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Biomedical subjects

M Simon

Publications and source records attributed to M Simon.

At least 649 records · Page 36Linked to original sources
PubMed1979

Phase variation in Salmonella: genetic analysis of a recombinational switch.

The alternative expression of Salmonella genes H1 and H2, which specify different flagellar antigens, results in the oscillation of phenotype known as phase variation. This alternation is controlled by the inversion of an 800-base-pair sequence of DNA adjacent to, or including part of, the H2 gene. The invertable region was presumed to regulate the function of a promoter and to include specific sites at which a recombinational event, resulting in the inversion, could occur. Here we report genetic manipulations of hybrid lambda phage carrying the H2 gene that were used to define the H2 promoter region and the recombinational sites. The H2 gene fragment was inserted on a hybrid lambda phage next to the cheW gene, which lacked a promoter element. In the resulting fusion, cheW gene activity was restored, the expression of the H2 and cheW genes was controlled coordinately by the inversion, and the polarity of transcription and location of the H2 gene could be determined. Evidence from this type of gene fusion suggested that the H2 gene promoter is included in the inversion region. Hybrid H2 phage were constructed that contained substitutions for regions of the H2 gene. In contrast to hybrid lambda containing the H2 gene, which alternate between "on" and "off" states, several substituted lambdaH2 were fixed in the "on" state. A site necessary for the recombinational event must have been removed in these fixed lambdaH2.

Bacterial Proteins↗
PubMed1979

Propranolol in serum by high pressure liquid chromatography using nitrile (CN) bonded columns in reverse phase.

A method for monitoring therapeutic levels of the beta-blocking and antiarrhythmic drug propranolol in serum has been developed as a high performance liquid chromatography technique using bonded nitrile columns in a reverse phase mode with an aqueous methanol mobile phase containing acetate as a counterion. The performance characteristics of eight different types of reverse phase columns are discussed with evaluation for use in the method. The present method combines basic organic (cyclohexane) extraction with fluorescence detection of the chromatographic effluent to provide a specific, rapid, precise, and reliable technique that has been successfully used to monitor propranolol metabolites or other drugs. The method is shown to compare well with other methods and is suitable for therapeutic drug monitoring by routine clinical laboratories.

Chromatography, High Pressure Liquid↗
PubMed1979

HLA determinants in idiopathic hemochromatosis.

HLA-A and B antigens were defined in 154 unrelated idiopathic hemochromatosis patients. The study confirmed the highly significant positive association with HLA antigens A3 (corrected P less than 10(-10)) and B14 (corrected P less than 10(-9)). HLA-DR typing showed increased frequency of the specificity DRw6, which was frequently associated with the phenotype A3, B14 and antigen B14, suggesting linkage disequilibrium. This was borne out by PLT data.

Epitopes↗
PubMed1979

Flagellar-phase variation: isolation of the rh1 gene.

In Salmonella, expression of flagellar antigen alternates between two serotypes (phases) encoded by two genes, H1 and H2. The mechanism which controls the alternative expression of the H1 and H2 genes was examined by cloning these genes and the genetic elements which control their activity on hybrid vehicles in Escherichia coli. H2 gene activity was shown to be controlled by a recombinational switch located adjacent to the H2 gene. Activity of the H1 gene is thought to be repressed, when the H2 gene is expressed, by the product of another gene, rh1 (repressor of H1), which is controlled coordinately with the H2 gene. In this report, we describe the construction of hybrid lambda vehicles which contain, in addition to the H2 gene, a genetic activity corresponding to rh1. Variation of flagellar antigens analogous to that observed in Salmonella was observed when E. Coli strains were transduced with the hybrid lambda. By using the lambdaH2rh1 hybrid to program protein synthesis in UV-irradiated cells, the synthesis of a polypeptide was correlated with rh1 gene product activity. We conclude that the H2 region consists of two cotranscribed genes, H2 and rh1. The expression of both gene products is regulated by the same recombinational event.

Bacterial Proteins↗
PubMed1979

Advances in radiologic reporting with Computerized Language Information Processing (CLIP).

Computerized Language Information Processing (CLIP) is a system of radiologic reporting in which the user interacts with a computer keyboard and cathode-ray tube terminal to generate coded reports. The hierarchical medical classification on which the code is based permits rapid on-line compilation of reports of any degree of complexity. The system provides organized sets of pre-assembled statements that are rapidly accessed and modified for each examination. Although the reports are printed in English, they are held in the computer as a succinct code that is eminently suited for permanent storage and rapid retrieval.

