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Biomedical subjects

C Fischer

Publications and source records attributed to C Fischer.

At least 109 records · Page 6Linked to original sources

Miltefosine, an oral agent, for the treatment of Indian visceral leishmaniasis.

BACKGROUND: There is no effective orally administered medication for any leishmania infection. We investigated miltefosine, which can be taken orally, for the treatment of Indian visceral leishmaniasis. Miltefosine is a phosphocholine analogue that affects cell-signaling pathways and membrane synthesis. METHODS: The study was an open-label, multicenter, phase 2 trial in which four 30-person cohorts received 50, 100, or 150 mg of miltefosine per day for four or six weeks. The 120 patients, who ranged in age from 12 to 50 years, had anorexia, fever, and splenomegaly with at least moderate (2+) leishmania in a splenic aspirate. A parasitologic cure was defined by the absence of parasites in a splenic aspirate obtained two weeks after completion of treatment. The clinical response was assessed at six months. RESULTS: In all 120 patients there was an initial parasitologic cure. Six patients had clinical and parasitologic relapses; the remaining 114 patients had not relapsed by six months after treatment, for a cure rate of 95 percent (95 percent confidence interval, 89 to 98 percent). With the regimen of 100 mg of miltefosine per day (approximately 2.5 mg per kilogram of body weight per day) for four weeks, 29 of 30 patients (97 percent) were cured. Gastrointestinal side effects were frequent (occurring in 62 percent of patients) but mild to moderate in severity, and no patient discontinued therapy because of gastrointestinal side effects. In two patients, treatment was discontinued because of elevated levels of aspartate aminotransferase or creatinine; in both patients the levels rapidly returned to normal. In 12 other patients, the level of aspartate aminotransferase increased to 100 to 150 U per liter during treatment. CONCLUSIONS: Orally administered miltefosine appears to be an effective treatment for Indian visceral leishmaniasis.

Administration, Oral↗

Differential effects of lipopolysaccharide and tumor necrosis factor on monocytic IkappaB kinase signalsome activation and IkappaB proteolysis.

The inflammatory mediators lipopolysaccharide (LPS) and tumor necrosis factor (TNF) are potent activators of NF-kappaB. This study compared the effect of these stimuli on endogenous IkappaB kinase (IKK) signalsome activation and IkappaB phosphorylation/proteolysis in human monocytic cells and investigated the role of the signalsome proteins IKK-alpha, IKK-beta, NF-kappaB-inducing kinase (NIK), IKK-gamma (NF-kappaB essential modulator), and IKK complex-associated protein. Kinase assays showed that TNF elicited a rapid but short-lived induction of IKK activity with a 3-fold greater effect on IKK-alpha than on IKK-beta, peaking at 5 min. In contrast, LPS predominantly stimulated IKK-beta activity, which slowly increased, peaking at 30 min. A second peak was observed at a later time point following LPS stimulation, which consisted of both IKK-alpha and -beta activity. The endogenous levels of the signalsome components were unaffected by stimulation. Furthermore, our studies showed association of the IKK-alpha/beta heterodimer with NIK, IkappaB-alpha and -epsilon in unstimulated cells. Exposure to LPS or TNF led to differential patterns of IkappaB-alpha and IkappaB-epsilon disappearance from and reassembly with the signalsome, whereas IKK-alpha, IKK-beta, and NIK remained complex-associated. NIK cannot phosphorylate IkappaB-alpha directly, but it appears to be a functionally important subunit, because mutated NIK inhibited stimulus-induced kappaB-dependent transcription more effectively than mutated IKK-alpha or -beta. Overexpression of IKK complex-associated protein inhibited stimulus-mediated transcription, whereas NF-kappaB essential modulator enhanced it. The understanding of LPS- and TNF-induced signaling may allow the development of specific strategies to treat sepsis-associated disease.

Enzyme Activation↗

Multiple NF-ATc isoforms with individual transcriptional properties are synthesized in T lymphocytes.

