Biomedical subjects

Martin Jung

Publications and source records attributed to Martin Jung.

25 records · Page 2Linked to original sources

PubMed2003

Transport of the intracisternal A-type particle Gag polyprotein to the endoplasmic reticulum is mediated by the signal recognition particle.

Intracisternal A-type particles (IAP) are defective endogenous retroviruses that accumulate in the endoplasmic reticulum (ER) of rodent cells. The enveloped particles are produced by assembly and budding of IAP Gag polyproteins at the ER membrane. In this study, we analyzed the specific ER transport of the Gag polyprotein of the IAP element MIA14. To this end, we performed in vitro translation of Gag in the presence of microsomal membranes or synthetic proteoliposomes followed by membrane sedimentation or flotation. ER binding of IAP Gag occurred mostly cotranslationally, and Gag polyproteins interacted specifically with proteoliposomes containing only signal recognition particle (SRP) receptor and the Sec61p complex, which form the minimal ER translocation apparatus. The direct participation of SRP in ER targeting of IAP Gag was demonstrated in cross-linking and immunoprecipitation experiments. The IAP polyprotein was not translocated into the ER; it was found to be tightly associated with the cytoplasmic side of the ER membrane but did not behave as an integral membrane protein. Substituting the functional signal peptide of preprolactin for the hydrophobic sequence at the N terminus of IAP Gag also did not result in translocation of the chimeric protein into the ER lumen, and grafting the IAP hydrophobic sequence onto preprolactin failed to yield luminal transport as well. These results suggest that the N-terminal hydrophobic region of the IAP Gag polyprotein functions as a transport signal which mediates SRP-dependent ER targeting, but polyprotein translocation or integration into the membrane is prevented by the signal sequence itself and by additional regions of Gag.

Amino Acid Sequence↗

PubMed2003

Bristle end rounding of manual toothbrushes and reproducibility of end rounding classification.

PURPOSE: To evaluate the bristle end rounding quality of the toothbrushes selected. Furthermore the reproducibility of the bristle tip classification method was assessed. METHODS: Fifteen different manual toothbrushes were examined by taking into account the traumatic potential of toothbrushing caused by sharp and edged bristle end geometry. Three brushes for young children (0-4 years of age), eight brushes for children of 5-14 years of age and four brushes for juveniles and adults were included. The macroscopic criteria to which the selected brushes had to conform were: a compact toothbrush handle, a small brush head with rounded contours and a medium or soft bristle stiffness. Bristle tip geometry was investigated under SEM according to a modified scale by Silverstone & Featherstone. End rounding was examined in five regions equally distributed over the brush head. Two brushes of each brand were included in the SEM investigation. For evaluation of reproducibility , end roundings of 119 bristle tips were assessed twice by one experienced examiner and once by two additional unexperienced examiners. RESULTS: The proportion of acceptably rounded bristle tips varied widely from 65.2 - 99%. Half of the products examined achieved a level of at least 90% acceptable bristle end rounding. Five of the toothbrushes examined had between 70 and 90% acceptable bristle end geometries, while two products had less than 70%. Intraindividual reproducibility regarding acceptable and unacceptable end rounding was 99.16%, interindividual reproducibility varied between 90.76% and 94.96%.

Adolescent↗

PubMed2002

Tail-anchored and signal-anchored proteins utilize overlapping pathways during membrane insertion.

Tail-anchored proteins are a distinct class of membrane proteins that are characterized by a C-terminal membrane insertion sequence and a capacity for post-translational integration. Although it is now clear that tail-anchored proteins are inserted into the membrane at the endoplasmic reticulum (ER), the molecular basis for their integration is poorly understood. We have used a cross-linking approach to identify ER components that may be involved in the membrane insertion of tail-anchored proteins. We find that several newly synthesized tail-anchored proteins are transiently associated with a defined subset of cellular components. Among these, we identify several ER proteins, including subunits of the Sec61 translocon, Sec62p, Sec63p, and the 25-kDa subunit of the signal peptidase complex. When we analyze the cotranslational membrane insertion of a comparable signal-anchored protein we find the nascent polypeptide associated with a similar set of ER components. We conclude that the pathways for the integration of tail-anchored and signal-anchored membrane proteins at the ER exhibit a substantial degree of overlap, and we propose that this reflects similarities between co- and post-translational membrane insertion.

Cell Membrane↗

PubMed2002

Risk factors for lethal outcome in patients with bullous pemphigoid: low serum albumin level, high dosage of glucocorticosteroids, and old age.

BACKGROUND: Although bullous pemphigoid (BP) is the most frequent autoimmune bullous disease and is associated with a considerable case-fatality rate, little is known about factors that influence its prognosis. OBJECTIVE: To identify prognostic factors for lethal outcome in the first year after the initial hospitalization in patients with BP. DESIGN: A multicenter retrospective cohort study. SETTING: Seven dermatologic university hospitals in Germany. PARTICIPANTS: A total of 369 patients diagnosed as having BP between January 1, 1987, and December 31, 1997. STATISTICS: Univariate (Kaplan-Meier) and multivariate (Cox regression) analysis. RESULTS: Of the 369 patients with BP, 209 (57%) died, 106 (29%) within the first year after hospitalization. Fifty-four percent were women. The mean +/- SD age at entry was 77.3 +/- 11.1 years. The patients with BP were followed up to 10.5 years, with a median time of 1.8 years to death or interview (25th and 75th quartiles, 0.5 and 4.0 years). The major risk factors for lethal outcome in the first year after hospitalization were an increased age, with a multivariate risk estimate of 3.2 (95% confidence interval [CI], 1.9-5.2) for age greater than 80.4 years (median); a daily glucocorticosteroid dosage of more than 37 mg (75th quartile) at discharge, with a multivariate risk estimate of 2.5 (95% CI, 1.5-4.3); serum albumin levels of 3.6 g/dL or less (25th quartile), with a multivariate risk estimate of 2.6 (95% CI, 1.5-4.4); and an erythrocyte sedimentation rate greater than 30 mm/h (75th quartile), with a multivariate risk estimate of 1.7 (95% CI, 1.1-2.8). CONCLUSIONS: There is a considerable case-fatality rate in patients with BP. Older patients who require a higher dosage of oral glucocorticosteroids at hospital discharge and who have low serum albumin levels are at greater risk of death within the first year after hospitalization. These prognostic factors should be considered in the care of patients with BP as well as in the design of future clinical trials.

