The anti-fibrotic effect of liver growth factor is associated with decreased intrahepatic levels of matrix metalloproteinases 2 and 9 and transforming growth factor beta 1 in bile duct-ligated rats

Liver growth factor (LGF), a mitogen for liver cells, behaves as an anti-fibrotic agent even in extrahepatic sites, but its mechanistic basis is unknown. We aimed to determine the intrahepatic expression pattern of key modulators of liver fibrosis in bile duct-ligated rats (BDL) after injection of LGF. BDL rats received either LGF (4.5 microg/ratXdose, two doses/week, at time 0 or 2 or 5w after operation, depending on the group (BDL+LGF groups, n=20) or saline (BDL+S groups, n=20). Groups were compared in terms of fibrosis (histomorphometry), liver function (aminopyrine breath test), matrix metalloproteinases MMP-2 and MMP-9, transforming growth factor beta 1 (TGF-beta1) and liver endoglin content (Western blotting), and serum tissue inhibitor of metalloproteinases 1 (TIMP-1) levels (ELISA). In BDL+LGF rats, the fibrotic index was significantly lower at 5w, p=0.006, and at 8w, p=0.04, than in BDL+S rats. Liver function values in BDL+LGF rats were higher than those obtained in BDL+S rats (80% at 5w and 79% at 8w, versus 38% and 29%, p<0.01, taking healthy controls as 100%). Notably, in BDL+LGF rats the intrahepatic expression levels of both MMPs were lower at 2w (MMP-2, p=0.03; MMP-9, p=0.05) and 5w (MMP-2, p=0.05, MMP-9, p=0.04). In addition, the hepatic TGF-beta1 level in BDL+LGF rats was lower at 2w (36%, p=0.008), 5w (50%) and 8wk (37%), whereas intrahepatic endoglin expression remained constant in all BDL rats studied. LGF ameliorates liver fibrosis and improves liver function in BDL rats. The LGF-induced anti-fibrotic effect is associated with a decreased hepatic level of MMP-2, MMP-9 and TGF-beta1 in fibrotic rats.     

Advantages of q-PCR as a method of screening for gene targeting in mammalian cells using conventional and whole BAC-based constructs

We evaluate here the use of real-time quantitative PCR (q-PCR) as a method for screening for homologous recombinants generated in mammalian cells from either conventional gene-targeting constructs or whole BAC-based constructs. Using gene-targeted events at different loci, we show that q-PCR is a highly sensitive and accurate method for screening for conventional gene targeting that can reduce the number of clones requiring follow-up screening by Southern blotting. We further compared q-PCR to fluorescent in situ hybridization (FISH) for the detection of gene-targeting events using full-length BAC-based constructs designed to introduce mutations either into one gene or simultaneously into two adjacent genes. We find that although BAC-based constructs appeared to have high rates of homologous recombination when evaluated by FISH, screening by FISH was prone to false positives that were detected by q-PCR. Our results demonstrate the utility of q-PCR as a screening tool for gene targeting and further highlight potential problems with the use of whole BAC-based constructs for homologous recombination.     

Antioxidant Defenses in Fish: Biotic and Abiotic Factors

Oxygen in its molecular state O₂, is essential for many metabolic processes that are vital to aerobic life. Aerobic organisms cannot exist without oxygen, which nevertheless is inherently dangerous to their lives. Like all aerobic organisms, fish are also susceptible to the effects of reactive oxygen and have inherent and effective antioxidant defenses that are well described in the literature. This review investigates the influence of different biotic and abiotic factors (age, phylogenetic position, feeding behavior, environmental factors, oxygen, temperature, presence of xenobiotics) on antioxidant defenses in fish. Studies of antioxidant activity in fish open a number of novel research lines providing greater knowledge of fish physiology, which will benefit various aspects of fish farming and artificial production.     

