Changes in electrical impedance of the vaginal medium during the menstrual cycle of female rhesus monkeys (Macaca mulatta)

Changes in electrical impedance of the vaginal medium during the menstrual cycle were recorded in female Rhesus monkeys using electrical probe and were correlated with estradiol-17 beta and progesterone plasma concentrations. A gradual decrease in impedance was observed during the follicular phase, the lowest values being observed between days 12-17 of the cycle. Impedance increased again during the first third of the luteal phase until day 21. The reversal of the impedance gradient's sign was nearly concomitant with the appearance of a detectable plasma progesterone concentration. These results support the use of vaginal impedance measurements as a help for the diagnosis of the periovulatory time in the female Rhesus monkey.     

The 2-phase action on mice of immunoglobulins isolated from the blood of a myasthenia patient

Single injection of Ig preparations from the myasthenia-patient-blood on C57Bl mice, revealed two phases in the development of the myasthenic syndrome. The first phase started one-two hours after the injection only of the IgM preparation in a dose 2-10 mg. This phase was in progress for two days. The second phase developed during the injection of either the Igm or IgG preparations in a dose 6-10 mg (IgG) of 2-10 mg (IgM). This phase was characterized by the appearance of long myasthenic disorders in two-three week time after the experiment. Some of these mice perished. It was assumed that the absence of strict correlation between the concentration of anti-AChR-IgG antibodies and the gravity of myasthenia is connected with the IgM participation in the pathogenesis of the myasthenia and/or with the appearance of secondary autoantibodies towards the targets which differ from AChR's myoneural synapsis.     

NaK ATPase activity in the rat hippocampus: A study in the pilocarpine model of epilepsy

Biochemical abnormalities have been implicated in possible mechanisms underlying the epileptic phenomena. Some of these alterations include changes in the activity of several enzymes present in epileptic tissues. Systemic administration of pilocarpine in rats induces electrographic and behavioral limbic seizures and status epilepticus, that is followed by a transient seizure-free period (silent period). Finally a chronic phase ensues, characterized by spontaneous and recurrent seizures (chronic period), that last for the rest of the animal's life. The present work aimed to study the activity of the enzyme Na⁺ K⁺ ATPase, in rat hippocampus, during the three phases of this epilepsy model. The enzyme activity was determined at different time points from pilocarpine administration (1 and 24 h of status epilepticus, during the silent and chronic period) using a spectrophotometric assay previously described by Mishra and Delivoria-Papadopoulos [Neurochem. Res. (1988) 13, 765–770]. The results showed decreased enzyme activities during the acute and silent periods and increased Na⁺K⁺ ATPase activity during the chronic phase. These data show that changes in Na⁺K⁺ ATPase activity could be involved in the appearance of spontaneous and recurrent seizures following brain damage induced by pilocarpine injection.     

The neuronal organization of a focus of conditioned excitation in the cat sensory-motor cortex]

The activity of single units in the focus of conditioned excitation was studied during defensive conditioning to direct electrical stimulation of the cat sensorimotor cortex. Reorganizations of spike activity set in during the period of reflex elaboration, were manifest in the increased number of excited neurones and those which respond both to the conditioned and unconditioned stimuli. In the course of elaboration, the inhibitory phase of unit responses to direct electrical stimulation of the sensorimotor cortex was reduced, while the frequency of background unit spike activity was enhanced. Acute extinction of the reflex restored the initial duration of the inhibitory phase and reduced the frequency of the background activity.     

The dynamics of the morphological changes in the tissues after the subcutaneous administration of vaccines against Q fever]

The comparative study of the dynamics of morphological changes in tissues of guinea pigs after the subcutaneous injection of chemical, live and combined vaccines against Q fever during the period from 12 hours to 90 days was made. All vaccines under study were shown to produce a pronounced local damaging effect. Two periods were tentatively discriminated in the dynamics of changes: the early phase (till 48 hours) and the late phase (days 2-90). At the early stage the most pronounced changes were registered after the injection of the combined vaccine. At the late phase the use of the chemical and combined vaccines was accompanied by the appearance of secondary hemorrhages into newly formed connective tissue. Starting from day 30, practically no deviation from the normal state of tissues were registered at the site of injection.     

