Biomedical subjects

N Ishihara

Publications and source records attributed to N Ishihara.

151 records · Page 9Linked to original sources

PubMedDate not supplied

Metal concentrations in human pancreatic juice.

Concentrations of 11 metals (cadmium [Cd], lead [Pb], copper [Cu], iron [Fe], manganese [Mn], cobalt [Co], chromium [Cr], nickel [Ni], zinc [Zn], magnesium [Mg], and calcium [Ca]) and protein in human pancreatic juice were studied. Human pancreatic juice was sampled by endoscopic cannulation after administration of secretin (intravenous [i.v.], 1 mu/kg). There were 19 subjects (11 males and 8 females) and the means of their ages were 50.3 yr (male, 20-68 yr) and 52.5 yr (female, 45-64 yr). Diagnoses were: normal, 5; early pancreatic cancer, 9; and chronic pancreatitis, 5. None had symptoms suggestive of disturbances in endocrine and exocrine functions of the pancreas. Concentrations of metals and protein in pancreatic juice did not change significantly between males and females or with pathological changes in the pancreas. Assuming the flow rate of pancreatic juice to be 1500-2000 ml/day, the daily excretions of metals into duodenum via pancreatic juice were calculated as follows (mumoles of metal/day): Cd, 0.012-0.012; Pb, 0.216-0.288; Cu, 6.20-8.26; Fe, 2.34-3.12; Mn, 0.100-0.133; Co, 0.165-0.220; Zn, 7.46-9.94; Cr, 0.084-0.112; Mg, 274.1-365.4; Ni, 1.64-2.18; and Ca, 0.221-0.295. Toxic (Cd and Pb) and essential metals (Cu, Zn, Fe, Mn, Cr, and Ni) are excreted daily into duodenum via pancreatic juice.

Adult↗

PubMedDate not supplied

Influence of adrenergic receptor blockade on circulatory and metabolic effects of disordered neurotransmitter function in stroke patients.

Cerebral hemispheric blood flow and metabolism were measured before and after therapy with intracarotid infusion of combined PBZ and PPL in 15 patients with recent cerebral infarction. HBF was unaltered despite decrease in cerebral perfusion pressure. Cerebral hemispheric oxygen comsumption and carbon dioxide production decreased while cerebral hemispheric lactate production increased. Biphasic cerebral uptake of tyrosine was observed during and immediately after PBZ and PPL infusion. CSF HVA increased, indicating altered DA turnover. CSF 5HIAA levels also increased, suggesting altered 5HT turnover after PBZ and PPL. Release of cyclic AMP from ischemic brain into cerebral venous blood seen in the steady state was abolished after therapy. Cerebral hemodynamic studies suggest a functional balance between monaminergic neurogenic influences in the control of cerebral circulation. Imbalance of such controlling factors in ischemic brain may lead to paradoxical vascular responses to induced hypertension and hypotension. PBZ and PPL enhance such responses perhaps by increasing central neurotransmitter turnover and release. Further shift toward cerebral anaerobic metabolism may occur in ischemic brain following the use of phenoxybenzamine and propranolol. Worsening of neurological deficit occurred in four cases. Combined therapy with PBZ and PPL does not appear beneficial in the therapy of patients with recent stroke.

Adult↗

PubMedDate not supplied

Effect of cerebrospinal fluid removal on cerebral blood flow and metabolism in patients with Alzheimer's disease versus recent stroke.

Cerebral hemispheric blood flow (HBF) and metabolism were measured before and after withdrawal of 20 to 30 ml of cerebrospinal fluid (CSF) over a 10-minute interval in eight patients with recent cerebral infarction and in four patients with Alzheimer's disease (AD). Immediately after CSF removal HBF decreased significantly in the AD group (-14%) but showed no significant change in the stroke group (-5%). There was rapid reduction in cerebral venous O2 content and some increase in cerebral venous PCO2 appearing within 60 seconds of CSF withdrawal, interpreted as a rapid reduction of cerebral blood flow (CBF) as judged by cerebral A-VO2 differences. The reduction in CBF was confirmed by the hydrogen clearance method. Reduction of CBF in response to lowering CSF pressure is presumably of neurogenic origin since it was rapid and occurred without changes in PaCO2 or MABP. Furthermore, measurement of HBF demonstrated that cerebral metabolism constant after CSF removal. It is postulated that in AD, reduction of HBF following CSF withdrawal is mediated by a disordered neurogenic veno-arterial vasoconstriction reflex which is stimulated by rapid reduction in CSF pressure (CSFP). In patients with stroke, when cerebral perfusion pressure is increased by lowering CSFP, CBF is maintained constant most likely by a physiological cerebral veno-arterial vasoconstrictive reflex. Apparently, this vasocontrictive reflex becomes excessive in Alzheimer's disease, possibly due to cerebral neurogenic imbalance.

