PubMed Health⌕ Search

Biomedical subjects

W Armstrong

Publications and source records attributed to W Armstrong.

29 records · Page 2Linked to original sources
PubMed1989

Molecular basis of spontaneous mutation at the aprt locus of hamster cells.

Mutations occurring spontaneously at the hamster aprt locus were examined at the base-pair level by amplifying target sequences using the polymerase chain reaction and then directly sequencing the double-stranded products. In a collection of 89 sequenced genes, all types of mutations were found, with transitions (mostly G.C to A.T) constituting the largest class (35%), transversions accounting for 27%, and small deletions/duplications for 25%. Simple base substitutions were distributed throughout the aprt structural gene with few sites having recurring mutations and G.C base-pairs being the predominant substitution target. Small deletions, on the other hand, were not distributed so evenly, being concentrated in a region of aprt rich in short direct and inverted repeat sequences. The base substitutions were predominantly missense, while about 10% produced nonsense codons. Splice junctions, and start and stop codons were also significant targets for mutation. No alterations were detected in three aprt-deficient strains after sequencing all exons and substantial upstream and downstream regions.

Adenine Phosphoribosyltransferase↗
PubMed1989

Non-invasive diagnosis of ischemic heart disease using stress thallium scintigraphy and digital exercise 2-dimensional echocardiography.

The introduction of computer technology has overcome many of the technical difficulties in performing and interpreting echocardiograms obtained from exercising individuals and has made stress echocardiography a potentially practical examination. Additional data, however, are necessary to establish the accuracy of exercise echocardiography. The purpose of this study is to compare exercise echocardiography and planar thallium studies for accuracy in detecting coronary artery disease. The study was performed on 50 patients, 41 of whom underwent coronary angiography. For the remaining 9 patients accuracy was defined as concordance of clinical information, treadmill ECG results, thallium data and the exercise echocardiogram. If there was any discrepancy among these tests, the patient was not included in the analysis. The sensitivity of exercise 2D digital echocardiography was comparable to stress thallium (0.86 vs 0.85) and was better than treadmill test alone (0.66). There were no false positive tests with echocardiographic study, while 1 false positive thallium examination was detected. The diagnostic accuracy of stress echocardiography was 0.90, stress thallium 0.85 and treadmill test only 0.75. In conclusion, exercise echocardiography appears to give results comparable to stress planar thallium studies. In addition, the ultrasonic procedure has several advantages: it is totally non-invasive, does not require a reperfusion study 4 hours later, avoids radiation and is less expensive.

Adult↗
PubMed1986

Oxitropium bromide, a new anticholinergic bronchodilator.

Oxitropium bromide (OB) is a quaternary ammonium congener of hyoscine with anticholinergic properties. We studied its bronchodilating properties in 14 patients with chronic obstructive lung disease without features of asthma in whom theophylline and other bronchodilators were withheld. Five doses of OB(20, 40, 100, 200, and 400 micrograms) as well as 150 micrograms of isoproterenol (ISO) and placebo were administered by metered-dose inhaler on separate occasions in a double-blind fashion. Pulmonary function (flow volume loops and airways resistance), blood pressure, and pulse rate were measured at baseline and periodically for eight hours after drug administration. Onset of bronchodilator effect was within five minutes for OB (P less than .025). Duration of action of OB was at least eight hours (P less than .025). The dose response characteristics of OB were examined by correlating the log dose with the areas under the time-FEV1 curve (r = .97, P less than .01), the time-forced vital capacity curve (r = .98, P less than .01), and the time-SGAW curve (r = .83, P less than 0.1). For FEV1, doses of 40 to 400 micrograms were significantly better than placebo and 100 to 400 micrograms were better than ISO (P less than .01). For forced vital capacity, all doses of OB were better than placebo (P less than .05). For SGAW, the response to the 100- and 400-micrograms doses were significantly better than placebo and isoproterenol (P less than .05). There were no significant effects of OB on pulse, blood pressure, or electrocardiogram. No side effects were noted from the use of OB.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Prediction of survival in progressive systemic sclerosis by multivariate analysis of clinical features.