Electromyographic studies of the musculus rectus nasalis in postnatal growing rabbits while turning the animal on the horizontal level]

In rabbits aged 1-15 days and in a comparative group of adult animals, the EMG of the musculus rectus nasalis was recorded during a turn after speed jumps from 0 degrees/sec to 30 degrees/sec, 60 degrees/sec and 144 degrees/sec, respectively, through a path of 360 degrees. From the first day of life, an electrical activity consistent with the rapid and slow phase of the nystagmus was found. The EMG potentials, the so-called bursts, underwent qualitative changes with age that can be taken to reflect increasing maturation both of centralnervous mechanisms of inhibition and a functional transformation of the eye-muscles. The number of bursts increased with age during the turn; the latency period from the onset of turning to the appearance of the bursts was reduced. The differences observed at the three turning speeds are discussed with regard to the age of the animals.     

Interhemispheric relationships of electrical activity in the blinking dominant in rabbits

The study of intercentral and interhemispheric relations of the electrical activity of the cerebral cortex during formation and functioning of winking dominant, by the method of spectral-correlation analysis, has shown that the dominant focus is characterized by an increase of spectrum power in the range of delta-frequencies and a raise of coherence level of potentials in the same range that leads to the appearance of interhemispheric asymmetry according to these parameters. Appearance of the dominant state in the opposite hemisphere is accompanied by a reconstruction of the electrical activity characteristic of dominant focus.     

Radular mechanosensory neuron in the buccal ganglia of the terrestrial slug,Incilaria fruhstorferi

A radular mechanosensory neuron, RM, was identified in the buccal ganglia of Incilaria fruhstorferi. Fine neurites ramified bilaterally in the buccal ganglia, and main neurites entered the subradular epithelium via buccal nerve 3 (n3). When the radula was distorted by bending, RM produced an afferent spike which was preceded by an axonic spike recorded at n3. The response of RM to radular distortion was observed even in the absence of Ca²⁺, which drastically suppressed chemical synaptic interactions. Therefore, RM was concluded to be a primary radular mechanoreceptor.During rhythmic buccal motor activity induced by food or electrical stimulation of the cerebrobuccal connective, RM received excitatory input during the radular retraction phase. In the isolated buccal ganglia connected to the radula via n3s, the afferent spike, which had been evoked by electrical stimulation of the subradular epithelium, was broadened with the phasic excitatory input. Since the afferent spike was also broadened by current injection into the soma, depolarization due to the phasic input may have produced the spike broadening.Spike broadening was also observed during repetitive firing evoked by current injection. The amplitude of the excitatory postsynaptic potential in a follower neuron increased depending on the spike broadening of RM.Abbreviations CBC cerebrobuccal connective - EPSP excitatory postsynaptic potential - n1,n3 buccal nerves 1 and 3 - RBMA rhythmic buccal motor activity - RM radular mechanosensory neuron - SMT supramedian radular tensor neuron     

Circadian control of the cellular response to β-ecdysone in Drosophila lebanonensis

Drosophila lebanonensis displays a strict circadian rhythm with regard to the puparium formation and the occurrence of ecdysone-specific puffs in the salivary gland chromosomes. In normal development these puffs occur 3–4 hours before puparium formation. Injection of β-ecdysone at periods before ecdysone puffs are present, induces in all instances their appearance within 30 minutes, irrespective of the phase of the circadian oscillation at the time of injection. In spite of the appearance of the hormone specific puffs following β-ecdysone injection, puparium formation did not occur 3–4 hours after the puffs became active. Depending upon the time of injection within the circadian cycle, puparium formation occurred 5–6 hours after injection (when injection was performed close to a “gate” period), or occurred during the next “gate” of the circadian oscillation.     

