Biomedical subjects

J R Strahler

Publications and source records attributed to J R Strahler.

34 records · Page 2Linked to original sources

PubMed1991

Expression of a novel nuclear protein in activated and in tat-I expressing T cells.

The intracellular events that occur in T lymphoid cells after activation or after infection with HIV-1 are not well defined. In the case of HIV-1 infection, it is unknown whether the tat-I gene, an essential gene for viral replication, affects host cell nuclear factors. Using two-dimensional PAGE, we have identified a novel nuclear protein, designated nuclear protein-28,000 (NP-28), which is induced in Jurkat T cells by stimulation with PMA and/or PHA or ionomycin. This nuclear protein has an apparent molecular mass of 28,000 Da and an isoelectric point of 4.6. Interestingly, Jurkat cells transfected with tat-I express higher levels of NP-28 constitutively, without added stimulation. Incubation of Jurkat cells expressing tat-I with PMA and/or PHA or ionomycin causes superinduction of NP-28. We have therefore identified a novel lymphoid nuclear protein induced by T cell activation that occurs in tat-I expressing cells in the absence of activating agents.

Genes, tat↗

PubMed1991

Temperature-dependent spot positional variability in two-dimensional polypeptide patterns.

The effect of temperature, at which isoelectric focusing with immobilized pH gradients is performed, on spot positions and pattern quality in two-dimensional (2-D) electrophoresis was examined. Increased temperatures revealed improved 2-D patterns with respect to sample entry, resolution, and background staining. Focusing at 20 degrees C was superior to focusing at 10 and 15 degrees C. Even at 30 degrees C, a pattern of well-resolved polypeptide spots with a minimum amount of horizontal streaking at the basic end was observed. A computer-based analysis showed that a substantial proportion of polypeptides assumed altered positions in the 2-D pattern in relation to temperature. Mobility shifts of polypeptides were more variable on the neutral part than on the acidic or basic end. The mobility shifts were not restricted to one direction for all the spots whose migration was altered. However, for any given spot, the direction was the same with subsequent increments of temperature. The results clearly demonstrate that a defined temperature for first-dimensional isoelectric focusing is a requirement for the reproducibility of 2-D electrophoresis. After elimination of the cathodic drift, a major source of variability in 2-D patterns, associated with carrier ampholytes, temperature control becomes a critical parameter.

Electrophoresis, Gel, Two-Dimensional↗

PubMed1991

High levels of p19/nm23 protein in neuroblastoma are associated with advanced stage disease and with N-myc gene amplification.

The gene encoding a novel protein designated nm23-H1, which was recently identified as identical to the A subunit of nucleotide diphosphate kinase from human erythrocytes, has been proposed to play a role in tumor metastasis suppression. We report that untreated neuroblastoma tumors contain a cellular polypeptide (Mr = 19,000) designated p19, identified in two-dimensional electrophoretic gels, which occurs at significantly higher levels (P = 0.0001) in primary tumors containing amplified N-myc gene. The partial amino acid sequence obtained for p19 is identical to the sequence of the human nm23-H1 protein. An antibody to the A subunit of erythrocyte nucleotide diphosphate kinase reacted exclusively with p19. In this study, significantly higher levels of p19/nm23 occurred in primary neuroblastoma tumors from patients with advanced stages (III and IV) relative to tumors from patients with limited stages (I and II) of the disease. Even among patients with a single copy of the N-myc gene, tumors from patients with stages III and IV had statistically significantly higher levels of p19/nm23 than tumors from patients with stages I and II. Our findings indicate that, in contrast to a proposed role for nm23-H1 as a tumor metastasis suppressor, increased p19/nm23 protein in neuroblastoma is correlated with features of the disease that are associated with aggressive tumors. Therefore, nm23-H1 may have distinct if not opposite roles in different tumors.

Amino Acid Sequence↗

PubMed1990

Identification of two related markers for common acute lymphoblastic leukemia as heat shock proteins.

By direct analysis of the polypeptide constituents of leukemic cells, we have previously detected several polypeptides that are restricted in their expression to acute lymphoblastic leukemia (ALL). In this study, we provide evidence that two polypeptides designated L2 and L4 are structurally related and represent novel markers for common ALL. Partial amino acid sequence analysis did not uncover differences between L2 and L4. The sequences obtained correspond to a previously cloned human gene designated hsp 27 that is expressed, following heat shock treatment, in a variety of cells. 32Pi incorporation studies indicate that L4 is an unphosphorylated form and L2 is a phosphorylated form of hsp27. The two forms were inducible by heat shock in leukemic and nonleukemic lymphoid cells. Thus, in acute leukemia, the common ALL subtype is uniquely characterized by the constitutive expression of a polypeptide that represents a major cellular phosphoprotein.

Amino Acid Sequence↗

PubMed1989

Molecular cloning of a novel human leukemia-associated gene. Evidence of conservation in animal species.

