Blood-pressure screening and supervision in general practice.

Since April 1975 all men aged 35-69 years registered with four general practices in west central Scotland have had their blood pressure checked whenever they visit the surgery. Although the practice locations range from rural to city centre and observers comprise receptionists, nurses, and doctors, a standard procedure has been adopted for the examination, recording, follow-up, and management of high blood pressure. The results confirm that raised blood pressure is common and often goes undetected. Even when hypertension is known, casual blood pressure readings often exceed accepted normal levels. The findings also show that a population may be routinely examined through normal contact with the family doctor, and that this can provide a convenient, acceptable, and effective means of detecting and reducing raised blood pressure.     

Biological properties of human melanoma cells in culture

Summary Three human melanoma cell lines derived from one primary and two metastatic tumors from three different patients were characterized for growth properties usually associated with malignant transformation; these include cell morphology, growth rate, saturation density, growth in semisolid media, colony-forming ability on contact-inhibited monolayers of normal fibroblasts and epithelial cells, and tumorigenicity in immunosuppressed mice. Variations in expression of aberrant properties were evident among the lines. One of the metastatic lines satisfied all the parameters of malignancy tested and the other showed a number of these properties, whereas the primary essentially fulfilled only one. These results suggest that cultured melanoma cells reflect the clinical variability often observed among melanoma patients and the metastatic melanoma seems to display a higher degree of malignant transformation than the primary. THis work was supported in part by USPHS Grant No. 5 T01 AI00332-06 from the National Institutes of Health, Contract E73-2001-N01-CP-3-3237 from the Virus Cancer Program of the National Cancer Institute, and USPHS Grant No. 0H00714-02 from the National Institute for Occupational Safety and Health.     

Pyrroline-5-carboxylic acid reductase from soybean leaves

Pyrroline-5-carboxylic acid reductase was purified 40-fold from soybean leaves (Glycine max L. var Corsoy). The enzyme was fairly unstable, had a broad pH optimum, and was inactivated by heat and acid; NADH and NADPH both served as cofactors. It had a higher activity with NADH (about 4 ×) compared to NADPH, but a lower K_m for NADPH. NADP⁺ inhibited both the NADH- and NADPH-dependent activity. Sulfhydryl group blocking agents reduced the activity as did the carbonyl blocking agent, NH₂OH. Thiazolidine-4-carboxylic acid and phosphate inhibited the enzyme and proline inhibited only at high concentrations. ATP, GTP, and CTP were all effective inhibitors of both the NADH- and NADPH-dependent activity. Phosphorylated nucleotide inhibition was reversed by Mg²⁺ ions.     

Pyridine nucleotide metabolism in imaginal discs of Drosophila melanogaster

The pyridine nucleotide metabolism of imaginal discs of Drosophila melanogaster has been studied in vitro by incubating discs with labeled nicotinic acid in the presence and absence of ecdysterone. The major labeled compounds found within the discs are NAD, NADP, and nicotinic acid. There is preferential uptake of nicotinamide over nicotinic acid, although the Priess-Handler pathway is used exclusively. The presence of ecdysterone produces a small increase in the NADP/NAD ratio, and an increase in NAD synthesis, probably to compensate for increased NAD turnover.Supported by Grant GB 43569 from the National Science Foundation.     

CHANGES IN THE PROLIFERATION RATE OF MOUSE EPIDERMIS AFTER IRRADIATION: CONTINUOUS LABELLING STUDIES

The proliferative response of mouse skin to damage caused by X-irradiation has been tested by giving repeated injections of tritiated thymidine and scoring the percentage of labelled cells in high resolution autoradiographs. Four, nine and fourteen daily fractions of 300 rads of X-rays were used and labelling commenced 4 days after the last fraction. The epidermis of the upper surface and the sole of the foot were scored separately and were compared with the skin of unirradiated feet. In unirradiated skin the proliferation rate of the basal layer cells is more rapid on the sole than on the upper surface. The cell cycle times deduced from continuous labelling curves were 81 hr and 111 hr respectively and the growth fractions were 97% and 85%. After irradiation with small daily doses the homeostatic response to cell killing was slow. More rapid proliferation occurred after nine fractions in the sole, but was not apparent in the skin of the upper surface until fourteen fractions had been given. After fourteen fractions the cell cycle time was about 24 hr on both surfaces and the growth fraction was about 90%. The initial labelling index after a single thymidine injection was a poor measure of proliferation rate. The delay in the time of onset of faster proliferation is similar, both qualitatively and quantitatively, to that measured previously from the additional dose increments needed if large doses were given at different times after the multifraction treatments (Denekamp, 1973).     

