PubMed Health⌕ Search

Biomedical subjects

C Porter

Publications and source records attributed to C Porter.

At least 55 records · Page 3Linked to original sources
PubMed1995

Metabolism and pharmacokinetics of N1,N11-diethylnorspermine.

The pharmacokinetics and metabolism of N1,N11-diethylnorspermine (DENSPM) is described. When administered to dogs as an intravenous bolus, DENSPM was shown to have a plasma half-life of 72.8 +/- 11.8 min, with an early distribution phase half-life of approximately 4 min and an apparent volume of distribution of 0.216 +/- 0.032 liter/kg. The renal clearance half-life was 59.7 +/- 7.6 min, with 48.8 +/- 12.5% of the drug recovered in the urine between 0-4 hr unchanged. In three other experiments, the drug was administered to dogs by constant rate intravenous infusion over periods ranging from 10 min to 2 hr. Analysis of plasma concentration-time data and urinary excretion data yielded pharmacokinetic parameters in general agreement with the intravenous bolus experiments. DENSPM metabolites were identified in both beagle dog and mouse tissues. Tissues were sampled from a single beagle 24 hr posttreatment, and rodent samples were examined at 12, 24, 48, and 96 hr posttreatment. Both the concentration of DENSPM and the metabolic profile were shown to vary in the lung, liver, spleen, and kidney. Although all the tissues examined contained DENSPM and its metabolites, the liver and kidney had the highest level of metabolites that included N1-ethylnorspermine, N1-ethylnorspermidine, N1-ethyl-1,3-diaminopropane, and norspermidine. These data suggest that DENSPM is metabolized by N-deethylation and step-wise removal of aminopropyl equivalents by spermine/spermidine N1-acetyltransferase/polyamine oxidase, a metabolic pathway unique to the polyamines.

Animals↗
PubMed1994

Face mask therapy of preadolescents with unilateral cleft lip and palate.

This study evaluates 21 children treated with maxillary expansion and protraction appliances for skeletal discrepancies associated with unilateral cleft lip and palate (UCLP). The subjects were treated by the same orthodontist, using the same techniques and appliances. Mean pre- and posttreatment ages were 7.3 and 8.7 years, respectively. Each child was matched by ethnicity, sex, age, and the SN/MP angle to an untreated (non UCLP) control. Stable cranial and cranial base reference structures were used for superimposing serial cephalograms. The results showed definite protraction of the maxilla for the UCLP group. The posterior maxilla of the UCLP group underwent anterior displacement; the posterior maxilla of the control group displayed posterior growth changes. The maxillary incisor tips of the UCLP group demonstrated greater anterior movement than expected for untreated controls. Vertical changes of the maxilla showed no significant group differences. The mandible of the UCLP group was rotated inferiorly and posteriorly; the control group showed inferior/anterior changes. The lower incisor of the UCLP and control groups remained stable and moved anteriorly, respectively. The UCLP group showed significantly greater inferior movements of the anterior mandible than the control group. We concluded that differences between the control and UCLP groups are primarily related to mandibular clockwise rotation and secondarily to anterior maxillary repositioning.

Analysis of Variance↗
PubMed1994

Patient and staff exposure to glutaraldehyde from KeyMed Auto-Disinfector endoscope washing machine.

