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At least 937 records · Page 52Linked to original sources
PubMed2005

Human T-lymphotropic virus type 1 mitochondrion-localizing protein p13II sensitizes Jurkat T cells to Ras-mediated apoptosis.

Human T-lymphotropic virus type 1 (HTLV-1) is the etiological agent of adult T-cell leukemia. In addition to typical retroviral structural and enzymatic gene products, HTLV-1 encodes unique regulatory and accessory proteins, including a singly spliced pX open reading frame II (ORF II) product, p13(II). We have demonstrated that proviral clones of HTLV-1 which are mutated in pX ORF II fail to obtain typical proviral loads and antibody responses in a rabbit animal model. p13(II) localizes to mitochondria and reduces cell growth and tumorigenicity in mice, but its function in human lymphocytes remains undetermined. For this study, we analyzed the functional properties of Jurkat T cells expressing p13(II), using both transient and stable expression vectors. Our data indicate that p13(II)-expressing Jurkat T cells are sensitive to caspase-dependent, ceramide- and FasL-induced apoptosis. p13(II)-expressing Jurkat T cells also exhibited reduced proliferation when cultured at a high density. Furthermore, preincubation of the p13(II)-expressing cells with a farnesyl transferase inhibitor, which blocks the posttranslational modification of Ras, markedly reduced FasL-induced apoptosis, indicating the participation of the Ras pathway in p13(II)'s influence on lymphocyte survival. Our data are the first to demonstrate that p13(II) alters Ras-mediated apoptosis in T lymphocytes, and they reveal a potential mechanism by which HTLV-1 alters lymphocyte proliferation.

Apoptosis↗
PubMedDate not supplied

Familial versus mass selection in small populations.

We used diffusion approximations and a Markov-chain approach to investigate the consequences of familial selection on the viability of small populations both in the short and in the long term. The outcome of familial selection was compared to the case of a random mating population under mass selection. In small populations, the higher effective size, associated with familial selection, resulted in higher fitness for slightly deleterious and/or highly recessive alleles. Conversely, because familial selection leads to a lower rate of directional selection, a lower fitness was observed for more detrimental genes that are not highly recessive, and with high population sizes. However, in the long term, genetic load was almost identical for both mass and familial selection for populations of up to 200 individuals. In terms of mean time to extinction, familial selection did not have any negative effect at least for small populations (N< or =50). Overall, familial selection could be proposed for use in management programs of small populations since it increases genetic variability and short-term viability without impairing the overall persistence times.

Family↗
PubMed2004

Human T lymphotropic virus type-1 p30II alters cellular gene expression to selectively enhance signaling pathways that activate T lymphocytes.

BACKGROUND: Human T-lymphotropic virus type-1 (HTLV-1) is a deltaretrovirus that causes adult T-cell leukemia/lymphoma and is implicated in a variety of lymphocyte-mediated disorders. HTLV-1 contains both regulatory and accessory genes in four pX open reading frames. pX ORF-II encodes two proteins, p13II and p30II, which are incompletely defined in the virus life cycle or HTLV-1 pathogenesis. Proviral clones of the virus with pX ORF-II mutations diminish the ability of the virus to maintain viral loads in vivo. Exogenous expression of p30II differentially modulates CREB and Tax-responsive element-mediated transcription through its interaction with CREB-binding protein/p300 and represses tax/rex RNA nuclear export. RESULTS: Herein, we further characterized the role of p30II in regulation of cellular gene expression, using stable p30II expression system employing lentiviral vectors to test cellular gene expression with Affymetrix U133A arrays, representing approximately 33,000 human genes. Reporter assays in Jurkat T cells and RT-PCR in Jurkat and primary CD4+ T-lymphocytes were used to confirm selected gene expression patterns. Our data reveals alterations of interrelated pathways of cell proliferation, T-cell signaling, apoptosis and cell cycle in p30II expressing Jurkat T cells. In all categories, p30II appeared to be an overall repressor of cellular gene expression, while selectively increasing the expression of certain key regulatory genes. CONCLUSIONS: We are the first to demonstrate that p30II, while repressing the expression of many genes, selectively activates key gene pathways involved in T-cell signaling/activation. Collectively, our data suggests that this complex retrovirus, associated with lymphoproliferative diseases, relies upon accessory gene products to modify cellular environment to promote clonal expansion of the virus genome and thus maintain proviral loads in vivo.

