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Biomedical subjects

T C Evans

Publications and source records attributed to T C Evans.

At least 37 records · Page 2Linked to original sources
PubMed1994

Calcium and membrane-binding properties of monomeric and multimeric annexin II.

The calcium-dependent interaction of several annexins with membranes was studied. A novel technique was developed that allowed estimation of calcium binding to aggregating systems. This consisted of immobilized phospholipids on phenyl-Sepharose. Proteins associated with this affinity gel in the presence of radioactive calcium and were eluted with the same buffer containing excess EGTA. This produced an elution profile with a peak of excess calcium. Protein extinction coefficients were estimated in order to quantitate the protein more accurately. Association of annexin II with the membrane was of very high affinity and involved a calcium stoichiometry of 11 +/- 1 at 12.5 microM free Ca2+ and 10 +/- 2 at 50 microM free Ca2+. (AII)2(p11)2, a heterotetramer of two annexin II and two p11 subunits, bound 12 +/- 1 Ca2+ at 12.5 microM Ca2+ and 15 +/- 1 Ca2+ at 50 microM Ca2+. These stoichiometries showed a pattern of "all or none" calcium binding where the number of calcium ions bound to a protein-membrane complex was virtually independent of the free calcium concentration or the density of protein on the membrane. (AII)2(p11)2 contains two annexin II subunits so that calcium stoichiometry was not directly related to the number of potential sites. (AII)2(p11)2 required less calcium to support membrane binding than did annexin II. Thus, dimerization of the membrane binding unit may be needed for annexins to function at intracellular calcium levels. Annexin VI contains twice as many putative calcium binding units as annexin V and the same pattern of behavior occurred for this pair of proteins. At 25 microM free calcium, (AII)2(p11)2 alone bound no detectable calcium (< 0.1 mol of calcium/mol of protein) and annexin II bound only 0.3-0.6 calcium ions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Translational control of maternal glp-1 mRNA establishes an asymmetry in the C. elegans embryo.

In C. elegans, the glp-1 gene encodes a membrane receptor that is required for anterior cell fates in the early embryo. We report that GLP-1 protein is localized to anterior blastomeres in 2- to 28-cell embryos. By contrast, glp-1 mRNA is present in all blastomeres until the 8-cell stage. Furthermore, the glp-1 3' untranslated region can restrict translation of a reporter mRNA to anterior blastomeres. Therefore, the translation of maternal glp-1 mRNA is temporally and spatially regulated in the C. elegans embryo. The regulation of maternal glp-1 mRNA has striking parallels to the regulation of maternal hunchback mRNA in the Drosophila embryo. Thus, the establishment of embryonic asymmetry in diverse organisms may involve conserved mechanisms of maternal mRNA regulation.

Animals↗
PubMed1994

GLP-1 is localized to the mitotic region of the C. elegans germ line.

In C. elegans, germline mitosis depends on induction by the somatic distal tip cell (DTC) and on activity of the glp-1 gene. Using antibodies to GLP-1 protein, we have examined GLP-1 on western blots and by immunocytochemistry. GLP-1 is tightly associated with membranes of mitotic germline cells, supporting its identification as an integral membrane protein. Furthermore, GLP-1 is localized within the germ line to the mitotic region, consistent with the model that GLP-1 acts as a membrane receptor for the distal tip cell signal. Unexpectedly, GLP-1 and the zone of mitosis extend further than the DTC processes. We present three models by which the DTC may influence GLP-1 activity and thereby determine the zone of mitosis. The spatial restriction of GLP-1 appears to be controlled at the translational level in hermaphrodites. We suggest that down-regulation of GLP-1 may be required to effect the transition from mitosis into meiosis.

Animals↗
PubMed1993

Translational regulation of tra-2 by its 3' untranslated region controls sexual identity in C. elegans.

C. elegans hermaphrodites make sperm and then oocytes in an otherwise female animal. Gain-of-function mutations in the sex-determining gene tra-2 (tra-2(gf)) transform hermaphrodites into females (spermless hermaphrodites). The tra-2(gf) mutations map to a perfect direct repeat in the 3' untranslated region; each repeat is called a direct repeat element (DRE). Three experiments demonstrate that DREs repress tra-2 at the translational level. First, tra-2(gf) mRNAs are associated with larger polysomes than are their wild-type counterparts. Second, translation of a reporter RNA is inhibited by DREs. Third, disruption of DREs does not increase tra-2 mRNA levels. An RNA binding activity specifically associates with the DREs. We propose that tra-2 translation is inhibited by association of an RNA binding-factor with the DREs and that this translational control is essential for development of C. elegans as a hermaphrodite/male species.

