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Biomedical subjects

Q V Nguyen

Publications and source records attributed to Q V Nguyen.

At least 19 recordsLinked to original sources
PubMed2003

[Orthostatic proteinuria and compression of the left renal vein (nutcracker syndrome)].

INTRODUCTION: The pathogenic mechanism of orthostatic proteinuria has not yet been clearly established. OBSERVATION: In a tall, thin, 21 year-old man, isolated proteinuria was discovered during an urological control conducted one year after a bilateral orchidopexy following left testicular torsion. Proteinuria was orthostatic. Doppler examination of the kidney revealed an entrapment of the left renal vein (nutcracker phenomenon-NCP). COMMENTS: An NCP was diagnosed in a young patient presenting with orthostatic proteinuria. By provoking modifications in intraglomerular haemodynamics, the NCP may, in nearly half of the cases, be at the origin of orthostatic proteinuria. Doppler examination is the diagnostic method of choice in the screening for NCP.

Adult↗
PubMed2001

Sensitivity to meat protein intake and hyperoxaluria in idiopathic calcium stone formers.

BACKGROUND: High protein intake is an accepted risk factor for renal stone disease. Whether meat protein intake affects oxaluria, however, remains controversial in healthy subjects and in stone formers. This study was designed (1) to test the oxaluric response to a meat protein load in male recurrent idiopathic calcium stone formers (ICSFs) with and without mild metabolic hyperoxaluria (MMH and non-MMH, respectively), as well as in healthy controls, and (2) to seek for possible disturbed vitamin B(6) metabolism in MMH, in analogy with primary hyperoxaluria. METHODS: Twelve MMH, 8 non-MMH, and 13 healthy males were studied after five days on a high meat protein diet (HPD; 700 g meat/fish daily) following a run-in phase of five days on a moderate protein diet (MPD; 160 g meat/fish daily). In both diets, oxalate-rich nutrients were avoided, as well as sweeteners and vitamin C-containing medicines. Twenty-four-hour urinary excretion of oxalate was measured on the last day of each period, along with 4-pyridoxic acid (U(4PA)) and markers of protein intake, that is, urea, phosphate, uric acid, and sulfate. Serum pyridoxal 5' phosphate (S(P5P)) was measured after protein loading. RESULTS: Switching from MPD (0.97 +/- 0.18 g protein/kg/day) to HPD (2.26 +/- 0.38 g protein/kg/day) led to the expected rise in the urinary excretion rates of all markers of protein intake in all subjects. Concurrently, the mean urinary excretion of oxalate increased in ICSFs taken as a whole (+73 +/- 134 micromol/24 h, P = 0.024) as well as in the MMH subgroup (+100 +/- 144 micromol/24 h, P = 0.034) but not in controls (-17 +/- 63 micromol/24 h). In seven ICSFs (4 MMH and 3 non-MMH) but in none of the healthy controls (P = 0.016, chi square), an increment in oxaluria was observed and considered as significant based on the intra-assay coefficient of variation at our laboratory (8.5%). There was no difference in S(P5P)nd U(4PA)etween the groups after protein loading. CONCLUSION: Approximately one third of ICSFs with or without so-called MMH are sensitive to meat protein in terms of oxalate excretion, as opposed to healthy subjects. Mechanisms underlying this sensitivity to meat protein remain to be elucidated and do not seem to involve vitamin B(6) deficiency.

Adult↗
PubMed1999

A systematic review of the relationship between overjet size and traumatic dental injuries.

The aim of this study was to aggregate the risk of traumatic dental injury due to overjet using several published papers and performing a meta-analysis on the results. The 11 articles involved in this investigation were identified by a literature search of Medline (1966-1996) and Exerpta Medica (1985-1996) databases using predetermined keywords, and inclusion and exclusion criteria. In order to assess the quality of each paper, a methodological checklist for observational studies was developed resulting in a score between 0 and 100. The relative risk of overjet, compared with a reference, was expressed as an Odds Ratio (OR). For each study, the OR was computed using the data presented and, subsequently, these ORs were pooled across studies. The effect of confounders (i.e. age, gender), which could bias the relationship between overjet and dental injury was taken into account. Furthermore, the influence of quality of the study on the pooled OR was addressed. The average methodological score was 41. From the results, it can be concluded that children with an overjet larger than 3 mm are approximately twice as much at risk of injury to anterior teeth than children with an overjet smaller than 3 mm. The effect of overjet on the risk of dental injury is less for boys than for girls in the same overjet group. In addition, risk of injury of anterior teeth tends to increase with increasing overjet size. Furthermore, the pooled OR does not seem to be affected by the quality of the studies.

