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Prostaglandin E2 (PGE2) exerts its effects through the PGE receptor that consists of four subtypes (EP1, EP2, EP3, and EP4). Osteoclast formation in the coculture of primary osteoblastic cells (POB) and bone marrow cells was enhanced more by 11-deoxy-PGE1 (an EP4 and EP2 agonist) than by butaprost (an EP2 agonist) and other agonists, which suggests that EP4 is the main factor in PGE2-induced osteoclast formation. PGE2-induced osteoclast formation was not observed in the coculture of POB from EP4-deficient (EP4 k/o) mice and spleen cells from wild-type (w/t) mice, whereas osteoclasts were formed in the coculture of POB from w/t mice and spleen cells from EP4-k/o mice. In situ hybridization (ISH) showed that EP4 messenger RNA (mRNA) was expressed on osteoblastic cells but not on multinucleated cells (MNCs) in w/t mice. These results indicate that PGE2 enhances osteoclast formation through its EP4 subtype on osteoblasts. Osteoclast formation by interleukin 1alpha (IL-1alpha), tumor necrosis factor alpha (TNF-alpha), basic fibroblast growth factor (bFGF), and lipopolysaccharide (LPS) was hardly observed in the coculture of POB and bone marrow cells, both from EP4-k/o mice, which shows the crucial involvement of PG and the EP4 subtype in osteoclast formation by these molecules. In contrast, osteoclast formation by 1,25-hydroxyvitamin D3 (1,25(OH)2D3) was not impaired and that by parathyroid hormone (PTH) was only partially impaired in EP4-k/o mice, which may be related to the fact that EP4-k/o mice revealed no gross skeletal abnormalities. Because it has been suggested that IL-1alpha, TNF-alpha, bFGF, and LPS are involved in inflammatory bone loss, our work can be expected to contribute to an understanding of the pathophysiology of these conditions.

There is recent evidence that natriuretic peptides are important regulators of bone and cartilage, although they were originally identified as the cardiac hormones causing natriuresis and hypotension. Three members of natriuretic peptide family are known: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). The biologically active receptors for these peptides are particulate guanylate cyclases; the two known types are GC-A and GC-B. ANP and BNP have high affinities for GC-A, and CNP is the preferred ligand for GC-B. In this paper we report the results of our study of the expression and possible role(s) of natriuretic peptides in the ROB-C26 cell, which is an osteogenic cell line with multiple potentials for differentiating into myoblast, osteoblast, and adipocyte. ROB-C26 cells produced cGMP in response to natriuretic peptides at both their basal state and after enhanced differentiation into osteoblast which was induced by bone morphogenetic protein [(BMP)-2]. CNP was far more potent than ANP in cGMP production. In contrast, enhanced differentiation into adipocyte by dexamethasone resulted in the marked decrease in their responsiveness to natriuretic peptides. Although the messages for GC-A and GC-B were demonstrated by Northern blot analysis at both the basal stage and after BMP treatment, they were down-regulated after dexamethasone treatment. The presence of CNP was shown by RT-PCR and immunohistochemistry in ROB-C26 cells. C3H10T1/2, which is another and more primitive mesenchymal cell line, also produced cGMP in response to CNP, and less potently to ANP. Culturing ROB-C26 cells with CNP or 8-bromo cGMP decreased [(3)H]thymidine uptake and slightly increased the message for alkaline phosphatase, which is a marker for osteoblast differentiation. These results suggest that the CNP/GC-B system is preferentially expressed in the cells of osteogenic lineage and their expression is down-regulated with differentiation into adipocyte lineage. The CNP/GC-B system is likely to be an autocrine/paracrine regulator of osteoblast growth and differentiation.

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The natriuretic peptide family consists of three structurally related endogenous ligands: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). The biological actions of natriuretic peptides are thought to be mediated through the activation of two guanylyl cyclase (GC)-coupled receptor subtypes (GC-A and GC-B). In this study, we examined the effects of ANP and CNP, which are endogenous ligands for GC-A and GC-B, respectively, on bone growth using an organ culture of fetal mouse tibias, an in vitro model of endochondral ossification. CNP increased the cGMP production much more potently than ANP, thereby resulting in an increase in the total longitudinal bone length. Histological examination revealed an increase in the height of the proliferative and hypertrophic chondrocyte zones in fetal mouse tibias treated with CNP. The natriuretic peptide stimulation of bone growth, which was mimicked by 8-bromo-cGMP, was inhibited by HS-142-1, a non-peptide GC-coupled natriuretic peptide receptor antagonist. The spontaneous increase in the total longitudinal bone growth and cGMP production was also inhibited significantly by HS-142-1. CNP mRNA was expressed abundantly in fetal mouse tibias, where no significant amounts of ANP and BNP mRNAs were detected. A considerable amount of GC-B mRNA was present in fetal mouse tibias. This study suggests the physiologic significance of the CNP/GC-B pathway in the process of endochondral ossification.

