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Biomedical subjects

P Fischer

Publications and source records attributed to P Fischer.

At least 181 records · Page 10Linked to original sources
PubMed1994

Efficiency of MHC class I antigen processing: a quantitative analysis.

Listeria monocytogenes is an intracellular pathogen that secretes proteins into host cell cytosol. One such protein, the murein hydrolase p60, is processed by the host cell into the nonamer peptide p60 217-225 and presented to cytotoxic T lymphocytes by the H-2Kd MHC class I molecule. Using strains of L. monocytogenes that secrete different amounts of p60, we show that the rate of p60 217-225 production is proportional to the quantity of intracellular antigen. The appearance of p60 217-225 is coupled to the degradation of newly synthesized p60. By accounting for the rate of intracellular antigen secretion and degradation, we estimate that approximately 35 p60 molecules are degraded to produce one p60 217-225 epitope. These findings provide an estimate of the efficiency of antigen processing and shed light on the capacity of the MHC class I antigen processing pathway to accommodate foreign antigens.

Animals↗
PubMed1994

Inability of muconate cycloisomerases to cause dehalogenation during conversion of 2-chloro-cis,cis-muconate.

The conversion of 2-chloro-cis,cis-muconate by muconate cycloisomerase from Pseudomonas putida PRS2000 yielded two products which by nuclear magnetic resonance spectroscopy were identified as 2-chloro- and 5-chloromuconolactone. High-pressure liquid chromatography analyses showed the same compounds to be formed also by muconate cycloisomerases from Acinetobacter calcoaceticus ADP1 and Pseudomonas sp. strain B13. During 2-chloro-cis,cis-muconate turnover by the enzyme from P. putida, 2-chloromuconolactone initially was the major product. After prolonged incubation, however, 5-chloromuconolactone dominated in the resulting equilibrium. In contrast to previous assumptions, both chloromuconolactones were found to be stable at physiological pH. Since the chloromuconate cycloisomerases of Pseudomonas sp. strain B13 and Alcaligenes eutrophus JMP134 have been shown previously to produce the trans-dienelactone (trans-4-carboxymethylene-but-2-en-4-olide) from 2-chloro-cis,cis-muconate, they must have evolved the capability to cleave the carbon-chlorine bond during their divergence from normal muconate cycloisomerases.

4-Butyrolactone↗
PubMed1994

Degradation of fluorene by Brevibacterium sp. strain DPO 1361: a novel C-C bond cleavage mechanism via 1,10-dihydro-1,10-dihydroxyfluoren-9-one.

Angular dioxygenation has been established as the crucial step in dibenzofuran degradation by Brevibacterium sp. strain DPO 1361 (V. Strubel, K. H. Engesser, P. Fischer, and H.-J. Knackmuss, J. Bacteriol. 173:1932-1937, 1991). The same strain utilizes biphenyl and fluorene as sole sources of carbon and energy. The fluorene degradation sequence is proposed to be initiated by oxidation of the fluorene methylene group to 9-fluorenol. Cells grown on fluorene exhibit pronounced 9-fluorenol dehydrogenase activity. Angular dioxygenation of the 9-fluorenone thus formed yields 1,10-dihydro-1,10-dihydroxyfluoren-9-one (DDF). A mechanistic model is presented for the subsequent C-C bond cleavage by an NAD(+)-dependent DDF dehydrogenase, acting on the angular dihydrodiol. This enzyme was purified and characterized as a tetramer of four identical 40-kDa subunits. The following Km values were determined: 13 microM for DDF and 65 microM for 2,3-dihydro-2,3-dihydroxybiphenyl. The enzyme also catalyzes the production of 3-(2'-carboxyphenyl)catechol, which was isolated, and structurally characterized, in the form of the corresponding lactone, 4-hydroxydibenzo-(b,d)-pyran-6-one. Stoichiometry analysis unequivocally demonstrates that angular dioxygenation constitutes the principal pathway in Brevibacterium sp. strain DPO 1361.

