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Y Oka

Publications and source records attributed to Y Oka.

At least 379 records · Page 21Linked to original sources
PubMed1991

Substitution of leucine for tryptophan 412 does not abolish cytochalasin B labeling but markedly decreases the intrinsic activity of GLUT1 glucose transporter.

GLUT1 glucose transporter cDNA was modified to introduce a single amino acid substitution of leucine for tryptophan 412, a putative cytochalasin B photo-affinity labeling site. Although the mutated transporter was expressed into plasma membranes of Chinese hamster ovary cells, glucose transport activity of the mutated transporter was observed to be only 15-30% of that of the wild-type GLUT1 when glucose transport activity was assessed by 2-deoxyglucose uptake at 0.1-10 mM concentrations. Analysis of glucose uptake kinetics depict that a mutation induced a 3-fold decrease in turnover number and a 2.5-fold increase in Km compared with the wild-type GLUT1. Importantly, cytochalasin B labeling was not abolished but decreased by 40%, and cytochalasin B binding was also decreased. In addition, the results obtained with side-specific glucose analogs suggested that the outer glucose binding site of the mutant appeared intact but the inner binding site was modulated. These results indicate 1) tryptophan 412 is not a cytochalasin B labeling site(s), although this residue is located in or close to the inner glucose binding site of the GLUT1 glucose transporter, 2) substitution of leucine for tryptophan 412 decreases the intrinsic activity of GLUT1 glucose transporter, which is definable as the turnover number/Km, to approximately 15% of that of the wild-type.

Affinity Labels↗
PubMed1991

Ultrastructure of the ganglion cells of the terminal nerve in the dwarf gourami (Colisa lalia).

In our previous light microscopic studies (Oka et al., Brain Res. 367: 341-345, '86; Oka and Ichikawa, J. Comp. Neurol. 300: 511-522, '90), we reported that there are at least two types of terminal nerve (TN) cells based on cell size and immunoreactivity: type I cells had large cell bodies, while type II cells had smaller cell bodies. Type I TN cells were immunoreactive to gonadotropin-releasing hormone (GnRH) and may be the major source of GnRH-immunoreactive fibers that are widely distributed throughout the brain. Type II TN cells, on the other hand, were not immunoreactive to GnRH. In the present paper, we examined the cytology and synaptology of these two types of TN cells with electron microscopy. Type I TN cell bodies were found to have morphological characteristics similar to those of other peptide-synthesizing neurons and are likely to be actively synthesizing GnRH. The frequent occurrence of coated vesicles close to the plasma membrane of the cell body was suggestive of membrane retrieval following exocytosis of the vesicular contents from the cell surface. Neighboring TN cells were either in direct juxtaposition with one another or made specialized "glomeruloid" cell-to-cell contacts; these specializations may be relevant for nonsynaptic intercellular communications among the TN cells. Within these glomeruloid complexes, the somatic processes of TN cells received inputs from two types of synaptic terminals: one containing only spherical synaptic vesicles and another containing a small number of dense-cored vesicles in addition to the spherical synaptic vesicles. Axosomatic synapses were rare on type I TN cell bodies. In contrast, type II TN cell bodies had morphological characteristics similar to those of neurons in other brain regions. These receive axosomatic inputs from synaptic terminals containing only spherical synaptic vesicles and those with a small number of dense-cored vesicles in addition to the spherical synaptic vesicles. Thus, each type of TN cell has unique fine structural characteristics which may correlate to their different functional roles.

Animals↗
PubMed1991

Stimulation of putrescine production by epidermal growth factor in rat liver after partial hepatectomy.

