Effect of modification of membrane saccharides on hormonal imprinting in Tetrahymena

Concanavalin-A (Con-A) competes with insulin for the insulin binding sites of the receptor, an event resulting in overlapping bonds. If the saccharide components of the receptor are subjected to periodate treatment the binding of insulin decreases and so does the imprinting evoked by it. Simultaneously, the binding of Con-A increase immediately after the treatment and 24 hours following the insulin imprinting. This phenomenon indicates that though the two ligands (i.e. insulin and Con-A) overlap on the intact receptor, alterations in the saccharide component influence their binding though not in the same manner and not in the same direction. Periodate treatment, similarly as observed in mammalian lymphocyte cultures, enhanced the division of Tetrahymenas and the peak of Con-A binding occurred parallel to the peak of division after periodate treatment of equal duration. Periodate treatment disturbed not only the binding of Con-A but that of other lectins as well. It has been concluded that hormonal imprinting requires a physiological condition of the membrane and any disturbance of the membrane will lead to a decrease in the efficacy of imprinting.     

MicroRNA in hormonal mechanisms of regulation of NK cell function

We investigated the effect of human chorionic gonadotropin, estriol, leptin, ghrelin, and kisspeptin on the microRNA expression in separated NK cells. All of these hormones are able to effectively modulate the expression of microRNAs both stimulating and suppressing the cytotoxic potential of NK cells and thereby indirectly regulate the functions of these lymphocytes.     

Metabolic and hormonal responses in theophylline-increased cold resistance in males

The effects of theophylline (a phosphodiesterase inhibitor-adenosine receptor antagonist) and substrate feeding (Ensure, 250 kcal/235 ml) on cold resistance were studied in seminude males undertaking submaximal (50% maximum O2 consumption), intermittent (34% of total time) exercise in the cold (-5 to 15 degrees C, individually adjusted) for 3 h. Each subject (n = 7) served as his own control and was tested on a weekly schedule. Under control treatment, rectal temperature (Tre) decreased by 0.9 degrees C to approximately 36.2 degrees C after cold exposure, whereas under theophylline and Ensure, the decrease of Tre was only 0.4 degrees C, indicating a significant increase (P less than 0.05) in cold resistance (50% better than control). The plasma concentration of theophylline was 4.8-5.9 micrograms/ml and was positively correlated with plasma concentration of free fatty acids. Plasma norepinephrine (NE) increased significantly during cold exposure; the absolute concentration was significantly higher after theophylline pretreatment. The plasma concentrations of glucose, epinephrine, cortisol, and adenosine 3',5'-cyclic monophosphate did not change and the changes of free thyroxine and triiodothyronine were minor. Together, the effectiveness of theophylline + Ensure in acutely increasing cold resistance may be due to increased substrate availability for thermogenesis, part of which, through theophylline's potentiation of both sympathetic release of NE and NE-stimulated lipolysis and part of which, through supplementary feeding of Ensure.     

Effect of prostaglandins on hormonal function of cultured rat Leydig cells

The effect of PGF2 alpha and its analogues on androgen production and activity of delta 5,3 beta-hydroxysteroid dehydrogenase in rat Leydig cells in vitro was investigated. Prostaglandin of the F type inhibit the enzyme activity and hormone secretion by cultured Leydig cells. This effect was considerably stronger in Leydig cells isolated from mature rats, than by Leydig cells from immature animals.     

Regulation of cell adhesion using a signal-responsive membrane substrate

We have developed a novel cell culture material that regulates cell adhesion by changes in potassium ion concentration. The material is a polyethylene substrate grafted to a copolymer of the thermoresponsive polymer N-isopropylacrylamide (NIPAM) and benzo-18-crown- 6-acrylamide (BCAm), with a pendant crown ether as sensor. The crown ether recognizes potassium ion concentrations and NIPAM conformational changes lead to changes in the hydrophobicity/hydrophilicity balance of the entire polymer at constant cell culture temperatures. Although cells were successfully cultured on the ion recognition material in normal culture medium at 37 degrees C, the cells could be detached from the material surface by adding potassium ions alone, without proteolytic enzymes, because the surface to which the cells were attached altered its surface characteristics to a more hydrophilic state. Therefore, cell layers with intact cell-to-cell junctions and high activities were successfully recovered. Furthermore, by changing the target sensors, this material will be able to control cell adhesion through various cellular signals.     

