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Biomedical subjects

H Kaji

Publications and source records attributed to H Kaji.

At least 145 records · Page 8Linked to original sources
PubMed1994

Metabolic activation of nitrodibenzofurans by rat liver in Salmonella/mutagenicity test.

The effect of metabolic activation on the mutagenicity of nitrodibenzofurans (NDF) by rat liver S9 was evaluated with S. typhimurium tester strains. Except for 1-nitrodibenzofuran (NDF), five tested NDFs were mutagenic in strains TA98 and TA98/1,8-DNP6 without S9 mix but were not mutagenic in strain TA98NR. NDFs mutagenized strain TA98NR with S9 mix, and the NAD(P)H system plus 3-methylcholanthrene-induced S9 (3-MC-S9) was the most effective. The specificity of S9 enzyme(s) participating in the activation of NDFs was different from that of endogenous enzyme(s) in strain TA98, i.e., the order of mutagenic potency of NDFs in strain TA98 without S9 mix was 2,8- = 2,7-->3-->2-->4-->1-nitrated dibenzofuran and 2-NDF and 2,8-dinitrodibenzofuran (DNDF) were more mutagenic than 3-NDF and 2,7-DNDF, respectively, in strain TA98NR with S9 mix. The mutagenic potency of 2-NDF, 4-NDF, 2,7-DNDF and 2,8-DNDF in strain TA98NR with S9 mix was stronger than those in strain TA98 without S9 mix and the cytosolic fraction of the 3-MC-S9 accounted for more of the activation than the microsomal fraction. Studies with electron donors and inhibitors indicated that xanthine oxidase and/or NAD(P)H-quinone oxido-reductase (NQOR) participated in the activation of NDFs. The mutagenic potency of NDFs in strain TA98NR with S9 mix (3-MC-S9) was reflected in the induction of NQOR by pretreatment of rats with 3-MC.

Animals↗
PubMed1994

Retention behavior of conjugated metabolites of vitamin D and related compounds in high-performance liquid chromatography.

The retention behavior of sulfates or glucuronides of provitamin D, vitamin D, and 25-hydroxyvitamin D3, together with its fluorescent derivatives, are examined with reversed-phase high-performance liquid chromatography. Inclusion chromatography using cyclodextrin as a mobile-phase additive is also used for this purpose. Conventional reversed-phase high-performance liquid chromatography clearly separates the positionally isomeric conjugates of 25-hydroxyvitamin D3. The addition of the host compound to the mobile phase is effective in separating the pairs of fluorescent derivatives of vitamin-D3 and -D2 conjugates or provitamin-D3 and -D2 conjugates.

Calcifediol↗
PubMed1994

The role of microfilaments and microtubules during pH-regulated morphological transition in Candida albicans.

Yeast cells of Candida albicans produced germ tubes in a salt-glucose medium containing 4% calf serum at pH 7 and 37 degrees C. Hyphal growth continued for 24 h and the filaments did not revert to yeast cells. When cells were grown at pH 4, reversion to yeast growth was observed, despite the presence of serum. The elongation of hyphae was inhibited within 30 min. The distribution of microtubules and microfilaments during pH-regulated morphological transition was studied by an immunofluorescence technique using an antitubulin antibody with a FITC-conjugated secondary antibody, and by staining with tetramethylrhodaminyl phalloidin for filamentous actin and actin granules. After changing to acidic conditions, microtubules were distributed normally in the cytoplasm; however, microfilaments disappeared from hyphal cells, and actin granules were localized at the site of budding. These results show that microfilaments play an important role during pH-regulated morphological transition.

Actin Cytoskeleton↗
PubMed1994

Constitutive c-fos expression in osteoblastic MC3T3-E1 cells stimulates osteoclast maturation and osteoclastic bone resorption.

The effect of culture supernatants of c-fos-transfected MC3T3-E1 osteoblastic cells on osteoclastic bone resorption was studied. Human c-fos cDNA was integrated in the expression vector pH8, and the cells were transfected using the calcium phosphate precipitation technique. Osteoclastic bone resorption was quantified by the pit formation assay, and the osteoclast maturation from precursor was assessed by the generation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNC). The culture supernatants of MC3T3-E1 transfectants constitutively expressing c-fos gene enhanced osteoclast-like MNC formation from haematopoietic blast cells compared with those of control transfectants (P < 0.01). The culture supernatants also promoted osteoclastic bone resorption: the pit number, 118.7 +/- 38.5, was significantly higher than 19.0 +/- 10.1 of the control (P < 0.05). The absorption area, 12,394 +/- 3145 mm2, was significantly larger than 1646 +/- 314 mm2 of the control (P < 0.05). The culture supernatants also promoted bone resorption by purified chick osteoclasts (P < 0.05). The results show that constitutive expression of c-fos gene in osteoblastic MC3T3-E1 cells stimulates osteoclast maturation and osteoclastic bone resorption by releasing humoral mediator(s).

