Emerging evidence suggests that parathyroid hormone-related peptide (PTHrP) serves as a regulator of the development and/or differentiation of a number of organs, including endochondral bone, the tooth, and the mammary gland. Although disruption of the PTHrP gene by homologous recombination results in a lethal chondrodystrophy, PTHrP-knockout mice that have been rescued by the transgenic replacement of the peptide in cartilage display abnormalities in ectodermally derived structures including the skin. At 6-8 wk of age, these rescued PTHrP-knockout mice displayed a markedly thinned epidermis and striking hyperkeratosis, hypoplastic sebaceous glands, and a fibrotic dermis. In contrast, transgenic mice that overexpress PTHrP by virtue of the human keratin-14 promoter displayed a thickened ventral epidermis with marked acanthosis and papillomatosis, hyperplastic sebaceous glands, and a cellular dermis. The absence of PTHrP appeared to result in the reduction of the basal keratinocyte compartment and premature acquisition of suprabasal and granular differentiation markers, whereas overexpression of the peptide generated reciprocal findings. No difference in the epidermal proliferation rate was found in PTHrP-null skin and although an increase was observed in keratin 14-PTHrP transgenic animals, their epidermis did not express the hyperplasia marker K6. Finally, the replacement of PTHrP in the basal keratinocytes of rescued PTHrP-knockout mice under the direction of the keratin 14 promoter reversed the abnormalities seen in PTHrP-null skin. These findings suggest that PTHrP regulates the rate of keratinocyte differentiation in the skin of adult mice.
Breast cancer metastasis to bone triggers a vicious cycle of tumor growth linked to osteolysis. Breast cancer cells and osteoblasts express the epidermal growth factor receptor (EGFR) and produce ErbB family ligands, suggesting participation of these growth factors in autocrine and paracrine signaling within the bone microenvironment. EGFR ligand expression was profiled in the bone metastatic MDA-MB-231 cells (MDA-231), and agonist-induced signaling was examined in both breast cancer and osteoblast-like cells. Both paracrine and autocrine EGFR signaling were inhibited with a neutralizing amphiregulin antibody, PAR34, whereas shRNA to the EGFR was used to specifically block autocrine signaling in MDA-231 cells. The impact of these was evaluated with proliferation, migration and gene expression assays. Breast cancer metastasis to bone was modeled in female athymic nude mice with intratibial inoculation of MDA-231 cells, and cancer cell-bone marrow co-cultures. EGFR knockdown, but not PAR34 treatment, decreased osteoclasts formed in vitro (p<0.01), reduced osteolytic lesion tumor volume (p<0.01), increased survivorship in vivo (p<0.001), and resulted in decreased MDA-231 growth in the fat pad (p<0.01). Fat pad shEGFR-MDA-231 tumors produced in nude mice had increased necrotic areas and decreased CD31-positive vasculature. shEGFR-MDA-231 cells also produced decreased levels of the proangiogenic molecules macrophage colony stimulating factor-1 (MCSF-1) and matrix metalloproteinase 9 (MMP9), both of which were decreased by EGFR inhibitors in a panel of EGFR-positive breast cancer cells. Thus, inhibiting autocrine EGFR signaling in breast cancer cells may provide a means for reducing paracrine factor production that facilitates microenvironment support in the bone and mammary gland.
Type E botulinum neurotoxin is produced by Clostridium botulinum along with a neurotoxin binding protein which helps protect the neurotoxin from adverse pH, temperature, and proteolytic conditions. The neurotoxin binding protein has been purified as a 118-kDa protein. Secondary structure content of the neurotoxin binding protein as revealed by far-UV circular dichroism spectroscopy was 19% alpha-helix, 50% beta-sheets, 28% random coils, and 3% beta-turns. This compared to 22% alpha-helix, 44% beta-sheets, 34% random coils, and no beta-turns of the type E botulinum neurotoxin. The complex of the two proteins revealed 25% alpha-helix, 45% beta-sheets, 27% random coils, and 3% beta-turns, suggesting a significant alteration at least in the alpha-helical folding of the two proteins upon their interaction. Tyrosine topography is altered considerably (28%) when the neurotoxin and its binding protein are separated, indicating strong interaction between the two proteins. Gel filtration results suggested that type E neurotoxin binding protein clearly complexes with type E neurotoxin. The interaction is favored at low pH as indicated by an initial binding rate of 8.4 min-1 at pH 5.7 compared to 4.0 min-1 at pH 7.5 as determined using a fiber optic-based biosensor. The neurotoxin and its binding protein apparently are of equivalent antigenicity, as both reacted equally on enzyme-linked immunosorbent assay to polyclonal antibodies raised against the toxoid of their complex.
556JBE VIRUS IN TISSUE CULTURE ministered in stimulating or depressing dosage. I t was not possible to test the therapeutic efficacy of reserpine after serotonin administration, as the neurological symptoms induced by intra-arterially injected serotonin were of too short duration.SuInzIncIr?1. 1) Serotonin. administered into brain-tissue via an estravascular route. induces edema. possibly due to its musculotropic property. 2 ) Serotonin was confirmed to have a neurotropic action which appeared to be responsible for the reversible hemiplegic symptoms.3 ) The neurotropic effect of serotonin is biphasic. i.c. when administered in low dosage via internal-carotid artery, it causes transient spastic paralyses. In high dosage. it causes flaccid paralyses without inducing cerebral edema. 4) Chlorpromazine and reserpine both block the edema-inducing action of serotonin. Reserpine is, however, effective in a much lower dosage. 5 ) Chlorpromazine potentiates the neurotropic depressant effect of serotonin. but apparently does not alter its stirnulatins action. 6 ) Reserpine inhibits the neurotropic effect of serotonin. This holds true for the spastic as well as for the flaccid symptoms. 7) Therapeutic considerations suggest that reserpine may be specifically indicated in prophylactic treatment of apoplexy.1. Ronnameaux, Y., Lecomte, J.. A d z . Internal.
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