Apoptosis↗
PubMed2005

High level of hepatitis B virus DNA after HBeAg-to-anti-HBe seroconversion is related to coexistence of mutations in its precore and basal core promoter.

AIM: G1896A mutation in precore or A1762T/G1764A mutations in basal core promoter are suspected to be responsible for patients with detectable level of HBV DNA in serum after seroconversion from HBeAg to anti-HBe. However, G1896A variant has impaired, while A1762T/G1764A variant may have intact replication ability. They themselves or their coexistence status may play different roles in such meaningless seroconversion. For these reasons, the significances of these two types of mutations were comparatively investigated in this study. METHODS: One hundred and sixty-five sera with positive anti-HBe and HBV DNA were collected from different patients. Mutations of G1896A and A1762T/G1764A among these serum samples were detected using competitively differentiated PCR. HBV DNA was demonstrated using real-time quantitative PCR. RESULTS: G1896A and/or A1762T/G1764A mutations were detected in 89.1% (147/165) out of patients with detectable HBV DNA in serum after HBeAg-to-anti-HBe seroconversion. The positive rate of G1896A variants was significantly higher than that of A1762T/G1764A mutations (77.6% vs 50.3%, chi2 = 26.61, P<0.01). The coexistence positive rate of these two types of mutations was 38.8% (64/165). Coexistence mutations were found in 77.1% (64/83) out of sera with A1762T/G1764A mutations, and in 50.0% (64/128) out of sera with G1896A mutation. Compared with variants with G1896A mutation only, the coexistence mutations were predominant in patients with high level of serum HBV DNA, and related to higher total bilirubin, lower serum albumin and progressive liver diseases. CONCLUSION: The coexistence of G1896A mutation and A1762T/G1764A mutations is very common, and responsible for the major cases with high level of HBV DNA in serum and progressive liver diseases after HBeAg-to-anti-HBe seroconversion. This coexistence mutation variant may have higher pathogenicity and replication ability.

Adult↗
PubMed2002

Hemochromatosis and porphyria.

A 52-year-old man presented to his primary care physician with blisters and sores on the backs of his hands. Laboratory studies supported a diagnosis of porphyria cutanea tarda, complicated by the presence of both the C282Y and H63D mutations in the HFE gene, with susequent iron over-load. This case illustrates the need to understand the pathogenesis of porphyria cutanea tarda, particularly the role of excess iron in the overproduction of uroporphyrin. Iron, by catalyzing the formation of reactive oxygen species, can enhance uroporphyrin formation by increasing the rate at which uroporphyrinogen is oxidized to urophophyrin. Iron may also act indirectly to inhibit uroporphyrinogen decarboxylase activity by enhancing the formation of non-porphyrin products of porphyrinogen oxidation that are themselves direct inhibitors of the enzyme. Finally, iron can act to increase urophorphyrin production by inducing delta-aminolevulinic acid synthase, thus increasing the amount of delta-aminolevulinic acid, the precursor to uroporphyrinogen, present in the cell. After the diagnosis, the patient underwent an aggressive series of therapeutic phlebotomies to reduce iron levels, and gradually the cutaneous manifestations of porphyria cutanea tarda improved.

Diagnosis, Differential↗
PubMed2003

Individualized therapy for the treatment-experienced patient.

Treatment failure is still common in HIV-infected patients despite the use of multidrug antiretroviral therapy. In the absence of maximal suppression of viral replication during antiretroviral therapy, the selection for and accumulation of drug-resistant mutations is inevitable. This is reflected by a detectable viral load; in this setting, the therapy is changed in an attempt to better control viral replication. Strategies used when selecting salvage therapy include resistance testing to help guide the choice of regimen, exploiting pharmacokinetic interactions by boosting protease inhibitor trough levels, and counseling the patient on adherence. Salvage regimens should include as many new agents to which no or minimal resistance is anticipated as are available and an agent in a class that has not been previously used. The selection of salvage therapy remains complex and needs to be individualized.

