Relationship between intracellular free calcium concentrations and the intracellular development of Toxoplasma gondii

We measured intracellular free calcium concentrations ([Ca++]i) in the subcellular compartments of Toxoplasma gondii infected living cells using microspectrofluorometry and Indo-1 staining. [Ca++]i mapping was defined in infected and uninfected cells and in the neoformed parasitophorous vacuole (PV) 24 and 48 hr after parasite inoculation. At 24 hr after infection, a [Ca++]i gradient (PV/cytoplasm) was observed in favor of the PV in 72% of infected cells (p<0.001). Inside of the PV (lumen and parasites), [Ca++]i values appeared to be homogeneously distributed. At 48 hr after infection, the parasites had replicated and formed typical rosettes of more than 16 parasites. At this step, a positive [Ca++]i gradient (PV/cytoplasm) was detected in all analyzed cells (p<0.001). This result suggests that the PV (lumen and parasites) represents an individual subcellular compartment within the host cell that includes an independent [Ca++]i. Moreover, after 48 hr the cytoplasmic [Ca++]i decreased significantly (39 nM) compared with that measured from uninfected cells (53 nM) (p <0.05). Furthermore, the exit of Toxoplasma mediated by the calcium ionophore 4BrA23187 was preceded by a rise of [Ca++]i to 1 mM in the PV. The [Ca++]i rise and the liberation of parasites from their host appear to be correlated. On the basis of these observations, we suggest that the increase of [Ca++]i in the vacuole may act as a signal that triggers the egress of T. gondii.     

Intralymphocyte free magnesium in a group of subjects with essential hypertension

Despite the importance of magnesium in essential hypertension, few data are available on the ionized intracellular concentration of this ion. We therefore studied intralymphocyte free intracellular magnesium (Mgi) in 32 untreated essential hypertensive subjects and 27 normotensive control subjects by means of a fluorimetric technique based on the use of the new magnesium-sensitive dye furaptra. We also measured intralymphocyte ionized calcium (Cai) with fura 2. No statistically significant differences were found in Mgi in hypertensive compared with normotensive subjects (essential hypertensive, 0.291 +/- 0.053 mmol/L; normotensive, 0.293 +/- 0.043 [mean +/- SD]). A statistically significant inverse correlation was established between Mgi and plasma triglycerides in essential hypertensive subjects (r = -.521, P = .002). The hypertensive group was arbitrarily divided into two subgroups according to plasma triglyceride levels (> 2 [n = 10] or < 2 mmol/L [n = 22]), and Mgi proved to be significantly lower in the subgroup with high plasma triglyceride levels compared with either the subgroup with normal triglycerides (P = .009; 95% confidence interval, 0.013-0.088) or the normotensive control group as a whole (P = .03; 95% confidence interval, 0.003-0.069) (high-triglyceride hypertensive subgroup, Mgi = 0.256 +/- 0.045 mmol/L; normal-triglyceride hypertensive subgroup, Mgi = 0.307 +/- 0.049). No statistically significant differences were found in Cai in hypertensive compared with normotensive subjects (hypertensive, 53 +/- 12 nmol/L; normotensive, 54 +/- 14). We did not find statistically significant correlations between Cai and plasma triglycerides, nor did we find any differences in Cai between the subgroup of hypertensive subjects with high plasma triglyceride levels and either the subgroup of hypertensive subjects with normal triglycerides or the normotensive control group as a whole. The discrepancies between our results in lymphocytes and data relating to either erythrocytes or platelets emphasize the need for caution before the results are extrapolated from one tissue to the other. The decreased Mgi levels in the subgroup of high-triglyceride hypertensive subjects may suggest a role for magnesium in plurimetabolic syndrome.     

