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Biomedical subjects

M E Levin

Publications and source records attributed to M E Levin.

At least 19 recordsLinked to original sources
PubMed2006

The reactivity of sodium borohydride with various species as characterized by adiabatic calorimetry.

The reactivity of sodium borohydride in the presence of other species has been examined by adiabatic calorimetry. In combination with water, sodium borohydride exhibits an exotherm at room temperature accompanied by generation of gas (presumed to be hydrogen). Addition of potassium hydroxide to a sodium borohydride-water mixture is found to stabilize the solution and require a higher temperature for reaction to occur. However, if iron oxide is also included, reaction takes place near room temperature. Very rapid reaction was found when a metal chloride was brought in contact with a solution containing sodium borohydride, water, and potassium hydroxide. When sodium borohydride was added to an oxygenated hydrocarbon, reaction at room temperature also took place, but to a more limited extent. Peak temperatures above 200 degrees C and maximum pressures in excess of 2000 psia were observed in most cases. Kinetics extracted from the calorimetry data are presented for some of the sodium borohydride combinations.

Borohydrides↗
PubMed2006

Language as a barrier to care for Xhosa-speaking patients at a South African paediatric teaching hospital.

BACKGROUND: Disease is closely linked to the social context in which we live. Difficulty with communication, cultural incompatibility between patients and health care providers and socioeconomic obstacles are important barriers to quality care when doctors and patients come from different backgrounds and speak different languages. Red Cross War Memorial Children's Hospital (RCH) is a paediatric teaching hospital in Cape Town where staff members communicate mainly in English or Afrikaans, while many patients speak Xhosa as their first language. OBJECTIVES: The study aimed to identify barriers to optimal care for Xhosa-speaking parents of patients at RCH. The contribution of language difficulties was assessed as a possible barrier to health care for this group. DESIGN: A questionnaire was developed and administered to 53 Xhosa-speaking parents of children admitted to the short-stay ward at RCH. The questionnaire examined parents' perceptions of barriers to their children's care, using openended questions, closed-ended questions and selection from lists. RESULTS: Parents experienced significant structural and socioeconomic barriers to access of health care for their children. Language and cultural barriers were cited by more parents as a major barrier to health care than structural and socioeconomic barriers. Parents did not have access to same-language practitioners, as only 6% of medical interviews were conducted partly or wholly in the patient's home language. Of the 94% of interviews where no Xhosa was spoken by medical staff, 21% were conducted with the aid of an interpreter (formal or ad hoc) and in 79% no interpreter was used. Parents experienced difficulties with understanding the doctors (64%), making themselves understood (54%) and asking questions (38%). Sixty-nine per cent of parents were dissatisfied with communication between themselves and their doctors and 45% were concerned about negative effects of poor communication on them or their children. Parents tended to blame their own linguistic limitation rather than those of the doctors.

Adolescent↗
PubMed2006

Different use of medical terminology and culture-specific models of disease affecting communication between Xhosaspeaking patients and English-speaking doctors at a South African paediatric teaching hospital.

BACKGROUND: Language and cultural differences between patients and health care providers may have adverse health consequences. Red Cross War Memorial Children's Hospital is a paediatric teaching hospital in Cape Town where staff communicate mainly in English or Afrikaans, while many patients speak Xhosa as their first language. OBJECTIVES: To examine whether differences in the definitions of common respiratory medical terminology by patients and doctors cause miscommunication and to explore culture-specific models if used by parents in their definitions. DESIGN: In-depth, semi-structured interviews were conducted with three speech communities, viz. 8 English-speaking doctors and 33 Xhosa-speaking parents, educated to grade 12 level or less and recruited from two areas in the hospital, the short-stay ward (Xhosa s-s) and the allergy clinic (Xhosa allergy). The sum of both groups of Xhosa-speaking patients are referred to as 'Xhosa all'. Definitions were elicited for common respiratory terminology in both Xhosa and English. Contrastive linguistic analysis was used to identify the semantic properties for each group in order to condense the groups' definitions into representative 'core definitions'. Differences in the definitions of terminology were identified and words were classified as concordant (used in the same way) or discordant (used in different ways) by the three speech communities. RESULTS: Parents experience difficulty in understanding terms used by doctors and words in common use were understood differently by these two groups. Most Xhosa words were not in the doctors' vocabulary, and some common English words were not in the parents' vocabulary. Where words were in the vocabulary of both groups, significant differences existed in the number and range of definitions, with many clinically significant discordances of definition being apparent. Some common examples relevant to paediatric respiratory problems are presented. Three culture-specific explanatory models of respiratory illness, ingqele, xakaxa and idliso, are illustrated.

