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Biomedical subjects

L K Pickering

Publications and source records attributed to L K Pickering.

At least 163 records · Page 9Linked to original sources
PubMed1983

Protection of suckling mice from the heat-stable enterotoxin of Escherichia coli by human milk.

Human milk contained a factor or factors that protected suckling mice from lethal fluid loss due to Escherichia coli heat-stable toxin. This protective effect was present throughout lactation. The factor was heat stable, acid and alkali stable (pH 2 and 12), and of low molecular weight. Ion-exchange chromatography indicated that it was uncharged at neutral pH. The factor was insensitive to proteinase K digestion and partitioned in the aqueous phase in 2:1 (vol/vol) chloroform-methanol. Acid hydrolysis (2 N HCl at 100 C for 3 hr) destroyed the protective effect. Neither an amino acid mix simulating human milk nor lactose in phosphate-buffered saline was protective. These data indicate that the protective factor in human milk is neither a lipid nor a protein but appears to be a carbohydrate.

Amino Acids↗
PubMed1983

Transmission dynamics of enteric bacteria in day-care centers.

The role of fomites in the transmission of diarrhea in day-care centers was evaluated. During a nine-month period (December 1980-August 1981), inanimate objects and hands of children and staff in five Houston day-care centers were cultured monthly and again during outbreaks of diarrhea. Air was sampled from the classrooms and bathrooms using a single-stage sieve sampler. When a diarrhea outbreak occurred, stool specimens were collected from ill and well children and from staff in the affected rooms. Multiple pathogens accounted for 3 of 11 outbreaks. The rates of isolation of fecal coliforms from hands and classroom objects on routine sampling were 17% (22/131) and 13% (8/64), respectively. During outbreaks of diarrhea, fecal coliforms were recovered with significantly greater frequency from hands (32%; p less than 0.005) and from classroom objects (36%; p less than 0.005). There was no difference in the level of fecal contamination in the toilet areas during outbreak and nonoutbreak periods. Shigella was not isolated in the study; salmonella was isolated on one occasion from a table during an outbreak of salmonellosis. Contamination of hands, communal toys and other classroom objects appeared to play a role in the transmission of enteropathogens in day-care center diarrhea outbreaks and helped to explain the presence of multiple pathogens among those affected.

Air Microbiology↗
PubMed1983

Survival and detection of rotaviruses on environmental surfaces in day care centers.

Previously, we demonstrated that children in day care centers commonly experience diarrhea due to rotavirus, giardia, and bacterial pathogens. Multiple agents frequently coexist, and the environment is heavily contaminated with enteric bacteria during outbreaks. A study of environmental surface contamination with rotavirus was performed during three non-outbreak periods. Of 25 samples collected from environmental surfaces and teachers hands at a day care center, 4 (16%) were positive for rotavirus antigen when a fluorescence assay was used. We also examined the survival of two animal viruses, rotavirus SA-11 and poliovirus type 1, and bacteriophage 12 on similar environmental surfaces in a laboratory. Poliovirus type 1 and bacteriophage f2 were more resistant to drying than rotavirus SA-11 and could be recovered after a 90-min exposure on a dry surface. Rotavirus SA-11 could be detected for 30 min. All three viruses survived longer when they were suspended in fecal material than when they were suspended in distilled water. These data suggest that several agents, including rotavirus, can remain viable on contaminated surfaces long enough to be transmitted to susceptible children. This finding helps explain why rotavirus shows a mode of spread like that of parasitic and bacterial agents within day care center settings.

Child Day Care Centers↗
PubMed1983

Inhibition of human polymorphonuclear leukocyte function by components of human colostrum and mature milk.

To compare the effect of human colostrum (days 1 to 3 postpartum) and mature milk (days 170 +/- 24 postpartum) on the function of polymorphonuclear leukocytes (PMNL), Ficoll-Hypaque-separated PMNL from the blood of 60 healthy volunteers were incubated with whole colostrum, colostral lipid, and colostral aqueous phase from 30 mothers, or with mature whole milk and its separated components from 30 mothers, and tested for resting and zymosan-stimulated oxidative metabolism, functional activity, and the presence of Fc receptors. Stimulated oxygen consumption, quantitative nitroblue tetrazolium dye reduction, [1-(14)C]glucose utilization, and Fc receptors were significantly (P < 0.05 to P < 0.001) less in PMNL exposed to whole human colostrum or colostral lipid than in non-lipid-exposed cells or cells exposed to the aqueous phase of colostrum. In contrast, PMNL exposed to whole mature milk or to its lipid or aqueous phase caused no significant decrease in any of these parameters when compared to nonexposed cells. In assays of phagocytosis, colostral PMNL or blood PMNL exposed to colostral lipid had a significant (P < 0.001) decrease in their ability to ingest [methyl-(3)H]thymidine-labeled Staphylococcus aureus when compared to non-lipid-exposed PMNL. Blood PMNL exposed to lipid from mature milk had no decrease in ability to ingest S. aureus. Analysis of total lipid and total and individual fatty acid content revealed a uniform increase in all components in mature milk when compared to colostrum. Lipid or lipid-soluble material present in human colostrum but not mature milk causes inhibition of phagocytosis and respiratory burst-related activities of PMNL.

