Sister chromatid exchange in methotrexate resistant and sensitive C3H10T1/2 mouse cells

Sister chromatid exchange (SCE) induction by methotrexate (MTX) was analyzed in C3H10T1/2 clone 8 mouse cells and in two MTX-resistant subclones with numerous double minute chromosomes (DM) present in the majority of cells. Significantly higher SCE levels were found, as expected, in sensitive cells after treatments with 10^-2 or 10^-5M MTX but not in resistant cells permanently growing in the presence of a high concentration of MTX (2×10^-3M) and characterized by a markedly lower cell cycle replication index (R.I.), i.e. in conditions that are known to otherwise favour SCE induction. These observations suggest, for the MTX-resistant cells under study, the existence of conditions limiting SCE formation.     

Effect of the different supramolecular organization on the uptake and metabolization of exogenous GM1 ganglioside by human fibroblasts

In this report we have investigated the differences in the uptake and metabolization of exogenous GM1 by human fibroblasts, as a function of its supramolecular organization in solution. For this we used a tritium labelled GM1, given alone or inserted in dispersions of phosphatidylcholine (PC) or sulphatide. The addition of fetal calf serum (FCS) to these dispersions was also studied. With respect to GM1 pure micelles, the presence in the medium of a sulphatide/GM1, 10:1 molar ratio, greatly increased the incorporation of GM1-associated radioactivity by the cultured cells. Conversely, the presence of PC dramatically diminished the GM1 incorporation values. The metabolization of exogenous GM1 was favoured by the presence of FCS, regardless of the presence of sulphatide. The obtained data provide useful information on the appropriate procedure for feeding cultured fibroblasts with gangliosides.     

Production of antiserum to CRF associated with adrenal atrophy in a rabbit

Corticotropin releasing factor (CRF) was recently isolated from ovine hypothalami by its ability to stimulate adrenocorticotropin (ACTH) and β-endorphin release from dispersed rat pituitary cells. Intramuscular injection of synthetic ovine CRF conugated to bovine thyroglobulin with 1-ethyl-3(3-dimethylaminopropyl) carbodiimide and emulsified with Freund's complete adjuvant into a random bred New Zealand white rabbit resulted in antiserum production to CRF associated with adrenal atrophy. A decrease in the level of plasma coticosteroids was associated with an increase in mean total binding of ¹²⁵I-N-Tyr-CRF. Upon sacrifice, a decrease in pituitary content of ACTH and a decrease in adrenal weight and content of corticosteroids was observed in the rabbit producing antiserum to CRF. Adrenal atrophy was histologically verified with an observed decrease in the adrenal cortical zone not reflected in the zona glomerulosa. Individual cells were relatively larger either with more abundant pale cytoplasm or with distinctly vacuolated cytoplasm. The results presented here are consistent with a physiologically necessary role for this CRF or peptides with similar structures in the hypothalamic-pituitary-adrenal axis.     

Liver tissue graft rejection in murine major histocompatibility complex mutants

Liver tissue grafts between seven H-2 mutants and their parental strains have been studied. Each of these mutants was originally identified by reciprocal mutant—parental strain skin graft rejection. However, liver grafts among mutants and parental standard strains are not uniformly rejected. Liver graft rejection also fails to correlate with mutant—parental stimulation in CML and MLC. In addition, the immune reaction pattern of female mutant animals against grafts of male liver differs from the reaction pattern found in parental standard strains. Several explanations for the differences between immune response to liver and skin grafts are proposed, including different T cell subsets involved in recognition, availability of antigenic sites to immunocompetent cells, and structural differences between mutant and parental H-2 antigens. Abbreviations used in this paper: bml, 2, 3, 4,14; dml; fm2=mutants of strains C57BL/6, B10.D2 and B10.M respectively; B6=C57BL/6     

Studies on the mechanism of action of hexamethylene bisacetamide, a potent inducer of erythroleukemic differentiation

