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Biomedical subjects

M Simon

Publications and source records attributed to M Simon.

At least 685 records · Page 38Linked to original sources
PubMed1977

Chemotaxis in Escherichia coli: methylation of che gene products.

The products of three chemotaxis-specific genes in Escherichia coli, cheM, cheD, and cheZ, are methylated. The cheZ gene codes for the synthesis of a 24,000 molecular weight polypeptide that appears in the cytoplasm. cheM codes for the synthesis of a membrane-bound polypeptide with a molecular weight of 61,000. cheD codes for another membrane-bound polypeptide with an apparent molecular weight of 64,000. CheM(-) mutants show chemotaxis toward some attractants (Tar(-) phenotype), while CheD(-) mutants respond to other attractants (Tsr(-) phenotype). The double mutant (CheD(-), CheM(-)) does not respond to any attractant or repellent tested. Therefore, these polypeptides play a central role in chemotaxis. They collect information from two subsets of chemoreceptors and act as the last step in the chemoreceptor pathway and the first step in the general processing of signals for transmission to the flagellar rotor. It is suggested that they may be involved in both an initial process that reflects the instantaneous state of the chemoreceptors and in an integrative, adaptive process. Two other genes, cheX and cheW, are required for the methylation of the cheD and cheM gene products.

Bacterial Proteins↗
PubMed1977

Serologically defined specificities of the pig main histocompatibility complex (SL-A).

Six antigens detectable by the complement-dependent lymphocytotoxic technique were determined in pigs by six groups of alloimmune sera. It was confirmed that these specificities are controlled by the main histocompatibility region (SL-A). Serological and genetic studies showed that the given specificities (provisionally designated L1 to L6) form at least 6 haplotypes. In addition, family studies confirmed the linkaged between SL-A region and C blood group locus. Maximum lod score values are in recombination fraction omicron = 0.2.

Animals↗
PubMed1977

Heredity of idiopathic haemochromatosis: a study of 106 families.

More than 80% of the first degree relatives of 106 patients with iron overload - 97 with idiopathic haemochromatosis (I.H.) and nine with haemosiderosis secondary to alcohol induced liver disease (A.H. - were examined. Physical examination and measurement of plasma iron level and UIBC were done in all subjects; relatives who presented with some anomaly were submitted to a desferrioxamine test and, if the latter showed a high urinary iron output, to a liver biopsy. While absent in relatives of A.H. patients, iron overload was present in 78 out of 499 relatives of I.H. patients: 29 major and 49 minor forms. The major forms involved the sibships almost exclusively. The genetic analysis showed much evidence in favour of a recessive or rather intermediate form of inheritance, with heterozygous developing minor forms. However, other modes of transmission, especially polygenic (probably oligogenic), cannot be totally excluded. Data from recent studies showing a strong correlation between I.H. and certain HLA antigens do not conflict with the above conclusions.

Adolescent↗
PubMed1977

Characterization of lambda Escherichia coli hybrids carrying chemotaxis genes.

Molecular cloning techniques were used to construct hybrid Escherichia coli lambda phage and isolate Col E1 factors that carried the cheB region of the E. coli genome. The products of these genes were examined by using a series of deletions in the phage to stimulate specific polypeptide synthesis in ultraviolet-irradiated cells and by using Col factor to program protein synthesis in minicells. Seven flagellar related polypeptides were synthesized. Three of these with apparent molecular weights of 38,000, 28,000, and 8,000 were associated with the cheB region; three polypeptides 63,000, 61,000, and 60,000 were associated with the region that maps between cheB and cheA. These bands were referred to as the triplet group. We suggest that these polypeptides are the same as the methyl-accepting chemotaxis protein described by Kort et al. (Proc. Natl. Acad. Sci. U.S.A. 72:3939-3943, 1975). Another polypeptide with a molecular weight of 12,000 is associated with the cheA region which also produces at least three gene products. We conclude that the cheA-cheB region in E. coli is complex. Further genetic and biochemical analyses are required to describe all of these products.

Bacterial Proteins↗
PubMed1977

Identification of polypeptides necessary for chemotaxis in Escherichia coli.

Molecular cloning techniques were used to construct Escherichia coli-lambda hybrids that contained many of the genes necessary for flagellar rotation and chemotaxis. The properties of specific hybrids that carried the classical "cheA" and "cheB" loci were examined by genetic complementation and by measuring the capacity of the hybrids to direct the synthesis of specific polypeptides. The results of these tests with lambda hybrids and with a series of deletion mutations derived from the hybrids redefined the "cheA" and "cheB" regions. Six genes were resolved: cheA, cheW, cheX, cheB, cheY, and cheZ. They directed the synthesis of specific polypeptides with the following apparent molecular weights: cheA, 76,000 and 66,000; cheW, 12,000; cheX, 28,000; cheB, 38,000; cheY, 8,000; and cheZ, 24,000. The presence of another gene, cheM, was inferred from the protein synthesis experiments. The cheM gene directed the synthesis of polypeptides with apparent molecular weights of 63,000, 61,000, and 60,000. The synthesis of all of these polypeptides is regulated by the same mechanisms that regulate the synthesis of flagellar-related structural components.

