Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To determine the positive and negative classification error rates associated with the HTA in our laboratory, F1 sons of TEM-exposed CD-1 male mice were evaluated by the sequential fertility method with subsequent cytogenetic analysis. Males who sired three litters of size 10 or less when mated to primiparous females from either the B6C3F1 or the BCF1 strain were classified as partial steriles. When meiotic chromosome analyses revealed the presence of at least two cells containing multivalent figures, males were classified as translocation heterozygotes. When the fertility evaluation and the cytogenetic analysis were compared, normal fertility was observed on 5 of 83 (6.02%) translocation-bearing F1 males mated to B6C3F1 tester females and on 3 of 83 (3.61%) F1 males mated to BCF1 tester females. Thus, the false-negative error rates were 6.02% and 3.61% with these two tester strains. Multivalent figures were not observed in the meiotic chromosomes of 410 F1 males. Of these, 12 (2.93%) had reduced fertility when mated to the B6C3F1 tester strain as did 7 (1.71%) mated to the BCF1 strain. Thus, the false-positive error rates with these two tester strains were 2.93% for the B6C3F1 strain and 1.71% for the BCF1 strain. Our results indicate that non-zero error rates, both false-positive and false-negative, are associated with the sequential mating method HTA. In addition, the magnitude of these error rates was influenced not only by the tester female strain but also by the genotype of the F1 male.
Environ Mol Mutagen 1988
PMID:Detection of TEM-induced reciprocal translocations in F1 sons of CD-1 male mice: comparison of sequential fertility evaluation and cytogenetic analysis. 334 38

Due to the ubiquitous nature of airborne endotoxin, an understanding of pulmonary alterations which follow inhalation of environmentally realistic concentrations of purified bacteria derived lipopolysaccharide (LPS) is important. Using LPS derived from Enterobacter agglomerans, a bacterium found in cotton and cotton mill dust, aqueous aerosols (effective LPS concentration 4 micrograms/m3) were generated and used to expose either normal hamsters (N = 6) or those rendered endotoxin tolerant by pre-ip injection of 0.1 LD50 LPS. Control groups (normal--N = 6; tolerant--N = 6) received saline aerosol only. At 6 hr after 5-hr aerosol exposure, lungs of all animals were fixed, processed for light and transmission electron microscopy, and subject to qualitative and to multitiered morphometric analysis using standard point counting techniques. Qualitative evaluation of TEM micrographs from LPS aerosolized-nontolerant hamsters showed endothelial alteration (focal disruption, subendothelial space formation, and cytoplasmic blebbing) but volume and number of endothelial cells were not changed indicating only slight, focal endothelial damage. Quantitatively, septal capillary blood space in nontolerant, LPS aerosolized hamsters showed increased Vv of PMNs and platelets. These changes were not seen in tolerant induced-LPS aerosolized hamsters. Independent of tolerization treatment, LPS inhalation led to a decrease in fixed lung volume and an increase in numerical density of endothelial pinocytotic vesicles. It is concluded that the inhalation of realistic, environmental levels of bacterial endotoxin may induce significant changes in distal lung and may be important in the pathogenesis of byssinosis and adult respiratory distress syndrome.
Exp Mol Pathol 1985 Dec
PMID:Morphometric changes of the lung induced by inhaled bacterial endotoxin. 406 10

We have characterized pBP201 one of the plasmids from a collection of 46 strains producing adenylyltransferase ANT(2") (Schmidt 1984). It confers resistance to sulphonamides and produces aminoglycoside adenylyltransferases AAD(3") and ANT(2") and beta-lactamase TEM-1. Plasmid pBP201 has a size of 24.8 kilobases (kb) and contains TnA and a Tn21-related element, Tn4000 delta, with deletions in mer and the termini and a substitution at tnpR. In complementation assays with transposition-deficient mutants of Tn21 the element in pBP201 appears to be TnpA+ but TnpR-. It represents a naturally occurring defective transposon. The sequence organization of pBP201 has been compared with that of Tn21-related elements such as Tn2410, Tn2603, Tn2424, Tn1696, and Tn4000. In these transposons the integration sites of resistance genes cat, bla, aacA, aacC or aadB have been identified at two preferential locations; these are at the termini of the streptomycin resistance gene aadA. Two additional sites have been localized in the Tn21 backbone to the right of the mer operon and at res (internal resolution site) and are probably involved in the evolution of these elements. Based on these results a model for the possible genealogy of class II transposons is presented.
Mol Gen Genet 1984
PMID:Evolutionary relationship between Tn21-like elements and pBP201, a plasmid from Klebsiella pneumoniae mediating resistance to gentamicin and eight other drugs. 609 67

