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H Eyssen

Publications and source records attributed to H Eyssen.

At least 19 recordsLinked to original sources
PubMed1996

Tauroconjugation of cholic acid stimulates 7 alpha-dehydroxylation by fecal bacteria.

We examined the effect of the type of cholic acid conjugation (taurine-conjugated, glycine-conjugated, or unconjugated cholic acid) on cholic acid 7 alpha-dehydroxylation by intestinal flora. Cholic acid 7 alpha-dehydroxylation in fecal cultures, in cultures of a defined limited flora consisting of a mixture of seven bacterial species isolated from the intestinal tract, and in a binary culture of a 7 alpha-dehydroxylating Clostridium species plus a cholic acid-deconjugating Bacteroides species was studied. We found that tauroconjugation of cholic acid significantly (P < 0.05) increased bacterial 7 alpha-dehydroxylation of cholic acid into deoxycholic acid from 34 to 55% in fecal cultures, from 45 to 60% in defined limited fecal cultures, and from 75 to 100% in binary cultures. Equimolar concentrations of free taurine did not stimulate 7 alpha-dehydroxylation in fecal cultures or in the defined limited flora, but free taurine did stimulate 7 alpha-dehydroxylation in the binary culture. In the binary culture of Clostridium species strain 9/1 plus Bacteroides species strain R1, the minimal flora capable of increased 7 alpha-dehydroxylation of taurocholic acid, strain R1 deconjugated taurine and rapidly reduced it to H2S. Bacteroides species strain R1 did not grow unless taurine or another appropriate reducible sulfur source was present. Clostridium species strain 9/1 did not grow or 7 alpha-dehydroxylate unless H2S or another source of reduced sulfur was present. We conclude that the increased 7 alpha-dehydroxylation of tauroconjugated cholic acid depends on the reduction of taurine to H2S, which is a necessary growth factor for the 7 alpha-dehydroxylating bacteria.

Bacteria↗
PubMed1995

Analysis of the open reading frames of the main capsid proteins of actinophage VWB.

The nucleotide sequence of a 6 kb fragment encoding the main late proteins (p14, p38 and p24) of actinophage VWB was obtained. Sequence comparison of the encoded proteins with those filed in databases indicated that the phage VWB main late proteins were all novel. A search for special motifs revealed that p14 (13.3 kDa) has a P-loop sequence commonly found in ATP- and GTP-binding proteins. This observation might indicate that p14 is important for ATP-driven DNA translocation during encapsidation of VWB phage DNA into the phage head. Furthermore, the polypeptide ORF2 (26.9 kDa) has an unusual primary structure consisting of 3 stretches of acidic amino acid residues and a glycine/arginine rich C-terminal end. From comparison with other proteins including the bacteriophage T4 prohead core component and from the data of special motif analysis the ORF2 gene product is probably involved in prohead core formation.

Amino Acid Sequence↗
PubMed1995

Full- vs. partial-mouth disinfection in the treatment of periodontal infections: short-term clinical and microbiological observations.

In a standard periodontal treatment strategy with consecutive root planings (per quadrant at a one- to two-week interval), re-infection of a disinfected area might occur before completion of the treatment. This study examines, both clinically and microbiologically, whether a full-mouth disinfection within 24 hours significantly improves the outcome of periodontal treatment. Ten patients with advanced chronic periodontitis were randomly allocated to a test and a control group. The patients from the control group received scalings and root planings as well as oral hygiene instructions per quadrant at two-week intervals. Full-mouth disinfection in the test group was sought by the removal of all plaque and calculus (in two visits within 24 hours). In addition, at each of these visits, the tongue was brushed with a 1% chlorhexidine gel for one min and the mouth rinsed with a 0.2% chlorhexidine solution for two min. Furthermore, subgingival chlorhexidine (1%) irrigation was performed in all pockets. The recolonization of the pockets was retarded by oral hygiene and 0.2% chlorhexidine rinses during two weeks. The clinical parameters were recorded, and plaque samples were taken from the right upper quadrant at baseline and after one and two months. The test group patients showed a significantly higher reduction in probing depth for deep pockets at both follow-up visits (p < 0.05). At the one-month visit, differential phase-contrast microscopy revealed significantly lower proportions of spirochetes and motile rods in the test group (p = 0.01). Culturing showed that the test group harbored significantly fewer pathogenic organisms at one month (p = 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Efficient secretion of biologically active mouse tumor necrosis factor alpha by Streptomyces lividans.

