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Biomedical subjects

K Hirokawa

Publications and source records attributed to K Hirokawa.

At least 145 records · Page 8Linked to original sources
PubMed1991

Production of a monoclonal antibody strongly reacting with immature thymic T lymphocytes and its immunohistological application.

A monoclonal antibody Th-5 has been produced against mouse immature thymic lymphocytes and employed to study the process of T cell differentiation in the thymus. Immunohistologically, Th-5 positive thymic T lymphocytes were first found at Day 12 of gestation. They increased in number as well as staining intensity until Day 18 of gestation and decreased thereafter. Th-5 antigen expression was not seen in lymphoid cells in the fetal liver. In the newborn thymus, lymphocytes in the subcapsular layer were still strongly positive, while other cortical lymphocytes became moderately positive for Th-5. Th-5 positiveness was more pronounced in the medulla than in the cortex in the thymus of young adult mice. The staining pattern of Th-5 in the thymus was apparently different from those with other T cell markers (Thy-1, CD3, CD4, CD5, CD8) including J11d, Pgp-1, IL-2R, and 3A10 (TCR gamma delta). Flow cytometric analyses showed that the expression of Th-5 was mostly associated with the Thy-1 antigen. However, the fluorescent intensity of Th-5 gradually declined with ontogenic development of the thymus, and the molecular size of the antigen was approximately 100 kDa, which is different from Thy-1 antigen (25-30 kDa). Considering these findings, the strong expression of Th-5 could be one of the markers of immature thymic T lymphocytes in the early phase of the ontogenic development.

Animals↗
PubMed1991

Up-regulation of thrombomodulin by activation of histamine H1-receptors in human umbilical-vein endothelial cells in vitro.

Previous reports demonstrated that the expression of thrombomodulin (TM) in endothelial cells was modulated by various agents. Although TM was down-regulated by endotoxin or cytokines, up-regulation of TM was accomplished when endothelial cells were stimulated with unphysiologically high concentrations of cyclic AMP derivatives or tumour-promoting phorbol esters. We investigated the expression of TM in human umbilical-vein endothelial cells (HUVECs) by physiological substances that can be released into the bloodstream. Histamine (0.1-10 microM, 1-48 h) increased TM activity, TM antigen in cell lysates and TM mRNA levels, but 5-hydroxytryptamine and bradykinin had no effect. Enhancement of TM activity by histamine was completely blocked by the H1-selective antagonist pyrilamine, whereas the H2-antagonist cimetidine had no effect, showing that histamine up-regulates TM activity via H1-receptors on HUVECs. Enhanced TM activity by histamine and the resultant increase in protein C activation might play a role in a feedback regulation for prevention of vascular thrombosis.

Antigens↗
PubMed1991

Regulatory mechanisms for thrombomodulin expression in human umbilical vein endothelial cells in vitro.

It has been reported that thrombomodulin (TM) expression in endothelial cells is modulated by various agents. We investigated cellular regulatory mechanisms for TM expression in human umbilical vein endothelial cells (HUVECs), incubated with agents, by measuring the time course changes in surface TM activity, total TM antigen in cell lysates, and TM mRNA levels. While dibutyryl cAMP (3 mM) increased TM mRNA levels in HUVECs and was followed by increased TM activity, dibutyryl cGMP had no effect on TM activity. Phorbol myristate acetate (PMA) induced rapid loss of surface TM activity (approximately 8 h) and later increased TM mRNA levels between 4 h and 40 h (maximum at 24 h), resulting in biphasic effects on TM activity. Tumor necrosis factor or interleukin-1 beta suppressed surface TM activity and TM mRNA levels. Internalization/degradation of TM in HUVECs incubated with PMA or cytokines was suggested by co-culture with chloroquine. The decrease in surface TM activity observed was not caused by the release of TM molecules from the cells into the conditioned media. These results suggest that TM activity in HUVECs is modulated by independent mechanisms involving cytoplasmic TM mRNA levels and internalization/degradation of TM molecules. These regulatory mechanisms may involve protein kinase A and protein kinase C-dependent mechanisms but are independent of protein kinase G.

Blotting, Northern↗
PubMed1991

Immunohistological study on brains of Alzheimer's disease using antibodies to fetal antigens, C-series gangliosides and microtubule-associated protein 5.

