Effect of trifluoperazine and calcium ions on gregarine gliding

Summary The drug trifluoperazine (TFP) inhibits the gliding motility of gregarine protozoans. This suggests that the Ca⁺⁺ binding protein, calmodulin, plays a role in the motility process. However the presence of extracellular Ca⁺⁺ was not required for gliding to occur.Acknowledgments. We should like to thank L. Cooper for technical assistance, Smith, Kline and French for the gift of trifluoperazine, and Terry Preston for valuable discussion.     

Development of the maximum isometric force at short sarcomere lengths in calcium-activated muscle myofibrils

Summary Studies on the sarcomere length-force relation in Ca⁺⁺-activated vertebrate muscle myofibrils indicate that the maximum isometric force can be generated even at sarcomere lengths around 1 m, indicating that the ascending limb of the sarcomere length-force relation is virtually absent.We thank Miss S. Gomi for her technical assistance. This work was supported by the grant (No. 587028) form the Ministry of Education, Science and Culture of Japan.     

Correlation of ammonia liberation and calcium deposition by the avian egg and blood ammonia levels in the laying hen

Zusammenfassung Mittels biochemischer Daten wird der Nachweis erbracht, dass im Ovidukt des Huhnes während der Schalenbildung zwar vermehrt NH₄ ⁺ freigesetzt wird, jedoch eine negative Korrelation zwischen NH₄ ⁺-Produktion und Ca⁺⁺-Abscheidung besteht.

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Supported by a training grant from the U.S. Public Health Service No. 5-T1-DE-118. We thank Dr.P. R. Tramell for his help during the initial stage of this investigation.     

Sodium and calcium action potentials in human anterior pituitary cells

Summary Human anterior pituitary cells derived from a somatotropin-secreting adenoma were capable of generating action potentials with Ca²⁺ and tetrodotoxin-sensitive Na⁺ components. A major fraction of the action current was carried by Na ions.We wish to thank Dr O. Sand for correcting the English and Miss Michiko Takano for technical assistance. We also acknowledge the collaboration of Dr S. Miyazaki in the electron microscope.     

Effects of cadmium on the immune system of mice

Summary Chronic oral exposure of mice to Cd⁺⁺ inhibits cell-mediated immunity of delayed type hypersensitivity induced by sheep red blood cells (SRBC). No effect was detected on humoral immune response to SRBC. Spleen cells derived from mice exposed to Cd⁺⁺ showed in vitro enhanced response to T and B cell mitogens. These results demonstrate that Cd⁺⁺ exposure alters the immune system of mice.Dedicated to Prof. Georg Henneberg on the occasion of his 70th anniversary on 12.10.1978.Acknowledgments. Supported by a grant from the Umweltbundesamt. We thank Ms Odenwald, Ms Schulz, Klinikum Steglitz, and Ms Emeis, Robert Koch-Institut Abt. Immunologie, for the excellent technical assistance.     

Influence of ethanol on calcium,inositol phospholipids and intracellular signalling mechanisms

Summary Studies have implicated Ca⁺⁺ in the actions of ethanol at many biochemical levels. Calcium as a major intracellular messenger in the central nervous system is involved in many processes, including protein phosphorylation enzyme activation and secretion of hormones and neurotransmitters. The control of intracellular calcium, therefore, represents a major step by which neuronal cells regulate their activities. The present review focuses on three primary areas which influence intracellular calcium levels; voltage-dependent Ca⁺⁺ channels, receptor-mediated inositol phospholipid hydrolysis, and Ca⁺⁺/Mg⁺⁺-ATPase, the high affinity membrane Ca⁺⁺ pump.Current research suggests that a subtype of the voltage-dependent Ca⁺⁺ channel, the dihydropyridine-sensitive Ca⁺⁺ channel, is uniquely sensitive to acute and chronic ethanol treatment. Acute exposure inhibits, while chronic ethanol exposure increases⁴⁵Ca⁺⁺-influx and [³H]dihydropyridine receptor binding sites. In addition, acute and chronic exposure to ethanol inhibits, then increases Ca⁺⁺/Mg⁺⁺-ATPase activity in neuronal membranes. Changes in Ca⁺⁺ channel and Ca⁺⁺/Mg⁺⁺-ATPase activity following chronic ethanol may occur as an adaptation process to increase Ca⁺⁺ availability for intracellular processes. Since receptor-dependent inositol phospholipid hydrolysis is enhanced after chronic ethanol treatment, subsequent activation of protein kinase-C may also be involved in the adaptation process and may indicate increased coupling for receptor-dependent changes in Ca⁺⁺/Mg⁺⁺-ATPase activity.The increased sensitivity of three Ca⁺⁺-dependent processes suggest that adaptation to chronic ethanol exposure may involve coupling of one or more of these processes to receptor-mediated events.     