Adolescent↗
PubMed1998

Early human T cell activation events with engagement of surface MHC class II.

Major histocompatibility complex (MHC) class II are expressed on most activated human lymphocytes. They direct antigen presentation events in dendritic cells and B cells (collectively called antigen presenting cells), but the role for MHC class II in human T cells is not well understood. To understand the role of surface MHC class II and to identify the molecules involved in signaling, we have defined the early activation sequence in T cells when MHC class II are engaged by a specific antibody. Specifically, we have characterized the involvement of phosphotyrosine kinases, phospholipase C (PLC), and Ca2+ mobilization. With the engagement by either whole anti-class II antibody or its Fab fragments, the enzymatic activity of p56lck and ZAP-70 increased, but there was no increase in p59fyn activity. In addition, the intracellular free Ca2+ increased, which was due to enhanced influx and not to the mobilization of intracytoplasmic Ca2+. These events did not require cross-linking because they were not significantly augmented by the addition of antispecies antibody. The coimmunoprecipitation of tyrosine phosphorylated PLC-gamma1 with surface MHC class II suggested that PLC-gamma1 could be recruited to MHC class II after engagement. These results show the complexities of the early signals transduced by the engagement of surface MHC class II on T cells.

Antibodies, Monoclonal↗
PubMed1997

Brefeldin A-induced alterations in processing of MHC class II-Ii complex depend upon microtubular function.

The role of microtubules in the brefeldin A (BFA)-associated relocation of major histocompatibility complex (MHC) class II alphabeta chains (alphabeta) and the invariant chain (Ii) was characterized in Raji cells by the use of nocodazole (ND). BFA blocked the transport of alphabeta Ii proteins through the Golgi and redistributed them to the endoplasmic reticulum (ER) along with Golgi-resident enzymes. The result of the colocalization of processing enzymes and newly synthesized proteins was a downshift of alphabeta Ii molecular weight (MW) of 2 kDa, and their resistance to endoglycosidase H (endo H) after 6 hr of chase. ND by itself had no effect on the processing and transport of alphabeta to the cell surface. The addition of ND to BFA-treated cells downshifted alphabeta Ii by 4 kDa. Additionally, alphabeta Ii proteins remained sensitive to neuraminidase after 16 hr of chase. In vitro alpha-mannosidase treatment of immunoprecipitated alphabeta Ii generated a similar 4-kDa downshift of MW. Either 1-deoxymannojirimycin (DJN) or swainsonine (SWN) blocked the MW downshift caused by BFA + ND treatment. These observations indicated that in Raji cells, most of the BFA-associated relocations of cis-, medial Golgi proteins, and the addition of sialic acid from the trans-Golgi were microtubule-independent. The retrograde transport of the medial Golgi enzyme N-acetylglucosamine transferase, however, required microtubular function. Microtubule disrupters could affect BFA treatment of viral infections by further disrupting viral protein processing.

Biological Transport↗
PubMed1995

Structural analysis of invariant chain subsets as a function of their association with MHC class II chains.

