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Charles H. Tator and Michael L. Schwartz

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Michael L. Schwartz, Charles H. Tator and Harold J. Hoffman

✓ At 2, 10, and 60 min after intravenous injection of tritiated hydrocortisone into tumor-bearing mice, samples of brain and tumor were taken for autoradiography. Within 2 min of injection, large amounts of the steroid had left the bloodstream and had penetrated normal brain. By 60 min virtually all the drug had left the brain. The most radioactive structure was the choroid plexus. Within the normal and edematous brain, hydrocortisone was not found in cells alone but was spread randomly throughout the tissue. Edematous brain adjacent to implanted tumor contained much more steroid than normal brain. This difference was maximal at 10 min after injection. Edematous white matter adjacent to tumor was usually as radioactive as tumor. In the ependymoblastoma at 2 min after injection, neoplastic cells and interstitial tissue adjacent to blood vessels contained much hydrocortisone. At 10 min the drug was uniformly spread through the tumor tissue and by 60 min was largely gone. The uptake of the drug by the edematous brain suggests a direct local action. The high choroid plexus concentration may indicate a direct action there, perhaps to reduce cerebrospinal fluid production.

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Lüder Deecke and Charles H. Tator

✓ Controlled compression of the spinal cord at a given pressure using the circumferential cuff technique has yielded consistent, reproducible cord injury in primates. To test the constancy of the mechanical factors involved, functional tests were performed to study spinal cord conduction before, immediately after, and up to 3 hours after the injury. Two long fiber tracts were tested, the dorsal funiculus and the pyramidal tract. Afferent conduction testing was carried out extradurally recording the afferent volley in the posterior column following sciatic nerve stimulation. The normal triphasic volley before injury changed after injury into a large monophasic positive “killed end potential” at the site of the lesion; an iso-electric line rostral to the lesion site indicated a complete afferent conduction block up to the end of the experiment (3 hours after injury). Efferent conduction was tested by stimulating the pyramidal tract in the cord above the injury site with a special extradural electrode and observing the most distal hind limb movements (flexion of the hallux). The neurophysiology of this type of spinal cord recording and stimulation is discussed as well as its possible importance in establishing the severity of a spinal cord injury, the response to treatment, and the prognosis in patients with spinal cord injuries.

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Charles H. Tator and Lüder Deecke

✓ Investigations were performed to determine the relative therapeutic value of local hypothermic perfusion, local normothermic perfusion, and durotomy in monkeys injured by circumferential compression of the spinal cord at T9–10. A new method of cord compression was used consisting of an inflatable Silastic cuff which was passed around the cord extradurally and inflated to either 350 or 400 mm Hg. At the lower compression force, both hypothermic and normothermic perfusion improved the neurological recovery compared to that in control animals. However, at the higher degree of compression only normothermic perfusion produced significantly better recovery. Durotomy was excluded as a contributing factor. The results indicate that normothermic perfusion is a better method of treatment and that the beneficial effect of hypothermic perfusion is probably due to the perfusion rather than the hypothermia. The mechanism by which perfusion exerts its beneficial effect is unknown, but it is suggested that dialysis of noxious substances from the injured cord may play a role.

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Willem Wassenaar, Charles H. Tator and Wei Sum So

✓ The authors describe a brain tumor model for chemotherapy studies. The tumor is an intracerebral ependymoblastoma that kills the host in a short time (median survival, 27.5 days) and yields consistent, uniform survival curves. A suspension of tumor cells is injected into the right frontal lobe of the mouse by means of a stereotaxic frame, and produces a highly invasive, almost entirely intracranial brain tumor. The use of mice permits extensive chemotherapeutic trials for brain tumors at low cost. It is felt that this model will prove to be very useful for studies of brain tumor chemotherapy.

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Paul K. O'Brien, John W. Norris and Charles H. Tator

✓ Five cases of acute subdural hematoma associated with bleeding from cortical arteries are described. In the four cases in which the affected vessel was examined histologically, there was a defect in the arterial wall secondary to avulsion of a small surface twig, which had apparently been traversing the subdural space. The possible mechanisms for damage to the vessel wall and the role of this arterial bleeding in subdural hematomas are discussed.