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Biomedical subjects

E Schwarz

Publications and source records attributed to E Schwarz.

At least 19 recordsLinked to original sources
PubMed1995

The role of the GrpE homologue, Mge1p, in mediating protein import and protein folding in mitochondria.

Mge1p, a mitochondrial GrpE homologue, has recently been identified in the yeast Saccharomyces cerevisiae and a role for this protein in precursor import has been reported. To dissect the molecular mechanism of Mge1p function, conditional mge1 mutants were constructed. Cells harbouring mutant mge1 accumulated precursor proteins at restrictive temperature. Both kinetics and efficiency of import were reduced in mitochondria isolated from strains possessing mutant mge1. Binding of mitochondrial-Hsp70 (mt-Hsp70) to incoming precursor proteins was abolished at restrictive temperature. Nucleotide-dependent dissociation of mt-Hsp70 from the import component MIM44 was reduced in mitochondria from mutant mge1 strains. Furthermore, at restrictive temperature an increase of incompletely folded, newly imported protein and enhanced protein aggregation was observed in mitochondria isolated from the mutant strains. We conclude that Mge1p exerts an essential function in import and folding of proteins by controlling the nucleotide-dependent binding of mt-Hsp70 to substrate proteins and the association of mt-Hsp70 with MIM44.

Bacterial Proteins↗
PubMed1995

Sorting of cytochrome b2 to the intermembrane space of mitochondria. Kinetic analysis of intermediates demonstrates passage through the matrix.

Precytochrome b2 is targeted to the mitochondrial intermembrane space by a dual targeting sequence comprising 80 amino acids. A kinetic analysis of intramitochondrial sorting was performed. The intermediate-size form accumulated transiently in the matrix. When import was performed in the presence of metal chelators to prevent the first processing by the matrix processing peptidase, > 40% of the imported precursor was localized in the matrix. A deletion of 13 amino acids in the intermembrane space sorting sequence caused partial inhibition of the first processing, and a transient accumulation of the precursor form in the matrix was also observed. The decrease in this matrix-localized precursor form paralleled an increase in the mature-size form in the intermembrane space. A point mutation in the mitochondrial targeting sequence (N-terminal to the sorting sequence) resulted in missorting to the matrix space. Furthermore, a chimeric protein consisting of the initial 85 residues of cytochrome b2 fused to dihydrofolate reductase was partially targeted to the matrix at 15 degrees C, but not at 25 degrees C. Together, the results presented here indicate that cytochrome b2 passes through the matrix on its sorting pathway to the intermembrane space.

Amino Acid Sequence↗
PubMed1995

Dental anxiety in Danish and Chinese adults--a cross-cultural perspective.

The aim of this study was to correlate dental anxiety as reported by two different ethnic groups with socio-demographic factors, dental status, and dental behaviour. Two randomly selected populations aged 35-44 years and 65-74 years were interviewed. The populations comprised 214 and 99 Danes and 384 and 497 Hong Kong Chinese respectively. Dental anxiety was assessed by the Corah Dental Anxiety Score (DAS). Mean DAS scores were significantly higher in Chinese than in Danes (8.7-10.3 and 6.7-8.2, respectively) and higher in the younger than in the older groups. Moderate to phobic dental anxiety was reported by 15% of the Danes and 30% of the Chinese, the latter proportion far beyond what is usually reported in Western populations. Only in the Chinese group did women report more anxiety than men. Regression analysis indicated that only a few of the variables selected to explain anxiety determinants had significant explanatory value. Among Chinese, gender was the most predominant in both age groups followed by perceived condition of teeth in the younger age group. Among Danes, perceived condition of teeth had an explanatory value for both age groups and dental visit pattern was the strongest for the younger age group. In spite of statistical significance, all explanatory values were small and indicate that variables not included in this analysis may exert a greater influence on the variation in dental anxiety. DAS, seemingly, was able to highlight variations in dental anxiety in the populations in spite of their differences and made interpretations feasible with regard to contrasting dental care behaviour and dental status.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Oral health and dental care in Hong Kong.

