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PubMed1990

Quantitative structure-activity relationships for sea anemone polypeptide toxins.

Sea anemone polypeptides vary considerably in their affinities for sodium channels occurring in different excitable cells. The amino acid sequence variation in a set of six sea anemone type I polypeptide toxins (46-49 residues long), was parameterized using descriptor scales z1, z2, and z3, derived from a large number of amino acid physicochemical properties. The pharmacological properties of the toxins were represented by the results from four bioassays on crab, mouse, and rat brain and from rat heart. By means of the descriptor scales and the multivariate data analytical method PLS (partial least squares projections to latent structures), it was possible to develop quantitative structure-activity relationships (QSAR). Using the QSARs derived from the set of six polypeptide toxins the pharmacological properties of two homologous sea anemone polypeptide toxins were predicted. Thus it is shown that QSARs may be formulated for relatively long bioactive polypeptides. The QSARs indicate that 11 different amino acid positions may be of importance, but that positions no. 5, 21, 28, 34, 37, and 40 were of main importance in modeling the relative toxicities of the six polypeptides.

Amino Acid Sequence↗
PubMed1999

Stunned myocardium and cellular damage in patients undergoing valvular cardiac surgery and pretreated with captopril.

BACKGROUND: Following extracorporeal cardiac surgery, transient myocardial dysfunction (stunning) and cellular damage may develop in relation, among other mechanisms, to the production of free radicals (FR) during reperfusion. The purpose of this study is to evaluate whether captopril (CTP), an angiotensin converting enzyme inhibitor with a thiolic group, which has been shown to be useful as an antioxidant agent both in in vitro and in vivo studies, can prevent emergence of those problems when used as pretreatment within 24 hours in patients undergoing valvular cardiac surgery. METHODS EXPERIMENTAL DESIGN: prospective and randomized study. Comparison of data pre-ischemic (pre-aortic clamping) and post-reperfusion (post-cardiac rewarming) was performed. Ejection fraction was compared pre-surgery, after surgery and after 3 months. SETTING: cardiology and cardiovascular surgery services in a general hospital. PATIENTS OR PARTICIPANTS: thirty patients who had to undergo valvular replacement surgery were randomly allocated to two similar groups, one group pretreated with captopril (CTP group, n = 15) and the other group without it (CON group, n = 15). Exclusion criteria (left ventricular ejection fraction <40%, evidence of angiographic coronary disease or prior myocardial infarction and peroperative myocardial infarction). INTERVENTION: in CTP group, the dose of captopril administered was 12.5 mg every 8 hours orally, from 24 hours before. MEASURES: using electron microscopy of myocardial biopsies taken prior to aortic clamping and post-reperfusion, a semi-quantitative analysis was performed on the degree of myocytic damage (MD), mitochondrial swelling (MS), sarcoplasmic reticulum swelling (SRS) and content in glycogen granules (GLY). Left ventricular ejection fraction was evaluated isotopically at three timepoints, preoperatively (EF1), at 2-3 days (EF2) and at 3 months (EF3). Also, analytical data were collected from the coronary sinus to determine creatine phosphokinase (CPK) and activity of the angiotensin converting enzyme (ACE). RESULTS: We noted that, in general, cellular damage resulting from valvular surgery is low, the degree of MS and SRS being lower in the CTP group. In the CTP group, however, there is a stunning phenomenon (EF1: 54.9+/-6.9%; EF2: 50.8+/-8.5%; EF3: 57.7+/-7.7%) which does not occur in the CON group (EF1: 58.0+/-8.3%; EF2: 60.8+/-10.9%; EF3: 63.0+/-9.3%). CONCLUSIONS: We conclude that the cellular damage caused during valvular replacement surgery is small, and emphasize that pretreatment with CTP further minimizes both MS and SRS; however, for reasons as yet unknown, CTP pretreatment may induce myocardial stunning, an indication that at these low rates of cellular damage, CTP has no beneficial effect, either because it is ineffective as an antioxidant agent or because FR formation has little repercussion in human beings, pointing out to the likely existence of other mechanisms that may induce an appearance of postsurgical myocardial stunning.

