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Biomedical subjects

K Chihara

Publications and source records attributed to K Chihara.

At least 19 recordsLinked to original sources
PubMed1995

Neurokinin receptor antagonists inhibit the binding of growth hormone-releasing peptide to EP-1 human neuroblastoma cells.

KP-102, a second generation growth hormone-releasing peptide, specifically bound to the human neuroblastoma cell line, EP-1, cultured in vitro with a Kd value comparable to that in cell membranes of rat pituitary and hypothalamus. By crosslinking study, the molecular size of the KP-102-receptor complex was found to be approximately 80kDa. Substance P analogue, as well as nonpeptidyl antagonists of the neurokinin receptor, competed with KP-102 in its binding to EP-1 cells, although neither substance P nor substance K affected the binding. These results suggest that KP-102 binds to a receptor-like molecule resembling neurokinin receptor.

Alprostadil↗
PubMed1995

Cholecystokinin-B/gastrin receptor: a novel molecular probe for human small cell lung cancer.

The brain-gut hormones, gastrin and cholecystokinin, have a trophic effect on the gastrointestinal mucosa in vivo and promote the growth of several neoplastic cell lines. In this study, cholecystokinin-B/gastrin receptor has been demonstrated to provide a novel molecular marker for the diagnosis of small cell lung cancer by using biopsy specimens. Physiological expression of the receptor mRNA is detectable in particular areas of the human brain, stomach, and pancreas but not in the lung. The receptor mRNA was detected selectively in all small cell lung cancer (10 cases) with a RT-PCR assay. By contrast, it was detectable in only 1 of 13 squamous cell carcinomas or 21 adenocarcinomas of the lung. Thus, the cholecystokinin-B/gastrin receptor could be an attractive therapeutic target for small cell lung cancer.

Adenocarcinoma↗
PubMed1995

EDA-containing fibronectin is synthesized from rheumatoid synovial fibroblast-like cells.

OBJECTIVE: To identify the cells that synthesize EDA-containing fibronectin (FN) and examine the role of EDA+FN in the pathogenesis of rheumatoid joint lesions. METHODS: Localization of EDA+FN and c-Fos protein in rheumatoid joints was studied immunohistochemically by utilizing antibodies for EDA+FN and c-Fos. Expression of EDA+FN was studied by immunoelectron microscopy and in situ hybridization. The amount of EDA+FN was measured by enzyme-linked immunosorbent assay. RESULTS: EDA+FN was specifically localized in the synovial lining layer of synovium with active rheumatoid arthritis (RA) (n = 17), but not in that with osteoarthritis (n = 4) or with inactive fibrous RA (n = 2). EDA+FN messenger RNA was localized in the synovial lining layer. EDA+FN was immunoelectron microscopically localized in the synovial lining fibroblast-like (type B) cells. EDA+FN was also detected at the cartilage-pannus junction and on the surface of RA cartilage. Double staining showed that EDA+FN colocalized with c-Fos protein in the rheumatoid synovial lining layer. Quantification of EDA+FN showed that it was highly concentrated in rheumatoid synovial fluids. CONCLUSION: EDA+FN is synthesized by the synovial lining fibroblast-like (type B) cells in situ in rheumatoid synovium, and appears to be expressed in association with activated or transformed states of synovium.

Animals↗
PubMed1995

Competition between c-fos and 1,25(OH)2 vitamin D3 in the transcriptional control of type I collagen synthesis in MC3T3-E1 osteoblastic cells.

