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Biomedical subjects

M Oka

Publications and source records attributed to M Oka.

At least 577 records · Page 32Linked to original sources
PubMed1988

Stimulatory effect of vasoactive intestinal polypeptide on catecholamine secretion from isolated guinea pig adrenal chromaffin cells.

The stimulatory effect of vasoactive intestinal polypeptide (VIP) on catecholamine (CA) secretion from isolated guinea pig adrenal chromaffin cell was studied. VIP (1-10 microM) induced dose-dependent CA secretion, which was slow and continued for at least 30 min. This VIP-induced CA secretion was dependent on the presence of Ca2+ in the medium, but no significant increase in Ca2+ uptake by the cells was observed during their stimulation with VIP. Studies on the intracellular free Ca2+ level ([Ca2+]i) using fura-2 showed that acetylcholine and muscarine induced a marked increase in the [Ca2+]i, but that VIP induced only a slight increase. Thus VIP may induce CA secretion by increasing the sensitivity of the secretion of CA to Ca2+.

Adrenal Medulla↗
PubMed1988

Muscarinic stimulation of guinea pig adrenal chromaffin cells stimulates catecholamine secretion without significant increase in Ca2+ uptake.

In isolated guinea pig adrenal chromaffin cells, not only nicotine, but also muscarine stimulated catecholamine (CA) secretion, the stimulation by muscarine being the greater. The secretions of CA by muscarine and nicotine were both dependent on the presence of Ca2+ in the medium, but only the latter was associated with a rapid increase in 45Ca2+ uptake. Experiments with the fluorescent Ca2+ indicator quin 2, showed that muscarine caused an increase in cytoplasmic free Ca2+ concentration [( Ca2+]i). Moreover, the intracellular Ca2+ antagonist 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) inhibited both CA secretion and increase in [Ca2+]i induced by muscarine. These results indicate that in isolated guinea pig adrenal chromaffin cells, nicotine stimulated CA secretion by increasing Ca2+ uptake by the cells, whereas muscarine stimulated CA secretion by mobilizing Ca2+ from the intracellular pool.

Adrenal Medulla↗
PubMed1988

Antibodies against native type II collagen do not precede the clinical onset of rheumatoid arthritis.

Serum levels of IgG and IgM antibodies to native human type II collagen were determined in 22 pre-illness sera from subjects who developed seropositive rheumatoid arthritis (RA) 4 months to 5 years after sera were obtained, in 51 specimens from 35 healthy controls, and in 4-5 specimens from 58 patients with recent-onset RA. The antibody levels in all pre-illness serum specimens fell within the range seen for the healthy controls. Four RA patients had an IgG class antibody level and 4 had an IgM class antibody level that was above the highest level observed for controls, in at least 1 serum sample. No significant difference in the mean level of anticollagen antibodies was observed in the followup specimens from RA patients.

Adolescent↗
PubMed1988

Apatite-wollastonite containing glass ceramic-fibrin mixture as a bone defect filler.

The purpose of this study was to evaluate the usefulness of a mixture of apatite-wollastonite containing glass ceramic (A-W.GC, 42-60 mesh in granule size) with fibrin as a bone defect filler. A bone defect was drilled in the proximal metaphysis of the rat tibia and was filled with (1) fibrin glue, (2) A-W.GC granules, or (3) A-W.GC-fibrin mixture. Nothing was placed in the defect of the controls. The animals were serially sacrificed until 8 weeks after the operation, and the defect site was histologically examined and histomorphometrically analyzed for quantitative evaluation of newly formed bone and blood vessels. The use of fibrin glue as the binder markedly increased the ease of handling the A-W.GC granules. In the controls, little trabecular regeneration was observed in the defect site. Early vascularization (confirmed by microangiography) increased and the repairing process was accelerated in the defects filled with fibrin. In these defects filled with A-W.GC granules, good bone formation was observed around the granules. Bone formation was accelerated in the defects filled with A-W.GC fibrin mixture. Thus, the mixture showed good osteoconductive potential as well as acceleration of the repair process. Therefore, A-W.GC-fibrin mixture is considered to be a useful bone defect filler.

Animals↗
PubMed1988

Strength of bonding between A-W glass-ceramic and the surface of bone cortex.

We examined the bonding strength of apatite- and wollastonite-containing glass-ceramics (A-W.GC) to the surface of bone cortex. Semi-column-shaped blocks of A-W.GC were fixed with screws on the surface of the tibiae of rabbits. The blocks of alumina-ceramic were used as the control. The load required to detach the implant from the surface of bone cortex was measured 2, 4, 8, and 25 weeks after the implantation. The bonding strength between A-W.GC and the surface of bone cortex increased with time. It increased remarkably 4 weeks after the implantation, suggesting that the chemical bonding advanced rapidly between 2 and 4 weeks after the implantation. The tensile strength of bonding reached a maximum of 15.1 +/- 3.1 kg/cm2 25 weeks after the implantation. The shear strength of bonding reached a maximum of 17.1 +/- 2.3 kg/cm2 25 weeks after the implantation. From these studies, we conclude that A-W.GC has a capability of making relatively quick bonding to the surface of bone cortex.

