Herman Kabat

Decerebration in the Dog by Complete Temporary Anemia of the Brain

In many investigations, it is desirable to perform experiments upon animals in the absence of anesthetics. The usual procedure is that of Sherrington, namely, to decerebrate surgically under ether, to stop the anesthesia, and to proceed at once with the experiment. 1 Under such conditions, profound shock and the depression due to the residual anesthetic agent throw some doubt on the reliability of the results. A more delicate method of decerebration has been devised for the cat by Pollock and Davis. 2 In this method, an anemic decerebration is produced by ligation of the basilar and carotid arteries under ether anesthesia. In the dog, the inaccessibility of the basilar artery makes this a difficult method. It has been shown that the nerve cells of the brain stem are much more resistant to anemia than are those of the cerebral hemispheres, 3 It is therefore possible to produce extensive cerebral damage by a period of anemia which will allow the cells of the brain stem to recover. Guthrie, Pike and Stewart 4 and Gildea and Cobb 5 studied the effects of temporary occlusion of the 4 chief cerebral vessels in the neck under ether anesthesia, and were unable to predict the severity of the destruction produced by a given period of such occlusion. The variability in their results was due primarily to their failure to interrupt the flow in the spinal arteries, which is not constant from animal to animal. A further uncertainty must have resulted from variations in the depth of anesthesia just prior to the occlusion of the cerebral vessels. We have devised a method of decerebration depending upon complete temporary anemia of the brain of the dog in the absence of anesthetics. A preliminary surgical procedure is used, consisting in removal of both laminæ and spine of the second cervical vertebra and ligation of both vertebral arteries. After an interval of one to 2 weeks, the dog is given one to 2 mg of atropin sulfate to prevent vagal cardiac inhibition, and placed, back down, on the table.

Behavior of Dogs after Complete Temporary Arrest of the Cephalic Circulation.

The authors have previously reported a method of decerebration of the dog by means of cephalic vascular stasis. 1 The emphasis at that time was upon the use of the procedure as a method for preparing decerebrate animals. Since that time our interest has shifted to the evidence that could be gained concerning the resistance of various cells in the brain to temporary cessation of blood flow and the correlation of these changes with changes in the behavior of the animal. The technic has been modified to the following form: Two days after laminectomy at the second cervical level, the animal is atropinized, and a metal tracheal tube is inserted orally. A blood pressure cuff is wrapped about the neck, and the pressure is raised quickly to 700 mm Hg, at which level it is maintained as long as vascular arrest is desired, artificial respiration being administered through the tracheal tube. The completeness of circulatory arrest in the head is determined by ophthalmoscopic examination of the retinal vessels. With this technic, consciousness is lost in a very few seconds, the corneal reflex disappears in from 20 to 40 seconds, and spontaneous respiration ceases in from 40 to 90 seconds. In 6 adult animals there was complete cessation of cephalic blood flow for periods of from 2 to 10 minutes. In the dogs subjected to 8 minutes or less of compression the lid wink returned in 5 to 8 minutes; in 2 animals treated for 10 minutes it did not return till later. The first gasp occurred in 1 to 5 minutes and satisfactory spontaneous respiration returned in 2 to 11 minutes, the slowest return being after the longest compression. Intermittent spontaneous, high-pitched vocalization, associated with vigorous running movements of all 4 limbs, with the dog lying on his side, often occurred during the first few hours.

Influence of K-Strophanthosid on Elasticity of the Tortoise Ventricle

Summary The cardiac glucoside K-Strophanthosid has no effect on the diastolic elasticity of tortoise ventricle with doses and within times which result in very large increases in tension set up and work done. Larger doses produce after a time great increases in diastolic elasticity, up to the point of contracture, but when such increases occur the work and tension production fall off. The increase in work capacity of tortoise ventricular muscle produced by this glucoside is not positively correlated with diastolic elasticity changes. Inferences from observations on the failing mammalian heart are confused by the fact that anoxia itself alters elasticity, and therefore the increased efficiency produced by digitalis would in itself be expected to increase diastolic elasticity. Such an indirect effect is a secondary result of the primary action of the drug upon work performance.

