Pigmentation phenotype instability in Myxococcus xanthus.

Cells of Myxococcus xanthus FB2 produce tan or yellow colonies. Subcultures of tan colonies yielded tan and yellow colonies and subcultures of most yellow colonies yielded only yellow colonies. Strain FB2 variants in which the color type is more stable were obtained. Yellow cells were distinguishable from tan by the presence of pigment(s) with an absorption maximum at 379 nm. Fluctuation Test experiments and the presence of this pigment(s) in liquid cultures of FB2 indicated that tan phenotype cells spontaneously became or segregated yellow cells in liquid culture. The frequency of appearance of yellow cells was increased in low density cultures (less than 10(6)/ml). The increase cannot be explained by differences in growth rates of the two phenotypes. No evidence that cell-cell contact or culture medium constituents affect the appearance of the yellow phenotype was found. Ultraviolet irradiation of FB2 resulted in an increased proportion of cells producing yellow colonies among the survivors. Greater UV resistance of yellow cells and UV-induced conversion of tan to yellow accounts for this increase. Low level photoreactivation of viability and of the tan phenotype occurred. Incubation of FB2 in medium containing mitomycin C, nalidixic acid, phenethyl alcohol, or at 36.5 degrees C also resulted in conversion of tan to yellow cells.     

Low-molecular-weight Ia antigens in normal mouse serum

Low-molecular-weight Ia antigens can be detected in mouse serum. A procedure for isolating these antigens from serum in high yield is described. The Ia antigen preparation was found to be rich in carbohydrate, low in protein, and strongly bound to Concanavalin A andLotus lectins. Furthermore, the Ia antigenicity was destroyed by periodate oxidation and neuraminidase treatment, but was unaffected by pronase. These observations strongly suggest that the Ia antigens in serum are oligosaccharide in nature. Such a conclusion implies that at least some of the genes in theI region of theH-2 gene complex code for glycosyl transferase enzymes.     

Issues in using whole slide imaging for diagnostic pathology: “routine” stains,immunohistochemistry and predictive markers

The traditional microscope, together with the “routine” hematoxylin and eosin (H & E) stain, remains the “gold standard” for diagnosis of cancer and other diseases; remarkably, it and the majority of associated biological stains are more than 150 years old. Immunohistochemistry has added to the repertoire of “stains” available. Because of the need for specific identification and even measurement of “biomarkers,” immunohistochemistry has increased the demand for consistency of performance and interpretation of staining results. Rapid advances in the capabilities of digital imaging hardware and software now offer a realistic route to improved reproducibility, accuracy and quantification by utilizing whole slide digital images for diagnosis, education and research. There also are potential efficiencies in work flow and the promise of powerful new analytical methods; however, there also are challenges with respect to validation of the quality and fidelity of digital images, including the standard H & E stain, so that diagnostic performance by pathologists is not compromised when they rely on whole slide images instead of traditional stained tissues on glass slides.     

Immunoperoxidase localization of GCDFP-15 with mouse monoclonal antibodies versus rabbit antiserum

Five monoclonal antibodies (Mabs) raised against separate determinants on a breast gross cystic disease fluid protein of 15 KD (GCDFP-15) were compared to one another and to a rabbit antiserum (Rb) against GCDFP-15 by radioimmunoassay (RIA) and by immunoperoxidase localization in paraffin-embedded tissues. All five Mabs and the Rb were equivalent in recognition of GCDFP-15 in solution, as determined by RIA. However, two of the Mabs (A5, B15) showed only minimal binding to GCDFP-15 in paraffin-embedded tissues, whereas the other three Mabs (B1, B4, D6) were equivalent to the Rb in staining intensity. These latter three Mabs and the Rb were evaluated by the immunoperoxidase technique on a variety of benign and malignant neoplasms as well as normal tissues (150 specimens) for staining specificity. Immunoperoxidase staining by the three Mabs vs the Rb was equivalent in apocrine glands, metaplastic apocrine epithelium of breast, and breast carcinomas with apocrine features. No staining of the Mabs or Rb was seen in the other tissue specimens.