Burton L. Wise

PENETRATION OF C14-LABELLED MANNITOL FROM SERUM INTO CEREBROSPINAL FLUID AND BRAIN.

Fifty microcuries of radioactive labelled mannitol (d-mannitol-1-C14) was administered to each of eight dogs. In six it was mixed with unlabelled mannitol (3 gm/kg); in two, it was mixed with an equivalent volume of normal saline. Determination of concentration of radioactivity in serum, urine, CSF and brain was done at intervals up to 6 hours. Seventy-five per cent of the C14 introduced with inert mannitol was excreted in 6 hours. The peak concentration of radio-activity in the CSF was reached at about 2 hours from the start of the infusion. However, the serum radioactivity concentration at this time was considerably higher than CSF. The maximum ratio of CSF/serum concentrations of C14 was 0.37, at 6 hours, and the brain/serum ratio of C14 concentrations at this time was 0.62. If a small percentage of mannitol undergoes metabolism in the body, the actual concentration of mannitol may be even lower than assumed from counting the C14 tracer. At no time during the study of the six animals given tracer with unlabelled mannitol did the CSF or brain concentration of C14 approach that in the serum.

NEURAL PATHWAYS MEDIATING THE INCREASE IN ADRENAL MEDULLARY SECRETION PRODUCED BY HYPOGLYCEMIA.

Summary Insulin-induced hypoglycemia produced a marked increase in epinephrine secretion in fasted dogs. The rise was not abolished by transection of the midbrain or cervical spinal cord. It was completely abolished by removal of the thoracic and upper lumbar spinal cord in 4 of 6 dogs studied. It was also blocked by localized resection of the fifth to seventh thoracic segments of the spinal cord, but not by removal of more caudal segments. These data indicate that the portion of the spinal cord above the seventh thoracic segment is the only part of the central nervous system which is essential in the dog for the increase in epinephrine secretion produced by insulin-induced hypoglycemia.

Relation of Brain Stem to Renal Electrolyte Excretion.

Summary In anesthetized dogs, bipolar stimulation (0.5 volt, 5/sec.) of the caudal portion of the floor of the fourth ventricle resulted in increased renal excretion of sodium and chloride, and a smaller increase in potassium excretion in 5 instances, slight changes in 3, and decreased excretion in 2. In 2 dogs, increasing the stimulus to 1 volt resulted in a decreased excretion rate of these electrolytes.

Neurogenic hyperosmolarity (hypernatremia)

Intake consisted mainly of intravenous fluids or feedings by tube, the constituents of which were readily calculated. The analytic methods used were the same as those cited in a previous article.5 The method of charting is described in the cutlines for each figure. In instances where fluid intake and urinary output were known, they were charted as a crude ‘balance” with full understanding of the limitations of this balance.6 In charting balance, intake was charted upward from the baseline, output downward from the intake line. The difference is the balance, which is stippled if positive, black if negative.

Effect of removal of various parts of the brain on ACTH secretion in dogs.

Summary The adrenocortical response to the trauma of cannulating the adrenal vein has been tested in dogs 4 hours after removal of various parts of the brain. Compared to controls, 17-hydroxycorticoid output in adrenal venous blood is slightly decreased in dogs in which all brain tissue above the pons except the hypothalamus has been removed. Output was significantly lower, but still definitely above basal levels in dogs in which the entire brain above the pons had been removed. It was in the same range when the entire brain had been removed. Acute section of the pituitary stalk decreased the adrenocortical response to an approximately equal degree. Removal of the pituitary as well as the brain reduced output to low levels. These data do not support the hypothesis that the hindbrain secretes a factor which stimulates the pituitary to secrete ACTH. Other possible explanations of the results are discussed.

Effect of Brain Removal in Dogs Previously Subjected to Pituitary Stalk Section.

Summary The effects on adrenal cortical function of removing the hypothalamus and other neural tissue above the midbrain were determined in 11 dogs in which the pituitary stalk had been sectioned previously and a plastic plate placed over the pituitary. There was a clear-cut response to stress 2 to 10 weeks after stalk section, and 17-hydroxy-corticoid output in the unstressed state 24 hours after adrenal vein cannulation (before brain removal) was low. However, following subsequent brain removal, 17-hydroxycorti-coid output was elevated. All neurohypo-physeal tissue below the plastic plate was atrophic in these dogs. There was no marked adrenocortical atrophy. The results suggest that the stress response in severely stressed dogs is not due entirely to CRF from the hypothalamus, and may be due in part to an ACTH-stimulating humoral agent liberated from traumatized tissues.

Spontaneous carotid thrombosis; unusual arteriographic appearance.

IN RECENT YEARS, carotid thrombosis has been diagnosed with greater frequency than several decades ago, mainly because of the increased use of cerebral arteriography. The clinical picture of this condition is variable. Johnson and Walker1 reviewed 107 cases and noted three different patterns of onset, namely, sudden catastrophic onset, slowly progressive course, and transient attacks. Fisher2 has emphasized the frequency of carotid artery occlusion both with and without symptoms. In a series of 432 consecutive autopsies, complete unilateral or bilateral carotid occlusion was present in 28 and there was marked narrowing of the artery in 13. The following case is reported because of the unusual appearance of the carotid angiograms, the manner of onset, and the treatment by carotid thrombectomy.

The effect of hypertonic sorbitol solution on cerebrospinal fluid pressure in the dog

Abstract The effect of intravenous infusion of hypertonic solution of sorbitol (3.1 g/kg) on the pressure of the CSF of six normal dogs was studied. Sorbitol tended to cause a slight initial rise in the pressure of the CSF, followed by a mean drop of 65% and a return to base line in four hours. In three of six dogs, however, there was a slight secondary rise in pressure of the CSF above the original level. Significant diuresis occurred in all animals. There were no significant changes in blood pressure. Serum sodium concentration rose slightly after the infusion in two dogs.