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Biomedical subjects

R Stoll

Publications and source records attributed to R Stoll.

At least 19 recordsLinked to original sources
PubMed2002

Marginal adaptation of partial crowns cast in pure titanium and in a gold alloy - an in vivo study.

The aim of the present study was to assess in vivo the marginal integrity of partial crowns cast in pure titanium and in a gold alloy. For this purpose, two groups of 25 molars were prepared for partial crowns and then restored with partial crowns cast in Degulor M gold alloy and in pure titanium. At a subsequent session, replicas were produced using a special impression-taking technique. The scanning electron microscope (SEM) technique was used to perform quantitative margin analysis (Tiffmess 1.8 program). The gold alloy partial crowns displayed significantly (P < 0.05) more continuous margin (marginal quality A, <50 microm), and the titanium partial crowns significantly more marginal quality B (50-100 microm) and C (>100 microm). The results show that better marginal integrity can be achieved with gold alloy than with titanium partial crowns. However, in practical terms the difference in marginal quality is only slight, so that the use of pure titanium for single-tooth restorations is justified.

Cementation↗
PubMed2001

The extracellular human melanoma inhibitory activity (MIA) protein adopts an SH3 domain-like fold.

Melanoma inhibitory activity (MIA) protein is a clinically valuable marker in patients with malignant melanoma, as enhanced values diagnose metastatic melanoma stages III and IV. Here we show that the recombinant human MIA adopts an SH3 domain-like fold in solution, with two perpendicular, antiparallel, three- and five-stranded beta-sheets. In contrast to known structures with the SH3 domain fold, MIA is a single-domain protein, and contains an additional antiparallel beta-sheet and two disulfide bonds. MIA is also the first extracellular protein found to have the SH3 domain-like fold. Furthermore, we show that MIA interacts with fibronectin and that the peptide ligands identified for MIA exhibit a matching sequence to type III human fibronectin repeats, especially to FN14, which is close to an integrin alpha4beta1 binding site. The present study, therefore, may explain the role of MIA in metastasis in vivo, and supports a model in which the binding of human MIA to type III repeats of fibronectin competes with integrin binding, thus detaching cells from the extracellular matrix.

Amino Acid Sequence↗
PubMed2001

Chalcone derivatives antagonize interactions between the human oncoprotein MDM2 and p53.

The oncoprotein MDM2 inhibits the tumor suppressor protein p53 by binding to the p53 transactivation domain. The p53 gene is inactivated in many human tumors either by mutations or by binding to oncogenic proteins. In some tumors, such as soft tissue sarcomas, overexpression of MDM2 inactivates an otherwise intact p53, disabling the genome integrity checkpoint and allowing cell cycle progression of defective cells. Disruption of the MDM2/p53 interaction leads to increased p53 levels and restored p53 transcriptional activity, indicating restoration of the genome integrity check and therapeutic potential for MDM2/p53 binding antagonists. Here, we show by multidimensional NMR spectroscopy that chalcones (1,3-diphenyl-2-propen-1-ones) are MDM2 inhibitors that bind to a subsite of the p53 binding cleft of human MDM2. Biochemical experiments showed that these compounds can disrupt the MDM2/p53 protein complex, releasing p53 from both the p53/MDM2 and DNA-bound p53/MDM2 complexes. These results thus offer a starting basis for structure-based drug design of cancer therapeutics.

Antineoplastic Agents↗
PubMed2001

Marginal adaptation of cast partial crowns made of pure titanium and a gold alloy under influence of a manual burnishing technique.

The aim of this study was to determine the marginal adaptation of partial crowns from pure titanium and a gold alloy after two different cementation techniques. Forty freshly extracted human molars were prepared and randomly divided in four groups. Two groups were restored with partial crowns using the gold alloy Degulor M*. In one group, the crowns were fixed on the tooth by using a zinc phosphate cement. In the other group the margins were additionally burnished by using a hand burnisher No. 660. In the other two groups, partial crowns from pure titanium were cemented in the same way. The marginal quality was determined by quantitative margin analysis in the SEM using a replica technique. Partial crowns from a gold alloy showed significantly (P < 0.05) more margin quality A (vertical marginal discrepancy < 50 microm) while partial crowns from pure titanium had significantly (P < 0.05) more margin quality B (vertical marginal discrepancy 50-100 microm) and over-extended margins (quality D). No significant (P < 0.05) difference was found between the conventional cementation technique and the technique with manual burnishing in both material groups.

