Search PubMed⌕ Search

Biomedical subjects

Y Katayama

Publications and source records attributed to Y Katayama.

At least 631 records · Page 35Linked to original sources
PubMed1990

[Fluid shear stress effects on intracellular calcium concentrations in cultured vascular endothelial cells].

Vascular endothelial cells are known to modulate their functions in response not only to humoral stimuli but also to such physical stimuli as fluid shear stress generated by blood flow. However, the mechanisms by which the hemodynamic force acts on endothelial cells are not yet well understood. We have studied how endothelial cells recognize the shear stress and mediate it to intracellular organelles. Cultured monolayers of bovine aortic endothelial cells loaded with the highly fluorescent Ca+(+)-sensitive dye Fura 2 were exposed to different levels of fluid shear stress in a specially designed flow chamber and simultaneous changes in intracellular-free Ca+(+) concentration were measured using photometric fluorescence microscopy. Application of shear stress to cells by fluid perfusion led to an immediate several-fold increase in Ca+(+) concentration within 1 min, followed by a rapid decline, and finally a plateau somewhat higher than control levels during the entire period of the stress application. The early part of the response, but no plateau, was observed even in Ca+(+)-free medium added with 2 mM EDTA, and in the presence of calcium antagonists (e.g. 2 x 10(-5) M nicardipine). Thus, endothelial cells may have a flow-sensing property which recognize the shear stress on the membrane as a stimulus and mediates the signal to increase intracellular free Ca(+)+ which is a major component of the internal signalling system of the cell.

Animals↗
PubMed1990

[Changes in lymphocyte subsets, neutrophil function and complement levels in patients with complications following open heart surgery].

In order to evaluate the immune response during and after open heart surgery, we have studied 34 patients who received open heart surgery under extracorporeal circulation. Age range of these patients were from 41 to 76 years. These patients were divided into three groups, depending upon existence of multiple organ failure (MOF), low output syndrome (LOS) and non-LOS and non-MOF diagnosed from our criteria. The following cytological and immunological study has been performed pre-operatively, immediately after and on 1, 2, 7 and 14th postoperative day; 1) the leukocyte differential cell count, 2) function test of neutrophils, 3) lymphocyte subpopulation and subsets, 4) serum level of complement fractions (C3, C4) and CH 50. By lymphocytes analysis, postoperative early reduction of OKT 3 (CD 3) and OKT 4 (CD 4) was observed in patients with poor prognosis. Patients with the postoperative high activity of NBT reduction test was developed into MOF. Complement activity (C3, C4, CH50) decreased during surgery and recovered to preoperative level in patients without LOS and MOF. However in MOF patients, these values showed lower level than that of patients without LOS and MOF. Our data suggested that lymphocytes and leukocytes tests were useful to evaluate the prognosis in open heart surgery.

Adult↗
PubMed1990

[Surgical treatment and long-term results of aneurysms of Valsalva sinus in 24 cases].

Twenty-four patients with aneurysm of Valsalva sinus were surgically repaired over a 23 year period (1965-1988). These patients were ranged 2 to 54 years of age and eleven of them were male. Rupture of aneurysm of Valsalva sinus was combined with aneurysm in 20 cases, ventricular septal defect in 12 cases and aortic regurgitation in 6 cases. At present, our routine operative procedure for ruptured aneurysm is direct closure of the defect with patch closure of aneurysm after resection of the aneurysm, but when the diameter of aneurysm is smaller than 7 mm, direct closure of the defect of the aneurysm was used. Only one patient after patch closure of ruptured sinus of Valsalva (Konno type I) required reoperation for penetration into left ventricle. This case might be avoided if patch was sutured to annulus of aortic valve. There were two operative death and one late death. The former died of cerebral infarction and low output syndrome, the latter died of sepsis. The mean follow-up period (+/- standard deviation) was 8.2 +/- 6.0 years. All patients that were followed were thirteen and found to be in New York Heart Association class I.

Adolescent↗
PubMed1990

[Asynchronus rejection of intrathoracic heart-lung transplantation rats].

