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Biomedical subjects

M Hirata

Publications and source records attributed to M Hirata.

At least 199 records · Page 11Linked to original sources
PubMed1997

Distinct specificity in the binding of inositol phosphates by pleckstrin homology domains of pleckstrin, RAC-protein kinase, diacylglycerol kinase and a new 130 kDa protein.

The pleckstrin homology domains (PH domains) derived from four different proteins, the N-terminal part of pleckstrin, RAC-protein kinase, diacylglycerol kinase and the 130 kDa protein originally cloned as an inositol 1,4,5-trisphosphate binding protein, were analysed for binding of inositol phosphates and derivatives of inositol lipids. The PH domain from pleckstrin bound inositol phosphates according to a number of phosphates on the inositol ring, i.e. more phosphate groups, stronger the binding, but a very limited specificity due to the 2-phosphate was also observed. On the other hand, the PH domains from RAC-protein kinase and diacylglycerol kinase specifically bound inositol 1,3,4,5,6-pentakisphosphate and inositol 1,4,5,6-tetrakisphosphate most strongly. The PH domain from the 130 kDa protein, however, had a preference for inositol 1,4,5-trisphosphate and 1,4,5,6-tetrakisphosphate. Comparison was also made between binding of inositol 1,4,5-trisphosphate, inositol 1,3,4,5-tetrakisphosphate and soluble derivatives of their corresponding phospholipids. The PH domains examined, except that from pleckstrin, showed a 8- to 42-times higher affinity for inositol 1,4,5-trisphosphate than that for corresponding phosphoinositide derivative. However, all PH domains had similar affinity for inositol 1,3,4,5-tetrakisphosphate compared to the corresponding lipid derivative. The present study supports our previous proposal that inositol phosphates and/or inositol lipids could be important ligands for the PH domain, and therefore inositol phosphates/inositol lipids may have the considerable versatility in the control of diverse cellular function. Which of these potential ligands are physiologically relevant would depend on the binding affinities and their cellular abundance.

Amino Acid Sequence↗
PubMed1997

Inositol 1,4,5-trisphosphate receptor subtypes differentially recognize regioisomers of D-myo-inositol 1,4,5-trisphosphate.

The Ins(1,4,5)P3 regioisomers, Ins(1,4,6)P3 and Ins(1,3,6)P3, which can mimic the 1,4,5-arrangement on the inositol ring of Ins(1,4,5)P3, were examined for Ca2+ release by using four types of saponin-permeabilized cell possessing various abundances of receptor subtypes, with special reference to the relation of potency to receptor subtype. Ins(1,4,6)P3 and Ins(1,3,6)P3 were weak agonists in rat basophilic leukaemic cells (RBL cells), which possess predominantly subtype II receptors, with respective potencies of 1/200 and less than 1/500 that of Ins(1,4,5)P3 [the EC50 values were 0.2, 45 and more than 100 microM for Ins(1,4,5)P3, Ins(1,4,6)P3 and Ins(1,3,6)P3 respectively]. Similar rank order potencies were also evaluated for the displacement of [3H]Ins(1,4,5)P3 bound to RBL cell membranes by these regioisomers. However, they caused Ca2+ release from GH3 rat pituitary cells possessing predominantly subtype I receptors more potently; Ins(1,4,6)P3 and Ins(1,3,6)P3 evoked release at respective concentrations of only one-third and one-twentieth that of Ins(1,4,5)P3 (the EC50 values were 0.4, 1.2 and 8 microM for Ins(1,4,5)P3, Ins(1,4,6)P3 and Ins(1,3,6)P3 respectively). In COS-1 African green-monkey kidney cells, with the relative abundances of 37% of the subtype II and of 62% of the subtype III receptor, potencies of 1/40 and approx. 1/200 for Ins(1, 4,6)P3 and Ins(1,3,6)P3 respectively were exhibited relative to Ins(1,4,5)P3 (the EC50 values were 0.4, 15 and approx. 80 microM for Ins(1,4,5)P3, Ins(1,4,6)P3 and Ins(1,3,6)P3 respectively). In HL-60 human leukaemic cells, in spite of the dominant presence of subtype I receptors (71%), similar respective potencies to those seen with COS-1 cells were exhibited (the EC50 values were 0.3, 15 and approx. 100 microM for Ins(1,4,5)P3, Ins(1,4,6)P3 and Ins(1,3,6)P3 respectively). These results indicate that these regioisomers are the first ligands that distinguish between receptor subtypes; the present observations are of significance for the future design of molecules with enhanced selectivity.

