All seven of a set of CD34 monoclonal antibodies that recognize epitopes on an approximately 110 Kd glycoprotein on human hemopoietic progenitor cells also bind to vascular endothelium. Capillaries of most tissues are CD34 positive, as are umbilical artery and, to a lesser extent, vein, but the endothelium of most large vessels and the endothelium of placental sinuses are not. Angioblastoma cells and parafollicular mesenchymal cells in fetal skin are also CD34 positive, as are some stromal elements. An approximately 110 Kd protein can be identified by Western blot analysis with CD34 antibodies in detergent extracts of freshly isolated umbilical vessel endothelial cells, and CD34 mRNA is present in cultured umbilical vein cells as well as other tissues rich in vascular endothelium (breast, placenta). These data indicate that the binding of CD34 antibodies to vascular endothelium is to the CD34 gene product, and not to crossreactive epitopes. Despite the presence of CD34 mRNA in cultured, proliferating endothelial cells, the latter do not bind CD34 antibodies. In addition, CD34 antigen cannot be upregulated by growth factors. We conclude that under these conditions, CD34 protein is downregulated or processed into another form that is unreactive with CD34 antibodies. Electron microscopy of umbilical artery, breast, and kidney capillary vessels reveals that in all three sites, CD34 molecules are concentrated on membrane processes, many of which interdigitate between adjacent endothelial cells. However, well-established endothelial cell contacts with tight junctions are CD34 negative. CD34 may function as an adhesion molecule on both endothelial cells and hematopoietic progenitors.

All seven of a set of CD34 monoclonal antibodies that recognize epitopes on an approximately 110 Kd glycoprotein on human hemopoietic progenitor cells also bind to vascular endothelium. Capillaries of most tissues are CD34 positive, as are umbilical artery and, to a lesser extent, vein, but the endothelium of most large vessels and the endothelium of placental sinuses are not. Angioblastoma cells and parafollicular mesenchymal cells in fetal skin are also CD34 positive, as are some stromal elements. An approximately 110 Kd protein can be identified by Western blot analysis with CD34 antibodies in detergent extracts of freshly isolated umbilical vessel endothelial cells, and CD34 mRNA is present in cultured umbilical vein cells as well as other tissues rich in vascular endothelium (breast, placenta). These data indicate that the binding of CD34 antibodies to vascular endothelium is to the CD34 gene product, and not to crossreactive epitopes. Despite the presence of CD34 mRNA in cultured, proliferating endothelial cells, the latter do not bind CD34 antibodies. In addition, CD34 antigen cannot be upregulated by growth factors. We conclude that under these conditions, CD34 protein is downregulated or processed into another form that is unreactive with CD34 antibodies. Electron microscopy of umbilical artery, breast, and kidney capillary vessels reveals that in all three sites, CD34 molecules are concentrated on membrane processes, many of which interdigitate between adjacent endothelial cells. However, well-established endothelial cell contacts with tight junctions are CD34 negative. CD34 may function as an adhesion molecule on both endothelial cells and hematopoietic progenitors.

Distal pancreatectomy for chronic pancreatitis from any etiology can be performed with low mortality and a good outcome in terms of pain relief and return to work in approximately 60% of patients. Little effect is seen on exocrine function of the pancreas, but there is a diabetic risk of 46% over 2 years. Pseudocyst disease is associated with the best outcome, but other manifestations of this disease, including strictures, calcification, and limited concomitant disease in the head of the pancreas, can still be associated with a good outcome.

The modification of tyrosine residues in proteins to 3-nitrotyrosine by peroxynitrite or other potential nitrating agents has been detected in biological systems that are subject to oxidative stress. A convenient semi-quantitative method has been developed to assay nitrated proteins in biological fluids and homogenates using a competitive ELISA developed in our laboratory. This assay selectivity detected 3-nitro-l-tyrosine residues in a variety of peroxynitrite-treated proteins (BSA, human serum albumin (HSA), alpha1-antiprotease inhibitor, pepsinogen and fibrinogen) and also in a nitrated peptide, but had a low affinity for free 3-nitro-L-tyrosine and 3-chloro-L-tyrosine. The IC50 values for the inhibition of antibody binding by different nitrated proteins were in the range 5-100 nM, suggesting that the antibody discriminated between nitrotyrosine residues in different environments. The presence of nitrotyrosine in plasma proteins was detected by Western blot analysis and quantified by the ELISA. A concentration of 0. 12+/-0.01 microM nitro-BSA equivalents was measured in the proteins of normal plasma which was increased in peroxynitrite-treated plasma and was elevated in inflammatory conditions. HSA and low-density lipoprotein (LDL) isolated from plasma contained 0.085+/-0.04 and 0. 03+/-0.006 nmol nitro-BSA equivalents/mg protein, respectively. Comparison of the level of nitration in peroxynitrite-treated HSA and LDL in the presence and absence of plasma indicates that nitration and presumably oxidation is inhibited by plasma antioxidants. The presence of nitrotyrosine in LDL is consistent with previous reports implicating peroxynitrite in the oxidative modification of lipoproteins and the presence of a low concentration of oxidized LDL in the blood.

