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J Klein

Publications and source records attributed to J Klein.

At least 685 records · Page 38Linked to original sources
PubMed1985

Catabolism of leukotriene A4 into B4, C4, and D4 by rat liver subcellular fractions.

[3H]Leukotriene A4 was incubated with various subcellular fractions of rat liver homogenates. After solvent extraction and purification on C18 Sep-Pak cartridges, tritiated products migrating on reversed-phase HPLC with authentic unlabelled leukotriene C4, D4 and B4 were observed. The identity of leukotriene C4 was confirmed through enzymatic conversion into D4 by gamma-glutamyl transpeptidase as well as by bioassay on the rat stomach fundus after HPLC purification. The contractile response to the extracted material was blocked by the SRS antagonist, FPL 55712. Leukotriene B4 synthesis was located in the 100 000 X g supernatant, while C4 synthesis was present in the corresponding pellet. Leukotriene C4 formation was enhanced when reduced glutathione was supplemented in the incubation medium. These results demonstrate the presence in rat liver of various enzymatic steps in leukotriene A4 catabolism.

Animals↗
PubMed1985

Conservation of RNA sequence and cross-linking ability in ribosomes from a higher eukaryote: photochemical cross-linking of the anticodon of P site bound tRNA to the penultimate cytidine of the UACACACG sequence in Artemia salina 18S rRNA.

The complex of Artemia salina ribosomes and Escherichia coli acetylvalyl-tRNA could be cross-linked by irradiation with near-UV light. Cross-linking required the presence of the codon GUU, GUA being ineffective. The acetylvalyl group could be released from the cross-linked tRNA by treatment with puromycin, demonstrating that cross-linking had occurred at the P site. This was true both for pGUU- and also for poly(U2,G)-dependent cross-linking. All of the cross-linking was to the 18S rRNA of the small ribosomal subunit. Photolysis of the cross-link at 254 nm occurred with the same kinetics as that for the known cyclobutane dimer between this tRNA and Escherichia coli 16S rRNA. T1 RNase digestion of the cross-linked tRNA yielded an oligonucleotide larger in molecular weight than any from un-cross-linked rRNA or tRNA or from a prephotolyzed complex. Extended electrophoresis showed this material to consist of two oligomers of similar mobility, a faster one-third component and a slower two-thirds component. Each oligomer yielded two components on 254-nm photolysis. The slower band from each was the tRNA T1 oligomer CACCUCCCUVACAAGp, which includes the anticodon. The faster band was the rRNA 9-mer UACACACCGp and its derivative UACACACUG. Unexpectedly, the dephosphorylated and slower moving 9-mer was derived from the faster moving dimer. Deamination of the penultimate C to U is probably due to cyclobutane dimer formation and was evidence for that nucleotide being the site of cross-linking. Direct confirmation of the cross-linking site was obtained by "Z"-gel analysis [Ehresmann, C., & Ofengand, J. (1984) Biochemistry 23, 438-445].(ABSTRACT TRUNCATED AT 250 WORDS)

Anticodon↗
PubMed1985

Fine specificity analysis of lactate dehydrogenase B-specific proliferating T cell clones: implications for the mechanism of alloreactivity.

T cell clones of C57BL/6 origin which recognize porcine lactate dehydrogenase B (LDH-BP) together with the Ab molecule were characterized in terms of fine specificity for both LDH-B and self-major histocompatibility complex determinants. Using antigen-presenting cells from the Ab-mutant strain B6.C-H-2bm12 (bm12), three clonotypes could be distinguished: the first responds to LDH-BP + bm12, the second fails to respond and the third is alloreactive to bm12. The last clone exhibits additional alloreactivities to A molecules expressed in strains of H-2 haplotypes f, r, s, u, w6, w7, w16, w17 and w23. All three clonotypes give identical response patterns to a panel of 17 different dehydrogenase enzymes, and react to the same tryptic peptide of LDH-BP. Thus, these clones appear to recognize the same LDH-B epitope together with at least 3 different determinants of the Ab molecule. The data suggest that alloreactivity is more closely related to T cell specificity for self-major histocompatibility complex than to specificity for foreign antigen.

