SEARCH · PubMed Health

Results for “Colorimetry”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38Linked to original sources

PubMed2001

Analysis of single polymer beads for solid phase combinatorial synthesis: the determination of reactive thiol and within batch polydispersity of bead loadings.

Polymer beads are the starting point of many synthetic protocols, and in a number of combinatorial syntheses such studies are based on single beads. It has therefore become important that individual beads carry the same functional group activity and quality control of populations of beads requires a knowledge of the distribution of activity between the individual beads. A procedure was developed for the measurement of the thiol loading of single copolymer beads which is based on the bleaching of Michler's hydrol [4,4'-bis(dimethylamino)-diphenylcarbinol (BDC-OH)]. Flow injection colorimetry permits the small volumes of solution generated from single beads to be measured with rapid turnover and with a reproducibility of ca. 2%. The solution detection limit of 0.17 mM corresponds to a bead thiol concentration of 0.33 mmol g-1. The procedure and the variability of a bead population were demonstrated using modified styrene-divinylbenzene copolymer beads. The apparatus allowed fast, simple and accurate determinations to be carried out on the individual polymer beads. Within a single batch of thiol-modified styrene-divinylbenzene beads thiol loadings ranged from < 0.35 to 2.07 mmol g-1 or 0.12 to 1.3 mumol per bead. Polydispersity may therefore significantly influence screening decisions based on single bead syntheses.

Journal Article↗

PubMed2001

Sampling and analysis of gaseous pollutants and related particulate matter in a Mediterranean site: Antalya-Turkey.

Gas phase pollutants. nitric acid (HNO3), sulfur dioxide (SO2), ammonia (NH3) and particulate matter, were collected simultaneously for six months from the Eastern Mediterranean atmosphere (Küçük Calticak, Antalya) using a "filter pack" system developed in our laboratory. This system is a combination of chemically treated filters for the collection of gaseous ammonia and sulfur dioxide. and Teflon and nylon filters for the collection of particulate matter and gaseous nitric acid, respectively. After pre-treatment, Teflon, nylon and the treated filters were analyzed by ion chromatography (IC) for major ionic species: SO4(2-) NO3- and Cl, and by colorimetry for NH4+ ion. Comparison of the SRM (Standard Reference Material) results with measured concentrations showed a good precision for the IC analyses: 3%, 1% and 2% for Cl-, NO3 and SO4(2-) ions. respectively. Most of the measured parameters were log-normally distributed. Chloride ion had the highest (4.30 microg m(-3) and HNO3 had the lowest (0.42 microg m(-3)) concentrations. Total acidity in the Eastern Mediterranean is controlled by 47.7% HNO3 and 52.8% by H2SO4. Ammonium, nss-SO4(2-) (non-sea salt sulfate) and NO3 did not show a strong correlation, (r = 0.4), which means that ammonia is not the major neutralizing species in the Eastern Mediterranean atmosphere.

Air Pollutants↗

PubMed2005

Feasibility study of preparation and certification of reference materials for nitrogen dioxide and sulfur dioxide in diffusive samplers.

This paper presents the results of a feasability study for the preparation and certification of reference materials (RMs) for nitrogen dioxide (NO(2)) and sulfur dioxide (SO(2)) in diffusive samplers. RMs for NO(2) were prepared by exposure to gas mixtures in a chamber while the RMs for SO(2) were prepared by liquid spiking. Certification of RMs for NO(2) was found feasible with a certified uncertainty of 5.8% and a proposed shelf life of 5 years. The uncertainty was calculated with contribution from the homogeneity of preparation, stability and transport of the CRMs and from an external verification of the certified value. To reach 5.8% of uncertainty, the contribution of the differences between the results of analysis by ion chromatography and colorimetry must be eliminated. It is proposed to solve this by pre-extracting the samplers with water before analysis. The results of this study indicate that the samplers are stable for at least two years before and after exposure when stored in a refrigerator. By contrast, the certification of RMs for SO(2) was found to not be feasible due to instability problems. This instability was attributed to reaction of sulfate on the walls of the samplers. Alternatively, the preparation of RMs by simultaneous exposure to SO(2) and NO(2) has been tested. Satisfying homogeneities has been reached both for NO(2) and SO(2).

