Search PubMed⌕ Search

Biomedical subjects

J Evans

Publications and source records attributed to J Evans.

At least 379 records · Page 21Linked to original sources
PubMed1989

Altitudinal neglect following traumatic brain injury: a case report.

We present an analysis of altitudinal neglect in a patient who following traumatic brain injury showed extinction to a visual stimulus presented in the lower field when another stimulus was simultaneously presented in the upper field. When estimating the midpoint of vertically-oriented rods presented below eye level using visual cues, tactile/kinesthetic cues or a combination of these cues, she consistently pointed higher than control subjects did. She showed less severe impairments when the rods were presented at or above eye level. When estimating the midpoint between two clicks presented above and below her head, she pointed higher than did control subjects. These deficits cannot be accounted for by sensory or motor disorders and appear to be due to a disorder in attending to stimuli in the lower half to space.

Adult↗
PubMed1989

Cellular responses to Pyrularia thionin are mediated by Ca2+ influx and phospholipase A2 activation and are inhibited by thionin tyrosine iodination.

Pyrularia thionin, isolated from nuts of Pyrularia pubera, is a strongly basic peptide of 47 amino acids. The amino acid sequence and configuration of its four disulfide bonds place this plant peptide, known to be hemolytic, cytotoxic, and neurotoxic, among the thionins. We report and compare several cellular responses mediated by Pyrularia thionin: hemolysis of human erythrocytes, activation of an endogenous phospholipase A2 in Swiss 3T3 cells, cytotoxicity toward HeLa and mouse B16 melanoma cells in culture, viability of rat hepatocytes and lymphocytes measured by trypan blue exclusion, and lethality in mice. Cellular responses related to ion movement include a toxin-mediated influx of Ca2+ into mouse P388 cells measured by Fura-2 fluorescence, depolarization of mouse P388 plasma membrane measured by fluorescence of bis(1,3-diethylthiobarbituric acid)trimethine oxonol (bisoxonol), and depolarization of frog (Rana pipiens) sartorius muscle determined by direct measurement of membrane potential. Graded iodination of Pyrularia thionin leads to a related loss of activity for hemolysis, phospholipase A2 activation, cytotoxicity, and lethality in mice. The mediated Ca2+ influx into and depolarization of P388 cells require Ca2+ in the external medium and are inhibited by 100 microM Ni2+. Depolarization of sartorius muscle by Pyrularia thionin also requires a functional Ca2+ channel, as shown by verapamil inhibition. This muscle depolarization also involves phospholipase A2 activation because dexamethasone and quinacrin, but not indomethacin, protect against depolarization. The IC50 values for viability of rat hepatocytes and splenic lymphocytes measured by trypan blue exclusion were 0.17 and 40 microM, respectively. The general response of cells to Pyrularia thionin involves a membrane alteration leading to depolarization and a channel-mediated influx of Ca2+. There is a related activation of phospholipase A2 that results in loss of membrane integrity, hemolysis in the case of erythrocytes, and eventually cell death. Iodination of Pyrularia thionin leads to a corresponding inhibition of all three cellular responses, which indicates an essential role for tyrosine in either maintenance of peptide structure or interaction of the peptide with cellular membranes.

Animals↗
PubMed1989

Double duodenal webs in an adult.

The duodenal web is an unusual cause of gastric outlet obstruction, but one that must be kept in mind in patients with postprandial nausea, vomiting, and epigastric pain. We suggest endoscopic evaluation of the second and third portions of the duodenum in all such patients. At surgery, direct inspection of the duodenal lumen or the confirmation of its patency by passage of a Foley balloon should be routine. If a duodenal web is encountered, the procedure of choice should be duodenostomy with simple excision of the web.

Adult↗
PubMed1989

Diminished expression of the T cell receptor on the expanded lymphocyte population in MRL/Mp-lpr/lpr mice.

