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Biomedical subjects

S Mikami

Publications and source records attributed to S Mikami.

At least 73 records · Page 4Linked to original sources
PubMed1987

Effects of vitamin E deficiency on the hormone secretion of the pituitary-gonadal axis of the rat.

Chronological changes of gonadotropin (FSH and LH) and testosterone concentrations in the serum were measured in vitamin E deficient rats to investigate the effects of vitamin E deficiency on the pituitary-gonadal function in rats. The receptor sites and association constant (Ka) for LH and the formation of cyclic AMP in the Leydig cells were also investigated. The results obtained in the present study are as follows: 1) The vitamin E deficient rats showed almost complete hemolysis and extremely increased TBA reacting substances (TBARS) in the serum and liver. 2) The serum LH concentration in the vitamin E deficient group was slightly higher than in the vitamin E supplemented group during the later periods of experiment. 3) The serum FSH concentration in the vitamin E deficient group did not differ significantly from that in vitamin E supplemented group, but became significantly higher than that in the latter at 186 days of experiment. 4) The serum testosterone concentration was always lower in the vitamin E deficient group than in the control. 5) The vitamin E deficient group showed slightly large number of LH/hCG receptor and significantly small Ka (low affinity), as compared with vitamin E supplemented group. The formation of cyclic AMP by Leydig cells decreased significantly in vitamin E deficient group. These results suggest that the vitamin E deficiency exerted a suppressive effect directly on the gonadal function to decrease the hormone synthesis in the Leydig cells and caused the increased secretion of pituitary LH owing to the feedback mechanism.

Animals↗
PubMed1986

Studies on immunological assay of vitamin K dependent factors. I. Measurement of factor VII antigen by radioimmunoassay.

A radioimmunoassay (RIA) for factor VII was developed using 125I-factor VII, anti-factor VII rabbit serum and anti-rabbit IgG goat serum. The lower limit of sensitivity in normal reference plasma was 3 X 10(-3) units/ml. Although the level of factor VII antigen (VII:Ag) in normal plasma samples (n = 20) 0.944 +/- 0.176 units/ml, correlated with that of factor VII coagulant activity (r = 0.89), VII:Ag level in paired normal sera showed a higher value (1.469 +/- 0.376 units/ml). The level of antigen according to RIA of factor VIIa activated by factor Xa increased 2.5-fold compared with that of unactivated factor VII. It is suggested that the polyclonal anti-factor VII produced in a rabbit had higher affinity for factor VIIa than for factor VII. In two out of seven patients with congenital factor VII deficiency, VII:Ag was detectable (0.04, 0.31 units/ml, respectively) whereas VII:C was less than 0.01 units/ml. In 12 warfarin-treated individuals, VII:C showed a lower level (0.121 +/- 0.063 units/ml) that that of VII:Ag (0.518 +/- 0.186 units/ml). During 4 weeks observation after stopping warfarin, VII:C and VII:Ag reached normal levels in 1 week. However, VII:C did not reach equivalence with VII:Ag until 4 weeks had elapsed.

Animals↗
PubMed1986

Studies on immunological assay of vitamin K dependent factors. II. Comparison of four immunoassay methods with functional activity of protein C in human plasma.

We describe and compare five assay systems for Protein C (PC) in human plasma; a functional assay for PC activity, Laurell electroimmunoassay with EDTA or calcium (EDTA-Laurell or Ca-Laurell), radioimmunoassay (RIA) and immunoradiometric assay (IRMA). The lower limit of sensitivity of PC in normal reference plasma was 2 X 10(-3) units/ml by RIA and 1 X 10(-4) units/ml by IRMA, but the ratio of maximum binding to blank binding was superior in RIA. In normal plasma (n = 20), there was no significant discrepancy of PC levels between RIA, Laurell (EDTA- and Ca-) and functional assay. In normal serum, PC antigen (PC:AG) measured by Ca-Laurell showed a high value (1.37 +/- 0.24 units/ml) compared to the other assays. PC:AG of a purified sample increased its level by Ca-Laurell method during activation by thrombin. Activated PC (PCa) has decreased affinity for anti-PC rabbit IgG, similarly to decarboxy (warfarinized) PC. In warfarin-treated individuals (n = 12) who were anticoagulated orally for more than 3 weeks, functional activity was lower (0.27 +/- 0.12 units/ml) than that measured by RIA (0.64 +/- 0.12 units/ml) or EDTA-Laurell (0.62 +/- 0.06 units/ml), whereas PC:AG measured by CA-Laurell had a normal value of 0.96 +/- 0.40 units/ml. After stopping administration, the activity showed a gradual increase to the normal at 2 weeks, while PC:AG increased more rapidly to normalize in 1 week.