Child↗
PubMed2005

Kinetics of acid-catalyzed cleavage of cumene hydroperoxide.

The cleavage of cumene hydroperoxide, in the presence of sulfuric acid, to form phenol and acetone has been examined by adiabatic calorimetry. As expected, acid can catalyze cumene hydroperoxide reaction at temperatures below that of thermally-induced decomposition. At elevated acid concentrations, reactivity is also observed at or below room temperature. The exhibited reactivity behavior is complex and is significantly affected by the presence of other species (including the products). Several reaction models have been explored to explain the behavior and these are discussed.

Benzene Derivatives↗
PubMed2004

The reactivity of 1,3-butadiene with butadiene-derived popcorn polymer.

Adiabatic calorimetry performed on butadiene-derived popcorn polymer samples from industrial facilities has revealed exothermic behavior accompanied by non-condensible gas production, indicative of possible decomposition, at elevated temperatures. In the presence of low concentrations of 1,3-butadiene, reactivity is observed at temperatures of 60-70 degrees C; that is, 20-30 degrees C below those usually seen for butadiene alone. Once the butadiene is consumed, the reaction behavior reverts to that of the popcorn polymer alone. At higher butadiene concentrations, the low temperature reaction persists, eventually merging with typical butadiene behavior. The butadiene reactivity with popcorn polymer is attributed to polymerization reaction at free radical sites in the popcorn polymer. Different popcorn polymer samples exhibit distinct extents of reactivity, presumably depending on the nature and concentration of the free radical sites and the structure of the material. Uninhibited butadiene exposed to 100 psia air, which may act to generate peroxide species, shows a small, additional exotherm around 50-80 degrees C. Contact of butadiene with lauroyl peroxide, providing free radicals upon decomposition, generates an exotherm at temperatures as low as 60 degrees C.

Air Pressure↗
PubMed2003

The reactivity of ethylene oxide in contact with iron oxide fines as measured by adiabatic calorimetry.

Samples of various iron oxides suspended above ethylene oxide in an adiabatic calorimeter exhibit exothermic activity at temperatures as low as room temperature. A gamma-Fe(2)O(3) sample was found to show the highest reactivity with ethylene oxide. Ethylene oxide in combination with most of the iron oxide fines tested displayed exothermic activity below 100 degrees C. Self-heat rates near 2000 degrees C/min were observed for the gamma-Fe(2)O(3) fines while rates in excess of 100 degrees C/min were found for other fines (alpha-Fe(2)O(3) and hydrated alpha-Fe(2)O(3)). In two cases (alpha-Fe(3)O(4) and alpha-Fe(2)O(3)), pressurization rates above 1000 psi/min took place. No reactivity was observed for ethylene oxide with the FeO. Thermal inertia effects in commercial operation, such as heat uptake by the equipment to which fines are attached, are presumed to be a factor in limiting the occurrence of related exotherms in ethylene oxide manufacturing facilities.

Disinfectants↗
PubMed2001

Temporally and spatially regulated expression of a candidate G-protein-coupled receptor during cerebral cortical development.

Genes expressed in layer-specific patterns in the mammalian cerebral cortex may play a role in specifying the identity of different cortical layers. Using PCR-differential display, we identified a cDNA that encodes rCNL3, a gene cloned previously by sequence homology to G-protein-coupled receptors. rCNL3 is expressed predominantly in layers 2-4 of the young rat cortex and in the developing and adult striatum. Cortical expression of rCNL3 begins postnatally at P3 and continues at high levels until around P15, while striatal expression begins at E20 and continues through adulthood. rCNL3 expression is not detectable in the ventricular zone precursors that generate the neurons of layers 2-4. The expression pattern of rCNL3 in the developing cortex suggests that rCNL3 is not involved in the initial specification of laminar fate, but rather may be involved with later differentiation events within the superficial cortical layers.

Age Factors↗
PubMed1999

Cortical neurons require Otx1 for the refinement of exuberant axonal projections to subcortical targets.

Information processing in the nervous system depends on the creation of specific synaptic connections between neurons and targets during development. The homeodomain transcription factor Otx1 is expressed in early-generated neurons of the developing cerebral cortex. Within layer 5, Otx1 is expressed by neurons with subcortical axonal projections to the midbrain and spinal cord. Otx1 is also expressed in the precursors of these neurons, but is localized to the cytoplasm. Nuclear translocation of Otx1 occurs when layer 5 neurons enter a period of axonal refinement and eliminate a subset of their long-distance projections. Otx1 mutant mice are defective in the refinement of these exuberant projections, suggesting that Otx1 is required for the development of normal axonal connectivity and the generation of coordinated motor behavior.

