Lipid peroxidation in plumbagin administered rats

Plumbagin was administered to rats at a concentration of 1,2,4,8 and 16 mg per kg body weight. After 24 h lipid peroxide levels were found to decrease in subcellular fractions of liver. Plumbagin inhibited ascorbate and nicotinafde adenine dinucleotide phosphate (reduced) dependent lipid peroxidation but was without any effect on cumene hydroperoxide dependent lipid peroxidation. Injection of 16 mg of plumbagin per kg body weight was found to decrease liver total reduced glutathione and also fcrosomal glucose-6-phosphatase. The results are discussed with reference to the anti- and prooxidant properties of plumbagin.     

Subcellular location of enzymes involved in the N-glycosylation and processing of asparagine-linked oligosaccharides in Saccharomyces cerevisiae

A particulate translation system isolated from the yeast Saccharomyces cerevisiae was shown to translate faithfully in-vitro-transcribed mRNA coding for a mating hormone precursor (prepro-alpha-factor mRNA) and to N-glycosylate the primary translation product after its translocation into the lumen of the microsomal vesicles. Glycosylation of its three potential sugar attachment sites was found to be competitively inhibited by acceptor peptides containing the consensus sequence Asn-Xaa-Thr, supporting the view that the glycan chains are N-glycosidically attached to the prepro-alpha-factor polypeptide. The accumulation in the presence of acceptor peptides of a membrane-specific, unglycosylated translation product (pp-alpha-F0) differing in molecular mass from a cytosolically located, protease-K-sensitive alpha-factor polypeptide (pp-alpha-Fcyt) by about 1.3 kDa, suggests that, in contrast to previous reports, a signal sequence is cleaved from the mating hormone precursor on/after translocation. This conclusion is supported by the observation that the multiply glycosylated alpha-factor precursor is cleaved by endoglucosaminidase H to a product with a molecular mass smaller than the primary translation product pp-alpha-Fcyt but larger than the membrane-specific pp-alpha-F0. Translation and glycosylation experiments carried out in the presence of various glycosidase inhibitors (e.g. 1-deoxynojirimycin, N-methyl-1-deoxynojirimyin and 1-deoxymannojirimycin) indicate that the N-linked oligosaccharide chains of the glycosylated prepro-alpha-factor species are extensively processed under the in vitro conditions of translation. From the specificity of the glycosidase inhibitors applied and the differences in the molecular mass of the glycosylated translation products generated in their presence, we conclude that the glycosylation-competent microsomes contain trimming enzymes, most likely glucosidase I, glucosidase II and a trimming mannosidase, which process the prepro-alpha-factor glycans down to the (Man)8(GlcNAc)2 stage. Furthermore, several arguments strongly suggest that these three enzymes, which apparently represent the full array of trimming activities in yeast, are exclusively located in the lumen of microsomal vesicles derived from endoplasmic reticulum membranes.     

Phorbol ester binding and protein kinase C activity in normal and transformed human keratinocytes

Normal keratinocytes, SV40-transformed keratinocytes (SVK14), and various squamous carcinoma cell (SCC) lines have been used as an in vitro model system to study the properties of phorbol ester receptor and protein kinase C expression during keratinocyte differentiation. The cell lines used exhibit a decreasing capacity to differentiate in the order of keratinocytes approximately SVK14 greater than SCC-12F2 greater than SCC-15 greater than SCC-4; moreover, all cell lines respond to a low external Ca2+ concentration by a decreased capacity to differentiate. Normal keratinocytes exhibited the highest number of phorbol ester receptors as compared to the other cell lines, while each individual cell line exhibited a higher number of phorbol ester receptors during growth under normal Ca2+ conditions as compared to cells grown under low Ca2+ conditions. The apparent dissociation constant (Kd) demonstrated only small variations in the various cell lines. In contrast, the cytoplasmic protein kinase C activity, was found to be higher in cells grown under low Ca2+ conditions than in cells grown under normal Ca2+ conditions, indicating the absence of a causal relationship between cytoplasmic protein kinase C activity and phorbol ester receptor expression. Therefore the properties of protein kinase C have been determined in more detail in normal keratinocytes and SCC-15 cells. These studies revealed differences between protein kinase C properties from the two cell lines grown under normal and low Ca2+ conditions. The differences included the effect of phorbol 12-myristate 13-acetate (PMA) on the redistribution pattern of protein kinase C between the cytoplasmic and particulate fractions as well as the activating effect of diolein in vitro on protein kinase C activity, partly purified from particulate or cytoplasmic fractions. These observations demonstrate that the functional protein kinase C activity of keratinocytes is determined by various endogenous and exogenous activators and that these activators are modulated differently in various cell lines, under various growth conditions (low Ca2+ versus normal Ca2+).     

Aortic diastolic caliber changes as a determinant for complete aortic baroreceptor resetting

It is well known that baroreceptors reset to operate at higher pressure in hypertension. The time course and mechanisms responsible for resetting are still unclear. There is a rapid or acute partial resetting that reaches its maximum within the first 5-15 min but changes little within the first hours. This resetting is, however, partial and becomes complete only if the pressure change is held permanently. Resetting is complete when the change in pressure threshold for baroreceptor activation matches the total pressure change. In the rat, complete resetting to hypo- or hypertension occurs in 48 h. The aortic caliber was studied in freely moving rats during the development of sustained hypertension produced by subdiaphragmatic aortic constriction. A striking coincidence was observed between the time taken for the diastolic caliber to reach maximal dilation and the time taken for complete resetting of the aortic baroreceptors. Moreover, during sudden pressure increases, the displacement of the diastolic caliber is much greater than the increase in pulsation, which indicates that in conscious rats the operational level of the resting diastolic caliber is an important factor for aortic baroreceptor distortion.     