Animals↗
PubMed1986

Studies on immunological assay of vitamin-K dependent factors. III. A double monoclonal immunoradiometric assay for factor IX antigen.

Two-site immunoradiometric assays (IRMAs) for factor IX antigen (IX:Ag) were developed using a monoclonal antibody (RFF-IX/1) on the solid-phase and either another monoclonal antibody (RFF-IX/4) or a human polyclonal inhibitor antiserum as tracer (M-M and M-I IRMA respectively). The lower sensitivity limits of these two assays for IX:Ag in normal reference plasma were 4 X 10(-4) (M-M IRMA) and 2 X 10(-4) (M-I IRMA) units/ml. In 20 samples of normal plasma, levels of factor IX coagulation activity (IX:C) and of factor IX antigen measured by both IRMAs were highly correlated. Mean values of approximately 1.0 units/ml were obtained in all three assays. In normal serum, IX:Ag levels were lower with means of 0.84 (M-M IRMA) and 0.83 (M-I IRMA) units/ml. 4/25 patients with haemophilia B were CRM neg., two were CRM + and the remaining 19 patients were CRMr variants. In two of these, IX:Ag was detectable by M-I IRMA whilst IX:C and IX:Ag measured by M-M IRMA were undetectable. In plasma from a fetus subsequently terminated on eugenic grounds, IX:C and IX:Ag by both M-M and M-I IRMA were undetectable. In warfarin-treated plasma (n = 12), the level of IX:C was low (mean 0.39 units/ml). The levels of IX:Ag measured by M-M IRMA (mean of 0.80 units/ml) and by M-I IRMA (0.70 units/ml) showed a discrepancy. M-M IRMA reflects the real amount of IX:Ag in warfarinized plasma because both monoclonal antibodies bind to epitopes distant from the light chain carboxylated region. Western blotting of denatured factor IX demonstrated that RFF-IX/1 binds an epitope that is lost after XIa activation. RFF-IX/4 binds the heavy chain. Antigen measured after activation but without denaturing showed loss of 60% reactivity after XIa activation but no change after RVV activation. These data indicate a binding site for RFF-IX/1 within the activation peptide (residues 146-180).

Antibodies, Monoclonal↗
PubMed1986

Effects of vitamin E deficiency and non-biological antioxidant (DPPD) on the function of the pituitary-gonadal axis of the rat.

The effects of vitamin E deficiency on pituitary-gonadal function in rats and the preventive effects of N,N'-diphenyl-p-phenylene diamine (DPPD) administration were examined by measuring levels of pituitary and plasma follicle-stimulating hormone (FSH) and luteinizing hormone (LH), serum and testicular levels of testosterone, and affinity and receptor sites of FSH and LH in the testis by radioimmunoassay, at 180 days after feeding of a vitamin E-deficient diet and DPPD-administered diet. Light and electron microscopic examinations were also performed on the pituitary gland and testis. In the vitamin E-deficient rats, serum and liver alpha-tocopherol concentrations decreased significantly and erythrocyte hemolytic rate and serum and tissue malondialdehyde levels increased significantly. However, the increase of hemolytic rate and malondialdehyde concentration in the vitamin E-deficient rats was somewhat lessened by the administration of DPPD. In the vitamin E-deficient rats, the gonadotropic cells in the pituitary gland manifested accelerated secretory function indicated by enlargement of cells, development of Golgi apparatus and accumulation of secretory granules, while FSH and LH concentrations in the pituitary and serum were not affected by vitamin E deficiency. However, the testosterone concentrations in the plasma and testis were significantly lower in the vitamin E-deficient rats. The decrease of testosterone in plasma and tissue was prevented by the administration of DPPD, while the degeneration of seminiferous tubules was not completely restored by DPPD. It is concluded that DPPD can compensate to some degree for the lack of antioxidative activity due to vitamin E deficiency.

