Purification of putative Ca2+ channel protein from rabbit skeletal muscle. Determination of the amino-terminal sequence

A putative Ca2+ channel protein was purified from rabbit skeletal muscle transverse tubules with the combined use of lectin affinity chromatography and ion-exchange chromatography, followed by sucrose density gradient centrifugation. The major component of the purified preparation detected by sodium dodecyl sulfate-gel electrophoresis was a protein of 150 kDa when reduced with 20 mM dithiothreitol and a 191-kDa protein when treated with 20 mM N-ethylmaleimide. Therefore, this protein appears to be identical with the alpha subunit previously described (Curtis, B. M., and Catterall, W. A. (1984) Biochemistry 23, 2113-2118). This protein was purified by preparative sodium dodecyl sulfate-gel electrophoresis, followed by electroelution and/or electroblotting, and its amino acid composition and NH2-terminal sequence were determined. The NH2-terminal sequence is: NH2-Glu-Pro-Phe-Pro-Ser-Ala-Val-X-Ile-Lys-Ser-X-Val-X-Lys-Met-Gln-.

Transcranial Doppler ultrasound for the assessment of intracranial arterial flow velocity--Part 1. Examination technique and normal values

We present the examination technique and normal values of flow velocity from intracranial basal cerebral arteries for a recently developed pulsed Doppler system operating at 2 MHz emitting frequency. Peak systolic, peak diastolic, and mean flow velocity values are analyzed from fast-Fourier transformed (FFT) Doppler spectra at selected depths for 50 presumed normal subjects ranging in age from 22 to 79 years. Interindividual variation is high for peak flow but moderate for mean flow velocity values, which hence are more likely to discriminate normal from abnormal. Flow velocity values within the posterior cerebral artery (PCA) and the basilar artery (BA) are significantly lower than in the anterior cerebral artery (ACA) and the middle cerebral artery (MCA), which is also unique in showing significantly decreasing values with increasing age: calculated mean flow velocities are 47.3 +/- 13.6 and 45.3 +/- 13.5 cm/sec in the ACA, and 58.4 +/- 8.4 and 44.7 +/- 11.1 cm/sec in the MCA in patients less than 40 years and greater than 60 years, respectively, but 34.2 +/- 7.8 and 29.9 +/- 9.3 (PCA) (patients less than 40 years and patients greater than 60 years), and 34.9 +/- 7.8 and 30.5 +/- 12.4 (BA) (patients less than 40 years and patients greater than 60 years). A new scanning system is introduced, which we suggest will reduce interindividual variations and improve the accurate separation of nearby vessels, which are major causes for the comparatively large standard deviations at present.

[CT follow-up of neurocysticercosis treated with praziquantel]

Praziquantel therapy has produced a much better prognosis in neurocysticercosis since 1980. The computed tomographic findings and follow-up study in 4 patients with neurocysticercosis before and after praziquantel therapy are described. The special difficulties of differential diagnosis and further diagnostic procedures are discussed in cases in which calcifications are absent and only solitary foci can be found.

A possible role for the endothelium in porcine coronary smooth muscle responses to dihydropyridine calcium channel modulators

The role of the endothelium in contraction and relaxation produced by the dihydropyridine calcium channel modulators was examined in porcine coronary smooth muscle. The optically pure dihydropyridine calcium agonists (+)-S202-791 and (-)-Bay k 8644 both produced greater contractions in tissues without endothelium compared with tissues with intact endothelium. In contrast, histamine produced the same degree of contraction in tissues with and without endothelium. In the presence of KCl-induced active muscle tone, the optically pure calcium antagonists (-)-R202-791 and (+)-Bay k 8644 and the nitrovasodilator isosorbide dinitrate all produced the same degree of relaxation in tissues with and without endothelium. These results suggest that the endothelium plays an inhibitory role in dihydropyridine-induced contraction. When coronary rings with intact endothelium were pretreated for 60 min with 10 or 100 nM (-)-R202-791, the contraction to subsequent addition of (+)-S202-791 was significantly greater than in control tissues pretreated with only solvent. However, in rings with denuded endothelium, pretreatment with (-)-R202-791 resulted in a rightward shift of the dose-response curve to (+)-S202-791, and a depression of the maximal contraction compared with controls. Thus, the interaction between the calcium agonist [(+)-S202-791] and antagonist [(-)-R202-791] is more complex than competitive inhibition. We suggest that the calcium agonists produce two effects, a release of endothelium-derived relaxant factor and a direct contraction of smooth muscle; the calcium antagonists can inhibit both processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of ONO-3144, a new cardioplegic agent, in the reoxygenation injury in the anoxic myocardium

