Impacts of 25 years of groundwater extraction on subsidence in the Mekong delta, Vietnam.

Many major river deltas in the world are subsiding and consequently become increasingly vulnerable to flooding and storm surges, salinization and permanent inundation. For the Mekong Delta, annual subsidence rates up to several centimetres have been reported. Excessive groundwater extraction is suggested as the main driver. As groundwater levels drop, subsidence is induced through aquifer compaction. Over the past 25 years, groundwater exploitation has increased dramatically, transforming the delta from an almost undisturbed hydrogeological state to a situation with increasing aquifer depletion. Yet the exact contribution of groundwater exploitation to subsidence in the Mekong delta has remained unknown. In this study we deployed a delta-wide modelling approach, comprising a 3D hydrogeological model with an integrated subsidence module. This provides a quantitative spatially-explicit assessment of groundwater extraction-induced subsidence for the entire Mekong delta since the start of widespread overexploitation of the groundwater reserves. We find that subsidence related to groundwater extraction has gradually increased in the past decades with highest sinking rates at present. During the past 25 years, the delta sank on average ∼18 cm as a consequence of groundwater withdrawal. Current average subsidence rates due to groundwater extraction in our best estimate model amount to 1.1 cm yr-1, with areas subsiding over 2.5 cm yr-1, outpacing global sea level rise almost by an order of magnitude. Given the increasing trends in groundwater demand in the delta, the current rates are likely to increase in the near future.

Serum CA 125 levels in epithelial ovarian cancer: relation with findings at second-look operations and their role in the detection of tumour recurrence.

Pre-operative serum CA 125 levels were elevated (greater than 35 U/ml) in 44 of 46 (96%) patients with epithelial ovarian cancer. Their serum CA 125 levels ranged from 36 to 8670 U/ml and a correlation with tumour stage was found. Also, during progressive disease, 49 of 53 patients showed elevated levels. At the time of second-look operations, elevated serum CA 125 levels indicated the presence of tumour. However, the presence of small tumour residues (less than 2 cm) and of microscopically detectable tumour in biopsies were not associated with raised CA 125 levels, only a few patients (2 of 13 and 2 of 17, respectively) showed levels higher than 35 U/ml before the second-look operation. Rising levels preceded the clinical discovery of a relapse in 15 of the 22 patients with a median lead time of 3.5 months (1-17 months), and in three patients rising levels were found at the time the tumour recurrence was detected. It is concluded that CA 125, despite its general usefulness, is unable to detect tumour nodules of less than 2 cm in size, but it proved to be a sensitive and early indicator of tumour recurrence and progression.

Effect of histamine H2-receptor stimulation on bombesin- and peptone-stimulated gastrin release in man.

This study was undertaken to determine whether histamine H2-receptors are involved in the regulation of gastrin secretion in man. Since previous studies on the effect of histamine H2-receptor blockade on gastrin release are conflicting, we have studied the effect of histamine infusion (130 nmol/kg/hr) with simultaneous H1-receptor blockade on gastrin release in healthy male subjects. Intragastric pH was maintained at 4.5 by continuous intragastric titration during all studies. Histamine did not affect gastrin release stimulated by infusion of bombesin (90 pmol/kg/hr) or by a peptone meal. Integrated gastrin secretion during bombesin plus histamine was 767 +/- 151 pmol X min/liter (+/- SEM), compared to 757 +/- 144 pmol X min/liter during bombesin plus saline (not significant), whereas integrated meal-stimulated gastrin release was 1666 +/- 456 pmol X min/liter during histamine and 1856 +/- 492 pmol X min/liter during saline. It is concluded that histamine H2-receptors do not seem to be involved in the regulation of gastrin secretion in man.

High-resolution CT and air CT cisternography in the diagnosis of acoustic neuromas.

High-resolution thin-section computed tomography (CT) is helpful in determining the real extent of large acoustic neuromas by means of multiplanar reconstructions. High-resolution CT has to be performed early in the work-up of any patient suspected of acoustic neuroma. Small acoustic neuromas, however, can easily be overlooked because a high percentage of these tumors has an almost isodense appearance (54%), and because 53% enhances after intravenous contrast injection. High-resolution air CT cisternography has to be considered the method of choice for the detection or exclusion of small acoustic neuromas. This procedure also demonstrates ingrowth of the tumor into the neurovascular bundle.