Starch utilization by Bacteroides ovatus isolated from the human large intestine

OBJECTIVE: It was hypothesized that there is an inverse relationship between resin-enamel bond strength and bonded cross-sectional area, and that there are regional differences in resin-enamel bond strength. METHODS: The facial and lingual surfaces of extracted human third molars were ground down 0.3 mm using 240 grit abrasive paper and were then bonded with either Clearfil Liner Bond 2 or Scotchbond Multi-Purpose Plus adhesive systems using the manufacturer's instructions. The bonded surfaces then received a resin composite build-up. After 24 h of storage in water, the bonded teeth were vertically serially sectioned into 1.0 mm thick slabs using a diamond saw, and the bonded surface area at the resin-enamel interface was varied from 0.5 to 3.0 mm2 using a diamond saw under microscopic observation. The trimmed region was varied from the occlusal third of the facial or lingual enamel to the middle third, to the cervical third. The trimmed specimens were then glued to a Bencor Multi-T device, placed in an Instron testing machine and stressed to failure at 1 mm/min. A three-factor ANOVA was used to compare bond strengths (buccal vs. lingual, occlusal vs. middle vs. cervical-third, vs. materials). Regression analysis was used to examine the relationship between bond strength and bonded cross-sectional area for each material on occlusal enamel. RESULTS: For both bonding systems, there was a highly significant (p < 0.001) inverse exponential relationship between tensile bond strength (y axis) and bonded cross-sectional area (x axis) with y intercepts of 51 and 59 MPa for Clearfill Liner Bond 2 and Multi-Purpose Plus, respectively. Using both materials, the highest bond strengths were measured in the occlusal third, which were significantly higher (p < 0.05) than those made to cervical enamel. SIGNIFICANCE: Like resin-dentin bonds, resin-enamel bonds exhibit an inverse relationship with cross-sectional area. This relationship becomes more apparent at bonded surface areas below 2 mm2 and is probably due to reductions in the number of interfacial stress-raisers as samples are made smaller.     

Determination of sumatriptan succinate in human plasma by high-performance liquid chromatography with coulometric detection and utilization of solid-phase extraction

Sumatriptan succinate (the analyte) and naloxone (the internal standard) were extracted from plasma with a solid-phase extraction technique. Chromatography and detection were performed by isocratic reversed-phase high-performance liquid chromatography with coulometric end-point detection. The standard curve was linear over the range 0-100 ng/ml of sumatriptan succinate in plasma. The reproducibility (as defined by the coefficient of variation, C.V.) over the range of the standard curve was 4.9-7.3%. The recovery averaged 83%. The sensitivity was 0.25 ng of sumatriptan on column (allowing a concentration of 0.5 ng/ml to be determined from a 1-ml plasma sample volume). Plasma profiles of the analyte following subcutaneous (s.c.) administration in eight normal male volunteers, are presented.     

A rapid method for the determination of plasma mexiletine levels by gas chromatography

We used the computed tomographic scanner in the assessment of ten cases of retinoblastoma in children. With each patient the stage of the disease before operation could be more accurately defined and therefore more definite treatment could be undertaken.     

A rapid micromethod for measuring theophylline in serum by reverse-phase high-performance liquid chromatography

We describe an assay system for measuring theophylline in 25 microliters of serum. The procedure involves extraction with a 95:5 mixture of chloroform:isopropanol containing beta-hydroxypropyltheophylline as internal standard, and reverse-phase chromatography on a 4 mm x 30 cm column containing "micron Bondapak C18." Theophylline and beta-hydroxypropyltheophylline are eluted with a 90:10 mixture of sodium acetate butter (20 mmoles/litre pH 4.0) and acetonitrile at a flow rate of 1.8 ml/min., are detected by their absorbance at 254 nm, and quantitated by measuring peak areas. Column temperature has not been found to be critical in this analysis. Each analysis requires 9 minutes of chromatography time with a total analysis time of 20 minutes. Analytical recoveries were found to be 71 to 75% for theophylline and 94% for beta-hydroxypropyltheophylline. This difference in recovery is corrected when determining the theophylline concentration in unknown samples. The method has good precision (coefficients of variation between 7.0% and 7.9% for therapeutic and toxic concentrations). The results obtained with this method compare favourably with results obtained by a published cation-exchange high-performance liquid chromatographic method. None of the metabolites of theophylline, common compounds related to theophylline in structure or drugs tested have been found to interfere with the analysis described.     

