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Biomedical subjects

M Oka

Publications and source records attributed to M Oka.

At least 505 records · Page 28Linked to original sources
PubMed1991

A bioabsorbable delivery system for antibiotic treatment of osteomyelitis. The use of lactic acid oligomer as a carrier.

We prepared a composite of D,L-lactic acid oligomer and dideoxykanamycin B for use as a biodegradable antibiotic delivery system with sustained effect. The composite was implanted in the distal portion of the rabbit femur, and the effective concentration of the antibiotic was measured in the cortex, the cancellous bone, and the bone marrow. In all bone tissues around the implant, the concentration of antibiotic exceeded the minimum inhibitory concentration for the common causative organisms of osteomyelitis for six weeks. Most of the implant material had been absorbed and the bone marrow had been repaired to a nearly normal state within nine weeks of implantation. The implant caused no systemic side effects, and it is likely to prove clinically useful as a drug delivery system for treating chronic osteomyelitis.

Absorption↗
PubMed1991

[Chick embryo culture using duck egg shell--first successful hatch ].

The suitability of duck egg shell (DES) for chick embryo culture was investigated. Chick embryos were transferred into DESs with all egg contents after 3 days of normal incubation and cultured. The vessels made of polyethylene cling film were used for shell-less control. Among 35 embryos cultured in DESs, 21 survived until 16 days of incubation (13 days after transfer) and finally 3 newly hatched chicks were obtained at 22 days of incubation. One of them died 4 days later, but remaining two became full-grown cocks showing normal body weight and production of fertile sperms. Among 37 embryos cultured in polyethylene vessels, none survived over the period of 19 days of incubation. It is suggested that DES culture system may be useful for the various experiments using chick embryos.

Animals↗
PubMed1991

Postpalatoplasty decrease in respiratory dead space in young children.

In 20 children with cleft palates age 1.5 to 2 years, respiratory parameters were evaluated before, 15 minutes after, and 1 hour after palatoplasty. The dead space (VD) in the palatoplasty group decreased from 25.2 +/- 4.7 ml preoperatively to 12.3 +/- 9.1 ml postoperatively. This decrease improved respiratory efficiency. A significant difference was found postoperatively in the partial pressure of CO2 in arterial blood (PaCO2) between the palatoplasty and control groups. No significant differences were found in base excess (BE), arterial pH, pulmonary shunt ratio, and the alveolar-arterial O2 difference (A-aDO2) between the groups pre- and postoperatively. This finding indicated that temporary respiratory failure may exist postoperatively; the phenomena were improved in the recovery room. Since lung compliance and airway resistance may also participate in the decrease in VD, further evaluation of these factors are necessary.

Carbon Dioxide↗
PubMed1991

Melanostatin, a new melanin synthesis inhibitor. Production, isolation, chemical properties, structure and biological activity.

Melanostatin, a new antibiotic with melanin synthesis inhibitor activity, was isolated from the fermentation broth of Streptomyces clavifer No. N924-2. Its structure was determined by spectral analysis and degradation experiments. Melanostatin strongly inhibited melanin formation in Streptomyces bikiniensis NRRL B-1049 and B16 melanoma cells.

Chromatography, Thin Layer↗
PubMed1991

Cloning and nucleotide sequences of the AccI restriction-modification genes in Acinetobacter calcoaceticus.

The genes of the AccI restriction-modification system specific for GT(A/C) (G/T)AC were cloned from the chromosomal DNA of Acinetobacter calcoaceticus, and their nucleotides sequenced. The restriction and modification genes coded for polypeptides with calculated molecular weights of 42,494 and 63,078, respectively. Both the enzymes were coded by the same DNA strand and the restriction gene was upstream of the methylase gene, separated by 2 bp. The restriction gene was significantly expressed in E. coli cells, so that the AccI restriction endonuclease could be purified to homogeneity. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration indicated that the catalytically active form of the endonuclease was tetrameric. Sequence comparison with related enzymes indicated that AccI methylase contained a segment of tetra-amino acids, NPPY, characteristic of N6-adenine methylases. In addition, some homologous regions were found in the sequence of HincII methylase specific for GT(C/T) (A/G)AC.

Acinetobacter↗
PubMed1991

[A case of recurrent pelvic tumor of sigmoid colon cancer showing partial response to lipiodolization].

