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Biomedical subjects

A Smit

Publications and source records attributed to A Smit.

At least 19 recordsLinked to original sources
PubMed2001

Biochemical genetic markers to identify two morphologically similar South African Mastomys species (Rodentia: Muridae).

The two common southern African mice species (Mastomys coucha and M. natalensis) are morphologically almost identical, making field identification impossible at present. Specimens from two localities were collected and tissue and blood samples taken. The habitat type of each locality was studied, and a distribution map compiled. A definite correlation between biome-type and species range was found to be present. Three isozyme markers were identified: glucose phosphate isomerase in liver, and two general (non-specific) protein coding loci in muscle. In addition, we also identified species characteristic haemoglobin components in both species. This is the first study to report genetic variation within, and differentiation between these species. Our results are of medical importance because Mastomys coucha carries bubonic plague and M. natalensis carries Lassa Fever.

Journal Article↗
PubMed2001

Comparison of immulite with vidas for detection of infection in a low-prevalence population of pregnant women in The Netherlands.

A comparative evaluation of the Vidas system (bioMérieux, Marcy l'Etoile, France) and the Immulite System (Diagnostic Products Corporation) was performed using 500 prospectively collected serum samples. As part of a routine antenatal screening program, these samples were tested for hepatitis B surface antigen, and immunoglobulin G (IgG) and IgM antibodies to Toxoplasma gondii and rubella virus. The overall agreement between the two assay systems ranged from 98.0 to 99.8%. After discrepancy analysis the outcome in terms of relative sensitivity and specificity varied from 97.5 to 100%.

Animals↗
PubMed2001

Accuracy of general practitioner's prognosis of the 1-year course of depression and generalised anxiety.

BACKGROUND: A prognosis serves important functions for the management of common mental disorders in primary care. AIMS: To establish the accuracy of the general practitioner's (GP) prognosis. METHOD: The agreement between GP prognosis and observed course was determined for 138 cases of ICD-10 depression and 65 of generalised anxiety disorder, identified among consecutive attenders of 18 GPs. RESULTS: Modest agreement between GP prognosis and course was found, both for depression (kappa=0.21) and generalised anxiety (kappa=0.11). Better agreement (kappa=0.45 for depression, and kappa=0.33 for generalised anxiety) was observed between the course and predictions from a statistical model based on information potentially available to the GP at the time the prognosis was made. This model assesses attainable performance for GPs. CONCLUSIONS: General practitioners do a fair job in predicting the 1-year course of depression and generalised anxiety. Even so, their performance falls significantly short of attainable performance.

Adolescent↗
PubMed2000

PipMaker--a web server for aligning two genomic DNA sequences.

PipMaker (http://bio.cse.psu.edu) is a World-Wide Web site for comparing two long DNA sequences to identify conserved segments and for producing informative, high-resolution displays of the resulting alignments. One display is a percent identity plot (pip), which shows both the position in one sequence and the degree of similarity for each aligning segment between the two sequences in a compact and easily understandable form. Positions along the horizontal axis can be labeled with features such as exons of genes and repetitive elements, and colors can be used to clarify and enhance the display. The web site also provides a plot of the locations of those segments in both species (similar to a dot plot). PipMaker is appropriate for comparing genomic sequences from any two related species, although the types of information that can be inferred (e.g., protein-coding regions and cis-regulatory elements) depend on the level of conservation and the time and divergence rate since the separation of the species. Gene regulatory elements are often detectable as similar, noncoding sequences in species that diverged as much as 100-300 million years ago, such as humans and mice, Caenorhabditis elegans and C. briggsae, or Escherichia coli and Salmonella spp. PipMaker supports analysis of unfinished or "working draft" sequences by permitting one of the two sequences to be in unoriented and unordered contigs.

Animals↗
PubMed2000

Biosynthesis of isoprenoids via mevalonate in Archaea: the lost pathway.

