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Biomedical subjects

M Oka

Publications and source records attributed to M Oka.

At least 19 recordsLinked to original sources
PubMed1992

Deconjugating activity for sulfoconjugated dopamine in homogenates of organs from dogs.

To clarify the possibility that sulfoconjugated dopamine (DA) may play a physiological role by being converted to active free DA, we examined the deconjugating activity in homogenates of organs from dogs. Each tissue homogenate was incubated with sulfoconjugated DA, and the deconjugating activity of the organs was compared. The kidney and liver exhibited the highest deconjugating activities. In contrast, the intestine and heart showed lower arylsulfatase activities, and almost no activity was found in the brain or skeletal muscle. Moreover, in the heart, the deconjugating activity for sulfoconjugated DA was higher in the atrium than the ventricle. These results indicate that sulfoconjugated DA is converted to active free DA in homogenates of organs from dogs and that the deconjugating activity varies between different parts of an organ. Sulfoconjugated DA must be looked upon as a possible precursor or reservoir for the production of active free DA.

Animals↗
PubMed1992

An iatrogenic foreign body (dental bur) in the maxillary antrum: a report of two cases.

Two cases of foreign bodies of the antrum are reported. One was a turbine bur which presumably entered through an oro-antral fistula after a tooth extraction. The other was also a turbine bur where the mode of entry was not clear (lack of oro-antral fistula), but it presumably entered through the socket of the extracted tooth. The mucosa of the antrum appeared normal in spite of the lengthy presence of the foreign body.

Adult↗
PubMed1992

Role of lysophosphatidylcholine in T-lymphocyte activation: involvement of phospholipase A2 in signal transduction through protein kinase C.

2-Lysophosphatidylcholine (lysoPtdCho), a product of the hydrolysis of phosphatidylcholine catalyzed by phospholipase A2, greatly potentiates the activation of human resting T lymphocytes that is induced by a membrane-permeant diacylglycerol plus a calcium ionophore, as determined by the expression of the alpha subunit of the interleukin 2 receptor and thymidine incorporation into DNA. LysoPtdCho per se is inactive unless both diacylglycerol and a calcium ionophore are present. This effect of lysoPtdCho is also observed when diacylglycerol is replaced by a tumor-promoting phorbol ester. Other lysophosphatides including lysophosphatidylserine, lysophosphatidylinositol, and lysophosphatidic acid are inert except for lysophosphatidylethanolamine, which is far less effective than lysoPtdCho. Tracer experiments with radioactive choline indicate that, when T lymphocytes are stimulated with an antigenic signal, lysoPtdCho is indeed produced in a time-dependent fashion, although the concentration of this lysophospholipid accumulated remains to be quantitated. It suggests that phospholipase A2 is directly involved in the signal transduction pathway through protein kinase C to induce long-term cellular responses.

Calcium↗
PubMed1992

Induction of heat shock protein closely correlates with protection against Toxoplasma gondii infection.

Heat shock proteins (HSPs) are evolutionarily highly conserved polypeptides that appear to be produced by many cells to preserve cellular functions under a variety of conditions of stress, including infections. We report that a 65-kDa HSP is present in mouse peritoneal cells that have been infected with a low-virulence (Beverley) strain of Toxoplasma gondii, as determined by electroblot assay using a monoclonal antibody specific for microbial HSP65. This HSP is, however, not expressed when infection occurs with the high-virulence RH strain of T. gondii. Furthermore, HSP was demonstrable in mice that acquired resistance against infection with a lethal dose of bradyzoites of the Beverley strain or even of an inoculum of a highly virulent strain of T. gondii (RH). From these results, it can be suggested that HSPs play an important role in developing effective defenses that include effective immune responses against infection with Toxoplasma parasites in vivo.

Animals↗
PubMed1992

The signal-induced phospholipid degradation cascade and protein kinase C activation.

Acting in synergy with diacylglycerol, unsaturated free fatty acids such as arachidonic, oleic, linoleic, linolenic and docosahexaenoic acids dramatically activate some members of the protein kinase C family at the basal level of Ca2+ concentration. It is plausible that phospholipase C and phospholipase A2, and possibly phospholipase D as well, are involved in the activation of protein kinase C. Presumably, this enzyme activation is integrated into the signal-induced membrane phospholipid degradation cascade, prolonging the activation of protein kinase C. The sustained activity of this enzyme appears to be of importance for long-term cellular responses such as development of neuronal plasticity and gene activation.

Animals↗
PubMed1992

Prognostic significance of regional lymph node reaction after curative resection of advanced gastric cancer.