We have studied the production of mouse tumor necrosis factor alpha (mTNF) with Streptomyces lividans as host. mTNF cDNA was fused to the alpha-amylase-encoding gene (aml) of Streptomyces venezuelae ATCC15068 at 12 amino acids (aa) downstream from the signal-peptidase cleavage site so that the aa surrounding this processing site were conserved. S. lividans containing this construct secreted mTNF at moderately high levels (1-10 micrograms/ml) as a biologically active compound of high specific activity (1 x 10(8) units/mg protein). No unprocessed pre-protein and virtually no processed protein could be detected in the cell lysates. N-terminal aa sequence analysis indicated microheterogeneity (-3 to -6 forms) at the N-terminal site of secreted mTNF. It was demonstrated that this microheterogeneity was due to aminopeptidase activity.

Amino Acid Sequence↗
PubMed1994

Microbial penetration along the implant components of the Brånemark system. An in vitro study.

This study examined in vitro the existence of microbial leakage along the components of the Brånemark implant system. Thirty-two implant/abutment assemblies were installed in a liquid blood medium previously inoculated with oral micro-organisms. To examine the leakage at the implant-abutment interface, 16 assemblies were partially immersed. The remaining 16 were completely immersed to observe the leakage at both the implant-abutment and abutment-prosthesis interface. After 7 days of anaerobic incubation, the micro-organisms in the internal part of the implants were collected and incubated on blood agar plates in anaerobic conditions. Micro-organisms were found in the completely immersed assemblies and at lower numbers in the partially immersed implants, indicating that bacterial leakage at both levels seems to exist. Several penetrating bacteria have been associated with peri-implantitis. The clinical importance of this bacterial leakage is not yet well understood. Although the longevity of the Brånemark implants is well documented, this bacterial leakage might play a role in peri-implantitis, both in the etiology as well as in the treatment.

Biofilms↗
PubMed1993

Conventionalization of germ-free rats reverses the disability of rhein anthrone to induce laxation.

This study shows that rhein anthrone has no laxative potency in germ-free rats because after intracaecal administration of a dose of 50 mg/kg the large intestine transit exceeded 240 min. The time course of the laxative potency of rhein anthrone injected intracaecally was evaluated after peroral inoculation of germ-free rats with the caecal contents of conventional rats. Large intestine transit was measured at consecutive periods, on days 0, 1, 2, 3 and 5 after peroral inoculation. It appeared that 1 day after peroral inoculation the laxative potency of rhein anthrone was already established (large intestinal transit < 10 min) and laxation remained on the following days (days 2, 3 and 5). We concluded that rhein anthrone is inactive in germ-free rats and acquires laxative potency after peroral inoculation of germ-free rats with caecal contents of conventional rats.

Animals↗
PubMed1992

The effect of rhein and rhein anthrone on intestinal fluid transport and on large intestine transit in germ-free rats.

The effect of rhein and rhein anthrone on the transit and the transport of water and electrolytes in the large intestine was investigated in germ-free rats. After intracaecal administration, neither of the two compounds was found to accelerate the transit of a colour marker through the large intestine. Both drugs reduced the net absorption of sodium and chloride in the colon and enhanced net potassium secretion. Net water absorption was decreased by rhein and even reversed into net secretion by rhein anthrone. Our results show that the secretagogue activity of the compounds is not sufficient to induce laxation in germ-free rats. Furthermore rhein and rhein anthrone had no laxative properties under our experimental conditions.