Animals↗
PubMed1994

Negative regulation of hypothalamic growth hormone-releasing factor messenger ribonucleic acid by growth hormone and insulin-like growth factor I.

Increased growth hormone-releasing factor messenger ribonucleic acid (GRF mRNA) and decreased somatostatin (SRIF) mRNA levels have been reported in the hypothalamus of hypophysectomized rats as well as of dwarf mice. In order to elucidate the effect of the growth hormone-insulin-like growth factor I (GH-IGF-I) axis on hypothalamic GRF and SRIF synthesis, we measured levels of mRNA coding for GRF and SRIF and for pituitary GH in pubertal male rats treated for 3 weeks with antirat GRF gamma-globulin (GRF-ab), anti-SRIF gamma-globulin (SRIF-ab) or both. Immunoneutralization of circulating endogenous GRF resulted in a marked decrease in serum IGF-I and pituitary GH mRNA levels in Northern blot analysis, whereas it caused a significant increase in GRF mRNA levels in the arcuate nucleus as assessed by both Northern blot and in situ hybridization analysis. SRIF mRNA levels in the periventricular nucleus were slightly decreased by GRF-ab treatment when analyzed by in situ hybridization, but not significantly after Northern blot analysis. Immunoneutralization of circulating endogenous SRIF failed to affect mRNA levels of hypothalamic GRF and SRIF but caused a slight reduction in pituitary GH mRNA levels. Levels of mRNA coding for hypothalamic GRF and pituitary GH were also measured by Northern blot analysis in young male rats treated with rat GRF-ab for 2 weeks and replaced with rat GH or IGF-I for the second 1 week. Replacement with either rat GH or IGF-I suppressed the increased hypothalamic GRF mRNA levels. These data indicate that endogenous GRF is essential for normal synthesis of pituitary GH and that both GH and IGF-I negatively regulate the synthesis of hypothalamic GRF.

Animals↗
PubMed1994

Molecular genetics of growth hormone-releasing factors.

To elucidate the effects of GRF on GH synthesis and of the GH-IGF-I axis on hypothalamic GRF synthesis, we measured the mRNA levels of hypothalamic GRF and pituitary GH in pubertal male rats treated for 3 weeks with antirat GRF gamma-globulin (GRF-ab), antisomatostatin gamma-globulin (SRIF-ab) or both. Immunoneutralization of circulating endogenous GRF resulted in a marked decrease in serum IGF-I and pituitary GH mRNA levels in Northern blot analysis, whereas it significantly increased GRF mRNA levels in the arcuate nucleus in both Northern blot and in situ hybridization analysis. Immunoneutralization of circulating endogenous SRIF failed to affect GRF mRNA levels but caused a slight reduction in pituitary GH mRNA. Then, we examined the effect of systemic replacement with rat GH or IGF-I for 1 week on GRF mRNA levels in the hypothalamus of rats treated with GRF-ab for 2 weeks. Replacement with either rat GH or IGF-I significantly suppressed the increased hypothalamic GRF mRNA levels. These data indicate that endogenous GRF is essential in normal synthesis of pituitary GH and that both GH and IGF-I negatively regulate the synthesis of hypothalamic GRF.

Amino Acid Sequence↗
PubMed1994

Carboxyl-terminal parathyroid hormone fragments stimulate osteoclast-like cell formation and osteoclastic activity.

