Computer simulated discharges of thalamic ventrobasal neurones during sleep and wakefulness

A theoretical model is described which in response to combinations of poissonian pulse trains with different mean frequencies on three independent incoming lines, generated output signals simulating spontaneous discharges of thalamic ventrobasal (VB) neurones during sleep and wakefulness. Some dynamic neuronal properties as refractoriness, facilitation, short term memory were simulated and characteristics of response to single pulses on different lines properly selected to reproduce those exhibited by VB neurones upon artificial stimulation of thalamic afferent systems. The data obtained from the model are briefly discussed in relation to possible contributions of specific and nonspecific afferent systems in producing spontaneous VB discharges characteristic of different levels of vigilance.     

Intrinsic viscosities and other solution properties of sugars and their possible relation to sweetness

The intrinsic viscosities, apparent molar volumes, apparentspecific volumes and apparent solution parachors of selectedsugars were determined with the aim of investigating the possiblerelationship of these solution properties to the published sweetnessvalues of sugars. For a given sugar, there is no clear relationshipbetween its intrinsic viscosity and other solution propertiesstudied. The values of apparent specific volume and intrinsicviscosity differ greatly even though both parameters reflectthe amount of water surrounding 1 g of the solute. There isalso no observable correlation between the intrinsic viscositiesand the literature values on the relative sweetness of sugars.The intrinsic viscosity of a solute molecule reflects its extentof hydration. It is greatly influenced by the conformation andconfiguration of the sugar molecules. Equatorial OH groups aremore favourable for hydration than the axial OH groups. Thus,the more OH groups in the equatorial position, the higher theintrinsic viscosity.     

Dynamic characteristics of central auditory neurons and their relation to selective-combination mechanisms of organization of brain functions

Unit responses of the torus and caudal neostriatum of hens to stimuli of differing ecological significance (pure tones, white noise, species-specific stimuli) were investigated. The range of frequencies receivable by central auditory neurons was shown to correspond to the frequency composition of the stimuli emitted by the animals. Neurons selectively responding to species-specific stimuli (song, alarm signals) were found in the forebrain. The specific character of the functional organization at different levels of the auditory system is examined in the light of the selective-combination principle of stimulus integration, which may lie at the basis of the mechanism of both inborn and acquired memory.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 8, No. 4, pp. 335–342, July–August, 1976.     

Mobile dispersed genetic elements and their possible relation to carcinogenesis

In this paper, a hypothesis is described according to which mobile dispersed genetic elements are related to endogenous viral genomes and may be involved in oncogenic transformation by uptaking cellular genes important for cellular growth. It is also possible that, in certain cases, they can switch off the genes involved in the control of differentiation.     

Distribution of dynamins in testis and their possible relation to spermatogenesis

Dynamin 2 and dynamin 3 are highly expressed in testis. However, their functions in the tissue remain unclear. Considering that dynamin 1, neuron-specific isoform of dynamin, plays a pivotal role in endocytosis, functions of dynamin 2 and dynamin 3 in testis must be essential. Cellular expression and subcellular localization of dynamin 2 and dynamin 3 in testis were investigated. Dynamin 2 and dynamin 3 were highly expressed in germ cells and Sertoli cells, constituents of seminiferous tubules. By immunofluorescence it was revealed that dynamin 2 colocalizes with clathrin both at the plasmamembrane and at Golgi in a cell line of Sertoli cells. Immunoreactivity for dynamin 3, on the other hand, appeared as finer puncta, which did not colocalize with clathrin, suggesting that these two dynamins have distinct functions in Sertoli cells. In the klotho deficient mouse testis, which demonstrates disorder in spermatogenesis, expression of dynamin 2 and dynamin 3 was drastically reduced indicating possible association of these proteins with spermatogenesis.     

Thermophilic methanogenic Archaea in compost material: occurrence, persistence and possible mechanisms for their distribution to other environments

Since compost is widely used as soil amendment and the fact that during the processing of compost material high amounts of microorganisms are released into the air, we investigated whether compost may act as a carrier for thermophilic methanogens to temperate soils.

All eight investigated compost materials showed a clear methane production potential between 0.01 and 0.98 μmol CH₄ g dw⁻¹ h⁻¹ at 50 °C. Single strand conformation polymorphism (SSCP) and cloning analysis indicated the presence of Methanosarcina thermophila, Methanoculleus thermophilus, and Methanobacterium formicicum.

Bioaerosols collected during the turning of a compost pile showed both a highly similar SSCP profile compared to the corresponding compost material and clear methane production during anoxic incubation in selective medium at 50 °C. Both observations indicated a considerable release of thermophilic methanogens into the air.