When epidermal growth factor was given to rats after partial hepatectomy, hepatic putrescine content was significantly increased at 4, 6 and 10 hr compared with control rats. Ornithine decarboxylase activity was also increased. Hepatic ornithine decarboxylase messenger RNA content was significantly greater than control levels at 2 hr after epidermal growth factor treatment, but not at 10 hr, when the amount of ornithine decarboxylase messenger RNA in control animals was four times that at 2 hr. When actinomycin D was administered 6 hr after partial hepatectomy, hepatic ornithine decarboxylase activity at 10 hr was reduced to half the control levels. This reduction was attenuated by epidermal growth factor treatment at 6 and 8 hr. Hepatic immunoreactive ornithine decarboxylase protein content showed a highly positive correlation with hepatic ornithine decarboxylase activity at 4, 6 and 10 hr, irrespective of epidermal growth factor treatment. Hepatic spermidine N1-acetyltransferase activity was significantly increased at 6 hr compared with control rats. These results suggest that, after partial hepatectomy in rats, exogenous epidermal growth factor may stimulate hepatic putrescine production by increasing ornithine decarboxylase messenger RNA content and altering posttranscriptional ornithine decarboxylase regulation, as well as enhancing spermidine N1-acetyltransferase activity.

Acetyltransferases↗
PubMed1991

Altered expression of glucose transporter isoforms with aging in rats--selective decrease in GluT4 in the fat tissue and skeletal muscle.

To elucidate the cellular mechanisms of glucose intolerance associated with aging, both the protein and mRNA levels of glucose transporter isoforms were studied in the various tissues of young (7-week-old) and aged (20-month-old) rats. GluT4 (adipose/muscle-type glucose transporter) protein, which is specifically expressed in insulin-responsive tissues, was selectively decreased per milligram of cellular membrane protein in both the epididymal fat tissues and the gastrocnemius muscle of the aged rats compared with the young rats. When the changes in total cellular membranes per gram of tissue are taken into account, a further decrease in GluT4 protein per gram of tissue was observed in the tissues of the aged rats compared with the young rats. The decreased amount of GluT4 protein in the fat tissues of the aged rats is probably due to the decreased protein synthesis rather than the stability, since GluT4 mRNA/micrograms of cellular total RNA was also decreased. In contrast, GluT4 mRNA in the gastrocnemius muscle was rather increased and a ratio of GluT4 protein/GluT4 mRNA was decreased by 70% in the aged rats, suggesting that the translational efficiency and/or stability of GluT4 protein is decreased in the skeletal muscle of the aged rats compared with the young rats. GluT2 (liver-type glucose transporter) protein and mRNA in the liver were also decreased in the aged rats, while no apparent decrease in GluT1 (HepG2/brain-type glucose transporter) protein/mg of cellular membrane protein was observed in the skeletal muscle and fat tissues of the aged rats compared with the young rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1991

Insulin and glucagon therapy of acute hepatic failure.

When insulin and glucagon are administered to rats with severe liver injury, survival is enhanced with an attenuation of the liver injury compared to that of untreated controls. In rats with acute liver injury both hormones produce a rapid normalization of hepatic protein content following initiation of DNA synthesis. When rats receive both hormones after partial hepatectomy, the first burst of DNA synthesis reaches a maximum earlier than that seen in controls. Both hormones enhance the increment of hepatic putrescine essential for DNA synthesis through activation of ornithine decaroxylase and/or spermidine-N1-acetyltransferase. The enhancement of putrescine content by each hormone is additive. Putrescine supplementation promotes hepatic DNA synthesis after hepatectomy. Based on these data, we conclude that a combination of insulin and glucagon is effective in the therapy of acute hepatic failure in rats. The restoration of liver function as well as the stimulation of liver cell proliferation via putrescine production may contribute to this effect.

Acetyltransferases↗
PubMed1991

New applications of two-dimensional transesophageal echocardiography in cardiac surgery.

This article describes new applications of two-dimensional transesophageal echocardiography (2D-TEE), including (1) detection of pleural fluid (PF) and atelectasis (AT), and (2) evaluation of various cannulation techniques. The left and right pleural spaces were visualized by rotating the probe counterclockwise and clockwise, respectively, from the four-chamber view. PF was depicted as a crescent-shaped echo-free space, enclosed by the lung and posterior chest wall on both sides. AT was often accompanied by PF and was depicted as a less echogenic area in the lung parenchyma. During removal of PF, the echo-free space gradually decreased in size to the point of disappearing completely, while the lung parenchyma expanded and became more echogenic. TEE was advantageous in detecting PF and AT located in the most dorsal parts of the pleural space and lung parenchyma. The aorta acted as an acoustic window on the left side. TEE was found useful in evaluating the cannulae position of the intraaortic balloon pump (IABP) and ventricular assist device (VAD), and femoral cannulae for cardiopulmonary bypass (CPB). During use of the IABP, the chamber and shaft were visualized clearly and both malposition of the catheter tip and malfunction of the balloon were easily detected. For VAD, TEE readily showed the collapse of the ventricular cavity due to excessive drainage of blood from the left ventricle, as well as the favorable result of immediate reduction of flow rate. For femorofemoral extracorporeal bypass, TEE detected improper position of the venous cannula. These new applications of TEE can be performed with minimal manipulation of the probe, enabling early detection of the problems and initiating timely and appropriate therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Catheterization↗
PubMed1991

