Canalicular system of enterocytes at rest and its changes during lipid absorption

A study was made of the structural changes in different organoids of enterocytes of the rat small intestine at "rest" and during lipid absorption using ultrathin sections, impregnation with Ur-Pb-Cu, and continuous impregnation with OsO4. With the latter technique a specific canalicular system was found in the enterocytes, which we failed to observe on ultrathin sections. During lipid absorption the canalicular system underwent fragmentation. The vesicules on the trans-surface of the Golgi apparatus were enlarged, and the number of flattened cisterns was significantly lower. The changes in cellular organoids and their interrelations observed in the present study support the earlier hypothesis of the resynthesis of triglycerides within the enterocytes, the formation of chylomicrons and their transfer into the intercellular space.     

Rhythmic components of the EEG of 6-month-old children

Spectral EEG characteristics were studied in 12 six-month healthy children in a state of attention, attracted by visual stimuli and also at lowering of the level of visual afferentation and in drowsiness. 12 parts of EEG records free from artefacts were used, with analysis epoch 5 s and discretion frequency 100 counts/s. Three independent rhythmic EEG components have been revealed in alertness state, corresponding by criteria of functional reactivity and topographic localization to theta, alpha and mu EEG rhythms of the adult man. It is suggested that formation of dominating EEG rhythm with age occurs due to changes in dominant relations of the key rhythmic successions with independent genesis.     

Autoradiographic, ultrastructural and interferometric analyses of the temperature effect on the synthesis and migration of ribosomes in root meristem cells of Helianthus annuus L. relation to S phase initiation

Experimental model consisted in blocking cells in G1 phase by cold treatment (12 h, 10 degrees C); following 3 h of postincubation at 20 degrees C, cells initiated S phase. In the present studies it has been shown that 2 h postincubation at 20 degrees C of cold-treated young seedlings of Helianthus annuus L. results in transformation of inactive meristematic nucleoli, characterized by small sizes, reduced amount of dry mass and granular component and by the presence of few and large fibrillar centres into large active nucleoli displaying high dry mass and granular component contents, numerous and small fibrillar centres. After 3 h of postincubation at 20 degrees C, nucleoli lose their granular component, decrease in size and dry mass content. At this moment cytoplasm enriches in ribosomes and its dry mass increases. Maximum of nucleolar activity is preceded by an accumulation of proteins in nucleoli. It is concluded that an enhanced transport of ribosomes is one of the conditions of S phase initiation.     

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+).     

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.     

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.     

Binding of chondroitin sulfate, dermatan sulfate and fat-storing cell-derived proteoglycans to rat hepatocytes

1. The interaction of isolated rat hepatocytes with exogenous 3H-labeled chondroitin-4-sulfate and dermatan sulfate and with biosynthetically 35S-labeled proteoglycans secreted by cultured rat liver fat-storing cells has been studied. 2. All ligands are bound by hepatocytes in a concentration-dependent manner. Scatchard-plot analysis of the data revealed the existence of high- and low-affinity binding modes. 3. The cell-bound exogenous [3H]glycosaminoglycans could be displaced by each unlabeled ligand and by heparin, whereas displacement of the endogenous material was less effective. 4. Binding of all ligands to hepatocytes increased with time. For the exogenous glycosaminoglycans the two- to threefold amount was retained at 37 degrees C as compared to 4 degrees C; it was markedly reduced by pretreatment of the cells with trypsin. 5. Degradation of the exogenous ligands could be detected neither for the cell-bound fraction nor for the free glycosaminoglycans in the culture medium. 6. The binding of the ligands to hepatocytes is viewed as a cell-matrix interaction. Its possible pathobiochemical relevance in liver fibrosis or neoplasia is discussed.     

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.