Quantitation of red cell-bound IgG by an enzyme-linked antiglobulin test in human immunodeficiency virus-infected persons

Anemia, thrombocytopenia, and neutropenia have been observed in patients with acquired immune deficiency syndrome (AIDS) and AIDS-related complex. To investigate whether red cells (RBCs) of patients with human immunodeficiency virus infection were coated with IgG and/or complement (C3), blood samples of 239 patients were tested. The prevalence of a positive direct antiglobulin test on RBCs was 16.7 percent. By use of an enzyme-linked antiglobulin test (ELAT) to measure more accurately the number of IgG molecules per RBC in a group of 67 patients, 30 of the 67 individuals were observed to have increased numbers (mean, 155) compared to normal controls and to patients with hypergammaglobulinemia due to multiple myeloma or chronic liver disease. Hemoglobin level was correlated with the number of IgG molecules per RBC (p = 0.008), but no correlation could be demonstrated between those numbers and serum immunoglobulin (p = 0.10) or circulating immune complexes (p = 0.38). Our results with ELAT suggest that some AIDS patients may have specific binding of IgG on the surface of their RBCs, rather than nonspecific uptake; further clinical correlations are necessary to confirm these findings.     

Human HL-60 myeloid leukemia cells transport dehydroascorbic acid via the glucose transporters and accumulate reduced ascorbic acid

The cellular accumulation of vitamin C, a substance critical to human physiology, is mediated by transporters located at the cell membrane, and is regulated in a cell-specific manner. Neoplastic cells may have special needs for vitamin C. Therefore, we investigated the transport of vitamin C in a human myeloid leukemia cell line (HL-60). The HL-60 cells lacked the capacity to transport the reduced form of vitamin C, ascorbic acid, but they showed a remarkable ability to transport the oxidized form of vitamin C, dehydroascorbic acid (DHA). Uptake- accumulation studies indicated that the HL-60 cells accumulated ascorbic acid when provided with DHA. Kinetic analysis showed the presence of two functional activities involved in the uptake of DHA, one with low affinity and one with high affinity. Cytochalasin B and phloretin, which inhibit the passage of glucose through the facilitative glucose transporters, also inhibited the transport of DHA by HL-60 cells. Transport of DHA was completed by D- but not L-hexoses, and was sensitive to D-hexose-dependent counter transport acceleration. These data support the concept that HL-60 myeloid leukemic cells transport DHA through the facilitative hexose transporters (glucose transporters) and accumulate the reduced form of ascorbic acid.     

Complete recovery of right intraventricular thrombus and pulmonary arteritis in Behcet's disease

We report on a patient who presented with sustained fever, weight loss, haemoptysis and elevated erythrocyte sedimentation rate. The diagnosis of Behcet's disease was based on recurrent oral and genital aphthae, pseudofolliculitis and a history of thrombophlebitis. A right intraventricular thrombus and bilateral pulmonary aneurysms were discovered. Their complete recovery was observed within 6 months after a combination of prednisone, azathioprine, colchicine and aspirin therapy was started.      

A gene for hereditary pancreatitis maps to chromosome 7q35

BACKGROUND & AIMS: Hereditary pancreatitis (HP) is an autosomal- dominant disorder with incomplete penetrance characterized by recurrent bouts of severe epigastric pain with onset usually at 5-10 years of age. A genetic linkage study was designed to identify the HP gene. METHODS: A 500-member pedigree was constructed from a U.S. kindred centered in eastern Kentucky and western Virginia. A genome-wide search strategy was employed using a 36-member subset of this family to determine the genetic locus for HP. Testing for linkage to microsatellite loci was performed at 20-cM intervals. RESULTS: Linkage was established between the HP phenotype and chromosome 7q in this subset of the family. Modeled as an autosomal dominant disorder with 80% penetrance, a maximal multipoint logarithm of the odds score of 4.3 was obtained using a four-point analysis consisting of markers D7S684, D7S661, D7S505, and the HP locus. Two microsatellite markers, D7S661 and D7S505, that correspond to the 7q35 region of chromosome 7 spanning a 6-cM region did not evidence obligate recombinations with HP. The centromeric and telomeric limits are defined by recombinations at D7S684 and D7S483, respectively, which generates a 19-cM locus for HP. Utilizing family members from the extended pedigree, a break in the high-risk haplotype between D7S684 and D7S661 was observed, which suggests it may be possible to exclude an additional 8 cM from the HP locus. A maximal pairwise logarithm of the odds score of 4.73 at a recombination fraction of theta at D7S684 was obtained with the addition of these extended family members. CONCLUSIONS: Linkage of HP to 7q35 represents a major advancement in our understanding of the genetic basis of this disorder. (Gastroenterology 1996 Jun;110(6):1975-80)     