Isoprenoid compounds are ubiquitous in living species and diverse in biological function. Isoprenoid side chains of the membrane lipids are biochemical markers distinguishing archaea from the rest of living forms. The mevalonate pathway of isoprenoid biosynthesis has been defined completely in yeast, while the alternative, deoxy-D-xylulose phosphate synthase pathway is found in many bacteria. In archaea, some enzymes of the mevalonate pathway are found, but the orthologs of three yeast proteins, accounting for the route from phosphomevalonate to geranyl pyrophosphate, are missing, as are the enzymes from the alternative pathway. To understand the evolution of isoprenoid biosynthesis, as well as the mechanism of lipid biosynthesis in archaea, sequence motifs in the known enzymes of the two pathways of isoprenoid biosynthesis were analyzed. New sequence relationships were detected, including similarities between diphosphomevalonate decarboxylase and kinases of the galactokinase superfamily, between the metazoan phosphomevalonate kinase and the nucleoside monophosphate kinase superfamily, and between isopentenyl pyrophosphate isomerases and MutT pyrophosphohydrolases. Based on these findings, orphan members of the galactokinase, nucleoside monophosphate kinase, and pyrophosphohydrolase families in archaeal genomes were evaluated as candidate enzymes for the three missing steps. Alternative methods of finding these missing links were explored, including physical linkage of open reading frames and patterns of ortholog distribution in different species. Combining these approaches resulted in the generation of a short list of 13 candidate genes for the three missing functions in archaea, whose participation in isoprenoid biosynthesis is amenable to biochemical and genetic investigation.

Amino Acid Motifs↗
PubMed2000

Pseudolikelihood estimation of the Rasch model.

An estimation method is proposed for the Rasch model on the basis of the pseudolikelihood theory of Arnold and Strauss (1988). A simulation study was conducted to compare the proposed maximum pseudolikelihood estimates with the well known conditional maximum likelihood and unconditional maximum likelihood estimates for the item parameters of the Rasch model. The results show great similarity between the methods.

Analysis of Variance↗
PubMed1999

Training primary-care physicians to recognize, diagnose and manage depression: does it improve patient outcomes?

BACKGROUND: We developed a comprehensive, 20-hour training programme for primary-care physicians, that sought to improve their ability to detect, diagnose and manage depression. We evaluated the effects of physician training on patient outcomes, using a pre-post design. METHODS: In the pre-training phase of the study, we sampled 1834 consecutive patients of 17 primary-care physicians and evaluated 518 of these patients for the presence of depression. We measured outcomes of all patients with depression at 3 months and 1 year. The outcome measures were: severity of psychopathology; duration of depressive episode; and level of daily functioning. After the 17 physicians completed the training, we drew a new sample from their practices (498 of 1785 consecutive patients were evaluated for depression) and measured outcomes for the depressed patients. RESULTS: We found an effect of the training on short-term outcome, particularly for patients with a recent-onset depression. At 3-month follow-up depressed patients whose physicians had received training had less severe psychopathology and patients with recent-onset depression also showed higher levels of daily functioning than patients of the same physicians prior to the training. The patients with a recent-onset depression that was recognized by trained physicians had shorter depressive episodes, but this was not statistically significant. At 1-year follow-up, all training effects had faded away. CONCLUSIONS: Training primary-care physicians to recognize, diagnose and manage depression can improve short-term patient outcomes, especially for patients with a recent onset of depression. Patients suffering from a recurrent or chronic depression may need more specific interventions, both for acute treatment and long-term management.

Adult↗
PubMed1999

Practical management of therapeutic diphenylhydantoin concentrations in children.

