Transmembrane Calcium Flux Research Articles

P-115. Vigorous intracytoplasmic injection may disrupt the transmembrane calcium flux in oocytes

P-115. Vigorous intracytoplasmic injection may disrupt the transmembrane calcium flux in oocytes

On the putative mechanistic basis for intraoperative propofol-induced penile erections.

Propofol is an hypnotic drug used in anesthesia which was noted to induce marked vasodilation in vivo and in vitro, and to elicit intraoperative penile erections. The goal of this study was to assess the putative mechanistic basis for this later observation by confirming its action in vivo in a rat model of penile erection, as well as by studying its effects in vitro on cultured human corporal smooth muscle cells and isolated corporal tissue strips. In vivo experiments were conducted on Fisher 344 rats anesthetized with sodium pentobarbital or propofol. Intracavernosal pressure was recorded during current stimulation of cavernous nerves. A significant increase in the intracavernous pressure response was recorded at all levels neurostimulation, ranging from 1-10 mA. In vitro experiments were conducted utilizing digital imaging microscopy to assess the effects of propofol (3-12 micrograms/mL) on ET-1-induced (50 nM) intracellular Ca2+ transients [Ca2+]i in Fura-2-loaded cultured human corporal smooth muscle cells (passage 3-4) as well as to evaluate the effects of propofol on phenylephrine (PE)-induced contractile responses on isolated corporal tissue strips. With respect to the former, resting cytosolic calcium levels were not altered during preincubation with propofol alone at clinically effective concentrations (12 micrograms/mL). However, propofol produced a concentration-dependent decrease in the peak amplitude of the transient ET-1-induced (50 nM) [Ca2+]i response (P < 0.001). Preincubation of the cells with calcium free/EGTA (1 mM) buffer produced a reduction in the peak amplitude of the ET-1-induced [Ca2+]i transient (55.5 +/- 6% (n = 10 cells, P < 0.01)) which was indistinguishable from that produced by 8 micrograms/mL of propofol (53.4 +/- 5.6% (n = 12 cells, P < 0.01)). However, propofol had no effect on the histamine-induced [Ca2+]i response. Lastly, preincubation of isolated human corporal tissue strips with propofol (100-200 microM; 30 min) caused a significant diminution in the peak amplitude of the PE-induced contractile response. Taken together, these data indicate that the mechanistic basis for intraoperative penile erections observed with propofol may be related, at least in part, to altered transmembrane calcium flux through voltage-dependent calcium channels, and thus, decreased corporal smooth muscle tone.

Transmembrane Calcium Flux Regulates LDL Oxidation by Arterial Smooth Muscle Cells

Although clinical and experimental studies have supported a role of calcium in atherogenesis, the nature of this relationship has not been determined. The following investigation was performed to examine the effect of transmembrane calcium flux on the oxidative modification of low-density lipoprotein (LDL) by arterial smooth muscle cells (SMC). Confluent SMC were incubated in basal medium alone or in medium containing either nifedipine (0.25 μM), a calcium channel blocker, or dantrolene (10 μM), a blocker of calcium release from the endoplasmic reticulum. Cells were then suspended in medium with either physiologic (1.25 mM) or supraphysiologic (2.5 mM) calcium concentrations ([Ca2+]e) and were exposed to oxidized LDL (20 μg/protein/ml; 4.96 ± 0.76 nmole malondialdehyde/mg LDL protein). Changes in cytosolic calcium ([Ca2+]i) were measured by spectrofluorometric analysis using a Fura 2-AM indicator. In similar studies, the cellular oxidation of native LDL was determined by fluorometric measurement of thiobarbituric acid-reactive substances in the media. Nifedipine and, to a lesser extent, dantrolene lowered steady-state [Ca2+]iat supraphysiologic [Ca2+]e(2.5 mM; P< 0.0002). Exposure of SMC to Ox-LDL increased [Ca2+]i(P< 10−7), which was further augmented by increasing [Ca2+]e(P< 10−7). Nifedipine significantly reduced the calcium response to Ox-LDL proportionate to [Ca2+]e(P< 0.0002). A similar reduction in [Ca2+]ivs control was seen with dantrolene, but was independent of [Ca2+]e. TBARS assays revealed a significantly greater degree of cellular oxidation of native LDL following preincubation of SMC with Ox-LDL (P< 10−8). This effect was markedly inhibited by both nifedipine (P< 10−8) and dantrolene (P< 10−8), which showed some degree of synergism. These results indicate that the increase in cytosolic calcium in SMC exposed to Ox-LDL may occur through both membrane channels and reticular release. Inhibition of transmembrane calcium flux severely limits the cellular oxidation of low-density lipoprotein. These alternate means of calcium signal generation may allow a more varied response of the SMC to atherogenic stimuli and provide an opportunity for specific therapeutic intervention.

