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Biomedical subjects

M Iwamoto

Publications and source records attributed to M Iwamoto.

At least 325 records · Page 18Linked to original sources
PubMed1988

Effects of limited exposure of rabbit chondrocyte cultures to parathyroid hormone and dibutyryl adenosine 3',5'-monophosphate on cartilage-characteristic proteoglycan synthesis.

Treatment of rabbit chondrocyte cultures with PTH or (Bu)2cAMP for 30 h increased by 2- to 3-fold the incorporation of [35S]sulfate and 3H radioactivity with glucosamine as the precursor into large chondroitin sulfate proteoglycans characteristically found in cartilage matrix. However, PTH and (Bu)2cAMP did not increase either [35S]sulfate incorporation into small proteoglycans or the incorporation of 3H radioactivity into hyaluronic acid and other glycosaminoglycans. PTH and (Bu)2cAMP also increased the incorporation of [3H] serine into both proteoglycans and total protein. In all cultures described above, the stimulation of [3H]serine incorporation into proteoglycans exceeded that of [3H]serine incorporation into total protein. These data indicate that PTH and (Bu)2cAMP selectively stimulate cartilage proteoglycan synthesis while they increase total protein synthesis. Since cAMP seems to play a mediatory role in the action of PTH, we elected to examine the effects of a limited exposure of chondrocytes to PTH or (Bu)2cAMP on the synthesis of proteoglycans. Treatment with PTH or (Bu)2cAMP for only the initial 2-7 h did not increase the rates of incorporation of [35S]sulfate, the 3H radioactivity with glucosamine, and [3H]serine into proteoglycans, as measured at 30 h, despite the fact that this treatment brought about a rapid and transient rise in the cAMP level. Furthermore, the application of prostaglandin I2 at concentrations that increased cAMP levels in a similar fashion as did PTH did not affect [35S] sulfate incorporation into proteoglycans. These observations suggest that in addition to the transient rise of cAMP, other biochemical changes are required for elaboration of the effect of PTH on proteoglycan synthesis. Although cAMP analogs mimic some of the effects of PTH in chondrocytes, the nucleotides and PTH appear to stimulate proteoglycan synthesis by different mechanisms.

Animals↗
PubMed1988

Rabbit articular chondrocytes in soft agar are useful to test the effect of non-steroidal anti-inflammatory drugs on chondrocyte replication.

The effect of non-steroidal anti-inflammatory drugs (NSAIDs) on rabbit articular chondrocyte proliferation was examined in soft agar and in conventional cultures on plastic dishes. Indomethacin, acetylsalicylate, and naproxen (10(-4) M) decreased the efficiency of colony formation by chondrocytes in soft agar in the presence of fibroblast growth factor, although the drugs had little effect on the proliferation of chondrocytes on plastic dishes. On the other hand, tiaprofenic acid (10(-4) M) did not have any adverse effect on chondrocyte replication in either culture the two systems. Rabbit articular chondrocyte growth in soft agar will be a useful test system for examining the effects of anti-arthritic drugs on cartilage metabolism and repair.

Agar↗
PubMed1988

[Growing skull fracture with rapid growth: a case report].

A case of growing skull fracture with rapid growth is presented. A 4-month-old male fell and struck the right side of his head. Skull X-ray just after injury showed a right parietotemporal linear skull fracture with the maximum width of 4 mm. The width of the fracture line increased to 9 mm 7 hours after injury. Serial CT scan demonstrated growth of contusional hematoma just beneath of the fracture. Six days later, a pulsatile mass was palpated beneath the scalp, although neurological state was normal. The width of the fracture line was demonstrated to increase up to 11 mm on X-ray at that time. CT scan revealed subgaleal cerebral herniation surrounded by brain edema. He was operated 11 days after injury. It is thought that the contusional hematoma and following brain edema played an important role in the genesis of rapid growth of the skull fracture.

Encephalocele↗
PubMed1987

Role of the essential thiol group in the thiol-activated cytolysin from Clostridium perfringens.

A hemolysin, 0-toxin, produced by Clostridium perfringens has one cysteinyl residue in the free thiol form which is essential for its hemolytic activity. The cysteinyl residue was shown to be located at a position about 5 kDa from the C terminus of the molecule by the method of cysteine-specific chemical cleavage. Modification of the residue with a thiol-blocking agent, 5,5'-dithiobis(2-nitrobenzoic acid), reduced the binding affinity of the toxin to sheep erythrocytes to 1/100 that of intact toxin, resulting in a failure of binding at low cell concentrations (0.5%). Thus the failure of hemolysis at low cell concentrations is primarily ascribed to a decreased affinity of the toxin for erythrocytes. Effects of the modification on the lytic processes were examined using high cell concentrations where considerable amounts of modified toxin bound to the cells. The modified toxin hemolyzes erythrocytes once it binds to them; however, the efficiency of hemolysis is reduced by the modification. These, and additional results indicating that modification alters the sensitivity of toxin molecules to protease digestion, show that thiol-modification inactivates the toxin by affecting both binding and the subsequent lytic processes, probably through a conformational change introduced in the toxin molecules.