Animals↗
PubMed1985

Inbred and wild mice carry identical deletions in their E alpha MHC genes.

Several inbred strains and a certain percentage of wild mice bear a deletion in the E alpha gene of the mouse major histocompatibility complex (H-2). This mutation prevents transcription of the E alpha gene and hence functional expression of the E alpha E beta dimer on the cell surface. Two strains were selected for a more precise localization of this deletion. BALB.B is a congenic line carrying the H-2b haplotype on the BALB/c background. CRO435 is an outbred stock derived from a wild mouse captured near Cairo, Egypt; it carries the H-2w37 haplotype including a null Ew28 alpha allele, as well as semi-lethal mutations in the H-2 linked t complex (tTuw7). From these two strains, we have isolated genomic clones that contain fragments spanning the E alpha deletion, and have sequenced the breakpoint region. The deletions in the two strains are identical, spanning 627 bp which include the promoter region and the signal peptide exon of the E alpha gene. Limited sequence comparison suggests that the Eb alpha allele of BALB.B is more closely related to the Ew28 alpha allele of CRO435 than both of these are to an E alpha-expressor allele, Ed alpha. It is therefore likely that the Eo deletions in the various inbred strains and wild mice are of the same origin, and we propose that they have been disseminated throughout the mouse population because of linkage to the t complex.

Animals↗
PubMed1985

Restriction fragment length polymorphism of C4 genes in mice with t chromosomes.

Genomic DNA was isolated from 29 t strains and 4 congenic lines of mice, digested with restriction endonucleases, and hybridized with a probe representing the complement component 4 (C4) gene. All but one of the enzymes revealed restriction fragment length polymorphism in this sample of C4-related genes. Double digestion analysis suggested the presence of three C4 gene copies in some of the t chromosomes and two copies in others. The enzymes distinguished 16 different haplotypes among the 33 strains tested. Based on their restriction fragment length patterns, the t strains could be divided into four groups with strains in each group more closely related to each other with respect to their C4-region genes than strains belonging to different groups. At least three of these four groups represent different branches of the evolutionary tree constructed for the t chromosomes. The C4-related genes of the chromosomes are in strong linkage disequilibrium with the class II genes of the H-2 complex. Typing for the Ss and Slp allotypes of C4 has revealed the presence of the Ss1 phenotype in two t strains and of the Slpa phenotype in one strain.

Animals↗
PubMed1985

How polymorphic are class II loci of the mouse H-2 complex?

DNA was isolated from 75 mouse strains carrying classical H-2 haplotypes as well as haplotypes derived from wild mice. The DNA was digested with three restriction endonucleases, Bst EII, Eco RI, and Bam HI, the digests hybridized, using the Southern blotting technique, with probes for the class II genes A alpha, A beta, E alpha, and E beta, and the restriction fragment length polymorphism at these loci determined. The analysis revealed that the most polymorphic of the four loci is A beta, followed by E beta, and, at a different level, by E alpha and A alpha. There is a large difference in the degree of polymorphism between the A beta and E beta genes, on the one hand, and the A alpha and E alpha genes, on the other hand. There is no difference in the degree of polymorphism between the A alpha and E alpha genes. These findings do not substantiate previous postulates of a high A alpha polymorphism and they do not agree with the hypothesis that the class II region is divided into highly polymorphic centromeric and less polymorphic telomeric subregions. Rather, it appears that the differences in the degree of polymorphism of the different segments of the class II region are determined by the class II loci themselves. The polymorphism of the less polymorphic class II genes is, however, still greater than the polymorphism of certain other genes on chromosome 17, notably the alpha 4-globin pseudogene. The distribution of polymorphisms at the A beta and E beta loci suggests that even populations occupying relatively small geographical regions differ in alleles at these loci. Sharing of A beta alleles between unrelated populations is yet to be detected. A certain degree of linkage disequilibrium exists among the A alpha, A beta, and E beta loci; by contrast, the E alpha locus appears to vary largely independently of the other class II loci.