The Biological Significance of Yawning Elicited by Application of Electromagnetic Fields in Multiple Sclerosis

To the Editor: Brief extracerebral applications of AC pulsed electromagnetic fields (EMFs) in the picotesla range intensity have been reported beneficial in the symptomatic treatment of patients with multiple sclerosis (MS) with either a relapsing-remitting or a chronic progressive course (Sandyk, 1992, 1994 a, b, 1995 a; Sandyk & Derpapas, 1993 a, b; Sandyk & Iacono, 1993, 1994 a, b; Sandyk & Dann, 1994, 1995. This treatment modality is effective also in the symptomatic management of acute exacerbation of symptoms and has also been shown to stabilize the course of the disease (Sandyk & Derpapas, 1993b; Sandyk & Dann, 1995; Sandyk, in press). The mechanisms by which administration of these EMFs improves symptoms of MS remain elusive. Application of DC EMFs of higher intensities has been shown to alter synaptic conductivity by modifying the release of neurotransmitters through an effect involving changes in transmembrane calcium flux (Bawin & Adey, 1976; Jaffe et al, 1980; Blackman, 1988; Rusovan & Kanje, 1992. In addition, exposure to EMFs has been shown to alter the circadian release of pineal melatonin (Welker et al, 1983; Semm, 1992) which, in turn, influences synaptic neurotransmission and immune mechanisms

Rhythm generation in organotypic medullary cultures of newborn rats

Organotypic transverse medullary slices (obex level) from six-day-old rats, cultured for two to four weeks in chemically defined medium contained rhythmically discharging neurones which were activated by CO2 and H+. The mechanisms underlying this rhythmicity and the spread of excitation and synaptic transmission within this organotypic tissue were examined by modifying the composition of the external solution. Our findings showed that (1) Exposure to tetrodotoxin (0.2 μM) or to high magnesium (6 mM) and low calcium (0.2 mM) concentrations abolished periodic activity. (2) Neither the blockade of GABAergic potentials with bicuculline methiodide (200 μM) and/or hydroxysaclofen (200 μM) nor the blockade of glycinergic potentials with strychnine hydrochloride (100 μM) abolished rhythmicity. (3) While atropine sulphate (5 μM) was ineffective in modulating periodic discharges nicotine (100 μM) — like CO2 — shortened the intervals between the periodic events; hexamethonium (50–100 μM) reduced both periodic and aperiodic activity. (4) Exposure to the NMDA antagonist 2-aminophosphonovaleric acid (50 μM) suppressed periodic events only transiently. In the presence of 2-aminophosphonovaleric acid rhythmicity recovered. However, the AMPA-antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (10–50 μM), abolished periodic activity reversibly within less than 5 min. When 6-cyano-7-nitroquinoxaline-2,3-dione and nicotine were administered simultaneously periodic events persisted for up to 10 min. These findings indicate that synaptic excitatory drive is a prerequisite for the generation of rhythmic discharges of medullary neurones in this preparation. This drive may activate voltage-dependent channels or it may facilitate endogenous cellular mechanisms which initiate oscillations of intracellular calcium concentration. To test the latter possibility (5) calcium antagonists were added to the bath saline. The organic calcium antagonists verapamil and flunarizine (50–100 μM each) and the inorganic calcium antagonists cobalt (2 mM) and magnesium (6 mM) suppressed periodic activity and abolished or weakened the chemosensitivity towards CO2/acidosis. (6) Dantrolene (10 μM), an inhibitor of intracellular calcium release decreased the periodicity, while thapsigargin (2 μM) which blocks endoplasmic Ca2+-ATPase, transiently accelerated the occurrence of periodic events. (7) Oscillations of intracellular free calcium concentrations in Fura-2 AM-loaded cells were weakened or abolished by cobalt (2 mM). The results of (5)–(7) indicate that transmembrane calcium fluxes as well as intracellular Ca2+-release and -clearance mechanisms are a prerequisite for intracellular free calcium oscillations which may be important in the generation of rhythmic discharges in medullary neurones.

Excitatory amino acids in health and disease.

