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Biomedical subjects

A Taylor

Publications and source records attributed to A Taylor.

At least 343 records · Page 19Linked to original sources
PubMed1996

Degradation by proteases Lon, Clp and HtrA, of Escherichia coli proteins aggregated in vivo by heat shock; HtrA protease action in vivo and in vitro.

Thermally aggregated, endogenous proteins of Escherichia coli form a distinct fraction, denoted S, which is separable by sucrose-density-gradient centrifugation. It was shown earlier that DnaK, DnaJ, IbpA and IbpB heat-shock proteins are associated with the S fraction. Comparison of the rise and decay of the S fraction in mutants defective for heat-shock proteases Lon (La), Clp, HtrA (DegP, Do) and in wild-type strains made studies of proteolysis and the function of the heat-shock response possible in vivo. Different timing and the extent of action of particular proteases was revealed by the initial size and decay kinetics of the S fraction. The proteases Lon, Clp, and HtrA all participated in removal of the aggregated proteins. Mutation in the gene encoding ClpB caused the most prominent effect (47% stabilization of the S fraction). The correlation between the disappearance of the S fraction and proteolytic activity was supported by the result of the in vitro reaction. Approximately one third of the isolated S fraction was converted to trichloroacetic acid-soluble products by the purified HtrA protease. Mg2+ ions stimulated the reaction, in contrast to the reaction of the HtrA protease with casein. The digestion of the aggregated proteins, unlike the digestion of casein, by HtrA protease in vitro was inhibited by added DnaJ, which might reflect protection of the aggregated proteins in vivo by DnaJ from excessive degradation. One might expect that such an activity of DnaJ would promote denatured protein renaturation versus proteolysis. Moreover, among the aggregated proteins that are discernible by electrophoresis, none could be identified as being more susceptible than any other to HtrA degradation. The separation pattern of these proteins before and after the in vitro digestion did not show a difference corresponding to the loss of about 30% of constituting proteins. This was interpreted as recognition by the HtrA protease of a state of protein denaturation rather than specific amino acid sequences in particular proteins. We conclude that the fraction consisting of proteins heat-aggregated in vivo (i.e. the S fraction) contains endogenous substrates for the heat-shock proteases tested. Their use for in vitro reaction reveals information that is in some respects different from that obtained with exogenous substrates such as casein.

ATP-Dependent Proteases↗
PubMed1996

Metabolism of [U-13C5] glutamine in cultured astrocytes studied by NMR spectroscopy: first evidence of astrocytic pyruvate recycling.

Metabolism of [U-13C5]glutamine was studied in primary cultures of cerebral cortical astrocytes in the presence or absence of extracellular glutamate. Perchloric acid extracts of the cells as well as redissolved lyophilized media were subjected to nuclear magnetic resonance and mass spectrometry to identify 13C-labeled metabolites. Label from glutamine was found in glutamate and to a lesser extent in lactate and alanine. In the presence of unlabeled glutamate, label was also observed in aspartate. It could be clearly demonstrated that some [U-13C5]glutamine is metabolized through the tricarboxylic acid cycle, although to a much smaller extent than previously shown for [U-13C5]glutamate. Lactate formation from tricarboxylic acid cycle intermediates has previously been demonstrated. It has, however, not been demonstrated that pyruvate, formed from glutamate or glutamine, may reenter the tricarboxylic acid cycle after conversion to acetyl-CoA. The present work demonstrates that this pathway is active, because [4,5-13C2]glutamate was observed in astrocytes incubated with [U-13C5]-glutamine in the additional presence of unlabeled glutamate. Furthermore, using mass spectrometry, mono-labeled alanine, glutamate, and glutamine were detected. This isotopomer could be derived via the action of pyruvate carboxylase using 13CO2 produced within the mitochondria or from labeled intermediates that had stayed in the tricarboxylic acid cycle for more than one turn.

Alanine↗
PubMed1996

Bacteriophage lambda lysis gene product modified and inserted into Escherichia coli outer membrane: Rz1 lipoprotein.