We have reported intrathoracic heart-lung transplantation in rats could be made easily by using Internal Shunt Method as described elsewhere. In this study, we examined the rejection of intrathoracic heart-lung allografts in this model to determine whether acute pulmonary rejection precedes cardiac rejection following heart-lung transplantation or not. Ten heart-lung allografts (no immunosuppressive agent was given) and four isografts were examined pathologically. There was no pathologic change except perivascular or peribronchiolar edema in isografts, which was attributed to operative damage. Acute pulmonary rejection apparent pathologically 3 days after transplantation and lung allografts lost its function 6 days after transplantation. Otherwise, acute cardiac rejection first became apparent pathologically 5 days after transplantation. And their pulsation appeared well 6 days after it. It is concluded that pulmonary rejection precedes cardiac rejection following heart-lung transplantation.

Animals↗
PubMed1989

Detection and localization of a new enzyme catalyzing the beta-aryl ether cleavage in the soil bacterium (Pseudomonas paucimobilis SYK-6).

Cleavage of the arylglycerol-beta-aryl ether linkage is the most important process in the biological degradation of lignin. We determined the activity of the enzyme cleaving the beta-aryl ether linkage in membranes of Pseudomonas paucimobilis SYK-6. This enzyme was tightly associated with the cellular membrane and catalyzed the unique and reductive cleavage of compound II but not cleavage of compound I. This enzymatic activity was stimulated by addition of NADH. On the basis of this evidence, we present a model of the specific cellular assimilation of beta-aryl ether by P. paucimobilis SYK-6.

Bacterial Proteins↗
PubMed1989

Somatostatin presynaptically inhibits transmitter release in feline parasympathetic ganglia.

Intracellular recordings were made from neurons in cat parasympathetic ciliary ganglia in vitro. Somatostatin (30 nM-3 microM) reduced the amplitude of excitatory postsynaptic potentials (EPSPs), whereas the peptide did not affect acetylcholine (ACh)-induced depolarizations. Thus somatostatin depressed the EPSPs without changing the postsynaptic sensitivity to ACh. The inhibitory action of somatostatin on the EPSPs was passed off even in the presence of the peptide at concentrations higher than 100 nM. When paired stimuli at an interval of 50 ms were applied to preganglionic nerves, the second EPSP was facilitated, being larger in amplitude than the first one; this facilitation was reversibly inhibited in the presence of the peptide. Somatostatin reversibly reduced the frequency of spontaneous EPSPs without appreciably changing their mean amplitude. All of these results indicate that somatostatin may presynaptically reduce the amount of ACh released. The mechanism underlying this action was discussed.

Acetylcholine↗
PubMed1989

Human urinary prokallikrein--structural analysis on activation mechanism.

The complete amino acid sequence of human urinary kallikrein has been determined. The enzyme was a single polypeptide which comprised 238 amino acid residues. In the case of prokallikrein, a propeptide which was consisted of seven amino acid residues was attached to N-terminal isoleucine of kallikrein. The sequence of Asn-X-Thr(Ser), common to glycosylation site, was identified at positions 78-80, 84-86 and 141-143. It has been shown from the sequence of kallikrein that Arg(-1)-Ile(1) and Arg(87)-Gln(88) bonds are hydrolyzed with trypsin on rapid activation of prokallikrein and the formation of disulfide-linked two chain kallikrein.

Amino Acid Sequence↗
PubMed1989

Purification and immunological properties of human urinary kallikrein and prokallikrein.

Human urinary prokallikrein and kallikrein have been purified from the same source of urine simultaneously. The anti-kallikrein and anti-prokallikrein antibodies were raised in rabbits using the purified preparations. With respect to solid phase enzyme immunoassay (EIA), immunoaffinity column chromatography, and single radial immunodiffusion, reactivity of each antibody with kallikrein was distinctly different from that with prokallikrein. Kallikrein could be determined by anti-kallikrein antibody-immobilized EIA below 20 ng per ml, whereas prokallikrein was undetectable. Prokallikrein became detectable at higher concentrations, although it was less reactive than kallikrein. The anti-prokallikrein antibody-immobilized EIA detected both kallikrein and prokallikrein with the same sensitivity. However, the binding capacity for kallikrein was about one-third less than that for prokallikrein. The results show that kallikrein in human urine may be determined directly and selectively. Similar difference in reactivity was observed with immunoaffinity column chromatography and single radial immunodiffusion. The presence of 3-4 antigenic sites per molecule was indicated by quantitative precipitin reaction, and it is suggested from analysis of amino acid sequence of kallikrein by the method of Hopp and Woods that four hydrophilic regions exist in kallikrein molecule.