To review the role of excitatory neurotransmitters in normal mammalian brain function, the concept of excitotoxic neuronal death as an important final common path in a variety of diseases, and modification of excitatory synaptic transmission as an important new pharmacological principle. These principles are discussed, with special emphasis on diseases of importance to older adults. A MEDLINE search from 1966 to May 1995 was undertaken, as well as a manual search of current issues of clinical and basic neuroscience journals, for articles that addressed glutamate N-methyl-D-aspartate and/or excitotoxicity. A total of 5398 original and 68 review articles were identified that addressed animal and human experimentation relevant to excitotoxic neuronal death. There were 364 articles with potential significance for clinical application identified; 132 of the most recent references are provided. All articles were classified into three categories: general receptor, biology pathogenesis of disease, and pharmacotherapy. Glutamic and aspartic acids are the physiological mediators of most excitatory synaptic transmission. This is critical to several normal nervous system functions, including memory and long-term modification of synaptic transmission and nociception. Activation of the inotropic NMDA and non-NMDA receptors increases transmembrane calcium and sodium fluxes, and the metabotropic glutamate receptor activation results in generation of inositol triphosphate and inhibition of adenylate cyclase. Numerous modulatory sites exist, especially on the NMDA receptor. Nitric oxide, arachidonic acid, superoxide, and intracellular calcium overload are the ultimate mediators of neuronal death. Glutamate re-uptake transporters belong to a unique family of amino acid transport systems, the malfunction of which is intricately involved in disease pathogenesis. Ischemic stroke, hypoglycemia, Parkinson's disease, alcohol intoxication and withdrawal, Alzheimer's disease, epilepsy, and chronic pain syndromes are only some of the important clinical neurological disorders with a major pathogenic role for the excitatory amino acids. Pharmacological manipulation of the excitatory amino acid receptors is likely to be of benefit in important and common diseases of the nervous system. Only a few of the currently available drugs that modify excitatory neurotransmission, such as remacemide, lamotrigine, and tizanidine, have an acceptable therapeutic index. The identification of numerous receptor subtypes, topographic variabilities of distribution, and multiple modulatory sites will provide a true challenge to the neuropharmacologist.

Suppression of rhythmic discharges of medullary neurones in organotypic cultures of new-born rats by calcium antagonists

The contribution of transmembrane calcium flux to the generation of periodic bioelectric activity in cultured organotypic medullary tissue of 6 day old rats was determined by adding calcium antagonists (CA) to the recording saline and by lowering the calcium concentration of this saline. Organic CA flunarizine and verapamil (50–100 μmol/l) reversibly suppressed rhythmic discharge and diminished the CO 2 response of medullary neurones within 30–60 min. Inorganic CA cobalt and magnesium exerted the same effects within a few minutes. After lowering the calcium concentration rhythmic activity became unstable, but recovered on exposure to increased CO 2 concentration, the excitatory effect of which was strongly reduced. These findings point to a significant role for transmembrane calcium flux and intracellular calcium concentration in sustaining both periodic activity and the C0 2 response of medullary neurones.

Verapamil treatment attenuates immunoreactive GFAP at cerebral cortical lesion site

Cerebral cortical lesions were produced using a stereotactic injection system in Sprague-Dawley rats randomly assigned to three groups: (1) needle lesioned and uninjected (Lesioned), (2) needle lesion and stimultaneous local injection of 50 or 100 μl 0.9% saline (L/Saline), and (3) needle lesion and simultaneous local injection of 50 or 100 μl Verapamil-HCl (VHCL) (2.5 mg/ml (5 mM) Abbott Labs, Chicago, IL), a passive, L-type calcium channel blocker (L/VHCL). The lesioning induced expression of glial fibrillary acidic protein (GFAP), a type of intermediate filament protein expressed in reactive astrocytes, at the lesion site. There was a reduction in GFAP-like immunoreactivity (GFAP-IR) in the L/VHCL group versus the Lesioned and the L/Saline groups. There was a five-fold increase of GFAP-IR at 24 h post lesion in the L/Saline group, but no statistically increase seen in the Lesioned or L/VHCL groups at either volume. Pretreatment of the anti-GFAP with VHCL did not impair the antigen labeling. To determine whether differences in pHs, or volume could account for these findings, a second experiment was performed using pH-matched saline or VHCL in 10 μl volume injected into contralateral hemispheres at the time of lesioning. There was an 80% reduction in GFAP-IR in the L/VHCL group at 72 h compared with the L/Saline group. These data suggest that VHCL may suppress the early increase of GFAP-IR in response to cortical lesion and that reducing transmembrane calcium flux through L-type calcium channels may be the mechanism involved.

