Biomedical subjects

M Okada

Publications and source records attributed to M Okada.

At least 325 records · Page 18Linked to original sources

PubMed1999

Cholinergic and glutamatergic transmission in medial vestibular nucleus neurons responding to lateral roll tilt in rats.

The responses of the medial vestibular nucleus (MVN) neurons to lateral tilt and the neurotransmitters mediating otolith information to MVN neurons were investigated using rats. A computer-operated goniometer was tilted 20 degrees clockwise and counterclockwise at an angular speed of 5 degrees /s and paused in the inclined positions for 10 s to record neuronal responses in the static phase. The 185 MVN neurons recorded were classified into eight types according to their responses to tilt (alpha, beta, gamma, delta, epsilon, zeta, eta and theta). A majority showed increased firing in response to ipsilateral tilting and decreased firing in response to contralateral tilting (alpha type: 31.4%) or exhibited the reverse pattern (beta type: 36.8%). Further, other groups of neurons increased (gamma type) or decreased (delta type) firing rates to either side tilting and increased (epsilon and zeta type) or decreased (eta and theta type) firing only on one side. Atropine or L-glutamic acid diethyl ester hydrochloride (GDEE) applied microiontophoretically antagonized tilt-induced firing of alpha type neurons in 58.8% or 60.0%, respectively, and of beta type neurons in 66.7% or 58.3%, respectively. When the effects of atropine and GDEE were examined in the same neurons, antagonizing effects of both drugs on tilt-induced firing were obtained in 28.6% and 40.0% of alpha and beta type neurons, respectively. These results suggest that both acetylcholine and glutamate act as neurotransmitters in the transmission of otolith information to most MVN neurons.

Animals↗

PubMed1999

Elevated serum haptoglobin in pigs infected with porcine reproductive and respiratory syndrome virus.

We examined the two acute phase proteins, alpha (alpha)-1 acid glycoprotein (AGP) and haptoglobin (HP), in serum of pigs following experimental porcine reproductive and respiratory syndrome (PRRS) virus infection. Increased levels of serum HP, but not AGP, were observed from 7 to 21 days post-inoculation in the infected pigs. Furthermore, serum IL-6 increased in the infected pigs, but TNF-alpha did not. The increase of serum IL-6 in pigs following PRRS virus infection may induce production of HP. Also, in the field investigation, serum HP in pigs was dramatically increased after exposure to the PRRS virus.

Acute-Phase Proteins↗

PubMed1999

Structural organization of the 5'-end and chromosomal assignment of human placental leucine aminopeptidase/insulin-regulated membrane aminopeptidase gene.

Placental leucine aminopeptidase (P-LAP) which is identical with cystine aminopeptidase as oxytocinase was found to be a homologue of rat insulin-regulated membrane aminopeptidase (IRAP) by cDNA cloning. In this study, we confirmed 5'-end cDNA sequence of P-LAP and isolated genomic clones containing the upstream region of human P-LAP gene. The transcription initiation sites determined by primer extension located 478 and 480 bp upstream of the initiation methionine codon, 38 bp downstream of TATA box-like motif. The 5'-flanking region of human P-LAP gene contained DNA-binding motifs for several ubiquitous transcription factors such as SP1 and AP2. Chromosomal localization by fluorescence in situ hybridization showed that the gene was assigned to 5q14.2-q15 of the human chromosome. This study establishes the genetic basis for P-LAP gene research, thereby leading to better understanding of the molecular mechanism underlying the P-LAP gene.

Aminopeptidases↗

PubMed1999

CD45 negatively regulates lyn activity by dephosphorylating both positive and negative regulatory tyrosine residues in immature B cells.

Using CD45-deficient clones from the immature B cell line, WEHI-231, we previously demonstrated that CD45 selectively dephosphorylates the Src-family protein tyrosine kinase Lyn and inhibits its kinase activity. To further define the mechanisms of CD45 action on Lyn, we metabolically labeled Lyn from CD45-positive and -negative WEHI-231 cells and analyzed cyanogen bromide fragments by SDS-PAGE analysis. Phosphoamino acid analysis confirmed that Lyn is tyrosine phosphorylated with little serine or threonine phosphorylation. In CD45-negative cells, two bands at 8.2 and 4.1 kDa were phosphorylated in the absence of B cell Ag receptor (BCR) ligation. The 8.2-kDa band corresponded to a fragment containing the positive regulatory site (Tyr397), as assessed by its size and its phosphorylation in an in vitro kinase assay. The 4.1-kDa band was phosphorylated by COOH-terminal Src kinase, suggesting that it contains the COOH-terminal negative regulatory site (Tyr508). CD45 was also shown to dephosphorylate autophosphorylated Lyn in vitro. Thus, CD45 dephosphorylates not only the negative but also the positive regulatory tyrosine residues of Lyn. Furthermore, coimmunoprecipitations using anti-Igalpha Ab demonstrated that Lyn associated with the resting BCR was constitutively phosphorylated and activated in CD45-negative cells. In the parental cells, both regulatory sites were phosphorylated on BCR ligation. Taken collectively, these results suggest that CD45 keeps both BCR-associated and total cytoplasmic pools of Lyn in an inactive state, and a mechanism by which Lyn is activated by relative reduction of CD45 effect may be operative on BCR ligation.