Cementation↗
PubMed2001

Eradication of Helicobacter pylori restores the inhibitory effect of cholecystokinin on gastric motility in duodenal ulcer patients.

BACKGROUND: Increased gastric emptying and defective action of endogenous cholecystokinin (CCK), that is known to inhibit this emptying, have been implicated in the pathogenesis of duodenal ulcer (DU). The aim of this double blind study was to assess whether CCK and somatostatin participate in the impairment of gastric motility in active DU patients before and after Helicobacter pylori eradication. METHODS: Tests were undertaken in 10 DU patients without or with elimination of the action of endogenous CCK using loxiglumide, a selective CCK-A receptor antagonist, before and 4 weeks after eradication of H. pylori with 1 week triple therapy that resulted in healing of all DUs tested. The gastric emptying rate after feeding was determined using the 13C-acetate breath test. Before each test, samples of gastric juice were obtained by aspiration using a nasogastric tube for determination of somatostatin using specific radioimmunoassay. RESULTS: Prior to H. pylori eradication gastric emptying half-time was 31 +/- 6 min in placebo-treated DU patients and this emptying rate was not significantly affected in tests after pretreatment with loxiglumide (10 mg/kg i.v.). Following eradication of H. pylori, in tests with placebo gastric emptying half-time was significantly longer (48 +/- 9 min) compared to that prior to H. pylori eradication. Pretreatment with loxiglumide in H. pylori eradicated DU patients significantly enhanced the gastric emptying rate with an emptying half-time of only 33 +/- 4 min. Eradication of H. pylori resulted in a significant increase in somatostatin concentration in gastric juice and loxiglumide significantly reduced this luminal somatostatin in H. pylori-eradicated subjects compared to values before anti-H. pylori therapy. CONCLUSIONS: 1) H. pylori infection in DU patients is accompanied by enhanced gastric emptying and reduction in luminal release of somatostatin; 2) the failure of loxiglumide to affect gastric emptying in H. pylori-infected DU patients might be attributed, at least in part, to the failure of endogenous CCK to control gastric motility due to deficient release of somatostatin; and 3) H. pylori-infected patients appear to exhibit a deficient somatostatin release by endogenous CCK that can be reversed by the eradication of H. pylori indicating that both CCK and somatostatin may contribute to normalization of gastric emptying following H. pylori eradication in DU patients.

Adolescent↗
PubMed2000

Influence of a high-speed polymerization method on the marginal integrity of composite fillings in Class-II cavities.

The aim of this study was to evaluate the effect of a rapid photopolymerization method on the marginal integrity of composite fillings. Ninety two-surface cavities were prepared in extracted human molars using the SonicSys preparation system. All cavities were bonded with one bonding agent (Syntac) and filled with a microfilled composite (Herculite XRV), a heavy filled composite (Z100 MP), and an Ormocer (Definite) in two increments. Each increment had a thickness of approximately 1.5 mm and was polymerized using either halogen light or the plasma light of Apollo 95 E. In this process, six trial groups each containing 15 fillings were created. After replicas were made, the test teeth were subjected to a thermocycling process of 2000 temperature cycles (5 degrees C/55 degrees C) followed by a wear simulation of 50,000 stress cycles each with 50 N. This was followed by the creation of a second set of replicas, quantitative margin analysis, and dye penetration. A significant (P < 0.05) influence of the thermomechanical stress and a significant (P < 0.05) influence of the factor "material" were shown for the margin criterion "continuous margin" using MANOVA. The factor "light source" produced no significant influence (P = 0.57) on the amount of continuous margin. During the dye penetration, no significant differences between the polymerization methods could be established with the materials Herculite XRV and Z100 MP (H-test according to Kruskall and Wallis). Only with the material Definite was a significantly higher dye penetration observed at the occlusal measuring point in the plasma light group. A rapid polymerization with high light intensity had no adverse effects on the margin quality within the limitations of this in vitro study. However the marginal integrity might have been influenced by the chosen adhesive system/composite resin combination, which does not represent the respective product line. Additionally, further studies ought to show which exposure time is necessary for a sufficient degree of conversion.

Acrylates↗
PubMed2000

Characterization of M cell development during indomethacin-induced ileitis in rats.

