PubMed Health⌕ Search

Biomedical subjects

M Karl

Publications and source records attributed to M Karl.

At least 19 recordsLinked to original sources
PubMed2007

Comparison between computer-aided testing and traditional multiple choice: an equivalence study.

AIMS: Computer-aided learning (CAL) is a viable alternative to traditional teaching methods. While CAL is used for teaching only, computer-aided testing (CAT) can be applied as a computer-based examination method. The aim of the present study was to compare the performance of undergraduate students in computer-interactive tests and traditional multiple choice tests and to evaluate the influence of question length and language skills on test results. MATERIALS AND METHODS: Fifty-two native German-speaking students and five non-native speaking students were randomly assigned to two groups. They were required to answer 20 conventional multiple choice questions and 20 questions using the interactive MobiTed system. An analysis of variance and t-tests (alpha = 0.05) were used to compare scores. RESULTS: Non-native speakers scored significantly lower on the interactive test compared with the native speaking students (P = 0.048 for long questions and P = 0.003 for short questions). There were no significant group differences on the conventional multiple choice test (P = 0.052 for long questions and P = 0.089 for short questions). Based on the results of the native speaking students neither test method nor question length had an influence on overall performance. CONCLUSION: Interactive multiple choice tests may provide an alternative to written tests, especially when considering time expenditure. Language skills and question length should be taken into account when setting time limits for examination.

Computer-Assisted Instruction↗
PubMed2001

Upregulation of CD40 and CD40 ligand (CD154) in patients with moderate hypercholesterolemia.

BACKGROUND: Hypercholesterolemia, a risk factor for cardiovascular disease, is associated with inflammation and hypercoagulability. Both can be mediated by the CD40 system. This study investigated whether the CD40 system is upregulated in patients with moderate hypercholesterolemia and whether it is influenced by therapy with a hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitor. METHODS AND RESULTS: Fifteen patients with moderate hypercholesterolemia and 15 healthy control subjects were investigated. CD154 and P-selectin were analyzed on platelets and CD40 was analyzed on monocytes before and under therapy with the statin cerivastatin by double-label flow cytometry. Blood concentrations of soluble CD154 and monocyte chemoattractant protein-1 (MCP-1) were evaluated. Our main findings were as follows. Patients with moderate hypercholesterolemia showed a significant increase of CD154 and P-selectin on platelets and CD40 on monocytes compared with healthy subjects. Soluble CD154 showed a nonsignificant trend for higher plasma levels in patients. A positive correlation was found for total or LDL cholesterol and CD154, but not for CD40 on monocytes. The latter was upregulated in vitro by C-reactive protein, which was found to be significantly elevated in patients with moderate hypercholesterolemia. CD154 on platelets proved to be biologically active because it enhanced the release of MCP-1, which was markedly elevated in an in vitro platelet-endothelial cell coculture model and in the serum of patients. Short-term therapy with a HMG-CoA reductase inhibitor significantly downregulated CD40 on monocytes and serum levels of MCP-1. CONCLUSION: Patients with moderate hypercholesterolemia show upregulation of the CD40 system, which may contribute to the known proinflammatory, proatherogenic, and prothrombotic milieu found in these patients.

Adult↗
PubMed2000

Comparison of central nervous system adverse effects of amantadine and rimantadine used as sequential prophylaxis of influenza A in elderly nursing home patients.

BACKGROUND: Amantadine hydrochloride and rimantadine hydrochloride are recommended by the Centers for Disease Control and Prevention for prophylaxis of influenza A. While data suggest that rimantadine is better tolerated, there are no data examining the rate of adverse reactions in elderly patients who receive amantadine vs rimantadine. Our objective was to assess the adverse reaction rate in elderly nursing home patients receiving sequential amantadine and rimantadine for influenza A prophylaxis. METHODS: Data were collected in 156 nursing home patients (70% women; mean+/-SD age, 83.7+/-10.1 years) in a single care setting who received sequential therapy with amantadine and rimantadine during the 1997-1998 influenza season. Patients were assessed for central nervous system adverse effects and therapy discontinuation occurring with each agent. RESULTS: Twenty-nine (18.6%) of the 156 patients experienced an adverse effect when receiving amantadine compared with 3 patients (1.9%) when rimantadine was given (P<.01). Drug use was discontinued due to adverse events in 17.3% (n = 27) of the amantadine courses and 1.9% (n=3) of the rimantadine courses (P<.001). Confusion was the most frequently observed adverse event (amantadine, 10.6%; rimantadine, 0.6%; P<.001). Multivariate logistic regression analysis showed that significant risk factors for central nervous system adverse events included male sex (odds ratio, 3.65), reduced calculated creatinine clearance (odds ratio, 1.78), and use of amantadine (odds ratio, 12.73). CONCLUSIONS: Amantadine use was associated with a significantly higher incidence of central nervous system adverse events than rimantadine use in this elderly population receiving influenza prophylaxis. In addition, the discontinuation rate of amantadine was significantly higher than that with rimantadine.

