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Biomedical subjects

C Moyer

Publications and source records attributed to C Moyer.

18 recordsLinked to original sources
PubMed2004

Analysis of vascular endothelial growth factor (VEGF) and a receptor subtype (KDR/flk-1) in the liver of rats exposed to riddelliine: a potential role in the development of hemangiosarcoma.

Riddelliine alters hepatocellular and endothelial cell kinetics and function including stimulating an increase in hepatocytic vascular endothelial growth factor (VEGF) in the absence of increased serological levels of VEGF (NYSKA et al. 2002). The objective of this study was to further assess hepatic VEGF and KDR/flk-1 synthesis and expression by hepatic cells under riddelliine treatment conditions. Forty-two male F344/N rats were dosed by gavage with riddelliine (0, 1.0, and 2.5 mg/kg/day) for 6 weeks. Seven animals/group were sacrificed after 8 consecutive daily doses; remaining rats were terminated after 30 daily doses, excluding weekends. Hepatic tissues were evaluated by immunohistochemistry and in situ hybridization. The results showed that VEGF mRNA expression was observed in control and treated animals; however, qualitative differences were noted. Treated animals exhibited VEGF mRNA in clustered, focal hepatocytes and bile duct epithelium, whereas VEGF mRNA in hepatocytes from vehicle control rats was distributed evenly across all hepatocytes. Results evaluating the distribution of the VEGF cognate receptor, KDR/flk-1 showed that randomly distributed, rare sinusoidal endothelium, including those demonstrating karyomegaly and cytomegaly expressed KDR/flk-1. Phosphorylation of KDR/flk-1 at pTyr996 and pTyr1054/1059, but not pTyr951, was also detected, evidence that endothelial cell KDR/flk-1 was activated. These results suggest that both hepatocytes and endothelial cells are targets of riddelliine-induced injury. We speculate that damage to both populations of cells may lead to dysregulated VEGF synthesis by hepatocytes and activation of KDR/flk-1 by endothelium leading to the induction of sustained endothelial cell proliferation, culminating in the development of hepatic hemangiosarcoma.

Administration, Oral↗
PubMed1998

Lack of nephrotoxicity and renal cell proliferation following subchronic dermal application of a hydroquinone cream.

Hydroquinone (HQ) is used in over-the-counter formulations of skin-lightening creams sold in the United States and European Union. HQ was introduced into these formulations to provide a safe and effective alternative to mercury and other less effective ingredients. Recent studies involving subchronic oral exposure of male F344 rats to HQ have shown nephrotoxicity and renal tubule cell proliferation (English et al., 1994), while chronic exposures of male F344 rats were reported to cause renal cell adenomas (NTP, 1989). Previous subchronic dermal toxicity studies (CTFA, 1986; NTP, 1989) with HQ failed to detect nephrotoxicity; however, these studies were not specifically designed to assess renal structure and function. More sensitive endpoints were used in the present subchronic study to address concerns over potential toxicity from repeated dermal exposure to HQ. Male and female F344 rats were given topical applications with 0, 2.0, 3.5, or 5.0% HQ in an oil-in-water emulsion cream for 13 wk (5 days/wk). Body weights, feed consumption and water consumption were monitored, and animals were observed for clinical signs of toxicity and dermal irritation. Blood taken at termination was analysed for haematological and clinical chemistry effects. Erythema, which abated when exposure stopped, was the only dermatological effect seen at the HQ-cream application sites. Cell proliferation in the kidneys was evaluated after 3, 6 and 13 wk of treatment using bromodeoxyuridine (BrdU) labelling, but no changes indicative of sustained cell proliferation were seen. The renal histopathological lesions noted after oral exposure to HQ were not present after dermal exposure. Thus, topical exposure to HQ does not result in the renal toxicity observed in previous studies with F344 rats given HQ orally.

Administration, Cutaneous↗
PubMed1997

Isolation and characterization of novel iron-oxidizing bacteria that grow at circumneutral pH.