Respective subsets of human invariant chain (Ii), as identified with antibodies to two different epitopes, were characterized as a function of their associations with major histocompatibility complex (MHC) class II alpha,beta chains and intracellular processing. E1 antiserum to Ii(183-193) and VIC-Y1 monoclonal antibody to an N-terminal determinant identified Ii(E1) and Ii(VIC) populations, respectively. Ii proteins comprise several species which have been defined with either genomic or post-translational processes: Ii itself; IpN and IpO, which represent the glycosylated forms on asparagine or threonine/serine, respectively; gamma 2 and gamma 3, which originate from an alternative initiation site for transcription; and p41, which has a 64-amino-acid insert which originated from an additional exon placed after the sixth exon of Ii. Immunoprecipitates of detergent-solubilized protein complexes from [35S]methionine-labeled Raji cells showed that Ii(E1) consisted of Ii, p41, IpN, and immature alpha chain, while Ii(VIC) consisted of Ii, processed Ii with N- and O-linked glycosylation (IpN,IpO), p41, and associated MHC class II alpha,beta chains. In the MHC class II-deficient P3HR-1 cells, Ii(E1) and Ii(VIC) were virtually identical. Ii(E1) was resistant to cathepsin B digestion while Ii(VIC) was sensitive. In pulse-chase radiolabeling experiments with brefeldin A (BFA)-treated cells, Ii(VIC) progressively became resistant to endoglycosidase H (endo H) and had a longer half-life than that in cells not treated with BFA, but Ii(E1) remained susceptible to endo H and its half-life was unaffected by BFA. Since BFA redistributes Golgi enzymes to the endoplasmic reticulum, this observation suggests that Ii(E1) is protected from processing enzymes while Ii(VIC) is not. These studies define association of Ii with MHC class II molecules when certain epitopes on Ii are exposed or not. These differences relate to intracellular transport of Ii and to its release for the binding of antigenic peptides.

Antibodies, Monoclonal↗
PubMed1993

Effects of brefeldin A on cleavage of invariant chain to p21 and p10 and the appearance of Ii-freed class II MHC dimers.

Intracellular cleavage of class II MHC-associated Ii to p21 and p10 and the appearance of Ii-freed alpha, beta dimers were concurrent events lasting from 1 to 6 hr after synthesis of alpha, beta, Ii trimers, possibly related to charging of foreign peptides to the class II MHC antigen-binding site. Sequential immunoprecipitations of pulse-chase radiolabeled cells were made four times with anti-Ii monoclonal antibody to remove Ii and alpha, beta, Ii trimers and then with anti-class II antibody to detect the time-dependent appearance of Ii-freed alpha, beta dimers. The cleavage of Ii to p21 and p10 was revealed in leupeptin-treated cells. Cell treatment with Brefeldin A (BFA) was associated with a decrease in Ii-freed alpha, beta dimers, with inhibition of leupeptin-revealed cleavage of Ii to p21 and p10, and with persistence of endoglycosidase H susceptibility of Ii and class II alpha, beta chains. We conclude that in untreated cells, cleavage and release of Ii from class II MHC alpha and beta chains occur after those complexes traverse a BFA-sensitive step in the Golgi apparatus.

Antigen-Presenting Cells↗
PubMed1993

Characterization of the invariant chain C-terminus (Glu183-Glu193) epitope which is obscured in processed Ii, MHC alpha,beta trimers.

The E1 serum was developed against invariant chain peptide Ii (183-193) in order to study the function of the Ii protein which associates with class II MHC alpha,beta chains from time of synthesis until cleavage and release, possibly regulating the binding of antigenic peptides. Subpopulations of Ii, Ii(VIC) and Ii(E1), respectively, were demonstrated by sequential immunodepletions and immunoprecipitations with: (1) VIC-Y1 monoclonal antibody to an N-terminal epitope of Ii, and (2) E1 rabbit antiserum to Ii(183-193). In 3 hr radiolabeled cells, VIC-Y1 recognized Ii, Ii and N- and O-linked glycosylation (IpN, IpO), p41 and co-precipitated class II alpha,beta chains, while E1 recognized Ii, IpN and immature Ii-alpha complex. In 15 min radiolabeled cells, each antibody recognized similar, immature Ii forms without alpha,beta. Urea denaturation of Ii(VIC) rendered the main Ii species but not IpO immunoprecipitable with E1. E1 recognized O-glycanase-treated Ii (VIC). We conclude that the Ii(183-193) epitope was obscured by interactions of Ii with class II alpha,beta chains and by the O-linked glycosylation of Thr187, which may in part regulate association of Ii to class II alpha and beta chains.

Antibody Specificity↗
PubMed1991

Antibody-dependent cell-mediated cytotoxicity directed by a human monoclonal antibody reactive with gp120 of HIV-1.

