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Biomedical subjects

K Fischer

Publications and source records attributed to K Fischer.

At least 19 recordsLinked to original sources
PubMed1999

Continuous in vitro propagation and differentiation of cultures of the intramolluscan stages of the human parasite Schistosoma mansoni.

The metazoan parasitic blood flukes, Schistosoma spp., infect over 200 million people worldwide and cause extensive human morbidity and mortality. Research strategies for development of anti-schistosomal agents are impeded by the organism's complex molluscan-mammalian life cycle, which limits experimental approaches and availability of material. We derived long-term continuously proliferative cultures of Schistosoma mansoni sporocysts capable of generating cercariae in vitro. Cultured organisms retained the ability to parasitize the host, and they exhibited developmental regulation of candidate stage-specific genes in the host-free culture system. Evidence for expression of a reverse transcriptase also was found in the cultured organisms, pointing to this activity as a possible mechanistic contributor to the dynamic relationship between the parasite and its hosts. Continuous in vitro propagation of the asexual sporocyst stage allows isolation of clonally derived parasite populations and provides a means to study schistosomal molecular genetics, metabolism, and evasion of host defenses.

Animals↗
PubMed1999

Laser angioplasty of restenosed coronary stents: results of a multicenter surveillance trial. The Laser Angioplasty of Restenosed Stents (LARS) Investigators.

OBJECTIVES: This study evaluated safety and efficacy of excimer laser angioplasty for treatment of restenosed or occluded coronary stents. BACKGROUND: Balloon angioplasty of in-stent restenosis is limited by a high recurrence rate. Debulking by laser angioplasty is a novel concept to treat in-stent restenosis. METHODS: A total of 440 patients with restenoses or occlusions in 527 stents were enrolled for treatment with concentric or eccentric laser catheters and adjunctive balloon angioplasty. RESULTS: Laser angioplasty success (< or =50% diameter stenosis after laser treatment or successful passage with a 2.0-mm or 1.7-mm eccentric laser catheter) was achieved in 92% of patients. Adjunctive balloon angioplasty was performed in 99%. Procedural success (laser angioplasty success followed by < or =30% stenosis with or without balloon angioplasty) was 91%. There was neither a significant difference in success with respect to lesion length, nor were there differences between small and large vessels or native vessels and vein grafts. Success was higher and residual stenosis lower using large or eccentric catheters. Serious adverse events included death (1.6%, not directly laser catheter related), Q-wave myocardial infarction (0.5%), non-Q-wave infarction (2.7%), cardiac tamponade (0.5%) and stent damage (0.5%). Perforations after laser treatment occurred in 0.9% of patients and after balloon angioplasty in 0.2%. Dissections were visible in 4.8% of patients after laser treatment and in 9.3% after balloon angioplasty. Reinterventions during hospitalization were necessary in 0.9% of patients; bypass surgery was performed in 0.2%. CONCLUSIONS: Excimer laser angioplasty with adjunctive balloon angioplasty is a safe and efficient technology to treat in-stent restenoses. These data justify a randomized comparison with balloon angioplasty.

Adult↗
PubMed1999

Increased doxorubicin uptake and toxicity in multicellular tumour spheroids treated with DC electrical fields.

Electrochemotherapy (ECT) is a new approach to the treatment of tumours. In the present study, multicellular prostate tumour spheroids were treated with non-lethal direct current (DC) electrical fields, and uptake and toxicity of doxorubicin were investigated. An electrical field with a field strength of 500 Vm(-1) applied for a duration of 90 s resulted in neither reversible nor irreversible membrane breakdown as revealed by fluid phase uptake studies of the membrane impermeant tracer Lucifer yellow. However, treated spheroids showed an increased uptake of doxorubicin and, consequently, an increased toxicity following electrical field exposure. The electrical field raised intracellular reactive oxygen species (ROS) as revealed using 2',7'-dichlorofluorescein diacetate (H2DCFDA) as an indicator. ROS induced membrane lipid peroxidation since the lipid peroxidation end products malondialdehyde (MDA) and 4-hydroxy-2-(E)-nonenal (4-HNE) were detected after electrical field treatment. Moreover, lipid peroxidation decreased the lipid diffusion coefficient D from 4.2 x 10(-10) cm2 s(-1) to 2.7 x 10(-10) cm2 s(-1) in the control and treated sample, respectively, as revealed by fluorescence recovery after photobleaching (FRAP) experiments. The field effects could be mimicked by incubating spheroids with 100 nM hydrogen peroxide and were inhibited by the radical scavengers dehydroascorbate (DHA) and alpha-tocopherol (vitamin E), indicating that the increased uptake of doxorubicin after electrical field treatment is owing to lipid peroxidation and decreased membrane lipid mobility. Treatment of tumours with low intensity electrical fields may be useful to improve the cytotoxic capacity of anthracyclines.

