Benthic algal biomass and productivity in high subarctic streams,Alaska

Year-round measurements of the standing crop of epilithic algae (as chlorophyll a concentration) in two streams — one second and one fourth order (map scale 1:63 360) — in interior Alaska (64°–65° N) were only about one tenth that reported from streams of temperate North America. Cell densities in these streams, however, were similar to those in comparable temperate streams. Year-round domination of the benthic flora by very tiny diatoms (Achnanthes spp.) may explain the apparent disparity between low chlorophyll a content and nearly average cell densities. Chlorophyll a standing crop in a more alkaline groundwater-fed stream, however, was higher and within the range of similarly sized temperate streams. Maximum chlorophyll a standing crop varied positively with alkalinity in 5 clear-water streams where standing crop was measured on natural or artificial substrates. Seasonal mean concentrations of sestonic chlorophyll a (used as estimates of benthic algal chlorophyll a standing crop) varied directly and significantly with alkalinity among ten clear-water streams; and, with total phosphorus among 8 of 10 clear-water and 5 brown-water streams studied. During the summer, when there is little darkness, gross primary productivity (as estimated by the diurnal dissolved-oxygen method) was similar to that of northern temperate streams. Gross primary productivity was also seen to vary directly with alkalinity in 5 clear-water streams of this region.U.S. Fish and Wildlife Service     

Training for general practice: a national survey.

OBJECTIVES--(a) To compare current vocational training in general practice with that ascertained by a survey in 1980; (b) to compare the training of trainees in formal training schemes with that of trainees arranging their own hospital and general practice posts. DESIGN--National questionnaire survey of United Kingdom and armed services trainees who were in a training practice on 1 April 1989. Questionnaires were distributed by course organisers. SETTING--Research project set up after an ad hoc meeting of trainees at the 1988 national trainee conference. SUBJECTS--2132 Of the 2281 trainees (93%) known to be in a training practice on 1 April 1989. RESULTS--1657 Trainees returned the questionnaires, representing 73% of all trainees known to be in a training practice on 1 April 1989. Between 1980 and 1989 there were significant improvements in the trainee year, and there was also evidence of improvements in general practice study release courses. There was no evidence of improvement in other aspects of training. General practice trainees spent an average of three years in junior hospital posts, which provided very little opportunity for study related to general practice. Training received during tenure of hospital posts differed significantly between trainees in formal schemes and those arranging their own hospital posts. During the trainee year training was almost the same for those in formal schemes and those arranging their own posts. Regions varied significantly in virtually all aspects of general practice training. CONCLUSIONS--The trainee year could be improved further by enforcing the guidelines of the Joint Committee on Postgraduate Training for General Practice. The poor training in junior hospital posts reflected the low priority that training is generally given during tenure of these posts. A higher proportion of general practice trainees should be attached to vocational training schemes. More hospital trainees could attend general practice study release courses if these were designed specifically with the needs of hospital doctors in mind.     

A catalogue of Clostridium thermocellum endoglucanase, β-glucosidase and xylanase genes cloned in Escherichia coli

Abstract Two independent collections of clones containing Clostridium thermocellum genes involved in cellulose have been previously obtained at IAPGR, Cambridge, and at the Pasteur Institute, Paris. The two collections were compared for cross-hybridization, restriction maps and enzyme phenotypes. Truly distinct genes were one β-glucosidase gene, two xylanase genes, and fifteen endogluconase genes. Two of the cloned fragments contained extraneous DNA which was absent from their respective counterparts isolated in the other collection. The dicrepancies resulted from in vivo rearrangements which had occurred in either of the C. thermocellum NCIB 10682 stocks used to generate the two gene banks.     

Factors affecting the activity patterns of black-backed jackals Canis mesomelas

Daily activity levels of black-backed jackals Canis mesomelus were determined in southern Africa through direct observation and radio-tracking. Jackals have a bigeminus activity pattern that is closely paralleled by the activity levels of some of their most important prey. Although differences due to sex, age, study area and season of year were found, this activity pattern was most markedly influenced by light conditions during both the crepuscular and the nocturnal periods.     

