The effect of microwaves on the neuronal activity of the hyperstriatum in chick embryos at the critical developmental period]

Studies have been made on multineuronal activity in the dorsal hyperstriatum of chick embryos exposed to microwave radiation (2.375 MHz) at critical stage of development of the structure (19th day of incubation). One day after microwave exposition, activation of neurones was observed in a form of the increase in the discharge frequency and the increase of outburst form of the activity. Cyclic form of outburst activity was absent in experimental animals being present in control embryos of the same age and associated presumably with self-organization of microsystems of neurones in the developing brain. Changes in multineuronal activity were found only in the left hyperstriatum, which is probably due to different levels of the development and functional activity of the right and left hyperstriatum at this stage resulting from asymmetric intensity of visual afferentation which depends on the position of embryo inside the egg.     

Proliferation of piriform neurons in the rat cerebellar cortex in the pre- and postnatal periods of development]

The method of histoautoradiography with the use of H3-thymidine was applied to the study; there were established the periods of appearance in the cerebellar anlage of albino rats of neuroblasts differentiated into the piriform neurones of the cerebellar cortex; dynamics of the proliferative activity of these cellular elements in the course of the pre- and postnatal periods of development of the experimental animals was investigated. On the basis of the material obtained a conclusion was drawn that the last cell divisions (the result of cell differentiation were Purkinje's cells of the cerebellar cortex) stopped by the 13th--15th day of the embryonic development. No incorporation of the labeled precursor into the DNA of the nuclei of the differentiating piriform neurons occurred later.     

Ultrastructure of tissue basophils and capillaries during different periods of pre- and postnatal development of the dermis in the rat

Dynamics of ultrastructure of mast cells (MC) and that of the capillaries of the derma have been studied by means of electron morphometry methods in rats during pre- and postnatal ontogenesis. The dynamics of the Golgi complex volume, that of the mitochondria and specific granules have been calculated in the total volume of the MC membrane organelles. Certain new data have been obtained on the process of the MC specific granules formation in the derma from progranules up to the stage of a mature granule. The process mentioned is most intensive during the first weeks of the postnatal ontogenesis. At the age of two weeks, signs of an active exocytosis of the granules are noted. Judging by certain morphological signs, development of transendothelial transport of substances in capillaries takes place in parallel with formation of the specific granules and corresponds to the beginning of exocytosis of substances in the MC granules. The correlative analysis proves that formation of the MC specific granules is connected with the number of microvesicles in cytoplasm of endotheliocytes.     

The ultrastructure of the pecten oculi in the chick

Summary The ultrastructure of the bridge of the pecten oculi was studied in the newlyhatched chick. Whereas most of the bridge resembled the pleats in being composed of small blood vessels and intervening pigment cells, the distal portion of the bridge consisted of polarized pigment cells only. The processes of the pigment cells extended into the vitreous body and were covered by a discontinuous dense lamina, believed to be continuous with that of the internal limiting membrane of the retina. It did not form a complete separation between the bridge and the vitreous body. Intercellular spaces were not conspicuous, although the considerable structural variations dependent on the techniques employed need to be stressed.     

Dynamics of the ultrastructure of fibroblasts during pre- and postnatal development of the dermis in the rat according to electronic morphometry

Fibroblasts have been investigated in 18-day-old embryos, in newborns, in 2-week-old and in 2-month-old rats of postnatal development. Comparison of fibroblasts population is specific for each stage. Average section area of the fibroblasts nucleus is progressively decreasing during ontogenesis. Average section area of cytoplasm reaches its maximum by the end of the second week of the life and then decreases sharply, and therefore the nucleus/cytoplasm ratio in the fibroblasts is minimal at the age of two weeks. The Golgi complex section area decreases significantly in mature animals as compared to the young ones. Summational extent of the granular endoplasmic reticulum membranes in the fibroblast section in the 2-week-old animals is 2.5 times as great as the corresponding parameters in the fetuses, newborns and mature animals. This parameter is greatly informative for determining the fibroblast type in accordance with its synthetic activity.     

The effect of forelimb deafferentation in early postnatal ontogeny on the development of synaptic transmission in the hippocampus]

Hippocampal slices from 15-20-day-old Wistar rats were used to study the development of some features of synaptic transmission in hippocampus and the influence of partial limitation of the sensory inflow in the early ontogeny of this transmission. The dynamics of population spike changes was observed in the CA1 hippocampal field in response to stimulation of Schaffer collaterals. The early ontogenetic limitation of the sensory inflow was accomplished by cutting n. medianus on the 13th day. Between the 15th and 20th days, the dynamics of the population spike amplitude increase in the control and experimental animals was similar, however, the response amplitude of the control rats remained higher than in the experimental animals throughout the whole period of observation. It is suggested that the partial limitation of sensory inflow from a forelimb at the early stages of the ontogeny alters the formation of synaptic transmission in hippocampus.     

