The relationship of the potassium transport function of human erythrocyte membranes to the structural state of the glycocalyx

The two structural-functional state parameters of erythrocyte membrane in healthy donors and ischemic heart disease patients have been compared--the potassium exchange rate constant (x), and the quantity of Alcian blue sorption capacity of glycocalyx (y). The connection between the first parameter--x--and the other one--y--has been observed in cases, when the value of the latter experienced both the seasonal oscillations (the coefficient of lineal correlation was: r = -0.87, P less than 0.01) and the changes in the cause of ischemic heart disease (r = -0.72, P less than 0.01) and its treatment (the coefficients of correlation attitude of each of parameter changes were: eta xy = 0.83, P less than 0.01; eta yx = 0.52, P less than 0.05). The above connection may indicate the participation of membrane glycoproteins and glycolipids in a regulation of the cation transport function of the erythrocyte membrane.     

Circadian variations of total renin, active renin, plasma renin activity and plasma aldosterone in clinically healthy young subjects

The direct assay of total renin (TRC) and active renin concentration (ARC) is a reality due to the availability of monoclonal antibodies against human renin. Because of this, a study has been performed in order to assess the circadian rhythmicity of TRC and ARC. The study was extended to plasma renin activity (PRA) and plasma aldosterone concentration (PAC) for a more complete assessment of the renin-angiotensin-aldosterone system (RAAS). Twelve clinically healthy subjects (6 males and 6 females, age from 20 to 25 years) volunteered for this study. Time-qualified data series were analysed by means of chronobiological procedures in order to validate the circadian rhythm and to correlate the sinusoidal profiles. The circadian rhythm was validated at a high significance for TRC, ARC, PRA and at a borderline significance for PAC. The periodic oscillations were significantly correlated, demonstrating that TRC, ARC, PRA and PAC cycles oscillate in synchronism during the 24-hour span.     

Relationships between lipid peroxidation or cyclic nucleotides and motility in human asthenozoosperm and normosperm]

The relationships between sperm lipid peroxidation (LP) or cyclic nucleotides and sperm motility in normospermic and asthenozoospermic specimens were analyzed. Sperm motility was measured by the transmembrane migration method; LP was measured by thiobarbituric acid (TBA) method and the intracellular cAMP and cGMP contents was measured by radioimmunoassay in 20 fertile and 20 asthenozoospermic infertile human semen specimens. Results showed that in both fertile and infertile individual, there was a close negative correlation between sperm LP formation and motility (r = -0.76; P < 0.001 and r = -0.68; P < 0.001); there were significant positive correlations between intracellular cAMP (r = 0.64; P < 0.01 and r = 0.59; P < 0.01) or cGMP (r = 0.60; P < 0.01 and r = 0.55; P < 0.05) and sperm motility; and the correlation between LP and motility was the closest. These results suggest a causative role for LP in the aetiology of male infertility due to defective sperm motility, and confirmed that intra-cellular cyclic nucleotides likely also have influences on sperm motility.     

The Paramecium circadian clock: synchrony of changes in motility, membrane potential, cyclic AMP and cyclic GMP

The behavior of a ciliate protozoan, Paramecium, is known to represent the electrical state of the cell membrane, and regulation of the membrane potential and ciliary motion are known to involve cAMP and cGMP. The present study shows the synchrony of circadian changes in motility, resting membrane potential and cyclic nucleotides in P. multimicronucleatum. Using an automated system for tracking isolated single microorganisms, the isolated Paramecium cells are confirmed to swim fast and straight during the day (and subjective day) and slowly, with frequent turning, at night (and subjective night). The resting membrane potential is more negative during the day than at night. cAMP and cGMP concentrations oscillate in a manner, such that both cAMP and cGMP are higher during the day (or subjective day) than at night (or subjective night). The ratio of cGMP to cAMP during the light and dark cycle (LD) fluctuates, paralleling the fluctuation of the resting membrane potential measured during the LD. These results suggest that the Paramecium will provide an excellent model to explore daily and circadian orchestration of second messengers mediating signals from ambient light/dark cycles and circadian pacemaker to ion channels and cilia, directly involved in daily and circadian cellular outputs of resting membrane potential and motility. Accepted: 23 January 1997     

