ABSTRACT
Somatostatin (SRIF, SRIF-14) is a known product of the normal and malignant parafollicular cell of the thyroid. In this report we characterize SRIF production by the TT cells, a line of transformed calcitonin-producing cells derived from a human medullary thyroid carcinoma. The cells were found to contain (5-12 ng/10(6) cells) and secrete (3-10 ng/10(6) cells X 48 h) immunoreactive SRIF. Molecular sieve chromatography of cell extracts under denaturing conditions showed a major peak with a mol wt slightly larger than 12,700, probably representing pro-SRIF and a second peak which coeluted with SRIF; in one gel chromatogram a very small peak was also noted which coeluted with SRIF-28, but represented less than 0.4% of the total immunoreactive SRIF. Short term secretion of calcitonin and SRIF was stimulated by calcium in vitro (0.5-4 mM) in a dose-related manner. mRNA isolated from the TT cells hybridized to a specific bovine fetal pancreatic SRIF DNA (BFPS-2); there was no hybridization to identical amounts of mRNA from the atT-20/D16, 3T3, or RINC5F cell lines. In vitro translation of the TT cell mRNA followed by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the product revealed a single protein band of approximately 13,000 daltons. It was completely abolished when the immunoprecipitation was performed in the presence of excess unlabeled SRIF. Northern transfer of TT cell cytoplasmic RNA and hybridization with FBPS-2 cDNA showed a single hybridizing band with an apparent size of approximately 750 nucleotides. Our observations demonstrate the production of SRIF by a continuous line of human medullary thyroid carcinoma cells and provide a model for studying the biosynthesis and secretion of SRIF in the parafollicular cell.
Subject(s)
Somatostatin/biosynthesis , Thyroid Neoplasms/metabolism , Animals , Calcium/pharmacology , Cattle , Cell Line , Chromatography, Gel , DNA/analysis , Dose-Response Relationship, Drug , Humans , Nucleic Acid Hybridization , Potassium/pharmacology , RNA, Messenger/analysis , Radioimmunoassay , Somatostatin/geneticsABSTRACT
A survey of all Canadian hospitals was undertaken in 1986 to determine the extent of the reuse of disposable medical devices meant for "single use only." It was found that 41% of hospitals regularly reused disposable medical devices, and reuse was significantly higher in hospitals with more than 200 beds. Only 38% of hospitals that regularly reused had written procedures for reuse, and 32% indicated a mechanism for determining the number of times a device was reused. Cost analysis studies had been undertaken by only 29% of regular reusers, and items of respiratory therapy equipment were the most commonly reused devices.
Subject(s)
Cross Infection/prevention & control , Disposable Equipment/standards , Equipment Safety , Equipment and Supplies, Hospital/standards , Canada , Humans , Surveys and QuestionnairesSubject(s)
Acrylates/pharmacology , Alkylating Agents/pharmacology , Antibody Formation/drug effects , Methacrylates/pharmacology , Neoplasms, Experimental/immunology , 9,10-Dimethyl-1,2-benzanthracene , Adenocarcinoma/immunology , Animals , Antigens, Neoplasm , Benzyl Compounds/pharmacology , Breast Neoplasms/immunology , Dinitrobenzenes/pharmacology , Female , Humans , Mice , Mice, Inbred C3H , Neoplasm Metastasis , Neoplasm Transplantation , Neoplasms, Experimental/chemically induced , Transplantation, HomologousABSTRACT
There have been few studies of physiological importance on the regulation of somatostatin by hormones. We have studied the effect of the synthetic glucocorticoid dexamethasone on somatostatin production in the human medullary thyroid carcinoma TT cell line, a model for somatostatin production by the parafollicular cell. Dexamethasone inhibited somatostatin production in a dose-related manner with a maximal effect at a concentration of 10(-6) M. TT cells treated with dexamethasone (10(-6) M) showed an almost complete inhibition of somatostatin peptide production by 48 h of treatment. Molecular sizing chromatography demonstrated a decrease in both the probable somatostatin precursor (13,000 dalton) and the fully processed peptide. Analysis of mRNA content by hybridization revealed that dexamethasone also caused a decrease in detectable somatostatin mRNA. The hybridizable somatostatin mRNA decreased to approximately 50% of basal levels within 12 h of treatment. Northern blot hybridization showed a decrease in a single RNA species representing mature somatostatin mRNA. Dose-response experiments revealed inhibition of both peptide and mRNA at concentrations from 1 X 10(-8) to 1 X 10(-5) M dexamethasone. Four days after withdrawal from dexamethasone treatment, peptide and mRNA levels were higher than dexamethasone-treated controls. The sex steroid estradiol had no inhibitory effect on somatostatin production. These results suggest a potential regulator of somatostatin production and provide a system for the study of somatostatin gene regulation.