Interaction between c-fos and 1,25(OH)2 vitamin D3 (VD) on the type I collagen synthesis was studied. VD inhibited collagen synthesis and type I collagen mRNA expression in MC3T3-E1 osteoblastic cells. In contrast, VD reversed the inhibition of collagen synthesis and mRNA expression of the c-fos transfectants that overexpressed c-fos gene to a comparable level as those of the control transfectants. The gel shift assay showed the vitamin D receptor (VDR) complex binding to vitamin D responsive element (VDRE) was inhibited under constitutively expressed c-fos gene, suggesting that c-fos gene product, c-Fos, may inhibit the binding of VDR complex to VDRE by making a c-Fos-VDR complex. The result suggests the existence of a fine tuning between c-fos and VD in the bone metabolism which may be relevant to the pathogenesis of rheumatoid bone lesion.

3T3 Cells↗
PubMed1995

Retinoic acid induces osteoclast-like cell formation by directly acting on hemopoietic blast cells and stimulates osteopontin mRNA expression in isolated osteoclasts.

Although retinoic acid (RA) has been considered to be a bone-resorbing agent both in vivo and in vitro, its mechanism remains still unclear. The present study was performed to examine the effect of RA on osteoclast-like cell formation in the presence or absence of osteoblasts and to study whether RA would affect osteopontin mRNA expression in isolated rabbit osteoclasts. RA (10(-8) and 10(-6) M) significantly stimulated the formation of osteoclast-like cell in osteoblast-containing mouse bone cell cultures. Also, RA caused a stimulation of osteoclast-like cell formation from hemopoietic blast cells supported by granulocyte macrophage-colony stimulating factor (GM-CSF) in mouse spleen cell cultures. However, RA did not affect blast cell number in these cultures and significantly inhibited GM-CSF-stimulated proliferation of hemopoietic blast cells. On the other hand, RA stimulated the bone-resorbing activity of mature osteoclasts in mouse bone cell cultures. Moreover, RA caused a stimulation of osteopontin mRNA expression in isolated rabbit osteoclasts. The present study demonstrated for the first time that RA stimulated osteoclast-like cell formation, presumably through directly acting on the hemopoietic blast cells, and that RA stimulated osteopontin mRNA expression in isolated rabbit osteoclasts.

Animals↗
PubMed1995

Effect of fasting and growth hormone (GH) administration on GH receptor (GHR) messenger ribonucleic acid (mRNA) and GH-binding protein (GHBP) mRNA levels in male rats.

To elucidate whether GHR and GHBP are coordinately regulated or not, we studied the effect of fasting with or without GH administration on the GHR and GHBP mRNAs in the liver as well as in extrahepatic tissues in rats. Tissues were collected from 7-week-old male rats by decapitation 1,3, and 7 days after the start of fasting. Liver GHR mRNA levels were not affected 1 day after the start of fasting but progressively decreased for the subsequent 3 and 7 days of fasting as compared with those in control rats fed ad libitum. In contrast, liver GHBP mRNA levels significantly rose after 1 day fasting, returned to the control level after 3 days and further reduced after 7 days of fasting. Changes in GHBP mRNA level after fasting were different among the tissues. A transient increase in GHBP mRNA levels was observed in muscle and heart as well as liver, while the GHBP mRNA levels in fat tissues did not change throughout 7 days of fasting. Next, bovine GH(bGH) was administered ip to the fasted rats and control fed rats for either 1 day(100 micrograms [corrected], tid) or 5 days(150 micrograms [corrected], daily). In fed rats, liver GHR mRNA level was significantly increased by 1 day bGH treatment, but after 5 days treatment with bGH it was not different from the level in saline-injected control. Accordingly, net increment of plasma IGF-I was 296.0 ng/ml with 1 day bGH treatment and 234.2 ng/ml with bGH administration for 5 days. In fasted rats, liver GHR mRNA level did not changed after 1 day treatment with bGH, but markedly decreased 5 days after bGH administration. Net increment of plasma IGF-I was slightly reduced to 284 ng/ml with 1 day treatment with bGH, and markedly decreased to 37.0 with bGH administration for 5 days. The effect of GH administration on liver GHBP mRNA level was virtually absent in either fasting or fed state. These findings suggest that GHR and GHBP mRNAs in the liver are expressed in different ways and that expression of GHBP mRNA is differently regulated among tissues.