Blood Bactericidal Activity↗
PubMed1983

Mechanisms of intralipid effect on polymorphonuclear leukocytes.

The effect of Intralipid, a lipid emulsion used in total parenteral nutrition, on polymorphonuclear leukocytes (PMNL) was studied in vitro. Preincubation of PMNL with Intralipid was found to depress oxidative metabolic and phagocytic functions. Preincubation of PMNL with intralipid also caused a decrease in Fc receptors. However, when Intralipid was added at the start of metabolic assays, it stimulated the respiratory burst. We interpret these findings as suggesting that Intralipid, acting as a particulate stimulus, activated and exhausted metabolic pathways involved in the respiratory burst and phagocytosis and that it also decreased numbers or availability of Fc receptors on PMNL. Individual components of Intralipid did not induce these changes. This dysfunction may contribute to the infections seen in patients receiving parenteral hyperalimentation with Intralipid supplementation.

Adult↗
PubMed1983

Modulation of polymorphonuclear leukocyte function by doxorubicin (Adriamycin) and alpha tocopherol (vitamin E).

The effect of various concentrations of Adriamycin alone and Adriamycin plus vitamin E on human polymorphonuclear leukocyte (PMNL) function was determined. Aliquots of PMNLs were incubated at 37 degrees C with saline or vitamin E and then exposed to Adriamycin. A significant decrease in 1-14C glucose utilization and oxygen consumption by zymosan stimulated PMNLs occurred when PMNLs were incubated with 1, 10, 20, 1000 and 200 micrograms/ml concentrations of Adriamycin. Preincubation of the PMNLs with vitamin E afforded partial protection at lower concentrations. The total uptake at 3, 10 and 20 min of methyl 3H thymidine labeled S. aureus by control PMNL was significantly greater than by PMNLs exposed for 60 min to 100 micrograms/ml of Adriamycin. Intracellular Adriamycin concentrations increased in a dose dependent fashion. Viability of cells before and after incubation was 95%. Adriamycin inhibited oxidative metabolic and functional activity of PMNLs in a dose related manner. Preincubation of PMNLs with vitamin E partially protected them from the effects of Adriamycin.

Chromatography, High Pressure Liquid↗
PubMed1982

Influence of subsalicylate bismuth on absorption of doxycycline.

The influence of a typical 60-mL dose of subsalicylate bismuth (Pepto-Bismol) on the absorption of 200 mg of orally administered doxycycline hyclate was studied. Bioavailability of doxycycline was significantly reduced by 37% and 51%, respectively, when subsalicylate bismuth was given simultaneously and as a multiple-dose regimen before doxycycline. Peak serum concentrations of doxycycline were significantly decreased when subsalicylate bismuth was given two hours before doxycycline but not when given two hours after doxycycline. Subsalicylate bismuth should not be taken when doxycycline is used for therapeutic purposes, and we suggest travelers should not take the agents together in an effort to prevent diarrhea.

Adult↗
PubMed1982

Leukocyte function in healthy neonates following vaginal and cesarean section deliveries.

Oxidative metabolic activities of polymorphonuclear leukocytes from cord blood of 15 full-term infants delivered by cesarean section without labor, five infants delivered by cesarean section with labor, and 15 infants delivered vaginally, as well as 35 healthy adult control subjects, were evaluated. The absolute polymorphonuclear leukocyte counts of cord blood from infants delivered vaginally and by cesarean section with labor were significantly higher when compared to cord blood APCs from infants delivered by cesarean section without labor and healthy adult control APCs. Zymosan-stimulated oxygen consumption, hexose monophosphate shunt activity, and quantitative nitroblue tetrazolium dye reduction were significantly lower in cord blood PMNLs from infants delivered vaginally and by cesarean section with labor than in cord blood PMNLs from infants delivered by cesarean section without labor or control PMNLs. Metabolic activity of PMNLs from healthy adults and infants born by cesarean section without labor did not differ significantly. This study indicates that the function of PMNLs isolated from cord blood varies with the method of delivery. These observations may explain previous discrepancies in the literature as well as the propensity of certain neonates to infection.

