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Biomedical subjects

K Kojima

Publications and source records attributed to K Kojima.

At least 667 records · Page 37Linked to original sources
PubMed1984

A possible prebiotic peptide formation from glycinamide and related compounds.

We examined an experimental approach to the genesis of protocells in the primeval sea. Glycine polymers with an average chain length of 12 were formed from glycinamide in fluctuating systems (pH 7.2, 80 degrees C, 20 cycles). The resulting glycine polymers gave aggregated leaflet-like structures. A solution of the glycine polymers provided stacked disc-shaped structures in the presence of LiBr and gave sheet structures in the presence of dichloroacetic acid. The shapes of these organized structures were correlated with their molecular structures.

Glycine↗
PubMed1984

Detection of inactive or less active forms of tyrosine hydroxylase in human adrenals by a sandwich enzyme immunoassay.

A sensitive sandwich enzyme immunoassay for tyrosine hydroxylase (TH) from bovine and human adrenals has been developed. Anti-TH antibody was prepared from bovine adrenal TH. The assay system consisted of an antibody F(ab')2 immobilized on polystyrene beads as a solid phase and of beta-D-galactosidase-conjugated antibody. This method was highly sensitive and specific for the assay of TH. Human adrenal TH level was determined by similar sensitivity as bovine adrenal TH, suggesting the presence of common antigenic sites between human and bovine adrenal enzymes. The presence of inactive or less active forms of TH in human adrenals was revealed by purification of the enzyme and monitoring with this enzyme immunoassay as well as with enzyme activity assay.

Adrenal Glands↗
PubMed1984

Dihydropyridine calcium agonist and antagonist effects on aldosterone secretion.

The effects of the dihydropyridine calcium antagonists nimodipine, nitrendipine, and nisoldipine were studied on K+-induced and angiotensin II (ANG II)-induced aldosterone secretion from isolated calf adrenal glomerulosa cells. These drugs were more effective inhibitors of K+-induced secretion than ANG II-induced secretion. However, when the ANG II-induced release of intracellular calcium was blocked by prior treatment of cells with dantrolene, then nitrendipine was equally as effective in blocking ANG II- as K+-induced secretion. On the other hand, the dihydropyridine agonist, BAY K8644, was found to enhance K+-induced secretion to a greater extent than ANG II-induced secretion when the latter was studied in either the absence or presence of dantrolene. It is concluded that K+ and ANG II mobilize calcium from different sources for stimulus-response coupling in these cells and that there is no difference in the sensitivity to nitrendipine of the plasma membrane calcium channels operated by these two different agonists.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1984

Changes in the cell membrane of erythrocytes in tumor-bearing rats.

Cell electrophoresis of erythrocytes taken from AH 7974 hepatoma-bearing rats showed a marked decrease in the surface negative charge, as represented by a decrease in cell mobility. This change in the erythrocyte membrane began during the stationary phase of growth of transplanted tumor cells and became more pronounced in the late phase, during which time a marked decrease in the amount of sialidase-sensitive sialic acid present in the plasma membrane also took place. The erythrocytes of AH 7974F-bearing rats (which died from tumor growth much earlier than the AH 7974-bearing rats) had a similar, but less marked, decrease in their electrophoretic mobility and in the amount of sialidase-sensitive sialic acid present. These erythrocytes all had somewhat abnormal cell morphology, their shapes being slightly spherocytic.

Animals↗
PubMed1984

[An evaluation of radioactive colloid for measuring the volume of effective liver].

A methods for liver scintigraphy for finding the effective liver volume were developed. Matrix ROI (region of interest) was set on the anterior liver scintigram with 99mTc tin colloid and 198Au colloid, respectively. The various depths of liver under matrix ROI were calculated from the count rate noting the absorption coefficient. The effective liver volume was the sum total of the areas of matrix ROI to the various depths. In order to check the accuracy of this method, the effective liver volume was calculated using the liver phantom and the patient's liver scintigraphy. The volume obtained for the liver phantom was nearly equal to the real volume. The liver volume in 19 patients using 99mTc tin colloid and 198Au colloid showed good correlation with the volume as measured by computed tomography (CT) scan (r = 0.841, r = 0.749).

Aged↗
PubMed1984

Some recent pharmacological findings with nitrendipine.

