General transcription factor TAF4 antagonizes epigenetic silencing by Polycomb to maintain intestine stem cell functions

Taf4 (TATA-box binding protein-associated factor 4) is a subunit of the general transcription factor TFIID, a component of the RNA polymerase II pre-initiation complex that interacts with tissue-specific transcription factors to regulate gene expression. Properly regulated gene expression is particularly important in the intestinal epithelium that is constantly renewed from stem cells. Tissue-specific inactivation of Taf4 in murine intestinal epithelium during embryogenesis compromised gut morphogenesis and the emergence of adult-type stem cells. In adults, Taf4 loss impacted the stem cell compartment and associated Paneth cells in the stem cell niche, epithelial turnover and differentiation of mature cells, thus exacerbating the response to inflammatory challenge. Taf4 inactivation ex vivo in enteroids prevented budding formation and maintenance and caused broad chromatin remodeling and a strong reduction in the numbers of stem and progenitor cells with a concomitant increase in an undifferentiated cell population that displayed high activity of the Ezh2 and Suz12 components of Polycomb Repressive Complex 2 (PRC2). Treatment of Taf4-mutant enteroids with a specific Ezh2 inhibitor restored buddings, cell proliferation and the stem/progenitor compartment. Taf4 loss also led to increased PRC2 activity in cells of adult crypts associated with modification of the immune/inflammatory microenvironment that potentiated Apc-driven tumorigenesis. Our results reveal a novel function of Taf4 in antagonizing PRC2-mediated repression of the stem cell gene expression program to assure normal development, homeostasis, and immune-microenvironment of the intestinal epithelium.

Recovery after anaesthesia for pulmonary surgery: desflurane, sevoflurane and isoflurane

We have studied maintenance and recovery profiles after general anaesthesia with sevoflurane, desflurane and isoflurane in 100 patients undergoing pulmonary surgery. End-tidal concentrations of anaesthetic required to maintain mean arterial pressure and heart rate within 20% of baseline values were 1.4 +/- 0.6% for sevoflurane, 3.4 +/- 0.9% for desflurane and 0.7 +/- 0.3% for isoflurane. The three anaesthetics had comparable haemodynamic effects and arterial oxygenation during one-lung ventilation. Emergence was twice as fast with desflurane than with sevoflurane or isoflurane (mean times to extubation: 8.9 (SD 5.0) min, 18.0 (17.0) min and 16.2 (11.0) min for desflurane, sevoflurane and isoflurane, respectively). Early recovery (Aldrete score, cognitive and psychomotor functions) was also more rapid after desflurane. In pulmonary surgery, desflurane, but not sevoflurane, allowed more rapid emergence and earlier recovery than isoflurane.

[Exclusive use of calcium channel blockers and cardioselective beta-blockers in the pre- and per-operative management of pheochromocytomas. 70 cases]

The pre and intraoperative use of calcium channel blockers (CCB) has been suggested for the management of either eutopic or ectopic pheochromocytomas. We report our experience of 70 pheochromocytomas, operated between 1988 and 1996 and managed with CCB, especially nicardipine. 59 were hypertensive (84.2%). Preparation consisted of nicardipine in 61 patients or another CCB in 9 cases with duration ranging from 24 hours to several weeks depending on plasma volume and blood pressure control. Intraoperatively, nicardipine infusion was started after intubation, adjusted according to systolic blood pressure (SBP) and stopped before ligation of the tumor venous drainage. Increases in SBP greater than 200 mmHg were observed in 10 patients and were effectively controlled by nicardipine in all cases. In 16 patients, the S > BP remained less than 150 mmHg throughout anesthesia. Heart rate greater than 100 b p m occureed in 51 patients and was easily controlled with esmolol whenever used (n = 27). Arythmias were unfrequent (n = 4) and required treatment in only one case. This study confirms the ability to adequately manage pheochromocytomas with the use of nicardipine as sole vasodilating agent.