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Biomedical subjects

B Rabinovitch

Publications and source records attributed to B Rabinovitch.

At least 19 recordsLinked to original sources
PubMed1985

Effects of separate rib cage and abdominal restriction on exercise performance in normal humans.

We assessed the effects of selective restriction of movements of the rib cage (Res,rc) and abdomen (Res,ab) on ventilatory pattern, transdiaphragmatic pressure (Pdi), and electrical activity of the diaphragm (Edi) in five normal subjects exercising at a constant work rate (80% of maximum power output) on a cycle ergometer till exhaustion. Restriction of movements was achieved by an inelastic corset applied tightly around the rib cage or abdomen. Edi was recorded by an esophageal electrode, rectified, and then integrated, and peak values during inspiration were measured. Each subject exercised at the same work rate on 3 days: with Res,rc, with Res,ab, and without restriction (control). Res,rc but not Res,ab reduced exercise time (tlim). Up to tlim, minute ventilation (VE) was similar in all three conditions. At any level of VE, however, Res,rc decreased tidal volume and inspiratory and expiratory time, whereas Res,ab had no effect on the pattern of breathing. Res,ab was associated with higher inspiratory Pdi swings at any level of VE, whereas peak Edi was similar to control. Inspiratory Pdi swings were the same with Res,rc as control, but the peak Edi for a given Pdi was greater with Res,rc (P less than 0.05). During Res,rc the abdominal pressure swings in expiration were greater than with Res,ab and control. We conclude that Res,rc altered the pattern of breathing in normal subjects in high-intensity exercise, decreased diaphragmatic contractility, increased abdominal muscle recruitment in expiration, and reduced tlim. On the other hand, Res,ab had no effect on breathing pattern or tlim but was associated with increased diaphragmatic contractility.

Abdomen↗
PubMed1983

Predicting the results of radial keratotomy.

Radial keratotomy on 251 patient eyes was performed. Patients traversing the one-year gate after surgery have demonstrated a refractive change best predicted by the optical zone size, the number of incisions, the corneal dissymmetry, and the age of the patient. One year after surgery, a 16-incision radial keratotomy with 3.0-mm optical zone produced 4.66 diopters of refractive change if the limbus was traversed (N = 13), and 5.18 diopters of refractive change if all incisions remained in clear cornea (N = 39). An eight-incision, 3.0-mm optical zone radial keratotomy produced 5.21 diopters of refractive change at one year (N = 37). A 3.5-mm optical zone, eight-incision radial keratotomy produced 3.66 diopters of change at one year (N = 6). A 4.0-mm optical zone produced 2.67 diopters of change with 16 incisions (N = 8), and 3.45 diopters of change with eight incisions at one year (N = 9). Although older patients appear to have significantly greater refractive change with radial keratotomy at the three-month gate, this difference is not yet confirmed at one year after surgery. The shape of the cornea before surgery contributes to the predictability of the refractive results when the horizontal and vertical keratometer measurements are analyzed. Corneal dissymmetry produces greater refractive results with steeper horizontal K when against-the-rule astigmatism is present before surgery.

Adult↗
PubMed1979

Optical monitor of glucose.

Methods have been described to noninvasively monitor the glucose of the aqueous humor, a fluid with glucose in constant equilibrium with the bloodstream. A feasibility study has been performed showing that the optical rotation of the aqueous humor reflects aqueous humor glucose concentration in the range of hypo- and moderately hyperglycemic conditions. Preliminary data show that specificity for glucose may be enhanced by simultaneously measuring the optical rotation at 984 nm and 775 nm.

Animals↗
PubMed1967

Enzyme-substrate reactions in very high magnetic fields. I.

The availability of very high magnetic fields of up to 170,000 gauss made it worthwhile to pursue the search for a critical change in the rate of four enzyme substrate reactions. The four enzymes were ribonuclease, polyphenol oxidase, peroxidase, and aldolase. The experiments showed that, to within +/-3%, no detectable change was observable in the rate of reaction of any of the systems for periods of exposure to the magnetic field of up to 20 min.

Alcohol Oxidoreductases↗
PubMed1967

Enzyme-substrate reactions in very high magnetic fields. II.

We have examined the effect of conditioning the enzyme trypsin in solution at pH 8.2 in a large magnetic field before determining its reactivity towards a synthetic substrate N-benzoyl DL-arginine p-nitroanilide (BAPA). This "pretreatment" was allowed to proceed for as long as 3(2/3) hr in a magnetic field of 208 kgauss at temperatures 26 and 36 degrees C. No effect on reactivity was observed when such pretreated enzyme solutions were compared with identical but untreated enzyme solutions. A single such reaction, allowed to proceed directly in a magnetic field of 220 kgauss for 9 min, similarly showed no difference in rate from its control.

Anilides↗
PubMedDate not supplied

Noninvasive glucose monitoring of the aqueous humor of the eye: Part I. Measurement of very small optical rotations.

We have described the concept of using the aqueous humor glucose as a measure of the blood glucose concentration, with a view to developing a noninvasive glucose monitor for diabetic individuals. We have conceived of a scleral lens that houses a light source, polarizers, other electro-optic units, and a light detector, and which measures the optical rotation of the aqueous humor continuously. We have built an optical bench mock-up of the glucose sensor and assessed the limits of its capabilities. We have described a physical method, employing the Faraday effect, that modulates the incident light and uses a compensator to introduce a feedback mechanism giving a null-point technique capable of measuring extremely small rotations with an accuracy of 0.4 s of arc. We have used this and have measured the optical rotations of glucose solutions from 0.02 to 0.1%, and have demonstrated linearity in both cases. Miniaturization of the technique is discussed.

Animals↗