An immunohistological study of Alzheimer's brains was performed using antibodies to C-series gangliosides and microtubule-associated protein 5 (MAP5), and their staining patterns were compared with those of antibodies to tau and beta-amyloid precursor protein. Antibodies to C-series gangliosides and MAP5, both of which are known to preferentially expressed in the fetal brains, immunostained dystrophic neurites of senile plaques, neurofibrillary tangles and neuropil threads abundant in 3rd and 5th layers in the cerebral cortex, all of which are considered to be pathological hallmarks of Alzheimer's disease. The immunostaining patterns of these structures by antibodies to C-series gangliosides and MAP5 were similar to those by the antibody to tau. These three antibodies also immunostained some neurons in Alzheimer's brain, although their staining patterns were slightly different from one another; i.e., both diffuse and granular patterns were seen by the antibody to tau, but only granular pattern by the antibodies to C-series gangliosides and MAP5. These neurons immunostained by these three types of antibodies appeared to be the precursors of the classical neurofibrillary tangles, as positively stained neurons were not seen in the brains of non-demented cases. The presence of fetal antigens such as the C-series gangliosides and MAP5 in Alzheimer's brain may suggest that regeneration or sprouting of neurons is ongoing in association with the re-induction of gene expression characteristic for the brain in the early stage of development.

Aged↗
PubMed1991

A novel cofactor produced by a thymic epithelial cell line: promotion of proliferation of immature thymic lymphocytes by the presence of interleukin-1 and various mitogens.

Three thymic epithelial cell lines (TEC1C5, TEC1-4, and TEC2-3) were established from the thymus of newborn C57BL/6 mice. TEC1C5 was revealed to be an interleukin (IL)-1 producing cell line. TEC1-4 produced a cofactor to promote proliferation of double negative (CD4-8-) thymic lymphocytes by the presence of IL-1. Production of the same cofactor was also seen in TEC2-3, but only when it was cultured by the presence of indomethacin. The chemical analysis of the TEC1-4 culture supernatant by ion-exchange column and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the factor was approximately 35 kDa in molecular weight. The present study revealed that a factor produced by TEC1-4 acted as a cofactor to promote the proliferation of immature T cells stimulated by IL-1 and various mitogens and was considered to be a new one in terms of molecular weight.

Animals↗
PubMed1991

Age influence on the thymic capacity to promote differentiation of T cells: induction of different composition of T cell subsets by aging thymus.

Three kinds of experiments were performed to see the differential effect of aging thymus on T cell differentiation in nude mice and thymectomized mice. In the experiment of thymus grafting into nude mice, the thymic capacity to promote T cell differentiation was the highest at newborn stage, and declined to 80% of the peak level at as early as 1 week of age. The level at 4 weeks of age was 50-60% of the peak level and did not greatly change thereafter with advancing age of thymus donors, up to 24 months of age. However, composition of T cell subsets differed with age of thymus graft; i.e. L3T4(CD4)+ T cells were more easily induced than Lyt-2(CD8)+ T cells by aging thymus, resulting in an increase of the ratio of L3T4+/Lyt-2+ T cells with advancing age of thymus donors. The decreased number of T cells and their subsets in the mice thymectomized at 4 weeks of age could be almost totally recovered by the grafting of newborn thymus, but less efficiently by the grafting of 24-month-old thymus. In the latter case again, L3T4+ T cells were more easily induced than Lyt-2+ T cells, resulting in an increase of the ratio of L3T4+/Lyt-2+ T cells by the grafting of the old thymus. In neonatal mice thymectomized 3 days after the birth, Lyt-2+ T cells were more severely affected than L3T4+ cells, resulting in high ratio of L3T4+/Lyt-2+ T cells. It was suggested that the capacity of the thymus to induce T cells started to decline as early as 1 week of age and did not greatly change between 4 weeks and 24 months of age. However, the composition of T cell subsets induced by the thymus changed with age, with preference for L3T4+ T cells over Lyt-2+ T cells.

Aging↗
PubMed1991

The biosynthesis of thrombomodulin and its enhancement by dibutyryl cAMP in a human megakaryoblastic cell line, UT-7.

Thrombomodulin (TM) is an endothelial cell membrane glycoprotein which modulates coagulation via the formation of thrombin-TM complexes. We investigated the human megakaryoblastic cell line (UT-7) for the presence of functional TM on the cell surface and in cell lysates using a specific enzyme-linked immunosorbent assay, a functional assay, and analysis by fluorescent activated cell sorter. We also examined the effect of cyclic nucleotides on TM in UT-7 cells. Quiescent UT-7 cells contained TM protein in cell lysates, but no TM antigen was observed on the cell surface. Dibutyryl cyclic AMP up-regulated TM: UT-7 cells transiently expressed functional TM antigen on the cell surface via de novo synthesis of TM protein resulting from increased TM mRNA levels. In contrast, dibutyryl cyclic GMP did not significantly affect TM antigen levels. The results suggest that megakaryocytes produce TM antigen and protein kinase A are involved in cellular mechanisms of TM expression.

Bucladesine↗
PubMed1991

Determination of interleukin 2 receptor number of Con A stimulated human lymphocytes with aging.

