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C Bojarski

Publications and source records attributed to C Bojarski.

16 recordsLinked to original sources
PubMed2004

Downregulation of epithelial apoptosis and barrier repair in active Crohn's disease by tumour necrosis factor alpha antibody treatment.

BACKGROUND AND AIMS: Barrier dysfunction is an important feature contributing to inflammation and diarrhoea in Crohn's disease (CD). Recently, tumour necrosis factor alpha (TNF-alpha) antibodies were recognised as effective in steroid refractory CD. The aim of this study was to characterise the effects of this therapy on the epithelial barrier. PATIENTS AND METHODS: Forceps biopsies were obtained from the sigmoid colon before and 14 days after TNF-alpha antibody therapy in 11 patients treated for chronic active CD (Crohn's disease activity index >150). Epithelial apoptoses were measured after terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labelling (TUNEL) and 4',6-diamidino-2-phenylindole staining. Epithelial resistance was determined by alternating current impedance analysis in miniaturised Ussing chambers. Occludin, claudin 1, and claudin 4 expression was quantified in immunoblots. RESULTS: The epithelial apoptotic ratio was 2.1 (0.2)% in controls and increased to 5.3 (1.0)% in CD. TNF-alpha antibody therapy decreased the apoptotic ratio to 2.9 (1.0)% (normalised in 10 of 11 patients). In parallel, epithelial resistance was lower in CD than in controls (24 (3) v 42 (3) Omegaxcm(2)) and improved to 34 (3) Omegaxcm(2) after therapy. Occludin, claudin 1, and claudin 4 were not affected by TNF-alpha antibody therapy. In support of a functional role of epithelial apoptoses in CD, a similar decrease in resistance of -40% was observed when the apoptotic rate was selectively upregulated from 2.6% to 5.4% with camptothecin in HT-29/B6 cells. CONCLUSIONS: Epithelial apoptoses were upregulated in the colon in CD and restored to normal in 10 of 11 patients by TNF-alpha antibody therapy. This is the structural correlate of epithelial barrier dysfunction measured as epithelial resistance while expression of tight junction proteins did not contribute to this therapeutic effect.

Antibodies, Monoclonal↗
PubMed2003

Excitation energy transport and trapping in concentrated solid solutions of flavomononucleotide.

Excitation energy transport and trapping is studied for monomer-fluorescent dimer system of flavomononucleotide (FMN) in polyvinyl alcohol films (PVA). It is shown that the theory neglecting reverse energy transfer (RET) from dimers to monomers does not allow for the explanation of concentration quenching and concentration depolarization results presented herein. Much better agreement has been obtained using generalized energy transport theory in which fluorescent dimers are treated as imperfect traps for excitation energy. Such parameters like the dimer quantum yield and its emission anisotropy are estimated.

Dimerization↗
PubMed2001

Permeability of human HT-29/B6 colonic epithelium as a function of apoptosis.

1. The barrier function of colonic epithelia is challenged by apoptotic loss of enterocytes. In monolayers of human colonic HT-29/B6 cells, apoptosis induced by camptothecin was assessed by poly-(ADP-ribose)-polymerase (PARP) cleavage, histone ELISA and DNA-specific fluorochrome staining (with 4',6'-diamidino-2'-phenylindoladihydrochloride (DAPI)). Epithelial barrier function was studied in Ussing chambers by measuring transepithelial conductivity and unidirectional tracer fluxes. The ion permeability associated with single cell apoptoses was investigated with the conductance scanning technique. 2. The spontaneous rate of apoptotic cells was 3.5 +/- 0.3 % with an overall epithelial conductivity of 3.2 +/- 0.1 mS cm(-2). Camptothecin induced a time- and dose-dependent increase of apoptosis and permeability. With 20 microg ml(-1) of camptothecin for 48 h, apoptosis increased 4.1-fold to 14.3 +/- 1.5 % and the conductivity doubled to 6.4 +/- 1.0 mS cm(-2). 3. While 3H-mannitol flux increased 3.8-fold and 3H-lactulose flux increased 2.6-fold, the flux of 3H-polyethylene glycol 4000 remained unchanged. Hence, the higher permeability was limited to molecules < 4000 Da. 4. The local epithelial conductivity was higher at the sites of apoptosis than in non-apoptotic areas. With camptothecin the leaks associated with apoptosis became more numerous and more conductive, while in non-apoptotic areas the conductivity remained at control level. Hence, the camptothecin-induced increase in epithelial conductivity reflected the opening of apoptotic leaks and thus the results described, for the first time, epithelial permeability as a function of apoptosis only. 5. The conductivity of apoptotic leaks contributed 5.5 % to the epithelial conductivity of controls and 60 % to the conductivity of monolayers treated with 20 microg ml(-1) of camptothecin. Thus apoptosis increased the contribution of paracellular pathways to the overall epithelial permeability. Under control conditions the paracellular conductivity (G(para)) was smaller than the transcellular (G(trans)), but with 12 % apoptosis, G(para) exceeded G(trans). By definition, the epithelium became 'leaky'.