We performed lipiodolization and immunochemotherapy for recurrent pelvic tumor of sigmoid colon cancer using an infuserport which was implanted and connected to the catheter placed in the right internal iliac artery. Following lipiodolization, the level of CEA (980 ng/ml) decreased to within the normal range. MRI showed necrotic change and regression (more than 50%) of tumor. DSA revealed disappearance of tumor neovascularity. No serious side effect but skin erosion in the gluteal region was encountered after lipiodolization. This result suggests that lipiodolization is worth performing in further clinical trials for pelvic tumor.

Aged↗
PubMed1991

[Effect of liposome-entrapped lidocaine on limbic status epilepticus in rats].

Liposomes (LIPO), which are concentric lipid layers alternating with aqueous compartments, have been suggested as a potential carrier for various drugs. In the previous studies, we have demonstrated that anticonvulsant drugs such as valproic acid, phenytoin, and DN-1417 (an analog of thyrotropin-releasing hormone) entrapped into LIPO exert more prominent therapeutic efficacy than parent drugs. In the present study, we examined the comparative effects of Lidocaine (LDCA) which acts as a proconvulsant as well as an anticonvulsant, and LIPO-entrapped LDCA (LDCA-L) on limbic status epilepticus originating in the amygdala (AM) of rats. LDCA (LDCA hydrochloride) was dissolved in distilled water as a vehicle at a concentration of 2.5 mg/ml or 10 mg/ml. LIPO and LDCA-L were prepared from L-alpha-phosphatidylcholine, cholesterol, and stearylamine. Status epilepticus was induced by intra-AM injection of combined dibutyryl (db)-cAMP-200 micrograms/ethylene diaminetetraacetic acid (EDTA)-67.2 micrograms through the implanted cannula. The animals were divided into 4 groups which received vehicle (n = 6), LIPO (n = 5), LDCA (n = 9), and LDCA-L (n = 10). LDCA group was subdivided into 5 mg/kg (n = 4) and 20 mg/kg (n = 5) groups. LDCA-L group was treated with 5mg/kg (n = 4) or 20mg/kg (n = 6). All drugs were intravenously given at a volume of 2ml/kg via teflon tube previously inserted into cervical vein 30 min after db-cAMP/EDTA injection. Vehicle or LIPO alone did not alter the pattern of electroclinical ictal responses produced by intra-AM injection of db-cAMP/EDTA.(ABSTRACT TRUNCATED AT 250 WORDS)

Amygdala↗
PubMed1991

Tetrodotoxin-insensitive Na+ channel activator palytoxin inhibits tyrosine uptake into cultured bovine adrenal chromaffin cells.

The effects of the tetrodotoxin-insensitive Na+ channel activator palytoxin on both the secretion of endogenous catecholamines and the formation of 14C-catecholamines from [14C]tyrosine were examined using cultured bovine adrenal chromaffin cells. Palytoxin was shown to cause the stimulation of catecholamine secretion in a concentration-dependent manner. However, this toxin caused the reduction rather than the stimulation of 14C-catecholamine formation at the same concentrations. Palytoxin failed to cause any alteration in the activity of tyrosine hydroxylase prepared from bovine adrenal medulla. Furthermore, the uptake of [14C]tyrosine into the cells was shown to be inhibited by this toxin under the conditions in which the suppression of 14C-catecholamine formation was observed, and this inhibitory action on tyrosine uptake was closely correlated with that on catecholamine formation. The inhibitory action of palytoxin on tyrosine uptake into the cells was observed to be noncompetitive, and this effect was not altered by the removal of Na+ from the incubation mixture. These results suggest that palytoxin may be able to inhibit the uptake of [14C]tyrosine into the cells, resulting in the suppression of 14C-catecholamine formation, probably through its direct action on the plasma membranes of bovine adrenal chromaffin cells.

Acrylamides↗
PubMed1991

Activation of hepatitis B virus infection by chemotherapy containing glucocorticoid in hepatitis B virus carriers with hematologic malignancies.

