Systemic and organic changes in the microcirculatory bed in experimental dehydration of the body

Among systemic mechanisms of microvascular reactivity of the musculus spinotrapezius, pancreas and small intestine mesentery at dehydration, a special role play the changes directed to maintenance of harmony between the capacity of the blood bed and volume of the circulatory blood, morpho-functional factors on regulation of hemodynamics, as well as mechanism of liquor resource++ elimination from the blood bed. The organic peculiarities of the microvascular reactivity at dehydration are determined by topic and quantitative character of their changes.     

Different properties of two groups of orientation discriminators in the cat visual cortex

The properties of 149 neurons, divided into two groups, were investigated during acute experiments on immobilized cats. These consisted of "timers" (37%) in which latency of response and time taken for reaction to peak changed in an orientation range of not more than 10 msec. The remaining 63% consisted of "scanners" [2]. "Timers" reliably differed from "scanners" in their shorter latent periods, rising time of discharge rate, duration of response, and higher rate of impulsation at all orientations of the stimulus. "Scanners" display greater orientational tuning and "scan" much more frequently throughout the orientation range. The pattern of acuity of orientational tuning is counterphasic during response in neurons of these two groups, while the distribution of their preferred orientation is complementary in nature. Both timers and scanners were found in the orientation columns of the visual cortex on most occasions, with the latter predominating. Columns consisting of only timers or scanners were met with more seldom. The significance of the differences between the properties of the two groups of neurons in the visual cortex is discussed with a view to orientational discrimination.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 1, pp. 85–92, January–February, 1986.     

Dynamics of orientational tuning of feling visual cortex neurons under the effects of sombrevine

Dynamics of orientational tuning in 59 primary visual cortex neurons were investigated before and after sombrevine-induced anesthesia during acute experiments on immobilized cats using temporal slice techniques. A dynamic shift in preferred orientation of a flashing light strip, during which peak amplitude of spike discharges was noted (at an angle of between 22 and 157°) occurred as response developed in two-thirds of the cells. We had previously named this effect "scanning the orientational range" [9]. Scanning declined significantly in 45% of the sample, culminating in complete disappearance of this effect in some cells following sombrevine action. Scanning intensified in 30%, while dynamics of tuning remained unchanged in 25% of units. Sombrevine administration induced change in the preferred stimulus orientation of 60% of the neurons (referred to as "unstable" cells) and remained constant in "stable" cells (= 40%). Dynamic changes in preferred stimulus orientation were 2.5 times as high as those of stable cells in the waking state. The scanning effect declined significantly in 60% of "unstable" neurons under the action of anesthesia and remained unchanged in not more than 6%. At the same time, orientational tuning did not alter in the "stable" cell group in 46% of units, either declining (25%) or increasing (29%) in the remaining scanning ranges.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 107–113, January–February, 1990.     

Tuning for cruciform stimuli in visual cortex neurons of cat

In the primary visual cortex of an immobilized awake cat, nearly one-third of the neurons studied (8 out of 22) were found to respond to flashing cruciform light stimuli 1.5–4 times better than to single stimulations with the strips of preferred orientation. It is suggested that such neurons can detect angles and line intersections.Neirofiziologiya/Neurophysiology, Vol. 25, No. 5, pp. 362–364, September–October, 1993.     

Structure and function of the microcirculatory bed in the preserved heart]

The morphological analysis of the state of the heart during hypertermal perfusion with different conservants reveals clear dependence of the microcirculation and the activity of the heart upon the type of the conservant. Perfusion with a salt solution and hemodilution is accompanied by pronounced disorders in microcirculation and unsatisfactory parameters of the cardiac activity. Conservation with cryoprecipitated plasma is characterized by comparatively less microcirculatory disorders, but fails to give a reliable safety of the heart. When using medium 199, changes in microcirculation were found to be minimal and parameters of cardiac activity were satisfactory. In the complex of non-specific changes in microcirculatory vessels the maximum structural lability was revealed in blood capillaries and vessels of the postcapillary-venular link.     

