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Biomedical subjects

J Thompson

Publications and source records attributed to J Thompson.

At least 703 records · Page 39Linked to original sources
PubMed1981

The binding site for ribosomal protein L11 within 23 S ribosomal RNA of Escherichia coli.

Ribosomal protein L11 of Escherichia coli was bound to 23 S rRNA and the resultant complex was digested with ribonuclease T1. A single RNA fragment, protected by protein L11, was isolated from such digests and was shown to rebind specifically to protein L11. The nucleotide sequence of this RNA fragment was examined by two-dimensional fingerprinting of ribonuclease digests. It proved to be 61 residues long and the constituent oligonucleotides could be fitted perfectly between residues 1052 and 1112 of the nucleotide sequence of E. coli 23 S rRNA.

Bacterial Proteins↗
PubMed1981

The clinical implications and the pathogenetic significance of circulating immune complexes in infective endocarditis.

Circulating immune complexes were determined with the 125I-Clq binding assay and the conglutinin binding assay in a prospective, longitudinal study of 40 patients with infective endocarditis, 34 patients with endocardial defects and nonseptic fever and 25 patients with septicemia without endocarditis. Fourteen patients with uncomplicated valvular lesions constituted a control group. Upon admission, 63 percent of the patients with infective endocarditis had a positive 125I-Clq binding assay versus 9, 12 and 7 percent, respectively, of the other three groups (p less than 0.001). The incidence of positive conglutinin binding assays became significantly higher during the course of infective endocarditis (53 percent) than during the course of nonseptic fever (21 percent), but, upon admission, this difference was not significant. The high incidence of Clq-binding immune complexes among patients with infective endocarditis could be attributed mainly to those patients with the characteristic features of subacute endocarditis. The incidence of circulating immune complexes in acute endocarditis was low and did not contribute to making the clinically important distinction from septicemia without endocarditis. A rise in the 125I-Clq binding assay levels during the course of infective endocarditis correlated significantly (p less than 0.01) with failure of antibiotic treatment. With the 125I-Clq binding assay, significantly higher levels were found in patients with signs of renal involvement of cutaneous vasculitis than in patients without these extracardiac manifestations of endocarditis. These results show that the determination of circulating immune complexes has clinical implications for both the diagnosis and the management of infective endocarditis and that circulating immune complexes are probably involved in the development of glomerulonephritis and vasculitis.

Adolescent↗
PubMed1981

Embryonic erythroid differentiation in the human leukemic cell line K562.

K562 human leukemia cells synthesize embryonic hemoglobins after culture in the presence of hemin. We have rigorously identified these hemoglobins by globin chain analysis and peptide mapping. No adult hemoglobin could be detected, and beta-globin synthesis was less than 2 ppm of total protein synthesis. Persistent embryonic globin gene expression is known to occur as a consequence of globin gene deletions. However, restriction endonuclease mapping showed that the globin gene complexes in K562 cells are indistinguishable from normal. Hemin increased the rate of embryonic globin synthesis. The pattern of hemoglobin synthesis proved to be stable when cells from different laboratories were compared. One line, however, synthesized large amounts of Hb X and very little Hb Portland in response to hemin. Hb X has been previously detected in human embryos; we show here that it has the composition epsilon 2 gamma 2 and is diagnostic of imbalanced chain synthesis or "zeta thalassemia." We have identified several agents that induce hemoglobin synthesis in K562 cells. Different inducers induced different patterns of embryonic hemoglobin synthesis but never any adult hemoglobin synthesis.

Cell Differentiation↗
PubMed1981

The mode of action of nosiheptide (multhiomycin) and the mechanism of resistance in the producing organism.

The mode of action of nosiheptide (multhiomycin) on bacterial protein synthesis is closely similar to that of thiostrepton. Both antibiotics inhibit functions of elongation factors Tu and G and greatly reduce the synthesis of guanosine penta- and tetraphosphates in response to stringent factor. Furthermore, the actinomycetes which produce these antibiotics defend themselves against their products in similar fashion. This involves specific pentose-methylation of 23S ribosomal RNA.

Anti-Bacterial Agents↗
PubMed1981

Concerning the mode of action of micrococcin upon bacterial protein synthesis.

