Starvation reduces norepinephrine activities in both hypothalamus and heart in rats

Norepinephrine (NE) activities in both hypothalamus and heart were simultaneously assessed in rats after food-deprivation for 2 days. The technique of gas chromatography-mass spectrometry was employed for the analysis of NE and its primary neuronal metabolite, 3,4-dehydroxyphenylethylene glycol (DHPG), and the ratio of DHPG to NE was used as an index of NE activity. Hypothalamic DHPG/NE ratio was significantly decreased by fasting and was completely reversed by a single day of refeeding. These changes in hypothalamic DHPG/NE ratio were parallel to those in cardiac DHPG/NE ratio. Supporting the concept in which hypothalamic NE neurons play an important role in modulating the sympathetic outflow, it is suggested the decrease in hypothalamic NE activity contributes to the reduction in cardiac NE activity during fasting.     

Beta-endorphin and endoloxone: Hormones of the autonomic nervous system for the conservation or expenditure of bodily resources and energy in anticipation of famine or feast

Two new divisions of the autonomic nervous system are postulated that direct the conservation or expenditure of bodily resources (water, CO₂, Na⁺, Ca⁺⁺, heat, fuels) and energy and coordinate these movements with the degree of anticipated nutrient shortage or excess in the environment. One division employs opioids to increase the inflows and to decrease outflows. The other division employs endogenous naloxone-like substances which decrease the inflows while they increase the outflows. Integrated and widespread actions of these systems influence almost every tissue in the body. The roles of these systems in hibernation and arousal help to clarify their functions.     

Lack of anorexia following prolonged intragastric feeding in rats

Adult rats starved for 5 days ate less than normal when food was reintroduced, whereas rats fed a non-nutritive diet by gastric intubation for 6 days and rats fed a complete diet by gastric intubation for fourteen days showed no such anorexia. The lack of eating experience did not interfere with normal eating upon reintroduction of food, indicating that poststarvation anorexia may be a result of gastrointestinal changes caused by a lack of dietary bulk.     

Comment gérer la progression calorique lors de la renutrition

Total or partial starvation decrease both body fat mass and lean body mass. The latter comes along with a spectacular drop in intracellular glycogen and nucleotides phosphate, associated with decreased intracellular fluid volume and total body potassium, magnesium and phosphate pools. Upon renutrition, the provision of carbohydrate and the ensuing hyperinsulinemia cause a swift reversal of cellular hypometabolism, and to a rapid transport of extracellular phosphate, potassium and magnesium into the cells. This is more specifically related administration of carbohydrate and a rapid rise in plasma insulin concentration, which is responsible for an immediate increase in cellular energy metabolism, inhibition of lipid oxidation and stimulation of glycogen synthesis. These phenomenons can be some times at the origin of set of acute hydro-electrolytic imbalances and cardiac and neural dysfunctions known as “the refeeding syndrome”. Occurrence of this syndrome can be largely prevented by a slow, graded administration of energy and carbohydrate upon initiation of refeeding and by the systematic administration of potassium supplement. The initial phase of refeeding also requires a careful monitoring of blood phosphate and magnesium concentrations, with administration of exogenous supplements when required.     

Nociceptive thresholds following food restriction and return to free-feeding

Nine rats were placed on a restricted food diet for 14 days and nociceptive thresholds were measured by the tail-flick procedure. After 24 hr of food restriction nociceptive thresholds increased. This initial increase in nociceptive threshold was followed by a decrease in pain threshold on the second day of food restriction. Nociceptive thresholds returned to pre-deprivation levels on the remaining 11 days of food restriction. When the rats were given free access to food after 14 days of food restriction, nociceptive thresholds increased 24 hr after the reintroduction of food and decreased during the next 24 hr. Thus, the results of the present experiment demonstrate that both food restriction and a return to free feeding after 14 days of food restriction produced the same biphasic pattern of changes in nociceptive thresholds.     

Influence of a 3.5 day fast on physical performance

Summary Eight young men were tested for strength, anaerobic capacity and aerobic endurance in a post absorptive state and after a 3.5 day fast. Strength was tested both isokinetically (elbow flexors, 0.52 rad·s^–1 and 3.14 rad·s^–1) and isometrically. Anaerobic capacity was evaluated by having subjects perform 50 rapidly repeated isokinetic contractions of the elbow flexors at 3.14 rad·s^–1. Aerobic endurance was measured as time to volitional fatigue during a cycle ergometer exercise at 45% . Measures of , V _E, heart rate, and ratings of perceived exertion were obtained prior to and during the cycle exercise. The 3.5 day fast did not influence isometric strength, anaerobic capacity or aerobic endurance. Isokinetic strength was significantly reduced ( 10%) at both velocities. , V _E and perceived exertion were not affected by fasting. Fasting significantly increased heart rate during exercise but not at rest. It was concluded that there are minimal impairments in physical performance parameters measured here as a result of a 3.5 day fast.     