Effect of emotional-algesic stress on the hormonal function of thyroid and parathyroid glands

Experiments on 215 Wistar rats have revealed that the state of the endured stress is an essential factor inducing disturbance in functioning of the hypothalamus-adenohypophysis-thyroid gland system accompanied by disturbance in regulation of the thyrotropin and triiodothyronine formation under conditions of myocardium necrosis development.     

Blocked ricin-conjugated T cell immunotoxins: Effect of anti-CD6-blocked ricin on normal T cell function

Summary The biological properties of an immunotoxin composed of an anti-CD6 monoclonal antibody conjugated to whole ricin, which had been modified so that the galactose-binding sites of the B chain were blocked (blocked ricin), were examined. Treatment of peripheral blood lymphocytes with anti-CD6-blocked ricin for a 24-h period prevented T cell proliferation induced by phytohemagglutinin in a dose-dependent manner with concentrations causing 50% inhibition (IC₅₀) ranging from 5 pM to 30 pM. In contrast, treatment with either blocked ricin alone or with a control immunotoxin prepared with a B-cell-lineage-restricted monoclonal antibody gave IC₅₀ values of approximately 2 nM. Although shortening the duration of the anti-CD6-blocked ricin treatment to as little as 3 h had little significant effect on the observed inhibition, T cell viability experiments demonstrated that the magnitude of immunotoxin-induced killing after a given time period is significantly higher when the target cells become activated. Thus, from the initial concentration of cells treated with anti-CD6-blocked ricin placed in culture, 40%–45% viable cells remained after 2 days yet only 3%–9% remained if phorbol ester and Ca²⁺ ionophore were added; activation of T cells after mock treatment using blocked ricin plus nonconjugated anti-CD6 demonstrated that this effect was not the result of activation alone. The toxicity of anti-CD6-blocked ricin was also measured by inhibition of PHA-induced clonogenic growth of normal T cells. Continuous treatment of the cells using anti-CD6-blocked ricin at 0.1 nM resulted in a surviving fraction of about 3.5 × 10^–3; when immunotoxin treatment was for 24 h or less, the surviving fraction was only about 10^–1. As an indication of the unique specificity of anti-CD6-blocked ricin, immunotoxin pretreatment of potential responder cells prevented the generation of allogeneic cytolytic T lymphocytes in mixed lymphocyte cultures yet had little effect on the generation of interleukin-2-induced lymphokine-activated killer cell activity. We conclude that anti-CD6-blocked ricin demonstrates a cellular specificity and potency that make it a highly promising anti-T cell reagent.     

Toxic substances and cell membrane function.

The exposed location and functional importance of cell membranes make them particularly susceptible to the toxic effects of many chemicals. The likelihood of such effects has been appreciated for many years. However, the recent advent of new techniques has greatly increased our understanding of the complexities of membrane structure and function. These data make it quite clear that the interaction of toxic compounds with either the protein or the lipid component of cell membranes may substantially alter membrane function. This paper summarizes the current concepts of membrane structure and function and discusses the techniques currently in use to study cell membranes. Several examples are presented in which xenobiotics significantly alter membrane function. These include effects of heavy metals on passive ion permeability, impairment of osmoregulation and calcium transport by organochlorine pesticides, inhibition of the transport of neurotransmitter metabolites by phenoxyacetic acid herbicides in choroid plexus, and reduction in intestinal nutrient transport by heavy metals. Hence the study of the interactions of foreign compounds with membrane function may enhance our understanding of mechanisms both of toxicity and of basic membrane function.     

Effect of substances that disrupt cell adhesion to the substrate on the glycoprotein spectrum of normal fibroblasts in culture]

Alterations of glycoproteins pattern of normal mouse and chick embryo fibroblasts, caused by chemicals impairing cell-substrate adhesion were studied in culture. The chemicals used were proteases (trysin, pronase and papain), EDTA and urea. Using sodium dodecyl sulfat polyacrylamide gel electrophoresis, it was shown that mouse fibroblasts contained four major high-molecular mass glycoproteins that were removed from cells when the adhesion was impaired. Their apparent molecular masses were estimated to be 268 000 (GP-268), 260 000 (GP-260), 211 000 (GP-211) and 196 000 (GP-196). Each glycoprotein proved to be senitive only to one treatment: GP-268 - to very low doses of proteases (1--10 microgram/ml, 10 min), GP-260 - to long treatment with urea (1 M, 2h), GP-211 and GP-196 - to cell rounding and detachment from the substrate caused by long treatment with EDTA (200 microgram/ml, 30 min). In contrast to mouse cells, chick fibroblasts contained only one major high-molecular mass glycoprotein with an apparent molecular mass 266 000 (GP-266) sensitive to all the treatments tested, but to a different degree. The role of glycoproteins studied in the process of cell-substrate adhesion as well as the dependence of certain glycoproteins (GP-211 and GP-196) on the cell shape is discussed.     