We have recently described an 18-kilodalton polypeptide (p18) that is present in much greater abundance in acute leukemic blast cells (myeloid and lymphoid) than in resting or proliferating nonleukemic lymphoid cells or chronic lymphoid and myeloid leukemic cells. In this report we describe the cloning of two different sized full-length cDNAs that code for p18. The two cDNAs differ in their 3'-noncoding regions as a result of alternative polyadenylation. Analysis of the complete nucleotide sequence and the corresponding amino acid sequence did not reveal significant homology to any previously described sequences. We show evidence that this gene is highly conserved in several animal species and low stringency hybridization studies suggest that the p18 gene may be a member of a family of partially homologous genes in the human genome.

Amino Acid Sequence↗

PubMed1989

Advances in two-dimensional electrophoresis.

New developments in the first dimension step of two-dimensional electrophoresis have expanded the utility of the technique in cell and molecular biology.

Cell Physiological Phenomena↗

PubMed1988

Identification of a polypeptide associated with the malignant phenotype in acute leukemia.

A novel polypeptide, designated p18, was detected in a variety of hematopoietic cells by two-dimensional polyacrylamide gel electrophoresis. Quantitative analysis of p18 indicated its occurrence in a substantially greater amount in acute leukemia relative to nonleukemic cells. The increased amount of p18 in leukemia could not be explained on the basis of specific lineage, differentiation stage, or cell proliferation and thus appears to be a part of the malignant phenotype of the leukemic cells.

Acute Disease↗

PubMed1988

Approach to stationary two-dimensional pattern: influence of focusing time and immobiline/carrier ampholytes concentrations.

Horizontal two-dimensional (2-D) electrophoresis with immobilized pH gradients (IPG) in the first dimension for buffer soluble proteins and for complex proteins solubilized in the presence of Nonidet P-40 (Görg et al., Electrophoresis 1987, 8, 45-51), has been extended to analyze basic proteins of yeast cells focused under non-equilibrium and equilibrium conditions. Transient state isoelectric focusing (IEF) in IPG gels revealed sample smearing and background staining, displaying horizontal streaks in the resultant 2-D patterns. Inclusion of 0.5% carrier ampholytes (CA) to the IPG gel (IPG-CA), resulted in the formation of many sharp protein bands after transient state IEF with resultant distinct spots in the 2-D patterns; however, resolution was poor and the gel contained heavy background staining. With prolonged focusing time, background staining disappeared and there was less difference in the final steady state IEF patterns obtained with IPG and IPG-CA. Reduction of the Immobiline concentration to one third the manufacturer's recommended amount did not improve IEF resolution with respect to streaking and background staining under either transient state or equilibrium conditions. In general, spot intensities were less on 2-D gels using diluted IPG gels than with "standard" IPG gels. Optimization of 2-D electrophoresis with IPGs in the first dimension was strongly related to IEF conditions. The use of IPG gels focused to equilibrium should not only improve inter-gel reproducibility and resolution but also the quality of the final 2-D patterns with respect to background staining and horizontal streaking.

Ampholyte Mixtures↗

PubMed1988

Effect of salt on the performance of immobilized pH gradient isoelectric focusing gels.

The effect of salt and buffer ions in the sample or in an immobilized pH gradient (IPG) on sample entry into the gel and on the final focused pattern are presented. During the initial phase of electrofocusing, ions present in the gel, either as counter ions to the immobilized charge groups of the IPG gel or added to the gel matrix during the rehydration process, are transported toward the electrodes. For ions present at a concentration exceeding approximately 1 mM the transport can be followed by the refractile line marking the trailing edge of an ion-containing zone. Gradual sample entry may be achieved by applying the sample at a site (near the anode or cathode) opposite to that from which the sharpest refractile line, marking the ion present in the highest concentration, approaches the sample. Additionally, lateral band spreading of the sample is avoided. Thus, sample applied at the cathode for IPG gels rehydrated with 1-2 mM Tris base, or at the anode for gels rehydrated with 1-2 mM acetic acid or sodium acetate, enters the gel matrix gradually without lateral band spreading. In contrast, sample applied at the anode, for Tris-containing gels, or at the cathode, for acetate-containing gels, enters rapidly in a sharp zone when the refractile line reaches the sample zone. This results in a high local protein concentration in the zone immediately behind the boundary with lateral band spreading.(ABSTRACT TRUNCATED AT 250 WORDS)

Gels↗

PubMed1988

Somatic mutation studies in human lymphoid cells: the detectability of quantitative genetic variants in two-dimensional gels.

