Genetic differences in red cell osmotic fragility: analysis in allophenic mice

Mice of strain DBA/2J were found to produce red cells considerably more resistant to osmotic lysis than cells from C57BL/6J or the F1 hybrid between the two strains. Such strain-specific differences in osmotic fragility could be the result of genetically determined humoral or other systemic differences that indirectly influence red cell properties. Alternatively, this phenotypic variation might be an inherent property of the erythrocyte themselves and be directly controlled by their genotype. Analysis of red cells from allophenic (mosaic) mice of the strain composition C57BL/6J in equilibrium DBA/2J demonstrated that the latter possibility is the case. In such mice, erythrocytes of the DBA/2J genotype are relatively more resistant to osmotic lysis than are those of the C57BL/6J genotype; partial lysis of allophenic blood at intermediate salt concentrations results in marked enrichment for DBA/2J cells among the survivors. Future experiments designed to determine the mechanism underlying this difference can now focus on the properties of the red blood cells per se with the certainty that this property is inherent to the genotype of each cell.     

Purification and biologic characterization of plasma-derived megakaryocyte growth and development factor

The isolation and cloning of the ligand for the cytokine receptor, Mpl, have been recently described. In this report we present details of the purification of this novel cytokine (megakaryocyte growth and development factor [MGDF]) from aplastic canine plasma. Two forms of canine MGDF, with apparent molecular weights of 25 kD and 31 kD and sharing a common N-terminal amino acid sequence, were isolated. The sole contaminant detected in purified 25-kD or 31-kD MGDF was canine Ig. Canine MGDF is characterized as a human megakaryocyte colony- stimulating factor that acts synergistically with human recombinant stem cell factor but not interleukin-3. MGDF also appears to be physiologically regulated in response to platelet demand. In canine and murine models, serum levels of MGDF activity peak during the thrombocytopenic periods after irradiation, 5-fluorouracil, or antiplatelet antisera injections. These data indicate that the megakaryocyte-stimulating activity that accumulates in plasma in response to platelet losses is a novel cytokine that functions through an interaction with the Mpl cytokine receptor.     

胃黏膜保护的基础与临床研究进展

长期以来胃黏膜保护一直是基础和临床研究的重点与热点.近年来人们对胃黏膜保护的细胞和分子机制已有了全面深入的认识,发现具有胃黏膜细胞保护作用的物质有很多种,具有细胞保护作用的器官和组织也不仅仅限于胃黏膜,在胰腺、肝脏、肾脏、心脏和脑等都发现有类似现象.因此细胞保护概念的内涵和外延都有拓展.我们对三叶因子、氧自由基、幽门螺杆菌、酒精、非甾体类抗炎药及细胞因子等研究热点与胃黏膜保护相互作用的机制进行初步的探讨.     

Effects of an antiplatelet glycoprotein Ib antibody on hemostatic function in the guinea pig