OBJECTIVE: Development of easy, practical methods for the management and optimisation of therapeutic diphenylhydantoin (DPH) concentrations in children. DESIGN: Investigation of DPH concentration profiles and pharmacokinetic parameters in children with poorly controlled epilepsy. Subsequent determination of individual-specific DPH maintenance dosage and volume of distribution data suitable for use in routine therapeutic concentration management procedures. SETTING: Department of Paediatrics and Child Health and Department of Pharmacology, University of Stellenbosch, Tygerberg Hospital. SUBJECTS: Children of both sexes between the ages of 4 and 12 years with poorly controlled epilepsy receiving DPH as sole medication. RESULTS: In all subjects evaluated epilepsy was unsatisfactorily controlled because of inadequate DPH dosage regimens. Individual-specific maintenance dosage and volume of distribution data could be calculated for all individuals participating in the trial. The calculated data were suitable for use in routine management procedures and in no instance was it necessary to recalculate parameters in a 12-month follow-up period subsequent to evaluation. CONCLUSIONS: Therapeutic DPH concentration profiles can be managed satisfactorily in children in individual-specific DPH pharmacokinetic parameters are derived and skillfully applied.

Anticonvulsants↗
PubMed1998

[Polymorphism of the HLA-DRB1 04 gene in inhabitants of Tuva].

Data on the HLA-DRB1 04 gene typing among Tuvinians from Kyzyl are presented. Experiments were conducted by using the hybridization of allele-specific oligonucleotides with the amplified fragments of high molecular-weight DNA and reverse hybridization. The HLA-DRB1 0401 allele was most frequent among DR4-positive individuals. The HLA-DRB1 0405 and HLA-DRB1 0403 alleles were found at somewhat lower frequencies. In one individual, the rare HLA-DRB1 0410 subtype differing from HLA-DRB1 0405 subtype by the substitution of glycine for valine in codon 86 was detected.

Adolescent↗
PubMed1998

Two-year follow-up study to evaluate the reduction of left ventricular mass and diastolic function in mild to moderate diastolic hypertensive patients.

OBJECTIVE: To compare the effects of two antihypertensive agents, amlodipine and lisinopril, on left ventricular mass and diastolic filling in patients from primary care centers with mild to moderate diastolic hypertension. STUDY DESIGN: A second-year, open follow-up of a prospective, double-blind, randomized, parallel group, comparative study. METHODS: Male and female patients between 25 and 75 years-of-age with elevated diastolic blood pressure (four measurements > or = 95 mmHg from multiple measurements taken on three occasions and average diastolic blood pressure < 115 mmHg) were recruited from a population survey. After 4 weeks' placebo run-in, 71 patients were included of whom 60 finished the first study year and 51 finished the second study year. Patients were randomly assigned to receive doses of 5-10 mg amlodipine or 10-20 mg lisinopril, which were titrated on the basis of the effects on blood pressure. Primary endpoints were left ventricular mass index (LVMI) and early to atrial peak filling velocity. Office and ambulatory blood pressure were considered secondary endpoints. RESULTS: The decrease in blood pressure was equal for both treatment regimens in the first year. A statistically significant (P< 0.001) decrease in LVMI in both treatment groups was observed in the first year [-11.0 g/m2 (95% Cl -6.0 to -16.1) in the amlodipine group and -12.6 g/m2 (95% Cl -8.2 to -17.0) in the lisinopril group]. Early to atrial peak filling velocity did not change significantly within the treatment groups in the first year [+0.07 (95% CI -0.01 to +0.15) in the amlodipine group and +0.01 (95%9 Cl -0.06 to +0.08) in the lisinopril group. Blood pressure, LVMI and early to atrial peak filling velocity did not change in the second year of treatment. No significant differences in primary and secondary endpoints between treatment groups were found in the first or second year. CONCLUSION: The effects of amlodipine and lisinopril on left ventricular mass and early to atrial filling peak velocity after 2 years of treatment were similar and these effects were already observed after 1 year of treatment. Additional studies of longer duration (> or = 4 years) and with a larger sample size are recommended.

Adult↗
PubMed1997

The plaque acidogenic response to carbohydrates of children from three ethnic groups in South Africa.

The plaque acidogenic response of children from three ethnic groups in South Africa to four different carbohydrates was investigated using the plaque sampling method. A total of 30, 12-year-old children, ten black, ten 'coloured' and ten white, completed this study. The foods tested were 10 per cent sucrose solution, maize porridge, strawberry flavoured yoghurt and banana. The blacks produced an intermediate plaque pH response to sucrose compared with the 'coloureds' and whites but the smallest response for the other carbohydrate challenges. It was concluded that a difference exists in the plaque acidogenic response to carbohydrate between the three ethnic groups and that this may in part account for differences in caries prevalences.