Chromatography, Affinity↗
PubMed1989

Calcium-dependent slow outward current in visceral primary afferent neurones of the rabbit.

Slow outward currents were recorded from voltage-clamped neurones in nodose ganglia excised from rabbits. In the majority of Type C neurones, a short depolarizing command pulse evoked a slow outward tail current (ISAH) with a decay time constant ranging from 0.5 to 2 s. The ISAH was due to an increase in membrane conductance to K+ because its reversal potential was approximately equal to the Nernst potential for K+. The ISAH was reversibly blocked by removal of external Ca2+ or by Ca2+ antagonists. A Ca2+ ionophore, A23187, produced an outward current which was similar to the ISAH. The ISAH was resistant to tetraethylammonium and depressed by Ba2+, whereas it was not affected by Cs+ and 4-aminopyridine. The ISAH was initially augmented and subsequently depressed by apamin (1-10 nM) and (+)-tubocurarine (100-600 microM). It is concluded that the ISAH in visceral primary neurones may be due to a long-lasting increase in K+ conductance caused by an increase in the concentration of intracellular Ca2+, resulting from Ca2+ entry during the depolarizing command pulse.

Animals↗
PubMed1989

Afferent and efferent connections of the cholinoceptive medial pontine reticular formation (region of the ventral tegmental nucleus) in the cat.

Following minor concussive brain injury when there is an otherwise general suppression of CNS activity, the ventral tegmental nucleus of Gudden (VTN) demonstrates increased functional activity (32). Electrical or pharmacological activation of a cholinoceptive region in this same general area of the medial pontine tegmentum contributes to certain components of reversible traumatic unconsciousness, including postural atonia (31, 32, 45). Therefore, in an effort to examine the neuroanatomical basis of the behavioral suppression associated with a reversible traumatic unconsciousness, the afferent and efferent connections of the VTN and putative cholinoceptive medial pontine reticular formation (cmPRF) were studied in the cat using the retrograde horseradish peroxidase (HRP), HRP/choline acetyltransferase (ChAT) double-labeling immunohistochemistry, and anterograde HRP and autoradiographic techniques. Based upon retrograde HRP labeling, the principal afferents to the VTN region of the cmPRF originated from the medial and lateral mammillary nuclei, and lateral habenular nucleus, and to a lesser extent from the interpeduncular nucleus, lateral hypothalamus, dorsal tegmental nucleus, superior central nucleus, and contralateral nucleus reticularis pontis caudalis. Other afferents, which were thought to have been labeled through spread of HRP into the medial longitudinal fasciculus (MLF), adjacent paramedian pontine reticular formation, or uptake by transected fibers descending to the inferior olive, included the nucleus of Darkschewitsch, interstitial nucleus of Cajal, zona incerta, prerubral fields of Forel, deep superior colliculus, nucleus of the posterior commissure, nucleus cuneiformis, ventral periaqueductal gray, vestibular complex, perihypoglossal complex, and deep cerebellar nuclei. In HRP/ChAT double labeling studies, only a very small number of cholinergic VTN afferent neurons were found in the medial parabrachial region of the dorsolateral pontine tegmentum, although the pedunculopontine and laterodorsal tegmental nuclei contained numerous single-labeled ChAT-positive cells. Anterograde HRP and autoradiographic findings demonstrated that the VTN gave rise almost exclusively to ascending projections, which largely followed the course of the mammillary peduncle (16,21) and medial forebrain bundle, or the tegmentopeduncular tract (4). The majority of fibers ascended to terminate in the medial and lateral mammillary nuclei, interpeduncular complex (especially paramedian subnucleus), ventral tegmental area, lateral hypothalamus, and the medial septum in the basal forebrain. Labeling that joined the mammillothalamic tract to terminate in the anterior nuclear complex of the thalamus was thought to occur transneuronally. Some projections were also observed to nucleus reticularis pontis oralis and caudalis, superior central nucleus, and dorsal tegmental nucleus adjacent to the VTN...

