Inverse behaviour of "synaptic" ribbon and spherule numbers in the pineal gland of male guinea-pigs exposed to continuous illumination

Summary There is increasing evidence that pineal synaptic ribbons are a heterogeneous population of organelles. In addition to synaptic ribbons (SR) sensu stricto, which consist of an electron-dense rod surrounded by electronlucent vesicles, synaptic spherules (SS) exist, the electrondense core of which is round and much wider than that of the SR. In the guinea-pig SR and SS numbers exhibit an inverse day/night rhythmicity. To gain more insight into the functional significance of SR and SS, guinea-pigs were exposed to continuous illumination for approximately 4 months (LL) and the respective structures in the pineal gland were quantitated under the electron microscope and compared with control animals kept under a lighting regiment of 12 h light and 12 h dark. It was found that SR numbers increase following LL whereas SS numbers decrease. The proximal, intermediate and distal parts of the dumbbell-shaped organ respond differently. The increase in SR numbers is significant in the distal and intermediate regions only, whereas the decrease in SS numbers is significant in the proximal and the intermediate regions only. Within each pineal region analyses of parenchymal subareas measuring 65 m by 65 m exhibit an inverse correlation of SR and SS numbers indicating that there are parenchymal domains in which either SR or SS predominate. Morphometric analyses of a number of pinealocytic parameters reveal minor differences between different pineal regions and that exposure to LL does not strikingly affect the pinealocyte perikarya. By contrast, the numbers of pinealocyte processes increase significantly after LL in the distal and intermediate, but not the proximal region of the pineal gland. These observations suggest structural and functional differences between different parts of the guinea-pig pineal gland.     

Effects of electrical stimulation of the superior cervical ganglia on the number of “synaptic” ribbons and the activity of melatonin-forming enzymes in the rat pineal gland

Summary Melatonin metabolism in the mammalian pineal gland is under the clear influence of sympathetic fibers originating in the superior cervical ganglia (SCG). Previous studies suggested that pineal synaptic ribbons (SR) as well are regulated by the gland's sympathetic innervation. To gain more insight into the mechanisms involved, we examined the effects of sympathetic stimulation on SR number and on the activity of melatonin forming enzymes, serotonin N-acetyltransferase (NAT) and hydoxyindole-O-methyltransferase (HIOMT). The SCG in adult male rats were stimulated electrically during daytime for either 15 or 120 min. Immediately following stimulation, the glands were removed and processed for electron microscopy and for the determination of NAT and HIOMT activities. No differences in pineal SR number, size or location were found in rats stimulated with either parameters when compared with sham-stimulated or control animals. While the activity of HIOMT remained unchanged, the activity of NAT was also unaltered following 15 min of stimulation, but was augmented approximately three-fold in animals stimulated for 120 min. It is concluded that if SR in the rat pineal gland are under sympathetic control, the regulation is different from that involved in melatonin formation.     

Effect of “flow anoxia” and “non flow anoxia” on the NAD/NADH redox state of the intact brain cortex of the cat

In the present study, we compared the nicotin-amide adenine dinucleotide (NAD) reducing potencies of flow anoxia and non flow anoxia in the cat brain cortex. In animals anaesthetized with alpha-D-glucochloralose flow anoxia and non flow anoxia were produced by ventilating for 2 and 25 min, respectively, with nitrogen gas. Following non flow anoxia, the brain cortices of dead animals were superfused with oxygen saturated artificial cerebrospinal fluid (mock CSF), and subsequently with CSF containing various concentrations (10^–3–10^–1 M) of potassium cyanide. NADH (reduced NAD) fluorescence of the brain cortex was measured through a cranial window with microscope fluororeflectometer. Ventilating the animals for 2 and 25 min with nitrogen gas increased cortical NADH fluorescence (NAD reduction) by 43.5±2.8% and 135.3±6.1%, respectively. Oxygen saturated CSF superfusion of the ischemic brain cortex restored the cortical NAD/NADH redox state to the preanocic level (oxidation of NADH). 10^–1 M cyanide, applied after superfusion of the brain cortex with oxygen saturated CSF resulted in comparable NAD reduction to that produced by non flow anoxia. On the basis of these findings it is suggested that non flow anoxia leads to much greater cortical NAD reduction than flow anoxia, because oxygen tension in the cortex may not fall to zero mm Hg during nitrogen anoxia lasting for 2 min. Besides this, a more pronounced substrate mobilization and acidosis may also contribute to the greater NAD reducing potency of non flow anoxia. Finally, since 10–15 min after the death of the animal the cerebral carbohydrate reserves are completely exhausted, and in our experiments non flow anoxia, reoxygenation of the ischemic brain cortex and inhibition of the cortical mitochondrial electron transport by cyanide (10^–1 M) resulted in comparable redox state changes (as far as their magnitude is concerned), it is concluded that the recorded changes in NADH fluorescence were of mitochondrial origin.     

