[Water and electrolyte metabolism in adrenal insufficiency].
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Biomedical subjects
Publications and source records attributed to R Okazaki.
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Hypothalmic-pituitary-gonadal hormones are regulated by number of factors including GnRH, LH and FSH, and gonadal hormones. They are regulated also by pituitary prolactin, activin and inhibin. Hypogonadism is divided into primary and secondary hypogonadism. Secondary hypogonadism is caused by various lesions involving either the hypothalmus or the pituitary. In this paper, etiology, diagnosis and treatment of the secondary hypogonadism are described. The most frequent causes of hypothamic hypogonadism are hypothalamic tumors, such as germinoma. As the pituitary hypogonadism, pituitary tumors, and Sheehan's syndrome are most common disorders. Diagnosis of the secondary hypogonadism is made based on the diagnostic criteria established by The Research Group of the Japanese Ministry of Health and Welfare. The criteria includes signs and symptoms in addition to laboratory examinations such as measurement of serum gonadotropin, sex steroid and LH-RH test. First choice of the treatment of hyothalmic hypogondism is continuous pulsatile injection of synthetic LH-RH. In the pituitary hypogonadism, hCG, hMG, estrogen and testosterone or the combination of these are applied depending upon the age and other factors of the patients.
Trabecular bone turnover and bone marrow capacity for the development of bone cells in the tibia were assessed after sciatic neurectomy (NX) in mice. The right hindlimbs of 6-week-old DDY mice were neurectomized and left hindlimbs were sham-operated and served as NX controls. Histomorphometrical analyses of the trabecular bone of the proximal tibia demonstrated the initial decrease in bone formation rate for the first 14 days and the subsequent increase in osteoclast surface for the next 14 days. The number of adherent stromal cells per tibia obtained for the NX limbs was reduced on days 7 and 10 postsurgically, and then recovered on day 12. However, the alkaline phosphatase activity of the cells was persistently depressed. The formation of osteoclast-like multinucleated cells in the marrow cultures obtained from NX limbs at days 10, 12, and 14 showed a significant increase in the medium containing parathyroid hormone (PTH). The number of colonies cultured for colony forming units-fibroblastic (CFU-f) that developed from the marrow cells did not differ in the NX and the contralateral limbs at any time during the period. On the other hand, the number of colonies cultured of colony forming units for granulocytes and macrophages (CFU-GM) was markedly increased for both the NX and the contralateral tibiae at days 12 and 14. This study clearly demonstrates that there are two stages in the development of osteopenia after NX. During the first 14 days, trabecular bone formation and number of marrow stromal cells are reduced. In the second 14 day period, the trabecular osteoclast number is increased and osteoclast formation from the bone marrow cells is enhanced in the presence of PTH. However, neither the CFU-f nor the CFU-GM assay could identify the changes in osteogenic or osteoclastogenic potential of the bone marrow. These in vitro assays provide limited information on the shifts in bone marrow cell lineages and the local environment producing osteopenia in the immobilized limb in vivo.
OBJECTIVE: To clarify the effects of transforming growth factor beta 1 (TGF beta 1), TGF beta 2, and basic fibroblast growth factor (bFGF) on cell proliferation and proteoglycan (PG) synthesis in articular chondrocytes obtained from immobilised rabbit knees. METHODS: The right knees of rabbits were immobilised in full extension for up to 42 days using fiberglass casts. Specimens for histology were stained with safranin O. Chondrocytes were isolated from the weight bearing regions of the femur and tibia of the immobilised knees and cultured with combinations of growth factors. Cell proliferation and PG synthesis were determined by 3H-thymidine and 35S-sulphate incorporations. RESULTS: Histological study revealed loss of metachromasia in the articular cartilage at seven days, fissuring and cell clusters at 28 days, and loss of cartilage layers 42 days after immobilisation. Radioisotope assay of the chondrocytes revealed no remarkable change in DNA synthesis in the presence of either TGF beta 1 or TGF beta 2 alone. bFGF markedly stimulated cell proliferation in specimens obtained 0 to seven days after immobilisation. The combination of either TGF beta 1 or TGF beta 2 with bFGF had a synergistic effect, inducing significant increases in DNA synthesis four, seven, and 14 days after immobilisation. PG synthesis by chondrocytes from immobilised joints was not significantly altered by these agents. CONCLUSION: TGF beta 1 or TGF beta 2 in combination with bFGF exert synergistic effects on cell proliferation in articular chondrocytes obtained from the rabbit knee during the early days after immobilisation by a cast. These results suggest a critical role of cytokine combinations in the development of articular cartilage degeneration after immobilisation.
