PubMed Health⌕ Search

Biomedical subjects

C Roifman

Publications and source records attributed to C Roifman.

At least 19 recordsLinked to original sources
PubMed1998

Two novel mutations in exon 11 of the PAH gene (V1163del TG and P362T) associated with classic phenylketonuira and mild phenylketonuria. Mutations in brief no. 143. Online.

PKU is one of the commonest genetic disease in man, affecting 1/10,000 individuals. It presents a wide phenotypical spectrum, from classic PKU to moderate Hyperpheylalaninemia depending on the residual enzymatic activity. Two novel mutations 1163/1164delTG and P362T in exon 11 have been detected during the mutational screening of the PAH gene in 84 families. 1163/1164delTC can be confused with V388M if the mutational screening is performed with BsaAI restriction enzyme, this mutation in heterozigosis presents a moderate phenotype. P362T mutation in heterozigosis with V388M shows a classical PKU phenotype. We report here two new mutations in exon 11 of the PAH gene (GenBank U49897), V1163delTG and P362T (using cDNA sequence), detected during the analysis of 57 PKU and 36 HPA patients belonging to 84 unrelated families detected under a neonatal screening program performed in Catalonia.

DNA Mutational Analysis↗
PubMed1995

Three new adenosine deaminase mutations that define a splicing enhancer and cause severe and partial phenotypes: implications for evolution of a CpG hotspot and expression of a transduced ADA cDNA.

We report three novel adenosine deaminase (ADA) mutations with interesting implications. A Somali child with severe combined immunodeficiency disease (SCID) had reduced ADA mRNA in T cells and was homozygous for the nonsense mutation Q3X. Unexpectedly, her healthy father was a compound ADA heterozygote whose second allele carried a 'partial' mutation, R142Q, due to a G-->A transition of a CpG dinucleotide. A C-->T transition of the same CpG produced a nonsense mutation, R142X, in two homozygous Canadian Mennonite infants with SCID. The severe and healthy phenotypes associated with R142X and R142Q, the high frequency of 'partial' ADA mutations arising from CpGs in healthy individuals of African descent and the presence of CAA (glutamine) at codon 142 in murine ADA, suggest selection for replacement of this CpG hotspot by CpA during ADA evolution. R142X, located within a purine-rich segment at nt 62/116 of exon 5, caused skipping of the exon, possibly by disrupting a splicing enhancer. Absence of exon 5 in T cell ADA mRNA and low ADA activity in T cells and erythrocytes obtained at age 18-22 months from one of the Mennonite children, indicate limited expression of a normal ADA cDNA from retrovirally transduced CD34+ umbilical cord leukocytes infused shortly after birth in an attempt at stem cell gene therapy.

Adenosine Deaminase↗
PubMed1994

Envelope glycoproteins of HIV-1 interfere with T-cell-dependent B cell differentiation: role of CD4-MHC class II interaction in the effector phase of T cell help.

T-cell-dependent B cell differentiation involves two phases: an inductive phase of T cell activation followed by an effector phase, which involves stimulation of B cells by activated T cells. We have previously demonstrated that anti-CD3 mAb and antigen-induced T-cell-dependent B cell functions are inhibited by HIV-1 envelope glycoprotein, gp120, at the inductive phase of T-cell-dependent B cell response. In this study we have investigated whether gp120 also inhibits the effector phase of interactions involved in T-cell-dependent-B cell differentiation response. For these studies, CD4+ T cells were first activated with antigen or pokeweed mitogen, cultured with soluble HIV-gp120 or medium for 2 hr, and washed. Coculture of gp120-treated preactivated T cells with autologous B cells resulted in impairment of IgG secretion, but did not affect IgM secretion significantly. The IgG secretion was restored by the addition of PMA (activator of protein kinase C) or forskolin (activator of adenylate cyclase), but not by the addition of ionomycin (inducer of intracellular calcium) to the T plus B cell cultures. A similar pattern of Ig secretion (IgM, no IgG) was observed with B cells of a patient with bare lymphocyte syndrome, indicating a requirement for MHC class II molecule interaction with T cells. These studies suggest that the effector phase of T-B cell interactions are impaired by gp120, and that the mechanism involves a signal transducing event(s), which is dependent upon cyclic AMP and/or protein kinase C. Furthermore, these latter reactions occur subsequent to T-B cell contact-dependent interactions at the effector phase, which involve MHC class II molecules on B cells and CD4 molecules on T cells.