Alcohol Oxidoreductases↗
PubMed1994

Identification of a hydride-Meisenheimer complex as a metabolite of 2,4,6-trinitrotoluene by a Mycobacterium strain.

A bacterial strain, Mycobacterium sp. strain HL 4-NT-1, enriched with 4-nitrotoluene as its sole source of nitrogen, was able to metabolize 2,4,6-trinitrotoluene under aerobic conditions. The dark red-brown metabolite, which accumulated in the culture fluid, was identified as a hydride-Meisenheimer complex by comparison with an authentic synthetic sample.

Biotransformation↗
PubMed1994

Phase II trial of paclitaxel shows antitumor activity in patients with previously treated germ cell tumors.

PURPOSE: A trial of paclitaxel was conducted in patients with previously treated germ cell tumors (GCT). As the identification of new agents in GCT may be compromised by restricting entry criteria to heavily pretreated patients, an alternative trial design was used in which eligibility was restricted to patients with limited prior therapy. PATIENTS AND METHODS: Patients were eligible if their prior therapy was limited to one cisplatin-based regimen or < or = six cycles of prior cisplatin-based therapy. Paclitaxel 250 mg/m2 was administered by continuous infusion over 24 hours every 21 days. The dose of paclitaxel was modified for each patient based on toxicity. Granulocyte colony-stimulating factor (G-CSF) 5 micrograms/kg/d was administered during nadir periods. RESULTS: Thirty-one patients were treated; eight patients (26%) achieved a partial (n = 5) or a complete (n = 3) response. Responses were achieved in patients who had failed to respond to treatment with cisplatin, ifosfamide, and etoposide, and in patients with poor prognostic features, ie, mediastinal primary tumor site and patients with a best prior response of an incomplete response to cisplatin therapy. One complete responder remains continuously free of disease at 13+ months and one of the five patients who achieved a partial response remains progression-free at 14+ months. CONCLUSION: Paclitaxel has antitumor activity in GCT and warrants continued study in combination chemotherapy. Phase I/II trials will address its role in combination with cisplatin and ifosfamide and as a part of dose-intensive therapy. Furthermore, the study showed that a trial design in which eligibility criteria limits prior therapy was feasible, resulted in the identification of antitumor activity in a new agent, and may be considered in future trials for other promising new agents in GCT.

Adolescent↗
PubMed1993

Neuropathological staging of Alzheimer lesions and intellectual status in Alzheimer's and Parkinson's disease patients.

In both Alzheimer's disease (AD) and Parkinson's disease (PD), neurofibrillary tangles (NFT), in contrast to amyloid deposits, show a hierarchical spreading pattern from the allocortex to isocortical association areas with early involvement of the entorhinal region, a major relay station between hippocampus and isocortex. Based on the distribution pattern of NFT in human brain, a neuropathological staging of neuritic AD pathology has been proposed. Comparative studies of this neuropathological staging of neuritic AD changes with psychometrically assessed intellectual status (mini-mental state) in prospective cohorts of 29 aged individuals and 28 PD patients showed a linear correlation of morphological AD staging with the psychostatus in both disorders. The pattern of neuronal degeneration associated with neuritic AD pathology in both AD and PD may be an important basis of cognitive decline in both disorders.

Aged↗
PubMed1993

Synaptic pathology of Alzheimer's disease.