Failure of platelet angiotensin II binding to predict pregnancy-induced hypertension

OBJECT: Nimodipine therapy has become a standard component of the treatment regimen used in patients with aneurysmal subarachnoid hemorrhage (SAH). Its prescribed use at 60 mg every 4 hours for 21 days is based on reputable, randomized prospective studies. However, because only 20 to 30% of patients with SAH suffer clinical cerebral vasospasm, it is clear that most patients do not actually need the drug. Of course, this fact is not evident until several treatment days have passed. It is common practice, without well-documented consequences, to terminate nimodipine therapy before 21 days in certain clinical circumstances. The aim of this study was to evaluate the effectiveness of abbreviating the duration of nimodipine treatment in the setting of a good-grade aneurysmal SAH. METHODS: A retrospective clinical review was made of 90 consecutive patients who experienced a Hunt and Hess Grade I through III aneurysmal SAH and were treated with nimodipine for 15 days or less. CONCLUSIONS: None of the patients studied suffered a delayed neurological deficit as a result of the abbreviated course of nimodipine.     

Cardioprotective effect of enalapril in renovascular and angiotensin II hypertension

The influence of chronic treatment with enalapril or losartan (10 or 30 mg/kg/24h, respectively) on cardiac mass was evaluated in one-kidney, one clip (1K-1C) hypertensive rats submitted to sodium restriction 3 weeks after clipping and in rats infused for 10 days with angiotensin II (ANGII: 200 ng/kg/min). In 1K-1C hypertension, cardiac mass and arterial pressure were reduced to a similar extent by enalapril and losartan. In ANGII hypertension, enalapril and losartan blunted the increase in cardiac mass whereas losartan but not enalapril prevented the development of hypertension. The cardioprotective effect of enalapril was attenuated by concomitant blockade of bradykinin receptors (Hoe140: 300 micrograms/kg/24h) in both models. The beneficial influence of enalapril on cardiac mass appears to be independent of its effect on blood pressure and ANGII generation and seems partly mediated by endogenous bradykinin in these high ANGII models of hypertension.     

Extracellular and intracellular magnesium concentrations in asthmatic patients

Magnesium deficiency is associated with increased contractility of smooth muscle cells. Since contractility of bronchial smooth muscle is important in patients with asthma, magnesium deficiency could negatively influence the clinical condition. We wanted to assess whether magnesium deficiency exists in patients with asthma. Extracellular (plasma) and intracellular (erythrocytes and mononuclear leucocytes) concentrations of magnesium were determined in 20 mildly symptomatic patients with asthma and compared to 20 healthy controls. In asthmatic patients, the mean +/- SD magnesium level in plasma was 0.81 +/- 0.05 mmol.l-1, in erythrocytes 0.20 +/- 0.02 fmol.cell-1, and in mononuclear leucocytes 5.10 +/- 2.55 fmol.cell-1; these values did not differ significantly from those of the healthy controls: 0.79 +/- 0.06 mmol.l-1, 0.19 +/- 0.02 fmol.cell-1, and 4.61 +/- 1.75 fmol.cell-1, respectively. No evidence for the existence of a magnesium deficit needing chronic magnesium supplementation was, thus, found in these patients.     

Effects of angiotensin II and losartan in the forearm of patients with essential hypertension