Mass screening for histidinaemia:rationalization by selective thin layer chromatography. First results

Since 1974 histidine and urocanic acid was estimated by thin layer chromatography (TLC) in all newborn infants in whom histidine blood levels had to be controlled because of an abnormal Guthrie-test. This entailed using dried blood spotted on filter paper to rationalize newborn screening for histidinaemia thus reducing the work involved. Three cases of histidinaemia were found amongst 66.064 newborn infants. In order to find these, 830 initialy suspicious Guthrie tests had to be checked. This is a control frequency of 1:80. 384 controls were necessitated by inhibition-zones, 482 by initialy elevated blood levels. Histidine and urocanic acid concentrations generally correlated well in the TLC; only 9 newborn infants showed results suggesting histidinaemia (elevated histidine and absent urocanic acid). All three histidinaemias discovered by Guthrie-test aswell were among them, so that in the end, with only 9 controls combining Guthrie-test and TLC, the same effectiveness could have been reached, as compared to 830, when using the Guthrie-test alone.     

Determination of free bile acids in pharmaceuticals by thin layer chromatography and high performance liquid chromatography

High-performance liquid chromatography with evaporative light scattering detection (HPLC-ELSD) and thin layer chromatography with flame ionization detection (TLC-FID) have been applied to the separation of five main free bile acids present in humans: cholic (CA), chenodeoxycholic (CDCA), deoxycholic (DCA), lithocholic (LCA) and ursodeoxycholic (UDCA) acid. HPLC separation was performed on Biospher Si 100 column using a mixture of n-heptane, isopropanol, ethylacetate, methanol and glacial acetic acid as a mobile phase. All the compounds were separated in less than 12 minutes by using a gradient elution mode. TLC-FID separation was performed on S-II Chromarods with a mixture of isooctane, ethylacetate and glacial acetic acid as a mobile phase. HPLC-ELSD method was applied to the determination of CDCA and UDCA in pharmaceuticals and their purity control when LCA, DCA and CA were considered as impurities.     

Thin layer chromatographic fingerprint of Rhizomata of Coptis spp

This paper introduces the use of optimized solvent system with twice-ascending-development in twin trough chamber on TLC silica gel plate for the separation of protoberberine-type alkaloids contained in Rhizomata of Coptis spp. Nine to eleven spots including the main and the 'minor' alkaloids in the samples can be observed on the chromatograms obtained under controlled conditions. The fluorescence and UV-absorption TLC scanning profile can serve as fingerprint for the analysis of commercial samples of Rhizomata of Coptis spp.     

Identification of dextrans using rapid fluid chromatography

It is reported about an analytical method for routine control of clinical dextrans, a method which is considerably quicker than the previously used ones. It is based on the application of HPLC (high pressure liquid chromatography) to permeation chromatography of dextrans on controlled pore glass beads (CPG). The time required for a permeation chromatogram of a dextran sample could be reduced to less than one hour. Calibration curves, necessary for the evaluation of the chromatograms, were established by use of Pharmacia-Testdextrans.     

Simple and rapid method for determining nicotinamide adenine dinucleotide synthetase activity by high-performance liquid chromatography

A method is described for the determination of nicotinamide adenine dinucleotide synthetase (NADS) activity in human blood. Using high-performance liquid chromatography (HPLC), the formed NAD is separated from the substrates and the other blood components in less than 13 min. The activity of NADS determined by HPLC is closely correlated with that determined by the conventional spectrophotometric method, which requires two steps of enzyme reaction. The present method is simple and reliable and facilitates the routine analysis of NADS activity.     

