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Biomedical subjects

S Lewis

Publications and source records attributed to S Lewis.

At least 379 records · Page 21Linked to original sources
PubMed1986

Fourteen years' experience with the Björk-Shiley tilting disc prosthesis.

Between 1970 and 1984, 1,574 Björk-Shiley valve prostheses have been implanted in 1,171 patients in Glasgow. Between 1970 and 1980, 1,023 standard disc prostheses were implanted in 729 patients: 184 had aortic valve replacement, 323 mitral, and 222 multiple valve replacement. Between 1980 and 1984, 551 convexo-concave valves were implanted in 442 patients: 125 had aortic, 228 mitral, and 89 multiple valve replacement. Concomitant coronary artery bypass grafting was performed in 9.2% of the latter group as compared with 2.7% of the earlier group. The overall hospital (30 day) mortality for the group with the standard disc prosthesis was 10.4% and for patients with the convexo-concave prosthesis, 7.0%. Cumulative follow-up extends to 4,125 patient-years--standard disc group 3,378 patients-years, range 4 to 14 years (mean 5.2 years); convexo-concave group 747 patient-years, range 1.5 to 5.3 years (mean 1.9 years). The late mortality is 3.8% per patient-year--standard disc group 2.9% per patient-year and convexo-concave group 4.3% per patient year (no significant difference). Actuarial survival rate at 12 years for the whole group, excluding operative deaths, is 69.4% +/- 6.3%. The freedom from all valve-related complications at 12 years is 65.9% +/- 6.5%. there is no significant difference in the incidence of most major complications between the standard disc and convexo-concave prostheses apart from the occurrence of mitral valve thrombosis (p less than 0.05) in the standard disc group and outlet strut fracture (p less than 0.005) in the convexo-concave group. These results confirm the excellent long-term performance of the Björk-Shiley tilting disc prosthesis.

Actuarial Analysis↗
PubMed1985

DNA elements are asymmetrically joined during the site-specific recombination of kappa immunoglobulin genes.

Immunoglobulin K genes are constructed during lymphocyte differentiation by the joining of two DNA elements, VK and JK, to form both a VKJK coding unit and a reciprocal recombination product. The two products formed in single VK-to-JK joining events can be directly isolated through the use of a retrovirally introduced recombination substrate. The structural analysis of a number of recombinants and the derivation of secondary recombination products define some of the basic features of the mechanism of immunoglobulin gene assembly.

Animals↗
PubMed1985

Gas chromatographic-mass spectrometric determination of isotopic enrichment of 6-15NH2 in adenine nucleotides.

A gas chromatographic-mass spectrometric method for the determination of isotopic abundance in [6-15NH2]adenine nucleotides is described. The method involves formation of the di-t-butyldimethylsilyl (TBDMS) derivative of adenine following isolation of the nucleotide fraction with solid-phase ion-exchange chromatography and subsequent acid hydrolysis of nucleotides to free base. Mass spectra for both adenine-diTBDMS and [6-15NH2]adenine-diTBDMS were obtained to identify those ions containing the 6-NH2 moiety. The base peak (m/z 306) was formed by loss of C4H9 (57) and constitutes approximately one-third of the total ion current. Using selected ion monitoring of the m/z 306/m/z 307 ratio, levels of isotopic abundance of 1.0-50.0 mol% excess could be measured reproducibly with the injection of 10-20 pmol of the adenine-diTBDMS derivative obtained from isolated rat hepatocytes. Confirmation that measured isotopic abundance was referable to labeling of the 6-15NH2 group was obtained by oxidation of adenine to hypoxanthine and determination of enrichment in the hypoxanthine-diTBDMS derivative. The method was used to study the formation of [6-15NH2]adenine nucleotides during the incubation of isolated rat hepatocytes with [15N]alanine. A level of approximately 6.0 mol% excess was observed at 60 min incubation.

Adenine↗
PubMed1985

Contemporary developments in thin-layer chromatography.

Qualitative and quantitative applications of thin-layer chromatography (TLC) in the biomedical and pharmaceutical fields are briefly surveyed. Some recent developments, including high-performance TLC (HPTLC) and reversed-phase TLC (RPTLC), together with techniques such as multiple development and continuous development, are considered. Instrumentation for HPTLC, and new developments in the detection and spectroscopic characterization of substances on TLC plates, are briefly described.

Journal Article↗
PubMed1985

Evaluation of acute scrotum pain with testicular scanning.

Emergency room physicians frequently are faced with the evaluation of the patient with acute testicular pain. The rapid differentiation between testicular torsion and acute epididymitis is necessary although frequently difficult due to an atypical presentation. We describe four patients with testicular pain in whom testicular scanning provided useful adjunctive information regarding diagnosis. This technique clearly differentiates acute torsion, acute epididymitis, testicular rupture, and missed torsion with abscess formation, prompting appropriate therapy in each case. Testicular scanning provides a rapid, noninvasive method to assist in the evaluation of testicular pain.

Adolescent↗
PubMed1985

Reversible renal failure due to psychogenic urinary retention.

A case of advanced, reversible renal failure due to psychogenic urinary retention occurring in a 17 year old female, is reported. The diagnosis of psychogenic urinary retention was made on the basis of existent florid psychopathology and the concomitant exclusion of an organic cause. Family psychodynamics are discussed. Psychosocial intervention led to a resumption of normal micturition, the disappearance of the urinary retention with resultant improvement of renal function.

Acute Kidney Injury↗
PubMed1984

Low level antigen responses in guinea-pig lung strip.