Transmembrane calcium fluxes during Al stress

Transmembrane calcium fluxes during Al stress

Erythropoietin and testicular steroidogenesis: the role of second messengers.

It has been demonstrated that erythropoietin (EPO) influences rat and human Leydig cell steroidogenesis, stimulating testosterone production through a direct and specific receptor-mediated mechanism. The aim of this study was to investigate the mechanism by which recombinant human erythropoietin (rHuEPO) exerts its stimulatory effect on rat Leydig cells. Recombinant human EPO did not induce, at any dose tested (10(-10) to 10(-13) mol/l), an increase in either cAMP or cGMP, suggesting that in Leydig cells the effect of rHuEPO does not involve the adenylate or guanylate-cyclase systems. The role of transmembrane calcium flux in rHuEPO-stimulated steroidogenesis was studied by evaluating the effect of calcium channel blocker, verapamil, and by the 45Ca2+ uptake method. Verapamil did not influence rHuEPO-induced testosterone secretion and rHuEPO did not modify calcium recycling, indicating that calcium transmembrane flux is not involved in the rHuEPO effect. The protein kinase C inhibitor staurosporine (10, 30, 100 and 300 nmol/l) inhibited rHuEPO-stimulated testicular steroidogenesis in a dose-dependent manner. This indirect evidence suggests that the stimulatory effect of rHuEPO on rat Leydig cells may involve protein kinase C activation.

Supplementation of Immunosuppressive Regimens with Calcium Channel Blockers

Calcium channel blockers (calcium antagonists) are a diverse group of drugs that are currently approved for the treatment of hypertension and angina pectoris. They share a similar activity, despite their dissimilar chemical structures: attenuation of the cellular influx of calcium. Since the transmembrane flux of calcium is a common signalling system for cellular biochemical processes, calcium antagonists may influence numerous cellular functions. Many of these physiological processes are important in mediating responses to vasoconstrictor substances, such as may be involved in cyclosporin-mediated hypertension, nephrotoxicity and delayed graft function.

Activation of MAP2-kinase in B lymphocytes by calcium ionophores.

The role of increases in intracellular calcium levels on tyrosine phosphorylation in human B lymphocytes was studied. Stimulation of normal, resting B lymphocytes or B lymphoblastoid cells with the calcium ionophores ionomycin or A23187 induced the tyrosine phosphorylation and the enzymatic activation of microtubule-associated protein-2 kinase (MAP2-K). Treatment of these cells with PMA induced tyrosine phosphorylation of a protein with the identical mobility, as well as the enzymatic activation of MAP2-K. Stimulation of these cells with ionomycin also resulted in increased ribosomal S6 kinase activity. Activation of MAP2-K in B lymphocytes by calcium ionophore was rapid (detectable within 1 min), transient (returning to background levels by 45 min), and dependent on extracellular calcium. These results demonstrate that transmembrane calcium flux induced by calcium ionophore results in the tyrosine phosphorylation and enzymatic activation of MAP2-K in human B cells.

Calcium plays a central role in phase shifting the ocular circadian pacemaker of Aplysia.

The eye of the marine mollusk Aplysia californica contains an oscillator that drives a circadian rhythm of spontaneous compound action potentials in the optic nerve. Both light and serotonin are known to influence the phase of this ocular rhythm. The aim of the present study was to evaluate the role of extracellular calcium in both light and serotonin-mediated phase shifts. Low calcium treatments were found to cause phase shifts which resembled those produced by the transmitter serotonin. However, unlike serotonin, low calcium neither increased ocular cAMP levels nor could these phase shifts be prevented by increasing extracellular potassium concentration. Low calcium-induced phase shifts were prevented by the simultaneous application of the translational inhibitor anisomycin and low calcium treatment resulted in changes in [35S]methionine incorporation into several proteins as measured by a two-dimensional electrophoresis gel analysis. Finally, light treatments failed to produce phase shifts in the presence of low calcium or the calcium channel antagonist nickel chloride. These results are consistent with a model in which serotonin phase shifts the ocular pacemaker by decreasing a transmembrane calcium flux through membrane hyperpolarization while light-induced phase shifts are mediated by an increase in calcium flux.

Ion-translocating ATPases in tendrils of Bryonia dioica Jacq.

