Stimulation of mycelial growth of Endothia parasitica by heavy metals

Of 16 metal cations tested on agar medium, only copper and iron stimulated mycelial growth of Endothia parasitica in relatively high concentrations. Similarly enhanced growth was produced in high (32%) glucose concentrations and also when the fungus was grown on cellophane placed over the agar surface. E. parasitica secreted large amounts of oxalate that precipitated primarily as calcium oxalate at the periphery of the fungal colony, causing an opaque halo in the medium. Mycelial growth was retarded greatly when calcium oxalate accumulated, but retardation was reversed by copper and iron salts that prevented accumulation of the calcium oxalate crystals. E. parasitica grew well on media containing copper oxalate and copper-calcium oxalate but grew poorly with calcium oxalate as the carbon source and was inhibited by sodium oxalate in the medium. The specificity by which only copper and iron salts stimulated mycelial growth suggested that the metal and oxalate ions interact to form specific oxalate complexes that reverse the inhibition of simple oxalate salts. This probably accounts for enhanced growth in the presence of otherwise toxic levels of metals and oxalate. The stimulation did not occur in liquid cultures.

Adenosine triphosphate--dependent calcium uptake by rat submaxillary gland microsomes

Microsomes from rat submaxillary glands are able to take up calcium from the suspension media. Calcium uptake is greatly increased by the presence of ATP. This effect of ATP is not detected at 0 degrees C. ADP cannot replace ATP to potentiate calcium uptake. ATP-dependent calcium uptake is not observed in the absence of magnesium. ATP-dependent calcium uptake is enhanced by oxalate and, to a lesser degree, by inorganic phosphate. Total calcium per milligram of microsomal protein observed when tests were performed without oxalate closely parallels the amounts for skeletal and cardiac muscles reported by several authors. Calcium uptake in salivary gland microsomes is slower than in muscle microsomes. Speculations are considered about the role of ATP-dependent calcium uptake. It is suggested that a decrease in intracellular free calcium levels returns these cells to the resting state after secretion.

Isolation and preliminary characterization of an extracellular protease of Cytophaga sp

The extracellular protease(s) of Cytophaga sp. is present naturally as a complex with acidic polysaccharides of the slime layer. The protein was separated from the slime by selective precipitation of the polysaccharide with a cationic detergent and the enzyme was purified about 100-fold by precipitation with alcohol and by chromatography on DEAE-cellulose. Inhibitor studies indicated that this alkaline protease was not of the trypsin/chymotrypsin type. Ca2+ had a strong stabilizing effect on the enzyme. The complex of basic protein (enzyme) and acidic slime polysaccharides has led to the conclusion that the enzyme is perhaps not truly extracellular but rather is surface bound. The slime layer would appear to have a role in attaching the bacterial cells to insoluble substrates as well as ensuring that degradative enzymes are kept in close contact with the substrate.

Effects of papaverine and eupaverin on calcium uptake by isolated sarcoplasmic vesicles

Papaverine and eupaverin increase the rate of uptake of calcium by sarcoplasmic vesicles isolated from rabbit white skeletal muscle. The degree of activity of the above drugs is clearly affected by changes of ATP, oxalate and Ca2+ concentrations. The results are discussed in view of present knowledge about the effects of papaverine-like drugs upon muscular contraction.

Monitoring heparin therapy with the activated partial thromboplastin time

Difficulties associated with the whole blood clotting time (W.B.C.T.) as a method of monitoring heparin therapy have led to the investigation of the activated partial thromboplastin time (A.P.T.T.) as an alternative. The conclusion is reached that the latter procedure possesses several advantages. Using the method described and a citrate-preserved blood sample collected just prior to the administration of the next serial dose of heparin, the suggested therapeutic duration of the A.P.T.T. is 70 seconds or twice the mean control value. A practical range for this method is 60 to 70 seconds.