Effect of platelet activating factor on guinea-pig papillary muscle

Summary Platelet activating factor (PAF) induces a biphasic effect on guinea-pig papillary muscle: 1. a transient positive inotropic effect preceded by an increase in action potential duration (APD); 2. a marked negative effect on inotropism and on APD. Since Ca⁺⁺ slow action potentials were initially enhanced by PAF and then markedly depressed, it is suggested that PAF specifically interferes with the Ca⁺⁺ slow channel.     

Enhanced excitability in locust muscle fibres induced by calcium free saline

Summary The membrane of locust muscle fibres normally exhibits a graded electrical response to outward current pulses of increasing strength. On removal of Ca⁺⁺ ions from the external medium, these fibres are shown to exhibit depolarizing membrane responses of variable time course and duration. These responses are abolished in Na⁺-free solutions, and by the addition of Mn⁺⁺ ions.D.A.M. was the recipient of a Royal Society and Science Research Council European Exchange Fellowship. We thank the Centre for Overseas Pest Research, Kensington for supplying the locusts.     

Possible role of intestinal alkaline phosphatase activity in thiamine transport

Summary Thiamine deficiency caused a marked decrease of intestinal alkaline phosphatase (al-Pase) activity, but had no effect on the Ca⁺⁺-ATPase activity and Ca⁺⁺-absorption in rats. The al-Pase activity was significantly decreased 1 h after oral administration of ethanol at 0.5 and 2.5 g/kg. In contrast, Mg⁺⁺-, Ca⁺⁺- and (Na⁺+K⁺)-ATPase activities did not change after the administration of ethanol. These findings show that the al-Pase activity, unlike the Ca⁺⁺-ATPase activity, is not related to Ca⁺⁺-absorption. A possible role of al-Pase activity in the active transport of thiamine in the intestine was discussed.     

Effect of ouabain on volume regulation of rabbit kidney cortex slices in hypo-osmotic media

Summary The volume regulation process at work in rabbit kidney cortex slices submitted to hypo-osmotic media show both a swelling limitation and a volume readjustment phase. Swelling limitation is Na⁺ dependent and is blocked by ouabain 10^–3 M. There is, however, no need to implicate the activity of a ouabain sensitive Na⁺/K⁺ pump in this process.This work has been aided by a grant 1.5.422.82F from the FNRS to R.G. We wish to thank Mr J.M. Theate for his skilful assitance.     

Hypothyroidism lowers blood pressure,adenylate cyclase and Na+, K+-and K+, Ca++-ATPase activities in normotensive and spontaneously hypertensive rats

Summary Myocardial isoproterenol-stimulated adenylate cyclase, Na⁺, K⁺-ATPase and K⁺, Ca⁺⁺-ATPase activities are elevated in the spontaneously hypertensive rat and can be lowered by methimazole-induced hypothyroidism which also prevents the development of hypertension. Although thyroid hormone levels are similar between untreated SHRs and WKY rats, the thyroid is apparently necessary for the expression of spontaneous hypertension.Acknowledgments. Supported by North Carolina Heart Grant No. 40301 and a grant from Sigma Xi.     

Myofibrillar ATPase activities of red and white myotomal muscles of marine fish

Zusammenfassung Die Ca⁺⁺-und nicht-Ca⁺⁺-abhängige ATPase-Aktivität von isolierten Myofibrillen der roten und weissen Muskeln von drei Meerfischen wurde gemessen und festgestellt, dass die weissen Muskeln eine höhere Aktivität besitzen.

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I. A. Johnston was in receipt of a Science Research Council Research Studentship.

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This work was also supported by a Natural Environment Research Council grant to Dr.G. Goldspink.     

Quercetin enhances water transport in toad bladder

Summary A highly significant enhancement of the hydrosomotic actions both of vasopressin and of exogenous cAMP was seen in the presence of quercetin. The hypothesis is advanced that quercetin affects the intracellular coupling between Ca⁺⁺ and cAMP.This work was supported by the Swiss National Science Foundation, grant No. 3.043-0.76.     