Defective proliferative responses of lymphocytes from elderly donors to various mitogens have been reported in numerous studies. The aim of the present work was to monitor the kinetic response of lymphocytes obtained from elderly and young individuals regarding the Con A stimulated proliferative response and IL-2 receptor expression. The studies were performed by flow cytometric analysis using FITC conjugated anti-IL-2 receptor monoclonal antibody. The data obtained show that beside a detectable decrease in the proliferative capacity of peripheral blood lymphocytes from elderly subjects, the mean IL-2 receptor number/cell did not decrease, but even slightly increased under ConA stimulation. The pattern of distribution of IL-2 receptor positive lymphocytes is different in young and elderly individuals. These data suggest that the decreased proliferative response observed with aging is not due to the decrease of IL-2 receptor number, but most probably to an altered post-receptorial signal transduction mechanism, coupled to changes in responsive cell populations.

Adult↗
PubMed1991

[Observation of cellular communication in the corneal endothelium using a small molecular weight fluorescent dye].

The metabolic and functional connection between corneal endothelial cells is thought to depend on the transfer of small molecules via gap junctions, as has been reported for other tissues. Cell-to-cell communication in the corneal endothelium was studied by monitoring the spread of fluorescence following the direct injection of Lucifer Yellow CH into single endothelial cells of the excised rabbit cornea. The image of the endothelial cells was observed during the injection and post-injection periods using specular microscopy and fluorescence microscopy. In the fresh cornea, the dye transferred readily from the injected endothelial cell to its neighbors. In damaged cells, dye transfer was slower or did not occur. After 5 hours of incubation in tissue culture medium 199, the specular microscopic image degraded, lowered cell membrane potential and decreased dye transfer rate were measured. This study showed that in normal corneal endothelial cells there were efficient cell communication channels between neighboring cells, and as the endothelium becomes less viable, cell communication is inhibited.

Animals↗
PubMed1990

Distribution of immunoglobulins and secretory component in gastric cancer of the aged.

The secretory immune system plays an important role in the local humoral immunity of the gastrointestinal tract. In order to evaluate humoral immunity in gastric cancer, distribution of immunoglobulins (Ig) and secretory component was immunohistochemically studied in 74 early and 15 advanced primary gastric cancers. In non-cancerous gastric mucosa, IgA and IgM, and secretory component were mainly identified in the cytoplasm of the intestinal metaplasia. In early gastric cancer of well-differentiated type, the localization of IgA and IgM, and secretory component was similar to that of intestinal metaplasia. In advanced gastric cancer, they were faintly observed and showed low positivity. The number of Ig-containing cells infiltrating cancerous stroma was enumerated. Immunoglobulin A-containing cells were dominant in the stroma of early gastric cancer. On the other hand, there were few Ig-containing cells in the stroma of advanced gastric cancer, and the number of IgA-containing and IgM-containing cells was also decreased. These results suggest that local humoral immunity is suppressed in gastric cancer, especially in advanced gastric cancer.

Aged↗
PubMed1990

Expression of the human MHC, HLA-DQW6 genes alters the immune response in C57BL/6 mice.

In an attempt to obtain direct evidence for the critical role of HLA class II molecules in regulating the immune response, genomic genes for alpha- and beta-chains of HLA-DQw6 from HLA-Dw12 haplotype were introduced into the C57BL/6 (B6) strain of mouse and a line of HLA-DQw6 transgenic mouse was obtained. Tissue specificity of the expression of the transgenes was much the same as that of murine I-Ab genes. DQw6 molecules were expressed on B cells and macrophages in spleen cells and about 30 to 40% of the I-Ab+ spleen cells were positive for DQw6. The HLA-DQw6 transgenic B6 mouse became tolerant to the DQw6 molecules, as evidenced by the MLR and antibody production specific to the DQw6 molecules. The HLA-DQw6 transgenic B6 mouse showed a strong immune response to streptococcal cell wall antigen (SCW), whereas the B6 mouse was a low responder to SCW. The SCW-specific T cell line was established from the transgenic mouse and this T cell line recognized SCW in the context of HLA-DQw6 molecules expressed on the mouse L cell transfectant or on human monocytes. The proliferative response to SCW of primed lymph node T cells and the SCW-specific T cell line derived from the transgenic mice was inhibited by anti-HLA-DQ mAb. Thus, it is clear that the HLA-DQw6 genes acted as major histocompatibility genes in these transgenic mice.

Animals↗
PubMed1990

A comparison of patterns of metastasis in gastric cancer by histologic type and age.

