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Biomedical subjects

N Pearson

Publications and source records attributed to N Pearson.

30 records · Page 2Linked to original sources
PubMed1993

Effects of lindane on macroinvertebrates and periphyton in outdoor artificial streams.

A system of six outdoor artificial streams (dimensions 5.0 X 0.35 X 0.25 m) was used to study the biological effects of lindane in flowing water. Lindane was continuously applied during 28 days to four of the streams while two were left as untreated controls. The nominal concentrations were 4.0, 8.0, 16.0, and 32.0 micrograms liter-1 and the mean measured concentrations of lindane in stream water over 28 days were 3.1, 5.7, 11.1, and 20.3 micrograms liter-1. Effects were observed on population densities of the freshwater shrimp Gammarus pulex, drift of G. pulex and mayflies (Baetis spp.), and on community photosynthesis. An increase in photosynthetic production of oxygen, a result of increased periphyton standing crop, followed the loss of macroinvertebrates, via drift, from the treated streams. This established a clear link between a direct effect of lindane on macroinvertebrates and an indirect effect on periphyton production. Drift and community photosynthesis were the most sensitive of the biological parameters measured and effects were detected in all treated streams. During a 28-day experiment with lower concentrations of lindane, nominally 0.25 and 1.0 micrograms liter-1, there were minor effects on the drift of Baetis spp. but only at the higher concentration. There were no detected effects on population densities or on community photosynthesis. Results from the two experiments provided a measured no observed effect concentration for lindane of 0.2 micrograms liter-1 and the threshold concentration for sustained effects on the stream communities was in the range 0.8 to 3.1 micrograms liter-1.

Animals↗
PubMed1993

Rapid broth macrodilution method for determination of MICs for Mycobacterium avium isolates.

A multicenter study was done to investigate the accuracy and reproducibility of a method for determining the MICs of antimicrobial agents against the Mycobacterium avium complex in 7H12 broth with the BACTEC system. In phase I, with eight drugs and 10 strains, intralaboratory reproducibility was 95.7 to 100%, allowing a 1-dilution difference upon repeat testing. The results of phase II testing with 41 additional strains were consistent with those obtained in phase I, with good interlaboratory reproducibility. The radiometric method was validated by sampling and plating of the same broth cultures and determining, by the number of CFU per milliliter, the lowest drug concentration that inhibited more than 99% of the initial bacterial population. Three test concentrations of each drug and the tentative interpretation of results are proposed. Radiometric MIC determination has the potential to become the method of choice for clinical microbiology laboratories and evaluation of new agents for the treatment of M. avium infections, both pulmonary and disseminated.

Anti-Bacterial Agents↗
PubMed1993

Effects of simulated high altitude exposure on long-latency event-related brain potentials and performance.

The N100, P200, N200 and P300 components of the auditory event-related potential were recorded from 10 male subjects at 0900, 1600, and 1830 hours at sea level and again following a rapid ascent to simulated 4300 m altitude. Amplitude and latency of components, ear oximetry, and concurrent performance measures (reaction time and counting errors) were assessed. Amplitude of P300 decreased, while P300 latency and reaction time increased, following ascent to altitude. However, the time course of altitude effects differed for amplitude versus latency. Components N100, P200, N200, and counting errors were unaffected by altitude. The results indicate that central measures of cognitive capacities are differentially sensitive to high altitude. The time course of altitude effects on P300 amplitude versus P300 latency suggests that the two measures reflect different aspects of a response to hypobaric hypoxia exposure.

Adult↗
PubMed1989

A 1.5-megabase restriction map surrounding MYC does not include the translocation breakpoint in familial renal cell carcinoma.

A constitutional translocation t(3;8)(p14.2;q24.1) segregates concordantly with a familial form of renal cell carcinoma (RCC). This translocation moves the MYC oncogene, located at 8q24.1, onto the short arm of chromosome 3. Chromosome rearrangements that break in or near MYC can result in altered expression of this gene and are thought to be a primary change leading to the transformed phenotype in certain neoplastic diseases, particularly Burkitt lymphoma. Possible rearrangements of this gene in familial RCC have so far not been detected using standard Southern blot analysis. We used pulsed field gel (PFG) analysis to construct a restriction map that covers a 1500-kb region surrounding MYC, including over 1000 kb to the 5' and 550 kb to the 3' side of this gene. The 5' end of MYC contains a cluster of cleavage sites for rare-cutting restriction endonucleases, indicating the presence of an HTF island. PFG analysis of DNA containing the t(3;8) rearrangement shows that the breakpoint is not located in the mapped region, making it unlikely that MYC is involved in this form of renal cell carcinoma. The map should facilitate study of other chromosome 8 rearrangements thought to break near MYC.

