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PubMed2000

Ranitidine hydrochloride X-ray assay using a neural network.

A simple X-ray powder diffractometric (XRD) method with artificial neural networks (ANNs) for data modelling was developed to recognize and quantify two crystal modifications of ranitidine HCl in mixtures and thus, provide information about the solid state of the bulk drug. The method was also used to quantify ranitidine HCl from tablets in the presence of other components. An ANN consisting of three layers of neurons was trained by using a back-propagation learning rule. A sigmoid output function was used in the hidden layer to facilitate non-linear fitting. Unlike other techniques the ANN method described here employed pattern recognition on the entire XRD pattern. Correct classification was mainly influenced by the XRD pattern resolution. It was shown that data transformations improved the quantitative performance when the XRD patterns were not contaminated by other components. Only smoothed X-ray diffractograms were required to distinguish between the two crystalline forms in a mixture. In the case of ranitidine-HCl quantification from tablets, where significant interference with tablet excipients was present, better results were obtained without data transformations. The trained ANN perfectly quantified ranitidine HCI polymorphic forms from mixtures (mean sum of squared error was less than 0.02%) and ranitidine HCl form 1 from tablets (recovery = 98.65). Excellent quantification performance of the ANN analysis. demonstrated in this study, serves as an indication of the broad potential of neural networks in pattern analysis. While the system described has been developed to interpret XRD patterns, peak detection has implications in every chemical application where the recognition of peak-shaped signals in analytical data is important.

Anti-Ulcer Agents↗

PubMed2001

Estimates of the theoretical maximum daily intake of phenolic antioxidants BHA, BHT and TBHQ in Brazil.

The theoretical maximum daily intakes (TMDI) of the phenolic antioxidants butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tertbutyl hydroquinone (TBHQ) in Brazil were estimated using food consumption data derived from a household economic survey and a packaged goods market survey. The estimates were based on maximum levels of use of the food additives specified in national food standards. The calculated intakes of the three additives for the mean consumer were below the ADIs. Estimates of TMDI for BHA, BHT and TBHQ ranged from 0.09 to 0.15, 0.05 to 0.10 and 0.07 to 0.12 mg/kg of body weight, respectively. To check if the additives are actually used at their maximum authorized levels, analytical determinations of these compounds in selected food categories were carried out using HPLC with UV detection. BHT and TBHQ concentrations in foodstuffs considered to be representive sources of these antioxidants in the diet were below the respective maximum permitted levels. BHA was not detected in any of the analysed samples. Based on the maximal approach and on the analytical data, it is unlikely that the current ADI of BHA (0.5 mg/kg body weight), BHT (0.3 mg/kg body weight) and TBHQ (0.7 mg/kg body weight) will be exceeded in practice by the average Brazilian consumer.

Antioxidants↗

PubMed1998

Multiple parameter cross-species protein identification using MultiIdent--a world-wide web accessible tool.

Recent increases in the number of genome sequencing projects means that the amount of protein sequence in databases is increasing at an astonishing pace. In proteome studies, this is facilitating the identification of proteins from molecularly well-defined organisms. However, in studies of proteins from the majority of organisms, proteins must be identified by comparing analytical data to sequences in databases from other species. This process is known as cross-species protein identification. Here we present a new program, MultiIdent, which uses multiple protein parameters such as amino acid composition, peptide masses, sequence tags, estimated protein pI and mass, to achieve cross-species protein identification. The program is structured so that protein amino acid composition, which is highly conserved across species boundaries, first generates a set of candidate proteins. These proteins are then queried with other protein parameters such as sequence tags and peptide masses. A final list of database entries which considers all analytical parameters is presented, ranked by an integrated score. We illustrate the power of the approach with the identification of a set of standard proteins, and the identification of proteins from dog heart separated by two-dimensional gel electrophoresis. The MultiIdent program is available on the world-wide web at: http://www.expasy.ch/sprot/multiident.h tml.