We have investigated the effect of ONO-3144 (2-aminomethyl-4-tert-butyl-6-propionylphenol), which facilitates the conversion of prostaglandin G2 to H2 and acts as a scavenger of free radicals, on the reoxygenation injury in the anoxic heart. Rat hearts were perfused retrogradely with Krebs-Henseleit (KH) medium for 30 min (n = 8) in Group I. In Group II, the hearts which were perfused with anoxic KH medium for 40 min were reoxygenated for 30 min (n = 8). Group III hearts were similar to those in Group II except that 4 mg ONO-3144/liter was added to both anoxic and reoxygenation media (n = 8). Coronary effluent was collected for creatine kinase (CK) loss. Four rats hearts in each group were fixed for electron microscopic study and the remaining hearts were frozen in liquid nitrogen for measurement of adenosine triphosphate (ATP). A six-fold increase in CK leakage, observed after reoxygenation of anoxic heart, was prevented by ONO-3144. Tissue ATP was reduced from 22.2 +/- 0.9 mumol/g dry weight (Group I) to 5.5 +/- 1.1 mumol/g dry weight (Group II). A significant amount of ATP (9.05 +/- 1.22 mumol/g dry weight) was preserved in the treated Group III. The number of normal cells obtained by morphometrical analysis increased significantly from 56.7 +/- 7.8% (Group II) to 86.2 +/- 1.0% (Group III) and moderately injured cells were reduced to 3% in Group III as compared to 16% in the untreated Group I. Injury to the severely injured cells was not prevented by the drug treatment. At electron microscopic level, the cellular membranes, mitochondria and glycogen deposits were well preserved in Group III. Thus, ONO-3144 treatment provides a protection against reoxygenation injury in the anoxic myocardium by scavenging. .OH or other closely related species of free radicals. Therefore, free radicals generated through the conversion of prostaglandin G2 to H2 might play an important role in the reoxygenation injury of the anoxic myocardium.

A comparison between the binding and electrophysiological effects of dihydropyridines on cardiac membranes

To investigate the mechanism of action of dihydropyridines on calcium channels, both receptor binding and the electrophysiological effects of optically pure enantiomers of Bay k 8644, Sandoz 202-791, nimodipine, and PN200-110 were studied in a guinea pig ventricular preparation. The radioligand binding studies are consistent with other reports that the inhibitory and excitatory dihydropyridines share a single binding site. The patch clamp method was used for recording whole cell calcium currents. (-)-Bay k 8644 and (+)-202-791 produced voltage-dependent increases in the calcium currents. The magnitude of the effect was dependent on the holding potential. At holding potentials between -40 and -90 mV these activators increased calcium currents in a concentration-dependent manner with EC50 values of 25 nM and 80 nM, respectively. The inhibitors (+)-Bay k 8644, (-)-202-791, (+)- and (-)-nimodipine, and (+)-PN200-110 blocked the calcium currents with potencies that depended upon holding potential. The IC50 values for these enantiomers measured at a holding potential of -80 mV were, respectively, 8000, 200, 2000, 450, and 400 nM, and IC50 values measured at a holding potential of -30 mV were 26, 1.0, 52, 4.0, and 4.5 nM. The dissociation constants calculated for some dihydropyridines are similar to the Kd values determined by radioligand binding. However, for other dihydropyridines, large discrepancies between the concentrations giving rise to half-maximal electrophysiological effects and the Kd values from binding studies could not be reconciled by voltage-dependent binding alone. We suggest that each dihydropyridine also produces unique effects on the voltage-dependent gating of calcium channels.

Characterization of the ternary complexes formed in the reaction of cis-diamminedichloroplatinum (II), ethidium bromide and nucleic acids