Aged↗

PubMedDate not supplied

An ultrastructural assessment of an embolic method of producing cerebral ischemia.

This study presents ultrastructural confirmation of the embolic method of producing an ischemic lesion. The embolic method was shown to produce more advanced parenchymal changes than those reported for the same postocclusion period following vascular clipping. With this method there was less alteration in the morphological intergrity of occluded extraparenchymatous areas of the arterial bed, especially in the associated nerve bundles.

Animals↗

PubMedDate not supplied

Effect of cerebrospinal fluid removal on cerebral blood flow and metabolism in the baboon: influence of tyrosine infusion and cerebral embolism on cerebrospinal fluid pressure autoregulation.

Cerebral blood flow (CBF) and metabolism were measured before and after withdrawal of 5 to 6 ml of cerebrospinal fluid (CSF) in 17 baboons. The measurements were made before and after infusion of tyrosine, the precursor amino acid of the putative neurotransmitters, dopamine and norepinephrine, in the brain. The same observations were made in another experimental group, i.e., before and after acute cerebral multiembolization induced by microfil emboli. In the steady state CBF was unaltered following reduction of intracranial pressure by removal of CSF. After infusion of tyrosine, CBF was decreased, and cerebrovascular resistance increased significantly on removal of CSF. Cerebral embolization did not influence changes in CBF at reduced intracranial pressure. It appears that the cerebral resistance vessels constrict following reduction of intracranial pressure by removal of CSF and that cerebrospinal fluid pressure-CBF autoregulatory mechanisms are resistant to cerebral ischemia induced by middle cerebral artery embolization.

Animals↗

PubMedDate not supplied

Improved method for noninvasive measurement of regional cerebral blood flow by 133Xenon inhalation. Part I: description of method and normal values obtained in healthy volunteers.

A clinical method for noninvasive measurement of regional cerebral blood flow (rCBF) and blood volume (rCBV) is described, based on Obrist's 10 minute, desaturation method after 1 minute inhalation of 133Xe. Sixteen collimated probes are placed over both hemispheres and brain stem-cerebellar regions. End-tidal 133Xe curves are used for correction of recirculation. KEV discriminators are set to record gamma and x-ray activity separately. Values are printed out automatically by a computer on a brain map. Extracerebral contamination is reduced by 1) computing curves from gamma activity, 2) applying pressure on the scalp beneath the probes, 3) 1 minute inhalation of 133Xe and recording desaturation curves for 10 minutes, thereby minimizing slow clearance from extracranial tissues. Normal values for both fast and slow compartments are reproducible and are in good agreement with the carotid injection method. The speech dominant hemishpere has higher flow than the right under conditions described. Posterior portions of the cranium over the cerebellum and brain stem appear to have higher flow gray values than the cerebral cortex. Gray matter flow decreases with advancing age.

Adult↗

PubMedDate not supplied

Micronucleus tests on N-ethyl-N-nitrosourea with mouse peripheral blood reticulocytes using acridine orange-coated slides.

The micronucleus test with peripheral blood using acridine orange-coated slides was validated in male CD-1 mice treated once with N-ethyl-N-nitrosourea (ENU) at doses of 6.25, 12.5, 25.0, and 50.0 mg/kg body weight. Peripheral blood preparations were made 0, 24, 48, and 72 h after treatment. The frequencies of micronucleated peripheral reticulocytes in the ENU-treated groups increased dose-dependently, peaking at 48 h after treatment. The results indicate that the method used in the present study can be an alternative to the method using bone marrow polychromatic erythrocytes.

Acridine Orange↗