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Biomedical subjects

M G Johnson

Publications and source records attributed to M G Johnson.

At least 19 recordsLinked to original sources
PubMed2006

Does soil CO2 efflux acclimatize to elevated temperature and CO2 during long-term treatment of Douglas-fir seedlings?

We investigated the effects of elevated soil temperature and atmospheric CO2 on soil CO2 efflux (SCE) during the third and fourth years of study. We hypothesized that elevated temperature would stimulate SCE, and elevated CO2 would also stimulate SCE with the stimulation being greater at higher temperatures. The study was conducted in sun-lit controlled-environment chambers using Douglas-fir (Pseudotsuga menziesii) seedlings grown in reconstructed litter-soil systems. We used a randomized design with two soil temperature and two atmospheric CO2 treatments. The SCE was measured every 4 wk for 18 months. Neither elevated temperature nor CO2 stimulated SCE. Elevated CO2 increased the temperature sensitivity of SCE. During the winter, the relationship between SCE and soil moisture was negative but it was positive during the summer. The seasonal patterns in SCE were associated with seasonal changes in photosynthesis and above-ground plant growth. SCE acclimatized in the high-temperature treatment, probably because of a loss of labile soil carbon. Elevated CO2 treatment increased the temperature sensitivity of SCE, probably through an increase in substrate availability.

Acclimatization↗
PubMed2006

Elevated CO(2) and elevated temperature have no effect on Douglas-fir fine-root dynamics in nitrogen-poor soil.

Here, we investigate fine-root production, mortality and standing crop of Douglas-fir (Pseudotsuga menziesii) seedlings exposed to elevated atmospheric CO(2) and elevated air temperature. We hypothesized that these treatments would increase fine-root production, but that mortality would be greater under elevated temperature, leading to a smaller increase in standing crop. Seedlings were grown in outdoor, sun-lit controlled-environment chambers containing native soil. They were exposed in a factorial design to two levels of atmospheric CO(2) and two levels of air temperature. Minirhizotron methods were used to measure fine-root length production, mortality and standing crop every 4 wk for 36 months. Neither elevated atmospheric CO(2) nor elevated air temperature affected fine-root production, mortality, or standing crop. Fine roots appeared to root deeper in the soil profile under elevated CO(2) and elevated temperature. Low soil nitrogen (N) levels apparently limited root responses to the treatments. This suggests that forests on nutrient-poor soils may exhibit limited fine-root responses to elevated atmospheric CO(2) and elevated air temperature.

Carbon Dioxide↗
PubMed2005

Respiratory infection of turkeys with Listeria monocytogenes Scott A.

The pathogenesis of L. monocytogenes strain Scott A was studied by challenging day-old male turkey poults by air sac inoculation with tryptose phosphate broth containing 10(0) cfu (control), 10(4), 10(5), and 10(6) cfu (low challenge), or 10(7) and 10(8) cfu (high challenge) of the Scott A (serotype 4b) strain of L. monocytogenes. Mortality at 2 wk postinfection (PI) ranged from 25% for low challenge to 100% for high challenge (P= 0.0001). Gross and histopathological lesions were observed in heart, liver, spleen, lung, and bursa of Fabricius of mortalities at 4 days PI. Listeria monocytogenes challenge resulted in significantly decreased relative weight of the bursa of Fabricius and increased relative weight of the spleen, and L. monocytogenes was isolated by direct plating of liver, pericardium, brain, and both left and right stifle joint synovium (knee) cultures, as well as gall bladder, yolk sac, and cecal tonsil from transfer swabs onto Listeria-selective agar. Isolates were confirmed as positive using Gram stain, biochemical tests, and the Biolog system. High challenge resulted in confirmed L. monocytogenes isolation from 48% of left knee and 59% of right knee cultures. Low challenge resulted in isolation of L. monocytogenes from 11% of both left and right knee cultures. These results suggest that L. monocytogenes Scott A colonization of turkey knee synovial tissue can initiate in day-of-age poults and that L. monocytogenes Scott A can be invasive through air sac infection.

