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Biomedical subjects

N Oka

Publications and source records attributed to N Oka.

At least 19 recordsLinked to original sources
PubMed1996

Soluble adenylyl cyclase from Spodoptera frugiperda (Sf9) cells. Purification and biochemical characterization.

An insect ovarian cell, Spodoptera frugiperda (Sf9), has been widely used to express recombinant proteins, including adenylyl cyclase, as a host cell in the baculovirus expression system. We report the presence and characterization of a soluble adenylyl cyclase (sAC) distinct from a membrane-bound form of adenylyl cyclase (mAC) that is also present in Sf9 cells. sAC was purified 3,500-fold to near homogeneity; a single band at 25 kDa on SDS-polyacrylamide gel electrophoresis correlated well with adenylyl cyclase catalytic activity. The purified enzyme had a catalytic activity of 0.1 micromol/min.mg and the Km of 0.55 mM for the substrate ATP. In contrast to mAC, sAC was heat-stable. Enzymatic activity of sAC was not stimulated by forskolin and was inhibited by salts at high concentrations. sAC utilized both manganese- and magnesium-ATP as substrate. Di- or triphosphate-containing nucleotides, such as GTP and GDP, as well as pyrophosphate, noncompetitively inhibited sAC. Our data suggest that the physical and biochemical characteristics of sAC are different from those of mAC in Sf9 cells as well as from those of other known forms of adenylyl cyclase in animal cells; sAC in Sf9 cells may constitute a new member of adenylyl cyclase found in animals.

Adenylyl Cyclase Inhibitors↗
PubMed1996

Regulation of type V adenylyl cyclase by PMA-sensitive and -insensitive protein kinase C isoenzymes in intact cells.

Abstract Type V adenylyl cyclase (AC) was stably over-expressed in HEK293 cells (293AC-V). Forskolin-stimulated cAMP accumulation in 293AC-V was 5 times as great as that in control cells. PMA, a protein kinase C (PKC) activator, enhanced cAMP accumulation in 293AC-V cells dose-and time-dependently and this enhancement was abolished by staurosporine. Insulin also enhanced cAMP accumulation in 293AC-V cells. Co-transfection of PKC-zeta, but not PKC-alpha, potentiated the effects of insulin. These data suggest that type V AC activity is regulated in cells by PKC isoenzymes through different extracellular stimuli.

Adenylyl Cyclases↗
PubMed1996

Immunohistochemical localization of brain-derived neurotrophic factor in adult rat brain.

To investigate the role of brain-derived neurotrophic factor in the central nervous system, we produced an anti-peptide antibody that specifically recognized brain-derived neurotrophic factor and performed immunohistochemistry for brain-derived neurotrophic factor-like immunoreactivity in normal adult rat brain. A synthetic peptide (EKVPVSKGQL), derived from mature brain-derived neurotrophic factor, was conjugated to bovine thyroglobulin at a ratio of 1:3 and used as an immunogen to produce a high-titre anti-brain-derived neurotrophic factor polyclonal antibody in Japanese white rabbits. Dot blotting demonstrated that the antiserum could detect 3.91 pmol of synthetic peptide, and Western blotting showed that the antiserum recognized one band with a molecular weight consistent with that of brain-derived neurotrophic factor. In immunohistochemistry, brain-derived neurotrophic factor-like immunoreactivity was widespread in adult rat brain, including cerebral cortex, hippocampus, basal forebrain, striatum, hypothalamus, brainstem and cerebellum. Not only neuronal somata but also nerve fibres showed positive staining. Our data suggest that brain-derived neurotrophic factor is transported through axons in a subpopulation of neurons in adult rat brain, and that brain-derived neurotrophic factor influences a great variety of neurons and acts as a neurotrophic factor in the central nervous system.

Animals↗
PubMed1996

The effect of ovariectomy on the temporomandibular joints of growing rats.

