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Biomedical subjects

N Burns

Publications and source records attributed to N Burns.

At least 19 recordsLinked to original sources
PubMed1998

Electrostatic and Hydrophobic Effects of Oligopeptide Insertions on Protein Adsorption.

The effects of oligopeptide insertions on the adsorption of the protein ZZ, where Z is the IgG binding domain of staphylococcal Protein A, was investigated by in situ ellipsometry. In particular, the interplay between hydrophobic and electrostatic interactions as driving force for adsorption was investigated by studying the effects of oligopeptide insertions of the type Tn((AlaTrpTrpPro)n), Nn((AlaTrpTrpAspPro)n), and Pn((AlaTrpTrpLysPro)n) on the adsorption at silica, methylated silica, and diaminocyclohexane (DACH) plasma polymer surfaces. For comparison, the adsorption of the inserted peptide stretches was also investigated. It was found that the adsorption of all the peptides increases with the molecular weight at methylated silica. At silica, only the Pn peptides were found to adsorb. The net negatively charged proteins modified through peptide insertions did not adsorb at the hydrophilic and negatively charged silica, irrespective of the peptide insertion, whereas an extensive adsorption was found for the positively charged DACH surface for all the proteins investigated. For hydrophobic and negatively charged methylated silica, on the other hand, the peptide insertions were found to have a major influence on the protein interfacial behavior, and the adsorption followed the peptide stretch charge, thus increasing in the order ZZNn < ZZTn < ZZPn. These effects are discussed in terms of the relative importance of hydrophobic and electrostatic interactions as driving force for the adsorption. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Development of the Rural-Urban Demand Indicator (RUDI).

In this article we describe development of RUDI (Rural-Urban Demand Indicator), a multivariate interval level measure of demand for health services. RUDI ranks counties by population and purchasing power and was developed for use in a wide variety of health-related research and for policy analyses. RUDI is based on microeconomic theory and Grossman's (1972) extension of the theory, that the family produces health and that the family's demand for health services is derived from the demand for health. Two factors define RUDI: DEMOS (demographics) and EWB (economic well-being). These two factors accounted for 66.2% of the variance observed in 1990 census data. A variety of other analyses offer evidence of known- groups, convergent, factorial, and predictive validity.

Analysis of Variance↗
PubMed1996

The role of L-aromatic amino acid decarboxylase in serotonin-stimulated aldosterone secretion in response to salt intake.

In this study we tested a new hypothesis namely that serotonin (5-hydroxytryptamine, 5-HT) could be synthesised within the zona glomerulosa of the rat adrenal gland from exogenous 5-hydroxytryptophan (5-HTP) by the enzyme L-aromatic amino acid decarboxylase (L-AAAD). A specific monoclonal antibody against L-AAAD showed that the enzyme was present predominantly in the adrenal medulla but also in the zona glomerulosa and zona fasciculata. Wistar rats, maintained on a normal (NS), low (LS) or high (HS) salt diet for one week, were sacrificed by decapitation, blood samples taken and the adrenal glands removed. Plasma aldosterone concentrations were significantly higher in the LS diet group (2.91 +/- 0.35 nM) and significantly lower in the HS diet group (0.261 +/- 0.55 nM) compared with the NS diet group (1.025 +/- 0.133 nM) (p < 0.001). Capsules from the LS diet group synthesised significantly higher maximal levels of 5-HT (2615.463 +/- 480.88 nM/mg protein) than capsules from the NS (1219.117 +/- 150.259 nM/mg protein) and the HS (968.477 +/- 214.485 nM/mg protein) salt diet groups (p < 0.05). Maximal aldosterone secretion in adrenal capsules obtained from rats on the LS diet (73.428 +/- 4.053 nM/mg protein) was significantly higher than in those obtained from rats on the NS diet (41.658 +/- 1.87 nM/mg protein) (p < 0.05). Maximal aldosterone secretion in adrenal capsules from the HS diet group (30.624 +/- 2.114 nM/mg protein) was significantly lower than in the capsules from both the LS and NS groups (p < 0.05). Carbidopa (10(-4) M), a specific inhibitor of L-AAAD, markedly attenuated the secretion of aldosterone when adrenal capsules from all three salt diet groups were incubated with 10(-4) M 5-HTP (p < 0.05), but had no significant effect on basal aldosterone secretion. These results clearly demonstrate that L-AAAD is not only present in the medulla, but also in the zona glomerulosa and zona fasciculata of the rat adrenal gland. In addition, 5-HT can be synthesised in the zona glomerulosa/capsular region of the rat adrenal gland and both its biosynthesis and its ability to stimulate aldosterone secretion is increased by sodium depletion and attenuated by sodium loading. This raises the interesting possibility that L-AAAD could play a role in the regulation of aldosterone secretion during sodium deficiency in the rat by converting circulating 5-HTP (which is present in blood at concentrations exceeding 1 micromolar) into 5-HT within the adrenal cortex.

5-Hydroxytryptophan↗
PubMed1996

Effects of ecstasy on aldosterone secretion in the rat in vivo and in vitro.