The transcription factor NF-ATc that controls gene expression in T lymphocytes and embryonic cardiac cells is expressed in three prominent isoforms. This is due to alternative splice/polyadenylation events that lead to the predominant synthesis of two long isoforms in naive T cells and a shorter NF-ATc isoform in effector T cells. Whereas the previously described isoform NF-ATc/A contains a relatively short C terminus, the longer isoforms, B and C, span extra C-terminal peptides of 128 and 246 aa, respectively. We show here that in addition to the strong N-terminal trans-activation domain, TAD-A, which is common to all three NF-ATc isoforms, NF-ATc/C contains a second trans-activation domain, TAD-B, in its C-terminal peptide. Various stimuli of T cells that induce the activity of TAD-A also enhance the activity of TAD-B, but, unlike TAD-A, TAD-B remains unphosphorylated by protein from 12-O-tetradecanoyl 12-phorbol 13-acetate-stimulated T cells. The shorter C-terminal peptide of isoform NF-ATc/B exerts a suppressive transcriptional effect. These properties of NF-ATc/B and -C might be of importance for gene regulation in naive T lymphocytes in which NF-ATc/B and -C are predominantly synthesized.

Amino Acid Sequence↗

4-Hydroxynonenal prevents NF-kappaB activation and tumor necrosis factor expression by inhibiting IkappaB phosphorylation and subsequent proteolysis.

Extensively oxidized low density lipoprotein (ox-LDL), a modulator of atherogenesis, down-regulates the lipopolysaccharide (LPS)-induced activation of transcription factor NF-kappaB. We investigated whether 4-hydroxynonenal (HNE), a prominent aldehyde component of ox-LDL, represents one of the inhibitory substances. NF-kappaB activation by stimuli such as LPS, interleukin (IL)-1beta, and phorbol ester, but not tumor necrosis factor (TNF), was reversibly inhibited by HNE in a dose-dependent manner in human monocytic cells, whereas AP-1 binding was unaffected. Using similar HNE concentrations, LPS-induced kappaB- and TNF or IL-8 promoter-dependent transcription was prevented. Furthermore, pretreatment with HNE suppressed TNF production but not lactate dehydrogenase levels. Under these conditions the binding of LPS to monocytic cells was not significantly affected. However, induced proteolysis of the inhibitory proteins IkappaB-alpha, IkappaB-beta, and, at a later time point, IkappaB-epsilon was prevented. This is not due to inhibition of the proteasome, the major proteolytic activities of which remain unaffected, but rather to a specific prevention of the activation-dependent phosphorylation of IkappaB-alpha. This is the first report which demonstrates that HNE specifically inhibits the NF-kappaB/Rel system. Down-modulation of NF-kappaB-regulated gene expression may contribute at certain stages of atherosclerosis to low levels of chronic inflammation and may also be involved in other inflammatory/degenerative diseases.

Aldehydes↗

Ethylnitrosourea-induced development of malignant schwannomas in the rat: two distinct loci on chromosome of 10 involved in tumor susceptibility and oncogenesis.

Inbred rodent strains with differing sensitivity to experimental tumor induction provide model systems for the detection of genes that either are responsible for cancer predisposition or modify the process of carcinogenesis. Rats of the inbred BD strains differ in their susceptibility to the induction of neural tumors by N-ethyl-N-nitrosourea (EtNU). Newborn BDIX rats that are exposed to EtNU (80 microg/g body weight; injected s.c.) develop malignant schwannomas predominantly of the trigeminal nerves with an incidence >85%, whereas BDIV rats are entirely resistant. A T:A-->A:T transversion mutation at nucleotide 2012 of the neu (erbB-2) gene on chromosome 10, presumably the initial event in EtNU-induced schwannoma development, is later followed by loss of the wild-type neu allele. Genetic crosses between BDIX and BDIV rats served: (a) to investigate the inheritance of susceptibility; (b) to obtain animals informative for the mapping of losses of heterozygosity (LOH) in tumors with polymorphic simple sequence length polymorphisms (SSLPs); and (c) to localize genes associated with schwannoma susceptibility by linkage analysis with SSLPs. Schwannoma development was strongly suppressed in F1 animals (20% incidence). All of the F1 schwannomas displayed LOH on chromosome 10, with a consensus region on the telomeric tip encompassing D10Rat3, D10Mgh16 and D10Rat2 but excluding neu. A strong bias toward losing the BDIV alleles suggests the involvement of a BDIV-specific tumor suppressor gene(s). Targeted linkage analysis with chromosome 10 SSLPs in F2 intercross and backcross animals localized schwannoma susceptibility to a region around D10Wox23, 30 cM centromeric to the tip. Ninety-four % of F1 tumors exhibited additional LOH at this region. Two distinct loci on chromosome 10 may thus be connected with susceptibility to the induction and development of schwannomas in rats exposed to EtNU.

