Effects of cadmium on the immune system of mice.

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.     

Enzymatic characteristics of the guanylate cyclase of KB cells: their change as a function of the development of the cultures]

We have localized 71% of the guanylate cyclase activity in the (G X 105,000) supernatent fraction of broken KB cells. The reaction follows Michaelis-Menten kinetics, the apparent Km for GTP is 0,5 mM, as long as GTP is lower than a limited concentration, then activity is inhibited. The ion Mn++ is an absolutely required activator, it does not change enzyme-substrate affinity. The enzyme shows several types of binding sites of Mn++. Guanylate cyclase, studied over a period of development of culture, shows, in KB cells without cell contact, an activity higher than that observed in confluent cells. This is not due to the fact of a change in enzyme-substrate affinity but to a modification of Mn++ influence.     

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

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 increases 45Ca++-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.     

Role of calcium in the histamine release induced by D-galactosamine from rat mast cells

Rat peritoneal mast cells were isolated and purified by differential centrifugation in Ficoll. Cells pooled from three to four rats were suspended at approximately 10(6) cells/ml in a buffered salt solution and incubated for 1 h at 37 degrees C in 300 microliter volumes in the absence or presence (9 X 10(-4) M) of calcium chloride. Addition of D-galactosamine hydrochloride (DGM; 2.8 X 10(-4)M) caused (in addition to basal release) a mean +/- SEM percent histamine release of 15.7 +/- 5.2 in the presence of Ca++ and 19 +/- 4.9 in the absence of Ca++ (p greater than 0.05). It is suggested that D-galactosamine does not require extracellular Ca++ for the release of histamine from the rat mast cell.     

Purification from a total cellular lysate of a protein modifying the sensitivity of Na+/K+ ATPase to ouabain]

A protein (32,000 dalton) has been purified from M2FS cells derived from the murine plasmocytoma MOPC 173. Like tropomyosin, this protein when added with Ca++ to EDTA-treated plasma membranes prepared from the same cell, induced a drastic increase in the Na+/K+ atpase resistance to ouabain.     

Specific inhibition of a calcium dependent activation of brain cyclic AMP phosphodiesterase activity by vinblastine.

Vinblastine selectively inhibits the activation of brain cyclic AMP phosphodiesterase activity by Ca++-protein activator (50% inhibition by 2 x 10(-5) M). This inhibitory effect was reversed by excessive amounts of the activator, whereas large quantities of Ca++ caused only a slight suppression of the vinblastine effect. This result of vinblastine suggests a new site of its action and also suggests the possible role of protein activator, phosphodiesterase proteins or cyclic nucleotides in the previously known effects of vinblastine in vivo and in vitro.     

Kinetic study of membrane 5'-nucleotidase activity in cultured diploid cells]

5'-nucleotidase activity of cultured diplo?d cells was measured using intact suspended cells. This depended on the substrate amount, but did not vary with Mg ++ concentration-Kinetic data were determined using Con. A,a specific inhibitor.     

Primary tissue cultures from organ fragments: a simplified method.

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.     

Possible role of intestinal alkaline phosphatase activity in thiamine transport.

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.     

Early effect of poliomyelitis virus on 5'-nucleotidase activity in HeLa cells]

One of the earlier effects of poliovirus was the maintaining of a high level of Hela cells 5'-nucleotidase activity (maximal efficiency for a virus/cell ratio = 500 ID 50/cell) (ID50:50% Infections Dose). The activity decreased when cells were suspended in the presence of EDTA(EDTA:Ethylene Diamine Tetracetic Acid) and was partially restored by adding 10 mM Mg++ interactions are discussed.     

The effects of diverse agents (Ca++ and K++ ionophores, organomercurials, dithiols, colchicine, and cytochalasin B) on the maturation and differentiation without cleavage in Chaetopterus eggs]

Induction of maturation in Chaetopterus oocytes requires the presence of Ca++ ions in the medium, but differentiation without cleavage can proceed in the absence of this cation. The Ca++ ionophore A 23187 induces both maturation and the cortical reaction provided that Ca++ ions are present in the medium differentiation without cleavage may follow. Valinomycin slowly induces germinal vesicle breakdown, which is followed by a sharp segregation between hyaloplasm and yolk. PHMPS, but not DTT, induces maturation. Differentiation without cleavage is more sensitive to colchicin than to cytochalasin B.     