Animals↗
PubMed1993

Social work technician program.

The increasing use of US emergency departments has resulted in increased patient delays and resultant dissatisfaction on the part of the patients and their families. Furthermore, recent studies have indicated that these delays may jeopardize the health of the ED patient. We describe a program designed to address these concerns. The Social Work Technician Program employs social work students nearing graduation as liaisons between medical personnel and ED patients and their families. This program has been found to promote patient satisfaction and welfare while providing the students with a valuable educational experience.

Clinical Clerkship↗
PubMed1993

Clinical study of bendazac lysine for in vivo contact lens cleaning.

Bendazac Lysine (BZL), a nonsteroidal anti-inflammatory drug (NSAID), prevents denaturation of proteins secondary to chemical and physical activity. The major protein deposited on soft contact lenses is lysozyme, derived from the preocular tear film. We evaluated the effectiveness of eye drops formulated with BZL for in vivo prevention of proteinaceous deposits on contact lenses and found them to be useful in inhibiting protein deposition during a 6-month clinical trial.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1993

Acute pulmonary disease in the aged.

Due to the changes within the respiratory system that occur physiologically with aging as well as preexisting medical conditions, elderly persons are less tolerant of the insults discussed in this article. For this reason, clinicians must be particularly vigilant in their approach to the diagnosis and management of pulmonary complaints in this population.

Acute Disease↗
PubMed1991

The red blood cell distribution width.

The availability of automated blood cell analyzers that provide an index of red blood cell distribution width (RDW) has lead to new approaches to patients with anemia. While the emergency physician is primarily responsible for the detection of patients with anemia, the inclusion of the RDW in the complete blood count has made diagnosing certain anemias easier, especially those that are microcytic. The derivation of the RDW and its clinical application to emergency physicians is discussed and a categorization of anemias based on the mean corpuscular volume (MCV) and RDW is included.

Adult↗
PubMed1991

Flumazenil for the reversal of refractory benzodiazepine-induced shock.

Benzodiazepines are known to cause central nervous system and centrally mediated cardiovascular depression. The benzodiazepine antagonist flumazenil has been shown to antagonize benzodiazepine-induced central nervous system depression. We report a case in which cardiovascular depression secondary to benzodiazepine use was reversed by this agent.

Aged↗
PubMed1989

The cilia of Paramecium tetraurelia contain both Ca2+-dependent and Ca2+-inhibitable calmodulin-binding proteins.

To identify protein targets for calmodulin (CaM) in the cilia of Paramecium tetraurelia, we employed a 125I-CaM blot assay after resolution of ciliary proteins on SDS/polyacrylamide gels. Two distinct types of CaM-binding proteins were detected. One group bound 125I-CaM at free Ca2+ concentrations above 0.5-1 microM and included a major binding activity of 63 kDa (C63) and activities of 126 kDa (C126), 96 kDa (C96), and 36 kDa (C36). CaM bound these proteins with high (nanomolar) affinity and specificity relative to related Ca2+ receptors. The second type of protein bound 125I-CaM only when the free Ca2+ concentration was below 1-2 microM and included polypeptides of 95 kDa (E95) and 105 kDa (E105). E105 may also contain Ca2+-dependent binding sites for CaM. Both E95 and E105 exhibited strong specificity for Paramecium CaM over bovine CaM. Ciliary subfractionation experiments suggested that C63, C126, C96, E95, and E105 are bound to the axoneme, whereas C36 is a soluble and/or membrane-associated protein. Additional Ca2+-dependent CaM-binding proteins of 63, 70, and 120 kDa were found associated with ciliary membrane vesicles. In support of these results, filtration binding assays also indicated high-affinity binding sites for CaM on isolated intact axonemes and suggested the presence of both Ca2+-dependent and Ca2+-inhibitable targets. Like E95 and E105, the Ca2+-inhibitable CaM-binding sites showed strong preference for Paramecium CaM over vertebrate CaM and troponin C. Together, these results suggest that CaM has multiple targets in the cilium and hence may regulate ciliary motility in a complex and pleiotropic fashion.

