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Biomedical subjects

S Higashi

Publications and source records attributed to S Higashi.

At least 109 records · Page 6Linked to original sources
PubMed1995

Immunohistochemical alterations of fibronectin during the formation and proliferative repair of experimental cerebral aneurysms in rats.

BACKGROUND AND PURPOSE: To determine whether distributional changes of fibronectin, a factor promoting wound healing, occur during the formation and repair of cerebral saccular aneurysms, we performed immunohistochemical analyses in experimental aneurysms. METHODS: Cerebral aneurysms were induced in rats by both the ligation of the unilateral common carotid artery and induced hypertension. Intimal proliferation in aneurysmal walls was induced by the ligation of the preserved common carotid artery 3 months after the first operation. The distribution of fibronectin was examined by immunohistochemistry in anterior cerebral artery-olfactory artery bifurcations under the following three conditions: normal bifurcations in control rats, early aneurysmal lesions during the aneurysm induction, and aneurysmal lesions with intimal proliferation. Furthermore, the immunohistochemical distributions of type I and IV collagens were examined to evaluate the specificity of fibronectin immunoreactivity. RESULTS: In the normal bifurcations, fibronectin was positive in the subintimal space, the surrounding area of the medial smooth muscle cells, and the adventitial fibrous tissue. In early aneurysmal lesions, linear staining of fibronectin and type I and IV collagens in the subendothelial space disappeared with the loss of the internal elastic lamina. In the intimal proliferation of early aneurysmal lesions, fibronectin was strongly immunostained in the subendothelial space and diffusely immunostained in the widened extracellular space surrounding proliferated cells. In contrast, the stainings of type I and IV collagens were sparse or negative. CONCLUSIONS: Although the present findings regarding dynamic changes of fibronectin distribution do not prove any causality in the process of aneurysm formation and repair, these immunohistochemical changes may constitute the crucial sequela of intimal endothelial damage and its subsequent recovery in cerebral aneurysms.

Animals↗
PubMed1995

Quantitative cryoimmunogold electron microscopic studies on induction of serine: pyruvate aminotransferase in rat liver mitochondria by administration of glucagon.

Induction of mitochondrial serine: pyruvate aminotransferase (SPT) in rat liver by administration of glucagon was studied quantitatively by immunoblot analysis and cryoimmunogold electron microscopy. Immunoblot analysis revealed that two daily injections of glucagon produced marked increase of SPT protein mass to a level as much as 18 times that of the untreated rat. Cryoimmunogold electron microscopic analysis showed that the labeling density of the mitochondria increased in a parallel manner. Thus the induction of SPT analyzed by two methods showed an excellent correlation with a relative correlation coefficient of 0.98, indicating that the induction of SPT can be analyzed quantitatively by immunogold electron microscopy on cryoultrathin sections.

Animals↗
PubMed1995

Backscattered electron imaging and energy-dispersive X-ray microanalysis studies of evidence for calcium salt heterogeneity in fifteen gallstones from an elderly human.

We examined 15 variably-sized gallstones, taken from an elderly male, by backscattered electron imaging and energy-dispersive X-ray microanalysis to learn the structural and distribution patterns of gallstone calcium (Ca-) salts. Of the 13 cholesterol-rich stones, nine stones had peripheral concentric layers of Ca-carbonate, whereas 2 stones had peripheral layers of Ca-phosphate. No Ca-salts were detected from 2 cholesterol-rich stones. The 2 stones containing Ca-phosphate had no Ca-salt cores, whereas the stones containing Ca-carbonate were separated into 3 different types: two stones with a Ca-carbonate core, four stones with several Ca-bilirubinate cores of glass-like structure, and 3 stones lacking Ca-salt cores. A closer view of the Ca-salt layers, which may be occasionally coexistent with Ca-bilirubinate, mainly showed either laminate deposits or numerous globules with a few laminae. Of the 2 cholesterol-poor stones, one had dispersed particles mainly of Ca-phosphate, and the other had loosely dispersed particles with small amounts of Ca-phosphate, bilirubinate, and/or palmitate. Some relationship between the size and Ca-salt species of these gallstones was suggested. Gallstones collected from the same individual showed a considerable heterogeneity of Ca-salts.