Prospective clinico-pathological studies on dementia in Alzheimer's disease (AD), performed during the past decades, revealed a relatively poor correlation between the degree of clinical deficit and the severity of the typical neuropathological lesions of AD, the amyloid plaques and the neurofibrillary tangles. More recent data, obtained by electron microscopy, immunocytochemical as well as immunochemical techniques indicate that synaptic loss may be a better structural correlate of dementia than other brain lesions. Synaptic pathology is reflected by a loss of all major components of small synaptic vesicles and most peptides, stored in large dense cored vesicles. The significant increase of chromogranin A proprotein, a major component of large dense cored vesicles, may rather represent a defect of protein processing than preservation of a specific synaptic subpopulation. Within the brain of AD patients, the degree of synaptic loss is uneven. Most prominent reduction of synapses is found in the outer parts of the dentate gyrus molecular layer, possibly reflecting the destruction of neurons, located in the layer 2 of the entorhinal cortex. However, within the neocortex, no preferential loss of synapses in any of the cortical layers has been found. Cerebral amyloid deposition in diffuse plaques has little effect on synapse density and structure. However, within the dense amyloid core of a classical plaque, synapses are completely lost. In the surrounding neuritic portion of the plaques, synaptophysin reactivity is frequently increased, due to enlargement of synaptic boutons and to accumulation of synaptophysin in dystrophic axons. Although the reason for synapse loss in AD is yet unknown, most results suggest that it may reflect degeneration of neurons, projecting into the respective cortical areas.

Alzheimer Disease↗
PubMed1993

C-MYC translocations in de novo B-cell lineage acute leukemias with t(14;18)(cell lines Karpas 231 and 353).

Rare de novo acute leukemias of mature B cells may exhibit the chromosomal translocation t(14;18)(q32.3; q21.3). We report the preliminary characterization of two cases that exhibited not only t(14;18)(q32.3;q21.3) but also the novel translocation t(8;9)(q24.1;p13.3), involving the C-MYC locus with unknown sequences at 9p13.3. From these cases, two Epstein-Barr virus negative cell lines (Karpas 231 and 353) with features identical to those seen in fresh cells from the patient have been derived. Both cell lines have complex karyotypes: in addition to both t(14;18)(q32.3;q21.3) and t(8;9)(q24.1;p13.3), cell line Karpas 231 exhibited three-way translocation t(1;3;11) (q42.3;q27.1;q23.1), whereas Karpas 353 exhibited t(1;3;7)(p32.1;q21.1;q22.1). Both cases retained immunophenotypes characteristic of mature B cells with no evidence for commitment to other hematopoietic lineages. Both cases expressed abundant, normal-sized C-MYC transcript, but no rearrangement of C-MYC DNA sequences could be detected using probes that span 80 kb around the C-MYC coding sequences. Breakpoints within the BCL-2 gene were divergent. In Karpas 353 the BCL-2 breakpoint occurred within the 3' untranslated major breakpoint region (mbr) of the gene, whereas, in Karpas 231, breaks in both the 3' mbr and in the region 5' of the gene were detected. The cytogenetic combination of t(14;18)(q32.3;q21.3) and t(8;9)(q24.1;p13.3) has been previously reported in diffuse B cell lymphomas. This combination may be a new recurrent abnormality, of central pathogenic importance in the transformation of B cells to high grade malignancies through simultaneous deregulation of BCL-2 and C-MYC genes, constitutive expression of C-MYC being driven by currently unknown DNA sequences on chromosome 9p13.3. The presence of other complex translocations including those affecting 11q23.1 may further accelerate the process of acute transformation.

Acute Disease↗
PubMed1993

Exercise-induced myalgia in hypothyroidism.

Recurrent rhabdomyolysis is very uncommon in hypothyroid myopathy. A 30-year-old woman is reported, who presented with exercise-induced myalgias and high levels of serum creatine kinase but no muscle weakness. Muscle biopsy showed signs of a recurrent rhabdomyolysis. Hypothyroidism was diagnosed by serum hormone levels. The myopathy rapidly improved with thyroxine treatment.

Adult↗
PubMed1993

Heterozygotic gene expression in endomyocardial biopsies: a new diagnostic tool confirms the Duchenne carrier status.

