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PubMedDate not supplied

A 4-year retrospective clinical study of Class I and Class II composite restorations.

OBJECTIVES: The purpose of this study was to determine the longevity and quality of Class I and Class II resin composite (Herculite XR) restorations placed in private practice. METHODS: One thousand two hundred and nine Class I and Class II composite restorations with margins in enamel were evaluated clinically after periods of between 12 months and 4.5 years in clinical service by two calibrated examiners using a modified version of established criteria. RESULTS: Of the restorations investigated 94.8% were rated as 'good' (Alpha 79.3%) or 'clinically acceptable' (Bravo 15.5%). Significantly more restorations in premolar teeth were rated as Alpha (82%) than in permanent molar teeth (77%). The survival rate after 4 years was around 87%. The 50% survival-time, calculated by extrapolation according to Weibull, was approximately 9 years. CONCLUSIONS: It is concluded that the composite investigated is an appropriate material for the restoration of Class I and Class II lesions with margins located in enamel in premolar and permanent molar teeth.

Bicuspid↗

PubMed2000

The teaching of Class I and Class II direct composite restorations in European dental schools.

OBJECTIVES: The purpose of this descriptive study was to provide updated data on the teaching of Class I and Class II direct composite restorations in Europe as part of a survey of this aspect of the primary dental curriculum in Europe and North America. METHODS: Data on the teaching of posterior composite restorations and related matters were collected by means of a postal questionnaire sent to 185 dental schools known to exist in Europe. Non-respondents were sent a second questionnaire after two months. Further information pertaining to student requirements was sought after six months from all respondents. RESULTS: The response ranged from 92% for dental schools in Scandinavia to 40% from dental schools in Southern Europe with an overall response of 56%. All but four of the 104 participating schools were found to teach the use of composites in Class I and Class II, two-surface situations in at least premolar teeth. Contraindications and techniques taught for posterior composites varied within and between the country groupings of Northern and Central Europe. Scandinavia, Southern Europe and Eastern Europe. However, certain consensus views were identified. The experience of adverse biological reactions to the use of resin-based restoratives in European dental schools was found to be limited. CONCLUSIONS: Notwithstanding the variation in the response from the four geographic regions investigated and the relatively low overall response to the questionnaire, it is concluded that the data reported indicates that most dental schools in Europe teach the use of composites in selected Class I and Class II situations. However, considerable variation exists both within and between the regions investigated in relation to this teaching. Further research and consensus conferences should be planned to reduce variability across Europe in relation to the contraindications and techniques taught for posterior composites.

Composite Resins↗

PubMed1988

Class I and class II loci of the human major histocompatibility complex.

The structure of major histocompatibility complex class I (HLA-A, B and Cw) and class II (HLA-DP, DQ and DR) genes and their products is now well understood. Knowledge of the high degree of polymorphism which occurs at all MHC gene loci, primarily derived from serological studies, has largely been confirmed and extended by the application of functional, biochemical and molecular techniques. The frequencies of class I and class II antigenic products are variable between ethnic groups and also between many diseased and healthy populations. In many cases the occurrence together of two or more MHC gene products (allelic association) provides haplotypic markers specific for diseases. The function of MHC products is widely speculated upon but little is known of the precise mechanisms whereby class I and class II molecules mediate their prescribed functions of co-ordinating cell-cell interactions, their involvement in susceptibility to disease or their established role in the artificial situation of organ allografting.

Gene Frequency↗

PubMed2006

Interaction and comparison of a class I hydrophobin from Schizophyllum commune and class II hydrophobins from Trichoderma reesei.