Among 262 inpatients with hematologic diseases who were referred for chemotherapy or immunosuppressive therapy between January, 1985, and December, 1989, nine (3.4%) patients, including two with Hodgkin's disease (HD), three with acute myeloblastic leukemia, one with chronic myelogenous leukemia, two with multiple myeloma and one with aplastic anemia, were found to be hepatitis B virus (HBV) carriers before their chemotherapy began. All six HBV carriers who received chemotherapy containing glucocorticoid showed mild-to-moderate elevations in serum transaminase levels after the chemotherapy. Five showed a rise in titer of the hepatitis B surface antigen, HBsAg. In contrast, three HBV carriers not receiving glucocorticoid showed no change in serum transaminase after chemotherapy. One HBV carrier with HD suffered from severe icteric hepatitis after the withdrawal of multiagent chemotherapy containing glucocorticoid. The HBV-DNA polymerase rose markedly and was accompanied by a marked rise in titer of HBsAg. The results warn us to keep in mind the possibility of glucocorticoid inducing an activation of HBV infection, which may result in severe hepatitis in some HBV carriers. Although further investigation is required, it is recommended that HBsAg-positive patients with hematologic malignancies should, if possible, be treated without glucocorticoid.

Adult↗
PubMed1991

Mechanical strength of osteochondral junction.

The junction between articular cartilage and bone in adult humans was tested in shear to determine their bonding strength in relation to the tensile strength of full thickness articular cartilage and shear strength of underlying subchondral bone. The site of failures was also studied under light microscope and scanning electron microscope. The junction failed at a shear strength of 7.25 +/- 1.35 MPa (n = 18). On the other hand, the tensile strength of cartilage and shear strength of subchondral bone were 3.75 +/- 0.75 MPa (n = 17) and 2.45 +/- 0.85 MPa (n = 15) respectively. Light and scanning electron microscopic examination revealed that in fact, failures occurred at the tidemark. The ultrastructure of the tidemark suggested that this region might have structural weakness against mechanical stresses. The relevance of the results were discussed in relation to the osteochondral fractures in adult humans.

Adult↗
PubMed1991

[Regional immunochemotherapy for liver metastasis of esophageal cancer in a patient with variant hepatic artery].

A patient with metastatic liver tumor from esophageal cancer having an anomaly of the hepatic artery was treated by regional immunochemotherapy using two infuserports, which were implanted transfemoral to the right and the left hepatic artery, respectively. The schedule of this therapy was as follows: CDDP (30 mg/m2) on day 1 and 8, 5-FU (1,000 mg/m2) on day 1, 2, 8, 9, 15 and 22, and OK-432 (1 KE/body) on day 3-6, 10-13 and 16-20 were administered via the hepatic artery; and OK-432 (5 KE/body) was also injected intramuscularly three times a week. After the first course of this therapy was performed via the left hepatic artery, metastatic foci in the left lobe regressed, while those in the right lobe progressed markedly. Thereafter, the second course was performed via the right hepatic artery, and then the third course was via both right and left hepatic artery. Following these trials, metastatic foci of the right and the left lobes showed remarkable regression. These results suggest that the effect of immunochemotherapy is closely related with the local concentration of anti-cancer agents.

Administration, Oral↗
PubMed1990

Maturational arrest from CD4+8+ to CD4+8- thymocytes in a mutant strain (LEC) of rat.

A mutant strain (LEC) of rats was found to have a novel defect in T cell maturation, that is, arrest of differentiation from CD4+8+ to CD4+8- but not to CD4-8+ thymocytes. FACS analyses demonstrated a deficiency in the CD4+8- T cell subset in the thymus and a marked decrease in CD4+ T cells in peripheral lymphoid organs. Expression of the T cell receptor (TCR)/CD3 complex in CD4+8+ and CD4-8+ thymocytes of LEC rats was normal. Expression of class II major histocompatibility complex (MHC) in the thymus of LEC rats was also the same as that of normal rats. These results indicate that maturational arrest occurs only in the transition pathway from CD4+8+ to CD4+8- thymocytes, and that this mutation can not be attributed to the default of expression of either TCR/CD3, CD4, or class II MHC antigen. Consequently, dysfunction of helper T cells was observed in LEC rats, while killer T cells and B cells functioned normally. Although the complete identification of the origin of this mutation requires further studies, it is hoped that such investigations will throw light on the mechanism of positive selection.

Animals↗
PubMed1990

Stimulatory actions of bioflavonoids on tyrosine uptake into cultured bovine adrenal chromaffin cells.

The effects of flavonoids on L-[14C]tyrosine uptake into cultured adrenal chromaffin cells were examined. Flavone markedly stimulated tyrosine uptake into these cells in a manner dependent on its concentration. Apigenin also caused a moderate stimulatory action, but quercetin had no significant effect on the uptake. Flavone also stimulated the uptake of histidine, but did not affect the uptake of serine, lysine, or glutamic acid. These results are considered to propose the possibility that flavonoids may be able to stimulate the precursor uptake into the cells, resulting in an enhancement of the biogenic amine production.

