The epizootiology and pathogenesis of thyroid hyperplasia in coho salmon (Oncorhynchus kisutch) in Lake Ontario.
The thyroid glands of coho salmon collected at different stages of their anadromous migration exhibited progressive and extensive hyperplasia and hypertrophy. The incidence of overt nodule formation rose from 5% in fish collected in August to 24% in fish collected in October. The histological picture of the goiters was similar to that found in thiourea-treated teleosts and thiouracil-treated mammals. There was a concomitant, significant decrease in serum thyroxine and triiodothyronine values between September and October (thyroxine, 1.0+/-0.3 mug/100 ml and 0.4 mug/100 ml in September and October, respectively; triiodothyronine, 400.3+/-51.6 ng/100 ml and 80.2 ng/100 ml in September and October, respectively) and marked hypertrophy and hyperplasia of thyrotrophs. These data indicate a progressive hypothyroid condition which, although it may be linked to iodide deficiency, may well be enhanced by other environmental factors. The evidence for involvement of other factors is discussed. (+info)
Natural history of papillary lesions of the urinary bladder in schistosomiasis.
Variable epithelial hyperplasia was observed in urinary bladder of nine capuchin monkeys (Cebus apella) when examined at cystotomy 94 to 164 weeks after infection with Schistosoma haematobium. These hosts were followed for 24 to 136 weeks postcystotomy to determine the status of bladder lesions in relation to duration of infection and to ascertain whether lesion samples removed at cystotomy reestablished themselves in autologous and heterologous transfers. There was involution of urothelial hyperplasia in eight of nine animals and no evidence for establishment of transplanted bladder lesions. (+info)
Ganglioneuromas and renal anomalies are induced by activated RET(MEN2B) in transgenic mice.
Multiple endocrine neoplasia type 2B (MEN2B) is an autosomal dominant syndrome characterized by the development of medullary thyroid carcinoma, pheochromocytomas, musculoskeletal anomalies and mucosal ganglioneuromas. MEN2B is caused by a specific mutation (Met918-->Thr) in the RET receptor tyrosine kinase. Different mutations of RET lead to other conditions including MEN2A, familial medullary thyroid carcinoma and intestinal aganglionosis (Hirschsprung disease). Transgenic mice were created using the dopamine beta-hydroxylase promoter to direct expression of RET(MEN2B) in the developing sympathetic and enteric nervous systems and the adrenal medulla. DbetaH-RET(MEN2B) transgenic mice developed benign neuroglial tumors, histologically identical to human ganglioneuromas, in their sympathetic nervous systems and adrenal glands. The enteric nervous system was not affected. The neoplasms in DbetaH-RET(MEN2B) mice were similar to benign neuroglial tumors induced in transgenic mice by activated Ras expression under control of the same promoter. Levels of phosphorylated MAP kinase were not increased in the RET(MEN2B)-induced neurolglial proliferations, suggesting that alternative pathways may play a role in the pathogenesis of these lesions. Transgenic mice with the highest levels of DbetaH-RET(MEN2B) expression, unexpectedly developed renal malformations analogous to those reported with loss of function mutations in the Ret gene. (+info)
Anti-monocyte chemoattractant protein-1/monocyte chemotactic and activating factor antibody inhibits neointimal hyperplasia in injured rat carotid arteries.
Monocyte chemoattractant protein-1 (MCP-1)/monocyte chemotactic and activating factor (MCAF) has been suggested to promote atherogenesis. The effects of in vivo neutralization of MCP-1 in a rat model were examined in an effort to clarify the role of MCP-1 in the development of neointimal hyperplasia. Competitive polymerase chain reaction analysis revealed maximum MCP-1 mRNA expression at 4 hours after carotid arterial injury. Increased immunoreactivities of MCP-1 were also detected at 2 and 8 hours after injury. Either anti-MCP-1 antibody or nonimmunized goat IgG (10 mg/kg) was then administered every 12 hours to rats that had undergone carotid arterial injury. Treatment with 3 consecutive doses of anti-MCP-1 antibody within 24 hours (experiment 1) and every 12 hours for 5 days (experiment 2) significantly inhibited neointimal hyperplasia at day 14, resulting in a 27.8% reduction of the mean intima/media ratio (P<0.05) in experiment 1 and a 43.6% reduction (P<0.01) in experiment 2. This effect was still apparent at day 56 (55.6% inhibition; P<0.05). The number of vascular smooth muscle cells in the neointima at day 4 was significantly reduced by anti-MCP-1 treatment, demonstrating the important role of MCP-1 in early neointimal lesion formation. However, recombinant MCP-1 did not stimulate chemotaxis of vascular smooth muscle cells in an in vitro migration assay. These results suggest that MCP-1 promotes neointimal hyperplasia in early neointimal lesion formation and that neutralization of MCP-1 before, and immediately after, arterial injury may be effective in preventing restenosis after angioplasty. Further studies are needed to clarify the mechanism underlying the promotion of neointimal hyperplasia by MCP-1. (+info)
Myometrial zonal differentiation and uterine junctional zone hyperplasia in the non-pregnant uterus.