Adverse Drug Reaction Reporting Systems↗
PubMed1999

Imbalanced expression of the glucocorticoid receptor isoforms in cultured lymphocytes from a patient with systemic glucocorticoid resistance and chronic lymphocytic leukemia.

The human glucocorticoid receptor (GR) is expressed as two alternatively spliced isoforms, GRalpha and GRbeta. Whereas GRalpha is a hormone-activated transcription factor, GRbeta does not bind glucocorticoids (GCs), is transcriptionally inactive, and is a potential inhibitor of activated GRalpha. Differential expression of GR isoforms may play a role in generalized or tissue-specific GC resistance. GCs induce apoptosis in neoplastic lymphoid cells; and, defective apoptosis is implicated in the genesis of chronic lymphocytic leukemia (CLL). We studied a patient with generalized GC resistance and CLL. GR number in the patient's transformed lymphocytes was approximately one half that of control cells with a approximately 10-fold reduction in binding affinity for dexamethasone. In vitro apoptosis induction in CLL cells was delayed in response to GCs, but not to other apoptosis inducers. Sequencing of the GR cDNA and gene including the 2.3-kb coding region, the intron/exon junctions, the known 5'-regulatory region, and approximately 300 bp of the 3'-region revealed no alterations. Western blot with an N-terminal antibody showed normal levels of immunoreactive GR, but quantitative analysis with isoform-specific C-terminal antibodies revealed a markedly reduced GRalpha expression, and high GRbeta expression. These findings indicate that imbalanced expression of the GR isoforms may be a mechanism of GC resistance, and may have implications for tumorigenesis by enhancing cell survival.

Adult↗
PubMed1999

Androgen receptor-mediated hypersensitivity to androgens in women with nonhyperandrogenic hirsutism: skewing of X-chromosome inactivation.

Idiopathic hirsutism may result from an increase in the androgen receptor (AR)-mediated sensitivity of the hair follicle. The AR gene is located on the X-chromosome and contains a highly polymorphic trinucleotide repeat (CAGn) in its first exon, whose length and methylation pattern affect both AR expression and function. We analyzed these CAG repeats in the genomic DNA from 16 nonhyperandrogenic hirsute patients (Ferriman score: 16 +/- 4.7, mean +/- SD) and 10 normal controls (Ferriman score: 3 +/- 1.4), who were similar in their hormonal profiles. We found no difference in the number of CAG repeats between hirsute patients and controls, and no correlation between number of repeats and the Ferriman score or hormonal values. However, after DNA digestion with methylation-sensitive HpaII and measurement of the optical density, we found a marked decrease in the hirsute group (P < 0.0001), which was greater than in the control group (P = 0.0003). In addition, in the hirsute patients, the shorter of the two alleles was preferentially less methylated (P = 0.007), suggesting skewing of X-chromosome inactivation in the patients but not in the controls. When the mean optical density of both alleles was correlated with the Ferriman score, we observed a significant negative correlation (P = 0.02, r = -0.45), which became stronger when the shorter alleles were analyzed separately (P = 0.01; r = 0.48). We conclude that nonhyperandrogenic hirsutism is associated with skewing of X-chromosome inactivation in peripheral blood lymphocytes. This leads to the longer of the two AR alleles being preferentially methylated, allowing for the shorter (and presumably, more functional) allele to be expressed on the active X-chromosome. Further studies need to be performed to investigate whether this phenomenon is present in androgen-sensitive tissues in these patients.

