Biomedical subjects

K W Sykora

Publications and source records attributed to K W Sykora.

29 records · Page 2Linked to original sources

PubMed1994

Differential regulation of stem cell factor mRNA expression in human endothelial cells by bacterial pathogens: an in vitro model of inflammation.

Production of hematopoietic growth factors by endothelial cells plays a pivotal role during inflammatory processes. Stem cell factor (SCF) is known to be expressed constitutively in endothelial cells. To investigate the regulation of this cytokine expression by inflammatory stimuli, we cocultured human umbilical vein endothelial cells (HUVEC) with various gram-negative bacterial strains (Escherichia coli, Yersinia enterocolitica, Chlamydia trachomatis, and Neisseria meningitidis, respectively). Experiments were performed with bacterial concentrations ranging from 10(2) to 10(7) bacteria/mL for 3 hours. SCF-specific mRNA expression was studied using Northern blot analysis. Stimulation with the enteropathogenic bacterial strains Y enterocolitica and E coli resulted in a significant concentration-dependent increase of SCF mRNA expression. Similar results were obtained in coculture experiments with N meningitidis. As shown in experiments with E coli, the accumulation of SCF transcripts was also time-dependent. In contrast, coculture of HUVEC with the intracellular gram-negative strain C trachomatis had no effect on SCF mRNA expression. To elucidate the role of the gram-negative bacterial cell wall components, we stimulated HUVEC with bacterial lipopolysaccharide (LPS). LPS induced a maximal SCF mRNA accumulation within 2 hours followed by decrease of SCF-specific transcripts to the basal level after 24 hours. In addition, we exposed HUVEC to the classical inflammatory cytokine interleukin-1 alpha (IL-1 alpha). Kinetic experiments showed a similar pattern of regulation with an increase of SCF mRNA within 2 hours, persisting up to 12 hours, and a decrease to basal transcription after 24 hours. From these data, we conclude that SCF expression is regulated by inflammatory stimuli, such as IL-1 alpha and bacterial pathogens, suggesting an important role of SCF during inflammation.

Cells, Cultured↗

PubMed1994

Type II congenital dyserythropoietic anemia in a patient with ectodermal dysplasia. Distinction from dyskeratosis congenita.

PURPOSE: We describe a patient who presented with severe anemia and ectodermal dysplasia. PATIENTS AND METHODS: This is a case report of a patient whose anemia was evaluated at New York Hospital and then returned to Australia where further testing was performed. RESULTS: The history indicated that this was a chronic anemia. Bone marrow examination showed binucleated late normoblasts consistent with congenital dyserythropoietic anemia type II (CDA II) and not dyskeratosis congenita. Paroxysmal nocturnal hemoglobinuria was excluded despite the presence of a positive sucrose hemolysis test. Other types of acquired and congenital anemias were excluded by testing. CONCLUSIONS: This is the first patient reported with coincident CDA II and ectodermal dysplasia.

Anemia, Dyserythropoietic, Congenital↗

PubMed1990

Ophthalmic neoplasms in infancy and childhood.

The most common ocular and orbital tumors presenting in infancy, childhood and adolescence are presented and discussed in this review. It has been prepared specifically for the clinical pediatrician and focuses on the clinical recognition of ophthalmic neoplasms, their diagnostic evaluation employing the use of advanced imaging techniques, biopsy when indicated and extent of disease workup. In addition, current treatment modalities are discussed. Ocular tumors addressed include: retinoblastoma, capillary hemangioma, lymphangioma, dermoid and epidermoid cysts, teratoma, glioma, astrocytic hamartoma, neurofibroma, rhabdomyosarcoma and fibrous tumors. Two aggressive and potentially fatal tumors, rhabdomyosarcoma and retinoblastoma, are presented in detail. In addition, the ocular tumors associated with the phakomatoses (von Hippel-Lindau, tuberous sclerosis and neurofibromatosis) are reviewed.

Adolescent↗

PubMed1987

T-cell activation defect in common variable immunodeficiency: restoration by phorbol myristate acetate (PMA) or allogeneic macrophages.

