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Biomedical subjects

M Mock

Publications and source records attributed to M Mock.

At least 91 records · Page 5Linked to original sources
PubMed1986

A pH-induced increase in hydrophobicity as a possible step in the penetration of colicin E3 through bacterial membranes.

Exposure to low pH triggers an increase in the hydrophobicity of the colicin E3 molecule. Using a [3H] Triton X-100 binding assay we have shown that the amount of detergent (at supramicellar concentrations) associated with colicin E3 increased dramatically at pH 3.8 and below. Interaction of colicin E3 with asolectin vesicles was monitored by following its cross-linking with two different photoactivatable radioactive phospholipid analogues. At neutral pH colicin E3 was cross-linked with the phospholipid probing the membrane surface whereas at pH 4.5 and below, the bacteriocin reacted with the phospholipid probing the hydrophobic core of the bilayer. With the use of phase partitioning of proteins in Triton X-114 it was shown that at acidic pH whole colicin E3 and its immunity protein segregated in the detergent phase. After trypsin digestion of the colicin-immunity complex, the N-terminal portion of E3 (T1) and the immunity partitioned in the detergent phase at low pH. In contrast, the enzymic domain of the colicin (T2) remained in the aqueous phase and was recovered in a highly active form as a consequence of its dissociation from the immunity protein. These results are discussed in relation to the mechanism of entry of colicin E3 into bacterial cells.

Carbon Radioisotopes↗
PubMed1986

Myotonic dystrophy and pregnancy: a review.

The previous reports of 20 women with myotonic dystrophy and pregnancy are reviewed, and a new case report added. Myotonic dystrophy is often unrecognized in early life due to vague symptoms, and is often first diagnosed during pregnancy which is known to worsen the main features of muscular weakness and myotonia. Complications of pregnancy and delivery are frequent and serious and should be known to all those dealing with pregnant women. A history of fetal wastage or a child suffering from symptoms of congenital myotonic dystrophy may be a clue to the diagnosis and these patients should be closely followed until safe delivery. The neonatologist should be involved as feeding and respiratory problems in the neonate may indicate that the infant is affected.

Abortion, Spontaneous↗
PubMed1984

Genetic analysis of the functional relationship between colicin E3 and its immunity protein.

Partial deletions in the immunity gene of the colicin E3 operon were used to study possible functions of the immunity protein besides protection against exogenous colicin. Nuclease BAL-31 was used to create a series of carboxyl-terminal deletions of the immunity gene. Mutants displaying lowered immunity against exogenous colicin were found, and six that had reduced but detectable levels of immunity were chosen for further analysis. DNA sequence analysis of the deletions showed that all six terminated within the last five codons of the immunity gene. The wild-type immunity gene was replaced by each of the six mutated immunity genes in a plasmid containing an otherwise functional colicin E3 operon. Transformants containing the resulting plasmids produced smaller colonies on solid medium and grew more slowly in liquid culture than transformants carrying the wild-type colicin and immunity genes. This result suggested that immunity protein was required to protect the cell against endogenous colicin E3. This idea was confirmed in experiments in which the colicin E3 and immunity genes were independently cloned on two compatible plasmid vectors.

Amino Acid Sequence↗
PubMed1983

Nucleotide sequence for the catalytic domain of colicin E3 and its immunity protein. Evidence for a third gene overlapping colicin.

We have determined the nucleotide sequence of a segment of Co1E3 DNA coding for the carboxyl-terminal, catalytic peptide of colicin E3 and for the immunity protein. The end of the colicin E3 gene is separated from the beginning of the immunity gene by a nine-basepair intercistronic region, suggesting the two genes are expressed as a single transcriptional unit. The immunity gene is expressed, however, in E. coli strains containing Co1E3-pBR322 hybrid plasmids deleted for the 5'-end of the colicin gene. The DNA sequence also contains an unexpected open reading frame (ORF). This ORF is contained within the colicin gene and is in the +1 reading frame with respect to that gene. Plasmids containing the ORF, directed the synthesis of an 11 kilodalton protein in a cell-free, transcription-translation system.