Effect of carnosine on the erythrocyte membrane in normal states and in diabetes

Administration of carnosine (beta-alanyl-L-hystidine) at 5 mg/100 g body weight per os was defined as normalising the acid erythrogram parameters in the experiments on rats with streptozotocin-induced diabetes.     

Influence of increased membrane cholesterol on membrane fluidity and cell function in human red blood cells

Cholesterol and phospholipid are the two major lipids of the red cell membrane. Cholesterol is insoluble in water but is solubilized by phospholipids both in membranes and in plasma lipoproteins. Morever, cholesterol exchanges between membranes and lipoproteins. An equilibrium partition is established based on the amount of cholesterol relative to phospholipid (C/PL) in these two compartments. Increases in the C/PL of red cell membranes have been studied under three conditions: First, spontaneous increases in vivo have been observed in the spur red cells of patients with severe liver disease; second, similar red cell changes in vivo have been induced by the administration of cholesterol-enriched diets to rodents and dogs; third, increases in membrane cholesterol have been induced in vitro by enriching the C/PL of the lipoprotein environment with cholesterol-phospholipid dispersions (liposomes) having a C/PL of >1.0. In each case, there is a close relationship between the C/PL of the plasma environment and the C/PL of the red cell membrane. In vivo, the C/PL mole ratio of red cell membranes ranges from a normal value of 0.9–1.0 to values which approach but do not reach 2.0. In vitro, this ratio approaches 3.0. Cholesterol enrichment of red cell membranes directly influences membrane lipid fluidity, as assessed by the rotational diffusion of hydrophobic fluorescent probes such as diphenyl hexatriene (DPH). A close correlation exists between increases in red cell membrane C/PL and decreases in membrane fluidity over the range of membrane C/PL from 1.0 to 2.0; however, little further change in fluidity occurs when membrane C/PL is increased to 2.0–3.0. Cholesterol enrichment of red cell membranes is associated with the transformation of cell contour to one which is redundant and folded, and this is associated with a decrease in red cell filterability in vitro. Circulation in vivo in the presence of the slpeen further modifies cell shape to a spiny, irregular (spur) form, and the survival of cholesterol-rich red cells is decreased in the presence of the spleen. Although active Na-K transport is not influenced by cholesterol enrichment of human red cells, several carrier-mediated transport pathways are inhibited. We have demonstrated this effect for the cotransport of Na + K and similar results have been obtained by others in studies of organic acid transport and the transport of small neutral molecules such as erythritol and glycerol. Thus, red cell membrane C/PL is sensitive to the C/PL of the plasma environment. Increasing membrane C/PL causes a decrease in membrane fluidity, and these changes are associated with a reduction in membrane permeability, a distortion of cell contour and filterability and a shortening of the survival of redcells in vivo.     

Lipid regulation of cell membrane structure and function

Recent studies of structure-function relationships in biological membranes have revealed fundamental concepts concerning the regulation of cellular membrane function by membrane lipids. Considerable progress has been made in understanding the roles played by two membrane lipids: cholesterol and phosphatidyl-ethanolamine. Cholesterol has been shown to regulate ion pumps, which in some cases show an absolute dependence on cholesterol for activity. These studies suggest that an essential role that cholesterol plays in mammalian cell biology is to enable crucial membrane enzymes to provide function necessary for cell survival. Studies of phosphatidylethanolamine regulation of membrane protein activity and regulation of membrane morphology led to hypotheses concerning the roles for this particular lipid in biological membranes. New information on lipid-protein interactions and on the nature of the lipid head groups has permitted the development of mechanistic hypotheses for the regulation of membrane protein activity by phosphatidyl-ethanolamine. In addition, intermediates in the lamellar-nonlamellar phase transitions of membrane systems containing phosphatidylethanolamine, or other lipids with similar properties, have recently been implicated in facilitating membrane fusion. Finally, studies of transmembrane movement of lipids have provided new insight into the regulation of membrane lipid asymmetry and the biogenesis of cell membranes. These kinds of studies are harbingers of a new generation of progress in the field of cell membranes.     