Patterns of metastasis were examined in 173 autopsy cases of gastric cancer in which the primary tumor had not been resected and the death was mainly caused by growth and metastasis of the cancer. The results were compared by different histologic types as well as different age groups. From the histologic viewpoint, gastric cancer of glandular type showed preferential metastasis to the liver, whereas the nonglandular type showed a preference for peritoneal involvement and lymph node metastasis. With regard to age, peritoneal involvement was more frequently observed in younger patients for both glandular and nonglandular types. Younger patients also had a higher incidence of lymph node metastasis of gastric cancer of nonglandular type, but not for the glandular type. Regarding liver metastasis, there was no difference in incidence between different age groups.

Adult↗
PubMed1990

Deficiency of kallikrein-like enzyme activities in cerebral tissue of patients with Alzheimer's disease.

We examined the changes in the intracerebral activities, at the time of postmortem autopsy, in patients with Alzheimer's disease. When compared with the control group, the activity of kallikrein-like enzyme was significantly decreased, while prolyl endopeptidase activity increased, in the patients group. Aprotinin inhibited 50% of the activity of the former enzyme at 2 x 10(-7) M. Taken together with the results of a multivariate study, the above findings may indicate that intracerebral kallikrein deficiency plays an important role in the pathogenesis of Alzheimer's disease.

Aged↗
PubMed1990

Immunohistological study of senile brains by using a monoclonal antibody recognizing beta amyloid precursor protein: significance of granular deposits in relation with senile plaques.

Immunochemical analyses revealed that a monoclonal antibody Am-3 recognized beta amyloid precursor protein (beta APP) in senile plaques extracted from Alzheimer's brain, but did not recognize beta amyloid protein. Immunohistochemically, however, the staining pattern of Am-3 in frozen section of Alzheimer's brain was almost the same with that of rabbit polyclonal antibody to beta amyloid peptide which could recognize both beta amyloid protein and beta APP. In other words, beta APP was present in senile plaques of various types, cerebrovascular amyloid and granular deposits. The granular deposits were 5-10 microns in size and laminarily distributed in the 1st, 3rd and 4th layers of cerebral cortex. They were especially abundant in 1st and 4th layers where senile plaques were usually fewer in number. Although the distribution in the cerebral cortex was different between the senile plaques and the granular deposits, the number of the granular deposits was well correlated with that of senile plaques. The granular deposits were negative in Congo-red birefringence, but contained beta amyloid protein as well as beta APP fragment judging from positive staining by both Am-3 and polyclonal antibody to synthetic beta amyloid peptide. Thus, they could be regarded as "pre-amyloid".

Aged↗
PubMed1990

Age-related hyperplasia of the thymus and T-cell system in the Buffalo rat. Immunological and immunohistological studies.

This report describes the development of hyperplasia of both the thymus and the peripheral T-cell system with advancing age in the Buffalo rat. Buffalo/Mna rats do not show age-related thymic involution, but rather develop thymic hyperplasia with advancing age. This thymic growth is expansile and there is no infiltration of the surrounding tissues. Because the enlarging thymus occupies the thoracic cavity, most of the rats die of respiratory failure by the age of 24 months. Thymic enlargement is due to primary hyperplasia of cortical epithelial cells and the large number of proliferating lymphocytes. The hyperplastic epithelial cells are bizarre in shape and strongly positive when stained with Th-3 monoclonal antibody (MoAb), anti-thymosin antibody and anti-EGF antibody, but negative with Th-4 MoAb. The patterns of distribution of CD-5+, CD-4+ and CD-8+ lymphocytes within the hyperplastic thymus are similar to those seen in young rats of other species. The high level of T-cell emigration from the thymus to the periphery appears to persist throughout life, since the percentage of normal splenic T-cells also increase with advancing age and exceed 70% of the total by 24 months of age. This thymic enlargement with abnormal hyperplasia of cortical epithelial cells can be prevented by hypophysectomy.

Aging↗
PubMed1990

Immunohistological study on the distribution of alpha 1-antichymotrypsin in Alzheimer's brain, compared to beta-amyloid precursor protein and beta-amyloid protein.

Distribution of alpha 1-antichymotrypsin was immunohistologically examined in Alzheimer's brains and compared with those of beta-amyloid precursor protein and beta-amyloid protein. Immunoblotting study revealed that alpha 1-antichymotrypsin existed in senile plaques extracted from Alzheimer's brain. Immunohistologically, rabbit polyclonal antiserum to alpha 1-antichymotrypsin reacted not only with well-defined amyloid deposits such as typical, primitive, core plaques and cerebrovascular amyloid, but also with so-called preamyloid deposits including large amorphous materials (diffuse plaques), subpial amorphous materials and granular deposits. The staining pattern of alpha 1-antichymotrypsin was almost the same as those of beta-amyloid precursor protein and beta-amyloid protein. The present study indicated that alpha 1-antichymotrypsin could play an important role in the formation of various kinds of amyloid deposits including preamyloid ones in Alzheimer's brain.

Aged↗