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Biomedical subjects

D R Scott

Publications and source records attributed to D R Scott.

70 records · Page 4Linked to original sources
PubMed1984

Influence of mercurial sulfhydryl agents on aqueous outflow pathways in enucleated eyes.

Enucleated calf and primate eyes were perfused with either p-chloromercuribenzene sulfonate (PCMBS) or p-chloromercuribenzene (PCMB). Both caused a decrease in aqueous outflow that did not result from inhibition of glycolysis in trabecular cells. Morphologic studies of PCMBS-treated primate eyes suggested that the reduction in aqueous outflow occurred as the result of cellular swelling in the trabecular meshwork and, particularly, in the juxtacanalicular connective tissue. These findings suggest that changes in cell volume may influence trabecular outflow resistance and that mercurial-sensitive membrane sulfhydryl groups could participate in the regulation of aqueous outflow.

4-Chloromercuribenzenesulfonate↗
PubMed1984

Glutathione peroxidase of calf trabecular meshwork.

Glutathione peroxidase was extracted from calf trabecular meshwork. The kinetics of this enzyme were examined, varying the substrates hydrogen peroxide (H2O2), tert- butylhydroperoxide ( tBHP ), and glutathione. The activity of the enzyme in nonpurified homogenates was 596 nmole H2O2 reduced/min/gm wet weight and 680 nmole tBHP reduced/min/gm wet weight (27-28 nmole peroxide reduced/min/mg protein). The apparent Michaelis--Menten constants for H2O2, tBHP , and GSH were 0.012, 0.102, and 2.89 mM, respectively. These data, together with published levels of glutathione in trabecular meshwork, suggest that the trabecular endothelial cell actively detoxifies H2O2.

Animals↗
PubMed1982

Duration as a cue to the perception of a phrase boundary.

The presence of a phrase boundary is often marked in speech by phrase-final lengthening-a lengthening of the final stressed syllable of the phrase and pause at the phrase boundary. The present study investigates (a) whether listeners use the feature of phrase-final lengthening to parse syntactically ambiguous sentences such as "Kate or Pat and Tony will come," where the position of a phrase boundary after "Kate" represents one meaning, and after "Pat" another meaning, and (b) whether listeners use phrase-final lengthening directly to parse the sentence or indirectly via the effect that phrase-final lengthening has on the rhythm of the feet (the onsets of the stressed syllables) of the sentence. Four experiments are reported in which listeners are asked to judge the meaning of sentences which have been temporally manipulated so that the foot which originally did not contain the crucial phrase boundary is lengthened by (i) inserting a pause at the "false" phrase boundary [experiment I], (ii) inserting a pause and lengthening the final stressed syllable at the "false" phrase boundary [experiments II], (iii) lengthening all segments contained in the foot [experiment III], and (iv) lengthening only the conjunction within the foot [experiment IV]. The results indicate that both rhythm of the inter-stress intervals and the presence of phrase-final lengthening influence listeners' perception of a phrase boundary, although the stress rhythm appears to be the more powerful perceptual cue.

Humans↗
PubMed1981

Evaluation of a direct blood culture disk diffusion antimicrobial susceptibility test.

A total of 556 unique blood culture isolates of nonfastidious aerobic and facultatively anaerobic bacteria were examined by direct and standardized disk susceptibility test methods (4,234 antibiotic-organism comparisons). When discrepancies which could be accounted for by the variability inherent in disk diffusion susceptibility tests were excluded, the direct method demonstrated 96.8% overall agreement with the standardized method. A total of 1.6% minor, 1.5% major, and 0.1% very major discrepancies were noted.

Bacteria↗
PubMedDate not supplied

Influence of managed care and health maintenance organizations on the clinical microbiology laboratory.

This article outlines the main source of the relentless cost squeeze facing health care and clinical microbiology in the 1990s, the explosive growth in services available, services done, and services demanded. The author also explained why he believes some type of rationing is inevitable. Health care professionals must enter the debate on how to ration or face unpleasant consequences. The approach outlined here is one proven way to create testing and treatment guidelines based on health outcomes as well as consumer satisfaction and cost. The long-term best interests of all patients deserve nothing less.

Cost-Benefit Analysis↗
PubMedDate not supplied

The effects of lead toxication on learning in rats.

Impairment of learning resulting from lead poisoning has yet to be demonstrated in rats. The behavioral task used in previous studies to assess learning, however, may not have been sufficiently complex to serve as a discriminative index. The performance of rats injected with a lead acetate solution was compared to the performance of control rats in learning to run a complex maze. Though the learning acquisition rate was somewhat impaired in the lead-injected animals, the groups learned to complete the maze with equivalent success by the third training session. It was concluded that the study did not demonstrate convincing evidence of learning impairment in the lead-injected animals.

