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Biomedical subjects

W T Speck

Publications and source records attributed to W T Speck.

At least 19 recordsLinked to original sources
PubMed1990

Campylobacter pylori: a new pathogen.

There is now considerable evidence suggesting that C. pylori is a human pathogen. The strong association between C. pylori and gastroduodenal disease is well documented. A number of hypotheses have been suggested for the pathogenic mechanisms of C. pylori-induced gastroduodenal disease, including the production of cytotoxins and the mechanical disruption of the epithelium. At the present time, treatment with a combination of antimicrobial agents eradicates the infection in approximately 50% of cases. Until an ideal therapeutic regimen is available, antimicrobial therapy is recommended only for those patients who continue to be symptomatic following 6 to 8 weeks of treatment with an H2-receptor.

Animals↗
PubMed1989

Effects of topical anesthetic agents on Campylobacter pylori.

The susceptibility of Campylobacter pylori was determined for the two topical anesthetic agents commonly used prior to gastroscopy. Campylobacter pylori proved to be extremely sensitive to the anti-infective activity of benzocaine, the active ingredient in most commonly used topical anesthetic agents, with minimum inhibitory concentrations of 0.14 mg/ml. However, lidocaine-containing agents did not interfere with the growth of this microorganism. Specifically, in patients with histologic evidence of C. pylori, the bacterium was recovered from significantly more patients anesthetized with lidocaine than with benzocaine. Thus, the use of benzocaine-containing topical anesthetic agents limits recovery of Campylobacter pylori from clinical specimens and might account for the low colonization rates reported in some recent publications.

Administration, Topical↗
PubMed1987

Rapid clearance of a structural isomer of bilirubin during phototherapy.

During phototherapy for neonatal jaundice, bilirubin is converted into a variety of photoproducts. Determination of the relative importance of these photoproducts to the elimination of bilirubin requires knowledge of their rates of excretion. We have measured the rate at which the structural isomer of bilirubin, lumirubin, disappeared from the serum of nine jaundiced premature infants after the cessation of phototherapy. In all patients studied, the decline in serum lumirubin could be approximated by a first-order rate equation with a half-life of 80 to 158 min. This rate of disappearance is much faster than that previously determined for the other major bilirubin photoproducts. In samples of bile aspirated from the duodenum of infants undergoing phototherapy, lumirubin was the principal bilirubin photoproduct found. These results indicate that formation and excretion of lumirubin is an important route for bilirubin elimination during phototherapy.

Bile↗
PubMed1985

Effect of spectral distribution on isomerization of bilirubin in vivo.

The purpose of our study was to compare the effects of narrow-spectrum blue light and broad-spectrum white light on the production of bilirubin photo-isomers in human infants with jaundice. Twelve preterm infants were studied under both white and blue light. Irradiance at 450 nm was controlled at 12 microW/cm2/nm for both light sources. Each light condition (white or blue) was administered for 12 hours. Bilirubin isomers (4Z,15E-bilirubin and lumirubin) were measured before therapy and after 12 hours of each sequential light condition. The percentage of 4Z,15E-bilirubin was greater under blue light than under white light (P less than 0.01) phototherapy. There was no significant difference in percentage lumirubin under white or blue light therapy. Our data indicate that blue light is more effective than white light in producing 4Z,15E-bilirubin in vivo. Our study demonstrates that when irradiance in the bilirubin absorbance spectrum is constant, the color of light (spectral distribution) will determine the relative concentrations of photo-isomers produced.

Bilirubin↗
PubMed1985

Urinary excretion of an isomer of bilirubin during phototherapy.

Lumirubin, a water-soluble photoproduct of bilirubin formed in vivo during phototherapy, is excreted in the urine. In premature infants with little or no bilirubin conjugating activity, lumirubin is the principal yellow pigment found in the urine during phototherapy. The clearance rate of lumirubin in nine premature infants varied from 0.05 to 0.65 ml/min and increased with postconceptional age in parallel with increased creatinine clearance rate. The amount of lumirubin excreted per 24 h was estimated to be from 0.2 to 9.4 mg with a mean of 3.2 mg. The urinary excretion of lumirubin is a significant pathway for pigment elimination during phototherapy.

Bilirubin↗
PubMed1985

Phototherapy for neonatal jaundice: in vivo clearance of bilirubin photoproducts.

Phototherapy results in the conversion of native bilirubin to more water-soluble configurational and structural isomers. The serum half-life for the configurational isomer, the principal photoproduct in vivo, was determined by high pressure liquid chromatography in six premature infants following cessation of phototherapy. The mean half-life for this isomer was 15 h. The excretion of this isomer, calculated from the measured half-life, is less than half of daily bilirubin production, and therefore cannot account for the total bilirubin elimination observed during phototherapy. The serum concentration of the structural isomer, lumirubin, is lower than that of the configurational isomer; however, excretion is more rapid (serum half-life less than 2 h). Because of its rapid excretion, lumirubin may be an important pathway for bilirubin elimination during phototherapy.