We used a human monoclonal antibody (MAb; 15e) to identify an antibody-dependent cell-mediated cytotoxicity (ADCC) epitope on HIV-1 gp120. 15e has been shown to recognize a conformation-dependent epitope on gp120 which is important in both CD4 binding and neutralizing of HIV-1 infection. 15e binds to gp120 of HIV-1IIIB but not HIV-1RF. Using a standard ADCC assay, 15e was found to mediate ADCC against cells infected with HIV-1IIIB but not HIV-1RF. 15e did not mediate ADCC against cells with recombinant gp120 bound to surface CD4, indicating that 15e does not mediate innocent bystander ADCC against uninfected CD4 cells. To better define the 15e epitope, we performed ADCC against target cells infected with a vaccinia vector which expresses processed HIV-1IIIB gp160 from which the third variable region was deleted (amino acids, 312-328). MAb 15e efficiently mediated ADCC against cells expressing this altered form of gp120, indicating that this region is not contributing to the conformational epitope defined by 15e. 15e defines an important epitope in the human immune response to HIV-1 infection. Antibodies with 15e-like activity may be useful in immunoprophylaxis or immunotherapy of HIV-1 infection.

Antibodies, Monoclonal↗
PubMed1990

Clinical and microbiological evaluation of a postdilutional hemofiltration system with in-line production of substitution fluid.

Safety and efficacy of a recently developed hemofiltration (HF) system with in-line production of substitution fluid (GHS-10; Gambro, Lund, Sweden) based on a sterilizing filtration of acetate buffered dialysate has been evaluated in 4 patients over a 6-month period. Two patients were prematurely excluded from the study: 1 because of acetate intolerance and the other because of kidney transplantation. Two patients completed the study (240 HF sessions). Treatment adequacy was maintained in the 2 medium term treated patients according to the usual clinical and biochemical criteria and a mean exchange volume of 100-105 liters/week (30-35 liters/session three times weekly). Urea kinetic modeling analysis performed over all HF cycles gave the following results: dialysis index (urea clearance.time-on HF/urea volume space) (KT/V) approximately 1-1.1, urea time averaged concentration (UREA TAC) approximately 15-20 mmol/l, and protein catabolic rate (PCR) approximately 1.1-1.2 g/kg/day. Rare clinical adverse symptoms observed during the course of sessions were attributed to acetate intolerance. Microbiological safety was confirmed in vivo by the absence of pyrogenic reactions after 240 HF sessions (approximately 7 m3 substitution fluid infused intravenously) and in vitro by the constant absence of bacteria and/or endotoxin content limulus amaebocyte lysate (LAL) sensibility threshold 10 pg/l within the infusate produced during the sham HF sessions. The fluid mass balance obtained with the GHS-10 monitor was excellent. The electrolyte composition as judged by Na variation remained in a range of 2-3%. GHS-10 used in this study for postdilutional HF confirms that a large quantity of intravenous quality fluid may be safely produced by ultrafiltration from dialysate. It also introduced a new dimension in biocompatibility of dialysis by demonstrating that sterile dialysate may be routinely produced and used for routine dialysis.

Adult↗
PubMed1989

Time course of intracellular associations, processing, and cleavages of Ii forms and class II major histocompatibility complex molecules.

To determine how changing forms of class II major histocompatibility complex proteins and associated Ii molecules in intracellular compartments of human B lymphocytes might regulate or catalyze antigen processing or presentation, we analyzed immunoprecipitates of such molecules from subcellular fractions of [35S]methionine pulse-chase-labeled, 3-day-activated B lymphocytes after homogenization and distribution in Percoll density gradients. Two-dimensional gel electrophoresis of immunoprecipitates of subcellular fractions demonstrated: 1) progressive sialic acid addition to class II major histocompatibility complex beta chains and Ii but not to gamma 2, gamma 2', gamma 3, gamma 3' (p35), or p41 and its satellites; 2) association of p35 and p41 with class II complexes at 30-60 min after pulse labeling; 3) cleavage of an immature form of Ii without sialic acid at 15-30 min after pulse labeling to a COOH-terminal, 25,000-dalton fragment, p25, with a 60-90-min half-life; 4) the presence of Ii-related p29 at only 30-min chase times; 5) an effect of chloroquine or monensin, at maximal nontoxic doses, to increase (a) the time for associations of p35 and p41 with class II complexes and (b) the half-life of p25, which was then formed from Ii at reduced levels. In addition, while the half-lives of class II alpha and beta chains and Ii were comparable within intracellular fractions of any one density, in intracellular fractions of intermediate densities the complexes appeared to be longer lived (much greater than 6 h) than in lighter fractions (2-3-h half-lives).

