Is there a role for lymph in intestinal glucose absorption?

Although the role of the lymphatic circulation in the uptake of dietary fat is well established, the absorption of water-soluble compounds, secreted by the enterocyte into the lymph, has received little attention. In the present study an estimate is made of the amount of dietary glucose that can be absorbed via the lymphatic system in the rat.

Electrocardiographic abnormalities and left ventricular systolic function in Chagas' heart disease

In chagasic patients, the electrocardiogram becomes abnormal very late in the course of the disease. Most clinical studies concerning cardiac autonomic function of chagasic patients have been carried out in this very late stage of the disease. The purpose of this study was to assess accurately the left ventricular systolic function of chagasic patients with abnormal electrocardiograms. We performed left ventricular contrast cineangiography in 44 patients with positive complement fixation test for Chagas' disease and abnormal electrocardiograms. On the basis of the electrocardiographic abnormalities found in the electrocardiogram taken the night before the hemodynamic procedure, we divided our patients into three subgroups; those with rhythm disturbances, those with ventricular conduction abnormalities, and those with rhythm disturbances plus ventricular conduction abnormalities. The chagasic patients with only cardiac rhythm disturbances, had left ventricular volumes and ejection fractions which were similar to those of controls. On the other hand, the left ventricular volumes of the chagasic patients with ventricular conduction defects, although slightly larger, were still not different from those of controls. Finally, the chagasic patients, with cardiac rhythm disturbances and left ventricular conduction defects, had the largest left ventricular volumes (P less than 0.05), and the lowest ejection fractions (P less than 0.001) of all three subgroups. These findings clearly indicate that chagasic patients, in this very late stage of the disease, have a very variable degree of left ventricular systolic dysfunction. Furthermore, our results show a distinct tendency for the left ventricular volumes to increase, and for the ejection fraction to decrease; when the electrocardiogram becomes progressively more abnormal, and "mixed" electrocardiographic abnormalities appear.(ABSTRACT TRUNCATED AT 250 WORDS)

Glutamine as a major nitrogen carrier to the liver in suckling rat pups

We measured the amino acid concentrations in the afferent and efferent vessels of the liver in anaesthetized fed adult rats and in fed suckling rat pups. A much higher content of glutamine in the portal vein and the aorta than in hepatic veins suggests that this amino acid is actively taken up by the liver of fed suckling rat pups, conversely to what is found in adult rats. In an attempt to characterize further the mechanism(s) contributing to this enhanced glutamine uptake, we monitored the time course of 1 mM-glutamine transport into plasma-membrane vesicles purified from the livers of either adult or suckling rats. The concentrative Na+-dependent uptake of glutamine was lower in those vesicles obtained from pups than in those obtained from adult rats. Glutaminase and glutamine synthetase activities in livers from both experimental groups were also measured. Glutaminase and glutamine synthetase activities in suckling rats were about 3-fold higher and 2-fold lower respectively than those in adult rats. It is concluded that glutamine is a main nitrogen carrier to the liver in fed suckling rats. A high availability of this amino acid and an enzyme imbalance between glutamine-synthesizing and -degrading activities may account for the net uptake found in vivo.

Kinetic study of the enzyme NADPH cytochrome-C (P-450) reductase: non-Michaelian behaviour

1. Contrary to what has been accepted until now, the enzyme exhibits non-Michaelian kinetics both against NADPH and against cytochrome-c as substrates; deviations were detected that have led to the proposition of a rate equation of minimum degree 2:2. 2. A general mechanism is proposed that includes, apart from the binding of the enzyme to NADPH, the formation of an enzyme-cytochrome-c complex, both routes leading to the formation of a ternary-complex NADPH-enzyme-acceptor. 3. From the latter, a series of intermediate steps finally leads to the release of the enzyme in conditions to start a new catalytic cycle. 4. Application of the King-Altman method to this mechanism yields a kinetic equation of degree 2:2 with respect to the cytochrome-c and NADPH, in accordance with our experimental results.

Hepatic uptake of amino acids in late-pregnant rats. Effect of food deprivation

Hepatic availability, uptake and fractional extraction of amino acids were estimated in anaesthetized 21-day-pregnant and age-matched virgin rats, either fed or after 24 h starvation. Amino acid availability was unaltered in fed pregnant rats as compared with fed virgin controls. However, the hepatic uptake of these compounds was higher in the former than in the latter. These adaptations were mediated by an increase in the hepatic capability to take up amino acids in late-pregnant rats, as reflected by the changes found for the fractional extraction rates. The decrease in amino acid availability found after starvation was more pronounced in pregnant than in virgin rats. Nevertheless, the hepatic uptake was similar in both groups. These results indicate that amino acids are not limiting for ureagenesis during late pregnancy, strongly suggesting that the mechanism(s) which modulate urea synthesis may be intracellular in origin.

Hepatic uptake of amino acids at mid-lactation in the rat

Hepatic availability and uptake of amino acids were measured in fed virgin and 15-day-lactating rats. Lactation did not induce any change in total amino acid availability (expressed per 100 g body wt.). Virgin rats showed a nil hepatic balance, and lactation induced a high net uptake. The high drainage of amino acids by mammary gland does not affect hepatic availability.

Hepatic uptake of gluconeogenic substrates in late-pregnant and mid-lactating rats

Lactate uptake by liver is markedly increased in late-pregnant and mid-lactating rats without concomitant changes in its availability. Glycerol contribution to the liver 3-C unit uptake is only significant at term gestation (50% of lactate uptake) but almost negligible at mid-lactation (10% of lactate uptake). Pyruvate is only taken up by the liver of 15-day lactating rats. As a general trend, the livers of either pregnant or lactating rats are provided with an enhanced capacity to take up gluconeogenic substrates.

Kinetic studies on the formation of nitrosamines I. Formation of dimethylnitrosamine in aqeous solution of perchloric acid

The kinetics of nitrosation of dimethylamine (DMA) in aqueous perchloric acid solution have been studied using a differential spectrophotometric technique. The rate law is Initial rate = e[DMA]0 [nitrite]2 0 [H+]/(f + [H+])2 where [DMA]0 and [nitrite]0 represent initial stoichiometric concentrations. At 310.0 K and mu = 2.0 M, e = (2.2 +/- 0.2) X 10(-5) M-1 s-1 and f = (1.28 +/- 0.02) X 10(-3) M. The associated activation energy is 56 +/- 3 kJ mol-1. A clear inhibition of the nitrosation rate by ionic strength has been observed in which only the kinetic parameter (f) has an effective change. It is concluded that under the experimental conditions of this work only the dinitrogen trioxid is the effective carrier for the nitrosation.

Kinetics of oxidation of nitrite by hypochlorite ions in aqueous basic solution

The kinetics of oxidation of nitrite to nitrate by hypochlorite ions in aqueous basic solution [Formula: see text] have been studied using a dynamic spectrophotometric technique. The rate law is[Formula: see text]At 298.0 K and ionic strength 0.40 M, d = (3.4 ± 0.2) × 10−8 mol l−1 s−1 and e = (2.8 ± 0.2) × 10−6 s−1. The associated activation energies are 56 ± 3 and 61 ± 3 kJ mol−1 respectively. A mechanism is proposed involving the reversible initial step:[Formula: see text]with the NO2Cl undergoing two parallel subsequent reactions, one a unimolecular decomposition and the other an attack by NO2− on NO2Cl.