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PubMed2004

Is it the method or the process-separating the causes of low recovery.

During the development of a tablet formulation, a solvent capable of extracting 100% of the drug from the tablet excipients must be identified as part of the analytical assay method. When a low drug recovery from a tablet is observed with the assay method, it must be determined whether a problem with the manufacturing process exists, or if the extraction of the drug was incomplete. A solvent screen study was conducted with CP-122,721 prototype formulations to select a robust solvent for the assay method. However, low tablet assay values (ca. 95%) were routinely observed during tablet formulation development and process scale up. Drug-excipient interactions in a variety of solvents were subsequently evaluated to confirm the selection of the extraction solvent as capable of 100% extraction. At this point the focus of the investigation was placed on process-related sources of low recovery, such as loss of drug to manufacturing equipment and/or segregation during the tableting process. The results suggest that the low drug recovery observed for the CP-122,721 tablets was due to segregation during the manufacture, while the selected extraction solvent was able to eliminate any interactions between CP-122,721 and the tablet excipients.

Adsorption↗
PubMed2002

Selection bias in gene extraction on the basis of microarray gene-expression data.

In the context of cancer diagnosis and treatment, we consider the problem of constructing an accurate prediction rule on the basis of a relatively small number of tumor tissue samples of known type containing the expression data on very many (possibly thousands) genes. Recently, results have been presented in the literature suggesting that it is possible to construct a prediction rule from only a few genes such that it has a negligible prediction error rate. However, in these results the test error or the leave-one-out cross-validated error is calculated without allowance for the selection bias. There is no allowance because the rule is either tested on tissue samples that were used in the first instance to select the genes being used in the rule or because the cross-validation of the rule is not external to the selection process; that is, gene selection is not performed in training the rule at each stage of the cross-validation process. We describe how in practice the selection bias can be assessed and corrected for by either performing a cross-validation or applying the bootstrap external to the selection process. We recommend using 10-fold rather than leave-one-out cross-validation, and concerning the bootstrap, we suggest using the so-called .632+ bootstrap error estimate designed to handle overfitted prediction rules. Using two published data sets, we demonstrate that when correction is made for the selection bias, the cross-validated error is no longer zero for a subset of only a few genes.

Discriminant Analysis↗
PubMed2000

Quality attributes and storage stability of locally and mechanically extracted crude palm oils in selected communities in Rivers and Bayelsa states, Nigeria.

The effect of different extraction methods on the quality of crude palm oil processed using traditional (local) and mechanical methods in selected areas of Rivers and Bayelsa States and their storage stability were investigated. Certain quality determining parameters such as free fatty acids (FFA), peroxide value (PV), saponification value (SV), moisture, impurities and volatile matter (MIV) content were determined prior to and after storage for three months. The free fatty acids (FFA) ranged from 7 to 19 percent, peroxide value (PV) ranged from 3 mEq/kg to 6 mEq/kg and moisture, impurity and volatile matter (MIV) ranged from 0.21 to 0.64 percent for locally extracted crude palm oil samples and mechanically extracted crude palm oil samples. There was no significant difference (p > 0.05) in the FFA of samples A and E before and after storage for 3 months. Also two of the locally extracted crude samples (A and E) stored better while one of the samples (D) showed a high level of deterioration as shown in its high levels of FFA, PV and IV values. Samples A and E resulted in a better quality of oil in terms of FFA (av. 7.25%) and PV (av. 4.5 meg/kg) when compared to the mechanically extracted one (sample C) with FFA (10.0%) and PV (5.78 mEq/kg). However, all the locally and mechanically extracted crude palm oil samples could not meet the industrial and international standard quality for crude palm with FFA (2-5%) and PV (2-3.5 mEq/kg). Among the three different storage containers used under different storage conditions, plastic containers (PC) resulted in a better storage stability of the crude palm oils in terms of FFA, SV, and IV than transparent bottles stored on shelves (TBS) and amber-colored bottles stored on the bare floor (BPF).

Fatty Acids, Nonesterified↗
PubMed2005

Fast miniaturised sample preparation for the screening and comprehensive two-dimensional gas chromatographic determination of polychlorinated biphenyls in sludge.