Animals↗
PubMed1997

Expression of messenger RNA for the prostaglandin D receptor in the leptomeninges of the mouse brain.

The localization of prostaglandin D receptor in the mouse brain was examined by in situ hybridization histochemistry. The autoradiography showed significant hybridization signals of mRNA for prostaglandin D receptor in the leptomeninges covering the surface of the brain, but not in neurons or glia in the brain parenchyma. This finding was confirmed by Northern blot analysis using mRNA prepared from either the whole brain with the leptomeninges, brain parenchyma without the leptomeninges or the leptomeninges alone. A weak signal corresponding to the major 3.5-kbp transcript was detected in the whole brain. This band was significantly enriched in the leptomeninges, but was not detected in the brain parenchyma. These results suggest that prostaglandin D receptor is most highly, if not exclusively, expressed in the leptomeninges of the mouse brain.

Animals↗
PubMed1997

A simple method to confirm patency of the graft bile duct during living-related partial liver transplantation.

A bile duct stricture caused by an inadvertent ligation or suture during donor operation is rare, but not a negligible complication after living-related liver transplantation (LRLT). We present here a simple technique to prevent this kind of complication. Before bilioenteric anastomosis, a rod-shaped surgical probe was introduced into the bile ducts of the graft to examine their patency. The position of the surgical probe and the liver segment in which the probe proceeded was checked using ultrasonography. Using this technique in all of our 60 cases of LRLT, we have had no experience of this bile duct complication. We recommend this technique to be adopted in LRLT and split-liver transplantation to diminish the risk of biliary complications.

Adult↗
PubMed1997

Altered pain perception and inflammatory response in mice lacking prostacyclin receptor.

Prostanoids are a group of bioactive lipids working as local mediators and include D, E, F and I types of prostaglandins (PGs) and thromboxanes. Prostacyclin (PGI2) acts on platelets and blood vessels to inhibit platelet aggregation and to cause vasodilatation, and is thought to be important for vascular homeostasis. Aspirin-like drugs, including indomethacin, which inhibit prostanoid biosynthesis, suppress fever, inflammatory swelling and pain, and interfere with female reproduction, suggesting that prostanoids are involved in these processes, although it is not clear which prostanoid is the endogenous mediator of a particular process. Prostanoids act on seven-transmembrane-domain receptors which are selective for each type. Here we disrupt the gene for the prostacyclin receptor in mice by using homologous recombination. The receptor-deficient mice are viable, reproductive and normotensive. However, their susceptibility to thrombosis is increased, and their inflammatory and pain responses are reduced to the levels observed in indomethacin-treated wild-type mice. Our results establish that prostacyclin is an antithrombotic agent in vivo and provide evidence for its role as a mediator of inflammation and pain.

Animals↗
PubMed1997

Failure of parturition in mice lacking the prostaglandin F receptor.

Mice lacking the gene encoding the receptor for prostaglandin F2alpha (FP) developed normally but were unable to deliver normal fetuses at term. Although these FP-deficient mice showed no abnormality in the estrous cycle, ovulation, fertilization, or implantation, they did not respond to exogenous oxytocin because of the lack of induction of oxytocin receptor (a proposed triggering event in parturition), and they did not show the normal decline of serum progesterone concentrations that precedes parturition. Ovariectomy at day 19 of pregnancy restored induction of the oxytocin receptor and permitted successful delivery in the FP-deficient mice. These results indicate that parturition is initiated when prostaglandin F2alpha interacts with FP in ovarian luteal cells of the pregnant mice to induce luteolysis.

