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Biomedical subjects

R A Thomas

Publications and source records attributed to R A Thomas.

At least 37 records · Page 2Linked to original sources
PubMed1993

The influence of maternal nicotine exposure on neonatal lung alveolar epithelial status: an electron microscope study.

The aim of the present study was to investigate the effect of maternal nicotine exposure (1 mg nicotine/kg body mass/day) on neonatal lung alveolar epithelial cells. Rats (Wistar descendants) were used. The data illustrate that maternal nicotine exposure during pregnancy and lactation resulted in alveolar fenestrations, blebbing and rupturing of the blood-air barrier. The type I pneumocyte appears to be more sensitive to the effect of nicotine than the type II pneumocytes.

Animals↗
PubMed1993

Advanced use of tissue adhesive in hair transplantation.

BACKGROUND: Cobblestoning is an unsightly result of graft elevation in the recipient site after hair transplantation. OBJECTIVE: To describe the use of tissue adhesives for the avoidance of cobblestoning. RESULTS: The long-term cosmetic appearance of hair transplants may be improved through the use of cyanoacrylate adhesives is the virtual elimination of the common problem of graft elevation or cobblestoning, which produces an unsightly bumpiness in the recipient area. The choice of type of adhesive and the method of application are central to successful use of this technique. CONCLUSION: The indirect benefits of elimination of the need for postoperative bandages and restrictions in activities couple with the cosmetic results to produce a high degree of patient satisfaction.

Alopecia↗
PubMed1993

Heart rate response to exercise in normal women.

Heart rate is known to increase under the influence of increased sympathetic stimulation rates during exertion or stress. Few data are available regarding the rate response to exercise near the fatigue limit, for normal women. The effects on heart rate were studied of fatigue limiting exercise in 87 asymptomatic, normal female subjects employing a bicycle ergometer exercise protocol. The heart rate response to imposed exercise power closely followed a monotonic increasing, negative exponential function. Different age groups followed the same form of function but differed in parameter values. Group fitting was useful to develop parameters with which one group may be compared to another, establish referent ranges, and gain insight into cardiovascular models of exercise physiology.

Adolescent↗
PubMed1993

Significant left ventricular hypertrophy in subjects with normal resting pressures but exaggerated pressure response during light exertion.

Concentric left ventricular hypertrophy (LVH) frequently occurs in subjects with normal resting systolic and diastolic pressures (SP and DP, respectively). LVH in this normotensive-hypertrophic group (NH) may be due to an abnormally exaggerated pressure response to exercise. The SP and DP responses to exercise were studied in 130 subjects free from coronary artery disease or cardiomyopathy. The NH subjects (n = 35) had normal resting pressure (SP < or = 140 and DP < or = 85 mmHg) and increased LV wall thickness (T) by echocardiography (T > 1.1 cm). A normal control group (NN) (n = 57) and a hypertensive control group (HH) (n = 23) were simultaneously evaluated. The original groups, subgroups censored for age and weight, and matched-pair subgroups demonstrated greater exercise SP for NH than for NN (p < 0.005). Moreover, the rate of SP increase with exercise was greater for NH than for NN or HH (p < 0.05). Hence, an exaggerated exercise SP response may have been the stimulus for LVH in these NH subjects.

Adult↗
PubMed1990

Effects of a buffered propionic acid in diets on the performance of broiler chickens and on microflora of the intestine and carcass.

A buffered propionic acid (BPA) was added to broiler diets fed in floor pens with litter. The BPA was fed continuously at 0, .2, .4, and .8% in Trial 1 and at 0 and .4% in Trial 2. The BPA was also fed at .4% for the last 7 days in Trial 2. Natural salmonellae exposure versus periodic dosage with Salmonella typhimurium was compared in Trial 2. In Trial 1, the BPA supplement had no adverse effects on growth, feed utilization, or abdominal fat with a significant (P less than or equal to .05) increase in the female dressing value at .8% of buffered propionic acid. The total number of coliforms and of Escherichia coli in the duodenum were significantly reduced by .4% BPA; in the jejunum, by all levels used in the trials; and in the ileum, by .4% and .8% of buffered propionic acid. The intestinal pH was not influenced by the BPA addition. In Trial 2, the BPA at .4% fed continuously had no adverse effect on growth, feed utilization, the abdominal fat of females, or the dressing percentage of males while significantly reducing the abdominal fat for males and increasing the dressing percentage for females. Feeding .4% BPA for the last 7 days had no effect on any of these parameters. Periodic dosage with S. typhimurium had no effect on body weight, feed utilization, or abdominal fat and significantly increased the dressing percentage. There was a significant interaction between the Salmonella dosage and the time of feeding BPA on dressing percentage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Embryologic and other developmental considerations of thirty-eight possible variants of the DiGeorge anomaly.

The DiGeorge anomaly (DGA) represents a polytopic developmental field defect that can be caused by a number of different chromosomal, mendelian, toxic, or metabolic factors operating in early embryonic life. If the affected field is thought to be focused on either the fourth branchial arch or the third branchial pouch, with variable cephalad or caudad extension, 38 different combinations of malformations can include DiGeorge anomalies, 24 complete and 14 partial DGA, with the constraints that the field defect must be contiguous (involvement of more than one branchial arch or pouch requires involvement of all intervening arches or pouches) and complete (all derivatives of an affected branchial arch or pouch are deficient). The types and relative frequencies of abnormalities of structures other than the thymus and parathyroid glands in these possible "subsets" of DGA are discussed, and the need for more data on their occurrence in patients diagnosed as having DGA is emphasized.