Pathogenetic role of vascular angiotensin-converting enzyme in the spontaneously hypertensive rat.

1. This study was undertaken to examine the possibility that the level of angiotensin-converting enzyme (ACE) increases in vascular tissue, and that this may participate in the pathogenesis of hypertension in spontaneously hypertensive rat (SHR). 2. In SHR, at the established hypertensive stage, the prolonged antihypertensive effect induced by a single oral dose of spirapril was closely correlated to the long-lasting inhibition of ACE in aortae and mesenteric arteries. In contrast, ACE in plasma, lung, heart and kidney recovered from inhibition faster than in vessels. 3. Prolonged daily oral treatment of SHR with spirapril, initiated at the age of 8 weeks and continued for 8 weeks, prevented the development of hypertension with concomitant decrease in aortic ACE activity. Blood pressure continued to be suppressed after the drug was withdrawn, as did the aortic ACE activity. 4. Spontaneously hypertensive rats developed hypertension with age as well as with the increase in aortic ACE activity which became higher with age than that of Wistar-Kyoto (WKY) normotensive control rats. On the contrary, ACE activity in plasma and lung of SHR was substantially lower than that of WKY at any age from 4 to 20 weeks old. Brain ACE activity of SHR did not differ from that of WKY at any age. Aged SHR showed the lower enzyme activity in the kidney compared with that of age-matched WKY. 5. Our results support the hypothesis that increased vascular ACE may play an essential role in the development and maintenance of hypertension in SHR.

Aging↗
PubMed1991

Peptide-based radioimmunoassay specific for GLUT1 glucose transporter.

A radioimmunoassay for the GLUT1 glucose transporter was developed with a synthesized peptide based on the sequence of the cDNA for GLUT1. A peptide corresponding to the COOH-terminal domain of the GLUT1 glucose transporter (Thr-Pro-Glu-Glu-Leu-Phe-His-Pro-Leu-Gly-Ala-Asp-Ser-Gln-Val) was synthesized and conjugated to keyhole limpet hemocyanin through the NH2-terminal of the peptide. An antibody was raised against this complex and affinity purified with the immobilized peptide. A second peptide, with tyrosine residue added to the NH2-terminal of the above peptide, was synthesized and used as a standard and iodinated for preparation of the radioactive ligand. The assay is highly reproducible, sensitive, and specific for the COOH-terminal domain of the GLUT1 glucose transporter. It has no cross-reactivity with the other glucose-transporter isoforms GLUT2 and GLUT4. Furthermore, the results obtained with this radioimmunoassay on the number of glucose transporters in human erythrocytes were in good agreement with previous studies based on cytochalasin B binding, suggesting that this radioimmunoassay is able to quantify the number of glucose transporters. The assay is completed within 4 h and can be used for simultaneous measurement of GLUT1 in many samples. In addition, it can be applied to the measurement of GLUT1 in several types of tissue.

Amino Acid Sequence↗
PubMed1991

Intraluminal projection of descending thoracic aorta and intraaortic balloon pump catheter examined by transesophageal echocardiography in patients undergoing coronary artery bypass surgery.