Converting enzyme activity in human plasma

Human plasma converting enzyme activity was investigated by comparing biological with immunological activity of added or generated angiotensin after plasma incubation. Sodium citrate (2 x 10 -2 M ), 2:2'-dipyridyl (1 x 10 -4 and 1 x 10 -2 M ), chromotropic acid (3 x 10 -2 and 3 x 10 -3 M ) and desferrioxamine (10 and 100 mg/100 ml) did not interfere with converting enzyme. By contrast, EDTA (3 x 10 -3 M and 3 x 10 -2 M ), EGTA (3 x 10 -2 M ), 8-quinolinol (1 x 10 -2 M ), and oxalic acid (3 x 10 -2 M ) were shown to interfere with plasma converting enzyme activity. The EDTA inhibition of converting enzyme activity could be partially reversed by molar excess amounts of calcium, zinc and cobalt. The ability of these ions to restore converting enzyme activity to the plasma was quantitatively variable. Inhibition of converting enzyme activity by EDTA could not be reversed by the addition of iron, copper or manganese to the samples.

Some factors influencing vitamin B 12 production by Pseudomonas denitrificans

The effect of known precursors and cofactors on vitamin B12 production has been studied in a basal, chemically defined medium composed of sucrose, glutamic acid, and mineral salts. Only a carbon source, betaine, and Co2+ were found to be essential for vitamin B12 production. Known precursors such as methionine, δ-aminolevulinic acid, succinic acid, and 1-amino-2-propanol had no effect. Glycine was inhibitory to growth. Oxalic acid, lactic acid, 5,6-dimethylbenzimidazole, and Mo2+ stimulated vitamin B12 biosynthesis. Of special interest is oxalic acid, which at a level of 0.04% w/v increased vitamin production about 20%, and with washed cells could replace glutamic acid, which had been demonstrated to be essential for both growth and vitamin B12 production. When use of oxalate was followed, it was found that this acid disappeared during the period of rapid growth and vitamin production and then reappeared during the final stages of the fermentation cycle.

Intracellular calcium and myocardial contractility. 3. Reduced calcium uptake and ATPase of the sarcoplasmic reticular fraction prepared from chronically failing calf hearts

The function of the sarcoplasmic reticulum of the failing myocardiums was studied in vitro by comparing calcium uptake and calcium-activated ATPase in microsomes prepared from hearts of control calves and calves in which right ventricular failure developed during experimentally induced pulmonary hypertension. The rate of calcium uptake averaged .147 µmole·mg -1 ·min -1 at 25°C in the presence of oxalate in control preparations and was significantly reduced in preparations from failing right ventricles (avg .086 µmoles·mg -1 ·min -1 ). Calcium-activated ATPase was also diminished significantly in failure (avg .184 compared to .073 µmoles·mg -1 ·min -1 ). Although two preparations also showed diminished calcium activities in the nonfailing left ventricle, group these activities were not significantly depressed in preparations from ventricle in calves with failure. A similar reduction in calcium activities observed at 37°C with preparations further purified by sucrose gradient centrifugation. The uptake capacity of microsomes, measured as calcium uptake in the absence of oxalate, was not diminished in the preparations from failing hearts. Mitochondrial contamination did not appear to be a factor since azide inhibited calcium activity almost completely in mitochondria, whereas inhibition was less than 10% in microsomes of both control and failing hearts. Ouabain had no effect on the microsomes from failing hearts. These studies indicate that there is a defect in calcium transport in microsomes and a functional abnormality of the sarcoplasmic reticulum in the intact myocardial cell in heart failure which could lead to changes in the excitation-contraction coupling mechanisms of clinical importance.

Control of contractility in Spirostomum by dissociated calcium ions

The freshwater protozoan, Spirostomum ambiguum, exhibits generalized contraction when electrically stimulated with a DC pulse. Light and electron microscopic studies show a subcortical filamentous network, believed responsible for generating contractile tension, in association with vesicles which were shown to accumulate calcium oxalate precipitates. Organisms microinjected with the calcium-sensitive, bioluminescent protein, aequorin, emit light when stimulated to contract. Analyses of cinefilm records of electrically induced contraction indicate that contraction may occur up to 25 msec after the onset of stimulation at a point when the calcium-aequorin light emission is at a peak. The evidence shows that calcium release from an interval compartment is directly associated with the onset of contraction in Spirostomum, and that the removal of calcium, through some internal sequestering mechanism, signals relaxation.

