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Biomedical subjects

D D Brown

Publications and source records attributed to D D Brown.

At least 55 records · Page 3Linked to original sources
PubMed1993

Survival from out-of-hospital cardiac arrest: effects of patient age and presence of 911 Emergency Medical Services phone access.

The purpose of this investigation was to determine factors associated with survival from out-of-hospital cardiac arrest, including effects of 911 Emergency Medical Services telephone access and the age of patient. Subjects included 1,753 prehospital cardiac arrest patients in Iowa. Patient survival status and other variables were compared for patients with access to a 911 service with those who did not, and for different age categories, using univariate associations and multivariate logistic regression analysis. The presence of 911 telephone access was significantly associated with survival from out-of-hospital cardiac arrest (9.18% versus 5.35% survival for 911 versus no 911 groups, respectively). This association was partially the result of the significant association of 911 with decreased time from collapse to call for help, decreased time to cardiopulmonary resuscitation (CPR), and decreased time to first shock (if in ventricular fibrillation [VF]). Younger age was significantly associated with survival in univariate analyses (8.94% versus 6.26% survival for younger versus older age groups, respectively), but this was not an independent association, which is indicated by the lack of significance of age in the multivariate model.

Age Factors↗
PubMed1993

Citizen response to cardiopulmonary emergencies.

Since 1985, it has become apparent that the key to survival from adult sudden cardiac death is prompt defibrillation. Any delay from the time of collapse to the initial countershock will decrease the likelihood of survival. It also has been determined that CPR performed by lay rescuers is not begun promptly and, once started, often is performed for more than one minute before the emergency medical services (EMS) system is accessed, which significantly delays the time to defibrillation. In adults, therefore, the rescuer should phone first to activate the EMS system before performing CPR. In the pediatric population, respiratory arrests are far more common than cardiac arrests. Therefore, a rescuer should perform one minute of rescue support before activating the EMS system (a concept termed phone fast). It is recognized that this change is dependent upon a national EMS system that is still evolving. It is hoped that this change to phone first and phone fast will provide an impetus for rapid development of the EMS infrastructure.

Cardiopulmonary Resuscitation↗
PubMed1993

Re-examination of the incidence of exercise-induced hypoxaemia in highly trained subjects.

The purpose of this study was to examine the occurrence of exercise-induced hypoxaemia (EIH) during maximal exercise in highly trained athletes. Eleven trained cyclists (mean(s.d.) age 23(3.5) years; mean(s.d.) VO2max 66.9(4.8) ml kg-1min-1) performed a continuous, multistage (270 kpm min-1) cycle ergometer test to exhaustion. Measurements of arterial oxygen-haemoglobin saturation (%HbO2) were obtained simultaneously at rest, every 2 min during exercise, and at maximum exercise capacity from arterial blood sampling (%SaO2) and ear oximetry (%SpO2). Exercise induced hypoxaemia (%HbO2 < or = 91%) was present in 64% of the athletes examined when EIH was determined using pulse oximetry, whereas none of the subjects exhibited EIH when %HbO2 was determined using arterial blood. At rest the values for %HbO2 were similar with mean(s.d.) %SaO2 being 97.3(0.6)% and mean(s.d.) %SpO2 being 96.5(1.6)%. During exercise, statistically significant differences were found for %HbO2 between arterial blood and ear oximetry at the 6-min, 8-min, and maximal exercise sampling times (repeated measures analysis of variance, P < 0.05). The results indicate that ear oximetry overestimates the incidence of EIH and underestimates the oxyhaemoglobin saturation in highly trained cyclists during exercise in comparison with those measurements made from arterial blood.

Adult↗
PubMed1992

Thyroid hormone-induced gene expression changes in the developing frog limb.

Greater than 120 genes are up-regulated in Xenopus laevis limb buds within the first 24 h after induction of metamorphosis by thyroid hormone. Fourteen of these have been isolated and characterized. Four encode heat shock proteins. The identified regulated genes have in common a relatedness with cell growth as exemplified by the serum response of quiescent fibroblasts. Some of the genes respond directly to hormone. However, the majority appear to be secondary response genes judging from their delayed kinetics and cycloheximide sensitivity. This indicates that there are at least two periods of gene expression change in the first 24 h. DNA replication increases in the second 24 h. Growth of the limb bud occurs for several days before the genes that characterize terminal differentiation of its cell types are up-regulated.