OBJECTIVE: Angiotensin II type 1 receptor-mediated constrictor effects may be modulated by hypertension-related vascular changes, changes in receptor function and in neurohumoral activity. DESIGN: The forearm blood flow (FBF) effects of angiotensin II, methoxamine, and losartan were investigated in essential hypertensive patients. Minimal forearm vascular resistance was measured to determine structural vascular changes. METHODS: Seven hypertensive patients were selected, and seven matched normotensives. Angiotensin II (0.01-10 ng/kg per min) was infused during predilatation by sodium nitroprusside (6.1 +/- 0.6 ng/kg per min) before and during losartan infusion (0.3-3 microg/kg per min). Methoxamine (0.2-2 microg/kg per min) was co-infused with the nitric oxide synthase inhibitor NG-monomethyl-L-arginine. FBF, measured by venous occlusion plethysmography, was expressed as the change in FBF ratio (FBFinfused arm/FBFnon-infused arm). RESULTS: Baseline FBF (infused arm) was increased by sodium nitroprusside from 2.56 +/- 0.80 to 5.46 +/- 0.92 (P<0.05) and from 2.66 +/- 0.25 to 5.42 +/- 0.40 ml/100 ml per min (P<0.05) in the hypertensive and normotensive group, respectively. Baseline forearm vascular resistance (FVR) was higher in the hypertensive than in the normotensive group [51 +/- 8 versus 33 +/- 3 mmHg/ (ml/100 ml per min); P<0.05]. Angiotensin II caused a maximal change in FBF ratio (Emax) by -70 +/- 3 and -72 +/- 6% in the hypertensive and normotensive group, respectively (NS). Tachyphylaxis did not occur. Infusions of losartan at 0.3, 1 and 3 microg/kg per min reduced the Emax values from -70 +/- 3 to -50 +/- 5, -45 +/- 5 and -15 +/- 2%, respectively, in the hypertensive group, and from -72 +/- 6 to -62 +/- 4, -45 +/- 2 and -32 +/- 2%, respectively, in the normotensive group (NS). Infusion of methoxamine significantly reduced the FBF ratio by -58 +/- 6 and -69 +/- 5% in the hypertensive and normotensive groups, respectively (NS). Minimal FVR, after forearm ischemia, was the same in hypertensives and normotensives, namely 3.2 +/- 0.7 and 3.2 +/- 0.4 mmHg/(ml per 100 ml per min), respectively (NS). CONCLUSIONS: Angiotensin II type 1- and alpha1-mediated vascular effects were unchanged by essential hypertension. Baseline FVR was greater in the hypertensives than in the normotensives, while minimal FVR was the same. These results indicate that the forearm vascular bed of the patient group studied does not show important structural and renin-angiotensin system-related functional changes as a result of hypertension.     

Regulation of intracellular calcium concentrations by calcium and magnesium in cardioplegic solutions protects rat neonatal myocytes from simulated ischemia

The effects of calcium and magnesium ions in cardioplegic solutions on cardioprotection and intracellular calcium ion handling during ischemia and reoxygenation were investigated in cultured neonatal rat myocardial cells. Myocytes were subjected to simulated ischemia for 60 min at 37 degrees C in hyperkalemic cardioplegic solutions containing various concentrations of calcium and magnesium ions, followed by 30 min of reoxygenation. For each Ca2+ concentration (0.1, 0.6, 1.2, or 2.4 mM), the Mg2+ concentration was either 0, 1.2, 8, or 16 mM. The increase in intracellular Ca2+ concentration during ischemia and reoxygenation was suppressed by the addition of magnesium ion, independent of cardioplegic Ca2+ concentration. The recovery of spontaneous contraction rate and enzyme leakage (creatine phosphokinase and lactate dehydrogenase) during both ischemia and reoxygenation correlated with the degree of inhibition of intracellular Ca2+ accumulation. However, in the 0.1 mM Ca2+ groups in which the Mg2+ concentration was greater than 8 mM, the intracellular Ca2+ concentration increased during reoxygenation in a dose-dependent fashion of Mg2+, and was associated with increased enzyme leakage. The findings suggest that in immature cardiac myocytes, the concentrations of Ca2+ and Mg2+ present in cardioplegic solutions control the intracellular Ca2+ concentration during ischemia and reoxygenation, which, in turn, influences the cardioprotective effect of the cardioplegic solution.     

High magnesium concentration inhibits ligand-stimulated calcium influx and hormone secretion in rat pituitary lactotropes with involvement of intracellular free magnesium

The effects of extracellular magnesium concentration ([Mg2+]ex) on thyrotropin-releasing hormone (TRH)-stimulated intracellular free calcium mobilization and prolactin secretion were investigated concomitantly with measurement of the intracellular free magnesium concentration ([Mg2+]i). TRH-stimulated intracellular free calcium mobilization was significantly inhibited when the medium was replaced by high Mg2+ medium ([Mg2+]ex = 10 mM) in normal Ca2+ medium. The inhibitory effects of high Mg2+ became apparent concomitantly with an increase in [Mg2+]i from 0.7 to 1.3 mM. High Mg2+ significantly inhibited TRH-induced PRL secretion in a dose-dependent manner in normal Ca2+ medium. TRH-stimulated inositol triphosphate (IP3) production was rather augmented by the replacement with high Mg2+ medium. In summary, high Mg2+ inhibits Ca2+ influx stimulated by TRH in the rat pituitary lactotropes, possibly with the involvement of [Mg2+]i increase. These results have general importance in relation to high Mg(2+)-induced suppression of the biological functions of cells.     

