Search PubMed⌕ Search

Biomedical subjects

M Iwamoto

Publications and source records attributed to M Iwamoto.

At least 19 recordsLinked to original sources
PubMed1992

Effect of lipidic factors on membrane cholesterol topology--mode of binding of theta-toxin to cholesterol in liposomes.

We have previously suggested the existence of two distinct states for cholesterol in cell membranes as revealed by high- and low-affinity binding sites for theta-toxin of Clostridium perfringens. In liposomes, phospholipid and cholesterol compositions, but not membrane protein composition, have been shown to be major determinants for the topology of membrane cholesterol. The effects of lipidic factors on cholesterol topology were investigated in detail by analyzing toxin binding to large unilamellar liposomes composed of cholesterol and phospholipids (neutral phospholipids/phosphatidylglycerol = 82:18, mol/mol). The numbers of high- and low-affinity toxin-binding sites depend strictly on the cholesterol mole percentage in liposomes. High-affinity toxin-binding sites appear only in liposomes with high cholesterol contents. Liposomes whose cholesterol/phospholipid ratio is 0.4 or less have no high-affinity sites regardless of their phospholipid compositions, while low-affinity sites appear in liposomes with lower cholesterol contents. The threshold values for the cholesterol mole percentage above which high-affinity toxin-binding sites appear were examined. The values decrease in accordance with the increase in the mole fraction of 18-carbon hydrocarbon chains among the total 14-18 carbon-hydrocarbon chains of the liposomal phospholipids. Furthermore, both the partial replacement of phosphatidylcholine with phosphatidylethanolamine and the digestion of phospholipids with phospholipase C also affect the threshold values. Thus the cholesterol mole percentage, in combination with phospholipid chain length and other factors, determines the topology of membrane cholesterol providing distinctively different affinity sites for theta-toxin.

Bacterial Toxins↗
PubMed1992

Dopamine receptor antagonists increase markedly the quantity of retrograde transport of HRP in the rat masseteric motoneuron.

Horseradish peroxidase (HRP) was injected, bilaterally, into the rat masseter muscle, subsequent to an intramuscular or intraperitoneal injection of one of five dopamine antagonists (chlorpromazine and haloperidol as the D1 and D2 receptor antagonist, SCH 23390 as the specific D1 receptor antagonist, sulpiride and domperidone as the specific D2 receptor antagonist). Control rats received an injection of a corresponding vehicle solution. After a survival period of 16 h, the brainstem was cut into 60 microns cryosections and processed with the TMB technique. The amount of retrogradely transported HRP was quantitatively measured in terms of the amount of HRP reaction product present in the motoneuron by the method which we have developed using an image processing system combined with a light microscope and a TV camera. Chlorpromazine, haloperidol, SCH 23390 and sulpiride significantly raised the quantity of retrograde transport of HRP. On the contrary, domperidone which can not penetrate the blood-brain barrier showed no significant change in the amount of the retrograde transport. In addition, an intravenous injection of chlorpromazine (8 mg/kg) was found to increase the amplitude of monosynaptic masseteric reflex EMG activity evoked by stimulations of the mesencephalic trigeminal nucleus. These results suggest that a possible regulatory system involving the dopamine receptor in the uptake and retrograde transport of HRP from axon terminals to cell bodies of the masseteric motoneuron exists in higher order neurons which make synaptic contact with the motoneuron.

Animals↗
PubMed1992

The glycosaminoglycan of recombinant human soluble thrombomodulin affects antithrombotic activity in a rat model of tissue factor-induced disseminated intravascular coagulation.