Aged↗
PubMed1999

A logistic regression based extension of the TDT for continuous and categorical traits.

The transmission disequilibrium test (TDT), designed as a test of linkage in the presence of association (i.e. linkage disequilibrium), has received considerable attention in the recent statistical genetics literature due to its advantages over other within-family analytic methods. One limitation of the conventional TDT is its application solely to linkage disequilibrium between a genetic marker and a single categorical trait (e.g. presence or absence of a disease). In this paper, we present an extension of the TDT using logistic regression to examine the relation between a candidate gene or genetic marker and one or more continuous or categorical explanatory variables. This logistic regression extension of the TDT possesses all of the desirable features of the conventional TDT, as well as many advantages associated with traditional regression analysis. We describe the model and its properties, as well as a number of its possible applications, and apply it to examine linkage disequilibrium between the dopamine receptor D2 gene (DRD2) and symptoms of childhood attention deficit hyperactivity disorder (ADHD). We also briefly compare the logistic regression TDT to other quantitative TDTs that have been proposed in the literature, and highlight the advantages of a regression-based approach for examining the relation between a candidate gene and one or more continuous or categorical traits. Given its features, we regard the logistic regression extension of the TDT as a flexible new data analytic method with extensive potential applications to problems in medical, psychiatric, and behavioral genetics.

Attention Deficit Disorder with Hyperactivity↗
PubMed1992

Short-term intraindividual variability in lipoprotein measurements: the Atherosclerosis Risk in Communities (ARIC) Study.

Much epidemiologic research is based on estimation of an association between a putative risk factor and a health outcome--for example, plasma concentration of lipoproteins and ischemic heart disease. Since the repeatability of a risk factor measurement determines, in part, the ability to ascertain its association in populations, the Atherosclerosis Risk in Communities (ARIC) Intraindividual Variability Study was conducted to estimate various components of variation in analyte data and to estimate the repeatability of these measurements. A total of 40 subjects (17 males and 23 females) from Forsyth County, North Carolina, Minneapolis, Minnesota, Jackson, Mississippi, and Washington County, Maryland, were studied in 1988. Fasting blood was collected three times from each subject, with a 1- to 2-week interval between each visit. The contributions of between-person variability, within-person variability, and processing and assay variability were estimated. From these components, the reliability coefficient, R, the correlation between measures made at repeat visits, was estimated. R was above 0.85 for total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglycerides, and lipoprotein(a). Low repeatability was obtained for apolipoprotein A-I (R = 0.60). High density lipoprotein subfractions 2 and 3 were intermediate in repeatability. Reliability coefficients from the ARIC Intraindividual Variability Study are generally higher than those found in other studies, and this is related to relative variability in populations studied, to the time between measurements, and to differences in laboratory variability. Only for apolipoprotein A-I would the findings strongly suggest the need to adjust for measurement variability in estimation using one of these analytes as an independent variable.

Cardiovascular Diseases↗
PubMed1991

Understanding the effects of age, period, and cohort on incidence and mortality rates.

Time trends for population-based disease rates often are summarized by using direct adjustment by period of diagnosis or death. Similarly, the effect of age often is presented graphically as age-specific rates for a given period of diagnosis. These approaches may be necessary if there is an absence of long-term data, as they provide a natural way for annually updating information when monitoring trends, or they may be a convenient way of summarizing a large amount of data (7, 10, 11, 39, 45). However, these summaries only can adjust for the effect of age in a given period; they implicitly ignore the cohort effect. The effect of cohort is an important factor in understanding time trends for many diseases. Thus, it is not advisable to use data analytic strategies that routinely ignore it. Another alternative to modeling is to give a graphical presentation of the age-specific rates themselves. As I noted in the introduction, some of the first analyses to identify the effect of cohort on diseases, such as tuberculosis and lung cancer, relied entirely on a graphical analysis. Although graphs certainly are an important part of the interpretation of time trends, it would be a mistake to limit your analysis to impressions of points on a graph. For example, such a perusal would not give an objective indication of the statistical significance of a particular pattern. Regression analysis forces us to recognize a fundamental problem with interpreting time trends in disease rates--a problem that you should remember, even when trying to understand a graphical display of time trends in age-specific rates.