Animals↗

PubMed1999

Identification and characterization of a haploid germ cell-specific nuclear protein kinase (Haspin) in spermatid nuclei and its effects on somatic cells.

We have cloned the entire coding region of a mouse germ cell-specific cDNA encoding a unique protein kinase whose catalytic domain contains only three consensus subdomains (I-III) instead of the normal 12. The protein possesses intrinsic Ser/Thr kinase activity and is exclusively expressed in haploid germ cells, localizing only in their nuclei, and was thus named Haspin (for haploid germ cell-specific nuclear protein kinase). Western blot analysis showed that specific antibodies recognized a protein of Mr 83,000 in the testis. Ectopically expressed Haspin was detected exclusively in the nuclei of cultured somatic cells. Even in the absence of kinase activity, however, Haspin caused cell cycle arrest at G1, resulting in growth arrest of the transfected somatic cells. In a DNA binding experiment, approximately one-half of wild-type Haspin was able to bind to a DNA-cellulose column, whereas the other half was not. In contrast, all of the deletion mutant Haspin that lacked autophosphorylation bound to the DNA column. Thus, the DNA-binding activity of Haspin may, in some way, be associated with its kinase activity. These observations suggest that Haspin has some critical roles in cell cycle cessation and differentiation of haploid germ cells.

Amino Acid Sequence↗

PubMed1999

Attenuation of interleukin 2 signal in the spleen cells of complex ganglioside-lacking mice.

T cell development and function in complex ganglioside-lacking (GM2/GD2 synthase gene-disrupted) mice were analyzed. GM1, asialo-GM1, and GD1b were representative gangliosides expressed on T cells of the wild type mice and completely deleted on those of the mutant mice. The sizes and cell numbers of the mutant mice spleen and thymus were significantly reduced. Spleen cells from the mutant mice showed clearly reduced proliferation compared with the wild type when stimulated by interleukin 2 (IL-2) but not when treated with concanavalin A or anti-CD3 cross-linking. Expression levels of IL-2 receptor alpha, beta, and gamma were almost equivalent, and up-regulation of alpha chain after T cell activation was also similar between the mutant and wild type mice. Activation of JAK1, JAK3, and SAT5 after IL-2 treatment was reduced, and c-fos expression was delayed and reduced in the mutant spleen cells, suggesting that the IL-2 signal was attenuated in the mutant mice probably due to the modulation of IL-2 receptors by the lack of complex gangliosides.

Animals↗

PubMed1999

cDNA cloning and mapping of a novel subtype of glutamine:fructose-6-phosphate amidotransferase (GFAT2) in human and mouse.

We subcloned human and mouse full-length cDNAs of a novel subtype of glutamine:fructose-6-phosphate amidotransferase (GFAT), which was designated GFAT2 (the previously reported GFAT was named GFAT1). Both the human and the mouse GFAT2 proteins deduced from their open reading frame sequences are composed of 682 amino acids of approximately 77.0 kDa. At the amino acid level, homologies between the human GFAT1 and GFAT2, between the mouse GFAT1 and GFAT2, and between the human GFAT2 and the mouse GFAT2 were 75.6, 74.7, and 97. 2%, respectively. Northern blot analysis using probe specific to human GFAT1 or GFAT2 showed that major transcripts were approximately 3.0 kb in both the human GFAT subtypes. The analysis also revealed different tissue distribution between GFAT1 and GFAT2: GFAT1 was more highly expressed in the placenta, pancreas, and testis than GFAT2; GFAT2 was expressed throughout the central nervous system, especially in the spinal cord, but GFAT1 expression was weak. The locus was mapped to human chromosome 5q and mouse chromosome 11, where a synteny between the two species has been known. GFAT2 can provide insights into understanding the roles of the hexosamine pathway in various tissues, particularly with the development of glucose toxicity and diabetes complications.

