Gastrointestinal stromal tumors: an ultrastructural study

Gastrointestinal stromal tumors (GISTs) represent an enigmatic group of lesions of uncertain phenotype and biologic potential. Although earlier studies suggested smooth muscle cells, schwann cells, or neuronal differentiation, more recent evidence indicates that these tumors show phenotypic features that are similar to the interstitial cells of Cajal. Recently, investigators have begun to evaluate these lesions in a site-specific manner and have found that, in addition to morphologic differences between them, their biologic behavior also appears to be linked to their anatomic location. Many of these studies have emphasized the histologic and immunophenotypic features of GISTs in relation to their sites of origin, however, their site-specific ultrastructural characteristics have received little attention in the literature. In this study, we evaluated 34 GISTs (15 gastric, 12 small intestinal, 4 colonic, and 3 omental) for a variety of ultrastructural features in an effort to identify site-specific similarities and differences. Tumors predominantly composed of epithelioid cells were more commonly seen in gastric (60%) and omental (67%) tumors than in those of the small intestine (33%) and colon (0%). Cytoplasmic filaments and intercellular junctions were commonly seen in tumors from all locations, the filaments frequently forming paranuclear aggregates in the epithelioid cells. Tumors from all sites were composed of cells with surface filopodia and interdigitating cell processes, but in tumors of the stomach and omentum the filopodia were usually short and minimally intertwined, whereas those of small and large intestinal GISTs were characteristically long and complex. Basal lamina, though poorly formed, was present only in tumors of gastric and omental origin (13% and 67%, respectively). Pinocytotic vesicles were also seen in tumors from these sites (33% of gastric tumors and 67% of omental lesions) as well as those of the small intestine (17%) and the colon (25%). None of the gastric or omental tumors had microtubules; they were, however, seen in small intestinal (33%) and colonic (25%) stromal tumors. Skenoid fibers were seen in 33% of small intestinal GISTs and 1 metastatic gastric GIST. Overall, gastric and omental tumors have better developed features of myogenic differentiation and have blunt filopodia and minimally intertwined cell processes. Indeed, these 2 groups are indistinguishable ultrastructurally, raising the possibility that the genesis of omental GISTs is similar to that of gastric stromal tumors. Small intestinal stromal tumors have characteristic interdigitating cell processes and numerous elongate filopodia-like structures harboring intercellular junctions as well as microtubules and extracellular skenoid fibers. The constituent cells in colonic stromal tumors, while more reminiscent of small intestinal stromal, were frequently more primitive in appearance. In conclusion, GISTs from different anatomic locations share many overlapping ultrastructural characteristics; however, a few features are distinctive. It is hoped that these findings will aid in their recognition and contribute to the classification of this heterogeneous group of neoplasms.     

Production and use of monoclonal antibodies for the detection of apple chlorotic leaf spot virus

Stable hybridoma cell lines secreting antibodies specific for the apple chlorotic leaf spot virus (CLSV) were produced by fusing spleen cells of a Biozzi mouse immunized with CLSV P863 strain, with the non-secretory P3 X63 Ag8.653 myeloma cell line. Two hybridoma clones producing monoclonal antibodies of the IgG1 subclass were obtained. These monoclonal antibodies were used for virus detection by enzyme-linked immunosorbent assay (ELISA). In contrast to polyclonal antisera to CLSV, which always contain some antibodies to host components, monoclonal antibodies are highly specific for the virus. It was thus possible to develop a detection assay which is more sensitive and specific than the assays using polyclonal antibodies. Using monoclonal antibodies, it was possible to detect less than 0.1 ng/ml of purified virus. In addition, these two monoclonal antibodies recognize 17 strains or isolates maintained in our laboratory and representing most of the known CLSV strains.     

Identification of an N-linked glycan in the V1-loop of HIV-1 gp120 influencing neutralization by anti-V3 antibodies and soluble CD4

Summary Glycosylation is necessary for HIV-1 gp120 to attain a functional conformation, and individual N-linked glycans of gp120 are important, but not essential, for replication of HIV-1 in cell culture. We have constructed a mutant HIV-1 infectious clone lacking a signal for N-linked glycosylation in the V1-loop of HIV-1 gp120. Lack of an N-linked glycan was verified by a mobility enhancement of mutant gp120 in SDS-gel electrophoresis. The mutated virus showed no differences in either gp120 content per infectious unit or infectivity, indicating that the N-linked glycan was neither essential nor affecting viral infectivity in cell culture. We found that the mutated virus lacking an N-linked glycan in the V1-loop of gp120 was more resistant to neutralization by monoclonal antibodies to the V3-loop and neutralization by soluble recombinant CD4 (sCD4). Both viruses were equally well neutralized by ConA and a conformation dependent human antibody IAM-2G12. This suggests that the N-linked glycan in the V1-loop modulates the three-dimensional conformation of gp120, without changing the overall functional integrity of the molecule.     