Mammalian D-2-hydroxy acid dehydrogenase. Effect of inhibitors and reaction sequence

1. The reaction of d-2-hydroxy acid dehydrogenase with d-lactate and 2,6-dichlorophenol-indophenol (DCIP) at pH8.6 yields reciprocal plots of 1/rate versus 1/[d-lactate], at different DCIP concentrations, which appear to be parallel. However, at pH7.55, or in the presence of the competitive inhibitor oxalate at pH8.6, the plots are convergent. This is inconsistent with the mechanism previously proposed for this enzyme. 2. The pattern of inhibition by the product, pyruvate, is consistent with either an Ordered mechanism or an Iso Theorell-Chance mechanism. 3. The observation that the enzyme forms a complex with d-lactate favours the Ordered reaction. In this, first d-lactate and then DCIP bind to the enzyme to form a ternary complex, from which pyruvate and reduced DCIP dissociate in that order.

Biochemical properties of trypanosomatid lactate dehydrogenases

Lactate dehydrogenase (LDH, E.C.1.1.1.27) was found in supernatant (cytoplasmic enzyme) fractions of the trypanosomatid flagellates Trypanosoma conorhini and Crithidia fasciculata if 10 mm cysteine was present in the homogenizing medium. The T. conorhini LDH activity with pyruvate as substrate was increased 35% if 5 mm cysteine was also included in reaction mixtures. K(m) values for the T. conorhini enzyme were 3.3 x 10(-4)m with pyruvate, and 1.6 x 10(-4)m with alpha-ketobutyrate. Cysteine inhibited alpha-ketobutyrate reduction. Comparison of trypanosomatid and human serum LDH enzymes with respect to K(m), substrate activity and inhibition, pH optima, and K(i) values for oxalate and oxamate indicated that the trypanosomatid isoenzymes differed significantly from serum LDH. C. fasciculata LDH was extremely labile, since 59% of the activity was lost 90 min after isolation. The role of LDH enzymes in trypanosomatid metabolism is discussed, and the results are related to other trypanosomatid LDH enzymes. The comparison of homologous enzymes in host and parasite is discussed with regard to metabolic function and a possible model system for chemotherapy.

Energy-linked calcium transport in subcellular fractions of the failing rat heart

The isolated rat heart perfused without substrate provides a good model in which to study biochemical changes in the failing myocardium. In this preparation, there is a decline in the ability of both the mitochondria and the sarcoplasmic reticulum to accumulate calcium in the absence of oxalate after 30 minutes of perfusion. Calcium binding by mitochondria fell from control levels of 47 ± 8 mµmoles/mg protein to 17.5 ± 4.9 mµmoles/mg protein and that by microsomes from 29.8 ± 5.1 mµmoles/mg protein to 15.2 ± 4.8 mµmoles/mg protein. This drop coincided with die start of the decline in myocardial contractility. The calcium uptake by the sarcoplasmic reticulum in the presence of oxalate decreased from control levels of 534.1 ± 32.0 to 160.5 ± 27.2 mµmoles/mg protein after 2 hours of perfusion, at which time the myocardial contractility had dropped to below 10% of control levels. This change in the calcium uptake by the sarcoplasmic reticulum is associated with an increase in its ATPase activity from 1.91 ± 0.21 to 3.00 ± 0.31 µmoles P 1 /mg protein/min over 2 hours of perfusion without substrate. This suggests that there is an uncoupling of the microsomal ATP-dependent calcium pump in these late stages of heart failure due to substrate lack. The change in calcium binding to reticulum occurred in association with the onset of contractile failure, whereas changes in calcium uptake in the presence of oxalate were delayed and probably represent irreversible disorganization of the intracellular membranes.