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Biomedical subjects

J Schultz

Publications and source records attributed to J Schultz.

At least 73 records · Page 4Linked to original sources
PubMed1997

Regulation of the human IgE receptor (Fc epsilonRII/CD23) by Epstein-Barr virus (EBV): Ku autoantigen binds specifically to an EBV-responsive enhancer of CD23.

An early and critical event in immortalization of human B cells by Epstein-Barr virus (EBV) is induction of CD23 expression. CD23 is constitutively expressed in all EBV-immortalized B cells and its expression is tightly linked with immortalization. We have previously shown that activation of CD23 by EBV occurs at the transcriptional level and is mediated, in part, by EBV-responsive enhancer elements in the region of the type a promoter. We have localized one EBV-responsive enhancer (designated EBVRE) to a 37 bp sequence in intron 1 of type a CD23 that contains a GC-rich sequence that binds nuclear protein(s) from EBV-positive but not EBV-negative cells with sequence specificity. This EBVRE-binding activity was enhanced by protein phosphorylation and did not react with antibodies to the ubiquitous GC box transcription factor, Sp1. We have now shown by protein purification with peptide sequencing and immunological reactivity that p70/p80 Ku autoantigen [the DNA-binding component of DNA-dependent protein kinase (DNA-PK)] binds to this EBVRE with high affinity and sequence specificity. Although Ku autoantigen is ubiquitously expressed, an EBV-specific DNA-protein complex that contains Ku was elicited from EBV-positive but not EBV-negative nuclear extracts. Furthermore, the formation of this EBV-specific DNA-Ku complex was dramatically enhanced by protein phosphorylation. Thus, we have identified EBVRE-binding activity that contains the Ku autoantigen, is DNA sequence specific and is present in EBV-positive but not EBV-negative nuclear extracts. The possible functional significance of the Ku autoantigen-EBVRE interaction is discussed in light of the role of DNA-PK in phosphorylation and activation of several transcription factors. We suggest that phosphorylation of the EBV-specific EBVRE-binding activity by DNA-PK may modulate its activity as a transcription factor.

Amino Acid Sequence↗
PubMed1997

Standards and practice guidelines as the foundation for clinical practice.

The structure and organization of health care delivery are in the midst of rapid change. Health care providers from a variety of disciplines are being challenged to define their practice and the expected patient outcomes resulting from their processes of care delivery. Standards and clinical practice guidelines are important tools for enhancing the quality of health care delivery and for documenting care. The article describes a process for developing standards and clinical practice guidelines and presents an organizational scheme for them. Based on recommendations from diverse national groups, a format for practice guidelines is presented, and a system for implementation and ongoing evaluation is recommended.

American Nurses' Association↗
PubMed1997

Superantigen-based immunotherapy: a phase I trial of PNU-214565, a monoclonal antibody-staphylococcal enterotoxin A recombinant fusion protein, in advanced pancreatic and colorectal cancer.

PURPOSE: To establish the maximum-tolerated dose (MTD) and define the toxicities of a single-dose infusion of PNU-214565, a recombinant Escherichia coli-derived fusion protein of Staphylococcal enterotoxin A (SEA) and the Fab-fragment of the C242 monoclonal antibody in patients with advanced colorectal and pancreatic carcinomas. To investigate the capability of PNU-214565 to induce a superantigen (SAg) response resulting in cytokine production and tumor regression. PATIENTS AND METHODS: Twenty-one patients (age range, 39 to 76 years; median, 64; 12 men, nine women; 18 colorectal, three pancreatic cancers) were treated with a single 3-hour infusion of PNU-214565, with doses ranging from 0.01 to 1.5 ng/kg. All patients had prior chemotherapy and a good performance status Eastern Cooperative Oncology Group [ECOG] performance status [PS] = 0 [n = 10]; PS = 1 [n = 11]), 10 had prior radiation, and 18 had prior surgery. RESULTS: Fever and hypotension were the most common toxicities. Fever of any grade occurred in 16 of 21 patients (76%): four of 21 (19%) with grade 2 and two of 21 (9.5%) with grade 3. Hypotension of any grade occurred in 13 of 21 (62%): four of 21 with grade 2 and one of 21 (5%) with grade 3. Interleukin-2 (IL-2) and tumor necrosis factor alpha (TNF alpha) induction correlated with toxicity. In the two patients with grade 3 fever, peak IL-2 and TNF alpha levels were 2.9 IU/mL and 165 pg/mL, and 8.3 IU/mL and 245 pg/mL, respectively. Transient, > or = 50% decreases in circulating monocytes were observed in 17 of 21 patients as early as 0.5 hours (median time, 2 hours) from the start of infusion. Decreases (mean 33%) in circulating lymphocytes were observed in seven of 21 patients. All three patients with grade 3 toxicity were treated at the 0.5-ng/kg dose. The significance of baseline anti-SEA, human antimouse antibody (HAMA), CA242-soluble antigen levels, and T-cell receptor variable beta region (TCR V beta) subsets and histocompatibility leukocyte antigen-DR (HLA-DR) genotypes was assessed as possible predictors of toxicity. All toxicities were transient and easily managed. No grade 3 toxicity occurred at the higher dose levels. CONCLUSION: PNU-214565, a SAg-based tumor targeted therapy, is safe when given as a single 3-hour infusion at doses up to 1.5 ng/kg. The MTD for a single dose was not determined. The safety of a repeated dose schedule is currently under investigation, beginning with doses determined to be safe in this trial.

