Nerve growth factor (NGF)- and epidermal growth factor (EGF)-stimulated microtubule-associated protein (MAP) kinase activities from PC-12 cells were recently found to be resolvable into two peaks (MAP kinases I and II) by ion-exchange or hydrophobic-interaction HPLC. To compare MAP kinases detected in PC-12 cells with growth factor-sensitive MAP kinases in other cells, a number of tissue culture cells were treated with various growth factors such as NGF, EGF, platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and endothelial cell growth factor (ECGF); and lysates of the cells were assayed for MAP kinase activity. Cells transfected with the NGF receptor gene (CHO-1Q) and those overexpressing the EGF receptor (A-431) had a high background level of MAP kinase activities. On the other hand, overexpression of tyrosine kinase activities causes the down regulation and the desensitization of the growth factor responses in SR-3Y1 and trk-3T3 cells. No detectable EGF receptor was observed in SR-3Y1 and trk-3T3 cells. The level of MAP kinases I and II activation by growth factors was cell line dependent, but the two forms of MAP kinases, I and II, were detected in all cultured cells examined and activated by various growth factors. These data suggest that the activation of these two forms of MAP kinase are commonly involved in the signal transduction pathways induced by various growth factors.
Nerve growth factor (NGF)- and epidermal growth factor (EGF)-stimulated MAP kinase activities from PC-12 cells were recently found to be resolvable into two peaks (microtubule-associated protein [MAP] kinases I and II) by ion-exchange or hydrophobic-interaction HPLC, and both kinases I and II were activated by various growth factors, by okadaic acid, and by phorbol esters. In the present study both MAP kinases I and II were also activated by bombesin/gastrin-releasing peptide (GRP) in Swiss 3T3 cells, and the peak of activation in response to GRP occurred earlier than that observed with EGF. In this work, we confirmed the results reported by Bierman et al. (J. Cell. Phys., 142, 441-448). Since the cDNA for the bombesin/GRP receptor indicates that this receptor has a transmembrane topology like that of other G-protein-coupled receptors, an alternative signal transduction pathway may mediate the activation of MAP kinase by bombesin/GRP.
Caffeine through drinking water, at low (100μg/ml), moderate (200 and 400μg/ml) and high (800μg/ml) doses, as well as by intragastric administration at 40 and 160mg/kg doses, increased the hepatic and pulmonary cytochrome P-450 (Cyt. P-450) levels in mice. The extent of elevation in the enzyme levels was dependent on the dose of caffeine. Maximum inducibility of hepatic arylhydrocarbon hydroxylase (AHH) was observed at the highest doses of caffeine by the two modes of treatment. However, the activities of AHH at the highest doses were not statistically different from the enzyme activities at the lowest doses. Caffeine treatment of animals through drinking water did not change the pulmonary AHH activity, whereas the intragastric administration of caffeine increased the enzyme activity in the lungs. Moreover, intragastric administration was more effective in inducing the hepatic AHH activity. Maximum increases in hepatic and pulmonary glutathione-S-transferase (GST), and in hepatic reduced glutathione (GSH), by the two modes of caffeine treatment of the animals was similar. The enhancement in AHH, Cyt. P-450, GST, and GSH may account for the anticarcinogenic activity of caffeine.
The activities of enzymes involved in the degradation of lipid peroxides, viz., glutathione peroxidase, glutathione S-transferase (GST), glutathione reductase (GR), and glucose-6-phosphate dehydrogenase (G-6-PDH), were measured in the erythrocytes, liver, brain, and heart of male SAM-P/1 mice (accelerated senescence-prone mice) over a period from 1 to 10 months after birth in comparison with those of age-matched male SAM-R/1 mice (accelerated senescence-resistant mice). Among the enzyme activities examined, GR activity in SAM-P/1 mice was markedly lower than that in SAM-R/1 mice in the erythrocytes and all organs tested. GST activity in the liver of the former mice was also lower than that of the latter mice. These results would explain, at least in part, the increased level of lipid peroxides in the former mice as compared with that in the latter. It was noted that G-6-PDH activity increased in the erythrocytes and liver of SAM-P/1 mice.
The susceptibility of red blood cells to hydrogen peroxide-induced lipid peroxidation was determined for 30 pregnant women in the second stage of labor before and after hyperbaric oxygen therapy. Thirty non-pregnant women were chosen and studied as healthy controls. The results obtained before and after hyperbaric oxygen therapy were compared, and the oxygen therapy was found to cause a significant increase in erythrocyte susceptibility to lipid peroxidation (p<0.001), an increased plasma lipid peroxide value (p<0.001), and a significant decrease in glutathione level (p<0.001). Osmotic fragility curves showed that oxygen therapy caused the appearance of a population of slightly fragile cells, as evidenced by tailing. Reactive oxygen radical formation, their toxic effects in causing lipid peroxidation, and the possible measures that can be taken in such a case are discussed.
The concentration of selenium (Se) and the activity of glutathione peroxidase (GSH-Px) in plasma and erythrocytes were measured in healthy men and in patients with Duchenne-type progressive muscular dystrophy (DMD). In healthy men, the Se concentration in erythrocytes showed a steep rise with aging and ascended gradually in plasma. The GSH-Px activity in both plasma and erythrocytes clearly increased with aging. The relationship between the Se concentration and the GSH-Px activity in healthy men showed a parallel rise with aging, but the coefficients of correlation were not very high (r=0.44 and 0.56 in plasma and erythrocytes, respectively). In DMD patients, on the other hand, the Se concentration in erythrocytes decreased steeply with aging, and it decreased gradually in plasma. The GSH-Px activity in both plasma and erythrocytes apparently increased as in healthy men with aging, but the level was about 80% of that of healthy men. These data suggest that a lower GSH-Px activity in DMD patients may explain in part why the disease may intensify with aging.
This study examined fish oil storage using samples from 7 autopsied patients. Four of these seven patients had been under intravenous alimentation for more than 2 months without supplementation of fish oils. Both subcutaneous and omental adipose tissues were rich in n-9 and n-6 fatty acids but poor in the n-3 fatty acids EPA and DHA. In contrast, fish oil fatty acids were abundant in liver lipids, especially in phospholipids. The absolute amounts of EPA and DHA in total lipids were calculated based on the actual weighed liver and on the estimated total adipose tissue mass. The mean liver EPA and DHA contents were 2.59 and 9.65g, respectively, whereas mean adipose tissue EPA was 0.89g and DHA 2.90g. Thus the absolute fish oil fatty acid content in liver was about 3 times greater than that in the adipose tissue mass. Gas liquid chromatographic chemical-ionization mass spectrometry clearly identified the fish oil fatty acids from the autopsied patients as being the same as authentic standards purified from fish. These findings provide evidence that ingested fish oils are stored in the human liver for more than 2 months.
Plasma, red blood cells (RBC), and platelets from young female subjects on varying intakes of vitamin E (VE) as butter or margarine (rich in VE) were analyzed for tocopherols to estimate which blood components most closely followed changes in the dietary intake. The VE nutritional status of the subjects at the beginning of the study was marginally deficient from the normal range of RBC α-tocopherol. No significant changes in the plasma α-tocopherol concentrations were observed, even though the VE intake had increased. The α-tocopherol level in RBC, however, increased with an increase in VE intake; and that in platelets, to a lesser extent. The plasma lipid peroxide levels were lowered with increased VE intake, showing an inverse change to the α-tocopherol levels in red blood cells and platelets. Consequently, changes in α-tocopherol levels in RBC closely followed varying dietary intakes of VE when compared with data from platelets and plasma.