Antineoplastic Agents↗
PubMed1999

[Transpupillary thermotherapy of choroidal melanoma].

PURPOSE: The purpose of this report is to evaluate the efficacy of transpupillary thermotherapy (TTT) to treat choroidal melanoma. PATIENTS AND METHOD: 17 patients with choroidal melanoma were treated, 6 patients with small tumors close to posterior pole received TTT only 11 patients were treated simultaneously with TTT and Ru 106 brachytherapy. To perform TTT a diode laser with a beam diameter of 1.5 to 3 millimeters was used. Exposure time ranged from 60 to 90 seconds until a light grey appearance of the retinal surface was reached. Follow-up examinations were performed at 1-month intervals. If the tumor was partially regressed additional TTT was performed to reach the endpoint of a chorioretinal scar. RESULTS: All tumors exhibited a reduction of tumor height in a mean follow-up period of 14.25 months. Side effects were minimal. CONCLUSIONS: Treatment with TTT may be useful as a complementary modality to brachytherapy. A longer follow-up time is necessary for final evaluation.

Adult↗
PubMed1998

Coronary-artery stenting compared with balloon angioplasty for restenosis after initial balloon angioplasty. Restenosis Stent Study Group.

BACKGROUND: Intracoronary stenting reduces the rate of restenosis after angioplasty in patients with new coronary lesions. We conducted a prospective, randomized, multicenter study to determine whether intracoronary stenting, as compared with standard balloon angioplasty, reduces the recurrence of luminal narrowing in restenotic lesions. METHODS: A total of 383 patients who had undergone at least one balloon angioplasty and who had clinical and angiographic evidence of restenosis after the procedure were randomly assigned to undergo standard balloon angioplasty (192 patients) or intracoronary stenting with a Palmaz-Schatz stent (191 patients). The primary end point was angiographic evidence of restenosis (defined as stenosis of more than 50 percent of the luminal diameter) at six months. The secondary end points were death, Q-wave myocardial infarction, bypass surgery, and revascularization of the target vessel. RESULTS: The rate of restenosis was significantly higher in the angioplasty group than in the stent group (32 percent as compared with 18 percent, P= 0.03). Revascularization of the target vessel at six months was required in 27 percent of the angioplasty group but in only 10 percent of the stent group (P=0.001). This difference resulted from a smaller mean (+/-SD) minimal luminal diameter in the angioplasty group (1.85+/-0.56 mm) than in the stent group (2.04+/-0.66 mm), with a mean difference of 0.19 mm (P=0.01) at follow-up. Subacute thrombosis occurred in 0.6 percent of the angioplasty group and in 3.9 percent of the stent group. The rate of event-free survival at 250 days was 72 percent in the angioplasty group and 84 percent in the stent group (P=0.04). CONCLUSIONS: Elective coronary stenting was effective in the treatment of restenosis after balloon angioplasty. Stenting resulted in a lower rate of recurrent stenosis despite a higher incidence of subacute thrombosis.

Aged↗
PubMed1998

stevor and rif are Plasmodium falciparum multicopy gene families which potentially encode variant antigens.

Several multicopy gene families have been described in Plasmodium falciparum, including the var genes that code for the variant surface antigen PfEMP1, the stevor family of subtelomeric open reading frames and the rif interspersed repetitive elements. This report documents the chromosomal location of stevor genes, their transcription and characteristics of the deduced protein. On 14 chromosomes, 34 stevor copies were identified from the Dd2 parasite line. Most are in subtelomeric regions within 50 kb of the telomere. stevor genes are located close to var genes and rij. All stevor genes sequenced had two exons: a short exon 1 encoding a start codon and a transmembrane domain; exon 2 encoding for the remainder of the approximately 30 kDa protein and including two more transmembrane segments. A similar structure was found for copies of rif and its predicted protein. In both STEVOR and RIF proteins, a highly polymorphic region is predicted to be a loop on the outer side of the membrane. We propose that stevor and rif are members of a larger superfamily. The number of copies of stevor and rif, their location close to the var genes, their extreme polymorphism and the predicted structure of the proteins suggest that stevor and rif code for variant surface antigens.