Association between angiotensin II type I receptor gene and human essential hypertension]

Reports of prolonged sleep periods in idiopathic central nervous system hypersomnia, as shown by ad libitum sleep recordings, are rare. A patient with idiopathic hypersomnia with extremely long sleep periods and sleep drunkenness after awakening is described. Polysomnographic recordings showed a spontaneous sleep period of 19.4 h and a normal Multiple Sleep Latency Test. These polysomnographic findings are clearly abnormal but essentially different form those of narcolepsy. Unlike narcolepsy, 'idiopathic hypersomnia' does not seem to be a distinct clinical entity but a category for different heterogenous subtypes.     

Influence of the angiotensin II antagonist valsartan on left ventricular hypertrophy in patients with essential hypertension

BACKGROUND: Left ventricular hypertrophy (LVH) represents an independent risk factor in patients with essential hypertension. Because reversal of LVH may be associated with an improvement of prognosis, the influence of new antihypertensive compounds, such as angiotensin II AT1 receptor antagonists, on LVH should be determined. METHODS AND RESULTS: In a randomized, double-blind trial, 69 predominantly previously untreated hypertensive patients with echocardiographically proven LVH, ie, left ventricular mass index (LVMI) >134 g/m2 in men and >110 g/m2 in women and/or end-diastolic septal thickness >12 mm, received either the angiotensin II antagonist valsartan or atenolol for 8 months. Echocardiographic data of 58 patients were available. After 8 months of valsartan treatment (n=29), LVMI decreased from 127+/-23 to 106+/-25 g/m2 (ratio [R]=0.83; 95% CI, 0.79 to 0.87; P<0.0001 versus baseline). Under atenolol (n=29), LVMI decreased to a smaller extent, from 127+/-25 to 117+/-27 g/m2 (R=0.92; 95% CI, 0.86 to 0.98; P=0.0082 versus baseline). The mean reduction of LVMI came to 21 g/m2 under valsartan and only to 10 g/m2 under atenolol (R=0.91; 90% CI, 0.85 to 0.97 versus atenolol). Baseline mean blood pressure values were determined to be 163+/-12/101+/-6 mm Hg before treatment with valsartan and 160+/-14/103+/-6 mm Hg before atenolol treatment. After 8 months of treatment, mean blood pressure decreased to 146+/-13/90+/-7 mm Hg with valsartan and to 147+/-18/90+/-7 mm Hg with atenolol. Nine patients in the valsartan group and 8 patients in the atenolol group required additional medication with hydrochlorothiazide. CONCLUSIONS: Antihypertensive treatment with the angiotensin II antagonist valsartan for 8 months produced a significant regression of LVH in predominantly previously untreated patients with essential hypertension. The drug may be safely administered in this subset of hypertensive patients; however, the long-term benefit in terms of risk reduction has still to be evaluated in further trials.     

Comparison of the angiotensin II antagonist losartan with the angiotensin converting enzyme inhibitor enalapril in patients with essential hypertension

OBJECTIVE: To evaluate the blood pressure lowering efficacy as well as tolerability and safety of the angiotensin II antagonist losartan compared with that of the angiotensin converting enzyme inhibitor enalapril in patients with mild-to-moderate essential hypertension. DESIGN AND METHODS: The study was a multicentre, double-blind, double-dummy, randomized, parallel study. Patients (n = 407) with diastolic blood pressure > or = 95 and < or = 120 mmHg at the end of a 2-week baseline placebo period were randomly allocated to receive either 50 mg losartan once a day or 20 mg enalapril once a day for 12 weeks. Blood pressure, clinical and laboratory safety, specific symptoms including coughing determined using a symptoms questionnaire and metabolic variables were examined at baseline and at weeks 6 and 12. RESULTS: Both losartan and enalapril decreased systolic and diastolic blood pressure from baseline at weeks 6 and 12. Blood pressure changes from baseline at trough (22-26 h after the dose) did not differ between the two groups in the per-protocol analysis. Response to treatment at trough was excellent or good (diastolic blood pressure < 90 mmHg or reduction in diastolic blood pressure of 10 mmHg) in 51 and 53% of the patients in the losartan and enalapril groups, respectively. Enalapril administration increased dry coughing symptoms whereas losartan did not. The incidence of dry coughing was 1.0 and 12.2% as a spontaneously reported discomfort at week 12 and 3.0 and 15.1% as a clinical adverse experience in the losartan and enalapril groups, respectively. The difference from baseline at week 12 in the incidence of dry coughing between the two groups was 14.9% as a specific symptom in the symptoms questionnaire. Losartan reduced serum uric acid concentration, whereas effects on other metabolic parameters did not differ between the groups. CONCLUSIONS: Losartan is an effective and well-tolerated antihypertensive drug showing similar blood-pressure-lowering efficacy to that of enalapril at trough. However, in contrast to enalapril, losartan does not increase the incidence of dry coughing. Thus, the angiotensin II antagonist losartan provides a promising new approach to treatment of hypertension.     