Hydrophobins fulfill a wide spectrum of functions in fungal growth and development. These proteins self-assemble at hydrophilic-hydrophobic interfaces into amphipathic membranes. Hydrophobins are divided into two classes based on their hydropathy patterns and solubility. We show here that the properties of the class II hydrophobins HFBI and HFBII of Trichoderma reesei differ from those of the class I hydrophobin SC3 of Schizophyllum commune. In contrast to SC3, self-assembly of HFBI and HFBII at the water-air interface was neither accompanied by a change in secondary structure nor by a change in ultrastructure. Moreover, maximal lowering of the water surface tension was obtained instantly or took several minutes in the case of HFBII and HFBI, respectively. In contrast, it took several hours in the case of SC3. Oil emulsions prepared with HFBI and SC3 were more stable than those of HFBII, and HFBI and SC3 also interacted more strongly with the hydrophobic Teflon surface making it wettable. Yet, the HFBI coating did not resist treatment with hot detergent, while that of SC3 remained unaffected. Interaction of all the hydrophobins with Teflon was accompanied with a change in the circular dichroism spectra, indicating the formation of an alpha-helical structure. HFBI and HFBII did not affect self-assembly of the class I hydrophobin SC3 of S. commune and vice versa. However, precipitation of SC3 was reduced by the class II hydrophobins, indicating interaction between the assemblies of both classes of hydrophobins.

Air↗

PubMed1990

Synthesis and cardiac electrophysiological activity of aryl-substituted derivatives of the class III antiarrhythmic agent sematilide. Potential class I/III agents.

Twelve novel derivatives of the selective class III antiarrhythmic agent sematilide were prepared in an attempt to incorporate both class I and class III electrophysiological properties into a single molecule. Electrophysiological activity was determined by standard microelectrode techniques in canine cardiac Purkinje fibers. Initial assessment of class I efficacy was carried out in a ouabain-induced arrhythmia model in guinea pigs. All of the compounds prolonged action potential duration in Purkinje fibers (class III activity), and three were active against ouabain-induced arrhythmias (class I activity). Selected compounds were evaluated further in dogs for efficacy against arrhythmias occurring 24 h following coronary ligation (automatic arrhythmias) and induced by using programmed electrical stimulation techniques (reentrant arrhythmias). The most effective compounds from the series are 3g and -j, which were effective in both canine models. Molecular modeling and structure-activity relationships are discussed.

Action Potentials↗

PubMed2000

Multiple sclerosis: a modifying influence of HLA class I genes in an HLA class II associated autoimmune disease.

Multiple sclerosis (MS) is a presumed autoimmune disease of the central nervous system, shown to be associated with the HLA class II haplotype DRB1*15,DQB1*06. Carrying the HLA class II haplotype DRB1*15,DQB1*06 increases the risk of MS by 3.6. By adopting a polymerase chain reaction (PCR)-based typing technique for HLA class I and class II genes, 200 Swedish MS patients and 210 Swedish healthy controls were analysed for their HLA alleles. Additional HLA class I alleles that increase and decrease the genetic susceptibility to MS were identified. The HLA-A*0301 allele increases the risk of MS (odds ratio=2.1) independently of DRB1*15,DQB1*06. HLA-A*0201 decreases the overall risk (odds ratio= 0.52) and the presence of A*0201 reduces the risk of MS for DRB1*15,DQB1*06 carriers from 3.6 to 1.5. Our findings are the first to identify a major modulating effect of HLA class I alleles on the susceptibility to a human autoimmune disease; a phenomenon that has previously only been observed in animal models.

Alleles↗

PubMed2006

Comparison of psychosocial status in treatment-seeking women with class III vs. class I-II obesity.

OBJECTIVE: This study compared the psychosocial status and weight loss expectations of women with extreme (class III) obesity who sought bariatric surgery with those of women with class I-II obesity who enrolled in a research study on behavioral weight control. RESEARCH METHODS AND PROCEDURES: Before treatment, all participants completed the Beck Depression Inventory-II and the Weight and Lifestyle Inventory. This latter questionnaire assesses several domains including symptoms of depression and low self-esteem, history of psychiatric complications, current stressors, and weight loss expectations. RESULTS: Women with class III obesity, as compared with class I-II, reported significantly more symptoms of depression. Fully 25% of women in the former group appeared to have a significant mood disorder that would benefit from treatment. As compared with women with class I-II obesity, significantly more women with class III obesity also reported a history of psychiatric complications, which included physical and sexual abuse and greater stress related to their physical health and financial/legal matters. Both groups of women had unrealistic weight loss expectations. Those who sought surgery expected to lose 47.6 +/- 9.3% of initial weight, compared with 24.8 +/- 8.7% for those who enrolled in behavioral weight control. DISCUSSION: These findings suggest that women with extreme obesity who seek bariatric surgery should be screened for psychosocial complications. Those determined to have significant psychiatric distress should be referred for behavioral or pharmacological treatment to alleviate their suffering. Long-term studies are needed to provide definitive guidance concerning the relationship between preoperative psychopathology and the outcome of bariatric surgery.