Animals↗
PubMed1998

Prevention and treatment of diabetic foot wounds.

The diabetic foot ulcer is one of the most common and devastating complications of diabetes mellitus. These ulcers account for most of the hospital admissions for patients with diabetes, and they represent a common precursor for amputation. When a diabetic foot ulcer becomes infected, gangrene and amputation can follow in rapid succession. Recent reviews concerning diabetic foot lesions and amputations have stressed the magnitude and importance of aggressive management. This management is complicated, and typically requires radical débridement, appropriate antibiotics, non-weight-bearing, and vascular surgery when indicated. A variety of adjunctive therapy can be helpful, including hyperbaric oxygen and topical growth factors. The most important step in preventing ulceration of the foot is patient education in foot care.

Amputation, Surgical↗
PubMed1997

The diabetic foot.

Explore the source record for details and available documents.

Diabetic Foot↗
PubMed1996

Foot lesions in patients with diabetes mellitus.

Diabetic foot ulcers are common. If treatment is delayed or is inappropriate, the lesions can become infected, resulting in gangrene and amputation. Physicians and clinics that perform aggressive therapy for these ulcers, provide revascularization when indicated, practice a team approach, suggest the use of therapeutic shoes, and repeatedly educate patients in foot care have reduced their amputation rates by 50% or greater. Goals of the United States Department of Health for the year 2000 include a 40% reduction in the amputation rate in patients with diabetes. This should be the goal of everyone providing care for patients with diabetes.

Diabetes Complications↗
PubMed1995

Transcriptional regulation of repressor synthesis in mycobacteriophage L5.

Mycobacteriophage L5 is a temperate phage of the mycobacteria that forms stable lysogens in Mycobacterium smegmatis. Lysogeny is maintained by the putative repressor, the gene 71 product, which also mediates immunity to superinfection. We show here that there are three promoters located upstream of gene 71 which are active in an L5 lysogen but which do not require any phage-encoded proteins. In early lytic growth, gene 71 is also transcribed from a promoter, Pleft, located at the right end of the genome and which appears to be a target of gp71 regulation. A model is given for the regulation of L5 life cycles.

Amino Acid Sequence↗
PubMed1994

Otx1 and Otx2 define layers and regions in developing cerebral cortex and cerebellum.

Within the cerebral and cerebellar cortices, neurons are organized in layers that segregate neurons with distinctive morphologies and axonal connections, and areas or regions that correspond to distinct functional domains. To explore the molecular underpinnings of pattern formation in layered regions of the CNS, we have characterized the patterns of expression of two homeodomain genes, Otx1 and Otx2, by in situ hybridization during embryonic and postnatal development in the rat. Otx1 and Otx2 are vertebrate homologs of the Drosophila gap gene orthodenticle, and are expressed during the development of the murine CNS (Simeone et al., 1992). Here we report that Otx1 mRNA is expressed in a subpopulation of neurons within cortical layers 5 and 6 during postnatal and adult life. This gene is also expressed by the precursors of deep-layer neurons within the developing cerebral ventricular zone, but is apparently downregulated by the progenitors of upper-layer neurons; Otx1 is never expressed by the neurons of layers 1-4. The spatial and temporal patterns suggest that Otx1 may play a role in the specification or differentiation of neurons in the deep layers of the cerebral cortex. Within the cerebellum, mRNAs for Otx1 and Otx2 are found within the external granular layer (EGL), but in three spatially distinct domains. During postnatal development, Otx1 is expressed within anterior cerebellar lobules; Otx2 mRNA is localized posteriorly, and a region of overlap in mid-cerebellum defines a third domain in which both genes are expressed. The boundaries of Otx1 and Otx2 expression correspond to the major functional boundaries of the cerebellum, and define the vestibulocerebellum, spinocerebellum, and pontocerebellum, respectively. Spatially restricted patterns of hybridization are observed early in postnatal life, at times that correspond roughly to the invasion of spinal and pontine afferents into the cerebellum (Arsénio-Nunes and Sotelo, 1985; Mason, 1987). These results raise the possibility that Otx1 and Otx2 play a role in cerebellar regionalization during early development.

Amino Acid Sequence↗