Keratin-positive reticulum cells in fine needle aspirates and touch imprints of hyperplastic lymph nodes. A possible pitfall in the immunocytochemical diagnosis of metastatic carcinoma.

Fine needle aspirates and touch imprints of 36 hyperplastic (reactive) lymph nodes were tested for the presence of keratin and desmin. Keratin-positive cells with morphologic characteristics corresponding to extrafollicular (fibroblastic) reticulum cells were found in 18% of the fine needle aspirates and 42% of the touch imprints. The number of keratin-positive reticulum cells varied from 1 to greater than 30 per slide. Desmin-positive cells with similar morphology were found in 23% of fine needle aspirates and 37% of touch imprints, and the number of such cells per slide ranged from 2 to greater than 70. The relatively frequent occurrence of keratin-positive reticulum cells in these preparations from hyperplastic lymph nodes should be taken into account if keratin antibodies are used to search for carcinoma micrometastases.     

Decisive role of intermediate filament typing of tumor cells in the differential diagnosis of difficult fine needle aspirates

Thirty-six diagnostically difficult fine needle aspirates from enlarged lymph nodes and malignant soft tissue tumors, containing tumor cells with scanty or no obvious light microscopic features indicative of their differentiation, were assessed by a panel of six cytopathologists. Their diagnoses were recorded and then compared with the definitive diagnosis established by combining the cytologic findings with the results of intermediate filament typing of tumor cells in the smears using monoclonal antibodies specific for each filament type. The results show that use of these antibodies can markedly improve the accuracy of the cytologic diagnosis of tumor type as well as revise or prevent erroneous cytologic diagnoses in difficult cases. This pertains especially to the differential diagnoses of carcinoma versus malignant lymphoma, carcinoma versus malignant melanoma, carcinoma versus sarcoma and squamous carcinoma versus carcinoma of simple epithelia. Intermediate filament typing of tumor cells in aspirates as an objective histogenetic criterium makes the differential diagnosis of the difficult aspirates much more reliable and reproducible, provided that appropriate questions are asked, monoclonal antibodies with well-defined specificities are used and the antigenicity of the intermediate filaments in smears is preserved.     

Transforming c-Ki-ras mutation is a preneoplastic event in mouse mammary carcinogenesis induced in vitro by N-methyl-N-nitrosourea.

Mouse mammary epithelial cells can be transformed in primary cultures to preneoplastic and neoplastic states when treated with N-methyl-N-nitrosourea (MNU). Mammary carcinomas arising from MNU-induced hyperplastic alveolar nodules (a type of mouse mammary preneoplastic lesion) contained transforming c-Ki-ras genes when examined by the NIH 3T3 focus assay. Hybridization of allele-specific oligonucleotides to c-Ki-ras sequences amplified by the polymerase chain reaction demonstrated the presence of a specific G-35----A-35 point mutation in codon 12 in each of the NIH 3T3 foci as well as the mammary carcinomas. This mutation resulted in the substitution of the normal glycine with an aspartic acid. Furthermore, this mutation in the c-Ki-ras proto-oncogenes was also detected in 9 of 10 hyperplastic alveolar nodules. These results demonstrate that the specific c-Ki-ras mutation is a preneoplastic event in MNU-induced mouse mammary carcinogenesis.     

Small-scale turbulence and plankton contact rates

Theoretical and empirical studies of plankton trophodynamicsare usually based on some function of the relative density ofpredator-and-prey plankton. Such approaches based only on therelative density of predator and prey generally underestimatepredator-prey contact rates because contact depends on boththe relative density and the relative velocity of predator andprey. We estimate the components of predator-and-prey contactthat are due to small-scale turbulence. The small-scale turbulenceeffect suggests reconsidering estimates of plankton food requirements,energy gain-and-loss from foraging and mechanisms associatedwith patch formation and dissipation.     

Characterization and comparison of arcelin seed protein variants from common bean

Four variants of arcelin, an insecticidal seed storage protein of bean, Phaseolus vulgaris L., were investigated. Each variant (arcelin-1, -2, -3, and -4) was purified, and solubilities and M_rs were determined. For arcelins-1, -2, and -4, the isoelectric points, hemagglutinating activities, immunological cross-reactivities, and N-terminal amino acid sequences were determined. On the basis of native and denatured M_rs, the variants were classified as being composed of dimer protein (arcelin-2), tetramer protein (arcelins-3 and -4), or both dimer and tetramer proteins (arcelin-1). Although the dimer proteins (arcelins-1d and -2) could be distinguished by M_rs and isoelectric points, they were identical for their first 37 N-terminal amino acids and had similar immunological cross-reactions, and bean lines containing these variants had a DNA restriction fragment in common. The tetramer proteins arcelin-1t and arcelin-4 also could be distinguished from each other based on M_rs and isoelectric points; however, they had similar immunological cross-reactions and they were 77 to 93% identical for N-terminal amino acid composition. The similarities among arcelin variants, phytohemagglutinin, and a bean α-amylase inhibitor suggest that they are all encoded by related members of a lectin gene family.     

Bean lectins

Summary Seeds of forty bean cultivars having different lectin types based on two-dimensional isoelectric focusing-sodium dodecyl sulfate polyacrylamide gel electrophoresis (IEF-SDS/PAGE) were analyzed for quantities of lectin, phaseolin and total protein. Significant differences were found among groups of cultivars with different lectin types for the quantity of lectin and phaseolin. Cultivars with more complex lectin types based on IEF-SDS/PAGE tended to have higher quantities of lectin and lower quantities of phaseolin than cultivars with simple lectin types. An association between lectin type and the quantity of lectin and phaseolin was found also in the seeds of F₂ plants that segregated in a Mendelian fashion for two lectin types. Seeds from plants with the complex lectin type had more lectin and less phaseolin than seeds from plants with the simple lectin type. Therefore, the genes controlling qualitative lectin variation also may influence the quantitative variation of lectin and phaseolin. The results of this study are related to other studies on the quantitative variation for seed proteins and to the possible molecular basis for variation in the quantity of lectins in beans.     

Monoclonal antibodies specific for glial fibrillary acidic (GFA) protein and for each of the neurofilament triplet polypeptides

A panel of 10 mouse monoclonal antibodies specific for glial fibrillary acidic protein (GFA) has been isolated using porcine GFA as antigen. Although all antibodies recognize GFA purified from porcine spinal cord in the western blot technique, they can be subdivided into at least three groups on the basis of their reactivity against defined fragments of the molecule. Immunofluorescence staining patterns with the monoclonal antibodies performed on tissues and cell lines resemble those reported with conventional polyclonal antibodies directed against GFA. In particular astrocytes and Bergmann glia are strongly stained. In addition mouse monoclonal antibodies specific for either the 200 kd, or the 160 kd, or the 68 kd neurofilament triplet protein have been isolated and characterized. These antibodies are specific for neuronal cells and support conclusions made with similar antigen affinity-purified polyclonal antibodies. The combined set of monoclonal antibodies seems a valuable tool to characterize the different cell types of the nervous system.