Common variable immunodeficiency (CVI) represents a group of familial and sporadic diseases characterized by a range of B-cell, T-cell, and macrophage defects. A defect in T-cell activation, involving reduced proliferation and IL-2 production after stimulation with OKT3 antibody, has been described previously. In the present study we found that these defects could be corrected in vitro by adding phorbol myristate acetate (PMA) to OKT3-stimulated peripheral blood mononuclear cells (PBMC) of 14 patients with CVI. PBMC of 6 out of 7 patients with CVI studied also exhibited a profound defect in IL-2 receptor expression when incubated with OKT3 antibody. IL-2 receptor expression after stimulation with PMA alone was normal, indicating that the OKT3- but not the PMA-induced pathway of IL-2 receptor expression was defective. On the RNA level, the genes for IL-2 and IL-2 receptor were expressed after stimulation with OKT3 antibody. IL-2 and IL-2 receptor gene expression were normal, indicating a possible post-transcriptional defect. To investigate whether the defect in T-cell activation was at the macrophage or the T-cell level, we prepared adherent cells and monocyte-depleted T cells (E+) from 3 patients with CVI and from normal blood donors. Incubating CVI E+ cells with normal adherent cells resulted in normal proliferation and IL-2 production in the presence of OKT3, whereas incubation of normal E+ cells with adherent cells from patients with CVI under the same conditions showed reduced IL-2 production and proliferation, suggesting the macrophage as the origin of the failure in T-cell activation in the patients with CVI studied. Inhibition by macrophage-secreted prostaglandins was excluded by failure to correct the IL-2 production and proliferation defects in the presence of indomethacin.

Adult↗

PubMed1985

Interleukin 2: a review.

Interleukin 2 (IL 2) is a central mediator of the growth and functional activity of B- and T-cells, and cytotoxic cells, including Natural Killer and Lymphokine Activated Killer cells. Significant defects in the production of, and response to, IL 2 have been described in a variety of congenital and acquired immunodeficiency states. IL 2 has demonstrated major anti-tumor activity in animal models. The biochemistry and molecular biology of IL 2 and its gene are reviewed, along with data regarding the IL 2 receptor, normal T-cell activation, abnormalities in IL 2 production and response in immunodeficiency states and leukemia, and initial explorations of IL 2 in the treatment of human cancer.

Acquired Immunodeficiency Syndrome↗

PubMed1984

Human interleukin 2 gene is located on chromosome 4.

The interleukin-2 (IL2) gene is assigned to human chromosome 4. A synthetic oligonucleotide representing bases 285 to 324 of the IL2 cDNA clone described by Taniguchi et al. [Nature (London) 302:305-310, 1983] was used as hybridization probe in Southern blots. Eco RI digests of DNA derived from 11 somatic mouse-human cell hybrid clones were used. The IL2 gene was localized to human chromosome 4 based on the observed combinations of segregating chromosomes and bands. Under the conditions of stringency utilized, a single 3.6 kilobase Eco RI fragment hybridized to the oligonucleotide. Molecular weight standards were provided by rehybridizing the blots with an actin cDNA clone, pAct 1, which identified actin gene Eco RI fragments of defined size.

Animals↗

PubMed1981

Properties of the avian viral protein p12.

The avian RNA tumour virus structural protein p12 was purified from avian myeloblastosis virus (AMV) by nucleic acid affinity chromatography to apparent homogeneity as judged from SDS--polyacrylamide gel electrophoresis. A filter binding assay was used for the identification of p12. High concentrations of p12 precipitated nucleic acids out of solution in the absence of MgCl2. Binding of p12 to single-stranded nucleic acids protected them from digestion with nucleases and resulted in a hyperchromic effect. These phenomena were reversible in the presence of salt. The affinity of p12 to nucleic acids was determined by competing for the binding of p12 to denatured radioactive DNA by various other nuclei acids. It was found that p12 bound preferentially to single-stranded nucleic acids and showed a higher affinity to poly(rI) than to poly(rC) and poly(rA). Purified RNA-dependent DNA polymerase activity from AMV was stimulated up to sixfold by p12, depending on the template. Solubilization of RNA in RNA--DNA hybrids by RNase H was inhibited in the presence of p12.

Avian Leukosis Virus↗

PubMed1979

The isolation of avian viral RNA and polypeptides.

From the same batch of virus, the four major avian viral structural proteins p27, p19, p15, and p12, the reverse transcriptase, the envelope glycoprotein gp85, and the high molecular weight 70 S RNA have been recovered. All proteins, except for gp85, have been purified by use of column chromatography procedures to apparent homogeneity as judged by sodium dodecyl sulfate-polyacrylamide gels and isoelectric focusing. A new isolation procedure for p12 by affinity column chromatography takes advantage of its nucleic acid binding properties. The recovery of nondenatured viral structural proteins is demonstrated by the proteolytic activity revealed by p15. The purified proteins were used for the production of monospecific antibodies. The 70 S RNA served as source for the isolation of 35 S RNA subunits.

Avian Leukosis Virus↗

PubMedDate not supplied

Cerebral venous sinus thrombosis in children with acute lymphoblastic leukemia carrying the MTHFR TT677 genotype and further prothrombotic risk factors.

