Thalamocortical transformations of periodic stimuli: the effect of stimulus velocity and synaptic short-term depression in the vibrissa–barrel system

Recent works on the response of barrel neurons to periodic deflections of the rat vibrissae have shown that the stimulus velocity is encoded in the corti cal spike rate (Pinto et al., Journal of Neurophysiology, 83(3), 1158–1166, 2000; Arabzadeh et al., Journal of Neuroscience, 23(27), 9146–9154, 2003). Other studies have reported that repetitive pulse stimulation produces band-pass filtering of the barrel response rate centered around 7–10 Hz (Garabedian et al., Journal of Neurophysiology, 90, 1379–1391, 2003) whereas sinusoidal stimulation gives an increasing rate up to 350 Hz (Arabzadeh et al., Journal of Neuroscience, 23(27), 9146–9154, 2003). To explore the mechanisms underlying these results we propose a simple computational model consisting in an ensemble of cells in the ventro-posterior medial thalamic nucleus (VPm) encoding the stimulus velocity in the temporal profile of their response, connected to a single barrel cell through synapses showing short-term depression. With sinusoidal stimulation, encoding the velocity in VPm facilitates the response as the stimulus frequency increases and it causes the velocity to be encoded in the cortical rate in the frequency range 20–100 Hz. Synaptic depression does not suppress the response with sinusoidal stimulation but it produces a band-pass behavior using repetitive pulses. We also found that the passive properties of the cell membrane eventually suppress the response to sinusoidal stimulation at high frequencies, something not observed experimentally. We argue that network effects not included here must be important in sustaining the response at those frequencies.

Home alone? Effect of weather-induced behaviour on spread of SARS-CoV-2 in Germany

In early 2020 the world was struck by the epidemic of novel SARS-CoV-2 virus. Like many others, German government has introduced severe contact restrictions to limit the spread of infection. This paper analyses effects of weather on the spread of the disease under the described circumstances. We demonstrate that regions reported lower growth rates of the number of the infection cases after days with higher temperatures, no rain and low humidity. We argue that this effect is channelled through human behaviour. The evidence suggests that “good” weather attracts individuals to outdoor (safer) environments, thus, deterring people from indoor (less safe) environments. Understanding this relationship is important for improving the measures aiming at combating the spread of the virus.     

Effect of pH on the Content of Glycolipids in Aureobasidium pullulans S–l

When Aureobasidium pullulans was cultivated with initial pH 6.0 and pH 2.5 in shaking flasks, only a slight difference was observed in the content of lipids in cells. On the other hand, when cultured with initial pH 2.5 in a jar fermenter, the content of lipids in mycelia was larger than that with initial pH 6.0. The content of sugars in the lipids showed a similar tendency. Glucolipids were easily hydrolyzed with dilute acid into glucose, glucooligo- saccharide and lipids.     

Effect of the “zero” Magnetic Field on Early Embryogenesis in Mice

It was shown that the 250-fold screening of the geomagnetic field (GMF) (“zero” magnetic field with an induction of 0.2?μT) affects early embryogenesis and the reproduction capacity of mice in vivo. Pregnant NMRI mice at the zygote stage placed in this “zero” magnetic field (MF) lost the ability to bear offspring babies although their embryos developed up to the blastocyst stage without any visible deviations from the norm. The abortion of development in the “zero” MF occurred after the exit of the blastocysts from the zona pellicida and invasion into the uterus during implantation. Histological analysis indicates that possible reasons of the abnormalities of postimplantation development are a decrease in the proliferative activity of embryonic cells and the impairment of the interaction between the trophoblast and endometrium, which finally results in the resorption of embryos in the uterus.     

A model of direction-selective “simple” cells in the visual cortex based on inhibition asymmetry

Direction selectivity is a prominent feature of single units in the central visual pathway of cat and monkey. Various mechanisms have been proposed for the generation of this property. Experimental evidence suggests that intracortical inhibition is a major factor contributing to direction selectivity.We have developed a one-dimensional computer model for direction selective simple cells in the visual cortex under two basic assumptions: 1) Inhibition is exerted upon a cortical cell by neighboring cells from either side within a retinotopic array, 2) The relative strength of inhibition from both neighbors can be varied, interneurons always having larger time constants than the simple cells. Summation in the model is linear, but is followed by an essential non-linearity. ON- and/or OFF-center cells of the sustained type (X-cells) are used as an input to the simple cells.The computer simulation demonstrates that various subtypes of direction-selective simple cells in area 17, as described by Schiller et al. (1976), can be generated by different amounts of inhibition asymmertry, different delays and by different spatial arrangements of the input. Only one type of input (ON or OFF) is required to generate direction selectivity, but a greater variety of cell subtypes is created by combining both. Length-summation, contributing to orientation selectivity, was not considered in this one-dimensional model.     