Atrial natriuretic peptide modulates the effect of angiotensin II on the concentration of free calcium in the cytosol of Mandin-Darby canine kidney cells

The effect of angiotensin II (ANG II) and atrial natriuretic peptide (ANP) on intracellular free calcium concentration [Ca2+]i was investigated in Mandin-Darby canine kidney (MDCK) cells in culture. Changes in [Ca2+]i were monitored fluorometrically with the Ca(2+)-sensitive probe fura-2/AM at 37 degrees C using a Perkin-Elmer LS-5 spectrofluorimeter (excitation 340/380 nm, slit 3 nm; emission 520 nm, slit 10 nm). MDCK cells exhibited a mean baseline [Ca2+]i of 98 +/- 10 nM. The addition of increasing concentrations of ANG II (1 pM to 1 microM) to the cell suspension led to a progressive increase in [Ca2+]i to 2-3 times basal levels. In contrast, addition of 1 microM ANP to the cell suspension led to a very rapid 60% decrease in [Ca2+]i. The addition of 1 pM to 1 microM ANG II immediately after 1 microM ANP caused an increase in [Ca2+]i which never exceeded the basal level in the absence of ANP. The data indicate that ANG II increases cell [Ca2+]i, as expected, and provide the new observation that ANP reduces [Ca2+]i in these cells. Furthermore, ANP reduces the increase in [Ca2+]i elicited by ANG II, thus modulating the effect of ANG II on [Ca2+]i.     

The effect of brief illumination on intracellular free calcium concentration in cells with 5-aminolevulinic acid-induced protoporphyrin IX synthesis

The effect of illumination on intracellular free calcium concentration, [Ca2+]i, was studied in a cell line (WiDr cells) derived from a primary adenocarcinoma of the rectosigmoid colon. In these cells the biosynthesis of protoporphyrin IX was stimulated by 5-aminolevulinic acid to reach levels of 600-700 pmol of protoporphyrin IX per mg cell protein. A brief (1-min) exposure of the cells to light (70% of light energy at 340-380 nm) resulted in an increase in [Ca2+]i. This increase was not reversible over a period of at least 20 min following illumination. Elevation of [Ca2+]i most probably represented an influx of calcium ions from the medium to the cell, since it was completely abolished in the presence of extracellular EGTA. The increased [Ca2+]i did not reflect general membrane damage, as determined by trypan blue staining as well as measurement of the intercalation of ethidium bromide into cellular DNA, and neither did the sustained elevation of [Ca2+]i lead to any substantial loss of clonogenicity following illumination of protoporphyrin-containing cells. Together these results indicate that an increased [Ca2+]i level is not per se a cause of cell death during photodynamic therapy.     