Activated glutaraldehyde (2%) is the recommended agent for disinfection of endoscopic equipment. Exposure to the disinfectant is associated with side-effects and guidelines have been set to avoid these complications. Endoscope washing machines are used to provide automated high level disinfection of endoscopes as well as reduce exposure to the irritant aldehyde. We report a design fault in an endoscope washing machine which results in patients and staff being exposed to activated glutaraldehyde. The Auto-Disinfector (KeyMed) comprises a washing chamber supplied by three separate reservoirs (detergent, disinfectant, and rinse water) via a common channel. After the first cycle endoscopes are processed using previously used detergent and rinse water. Rinse water glutaraldehyde concentrations were measured in four machines during routine endoscopy lists on at least two occasions and showed a progressive rise in glutaraldehyde concentration up to 0.1% after two to six cycles. This results in staff being exposed to glutaraldehyde present on the processed instrument and the disinfectant being pumped from the internal channels of the endoscope into direct contact with the gastrointestinal mucosa during endoscopy at concentrations of 200-1000 ppm. The present atmospheric limit for glutaraldehyde is 0.2 ppm. Skin and mucosal irritation occur at concentrations of 0.3 ppm and severe synovitis in experimental animals at 100 pm. Tongue swelling and bloody diarrhoea with characteristic mucosal histological changes have been reported in patients exposed to activated glutaraldehyde on inadequately rinsed equipment. To reduce this problem the rinse water should be changed after every cycle and the endoscope should be dried thoroughly before use.

Disinfection↗
PubMed1994

Graphic file compression on a Macintosh.

AutoDoubler, Compact Pro, DiskDoubler, StuffIt Deluxe, and StuffIt SpaceSaver compression applications for the Macintosh were tested for size of compressed files, and time to compress and expand. EPS, TIFF, PICT and Photoshop native format file types were used, in 1-bit, 8-bit greyscale, 8-bit colour (indexed), 24-bit colour (red, blue, green (RGB)), and 32-bit colour (cyan, magenta, yellow, black (CMYK)) modes. JPEG compression is illustrated by comparing an uncompressed image with three images compressed at different rates.

Computer Graphics↗
PubMed1993

Prevention of hypermenorrhea with leuprolide in premenopausal women undergoing bone marrow transplantation.

We report on the use of leuprolide to prevent heavy menstrual bleeding that often occurs before platelet engraftment in premenopausal women undergoing bone marrow transplantation (BMT). Leuprolide, a synthetic analog of gonadotropin-releasing hormone (Gn-RH-a), was given to 34 patients by intravenous bolus injection, 1 mg daily, until platelet recovery. The median duration of therapy was 50 days (range 16-170). When necessary, patients self-administered the drug after discharge from the hospital. No adverse effects could be related directly to the use of leuprolide. Leuprolide effectively prevented menstruation in 25 patients (73%), failed in seven (21%), and two patients were not evaluable. The success of leuprolide therapy was related to the time of onset of treatment, as anticipated from the gradual effect of Gn-RH-a on the menstrual cycle. The failure rate was only 6% (one of 16 patients) when leuprolide was started at least 2 weeks prior to the development of thrombocytopenia, compared to a failure rate of 33% (six of 18 patients) when leuprolide was started at a later time. We conclude that leuprolide as a single agent is a safe and effective method to prevent menstrual bleeding during BMT. Additional studies are needed to determine the best timing for the onset of therapy and the relative benefit of leuprolide compared to other prophylactic approaches in patients with lengthy thrombocytopenia.

Adolescent↗
PubMed1993

Co-existent cross-infection with Streptococcus pneumoniae and group B streptococci on an adult oncology unit.

An outbreak of respiratory infection in an adult oncology unit is described where there was evidence of co-existent cross-infection with Streptococcus pneumoniae serotype 14 and Lancefield group B streptococcus type Ia. The presumed route of transmission was droplet spread from patient to patient. No further cases arose after the ward had been closed to new admissions and all symptomatic patients were treated with erythromycin. We suggest that patients with pneumococcal pneumonia on units housing elderly debilitated patients should be isolated. Infection control teams should be aware of the ability of Lancefield group B streptococci to spread by cross-infection among adult patients.

Adult↗
PubMed1993

Effect of peritoneal dialysis effluent on superoxide anion production by polymorphonuclear neutrophils.