Human non-gravid myometrium differentiates in response to ovarian sex steroids into a subendometrial layer or junctional zone and an outer myometrial layer. Compared to the outer myometrial layer, the junctional zone myocytes are characterized by higher cellular density and lower cytoplasmic-nuclear ratio. These structural differences allow in-vivo visualization of the myometrial zonal anatomy by T2-weighted magnetic resonance (MR) imaging. The human myometrium is also functionally polarized. Video-vaginosonography studies have shown that propagated myometrial contractions in the non-pregnant uterus originate only from the junctional zone and that the frequency and orientation of these contraction waves are dependent on the phase of the menstrual cycle. The mechanisms underlying zonal myometrial differentiation are not known, but growing evidence suggests that ovarian hormone action may be mediated through cytokines and uterotonins locally released by the basal endometrial layer and endometrio-myometrial T-lymphocytes. Irregular thickening of the junctional zone due to inordinate proliferation of the inner myometrium, junctional zone hyperplasia, is a common MR finding in women suffering from menstrual dysfunction. Preliminary data suggest that junctional zone hyperplasia is further characterized by loss of normal inner myometrial function. Although irregular thickening of the junctional zone has been associated with diffuse uterine adenomyosis, the precise relationship between subendometrial smooth muscle proliferation and myometrial invasion by endometrial glands and stroma remains to be established. (+info)
Mechanism of parathyroid tumourigenesis in uraemia.
Clonal analysis has shown that in renal hyperparathyroidism (2-HPT), parathyroid glands initially grow diffusely and polyclonally after which the foci of nodular hyperplasia are transformed to monoclonal neoplasia. There is a great deal of information about genetic abnormalities contributing to the tumourigenesis of parathyroid neoplasia in primary hyperparathyroidism. It is speculated that allelic loss of the MEN1 suppressor gene and overexpression of cyclin D1 induced by rearrangement of the parathyroid hormone gene may be the major genetic abnormality in sporadic parathyroid adenoma but not in 2-HPT. The pathogenesis of 2-HPT, abnormality of the Ca2+-sensing receptor (CaR) gene and the vitamin D receptor gene may possibly contribute to parathyroid tumourigenesis in 2-HPT. However, this is not yet clear and heterogeneous and multiple genetic abnormalities may be responsible for the progression of secondary parathyroid hyperplasia. (+info)
Accelerated intimal hyperplasia and increased endogenous inhibitors for NO synthesis in rabbits with alloxan-induced hyperglycaemia.
1. We examined whether endogenous inhibitors of NO synthesis are involved in the augmentation of intimal hyperplasia in rabbits with hyperglycaemia induced by alloxan. 2. Four weeks after the endothelial denudation of carotid artery which had been performed 12 weeks after alloxan, the intimal hyperplasia was greatly augmented with hyperglycaemia. The degree of hyperplasia was assessed using three different parameters of histopathological findings as well as changes in luminal area and intima: media ratio. 3. There were positive and significant correlations between intima:media ratio, plasma glucose, and concentrations of N(G)-monomethyl-L-arginine (L-NMMA) and N(G), N(G)-dimethyl-L-arginine (ADMA) in endothelial cells, that is, the intima:media ratio became greater as plasma glucose and endothelial L-NMMA and ADMA were increased. Furthermore, endothelial L-NMMA and ADMA were increased in proportion to the increase in plasma glucose. 4. In contrast, there were inverse and significant correlations between cyclic GMP production by carotid artery strips with endothelium and plasma glucose, between cyclic GMP production and endothelial L-NMMA and ADMA, and between the intima:media ratio and cyclic GMP production. 5. Exogenously applied L-NMMA and ADMA inhibited cyclic GMP production in a concentration-dependent manner. IC50 values were determined to be 12.1 microM for the former and 26.2 microM for the latter. The cyclic GMP production was abolished after the deliberate removal of endothelium from the artery strips. 6. These results suggest that the augmentation of intimal hyperplasia with hyperglycaemia is closely related to increased accumulation of L-NMMA and ADMA with hyperglycaemia, which would result in an accelerated reduction in NO production/release by endothelial cells. (+info)
Expression of relaxin-like factor is down-regulated in human testicular Leydig cell neoplasia.
In addition to their role in steroidogenesis in the male, testicular Leydig cells constitutively express large amounts of the peptide relaxin-like factor (RLF), also known as Ley-IL. The Leydig cell-derived RLF belongs to the insulin-like superfamily, which also includes relaxin, insulin and the insulin-like growth factors, and within the testis is a specific marker of Leydig cells. Little information is available either on the regulation of gene expression or on the function of this Leydig cell-derived peptide. In the present study we have investigated the expression pattern of human RLF in patients with rare Leydig cell hyperplasia and adenoma. The expression of both mRNA and protein appear to be decreased in hyperplastic Leydig cells, whereas in the Leydig cell adenomas studied, large central areas of the adenoma were devoid of RLF mRNA and protein. Only Leydig cells located at the periphery of the adenoma displayed expression of RLF, with full agreement between in-situ hybridization and immunohistochemistry. It thus appears that the expression of the RLF gene and its products are down-regulated in Leydig cell hyperplasia and adenoma, consistent with a concomitant dedifferentiation of these cells. (+info)