Branchial Region↗
PubMed1986

Development of electrocardiographic teaching materials using an MC68000-based, interactive graphics microcomputer.

Interactive computer-graphics methods of computer-aided design (CAD) have been applied to problems in physical science and industry for several years; however, at the present time CAD methods have not been widely used to solve similar problems in medical education. Electrocardiogram waveform fabrication for the production of teaching materials seemed to be a well-defined area for CAD application. The availability of inexpensive, 16/32 bit word, MC68000-based microcomputers (e.g. Apple, Macintosh) and interactive graphics software (e.g. MacPaint and MacDraw) seemed to provide the necessary tools to make this application. This paper describes the authors' initial experience (from June 1984 to March 1985) in developing and employing an interactive computer graphics routine to produce ECG teaching materials.

Cardiovascular Diseases↗
PubMed1986

Abnormal growth of the thyroid cartilage in the DiGeorge syndrome.

Larynges from 17 patients with DiGeorge syndrome (DGS) and from 14 patients with tetralogy of Fallot (TOF) (11 non-DGS and 3 possible but unproven DGS) were dissected, measured, and compared to a control population of comparable body length. The patients with DGS and the 3 patients with TOF suspected of having DGS showed the following: small thyroid cartilages with increased anterior angle, abnormally short superior cornua, low ratio of mean superior cornual length to distance between superior cornual tips, and delayed time of maximal rate of increase in superior cornual length relative to increase in body length. The hypoplasia, delayed maximal growth rate and persistent fetal shape of the thyroid cartilage (predominantly a derivative of the fourth branchial arch) in DGS, indicates that the causative process in the syndrome affects not only the third and fourth branchial pouches, but also, by a contiguous field defect, other derivatives than great vessels of the fourth-sixth branchial arches.

DiGeorge Syndrome↗
PubMed1986

Description of a novel microcomputer program to analyze left ventricular segmental wall motion during normal sinus rhythm and sinus tachycardia.

The authors have written a program to describe left ventricular (LV) regional wall motion (RWM) for a Tektronix 4051 graphic system and an MC68000, 32-bit word based microcomputer utilizing interactive graphics methods. Proper wall motion of 16 defined regions of the LV endocardial perimeter (RAO angiographic views) were computed from the magnitudes of fixed vectors fixed to analogous positions along the LV perimeter from end-diastole to end-systole (Figure 1). It was assumed that (1) LV contraction, tangential to the perimeter, produced RWM at large angles to the direction of contraction, and (2) LV contraction occurred uniformly along the anterolateral and posteromedial perimeters. All motion vectors were computed following digitization of the LV perimeters from projected images of 35-mm cineangiographic frames corrected for linear and nonlinear distortion. Digitization input was accurate to less than 0.3 mm and area computation demonstrated errors of less than 1.5%. A normal group (NG) without coronary artery (CA) disease (N = 31) defined a set of Gaussian distributed referent values for mean WM (magnitude of motion vectors) for all segments. WM amplitudes for the CA disease group (N = 125) demonstrated significant diviation in the areas supplied by occluded or stenosed coronary arteries. Qualitative and quantitative evaluation of the adequacy of coronary circulation and/or collateral vessel development could be made by inspection of WM amplitude computer plots. Proper WM was found to be highly specific for numbers and distribution of coronary arteries diseased.

Cineangiography↗
PubMed1985

The nucleotide sequence of tobacco rattle virus RNA-2 (CAM strain).

The nucleotide sequence of the smaller genomic strand (RNA-2) of the bipartite tobacco rattle virus (CAM strain) has been determined. RNA-2 is capped at the 5' terminus and contains 1799 nucleotide residues. There is a single 223 codon long open reading frame extending from nucleotide 574 to 1242 which designates a protein of Mr 23,654. The derived amino acid composition, in percent, matches that previously determined for the virus capsid protein. The long open reading frame is flanked by 5' and 3' untranslated regions of 573 and 554 nucleotides, respectively. The 5' leader sequence contains two different sets of direct repeats, one of 119 nucleotides and the other of 76. It also contains 13 apparently unused AUG codons, four of which lie in the same frame as the capsid protein cistron. The 3' terminal sequence of RNA-2 is identical to that of the larger genomic strand (RNA-1) for 459 nucleotides.

Amino Acid Sequence↗
PubMed1978

Adenosine production in the ischemic kidney.

We conducted experiments to determine (1) tissue, blood, and urine levels of adenosine produced by the ischemic kidney under conditions of renal artery occlusion, and (2) the site(s) of production and release of adenosine by the kidney. Concentrations of adenosine, inosine, and hypoxanthine in the dog urine were found to increase after 2 minutes of renal artery occlusion as were concentrations of these metabolites in renal tissue after 10 minutes of renal artery occlusion. Renal venous plasma levels of inosine and hypoxanthine also were elevated after 3 minutes of arterial occlusion. In modified stop-flow experiments, adenosine appeared in the urine in a peak that corresponded most closely with proximal tubule fluid. 5'-Nucleotidase, the enzyme which catalyzes the dephosphorylation of 5'-AMP or 5'-IMP to adenosine or inosine, respectively, was found to be located primarily on the external membranes and mitochondria of proximal tubule cells, but not in distal tubule or collecting duct cells. Since adenosine has been demonstrated to elicit renal vasoconstriction and is produced by the ischemic kidney, it is suggested that adenosine may be involved in the mediation of postocclusion renal ischemia.

Adenosine↗