Effect of thyroid deficiency on Go α-subunit isoforms in developing rat cerebral cortex

Postnatal development of G_o isoforms in rat cerebral cortex was studied by SDS-PAGE and immunoblotting. When rat cerebral cortical membranes were resolved on separating gels containing 9% acrylamide and 8 M urea, three electrophoretically distinct G_o-immunoreactive proteins were evident. Comparison of their electrophoretic mobilities and partial tryptic digest pattern with recombinant G_o1 or G_o1-specific antibody revealed that the slowest and intermediate-migrating bands represent unmodified and fatty acylated forms of G_o1 protein, respectively. The fastestmigrating band corresponds to G_o2. While the fatty acylated form of G_o1 is the predominant species, its appearance paralleled that observed for G_o2 in developing rat cortex. Perinatal hypothyroidism induced by methimazole treatment did not significantly alter the appearance of cerebral cortical G_o1 and G_o2 between days 1 and 22 postpartum. Our findings support the earlier idea that heterogeneity of G_o proteins in mammalian brain is likely the result of different co- or post-translational processings of each splice variant of G_o. While the appearance of G_o isoforms is developmentally regulated, they likely do not play an obligatory role in neonatal brain development. Alternatively, the expression of G_o isoforms in developing rat cortex may be controlled by an intrinsic signal(s) that is independent of the thyroid status.     

Simulating the effect of quarantine on the spread of the 1918–19 flu in Central Canada

Quarantine is often proposed and sometimes used to control the spread of infectious diseases through a human population. Yet there is usually little or no information on the effectiveness of attempting to quarantine humans that is not of an anecdotal or conjectural nature. This paper describes how a compartmental model for the geographic spread of infectious diseases can be used to address the potential effectiveness of human quarantine. The model is applied to data from the historical record in central Canada around the time of the 1918–19 influenza epidemic. Information on the daily mobility patterns of individuals engaged in the fur trade throughout the region prior to, during, and immediately after the epidemic are used to determine whether rates of travel were affected by informal quarantine policies imposed by community leaders. The model is then used to assess the impact of observed differences in travel on the spread of the epidemic. Results show that when mobility rates are very low, as in this region, quarantine practices must be highly effective before they alter disease patterns significantly. Simulation results suggest, though, that effectiveness varies depending on when the limitation on travel between communities is implemented and how long it lasts, and that a policy of introducing quarantine at the earliest possible time may not always lead to the greatest reduction in cases of a disease.     

Effect of division of cortico — Subcortical connections on spontaneous unit activity in the lateral geniculate body and visual cortex

In acute experiments on cats the cortical projection connections of one hemisphere were divided, and the principal characteristics of spontaneous unit activity were studied in the lateral geniculate bodies (LGB) and visual cortex (area 17). After the operation the same types of spontaneous activity were found in these structures as in the intact structures. However, the number of spontaneously active cells in the structures on the side of the operation was considerably reduced. In the isolated visual cortex there was a redistribution of the relative percentage of neurons with spontaneous activity in the various layers: these cells were most numerous in layers IV–V, whereas in the normal cortex they are more numerous in layers III–IV. The mean firing rate of all types of cells was reduced in the isolated cortex. In LGB on the side of the operation a relative decrease in the number of cells with a high firing rate was observed.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 4, No. 1, pp. 47–53, January–February, 1972.     