Polychlorinated biphenyls (PCBs) in sludge are usually extracted by a technique such as Soxhlet with subsequent fractionation prior to long GC runs using GC-ECD or GC-HRMS. In this study, the extraction of selected chlorinated biphenyls (CBs) from a spiked sludge sample by three rapid techniques, i.e. ultrasonic (USE), pressurised-liquid (PLE), and microwave-assisted (MAE) extraction using a domestic microwave, was studied, with subsequent direct GC-ECD, GC-MS, or GC x GC-microECD analysis of the extracts. The main goal was to select an appropriate, and miniaturised, extraction method after only a brief optimisation and demonstrate the power of GC x GC analysis of dirty extracts. For PLE similar CB recoveries were found when extracting with either n-hexane or n-hexane/acetone (1/1). For USE and MAE, n-hexane/acetone (1/1) was the preferred extraction solvent. USE gave the best recoveries (80-95%; except 130% for CB 105). The only clean-up needed prior to GC-MS or GC x GC-gECD analysis was the removal of sulphur-containing compounds. GC-ECD was not suitable for these dirty extracts. The lowest LODs for the CBs (20 fg or 0.1 ng/g sludge) were found when combining USE and GC x GC-microECD, because of the powerful extraction, high separation power and excellent detectability provided by this technique.

Calibration↗
PubMed1983

High-performance liquid chromatography determination of dipotassium clorazepate and its major metabolite nordiazepam in plasma.

A rapid and sensitive high-performance liquid chromatographic method is described for the quantitative analysis of dipotassium clorazepate (CZP) and its major metabolite nordiazepam (ND) in fresh human and dog plasma. The method consists of two separate selective ND extractions from a plasma sample without and with conversion of all the CZP to ND. For quantitation, diazepam (DZP) is used as the internal standard. The chromatographic phase utilized in a reversed-phase Hibar EC-RT analytical column prepacked with LiChrosolv RP-18 with a solvent system consisting of acetonitrile-0.05 M sodium acetate buffer, pH 5.0 (45:55). The UV absorbance is monitored at 225 nm using a variable-wavelength detector. The mean assay coefficient of variation over a concentration range of 20-400 ng per ml of plasma is less than 3% for the within-day precision. Recoveries of ND, DZP and CZP (as ND) are essentially quantitative at all levels investigated. The calibration curves of ND are rectilinear (r2 = 0.99) from the lower limit of sensitivity (2 ng/ml) to at least 2000 ng/ml in plasma. Applicability of the method to CZP and ND disposition studies in the anaesthetized mongrel dog is illustrated. When the two separate selective nordiazepam extractions from plasma cannot be performed immediately after blood sampling, an extrapolation kinetic method is suggested for the estimation of CZP concentration. In all previous in vivo studies, CZP has been determined only with gas-liquid chromatographic methods.

Animals↗
PubMed2000

Antibacterial activity of plant extracts from the families Fabaceae, Oleaceae, Philadelphaceae, Rosaceae and Staphyleaceae.

The selected plant extracts exhibited antibacterial activity. The strongest effect was manifested by extracts prepared from Gymnocladus dioicus, Amelanchier ovalis, Exochorda racemosa, Holodiscus discolor, Philadelphus microphyllus, Philadelphus coronarius and Pelargonium tabulare. The percentage inhibition of bacterial growth was 0-41.8%. In addition it was found that extracts isolated from Amelanchier ovalis, Exochorda racemosa and Pelargonium tabulare were specifically effective only against the bacterial strains tested.

Anti-Bacterial Agents↗
PubMed2001

Selective leaching of elements associated with Mn-Fe oxides in forest soil, and comparison of two sequential extraction methods.

For selective dissolution of Mn oxides as components of soil (easily reducible oxides) 0.05 mol L(-1) and 0.1 mol L(-1) NH2OH.HCl acidified to pH 2 and for dissolution of Fe oxides (crystalline form of the oxides) 0.25 mol L(-1) NH2OH.HCl in 25% acetic acid, 0.2 mol L(-1) oxalate buffer and 0.1 mol L(-1) ascorbic acid in oxalate buffer were tested. Dissolved elements were determined by ICP-MS and ICP-OES. The studies indicate that the use of 0.05 mol L(-1) NH2OH.HCl in nitric acid solution (pH 2) and 0.1 mol L(-1) ascorbic acid in 0.2 mol L(-1) oxalate buffer led to selective leaching of trace metals bound by Mn and Fe oxide phases in soil. Comparison of different extraction schemes indicates that the trace elements investigated are mainly bound to minerals consisting of crystalline Fe oxides and insoluble minerals (under the extraction conditions used). The studies also indicate that Mn oxides and organic matter retain a major mobile fraction of the elements investigated in the soil.