Air Pollutants↗

PubMed1991

A study of thyroglobulin and peroxidase activity in the thyroid tissue of patients with non-endemic non-toxic nodular goitre.

1. A study was made of the activity of the enzyme thyroid peroxidase and of the concentration, carbohydrate composition and the degree of iodination of thyroglobulin in the thyroid glands of 60 patients with non-endemic non-toxic goitre in the nodular phase and in those of 25 control subjects. 2. Thyroid peroxidase activity was determined by the guaiacol assay and was significantly higher in patients with non-endemic non-toxic goitre than in control subjects (3.60 +/- 2.51 and 2.07 +/- 1.08 mumol of guaiacol oxidized min-1 g-1 of tissue, respectively; ranges 0.16-10.57 and 0.52-4.85 mumol of guaiacol oxidized min-1 g-1 of tissue, respectively; P less than 0.05). 3. Thyroglobulin was purified by precipitation with ammonium sulphate and Sephadex G-200 gel filtration. Two protein peaks were obtained which were identified as thyroglobulin and measured by radioimmunoassay. The concentration of thyroglobulin in the first peak was 98.94 (SD 84.87, range 0.60-455.54) mg/g of tissue for the patients with non-endemic, non-toxic goitre and 51.41 (SD 28.34, range 14.99-106.39) mg/g of tissue for the control subjects (P less than 0.01). The second peak showed 1.26 (SD 1.27, range 0.09-6.50) mg of thyroglobulin/mg of tissue for the group with non-endemic non-toxic goitre and 0.51 (SD 0.25, range 0.15-0.98 mg of thyroglobulin/mg of tissue) for the control subjects (P less than 0.01). 4. The carbohydrate composition of thyroglobulin was determined by acid hydrolysis and colorimetry, evaluating the levels of hexoses, hexosamines and sialic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1998

The calcipotriol dose-irritation relationship: 48 hour occlusive testing in healthy volunteers using Finn Chambers.

Calcipotriol is widely used in the treatment of psoriasis. Adverse lesional and perilesional irritation may occur. Allergy may occasionally be suspected. Allergy patch testing with calcipotriol may be difficult or impossible because calcipotriol is a local irritant. The aim of the present study was to assess the calcipotriol dose-irritation relationship, and establish a non-irritant patch test concentration for calcipotriol allergy patch testing. The study was a prospective, double-blind, randomized, dose titration evaluation in 180 healthy volunteers never previously exposed to calcipotriol. All individuals were patch tested with a calcipotriol dilution series (range 0.016-250 micrograms/mL). Clinical reading of test sites and measurement of erythema using a Minolta ChromaMeter were performed on days 2 and 3. Laser Doppler perfusion imaging of cutaneous blood flow was performed on day 3. Doubtful reactions (score 1/2) and weak reactions (score 1) were frequent and observed even at low dose exposure. Reactions declined in strength between the readings on day 2 and day 3. Only score 2 reactions with moderate erythema and some infiltration showed a threshold of no irritation. This threshold was confirmed by colorimetry and flowmetry. Cases of suspected allergy to calcipotriol may to avoid irritant reaction and false positive readings, be patch tested with calcipotriol 2 micrograms/mL citrate-buffered isopropanol solution applied under occlusion for 48 h using small Finn Chambers. Score 1/2 and 1 reactions are likely to reflect irritation. A positive test should be repeated after a minimum period of 3 months to ensure its consistency over time. A repeated open application test may be indicated.

Adolescent↗

PubMed1999

Effect of barrier perturbation on cutaneous salicylic acid penetration in human skin: in vivo pharmacokinetics using microdialysis and non-invasive quantification of barrier function.