Animals↗
PubMedDate not supplied

The closing behavior of Medtronic Hall mechanical heart valves.

The rapid deceleration of mechanical heart valve leaflets or discs at closure, and their rebound after impact between the leaflets or discs and housing may produce conditions that favor cavitation inception. Precision measurements of the disc closing velocity using a laser sweeping technique (LST) were made on two Medtronic Hall (Med Hall) mitral valve models, the 29 mm Standard and D-16 Med Hall valves. The experiment was carried out in a pulsatile mock flow loop (PFL) by installing the tested valve in the mitral position of the PFL. Tests were conducted under physiologic pressures at heart rates of 70, 90, and 120 beats/min with flow rates of 5, 6, and 7.5 l/min, respectively. For each valve tested, the experimental series was carried out to include both a flexible mounting and a rigid mounting mechanism. The time history of the disc closing velocity during the last 3 degrees before final closure was measured. Results show that the disc approached the valve housing at a near constant velocity of approximately 1.3, 1.5, and 2.0 m/sec for the Med Hall Standard valve, and 1.9, 2.5, and 2.6 m/sec for the Med Hall D-16 valve at 70, 90, and 120 beats/min, respectively. After impact, the valve of disc rebounded with velocities that depended on the mounting modalities and heart rates. In the rigid mounting, the disc rebound velocities of the Med Hall Standard and D-16 valves were about 60%-70% and 70%-80% of their respective approaching velocities. For the flexible mounting, the rebound velocities were 15%-25% and 20%-30% of their respective approaching velocities. The results demonstrate that a slight modification in the seat stop geometry of Med Hall valves can significantly affect disc closure behavior.

Biomechanical Phenomena↗
PubMedDate not supplied

Determinants of genital human papillomavirus infection in low-risk women in Portland, Oregon.

OBJECTIVES: To confirm the risk factors for genital human papillomavirus (HPV) infection. GOAL OF THIS STUDY: To investigate risk factors for HPV detection independent of the correlated risk factors for cervical neoplasia in a low-risk population. STUDY DESIGN: HPV DNA was assessed among 483 cytologically normal women with no known history of cervical neoplasia. A cervicovaginal lavage was collected for HPV detection and typing using a PCR-based DNA amplification system. Information on risk factors of subjects was obtained through a questionnaire. RESULTS: HPV DNA was found in 17.7% of study women. On univariate analysis, factors associated with increasing HPV prevalence included younger age, fewer years of education, lower income, higher lifetime number of sex partners, lower age at first intercourse, nulliparity, oral contraceptive use, and current smoking. After statistical adjustment, we found younger age and higher number of sex partners were strongly and independently associated with higher HPV prevalence. We also observed increased HPV prevalence among women with lower levels of education and lower incomes. CONCLUSION: These findings and corroborative data from the companion reports in this issue of the journal support the sexual route of transmission of the virus.

Adolescent↗
PubMedDate not supplied

Acid, protons and Helicobacter pylori.

The anti-ulcer drugs that act as covalent inhibitors of the gastric acid pump are targeted to the gastric H+/K+ ATPase by virtue of accumulation in acid and conversion to the active sulfenamide. This results in extremely effective inhibition of acid secretion. Appropriate dosage is able to optimize acid control therapy for reflux and peptic ulcer disease as compared to H2 receptor antagonists. However, clinical data on recurrence show that Helicobacter pylori eradication should accompany treatment of the lesion. These drugs have been found to synergize with many antibiotics for eradication. The survival of aerobes depends on their ability to maintain a driving force for protons across their inner membrane, the sum of a pH and potential difference gradient, the protonmotive force (pmf). The transmembrane flux of protons across the F1F0 ATPase, driven by the pmf, is coupled to the synthesis of ATP. The internal pH of H. pylori was measured using the fluorescent dye probe, BCECF, and the membrane potential defined by the uptake of the carbocyanine dye, DiSC3 [5] at different pHs to mimic the gastric environment. The protonmotive force at pH 7.0 was composed of a delta pH of 1.4 (-84mV) and a delta potential difference of -131mV, to give a pmf of -215 mV. The effect of variations in external pH on survival of the bacteria in the absence of urea correlated with the effect of external pH on the ability of the bacteria to maintain a pmf. The effect of the addition of 5 mM urea on the pmf was measured at different medium pH values. Urea restored the pmf at pH 3.0 or 3.5, but abolished the pmf at pH 7.0 or higher, due the production of the alkalinizing cation, NH3. Hence H. pylori is an acid-tolerant neutrophile due to urease activity, but urease activity also limits its survival to an acidic environment. These data help explain the occupation of the stomach by the organism and its distribution between fundus and antrum. This distribution and its alteration by proton pump inhibitors also explains the synergism of proton pump inhibition and antibiotics such as amoxicillin and clarithromycin in H. pylori eradication.

Gastric Acid↗