Acids↗
PubMed1997

A comparison of three electrodes for the measurement of pH in small volumes.

An ion-sensitive field effect transistor (ISFET, Sentron, Sentron, Inc.) electrode was compared with a glass combination micro-electrode (MI-410, Micro-electrodes, Inc.) and a solid-state metal wire oxide pH sensor (Beetrode, World Precision Instruments, Inc.) with a liquid junction reference electrode (MERE1, World Precision Instruments, Inc.). The electrodes were assessed for linearity, reproducibility, accuracy, drift from the initial calibration between pH 4 and pH 7 and the time taken to record a stable reading. The ISFET was used to determine the pH in dental plaque samples (1 mg suspended in 20 microliters). The pH values correlated with the hydrogen ion concentration for all the electrodes (r = 0.98). The MI-410 fractured before this evaluation was completed. Coefficients of variation were 0.65% (pH 4) and 0.08% (pH 7) for the ISFET and 4.69% (pH 4) and 3.46% (pH 7) for the Beetrode. Both electrodes gave readings that differed significantly from the initial calibration, but the drift was greater for the Beetrode (F = 7.93; p = 0.0005) than the ISFET (F = 1.89; p = 0.1519). However, this drift was smaller than the change in pH as measured in dental plaque samples. The Beetrode gave a stable reading after 3.39 +/- 0.83 s and the ISFET after 2.2 +/- 0.76 s, while the MI-410 required at least 20 s. The ISFET type electrode is suitable for use in small volumes such as plaque suspensions, is easier to operate and yields results closer to the initial calibration than the Beetrode and is more robust than the MI-410 and the Beetrode.

Analysis of Variance↗
PubMed1992

Plaque quantitation through protein measurement.

This study was undertaken to establish whether the quantitation of dental plaque protein by a dye-binding method (Coomassie G-250) may be used as an index of the amount of dental plaque sampled. Ten sites were sampled in 34 children on 5 occasions at 4 month intervals. The mean protein concentration in 1391 plaque samples was 6.9 +/- 4.1 micrograms (micrograms) (mean +/- standard deviation). A three-way analysis of variance showed that the plaque protein concentration was similar at the different sampling sites in the same child (p = 0.14), but statistically significant differences were observed with respect to time of sampling (F = 36.24; p = 0.0001) and individual sampled (F = 5.69; p = 0.0001). These observations indicate that plaque bacterial counts may be expressed as units of protein concentration and this method may be useful to relate the number of viable bacteria to an estimate of the amount of plaque collected. This ratio allows standardisation for any variation in the amount of plaque collected.

Analysis of Variance↗
PubMed1989

Structure and function of the androgen receptor.

The androgen receptor in several species (human, rat, calf) is a monomeric protein with a molecular mass of 100-110 kDa. The steroid binding domain is confined to a region of 30 kDa, while the DNA-binding domain has the size of approx. 10 kDa. A 40 kDa fragment containing both the DNA and steroid binding domain displayed a higher DNA binding activity than did the intact 100 kDa molecule. cDNA encoding the major part of the human androgen receptor was isolated. The cDNA contains an open reading frame of 2,277 bp but still lacks part of the 5'-coding sequence. Homology with the progesterone and glucocorticoid receptor was about 80% in the DNA binding domain and 50% in the steroid binding domain. The present data provide evidence that the androgen receptor belongs to the superfamily of ligand responsive transcriptional regulators and consists of three distinct domains each with a specialized function.

Amino Acid Sequence↗
PubMed1986

Plasma volume in black women with eclampsia.

Plasma volume was estimated in 11 black women with eclampsia and compared with 9 normotensive primigravidas. With respect to age, weight and height the two groups were similar and although plasma volume was 4.1% less in the reference group, this difference was not statistically significant.

Eclampsia↗