With a population of six million people and situated at the South-eastern corner of mainland China, Hong Kong is considered as the gateway between East and West, often playing a role disproportionate to its territorial or population size. The FDI World Dental Congress 1995 provides an impetus to familiarise colleagues worldwide with the oral health and dental care situation in Hong Kong. Water fluoridation was introduced in 1961, which has achieved a continuous low and stable caries prevalence in children as well as in adults. Edentulousness among adults is usually not apparent until after age 55, but at much lower rates than in comparable western industrialised populations. Periodontal conditions in adults are dominated by calculus and shallow pockets. Overall, treatment needs are mainly oral hygiene and simple restorative treatment. Dental awareness is considered low with only a minority of the population seeking dental care on a regular basis. Traditional Chinese health beliefs are common and may influence health behaviour in terms of self- or professional care. Dental care is mainly provided by around 1000 private dental practitioners but special government dental programmes are established for primary school children, who are mainly treated by dental therapists, and for civil servants and their dependents. Dental hygienists are trained in very limited numbers. Dental specialties are under development as part of a newly established Academy of Medicine. Developments are under way to introduce new preventive oriented programmes for pre-school and secondary school age groups.

Adult↗
PubMed1995

Prevalence and structure of dental benefit schemes in Hong Kong.

Before the impact of employer-provided dental benefit schemes on the dental care delivery system can be evaluated in Hong Kong, the prevalence of these schemes and their structures must be established. A mailed questionnaire survey was conducted of a representative group of companies with more than 100 employees (n = 495). Response rate to the mail survey was 38 per cent (n = 186). Non-respondents were stratified according to their nature of business and one third was randomly selected for a follow-up by telephone to which 84 per cent responded (n = 81). After adjustment, 16 per cent of companies of that size were found to be providing dental benefit schemes to their staff. The prevalence was related to the nature of business of the companies. Among companies providing dental benefits, administrators from selected companies were interviewed. It was found that dental benefit schemes could be broadly divided into two types: One characterised by cash-benefit and the other by service-benefit. Treatment items covered by the schemes were mostly simple services such as diagnostic items, simple restorations and simple extractions. The influence of these dental benefit schemes on the dental care-seeking behaviour of the beneficiaries is under investigation.

Health Benefit Plans, Employee↗
PubMed1993

Molecular cloning of integrin-associated protein: an immunoglobulin family member with multiple membrane-spanning domains implicated in alpha v beta 3-dependent ligand binding.

Integrin Associated Protein (IAP) is a 50-kD membrane protein which copurifies with the integrin alpha v beta 3 from placenta and coimmunoprecipitates with beta 3 from platelets. IAP also is functionally associated with signal transduction from the Leukocyte Response Integrin. Using tryptic peptide sequence, human and murine IAP cDNAs have been isolated. The protein has an extracellular amino-terminal immunoglobulin domain that binds all monoclonal anti-IAP antibodies. The carboxy-terminal region is highly hydrophobic with three or five membrane-spanning segments and a short hydrophilic tail. Immunofluorescence microscopy suggests that this hydrophilic tail is located on the inside of the cytoplasmic membrane. Monoclonal anti-IAP antibody inhibits the binding of vitronectin-coated beads to alpha v beta 3 on human erythroleukemia cells, and polyclonal anti-IAP recognizes hamster IAP on CHO cells and inhibits vitronectin bead binding. When CHO cells are transfected with human IAP, monoclonal anti-human antibody completely inhibits vitronectin bead binding. These data suggest a model in which ligand binding by alpha v beta 3 is regulated by IAP.

Amino Acid Sequence↗
PubMed1992

Nucleotide sequence and functional properties of a sodium-dependent citrate transport system from Klebsiella pneumoniae.