Animals↗
PubMed1992

In vitro reduction of rhein anthraquinone to rhein anthrone by rat cecal microflora and some intestinal bacterial strains.

After in vitro incubation of cecal content from CVL or gnotobiotic rats with rhein anthraquinone (1 mg g-1) for 18 h at 37 degrees, the anthraquinone was converted to rhein anthrone for 23.5 (SD +/- 3.4) per cent and 19.4 (+/- 4.7) per cent, respectively. Liquid cultures of some strictly anaerobic fecal bacteria of man and mouse incubated with rhein anthraquinone (62.5 micrograms ml-1) for 48 h at 37 degrees, revealed only small amounts of reduced substance. Although the underlying mechanisms of the differences in both conditions remain unclear, the experimental data accentuate the need for using cecal content when exploring the in vitro metabolism of anthranoids by the intestinal microflora. The conversion was chemically proven by derivatization of the anthrone with 4-nitroso-N-N-dimethylaniline in pyridine, followed by hydrolysis and identification of the released anthranoid by mass spectrometry. The in vitro reduction capacity of the cecal content of CVL rats was drastically decreased by oral administration to rats of different combinations of neomycin sulfate, metronidazole, bacitracin and Na-penicillin G. In these cases the conversion ranked between 0.2 per cent and 5.2 per cent the first day after administration. It is concluded that rhein anthraquinone in cecal content is reduced to the highly reactive and labile rhein anthrone, which accounts for the in vivo disappearance of dihydroxy-anthranoid equivalents in routine analysis after oral administration of anthraquinones to experimental animals.

Animals↗
PubMed1991

Partial characterization of the steroidsulfatases in Peptococcus niger H4.

The strictly anaerobic intestinal Peptococcus niger H4 synthesizes three different steroidsulfatase enzymes: a constitutive arylsulfatase and two inducible alkylsteroidsulfatases. The arylsulfatase desulfates estrogen-3-sulfates and phenylsulfates. The two alkylsteroidsulfatases desulfate, respectively, 3 alpha-sulfates and 3 beta-sulfates of delta 5, 5 alpha, and 5 beta androstanes, pregnanes, and bile acids. Cholesterol-3 beta-sulfate was not desulfated by the alkylsteroidsulfatases nor were steroids or bile acids that were sulfated in positions other than the 3 position. The alkylsteroidsulfatases were induced by their substrates; bile acid sulfates, however, were poor inducers of the 3 beta-sulfatase and did not induce the 3 alpha-sulfatase activity. In intact bacterial cells, taurine and sulfite suppressed the induction of the alkylsteroidsulfatases and inhibited the activity of the arylsulfatase and alkylsteroidsulfatases. In cell homogenates, the arylsulfatase and alkylsteroidsulfatases activities were inhibited by sulfite and sulfate but not by taurine. Our results support the hypothesis that the main function of the steroidsulfatases in P. niger H4 is to provide the bacteria with sulfur for dissimilatory purposes.

Arylsulfatases↗
PubMed1991

Variation of slow-wave frequency and locking during the migrating myoelectric complex in dogs.

Slow waves determine rhythm and polarity of spike bursts. We measured the variation of slow-wave frequency (swf) and locking (swl) in the canine jejunum during the various phases of the migrating myoelectric complex (MMC) and during induced phase III (erythromycin 125 micrograms/kg iv bolus or somatostatin 2.5 micrograms.kg-1.h-1 iv infusion), blocked phase III (atropine 20 micrograms/kg iv bolus), and so-called stationary phase III activity (cisapride 150 micrograms/kg iv bolus). The EMG of 4 dogs, implanted with 10 bipolar electrodes, was recorded on a polygraph. Our results indicate that swf and swl change during the MMC from a stepwise swf gradient with slow waves locked in plateaus during phase I to a continuous swf gradient without or with significantly reduced phase locking during phase III. The length of the first swf plateau decreases significantly from 42 +/- 12 cm post Treitz during phase I to 11 +/- 4 cm during spontaneous phase III. Atropine block of phase III activity prevents phase unlocking and development of a continuous swf gradient. Our hypothesis is that phase unlocking may be one of the induction mechanisms of spike-burst activity.