Novel biochemical properties of a CRP/FNR family transcription factor from Mycobacterium tuberculosis

Cyclic AMP (cAMP) receptor protein (CRP)/fumarate nitrate reductase regulator (FNR) family proteins are actively associated with defense against low oxygen stress, starvation and extreme temperature conditions. They are DNA-binding proteins and regulate target genes carrying the regulatory CRP/FNR cognate nucleotide sequence elements. Recombinant protein encoded by the Mycobacterium tuberculosis ORF Rv3676, a putative CRP/FNR regulator, was purified from Escherichia coli and was found to exist as dimer, devoid of any metal cation cofactor. Purified rRv3676 exhibited cAMP binding in a concentration-dependent manner. At lower concentrations of cAMP (6-10 microM) rRv3676 shows positive cooperativity; at 10 microM cAMP the protein exists in the most open conformation. rRv3676 could bind specifically to the putative CRP/FNR nucleotide sequence elements as evident from electrophoretic mobility shift assay.     

Regulatory interplay of RpoS and RssB controls motility and colonization in Vibrio cholerae

Cholera is a life-threatening diarrheal disease caused by the human pathogenic bacterium Vibrio cholerae. Regulatory elements are essential for bacterial transition between the natural aquatic environment and the human host. One of them is the alternative sigma factor RpoS and its anti-sigma factor RssB. Regulation principles seem to be conserved among RpoS/RssB interaction modes between V. cholerae and Enterobacteriaceae species, however the associated input and output pathways seem different. In Escherichia coli, RpoS/RssB is important for the activation of an emergency program to increase persistence and survival. Whereas, it activates motility and chemotaxis in V. cholerae, used strategically to escape from starvation conditions. We characterised a starvation-induced interaction model showing a negative feedback loop between RpoS and RssB expression. We showed by genotypic and phenotypic analysis that rssB influences motility, growth behaviour, colonization fitness, and post-infectious survival. Furthermore, we found that RssB itself is a substrate for proteolysis and a critical Asp mutation was identified and characterised to influence rssB phenotypes and their interaction with RpoS. In summary, we present novel information about the regulatory interaction between RpoS and RssB being active under in vivo colonization conditions and mark an extension to the feedback regulation circuit, showing that RssB is a substrate for proteolysis.     

Some effects of a split litter cross foster design applied to 15 day old rat pups

Rat litters were divided and cross fostered on a postnatal Day 15 so that each mother had 4 of her own pups and 4 pups of a second litter, until weaning at 21 days. Daily weight and body temperature measurements made between Day 15 and 21 showed no differences between foster pups and pups who stayed with their biological mothers. However, by the age of 30 days, foster pups weighed less than pups reared by their own (biological) mothers; and foster pups at that age did not survive food deprivation as well as the pups reared by their biological mothers. In their Day 30 weights and the capacity to survive food deprivation, foster pups resembled pups that had been permanently separated from their mothers on postnatal Day 15. We conclude that the split cross foster design may introduce variability rather than reduce it. Nonetheless, this design may be useful in the experimental investigation of maternal behavior and mother-pup interactions in the rat.     

Experimental study of non-alcoholic fatty liver disease (NAFLD) on a model of starving chickens: is generalization of steatosis accompanied by fibrosis of the liver tissue?

The objective of this work was to study the mechanism of liver parenchyma development under the influence of restriction of diet. Useful information is presented about the pathologic features associated with diet restriction in a chicken animal model of NAFLD. There were 96 chickens of two genotypes, Ross 308 and Cobb 500, in the experiment. The control group was fed a standard mixture ad libitum (ADL). The first experimental group, under restriction from the age of 2 weeks, was fed 80% ADL. The second experimental group was fed 65% ADL from the age of 2 weeks. There were 16 animals in each group. The experiment lasted 5 weeks. Liver parenchyma samples were obtained at the age of 35 days by the necropsy method and then processed by standard histologic methods. The slices were stained by standard staining: hematoxylin-eosin and by Sirius red kit for collagen type I and reticulin visualization. Hepatocyte diameter and the proportion of interstitial tissue to the parenchyma of the liver were measured objectively. Microvesicular liver steatosis was observed after 35 days of restriction. Hepatocyte diameter was significantly influenced by sex, genotype, and the experimental group. The proportion of interstitial tissue to the liver parenchyma was highly influenced by genotype and group, but there were no interactions. An increase in the steatosis histologic grade is associated with inflammatory changes, with decrease of hepatocyte diameter and with a decreasing proportion of interstitial tissue to the liver parenchyma. The results show that early restriction is not associated with the development of fibrosis of the liver tissue.