contributed equally to this work Phospholipase D (PLD) has been proposed to mediate cytoskeletal remodeling and vesicular traf®cking along the secretory pathway. We recently described the activation of an ADP ribosylation factor-regulated PLD at the plasma membrane of chromaf®n cells undergoing secretagogue-stimulated exocytosis. We show here that the isoform involved is PLD1b, and, using a real-time assay for individual cells, that PLD activation and exocytosis are closely correlated. Moreover, overexpressed PLD1, but not PLD2, increases stimulated exocytosis in a phosphatidylinositol 4,5-bisphosphate-dependent manner, whereas catalytically inactive PLD1 inhibits it. These results provide the ®rst direct evidence that PLD1 is an important component of the exocytotic machinery in neuroendocrine cells.

Phosphatidic acid (PA) is the simplest phospholipid naturally existing in living organisms, but it constitutes only a minor fraction of total cell lipids. PA has attracted considerable attention because it is a phospholipid precursor, a lipid second messenger, and a modulator of membrane shape, and it has thus been proposed to play key cellular functions. The dynamics of PA in cells and in subcellular compartments, however, remains an open question. The recent generation of fluorescent probes for PA, by fusing GFP to PA-binding domains, has provided direct evidence for PA dynamics in different intracellular compartments. Here, three PA sensors were characterized and their preferences for different PA species in particular lipidic environments were compared. In addition, the localization of PA in macrophages during frustrated phagocytosis was examined using these PA sensors and was combined with a lipidomic analysis of PA in intracellular compartments. The results indicate that the PA sensors display some preferences for specific PA species, depending on the lipid environment, and the localization study in macrophages revealed the complexity of intracellular PA dynamics.

No abstract

Previously unsuspected pituitary tumors (incidentalomas) were analyzed in autopsies (4.8-27%) and magnetic resonance imaging (MRI) (10-37%), most of them being micro-pituitary incidentalomas (PI). However, patients with PIs sometimes had macroadenomas which may relate to previously unsuspected neurological and/or endocrine abnormalities. This study aims to establish the incidence of macro- vs. micro-PIs, the need for medical and/or surgical treatment and the neurological and endocrine dysfunction in a retrospective evaluation of patients with PIs studied over six years (1994-2000). Thirty-eight of 46 patients with PIs (22 males), aged 16-77, were followed for a mean of 3.2 years. Initial hormonal testing, ophthalmologic evaluation and MRI were repeated during follow-up. Twenty-nine (63%) of 46 patients had macro-PIs and 17 (17%) micro-PIs. Twenty-three males (75%) had macro-PIs, 10 (34.5%) with visual field defects. Consultations leading to PI diagnosis were chronic headache (28%), cranial trauma (15.3%), sinusitis (13%) and stroke (13%). Partial deficiencies of the anterior pituitary function were confirmed in 19 PIs (41.3%), with secondary hypogonadism prevailing (30%). Seven PIs (15%) were prolactinomas treated with dopamine agonists. Seventeen PIs (37%) underwent surgery. Immunohistochemical analysis showed gonadotrophinomas (30%), plurihormonal non-secreting adenomas (40%), and pituitary adenomas not reacting to any of the anterior pituitary hormone antibodies (30%). One operated macro-PI was a craniopharyngioma. Our data show a high percentage of PIs are macro-incidentalomas against expectations from necropsy and imaging studies. Most macro-PIs are found in males and are clinically non-functioning adenomas, 37% requiring surgery and hormonal substitution.