Adult↗

PubMed1983

The pH-dependence of class B and class C beta-lactamases.

The classification by structure allots beta-lactamases to (at present) three classes, A, B and C. The pH-dependence of the kinetic parameters for class B and class C have been determined. They differ from each other and from class A beta-lactamases. The class B enzyme was beta-lactamase II from Bacillus cereus 569/H/9. The plots of kcat against pH for the hydrolysis of benzylpenicillin by Zn(II)-requiring beta-lactamase II and Co(II)-requiring beta-lactamase II were not symmetrical, but those of kcat/Km were. A similar feature was observed for the hydrolysis of both benzylpenicillin and cephalosporin C by a class C beta-lactamase from Pseudomonas aeruginosa. The results have been interpreted by a scheme in which two ionic forms of an intermediate can give product, but do so at differing rates.

Cephalosporinase↗

PubMed1989

Effect of the binding of bilirubin to either the first class or the second class of binding sites of the human serum albumin molecule on its photochemical reaction.

The kinetics of the photochemical changes of bilirubin were studied at a constant concentration of bilirubin bound either to the first class or to the second class of binding sites of the human serum albumin molecule. The more the bilirubin binds to the first class of binding sites in the human serum albumin molecule, the more readily geometric photoequilibrium to give (ZE)-bilirubin takes place. The more the bilirubin binds to the second class of binding sites or allosterically transformed binding sites induced by added SDS, the more readily structural photoisomerization, i.e. the formation of (EZ)-cyclobilirubin, takes place. When the serum bilirubin concentration is at low, safe, values bilirubin binds exclusively to the first class of binding sites and serves as an antioxidant [Onishi, Yamakawa & Ogawa (1971) Perinatology 1, 373-379]; at these concentrations human serum albumin protects bilirubin from irreversible photodegradation by only allowing readily reversible geometric photoisomerization. As the serum bilirubin concentration increases to high, and potentially dangerous, values, bilirubin binds to the second class of binding sites, and under these conditions human serum albumin seems to promote the photocyclization of bilirubin. During irradiation human serum albumin seems to act by retaining low, useful, concentrations of bilirubin while facilitating irreversible photoisomerization of excess bilirubin.

Bilirubin↗

PubMed1997

Discovery of disseminated J96-like strains of uropathogenic Escherichia coli O4:H5 containing genes for both PapG(J96) (class I) and PrsG(J96) (class III) Gal(alpha1-4)Gal-binding adhesins.

The pyelonephritis-associated adhesin gene papG of Escherichia coli occurs in three variants. Whereas the class II and class III variants are common among human urinary tract infection isolates, the class I allele, despite being the first cloned, has previously been found only in source strain J96. Five strains have been discovered from geographically diverse locales that, like J96, contain both the class I and class III papG alleles. One strain caused bacteremia, whereas 4 caused cystitis. Like J96, all 5 had group III capsule genes, expressed the H5 flagellar antigen and the F13 fimbrial antigen, and exhibited similar genomic patterns and virulence factor profiles. These findings demonstrate that the class I papG allele is not unique to J96 but is present in a group of extraintestinal isolates of E. coli O4:H5 that represent a disseminated virulent clonal group.

Adhesins, Escherichia coli↗

PubMedDate not supplied

Subcellular localization of class I (A,B,C) and class II (DR and DQ) MHC antigens in jejunal epithelium of children with coeliac disease.

