Gastrointestinal microflora,food components and colon cancer prevention

Evidence that the intestinal microbiota is intrinsically linked with overall health, including cancer risk, is emerging. Moreover, its composition is not fixed but can be influenced by several dietary components. Dietary modifiers, including the consumption of live bacteria (probiotics) and indigestible or limited digestible food constituents such as oligosaccharides (prebiotics) and polyphenols or both (synbiotics), are recognized modifiers of the numbers and types of microbes and have been reported to reduce colon cancer risk experimentally. Microorganisms also have the ability to generate bioactive compounds from food components. Examples include equol from isoflavones, enterodiol and enterolactone from lignans and urolithins from ellagic acid, which have also been demonstrated to retard experimentally induced cancers. The gastrointestinal microbiota can also influence both sides of the energy balance equation, namely, as a factor influencing energy utilization from the diet and as a factor that influences host genes that regulate energy expenditure and storage. Because of the link between obesity and cancer incidence and mortality, this complex complexion deserves greater attention. Overall, a dynamic interrelationship exists between the intestinal microbiota and colon cancer risk, which can be modified by dietary components and eating behaviors.     

Properties and uses of protein hydrolysates (Review)

Properties of protein hydrolysates and possible uses of these substances in research and various branches of industry are considered. The main problem discussed in this paper is the relationship between the degree of protein conversion and characteristics (structural-functional and physicochemical) of hydrolysates.     

Monoclonal antibodies to alpha-chain regions of human fibrinogen that participate in polymer formation

Monoclonal antibodies have been generated against a cross-link-containing derivative of alpha polymer (alpha XLCNBr), isolated following CNBr digestion of fibrin [Sobel, J. H., Ehrlich, P. H., Birken, S., Saffran, A. J., & Canfield, R. E. (1983) Biochemistry (preceding paper in this issue)]. One cloned cell line (F-102) was chosen for characterization based on its apparent specificity for the A alpha-chain region A alpha 518-584 (CNBr X). A second line (F-103) was selected because of its anti-A alpha 241-476 (CNBr VIII) properties. These two regions of the A alpha chain have previously been implicated as major contributors to the cross-linking process that leads to alpha-polymer formation. Radioimmunoassays have been developed, employing the immunoglobulins produced by clones F-102 and F-103. These assays have been applied, in conjunction with high-performance liquid chromatography purified tryptic and chymotryptic derivatives of CNBr VIII and CNBr X, to localize the respective determinants involved in antibody binding. In each case, virtually full immunoreactivity was exhibited by both the CNBr fragment and a single tryptic or chymotryptic peptide originating from it. These findings indicate that sequence-specific, rather than conformational, determinants were operative in the generation of antibodies F-102 and F-103. The epitope recognized by F-102 was localized to the region of A alpha 540-554, while the F-103 binding site resided within A alpha 259-276. When these radioimmunoassays were applied to study the relative immunoreactivity exhibited by a variety of fibrinogen derivatives, the results obtained support earlier suggestions that the COOH-terminal portion of the A alpha chain contains regions of random conformation.     

Segmentally repeated pattern of expression of a cell surface glycoprotein in Drosophila embryos

We report here that a previously described cell surface antigen (Brower, Smith & Wilcox, 1980) is expressed in a segmentally repeating pattern of stripes in the epidermis and nervous system of segmented Drosophila embryos. We also report that the antigenic activity is found on two closely related cell surface glycoproteins. The pattern of expression of this antigen is reminiscent of the expression of some segmentation genes and is affected by mutation of at least two of these genes, fushi tarazu and paired. Thus these glycoproteins are candidates for cell surface molecules involved in carrying out the patterning processes controlled by segmentation genes.     