Animals↗
PubMed1987

Effects of kringles derived from human plasminogen on fibrinolysis in vitro.

Plasminogen kringle 1+2+3 (K1-3) containing lysine-binding sites inhibited the reaction of plasmin with alpha 2-plasmin inhibitor (alpha 2PI), in a rate assay using a synthetic chromogenic substrate, S-2251. However, K1-3 did not inhibit the reaction to any degree between alpha 2PI and mini-plasmin which lacked the kringle 1 to 4 portion of plasmin. These results suggest that K1-3 blocked the binding of alpha 2PI to the lysine-binding site of plasmin. In the urokinase (UK)-induced fibrinolysis, K1-3 shortened the human plasma clot lysis time at low concentration (0.5-6 microM), and prolonged the lysis time at a high concentration (20 microM). Similar results were obtained in the lysis time of a fibrin clot consisting of plasminogen, fibrinogen and alpha 2PI isolated from human plasma. The kringle 4 (K4) of human plasminogen did not accelerate human plasma clot lysis at any concentration (1.2-24.1 microM). Furthermore, in the tissue plasminogen activator (TPA)-induced fibrinolysis, K1-3 also shortened both the lysis time of human plasma clot and fibrin clot as observed in UK-induced fibrinolysis, but K4 did not. The above findings indicate that the reaction of alpha 2PI with the lysine-binding site of plasmin is involved in the inhibition of plasmin activity by alpha 2PI, and in the presence of an inhibitor of this reaction, the balance of coagulofibrinolytic activity in plasma will be shifted towards the fibrinolytic side.

Fibrinolysin↗
PubMed1987

Delayed memory dysfunction by transient hypoxia, and its prevention with forskolin.

Rats exposed to 40 min hypoxia 3 h before a one-trial learning passive avoidance task showed impaired memory retention 24 h later. this model was used to assess the ability of forskolin to restore the delayed memory dysfunction. Significant amelioration of memory retention was observed when forskolin (500 micrograms/kg, i.p.) was injected just after hypoxia. Forskolin is suggested to enhance cerebral blood flow and to facilitate memory function through the action of increased cyclic adenosine monophosphate (cAMP).

Animals↗
PubMed1987

Fibroblast growth factor stimulates colony formation of differentiated chondrocytes in soft agar.

The effect of fibroblast growth factor (FGF) on the growth of chondrocytes in soft agar was examined. FGF induced colony formation by chick embryo and rabbit chondrocytes. The colony-forming efficiency of FGF-exposed chondrocytes was similar to that of Rous sarcoma virus-transformed chondrocytes (15-20%). Other mitogenic agents tested, such as epidermal growth factor, insulin, insulin-like growth factor-l, and platelet-derived growth factor, induced very low levels of colony formation. The induction of growth in soft agar of chondrocytes by FGF was not due to cells' phenotypic transformation, because chondrocytes grown in soft agar with FGF retained the ability to synthesize cartilage-characteristic proteoglycan. FGF did not induce growth in soft agar of chondrocytes whose phenotypic expression was suppressed by retinoic acid or 5-bromodeoxyuridine. In addition, FGF did not induce growth in soft agar of primary fibroblasts and normal rat kidney (NRK) cells. These results suggest that FGF selectively stimulates growth of differentiated chondrocytes in soft agar.

Agar↗
PubMed1987

Effect of vanadate on cartilage-matrix proteoglycan synthesis in rabbit costal chondrocyte cultures.

The effect of vanadate on proteoglycan synthesis by cultured rabbit costal chondrocytes was examined. Rabbit chondrocytes were seeded at low densities and grown to confluency in medium supplemented with 10% fetal bovine serum, and then the serum concentration was reduced to 0.3%. At the low serum concentration, chondrocytes adopted a fibroblastic morphology. Addition of 4 microM vanadate to the culture medium induced a morphologic differentiation of the fibroblastic cells to spherical chondrocytes, and increased by two- to threefold incorporation of [35S]sulfate and [3H]glucosamine into large, chondroitin sulfate proteoglycans. The stimulation of incorporation of labeled precursors reflected real increases in proteoglycan synthesis, in that chemical analyses showed increases in the accumulation of macromolecules containing hexuronic acid and hexosamine in vanadate-maintained cultures. However, vanadate had only a marginal effect on [35S]sulfate incorporation into small proteoglycans and [3H]glucosamine incorporation into hyaluronic acid and chondroitinase AC-resistant material. These results provide evidence that vanadate selectively stimulates the synthesis of proteoglycans characteristically found in cartilage by rabbit costal chondrocyte cultures.

Animals↗
PubMed1987

Stimulatory effect of prostaglandin E2 on the configuration of normal human melanocytes in vitro.

Normal human epidermal melanocytes became swollen and more dendritic when they were cultured for 6 days with prostaglandin (PG) E2, but not with PGE1, although the amount of immunoreactive tyrosinase in the melanocytes did not appear to be increased markedly after these treatments. From these data we suggest that PGE2 may be one of the factors responsible for the induction of postinflammatory hyperpigmentation of the skin.