严重烧伤早期红细胞膜胆固醇含量及Na+-K+-ATP酶活性的变化

目的 :研究严重烧伤患者早期红细胞滤过指数 (EFI)与红细胞膜胆固醇含量、Na K ATPase活性的变化。探讨其在严重烧伤早期中的相互关系及意义。方法 :采用核孔滤膜法测定红细胞滤过指数 (EFI) ,用化学修饰电极法测定红细胞膜胆固醇含量 ,应用定磷法测定红细胞膜Na K ATPase活性。结果 :4 7例严重烧伤早期患者EFI较 6 0例正常对照组下降 (P <0 .0 1) ,红细胞膜胆固醇含量、Na K ATPase活性均高于正常对照组 (P <0 .0 1) ,且红细胞膜胆固醇含量、Na K ATPase活性与EFI呈密切负相关 (rcho =- 0 .871,rATPase =- 0 .80 1,P <0 .0 1)。结论 :严重烧伤早期EFI下降 ,变形性明显减低是导致血液粘度和微循环改变的原因之一 ,红细胞膜胆固醇含量和Na K ATPase活性的变化则是引起EFI下降、变形性减低的重要因素     

Plasma renin activity, active and inactive renin concentrations, and their responses to beta 1-adrenoceptor blockade with metoprolol in hyperthyroidism

Plasma renin activity (PRA), plasma renin concentration (PRC), inactive renin concentration (IRC) and total renin concentration (TRC) were measured in 31 normal controls and in 8 patients with hyperthyroidism. TRC was determined as angiotensin I generated with sheep renin substrate after an acid activation of plasma. The angiotensin I of non-acidified plasma was expressed as PRC. IRC was calculated as TRC minus PRC. The mean values for PRA, PRC, IRC and TRC were significantly (P less than 0.05 to P less than 0.01) higher in the hyperthyroid patients than in the normal or euthyroid controls. The administration of a beta 1-adrenergic blocker, metoprolol (120 mg/day for 14 days), produced a significant (P less than 0.05 to P less than 0.01) fall in levels of T4, PRA and TRC, and reduced the active renin ratio calculated from PRC/TRC significantly (P less than 0.025), as compared to the pretreatment values. Our observations support the idea that the higher PRA in hyperthyroidism is due to an increased secretion of renin. Furthermore, the results may indicate that the conversion of inactive to active renin is accelerated in hyperthyroidism, possibly by an increased sympathetic activity.     

The effect of ATP, GTP and cAMP on the cGMP-dependent conductance of the fragments from frog rod plasma membrane

Using a 'patch-clamp' method in the 'inside-out' configuration, ATP, ADP, AMP-PCP and AMP-PNP have been shown to increase the cGMP-dependent component of the rod plasma membrane conductance 2-4-fold and GTP, GDP but not GMP or nonhydrolyzable GTP analogs GMP-PNP and GTP-gamma-S to abolish the ATP action. The ATP and GTP effects were observed at [EDTA] = 1 mM when magnesium and calcium ions were absent. In about half of the experiments the cGMP-dependent conductance was shown to be increased by cAMP in the micromolar concentration range by 10-50%, the cAMP action did not depend on the presence of nucleoside triphosphates. In vivo ATP, GTP and cAMP are assumed to modulate the sensitivity of the photoreceptor plasma membrane to cGMP.     

Progesterone and corticosteroids in the initiation of lactation in the sow

The concentration of lactose in the mammary secretion from individual glands of two sows increased significantly (P less than 0.01) between 0 and 24 h after parturition. In six sows studied during the perinatal period there was a negative correlation (r = -0.80; P less than 0.02) at parturition between the concentration of progesterone in the blood and the concentration of lactose in the mammary secretion. Furthermore, the increase in concentration of lactose in the mammary secretion after parturition was related to the timing of the decline of plasma progesterone to low levels. The results indicate that the initiation of lactation occurs within 24 h of parturition in most sows, and the results are consistent with the hypothesis that progesterone withdrawal acts as the 'trigger'. Neither the changes in corticosteroid binding globulin nor the changes in total corticosteroids were temporally related to the initiation of lactation. However, a circadian rhythm was observed for total corticosteroids in the blood of three out of nine lactating and pregnant sows, whereas no circadian rhythm was observed in progesterone of the four pregnant sows. The results are discussed in relation to the disease complex mastitis-metritis-agalactia.     