Animals↗
PubMed1995

Possible discrimination of Gitelman's syndrome from Bartter's syndrome by renal clearance study: report of two cases.

We observed two patients who had hypokalemic metabolic alkalosis as well as hypomagnesemia and hypocalciuria with elevated serum renin levels. In renal clearance studies in our patients using furosemide or thiazide, urine volume and chloride clearance (CCI) were increased after furosemide administration but not after thiazide administration. Furthermore, the distal fractional chloride reabsorption [CH2O/(CH2O + CCI)] was dramatically decreased by furosemide administration in our patients, whereas thiazide had little effect on it, suggesting the presence of a defect in the distal tubule rather than in the thick ascending loop of Henle. These findings are compatible with the concept of Gitelman's syndrome, a variant form of Bartter's syndrome.

Adult↗
PubMed1995

Successful treatment of hyperphosphatemic tumoral calcinosis with long-term acetazolamide.

We describe a patient with tumoral calcinosis, in which acetazolamide (ACZ) was, for the first time, tested for its therapeutic efficacy. The 19-year-old Japanese man had been suffering from multiple recurrent calcific masses with tenderness around the finger, knee, and toe joints since 10 months of age. Radiographs revealed several calcific subcutaneous masses around the finger joints, and calcific myelitis around the right knee joint and in the calvarium. The patient had hyperphosphatemia with elevated maximal threshold of renal phosphate excretion in the presence of normal kidney function and normocalcemia, suggesting a reduced ability to excrete phosphorus in the urine. A delay of disappearance of orally administered phosphate from the blood stream was found. A serum parathyroid hormone (PTH) level was normal, and responses to PTH and ACZ were also normal regarding the induction of phosphaturia. Since the masses tended to recur easily despite repeated surgical resections, we started medical treatment with phosphorus deprivation by oral aluminum hydroxide. However, the drug alone had no effect on hyperphosphatemia or calcific lesions, and ACZ was added in expectation of making the patient's phosphorus balance negative by its phosphaturic effect. Fourteen years of administration of the two drugs apparently improved the patient's symptoms, the biochemical findings, and the calcific lesions on radiographs. Thus, ACZ appeared to be useful for tumoral calcinosis resistant to phosphorus deprivation by aluminum hydroxide alone.

Acetazolamide↗
PubMed1995

Hydrolysis of a carboxy-terminal fragment of parathyroid hormone-related protein by rat kidney: evidence for a crucial role of meprin.

Although parathyroid hormone-related protein (PTHrP) is known to be secreted into the circulation as heterogeneous forms, with its N-terminal and C-terminal fragments as well as the intact form, the fate of these molecules in the plasma has not been fully understood. As for a C-terminal fragment, the kidney seems to be physiologically important in its metabolism, because it is elevated in circulating plasma in patients with chronic renal failure. In this study, we examined the mechanism by which a C-terminal fragment of PTHrP was metabolized by rat kidney and by other rat organs in vitro. When human (h) PTHrP-(109-141) was incubated for 2 h with an extract of rat kidney, it was almost completely hydrolyzed. This hydrolysis was readily blocked by the additions of o-phenanthrolline and dithiothreitol, indicating the participation in this process of a metallo-protease possessing disulfide bonds. This hydrolytic activity showed a meprin-like character, with being sensitive to actinonin but not to phosphoramidon. Furthermore, the participation of meprin itself in this process was directly confirmed by the experiment comparing degradation products of the peptide by the microvillar membranes of rat kidney with those by a purified rat meprin, in which a large part of the metabolites by rat kidney membranes corresponded to those by rat meprin. Among other rat organs examined, the extracts of the small intestine pancreas, spleen and urinary bladder exerted remarkable hydrolytic activities for hPTHrP-(109-141).(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Fasting increases the expression of basic fibroblast growth factor (FGF-2) messenger ribonucleic acid in rat hypothalamus.