Classification↗
PubMed1979

A safe technique for introduction of the Kimray-Greenfield filter.

A modification in the introduction of the Kimray-Greenfield filter is described. Rather than advancing the stylet toward the Luer-lok assembly and thereby discharging the filter, the authors propose positioning the carrier containing the closed filter farther into the inferior vena cava, then withdrawing the catheter and carriage while holding the stylet in place. This method reduces the chance for damaging the caval wall.

Aged↗
PubMed1979

Reexpansion pulmonary edema.

A case of pulmonary edema following reexpansion of a collapsed lung due to pneumothorax is described and illustrated. The importance of recognizing this relatively uncommon phenomenon is stressed. The development of such edema can be prevented by avoiding application of sudden and excessive negative pleural pressures during the evacuation of a pneumothorax or a pleural effusion. The edema generally occurs in a lung that has been collapsed for more than three days. The importance of the duration of pulmonary collapse in the causation of edema is demonstrated in this patient.

Adolescent↗
PubMed1979

Evaluation of the participation of parietal peritoneum in dialysis: physiological, morphological and pharmacological data.

Bidirectional fluxes of Na+, K+ and Ca++ were estimated under in vitro conditions through isolated patches of rat peritoneal membranes (parietal and visceral). Morphological (TEM) and functional (changes in fluxes) data are presented to show that mesothelium lining the parietal peritoneum forms a barrier than limits diffusion of ions across this membrane. In addition, it was found that Furosemide and nitroprusside change the permeability of the mesothelium for sodium or potassium, respectively.

Animals↗
PubMed1978

"Long-distance" bactericidal effectiveness of formalin on permanent human teeth.

The long distance bactericidal effectiveness of 0.005 ml. 25 percent formalin in 80 percent ethanol applied on a cotton pellet to pulp chambers for one week in unreamed, unirrigated permanent human teeth with initial postive cultures was studied. The results showed 59 percent negative cultures on subsequent examination.

Bacteria↗
PubMed1978

Regulation of gene expression by site-specific inversion.

A site-specific inversion event is responsible for phase transition in Salmonella, as indicated by heteroduplex analysis of recombinant molecules carrying the gene coding for H2 flagellin in Salmonella. The inversion region corresponds to approximately 800 base pairs in length, and the inversion process does not appear to be dependent upon the E. coli RecA recombination pathway. Specific deletion derivatives of the cloned fragments no longer produce H2-specific flagella, effectively mapping the H2 gene within about 300 bp of the inversion region. Recombinant products of the hybrid molecules arose spontaneously, and they were used in the mapping of restriction sites within the inversion region. The restriction maps further demonstrate the extent and nature of the inversion.

Bacterial Proteins↗
PubMed1978

Association of mitochondria with microtubules in cultured cells.

By indirect immunofluorescence techniques, microtubules and mitochondria were localized in normal rat kidney cells, human WI38 fibroblasts, mouse peritoneal macrophages, and a putative smooth muscle rat cell line, in monolayer culture. The mitochondria were found to be arranged along the cytoplasmic microtubules in each cell type. Disruption of the microtubules with colcemid caused a redistribution of the mitochondria in these cells. There was no correlation between the location of the mitochondria and actin-containing filaments. This evidence suggests that mitochondria are directly or indirectly associated with microtubules in these cells.

Actins↗
PubMed1978

SLB, a new alloantigenic system of the pig.

An alloantigen segregating in the double back-cross families, distinct from serologically determinalble transplantation antigens controlled by the major histocompatibility complex (SLA), was detected in pigs by the complement-dependent lymphocytotoxic technique. The system was designated SLB and its product (antigen SLB-A1) was demonstrated in all lymphocytes from the lymph nodes, thymus and peripheral blood, but not in the erythrocytes. Back-cross matings supplied evidence of the dominant heredity of SLB-A1. Detection of further SLB antigens was unsuccessful, so that only two alleles (SLB-A1 and SLB-A-) could be determined in families. Double back-cross families revealed a close linkage between the SLB locus and the L blood group locus. Maximun lod score values were calculated in recombination fraction theta=theta.10.

Animals↗