The gene of the sodium-dependent citrate transport system from Klebsiella pneumoniae (citS) is located on plasmid pES3 (Schwarz, E., and Oesterhelt, D. (1985) EMBO J. 4, 1599-1603) and encodes a 446-amino acid protein. Transport of citrate via this citrate transport protein (CitS) is dependent on the presence of sodium ions and is inhibited by magnesium ions. The delta pH (pH gradient across the membrane) is the major driving force for uptake. It is postulated that, in analogy with the proton-dependent citrate carrier (CitH) of K. pneumoniae (van der Rest, M. E., Abee, T., Molenaar, D., and Konings, W. N. (1990) Eur. J. Biochem. 195, 71-77), only one of the protonated species of citrate is recognized by CitS and that citrate is translocated across the membrane in symport with protons and sodium ions. The hydrophobicity profile of CitS suggests that the protein is very hydrophobic and contains 12 membrane-spanning segments. These segments are not centered around a hydrophilic core as has been suggested for other transport proteins, but the protein is asymmetrical with seven transmembrane segments in front of a large hydrophilic loop and five after this loop. The amino acid sequence is highly similar to a citrate transport system of Lactococcus lactis subsp. lactis var. diacetylactis (CitP) (David, S., van der Rest, M. E., Driessen, A. J. M., Simons, G., and de Vos, W. M. (1990) J. Bacteriol. 172, 5789-5794) and less similar to CitH of K. pneumoniae. We conclude that the citS gene of K. pneumoniae encodes a sodium-dependent citrate transport system that belongs to a novel subclass of transport proteins.

Amino Acid Sequence↗
PubMed1992

Retinoic acid-mediated repression of human papillomavirus 18 transcription and different ligand regulation of the retinoic acid receptor beta gene in non-tumorigenic and tumorigenic HeLa hybrid cells.

Human papillomavirus type 18 (HPV18) belongs to the group of genital papillomaviruses involved in the development of cervical carcinomas. Since retinoic acid (RA) is a key regulator of epithelial cell differentiation and a growth inhibitor in vitro of HPV18-positive HeLa cervical carcinoma cells, we have used HeLa and HeLa hybrid cells in order to analyse the effects of RA on expression of the HPV18 E6 and E7 oncogenes and of the cellular RA receptor genes RAR-beta and -gamma. We show here that RA down-regulates HPV18 mRNA levels apparently due to transcriptional repression. Transient cotransfection assays indicated that RARs negatively regulate the HPV18 upstream regulatory region and that the central enhancer can confer RA-dependent repression on a heterologous promoter. RA treatment resulted in induction of RAR-beta mRNA levels in non-tumorigenic HeLa hybrid cells, but not in tumorigenic hybrid segregants nor in HeLa cells. No alterations of the RAR-beta gene or of the HeLa RAR-beta promoter could be revealed by Southern and DNA sequence analysis, respectively. As determined by transient transfection assays, however, the RAR-beta control region was activated by RA more strongly in non-tumorigenic hybrid cells than in HeLa cells, thus indicating differences in trans-acting regulatory factors. Our data suggest that the RARs are potential negative regulators of HPV18 E6 and E7 gene expression, and that dysregulation of the RAR-beta gene either causatively contributes to or is an indicator of tumorigenicity in HeLa and HeLa hybrid cells.

Base Sequence↗
PubMed1992

The glucose kinase gene of Streptomyces coelicolor A3(2): its nucleotide sequence, transcriptional analysis and role in glucose repression.

Mutants (glk) of Streptomyces coelicolor A3(2) that are resistant to the non-utilizable glucose analogue 2-deoxyglucose are deficient in glucose kinase activity, defective in glucose repression, and usually unable to utilize glucose. A 2.9 kb BclI fragment, previously shown to restore a wild-type phenotype to a glk deletion mutant that lacks the entire segment, contains two complete open reading frames that would encode proteins of 20.1 kDa (ORF2) and 33.1 kDa (ORF3). ORF3 is transcribed from its own promoter, and also from a promoter that initiates transcription upstream of ORF2. A derivative of the temperate phage phi C31 containing ORF3 alone restored a wild-type phenotype when used to lysogenize the deletion mutant. The product of ORF3 is homologous to members of a family of repressor proteins encoded by xylR in Bacillus subtilis and Lactobacillus pentosus, and by nagC in Escherichia coli. Although this might suggest that ORF3 encodes a positive activator for glucose kinase, rather than the enzyme itself, ORF3 restored the ability to metabolize glucose to an E. coli glk mutant, and activity gels of cell extracts of E. coli containing ORF3 cloned in the pT7-7 expression vector demonstrated that the ORF3 product has glucose kinase activity.

Amino Acid Sequence↗
PubMed1991

Small-angle X-ray study on the quaternary structure of erythrocruorin from Caenestheria inopinata.