BACKGROUND: M cells play an important role in the intestinal immune system as they have a high capacity for transcytosis of a wide range of microorganisms and macromolecules. However, little is known about the role of M cells during intestinal inflammation. AIM: We studied M cell development during indomethacin-induced intestinal inflammation in rats. METHODS: Ileitis in rats was induced by two subcutaneous injections with indomethacin (7.5 mg/kg) given 24 h apart. Rats were sacrificed after 14 days and tissue was analysed by fluorescence microscopy and electron microscopy. M cells could be visualized by using the FITC-labelled mAb anti-cytokeratin (CK)-8 (clone 4.1.18), which was recently identified as specific M cell marker in rats. The number of cytokeratin-8 positive M cells was related to the surface of the follicle associated epithelium. For morphological studies, we used both transmission electron microscopy (T.E.M.) and scanning electron microscopy (S.E.M.). RESULTS: In non-inflamed ileum M cells were scarce. Only 4% of the follicle associated epithelium were M cells, whereas an increase of M cells up to 11% was found in inflamed follicle associated epithelium (P < 0.001). The rate of M cell induction depended on the macroscopic degree of inflammation. T.E.M./S.E.M. studies showed that in inflamed tissue most M cells underwent apoptosis with typical morphological signs. In contrast to apoptotic M cells, the neighbouring enterocytes usually appeared intact. The number of mononuclear cells below the follicle associated epithelium was significantly increased. S.E.M. studies revealed that during induced ileitis mononuclear cells migrated from the lamina propria into the gut lumen by passing through apoptotic M cells. CONCLUSIONS: During indomethacin-induced ileitis in rats the increase in M cell number in association with apoptosis of M cells may alter the intestinal barrier function. These observations may play a pivotal role in the pathogenesis of chronic intestinal inflammation, e.g. in inflammatory bowel disease.

Animals↗
PubMed2000

Role of M cells in intestinal barrier function.

M cells are known as specialized epithelial cells of the follicle-associated epithelium of the gastrointestinal tract. As M cells have a high capacity for transcytosis of a wide range of microorganisms and macromolecules, they are believed to act as an antigen sampling system. The primary physiological role of M cells seems to be the rapid uptake and presentation of particular antigens and microorganisms to the immune cells of the lymphoid follicle to induce an effective immune response. In contrast to absorptive enterocytes, M cells do not exert direct defense mechanisms to antigens and pathogens in the gut lumen. Therefore, they provide functional openings of the epithelial barrier. Although M cells represent a weak point of the epithelial barrier, even under noninflamed conditions, there seems to be a balance between antigen uptake and immunological response. The low number of M cells in the gastrointestinal tract and the direct contact to immune cells in the lamina propria usually prevent the occurrence of mucosal inflammation. During chronic intestinal inflammation we observe an increase of M cell number and apoptosis selectively in M cells. M cell damage seems to be responsible for the increase of the uptake of microorganisms that is observed during intestinal inflammation. Under inflammatory conditions in the intestine, the maintenance of the epithelial barrier is broken and M cells seem to play a major role during this process.

Animals↗
PubMed2000

Marginal characteristics of different filling materials and filling methods with standardized cavity preparation.

PURPOSE: The aim of the present study was to investigate the influence of different filling materials and methods on marginal integrity in Black Class I fillings. MATERIALS AND METHODS: Standardized occlusal cavities were prepared in 80 extracted human molars. The preparations were filled with composite resin (1), with composite resin using the incremental technique (2), an experimental glass-fiber-reinforced (3) and polyester-reinforced (4) composite resin, a direct composite inlay (5), a ceramic insert (6), a Cerafil inlay (7), and with an experimental direct filling using Dyract AP compomer (8). Allocation of the teeth to the test groups was randomized; further processing was done on a blind basis. After the preparation of replicas, the teeth were subjected to a thermomechanical cycling process of 2,000 temperature cycles (5 degrees C/55 degrees C) and 50,000 stress cycles (50 N). This was followed by production of a second set of replicas and quantitative margin analysis by SEM (200X). A dye penetration test was then performed on the mesiodistal section. RESULTS: Groups 1, 2, 5, 6 and 7 displayed a good primary marginal quality, with the proportion of continuous margins reaching more than 85%. Significantly poorer results were recorded for the experimental glass-fiber-reinforced composite resins and Dyract compomer, where the proportion of perfect margins was only between 36% and 73%. In groups 1, 2, 5, 6 and 7, marginal integrity remained stable after the thermomechanical stress cycles, with the Cerafil inlays recording the best values: 89% perfect margins and 3% marginal gaps. In contrast, the experimental composite resins and the compomer underwent a significant (p < 0.05) increase in the proportion of marginal gaps and a significant (p < 0.05) reduction in the proportion of continuous margin. CONCLUSION: The results of this study show that neither Dyract compomer nor the glass-fiber-reinforced composite resins tested can be recommended for use in the occlusally stressed posterior region, whereas the other filling materials and methods were sufficiently stress resistant.