Identification of the defective gene and the absent gene product dystrophin can substantiate the clinical evidence for manifesting X-linked Duchenne type muscular dystrophy (DMD). It is not always possible, however, to rule out definitely a clinically asymptomatic carrier status in question, since even in the proven carrier DNA analysis is often inconclusive, and multinucleated skeletal muscle fibers express a basically normal membrane dystrophin. To substantiate the value of endomyocardial biopsy as a new tool for detection of the DMD carrier status we examined an endomyocardial biopsy of a volunteer who met the clinical criteria of a DMD carrier. Dystrophin immunohistochemistry and western blot of her skeletal muscle biopsy were inconclusive, and polymerase chain reaction and cDNA analysis failed to locate directly the X-chromosomal defect. We observed a clearcut mosaic of dystrophin-positive and -negative mononucleated cardiac muscle cells, reflecting a heterozygote carrier status in her endomyocardial biopsy, whereas 20 controls were uniformely positive. The incidence of DMD (1:3000 males) and especially the 30% spontaneous mutation rate, still the major pitfall in DNA analysis, show the need for an additional diagnostic tool.

Adult↗
PubMed1993

Reactive Maillard intermediates leading to coloured products-5-hydroxymethyl- and 5-(1,2-dihydroxyethyl)-3(2H)-furanone.

In the course of the Maillard reaction, labile sugar degradation products are formed that are susceptible to secondary reactions and therefore have a decisive influence on the product spectrum. Such reactive intermediates may be transformed into stable derivatives with trapping reagents, and thus be protected from further reactions. Secondary processes may also be forestalled if the primary products are removed from the reaction mixture by high-vacuum distillation. By this procedure, 5-hydroxymethyl- and 5-(1,2-dihydroxyethyl)-3(2H)-furanone have been identified directly from Maillard reaction mixtures for the first time. The activated methylene group of these 3(2H)-furanones can easily enter into condensation reactions. The coloured condensation products in turn react with primary amines to pyrrolinone derivatives, which may also contribute to the colouring observed in non-enzymatic browning.

Chromatography, Gas↗
PubMed1993

Fibre type specific expression of Leu19-antigen and N-CAM in skeletal muscle in various stages after experimental denervation.

Leu-19 antigen, which seems to be identical with neural cell adhesion molecule (N-CAM), plays a major role in the innervation of muscle cells, and in adult muscle appears after denervation and during regeneration of muscle fibres, where it acts as part of a signalling system increasing the probability of re-innervation. This combined enzyme-histochemical and immunohistochemical study examined whether this signalling process was regulated in a uniform or differential pattern for type 1 and type 2 muscle fibres. The subscapular nerve of 18 rabbits was transsected with subsequent complete denervation of the supraspinatus muscle. Leu-19 and N-CAM immunohistochemistry was performed 2 to 64 days after surgery. Whereas in normal muscle there are virtually no Leu-19/N-CAM positive muscle fibres; from day 2 after denervation an increasing proportion of fibres expressed Leu-19/N-CAM, prior to any neurogenic atrophy. In the early stage of denervation Leu19/N-CAM expression was confined to type 1 fibres. After 11 days nearly all fibres were Leu19/N-CAM positive irrespective of their fibre type. Sixty-four days after denervation type 1 fibres became Leu19/N-CAM negative, while atrophic type 2 fibres showed intensive staining. Thus, expression of Leu-19 antigenicity is differently regulated in both fibre types.

Animals↗
PubMed1993

Myositis in Lyme borreliosis: an immunohistochemical study of seven patients.

Myositis is a rare complication of Lyme disease. In order to get information about the pathogenesis of this disorder, muscle specimens of 7 patients suffering from myositis as a manifestation of Lyme borreliosis were examined by immunohistology. Lyme spirochetes could be found in muscle biopsies of 6 patients. Infiltrates consisted mainly of macrophages and T helper/inducer cells. The T4/T8 ratio was 1.7 in the endomysium and 2.1 in the perimysium. Increased expression of MHC-I molecules by several muscle fibers was observed in 2 subjects only. No MHC-II molecules were expressed by muscle fibers. Lymphocytes expressing the interleukin-2 receptor were detected in 2 patients. Leu-15+ and Leu-11+ cells were found only to a slight extent in 2 patients. In conclusion the immunohistochemical findings in myositis due to Lyme borreliosis are different from other manifestations of this disease, and also from other forms of myositis.

Adult↗