We have used microdialysis in the dermis for assessing penetration kinetics of salicylic acid (SA) in healthy volunteers (n = 18), following application on the volar aspect of the left forearm. Penetration was monitored at four locations: in normal (unmodified) skin and in skin with perturbed barrier function from (i) repeated tape stripping (ii) irritant dermatitis from 1 or 2% sodium lauryl sulphate (SLS) for 24 h and (iii) delipidization by acetone. The order of the treatments was randomized according to a latin square design. Epidermal barrier function and skin irritation were assessed in each location using evaporimetry and colorimetry. Transepidermal water loss (TEWL) values confirmed that both mild (acetone), moderate (1% SLS) and severe barrier damage (tape stripping and 2% SLS) had occurred. Microdialysis sampling with two parallel probes in the dermis was performed in each of the four treatment areas for every subject. SA (5% in ethanol) was applied in a chamber glued to the skin overlying the microdialysis probes and sampling was continued for 4 h. SA was detectable in all samples and measurable in all samples from penetration through perturbed skin. Comparing the SA penetration in barrier-perturbed skin with the penetration in unmodified skin in the same subject, the mean SA penetration increase was 2.2-fold in acetone-treated skin (P = 0.012), 46-fold in mild dermatitis and 146- and 157-fold in severe dermatitis and tape stripped skin, respectively (P < 0.001). The penetration of SA significantly correlated with the measurements of barrier perturbation by TEWL (P = 0.01) and erythema (P = 0.02) for each individual. Microdialysis sampling of SA penetration was more sensitive than non-invasive measuring techniques in detecting significant barrier perturbation in acetone-treated skin. A positive dose-response relationship for the percutaneous penetration of SA in response to increasing SLS pretreatment concentrations and thus the degree of irritant dermatitis was found. When analysing data by location on the forearm, a tendency towards an intraregional variation in the reactivity to barrier damage was found, with the most proximal location displaying higher reactivity scores than the most distal location in response to the same barrier perturbation procedures. The penetration of SA was not significantly different between locations. In conclusion, using microdialysis in the dermis to obtain real-time dermal pharmacokinetics in the target organ, this study demonstrates highly increased and differentiated cutaneous penetration of SA in barrier-perturbed skin. The measured drug penetration was demonstrated to correlate with non-invasive quantification of barrier damage.

Administration, Topical↗

PubMed2002

A randomized, controlled study of the safety and efficacy of topical corticosteroid treatments of sunburn in healthy volunteers.

Topical glucocorticosteroids are frequently used for the treatment of sunburn despite the scarcity of randomized, double-blind controlled trials to support this indication. This randomized, intra-individually controlled trial compared the efficacy and safety of two topical glucocorticosteroids, 0.1% methylprednisolone aceponate milk (MPA) and 0.1% hydrocortisone 17-butyrate emulsion (HCB), for treatment of sunburn in 24 healthy volunteers of skin type III. After irradiation of the skin by simulated sunlight, treatments were blinded and randomly allocated to 36 cm2 test areas on both sides of the spine. Volunteers were treated twice daily for 7 days and assessed daily with 1-day follow-up. The untreated area was not blinded. Primary efficacy measures were sum score and sunburn reaction based on erythema, oedema, burning and itching. Secondary efficacy measures were physician's global assessment, individual signs/symptoms, colorimetry, dermatological improvement, and time to healing. Intra-individual comparisons were made. Differences in sum score were apparent on days 3-4 and significant on days 4-5 for corticosteroids compared with nontreatment. Treated areas had significantly lower sunburn reaction than untreated areas (P = 0.1% and P = 0.5% for MPA and HCB, respectively). Differences between treatments were not significant. Secondary efficacy measures were in line with these findings. None of the three adverse events reported were considered to be related to treatment. We conclude that MPA and HCB are safe and effective in the treatment of sunburn.

Administration, Topical↗

PubMed2000

Microcirculatory response of skin to benzoic acid and methyl nicotinate in patients with diabetes.