Cesarean Section↗
PubMed1982

Successful moxalactam therapy for gram-negative bacillary meningitis in neonates.

Three neonates with gram-negative bacillary meningitis were treated with moxalactam after therapy with ampicillin plus aminoglycoside, trimethoprim-sulfamethoxazole, or chloramphenicol failed to sterilize the CSF. Clinical improvement and CSF sterility occurred after therapy with moxalactam was initiated. Moxalactam concentrations in CSF exceeded MICs of each organism. All three patients were cured of their infection. Moxalactam appears to be an effective antibiotic for the treatment of neonatal gram-negative bacillary meningitis.

Bacterial Infections↗
PubMed1982

Virus-infected colostral cell cytokine stimulation of human leukocyte natural killer cytotoxicity.

Natural killer cytotoxicity is an important antiviral defense mechanism. Human peripheral blood mononuclear cells cultured with herpes simplex virus (HSV)-infected cells produced a cytokine. This substance stimulated adult natural killer cytotoxicity from 53.0 +/- 10.5% to 79.8% (P less than 0.01) against HSV-infected target cells. These data resulted in a calculated cytokine-dependent cellular cytotoxicity (CDCC) value of 65.8%. Cytokine production was not stimulated by uninfected cells and was independent of the presence or absence of antibodies to HSV in sera of donors and mononuclear cells. Cells from human colostrum also produced an HSV-stimulated cytokine which mediated CDCC by using both adult (19.8 +/- 3.9%) and neonatal (18.6 +/- 3.4%) mononuclear effectors cells. Colostral cell cytokine production was also independent of donor HSV serology. Not all colostral cultures produced the cytokine, and in general colostrum-stimulated CDCC was lower than peripheral blood leukocyte-stimulated CDCC. Colostral cell cytokine stimulation of neonatal natural killer cytotoxicity may account in part for the increased nonspecific resistance of breast-fed infants to viral infection.

Biological Products↗
PubMed1982

The effect of route of delivery on neonatal natural killer cytotoxicity and antibody-dependent cellular cytotoxicity to herpes simplex virus-infected cells.

The ability of human neonatal and adult Ficoll-hypaque purified mononuclear cells to mediate natural killer cytotoxicity (NKC) and antibody-dependent cellular-cytotoxicity (ADCC) against 51Cr labeled herpes simplex virus-infected (HSV-infected) and uninfected cells was evaluated in healthy term infants delivered vaginally or by Cesarean (C)-section without labor, and in healthy adult controls. Cord blood NKC to HSV-infected cells (12.5 +/- 7.0) was lower (P less than 0.01) than adult controls NKC (29.5 +/- 7.0). NKC to HSV-infected cells of babies delivered vaginally (16.6 +/- 3.4) was lower (P less than 0.05) than adult controls (28.4 +/- 4.2). NKC to HSV-infected cells of neonates delivered by C-section without labor (7.6 +/- 2.8) was also lower (P less than 0.001) than adult controls (30.7 +/- 4.0) and lower (P less than 0.05) than that of neonates delivered vaginally. Cord blood ADCC (43.1 +/- 9.0) was lower (P less than 0.05) than ADCC of adult controls (58 +/- 10). ADCC of neonates delivered vaginally (50 +/- 5.9) was similar to ADCC of adult controls (57.4 +/- 6.9). ADCC of neonates delivered by C-section without labor (30.4 +/- 7.2) was lower than ADCC of adult (58.5 +/- 7.4) and was lower (P less than 0.05) than ADCC of neonates delivered vaginally. These findings demonstrate that the method of delivery influences subsequent neonatal leukocyte NKC and ADCC. Further experiments will delineate the cause of these variations, which probably include labor or stress related hormonal changes in the mother or neonate.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1982

Effect of glucose concentration and time on polymorphonuclear leukocyte function.

Polymorphonuclear leukocyte (PMNL) to oxidative metabolism and functional activities were assayed after varying periods of exposure to glucose concentrations ranging from 100-600 mg/dl. Oxygen consumption, superoxide generation and phagocytosis and killing of radiolabeled S. aureus by PMNL were not affected by hyperglycemic conditions for incubation periods up to 18 hours. Elevated glucose levels per se do not appear to be responsible for PMNL abnormalities reported in patients with diabetes mellitus.

Diabetes Mellitus↗