V. E. Hall

THE MUSCULAR ACTIVITY AND OXYGEN CONSUMPTION OF URECHIS CAUPO

The greater part of the muscular activity of the echiuroid worm Urechis caupo is involved in pumping a current of water through its U-shaped burrow. The magnitude of this current was studied in artificial burrows, food-free water being supplied to the animals. When the animal is not feeding, the current amounts to about eleven cubic centimeters per minute. During feeding periods, the rate of pumping rises to about twenty-nine cubic centimeters per minute. The frequency, duration and course of activity during these feeding periods has been studied. The significance of the stream in relation to provision of oxygen and food is discussed.The oxygen consumption of the animals in U-tubes amounts to 0.00021 cc. per gram per minute, being comparable to that of related forms. It is independent of the oxygen pressure down to a value of 70 mm. Hg.The oxygen consumption of the worms when placed in covered jars decreases with falling oxygen pressure throughout the range investigated, 115 to 4 mm. Hg. The reasons for t...

Influence of Dinitrophenol on Body Temperature Threshold for Thermal Polypnea.

Conclusion We may conclude that DNP in doses of 10 and 20 mg per kg, although it does not prevent the occurrence of thermal polypnea, does significantly increase the rectal temperature level at which such polypnea appears. It accordingly appears that DNP does not sensitize the heat defense mechanism as would be required by the second hypothesis stated above. Rather it suggests that DNP depresses both heat and cold defense mechanisms by a nonspecific toxic action.

Influence of Respiratory Inspiration on the Heart Rate

Summary and Conclusion The slowing of the heart produced by sustained deep inspiration is not due to the reflex consequences of lowered intrathoracic pressure nor to any other hitherto recognized reflex mechanism. It is probably caused by some influence activated by the assumption of the inspiratory position of the chest.

Non-Utilization of Intravenously Administered Acetyl-dl-tryptophane

Summary Acetyl-dl-tryptophane in aqueous solution was administered intravenously to 3 human subjects. Seventy to 83% of the administered substance was excreted unchanged, almost all within the first 6 hours after injection. The substance excreted was racemic: there was no preferential utilization or retention of acetyl-l-tryptophane.

Monoiodoacetic Acid Poisoning in Albino Rats: Symptoms, Minimum Lethal Dose.

The finding of Lundsgaard 1 that monoiodoacetic acid injection into frogs inhibited the production of lactic acid by skeletal muscles on stimulation, without abolishing contraction, has revolutionized theories of the chemical mechanism of muscular contraction. Accordingly, it seemed valuable to prepare for the extension of this work to mammals by determination of the dosage required for the various symptoms, and for death. Solutions of monoiodoacetic acid, brought to pH 7.2 by addition of sodium hydroxide, were injected intraperitoneally into unanesthetized female albino rats of 130 to 250 gm. weight, the dosage range being from 30 to 400 mg. per kg. body weight. A group of 5 animals received each dose. The rats had been starved for a period of 48 hours previous to injection. In all animals receiving 120 or more mg. per kg. death occurred within 20 minutes. The time of onset of symptoms varied from 2 minutes with the largest dose to 8 minutes with 120 mg. per kg. The first alteration of behavior was the appearance of marked general hypoactivity, interrupted by sudden attacks of hyperactivity—running, climbing or biting, in which the movements soon became definitely ataxic. Circus movements appeared in a number of cases. Distinct hyperpnea next appeared, which often progressed to a definite inspiratory dyspnea. The hind legs became paralyzed, being dragged in an abducted posture. The animal soon became prostrate, lying on the side and making no righting movements if placed on the back. Occasionally tremors or mild clonic convulsions occurred. During various of the above stages the animals squeaked loudly, if touched or convulsed, in a manner suggesting hypersensitivity. Finally there appeared a violent tonic convulsion involving the whole body, lasting only about 10 seconds, but leaving the animal in extreme rigor in the posture given to it by the convulsion; mouth open, marked opisthotonus, elbows and wrists flexed; digits of fore feet flexed and adducted; hip, knee and ankle extended; digits of hind feet extended and abducted.

Lactate Production in Muscle Stimulated Briefly.

In dogs anesthetized with amytal we have observed the lactate concentration in gracilis muscles immediately after brief periods of activity induced by short tetanizations repeated rhythmically. The muscles were stimulated in situ through the obturator nerve. The circulation was intact and the arterial pressure satisfactory. As soon as possible after stimulation ceased they were frozen in situ with carbon dioxide snow, excised and ground to powder in liquid air. Lactate determinations were made by the method of Friedmann, Cotonio and Shaffer. 1 For comparison rectus femoris muscles of the same animals were excised in the same manner without previous stimulation and tested for lactates according to the same technique. Results are as follows: The increases in lactate resulting from these brief periods of activity are equal to or greater than the increases reported by us after 15 minutes of tetanization under similar conditions. 2

Tissue Lactates and Blood Lactates as Affected by Muscular Exercise.

In dogs anesthetized with amytal the following preparations were made: 3 fore limb muscles and 2 hind limb muscles were prepared for rapid excision, with care to avoid injury to said muscles or interference with their blood and nerve supply. A carotid artery was cannulized, and a brachial vein and the inferior vena cava below junction with the renal veins were exposed. The blood vessels leading to both kidneys were tied off. Stimulating electrodes were imbedded under the skin of the back at the levels of the first lumbar and last sacral vertebrae. 1 Continuous records of arterial blood pressure and of oxygen consumption were made. At the end of a 15-minute basal period a sample of arterial blood was drawn and one fore limb muscle rapidly excised and thrown at once into liquid air. Artificial exercise (confined to the hind quarters by the location of the electrodes) was then induced for 15 minutes. At the end of the exercise period blood samples were drawn from the cannulized artery, from the inferior vena cava (representing the outflow from worked muscles) and from the brachial vein (representing the outflow from non-worked muscles). One hind limb muscle (worked) and one fore limb muscle (non-worked) were excised rapidly and thrown into liquid air. At the end of a recovery period approximately one hour in length blood samples were again drawn, as above, and one previously worked and one non-worked muscle excised and thrown into liquid air. Blood and muscle lactates were determined by the method of Friedmann, Cotonio and Shaffer. 2 The results of 5 experiments are summarized in Table I.

Blood Lactates in Various Anoxemic States.

In the course of an investigation on the general subject of the oxidative aspect of functional metabolism which is being carried on in this laboratory, it seemed desirable to test the validity of the hypothesis of A. V. Hill 1 that lactic acid serves as a “governor” of recovery oxidation. To this end two techniques have been developed for the production in the anesthetized dog of anoxemic states, which have been shown by Fletcher and Hopkins, 2 and others, to be the sole cause of excess tissue lactates. Throughout, dogs anesthetized by intraperitoneal injection of amytal were employed. Samples of blood for analysis were drawn from the femoral artery. The recently published method of Friedemann, Cotonio and Shaffer 3 was used for the determination of lactic acid in the blood so obtained. Artificial Exercise. Two sheet brass electrodes were implanted in the subcutaneous tissues over the midcervical and sacral regions of the spinal cord. By means of faradic stimulation, a regular series of short, vigorous, tetanic contractions, involving the muscles of the trunk and extremities, were produced over a period of 15 minutes. During this intense muscular activity the oxygen consumption of the animal increased eight-fold. The observed changes in blood lactates are shown in Table I.