Antigen Presentation↗
PubMed1994

Localised pulmonary resection for bronchiectasis in hypogammaglobulinaemic patients.

BACKGROUND: Bronchiectasis and pulmonary infections are common in patients with hypogammaglobulinaemia. Despite intravenous gammaglobulin treatment and appropriate antibiotics, a subgroup of patients remains with persistent localised pulmonary infection in segments where bronchiectasis had developed before appropriate treatment. As such localised pulmonary suppuration (segmental or lobar) may serve as a focus for progression of bronchiectasis, surgical resection of the involved segments may be considered. The outcome of pulmonary resection in four such patients is reported. RESULTS: Surgery was well tolerated except for one postoperative empyema. Information on follow up is available from 3.5 to 5 years. All patients experienced considerable reduction of symptoms including cough, sputum production, antibiotic use, and hospital admissions. CONCLUSIONS: Surgical resection of localised bronchiectatic segments should be considered in patients with hypogammaglobulinaemia with persistent localised suppuration and symptoms refractory to medical treatment.

Adolescent↗
PubMed1991

Constitutive expression and role in growth regulation of interleukin-1 and multiple cytokine receptors in a biphenotypic leukemic cell line.

A cell line (B1) was established from the bone marrow of a patient with a relapse of acute leukemia characterized by a 4;11 chromosomal translocation and biphenotypic features of early B and myeloid lineages. Analysis of the growth requirements of this cell line showed density-dependent growth and secretion of an autostimulatory growth factor, suggesting an autocrine mechanism. Several lines of evidence implicate the participation of interleukin-1 (IL-1) in the autocrine growth regulation of B1 cells. These cells constitutively express the messenger RNA (mRNA) for IL-1 and IL-1 receptor and secrete IL-1; recombinant IL-1 stimulated the growth of colonies when cells were seeded at low density, and anti-IL-1 antibodies inhibited the growth of colonies with cells seeded at higher density. B1 cells do not express detectable levels of mRNA for any of the other cytokines tested, and other cytokines failed to support the growth of B1 cells at low density. In addition, B1 cells express multiple cytokine receptor genes, including the receptors for IL-6, IL-7, tumor necrosis factor and gamma-interferon. Addition of the respective cytokines to the B1 cells resulted in inhibition of the growth of leukemic cells in vitro. The multiplicity of growth-inhibitory cytokine receptors on this leukemic cell line might be due to its biphenotypic lineage and may suggest new therapeutic possibilities in controlling leukemic cell proliferation.

Acute Disease↗
PubMed1989

The diacylglycerol analogue, 1,2-sn-dioctanoylglycerol, induces an increase in cytosolic free Ca2+ and cytosolic acidification of T lymphocytes through a protein kinase C-independent process.