Adult↗
PubMed2003

International comparison of quality indicators in United States, Icelandic and Canadian nursing facilities.

AIM: To discuss the results of a comparison using minimum data set (MDS)-based quality indicators (QIs) for residents in nursing facilities in three countries (Iceland; Ontario, Canada; and Missouri, United States) together with implications regarding nursing practices and resident outcomes in these countries. METHOD: Data were extracted from databases in each country for four consecutive quarterly periods during 1997 and 1998. All facilities investigated had the required consecutive quarterly data. Analytical techniques were matched to measure resident outcomes using the same MDS-based QIs in the three countries. RESULTS: Similarities among the three countries included the use of nine or more multiple medications, weight loss, urinary tract infection, dehydration, and behavioural symptoms that affect others. Differences among the three countries included bowel and bladder incontinence, indwelling catheter use, fecal impaction, tube feeding use, development of pressure ulcers, bedridden residents, physical restraint use, depression without receiving antidepressant therapy, residents with depression, use of anti-anxiety or hypnotic drugs, use of anti-psychotic drugs in the absence of psychotic and related conditions, residents spending little or no time in activities, and falls. CONCLUSIONS: Comparisons highlighted differences in clinical practices among countries, which may account for differences in resident outcomes. Learning from each other's best practices can improve the quality of care for older people in nursing homes in many countries.

Aged↗
PubMed2004

Case-control association studies with matching and genomic controlling.

Family-based association studies have gained in popularity for mapping disease-susceptibility gene(s) of complex diseases. However, recruiting family controls is often more difficult than recruiting unrelated controls. The author proposes a case-control study, where the possible biases due to population stratification are controlled by matching in the design stage and by genomic controlling in the data-analytic stage. The matching is based on a set of "stratum-delineating variables," such as, race, ethnicity, nationality, ancestry, and birthplace; and the genomic controlling is based on typing a number of null markers across the genome and applying the principle of multiplicative scaling of chi-square distribution. It pays to match carefully to have a higher proportion of correctly matched sets, as computer simulation showed that this would increase the power of the study. If matching is crude, one loses power but still has the correct type I error rate after genomic controlling. Power studies showed that the numbers of affected subjects required for the pair-matched study are comparable to those required by the case-parents design, if the study was conducted in a homogeneous population. As the (control-to-case) matching ratio increases, the number of affected subjects required decreases. With matching ratio tending toward infinity, the number required shrinks roughly by half. The case-control study with matching and genomic controlling frees us from family bondage, and the genetic problem as complicated as mapping genes can now be studied using simple epidemiologic methods.

Case-Control Studies↗
PubMed1987

Acute-subacute lead poisoning. Clinical findings and comparative study of diagnostic tests.

A prospective study of an epidemic outbreak of acute lead poisoning characterized by unusual clinical and analytic manifestations was carried out. Its source was traced to lead-contaminated flour. Thirty-two adult patients presented with classic clinical symptoms of saturnism; however, 13 severely poisoned patients simultaneously manifested unusual clinical features such as hemolytic anemia and multiorgan dysfunction. We compared the diagnostic value of the different toxicity markers in 68 of 136 adults exposed to lead. Porphyrin precursors, urine levels of lead, and results from an edetic acid-provocative test gave poor diagnostic information and low correlation values with lead levels in blood. However, erythrocyte delta-aminolevulinic acid dehydratase activity showed a closer correlation with lead levels in blood, although we observed a frequent overlap of results in severe cases. The test for levels of lead in blood was the most reliable, suitable, and simplest test performed, and gave the best correlation with the external dose of lead, the clinical situation, and the toxicologic effects described by 12 different analytic data.

Acute Disease↗
PubMed1998

Tuberculous pleurisy: a study of 254 patients.