The purpose of this study was to characterize the ternary complexes formed in the reaction of cis-diamminedichloroplatinum (II) (cis-DDP) and nucleic acids, in the presence of the intercalating compound ethidium bromide (EtBr). In these ternary complexes, some EtBr is tightly bound to the nucleic acids. Tight binding is defined by resistance to extraction with butanol, assayed by filtration at acid pH or thin layer chromatography at basic pH. These ternary complexes are formed with double stranded but not with single stranded nucleic acids. They are not formed if cis-DDP is replaced by transdiamminedichloroplatinum(II). The amount of tightly bound EtBr depends upon the sequence of the nucleic acid, being larger with poly (dG-dC).poly(dG-dC) than with poly(dG).poly(dC). Spectroscopic results support the hypothesis that the tight binding of the dye is due to the formation of a bidentate adduct (guanine-EtBr)cis-platin. The visible spectrum of the ternary complexes is blue-shifted as compared to that of EtBr intercalated between the base pairs of unplatinated DNA and it depends upon the conformation of the ternary complex. The fluorescence quantum yield of the ternary complexes is lower than that of free EtBr in water. Tightly bound EtBr stabilizes strongly the B form versus the Z form of the ternary complex poly(dG-dC)-Pt-EtBr and slows down the transition from the B form towards the Z form. The sequence specificity of cis-DDP binding to a DNA restriction fragment in the absence or presence of EtBr is mapped by means of the 3'----5' exonuclease activity of T4 DNA polymerase. In the absence of the dye, all the d(GpG) sites and all the d(ApG) sites but one in the sequence d(TpGpApGpC) are platinated. The d(GpA) sites are not platinated. In the presence of EtBr, some new sites are detected. These results might help to explain the synergism for drugs used in combination with cis-DDP and in the design of new chemotherapeutic agents.

The relationship between the binding site of [3H]-d-cis-diltiazem and that of other non-dihydropyridine calcium entry blockers in cardiac sarcolemma

[3H]-d-cis-Diltiazem binds to canine cardiac sarcolemma in a specific, saturable, and reversible manner with a KD = 58.0 +/- 9.5 nM and a receptor site density (maximum binding) of 2.19 +/- 0.24 pmol/mg of protein. Bepridil and verapamil, Ca2+ channel inhibitors, can completely inhibit this binding at nM concentrations. This inhibition was determined from saturation binding data to be due to a change in affinity of the radioligand, suggesting a competitive interaction between the three drugs. However, in dissociation experiments, both bepridil and verapamil increased the dissociation rate of the radioligand. This effect is uncharacteristic of competitive inhibitors and suggests that bepridil and verapamil regulate [3H]-d-cis-diltiazem binding in a negative allosteric fashion through their own distinct binding sites.

Receptor pharmacology of calcium entry blocking agents

The mechanism of action of calcium channel modulators, a class of drugs that includes 3 chemical groups--1,4-dihydropyridines, phenylalkylamines and benzothiazepines--has been extensively reviewed. The best known representatives of these 3 groups are nifedipine, verapamil and diltiazem, respectively. These drugs bind reversibly, stereospecifically and with high affinity to both the membrane-bound and the purified receptor complex. Non-dihydropyridines allosterically regulate dihydropyridine binding. This has been shown by using (-) [3H]202-791 and (+) [3H]PN200-110 as labeled ligands. The purified receptor complex that possesses binding sites for all 3 chemical groups is likely to be related to the voltage-dependent calcium channel. As the result of a drug-receptor interaction, voltage-dependent calcium channels are either activated or inactivated. The drugs that activate channels act by promoting long-lasting channel openings. The drugs that inhibit calcium channels, the calcium entry-blocking agents, act by preventing channel openings upon membrane depolarization. A complex pharmacologic, electrophysiologic, biochemical, immunologic and molecular genetic approach is required to determine the molecular mechanism of action of calcium channel modulators. Clinically, calcium entry-blocking agents are recommended for the treatment of angina pectoris, hypertension, posthemorrhagic cerebral vasospasm, supraventricular tachycardia, migraine and asthma and the protection of the ischemic myocardium.

Drives, affects, behavior--and learning: approaches to a psychobiology of emotion and to an integration of psychoanalytic and neurobiologic thought

Drawing on concepts and data from psychoanalysis, neuroscience, ethology, and experimental psychology, this paper suggests that affects are the prime movers of human motivation and have, in addition, these properties: they are neurophysiologically generated, sensationlike signals originating not in classical sensory systems, but in limbic structures; activation of the neurobiologic affect generators reliably triggers motor stereotype--like facial expression, posture, and tone of voice--which in turn transmit the physical data underlying empathy and emotional communication; and appetitively sought pleasant emotions-sensations and aversive dysphoric feelings serve respectively as the ultimate, "brain-synthesized" positive and negative reinforcers of emotional learning. The latter ideas point to derivative hypotheses: that parental nonverbal behavior and communication evoke in children the affects that guide character development and choice of defense, and that these processes are consistent with an affect-reinforced associative learning model comprising both operant and classical conditioning paradigms. Psychoanalysis as therapy, then, may mechanistically rely for its clinical effectiveness on extinctionlike processes in which new experience in the analyst-patient relationship leads to the modulation or extinction of initially crippling signal affects associatively linked to various other affects, appetites, and behaviors. Finally, the core hypotheses mesh both with recent findings from the cellular study of affect and learning mechanisms and with associative learning-unlearning assumptions variably explicit in psychoanalytic writings since the time of Freud's (1895) Project.