Previous studies on recombinant human soluble thrombomodulin (rsTM) from Chinese hamster ovary cells revealed that rsTM was expressed as two proteins that differed functionally in vitro due to the presence (rsTM beta) or absence (rsTM alpha) of chondroitin-4-sulfate. The current study evaluates the in vivo behavior of rsTM in rats and in a rat model of tissue factor-induced disseminated intravascular coagulation (DIC). rsTM beta was more potent than rsTM alpha for prolongation of the activated partial thromboplastin time (APTT) and their in vivo half-lives determined by ELISA were 20 min for rsTM beta and 5.0 h for rsTM alpha. Injection of a tissue factor suspension (5 mg/kg) resulted in DIC as judged by decreased platelet counts and fibrinogen concentrations, prolonged APTT, and increased fibrin and fibrinogen degradation products (FDP) levels. A bolus injection of either rsTM (0.2 mg/kg) 1 min before induction of DIC essentially neutralized effects on platelets, fibrinogen, and FDP levels, and had only a moderate effect on APTT prolongation. The dose of anticoagulant to inhibit the drop in platelet counts by 50% (ED50) was 0.2 mg/kg rsTM alpha, 0.07 mg/kg rsTM beta, and 7 U/kg heparin. The effect of increasing concentrations of rsTM and heparin on bleeding times were compared in experiments involving incision of the rat tail. Doubling of the bleeding times occurred at 5 mg/kg rsTM alpha, 3 mg/kg rsTM beta or 90 U/kg heparin. These values represent a 25-fold increase over the ED50 for rsTM alpha, 43-fold for rsTM beta and 13-fold for heparin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Inhibitory effects of beta-alanine on the vagal efferent and afferent excitatory responses of the stomach to stimulation of vagal trunk in cats.

The effects of beta-alanine on the electrically evoked vagal efferent (hexamethonium-sensitive initial excitatory response) and afferent (hexamethonium-resistant delayed excitatory response) responses of the cat stomach were studied. beta-alanine (30 to 300 micrograms/kg, i.v.) dose-dependently inhibited both the efferent and afferent response. The IC50 values of beta-alanine on the efferent and afferent response were 296 +/- 65 micrograms/kg and 128 +/- 35 microgram/kg, respectively. Maximal inhibitory effects of beta-alanine (300 micrograms/kg, i.v.) appeared about 1 hr after the injection. Glycine and taurine (100 to 10,000 micrograms/kg) did not affect these responses. Treatment with hexamethonium (10 mg/kg, i.v.) prevented the efferent response, but augmented the afferent response. The treatment with hexamethonium abolished the inhibitory effect of beta-alanine on the afferent response. Both picrotoxin (100 and 500 micrograms/kg, i.v.) and bicuculline (2000 micrograms/kg, i.v.) antagonized the inhibitory effects of beta-alanine on the vagal efferent and afferent responses of the stomach. The present experiments clearly demonstrated that beta-alanine inhibited both the vagal efferent and afferent excitatory responses of stomach to electrical stimulation of vagal trunk in cats.

Animals↗
PubMed1992

Penetrating ocular fish-hook injuries. Surgical management and long-term visual outcome.

BACKGROUND: Ocular penetrating fish-hook injuries represent a rare yet potentially devastating ocular trauma. To date, only five cases have been reported in the medical literature. The authors present five new cases with long-term follow-up. METHODS: All individuals who presented to the Wilmer Ophthalmological Institute emergency room with ocular fish-hook injuries between 1974 and 1990 were identified, and ophthalmic follow-up evaluations were performed. RESULTS: Individuals were male, between the ages of 10 and 27, with follow-up evaluation of 2.0 to 15.5 years (mean, 6.7 years). The left eye was involved in 80% and in no instance had a single hook penetrated the lid and globe simultaneously. Initial visual acuity was uniformly poor (20/200 or worse). Using specialized surgical techniques, ultimate visual outcome was excellent in 80% of cases (4 of 5 with visual acuity of 20/30 or better). One eye was enucleated because of panendophthalmitis after delayed wound closure. Similar overall results are achieved when previous reports are included in the analysis (90% with visual acuity of 20/40 or better). CONCLUSIONS: These results suggest that penetrating ocular fish-hook injuries may have an excellent long-term prognosis if prompt, appropriate surgical intervention is accomplished.