Basic fibroblast growth factor (FGF-2) has been isolated from the brain, but the regulation of FGF-2 synthesis in the brain is not yet fully understood. Since exogenously administered FGF-2 has been reported to suppress food intake as well as the secretion of gastric acid and pepsin in rats, we examined the effect of fasting on FGF-2 mRNA levels in the hypothalamus and the cerebral cortex of male rats, using RNase protection assay. Fasting for 72 h resulted in an approximately 2-fold increase in FGF-2 mRNA level in the hypothalamus but did not affect FGF-2 mRNA level in the cerebral cortex significantly. These findings support the hypothesis that FGF-2 plays a significant role in regulation of hypothalamic function.

Adrenalectomy↗
PubMed1995

Establishment of a myeloid leukaemic cell line (SKNO-1) from a patient with t(8;21) who acquired monosomy 17 during disease progression.

A novel cell line SKNO-1 was established from the bone marrow cells of a 22-year-old male suffering from acute myeloblastic leukaemia (AML) M2 with t(8;21) whose disease became resistant to chemotherapy after acquisition of 17 monosomy. SKNO-1 has been maintained for more than 36 months as a granulocyte-macrophage colony-stimulating factor (GM-CSF) dependent line. Morphologically, SKNO-1 cells were myeloblasts somewhat matured. The cells grow in suspension with a doubling time of 48-72 h. The survival and growth of SKNO-1 cells was absolutely dependent on granulocyte-macrophage colony stimulating factor (GM-CSF). SKNO-1 cells possessed t(8;21) and monosomy 17 which were observed in original leukaemic cells. We confirmed that the AML1 gene, located on chromosome 21, was rearranged and the AML1-MTG8 fusion transcript was expressed in SKNO-1 cells. Over-expression and mutation of the p53 gene were also detected in SKNO-1. It is likely that alterations of AML1 or MTG8 gene and p53 gene contribute to a disease progression in this case. Since t(8;21) translocation is a common chromosome abnormality in AML, and inactivation of the p53 gene may play a crucial role in disease progression in AML, SKNO-1 would be a useful tool for analysing the molecular mechanisms in myeloid leukaemogenesis.

Adult↗
PubMed1995

Human TRH receptor messenger ribonucleic acid levels in normal and adenomatous pituitary: analysis by the competitive reverse transcription polymerase chain reaction method.

OBJECTIVE: Little is known about the mechanism of diversity in in-vivo hormonal responsiveness to TRH in patients with functional pituitary adenomas. In order to clarify the relation between the responsiveness to TRH and TRH receptor messenger ribonucleic acid (mRNA) expression, we attempted to measure TRH receptor mRNA levels in human pituitary adenoma tissues by competitive reverse transcription polymerase chain reaction (RT-PCR) method. PATIENTS: Pituitary tissue samples were obtained at autopsy from 5 patients without pituitary disease. Pituitary adenoma tissue samples were obtained at surgery from 18 patients with pituitary adenoma (4 non-functioning, 8 prolactinoma, 4 acromegaly, 1 Cushing's disease and 1 FSH producing adenoma). METHODS: Partial TRH receptor cDNA from a human GH producing adenoma cDNA library was amplified by PCR under low stringency conditions using primers encoding the transmembrane domains III and VI of pituitary TRH receptor cDNA. The partial sequence of the amplified cDNA determined by a dideoxy-chain termination method was identical to the corresponding sequence of human TRH receptor cDNA. A competitor was generated by deleting the inner 111 bp from the amplified TRH receptor cDNA and subcloning. RNA extracted from human pituitary was reverse transcribed and co-amplified with competitor by PCR under higher stringency conditions. The TRH receptor mRNA levels, expressed as the relative intensity against the amplified levels of competitor, were compared among various pituitary tissues. RESULTS: The relative TRH receptor mRNA levels of pituitary tissues in patients without pituitary disease were detectable and variable (M +/- SD) (0.370 +/- 0.231, n = 5), and slightly but not significantly lower than those in patients with pituitary tumours (0.598 +/- 0.265, n = 18). In patients with prolactinoma, the relative levels of TRH receptor mRNA were quite variable (0.02-1.170, 0.604 +/- 0.358, n = 8) and not correlated with PRL responsiveness to TRH (responder 0.457; non-responder 0.340-0.950). In patients with acromegaly, TRH receptor mRNA was detectable not only in the paradoxical GH responder to TRH (0.718) but also in the non-responder (0.758 and 0.765). In one patient with Cushing's disease, a relatively low level of TRH receptor mRNA could be detected (0.415). In the patient with a FSH producing tumour whose plasma FSH did not respond to TRH, a small amount of TRH receptor mRNA was detectable (0.447). CONCLUSIONS: In patients with functioning pituitary adenomas, hormonal responsiveness to TRH in vivo might not be assessable by TRH receptor mRNA levels in the adenoma cells.