Macrozoobenthos of three Pennsylvania lakes: responses to acidification

The littoral macrozoobenthos (MZB) of three northeastern Pennsylvania lakes was sampled seasonally from summer 1981 until summer 1983, to determine if any changes were occurring in response to acid deposition. In the acidified lake (total alkalinity 0.0 eq L^–1) the mean pH decreased from 5.5 in 1981 to 4.2 in 1983. Chironomidae comprised 71.30% of the MZB numbers and 19.6% of the wet weight. Over the study period the wet weight of Chironomidae increased (p < 0.04) as did the total numbers of Chironomidae in general (p < 0.01) and Tanytarsini (p < 0.01) in particular. Total numbers of MZB also increased (p < 0.02) in the acidified lake, but there was no significant change in the number of taxa, diversity or total wet weight. In the moderately sensitive lake (total alkalinity 47.4 eq L^–1, mean pH 6.1) Chironomidae were numerically (43%) dominant but Odonata (18.6%) and Mollusca (12.7%) dominated wet weight. There were no significant changes in the MZB of the moderately sensitive lake over the study period. In the least sensitive lake (total alkalinity 190 eq L^–1, mean pH 6.6) the Amphipoda (31.3%) and Chironomidae (27.3%) together provided 58.6% of the MZB numbers, and the Mollusca formed 55.1% of wet weight. Wet weight at the least sensitive lake was higher (p < 0.01) and there were more Ephemeroptera, Pelecypoda and Gastropoda than at the other two lakes. There were no differences in total numbers, diversity or number of taxa among the three lakes.     

Spontaneous mutation of the H-2b-haplotype in C57BL/10SnY mice

A new spontaneous mutation of the H-2b haplotype was found in skin graft tests with BC3 mice derived from B10.R111 (71NS) and C57BL/10SnY outcrossing. The mutation site localized in the F1 test in the H-2Kb gene is nonidentical to and noncomplementary with bm1, bm3, bm4 mutations. The novel mutation is maintained as B10.R111-H-2bm25 strain.     

Cytogenetic study of the effect of gossypol on mouse germ cells

The clastogenic and mutagenic activities of a new antifertility and antitumor agent gossypol were studied in the mouse male germ cells. Results of the present work indicate that at the doses 125 and 250 mg/kg the drug does not significantly increase frequencies of the micronuclei in the early spermatids and sperm head abnormalities. Hence, genotoxic influence can not be proposed as responsible for the antifertility effect of gossypol.     

Primary structures of and genes for new ribosomal proteins A and B in Escherichia coli

We determined the partial primary structures of and identified the genes for new basic proteins A and B in Escherichia coli ribosomal 50S subunits, found by means of an improved two-dimensional gel electrophoresis method. The sequence up to the 17th amino acid of protein B was in agreement with that of the X gene in the spc operon. The gene for protein A was searched for in the GenBank data base using the sequence up to the 35th amino acid, and was found at a locus between infC and rplT. The base sequence indicated that protein A contained 64 amino acids and had a molecular weight of 6,984. We conclude that proteins A and B are intrinsic ribosomal proteins, and propose calling their genes, rpmI and rpmJ, respectively.     

The physiology of Clostridium sporogenes NCIB 8053 growing in defined media

The physiology of Clostridium sporogenes was investigated in defined, minimal media. In batch culture, the major end products of glucose dissimilation were acetate, ethanol and formate. When L-proline was present as an electron acceptor, acetate production was strongly enhanced at the expense of ethanol. As judged by assay of the relevant enzymes, glucose was metabolized via the Embden-Meyerhof-Parnas pathway. The growth energetics of Cl. sporogenes were investigated in glucose- or L-valine-limited chemostat cultures. In the former case, the addition of L-proline to the medium caused a significant increase in the molar growth yield (as calculated by extrapolation to infinite dilution rate). This finding adds weight to the view that the reduction of L-proline by Cl. sporogenes is coupled to the conservation of free energy.     

Radiation cell survival and growth delay studies in multicellular spheroids of small-cell lung carcinoma

The radiation sensitivity of two small-cell lung carcinoma cell lines growing as multicellular spheroids in static culture was determined using clonogenic cell survival and growth delay as endpoints. Growth delay determination suggested that clonogenic cell kill was less than was obtained by direct assay of cell survival. Recovery from potentially lethal damage was assayed in one line (HC12) but was not demonstrable, and clonogenic cell survival decreased with time in treated spheroids with diameters greater than 300 microns which contained a hypoxic cell population. Microscopic examination of the treated spheroids showed the emergence of an abnormal giant-cell population, and the progressive clonogenic cell loss that occurred after treatment was thought to be due to oxygen and nutrient deprivation of the remaining viable cells by this doomed cell population. Correction of the growth delay measurements for changes in cell size and clonogenic cell population allowed correlation of the growth delay and cell survival data.