Amino Acid Sequence↗
PubMed1998

Urokinase induces proliferation of human ovarian cancer cells: characterization of structural elements required for growth factor function.

Ovarian cancer metastasis is associated with an increase in the urokinase-type plasminogen activator (uPA) and its receptor uPAR. We present evidence that binding of uPA to uPAR provokes a mitogenic response in the human ovarian cancer cell line OV-MZ-6 in which endogenous uPA production had been significantly reduced by stable uPA 'antisense' transfection. High molecular weight (HMW) uPA, independent of its enzymatic activity, produced an up to 95% increase in cell number concomitant with 2-fold elevated [3H]thymidine incorporation as did the catalytically inactive but uPAR binding amino-terminal fragment of uPA, ATF. uPA-induced cell proliferation was significantly decreased by blocking uPA/uPAR interaction by the monoclonal antibody IIIF10 and by soluble uPAR. The efficiency of the uPAR binding synthetic peptide cyclo19,31 uPA19-31 to enhance OV-MZ-6 cell growth proved this molecular domain to be the minimal structural determinant for uPA mitogenic activity. Dependence of uPA-provoked cell proliferation on uPAR was further demonstrated in Raji cells which do not express uPAR and were thus not induced by uPA. However, upon transfection with full-length uPAR, Raji cells acquired a significant growth response to HMW uPA and ATF.

Antibodies, Monoclonal↗
PubMed1998

Immunophenotypic and genotypic features, clinical characteristics, and treatment outcome of adult pro-B acute lymphoblastic leukemia: results of the German multicenter trials GMALL 03/87 and 04/89.

In contrast to childhood acute lymphoblastic leukemia (ALL), the cell-biological features, clinical characteristics, and treatment outcome of CD10(-) pro-B ALL have not yet been determined in larger series of adult patients. Therefore, we studied 57 adult patients with newly diagnosed pro-B ALL (median age, 30 years) enrolled in two consecutive German multicenter ALL studies (03/87 and 04/89). Extensive immunophenotypic characterization of leukemic blasts could be performed on all patients, whereas adequate cytogenetic data were available in 33 cases and molecular studies in 18 cases, using reverse transcription-polymerase chain reaction to detect MLL-AF-4 transcripts. Twenty-two patients demonstrated a t(4;11)(q21;q23) and/or MLL-AF-4 rearrangements, and 6 patients had other structural abnormalities, including a t(9;22)(q34;q11) (N = 2). Nine patients had a normal karyotype. Patients with 11q23 abnormalities tended to be younger (median age, 29 years) and were characterized by male predominance (64%), hyperleukocytosis (median leukocyte count, 168 x 10(9)/L), and a frequent coexpression of CD65s (64%) as compared with patients with other cytogenetic abnormalities or a normal karyotype. Twelve of 16 (75%) pro-B ALL patients in study 03/87 and 30 of 41 (73%) in study 04/89 achieved a complete remission (CR). Sixteen of 30 patients in study 04/89 remain in continuous CR (CCR) in contrast to only 2 of 12 patients in study 03/87. Interestingly, all 7 patients treated with high-dose cytarabine and mitoxantrone as consolidation in study 04/89 remain alive and leukemia-free. One patient in study 03/87 and 8 in study 04/89 underwent autologous (N = 2) or allogeneic (N = 7) bone marrow transplantation (BMT). The median remission duration was 420 days for patients in study 03/87 and has not yet been reached in study 04/89. The median survival time of all pro-B ALL patients was 571 days in study 03/87 and 747 days in study 04/89. Among the 22 patients with a t(4;11) and/or MLL-AF-4 rearrangements, 17 achieved a CR and 8 are still in CCR, of whom 4 underwent an allogeneic BMT. Remission duration and overall survival did not differ significantly between pro-B ALL patients with 11q23 abnormalities and those with a normal karyotype or other structural abnormalities. These data indicate that intensification of postremission treatment may improve the prognosis of adult pro-B ALL, including patients with a t(4;11).

Adolescent↗
PubMed1998

Characterization and cloning of the gene encoding the vacuolar membrane protein EXP-2 from Plasmodium falciparum.