Amino Acid Sequence↗
PubMed1983

Prognostic value of angiographic indices of coronary artery disease from the Coronary Artery Surgery Study (CASS).

The Coronary Artery Surgery Study, CASS, enrolled 24,959 patients between August 1975 and June 1979 who were studied angiographically for suspected coronary artery disease. This paper compares the prognostic value for survival without early elective surgery of eight different indices of the extent of coronary artery disease: the number of diseased vessels, two indices using the number of proximal arterial segments diseased, two empirically generated indices from the CASS data, and the published indices of Friesinger, Gensini, and the National Heart and Chest Hospital, London. All had considerable prognostic information. Typically 80% of the prognostic information in one index was also contained in another. Our analysis shows that good prediction from angiographic data results from a combination of left ventricular function and arteriographic extent of disease. Prognosis may reasonably be obtained from three simple indices: the number of vessels diseased, the number of proximal arterial segments diseased, and a left ventricular wall motion score. These three indices account for an estimated 84% of the prognostic information available. 6-yr survival varies between 93 and 16% depending upon the values of these three indices.

Angiography↗
PubMed1982

The BtuB group col plasmids and homology between the colicins they encode.

Colicins A, E1, E2, E3, E4, E5, E6, and E7 exhibited reduced activity against BtuB mutants of Escherichia coli K-12 and also against wild-type cells in the presence of vitamin B12. Plasmids encoding representatives of these colicins were specifically immune to high levels of the homologous colicin. Col(+) cells grown in media containing mitomycin C accumulated large amounts of colicin polypeptide. ColE2(+), ColE3(+), ColE4(+), ColE5(+), and ColE6(+) cultures also synthesized large amounts of second, lower-molecular-weight protein under these conditions. Colicins E2 through E7, but not A or E1, reacted with antiserum raised against purified colicin E3. Colicins E2 and E7 induced synthesis of beta-galactosidase encoded by lacZ under the control of the colicin Ib gene promotor on a derivative of Col plasmid ColIb.P9. This promotor is usually active only when the cells are treated with agents which damage DNA or block replication. Plasmids encoding various mutant forms of colicin E3 (M. Mock and M. Schwartz, J. Bacteriol. 142:384-390, 1980) recombined with ColE2, ColE4, ColE5, or ColE6 plasmids at a frequency of 10(-4) per cell to produce a colicin active against ColE2(+), E4(+), E5(+), or E6(+) cells. ColE5 and ColE6 plasmids recombined with ColE3 plasmids bearing mutations affecting colicin E3 receptor recognition, envelope penetration, and catalytic activities. ColE2 and ColE4 plasmids recombined only with ColE3 plasmids bearing mutations affecting receptor recognition and envelope penetration. Recombinants between mutant ColE3 plasmids and ColA, ColE1, or ColE7 plasmids were not detected. We propose the designation BtuB group for the colicins described here, and we divide the group into two classes comprising colicins A and E1, which act on the cytoplasmic membrane, and the related colicins E2 through E7, which have known or putative nuclease activities.

Bacteriocin Plasmids↗
PubMed1981

Preservation of the myocardium during coronary artery bypass grafting.

The influence of three methods of myocardial preservation used during coronary artery bypass grafting on operative mortality and perioperative myocardial infarction was evaluated in seven institutions participating in the Coronary Artery Surgery Study (CASS). Both operative mortality and perioperative infarctions were comparable with either normothermic and topical hypothermic myocardial preservation. The addition of potassium cardioplegia to hypothermia lowered both operative mortality and perioperative myocardial infarction (p less than 0.01 and p less than 0.001, respectively). Stepwise multivariate discriminant analysis revealed that the high-risk clinical and angiographic variables were the most important determinants of operative mortality, followed by surgical priority and the use of potassium cardioplegia. However, none of the clinical, angiographic and surgical variables other than the use of potassium cardioplegia influenced the incidence of perioperative myocardial infarction.

