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Biomedical subjects

L Shaw

Publications and source records attributed to L Shaw.

At least 217 records · Page 12Linked to original sources
PubMed1979

Value of bitewing radiographs in detection of occlusal caries.

A system of diagnosing occlusal caries from bitewing radiographs was developed in an attempt to overcome the problems of clinical diagnosis found in other studies. Standardised bitewing radiographs for 1172 Berkshire schoolchildren aged 11-13 years who were participating in a toothpaste trial, were assessed for occlusal caries under uniform magnification and illumination. The radiographic scores were then compared with the clinical records for these subjects. The radiographic technique proved to be acceptably reproducible at 82.6%. However, only 33.2% of the lesions present were detected on the radiographs. It is concluded that bitewing radiographs for the detection of occlusal caries are of little value in epidemiological studies.

Adolescent↗
PubMed1977

A new index for measuring extrinsic stain in clinical trials.

A staining index has been proposed which is simple to use clinically and yet is sensitive enough to detect small changes in staining levels between different groups. Accurate scale drawings from An atlas of tooth form were reproduced. Outlines of the labial and lingual surfaces of all eight incisor teeth were enlarged to scale (magnification X 4) and each tooth face divided into 4-mm squares. All areas of extrinsic stain were drawn by the examiner on the grid system. This method has been tested in three clinical trials and the reproducibility investigated. In 161 duplicate examinations a total of 1,830 stained squares were scored by one examiner, compared with 1,853 squares by the second examiner; the reproducibility ratio was 0.155 and the coefficient of correlation was 0.956. The method proved sufficiently sensitive to record differences in staining levels in groups using two dentifrices; one was a normal commercial product with an abrasivity against dentin approximately two-thirds that of the other paste. The proposed Extrinsic Stain Index provides data which can be analyzed by appling parametric or nonparametric tests.

Adult↗
PubMed1976

Cardiac effects of succinyldicholine and succinylmonocholine.

The present study evaluated possible contribution of succinylmonocholine in producing serious cardiovascular effects with or without succinyldicholine, using albino rabbits as the experimental animal. Forty-eight experiments were performed, 22 in vivo and 26 in vitro (Langendort heart). Succinyldicholine and succinylmonocholine administered separately or together produced an immediate bradycardia in vivo as well as in vitro. The combination of these drugs had a direct arhythmogenic effect as well as an indirect reflux mediated cardiac effect. When succinyldicholine was given within five minutes following a dose of succinylmonocholine there was significant nodal and ventricular ectopic beats, but no bradycardia. Dysrhythmias in in vivo hearts were abolished by cord trans-section, trimethaphan and reserpine pretreatment. There was no evidence in vivo that succinylmonocholine produced more serious bradycardia, dysrhythmias or hypotension than succinyldicholine,

Animals↗
PubMed1975

Active transport in Escherichia coli B membrane vesicles. Differential inactivating effects from the enzymatic oxidation of beta-chloro-L-alanine and beta-chloro-D-alanine.

Isolated membrane vesicles from Escherichia coli B grown on DL-alanine and glycerol carry out amino acid active transport coupled to a membrane-bound D-alanine dehydrogenase (Kaczorowski, G., Shaw, L., Fuentes, M., and Walsh, C. (1975) J. Biol. Chem. 250, 2855). Certain L-amino acids can also energize solute transport by conversion to their D isomers via an alanine reacemase. Both D-chloroalanine and L-chloroalanine initially drive amino acid and methyl-beta-thiogalactose uptake. The D isomer however causes rapid inactivation of both dehydrogenase-coupled transport and the phosphotransferase system. Transport functions can be protected by dithiothreitol which is postulated to act as a scavenging nucleophile. This inactivation by the D isomer is time-dependent and irreversible not only for proline transport but also for alpha-methylglucoside uptake. Unlike the D isomer, beta-chloro-L-alanine does not inactivate transport. L-Chloroalanine is not racemized to the D isomer but rather undergoes a racemase catalyzed beta elimination of chloride ion to produce pyruvate. Pyruvate can subsequently be oxidized to stimulate active transport. This pyridoxal phosphate-dependent racemase is inactivated by low concentrations of D-chloroalanine but the L isomer can only cause inactivation at a 40-fold higher concentration and longer times of exposure. The D-alanine dehydrogenase-catalyzed oxidation product of D-chloroalanine is chloropyruvate, and this keto acid is hypothesized to be the inactivating species of transport for the following reasons. Chloropyruvate has been isolated from D-chloroalanine oxidation but not from oxidation of the L isomer. Chlorolactate which can be oxidized to chloropyruvate (via membrane-bound lactate dehydrogenases) also causes inactivation of transport in E. coli K-12 membrane vesicles. Mutants having diminished lactate dehydrogenase activity show a slower rate of inactivation with chlorolactate. Moreover, synthetic chloropyruvate irreversibly inactivates both active transport of proline and phosphotransferase system-dependent group translocation of alpha-methylglucoside. The effects of D- and L-chloroalanine and chlorolactate on transport in membrane vesicles are also seen in whole cells.

Aerobiosis↗
PubMed1975

Coupling of alanine racemase and D-alanine dehydrogenase to active transport of amino acids in Escherichia coli B membrane vesicles.