Animals↗
PubMed1992

The readers' NIH.

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Financing, Government↗
PubMed1992

Genomic organization and alternative promoter usage of the two thyroid hormone receptor beta genes in Xenopus laevis.

Each of the two Xenopus laevis thyroid hormone receptor beta genes is at least 70 kilobases in length with similar intron-exon organization. There are up to eight alternatively spliced exons in the 5'-untranslated region. Excluding the extreme amino terminus, each receptor is encoded by six exons spanning about 6 kilobases of the genome, in which each of the two zinc fingers that comprise the DNA-binding domain is encoded by a separate exon and the hormone-binding domain is split into three exons. The last exon of the coding region also contains at least 600 base pairs of the 3'-untranslated region, which is about 8 kilobases. Each of the receptor genes has two promoters and just one of them is up-regulated in tadpoles by the administration of thyroid hormone.

Amino Acid Sequence↗
PubMed1992

The regulation of thyroid hormone receptor beta genes by thyroid hormone in Xenopus laevis.

The mRNA level of the two Xenopus laevis thyroid hormone receptor beta (TR beta) genes is up-regulated in tadpoles and cultured cells by the addition of thyroid hormone (TH). Up-regulation of transcripts of the 5' most exon is detectable 2-3 h before that of full-length TR beta mRNA, strongly suggesting that up-regulation is under transcriptional control. The TH-induced up-regulation in cultured cells is inhibited by cycloheximide when measured either by a transcription initiation assay that measures transcripts of the 5' most exon or by synthesis of full-length TR beta mRNA. From this we conclude that in cultured cells protein synthesis is required for up-regulation of TR beta mRNA. The up-regulation of TR beta mRNA by TH in tadpoles is only partially inhibited by protein synthesis inhibitors. A survey of "thyroid response" genes in the literature reveals that the reported change in gene expression is, in most cases, sensitive to protein synthesis inhibition. This is true of genes with demonstrable thyroid hormone response elements. If an unknown protein must be synthesized to effect up-regulation of a thyroid hormone response gene, it calls into question assays that only take into account the binary reaction between thyroid hormone receptor and a putative thyroid hormone response element.

Animals↗
PubMed1992

The use of conjunctival flaps in the treatment of herpes keratouveitis.

Conjunctival flaps have been used in the treatment of corneal diseases since the 1800s, although in recent years their use has decreased. In selected cases, however, the placement of a conjunctival flap still may be the treatment of choice. We report our experience with the use of conjunctival flaps in patients with herpes keratouveitis who had persistent corneal epithelial defects. Preoperatively, all patients had chronic or recurrent epithelial defects and intraocular inflammation with or without recurrent live viral infection requiring frequent medicine application and office visits. Postoperatively, all patients had an intact, healthy ocular surface and a noninflamed eye requiring few to no medications and infrequent office visits. No patient has had recurrent live viral activity.

Conjunctiva↗
PubMed1992

Diagnostic image use by nonradiologist lecturers in an introductory clinical medicine course.

RATIONALE AND OBJECTIVES: A curriculum-tracking study was designed to determine the type and amount of diagnostic imaging used by nonradiologists teaching an Introduction to Clinical Medicine (ICM) course to second-year medical students. METHODS: Two second-year medical students independently recorded the type and number of images shown, the length of the lecture, the departmental affiliation of the lecturer, and the amount of time devoted to either didactic radiology or radiologic images during each of 288 lectures in the 1990 ICM course. RESULTS: A total of 35.2% of the lectures presented some type of diagnostic image, and 7.0% of all lecture time was devoted to radiology. No mammography or diagnostic nonangiographic interventional images were shown. CONCLUSIONS: The results suggest that a more consistent and uniform presentation of diagnostic images across disciplines is required, emphasizing the need for more coordination of radiology instruction through consultation with the Department of Radiology.

Clinical Medicine↗
PubMed1991

A gene expression screen.