Adult↗
PubMed1980

Mutations which affect the structure and activity of colicin E3.

Among 69 ColE3 mutant plasmids selected on the basis of their inability to produce an active colicin, seven (cop-1 to cop-7) were found to bear a mutation affecting the structural gene for colicin. Three of these (cop-1, cop-2 and cop-3) lead to the production of an inactive colicin molecule which has the same molecular weight as wild-type colicin E3 (67,000). These three inactive colicins are still able to interact with the outer membrane receptor. The cop-1 protein retained the ability to inhibit protein synthesis in vitro and therefore seems specifically affected in it ability to penetrate the cell envelope. The cop-2 and cop-3 proteins lost the ability to inhibit protein synthesis in vitro, and activity which is normally associated with the C-terminal part of the colicin molecule. On the basis of this and further evidence, it is suggested that the cop-2 and cop-3 mutations affect the structure of the C-terminal part of the colicin molecule. The other four mutations (cop-4 to cop-7) lead to the production of colicin-related polypeptides of lower molecular weight (29,000 to 45,000) which display a reaction of partial immunological identity with wild-type colicin. These four polypeptides are unable to interact with the cell surface receptor. Three of these mutants are shown to carry a nonsense mutation.

Bacterial Proteins↗
PubMed1979

[Serologic data from 537 patients with a positive direct Coombs' test (Vienna 1949 to 1979)].

In the period from 1949--1979 537 patients with positive direct Coombs-reaction were observed, their serological findings are presented and analysed regarding correlations to ABO, Rh, age and sex. Close connexions between the strength of the direct Coombs-reaction, autoantibodies in the serum and the absence of haptoglobin were found as it was expected. The sensitivity of different methods to detect autoantibodies, frequencies and specificities are discussed. Two causes of autoimmune hemolytic anemia with monospecific autoantibodies and four healthy blood donors with unexpected and inexplicable positive direct Coombs-reaction are described.

ABO Blood-Group System↗
PubMed1978

Mechanism of colicin E3 production in strains harboring wild-type or mutant plasmids.

As previously reported by others, more than 90% of the colicin E3 synthesized soon after induction of colicinogenic bacteria was found to be cell bound, about half of it being in a salt-extractable state at the cell surface. Evidence is presented that the colicin molecules remain preferentially bound to the cell which produced them, rather than being secreted and randomly distributed in the cell population. Secretion of colicin E3 may in fact never occur, all or most of the colicin found free in the medium perhaps being released during lysis of the producing cells long after induction. Among 19 mutant plasmids selected on the basis of their inability to produce an active colicin, only 3 were found to code for a protein which although it lacked any bactericidal activity, had the same molecular weight as wild-type colicin E3 and displayed a reaction of immunological identity with it. These three inactive colicins fail to be exported to the cell surface and seem to be blocked at some intermediate stage in the export process.

Bacterial Proteins↗
PubMed1976

[Bacterial adjuvants in cell mediated immunity. Recent data].

Only some bacterial adjuvants are able to stimulate cell-mediated immunity. It has been shown recently that this property is due to a cell-wall component, the peptidoglycan. The relevance of these findings to tumor immunity has been discussed.

Adjuvants, Immunologic↗
PubMed1975

[Effect of pH on bacteria in early log phase].

The bacteria harvested in the early log phase lyse when they are submitted to a pH above 10. The peptidoglycan is not degraded in these conditions. Thus, the authors used these properties to extract the peptidoglycan from several gram negative and gram positive bacteria.

Bacillus megaterium↗
PubMed1974

Action of lysozyme on penicillin-induced filaments of Proteus vulgaris.

Penicillin-induced filaments of Proteus vulgaris P 18 had a seemingly unaltered cell envelope. Lysozyme, however, reduced the wall part of these filaments into a three-layered structure and caused transformation into spheroplasts. Although cross walls and membrane septa were absent in the filaments, most of the lysozyme-induced spheroplasts remained attached to each other.

Animals↗