The effect of endotoxin on neonatal erythrocyte intracellular calcium concentration

Erythrocyte membrane deformability is dependent on the maintenance of "normal" intracellular calcium (Ca) levels. Red cell flexibility is known to be altered in the septic neonate. In turn, this adversely affects viscosity and compromises flow in the microcirculation. It has been suggested that this may play a role in the mesenteric hypoperfusion associated with necrotizing enterocolitis. This study was designed to determine the effect of endotoxin on erythrocyte Ca homeostasis in the neonate. Paired specimens were obtained from the umbilical cord of 10 healthy neonates. The samples were incubated with either buffered saline (control) or 2 micrograms/mL of Escherichia coli endotoxin (LPS). Erythrocytes were then isolated, washed, and loaded with the fluorescent Ca chelator, FURA-2. The free cytosolic Ca concentration was determined by spectroscopic analysis of the ratio of fluorescent intensities at 340 nm and 380 nm. Results were obtained every 1.8 seconds for 1 minute, and the mean value was used for analysis. In 10 additional neonates, the white blood cells were removed before incubation in saline and LPS, and the erythrocytes were evaluated as described above. Differences were analyzed statistically by the paired t test. In the presence of white blood cells, endotoxin resulted in a significant increase in free cytosolic Ca concentration (LPS, 42.602 +/- 5.166 nmol; control, 31.661 +/- 4.002 nmol; P < .02). However, no significant difference were detected when cells were incubated in the absence of white blood cells (LPS, 32.374 +/- 2.479 nmol; control, 34.021 +/- 2.549 nmol). Endotoxin induces a significant increase in neonatal free cytosolic Ca concentration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Activation of calcium sparks by angiotensin II in vascular myocytes

Contraction in smooth muscle is triggered by an increase in cytoplasmic free calcium ([Ca2+]i) which depends on both Ca2+ influx through L-type Ca2+ channels and Ca2+ release from the sarcoplasmic reticulum (SR). Two mechanisms have been shown to be involved in SR Ca2+ release, one is stimulated by Ca2+ and involved ryanodine-sensitive Ca2+-release channels; the other is stimulated by an increase in inositol 1,4,5-trisphosphate (InsP3) generation induced by various mediators and involved InsP3-sensitive Ca2+ release channels. Here, we examined the effects of angiotensin II on [Ca2+]i in single rat portal vein myocytes using both the whole cell patch-clamp method and a laser scanning confocal microscope. Elementary Ca2+ release events (Ca2+ sparks) were obtained spontaneously or in response to L-type Ca2+ channel current activation, and resulted from activation of ryanodine-sensitive Ca2+-release channels in the SR. We show that angiotensin AT1 receptors stimulate Ca2+ sparks through activation of L-type Ca2+ channels without involving InsP3-induced Ca2+ release. This novel transduction pathway may be a common mechanism for vasoconstrictors which do not stimulate generation of chemical second messengers.     

Maintenance of baseline angiotensin II potentiates insulin hypertension in rats

Chronic insulin infusion in rats increases mean arterial pressure (MAP) by a mechanism dependent on angiotensin II (Ang II). However, the fact that plasma renin activity (PRA) decreases with insulin infusion suggests that Ang II sensitivity is increased and that the parallel reduction in Ang II may partly counteract any hypertensive action of insulin. This study tested that hypothesis by clamping Ang II at baseline levels during chronic insulin infusion. Sprague-Dawley rats were instrumented with artery and vein catheters, and MAP was measured 24 hours per day. In seven angiotensin clamped rats (AC rats), renin-angiotensin II system activity was clamped at normal levels throughout the study by continuous intravenous infusion of the angiotensin-converting enzyme inhibitor benazepril at 5 mg/kg per day (which decreased MAP by 18+/-2 mm Hg) together with intravenous Ang II at 5 ng/kg per minute. Control MAP in AC rats after clamping averaged 99+/-1 mm Hg, which was not different from the 101+/-2 mm Hg measured before clamping Ang II levels. Control MAP in the 8 vehicle-infused rats averaged 105+/-2 mm Hg. A 7-day infusion of insulin (1.5 mU/kg per minute IV) plus glucose (20 mg/kg per minute IV) increased MAP in both groups of rats; however, the increase in MAP was significantly greater in AC rats (12+/-1 versus 5+/-1 mm Hg). This enhanced hypertensive response to insulin in AC rats was associated with a greater increase in renal vascular resistance (153+/-10% versus 119+/-6% of control) and a significant increase in renal formation of thromboxane (149+/-11% of control). Thus, decreased Ang II during insulin infusion limits the renal vasoconstrictor and hypertensive actions of insulin, and this may be caused, at least in part, by attenuation of renal thromboxane production.     

