival rate of the variants was found in cells freeze-dried in a protective medium containing 10% of sucrose +1% of gelatin as well as in a 0.85% solution of NaCl.The survival rate of te variants differed by 2--3 orders of magnitude in cells freeze-dried with sodium glutamate or suspended in distilled water. The proportion between the R, S and M variants in the population noticeable changed after storage under these conditions.     

Synthesis, biodistribution, and autoradiography of radiolabeled S-2-(3-methylaminopropylamino)ethylphosphorothioic acid (WR-3689)

35S- and 3H-labeled S-2-(3-methylaminopropylamino)ethylphosphorothioic acid (WR-3689) have been synthesized in our laboratory and used to study organ and cellular level distribution in C3H/Km mice bearing RIF-1 tumors. Tissue biodistributions obtained with 35S-WR-3689 showed that blood levels peak at 15 min postinjection and decline gradually over 60 min. At 30 min after drug injection the highest uptake is in kidney and submandibular salivary gland, with lowest levels in brain and moderate to low levels in the RIF-1 tumor, comparable to levels in skin and muscle. High resolution diffusible substance autoradiography with 3H-WR-3689 reveals a homogenous distribution of label over cells in liver and lung and nonuniform distribution of silver grains over the cytoplasm of cells in the kidney cortex, parotid and submandibular salivary glands, and small intestine. There are no indications of preferential nuclear location of label from protective drug in any tissue. Correlations of biodistribution and autoradiography data with measures of radioprotection in different tissues will be useful in interpreting mechanisms of radioprotection with this phosphorothioate.     

A trial of cybernetic explanation of the development and regression of benign child epilepsy

Using as an example the verification of a hypothetic mechanism of the course of benign child epilepsy the authors demonstrate a method of simulation investigations of neuron-like networks. The structure and possibilities of a digital system for network modelling are discussed, including the properties of the neuron-like element used presently for the experiments. The results of the simulation investigations described in the second part of the paper confirm the hypothesis that an attack of benign child epilepsy is a result of transgressing of the stability border by a fragment of the neuronal network with development in it of a self-exciting activity of a neuronal group.     

Non-temperature related effects of osmotic pressure on inward sodium current in the membrane of isolated rat spinal ganglia neurons

The effects of osmotic pressure on inward sodium current during a change in temperature were investigated during experiments on isolated rat spinal ganglia neurons using techniques of intracellular perfusion and voltage clamping. It was found that the effect of osmotic pressure on the kinetic parameters of sodium current does not depend on temperature over a wide range of 8–40°C; the apparent values of activation energies for the activation and inactivation processes do not dependent on degree of osmolality. Overall findings would appear to indicate that the osmotic pressure effect is actually initiated by association with aqueous transmembrane flux. Opinions are expressed as to the location of the structures through which this aqueous flux passes and of the sodium channel gating mechanism, together which the molecular mechanisms of interaction between these two elements.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 4, pp. 518–525, July–August, 1986.