ABSTRACT
Two permanent sampling sites were selected at the two extremes of a rainfall gradient in natural forests of Quercus pyrenaica Willd. located in the Sierra de Gata (Salamanca Province, Spain). During 1991 and 1992, diurnal courses of transpiration rate (E), stomatal conductance (g(s)) and leaf water potential (Psi(l)) were studied at different levels in the tree canopy. Leaf water potential fell from a high value in the early morning to a minimum at midday and then increased again in the afternoon. Values of Psi(l) in the early morning and at midday were lower at Fuenteguinaldo (dry site) than at Navasfrías (wet site) and were related to soil water availability. Stomatal conductance increased during the morning and maximum g(s) occurred about 3 h before Psi(l) was at its lowest value. The highest values of g(s) were found at Navasfrías during July. The lowest Psi(l) values were found in the upper parts of the canopy and differences among canopy levels were greatest when soil water availability was low. In August, minimum values of Psi(l) differed among canopy levels by 1.0 MPa at Navasfrías and by 0.8 MPa at Fuenteguinaldo. The maximum difference in g(s) among canopy levels was about 150 mmol m(-2) s(-1) at Navasfrías and about 300 mmol m(-2) s(-1) at Fuenteguinaldo. The results indicate a nonconservative pattern of water use in Quercus pyrenaica.
ABSTRACT
The effects of diet composition (equilibrated and fat- and protein-rich) in combination with chronic ethanol ingestion on pancreatic exocrine secretion were studied in rats after a 7-month treatment period, also analyzing under these experimental conditions the acute effects of intraduodenal administration of 20% ethanol. Chronic consumption of ethanol affected pancreatic flow but its acute administration stimulated the secretion of fluid, especially in control rats. Total protein secretion is depressed in all rats receiving ethanol as fluid, but this was increased when rats drank water. Amylase activity depends on carbohydrate levels, decreased with fat and protein-rich diet but not with ethanol ingestion. Diet composition by itself did not affect specific trypsin activity but this increased significantly when a fat- and protein-rich diet was administered together with ethanol. Trypsin activity remained unchanged when ethanol was perfused into the duodenum in animals receiving ethanol chronically.
Subject(s)
Alcoholism/metabolism , Diet , Ethanol/pharmacology , Pancreas/metabolism , Alcoholism/pathology , Amylases/metabolism , Animals , Body Weight/drug effects , Duodenum , Eating , Energy Intake , Ethanol/administration & dosage , Growth/drug effects , Intubation, Gastrointestinal , Male , Pancreas/drug effects , Pancreatic Juice/drug effects , Pancreatic Juice/metabolism , Rats , Rats, Wistar , Trypsin/metabolismABSTRACT
1. The effects of a diet rich in protein and fat, compared with a control diet, with or without chronic ingestion of ethanol on the pancreatic response to cholecystokinin were studied in rats after a 7-month treatment period. The acute effects of intraduodenal administration of 20% (v/v) ethanol were also analysed under these experimental conditions. 2. Animals receiving a diet rich in protein and fat showed a greater percentage increase in pancreatic output in response to cholecystokinin. 3. Chronic ethanol consumption reduced the basal secretion of protein and amylase; and even though the response capacity to cholecystokinin (considered as the percentage secretion on cholecystokinin stimulation with respect to basal secretion) was maintained, this led to hormone-stimulated secretion being decreased in comparison with the animals receiving water. In contrast, a lack of inhibition of basal volume flow and flow after cholecystokinin stimulation was seen after long-term ingestion of ethanol. 4. Acute administration of ethanol generally depressed cholecystokinin-stimulated pancreatic secretion. 5. On stimulation with cholecystokinin, the diet rich in protein and fat combined with long-term ingestion of ethanol led to non-parallel changes in the release of pancreatic enzymes, since an increase in trypsin secretion and a decrease in amylase secretion occurred concomitantly.