Adenoma↗
PubMed1995

Regional distribution of growth hormone-releasing hormone (GHRH) receptor mRNA in the rat brain.

We examined the tissue distribution of growth hormone-releasing hormone (GHRH) receptor mRNA in the rat brain because several lines of evidence have suggested that GHRH plays a functional role in the brain. GHRH receptor mRNA was detected in the hypothalamus as well as pituitary, but not in olfactory bulb, caudate putamen, cerebral cortex, hippocampus, cerebellum, or brainstem by RNase protection assay. To clarify the precise localization of GHRH receptor mRNA in the hypothalamus, reverse transcription-polymerase chain reaction (RT-PCR) was used. A PCR product of the predicted size (564 bp) was detected in the periventricular, arcuate, and ventromedial nuclei, and the anterior hypothalamic area, but not in the paraventricular nucleus in the hypothalamus. These areas where GHRH receptor mRNA was detected are possible sites of GHRH action. Another band, smaller in size than that of the predicted PCR amplification product, was detected in the anterior hypothalamic area and arcuate nucleus, respectively. Hybridization analysis with a cDNA probe for GHRH receptor demonstrated that the smaller bands as well as that of the predicted size corresponded to GHRH receptor cDNA. The role of the short form of the GHRH receptor remains unknown.

Animals↗
PubMed1995

Carboxyl-terminal peptides from parathyroid hormone-related protein stimulate osteoclast-like cell formation.

The role of the carboxyl (C)-terminal portion of PTH-related protein (PTHrP) in bone resorption continues to be controversial. The present study was performed to examine the effect of C-terminal PTHrP peptides on osteoclast-like cell formation as well as bone resorption in mice. C-Terminal PTHrP peptides [human (h) PTHrP-(107-139) and hPTHrP-(107-111); 10(-10)-10(-8) M] stimulated osteoclast-like cell formation in a concentration-dependent manner in osteoblast-containing mouse bone cell cultures. Moreover, osteoclast-like cells newly formed by these peptides possessed the ability to form pits on the dentine slices. The conditioned medium from UMR-106 cells and MC3T3-E1 cells pretreated with the C-terminal peptides did not affect osteoclast-like cell formation from mouse hemopoietic blast cells derived from spleen cells. The C-terminal peptides as well as hPTHrP-(1-34) stimulated osteoclast-like cell formation from mouse hemopoietic blast cells in the absence of osteoblasts, although both amino- and C-terminal peptides were unable to support hemopoietic blast cells. Protein kinase-C inhibitors (H-7 and staurosporine) almost completely inhibited the stimulation of osteoclast-like cell formation by the C-terminal peptides in both the presence and absence of osteoblasts. The C-terminal peptides did not affect bone resorption by mature osteoclasts in osteoblast-containing mouse bone cell cultures. The present study indicates that C-terminal PTHrP peptides possess the ability to stimulate osteoclast-like cell formation in both the presence and absence of osteoblasts, possibly through the pathway involving protein kinase-C activation.

