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Biomedical subjects

A Arregui

Publications and source records attributed to A Arregui.

35 records · Page 2Linked to original sources
PubMed1982

Increased brain dopamine and dopamine receptors in schizophrenia.

In postmortem samples of caudate nucleus and nucleus accumbens from 48 schizophrenic patients, there were significant increases in both the maximum number of binding sites (Bmax) and the apparent dissociation constant (KD) for tritiated spiperone. The increase in apparent KD probably reflects the presence of residual neuroleptic drugs, but changes in Bmax for tritiated spiperone reflect genuine changes in receptor numbers. The increases in receptors were seen only in patients in whom neuroleptic medication had been maintained until the time of death, indicating that they may be entirely iatrogenic. Dopamine measurements for a larger series of schizophrenic and control cases (n greater than 60) show significantly increased concentrations in both the nucleus accumbens and caudate nucleus. The changes in dopamine were not obviously related to neuroleptic medication and, unlike the receptor changes, were most severe in younger patients.

Adolescent↗
PubMed1982

Angiotensin converting enzyme in Alzheimer's disease increased activity in caudate nucleus and cortical areas.

The activity of the dipeptidyl carboxypeptidase, angiotensin converting enzyme, was assayed in several brain regions of patients dying with Alzheimer's disease and compared to that of appropriately age-matched controls. Enzyme activity was found to be elevated by 44% and 41% in the medial hippocampus and parahippocampal gyrus, respectively, and by 27% and 29% in the frontal cortex (area 10 of Brodman) and caudate nucleus, respectively, in Alzheimer's disease patients. Converting enzyme activity did not differ from controls in the nucleus accumbens, substantia nigra, temporal cortex, anterior or posterior hippocampus, amydgala, and septal nuclei.

Alzheimer Disease↗
PubMed1981

Neurochemical activities in human temporal lobe related to aging and Alzheimer-type changes.

Activities relating to 3 neurotransmitter and 4 neuropeptide systems have been examined in human temporal lobe (post mortem) for their relationships with age and Alzheimer-type changes (senile plaques and cognitive function). Significant alterations with increasing age (from 61 to 92 years) in a series of non-demented cases included a reduction of the cholinergic enzyme, choline acetyltransferase, and an increase in vasoactive intestinal peptide immunoreactivity. In cases of alzheimer's disease the only neurochemical activity investigated which correlated significantly with cognitive impairment (assessed from a Mental Test Score obtained shortly before death) and with the severity of Alzheimer-type abnormalities (senile plaques density) was choline acetyltransferase. Further analyses of the data in relation to the severity of plaque formation suggest that alterations in other neurochemical activities including reductions in dopamine-beta-hydroxylase activity, cholecystokinin octapeptide (aqueous extracted) and somatostatin immunoreactivities and an increase in substance P immunoreactivity, may occur at later stages of the disease process. These comparative data suggest that biochemical changes in this brain area associated with age and earlier stages of Alzheimer's disease may be relatively selective.

Aged↗
PubMed1980

Regional distribution of methionine-enkephalin and substance P-like immunoreactivity in normal human brain and in Huntington's disease.

The regional distributions of substance P and Methionine-enkephalin (Met-enkephalin) were determined in normal human brains and in Huntington's disease using sensitive radioimmunoassays. Model experiments showed that both Met-enkephalin- and substance P-like immunoreactivities were stable for up to 72 h post-mortem in mouse brain. The results of high pressure liquid chromatography (HPLC) analyses indicated that the majority of the immunoreactivity detected in human globus pallidus corresponded to the native peptides, substance P or Met-enkephalin. In Huntington's disease the present results confirm that there is a substantial drop (> 80%) in the substance P content of the globus pallidus (both medial and lateral segments) and substantia nigra, and there was also a reduction (> 50%) in the Met-enkephalin content of these areas. This result suggests the loss of striato-pallidal and striato-nigral substance P and enkephalin-containing projections in Huntington's disease.