Using a recently developed human osteoblastic cell line (hFOB/ER9) with high levels (approximately 4,000 per nucleus) of estrogen receptors and the characteristic phenotype of the mature osteoblast, we tested the hypothesis that estrogen decreases bone formation by inhibiting the action of the insulin-like growth factor (IGF) paracrine/autocrine system. IGF-II, the predominant IGF produced by osteoblastic cells, was measurable in hFOB/ER9-conditioned medium (approximately 10 ng/mL) and its level did not change significantly after treatment with 17 beta-estradiol (E2) or anti-estrogens. Treatment with E2 at 0.1-100 nM decreased [3H]thymidine uptake to 53% of control (p < 0.001) in a dose-dependent fashion. The predominant IGF-binding proteins (IGFBPs) produced by hFOB/ER9 and by normal trabecular osteoblasts are IGFBP-3 and IGFBP-4, of which IGFBP-4 is consistently inhibitory of IGF action. Treatment with E2 at 0.01-10 nM for 48 h increased IGFBP-4 mRNA to 346% +/- 90% (mean +/- SE) of control (p < 0.05) and IGFBP-4 protein to 278% +/- 75% of control (p < 0.01) in a dose-dependent fashion but did not alter IGFBP-3 mRNA or protein. E2 treatment also attenuated IGF-dependent, IGFBP-4 specific proteolysis to approximately 50% of control. ICI 182,780, a pure anti-estrogen, completely blocked E2-mediated decreases in cell proliferation and increases in levels of IGFBP-4 mRNA and protein. Treatment of the hFOB/ER9 cells with recombinant human IGFBP-4 (200 ng/mL) decreased cell proliferation to 55% of control (p < 0.01). Thus, E2 acts on osteoblastic cells to increase availability of inhibitory IGFBP-4, by both increasing its production and decreasing its degradation, which may oppose the mitogenic effect of the IGFs on osteoblastic cells. This action may mediate, at least in part, the decreases in bone formation that are observed after estrogen treatment in vivo.
In this study, we examined regulation of insulin-like growth factor I (IGF-I) gene expression and transcript splicing in normal human osteoblast-like cells. Previous studies in rat osteoblastic cells have indicated that transforming growth factor-beta (TGF-beta) inhibits IGF-I expression, whereas inducers of intracellular cAMP stimulate IGF-I expression. However, in human osteoblast-like cells both TGF-beta and forskolin increased IGF-I mRNA levels in a time- and dose-dependent manner. All 4 classes of IGF-I transcript that can result from alternate leader exon usage and splicing of the human IGF-I gene were induced proportionally. Although human osteoblasts increase IGF-I mRNA in response to important skeletal regulatory factors, some responses may be species-specific.
Insulin-like growth factors I (IGF-I) and II (IGF-II) are anabolic for osteoblastic cells. Although expression of IGF-I and IGF-II mRNA has been demonstrated in rodent osteoblastic cells, little is known about IGF gene expression in human osteoblastic cell models. In this study we characterized IGF-I and -II mRNA expression in (1) normal human osteoblast-like (hOB) cells, (2) a simian virus 40 immortalized hOB (HOBIT) cell line, and (3) human osteosarcoma cell lines SaOS-2, TE-85, MG-63, and U-2. Since cross-hybridization of IGF cDNA probes with ribosomal RNA obscures detection of some of the multiple IGF transcripts in human cells, we replaced Northern analysis with the more specific ribonuclease protection assay (RPA). We also used the reverse transcriptase-polymerase chain reaction (RT-PCR) to assess whether mRNAs were present at trace levels. IGF-I mRNA expression was consistently observed in normal hOB cells only and by both RT-PCR and RPA. Among IGF-I transcript variants, Ea IGF-I mRNA was more abundant than the Eb mRNA in normal hOB cells. Trace levels of IGF-I mRNA were variably detected in SaOS-2 and U-2 osteosarcoma cells when RT-PCR was performed, but we found no IGF-I mRNA in HOBIT, TE-85, or MG-63 cells. IGF-II mRNA was expressed in normal hOB, HOBIT, TE-85, and U-2 cells as assessed by either method.(ABSTRACT TRUNCATED AT 250 WORDS)
Metabolic changes of basement membrane proteins, collagenous and non-collagenous, will be followed by morphological changes and develop into diabetic microangiopathy. In this study, serum concentrations of laminin and type IV collagen were measured in 87 cases o f non-insulin-dependent diabetes mellitus (NIDDM) and examined with the development of diabetic nephropathy and retinopathy. Serum type IV collagen was measured by two methods, assays of the 7S portion (7S-RIA) and of both the 7S and central triple helical domain (IV-EIA). IV-EIA showed more significant elevation with development of diabetic microangiopathy than 7S-RIA and laminin. After measurement of basement membrane proteins, 66 cases were followed clinically for 3 or 4 years. In 45 cases without worsening of diabetic nephropathy, IV-EIA and laminin concentrations in serum were significantly lower than those in 21 cases who showed worsening of diabetic nephropathy in the same period, Multivariate analysis revealed a good model including three dependent variables of serum values of laminin, IV-EIA and mean blood pressure for discriminating between the worsened group and the non-worsened group. High values of IV-EIA and laminin in serum may be useful in predicting the worsening of diabetic nephropathy.
