The class-I mutants have provided a model system for understanding the generation of diversity of the genes encoding the histocompatibility molecules K, D, and L, and the relationship of their ...structure to function. The complex nature of the alterations found in Kb molecules from mutant mice has been documented at the nucleic acid level for eight mutants. The clustered changes in the mutant genes are consistent with the hypothesis that genetic recombination between class-I genes generates the Kb mutants. Techniques using synthetic oligonucleotide probes to mutant DNA sequence demonstrated that other class-I genes were available as donors for interaction with the Kb gene to produce the mutations. Intriguingly, donor genes found in the K region (K1) and the D region (Db), as well as the Qa regions (Q4, Q10), were capable of the interactions. The amount of genetic transfer to Kb from other class-I donor genes may range from a potential minimum of 5 nucleotides to a potential maximum of 95 nucleotides. Genealogical analysis of several bm mutants has further indicated that at least some, if not all, of the gene interaction events generating Kb mutations occurred during mitotic amplification of the germ cells. Genetic recombination among class-I genes occurring in nature to the extent observed for the Kbm mutants could readily generate mosaic transplantation genes containing sequences derived from other class-I genes. Thus, it seems likely that genetic interaction plays a major role in the diversification and ongoing evolution of the MHC. The localization of altered amino acids in the in vivo mutant Kb molecules has directed our attention to recognition regions on the Kb product that play a major role in determining alloreactivity and H-2 associative recognition. The replacement of one or a few amino acids in either of the postulated recognition regions located in the alpha 1 domain (residues 70-90) or alpha 2 domain (residues 150-180) can have marked effects on biological function. While the majority of monoclonal antibodies recognize epitopes in one or the other recognition region, CTL recognize determinants dependent on the apparent interaction of amino acids located in both regions. These overall conclusions are supported to a large extent by studies on mutants derived from several sources, i.e. spontaneous mutants, mutagen-induced somatic variants, and products of hybrid H-2 genes. Studies of in vitro variants can provide a more refined approach for analysis of structure-function relationships through the introduction of minimal biochemical changes.
The analysis of H-2K products from spontaneously generated major histocompatibility complex (MHC) mutants and of the primary structure of other class I antigens suggests the genetic hypothesis that ...diversity in the MHC results from a copy mechanism analogous to gene conversion. The hypothesis was tested by making precise structural predictions about three partially characterized MHC mutants (bm1, bm3, and bm8). The predictions were based on consensus sequences among class I genes that differ from H-2Kbin the same region of the molecule as do the Kbmutants. In two cases (bm3 and bm8) we successfully predicted the correct amino acid substitution at positions known to be altered but for which the specific nature of the substitution had not been determined. In two additional cases (bm1 and bm8) we predicted and found both new mutation sites and the specific amino acid substitutions. The positions and identifications of the variant amino acids were determined by radiolabeled amino acid sequence analysis and DNA restriction endonuclease analysis. The interaction of MHC genes through a copy mechanism to generate diversity permits the introduction of multiple nucleotide base substitutions into class I sequences by a single genetic event. Such a mechanism may account in part for the large structural divergence among alleles of MHC loci and the high degree of MHC polymorphism among wild mice.
The method described here results in simple visual analysis of 1, 2, or 3 ethidium bromide-stained bands corresponding to the PlA1, PlA2 or PlA1/A2 phenotypes, respectively. The amplification ...primers, designed to yield a 711bp product which encompasses exon 2 and substantial intronic sequence both 5' and 3' of the exon enable exquisite resolution of the restriction enzyme digestion products which define the alleles. In addition to prediction of fetal risk of neonatal alloimmune thrombocytopenia using this method, an ethnically heterogeneous pool of platelet donors was screened for the platelet antigen PlA (HPA-1) and gave unequivocal results which should be useful for platelet matching.
Gastrointestinal endoscopies are increasingly being carried out with sedation. All of the drugs used for sedation are associated with a certain risk of complications. Data currently available on ...sedation-associated morbidity and mortality rates are limited and in most cases have substantial methodological limitations. The aim of this study was to record severe sedation-associated complications in a large number of gastrointestinal endoscopies.
Data on severe sedation-associated complications were collected on a multicentre basis from prospectively recorded registries of complications in the participating hospitals (median documentation period 27 months, range 9 - 129 months).
Data for 388,404 endoscopies from 15 departments were included in the study. Severe sedation-associated complications occurred in 57 patients (0.01 %). Forty-one percent of the complications and 50 % of all complications with a fatal outcome (10/20 patients) occurred during emergency endoscopies. In addition, it was found that 95 % of the complications and 100 % of all fatal complications affected patients in ASA class ≥ 3.
Including nearly 400,000 endoscopies, this study represents the largest prospective, multicenter record of the complications of sedation worldwide. The analysis shows that sedation is carried out safely in gastrointestinal endoscopy. The morbidity and mortality rates are much lower than previously reported in the literature in similar groups of patients. Risk factors for the occurrence of serious complications include emergency examinations and patients in ASA class ≥ 3.