The effect of light and dark periods on the production of ethylene from water-stressed wheat leaves

Light was found to inhibit substantially (i.e. up to 88%) the production of ethylene induced by water stress in excised wheat leaves and from the shoots of intact plants. The relatively small amounts of ethylene emanating fron non-stressed leaves were also inhibited by light but to a smaller degree (i.e. up to 61%). In water-stressed leaves the degree of light inhibition of ethylene production was shown to be related to the age of the leaves; the amounts of ethylene diffusing from young leaves (i.e. 6-days old) was inhibited 52% by light whereas in older leaves (i.e. 9-days old) it was inhibited by 85%. Previous studies [Wright (1979) Planta 144, 179–188 and (1980) Planta 148, 381–388] had shown that application of 6-benzyladenine (BA) to leaves a day before wilting, greatly increases the amount of ethylene diffusing from the leaves following wilting (e.g. 8-fold), and to smaller degrees do applications of indole-3-acetic acid (IAA) and gibberellic acid (GA₃). On the other hand abscisic acid (ABA) treatment reduces the amount of ethylene produced. In these earlier experiments the ethylene was collected from leaves held under dark or near-dark conditions, so in the present study the activities of these growth regulators (10^-4 mol l^-1 solutions) under dark and light conditions were compared. It was found that they maintained the same relative activities on ethylene emanation (i.e. BA>IAA>GA₃>water controls>ABA) under both light and dark conditions. However, because of the inhibitory effect of light, the absolute amounts of ethylene produced from all treatments were always much higher in the dark than in the light (usually about a 6-fold difference). An interesting effect of light treatment on ethylene biosynthesis was found when water-stressed leaves were kept in dark chambers for 41/2 h and then transferred to light. Quite unexpectedly, instead of the rate of ethylene production falling immediately, it continued to be produced at the dark rate (i.e. no light inhibition!) for over 2 h before the rate began to decline, and for a much longer period (i.e. in excess of 41/2 h) if the leaves had previously been sprayed with BA. Predictably, leaves placed in the light (i.e. in leaf chambers) and then transferred to darkness, immediately or very soon produced ethylene at the dark rate. One explanation of these results, which is discussed, would be that the biosynthesis of an ethylene precursor requires an obligatory dark stage. The possible implications of these studies to a survival role of ethylene in plants during periods of water stress is discussed.Abbreviations ABA abscisic acid - ACC 1-aminocyclopropane-1-carboxylic acid - BA 6-benzyladenine - GA₃ gibberellic acid - GLC gas-liquid chromatography - IAA indole-3-acetic acid - TLC thin-layer chromatography - _leaf leaf water potential     

The effect of synaptic stimulation on RNA and protein metabolism in the R2 soma of Aplysia

Excitatory synaptic stimulation of the R2 neuron in the abdominal ganglion of Aplysia californica causes an increased incorporation of ³Huridine into RNA. However, this could be the result of a change in precursor specific activity rather than an increase in RNA synthesis. We find that at low external uridine concentrations (1.5 μM) there is no increase in ³H-uridine incorporation correlated with synaptic stimulation. In addition, no change in incorporation of ³H-leucine into total protein or in the pattern of newly-synthesized proteins, resolved by electrophoresis on SDS-polyacrylamide gels, was detected with stimulation. Since the R2 neuron can be stimulated without a detectable change in RNA or protein synthesis, we conclude that the increase in incorporation observed at high external uridine concentrations (100 μM) could be caused by increased specific activity in a precursor pool rather than by an RNA synthesis change.     

Organization of impulse flows and selective neuronal death in the hyperstriatum of chick embryos and chicks

Studies have been made on changes in the number of neurones per volume unit of the tissue of hyperstriatum tissue in chick embryos from the 18th day of incubation to the 3rd day after hatching. Significant interhemispheric asymmetry in migration rate and cell death was revealed in the dorsal hyperstriatum from the 19th day of embryogenesis, which may be due to asymmetry in the intensity of visual afferentation which depends on the stationary position of the embryo in the egg. In the activity of neuronal populations within the dorsal hyperstriatum at a stage which immediately precedes mass death of cells (up to 40%), a structure of impulse volley was found which is characterised by the onset of impulse discharges following each other in a form of short series. Sometimes it is possible to reveal correlation between the duration of dominating interdischarge intervals and the extremes in the recovery of excitability of neuronal pools, which indirectly indicates putative reverberative origin of impulse cyclic phenomenon.     

Studies of cardiac ganglia in pre- and postnatal rabbits

Summary This investigation was undertaken to describe the ultrastructure of cardiac ganglia in rabbits from day 18 of gestation to day 35 postpartum. Special attention was directed to the types of synaptic contacts made with the principal neurons and with the small granule-containing cells. The cardiac ganglia in all animals consisted mainly of parasympathetic postganglionic neurons, supporting cells, and small granule-containing (small intensely fluorescent) cells. The neurons received afferent synaptic terminals of two types. One type contained mainly small clear vesicles typical of most cholinergic terminals. The second type contained mainly small dense-core vesicles (these were most prominent after treatment of the animal with 5-hydroxydopamine), and were considered to be adrenergic terminals. These adrenergic terminals are probably part of an inhibitory system in the ganglia. The small granule-containing cells received typical afferent synaptic terminals of the cholinergic type, and also formed specialized contacts with certain axonal terminals. These latter specializations are considered to be reciprocal synapses which probably have a role in modulating ganglionic transmission.Supported by the Kentucky Heart Association and the Heart Association of Louisville and Jefferson County