Lysis proteins of bacteriophage lambda were localized in different parts of the host envelope: S in the inner membrane,36 Rz in the membrane adhesion sites,14 and Rz1 in the outer membrane. The R gene product, the transglycosylase destroying bacterial murein, is a soluble protein. Computer-assisted analysis of the Rz1 protein amino acids sequence revealed that its N-terminal part contained the site 15VVVG [symbol: see text] C20, which could be recognizable for the SPase II and cleaved leaving lipid modified C20 as the N-terminal amino acid of the mature protein. Microsequencing of the Rz1 protein isolated from the expression products of E. coli [pSB54] carrying the Rz1 gene showed that the N-terminal part of the protein was cleaved as predicted. Lipid labeling with [3H]palmitate confirmed the expectation that Rz1 was a lipoprotein. E. coli [pSB54] treated with globomycin accumulated prolipoprotein, the Rz1 precursor, which was detectable by the anti-Rz1 serum on electropherograms as the 6.5-kDa protein, larger than mature protein. Physiological function of the Rz1 protein remains to be discovered, but as a first hint we noticed that it evokes increase of the fraction of adhesion sites of outer and inner membranes when overproduced from pSB54. The same effect was observed in induced E. coli (lambda) just before the lysis onset, however, one should be cautious in interpreting the results obtained in conditions of the overproduction of the Rz1 lipoprotein.

Amino Acid Sequence↗
PubMed1996

The timing of pronuclear formation, DNA synthesis and cleavage in the human 1-cell embryo.

The timing of pronuclear formation and breakdown, DNA synthesis and cleavage during the first cell cycle of human embryogenesis are described. Pronuclei formed between 3 and 10 h post-insemination (hpi; median 8 hpi). S-phase commenced between 8 and 14 hpi, and was completed between 10 and 18 hpi. M-phase was observed between 22 and 31 hpi (median duration 3 h), and cleavage to the 2-cell stage took place between 25 and 33 hpi. The timing of the same events was determined in 1-cell embryos derived from re-inseminated human oocytes that had failed to fertilize during therapeutic in-vitro fertilization (IVF). In these embryos, pronuclei formed between 3 and 8 h post-re-insemination (hpr-i), coinciding with the beginning of S-phase. While S-phase was completed as early as 10 hpr-i in some embryos, it extended until at least 16 hpr-i in others. Pronuclear breakdown and cleavage occurred from 23 and 26 hpr-i respectively; however, they did not occur in some embryos until after 46 hpr-i. The results demonstrate a markedly greater degree of variation in the timing of these events in embryos derived from re-inseminated oocytes compared with embryos derived from conventional IVF, and thus throw into question the validity of using the former as models for studies of the first cell cycle of human embryogenesis.

Cell Cycle↗
PubMed1996

Dynamic lymphoscintigraphy to identify the sentinel and satellite nodes.

Lymphoscintigraphy is increasingly used to identify the first draining node (sentinel node) in patients with malignant melanoma or breast cancer. If the sentinel node is tumor free then the remainder of the nodes in that specific nodal bed are likely to be free of metastases. Localization and biopsy of the sentinel node with an intraoperative surgical probe may obviate more radical lymph node dissection. Lymphoscintigraphy is conventionally performed by injecting the radioactive tracer in the four quadrants around the primary tumor and imaging the appropriate nodal beds approximately 30 minutes later. The visualized node nearest the tumor usually is assumed to represent the sentinel node. To test this assumption, a dynamic acquisition was obtained in 16 patients with malignant melanoma to determine if the node nearest the tumor was actually the first draining node. In one of 16 patients, the radioactive tracer injected around a thigh melanoma drained first to an inguinal node and then drained inferiorly to a second inguinal node located closer to the tumor. The distinction between the sentinel and satellite (secondary draining nodes) may have important clinical implications regarding the number of nodes that require surgical excision. In summary, static images do not define the pattern of lymph flow and the node nearest the tumor is not necessarily the sentinel node. Failure to obtain dynamic images may lead to misdiagnosis of the sentinel node in a small percentage of patients.

