Gelatin In Situ Zymography on Fixed, Paraffin-embedded Tissue: Zinc and Ethanol Fixation Preserve Enzyme Activity

In situ zymography is a method for the detection and localization of enzymatic activity in tissue sections. This method is used with frozen sections because routine fixation of tissue in neutral-buffered formalin inhibits enzyme activity. However, frozen sections present with poor tissue morphology, making precise localization of enzymatic activity difficult to determine. Ethanol- and zinc-buffered fixative (ZBF) are known to preserve both morphological and functional properties of the tissue well, but it has not previously been shown that these fixatives preserve enzyme activity. In the present study, we show that in situ zymography can be performed on ethanol- and ZBF-fixed paraffin-embedded tissue. Compared with snap-frozen tissue, ethanol- and ZBF-fixed tissue showed stronger signals and superior morphology, allowing for a much more precise detection of gelatinolytic activity. Gelatinolytic enzymes could also be extracted from both ethanol- and ZBF-fixed tissue. The yield, as analyzed by SDS-PAGE gelatin zymography and Western blotting, was influenced by the composition of the extraction buffer, but was generally lower than that obtained from unfixed tissue. (J Histochem Cytochem 58:29–39, 2010)     

Secretion of proteases in serglycin transfected Madin-Darby canine kidney cells

Madin-Darby canine kidney (MDCK) cells, which do not normally express the proteoglycan (PG) serglycin, were stably transfected with cDNA for human serglycin fused to a polyhistidine tag (His-tag). Clones with different levels of serglycin mRNA expression were generated. One clone with lower and one with higher serglycin mRNA expression were selected for this study. 35S-labelled serglycin in cell fractions and conditioned media was isolated using HisTrap affinity chromatography. Serglycin could also be detected in conditioned media using western blotting. To investigate the possible importance of serglycin linked to protease secretion, enzyme activities using chromogenic substrates and zymography were measured in cell fractions and serum-free conditioned media of the different clones. Cells were cultured in both the absence and presence of phorbol 12-myristate 13-acetate (PMA). In general, enzyme secretion was strongly enhanced by treatment with PMA. Our analyses revealed that the clone with the highest serglycin mRNA expression, level of HisTrap isolated 35S-labelled serglycin, and amount of serglycin core protein as detected by western blotting, also showed the highest secretion of proteases. Transfection of serglycin into MDCK cells clearly leads to changes in secretion levels of secreted endogenous proteases, and could provide further insight into the biosynthesis and secretion of serglycin and potential partner molecules.     

Peripherally administered growth hormone increases brain dopaminergic activity and swimming in rainbow trout

There is increasing evidence that growth hormone (GH) has important behavioral effects in fish, but the underlying mechanisms are not well understood. To investigate if peripherally administered GH influences the monoaminergic activity of the brain, and how this is correlated to behavior, juvenile rainbow trout were implanted intraperitoneally with ovine GH. Fish were either kept isolated or in groups of five. The physical activity and food intake of the isolated fish were observed after 1 and 7 days, when brains were also sampled. The content of serotonin, dopamine, and noradrenaline and their metabolites in hypothalamus, telencephalon, optic tectum, and brain stem was then analyzed. For fish kept isolated for 7 days following implant, GH increased swimming activity and the levels of the dopamine metabolite 3, 4-hydroxy-phenylacetic acid (DOPAC) were higher in all brain parts examined. In the optic tectum, the levels of the dopamine metabolite homovanillic acid (HVA) were lowered by the GH treatment. One-day GH implant did not affect behavior or monoamine levels of isolated fish. In the fish kept in groups, a 7-day GH implant increased the hypothalamic levels of DOPAC, but not in the other brain parts examined, which may indicate an effect on the brain dopaminergic system from social interactions. It can be concluded that peripherally administered GH may function as a neuromodulator, affecting the dopaminergic activity of the rainbow trout brain, and this is associated with increased swimming activity.     

Sequential DEXAS: a method for obtaining DNA sequences from genomic DNA and blood in one reaction

Sequential DEXAS (direct exponential amplification and sequencing), a one step amplification and sequencing procedure that allows accurate, inexpensive and rapid DNA sequence determination directly from genomic DNA, is described. This method relies on the simultaneous use of two DNA polymerases that differ both in their ability to incorporate dideoxynucleotides and in the time at which they are activated during the reaction. One enzyme, which incorporates deoxynucleotides and performs amplification of the target DNA sequence, is supplied in an active state whereas the other enzyme, which incorporates dideoxynucleotides and performs the sequencing reaction, is supplied in an inactive state but becomes activated by a temperature step during the thermocycling. Thus, in the initial stage of the reaction, target amplification occurs, while in the second stage the sequencing reaction takes place. We show that Sequential DEXAS yields high quality sequencing results directly from genomic DNA as well as directly from human blood without any prior isolation or purification of DNA.     

NotI passporting to identify species composition of complex microbial systems

We describe here a new method for large-scale scanning of microbial genomes on a quantitative and qualitative basis. To achieve this aim we propose to create NotI passports: databases containing NotI tags. We demonstrated that these tags comprising 19 bp of sequence information could be successfully generated using DNA isolated from intestinal or fecal samples. Such NotI passports allow the discrimination between closely related bacterial species and even strains. This procedure for generating restriction site tagged sequences (RSTS) is called passporting and can be adapted to any other rare cutting restriction enzyme. A comparison of 1312 tags from available sequenced Escherichia coli genomes, generated with the NotI, PmeI and SbfI restriction enzymes, revealed only 219 tags that were not unique. None of these tags matched human or rodent sequences. Therefore the approach allows analysis of complex microbial mixtures such as in human gut and identification with high accuracy of a particular bacterial strain on a quantitative and qualitative basis.     

Calcium-induced activation and truncation of promatrix metalloproteinase-9 linked to the core protein of chondroitin sulfate proteoglycans.

In the leukemic macrophage cell-line THP-1, a fraction of the secreted matrix metalloproteinase 9 (MMP-9) is linked to the core protein of chondroitin sulfate proteoglycans (CSPG). Unlike the monomeric and homodimeric forms of MMP-9, the addition of exogenous CaCl2 to the proMMP-9/CSPG complex resulted in an active gelatinase due to the induction of an autocatalytic removal of the N-terminal prodomain. In addition, the MMP-9 was released from the CSPG through a process that appeared to be a stepwise truncation of both the CSPG core protein and a part of the C-terminal domain of the gelatinase. The calcium-induced activation and truncation of the MMP-9/CSPG complex was independent of the concentration of the complex, inhibited by the MMP inhibitors EDTA, 1,10-phenanthroline and TIMP-1, but not by general inhibitors of serine, thiol and acid proteinases. This indicated that the activation and truncation process was not due to a bimolecular reaction, but more likely an intramolecular reaction. The negatively charged chondroitin sulfate chains in the proteoglycan were not involved in this process. Other metal-containing compounds like amino-phenylmercuric acetate (APMA), NaCl, ZnCl2 and MgCl2 were not able to induce activation and truncation of the proMMP-9 in this heterodimer. On the contrary, APMA inhibited the calcium-induced process, whereas high concentrations of either MgCl2 or NaCl had no effect. Our results indicate that the interaction between the MMP-9 and the core protein of the CSPG was the causal factor in the calcium-induced activation and truncation of the gelatinase, and that this process was not due to a general electrostatic effect.