Aged↗
PubMed1995

Occipital dermal sinus associated with dermoid cyst in the fourth ventricle.

MR was helpful in demonstrating the spatial relationship between a dermoid cyst in the fourth ventricle and an occipital dermal sinus. T1-weighted images clearly showed the mixed hypointense mass in the fourth ventricle and above the vermis, which appeared to be connected to an occipital dermal dimple.

Adult↗
PubMed1995

Synchronous circadian rhythms of mRNA levels and activities of cholesterol 7 alpha-hydroxylase in the rabbit and rat.

Cholesterol 7 alpha-hydroxylase, the key enzyme in a series of metabolic changes for the production of bile acids from cholesterol, shows circadian rhythms. The mechanism of the circadian rhythms is the subject of controversy; moreover, few pieces of information are presently available. Because the rabbit is a good animal model for the study of human cholesterol-bile acid metabolism, in the present study we isolated a complete cDNA encoding rabbit cholesterol 7 alpha-hydroxylase (3022 base pairs (bp) long and 1503 bp open-reading frame encoding 501 amino acid residues). Using this isolate rabbit cDNA and the rat cDNA as probes, the circadian rhythms of this enzyme were studied in normal male rabbits and rats. The animals were maintained on a 12-h light-dark cycle. Three subjects each were then killed every 3 h for 1 day. The livers were harvested, and the mRNA levels and the activities of the enzyme were measured. Both mRNA levels and activities of the enzyme showed remarkable circadian rhythms, with higher values during the dark phase and lower values reaching minimum during the light phase. The enzyme activities correlated well with the mRNA levels. There was no shift in the cycles of the enzyme activities and the mRNA levels. These findings suggest that pretranslational regulation is the most likely mechanism for the circadian rhythms of cholesterol 7 alpha-hydroxylase. Because the rhythms of mRNA levels and activities of this enzyme are synchronous, the turnover of the enzyme should be as fast as that of the mRNA, and we can hereafter measure the mRNA levels instead of the enzyme.

Amino Acid Sequence↗
PubMed1995

Fine incremental lines observed on the enamel surfaces with a prismless structure in human teeth after phosphoric acid etching.

In human tooth enamel, the surface prismless layer contains liner laminas homologous to the cross-striations of enamel prisms other than the Retzius lines, while these lines terminate on the perikymata or run in parallel with the enamel surface. In our present scanning electron microscope observations after phosphoric acid etching, many fine incremental lines (FIL) running transversely were found on the inner occlusal enamel with a prismless structure in a young permanent premolar. Almost the same structures were also found on the upper-coronal enamel with scattered prismless and indistinct prism structures in an exfoliated deciduous molar, and the FIL occasionally went across the indistinct prisms or caused the lower half of the prisms to disappear. Their intervals ranged from about 0.5 to 2 microns; less than the diameter of the prisms. Such results suggest that the FIL are not the termination of the laminate striations in the surface prismless layer, but that the previously unnoticed patterns sometimes formed by the sequential completion of the activity of ameloblasts which interact with each other in a transverse row at the final stage of matrix formation.

Acid Etching, Dental↗
PubMed1995

[A case report of surgical repair for distal aortic arch aneurysm with abdominal aortic aneurysm].

A 77-year-old female was referred to our hospital with hoarseness and an abnormal shadow on her chest X ray film. Computed tomography and aortography revealed aneurysms of the distal aortic arch and the infrarenal abdominal aorta. Total aortic arch replacement was performed successfully on the patient, utilizing hypothermic selective cerebral perfusion. The operation employed three technical characteristics for avoidance of cerebral complication. Those were as follows: First, total aortic arch replacement was performed instead of distal aortic arch replacement because of severe sclerosis of the proximal aortic arch. Secondly, to prevent cerebral embolism due to the thrombi on the wall of the abdominal aortic aneurysm, an arterial cannula for cardiopulmonary bypass was inserted in the ascending aorta initially and after completion of the distal anastomosis, it was placed on the graft. Thirdly, the so called "non clamping technique" operation was employed because clamping onto the sclerotic arteries might have caused cerebral embolism. There was no cerebral complication and the postoperative course was satisfactory.