Evidence that potassium channels mediate the effects of serotonin on the ocular circadian pacemaker of Aplysia

Summary The eye of the marine mollusk Aplysia californica contains a photo-entrainable circadian pacemaker that drives an overt circadian rhythm of spontaneous compound action potentials in the optic nerve. Serotonin is known to influence the phase of this ocular rhythm. The aim of the present study was to evaluate whether potassium channels are involved in effects on the ocular circadian rhythm. Our experimental approach was to study the effect of the potassium channel antagonist barium on serotonin-induced phase shifts of this rhythm. The application of barium was found to block serotonininduced phase shifts whereas barium alone did not cause significant phase shifts. The effects of barium were found to be dose dependent. In addition, barium blocked forskolin-induced phase advances but did not interfere with serotonin-induced increases in cAMP content. Finally, barium antagonized serotonin-induced suppression of compound action potential activity. These results are consistent with a model in which the application of serotonin phase shifts the ocular pacemaker by causing a membrane hyperpolarization which is mediated by a cAMP-dependent potassium conductance.Abbreviations ASW artificial seawater - Ba^{+ +} barium - CAP compound action potential - CT circadian time - 5-HT serotonin - TEA tetraethylammonium     

Lipid peroxides, spermatozoa quality and activity of glutathione peroxidase in bull semen

In bull semen spontaneous lipid peroxidation measured by the level of endogenous lipid peroxides and the consequences of this process for morphological and biochemical changes was studied. Glutathione peroxidase activity as protective enzyme against peroxidative damage was also determined. Obtained results showed that approximately two thirds of GSH-Px activity in bull semen was non Se-dependent glutathione peroxidase activity. Malonaldehyde (MDA) level was negative correlated with selenium-dependent GSH-Px activity (r = = -0.38, P less than 0.01). Spermatozoa with acrosome entirely lost appeared to increase as the MDA level increased (r = 0.18, P less than 0.05). The negative correlation between Se GSH-Px activity and spermatozoa with acrosome separation from head (r = -0.28, P less than 0.01) and entirely lost (r = -0.21, P less than 0.05) suggest that selenium-dependent GSH-Px plays role in protecting the acrosome against disruption of the acrosomal membrane. The total glutathione peroxidase activity was unrelated to studied variables of bull semen.     

Plasma atrial natriuretic peptide and cyclic nucleotide levels before and after a marathon

Plasma alpha-atrial natriuretic peptide (alpha-ANP) concentration and levels of cyclic nucleotides [guanosine 3',5'-cyclic monophosphate (cGMP) and adenosine 3',5'-cyclic monophosphate (cAMP)] were studied in 23 runners before and after a marathon race. Blood samples were drawn from an antecubital vein the morning before the race (base line), at 3 P.M. (i.e., 2 h before the start), on arrival, and 12 and 36 h and 7 days later. Compared with the base-line values of plasma alpha-ANP (5 pmol/l), cGMP (3.8 nmol/l), and cAMP (15.8 nmol/l), the plasma levels of alpha-ANP, cGMP, and cAMP were increased immediately after the marathon, respectively, to 12.0 pmol/l, 12.7 nmol/l, and 50.5 nmol/l. The increase in the plasma alpha-ANP concentration was related (r = 0.85; P less than 0.001) to the changes in plasma cGMP, plasma lactate, hematocrit, and body weight. The plasma cGMP and cAMP concentrations had returned to the prerace levels 12 h after the marathon, whereas the plasma alpha-ANP concentration was significantly lower (3.1 pmol/l) than the base-line values and increased above the prerace values 36 h (7.5 pmol/l) and 7 days (6.8 pmol/l) after the marathon. The plasma cGMP level was also higher 36 h (5.4 nmol/l) and 7 days (5.0 nmol/l) after the marathon race.     

Increased erythrocyte catalase activity in patients with hyperthyroidism

Levels of human erythrocyte catalase activity were determined in 38 patients with thyroidal dysfunction. In patients with hyperthyroidism, erythrocyte catalase activities were found to be higher than the levels of normal subjects (P less than 0.001). In hypothyroidism, erythrocyte catalase activities were of the same order as those of normal subjects. Significantly high positive correlation was found between erythrocytes catalase activity and the levels of thyroxine (r = 0.5794, n = 36, P less than 0.001), and slight positive correlation was detected between catalase activity and the levels of triiodothyronine (r = 0.3978, n = 33, P less than 0.05). A decreased erythrocyte catalase activity was observed when erythrocytes lysate was incubated with thyroid hormones. It was suggested that erythrocyte catalase activity had close relationship with thyroid state, however, direct effect of thyroid hormones were not observed on erythrocyte catalase assay system in vitro.     