Isolated membrane vesicles from Escherichia coli B grown on DL-alanine-glycerol carry out amino acid active transport coupled to D-alanine oxidation by a membrane-bound dehydrogenase. Several other D-amino acids are substrates for this D-alanine dehydrogenase and also drive concentrative uptake of solutes. Additionally, L-alanine and L-serine can energize solute transport by virtue of conversion to oxidizable D isomers by a membrane-bound alanine racemase. No other physiological L-amino acids were effective. Both membrane enzymes and consequent solute transport are markedly reduced in vesicles from glucose-grown cells. Respiratory chain uncouplers abolish the racemase-dehydrogenase-supported transport activity. When amino-oxyacetate at 10-4 M is added to the vesicles, the racemase activity and transport driven by L-alanine and L-serine is specifically and reversibly inhibited. D-Alanine-driven transport is unaffected. Similarly beta-chloro-L-alanine is an irreversible inactivator of the bound racemase but not the D-alanine dehydrogenase. Both the D and L isomers of beta-chloroalanine support oxygen uptake by the vesicles and initially stimulate L-(14C)proline active transport. However, oxidation of the beta-chloro-D-alanine rapidly uncouples active transport from substrate oxidation. This transport inactivation can be protected partially by dithiothreitol, putatively scavenging a reactive product of chloroalanine oxidation. Authentic beta-chloropyruvate produces the same transport uncoupling. When beta-chloro-L-alanine is employed as a substrate, no such transport inactivation is observed. This difference may stem from the possibility that the alanine racemase eliminates HCl from beta-chloro-L-alanine producing pyruvate, not the beta-chloropyruvate that would arise from racemization and then dehydrogenation. We have shown that exogenous pyruvate is oxidized by the vesicles and will also stimulate active transport of amino acids.

Acetates↗
PubMed1975

Errors in diagnosis of approximal caries on bitewing radiographs.

The number of overlapped and unreadable surfaces occurring on bitewing radiographs of 1,417 children participating in a clinical trial was recorded. Of erupted surfaces, only 73.3% were completely visible to both participating examiners. Interexaminer and intraexaminer reproducibility ratios were calculated according to the F.D.I. recommendations. The ratios obtained in the present study ranged from 0.06 to 0.36. Almost 57% of approximal cavities were diagnosed on radiographic examination only: 21% were diagnosed clinically, but were not apparent on the radiographs.

Child↗
PubMed1975

Vinylglycolate resistance in Escherichia coli.

Escherichia coli K-12 vinylglycolate-resistant mutants have been isolated and characterized. Two of the mutants, JSH 150 and JSH 151, have been determined to be double mutants, lacking both membrane-bound L-and D-lactate dehydrogenases. The lactate transport system is intact in all strains; both radioactive lactate and vinylglycolate are actively taken up. Likewise, the phosphoenolypyruvate-dependent phosphotransferase system for hexose uptake is active. Vinylglycolate, previously shown to inhibit the phosphoenolpyruvate-dependent phosphotransferase system, has very little effect in the double mutants. The extent of vinylglycolate inhibition in other mutants seems directly related to the activity of the lactate dehydrogenases. This indicates that vinylglycolate is oxidized to 2-keto-3-butenoate before inactivating the phosphoenolpyruvate-dependent phosphotransferase system. These results were found in whole cells and confirmed in isolated membrane vesicles.

Biological Transport, Active↗
PubMed1975

Inter-examiner and intra-examiner reproducibility in clinical and radiographic diagnosis.

The first technical report to be published by the FDI considered the principal requirements for controlled clinical trials of caries preventive agents and procedures. This document advocated the use of a simple reproducibility ratio as a measure of variability in caries diagnosis. In accordance with the FDI recommendations available figures from published work on duplicated examinations are presented in terms of this reproducibility ratio. The data refers to intra- and inter-examiner variability with respect to both clinical and radiographic examinations. Reproducibility studies carried out as a pre-calibration investigation and during the baseline examinations of a current clinical trial are also included. Considerable diversity is apparent, the intra- and inter-examiner variation for clinical examinations ranging from 0-13 to 0-61, and for radio-graphic assessments from 0-06 to 0-60. If an acceptable range of reproducibility ratios is to be formulated then this wide variation will have to be taken into account. Ultimately, if examiner variability cannot be maintained within reasonable limits, then the choice of an examiner could be just as important as the choice of the test substance.

Child↗
PubMedDate not supplied

Dipyridamole technetium 99m sestamibi myocardial tomography as an independent predictor of cardiac event-free survival after acute ischemic events.

BACKGROUND: A total of 137 consecutive patients with recent uncomplicated myocardial infarction (n = 31) or unstable angina (n = 106) were studied to determine the relative prognostic value of predischarge clinical risk stratification and intravenous dipyridamole stress sestamibi (MIBI) myocardial tomography in patients unable to exercise maximally after an acute ischemic coronary event. METHODS AND RESULTS: Patients were followed up after the index study for 10 +/- 5 months (range 1 to 23 months) to ascertain cardiac events that occurred in 20 patients (15%): nonfatal myocardial infarction (n = 5) or cardiac death (n = 15). Cardiac event rates were 35% in patients with a recent myocardial infarction and 8% in the group with unstable angina (p < 0.001). Patients with these cardiac events had more frequent abnormal MIBI study results, fixed defects, and reversible plus fixed (combined) defects (all p < 0.05). The univariate relative risk of death or myocardial infarction associated with an abnormal MIBI study was 6.0 (95% confidence limits 0.8 to 44.7). Multivariate stepwise logistic regression models identified an abnormal MIBI study and either fixed or reversible MIBI defects as being predictive of death or myocardial infarction (all p < 0.05). The Mantel-Haentzel 1-year cardiac event-free survival rate was excellent in 27 patients with a normal MIBI single-photon computed emission tomographic scan (100%) but significantly reduced in the 110 patients with an abnormal MIBI study (80%; p < 0.05 vs normal subjects). The presence of combined MIBI defects was associated with the poorest event-free survival rate (66%; difference not significant vs fixed or reversible defects only). CONCLUSION: We conclude that predischarge dipyridamole MIBI tomography provided independent prognostic information in this population of patients who were unable to exercise after a recent acute ischemic coronary event.

Aged↗