The thoracic descending aorta (DTA) was examined in 57 patients undergoing coronary artery bypass grafting (41 men and 16 women: 63.0 +/- 10.6 years old) using two-dimensional transesophageal echocardiography. An intraaortic balloon pump (IABP) was instituted in ten patients. A short-axis view of DTA was examined for intraluminal projection from the diaphragm level to the aortic arch level. In a frozen-frame image, the area and the height of the projection at each clockwise direction was measured. Four patients with preoperative insertion of an IABP catheter were excluded from the analysis. Seventy projections were found in 40 of 53 patients (75.5%), most frequently found at the 3 to 6 o'clock position. The tip of the IABP catheter was also located in the area between 3 and 6 o'clock of the aortic lumen in 6 of 10 patients. In one case, the area of projection was reduced from 1.1 cm2 to 0.7 cm2. In two of four patients with preoperative institution of an IABP catheter, projections were found near the catheter tip. Both intraluminal projections and IABP catheter tip were most commonly located in the same region of the DTA, suggesting a possible dislodging of the projection while advancing the catheter. This was demonstrated in one case. The catheter tip may damage the aortic intima and/or cause a formation of abnormal projection. We conclude that intraoperative examination of DTA in addition to routine monitoring can provide useful information which is helpful for minimizing complications at the time of insertion of an IABP catheter.

Aged↗
PubMed1991

Inhibitory effect of pentoxifylline and prostaglandin E1 on the release of neutrophil elastase from FMLP-stimulated neutrophils.

We measured the enzymatic and immunologic activities of neutrophil elastase to determine whether pentoxifylline and prostaglandin E1 are useful for inhibiting the enzymatic activity of released neutrophil elastase. Both activities in the medium decrease in the presence of pentoxifylline and prostaglandin E1. These results showed that pentoxifylline and prostaglandin E1 inhibited the release of neutrophil elastase from activated neutrophils, and that they may be useful in the improvement of neutrophil-mediated cellular injury.

Alprostadil↗
PubMed1991

[A case of meningioangiomatosis in an infant].

We report here a rare case of meningioangiomatosis in an infant, not associated with von Recklinghausen's disease. A 14-month-old female was admitted because of seizures. Neurological findings on admission were normal. Computed tomography showed a slightly high density mass with marked contrast enhancement in the left temporoparietal lobe. Magnetic resonance image (MRI) revealed a slightly hypointensive lesion surrounded by an isointensive band on T1-weighted image, and a hyperintensive lesion surrounded by a slightly hypointensive band on T2-weighted image. Brain edema was shown to a certain extent around the lesion on MRI. Left carotid angiography demonstrated a slightly upward shift of the left middle cerebral artery, but no abnormal vascularity was shown. A temporoparietal craniotomy was performed. A yellowish red, elastic soft tumor was observed in the left temporal lobe. The tumor resembled hyperemic hypertrophic gyri and was well demarcated. Total removal of the tumor was performed. Pathological diagnosis was meningioangiomatosis. The patient is still doing well 3 years and 5 months after the operation. There was no evidence of recurrence on computed tomography at the 3-year follow up. She didn't have any stigmata, such as café au lait spots or neurofibromas suggesting von Recklinghausen's disease.

Angiomatosis↗
PubMed1991

[A case of coronary-pulmonary artery fistula with saccular aneurysm].

Recently, due to the wide-spread use of coronary angiography (CAG), reports of coronary-pulmonary artery fistula have become more frequent. However, a case of coronary-pulmonary artery fistula with saccular aneurysm is very rare. We report a case of coronary-pulmonary artery fistula with saccular aneurysm which was discovered as an abnormal chest shadow. A sixty-two-year old female was admitted to our hospital with an abnormal chest shadow. CAG showed fistula from the left anterior descending coronary artery (LAD) proximal to the pulmonary artery (PA), and also from the LAD distal to the PA, with saccular aneurysm. Due to the risk of a rupture of the saccular aneurysm, we performed a resection. After this operation, no abnormal chest shadows appeared on the chest X-rays. CAG showed no saccular aneurysm and she is progressing favorably.

Coronary Aneurysm↗
PubMed1990

Affinity purification of human granulocyte macrophage colony-stimulating factor receptor alpha-chain. Demonstration of binding by photoaffinity labeling.