Spontaneous electrical activity of the claustrum

The dynamics of spontaneous electrical activity of the rostral, dorsal, ventral, and caudal parts of the claustrum were studied in chronic experiments on 12 dogs with implanted electrodes during extinction of orienting reactions and during biologically meaningful changes in the animals' functional state. In the animal at rest, electrical activity of the claustrum was similar to that of subcortical structures, but in a state of attention, its activity began to resemble that of the electrocorticogram, in agreement with the view that this nucleus occupies an intermediate position between cortical and subcortical structures. Enhancement of fast activity in the claustrum with the appearance of orienting reactions was expressed more intensively, and during extinction it was preserved for a longer time, in the dorsal and ventral parts of the claustrum than in the rostral and caudal parts, evidence of structural heterogeneity of the nucleus. Under conditions of increased food excitability the amplitude and frequency of the fast waves recorded from the rostral and caudal parts of the claustrum were selectively increased, whereas during reflexes to a rejected stimulus (acids) and in defensive reflexes they were increased in recordings from the dorsal and ventral parts, on which basis the existence of specialized efferent zones participating in biologically different types of activity can be postulated. Enhancement of fast activity in the claustrum during reflexes to food and acid differed in its genesis: The switch from the first to the second took place through a phase of suppression of the first. Differentiation of a food-conditioned stimulus was accompanied by the development of active inhibition in the "food zones" of the claustrum and by enhancement of activity in the "zones of orienting reactions."A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 2, pp. 155–164, March–April, 1980.     

Changes in seizure activity thresholds of the cat brain in various stages of sleep and wakefulness

Changes in seizure activity of the brain evoked by electrical stimulation of the dorsal hippocampus in various stages of sleep and wakefulness were studied in adult cats. During slow sleep, when the EEG is dominated by high-voltage slow waves, near-threshold epileptogenic hippocampal stimulation evokes well-marked paroxysmal discharges. During wakefulness or the paradoxical phase of sleep, when the EEG is desynchronized, this hippocampal stimulation is less effective: either no seizure discharges are produced or they are weak. Activation of the mesencephalic reticular formation before epileptogenic hippocampal stimulation hinders the appearance of seizure activity whereas activation after hippocampal stimulation does not inhibit paroxysmal discharges already in progress; on the contrary, in some cases they are actually strengthened a little. One of the main factors limiting the appearance and spread of seizure activity is considered to be the tonic inhibitory influence of the neocortex on other parts of the brain.     

Effect of pentobarbital on unit activity of reticular and ventrolateral thalamic nuclei in cats

Responses of single units in the reticular and ventrolateral thalamic nuclei were studied in acute experiments on curarized cats before and after intravenous injection of small doses (0.5–15 mg/kg) of pentobarbital, with simultaneous derivation of activity by two electrodes. After injection of pentobarbital, unit activity in the reticular nucleus consisted of high-frequency grouped (52.5% of 40 neurons) or continuous (30%) discharges as long as barbiturate spindles were present in the electrocorticogram. Activity of only four neurons (10%) of this nucleus was inhibited during the presence of spindles. In all other neurons of the reticular nucleus (7.5%) the character of discharges was unchanged after injection of pentobarbital. The appearance of grouped discharges, repeated several times (66.5% of 40 neurons), or blocking of activity (30%) throughout the period of spindle recording was observed in neurons of the ventrolateral nucleus. The remaining neurons of that nucleus (3.5%) did not respond to intravenous pentobarbital. The appearance of high-frequency discharges in neurons of the reticular nucleus while spindles were recorded coincided with a period of silence in neurons of the ventrolateral nucleus (58.5% of 34 pairs of neurons). High-frequency electrical stimulation of the mesencephalic reticular formation led to asynchronous activation of neurons of the ventrolateral nucleus (82%) and inhibition of unit activity in the reticular nucleus (88%).I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 14, No. 5, pp. 517–524, September–October, 1982.     