Aged↗
PubMed1995

The structural patterns and mineralization values of prismless enamel, a case of mild enamel hypoplasia.

In examining the prismless enamel (PL) distribution from the inner to surface layers of a human incisor with hypoplastic perikymatas with enamel pits, we determined the structural patterns and mineralization values by microradiographic, optical, and scanning electron microscopic observations. The PL containing abnormal prisms ranged from 20 to 250 micrometers in thickness. The alternated layers of the PL and prismatic enamel, in parallel with the Retzius lines, showed a roughly zigzag pattern based on the main orientation of enamel crystals. Such a pattern suggests an alternation of the disappearance and reappearance of Tomes' processes, which may have strong restorative and reactive capacities. In the mineralization values determined by microradiography, the PL was higher in the well-marked lines of Retzius, while the PL under the hypoplastic enamel pit and an area within the thick PL showed hypomineralization. The backscattered electron images indicated that the fine laminate striations and abnormal prismatic rows within the PL were hypomineralized, and the PL in the inner enamel showed a lower mineralization than the adjacent prismatic layer. Thus, the disappearance of Tomes' processes, which form prismless structures, may be unrelated to changing the mineral amount in amelogenesis.

Ameloblasts↗
PubMed1994

[Effects of urography performed twice at a close interval with contrast media on renal function and morphology in rabbits].

This study was carried out in order to clarify the effects of rapid intravenous urography performed twice at a three-day interval with contrast medium on renal function and morphologic change in normal rabbits as a means to observe progress or to reexamine patients. The ionic high-osmolal amidotrizoate, non-ionic low-osmolal iopamidol, and ionic low-osmolal ioxaglate were used. A second urography was performed and curves of kidney density plotted against time and nephrograms were obtained. Serum BUN and creatinine were measured, and the kidneys were removed for histologic observations. Following amidotrizoate administration, curves of kidney density showed significantly slower clearance than with iopamidol and ioxaglate. Nephrograms at 40 seconds showed that opacification of the renal pelvis and urinary tracts also was poor. Serum creatinine following the second administration of amidotrizoate was significantly higher than the values before and at the first urography, and both serum BUN and creatinine were significantly higher than they were after iopamidol and ioxaglate. Although light microscopic changes were obscure, marked changes were observed by electron microscopy. In conclusion, intravenous urography conducted twice at a close interval with amidotrizoate induces impairment of glomerular function and morphologic change.

Animals↗
PubMed1994

Identification of regions of bovine factor VII essential for binding to tissue factor.

Initiation of the extrinsic blood coagulation pathway is mediated by a complex formed between plasma-derived factor VII/VIIa and cell-derived tissue factor (TF). To identify the site(s) of interaction, zymogen VII and VIIa were enzymatically and chemically modified, and their affinities for TF were estimated by measuring their inhibitory effects on the amidolytic activity enhanced after formation of the VIIa-TF complex. We found that the VIIa-light chain (Ki = 3.5 x 10(-7) M) and its fragment consisting of the gamma-carboxyglutamic acid (Gla)-domain and the first epidermal growth factor (EGF)-like domain (Gla-EGF1 peptide; Ki = 1.0 x 10(-6) M) have an affinity for TF. Therefore, one of the binding sites of VII with TF is probably located in the Gla-EGF1 region. On the other hand, a dansyl-Glu-Gly-Arg chloromethyl ketone-treated Gla-domainless VIIa (Ki = 0.7 x 10(-7) M) showed a high affinity for TF, whereas the corresponding Gla-domainless VII similarly treated showed no binding potential, thereby indicating that binding site(s) other than in the Gla-EGF1 region are present in VIIa but not in VII. Acetylation or carbamylation of the alpha-amino group of the NH2-terminal Ile-153 of VIIa resulted in the loss of binding affinity for TF; such modifications convert VIIa into a zymogen-like inactive form by destroying the salt bridge between Ile-153 and Asp-343 in VIIa. The rate of carbamylation of VIIa was reduced in the presence of TF. Protection of the alpha-amino group of Ile-153 from carbamylation after complex formation was consistent with salt bridge formation between Ile-153 and Asp-343 in the VIIa-TF complex. Therefore, binding of TF with the heavy chain of VIIa may induce a conformational change that brings the alpha-amino group of Ile-153 close to the beta-carboxyl group of Asp-343 to make a stable salt bridge.