Animals↗
PubMed2005

Transmission electron microscopy study of enterohemorrhagic Escherichia coli O157:H7 in apple tissue.

We investigated the ability of enterohemorrhagic Escherichia coli O157:H7 to spread in wounded apple tissue by transmission electron microscopy. Red Delicious apples were wounded with an artist knife (7 mm depth) and either inoculated with 10 microl per wound of decimally diluted E. coli O157:H7 or submerged into E. coli O157:H7 suspended in sterile distilled water and then stored at 37 degrees C for 24 h. Transmission electron microscopy showed E. coli O157:H7 formed bacterial aggregates near the apple cell walls, and single cells were in close proximity to the apple cell wall surfaces and to plasma membranes. E. coli O157:H7 presence caused degradation of plasma membranes and release of the cytoplasm contents of the apple cortical cells into the central vacuole. Apple tissue turgor pressure tests showed that the apple cells infected with E. coli O157:H7 isolates were more likely to rupture than the control noninoculated apple cells. E. coli O157:H7 cells grown in apple tissue showed the formation of granules and vesicles within the bacterial cytoplasma and separation of the plasma membranes. Our study shows that E. coli O157:H7 can grow and survive in the apple tissue environment by causing degradation of the apple cellular components.

Colony Count, Microbial↗
PubMed2005

Fate of Listeria monocytogenes inoculated onto the surface of model Turkey frankfurter pieces treated with zein coatings containing nisin, sodium diacetate, and sodium lactate at 4 degrees C.

The antimicrobial effects of zein coatings containing nisin, sodium lactate, and sodium diacetate against Listeria monocytogenes on turkey frankfurters at 4 degrees C were determined. Our objectives were to determine whether zein, nisin, lactate, and diacetate alone or in combination could control the growth of L. monocytogenes on full-fat turkey frankfurters at 4 degrees C and to determine whether lactate or diacetate had any synergistic effect on the activity of nisin. Turkey frankfurter pieces surface inoculated with L. monocytogenes strain V7 were treated with zein-ethanol-glycerol (ZEG), zein-propylene-glycol (ZPR), ethanol-glycerol (EG), propylene glycol (PR), nisin (N), sodium lactate (L), or sodium diacetate (D) alone or in combination. Over 28 days, treatment with N or D alone reduced L. monocytogenes counts on frankfurters by 6.6 or 6.3 log CFU/g, respectively. N-D treatment reduced L. monocytogenes by 6 log CFU/g. The zein solvents EG and PR reduced L. monocytogenes by about 5.6 and 5.2 log CFU/g, respectively, similar to the results obtained with ZEG and ZPR, which suggests that zein powder per se had no antimicrobial activity. After 28 days, ZEG-N-D, ZEG-N-D-L, ZPR-N-D, and ZPR-N-D-L yielded no detectable CFU. L alone was ineffective. No synergies were observed. N and D when used singly and the combinations of N-D, ZEG-N-D, ZEG-N-D-L, ZPR-N-D, ZPR-N-D-L, EG, and PR were effective as inhibitors of the growth of recontaminating L. monocytogenes cells on full-fat turkey frankfurters.

Animals↗
PubMed2004

A multicentre randomised controlled trial of an intervention to improve the accuracy of linear growth measurement.