As a contribution to the characterization of the parasitophorous vacuolar membrane from Plasmodium falciparum we have begun the identification of vacuolar membrane proteins. Exported protein-2 (EXP-2) is a vacuolar membrane protein exposed into the vacuolar space. To further characterize EXP-2, it was purified, and the 45 N-terminal amino acids were determined by micro-sequencing. Based on this information, partial cDNA and genomic fragments were amplified by PCR and used as probes for the isolation of complete cDNA and genomic DNA clones. The single copy gene is located on chromosome 14, and is transcribed during the ring stage of parasite development. The open reading frame encodes an N-terminal signal sequence which is cleaved from the mature protein. The amino acid composition of EXP-2 is characterized by charged amino acids, with a high abundance of aspartate residues in the C-terminal portion of the protein. In contrast to EXP-1, an integral protein of the vacuolar membrane, EXP-2 lacks a typical hydrophobic transmembrane domain. We suggest that EXP-2 may associate with the vacuolar membrane via an amphipathic helix located in the N-terminal half of the protein.

Amino Acid Sequence↗
PubMed1998

[Argon plasma surgery (APC) in the upper aerodigestive tract. Initial results].

Cold knife surgery, electrosurgery and laser surgery all offer techniques, instruments, equipment and systems for resecting and destroying mucosal lesions and for hemostasis in the upper aerodigestive tract. When used in the head and neck, argon plasma surgery (APS) offers a new, contact-free, electrosurgical technique in which high frequency current is applied through ionized, and thus electrically conductive, argon(argon plasma) to the tissue undergoing treatment. Especially noteworthy in APS are its advantages for removing a lesion and controlling bleeding: the technique is easy to control, and the depth of the thermal tissue destruction is limited to a maximum of 3 mm even in wide-area application, so that damage to adjacent or submucosal tissues can be avoided. Initial results with APS in the reduction of hyperplastic nasal turbinates, treatment of hereditary hemorrhagic teleangiectasia (Osler's disease) in the nasal mucosa, and in treating progressive juvenile papillomatosis of the larynx have shown clear advantages for APS over other methods used.

Adolescent↗
PubMed1998

[Trans-pupillary hyperthermia of malignant choroid melanoma. Initial experiences].

UNLABELLED: The purpose of this report is to evaluate the efficacy of transpupillary thermotherapy (TTT) to treat choroidal melanoma. PATIENTS AND METHODS: Twelve patients with choroidal melanoma were treated. Four with small tumors close to the posterior pole received TTT alone; 8 were treated simultaneously with TTT and Ru-106 brachytherapy. To perform TTT a diode laser with a beam diameter of 3 mm was used. Exposure time ranged from 60 to 90 s until the retinal surface became light gray. Follow-up examinations were performed at 1-month intervals. If the tumor was partially regressed, additional TTT was performed to reach the endpoint of a chorioretinal scar. RESULTS: All tumors exhibited a reduction of tumor height in a maximal follow-up period of 6 months. Four cases showed complete regression within 3 months. Side effects were minimal. CONCLUSIONS: Treatment with TTT may be useful as a complementary modality to brachytherapy. A longer follow-up time is necessary for final evaluation.

Adult↗
PubMed1998

The use of the Port-A-Cath in children with haemophilia--a review.

Port-A-Caths have been used increasingly in children with severe haemophilia. In non-inhibitor patients where Port-a-Caths were used to facilitate long-term prophylaxis, the infection rate is rather low and ranges in the various studies from 0 to 29%, with a median follow-up time of about 27 months. Patients that received the Port-A-Cath for the induction of immune tolerance (inhibitor patients) have a high infection rate of 50% to 83%. Although this percentage is high, good venous access is extremely important, especially in this group. The number of both inhibitor and non-inhibitor patients in the studies are very small, and a prospective survey is important to obtain more adequate data.

Catheterization, Central Venous↗
PubMed1998

Molecular characterization of a carbon transporter in plastids from heterotrophic tissues: the glucose 6-phosphate/phosphate antiporter.