Carcinoma, Renal Cell↗
PubMed1981

In-vitro activity of the novel oxa-beta-lactam antibiotic moxalactam (LY 127935) against dense populations of selected Gram-negative bacilli.

The activity of moxalactam, a new beta-lactam antibiotic with a novel molecular structure, was examined against dense populations of a variety of Gram-negative bacilli. The lytic activity of moxalactam against ampicillin-sensitive strains was similar to ampicillin, but the activity was maintained against ampicillin-resistant strains, including Pseudomonas aeruginosa, irrespective of whether the ampicillin resistance was 'intrinsic' (non-enzymic) or due to beta-lactamase. Of the 18 strains tested only one, a Hafnia sp., failed to respond to moxalactam.

Ampicillin↗
PubMed1980

Comparative in vitro activities of cefotaxime and ceftizoxime (FK749): new cephalosporins with exceptional potency.

Cefotaxime and its desacetoxymethyl derivative, ceftizoxime (previously known as FK749), are both extremely active against a wide spectrum of bacteria. In the present comparative study, the activity of ceftizoxime exceeded that of cefotaxime by a factor of four or more for strains of Klebsiella, Enterobacter, Providencia, Serratia, and Bacteroides; the only species for which the activity of cefotaxime exceeded that of ceftizoxime by a factor of four was Vibrio cholerae. Against other species, the activity of the two drugs was roughly comparable. Both showed outstanding activity against Haemophilus influenzae and Neisseria gonorrhoeae. Comparative turbidimetric and morphological studies revealed that ceftizoxime was able to induce spheroplast formation and rapid lysis in Escherichia coli strains at lower concentrations than cefotaxime. This difference was not found, however, when E. coli strains resistant to ampicillin by an intrinsic (nonenzymic) mechanism were tested.

Bacteria↗
PubMed1980

A microcomputer-based research system for the optical analysis of agar-cultured micro-organism colonies.

A system which has been developed for the automatic of agar-cultured microorganism colonies is described. A camera of the line-scanning type is used to scan the plates and details of the hardware and software development are explained. Flow diagrams are included which illustrate the operation of the system, but, as yet, no results are available. The prototype machine is undergoing evaluation testing.

Agar↗
PubMedDate not supplied

Effects of Ca channel blockers on Ca transport and Ca ATPase in skeletal and cardiac sarcoplasmic reticulum vesicles.

Several Ca channel blockers--verapamil, nifedipine, nimodipine (Bay e 9736), and nitrendipine (Bay e 5009)--had different effects on Ca transport by sarcoplasmic reticulum vesicles from either skeletal or cardiac muscle. Both nimodipine and nitrendipine (1 X 10(-4) M) stimulated Ca sequestration in the absence of a Ca-precipitating anion by either cardiac or skeletal sarcoplasmic reticulum (SR), with nitrendipine being the more potent stimulator. Nifedipine (1 X 10(-4)M) had no significant effect, whereas at higher concentrations (3 X 10(-3) M) verapamil inhibited the Ca sequestration reaction. Nitrendipine stimulated Ca ATPase and Ca sequestration to a similar extent. Stimulation of Ca sequestration by nitrendipine was dependent on drug/membrane phospholipid mole ratios of between 1:4 and 3:1, as well as absolute drug concentration thus suggesting an interaction of the drug with membrane phospholipids. Nifedipine, nitrendipine, nimodipine, and verapamil (1 X 10(-4)M) had no effect on phosphate-supported Ca uptake by skeletal SR, whereas higher concentrations of verapamil (3 X 10(-3)M) inhibited this reaction by either cardiac or skeletal SR. The results of this study suggest that (a) Ca channel blockers have complex and variable effects on SR membranes, (b) these effects are similar in cardiac and skeletal SR, and (c) the effects are in part mediated through an interaction with membrane phospholipids or hydrophobic portions of the Ca ATPase.

Absorption↗