The induction of tyrosine aminotransferase by a variety of steroids was studied in cells from a hepatoma tissue culture (HTC). We have defined a class of steroids that induce TAT synthesis to a higher level than optimal inducers described earlier; these are called supra-inducers. When TAT induction is compared with the binding of the steroids to the cytoplasmic receptor or to their binding in the whole cell, a good correlation between binding in vivo of the hormone and its induction capacity can be established, whereas such a correlation was not systematically observed in vitro. A very short exposure of HTC cells to either dexamethasone or corticosterone is sufficient to induce TAT. When the inducer is removed from the culture medium a few minutes after its administration, the intracellular hormone concentration decreases very rapidly but TAT will be synthesized at its maximal rate. Thus the hormones behave as a starting signal for the optimal synthesis of the enzyme, and their presence in the culture medium is not necessary throughout the entire induction period.
Mol Cell Endocrinol 1981 May
PMID:Relations between steroid-cell contact, steroid-binding and induction of tyrosine aminotransferase. 611 76

The osmotic behavior of control lymphocytes (CL) and polymorphonuclears (CPMN) was compared with that of cells from patients with chronic lymphocytic leukemia (CLL) and chronic myelocytic leukemia (CML), using the method of gradual dialysis against distilled water. The results were evaluated with a fragiligraph, and by scanning (SEM) and transmission (TEM) electron microscopy. The fragiligraphy curves showed that CLL cells are more resistant to osmotic pressure than the CL, whereas the curves for CPMN and CML cells showed an overlap. Surface alterations in CL appeared as early as 1 min of dialysis, while in CLL cells the membrane did not show major alterations even after 5 min of dialysis. CPMN also showed alterations earlier than CML cells, but this difference was not as prominent as in the case of lymphocytes and was observed for a maximum of 3 min of dialysis. The internal structure of the cells was altered earlier than the surface membrane and this was expressed mainly in the nucleus in both control and leukemic cells. Also in this respect, the internal structure of CL was altered earlier than that of CLL cells, whereas no major differences were observed between CPMN and CML cells.
Virchows Arch B Cell Pathol Incl Mol Pathol 1982
PMID:SEM and TEM studies on the osmotic behavior of control and leukemic lymphocytes and polymorphonuclears. 612 53

Isolated rat hepatocytes in early primary culture were incubated in the presence of three substituted nitroimidazoles currently of clinical interest as tumour radiosensitisers. The effects of 3h treatments with Misonidazole (MISO), Desmethylmisonidazole (DESMISO) and the basic compound Ro 03-8799 were monitored both directly from treatment and following a 24h 'recovery' period. Morphological changes were observed by SEM and TEM and included effects on the plasma membrane and the nucleus. The plasma membrane of DESMISO and 03-8799 treated cells was characterised by blebbed regions not present in control cultures, and considered indicative of an early toxic insult. Blebs were most evident in 03-8799 treated hepatocytes where they often contained coils of endoplasmic reticulum within the ground plasma. Blebbed areas were less evident 24h after the removal of the drugs from surviving cells. An increased aggregation of peripherally located heterochromatin within the nucleus was the other main morphological alteration induced by nitroimidazole treatment. This was again more prevalent in 03-8799 and DESMISO exposures; and particularly in cells demonstrating membrane damage. Parallel viability studies indicated an efficacy of the nitroimidazole towards rat liver parenchymal cells in primary culture of Ro 03-8799 greater than DESMISO greater than MISO. This fitted the order predicted from the morphological findings and from previously published clinical data. The validity of monitoring structural parameters as a means of initially indicating lesion sites following drug treatments in the hepatocyte cytotoxic screening model is considered.
Virchows Arch B Cell Pathol Incl Mol Pathol 1984
PMID:Morphological changes in rat hepatocytes in primary culture induced by Misonidazole, desmethylmisonidazole and Ro 03-8799. 614 29

The promoter and operator sequences of the Tn10-encoded tetracycline resistance operon are determined in vitro by transcription studies of purified DNA restriction fragments, protection of guanosine from methylation by dimethylsulphate, and DNase I footprinting employing the purified TET repressor protein. In vitro transcription reveals three promoters with overlapping consensus sequences. Two of them, designated PR1 and PR2, are directed towards the tet repressor gene and the third, called PA, initiates transcription of the tet resistance gene. All three promoters are regulated simultaneously by the TET repressor protein, as demonstrated by in vitro transcription. Tetracycline functions as an inducer in these experiments. Two palindromic operator sequences in the tet operon control region, called O1 and O2, are occupied simultaneously by the TET repressor. Four guanosine residues in symmetric positions close to the centre of the palindromic operator sequences are protected from methylation in the repressor-operator complex. However, only one guanosine residue exhibits an enhanced reaction with dimethylsulphate under these conditions. Footprinting experiments reveal protection of phosphodiester bonds against DNase I slightly further than the palindromic sequence arrangement. Several phosphodiester bonds between the two operators are accessible for cleavage by DNase I in the repressor-operator complex. Two phosphodiester bonds within each operator sequence are cleaved by DNase I. This feature shows a clear assymmetry with the two inside cleavage positions of O1 and O2 being much less accessible for DNase I as compared to the two outside positions. A molecular mechanism of regulation of the Tn10-encoded tetracycline resistance operon is presented based on these and previous results.
J Mol Biol 1984 Jan 15
PMID:Control of expression of the Tn10-encoded tetracycline resistance operon. II. Interaction of RNA polymerase and TET repressor with the tet operon regulatory region. 622 40