AIMS: In view of the relationship between microvascular pathology and organ complications in diabetes mellitus, the aim of the present study was to examine the microvascular response of upper arm skin to non-immunological contact irritants in 17 insulin-dependent diabetic patients and 11 non-diabetic controls. METHODS: Non-immunological contact urticaria, an inflammatory reaction mediated in a unique way, not previously studied in diabetic patients, was examined. The test agents were benzoic acid and methyl nicotinate. The intensity of the reactions was measured using laser-Doppler flowmetry and colorimetry. The patients were divided into two groups, depending on whether they had had diabetes for less or more than 10 years. RESULTS: There were no differences in the maximal blood flow responses between the groups, but the diabetic patients showed increased blood flow responses to the lowest irritant concentrations compared to the controls. The reactions in the two groups of diabetic patients were similar. CONCLUSIONS: The present study suggests that the microvascular reactivity of diabetic skin to non-immunological contact irritants is increased.

Adult↗

PubMed2003

Analytic quantification of solar lentigines lightening by a 2% hydroquinone-cyclodextrin formulation.

BACKGROUND: The innate melanin pigmentation of skin is modulated during lifetime by a series of factors, including ageing and chronic ultraviolet light exposure. Actinic lentigines may be of particular concern from a cosmetic point of view. Conventional hypopigmenting agents are usually deceptive. Using cyclodextrins to form inclusion compounds with these agents might represent a more active drug delivery system. OBJECTIVE: To assess sensitive and objective methods predicting the effects of a 2% hydroquinone-cyclodextrin formulation on solar lentigines. STUDY DESIGN: Thirty Asian adults applied a 2% hydroquinone-cyclodextrin formulation once daily on solar lentigines of a forearm for 2 months. The other untreated forearm served as a control. Monthly assessments were performed using skin colorimetry and fluorescence video recording combined with image analysis. Corneomelametry following photodensitometry of cyanoacrylate skin surface strippings was performed after melanin staining of the samples. RESULTS: The control untreated solar lentigines showed no significant variations in the biometrological parameters. By contrast, the test formulation induced lightening of the solar lentigines. Corneomelametry disclosed improvement after 1 months' treatment, whereas the other assessments only reached significance after 2 months. CONCLUSIONS: A 2% hydroquinone-cyclodextrin formulation proved to be effective in lightening actinic lentigines. Corneomelametry predicted the effects discernible at a later stage by in vivo colour assessments of the melanin content.

Administration, Topical↗

PubMed1999

Fibronectin augments monocyte adhesion to low-density lipoprotein-stimulated mesangial cells.

BACKGROUND: Glomerular monocyte infiltration is an early feature of lipid-mediated renal injury in animal models. Interactions between mesangial and infiltrating mononuclear cells may contribute to the development of glomerular scarring. METHODS: Adherence of U-937 monocytes to low-density lipoprotein (LDL)- or tumor necrosis factor alpha (TNFalpha)-prestimulated human mesangial cells was assessed by colorimetry of nuclear staining with crystal violet. Blocking antibodies were added to examine the mechanisms of binding. Adhesion molecule expression and fibronectin synthesis were measured by ELISA. RESULTS: Preincubation of mesangial cells for 24 hours with LDL (100 micrograms/ml) or mildly oxidized (minimally modified) LDL (MM-LDL) increased monocyte adhesion by 207% and 240%, respectively, compared with control nonstimulated cells (100%). TNFalpha (100 U/ml) enhanced binding by 335% and up-regulated intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression by 505% and 179%, respectively, as compared with MM-LDL (120% and 116%) and LDL, which had no effect. Blocking antibodies to these adhesion molecules inhibited monocyte binding to TNFalpha- and, to a lesser extent, MM-LDL-primed mesangial cells, but had no effect after LDL pretreatment. In contrast to TNFalpha, MM-LDL and LDL increased mesangial cell-associated fibronectin, whereas antibodies to fibronectin inhibited monocyte binding to lipoprotein-stimulated but not TNFalpha-stimulated cells. CONCLUSIONS: Although enhanced monocyte adhesion to TNFalpha- and, to a lesser extent, MM-LDL-stimulated mesangial cells is mediated by changes in ICAM-1 and VCAM-1 expression, both LDL and MM-LDL promote similar cellular interactions as a result of increased fibronectin production.

Cell Adhesion↗

PubMed2000

Analysis of nanoliter samples of electrolytes using a flow-through microfluorometer.