Humans↗
PubMed1996

Characterisation of strains of Salmonella serotype Livingstone by multiple typing.

Isolates of Salmonella serotype Livingstone (6,7:d:1,w) from man, water and various animals and animal products in Canada, England, France, Israel and Scotland were examined for ribotype, biotype and plasmid profile. Analysis by these methods indicated that an epidemic strain of Livingstone of ribotype 1/biotype 8/plasmid-type 6 was responsible for the major upsurge of Livingstone infection that occurred in man in Tayside (Scotland) between 1989 and 1991; that type was also isolated from spring water, animal feed and poultry. Livingstone isolates of ribotype 1/biotype 8 with plasmid profiles other than type 6 were also present in Scotland, England and France at that same time. Among representative Livingstone isolates from England, a strain of ribotype 2/biotype 1 was predominant in man and poultry products between 1988 and 1992, although strains of other ribotypes (1, 3 and 4) were also present. Strains of ribotype 3 of different biotypes were obtained from poultry and animal feed sources in Canada. A strain of ribotype 5/biotype 3 caused human infections in Israel between 1968 and 1992. Ribotyping, biotyping and plasmid profile analysis used together have helped to trace the sources and extent of spread of human infections caused by Salmonella Livingstone.

Animals↗
PubMed1996

Postanaesthetic shivering in children.

This study was designed to assess the incidence, severity and possible aetiological factors of postanaesthetic shivering in children. Three hundred and seventy-six children undergoing general anaesthesia were enrolled in the study. Tympanic membrane temperatures were recorded pre-operatively and every 15 min postoperatively in the recovery room until discharge to the ward. Also recorded were all anaesthetic data including fluid administration, methods of temperature preservation used, sedation scores and shivering (using a four-point scale). The overall incidence of shivering was 14.4%. Multiple regression analysis identified three factors that were significantly related to shivering: age, the administration of atropine and peri-operative temperature changes. Children who shivered rewarmed faster in the recovery room.

Adolescent↗
PubMed1996

The effects of platinum chemotherapy on essential trace elements.

The effects of cisplatin chemotherapy on the metabolism of essential trace elements were investigated in 12 patients before and after treatment with cisplatin. In serum, the mean post-treatment concentrations of Cu 913.91 mumol 1-1), Zn (9.57 mumol 1-1) and Mg (0.54 mumol 1-1) were significantly reduced compared with the pre-treatment levels 919.35, 11.86 and 0.67) while Se, caeruloplasmin and C-reactive protein concentrations were unaltered. Urinary excretion of Cu, Mg and Zn were enhanced. The urinary N-acetyl-beta-D-glucosaminidase activity (a marker of proximal renal tubular dysfunction) was also increased and suggests that the mechanism for decrease of certain trace elements in serum during treatment could be increased urinary excretion caused by impaired cellular metabolism. It is not clear whether the loss of trace elements via the urine has any implication for the clinical status of cancer patients treated with cisplatin.

Adolescent↗
PubMed1996

Inhibition of fibro-intimal hyperplasia in a polytetrafluoroethylene vascular graft with standard heparin and low molecular weight heparin.

BACKGROUND: Fibro-intimal hyperplasia is a significant cause of late prosthetic vascular graft failure. The influence of standard unfractionated sodium heparin (SH) and low molecular weight heparin (LMWH) on intimal hyperplasia was studied in a sheep polytetrafluoroethylene (PTFE) end-to-side carotid artery vascular graft model. METHODS: Sodium heparin was administered subcutaneously in a dose of 7250 units twice daily (n = 6). Enoxaparin, an LMWH, was administered subcutaneously in two different dose regimens of 2 mg/kg (n = 6) and 5 mg/kg (n = 6) daily. At 1 month the animals were killed and the grafts sectioned. An intima to media ratio was obtained under light microscopy, using an eyepiece graticule, from measurements taken from the floor of the native artery. Results were analysed with a rank-sum correlation test. RESULTS: Control sheep had a median ratio of 0.104, an SH level of 0.021, a low-dose LMWH level of 0.035 and a high-dose LMWH level of 0.017. There was a significant difference between control and SH (P < 0.001), control and high-dose LMWH (P < 0.05), and SH and low-dose LMWH (P < 0.05), but there were no differences between SH and high-dose LMWH or between the two LMWH groups. Both LMWH groups recorded high anti-Xa levels but only slight prolongation of thrombin time. CONCLUSIONS: Low molecular weight heparin has a similar effect to SH on the inhibition of fibro-intimal hyperplasia in this animal model but is safer, with less bleeding potential, and is more convenient to administer as a once-daily dose.

