The Influence of pH and Temperature on Cellulolytic and Pectolytic Activity of Cylindrocarpon destructans (Zins.) Scholt.

In studies on the effect of pH and temperature on cellulolytic and pectolytic activity of C. destructans, it was found that the isolates used produced only endoglucanases. The temperature and pH affected the synthesis of these enzymes. Fungi cultured at 26°C produced more of these enzymes than those grown at the two other temperatures. At 10°C, only one isolate produced minute amounts of endoglucanases. None of fungi studied exhibited cellulolytic activity in cultures grown at 20°C. Cellulolytic activity was found only in acidic media (pH 5.0). The fungi studied exhibited higher pectolytic than cellulolytic activity. In the post culture liquids of these organisms, both types of pectolytic enzymes (exo- and endo-PMG) were detected. Different temperature and pH values affected the production of these enzymes differently in various isolates.     

Genetic analysis of murine strains C57BL/6J and C3H/HeJ to confirm the map position ofAth-1, a gene determining atherosclerosis susceptibility

Previous results suggested that strains C57BL/6J and C3H/HeJ differed in a single gene for atherosclerosis susceptibility, calledAth-1. Based on data from recombinant inbred strainsAth-1 was tentatively assigned to chromosome 1 linked toAlp-2. In this report, a cross between C57BL/6 and C3H/HeJ was carried out in order to test whether the tentative map position was correct. Parental strains and F₁ and F₂ progeny were examined. Susceptible alleles ofAth-1, found in C57BL/6, are associated with relatively low levels of high-density lipoprotein (HDL)-cholesterol in animals fed an atherogenic diet; resistant alleles ofAth-1 are associated with relatively high levels of HDL-cholesterol. F₁ progeny have HDL levels that are intermediate between these of the two parental strains. Among the F₂ progeny,Alp-2 andAth-1 cosegregated, providing confirmatory evidence thatAth-1 is linked toAlp-2 on chromosome 1. Three mice recombinant forAlp-2 andAth-1 were found among the 60 chromosomes tested, giving an estimated map distance between these two genes of 5.0±2.8 (SE) cM. The phenotypic characteristics ofAth-1 resemble a genetic trait in humans, hyperalphalipoproteinemia, which is characterized by elevated levels of HDL-cholesterol, reduced risk of heart disease, and increased longevity.This work was supported by Grant HL-32087 from the Heart, Lung, and Blood Institute, National Institutes of Health, Grant 1858 from the Council for Tobacco Research, Grant 86-1387 from the American Heart Association with funds contributed in part by the Alameda, Orange, and Santa Barbara County Chapters, and Grants 85-N132A and 85-N136A from the California Affiliate of the American Heart Association.     

Epidermal growth factor and basic fibroblast growth factor suppress the spontaneous onset of apoptosis in cultured rat ovarian granulosa cells and follicles by a tyrosine kinase-dependent mechanism.

Recent biochemical studies have suggested that apoptotic cell death is the molecular mechanism underlying the degeneration of ovarian follicles during atresia. Using a sensitive autoradiographic method for the detection of DNA fragmentation, we studied apoptosis in ovarian granulosa cells or intact follicles placed in serum-free culture as model systems to elucidate the hormonal regulation of atresia. Immature rats (25 days old) were primed for 2 days with 10 IU equine CG to induce a homogeneous population of mature preovulatory follicles. Granulosa cells isolated from these follicles contained predominantly intact high mol wt DNA. However, a time-dependent, spontaneous onset of internucleosomal DNA fragmentation characteristic of apoptotic cell death occurred in granulosa cells during culture. Treatment of granulosa cells with epidermal growth factor (EGF), transforming growth factor-alpha (TGF alpha), or basic fibroblast growth factor (bFGF) inhibited the spontaneous onset of apoptotic DNA cleavage found during culture by 40-60%. In contrast, insulin-like growth factor I, insulin, TGF beta and tumor necrosis factor-alpha were ineffective. Likewise, activation of the protein kinase A or C pathways with forskolin or phorbol 12-myristate 13-acetate, respectively, did not prevent the onset of DNA fragmentation, although inclusion of a tyrosine kinase inhibitor (genistein) completely blocked the ability of EGF, TGF alpha, and bFGF to suppress apoptosis in granulosa cells. Similar to cultured granulosa cells, a spontaneous onset of apoptosis was also observed to occur in isolated preovulatory follicles during culture. Furthermore, treatment of follicles with EGF or bFGF inhibited the spontaneous initiation of apoptosis, and the suppressive effects of these growth factors were also attenuated by co-treatment with genistein.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clonal variations in keratin : Intermediate filament expression by human somatic cell hybrids

The intermediate filament composition of differentiated vertebrate cells provides a stable phenotype which appears to be specifically regulated in each cell type. In order to analyse the regulation of intermediate filament expression we have constructed human somatic cell hybrids from the fusion of the HeLa-derived cell line HEB7A and a normal human diploid fibroblast, GM2291. These parental cells differ with respect to the presence or absence of keratin intermediate filaments. Isolation of independently arising clones produced two classes of hybrids. One class expresses keratin in a stable manner and the other class lacks keratin altogether. Indirect immunofluorescence of hybrid cells using antikeratin antiserum demonstrates that there are variations in the intensity and organization of cytoskeletal keratin staining. SDS-PAGE comparisons of cell extracts from these hybrids indicates that there are quantitative differences in the relative amounts of individual keratin polypeptides as well. These clonal variations have allowed us to begin assessing the consequences of genetic interactions between cell types that are normally capable of closely regulating different subsets of intermediate filament genes.