Animals↗
PubMed1997

Structure and function of a new STAT-induced STAT inhibitor.

The signalling pathway that comprises JAK kinases and STAT proteins (for signal transducer and activator of transcription) is important for relaying signals from various cytokines outside the cell to the inside. The feedback mechanism responsible for switching off the cytokine signal has not been elucidated. We now report the cloning and characterization of an inhibitor of STAT activation which we name SSI-1 (for STAT-induced STAT inhibitor-1). We found that SSI-1 messenger RNA was induced by the cytokines interleukins 4 and 6 (IL-4, IL-6), leukaemia-inhibitory factor (LIF), and granulocyte colony-stimulating factor (G-CSF). Stimulation by IL-6 or LIF of murine myeloid leukaemia cells (M1 cells) induced SSI-1 mRNA expression which was blocked by transfection of a dominant-negative mutant of Stat3, indicating that the SSI-1 gene is a target of Stat3. Forced overexpression of SSI-1 complementary DNA interfered with IL-6- and LIF-mediated apoptosis and macrophage differentiation of M1 cells, as well as IL-6 induced tyrosine-phosphorylation of a receptor glycoprotein component, gp130, and of Stat3. When SSI-1 is overexpressed in COS7 cells, it can associate with the kinases Jak2 and Tyk2. These findings indicate that SSI-1 is responsible for negative-feedback regulation of the JAK-STAT pathway induced by cytokine stimulation.

Amino Acid Sequence↗
PubMed1997

Identification of domains conferring ligand binding specificity to the prostanoid receptor. Studies on chimeric prostacyclin/prostaglandin D receptors.

To identify domains conferring ligand binding specificity to prostanoid receptors, we constructed a series of chimeric receptors by successively replacing the regions from the carboxyl-terminal tail of mouse prostacyclin (prostaglandin I (PGI)) receptor (mIP) with the corresponding regions of the mouse PGD receptor (mDP). The mIP receptor expressed in COS 7 cells bound [3H]iloprost, a PGI2 analog, and [3H]PGE1 with Kd values of 13 and 27 nM, respectively. This receptor did not bind [3H]PGD2, [3H]PGE2, and [3H]PGF2alpha. The mDP receptor bound only [3H]PGD2 with a Kd value of 43 nM. The chimeric IPN-VII/DPC receptor with replacement of the carboxyl tail of the mIP receptor with that of the mDP receptor showed 12-16-fold higher affinities for [3H]iloprost and [3H]PGE1 than the mIP receptor. The region extending from the sixth transmembrane domain to the carboxyl terminus of the mIP receptor was next replaced with the corresponding region of the mDP receptor. This chimeric IPN-V/DPVI-C receptor acquired the ability to bind [3H]PGD2 and [3H]PGE2 without decreasing the affinities of the mIP receptor to [3H]iloprost and [3H]PGE1. These binding characteristics did not change when the fourth and fifth transmembrane domains of the mIP receptor were further replaced with the corresponding regions of the mDP receptor. However, when the first extracellular to second intracellular loop of the mIP receptor containing the third transmembrane domain was further replaced with those of the mDP receptor, the affinities for [3H]PGE1, [3H]PGE2, and [3H]iloprost were markedly decreased, whereas that for [3H]PGD2 was increased by about 2-fold. [3H]PGF2alpha showed no affinity for the mIP, mDP, and all the chimeric receptors. These results suggest that the sixth to seventh transmembrane domain of the mIP receptor confers the specificity of this receptor to bind selectively to PGE1 and not to PGE2 and that the third transmembrane domain of the mDP receptor confers the selective binding of PGD2 to this receptor.