Growth hormone releasing hormone-sensitive adenylate cyclase activity in growth hormone-producing pituitary adenoma: correlation to the response of plasma growth hormone to growth hormone releasing hormone in patients with acromegaly

The correlation between response of plasma GH to GHRH and the GHRH-induced stimulation of the intracellular adenylate cyclase (AC) activity in pituitary adenoma cell membranes in acromegalic patients was investigated. Each peak plasma GH level after iv administration of GHRH ranged from 1.1 to 13.8 times the basal level in 13 acromegalic patients. On the other hand, the maximal stimulation of intracellular AC activity (cAMP production) induced by GHRH varied from 1.4 to 6.4 times the control level in each GH-producing pituitary adenoma cell membrane. A significant positive correlation (r = 0.89, P less than 0.005) between plasma GH response to GHRH and intracellular cAMP production stimulated by GHRH was observed in nine of the acromegalic patients. In contrast, the response of plasma GH to GHRH was significantly blunted, despite a fairly large production of intracellular cAMP stimulated by GHRH, in the other four acromegalic patients. These results suggest that GHRH-induced GH release from GH-producing pituitary adenomas of patients with acromegaly may be regulated not only by GHRH receptor-adenylate cyclase system but also modified by several other factors including somatostatin and Sm-C.     

Erythrocyte insulin receptor characteristics and erythrocyte membrane lipid composition in healthy men

The cell membrane plays an important role in the mechanism of insulin action. To test whether erythrocyte insulin receptor characteristics are related to the erythrocyte membrane lipid composition, 11 healthy volunteers were studied. The relationship between insulin binding to erythrocytes, the number of receptors per cell and the affinity of receptors to insulin on the one hand and total phospholipid fatty acid (FA) composition and cholesterol/phospholipid molar ratio in the erythrocyte membrane on the other hand were evaluated. 1. We found a significant negative correlation between specific insulin binding and the proportion of n-6 essential FA in erythrocyte membrane phospholipids, especially linoleic acid (r = -0.82, p less than 0.01) and arachidonic acid (r = -0.73, p less than 0.05). On the other hand, a significant positive correlation between insulin binding and the proportion of nonessential FA (r = +0.65, p less than 0.05) was seen. Number of receptors per cell and the affinity of receptors were not significantly related to phospholipid FA composition. 2. There was no significant correlation between insulin receptor characteristics and the cholesterol/phospholipid molar ratio in the erythrocyte membrane. The data presented support the hypothesis that the FA pattern of membrane total phospholipids may modify the properties of insulin receptors.     

The effects of circadian rhythmicity of salivary cortisol and testosterone on maximal isometric force, maximal dynamic force, and power output

The study investigated the effects of circadian rhythm of cortisol (C) and testosterone (T) on maximal force production (Fpeak) and power output (Ppeak). Twenty male university students (mean age = 23.8 ± 3.6 years, height = 177.5 ± 6.4 cm, weight = 78.9 ± 11.2 kg) performed 4 time-of-day testing sessions consisting of countermovement jumps (CMJs), squat jumps (SJ), isometric midthigh pulls (IMTPs), and a 1-repetition maximum (1RM) squat. Saliva samples were collected at 0800, 1200, 1600, and 2000 hours to assess T and C levels on each testing day. Session rate-of-perceived exertion (RPE) scores were collected after each session. The results showed that Fpeak and Ppeak presented a clear circadian rhythm in CMJ and IMTP but not in SJ. One repetition maximum squat did not display a clear circadian rhythm. Session RPE scores collected at 0800 and 2000 hours were significantly (p ≤ 0.05) higher than those obtained at 1200 and 1600 hours. Salivary T and C displayed a clear circadian rhythm with highest values at 0800 hours and lowest at 2000 hours; however, no significant correlation was found between T and C with Fpeak and Ppeak. A very strong correlation was found between Taural with Fpeak of CMJ and IMTP and Ppeak of CMJ (r = 0.86, r = 0.84 and r = 0.8, p ≤ 0.001). The study showed the existence of a circadian rhythm in Fpeak and Ppeak in CMJ and IMTP. The evidence suggests that strength and power training or testing should be scheduled later during the day. The use of Taural seemed to be a more effective indicator of physical performance than hormonal measures, and the use of session RPE should also be closely monitored because it may present a circadian rhythm.     

Further evidence for the usefulness of the salivary testosterone radioimmunoassay in the assessment of androgenicity in man in basal and stimulated conditions

Since correct assessment of testicular function and androgenic status in humans requires multiple sampling, a sensitive and accurate radioimmunoassay (RIA) of testosterone (T) was established for male and female saliva samples. This easily collected biological fluid, which contains nonprotein-bound T, may represent an attractive alternative or a complement to total plasma T assays. In saliva samples from 5 normal males, a clear circadian rhythm was observed, and morning concentrations (135 +/- 31 pg/ml) were significantly higher (p less than 0.02) than evening samples (85 +/- 23 pg/ml). In 11 normal females, morning saliva levels were 12.8 +/- 1.8 pg/ml. The levels of T in male saliva, in response to both exogenous T administration (100 mg i.m.) and HCG stimulation (2 X 2,000 IU i.m.), accurately reflected the changes observed in plasma T, and the magnitude of increase in T levels was clearly greater in saliva than in plasma samples during the intramuscular administration of the long-acting T preparation. In males, significant correlations were observed between salivary and plasma T concentrations in morning samples (r = 0.61, p less than 0.01), following HCG stimulation (r = 0.89, p less than 0.05) and during T administration (r = 0.87, p less than 0.05). In women, the correlation at 8 a.m. was also significant (r = 0.82, p less than 0.05).     