AIMS: To evaluate linear growth assessment and the effect of an intervention on measurement accuracy in primary care practices (PCP) within eight US geographical areas. METHODS: In this multicentre randomised controlled intervention study, paediatric endocrine nurses as site coordinators (SC) visited 55 randomly assigned PCP to evaluate growth assessment of staff performing linear measurements. SC observed 127 measurers assessing a total of 878 children: 307 (baseline), 282 (3 months), and 289 (6 months). Accuracy was determined by SC re-measuring each child with correct technique and equipment. State of the art equipment and a standardised growth training session were provided to the intervention group (IG) following the baseline visit. SC repeated data collection at all PCP at 3 and 6 months. RESULTS: There were no baseline differences between IG and CG equipment, technique, or accuracy; only 30% of measurements were accurate (< or =0.5 cm from SC). Post-intervention, significantly more IG measurements were accurate: IG = 55%, CG = 37% at 3 months; IG = 70%, CG = 34% at 6 months. Odds ratio of accuracy for IG versus CG was 2.1 at 3 months and 4.5 at 6 months. At 6 months, mean difference from the SC measurements was 0.5 cm in IG and 1.1 cm in CG. CONCLUSIONS: In PCP, children are measured inaccurately. Our intervention significantly improved measurement accuracy. Improved accuracy could yield more rapid detection and diagnosis of paediatric growth disorders.

Adolescent↗
PubMed2004

Radiation resistance and virulence of Listeria monocytogenes Scott A following starvation in physiological saline.

The influence of starvation on the resistance of Listeria monocytogenes Scott A to electron beam irradiation in 0.85% (wt/vol) NaCl (saline) and in ground pork was investigated. Exponential- or stationary-phase cells (control) were grown at 35 degrees C in tryptic soy broth supplemented with 0.6% yeast extract. Washed cells were starved for 12 days in saline, and virulence of the pathogen was evaluated at 0, 8, and 12 days during starvation. Samples of saline and irradiation-sterilized ground pork, inoculated with control or starved cells, were irradiated at doses ranging from 0.0 to 2.5 kGy. L. monocytogenes survivors were determined by plating diluted samples of saline or pork on tryptic soy agar supplemented with 0.6% yeast extract and counting bacterial colonies following incubation (35 degrees C, 48 h). Virulence of starved cells and control was not significantly different (P > 0.05). Cells exhibited the highest radiation resistance at 8 days of starvation. Irradiation (0.5 kGy) in saline resulted in approximately 7.14, 5.55, and 2.38 log reduction in exponential, stationary, and starved cells, respectively. Irradiation of ground pork at 2.5 kGy reduced controls by approximately 6.0 log, whereas starved cells were reduced by only 3.8 log. Starved cells consistently exhibited higher irradiation D10-values than controls (P < 0.05). D10-values for exponential, stationary, and starved cells were 0.07, 0.09, and 0.21 kGy and 0.35, 0.42, and 0.66 kGy in saline and ground pork, respectively. These results indicate that starvation cross-protects L. monocytogenes Scott A against radiation inactivation and should be considered when determining this pathogen's irradiation D-value.

Adaptation, Physiological↗
PubMed2003

The role of dietary vitamin E in experimental Listeria monocytogenes infections in turkeys.

The current study was designed to determine if dietary vitamin E influenced either the gut clearance or levels of peripheral blood CD4+ and CD8+ T lymphocytes in adult turkeys experimentally infected with Listeria monocytogenes. Turkeys were fed vitamin E (0, 100, or 200 IU) from day of hatch to time of necropsy. After 6 wk on the experimental diet, turkeys were orally inoculated with L. monocytogenes (approximately 10(9) cfu). To monitor infection status, cloacal swabs were taken on selected days post-inoculation (DPI). At necropsy, samples of viscera, including liver, spleen, cecum, duodenum, ileum, and colon were collected and cultured for L. monocytogenes. In experiments 1 and 2, recovery of L. monocytogenes from cloacal swabs, tissues, and intestines from turkeys fed vitamin E was generally lower than that from turkeys fed the control diet, although these differences were not statistically significant. When data from both trials were combined, L. monocytogenes was cultured less frequently from cloacal swabs of the vitamin E-treated group (200 IU) on 2 and 3 DPI, when compared to controls (0 IU, P < 0.01). There were no changes in virulence characteristics of L. monocytogenes cells, as measured by in vitro killing of Ped-2E9 cells, recovered from cloacal swabs or tissues of experimentally infected turkeys fed the control or a vitamin E treatment diet. Flow cytometric analysis indicated that CD4+ and CD8+ peripheral blood T lymphocytes were elevated at 6 and 8 DPI in infected turkeys given 200 IU vitamin E.

