The delay of anoikis due to the inhibition of protein tyrosine dephosphorylation enables the maintenance of normal rat colonocyte primary culture

Apoptosis induced by detachment of cells from the extracellular matrix (anoikis) appears to be one of the main obstacles in attempts to establish long-term primary culture of normal colonocytes. In the present study, the dynamics of molecular events related to apoptosis of isolated normal rat colonocytes was investigated. The whole colonic crypts were isolated using collagenase/dispase digestion technique. DNA fragmentation typical for the apoptosis and the apoptotic morphology of cells were observed already at the end of their isolation. Considerable increase in caspase-3 activity was noted during the first two hours of cell cultivation. Delaying of apoptosis by treatment of cells with sodium orthovanadate, the specific protein tyrosine phosphatase inhibitor, was found to be possible. It may facilitate long-term culture of intestinal epithelial cells.

Biological activity of Desulfovibrio desulfuricans lipopolysaccharides evaluated via interleukin-8 secretion by Caco-2 cells

BACKGROUND

Although Desulfovibrio desulfuricans species, besides existing in the natural environment, is also found in the human digestive tract, no information is currently available on its role in the intestinal ecosystem and its activity in regard to the intestinal mucosa. Bacterial products (lipopolysaccharides, LPSs) are generally known for their ability to trigger inflammatory response by stimulating cytokine expression, such as interleukin-8 (IL-8).

METHODS

Colonic Caco-2 cells were exposed to LPSs isolated from the soil type and intestinal wild strains of D. desulfuricans bacteria. The amount of IL-8 secreted was measured by ELISA. The effects of sodium butyrate and cell preincubation with sodium butyrate on the IL-8 secretion in response to LPSs were also analysed.

RESULTS

LPSs from D. desulfuricans down-regulated IL-8 secretion by the cells. Incubation of these cells with butyrate alone resulted in a dose-dependent stimulation of IL-8 release. Butyrate also modulated IL-8 secretion by cells stimulated with LPSs.

CONCLUSIONS

Our findings suggest the lack of inflammatory response of intestinal mucosa in the presence of LPSs of D. desulfuricans. This response can be conditioned by the natural bacterial product, butyrate, which exerts a stimulatory effect on the IL-8 secretion and modulates its release in response to LPSs.

Susceptibility to antibiotics and biochemical properties of Desulfovibrio desulfuricans strains

Susceptibility to several antibiotics and biochemical properties of intestinal and soil strains of Desulfovibrio desulfuricans bacteria were investigated using the tests: ATB ANA, Sceptor Anaerobic MIC/ID and API ZYM. It was demonstrated that the D. desulfuricans strains were resistant to penicillin, cefoxitin, clindamycin, metronidazole, erythromycin, rifampicin and teicoplanin. The strains initially susceptible to imipenem became resistant to this drug following 72 h incubation with it. Of 25 analyzed antibiotics there was none that after 72 h action on the bacteria was effective in relation to all of the investigated strains. The differences in susceptibility of D. desulfuricans strains to antibiotics were not associated with the strains' biochemical properties.

Changes in DNA supercoiling in fibroblasts cultured in the presence of hydralazine

We have analyzed changes in the supercoiling of nucleoid DNA of murine fibroblasts cultured in the presence of hydralazine. The entire DNA attached to the nuclear matrix was extracted from the cells and sedimented in neutral sucrose density gradients containing ethidium bromide. Nucleoids from cells treated with hydralazine responded to increasing ethidium bromide concentrations in a different way than those from control cultures. That is, supercoiled loops of DNA unwound with lower concentrations of ethidium bromide sedimented less rapidly than those of control cells, indicating that hydralazine reduced the degree of DNA supercoiling. Also, nucleoids from the drug-treated cells resisted the transition from relaxed to positive supercoiling at higher concentrations of ethidium bromide. Changes in nucleoid DNA supercoiling correlated directly with the dose of hydralazine in the fibroblast culture.

