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A Perl

Publications and source records attributed to A Perl.

At least 19 recordsLinked to original sources
PubMed2000

The three-dimensional structure of human transaldolase.

The crystal structure of human transaldolase has been determined to 2.45 A resolution. The enzyme folds into an alpha/beta barrel structure and is thus similar in structure to other class I aldolases. Structure-based sequence alignment of available sequences of the transaldolase subfamily reveals that eight active site residues are invariant in the whole subfamily. Other invariant residues are mainly involved in the formation of the hydrophobic core of the enzyme. Noteworthy is a hydrophobic cluster consisting of five invariant residues. Human transaldolase has been implicated as an autoantigen in multiple sclerosis and four immunodominant peptide segments are located at the surface of the enzyme, accessible to autoantibodies.

Amino Acid Sequence↗
PubMed2000

Human transaldolase-associated repetitive elements are transcribed by RNA polymerase III.

Repetitive elements flanked by exons 2 and 3 of the human transaldolase gene, thus termed transaldolase-associated repetitive elements, TARE, were identified in human DNA. Nonpolyadenylated TARE transcripts were detected by Northern blot analysis and cloned by reverse transcriptase-mediated polymerase chain reaction from human T lymphocytes. A dominant 1085-nucleotide long transcript, TARE-6, contained two adjacent Alu elements, a right monomer and a complete dimer, oriented opposite to the direction of transcription of the transaldolase gene. Reverse transcriptase-polymerase chain reaction and in vitro transcription analyses showed that transcription of TARE-6 proceeded in the orientation of the RNA pol III promoter of the Alu dimer and opposite to the orientation of the TAL-H gene. TAREs lacking RNA polymerase III promoter showed no transcriptional activity. In vitro transcription of TARE-6 was resistant to 1 microg/ml alpha-amanitin but sensitive to 100 microg/ml alpha-amanitin and tagetitoxin, suggesting involvement of RNA polymerase III. TAREs in both the transaldolase and HSAG-1 genomic loci were surrounded by TA target site duplications. Homologies between transaldolase and HSAG-1 break off internally at splice donor and acceptor sites. The results suggest RNA polymerase III-mediated transcription of TARE may be a source of repetitive elements, contributing to distinct genes and thus shaping the human genome.

Base Sequence↗
PubMed2000

Adequacy of a food composition database to estimate fat and fatty acid intake.

This work examined the adequacy of the only food composition database available in Croatia to estimate fat and fatty acid intake. A 7-day food record with 39 participants was carried out. In addition to Croatian food composition tables (FCT1), the Swedish food tables (FCT2) were used to convert food records into quantities of total fat and saturated, monounsaturated and polyunsaturated fatty acids, respectively. The subjects simultaneously collected duplicates of all consumed food. The chemical analysis of duplicates to determine total fat and fatty acids included extraction of fat, followed by methylation of fatty acids and GC analysis. According to the comparison of methods, FCT2 are a better predictor of fat and fatty acid intake than FCT1 because of their closer agreement with analysed values. The correlation coefficients imply that both food tables estimate most of these nutrients similarly to a reference method. However, food records combined with either of the food tables could not predict intake of polyunsaturated fatty acids by men. In order to improve applicability of FCT1 in dietary surveys concerned with fat and fatty acids, the next issue should include changes in respect to an identified systematic error, as well as a greater choice of food items and their varieties. Accuracy of food records based on FCT1 could further be increased with subjects giving details on recipe ingredients, analysis of missing foods, etc.

Adult↗
PubMed2000

Stimulation of the pentose phosphate pathway and glutathione levels by dehydroascorbate, the oxidized form of vitamin C.