Adult↗
PubMed1996

Mechanism and specificity of human alpha-1,3-fucosyltransferase V.

Human alpha-1,3-fucosyltransferase catalyzes the transfer of the L-fucose moiety from guanosine diphosphate-beta-L-fucose (GDP-Fuc) to acceptor sugars to form biologically important fucoglycoconjugates, including sialyl Lewis x (SLex). Evidence for a general base mechanism is supported by a pH-rate profile that revealed a catalytic residue with a pKa of 4.1. The characterized solvent kinetic isotope effect (Dv = 2.9, Dv/k = 2.1) in a proton inventory study indicates that only one-proton transfer is involved in the catalytic step leading to the formation of the transition state. Evidence for Mn2+ as an electrophilic catalyst was supported by the observation that the nonenzymatic transfer of L-fucose from GDP-Fuc to the hydroxyl group of water in the presence of 10 mM MnCl2 at 20 degrees C was accelerated from K(obs)= 3.5 x 10(-6) to 3.8 x 10(-5) min-1. Using the GDP-Fuc hydrolysis as the nonenzymatic rate, the enzymatic proficiency of FucT V, (Kcat/Ki,GDP-fuc. K(m),1.acNAc)/K(non), was estimated to be 1.2 x 10(10) M-1 with a transition-state affinity of 8.6 x 10(-11) M. The Km for Mn2+ was determined to be 6.1 mM, and alternative divalent metal cofactors were identified as Ca2+, Co2+, and Mg2+. Detailed kinetic characterization of the acceptor sugar specificity indicated that incorporation of hydrophobic functionality [e.g. -O-(CH2)5CO2CH3] to the reducing end of the acceptor sugar substantially decreased the K(m),acceptor by over 100-fold. The role of the nucleotide was investigated by studying the inhibition of nucleotides, including the guanosine series. The inhibitory potency trend (GTP approximately GDP > GMP > > guanosine) is consistent with bidentate chelation of Mn2+ by GDP-Fuc. The role of charge and distance in the synergistic inhibitory effect by the combination of GDP, an aza sugar, and the acceptor sugar was probed. A mechanism for fucosyl transfer incorporating these findings is proposed and discussed.

1-Deoxynojirimycin↗
PubMed1996

Structure of the WW domain of a kinase-associated protein complexed with a proline-rich peptide.

The WW domain is a new protein module with two highly conserved tryptophans that binds proline-rich peptide motifs in vitro. It is present in a number of signalling and regulatory proteins, often in several copies. Here we investigate the solution structure of the WW domain of human YAP65 (for Yes kinase-associated protein) in complex with proline-rich peptides containing the core motif PPxY. The structure of the domain with the bound peptide GTPPPPYTVG is a slightly curved, three-stranded, antiparallel beta-sheet. Two prolines pack against the first tryptophan, forming a hydrophobic buckle on the convex side of the sheet. The concave side has three exposed hydrophobic residues (tyrosine, tryptophan and leucine) which form the binding site for the ligand. A non-conserved isoleucine in the amino-terminal flanking region covers a hydrophobic patch and stabilizes the WW domain of human YAP65 in vitro. The structure of the WW domain differs from that of the SH3 domain and reveals a new design for a protein module that uses stacked aromatic surface residues to arrange a binding site for proline-rich peptides.

Adaptor Proteins, Signal Transducing↗
PubMed1996

The protein phosphatase 2C (PP2C) superfamily: detection of bacterial homologues.

A thorough sequence analysis of the various members of the eukaryotic protein serine/threonine phosphatase 2C (PP2C) family revealed the conservation of 11 motifs. These motifs could be identified in numerous other sequences, including fungal adenylate cyclases that are predicted to contain a functionally active PP2C domain, and a family of prokaryotic serine/threonine phosphatases including SpoIIE. Phylogenetic analysis of all the proteins indicates a widespread sequence family for which a considerable number of isoenzymes can be inferred.

