G-protein signaling is required for increasing germline stem cell division frequency in response to mating in Drosophila males.

Adult stem cells divide to renew the stem cell pool and replenish specialized cells that are lost due to death or usage. However, little is known about the mechanisms regulating how stem cells adjust to a demand for specialized cells. A failure of the stem cells to respond to this demand can have serious consequences, such as tissue loss, or prolonged recovery post injury. Here, we challenge the male germline stem cells (GSCs) of Drosophila melanogaster for the production of specialized cells, sperm cells, using mating experiments. We show that repeated mating reduced the sperm pool and increased the percentage of GSCs in M- and S-phase of the cell cycle. The increase in dividing GSCs depended on the activity of the highly conserved G-proteins. Germline expression of RNA-Interference (RNA-i) constructs against G-proteins, or a dominant negative G-protein eliminated the increase in GSC division frequency in mated males. Consistent with a role for the G-proteins in regulating GSC division frequency, RNA-i against seven out of 35 G-protein coupled receptors (GPCRs) within the germline cells also eliminated the capability of males to increase the numbers of dividing GSCs in response to mating.

Outcome of patients with nonspecific pleuritis/fibrosis on thoracoscopic pleural biopsies.

OBJECTIVE: Medical thoracoscopy is recommended in the investigation of patients with exudative pleural effusions, especially when pleural fluid analysis is uninformative. The histological finding of 'nonspecific pleuritis/fibrosis' is common in thoracoscopic biopsies and presents a great uncertainty for clinicians and patients as the long-term outcome of these patients is unclear, and anxieties about undiagnosed malignancy persist. METHOD: A retrospective case-note study of 142 patients who underwent medical thoracoscopy over a 58-month period in a tertiary referral centre with a high incidence of mesothelioma. Patients with 'nonspecific pleuritis/fibrosis' were followed up until death or for a mean (±SD) period of 21.3 (±12.0) months. RESULTS: A definitive histological diagnosis was achieved in 98 (69%) patients. A total of 44 (31%) patients had 'nonspecific pleuritis/fibrosis'. Five (12%) were subsequently diagnosed with malignant pleural disease after a mean interval of 9.8 (±4.6) months. All five patients had histologically confirmed mesothelioma. In 26 patients with 'nonspecific pleuritis/fibrosis', no cause for the pleural effusion was discovered. The false-negative rate of thoracoscopic biopsy for the detection of pleural malignancy was 5%, with a diagnostic sensitivity of 95% and negative predictive value of 90%. Pleural effusion recurrence was more frequently associated with a false-negative pleural biopsy result. However, there was no correlation with other patient characteristics or the thoracoscopist's prediction based on macroscopic appearances. CONCLUSION: Thoracoscopic pleural biopsy is valuable in the diagnosis of pleural malignancies. Patients with 'nonspecific pleuritis/fibrosis' require follow-up as a malignant diagnosis (especially mesothelioma) may eventually be established in approximately 12% of cases.