Low Calcium Ion Concentrations Research Articles

The effects of divalent cations on the ionic permeability of cell membranes in normal and tumour tissues

It is shown that the ability of three strains of transplanted rat tumours to maintain cellular potassium contents on incubation in media devoid of calcium salts is due to a tumour calcium requirement which is satisfied by concentrations of at least an order of magnitude less than required by the normal tissues yet studied. The evidence is that potassium loss by the tumours on incubation in the presence of very low free calcium ion concentrations maintained by metal-ion buffers, is due to an increase of plasma membrane permeability, similar to those which are believed to occur in normal tissues where the calcium ion “thresholds” are much higher. The cell membranes of the tumours are thus more resistant to lowering of the calcium ion concentration than the normal tissues. Differences also occur in the extent to which other divalent cations, in particular magnesium, can substitute for calcium.

Effect of Calcium Ions on Synthesis of T5-Specific Ribonucleic Acid

Abstract The arrest in the development of bacteriophage T5 and in the synthesis of phage-specific proteins in Escherichia coli F cells infected at a low calcium ion concentration (10-4 m) has been traced to a deficiency in the system for synthesis of a specific class of viral RNA. Previous studies have recognized that during an infection under standard conditions at 10-3 m Ca++ three classes of RNA are formed in sequence during the infective cycle. They are Class I RNA, which appears between 0 and 4 min after infection, and Class II and Class III RNA, commencing at 4 and 9 min, respectively. The predominant RNA species formed during the first 4 min of infection at 10-4 m Ca++ appears to be identical with that synthesized immediately after infection of cells at 10-3 m Ca++ and is therefore Class I RNA. By this time, however, the rate of RNA synthesis has fallen rapidly and thereafter there is a marked change in the composition of the RNA species. At 20 min after infection 75% of the product is Class II RNA. Upon elevation of the Ca++ concentration to 10-3 m the rate of RNA synthesis increases markedly. Class II RNA at greatly elevated levels is the immediate product, and 5 to 6 min later Class III is formed. The arrest in RNA synthesis at 10-4 m Ca++ does not result from the failure of the T5 DNA to inject completely into the host cell nor from a loss of the metabolic capacity of cells to generate nucleoside triphosphates and maintain them within the cell. The interruption in viral development at low calcium ion concentrations probably represents a malfunction of the machinery for DNA transcription beginning with the synthesis of Class II RNA. The cessation of Class I RNA synthesis at either high or low Ca++ concentration probably results from the action of a protein formed early in the infective cycle.

Detection of endotoxin in human blood and demonstration of an inhibitor.

Abstract Gelation of a lysate of amebocytes of Limulus, the horseshoe crab, is a sensitive indicator of the presence of a variety of endotoxins. Amebocyte lysate is stable. The reaction between lysate and endotoxin is reproducible and easy to measure. The rate of the reaction between amebocyte lysate and endotoxin is dependent upon the concentration of endotoxin. The reaction is capable of detecting as little as 0.0005 μg per milliliter of endotoxin in human blood plasma and serum. Addition of endotoxin to normal blood resulted in loss of detectable endotoxin activity when undiluted plasma or serum prepared from such blood samples was compared with saline controls. Coagulation resulted in additional loss of endotoxin activity. Preincubation of endotoxin with blood or a low calcium ion concentration was not necessary for the demonstration of inhibition. The inhibitory effect could be eliminated almost completely by dilution of serum or plasma to 1 to 10 per cent. Extraction of plasma with chloroform for 60 minutes permitted essentially total recovery of endotoxin which had been added to whole blood or plasma. The increase in positive tests, following dilution or chloroform extraction of serum or plasma, suggested that the inhibitory nature of blood is primarily the result of reversible binding between endotoxin and serum protein(s), rather than destruction of endotoxin. This test is the most sensitive in vitro assay for endotoxin which has been reported. The technique should have application both for clinical and experimental studies of endotoxin and endotoxemia.

Inhibition of streaming in amoeba by pinocytosis inducers: Possible mechanisms

1. 1. A simple technique is presented for the assay of resumption of streaming in small populations of cells (20–30). 2. 2. Pinocytosis inducers of group II (basic dyes and proteins) temporarily inhibit streaming after treatment and washing of amoebae in the cold; the effect is a function of the concentration used in the pre-treatment. Acid dyes had no effect. Intermediate concentrations that have little effect on streaming produce monopodal forms. 3. 3. Reversible inhibition of streaming is also produced by 2–5 m M ATP, ITP, GTP and EDTA but not significantly by 5 m M AMP, 10 m M NaCl or 10 m M CaCl 2. Both ATP and EDTA inhibition are prevented by addition of excess calcium ions to the medium. However, at low calcium ion concentration (5 × 10 −4 M) ATP has an effect in addition to its chelating action. 4. 4. Possible interrelationships between the pinocytosis inducers, calcium ions and ATP are considered.

