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Biomedical subjects

S A Murrell

Publications and source records attributed to S A Murrell.

36 records · Page 2Linked to original sources
PubMed1985

Purification and properties of the heat-released nucleotide-modifying group from the inactive iron protein of nitrogenase from Rhodospirillum rubrum.

Nitrogenase in Rhodospirillum rubrum is regulated in vivo by the covalent modification of the Fe protein. This paper reports the isolation, purification, and properties of the modifying group that has been heat released from the Fe protein. The molecule is isolated from the heated mixture by binding to a boronate affinity column. Purification is achieved on an ion-exchange high-performance liquid chromatography column. Structural properties of the molecule have been investigated by using proton and phosphorus NMR, mass spectrometry, enzyme susceptibility, and chromatographic methods. The heat-released modifying group exhibits an unusual signal in the proton NMR spectrum at 1.26 ppm. The molecule also contains a functional group which can be reduced by borohydride. This group is lost on breakdown of the molecule or upon treatment of the molecule with 5'-nucleotidase. The identity of the base and the pentose of modifying group as adenine and ribose, respectively, is confirmed. Ratios of the known components of the modifying group are established.

Chromatography, High Pressure Liquid↗
PubMed1985

Covalent modification of the iron protein of nitrogenase from Rhodospirillum rubrum by adenosine diphosphoribosylation of a specific arginine residue.

Nitrogenase in Rhodospirillum rubrum is inactivated in vivo by the covalent modification of the Fe protein with a nucleotide. The preparation of two modified peptides derived from proteolytic digestion of the inactive Fe protein is described. The modifying group is shown to be adenosine diphosphoribose, linked through the terminal ribose to a guanidino nitrogen of arginine. The structural features were established by using proton and phosphorus NMR, positive- and negative-ion fast atom bombardment mass spectrometry, and fast atom bombardment/collisionally activated decomposition mass spectrometry. Spectral methods along with chromatographic analysis and sequential degradation established the sequence of the modification site of Fe protein as Gly-Arg(ADR-ribose)-Gly-Val-Ile-Thr. This corresponds to the sequence in the Fe protein from Azotobacter vinelandii for amino acid residues 99 to 104.

Adenosine Diphosphate Ribose↗
PubMed1985

Properties and regulation of glutamine synthetase from Rhodospirillum rubrum.

Glutamine synthetase from Rhodospirillum rubrum was purified and characterized with respect to its pH optimum and the effect of Mg2+ on its active and inactive forms. Both adenine and phosphorus were incorporated into the inactive form of the enzyme, indicating covalent modification by AMP. The modification could not be removed by phosphodiesterase. Evidence for regulation of the enzyme by oxidation was obtained. Extracts from oxygen-treated cells had lower specific activities than did extracts from cells treated anaerobically. Glutamine synthetase activity was found to decrease in the dark in phototrophically grown cells; activity was recovered on re-illumination.

Adenine↗
PubMed1984

Resources, life events, and changes in positive affect and depression in older adults.

Hypotheses from a prospective conceptual framework were tested on a sample of 1,166 adults, age 55 and older, who were interviewed three times at 6-month intervals. Older adults with stronger resources had significantly more positive psychological states initially than those with weaker resources, and this advantage was maintained regardless of the levels of life events. There were significant main effects for desirable events and for undesirable events. Those with higher desirable events showed less decline in positive affect. Contrary to the "booster" hypothesis, there was no significant interaction between resources and desirable events. There was a significant interaction between resources and undesirable events on depression but detailed analyses showed that increases in depression over time were limited to the combined condition of weak resources and high levels of undesirable events. Weak resource persons with low or moderate undesirable events, in fact, showed modest improvements in depression.

Adaptation, Psychological↗
PubMed1984

The prevalence and correlates of anxiety symptoms in older adults.

An anxiety symptom scale was administered to a community sample of 713 males and 1338 females representative of persons aged 55 and older in Kentucky and quite similar to that of the US population in that age range. On the basis of a cutting point established previously, 17.1% of the males and 21.5% of the females were estimated to experience sufficient anxiety symptoms to place them at risk so as to require some form of intervention. In addition to gender and marital status differences, the study found a systematic but complex relationship between anxiety and age within this age range. Anxiety was inversely associated with socioeconomic status, education, and urban dwelling. Anxiety was inversely and highly correlated with physical health, and related to the presence of nine specific medical conditions and the need for and use of a number of medical services. The implications of the findings regarding the use of medical services for early diagnosis and treatment for mental health needs are discussed.

Age Factors↗
PubMed1984

Carbon monoxide dehydrogenase from Rhodospirillum rubrum.

The carbon monoxide dehydrogenase from the photosynthetic bacterium Rhodospirillum rubrum was purified over 600-fold by DEAE-cellulose chromatography, heat treatment, hydroxylapatite chromatography, and preparative scale gel electrophoresis. In vitro, this enzyme catalyzed a two-electron oxidation of CO to form CO2 as the product. The reaction was dependent on the addition of an electron acceptor. The enzyme was oxygen labile, heat stable, and resistant to tryptic and chymotryptic digestion. Optimum in vitro activity occurred at pH 10.0. A sensitive, hemoglobin-based assay for measuring dissolved CO levels is presented. The in vitro Km for CO was determined to be 110 microM. CO, through an unknown mechanism, stimulated hydrogen evolution in whole cells, suggesting the presence of a reversible hydrogenase in R. rubrum which is CO insensitive in vivo.

Aldehyde Oxidoreductases↗
PubMed1983

Quality of life as the criterion for need assessment and community psychology.