Animals↗
PubMed1997

Lineage- and differentiation stage-specific expression of LSM-1 (LPAP), a possible substrate for CD45, in human hematopoietic cells.

CD45, a transmembrane tyrosine phosphatase, is found on almost all nucleated hematopoietic cells and plays a crucial role in lymphocyte activation and differentiation. We recently achieved isolation of the human LSM-1 (hLSM-1) gene, whose product is a possible substrate for CD45, and we raised antibodies against the hLSM-1 protein. hLSM-1 expression in hematopoietic cells was examined with Northern and Western blot, fluorescence-activated cell sorter, and immunocytochemical analyses. It was found that in the lymphoid lineage, T and B lymphocytes as well as NK cells expressed LSM-1, whereas terminally differentiated plasma cells did not. As for the myeloid lineage, immature myeloid cells expressed LSM-1, whereas terminally differentiated granulocytes and monocytes did not. In the erythroid lineage, normal erythroblasts expressed very low levels of LSM-1, while erythroid cell lines (K562 and HEL) did not. Megakaryocytes did not express LSM-1. Both CD34+/CD33- and CD34+/CD33+ hematopoietic progenitor cells weakly expressed LSM-1. These results showed that LSM-1 is expressed in a lineage- and differentiation stage-specific fashion.

Blotting, Western↗
PubMed1997

Effects of electrochemotherapy on CaSki cells derived from a cervical squamous cell carcinoma.

Electrochemotherapy is a new approach to the treatment of tumors that takes advantage of the permeabilization of the cell membranes by electric pulses to facilitate the intracellular delivery of chemotherapeutic drugs into cells. Using the female genital squamous cell carcinoma cell line, CaSki, the antitumor effectiveness of electrochemotherapy was tested. In vitro studies showed that the cytotoxicity of some anticancer drugs, especially bleomycin, can be greatly enhanced by exposing cells to noncytotoxic electric pulses. This enhancement was significantly greater when the electric treatment was given after exposure to the drug than when applied preexposure. Treatment of nude mice bearing subcutaneous transplanted tumors with noneffective intraperitoneal doses of bleomycin followed by local delivery of electric pulses similar to those performed in vitro resulted in tumor reduction and complete disappearance after 12 days this electrochemotherapy. Histological changes in tumor tissue such as necrosis and degeneration were extensive even 6 hr after the electrochemotherapy. Thus the antitumor effects of bleomycin in mice can be considerably potentiated by local electric pulses, suggesting that electrochemotherapy with bleomycin may have promise for treatment of vulvar or ectocervical squamous cell carcinomas with early invasion.

Animals↗
PubMed1997

Immunosuppressant pharmacodynamics on lymphocytes from healthy subjects and patients with chronic renal failure, nephrosis, and psoriasis: possible implications for individual therapeutic efficacy.

BACKGROUND: In organ transplantation, patients with peripheral blood mononuclear cells (PBMCs) that exhibit resistance to cyclosporine (INN, ciclosporin) or glucocorticoids in vitro are refractory to therapy based on these drugs in vivo. However, detection or distribution of the resistant patients with immunologic disorders remains to be documented. METHODS: Drug sensitivity tests were performed with PBMCs from four subject groups: 69 healthy subjects, 100 patients with chronic renal failure, 38 patients with nephrosis, and 51 patients with psoriasis. The values for the concentration that produces 50% lymphocyte-mitosis inhibition (IC50) of the drugs on PBMC blastogenesis were estimated, and individual variations or group differences in the IC50 values were examined. RESULTS: The median cyclosporine IC50 values of the four subject groups were similar, but large individual deviations in the IC50 values were observed. Individual differences in prednisolone IC50 values were spread from 1 to 3500 ng/ml. When compared with healthy subjects, a significantly large number of the patients with chronic renal failure group exhibited low responses to prednisolone (p < 0.04). In contrast, no significant difference in the methylprednisolone IC50 was observed among the groups. Normal upper thresholds for IC50 values of these drugs were estimated from the mean + 2 standard deviations (SD) of the IC50 values of healthy PBMCs, and the patients with IC50 values above these levels were considered to be resistant. The incidence of resistant patients with nephrosis or psoriasis was similar to that of healthy subjects; however, the incidence of cyclosporine- or prednisolone-resistant subjects with chronic renal failure was significantly higher (p < 0.04). Significant correlations between PBMC sensitivity to cyclosporine in vitro and clinical efficacy of the drug in vivo were observed in renal transplant recipients and in patients with psoriasis. CONCLUSIONS: A large subset of patients with chronic renal failure showed PBMC resistance to cyclosporine and prednisolone. Hyperresistant patients have a high risk of being refractory to immunosuppressive therapy with one of these drugs. Alternative treatment should be considered according to the individual drug-sensitivity data.

