Neuronal responses in the limbic cortex of awake cats during defensive conditioning

Spike activity was investigated in limbic cortex neurons during defensive conditioning to acoustic stimulation in chronic experiments on cats. A relationship was found between the numbers of neurons responding, their contribution to formation of a temporal connection, and the duration of the acoustic stimulus. Phasic responses of 50–500 msec duration with latencies of 15–50 msec were observed for the most part. Intensive spike response with a minimum latency of 15 msec and a duration of between 200 msec and 2.5 sec evolved in most cells (95.1% in field 24 and 83% in field 32) in response to electrical stimulation. Response to acoustic stimulation rose during defensive conditioning in 33.3% cells and declined and finally disappeared in 13.3%, but response at the site where reinforcement was abolished was reproduced in all these cells. It was thus found that the numbers of limbic cortex neurons responding to sound not only fails to increase but actually decreases after training. The limbic cortex is thought to play its most active part in conditioning response to a recognized signal during the period preceding the awaited painful reinforcement.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 5, pp. 660–669, September–October, 1986.     

Prenatal diagnosis in 200 pregnancies with a 1-in-4 risk of cystic fibrosis

Summary Prenatal diagnosis of cystic fibrosis was performed in 200 pregnancies with a 1-in-4 risk, and was based on significant modifications in amniotic fluid taken at 17, 18, 19 weeks of pregnancy, of six enzymatic assays: gamma-glutamyl-transpeptidase, aminopeptidase M, and alkaline phosphatase (total and isoenzymes). On the basis of normal values, normal outcome was predicted in 135 pregnancies reaching term, all the babies were normal. On the basis of significantly abnormal enzymatic values, an affected fetus was predicted in 56 pregnancies, 53 were terminated, and 3 went to term; the infants were affected. There were discrepancies in enzymatic values in nine cases, in eight cases normal outcome was predicted, six babies were normal and two were affected; in one case an affected baby was predicted, the pregnancy went to term and the baby is normal. Criteria giving evidence for cystic fibrosis in fetuses have been described: macroscopic observation of a typical meconium ileus, significant increase of albumin content in the meconium, and PAS-positive mucus-like material in some pancreatic acini. Using these criteria, diagnosis of cystic fibrosis has been confirmed in all the examined fetuses. The recurrence rate of cystic fibrosis was 22.5% in 147 diagnoses in which the index case had cystic fibrosis without a history of meconium ileus at birth, but was 47.5% when the index case had meconium ileus. The results of the study suggest that prenatal diagnosis of cystic fibrosis can be performed with an accuracy of 98%.     

Blocking action of furosemide on chloride conductance induced by acetylcholine and gaba in molluscan neuron membrane

Experiments on isolated neurons of the molluskPlanorbarius corneus under membrane voltage clamp conditions showed that furosemide (2×10^?4 to 1×10^?3 g/mg) inhibits the increase in chloride conductance evoked by iontophoretic application of acetylcholine, suberyldicholine, and gamma-aminobutyric acid (GABA). If microelectrodes filled with potassium sulfate were used in the experiments furosemide did not shift the reversal potential, but when microelectrodes filled with potassium chloride were used the reversal potential of the chloride-dependent responses became less negative. In the last case, the action of furosemide evidently was exhibited not only on passive chloride conductance of the chemoreceptive membrane, but also on active chloride transport. Furosemide had no effect on sodium- and potassium-dependent responses evoked by activation of choline receptors. Unlike D-tubocurarine, which selectively blocks acetylcholine effects, furosemide also depressed conductance evoked by GABA. In the presence of furosemide chloride-dependent responses not only were reduced in amplitude, but also developed more slowly. It is postulated that the action of furosemide is aimed not at receptors, but at chloride channels of the chemoreceptive membrane common to both acetylcholine and GABA.     