Because the osteoporosis occurring in chronic cholestatic liver disease (CCLD) is associated with decreased bone formation and is reversible by liver transplantation, substances retained in plasma during cholestasis may impair osteoblast function. This hypothesis was tested using a new bioassay that measures plasma mitogenic activity (PMA) for normal human osteoblast-like (hOB) cells. In 29 jaundiced patients, mean PMA was 56.4% (P < 0.001) of that in 29 age- and sex-matched normal subjects, and the decrease in PMA was similar in the 14 with CCLD and the 15 with other causes of jaundice. Bile acids and bilirubin are the two major groups of products retained during cholestasis. The common conjugated bile acids and bilirubin were added to normal human plasma in concentrations simulating those found in patients with CCLD. Various bile salts had no effect on PMA whereas unconjugated bilirubin decreased PMA in a dose-dependent fashion (r = -0.98, P < 0.0001) without affecting cell viability. Relatively selective removal of bilirubin from the plasma by photobleaching normalized the decreased PMA in five jaundiced patients but produced no apparent change in five normal subjects. These data support the hypothesis that hyperbilirubinemia or possibly other photolabile substances impair osteoblast proliferative capacity and thus may play a major role in the pathogenesis of the osteoporosis associated with CCLD.
Insulin-like growth factor-binding protein-4 (IGFBP-4) is an important regulator of insulin-like growth factor-I (IGF-I) anabolic activity in bone. Although cultured human osteoblast-like (hOB) cells have been reported to secrete IGFBP-4, we could not detect IGFBP-4 protein in 8 of 27 individual donor-derived hOB-cell conditioned medium (hOB-CM) samples examined by Western ligand blotting. Nonetheless, this subset of hOB cells had normal IGFBP-4 messenger ribonucleic acid expression and protein secretion. Regulation of IGFBP-4 levels in hOB cultures appeared to occur extracellularly. hOB cells produce an IGFBP-4 proteinase that requires the presence of IGF for cleavage of the IGFBP-4 molecule into 2 fragments of approximately 18 and 14 kilodaltons. These fragments are not detected by Western ligand blotting. Our data indicate that elevated endogenous levels of IGF can activate IGFBP-4 proteolysis, because in hOB cultures lacking detectable IGFBP-4 protein 1) basal IGF messenger ribonucleic acid expression was increased; 2) IGF-II peptide levels were elevated; 3) IGF-neutralizing antibodies added to hOB-CM attenuated the proteolysis of exogenous IGFBP-4; and 4) recombinant human IGFBP-4 was proteolyzed into 2 immunoreactive fragments of approximately 18 and 14 kilodaltons during cell-free incubations in these hOB-CM without the addition of exogenous IGF. In conclusion, elevated IGF expression and secretion can contribute to enhanced proteolysis of endogenous and exogenous IGFBP-4 via a proteinase secreted by cultured hOB cells. Levels of endogenous IGF peptide may determine IGFBP-4 availability in the bone microenvironment and, thus, modulate the local cell response to IGF-I.
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Glucocorticoid (GC) modulates insulin-like growth factor (IGF) action in bone through mechanisms that are complex and not well understood. Because the family of IGF-binding proteins (IGFBP-1 through -6) is important in the regulation of IGF availability and bioactivity, we examined the effect of GC on IGFBP expression in normal human osteoblast-like (hOB) cells. As assessed by Western ligand blot, hOB cells release IGFBP-3, IGFBP-4, and a 31-kilodalton IGFBP, which appeared to be IGFBP-5. Northern analysis revealed that hOB cells express abundant IGFBP-3, IGFBP-4, IGFBP-5, and IGFBP-6 mRNA, with barely detectable IGFBP-1 mRNA. GC treatment resulted in time- and dose-dependent decreases in IGFBP-3, IGFBP-4, and 31-kilodalton IGFBP levels in culture medium, with corresponding decreases in IGFBP-3, IGFBP-4, and IGFBP-5 mRNA levels. In addition, GC treatment increased steady state levels of IGFBP-1 mRNA and did not alter IGFBP-6 mRNA levels. Although hOB cells secrete an acid-activated IGFBP-3 protease and an IGF-dependent IGFBP-4 protease, GC had little effect on these protease activities and did not alter degradation of the secreted IGFBPs. Our results indicate that GC has dramatic effects on IGFBP gene expression and suggest that differential regulation of IGFBPs by GC may modulate hOB cell responsiveness to IGFs.