Adult↗
PubMed1998

Multiple polypeptides immunologically related to beta-poly(L-malate) hydrolase (polymalatase) in the plasmodium of the slime mold Physarum polycephalum.

Plasmodia of Physarum polycephalum contain large amounts of the cell-type-specific polyanion beta-poly(L-malate) and of a corresponding specific hydrolase (polymalatase), both expressed in the plasmodial form of the organism. We have partially purified polymalatase, the preparation consisting of several polypeptides, which could not be separated without destroying the hydrolase activity. Polypeptides of 68 kDa and 97 kDa were identified as polymalatases. Both were glycosylated, the 68-kDa form giving rise to a 54-kDa form when deglycosylated, and the 97-kDa form giving rise to an 88-kDa polypeptide that was indistinguishable from an 88-kDa inactive species also contained in the enzyme preparation. Antisera against each of these proteins were used to detect the intracellular distribution of the proteins. We found that the antisera crossreacted with the three proteins and, furthermore, with a multiplicity of polypeptides ubiquitously distributed over the plasmodium. Results of a two-dimensional non-denaturing in the first dimension and SDS-denaturing polyacrylamide gel electrophoresis in the second dimension suggested that the proteins were derived from a 200-kDa 'precursor' protein by proteolytic fragmentation. Polymalatase activity could be generated from a high molecular-mass precursor. According to several pieces of evidence, the proteolytic nicking occurred within plasmodia. The fragments were sticky and gave rise to preferred sizes of nicked macromolecules. The observed multiplicity varied as a function of the age of the cultures. The cellular distribution and the intracellular pH value were not compatible with an in situ polymalatase activity and suggested other, presently unknown, function(s) such as in the transportation of beta-poly(L-malate) from the nucleus to the culture medium.

Animals↗
PubMed1998

Localization and expression of adrenocorticotropic hormone receptor mRNA in normal and neoplastic human adrenal cortex.

The recent cloning of the ACTH receptor (ACTH-R) gene allows investigation of the tissue localization and relative abundance of ACTH-R mRNA in normal and neoplastic adrenal cortex. Using in situ hybridization (ISH) we studied the expression of ACTH-R mRNA in four adult adrenals of brain-dead patients, two cortisol-producing adenomas (CPA), three aldosterone-producing adenomas (APA), one non-functional adenoma (NFA), and three carcinomas. The results were compared with the mRNA expression of key steroidogenic enzymes and of the glucocorticoid receptor (GR) mRNA using Northern blotting. In adult adrenals, messenger RNA encoding ACTH-R was localized in all three zones of the adrenal cortex, in accordance with the stimulatory role of ACTH on mineralocorticoid, glucocorticoid and adrenal androgen secretion. In comparison, expression of side-chain cleavage enzyme (P450scc) showed a similar tissue distribution with mRNA abundance in all three zones, whereas 17-hydroxylase/17-20 lyase (P450c17) mRNA expression was only detected in the zona fasciculata and zona reticularis. All CPAs and APAs expressed significant levels of ACTH-R mRNA whereas an NFA showed low expression of ACTH-R mRNA. Two of three adrenocortical carcinomas expressed ACTH-R mRNA. Northern analysis using dot blot was employed to quantify ACTH-R and GR mRNA expression and confirmed the ISH data: ACTH-R mRNA expression was high in CPAs (275 and 195% vs 100 +/- 25% in adult adrenals), APAs (127, 200 and 221%) and two carcinomas (99 and 132%), but low in the NFA (7%) and in an androgen secreting carcinoma (16%). GR mRNA expression was high in the NFA (195%) and in two of three carcinomas (93, 188, 227%). We conclude that ACTH-R mRNA is upregulated in functional adenomas by yet unidentified mechanisms. The tissue distribution of ACTH-R and P450 enzyme mRNA expression is highly variable in neoplastic adrenals and does not allow a clear differentiation between benign and malignant tumors.

Adenoma↗
PubMed1997

Lack of association between five polymorphisms in the human glucocorticoid receptor gene and glucocorticoid resistance.