Amino Acid Sequence↗

PubMed1997

Factor V Leiden mutation and the risks for thromboembolic disease: a clinical perspective.

BACKGROUND: A single point mutation in the gene coding for coagulation factor V results in a form of factor Va that is resistant to degradation by activated protein C and leads to a relative hypercoagulable state. This mutation, factor V Leiden, is found in 4% to 6% of the U.S. population. PURPOSE: To review clinical data on factor V Leiden mutation, with emphasis on prevalence of and risks for thromboembolism and implications for screening and management. DATA SOURCES: A MEDLINE search of the English-language literature published between 1993 and April 1997 and an extensive bibliography review. STUDY SELECTION: Case-control and prospective cohort studies were reviewed if clinical features of thromboembolic disease associated with factor V Leiden mutation or resistance to activated protein C were presented. Original research articles were reviewed if they addressed the identification of the laboratory abnormality of activated protein C or factor V Leiden mutation. Case reports and case series were reviewed when no analytic data were available. DATA EXTRACTION: Review of the identified articles. DATA SYNTHESIS: Factor V Leiden mutation is associated with three- to sixfold increases in risks for primary and recurrent venous thromboembolism, especially in patients without transient risk factors, such as surgery or trauma. Risks for venous thromboembolism in genetically affected persons are substantially higher among patients with coexistent predispositions for thrombosis, such as advanced age, use of oral contraceptives, hyperhomocystinemia, and deficiencies of protein C and protein S. Factor V Leiden mutation does not seem to increase risks for arterial thrombosis. Whether patients with the mutation would benefit from more intense or prolonged anticoagulation is unknown. CONCLUSIONS: The presence of factor V Leiden mutation predisposes patients to venous thromboembolism, but screening for this disorder is of uncertain utility. Decisions about whether to screen for the mutation will depend on the results of clinical trials designed to evaluate the benefit-to-risk ratio of long-term anticoagulation in the secondary prevention of venous thromboembolism in patients with resistance to activated protein C.

Contraceptives, Oral↗

PubMed2000

Basic concepts of artificial neural network (ANN) modeling and its application in pharmaceutical research.

Artificial neural networks (ANNs) are biologically inspired computer programs designed to simulate the way in which the human brain processes information. ANNs gather their knowledge by detecting the patterns and relationships in data and learn (or are trained) through experience, not from programming. An ANN is formed from hundreds of single units, artificial neurons or processing elements (PE), connected with coefficients (weights), which constitute the neural structure and are organised in layers. The power of neural computations comes from connecting neurons in a network. Each PE has weighted inputs, transfer function and one output. The behavior of a neural network is determined by the transfer functions of its neurons, by the learning rule, and by the architecture itself. The weights are the adjustable parameters and, in that sense, a neural network is a parameterized system. The weighed sum of the inputs constitutes the activation of the neuron. The activation signal is passed through transfer function to produce a single output of the neuron. Transfer function introduces non-linearity to the network. During training, the inter-unit connections are optimized until the error in predictions is minimized and the network reaches the specified level of accuracy. Once the network is trained and tested it can be given new input information to predict the output. Many types of neural networks have been designed already and new ones are invented every week but all can be described by the transfer functions of their neurons, by the learning rule, and by the connection formula. ANN represents a promising modeling technique, especially for data sets having non-linear relationships which are frequently encountered in pharmaceutical processes. In terms of model specification, artificial neural networks require no knowledge of the data source but, since they often contain many weights that must be estimated, they require large training sets. In addition, ANNs can combine and incorporate both literature-based and experimental data to solve problems. The various applications of ANNs can be summarised into classification or pattern recognition, prediction and modeling. Supervised 'associating networks can be applied in pharmaceutical fields as an alternative to conventional response surface methodology. Unsupervised feature-extracting networks represent an alternative to principal component analysis. Non-adaptive unsupervised networks are able to reconstruct their patterns when presented with noisy samples and can be used for image recognition. The potential applications of ANN methodology in the pharmaceutical sciences range from interpretation of analytical data, drug and dosage form design through biopharmacy to clinical pharmacy.