Thin frozen sections of 11 jejunal biopsies from 10 children at different stages of coeliac disease were stained by immunofluorescence technique using a panel of anti-HLA class I (A, B, C) and anti-HLA class II (DR and DQ) monoclonal antibodies. On the epithelium of flattened mucosa, in contrast with control sections, the intensity of the labeling on the basolateral membranes with both anti-class I and class II DR antibodies decreased strongly from the bottom to the upper part of the crypts, and no bright patchy staining was observed on the apical part of enterocytes with anti-HLA DR antibodies. Numerous cells with large granules expressing class I and class II DR antigens were found in the epithelium of the small intestine. Children with a fully recovered mucosa expressed MHC antigens identical to those previously observed in normal epithelium. On the other hand, children with intermediate mucosal lesions showed the presence of MHC antigens in varying degrees. The results of this report indicate that immunological mechanisms may play a prominent role in coeliac disease.

Celiac Disease↗

PubMed1992

Phylogeny of LCR-1 and OXA-5 with class A and class D beta-lactamases.

The nucleotide sequences of blaLCR-1 and blaOXA-5 beta-lactamase genes have been determined. Polypeptide products of 260 and 267 amino acids with estimated molecular masses of 27 120 Da and 27,387 Da were obtained for the mature form of LCR-1 and OXA-5 proteins. A progressive alignment was used to evaluate the extent of identity between LCR-1 and OXA-5 with 29 other beta-lactamase amino acid sequences. The data showed that both belong to class D. We identified amino acids conserved in 24 positions for class A beta-lactamases and in 28 positions for five class D enzymes. The structural similarities between class A and class D beta-lactamases are more extensive than indicated by earlier biochemical studies with overall 16% identity between both classes. From the alignment, dendograms were constructed with a distance-matrix and parsimony methods which defined three major groups of proteins subdivided into clusters giving insight on beta-lactamase phylogeny and evolution.

Amino Acid Sequence↗

PubMed1993

Increased levels of alpha-class and pi-class glutathione S-transferases in cell lines resistant to 1-chloro-2,4-dinitrobenzene.

Glutathione S-transferase (GST) enzymes are often over-expressed in tumor cells made resistant to cytotoxic drugs but it is unclear whether GST over-expression is directly linked to the resistance mechanism. We have made a human lung tumor cell line resistant to 1-chloro-2,4-dinitrobenzene (CDNB) in order to establish whether selection for resistance with a model GST substrate results in selection of a cell line with higher GST levels. The resistant line (CDNBr), although only twofold more resistant to this compound, exhibited a marked (15-fold) increase in GST activity compared to the wild-type cell line (28 +/- 10 versus 357 +/- 30 nmol CDNB conjugated.min-1 x mg-1 protein, respectively). Resistance to CDNB was associated with a marked increase in the level of both alpha-class and pi-class GST. Resolution of the GST by reverse-phase HPLC demonstrated that the increase in the expression of the alpha-class enzymes was due to elevated levels of both the B1 and B2 subunits. The increased levels of alpha-class and pi-class GST in the CDNBr cells was not due to either gene amplification or increased mRNA levels and appears to involve either altered mRNA utilization or protein stabilization. In addition to being resistant to CDNB, the CDNBr cell line also showed a 2.5-fold resistance to cumene hydroperoxide but was not cross-resistant to the anticancer drug chlorambucil. To demonstrate that the increased GST level was part of the resistance mechanism the alpha-class GST B1 cDNA under control of the beta-actin promoter was stably expressed in the breast tumor cell line MCF-7. The cell lines generated were twofold more resistant to CDNB relative to the parental line.

Benzene Derivatives↗

PubMed1991

Ethanol influences class I and class II MHC antigen expression on human fetal islet-like cell clusters.

Several autoimmune diseases have been linked to an aberrant expression of major histocompatibility complex (MHC) products Ethanol enhances Class I and Class II products on a variety of cell types, and there is evidence for an autoimmune etiology in numerous pathologies associated with alcoholism. We examined whether ethanol alters the expression of Class I and Class II MHC products on human fetal islet-like cell clusters. Incubation of islet-like clusters for 48 hr in ethanol at a starting concentration of 1.5% increased the percentage of single cells expressing Class I. The percentage of cells expressing Class II did not change, but their relative mean fluorescence increased significantly. These findings suggest that alcohol ingestion could alter MHC expression on pancreatic islet cells in vivo perhaps affecting the development of diabetes in genetically predisposed individuals. These findings also support the hypothesis that the rising incidence of type 1 diabetes seen in areas of the world where the per capita consumption of alcohol is also increasing may be a consequence of the immunological effects of alcohol intake.