Animals↗
PubMed2002

Survival differences of Escherichia coli O157:H7 strains in apples of three varieties stored at various temperatures.

Differences in survival and growth among five different Escherichia coli O157:H7 strains in three apple varieties were determined at various temperatures. Jonathan, Golden Delicious, and Red Delicious apples were wounded and inoculated with E coli O157:H7 strains C7929 (apple cider isolate), 301C (chicken isolate), 204P (pork isolate), 933 (beef isolate), and 43890 (human isolate) at an initial level of 6 to 7 log CFU/g. The inoculated apples were stored at a constant temperature of 37, 25, 8, or 4 degrees C or at 37 degrees C for 24 h and then at 4 degrees C, and bacterial counts were determined every week for 28 days. By day 28, for Jonathan apples at 25 degrees C, the apple isolate counts were significantly higher than the chicken and human isolate counts. At 4 degrees C for 28 days, the human isolate inoculated into Jonathan, Golden Delicious, and Red Delicious apples was present in significantly smaller numbers than the other strains. The apple isolate survived significantly better at 4 degrees C, yielding the highest number of viable cells. By days 21 and 28, for apples stored at 37 degrees C for the first 24 h and then at 4 degrees C, the counts of viable E. coli O157:H7 apple and human isolates were 6.8 and 5.8 log CFU/g at the site of the wound, whereas for apples kept at 4 degrees C for the duration of storage, the respective counts were 5.6 and 1.5 log CFU/g. Our study shows that E. coli O157:H7 strains responded differentially to their ability to survive in these three apple varieties at 25 or 4 degrees C and produced higher viable counts when apples were temperature abused at 37 degrees C for 24 h and then stored at 4 degrees C for 27 days.

Colony Count, Microbial↗
PubMed2001

Expression, purification, and characterization of active recombinant prostate-specific antigen in Pichia pastoris (yeast).

BACKGROUND: Prostate-specific antigen (PSA), a member of the kallikrein family of serine proteases, is a chymotrypsin-like glycoprotein produced by the prostate epithelium. Elevated serum PSA (> 4 ng/ml) is a tumor marker for prostatic cancer and benign prostatic hypertrophy; increasing serum PSA over time is indicative of metastatic disease. It has been suggested that PSA may contribute to tumor metastasis through degradation of extracellular matrix glycoproteins, as well as cleavage of IGF binding protein-3, a modulator of IGF-1. To elucidate the role of PSA in the development and progression of prostatic cancer, it is necessary to have a reliable, cost-effective source of enzymatically active protein. Previous efforts to express recombinant PSA (rPSA) produced inactive proPSA, or mixtures of active and inactive PSA requiring activation by removal of the propeptide. We describe the expression of active recombinant mature PSA in yeast. METHODS: Stable chromosomal integration of a construct consisting of the yeast alpha-factor signal sequence preceding the mature PSA sequence resulted in secretion of rPSA. The rPSA was purified from the yeast cell culture supernatant to homogeneity by strong cation-exchange chromatography, and characterized by SDS-PAGE, Western analysis, electrospray mass spectrometry, N-glycanase digestion, N-terminal amino acid sequencing, and inactivation by a PSA-specific inhibitor. RESULTS: We report the production of active, mature rPSA in Pichia pastoris. Two forms of rPSA varying slightly in glycosylation were identified. The specific activity of the rPSA was equal to that of human seminal plasma PSA (0.56 micromol/min mg) as determined using a chromogenic substrate. CONCLUSIONS: Large-scale production of active rPSA will be useful in the exploration of PSA effects on tumor cell proliferation, migration and metastasis. In addition, a large supply of enzyme should facilitate the discovery of novel inhibitors for in vitro and in vivo evaluation, and may provide a reproducible source of rPSA for use as a standard in diagnostic testing.