Potency of L-364,718 as an antagonist of the behavioral effects of peripherally administered cholecystokinin

A new antagonist of the peripheral cholecystokinin receptor, L-364,718, was found to block the reductions in food intake and exploratory activity induced by intraperitoneal administration of cholecystokinin octapeptide sulfate. L-364,718 significantly reversed the cholecystokinin-induced reduction in feeding at doses of 10 micrograms/kg - 10 mg/kg i.p. L-364,718 significantly reversed the cholecystokinin-induced reduction in exploratory activity at doses of 500 ng/kg - 10 mg/kg i.p. The time course of antagonist activity of L-364,718 was immediate to 90 minutes after intraperitoneal administration. L-364,718 had no significant effect on food intake or exploratory activity when administered alone, over the dose range of 100 ng/kg-10 mg/kg i.p. This compound appears to be at least one hundred times more potent than proglumide or benzotript as an antagonist of the behavioral effects of peripherally administered cholecystokinin.     

Response of aromatic-pathway enzymes to changing physiological states of growth in suspension cultures of Nicotiana silvestris

The activity levels of enzymes of aromatic amino acid biosynthesis respond to changing physiological states of growth, as illustrated by results obtained from suspension-cultured cells of Nicotiana silvestris Speg. et Comes line ANS 1 (2N=24). The experimental system provides a foundation for interpretations about overall regulation of enzyme levels in relationship to growth physiology. Levels of activity for shikimate dehydrogenase (EC 1.1.1.25), prephenate aminotransferase and arogenate dehydrogenase were followed throughout a growth cycle obtained by a conventional subculture protocol. Enzyme date were also obtained from cell cultures maintained in continuous exponential growth for greater than 10 generations (EE cells). Both shikimate dehydrogenase and prephenate aminotransferase exhibited elevated stationary-phase levels of enzyme, much of which was carried over into a subsequent subculture. At least 4 generations of exponential growth were required before diminution of the latter two enzymes to the levels characteristic of truly exponential-phase growth (EE cells) occurred. This is reminiscent of the overall behavior of 3-deoxy-D- arabino -heptulosonate 7-phosphate (DAHP) synthase (EC 4.1.2.15), specifically attributed to the properties of the cytosolic isozyme species (DAHP synthase-Co). Elevation of arogenate dehydrogenase also occurred in stationary-phase cells, but diminished rapidly during lag phase to reach the level characteristic of EE cells.     

Exposure to p-phenylendiamine in hairdressing parlours

Summary The purpose of this study is to verify and assess, in working conditions, the respiratory exposure to PPD of hairdressing parlour personnel. Several air samples collected in a hairdressing parlour during the time required for 8 applications of dyeing products containing PPD 2.52% have been analyzed. Tests are also carried out by extracting air immediately above the bowls containing the dyeing products, both at room temperature and at 37°C. PPD was assessed by means of HPLC. Only air sampled directly on bowls at 37°C has shown a level of 1 g, corresponding to an environmental release of PPD equivalent to 8 applications of dyeing products. On the basis of these experimental data, the PPD concentration in the air according to the parlour volume and to the supposed air exchanges has been calculated. Our results show a substantial insignificance of the concentration of PPD released in the environmental air during normal operations of hair dyeing: authors are of the opinion that hairdressers can't be truly considered as a PPD-asthmatic risk category like other workers exposed to PPD dust dispersed in the air of their working environment.     

HLA class I nucleotide sequences, 1991

The HLA class I sequences included in this compilation are taken from publications listed in the accompanying paper, Nomenclature for factors of the HLA system, 1990 (Bodmer et al. 1991) and Nomeclature for factors of the HLA system, 1989 (Bodmer et al. 1990). Where discrepancies have arisen between reported sequences the original authors have been contavted where possible, and necessary amendments to published sequences have been incorporated into this alignment. Future sequencing may identify errors in this list and we would welcome any evidence that helps to maintain the accuracy of this compilation. In the sequence alignments identify between residues is indicated by a hyphen (-). Unavailable sequence is indicated by a period (.). Gaps in the sequence are inserted to maintain the alignment between different alleles showing variation in amino acid number.