Ackerman, Eugene

Abstract A glucose oxidase-peroxidase method for continuous automated monitoring of blood glucose has been developed. The response is linear over the range 0-800 mg/100 ml. Sensitivity can be maintained for 24 hr or longer and can be restored by rinsing the analytic system with sulfuric acid to permit studies of longer than 48 hr in duration. A precision of ± 1% can be maintained between rinses for samples containing 100-600 mg of glucose per 100 ml. This method is satisfactorily specific for glucose: The response with other sugars is less than 1% of the response obtained with the same concentration of glucose. Ascorbic acid causes no significant inhibition of the response to glucose. The inhibition by uric acid has been reduced fifty-fold compared to that in other methods. Transit through the sampling catheter and analytic system requires 15 min. Timed from the first detectable response to a change in concentration, 25% of total response is achieved in 30 sec and 90% in 80 sec. Fifty percent of an oscillation with a half-period of 45 sec can be detected; no oscillations this short were observed in records of human blood glucose. Applicability and feasibility of this method have been demonstrated in over 2000 hr of repeated blood glucose recordings in 12 diabetic and 6 normal subjects.

Three normal, three stable diabetic, and eight unstable diabetic subjects were investigated, with continuous automated blood glucose analysis for forty-eight-hour periods, during metabolic balance studies of six days' duration under near normal conditions (fed and ambulatory) after the attainment of clinically optimal diabetic regulation. The studies on unstable diabetics were performed during constant dietary intake, with one or two daily injections of intermediate-acting insulin and then repeated with four daily injections of short-acting insulin. A characteristic of blood glucose behavior, the mean amplitude of glycemic excursion (MAGE), was measured. MAGE was small for normals (range, 22 to 60 mg./100 ml.), larger for stable diabetics (67 to 82 mg./100 ml.), and largest for unstable diabetics (119 to 200 mg./100 ml.). Associated with a significant decrease (p = 0.004) in the mean diurnal glycemic level (from 146 to 244 mg,/100 ml. to 101 to 152 mg./100 ml.) achieved through the use of four daily doses of short-acting insulin there was a significant increase (p = 0.006) in hypoglycemic episodes (from 0 to 4/48 hr. to 3 to 6/48 hr.) without significant change in MAGE. The persistently large value of MAGE despite therapy with multiple injections of short-acting insulin appears to be a characteristic of unstable diabetes.

Canine blood was diluted with isotonic Rous-Turner solution at pH 5.8 or at 7.0. The suspended erythrocytes were exposed to ultrasonic energy at 495 kc/sec with cavitation either occurring or being suppressed by excess pressure. The same power was applied to the transducer whether or not cavitation was occurring. The rupture of the cells was measured spectrophotometrically. In addition, the osmotic fragility of the exposed cells was compared with that of control cells. The results were analyzed and graphed, using an IBM-1620 computer. These studies indicated that (1) canine erythrocytes can be ruptured in the absence of cavitation, albeit more slowly; (2) mechanical strength as determined ultrasonically is not simply related to osmotic fragility; (3) the changes of osmotic fragility after ultrasonic treatment were different from those after heating; (4) the destruction not due to cavitation occurred at intensities between those used for surgery and those used for physical therapy. [This work, performed with the technical assistance of N. Nolder, A. Hildestad, and L. C. Gatewood, was aided by National Institutes of Health grants GM 08299-02 and FR-00007.]

The present series of experiments was undertaken in an effort to delineate those aspects of ultrasonic irradiation that might be destructive to malignant tumors of bone. The experiments were performed on rabbits having Vx-2 carcinoma implanted within the tibias. In preliminary, experiments, it was shown that the destructive effect of ultrasound on normal bone and on the circulation through normal bone was probably primarily due to heat. In the current series of experiments, it was shown that the heating of the bone was critically dependent on the exact location of the focus of the ultrasonic transducer within the rabbit leg. Our experiments suggested that (1) exposure of Vx-2 carcinoma to a temperature of 50°C for at least 10 min is sufficient to destroy the transmissible characteristics of this tumor, (2) exposure of Vx-2 carcinoma to ultrasonic fields with intense cavitation (applied in the absence of heat) has an effect that is far less than that of heating to 50°C for 10 min, and (3) controlled ultrasonic heating can increase the temperature of a bone to levels sufficient to destroy tumor growth within the bone.

Direct measurements were made of the displacement of the guinea-pig eardrum when acted upon by acoustic pressures (200–6000 cps). The mechanical nonlinearities of the ear were studied by introducing a static pressure (0 to ±3000 dyn/cm2) in the middle-ear cavity. Below 1000 cps, the ratio of the tympanum displacement to the sound pressure was frequency-independent, with a value of about 4×10−7 cm3/dyn. Above 1000 cps, this ratio exhibited a series of maxima and minima. A static-pressure difference across the tympanum changed the frequency at which the maximum occurred and generally decreased the displacement/pressure ratio. It was concluded (1) for low frequencies, the lumped-parameter description of the ear as a cavity was valid; (2) the tympanum acts as a flexible, conical plate under slight tension; (3) the measurements were best explained in terms of two nonlinearities: hysteresis and a nonlinearity of the elastic properties of the ear.

Dilute suspensions of canine erythrocytes were exposed to 1 Mc focused ultrasonic fields with maximum acoustic pressures estimated at 10 atm. In standing wave patterns in which circulation was inhibited, the cells clumped rapidly at the nodes and no changes were found. With a free surface, fountaining and stirring occurred. Exposure at 1 atm ambient pressure then resulted in rapid lysis. Erythrocytes exposed briefly in isotonic Rous-Turner mixture and controls were both diluted with sodium chloride solutions of varying concentration. The optical density at 650 mμ was plotted as a function of salt concentration. The exposed samples showed a greater fractional decrease in optical density at low sodium chloride concentrations than did the controls. Other samples exposed in hypotonic solutions showed both the greater sensitivity to low sodium chloride concentrations and a smaller change in optical density as the sodium chloride was varied from isotonic to 70% isotonic. It has not been possible to demonstrate that any factor other than cavitation was responsible for the observed changes in osmotic fragility.

By use of a high-power, corona type loudspeaker we have been able to demonstrate behavioral and endocrine responses of laboratory rodents to measured high sound-pressure levels at the frequencies at which their hearing is most sensitive, namely, 10 to 40 kc. The corona type loudspeaker behaves in the fashion predicted by the theoretical analysis reviewed in this paper. It is limited by extremely low efficiency (2.5%) and high production of ozone. At high frequencies it is limited by the volume of the corona, and at low frequencies by the failure of the quasi-adiabatic condition within the corona. Despite these limitations its performance has not been equaled by other types of loudspeakers; it is a unique tool for studying the responses of laboratory rodents to sound fields.