OBJECTIVES: To determine the age at which tuberculous pleural effusions occur, the radiological and biochemical characteristics of the effusions, the sensitivities of the various diagnostic tests, and the utility of combining clinical, radiological, and analytic data in diagnosis. METHODS: We studied the case histories of 254 patients in whom tuberculous pleural effusions were diagnosed with certainty between January 1, 1989, and June 30, 1997, in a Spanish university hospital in a region with a high incidence of tuberculosis. RESULTS: The mean (+/-SD) age of the patients was 34.1+/-18.1 years, and 62.2% were younger than 35 years. The effusion was on the right side in 55.9% of patients, on the left side in 42.5% of patients, and on both sides in 1.6% of patients. In 81.5% of patients, less than two thirds of the hemithorax was affected. Associated pulmonary lesions were detected in 18.9% of patients, of whom 14.6% exhibited cavitation. In 93.3% of the effusions, more than 50% of leukocytes were lymphocytes, and almost all had the biologic characteristics of exudates (98.8% had high total protein contents, 94.9% had high cholesterol levels, and 82.3% had high lactate dehydrogenase levels). All but 1 effusion (99.6%) had an adenosine deaminase (ADA) concentration higher than 47 U/L, 96.8% (123/127) of the effusions had high ADA2 levels, and 89% (73/82) of the effusions had high interferon gamma levels. Adenosine deaminase 2 contributed 72.2%+/-12.5% (mean +/- SD) of total ADA activity. Total ADA activity was significantly correlated with ADA2 (r = 0.83) and with interferon gamma (r = 0.30) levels. Definitive diagnosis was based on the observation of caseous granulomas in pleural biopsy tissue samples in 79.8% of patients, on the results of biopsy cultures in 11.7% of patients, and on pleural effusion cultures in the remaining 8.5% of patients. Results of the tuberculin skin test were positive in only 66.5% of patients. CONCLUSIONS: In these patients, lymphocyte-rich exudative pleural effusions occurred, on average, at a young age, with no preference for either the right or the left side; normally affected no more than two thirds of the hemithorax; and were generally unaccompanied by pulmonary infiltrates. High ADA concentration was a highly sensitive diagnostic sign and was caused by a rise in ADA2 concentration. The most sensitive criterion based on pleural biopsy was the observation of caseous granulomas, and culture of biopsy material further increased overall sensitivity. Negative skin test results were no guarantee of the effusion being nontuberculous. This, together with the low mean age of the patients and the low frequency of associated pulmonary lesions, suggests that tuberculous pleural effusion is a primary form of tuberculosis in this region.

Adenosine Deaminase↗
PubMed1977

Macular cherry-red spots and beta-galactosidase deficiency in an adult. An autopsy case with progressive cerebellar ataxia, myoclonus, thrombocytopathy, and accumulation of polysaccharide in liver.

An adult patient with macular cherry-red spots, a gargoyle-like physical appearance, cerebellar ataxia, myoclonus, convulsive seizures, and pyramidal tract signs showed a profound deficiency of beta-galactosidase in liver and brain. Thrombocytopathy of undetermined etiology was evident since childhood, and the patient died of intracranial bleeding at age 22. Cerebral ganglioside pattern was normal. Hepatic mucopolysaccharides were not increased. GM1-gangliosidosis and mucopolysaccharidosis were ruled out by those analytical data. However, a large amount of amylopectin-like polysaccharide was found to be accumulated in liver. Hepatocyte contained numerous inclusion bodies with granulofibrillary structure similar to Lafora bodies, corpora amylacea, and inclusion bodies in glycogenosis type IV. This case seems to represent a new inborn metabolic disease closely related to GM1-gangliosidosis and mucopolysaccharidosis. The primary metabolic defect is not known at present.

Adult↗
PubMed2002

Identification of population subgroups of children and adolescents with high asthma prevalence: findings from the Third National Health and Nutrition Examination Survey.