Animals↗
PubMed1985

Fine structure of the epithelia of the vomeronasal organ of horse and cattle. A comparative study.

The vomeronasal organ of both horses and cattle is a tubular structure situated bilaterally at the base of the nasal septum. In frontal plane the shape of its lumen is semilunar to crescent. The sensory epithelium lining the medial wall of the lumen contains receptor, supporting and basal cells with some surface modifications in both species. In the horse, a structure similar to a microprocess was observed among the microvilli of receptor cells. In cattle, a large mass of the cytoplasm of the receptor cell occasionally protrudes to form a bleb-like structure. The supranuclear cytoplasm of the receptor cells contain mitochondria, free ribosomes, rough endoplasmic reticula, Golgi apparatus, lysosomes and multivesicular bodies. Some receptor cells were pyknotic. In both species the respiratory epithelia of the lateral wall of the lumen contain ciliated, non-ciliated and basal cells. In the horse, this epithelium differs from that of other species in evidence of prominent secretory function.

Animals↗
PubMed1985

Immunohistochemical localization of corticotropin-releasing factor (CRF)-containing neurons in the hypothalamus of the Japanese quail, Coturnix coturnix.

Immunohistochemical localization of corticotropin-releasing factor (CRF)-like immunoreactivity in the brain of the Japanese quail was studied by means of the peroxidase anti-peroxidase (PAP) method. CRF-immunopositive perikarya of parvocellular neurons were observed mainly in the nucleus praeopticus medialis and nucleus paraventricularis. Additional perikarya were also detected in the nucleus hypothalamicus posterior medialis in the hypothalamus and in the non-hypothalamic nucleus accumbens, nucleus septalis lateralis and nucleus dorsomedialis and dorsolateralis thalami. No CRF immunoreaction was found to coexist with the vasotocin (Vt)-containing system in comparative examination of consecutive sections treated with anti-vasopressin (Vp) serum. The CRF-immunoreactive fibers were detected mainly in the external layer of the anterior median eminence but not in its posterior division. Unilateral adrenalectomy induced the marked reduction in number of the CRF immunopositive fibers in the anterior median eminence.

Adrenalectomy↗
PubMed1985

Light and electron microscopic immunocytochemistry of the pituitary gland of the tortoise.

The pars distalis of the tortoise, Geoclemis reevesii, was studied immunocytochemically with regards to its fine structure and distribution of different cell types. The pars distalis consists of cephalic and caudal lobes and a zona tuberalis, each with distinct cellular components. The cephalic lobe contains ACTH cells and prolactin (PRL) cells, while the caudal lobe consists of STH (GH) cells, TSH cells and FSH/LH (GTH) cells. The zona tuberalis contains GTH cells and a small number of TSH cells. ACTH cells, found exclusively in the cephalic lobe, are amphophilic cells containing ACTH immunoreactive secretory granules 200-240 nm in diameter. PRL cells occur only in the cephalic lobe and are large oval or columnar cells containing large secretory granules 300-500 nm in diameter. The cells immunoreactive to anti-chicken LH serum are also reactive to anti-chicken FSH serum, and were identified as GTH cells. They are distributed in the caudal lobe and zona tuberalis, with a few in the pars tuberalis. The GTH cells contain numerous secretory granules of varying density and diameter 200-280 nm, and large globules. TSH cells are small rounded cells containing small secretory granules 180-240 nm in diameter, and distributed in the caudal lobe and zona tuberalis. After thyroidectomy, these cells are hypertrophied and develop to thyroidectomy cells containing large vacuoles and a few secretory granules. GH cells are typical orangeophiles distributed in the caudal lobe. They contain secretory granules 200-400 nm in diameter. The zona tuberalis, which covers the antero-lateral portion of the cephalic lobe, is closely similar in cellular constitution to that of caudal lobe. It may presumably be a structure extended from the caudal lobe and not a homologue of the mammalian zona tuberalis.

Adrenocorticotropic Hormone↗
PubMed1984

Immunohistochemistry of the hypothalamic neuropeptides and anterior pituitary cells in the Japanese quail.