Glucocorticoid resistance due to mutations in the gene for the glucocorticoid receptor has been suggested to be more common than is thought at present, owing to the relative mildness of its symptoms and the difficulty of its diagnosis. To investigate the prevalence of mutations in the glucocorticoid receptor gene responsible for relative insensitivity to glucocorticoids, we carried out polymerase chain reaction/single-strand conformation analysis of the glucocorticoid receptor gene in a group of 20, otherwise healthy, persons with a reduced response in a dexamethasone suppression test and in 20 controls. We did not find mutations or polymorphisms associated with a reduced sensitivity to glucocorticoids. However, we identified five novel polymorphisms in the gene for the human glucocorticoid receptor, which may be useful in analyzing whether loss of (part of) the glucocorticoid receptor gene plays a role in glucocorticoid-resistant malignancies. Although relative resistance to glucocorticoids seems to be rather frequent in otherwise healthy persons, it is not usually associated with mutations or polymorphisms in the glucocorticoid receptor gene.

Aged↗
PubMed1997

Comparison of ultrasonic and histopathological features of carotid artery stenosis.

Besides the degree of carotid artery stenosis, the composition of the plaque may help to predict the thromboembolic risk. Low echogenicity on ultrasound and hemorrhage into the atheroma demonstrated histopathologically have been shown to be associated with a higher risk of embolism. Twenty-nine consecutive patients with carotid artery stenosis and scheduled for carotid endarterectomy were investigated preoperatively by B-mode ultrasound. Post-operatively the endarterectomy specimens were examined histopathologically. Neither atheroma with hemorrhage nor atheroma without hemorrhage were significantly associated with echolucent ultrasound presentation. Out of the 10 lesions echolucent and homogeneous on ultrasound, six corresponded to atheroma with hemorrhage, two corresponded to atheroma with hemorrhage plus thrombus, two corresponded to fibrous plaque plus thrombus, and one corresponded to pure thrombus. Out of the 4 lesions heterogeneous and predominantly echolucent, one corresponded to atheroma without hemorrhage plus thrombus, one corresponded to atheroma with hemorrhage, one corresponded to atheroma with hemorrhage plus thrombus, one corresponded to atheroma with hemorrhage plus fibrous plaque. Seven out of the 18 atheromas with hemorrhage did not present as purely or predominantly echolucent lesions, six of them were even homogeneously echogenic. Plaque surface could not reliably be predicted by ultrasound. In our study, there was no significant correlation between ultrasound and histology of the lesion.

Aged↗
PubMed1997

Differential hormone-dependent transcriptional activation and -repression by naturally occurring human glucocorticoid receptor variants.

The molecular mechanisms underlying primary glucocorticoid resistance or hypersensitivity are not well understood. Using transfected COS-1 cells as a model system, we studied gene regulation by naturally occurring mutants of the glucocorticoid receptor (GR) with single-point mutations in the regions encoding the ligand-binding domain or the N-terminal domain reflecting different phenotypic expression. We analyzed the capacity of these GR variants to regulate transcription from different promoters, either by binding directly to positive or negative glucocorticoid-response elements on the DNA or by interfering with protein-protein interactions. Decreased dexamethasone (DEX) binding to GR variants carrying mutations in the ligand-binding domain correlated well with decreased capacity to activate transcription from the mouse mammary tumor virus (MMTV) promoter. One variant, D641V, which suboptimally activated MMTV promoter-mediated transcription, repressed a PRL promoter element containing a negative glucocorticoid-response element with wild type activity. DEX-induced repression of transcription from elements of the intercellular adhesion molecule-1 promoter via nuclear factor-kappaB by the D641V variant was even more efficient compared with the wild type GR. We observed a general DEX-responsive AP-1-mediated transcriptional repression of the collagenase-1 promoter, even when receptor variants did not activate transcription from the MMTV promoter. Our findings indicate that different point mutations in the GR can affect separate pathways of gene regulation in a differential fashion, which can explain the various phenotypes observed.

Animals↗
PubMed1996

The PC12 rat pheochromocytoma cell line expresses the prodynorphin gene and secretes the 8 kDa dynorphin product.

