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Biomedical subjects

T Simon

Publications and source records attributed to T Simon.

At least 109 records · Page 6Linked to original sources
PubMed1988

A GABAergic mechanism in the posterior hypothalamus modulates baroreflex bradycardia.

Several laboratories have shown that electrical stimulation in the posterior hypothalamus inhibits the baroreceptor reflex. However, the results of these studies are difficult to interpret since it is not known if the attenuation of the baroreflex results from activation of axons of passage or from stimulation of hypothalamic cell bodies. The purpose of this study was to determine the effects of chemical stimulation of posterior hypothalamic neurons upon the baroreflex. Arterial baroreceptors were activated by increasing the pressure in an isolated carotid sinus in anesthetized cats and by an increased arterial pressure following intravenous injection of phenylephrine in both anesthetized cats and rats. The baroreceptor reflex was evaluated before and after a GABA antagonist (picrotoxin) was microinjected into the posterior hypothalamus. The bradycardia, but not the depressor response, elicited by increasing carotid sinus pressure was attenuated after unilateral microinjections of picrotoxin into the posterior hypothalamus. In addition, the heart rate response to a phenylephrine-evoked rise in arterial pressure was reduced after picrotoxin was microinjected in both the cats and the rats. Microinjection of a GABA agonist (muscimol) into the same hypothalamic site returned resting heart rate and arterial pressure to levels seen prior to picrotoxin. These results show that the depression of the bradycardia produced by hypothalamic stimulation results from activation of cell bodies in the posterior hypothalamus. This hypothalamic effect upon the baroreflex bradycardia may involve a GABAergic mechanism.

Animals↗
PubMed1988

Localization of the McLeod locus (XK) within Xp21 by deletion analysis.

The McLeod phenotype is an X-linked, recessive disorder in which the red blood cells demonstrate acanthocytic morphology and weakened antigenicity in the Kell blood group system. The phenotype is associated with a reduction of in vivo red cell survival, but the permanent hemolytic state is usually compensated by erythropoietic hyperplasia. The McLeod phenotype is accompanied by either a subclinical myopathy and elevated creatine kinase (CK) or X-linked chronic granulomatous disease (CGD). Seven males with the McLeod red-blood-cell phenotype and associated myopathy but not CGD, one male with the McLeod phenotype associated with CGD, and two males known to possess large deletions of the Duchenne muscular dystrophy (DMD) locus were studied. DNA isolated from each patient was screened for the presence or absence of various cloned sequences located in the Xp21 region of the human X chromosome. Two of the seven males who have only the McLeod phenotype and are cousins exhibit deletions for four Xp21 cloned fragments but are not deleted for any portion of either the CGD or the DMD loci. Comparison of the cloned segments absent from these two McLeod cousins with those absent from the two DMD boys and the CGD/McLeod patient leads to the submapping of various cloned DNA segments within the Xp21 region. The results place the locus for the McLeod phenotype within a 500-kb interval distal from the CGD locus toward the DMD locus.

Adult↗
PubMed1987

CAP Comprehensive Blood Bank Survey--1984.

An average of 2750 laboratories participated in the 1984 Comprehensive Blood Bank Survey of the College of American Pathologists. Results from 16 laboratories were utilized to validate results and assure maintenance of specimen character during shipment. Results of ABO grouping, D typing, special antigen typing, antibody detection, and antibody identification by participants remained good and are discussed. Special ungraded samples were provided as additional challenges. The results of these studies and the responses to supplementary questions are discussed.

ABO Blood-Group System↗
PubMed1984

Mesenteric venous thrombosis as sole complication of decompression sickness.

A 27-year-old male commercial diver developed massive mesenteric venous thrombosis following a dive. Symptoms at presentation included abdominal pain and diarrhea. A severe upper gastrointestinal bleed developed. Exploratory laparotomy demonstrated 130 cm of infarcted small bowel. The pathophysiologic events in decompression sickness predispose to vascular obstruction and venous infarction. This patient had a past history of possible thrombophlebitis and pulmonary embolism associated with diving but no identifiable coagulopathy.

Adult↗
PubMed1984

99mTc-pyrophosphate imaging in patients with acute myocardial infarction: comparison of planar imaging with single-photon tomography with and without blood pool overlay.

To test the hypothesis that single-photon emission computed tomography (SPECT) of 99mTc-pyrophosphate (99mTc-PPi) with and without the overlay of tomographic blood pool scintigrams might detect small infarcts not identified by planar imaging, 52 patients were studied 3.2 +/- 2.0(SD) days after hospital admission for suspected acute myocardial infarction. Patients were chosen prospectively for tomographic study primarily, but not exclusively, because planar four-view imaging with 99mTc-PPi was either negative or equivocal. SPECT was performed with a commercial rotating detector system immediately after planar imaging on one occasion. Corresponding 99mTc-PPi and blood pool sections were mapped into opposite halves of a bichromic color table and displayed as an overlay. Planar images, SPECT and SPECT with blood pool overlay were interpreted separately and in random order without knowledge of clinical data. Seventeen patients had transmural infarcts (four anterior, 13 inferior), 19 had nontransmural infarcts, and 16 patients did not have acute myocardial infarction. The sensitivity of SPECT with blood pool overlay was significantly better than planar imaging for the entire group with myocardial infarction (97% vs 78%; p less than .025); this was primarily due to increased sensitivity in the detection of nontransmural myocardial infarction (95% vs 67%; p less than .05), although in one additional patient inferior transmural myocardial infarction was also detected by the SPECT overlay technique. The specificities of the SPECT overlay technique and planar imaging were not significantly different; however, receiver operating characteristic analysis showed enhanced observer confidence with the tomographic method. SPECT without overlay was intermediate in sensitivity and specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1980

Theophylline pharmacokinetics: variations between two similar study populations using oral oxtriphylline syrup.

The pharmacokinetics of two unmatched populations of asthmatic children, one from an asthmatic convalescent center in Denver and the other from an urban outpatient clinic, are compared after single and repeated dosing of a new asthma formulation, oxtriphylline syrup. Significant differences (p less than 0.05) in populations' theophylline total body clearance, apparent volume of distribution and absorption rates suggest future studies of multiple center design representing patterns of asthma more typical to the population at large would be more appropriate for selection of theophylline dosage guidelines.

Administration, Oral↗
PubMed1980

Pharmacokinetics and taste acceptance of an alcohol-free oxtriphylline solution.

As follow-up to earlier studies done on the pharmacokinetics of theophylline preparations in young children, an alcohol-free oxtriphylline syrup preparation was studied. Oxtriphylline syrup demonstrated no appreciable change in the pharmacokinetic parameter of half-life in this young age group. Therapeutic dose relationship were studied in conjunction with trough level measurements. Patient acceptance of this preparation is judged to be excellent.

Asthma↗