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Biomedical subjects

B Levy

Publications and source records attributed to B Levy.

At least 145 records · Page 8Linked to original sources
PubMed1985

Rigid gas-permeable lenses for extended wear--a 1-year clinical evaluation.

A 1-year evaluation of the feasibility of the use of gas-permeable rigid lenses for extended wear was carried out, using two different materials. Forty subjects were entered into the study. Fifteen were fitted with the Polycon II lens and another 15 with the Boston IV lens. These two groups wore the lenses on a weekly basis for the duration of the study. Two other groups, the controls, were fitted with the same types of lenses as the experimental groups, but wore the lenses on a daily basis. All lenses were made to the Syntex specifications for the Polycon lens and the groups were comparable with regard to age, sex, refractive error, corneal astigmatism, and any pre-existing ocular pathology. All subjects carried out the same care regimen for their lenses and were examined after 24 h, 1 week, 1 month, 3 months, 6 months, and 1 year. Examinations performed at the follow-up visits were to determine any clinically observable effects of lens wear in each patient in all groups. The results of the study suggest that the extended wear of gas-permeable rigid materials is a viable option. However, the results also indicate that extended wear is not without problems, and these need to be studied more fully before the use of gas-permeable rigid lenses for extended wear can be recommended.

Adult↗
PubMed1985

Environmental influence on shape of the crystalline lens: the amphibian example.

Amphibians are faced with the problem of adapting to aerial vision when undergoing metamorphosis. The rate and extent of ocular change has been examined in five species with widely varying life histories. Ocular effects and in particular lens shape changes were determined from measurements of gross anatomy at various metamorphic stages using a freeze-sectioning technique. In addition, refractive states were measured retinoscopically in air and water where possible. All larval animals have the ocular structure and optics typical of teleost fish. Adults show varying levels of adaptation to aerial vision, depending on the degree of departure from an aquatic style of behavior. In certain cases the spherical aquatic shape of the lens is maintained while in others, lens shape is altered markedly to a flattened elliptical form. Histological study indicates that change in lens shape is brought about by a rapid increase of mitotic activity of equatorial epithelial cells at critical periods during metamorphosis.

Adaptation, Physiological↗
PubMed1984

Effect of descending thoracic aorta clamping and unclamping on phasic coronary blood flow.

Myocardial infarctions during aortic surgery often occur after aortic clamping and unclamping. In order to investigate the aortic blood pressure (AoBP)-coronary blood flow (CBF) relationship, hemodynamic parameters and phasic circumflex CBF in 15 anesthetized and open-chest dogs during clamping and unclamping of the thoracic descending aorta have been recorded. During clamping, mean aortic blood pressure (MAoBP) rose from 97 + 17 to 150 + 42 mm Hg (P less than 0.001), and total combined left-ventricular power (Wtc) from 692 + 232 to 923 + 402 mW (P less than 0.001) while the ascending aortic blood flow (AoBF) and heart rate did not change significantly. The mean circumflex blood flow (MCBF) increased from 67 + 30 to 88 + 30 ml/min. The increase in systolic coronary blood flow (+73%) was larger than that in diastolic coronary blood flow (DCBF) (19%). The late coronary resistances were increased 39%. Conversely, after unclamping, MAoBP decreased while AoBF and Wtc increased. During the first cardiac cycles after aortic unclamping DCBF decreased 50% with a decrease in the diastolic blood pressure (DBP). Four cycles later, DCBF reincreased while DBP kept on decreasing. This may be related to an active coronary vasodilatation. A linear relationship between DCBF and DBP has been obtained during acute change in DBP due to clamping or unclamping. From these linear relationships, the change in diastolic zero flow pressure (PfO) has been found to be about + 40 mm Hg during clamping. This change in PfO may be responsible for the observed large fall in DCBF during unclamping. The decrease in DCBF associated with the increase in Wtc accounts for the delayed active vasodilatation.

Animals↗
PubMed1984

Nosocomial endocarditis.

We analyzed 14 cases of nosocomial infective endocarditis which occurred over a seven-year period at the Beth Israel Hospital in Boston, and compared them with 90 cases of community-acquired endocarditis. Patients with nosocomial endocarditis were older, more often female, and had a greater incidence of underlying valvular heart disease and bacteremia precipitating invasive procedures (93% v 50%, p less than .05). Forty-three percent of patients had infection at the site of prosthetic valves or intracardiac prosthetic material. The disease carried a significantly higher mortality than community-acquired endocarditis (43% v 11%, p less than .01). The clinical presentation was acute and the infecting organisms reflected the site of origin of bacteremia, with staphylococci from skin and enterococci from urinary sources. Half of the cases in this series may have been prevented by the application of currently recommended preventive and therapeutic practices. Nosocomial endocarditis occurs in a definable sub-population of hospitalized patients and is potentially preventable.

Catheters, Indwelling↗
PubMed1984

Incidence of oculo-visual anomalies in an adult population of mentally retarded persons.