Ethanol↗

PubMed1986

Expression of class I and class II major histocompatibility complex antigens on epithelial cells in recurrent aphthous stomatitis.

The concept of an immunopathogenesis in the establishment and progression of the recurrent aphthous stomatitis (RAS) lesion is well accepted. In this study the expression of Class I and Class II major histocompatibility complex (MHC) antigens on the epithelial cells in the preulcerative, ulcerative and healing phases of RAS lesions was investigated using monoclonal antibodies in an immunohistological technique. Both Class I and Class II MHC antigens were found on the basal cells in preulcerative lesions. As the lesions progressed to the ulcerative phase, antigen expression occurred on the cell membranes throughout the entire thickness of the epithelium. With healing, the expression of both Class I and Class II MHC antigens on epithelial cells declined to a stage where there was little or no detectable antigen on the cell membranes. Although cytotoxicity of epithelial cells in RAS lesions is accepted, the role of MHC antigen expression on these cells is uncertain and remains to be ascertained. Nevertheless, the results of the present study indicate that MHC antigens are expressed by epithelial cells in RAS and their expression follows a defined sequence.

Epithelium↗

PubMed1989

Purification, cyanogen bromide cleavage, and amino terminus sequencing of class 1 and class 3 outer membrane proteins of meningococci.

Meningococcal class 1 and 3 outer membrane proteins (OMPs) were subjected to cyanogen bromide treatment. The class 3 OMP was found to be resistant to cyanogen bromide, while the class 1 OMP was cut into two main fragments of 25 and 17 kilodaltons. The N-terminal sequences were determined for class 1 and class 3 proteins, which exhibit similarities to one another and to OMP I of gonococci. The C-terminal class 1 OMP fragment bound the bactericidal monoclonal antibodies tested.

Amino Acid Sequence↗

PubMed1996

Genomic localization of the human gene encoding Dr1, a negative modulator of transcription of class II and class III genes.

Dr1 is a nuclear protein of 19 kDa that exists in the nucleoplasm as a homotetramer. By binding to TBP (the DNA-binding subunit of TFIID, and also a subunit of SL1 and TFIIIB), the protein blocks class II and class III preinitiation complex assembly, thus repressing the activity of the corresponding promoters. Since transcription of class I genes is unaffected by Dr1. it has been proposed that the protein may coordinate the expression of class I, class II and class III genes. By somatic cell genetics and fluorescence in situ hybridization, we have localized the gene (DR1), present in the genome of higher eukaryotes as a single copy, to human chromosome region 1p21-->p13. The nucleotide sequence conservation of the coding segment of the gene, as determined by Noah's ark blot analysis, and its ubiquitous transcription suggest that Dr1 has an important biological role, which could be related to the negative control of cell proliferation.

Animals↗

PubMed1996

IgA class switch in I alpha exon-deficient mice. Role of germline transcription in class switch recombination.

Studies have implicated defective Ig class switch in the pathogenesis of IgA deficiency. To understand better the molecular events that regulate IgA class switch, a 1.4-kb region of the IgA locus containing the I alpha exon was replaced with a human hypoxanthine phosphoribosyltransferase minigene by gene targeting in murine embryonic stem cells. The I alpha exon-deficient mice derived from these embryonic stem cells had normal IgA levels in serum and secretions and normal numbers of IgA B cells in Peyer's patches and spleen. Further, I alpha exon-deficient B cells efficiently underwent IgA class switch in vitro, despite the absence of I alpha exon-containing germline transcripts. Notably, I alpha exon-deficient B cells did not require TGF-beta for IgA class switch since stimulation with LPS alone led to IgA expression. Nonetheless, whereas I alpha exon-deficient B cells constitutively expressed human hypoxanthine phosphoribosyltransferase transcripts, they did not produce IgA in the absence of LPS stimulation. These results demonstrate that the I alpha exon or transcripts containing the I alpha exon are not required for IgA class switch. Further, the effects of TGF-beta on I alpha locus transcription can be supplanted by expression of a heterologous minigene at that locus, but a second signal is required for the induction of IgA class switch.

Animals↗