Bacterial Proteins↗
PubMed1977

Genetic analysis of Escherichia coli K-12 region I flagellar mutants.

Flagellar mutants in Escherichia coli region I were obtained by selection for resistance to the flagellotropic phage chi. F' elements carrying this region of the E. coli genome were then constructed. Stable merodiploid strains with a flagellar defect on the exogenate and another on the endogenote were prepared. These merodiploids yielded information on the complementation behavior of mutations in this region. Region I was shown to include at least six cistrons, flaV, flaK, flaL, flaM, flaS, and flaT. Mu-induced and deletion fla mutants were also isolated. By using these mutant strains, the transcriptional order was shown to be flaV-flaK-flaL-flaM-flaS-flaT. The definition of region I fla genes and their transcriptional relationships were confirmed by genetic tests with hybrid A phage carrying fla genes in this region.

Chromosome Mapping↗
PubMed1977

Synthesis of mot and che gene products of Escherichia coli programmed by hybrid ColE1 plasmids in minicells.

Hybrid Escherichia coli ColE1 plasmids carrying the genes for motility (mot) and chemotaxis (che) were transferred to a minicell-producing strain. The mot and che genes on the hybrid plasmid directed protein synthesis in minicells. Polypeptides synthesized in minicells were identical to the products of the motA, motB, cheA, cheW, cheM, cheX, cheB, cheY, and cheZ genes previously identified by using hybrid lambda and ultraviolet-irradiated host cells (Silverman and Simon, J. Bacteriol. 130:1317-1325, 1977), thus confirming these gene product assignments. The products of some che genes (cheA and cheM) appeared as more than one band on polyacrylamide gel electrophoresis, but analysis of partial peptide digests of these polypeptides suggested that the multiple forms were coded for by a single gene. Measurement of the physical length of the hybrid plasmids allowed an estimate of the amount of coding capacity of the cloned deoxyribonucleic acid, which was devoted to the synthesis of the mot and che gene products. These estimates were also consistent with the hypothesis that the multiple polypeptides corresponding to cheA and cheM were the products of single genes.

Bacterial Proteins↗
PubMed1977

Cutaneous manifestations of idiopathic hemochromatosis. Study of 100 cases.

Skin manifestations of idiopathic hemochromatosis (IH) are presented in 100 cases with emphasis on the previously unrecognized high frequency of ichthyosis-like states and koilonychia. In 50 cases with treated and nontreated groups, histological siderosis and clinical skin pigmentation were found to decrease postphlebotomy whereas melanosis, histologically, did not. By skin biopsy in 50 cases versus controls, the location of siderosis in eccrine sweat glands seems specific for IH providing a strong basis for a probable diagnosis of the disease. There are correlations between skin manifestations and other signs of the disease.

Adult↗
PubMed1977

Idiopathic hemochromatosis and iron overload in alcoholic liver disease: differentiation by HLA phenotype.

HLA A and B antigens were determined in two groups of patients: 38 patients with idiopathic hemochromatosis (IH) and 22 patients with iron overload accompanying alcoholic liver disease (AH). As previously described, HLA A3 and HLA B14 antigens appeared more frequently in the IH group (76.3 and 28.9%, respectively) than in a control group of 204 subjects (27 and 3.4%). In the AH group the frequency of A3 (22.7%) and B14 (13.6%) was not significantly different from that observed in controls. The frequency of A3 was significantly lower in the AH group than in the IH group (P less than 0.001). On this basis a clear difference appears between the two conditions with iron overload, and genetic analysis of the results rules out the hypothesis that AH would be a heterozygous form of IH exposed by alcohol.

Adult↗
PubMed1977

A vena cava filter using thermal shape memory alloy. Experimental aspects.

Surgical ligation of the vena cava in the treatment of pulmonary embolism is already being superseded by devices introduced via a peripheral vein. A new metal alloy (nitinol) with unique memory characteristics forms the basis of an experimental device which promises even greater safety, simplicity and speed of introduction. It is inserted as a straight thin wire via the small bore catheter used for angiographic diagnosis. Upon reaching the lumen of the inferior vena cava and sensing body temperature, it reverts to its preset complex filter shape and locks into place permanently. It will trap further thromboemboli from the pelvis or lower limbs.

Alloys↗