Most adrenal chromaffin cells synthesize opioids derived from proenkephalin but not from prodynorphin. However, human pheochromocytomas and the PC12 rat pheochromocytoma cell line synthesize dynorphins. The aim of this study was to confirm the presence of the authentic prodynorphin transcript and its dynorphin product in PC12 cells. We have found that the sequence of a 458 bp cDNA fragment derived from RT-PCR amplification of total PC12 RNA was in complete accordance with the published sequence of the equivalent region of the prodynorphin gene. It encodes the potent endogenous kappa opioid agonists alpha-neo-endorphin, dynorphin A and dynorphin B. Furthermore, immunoaffinity-purified PC12 cell extracts were subjected to RP-HPLC. Most of its IR-dynorphin eluted on a peak exhibiting the retention time of similarly treated rat anterior pituitary. The expression of the prodynorphin gene in pheochromocytomas can be explained as either the result of (a) the process of dedifferentiation of chromaffin cells to pheochromocytoma which may thus cause the expression of a previously unexpressed prodynorphin or that (b) those pheochromocytomas expressing the prodynorphin gene derive from the few, centrally located chromaffin cells, which express this gene even under normal conditions.

Adrenal Medulla↗
PubMed1996

Carney complex, a familial multiple neoplasia and lentiginosis syndrome. Analysis of 11 kindreds and linkage to the short arm of chromosome 2.

Carney complex is an autosomal dominant syndrome characterized by multiple neoplasias, including myxomas at various sites and endocrine tumors, and lentiginosis. The genetic defect(s) responsible for the complex remain(s) unknown. We studied 101 subjects, including 51 affected members, from 11 North American kindreds with Carney complex. Blood samples were collected from patients and their family members. Hospital records, photographs, and tissue specimens of deceased individuals were reviewed. DNA was extracted from blood samples, patient-derived cell lines, and/or paraffin-embedded tissues. Linkage analysis was performed with highly polymorphic microsatellite markers, distributed over areas of the human genome harboring the most likely candidate genes. The most prevalent clinical manifestation in patients with Carney complex was spotty skin pigmentation, similar to that observed in Peutz-Jeghers and other lentiginosis syndromes. Skin and cardiac myxomas, Cushing syndrome, and acromegaly were present in 62, 30, 31 and 8 percent of the patients, respectively. Linkage was obtained for three markers on the short arm of chromosome 2 (2p16), with a maximum two-point lod score of 5.97 at theta = 0.03 for the marker CA-2 (odds in favor of linkage 10(6):1. The flanking markers CA7 and D2S378 defined a region of approximately 6.4 cM that is likely to contain the gene(s) associated with Carney complex. Candidate genes in the proximity, including the propiomelanocortin and the DNA-mismatch repair hMSH2 genes, were excluded. We conclude that the genetic defect(s) responsible for Carney complex map(s) to the short arm of chromosome 2 (2p16). This region has exhibited cytogenetic aberrations in atrial myxomas associated with the complex, and has been characterized by microsatellite instability in human neoplasias.

Canada↗
PubMed1996

Nelson's syndrome associated with a somatic frame shift mutation in the glucocorticoid receptor gene.

Nelson's syndrome is the appearance and/or progression of ACTH-secreting pituitary macroadenomas in patients who had previously undergone bilateral adrenalectomy for Cushing's disease. Extremely high plasma ACTH levels and aggressive neoplastic growth might be explained by the lack of appropriate glucocorticoid negative feedback due to defective glucocorticoid signal transduction. To study the glucocorticoid receptor (GR) gene in Nelson's syndrome, DNA was extracted from pituitary adenomas and leukocytes of four patients with this condition and amplified by PCR for direct sequence analysis. In one of the tumors, a heterozygous mutation, consisting of an insertion of a thymine between complementary DNA nucleotides 1188 and 1189, was found in exon 2. This frame-shift mutation led to premature termination at amino acid residue 366 of the wild-type coding sequence, excluding the expression of a functioning receptor protein from the defective allele. The mutation was not detected in the sequence of the GR gene in the patient's leukocyte DNA, indicating a somatic origin. By lowering the receptor number in tumorous cells, this defect might have caused local resistance to negative glucocorticoid feedback similar to that caused by the presence of a null allele in a kindred with the generalized glucocorticoid resistance syndrome. P53 protein accumulation, previously reported in 60% of corticotropinomas, could not be detected in any of the four pituitary tumors examined by immunohistochemistry. We suggest that a somatic GR defect might have played a pathophysiological role in the tumorigenesis of the corticotropinoma bearing this mutation.