Previous studies in the guinea pig model system have established a close structural homology between human and guinea pig glycoproteins Ib (GPIb) and IIb/IIIa (GPIIb/IIIa). Moreover, the murine monoclonal antibody (MoAb) PG-1, which recognizes GPIb in guinea pig platelets and megakaryocytes, exerted full inhibition on von Willebrand factor (vWF)- dependent platelet agglutination without inhibiting aggregation induced by ADP, collagen, or thrombin. The present research extends this animal model system to study of the effects on hemostatic function following the in vivo injection of MoAb PG-1 or its F(ab')2 fragments. A hind limb template bleeding time methodology was developed for use in guinea pigs. Normal bleeding time was determined to be 2.7 +/- 0.5 minutes (mean +/- SD), with an observed range of two to four minutes. Platelet counts in these same animals were 501 +/- 82 x 10(3)/microL. After intraperitoneal (IP) injection of busulfan, guinea pigs became increasingly thrombocytopenic. As long as the platelet count remained above approximately 150 x 10(3)/microL, the bleeding time was not more than five minutes; however, further decrease in the platelet count was accompanied by more marked prolongations of the bleeding time. For 14 to 72 hours after IP injection of 1.3 mg/kg intact PG-1 MoAb, a hemorrhagic state was produced with a bleeding time greater than 20 minutes. The platelet count concurrently decreased to approximately 50% of its baseline value but could not be further decreased either by raising the initial PG-1 dosage tenfold or by administering a second, equal dose 24 hours after the initial injection. This finding may reflect a heterogeneity of circulating platelets with respect to GPIb, to Fc receptors, or to an interaction between them. After IP injection of 0.63 to 2.5 mg/kg PG-1 F(ab')2 fragment, platelet counts did not decrease more than 21% below baseline levels in a 72-hour period, and bleeding times never increased by more than one minute over baseline values. Nevertheless, platelets obtained from animals 24 hours after injection of 2.5 mg/kg PG-1 F(ab')2 showed full inhibition of agglutination induced by ristocetin. The response of these platelets to aggregation by asialo-vWF was also severely inhibited as compared with control platelets. PG-1 F(ab')2 produced no effect on aggregation induced by ADP. These studies show that virtually complete functional block of the vWF receptor by F(ab')2 fragments of the anti-GPIb MoAb PG- 1 is not sufficient to produce a hemorrhagic state in the guinea pig animal model system.(ABSTRACT TRUNCATED AT 400 WORDS)     

Platelet-type von Willebrand's disease: characterization of a new bleeding disorder

An autosomally transmitted bleeding diathesis sharing some, but not all, features previously described in von Willebrand's disease (vWd) was studied in five patients representing three generations of a single family. Bleeding times in the upper normal range in conjunction with low-normal platelet counts, normal factor VIII coagulant activity and VIII-related antigen, decreased VIII-ristocetin cofactor activity, selective decrease of the higher molecule weight factor VIII/von Willebrand factor (VIII/vWF) multimers, and increased ristocetin- induced platelet agglutination at low ristocetin concentrations were characteristic. Binding of patient VIII/vWF to washed normal platelets was within normal limits, whereas binding of normal VIII/vWF to patient platelets was significantly increased (p less than 0.001 at 0.6 mg/ml ristocetin). This disorder accordingly appears to involve an intrinsic platelet abnormality affecting platelet-VIII/vWF interactions. It is proposed that the concept of vWD be broadened to include patients with this abnormality, which may appropriately be called "Platelet-type von Willebrand's disease."     

The expression of p53 protein in non-Hodgkin's lymphomas is not always dependent on p53 gene mutations

p53 overexpression has been found to be a fairly common feature in high grade lymphomas in the majority of tumoral cells. The results vary from series to series, from 25% to 33% of cases. To assess whether immunohistochemical positivity for p53 correlated with the presence of structural gene abnormalities, DNA from 16 non-Hodgkin's lymphomas with high and low p53 values was amplified and sequenced to determine the existence of point mutations in the highly conserved regions of the p53 gene. In the group of 8 cases containing high levels of protein, 3 cases showed missense point mutations at the codons mapping between exons 5 through 8. Of the 8 cases of tumors containing undetectable or low levels of p53 protein, 1 case presented a nonsense point mutation giving a stop codon. No missense mutations were detected in this group. The finding of p53 mutations in 4 of 16 cases confirms the presence of p53 gene mutations in high grade lymphomas distributed over different histologic groups. These include Burkitt's lymphoma, together with centroblastic, immunoblastic, and large cell lymphoma of mucosa origin. Nevertheless, the absence of mutations in 5 of the 8 cases that overexpressed p53 suggests that the nuclear or cytoplasmic stabilization of p53 protein could also depend on other factors. The absence of detectable levels of p53 protein cannot discount the existence of p53 mutations, as is shown by a case of Burkitt's lymphoma in which a nonsense mutation was detected. The impact of this range of p53 alterations on clinical course and treatment response of the patients deserves to be explored, in an attempt to differentiate the specific consequences of each one.     

