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Biomedical subjects

R Laskowski

Publications and source records attributed to R Laskowski.

16 recordsLinked to original sources
PubMed2000

Comparative in vitro activity of gatifloxacin, grepafloxacin, levofloxacin, moxifloxacin and trovafloxacin against 4151 Gram-negative and Gram-positive organisms.

Gatifloxacin, grepafloxacin, moxifloxacin and trovafloxacin are fluoroquinolones with enhanced Gram-positive activity while retaining broad-spectrum activity against Gram-negative pathogens. Levofloxacin and ciprofloxacin are older quinolones with broad activity against Gram-negative pathogens and borderline activity against some Gram-positive organisms. We compared the in vitro activity of these compounds against 4151 Gram-negative and -positive organisms. Gatifloxacin, grepafloxacin, moxifloxacin and trovafloxacin were highly active against penicillin sensitive and resistant Streptococcus pneumoniae, Staphylococcus aureus, Streptococcus pyogenes and Streptococcus agalactiae. Ciprofloxacin and levofloxacin were active but less potent. All compounds were highly active (overall) against Gram-negative pathogens with ciprofloxacin being the most active agent against Pseudomonas aeruginosa. Our data indicate that the advanced fluoroquinolones will be important compounds for treating infections caused by Gram-positive and Gram-negative pathogens.

Anti-Infective Agents↗
PubMed1999

In-vitro activity of cefepime and seven other antimicrobial agents against 1518 non-fermentative Gram-negative bacilli collected from 48 Canadian health care facilities. Canadian Afermenter Study Group.

Non-fermentative bacilli are primarily nosocomial pathogens, and are also often resistant in vitro to a broad range of antimicrobial agents. In this large Canadian study, we collected 1466 clinical, non-repeat isolates of Pseudomonas aeruginosa, 21 of Acinetobacter spp. and 31 Stenotrophomas maltophilia. MICs of eight antibiotics were determined by the NCCLS microdilution method in a central laboratory. Tobramycin was the most active agent against P. aeruginosa (94.5% susceptible); amikacin and imipenem were the most active against Acetinobacter spp. (100%) and ceftazidime was the most active against S. maltophilia (40.6%). Against each group of isolates, cefepime was active against 87, 86.4 and 15.6%, respectively. This in-vitro study showed that cefepime may be a useful additional agent in the treatment of infections caused by P. aeruginosa and Acinetobacter spp., but not when S. maltophilia is considered pathogenic.

Anti-Bacterial Agents↗
PubMed1998

Effect of heavy metals and storage time on two types of forest litter: basal respiration rate and exchangeable metals.

Two types of forest litter, MOR and MULL, were treated with 0 (control), 25, 100, 400, 1600, and 6400 mg kg-1 Cd, Cu, Pb, or Zn after different storage times (35, 75, and 125 days at approx 5 degreesC). Highly significant effects on respiration rate were observed for dose of heavy metals, type of litter, type of metal, and storage time. The respiration rate of untreated MULL litter was lower than that of untreated MOR in all incubations, and the slope of the relation to the dose of metals was steeper for MOR. Respiration rates after storage were lower than in fresh litter, and the slope of the relation between respiration rate and metal dose was less steep after storage. In the first incubation, MULL litter was more sensitive to Cd, Cu, and Pb and less sensitive to Zn than MOR litter. After 125 days of storage, no single significant effect was found in MULL litter, whereas in MOR litter all metals still inhibited respiration rate significantly. The relative toxicity of metals was similar for both litter types, and the average EC50respiration values were (mg kg-1) Cu=3880, Zn=5610, Cd=6320, and Pb=24800. The percentages of exchangeable metals (1 M NH4OAc, pH=7) in MULL litter were lower on average than in MOR litter, and the order of solubility of the metals was Cd>Zn>Pb>Cu. Storage caused no significant difference in the average percentage of exchangeable metal. The highest doses of heavy metals increased the amounts of Ca, K, Mg, and Na extracted.

Cadmium↗
PubMed1997

Heat shock proteins (HSP70) as biomarkers in ecotoxicological studies.

Hsp70, so-called stress proteins, were studied in the centipede Lithobius mutabilis when exposed in laboratory tests to different concentrations of the insecticide dimethoate (DMT; 0, 0.012, 0.111 mg kg-1 dwt), the detergent linear alkilobenzene sulfonate (LAS; 0, 16, 80, 400, 2000, 10,000 mg kg-1 dwt), and copper (Cu; 0, 56, 167, 500, 1000, 1500 mg kg-1 dwt) and in the field in captured animals from polluted (2 and 4 km from a zinc-and-lead smelter) and unpolluted (35 and 40 km from the smelter) areas. Hsp70 in centipedes were also tested for seasonal differences (March and September) in field-captured animals and for a temperature effect under laboratory conditions (5, 15, and 25 degrees C). Moreover, hsp70 were examined in housefly (Musca domestica) pupae after rearing larvae on food medium contaminated with DMT or LAS. Hsp70 were found in all animals tested, including controls, and their levels were not clearly related to the laboratory treatment with chemicals or temperature or to the degree of contamination in polluted areas. In centipedes from unpolluted areas, a significant seasonal difference in hsp70 content was found. The problems with using hsp70 as a universal biomarker in ecotoxicological studies are discussed.

Animals↗
PubMed1996

Effect of Zn, Cu, Pb, and Cd on fitness in snails (Helix aspersa).

Juveniles and adults of the Brown garden snail (Helix aspersa Müll.) were fed on an artificial diet contaminated with Zn (ca. 40-12,000 micrograms.g-1 dry wt), Cu (ca. 9-1600 micrograms.g-1 dry wt), pb (ca. 0.4-12,700 micrograms.g-1 dry wt), Cd (ca. 0.16-145 micrograms.g-1 dry wt), and all four metals mixed together for 120 days. Significant negative exponential regressions of food consumption and fecundity on concentrations were found for all treatments. Growth rate was affected significantly only by Zn and mixed treatments. The calculated EC20(consumption) values for juveniles were (in microgram.g1): Zn, 855; Cu, 248; Pb, 5290; Cd, 60; and for adults: Zn, 1240; Cu, 275; Pb, 3120; Cd, 147. In mixed treatment EC20(consumption) values were substantially lower indicating the additive effect of pollution with these four metals. EC20(consumption) for Zn in mixed treatment was 329 micrograms.g-1 for juveniles and 661 micrograms.g-1 for adults. The following EC20 values were estimated for fecundity (in micrograms.g-1): Zn, 1740; Cu, 533; Pb, 6140; Cd, 120; Zn in mixed treatment, 2210. The relative toxicities of the four metals were compared with their ratios in contaminated field sites. Comparing Zn and Cd, for example, even though Zn is ca. 13-24 times less toxic than Cd, it is usually present in plants and forest litter in concentrations ca. 100 times greater than those of Cd. Thus, of these two metals, Zn appeared to be potentially the most important pollutant in ecologically relevant situations. No effect of any treatment on mortality was found during the 4-month experiment. The calculated scenarios of population dynamics under the stress of chronic pollution with mixtures of the four metals revealed that the delayed reproduction due to estivation of snails may be the main cause of population decline at high metal concentrations in food. However, at concentrations at and below ca. 1000 micrograms Zn.g-1 in food, if the reproduction is not delayed the population may persist for a long time (0.25 control number after 50 years).

Aging↗