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Biomedical subjects

M A Stephens

Publications and source records attributed to M A Stephens.

At least 73 records · Page 4Linked to original sources
PubMed1984

A promoter whose utilization is temporally regulated during sporulation in Bacillus subtilis.

The formation of endospores in the Gram-positive bacterium Bacillus subtilis proceeds according to a temporally ordered program of gene activation. To investigate timing mechanisms in sporulation gene expression, we have isolated and sequenced the promoter region for a B. subtilis gene known as 0.3 kb whose transcription is switched on at about stage III of development. The 5' terminus of the 0.3 kb mRNA was mapped by the S1 nuclease procedure to a position just upstream from its apparent ribosome binding site and initiation codon and just downstream from the transcription termination site for an adjacent gene. This information enabled us to construct a transcriptional fusion in which the 5' region of the 0.3 kb gene was joined to the lacZ gene of Escherichia coli. When introduced into cells of B. subtilis, the 0.3 kb-lacZ fusion caused the synthesis of a fusion-specified RNA that originated from within the 0.3 kb promoter region and extended into the adjacent E. coli DNA, and the induction of beta-galactosidase synthesis at the third to fourth hour of sporulation. Enzyme synthesis required the 0.3 kb promoter, since a deletion of the 5' region of the 0.3 kb gene in the transcription fusion eliminated the production of beta-galactosidase. Induction of the 0.3 kb-lacZ fusion was under developmental control, since the production of beta-galactosidase was blocked or substantially impaired by chromosomal mutations in the sporulation genes spoOB, spoIIA, spoIIE and spoIIIE, but not by a spoIIC mutation. We conclude that the 0.3 kb gene promoter is subject to a developmental clock, which delays its utilization until an intermediate stage of sporulation, and discuss models for how the timing of gene expression is regulated.

Bacillus subtilis↗
PubMed1984

On considering the unintended impact of evaluation: reactive distortions in program goals and activities.

The relationship between program planning and evaluation can be viewed as bidirectional; that is, evaluation methods, procedures, instruments, and criteria not only are determined by, but also influence, program goals and activities. Within the human services context, several factors or sources of reactivity between evaluation and program planning can be identified. These involve (a) quantification of goals and activities, (b) preferences by different audiences for various kinds of evaluation data, (c) values and evaluation criteria, and (d) evaluation requirements and resource availability. Effects of these reactive features are discussed and illustrated with examples drawn from mental health evaluation and accountability practices. It is argued that for evaluation to be a credible and useful practice, evaluators should plan their efforts and assess their own effectiveness within the larger context of human service systems.

Community Mental Health Centers↗
PubMed1984

The topography of binge eating.

The present study investigated the topography of binge eating by comparing characteristics of eating episodes recorded by individuals who engage in binge eating (n = 29) with those who do not (n = 27), and characteristics of binge and non-binge episodes recorded by individuals who binge eat. For 2 weeks, subjects continuously recorded the type and quantity of food eaten during each eating episode, time and place of consumption, number of persons present, mood while eating, and whether the food eaten was part of a meal or snack. Results indicated binge eaters experienced negative moods during a significantly greater proportion of their eating episodes than non-binge eaters. Within the group of binge eaters, negative moods were experienced during a significantly greater proportion of binge episodes than non-binge episodes. Furthermore, binge episodes occurred significantly more often than non-binge episodes from 6:00 to 12:00 p.m. and significantly less often at appropriate places. Clinical implications of these findings are discussed.

Emotions↗
PubMed1984

Chemopotentiation by CB 1954: the importance of postincubations and the possible involvement of poly(ADP-ribosylation).

CB 1954 potentiates the cytotoxic action of the bifunctional alkylating agent melphalan (L-PAM). In vitro, this potentiation does not require the preincubation in hypoxia normally needed for other nitroaromatic compounds such as misonidazole. Chemopotentiation is observed when cells are held in CB 1954 in air after treatment with L-PAM. This may reflect an inhibition of DNA repair process(es). Structural considerations suggested that CB 1954 might be acting as an inhibitor of poly(ADP-ribosylation). However, an inhibition of the drop in NAD levels consequent on exposure to melphalan was not obtained. Furthermore, unlike the known poly(ADP-ribose) inhibitor, 3-aminobenzamide, CB 1954 does not potentiate the cytotoxicity of the monofunctional alkylator N-methyl-N nitro N-nitrosoguanidine, or inhibit NAD depletion caused by this agent. Therefore the evidence suggests that CB 1954 is not an inhibitor of poly(ADP ribosylation).