Procedures have been developed which allow the preparation of highly pure endoplasmic reticulum and plasma membrane from tendrils of Bryonia dioica. These and further membrane fractions were used to study vanadate-sensitive ATPase activity as well as Mg2+ATP-driven transport of 45Ca2+. Calcium-translocating ATPases were detected in the endoplasmic reticulum, the plasma membrane and the mitochondrial fraction and characterized kinetically and with respect to the effects of various inhibitors. The endoplasmic-reticulum Ca2+-translocating ATPase was stimulated by KCl and was calmodulin-dependent. The plasma-membrane enzyme was not affected by these agents. These, as well as the inhibitor data, show that the Ca2+-translocating ATPases of the endoplasmic reticulum and the plasma membrane are distinctly different enzymes. Upon mechanical stimulation, the activities of the vanadate-sensitive K+, Mg2+-ATPase and the Ca2+-translocating ATPase(s) increased rapidly and transiently, indicating that increasing transmembrane proton and calcium fluxes are involved in the early stages of tendril coiling.

Epileptogenic actions of xanthines in relation to their affinities for adenosine A 1 receptors in CA3 neurons of hippocampal slices (guinea pig)

In order to analyze the epileptogenic mechanisms of caffaine and related xanthines, putative effects of these drugs were studied on adenosine receptors of CA3 neurons in hippocampal slices. Epileptogenic concentrations of different xanthine derivatives strongly correlated with their affinities for the inhibitory A 1 adenosine receptor subtype. The A 1 receptor agonists adenosine and R-PIA reversibly depressed xanthine-induced epileptic activity without effects on the resting membrane potential or on spontaneously occuring action potentials. These findings suggest that the epileptogenic potency of xanthines is primarily due to the blockade of the A 1 receptors through an abnormal rise of intracellular cAMP and to the excessive transmembrane calcium fluxes underlying paroxysmal depolarization shifts.

Omega-conotoxin prevents myelin-evoked growth cone collapse in neonatal rat locus coeruleus neurons in vitro

The response of neonatal rat locus coeruleus neurons to contact with myelin extracts prepared from the CNS and PNS was examined. The growth cones of these neurons collapsed following contact with central myelin, but continued to elongate on contact with peripheral myelin. Central myelin elicited an increase in the intracellular free calcium concentration in these growth cones, while peripheral myelin did not. This increase appeared to require transmembrane calcium flux, since it was blocked by extracellular EGTA, and also by extracellular cobalt. These neurons express N- and L-type calcium channels. Exposure to 5 microM omega-conotoxin GVIA, a specific blocker of N-type channels, prevented both the myelin-evoked increase in growth cone calcium concentration and the collapse of growth cones.

Requirement for transmembrane sodium flux in maintenance of cytosolic calcium levels in rat Sertoli cells.

The prompt rise in cytosolic calcium induced by follicle-stimulating hormone (FSH) in rat Sertoli cells suggests a role for calcium in FSH signal transduction. To evaluate the requirement for sodium in transmembrane calcium fluxes in Sertoli cells, we measured intracellular calcium concentration under sodium-free conditions and during stimulation by monensin and veratridine, used to elevate cytosolic sodium. Cytosolic calcium levels were measured by dual-wavelength spectrofluorimetry using freshly isolated cells loaded with fura-2 acetoxymethyl ester. Whereas, removal of extracellular sodium lowered cytosolic calcium in unstimulated cells from 89 +/- 4 to 75 +/- 8 nM, treatment with monensin and veratridine increased cytosolic calcium to 142 +/- 19 and 126 +/- 13 nM, respectively. Without extracellular calcium, monensin still produced 47% of the rise in cytosolic calcium observed in the presence of extracellular calcium, indicating approximately equal contributions of calcium from intracellular and extracellular sources. Blockade of voltage-sensitive or/and voltage-insensitive calcium channels by verapamil and ruthenium red was unable to completely prevent the monensin-induced elevation of cytosolic calcium. In addition tetrodotoxin failed to block the FSH-induced rise in cytosolic calcium. These observations, together with the considerable reduction in monensin-induced rise in cytosolic calcium under extracellular sodium-free condition, support the hypothesis that sodium-calcium exchange rather than the specific calcium or sodium channels regulate basal and monensin-induced transmembrane sodium and calcium fluxes in Sertoli cells.

