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Biomedical subjects

N Muller

Publications and source records attributed to N Muller.

At least 19 recordsLinked to original sources
PubMed2006

Soft tissue tumours and mass-like lesions of the chest wall: a pictorial review of CT and MR findings.

Soft tissue tumours and tumour-like lesions of the chest wall are uncommon. The purpose of this pictorial essay is to describe the imaging findings of chest wall soft tissue tumours and tumour-like lesions. We searched the radiological and pathological archive at our institution retrospectively and reviewed the literature on soft tissue tumours of the chest wall. Common chest wall soft tissue tumours and mass-like lesions include peripheral nerve tumours, lipomas, liposarcomas, haemangiomas, elastofibromas, metastases, lymphoma and abscesses. Other lesions encountered include desmoid tumours and malignant fibrous histiocytoma. Many have distinctive radiological findings or occur in specific locations, allowing a specific radiological diagnosis to be suggested.

Adult↗
PubMed2006

Schizophrenia as an inflammation-mediated dysbalance of glutamatergic neurotransmission.

This overview tries to bridge the gap between psychoneuroimmunological findings and recent results from pharmacological, neurochemical and genetic studies in schizophrenia. Schizophrenia is a disorder of dopaminergic neurotransmission, but modulation of the dopaminergic system by glutamatergic neurotransmission seems to play a key role. This view is supported by genetic findings of the neuregulin- and dysbindin genes, which have functional impact on the glutamatergic system. Glutamatergic hypofunction, however, is mediated by the N-methyl-D-aspartate (NMDA)-receptor antagonism. The only endogenous NMDA receptor antagonist identified up to now is kynurenic acid (KYNA). Despite the NMDA receptor antagonism, KYNA also blocks, in lower doses, the nicotinergic acetycholine receptor, i.e., increased KYNA levels can explain psychotic symptoms and cognitive deterioration. KYNA levels are described to be higher in the cerebrospinal fluid (CSF) and in critical central nervous system (CNS) regions of schizophrenics as compared to controls. Another line of evidence suggests that a (prenatal) infection is involved in the pathogenesis of schizophrenia. Due to an early sensitization process of the immune system or to a (chronic) infection, which is not cleared through the immune response, an immune imbalance between the type-1 and the type-2 immune responses takes place in schizophrenia. The type-1 response is partially inhibited, while the type-2 response is over-activated. This immune constellation is associated with inhibition of the enzyme indoleamine dioxygenase (IDO), because IDO - located in astrocytes and microglial cells - is inhibited by type-2 cytokines. IDO catalyzes the first step in tryptophan metabolism, the degradation from tryptophan to kynurenine, as does tryptophan 2,3-dioxygenase (TDO). Due to the inhibition of IDO, tryptophan-kynurenine is predominantly metabolized by TDO, which is located in astrocytes, not in microglial or other CNS cells. In schizophrenia, astrocytes in particular are activated, as increased levels of S100B appear. Additionally, they do not have the enzymatic equipment for the normal metabolism-route of tryptophan. Due to the lack of kynurenine hydroxylase (KYN-OHase) in astrocytes, KYNA accumulates in the CNS, while the metabolic pathway in microglial cells is blocked. Accordingly, an increase of TDO activity has been observed in critical CNS regions of schizophrenics. These mechanisms result in an accumulation of KYNA in critical CNS regions. Thus, the immune-mediated glutamatergic-dopaminergic dysregulation may lead to the clinical symptoms of schizophrenia. Therapeutic consequences, e.g., the use of anti-inflammatory cyclo-oxygenase-2 inhibitors, which can also decrease KYNA directly, are discussed.

Animals↗
PubMed2005

Induction of UGT1A6 isoform by inflammatory conditions in rat astrocytes.