Human T-cell leukemia virus type I (HTLV-I) is the etiologic agent of adult T-cell leukemia (ATL), and hypercalcemia frequently associated with ATL is mediated by parathyroid hormone-related peptide (PTHRP). The present study was undertaken to clarify the role of cAMP second messenger system in the regulation of human PTHRP gene expression in ATL cells, using an HTLV-I-infected T-cell line, MT-2. Forskolin and dibutyryl cAMP (Bt2cAMP) caused a marked and transient increase in the steady-state level of PTHRP mRNA. The effects of these agents were dose-dependent, and the maximal effects were observed at 3 h. Nuclear runoff transcription assay showed that forskolin and Bt2cAMP caused an increase in the transcription rate of the human PTHRP gene. In contrast, the stability of PTHRP mRNA was only modestly increased by these agents. Forskolin and Bt2cAMP also increased the secretion of PTHRP by MT-2 cells, as determined by both a newly established immunoradiometric assay using two antibodies against human PTHRP-(1-34) and PTHRP-(50-83) and a radioimmunoassay using an antibody against human PTHRP-(109-141). Prostaglandin E1 (PGE1) caused a marked stimulation of intracellular cAMP production in MT-2 cells, whereas PGE2 and PGF2 alpha had only modest effects. The ability of these PGs to stimulate cAMP production correlated well with their ability to increase PTHRP mRNA level and the secretion of PTHRP. Indomethacin did not affect the basal level of cAMP production or PTHRP mRNA, suggesting that endogenous PG was not involved in the basal production of cAMP or PTHRP. When PGE1 was given to MT-2 cells together with interleukin 2, which is another stimulator of PTHRP gene expression, PTHRP secretion was synergistically stimulated. These results suggest that the transcription of the human PTHRP gene is enhanced through a cAMP-dependent pathway by PGE1 and that PGE1, as well as interleukin 2, plays an important role in the overexpression of the human PTHRP gene in HTLV-I-infected T cells leading to the development of hypercalcemia in ATL patients.
Previous reports demonstrated that the administration of large doses of 24R,25-dihydroxyvitamin D3 [24R,25(OH)2D3] to animals with normal vitamin D supply causes an increase in bone volume with reduced bone resorption and decreased osteoclast number. The present study was undertaken to clarify if 24R,25(OH)2D3 has any inhibitor effect on the formation and function of osteoclasts. The effect of 24R,25(OH)2D3 on the formation of osteoclastic cells was examined by measuring the number of tartrate-resistant acid phosphatase-positive multinucleated cells (MNCs) formed from hemopoietic progenitor cells obtained from spleens of 5-fluorouracil-treated mice. Treatment with 1,25(OH)2D3 or parathyroid hormone fragment 1-34 [PTH(1-34)] stimulated osteoclast-like MNC formation in a dose-dependent manner. Addition of 24R,25(OH)2D3 alone showed a weak stimulatory effect on MNC formation at 10(-6) M, which appeared to be due to its binding to 1,25(OH)2D3 receptors. In contrast, when 24R,25(OH)2D3 was added together with 1,25(OH)2D3 or PTH(1-34), it inhibited osteoclast-like MNC formation stimulated by these hormones. A significant inhibition of MNC formation was observed with 10(-7) M 24R,25(OH)2D3, and the stimulatory effect of 1,25(OH)2D3 or PTH(1-34) was almost completely eliminated with 10(-6) M 24R,25(OH)2D3. Neither 24S,25(OH)2D3 nor 25(OH)D3 exhibited a similar inhibitory effect. The effect of 24R,25(OH)2D3 on the resorptive function of osteoclasts was examined by measuring the formation of resorption pits by mouse bone cells on dentine slices. Treatment with 24R,25(OH)2D3 also inhibited the resorption pit formation stimulated by 1,25(OH)2D3 or PTH(1-34) with similar dose response.(ABSTRACT TRUNCATED AT 250 WORDS)
Although parathyroid hormone-related peptide (PTHRP) is produced by adult T cell leukemia (ATL) cells and causes hypercalcemia in ATL patients, very little is known about the regulation of PTHRP gene expression in the leukemic cells. The present study was undertaken to clarify the role of T cell growth factor, interleukin-2 (IL-2), in the expression of PTHRP gene, using a human T cell leukemia virus type I (HTLV-I)-infected T cell line, MT-2. Recombinant human IL-2 caused a transient increase in the steady state level of PTHRP messenger RNA (mRNA) in MT-2 cells, and a maximal effect was observed at 3-6 h. The effect of IL-2 was dose dependent, with a maximal response