Characterization of the glucose transport systems in Neurospora crassa sl.

Neurospora crassa sl, a mutant that lacks a rigid cell wall, exhibits transport systems for glucose similar to those of wild-type strain 1A. When the orgnism is grown in a medium containing 50 mM glucose as the carbon source, glucose is transported primarily by a glucose-facilitated diffusion system (GluI). When it is grown in a medium with little or no glucose present, a glucose active transport system (Glu II) is expressed. Both of these systems are similar kinetically to those in the wild type. Significant differences do exist between strains sl and 1A with respect to genetic regulation of the glucose active transport system.     

Histochemical specificity of beta-galactose binding lectins from Arachis hypogaea (peanut) and Ricinus communis (castor bean)

Previous histochemical studies have demonstrated disparities in the binding of two lectins with a nominal specificity for terminal beta-D-galactose. Biochemical studies have shown that the most complementary structure for binding peanut agglutinin (PNA) is the terminal disaccharide Gal-(beta 1----3)-GalNAc, whereas the most complementary structure for binding Ricinus communis agglutinin I (RCA I) is the terminal disaccharide Gal-(beta 1----4)-GlcNAc. However, it is not known if only these differences in affinity account for the different histochemical staining reactions observed on tissue sections. In the present study we compared the staining patterns of PNA and RCA I by inhibiting in situ the binding of each lectin conjugated to horseradish peroxidase (HRP) with increasing concentrations of unlabeled PNA or RCA I. The PNA-HRP conjugate did not stain most tissue sites suspected of containing an abundance of glycoconjugates with terminal Gal-(beta 1----4)-GlcNAc. Moreover, unlabeled PNA failed to significantly inhibit strong RCA I-HRP staining in these sites. In loci thought to contain variable amounts of glycoconjugates with terminal Gal-(beta 1----3)-GalNAc, unlabeled RCA I decreased PNA-HRP reactivity only slightly or not at all, whereas weak to strong RCA I-HRP staining was diminished or abolished by unlabeled PNA. The results suggest that PNA staining is restricted to glycoconjugates with terminal Gal-(beta 1----3)-GalNAc. RCA I apparently reacts most strongly with glycoconjugates having the terminal disaccharide Gal-(beta 1----4)-GlcNAc, but also stains sites containing a moderate to abundant amount of glycoconjugates with the terminal Gal-(beta 1----3)-GalNAc sequence.     

Identification and characterization of the human Pgp-1 glycoprotein

Two monoclonal antibodies have been raised against human Pgp-1 by the immunization of mice with human fibroblasts. The human molecule, like the previously identified mouse counterpart, is an abundant membrane protein (M_r approximately 95 000) with a broad tissue distribution. Pgp-1 is phosphorylated, and phosphoamino acid analysis demonstrates that this occurs exclusively on serine residues. A major difference between the mouse and the human is that 50–60% of human thymocytes are Pgp-1⁺ compared to 5–10% of mouse thymocytes at an equivalent stage in development. Immunofluorescence studies of cryostat sections showed that the majority of human medullary thymocytes are strongly stained with Pgp-1-specific antibody, whereas the expression of Pgp-1 on cortical thymocytes is much more heterogenous.     

Immunocytochemical characterization of large-cell carcinomas of the lung. Role, limitations and technical considerations.

To clarify the use of cytologic preparations, particularly those previously stained by the Papanicolaou method, for the immunocytochemical evaluation of large-cell carcinomas (LCCs), 37 cytologic preparations from cases diagnosed as LCC were examined using a battery of immunocytochemical stains for keratin, chromogranin, common leukocyte antigen (CLA) and B72.3. Thirty-two specimens were from the thoracopulmonary region (12 fine needle aspirates of the lung, 7 bronchial brushings, 5 bronchial washings, 2 sputa and 6 pleural fluids); the remaining specimens were fine needle aspirates of 3 lymph nodes, 1 vertebral body and 1 liver. Of the specimens analyzed, 30 of 37 were positive for keratin and 7 of 35 were positive for B72.3 (6 were positive for both). Only 1 of 37 was positive for CLA while none of 37 was positive for chromogranin. Six specimens showed no reaction with either keratin, B72.3 or chromogranin. These results confirm that the majority of LCCs consist of epithelial cells of either a squamous or an adenocarcinomatous type. They also show that immunocytochemistry is a useful diagnostic adjunct that can be applied to cytologic preparations previously stained by the Papanicolaou method; this is important since immunostaining is often considered after undifferentiated malignant cells are encountered in a previously stained preparation. However, a thorough understanding of some technical limitations is critical in the evaluation of the results of this technique when it is applied to cytologic specimens.