Adolescent↗
PubMed1992

Expression and characterization of kinase-active v-erbB protein using a baculovirus vector system.

The v-erbB gene is an oncogene of the avian erythroblastosis virus encoding a protein that is a truncated version of the epidermal growth factor receptor. The v-erbB protein was expressed alone or as polyhedrin-erbB fusion proteins using the Bombyx mori nuclear polyhedrosis virus vector. The expression level of the fusion protein whose polyhedrin portion consisted of only 8 amino-terminal amino acids was more than ten times higher than that of the non-fusion protein. Studies with tunicamycin showed that the recombinant v-erbB proteins were glycosylated. The recombinant protein autophosphorylated tyrosine residues, and phosphorylated a synthetic tyrosine-containing peptide and lipocortin I. These observations indicate that functional v-erbB protein can be expressed in silkworm-derived cells, and furthermore, that this system can be used for large-scale production.

Amino Acid Sequence↗
PubMed1992

[Antigen detection in the murine models of systemic candidiasis].

We compared two latex agglutination tests for serum candidal antigen in murine models of systemic infection and gastrointestinal colonization. In the intravascular-infection model, mannan detection test was positive at 2 hours after inoculation, but Cand-Tec was less sensitive than mannan detection test in this model. In the gastrointestinal colonization model followed by systemic infection in neutropenic mice, the mannan antigen test became positive after 3 weeks of colonization with increased number of Candida of the stool, and Cand-Tec became positive after 5 weeks in neutropenic mice.

Animals↗
PubMed1992

A probable case of superfecundation.

Discordant twins are of obstetrical concern because of high morbidity and mortality of either the smaller or the larger twin, or both. The discordance becomes apparent usually in the second trimester. We report a case of discordant twins diagnosed in the 10th week of gestation, which was concluded to be a case of superfecundation. The discordancy was persistent up to the 35th week of gestation, when 2 baby boys were born by cesarean section because of preeclampsia. The postnatal courses of the babies were uneventful.

Adult↗
PubMed1992

Amino acids and peptides. XVI. Synthesis of N-terminal tetrapeptide analogs of fibrin alpha-chain and their inhibitory effects on fibrinogen/thrombin clotting.

N-Terminal tetrapeptide analogs of fibrin alpha-chain were synthesized by the solution method using a new active ester, the ester of the oxime of p-nitroacetophenone, and by the solid-phase method. Their inhibitory effects on fibrinogen/thrombin clotting were examined. Of the synthetic peptides, amide analogs of Gly-Pro-Arg-Pro exhibited a more potent inhibitory effect.

Amino Acid Sequence↗
PubMed1992

[Malignant transformation of benign mixed tumor of lacrimal gland to squamous cell carcinoma 19 years after initial surgery: report of a case].

A case of malignant transformation of benign mixed tumor (pleomorphic adenoma) arising from the right lacrimal gland is reported. A 63-year-old man was referred to our clinic because of visual disturbance and protrusion of the right eye in January, 1989. His past history revealed that he had had a benign mixed tumor of the right lacrimal gland resected 19 years ago. On CT scan, an iso-density lesion homogeneously enhanced with contrast medium was found in the right orbit. This tumor was partially cystic and invaded the cranial cavity. On T1 and T2 weighted MRI, the tumor appeared as an iso-intensity area. At surgery, the tumor was subtotally resected via the combined fronto-orbital approach on February 3, 1990. Histological diagnosis of the tumor was squamous cell carcinoma, and it was construed to be a malignant transformation of mixed tumor of the lacrimal gland. Postoperatively he was placed on a course of external radiation therapy (63 Gy in total) in combination with intra-carotid Cisplatin injection therapy. The first sign of the recurrence was seen as multiple metastatic lesions in both lungs about 4 months after the surgery. In December, 1990, protrusion of the left eye and disturbance of ocular movement became progressively worse. On CT scan, recurrent metastatic tumor was seen in the left orbit and paranasal sinuses. Although additional chemotherapy and irradiation brought about a short period of symptomatic relief he succumbed to pneumonia in April 18, 1990. Metastatic squamous cell carcinoma was confirmed in the lung at autopsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Carcinoma, Squamous Cell↗
PubMed1992

[Hematological values in fetal blood by cordocentesis].