Amidohydrolases↗
PubMed2001

Interactive effects of CO2 and O3 on a ponderosa pine plant/litter/soil mesocosm.

To study individual and combined impacts of two important atmospheric trace gases, CO2 and O3, on C and N cycling in forest ecosystems; a multi-year experiment using a small-scale ponderosa pine (Pinus ponderosa Laws.) seedling/soil/litter system was initiated in April 1998. The experiment was conducted in outdoor, sun-lit chambers where aboveground and belowground ecological processes could be studied in detail. This paper describes the approach and methodology used, and presents preliminary data for the first two growing seasons. CO2 treatments were ambient and elevated (ambient + 280 ppm). O3 treatments were elevated (hourly averages to 159 ppb, cumulative exposure > 60 ppb O3, SUM 06 approximately 10.37 ppm h), and a low control level (nearly all hourly averages <40 ppb. SUM 06 approximately 0.07 ppm h). Significant (P < 0.05) individual and interactive effects occurred with elevated CO2 and elevated O3. Elevated CO2 increased needle-level net photosynthetic rates over both seasons. Following the first season, the highest photosynthetic rates were for trees which had previously received elevated O3 in addition to elevated CO2. Elevated CO2 increased seedling stem diameters, with the greatest increase at low O3. Elevated CO2 decreased current year needle % N in the summer. For 1-year-old needles measured in the fall there was a decrease in % N with elevated CO2 at low O3, but an increase in % N with elevated CO2 at elevated O3. Nitrogen fixation (measured by acetylene reduction) was low in ponderosa pine litter and there were no significant CO2 or O3 effects. Neither elevated CO2 nor elevated O3 affected standing root biomass or root length density. Elevated O3 decreased the % N in coarse-fine (1-2 mm diameter) but not in fine (< 1 mm diameter) roots. Both elevated CO2 and elevated O3 tended to increase the number of fungal colony forming units (CFUs) in the AC soil horizon, and elevated O3 tended to decrease bacterial CFUs in the C soil horizon. Thus, after two growing seasons we showed interactive effects of O3 and CO2 in combination, in addition to responses to CO2 or O3 alone for a ponderosa pine plant/litter/soil system.

Atmosphere Exposure Chambers↗
PubMed2001

Thermal inactivation of Salmonella senftenberg and Listeria innocua in ground chicken breast patties processed in an air convection oven.

Ground chicken breast patties were thermally processed in a lab-scale air convection oven at air temperatures of 163, 177, 190, 204, or 218 C to final patty center temperatures of 50, 55, 60, 65, 70, 75, or 80 C. The cooking time increased with increasing product temperature and decreased with increasing oven air temperature. Prior to thermal processing, approximately 7 log10(cfu/g) of Salmonella senftenberg and Listeria innocua were inoculated into the chicken patties. Survival of S. senftenberg and L. innocua decreased with increasing patty temperature. After the patties were processed to a final center temperature of 70 to 80 C, 1 to 4 log10 (cfu/g) of S. senftenberg and 3 to 5 log10(cfu/g) of L. innocua were detected in the cooked patties. A significant difference in the thermal inactivation of S. senftenberg and L. innocua was obtained between the chicken patties cooked in an air convection oven and the patties cooked in a water bath. More surviving S. senftenberg and L. innocua were found in the patties cooked in an air convection oven than in the patties cooked in a water bath.

Animals↗
PubMed2001

Foliar nitrogen concentrations and natural abundance of (15)N suggest nitrogen allocation patterns of Douglas-fir and mycorrhizal fungi during development in elevated carbon dioxide concentration and temperature.

Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir) seedlings were grown in a 2 x 2 factorial design in enclosed mesocosms at ambient temperature or 3.5 degrees C above ambient, and at ambient CO2 concentration ([CO2]) or 179 ppm above ambient. Two additional mesocosms were maintained as open controls. We measured the extent of mycorrhizal infection, foliar nitrogen (N) concentrations on both a weight basis (%N) and area basis (Narea), and foliar delta15N signatures (15N/14N ratios) from summer 1993 through summer 1997. Mycorrhizal fungi had colonized nearly all root tips across all treatments by spring 1994. Elevated [CO2] lowered foliar %N but did not affect N(area), whereas elevated temperature increased both foliar %N and Narea. Foliar delta15N was initially -1 per thousand and dropped by the final harvest to between -4 and -5 per thousand in the enclosed mesocosms, probably because of transfer of isotopically depleted N from mycorrhizal fungi. Based on the similarity in foliar delta15N among treatments, we conclude that mycorrhizal fungi had similar N allocation patterns across CO2 and temperature treatments. We combined isotopic and Narea data for 1993-94 to calculate fluxes of N for second- and third-year needles. Yearly N influxes were higher in second-year needles than in third-year needles (about 160 and 50% of initial leaf N, respectively), indicating greater sink strength in the younger needles. Influxes of N in second-year needles increased in response to elevated temperature, suggesting increased N supply from soil relative to plant N demands. In the elevated temperature treatments, N effluxes from third-year needles were higher in seedlings in elevated [CO2] than in ambient [CO2], probably because of increased N allocation below ground. We conclude that N allocation patterns shifted in response to the elevated temperature and [CO2] treatments in the seedlings but not in their fungal symbionts.

Carbon Dioxide↗
PubMed2001

Survival and growth of Salmonella and Listeria in the chicken breast patties subjected to time and temperature abuse under varying conditions.

Chicken breast patties were inoculated with a mixture of Salmonella Senftenberg, Salmonella Typhimurium, Salmonella Heidelberg, Salmonella Mission, Salmonella Montevideo, Salmonella California, and Listeria innocua. The initial inoculation of bacteria was approximately 10(7) log10 CFU/g. The inoculated patties were processed in a pilot-scale air convection oven at an air temperature of 177 degrees C, an air velocity of 9.9 m3/min, and a low (a wet bulb temperature of 48 degrees C) or high (a wet bulb temperature of 93 degrees C) humidity condition. The patties were processed to a final center temperature of 65 to 75 degrees C. The survivors of Salmonella and Listeria in the processed patties were evaluated. Processing humidity affected the survivors of bacteria. More survivors of Salmonella and Listeria (>2 logs) were obtained for the patties cooked at low humidity than at high humidity. After thermal processing, the patties were stored under air, vacuum, or CO2 at refrigerated (4 degrees C) or thermally abused (8 to 15 degrees C) temperatures. Storage temperature, time, and gas environment affected the bacteria growth. Higher storage temperature and longer storage time correlated to an increased growth of bacteria in the cooked chicken patties. Less Salmonella (2 logs) and Listeria (0.5 to 1 log) cells were obtained in the patties stored under vacuum than in air. Storing the patties in 30% CO2 reduced the growth of Salmonella more than 2 log10 CFU/g. At a CO2 level of 15%, 1 log10 CFU/g of reduction was obtained for Listeria in cooked chicken patties.

Aerobiosis↗
PubMed2001

Survival and death of Salmonella typhimurium and Campylobacter jejuni in processing water and on chicken skin during poultry scalding and chilling.