OBJECTIVES: To provide national estimates of asthma prevalence in African-American, Mexican American and white (non-Latino) children and adolescents using several common definitions; to evaluate familial, sociodemographic, and environmental risk factors that are independently associated with current asthma in children; and to identify subgroups at particular risk for current asthma using 2 complementary data analytic approaches. DESIGN: Cross-sectional study, using the Third National Health and Nutrition Examination Survey, 1988-1994. SETTING: Eighty-nine mobile examination centers in the United States. PARTICIPANTS: Twelve thousand three hundred eighty-eight African American, Mexican American, and white (non-Latino) children and adolescents, aged 2 months through 16 years, selected from a systematic random, population-based, nationally representative sample. MAIN OUTCOME MEASURE: Current asthma, defined by caregivers who reported that their child currently had doctor-diagnosed asthma. RESULTS: The overall prevalence of current asthma was 6.7% (95% confidence interval [CI], 5.6-7.8). Odds ratios for current asthma from the multiple regression analysis were 4.00 (95% CI, 2.90-5.52) for children with a parental history of asthma or hay fever, 1.94 (95% CI, 1.09-3.46) for children with body mass index (calculated as weight in kilograms divided by the square of height in meters) greater than or equal to the 85th percentile, and 1.64 (95% CI, 1.20-2.26) for children of African American ethnicity. African American and Mexican American children showed a consistent prevalence of current asthma across age while white children showed an increase in prevalence with age. The 2 highest-risk subgroups identified by the signal detection analysis were composed of children with a parental history of asthma or hay fever who were 10 years or older with a body mass index greater than or equal to the 85th percentile (31.0% current asthma), and children with a parental history who were 10 years or younger and of African American ethnicity (15.6% current asthma). CONCLUSIONS: The findings from this analysis show a strong independent association between obesity and current asthma in children and adolescents, and confirm previous reports of a parental history of asthma or hay fever and African American ethnicity as additional important risk factors.

Adolescent↗
PubMed1996

Urethane-protected alpha-amino acid N-carboxyanhydrides and peptide synthesis.

The preparation, physical properties and analytical data are reported for seventy urethane-protected (Boc, Cbz, FMOC) amino acid N-carboxyanhydrides (UNCAs). Most of the UNCAs are crystalline and the X-ray diffraction patterns for several of these are described. UNCAs are stable to routine laboratory manipulations and can be stored for extended periods of time (1-2 years at below 0 degrees C). Most are completely stable to the conditions commonly employed for peptide synthesis. The correct choice of base is key for the successful introduction of urethane protecting groups into NCAs. N-Methylmorpholine is used for the introduction of FMOC, Cbz or Boc from the chloroformates, and pyridine is used for the introduction of the Boc group from Boc anhydride. UNCAs represent a unique class of preactivated, isolable and stable amino acid derivatives that generate no side products or co-products, other than CO2, during condensation reactions. The application of UNCAs in peptide synthesis in both solid phase and in solution is reviewed in detail.

Amino Acid Sequence↗
PubMed1997

Multivariate reconstruction of lymphocyte profiles in a two-dimensional graphical model as a tool for the investigation of lymphocyte subset distribution in health and disease.

Advanced multivariate data-analytical techniques are proposed to concisely represent and evaluate complex lymphocyte profiles (i.e., compound lymphocyte subset distributions) of individual subjects in easily interpretable, two-dimensional, graphical correlation biplots. The lymphocyte profile of each subject is represented by its location in the model, and the score of a subject for a particular lymphocyte subset is inferred from the perpendicular projection on a rotated axis that coincides with this lymphocyte subset. Simultaneously, the model yields information about the correlation between the lymphocyte subsets. Furthermore, individuals with aberrant lymphocyte profiles can be easily identified. In case studies of 80 healthy donors and of 40 patients with multiple myeloma, 10 patients with monoclonal gammopathy of undetermined significance, and 50 age- and sex-matched healthy donors, reconstruction of the two-dimensional lymphocyte profiles from 27 flow-cytometric characterized lymphocyte subsets succeeded in representing 43% and 51% of the total information (variability) contained within the 80 x 27 (= 2,160) and 100 x 27 (= 2,700) flow cytometry measurements, respectively. It is concluded from the present studies that the correlation biplot represents a unique and powerful tool to concisely describe, represent, and analyze complex lymphocyte profiles of individual subjects and the heterogeneity in lymphocyte profiles among these subjects.