Reference ranges for four hematological parameters--hemoglobin, hematocrit, white blood cell and platelet count--in each gestation were established from values for fetal blood samples obtained by cordocentesis from 72 pregnancies at 16-39 weeks gestation. These 72 fetuses turned out as normal or single malformations which should not affect fetal hematological values. Significant correlations were observed between hemoglobin, hematocrit and platelet counts and the number of weeks of gestation. No correlation was found between the white blood cell count and gestational age. Fetal anemia (hematocrit was below the lower limit of the 95% confidence interval) was found in 18 (7%) of all the fetuses that underwent cordocentesis, including nonimmune hydrops fetalis (8 cases), Rh isoimmunization (4 cases), twin-to-twin transfusion syndrome (3 cases), trisomy 18 (2 cases) and autoimmune thrombocytopenia (1 case). Of 26 hydropic fetuses, 8 (31%) were anemic. The prognosis of those fetuses depended on either the gestational age or the severity of the fetal anemia. Our results are useful in diagnosing fetal hematological disorders and to make decisions for fetal therapy.

Anemia↗
PubMed1992

[Laboratory and clinical studies on levofloxacin].

A newly developed broad-spectrum fluoroquinolone, levofloxacin (LVFX, DR-3355), was evaluated in vitro and in vivo in comparison with ciprofloxacin (CPFX), ofloxacin (OFLX) and norfloxacin (NFLX). The results were as follows. 1. Antimicrobial activity Minimal inhibitory concentrations (MICs) against 480 clinical isolates including 16 different species were determined using the microbroth dilution method. LVFX showed excellent antimicrobial activities against Gram-positive and -negative bacteria. The MIC values of LVFX for Gram-positive bacteria were superior to those of the other quinolones tested. The MIC values of LVFX for Gram-negative bacteria were comparable to those of CPFX and superior to those of OFLX and NFLX. 2. LVFX concentrations in serum and sputum LVFX was orally administered in a single dose of 200 mg to 2 patients with chronic lower respiratory tract infections, and its concentrations in serum and sputum were measured at intervals using bioassay. The peak concentrations of LVFX in serum were 1.52 and 1.24 micrograms/ml, and 84-95% of serum level were detected in sputum. From these data, it appeared that LVFX penetrate well into the lung. 3. Clinical efficacy and adverse reactions Fifteen patients with respiratory tract infections were treated with LVFX, and the overall efficacy rate was 78.6% (excellent in 3 cases, good in 8, fair in 3, poor in 0). As adverse reactions, anorexia was observed in 2 cases, diarrhea in 1 case and tremor of finger in 1 case. Although an elevation of total bilirubin in serum was observed in a case as an abnormal laboratory finding, it was mild, transient and improved rapidly after the completion of LVFX treatment.

Adult↗
PubMed1991

Effect of ticlopidine and other antithrombotics on the venous thrombosis induced by endothelial damage of jugular vein in rats.

A venous thrombosis model was produced by vessel wall damage generated by freezing a small segment of the rat jugular vein. The process of thrombus formation was investigated by electron microscopic study. Ultrastructural studies demonstrated that the initiation of thrombus formation could be deendothelialization caused by freezing of vessel. When blood flow was reestablished, platelets adhered to subendothelium within 1 min. Then platelets aggregated on the adhering platelets, and fibrin net was formed. Finally, thrombi composed predominantly of fibrin and red blood cells with platelet aggregates and leukocytes were generated. An anti-platelet agent, ticlopidine, revealed a potent antithrombotic effect in this model. Because ticlopidine decreased the number of platelet aggregates, reduced the size of aggregates, and inhibited platelet degranulation, it is conceivable that platelet aggregation in early phase of thrombus formation plays a crucial role even in venous thrombosis model. A synthetic thrombin inhibitor, argatroban, also showed a potent antithrombotic effect, but a thrombolytic agent, urokinase, was less effective. In conclusion, this model is both platelet- and coagulation-dependent.