Animals↗
PubMed1984

Nucleotide sequence of the 5' region of the Bacillus licheniformis alpha-amylase gene: comparison with the B. amyloliquefaciens gene.

The DNA sequence of the 5' region of the Bacillus licheniformis alpha-amylase gene is reported. Comparison of the inferred amino acid sequence of the B. licheniformis alpha-amylase gene with that of the Bacillus amyloliquefaciens gene shows that whereas the amino acid sequences of the mature proteins have considerable homology, the sequences for the signal peptides are distinct.

Amino Acid Sequence↗
PubMed1983

Patient behavior monitoring through self-reports.

This research examined the accuracy of data obtained by a self-observation and report technique (SORT) developed to record patients' ongoing everyday behaviors, where the behaviors occur, whether aid is provided, and if so, by whom. Over 2 consecutive weeks 10 persons with recent spinal cord injuries hospitalized at a major rehabilitation center reported their behaviors during 8 half-day periods. Assessments of reporting accuracy compared self-reports with data recorded by independent observers. Minute-by-minute comparisons of self-report and independent observations indicated moderate levels of agreement. Weekly measures of performance derived from the 2 kinds of records showed high agreement. Reporting accuracy was relatively unaffected by the amount of time between the occurrence of a behavior and its report and the personal importance of various behaviors to the patients. The SORT provides a dependable, flexible and cost-efficient means for assessing what patients do on a day-to-day basis and it offers many options for monitoring patients' functional performance in rehabilitation.

Adolescent↗
PubMed1981

Are surveillance of resistant enteric bacilli and antimicrobial usage among neonates in a newborn intensive care unit useful?

From March 1976 through December 1978, the prevalence of ampicillin- and gentamicin-resistant enteric bacilli was monitored in fecal cultures of neonates in an intensive care unit. Substantial fluctuations in colonization rates were observed which did not correlate with the occurrence of sepsis due to these organisms nor with variations in antibiotic use. This experience suggests that the availability of these surveillance data did not result in more effective control of neonatal sepsis due to enteric bacilli.

Ampicillin↗
PubMed1981

Patient behavior as a predictor of outcomes in spinal cord injury.

This study explores relationships between behavior of spinal cord injured persons during hospitalization and their medical and behavioral status after discharge. It illustrates a logic for identifying, selecting and testing indicators of patient performance that predict important aspects of outcome. Key behavioral measures were obtained for 14 patients, including independence, diversity, level of activity, and mobility. Factor analysis and multiple regression analysis were used to identify significant predictors of outcome. A subset of inhospital measures predicted an estimated 39% of the variance in unscheduled readmissions to the rehabilitation center, and 70% of the variance in independent functioning after discharge. Inhospital mobility predicted an estimated 68% of the variance in the rate of activities performed outside the home. In general, measures obtained late in hospital stays were the best predictors of both medical and behavioral status. Patient behavior during hospitalization can have practical implications for planning health care services and clinical practice.

Activities of Daily Living↗
PubMed1979

Mutation and inactivation of cultured mammalian cells exposed to beams of accelerated heavy ions. II. Chinese hamster V79 cells.

Inactivation and mutation to thioguanine-resistance of V79 hamster cells were studied after irradiation with accelerated helium, boron or nitrogen ions covering a range of linear energy transfer from 28 to 470 keV micrometers-1. For all radiation qualities a dose-dependent increase in mutant frequency was found for doses giving surviving fractions greater than about 0.20. The effectiveness per unit dose for both inactivation and mutation induction increased with the linear energy transfer of the radiation to a maximum in the range 90-200 keV micrometer-1. However, the maximum mutagenic effectiveness relative to gamma-rays was about two or more times that for inactivation. It is suggested that a proportion of the radiation-induced mutants suffer extensive genetic damage, and that some forms of this damage may be induced with high efficiency by radiations of high linear energy transfer.

Animals↗
PubMed1978

Mutation to ouabain-resistance in Chinese hamster cells: induction by ethyl methanesulphonate and lack of induction by ionising radiation.