Reduced intramembrane charge movement in the dysgenic skeletal muscle cell

Intramembrane charge movement in skeletal muscle cells has been proposed to underlie the process leading to Ca release from the sarcoplasmic reticulum. A number of recent studies suggest that the dihydropyridine receptor located in the transverse-tubular membrane is responsible for the generation of intramembrane charge movement. The skeletal muscle cell of the mutant mouse with Muscular Dysgenesis is characterized by absence of excitation-contraction coupling. Here we investigated the charge movement in freshly dissociated skeletal muscle cells from dysgenic mice. In 9 out of 34 dysgenic mouse cells the charge movement was completely absent, in the remaining cells the charge movement was never more than 30 % of control. The amount of maximum charge movement (Q_max) in mutant muscle cells was less than 30 % of Q_max in normal muscle. Nifedipine, a dihydropyridine derivative, reduced the amount of charge movement in normal muscle cells but it was less effective on charge movement in mutant muscle cells. We conclude that there is an alteration of nifedipine-sensitive charge movement in the skeletal muscle cells from the mutant mice.     

Disturbances of the control of renin secretion in chronic one-kidney-goldblatt hypertension in the rat

Summary Systolic blood pressure (BP) and plasma renin level (p.r.l.) were measured 1. in rats with chronic one-kidney-Goldblatt hypertension before, 1 1/2 h, 6 or 24 h after unclamping or sham-operation. 2. 6 h after 50 mg/kg furosemide i.p., and again 2 h after a subsequent nephrectomy.P.r.l. in the chronic stage of one-kidney-Goldblatt hypertension did not differ from that in normal control animals. Sham-unclamping did not influence BP and did not cause a significant increase of p.r.l.1 1/2 h after unclamping BP fell considerably to still hypertensive levels while p.r.l. fell to less than half its normal value. 6 to 24 h after unclamping, BP continued to fall, while p.r.l. progressively rose to reach 78% of its normal value. Furosemide diuresis caused an increase of p.r.l., but no fall of BP. 2 h after subsequent nephrectomy p.r.l. fell to undetectable levels and BP to its normal value.The data suggest that the normal p.r.l. in the chronic stage of Goldblatt hypertension may be considered as inappropriate elevated in relation to blood pressure and sodium balance state due to partial protection of the kidney against regulatory influences by the presence of a clamp on the renal artery.Preliminary communication: Helmchen and Kneissler, 1971.Supported by Deutsche ForschungsgemeinschaftSupported by Fonds National Suisse de la Recherche Scientifique, Grants No. 5313.3 and 3369.70.     

Skeletal muscle: Dependence of potassium contractures on extracellular calcium

Summary The effects of Ca-free salines were tested in frog skeletal muscle fibres. It was found that the decrease of the (Ca) in the saline from 1.8 mM to about 3.2×10^–10 M (with 4 mM Mg present) did not change the resting potential of the fibres and the depolarizations induced by 40 and 80 mM K. The action potentials, however, were significantly reduced in amplitude and duration by 24% and 33% respectively. K contractures induced with a 117 mM KCl saline had a peak and a slow component. The exposure of the fibres to a Ca-free saline [(Ca)ca. 1.6×10^–9M] for 40 sec reduced the slow component to 39±16.5% (mean±s.e; 6 fibres) of the control value. The peak component, on the other hand, was slightly decreased to 78±10.5%. These effects were reversible.The inhibition of the K contractures by extremely low (Ca)_o cannot be explained by an alteration of the electrical properties of the muscle fibres or by a depletion of the Ca content of the sarcoplasmic reticulum. It is postulated that the drastic removal of external Ca reduces the driving force for a Ca influx that may take place during the excitation of the muscle and that may be essential for the excitation-contraction coupling.This work was supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina (CONICET) and, partially, from the USPHS (ROI-NS 06935-03NEUA).     

Discussion of genetics and mental health

The preceding articles by Kety, Gershonet al., and Omenn are discussed. Ongoing research on children of one or two schizophrenic parents is described as representing the opportunity to study precipitating environmental factors.This was presented at the Annual Meeting of the American Society of Human Genetics, Portland, Oregon, October 18, 1974.     