Alleles↗
PubMed1985

Major histocompatibility complex of the mole-rat. II. Restriction fragment polymorphism.

The major histocompatibility complex (Mhc) is a group of loci coding for lymphocyte membrane glycoproteins that provide the context for the recognition of foreign antigens in the initial phase of the immune response. The complex contains a large number of loci, some of which are highly polymorphic. The complexity and polymorphism pose a number of questions concerning the evolution of the Mhc. In an attempt to answer some of these questions, we have begun to study the Mhc of the mole-rat, Spalax ehrenbergi, a rodent representing a complex of sibling species occupying ecologically and geographically clearly delineated regions within the borders of Israel. In an earlier publication we identified the Spalax major histocompatibility (Smh) complex serologically and biochemically. Here, we analyze the Smh by Southern blotting of DNA fragments produced by restriction enzyme digestion. The fragments were hybridized to mouse probes specific for class I, class II, and C4 genes. The analysis has revealed that the Smh complex contains as many class I genes as the mouse does and that these genes are polymorphic. The number of class II genes could not be determined with certainty, but it is probably not greater than in the mouse. Polymorphism was also detected at the loci coding for the complement component 4 (C4), which are probably closely linked to the Smh complex. The polymorphism of mole-rat class I loci contrasts with the reported monomorphism of these loci in the Syrian hamster. Since the mole-rat leads a solitary, subterranean life, as the Syrian hamster does, ecology cannot be an explanation for the lack of class I polymorphism in the latter species.

Animals↗
PubMed1985

Adrenal dysfunction in glycerol kinase deficiency.

The infantile form of glycerol kinase deficiency appears to be an X-linked disorder which is consistently characterized by developmental delay and adrenal cortical insufficiency and hypoplasia. We propose that the inherited deficiency of outer mitochondrial membrane-bound glycerol kinase restricts glycerophospholipid synthesis, and, hence, the activation of steroidogenesis. This would limit the conversion of cholesterol to pregnenolone, the precursor for glucocorticoids in the adrenal cortex. The deficiency in cortisol production, with a lack of feedback to the pituitary, would result in increased ACTH production and hypertrophy of the fascicular zone at the same time that replication of the cells within this zone would be inhibited. Similarly, the decreased mineralocorticoid production by the sparse glomerulosal zone would limit the ability of the individual to respond to stress, and would result in development of potentially fatal hyponatremia and hyperkalemia. Organization of the pathway for glycerophospholipid synthesis at the outer mitochondrial membrane would make this pathway particularly vulnerable to mutations disrupting the compartmented production of the parent compound, glycerol 3-phosphate, by mitochondrial-bound glycerol kinase.

Adrenal Cortex↗
PubMed1985

Multiple duplications of complement C4 gene correlate with H-2-controlled testosterone-independent expression of its sex-limited isoform, C4-Slp.

Mouse liver cDNA clones related to the C4 and C4-Slp isoforms of the fourth component of complement differ by few nucleotide changes within a region of substantial divergence from human C4. It is suggested that the mouse C4 gene duplication is an evolutionarily recent event with respect to the time of mammalian radiation. This conclusion is reinforced by the presence of a single C4 gene in the Syrian hamster. Most H-2 haplotypes, including those characterized by an undetectable C4-Slp protein, possess two C4 gene copies which, in contrast to the neighboring factor B, show a marked restriction site polymorphism. The genetic variation of this region is emphasized by the presence in the mouse of a rare "polymorphism" for C4 gene number. Multiple C4-related gene copies characterize those exceptional wild-derived H-2 haplotypes, H-2w7, H-2w16, and H-2w19, that determine the expression of the C4-Slp protein in female animals.

Animals↗