Die Abhängigkeit der Ca++-Aufnahme isolierter Mitochondrien des Herzmuskels von der Na+-und K+-Konzentration als mögliche Ursache der inotropen Digitaliswirkung

Summary In isolated mitochondria of heart muscle from rabbits and oxen there is, under suitable conditions, an accumulation of Ca⁺⁺, which is significantly enhanced by elevating the K⁺/Na⁺ quotient of the incubation medium. K-strophanthine (10^–5–10^–7) does not influence the accumulation of Ca⁺⁺ by the mitochondria of heart muscle. Therefore the intracellular increase in exchangeable Ca⁺⁺ observed after digitalis-glycosides could be explained by a decrease of the intracellular K⁺/Na⁺ quotient, which is caused by inhibition of the membrane ATPase and diminishes the capacity for Ca⁺⁺ accumulation in mitochondria.     

Primary tissue cultures from organ fragments: A simplified method

Summary Organ fragments washed in Ca⁺⁺ and Mg⁺⁺-free saline, treated with trypsin and placed directly into culture flasks adhered within seconds to the vessel surface. If the fragments were suspended in culture medium before they were added to the flasks, they did not adhere. This technique permits the rapid attachment and subsequent growth of the primary tissue cultures.Adapted from a thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at Florida Atlantic University.Acknowledgment. This work was carried out in the laboratory of J.X. Hartmann, whom I thank for his generosity and helpful discussion.     

Sensitivity of the developing chick myocardium to the positive inotropic effects of calcium and isoproterenol

Summary The present results show that the sensitivity of the chick myocardium to the positive motropic effect of Ca⁺⁺ decreases during development and that the Ca⁺⁺ concentration of the physiological solution used must be lowered below normal to study the effects of positive inotropic agents in preparations from younger embryos. Isoproterenol elicits positive inotropic responses in 7–9-day embryonic ventricle and in newborn chick atria; however, the 4-day embryonic myocardium is unresponsive to isoproterenol.This work was supported by Grant No. HL-15995 from the National Heart Institute (USPHS).The authors would like to thank Dr.F. E. Shideman for the isolated tissue baths used in these experiments.     

Relaxation by glucagon of potassium contracture in cat ventricle

Summary Glucagon reduces K⁺-contracture, increases peak active force, but does not alter time to peak force and relaxation of the isometric twitch of cat ventricle.This study was supported by a grant-in-aid from the Florida Heart Association-Suncoast Chapter, National Institute of Health Research grant HL 19044 and NSRA Awards HL 05849 and HL 07188.The authors wish to thank Mr William Fitterman for his valuable technical and illustrative assistance.     

Increased in vitro phosphorylation of rat liver nucleolar proteins following triiodothyronine administration

Summary It has been shown that triiodothyronine (T₃) administration to thyroidectomized rats induces an increase in the in vitro net³²P uptake into liver nucleolar proteins. Such an increase depends on a stimulation of the nucleolusassociated protein kinase activity and not on a lower dephosphorylation rate.We wish to thank MissAdriana Voci for excellent technical assistance. This study was partly supported by a grant from Consiglio Nazionale delle Ricerche (CNR), Italy.     

Cytochemical gradients and mitochondrial exclusion in the apices of vegetative hyphae

Summary Apical maximal acidity (shown by subapically increasing pH) and maximal concentration of inorganic phosphate (shown by a subapically decreasing gradient of yellow phosphomolybdate) contrast with the subapical, mainly mitochondrial sequestration of calcium ions. Such gradiential control of calcium concentration appears to be the requisite for the Ca⁺⁺ sensitive gelation of the apical hyaloplasm preventing the mitochondria from entering into this continuosly elongating zone of growing hyphae.The support of the founds National Suisse de la Recherche Scientifique is acknowledged and we thank Miss E. Herz for her technical assistance.     

Ambiguous effect of caffeine upon the transmembrane Ca current in mammalian ventricular myocardium

Zusammenfassung Coffein (20 mM) wirkt auf den transmembranären Ca⁺⁺-Strom der Warmblütermyokardfaser biphasisch. Zunächst nimmt der Ca⁺⁺-Strom zu, was auf einer Verbesserung der Ca⁺⁺-Leifähigkeit des langsamen Membrankanals beruht. Nach längerer Einwirkungsdauer von Coffein kommt es dagegen zu einer Abnahme des Ca⁺⁺-Stroms. Als Ursache hierfür wird vor allem eine Verminderung des transmembranären Konzentrationsgradienten für Ca⁺⁺ — infolge eines Anstiegs der freien Ca⁺⁺-Konzentration im Zellinnern — postuliert.