The pars distalis of the avian adenohypophysis consists of well-defined cephalic and caudal lobes which are distinct in their cellular constituents. Immunocytochemical investigations on the pituitary hormones of the pars distalis of the Japanese quail reveal five types of secretory cells, adenocorticotropin (ACTH) cells, prolactin (PRL) cells, thyroid-stimulating hormone (TSH) cells, growth hormone GH (STH) cells, and FSH/LH (gonadotropic) cells. The ACTH cells, TSH cells, and PRL cells are restricted to the cephalic lobe, and GH (STH) cells are confined to the caudal lobe, while FSH/LH cells are distributed throughout the cephalic and caudal lobes. The median eminence of birds has distinct anterior and posterior divisions, each with different neuronal components. The avian hypophysial portal vessels also consists of two groups, anterior and posterior. The peculiar arrangement and distribution of the avian hypophysial portal vessels are possibly related to the distribution of neuropeptides in the two divisions of the median eminence and to the cytological and functional differentiation of two lobes of the pars distalis. The localization of perikarya and fibers containing luteinizing hormone releasing hormone (LHRH), somatostatin, vasotocin, mesotocin, corticotropin-releasing factor (CRF), vasoactive intestinal polypeptide (VIP), glucagon, metenkephalin, and substance P in the hypothalamus and median eminence of the Japanese quail has been investigated by means of immunohistochemistry using antisera against the respective neuropeptides. LHRH-, somatostatin-, VIP-, met-enkephalin-, and substance P-immunoreactive fibers are localized in the external layer of the anterior and posterior divisions of the median eminence, while CRF- and vasotocin-reactive fibers are demonstrated only in the external layer of the anterior division of the median eminence. The metenkephalin fibers are thicker in the anterior median eminence but the substance P fibers are more abundant in the posterior division. Mesotocin fibers occur only in the internal layer of the median eminence and neural lobe.

Adrenocorticotropic Hormone↗
PubMed1984

Enhancement of DEN initiation of liver carcinogenesis by inhibitors of NAD+ ADP ribosyl transferase in rats.

The effect of inhibitors of NAD+ ADP ribosyl transferase (ADPRT) on the early stage of liver carcinogenesis of diethylnitrosamine (DEN) was studied by estimating the number and size of gamma-glutamyltranspeptidase (gamma-GTP) positive foci assayed as markers of cell populations initiated by DEN in the rat liver. ADPRT inhibitors investigated were 3-aminobenzamide (ABA), 5-methylnicotinamide (MNAM), and thymidine. A single i.p. injection of ABA at greater than 150 mg/kg body weight (B.W.) enhanced dose-dependently the induction of gamma-GTP positive foci in rat liver initiated by 20 mg/kg B.W. of DEN. The magnitude of the effect was similar to that observed when partial hepatectomy (PH) was performed instead of ABA administration. Single i.p. injections of MNAM or thymidine at a dose of 600 mg/kg B.W. also enhanced the induction of foci in rat liver initiated by the 20 mg/kg dose of DEN. Based on the above results, ABA was used as a representative ADPRT inhibitor for clarifying the mechanisms underlying the effects. Administration of ABA at a dose of 600 mg/kg B.W. was effective in enhancing the induction of foci if given 1 day before DEN, simultaneously to DEN, and 1 day after DEN initiation but it was ineffective if it was given 3 days after DEN or thereafter. Liver cell necrosis was not detectable either by analysis of serum enzymes or histologically 1, 3, 5, 7 and 14 days after 20 mg/kg B.W. of DEN with or without administration of 600 mg/kg B.W. of ABA. No initiating activity was observed for ABA administered at doses of 600 and 1200 mg/kg B.W. as assayed by development of gamma-GTP positive foci. Long term ABA administration in the diet at concentrations of 0.05, 0.1 and 0.2% did not show any promoting activity for liver carcinogenesis initiated by DEN. Furthermore, chronic administration of 0.2% ABA in the diet did not result in detectable toxicity and/or carcinogenic effects. These results suggest that ADPRT and associated DNA repair plays an important role in the early initiating stage of liver carcinogenesis and provide the basis for a new experimental approach to the analysis of the mechanisms of chemical carcinogenesis and in establishing a more sensitive assay system for liver carcinogenesis in rats.

Animals↗