Characterization of binding of human fibrinogen to the surface of germ-tubes and mycelium of candida albicans

The binding of human fibrinogen to germ-tubes and mycelium of Candida albicans, forms usually found in infected tissues, was studied in vitro by an immunofluorescence assay. Binding was quantified by using 125I-labelled fibrinogen. The degree of binding differed according to the morphological form of the fungus. Binding relative to that of the yeast form was greater for mycelium (12-fold) than for germ-tube (7.7-fold). Pretreatment of yeasts with fragments D and E (terminal degradation products of fibrinogen) before fibrinogen binding showed that fragment D possessed a higher affinity for C. albicans than fragment E. Binding of fibrinogen was diminished when C. albicans was pretreated with 2-mercaptoethanol alone or in combination with pronase, or pretreated with alpha-mannosidase or trypsin. Binding was not decreased by pretreatment with pronase alone or chitinase. Inhibition experiments using C. albicans dialysed culture filtrate, C. albicans mannan, chitin, sugars or amino sugars were done by preabsorbing the fibrinogen with each of the above mentioned compounds. C. albicans dialysed culture filtrate inhibited the binding more strongly than C. albicans mannan. However, fibrinogen binding to C. albicans was not significantly reduced by mannose, several other sugars or chitin. These studies demonstrate the existence of a fibrinogen-binding factor (FBF) strongly associated with the surface of germ-tube and filamentous forms of C. albicans, and indicate a possible role for FBF in the pathogenicity of C. albicans.     

Use of latex balls labelled by lectins in the demonstration of Salmonella-Schistosoma mansoni receptor sites

Surface tegumental membrane of adult stage Schistosoma mansoni were examined using the latex sphere coated with Concanavalin A (Con A). Wheat germ agglutinin (WGA) and Protein A (PA). Competitive saccharide inhibitors glucose, mannose and methyl alpha-D-glucopyranoside were used for Con A.     

β-Adrenergic receptor-coupled adenylate cyclase

Beta-adrenergic receptor-coupled adenylate cyclase is regulated by both amplification and desensitization processes. Desensitization of adenylate cyclase is divided into two major categories. Homologous desensitization is initiated by phosphorylation of the receptors by a beta-adrenergic receptor kinase. This reaction serves to functionally uncouple the receptors and trigger their sequestration away from the cell surface. These sequestered receptors can rapidly recycle to the cell surface or, with time, become down regulated, being destroyed within the cell. Dephosphorylation of the receptors is accomplished in the sequestered compartment of the cell, which may functionally regenerate the receptors and allow their return to the cell surface. In heterologous desensitization, receptor function is also regulated by phosphorylation, but in the absence of receptor sequestration or down regulation. In this case, phosphorylation serves only to functionally uncouple the receptors, that is, to impair their interactions with the guanine nucleotide regulatory protein Ns. Several protein kinases are capable of promoting this phosphorylation, including the cAMP-dependent kinase and protein kinase C. In addition to the receptor phosphorylation, heterologous desensitization is associated with modifications at the level of the nucleotide regulatory protein Ns and perhaps Ni. Adenylate cyclase systems are also subject to amplification that involves a protein kinase C-mediated phosphorylation of the catalytic unit of the enzyme. Phosphorylation of the catalytic unit enhances its catalytic activity and results in amplified stimulation by the regulatory protein Ns. Other receptor/effector systems exhibit qualitatively similar regulatory phenomena, suggesting that covalent modification (phosphorylation) may represent a general mechanism for regulating receptor function.     

Mucosal epithelial cells and Langerhans cells are targets for infection by the immunosuppressive type D retrovirus simian AIDS retrovirus serotype 1

Simian acquired immune deficiency syndrome (SAIDS) caused by the type D retrovirus SRV-1 results in opportunistic infections and a spectrum of oral lesions similar to those seen in humans with AIDS. To better understand the pathogenesis of these oral lesions we have retrospectively examined the oral mucosa from ten rhesus monkeys that died with SAIDS and prospectively examined the oral mucosa of ten additional animals inoculated with SRV-1 to determine at what time, and in what cells SRV-1 infection of the oral mucosa occurs. Using single and double label immunohistologic techniques, and electron microscopy we detected SRV-1 in clusters of oral epithelial cells and rare Langerhans cells as early as 1 month postinoculation.     

Sensitivity of the cell cycle to TGFβ1 does not correlate with transformation of a rat liver epithelial cell line

The effects of TGF1 on cell cycle events in a rat liver derived epithelial cell line (BL9) and in two in vitro transformants of this line were studied by flow cytometry. Using either ethidium bromide staining or the incorporation of bromodeoxyuridine to evaluate DNA synthesis it was shown that TGF1 prevented the entry of G0/G1 phase BL9 cells into S phase. TGF1 did not exert its inhibitory effect(s) on DNA synthesis by the modulation of early events in the cell cycle. The tumorigenic transformed BL9 cell lines gave contrasting responses to the effects of TGF1. DNA synthesis in a BL9 cell line derived by transfection with an active N-ras oncogene was unaffected by TFG1 and thus appeared refractory to its growth controlling effects. On the other hand cells from a BL9 cell line derived by in vitro transformation with activated aflatoxin B₁ retained their sensitivity to the effects of TGF1. Thus the loss of the inhibitory effect of TGF1 on DNA synthesis is not obligatory for the malignant transformation of rat liver epithelial cells.Abbreviations TGF1 transforming growth factor 1 - BSA bovine serum albumin - FBS foetal bovine serum - BrdUrd bromodeoxyuridine - PI propidium iodide - PBS phosphate buffered saline     

