Suspension of non-viable fungal spores as a standard for platelet counting.

In the search among biological particles for a standard for counting human platelets, a strain of Absidia corymbifera was found to have spores that resembled platelets. After fixing in formalin and autoclaving the spores had a similar mean cell volume to that of human platelets. A suspension of these killed spores was tested in 100 laboratories and gave consistent results as a standard for human platelet counting.

Kinetics of nitrosamine formation in the presence of micelle-forming surfactants.

The nitrosation of dihexylamine by nitrite was catalyzed in the presence of micelles of the cationic surfactant decyltrimethylammonium bromide. Rate enhancements up to 800-fold were observed. The magnitude of the rate enhancements was dependent on the amine structure, particularly the alkyl chain length.

Bacterial colonisation and infection in spina bifida babies.

A Series of bacteriological investigations was carried out on 17 babies with spina bifida. Results showed that despite colonisation of their eyes, nose, throat, skin, umbilicus, wounds, urine and faeces with potentially pathogenic microorganisms, infections other than those of the urinary tract and brain were relatively uncommon.

Gastric cancer in Colombia. I. Cancer risk and suspect environmental agents.

A case control study of patients discharged from hospitals revealed fourfold differences in geographic variation in stomach cancer risk within the Department of Narino (Colombia). Data from gastroscopic surveys of population groups, samples of water supplies, and urine and saliva in Narino also indicated a generally positive correlation among the following parameters: 1) gastric cancer risk, 2) prevalence of chronic atrophic gastritis and intestinal metaplasia, 3) nitrate content of well waters, and 4) nitrate excretion by the population. Urinary excretion reflected the ingestion of nitrates, and this implied a higher average intake of nitrates in the populations at high risk for stomach cancer.

Deuterium isotope effect in the microsomal metabolism of dimethylnitrosamine.

The rates of N-demethylation of dimethylnitrosamine and dimethylnitrosamine-d6 by rat liver microsomes were studied by monitoring formaldehyde production. Deuterium isotope effects of 1.6 and 3.

Preparation and properties of bacterial chromatophores entrapped in polyacrylamide.

The immobilization of Rhodospirillum rubrum chromatophores was successfully performed by entrapping them in polyacrylamide. Their photophosphorylating activity was about 40% of native chromatophores. The temperature and pH optima for immobilized chromatophores were similar to the native photosynthetic apparatus and kinetic parameters showed that the rate of photophosphorylation in polyacrylamide particles was diffusion controlled.

Photosynthetic regeneration of ATP using bacterial chromatophores.

We have demonstrated the use of bacterial chromatophores for the continuous photosynthetic regeneration of ATP from ADP in an ultrafiltration reactor. Biphasic kinetics of the degradation of chromatophore activity are described. Using chromatophores in combination with the enzyme adenylate kinase, we have also demonstrated continuous regeneration of ATP from AMP.

Reaction of nitrosamines in the Udenfriend system: principal products and biological activity.

Reaction of diethylnitrosamine in the non-enzymatic, ascorbic acid-dependent, hydroxylating system of Udenfriend yielded N-nitroso-2-(ethylamino)-ethanol as the major product extracted into methylene chloride. The major product derived from nitrosopiperidine in the same system was N-nitroso-4-piperidone. These products, however, were mutagenic to Salmonella typhimurium TA 1535 only when activated by a rat liver microsomal preparation.

Structure-activity relationships in nitrosamine carcinogenesis.

Statistically significant correlations have been demonstrated between carcinogenic activity, toxicity and number of carbons per molecule for an extensive set of nitrosamines. Such correlations, involving only bulk molecular properties indicate that the chemical nature of the alkyl substituents need not be the sole determinants of carcinogenic activity. These structure-activity relationships can be used to estimate carcinogenic activity with some degree of confidence.

Inhibitor of Clostridium perfringens formed by heating sodium nitrite in a chemically defined medium.

An inhibitor of Clostridium perfringens formed when low levels of nitrite were autoclaved with a defined chemical medium. A systematic study of the medium revealed that only amino acids and mineral salts were involved in the production of this inhibitor, which was proven to be a toxic compound formed from cysteine, ferrous sulfate, and sodium nitrite. The inhibitor was compared to several known compounds.

Carcinogenicity of nitrosation products of ephedrine, sarcosine, folic acid, and creatinine.

Carcinogenic activity of several synthetic N-nitroso compounds was evaluated in C57BL/6J X C3HeB/FeJ F1 mice. Test substances, suspended in trioctanoin, were injected i.p.

A model for gastric cancer epidemiology.

It is postulated that one major subtype of gastric carcinoma ("intestinal type") is the end- result of a series of mutations and cell transformation begun in the first decade of life. The mutagen could be a nitroso compound synthesised in the upper gastrointestinal tract by the action of nitrite (i.e.

Reaction of nitrite with ascorbate and its relation to nitrosamine formation.

In this study of the nitrosation of morpholine in the presence of ascorbic acid, the amount of ascorbate required to inhibit completely the formation of nitrosomorpholine depended on whether oxygen was present in the system. The nitric oxide (produced during the oxidation of ascorbate by nitrous acid) might have reacted with oxygen to yield additional oxidizing equivalents, or oxygen might have directly oxidized the ascorbate semiquinone intermediate produced in the initial step of oxidation reaction. A pH- dependent induction period observed during the nitrosation of morpholine in the presence of ascorbate and excess nitrite was accounted for by the kinetics of the reactions.

Chromatographic separation of conformers of substituted asymmetric nitrosamines.

The syn and anti conformers of N-nitrosoproline, N-nitrososarcosine and N-nitroso-2-(ethylamino)-ethanol, have been separated by liquid chromatography. These conformers result from hindered rotation about the N-N bond. Separation was achieved using adsorption, reversed-phase, and ion-exchange modes.

Daily rhythm in human urinary melatonin.

The melatonin in urine samples from six healthy adult volunteers was concentrated on Amberlite XAD-2 resin, eluted with organic solvents, and quantitated by use of a bioassay technique (the dermal melanaphore response of larval anurans to melatonin in their bathing medium). The melatonin content of samples collected between 11 p.m.