The erythrocruorin of the clam shrimp Caenestheria inopinata was studied in sodium phosphate buffer at pH 6.8 by small-angle X-ray scattering. The following molecular parameters were determined: radius of gyration 4.77 +/- 0.05 nm, maximum dimension 14.0 +/- 0.5 nm and a volume of 640 +/- 40 nm3. A model which fits the experimental data well is presented. The model is composed of 10 subunits arranged symmetrically in two layers, whereby five subunits are always forming a ring.

Animals↗
PubMed1991

Human papillomavirus type 18 E6*, E6, and E7 protein synthesis in cell-free translation systems and comparison of E6 and E7 in vitro translation products to proteins immunoprecipitated from human epithelial cells.

Expression of the E6 and E7 transforming genes of human papillomavirus type 18 (HPV18) occurs via structurally bicistronic mRNAs in which the downstream open reading frame (ORF) E7 is preceded either by the full-length ORF E6 or by a spliced ORF, E6*. We have used in vitro transcription and translation of HPV18 cDNAs in order to analyze the synthesis of E6*, E6, and E7 proteins and to compare the E6 and E7 in vitro translation products with the authentic proteins immunoprecipitated from cervical cancer cells. In wheat germ extract, in vitro translation resulted in the production of all three proteins, E6*, E6, and E7. In rabbit reticulocyte lysate, however, only the E6 and E7 proteins were produced. The lack of E6* protein was due neither to template RNA degradation nor to an inhibitory influence of the RNA 5' leader sequences, thus indicating the possibility of either inhibition of synthesis or degradation of E6* protein in reticulocyte lysate. The E7 protein was synthesized from both E6*-E7 and E6-E7 RNAs. In vitro-synthesized and authentic HPV18 E7 proteins revealed identical electrophoretic mobilities in two-dimensional gel electrophoresis, thus indicating similar modifications. By using a monoclonal antibody against the N terminus of HPV18 E6* and E6, an 18-kDa protein was detected not only in HPV18-positive but also in HPV18-negative epithelial cells. The 18-kDa proteins and the in vitro-synthesized HPV18 E6 protein exhibited comparable electrophoretic characteristics in two-dimensional gels. These results suggest the possible existence of a cellular protein related to HPV18 E6.

Cell-Free System↗
PubMed1991

The early genes E6 and E7 of cancer associated human papilloma viruses as targets of tumor suppression?

We have transplanted HPV 18 positive nontumorigenic hybrid cells and tumorigenic hybrid segregants as well as nontumorigenic and tumorigenic human keratinocytes immortalized by HPV 16-DNA transfection (HPK cells and HPK-ras cells) into nude mice and grown them under in vivo conditions for different periods of time. By analyzing gene expression at the mRNA level of the early viral genes E6/E7 and a number of cytoskeletal cellular genes we wanted to test the hypothesis that the nontumorigenic phenotype of these cells in vivo may be determined by the specific downregulation of expression of the oncogenic E6/E7 genes by the product(s) of tumor suppressor gene(s). The results obtained showed that: 1) The nontumorigenic hybrid cells (in contrast to tumorigenic segregants) stopped to proliferate about 3 days after transplantation. At this time E6/E7 gene expression was already drastically reduced, whereas at day 2 expression was still high. This suppression specifically affected the HPV 18 E6/E7 genes and preceded cell death by at least 10 days. 2) The same specific suppression of HPV E6/E7 gene expression occurred during in vivo growth of the nontumorigenic HPK cells. These cells gave rise to transiently growing cysts, but had retained the in vivo differentiation potential of normal keratinocytes (orderly expression of cytokeratins 1 and 10, involucrin and filaggrin). HPV 16 E6/E7 gene expression was very low and clearly restricted to a small subset of basal cells, thus showing an inverse relationship to terminal differentiation. In contrast, in the tumors induced by HPK-ras cells E6/E7 gene expression extended from the basal cells into suprabasal cells and terminal differentiation was retarded. These results support the hypothesis that during in vivo growth tumor suppressor gene(s) negatively regulated HPV E6/E7 gene expression resulting in the stop of proliferation of the nontumorigenic cells.

Animals↗
PubMed1990

The tertiary structure of a bacterial cellulase determined by small-angle X-ray-scattering analysis.