Animals↗
PubMed1988

Dopamine 4-sulfate: effects on isolated perfused rat heart and role of atria.

We studied the effects of sulfate conjugate of dopamine on the isolated perfused rat heart (Langendorff preparation). In the experimental group, we removed atria from half number of the hearts. In the hearts with intact atria, dopamine 4-sulfate significantly improved the DT (developed tension), +dT/dt max (maximal rate of contraction), -dT/dt max (maximum rate of relaxation) over baseline values. But when atria were removed, dopamine 4-sulfate had no effect on the mechanical functions of heart. We analysed the effluent perfusate for the free and conjugated catecholamines. In the control group (no drug), and when atria were excised, the free catecholamine levels were negligible. But when the atria were kept intact, the effluent contained significant amount of free dopamine (DA), and norepinephrine (NE). These data suggested that dopamine sulfate had no direct effect on the ventricular muscle of rat heart, but was converted within the atrial tissues into free catecholamines which might be responsible for the positive inotropic actions.

Animals↗
PubMed1988

Squamous cell carcinoma antigen in the serum of oromaxillary cancer.

Squamous cell carcinoma (SCC) antigen levels in sera and several tissues were estimated in patients with oral and maxillary cancer. The normal value of serum SCC antigen level was 1.7 ng/ml in this experiment, and 43.3% of squamous cell carcinoma was positively higher than 1.7 ng/ml as a whole, including cases of carcinoma in situ and of recurrence and metastasis in the oral region. In relation to the clinical staging of tumors, 20.0% in stage I, 14.3% in stage II, 42.9% in stage III, and 77.8% in stage IV were positive for SCC antigen. In the group with definite regional lymph node metastases, 80% of patients revealed a higher value than the normal cut-off value. Patients with recurrent SCC demonstrated elevated SCC antigen values in sera except 1 case with an early condition of recurrence. Serum SCC antigen also presented good responses to various cancer treatments. The measurement of SCC antigen does not appear to be useful for the detection of early stage oral and maxillary SCC; however, for detection of recurrence and for lymphatic and/or remote metastases in the follow-up period, it would appear that SCC antigen level would be some value.

Adult↗
PubMed1988

A novel class of potential central nervous system agents. 3-Phenyl-2-(1-piperazinyl)-5H-1-benzazepines.

A series of 3-phenyl-2-piperazinyl-5H-1-benzazepines and related compounds were synthesized and evaluated for potential neuroleptic activity. The preparation of these compounds was carried out by 2,3-dichlorination of 3-phenyl-2,3,4,5-tetrahydro-1H-1-benzazepin-2-ones with phosphorus pentachloride followed by amination and concurrent dehydrochlorination. Compounds having the 4-chloro or 4-fluoro substituent in the 3-phenyl group were found to possess the neuroleptic-like activity. Among them, 2-(4-methyl-1-piperazinyl)-3-(4-fluorophenyl)-5H-1-benzazepine dihydrochloride (23) was comparable to chlorpromazine in inhibiting exploratory activity, conditioned avoidance response, and self-stimulation response and more potent than chlorpromazine in antagonizing apomorphine-induced emesis. These neuroleptic effects may be based on an antidopaminergic property of the compound. In causing catalepsy or ptosis, however, 23 was weaker than chlorpromazine. Therefore, this ring system is of interest as a novel class of neuroleptics. Some compounds having the 7-chloro or 7-bromo substituent showed potent anticonvulsant effects against maximal seizures induced by electroshock or pentylenetetrazole.

Animals↗
PubMed1988

Polyclonal B-cell stimulative and immunosuppressive activities at different developmental stages of Trypanosoma gambiense.

Bloodstream trypomastigote and cultured procyclic (insect midgut) forms of a monomophic strain of Trypanosoma gambiense were tested for their abilities to induce polyclonal B-cell activation (PBA) and immunosuppression (IS) in mice. Injection of a cell homogenate of bloodstream trypomastigotes induced both PBA and IS, while neither PBA nor IS was observed in mice injected with a cell homogenate of cultured procyclics. The results indicate that the substance(s) inducing PBA or IS is related to the developmental stage of the parasites.

Animals↗
PubMed1988

Requirement of ATP for exocytotic release of catecholamines from digitonin-permeabilized adrenal chromaffin cells.

Cultured chromaffin cells were preincubated with digitonin to deplete endogenous ATP from the cell cytoplasm. Catecholamine release from these digitonin-pretreated cells was then studied in the presence and absence of exogenous ATP to elucidate a possible involvement of the cytoplasmic ATP in the exocytotic process. The preincubation of the cells with digitonin in the ATP-free permeabilizing medium resulted in a marked decline of the releasing response to a calcium challenge. Furthermore, the declined activity of catecholamine release caused by digitonin pretreatment was restored by the presence of ATP, but not by other adenine nucleotides, and this recovery was observed in a manner dependent on the concentration of ATP. These findings, therefore, seem to indicate that a decrease in the releasing activity of the digitonin-pretreated cells may be due to the removal of endogenous ATP from the cytoplasmic space of the cells, thus suggesting that the cytoplasmic ATP may be involved in the exocytotic mechanism of catecholamine secretion.