PURPOSE: This investigation studied the effects of ovariectomy, on the temporomandibular joints (TMJ) of young rats. MATERIALS AND METHODS: Four-week-old female Wistar rats were ovariectomized and killed at the intervals of 1, 2, 4, and 8 weeks postoperatively. Histomorphometric study of the TMJ was performed in a synchronous manner with an age-matched sham-operated control group. The serum levels of estrogen, calcitonin, and C-terminus parathyroid hormone were also determined. RESULTS: In the sham-operated control group, the serum levels of estrogen and calcitonin increased with age. An increase of the bone volume, with a concomitant increase of the osteoid surface, was observed at 12 weeks. Thickness of the articular soft tissue was decreased with increasing age. In the ovariectomized animals, serum estrogen was not detected during the experiment. A biphasic change in the parathyroid hormone level, with decreases at 1 and 2 weeks after the ovariectomy and increases at 4 and 8 weeks postoperatively, was observed, whereas a constant value was noted in the calcitonin level. Thickness of the articular soft tissue was increased in the anterior and central portions of the condyle at 1, 2, and 4 weeks after the ovariectomy, whereas no appreciable changes were observed in the posterior portion. The bone volume was decreased during the experiment, particularly in the posterior portion. An osteophyte in the anterior region was also observed 8 weeks postoperatively. CONCLUSIONS: Estrogen deficiency in rats during puberty predisposes to alterations of the TMJ through changes in serum calcitonin and parathyroid hormone levels.

Analysis of Variance↗
PubMed1996

[Acoustic neurinoma located exclusively in cerebellopontine angle cistern ("cisternal" acoustic neurinoma): a case report].

This is a case report of acoustic neurinoma which was located exclusively in the cerebellopontine angle (CPA) cistern and which did not extend into the internal auditory meatus ("cisternal" acoustic neurinoma). The 43-year-old female patient had signs of the left trigeminal nerve impairment including left face neuralgia. However, she did not have any neurootological symptom. No abnormal bony changes in the internal auditory meatus (IAM) were found by high-resolution bone-window CT. MRI showed a left CPA tumor of 25mm not extending into the IAM. The tumor was totally removed by the lateral suboccipital approach. It originated from the vestibular nerve medial to the porus acusticus and was located exclusively in the CPA cistern. No tumor extension into the IAM was confirmed. The cochlear nerve was involved in the tumor capsule and could not be preserved. The pathological diagnosis was that it was a neurilemmoma. Early diagnosis of "cisternal" acoustic neurinoma is difficult because it does not show neurootological symptoms in the early stage. The lateral suboccipital approach is appropriate for the removal of a "cisternal" acoustic neurinoma. However, in spite of the good preoperative hearing, the preservation of hearing is difficult because of the large tumor size.

Cerebellar Neoplasms↗
PubMed1995

Ascorbic acid stimulates barrier function of cultured endothelial cell monolayer.

The macromolecular permeability of cultured bovine aortic, bovine venous, and human umbilical vein endothelial cell monolayers was decreased significantly in culture medium containing L-ascorbic acid (Asc Acid; 0.01-0.1 mM) and L-ascorbic acid 2-phosphate (Asc 2-P). Dithiothreitol, which shows reducing activity equivalent to that of Asc Acid, did not affect endothelial permeability. Asc Acid induced a sixfold increase in collagen synthesis by the endothelial cells. The coexistence of L-azetidine 2-carboxylic acid, an inhibitor of collagen synthesis, attenuated the effect of Asc 2-P in a dose-dependent manner. Another collagen synthesis inhibitor, ethyl-3,4-dihydroxybenzoate, also inhibited collagen synthesis and increased endothelial permeability. The decrease in permeability of the endothelial monolayer was dependent on a reduction of the permeability coefficient of the endothelial monolayer. These findings indicate that endothelial barrier function is stimulated by Asc Acid via an increase in collagen synthesis.

Animals↗
PubMed1995

Lectin binding to Renaut bodies.

Localization of sugar residues of Renaut bodies in human sural nerves was studied using lectin histochemistry. Lens culinaris specific to mannose and Triticum vulgaris specific to glcNAc bound to the capsular and core portions of Renaut bodies strongly. Arachis hypogaea specific to galb(1-3)galNAc and Ulex europaeus I specific to L-fucose bound to Renaut bodies granularly. Lectins specific to galactose or terminal galNAc bound to nowhere. The perineurium showed similar lectin binding to Renaut bodies. Our result suggests that Renaut bodies are rich in mannose and glcNAc. Renaut bodies may be originated from the perineurium.

