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Biomedical subjects

D Yashon

Publications and source records attributed to D Yashon.

At least 19 recordsLinked to original sources
PubMed1996

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.

Animals↗
PubMed1980

Myelin and microsomes from rhesus monkey spinal cord: isolation and effects of trauma.

Dispersions of rhesus monkey spinal cord and brain were separated into large particle (crude mitochondrial plus nuclear) and small particle (crude microsomal) fractions; myelin was isolated from each of these preparative fractions. In brain preparations, almost all myelin was found in the large particle fraction; in contrast, almost half the myelin from spinal cord preparations was found in the small particle fraction. In addition, much larger amounts of partially degraded myelin were found in the fraction floating on 0.32 M sucrose and in the cytosol fraction of the spinal cord preparation in comparison to those of the brain preparations. These results suggest that rhesus monkey spinal cord myelin is more fragile than brain myelin; upon dispersion of spinal cord, more small myelin vesicles (isolated from the crude microsomal fraction) and more 0.32 M sucrose floating fraction (partially degraded myelin) are formed. After trauma of the spinal cord, the proportion of small vesicle myelin was increased at the expense of large vesicle myelin, lending further support to the hypothesis that spinal cord myelin is more fragile than brain myelin. Although the lipid compositions were similar, spinal cord myelin had a lower protein content and a lower 2',3'-cyclic nucleotide phosphodiesterase specific activity than did brain myelin. The lipid composition of microsomes from brain differed somewhat from that of spinal cord microsomes.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1977

Vasoactive properties of prostaglandin compounds on the in vitro human basilar artery.

The action of six prostaglandins A1, E1, (A2, E2, F1 alpha, F2 alpha) on in vitro human basilar artery circumferential strips was evaluated to assess relative vasoreactivity. Degree of contraction was compared with 5-hydroxytryptamine (5-HT), hitherto the most active in this laboratory. The three most vasoactive prostaglandins were E1, E2, and F2, alpha. The three PGs giving highest magnitude of response were F1 alpha, F2 alpha, and E2. Most were more active when compared to 5-HT. Vasodilation did not occur. Because of their vasoconstrictive qualities, prostaglandins may participate in arterial vasospasm. It is postulated that prolonged vasoconstriction may lead to vasospasm and that the latter may result from one or more autacoids acting along or synergistically.

Basilar Artery↗
PubMed1976

Narrow lumbar spinal canal with "vascular" syndromes.

Symptoms suggestive of vascular origin, both venous and arterial, may be the presenting complaints in patients with lumbar spondylosis. Fourteen patients suspected of having vascular intermittent claudication were found to be free of vascular disease, but had cauda equina compromise from herniated disk, osteoarthritis, and hypertrophic ligaments. Complete follow-up data were available for seven patients. In three, claudication seemed typical; in four, atypical. At operation, herniated intervertebral disks, osteophytic bone, or hypertrophied ligamenta flava, or a combination, were found. All benefited from lumbar laminectomy. When patients with vascular-like symptoms are found to be free of arterial or venous disease, lumbar spondylosis (narrow lumbar canal syndrome) should be considered. Chronic incapacitation pain without vascular disease provides a clue, as does electromyography. Plain X-ray films of the lumbar spine do not show the abnormality; thus, myelography should be carried out even in the absence of neurologic signs.

Aged↗
PubMed1976

Effects of anesthesia level and stimulus characteristic on the amplitude and latency of the somatosensory evoked response in monkeys.

The effect on the somatosensory evoked response (SER) of the level of anesthesia, and the effect of the site, intensity, duration, and frequency of the stimulus on the amplitude and latency of various components of the SER were studied in 8 Rhesus monkeys. Peroneal nerve stimulation produced similar patterns over both sides of the head, with a slightly larger amplitude over the contralateral cortex. With ulnar nerve stimulation, significantly different patterns were observed over the contralateral and ipsilateral cortex; however, the former still had a slightly larger amplitude. The latency of the various components in the SER's was not influenced by the level of anesthesia or by the intensity, duration, or frequency of the stimulus. As the level of anesthesia decreased, there was a general increase in amplitude of the SER's with peroneal nerve stimulation and no consistent change with ulnar nerve stimulation. The amplitudes of the SER increased with the increase in stimulus intensity or duration, and with a decrease in stimulus frequency.

Afferent Pathways↗
PubMed1976

A neuroanatomical analysis of spinal cord injury in the rhesus monkey (Macaca mulatta).

Thirteen rhesus monkeys were subjected to impacts of either 200, 300, 400, oe 500 g-cm, on the dorsal surface of the spinal cord (Allen 1911). Six monkeys served as controls to determine the results of transection of the cord as well as the optimal survival time, and 2 additional subjects underwent the operative procedures only. Most of the animals were sacrificed 1 week postoperatively and the brains and spinal cords were processed by the Fink and Heimer (1967) technique for degenerating axons. Two contrils and 1 experimental subject, sacrificed at 1 week, were prepared for electron-microscopic analysis...

Afferent Pathways↗
PubMed1976

Chromophobe adenoma and chiasmal syndrome without enlargement of the bony sella.

Four cases of chiasmal syndrome resulting from chromophobe adenoma with normal-sized sella turcica are reported. The predominantly suprasellar growth of these tumors was probably the result of a well-pneumatized sphenoid sinus and/or a congenitally deficient diaphragma sellae. In patients with chiasmal syndrome, a high suspicion of a surgically treatable lesion must be maintained in spite of radiographs showing a normal-sized sella. In spite of the difficulties presented by normal variations, subtle findings should be searched for on the plain films and given additional weight in the patient with a chiasmal syndrome. An aggressive diagnostic work-up, including pneumoencephalography with thin-section tomography, should be pursued in all such patients before accepting some alternate explanation, such as demyelinating disease, for visual impairment.

Adenoma, Chromophobe↗
PubMed1975

Astrocytic processes: A route between vessels and neurons followingblood-brain barrier injurt.

The fluorescent tracer Evans blue (EB) was studied after circulation time ranging from 30 seconds to 5 minutes following blood-brain barrier (BBB) injuries in 42 dogs. Selective neuronal stainings (sns), associated with BBB injuries, occurred to a high degree. This phenomenon was examined by modifications in existing fluorescence techniques. The mechanism of SNS was seen to lie in an almost imperceptible transport of EB along astrocytic processes connecting SNS with the adjacent vasculature. This report presents visual evidence under pathological conditions, and supports the concept of astrocytic processes as the normal route of transport between blood vessels and neurons. This requires long exposure photomicrographs since the fluorescing material is subtle within the neuroglial processes.

Animals↗
PubMed1975

Blood flow in normal and injured monkey spinal cord.

The authors used indicator fractionation techniques to determine blood flow in normal and bluntly traumatized spinal cords of Macaca rhesus monkeys. Normal flow rates were determined for several levels of spinal cord as well as differential values for white and gray matter from representative areas. Flow rates in traumatized tissue, obtained at several different time intervals up to 4 hours after injury, demonstrated marked differences in regional perfusion of the white matter and gray matter after trauma. Gray matter perfusion was nearly obliterated while white matter blood flow persisted and in fact was higher than uninjured controls. The findings do not support the concept of ischemia as a factor in white matter failure. If toxic pathobiochemical alterations are induced by trauma, it may be possible to reverse these changes by exploiting the preserved white matter blood flow for chemotherapeutic intervention.

Animals↗