Why don't corticotroph tumors always produce Cushing's disease?

OBJECTIVE: Silent corticotroph tumors are a pituitary neuroendocrine tumor subtype of corticotroph lineage that do not clinically express Cushing's disease. The silencing of this type of tumor is not fully understood. The aim of the present study was to delve into the lack of secretory activity, studying the post-transcriptional and post-translational regulation of POMC/ACTH in a series of molecularly identified functioning and silent corticotroph tumors. DESIGN: We analyzed 24 silent corticotroph, 23 functioning corticotroph and 25 silent gonadotroph tumors. METHODS: We used Sanger sequencing, quantitative real-time PCR and Western blot to analyze genetic alterations in POMC, gene expression of TBX19, NEUROD1, POMC, PCSK1, PCSK2, CPE and PAM and protein expression of POMC, PC1/3, PC2, CPE and PAM. RESULTS: We found different polymorphisms in the POMC gene of corticotroph tumors, some of them related to deficiency of proopiomelanocortin. Silent corticotroph tumors showed lower PC1/3 gene and protein expression than functioning ones, especially compared to micro-functioning corticotroph tumors (all P < 0.05). Moreover, we found a positive correlation between PC2 and CPE gene and protein expression (rho ≥ 0.670, P < 0.009) in silent corticotroph tumors compared with functioning ones. CONCLUSIONS: By studying the post-transcriptional and post-translational processing of POMC and ACTH, respectively, in a large series of silent and functioning corticotroph tumors, we found that the lack of secretory activity of these tumors is related to an impaired processing of POMC and a high degradation of ACTH, with the macro-functioning corticotroph tumor behaving as an intermediate state between micro-functioning and silent corticotroph tumors.

Induction of lytic enzymes by the interaction of Ustilago maydis with Zea mays tissues.

The nonpathogenic (FB-2) and pathogenic (FB-D12) strains of Ustilago maydis were grown in medium supplemented with different carbon sources including monosaccharides, polysaccharides, and plant tissues. Both strains were able to grow on all substrates, with doubling times varying from 2 to 25 h depending on the carbon source. Plant tissues supplied as carbon source induced lytic enzymes differentially; pectate lyase and cellulase activities were induced preferentially by apical stem meristem in strain FB-D12, whereas leaves preferentially induced xylanase and cellulase activities in strain FB2. Stems induced polygalacturonase activity in both strains. All enzyme activities, except cellulase in the FB-D12 strain, were detected at a low level when U. maydis was grown on glucose. In planta, chlorosis and production of teliospores were paralleled by an increase in pectate lyase activity. Anthocyanin production and formation of galls and teliospores correlated with polygalacturonase expression whereas cellulase activity increased only during the stage of anthocyanin production and gall formation. Expression of xylanase activity coincided with the last stage of teliospore formation.

[Chlamydia trachomatis and cervix dysplasia]. / Chlamydia trachomatis y displasia cervical.

Fifty patients between 18 and 70 years of age from Gynecology and Obstetrics Department, Hospital General "Gonzalo Castañeda" ISSSTE, were studied. Patients were referred for bearing positive cytology with mild, moderate and severe dysplasia; also intentional search for Chlamydia trachomatis was made, both in cytology as well as with the immunofluorescence method, and also directed biopsy. A positive association was found in 10 patients (20%) proving that Chlamydia trachomatis is a promotor and modifier of cervical atypia.

Chitin synthetase activity is bound to chitosomes and to the plasma membrane in protoplasts of Saccharomyces cerevisiae.

The sub-cellular distribution of chitin synthetase was studied in homogenates of Saccharomyces cerevisiae protoplasts. Use of a mild disruption method minimized rupture of vacuoles and ensuing contamination of subcellular fractions by vacuolar proteinases. After fractionation of whole or partially purified homogenates through an isopycnic sucrose gradient chitin synthetase activity was found to be distributed between two distinct particulate fractions with different buoyant density and particle diameter. When whole homogenates were used, about 52% of the chitin synthetase loaded was localized in a microvesicular population identified as chitosomes (diameter 40-110 nm; buoyant density (d) = 1.146 g/cm3). Another vesicular population containing 26% of the activity was identified as plasma membrane vesicles because of its large mean diameter (260 nm), its high buoyant density (d = 1.203 g/cm3) and by the presence of the vanadate-sensitive ATPase activity. Moreover, after surface labeling of protoplasts with 3H-concanavalin A, the label cosedimented with the presumed plasma membrane vesicles. There was a negligible cross-contamination of the chitosome fraction by yeast plasma membrane markers. In both the plasma membrane and the chitosome fractions, the chitin synthetase was stable and essentially zymogenic. Activation of the chitosome fraction produces microfibrils 100-250 nm in length. Our results support the idea that chitosomes do not originate by plasma membrane vesiculation but are defined sub-cellular organelles containing most of the chitin synthetase in protoplasts of Saccharomyces cerevisiae.