In this paper, we demonstrate that low concentrations (0.5-2.5 microM) of 1,2-sn-dioctanoylglycerol (DiC8), a potent diacylglycerol used in many previous studies to probe the role of protein kinase C (PKC) in cell activation, cause cytosolic alkalinization of human, mouse and pig T lymphocytes through PKC-mediated activation of the Na+/H+ antiport. However, at higher concentrations (greater than or equal to 12.5 microM), the effect on cytosolic pH (pHi) is reversed, resulting in a marked cytosolic acidification, followed by a gradual return of pHi to baseline values. DiC8 also induces marked changes in cytosolic free calcium concentrations ([Ca2+]i), initially by releasing calcium from intracellular stores, followed by a net transmembrane influx of calcium. The DiC8-induced cytosolic acidification, the resultant return to baseline pH and the increase in [Ca2+]i are independent of activation of PKC. Unlike many other agents which increase [Ca2+]i, DiC8 does not induce phosphatidylinositol hydrolysis with the resultant production of inositol phosphates. Other compounds known to activate PKC, including the closely related diacylglycerol analogues, 1,2-sn-dihexanoylglycerol and 1,2-sn-didecanoylglycerol, phorbol esters and mezerein, did not induce changes in [Ca2+]i or cytosolic acidification in T lymphocytes. Thus the action of DiC8 on intact lymphocytes is different from that of phorbol esters and other diacylglycerols, and is specific to the length of the acyl chains. Because changes in [Ca2+]i are often associated with cell proliferation and cell differentiation, some effects of DiC8 on intact cells may be a consequence of changes in [Ca2+]i.

Animals↗
PubMed1989

Physiologic activation of protein kinase C limits IL-2 secretion.

Interaction of Ag, antibodies against the T cell receptor complex, or mitogenic lectins with T lymphocytes induces hydrolysis of membrane phospholipids leading to the production of diacylglycerol (DAG). DAG then activates the Ca2+- and phospholipid-dependent phosphotransferase, protein kinase C (PKC). Increases in DAG concentrations are transient as is the increase in PKC activity. Phorbol esters, which induce potent, prolonged activation of PKC, augment many T lymphocyte responses, including cell proliferation and secretion of the T cell growth factor IL-2. Therefore, it has been suggested that activation of PKC is a positive regulatory signal in T lymphocytes. We have determined the consequences of transient stimulation of PKC, and of depletion of PKC, on early cell activation signals and on production of IL-2 by the murine lymphoma line LBRM 331A5. When this cell line is depleted of PKC overnight incubation in high concentrations of phorbol esters, lectin-induced IL-2 secretion is augmented. Similarly, mitogen-induced changes in [Ca2+]i and phosphoinositide metabolism were augmented in these cells. In contrast, a short preactivation of PKC abrogated these early transmembrane signaling events. This suggested that normal physiologic activation of PKC may limit cell activation and decrease IL-2 production. We compared the effects of phorbol esters and mezerein, which produce prolonged activation of PKC, with those of diacylglycerol analogs, which induce transient activation of PKC. At concentrations that give similar levels of PKC activation, phorbol esters and mezerein, but not DAG analogs, increased IL-2 secretion. This suggests that prolonged, nonphysiologic activation of PKC is required to augment IL-2 secretion. Therefore, physiologic activation of PKC may not augment T cell activation but instead may function to decrease cell activation and limit IL-2 secretion.

Animals↗
PubMed1987

Corticosteroids-salicylate interaction in a case of juvenile rheumatoid arthritis.

In an 11-year-old child with juvenile rheumatoid arthritis (JRA), the addition of prednisone caused a significant decrease in salicylate serum concentrations. A pharmacokinetic assessment suggested that these changes were not the result of altered compliance or impaired absorption of salicylate but rather an increase in salicylate clearance induced by the corticosteroid.

Arthritis, Juvenile↗
PubMed1987

The regulatory role of interleukin 2-responsive T lymphocytes on human marrow granulopoiesis.

