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Biomedical subjects

S Shepherd

Publications and source records attributed to S Shepherd.

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

Three-dimensional magnetic resonance imaging evaluation of pediatric tracheobronchial tree.

Magnetic resonance imaging (MRI) of the airway has recently emerged as a diagnostic tool for evaluating tracheobronchial obstruction in pediatric patients. Computer-assisted reconstructions of transaxial images have enabled three-dimensional reconstructions of the airway to be manipulated in any plane and visualized in relation to adjacent anatomical structures. Eight patients in whom magnetic resonance imaging was used to diagnose a variety of airway obstructive lesions are presented. A protocol for the evaluation of pediatric tracheobronchial obstruction is presented, with the role of three dimensionally reconstructed MR imaging emphasized.

Airway Obstruction↗
PubMed1993

Alternative or additional medicine? An exploratory study in general practice.

In a South London general practice a substantial proportion of patients in some age groups (35 and 45 yr) had tried alternative treatment. Satisfaction with the outcome was limited. The use of alternatives was associated with higher general practice consultation rates, especially among women. Qualitative interviews with users suggested that rapid cures for chronic conditions were rarely expected; rather, an alternative explanation for health problems was sought and a greater sense of autonomy in dealing with them. Negative attitudes towards modern medicine arose from perceptions of excessive technological intervention and iatrogenic disorders arising from long term drug treatment.

Adult↗
PubMed1993

Evaporation versus iced peritoneal lavage treatment of heatstroke: comparative efficacy in a canine model.

The authors compared the speed of cooling and treatment efficacy for evaporative cooling versus iced peritoneal lavage in a canine heatstroke model. Nine random-source, mongrel dogs were anesthetized, shaved, and internally heated until the core temperature reached 43.0 degrees C. The animals were then randomly assigned to be cooled to 37 degrees C either by sterile normal saline (6 degrees C) continuous peritoneal lavage at 250 mL/min (n = 4), or by spraying with tap water (15 degrees C, 12 L/min) before a large fan blowing room temperature air (23 degrees C) across the dog at 0.5 m/sec from a height of 50 cm (n = 5). Temperatures were monitored by thermocouples in both tympanic membranes. Electrocardiogram, blood pressure, and pulse were continuously monitored. Evaporative cooling was as rapid as iced peritoneal lavage (0.18 +/- .03 versus 0.17 +/- .07 degrees C/min/m2, P = NS). All animals survived, although one animal in each treatment group demonstrated a moderate neurologic deficit when measured 48 hours following resuscitation. A simple noninvasive evaporative cooling technique, readily available in the emergency department, appears to be as rapid readily available in the emergency department, appears to be as rapid and effective as aggressive peritoneal lavage for cooling and treating heatstroke in the dog.

Animals↗
PubMed1993

Serologic and molecular studies of two kindreds expressing recombinant HLA DR1/DR2 haplotypes.

We have recently identified two unrelated kindreds in which DR1 and DR2 co-segregate as a single haplotype spanning several generations. Serology, PCR-RFLP and sequence-specific oligonucleotide probes were used to characterize the presence and segregation of the DRB1 and DRB5 loci in these two kindreds. In both families, the recombination resulted in co-expression of a DRB1 locus that encoded a DR1 serologic phenotype and a DRB5 locus that encoded a "short" DR2 serologic phenotype. One of these kindreds co-expressed the DR1 and DR15 (DRB5*01). The other kindred co-expressed the DR1 and DR16 (DRB5*02). Our data indicate that the recombination event occurred in the region between the DRB1 locus and the DRB5 locus. This recombinant haplotype produces a DR2 phenotype which lacks the epitopes normally encoded by the DRB1 locus, resulting in a serologic "short" antigen. The clinical significance of such a recombinational event becomes evident when patients with such a genotype require allogeneic bone marrow transplantation.

Alleles↗
PubMed1992

Sphingolipid long-chain-base auxotrophs of Saccharomyces cerevisiae: genetics, physiology, and a method for their selection.

