Maternal, fetal, and newborn tissue PO2 in sheep measured with galvanic oxygen electrodes.

Tissue PO2 was measured with galvanic oxygen electrodes chronically implanted in maternal and fetal tissues of two pregnant ewes. Labor commenced after 3 days in one ewe and after 11 days in the other. Tissue PO2 was measured in both newborn lambs. Fetal tissue PO2 during labor was less than 3 mm Hg but rose to values similar to those found in adult tissues in the newborn period. Function of the electrode and response of the tissue to change in oxygenation was challenged by administration of 100% oxygen to the pregnant ewe or newborn lamb, and by administration of intravenous epinephrine to the ewe. These tests suggested that all electrodes were functioning satisfactorily in vivo and that tissue PO2 was responding as anticipated. Recalibration of electrodes after removal from the tissues confirmed that their response in vitro was similar to that obtained before implantation.

The implantation of a closed loop artificial beta cell in dogs.

1. Seven more diabetic dogs have been implanted with complete feedback artificial beta cell systems. 2. All of these units have functioned fairly well with maintenance of the animals in the process of extensive surgery but none have brought the animals under complete control. 3. The glucose sensors are at fault because they are insensitive to the glucose levels giving readings that appear functionally to be about half of true readings. 4. The defective function of the electrodes has been traced to the design of the electrodes which does not take the Km of glucose oxidase for oxygen into consideration. 5. Redesign of the electrodes by inclusion of a convertor for pO2 based on the reading of the reference electrodes leads to a reliable glucose reading. 6. It is recommended that all glucose electrodes which are based on glucose oxidase be redesigned to include an oxygen electrode to permit correction of the readings to account for the effect of local pO2 on their function.

Continuous extracorporeal monitoring of animal blood using the glucose electrode.

A continuous extracorporeal monitoring system for blood glucose employing an electrochemical sensor is described. The sensor, about the size of a nickel, is rapid, is specific for glucose, generates its own power, and consists of two galvanic oxygen electrodes. Over one oxygen electrode is affixed a plastic matrix to which glucose oxidase is covalently bound; a blank matrix is over the other, which serves as a reference. Oxygen is consumed in the glucose-oxidase-containing matrix, decreasing the current from the underlying oxygen electrode. The current decrease is nonlinearly proportional to the glucose concentration. The sensor is clamped between small blocks of plastic fitted with inlet and outlet nipples so that blood pumped from the animal passes over the two electrodes and thence to an automated chemical analysis for comparison. Blood is collected and anticoagulant added in a double-lumen catheter. Blood is withdrawn at the rate of 1 cc. per hour. Results obtained by use of the system in rabbits are reported. The capacity of the system to continuously monitor changes in blood glucose produced by repeated glucose tolerances is shown in hypo-, normo-, and hyperglycemic animals. Some properties of the system and its calibration are discussed.

ynergy of ethanol and a natural soporific--gamma hydroxybutyrate.

gamma-Hydroxybutyrate and ethanol, as well as gamma-butyrolactone and ethanol are potentiative with respect to duration of loss of the righting reflex (sleep time). The concentration of ethanol in the liver decreases from 30 to 90 minutes after rats are injected with ethanol, but there is no change when ethanol is injected with gamma-butyrolactone. In view of the fact that gamma-hydroxybutyrate is a natural intermediate in brain, the effects of ethanol on the central nervous system may be mediated through its interaction with gamma-butyrolactone.