Circadian variations of catecholamines and blood pressure in patients with pseudohypoparathyroidism and hypertension

The relationship between 24-h recumbent blood pressure levels and secretory patterns of catecholamines was investigated in 4 patients with pseudohypoparathyroidism (PsHP) and hypertension and in 9 patients with essential hypertension. A clear circadian rhythm of blood pressure and catecholamines was documented in both groups with lowest levels of blood pressures and catecholamines occurring during sleep. During the 24-h period of recumbency mean arterial blood pressure (MAP) was correlated (r = 0.63, p less than or equal to 0.01) with plasma norepinephrine (N) in the patients with essential hypertension, but this correlation was weaker in patients with PsHP (r = 0.38, p less than or equal to 0.05). MAP was more closely related to plasma epinephrine (E) (r = 0.62, p less than or equal to 0.01) than to plasma NE in patients with PsHP. Plasma NE and E levels were considerably lower in patients with PsHP than in patients with essential hypertension throughout the 24-h recumbent period. The sleep-related decline in blood pressure and NE was less than in patients with essential hypertension. These results suggest that while the sympathetic nervous system may have a role in hour-to-hour maintenance of blood pressure in patients with PsHP and hypertension, it does not appear to be responsible for the elevated arterial pressure in these patients. Factors other than those investigated, such as obesity, alterations in sodium homeostasis of refractoriness of the vascular smooth muscle to the vasodilatory effect of PTH may be involved in the pathogenesis of hypertension in PsHP.     

Endogenous activity of cyclic nucleotide-dependent protein kinase in plasma membranes isolated from Strongylocentrotus purpuratus sea urchin sperm.

Activity of cyclic nucleotide-dependent protein kinase was investigated in flagellar plasma membranes of sea urchin sperm (S. purpuratus). Membranes incubated with [gamma-32P]ATP showed in the presence of 1 microM cAMP an increased phosphorylation in multiple polypeptides. Half maximal response was seen at 0.6 microM of cAMP. In contrast, higher concentrations (100 microM) of cGMP were required to cause the same amount of protein phosphorylation. 80% of the protein kinase activity stimulatable by cAMP was resistant to extraction by 10 mM EGTA and sonication but it was entirely recovered in a detergent-solubilized fraction. Membranes pretreated with 200 microM cAMP, ultracentrifuged and resuspended in buffer solution did not undergo cAMP-stimulated phosphorylation in their polypeptides. This study demonstrates that flagellar plasma membranes isolated from S. purpuratus sea urchin sperm have an endogenous cAMP-dependent protein kinase, which may be bound to the membrane via its regulatory subunit.     

Insulin receptor changes in type 2 diabetes after short term insulin treatment

We have studied erythrocyte insulin receptor changes before and after 8 days of continuous subcutaneous insulin infusion by a pump in 11 uncontrolled obese non-insulin-dependent diabetics (type 2), diet and drug resistant for at least three months previously. All the patients were hospitalized. On day 1 of the study, their oral hypoglycemic agents were stopped and hypocaloric diet (1000 Kcal/day) was maintained (strictly reinforced). This period of reinforced treatment was not accompanied by correction of hyperglycemia. On day 9 patients were placed for 12 hours on artificial pancreas in order to bring their fasting blood glucose levels down to normal values. Then they were submitted to a continuous subcutaneous insulin infusion (CSII) for the following 8 days. There was a significant decrease in mean fasting plasma glucose (P less than 0.001) and a rise in insulin (P less than 0.05) levels after insulin treatment. Mean specific insulin binding was also significantly increased (P less than 0.01). The increase in binding (with insulin therapy) correlated with the fall in fasting hyperglycemia (r = 0.786, P less than 0.01). In addition, the increase in binding correlated negatively with changes in fasting plasma insulin levels (r = -0.867, P less than 0.01), under treatment, on one hand and with the dose of exogenous insulin administered (r = -0.681, P less than 0.05) on the other hand. There was no correlation between binding and fasting plasma insulin levels (before and after insulin therapy), or between diabetes duration and any of the previous parameters.(ABSTRACT TRUNCATED AT 250 WORDS)