Chemistry Techniques, Analytical↗
PubMed2002

Current use of pressurised liquid extraction and subcritical water extraction in environmental analysis.

This review updates our knowledge about pressurised liquid extraction (PLE) and subcritical water extraction (SWE), two sample preparation techniques which are increasingly used for the extraction of moderately and non-volatile organic pollutants from a variety of solid and semi-solid environmental matrices. Parameters influencing the extraction yield and selectivity are discussed. The results deriving from the analysis of several different classes of compounds in a variety of matrices are compared with a reference method, e.g., Soxhlet extraction. PLE and SWE are both promising techniques due to the short extraction times and low solvent consumption. In addition, SWE offers a wide range of polarities by changing the temperature and can easily provide class-selective extraction by temperature programming and/or the addition of modifier(s). This indicates that, even though many applications have already been reported, more can be expected.

Environmental Monitoring↗
PubMed1993

[Effect of pollen extracts (cernitin preparation) on selected biochemical parameters of liver in the course of chronic ammonium fluoride poisoning in rats].

The aim of the paper has been the experimental evaluation of protracted exposure to ammonium-fluoride vapours exerted on selected biochemical parameters in serum as well as microsomal fraction of the liver in animals. An attempt was made to ameliorate eventual changes by using Cernitin preparation. The experiment was performed on male rats of Wistar strain. The rats were exposed to NH4F in a toxicological chamber with controlled parameters. Cernitin was added to standard diet and given to animals in the form of balls. The studies were carried out after 3 and 6 month-long exposure. The range of the performed studies covered: activity of enzymes (AspAT, AlAT, AP, ChE) and content of bilirubin as well as lipids were studied in the blood serum. Content of proteins, cholesterol and phospholipids was investigated in the liver homogenate. It has been shown that chronic exposure to NH4F vapours causes a rise in the activity of studied aminotransferases and alkaline phosphatase, and a decreases in activity of cholinesterase. The changes in activity were accompanied by an increase in the content of lipids. Prophylactic application of Cernitin preparation normalizes the disorder involving the studied enzymatic and lipid parameters.

Ammonium Compounds↗
PubMed2000

Early emergency department treatment of acute asthma with systemic corticosteroids.

BACKGROUND: The airway edema and secretions associated with acute asthma are most effectively treated with anti-inflammatories such as corticosteroids delivered by inhaled, oral, intravenous or intra-muscular routes. There is an unresolved debate about the use of systemic corticorticoids in the early treatment of acute asthma for emergency department patients. OBJECTIVES: To determine the benefit of treating patients with acute asthma with systemic corticosteroids within an hour of presenting to the emergency department (ED). SEARCH STRATEGY: Randomised controlled trials were identified from the Cochrane Airways Group Asthma Register. Primary authors and content experts were contacted to identify eligible studies. Bibliographies from included studies and known reviews were searched. SELECTION CRITERIA: Only randomised controlled trials (RCTs) or quasi-randomised trials were eligible for inclusion. Studies were included if patients presenting to the ED with acute asthma were treated with IV/IM or oral corticosteroids (CS) vs. placebo within 1 hour of arrival and either admission rate or pulmonary function results were reported. DATA COLLECTION AND ANALYSIS: Trial selection, data extraction and quality assessment were carried out independently by two reviewers, and confirmed with corresponding authors. MAIN RESULTS: Twelve studies involving 863 patients (435 corticosteroids; 428 placebo) were included. Early use of CS for acute asthma in the ED significantly reduced admission rates (N = 11; pooled OR: 0.40, 95% CI: 0.21 to 0.78). This would correspond with a number needed to treat of 8 (95% CI: 5 to 21). This benefit was more pronounced for those not receiving systemic CS prior to ED presentation (N = 7; OR: 0.37, 95% CI: 0.19 to 0.70) and those with more severe asthma (N = 7; OR: 0.35, 95% CI: 0.21 to 0. 59). Oral CS therapy in children was particularly effective (N = 3; OR: 0.24, 95% CI: 0.11 to 0.53); no trials in adults used the oral route. Side effects were not significantly different between corticosteroid treatments and placebo. REVIEWER'S CONCLUSIONS: Use of corticosteroids within 1 hour of presentation to an ED significantly reduces the need for hospital admission in patients with acute asthma. Benefits appear greatest in patients with more severe asthma, and those not currently receiving steroids. Children appear to respond well to oral steroids.