Apoptosis↗
PubMed2000

Patients with dyspepsia benefit from eradication of Helicobacter pylori if other organic causes for dyspepsia were carefully ruled out.

AIM: In order to investigate the potential of Helicobacter pylori (HP) to induce dyspepsia, we performed a randomized prospective study on the long-term effect of HP-eradication on symptoms of HP-positive dyspeptic patients in whom other organic causes for dyspepsia were carefully ruled out. PATIENTS: 201 patients referred to our endoscopy unit with dyspeptic symptoms for at least six months entered the study. Patients with previous peptic ulcer were excluded. METHODS: After endoscopy of the upper alimentary tract and 13C-urea breath test, patients with active peptic ulcer, hiatal hernia, macroscopic evidence for esophagitis and negative HP-status were excluded. The remaining patients underwent abdominal sonography, H2-exhalation test with lactose, and 24-h pH monitoring in order to exclude other organic causes for dyspepsia. In 20 patients, dyspepsia was assumed to be due to HP-gastritis. Patients received eradication therapy and were controlled as assessed by the 13C-urea breath test six weeks and six months after completion of the therapy. Dyspeptic symptoms were monitored by means of a validated symptom score. RESULTS: Out of 20 patients with HP-gastritis the first eradication treatment was successful in 13, while seven patients remained HP-positive after antibiotic treatment. Six months after completion of therapy the symptoms of HP-eradicated patients improved considerably (score values 17.4 +/- 1.5 and 10.2 +/- 0.8, respectively, p < 0.01) whereas symptoms of patients with persistent infection remained unchanged (21.1 +/- 1.7 and 20.4 +/- 1.5, n.s.) and only improved after successful retherapy (20.4 +/- 1.5 and 11.7 +/- 2.1, p < 0.05). In total, 17 of 20 patients (85%) improved after successful eradication. Also, neutrophil infiltration in the gastric mucosa correlated to both dyspeptic symptoms before therapy (r = 0.85) and the decrease in symptom score after HP-eradication (r = 0.61). In contrast, the symptoms of eight patients with gastroesophageal reflux disease were not improved after eradication (20.0 +/- 1.1 and 18.2 +/- 1.0, n.s.) CONCLUSIONS: HP-infection per se contributes to dyspepsia. 17 of 20 (85%) HP-positive dyspeptic patients improved after HP-eradication, when other potential organic causes for dyspepsia had been ruled out. However, many patients did not completely recover but the symptoms only partly decreased which parallels the persistence of part of the inflammatory infiltration in the gastric mucosa. This emphasizes the importance of HP-gastritis as an organic disease causing dyspeptic symptoms.

Adult↗
PubMed2000

Apoptosis and intestinal barrier function.

The signal transduction pathways of the induction of apoptosis in the gastrointestinal tract have in part been discovered. However, almost nothing is known about the functional influence of apoptotic signals on intestinal barrier function. In this study the effect of camptothecin-induced apoptosis in HT-29/B6 monolayers and the influence of apoptosis on epithelial barrier function were characterized. We demonstrated that camptothecin causes a decrease of transepithelial resistance and an increase in fluxes of the paracellular marker [3H]mannitol. Camptothecin increased the apoptotic rate and the conductance of single-cell apoptosis as measured by the conductance scanning technique. We conclude that in our model of HT-29/B6 cells camptothecin is a potent inductor of apoptosis that causes significant barrier defects measured by the Ussing chamber technique and the conductance scanning technique. Based on these results we are able to investigate the effect of other cytokines--TGF-beta, for instance, and its role in apoptotic conditions.

Apoptosis↗
PubMed1998

Spectroscopic manifestations of flavomononucleotide dimers in polyvinyl alcohol films.

Absorption and fluorescence spectra of flavomononucleotide (FMN) in polyvinyl alcohol films (PVA) over a very wide concentration range are investigated. The dimerization constant as well as the pure monomer and dimer spectra are calculated and the structural parameters of FMN dimer are established. Excitation wavelength and temperature dependencies of FMN/PVA fluorescence spectra for different FMN concentrations were carried out. These measurements together with those of absorption reveal that dimers are imperfect traps for excitation energy and that the energy transfer can occur both in forward and in reverse direction. Moreover, it was shown that the observed temperature changes in fluorescence spectra may be qualitatively explained by the effect of inhomogeneous broadening of FMN energy levels and by the presence of fluorescent dimers.