Animals↗

[Linkage studies of a familial spastic paraplegia pedigree from Tibet].

OBJECTIVE: To study the location of disease-related gene in a hereditary spastic paraplegia family with autosomal dominant inheritance in Tibet. METHODS: The AD-HSP family in Tibet was analyzed by linkage studies using 9 highly polymorphic microsatellite DNA markers at three chromosomal regions. RESULTS: The maxium Lod- Score of D14S264 was 0.5163(theta=0.05); of D14S75, 2. 1072 (theta=0);+D14S69, 0.2840 (theta=0.10); of D14S266, 0.9311 (theta=0);of D14S66, 0.7991(theta=0);OF GABRB3, 0(theta =0.40);of D15S128, 0(theta=0.40); of D2S2255, 0 (theta=0.40);and of D2S2347,0(theta=0.40). CONCLUSION: In this Tibetian family, the disease-related gene is linked to D14S75 locus of SPG3 region.

Female↗

A selective imaging of tinnitus.

We selectively imaged the neural correlates of tinnitus, by contrasting a condition with no phantom auditory sensation with a condition during which tinnitus is present, using a rare form of tinnitus elicited by eye movements. Using positron emission tomography (PET), we demonstrate that phantom auditory sensation increases regional cerebral blood flow bilaterally in temporo-parietal association auditory areas but not in the primary auditory cortex. These results confirm that conscious perception does not necessarily require activation in primary areas and suggest that the perceptual qualities of tinnitus, e.g. intensity, frequency and spatial localization, are represented in temporo-parietal regions. Activation in these regions is compatible with cortical processing of ascending auditory messages generated at subcortical levels.

Adult↗

Synthesis of non proteinogenic dipeptides by asymmetric hydrogenation.

N-Boc protected non-proteinogenic dipeptides with D,L- and L,L-configuration were prepared by catalytic asymmetric hydrogenation of the corresponding dehydrophenylalanyl-(L)-phenylalanine derivatives. The configuration of the new stereogenic centre depends first of all on the catalyst configuration and is less influenced by the substrate configuration. Diastereomeric excesses in the range of 80-96% de could be increased up to 99% by recrystallization. Analytical data of selected new compounds are given.

Dipeptides↗

Asymmetric hydrogenation of dehydrodipeptide esters bearing different protective groups.

N-[(Z)-N-Benzoyl- or N-Boc-(2-fluorophenyl)dehydroalanyl]-(R)- or (S)-phenylalanine esters were synthesized and hydrogenated to give the corresponding dipeptide derivatives with optical yields in the range of 53-87% de using the cationic rhodium complexes of PROPRAPHOS and BPPM. The efficiency of chiral diphosphine ligands as well the effect of the chiral center in the substrate on the catalytic asymmetric induction was studied.

Amino Acids↗

Inhibition of thiopurine S-methyltransferase activity by impurities in commercially available substrates: a factor for differing results of TPMT measurements.