A selection method for sphingolipid long-chain-base auxotrophs of Saccharomyces cerevisiae was devised after observing that strains that require a long-chain base for growth become denser when starved for this substance. Genetic analysis of over 60 such strains indicated only two complementation classes, lcb1 and lcb2. Mutant strains from each class grew equally well with 3-ketodihydrosphingosine, erythrodihydrosphingosine or threodihydrosphingosine, or phytosphingosine. Since these metabolites represent the first, second, and last components, respectively, of the long-chain-base biosynthetic pathway, it is likely that the LCB1 and LCB2 genes are involved in the first step of long-chain-base synthesis. The results of long-chain-base starvation in the Lcb- strains suggest that one or more sphingolipids have a vital role in S. cerevisiae. Immediate sequelae of long-chain-base starvation were loss of viability, exacerbated in the presence of alpha-cyclodextrin, and loss of phosphoinositol sphingolipid synthesis but not phosphatidylinositol synthesis. Loss of viability with long-chain-base starvation could be prevented by also blocking either protein or nucleic acid synthesis. Without a long-chain-base, cell division, dry mass accumulation, and protein synthesis continued at a diminished rate and were further inhibited by the detergent Tergitol. The cell density increase induced by long-chain-base starvation is thus explained as a differential loss of cell division and mass accumulation. Long-chain-base starvation in Lcb- S. cerevisiae and inositol starvation of Inos- S. cerevisiae share common features: an increase in cell density and a loss of cell viability overcome by blocking macromolecular synthesis.

Cell Division↗
PubMed1992

Capsular polysaccharide serotyping scheme for Staphylococcus epidermidis.

A scheme for the capsular typing of Staphylococcus epidermidis that is based on direct slide agglutination between proteinase-treated bacterial cells and specific antisera is described. Antisera were prepared from serum from rabbits immunized with two selected strains of encapsulated S. epidermidis isolated from bacteremic patients. Antisera were shown to be type specific and designated type 1 and type 2. Blood isolates of S. epidermidis from hospitals in different locations within the United States and Europe were serotyped, and it was found that over 90% of all strains were of type 1 or type 2. Type-specific antibodies mediated type-specific opsonophagocytosis and killing of S. epidermidis. The specificity was shown to be due to two distinct capsular polysaccharides. The data presented in this report may open a new window on the pathogenesis of S. epidermidis which could lead to the development of new vaccines and therapies.

Antibodies, Bacterial↗
PubMed1991

The cutaneous microcirculation of the forearm in young and old subjects.

Previous studies have shown a reduced cutaneous circulatory response to direct heat stress in the forearm circulations of older (60 to 80 year) subjects. The purpose of this study was to test the hypothesis that this aging effect is due to a reduced ability of the cutaneous microvessels in the forearm to respond to direct heat. Two groups of male subjects consented to participate; a group of 15 young individuals (Y; 20-39 year) and a group of 11 older (O; 60-79 year) individuals. The subjects rested in a supine position with the right forearm situated on the stage of a Leitz epiilumination microscope which was used to view the superficial cutaneous microvessels. The width of the red cell column (WRC), an index of vascular diameter, and the blood cell velocity (BCV) within the microvessels were measured by videomicroscopy at the presenting skin temperature (Ts) of 32 degrees, and then again after Ts had been elevated to 35 degrees then 40 degrees. At a Ts of 32 degrees, WRC and BCV for the Y group, respectively, averaged 6.6 microns and 0.22 mm/sec. Corresponding averages for the O subjects were 8.4 microns and 0.17 mm/sec. Between-group differences were not significant. At a skin temperature of 40 degrees, BCV was significantly higher compared to that at 32 degrees and 35 degrees for both groups (P less than 0.05); whereas, WRC did not significantly change. There were no significant between-group differences in BCV at the higher two temperatures. These results argue against a diminished blood flow response of superficial microvessels being responsible for the reduced cutaneous circulatory response to heat stress in older individuals.

Adult↗
PubMed1991

Effects of invariant sympathetic activity on cutaneous circulatory responses to heat stress.

This study investigated the role of sympathetic withdrawal on blood flow responses in cutaneous arteriovenous anastomoses (AVAs) and capillaries to direct and indirect heat stress. This was achieved by clamping sympathetic activity (SC) to the tail of anesthetized rats so that constrictor tone remained invariant during exposure of either the animal's tail (direct heating) or body (indirect heating) to a 35 degrees C environment. Flow through the AVAs in the tail was evaluated by laser-Doppler flowmetry (LDF), while capillary flow was investigated by videodensitometry measurements of blood cell velocity (CBV) in single capillaries within the subepidermal vascular plexus. Both direct and indirect heating significantly increased LDF and CBV. In comparison to blood flow responses in sham-operated control rats, the SC procedure resulted in significantly lower LDF responses to both direct and indirect heat stress. By contrast, the response of CBV was not significantly affected by SC during either mode of heating. These results indicate that the withdrawal of sympathetic constrictor tone plays a role in the response of cutaneous AVAs, but not precapillary arterioles, to direct as well as indirect heat stress. Additional studies on unanesthetized animals showed that superimposing body heating on a base of local heating elicited a further increase in LDF, suggesting that local heating does not deplete neural mediated dilatory reserve.