Functional identity of rat-liver microsomal glucose 6-phosphatase and inorganic pyrophosphatase

The functional identity has been demonstrated of glucose 6-phosphatase and inorganic pyrophosphatase in rat-liver microsomes. Both enzyme activities were reduced, in a parallel manner, following the administration to rats of coumarin by mouth or carbon tetrachloride subcutaneously. Glucose 6-phosphatase and inorganic pyrophosphatase were both inhibited in vitro by o-hydroxyphenylacetic acid and activated by o-tyrosine. The effects of cations were also similar. Low concentrations of ferrous or calcium ions activated both enzymes while higher concentrations caused inhibition. Magnesium and potassium ions elicited smaller increases in activity. It is considered that these findings indicate the functional identity of the two enzymes.

Ionenregulation bei zwei Arten estuariner Kurzschwanzkrebse

In low salinities sodium, potassium and calcium ion concentrations in the blood of both species, Hernigrapsus nudus and H. oregonensis, are hypertonic to the media. In high salinities, ion regulation is less effective and concentrations approach isotonicity. This regulation is effected by extra-renal processes, since U/B ratios approximate unity. Blood concentration of magnesium is regulated in both species at a hypotonic level, one-third that of the medium concentration in all salinities. It is suggested that the principal site of ion uptake from the medium in Hernigrapsus is the lamelIar epithelium of the gill. Winter animals of both species appear to be more effective regulators of the calcium ion in low salinities. All other ion concentrations are similar, summer and winter. No consistent temperature effect could be demonstrated for ion concentration in blood or urine. The principal function of the antennary glands is to maintain a blood magnesium concentration hypotonic to all salinities. It is suggested that this regulation of magnesium is necessary to facilitate neuromuscular transmission and is a characteristic feature of ionregulation in active decapod crustacea. Ion regulatory ability of the two species differed only with respect to winter blood levels of sodium. H. oregonensis more effectively regulates this ion at hypotonic blood levels in high salinities. Chloride regulation in the two species demonstrates that the blood is hyperosmotic in low salinities and hyposmotic in higher salinities. Urine is hyperosmotic over the entire salinity range and is approximately 35 to 40 o/0 higher than the blood. Blood concentrations of chloride approximate a gradient of 15 to 30% above the experimental media. U/B ratios suggest that the antennary gland is not solely responsible for the regulation of this ion. Chloride regulation in the muscle of H. nudus demonstrates that in a high blood chloride environment, muscle chloride remains low, about one-third that of blood. Consideration of muscle cations of H. nudus shows that blood sodium is about

Review of Anticorrosion Water Treatment

This article discusses studies that indicate that the best anticorrosion treatment of softened surface waters consists of maintaining a driving‐force index (DFI) of 15‐20 and a momentary excess (ME) of 12‐15, in conjunction with low calcium and high carbonate ion concentrations. In the pH range of 9.5‐10.0, a rough indication of this is a saturation index (SI) of 1.0 or more. As such waters would cause trouble by plugging mains with calcium carbonate scale, 0.5 ppm of a polyphosphate should be applied. Soft surface waters seem to be given insufficient anticorrosion treatment after the pH has been reduced by alum. By increasing the pH to 8.8‐9, a DFI and ME of sufficient magnitude could be obtained to give the desired protection. This could be done by the addition of lime, caustic soda, or sodium carbonate. Aerated and lime‐softened well waters require about the same treatment as lime‐softened surface waters. Oxygen‐free, lime‐softened well waters can probably be treated to ME values of 12‐15, but to a lower DFI.

Trace metal requirements of Azotobacter.

SummaryMolybdenum, iron and calcium ions have been shown to be specifically required when Azotobacter vinelandii O is fixing atmospheric nitrogen. Ammonium ion eliminates the need for molybdenum and calcium and has a sparing action on the requirement for iron. High levels of iron stimulate the knallgas reaction of A. vinelandii O fixing N2 in the presence of H2, but molybdenum in the range tested had no effect on this reaction. Low concentrations of calcium ions in a nitrogen-fixing culture result in an extended lag phase of growth. Decrease in the concentration of phosphate in the presence of low levels of calcium brings about a further increase in the lag, but this increase is not observed if the calcium supply is adequate.

On the mechanism of the yolk-lysis reaction

(1) The reaction by which yolk platelets isolated from frog eggs undergo lysis in the presence of low concentrations of calcium ions is described and kinetic data are presented. (2) A crude yolk precipitate, prepared by salting-in and reprecipitating the material of intact yolk platelets, undergoes the same reaction as do the intact platelets. (3) Data are presented on the pH dependence and thermal inhibition of the reaction. (4) The yolk contains a material, perhaps a protein, which catalyzes the lysis reaction. This material is not the soluble product of the reaction, since the kinetics are not those of an autocatalytic process. (5) A possible mechanism for the reaction is discussed.

Determination of the content of calcium ions in milk ultrafiltrate.

THE determination of free calcium ions is very important in human and veterinary pathology and in dairy chemistry. Evidence has been obtained that the instability of milk known as the ‘Utrecht abnormality of milk’ is caused by an abnormally high level of the concentration of calcium ions1. On the other hand, there are some indications that an increased curdling time of milk may be due to a low concentration of calcium ions.