The spontaneous frequency of mutants resistant to growth inhibition by ouabain (OUAR mutants) was found to be about 5:10(-5) per viable cell in uncloned cultures of Chinese hamster V79-4 cells. In freshly-isolated clones or cultures started from a few cells this frequency was initially reduced to about 1.10(-6) in 1 mM ouabain. No increase in the frequency of OUAR mutants was found in cultures treated with gamma-rays despite exploration of such variables as radiation dose, ouabain concentration, post-treatment interval before selection, cell density in selective medium, and clonal state of the cells at the time of adding ouabain (in situ vs. respreading method). A similar negative result was found for accelerated helium ions, for which the mutagenic effectiveness per unit dose has been shown to be about 10 times higher than gamma-rays for the induction of thioguanine-resistant mutants in these cells. Some evidence was found for an interaction between cellular radiation damage and ouabain-resistance, which may lead to a reduction in the survival of OUAR mutants in irradiated populations, but this damage seemed insufficient to account for inability to detect radiation-induced OUAR mutants. Reproducibly large increases in the frequency of OUAR mutants were found in cultures treated with various concentrations of ethyl methanesulphonate (EMS) by respreading cells in 1 mM ouabain for up to 8 days after EMS treatment. The concentration-OUAR mutant induction curve was approximately linear with low EMS concentrations. Recent evidence is reviewed in support of the suggestion, made in earlier studies, that ionising radiation is unable to induce OUAR mutants because of the severity of the genetic damage it causes.

Cell Line↗
PubMed1977

Th induction of thioguanine-resistant mutants of Chinese hamster cells by gamma-rays.

The induction of mutation to purine analogue resistance was assessed in Chinese hamster V79-4 cells exposed to gamma-radiation. After irradiation, the cells were grown in non-selective medium for different time intervals before respreading into medium containing 0.5-0.7 mug/ml thioguanine. In some experiments colonies arising in thioguanine-medium were counter-selected in medium containing the glutamine analogue azaserine, which distinguishes mutants with very little activity of the enzyme hypoxanthine-guanine phosphoribosyl transferase. Only these mutants were increased in frequency by radiation, the maximum measured frequencies occuring in cells respread after 2 days growth in non-selective medium. With longer intervals of post-irradiation growth in non-selective medium a fraction of the induced mutants was lost, and after large doses of radiation it is doubtful if the maximum frequency observed after 2 days post-irradiation growth represents the true induced frequency. The detection of freshly-induced mutants seemed to depend upon the dilution and decay of products formed from the genes prior to their mutation by radiation, since (a) selection of mutants in a higher concentration of thioguanine (2 mug/ml) increased the post-irradiation growth interval required to detect the maximum frequency of induced mutants, and (b) with increasing duration of post-irradiation growth in the non-selective medium, induced mutant cells were able progressively to overcome the growth-limiting effects of the analogue, to give large colonies when respread in thioguanine-medium. The radiosensitivities of 7 isolated mutant lines were indistinguishable from that of wild type cells, but the mutants were at a slight disadvantage when grown in competition with wild type cells. This disadvantage was consistent with the expected fitness of mutants relative to wild type cells calculated from estimates of the spontaneous mutation rate and the mean spontaneous mutation frequency. The induction of mutation to thioguanine resistance was non-linear with dose, yielding induced frequencies per rad of 5-10(-8) to 3-10(-7), but a plot of induced mutation frequency against log surviving fraction gave an approximately linear relationship. The same linear relationship holds for recently-published data on human and mouse cell cultures, so that all three mammalian cell types exhibit the same fixed probability of mutation induction relative to the extent of inactivation caused by ionising radiation.

Cell Division↗
PubMed1976

Factors affecting the efficiency of purine analogues as selective agents for mutants of mammalian cells induced by ionising radiation.

In the Chinese hamster cell line V79-4, the frequencies of the cells selected for their resistance to purine analogues do not always reflect the true frequencies of resistant mutants. The frequency of cells resistant to 8-azaguanine varied widely, especially when different sources of serum were used in the selective medium. Even with the more efficient analogue, 6-thioguanine, small colonies arose in the selective medium at a frequency which was strongly dependent upon analogue concentration and viable cell seeding density. These colonies were shown to have a phenotype which was indistinguishable from wild type. Hence with irradiated cells, where the viability of the cell population is reduced to an extent varying with the dose and the interval allowed for mutant expression, the counting of all colonies arising in selective medium can lead to spuriously variable, and sometimes very high, "mutation frequencies". Although the frequency of wild type colonies selected in thioguanine was diminished by the use of high concentrations of the analogue, a loss of induced mutants also occurred at these concentrations. Further, the V79-4 line contained two distinct types of mutant with different levels of hypoxanthine-guanine phosphoribosyl transferase (HGPRT) activity, and only of these types (HGPRT-negative mutants) increased in frequency with radiation dose. These results can account for many of the anomalies encountered in previous studies with purine analogues as selective agents, and show that some care has to be taken to characterize the mutants selected by resistance to purine analogues before meaningful dose-response relationships can be established.

Aneuploidy↗