Extended retinal tamponade in the treatment of retinal detachment with proliferative vitreoretinopathy

We have used intraocular sulphur hexafluoride or liquid silicone as an adjunct to vitreous surgery in the treatment of a non-randomised sequential series of 19 eyes with retinal detachment complicated by proliferative vitreoretinopathy. We have studied the surgical results and complications of these two tamponades and drawn preliminary conclusions on their use in retinal reattachment surgery. After a seven-month minimum follow-up 13 (68%) of the eyes have reattached retinas. Six (60%) of 10 eyes treated only with silicone have reattached retinas, and four (67%) of six eyes treated only with sulphur hexafluoride gas tamponade have reattached retinas. An additional three eyes treated initially with silicone oil subsequently developed retinal detachments; all were successfully reattached with sulphur hexafluoride tamponade after silicone oil removal. Intraoperative pneumatic retinal reattachment to assess relief of retinal traction combined with the production of widespread chorioretinal adhesions to wall off persistent anterior traction and detachment, as well as extended postoperative gas tamponade of the retina, appears to enhance the surgical results in retinal detachment complicated by proliferative vitreoretinopathy. Silicone oil tamponade of the retina appears to be useful in cases where retinal traction cannot be entirely relieved and in patients who are unable to tolerate the head positioning required for effective gas tamponade of the retina. A controlled clinical study recently begun will be required to define further the precise role of these methods of retinal tamponade.

Myocardial Na, K-ATPase in one-kidney, one-clip hypertensive rats

Myocardial ventricular Na, K-ATPase activity of normotensive rats was compared with that of healthy rats with chronic benign one-kidney, one-clip hypertension. The yield of protein (mg/g wet wt left plus right ventricles) in microsomal and sarcolemmal membrane fractions was the same for both normotensive and hypertensive rat ventricles. However, the yield of protein (mg/ventricle) was 26% greater in the hypertensive relative to the normotensive animals, consistent with the presence of hypertrophy, as also indicated by an increase in the ratio of ventricular to body weight and a shift in the isomyosin composition. Na, K-ATPase activity, sodium-dependent phosphorylation and ouabain binding were significantly (P less than 0.05) decreased (by 20%, 40%, and 45%, respectively) in the hypertensive rat ventricles when the data were expressed in units/g tissue wet weight. However, when expressed in units per ventricle, values in normotensive and hypertensive animals were similar. The molecular activity or turnover number of ventricular (and also renal) Na, K-ATPase activity was the same in both groups of animals. These results suggest that the decrease in myocardial specific Na, K-ATPase activity in the rat made hypertensive by removing one kidney and constricting the renal artery of the other kidney is related to the presence of cardiac hypertrophy.

Lymphoid hypophysitis associated with sudden maternal death: report of a case review of the literature

A case of lymphoid hypophysitis in a woman who died during labor is presented. From a review of the 14 previously reported cases it is apparent that this is a specific disease entity, that it involves only woman, especially in association with pregnancy, and that it may have a fatal outcome. The clinical manifestations are either related to hypopituitarism, or those of a space occupying lesion. Attention drawn to the possible occurrence of the disease may result in earlier recognition of the disease and a better outcome of this potentially fatal disease.

Experimental evaluation of absorbable copolymer staples for hysterectomy

Absorbable copolymer staples of three different variants were tested for retention of tensile strength after implantation into the peritoneal cavity of rats. One type maintained tensile strength for two weeks, but then lost it rapidly over the next week. The same three staple compounds were further compared after use for vaginal vault closure during ovariohysterectomy in adult sheep. In all ewes the absorbable staples were effective in providing a stable vaginal cuff closure. The postoperative tissue reaction was minimal. The goal of developing an absorbable staple that would degrade rapidly without compromising wound stability was achieved.