The prognosis of patients with advanced gastric cancer who undergo curative resection is still unsatisfactory. The relationship between prognosis and various factors such as stage, lymph node metastasis, serosal invasion and regional lymph node reaction (follicular hyperplasia and sinus histiocytosis) was evaluated. Of the factors studied, the only one that correlated well with survival was sinus histiocytosis. Lymph node metastasis was related weakly to prognosis. No correlation between prognosis and stage, serosal invasion or follicular hyperplasia was observed. Sinus histiocytosis may represent the morphological tumour-host immune reaction. Lymph node metastases or histological types were not related to regional lymph node reaction. These results suggest that sinus histiocytosis could be a useful prognostic factor for gastric cancer. Intensive postoperative follow-up for recurrence may be necessary even for patients with low-grade sinus histiocytosis in whom curative surgery is attempted.

Adenocarcinoma↗
PubMed1992

In vitro and in vivo studies on bioabsorbable ultra-high-strength poly(L-lactide) rods.

Ultra-high-strength poly(L-lactide) (PLLA) rods were fabricated using a drawing technique. Rods with a diameter of 3.2 mm and a draw ratio of 2.5:1 showed initial bending strength and modulus values of 240 MPa and 13 GPa, respectively. The purpose of this study was to investigate the in vitro and in vivo degradation of PLLA rods with a draw ratio of 2.5:1. The greater the rod diameter, the longer the bending strength was maintained in phosphate buffered saline at 37 degrees C. The bending strength retention of rods (diam. 3.2 mm) implanted in the subcutis of rabbits was almost equal to that of rods in the in vitro study, while those rods implanted in the medullary cavity of rabbit femora showed a slightly lower bending strength retention. Molecular weight was reduced to the greatest extent in the medullary cavity, followed by in the subcutis and in vitro. The weight of PLLA rods in the medullary cavity was reduced by 22% at 52 weeks and by 70% at 78 weeks after implantation. Histologically, no inflammatory or foreign body reaction was observed in the medullary cavity for 52 weeks. The drawn PLLA rods maintained a bending strength exceeding that of human cortical bone in the medullary canal for a period of 8 weeks, suggesting that the drawn PLLA rods may be useful in the repair of fractured human bones.

Absorption↗
PubMed1992

An extract of seeds from Aeginetia indica L., a parasitic plant, induces potent antigen-specific antitumor immunity in Meth A-bearing BALB/c mice.

The antitumor activity of an extract of seeds from Aeginetia indica L., a parasitic plant, was investigated. BALB/c mice, inoculated i.p. 1 x 10(5) syngeneic Meth A tumor cells, were administered 2.5 mg/kg A. indica extract i.p. every 2 days from day 0. The untreated mice died of an ascitic form of tumor growth within 21 days, whereas all the treated mice completely recovered from tumor challenge without any side-effects. The extract did not exert direct cytotoxic activity against Meth A in vitro. Mice that survived after the first challenge as a result of A. indica treatment overcame the rechallenge with homologous Meth A without additional administration of the extract. On the other hand, those mice could not survive after rechallenge with Meth 1 tumor cells, which were also established in BALB/c mice but were different in antigenicity from Meth A, suggesting the development of antigen-specific concomitant immunity in the A. indica-cured mice. In the induction phase of antitumor resistance in this system, CD4+ T cells appeared to be the main contributors, since in vivo administration of anti-CD4 mAb completely abolished such resistance. In contrast, anti-CD8 mAb administration did not influence the effect of A. indica. The importance of CD4+ T cells in antitumor immunity was again clarified by Winn assay; that is, spleen and lymph node cells depleted of CD4+ T cells in vitro prior to assay abolished antitumor activity on co-grafted Meth A tumor cells in vivo.

Animals↗
PubMed1992

Immunological analysis and clinical effects of intraabdominal and intrapleural injection of lentinan for malignant ascites and pleural effusion.

Twenty effusions in sixteen patients with malignant peritoneal and/or pleural effusions were treated with intracavitary injection of lentinan. Lentinan was injected at a dosage of 4 mg/week for 4 weeks. In total, sixteen (80%) of twenty lesions demonstrated clinical responses. Performance status was improved in seven patients. The average survival time in responders was 129 days, while, in non-responders, it was 49 days. Serious toxicities were not observed. NK activity of PBMC significantly decreased after lentinan injection. NK activity of PEC in responders was augmented significantly. Anti-Daudi and lymphokine activated killer activity were also augmented or maintained after lentinan injection.

Adult↗
PubMed1992

Changes in plasma free and sulfoconjugated catecholamines before and after acute physical exercise: experimental and clinical studies.