Adult↗
PubMedDate not supplied

DNA adducts produced by oils, oil fractions and polycyclic aromatic hydrocarbons in relation to repair processes and skin carcinogenesis.

Ten polycyclic aromatic hydrocarbons (PAHs) mainly with three or four aromatic rings were tested for their ability to induce DNA adduct formation in mouse skin. Four of these were selected to investigate adduct formation and loss over a period of 8 days. Three mineral oils were also examined for their adduct forming ability and one was selected for adduct formation and loss over a period of 8 days. In addition, fractions derived from the same oil containing 2-3- and 4-6-ring aromatic compounds were applied to mouse skin in a non-carcinogenic oil vehicle and adduct levels were observed over an 8-day period. It was found that PAHs that had no mutagenic, initiating or carcinogenic activity and those that had mutagenic activity in bacteria but no initiating activity in mouse skin failed to produce DNA adducts in mouse skin. Two of the three PAHs with initiating activity and both complete carcinogens produced clear evidence of adduct formation, the adduct levels produced by complete carcinogens being 100-1000 times greater than those produced by initiators. Examination of adduct formation and loss with the carcinogenic PAHs benzo[a]pyrene and 5-methylchrysene over an 8-day period showed a peak at 24 h and an apparent two-phase process of adduct loss. It is suggested that the first steep loss was due to DNA repair and that the more gradual subsequent loss was probably due to epidermal hyperplasia and desquamation. With the initiator 1, 4-dimethylphenanthrene (three rings) a peak of adduct formation was seen at 2 days and adduct levels were not reduced much by 8 days. This suggested that, with initiators, adduct formation and repair may be spread over a longer period than with complete carcinogens. With the whole oils, clear evidence of adduct formation was seen with both a carcinogenic non-solvent-refined oil and with a non-carcinogenic residual oil. The level of adduct formation with the residual oil, however, was much lower than with the carcinogenic oil. When adduct formation by the carcinogenic oil was examined over 8 days, the pattern of adduct formation and loss was similar to that of a tumour initiator rather than a complete carcinogen. Peak adduct levels on the diagonal of the thin-layer chromatography (TLC) plates seemed to occur at 1 and 4 days after treatment, with no clear reduction after 8 days. From examination of adducts formed by the 2-3-ring and 4-6-ring aromatic fractions, it appeared that the main adduct spots produced by the carcinogenic oil were due to the 2-3-ring aromatic components of the oil. Adduct spots near the vertical axis of the TLC plates were also seen with the 2-3-ring and 4-6-ring fractions. The relevance of these spots is uncertain, but if they truly represent adducts, the findings suggest that they are due mainly to 4-ring PAHs. The studies suggest that the activity of carcinogenic oils is largely due to substituted 3- and 4-ring polycyclic aromatic compounds and that more attention should be paid to substituted 3-ring compounds in predicting the carcinogenic potential of oils from analytical data.

Animals↗
PubMed1998

Factors influencing informal care-giving.

