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Biomedical subjects

M D Yahr

Publications and source records attributed to M D Yahr.

At least 19 recordsLinked to original sources
PubMed1992

Changes in body temperature markedly affect striatal dopamine release and metabolism: an in vivo study.

Dopamine release and metabolism in the corpus striatum increased markedly when the core body temperature of anesthetized rats was increased from 35 degrees to 41 degrees C while temperatures below 34 degrees were associated with a marked attenuation of dopamine release. These observations may have clinical relevance in cases where alterations in body temperature are associated with extrapyramidal dysfunction.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Hypotension-induced vasopressin release distinguishes between pure autonomic failure and multiple system atrophy with autonomic failure.

To investigate whether activation of afferent and central baroreceptor pathways could differentiate between pure autonomic failure (PAF) and multiple system atrophy with autonomic failure (MSA), we determined the effect of upright tilt on circulating levels of vasopressin in patients with PAF and patients with MSA. We also studied 14 normal subjects, nine of whom developed acute hypotension due to vasovagal syncope. In patients with PAF and in normal subjects with vasovagal syncope, upright tilt induced marked hypotension and a pronounced increase in the plasma concentration of vasopressin (1.1 +/- 0.3 to 38.0 +/- 8.0 pmol/l in PAF and 1.0 +/- 0.2 to 27.4 +/- 7.2 pmol/l in vasovagal syncope, p less than 0.005 for both). In patients with MSA, upright tilt also elicited profound hypotension but circulating levels of vasopressin increased little (0.5 +/- 0.1 to 1.5 +/- 0.3 pmol/l, p less than 0.05). During upright tilt, the plasma concentration of norepinephrine significantly increased in normal subjects but did not increase in patients with autonomic failure. Our results indicate that afferent and central baroreceptor pathways involved in vasopressin release are normal in patients with PAF but are impaired in patients with MSA. Thus, measurement of baroreceptor-mediated vasopressin release appears to provide a clear marker to differentiate between patients with PAF and patients with MSA.

Adult↗
PubMed1992

Catechol-O-methyltransferase inhibition increases striatal L-dopa and dopamine: an in vivo study in rats.

We administered Ro 40-7592, an inhibitor of the enzyme catechol-O-methyltransferase (COMT) that crosses the blood-brain barrier, to rats and monitored extracellular catecholamine levels in the corpus striatum before and after the intraperitoneal administration of a bolus of l-dopa. Acute administration of Ro 40-7592 increased basal levels of l-dopa and dihydroxyphenylacetic acid (DOPAC) and decreased basal homovanillic acid (HVA) levels, but did not affect basal dopamine levels. In rats treated with Ro 40-7592, l-dopa administration produced a greater increase in striatal levels of l-dopa, dopamine, and DOPAC than it did in controls, while HVA formation was attenuated. We conclude that inhibition of COMT activity promotes central dopamine synthesis and release following administration of pharmacologic doses of l-dopa.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Lewy bodies in parkinsonism share components with intraneuronal protein bodies of normal brains.

Histochemical characteristics of the Lewy bodies, in catecholamine neurons of 10 Parkinsonian patients, were compared to those of the spherical protein bodies, the basic protein-rich markers of catecholamine neurons in man. Special methods for proteins and lipids showed that the core of the Lewy bodies, in the neurons of the locus coeruleus and the substantia nigra, contains basic proteins and lipids normally found in the protein bodies. Acid fuchsin and the lipid-soluble fluorescent dye rhodamine B stained the entire core of the Lewy body in the parkinsonian brains and the entire sphere of the protein body in the control brains. Bromsulfophthalein, another acidic dye, which selectively binds to the enzyme gluthathione-S-transferase, had affinity only for a ring-like lamina at the outer layer of the core of the Lewy body and for the outer rim of the protein body. These results demonstrate that Lewy bodies and protein bodies contain similar macromolecular components, that is lipids and two different types of proteins, which also show similar stratification in the two structures. On the other hand, the presence in several neurons of the Parkinsonian patients, of aggregates representing transitional forms between protein bodies and Lewy bodies, indicates that abnormalities of protein bodies precede, and are somehow linked to Lewy body production.

Brain Stem↗
PubMed1991

Effect of yohimbine on brain monoamines: an in vivo study.

Following the administration of yohimbine, an alpha 2-adrenoreceptor antagonist, the levels of norepinephrine (NE), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5HIAA) increased significantly in the lateral ventricular fluid of rats. These increases were abolished when animals were pretreated with alpha-methyl-para-tyrosine or reserpine. Dopamine (DA) was not detected in ventricular fluid either before or after yohimbine administration. Yohimbine administration did, however, increase intracellular DA levels in the corpus striatum. These findings indicate that yohimbine promotes NE and DA release in the brain and suggest that it also modifies the activity of the serotonin system.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Effect of dietary protein on striatal dopamine formation following L-dopa administration: an in vivo study.