Longitudinal bone growth is determined by the process of endochondral ossification in the cartilaginous growth plate, which is located at both ends of vertebrae and long bones and involves many systemic hormones and local regulators. Natriuretic peptides organize a family of three structurally related peptides: atrial natriuretic peptide, brain natriuretic peptide (BNP), and C-type natriuretic peptide. Atrial natriuretic peptide and BNP are cardiac hormones that are produced predominantly by the atrium and ventricle, respectively. C-type natriuretic peptide occurs in a wide variety of tissues, where it acts as a local regulator. These peptides can influence body fluid homeostasis and blood pressure control through the activation of two guanylyl cyclase (GC)-coupled natriuretic peptide receptor subtypes—GC-A and GC-B. We report here marked skeletal overgrowth in transgenic mice that overexpress BNP. Transgenic mice with elevated plasma BNP concentrations exhibited deformed bony skeletons characterized by kyphosis, elongated limbs and paws, and crooked tails. Bone abnormalities resulted from a high turnover of endochondral ossification accompanied by overgrowth of the growth plate. Studies using an in vitro organ culture of embryonic mouse tibias revealed that BNP increases the height of cartilaginous primordium directly, thereby stimulating the total longitudinal bone growth. The present study demonstrates that natriuretic peptides can affect the process of endochondral ossification.

Background C-type natriuretic peptide (CNP), which exerts its biological actions by binding a subtype of receptor, guanylyl cyclase-B (GC-B), is implicated in the endochondral bone growth and the gene disruption of CNP or GC-B results in marked dwarfism due to the defect of the endochondral bone formation in both animals and humans. Meanwhile, the physiological role of the CNP/ GC-B system in the growth plate cartilage is still unclear, because the CNP/GC-B system is widely distributed not only in the growth plate of the bone but also in the central and peripheral nervous system, gonad, vascular endothelial cells, macrophages and cardiac fibroblasts. Results In order to further elucidate the physiological role of the local CNP/GC-B system in the growth plate cartilage, we have performed targeted depletion of CNP or GC-B gene in the growth plate cartilage, using the Cre-loxP system. The growth of bones formed through the endochondral ossification was severely impaired in cartilage-specific CNP knockout mice, resulting in a prominent short-stature phenotype. The severity of impairment of endochondral bone growth observed in cartilage-specific CNP knockout mice was almost the same as in the systemic CNP knockout mice. The bone phenotype of cartilage specific GC-B knockout mice was essentially the same as that of CNP knockout mice, however, the shortening of bones was severer in cartilage specific GC-B knockout mice than that in cartilage specific CNP knockout mice. Histological examination revealed that the hypertrophic chondrocyte layer of the growth plate was drastically reduced and the thickness of the proliferative chondrocyte layer, along with the proliferation of chondrocytes in that region, was moderately reduced in both cartilage specific knockouts. On pulverized feed, the survival rate of cartilage specific CNP and GC-B knockout mice was comparable to that of systemic CNP knockout mice. Conclusion These results demonstrate that the local CNP/GC-B system in growth plates is responsible for the physiological endochondral bone growth.

Indian women who are professionals have made their presence felt the world over by their hard work and dedication. India's prestige has been projected and held up high because of the industriousness shown by these women in the international arena and these women are usually from families that give a lot of importance for education and career. Even in India the women from various sections of the society have proved their mettle and women form major part of the work force. When there is difference of agreement among individuals conflicts arise and conflicts induce role conflicts in women who are the victims as they are forced to perform a variety of roles through their lives that leads them to lose their identity. Women working outside their homes face major role conflicts that lead them to various difficulties including health problems.

A 59-year-old man visited Kyoto University Hospital because of general malaise, polyuria, and polydipsia. The diagnosis of primary hyperparathyroidism was made based on hypercalcemia and an elevated circulating PTH level. A nodule was palpable in the left anterior neck. Two weeks later, the serum calcium level was normalized and his symptoms subsided. A temporary expansion, followed by reduction of the tumor size was observed by serial ultrasonography. Histology of the resected tumor showed central necrotic tissue, with some peripherally remaining glandular tissue. We report here a rare case of primary hyperparathyroidism with spontaneous remission due to hemorrhagic infarction in the adenoma.

A rare case of functioning oxyphil parathyroid adenoma associated with primary hyperparathyroidism and marked hungry bone syndrome was revealed in a 29-year-old man with hypercalcemia and elevated circulating parathyroid hormone (PTH) level. A large parathyroid tumor weighing 8.4 g was resected and proved to be an oxyphil adenoma. Hypocalcemia was sustained after the operation, despite intensive calcium supplementation. During the postoperative 8 months, bone mineral density at the lumbar spine increased dramatically from 0.892 g/cm2 to 1.244 g/cm2, and whole body bone mineral content increased from 1, 913.4 g to 2, 419.2 g. This case gives insight to the reversibility of bone loss in this disorder.(Internal Medicine 35: 545-549, 1996)

C-type natriuretic peptide (CNP) is a local regulator in the brain and vascular wall. We present data to demonstrate the production and action of CNP in the osteoblast. CNP increased cGMP production, far more potently than atrial natriuretic peptide (ANP) in an osteoblastic cell line, MC3T3-E1. Since ANP and CNP are the ligands for two particulate guanylate cyclases, guanylate cyclase-A (GC-A) and guanylate cyclase-B (GC-B), respectively, these results reveal the expression of GC-B in MC3T3-E1. In addition, CNP mRNA and CNP-like immunoreactivity were detected in cell extracts from MC3T3-E1 and its culture medium, respectively. Both CNP and 8-bromo cGMP dose-dependently decreased [3H]thymidine uptake, without affecting alkaline phosphatase activity. These results indicate that CNP is a novel autocrine/paracrine regulator of osteoblast and suggest the presence of "bone natriuretic peptide system."