Alteration of drug metabolism under diseased conditions is of clinical importance. We have investigated the effects of inflammatory conditions on phase II drug-metabolizing enzyme activity in rat cultured astrocytes. Lipopolysaccharide (LPS) treatment was used to promote inflammatory conditions. Thus, we reported that LPS initiates an inflammatory response, which is mediated by pro-inflammatory mediators and free radical generation. An increase in astrocyte glucuronidation activity was observed after a 48-h LPS treatment. This increase in glucuronidation activity was associated with an up-regulation of the UGT1A6 isoform mRNA level as shown by RT-PCR and gene reporter assay. Moreover, this endotoxin-induced increase in UGT1A6 expression level was blocked by actinomycin D and cycloheximide, indicating the requirement for RNA and protein synthesis. The UGT1A6 expression enhancement could be prevented by anti-inflammatory drugs (dexamethasone and NS398) or nitric oxide synthase inhibitors (L-NAME and L-NMMA). Moreover, gel shift assay revealed increased activator protein-1 (AP-1) binding activity after LPS treatment. We propose, based on the data presented, that the action of LPS to induce UGT1A6 isoform up-regulation may be mediated by pro-inflammatory mediator accumulation, and AP-1 binding activity increase.

Animals↗
PubMed2004

Psychological and/or educational interventions for the prevention of depression in children and adolescents.

BACKGROUND: Depression is the fourth most important disease in the estimation of the burden of disease Murray 1996 and is a common problem with prevalence rates estimated to be as high as 8% in young people. Depression in young people is associated with poor academic performance, social dysfunction, substance abuse, suicide attempts, and completed suicide (NHMRC 1997). This has precipitated the development of programmes aimed at preventing the onset of depression. This review evaluates evidence for the effectiveness of these prevention programmes. OBJECTIVES: To determine whether psychological and/or educational interventions (both universal and targeted) are effective in reducing risk of depressive disorder by reducing depressive symptoms immediately after intervention or by preventing the onset of depressive disorder in children and adolescents over the next one to three years. SEARCH STRATEGY: The Cochrane Depression, Anxiety and Neurosis Group trials register (August 2002), MEDLINE (1966 to December Week 3 2002), EMBASE (1980 to January Week 2 2003), PsychInfo (1886 to January Week 2 2003) and ERIC (1985 to December 2002) were searched. In addition, conference abstracts, the reference lists of included studies, and other reviews were searched and experts in the field were contacted. SELECTION CRITERIA: Each identified study was assessed for possible inclusion by two independent reviewers based on the methods sections. The determinants for inclusion were that the trial include a psychological and/or educational prevention programme for young people aged 5 to 19 years-old, who did not meet DSM or ICD criteria for depression and/or did not fall into the clinical range on standardised, validated, and reliable rating scales of depression. DATA COLLECTION AND ANALYSIS: The methodological quality of the included trials was assessed by two independent reviewers according to a list of pre-determined criteria, which were based on quality ratings devised by Moncrieff and colleagues (Moncrieff 2001). Outcome data was extracted and entered into Revman 4.2. Means and standard deviations for continuous outcomes and number of events for dichotomous outcomes were extracted where available. For trials where the required data were not reported or could not be calculated, further details were requested from first authors. If no further details were provided, the trial was included in the review and described, but not included in the meta-analysis. Results were presented for each type of intervention: targeted or universal interventions; and educational or psychological interventions and if data were provided, by gender. Where possible data were combined in meta-analyses to give a treatment effect across all trials. Sensitivity analysis were conducted on studies rated as "adequate" or "high" quality, that is with a score over 22, based on the scale by Moncrieff et al (Moncrieff 2001). The presence of publication bias was assessed using funnel plots. MAIN RESULTS: Studies were divided into those that compared intervention with an active comparison or placebo (i.e. a control condition that resembles the intervention being investigated but which lacks the elements thought to be active in preventing depression) and those that used a "wait-list" or no intervention comparison group. Only two studies fell into the former category and neither showed effectiveness although one study was inadequately powered to show a difference and in the other the "placebo" contained active therapeutic elements, reducing the ability to demonstrate a difference from intervention. Psychological interventions were effective compared with non-intervention immediately after the programmes were delivered with a significant reduction in scores on depression rating scales for targeted (standardised mean difference (SMD) of -0.26 and a 95% confidence interval (CI) of -0.40 to -0.13 ) but not universal interventions (SMD -0.21, 95% CI -0.48, 0.06), with a significant effect maintained on pooling data (SMD -0.26, 95% CI -0.36, -0.15). While small effect sizes were reported, these were associated with a significant reduction in depressive episodes. The overall risk difference after intervention translates to "numbers needed to treat" (NNT) of 10. The most effective study is the targeted programme by Clarke (Clarke 2001) where the initial effect size of -0.46 is associated with an initial risk difference of -0.22 and NNT 5. There was no evidence of effectiveness for educational interventions. Reports of effectiveness for boys and girls were contradictory. The quality of many studies was poor, and only two studies made allocation concealment explicit. Sensitivity analysis of only high quality studies did not alter the results significantly. The only analysis in which there was significant statistical heterogeneity was the sub-group analysis by gender where there was variability in the response to different programmes for both girls and boys. For the most part funnel plots indicate findings are robust for short term effects with no publication bias evident. There are too few studies to comment on whether there is publication bias for studies reporting long-term (12-36 month) follow-up. REVIEWER'S CONCLUSIONS: Although there is insufficient evidence to warrant the introduction of depression prevention programmes currently, results to date indicate that further study would be worthwhile. There is a need to compare interventions with a placebo or some sort of active comparison so that study participants do not know whether they are in the intervention group or not, to investigate the impact of booster sessions to see if effectiveness immediately after intervention can be prolonged, ideally for a year or longer, and to consider practical implementation of prevention programmes when choosing target populations. Until now most studies have focussed on psychological interventions. The potential effectiveness of educational interventions has not been fully investigated. Given the gender differences in prevalence, and the change in these that occurs in adolescence with a disproportionate increase in prevalence rates for girls, it is likely that girls and boys will respond differently to interventions. Although differences have been reported in studies in this review the findings are contradictory and a more definitive delineation of gender specific responses to interventions would be helpful.