To analyse the persistence of compost-borne thermophilic methanogens in temperate oxic soils, we therefore studied their potential activity in compost and compost/soil mixtures, which was brought to a meadow soil, as well as in an agricultural soil fertilised with compost. After 24 h anoxic incubation at 50 °C, all samples containing compost showed a clear methanogenic activity, even 1 year after application.

In combination with the in vitro observed resilience of the compost-borne methanogens against desiccation and UV radiation we assume that compost material acts as an effective carrier for the distribution of thermophilic methanogens by fertilisation and wind.     

Antimutagenic compounds and their possible mechanisms of action

Mutagenicity refers to the induction of permanent changes in the DNA sequence of an organism, which may result in a heritable change in the characteristics of living systems. Antimutagenic agents are able to counteract the effects of mutagens. This group of agents includes both natural and synthetic compounds. Based on their mechanism of action among antimutagens, several classes of compounds may be distinguished. These are compounds with antioxidant activity; compounds that inhibit the activation of mutagens; blocking agents; as well as compounds characterized with several modes of action. It was reported previously that several antitumor compounds act through the antimutagenic mechanism. Hence, searching for antimutagenic compounds represents a rapidly expanding field of cancer research. It may be observed that, in recent years, many publications were focused on the screening of both natural and synthetic compounds for their beneficial muta/antimutagenicity profile. Thus, the present review attempts to give a brief outline on substances presenting antimutagenic potency and their possible mechanism of action. Additionally, in the present paper, a screening strategy for mutagenicity testing was presented and the characteristics of the most widely used antimutagenicity assays were described.     

The effects of noise on sleep and their possible repercussions on health

Sleep is a physiological recuperative state susceptible to be disturbed or reduced in length under external stimuli, such as noise, one of the most frequent ambient factors. Sleep disturbance is often accompanied by a reduced quality of the following waking period. The health effects of prolonged exposure to noise concern life quality, as expressed subjectively by the sleeper, as well as probable effect on cardiovascular function through a non specific aggression related to stress.     

Electrophysiological characteristics of reticulospinal neurones in relation to the conduction velocity of their axons

Activity was recorded intracellularly from the bodies of 87 reticulospinal neurones in the cat's gigantocellular nucleus, whose axons had a conduction velocity of 18-148 m.s-1. Slow-conducting neurones (18-45 m.s-1, 23%) were characterized by a wider action potential, higher input resistance (3.8-7.0 M omega) and a lower rheobase (1.0-1.7 nA). They were also very sensitive to changes in membrane polarity and generated regular rhythmic activity. Fast-conducting neurons (45-148 m.s-1) were characterized by a short action potential, low input resistance (0.7-2.9 M omega) and a higher rheobase (1.5-5.2 nA). When depolarizing current pulses were applied, they generated responses with action potentials with a high frequency, especially in the initial phase of depolarization, but their thresholds for the initiation of activity and steady firing were higher than in the case of slow neurones. Slow reticulospinal neurones always responded to stimulation of the spinal funiculi (mainly the dorsal funiculus) by a characteristic large postsynaptic potential on which large numbers of spike potentials were superimposed and which did not occur in fast neurones. The differences observed in membrane properties and in the character of generation of action potentials draw attention to the phasic character of fast, and the tonic character of slow, reticulospinal neurones.     

Involuntary autobiographical memories and their relation to other forms of spontaneous thoughts

Involuntary autobiographical memories are memories of personal events that come to mind spontaneously—that is, with no conscious initiation of the retrieval process. Such spontaneously arising memories were long ignored in cognitive psychology, which generally has focused on controlled and strategic forms of remembering, studied in laboratory settings. Recent evidence shows that involuntary memories of past events are highly frequent in daily life, and that they represent a context-sensitive, and associative way of recollecting past events that involves little executive control. They operate by constraints that favour recent events and events with a distinct feature overlap to the current situation, which optimizes the probability of functional relevance to the ongoing situation. In addition to adults, they are documented in young children and great apes and may be an ontogenetic and evolutionary forerunner of strategic retrieval of past events. Findings suggest that intrusive involuntary memories observed clinically after traumatic events should be viewed as a dysfunctional subclass of otherwise functional involuntary autobiographical memories. Because of their highly constrained, situation-dependent and automatic nature, involuntary autobiographical memories form a distinct category of spontaneous thought that cannot be equated with mind wandering.This article is part of the theme issue ‘Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation’.     