Ascorbic acid, or vitamin C, generally functions as an antioxidant by directly reacting with reactive oxygen intermediates and has a vital role in defenses against oxidative stress. However, ascorbic acid also has pro-oxidant properties and may cause apoptosis of lymphoid and myeloid cells. The present study shows that dehydroascorbate, the oxidized form of vitamin C, stimulates the antioxidant defenses of cells, preferentially importing dehydroascorbate over ascorbate. While 200-800 microM vitamin C caused apoptosis of Jurkat and H9 human T lymphocytes, pretreatment with 200-1000 microM dehydroascorbate stimulated activity of pentose phosphate pathway enzymes glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and transaldolase, elevated intracellular glutathione levels, and inhibited H(2)O(2)-induced changes in mitochondrial transmembrane potential and cell death. A 3. 3-fold maximal glutathione elevation was observed after 48 h stimulation with 800 microM dehydroascorbate. In itself, dehydroascorbate did not affect cytosolic or mitochondrial reactive oxygen intermediate levels as monitored by flow cytometry using oxidation-sensitive fluorescent probes. The data reveal a novel mechanism for increasing glutathione levels through stimulation of the pentose phosphate pathway and identify dehydroascorbate as an antioxidant for cells susceptible to the pro-oxidant and proapoptotic properties of vitamin C.

Antioxidants↗
PubMed1999

Human transaldolase and cross-reactive viral epitopes identified by autoantibodies of multiple sclerosis patients.

Multiple sclerosis is mediated by an autoimmune process causing selective destruction of oligodendrocytes. Transaldolase, which is expressed in the brain selectively in oligodendrocytes, is a target of high affinity autoantibodies in serum and cerebrospinal fluid of multiple sclerosis patients. A three-dimensional model of human transaldolase was developed based on the crystal structure of the enzyme from Escherichia coli. To identify immunodominant epitopes, 33 peptides overlapping human transaldolase by 5 amino acids were synthesized. Ab 12484, raised against enzymatically active human transaldolase, recognized antigenic determinants corresponding to linear epitopes (residues 27-31 and 265-290) and alpha helices (residues 75-98 and 302-329). Four immunodominant peptides harboring charged amino acid residues with topographically exposed side chains were identified by sera from 13 multiple sclerosis patients with predetermined autoreactivity to transaldolase. Autoantibodies binding to the most prominent human transaldolase epitope, between residues 271 and 285, showed cross-reactivity with Epstein-Barr and herpes simplex virus type 1 capsid-derived peptides. Molecular mimicry between immunodominant autoepitopes and viral Ags may be a decisive factor in directing autoimmunity to transaldolase in multiple sclerosis patients.

Amino Acid Sequence↗
PubMed1999

Elevation of mitochondrial transmembrane potential and reactive oxygen intermediate levels are early events and occur independently from activation of caspases in Fas signaling.

Stimulation of the CD95/Fas/Apo-1 receptor leads to apoptosis through activation of the caspase family of cysteine proteases and disruption of the mitochondrial transmembrane potential (Deltapsim). We show that, in Jurkat human T cells and peripheral blood lymphocytes, Fas-induced apoptosis is preceded by 1) an increase in reactive oxygen intermediates (ROI) and 2) an elevation of Deltapsim. These events are followed by externalization of phosphatidylserine (PS), disruption of Deltapsim, and cell death. The caspase inhibitor peptides, DEVD-CHO, Z-VAD.fmk, and Boc-Asp.fmk, blocked Fas-induced PS externalization, disruption of Deltapsim, and cell death, suggesting that these events are sequelae of caspase activation. By contrast, in the presence of caspase inhibitors, ROI levels and Deltapsim of Fas-stimulated cells remained elevated. Because ROI levels and Deltapsim are regulated by the supply of reducing equivalents from the pentose phosphate pathway (PPP), we studied the impact of transaldolase (TAL), a key enzyme of the PPP, on Fas signaling. Overexpression of TAL accelerated Fas-induced mitochondrial ROI production, Deltapsim elevation, activation of caspase-8 and caspase-3, proteolysis of poly(A)DP-ribose polymerase, and PS externalization. Additionally, suppression of TAL diminished these activities. Therefore, by controlling the balance between mitochondrial ROI production and metabolic supply of reducing equivalents through the PPP, TAL regulates susceptibility to Fas-induced apoptosis. Early increases in ROI levels and Deltapsim as well as the dominant effect of TAL expression on activation of caspase-8/Fas-associated death domain-like IL-1beta-converting enzyme, the most upstream member of the caspase cascade, suggest a pivotal role for redox signaling at the initiation of Fas-mediated apoptosis.