Acid Etching, Dental↗
PubMed1999

Longevity of cast gold inlays and partial crowns--a retrospective study at a dental school clinic.

From 1963 to 1993, 890 patients were treated with 3518 cast gold restorations by students and postgraduate dentists. The longevity of these restorations was studied retrospectively using the patient files. Longevity was calculated using the method described by Kaplan and Meier. After the observation period, 111 (3.2%) of the examined restorations were not in place anymore. The most frequent reasons for failure were caries (33.7%), lack of retention (32.7%), endodontic treatment (29.6%), insufficient marginal adaptation (3.1%) and extraction (1%). The cumulative survival rate and a 95% interval of confidence was calculated for all restorations and for each of the locations and surfaces included in the trial. The 10-year survival rate for occlusal inlays was, 76.1% (12.1) for MO inlays 88.3% (4.2), for DO inlays 83.4% (4.6), for MOD inlays 87.5% (2.4), for partial crowns 86.1% (3.3) and 85.7% (1.7) for all restorations. Based on the statistical method used, the cast gold restorations demonstrated satisfactory longevity results.

Adult↗
PubMed1999

Interleukin (IL)-13 and IL-4 are potent inhibitors of IL-8 secretion by human intestinal epithelial cells.

Intestinal epithelial cells are able to produce soluble mediators that initiate or amplify inflammatory events in the intestinal mucosa. Interleukin (IL) -8 is suggested to be a cytokine playing a major role during the acute and chronic processes in inflammatory bowel disease (IBD). TH-2 cytokines have been described as down-regulating the inflammatory response. We analyzed the effects of IL-10, IL-13, and IL-4 on IL-8 secretion in intestinal epithelial cells. The human colonic epithelial cell line Caco-2 and freshly isolated intestinal epithelial cells were used. Cells were stimulated with IL-1beta after treatment with TH-2 cytokines. Levels of IL-8 were determined by employing enzyme-linked immunosorbent assay (ELISA). Stimulation with IL-1beta results in a time-dependent IL-8 secretion. The addition of IL-4 and IL-13, but not IL-10, to activated epithelial cells resulted in a strong decrease in IL-8 secretion. Maximal inhibition required that TH-2 cytokines be added up to 60 min before or simultaneous with stimulatory agents. We present novel findings that IL-4 and IL-13 strongly down-regulate IL-8 secretion from intestinal epithelial cells. A microenvironment containing high concentrations of IL-4 and IL-13 may alter the recruitment of immune cells to enterocytes at least partly by inhibiting IL-8 production. This inhibition might diminish the severity of the intestinal inflammatory response and, thus reduce clinical disease activity.

Caco-2 Cells↗
PubMed1999

Coincidence of cytomegalovirus retinitis and central retinal vein occlusion in a patient with hemophilia B and AIDS.

A 37-year-old man with hemophilia B, acquired immunodeficiency syndrome, and a unilateral cytomegalovirus retinitis developed a central retinal vein occlusion. This vascular complication occurred despite effective antiviral drug treatment with improvement of the fundus and despite decreased blood coagulability due to hemophilia B. Additional analyses of thrombophilic parameters did not reveal hints of systemic thrombophilia, suggesting that toxic and inflammatory effects of cytomegalovirus itself were responsible for the ophthalmologic aggravation.

AIDS-Related Opportunistic Infections↗
PubMed1998

Prevalence and quality of root canal fillings in a German adult population. A survey of orthopantomograms taken in 1983 and 1992.