The controversy still exists about the biological activity of carboxyl (C)-terminal PTH fragments. The present study was performed to examine the effect of C-terminal PTH fragments on osteoclast-like cell formation and bone-resorbing activity. In contrast to human (h) PTH-(1-34) or hPTH-(1-84), any C-terminal fragments examined [hPTH-(35-84), hPTH-(53-84), and hPTH-(69-84)] did not affect cellular cAMP production and intracellular calcium in osteoblastic UMR-106 cells. Although hPTH-(1-84) caused an increase in cAMP production and intracellular calcium less effectively than hPTH-(1-34) in UMR-106 cells, the former caused a stimulation of osteoclast-like cell formation in osteoblast-containing mouse bone cell cultures more effectively than the latter. All of the C-terminal fragments significantly stimulated osteoclast-like cell formation, and their effectiveness seemed to depend on the amino acid length of the fragments. The conditioned medium from UMR-106 cells pretreated with C-terminal PTH as well as amino-terminal PTH significantly stimulated osteoclast-like cell formation from mouse hemopoietic blast cells supported by granulocyte-macrophage colony-stimulating factor. Moreover, all of the C-terminal fragments stimulated osteoclast-like cell formation from hemopoietic blast cells even in the absence of osteoblasts, and their effectiveness seemed to depend on the length of fragments. As for bone-resorbing activity by mature osteoclasts, all of the C-terminal fragments stimulated bone resorption in osteoblast-containing mouse bone cell cultures, whereas these fragments did not affect the bone-resorbing activity of isolated rabbit osteoclasts. The present study first indicates that C-terminal PTH fragments stimulate osteoclast-like cell formation as well as bone-resorbing activity by mature osteoclasts in the presence of osteoblasts and accelerate osteoclast-like cell formation from hemopoietic blast cells in the absence of osteoblasts.

Animals↗
PubMed1994

Calcitonin inhibits osteopontin mRNA expression in isolated rabbit osteoclasts.

Recent evidence indicates that osteopontin (Opn), one of the bone matrix proteins, plays an important role in the attachment of osteoclasts to bone matrix. Besides being elaborated by osteoblasts, this protein is also produced by osteoclasts. The present study was performed to examine the effect of calcitonin (CT) on Opn mRNA expression of isolated rabbit osteoclasts and to clarify the second messenger signaling of this effect. Eel CT inhibited Opn mRNA expression as well as bone-resorbing activity of isolated rabbit osteoclasts. Eel CT caused a transient increase in intracellular calcium followed by a sustained increase as well as an increase in cAMP production in these cells. Dibutyryl-cAMP (10(-4) M) and Sp-cAMPS (10(-4) M), an activator of cAMP-dependent protein kinase (PKA), as well as A23187 (10(-7) M), a calcium ionophore, and phorbol myristate acetate (10(-7) M), an activator of protein kinase C (PKC), caused a significant inhibition of Opn mRNA expression, and suppressed bone-resorbing activity of isolated osteoclasts. The present study is the first to demonstrate that CT inhibits Opn mRNA expression in isolated rabbit osteoclasts, presumably through the activation of PKA and calcium/PKC pathways, by which the bone-resorbing activity might be attenuated subsequently.

Animals↗
PubMed1994

Lymphocytic hypophysitis, pustulosis palmaris et plantaris and eosinophilia.

We describe here a unique case of lymphocytic hypophysitis accompanied by pustulosis palmaris et plantaris and eosinophilia. The patient also suffered from panhypopituitarism with hyperprolactinemia and pituitary diabetes insipidus caused by lymphocytic hypophysitis. Complications of pustulosis palmaris et plantaris and eosinophilia with lymphocytic hypophysitis have not been reported previously. In the present case, the activities of the three diseases correlated well throughout the patient's course, suggesting that a common mechanism might possibly participate in their pathogenesis.

Adult↗
PubMed1994

Expression of basic fibroblast growth factor (FGF-2) messenger ribonucleic acid is regulated by testosterone in the rat anterior pituitary.

Evidence from in vivo studies supports the concept that growth factors are involved in the function of endocrine organs. We studied the effects of target endocrine organs (thyroid, adrenals, and gonads) on levels of basic fibroblast growth factor (FGF-2) messenger ribonucleic acid (mRNA) in the anterior pituitary and the hypothalamus of male rats using RNase protection assays. Castration significantly reduced the levels of FGF-2 mRNA in the anterior pituitary, but not in the hypothalamus. This decrease was restored by testosterone administration. The regulation of pituitary FGF-2 mRNA involves a specific hormone, i.e. testosterone, since neither adrenalectomy nor chemical thyroidectomy affects the expression of the gene for FGF-2.

Adrenalectomy↗
PubMed1994

Regulation of the growth hormone (GH) receptor and GH-binding protein mRNA.