Apoptosis↗
PubMed1999

Polymorphic genotypes of the HRES-1 human endogenous retrovirus locus correlate with systemic lupus erythematosus and autoreactivity.

Antinuclear autoantibodies are a hallmark of systemic lupus erythematosus (SLE). Autoantibodies to HRES-1/p28, a 28 000 M(r) nuclear protein, commonly occur in patients with SLE. HRES-1 is a single-copy endogenous retroviral element mapped to human Chromosome 1 at q42. A polymorphic Hin dIII site defines two different allelic forms of the genomic locus. The HRES-1/1 probe [5.5 kilobases (kb)] anneals to three polymorphic fragments and three genotypes can be differentiated: I, 5.5 kb fragment only; II, 3.7 kb and 1.8 kb fragments only; and III, all three polymorphic fragments. By cloning of the HRES-1 locus from homozygous type I and type II human DNA samples, the polymorphic Hin dIII site was identified as a G to C transition at position 653 of the long terminal repeat region. Family studies showed that Hin dIII genotypes of the HRES-1 locus are inherited in a Mendelian pattern. The relative frequency of genotype I with respect to genotype III was 3.1-fold lower in patients with SLE (14:40=0.35) in comparison to 100 ethnically matched control donors (47:43=1.09; P=0.0084). Frequency of genotype I vs genotype II alleles was lower in SLE (68/52) than in normal donors (137/63; P=0.033), suggesting that a genotype I allele of the HRES-1 locus may be protective against SLE. Western blot seroreactivity with recombinant HRES-1/p28 was noted in 4/14 (29%) of genotype I patients and 13/19 (68%) of genotype III patients (P<0.025). These data raise the possibility that the HRES-1 element or a gene in linkage disequilibrium with this genomic locus may influence autoimmunity in SLE.

Adolescent↗
PubMed1998

Adolescent acceptance of different foods by obesity status and by sex.

This work investigated possible differences in food preference between obese and normal-weight adolescents, as well as between female and male seventh-grade pupils (average age = 13.1 years). Survey of affinities for nine food groups was determined with a facial hedonic scale. The children were divided according to their BMI into normal-weight and obese group, respectively. In this sample of adolescents, we could not find any proof for the theory of increased preference for fattening foods by obese compared to normal-weight people. In fact, our normal-weight group showed greater liking of sweets, meat, and cereals than the obese group. Normal-weight boys also preferred meat and sweets more than normal-weight girls. We consider psychological and social factors (e.g., perception of ideal body shape or social stigmatism of obesity) as the most logical explanations for the observed differences. Further research should clarify whether food preference plays a significant role in the etiology of adolescent obesity.

Adolescent↗
PubMed1998

Molecular ordering in HIV-induced apoptosis. Oxidative stress, activation of caspases, and cell survival are regulated by transaldolase.

Dysregulated apoptosis may underlie the etiology of T cell depletion by human immunodeficiency virus type 1 (HIV-1). We show that HIV-induced apoptosis is preceded by an exponential increase in reactive oxygen intermediates (ROIs) produced in mitochondria. This leads to caspase-3 activation, phosphatidylserine (PS) externalization, and GSH depletion. Since mitochondrial ROI levels are regulated by the supply of NADPH from the pentose phosphate pathway (PPP), the effect of transaldolase (TAL), a key enzyme of PPP, was investigated. Jurkat and H9 human CD4+ T cells were transfected with TAL expression vectors oriented in the sense or antisense direction. TAL overexpression down-regulated glucose-6-phosphate dehydrogenase activities and GSH levels. Alternatively, decreased TAL expression up-regulated glucose-6-phosphate dehydrogenase activities and GSH levels. HIV-induced 1) mitochondrial ROI production, 2) caspase-3 activation, 3) proteolysis of poly(ADP-ribose) polymerase, and 4) PS externalization were accelerated in cells overexpressing TAL. In contrast, suppression of TAL abrogated these four activities. Thus, susceptibility to HIV-induced apoptosis can be regulated by TAL through controlling the balance between mitochondrial ROI production and the metabolic supply of reducing equivalents by the PPP. The dominant effect of TAL expression on oxidative stress, caspase activation, PS externalization, and cell death suggests that this balance plays a pivotal role in HIV-induced apoptosis.