Salmonella Typhimurium and Campylobacter jejuni were inoculated in scalding water, in chilled water, and on chicken skins to examine the effects of scalding temperature (50, 55, and 60 degrees C) and the chlorine level in chilled water (0, 10, 30, and 50 ppm), associated with the ages of scalding water (0 and 10 h) and chilled water (0 and 8 h), on bacterial survival or death. After scalding at 50 and 60 degrees C, the reductions of C. jejuni were 1.5 and 6.2 log CFU/ml in water and <1 and >2 log CFU/cm2 on chicken skins; the reductions of Salmonella Typhimurium were <0.5 and >5.5 log CFU/ml in water and <0.5 and >2 log CFU/cm2 on skins, respectively. The age of scalding water did not significantly (P > 0.05) affect bacterial heat sensitivity. However, the increase in the age of chilled water significantly (P < 0.05) reduced the chlorine effect. In 0-h chilled water. C. jejuni and Salmonella Typhimurium were reduced by 3.3 and 0.7 log CFU/ml, respectively, after treatment with 10 ppm of chlorine and became nondetectable with 30 and 50 ppm of chlorine. In 8-h chilled water, the reduction of C. jejuni and Salmonella Typhimurium was <0.5 log CFU/ml with 10 ppm of chlorine and ranged from 4 to 5.5 log CFU/ml with 50 ppm of chlorine. Chlorination of chilled water did not effectively reduce the bacteria attached on chicken skins. The D-values of Salmonella Typhimurium and C. jejuni were calculated for the prediction of their survival or death in the poultry scalding and chilling.

Animals↗
PubMed2001

Pharmacokinetics, metabolism, and excretion of linezolid following an oral dose of [(14)C]linezolid to healthy human subjects.

Linezolid (Zyvox), the first of a new class of antibiotics, the oxazolidinones, is approved for treatment of Gram-positive bacterial infections, including resistant strains. The disposition of linezolid in human volunteers was determined, after a 500-mg (100-microCi) oral dose of [(14)C]linezolid. Radioactive linezolid was administered as a single dose, or at steady-state on day 4 of a 10-day, 500-mg b.i.d. regimen of unlabeled linezolid (n = 4/sex/regimen). Mean recovery of radioactivity in excreta was 93.8 +/- 1.1% (range 91.2-95.2%, n = 15), of which 83.9 +/- 3.3% (range 76.7-88.4%) was in urine and 9.9 +/- 3.4% (range 5.3-16.9%) was in feces. There was no major difference in rate or route of excretion of radioactivity by dose regimen. Linezolid was excreted primarily intact, and as two inactive, morpholine ring-oxidized metabolites, PNU-142586 and PNU-142300. Other minor metabolites were characterized by high-performance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry and (19)F NMR spectroscopy. After the single radioactive dose, linezolid was the major circulating drug-related material accounting for about 78% (male) and 93% (female) of the radioactivity area under the curve (AUC). PNU-142586 (T(max) of 3-5 h) accounted for about 26% (male) and 9% (female) of the radioactivity AUC. PNU-142300 (T(max) of 2-3 h) accounted for about 7% (male) and 4% (female) of the radioactivity AUC. Overall, mean linezolid and PNU-142586 exposures at steady-state were similar across sex. In conclusion, linezolid circulates in plasma mainly as parent drug. Linezolid and two major, inactive metabolites account for the major portion of linezolid disposition, with urinary excretion representing the major elimination route. Formation of PNU-142586 was the rate-limiting step in the clearance of linezolid.

Acetamides↗
PubMed2000

Characterization by molecular cloning and sequencing of the gene encoding an aminopeptidase from Listeria monocytogenes.

The pepC gene of Listeria monocytogenes encodes aminopeptidase C that is predicted to share 72% amino acid sequence similarity and 53% sequence identity with the cysteine aminopeptidase PepC from Lactococcus lactis. The gene product also shows strong similarity to aminopeptidase C from Streptococcus thermophilus and Lactobacillus helveticus, and to a cysteine proteinase/bleomycin hydrolase from Saccharomyces cerevisiae. The enzyme from L. monocytogenes displayed broad N-terminal hydrolytic activity, with a similar substrate specificity to its lactic acid bacterial counterpart. The inhibition spectrum shows a great deal of similarity with enzymes from the family of lactic acid bacteria. In addition, one of the clones studied contained DNA sequences that could encode a regulatory protein of the deoR helix-turn-helix DNA binding protein family. The organization of the locus, designated pep, is presented along with the characterization of the gene products of the pep locus.

Amino Acid Sequence↗