ABSTRACT
BACKGROUND: Published data regarding effects of growth hormone (GH) on the renin system are controversial. The aim of this study therefore was to evaluate the effects of GH on the renin system in normal rats and rats with myocardial infarction (MI). METHODS: Normal rats received 2, 5, or 10 IU GH/kg/day or vehicle subcutaneously for 4 weeks. Furthermore rats with MI were randomized to receive 2 IU GH/kg/day or vehicle for 4 weeks. Subdivision into MI groups (mild, moderate, and large) was by histological determination of infarct size. Renal renin gene expression was assessed by RNAase protection assay and plasma renin activity by radioimmunoassay. In addition, isolated mouse juxtaglomerular cells were exposed to GH for 20 h, and renin secretion rates were assessed. RESULTS: GH treatment in normal rats for 4 weeks increased body weight, and kidney weight to body weight ratio, but did not affect renin secretion and renal renin gene expression. In rats with large MI, renal renin gene expression increased about fourfold, but was unchanged in rats with small and moderate MI as compared to normal rats. In rats with MI, body weight decreased and this decrease was partially reversed by GH treatment. GH treatment did not change renal renin gene expression, and renin secretion in rats with MI. Renin secretion of isolated juxtaglomerular cells was unaffected by GH. CONCLUSIONS: Our study demonstrates that GH treatment has no significant effect on renin secretion and on renal renin gene expression in normal rats and in rats with stimulated renin system due to MI in vivo. In isolated juxtaglomerular cells in vitro, renin secretion was also unaffected by GH.
Subject(s)
Gene Expression Regulation, Enzymologic/drug effects , Human Growth Hormone/pharmacology , Kidney/enzymology , Myocardial Infarction/enzymology , Renin/genetics , Animals , Humans , Juxtaglomerular Apparatus/enzymology , Kidney/drug effects , Male , Mice , Myocardial Infarction/genetics , Myocardial Infarction/pathology , Rats , Rats, Wistar , Recombinant Proteins/pharmacology , Reference Values , Renin/metabolismABSTRACT
Fracture surfaces of both monotonic and fatigue loaded bone cement samples were examined to investigate the fractographic characteristics of PMMA. Classic cleavage step river patterns were observed on all monotonically loaded samples, running downstream in the direction of crack propagation. All fatigue cracks initiated at internal pores and the direction of crack propagation of many cracks was discernible. Porosity, pore size, and pore size distribution were found to affect the crack initiation and fatigue behavior of bone cement. Statistical analysis revealed a strong negative correlation between two-dimensional porosity present on the fracture surfaces and the cycles to failure. The fractographic observations of these fatigue samples elucidate one reason why porosity reduction by centrifugation or vacuum mixing increases the fatigue life of PMMA bone cement.
Subject(s)
Biocompatible Materials , Bone Cements , Methylmethacrylates , Centrifugation , Equipment Failure , Materials Testing , Microscopy, Electron, Scanning , Stress, Mechanical , Surface Properties , Weight-BearingABSTRACT
A mathematical model for the prediction of lanthanide element concentrations in soil and plant samples is presented. A comparison between predicted and measured lanthanide values in soil and plant samples show, that the model produces good results for the elements in the soil samples and for most elements in plant material. The accuracy of prediction worsens with decreasing concentration of the heavier lanthanide elements. The mathematical model presented is not valid on other environmental samples like aerosols, because no data for these matrices are available yet to calibrate our normalized curves.
Subject(s)
Metals, Rare Earth/analysis , Plants/analysis , Soil/analysis , Mathematics , Models, TheoreticalSubject(s)
Equipment and Supplies/standards , Jurisprudence , Product Labeling , Drug Labeling , Humans , Risk , Safety , United StatesABSTRACT
The refinement of the product liability litigation process requires a continuing substantive dialogue between the legal and technical communities. The common problem-solving orientation of the two disciplines bodes well for such interaction. We have shared in the exciting beginnings of this legaltechnical interaction (7) and hope that in the field of product liability such joint efforts will lead to a more sophisticated and technologically sound litigation process, one in which the technologist can be true to himself while operating within a strong and responsive adversary system.