Effect of α-p-chlorophenoxyisobutyrate on the metabolism of isoprenoid compounds in the rat

1. Feeding of alpha-p-chlorophenoxyisobutyrate (CPIB) to rats increased ubiquinone concentration in the liver but not in other tissues. The increase was progressive with the time of feeding and related to the concentration of CPIB in the diet. 2. Incorporation of [1-(14)C]acetate, but not of [2-(14)C]mevalonate, into sterols in the liver in vivo or by liver slices in vitro was decreased on feeding the rats with CPIB. However, incorporation of mevalonate into ubiquinone increased. 3. CPIB, when added in low concentrations to liver slices, had no effect on isoprene synthesis from acetate; higher concentrations, however, were inhibitory. 4. No activation of ubiquinone synthesis from mevalonate was observed when CPIB was added to the liver slices synthesizing ubiquinone. 5. The increase in ubiquinone in CPIB-fed animals appears to be due to increased synthesis in the initial stages and to decreased catabolism in the later stages. 6. An inverse relationship was found between the concentration of ubiquinone in the liver and the serum sterol concentration in CPIB-fed rats.     

Effect of aging on the substance P receptor,NK–1, in the spinal cord of rats with peripheral nerve injury

Substance P (SP) levels in the spinal cords of very old rats are less than the levels in younger rats (Bergman et al., 1996). After injury to a peripheral nerve in young rats, immunoreactivity (ir) to the SP receptor, NK–1 (neurokinin-1), increases in the spinal cord ipsilateral to the injury and the increases are correlated with the development of thermal hyperalgesia (Goff et al., 1998). Thus we postulated that aged rats might display an increased sensitivity to thermal stimulation before peripheral nerve injury and that they might respond differently to injury than do younger rats. To test this hypothesis, we used the Bennett and Xie model (1988) of chronic constriction injury (CCI) to the sciatic nerve to induce a neuropathic pain condition. We investigated the effect of age on changes in NK-1 ir in superficial layers of the dorsal horn and on numbers of NK ir cells in deeper laminae at the L4-L5 levels of the spinal cord after CCI. NK-1 receptors were tagged immunohistochemically and their distribution quantified by use of computer-assisted image analysis. NK-1 ir changes were related to alterations in thermal and tactile sensitivity that developed after CCI in young, mature and aged (4-6, 14-16, and 24-26 months) Fischer F344 BNF1 hybrid rats. No differences in thermal or tactile sensitivity of young and aged rats were seen in the absence of nerve injury. After injury, aged rats developed thermal hyperalgesia and tactile allodynia more slowly than did the younger rats. NK-1 receptor ir and numbers of NK-1 ir cells in the dorsal horn increased with time post-injury in all three groups. NK-1 ir increases were correlated with the development of thermal hyperalgesia in those rats that displayed hyperalgesia. However, some rats developed an increased threshold to thermal stimuli (analgesia) and that also was correlated with increases in NK-1 ir. Thus NK-1 ir extent, while correlated with thermal sensitivity in the absence of injury, is not a specific marker for disturbances in one particular sensory modality; rather it increases with peripheral nerve injury per se.     

Effect of the association of IGF-I, IGF-II, bFGF, TGF-β1, GM-CSF, and LIF on the development of bovine embryos produced in vitro

This study examined the influence of the following growth factors and cytokines on early embryonic development: insulin-like growth factors I and II (IGF-I, IGF-II), basic fibroblast growth factor (bFGF), transforming growth factor (TGF-β), granulocyte-macrophage colony-stimulating factor (GM-CSF), and leukemia inhibitory factor (LIF). Synthetic oviduct fluid (SOF) was used as the culture medium. We studied the development of bovine embryos produced in vitro and cultured until Day 9 after fertilization. TGF-β1, bFGF, GM-CSF, and LIF used on their own significantly improved the yield of hatched blastocysts. IGF-I, bFGF, TGF-β1, GM-CSF, and LIF significantly accelerated embryonic development, especially the change from the expanded blastocyst to hatched blastocyst stages. Use of a combination of these growth factors and cytokines (GF-CYK) in SOF medium produced higher percentages of blastocysts and hatched blastocysts than did use of SOF alone (45% and 22% vs. 24% and 12%; P < 0.05) on Day 8 after in vitro fertilization and similar results to use of SOF + 10% fetal calf serum (38% and 16%, at the same stages, respectively). The averages of total cells, inner cell mass cells, and trophectoderm cells of exclusively in vitro Day-8 blastocysts for pooled GF-CYK treatments were higher than those for SOF and similar to those for fetal calf serum. The presence of these growth factors and cytokines in the embryo culture medium therefore has a combined stimulatory action on embryonic development; in particular through an increase in hatching rate and in the number of cells of both the inner cell mass and trophoblast. These results are the first to demonstrate that use of a combination of recombinant growth factors and cytokine, as IGF-I, IGF-II, bFGF, TGF-β1, LIF, and GM-CSF, produces similar results to 10% fetal calf serum for the development of in vitro-produced bovine embryos. This entirely synthetic method of embryo culture has undeniable advantages for the biosecurity of embryo transfer.     