B-Lymphocytes↗
PubMed1989

Time-dependent cleavage of a high-mannose form of Ii to p25 in an intracellular compartment.

The cleavage of a high-mannose form of Ii to p25 was demonstrated in an intracellular compartment of B cells. Subcellular fractions of 72 hr-activated B cells, separated by Percoll density gradient centrifugation, were immunoprecipitated with anti-class II or anti-Ii serum and characterized for 5'-nucleotidase, acid phosphatase, and radiolabeled transferrin. The cleavage of p25 from Ii as a C-terminal fragment occurred from 20 to 60 min after synthesis in an intracellular compartment which was intermediate in density between lysosomal and plasma membrane fractions and coincided with the lighter to two internalized transferrin compartments. Chloroquine or monensin treatments, at maximal nontoxic doses, which block Golgi and lysosomal functions, did not seem to alter the cleavage of Ii to p25. p25 molecules were reduced to about 10,500 daltons by treatment with endoglycosidases F or H. We conclude that p25 was generated from a high mannose form of Ii in the endoplasmic reticulum or cis-Golgi. This finding could either implicate that site for class II MHC desetope charging with foreign peptides or reflect a mechanism for degradation of "excess" Ii molecules.

Chemical Phenomena↗
PubMed1989

Inhibition by leupeptin and antipain of the intracellular proteolysis of Ii.

Intracellular cleavage of Ii was evaluated in immunoprecipitates of radiolabeled Raji cells treated with protease inhibitors (leupeptin, antipain, chymostatin, and pepstatin) or blockers of endosomal function (chloroquine and monensin). Immunoprecipitates with anti-class II and anti-Ii(12-28) sera and VIC-Y1 MoAb revealed Ii cleavage products of 21,000 and 10,000 daltons (p21 and p10) only in leupeptin- and antipain-treated cells. Both p21 and p10 were judged to be N-terminal products because they were recognized with anti-Ii(12-28) and not with anti-Ii(183-193) or anti-Ii(192-211) sera. p10 might be derived from p21 because its intensity was increased in inverse proportion to p21 as a function of leupeptin or antipain concentration. p21, but not p10, was recognized by anti-class II antibody and thus might originate from class II-associated Ii. In pulse-chase studies, p21 and p10 appeared at 2 hr and later after Ii synthesis. p25, an Ii C-terminal fragment, was about 60% reduced by leupeptin or antipain. Intracellular proteolytic cleavage of class II-associated Ii appeared to follow two pathways leading either to N-terminal p21 and p10 or to C-terminal p25. Such cleavages might regulate or catalyze foreign antigen binding to class II.

Antibodies, Monoclonal↗
PubMed1989

Germicidal effectiveness of Dialox, a new stable peroxyacetic acid solution, in the re-use of high-flux dialysers.

In this study we evaluate the effectiveness of a newly available peroxyacetic acid solution (Dialox) as a disinfecting agent in the re-use of highly permeable dialysers. The germicidal properties of Dialox were tested in an in vitro trial on previously used haemodiafilters (HF80, Fresenius) highly contaminated with Pseudomonas aeruginosa, Mycobacterium smegmatis or sporulated Bacillus cereus. Complete freedom from bacterial contamination was observed 5 min after the reprocessing treatment on a Renatron reprocessing machine, using the currently marketed Dialox concentrate.

Acetates↗
PubMed1989

Intracellular synthesis of Epstein-Barr virus membrane antigen gp350/220. Inhibitory effect of monensin on its expression.