Guinea-pigs were sensitized either by i.p. administration or by a novel procedure involving inhalation of ovalbumin (2, 0.2 and 0.002%) on days 0, 5 and 19 respectively. Lung strips from these guinea-pigs were challenged with both low (0.02 micrograms/ml) and high (10 micrograms/ml) concentrations of ovalbumin and the responses compared. Whereas the low level antigen gave consistent contractions following aerosol sensitization, no response was observed from the i.p. sensitized guinea-pig lung strips. Marked differences were also observed following the high ovalbumin challenge, where the aerosol sensitized lungs gave almost twice the response as tissue from the i.p. sensitized guinea-pigs, the former being approximately 140% of that observed with acetyl-beta-methyl choline (1 mM). Furthermore, the response elicited in the lungs from aerosol sensitized guinea-pigs were not modified by the addition of high concentrations of the H1-antagonist diphenhydramine (100 microM), before or subsequent to challenge. The data suggest that the aerosol sensitization procedure gives rise to a contractile response in guinea-pig lung strips which contains no observable histamine component.

Anaphylaxis↗
PubMed1984

Comparison of the influence of acute transmural and nontransmural myocardial infarction on ventricular function.

In order to assess the relative impact on left and right ventricular function of nontransmural and transmural acute myocardial infarction (AMI), we performed radionuclide ventriculography in 86 patients (54 men and 32 women) within 16 hours after a first infarct. Nontransmural infarction was present in 19 patients (11 anterior and 8 inferior). Transmural infarction was found in 67 patients (30 anterior and 37 inferior). Left ventricular ejection fractions were higher (0.57 +/- .014 vs 0.46 +/- 0.14, p less than 0.005) and left ventricular end-systolic volume lower (29 +/- 11 vs 42 +/- 20 ml/m2, p = 0.013) in patients with nontransmural infarction compared to those with transmural infarction. Right ventricular ejection fraction also may have been different in the two groups (0.63 +/- 0.15 vs 0.55 +/- 0.13, p = 0.057). In patients with inferior infarction, left and right ventricular ejection fractions were similar in patients with nontransmural and transmural infarction (0.60 +/- 0.09 vs 0.55 +/- 0.10, p = 0.119 and 0.58 +/- 0.14 vs 0.51 +/- 12, p = 0.226). On the other hand, patients with anterior transmural infarction had lower left ventricular ejection fractions (0.36 +/- 0.12 vs 0.54 +/- 0.17, p = 0.003) but similar right ventricular ejection fractions (0.60 +/- 0.13 vs 0.66 +/- 0.14, p = 0.14) compared to those with nontransmural anterior infarction. In 29 additional patients with a history of previous infarction, no differences in any of the parameters studied were found between those with transmural and those with nontransmural infarcts.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiography↗
PubMed1984

Beta-blocking autoantibodies in pediatric bronchial asthma.

We have used the inhibition of binding of a potent beta antagonist, iodohydroxybenzylpindolol, to canine lung-plasma membrane beta-adrenergic receptors as a test for beta-blocking autoantibodies in the sera of 376 mildly and severely asthmatic children. This binding inhibition assay, coupled with a variant test in which the binding assay was performed on selected sera (binding values below 2 SD from the mean) before and after immunodepletion of the sera (removal of IgG and IgA), permitted the conclusion that about 5% of the juvenile asthmatic population studied produce beta-blocking autoantibodies.

Adrenergic beta-Antagonists↗
PubMed1984

A new in vivo method for the measurement of repetitive anaphylactic responses in the guinea-pig.

The established Konzett-Rossler bronchorespiratory model has been combined with a unique ovalbumin sensitization procedure to give a novel method to measure anaphylaxis in the anaesthetized guinea-pig. Following antigen challenge, up to eight equal bronchoconstrictor responses to the same dose can be generated from a single animal over a 120 min period. Total inhibition of the anaphylactic response can be elicited by four different classes of compound, namely salbutamol, mepyramine, theophylline and dimaprit. Cromoglycate failed to cause any inhibition. The method is discussed with particular reference to the antigen sensitization procedure, which differs substantially from other regimens previously employed and gives rise to heat labile antibody.

Albuterol↗
PubMed1984

Static contraction of the quadriceps muscle in man: cardiovascular control and responses to one-legged strength training.

Knee extension strength training of one leg (ST) (120 maximal contractions per day, 5 days per week for 9 weeks) was performed by 9 healthy young men. Before and after ST, biopsies were obtained from the vastus lateralis muscle of each leg and static quadriceps contractions (SQC) lasting 2 min were performed with each leg under control conditions and after combined vagal and beta-adrenergic blockade with atropine and metoprolol. Maximal voluntary contraction strength (MVC) increased more for the trained leg (TL) than for the untrained leg (UTL) but thigh circumferences and muscle fibre diameters gave little evidence for muscle hypertrophy. In pre- vs. post-training comparisons during SQC at the same relative force (40% of MVC) mean blood pressure (MBP), heart rate (HR) and smoothed rectified electromyographic activity were similar for TL and UTL. Similar findings were obtained for MBP after attenuation of the HR response by autonomic blockade, indicating that MBP, per se, was closely linked to the relative force of SQC. Pre- to post-training reductions in MBP and HR during SQC with each leg at an absolute force of 40% of pre-training MVC were likely due to changes in the pattern of motor unit activation. A lower MBP response to SQC and TL than of UTL after training correlated with a greater capillary density and a lower muscle lactate level for TL.

Adaptation, Physiological↗