A gel-stabilized gradient method that employed opposing gradients of Fe2+ and O2 was used to isolate and characterize two new Fe-oxidizing bacteria from a neutral pH, Fe(2+)-containing groundwater in Michigan. Two separate enrichment cultures were obtained, and in each the cells grew in a distinct, rust-colored band in the gel at the oxic-anoxic interface. The cells were tightly associated with the ferric hydroxides. Repeated serial dilutions of both enrichments resulted in the isolation of two axenic strains, ES-1 and ES-2. The cultures were judged pure based on (i) growth from single colonies in tubes at dilutions of 10(-7) (ES-2) (ES-2) and 10(-8) (ES-1); (ii) uniform cell morphologies, i.e., ES-1 was a motile long thin, bent, or S-shaped rod and ES-2 was a shorter curved rod; and (iii) no growth on a heterotrophic medium. Strain ES-1 grew to a density of 10(8) cells/ml on FeS with a doubling time of 8 h. Strain ES-2 grew to a density of 5 x 10(7) cells/ml with a doubling time of 12.5 h. Both strains also grew on FeCO3. Neither strain grew without Fe2+, nor did they grow with glucose, pyruvate, acetate, Mn, or H2S as an electron donor. Studies with an oxygen microelectrode revealed that both strains grew at the oxic-anoxic interface of the gradients and tracked the O2 minima when subjected to higher O2 concentrations, suggesting they are microaerobes. Phylogenetically the two strains formed a novel lineage within the gamma Proteobacteria. They were very closely related to each other and were equally closely related to PVB OTU 1, a phylotype obtained from an iron-rich hydrothermal vent system at the Loihi Seamount in the Pacific Ocean, and SPB OTU 1, a phylotype obtained from permafrost soil in Siberia. Their closest cultivated relative was Stenotrophomonas maltophilia. In total, this evidence suggests ES-1 and ES-2 are members of a previously untapped group of putatively lithotrophic, unicellular iron-oxidizing bacteria.

Bacteria, Aerobic↗
PubMed1994

Measurement of cell proliferation in the kidneys of Fischer 344 and Sprague-Dawley rats after gavage administration of hydroquinone.

Oral administration of hydroquinone (HQ) over 2 years to male Fischer 344 (F344) rats results in a dose-related nephropathy and an increase in the incidence of renal tubule adenomas. Female F344 rats, B6C3F1 mice, and Sprague-Dawley (SD) rats are resistant to the chronic renal toxicity of HQ, and nephrotoxicity was not seen in dogs or humans following subchronic exposure. To better characterize the early development of renal toxicity in rats, cell proliferation was quantitated within the proximal (P1, P2, and P3) and distal tubule segments of the kidney in rats given 0, 2.5, 25, or 50 mg/kg HQ by gavage. Male and female F344 rats were treated for 1, 3, or 6 weeks, and male SD rats were treated for 6 weeks. Cell proliferation was quantitated by incorporation of bromodeoxyuridine, detected immunohistochemically, into newly synthesized DNA. At 6 weeks, renal cell proliferation was increased over vehicle-controls in male F344 rats dosed at 50 mg/kg. Significant elevations (p < 0.001) occurred in the P1 segments (87%) and in the P2 segments (50%) but the elevation in the P3 segment (34%) was not statistically significant. Urinalyses revealed increases in the rate of excretion of enzymes indicative of proximal tubular damage. Histopathologic evaluation of the kidneys was consistent with a dose-related tubular degeneration in the male F344 rat. No chemical-related effects were observed in the kidneys of female F344 and male SD rats. These data parallel the findings of sex- and strain-specific kidney adenomas in the 2-year bioassays, and suggest that chemically induced cell proliferation secondary to toxicity may be important in the pathogenesis of benign renal tumors in male F344 rats treated with HQ.

Animals↗
PubMed1991

Release of the cytokines colony-stimulating factor-1, granulocyte-macrophage colony-stimulating factor, and IL-6 by cloned murine vascular smooth muscle cells.

Vascular smooth muscle cells were cultured from the mesenteric arteries of MRL lpr/lpr, MRL +/+, CBA/J, or C3H/HeJ mice and evaluated for their ability to synthesize a range of cytokines. Vascular smooth muscle cells of MRL +/+, MRL lpr/lpr, and CBA/J origin released biologically significant amounts of CSF-1 and IL-6 and relatively low but detectable amounts of granulocyte macrophage-CSF (GM-CSF) but not IL-2, IL-3, or IL-4. Vascular smooth muscle cells of C3H/HeJ origin produced lower amounts of CSF-1 and IL-6, and GM-CSF was barely detectable. Production of these cytokines did not require the exogenous growth factors present in FCS and occurred, although at lower levels, in serum-free medium supplemented with insulin, transferrin, and albumin. Cloned lines of MRL +/+ vascular smooth muscle cells, with electron microscopic and immunochemical properties of vascular smooth muscle cells, produced CSF-1, IL-6, and GM-CSF, establishing that vascular smooth muscle cells were a direct source of CSF-1, IL-6, and GM-CSF. These observations highlight the need for experiments to directly address the question of whether vascular smooth muscle cells constitutively produce these cytokines under physiologic conditions in vivo and suggest that vascular smooth muscle cells may participate actively in inflammation by releasing cytokines that are active on lympho-hemopoietic and other cells.