Alprostadil↗
PubMed1987

[Malignant changes in a craniopharyngioma].

The authors report a rare case of a 10-year-old girl with craniopharyngioma which showed malignant change after the first operation and irradiation. In June 1981, the patient complained of headache, nausea and vomiting. CT revealed obstructive hydrocephalus due to the calcified mass lesion which extended to the third ventricle. In order to alleviate the high intracranial pressure, the right ventriculo-peritoneal shunt was first settled and after that, partial removal of the tumor was performed. The pathological diagnosis of the specimen was typical adamantinomatous type of craniopharyngioma without any findings of malignancy. After this operation irradiation was performed. The tumor almost disappeared and the patient was discharged from the hospital and went to school, showing some signs of panhypopituitarism. In May 1984, she complained of decreased left visual acuity, right temporal anopsia, headache, nausea and vomiting. CT revealed recurrence of the tumor which obstract the foramen of Monro bilaterally. As an emergency measure, the left ventriculo-peritoneal shunt was added and the state of the patient became recovered. In order to improve decreased visual acuity, the tumor located around the optic nerves and over the frontal base was removed in June 1984, resulting in partial improvement of visual acuity bilaterally. The pathological examination of the second specimen showed, in addition to the part of adamantinomatous type of craniopharyngioma which was the same as before, the existence of thick layer of stratified large atypical cells which partially covered the cyst wall and partially invaded into the surrounding tissues. The pathological diagnosis was poorly differentiated squamous cell carcinoma with craniopharyngioma of 'adamantinoma' type.(ABSTRACT TRUNCATED AT 250 WORDS)

Ameloblastoma↗
PubMed1987

[A case of multiple septic intracranial aneurysms--successful treatment with surgical and conservative therapy in the same case].

Here reported is a case of multiple septic intracranial aneurysms which were successfully treated with surgical and conservative therapy. A 44-year-old man was admitted to our hospital because of headache, vomiting and visual disturbance. He had had a fever and had been under treatment for a respiratory tract infection during the preceding 3 months. Physical examination on admission revealed pansystolic heart murmur over the cardiac apex. Neurological examination revealed neck stiffness, papilledema and right homonymous hemianopsia. Laboratory data showed the presence of inflammatory process. A CT scan showed a high density area in the left occipital region, and vertebral angiography showed a saccular aneurysm on a distal branch of the left occipitotemporal artery. Fourteen days after admission, the operation of clipping the neck of the aneurysmal artery was performed and the hematoma evacuated to lower the increased intracranial pressure. He had been well after the operation until 3 weeks later when a follow-up angiography showed a new unruptured aneurysm on a distal branch of the right middle cerebral artery with a relapse of the infection. Then, he was treated with appropriate antibiotics and antifibrinolytic agents. A repeated angiography 1 month later showed resolution of the aneurysm. The mechanism of resolution of septic aneurysm and its treatment are discussed.

Adult↗
PubMed1986

Use of 4-bromomethyl-7-methoxycoumarin for derivatization of pyrimidine compounds in serum analysed by high-performance liquid chromatography with fluorimetric detection.

Derivatization of the pyrimidine nucleobases and nucleosides with 4-bromomethyl-7-methoxycoumarin was studied with the aim of developing a sensitive and selective column liquid chromatographic method for these substances in serum. The labeling reactions and the nature of derivatives are discussed, together with the chromatographic properties of these derivatives. The derivatives are stable for at least several weeks. Typical detection limits are 50 pg for inosine, 150 pg for uridine, 50 pg for uracil, 50 pg for thymine and 100 pg for fluorodeoxyuridine, respectively. Within-day coefficients of variation averaged 5.0% for the stored-frozen serum pools; the mean day-to-day value was 5.2%. Thirty samples could be processed per working day.

Chromatography, High Pressure Liquid↗
PubMed1986

Cold-labile hemolysin produced by limited proteolysis of theta-toxin from Clostridium perfringens.

A nicked toxin whose hemolytic activity is temperature dependent was obtained by limited proteolysis of theta-toxin (Mr 54,000) with subtilisin. The nicked toxin (C theta) is a complex of two fragments: the N-terminal fragment (Mr 15,000) with basic isoelectric point and the C-terminal fragment (Mr 39,000) with the single cysteinyl residue of the toxin whose reduced form is essential for the hemolytic activity. C theta hemolyzes erythrocytes only at temperatures above 25 degrees C, whereas the native toxin hemolyzes them even at 10 degrees C. At temperatures below 25 degrees C, C theta does not hemolyze them although it does bind to membrane cholesterol and although no distinct difference was observed between the secondary structure of C theta and that of native toxin. It was found that C theta binds to the cells only in a reversible manner at low temperature, while the native one binds irreversibly to the cells within 10 min, which explains the cold lability of C theta on hemolysis. The structural basis of the cold lability was discussed through comparison of C theta with another nicked derivative of theta-toxin that was also obtained.

Amino Acid Sequence↗