The records of 64 patients with progressive systemic sclerosis (PSS) were reviewed. More than 100 items from the patient's history, physical examination, and laboratory tests were encoded. A two-tailed Gehan's test was used to evaluate the effect of each variable on patient survival. Variables significant at the 0.05 level were then analyzed simultaneously, using the Cox regression model, in order to determine which clinical features are most predictive of survival in PSS. By Cox regression, the presence of an S3 gallop and advanced age at onset of PSS related negatively to survival. The relative risk of death for a patient with an S3 gallop was 5.44 (ratio of risk) times that for a patient without an S3 gallop, and the risk of death for a 70-year-old patient at disease onset was 20 times that of a 20-year-old patient at disease onset. In addition, when patient selection was taken into account, corticosteroid administration had a significant effect, and seemed to actually shorten survival. Although one of the factors, age at onset, is not modifiable, the presence of either variable should alert the clinician to the patient being at high risk for short survival. The application of this technique should also prove helpful in analyzing the efficacy of various proposed therapies.

Adolescent↗
PubMed1983

Effects of KCN and Salicylhydroxamic Acid on the Root Respiration of Pea Seedlings.

Polarography, using cylindrical platinum electrodes, proved suitable for measuring changes in the internal apical O(2) concentration of the primary root of pea (Pisum sativum L. cv Meteor) effected by KCN and/or salicylhydroxamic acid (SHAM) in the bathing medium. An electrical rootaeration analog was used to help evaluate some of the results. Concentrations of KCN </=0.05 millimolar had no significant effect. In response to 0.1 millimolar KCN, the O(2) concentration rose substantially for approximately 2 hours, then declined, and after 10 hours had frequently fallen below the pretreatment level. Such changes suggest an initial inhibition of cytochrome oxidase-mediated O(2) uptake followed by an induction of the alternative, cyanide-resistant respiratory pathway. These treatments proved nonlethal. Changes in O(2) concentration similar to those described for 0.1 millimolar KCN were observed in response to 1 and 10 millimolar KCN but these treatments were lethal and the root apex became soft and often appeared flooded. Roots survived and showed no significant responses when treated with SHAM at concentrations </=5 millimolar. However, when the alternative pathway had been (apparently) induced by 0.1 millimolar KCN, the addition of 5 millimolar SHAM to the bathing medium caused a substantial and persistent rise in the root apical O(2) concentration, suggesting that this (nonlethal) concentration of SHAM could indeed inhibit O(2) uptake via the cyanide-resistant pathway.It is concluded that while O(2) uptake normally occurs by the cytochrome pathway in the primary pea root, the alternative, cyanide-resistant pathway can be induced by 0.1 millimolar KCN.

Journal Article↗
PubMed1982

Organization of the facial nucleus in the rat.

The topographic organization of the facial nucleus motoneurons in the rat was investigated with the horseradish peroxidase retrograde tracing method using tetramethyl benzidine as a chromogen. Facial muscles were 'represented' on the facial nucleus in an orderly fashion. For example, the motoneurons supplying the rostral (nasolabial) muscles are laterally placed, whereas those supplying the caudal (auricular) muscles are medially placed. Notable findings in this study are: (i) the relatively unremarkable size of the nasolabial (vibrissal) muscle representation; there does not seem to be an increase in size of this part of the nucleus, commensurate with the specialized sensory functions of the vibrissal area of the face and (ii) the neurons supplying the posterior belly of the digastric are found in the suprafacial nucleus which lies about 1 mm dorsal to the main facial nucleus.

Animals↗
PubMed1978

Permeability of interstitial space of muscle (rat diaphragm) to solutes of different molecular weights.

The transport characteristics of muscle interstitial space were determined using an isolated rat diaphragm preparation. Permeability of the interstitial space for extracellular solutes is one-thirtieth to one-fiftieth that of an equivalent thickness of water. However, most of this low permeability can be accounted for by correcting for the tortuosity and relative volume of interstitial space. The estimated diffusivity of solutes (mol. wt. 100-70,000) in the interstitial space of muscle is only about one-half to one-fifth less than in water alone.

Animals↗