1-Carboxyglutamic Acid↗
PubMed1994

Mutation of a fungal aspartic proteinase, Mucor pusillus rennin, to decrease thermostability for use as a milk coagulant.

Mutagenesis of a fungus Mucor pusillus, a producer of an aspartic proteinase named Mucor pusillus rennin (MPR), was performed to obtain the mutated enzymes with decreased thermostability, which is desirable for practical use of the enzyme as a milk coagulant for cheese manufacturing. A fungal mutant strain which produced the mutant enzyme with distinctly reduced thermostability was isolated. Two different mutant alleles of the mpr gene, one with a single amino acid exchange of Ala101 for Thr and the other of Gly186 for Asp, were cloned out of this mutant strain. The mutated mpr genes were expressed in Saccharomyces cerevisiae under the control of the yeast GAL7 promoter to produce the active enzymes in extracellular medium. Both of the mutations, especially Gly186Asp, were confirmed to cause a marked decrease in thermostability of the enzyme. All mutants possessing exchanges of Gly186 for various amino acids by site-directed mutagenesis showed a decrease in thermostability, indicating involvement of this residue to maintain a conformation of the enzyme. A double mutant having the both exchanges, Ala101Thr and Gly186Asp, in a single molecule showed the lowest thermostability without decrease in the enzymatic activity as well as the relative ratio of clotting to proteolytic activity.

Amino Acid Sequence↗
PubMed1994

Cloning of omega 3 desaturase from cyanobacteria and its use in altering the degree of membrane-lipid unsaturation.

Cyanobacteria respond to a decrease in temperature by desaturating fatty acids of membrane lipids to compensate for the decrease in membrane fluidity. Among various desaturation reactions in cyanobacteria, the desaturation of the omega 3 position of fatty acids is the most sensitive to the change in temperature. In the present study, we isolated a gene, designated desB, for the omega 3 desaturase from the cyanobacterium, Synechocystis sp. PCC 6803. The desB gene encodes a protein a 359 amino-acid residues with molecular mass of 41.9 kDa. The desB gene is transcribed as a monocistronic operon that produced a single transcript of 1.4 kb. The level of the desB transcript in cells grown at 22 degrees C was 10 times higher than that in cells grown at 34 degrees C. In order to manipulate the fatty-acid unsaturation of membrane lipids, the desB gene in Synechocystis sp. PCC 6803 was mutated by insertion of a kanamycin-resistance gene cartridge. The resultant mutant was unable to desaturate fatty acids at the omega 3 position. The desA gene, which encodes the delta 12 desaturase of Synechocystis sp. PCC 6803, and the desB gene were introduced into Synechococcus sp. PCC 7942. Whilst the parent cyanobacterium can only desaturate membrane lipids at the delta 9 position of fatty acids, the resultant transformant was able to desaturate fatty acids of membrane lipids at the delta 9, delta 12 and omega 3 positions. These results confirm the function of the desB gene and demonstrate that it is possible to genetically manipulate the fatty-acid unsaturation of membrane lipids in cyanobacteria.

Amino Acid Sequence↗
PubMed1994

Neuroendocrine studies in dementia patients: responses of plasma GH and PRL following bromocriptine administration.

Bromocriptine stimulates growth hormone (GH) secretion at the hypothalamus and suppresses prolactin (PRL) secretion at the pituitary level. We administered bromocriptine to 30 patients with dementia of the Alzheimer type (DAT), 30 patients with multi-infarct dementia (MID) and 22 age matched healthy controls, and compared response patterns of GH and PRL. Incomplete PRL suppressive responses (suppression rate < 50%) were seen in 36.7% of DAT patients and in 30.0% of MID patients, indicating that both groups had the same degree of pituitary dysfunctions. Blunted GH responses (< 5 ng/ml) were seen in 93.3% of DAT patients, in 63.3% of MID patients and in 31.8% of the controls. The results indicate that neuroendocrine regulation of GH is more selectively and severely damaged in DAT patients than in MID patients at the hypothalamus.