A "QOL-Contribution" model for resource allocation decisions is proposed that integrates concepts and values from community psychology, need assessment, and quality of life (QOL) studies. QOL is taken as the criterion for establishing the goodness-of-fit between a population and its environment. It is assumed that the characteristics of a given human group interact with the resources and the stressors of its environment, with its level of QOL as the result. The utility and the implications of the model for resource decisions are demonstrated with data from a statewide need assessment. In this application, different life domains, and different program targets within life domains, are prioritized according to their relative contributions to QOL. The findings for mental health and employment illustrate the specificity of the model's application. The model is then restated as the general task, and a unifying theme, for community psychology.

Adult↗
PubMed1983

Resources, life events, and changes in psychological states: a prospective framework.

A framework is presented that examines resources, environmental changes, and time in relation to one another and to changes in psychological affect. Resources in the aggregate are assumed to have both main effects and interactive effects on changes in psychological states. With undesirable life events, the resource interaction is assumed to be a buffer function, with resources making their strongest contribution at moderate levels of undesirable events. With desirable events, the resource interaction is assumed to be a multiplicative booster function, the effect of resources increasing as the level of desirable events increases. Cumulative undesirable demand is a variable with broader context than life events and is assumed to directly increase negative changes in psychological states. Time is considered a passive moderator, reducing the impact of either desirable or undesirable changes on psychological states. Alternative paths leading to positive change, status quo, and negative change in psychological states are then described, including the "false hope" hypothesis, and relations among variables are specified.

Adaptation, Psychological↗
PubMed1983

Reliability and validity of five mental health scales in older persons.

Five scales were assessed as mental health measures for older persons: Affect Balance, The Center for Epidemiological Studies Depression Scale, General Well-Being, LSI-Z Life Satisfaction, and Trait-Anxiety Inventory. These scales were administered to a community sample of 279 older persons and a clinical sample of 109 older persons who were in psychiatric inpatient units. In both samples, the internal consistency reliabilities for the anxiety, depression, and well-being scales were moderately high to high, for the life satisfaction scale they were acceptable, but the reliabilities for the affect balance scale suggest some caution in its use. For validity, multivariate analyses of variance found that all scales significantly discriminated between the two samples. The well-being and then depression scales were the strongest discriminators while the life satisfaction scale had the weakest validity. Cutting points for the well-being and depression scales are suggested for estimating the proportions of older persons who would be probable at-risk for disorder that requires intervention.

Aged↗
PubMed1983

Prevalence of depression and its correlates in older adults.

Depression was studied in a community sample of 962 males and 1555 females aged 55 years and over living in Kentucky in 1981. The sample was representative of the population in Kentucky in that age group and quite similar to that US population. The Center for Epidemiologic Studies Depression Scale was used as a measure of depression, and 13.7% of the males and 18.2% of the females were at or above a previously established cutpoint of 20 for adults over age 55 years. Significant relationships to depression were found in both sexes for age, education, income, housing quality, marital status, and health. For females, the age-depression relationship was not linear. By far the strongest relationship was with self-reported physical health. Significant proportions of those with self-reported kidney or bladder disease, heart trouble, lung trouble, hardening of the arteries, and stroke were above the depression cutpoint. For those conditions, physicians could expect high levels of concomitant depression in about one fourth of males and at least one third of females. These levels of depression were not found for those with high blood pressure, stomach ulcers, cancer, or diabetes. Over half of the sample reported taking prescribed medication and over half had needed a physician's care in the previous six months. Only 3.9% of the males and 3.2% of the females admitted to needing help for mental health problems. Thus, older adults with depression would probably be more likely to seek help from physicians than from services or professionals with explicit mental health labels.

Aged↗
PubMed1982

The Kentucky elderly need assessment: concurrent validity of different measures of unmet need.

The purpose was to examine the concurrent criterion-based validity of different measures used in a statewide in-home need assessment survey of a representative sample of 570 older persons. Need was measured and defined in four different ways in six problem areas. The criterion measure was a life satisfaction scale. The set of four need measures yielded a significant multiple R, indicating that the set would generally be related to life satisfaction in older persons. Individually, three of the four need measures made significant contributions. The set of six problem areas also yielded a significant multiple R, with four (Mental Health, Health, Income, Nutrition) making significant individual contributions. Implications for need assessment measurement included: that problem-focused measures are strongly and generally related to need satisfaction, whereas service-focused measures have problems; that both evaluative and descriptive measures appear to be related to need satisfaction; and the clear value of a multineed conception for measurement and for application to program planning and resource allocation. Suggestions for improvement in measures were made and cross-validation called for.

Aged↗
PubMed1980

Measuring citizen evaluations of services amidst community change.

Citizen surveys are increasingly being used by communities to evaluate services; however, previous work suggests that such evaluations of specific services may be influenced by generalization from other attitudes. Surveys repeated annually for 4 years allowed an examination of such possible "contagion" effects since they were done before, during, and after a highly visible, extensive change--court-ordered busing--which engendered intense negative attitudes. Evaluations of busing-related services underwent a significant decline during the onset of busing; evaluations of nonbusing services declined but not significantly, indicating that a contagion effect was not a strong factor. There were also no significant contagion effects on nonbusing services in city and suburban subsamples, nor on neighborhood or community-wide delivery levels. Neighborhood-level services were evaluated significantly more positively than community-wide services each of the 4 years. Rank order evaluations remained stable during the change. It was concluded that citizens do discriminate among services on citizen surveys even in the face of strong attitudes toward community changes, that their evaluations are generally stable over time, and that these are sensitive to at least highly visible program changes.

Adolescent↗
PubMed1975

Interaction patterns in families of autistic, disturbed, and normal children.

Six families with autistic children were compared with six families with disturbed children and six with normal children by means of a family interaction task. No differences were found between families with autistic children and those with normal children. Families with disturbed children were found to have less agreement between father and mother than did autistic or normal families.

Adult↗