We have defined the intracellular expression and localization of gp350/220, one of the Epstein-Barr virus (EBV) induced membrane antigens, on 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and n-butyrate-treated P3HR-1 cells. 1B6 monoclonal antibody (mAb) immunoprecipitated gp350/220 from [35S]-methionine-labeled cells, as confirmed with other mAbs (2L10, 72A1, and C1), to the same membrane antigen. The appearance of gp350/220 was observed about 14 h after TPA and n-butyrate activation and reached a maximal level at about 48 h. 1B6 mAb membrane immunofluorescence-positive and cytoplasmic fluorescence-positive cells appeared progressively in cell populations at the same frequencies. Cytoplasmic immunofluorescent staining with 1B6 mAb demonstrated a paranuclear complex which was identical to a rhodamine-labeled wheat germ agglutinin-stained pattern which has been ascribed to the Golgi apparatus. We investigated the effect of monensin on gp350/220 expression and processing. Monensin at 10(-7) M significantly inhibited membrane antigen expression in the Golgi apparatus and on the cell surface, but had a negligible effect on synthesis of viral capsid antigen, early antigen, and viral DNA. The inhibition of gp350/220 with monensin was further characterized by the immunoprecipitation of gp350/220 with anti-MA-positive human sera and mAbs. Monensin treatment resulted in the accumulation of a 165-kD molecule which was judged to be a precursor of gp350/220. These results were consistent with the view that the Golgi apparatus plays an important role as a place of synthesis, processing, and maturation of gp350/220.

Antigens, Viral↗
PubMed1988

Proteolytic cleavage of Ii to p25.

The 25,000-Da protein that is seen in immunoprecipitates with antibodies to class II MHC molecules or to Ii was shown to be a C-terminal fragment of Ii. [35S]Methionine pulse-chase labeling of polyclonally activated B lymphocytes or lymphoblastoid cell lines demonstrated maximal appearance of p25 in Percoll-separated endosomal fractions at 20- to 40-min chase times (studies in progress). This finding was consistent with the view that proteolysis of Ii to p25 and its release might catalyze the binding of digested foreign peptides to class II molecules and/or govern release of such charged complexes to traffic to the cell surface. We examined the structural relationship of p25 to Ii and the basis for cleavage of a relatively restricted site just external to the transmembranal segment. [35S]Methionine-labeled Ii and associated molecules were immunoprecipitated with a mAb to native Ii and then denatured, resolubilized, and subjected to a second immunoprecipitation with various antibodies. Two antisera to C-terminal peptides of Ii (183 to 193 and 192 to 211), but not antibodies to an N-terminal peptide (12 to 28), did immunoprecipitate p25. The three antibodies to C-terminal and N-terminal peptides all immunoprecipitated denatured Ii proteins. The mAb to Ii immunoprecipitated [35S]methionine-labeled p25 but not [35S]cysteine-labeled p25. This finding was consistent with loss of a portion of Ii containing the only cysteine in Ii, Cys28. Digestion of class II MHC Ag-Ii complexes with various proteases yielded proteins migrating at and near p25 in two-dimensional electrophoretic gels. Upon increasing the duration of protease digestion, the 25,000-Da fragments were relatively resistant to further digestion. This observation was consistent with the presence of secondary structures (domains) leaving a relatively protease-sensitive (Ig hinge-like) region in Ii near its insertion into the membrane.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1988

Inhibition of Epstein-Barr virus (EBV) release from P3HR-1 and B95-8 cell lines by monoclonal antibodies to EBV membrane antigen gp350/220.

Antibody-mediated inhibition of Epstein-Barr virus (EBV) release from the EBV-productive cell lines P3HR-1 and B95-8 was probed with two monoclonal antibodies (MAbs), 72A1 and 2L10, which immunoprecipitated the same EBV membrane antigen (MA) gp350/220 found with the 1B6 MAb with which inhibition of EBV release from P3HR-1 cells was first described. These three MAbs were not equivalent in either MA reactivities or functional effects, reflecting the variable expression of different epitopes of gp350/220. 1B6 recognized MA on P3HR-1 cells, which expressed predominately the gp220 form of MA. 1B6 did not recognize (or barely recognized) a determinant on B95-8 cells. MAbs 2L10 and 72A1 reacted as well with B95-8 cells as they did with P3HR-1 cells. MAbs 1B6 and 2L10 neutralized neither P3HR-1 nor B95-8 virus, but 72A1 neutralized both viruses. MAbs 1B6 and 72A1 inhibited P3HR-1 virus release, as measured by the assay for infectious virus and by DNA hybridization analysis of released virus, but 2L10 had no such activity. 72A1 (but not 1B6) inhibited release of EBV from B95-8 cells. These experiments pointed to the presence of three different epitopes on gp350/220, identified with the respective MAbs and having varying involvement in virus neutralization and virus release inhibition.

Antibodies, Viral↗