Peritoneal dialysis effluent (PDE) contains at least 2 factors capable of affecting superoxide generation by polymorphonuclear neutrophils (PMN) in response to both particulate and soluble stimuli. A low molecular weight fraction (< 1.2 kD) enhanced the response to the chemotactic peptide fMLP and to preopsonised Staphylococcus epidermidis and Candida guilliermondii. A higher molecular weight fraction (> 1.2 kD) inhibited superoxide production in response to phorbol myristate acetate (PMA). The effects of PDE were dose dependent over the range of 10-70% (v/v) and simply augmented and reduced the dose-response curve to fMLP and PMA, respectively. There was no alteration in the concentration of stimulus required to give maximal superoxide production in either case. These data suggest that factors capable of affecting superoxide production by PMN accumulate in uraemia and are removed from the circulation into dialysis fluid.

Candida↗
PubMed1993

Adolescents' risky behavior and mass media use.

OBJECTIVE: To understand better the relationship between adolescents' use of the mass media (including television, radio, and magazines) and their risky or unhealthy behaviors. DESIGN: Secondary data analysis of a 1987 in-home survey of 2760 randomly selected 14- to 16-year-old adolescents in 10 urban areas in the southeastern United States. MEASUREMENT: The extent of participation in eight potentially risky behaviors (sexual intercourse, drinking, smoking cigarettes, smoking marijuana, cheating, stealing, cutting class, and driving a car without permission) and the use of a variety of mass media. RESULTS: Adolescents who had engaged in more risky behaviors listened to radio and watched music videos and movies on television more frequently than those who had engaged in fewer risky behaviors, regardless of race, gender, or parents' education. White male adolescents who reported engaging in five or more risky behaviors were most likely to name a heavy metal music group as their favorite. Adolescents reported reading a wide diversity of magazines, and most reported reading at least one of a few selected magazines. Sports and music magazines were most likely to be read by adolescents who had engaged in many risky behaviors. CONCLUSIONS: Mass media health promotion efforts could more specifically target adolescents who are engaging in multiple risky behaviors.

Adolescent↗
PubMed1992

Abnormal cytoplasmic pH regulation during activation in uremic neutrophils.

Neutrophils isolated from ESRF patients demonstrated abnormal cytoplasmic pH changes after FMLP stimulation; the initial cytoplasmic acidification was absent (P less than 0.001 compared to controls) and the degree of alkalinization enhanced (P less than 0.05 compared to controls). This effect was not due to the absence of any of the factors associated with acidification in normal PMN since superoxide production was enhanced (P less than 0.05 compared to controls) and intracellular calcium release was normal. Our observations are not explicable by alterations in the function of the Na:H antiport since the kinetics of antiport activation by cytoplasmic pH were not different in uremic and control cells. Other factors must therefore be important in generating the abnormal pH response to chemotactic factors in uremic PMN. Cells from CAPD patients had some degree of initial acidification (P less than 0.001 compared to controls and P less than 0.05 compared to ESRF) and enhanced alkalinization (P less than 0.05 compared to controls). Preincubation of normal PMN in four-hour dwell PDE reproduced the responses of uremic PMN with absent acidification, enhanced alkalinization and enhanced superoxide generation after FMLP stimulation (P less than 0.05 compared to controls). Changes in the control of cytoplasmic pH in stimulated PMN may influence PMN function, and our observations may be relevant to the susceptibility of uremic patients to infection.

Adult↗
PubMed1992

Evaluation of four commercial automatic endoscope washing machines.

Four commercially available endoscope washing machines (Pyser System 83, Wolf Fiberscope Disinfector, Olympus EW20, Keymed Auto-Disinfector) were evaluated. In most cases the machines were expensive, immobile and noisy, and could only wash one endoscope per cycle. Daily use involved repetitive chores and contact with glutaraldehyde. Disinfection procedures were flawed; no machine auto-disinfected adequately. In conclusion, these machines are unsatisfactory and represent a potential source of serious infection.

Disinfection↗
PubMed1992

Evaluation of the E test by using selected gram-positive bacteria.