Animals↗
PubMed1990

Influence of intestinal bacterial desulfation on the enterohepatic circulation of dehydroepiandrosterone sulfate.

Selective association of germ-free (GF) rats with dehydroepiandrosterone sulfate (DHEAS) desulfating bacteria allowed us to assess the exact impact of intestinal bacterial desulfation on the excretion and enterohepatic circulation of orally administered DHEAS. Germ-free rats selectively associated with the DHEAS-desulfating strain Peptococcus niger H4 (H4 rats) excreted 50% of the total label recovered within 17 h vs 21 h in GF rats and 13 h 23 min in conventional (CV) rats. Germ-free rats excreted 30% of the total label recovered via their urine. However, association of GF rats with the desulfating microorganism increased urinary excretion to 46%, comparable to the 45.5% found in CV rats. Fractionation of fecal label yielded 70% sulfoconjugated DHEAS and 2% unconjugated dehydroepiandrosterone in GF rats vs 5 and 77% in CV rats, and 55 and 14% in H4 rats, respectively. Our results demonstrate that the intestinal bacterial desulfation of DHEAS stimulated the enterohepatic circulation of DHEAS. This in turn increased the urinary excretion of label resulting in an accelerated elimination of labeled DHEAS from the body.

Animals↗
PubMed1990

Optimum conditions for efficient transformation of Streptomyces venezuelae protoplasts.

Optimum conditions for protoplast regeneration and transformation of Streptomyces venezuelae ETH14630 have been established. Protoplasts from mycelium grown to the stationary phase and treated with lysozyme in P medium under mild conditions gave the best regeneration frequency. Transformation of protoplasts with naked DNA was very efficient using either polyethylene glycol of mol. wt. 4000 or 6000, at concentrations of 28.5% or 36% (w/v) respectively. About 10(7) transformants/micrograms DNA could be isolated using protoplasts derived from cells cultivated to the early exponential growth phase in LB medium containing 0.2%-0.6% glycine and subsequently treated at 30 degrees -32 degrees C with 20 mg lysozyme/ml in P medium for 30 min. Selection of the transformants occurred on MRYE plates containing less than 10(5) regenerating protoplasts per plate. Higher protoplasts densities considerably decreased the regeneration frequency of the transformants.

Biotechnology↗
PubMed1990

Further biological and molecular characterization of actinophage VWB.

The development cycle of the temperate actinophage VWB was investigated. Adsorption of most phage particles occurred within 30 min and the adsorption constant was 0.6 x 10(-8) ml min-1. The latent and rise periods were 140 and 100 min, respectively, and the burst size was estimated to be 130-250 p.f.u. Although phage VWB could infect only Streptomyces venezuelae ETH 14630 (ATCC 40755), of six different S. venezuelae strains tested, phage DNA could be introduced by transfection into most non-infectible strains. Upon transfection, phage DNA was propagated in these non-infectible strains and phage particles were released. In addition, the transfected strains could be lysogenized. By comparison of restriction fragments of VWB DNA, either free or integrated in the chromosomal DNA of the S. venezuelae ETH 14630 lysogen, the attachment site was localized. PAGE of the phage proteins revealed at least 17 different proteins with three major bands estimated as 16.5, 27.2 and 43 kDa in size. The N-terminal amino acid sequence of these supposed major head and tail proteins was determined. The corresponding DNA sequences on the phage genome were localized using oligonucleotides synthesized on the basis of the N-terminal amino acid sequences. The genes coding for the major structural proteins were shown to be clustered, as has been observed for other bacteriophages.

Amino Acid Sequence↗
PubMed1990

Determination of the packaging capacity of bacteriophage VWB.