Clinical examination of 298 mentally retarded adults revealed a higher frequency of ocular anomalies of all types than is typical of a group of nonretarded subjects of the same age. It also became apparent that fewer of the mentally retarded had had appropriate optometric care than an equivalent nonretarded sample. The evidence indicates that correcting their ocular problems helps the retarded, yet these subjects receive less than average care.

Adult↗
PubMed1983

[Cardiac effects of the flow in the arteriovenous fistula. Study in 66 chronic hemodialysis patients].

The effect on the heart of blood flow in the arterio-venous fistula created for haemodialysis was investigated in 66 patients with chronic renal impairment. Blood flow was measured by pulsed Döppler flowmetry. A significant (p less than 0.001) correlation was established between the signs of cardiac insufficiency and the fistula blood flow x fistula duration product. The arterio-venous fistula therefore constitutes a cardiac risk which should be quantified in chronically uraemic patients undergoing repeated haemodialysis.

Adolescent↗
PubMed1983

The HTP as a measure of change in dialyzed schizophrenic patients.

Used the House-Tree-Person as a measure of pathology in 10 schizophrenic patients of both sexes between the ages of 19 and 30 before and after experimental hemodialysis treatment. Results obtained through the quantitative HTP scoring method, and reflected in HTP IQs, indicate that significant improvement as a function of treatment is seen in pre- to post-dialysis drawings. Data analysis, using the Two Factor Repeated Measures Analysis of Variance (ANOVA), indicates that drawings done after dialysis improve at the .005 and .001 levels. The HTP evaluations support the continued use of hemodialysis as an effective treatment for schizophrenia.

Adult↗
PubMed1983

Circadian changes in heart rate in unanesthetized normotensive and spontaneously hypertensive rats.

Circadian changes in heart rate and heart rate variability were measured in spontaneously hypertensive (SHR) and normotensive (WKY) rats. Electrocardiograms (ECG) were continuously recorded, over a 24 hour period from freely moving conscious rats via three small metallic subcutaneous electrodes which were positioned a week before the recording period. The findings reported here show: 1/ Mean heart rate calculated over 24 hours were lower in both strains than previously reported. This difference probably reflects the lack of anesthesia and minimal stress in the present study. 2/ The timing of the circadian variations in both strains were the same, suggesting that were both entrained to the light-dark cycle. 3/ The 24 hours mean heart rate variability was significantly higher in SHR than in WKY but in each strain it was similar throughout the 24 hours. This suggests that the vagal tone in SHR was higher by a fairly constant amount throughout the light-dark cycle.

Animals↗
PubMed1983

Central brain morphology in chronic schizophrenic patients: a controlled CT study.

A comprehensive quantitative computed tomography (CT) study of the diencephalic region of 23 chronic schizophrenic patients and 23 normal controls was done. The third ventricle width, the Sylvian fissure widths, and the densities of the head of the caudate nucleus, thalamic nucleus, and medial temporal lobe were measured. In the schizophrenic patients, there was a significant increase in third ventricle and Sylvian fissure widths and a significantly greater density of both periventricular nuclei. The several explanations for this atypical association of atrophy with greater density are discussed.

Adult↗
PubMed1982

[Effect of nitroglycerin and N-ethoxycarbonyl-3-morpholinosydnonomine on the walls of large arteries].

Systemic arterial compliance was measured in 20 patients with left ventricular failure due to congestive cardiomyopathy. The method consisted in evaluating arterial compliance by analysing the exponential fall of the arterial pressure curve on a simple visco-elastic model. In the patient group, significant correlations were found between arterial compliance and age (r = 0,64 ; p less than 0,01) and arterial compliance and systolic blood pressure (r = -0,58 ; p less than 0,001). These relationships suggest that arterial compliance depends on the height of the systolic blood pressure and/or the elasticity of the arterial walls. Two groups of patients were defined : Group I (10 patients) given a single oral dose of 7,5 mg of nitroglycerine (Lenitral), and Group II (10 patients) giben a single oral dose of 4 mg N ethoxycarbonyl-3-morpholinosydnonomine (Molsidomine). There was no significant difference in the hemodynamic parameters or arterial compliance between the two groups before administration of these drugs. However, systolic blood pressure was significantly lower (p less than 0,01) and compliance significantly higher (p less than 0,05) after treatment in Group II. In Group I, nitroglycerine caused a significant increase in compliance (p less than 0,01), a significant decrease in systolic (p less than 0,02) and mean blood pressure (p less than 0,05) whilst heart rate, cardiac output and total systemic resistance remained unchanged. In Group II, Molsidomine caused a significant increase in arterial compliance (p less than 0,01), a decrease in systolic (p less than 0,001), diastolic (p less than 0,01) and mean blood pressure (p less than 0,01) and in cardiac output (p less than 0,01), whilst heart rate and total systemic resistance remained unchanged. This study shows that both drugs studied had significant effects on the walls of the large arteries.

Adult↗