The gene for H-2K class I major histocompatibility antigen on the bm8 variant was cloned and the DNA sequence compared with the parental gene. Sequence analysis demonstrated that seven nucleotides ...were changed with respect to the parental gene sequence spanning 24 nucleotides. These changes represent an alteration of four amino acids from the parent protein. As this mutation occurred in a single generation, a potential donor gene for such a complex mutation was suggested and identified. The Q4 gene class I-like molecule has a stretch of 95 nucleotides of identity in the region of the bm8 mutation. Genomic Southern analysis of the mutant and parental DNA with a gene-specific oligonucleotide demonstrated that the potential donor gene Q4 is a likely candidate sequence for such an event. The amino acid alterations for the H-2Kbm8 mutation are discussed in consideration of hte three-dimensional structure of the characterized human class I glycoprotein.
The research initiative CITY 2020+ assesses the risks and opportunities for residents in urban built environments under projected demographic and climate change for the year 2020 and beyond, using ...the city of Aachen as a case study. CITY 2020+ develops strategies, options and tools for planning and developing sustainable future city structures. The investigation focuses on how urban environment, political structure and residential behaviour can best be adapted, with attention to the interactions among structural, political, and sociological configurations and their impacts on human health. The interdisciplinary research is organized in three clusters. Within the first cluster, strategies of older people exposed to heat stress, and their networks as well as environmental health risks according to atmospheric conditions are examined. The second cluster addresses governance questions, urban planning and building technologies as well as spatial patterns of the urban heat island. The third cluster includes studies on air quality related to particulate matter and a historical perspective of city development concerning environmental issues and climate variability. However, it turns out that research topics that require an interdisciplinary approach are best addressed not by pre-structuring the work into related sub-projects but through combining them according to shared methodological approaches. Examples illustrating this rather practical approach within ongoing research are presented in this paper.
A rapid genotype assay for Pl A haplotypes Pfaffenbach, Gertrude M.; Bussel, James A.; Rubinstein, Pablo
Thrombosis research,
02/1996, Letnik:
81, Številka:
3
Journal Article
Recenzirano
The method described here results in simple visual analysis of 1, 2, or 3 ethidium bromide-stained bands corresponding to the Pl
A1, Pl
A2 or
Pl
A1
A2
phenotypes, respectively. The amplification ...primers, designed to yield a 711bp product which encompasses exon 2 and substantial intronic sequence both 5′ and 3′ of the exon enable exquisite resolution of the restriction enzyme digestion products which define the alleles. In addition to prediction of fetal risk of neonatal alloimmune thrombocytopenia using this method, an ethnically heterogeneous pool of platelet donors was screened for the platelet antigen Pl
A (HPA-1)and gave unequivocal results which should be useful for platelet matching.
The "bg" series of MHC mutations is the most prevalent type of mutations of Kb in C57BL/6 mice screened by reciprocal tail skin grafting. The basis for identification of this series of mutations is ...the incompatibility of grafts between the parental B6 and the mutant. This series takes the longest to reciprocally reject the skin grafts. The series can be subdivided into "bg 1" and "bg 2" groups based on Kb-restricted recognition of virus-infected mutant target cells. The biochemical basis for these mutations are amino acid substitutions at residues 116 and 121 of the Kb transplantation antigen. These substitutions do not alter monoclonal antibody binding sites. The structural basis of MAb binding and the genetic basis of the mutation are discussed.
Hintergrund:
Gastrointestinale Endoskopien werden in zunehmenden Umfang in Sedierung durchgeführt, um die Prozeduren schmerz- und stressfrei zu gestalten oder sie überhaupt zu ermöglichen. Ziel ...dieser Arbeit war es, schwere sedierungs-assoziierte Komplikationen im Rahmen von gastrointestinalen Endoskopien in deutschen Krankenhäusern zu erfassen. Als schwere sedierungs-assoziierte Komplikation wurden die Zwischenfälle definiert, die zu einer Notwenigkeit der intensivmedizinsichen Überwachung, Intubation und Reanimation führten.
Methoden:
Es erfolgte eine multizentrische Erfassung mittels elektronisch versendetem Fragebogen. Die Daten wurden aus prospektiv geführten Komplikationsregistern der teilnehmenden Kliniken entnommen.
Ergebnisse:
In die Studie wurden Daten von 388.404 Endoskopien aus 15 Abteilungen eingeschlossen. Schwere sedierungs-assoziierte Komplikationen traten bei 57 Patienten (0,01%) auf. 41% der Komplikationen und 50% aller Komplikationen mit letalem Ausgang (10/20 Patienten) ereigneten sich im Rahmen von Notfallendoskopien. Darüber hinaus zeigte sich, dass 95% der Komplikationen und 100% aller letalen Komplikationen Patienten betrafen, die der ASA-Klasse ≥3 zuzuordnen waren.
Zusammenfassung:
Die Auswertung der Komplikationsregister der ALGK-Studiengruppe zeigt, dass die Sedierung in der gastrointestinalen Endoskopie im Alltag deutscher Krankenhäuser sicher durchgeführt wird. Es ist mit Einschluss von knapp 400.000 Endoskopien die weltweit größte prospektive und multizentrische Erfassung von Sedierungskomplikationen. Die Komplikationsrate liegt deutlich niedriger als sie bisher in der Literatur bei ähnlichen Patientenkollektiven beschrieben worden ist. Dies gilt insbesondere für elektive Eingriffe und Patienten der ASA-Klasse I und II.
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