Protandry and sexual dimorphism in trans-Saharan migratory birds

Earlier arrival to reproductive sites of males relative to females(protandry) is widespread among migratory organisms. Diversemechanisms have been proposed that may select for protandry,including competition for limiting resources (e.g., territories)or mates. In species with large variation in male reproductivesuccess, such as polygamous species and those with intense spermcompetition, early arriving males may accrue a fitness advantagebecause they acquire more mates or have larger chances of paternity.Comparative studies of birds have shown that sexual size dimorphism(SSD) is positively associated with the level of polygyny, whereasintense sperm competition is associated with sexual dichromatism(SD). Positive correlations between protandry and SSD or SDcan therefore be expected to exist across avian species. Becauselarge males are predicted to be better able to cope with adverseecological conditions early in the breeding season, selectionfor protandry, in turn, may have a correlated response on SSDamong migratory species breeding in boreal latitudes. Althoughprevious studies of birds have analyzed the association betweenSSD and protandry, none has analyzed SD in relation to protandry.Here we analyze the association between protandry during springmigration, SSD, and SD in 21 trans-Saharan monogamous migratorybird species. The difference in median migration dates betweenfemales and males, reflecting protandry, was positively associatedwith SD but not with SSD. Because dichromatism is positivelyrelated to sperm competition across species, present resultsare consistent with predictions derived from sexual selectionhypotheses for the evolution of protandry mediated by spermcompetition.     

Co-production of ice nuclei and xanthan gum by transformed Xanthomonas campestris grown in sugar beet molasses

Two recombinant plasmids, expressing ice nucleation activity, were constructed and named pCPP30inaZ and pCPP38inaZ. They were transferred to the ice-negative, xanthan-producing Xanthomonas campestris pv. campestris by electroporation. The transformants were used for co-production of xanthan gum and ice nuclei from sugar beet molasses. The highest values obtained were 20 g l^–1 and 10¹⁸ ice nuclei ml^–1, respectively. The above values fulfil the criteria for industrial manipulation. This is the first report on co-formation of two products by a transformed X. campestris strain.     

5.3 S RNA is a discrete cleavage product from the 5′-terminus of 18 S RNA of rat liver ribosomes

A 5.3 S RNA species observed in urea-gel electrophoretic analysis of the RNA of the small ribosomal subunit of rat liver has been identified from its sequence as the 5′-terminal 133–134 base fragment of 18 S RNA. Presumably it is cleaved by an endogenous endonuclease when the ribosomal subunits are dissociated, because it usually is not observed in 18 S RNA obtained by direct extraction of cells or tissues.     

Sulfation of mono- and diaryl oximes by aryl sulfotransferase isozymes

Aryl sulfotransferases (3'-phosphoadenylsulfate:phenol sulfotransferase, EC 2.8.2.1) catalyze the sulfonation of a wide variety of hydroxyl-containing substrates, including numerous xenobiotics. The chemical diversity of aryl sulfotransferase substrates is in part attributable to the presence of multiple isozymes, each of which has broad substrate specificity. Of the aryl sulfotransferase isozymes in rat liver cytosol, two (designated isozymes I and II) have previously been shown to sulfonate phenolic compounds exclusively and, moreover, have very similar substrate specificity patterns. The recently reported unusually efficient, rapid isozyme I-catalyzed sulfonation of 9-fluorenone oxime (Mangold, J.B., Mangold, B.L.K. and Spina, A. (1986) Biochim. Biophys. Acta 874, 37-43) was therefore unexpected and suggested that aryl oximes may represent a useful class of model compounds to probe isozymic differences in substrate steric and electronic requirements. In the present study, several mono- and diaryl oximes have been prepared and tested as potential substrates for partially purified aryl sulfotransferases I and II from rat liver cytosol. The results indicate that steric factors, specifically planarity and hydroxyl group position, appear to be important requirements for enzyme-catalyzed sulfonation. In addition, although isozymes I and II had comparable activity with diaryl oximes, some striking differences in the ability of these two isozymes to sulfonate both substituted and unsubstituted monoaryl oximes were observed. This dissimilarity is consistent with distinct differences in the active sites of these isozymes.