“Exercise pyrogens”

Blood plasma taken from subjects either at rest or during muscular exercise was injected intravenously into rabbits. The rectal temperature of the animals changed differently: After injection of exercise plasma the temperature was at a higher level. This effect can be explained by the presence of exercise pyrogens in the plasma.Department of Physiology, Moscow Regional Institute of Physical Culture, Malakhova, Moscow Province. (Presented by Academician of the Academy of Medical Sciences of the USSR V. A. Negovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 88, No. 8, pp. 144–145, August, 1979.     

Distant intercellular electromagnetic interaction between two tissue cultures

Experimental data on distant intercellular electromagnetic interaction between two tissue cultures when one of them is exposed to factors of biological (viruses) or chemical (mercuric chloride) nature are presented; the characteristic response of the intact culture is in the form of a mirror cytopathic effect.Laboratory of Biophysics, Institute of Clinical and Experimental Medicine, Siberian Branch, Academy of Medical Sciences of the USSR, Novosibirsk. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 89, No. 3, pp. 337–339, March, 1980.     

Rapid effect of insulin on labelling of bis-phosphoenolpyruvate

Summary The time course of the insulin effect on 1,2-bis-phosphoenolpyruvate (bis-PEP), a glucose metabolite, has been investigated. Within 30 sec insulin causes an increase of 60% in the amount of bis-PEP accumulated in incubation media of rat diaphragms.     

Human arm stiffness characteristics during the maintenance of posture

Summary When the hand is displaced from an equilibrium position, the muscles generate elastic forces to restore the original posture. In a previous study, Mussa-Ivaldi et al. (1985) have measured and characterized the field of elastic forces associated with hand posture in the horizontal plane. Hand stiffness which describes the relation between force and displacement vectors in the vicinity of equilibrium position was measured and graphically represented by an ellipse, characterized by its size, shape and orientation. The results indicated that the shape and orientation of the stiffness ellipse are strongly dependent on arm configuration. At any given hand position, however, the values of these parameters were found to remain invariant among subjects and over time. In this study we investigate the underlying causes for the observed spatial pattern of variation of the hand stiffness ellipse. Mathematically analyzing the relation between hand and joint stiffness matrices, we found that in order to produce the observed spatial variations of the stiffness ellipse, the shoulder stiffness must covary in the workspace with the stiffness component provided by the two-joint muscles. This condition was found to be satisfied by the measured joint stiffness components. Using anatomical data and considering the effects that muscle cross-sections and changes in muscle moment arms have on the joint stiffness matrix, we found that these anatomical factors are not sufficient to account for the observed pattern of variation of joint stiffness in the workspace. To examine whether the coupling between shoulder and two-joint stiffnesses results from the coactivation of muscles contributing to these stiffnesses, EMG signals were recorded from shoulder, elbow and two-joint muscles. Our results indicated that, while some muscle coactivation may indeed exist, it can be found for only some of the muscles and in only part of the workspace.     

Development of traumatic shock accompanied by increased activity of polyspecific antibodies reacting with DNA and endotoxins

Department of Radiation Biochemistry, Research Institute of Medical Radiology, Academy of Medical Sciences of the USSR, Obninsk. Central Research Laboratory, Rostov Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Nasonova.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 111, No. 5, pp. 538–539, May, 1991.     

In vitro contractility of the hypertrophied right ventricle of rats with pulmonary hypertension due to confinement in “hypoxic cages”

Summary Four weeks' confinement of rats in individual airtight cages with walls of defined permeability for respiratory gases induced hypoxic pulmonary hypertension and right ventricular hypertrophy.Parameters of isometric contractility of strips of hypertrophied right myocardium did not show significant changes when compared with the parameters of the inotropic state of slices of normal right ventricle.     

A cyclin protein modulates mitosis in the budding yeast Saccharomyces cerevisiae

Summary For the budding yeast Saccharomyces cerevisiae the mitotic cell cycle is coordinated with cell mass at the regulatory step start. The threshold amount of cell mass (reflected as a critical size) necessary for start is proportional to nutrient quality. This relationship leads to a transient accumulation of cells at start, termed nutrient modulation, upon enrichment of nutrient conditions. Nutrient enrichment abruptly increases the critical size needed for start, causing the smaller cells, produced in the previous cell cycle, to be delayed at start while growing larger. Here we show that, in S. cerevisiae, a second cell-cycle step, at mitosis, also exhibits nutrient modulation, and is, therefore, another point of cell-cycle regulation. At both mitosis and start, nutrient modulation was found through mutation to be regulated by the activity of the cyclin-related WHI1 (CLN3) gene product.