Apoptosis↗
PubMed1997

The human transaldolase gene (TALDO1) is located on chromosome 11 at p15.4-p15.5.

Transaldolase (TAL) is a key enzyme of the pentose phosphate pathway, which is responsible for generation of reducing equivalents to protect cellular integrity from reactive oxygen intermediates. While exons 2 and 3 are highly repetitive, the complete TAL-H gene is mapped to a single genomic locus (TALDO1(2)) by several independent approaches. Southern blot hybridization of a 827-bp 3' EcoRI fragment of the TAL-H cDNA to human-mouse somatic cell hybrid DNA localized TALDO1 to the p13-->pter region of chromosome 11. Fluorescence in situ hybridization with a 15-kb genomic fragment harboring exons 1 and 2 mapped TALDO1 to 11p15.4-p15.5. A truncated and mutated segment of TAL-H exon 5 terminating with a poly(A) tail was identified in a pseudogene locus (TALDOP1) on chromosome 1. Reverse transcriptase-PCR studies of human-mouse somatic cell hybrids revealed the presence of the functional TAL-H gene on chromosome 11 and its absence on human chromosome 1. Mapping of radiation hybrids placed TALDO1 between markers WI-1421 and D11S922 on 11p15.

Base Sequence↗
PubMed1997

Comparative analysis of antibody and cell-mediated autoimmunity to transaldolase and myelin basic protein in patients with multiple sclerosis.

Antibody and T cell-mediated immune responses to oligodendroglial autoantigens transaldolase (TAL) and myelin basic protein (MBP) were examined in patients with multiple sclerosis (MS). Immunohistochemical studies of postmortem brain sections revealed decreased staining by MBP- and TAL-specific antibodies in MS plaques, indicating a concurrent loss of these antigens from demyelination sites. By Western blot high titer antibodies to human recombinant TAL were found in 29/94 sera and 16/23 cerebrospinal fluid samples from MS patients. Antibodies to MBP were undetectable in sera or cerebrospinal fluid of these MS patients. Proliferative responses to human recombinant TAL (stimulation index [SI] = 2.47+/-0.3) were significantly increased in comparison to MBP in 25 patients with MS (SI = 1.37+/-0.1; P < 0.01). After a 7-d stimulation of PBL, utilization of any of 24 different T cell receptor Vbeta gene segments in response to MBP was increased less than twofold in the two control donors and six MS patients investigated. In response to TAL-H, while skewing of individual Vbeta genes was also less than twofold in healthy controls, usage of specific Vbeta gene segments was differentially increased ranging from 2.5 to 65.9-fold in patients with MS. The results suggest that TAL may be a more potent immunogen than MBP in MS.

Adult↗
PubMed1997

Osteogenic sarcoma of the jaw. A clinicopathologic review of 12 patients.

OBJECTIVE: To review our experience with osteogenic sarcoma of the jaw. DATA SOURCE: The pathology and clinical files of the Mount Sinai Medical Center, New York, NY, were examined. STUDY SELECTION: For the past 6 years, 12 pathologically documented cases were identified. DATA EXTRACTION: Surgical resection margins, histological tumor grade and subtype, and treatment modality were reexamined with regard to effect on outcome. DATA SYNTHESIS: The mean age of occurrence was 32.6 years, ranging from 12 to 60 years. Male predominance was noted in both mandibular and maxillary tumors. Local recurrence occurred in 6 of 12 patients after 3 months to 5 years; 4 of these patients have either persistent disease or died of disease. In this recurrence group, only 2 patients remain disease free 7 and 12 years after initial diagnosis and 6.5 and 8 years after recurrence. CONCLUSIONS: This study is too small to draw statistically significant conclusions. However, the longest survivor in the group (disease free at 12 years) had a histologically low-grade mandibular tumor. We reiterate the findings in the literature, which agree that osteogenic sarcoma of the jaw is an aggressive disease. Patient prognosis may depend on the tumor grade and size on presentation, as well as the completeness of initial surgery as monitored by resection margins.