Animals↗
PubMed1995

Effects of 22-oxacalcitriol on bone metabolism in vitro: comparison with calcitriol--effects of 22-oxacalcitriol on osteoclast-like cell formation and bone-resorbing activity.

22-Oxacalcitriol (OCT), a synthetic vitamin D3 analog, can mimic the ability of calcitriol to differentiate leukemia and skin cells, to enhance the immune response and to suppress parathyroid hormone secretion, but has much less calcemic activity than that of calcitriol. The mechanism of this selective action remains not fully understood, and the actions of OCT on bone metabolism are little known. The present study was, therefore, designed to investigate the effects of OCT and calcitriol on: the proliferation and functions of osteoblastic MC3T3-E1 cells; osteoclast-like cell formation from hemopoietic blast cells in the absence of stromal cells as well as from unfractionated bone cells in the presence of stromal cells; bone resorption; and the proliferation of MC3T3-E1 cells via monocytes. 22-Oxacalcitriol and calcitriol inhibited [3H]thymidine (TdR) incorporation, alkaline phosphatase activity and collagen synthesis of MC3T3-E1 cells to a similar degree. Both OCT (10(-10)-10(-8) mol/l) and calcitriol significantly and similarly stimulated osteoclast-like cell formation from both hemopoietic blast cells and unfractionated bone cells. 22-Oxacalcitriol (10(-10) and 10(-8) mol/l) significantly stimulated bone resorption, although to a slightly lesser degree than did calcitriol. Human monocyte-conditioned medium (CM) significantly stimulated TdR incorporation into MC3T3-E1 cells. On the other hand, CM obtained from monocytes treated with calcitriol (10(-10)-10(-8) mol/l) significantly inhibited TdR incorporation in a dose-related fashion, whereas CM obtained from monocytes treated with OCT (10(-10)-10(-8) mol/l) significantly stimulated TdR incorporation in a dose-related fashion.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1994

Persistent expression of proto-oncogene c-fos stimulates osteoclast differentiation.

We analyzed c-fos mRNA expression by northern blotting analysis in chicken osteoclast precursors which spontaneously differentiate to multinucleated osteoclasts in 5-6 days. Osteoclast precursors as well as mature multinucleated osteoclasts showed constitutive expression of c-fos mRNA which is not found in osteoblasts. The c-fos expression was enhanced transiently by serum, dibutyryl cAMP (10(-4) M) and phorbol 12-myristate 13-acetate (TPA) (5 x 10(-7) M). To clarify the role of c-fos in osteoclast differentiation, c-fos DNA was transfected into osteoclast precursors. Greater than 2 fold increases in tartrate resistant acid phosphatase (TRAP) and bone resorptive activity were observed in the transfected cells compared to controls 3 days after transfection, suggesting that prolonged expression of c-fos caused enhanced osteoclast differentiation.

Acid Phosphatase↗
PubMed1994

Somatostatin receptor subtype SSTR2 mediates the inhibition of high-voltage-activated calcium channels by somatostatin and its analogue SMS 201-995.

Somatostatin and its analogue SMS 201-995 inhibit high voltage-activated (HVA) Ca2+ currents in the rat insulinoma cell line RINm5F which stably express cloned human somatostatin receptor subtype 2 (hSSTR2). In contrast, neither somatostatin nor SMS 201-995 suppresses the HVA Ca2+ currents in RINm5F which stably express cloned hSSTR1. These results suggest that somatostatin-induced inhibition of HVA Ca2+ currents is mediated by a specific receptor subtype and that inhibition of calcium influx through HVA Ca2+ channels is one of the mechanisms of SMS 201-995 action on inhibitory processes of hormone secretion and cell proliferation.

Animals↗