The immunoreactivity of a new monoclonal antibody to endothelium. QBEND/10, in formalin-fixed, paraffin-embedded sections from a variety of vascular and lymphatic tumours is described and compared to that of two other endothelial markers, von Willebrand factor and Ulex europaeus agglutinin, type 1. All the benign tumours of blood vascular origin showed immunoreactivity whereas only five out of eight lymphangiomas demonstrated a weak focal reaction with QBEND/10. Primitive lumina in epithelioid and spindle cell haemangioendotheliomas were highlighted in all the cases. Tumour cells in angiosarcoma forming vasoformative areas and solid areas showed immunopositivity to QBEND/10 in 17/23 and 13/24 cases respectively, and complementary immunoreactivity for von Willebrand factor was observed. Proliferating vessels and the majority of spindle cells in Kaposi's sarcoma were positive in all 40 cases. Only one of 54 cases of carcinoma showed luminal reaction to QBEND/10. However, 17 of 45 spindle cell tumours displayed a positive reaction. QBEND/10 is an additional marker for demonstrating endothelial differentiation and has some advantages over currently available antibodies.

Eighteen cases of cerebral tumour composed partly or totally of primitive embryonal cells are reported. These lesions comprise 2.8% of all primary cerebral hemisphere tumours in the histopathology files of The Royal Marsden Hospital between 1971 and 1980 inclusive. Most exhibited some degree of differentiation towards neuronal or glial elements and, as more than one type of differentiation was often present in the same lesion, we agree with others that the term primitive neuroectodermal tumour (PNET) is more appropriate to describe these lesions than terms based on histogenesis. The extent of the primitive component varied, but usually accounted for more than 80% of the tumour. Although the tumours bear some similarities to posterior fossa medulloblastomas, they exhibit important differences in histology, immunohistology, natural history and response to treatment. Nearly all PNETs examined expressed some glial fibrillary acidic (GFAP) both in primitive areas and zones of astrocytic differentiation. GFAP staining may thus be of value in distinguishing PNETs from undifferentiated non-neurogenic tumours. Of 14 patients referred for radiotherapy, the survival rate at 3 years was 29% (4/14) and 5 years 25% (3/12). Patients with tumours in which at least 90% of the tissue was undifferentiated exhibited an extremely poor prognosis with none of 9 patients still alive at 3 years in contrast to 3 of 5 patients (60%) with tumours showing less than 90% undifferentiation. Radical tumour removal, where feasible, followed by irradiation of the whole cerebrospinal axis is recommended. Adjuvant chemotherapy with such agents as CCNU and Vincristine may be of value: the 3 long term survivors in the present series (7-11 years), including one who presented disseminated intracranial disease, received such adjuvant treatment.

NO formation is increased in patients with primary RP or lSSc, but nitration of proteins and elevated ADMA is a particular feature of dSSc and may reflect abnormal NO regulation and/or contribute to endothelial dysfunction in SSc.

The flow cytometers that are currently supported by industry provide accurate CD4؉ -T-cell counts for monitoring human immunodeficiency virus disease but remain unaffordable for routine service work under resource-poor conditions. We therefore combined volumetric flow cytometry (measuring absolute lymphocyte counts in unit volumes of blood) and simpler protocols with generic monoclonal antibodies (MAbs) to increase cost efficiency. Volumetric absolute counts were generated using CD45/CD4 and CD45/CD8 MAb combinations in two parallel tubes. The percentage values for the various subsets were also determined within the leukocyte and lymphocyte populations utilizing a fully automated protocol. The levels of agreement between the newly developed method and the present industry standards, including both volumetric and bead-based systems using a full MAb panel for subset analysis, were tested by Bland-Altman analyses. The limits of agreement for CD4 counts generated by the volumetric methods using either CD45/CD4 (in a single tube) or the full Trio MAb panel (in three tubes) on the CytoronAbsolute flow cytometer were between ؊29 and ؉46 cells/mm 3 with very little bias for CD4 counts (in favor of the Trio method: ؉8 CD4 ؉ lymphocytes/mm 3 ; 0.38% of lymphocytes). The limits of agreement for absolute CD4 counts yielded by the volumetric CD45/CD4 method and the bead-based method were between ؊118 and ؉98 cells/mm 3 , again with a negligible bias (؊10 CD4 ؉ lymphocytes/mm 3 ). In the volumetric method using CD45/CD8, the strongly CD8 ؉ cells were gated and the levels of agreement with the full Trio showed a minor bias (in favor of the Trio; ؉40 CD8 ؉ cells/mm 3 ; 5.2% of lymphocytes) without a significant influence on CD4/CD8 ratios. One trained flow cytometrist was able to process 300 to 400 stained tubes per day. This workload extrapolates to a throughput of >30,000 samples per year if both CD45/CD4 and CD45/CD8 stainings are performed for each patient or a throughput of >60,000 samples if only CD45/CD4 counts are tested in a single tube. Thus, on the basis of the high efficiency and excellent agreement with the present industry standards, volumetric flow cytometers with automated gating protocols and autobiosamplers, complemented by generic CD45, CD4, and CD8 MAbs used in two-color immunofluorescence, represent the most suitable arrangements for large regional laboratories in resource-poor settings.Dedicated flow cytometers are designed to enumerate the absolute numbers and percentages of lymphocyte populations, such as subsets of T cells, B cells, and NK cells. In the clinical service for monitoring human immunodeficiency virus (HIV) disease, the primary aim is to deliver absolute CD4 ϩ -T-cell counts, and this is achieved with a remarkably high level of precision (9,24,26,29,30). Nevertheless, the various cytometric systems differ in complexity (9). It has recently been documented that routine CD4-T-cell enumeration can be simplified without compromising quality (13,18,32), leading to costeffective services for patie...