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Biomedical subjects

R Katzman

Publications and source records attributed to R Katzman.

At least 127 records · Page 7Linked to original sources
PubMed1977

Syndrome of normal pressure hydrocephalus: possible relation to hypertensive and arteriosclerotic vasculopathy.

A patient with clinical features of idiopathic normal pressure hydrocephalus, who responded dramatically to shunting, was found a necropsy to have a severe hypertensive and arteriosclerotic vasculopathy with multiple lacunar infarcts. There was no pathological evidence of thickened leptomeninges, fibrosis of the arachnoid villi, or Alzheimer's disease. An abnormal absorption mechanism was demonstrated with cisternography and by an increase in the concentration of homovanillic acid in the cerebrospinal fluid. It is suggested that vascular changes may play an important role in the pathophysiology in some cases of normal pressure hydrocephalus.

Aged↗
PubMed1976

The catecholamine pontine cellular groups locus coeruleus, A4, subcoeruleus in the primate Cebus apella.

The distrubution of CA neurons of areas A6 and A4 was delineated in Cebus apella monkey using the fluorescent histochemical technique of Falck and Hillarp. Cytospectroscopy was utilized for CA differentiation. The noradrenergic cellular regions A6, A4, and subcoeruleus have extensively increased in size in the Cebus as compared to the rat and appear to be separate nuclear regions. Area A4 is made up of two cellular subgroups: a more abundant lateral magnocellular area with cells as large as 45 mum and a smaller medial parvocellular group where the neurons are spindle-shaped and lie within 10-100 mum of the ependyma. The neuronal processes of A4 tend to be directed towards the flocculus and paraflocculus of the cerebellum. Some processes seem to enter the ependyma and others end subependymally. The functional significance of the pontine CA neurons is discussed.

Animals↗
PubMed1976

Maintenance of a constant brain extracellular potassium.

The development of potassium specific ion exchanger microelectrodes has enabled investigators to measure directly brain extracellular potassium ion activity. Although serum potassium in various species ranges between 3.5 and 6 mEq/l, brain extracellular potassium is maintained at a level close to 3 mEq/l independent of fluctuations in serum values. Despite this buffering of the internal brain environment by extracerebral changes, local variations in extracellular potassium occur in response to evoked neuronal activity, seizures, and spreading depression. Mechanisms involved in the maintenance of this ionic homeostasis in the brain include mediated transport at the level of the cerebral capillary and the choroid plexus epithelium. In addition, there are ouabain-sensitive clearance mechanisms presumably involving Na,K-ATPase that participate in the removal of excess potassium. The relative roles of simple diffusion, high glial cell conductance of potassium, and active ionic pumps in restoring basal potassium levels after activity are still controversial.

Animals↗
PubMed1975

Rat brain regional uptake and decarboxylation of L-DOPA following carotid injection.

Using the carotid injection technique, the regional uptake and decarboxylation of L-DOPA at the blood-brain barrier in the rat was studied. After a single intracarotid injection in the rat followed by decapitation 15 S later, the uptake of L-DOPA was measured relative to tritiated water injected simultaneously as a diffusible internal standard. Decarboxylation was investigated with an injection mixture of L-[carboxy-14C]DOPA and L-[2,3-3H]DOPA. Uptake of L-DOPA studied over the range of 15-5,076 nmol/ml appeared to be a composite of two separate mechanisms. The saturable component had a half-maximal velocity transport value, K-t, of 336 muG. A diffusional, nonsaturable component had a diffusion constant of 0.018. A regional study showed that uptake operated at approximately the same rate in the various brain areas despite marked regional variation in catecholamine concentration. The decarboxylation of L-DOPA also occurred at a similar rate in all regions. Even when L-DOPA was injected at a concentration of 3 mM, 33-51% was decarboxylated within the 15-S period. These results support the hypothesis that L-DOPA movement into the brain occures via a neutral amino acid transport mechanism common to cerebral capillaries of different regions of the brain.

Animals↗
PubMed1974

Enhancement of dopamine-stimulated adenylate cyclase activity in rat caudate after lesions in substantia nigra: evidence for denervation supersensitivity.

Unilateral radiofrequency lesions or chemical lesions with 6-hydroxydopamine were produced in the substantia nigra of rat brain in order to destroy dopaminergic innervations to caudate nucleus and thereby to produce functional denervation supersensitivity. Both types of lesions resulted in enhanced stimulation of caudate adenylate cyclase (EC 4.6.1.1) activity by dopamine at all dopamine concentrations tested, with more marked enhancement at the lower concentrations. Response to another dopamine agonist, 1-(3,4-dihydroxybenzyl)-4-(20pyrimidinyl) piperazine (S584) was also enhanced. 6-Hydroxydopamine lesions resulted in selective enhancement of the dopamine-stimulated component of adenylate cyclase, whereas radiofrequency lesions resulted also in a marked decrease in basal activity. It is postulated that the basal activity of caudate represents primarily an adenylate cyclase distinct from that stimulated by dopamine and destroyed only by the less selective radiofrequency lesion. The enhancement of dopamine-sensitive adenylate cyclase after lesions serves as indirect evidence for a significant role of this system in the transmitter function of dopamine and indicates, furthermore, that it is directly involved in dopamine receptor supersensitivity in vivo produced by denervation.

Adenylyl Cyclases↗