A gene expression screen identifies mRNAs that differ in abundance between two mRNA mixtures by a subtractive hybridization method. The two mRNA populations are converted to double-stranded cDNAs, fragmented, and ligated to linkers for polymerase chain reaction (PCR) amplification. The multiple cDNA fragments isolated from any given gene can be treated as alleles in a genetic screen. Probability analysis of the frequency with which multiple alleles are found provides an estimation of the total number of up- and down-regulated genes. We have applied this method to genes that are differentially expressed in amphibian tadpole tail tissue in the first 24 hr after thyroid hormone treatment, which ultimately induces tail resorption. We estimate that there are about 30 up-regulated genes; 16 have been isolated.

Alleles↗
PubMed1991

Cocaine-induced myocardial infarction in patients with normal coronary arteries.

OBJECTIVE: To review the reported cases of myocardial infarction temporally related to recreational and topical anesthetic use of cocaine, with special regard for underlying etiologic factors in patients subsequently found to have normal coronary arteries. DATA SOURCES: Personal records of three cases and a comprehensive literature review using MEDLINE and supplemented by Index Medicus and the bibliographies of case reports. DATA SYNTHESIS: A total of 114 cases of cocaine-induced myocardial infarction were identified. The coronary anatomy was defined by angiography or autopsy in 92 patients, 38% of whom had normal coronary arteries. In these 35 patients (average age, 32; range, 21 to 60 years), myocardial infarction typically involved the anterior left ventricular wall (77%). Moderate cigarette smoking with one or fewer associated coronary risk factors was prevalent (68%). Focal coronary vasospasm was shown convincingly in only two cases. Intracoronary thrombus was initially found on 9 of 11 angiograms (82%) done within 12 hours of the myocardial infarction. Experimental evidence suggests that cocaine has direct and indirect sympathomimetic effects on vascular smooth muscle, attenuates endothelium vasodilator capacity, exerts a potent depressant effect on cardiac myocytes, and promotes atherogenesis. CONCLUSIONS: Cocaine-induced myocardial infarction in patients with normal coronary arteries probably involves adrenergically mediated increases in myocardial oxygen consumption, vasoconstriction of large epicardial arteries or small coronary resistance vessels, and coronary thrombosis. Accelerated atherosclerosis and impairment of endothelium vasodilator function may occur after chronic cocaine use.

Adult↗
PubMed1991

Two forms of elongation factor 1 alpha (EF-1 alpha O and 42Sp50), present in oocytes, but absent in somatic cells of Xenopus laevis.

We have purified and partially sequenced the EF-1 alpha protein from Xenopus laevis oocytes (EF-1 alpha O). We show that the two cDNA clones isolated by Coppared et al. (Coppard, N. J., K. Poulsen, H. O. Madsen, J. Frydenberg, and B. F. C. Clark. 1991. J. Cell Biol. 112:237-243) do not encode 42Sp50, as claimed by these authors, but two very similar forms of EF-1 alpha O (EF-1 alpha O and EF-1 alpha O1). 42Sp50 is the major protein component of a 42S nucleoprotein particle that is very abundant in previtellogenic oocytes of X. laevis, 42Sp50 differs from EF-1 alpha O not only by its amino acid sequence, but also by several properties already reported. In particular, 42Sp50 has a low EF-1 alpha activity. It is distributed uniformly in the cytoplasm of previtellogenic oocytes, in contrast to EF-1 alpha O which is concentrated in a small region of the cytoplasm, known as the mitochondrial mass or Balbiani body.

Amino Acid Sequence↗
PubMed1991

Lisfranc fracture-dislocations: report of two cases.

Lisfranc fracture-dislocation is a rare but sometimes dramatic injury, most commonly associated with motor vehicle and industrial accidents, and falls from heights. Radiographic examination is a crucial point in the work-up of these patients. The most common findings on plain radiographs are separation of the bases of the first and second metatarsals and the "fleck" sign, a bony fragment resulting from a fracture of the base of the first or second metatarsal. These fractures are demonstrated in the two cases presented. We conclude that these lesions can usually be diagnosed with plain radiographs if scrupulous attention is paid when evaluating the normal anatomic alignments. Computed tomography should be reserved for equivocal cases.

Adult↗
PubMed1991

Effect of caffeine ingestion on alveolar ventilation during moderate exercise.