Adenosine Diphosphate↗
PubMed1988

Value of joint scintigraphy in the prediction of erosiveness in early rheumatoid arthritis.

The value of scintigraphy in predicting development of new erosions in small peripheral joints was studied by visual evaluation of scintigrams and by three computerised methods. In 13 patients with newly diagnosed rheumatoid arthritis a total of 387 joints were examined clinically, scintigraphically, and radiographically. The follow up period was 24 months. Four eroded joints in three patients were found at the onset. Of the joints which were to become eroded, 46/47 were scintigraphically active at all the check ups. Erosions were detected earlier in foot joints than in finger joints. New erosions were especially prone to appear in joints with persisting and high scintigraphic activity. On the contrary, inactive joints by repeated scanning never eroded. Scintigraphic and clinical activity and radiographic erosiveness correlated significantly with each other. The sensitivity and specificity of visual scintigraphic assessment and the relative pixel activity method proved to be superior to the region of interest methods and clinical evaluation for prediction of erosiveness.

Adult↗
PubMed1988

Bronchoalveolar lavage in primary pulmonary lymphoma with monoclonal gammopathy.

We performed bronchoalveolar lavage in a patient with pulmonary lymphoma and IgM lambda monoclonal serum gammopathy previously not diagnosed accurately by histologic examination and not treated for 5 yr after detection of a pulmonary infiltrate. The infiltrate increased slowly in size accompanied by coughing and sputum and a gradual increase in serum IgM throughout the 5-yr period. High IgM in the lavage fluid was noted with an IgM/albumin ratio 4.8 times higher in the lavage fluid than in the serum. Protein immunoelectrophoresis of the lavage fluid was identical to that of the serum. A primary pulmonary lymphoma was diagnosed on the basis of findings in the lavage fluid. The patient showed decreased serum IgM and marked improvement of the infiltrate by chemotherapy and radiation. Thus, bronchoalveolar lavage, including analysis of the proteins in lavage fluids, appears to be a simple and useful method for diagnosing primary pulmonary lymphomas.

Aged↗
PubMed1988

Influence of reduction of cytoplasmic ATP on catecholamine secretion from intact and digitonin-permeabilized adrenal chromaffin cells.

The effect of the metabolic inhibitor 2,4-dinitrophenol (DNP) on the concentration of cytoplasmic ATP and the activity of catecholamine secretion was studied using cultured bovine adrenal chromaffin cells. The pretreatment of the cells with DNP resulted in a decrease in the concentration of cytoplasmic ATP. Catecholamine secretion evoked by either carbamylcholine or high K+ was also reduced by DNP pretreatment. Oligomycin caused a significant decrease in both cytoplasmic ATP concentration and catecholamine secretion. In contrast, neither the ATP level nor the secretory response was affected by 2-deoxyglucose. Similarly, catecholamine release from digitonin-permeabilized chromaffin cells in response to a direct calcium challenge was reduced by pretreatment of the cells with DNP, and this reduction was partially prevented by the presence of ATP in the permeabilizing medium. These results suggest that ATP in the cell cytoplasm may play an important role in the regulation of catecholamine secretion as a factor modulating the activity of the exocytotic process in the adrenal chromaffin cell.

Adenosine Triphosphate↗
PubMed1988

Relation between bone erosions and rheumatoid factor IgA and IgM isotypes in recent onset rheumatoid arthritis.

In this prospective study 58 patients with early rheumatoid arthritis were followed up for two years with six-monthly assessments including rheumatoid factors (RF) of IgA and IgM subtypes. Initial and mean serum levels of IgA-RFs were raised in patients with an erosive disease course in comparison to non erosive disease. The cases with initially increased serum levels of RFs of both isotypes developed more eroded joints in their hands and feet during the study period than the rest of the patients. None of the differences, however, were statistically significant. Of the tested parameters only clinical rheumatoid activity (Mallya-index) was significantly related to the number of eroded joints during the follow-up. We conclude that serum IgA-type RFs are raised in erosive RA, but the determination of RFs of any kind cannot be used to prognosticate erosiveness.

Adolescent↗
PubMed1988

Glidobactins A, B and C, new antitumor antibiotics. I. Production, isolation, chemical properties and biological activity.

New antitumor antibiotic glidobactins A, B and C were isolated from the cultured broth of a gliding bacterium, Polyangium brachysporum sp. nov. No. K481-B101. They are novel molecules carrying the common cyclic tripeptide nucleus substituted with different alpha, beta, gamma, delta-unsaturated fatty acids. Glidobactins exhibit broad inhibitory activity against fungi and yeasts, and prolong the life span of mice inoculated with P388 leukemia cells.

Animals↗