Animals↗
PubMed1991

Reduction of basic fibroblasts growth factor receptor is coupled with terminal differentiation of chondrocytes.

Basic fibroblast growth factor (bFGF) stimulates proliferation of chondrocytes and their extracellular matrix synthesis but inhibits terminal differentiation to hypertrophic cells (Kato, Y., and Iwamoto, M., (1990) J. Biol. Chem. 265, 5903-5909). In the present study, we examined changes in bFGF binding during chondrocyte cytodifferentiation. In cultures of pelleted growth plate chondrocytes, binding of 125I-bFGF to 140-kDa receptors was observed during the mitotic and matrix-forming stages but decreased to a very low level as chondrocytes became hypertrophic. Scatchard plot analysis showed that the decrease in binding of bFGF was due to a decrease in the number not in the affinity of the receptor. The loss of bFGF receptor was associated with a decrease in biological responses to bFGF. On the other hand, the binding of transforming growth factor-beta and epidermal growth factor was constant throughout all stages of growth plate chondrocytes. A rapid decrease in bFGF binding was not observed with articular chondrocytes or bFGF-exposed growth plate chondrocytes, perhaps because they scarcely underwent terminal differentiation. A decrease in bFGF binding associated with terminal differentiation in situ was also demonstrated by examination of sequential slices of growth plates. These observations suggest that rapid reduction in bFGF receptor is a special event during terminal differentiation.

Alkaline Phosphatase↗
PubMed1991

The ultrastructural defect in conjunctiva from a case of recessive dystrophic epidermolysis bullosa.

The predominant feature in the several forms of epidermolysis bullosa is the formation of cutaneous bullous lesions arising after minimal mechanical trauma. Ocular involvement has been noted as a complication. To our knowledge to date, only four investigators have correlated clinical eye disease with light microscopic findings. Ultrastructure of the ocular lesions has not been described previously. We present four cases of recessive dystrophic epidermolysis bullosa emphasizing their associated ocular complications. Diagnosis was confirmed by skin biopsy specimen and in one patient by demonstrating light and electron microscopic findings in eyelid skin. This tissue exhibited ultrastructural recessive cutaneous lesions; namely, bullous separation occurring below the basal lamina and absence of anchoring fibrils in both bullous and nonbullous areas. By electron microscopy, the conjunctiva in this patient exhibited an absence of clear anchoring fibrils that were numerous in control tissue. This defect may increase the susceptibility of the conjunctiva to minor mechanical trauma, resulting in the bullous and cicatricial changes seen clinically.

Aged↗
PubMed1991

Monoclonal IgGs from an autoimmune MRL/Mp-lpr/lpr mouse induce an interleukin-3-dependent myeloid cell line to produce tumor necrosis factor alpha and interleukin-6.

We previously reported that two IgG mAbs, 1D11 and 1G10, derived from an autoimmune MRL/Mp-lpr/lpr(MRL/l) mouse, induced IL-3 synthesis in the IL-3-dependent myeloid cell line, FDC-P2/185-4. In this study, we found that these mAbs induced TNF-alpha and IL-6 production in FDC-P2/185-4 cells. Both TNF-alpha and IL-6 were secreted rapidly within 1 hr after the addition of mAb to the cells. Increases of TNF-alpha and IL-6 mRNA were also observed in FDC-P2/185-4 cells stimulated with MRL/l-derived mAb. The anti-Fc gamma RII mAb 2.4G2 suppressed TNF-alpha and IL-6 production induced by these mAbs. Our results suggest that some IgGs of MRL/l mice may have the capacity to induce cytokine synthesis in Fc gamma R-bearing cells.

Animals↗