Aged↗
PubMed1995

Antihypertensive effect of sesamin. I. Protection against deoxycorticosterone acetate-salt-induced hypertension and cardiovascular hypertrophy.

We investigated the antihypertensive effect of sesamin, a lignan from sesame oil, using deoxycorticosterone acetate (DOCA)-salt hypertensive rats. The animals were unilaterally nephrectomized, and then separated into a sham-operated group (sham group) and a DOCA-salt-treated group. The latter was further separated into a normal diet group (control group) and a sesamin-containing diet group (sesamin group). The systolic blood pressure of control group progressively increased in comparison with that of sham group. This DOCA-salt-induced hypertension was markedly suppressed by feeding a sesamin-containing diet. Systolic blood pressure after 5 weeks was 130.6 +/- 1.9 mmHg in the sham group, 198.1 +/- 7.3 mmHg in the control group and 152.5 +/- 8.4 mmHg in the sesamin group, respectively. The treatment with DOCA and salt for 5 weeks significantly increased the weight of the left ventricle plus the septum. However, this increase was significantly suppressed in the sesamin group. When the degree of vascular hypertrophy of the aorta and superior mesenteric artery was histochemically evaluated, there were significant increases in wall thickness, wall area and the wall-to-lumen ratio in the control group, compared with the sham. Sesamin feeding ameliorated the development of DOCA-salt-induced vascular hypertrophy in both the aorta and mesenteric artery. These findings strongly suggest that sesamin is useful as a prophylactic treatment in the development of hypertension and cardiovascular hypertrophy.

Animals↗
PubMed1995

Antihypertensive effect of sesamin. II. Protection against two-kidney, one-clip renal hypertension and cardiovascular hypertrophy.

We investigated the antihypertensive effect of sesamin, a lignan from sesame oil, using two-kidney, one-clip (2K,1C) renal hypertensive rats. After clipping the left renal artery, animals were assigned to either a normal diet group (control group) or a sesamin-containing (1% (w/w)) diet group (sesamin group). The sham-operated rats (sham group) were fed a normal diet and tap water. The systolic blood pressure of the control group increased progressively in comparison with the sham group. This 2K,1C-induced hypertension was markedly reduced by feeding the sesamin-containing diet. The systolic blood pressure after 4 weeks was 123.60 +/- 4.01 mmHg in the sham group, 187.43 +/- 5.69 mmHg in the control group and 145.57 +/- 6.78 mmHg in the sesamin group, respectively. There were significant increases in left ventricle plus septum weight-body weight ratio in the control group compared with the sham group. This rise was also significantly reduced in the sesamin group. When the thoracic aorta was histochemically evaluated, the wall thickness and wall-to-lumen ratio in the control group were significantly increased, compared with the sham group, indicating that vascular hypertrophy had occurred in the control group. The sesamin diet tended to ameliorate this vascular hypertrophy, although its effect was not statistically significant. These findings suggest that sesamin is useful as prophylactic treatment to combat the development of renal hypertension and cardiac hypertrophy.

Animals↗
PubMed1995

Accumulation of cells containing factor XIII subunit a around the foci of intense fibrosis in human epulides.

On the basis of clinical and biochemical findings, Factor XIII subunit a (FXIII A) has been conjectured to play an important role in fibrotic processes. Epulis samples at different stages of fibrotic tissue formation were used as a model system for studying the localization and tissue distribution of FXIII A during the course of connective tissue generation. Marker characteristics of cells containing FXIII A (FXIII A+ cells) were determined as well. In double immunofluorescent labelling systems, FXIII A was localized in monocyte-derived (CD-14+), activated (HLA-DR+), and phagocytosing (Ki-M7+) tissue macrophages, which are widely distributed homogeneously in granulation tissues, but start to accumulate around foci of fibrosis as soon as the foci appear. During the relatively long process of fibrosis, FXIII A+ macrophages continuously decrease in number, and their morphological appearance changes from stellate to spindle-shaped. The nuclei of these cells were not labelled by Ki-67 monoclonal antibody; this indicating that they represent a non-proliferating cell population in the connective tissue stroma. The present findings may help to link theories concerning the role of FXIII A and those of macrophages in the connective tissue formation so far found separately in the literature.