The antibiotic, micrococcin, binds to complexes formed between bacterial 23-S ribosomal RNA and ribosomal protein L11 and, in doing so, inhibits of thiostrepton. In assay systems simulating partial reaction of protein synthesis, micrococcin inhibits a number of processes believed to involve the ribosomal A site while stimulating GTP hydrolysis dependent upon ribosomes and elongation factor EF-G. The latter effect is not observed upon ribosomes lacking a protein homologous with protein L11. Nor is it apparent upon those containing 23-S RNA previously subjected to the action of a specific methylase known to render ribosomes resistant to thiostrepton. It is concluded that stimulation by micrococcin of factor-dependent GTP hydrolysis results from the binding of the drug to its normal target site which involves 23-S RNA and protein L11.

Anti-Bacterial Agents↗
PubMed1981

Regulation of methyl-beta-d-thiogalactopyranoside-6-phosphate accumulation in Streptococcus lactis by exclusion and expulsion mechanisms.

Starved cells of Streptococcus lactis ML3 (grown previously on galactose, lactose, or maltose) accumulated methyl-beta-D-thiogalactopyranoside (TMG) by the lactose:phosphotransferase system. More than 98% of accumulated sugar was present as a phosphorylated derivative, TMG-6-phosphate (TMG-6P). When a phosphotransferase system sugar (glucose, mannose, 2-deoxyglucose, or lactose) was added to the medium simultaneously with TMG, the beta-galactoside was excluded from the cells. Galactose enhanced the accumulation of TMG-6P. Glucose, mannose, lactose, or maltose plus arginine, was added to a suspension of TMG-6P-loaded cells of S. lactis ML3, elicited rapid expulsion of intracellular solute. The material recovered in the medium was exclusively free TMG. Expulsion of galactoside required both entry and metabolism of an appropriate sugar, and intracellular dephosphorylation of TMG-6P preceded efflux of TMG. The rate of dephosphorylation of TMG-6P by permeabilized cells was increased two-to threefold by adenosine 5'-triphosphate but was strongly inhibited by fluoride. S. lactis ML3 (DGr) was derived from S. lactis ML3 by positive selection for resistance to 2-deoxy-D-glucose and was defective in the enzyme IIMan component of the glucose:phosphotransferase system. Neither glucose nor mannose excluded TMG from cells of S. lactic ML3 (DGr), and these two sugars failed to elicit TMG expulsion from preloaded cells of the mutant strain. Accumulation of TMG-6P by S. lactis ML3 can be regulation by two independent mechanisms whose activities promote exclusion or expulsion of galactoside from the cell.

Biological Transport↗
PubMed1981

Uptake and metabolism of sucrose by Streptococcus lactis.

Transport and metabolism of sucrose in Streptococcus lactis K1 have been examined. Starved cells of S. lactis K1 grown previously on sucrose accumulated [14C]sucrose by a phosphoenolpyruvate-dependent phosphotransferase system (PTS) (sucrose-PTS; Km, 22 microM; Vmax, 191 mumol transported min-1 g of dry weight of cells-1). The product of group translocation was sucrose 6-phosphate (6-O-phosphoryl-D-glucopyranosyl-1-alpha-beta-2-D-fructofuranoside). A specific sucrose 6-phosphate hydrolase was identified which cleaved the disaccharide phosphate (Km, 0.10 mM) to glucose 6-phosphate and fructose. The enzyme did not cleave sucrose 6'-phosphate(D-glucopyranosyl-1-alpha-beta-2-D-fructofuranoside-6'-phosphate). Extracts prepared from sucrose-grown cells also contained an ATP-dependent mannofructokinase which catalyzed the conversion of fructose to fructose 6-phosphate (Km, 0.33 mM). The sucrose-PTS and sucrose 6-phosphate hydrolase activities were coordinately induced during growth on sucrose. Mannofructokinase appeared to be regulated independently of the sucrose-PTS and sucrose 6-phosphate hydrolase, since expression also occurred when S. lactis K1 was grown on non-PTS sugars. Expression of the mannofructokinase may be negatively regulated by a component (or a derivative) of the PTS.

Biological Transport↗
PubMed1981

CT approach to benign nasopharyngeal masses.