CenA from Cellulomonas fimi is a beta-1,4-endoglucanase that binds tightly to cellulose. X-ray-scattering analyses show that the enzyme is tadpole-shaped: the previously identified catalytic and cellulose-binding domains comprise the head and tail respectively. It appears that this structural and functional organization is common to several cellulases from bacteria and fungi.

Actinomycetales↗
PubMed1990

DNA sequence of a citrate carrier of Klebsiella pneumoniae.

The citrate transport determinant of plasmid pES1 from Klebsiella pneumoniae [Schwarz E. and D. Oesterhelt (1985) EM BO J. 4, 1599-1603] has been subcloned in Escherichia coli DH1. The DNA sequence of a 1723-base fragment that codes for the citrate carrier has been determined and the gene product has been characterized with the T7 promoter system. The DNA fragment contains an open reading frame of 1332 base pairs and codes for a protein of 444 amino acids. The hydropathy profile suggests that the protein is very hydrophobic and contains 12 membrane-spanning segments centered around a hydrophilic core. The gene for the citrate carrier has 66% similarity with a citrate carrier determinant from a naturally occurring plasmid responsible for secondary transport of citrate across the cytoplasmic membrane of E. coli.

Amino Acid Sequence↗
PubMed1990

Dental anxiety in young adult Danes under alternative dental care programs.

The purpose of the present report is to establish to what extent dental anxiety is expressed by young adults with a long history of regular dental care, to analyze whether expressions of dental anxiety vary during young adulthood in response to different dental care delivery programs, and to study which factors might account for existing expressions of dental anxiety. The study comprised 697 persons who participated in a longitudinal study on alternative dental care programs, running from the youngsters' 16th to their 19th yr. At the end, Corah Dental Anxiety Scale (DAS) was applied through self-completed questionnaires. Overall DAS-mean was 7.26; women expressed more anxiety than men (7.73; 6.78). Significant association between anxiety expressed at the end and at the start of the study indicated that dental anxiety was probably present at an early age. No association was found with utilization of dental services. A multiple regression analysis indicated early expressed dental anxiety and negative self assessment of dental health as important predictors for dental anxiety, while sex, negative assessment of gingival health, and dental program were of less importance, altogether explaining 22% of the DAS score variation. The risk group concept currently employed by the Public Child Dental Health Services might be extended to include expressions of dental anxiety.

Adolescent↗
PubMed1990

Suppression in vivo of human papillomavirus type 18 E6-E7 gene expression in nontumorigenic HeLa X fibroblast hybrid cells.

The E6 and E7 genes of the cancer-associated human papillomavirus (HPV) types 16 (HPV16) and 18 (HPV18) can induce cell immortalization in vitro in normal human keratinocytes. This, however, is not associated with tumorigenicity in vivo. On the other hand, tumorigenicity of HPV18-positive HeLa cervical carcinoma cells can be suppressed by fusion of HeLa cells with normal human keratinocytes or fibroblasts. We have addressed the question of whether suppression of tumorigenicity in HeLa x fibroblast hybrid cells might be due to a reduced ability of these cells to express the HPV18 E6-E7 genes in vivo. Nontumorigenic hybrid cells and tumorigenic hybrid segregants were transplanted as organotypical cultures or injected subcutaneously into immunocompromised mice and were analyzed for HPV18 E6-E7 gene expression by RNA-RNA in situ hybridization. The tumorigenic hybrid cells showed a continuous and invasive growth that was associated with high levels of HPV18 E6-E7 mRNAs at all time points examined. In contrast, the nontumorigenic hybrid cells stopped cell proliferation approximately 3 days after transplantation. At this time they expressed the E6-E7 genes at low levels, whereas at day 2 high expression levels were observed. However, the mRNA levels of the cytoskeletal genes beta-actin and vimentin remained high for at least 14 days, demonstrating that inhibition of growth and of HPV18 E6-E7 gene expression was not due to cell death. These results suggest that growth inhibition of the nontumorigenic HeLa x fibroblast hybrid cells in vivo might be caused by suppression of HPV18 E6-E7 gene expression and are compatible with the idea of an intracellular surveillance mechanism for HPV gene expression existing in nontumorigenic cells.

Blotting, Northern↗