To elucidate whether sulfoconjugated catecholamines in plasma, especially dopamine, serve as a source of free catecholamines, we examined the change in afterload on the deconjugating activity of catecholamines in isolated Langendorff perfused rat hearts. Dopamine-sulfate was administered under ordinary or high-work-load conditions. Free dopamine in the effluent was increased by the high-work-load of the hearts, whereas conjugated dopamine showed an apparent decrease. These results indicate the possibility that deconjugation of sulfoconjugated catecholamines is accelerated by a high-work-load. To obtain further evidence in humans, we also examined the changes in the plasma levels of free and sulfoconjugated catecholamines in healthy volunteers before and after marathon running. Free dopamine increased 1.99-fold from the baseline value after exercise, whereas conjugated dopamine decreased by 12%. Similarly, the plasma levels of free noradrenaline and adrenaline increased after exercise to 2.45- and 1.51-fold their respective baseline values, while conjugated noradrenaline and adrenaline both decreased. These clinical results, as well as those of the experimental studies, suggest that the increase in plasma free catecholamines after exercise is due not only to increased release from the sympathoadrenal system but also to accelerated conversion from sulfoconjugated catecholamines in the plasma.

Adolescent↗
PubMed1992

Further studies on the relationship between tyrosine supply and catecholamine production in cultured adrenal chromaffin cells.

To elucidate a possible role of tyrosine supply as a factor modulating catecholamine biosynthesis in the adrenergic cell, the transport of [14C]tyrosine into cultured bovine adrenal chromaffin cells was first examined, and the relationship between [14C]tyrosine transport and [14C]catecholamine formation was then investigated. Under the conditions which were routinely employed to determine the rate of catecholamine biosynthesis, tyrosine was taken up into the cells in a manner independent of extracellular Na+ and Ca2+, and this uptake was also insensitive to ouabain and various metabolic inhibitors. The stimulation of these cells with high K+ and other secretagogues caused no significant alteration in the uptake. While, tyrosine transport was markedly inhibited by tyrosine analogues and other L-aromatic amino acids, and this inhibition was accompanied by the reduction of [14C]catecholamine formation. In contrast, tyrosine transport was markedly enhanced by flavone, and this enhancement was also accompanied by the augmentation of catecholamine production under the same experimental conditions. These results seem to indicate that the transport of tyrosine into the cells may be closely related to catecholamine formation within the cells, thus providing an evidence for a possible role of tyrosine supply as one of the factors affecting catecholamine production in the adrenal chromaffin cell.

Adrenal Medulla↗
PubMed1992

Immunohistochemical detection of desmosomes in oral squamous cell carcinomas: correlation with differentiation, mode of invasion, and metastatic potential.

An expression of desmosomal glycoprotein 1 (DG 1) was immunohistochemically examined in 77 biopsies and 21 metastatic cervical lymph nodes of oral squamous cell carcinomas (SCC). In the primary tumors the DG 1 expression was significantly reduced at the invasive site of poorly differentiated and highly invasive tumors. In cases of metastases in cervical lymph nodes, the DG 1 staining at the invasive site of the primary tumor was significantly less than that of nonmetastatic cases. The DG 1 expression in the metastatic lymph nodes was as weak as that in the primary tumor. Thus, we suggest that immunohistochemical investigation of DG 1 expression in oral SCC is valuable in predicting tumor behavior.

Carcinoma, Squamous Cell↗
PubMed1992

Heterotopic salivary gland tissue in lymph nodes of the cervical region.

The occurrence and composition of intranodal salivary gland tissue (ISGT) in the head and neck region were investigated. ISGT was mainly composed of mature acini, intercalated ducts and intralobular ducts but immature acini (20.8%) and immature small ducts (18.8%) were also observed. The latter resembled salivary gland tissue in an early developmental stage. Various histological changes of ISGT were observed including cyst formation (16.7%), oncocytic metaplasia (8.3%), oncocytic adenomatous hyperplasia (8.3%) and ductal proliferation (20.8%). Thus ISGT may contain immature components with a potential for differentiation and proliferation.

Adult↗
PubMed1992

Endothelin-1 increases the pulmonary microvascular pressure and causes pulmonary edema in salt solution but not blood-perfused rat lungs.

Endothelin-1 (ET-1) is a potent vasoactive peptide that has been reported to cause lung edema. This study tested if the edemagenic effect of ET-1 is due to preferential venoconstriction and, if so, whether the site of resistance is similar with salt solution (PSS) and more physiologic blood perfusate. ET-1 caused concentration-dependent contraction of pulmonary arterial and venous rings, with an EC50 of 1.3 nM in artery and 0.6 nM in vein (p less than 0.05). In PSS-perfused lungs, 5 nM ET-1 caused a 7.0 +/- 0.8 torr pressor response that was associated with a 5.0 +/- 0.3 torr increase in microvascular pressure and a 530 +/- 20 mg increase in lung weight within 10 min. In contrast, KCl-treated lungs had an equivalent pressor response (7.4 +/- 1.1 torr), yet the microvascular pressure increased by only 2.5 +/- 0.4 torr (p less than 0.05 from ET-1) and the lung weight was unchanged. Meclofenamate did not prevent the effect of ET-1 on microvascular pressure or lung weight. In blood-perfused lungs, ET-1 caused a 7.3 +/- 0.1 torr pressor response but only a 2.0 +/- 0.5 torr increase in microvascular pressure and no increase in lung weight. ET-1 had no effect on permeability either of cultured endothelial cell monolayers or in the pulmonary microvasculature in vivo. We conclude that the edemagenic effect of ET-1 in PSS-perfused lungs is mediated through venoconstriction and an increase in microvascular pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Comparison of immunological effects of cholera toxin on autoimmune MRL/lpr and BXSB mice.