Influence of calmodulin antagonists and calcium channel blockers on triiodothyronine uptake by rat hepatoma and myoblast cell lines

The influence of calcium-related mechanisms on cellular uptake of triiodothyronine (T 3) has not yet been defined, although it is known that T 3 can stimulate cellular entry of calcium. We therefore investigated the saturable uptake of [ 125I]-T 3 (10 −11 mol/L) from serum-free medium in vitro by hepatoma (H4) cells and skeletal myoblast (L6) cells to establish the calcium-dependency of this process. We studied the effects of the following three structurally distinct types of calmodulin antagonists in H4 cells: the naphthalene sulfonamides W7, W12, and W13, calmidazolium, and trifluoperazine. Uptake of [ 125I]-T 3 as a percentage of control values (n = 4, 10 −4 mol/L antagonist) was as follows: W7, 42.0% ± 3.3% ( P < .001); W12, 87.5% ± 4.5% (NS); W13, 79.5% ± 2.5% ( P < .05); calmidazolium (10 −6 mol/L, n = 8), 55.1% ± 2.2% ( P < .001); and trifluoperazine (10 −5 mol/L, n = 6), 65.7% ± 4.1% ( P < .001). To investigate whether the calmodulin sensitivity of uptake was mediated via transmembrane calcium flux, we also studied the effects of three structurally distinct types of organic calcium channel blockers in both H4 and L6 cells. [ 125I]-T 3 uptake as a percent of control values (10 −4 mol/L blocker, n = 4) was as follows: nifedipine, 8.6% ± 0.9% (H4) and 16.7% ± 7.2% (L6); verapamil, 24.6% ± 3.2% (H4) and 61.9% ± 4.2% (L6); diltiazem, 62.7% ± 3.6% (H4) and 36.1% ± 5.4% (L6); all P < .001. Eadie-Hofstee analysis indicated competitive inhibition of T 3 uptake for both calmidazolium and nifedipine. Because calmodulin antagonists can also inhibit protein kinase C, we used phorbol myristic acetate (10 −6 mol/L) to stimulate protein kinase C (30-minute incubation at 37°C) and to inhibit protein kinase C (24-hour incubation at 37°C). Stimulation of protein kinase C did not enhance T 3 uptake. Although inhibition of protein kinase C diminished T 3 uptake to 74.0% ± 2.7% of the control value (n = 4, P < .01), this effect was insufficient to explain the inhibitory effect of the calmodulin antagonists. These studies demonstrate that saturable cellular uptake of [ 125I]-T 3 is inhibited by calmodulin antagonists and calcium channel blockers. We conclude that T 3 uptake in liver and skeletal muscle cells may occur by calcium-related processes.

T cell CD7 mRNA expression is regulated by both transcriptional and post-transcriptional mechanisms.

The CD7 molecule is a 40 kDa member of the Ig superfamily that is acquired early in human T cell ontogeny. Because of the putative three-dimensional structure of CD7 and its presence on T cell precursors, it has been postulated that CD7 serves as an adhesion molecule that facilitates early T cell maturation. Ligand binding to CD7 on mature peripheral blood (PB) T cells has been reported to deliver a co-mitogenic signal with CD3 mAb for T cell triggering. In previous work, we found that CD7 was upregulated on PB T cells following a non-mitogenic ionomycin-induced transmembrane calcium flux, which induced new T cell CD7 transcription without affecting CD7 mRNA stability. In this report, we have studied the upregulation of CD7 expression on PB T cells following stimulation by ionomycin, phytohemagglutinin (PHA), and CD3 mAb. PHA prolonged T cell CD7 mRNA stability without affecting CD7 transcription, while stimulation of PB T cells with CD3 mAb both increased T cell CD7 transcription and prolonged CD7 mRNA stability. Experiments with cycloheximide demonstrated superinduction of T cell CD7 mRNA and showed that new protein synthesis was not required for ionomycin-induced upregulation of T cell CD7 expression. Cyclosporin A inhibited ionomycin-induced T cell CD7 upregulation at the level of CD7 mRNA transcription and elongation. These data demonstrate that ionomycin, PHA, and CD3 mAb act via different mechanisms to increase T cell CD7 expression, and that both transcriptional and post-transcriptional mechanisms are used to modify CD7 mRNA levels.

Calcium-antagonistic effects of carbamazepine in epilepsies and affective psychoses.

Carbamazepine (CBZ) is known to have beneficial effects in the treatment of epilepsies and in the prophylaxis of affective disorders. Since increased transmembrane calcium fluxes and intracellular calcium concentrations play a key role in the generation of epilepsies and possibly also in the development of these psychiatric disorders the effects of CBZ on epileptic discharges (elicited by caffeine, penicillin and low Mg2+) in CA3 neurons of hippocampal slices were compared with those of the organic calcium antagonist verapamil and found to be almost the same.