BACKGROUND: The present study was designed to prospectively evaluate the role of prothrombotic risk factors in leukemic children treated according to the ALL-BFM 90/95 study protocols with respect to the onset of cerebral venous sinus thrombosis. PATIENTS: 317 consecutive leukemic children aged 6 months to 18 years were enrolled in this study. 288 of the 317 patients were available for thrombosis-free survival analysis. RESULTS: In 17 (5.9%) of these 288 patients cerebral venous sinus thrombosis occurred. The overall event-free survival of thrombosis in the central nervous system in patients with at least one prothrombotic defect (n = 12) was significantly reduced compared with patients without a prothrombotic defect (p < 0.0001). 15 patients showed acute clinical symptoms at onset of cerebral venous sinus thrombosis, two were asymptomatic. Three of the 17 patients affected (17.6%) died directly associated with the thrombotic event during induction therapy, the remaining 14 patients did not show prolonged clinical symptoms. CONCLUSIONS: Prothrombotic risk factors should be included in a screening program in ALL children treated according to the BFM study protocols. Further prospective studies are recommended to establish adequate prophylactic anticoagulant treatment during ALL (BFM) polychemotherapy.

Adolescent↗

PubMedDate not supplied

[Detection of translocation t(8;14)(q24;132) in pediatric Burkitt's lymphomas using "long distance" polymerase chain reaction: a new method for diagnosis of Burkitt's lymphomas].

The pediatric Non-Hodgkin's lymphomas are a heterogeneous group of malignancies of B- or T-cell origin. Approximately half of them are characterized as Burkitt's lymphomas. Typically, one of the reciprocal translocations t(8;14)(q24;q32), t(2;8)(p11;q24) or t(8;22)(q24;q11) is seen in the tumor cell, each involving the protooncogene c-myc on chromosome 8. Characteristically, in most patients the translocation occurs between the distal end of the long arm on chromosome 8 (c-myc) and chromosome 14 (immunoglobulin heavy chain locus, IgH). The breakpoint regions are distributed over a wide range of more than 10 Kb on chr. 8 and over several hundred Kb on chr. 14. With standard-PCR, fragments can only be amplified to a size of about 2 Kb. The development of PCR-applications to generate long products up to 20 Kb now allows a detection of these breakpoints. Several primer pairs from different regions of the IgH-gene and the c-myc-gene were tested in each patient. Until now, 20 patients with Burkitt's Lymphoma or B-ALL characterized by L3 morphology were examined. All patients were treated according the protocols of the NHL-BFM '90 or '95 study. In 11/20 patients, recombinations between chromosomes 8 and 14 could be detected with our primer pairs. In serial dilutions of DNA from malignant cells in DNA from healthy controls, sensitivities of one malignant cell in 2 x 10(4) normal cells could be obtained. This method will now allow us to characterize the involved breakpoints more exactly and to analyze patient samples (blood, bone marrow, aphereses products and residual tumors) during or after therapy for the existence of minimal residual tumor cells.

Adolescent↗

PubMedDate not supplied

[NHL-BFM 90 therapy study in treatment of malignant non-Hodgkin's lymphomas in children and adolescents. Part 1: Classification and allocation to strategic therapy groups. BIF study group].

One of the goals of the study NHL-BFM 90 was to investigate the distribution and prognosis of the different subtypes of Non-Hodgkin's Lymphoma (NHL) in children and adolescents according to histological, cytomorphological and immunological characteristics. From 4/1990 to 12/1992, 346 patients (pts) (84 females, 262 males) were enrolled (median age: 9.1 years; range: 0.8-17.9 years). Histology was available from 290 pts (84%), cytomorphology from 155 (44%), and immunophenotyping from 245 (70%). Cases with L1 oder L2 cytomorphology according to the French-American-British Classification were classified as lymphoblastic lymphoma and those with L3 cytomorphology as Burkitt-Type lymphoma or acute B-cell leukemia (B-ALL) if a histological classification was not available. By means of the combined analysis of all three diagnostic criterias the classification of the NHL according to the updated Kiel-classification was possible in 312 cases: 49% were classified as Burkitt-type-lymphoma (incl. B-ALL), 22% als lymphoblastic lymphoma, 10% as large cell anaplastic lymphoma (LCAL), 6% as centroblastic lymphoma, only few cases were classified as NHL of other subtypes, 3 pts (1%) suffered from low grade malignant lymphomas, and in 34 pts (10%) the NHL was not further classified. Patients were stratified according to NHL-subentities in 3 branches (Non-B-NHL, B-NHL, LCAL) of different treatment modalities. The estimated probability of a 3-year event free survival (pEFS) was 88 +/- 2% for the whole group (follow up 7 to 40 months, median 23 months) while pEFS of different subtypes was: lymphoblastic lymphoma: 91 +/- 4%; Burkitt-type-lymphoma/B-ALL: 90 +/- 2%; centroblastic lymphoma: 94 +/- 6%, LCAL: 88 +/- 6%. We conclude that the stratification of treatment modalities in study NHL-BFM 90 according to biological entities provided patients of different NHL-subtypes an equal chance to survive event free. The efficacy of the treatment strategy for rare subtypes, however, is not evaluable yet.

Adolescent↗