Several techniques have been developed to study the transport properties of nanoliter samples of renal tubule segments, such as continuous flow colorimetry and continuous fluorometry. We have extended the capability of the NANOFLO, a flow-through microfluorometer, designed for measurement of carbon dioxide, urea, ammonia, glucose, lactate, etc., to analyze sodium, calcium and chloride ions, using three commercially available fluorescent indicators for intracellular and extracellular measurements. The selection of fluorescent indicator for each electrolyte was dependent on the optimal match of the dissociation constant and the analyte concentration range of interest. Using Fluo-3 dye we achieved a detection limit for Ca2+ of 0.1 pmol and selectivity over Mg2+ of between 7:1 to 10:1. Using sodium green dye we achieved detection limit for Na+ of 12 pmol and a selectivity over K+ of 40:1. The detection limit for Cl- using lucigenin dye was 10 pmol. This technique can be readily adapted for the measurement of other physiologically important ultralow volume.

Acridines↗

PubMed2003

Monocyte adhesion to mesangial matrix modulates cytokine and metalloproteinase production.

BACKGROUND: Monocytes migrate into the glomerular mesangium during acute inflammatory renal disease, differentiate into macrophages, and may play a key role in the development and progression of glomerular scarring. Treatment strategies that inhibit monocyte infiltration ameliorate glomerular injury in animal models. Mesangial matrix contains several potential monocyte-binding domains that may contribute to monocyte entrapment and modulate cell activation. METHODS: Adhesion of peripheral blood-derived monocytes to matrix synthesized by human mesangial cells and to individual matrix proteins was assessed by colorimetry of nuclear staining with crystal violet. Monoclonal antibodies were used to identify the cell-surface integrins and matrix ligands involved. Monocyte proliferation was assessed by 3H-thymidine incorporation and cytokine production using enzyme-linked immunosorbent assay (ELISA). Secretion of metalloproteinases and their inhibitors was determined by zymography and ELISA, respectively. RESULTS: Monocytes bound to matrix synthesized by mesangial cells. Prestimulation of mesangial cells with tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta (TGF-beta) enhanced matrix fibronectin content (P < 0.001) and monocyte binding (P < 0.001). Blocking antibodies to fibronectin, as well as to the integrins very late antigen-4 (VLA-4) and VLA-5, reduced monocyte adhesion to mesangial matrix by approximately 50%. Incubation of monocytes with matrix, fibronectin, laminin and collagen IV enhanced production of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), TNF-alpha and metalloproteinase-9 (MMP-9) when compared to cells incubated in plastic wells. However, there was no apparent difference in proliferation rate and no change in production of metalloproteinase inhibitors. CONCLUSION: Monocyte activation within the glomerulus may be mediated by binding to mesangial matrix components, particularly fibronectin. Matrix-mediated activation enhances production of inflammatory cytokines and matrix-degrading enzymes.

Cell Adhesion↗

PubMed1998

Growth inhibitory and bactericidal activities of lansoprazole compared with those of omeprazole and pantoprazole against Helicobacter pylori.

BACKGROUND: Helicobacter pylori plays a role in the pathogenesis of both duodenal and gastric ulcers. The aim of this study was to evaluate the effect of the proton pump inhibitor (PPI), lansoprazole, commonly used in eradication regimens, on growth, bactericidal activity and morphology of H. pylori in vitro in comparison with other PPIs. MATERIALS AND METHODS: Growth inhibitory activity of each of the PPIs was evaluated by determining minimum inhibitory concentrations using an agar dilution method. Bactericidal activity was determined by analysis of the viable cells in culture at various time points after incubation with different concentrations of the PPIs. Bacterial morphology was examined using scanning electron microscopy of fixed cells after exposure to the test substances. Urease activity in cell extracts of H. pylori that had been incubated with increasing concentrations of the PPIs was determined by colorimetry. RESULTS: The growth inhibitory activity of lansoprazole was significantly more potent than that of omeprazole or pantoprazole (MIC90 6.25 vs. 25 and 100 micrograms/ml, respectively). Exposure of H. pylori to lansoprazole produced loss of viability and an aberrant bacterial morphology, which was more extensive than seen with omeprazole or pantoprazole. Lansoprazole dose dependently inhibited urease activity; its effectiveness was comparable with omeprazole but more potent than pantoprazole. CONCLUSIONS: The mechanism of action that leads to loss of viability of H. pylori cells appears to differ between the three PPIs investigated; lansoprazole was the most potent of the three agents in terms of growth inhibition and disruption of bacterial morphology.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1999

Review of modern techniques in detecting port-wine stain response to laser therapy.