Adolescent↗
PubMed2001

Urinary health in eldercare environments: an update from the NAFC.

The National Association For Continence elected to cancel its 2001 conference scheduled for October 2001 in Washington, DC in light of national events. Executive Director Nancy Muller has provided Ostomy/Wound Management with a synopsis of key issues, important considerations, and the syllabus. We are grateful for the opportunity to serve as a forum for this worthy organization.

Aged↗
PubMed2000

Infant and adolescent hepatitis B immunization up to 1999: a global overview.

This article presents a global overview of hepatitis B infant and adolescent immunization programmes. The 108 reported universal infant or adolescent immunization programmes and 87 reported national infant coverage rates fit a pattern, explained by hepatitis B endemicity, prosperity, policy emphasis, and immunization programme strength. Most East and Southeast Asian, Pacific, and Middle Eastern countries have intermediate to highly endemic hepatitis B. Most have achieved 65-100% coverage. South and Central Asia and sub-Saharan Africa have intermediate to high endemicity, with some countries having hepatitis B immunization programmes. Some Southern and Eastern European countries, with intermediate endemicity, have high coverage. Low endemic Northern European countries vaccinate higher risk groups; some have universal infant or adolescent programmes. Caribbean and Latin American countries have varying endemicity, and most started programmes. Low endemic North American countries have universal vaccination programmes. Universal immunization strategies have greatly reduced incidence and prevalence, and are cost-effective for many countries, but many have difficulties affording this vaccine. Globally, most infants are not being immunized against hepatitis B virus infection. Increasing coverage, and decreasing the numbers of people diseased and dying from this virus, may require delivering heat-stable vaccine beyond cold chains, creative financing to reduce prices, and multivalent vaccines.

Adolescent↗
PubMed2000

Topoisomerase I-mediated antiproliferative activity of enantiomerically pure fluorinated homocamptothecins.