Separation and detection of phencyclidine in urine by gas chromatography

A rapid, sensitive and selective analytical procedure for phencyclidine and one of its metabolites in urine has bee developed. Three techniques have been studied for extraction of the drug from the biological matrix: (a) reversed-phase XAD resin, (b) charcoal absorption, and (c) solvent extraction using chloroform. Temperature-programmed gas chromatography was used to quantitate the illicit drug. Solvent extraction appears to offer the most efficient separation of the drug and its metabolite, as the recovery was 94% and the technique required only 7-8 min per sample. Reversedphase column extraction is also quite useful; although more time-consuming for an indivisual sample, it would be useful for screening purposes.     

Extrachromosomal elements in a variety of strains representing the Bacteroides fragilis group of organisms

Previous nucleic acid association studies have identified at least nine deoxyribonucleic acid (DNA) homology classes of the Bacteroides fragilis group of organisms. Using these classes as a taxonomic framework, we have screened representative strains of the B. fragilis group for the presence of extrachromosomal (plasmid) DNA. [3H]thymidine-labeled cell lysates were subjected to sodium dodecyl sulfate-salt precipitation, and supernatant fractions from such preparations were analyzed using cesium chloride-ethidium bromide equilibrium centrifugation. One strain from each group was examined in this fashion. Five of the strains were judged to contain no detectable plasmid DNA; however, four strains were observed to yield satellite bands corresponding to covalently closed circular plasmid DNA. Plasmid DNA from such gradients was subjected to velocity sedimentation through both neutral and alkaline sucrose gradients to determine molecular size. A 23 X 10(6)-molecular-weight plasmid was found in a B. fragilis strain representing one DNA homology group of this species, whereas a 3 X 10(6)-molecular-weight plasmid was found in a B. fragilis strain representing a second homology group. Similarly, a 31 X 10(6)-molecular-weight plasmid was found in a Bacteroides thetaiotaomicron strain representing one DNA homology group of this species, whereas a 3 X 10(6)-molecular-weight plasmid was found in a B. thetaiotaomicron strain representing a second homology group. In all instances, the small-molecular weight plasmids were present to the extent of about 15 copies per chromosomal equivalent, whereas the large plasmids were present to the extent of approximately 1 copy per chromosomal equivalent. The biological function of these plasmids is unknown.     

Determination of netilmicin sulfate by liquid chromatography with pulsed electrochemical detection

The determination of netilmicin sulfate by liquid chromatography using a column packed with poly (styrene-di-vinylbenzene) and pulsed electrochemical detection on a gold electrode is described. The mobile phase consisted of an aqueous solution containing 35 g 1-1 of sodium sulfate, 0.5 g 1-1 of sodium octanesulfonate, 10 ml 1-1 of tetrahydrofuran and 50 ml 1-1 of 0.2 M phosphate buffer (pH 3.0). The total analysis time was not more than 25 min. The effects of the different chromatographic parameters on this selection were also investigated. When a number of commercial samples of netilmicin sulfate was analyzed using this method, eight different components were separated, three of which were of unknown identities.     

Measurement of nifedipine in plasma by gas--liquid chromatography and electron-capture detection

In this method for measuring nifedipine, a calcium-channel inhibitor now widely used in the treatment of cardiovascular disease, the drug is extracted from plasma under basic conditions into toluene, and an aliquot of the extract is injected directly into a gas chromatograph equipped with an OV-101 column and an electron-capture detector. The standard curve is linear between 1 and 100 micrograms/L; the assay measures not only nifedipine, but also a major metabolic product (found only after oral administration of the parent drug) and photodegradation products. The procedure is rapid and adequately sensitive for routine use in clinical monitoring of nifedipine in plasma.