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Biomedical subjects

R Welsh

Publications and source records attributed to R Welsh.

34 records · Page 2Linked to original sources
PubMed1994

Characterization of a new ion selective electrode for ionized magnesium in whole blood, plasma, serum, and aqueous samples.

Results from a novel ion selective electrode (ISE) for ionized magnesium (Mg2+) correlate well with atomic absorption spectroscopy on aqueous solutions containing from 0.1-3.0 mmol MgCl2/L. Day to day precision (coefficient of variation) of the electrode on protein-based controls is < 4%; aqueous-based controls < 6%. The new ISE is selective for Mg2+ with a selectivity constant for Ca2+ (KMgCa) of 8 x 10(-2). Adding pathophysiologic concentrations of Cd2+, Ca2+, Cu2+, Fe3+, K+, Na+, or Zn2+ to serum and aqueous solutions gave negligible to minimal changes in measured Mg2+. Ligand binding studies in aqueous solution indicate that pathophysiologic concentrations of different anions (e.g. heparin, lactate, bicarbonate, phosphate, acetate and sulfate) bind to Mg2+, effectively reducing its concentration in solution. Likewise, silicon (as either found in Vacuutainer tubes or as chlorosilane) failed to exert any significant effect on measured Mg2+. Addition of Intralipid (up to 500 mg/dL) gave negligible to minimal changes in Mg2+. Mg2+ measurements on whole blood, plasma, and serum for a given human subject's samples are virtually identical, at least within the reference range for Mg2+. Typically, Mg2+ is 71% of TMg, but varies from subject to subject; i.e. Mg2+ cannot be predicted from TMg. Clinical studies revealed that the Mg2+/TMg ratio could be remarkably consistent in sequential samples (e.g., throughout the course of coronary bypass surgery) taken from one patient, but that this ratio could differ dramatically from the ratio in sequential samples taken from another. Mg2+ is held within a narrow range (0.53-0.67 mmol/L) in normal, healthy subjects when compared to TMg (0.70-0.96 mmol/L).

Adult↗
PubMed1992

Comparison of Doppler echocardiography and cardiac catheterization in patients requiring valve surgery: search for a 'gold standard'.

OBJECTIVE: To compare the sensitivities of Doppler echocardiography and cardiac catheterization in the diagnosis of severe valvular heart disease in patients requiring valve surgery. DESIGN: Retrospective analysis of Doppler echocardiograms and cardiac catheterizations. SETTING: Tertiary referral cardiovascular centre in a university setting. PATIENTS: Sixty-nine patients undergoing valve surgery between July 1988 and July 1990. RESULTS: The sensitivities of echocardiography and cardiac catheterization were 84 and 87%, respectively (P = 1.0) in 32 patients who underwent aortic valve surgery primarily for severe aortic stenosis; 83 and 67%, respectively (P = 1.0) in six patients with severe aortic regurgitation, and 100 and 85%, respectively (P = 1.0) in seven patients with combined severe aortic stenosis and regurgitation. The sensitivities of echocardiography and cardiac catheterization in 11 patients who underwent mitral valve surgery for severe mitral stenosis were 73 and 91%, respectively (P = 0.6) and 69 and 92%, respectively (P = 0.3) in 13 patients with severe mitral regurgitation. Sensitivities of echocardiography and cardiac catheterization in the diagnosis of severe tricuspid regurgitation in five patients who had tricuspid valve repair were 100 and 80%, respectively (P = 1.0). Two patients with severe aortic stenosis by echocardiography, but not by catheterization, did not undergo aortic valve replacement during valvular surgery; both required aortic valve replacement within two years of initial surgery because of heart failure. Four patients with severe tricuspid regurgitation identified by echocardiography did not have tricuspid repair; three had pulmonary hypertension and these patients had resolution of tricuspid regurgitation on follow-up. One patient with severe tricuspid regurgitation and absence of pulmonary hypertension required reoperation for tricuspid valve repair 10 months after initial operation. CONCLUSIONS: The sensitivity of echocardiography and cardiac catheterization in the detection of severe valvular lesions requiring surgery is similar. Discordant results should be reviewed carefully with knowledge of the inherent pitfalls of both techniques in order to ensure optimal patient outcome.

Adult↗
PubMed1982

Histologic typing of lung cancer in Louisiana.

To determine whether histologic patterns differed in the high- and low-lung cancer mortality parishes (counties) of Louisiana and whether the findings in the state differed from those in other parts of the United states, we studied the available histopathologic materials for 272 persons of the 815 who died of lung cancer in ten southern, nonurban Louisiana parishes during a seven-year period from 1971-1977. Squamous-cell carcinoma and small-cell anaplastic carcinoma were the most common tumor types, closely followed in frequency by adenocarcinoma, confirming reports by other investigators of a change during the past decade in the prevalence of various histopathologic types of lung cancer. The distribution of histopathologic types was not different for high- and low-mortality parishes but differed significantly from other areas of the U. S. Three persons had diagnoses consistent with pleural mesothelioma. Occupational histories obtained from relatives showed that one of those persons was a homemaker and the other two were sugarcane farmers with no discernable exposure to asbestos.

Adenocarcinoma↗
PubMed1977

Staining myelin in brain with gallein: a new method.

A procedure is described in which gallein, mordant violet 25, C.I. 45445, is used to demonstrate myelinated nerve fibers in animal brain. Specimens are fixed in 10% neutral buffered formalin and processed in a routine manner. Microsections are stained in an iron gallein solution with subsequent differentiation in 0.25% oxalic acid and 0.1% sodium carbonate solutions that avoid overdifferentiation. Methyl green is used to demonstrate other tissue elements. Myelin is stained deep violet, as are erythrocytes, with neuronal cell bodies and microglia shades of green. The staining procedure requires 30 minutes.

Animals↗