BACKGROUND: As downsizing of institutional care continues, patients discharged are likely to have more severe mental illnesses, and to have experienced longer tenures within institutions than patients who have been discharged in the past. As greater numbers of patients are removed from mental hospitals, the objective burden experienced by informal care-givers may increase, particularly if formal care levels are inadequate. AIMS OF THE STUDY: This paper documents who assumes informal care-giver roles, and the form such care-giving takes for patients discharged from a state hospital. Specifically, this paper identifies (i) what factors affect a person's decision to assume a care-giver role, including the participation of other network members in care-giving, (ii) what factors influence whether care-giving is provided in time or in direct purchase of care and (iii) how the patient's treatment location affects the decision of the network member to assume any care-giving role. DATA AND ANALYTICAL METHODS: Data for this paper are taken from a longitudinal study of the closure of a state mental hospital in central Indiana. Seventy-seven patients were asked to identify their community networks. Ninety-eight network members were surveyed about the informal care, both in time or through direct expenditures, they provided to these patients one year after discharge. Care-giving relationships were estimated using a multivariate probit model. Such a model estimates the extent to which the decision to provide care in either form depends on the care-giving activities assumed by other network members associated with a given patient, as well as the characteristics of individual patients and network members. RESULTS: Forty-one per cent of network members provided some level of informal care, with 13.3% providing some care in time, and 35.7% providing some care through direct expenditures. A positive relationship was found between participation in informal care-giving and the perception by the network member that patient needs were not being met by professionals. The decision to provide informal care was also found to be sensitive to the level of informal and formal care received by the patient. Care-giving in expense was found to be positively related to the care-giving decisions of other informal care-givers, but care-giving in time was not. Network members were more likely to provide care in time for patients who had been recently discharged to the community than for patients who remained in institutional settings. CONCLUSIONS: These results suggest the transfer of persons with severe mental illnesses from state hospitals to the community may shift the care burden between formal and informal providers. If this is the case, discharge criteria should include such factors as the community resources available to the patient. IMPLICATIONS FOR HEALTH CARE PROVISION AND USE: The responsiveness of network members to perceived unmet need bespeaks the importance of informal care when the continuity of formal care cannot be assured. Findings also suggest there may be some substitution of formal and informal care when patients are discharged from institutions. Further analysis is required to determine whether network members' perceptions of unmet need are accurate, and means by which network members can be made better attuned to unmet needs actually experienced by patients.

Journal Article↗
PubMed2000

Structure and solid-state chemistry of anhydrous and hydrated crystal forms of the trimethoprim-sulfamethoxypyridazine 1:1 molecular complex.

The crystal structure of the equimolar trimethoprim (TMP) and sulfamethoxypyridazine (SMPD) complex in the anhydrous form (TMP. SMPD) and that of the species with 1.5 molecules of water of crystallization (TMP.SMPD.W) are reported in this article. X-ray powder diffraction patterns (both computer generated and experimental) and thermal analytical data from differential scanning calorimetry (DSC) and thermogravimetry useful for the characterization of TMP.SMPD and TMP.SMPD.W are provided. The stability of TMP.SMPD.W, which retains its crystallographic order under 0% relative humidity (RH) conditions at room temperature (22 degrees C) and 20 mmHg, is accounted for in terms of crystal structure and hydrogen bonding. Transformation of TMP.SMPD to the hydrate complex by exposure to approximately 100% RH, suspension in water, and wet granulation, and dehydration of TMP.SMPD.W by thermal treatment and by desiccation with methanol were investigated and tentatively interpreted in terms of crystal properties. Interactions in the physical mixture of TMP and SMPD by grinding, compression, heating, and contact with water were also studied. Water-mediated formation of TMP.SMPD.W by wetting and metastable eutectic melting-mediated formation of TMP.SMPD by heating was demonstrated. Mechanical activation by milling makes the physical mixture prone to solid-state transformation into dimorphic anhydrous cocrystals by supply of thermal energy during a DSC scan.

Crystallization↗
PubMed1999

Electronic Communication in C(4)-Bridged Binuclear Complexes with Paramagnetic Bisphosphane Manganese End Groups.

Building blocks for conducting polymers or NLO materials are the linear, unsaturated carbon chain bridged manganese complexes 1(n+) (n=0-2). All oxidation states were investigated spectroscopically and by X-ray structure determinations. The analytical data confirm a communication of the electrons over the C(4) chain-a prerequisite for electrical conductivity and NLO properties of oligo- or polymeric materials.

Journal Article↗
PubMed1990

Reliability and factorial structure of the Chinese version of the Beck Depression Inventory.

The Chinese version of the Beck Depression Inventory (C-BDI) was administered to 2,150 Chinese secondary school students. The BDI was found to have high internal consistency as a scale and high item-total correlations for most of the items. Factor analysis with a two-factor solution showed that two factors were abstracted from the scale, namely, general depression and somatic disturbances. By randomly splitting the total sample into two subsamples, these two factors could be reproduced reliably, and high coefficients of congruence were found. These findings generally suggest that the Chinese version of the BDI possesses acceptable psychometric properties, and the factor analytic data tend to support Beck's multi-dimensional view of depression as a construct.

Adolescent↗