Single-strand breaks and repair in nuclear DNA in the presence of hydralazine assayed by the nucleoid technique

The nucleoid sedimentation assay was used to study hydralazine-induced DNA structural changes and repair in the fibroblasts cultured in vitro. The drug induced a dose dependent loss in negative DNA supercoiling due to the physical breakage of the DNA. Relaxation of supercoiled DNA resulted in the nucleoids sedimenting with lower velocities than those of undamaged control cultures. Repair incubation of the cells did not cause the restoration of DNA supercoiling to control level. Unsuccessful repair of DNA damaged by hydralazine may result in maintaining the damaged DNA in the cell which could have immunologic consequences.

The antioxidant enzymes activity in the conditions of systemic hypersilicemia

The effect of an excessive inorganic silicon oral intake on the activity of basic antioxidant enzymes was studied in rats. Activities of superoxide dismutase, catalase, and glutathione peroxidase were measured in liver and kidney tissues of animals receiving per os sodium metasilicate nonahydrate (Na2SiO3.9H2O) (Sigma, [St. Louis, MO]) dissolved in their drinking water. A decrease of the activity of all the studied enzymes was found in the samples derived from the experimental group. The results obtained indicate the free oxygen radicals participation in the potential pathologic events in the conditions of systemic hypersilicemia.

Location of the human red cell spectrin tetramer binding site and detection of a related "closed" hairpin loop dimer using proteolytic footprinting

Head-to-head association of two spectrin alpha beta heterodimers to form tetramers involves the formation of two equivalent alpha-beta complexes. The sites on the alpha subunit N-terminal region and beta subunit C-terminal region that form these alpha beta complexes have been identified using protease footprinting and direct binding assays. The existence of a similar previously hypothesized internal head-to-head alpha beta interaction in dimers was also demonstrated. The discrete regions of both subunits that are protected from proteolysis in tetramers and dimers are not due to the laterally associated subunit since head-to-head complexes of a univalent alpha peptide with a univalent beta peptide show similar protection of the same sites. These sites are unshielded immediately after monomers assemble side-to-side to form heterodimers, demonstrating that reconstituted dimers are initially in an "open" conformation. Conversion of open dimers to a closed form through formation of the internal head-to-head alpha beta association, as demonstrated by restoration of protease protection, occurred on a time scale of hours at 0 degrees C. Analysis of peptide binding affinities as well as isolation and sequence analysis of head-to-head alpha beta noncovalent complexes further defined the regions required for association on both subunits. These regions are homologous to the 106-residue repetitive motif that comprises most of both chains. An algorithm designed to improve prediction accuracy of multiple homologous motifs was used to model the conformation of spectrin repetitive motifs as well as the contact regions. In this model, the separate alpha and beta binding sites are incomplete complementary parts of a triple stranded folding unit. Formation of the alpha beta head-to-head complex produces a triple stranded conformational unit that is slightly different from other homologous motifs in the protein. Most hemolytic anemia mutations that are known to disrupt tetramer association are located in the mapped regions, including several mutations that induce a conformational change in the paired subunit.

Properties of human red cell spectrin heterodimer (side-to-side) assembly and identification of an essential nucleation site

The antiparallel side-to-side association of spectrin alpha and beta monomers is a two-step process which occurs in seconds even at 0 degrees C and at low concentrations. Assembly involves initial contact of complementary nucleation sites on each subunit, which are located near the actin binding end of the long, flexible heterodimer rod. The minimum nucleation sites are comprised of approximately four contiguous 106-residue homologous segments or repeats. Three repeats in the nucleation site contain an 8-residue insertion and have the highest homology to the four spectrin-like repeats in alpha-actinin. The adjacent actin binding domain on the beta subunit and the adjacent EF hand motifs on the alpha subunit are not required for heterodimer assembly. The nucleation sites probably have a specific lock and key structure which defines the unique side-to-side pairing of the many homologous segments in both subunits. Assembly of spectrin heterodimers is probably most analogous to a zipper. After initial nucleation site binding, the remainder of the subunits quickly associate along their full lengths to reconstitute a normal dimer by supercoiling around each other to form a rope-like, flexible rod. Assembly is terminated if either polypeptide is interrupted by a protease cleavage. Heterozygotic mutations involving either nucleation site are predicted to affect allele incorporation into the mature membrane skeleton.

