Isolation of a src homology 2-containing tyrosine phosphatase.

Tyrosine phosphorylation is controlled by the opposing actions of tyrosine kinases and phosphotyrosine phosphatases (PTPs). src homology 2 domains (SH2) are found in several types of signaling proteins, including some tyrosine kinases. These domains bind phosphotyrosyl proteins and thus help promote signal transduction. Using mixed oligonucleotide-directed polymerase chain reactions, two previously undescribed rat PTP cDNA fragments were generated. Through subsequent screening of rat megakaryocyte and human erythroleukemia libraries, we obtained a full-length coding sequence for one of these fragments. This cDNA, SH-PTP1, encodes a tyrosine phosphatase containing two highly conserved SH2 domains. SH-PTP1, with a 2.4-kilobase mRNA, a predicted open reading frame of 595 amino acids, and a structure suggesting a nontransmembrane protein, is expressed primarily in hematopoietic and epithelial cells. When expressed in Escherichia coli, SH-PTP1 possesses PTP activity. The structure of SH-PTP1 establishes an additional branch of the tyrosine phosphatase family and suggests mechanisms through which tyrosine phosphatases might participate in signal transduction pathways.     

Application of Epstein-Barr virus (EBV) serology to the diagnosis of North American nasopharyngeal carcinoma

A cooperative study was established among a number of institutions in the USA to determine the clinical value of Epstein-Barr virus (EBV) serology for the diagnosis of different histopathological types of North American nasopharyngeal carcinoma (NPC) including occult primary tumors. One hundred-twenty-four patients with confirmed NPC have now been entered into the study. For each patient, anti-EBV antibody titers were determined at diagnosis and related to the histopathology as classified according to the World Health Organization (WHO). The results suggest that certain anti-EBV antibodies are of potential value for the diagnosis of undifferentiated types of NPC but not for the well-differentiated cancer. The IgA anti-VCA antibody response is the most specific for this disease and of the greatest diagnostic value when used alone or in combination with the anti-EA test. These tests have also been used successfully for the detection of occult NPC. These results indicate that these tests can be useful aids to the clinician for the diagnosis of certain histopathologic types of this disease.     

Preparative purification of the rat mast cell chymase. Characterization and Interaction with granule components

The rat mast cell granule chymotrypsinlike enzyme was purified to homogeneity from 1 M NaCl solubilized membrane and granule-rich fractions of concentrated rat peritoneal mast cells by a preparative technique utilizing chromatography on Dowex 1, filtration on Sephadex G-75, and affinity chromatography with D-tryptophan methyl ester. Acid disk gel electrophoresis of the purified chymase disclosed a single stained band with activity being eluted from a replicate sliced gel in the same region. SDS-polyacrylamide gel electrophoresis of purified protein gave a single stained band that did not change in position with reduction and alkylation. Mast cell chymase is thus a cationic protein of 25,000 mol wt composed of a single polypeptide chain. The apparent K(m) of the chymase for BTEE was 1.5 x 10(-3) M and the V(max) was 67.8 μmol/min per mg. The enzyme was inhibited by TPCK and not by TLCK. The chymase complexed with native macromolecular rat mast cell heparin in molar ratios of 12:1 and 16:1, and complete heparin uptake occurred at a 40:1 ratio of chymase to heparin. Chymase activity was partially masked by combination with heparin in the isolated granule or experimental chymase-heparin complex, and soluble purified chymase was inhibited by concentrations of 5-HT comparable to those present in mast cells. It is therefore possible that the active site of chymase in the mast cell granule is largely masked by the combined effects of macromolecular heparin and 5-HT.     

Progesterone receptors in carcinomas of the upper aerodigestive tract

This study had three major goals: (1) to vigorously verify the presence of progesterone receptors in squamous cell carcinoma of the upper aerodigestive tract (HN-SCC). Antiprogesterone receptor monoclonal antibodies revealed a distinct band at approximately 120 kilodaltons in samples taken from two of four patients with HN-SCC. These results illustrate that progesterone receptor in HN-SCC has the same molecular weight as progesterone receptor in normal human uterus and human breast cancer. Steroid specificity and saturability results support the evidence that it is true progesterone receptors that are measured and not other receptors or sex steroid-binding globulins; (2) to confirm the biochemical function of progesterone receptors in HN-SCC by assessing the binding of progesterone receptor to acceptor sites on chromosomes in the nucleus; and (3) to establish the clinical significance of progesterone receptor measurement. Patients with positive assays were more likely to be free of disease a mean of 6 months after resection. We used logistic regression to account for site of primary disease, grade of tumor, and stage of disease. This logistic regression was significant with a p = 0.014. Patients with a binding index greater than 2 (19 of 73 patients) were 4.34 times more likely to be free of disease than patients with negative assays.     

Synthèse de poly(oxyéthylène)s rendus biospécifiques par fixation de stéroïdes en extrémités de chaînes. Utilisation d'un poly(oxyéthylène) substitué par des groupes estradiol pour extraire l'isomérase Δ5→4 oxo-3 stéroïde,par partage d'affinité

In three consecutive steps involving halogenation, amination, and condensation with a convenient acyl derivative ( 1 or 2 ), α-hydro-ω-hydroxypoly(oxyethylene) ( 3 ) was transformed into poly(oxyethylene)s 7 containing 0,6 to 1,3 mol of 3-[3,17β-dihydroxy-1,3,5(10)-estratrien-7α-yl]butyroyl end groups or 0,7 mol of 3-oxo-4-androsten-17β-ylcarboxyl end groups per mol of polymer. Applying the method of affinity partitioning, the former poly(oxyethylene) derivative 7 was used to purify successfully Δ5→4 3-oxosteriod isomerase contained in a crude extract from Pseudomonas Testosteroni.