The effects of eprosartan, an angiotensin II AT1 receptor antagonist, on uric acid excretion in patients with mild to moderate essential hypertension

To test our hypothesis that arginine (Arg) and lysine (Lys) enhance immune activities via neuronal control of the thymus and the spleen, a jugular vein was cannulated for amino acid administration in male Wistar rats (approximately 300 g). In one group (n = 5), an efferent nerve filament of the vagal thymus was isolated. In another group (n = 5), splenic nerve efferents were isolated. Efferent firing rates were recorded before and for 60-90 minutes after 10 mM Arg-Lys in 0.5 ml saline intravenously (i.v.). Differences in firing rates were evaluated using analysis of variance (ANOVA) and t-test. I.v. Arg-Lys increased vagal efferent firing rate to the thymus; enhancing thymic lymphocyte release. I.v. Arg-Lys decreased firing rate in splenic efferents; enhancing natural killer (NK) cell activity. Therefore, Arg-Lys are detected by hepatoportal sensors, stimulating hepatic vagal afferents to the hypothalamus, with the efferent neuronal impulses from the hypothalamus modulating immune function in thymus and spleen, thereby demonstrating the mechanism of Arg and Lys immune enhancing activity.     

The effect of angiotensin II on myosin heavy chain expression in cultured myocardial cells

Angiotensin II (AII), the principal mediator of the renin-angiotensin system, is an important regulator of vascular and cardiac homeostasis. AII has also been shown to be a regulator of cardiac hypertrophy and of the corresponding changes in amount and composition of certain tissue proteins. We examined the trophic effects of AII on cultured myocytes derived from neonatal rat ventricles and followed, by Northern blot analysis and polyacrylamide gel electrophoresis, the expression of alpha- and beta-myosin heavy chain iso-mRNAs and isoproteins. Our findings show that a single administration of AII is sufficient to induce a trophic response in cultured beating myocytes and to enhance the expression of beta-myosin heavy chain iso-mRNA and isoprotein, having no effect on alpha-myosin heavy chain. Induction of alpha-myosin heavy chain expression by thyroid hormone before AII was administered showed that AII could not potentiate a shift from alpha- to beta-myosin heavy chain predominance. We suggest that the potency of AII to regulate the expression of myosin heavy chain isogenes is restricted to the beta isoform and is overridden by thyroid hormone.     

Differential effect of thyroid-stimulating hormone (TSH) on intracellular free calcium and cAMP in cells transfected with the human TSH receptor

The major part of research dealing with the biophysical and biochemical properties of airway smooth muscle is based on the assumption that the cells constituting the tissue are homogenous. For striated muscle this has been shown untenable. In recent years almost every property of vascular smooth muscle has been also demonstrated to be heterogeneous. This realization has been late in arriving on the airway smooth muscle research scene. Our own studies have shown that mechanical properties are, in quantitative terms, heterogeneously distributed down the airways and that contractility, for example, in extrapulmonary and intrapulmonary airways differs markedly. Another indication of heterogeneity is derived from studies of the biochemical properties of airway smooth muscle cells (ASMCs) in culture. Dramatic changes in phenotype expression were found with days in culture. Just after isolation from the tissue, the cells were of contractile type and contained mature isoforms of contractile, regulatory and cytoskeletal proteins. After the fourth day in culture the cellular phenotype changed such that contractile filaments diminished rapidly with smooth muscle isoforms being replaced by non-muscle isoforms. The cell assumed secretory or synthetic properties and commenced proliferating rapidly. It is possible that similar changes in phenotype could occur in vivo in cells undergoing hypertrophy or hyperplasia. Thus, a thickened medial layer of the type seen in the walls of airways from asthmatic airways is not necessarily one endowed with increased contractility and, in fact, the latter may be subnormal. Finally, using the so-called motility assay, we studied the velocity of translation of actin filaments by myosin molecules obtained from antigen-sensitized and control airway smooth muscle. We found no change in maximum velocity of actin translation. This was under conditions where the myosin light chain (MLC) was fully phosphorylated. However, in these tissues we found heterogeneity in myosin light chain kinase (MLCK) content which, we inferred, accounted for the difference in shortening velocity between control and sensitized muscle strips in vitro.