Adult↗
PubMed1997

TP53 mutations in stage I gallbladder carcinoma with special attention to growth patterns.

32 stage I cases of gallbladder carcinoma (GC) were examined to evaluate TP53 mutations with special attention to growth patterns. Their growth patterns were classified into two types: polypoid (P-type) and flat (F-type). 16 cases of GC were classified as P-type and 16 as F-type. p53 immunohistochemistry was performed using a mouse monoclonal anti-p53 antibody. Mutations in exons 5-8 were examined by polymerase chain reaction single strand conformation polymorphism (PCR-SSCP) and direct sequencing. The incidence of p53 immunoreactivity was greater in the cases of F-type (11/16, 69%) than those in P-type (14/16, 25%) (P < 0.05). PCR-SSCP or direct sequencing revealed that TP53 mutations were detected in all cases positive for p53 protein. These results suggest that TP53 mutations may contribute to the carcinogenesis of the F-type GC, and than this pathway in the F-type may differ from that in the P-type GC.

Adenocarcinoma↗
PubMed1997

Ligand binding specificities of the eight types and subtypes of the mouse prostanoid receptors expressed in Chinese hamster ovary cells.

1. Eight types and subtypes of the mouse prostanoid receptor, the prostaglandin D (DP) receptor, the prostaglandin F (FP) receptor, the prostaglandin I (IP) receptor, the thromboxane A (TP) receptor and the EP1, EP2, EP3 and EP4 subtypes of the prostaglandin E receptor, were stably expressed in Chinese hamster ovary cells. Their ligand binding characteristics were examined with thirty two prostanoids and their analogues by determining the Ki values from the displacement curves of radioligand binding to the respective receptors. 2. The DP, IP and TP receptors showed high ligand binding specificity and only bound their own putative ligands with high affinity such as PGD2, BW245C and BW868C for DP, cicaprost, iloprost and isocabacyclin for IP, and S-145, I-BOP and GR 32191 for TP. 3. The FP receptor bound PGF2 alpha and fluprostenol with Ki values of 3-4 nM. In addition, PGD2, 17-phenyl-PGE2, STA2, I-BOP, PGE2 and M&B-28767 bound to this receptor with Ki values less than 100 nM. 4. The EP1 receptor bound 17-phenyl-PGE2, sulprostone and iloprost in addition to PGE2 and PGE1, with Ki values of 14-36 nM. 16,16-dimethyl-PGE2 and two putative EP1 antagonists, AH6809 and SC-19220, did not show any significant binding to this receptor. M&B-28767, a putative EP3 agonist, and misoprostol, a putative EP2/EP3 agonist, also bound to this receptor with Ki values of 120 nM. 5. The EP2 and EP4 receptors showed similar binding profiles. They bound 16,16-dimethyl PGE2 and 11-deoxy-PGE1 in addition to PGE2 and PGE1. The two receptors were discriminated by butaprost, AH-13205 and AH-6809 that bound to the EP2 receptor but not to the EP4 receptor, and by 1-OH-PGE1 that bound to the EP4 but not to the EP2 receptor. 6. The EP3 receptor showed the broadest binding profile, and bound sulprostone, M&B-28767, GR63799X, 11-deoxy-PGE1, 16,16-dimethyl-PGE2 and 17-phenyl-PGE2, in addition to PGE2 and PGE1, with Ki values of 0.6-3.7 nM. In addition, three IP ligands, iloprost, carbacyclin and isocarbacyclin, and one TP ligand, STA2, bound to this receptor with Ki values comparable to the Ki values of these compounds for the IP and TP receptors, respectively. 7. 8-Epi-PGF2 alpha showed only weak binding to the IP, TP, FP, EP2 and EP3 receptor at 10 microM concentration.

