PubMed Health⌕ Search

Biomedical subjects

M Buck

Publications and source records attributed to M Buck.

179 records · Page 10Linked to original sources
PubMed1981

Iron-related modification of bacterial transfer RNA.

Transfer RNAs isolated from E. coli grown in media where ferric iron is not freely available show well characterized chromatographic changes due to the absence of the methylthio moiety of ms2i6A. The altered tRNA molecules include tRNA trp tRNA tyr, tRNA phe and two minor tRNA ser species. It has been suggested that methylthiolation of tRNA affects its function in regulation. We now show iron-related changes in tRNA trp from S. typhimurium, Ps. aeruginosa and K. pneumoniae. tRNA trp from S. typhimurium contains ms2i6A and it seems probable that the availability of iron affects the synthesis of ms2i6A-tRNA trp from i6A-tRNA trp in this organism. An iron-related methylthiolating system may also be operative in K. pneumoniae. S. marcescens tRNA trp, however was not affected by the availability of iron. Neither ms2i6A nor i6A was found in S. marcescens tRNA, although an, as yet unidentified, hydrophobic nucleoside was present.

Bacteria↗
PubMed1981

Regulation of aromatic amino acid transport by tRNA: role of 2-methylthio-N6-(delta2-isopentenyl)-adenosine.

E. coli growing rapidly in media where ferric iron is not freely available contain a population of specifically undermodified tRNAs. These tRNAs contain isopentenyl adenosine instead of the usual methylthioisopentenyl adenosine adjacent to the 3' end of the anticodon. Iron restricted E. coli also show an enhanced capacity to transport aromatic amino acids into the cell. Our work shows that undermodified tRNAs for phe, tyr and trp can function as positive regulatory elements of the aromatic amino acid transport system in E. coli. This iron related metabolic control, mediated through a specific post-transcriptional modification of the tRNAs, may be an important mechanism for adapting E. coli for growth in an iron restricted environment.

Adenosine↗
PubMed1981

Airway reactivity in cotton bract-induced bronchospasm.

Most healthy subjects challenged with cotton bract extract demonstrate some degree of bronchospasm. This response has been associated with the endogenous production of histamine by the inhalation of cotton bract extract. We examined whether this responsiveness reflects increased sensitivity to histamine. Thirty-one healthy subjects were screened for sensitivity to cotton bract extract administered by nebulization. Pulmonary function was measured using partial expiratory flow-volume curves on which flows at 60% of the control vital capacity below total lung capacity were measured (MEF40%(P)). Responders were defined as subjects who exhibited a 20% or greater decrease in MEF40%(P) after 10 min inhaling cotton bract extract. Of those screened, 10 subjects were responders. From the remaining nonresponders, 11 consecutive subjects were selected. The maximal decrease in MEF40%(P) in responders was 40.5 +/- 5.1%, compared to 10.9 +/- 2.2% in nonresponders. The dose-response relationship for histamine was measured in all subjects, using inhalations of progressively more concentrated histamine solutions. The mean +/- SEM threshold for the responders was 38.4 +/- 7.4 mg of histamine per ml, compared to 42.2 +/- 6.8 mg of histamine per ml for responders (difference not significant). The percentage decrease in MEF40%(P) at the threshold dose was 27.6 +/- 3.7% for responders and 32.4 +/- 5.2% for nonresponders (difference not significant). We conclude that healthy subjects sensitive to cotton bract extract do not exhibit increased reactivity to histamine. This suggests that responders are not, in general, subclinical asthmatics, and that the difference between responders and nonresponders to CBE is not due to increased histamine sensitivity among responders.

Adult↗
PubMed1978

Activity of 10-chloro-5-(2-dimethylaminoethyl)-7H-indolo [2,3-c]-quinolin-6(5H)-one hydrochloride against experimental tumors in mice and rats.

10-Chloro-5-(2-dimethylaminoethyl)-7H-indolo [2,3-c]-quinolin-6(5H)-one hydrochloride (CIQ) was shown to exert significant antitumor activity against the Ehrlich carcinoma and sarcoma 180 transplantable tumors in mice by the intraperitoneal (ip) or oral (po) routes and when incorporated into diet. A solid tumor induced in BALB/c mice by the subcutaneous (sc) implantation of nonproducer murine sarcoma virus-transformed BALB/3T3 cells was also inhibited by CIQ after ip or po treatment but there was no effect against leukemia L1210 ascites or a transplantable murine renal adenocarcinoma. When tested in rats, CIQ significantly reduced the growth of Flexner-Jobling carcinoma, Murphy-Sturm lymphosarcoma and Walker 256 carcinosarcoma when administered by the ip or po routes. Pretreatment, but not posttreatment, with CIQ slightly inhibited the humoral antibody response of mice to sheep red blood cells. CIQ therefore differs from immunosuppressive agents such as imuran, methotrexate, cytosine arabinoside, or 6-mercaptopurine which affect the antibody response of mice to sheep erythrocytes when administered after immunization.