MRL/lpr and BXSB mice were treated weekly or biweekly with cholera toxin (CT) in intravenous dose of 2 micrograms/mouse. CT treatment notably alleviated proteinuria in MRL/lpr mice, but did not influence the course of lupus nephritis in BXSB male mice. Flow cytometric analysis showed that anomalous B220+ T cells in spleen and thymus were reduced in CT-treated MRL/lpr mice while no significant change in lymphocyte populations was induced in BXSB male mice by this treatment. The suppressive effect of CT treatment on Con A response and the augmentative action on LPS response were observed in MRL/lpr mice. The latter may reflect increased B cells in relative number in the peripheral lymphoid organs. Mitogenic responses in CT-treated BXSB male mice remained unchanged in comparison with those of untreated group. Increased production of IL-6 by spleen cells was demonstrated in MRL/lpr mice treated with CT while in BXSB mice the level of IL-6 was not changed by the treatment with CT. Production of IFN gamma was suppressed by CT treatment in both strains of mice. This may be attributed to the inhibitory effect of CT on IFN gamma-producing Th1 cells as reported previously (Munoz et al, J. Exp. Med. 172: 95-103, 1990). However, CT treatment did not inhibit anti-DNA antibody production in BXSB mice, whereas the autoantibodies were markedly decreased in MRL/lpr mice treated with CT.

Animals↗
PubMed1992

Immunohistochemical and electronmicroscopic studies of obstructive lesions in submandibular glands.

Obstructive sialoadenitis was examined by immunohistochemical techniques for keratin (MoAb KL1, PKK1 and K8.12) and actin. Electronmicroscopy (EMS) was used to identify ultrastructural changes in myoepithelial cells and ductal basal cells. With immunohistochemistry, actin staining was used as a marker of myoepithelium, MoAbs KL1 and PKK1 for ductal luminal cells, and MoAb K8.12 for ductal basal cells. Histologic features of the lesion usually showed degenerative changes of acinar and duct cells with cell infiltration and fibrous replacement. Immunohistochemical findings indicated that actin staining in the changed myoepithelial cells was irregularly positive or negative, and also keratin staining in luminal and ductal basal cells was reduced or disappeared. Ultra-structural features of the changed myoepithelial cells indicated that these cells appeared less altered than adjacent acinar and ductal cells and showed increased amounts of lipid droplets and lipofuscin granules, and also wrinkled processes filled the prominent myofilament material.

Actins↗
PubMed1992

Beta-VLDL-induced cholesterol ester deposition in macrophages may be regulated by neutral cholesterol esterase activity.

We examined the role of enzyme activities involved in cholesterol ester metabolism in the accumulation of cholesterol ester in macrophages. When [3H]cholesterol linoleate-beta-very low density lipoproteins (beta-VLDLs) were incubated with rat resident peritoneal macrophages (RPMs), thioglycolate-elicited macrophages (TEMs), or alveolar macrophages (AMs), cholesterol ester accumulation was the greatest in TEMs and the least in AMs. The uptake of [3H]cholesterol linoleate-beta-VLDL into AMs was four times that into RPMs, and the uptake into TEMs was twice that into RPMs. The [3H]cholesterol released from [3H]cholesterol linoleate-beta-VLDL-loaded AMs was five times higher than from TEMs and RPMs, whereas those from RPMs and TEMs were almost the same. In studies using cell homogenates, the acid cholesterol esterase activity in AMs was 1.7 times that in TEMs and six times that in RPMs. The acyl-coenzyme A:cholesterol acyltransferase (ACAT) activities in AMs and TEMs were similar but were higher than that in RPMs. The neutral cholesterol esterase activity was seven times higher in AMs than in RPMs and TEMs. In the study using intact cells, the hydrolysis of loaded [3H]cholesterol linoleate-beta-VLDL in the presence of the ACAT inhibitor CL277,082 and the cholesterol [14C]oleate synthesis from [14C]oleate were enhanced in AMs about twofold compared with RPMs and TEMs. The reduction of de novo synthesized cholesterol [14C]oleate in the presence of CL277,082 was enhanced in AMs four times compared with TEMs or RPMs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