The effect of recombinant interleukin 2 (IL2) on marrow CFU-C colony formation was evaluated to define the role for T lymphocytes in human marrow granulopoiesis. The colony-stimulating factor (CSA) used in our experiments was found to contain IL2. IL2 depletion from CSA resulted in a reduction in CFU-C colony proliferation. Addition of exogenous IL2 caused an increase in CFU-C colony numbers in a dose-dependent manner. This increase could be prevented by anti-Tac, a monoclonal antibody (MoAb) to the IL2 receptor. Moreover, anti-Tac in the absence of exogenous IL2 resulted in an overall decrease in colony numbers. Depletion of either adherent cells or T lymphocytes abolished the effect of IL2 and anti-Tac on colony growth. In the presence of IL2, re-addition of T lymphocytes to the T-depleted marrow or adherent cells to adherent cell-depleted marrow resulted in a significant increase in CFU-C colony numbers, whereas no significant effect was found when IL2-depleted CSA was used. Although T lymphocytes were not themselves essential for CFU-C colony growth, our studies indicate that IL2 and IL2-responsive T cells can regulate in vitro granulopoiesis.

Antibodies, Monoclonal↗
PubMed1986

The regulatory role of interleukin 2-responsive T lymphocytes on early and mature erythroid progenitor proliferation.

To analyze the role of T lymphocytes in human erythropoiesis, we evaluated the effect of recombinant interleukin 2 (IL 2) on marrow CFU-E and BFU-E colony formation in vitro. IL 2 resulted in an increase in CFU-E and BFU-E colony numbers in a dose-dependent manner. This increase could be prevented by anti-Tac, a monoclonal antibody to the IL 2 receptor. Moreover, anti-Tac on its own resulted in an overall decrease in colony numbers. Depletion of marrow adherent cells did not alter the effect of either IL 2 or anti-Tac on colony growth. Following the removal of marrow T lymphocytes, CFU-E and BFU-E colony formation proceeded normally; however, the effects of IL 2 and anti-Tac were markedly diminished. Readdition of T lymphocytes to the cultures restored the IL 2 effect. Although T lymphocytes were not themselves essential for in vitro erythropoiesis, our studies suggest that IL 2 and IL 2-responsive T cells can regulate both early and mature stages of erythroid differentiation.

Animals↗
PubMed1984

Sinus node dysfunction in a healthy pediatric population.

ECG recordings of 624 healthy children (age range 6 to 12 years) from a rural population were analyzed for evidence of sinus node dysfunction. Twelve children were found to have the disorder and they underwent further assessment in order to establish any etiological factors or anatomical abnormalities. All the children were asymptomatic and physical examination was completely normal. Standard ECG taken during 24-h monitoring demonstrated that the most common finding, seen in 10 of 12 patients, was that of sinus arrest. Second-degree sinoatrial exit block, Mobitz type I, occurred in four children and Mobitz type II was seen in three. Two of the children were found to have holosystolic mitral valve prolapse, which was in the normal frequency range for a population of healthy children. After a 2-year follow-up and reassessment, there was no change in the symptomatology, the ECG tracings or the physical findings of any of the children.

Arrhythmia, Sinus↗
PubMedDate not supplied

Modification in framework region I results in a decreased affinity of chimeric anti-TAG72 antibody.

A mouse/human chimeric B72.3P-1-6 antibody was produced by construction of a novel expression vector mpSV2neo-EP2-V-Crl containing the same gene fragments as the expression vector mpSV2neo-EP1-V-Crl (Xiang J., Roder J. and Hozunni N., submitted to Molec. Immun., 1991) except the promoter (P2) fragment in which the translation start codon ATG is retained. The expression vector was transfected into a heavy chain loss mutant cell line, B72.3M1. The translation of the chimeric heavy chain may start at the exogenous start codon ATG within the P2 fragment, which is 27 base pairs upstream of the endogenous start codon ATG in B72.3 heavy chain V region cDNA fragment, leading to an alteration in leader sequence cleavage sites and the formation of chimeric heavy chain with an elongation in the FR1 region. Chimeric B72.3P-1-6 antibody retained binding specificity to TAG72 antigen, but showed an eight-fold decrease in binding affinity to TAG72 compared with chimeric B72.3-1-3 antibody. This suggests that residues in FRI contribute to the correct folding of the antibody binding region of the B72.3 antibody.

Amino Acid Sequence↗