David Yashon

CONTRIBUTION OF THE PENTOSE CYCLE TO THE METABOLISM OF GLUCOSE IN THE ISOLATED, PERFUSED BRAIN OF THE MONKEY

Abstract— Isolated brains from three adult monkeys were perfused for 1 hr with [2‐14C]glucose. Glycogen was isolated from the brain stem, cerebral hemispheres, cerebellum and the hypothalamic area at completion of the perfusions. The distribution of 14C in carbons of the glucose unit of glycogen was determined and from this the contribution of the pentose cycle to metabolism of glucose was calculated. The data indicate a maximum contribution by the pentose cycle of 5–8 per cent in brain. No significant difference was observed in the various portions of brain. Oxygen consumption was noted to be low in relation to the amount of glucose utilized, as measured in these experiments.

Electrical activity of the isolated macaque brain

Abstract The completely isolated brain (vascular as well as neurologic isolation) on donor perfusion showed excellent electrical activity of the cortex and reticular formation during all phases of its preparation including 1–4 hours of donor perfusion. As the various cranial nerves and spinal cord connections were severed from the brain stem, faster moderate voltage electrical activity appeared in cortex and reticular formation. These results were found in isolated preparations where no difficulties occurred in maintaining proper blood pressure, with minimal blood loss, and normothermic brain temperature. The neurogenically isolated brain (all cranial nerves severed) was maintained with little difficulty and appeared to show electrocortical activity similar to that in the completely isolated brain. Fast electrical activity appeared after the removal of the cranial nerves and spinal cord. Control of blood pressure, blood loss, and brain temperature was a prerequisite for optimum cortical activity. Severance of the brain stem between the mesencephalon and diencephalon (cervean isole) created first: a short period of synchronized slowing of electrical activity, followed by a longer period of extremely fast, low-voltage, desynchronized activity, then by phasic slow and fast activity. The intervals of slow activity increased in number and duration as the blood pressure became difficult to maintain, finally becoming very slow with high-voltage activity in the failing preparation. It appears that the isolated primate brain shows a range of electrophysiological activity including states characteristic of the aroused brain of an intact monkey.

Subacute necrotizing encephalomyelopathy of infancy and childhood

Subacute necrotizing encephalomyelopathy appears to be a distinct pathological entity occurring in infancy and childhood. The neurological manifestations are diverse but the course is one of progressive deterioration. The aetiology is not known and no treatment is available. Histologically the lesion is characterized by multiple areas of necrosis and is remarkable because of a lack of glial or small cell reaction. There is a predilection for the brain-stem but the entire neuraxis may be involved. The mammillary bodies are generally spared. Capillary proliferation and status spongiosus are seen either separately or more commonly in combination. Areas may be found in which no neural tissue is spared or a nucleus may selectively be involved with sparing of adjacent white matter, or occasionally only white matter is involved. In this account the twenty-first, twenty-second and twenty-third cases, one of which had a lesion in the mammillary body, are reported. Possible aetiological mechanisms are discussed.

Cerebral Lactate Accumulation and Glucose Exhaustion During Circulatory Arrest

Summary Glucose and lactate content in dog brain were measured before and during arrest of circulation in a standard preparation. Comparison with other studies of the same model allowed the guarded conclusion that the cerebral lactate level in dogs after 10 min of severe hypoxia may be indicative of an irreversible state. Lactate concentration rose and glucose levels fell during a 10-min period of ischemia. The increase in lactate concentration was sufficient to account for about one-fourth of the decrease in glucose content by way of anerobic glycolysis.

An anatomic basis for multimodal thalamic units

Abstract Lesions were placed in the inferior colliculi of seven opossum and degenerating axons were traced to the dorsal thalamus with the Nauta technique. The sites of terminal degeneration included the medial geniculate body, ventral posterior, and posterior thalamic nuclei (PO). This wide region of distribution provides an anatomic basis for the existence of cells in the ventral posterior and PO nuclei that are responsive to auditory stimuli.

Injuries of the Vertebral Column and Spinal Cord

Permanent paralysis as a result of accidental spinal injury during the prime of life is one of the most devastating occurrences which may befall a human being. In addition to its tragic effect on the patient, the resultant physical, psychologic, and financial burden severely taxes the resources of the family and the community. Spinal injuries result from accidents that are largely preventable and efforts to reduce their frequency and severity should be unremitting.

The isolation and transplantation of the brain. An historical perspective emphasizing the surgical solutions to the design of these classical models

Following an historical review of earlier attempts to develop separated head and brain preparations and their contributions to modern-day understanding of the neurophysiology and neurochemistry of the central nervous system, the experiments that eventually led to the first successful total isolation of the mammalian brain are presented. The operative strategies emphasizing the anatomical and physiological problems requiring solution that resulted in vascular and neurogenic separation from the parent body and cephalon are described. The innovative engineering concepts that were utilized in the design of miniaturized equipment to maintain the isolated brain in a living state under conditions of cross circulation, extracorporeal artificial perfusion and transplantation are elaborated. Investigations employing isolated brain and cephalic preparation documenting tissue substrate requirements, metabolic and rheological conditions prevailing at various low temperatures and the immunologically privileged state of the separated organ are briefly presented. The unique opportunities these isolated brain models offer for study are emphasized as well as the complexity of their surgical preparation, which, to date, has limited their universal applications.

Programmed management of acute cervical cord trauma

Results in ten patients admitted with the diagnosis of complete traumatic quadriplegia and with fracture-dislocation of the cervical spine are reviewed. Emphasis is placed on aggressive emergency surgical treatment of these lesions such as tracheostomy, laminectomy and cord cooling, incorporated into a detailed protocol of overall management.

Extracorporeal perfusion of dog and monkey brain during circulatory arrest

Abstract Cerebral viability (as evidenced by the persistence of EEG activity) has been maintained in situ for many hours by utilizing simplified extracorporeal (pump-oxygenator) perfusion systems to provide cephalo-cerebral circulation, in cardiac-arrested canine and monkey preparations. Additional studies using unicarotid mechanical perfusion and EEG monitoring demonstrated the limitations at present characterizing the pumping elements utilized in isolated cerebral perfusion.