Adrenal Medulla↗
PubMed1990

Localization and release of immunoreactive vasoactive intestinal polypeptide in bovine adrenal medulla.

The concentration of immunoreactive (IR) vasoactive intestinal polypeptide (VIP) in extracts from bovine adrenal medulla was 29.9 +/- 7.2 pmol/g wet wt., which was about 100 times that of IR neurotensin and 30 times that of IR somatostatin. Chromatographic analysis showed that most of the IR-VIP was the same molecular size as synthetic VIP(1-28). On retrograde perfusion of isolated bovine adrenal gland, release of VIP with catecholamine (CA) was marked on stimulation with high K+, but slight on stimulation with acetylcholine, which induced marked release of CA. These results suggest that most of the VIP is localized not in CA storing granules in chromaffin cells, but in other intraadrenal neuronal components. In immunohistochemical studies, IR VIP fibers with large varicosities were observed around the vessels in the adrenal medulla.

Acetylcholine↗
PubMed1990

Surface reactions of calcium phosphate ceramics to various solutions.

The surface reactions of calcium phosphate ceramics have been thought to play an important role in bonding with living bone. Hydroxyapatite (HA), tricalcium phosphate (TCP), and two kinds of apatite-containing glass ceramics were immersed in three types of solutions with different chemical constituents. The first solution was a physiological saline, the second contained phosphate (PO4), and the third was a balanced salt solution consisting of calcium (Ca), magnesium (Mg), and PO4. After serial incubation periods, changes in the solutions were assessed by measurement of total Ca, Mg, and PO4. The ceramic surfaces were studied using scanning electron spectroscopy, infrared reflection spectroscopy, and thin-film x-ray diffraction. The surface reactions of the ceramics were greatly affected by the chemical compositions of the surrounding media. In the complete solution with both Ca and PO4, a carbonated apatite layer was formed on the surfaces of HA, TCP, and the glass ceramics. In comparison to HA and TCP, the glass ceramics were characterized as Ca-releasing materials, the dissolved Ca creating an apatite layer on the surfaces in a few days, in conjunction with PO4 stock in the surrounding media. The immersion test with various solutions proved to be a simple and effective method of assessing surface conditions of ceramic materials.

Biocompatible Materials↗
PubMed1990

Enhancement by cytochalasin B of ouabain-stimulated catecholamine secretion from cultured bovine adrenal chromaffin cells: possible relation to alteration in Na+/K(+)-pump activity.

1. Catecholamine secretion evoked by ouabain from cultured bovine adrenal chromaffin cells has previously been shown to be markedly enhanced by pretreatment of the cells with cytochalasin B (Morita et al., 1988). To elucidate a possible mechanism of this enhancement, the stimulatory action of ouabain on Ca2+ influx as well as catecholamine secretion was then examined in the cells pretreated with or without cytochalasin B. The effect of cytochalasin B pretreatment on the inhibitory action of ouabain on the Na+/K+ pump was also examined by measuring 86Rb+ uptake into the cells. 2. Pretreatment of the cells with cytochalasin B caused enhancement of ouabain-induced catecholamine secretion, and this enhancement was accompanied by the elevation of ouabain-stimulated 45Ca2+ uptake into the cells. The inhibitory action of ouabain on 86Rb+ uptake was significantly enhanced by pretreatment of the cells with cytochalasin B under the same conditions. 3. These results indicate that the enhancement of ouabain-induced catecholamine secretion caused by cytochalasin B pretreatment may be due to the increase in ouabain-stimulated Ca2+ influx into the cells and, furthermore, suggest the possibility that this increase in Ca2+ influx may be attributed to the potentiation of the inhibitory action of ouabain on the Na+/K+ pump in the adrenal chromaffin cell. Thus, the present study provides an evidence for a possible role of microfilaments as one of the intrinsic factors modulating the plasma membrane functions.

Adrenal Medulla↗
PubMed1990

Submandibular sialoadenitis due to a foreign body.

A case of a painful swelling of a submandibular gland in a 62-year-old woman is reported. This eventually proved to be caused by a foreign body (fish bone) in the main intrasalivary duct of the gland.

Female↗