Anti-HIV Agents↗
PubMed2003

Treatment modalities for hepatitis B viral infection and resistance to antiviral therapy.

The worldwide problem of hepatitis B viral infection has been the focus of a large number of investigations. In the last decade advances have been made in the understanding of the viral function as well as strategies to combat the virus. Lamivudine, Hepsera, and interferon-alpha therapies that are currently used in the clinic are not optimal because of the emergence of resistance in the former modality and/or adverse effects. There are several new nucleosides that are under development for treatment of HBV. With the combination of a number of treatment protocols, it should be possible to bring down the viral load to undetectable levels and minimize the risk of generating mutations that confer resistance to the therapeutic agent.

Antiviral Agents↗
PubMed1990

Cystinuria.

Cystinuria is an hereditary disorder of renal and intestinal transport characterized by the excessive urinary excretion of cystine, arginine, lysine, and ornithine. It is inherited as a common recessive gene with allelic mutations. Complementary studies of the plasma response to oral cystine loading, intestinal mucosal transport patterns, and urine cystine excretion allow separation of homozygous cystinuric subjects into three groups. In type I, the most common form, there is no active transport of cystine or dibasic amino acids across the mucosal gradient, and heterozygous subjects show normal urine cystine values. Type II is characterized by markedly reduced or absent intestinal transport of cystine. Heterozygotes for type II show significantly elevated urine cystine but less than is seen in homozygotes. In type III there is diminished, although demonstrable, intestinal absorption of cystine and dibasic amino acids. Urine cystine in heterozygotes is intermediate between types I and II. Urolithiasis with its attendant complications is the sole clinical manifestation of cystinuria and is due to the relative insolubility of cystine in the urine. The urolithiasis may become clinically manifest at any time from infancy through the ninth decade, although the mean age is the second to third decade. Clinical presentation is similar to that of other types of urolithiasis. Although cystinuria accounts for only 1% to 2% of all urolithiasis and 6% to 8% of urolithiasis in pediatric populations, repeated stone formation in affected patients often causes considerable morbidity. Cystine crystals in the urine are diagnostic but show up in only 19% to 26% of homozygous cystinuric patients. Sodium cyanide nitroprusside is a suitable screening test that should identify homozygous stone formers but will not detect all heterozygotes. A positive screening test should be followed by quantitation of urinary amino acids. A homozygous patient can be functionally defined as one who excretes 250 mg or more of cystine/g of creatinine in a 24-hour urine collection. Other causes of excess urinary cystine must be excluded. Medical therapy will be directed toward dissolution of existing calculi and prevention of new stone formation. Increasing urine volume by generous oral fluid intake is beneficial. Dietary sodium restriction has a favorable effect on urinary cystine excretion. Cystine solubility can be improved by urinary alkalinization and where necessary by the administration of thiol chelators, particularly D-penicillamine or mercaptopropionylglycine. Because these chelators have significant adverse effects, they should be reserved for patients who do not respond to a more conservative program. Patients with infected, symptomatic, or obstructing stones require surgical intervention.(ABSTRACT TRUNCATED AT 400 WORDS)

Biological Transport↗
PubMed1999

Persistence of autoreactive T cell drive is required to elicit anti-chromatin antibodies in a murine model of drug-induced lupus.

Long-term treatment with procainamide and numerous other medications is occasionally associated with the development of drug-induced lupus. We recently established a murine model for this syndrome by disrupting central T cell tolerance. Two intrathymic injections of procainamide-hydroxylamine (PAHA), a reactive metabolite of procainamide, into (C57BL/6 x DBA/2)F1 mice resulted in the appearance of chromatin-reactive T cells and anti-chromatin autoantibodies. The current study explores in this model the role of autoreactive T cells in autoantibody production and examines why autoantibodies after a single intrathymic drug injection were much more limited in isotype and specificity. Injection of as few as 5000 chromatin-reactive T cells into naive, syngeneic mice induced a rapid IgM anti-denatured DNA response, while injection of at least 100-fold greater number of activated T cells was required for induction of IgG anti-chromatin Abs, suggesting that small numbers of autoreactive T cells can be homeostatically controlled. Mice subjected to a single intrathymic PAHA injection after receiving splenic B cells from an intrathymic PAHA-injected syngeneic donor also developed anti-chromatin Abs, but adoptive transfer of similarly primed T cells or of B cells without intrathymic PAHA injection of the recipient failed to produce an anti-chromatin response. However, anti-chromatin Abs developed after a single intrathymic PAHA injection in Fas-deficient C57BL/6-lpr/lpr mice, suggesting that activation-induced cell death limited autoimmunity in normal mice. Taken together, these results imply that chromatin-reactive T cells produced by intrathymic PAHA created a B cell population primed to somatically mutate and Ig class switch when subjected to a heavy load or second wave of autoreactive T cells.