Production of soluble P-selectin by platelets and endothelial cells

The distribution of a soluble form of a cell adhesion molecule, P-selectin, in human platelets and cultivated endothelial cells has been studied by enzyme-linked immunosorbent assay (ELISA). The concentration of soluble P-selectin in the blood plasma of healthy donors and patients with abnormal platelet count has also been determined. P-selectin was measured in the Triton X-100 lysate of platelets and endothelial cells (total P-selectin), in the 100,000g supernatant obtained after sedimentation of the membrane fraction from the homogenate of sonicated platelets and endothelial cells (intracellular soluble P-selectin), in the supernatant of activated and nonactivated platelets, and in the culture medium of endothelial cells. A soluble form of P-selectin which did not coprecipitate with the membrane fraction was detected in platelets and accounted for approximately 10% of the total P-selectin. Platelet activation by thrombin, ADP, or a thromboxane A2 analog resulted in the secretion of 30-50% of the intracellular soluble P-selectin. Measurements of P-selectin in endothelial cell culture revealed that endothelium from aorta contained about twofold more P-selectin than endothelium from umbilical vein. Intracellular soluble P-selectin was identified in both types of endothelial cells. In endothelial cells from the umbilical vein this form made up approximately 10% of the total P-selectin. Soluble P-selectin was also detected in the medium of cultivated endothelial cells, where its content correlated with the total cellular P-selectin. Concentration of P-selectin in blood plasma strongly correlated with the platelet count in the blood of healthy donors and patients with thrombocytosis and thrombocytopenia. These data indicate that platelets serve as one of the main source of plasma P-selectin. However, the presence of P-selectin in the plasma of patients with severe thrombocytopenia suggests that endothelium can also be involved in plasma P-selectin production. Thus, in vitro experiments as well as measurements of plasma P-selectin have shown that both platelets and endothelial cells can produce a soluble form of the protein. Platelet-derived soluble P-selectin and plasma P-selectin were shown to react with antibodies against the cytoplasmic domain of P-selectin. These data prove that at least part of soluble P-selectin is produced by synthesis employing special mRNA which lacks the sequence encoding the transmembrane domain, but not by the proteolytic shedding of the extracellular portion of membrane P-selectin.     

Ontogenetic approach to assessment of chufa response to culture conditions by the method of chlorophyll fluorescence induction

Application of earlier proposed ontogenetic approach to assessment of chufa (Cyperus esculentus L.) response to artificial-light culture growing conditions differing in illuminance and type of mineral nutrition is described. It was shown that, on biological soil-like substrate, plant productivity did not increase as a result of PAR level rising, and life time of chufa leaves was reduced to 11 days as compared with 18 days on the neutral substrate. Changes in the parameters of chlorophyll fluorescence induction (F _v/F _m, Yield = (F _m − F _t)/F _m, and ETR = 0.5 × 0.84 × Yield × PAR) analyzed on the basis of ontogenetic approach show that it can disclose nonoptimal culture conditions.     

Ligand-induced, p38-dependent apoptosis in cells expressing high levels of epidermal growth factor receptor and ErbB-2

Increased expression of the epidermal growth factor (EGF) receptor (EGFR) and ErbB-2 is implicated into the development and progression of breast cancer. Constant ligand-induced activation of EGFR and ErbB-2 receptor-tyrosine kinases is thought to be involved in the transformation of fibroblasts and mammary epithelial cells. Data herein show that ligand stimulation of cells that express both the EGFR and the ErbB-2 may result either in cell proliferation or apoptosis depending on the expression levels of EGFR and ErbB-2. Mammary tumor cells that express low levels of both receptors or high levels of ErbB-2 and low levels of EGFR survive and proliferate in the presence of EGF. In contrast, fibroblastic cells or mammary tumor cells, which co-express high levels of EGFR and ErbB-2 invariably undergo apoptosis in response to EGF. In these cells persistent activation of p38 MAPK is an essential element of the apoptotic mechanism. Also, the data implicate a p38-dependent change in mitochondrial membrane permeability as a downstream effector of apoptosis. Ligand-dependent apoptosis in cells co-expressing high levels of EGFR and ErbB-2 could be a natural mechanism that protects tissues from unrestricted proliferation in response to the sustained activation of receptor-tyrosine kinases.