New therapies in systemic idiopathic fibrosis

Medical treatment of systemic idiopathic fibrosis is first based on steroid therapy, of which efficacy is well known for nearly 75% of cases of retroperitoneal fibrosis, but less certain for the other localisations of the disease. Studies on the immuno-pathological mechanism of systemic fibrosis have led to immunosuppressive drug use, such as azathioprin, cyclophosphamide and methotrexate. Tamoxifen has been tried because of its efficacy on desmoid tumors and seems to be of great interest. Attention is focused on fibrosing cervicitis which may also be treated with immunosuppressive drugs.

Résumé

Le traitement médical des fibroses systémiques idiopathiques repose en première intention sur la corticothérapie. Son efficacité est certaine dans au moins les trois quarts des cas de fibrose rétropéritonéale, mais elle est plus aléatoire dans les autres localisations. La mise à jour progressive de leur mécanisme immunopathologique a suggéré l'utilisation de traitements immunosuppresseurs, comme l'aziothioprine, le cyclophosphamide et le méthotrexate. Le tamoxifène, utilisé par analogie avec son efficacité sur les tumeurs desmoïdes, pourrait être une alternative particulièrement intéressante à la corticothérapie.     

High frequency of somatic mutations in the VH genes expressed in prolymphocytic leukemia

Prolymphocytic leukemia (PLL) is a chronic lymphoproliferative disorder, characterized by prominent splenomegaly, prolymphocytes accounting for more than 55% of circulating lymphocytes, and short-term survival. To better characterize the nature of the cellular origin in this disease, we analyzed lg heavy chain variable region (VH) genes in eleven cases of de novo PLL Leukemic cells expressed a skewed repertoire characterized by predominant use of the V3 family members (73%), with preferential use of the V3-23 gene (50% of the VH3 genes). All sequences from expressed VH genes diverged from their putative germline counterpart, and in eight cases the divergence was greater than 5%. In seven cases, which expressed the V3-23 gene and VH4 family members, nucleotide substitutions could be confidently attributed to somatic mutations. The type and distribution of these mutations clearly indicated that in three cases the cells had been subjected to an antigen selection process. Taken together, these results suggest that B- PLL cells display a skewed repertoire of lg VH regions and probably represent, at least in some instances, expansion of postgerminal center cells that have undergone antigen driven selection.     

Cytokine-mediated regulation of transferrin synthesis in mouse macrophages and human T lymphocytes

Transferrin (Tf) plays an important role during immunologic activation by donating iron to activated lymphocytes. Therefore, synthesis by lymphomyeloid cells has been investigated. Mouse macrophages and macrophage cell lines synthesized Tf, with levels being markedly increased by gamma-interferon (gamma-IFN) and, to a lesser extent, by interleukin-1 beta (IL-1 beta), IL-6, and tumor necrosis factor alpha (TNF alpha). Tf was also produced by phytohemagglutinin-stimulated human T cells and two T-cell lines and was increased by IL-2. Even after appropriate activation, none was synthesized by human macrophages or monocytic cell lines or by mouse T cells, T-cell lines, or thymus cells. In both species, B-lineage cell lines were negative. Tf was also synthesised by macrophages from congenitally hypotransferrinemic mice and was responsive to gamma-IFN, but levels were lower than those from normal controls. Synthesis by human and murine hepatoma cells was increased by IL-6 but unaffected by IL-1, TNF alpha, or gamma-IFN. Iron decreased synthesis by hepatoma cells but had no effect on the lymphomyeloid cells. Tf mRNA levels paralleled protein synthesis, suggesting that regulation was pre-translational. Thus, Tf synthesis by lymphomyeloid cells is regulated differently from hepatic synthesis, which is consistent with the suggestion that Tf may act in a paracrine (mouse) or autocrine (human) manner on activated lymphocytes.