Amino Acid Sequence↗

PubMed1999

Dopamine D4-like binding sites labeled by [3H]nemonapride include substantial serotonin 5-HT2A receptors in primate cerebral cortex.

Dopamine D4-like binding sites are abundant in human cerebral cortex as detected by [3H]nemonapride. The extremely low density of D4 mRNA in human cerebral cortex is inconsistent with the high amount of D4-like binding sites. To investigate the nature of the D4-like receptors, [3H]nemonapride binding sites in the nonhuman primate cerebral cortex were characterized. Although [3H]nemonapride binding sites were D4-like, displaceable by clozapine but not raclopride, [3H]nemonapride binding was not displaced by selective D4 antagonists but was displaced by the selective 5-HT2A antagonist MDL100907. Using [3H]ketanserin as a 5-HT2A ligand, nemonapride showed high affinity for monkey (Ki = 10.4 nM) and cloned human (Ki = 9.4 nM) 5-HT2A receptors, while its affinity for rat receptors was lower (Ki = 140 nM). The present study demonstrates that cerebral cortical D4-like binding sites labeled by [3H]nemonapride in nonhuman primates consist of a very small portion of D4, but a substantial portion of 5-HT2A receptors. The unexpectedly high affinity of nemonapride for primate 5-HT2A receptor suggests reconsidering previous data from other studies using [3H]nemonapride, particularly those on D4-like receptors.

Animals↗

PubMed1999

Hepatocyte growth factor is a major mediator in heparin-induced angiogenesis.

Heparin has a potent angiogenic effect in experimental animals and patients with ischemic diseases; however, the precise mechanism behind this angiogenesis remains to be clarified. The aim of this study was to determine whether the administration of heparin affects the levels of heparin-binding angiogenic factors in human plasma, and to identify the molecule responsible for heparin-induced angiogenesis. Plasma levels of hepatocyte growth factor (HGF), basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) were measured before and after administration of 100 U, 3,000 U or 10,000 U of heparin in patients with coronary artery disease. Administration of 3,000 U or 10,000 U of heparin caused significant increases in plasma HGF (40- and 54-fold, respectively), in absence of obvious increases in bFGF and VEGF levels. Furthermore, compared with the serum collected before heparin administration, the serum collected after heparin administration had more prominent growth-promoting and vascular tube-inducing properties on endothelial cells, and these increased activities were completely inhibited by neutralization of HGF, whereas neutralization of bFGF and VEGF had no effect. These findings suggest that HGF plays a significant role in heparin-induced angiogenesis.

Aged↗

PubMed1999

Adenovirus-mediated overexpression of C-terminal Src kinase (Csk) in type I astrocytes interferes with cell spreading and attachment to fibronectin. Correlation with tyrosine phosphorylations of paxillin and FAK.

To examine the role of C-terminal Src kinase (Csk), a negative regulatory kinase of Src family tyrosine kinases, in the cell adhesion mechanism of the nervous system, wild-type Csk (Csk), and a kinase-deficient mutant of Csk (Csk-DeltaK) were overexpressed in primary cultured type I astrocytes by infecting them with the recombinant adenovirus. Overexpression of Csk repressed the in vitro kinase activity of Src to as little as 10% that of control cells and interfered with cell spreading and cell attachment to fibronectin. Focal adhesion assembly and the organization of actin stress fibers were also disrupted in cells overexpressing Csk. On the other hand, overexpression of Csk-DeltaK induced tyrosine phosphorylation of cellular proteins, including the paxillin and focal adhesion kinase (FAK) and enhanced to some extent the cytoskeletal organization and the rate of cell spreading on fibronectin, indicating that Src or its relatives was functionally activated in the cells. Paxillin was also tyrosine-phosphorylated in Csk-overexpressing cells, indicating that it can serve as a substrate of Csk. The phosphorylation state of paxillin in cells overexpressing Csk was indistinguishable from that in cells expressing Csk-DeltaK in that both phosphorylated paxillins bound equally to SH2 domain of Csk and were co-immunoprecipitated with Csk. In contrast, tyrosine phosphorylation of FAK and its in vitro autophosphorylation activity were increased only in cells expressing Csk-DeltaK. In Csk-expressing cells, the kinase activity of FAK was substantially decreased to 20-30% that of control cells, even though the expression level of FAK was rather increased. These findings suggest that Csk regulates Src family tyrosine kinases that play essential roles in the regulation of cell adhesion via a FAK-dependent mechanism and that the tyrosine phosphorylation of paxillin alone may not be sufficient for the regulation of the cell adhesion mechanism in astrocytes.