Algorithms↗

PubMed1991

Why do many Michaelian enzymes exhibit an equilibrium constant close to unity for the interconversion of enzyme-bound substrate and product?

1. The idea is advanced that an evolutionary pressure in the direction of increased metabolic fluxes should lead to the selection at any evolutionary stage of enzymes which are optimally efficient considering the total evolutionary effort which has been spent on their improvement as catalysts. Relationships are derived which may be used for determination of the optimal state of operation of a Michaelian enzyme at a given total evolutionary effort as measured, for instance, by the mean magnitude of variable rate constants in the reaction mechanism. These relationships are applied to characterize the dependence on the total evolutionary effort of the optimal value of the equilibrium constant (Kint) for the conversion of enzyme-bound substrate into enzyme-bound product. 2. The results show that the optimal value of Kint reflects primarily the magnitude of the overall equilibrium constant for the catalysed reaction, whether or not the enzyme operates close to equilibrium. When the total evolutionary effort tends towards infinitely high values, Kint approaches unity, regardless of the magnitude of the overall equilibrium constant and of the concentrations of substrate and product. Concomitantly, the enzyme approaches its ultimate state of catalytic perfection where all variable rate constants in the mechanism tend towards infinitely high values. 3. It is concluded from previously reported kinetic data that triosephosphate isomerase has been subjected to such a low total evolutionary effort that the enzyme cannot possibly have reached (or even significantly approached) the ultimate state of perfection where the Kint value necessarily becomes close to unity. The reason why this enzyme exhibits a Kint value relatively close to unity is that it catalyses a reaction with an equilibrium constant relatively close to unity. Evidence is presented to show that similar considerations may apply for other enzymes operating by the examined reaction mechanism. 4. Analytical data are reported which indicate that Kint ultimately approaches unity because forward and reverse rate constants for the interconversion of enzyme-bound substrate and product are equivalent with regard to the evolutionary effort required to increase their magnitude.

Biological Evolution↗

PubMed2003

Near-infrared spectroscopy for on-line monitoring of lube base oil processes.

Near-infrared (NIR) spectroscopy has been utilized for monitoring the pour point of the lube base oil (LBO) process. Using partial least-squares (PLS) regression, necessary spectral features were successfully extracted and correlated to the reference pour-point data. In a preliminary laboratory feasibility study, it was found that PLS calibration performance was largely governed by the accuracy of the reference pour-point analysis. The same NIR spectroscopic methodology was moved to monitor the pour point continuously in an on-line manner. At this time, the NIR spectrometer was calibrated with the existing on-line pour-point analyzer, which was more accurate. In comparison with the on-line pour-point analyzer, NIR spectroscopy provided faster and more repeatable analytical data. With the help of NIR analysis, LBO process variations during product switch can be detected earlier, and necessary process-control strategy can be applied to improve the process efficiency.

Algorithms↗

PubMed2004

Apolipoprotein E genotype frequency patterns in aged Danes as revealed by logistic regression models.

Although the ApoE gene has been intensively studied in aging research, most of the studies conducted so far have been based on the traditional case-control design with subjects consisting of young controls and long-lived cases. The genotype frequency pattern in and between the two age-groups has been rarely investigated due to limitations in either research design or data analytical method. In this study, we genotyped 748 individuals (including both twin pairs and unrelated individuals) aged from 73 to 95 with aim at examining the genotype frequency trajectory of ApoE gene at high ages. Binomial and multinomial logistic regression models have been applied to model the gene frequency as a function of age and to investigate the modes of gene function (dominant, recessive, additive). The generalized estimation equations (GEEs) are introduced to account for the intra-pair genotype correlation in the twin pairs included in the data. Both the observed and the fitted frequencies show a constantly declining pattern of ApoE epsilon4 allele as age advances indicating a significant and steadily deleterious effect of the dominant allele that increases the hazard of death at high ages.

Aged↗

PubMed1998

Validation of analytical methods and laboratory procedures for chemical measurements.