Nerve growth factor enhances antigen and other secretagogue-induced histamine release from rat peritoneal mast cells in the absence of phosphatidylserine

The effects of 2.5S nerve growth factor (NGF) and epidermal growth factor (EGF), isolated from mouse submaxillary glands, on histamine release from rat peritoneal mast cells (PMCs) were studied. In the absence of phosphatidylserine, NGF (1 ng/ml to 1 microgram/ml) did not cause histamine release from PMCs isolated from normal rats and those infected with the nematode Nippostrongylus brasiliensis. However, when PMCs (greater than 97% pure) were preincubated with NGF and then challenged with worm antigen (Ag), there was a marked enhancement of histamine release (approximately twofold with a maximum effect at 10 ng/ml of NGF [3.8 X 10(-10) mol/L]) compared with the release induced by Ag alone. EGF (1 ng/ml to 1 microgram/ml) neither produced histamine release from PMCs in the presence of phosphatidylserine nor enhanced Ag-induced histamine release. This suggests that NGF acts directly on PMCs by activation of cell-surface receptors. The early kinetics of Ag-induced histamine release were altered by NGF that increased the initial rate at 15 seconds but did not prolong the overall duration of histamine release. Simultaneous addition of Ag and NGF did not cause enhanced histamine release; thus, some preincubation time with NGF (5 minutes or less) was required for the activation of PMCs. Moreover, after PMCs were activated by NGF, that state persisted for 1 hour, even when unbound NGF was removed by washing, and thereafter subsided gradually. Further studies revealed that NGF enhanced histamine release induced by concanavalin A, compound 48/80, and ionophore A23187. These results suggest that NGF might be an important molecule in inflammatory responses through the regulation of mediator release from mast cells.     

Red cell 2,3-DPG,ATP, and mean cell volume in highly trained athletes

Summary 20 male elite long distance runners were compared to a control group of blood donors to determine the effect of training on red blood cells. The acute effects of exercise on red cells were investigated in 11 of the runners following a race of 15–30 km. The runners had elevated resting values of red cell 2,3-DPG (P<0.05) and mean cell volume (P<0.01); blood Hb and ATP were not different from concentrations in the control group. The red cell status of the athletes may be explained by an increased proportion of young erythrocytes in runners. No statistically significant changes in red cell 2,3-DPG, ATP, mean cell volume or blood Hb were found post exercise.     

Quantitation of antibody to particulate antigens using a radiolabelled anti-immunoglobulin reagent: application to estimation of antibody in farmer's lung syndrome

A method of wide applicability is described for the study of serological changes in response to particulate antigens. The practical and theoretical aspects of the method have been explored in estimation of antibody to Micropolyspora faeni in human cases of farmer's lung syndrome. This method, using a radiolabelled antiglobulin to detect cell-bound antibody, was found to be of high sensitivity and reproducibility. Antibody has been estimated in micrograms per millilitre of serum by correlation with the results of quantitative agglutination test.     

IgE in unselected like-sexed monozygotic and dizygotic twins at birth and at 6 to 9 years of age: high but dissimilar genetic influence on IgE levels

BACKGROUND: IgE is a major determinant of allergic disease. Twin analysis of serum levels of IgE has been carried out previously in children and adults with heritability estimates of 30% to 70% on the basis of ANOVA. OBJECTIVE: This study included the analysis of serum IgE in a population of 126 twins, 27 monozygotic pairs and 36 dizygotic pairs, studied at birth (cord blood [CB] IgE) and consecutively at the age of 6 to 9 years of age (serum IgE). METHODS: IgE was determined by means of RIA. ANOVA, correlation analysis, and structural equation modeling by maximal likelihood analysis was used for genetic analysis. RESULTS: Structural equation modeling by maximal likelihood analysis showed the best-fitting model to be the AE model (A for additive genetic variance and E for environmental variance) both at birth and later in childhood. The estimated heritability was 0.92 (95% CI, 0.84-0.95) for CB IgE and 0.78 (95% CI, 0.60-0.87) for serum IgE. The correlation between CB IgE and serum IgE was 0.04. CONCLUSIONS: The study demonstrated a higher genetic dependency of serum IgE than previously recognized. The low correlation between the IgE levels at birth and later in childhood suggested that different effector mechanisms may be operating at different ages.