OBJECTIVES: Thiopurine S-methyltransferase (TPMT) activity, when measured in red blood cells (RBC) with a recently published TPMT activity assay using 6-thioguanine (6-TG) as substrate, could not be reproduced in another laboratory. We investigated factors which could influence the results of the TPMT activity measurement. METHODS: We tested twelve 6-TG and four 6-mercaptopurine (6-MP) compounds from different suppliers as substrates and determined the enzyme kinetic parameters Km and Vmax. Furthermore, we studied the influence of different 6-TG compounds on the affinity of the methyl donor S-adenosyl-L-methionine (SAM) to the TPMT enzyme. RESULTS: All 6-TG products were of equal purity (declared >98% by the supplier): this was ascertained by HPLC. However, the rate of methylation obtained following incubation with 6-TG from different suppliers ranged from 10% to 100% when incubated with the same RBC lysate. The lowest apparent Km value for a 6-TG was 22.3 micromol x l(-1), while the product with the highest methylation rate showed a Km of 156 micromol x l(-1). From these results we assume that there is a contaminant in some 6-TG products, which acts as a strong inhibitor of TPMT activity. Compounds possibly used for the synthesis of 6-TG (guanine, pyridine, 6-chloroguanine) did not affect the methylation rate. Thioxanthine, which is known to be a strong inhibitor of TPMT when added to the assay system to give a 2% contamination, reduced TPMT activity from 100% to 72%. Using 6-MP from different suppliers as substrate resulted in Km values ranging from 110 to 162 micromol x l(-1) and Vmox values ranging from 54 to 68 nmol 6-MMP x g(-1)Hb x h(-1). The Km value for the methyl donor SAM was similar to and independent from the thiopurine substrates tested (range 4.9-11 micromol-l(-1) SAM). In contrast to other investigators, we found non-enzymatic S-methylation, which was negligible under our assay conditions (3% with 128 micromol x l(-1) SAM), but could become relevant in experiments using higher SAM concentrations. CONCLUSIONS: TPMT enzyme activity determined with 6-TG as substrate may be strongly inhibited by a contaminant in some of the 6-TG lots distributed.

Enzyme Inhibitors↗

Ventral transdural herniation of the thoracic spinal cord: surgical treatment in four cases and review of literature.

BACKGROUND: A specific cause of progressive Brown-Sequard syndrome has been identified: a ventral herniation of the thoracic spinal cord through the dural sleeve on one side. METHOD: Four female patients who were affected by a progressive Brown Sequard syndrome related to a transdural spinal cord herniation have been investigated and were submitted to surgery and postoperative evaluation. FINDINGS: The MRI scan showed atrophy and forward displacement of the spinal cord on one side and adhesion of the spinal cord to the dura mater. CT myelography demonstrated the disappearance of the premedullar rim at the level of the herniation and the shadow of the extradural herniation. Surgical treatment consisted in the excision of the arachnoid cyst when there was one, section of the dentate ligament, release of the adhesions, detachment of the spinal cord from the hernial orifice, and lastly suture of the dural tear or placement by a patch. Follow-up examination showed motor improvement with persistent sensory deficit in two cases and stabilisation in two cases. INTERPRETATION: The cause of the dural tear, either traumatic or congenital could not be confirmed in the four cases. Symptoms probably occur when herniation fills the orifice and strangulation happens which explains the late appearance and progressive evolution of this myelopathy. Mobilisation of the herniated spinal cord back into the intradural space can be achieved by surgery and may stop the evolution of the symptoms and signs.

Adult↗

Nephron-sparing surgery for renal cell carcinoma--is tumor size a suitable parameter for indication?