Modulation of elastase-like activity in fibroblasts stimulated with elastin peptides

Elastin-derived peptides, kappa-elastin, prepared by chemical degradation of insoluble elastin from bovine ligamentum nuchae, were shown to increase the elastase-like activity in the culture medium and cell fractions in fibroblasts. Preincubation of cells with nifedipine (calcium channel blocker) and trifluoperazine (calmodulin antagonist) induced a decrease in the activities of the enzyme under study. These data suggest the possibility of pharmacological modulation of the biological effects induced by elastin-derived peptides.

Spin label detection and free radical nature of DNA damage by hydralazine

1. Incubation with hydralazine was shown to induce degradative changes of calf thymus DNA spin-labeled with 3-(2-bromoacetamido)-2,2,5,5-tetramethyl-1-pyrrolidono-1-oxyl and 4-(2-bromoacetamido)-2,2,6,6-tetramethylpiperidino-1-oxyl detectable from electron spin resonance specta. 2. Hydralazine, especially in the presence of Fe2+ induced formation of thiobarbituric acid (TBA)-reactive DNA degradation products. 3. The formation of TBA-reactive products was prevented by catalase, EDTA and scavengers of .OH radicals and enhanced by superoxide dismutase which suggests that .OH radicals formed by the Fenton mechanism mediate the DNA damage by hydralazine-Fe2+.

Pharmacological modulation of the antioxidant enzymes activities and the concentration of peroxidation products in fibroblasts stimulated with elastin peptides

1. Elastin peptides (kappa-elastin) prepared by alcoholic potassium hydroxide degradation of insoluble elastin were shown to increase the activities of antioxidant enzymes (SOD, CAT, GSH-Px) and the lipid peroxide concentration within fibroblasts. 2. The preincubation of cells with nifedipine (calcium channel antagonist) and trifluoperazine (calmodulin antagonist) caused the decrease in the activities of studied enzymes and the concentration of TBA-reactive products in fibroblasts stimulated with kappa-elastin. 3. The preincubation with ketotifen (antiallergic drug) has no effect on the activities of SOD, CAT, GSH-Px and the lipid peroxide concentration in stimulated cells. 4. These data suggest the possibilities of pharmacological modulation of the biological effects induced by elastin-derived peptides.

Hydralazine stimulates production of oxygen free radicals in Eagle's medium and cultured fibroblasts

The effect of hydralazine on the oxygen free radical production was studied in whole cultured murine liver fibroblasts and mitochondrial and microsomal fractions of the cells by ESR spin trapping with DMPO and measurement of Tiron semiquinone formation. Hydralazine itself was found to generate free radicals in phosphate buffer and especially in Eagle's Minimal Essential Medium. Most of the adduct of the spin trap DMPO was due to its reaction with hydralazine-induced hydroxyl radical. Moreover, this compound stimulated free radical formation in fibroblasts. These data suggest that hydralazine alters the cellular free radical metabolism which may have implications for the biological activity of this drug.

Usefulness of granulosa cells culture for testing of FSH activity

The trials have been undertaken to elaborate the experimental conditions of granular cells cultivation for FSH activity testing.

Hyaluronic acid and other glycosaminoglycans of the human palatal tonsils

The aim of this study was to determine whether the proportions of individual glycosaminoglycans (GAGs) change with bacterial infection of the human palatal tonsils and after recovery as compared with the physiological state of the palatal tonsils. In tonsillitis the greatest changes were related to hyaluronic acid (decrease) and heparin (increase). In the cured palatal tonsils the content of GAG components was found to return to that of the physiological state of the tonsils. The changes in GAG components in the cured palatal tonsils may possible contribute to the reversal of the human tonsillitis. The supposition is drawn that also physiological function of the cured tonsils is resumed.