Effect of point substitutions in the MnSOD, GPX1, and GSTP1 genes on the risk of familial and sporadic breast cancers in residents of the Altaĭ region of the Russian Federation

The frequencies of the polymorphic gene variants MnSOD Ala9Val, GPX1 Pro198Leu, and GSTP1 Ile105 Val were estimated in female residents of Altai krai with breast cancer. The frequency distributions of the genotypes for all genes studied in both patients and control subjects fit the Hardy-Weinberg equilibrium. The estimated frequencies of the genotypes for the studied genes in the control group did not differ from those earlier reported for Caucasoid women living in Europe. The T(rs1050450) allele of the GPX1 gene was demonstrated to protect against sporadic breast cancer (OR = 0.74 (95% CI = 0.58-0.94), p = 0.012). Carriers of the genotype combination MnSOD CC + GPX1 CC were found to have a 1.6 times higher risk of sporadic breast cancer compared to the control group (OR = 1.59 (1.05-2.41), p = 0.0258). The polymorphic loci GSTP1 (rs1695) and MnSOD (rs4880) were not found to be significantly associated with the risk of familial or sporadic breast cancer.     

Effect of “Chemical” Hypoxia on the Potassium Conductance of the Membrane of Pheochromocytoma Cells

We studied the effect of “chemical” (induced by the action of sodium thiosulfate, STS) hypoxia on the potassium conductance of the membrane of pheochromocytoma cells. Application of 1 to 10 mM STS decreased in a dose-dependent manner the amplitude of integral potassium current without changes in the voltage dependence of its activation. The concentration dependence of the action of STS on the amplitude of potassium current was estimated using the Boltzmann equation. The value of concentration for 50% inhibition was 2.7 ± 0.2 mM, while the slope coefficient was 0.9 ± 0.2 mM⁻¹. In the presence of 10 mM STS, the decrease in the amplitude of potassium current reached, on average, 55%. Therefore, “chemical” hypoxia influences rather significantly the potassium conductance of the membrane of pheochromocytoma PC12 cells.     

Effect of Antihypertensive Drugs on the “Intrinsic” Heart Rate

“Intrinsic” heart rate in man was measured by giving simultaneous atropine and propranolol and used to study the direct effect of antihypertensive drugs on the heart. Though the intrinsic and control heart rates decreased significantly following the administration of reserpine, there was no significant difference between high and low doses. No similar effects were observed with debrisoquine sulphate and methyldopa, though in high doses the latter produced a decrease which was of some statistical significance.     

Effect of estradiol-17 β on the cytology of the liver,gonads and pituitary,and on plasma electrolytes in the female freshwater eel

Summary Female freshwater eels injected with estradiol-17 (E2) for 15–78 days appear paler and secrete more mucus than controls. The resulting strongly opalescent blood plasma indicates that vitellogenin synthesis occurs in the liver, which shows a significant hypertrophy, an increased vacuolization (lipid material) and glycogen depletion. Plasma sodium is lowered, but calcium levels are considerably increased. The gonosomatic index increases (0.92±0.1 to a maximum of 2.21). Oocytes are enlarged, but the incorporation of vitellogenin remains discrete. Gonadotrophs (GTH cells), small and scarcely visible in the pituitary of control eels, are hypertrophied and contain numerous glycoprotein granules after E2-administration. E2 may act on the pituitary and/or hypothalamus via a positive feedback to induce gonadotrophin (GTH) synthesis; GTH release seems to be very limited as indicated by the ovarian response. The differentiation of GTH cells in eels treated with fish pituitary extracts is most probably due to secretion of E2 by the ovary, which reacts on the pituitary. Various hypotheses are considered to explain the low GTH release.Thyrotrophs, somatotrophs and prolactin cells of the pituitary are stimulated. In the pars intermedia, MSH and PAS-positive cells appear less active. A possible antidopaminergic effect of E2 is discussed.E2 administration constitutes a simple and economic technique to induce the synthesis of GTH and will facilitate the biochemical and biological study of the latter hormone in eels.     

Effect of PLCβ4 in the thalamus on the EEG in REM sleep

Sleep and Biological Rhythms -