The human granulocyte macrophage colony-stimulating factor (GM-CSF) receptor alpha-chain, a low affinity component of the receptor, was solubilized and affinity-purified from human placenta using biotinylated GM-CSF. Scatchard analysis of 125I-GM-CSF binding to the placental membrane extract disclosed that the GM-CSF receptor had a dissociation constant (Kd) of 0.5-0.8 nM, corresponding to the Kd value of the GM-CSF receptor alpha-chain on the intact placental membrane. Affinity labeling of the solubilized protein using a photoreactive cross-linking agent, N-hydroxysuccinimidyl-4-azidobenzoate (HSAB), demonstrated a single specific band of 70-95 kDa representing a ligand-receptor complex. Approximately 2 g of the placental membrane extract was subjected to a biotinylated GM-CSF-fixed streptavidin-agarose column, resulting in a single major band at 70 kDa on a silver-stained sodium dodecyl sulfate gel. The radioiodination for the purified material disclosed that the purified protein had an approximate molecular mass of 70 kDa and a pI of 6.6. Binding activity of the purified material was demonstrated by photoaffinity labeling using HSAB-125I-GM-CSF, producing a similar specific band at 70-95 kDa as was demonstrated for the crude protein.

Affinity Labels↗
PubMed1990

Gonadotropin-releasing hormone (GnRH) immunoreactive system in the brain of the dwarf gourami (Colisa lalia) as revealed by light microscopic immunocytochemistry using a monoclonal antibody to common amino acid sequence of GnRH.

The present paper aims to give a morphological basis for the study of the terminal nerve system and its relation to the whole gonadotropin-releasing hormone (GnRH) immunoreactive (ir) neuronal system. We examined the GnRH-ir neuronal system of a tropical fish, the dwarf gourami, by using a recently developed monoclonal antibody against GnRH (LRH13) which recognizes the amino acid sequence common to all known variants of GnRH (Park and Wakabayashi, Endocrinol. Jpn. 33:257-272, '86). The ganglion cells of the terminal nerve (TN-ggl cells) in the transitional area between the olfactory bulb and the telencephalon reacted strongly with the LRH13. A distinct bundle of axons emanating from the TN-ggl cells ran caudally through the ventral telencephalon and the preoptic area. Some of these axons entered the optic nerve and innervated the retina. The remaining axons continued caudally to enter the hypothalamus and the midbrain. A second group of GnRH-ir cell bodies was found in the preoptic area. A distinct bundle of GnRH-ir fibers originating from these cell bodies innervated the pituitary. This pathway is equivalent to the preoptico-infundibular pathway of other vertebrates, and the GnRH in this pathway is presumed to function as hypophysiotrophic hormone to facilitate the release of gonadotropins from the pituitary. The distribution of GnRH-ir fibers in the brain was extensive. Most fibers apparently originated from the TN-ggl cells and covered various brain regions from the olfactory bulb to the spinal cord. They were especially abundant in the olfactory bulb, ventral telencephalon, preoptic area, optic tectum, and some hypothalamic areas. Thus, GnRH might function as a neuromodulator and/or neurotransmitter in these areas. The abundant GnRH-ir fibers in the ventral telencephalon and the preoptic area might affect some aspects of sexual behavior, since these areas have been suggested to be involved in the control of sexual behavior in teleosts.

Animals↗
PubMed1990

Unlinked regulation of cell growth and differentiation in immature B cell lines.

We established many immunoglobulin-null immature B cell lines transformed by tsOS-59, a temperature-sensitive mutant of Abelson murine leukemia virus. In different cell lines cell growth was depressed and cell differentiation (generation of intracytoplasmic mu-positive cells from Ig- cells) was induced by the shift of culture temperature from low (35 degrees C) to high (39 degrees C). Cell lines were categorized into four groups: (i) temperature sensitive (ts) to both cell growth and differentiation, (ii) ts to cell growth but not to cell differentiation, (iii) ts to cell differentiation but not to cell growth, and (iv) ts to neither cell growth nor differentiation. These results indicated that the depression of cell growth did not necessarily induce cell differentiation, and that cell differentiation was induced regardless of whether cell growth was depressed or not. Furthermore, the results showed that the depression of cell growth and the induction of cell differentiation occurred without the reduction of tyrosine kinase activity of P120gag-abl at high, nonpermissive temperature. Our cell growth and differentiation system described here should provide us with the interesting findings of the relation between B cell growth and differentiation.

Animals↗