In fasting rats, a transient increase in growth hormone-binding protein (GHBP) mRNA levels was observed after 1 day, in muscle, heart, and liver, but not in fat tissues. The liver GH receptor (GHR) mRNA level was significantly increased after 1 day (but not after 5 days) of bovine GH (bGH) treatment in fed rats. Both the liver GHR mRNA level and the net increment of plasma IGF-I markedly decreased after 5 days of bGH administration in fasting rats. These findings suggest that GHR and GHBP mRNAs in the liver are expressed in a different way and that the expression of GHBP mRNA is regulated differently between tissues, at least in rats. The results also suggest that refractoriness to GH in a sustained fasting state might be beneficial in preventing anabolic effects of GH. In humans, GHR mRNA in lymphocytes, from subjects with either GH-deficiency or acromegaly, could be detected by the reverse transcription-polymerase chain reaction method. In one patient with partial GH insensitivity, a heterozygous missense mutation (P561T) was identified in the cytoplasmic domain of GHR.

Animals↗
PubMed1993

Determination of blood and urine manganese (Mn) concentrations and the application of static sensography as the indices of Mn-exposure among Mn-refinery workers.

Early detection of neurophysiological abnormalities is believed to be most effective for the early diagnosis of chronic manganism. The static sensography was applied during the periodical health examination and the significance of total distance of the postural sway (i. e. postural sway index) as a neurophysiological index was studied in relation to the blood and urine manganese concentrations. Sixty-six workers in a manganese (Mn)-refining factory, aged 29-59 (mean 47) years, were examined from 1984 to 1989. Mn-exposed workers had been engaged in alternating shifts and the mean duration of Mn exposure was 22.6 years before the health examination in 1984. Air-borne dust and Mn levels in the working environment were 0.07-2.74 mg/m3 and 0.02-0.46 mg/m3. The mean values of the parameters in Mn-exposed workers fluctuated as follows: blood Mn concentrations 19.1-26.9 micrograms/l [control; Mean 17.8 (Standard deviation 5.2) micrograms/l], urine Mn concentration 2.60-4.22 micrograms/g Creatinine [control; Geometric mean 1.16 (Geometric standard deviation 1.93) micrograms/g Creat.] and postural sway index 51.4-94.6 cm/30 sec [control; Geometric mean 59.7 (Geometric standard deviation 1.4) cm/30 sec.]. Although there were no significant correlations between the postural sway index and blood and urine manganese concentrations, the usefulness of this kind of simple neurophysiological test should be further investigated in combination with other established examinations.

Adult↗
PubMed1993

Molecular cloning of the gene for bilirubin oxidase from Myrothecium verrucaria and its expression in yeast.

Myrothecium verrucaria bilirubin oxidase (EC 1.3.3.5) is an enzyme catalyzing the oxidation of bilirubin to biliverdin and other substrates. We have purified bilirubin oxidase from the medium of M. verrucaria and determined its partial amino acid sequence and isolated cDNA fragment amplified by polymerase chain reaction using oligonucleotide primers designed on the basis of the partial amino acid sequence. The gene for bilirubin oxidase has been cloned from a genomic library using the cDNA fragment as a probe. The gene encodes a precursor of bilirubin oxidase consisting of 572 amino acid residues, which comprises the prepro-region of 38 amino acid residues and the mature enzyme of 534 amino acid residues containing one cysteine. Five introns were found within the coding region. Sequence comparison of bilirubin oxidase with other blue copper proteins (laccase, ascorbate oxidase, human ceruloplasmin, plastocyanin, and azurin) revealed the presence of four domains corresponding to potential copper ligands. We have expressed this bilirubin oxidase gene in Saccharomyces cerevisiae under the repressible acid phosphatase promotor and found an active recombinant bilirubin oxidase, establishing the functional identity of the gene.

Amino Acid Sequence↗
PubMed1993

Involvement of dual signal transduction systems in the stimulation of osteoclast-like cell formation by parathyroid hormone and parathyroid hormone-related peptide.