Amino Acid Sequence↗
PubMed1996

Spatial heterogeneity of blood flow in the dog heart. I. Glucose uptake, free adenosine and oxidative/glycolytic enzyme activity.

The spatial heterogeneity of myocardial perfusion and metabolism was studied in 11 anaesthetized dogs under resting conditions. In each heart local myocardial blood flow was assessed using the tracer microsphere technique in 256 samples (mean mass: 83.1 mg) taken from the left anterior ventricular wall. In the same samples, the following biochemical parameters were determined: accumulation of [3H]-deoxyglucose (a measure of glucose uptake), free cytosolic adenosine (S-adenosylhomocysteine accumulation technique, a measure of tissue oxygenation and a possible mediator of blood flow regulation), and the specific activities of oxidative (citrate synthase, cytochrome-c-oxidase) and glycolytic (hexokinase, phosphoglycerate kinase) enzymes. Capillary density and mitochondrial and myofibril volume densities were determined by morphometry. Myocardial perfusion in each sample (average 0.77 ml min-1 g-1) varied between 0.1 and 2.5 times the mean (coefficient of variation 0.30+/-0.02). [3H]-deoxyglucose was deposited locally in proportion to perfusion. Samples showing low flow (<0.2 ml min-1 g-1) did not exhibit increased levels of cytosolic adenosine. The specific activities of the oxidative and glycolytic enzymes, however, were uniformly distributed between low and high flow areas. Furthermore, capillary density and mitochondrial and myofibril densities were similar in high and low flow regions. The results show firstly that local glucose metabolism in the heart occurs in proportion to local blood flow, suggesting that high flow regions have a higher than average metabolic rate. Secondly, regions of low flow are not compromized by critical oxygenation and most likely have a lower than average oxygen demand and finally, the homogeneous distribution of oxidative and glycolytic enzymes, as well as the homogeneous myocardial ultrastructure, suggest that areas with high and low blood flow under resting conditions may increase their metabolic rate to similar levels when required.

Adenosine↗
PubMed1996

Interactions of spermidine and methylspermidine with DNA studied by nuclear magnetic resonance self-diffusion measurements.

The NMR pulsed field gradient self-diffusion method has been used to study the self-diffusion of the polyamine spermidine and the polyamine analog methylspermidine (completely N-methylated spermidine). The self-diffusion coefficient, D, was measured in solutions of calf thymus DNA prepared from nucleosome core particles (with an average length of 120 base pairs) as a function of the concentration ratio of polyamine to DNA phosphate. A study of the self-diffusion quotient, D/Do (where Do is the diffusion coefficient for free polyamine, not associated with DNA), in additions of spermidine and methyl-spermidine to solutions of NaDNA/NaCl, gave almost identical results with complete association of polyamine to DNA in the initial part of the titrations, indicating similar affinities for DNA. A large influence on the measured self-diffusion coefficients was detected for methylspermidine in NaDNA solutions with different concentrations of NaCl, which shows a considerable salt effect on the polyamine-DNA association. No notable differences in D/Do for methylspermidine were observed in competitive titrations of solutions of Li- and NaDNA, indicating that sodium and lithium ions behave similarly in their interactions with DNA. In titration experiments of methylspermidine into MgDNA solution, the results showed that the polyamine association is less effective than in the case of NaDNA, because of competition from magnesium binding to DNA. Comparisons with calculations based on the electrostatic Poisson-Boltzmann cell model were performed. It is suggested that the interaction is primarily of electrostatic nature, with no binding to specific sites on the DNA molecule.

Animals↗
PubMed1996

Reduction of rat myocardial ischemia and reperfusion injury by sialyl Lewis x oligosaccharide and anti-rat P-selectin antibodies.

Polymorphonuclear leukocytes (PMN) are directly involved in development of ischemic myocardial injury. Adhesion of PMN to endothelial cells is an initial step that triggers a sequential process leading to acute inflammatory responses. Interaction between P-selectin and its oligosaccharide ligand, sialyl Lewis x (sLex), plays an important role in the early stage of the adhesion. To examine the role of P-selectin in various animal disease models especially in rats, we have cloned rat E- and P-selectin cDNAs and established monoclonal antibodies against these rat selectins. In this report, we describe the generation and characterization of anti-rat P-selectin antibodies (ARPs). These antibodies detect cell surface P-selectin on thrombin-stimulated rat platelets. More importantly, intravenous administration of ARP2-4 reduced infarction developed after 30 min of ischemia followed by 24 h of reperfusion in a rat myocardial injury model. In addition, similar protective effect was also observed by administration of a sLex-oligosaccharide. These results indicate that cell adhesion mediated via P-selectin is involved in the development of ischemia and reperfusion injury in rat heart.