Acute Disease↗
PubMed1997

Fish meal extract bile esculin agar (FMBE) a selective medium for Bacteroides fragilis group.

Fish meal extract bile esculin agar (FMBE) is prepared using Fish meal extract concentrate as the basal substance, for the selective isolation and presumptive identification of B.fragilis group. The efficiency of the medium was evaluated by growing stock cultures of B.fragilis groups as well as inoculating clinical specimens and comparing the results with Bacteroides bile esculin agar (BBE). All the 87 stock cultures of B.fragilis grew on FMBE and BBE. No other anaerobes tested grew on the medium. However 7 out of 65 neomycin resistant aerobes grew on the FMBE. From the 100 clinical samples, 62 strains of B. Fragilis group were recovered on FMBE and BBE, and 53 strains on supplemented BHIBA. The cost effectiveness, selectivity and the ability to detect esculin hydrolysis will enable FMBE as a suitable medium as comparable to that of BBE, if not superior.

Agar↗
PubMed1989

Selective initiation of replication at origin sequences of the rDNA molecule of Physarum polycephalum using synchronous plasmodial extracts.

A cell-free system using synchronous plasmodial extracts initiates replication selectively on the 60 kb rDNA palindrome of Physarum polycephalum. Preferential labeling of rDNA fragments by nuclear extracts, in which elongation is limited, indicates that initiation occurs at two positions corresponding to in vivo origins of replication estimated by electron microscopy. Both nuclear and whole plasmodial extracts initiate selectively within a plasmid, pPHR21, containing one of these origins. In this plasmid bubbles expand bidirectionally and generate DpnI-resistant DNA. Extracts made at prophase or early S phase, times when the nucleolus is disorganized, are most active in pPHR21 replication. Mapping positions of replication bubbles locates the initiation point in a 3.2 kb BstEII fragment at the upstream border of a series of 31 bp repeats 2.4 kb from the initiation point for ribosomal gene transcription.

Base Sequence↗
PubMed2003

Analysis of selected withanolides in plant extract by capillary electrochromatography and microemulsion electrokinetic chromatography.

Microemulsion electrokinetic chromatography (MEEKC) coupled with a diode-array detector was developed for the simultaneous analysis of natural steroidal compounds, withanolides including withaferin A, withacnistin and iochromolide. Optimal resolution was obtained with a microemulsion consisting of 70 mM octane, 800 mM 1-butanol, 100 mM sodium dodecyl sulfate (SDS), and 10 mM phosphate-borate buffer (pH 7) using a fused-silica capillary at 25 kV and 40 degrees C. Since this technique is not compatible with mass spectrometry detection, a capillary electrochromatographic method was developed to separate the investigated withanolides. The effects of mobile phase composition and pH were systematically investigated. Complete separation was obtained with a capillary electrochromatography (CEC) Hypersil C18 bonded silica column (packed length, 25 cmx100 microm ID and 375 microm OD), packed with 3 microm particles. The mobile phase consisted of formic acid-ammonia, pH 8 / acetonitrile (40/60 v/v); the voltage was set at 25 kV and the temperature at 20 degrees C. Under these conditions, resolution of these closely related compounds, including the critical pair withacnistin and iochromolide, was achieved in less than 5 min. The separations by MEEKC and CEC were compared with that obtained by reversed-phase liquid chromatography and showed similar retention order, indicating the analogy of the retention mechanism of these techniques. To further improve specificity and sensitivity, the developed CEC method was interfaced with electrospray ionization mass spectrometry using a Teflon connection between the CEC column and a void fused-silica capillary. Finally, the described methods were applied to the qualitative analysis of withanolides in Iochroma gesnerioides plant extract.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2003

Speciation of mercury in soil and sediment by selective solvent and acid extraction.

