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.     

Lipid/myelin basic protein multilayers. A model for the cytoplasmic space in central nervous system myelin

A multilayered complex forms when a solution of myelin basic protein is added to single-bilayer vesicles formed by sonicating myelin lipids. Vesicles and multilayers have been studied by electron microscopy, biochemical analysis, and X-ray diffraction. Freeze-fracture electron microscopy shows well-separated vesicles before myelin basic protein is added, but afterward there are aggregated, possibly multilayered, vesicles and extensive planar multilayers. The vesicles aggregate and fuse within seconds after the protein is added, and the multilayers form within minutes. No intra-bilayer particles are seen, with or without the protein. Some myelin basic protein, but no lipid, remains in the supernatant after the protein is added and the complex sedimented for X-ray diffraction. A rather variable proportion of the protein is bound. X-ray diffraction patterns show that the vesicles are stable in the absence of myelin basic protein, even under high g-forces. After the protein is added, however, lipid/myelin basic protein multilayers predominate over single-bilayer vesicles. The protein is in every space between lipid bilayers. Thus the vesicles are torn open by strong interaction with myelin basic protein. The inter-bilayer spaces in the multilayers are comparable to the cytoplasmic spaces in central nervous system myelins . The diffraction indicates the same lipid bilayer thickness in vesicles and multilayers, to within 1 A. By comparing electron-density profiles of vesicles and multilayers, most of the myelin basic protein is located in the inter-bilayer space while up to one-third may be inserted between lipid headgroups. When cytochrome c is added in place of myelin basic protein, multilayers also form. In this case the protein is located entirely outside the unchanged bilayer. Comparison of the various profiles emphasizes the close and extensive apposition of myelin basic protein to the lipid bilayer. Numerous bonds may form between myelin basic protein and lipids. Cholesterol may enhance binding by opening gaps between diacyl-lipid headgroups.     

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.     

The Electrical Conductivity of Bovine Milk in Mastitis Diagnosis

The electrical conductivity (EC) of milk is mainly a function of the electrolyte concentration in the milk and therefore raised in mastitis. The present investigation was aimed at elaborating, if possible, a diagnostic model for screening purposes based on EC determinations and consistent with the diagnostic procedures and interpretations commonly used in laboratory milk diagnosis in the Nordic countries (Klastrup 1975). According to this diagnosis (here called reference diagnosis) cell numbers above 300,000/ml (cell count or the corresponding CMT-score) in foremilk quarter samples during the main part of the lactation period and significantly above the lowest value on within-udder comparison during late lactation are considered indicative of mastitis and bacteriological examinations are made when called for.     

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.     

Expression of L3T4 molecules on Lyt-2+, class II-restricted antigen-specific T suppressor lymphocytes

Three bovine serum albumin-specific Lyt-2⁺ T suppressor (Ts) cell clones from CBA/J mice have been analyzed with regard to expression of L3T4 molecules. All three Ts-cell clones can be stained with monoclonal antibodies (mAb) to L3T4. Tested for the two clones restricted to recognition of E^k determinants, antigen-specific proliferation on antigen-presenting cells, but not the proliferation induced by conditioned medium can be inhibited by L314-specific mAb. In a similar way, Ts-cell cytolytic effector functions can be blocked by L3T4-specific mAb. Thus L3T4 structures seem to play a role in Ts-cell functions. Furthermore, the data support the view that L3T4 expression can be a property of class II-restricted T cells irrespective of their Lyt phenotype.