Animals↗
PubMed1989

Magnesium-to-calcium ratio in tap water, and its relationship to geological features and the incidence of calcium-containing urinary stones.

We examined the relationship among magnesium and calcium content in tap water, the geological features and urinary stone incidence in Japan. The magnesium-to-calcium ratio in tap water correlated negatively with the incidence of urolithiasis. There was no correlation between calcium and magnesium concentration in tap water and urinary stone incidence. Geological features in Japan were classified into 5 groups. The magnesium-to-calcium ratio in the basalt areas was higher than in the other areas, while ratio in the granite areas was low. In the sedimentary rock areas calcium and magnesium concentrations were high; the magnesium-to-calcium ratio in these areas was between those of the basalt and granite areas. The limestone areas had a much higher calcium concentration. The incidence of urinary stones in the sedimentary rock and basalt areas was lower than that of the granite areas, while that in the limestone areas was the highest. Thus, the incidence of urinary stone is related to the magnesium-to-calcium ratio in tap water and the geological area.

Calcium↗
PubMed1989

Fructose-added glycerol (Glyceol) for therapy of elevated intracranial pressure: analysis of the side effects of long-term administration in a multi-institutional trial.

The effects of long-term administration of fructose-added glycerol solution (Glyceol): 10% glycerol, 5% fructose, 0.9% sodium chloride; 600-2000 ml/d intravenously for 7-63 d) were evaluated in a multi-institutional trial involving 1346 cases. Improvement of the neurological signs and symptoms of elevated intracranial pressure was recognized by responsible physicians in close association with the administration of Glyceol (75.1%). The intracranial pressure measured directly also decreased in most cases following the administration of Glyceol (81.2%). No significant changes were observed in serum electrolytes and osmolarity at the end of the long-term administration. Unfavourable changes in clinical conditions which were considered very likely or suspected to be due to the long-term administration of Glyceol were recorded in 2 cases (0.1%) or 13 cases (1.0%), respectively. Most of these changes were abnormalities of serum electrolytes. It appeared, however, that the abnormalities of serum electrolytes may be readily correctable, and rarely induced if standard care of the serum water-electrolyte balance is carried out and unless too large doses are employed. Other changes appeared to be related more to preexistent complications and/or the administration of other drugs, rather than to the administration of Glyceol alone. Thus, administration of Glyceol appeared feasible for the therapy of elevated intracranial pressure over the long term.

Adult↗
PubMed1989

Effect of dichloroacetate on regional energy metabolites and pyruvate dehydrogenase activity during ischemia and reperfusion in gerbil brain.

The objective of this study was to determine whether administration of dichloroacetate (DCA), an activator of pyruvate dehydrogenase (PDH), improves recovery of energy metabolites following transient cerebral ischemia. Gerbils were pretreated with DCA, and cerebral ischemia was produced using bilateral carotid artery occlusion for 20 min, followed by reperfusion up to 4 h. DCA had no effect on the accumulation of lactic acid and the decrease in ATP and phosphocreatine (PCr) during the 20-min insult, nor on the recovery of these metabolites measured at 20 and 60 min reperfusion. However, at 4 h reperfusion, levels of ATP and PCr were significantly higher in DCA-treated animals than in controls, as PCr exhibited a secondary decrease in caudate nucleus of control animals. PDH was markedly inhibited at 20 min reperfusion in both groups, but was reactivated to a greater extent in DCA-treated animals at 60 min and 4 h reperfusion. These results demonstrate that DCA had no effect on the initial recovery of metabolites following transient ischemia. However, later in reperfusion, DCA enhanced the postischemic reactivation of PDH and prevented the secondary failure of energy metabolism in caudate nucleus. Thus, inhibition of PDH may limit the recovery of energy metabolism following cerebral ischemia.

Acetates↗