Antibodies, Monoclonal↗
PubMed1995

Characterization of cells containing factor XIII subunit a in benign and malignant buccal lesions.

In the present study, the distribution pattern and characteristics of cells containing Factor XIII subunit a (FXIII A) have been studied in benign and malignant lesions of human buccal mucosa. Tissues from four irritation fibromas and three squamous cell carcinomas were studied by means of double immunofluorescent staining techniques in which the detection of FXIII A was combined with a reaction with CD14 (recognizing a monocyte/macrophage differentiation marker antigen), Mac 387 (reacting with a special subset of macrophages), anti-HLA-DR, Ki-M7 (labelling phagocytosing macrophages) or Ki-67 (visualizing a nuclear antigen associated with cell proliferation) monoclonal antibodies. FXIII A was detected in cells of the connective tissue stroma in both benign and malignant buccal lesions. The number of these FXIII A-reactive cells (FXIII A+ cells) increased considerably in the tumour tissues, in particular in those surrounding tumour cell clusters. FXIII A+ cells scattered in the fibromatous tissues were spindle-shaped, whereas in the tumour stroma, large stellate cells predominated, and round cells were likewise labelled around blood vessels. FXIII A+ cells were labelled with CD14 and Ki-M7 in both fibromatous and tumoural buccal mucosa; however, they failed to show any reaction with Ki-67. FXIII A+ cells accumulated in the tumour stroma reacted for HLA-DR as well. These results indicate that in both the benign and malignant buccal lesions FXIII A is contained in a subpopulation of tissue macrophages, which represents a monocyte-derived (CD14+) and phagocytosing (Ki-M7+) cell population. The accumulation of the FXIII A+ cells in the tumour stroma is believed to be a result of direct migration from the circulating blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1995

[A case with hereditary motor and sensory neuropathy with multiple cranial nerves involvement].

We described a 62-year-old man presenting motor and sensory neuropathy with multiple cranial nerve involvement. He was admitted to our hospital for visual loss and gait disturbance. Visual disturbance appeared at age of 32 and have slowly progressed until admission. At age of 55, he noticed walking difficulty, which has progressed. On neurological examinations we found cranial nerve disturbance including the 2nd, 3rd, 4th, 5th, 6th, 7th and 12th nerves. Muscle atrophy and sensory disturbance were observed in four limbs, most strikingly at the distal lower limbs. The electromyographic study indicated chronic denervation in four limbs. The histological examination on sural nerve biopsy specimens showed neuronal type degeneration accompanied with a severe loss of myelinated fibers and proliferation of perineurial cells in this nerve. We diagnosed the present case as HMSN type 6 documented by Dyck. To our knowledge, the present case has been the initial case accompanied with multiple cranial nerve involvements.

Biopsy↗
PubMed1994

C-type natriuretic peptide inhibits intimal thickening of rabbit carotid artery after balloon catheter injury.

C-type natriuretic peptide (CNP) stimulated cGMP production in rabbit cultured vascular smooth muscle cells, and thymidine uptake was inhibited by CNP. We tested whether CNP inhibits the development of intimal lesions induced by balloon catheter injury in rabbit common carotid artery. CNP (1 microgram/kg/min) infusion through the left jugular vein by DIB balloon catheter pump was started at 30 min before injury and continued until sacrifice. The median of the mean ratio of intima to media in each rabbit after 14 days was 29.5% [14.5-57.8] for control group and 12.0% [2.5-29.8] for CNP group (p < 0.01). Maximum ratio was also significantly low in CNP group. These results suggest that CNP may act as local regulator which suppresses intimal thickening.

Animals↗
PubMed1994

Prostaglandin F2 alpha-stimulated phospholipase D activation in osteoblast-like MC3T3-E1 cells: involvement in sustained 1,2-diacylglycerol production.