The E test (AB Biodisk NA Inc.) was compared with standard reference methods using the National Committee for Clinical Laboratory Standards's recommendations for determining the MICs of four selected antibiotics against 208 clinical isolates of gram-positive bacteria. These bacteria included 32 strains of Streptococcus pneumoniae, 25 strains of Enterococcus faecium, 20 strains of oxacillin-sensitive Staphylococcus aureus (OSSA), 96 strains of oxacillin-resistant S. aureus (ORSA), and 35 strains of coagulase-negative staphylococci. Evaluation included MIC accuracy within 1 dilution, reproducibility testing, and cost analysis. There was 94% agreement between the E test and the reference method in testing S. pneumoniae and penicillin G. There was 92% agreement with ampicillin and 100% agreement with vancomycin in testing E. faecium isolates. Accuracy of the oxacillin E test with staphylococci was significantly improved by the use of salt-supplemented Mueller-Hinton agar, for an agreement of 100% with coagulase-negative staphylococci and oxacillin-sensitive S. aureus and that of 85% with oxacillin-resistant S. aureus, with no major discrepancies. The E test with American Type Culture Collection isolates and clinical strains gave excellent reproducibility and was less costly than microdilution panels when used to test fewer than three antibiotics. The E test is a simple, reliable, reproducible, and cost-effective method for MIC determination for gram-positive organisms.

Enterococcus faecalis↗
PubMed1991

Sudden infant death syndrome related to climate.

In Australia the single most important factor influencing the incidence of SIDS is the climate. The incidence in mid summer in South Australia is 0.7 per 1,000 live births, in mid winter in Tasmania it is 6.3 per 1,000 live births. It is predicted that if infants under 6 months of age in cold weather were tied into swaddling and placed supine to sleep as in Asia and Czechoslovakia, and older infants who may object to restriction of movement, had the cot made up with the infants' feet touching the lower end, warm clothing and no more than a single thin porous cover, the incidence of SIDS as in Asia and Czechoslovakia could be reduced to less than 1.0 per 1,000.

Australia↗
PubMed1991

Vectors of Leishmania braziliensis in the Petén, Guatemala.

During a 1-year study, 13 species of sand fly were collected in bite-landing collections on human attractants in Tikal, Guatemala. Using isoenzyme analysis, Leishmania braziliensis was identified among isolates from Lutzomyia ovallesi, Lu. panamensis, and Lu. ylephiletor. Lutzomyia ovallesi, Lu. shannoni, and Lu. cruciata were found with flagellates whose isoenzyme patterns matched unidentified flagellates isolated from a patient with mucosal lesions.

Animals↗
PubMed1989

Evolution of androgen-regulated ornithine decarboxylase expression in mouse kidney.

The analysis of naturally occurring variations in hormone-regulated gene expression generates insights into the mechanisms governing evolutionary changes in hormone response. In the mouse (genus Mus), kidney ornithine decarboxylase (ODC) expression, which is regulated by androgens, has been modified during evolution. This has resulted in intra- and interspecies variations that have accumulated over a 10-15 million year time period. We have examined ODC expression and its response to androgens in eight Mus species. Induced ODC levels were found to be similar in six of these species. Two species (M. cookii, M. pahari) contain diminished enzyme levels that are the result of different mechanisms. In M. cookii, the low ODC levels reflect reduced ODC mRNA induction in response to hormone. In M. pahari, on the other hand, the low ODC levels are not derived from altered mRNA concentrations, but appear to be due to translational and/or posttranslational effects. Nuclear run-on assays indicate that ODC mRNA induction is associated with increases in rates of ODC gene transcription. The low ODC mRNA level in induced M. cookii reflects a low rate of ODC gene transcription. Thus, both transcriptional and posttranscriptional mechanisms have contributed to modification of the ODC expression phenotype during evolution. The significance of these findings to the evolution of androgen-regulated ODC expression is discussed.

Androgens↗