being observed at 10(-10) M. A monoclonal antibody against IL-2 receptor (anti-Tac antibody) inhibited the IL-2-induced increase in PTHRP mRNA level. Recombinant human IL-1, IL-3, IL-4, and IL-6 failed to increase PTHRP mRNA level. Nuclear run-off transcription assay showed that the transcription rate of the PTHRP gene was modestly increased by IL-2. In addition, IL-2 caused a substantial increase in the stability of PTHRP mRNA, compared with control cells in which the apparent half-life of PTHRP mRNA was less than 30 min after RNA synthesis was inhibited by the RNA polymerase II inhibitor, dichlorobenzimidazole riboside. The secretion of PTHRP, as determined by both a newly established immunoradiometric assay using recombinant human PTHRP(1-87) as the standard and an RIA using an antibody against PTHRP(109-141), was increased by IL-2 but not by IL-1, IL-3, IL-4, or IL-6. The IL-2-induced increase in PTHRP secretion was completely inhibited by the addition of anti-Tac antibody. These results demonstrate that IL-2 stimulates the production and secretion of PTHRP by HTLV-I-infected T cells through specific binding to IL-2 receptor and that the effect of IL-2 is mediated by a posttranscriptional as well as a transcriptional mechanism. It is suggested that IL-2 may be involved in an auctocrine/paracrine fashion not only in the proliferation of HTLV-I-infected T cells but also in the enhanced production and secretion of PTHRP and thus the development of hypercalcemia in ATL patients.
We have studied the mechanism of targeted recombination in mammalian cells using a hemizygous adenine phosphoribosyltransferase-deficient (APRT-) Chinese hamster ovary (CHO) cell mutant as a recipient. Three structurally different targeting vectors with a 5' or a 3', or both, end-deleted aprt sequence, in either a closed-circular or linear form, were transfected to the cells with a mutated aprt gene by electroporation. APRT-positive (APRT+) recombinant clones were selected and analyzed to study the gene correction events of the deletion mutation. Some half of 58 recombinant clones obtained resulted from corrections of the deleted chromosomal aprt gene by either gene replacement or gene insertion, a mechanism which is currently accepted for homologous recombination in mammalian cells. However, the chromosomal sequence in the remaining half of the recombinants remained uncorrected but their truncated end of the aprt gene in the incoming vectors was corrected by extending the end beyond the region of homology to the target locus; the corrected vector was then randomly integrated into the genome. This extension, termed end extension repair, was observed with all three vectors used and was as far as 4.6-kilobase (kb) or more long. It is evident that the novel repair reaction mediated by homologous recombination, in addition to gene replacement and gene insertion, is also involved in gene correction events in mammalian cells. We discuss the model which may account for this phenomenon.
The present study was undertaken to clarify the relationship between c-fos and c-jun protooncogene expression and the differentiation and/or proliferation of osteoblasts, using osteoblast-like MC3T3-E1 (E1) cells. c-fos mRNA was barely detectable, whereas c-jun mRNA was constitutively expressed in E1 cells after serum deprivation for 24-72 h. When serum was added, a rapid and transient induction of c-fos and c-jun mRNAs was observed. The c-fos and c-jun mRNAs reached peak levels at 30 minutes, with a rapid disappearance of c-fos mRNA within 3 h and a much slower decrease in c-jun mRNA. The addition of serum together with cycloheximide, an inhibitor of protein synthesis, resulted in the superinduction of both c-fos and c-jun mRNAs. Among various growth factors, PDGF, EGF, and bFGF mimicked the serum effect, whereas IGF-I and TGF-beta failed to induce c-fos and c-jun mRNA. The effects of PDGF, EGF, and bFGF were completely abolished by pretreatment with actinomycin D, an inhibitor of RNA synthesis, suggesting a transcriptional mechanism. Nuclear runoff experiments showed that the transcription rate of c-fos and c-jun protooncogenes was increased by serum and growth factors. The effects of PDGF, EGF, and bFGF were inhibited by H-7 or staurosporine, inhibitors of protein kinase C (PKC), but not by HA1004 with a much weaker inhibitory activity, suggesting the involvement of PKC for the activation of the protooncogenes.(ABSTRACT TRUNCATED AT 250 WORDS)