Adult↗
PubMed1996

Glutathione levels and sensitivity to apoptosis are regulated by changes in transaldolase expression.

Transaldolase (TAL) is a key enzyme of the reversible nonoxidative branch of the pentose phosphate pathway (PPP) that is responsible for the generation of NADPH to maintain glutathione at a reduced state (GSH) and, thus, to protect cellular integrity from reactive oxygen intermediates (ROIs). Formation of ROIs have been implicated in certain types of apoptotic cell death. To evaluate the role of TAL in this process, Jurkat human T cells were permanently transfected with TAL expression vectors oriented in the sense or antisense direction. Overexpression of TAL resulted in a decrease in glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities and NADPH and GSH levels and rendered these cells highly susceptible to apoptosis induced by serum deprivation, hydrogen peroxide, nitric oxide, tumor necrosis factor-alpha, and anti-Fas monoclonal antibody. In addition, reduced levels of TAL resulted in increased glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities and increased GSH levels with inhibition of apoptosis in all five model systems. The effect of TAL expression on susceptibility to apoptosis through regulating the PPP and GSH production is consistent with an involvement of ROIs in each pathway tested. Production of ROIs in Fas-mediated cell death was further substantiated by measurement of intracellular ROI production with oxidation-sensitive fluorescent probes, by the protective effects of GSH precursor, N-acetyl cysteine, free radical spin traps 5,5-dimethyl-1-pyrroline-1-oxide and 3,3,5,5-tetramethyl-1-pyrroline-1-oxide, the antioxidants desferrioxamine, nordihydroguaiaretic acid, and Amytal, and by the enhancing effects of GSH depletion with buthionine sulfoximine. The results provide definitive evidence that TAL has a role in regulating the balance between the two branches of PPP and its overall output as measured by GSH production and thus influences sensitivity to cell death signals.

Apoptosis↗
PubMed1996

Inhibition of the catalytic activity of human transaldolase by antibodies and site-directed mutagenesis.

Transaldolase is a key enzyme of the pentose phosphate pathway. While antibody (Ab) 169, directed against the N-terminal 139 residues of human transaldolase (TAL-H), had no effect on enzyme activity, Ab 12484 raised against full length and functional recombinant TAL-H inhibited catalytic activity. This tentatively mapped the catalytic site to the C-terminal 140-336 amino acid portion of TAL-H. Dihydroxyacetone transfer reactions catalyzed by transaldolase depend on Schiff base formation by a lysine residue. Replacement of lysine-142 by glutamine using site-directed mutagenesis resulted in a complete loss of enzyme activity, suggesting that lysine-142 is essential for the catalytic activity of TAL-H.

Amino Acid Sequence↗
PubMed1996

Lysine and threonine metabolism are subject to complex patterns of regulation in Arabidopsis.

To study the regulation of lysine and threonine metabolism in plants, we have transformed Arabidopsis thaliana with chimeric genes encoding the two bacterial enzymes dihydrodipicolinate synthase (DHPS) and aspartate kinase (AK). These bacterial enzymes are much less sensitive to feedback inhibition by lysine and threonine than their plant counterparts. Transgenic plants expressing the bacterial DHPS overproduced lysine, but lysine levels were quite variable within and between transgenic genotypes and there was no direct correlation between the levels of free lysine and the activity of DHPS. The most lysine-overproducing plants also exhibited abnormal phenotypes. However, these phenotypes were detected only at early stages of plant growth, while at later stages, new buds emerged that looked completely normal and set seeds. Wild-type plants exhibited relatively high levels of free threonine, suggesting that in Arabidopsis AK regulation may be more relaxed than in other plants. This was also supported by the fact that expression of the bacterial AK did not cause any dramatic elevation in this amino acid. Yet, the relaxed regulation of threonine synthesis in Arabidopsis was not simply due to a reduced sensitivity of the endogenous AK to feedback inhibition by lysine and threonine because growth of wild-type plants, but not of transgenic plants expressing the bacterial AK, was arrested in media containing these two amino acids. The present results, combined with previous studies from our laboratory, suggest that the regulation of lysine and threonine metabolism is highly variable among plant species and is subject to complex biochemical, physiological and environmental controls. The suitability of these transgenic Arabidopsis plants for molecular and genetic dissection of lysine and threonine metabolism is also discussed.