Animals↗
PubMed1995

Signal transduction and growth control in yeast.

An understanding of how an extracellular stimulus causes changes in cell growth is emerging from the study of four signal transduction pathways in Saccharomyces cerevisiae: the pheromone-response, pseudohyphal differentiation, osmolarity-response, and protein kinase C activated pathways. Each of these pathways contains at its core a distinct mitogen-activated protein kinase cascade. Biochemical and molecular studies have determined the functional order of the kinases in the pheromone-response pathway and have suggested that they are organized into a complex by a protein scaffold. The cell surface sensor system for the osmolarity-response pathway has been identified. It shows striking similarity to bacterial two-component sensor-responder systems. Finally, components that integrate information from these pathways and communicate it to cell growth regulators have been revealed.

Glycerol↗
PubMed1994

Enhanced cytotoxicity of amyloid beta-peptide by a complement dependent mechanism.

Amyloid beta-peptide (A beta) has been shown to activate the classical complement pathway in vitro. Here, we demonstrate that this interaction is fully capable of killing cells and damaging cellular processes in mixed hippocampal cultures from embryonic day 18 rat fetuses. Lactic acid dehydrogenase (LDH) release and morphologic changes were used to evaluate toxicity.

Amyloid beta-Protein Precursor↗
PubMed1994

A mechanochemical study of MgDNA fibers in ethanol-water solutions.

Highly oriented calf-thymus MgDNA fibers, prepared by a wet spinning method, were studied with a simple mechanochemical set-up. The relative fiber length, L/Lo, was measured with the fibers submerged in ethanol-water solutions. In one type of experiment L/Lo was measured as a function of ethanol concentration at room temperature. No substantial decrease in L/Lo with increasing ethanol concentration was observed, indicating that MgDNA fibers stay in the B form even when the water activity is very low. For low ethanol concentrations the fiber structure is stable and does not dissolve even at very high water activities. In a second type of experiment, the heat-induced helix-coil transition was manifested by a marked contraction of the fibers. The transition temperature decreases linearly with increasing ethanol concentration between 52 and 68% ethanol. At higher ethanol concentrations the helix-coil transition temperature increases due to strong aggregation within the DNA fibers, and above 77% ethanol the fibers do not contract at all, not even at the upper temperature limit of the experiments, approximately 80 degrees C. This behavior is discussed with reference to dried DNA and the P form of DNA. The helix-coil transition temperature of the MgDNA fibers in 70% ethanol does not show any dependence on the MgCl2 concentration. It is shown that the Poisson-Boltzmann cylindrical cell model can account qualitatively for this lack of salt dependence.

Animals↗
PubMed1994

The yeast pheromone response pathway: new insights into signal transmission.

The yeast (Saccharomyces cerevisiae) pheromone response pathway is one of the best understood eukaryotic signal transduction pathways. Nonetheless, it is likely that components and regulators of the pathway remain to be identified. We have employed three approaches to learn about interactions among known pathway components and to identify new components. First, the two-hybrid system of Fields and Song revealed that STE5, a protein of unknown biochemical function, interacts with each member of the MAP kinase cascade. One interpretation of this finding is that STE5 facilitates interactions between members of the cascade and thereby makes signal transmission more efficient. Second, genetic studies have identified new gene functions that appear to be involved in pheromone response. One of these is homologous to RHO-GAP proteins, an observation that suggests that a RHO protein (members of the RAS super-family) is part of the response pathway. A second gene function, FAR3, appears to be required only for a specific facet of pheromone response, arrest of the mitotic cell division cycle in G1.

Adaptor Proteins, Signal Transducing↗
PubMed1993

Efficient enzymatic synthesis of the sialyl-Lewisx tetrasaccharide. A ligand for selectin-type adhesion molecules.

Sialyl-Lewisx (NeuAc alpha 2-->3Gal beta 1-->4[Fuc alpha 1-->3]GlcNAc] has been identified as a ligand for E-selectin, P-selectin and recently also for L-selectin. We have synthesized the sialyl-Lewisx tetrasaccharide by total enzymatic synthesis from N-acetyllactosamine using a placental alpha 2-->3-sialyltransferase specific for type-2 chain acceptors, followed by a cloned human alpha 1-->3-fucosyltransferase (FucTV, the 'plasma-type' enzyme). This procedure resulted in the tetrasaccharide in a 61% overall yield.

Amino Sugars↗