BACKGROUND: Traditional mechanisms of assessing port-wine stain response to laser therapy have rested mainly on subjective determinations by physician and patient. However, the wide variation in treatment response poses a profound need for objective devices to measure treatment outcomes so that maximum effectiveness of therapy can be achieved without unnecessary repeat treatments. OBJECTIVE: The purpose of this paper will be to review noninvasive techniques to measure port-wine stain response to laser therapy. METHODS: This report is based on a review of medical and bioscience literature. RESULTS: Several techniques including laser Doppler, reflectance spectrophotometry, tristimulus colorimetry, and videomicroscopy have been developed to address the need for objective measurement devices. CONCLUSION: While many instruments are available, these techniques are limited by cost, small test size area, and/or inconclusive correlation with clinical response. A number of experimental techniques may circumvent many of the problems inherent in currently-available commercial technologies.

Diagnostic Imaging↗

PubMed2002

Prediction of the risk of myocardial infarction from polymorphisms in candidate genes.

BACKGROUND: Although epidemiologic studies have suggested that several genetic variants increase the risk of myocardial infarction, large-scale association studies that examine many polymorphisms simultaneously are required to allow reliable prediction of the genetic risk of myocardial infarction. METHODS: We used a fluorescence- or colorimetry-based allele-specific DNA-primer-probe assay system to determine the genotypes of 112 polymorphisms of 71 candidate genes in 2819 unrelated Japanese patients with myocardial infarction (2003 men and 816 women) and 2242 unrelated Japanese controls (1306 men and 936 women). RESULTS: In an initial screening of the 112 polymorphisms for an association with myocardial infarction in 909 subjects, 19 polymorphisms were selected in men and 18 in women by means of logistic-regression analysis, after adjustment for age, body-mass index, and the prevalence of smoking, hypertension, diabetes mellitus, hypercholesterolemia, and hyperuricemia. In a large-scale study involving the selected polymorphisms and the remaining 4152 subjects, similar logistic-regression analysis revealed that the risk of myocardial infarction was significantly associated with the C1019T polymorphism in the connexin 37 gene (P<0.001) in men and the 4G-668/5G polymorphism in the plasminogen-activator inhibitor type 1 gene (P<0.001) and the 5A-1171/6A polymorphism in the stromelysin-1 gene (P<0.001) in women. CONCLUSIONS: Determination of the genotypes of the connexin 37, plasminogen-activator inhibitor type 1, and stromelysin-1 genes may prove reliable in predicting the genetic risk of myocardial infarction and might thus contribute to the primary prevention of this condition.

Case-Control Studies↗

PubMed2001

Changes of skin blood flow and color on lesional and control sites during PUVA therapy for psoriasis.

BACKGROUND: Although the colors of psoriatic lesions, largely determined by erythema and scales, are important clinical indicators, expressing them in an objective manner is difficult. Cutaneous blood flow (CBF) also affects erythema. Serial measurement of these parameters during phototherapy was almost nonexistent. OBJECTIVE: The objectives of our study were to observe the changes of color parameters and the CBF of psoriatic lesions during PUVA therapy and to determine their clinical significance. METHODS: CBF, measured by laser Doppler flowmetry, and color parameters, measured by tristimulus colorimetry and reflectance spectrophotometry, were assessed in 13 patients with psoriasis who received PUVA therapy. RESULTS: The values of CBF, erythema index (EI), and a(*) (color parameter representing red-green axis) in psoriatic lesions were significantly different from those observed in the control sites before therapy. The parameters of psoriatic lesions normalized according to the clinical improvement and approached those of the control sites as PUVA therapy progressed. The values of melanin index (MI), L(*) (color parameter representing white-black axis), and b(*) (color parameter representing yellow-blue axis) showed no significant difference between the psoriatic plaques and the control sites. They all displayed changes toward darkening and indicated tanning induced by PUVA therapy. Serial changes presented a generally unidirectional pattern in the control sites. However, this was not always the case in psoriatic lesions because scale, infiltration, and erythema also affected the measurement of blood flow and the color of the skin. CONCLUSION: Color parameters and CBF were closely related with clinical improvement according to consecutive phototherapy. They may serve as objective indices for the visible morphology and underlying lesional pathophysiology of psoriasis.