This study investigated the effects of Methylenedioxymethamphetamine (MDMA) on aldosterone and renin secretion via, (1) acute administration of MDMA to conscious Wistar rats, and (2) superfusion of whole rat adrenal capsules with 1 microM and 10 microM MDMA, in the presence of 5-HT. In study 1 basal aldosterone levels increased significantly from 3.490 +/- 1.1 nmol/l to 12.099 +/- 2 nmol/l after administration of MDMA (P < 0.05). Control rats showed no significant increase in aldosterone secretion. Basal plasma renin activity (PRA) was 6.86 +/- 1.65 ng/ml/hr in the MDMA treated animals increasing to 228.56 +/- 34.1 ng/ml/hr after administration (P < 0.05). In study 2 the aldosterone response to 5-HT was potentiated by 1 microM and 10 microM MDMA. No consistent stimulation of aldosterone was observed by MDMA alone. In conclusion, acute administration of MDMA to conscious rats causes activation of the renin-angiotensin-aldosterone system. In addition, MDMA can potentiate the direct action of 5-HT on aldosterone secretion in vitro by a mechanism which could be associated with the 5-HT transporter.

Adrenal Glands↗
PubMed1994

Structural similarity between the p17 matrix protein of HIV-1 and interferon-gamma.

The human immunodeficiency virus (HIV) matrix protein, p17, forms the outer shell of the core of the virus, lining the inner surface of the viral membrane. The protein has several key functions. It orchestrates viral assembly via targeting signals that direct the gag precursor polyprotein, p55, to the host cell membrane and it interacts with the transmembrane protein, gp41, to retain the env-encoded proteins in the virus. In addition, p17 contains a nuclear localization signal that directs the preintegration complex to the nucleus of infected cells. This permits the virus to infect productively non-dividing cells, a distinguishing feature of HIV and other lentiviruses. We have determined the solution structure of p17 by nuclear magnetic resonance (NMR) with a root-mean square deviation for the backbone of the well-defined regions of 0.9 A. It consists of four helices connected by short loops and an irregular, mixed beta-sheet which provides a positively charged surface for interaction with the inner layer of the membrane. The helical topology is unusual; the Brookhaven protein database contains only one similar structure, that of the immune modulator interferon-gamma.

Amino Acid Sequence↗
PubMed1994

Large-scale analysis of gene expression, protein localization, and gene disruption in Saccharomyces cerevisiae.

We have developed a large-scale screen to identify genes expressed at different times during the life cycle of Saccharomyces cerevisiae and to determine the subcellular locations of many of the encoded gene products. Diploid yeast strains containing random lacZ insertions throughout the genome have been constructed by transformation with a mutagenized genomic library. Twenty-eight hundred transformants containing fusion genes expressed during vegetative growth and 55 transformants containing meiotically induced fusion genes have been identified. Based on the frequency of transformed strains producing beta-galactosidase, we estimate that 80-86% of the yeast genome (excluding the rDNA) contains open reading frames expressed in vegetative cells and that there are 93-135 meiotically induced genes. Indirect immunofluorescence analysis of 2373 strains carrying fusion genes expressed in vegetative cells has identified 245 fusion proteins that localize to discrete locations in the cell, including the nucleus, mitochondria, endoplasmic reticulum, cytoplasmic dots, spindle pole body, and microtubules. The DNA sequence adjacent to the lacZ gene has been determined for 91 vegetative fusion genes whose products have been localized and for 43 meiotically induced fusions. Although most fusions represent genes unidentified previously, many correspond to known genes, including some whose expression has not been studied previously and whose products have not been localized. For example, Sec21-beta-gal fusion proteins yield a Golgi-like staining pattern, Ty1-beta-gal fusion proteins localize to cytoplasmic dots, and the meiosis-specific Mek1/Mre4-beta-gal and Spo11-beta-gal fusion proteins reside in the nucleus. The phenotypes in haploid cells have been analyzed for 59 strains containing chromosomal fusion genes expressed during vegetative growth; 9 strains fail to form colonies indicating that the disrupted genes are essential. Fifteen additional strains display slow growth or are impaired for growth on specific media or in the presence of inhibitors. Of 39 meiotically induced fusion genes examined, 14 disruptions confer defects in spore formation or spore viability in homozygous diploids. Our results will allow researchers who identify a yeast gene to determine immediately whether that gene is expressed at a specific time during the life cycle and whether its gene product localizes to a specific subcellular location.

Base Sequence↗
PubMed1994

Let the bed take the strain. An ergonomic approach to hospital bed provision.

1. The use of an ergonomic approach to risk assessment is advocated by the Manual Handling Operations Regulations. 2. Selection of hospital beds is a key factor in reducing the risk of injury from manual handling. 3. The use of electrically operated beds has eliminated many patient handling episodes. 4. The electrically operated beds have increased patient independence.

Beds↗
PubMed1989

Hospice: a design for home care for the terminally ill.

Hospice may appropriately be understood as a model of holistic care. As a model of holistic care, hospice provides numerous insights suitable for adoption in other health care settings. In addition, hospice provides a preeminent opportunity for nurses to practice within a nursing model; at the present time, nursing goals may be pursued more freely within hospice than in any other setting.

Holistic Health↗
PubMed1989

Standards for qualitative research.

One of the greatest obstacles to the identification of excellence in qualitative studies is the lack of generally accepted criteria. The criteria developed for quantitative studies are based on a different set of assumptions and are not appropriate. Those who critique qualitative studies need context flexibility, skills in inductive reasoning, skills in theory analysis, and the capacity to transform ideas across levels of abstraction. The following standards are proposed for critique of qualitative studies: (a) descriptive vividness; (b) methodological congruence; (c) analytic preciseness; (d) theoretical connectedness; and (e) heuristic relevance. Methodological congruence has four elements: rigor in documentation; procedural rigor; ethical rigor; and auditability. Heuristic relevance has three elements: intuitive recognition; relationship to existing body of knowledge; and applicability. Threats to each of these standards are identified. Creative strategies for improving the published presentation of qualitative studies must be developed to allow adequate critique.

Ethics, Nursing↗