Method validation is a key element in the establishment of reference methods and in the assessment of a laboratory's competence in producing reliable analytical data. Hence, the scope of the term "method validation" is wide, especially if one bears in mind the role of Quality Assurance/Quality Control (QA/QC). The paper puts validation in the context of the process generating chemical information, introduces basic performance parameters included in the validation processes, and evaluates current approaches to the problem. Two cases are presented in more detail: the development of European standard for chlorophenols and its validation by a full scale collaborative trial and the intralaboratory validation of a method for ethylenethiourea by using alternative analytical techniques.

Chemistry Techniques, Analytical↗

PubMed1987

Interpretation of red cell survival data for in vivo compatibility testing: a normal value study.

Short-term survival studies are sometimes required to determine the compatibility of donor red cells. The results of these studies are generally expressed as per cent survival at 60 min. The present study was undertaken to investigate the potential for more sophisticated data analytical techniques to improve sensitivity. In one group of eight healthy male volunteers, autologous red cells were labelled with 51chromium and injected immediately, while in a second group, red cells were stored for 5 d prior to injection. In both groups, eight to 10 samples were collected in the first 6 h and another 10-12 samples over the next 4 weeks. Estimation of the 60 min per cent survival was insufficiently sensitive to detect 'physiological' haemolysis following injection of 5-d-old autologous blood. Regression analysis of 6 h survival data, however, demonstrated significantly higher red cell clearance rates in these cases than in those receiving fresh cells, with a mean 24 h loss of 3.3% of activity. The upper limit for the 6 h red cell clearance rate was 1.63%/h after fresh autologous blood and 2.43%/h after 5-d-old blood. The significance of these findings is discussed and a protocol suggested for the analysis of short-term red cell survival data.

Adult↗

PubMed2006

Characterization and differentiation of autoimmune versus viral liver involvement in patients with Sjögren's syndrome.

OBJECTIVE: To analyze the prevalence and clinical significance of liver involvement in patients with Sjögren's syndrome (SS), focusing on the characterization and differentiation of autoimmune versus chronic viral liver disease. METHODS: We investigated liver involvement (clinical signs, analytical data, chronic viral infections, and autoantibodies) in 475 consecutive patients with SS. All patients fulfilled 4 or more of the 1993 European Community Study Group criteria for SS. RESULTS: Liver involvement was detected in 129 (27%) patients. After ruling out chronic illnesses or use of hepatotoxic drugs, the main etiologies were chronic viral liver disease in 64 (13%) cases [chronic hepatitis C virus (HCV) infection in 63 and HBV infection in one] and autoimmune liver diseases in 24 (5%; primary biliary cirrhosis in 16 patients and type-1 autoimmune hepatitis in 8). The analytical liver profile was not useful in differentiating between viral and autoimmune liver disease. In contrast, patients with SS and autoimmune liver disease presented higher mean values of erythrocyte sedimentation rate (p = 0.044), circulating gammaglobulins (p = 0.007), and a higher prevalence of antinuclear antibodies (p < 0.001), antimitochondrial antibodies (p < 0.001), anti-smooth muscle antibodies (p = 0.026), anti-Ro/SSA (p < 0.001), and anti-La/SSB (p = 0.01), while patients with chronic viral liver disease had a higher frequency of cryoglobulinemia (p < 0.001) and hypocomplementemia (p < 0.001). CONCLUSION: Chronic viral liver disease (associated overwhelmingly with HCV) was the main cause of liver involvement in our patients with SS, with a prevalence of 13%, nearly 3-fold greater than that observed for autoimmune liver involvement. The immunological pattern played a key role in the differentiation of viral (predominance of cryoglobulins and low complement levels) and autoimmune (higher frequency of autoantibodies) liver involvement.

Autoantibodies↗

PubMed2006

Mutually responsive orientation between parents and their young children: toward methodological advances in the science of relationships.