Adoptive Transfer↗
PubMed1978

[A new family with mutation of the structural gene of human ornithine carbamoyltransferase].

Studies of a child with hyperammonemia have demonstrated a deficiency in OCTase. The kinetic properties of the enzyme were studied and it could be shown that we have to deal with a new mutation which is different from the ones previously known. It is a mutation of the structural gene. The detection of a heterozygote is possible when the urinary orotic acid excretion is studied after a loading meal (2g of proteines per kilo of weight). A child with hyperammonaemia due to ornithine transcarbamylase deficiency is described. A new structural gene mutation is probable because the kinetic properties of the enzyme are different to previously described variants. The heterozygote could be detected by the measurement of the excretion of orotic acid in the urine following a protein load of 2 g/Kg.

Amino Acid Metabolism, Inborn Errors↗
PubMed2003

Tetrahydrobiopterin sensitivity in German patients with mild phenylalanine hydroxylase deficiency.

We report the results of tetrahydrobiopterin (BH4) loading tests in 10 German patients with mild phenylketonuria. A significant decline of phenylalanine values after application of BH4 was observed in all but one patients. Molecular genetic analyses revealed a range of different PAH gene mutations. Re-testing of one patient previously reported as non-responsive to BH4 loading showed a moderate response with a higher dose of BH4. Nevertheless, there appear to be kinetic differences in phenylalanine hydroxylation in patients with the same genotype. Non-responsiveness to 20 mg/kg BH4 was observed only in a single patient who was compound heterozygous for the novel mutation R176P (c.527G>C) and the common null-mutation P281L. In summary, our data are in line with recent reports indicating that BH4 sensitivity is a normal feature of most mild forms of PAH deficiency but may be influenced by other factors.

Administration, Oral↗
PubMed2003

Drug resistance mutations and outcome of second-line treatment in patients with first-line protease inhibitor failure on nelfinavir-containing HAART.

OBJECTIVES: To determine resistance mutations emerging in HIV-1-infected patients experiencing their first protease inhibitor (PI)-failure on nelfinavir-containing highly active antiretroviral therapy (HAART), and to assess virological response to rescue regimens. METHODS: Plasma HIV-1 RNA from 24 patients failing nelfinavir-containing HAART was sequenced. Failure was defined as two consecutive measurements of viral load > 400 HIV-1 RNA copies/mL. Patients with previous failure on other PIs were excluded. Data on response to second-line treatment was extracted from patient files. RESULTS: At failure primary protease mutations were found in 14 patients (58%). Ten patients had D30N (38%), five patients had L90M (19%), two patients had V82A/F (8%) and two patients had M46I/L (8%). Two patients had both D30N and L90M. Pronounced increases of secondary protease mutations were seen at codon 88 (Delta: 33%), codon 36 (Delta: 30%) and codon 71 (Delta: 17%). Of eight patients with N88D, seven also harboured D30N (P < 0.01). Polymorphisms at codon 63 were detected at baseline in all patients who developed primary resistance mutations at failure (P < 0.01). On rescue regimens, 78% achieved viral loads below limit of detection (BLD). The presence of primary protease mutations was not associated with a higher risk of failure on second-line treatment. CONCLUSION: In patients failing nelfinavir-containing HAART, D30N was detected frequently and L90M occasionally. A pronounced accumulation of the secondary protease mutations N88D, M36I, and A71V/T was found, and D30N was strongly associated with N88D. A high proportion of patients became undetectable on second-line treatment and the presence of primary resistance mutations did not negatively affect the outcome of rescue regimens.

Antiretroviral Therapy, Highly Active↗