Role of tropomyosin in the sensitivity of (Na+ + K+) ATPase to ouabain]

EDTA treatment of isolated plasma membranes from MF2S cells increased 1,000 fold the sensitivity of (Na+ + K+) ATPase activity to ouabain. The original sensitivity of the enzyme to the drug is recovered after addition of tropomyosin together with Ca++ ions to the treated membranes.     

Increase in spontaneous beating frequency in rat heart cells cultured in homologous serum]

Rat serum at different concentrations added to cultured Rat heart cells medium increased spontaneous beating frequency of myoblasts. This increase occurred instantaneously and lasted more than 24 hrs. It was related to the serum concentration used. Electrophysiological recording showed a decrease in the iso-electric phase duration of membrane potential, with no change in action potential. In spite of the beating frequency increase, cells remained sensitive to the chronotrope positive action induced by Isoprenaline. There was no difference between male and female sera. The global results could partly be explained by the action of Ca++ in Rat serum.     

Permeability of the isolated human amniotic membrane to divalent cations]

Membrane potential and resistance recordings, in vitro, show that Mg++ does not pass through the amnion from the inside of the amniotic compartment to the outside of the amniotic membrane. Mg++ may become fixed on the surface or in the midst of the amniotic membrane. However, Mg++ diffuses in the opposite direction. Ca++, Ba++, Sr++ diffuse in both directions across the amniotic membrane.     

Effect of platelet activating factor on guinea-pig papillary muscle

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.     

Enzymatic characteristics of the catalytic subunit of the protein kinase complex of human lymphocytes]

In earlier reports we have shown the existence in human lymphocytes homogenate, of a cyclic-AMP dependent protein-kinase activity. We demonstrate by affinity chromatography that two subunits display respectively cyclic-AMP binding and phosphorylating properties. Divalent cations such as Ca++, Mg++ or Mn++ are required for enzymatic activity. ATP which is an obligatory cosubstrate acts as an inhibitor when its concentration is higher than 10(-6)M.     

Some properties of external NADH oxidation by human placental mitochondria.

Isolated human term placenta mitochondria catalyse oxidation of external NADH in the presence of cytochrome c. This reaction is insensitive to the respiratory chain inhibitors such as rotenone and antimycin A, and is not coupled to phosphorylation. Comparison of the effect of Mg++ ion on NADH plus cytochrome c oxidation by human term placental, human skeletal muscle and rat skeletal mitochondria showed that Mg++ ion exerts an inhibitory effect in the case of human mitochondria and a stimulatory effect in the case of rat skeletal muscle mitochondria.     

Manganese action potentials in mammalian cardiac muscle.

The membrane potential in guinea-pig's papillary muscles from right ventricle was recorded by glass microelectrodes and stimulation was effected by current pulses applied through a sucrose-gap. Action potentials with overshoot were recorded in the solution lacking Na+ and Ca++ but containing 2-95 mM Mn++. The overshoot was increased with the increase of [Mn++]o by about 30 mV/decade. Similar Mn++ dependent action potentials were also obtained in Na-free solution containing 0.6 mM Ca++. The results indicate that Mn inward current is sufficient to generate action potentials in cardiac muscle.     

Presence of a specific uridine 5'-monophosphate pyrophosphorylase in baker's yeast.

Uridine 5'-monophosphate pyrophosphorylase was found to be present in baker's yeast. The enzyme preparation, purified about 30-fold, shows a strict specificity toward uracil and requires Mg++ for its activity.     

Physiological dissection of various effects of ruthenium red dye on Paramecium cells.

Polycationic dye ruthenium red, but not alcian blue, if externally applied to Paramecium cells quickly inhibits their phagocytosis. Ruthenium red combined with the cell surface diminishes frequency and duration of ciliary reversals and gradually inactivates the Ca++ gating mechanism. This effect persists for 1-3 after ruthenium red removal from the culture medium.