The transposon Tn10-encoded TET repressor controls the expression of tetracycline resistance as well as its own synthesis. The antibiotic tetracycline functions as an inducer for both genes, which are transcribed in divergent directions from a common start area. The interaction of the TET repressor with the regulatory sequence of the tetracycline resistance operon is investigated by equilibrium and kinetic methods. The wild-type control sequence contains two nearly identical operators separated by only ten base-pairs. A deletion mutant lacking one of the operators is constructed by controlled digestion with exonuclease Bal31. It serves to prove that the two TET operators are each occupied by a TET repressor dimer in the wild-type tet operon regulatory sequence. The association constants are approximately identical for both operators between 10(12) and 10(13) M-1 as derived from kinetic data. The half-life of the TET repressor--tet operator complex is 12 minutes when competed with tet operator DNA and two minutes when competed with the inducer tetracycline. The dissociation of the repressor--operator complex has no apparent activation enthalpy but has an activation entropy of -320 J/mol K, indicating the involvement of solvent or counterion condensation. The dissociation rate constant of the tetracycline--TET repressor complex depends strongly on temperature. The activation enthalpy is 160 kJ/mol, indicating extremely strong binding of the drug. This result is discussed with respect to the necessary sensitivity of a regulated resistance gene. The native structure of the TET repressor is a dimer, as demonstrated by molecular exclusion chromatography. The elution behavior of the TET repressor--tetracycline complex indicates clearly that the repressor--inducer complex remains a dimer. The results are discussed with respect to the regulatory functions of the components.
J Mol Biol 1983 Sep 25
PMID:Control of expression of the Tn10-encoded tetracycline resistance genes. Equilibrium and kinetic investigation of the regulatory reactions. 631 33

The TET-repressor encoded by the transposon Tn10 has been crystallized along with the repressor-tetracycline complex. Both crystals belong to the space group P43212 (or P41212) with cell dimensions a = b = 74.3(1) A, c = 94.2(2) A and a = b = 73.3(1) A, c = 94.6(2) A for the free and complexed repressor, respectively. There is one molecule of molecular weight 23,000 per asymmetric unit, and the biologically active dimer therefore consists of two identically formed subunits which are related by a crystallographic 2-fold axis. This isomorphism of TET-repressor and its tetracycline complex suggests that only minor, subtle changes in structure trigger binding to or release of the operator. The crystals of the native protein permit X-ray data collection to 3.2 A and those of the complexed repressor to 2.8 A.
J Mol Biol 1984 Dec 25
PMID:Crystallization of and preliminary X-ray diffraction data for TET-repressor and the TET-repressor-tetracycline complex. 652 88

An in frame gene fusion containing the coding region for mature beta-lactamase and the 3'-end of hylA encoding the haemolysin secretion signal, was constructed under the control of a lac promoter. The resulting 53 kDa hybrid protein was specifically secreted to the external medium in the presence of the haemolysin translocator proteins, HlyB and HlyD. The specific activity of the beta-lactamase portion of the secreted protein (measured by the hydrolysis of penicillin G), approximately 1 U/microgram protein, was close to that of authentic, purified TEM-beta-lactamase. This is an important example of a hybrid protein that is enzymatically active, and secreted via the haemolysin pathway. Previous studies have indicated that haemolysin is secreted directly into the medium, bypassing the periplasm, to which beta-lactamase is normally targeted. This study indicated, therefore, that normal folding of an active beta-lactamase, can occur, at least when fused to the HlyA C-terminus, without the necessity of entering the periplasm. Despite the secretion of approximately 5 micrograms/ml levels of the active beta-lactamase fusion into the medium, there was maximally only a 50% detectable increase in the LD50 for resistance to ampicillin at the individual cell level. This result suggests that, normally, resistance to ampicillin requires a high concentration of the enzyme close to killing targets, i.e. in the periplasm, in order to achieve significant levels of protection.
Mol Gen Genet 1995 Nov 15
PMID:Secretion of active beta-lactamase to the medium mediated by the Escherichia coli haemolysin transport pathway. 750 Sep 46


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>