Adenoviridae↗

PubMed1999

Heparin-binding EGF-like growth factor is expressed by mesangial cells and is involved in mesangial proliferation in glomerulonephritis.

Heparin-binding epidermal growth factor-like growth factor (HB-EGF), a new member of the EGF family, is mitogenic for several types of cells, through binding to cell surface heparan sulphate proteoglycans. This study has attempted to delineate HB-EGF expression by mesangial cells and to identify its role in experimental and human glomerulonephritis. Rat mesangial cells, cultured in the presence of phorbol acetate, hydrogen peroxide, interleukin-1beta, and tumour necrosis factor-alpha, expressed HB-EGF mRNA. Recombinant HB-EGF stimulated rat mesangial cells to proliferate and to express types I and III collagen. In the rat anti-Thy-1.1 nephritis, glomerular HB-EGF mRNA was up-regulated and peaked at days 5-7; its expression at the protein level in the glomerulus was prominent at days 5-10. By immunofluorescence, HB-EGF was positive predominantly in the mesangial area of renal tissues from 23 of 45 patients with various types of human glomerulonephritis, showing a significant correlation with the grade of mesangial proliferation; there was no staining in tissues from patients with minimal change nephrotic syndrome and normal kidney tissues. These data provide the evidence that HB-EGF is synthesized and expressed by mesangial cells and stimulates mesangial cell proliferation and collagen synthesis in vitro. HB-EGF is a potential mediator in mesangial cell proliferation and matrix expansion in experimental and human glomerulonephritis.

Animals↗

PubMed1999

Forearm heating band used in apheresis therapy that employs a positive-temperature coefficient polymer heater.

For standard apheresis therapy, blood is withdrawn from the ante-cubital vein of one arm and processed blood is returned to a vein of the opposite arm. For low-density lipoprotein apheresis or for the treatment of patients with Guillain-Barré syndrome, a sufficient quantity of blood is readily obtained by this method. In some patients with collagen diseases, however, it may be difficult to secure a reliable vein due to vasospasm or it may not be possible to obtain sufficient blood flow. We constructed a forearm heating band by employing a positive-temperature coefficient heater and evaluated the device to determine whether the application of heat to the forearm is effective in securing a sufficient quantity of blood in those patients with collagen disease (eight with systemic lupus erythematosus and one with multicentric Castleman's disease). Both forearms were heated by using this heating band, in addition to systemic warming with an electric blanket, starting 30 minutes before apheresis. The body surface temperature was sequentially monitored by employing a needle-type thermometer. The surface temperature of the heated area became constant at 37.6+/-0.3 degrees C within approximately 20 minutes (34.7+/-1.3 degrees C at the control site, P<0.001). It was found that this heating band makes it possible to obtain the quantity of blood that is necessary for apheresis and reduce the time required for the treatment. No adverse effects attributable to heating of the forearm were recognized.

Blood Component Removal↗

PubMed1999

Reduced C-terminal Src kinase (Csk) activities in hepatocellular carcinoma.

The proto-oncogene product pp60(c-src) is the cellular homologue of the Rous sarcoma transforming gene, and it is a non-receptor-linked and membrane-associated tyrosine kinase. There is a close correlation between elevated pp60(c-src) activity and cell transformation. We have recently reported that pp60(c-src) was activated in hepatocellular carcinoma (HCC) of human and Long-Evans cinnamon (LEC) rats. However, the mechanisms involved in this process remain unknown. C-terminal Src kinase (Csk) is a novel cytoplasmic protein tyrosine kinase that inactivates the members of the Src family protein tyrosine kinase in vitro. We investigated the role of Csk in hepatocarcinogenesis by analyzing the location, amount of Csk, and its kinase activity levels in nontumorous cirrhotic and tumorous sections of HCC of patients and an animal model of LEC rats. Csk tyrosine kinase activity was significantly reduced in tumorous tissues compared with nontumorous sections of patients as well as LEC rats. A single immunoreactive band at 50 kd was detected with Csk antibody in normal liver (NL), chronic hepatitis (CH), and nontumorous cirrhotic (NTC) segments of HCC of patients and LEC rats. In human tumorous tissues, Western blot revealed a 53-kd immunoreactive band, which was slightly larger than the usual 50-kd band of Csk. These results suggest that the reduced activity of tyrosine kinase of Csk may play an important role in the malignant transformation of hepatocytes in human and LEC rat, and the appearance of 53-kd Csk-related protein may be closely involved in the progression of cirrhosis to HCC in humans, and that 50-kd Csk may act as an antioncogene through the negative regulation of pp60(c-src) in the development of human HCC.