Adenocarcinoma↗
PubMed1977

Dihydroretinoic acids and their derivatives. Synthesis and biological activity.

The syntheses of the ring and four side-chain dihydroretinoic acids and/or their esters, 3-7, are described. The syntheses of several other retinoids containing a substituted aromatic ring are also included. The biological activity of the compounds was evaluated in vivo in a chemically induced mouse skin papilloma test and in vitro in two vitamin A deficient assays. The activity observed for 1a, 1c, and 2a in the former test was partially retained in the dihydro derivatives 4b, 4c, and 6b. Similar results were found in the in vitro assays.

Animals↗
PubMed1975

[Recent information on air pollution impact in North-Rhine-Westphalia (author's transl)].

Since 1963, air quality in the Rhine-Ruhr-area, one of the largest agglomerations of industry, population, and traffic in Europe, is systematically monitored and the levels are documented in the form of on air pollution cataster. The surveilled area comprises about 5000 km2. Within the first years, measurements were made with the air pollutants sulphur dioxide and dust fall out. Later, the following air pollutants were included into the monitoring program: Hydrogen fluoride, hydrogen chloride, suspended particles, as well as the determination of total organic substances. In smaller regions within the surveilled area, measurements of the following air polutants were made, too: Nitrogen monoxide, nitrogen dioxide, hydrogen sulphide, carbon disulphide, benzene, phenol, carbon monixide, oxidants, as well as determinations of lead, cadmium, and zinc content in suspended particles and dust fall out. Besides the demonstration of the tasks within the air quality monitoring program, the projection as well as the execution of air pollution measurements are discussed. Definitions of impact characteristics and the adjusted legal air quality standards are given in more detail. Finally, an evaluation of the results of this monitoring program is given for each pollutant. Furthermore, the trends of air pollution and its causes since the beginning of air quality monitoring in 1963 are evaluated.

Air↗
PubMedDate not supplied

Lysis-centrifugation blood cultures in the detection of tissue-proven invasive candidiasis. Disseminated versus single-organ infection.

Several studies have demonstrated significantly higher frequency and more rapid detection of candidemia with blood culture methods performed by lysis-centrifugation (LC) in comparison with other techniques. Little is known, however, about the ability of LC blood culture methods to detect tissue-proven invasive candidiasis. We therefore investigated the sensitivity of LC blood cultures in the detection of tissue-proven invasive candidiasis. Between 1985 and 1991, invasive candidiasis was detected in 41 (5.1%) of 803 autopsies at the Clinical Center of the National Institutes of Health (Bethesda, MD, USA). Cases were classified as single-organ (SO) candidiasis (n = 20) and as disseminated candidiasis (DI) (n = 21). Patients with DI were more likely than those with SO to have a hematologic malignancy (71% vs 15%, P < 0.001) and to have gastrointestinal mucosal candidiasis (76% vs 25%, P = 0.003). LC detected fungemia in 16 (43%) of all 37 cases with blood cultures. When analyzed by classification, Candida spp. were isolated from blood in 11 (58%) of 19 patients with DI and in five (28%) of 18 patients with SO (P = 0.13). When analyzed by number of organs infected, blood cultures were positive in seven (78%) of nine patients with > 3 organs infected by Candida in comparison to five (28%) of 18 patients with one organ infected (P = 0.024). The mean recovery time for Candida in blood cultures was 2.6 days in DI and 3.2 days in SO (P = 0.017). There was no difference in colonies of organisms per LC tube between patients with DI and those with SO.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Pharmacologic management of acute pain in the orthopaedic patient.

Postoperative pain remains undertreated. Barriers to adequate postoperative analgesia include lack of knowledge regarding pain and its management, inadequate assessment, preconceived notions by nurses and physicians regarding pain and addiction, and the continued use of PRN administration of medications instead of active intervention on a scheduled basis. Knowledge regarding the physiology of pain provides nurses with information necessary to control pain. Pharmacologic management includes the use of nonopioids, opioids, and various adjuvant drugs. Principles regarding the use of these analgesics guide the nurse to use these drugs to their greatest effect. The special needs of the very young and the elderly must also be considered.

Analgesics↗
PubMedDate not supplied

Time to go home.

Explore the source record for details and available documents.

Aged↗