Adrenocorticotropic Hormone↗
PubMed1996

Cushing's disease preceded by generalized glucocorticoid resistance: clinical consequences of a novel, dominant-negative glucocorticoid receptor mutation.

Generalized glucocorticoid resistance is associated with chronic hyperactivation of the hypothalamic-pituitary-adrenal axis, compensating for impaired glucocorticoid receptor function. We report a unique patient with sporadic generalized glucocorticoid resistance who, at age 33, presented with infertility and hypertension and, at 38, developed pituitary Cushing's disease. Leukocyte-binding studies revealed normal affinity of the glucocorticoid receptor but a reduction of binding sites by 50%. [3H]thymidine incorporation by this patient's lymphocytes was not suppressible by dexamethasone. He had a novel heterozygous missense mutation in the glucocorticoid receptor gene (isoleucine 559 to asparagine 559). The mutant receptor exhibited a strong dominant-negative effect on the ability of the wild-type receptor to induce gene transcription in vitro. The mutation was present in all of the patient's cultured lymphoblasts and fibroblasts as well as in 50% of his sperm, as demonstrated by single-cell polymerase chain reaction; it was not present in his parents and seven siblings. This novel mutation was thus both de novo and present in the germ line. Immunohistochemical staining of this patient's pituitary corticotropinoma revealed accumulation of p53 protein, indicating the presence of a putative somatic oncogenic mutation in the p53 gene in the tumor cells. Investigation of the lymphoblast and skin fibroblast cultures for p53 abnormalities did not show any aberration. Thus, a novel de novo germ line mutation of the glucocorticoid receptor with strong dominant-negative activity caused severe sporadic generalized glucocorticoid resistance, which preceded corticotroph adenoma formation. The latter probably was due to the combined effects of chronic corticotroph hyperstimulation, decreased glucocorticoid negative feedback, and at least one subsequent somatic defect in the control of the cell cycle.

Adult↗
PubMed1996

The non-ligand binding beta-isoform of the human glucocorticoid receptor (hGR beta): tissue levels, mechanism of action, and potential physiologic role.

BACKGROUND: Alternative splicing of the transcripts of the human glucocorticoid receptor gene results in two mutually exclusive products, the classic, ligand-binding glucocorticoid receptor (hGR alpha), and a dominant negative non-ligand-binding isoform, hGR beta. MATERIALS AND METHODS: We examined the existence of and quantified both hGR alpha and hGR beta isoforms in a panel of human tissues, as well as in intact and fractionated HeLa cells, using specific quantitative Western blots and/or immunocytochemistry. We studied the potential interactions of hGR beta with heat shock protein (hsp) 90 and/or hGR alpha using cross-immunoadsorption/precipitation procedures followed by Western blots. RESULTS: For the first time, we demonstrated the natural existence of the hGR beta protein, which was widely expressed in human tissues. The ratio of immunoreactive hGR alpha to hGR beta varied from 0.2 to 1.0 among different tissues, and was approximately 0.2 in HeLa cells. In the latter, both isoforms were distributed in the cytoplasm and nucleus in the absence of the hormonal ligand, and translocated into the nucleus after addition of dexamethasone. The cytosolic and nuclear hGR alpha-to-hGR beta ratio remained the same before and after dexamethasone exposure, suggesting that upon activation the two isoforms translocated into the nucleus in equal proportions. hGR alpha- and hGR beta-specific antibodies cross-adsorbed and precipitated cytosolic and nuclear glucocorticoid hGR alpha and hGR beta, respectively, as well as hsp90, suggesting that hGR alpha and hGR beta are in complex with hsp90 and/or each other. CONCLUSIONS: The hGR beta protein is widely expressed throughout the human body and present mostly in the cytoplasm of human cells, in complex with hsp90 and other proteins. In the presence of glucocorticoid, hGR beta probably heterodimerizes with ligand-bound hGR alpha and translocates into the nucleus to act as a dominant negative inhibitor of the classic receptor.

Alternative Splicing↗