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Biomedical subjects

D Shields

Publications and source records attributed to D Shields.

84 records · Page 5Linked to original sources
PubMed1978

Efficient cleavage and segregation of nascent presecretory proteins in a reticulocyte lysate supplemented with microsomal membranes.

The mRNA-dependent rabbit reticulocyte lysate of Pelham and Jackson (Pelham, H. R. B., and Jackson, R. J. (1976) Eur. J. Biochem. 67, 247-256) was supplemented with dog pancreas microsomal membranes and used to investigate the synthesis and processing of presecretory proteins. Highly efficient processing and segregation of the major bovine pituitary secretory proteins was observed upon mRNA translation. In contrast to the wheat germ cell-free protein synthesizing system, there was no significant inhibition of translation in the reticulocyte lysate even in the presence of high concentrations of dog pancreas microsomal membranes. Since the latter are required for processing and segregation of presecretory proteins, these reactions could be driven to virtual completion in the reticulocyte lysate without affecting the overall rate of protein synthesis.

Animals↗
PubMed1978

Nascent chicken ovalbumin contains the functional equivalent of a signal sequence.

Highly purified mRNA for chicken ovalbumin has been translated in a cell-free protein synthesizing system from rabbit reticulocytes in the presence or absence of EDTA-stripped microsomal membranes from dog pancreas. Nascent--but not completed--ovalbumin was transferred across the microsomal membrane, as demonstrated by cotranslational core glycosylation of ovalbumin nascent chains, by resistance to posttranslational proteolysis of only the glycosylated ovalbumin chains, and by cosedimentation with the membrane of exclusively the glycosylated form. Furthermore, nascent chains of bovine prolactin were observed to compete with nascent ovalbumin for transfer across the microsomal membrane. However, no competition for membrane sites was observed between nascent chains of rabbit globin and either nascent ovalbumin or prolactin. We interpret these results to suggest that nascent ovalbumin contains the functional equivalent of a signal sequence for transfer across membranes, and that membrane components involved in the segregation of secretory proteins with cleaved signal sequences also function in the segregation of ovalbumin.

Amino Acid Sequence↗
PubMed1978

Nursing care in labour and patient satisfaction: a descriptive study.

This study examined the subjective needs of labouring patients. A convenience sample of 80 postpartum patients was interviewed. They described the nursing care they had received, indicated the most helpful nursing measure received, and rated their satisfaction with their nursing care. These answers were categorized into types of nursing care. These were supportive care nursing, physical care nursing, medications and combinations of these three. X2 calculations done between these categories and satisfaction scores indicated a significant relationship between the type of care a patient received and her satisfaction scores. Patients found combined care very satisfying, but supportive care was the decisive factor in the way patients viewed their nursing care. The most frequently mentioned element in supportive care was the ability of the nurse to be a sustaining presence. The nurse's ability to assess and to meet the patient's need or non-need for her presence was major factor in patient satisfaction with nursing care in this sample. The relationship between congruency (agreement between time wanted and time spent by the nurse at the bedside) and satisfaction scores was highly significant. Thus the ability to recognize and respond to the patient's need or non-need for her presence was a crucial factor in patient satisfaction and in the way in which a nurse allocated her time. The relationships between numbers of nurses caring for a patient, parity, length of labour, presence of visitors, worries about the baby and patient satisfaction scores were examined. All were non-significant. However numbers of nurses caring for a patient was defined as a contributing factor to the delivery of supportive care nursing. More nurses contributed to more supportive care nursing being given, but was not the major factor in the delivery of supportive care nursing. Finally it was shown that the administration of syntocinon to patients in this sample decreased patient satisfaction with nursing care. Implications and possible reasons for these results are discussed.

Adolescent↗
PubMed1977

Cell-free synthesis of fish preproinsulin, and processing by heterologous mammalian microsomal membranes.