OBJECTIVES: Because patients with small renal cell carcinomas (RCC) are being treated by nephron-sparing surgery with increased frequency, a generally accepted parameter giving additional information as to which kind of tumor is suitable for this treatment is urgently required. METHODS: In a retrospective analysis of 245 patients who underwent radical nephrectomy for RCC, we investigated whether tumor size could provide the necessary information. We analyzed the association of tumor size with pTNM classification, grade, and the findings of the flow cytometric analysis of the DNA content analyzing the DNA index (DI). RESULTS: Stage pT1 was found in 23 patients (9.4%), pT2 in 100 (40.8%), pT3 in 109 (44.5%), and pT4 in 13 patients (5.3%). Grade 1 was found in 87 patients (35.5%), grade 2 in 120 (49.0%), and grade 3 in 38 patients (15.5%). A low DI was found in 71%, a moderately increased DI in 20%, and a high DI in 9%. Lymph node metastases were detected in 14% and -distant metastases in 22%. Closer examination of the tumors less than 2.5 cm (n = 23) revealed a significantly lower incidence (P <0.001) of infiltration of the renal capsule (n = 0) than in the rest of the group. Positive lymph nodes or distant metastases could not be found in this subgroup. A multifocal appearance of RCC was detected in only 2 (8.7%) of the 23 patients; it was detected in 67 (30.2%) of the 222 patients in the rest of the group. None of the 23 patients had grade 3 tumors (P <0.05). Fifty-two percent of the tumors were grade 1 and 48% grade 2. None of the 23 had a high DI; a moderately increased DI was found in 1 patient and a low DI in 22 of the 23 patients. Detailed examination of the tumors between 2.5 and 4 cm (n = 29) revealed an infiltration of the renal capsule in 11 (38%); lymph node metastases were found in 2 (6.9%) and metastases in 4 (13.8%). A multifocal appearance was found in 4 (13.9%) of the 29 patients; grade 3 tumors were detected in 3 (10.3%) of 29 patients, grade 2 tumors in 12 (41.4%), and grade 1 tumors in 14 (48.3%). In this subgroup, a high DI was found in 14% (not significant). The examination of tumors larger than 4 cm in size revealed worse results in the pTNM classification, grade, and flow cytometric results. CONCLUSIONS: Only tumors smaller than 2.5 cm should be considered suitable for nephron-sparing surgery in patients eligible for elective surgery. In patients in whom nephron-sparing surgery is imperative, even tumors between 2.5 and 4 cm appear to be suitable. In patients requiring extensive resection, however, the risk of local recurrence seems to be higher because of the higher incidence of multifocality.

Adult↗

Alternative polyadenylation events contribute to the induction of NF-ATc in effector T cells.

The transcription factor NF-ATc is synthesized in three prominent isoforms. These differ in the length of their C terminal peptides and mode of synthesis. Due to a switch from the use of a 3' polyA site to a more proximal polyA site, NF-ATc expression switches from the synthesis of the two longer isoforms in naive T cells to that of short isoform A in T effector cells. The relative low binding affinity of cleavage stimulation factor CstF-64 to the proximal polyA site seems to contribute to its neglect in naive T cells. These alternative polyadenylation events ensure the rapid accumulation of high concentrations of NF-ATc necessary to exceed critical threshold levels of NF-ATc for gene induction in effector T cells.

Amino Acid Sequence↗

Mismatch negativity and late auditory evoked potentials in comatose patients.

OBJECTIVES: The purpose of this study was to assess the patterns of mismatch negativity (MMN) and N100 component in comatose patients and to evaluate their prognostic value vis-à-vis return of consciousness. METHODS: MMN and auditory (early, middle-latency and late) evoked potentials were recorded in 52 normals and in 128 comatose patients (comas due to neurosurgical and neurological problems). At the time of recording, all patients scored lower than 8 on the Glasgow scale. RESULTS: Visually detected N100 and MMN were confirmed by cross-correlation of sub-averages. The MMN was present in 33/128 patients and the N100 component in 84/128. The amplitudes of MMN and N100 waves detected in comatose patients were statistically different from those of normal subjects. By 3 months after the onset of coma, 95 patients had returned to consciousness, most of them with moderate to severe disability. A ratio of 30/33 patients with MMN and 70/84 with N100 had regained consciousness. The presence of a MMN together with a N100 component was more specific (90.9%) than the presence of a N100 component irrespective of MMN (57.6%) in terms of predicting return to consciousness, but its sensitivity was lower (respectively 31.6% for MMN and 73.7% for N100). The mean period that elapsed between the recording of evoked potentials and a return to consciousness was 6.3+/-4 days. MLAEPs were also highly specific, but BAEPs were not. CONCLUSION: MMN and auditory evoked potentials provide a reliable assessment of the functional status of comatose patients. When present, MMN and the N100 differ from those found in normal subjects in terms of latencies and amplitudes. As a predictor of return of consciousness MMN had high specificity and low sensitivity, whereas the N100 had high sensitivity and low specificity. This study demonstrates that the recording of MMN and the auditory N100 can be a very useful aid in the assessment of coma and in predicting whether or not a patient will regain consciousness.