Aged↗

PubMedDate not supplied

Surface geometry of three packable and one hybrid composite after finishing.

This study compared the effects of different finishing techniques on the surface of a traditional hybrid composite and three packable composites. Four composites were used in the study (Herculite XRV/Kerr, Definite/Degussa, SureFil/Dentsply and Solitaire/Heraeus-Kulzer). Fifty specimens were made of each material, sized 7 x 7 x 4 mm. Fifteen specimens of each material were subjected to the following finishing procedures: (1) a 30 microm diamond, (2) a 30 microm and a 20 microm diamond and (3) a 30 pm diamond followed by a tungsten carbide finishing bur. As a reference, five specimens of each material were treated by Sof-Lex discs (3M). For quantitative surface evaluation, laser-stylus profilometry was used. Roughness parameters included average roughness (Ra) and profile-length-ratio (LR). Statistical analysis was performed with one- and two-way Anova and Scheffé post-hoc tests. Qualitative surface evaluation in SEM was performed at a tension of 25kV. Significant effects were found with both the composites and the finishing methods with respect to surface roughness (p < 0.001 for Ra and LR). A 30 microm diamond caused the greatest roughness on all composites, with Ra ranging from 2.015-2.079 microm (p<0.001). After finishing using methods 2 and 3, the Solitaire surfaces were significantly smoother (p < 0.001 for LR). The lowest roughness values were achieved after using disks; again, the Solitaire specimens yielded the lowest Ra and LR values (p < 0.001 except for Sure-Fil). With scanning electron microscopy, surface areas with signs of destruction were found after using a 30 microm diamond on Definite specimens.

Analysis of Variance↗

PubMedDate not supplied

Surface geometry of three packable and one hybrid composite after polishing.

This study evaluated the surface quality of four composite materials after polishing with six different polishing techniques. Eighty specimens were made using three packable composites (Definite/Degussa, SureFil/ Dentsply and Solitaire/Heraeus-Kulzer) and one hybrid composite (Herculite XRV/Kerr). Five specimens of each material were polished using flexible Sof-Lex discs. The remaining 75 specimens of each composite were prepared using three finishing protocols: a single 30 microm diamond (n = 25), two finishing diamonds (30/20 microm; n = 25) and a 30 microm diamond followed by a tungsten carbide finishing bur (n = 25). Final polishing of each of the three finishing groups was accomplished with SuperBuff, Diafix-oral, OneGloss, Astropol and HaWe Composite Polishers (n = 5, each). Surface roughness was evaluated quantitatively by laser-stylus profilometry. Average roughness (R(a)) was calculated; statistical analysis of the data was performed with two-way ANOVA and Scheffé post-hoc tests. The polished surfaces were examined qualitatively by SEM. The results showed significant effects on surface roughness from the different composites (p = 0.011) and polishing systems (p < 0.001). After polishing, the Solitaire surfaces (R(a) = 0.72 microm) were smoother than Definite (R(a) = 0.87 microm) and SureFil (R(a) = 0.89 microm) and significantly smoother than Herculite (R(a) = 0.92 microm; p = 0.011). Three of the polishing methods (SuperBuff, Diafix-oral and Astropol) achieved lower R(a)-values than Sof-Lex discs. The polishing quality of the one-step systems SuperBuff and Diafix-oral was strongly affected by the initial finishing protocol.

Aluminum Oxide↗

PubMedDate not supplied

Polishing occlusal surfaces of direct Class II composite restorations in vivo.

This study evaluated the effects of four polishing methods on the occlusal surfaces of direct Class II composite restorations under clinical conditions. Forty premolars and 40 molars were treated with direct Class II restorations using the hybrid composite Herculite XRV (Kerr). After placement of the restorations, all of which were on occlusal surfaces, they were finished with a sequence of 30 microm diamonds and tungsten carbide instruments. Twenty restorations each, consisting of 10 premolars and 10 molars, were polished with one of the four following methods: (1) Diafix-oral (Mueller-Dental), (2) MPS gel (Premier), (3) P 403-W (Dentsply) and (4) Occlubrush (KerrHawe). Selection of the polishing methods followed a randomized protocol. Replicas of the restored teeth were fabricated and the occlusal surfaces were evaluated quantitatively for roughness with the help of profilometry. Qualitative assessment of the surfaces by SEM was done with respect to roundness of contours and surface roughness. The results were analyzed statistically by two-way ANOVA, chi-squared test for crosstables and Kruskal-Wallis test. Analysis of the quantitative data showed that there was no significant effect of the polishing methods on occlusal surface roughness (p>0.05). Localization of the restoration in premolars or molars had no effect on surface roughness (p>0.05). With respect to occlusal relief, SEM examination revealed that the use of the Occlubrush resulted in significantly more edged contours compared to the other polishing methods (p=0.008). Qualitative roughness evaluation showed that there were no significant differences among the four polishing methods (p>0.05).

Adolescent↗