Seasonal changes in the cecal microflora of the high-arctic Svalbard reindeer (Rangifer tarandus platyrhynchus)

The dominant cecal bacteria in the high-arctic Svalbard reindeer were characterized, their population densities were estimated, and cecal pH was determined in summer, when food quality and availability is good, and in winter, when it is very poor. In summer the total culturable viable bacterial population was (8.9 +/- 5.3) X 10(8) cells ml-1, whereas in winter it was (1.5 +/- 0.7) X 10(8) cells ml-1, representing a decrease to 17% of the summer population density. Of the dominant species of cultured bacteria, Butyrivibrio fibrisolvens represented 23% in summer and 18% in winter. Streptococcus bovis represented 17% in summer and 5% in winter. Bacteroides ruminicola represented 10% in summer and 26% in winter. In summer and winter, respectively, the proportion of the viable population showing the following activities was as follows: fiber digestion, 36 and 48%; cellulolysis, 10 and 6%; xylanolysis, 33 and 48%; and starch utilization, 77 and 71%. The most abundant cellulolytic species in summer was Butyrivibrio fibrisolvens, representing 62% of the total cellulolytic population, and in winter it was Ruminococcus albus, representing 80% of the total cellulolytic population. The most abundant xylanolytic species in summer was Butyrivibrio fibrisolvens, and in winter it was Bacteroides ruminicola, representing 59 and 54% of the xylanolytic isolates in summer and winter, respectively. The cecal bacterial of the Svalbard reindeer have the ability to digest starch and the major structural carbohydrates of the diet that are not digested in the rumen. The cecum in these animals has the potential to contribute very substantially to the digestion of the available plant material in both summer and winter.     

L-proline uptake in human fibroblasts: evidence for a high-affinity system in addition to system A

Proline uptake was studied in human skin fibroblasts by simultaneous running of kinetic and inhibition experiments on the same cell lines. Two systems for proline uptake were shown: a high-affinity system not inhibited by alpha-(methylamino)isobutyric acid and a low affinity system inhibited by this amino acid (i.e. system A). These results appear to be of interest, firstly because up till now, system A was considered preferable for proline uptake in human fibroblasts, and secondly because they illustrate the need for combined inhibition and kinetic studies of amino acid uptake, especially when the substrate concentration range used and the respective Km of the systems do not allow their detection by kinetic analysis alone. Furthermore, this high-affinity system may have major physiological implications.     

Studies on a leukocyte elastase inhibitor present in the culture medium of inflamed synovial tissue

The spent medium of cultured inflamed synovial tissue contains a potent inhibitor of leukocyte elastase. This leukocyte elastase inhibitor has no effect on leukocyte cathepsin G and pancreatic elastase is only marginally affected. The inhibitor is a glycoprotein, stable to heat, acid and reductive alkylation. Pretreatment of the inhibitor with either trypsin or chymotrypsin results in its inactivation.     

Specificity of sterol-glucosylating enzymes from Sinapis alba and Physarum polycephalum.

1. Sinapis alba L. seedlings contain glycosyltransferase catalyzing the synthesis of sterol glucosides in the presence of UDPglucose as sugar donor. The major activity occurs in the membranous fraction sedimenting at 300--9000 x g. Successive treatment of the particulate enzyme fraction with acetone and Triton X-100 affords a soluble glucosyltransferase preparation which can be partly purified by gel filtration on Sephadex G-150. Molecular weight of the glucosyltransferase is 1.4 . 10(5). Apparent Km values for UDPglucose and sitosterol are 8.0 . 10(-5) M and 5.0 . 10(-6) M, respectively. 2. Comparison was made of the S. alba glucosyltransferase with a similar sterol-glucosylating enzyme isolated from non-photosynthesizing organism Physarum polycephalum (Myxomycetes). UDPglucose was the most efficient glucose donor in both cases but the enzyme from Ph. polycephalum can also utilize CDPglucose and TDPglucose. Glucose acceptors are, in case of both enzymes, sterols containing a beta-OH group at C-3 and a planar ring system (5 alpha-H or double bond at C-5). The number and position of double bonds in the ring system and in the side chain, as well as the presence of additional alkyl groups in the side chain at C-24 are of secondary importance. 3. The present results indicate that both enzymes can be regarded as specific UDPglucose:sterol glucosyltransferases. Certain differences in their specificity towards donors and acceptors of the glucosyl moiety suggest, however, a different structure of the active sites in both enzymes.