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Biomedical subjects

K Shimoji

Publications and source records attributed to K Shimoji.

226 records · Page 13Linked to original sources
PubMedDate not supplied

Arginine vasopressin increases perinuclear [Ca2+] in single cultured vascular smooth muscle cells of rat aorta.

The effects of arginine vasopressin (AVP, 10(-7) M) on the spatial dynamics of intracellular [Ca2+] in single cultured smooth muscle cells of the rat aorta were studied by digital imaging microscopy using the fluorescent Ca2+ indicator fura-2. The nuclear and cytosolic regions were distinguished by the fluorescent image excited at 380 nm. Changes in intracellular [Ca2+] were expressed as percent increases in the ratios of fluorescence intensity at 500 nm excited by 340 and 380 nm. AVP increased the nuclear and cytosolic [Ca2+] in Ca(2+)-containing (control) (285 +/- 27 and 172 +/- 22%, respectively) or Ca(2+)-free (203 +/- 26 and 121 +/- 15%, respectively) solutions. However, caffeine (20 mM) and ryanodine (20 microM) greatly attenuated the [Ca2+] increase induced by AVP in both regions (61 +/- 21 and 42 +/- 15%, respectively). On the ratio image, the nuclear region was discriminated from other regions at the peak response to AVP in preparations treated with caffeine and ryanodine, whereas the outline of the nuclear region was indistinct in untreated preparations. The finding implies that caffeine- and ryanodine-responsive Ca2+ storage sites may exist in the region surrounding the nucleus. The results suggest that the region surrounding the nucleus may be one of the important Ca2+ storage sites with regard to the responses of rat aortic smooth muscle cells to AVP.

Animals↗
PubMedDate not supplied

Production of cyclic nucleotides from normal human brain.

Concentrations of cyclic AMP and cyclic GMP in arterial and internal jugular venous (IJV) blood were determined at the resting wakeful state in thirty surgical patients without neurological deficits. The levels of cyclic AMP in artery and IJV were 32.1 +/- 3.0 and 40.0 +/- 4.1 pmol/ml (means +/- standard errors), respectively, while those of cyclic GMP in artery and IJV were 12.2 +/- 2.7 and 14.4 +/- 3.0 pmol/ml, respectively. Concentrations of both cyclic nucleotides in IJV were significantly higher (P less than 0.001) than those in artery. IJV-arterial differences for cAMP and cGMP were 7.9 +/- 1.7 and 2.1 +/- 0.5 pmol/ml, respectively. The results indicate that both cyclic nucleotides are constantly produced and released from the normal human brain.

Adolescent↗
PubMedDate not supplied

The effects of extreme hemodilutions on the autoregulation of cerebral blood flow, electroencephalogram and cerebral metabolic rate of oxygen in the dog.

The effects of profound (hematocrit value, Ht 20%) and extreme (Ht 5%) hemodilutions on the relationship between the mean arterial pressure (MAP) and the cerebral blood flow (CBF) were studied in pentobarbital-anesthetized dogs. A regression line was found between the CBF and Ht values during normotensive hemodilution (MAP 100 torr): CBF (ml/100g X min) = -98.9 log Ht (%) + 195.5 (p less than 0.001). The CBF was increased by hemodilution, but the range of its autoregulation was narrowed, suggesting a progressive susceptibility of CBF to blood pressure with hemodilution. The electroencephalogram (EEG) was not significantly changed by hemodilution within the range of the CBF autoregulation, below which it became slowed. In contrast, the cerebral metabolic rate of oxygen (CMRo2) was decreased by hemodilution even within the range of the CBF autoregulation, while there were no significant differences in CMRo2 values between MAPs of 100 and 40 torr. Thus, the brain function in terms of the EEG seemed to correlate more with the autoregulatory mechanism of the CBF than with the CMRo2 value in the hemodiluted states.

Animals↗
PubMedDate not supplied

Relation between spinal cord and epidural blood flow.

To test applicability of monitoring regional spinal cord blood flow by measuring regional epidural blood flow, both were simultaneously measured by the hydrogen clearance method in response to changes in PaCO2 and mean arterial blood pressure in rats anesthetized with pentobarbital. An excellent correlation was found between regional spinal and epidural blood flow over a physiological range of PaCO2 (27.8-66.7 torr) and blood pressure (30-130 torr), while a poor correlation was demonstrated between regional spinal or epidural blood flow and regional muscle blood flow in response to these same physiological parameters. Moreover, the rates of change in regional spinal and epidural blood flows were almost the same in response to both PaCO2 and blood pressure. These results suggest that both regional spinal and epidural blood flow are regulated by a similar mechanism and suggest that regional spinal cord blood flow can be monitored by regional epidural blood flow.

Animals↗