Adult↗

PubMed1975

A charcoal sampling method and a gas chromatographic analytical procedure for carbon disulfide.

Research is reported concerning an acceptable method for sampling and analyzing samples for carbon disulfide. Test atmospheres of carbon disulfide were generated dynamically using the syringe injection method, ant the theoretical concetnration verified by a liquid absorbent, colorimetric method. The CS2 was adsorbed on charcoal tubes, eluted with benzene, and quantitated with a gas chromatography equipped with a sulfer flame photometric detector. The results compared with the colorimetris analysis. The sensitivity of this method is 1 mug on a charcoal tube. The charcoal tubes were also tested for breakthrough volumes, holding power vs time, and the effect of air transport and temperature cycles.

Adsorption↗

PubMed2000

Antibiotics and Wolbachia in filarial nematodes: antifilarial activity of rifampicin, oxytetracycline and chloramphenicol against Onchocerca gutturosa, Onchocerca lienalis and Brugia pahangi.

The activity against filarial parasites of the antibiotics rifampicin, oxytetracycline and chloramphenicol was examined. In addition, transmission electron microscopy was used to study the effects of rifampicin and oxytetracycline on filarial tissues and on the endosymbiont bacterium, Wolbachia. When tested in vitro at a concentration of 50.0 microM, each of the three antibiotics significantly reduced the motility levels of male Onchocerca gutturosa. Rifampicin, however, was the most active, virtually immobilizing the parasite by the end of the 40-day trial and producing an 84% reduction in viability (as measured by formazan-based colorimetry). In tests against O. lienalis microfilariae (mff) in CBA mice, the numbers of mff recovered after treatment with oxytetracycline at 100, 25 or 6.5 mg/kg daily, for 15 days, were 56% (P < or = 0.03), 38% (P> 0.05) and 45% (P = 0.05) less than that recovered from the untreated controls, respectively. In another trial in mice, rifampicin (100 mg/kg daily for 15 days) was found to be the most active (causing a 74% reduction in the number of mff recovered--approximately equal to that achieved with the positive control of a single dose of ivermectin at 2 microg/kg), with chloramphenicol also showing significant activity (39% reduction). In further, in-vivo trials, at three dose levels (100, 25 or 6.25 mg/kg daily, for 15 days), all three antibiotics were tested against adult Brugia pahangi in the peritoneal cavities of jirds. None of the antibiotics produced a significant reduction in the numbers of live worms recovered, although a marginal effect was observed in eight of the nine antibiotic-treated groups. A further extended trial with rifampicin and oxytetracycline resulted in 43% and 38% reductions in worm recoveries, respectively (not statistically significant but consistent with a marginal effect); some of these worms appeared less motile and qualitatively in poor condition compared with those recovered from untreated jirds. Ultrastructural studies of these treated worms revealed that virtually all of the endosymbiont bacteria had been cleared from the parasite tissues. The tissues of the adult worms appeared to be largely intact but with a granulomatous response of host cells adhering to some specimens. However, developing uterine forms appeared to be abnormal and extensively damaged, showing an abrogation of embryogenesis. In contrast, worms recovered from control animals contained large numbers of Wolbachia, had no adherent host cells, and showed normal ultrastructure; the female worms exhibited a full range of intra-uterine developing stages from eggs to stretched mff. It is likely that the activity of these antibiotics against the endosymbiont Wolbachia causes the observed antifilarial activity, although some direct effect of each drug on filarial viability cannot be ruled out.

Animals↗