Adolescent↗

Frequency of CFTR gene mutations in males participating in an ICSI programme.

A higher prevalence of cystic fibrosis transmembrane regulator (CFTR) gene mutations has been suggested both in men affected by congenital aplasia of the vas deferens, and in individuals presenting with reduced sperm quality. In this case, an increased risk for offspring being affected by cystic fibrosis (CF) can be expected in couples who are planning to undergo intracytoplasmic sperm injection (ICSI), since most of the male partners suffer from infertility. In order to determine the risk for these couples more precisely, we offered them a test for the most frequent CF mutations prevalent in the German population. The frequency of mutations within the CFTR gene in the female group was in the same range as expected for the general population (six out of 150). In 10 out of 207 males tested, infertility could be explained by exogenous factors not related to CFTR. Among the remaining 197 males with idiopathic infertility, we detected 13 heterozygotes for a mutation within the CFTR gene. This slightly, but significantly (P = 0.014), elevated rate could indicate that infertile males have, compared with the general population, an increased risk of being a carrier of a CFTR gene mutation.

Cystic Fibrosis↗

MRI assessment of the anatomy of optic radiations after temporal lobe epilepsy surgery.

OBJECTIVE: The aim of this study was to determine the course of the temporal optic radiations. MATERIAL AND METHODS: Eighteen patients were included in this prospective study. All of them underwent a temporal lobectomy for epilepsy, including the mesial temporal structures and a variable extent of lateral neocortex (from 2 to 7 cm behind the temporal tip). An MRI was performed 2 months postoperatively, allowing assessment of the extent of lateral resection. Postoperative visual fields were determined by automatic static perimetry (ASP). RESULTS: (1) No patient complained of a disabling visual field deficit. (2) ASP, a highly sensitive technique, however, detected postoperative visual field deficits in 83% of patients, confined to the superior homonymous field contralateral to the resection. (3) A strong correlation was found between the presence of a visual field deficit and the extent of laterotemporal resection. (4) The smallest anteroposterior resection resulting in a field defect was limited to 20 mm from the temporal tip. CONCLUSION: (1) This study confirms a strong correlation between postoperative visual field deficits and the extent of lateral neocortical temporal resection. (2) The anterior limit of Meyer's loop is likely to be located more rostrally than previously believed. (3) Despite this, lateral resection remains useful in some cases for seizure control.

Adult↗

Enrichment of mutant alleles by chromatographic removal of wild type alleles: a new principle for the detection of alleles with unknown point mutations at excess of wild type alleles.

In human carcinomas, mutations that alter tumour genes such as the KRAS, P53, or APC genes, are mostly point mutations. The detection of mutant alleles of tumour genes in specimens such as urine, pancreatic juice, sputum, and stool holds great promise for an early diagnosis of cancer. In addition, the detection of mutant tumour genes in tissue samples, such as lymph nodes or resection margins, may allow a sensitive diagnosis of residual malignant disease. However, the reliable detection of mutant alleles in excess of wild type alleles remains an unresolved analytical problem when the mutations are not known a priori. In the present communication, a new approach is described which makes possible the detection of unknown point mutations in tumour genes at excess of wild type alleles. The method is based on the removal of wild type alleles by hybridisation to immobilised complementary oligonucleotides. Using this approach, an enrichment of mutant KRAS, P53 and APC alleles of one mutant in up to 10(3) normal alleles has been achieved. Parallel miniaturised separation units with oligonucleotides complementary to defined sequences of a wild type allele should allow the detection of unknown point mutations as well as small insertions or deletions which occur in the sequence range covered by the oligonucleotides.

Alleles↗