The authors captured mother-child and father-child relationships when children were 7 and 15 months old by coding 4 explicitly dyadic components of mutually responsive orientation (MRO): coordinated routines, harmonious communication, mutual cooperation, and emotional ambiance. These components were coded in 102 families in naturalistic contexts at home and in the laboratory. Using confirmatory factor analytic methods, the authors demonstrated that MRO (a) is a unidimensional latent construct, (b) can be distinguished from and is not reducible to the 2 interacting individuals' qualities (responsiveness and positive affect), and (c) has remarkable measurement equivalence from ages 7 to 15 months for both mother-child and father-child relationships and has remarkable measurement equivalence across both parent-child relationships at both child ages. This study represents an effort to advance the science of relationships by moving away from individual-based measures to dyadic measures and by using contemporary data analytic strategies.

Affect↗

PubMed1993

Reference materials and environmental specimen banking.

The preservation and protection of the environment has become a major challenge of our times since this has to be compatible with the ecological needs. The concept of Environmental Specimen Banking (ESB) acquires importance in providing the data base for deeper insight into ecochemical processes. Methodological development and preparation of reference materials (RMs) are also essential to such studies. Systematic efforts are to be made to acquire a good number of reference materials to be useful for analysis of toxic as well as essential components. Our experience has shown that it is possible to procure worthy and scientifically valuable specimens from soils and leafy food substances. Exploring preparation of suitable specimens from a country such as India might be a worthy exercise since it is possible to obtain clean specimens in this part of the world. Analytical data for determination of some trace and major elements in prepared RMs are presented.

Environmental Monitoring↗

PubMed2004

Measuring patient safety in ambulatory care: potential for identifying medical group drug-drug interaction rates using claims data.

OBJECTIVE: To evaluate the feasibility of using health-plan administrative data to measure potential drug-drug interaction (DDI) rates in the ambulatory setting at the medical-group level and to assess the potential use of DDI rates in performance measurement, quality improvement, and research in patient safety. STUDY DESIGN: We combined administrative and pharmacy claims data from 2 large health plans to calculate the rates at which member users of selected chronic medications were potentially exposed to a second drug known to pose a risk of harmful interactions. METHODS: We divided 44 medication combinations with risk of adverse interactions into those with DDIs of moderate/severe clinical significance and those with DDIs of mild significance. We then calculated yearly rates of potential DDIs in continuously enrolled members aged 19 and older from 1998 through 2001. Rates were calculated for all members, overall base-medication users, and, individual medical groups responsible for their care. RESULTS: The analytic data set included 756 047 patient-years of data and 110 to 123 medical groups per year. During the 4-year interval, one or more unique potential DDIs occurred in 6.2% to 6.7% of base-drug users and 2.0% to 2.3% of all adult health-plan members per year. Medical-group mean user rates were slightly lower (5.33%-5.81%), with wide variance (SD = 2.6%-3.1%) and high stability over time. CONCLUSION: Potential DDI rates calculated from health-plan data have promise for measurement in patient medication safety. This readily available and inexpensive evaluation tool has potential for monitoring, improvement, and research purposes if further studies validate their relationship to actual adverse events.

Adult↗

PubMed1994

Direct stopped-flow fluorescence polarization immunoassay of abused drugs and their metabolites in urine.

Kinetic methodology was applied to the direct determination of abused drugs (amphetamines, cocaine, and cannabinoids) in urine by stopped-flow fluorescence polarization immunoassay (SF-FPIA). This technique provides analytical data within a few seconds by measuring the variation of polarized fluorescence with time during development of immunochemical reactions. Methods based on this principle are particularly suitable for routine screening of these drugs in urine, being more expeditious than conventional FPIA methods. The dynamic ranges of the calibration curves were 20-300 micrograms/L for d,l-amphetamine, 15-300 micrograms/L for benzoylecgonine (a cocaine metabolite), and 10-400 micrograms/L for 11-nor-delta 8-tetrahydrocannabinol-9-carboxylic acid (a cannabinoid metabolite). The detection limits and within- and between-assay precision were better than those provided by conventional FPIA. Analytical recoveries ranged between 97.5% for d,l-amphetamine and 102.4% for the cannabinoid metabolite. The results for the three analytes were consistent with those obtained by conventional FPIA.