Homocamptothecin (hCPT) is an E-ring modified camptothecin (CPT) analogue bearing a methylene spacer between the alcohol and carboxyl functions of the CPT lactone. Combining pronounced inhibitory activity of topoisomerase I (Topo I) with enhanced plasma stability, hCPT constitutes an attractive template for the elaboration of new anticancer agents. Fluorinated hCPT analogues, prepared in enantiomerically pure form, were assayed by their stimulation of Topo I-mediated DNA cleavage. Translation into cytotoxicity against tumor cells was evaluated on HT29 human colon adenocarcinoma and on the multidrug resistant lung and bladder tumor cell lines, A549 and T24r. Good correlation is observed between the ability of the drugs to stimulate Topo I-mediated DNA cleavage and the respective 50% inhibitory concentrations (IC(50) values) of the HT29, A549, and T24r cell growth. Fluorine substitution in the A-ring of hCPT was found to have a pronounced influence on biological activity, providing several compounds which are up to 100-fold more potent than CPT in terms of IC(50). Among these, 10,11-difluoro-hCPT has been selected for further development.

Antineoplastic Agents↗
PubMed1999

Nephrotic syndrome in Namibian children.

BACKGROUND AND OBJECTIVES: Patterns of nephrotic syndrome vary between regions and countries, and influence approaches to management. In the mid-1970s the University of Stellenbosch became involved in providing tertiary care to Namibia, including a paediatric nephrology service. The aim of this study was to document the clinical, pathological and outcome features of nephrotic syndrome in Namibian children. SUBJECTS: Seventy black Namibian children with nephrotic syndrome were managed from 1975 to 1988. Sixty-eight renal specimens (67 biopsies and 1 autopsy specimen) were evaluated. RESULTS: Twenty-nine of the 70 children (41.4%) were hepatitis B virus (HBV) carriers, of whom 25 (86.2%) were male. Of the 29, 26 had predominantly membranous glomerulonephritis (MGN), 1 mesangiocapillary glomerulonephritis (MCGN), and 1 focal segmental glomerulosclerosis (FSGS); 1 child in advanced renal failure was not biopsied. Five children (7.4%) showed minimal change disease (MCD), 11 (16.2%) FSGS and 15 (22.1%) diffuse mesangial proliferative glomerulonephritis (DMP). The remaining 10 children showed diffuse glomerulosclerosis (6), MCGN (3) and endocapillary proliferative GN (1). Four of the 5 children with MCD went into remission on immunosuppressive treatment. Of the 15 with DMP, 4 improved spontaneously and only 1 of those treated did not improve. Only 2 of those with FSGS improved on treatment. The children with HBV-associated MGN and MCGN were offered symptomatic rather than specific treatment. Thirteen children presented with degrees of chronic renal failure. Eight are known to have died, 3 of relentless nephrotic syndrome and 4 (of whom 3 were HBV carriers) of end-stage renal failure. One child died of penicillin anaphylaxis. CONCLUSIONS: The pattern of nephrotic syndrome in black Namibian children differed greatly from the non-African pattern elsewhere in that MCD was uncommon and HBV-associated GN was the most common single group. The most frequent pattern of HBV-associated GN was MGN with some mesangiocapillary features showing marked male predominance. MCD and DMP were potentially treatable and could only be identified by biopsy. HBV carrier rates exert a major influence on the proportions of morphological subgroups of nephrotic syndrome in children. As these HBV carrier rates alter in future due to the influence of vaccination and urbanisation, the relative size of nephrotic subgroups seems likely to alter.