MRL mice homozygous for the recessive lpr gene develop an accelerated autoimmune syndrome and massive lymphadenopathy. Because the function of the expanded lymph node population is unclear, we have studied the subunits of the T cell receptor for antigen (TcR). DNA and RNA were prepared from MRL/Mp-lpr/lpr (lpr) and congenic MRL/Mp(-)+/+ (+/+) mice by standard techniques and studied by Southern blot, northern blot, and dot blot analysis using the cDNAs TT11, specific for the TcR alpha chain; 86T5, specific for the TcR beta chain; and T3 delta; specific for the subunit of the T3 molecule. Surface protein was immunoprecipitated with antisera 8177, which recognizes TcR framework determinants, and resolved by diagonal SDS-PAGE. FACS analysis was performed with a monoclonal antibody to murine T3, and with the KJ16-133 and F23.1 monoclonal antibodies, which recognize determinants encoded by the V beta 8 subfamily of beta chain variable region genes. When compared with +/+ controls, surface TcR density as detected by immunofluorescence using all three antibodies was significantly diminished on lpr spleen and lymph node cells, as well as on lpr lymph node cells which had been depleted of L3T4+ and Ly2+ cells by negative selection. There appeared, however, to be selective expression of the genes encoding the epitopes binding F23.1. Southern blot analysis of DNA showed polyclonal rearrangements of the TcR beta chain genes. There were increased alpha, beta, and T3 delta RNA transcripts in the double negative lymph node cells. The paradoxical decrease in TcR surface expression in the setting of large quantities of full length transcript is yet to be explained.

Animals↗
PubMed1989

[Geographical variations in mortality due to diseases amenable to medical intervention in Europe--Commission of European Communities: atlas of avoidable deaths].

The urgent need to develop measures of the outcome of health-care services has led to the collaboration of 10 countries of the European Community in the production of the European Community atlas of avoidable death (1974-1978). Seventeen disease groups were chosen for which it was considered that death within specified age groups should be either wholly or substantially avoidable when appropriate medical care is sought and provided in good time. Mortality from these causes was compared across 360 health-service administrative areas in the participating countries. For all diseases there was considerable variation in mortality both within and between the countries of the European Community and it is suggested that high levels of mortality from these causes should be viewed by health authorities as warning signals of potential failures of health-care services. Work is in progress on a further edition of the Atlas for the years 1980-1984. Changes in avoidable mortality over time could indicate which health authorities have persistent problems and which authorities are succeeding in reducing avoidable mortality.

Adolescent↗
PubMed1988

Special surgery opens.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Factors influencing the expression of dental extracellular matrix biomineralization.

The forming tooth organ provides a number of opportunities to investigate the cellular and molecular biology of cell-mediated extracellular matrix (ECM) biomineralization. Regulatory processes associated with tooth formation are being investigated by identifying when and where cell adhesion molecules (CAMs), substrate adhesion molecules (SAMs), dentine phosphoprotein and enamel gene products are expressed during sequential developmental stages. In vitro organotypic culture studies in serumless, chemically-defined medium, have shown that instructive and permissive signalling are required for both morphogenesis and cytodifferentiation. Intrinsic developmental instructions (autocrine and paracrine factors) act independently of long-range hormonal or exogenous growth factors and mediate morphogenesis from the initiation of the dental lamina to the crown stages of tooth development. This review summarizes the results of studies using experimental embryology, recombinant DNA technology and immunocytology to elucidate mechanisms responsive to instructive epithelial-mesenchymal interactions associated with ameloblast differentiation, odontoblast differentiation, and dentine and enamel ECM biomineralization.

Animals↗
PubMed1988

Metabolic expression of intrinsic developmental programs for dentine and enamel biomineralization in serumless, chemically-defined, organotypic culture.