In [3H]myristic acid-labelled osteoblast-like MC3T3-E1 cells, prostaglandin F2 alpha (PGF2 alpha)-induced PLD activity was assessed by measuring the [3H]phosphatidylethanol (PEt) formation in the presence of ethanol. Inhibition of the increase in intracellular Ca2+ concentration ([Ca2+]i) by U73122, an inhibitor of phosphoinositide-specific phospholipase C (PI-PLC), or chelation of extracellular Ca2+ with EGTA or of intracellular Ca2+ with BAPTA, suppressed PGF2 alpha-induced phospholipase D (PLD) activation. Neither protein kinase C (PKC) inhibitors nor PKC down-regulation with phorbol 12-myristate 13-acetate affected PGF2 alpha-induced [3H]PEt formation. In permeabilized cells, guanosine 5'-[gamma-thio]triphosphate enhanced PGF2 alpha 's potency in [3H]PEt formation in the presence of Ca2+. The pretreatment of intact cells with pertussis toxin failed to inhibit PGF2 alpha-induced [3H]PEt formation. PGF2 alpha caused a biphasic production of [3H]1,2-diacylglycerol ([3H]1,2-DAG) in [3H]glycerol-labelled cells. The initial transient phase was decreased by U73122, whereas the late sustained phase was decreased by ethanol and the phosphatidic acid phosphohydrolase inhibitor, propranolol. From these results, it was suggested that PGF2 alpha-induced PLD activation was mediated by the dual control of the [Ca2+]i increase due to PI-PLC activation and activation of pertussis-toxin-insensitive G-protein, but not mediated by PKC, and also that PLD activation was involved in the late sustained 1,2-DAG generation in MC3T3-E1 cells.

3T3 Cells↗
PubMed1994

Microtubules stability in human peripheral nerves.

We examined the cold stability of microtubules (MT) in biopsied sural nerves. In control nerves, cold treatment reduced the density of MT in unmyelinated axons. The proportion of cold-insoluble MT was approximately 30% by morphological study. By contrast, the extraction study using essentially the same nerves showed that the ratio of cold-insoluble tubulin was 60-75%. These findings suggest the existence of a subpopulation of cold-stable tubulin which may not make up MT. However, in 2 patients with acute dysautonomia the proportion of cold-stable MT or tubulin was decreased compared to that in controls in both the morphological and extraction study. This suggests the altered local process involving MT in primary axonal degeneration.

Adult↗
PubMed1994

Elevated serum levels of endothelial leukocyte adhesion molecules in Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy.

We determined the serum concentrations of the soluble form of endothelial leukocyte adhesion molecule-1 (sELAM-1) in 25 patients with Guillain-Barré syndrome, 14 patients with chronic inflammatory demyelinating polyneuropathy, 15 patients with amyotrophic lateral sclerosis, 15 patients with other polyneuropathies, 10 patients with acute stroke, and 12 healthy control subjects. The patients with Guillain-Barré syndrome in the acute stage had a higher sELAM-1 serum level compared with the control subjects (p < 0.001). In 7 of the 9 patients the elevated level returned to normal by 14 days after the onset of neurological symptoms. In addition, a significantly elevated serum level of sELAM-1 was found in patients with chronic inflammatory demyelinating polyneuropathy (p < 0.01). These findings suggest a role for ELAM-1 in the inflammatory process of these disorders.

Cell Adhesion↗
PubMed1994

Anti-GM1 antibodies and impaired blood-nerve barrier may interfere with remyelination in multifocal motor neuropathy.

Multifocal motor neuropathy has pure motor manifestation and nonremittent clinical courses. Antiganglioside antibodies, though variable in titers, are characteristically elevated in the majority of these patient. In our cases, pathological findings at the site of conduction block suggested impaired remyelination and disruption of blood-nerve barrier. These findings lead us to postulate that antibodies toward gangliosides or toward unknown antigens containing gangliosides initiate motor-specific demyelination. The lesion, once produced, may persist as a result of impaired remyelination caused by disrupted blood-nerve barrier. The antibodies bound to denuded axons may also interfere with a remyelinative process. If so, antibodies may not always be circulating, thus accounting for variable levels of titers.

Antibodies↗