Animals↗
PubMed1990

Successful allogeneic transplantation of rat islets expressing cytokine-induced major histocompatibility complex class II antigen.

Cultured neonatal rat (F344, RT1(1v1)) islets that were devoid of MHC class II (OX6) antigen and antigen-presenting cells were treated with recombinant murine interferon (IFN-gamma) and/or recombinant murine tumor necrosis factor (TNF-alpha) in vitro. The IFN-gamma and TNF-alpha resulted in some disruption of the integrity of the islets by 7 days of culture, but the combination resulted in disaggregation of the islets within 7-8 days. Insulin release into the medium and secretion in response to glucose were adversely affected by the cytokines. The IFN-gamma resulted in expression of class II antigen on about 10% of the endocrine cells after 3-4 days in culture. This effect of IFN-gamma was potentiated by TNF-alpha resulting in 27% of the cells expressing class II antigen. Islets treated with IFN-gamma and TNF-alpha alone or in combination were not rejected in a subsequent transplant underneath the kidney capsule of WF rats (RT1u). We conclude that expression of class II antigen alone is not sufficient to initiate an allogeneic rejection response, but that cytokine-mediated destruction of endocrine cells could be the basis of immune-mediated islet-cell loss in islet-allograft rejection or autoimmune diabetes.

Animals↗
PubMed1985

Two histopathologic types of inflammatory vascular disease in MRL/Mp autoimmune mice. Model for human vasculitis in connective tissue disease.

We have recently described 2 histopathologic types of inflammatory vascular disease (IVD) in patients with Sjögren's syndrome (SS): neutrophilic IVD (NIVD) and mononuclear IVD (MIVD). Autoimmune MRL/Mp mice, which have many features of SS, spontaneously develop IVD which is histopathologically indistinguishable from that observed in human SS patients. Both MRL/Mp-+/+ and MRL/Mp-lpr/lpr mice develop MIVD which evolves into NIVD and results in decreased survival; the transition to NIVD is accelerated by the lpr gene. The presence of the lpr gene on other genetic backgrounds does not result in a similar acceleration of IVD and associated decreased survival. Thus, the spontaneous autosomal recessive mutation lpr appears to modulate the development of IVD in a strain of mice with an underlying propensity for vasculitis. Based on our observations on IVD in SS patients and MRL/Mp mice, we propose a new model which may enhance our understanding of the immunopathogenesis of IVD in connective tissue disease.

Animals↗
PubMedDate not supplied

Failure of nonimmunogenic islet allografts to induce donor-specific immunological unresponsiveness [corrected].

Highly purified perinatal rat islets, isolated by a nonenzymic in vitro culture technique, have been successfully transplanted across complete MHC barriers without immunosuppression. Acceptance of these allogeneically transplanted islets is hypothesized to result from an absence of antigen presenting cells (APCs) within the islets. This study was designed to examine the effects of organ transplantation and cyclosporine (CsA) therapy on the development of immunological unresponsiveness in recipients receiving a graft of culture-isolated islets. Kidneys were successfully allotransplanted into unilaterally nephrectomized rats, across a complete MHC barrier (Rt1lv1 to Rt1u) using CsA therapy initiated on the day of transplantation (7.5 mg/kg, orally for 14 days). Remaining native kidneys were removed 14 days following renal allotransplantation. Limited mononuclear cell (MNC) infiltrates were observed in biopsies of renal allografts, taken 30 days posttransplant, but failure of the renal allograft was not observed. Animals bearing established renal allografts (n = 10) received allografts of approximately 200 highly purified perinatal islets (ACl, n = 5; F-344, n = 5), transplanted to the kidney subcapsule of the established renal allograft at least 30 days following renal allotransplantation (at least 16 days following termination of CsA). Islet allografts were not rejected, and, as expected, did not initiate rejection of the renal allograft. Similar results were observed in renal allograft recipients rendered diabetic by a single injection of streptozotocin (STZ, 65 mg/kg, n = 5) and receiving islet allografts of sufficient mass (approximately 1200-1400 islets) to reverse STZ-induced hyperglycemia. Further, neither islet nor renal allografts were rejected following challenge by 1 x 10(7) donor-strain dendritic cells (DCs).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