Animals↗
PubMed1979

Separation of human brain angiotensin-converting enzyme from enkephalin-degrading activity.

Angiotensin-converting enzyme and enkephalin-degrading enzyme activities were solubilized and purified from a particulate fraction of human diencephalon. Converting enzyme activity and enkephalin-degrading activity elute in different fractions following ion exchange chromatography on DEAE-cellulose, suggesting that they are different enzymes. Both enzymes were purified further by ion exchange chromatography on hydroxylapatite and by gel filtration on Sephadex G-200. The purified enzymes had markedly different sensitivities to known inhibitors of angiotensin-converting enzyme. The data do not support the hypothesis that angiotensin-converting enzyme and enkephalin degrading-enzyme are identical.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1978

Angiotensin-converting enzyme in substantia nigra: reduction of activity in Huntington's disease and after intrastriatal kainic acid in rats.

The substantia nigra of Huntington's disease brains shows a 78% reduction in angiotensin-converting enzyme activity in the pars reticulata and a 48% reduction in the pars compacta. The nucleus accumbens shows a 28% reduction in converting enzyme activity. In the rat, after intrastriatal injections of kainic acid (2.5 microgram), an agent which selectively destroys neuronal cell bodies, there is a 55% reduction in angiotensin-converting enzyme activity in the ipsilateral substantia nigra. Both human and animal data suggest that a major part of the angiotensin-converting enzyme in the substantia nigra is localized in nerve terminals whose cell bodies originate in the striatum.

Animals↗
PubMed1978

Angiotensin-converting enzyme: presence of high activity in choroid plexus of mammalian brain.

The activity of angiotensin-converting enzyme in rat choroid plexus was higher than that of any other organ, being 6--7 times higher than that in lung and more than 50 times higher than in any other region of brain. Rabbit choroid plexus also had high activity of enzyme while that of human choroid plexus was relatively low. The enzyme in rat choroid plexus showed similar biochemical properties to that in other tissues; it was inhibited by the nonapeptide SQ 20,881, by (Sar1-Ala8)-angiotensin II and by EDTA, and required chloride ions for activity. As in other tissues, the choroid plexus enzyme was associated with particulate fractions after differential centrifugation. The corpus striatum and substantia nigra had the highest activities in the various brain regions examined.

Animals↗
PubMed1977

Huntington's chorea: selective depletion of activity of angiotensin coverting enzyme in the corpus striatum.

The activity of angiotensin converting enzyme, which transforms the relatively inactive decapeptide angiotensin I to the active octapeptide angiotensin II by removal of an L-histidyl-L-leucine residue, has been assayed in numerous region of the calf brain and of the brains of humans with Huntington's chorea and controls. In calf brain there are pronounced regional variations in enzyme activity, with highest activity in the globus pallidus and area postrema. In human brain, enzyme activity is highest in the corpus striatum, with similar levels in the caudate, putamen, and globus pallidus. Converting enzyme activity is reduced by 83 to 92% in the globus pallidus in Huntington's chorea. The caudate and putamen of choreic patients display 62 to 69% reductions in enzyme activity. Converting enzyme activity in two cerebral cortical regions from choreic brains is not significantly different from control.

Animals↗
PubMed1972

Specific glycine--accumulating synaptosomes in the spinal cord of rats.

Subcellular fractionation of rat spinal cord on continuous sucrose density gradients provides evidence for the existence of a specific synaptosomal fraction (enriched in pinched-off nerve endings) that accumulates glycine selectively by way of a high-affinity transport system. The particles in this fraction sediment to a less-dense portion of sucrose gradients than do particles that accumulate neutral, basic, aromatic, and acidic amino acids. Particles accumulating gamma-aminobutyric acid are even less-dense than those storing exogenous glycine. The glycine-specific synaptosomal fraction also exists in the brain stem but not in the cerebral cortex. These findings provide neurochemical support for the suggestion that glycine has a specialized synaptic function, perhaps as neurotransmitter, in mammalian spinal cord.

Aminobutyrates↗