CD4 is involved in a post-binding event in the cytolytic reaction mediated by human CD4+ cytotoxic T lymphocyte clones

CTL lyse their target cells in discrete phases. First, the CTL bind to the target cell in a Mg2+-dependent manner followed by a Ca2+-dependent cytolytic phase. In the present study, we investigated the role of CD4 in the different phases of the cytolytic reaction mediated by human CD4+ class II MHC-specific CTL clones by using a single cell assay. It was found that the anti-CD4+ mAb OKT4A, which blocks cytotoxic reactions by CD4+ CTL clones as measured with a 51Cr release assay, only marginally affects the formation of conjugates. It appeared that OKT4A more strongly blocked the post-binding phase of the cytolytic reaction. In contrast, anti-leukocyte function-associated mAb strongly blocked the formation of conjugates but not the subsequent lytic phase. As was found previously with CD8+ CTL clones, anti-TCR mAb generally did not affect the formation of conjugates. One exception was noted. The activity of a CD4+ CTL clone, HY-640, could not be blocked by OKT4A, but was affected by an anti-TCR mAb. This anti-TCR mAb could partly reduce the formation of conjugates between HY-640 cells and their specific target cells. These results suggest that this clone has a high affinity TCR, which can contribute to the formation of conjugates. Although preincubation of the CTL clones with OKT4A only marginally affects the number of conjugates upon subsequent mixture with target cells, it was observed that incubation at 37 degrees C of preformed conjugates with OKT4A markedly reduced the number of conjugates. This dissociation of preformed conjugates was optimal only after 2 h of incubation. In contrast, an anti-leukocyte function-associated mAb induced a much more rapid dissociation of preformed conjugates.     

Enantioselective chromatography of the antimalarial agents chloroquine,mefloquine, and enpiroline on a α1 -acid glycoprotein chiral stationary phase: Evidence for a multiple-site chiral recognition mechanism

The effect of mobile phase pH and dimethyloctylamine (DMOA) on the retention (k') and stereoselectivity (α) of antimalarial agents mefloquine, enpiroline, and chloroquine on the α₁-acid glycoprotein chiral stationary phase (AGP-CSP) was investigated. An increase of k' with increasing pH was observed while the effect on α was a function of the solute. The magnitude and direction of changes induced by DMOA depended on pH and the structure of the solute. The results of this study are consistent with a change of the conformation of the AGP between pH 5 and 7. At pH 7, the effect of DMOA on mefloquine was relatively well described by a competitive displacement from one enantioselective site. The effect on chloroquine and enpiroline suggests a multiple-site mechanism in which both competitive and allosteric interactions are involved.     

Characteristics of responses of preoptic neurons to presentation of serial cortical stimuli

Responses of neurons of the medial (MPO) and lateral (LPO) preoptic region (RPO) and adjacent hypothalamic structures to serial stimuli (6–300/sec) of the prefrontal (area 8) and cingulate (area 24) cortex, piriform lobe (periamygdaloid cortex — RPA), and hippocampus (area CA3) were investigated in acute experiments on cats under ketamine anesthesia. Four main types of responses were found: excitatory, inhibitory, excitatory on-off effect, and inhibitory on-off effect. With the use of stimuli with increasing frequencies, the direction of the response remained constant, only its intensity changed. Neurons responding to presentation of serial stimuli were localized mainly in the central part of the MPO and basal part of the LPO, where the most pronounced foci of convergence were observed. During serial stimulation of cortical structures, inhibitory responses occurred considerably more often than excitatory (ratio 3.4:1). The presence of a gradient of inhibition was established from new to old (in a phylogenetic respect) brain formations in a number of stimulated structures. In the case of stimulating the neocortex (proreal gyrus), the predominance of inhibitory responses over excitatory was minimum (1.7:1); it increased (1.9:1) in the case of stimulating the intermediate cortex (cingulate gyrus), still more (4.5:1) under conditions of stimulating the paleocortex (periamygdaloid cortex), and in the case of stimulating the archicortex (10.2:1).A. M. Gorky Medical Institute, Ukrainian Ministry of Health, Donetsk. Translated from Neirofiziologiya, Vol. 23, No. 6, pp. 720–731, November–December, 1991.     

Origin of orthodromic evoked potential in the frog olfactory bulb

The functional organization of the primary olfactory center of the frog was investigated. The dynamics of changes in individual components of the potential evoked by electrical stimulation of the olfactory nerve corresponds to morphological evidence of the asymmetrical structure of the frog olfactory bulb. The character of spatial localization and of the properties of individual components of the orthodromically evoked potential suggests that a monosynaptic reciprocal activating system participates in the production of the main component of the response. The similarity between the durations of the inhibitory pauses in spontaneous activity of the mitral cells during stimulation of the olfactory nerves and of the lateral olfactory tract indicates that when all these methods of stimulation are used a single system controlling excitability of the secondary neurons is activated. It is postulated that inhibition of the mitral cells is evoked as a result of activation of a polysynaptic recurrent system incorporating interneurons.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 184–191, March–April, 1972.