The purpose of this study was to examine the effect of caffeine ingestion on alveolar ventilation and physiological dead space ventilation during exercise in high and low caffeine users. Eleven males (mean age 26.4 +/- 5.4 years), classified as either high caffeine users (greater than 350 mg/d, n = 6) or low caffeine users (less than 50 mg/d, n = 5) performed two treadmill exercise conditions at a constant work rate (50% VO2max) 45 min after ingestion of 3.3 mg of caffeine/kg body weight or placebo using a double-blind protocol. Open circuit spirometry was used to determine ventilatory and gas exchange variables every 10 min during the 50 min of walking exercise. Analysis of variance showed that caffeine produced significant differences in alveolar ventilation (VA) and the physiological dead space ventilation/tidal volume ratio (VD/VT) with VA increased from 1.36 to 1.54 L/breath and VD/VT decreased from 22.3 to 20.5% between the placebo and caffeine treatments, respectively. Additionally, caffeine ingestion produced a significant increase in tidal volume (VT) and a significant decrease in frequency of breathing (fb). We conclude that caffeine consumed prior to exercise enhances ventilatory dynamics during exercise without regard to prior habitual caffeine consumption.

Adult↗
PubMed1990

Three genes under different developmental control encode elongation factor 1-alpha in Xenopus laevis.

We have cloned cDNAs encoding two variants of the elongation factor for protein synthesis in Xenopus laevis, called EF-1 alpha. One of these (42Sp50) is expressed exclusively in immature oocytes. It is one of two protein components of a 42S RNP particle that is very abundant in previtellogenic oocytes. The 42S RNP particle consists of various tRNAs, 5S RNA, 42Sp50 and a 5S RNA binding protein (42Sp43). A major function served by 42Sp50 appears to be the storage of tRNAs for later use in oogenesis and early embryogenesis. The second EF-1 alpha variant (EF-1 alpha O) is expressed mainly in oocytes but transiently in early embryogenesis as well. Its mRNA cannot be detected after neurulation in somatic cells. EF-1 alpha O is closely related to a third EF-1 alpha (EF-1 alpha S), discovered originally by Krieg et al. (1). EF-1 alpha S is expressed at low levels in oocytes but actively in somatic cells. The latter two proteins are very similar to known eukaryotic EF-1 alpha from other organisms and presumably function in their respective cell types to support protein synthesis.

Amino Acid Sequence↗
PubMed1990

A finger protein structurally similar to TFIIIA that binds exclusively to 5S RNA in Xenopus.

A 5S RNA binding protein (p43) in Xenopus is a major constituent of oocytes and comprises part of a 42S ribonucleoprotein storage particle. We have cloned and sequenced p43 cDNA from X. laevis and X. borealis as well as the cDNA for X. borealis TFIIIA. Like TFIIIA, p43 has nine zinc fingers, seven of which are exactly the same size as their counterparts in TFIIIA. Amino acid homology between the two proteins is restricted mainly to conserved residues characteristic of zinc fingers. In contrast to TFIIIA, which binds specifically to both 5S RNA and 5S RNA genes, p43 binds exclusively to 5S RNA.

Amino Acid Sequence↗
PubMed1990

Physiological and biomechanical differences between wheelchair-dependent and able-bodied subjects during wheelchair ergometry.

The purpose of this study was to compare the physiological and biomechanical responses of wheelchair-dependent persons (WCD) to able-bodied persons (AB) during manual wheelchair ergometry. Five WCD and five AB performed a discontinuous wheelchair ergometer test starting at 12.8 W at 30 rev.min-1 (57 m.min-1) with increments of 7.0 W at 6-min intervals. Biomechanical data were collected 3.5 min into each stage followed by the collection of physiological data. After the fifth stage, peak oxygen consumption was determined by having the subject work against a resistance of 14.7-19.6 N at 30 rev.min-1. The WCD had significantly higher net mechanical efficiency at 26.7, 33.6 and 40.6 W in comparison to the AB. The WCD had significantly greater shoulder extension at the point of initial wheel contact as measured by the shoulder angle, while the AB had significantly greater shoulder range of motion at all work rates in comparison to the WCD. The results demonstrate that a significant physiological difference exists in the manner by which WCD and AB accomplish wheelchair ergometry. The biomechanical differences between AB and WCD were found to be a prominent factor contributing to the higher mechanical efficiency of WCD over AB. It was concluded that basic physiological and biomechanical differences exist between WCD and AB in manual wheelchair locomotion and that these differences are important considerations to the interpretation of data in wheelchair ergometry studies.

Adult↗