The few studies in which prevalence, technical quality, and success rates of root canal fillings performed in daily practice have been assessed demonstrated a high proportion of inappropriate root fillings and a great variety of periapical radiolucencies (25-60%). The aim of the present retrospective radiographic study was to determine if changes in prevalence, technical quality, and success of root canal fillings had occurred within a decade. To achieve this goal, orthopantomograms taken in patients who attended a University Dental Clinic for the first time in 1983 (group A) and in 1992 (group B) were evaluated by a calibrated examiner. The following criteria were applied to assess the root-filled teeth: length and homogeneity of the root fillings and the periapical state. The prevalence of root-filled teeth increased significantly from an average 0.5 per person in 1983 to 0.8 per person in 1992. The increase was proportionally greater in older patients. In group A, 55.2% of the root fillings ended 0-2 mm before the radiographic apex and in group B this percentage was 56.8. Insufficient homogeneity was found in 25.0% (group A) and 21.9% (group B) of the root fillings. The prevalence of root-filled teeth without periapical destructions was 76.1% (group A) and 74.1% (group B). It is concluded that, in the future, endodontic treatment need will increase because of the steadily growing number of older people. Further efforts in research and dental education should focus on the treatment of curved root canals.

Adolescent↗
PubMed1998

IL-10 synergizes with IL-4 and IL-13 in inhibiting lysosomal enzyme secretion by human monocytes and lamina propria mononuclear cells from patients with inflammatory bowel disease.

Tissue injury and inflammation in inflammatory bowel disease (IBD) are associated with enhanced monocytic lysosomal enzyme release. In this study, peripheral monocytes and lamina propria mononuclear cells (LPMNC) were isolated from IBD patients and normal controls. Cells were stimulated with lipopolysaccharide after treatment with IL-13, IL-4, and IL-10, and enzyme secretion was assessed by using the corresponding p-nitrophenyl glycosides as substrates. Molecular forms of cathepsin D were examined to describe the mode of enzyme release. IL-10 and IL-4 strongly down-regulate enzyme secretion in IBD monocytes. IBD monocytes showed a diminished responsiveness to the inhibitory effect of IL-13. Impaired monocyte response was not found with combinations of IL-13 and IL-10 or IL-4 and IL-10. LPMNC from involved IBD mucosa showed significantly higher enzyme secretion compared with LPMNC from noninvolved IBD mucosa but responded inefficiently to either IL-4, IL-13, or IL-10 alone. However, combined treatment with IL-10 and IL-4 or IL-10 and IL-13 strongly suppressed enzyme release by these cells. Both the precursor and mature forms of cathepsin D were elevated in IBD patients. While IL-13 reduced mainly the precursor form, the effect of IL-4 and IL-10 concerns both the precursor and mature form of cathepsin D. Our results favor the potent clinical utility of combined treatment, thus improving chances of developing effective treatments for human IBD.

Adult↗
PubMed1998

Eradication of Helicobacter pylori with lansoprazole, roxithromycin and metronidazole--an open pilot study.

BACKGROUND: The most extensively studied Helicobacter pylori eradication regimen comprises omeprazole, clarithromycin and metronidazole. Macrolide antibiotics other than clarithromycin should achieve similar efficacy, but they have not yet been thoroughly tested. AIM: To determine the efficacy and safety of a triple therapy regimen using lansoprazole, roxithromycin, and metronidazole on the basis of multicentre outpatient care in an open pilot study. METHODS: 163 patients with duodenal ulcer and proven H. pylori infection received lansoprazole 30 mg b.d., roxithromycin 300 mg b.d. and metronidazole 500 mg b.d. for 7 days followed by another 7 days of lansoprazole 30 mg once daily. H. pylori status was determined by urease quick test, histology, microbiology and 13C-urea breath test before starting and at least 4 weeks after completing treatment. RESULTS: 150 patients were available for evaluation; H. pylori was successfully eradicated in 84.7% (127/ 150) as determined by urease quick test, 78.0% (117/150) by histology, 81.3% (109/134) by 13C-urea breath test; and in 75.3% (113/150), at least two tests were negative. Side-effects were reported in 34 patients (most commonly diarrhoea and changes in liver function tests), in two cases the study medication was interrupted. Prior to treatment, 23% of the H. pylori isolates were resistant against metronidazole and 3.4% against roxithromycin. After unsuccessful treatment, 84% of the isolates were resistant against metronidazole and 21% against roxithromycin. Primary resistance to metronidazole increased the chance of treatment failure approximately sevenfold (7% vs. 53%). CONCLUSIONS: For H. pylori eradication, the combination of lansoprazole, roxithromycin and metronidazole proved to be as safe as other current triple therapy regimens, while a comparison of efficacy rates yet remains to be assessed in prospective controlled trials. The metronidazole-resistant H. pylori is not rare in Germany and, in the present study, has strongly influenced treatment success.

2-Pyridinylmethylsulfinylbenzimidazoles↗