Cefotetan pharmacokinetics in volunteers with various degrees of renal function

Twenty-six volunteers with various degrees of renal function were given a single 1-g dose of cefotetan intravenously over 30 min. Concentrations of cefotetan and cefotetan tautomer in plasma and urine were determined by high-performance liquid chromatography. The pharmacokinetic parameters for cefotetan were calculated according to a two-compartment open model. The mean plasma cefotetan concentration at the end of the intravenous infusion did not vary with renal function and ranged between 122 and 126 micrograms/ml. The mean terminal half-life was 4.2 h in normal volunteers and 9.9 h in volunteers with moderate renal impairment. There was a significant linear correlation between the systemic clearance of cefotetan and creatinine clearance. The cumulative amount of cefotetan excreted in the urine over 24 h in normal volunteers was approximately 49% of the dose, but this was reduced in volunteers with moderate renal impairment. The mean urinary cefotetan concentrations generally peaked during the 2- to 4-h interval after dosing. Cefotetan tautomer was sporadically detected in the plasma and urine of approximately 50% of the volunteers. The mean plasma cefotetan tautomer concentrations and mean total cumulative urinary recoveries of cefotetan tautomer were only minimal compared with those for cefotetan. The mean percentage of the dose excreted in the urine as cefotetan tautomer was not significantly affected by the degree of renal impairment. Recommendations for the dosing of cefotetan in renal-impaired patients are given.

Noninvasive transcranial Doppler ultrasound in intracranial angiomas

Transcranial Doppler ultrasound is a noninvasive method to evaluate flow velocities in the basal cerebral arteries. It can provide hemodynamic data like velocity distributions, intracranial steal phenomena, and functional stenoses in angiomas as illustrated in four patients. This information may supplement conventional neuroradiologic procedures for therapeutic decisions and follow-up.

Effects of bepridil and diltiazem on [3H]nitrendipine binding to canine cardiac sarcolemma. Potentiation of pharmacological effects of nitrendipine by bepridil

[3H]Nitrendipine binds to canine cardiac sarcolemma in a specific, saturable and rapid manner. Bepridil, a Ca++ channel inhibitor, stimulates this binding at submicromolar concentrations, but inhibits it noncompetitively at higher concentrations (IC50 = 15.8 microM). The increase in binding was due primarily to a 30% increase in the association rate constant (k+1) of [3H]nitrendipine, causing a decrease in the KD from a control value of 0.40 to 0.28 nM. In contrast to bepridil, diltiazem causes only an increase in [3H] nitrendipine binding without any inhibition. The increase was due primarily to an increase in receptor site density (maximum binding). These results show that the regulatory effects of bepridil and diltiazem on [3H]nitrendipine binding to cardiac tissue are different. The stimulatory effects of bepridil appeared to be pharmacologically relevant as low concentrations of bepridil potentiated the negative inotropic effect of nitrendipine in isolated perfused rat hearts.

Bepridil block of cardiac calcium and sodium channels

The effects of bepridil, a new Ca channel blocking agent with reported antiarrhythmic action, were examined in single isolated ventricular cells using whole-cell patch clamp techniques. Ca currents were studied in guinea-pig ventricular cells and Na currents were studied in cultured ventricular cells from neonatal rat, a preparation which is more suitable for Na current measurements than guinea pig. At low frequencies (0.1 Hz) and negative holding potentials (-50 mV for Ca currents and -100 mV for Na currents), bepridil produced a concentration-dependent decrease in both Ca and Na currents without any significant change in the current-voltage relations. Concentration-response curves for block of Ca and Na channels were fitted by a one-to-one drug-receptor occupancy model. Half-blocking concentrations (IC50) of bepridil were 5 x 10(-7) M for Ca currents and 3 X 10(-5) M for Na currents. Bepridil had no effect on the inwardly rectifying K current and the time-dependent outward current. The effects of bepridil on Ca and Na currents depend upon the holding potential. Inactivation curves of the Ca and Na currents were shifted to more negative potentials by the drug. The recovery of both the Ca and Na currents from inactivation was always prolonged by bepridil and the repriming of both currents usually displayed an added exponential component, attributed to slow release of the drug from the channels. The results indicate that bepridil, by inhibiting both Ca and Na currents, may have clinical usefulness in the treatment of certain ischemia-induced ventricular arrhythmias.

Distribution of 3H-nitrendipine in the isolated perfused rat heart as revealed by electron microscopic autoradiography

Subcellular distribution of 3H-nitrendipine was investigated in the isolated perfused rat heart by means of electron microscopic autoradiography. Mechanical measurements of cardiac contractile activity (dP/dt) were performed on the hearts used for autoradiography. There was a non-random pattern of silver grain distribution over the myocardial cells. The grain density, i.e. percentage of total grains/percentage of cell area, was determined for each cell component. A grain density higher than one was noted on the cell membrane, T-tubules and capillaries, indicating a significant incorporation of 3H-nitrendipine into the structures. Concentrations of unlabeled nitrendipine containing radiolabeled nitrendipine caused increased grain density and a decreased contractile activity (dP/dt) by 6% to 30%. It is therefore possible that the pharmacological action of nitrendipine is associated with the localization of 3H-nitrendipine on or in the cell membrane, T-tubules and capillaries.