Changes in the electric activity of the cerebral cortex in poisoning caused by Cl. perfringens toxin type A]

The electrical activity of the cerebral cortex was recorded in cats under mild nembutal anesthesia (15-20 mg/kg of body weight) during the development of Cl. perfringens, type A, toxin poisoning (the toxin was injected intramuscularly in a dose of 100 MLD per kg of body weight). Two phases of the changes in the electrical activity of the cerebral cortex were noted. The first phase was attended by the desynchronization of the electrical activity, persistence of the induced potentials and of the reaction of the rhythm reconstruction to the rhythmic light stimulus. No desynchronization occurred under conditions of preliminary section of the midbrain (on the mesencephalic preparation), this indicating the involvement of the reticular formation into the pathological process and pointing to its role in the desynchronization effect. A profound depression of the electrical activity of the brain, depression of induced potentials and disturbance of the reaction of the rhythm reconstruction occurred during the second phase.     

Regulation of Circadian and Acute Activity Levels by the Murine Suprachiasmatic Nuclei

The suprachiasmatic nuclei (SCN) coordinate the daily sleep-wake cycle by generating a circadian rhythm in electrical impulse frequency. While period and phase of the SCN rhythm have been considered as major output parameters, we propose that the waveform of the rhythm of the SCN also has significance. Using implanted micro-electrodes, we recorded SCN impulse frequency in freely moving mice and manipulated its circadian waveform by exposing mice to light-dark (LD) cycle durations ranging from 22 hours (LD 11∶11) to 26 hours (LD 13∶13). Adaptation to long T-cycles (>24 h) resulted in a trough in electrical activity at the beginning of the night while in short T-cycles (<24 h), SCN activity reached a trough at the end of night. In all T-cycle durations, the intensity of behavioral activity was maximal during the trough of SCN electrical activity and correlated negatively with increasing levels of SCN activity. Interestingly, small changes in T-cycle duration could induce large changes in waveform and in the time of trough (about 3.5 h), and accordingly in the timing of behavioral activity. At a smaller timescale (minutes to hours), we observed a negative correlation between SCN activity and behavioral activity, and acute silencing of SCN neurons by tetrodotoxin (TTX) during the inactive phase of the animal triggered behavioral activity. Thus, the SCN electrical activity levels appear crucially involved in determining the temporal profile of behavioral activity and controls behavior beyond the circadian time domain.     

Properties of spreading depression during different phases of cyclic excitation of the rat neocortex

Properties of cortical spreading depression were studied during different phases of cyclic excitation developing in the neocortex of rats under the influence of low-frequency electrical stimulation. Waves of spreading depression appeared in the cortex spontaneously or after microinjection of potassium chloride. During each excitation cycle a state preventing the passage and appearance of these waves developed in the region of electrical stimulation. The degree of blocking in other areas of the cortex outside the region of stimulation depended on the distance from the site of electrical stimulation and on generalization of excitatation over the cortex. After the end of the excitation phase, while the current continued to act, the ability of the cortex to conduct the depression wave was restored. In intervals of cyclic excitation the duration of the waves of spreading depression remained on average only half its duration in the absence of stimulation. The time course of development and the character of recovery of depression during the intervals confirm the hypothesis that activation of the potassium-sodium pump may have a role in the blocking mechanism and enable the temporal parameters of this process to be estimated.     

Effect of intracellular injection of cyclic amp on electrical characteristics of identified neurons in Helix pomatia

The effect of intracellular iontophoretic injection of cyclic AMP on electrical activity of neurons RPa1, RPa3, LPa2, LPa3, and LPl1 in the corresponding ganglia ofHelix pomatia was investigated. Injection of cyclic AMP into neuron LPl1 was found to cause the appearance of rhythmic activity (if the neuron was originally "silent"), an increase in the frequency of spike generation (if the neuron had rhythmic activity), and a decrease in amplitude of waves of membrane potential, in the duration of the interval between bursts, and in the number of action potentials in the burst (if the neuron demonstrated bursting activity). In the remaining "silent" neurons injection of cyclic AMP led to membrane depolarization. Injection of cyclic AMP into neurons whose membrane potential was clamped at the resting potential level evoked the development of an inward transmembrane current (cyclic AMP current), the rate of rise and duration of which increased proportionally to the size and duration of the injection. Theophylline in a concentration of 1 mM led to an increase in the amplitude and duration of the cyclic AMP current by about 50%. It is concluded that a change in the cyclic AMP concentration within the nerve cell may modify the ionic permeability of its membrane and, correspondingly, its electrical activity.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 517–525, September–October, 1980.     