Amphetamine↗

PubMed1996

[Succinylcholine induces hyperpotassemia in patients in critically ill patients].

OBJECTIVE: To study changes in kalemia caused by succinylcholine administration to patients in critical care, and the possible association of succinylcholine with clinical and analytical data, severity-of-disease classification, duration of stay in the intensive care unit (ICU) and immobility. PATIENTS AND METHODS: Twenty-three patients admitted to the ICU, none of whom suffered burns, polytrauma or neuromuscular disease, and who had received 1.5 mg/kg succinylcholine on 28 occasions, usually to facilitate tracheal intubation. Kalemia was analyzed before neuromuscular relaxation and 5 and 30 min afterwards. Electrocardiographic II and V5 derivations and invasive arterial pressure were monitored in all patients. The increase in kalemia at 5 min correlated with age, sex, weight, APACHE II score, days in ICU, current and accumulated immobility, and analytical parameters such as glycemia, creatinine, GOT, bilirubinemia, pH and creatine kinase. The kalemia of these patients was compared with that of 15 patients in acceptable general state who had undergone scheduled surgery. RESULTS: Kalemia increased significantly from a mean baseline level of 4.2 (0.9) mEq/l to 5.5 (1.4) at 5 min and 4.6 (0.9) at 30 min in ICU patients. In the non ICU patients there were no statistically significant changes. Kalemia at 5 min was correlated with baseline (r = 0.84; p < 0.0001), days in the ICU (r = 0.39; p < 0.05) and weight (r = 0.46; p < 0.05). The mean increase in kalemia at 5 min was 0.5 mEq/l in patients who stayed less than 10 days, 1.8 mEq/l in those whose stay was from 10 to 30 days and 1.4 mEq/l in patients who stayed longer than 30 days. The percent increase in kalemia correlated directly (r = 0.7; p < 0.001) with days in the ICU and with accumulated immobility in patients whose ICU stay was less than 30 days. For ICU stays longer than 30 days the correlation was negative (r = -0.98; p = 0.03). Electrocardiographic changes were recorded in 2 patients with brief sinus bradycardia having no hemodynamic repercussions. CONCLUSIONS: The use of succinylcholine in critically ill patients causes a brief but significant increase in kalemia, with slight and rare electrocardiographic changes. The effect varies according to the length of time spent in the ICU and the degree of immobility, with maximum increases seen when the ICU stay is between 10 and 30 days. Patient immobility may play an important pathophysiological role. The indications for use of succinylcholine in critically ill patients should be very strict, particularly during the period of greatest sensitivity.

Adult↗

PubMed1997

Interpretation and bias in case-crossover studies.

The case-crossover design is an innovative epidemiologic technique with distinct strengths and limitations. We review the fundamental logic of this self-matching non-randomized design and direct attention to 15 concerns related to the available data, unavailable data, analytic technique, quantitative statistics, and etiologic model. Implications for each concern are discussed in the context of a recent report on whether cellular telephone calls are associated with an increased risk of a motor vehicle collision. We suggest that an understanding of the case-crossover design may help investigators explore selected questions in behavioral medical research.

Bias↗

PubMedDate not supplied

Findings and actions by the IR-4 Project in response to a bushel of EPA inspections.

The IR-4 Project is dedicated to all aspects of minor crop pest management, in cooperation between USDA, universities, and other state or Federal entities. Human safety decisions made by EPA are based upon field raw data, analytical reports, and scientific review and interpretation. Quality Assurance personnel, an independent body of internal inspectors and auditors, assist both regulatory inspector and on-site field personnel during EPA site inspections. This article contains information gleaned from a large number of university and other test site inspections, which were conducted by EPA to fulfill requirements of Good Laboratory Practice regulations, 40 CFR 160.

Data Collection↗