Aged↗
PubMed1994

Insulin's effect on protein kinase C and diacylglycerol induced by diabetes and glucose in vascular tissues.

We have reported that membranous protein kinase C (PKC) activities and total diacylglycerol (DAG) levels are increased in the heart and aorta of diabetic rats, which cannot be easily reversed by euglycemic control. However, insulin treatment, which achieved euglycemia, can prevent the increase in PKC activities and DAG levels. Chronic exposure to elevated glucose levels (5.5 vs. 22 mM) increased DAG levels in cultured bovine and rat aortic endothelial cells and smooth muscle cells by 31, 140, and 143%, respectively, only after 3 days of incubation. Glyceraldehyde, which can stimulate the de novo synthesis of DAG, significantly increased DAG levels by 7.1 +/- 0.6-fold after only 16 h of incubation. Elevated glucose levels did not affect labeled DAG when all of the vascular cells were incubated with [3H]arachidonate, [3H]glycerol, or [3H]phosphatidylcholine, whereas [3H]palmitate- and [3H]oleic acid-labeled DAG levels were significantly increased, indicating that the glucose-stimulated increase in DAG is derived partially from the de novo synthesis pathway. Immunoblotting studies showed increases only in PKC isoform beta II but not alpha in aortic smooth muscle cells. The phosphorylation level of MARCKS protein, an intracellular substrate of PKC, was also increased, consistent with the PKC activity increase. These findings showed that diabetic and hyperglycemia-induced increases in PKC activity and DAG levels in the heart and aorta are preventable by insulin treatment.

Animals↗
PubMed1994

Giant fusiform aneurysm at the horizontal portion of the middle cerebral artery in a child--case report.

A 13-year-old boy with a rare giant fusiform aneurysm at the horizontal portion of the middle cerebral artery (M1) presented with progressively severe throbbing headache. The aneurysm was reconstructed by tandem application of nine fenestrated clips and coating of the remnant of the aneurysm. However, he was readmitted 3 months later because of recurrent aneurysms at the proximal and distal M1 portions which had been coated. The aneurysms were trapped after rupture occurred during a second operation. Aneurysm trapping combined with superficial temporal artery-middle cerebral artery bypass surgery may be a better method to treat such aneurysms.

Adolescent↗
PubMed1994

Effects of head elevation on intracranial hemodynamics in patients with ventriculoperitoneal shunts.

The present study was performed to investigate the effects of head elevation on intracranial hemodynamics in patients with ventriculoperitoneal (VP) shunts. The series included 35 hydrocephalic patients and five individuals without hydrocephalus who were used as controls. The hydrocephalic patients were divided into three groups: 15 patients who received VP shunts with a differential-pressure valve (DP group); 11 who received VP shunts with a variable-resistance valve (VR group), and 13 hydrocephalic patients (Hyd group) who had not received shunts (four underwent VP shunts later). The cerebral blood flow (CBF) of patients in the supine and upright positions was measured by technetium-99m hexamethylpropylenamine oxide (HMPAO) single-photon emission computerized tomography in each patient, using the subtraction technique. Cerebral perfusion pressure (CPP) was taken as the difference between the mean arterial blood pressure and ventricular fluid pressure, both referenced to the level of the foramen of Mono. The patients' heads were elevated stepwise from supine to upright. Percent changes of the mean CBF in the upright position (% delta mCBFupr) were 24.9% +/- 4.3% (mean +/- standard error of the mean) in the DP group, 6.2% +/- 2.7% in the VR group, 3.5% +/- 2.6% in the Hyd group, and 4.5% +/- 2.2% in the control group. Patients in the DP group showed a pathological increase in CPP with head elevation, whereas those in the Hyd and VR groups showed a physiological decrease in CPP. Three patients with differential-pressure valves, whose % delta mCBFupr was markedly high, developed low-intracranial pressure syndrome. In conclusion, shunted patients with a DP valve showed pathological intracranial hemodynamics in the upright position. This pathological hemodynamic stress in patients with long-standing differential-pressure valve implantation may induce pathological changes in the brain such as subependymal gliosis.

Adolescent↗