The feasibility of detecting quantitative genetic variants based on a decrease in the integrated intensity of polypeptide spots in two-dimensional polyacrylamide gels of human lymphoblastoid cell clones was investigated. A battery of 65 spots on 115 gels was studied to determine the distribution of quantitative measures for spots where no mutation had occurred. The corresponding distribution for spots which have decreased integrated intensity as a result of a mutation at one of two alleles coding for the spot was investigated by quantitating spots for which mutations were known to have occurred. These two distributions allowed the estimation of the rates of false positive and false negative errors for any particular strategy aimed at detecting null mutations, and thus provides a basis for the design of efficient strategies. Our silver stained gels have sufficient reproducibility of spot integrated intensities so that, for situations in which the mutation rate is relatively high, it is practical to monitor a subset of spots for null variants using the same digitized images as are used to detect structural variants.

Clone Cells↗

PubMed1987

Identification and characterization of a human transthyretin variant.

An apparent Mr variant of plasma transthyretin (TTR), previously detected using 2-D PAGE, is the first reported occurrence of this type of human TTR variant. We characterized the variant TTR to determine the nature of this difference. Comparative tryptic peptide maps of variant and normal TTR and sequencing of peptides which differed indicated the variant contained a single amino acid substitution of valine for tyrosine at position 116. Because such a change requires two nucleotide substitutions, we postulate the variant arose through mutation in codon 116 of a heretofore unrecognized polymorphic or rare variant allele of TTR.

Amino Acid Sequence↗

PubMed1986

Detection of electrophoretically silent mutations by immobilized pH gradients.

The detection of neutral amino acid mutants, by isoelectric focusing in immobilized pH gradients (IPGs), is exemplified by the separation of hemoglobin (Hb) Beirut (126 beta Val----Ala) from Hb A in a shallow pH 7.2-7.6 IPG gradient with 2% Ampholine pH 6-8. The mechanism of these separations appears to involve minute alterations in the pK values of ionizable groups bordering the mutation site, which are in turn reflected in tiny alterations in the net surface charge, delta pI. The delta pI values are of the order of 0.01 to 0.001 pH units, outside the resolving limits of conventional isoelectric focusing, and correspond to changes of the order of 0.1-0.01 unit charge (a proton or an electron).

Amino Acids↗

PubMed1985

Peripheral blood erythroid progenitors from patients with sickle cell anemia: HPLC separation of hemoglobins and the effect of a HbF switching factor.

We describe the use of HPLC for the separation and quantitation of hemoglobin and globin chains. Utilization of this sensitive technique allows the analysis of hemoglobin and globin chains in the total accumulated and newly synthesized hemoglobin. Using this methodology, we have studied the effect of a previously described HbF factor in fetal calf serum on peripheral blood BFUe-derived erythroblasts from patients with sickle cell anemia. As in previous studies of peripheral blood BFUe-derived erythroblasts from hematologically normal adults, this HbF factor promoted the increased synthesis of HbF in the BFUe-derived erythroblasts from the sickle cell anemia patients.

Anemia, Sickle Cell↗

PubMed1983

Separation of transferrin types in human plasma by anion-exchange high-performance liquid chromatography.

An anion-exchange high-performance liquid chromatographic procedure was developed for the separation of transferrin in human plasma. The procedure allowed the four molecular forms of transferrin, which differ with respect to bound iron, to be separated from each other and from other plasma proteins. Transferrin variants, including B and D types, could also be identified using anion-exchange high-performance liquid chromatography. The approach followed for optimizing the separation of transferrin included identification of the peaks in the chromatogram by two-dimensional polyacrylamide gel electrophoresis. This approach could be extended to other proteins in plasma or biological fluids in order to optimize their separation.

Blood Proteins↗

PubMed1983

A silent, neutral substitution detected by reverse-phase high-performance liquid chromatography: hemoglobin Beirut.

A substitution of alanine for valine at position 126 in the beta-chain of hemoglobin was discovered in a hematologically normal adult male of Lebanese extraction. The variant beta-globin was initially observed and subsequently purified by reverse-phase high-performance liquid chromatography (HPLC). Reverse-phase HPLC was also used to isolate the variant tryptic peptide of beta-T13 that has alanine replacing valine at residue 126. The discovery of hemoglobin Beirut illustrates the usefulness of reverse-phase HPLC for the detection of neutral amino acid substitutions in proteins. The ability to detect neutral substitutions in undigested proteins is pertinent to the monitoring of genetic variation in human populations.

Adult↗

PubMed1982

Two distinct pancreatic amylase genes are active in YBR mice.

The genetic determinants of pancreatic amylase expression in YBR mice differ in two respects from those of other inbred strains. First, there are two nonallelic amylase isozymes present in YBR pancreas, while most mouse strains express a single pancreatic amylase protein. In addition, the in vivo rate of total pancreatic amylase synthesis is 50% of that in other strains. Both these traits are determined by genetic sites in the region of the Amy-2 locus on mouse chromosome 3. To determine the molecular basis for the presence of two isozymes in this strain, we have compared portions of their amino acid sequences. Two differences between isozymes A1 and B1 were identified among the 77 residues compared. This result demonstrates that two distinct amylase genes are expressed in YBR pancreas.

Amino Acid Sequence↗