Dimerization↗
PubMed1998

Dual versus triple therapy: comparison of five antibiotic regimens for eradication of Helicobacter pylori in a prospective, randomized study.

We compared the efficacy of three dual and two triple therapies for eradication of Helicobacter pylori (HP), and evaluated the influence of smoking and omeprazole pretreatment on HP eradication. 220 patients with proven HP infection (histology and 13C-urea breath test [UBT]) were randomly allocated to one of the following regimes: BMT (bismuth subsalicylate 600 mg t. i. d. for 28 days, metronidazole 400 mg t. i. d. and tetracycline 500 mg q. i. d. for ten days). OA (omeprazole 40 mg o. d. and amoxicillin 750 mq q. i. d. for 14 days), OC (omeprazole 40 mg o. d. and clarithromycin 500 mg b. i. d. for 14 days), OT (omeprazole 40 mg o. d. and tetracycline 500 mg q. i. d. for 14 days), OMC (omeprazole 40 mg o. d., metroinidazole 400 mg t. i. d. and clarithromycin 250 mg b. i. d. for seven days). Eradication was defined as negative UBT six weeks after completion of the therapy. In an "all-patients-treated" ("per-protocol") analysis, the eradication rates were: BMT, 91% (93%); OA, 84% (90%); OC, 74% (74%); OT, 24% (24%); and OMC, 90% (93%). Smoking impaired the success of OA and OT (p < 0.05), but the efficacy of the triple regimens was not affected. Omeprazole pretreatment did not influence eradication rates. Thus, highest eradication rates were achieved with the two triple therapies tested. However, OA, given at a daily antibiotic dose of 3 g amoxicillin for 14 d, was also highly effective. After failure of triple therapy, OA was successful in seven of ten patients (70%). The efficacy of OC was lower than that of the triple therapies (p < 0.05). In conclusion, metronidazole- and clarithromycin-based triple therapies are highly effective first line therapies. OA, given at a dose of 3 g per day over 14 days, should be considered as a possible second line therapy, e.g. in retherapy after failed triple therapy.

Adolescent↗
PubMed1997

13C-urea breath test in Helicobacter pylori diagnosis and eradication. Correlation to histology, origin of 'false' results, and influence of food intake.

BACKGROUND: Which protocol is optimal for the 13C-urea breath test (UBT) for Helicobacter pylori detection is controversial. This study aimed to characterize a very simple UBT protocol for the clinical routine (two-point-analysis performed with 75 mg 13C-urea and citric acid) with special consideration of 'false' UBT results. RESULTS; UBT was evaluated in reference to histology (Warthin-Starry). In mismatching results re-gastroscopy was performed. By UBT, 74 of 77 patients with H. pylori-positive histology were detected (sensitivity, 96%). The false-negative UBTs were due to low colonization densities during spontaneous H. pylori elimination or pyloric obstruction. Seven of 49 patients with negative histology had a positive UBT, but re-gastroscopy showed that all of them had a positive histology when multiple antral biopsy specimens were taken (UBT specificity, 100%). UBT correlated only weakly with H. pylori colonization density. No correlation was found between UBT and gastric neutrophil and lymphocyte infiltration. UBT reproducibility was excellent (93 of 94 in a 6-month period). Non-fasting conditions induced a shift to lower UBT results in H. pylori-positive and to higher UBT results in negative patients, resulting in 2 of 10 false-positive and 1 of 10 false-negative UBTs. CONCLUSION: This simple version of the urea breath test combines the highest sensitivity with excellent reproducibility. It is superior to histologic detection of H. pylori in the clinical routine and an optimal tool for monitoring H. pylori eradication. Fasting conditions are required for the test.

Breath Tests↗
PubMed1994

Effects of prolactin and hCG treatment on luteal activity and the conceptus during delayed implantation in Schreibers' long-fingered bat (Miniopterus schreibersii).

In Schreibers' long-fingered bat (Miniopterus schreibersii) from South Africa, implantation is delayed from May to August during which time the corpus luteum is inactive and plasma progesterone and LH concentrations low. Treatment of pregnant long-fingered bats with exogenous prolactin for 10 days in early delayed implantation (May) resulted in changes in luteal ultrastructure that were consistent with increased steroidogenesis, high plasma progesterone concentrations and the initiation of implantation. Treatment of bats with hCG for 10 days in early delayed implantation induced similar changes in luteal ultrastructure and plasma progesterone concentrations, but did not initiate implantation. Treatment with exogenous progesterone during early delayed implantation had no influence on the corpus luteum or the conceptus. We conclude that prolactin is the most important pituitary hormone in the control of delayed implantation, although the route via which it induces implantation is unknown.