Cooperation or cooptation: A southwest French wine cooperative

Conclusion Cooperatives, with respect to the history of wine production in the southwest of France, require that they be graced as the outcome of the transformation from the era of captitalist markets to the era where the capitalist mode of production became dominant—a transformation marked by the creation of a market in labor as predominant among winegrowers. As Marx showed through his many works on the development of capitalism, the translation of market exchanges into a quantifiable economic entity only serves to mask the social relations on which it is based. It was therefore my intent in the first part of this essay to highlight, if only suggestively, the process that led to expanded commercialization of wine in the Aquitaine and the deployment of a specific system of labor. Although wine proprietors and growers were divided by social class early on, the market in labor matured slowly, especially in the sector of the production of table wines. The market in labor among winegrowers followed from the appearance of the grand crus in the eighteenth and nineteenth centuries and from the social consequences that ensued from the phylloxera in the late nineteenth and early twentieth centuries. The grand crus ushered in new specialized labor while the phylloxera intensified this process by turning wealthy merchants and large proprietors towards the volume production of table wines, thus usurping the last vestige of the small independent producer.Markets were not left to follow their own telos as the state played a central mediative role in creating legislation that both encouraged and pressured small independent producers to collectivize their resources in vinification cooperatives. This was not a conspiracy of the state legislature against the excesses of production on the part of the small producers. Wine cooperative legislature was an attempt on the part of the state legislature to resolve the periodic crises in viticulture caused by overproduction and to implement a long overdo agricultural policy The problems faced by the Sigouls Cooperative today are largely a product of the past history of wine production in the southwest of France. Currently, seventy-five percent of the Cooperative's plantation is in white wines. The high plantation in white wines reflects northern European preferences that are traceable to the sixteenth century and earlier. More recently, in France and elsewhere, there has been a gradual shift in consumer preferences from white to red wines. Consumer preferences in part can be attributed to the vicissitudes of taste. However, one must not overlook concerted efforts through advertising to shape consumer taste. Recently, the best known example is the enthusiasm for Beaujolais Nouveau cultivated through clever advertising in major urban centers such as Paris and New York. Since wine cooperatives have not had sufficient capital to invest in advertising and promotion to establish trends, they have had to settle for keeping pace with new developments. Although Sigouls has exceeded its neighboring cooperative, Monbazillac, in keeping pace with the latest trend, it must be recognized that it requires at least five years for a red wine stock such as merlot to mature after plantation.Although wine cooperatives can be seen as assimilatory institution in that they have served the absorption of small independent producers of wine into the capitalist mode of production, it should be recognized equally that wine cooperatives have been the only means available to small producers for continuing the cultivation of their vineyards given the constraints of capitalist social relations. With this in mind, one must avoid the conclusion that wine cooperatives are simply an instrument of the capitalist mode of production, French legislature, the ruling class and nothing else. Although the political motives that led some of the Sigouls Cooperative's early members to pool their vinification and marketing resources have given way to pragmatics, or as my informants related la rentabilité (profitability), the Cooperative has preserved, albeit in a transformed medium, an ageold meaningful livelihood, a sense of local pride in the production of wine, and some sense of independence from the fate of wage labor.Robert Ulin is Professor of Sociology & Anthropology, Allegheny College, Meadville, Pa.

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Inhibitors of Trichoderma reesei β-glucosidase activity derived from autohydrolysis-exploded Eucalyptus regnans

Summary Enzymic saccharification of Eucalyptus regnans pulps pretreated by autohydrolysis-steam explosion resulted in low cellulose conversions into glucose when using trichodermal cellulase preparations. The reduced levels of glucose were attributable to the production of compounds during enzymic hydrolysis which were inhibitory to -d-glucosidase of Trichoderma reesei C-30 and in Meicelase, but not to the cellulases. Aspergillus niger -glucosidase was not inhibited, nor were -d-xylosidase(s) and 1,4--d-xylanase(s). The inhibitory compound(s) could be extracted from the enzymic hydrolyzates with ethyl acetate. The ethyl acetate extractives inhibited -glucosidase in a competitive manner, and inhibitory action was not affected by pH. Addition of the inhibitory compound(s) to trichodermal cellulase digests of cellulose resulted in reduced glucose yields compared to a control. The inhibitory effects could be overcome when cellulase digests were supplemented with A. niger -glucosidase resulting in higher cellulose-to-glucose conversions. The inhibitory compound(s) were localized mainly in the heartwood of E. regnans. An inhibitor compound of this type has not hitherto been reported. The presence of inhibitory compound(s) in the autohydrolysis liquor fraction is also reported.     

The relationship between RNA catalytic processes

Proposals that an RNA-based genetic system preceeded DNA, stem from the ability of RNA to store genetic information and to promote simple catalysis. However, to be a valid basis for the RNA world, RNA catalysis must demonstrate or be related to intrinsic chemical properties which could have existed in primordial times. We analyze this question by first classifying RNA catalysis and related processes according to their mechanism. We define: (A) thedisjunct nucleophile class which leads to 5-phosphates. These include Group I and II intron splicing, nuclear mRNA splicing and RNase P reactions. Although Group I introns and its excision mechanism is likely to have existed in primordial times, present-day examples have arisen independently in different phyla much more recently. Comparative methodology indicates that RNase P catalysis originated before the divergence of the major kingdoms. In addition, alldisjunct nucleophile reactions can be interrelated by a proposed mechanism involving a distant 2-OH nucleophile. (B) theconjunct nucleophile class leading to 3-phosphates. This class is composed of self-cleaving RNAs found in plant viruses and the newt. We propose that tRNA splicing is related to this mechanism rather than the previous one. The presence of introns in tRNA genes of eukaryotes and archaebacteria supports the idea that tRNA splicing predates the divergence of these cell types.