The available evidence indicates that nitrendipine and other dihydropyridines with a similar pharmacological action exert their therapeutic effects by inhibiting Ca2+ channels. In our recent experiments, nitrendipine was shown to block K+-stimulated 45Ca2+ uptake and K+-induced contractions of isolated rabbit aortic rings. Its IC50 were 4.7 and 8.9 nM for inhibition of Ca2+ uptake and of contractions, respectively. There was no statistically significant difference between the two values. At higher concentrations, nitrendipine also reduced norepinephrine-induced 45Ca2+ uptake and norepinephrine-induced contractions of rabbit aortic strips. The norepinephrine-induced contractions were only slightly (21%) reduced by nitrendipine at 10 microM. Nitrendipine at 10 nM and higher concentrations inhibited K+- or angiotensin-II-(AII) induced release of aldosterone from isolated bovine adrenal glomerulosa cells. The drug was more potent and more effective in inhibiting K+- than AII-induced aldosterone release. Dantrolene, 25 microM, enhanced the inhibitory activity of nitrendipine on AII-stimulated aldosterone release. Acute renal failure produced by either glycerol or gentamicin in rats was antagonized by nitrendipine at oral doses of 15-25 mg/kg/day. Our studies confirmed previously reported observations that the usefulness of nitrendipine in the treatment of hypertension may be determined not only by its vasodilator action. We demonstrated that nitrendipine has a direct inhibitory effect on the release of aldosterone from adrenal glomerular cells. In addition to a previously described diuretic action, nitrendipine was shown to have renal cytoprotective activity.

Acute Kidney Injury↗
PubMed1984

Monoclonal antibodies to surface antigens of small cell carcinoma of the lung.

Monoclonal antibodies to membrane antigens of human small cell carcinoma of the lung were produced by fusion of P3X63/Ag8U1 mouse myeloma cells with spleen cells from BALB/c mice immunized against the intact cells of the small cell carcinomas grown in BALB/c nude mice. The hybrids were screened for antibody production using intact cells in a solid-phase radioimmunoassay or in a membrane fluorescence with a fluorescence-activated cell sorter. Four monoclonal antibodies were chosen that demonstrated reactivities with human small cell carcinoma of the lung and not with apparently normal diploid fibroblasts or lymphoblastoid cells. The antibodies designated as TFS-1 and TFS-2 rather demonstrated "pancarcinoma" reactivity, showing binding to the other types of lung cancer (adenocarcinoma, squamous cell carcinoma, and large cell carcinoma) and carcinomas derived from other organs, such as colon, pancreas, or stomach. The monoclonal antibodies TFS-3 and TFS-4 preferentially bound to small cell carcinoma cells and neuroblastoma cells, but not to non-small cell carcinomas (adenocarcinoma, squamous cell, or large cell). Especially, TFS-4 did not bind to a variety of other normal or malignant cells. Immunoprecipitation of the antigens by monoclonal antibodies and sodium dodecyl sulfate:polyacrylamide gel electrophoresis revealed that they had different molecular weights.

Animals↗
PubMed1984

Calcium as intracellular messenger: sensitivity modulation, C-kinase pathway, and sustained cellular response.

A model of information flow in the calcium messenger system is presented. When Ca2+ serves as an intracellular messenger in cells exhibiting a sustained response to an extracellular messenger, there are two branches by which information flows from cell surface to cell interior: One operates via amplitude modulation of calmodulin-regulated reactions and the other via sensitivity modulation of the calcium-sensitive, phospholipid-dependent protein kinase, C-kinase. It is postulated that the calmodulin branch is largely responsible for initiating, and the C-kinase branch for sustaining, cellular response in cells displaying sustained responses. The role of the C-kinase branch in the calcium messenger system provides a type of gain control in the process of cell activation. It is but one element of several which provides a considerable degree of plasticity in the operation of this cellular control system. Both cAMP and the biologically active intermediates of arachidonic acid metabolism--prostaglandins, thromboxanes, prostacyclin, and leukotrienes--provide additional inputs into this messenger system and a means of extending its adaptability to specific control needs. In particular, in some cell types it is possible that the cAMP messenger system provides the means of achieving gain control in the calcium messenger system either as an alternative to the C-kinase branch of the calcium messenger system or as a supplemental pathway to it.

Animals↗
PubMed1984

Analysis of asparagine-linked oligosaccharides from plasma membranes of rat normal liver and ascites hepatoma cells.

Isolated plasma membranes from rat liver and ascites hepatoma cells were shown by SDS-polyacrylamide gel electrophoresis and concanavalin A reactivity to contain a variety of glycoproteins having asparagine-linked oligosaccharides. Membrane oligosaccharides were released by almond glycopeptidase digestion, and the pyridylamino derivatives were analyzed by high-performance liquid chromatography. Forty-four percent of the total carbohydrates in the original membranes were released and suggested to be of the complex type. Hepatoma membranes showed different oligosaccharide patterns from normal.

Animals↗