Differential regulation of amino acid exchange and protein dynamics across splanchnic and skeletal muscle beds by insulin in healthy human subjects

To define the mechanism of insulin's anticatabolic action, the effects of three different dosages of insulin (0.25, 0.5, and 1.0 mU x kg(-1) x min(-1)) versus saline on protein dynamics across splanchnic and skeletal muscle (leg) beds were determined using stable isotopes of phenylalanine, tyrosine, and leucine in 24 healthy subjects. After an overnight fast, protein breakdown in muscle exceeded protein synthesis, causing a net release of amino acids from muscle bed, while in the splanchnic bed protein synthesis exceeded protein breakdown, resulting in a net uptake of these amino acids. Insulin decreased (P < 0.003) muscle protein breakdown in a dose-dependent manner with no effect on muscle protein synthesis, thus decreasing the net amino acid release from the muscle bed. In contrast, insulin decreased protein synthesis (P < 0.03) in the splanchnic region with no effect on protein breakdown, thereby decreasing the net uptake of the amino acids. In addition, insulin also decreased (P < 0.001) leucine nitrogen flux substantially more than leucine carbon flux, indicating increased leucine transamination (an important biochemical process for nitrogen transfer between amino acids and across the organs), in a dose-dependent manner, with the magnitude of effect being greater on skeletal muscle than on the splanchnic bed. In conclusion, muscle is in a catabolic state in human subjects after an overnight fast and provides amino acids for synthesis of essential proteins in the splanchnic bed. Insulin achieves amino acid balance across splanchnic and skeletal muscle beds through its differential effects on protein dynamics in these tissue beds.     

Ultrastructural evidence for bouton proliferation in the partially deafferented dentate gyrus of the adult rat

A quantitative morphological study of the changes in the dentate gyrus molecular layer in response to the removal of perforant path afferents was made utilizing electron microscopic techniques. Alterations in 1. the population of remaining afferents, 2. glial cells, and 3. granule cell dendrites are reported. The major observation was an increase in intact bouton density in the region of denervation which began at 5 days post-lesion and continued through 11 days post-lesion, the longest post-lesion survival time studied.     

Prediction of substrate temperature in dc ion-plating systems

The dominant control variables of a dc-biased ion-plating system have been described in terms of a generalized parameter U_s. U_s is related to the experimentally-determined temperatures of various non-cooled metal substrates (Ta, Mo, and mild-steel) by a linear expression T_s = 38.0 U_s + 19.0. This expression allows the substrate temperature to be predicted in degrees centigrade for different values of the control variables as an aid in the production of high-quality thin films.     

Hypercapnic respiratory acidosis precipitated by hypercaloric carbohydrate infusion in resolving septic acute respiratory distress syndrome: a case report

Complications may occur when nutritional support is administered either parenterally or enterally. Inappropriate nutritional formulas with high carbohydrate loads can precipitate respiratory failure in patients with compromised lung function, induce respiratory distress which manifests as dyspnea and tachypnea in an originally normal lung condition, produce hypercapnic acidosis in mechanically ventilated patients with chronic obstructive pulmonary disease (COPD) as well as patients recovering from acute respiratory distress syndrome (ARDS) without chronic lung disease, or result in difficult weaning. Hypercaloric mixed substrates administered either parenterally or enterally can also have profound impacts on gas exchange and energy expenditure. This report describes a patient who experienced exacerbation of respiratory distress and hypercapnic acidosis during recovery from septic ARDS as the result of a nutritionally-related increase in CO2 production. As carbohydrate calories were decreased, CO2 production diminished and the hypercapnia was resolved. The importance of indirect calorimetry cannot be overemphasized during tailoring of nutritional support for the critically ill patients.     

Postnatal growth of fetus-in-fetu

A 6-month-old-boy who presented with an abdominal mass disclosed a well-formed fetus in the retroperitoneum. This mass was retrospectively noted at the age of 1 month. Comparison of two radiographic examinations done 5 month apart clearly demonstrated the enlargement of an included fetus in the bearer's abdomen. Our report of this rare condition focuses on the growth of the fetus-in-fetu detected by roentgenograms.     

Effect of ethanol on nuclear casein kinase II activity in brain

The mutual enhancement of insulin release by glucose and amino acids is not clearly understood. In this study, the effects on electrical activity and insulin release of a mixture of amino acids and glucose at concentrations found in fed (aaFD) and fasted (aaFT) animals were determined using freshly isolated mouse islets. Islets perifused with aaFD mixture showed an oscillatory pattern of electrical activity at lower glucose concentrations (5 mmol/l) than in islets perifused with the aaFT mixture and with glucose (G) alone (10 mmol/l). The concentration/response curve for the fraction of time spent by the membrane potential in the active phase in aaFD-stimulated islets was found to be significantly shifted to the left and had a smaller slope than that for glucose-stimulated islets. Insulin release followed the same pattern. This resulted in a concentration/response curve for glucose that was closer to that recorded "in vivo". We have also found that four amino acids (leucine, isoleucine, alanine and arginine) are largely responsible for the observed effects and that there is a non-linear enhancement of insulin release as a consequence of the combined effect of amino acids and glucose. This effect was more pronounced in the second phase of insulin release and was dependent on intracellular Ca2+. These findings indicate that amino acids account for most of the left-ward shift in the concentration/response curve for glucose and that a reduction in the threshold for the glucose-induced oscillatory electrical activity response and in the generation of Ca2+ spikes accounts for the triggering of insulin release at lower glucose concentrations. Nevertheless, the effects on insulin release at high glucose concentrations cannot be explained solely by the increase in glucose-induced electrical activity.