The present study was performed to examine whether parathyroid hormone (PTH) and parathyroid hormone-related peptide (PTHrP) would stimulate osteoclast-like cell formation via soluble factor(s) released from osteoblasts and, if so, to characterize the involvement of PTH/PTHrP-responsive dual signal transduction systems [cAMP-dependent protein kinase (PKA) and calcium/protein kinase C(PKC)]. Osteoblasts-conditioned medium (CM) was obtained from rat osteoblastic osteosarcoma cells (UMR-106 cells), which had been cultured in serum free medium for 24 hrs after treatment with various kinds of reagents. The CM of osteoblasts treated with either 10(-7) M human(h) PTH-(1-34) or 10(-7)M hPTHrP-(1-34) equally stimulated osteoclast-like cell formation from hemopoietic blast cells derived from mouse spleen cells, although the CM treated with 10(-8) M 1,25dihydroxyvitamin D3 failed to affect it. The CM treated with both 10(-4) M dibutyryl-cAMP and a direct PKA activator, 10(-4)M Sp-cAMPS significantly increased osteoclast-like cell formation. The CM treated with a PKC activator, 10(-7)M phorbol 12-myristate 13-acetate (PMA) and calcium ionophores (10(-7)M A23187 and 10(-7)M ionomycin) also significantly enhanced osteoclast-like cell formation. The present study first indicated that osteoblast-mediated stimulation of osteoclast-like cell formation by PTH and PTHrP, and the participation of PTH/PTHrP-responsive dual signal transduction systems of osteoblasts in the stimulation of osteoclast-like cell formation by PTH and PTHrP.

Animals↗
PubMed1993

The regional distribution of thyrotropin-releasing hormone receptor messenger ribonucleic acid in the brain.

Messenger ribonucleic acid (mRNA) from mouse brain was reversely transcribed and complementary deoxyribonucleic acid (cDNA) encoding transmembrane domains (TM) 3 through TM6 of the thyrotropin-releasing hormone receptor (TRH-R) could be amplified by polymerase chain reaction (PCR). The partial cDNA of TRH-R was identical to that of the pituitary in size and sequence. The regional distribution of reverse transcription PCR products (partial cDNA of TRH-R) was similar to that of TRH-Rs themselves, except in cerebellum where TRH-R mRNA levels were relatively higher than the levels of TRH-Rs themselves previously reported.

Animals↗
PubMed1993

Effects of high calcium concentration on the functions and interactions of osteoblastic cells and monocytes and on the formation of osteoclast-like cells.

The present study was performed to clarify the role of high calcium concentration and the appearance of mononuclear cells at the resorptive site in bone remodeling. Our recent study revealed that the high concentration of extracellular calcium ([Ca2+]e) stimulated DNA synthesis in osteoblastic MC3T3-E1 cells not only directly but also indirectly via monocytes. Human monocyte-conditioned medium (CM) significantly stimulated DNA synthesis and inhibited alkaline phosphatase (ALP) activity. In contrast, when monocytes were cultured at high [Ca2+]e concentrations (more than 3 mM), CM from these monocytes significantly stimulated ALP activity in MC3T3-E1 cells. Such stimulatory effect of CM was not observed at a high magnesium concentration (Mg2+, 5 mM). Treatment of monocytes with the calcium ionophore A23187 did not affect the CM-induced effect on DNA synthesis and ALP activity in these cells. To determine the migration potency of MC3T3-E1 cells and monocytes toward the high [Ca2+]e, chemotaxis assay was performed. The increasing [Ca2+]e (more than 3 mM) induced a chemotactic response of MC3T3-E1 cells as well as monocytes, but the high concentration of Mg2+ (5 mM) did not induce it. On the other hand, treatment with high [Ca2+]e (more than 3 mM) or CM significantly inhibited the 1,25-(OH)2D3-induced formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNC) from their precursors derived from mouse spleen cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1993

Structural and functional changes of exocrine pancreas induced by FK506 in rats.

BACKGROUND: The pancreas has been reported as a possible target for FK506 toxicity. This study was conducted to examine the effects of FK506 on the structure and function of pancreatic acinar cells. METHODS: Male Sprague-Dawley rats received an intramuscular injection of saline or FK506, and pancreatic acini were isolated on the day of sacrifice. RESULTS: FK506 caused a time-dependent suppression in amylase secretory response to cholecystokinin or carbachol at days 3-14, and increases in amylase and trypsinogen content at days 7-14. The properties of cholecystokinin and scopolamine binding sites in acini were not altered by FK506. Amylase release by A23187 and secretin were decreased by FK506, but those by phorbol ester 12-O-tetradecanoylphorbol-13-acetate, forskolin, 5'-cyclic adenosine monophosphate and vasoactive intestinal peptide were not changed. Increases in cytosolic free calcium concentration induced by cholecystokinin were not changed by FK506. Histologically, a significant increase in cytoplasmic zymogen granules was observed in pancreas from FK506-treated rats. CONCLUSION: These data suggest that FK506 induced changes in function and metabolism in pancreatic acinar cells, and these changes might be caused by altering postreceptor loci in stimulus-secretion coupling.

Amylases↗