The most abundant polar impurities detected by ion-pair high-pressure liquid chromatography of sodium saccharin produced by the Maumee process were identified as 5- and 6-aminosaccharin. The combined levels of these compounds in the samples analysed ranged from 99 to 152 mg/kg. Other less abundant polar impurities identified in Maumee process sodium saccharin were 7-aminosaccharin and o-sulphamoylbenzoic acid. Mutagenicity assays of 5-aminosaccharin, 6-aminosaccharin and a polar impurity fraction isolated from Maumee saccharin, gave negative results.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Increased activity of catalase in tumor cells overexpressing IGFBP-2.

Elevated levels of IGFBP-2 are found in serum and tissues under various stressful conditions and in many malignancies. In previous studies, we have shown that overexpression of IGFBP-2 results in increased tumorigenic potential in Y-1 mouse adrenocortical tumor cells, and that these effects are presumably mediated through IGF-independent mechanisms. Here, we show that highly proliferative IGFBP-2-overexpressing Y-1 cells, but not control Y-1 cells, grow to very high cell densities. In order to evaluate whether the increased cell densities in IGFBP-2-transfected Y-1 cells were accompanied by alterations in the oxidative stress system, we analyzed the effect of IGFBP-2 overexpression on the activity of various antioxidative enzymes in two malignant cell lines. Among the tested antioxidative enzymes (catalase, superoxide-dismutase, glutathione peroxidase, glutathione S-transferase), only catalase enzyme activity was significantly higher in IGFBP-2-transfected Y-1 mouse adrenocortical tumor cells and in IGFBP-2-transfected human colon tumor cells (Caco-2) compared to control-transfected Y-1 and Caco-2 cells and non-tumor 293 human epithelial cells. However, overexpression of catalase in malignant cells did not result in increased resistance to oxidative stress as measured by cell viability and protein oxidation after treatment of the cells with hydrogen peroxide. This might be due to an upregulation of the GST enzyme activity after treatment with H (2)O (2) that we observed selectively in the control-transfected Y-1 cells and which might compensate for the higher catalase activity in the IGFBP-2 overexpressing cells. In summary, we found a strong and selective upregulation of the catalase activity in IGFBP-2 overexpressing malignant Y-1 and Caco-2 cell lines that might contribute to the highly malignant phenotype of IGFBP-2 overexpressing tumors through as yet unknown mechanisms.

Adrenal Cortex Neoplasms↗

PubMedDate not supplied

Differential autocrine regulation of intestine epithelial cell proliferation and differentiation by insulin-like growth factor (IGF) system components.

The mechanisms which regulate cell turnover in the intestinal epithelium are incompletely understood. The present study was performed to characterize the role of autocrine IGF system components in intestine epithelial cell proliferation and differentiation comparing rapidly growing crypt cells (IEC-6) with differentiating enterocytes (CaCo-2). The autocrine release of IGF-I, IGF-II and IGFBP-1 through -3 was determined by specific RIAs and western ligand blotting. In addition, binding and growth-promoting activity of insulin, IGF-I and IGF-II was investigated. Enterocytic differentiation was assessed by measuring the brush-border enzymes alkaline phosphatase and sucrase. During IEC-6 growth, the autocrine release of IGF-I and -II increased, whereas IGFBP-2 levels decreased. Specific receptors for IGF-I and IGF-II but not insulin could be detected. IGF-I was 100-fold more potent than insulin to stimulate IEC-6 cell proliferation. In contrast, CaCo-2 cells revealed higher binding of insulin than IGF-I/-II and no release of IGF-I. At switch from CaCo-2 cell proliferation to differentiation a marked increase in the secretion of IGF-II (10-fold), IGFBP-1 (2.5-fold), IGFBP-2 (3-fold), and IGFBP-3 (6-fold) was measured. Our data indicate that IGF system components differentially modulate enterocytic cell proliferation and differentiation.

Animals↗

PubMedDate not supplied

[Results of fluorescence microscopy studies of bone healing by direct stimulation with bipolar impulse currents and with the interference current procedure in the animal experiment].

42 cross-breed rabbit bastards of either sex were osteotomized on the left proximal third of the tibia. A teflonisolated stable plating was made by means of the polychromatically KF-AO-instrumentarium. The animals were fluorescentlabelled in weekly intervals. Tetraverinex, alizarin complexon, fluorexon, xylenol orange and calceine were used as colours. The animals were stimulated in the bipolar squaretopped pulse current procedure (1 Hz and 10 Hz, resp., +/- 25 and +/- 50 microA, resp., intensity, permanent stimulation) or in the interference current procedure (oscillation frequency 100 Hz, intensity 1 mA, 4 hours daily). An osteotomized group served as a control. The undecalcified bone sections were quantitatively measured in the area of the periosteal and endoosteal accummulation seams as well as in the area of the Haversians canals and compared by means of multiple variance analyses. A delay in the Haversian remodelling within the first 2 weeks was found in the animals only osteotomized. This delay could not be detected in all electrically stimulated groups. The electrical stimulation leads to a shortening of the fracture healing period by skipping the physiologically occurring delay of the Haversian remodelling in fractures and osteotomies. Further on there was derived a growth function of the osteones as a regression function r (t) = a + beta X e gamma t. For the rabbit the concrete formula expression r (t) = 50.9 X e-0.094 X t + 17.4 for the animals not treated and r (t) = 42.9 X e-0.067 X t + 8.5 for the electrical stimulated animals has been found.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

[Rate of maturation of osteons].

This paper examines the dynamics of Havers'ian remodelling and the concept of maturation rate of poly-chrome fluorescence-labeling osteons by means measurements of bone formation. It was used cortical bone of rabbit and merino sheep on various experimental conditions (Normal bone growth in the diaphysis of large bone and cortical bone of iliac crest, secondary fracture healing in tibia osteosyntheses with external fixation and oligotrophic pseudoarthrosis in rabbit. Gap healing of fractures in tibia osteosyntheses with external fixation and compression in the sheep). The diameters of labels were measured and the mathematical function of maturation rate of osteons was made out. The results were compared on the different experiment conditions. Statistical analyses have shown that the results of mathematical function and the values of their constants are not significantly different. These results seem to suggest that the rate of formation of the osteon is optimal on the various conditions and it is not use stimulating the osteoblastic activity with stimulation-therapy. The described model shows important informations of bone remodeling and adds new facts to the understanding of formal genesis of bone growth and fracture healing.

Animals↗