Biomineralization was investigated using embryonic mouse mandibular first molars (M1) cultured in the presence or absence of fetal calf serum. Metabolic features including cell division and Ca2+ and phosphate incorporation into dentine and enamel extracellular matrices were analyzed. The relative timing and magnitude of DNA synthesis for serumless cultures was comparable to in vivo controls. Isotopic calcium and phosphate incorporation into the mineral phase of dentine and enamel matrices, in the absence of serum, fluctuated during development. Molar tooth morphogenesis, cytodifferentiation, and extracellular matrix formation approximated late crown-stage development in serumless cultures. Von Kossa histochemical staining indicated calcium phosphate salt formation in serumless cultures. Analysis of anhydrous fixation-prepared enamel and dentine representing serumless cultured explants indicated that crystal size and orientation were comparable to in vivo enamel and dentine. In contrast, serum-supplemented cultures showed atypical crystal size and orientation. Calcium/phosphorous (Ca/P) ratio values for serumless cultures after 21 days showed Ca/P enamel values of 2.03 (SD +/- 0.04, p less than 0.025) and dentine values of 1.89 (SD +/- 0.01, p less than 0.025). Electron diffraction patterns of enamel and dentine formed in serumless cultures were principally those of highly-ordered crystalline hydroxyapatite. Our results suggest that tissue-specific dentine and enamel biomineralization is regulated by endogenous factors intrinsic to the developmental program of embryonic tooth organs during serumless culture.

Animals↗
PubMed1988

A comparison of psychologically-induced cardiovascular reactivity in laboratory and natural environments.

This study focused on the possible role of heart rate reactivity in the development of essential hypertension in female subjects. Baseline heart rate, systolic and diastolic blood pressures, taken over a 6 week period, were used for comparison with the same measures taken during a laboratory session involving relaxation, cold pressor, mental arithmetic and exercise, and before and after an academic examination. Information about personality and lifestyle was included in subsequent univariate and multivariate analyses. Significant increases were produced in heart rate by the mental arithmetic task (p less than 0.00005), in systolic pressure by the exercise task (p less than 0.00005) and in systolic pressure prior to the examination (p less than 0.001). No significant diastolic effects were found. When subjects were divided into high and low reactors, on the basis of their heart rate reactivity to mental arithmetic, there was little difference in cardiovascular activity between the groups in any other condition. Significant effects on reactivity were found for diet, regular daily exercise and type A personality. The results are discussed in terms of Obrist's theory of the genesis of essential hypertension.

Adaptation, Psychological↗
PubMed1988

Characterization of the conjugation system associated with the Staphylococcus aureus plasmid pJE1.

The conjugation system of Staphylococcus aureus that is conferred, at least in part, by plasmid pJE1, requires cell-to-cell contact. Optimum transfer was found when the numbers of donor and recipient cells were equal. Certain antibiotics increased the conjugation frequency. Fragments of plasmid pJE1 were cloned into a staphylococcal plasmid vector; although separate clones were isolated that conferred ethidium bromide resistance and gentamicin resistance, none of the clones carried the ability to conjugate. Transposon mutagenesis with Tn551 was used to create 26 mutants of pJE1. These were analysed for the position of the insertion and for their ability to conjugate. The sites of insertion were non-random. Only six mutants were unaffected in their conjugability; one showed increased ability to conjugate whilst the rest were either unable to conjugate or showed a reduced frequency. It is concluded that there are at least two separate regions necessary for conjugation and that the system is not obviously similar to that reported in streptococci.

Cloning, Molecular↗
PubMed1988

Comparison of capillary and arterial blood gas measurements in neonates.

One hundred and fifty eight paired arterial and capillary blood samples were obtained from 41 sick preterm infants in their first week of life and the pH, and PCO2, and PO2 concentrations were measured. Half of the capillary samples were obtained from unwarmed heels and half from heels warmed to 40 degrees C. A potentially significant discrepancy (arbitrarily defined as 0.05 units for pH. 1 kPa for PCO2, and 3 kPa for PO2) was found in 19 (24%) of cases for pH, in 9 (11%) for PCO2 and in 21 (26%) for PO2. Warming the heel produced no significant improvement in results. We conclude that capillary blood provides satisfactory measurements of pH and PCO2 for all but the most critical purposes, but that the usefulness of capillary PO2 estimations is limited to the exclusion of hypoxia.

Arteries↗