Species density and associations in Caribbean reef corals

The density of scleractinian corals on portions of two reefs in the Grenadine Islands, W. I. has been investigated by direct observation by SCUBA divers. Grid, transect, and random quadrat methods were compared with total samples to determine the precision and accuracy of these techniques. Transect methods were generally satisfactory provided at least 15% of a 400 m² total grid area was included in the sample. The data strongly indicated clumped distributions of all species, although numerical analysis does not indicate the distinct zones reported by other workers. Species associations based on Jaccard's coefficient and cluster analysis showed possible similarities in physical requirements, although few strong associations were found. Data based on 4 m² quadrats generally provided a more reliable estimate of species associations than did data based on 1 m² quadrats. It is suggested that surveys of these reef types may be better based on a number of parallel transects rather than a single transect, and that well-defined zones are more likely to be the exception than the rule.     

Specificity of alpha-chymotrypsin with exposed carboxyl groups blocked.

The 15 exposed carboxyl groups of alpha-chymotrypsin were modified with glycine ethyl ester at low pH using barbodiimide reagent. The specificity of the modified enzyme (Chy-15) was studied over the pH range of 4 to 9 with both N-acylated and non-N-acylated amino acid esters. The modified enzyme had lower reactivity toward N-acylated esters than non-N-acylated esters compared to the native enzyme. Typical substances such as acetyl- and benzoyl-L-tyrosine ethyl esters retained 4 and 9% activity, whereas phenylalanine ethyl ester was slightly more reactive with the modified than with the native enzyme. The pH-rate profiles of acetyl-L-phenylalanine ethyl ester and tryptophan ethyl and benzyl esters were investigated in detail. Analysis of these profiles revealed three pKa values of approximately 5, 7, and 9 related to a functional carboxyl, imidazoyl, and an amino group, respectively. Since similar pKa values occur for the native enzyme, modification did not block the carboxyl corresponding to pKa 5. A mechanism is proposed for catalysis which includes both the protonated and unprotonated form of the imidazoyl (His-57) and utilizes water rather than a carboxyl (Asp-102) as the proton sink.     

The incorporation of nitrogen into products of recent photosynthesis in Anabaena cylindrica Lemm.

In vivo tracer studies with ¹⁴C have been performed to help determine pathways of incorporation of newly assimilated nitrogen into N₂-fixing cells of Anabaena cylindrica. After photosynthesis in Ar:O₂:¹⁴CO₂ for 30 min, the addition of N₂ or NH ₄ ⁺ resulted in increased rates of ¹⁴CO₂-incorporation both in the light and dark, and in increased incorporation of ¹⁴C into amino acids at the expense of sucrose and sugar phosphates. Evidence of enhanced sucrose catabolism and increased pyruvate kinase activity was obtained on adding nitrogen, and, of the ¹⁴C-labelling entering the tricarboxylic acid cycle, more appeared in citrate and 2-oxoglutarate than in malate and oxaloacetate. The kinetics of ¹⁴C-incorporation into various amino acids suggest that in the light and dark the most important route of primary ammonia assimilation involves glutamine synthetase and that glutamate, aspartate, glycine and probably alanine are formed secondarily from glutamine.     

Isolation and Characterization of Amber Suppressors in Yeast

Nonsense suppressors were obtained in a haploid yeast strain containing eight nutritional mutations, that are assumed to be amber or ochre, and the cyc1-179 amber mutation that has a UAG codon corresponding to position 9 in iso-1-cytochrome c. Previous studies established that the biosynthesis and function of iso-1-cytochrome c is compatible with replacements at position 9 of amino acids having widely different structures (Stewart and Sherman 1972). UV-induced revertants, selected on media requiring the reversion of one or two of the amber nutritional markers, were presumed to contain a suppressor if there was the unselected reversion of at least one other marker. The 1088 suppressors that were isolated could be divided into 78 phenotypic classes. Only 43 suppressors of three classes caused the production of more than 50% of the normal amount of iso-1-cytochrome c in the cyc1-179 strain. Genetic analyses indicated that all of these highly efficient amber suppressors are allelic to one or another of the eight suppressors which cause the insertion of tyrosine at ochre (UAA) codons (Gilmore, Stewart and Sherman 1971). Furthermore, only tyrosine has been identified at position 9 in iso-1-cytochrome c in cyc1-179 strains suppressed with these efficient amber suppressors.     

Derepressed synthesis of cellulase by Cellulomonas.

A Cellulomonas sp. was isolated from the soil which hydrolyzed cellulose, as shown by clear-zone formation on cellulose agar medium. Catabolite repression of cellulase synthesis occurred when moderate levels of glucose were added to the medium. A stable mutant that no longer exhibits catabolite repression was produced through treatment of the wild-type organism with N-methyl-N'-nitro-N-nitrosoguanidine. Both enzyme concentration and specific activity, as determined by the rate of hydrolysis of carboxymethylcellulose, were greater with the mutant than with the wild-type organism under various test conditions. The wild type had no measurable cellulase activity when grown in the presence of either 1.0% glucose or cellobiose. Cellobiose, but not glucose, inhibited enzyme activity towards both cellulose and carboxymethylcellulose. Cellobiose, cellulose, and sophorose at low concentrations induced cellulase synthesis in both the wild-type and the mutant organism. Cellulase regulation appears to depend upon a complex relationship involving catabolite repression, inhibition, and induction.