Adolescent↗
PubMed1998

Efficient simulation of coherence transfer pathway selection by phase cycling and pulsed field gradients in NMR

The selection of well-defined coherence transfer pathways is an essential feature of all but the simplest NMR and EPR pulse sequences. This selection can be achieved by phase cycling and by pulsed field gradients. The properties of the RF-pulses (flip angle, offset effects, inhomogeneity) and transport phenomena (diffusion, flow) in conjunction with gradients cause a weighting of the different coherence transfer pathways. We present a method by which the selection process can be simulated efficiently and visualized easily. In its basic form it involves straightforward matrix manipulations without reference to the density matrix and the particular spin system. This method is implemented in a MATLAB program, called CCCP (Complete Calculation of Coherence Pathways). Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

The glycyl radical enzyme TdcE can replace pyruvate formate-lyase in glucose fermentation.

Mutants of Escherichia coli unable to synthesize a functional pyruvate formate-lyase (PFL) are severely impaired in their capacity to grow by glucose fermentation. In a functional complementation assay designed to isolate the pfl gene from Clostridium butyricum, we fortuitously identified a gene that did not encode a PFL but nonetheless was able to complement the phenotypic defects caused by an E. coli pfl mutation. The clostridial gene encoded a basic 14. 5-kDa protein (TcbC) which, based on amino acid similarity and analysis of immediately adjacent DNA sequences, was part of a transposase exhibiting extensive similarity to the product of the site-specific transposon Tn554 from Staphylococcus aureus. Our studies revealed that the clostridial TcbC protein activated the transcription of the E. coli tdcABCDEFG operon, which encodes an anaerobic L-threonine-degradative pathway. Normally, anaerobic synthesis of the pathway is optimal when E. coli grows in the absence of catabolite-repressing sugars and in the presence of L-threonine. Although anaerobic control of pathway synthesis was maintained, TcbC alleviated glucose repression. One of the products encoded by the tdc operon, TdcE, has recently been shown to be a 2-keto acid formate-lyase (C. Hesslinger, S. A. Fairhurst, and G. Sawers, Mol. Microbiol. 27:477-492, 1998) that can accept pyruvate as an enzyme substrate. Here we show that TdcE is directly responsible for the restoration of fermentative growth to pfl mutants.

Acetyltransferases↗
PubMed1997

Internal rotation of mutually interacting methyl groups: A 13C NMR study

The overall and intramolecular rotational diffusion behavior of 1,3, 7,10-tetramethylbenzo[c]cinnoline was determined from longitudinal 13C NMR relaxation and 1H-13C NOE measurements in dilute chloroform solution. The four methyl groups in this compound represent three different situations of sterical hindrance. One pair of methyl groups is in close mutual sterical contact, forming the ends of an open six-membered ring. Assuming completely anisotropic overall molecular tumbling combined with a 120 degrees jump model for the internal methyl rotations the jump rates of methyl groups were evaluated and compared to earlier results on different sterically hindered compounds, in particular with respect to a potential cogwheel-like intermethyl interaction. To characterize intermethyl interactions in different sterical situations, a new gauge-the "methyl interaction volume"-is introduced. Implications for correlated rotational diffusion of methyl groups are discussed. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Giardia lamblia infections in B-cell-deficient transgenic mice.

In the present study, we infected B-cell (and antibody-)-deficient transgenic mice with the Giardia lamblia clone GS/M-83-H7. These animals were inhibited in intestinal anti-Giardia immunoglobulin A (IgA) production and could not resolve the parasite infection, and antigenic diversification within the respective parasite populations occurred in an unusually slow manner. These findings indicate an important immunological function of local IgA antibodies which promotes antigenic variation of the parasite and is involved in control of the parasite infection.

Animals↗
PubMed1996

Pregnancy in partially remitted hepatitis B-associated membranous glomerulonephritis.

Hepatitis B-associated glomerulonephritis is a relatively common cause of nephrotic syndrome in endemic areas affecting especially male children. When this disease affects girls or women, both the glomerular disease and the hepatitis B carrier state could affect subsequent pregnancies. This may be the first reported case of such a pregnancy. In this patient the partially remitted renal disease and the reduced infectivity of the hepatitis B carrier state decreased the influence of the disease on the pregnancy.

Carrier State↗