Actin Cytoskeleton↗
PubMed1989

New mutants of Paramecium tetraurelia defective in a calcium control mechanism: genetic and behavioral characterizations.

The k-shy mutants of Paramecium tetraurelia are altered in several Ca2+-dependent functions which regulate ciliary motility. The isolation, genetics, and phenotypes of these mutants are described. Of six independent isolates, all contained recessive single-factor mutations and comprise two unlinked loci, ksA and ksB. All k-shy strains showed prolonged backward swimming responses to depolarizing stimuli, but gave infrequent responses to some stimuli. At least four k-shy strains displayed temperature sensitivity. Neither ksA nor ksB was allelic or linked to dancer, a mutation causing weak Ca2+ current inactivation and prolonged backward swimming. Analysis of ks+; Dn double mutants revealed synergism between the two mutations. The ksA mutant survived Ba2+ solutions longer than wild type, but was more sensitive to K+. Together with previous studies, these results are consistent with a defect in reducing intracellular Ca2+ causing both prolonged ciliary reversal and reduced Ca2+ channel activity due to more active Ca2+-dependent feedback mechanisms. The integration of the Ca2+-dependent stimulatory and inhibitory functions is therefore dependent on ks+ gene functions. The ksA mutant was rescued by microinjection of wild-type cytoplasm, suggesting a possible behavioral assay for factors related to the ksA+ gene product.

Animals↗
PubMed1988

Selective application of cervical spine radiography in alert victims of blunt trauma: a prospective study.

Four hundred sixty-seven adult victims of blunt trauma undergoing cervical spine radiography (CSR) were prospectively studied to identify any clinical parameters which would aid in the selective application of CSR. Eight persons (1.7%), six of whom were alert and two who presented comatose, sustained cervical spine injuries. In this study, persons injured in falls demonstrated a statistically significant greater risk of cervical spine injury compared to those injured in motor vehicle accidents (p = 0.001). In alert trauma victims, a statistical correlation with cervical spine injury was noted for individuals who had complaints of neck discomfort (p = 0.028) and for patients who manifested tenderness to neck palpation (p = 0.000039). No cervical spine injury was noted in any alert, not intoxicated, neurologically intact patient who had no complaints of neck discomfort upon questioning or palpation. We conclude that alert trauma victims with no complaints of neck discomfort upon questioning and with no tenderness on neck palpation need not undergo CSR.

Adolescent↗
PubMed1987

Electrophysiological evidence suggests a defective Ca2+ control mechanism in a new Paramecium mutant.

A new mutant of Paramecium tetraurelia, k-shyA, was characterized behaviorally and electrophysiologically. The mutant cell exhibited prolonged backward swimming episodes in response to depolarizing conditions. Electrophysiological comparison of k-shyA with wild type cells under voltage clamp revealed that the properties of three Ca2+-regulated currents were altered in the mutant. (i) The voltage-dependent Ca2+ current recovered from Ca2+-dependent inactivation two- to 10-fold more slowly than wild type. Ca2+ current amplitudes were also reduced in the mutant, but could be restored by EGTA injection. (ii) The decay of the Ca2+-dependent K+ tail current was slower in the mutant. (iii) The decay of the Ca2+-dependent Na+ tail current was also slower in the mutant. All other membrane properties studied, including the resting membrane potential and resistance and the voltage-sensitive K+ currents, were normal in k-shyA. Considered together, these observations are consistent with a defect in the ability of k-shyA to reduce the free intracellular Ca2+ concentration following stimulation. The possible targets of the genetic lesion and alternative explanations are discussed. The k-shy mutants may provide a useful tool for molecular and physiological analyses of the regulation of Ca2+ metabolism in Paramecium.

Animals↗
PubMed1987

Quincke's disease of the uvula.

Upper airway compromise may be the result of numerous factors, among which a swollen uvula should be considered in the differential diagnosis. We present a case of a 21-year-old man who presented with complaints of throat discomfort, altered voice, and tachypnea secondary to acute uvular edema. The patient was treated with sympathomimetic drugs both by injection and by inhalation with complete resolution of the swelling and his symptoms within 30 minutes. The uvula is a potential cause of upper airway obstruction and should be examined in persons presenting with airway-related complaints.

Adult↗