Bilirubin↗
PubMed1985

Bilirubin photoisomerization in premature neonates under low- and high-dose phototherapy.

Photoisomerization of native bilirubin to more polar configurational isomers (Z,E-bilirubin) and structural isomers (lumirubin) was studied in 20 premature infants with physiologic jaundice to determine the effect of low-dose (6 microW/cm2/nm) v high-dose (12 microW/cm2/nm) phototherapy. Patients were assigned prospectively to receive either low- or high-dose treatment. Study groups were comparable with regard to birth weight, gestational age, and total bilirubin prior to the initiation of phototherapy. Treatment was administered with white light produced by a commercially available halogen-tungsten lamp. Dose was measured periodically during the study to ensure a uniform distribution of irradiance and constant exposure. Sera for photoisomers were obtained before initiation of treatment and at two, four, and eight hours. Photoisomers expressed as a percent of total bilirubin were determined using high-pressure liquid chromatography. Serum proportion of both configurational and structural isomers increased with the duration of phototherapy in both treatment groups. There was no significant difference between the percent of configurational isomers in low- and high-dose phototherapy groups. However, high-dose treatment produced a significantly higher proportion of the structural isomer lumirubin after four hours (0.7% low dose v 1.3% high dose, P less than .05). These data confirm that phototherapy results in both configurational and structural isomerization of bilirubin in vivo. Furthermore, the previously described "dose" effect of phototherapy may be attributed to the production of the structural isomer, lumirubin.

Bilirubin↗
PubMed1984

Phototherapy for neonatal jaundice: in vitro comparison of light sources.

Phototherapy results in the conversion of bilirubin to more water-soluble isomers. Six clinically used phototherapy lamps which differ in their emission spectra have been compared in their ability to produce configurational and structural isomers of bilirubin in vitro. For all of the lamps, the initial rate of configurational isomerization was highly correlated (r = 0.969) with the intensity of irradiation falling within the bilirubin absorption band. The percentage of the total bilirubin converted to the configurational isomer at equilibrium was dependent upon the spectral distribution of the lamp, and was greatest (26.2 +/- 1.3%) with the special blue lamp, which has a narrow spectral output centered at 445 nm. The rate of formation of the structural isomer, lumirubin, was generally dependent upon the intensity of irradiation within the bilirubin absorption band.

Bilirubin↗
PubMed1984

Actinobacillus actinomycetemcomitans endophthalmitis with subacute endocarditis.

Endocarditis and unilateral endophthalmitis due to Actinobacillus actinomycetemcomitans heart disease. The ocular infection was notable for its localized presentation and slow evolution. Treatment with systemic, subconjunctival, and topical gentamicin sulfate and ampicillin sodium achieved 20/20 acuity with a residual chorioretinal scar in the nasal periphery. Intravitreal injection of the organism into a rabbit confirmed its minimal pathogenicity within the eye. This organism must now be considered in patients with differential diagnosis of endogenous endophthalmitis complicating endocarditis and septicemia.

Actinobacillus↗
PubMed1983

Phototherapy for neonatal jaundice: optimal wavelengths of light.

Phototherapy results in transformation of bilirubin to more water-soluble isomers. The efficacy of monochromatic visible light from 350 to 550 nm in the fastest photoisomerization reaction was quantitated by high-pressure liquid chromatography. The most effective wavelengths in vitro (i.e., leading to greater than 25% photoisomer) were in the blue spectrum from approximately 390 to 470 nm. Green light (530 nm) was not only ineffective for production of photoisomer, but capable of reversing the reaction. The results indicate that any clinically useful phototherapy unit must include the blue portion of the visible spectrum, and suggest that the effectiveness of phototherapy may be increased by elimination of green light.

Bilirubin↗
PubMed1983

Metronidazole.

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Adolescent↗
PubMed1983

Susceptibility of penicillin-resistant pneumococci to eighteen antimicrobials: implications for treatment of meningitis.

The minimal inhibitory concentrations (MICs) of 18 antibiotics including 16 beta-lactam antibiotics were determined by agar dilution on 70 strains of pneumococci (25 penicillin sensitive, 18 intermediate resistant and 27 resistant). The antimicrobials tested were penicillin G, ampicillin, carbenicillin, ticarcillin, piperacillin, mezlocillin, cephalothin, cefoxitin, cefamandole, latamoxef (moxalactam), cefotaxime, cefoperazone, ceftazidime, ceftriaxone, N-formimidoyl thienamycin, SCH 29482, chloramphenicol and vancomycin. Of these agents, only cefotaxime demonstrated greater activity than penicillin against intermediate penicillin-resistant strains while cefoperazone, ceftriaxone, N-formimidoyl thienamycin and vancomycin as well as cefotaxime demonstrated activity superior to penicillin against penicillin-resistant strains. Comparison of the MIC90s of these agents with the achievable cerebrospinal fluid levels suggests that meningitis caused by penicillin-resistant pneumococci should respond to treatment with cefotaxime, cefoperazone, ceftriaxone and vancomycin.

Anti-Bacterial Agents↗