The physical characteristics of the fascial planes of the nasopharynx provide a basis for categorizing growth patterns of the more common benign nasopharyngeal masses. Lymphoid hyperplasias are confined to the surface by the very dense pharyngobasilar fascia that lies beneath the submucosa. It takes a very aggressive process to cross this fascial plane. More laterally throughout the paranasopharyngeal space the loose areolar nature of the buccopharyngeal fascia permits benign tumors in this space to assume a spherical configuration. The carotid sheath is also a loose areolar arrangement that permits free movement of the carotid artery in the neck. Juvenile angiofibromas permeate natural foramina, displace bony septa, and extend widely but do not invade the carotid sheath. Neurogenic tumors and paragangliomas are intimately associated with contents of the carotid sheath; therefore, they obliterate the low density regions surrounding the carotid vessels.

Fascia↗
PubMed1981

Patterns of illness in the highly febrile young child: epidemiologic, clinical, and laboratory correlates.

Three hundred one episodes of fever greater than or equal to 103 F were documented in 375 infants and young children observed in a comprehensive care clinic during the period October 1974 to October 1978. Of such highly febrile illnesses 79% were accompanied by respiratory tract signs or symptoms, 7% by disease at a site other than the respiratory tract, and 22% of illnesses had no localizing signs or symptoms. Viral cultures were obtained from the respiratory tract in 178 cases and were positive in 68: 57/134 from respiratory illness; 2/4 from illness at sites other than the respiratory tract; and 9/40 in children without localizing disease. Bacterial cultures of the upper respiratory tract were obtained in 191 illnesses, but the overall rate of isolation of Haemophilus influenzae, Streptococcus pneumoniae and group A streptococci (46%) did not differ from that in a group of well children (39%). Bacterial cultures of the blood were obtained in 89 patients with fever greater than or equal to 103 F and in an additional 41 children with lower temperatures. Nine children had documented systemic bacterial disease (eight positive blood cultures and one positive CSF). The rate of clinically apparent systemic bacterial disease in these otherwise normal infants was one bacteremic episode per 94 years of child care.

Anti-Bacterial Agents↗
PubMed1981

Heterogeneity of malignant cells from a human colonic carcinoma.

Three subpopulations of malignant cells were isolated from a primary cell culture of a single human colonic carcinoma. The variant cells were established as cell lines designated HCT 116, HCT 116a, and HCT 116b, respectively. In vitro characterizations of the variant lines included growth in 0.5% agarose and growth on confluent layers of mouse fibroblasts. HCT 116a showed the highest colony formation in agarose and on confluent fibroblasts, while colony formation by HCT 116 was higher than that of HCT 116b in both of these systems. All of the variant lines were tumorigenic in athymic nude mice given injections of 10 x 10(6) cells, but the time between inoculation and tumor development (latency period) was approximately 10 times longer for HCT 116b as for HCT 116a and 8 times longer than for HCT 116. HCT 116b was not tumorigenic at an inoculum of 5 x 10(6) cells, while both HCT 116 and 116a were tumorgenic at this level. However, HCT 116a was clearly more tumorigenic than was HCT 116 on the basis of the number of animals developing tumors at inoculate of both 10 x 10(6) and 5 x 10(6) cells and on the basis of their differences in latency periods. While all the cell lines had near diploid numbers of chromosomes, each line showed a distinct histological pattern when grown as xenografts in athymic nude mice.

Animals↗
PubMed1981

The role of incompetence of the anterior cruciate and lateral ligaments in anterolateral and anteromedial instability. A biomechanical study of cadaver knees.

UNLABELLED: The anterolateral and anteromedial stability of seventeen fresh frozen cadaver knees was studied in a test apparatus designed to simulate physiological conditions. Statistically significant increases in internal rotation occurred in seven knees when only the anterior cruciate ligament was sectioned, and these increases were enhanced by subsequent sectioning of the posterolateral complex and the lateral collateral ligament, singly or in combination. On the other hand, sectioning of the posterolateral complex and of the lateral collateral ligament, leaving the anterior cruciate intact, did not produce significant increases in internal rotation until the anterior cruciate ligament was sectioned in seven knees. When the entire anterolateral capsule was sectioned as far posterior as the lateral collateral ligament in three knees, no changes in internal or external rotation occurred. Only when the posterolateral complex was sectioned was there a significant increase in external rotation in any of the ligament-sectioning sequences. Thus, it appears that for pathological internal rotation of the tibia on the femur to occur, the anterior cruciate ligament must be incompetent. CLINICAL RELEVANCE: The test apparatus and the results are useful in assessing which ligament structures contribute to clinically noted rotational knee instabilities.

Biomechanical Phenomena↗