The beta subunit of the interleukin-2 receptor mediates interleukin-2 induction of anti-CD3 redirected cytotoxic capability in large granular lymphocytes

The interleukin 2 (IL 2) receptor was studied in three cases of large granular lymphocyte (LGL) lymphocytosis. All cases were nonreactive with anti-Tac monoclonal antibody (MoAb; recognizing the p55 alpha subunit of the IL 2 receptor). Sodium dodecyl sulfate (SDS)/polyacrylamide gel electrophoretic analysis (PAGE) of cells to which radio-labeled rIL 2 had been chemically crosslinked revealed uniform expression of the p70/75 beta subunit of the IL 2 receptor in the absence of the alpha subunit. Stimulation of this receptor with 2 nmol/L rIL 2 for five days led to acquisition of anti-CD3 redirected cytotoxicity. This was accompanied by a fivefold to tenfold elevation in the activity of intracellular N-alpha-benzyloxycarbonyl-L-lysine thiobenzyl esterase, an LGL granule marker enzyme. These effects of IL 2 did not require induction of the Tac peptide.     

Efficient surface expression of platelet GPIIb-IIIa requires both subunits

Platelet membrane GPIIb-IIIa is a member of the integrin family of heterodimeric adhesion receptors. Processing and export of certain leukocyte and melanoma integrins is disrupted in cells lacking one subunit. We found that surface expression of GPIIb-IIIa, measured by fluorescent activated cell sorting or by surface labeling, required cotransfection of both subunits. In contrast, surface expression was not detected when the subunits were transfected individually. Immunoprecipitation of metabolically labeled transfected cells confirmed the presence of comparable levels of intracellular protein in all cases. When both subunits were transfected, post-translational cleavage of Pro-GPIIb to yield GPIIb heavy chain was also seen, while transfection with GPIIb alone resulted in coprecipitation of Pro-GPIIb with a second band that may be an endogenous beta subunit. Pro-GPIIb in these transfectants was not processed to yield GPIIb heavy chain. When transfected into COS cells alone, transiently expressed GPIIIa remained intracellular and did not appear to complex with any endogenous proteins. Thus, surface expression of processed GPIIb-IIIa depends on the presence of both subunits; the coordinate reduction of both subunits observed in some cases of Glanzmann's thrombasthenia may result from mutation affecting only one.     

Endogenous proteolysis of membrane-bound red cell cytochrome-b5 reductase in adults and newborns: its possible relevance to the generation of the soluble "methemoglobin reductase"

The problem of the low activity of so-called methemoglobin reductase in red cells from newborns was reinvestigated in view of our current knowledge of this enzyme, i.e., (1) its being cytochrome-b5 reductase and (2) its presence in two forms: soluble and membrane-bound. We found that red cells from cord blood and newborns exhibited a 50% decrease of soluble cytochrome-b5 reductase activity, whereas membrane-bound activity was in the adult range. Ghosts from these cells possessed diminished ability to solubilize membrane-bound cytochrome-b5 reductase in the course of in vitro auto-incubation. This autosolubilizing ability increased with age and reached adult level concomitantly with soluble cytochrome-b5 reductase activity at 6 mo. We conclude that the relative deficiency of soluble cytochrome-b5 reductase observed at birth is due to diminished post-translational processing of the membrane-bound enzyme during erythropoiesis of fetal cells. This processing is calcium-dependent related to calmodulin.     