Plastids of nongreen tissues import carbon as a source of biosynthetic pathways and energy. Within plastids, carbon can be used in the biosynthesis of starch or as a substrate for the oxidative pentose phosphate pathway, for example. We have used maize endosperm to purify a plastidic glucose 6-phosphate/phosphate translocator (GPT). The corresponding cDNA was isolated from maize endosperm as well as from tissues of pea roots and potato tubers. Analysis of the primary sequences of the cDNAs revealed that the GPT proteins have a high degree of identity with each other but share only approximately 38% identical amino acids with members of both the triose phosphate/phosphate translocator (TPT) and the phosphoenolpyruvate/phosphate translocator (PPT) families. Thus, the GPTs represent a third group of plastidic phosphate antiporters. All three classes of phosphate translocator genes show differential patterns of expression. Whereas the TPT gene is predominantly present in tissues that perform photosynthetic carbon metabolism and the PPT gene appears to be ubiquitously expressed, the expression of the GPT gene is mainly restricted to heterotrophic tissues. Expression of the coding region of the GPT in transformed yeast cells and subsequent transport experiments with the purified protein demonstrated that the GPT protein mediates a 1:1 exchange of glucose 6-phosphate mainly with inorganic phosphate and triose phosphates. Glucose 6-phosphate imported via the GPT can thus be used either for starch biosynthesis, during which process inorganic phosphate is released, or as a substrate for the oxidative pentose phosphate pathway, yielding triose phosphates.

Amino Acid Sequence↗
PubMed1998

Multifunctional potential of the plasminogen activation system in tumor invasion and metastasis (review).

Tumor cell migration and invasion into the surrounding tissue depend on the invasive capacity of cells leading to the loosening of cell-cell and cell-substratum contacts via cell surface associated proteolytic enzyme systems. Plasmin is one of the enzymes involved in these complex events. It is generated by the cleavage of the proenzyme plasminogen upon the action of the urokinase-type plasminogen activator (uPA). uPA is synthesized and secreted by tumor cells and normal cells and interacts with a specific cell surface receptor (uPAR) thereby focalizing enzymatic activity to the cell surface. The activity of uPA is controlled by plasminogen activator inhibitors type-1 and type-2. A strong statistically independent prognostic impact has been attributed to uPA and its inhibitor PAI-1 in a variety of malignancies. Besides its proteolytic activity, uPA in concert with uPAR exert biological effects characteristic for molecules with signal transducing properties including chemotaxis, migration/invasion, adhesion, and mitogenesis.

Cell Adhesion↗
PubMed1997

Hair concentrations and self-reported abuse history of 20 amphetamine and ecstasy users.

Hair samples of 20 volunteers of the techno-music scene, who more or less regularly consumed ecstasy tablets and speed and anonymously reported their abuse history, were analyzed in one to seven 3 cm segments for amphetamine (A), methamphetamine (MA), methylenedioxyamphetamine (MDA), methylenedioxymethamphetamine (MDMA), methylenedioxyethamphetamine (MDE) and N-methyl-1-(1,3-benzodioxol-5-yl)-2-butylamine (MBDB) by digestion in 1 M NaOH, subsequent extraction with C18 Bond Elut columns, derivatization with pentafluoropropionyl anhydride and GC/MS-SIM measurements using deuterated standards of A, MA, MDA and MDMA. The concentrations were in the regions 0.1 to 4.8 ng/mg for A (17 samples), 0.05 to 0.89 ng/mg for MDA (16 samples), 0.1 to 8.3 ng/mg for MDMA (16 samples), 0.12 to 15 ng/mg for MDE (13 samples) and 0.21 to 1.3 ng/mg for MBDB (2 samples). MA was not detected. For comparison the frequency and the concentration of these drugs in 124 different ecstasy tablets were determined by HPLC. The drug concentration in the hair segments were compared with the volunteers' reports. Despite the enormous interindividual differences qualitatively an increase of the total concentration of MDA, MDMA and MDE in the proximate 3 cm segments with increasing ecstasy abuse frequency during the last three month before sampling is recognized. In the individual comparison with the chronological consumer reports in most cases a longer interruption or a change of the abuse intensity is not clearly seen at the segment concentrations. As a reason the incorporation of the drugs from sweat into elder hair regions and the slow removal by washing are discussed.

Adolescent↗
PubMed1997

Construction and characterization of a Plasmodium vivax genomic library in yeast artificial chromosomes.

Here we describe the construction of a representative YAC library for the human malarial parasite Plasmodium vivax. As P. vivax cannot be maintained continuously under laboratory conditions, the P. vivax DNA necessary for the library construction was isolated from a single human patient presenting himself with vivax malaria to a local hospital in the Brazilian Amazon. Thus, this YAC library is the first of its kind to be generated from patient-derived material. The YAC library consists of 560 clones with an average insert size of 180 kb. Of 9 published P. vivax genes, 8 were found to be present in the library. In addition, 12 P. vivax telomeric YAC clones were identified.

Animals↗