Animals↗
PubMed1992

The influence of fluorescence concentration quenching on the emission anisotropy of flavins in glycerine-water solutions.

The measurements of the emission anisotropy r/r0 of flavomononucleotide (FMN) within a range of concentrations of 10(-5)-10(-1) mol/L in glycerine-water solutions of different viscosities--0.056 Pa/s (system I) and 0.256 Pa/s (system II) have been carried out. In the range of high concentrations the repolarization effect due to the sharp drop of the quantum yield has been observed. The experimental results have been compared with theoretical expressions evaluated by taking into account both concentration and rotation depolarization. A good agreement on the values of the theoretical parameters obtained from independent measurements has been found. It has been stated that in the investigated systems the excitation energy transfer may be treated as a Markov process.

Energy Transfer↗
PubMed1991

Patterns of Leydig cell and LH gonadotroph activity, and plasma testosterone concentrations in the seasonally reproducing Schreibers' long-fingered bat (Miniopterus schreibersii).

Spermatogenesis in Schreibers' long-fingered bat from approximately 33 degrees S in South Africa was seasonal, and occurred in the 3 months (February-April) preceding ovulation. The ultrastructure of the Leydig cells indicated a period of increased steroidogenesis at this time, and plasma testosterone concentrations were elevated from March to May (10.3 ng/ml). The reproductive accessory glands were secretorily active between March and May, and copulation occurred at the end of this period of activity. Changes in LH-beta immunoreactivity suggest that the LH gonadotrophs were secretorily active 1 month before the onset of spermatogenesis and that peak activity coincided with peak plasma testosterone concentrations, spermiogenesis and spermiation. During winter (May-August) there was no reproductive activity and the bats remained active, only entering prolonged periods of torpor during particularly cold spells. A secondary elevation in plasma testosterone concentration, during reproductive inactivity (October; 9.3 ng/ml), was not accompanied by any change in Leydig cell ultrastructure, and the biological significance of this peak is unknown. Such synchronous activity of the pituitary, Leydig cells, seminiferous epithelium and accessory glands is associated with the typical reproductive cycle of long-fingered bats in which copulation and fertilization are restricted to a brief period at the end of summer, and in which neither sperm storage nor a prolonged period of copulation occur.

Animals↗
PubMed1991

Plasma progesterone and luteinizing hormone concentrations and the role of the corpus luteum and LH gonadotrophs in the control of delayed implantation in Schreibers' long-fingered bat (Miniopterus schreibersii).

In Schreibers' long-fingered bat from South Africa (approximately 33 degrees S) copulation, ovulation and fertilization occurred in April and May, implantation was delayed until August, and parturition occurred in December. Delayed implantation coincided with winter, during which the bats remained active, only entering prolonged periods of torpor during particularly cold spells. Plasma progesterone concentration was low during non-pregnancy (1.54 ng/ml) and during delayed implantation (1.67 ng/ml), and thereafter increased to reach a peak mean of 64.82 ng/ml in late pregnancy. Changes in size and ultrastructure of the luteal cells indicated periods of steroidogenesis just after formation of the corpus luteum, and for about 2 months after implantation; reduced steroidogenic activity during delayed implantation; and luteolysis in the last 2 months of pregnancy. Plasma luteinizing hormone (LH) concentration and pituitary LH-beta immunoreactivity were highest during follicular development and peaked just before ovulation. During early delayed implantation, plasma LH concentration was low, and both plasma LH and pituitary LH-beta immunoreactivity increased from July, reaching peaks in late pregnancy. LH may be required to activate the corpus luteum and terminate delayed implantation, or, as in some small carnivores, it may be required for luteal maintenance.

Animals↗
PubMed1990

Investigations on the fluorescence concentration quenching of flavomononucleotide in glycerine-water solutions.

We measured concentration changes of the fluorescence quantum yield eta/eta 0 of flavomononucleotide (FMN) in glycerine-water solutions of various viscosities. The results obtained show that FMN dimers are traps for the exciting light energy as well as the energy transferred non-radiatively. Very good agreement between the experimental and theoretical eta/eta 0 results was obtained. It has been shown that in the investigated solutions non-radiative energy transfer from monomers to dimers takes place, preceded by the migration of energy. It has been stated that no monomer quenching occurs in these solutions. The contribution of the individual fluorescence concentration quenching mechanisms has been determined.

Flavin Mononucleotide↗