Poly(A)-containing mRNA isolated from the islets of Langerhans obtained from two species of fish, angler fish (Lophius americanus) and sea raven (Hemitripterus americanus), stimulated protein synthesis 16-fold in a wheat germ cell-free system. Characterization of the translation products by polyacrylamide gel electrophoresis in sodium dodecyl sulfate showed a major polypeptide weighing 11,500 daltons that was specifically precipitated by an antibody against angler fish insulin. Partial sequence analysis of the amino terminal revealed that this polypeptide is preproinsulin, in which the amino terminus of proinsulin is preceded by either 23 (angler fish) or 25 (sea raven) amino acid residues. Translation of fish islet mRNA in a wheat germ cell-free system in the presence of dog pancreas microsomal membranes led to the correct cleavage of the nascent preproinsulin, resulting in the synthesis of authentic fish proinsulin, as verified by partial sequence analysis. Moreover, the synthesized fish proinsulin was segregated, presumably into the luminal space of the dog pancreas microsomal vesicles, because it was found to be resistant to proteolysis by added trypsin and chymotrypsin. Our data thus suggest that the mechanisms and information for the transfer of secretory proteins across the microsomal membrane are highly conserved during evolution.

Animals↗
PubMed1976

Variable stabilities and recoveries of rat-liver RNA polymerases A and B according to growth status of the tissue.

1. The effect of growth status on the relative levels and recoveries of DNA-dependent RNA polymerase in rat liver nuclei was determined by two independent procedures: (a) measurement of RNA polymerase A and B activities in fraction IV [Roeder, R. G. and Rutter, W. J. (1970) Proc. Natl Acad. Sci. U.S.A. 65, 675--682] in the presence and absence of low concentrations of alpha-amanitin; (b) DEAE-Sephadex chromatography of fraction IV to resolve RNA polymerases A and B (and possibly other forms of the enzyme). 2. Growth was arrested in young rats (less than 100 g body weight) by hypophysectomy and stimulated by the administration of growth hormone or triiodothyronine. Under these conditions the rate of RNA synthesis in vivo or in isolated nuclei is known to be markedly depressed or stimulated relatively soon after hypophysectomy or hormone administration, respectively. RNA polymerases were obtained from animals under different growth conditions. There were no differences in the activities of nuclear RNA ploymerases per se, when these were separated from their endogenous template and assayed with heterologous denatured DNA. These reports contrast with earlier reports [Smuckler, E. A. and Tata, J. R. (1971) Nat. New Biol. 234, 37--39; Sajdel, E. M. and Jacob, S. T. (1971) Biochem. Biophys. Res. Commun. 45, 707--715]. 3. The discrepancy was resolved when a 'balance sheet' of enzyme recovery was established. Cessation of growth by hypophysectomy led to a marked reduction in the recovery of both forms A and B of the enzyme (less than 20% of the input RNA polymerase activity in fraction iv) following chromatography on DEAE-Sephadex. This effect was reversed within a short time after the administration of growth hormone (3--9 h) or triiodothyronine (18--24 h), leading to a doubling of the enzyme recoveries. These alterations which were more marked for RNA polymerase A, resulted in different elution profiles for RNA polymerases A and B upon chromatography. 4. It is concluded that the use of DEAE-Sephadex chromatography to compare the levels of RNA polymerases A and B isolated from tissues of different growth rate can give rise to over-estimates of apparent changes in their relative activities and that the measurement of enzyme activity in fraction IV is a better index of RNA polymerase levels. The relationship between growth rate of cells, the stability of RNA polymerases, and the importance of determining enzyme recoveries upon chromatography, are discussed.

Aging↗
PubMed1975

Stress modification of the toxicity of antimotion sickness drugs and aspirin.

The effect of environmental temperature on the toxicity of cyclizine, trimethobenzamide, and Aspirin were studied in mice. LD50s were compared at 30 degrees C (warm), 22 degrees C (normal), and 15 degrees C (cool). At 30 degrees C the toxicity of all three drugs increased, with that to aspirin being affected most. Cooling decreased the toxicity of cyclizine and had no significant effect on that of trimethobenzamide or Aspirin. These findings indicate that alterations in environmental temperature markedly affect drug toxicity. They emphasize that such alterations, and particularly increases in temperature, do not have to be particularly drastic, but that "mild' variations in the environment are effective in altering an animal's sensitivity to a drug.

Animals↗