Arabidopsis↗
PubMed1996

Establishment of an Agrobacterium-mediated transformation system for grape (Vitis vinifera L.): the role of antioxidants during grape-Agrobacterium interactions.

Very short exposures of embryogenic calli of Vitis vinifera cv. Superior Seedless grape plants to diluted cultures of Agrobacterium resulted in plant tissue necrosis and subsequent cell death. Antibiotics used for Agrobacterium elimination or as plant selectable markers were not responsible for this necrotic response. Rather, cell death seemed to be oxygen-dependent and correlated with elevated levels of peroxides. Therefore, we studied the effects on necrosis of various combinations of antioxidants during and after grape-Agrobacterium cocultivation. The combination of polyvinylpolypyrrolidone and dithiothreitol was found to improve plant viability. Tissue necrosis was completely inhibited by these antioxidants while Agrobacterium virulence was not effected. These treatments enabled the recovery of stable transgenic grape plants resistant to hygromycin.

Antioxidants↗
PubMed1995

Antibody reactivity to the HRES-1 endogenous retroviral element identifies a subset of patients with systemic lupus erythematosus and overlap syndromes. Correlation with antinuclear antibodies and HLA class II alleles.

OBJECTIVE: To evaluate the correlation between the presence of antibodies to an endogenous retroviral element-encoded nuclear protein autoantigen, HRES-1, and the presence of other antinuclear antibodies and HLA class II alleles in patients with systemic lupus erythematosus (SLE) and overlap syndromes. METHODS: Antibody reactivities to native and recombinant proteins and synthetic peptides were assessed by counterimmunoelectrophoresis, enzyme-linked immunosorbent assay, and Western blotting. HLA class II alleles were determined by oligonucleotide typing. RESULTS: Forty-eight percent of the 153 patients with autoimmune disease, and 52% of the subgroup with SLE, had HRES-1 antibodies. In contrast, 3.6% of 111 normal donors, and none of 42 patients with the acquired immunodeficiency syndrome or 50 asymptomatic human immunodeficiency virus 1-infected patients, had HRES-1 antibodies. Chi-square analyses revealed a significant association between anti-HRES-1 and anti-RNP and an inverse correlation between HRES-1 and Ro/La autoantibodies in patients with SLE or overlap syndromes. Antigenic epitopes of HRES-1 and the retroviral gag-related region of the 70-kd protein component of U1 small nuclear RNP, which share 3 consecutive highly charged amino acids (Arg-Arg-Glu), an additional Arg, and functionally similar Arg/Lys residues, represent cross-reactive epitopes between the two proteins. Selective removal of HRES-1 antibodies from sera of HRES-1-seropositive/RNP-seropositive patients by absorption on recombinant HRES-1/glutathione-S-transferase-conjugated agarose beads had no effect on anti-RNP reactivities. A comparative multivariate analysis of HLA class II genes revealed a differential segregation of DQB1 alleles in HRES-1-seropositive versus HRES-1-seronegative patients (P = 0.04). While a relative increase of DQB1*0402 among HRES-1-seropositive patients was noted across ethnic groups (P = 0.02), a decrease of DQB1*0201 and DQB1*0301 was found in white HRES-1-seropositive patients (P = 0.04). CONCLUSION: Autoantibodies to HRES-1 are detectable in a distinct subset of patients with autoimmune disease, primarily in those who do not have antibodies to Ro and La. Anti-HRES-1 and anti-RNP reactivities are mediated by cross-reactive but separate antibody molecules. HLA-DQB genes, rather than HLA-DRB or DQA genes, may have a more significant influence on generation of these antinuclear autoantibodies.

Alleles↗