DECREASE IN LACTIC ACID CONTENT OF THE BRAIN IN POLIOMYELITIS

over P205 gave carbon 51.4, nitrogen 9.0 and phosphorous 0.87 per cent. By extraction with alcoholether (3-1) and reextraction of the lipids with petroleum ether,5 6 the lipid fraction was 24 and the non-lipid fraction 77.76 per cent. of the material. The total lipid fraction was made up of 10.64 per cent. phospholipid, 5.67 per cent. cholesterol and 7.64 per cent. neutral fat. Of the total phosphorous, 52 per cent. were found in the lipid fraction. If the remainder of the phosphorous was present in nucleic acid, the virus would contain about 4.0 per cent. nucleic acid of the desoxypentose type. The total carbohydrate7 (as glucose) content of the whole virus was 10 per cent. The carbohydrate, apparently firmly bound in complex form, was greatly in excess of that expected for the amount of nucleic acid present. Subtracting this value from that of the non-lipid fraction, 77.76 per cent., the probable protein content of the virus was about 67.76 per cent. A similar finding has been encountered with influenza virus B (Lee strain), in which the total carbohydrate was 9.3 per cent. The infectious unit of the virus when inoculated in 0.05 ml volumes in chick embryos was 10-12.1 to 10-13.1 grams with an average of 10-12.74. One concentrate, purified by adsorption, elution and centrifugation and titrated in fivefold dilutions employing 40 embryos per dilution, gave the value 10-1311 grams; another concentrate purified by ultracentrifugation alone and titrated similarly in 40 embryos per dilution gave 1012.75 grams. The hemagglutinative activity of the concentrates was such that 10-6.16 to 10-6-.4 grams with an average of 10629 grams gave the 2 plus end point. A. R. TAYLOR D. G. SHARP I. W. MCLEAN, JR.8 DOROTHY BEARD J. W. BEARD9 J. H. DINGLE9 A. E. FELLER9 DEPARTMENT OF SURGERY, DUKE UNIVERSITY SCHOOL OF MEDICINE

Resistance of Young Dogs to Acute Arrest of the Cephalic Circulation.

The observation has been made by several investigators that the young animal is much less susceptible to asphyxia than the adult. 1 , 2 No information has been available, however, concerning the essential factors involved in the greater resistance of the young to asphyxia. It was of interest, therefore, to determine whether the brain itself is more resistant to anoxia and accumulation of metabolites in the young animal. This question has been investigated by comparing the effects of complete arrest of the cephalic circulation for various periods of time in adult dogs and in puppies. The method which has been employed to produce sudden complete stasis of blood in the head by means of a pressure cuff in the cervical region has been described 3 as has also the effects of this procedure on adult animals. 4 The adult dog rarely recovers consciousness after 8 minutes of complete vascular occlusion. It remains comatose as long as it lives, losing all sensation and retaining only very primitive responses on the reflex level. After 6 minutes of vascular stasis, consciousness is recovered in 24 to 48 hours as a rule and following this, the animal is very severely ataxic, restoration to normal requiring a period of weeks or months. Following 4 minutes of arrest of the cephalic circulation, consciousness returns in 18 to 24 hours and the residual ataxic symptoms, though somewhat less severe, are still present. After only 2 minutes of vascular occlusion, slight ataxia persists for a week or more. Complete arrest of the cephalic circulation was produced in 8 puppies using the same technic as had been employed in the study of adult animals. The results of temporary cessation of the brain circulation in these animals are in striking contrast to the effects of the procedure in the adult.

A New Method of Arterial Anastomosis for Acute Experiments Without Use of an Anticoagulant

In cross-circulation experiments and in acute transplantation experiments, it is often necessary to use coagulable blood because surgery is contemplated after the blood vessels have been connected. Various methods have been proposed to avoid thrombosis and assure adequate blood flow in such arterial anastomoses. 1 End-to-end anastomosis with silk sutures is satisfactory but is too time-consuming for acute experiments. Arterial anastomosis by means of Payr cannulae, the method recommended by Heymans and his co-workers, 2 proved unsatisfactory in our laboratory. The method of arterial anastomosis to be described is very simple and can be performed rapidly. It has been successful every time it was attempted and has been found to provide adequate blood flow for many hours. This method involves the use of a wire eversion frame (a, Fig. 1). One artery is pulled through the loop of the frame, is everted over the loop and then tied to the frame. The everted artery is now placed within the lumen of the second artery, which is also tied to the frame. The flowing blood touches only endothelium so that thrombosis does not occur.