Search results for "Reagents"

Biocompatibility of various collagen membranes in cultures of human PDL fibroblasts and human osteoblast-like cells

2004

The aim of the present study was to evaluate the biocompatibility of differently cross-linked collagen membranes in cultures of human PDL fibroblasts and human osteoblast-like cells. Four collagen membranes [BioGide (BG), BioMend (BM), Ossix (OS) and TutoDent (TD)] were tested. Cells plated on culture dishes (CD) served as positive controls. Six specimens of each membrane were incubated with (1) human PDL fibroblasts [2 x 10(4) cells] (n=24), and (2) human osteoblast-like cells (SaOs-2) [2 x 10(4) cells] (n=24) under standardized conditions. After 7 days, adherent cells were stained with hematoxylin and counted using a reflected light microscope and the cell density per square millimeter wa…

New spectrophotometric procedure for determining cefotaxime based on derivatization with 1,2-naphthoquinone-4-sulphonate into solid-phase extraction …

1998

Cefotaxime was derivatised with 1,2-naphthoquinone-4-sulphonate (NQS), extracted into solid-phase cartridges (C18) and detected using a UV-visible detection system. Optimum conditions for this new procedure were: hydrogencarbonate-carbonate buffer, pH 10.5, 5-min reaction time at 25 degrees C and an NQS concentration of 7.1x10(-3) mol l(-1). The accuracy and the precision of the liquid-solid procedure were tested. The procedure was used to measure cefotaxime in pharmaceutical and urine samples. The results obtained were contrasted with those reported for a HPLC method for urine samples. The generalized H-point standard additions method was used to measure cefotaxime in urine samples.

Lower strength of the human posterior patellar tendon seems unrelated to mature collagen cross-linking and fibril morphology

2009

The human patellar tendon is frequently affected by tendinopathy, but the etiology of the condition is not established, although differential loading of the anterior and posterior tendon may be associated with the condition. We hypothesized that changes in fibril morphology and collagen cross-linking would parallel differences in material strength between the anterior and posterior tendon. Tendon fascicles were obtained from elective ACL surgery patients and tested micromechanically. Transmission electron microscopy was used to assess fibril morphology, and collagen cross-linking was determined by HPLC and calorimetry. Anterior fascicles were markedly stronger (peak stress: 54.3 ± 21.2 vs.…

Acetic acid-guided biopsies after magnifying endoscopy compared with random biopsies in the detection of Barrett's esophagus: a prospective randomize…

2006

Background In contrast to standard video endoscopy, magnifying endoscopy after local acetic acid application enables recognition of mucosal surface architecture. Objective To investigate the diagnostic yield of magnifying endoscopy with acetic acid–targeted biopsies compared to random, 4-quadrant biopsies. Design Prospective randomized trial (ratio 1:1) with crossover design. Setting Two referral hospitals in Germany. Patients Thirty-one patients with Barrett's esophagus or visible columnar-lined lower esophagus. Interventions Patients were randomized to undergo either standard video endoscopy with 4-quadrant biopsies or magnifying endoscopy in conjunction with acetic acid application. All …

Comparison of computed virtual chromoendoscopy and conventional chromoendoscopy with acetic acid for detection of neoplasia in Barrett's esophagus.

2007

Background and study aims Computed virtual chromoendoscopy (CVC) is a new imaging technique that enhances mucosal surface contrast and highlights the vascular pattern without the need for dye-spraying as in conventional chromoendoscopy. The aim of this prospective randomized pilot study with a crossover design was to compare CVC with conventional chromoendoscopy with acetic acid (CAA) for the detection of high grade intraepithelial neoplasia (HGIN) or early cancer in patients with Barrett's esophagus. Patients and methods 57 patients with Barrett's esophagus (mean length 3.8 cm) and a history of HGIN/early cancer or suspected HGIN/early cancer were randomly allocated to undergo either CAA o…

Assessment of DNA-protein crosslinks in the course of aging in two mouse strains by use of a modified alkaline filter elution applied to whole tissue…

1999

Abstract Two different mouse strains have been used for determination of age dependence of DNA-protein crosslinks by alkaline filter elution: a long lived laboratory strain, NMRI and an accelerated senescence-prone, short lived strain, SAMP1. Five organs were selected: Brain, kidney, lung, heart and liver. Remarkably in all five organs of short lived SAMP1 mice crosslinks increased significantly with age. In NMRI however only in brain and heart a significant rise in old age has been observed, while in the other organs there was no increase in DNA-protein crosslinking. Appreciable mitotic activity which is lacking in brain and heart could be the reason for this difference. Poor repair in all…

Synthesis of terpenoid unsaturated 1,4-dialdehydes. Pi-facial selectivity in the Diels-Alder reaction of the 1-vinyl-2-methylcyclohexene moiety of po…

2000

High-pressure flow-injection assembly. Indirect determination of glycine by atomic absorption spectrometry.

1991

A procedure for the determination of glycine is described. The method is based on the reaction of the analyte with finely powdered, solid copper(II) carbonate in a continuous-flow assembly. The optimum experimental conditions of pH, temperature, sample volume, flow-rate, column length and internal diameter, and the linear range of calibration, were studied. Interference from foreign substances that accompany this amino acid in pharmaceutical formulations was studied, and the method was applied to the determination of glycine.

Selective determination of trimethylamine in air by liquid chromatography using solid phase extraction cartridges for sampling.

2004

Abstract The selective determination of trimethylamine (TMA) in air by liquid chromatography is reported. Sampling is effected by flushing air through C18-packed solid-phase extraction (SPE) cartridges at a flow rate of 15 mL/min for 15 min. Next, TMA is desorbed from the cartridges and injected into the chromatographic system. The analyte is then selectively retained on a precolumn ( 20 mm ×2.1 mm i.d., packed with 30 μm, Hypersil C18 phase), and derivatized on-line by injecting 9-fluorenylmethyl chloroformate (FMOC). Finally, the TMA-FMOC derivative is transferred to the analytical column ( 125 mm ×4 mm i.d., LiChrospher 100 RP18, 5 μm), and monitored at 262 nm. The method was applied to …

On-Line Derivatization into Precolumns for the Determination of Drugs by Liquid Chromatography and Column Switching:  Determination of Amphetamines i…

1996

A chromatographic system for the on-line derivatization of drugs using column switching is described. The system uses a 20 mm × 2.1 mm i.d. precolumn packed with a unmodified ODS stationary phase. This column is used for sample cleanup and enrichment of the analytes. Next, the trapped analytes are derivatized by injection of the derivatization reagent into the precolumn. Finally, the derivatives are transferred to the analytical column for their separation under reversed-phase conditions. The influence of several parameters such as the reaction time, the amount of derivatization reagent, or the system design has been studied using some amphetamines as model compounds and three derivatizatio…