Aged↗

PubMed1999

Laparoscopic adrenalectomy for solitary metachronous adrenal metastasis from lung cancer: report of a case.

We report herein the case of a 69-year-old man who underwent laparoscopic adrenalectomy for a solitary adrenal metastasis 10 months after a left lower lobectomy for T2N1M0 lung cancer. A 30 x 20 mm tumor was found in the left adrenal gland, and dissected using an ultrasonically activated scalpel. Histological examination revealed metastatic squamous cell carcinoma. The patient recovered uneventfully and his condition is now stable 18 months after the second operation, with no evidence of local recurrence or metastatic disease. Although laparoscopic resection for malignant adrenal tumors is still controversial, we consider that laparoscopic adrenalectomy may be an optional treatment for metastatic adrenal tumors, provided the tumor is solitary, small in size, and well-localized. To our knowledge, only 14 cases of laparoscopic adrenalectomy for malignant tumors have been reported to date; however, this is the first case of successful laparoscopic adrenalectomy for a metastasis from lung cancer.

Adrenal Gland Neoplasms↗

PubMed1999

Mild hypothermia for temporary brain ischemia during cardiopulmonary support systems: report of three cases.

Recovery without residual neurological damage after cardiac arrest with temporary cerebral ischemia is rare. Therefore, it is most important that every effort is made to prevent brain damage occurring immediately after successful cardiopulmonary resuscitation. We report herein the cases of three patients who suffered either cardiogenic or hypovolemic shock and were resuscitated by a cardiopulmonary support system followed by mild hypothermia. All three patients recovered completely without any neurologic damage. The outcomes of these three patients demonstrated that mild hypothermia may be important for cerebral preservation after cardiopulmonary resuscitation.

Aged↗

PubMed1999

The efficiency of absorbable clips in minimally invasive surgery.

This study was conducted to evaluate the efficiency of polymeric clips in minimally invasive surgery. Absorbable polymeric clips were applied to the cystic duct, appendicular stump, and blood vessels in 35 patients undergoing laparoscopic or thoracoscopic procedures. All patients were reviewed 3 months after their operations, and no complications related to the clips were observed. These findings indicate that absorbable clips have more advantages than metallic clips. We believe that as this clip is easy to operate with safety, it should be used in the majority of minimally invasive surgical procedures.

Hemostasis, Surgical↗

PubMed1999

Preventive influence of inhaled nitric oxide on lung ischemia-reperfusion injury.

In lung transplantation, lung ischemia-reperfusion injury is a serious problem when using long-term preserved grafts. A warm ischemic lung model was prepared using rabbits. NO was administered by inhalation (group I, n = 9). The control group was not administered NO (group II, n = 8). Severe ischemia-reperfusion injury occurred as evidenced by hypoxia and lung edema. PaO2 at 120 min after reperfusion was 325 +/- 41 mmHg in group I and 40 +/- 6 mmHg in group II. The pulmonary blood flow of the left lung at 120 min after reperfusion was 51% +/- 3% in group I and 20% +/- 5% in group II. The wet-to-dry weight ratio was 5.5 +/- 0.2 for the right lungs, 5.8 +/- 0.8 for the left lung in group I, and 6.1 +/- 0.4 for the left lung in group II. Histopathologically, marked hemorrhage, hyaline membrane formation, and leukocyte infiltration were observed in group II but not in group I. These data suggested that inhaled NO reduced warm ischemia-reperfusion injury in the lung, and also contributed to a better preserved lung function.

Administration, Inhalation↗

PubMed1999

Transabdominal inguinal hernioplasty combined with abdominal aortic aneurysm repair.

The number of patients being encountered with abdominal aortic aneurysm (AAA) and inguinal hernia is increasing. We describe herein a technique of performing a concomitant one-stage operation for both disorder. After conventional transperitoneal AAA repair, transabdominal preperitoneal hernia repair is carried out through the same incision using a prosthesis made from the same material as the graft used for AAA. The maneuver is similar to that of laparoscopic hernioplasty. We employed this technique in the treatment of four patients, none of whom developed any complications such as infection or recurrence of the inguinal hernia. Thus, we conclude that this one-stage operation for AAA and inguinal hernia may bring physical and economic benefits to patients who have both diseases concomitantly.

Aged↗