The fluidity of normal and virus-transformed cell plasma membrane.

1. The phospholipid composition and cholesterol/phospholipid ratio of plasma membrane is the same in normal as in transformed BHK (baby-hamster kidney) cells; no significant difference in length or degree of unsaturation of the contributing acyl chains is apparent. 2. The turnover of acetate-labelled phosphatidylcholine species in the plasma membrane of normal and transformed BHK cells is the same. 3. Intramembranous particles of normal and transformed 3T3-cell plasma membrane are randomly distributed, whether at 4degreesC or at 37degreesC, in sparse or in dense cultures. There is no correlation between distribution of particles and the movement of concanavalin A receptor sites. 4. It is concluded that transformation of fibroblastic cells by oncogenic viruses does not lead to major changes in the lipid fluidity of the plasma membrane. 5. Details of the phospholipid composition of nuclei, mitochondria and endoplasmic reticulum in normal and transformed BHK cells have been deposited as Supplementary Publication SUP 50061 (5 pages) at the British Library Lending Division, Boston, Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies may be obtained on the terms given in Biochem. J. (1976) 153, 5.     

Effect of proteolytic enzyme inhibitors on lung cell population function in normal mice and in the development of tourniquet shock

Cell populations of mice lungs have been studied for variations in the lavage and lumen of the alveoli. The development of the tourniquet shock induces a decrease in the number of macrophages and lymphocyte and an increase in the number of neutrophils, erythrocytes and epithelium cells. Application of the proteolysis enzyme inhibitors is found to stabilize the bronchoalveolar barrier and to prevent these changes.     

Dermatoglyphic asymmetry and testosterone levels in normal males

Dermatoglyphic prints and salivary samples were taken on a sample of 39 adult males. A statistical relationship between dermatoglyphic asymmetry and adult testosterone levels as measured in saliva was examined for seven dermatoglyphic variables by means of correlation, regression, and analysis of covariance, controlling for age and stature when necessary. The first two types of analyses indicated a significant effect of testosterone level upon the asymmetry of three dermatoglyphic variables: a-b ridge count, palmar pattern intensity, and the combined pattern intensity of palm and digits. Analysis of covariance, which examined the effect of testosterone level as a categorical variable, while holding age or stature constant, demonstrated the asymmetry of five variables to be significantly affected by testosterone level: radial digital count, digital pattern intensity, palmar pattern intensity, total digital ridge count, and the combined palmar and digital intensity. Although there is as yet only associational evidence linking levels of prenatal and secondary testosterone, the results of the present study lend support to the hypothesis that prenatal testosterone levels may have a significant effect on the development of dermatoglyphics. © 1993 Wiley-Liss, Inc.     

Effect of alpha-phenyl-N-tert-butylnitrone on brain cell membrane function and energy metabolism in experimental Escherichia coli meningitis in the newborn piglet

We evaluated the efficacy of alpha-phenyl-N-tertbutylnitrone as an adjunctive therapy in experimental bacterial meningitis in the newborn piglet. Meningitis was induced by intracisternal injection of 10(8) colony-forming units of Escherichia coli in 100 microl of saline. Alpha-Phenyl-N-tert-butylnitrone 100 mg/kg was given as a bolus intravenous injection 30 min before induction of meningitis. Although it completely abolished the elevated CSF tumor necrosis factor-a level observed in the meningitis group, alpha-phenyl-N-tert-butylnitrone did not down-modulate parameters of inflammatory responses such as increased intracranial pressure, hypoglycorrhachia, elevated CSF lactate level, and CSF leukocytosis observed in this group. However, alpha-phenyl-N-tert-butylnitrone treatment mitigated alterations in brain cell membrane structure and function during meningitis, evidenced by amelioration of increased brain cell membrane lipid peroxidation products (conjugated dienes) and decreased Na+, K+-ATPase activity. Reduced mean arterial blood pressure, cerebral perfusion pressure, brain glucose concentration, and cerebral energy stores and marginally increased brain lactate level observed in the meningitis group were also ameliorated. These results suggest that although it failed to attenuate the inflammatory responses, alpha-phenyl-N-tert-butylnitrone was effective in ameliorating brain injury in neonatal bacterial meningitis.