Animals↗
PubMed1996

Approaches to studies on neuronal/glial relationships by 13C-MRS analysis.

The use of different 13C-labelled precursors alone or in combination ([1-13C]glucose, [2-13C]glucose, [1-13C]acetate, [2-13C]acetate and [1,2-13C2]acetate) to study neuronal/glial metabolic relationships by MRS is discussed. Glutamine and citrate resonances represent glial metabolism if a combination of [1-13C]glucose + [2-13C]acetate is used, but only for short time periods. A combination of [2-13C]glucose + [2-13C]acetate will label -COO- groups from glucose and -CH2 groups from acetate, respectively, which distinguish well in theory. However, this approach is severely limited by the long T1S of -COO- groups and low S/N. Contributions of the anaplerotic pathway can be assessed using [2-13C]glucose, but again can be limited by the long T1S of -COO- groups. Labelling of glycerol-3-phosphate (believed to be produced in glia) from [1-13C]glucose is difficult to see under normal conditions but has proved useful in, e.g., hypoxia. We believe the most promising approach is the use of [1-13C] glucose with [1,2-13C2]acetate, by analysis of the multiplets ('isotopomers') of the amino acid resonances.

Acetates↗
PubMed1996

Social work with transport disabled persons: a wayfinding perspective in health care.

Transport disabled persons confront extensive architectural and psychosocial barriers during their travel to community based health care services by mass transit. The current health care reform movement affords social work an opportunity to consolidate its expertise with this population. The Certificate of Need program is a method with which social work can provide service to people with transportation disabilities. Social work can also continue its use of the Americans with Disabilities Act and the Urban Mass Transportation Act to assist people with transport disabilities to access community based health care services.

Delivery of Health Care↗
PubMed1996

Deviation from developmentally appropriate self-care autonomy. Association with diabetes outcomes.

OBJECTIVE: Treatment of IDDM in youth emphasized balancing children's self-care autonomy with their psychological maturity. However, few data exist to guide clinicians or parents, and little is known about correlates of deviations from this ideal. RESEARCH DESIGN AND METHODS: In this cross-sectional study, IDDM self-care autonomy of 100 youth was assessed using two well-validated measures. Three measures of psychological maturity (cognitive function, social-cognitive development, and academic achievement) were also collected for each child. Composite indexes of self-care autonomy and of psychological maturity were formed, and the ratio of the self-care autonomy index to the psychological maturity index quantified each child's deviation from developmentally appropriate IDDM self-care autonomy. Based on these scores, participants were categorized as exhibiting constrained (lower tertile), appropriate (middle tertile), or excessive (higher tertile) self-care autonomy. Between-group differences in treatment adherence, diabetes knowledge, glycemic control, and hospitalization rates were explored. RESULTS: Analysis of covariance controlling for age revealed that the excessive self-care autonomy group demonstrated less favorable treatment adherence, diabetes knowledge, hospitalization rates, and, marginally, glycemic control. Excessive self-care autonomy increased with age and was less common among intact two-parent families but was unrelated to other demographic factors. CONCLUSIONS: The findings indicate caution about encouragement of maximal self-care autonomy among youth with IDDM and suggest that families who succeed in maintaining parental involvement in diabetes management may have better outcomes.

Adolescent↗