Kinetics of factor VIII-von Willebrand factor association

The binding of factor VIII to von Willebrand factor (vWF) is essential for the protection of factor VIII against proteolytic degradation in plasma. We have characterized the binding kinetics of human factor VIII with vWF using a centrifugation binding assay. Purified or plasma vWF was immobilized with a monoclonal antibody (MoAb RU1) covalently linked to Sepharose (Pharmacia LKB Biotechnology, Uppsala, Sweden). Factor VIII was incubated with vWF-RU1-Sepharose and unbound factor VIII was separated from bound factor VIII by centrifugation. The amount of bound factor VIII was determined from the decrease of factor VIII activity in the supernatant. Factor VIII binding to vWF-RU1-Sepharose conformed to the Langmuir model for independent binding sites with a Kd of 0.46 +/- 0.12 nmol/L, and a stoichiometry of 1.3 factor VIII molecules per vWF monomer at saturation, suggesting that each vWF subunit contains a binding site for factor VIII. Competition experiments were performed with a recombinant vWF (deltaA2-rvWF), lacking residues 730 to 910 which contain the epitope for MoAB RU1. DeltaA2-rvWF effectively displaced previously bound factor VIII, confirming that factor VIII binding to vWF-RU1-Sepharose was reversible. To determine the association rate constant (k(on)) and the dissociation rate constant (k(off)), factor VIII was incubated with vWF-RU1-Sepharose for various time intervals. The observed association kinetics conformed to a simple bimolecular association reaction with k(on) = 5.9 +/- 1.9 x 10(6) M(-1) s(-1) and k(off) = 1.6 +/- 1.2 x 10(-3) s(-1) (mean +/- SD). Similar values were obtained from the dissociation kinetics measured after dilution of preformed factor VIII-vWF-RU1-Sepharose complexes. Identical rate constants were obtained for factor VIII binding to vWF from normal pooled plasma and to vWF from plasma of patients with hemophilia A. The kinetic parameters in this report allow estimation of the time needed for complex formation in vivo in healthy individuals and in patients with hemophilia A, in which monoclonally purified or recombinant factor VIII associates with endogenous vWF. Using the plasma concentration of vWF (50 nmol/L in monomers) and the obtained values for K(on) and K(off), the time needed to bind 50% of factor VIII is approximately 2 seconds.     

镁及镁合金在仿生体液中的腐蚀降解行为

目的:观察纯镁及镁锌系列合金在仿生体液中的腐蚀行为,分析其是否具有生物临床应用价值。方法:实验采用纯镁(99.9%)、镁锌锆(ZK60)、镁锌锆钇(Mg-5.6Zn-0.55Zr-0.9Y)3种合金材料,将试样分别放入仿生溶液中浸泡10d,仿生溶液恒温(37.0±0.5)℃。用BP211D电子天平测量了试样在仿生体液中的腐蚀失重,用LK98BII型电化学系统测量了试样在仿生体液中腐蚀时的Tafel曲线,同时观察仿生溶液pH值的变化结果:①在仿生体液中242h后,纯镁、镁锌锆和镁锌锆钇损失量分别为0.9%,3.1%和抗蚀性1.7%。②在实验条件下,腐蚀电流密度纯镁为2.03mA/mm2,镁锌锆为10.14mA/mm2,镁锌锆钇为4.42mA/mm2。③随着镁合金在仿生体液中浸泡时间延长,溶液的pH值增高,电势也随着pH值的增加而减小,镁及镁合金的腐蚀速率会降低。结论:①合金中杂质元素越少,耐腐蚀性能越好,选择纯镁或含Y的镁合金作为镁基生物材料的耐蚀性较好。②在镁锌合金中添加钇后其耐体液腐蚀性能得到了改善。     

Genetic control of the circulating concentration of transforming growth factor type beta1

The concentration of transforming growth factor beta (TGF-beta) in plasma has been correlated with the development of several diseases, including atherosclerosis and certain forms of cancer. However, the mechanisms that control the concentration of TGF-beta in plasma are poorly understood. In a study of 170 pairs of female twins (average age 57.7 years) we show that the concentration of active plus acid- activatable latent TGF-beta1 [(a+l) TGF-beta therefore is predominantly under genetic control (heritability estimate 0.54). Single strand conformation polymorphism (SSCP) mapping of the TGF-beta1 gene promoter has identified two single base substitution polymorphisms. The two polymorphisms (G-->A at position -800 bp and C-->T at position -509 bp) are in linkage disequilibrium (correlation coefficient Delta = 0.215, P < 0.01). The C-509T polymorphism is significantly associated with the plasma concentration of (a+l) TGF-beta1, explaining 8.2% of the additive genetic variance of (a+l) TGF-beta1 concentration. It is therefore possible that predisposition to atherosclerosis, bone diseases or various forms of cancer may be correlated with the presence of particular alleles at the TGFB1 locus.