Spontaneous unit activity of the monkey caudate nucleus under chronic experimental conditions

Spontaneous unit activity and changes in its statistical parameters during electrical stimulation of the palms at 25 or 50/min were studied in four monkeys under chronic experimental conditions. Altogether 337 recordings of the activity of 64 neurons for durations of 2 and 3 min were studied. The mean firing rate was relatively low (5.7 spikes/sec). As a rule the unit activity remained stable for several tens of minutes. It could change spontaneously to new patterns and again remain stationary. These transitions took place during recording of spontaneous activity and also during stimulation of the animal, but they were independent of it. Interspike interval histograms were varied and most were polymodal. Their pattern changed with changes in the firing rate of the neurons. The position of the modes along the time axis and the type of distribution were the most conservative characteristics of the histograms. The probability of appearance of intervals was highest at 30, 60, 90, and 210–240 msec. The presence of stable intervals with increased probability of appearance may be the result of the existence of chains of neurons in the caudate nucleus with fixed temporal parameters.     

Diurnal variations in physiological activities in the garden snail,Cryptozona ligulata

Summary Acetylcholinesterase (AChE) activity in the central nervous system and foot muscle in the garden snail,Cryptozona ligulata, was maximum at 20.00 h and minimum at 08.00 h during the 24 h period of the day. The cyclic variation in acetylcholine (ACh) was out of phase with that of AChE. In the body fluid, ACh content showed a rhythm with maximum at 00.00 h and minimum at 12.00 h, with AChE activity being in phase with it.The rhythm of spontaneous electrical activity of the nervous system was in phase with that of AChE activity in tissues. Perfusion with body fluid collected from snails at 20.00 h elevated the spontaneous electrical activity, while body fluid collected at 08.00 h inhibited the activity. Perfusion with extract prepared from the central nervous tissue isolated at 08.00 h elevated the electrical activity, while the extract prepared from nervous tissue isolated at 20.00 h inhibited the activity. Perfusion with 10^–4 M acetylcholine chloride solution elevated the electrical activity.It is suggested that the synthesis and release of ACh occur in a regular diel cycle in tissues. These changes, among others, may be responsible for the observed diurnal rhythmicity in electrical activity in the snail.     

The behavioral changes and the EEG of the rat brain induced by hyperactivation of the amygdaloid body under noradrenergic deficiency]

The brain NA deficit was produced by bilateral injection of 6-OHDA into the locus coeruleus. Three weeks later amygdala hyperactivation was initiated by local penicillin injection (1% solution, 0.5 mcl). Saline in the same volume was used in control groups in both cases. It was shown that the decrease in NA level facilitated the development of epileptiform activity in rat brain and appearance of immobility-related high-voltage spindles during waking. The amygdala hyperactivation after NA deprivation resulted in a decrease in exploratory activity and disruption of the reaction to novelty. The delta component of the EEG power spectrum increased. The alterations appeared 1-2 weeks after the experimental procedure and became more pronounced towards the end of the third week.     

Changes in local cerebral blood flow during increased general arterial pressure in animals]

General blood pressure was increased in normal rabbits and in the animals with experimental renal hypertension by intravenous injection of noradrenaline; local cerebral circulation was recorded in two areas of the cortex the white matter of the large hemispheres by the method of hydrogen clearance and also by EEG. A number of successive changes of the local cerebral circulation was observed; these changes could be unitypical or different by duration and character on different electrodes. The appearance of pathological forms of electrical activity was noted on the EEG.