Pharmacology of free radicals; recent views on their relation to inflammatory mechanisms

Production of free radicals from molecular oxygen during the inflammatory process can exhibit beneficial effects against the phlogistic stimulus and may act as a defence mechanism. Nevertheless, in many cases this production is associated with toxic reactions related to inflammatory response. Many compounds including bovine superoxide dismutase, non steroidal anti-inflammatory drugs, radical scavengers (e.g. acetaminophen), corticoids etc., have been shown to counteract this phenomenon. Their beneficial effects and mechanism of action are reviewed.     

Actions of calcitonin gene-related peptide on rat sensory ganglion neurones

The membrane actions of calcitonin gene-related peptide (CGRP) and the effect of CGRP on the Ca-dependent action potential of rat dorsal root ganglion (DRG) neurons have been studied by means of an intracellular recording technique in isolated DRG of 2-3-week-old rats in vitro. Bath application of CGRP (10(-8)-10(-6) M for 1-5 min) elicited a slow reversible hyperpolarization and this hyperpolarizing effect was still observed in the medium containing TTX and TEA. However, about half of the large cells, classified by duration of action potential, were depolarized by CGRP. These membrane effects of CGRP were associated with an increase in membrane input resistance (about 20%). In addition, CGRP increased the duration of Ca-dependent action potentials. Our results are consistent with the role of CGRP as an excitatory neurotransmitter or neuromodulator in DRG-spinal cord.     

Fluorescent granules in the guinea-pig hypothalamus and their possible relation to neurosecretory substance

Summary Sections of guinea-pig hypothalamus stained by various methods have been studied under bright-field and fluorescence microscopy to determine the characteristics of refractile granules originally observed in fixed tissue stained for cholinesterases but also seen in unfixed, unstained material.When sections of fresh tissue or tissue fixed in formaldehyde: Na₂SO₄ were examined by fluorescence microscopy, the granules emitted with a wave-length between 600 and 620 m. The density and distribution of the granules closely paralleled that of one of the components that stained with the aldehyde-fuchsin and chrome-alum techniques for neurosecretory substance; granules were absent, however, from the area characterized by Herring substance, and from the stained perikarya and beaded axons of the supraoptic and paraventricular nuclei.The granules were most numerous in the median eminence and infundibular nuclei. Their concentration was about average in mature males and in lactating and hypophysectomized females; they were more abundant in late pregnancy and after ovariectomy and were particularly plentiful some weeks after hysterectomy. They were virtually absent from immature males and females.The possible relation of the granules to releasing factors or to vasotocin-like neurosecretory material is discussed.The authors are most grateful to Dr. J. S. Perry who carried out the surgery involved in these experiments. They also wish to express their thanks to Dr. R. B. Heap who, with Dr. Perry, gave invaluable help in planning the experiments and assessing the data; to Mr. S.P. Mann and Dr. D. F. Sharman for advice on the fluorescence technique and to Miss M. Hamon for skilled technical assistance.Publication of the colour pictures was made possible by a generous grant from the Wellcome Foundation; this support is gratefully acknowledged.Thanks are also due to the University of Alberta for a contribution towards the cost of reprints.     

Structural elements of human parathyroid hormone and their possible relation to biological activities.

Human parathyroid hormone (hPTH) and several deletion analogues were examined for the presence of secondary structure using circular dichroism spectroscopy. The spectra of hPTH and the deletion analogues 8-84, 34-53, 53-84, 1-34, 13-34, 1-19, and 20-34, in neutral, aqueous buffer, gave no evidence for extensive secondary structure. An alpha-helical-like spectral contribution was found to arise from a region within peptide 13-34. This spectral contribution was speculated to arise from partial stability of a helix consisting of residues 17-29. Molecular dynamics simulations of peptide 1-34 suggested that this peptide tends to fold with a bend defined by residues 10-14, with the amino-terminal and carboxyl-terminal residues tending to be in more extended forms and the other residues in helical-like conformations. The addition of trifluoroethanol promoted the formation of alpha-helix, mainly in the 1-34 region. The putative helix comprised of residues 17-29 was stabilized by the addition of 10-20% TFE, while a second putative helix proximal to the amino terminus, and comprised of residues 3-11, was stabilized by slightly higher concentrations of TFE. An amphiphilic sequence was identified within the 20-34 fragment. The development of alpha-helix on binding this fragment, and other analogues containing this sequence, to palmitoyloleoylphosphatidylserine vesicles provided experimental evidence for the potential role of this amphiphilic sequence in binding to membranes or to a membrane receptor. The relationships between these alpha-helical regions in 1-34, either potentiated by trifluoroethanol or lipid vesicles, are discussed in terms of different receptor-binding regions within hPTH.