In order to characterize the mercury hazard in soil, a sequential extraction scheme has been developed to classify mercury species based on their environmental mobility and/or toxicity for either routine lab analysis or on-site screening purposes. The alkyl mercury species and soluble inorganic species that contribute to the major portion of potential mercury toxicity in the soil are extracted by an acidic ethanol solution (2% HCl+10% ethanol solution) from soil matrices as "mobile and toxic" species. A High-Performance Liquid Chromatography (HPLC) system coupled with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) detection has been developed to further resolve the species information into soluble inorganic species (Hg(2+)), methylmercury(II) (MeHg(+)) and ethylmercury(II) (EtHg(+)) species. Alternatively, these species can be separated into "soluble inorganic mercury" and "alkyl mercury" sub-categories by Solid-Phase Extraction (SPE). A custom Sulfydryl Cotton Fiber (SCF) material is used as the solid phase medium. Optimization of the SCF SPE technique is discussed. Combined with a direct mercury analyzer (DMA-80), the SCF SPE technique is a promising candidate for on-site screening purposes. Following the ethanol extraction, the inorganic mercury species remaining in soil are further divided into "semi-mobile" and "non-mobile" sub-categories by sequential acid extractions. The "semi-mobile" mercury species include mainly elemental mercury (Hg) and mercury-metal amalgams. The non-mobile mercury species mainly include mercuric sulfide (HgS) and mercurous chloride (Hg(2)Cl(2)).

Chemical Fractionation↗
PubMed2006

Atrial arrhythmias after cardiac surgery in patients with diabetes mellitus.

BACKGROUND: Postoperative atrial fibrillation (AF) is a common complication of cardiac surgery and has been associated with increased incidence of other complications and increased hospital length of stay (LOS). Prevention of AF is a reasonable clinical goal, and, consequently, many randomized trials have evaluated the effectiveness of pharmacological and non-pharmacological interventions for prevention of AF. To better understand the role of various prophylactic therapies against postoperative AF, a systematic review of evidence from randomized trials was performed. METHODS: MEDLINE search of English-language reports published between 1966 and July 2005 and a search of references of relevant papers were conducted. Clinical studies on AF after cardiac surgery were selected for this analysis. Relevant clinical information was extracted from selected articles. RESULTS: Postoperative AF is associated with increased morbidity and mortality and longer, more expensive hospital stays. Prophylactic use of beta-adrenergic blockers reduces the incidence of postoperative AF and should be administered before and after cardiac surgery to all patients without contraindication. Prophylactic amiodarone and atrial overdrive pacing should be considered in patients at high risk for postoperative AF (for example, patients with previous AF or mitral valve surgery). For patients who develop AF after cardiac surgery, a strategy of rhythm management or rate management should be selected. For patients who are hemodynamically unstable or highly symptomatic or who have a contraindication to anticoagulation, rhythm management with electrical cardioversion, amiodarone, or both is preferred. Treatment of the remaining patients should focus on rate control because most will spontaneously revert to sinus rhythm within 6 weeks after discharge. All patients with AF persisting for more than 24 to 48 hours and without contraindication should receive anticoagulation. CONCLUSIONS: AF frequently complicates cardiac surgery. Many cases can be prevented with appropriate prophylactic therapy. A strategy of rhythm management for symptomatic patients and rate management for all other patients usually results in reversion to sinus rhythm within 6 weeks of discharge.

Adrenergic beta-Antagonists↗
PubMed1985

Selected muscle and nerve extracts contain an activity which stimulates myoblast proliferation and which is distinct from transferrin.

Extracts from normal chicken anterior latissimus dorsi and dystrophic pectoralis major muscles and from normal chicken sciatic nerves induce a growth stimulation in chicken and rat myogenic cell cultures. Transferrin is only partially responsible for the observed stimulation since the addition of the extracts to transferrin-saturated cultures induces a further growth response and extracts from which transferrin has been removed by immunoabsorption still retain a substantial portion of their stimulation activity. The active fractions of muscle and nerve extracts display heat, acid, and organic solvent inactivation. Gel filtration of ammonium sulfate fractionated activity from the anterior latissimus dorsi muscle suggests the presence of a growth factor in the molecular weight range of 10,000 to 30,000.

Animals↗