A major advance of tropical Andean glaciers during the Antarctic cold reversal.

The Younger Dryas stadial, a cold event spanning 12,800 to 11,500 years ago, during the last deglaciation, is thought to coincide with the last major glacial re-advance in the tropical Andes. This interpretation relies mainly on cosmic-ray exposure dating of glacial deposits. Recent studies, however, have established new production rates for cosmogenic (10)Be and (3)He, which make it necessary to update all chronologies in this region and revise our understanding of cryospheric responses to climate variability. Here we present a new (10)Be moraine chronology in Colombia showing that glaciers in the northern tropical Andes expanded to a larger extent during the Antarctic cold reversal (14,500 to 12,900 years ago) than during the Younger Dryas. On the basis of a homogenized chronology of all (10)Be and (3)He moraine ages across the tropical Andes, we show that this behaviour was common to the northern and southern tropical Andes. Transient simulations with a coupled global climate model suggest that the common glacier behaviour was the result of Atlantic meridional overturning circulation variability superimposed on a deglacial increase in the atmospheric carbon dioxide concentration. During the Antarctic cold reversal, glaciers advanced primarily in response to cold sea surface temperatures over much of the Southern Hemisphere. During the Younger Dryas, however, northern tropical Andes glaciers retreated owing to abrupt regional warming in response to reduced precipitation and land-surface feedbacks triggered by a weakened Atlantic meridional overturning circulation. Conversely, glacier retreat during the Younger Dryas in the southern tropical Andes occurred as a result of progressive warming, probably influenced by an increase in atmospheric carbon dioxide. Considered with evidence from mid-latitude Andean glaciers, our results argue for a common glacier response to cold conditions in the Antarctic cold reversal exceeding that of the Younger Dryas.

Studies on the tolerance of medium chain triglycerides in dogs.

Two groups of five conscious dogs received total parenteral nutrition (about 100 kcal/kg body weight per 24 hr) continuously for 96 hr (0.28 g triglycerides/kg body weight per hr, constituting more than 55% of the energy supply). The only difference between the two groups was the nature of the 20% lipid emulsion. In one group, this emulsion contained only long-chain triglycerides (LCTs), and in the other it contained a mixture (vol/vol) of medium chain triglycerides (MCTs) and LCTs. MCTs thus were given in an amount of about 30% of the total energy supplied. During infusion with the MCT/LCT mixture, C8, C10, and C12 fatty acids appeared in the total plasma fatty acids. When the infusion was stopped, the medium-chain fatty acids disappeared; those with shorter chains did so more rapidly. The plasma triglyceride clearance was faster for the MCT/LCT mixture than for the LCTs, whereas phospholipid and cholesterol clearance seemed slower for the MCT/LCT mixture. With this mixture, there was a slight increase in the plasma concentrations of ketone bodies, lactate, and pyruvate, and a slight decrease in plasma glucose. The MCT/LCT mixture was well tolerated, causing no discernible problems, and, in particular, no signs of narcosis or encephalopathy.

[Diuresis, renal plasma flow and glomerular filtration in conscious and anesthetized sheep: the effects of a diet deficient in proteins]. / Diurèse, débit plasmatique rénal et filtration glomérulaire chez le mouton vigile et anesthésié: effets d'un régime carencé en protéines.

Determinations of renal plasma flow (RPF), glomerular filtration rate (GFR) and urine flow in sheep fed low protein diets have yielded controversial data. In the present experiment, 8 sheep were fed a regular diet and another 6 received a low protein ration. Water intake and urine output were measured over 10 days. RPF and GFR were determined on 2 consecutive days. The latter determinations were repeated on 5 anaesthetized animals (sodium thiopental) in each group. An important increase in water intake (58%) and urine output (98%) was observed in the sheep on the low protein diet. In these animals, blood urea averaged 0.1 g/l. Urine output was greater (with a lower osmolarity) when the blood urea level was the lowest. RPF and GFR were significantly lower in the sheep on the low protein diet (RPF: 13.5 versus 28.1 ml/min/kg in the control animals; GFR: 1.61 versus 4.01 ml/min/kg); no relationship could be established with the blood urea level. The only effect of the anaesthesia was a reduction in RPF, of the same magnitude in both groups of sheep (about 35%). In conclusion, when sheep are fed a low protein diet, the volume of plasma processed through the kidney is decreased. In the present experiment, the increased urine flow and the lowered urinary osmolarity indicate an impaired renal concentrating ability. Barbiturate anaesthesia does not affect this phenomenon.

[Effects of a diet with low fiber and thiamine contents on erythrocyte transketolase activity in goats]. / Effet d'une alimentation déficitaire en lest et appauvrie en thiamine sur l'activité transcétolasique érythrocytaire chez la chèvre.

To test the effects of an insufficient fiber content, a high percentage of readily fermentescible carbohydrate and non protein nitrogen uptake on thiamin nutrition, three goats were submitted during periods of 40 or 90 days to three diets with low fiber contents (1: 16.53%; 2: 12.37%; 3: 12.84%) and low thiamin contents (1: 0.07; 2: 0.08; 3: 0.05' mg/kg). The diets were basically composed of beet pulp and equilibrated in protein either with copra meal or with urea. Diets 2 and 3 were enriched with 20% lactose. Animals had no access to coarse forage or litter. Variations of blood transketolase activity, pyruvicemia and lactacidemia were followed. Preliminary standard values of transketolase activity were determined with a hay diet (38 +/- 10 Ul/l total blood) or a grass diet (47 +/- 13 Ul/l). In the same way, no decrease of food intake or clinical signs of thiamin deficiency could be observed. In none of the cases were noted impairment of blood transketolase activity or increase in lactacidemia or pyruvicemia. It was concluded that a diet deficient in fiber and rich in fermentescible carbohydrate cannot by itself induce a decrease in thiamin synthesis in so far as transitions between diets are not done abruptly.

Simple high-performance liquid chromatographic separation of oxazepam and its diastereoisomeric glucuronides in serum. Applications in a pharmacokinetic study in sheep.

This paper describes a highly specific and sensitive method for quantifying oxazepam and its diastereoisomeric glucuronides in serum. The method involves sample clean-up by solid-phase extraction on C18 cartridge followed by quantitation on a reversed-phase HPLC column. Diazepam is used as internal standard. Extraction recovery from serum proved to be more than 86%. Precision, expressed as C.V., was in the range 1.2-9.5%. The limits of quantification were 40, 400, and 200 nmol/l for oxazepam, S-(+)- and R-(-)-glucuronides, respectively. This method was applied to the determination of oxazepam and its diastereoisomeric glucuronides in serum collected during a pharmacokinetic study performed in sheep after oral administration of racemic oxazepam. S-(+)/R-(-) ratios were measured all along the sampling time collection and the pharmacokinetic parameters were determined.