Animals↗
PubMed1997

Serum amylase level on admission in the diagnosis of blunt injury to the pancreas: its significance and limitations.

OBJECTIVE: The objective of this study was to elucidate the significance and limitations of serum amylase levels in the diagnosis of blunt injury to the pancreas. SUMMARY BACKGROUND DATA: Several recently published reports of analyses of patients with blunt abdominal trauma have indicated that determination of the serum amylase level on admission seemed to be of little value in the diagnosis of acute injury to the pancreas. Few previous reports have described clearly the significance and the limitations of the serum amylase level in diagnosing injury to the pancreas. METHODS: Retrospective analysis of 73 patients with blunt injury to the pancreas during 16-year period from February 1980 to January 1996 was performed. The factors analyzed in the current study included age, gender, time elapsed from injury to admission, hypotension on admission, type of injury to the pancreas, intra-abdominal- and intracranial-associated injuries, and death. RESULTS: The serum amylase level was found to be abnormal in all patients admitted more than 3 hours after trauma. Various comparisons between patients with elevated (n = 61, 83.6%) and nonelevated (n = 12, 16.4%) serum amylase levels showed the statistical significance solely of the time elapsed from injury to admission (7 +/- 1.5 hours vs. 1.3 +/- 0.2 hour, p < 0.001). The major factor that influences the serum amylase level on admission appeared to be the time elapsed from injury to admission. Determination of the serum amylase level is not diagnostic within 3 hours or fewer after trauma, irrespective of the type of injury. CONCLUSIONS: To avoid failure in the detection of pancreatic injury, the authors advocate determination of serum amylase levels more than 3 hours after trauma.

Abdominal Injuries↗
PubMed1997

Carnitine depletion during total parenteral nutrition despite oral L-carnitine supplementation.

Carnitine CAR) plays an important role in the beta-oxidation of fatty acids. Less attention. however, has been paid to CAR compared to other nutrients even in total parenteral nutrition (TPN). To examine CAR metabolism during TPN and the effect of simultaneous oral L-CAR supplementation on CAR levels, the blood CAR level was measured in a 3-year-old boy receiving long-term TPN because of short bowel syndrome. Both the total and acyl CAR in the serum were evaluated under various nutritional conditions including oral supplementation of L-CAR. Low CAR concentrations were observed especially when lipid containing TPN regimens were in place. Oral L-CAR supplementation was not sufficient to restore the low CAR levels in the present index patient even when the dose was increased to 120 mg/kg in accordance with the result of the L-CAR absorption test that revealed poor intestinal absorption of this nutrient. Moreover, a markedly low CAR level was measured during the onset of sepsis in the patient, and the blood CAR was depleted when lipid metabolism was activated by lipid loading or sepsis. To date, the late effects of CAR depletion on child growth have not been well examined. It is recommended that the blood CAR level be maintained at normal levels before any prominent manifestations of the deficiency have developed. The intravenous administration of CAR appears to be necessary to supply a sufficient amount of CAR for patients with severe malabsorption.

Administration, Oral↗