Animals↗
PubMed1991

Age-related potentiation of the cutaneous capillary blood flow response to heat stress.

This study tested the hypothesis that the rarefaction of cutaneous capillaries with age is compensated by an increase in the response of remaining capillaries to heat stress. Experiments were performed on unanesthetized male Sprague Dawley rats of the following age groups: young (Y--age 4 mo.), middle aged (M--age 16 mo.) and old (O--age 27 mo.). The subepidermal vascular plexus of the tail was viewed by video microscopy from which measurements of blood cell velocity (BCV) in single plexus capillaries and the density of flowing capillaries (DFC) were made. The animal's body and tail were housed in separate chambers for respectively indirect and direct heat stress trials. At a neutral temperature of 25 degrees C there were no significant age differences in BCV, but DFC was decreased from the Y to the M to the O groups. During an indirect heat stress of 35 degrees C, there was a modest increase in DFC and the Y greater than M greater than O rank order persisted. By contrast, all groups experienced a marked increase in BCV during both indirect and direct heat stress, and the degree of the response was significantly greater for the O rats compared to the M or Y groups. These results support the hypothesis being tested.

Aging↗
PubMed1990

A model preclinical, clinical, and graduate educational curriculum in emergency medicine for medical students and rotating residents.

The Society for Academic Emergency Medicine model curriculum for medical students and rotating residents was developed over a two-year period. The document was created as a complementary work to the undergraduate Core Content to provide appropriate emphasis, structure, and suggestions on the teaching of emergency medicine core curriculum topics at all levels. Consensus on the curriculum contents was reached from a national sample of emergency medicine educators. An educational matrix format was used to enhance flexibility based on the educational level of the learner and the instructional strengths of the teacher, and allowing for incorporation of a problem-based learning format. An outline of document contents and representative samples from each section are included; the entire document is available from SAEM.

Curriculum↗
PubMed1989

numb, a gene required in determination of cell fate during sensory organ formation in Drosophila embryos.

Neurons and support cells of each sensory organ in Drosophila embryos are most likely derived from a single precursor cell. This cell lineage is affected in numb mutants. Morphological alterations of sensory structures, as well as changes in the number of cells expressing cell type-specific markers, indicate that sensory neurons in numb mutant embryos are transformed into lineage-related nonneuronal support cells. Thus the numb gene controls the fate of progeny derived from sensory organ precursors. The numb gene has been isolated by the plasmid rescue method. The structure of its predicted product is discussed.

Amino Acid Sequence↗
PubMed1989

Audit for all--but how?

Audit will soon be common-place and obligatory. The task will be difficult to perform manually but becomes simple and straightforward using the practice computer. Extensive clinical and financial audit may be easily derived from practice daily activities recorded on the computer.

Family Practice↗
PubMed1989

Sleep pattern alterations and brief airway obstructions in overweight infants.

The sleep characteristics of 10 overweight infants were monitored polysomnographically and compared with those of 10 age- and sex-matched control infants with no weight excess. The infants were selected from a well-babies clinic. Infants were assigned to the weight excess group if their weight was greater than 120% of ideal weight/height for age. There were six boys and four girls in both groups, with a median age of 23.5 weeks in the weight excess group and 22.0 weeks in the control group. The infants with weight excess spent significantly less time sleeping in non-rapid-eye-movement (NREM) sleep stage 3-4 and more time in indeterminate sleep than their matched controls. The infants with weight excess had also significantly more gross body movements and more sleep stage shifts than the control infants. Brief airway obstructions were found significantly more frequently in the weight excess group than in the control group. Seven overweight infants showed a total of 74 brief airway obstructions; 41 occurred in NREM sleep stage 1 or 2 and 14 in rapid-eye-movement (REM) sleep. The median duration of the obstructive episodes was 8 s (range 3-13 s). Of the 10 control subjects, only 2 had one obstructive episode each, lasting 3 and 4 s and occurring during REM sleep. Only one mixed apnea of 6.5 s was recorded in a 39-week-old overweight boy. The obstructive episodes were accompanied by a median fall in heart rate of 9% (range 0-51%) and by a median fall in oxygen saturation of 0.9% (range 0-10%).(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Obstruction↗