We varied the diet of rats and monitored extracellular levels of dopamine in the striatum. Following L-dopa administration, the increase in striatal dopamine levels was attenuated by 78% in rats that had consumed a high protein diet as opposed to a low protein diet. Similarly, the increase in striatal dopamine levels was attenuated by 61% in rats that had just eaten a protein-containing meal as compared to fasting animals. These findings demonstrate that dietary protein strongly affects brain dopamine formation from exogenous L-dopa.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1978

Antibodies against arboviruses in postencephalitic and idiopathic Parkinson's disease.

Serum and CSF from patients with classic von Economo's postencephalitic Parkinson's disease, idiopathic Parkinson's disease and non-Parkinsonian neurological controls were tested for hemagglutination-inhibition antibodies to 17 arboviruses. All 35 CSF specimens from patients with idiopathic Parkinson's disease and controls were negative (ie, no inhibition of hemagglutination) with all the antigens. Of the total of 124 serums from the three study groups, 105 were also negative with all antigens tested. The only positive results were given by 19 serum specimens against one or more of group B arbovirus antigens, and/or against Batai and western equine encephalomyelitis antigens. There were no definitive differences in the distribution of these positive serum titers among controls, idiopathic Parkinson's, and postencephalitic Parkinson's cases. A causal relationship of the arboviruses tested with either the classical postencephalitic or idiopathic Parkinson's disease is not supported by the results of this study.

Antibodies, Viral↗
PubMed1978

Protein-rich cytoplasmic bodies of substantia nigra and locus ceruleus. A comparative study in parkinsonian and normal brain.

A histochemical study of substantia nigra and locus ceruleus from postmortem brains showed the presence of small spherical cytoplasmic bodies stained selectively by the anionic phosphotungstic acid-hematoxylin (PTAH) stain at a pH of 2.5. The metachromatic reaction to PTAH indicates that these protein bodies contain a protein rich in free basic amino groups. The protein bodies are localized within the neuronal perikaryon as well as in their dendritic processes. These bodies abundantly present in the substantia nigra and locus ceruleus of normal brains were noticeably reduced or absent in parkinsonian brains. Lewy bodies when present show that their core gives the same metachromatic reaction to PTAH as do the protein bodies. These findings suggest that an abnormality of protein synthesis in the substantia nigra and locus ceruleus of parkinsonian brains may be related to the absence of protein bodies and the formation of Lewy bodies and play a role in pathogenesis of the parkinsonian state.

Aged↗
PubMed1978

Overview of present day treatment of Parkinson's disease.

In the light of present day knowledge, augmenting striatal dopaminergic activity is the most effective means for controlling the symptoms of parkinsonism. This is best accomplished by the administration of levodopa with a peripheral decarboxylase inhibitor. However, limitations in its benefits develop after long-term administration in a substantial number of patients. In an attempt to overcome these a number of pharmacological agents acting on striatal dopaminergic mechanisms have undergone clinical trial. Of those tried Deprenyl, an MAO-B inhibitor, given with levodopa and carbidopa has shown the most promise. Preliminary results in 35 patients indicate that it is useful in diminishing the incidence of "on-off" phenomena--one of the most limiting reactions to levodopa--as well as enabling some patients to recoup their loss of therapeutic benefits. Though far from resolving all of the therapeutic difficulties encountered with prolonged use of levodopa, it appears to be a valuable adjunctive agent for the long-term problem patient.

Adult↗
PubMed1978

Measurements of visual evoked potentials in Parkinson's disease.

Visual evoked potentials elicited by reversing grating patterns were recorded in 35 patients with Parkinson's disease and in 26 controls. The average latency of evoked potentials in patients with Parkinson's disease exceeded by two standard deviations the average of the age-matched control group of other neurological patients. Over two-thirds of all patients with Parkinson's disease had abnormal latency. In these patients latency did not correlate with age. In 5 patients the latency became less prolonged on levodopa therapy, suggesting that catecholaminergic pathways have either indirect or direct effects on the generation of visual evoked potentials. Extrapyramidal connections of the visual cortex, as well as retinal dopaminergic neurons, require further study in Parkinson's disease.

Age Factors↗
PubMed1977

Meningoencephalopathy secondary to infectious mononucleosis. Unusual presentation with stupor and chorea.

We report a case of infectious mononucleosis in which central nervous system involvement was the presenting and sole manifestation of the disorder. The major symptomatology consisted of stupor, chorea, and signs of aseptic meningitis. We also discuss the clinical and laboratory features of the neurological manifestations of infectious mononucleosis and the theories as to its pathogenesis.

Adolescent↗
PubMed1977

Adult onset autonomic dysfunction coexistent with familial dysautonomia in a consanguineous family.

A consanguineous family is described in which autonomic dysfunction developed in the father during adult life while the son had familial dysautonomia at birth. The father's condition is felt to be secondary to olivopontocerebellar atrophy. The concurrence in this family of an adult and a childhood form of dysautonomia may be an expression of the same genetic defect at different stages of development.

Adult↗