Hexamethylene bisacetamide (diacetyldiamino hexane) is a potent inducer of erythroid differentiation in murine erythroleukemia cells. Hexamethylene bisacetamide and the closely related pentamethylene bisacetamide were synthesized with radioactive labels in various portions of the molecule and the uptake, metabolism, and intracellular distribution determined. Bisacetamides are taken up by the cell; an intracellular concentration equal to the extracellular concentration is achieved by 6–8 h. Commitment to differentiation is not detected until at least 10 h after equilibration. Both uptake and commitment to differentiate are concentration and temperature dependent. The majority of the compound is deacetylated upon cell entry and the acetate portion incorporated nonspecifically into lipid and protein. Acetate competes with the incorporation of hexamethylene bisacetamide into protein and lipid, but does not affect inducing activity. The diamine portion of the molecule is detected only in the cytoplasm, in a trichloroacetic acid-soluble and acetylated form, whereas the acetate moiety is detected in both cytoplasm and nucleus and in both a trichloroacetic acid-soluble and insoluble form. The cellular uptake of diamines and bisacetamides (acetylated diamines) are similar, but acetylation of the diamine greatly increases inducing activity.     

Development of a nuclear polyhedrosis virus in midgut cells and penetration of the virus into the hemocoel of the armyworm,Pseudaletia unipuncta

The development of a nuclear polyhedrosis virus (NPV) in larval midgut cells of the armyworm, Pseudaletia unipuncta, is similar to that of other NPV. In the nucleus, the envelopes around the nucleocapsids seem to be derived de novo or from the inner layer of the nuclear envelope wich forms cisternae, blebs, or infoldings. The nucleocapsids are also enveloped by synhymenosis during passage through the nuclear membrane, the cell membrane, or the endoplasmic reticulum membrane. Both enveloped and unenveloped nucleocapsids may enter the cytoplasm through the nuclear pore or budding through the nuclear membrane. From the cytoplasm the virions may enter the hemocoel through the basal cell and basement membranes or through the endoplasmic reticulum, intercellular space, and the basement membrane.     

Fitness of Karyotypes in DROSOPHILA PSEUDOOBSCURA

In the dynamics of the survival of chromosomal polymorphism selection may be operating at the genic level, at the chromosomal level or at the supergene level. Tests designed to distinguish between these levels were run on Drosophila pseudoobscura. There was no evidence for heterosis, a necessary requirement for gene-determined chromosomal polymorphism. A strong chromosmal selection was observed. No evidence was found for the presence within one locality of more than a single superallele for each supergene (= gene order). These results are compared to those found by others.     

Apricot Melanoidins Prevent Oxidative Endothelial Cell Death by Counteracting Mitochondrial Oxidation and Membrane Depolarization

The cardiovascular benefits associated with diets rich in fruit and vegetables are thought to be due to phytochemicals contained in fresh plant material. However, whether processed plant foods provide the same benefits as unprocessed ones is an open question. Melanoidins from heat-processed apricots were isolated and their presence confirmed by colorimetric analysis and browning index. Oxidative injury of endothelial cells (ECs) is the key step for the onset and progression of cardiovascular diseases (CVD), therefore the potential protective effect of apricot melanoidins on hydrogen peroxide-induced oxidative mitochondrial damage and cell death was explored in human ECs. The redox state of cytoplasmic and mitochondrial compartments was detected by using the redox-sensitive, fluorescent protein (roGFP), while the mitochondrial membrane potential (MMP) was assessed with the fluorescent dye, JC-1. ECs exposure to hydrogen peroxide, dose-dependently induced mitochondrial and cytoplasmic oxidation. Additionally detected hydrogen peroxide-induced phenomena were MMP dissipation and ECs death. Pretreatment of ECs with apricot melanoidins, significantly counteracted and ultimately abolished hydrogen peroxide-induced intracellular oxidation, mitochondrial depolarization and cell death. In this regard, our current results clearly indicate that melanoidins derived from heat-processed apricots, protect human ECs against oxidative stress.