VWB is a temperate bacteriophage whose chromosome has cohesive ends. VWB can stably package modified chromosomes that contain insertions of up to about 4 kilobases of foreign DNA. Phage particles containing extra DNA differ from the wild type in their increased sensitivity to chelating agents. Because of these properties, VWB is a promising cloning vector for Streptomyces venezuelae.

Bacteriophages↗
PubMed1989

Interdigestive myoelectric complex in germ-free rats.

The effect of intestinal bacteria on the interdigestive myoelectric complex (IDMEC) was studied by recordings of the electrical activity of the proximal and distal small bowel in fasting germ-free (n = 6), gnotobiotic (n = 7), and conventional (n = 6) rats in vivo. Germ-free and gnotobiotic rats were operated and studied in germ-free or gnotobiotic conditions. The IDMEC period (mean +/- SD) in the proximal and distal small bowel was significantly longer in germ-free rats (20 +/- 2 min and 102 +/- 14 min) as compared to conventional rats (13 +/- 1 min and 58 +/- 5 min). Association of germ-free rats with a limited flora (gnotobiotic rats) decreased the IDMEC period significantly (15 +/- 1.5 min and 75 +/- 14 min). The migration velocity of the IDMEC was inversely related to the IDMEC period. These observations confirm previous data suggesting that the interdigestive motor complex has a role in the homeostasis of the bacterial content of the small bowel.

Animals↗
PubMed1989

Formation of delta 2- and delta 3-cholenoic acids from bile acid 3-sulfates by a human intestinal Fusobacterium strain.

We isolated two strains of an unnamed Fusobacterium species from human intestinal microflora, which stereospecifically transformed bile acid 3-sulfates into C-3-unsubstituted, ring A-unsaturated bile acids. Both 3 alpha- and 3 beta-sulfates of 5 beta-bile acids were metabolized to delta 3-5 beta-cholenoic acids; 3 beta-sulfates of 5 alpha-bile acids were converted into a mixture of delta 2-5 alpha-bile acids and 3 alpha-hydroxy-5 alpha-bile acids, whereas 3 alpha-sulfates of 5 alpha-bile acids were left intact. Unsulfated bile acids were not transformed into unsaturated derivatives. These strains differ from previously isolated intestinal bacteria, which desulfated bile acid sulfates without further transformation.

Bile Acids and Salts↗
PubMed1988

Effects of intestinal microbial bile salt sulfatase activity on bile salt kinetics in gnotobiotic rats.

Hepatic sulfation is thought to promote fecal excretion of lithocholate in humans by impairing the enterohepatic recirculation of the compound. Sulfatases produced by the gut flora may, at least in part, counteract this process. To investigate this interaction, female germfree rats, which are known to excrete considerable amounts of sulfated bile salts, were selectively associated with a bile salt desulfating flora. In these rats nearly all cecal, colonic, and fecal bile salt sulfate esters were hydrolyzed, resulting in a decrease of total fecal bile salt excretion of greater than 25% compared with gnotobiotic rats without a bile salt desulfating flora. Desulfation of allochenodeoxycholate, the major sulfated bile salt in germfree rats, led to an enhanced recirculation and 12 alpha-hydroxylation of the compound in the liver, resulting in an increased fecal output of allocholate. Microbial desulfation of intraperitoneally injected [24-14C]taurolithocholate-3-sulfate caused a fivefold decrease of the fecal plus urinary excretion rate of the isotope to approximately that found for unsulfated [24-14C]taurolithocholate. Coassociation of the gnotobiotic rats with a microflora that normalized the small intestinal transit time and cecal size led to a rise of total fecal bile salt excretion of greater than 30% and a twofold accelerated excretion of both sulfated and unsulfated injected [24-14C]taurolithocholate. We conclude that in rats the gut flora rapidly desulfates intestinal bile salt sulfates, enhancing the enterohepatic recirculation and subsequent hydroxylation of the desulfated bile salts. In addition, these data illustrate the importance of having a well-defined microflora to normalize intestinal transit time and cecal size of gnotobiotic animals when performing kinetic studies of enterohepatic circulating compounds.

Animals↗