Effects Of Short-term Food Deprivation Research Articles

STATE OF OXIDANT HOMEOSTASIS IN THE BODY OF DOGS WITH DIFFERENT TYPES OF HIGHER NERVOUS ACTIVITY

The relevance of the study is due to the lack of data on the cortical mechanisms of regulation of the activity of the antioxidant defense system in the body of dogs. In this regard, this article is aimed at revealing the specifics of the activity of key enzymes of the system of antioxidant protection of the blood of dogs with various types of higher nervous activity under the influence of short-term food deprivation. It was shown that short-term food deprivation in dogs caused a stressful state, which was accompanied not only by a change in the behavior of the animals, but also reflected the state of the enzymatic link of the antioxidant defense system in their body. In particular, a significant effect of short-term food deprivation on the activity of catalase in dog blood erythrocytes was established (F = 13.7 > FU = 4.15; p < 0.001). We note the increase in the influence of the force of nervous processes on the activity of catalase in the blood of dogs during the experiment from – gh²ᵪ = 0.20 (р < 0.05) in the intact state, to the indicator – гх²ᵪ = 0.68 (р < 0.001) by the third day of research. Also, under the influence of food deprivation, direct connections of the strength and balance of nervous processes with the activity of this enzyme appear (r = 0.52–0.78 (р < 0.05–0.001). Under such influence, after one day and three days after the action of the stress factor, the activity of catalase in the blood of dogs with a weak type of higher nervous activity is lower by 3.6–5.8% (P < 0.05) than that of dogs with a strong balanced mobile type of higher nervous activity blood erythrocytes also found a decrease in the activity of the glutathione link of the antioxidant protection system in the blood plasma of dogs, in particular, under the influence of a stress factor, the activity of glutathione reductase during the day in dogs with various types of higher nervous activity decreases by 11.6–16.9%, respectively (р < 0, 05–0.01), the activity of glutathione reductase also decreases. Prospects for further research consist in the development of new methods for the correction of substance metabolism based on the use of nanoaquachelates of biogenic metals, taking into account the individual characteristics of the dog’s body.

FEATURES OF CARBOHYDRATE-LIPID METABOLISM IN DOGS WITH DIFFERENT TYPES OF HIGHER NERVOUS ACTIVITY

The relevance of the study is due to the lack of data on the cortical mechanisms of regulation of carbohydrate and lipid metabolism in the body of dogs. In this regard, this article is aimed at revealing the issue of lipid and carbohydrate metabolism in dogs with various types of higher nervous activity under the influence of short-term food deprivation. It is shown that the effect of short-term food deprivation is characterized by changes in metabolism in the body of dogs, which are limited by the state of the nervous system of these animals. In the intact state, the glucose content in the blood of dogs with different types of higher nervous activity does not reliably differ, while the lactate content in the blood of dogs with a weak type of higher nervous activity is higher by 16.2% (P < 0.01), and pyruvate is lower by 6.3% (P < 0.001) from the indicators of dogs with a strong balanced mobile type. Within a day after the beginning of food deprivation, the glucose content in the blood of dogs decreases by 4.6–8.2% depending on the type of nervous activity (P < 0.05–0.01). During the day after the beginning of deprivation, the ratio of lactate to pyruvate in the blood of dogs, depending on the type of higher nervous activity, increases by 19.1–36.0% (Р < 0.01), the content of total cholesterol and triacylglycerols in the blood plasma decreases by 3, 5–12.9% and the ratio of lipids of different densities changes significantly. In particular, in the blood plasma of dogs of a strong balanced mobile type of higher nervous activity, the cholesterol content of high-density lipoproteins decreased during the day by 7.1% (Р < 0.05). Thanks to the conducted research, it was possible to obtain fundamental knowledge of the cortical mechanisms of regulation of carbohydrates and lipids in the body of dogs, which will form the basis of the development of new, modern methods of correction of metabolism, taking into account the type of higher nervous activity. Prospects for further research consist in the development of new methods of correction of metabolism based on the use of nanoaquachelates of biogenic metals, taking into account the individual characteristics of the body of dogs.

Effects of short-term food deprivation on catecholamine and metabolic-sensory biomarker gene expression in hindbrain A2 noradrenergic neurons projecting to the forebrain rostral preoptic area: Impact of negative versus positive estradiol feedback.

Hindbrain A2 noradrenergic neurons assimilate estrogenic and metabolic cues. In female mammals, negative- versus positive-feedback patterns of estradiol (E) secretion impose divergent regulation of the gonadotropin-releasing hormone (GnRH)-pituitary-gonadal (HPG) neuroendocrine axis. Current research used retrograde tracing, dual-label immunocytochemistry, single-cell laser-microdissection, and multiplex qPCR methods to address the premise that E feedback modes uniquely affect metabolic regulation of A2 neurons involved in HPG control. Ovariectomized female rats were given E replacement to replicate plasma hormone levels characteristic of positive (high-E dose) or negative (low-E dose) feedback. Animals were either full-fed (FF) or subjected to short-term, e.g., 18-h food deprivation (FD). After FF or FD, rostral preoptic area (rPO)-projecting A2 neurons were characterized by the presence or absence of nuclear glucokinase regulatory protein (nGKRP) immunostaining. FD augmented or suppressed mRNAs encoding the catecholamine enzyme dopamine-beta-hydroxylase (DβH) and the metabolic-sensory biomarker glucokinase (GCK), relative to FF controls, in nGKRP-immunoreactive (ir)-positive A2 neurons from low-E or high-E animals, respectively. Yet, these transcript profiles were unaffected by FD in nGKRP-ir-negative A2 neurons at either E dosage level. FD altered estrogen receptor (ER)-alpha and ATP-sensitive potassium channel subunit sulfonylurea receptor-1 gene expression in nGKRP-ir-positive neurons from low-E, but not high-E animals. Results provide novel evidence that distinct hindbrain A2 neuron populations exhibit altered versus unaffected transmission to the rPO during FD-associated metabolic imbalance, and that the direction of change in this noradrenergic input is controlled by E feedback mode. These A2 cell types are correspondingly distinguished by FD-sensitive or -insensitive GCK, which correlates with the presence versus absence of nGKRP-ir. Further studies are needed to determine how E signal volume regulates neurotransmitter and metabolic sensor responses to FD in GKRP-expressing A2 neurons.

Short-term fasting differentially regulates PI3K/AkT/mTOR and ERK signalling in the rat hypothalamus

It is known that insulin secreted by pancreatic β-cells enters the brain by crossing the blood–brain barrier. However, it was demonstrated that insulin expression occurs in various brain regions as well. Albeit the list of insulin actions in the brain is long and it includes control of energy homeostasis, neuronal survival, maintenance of synaptic plasticity and cognition, not much is known about the adaptive significance of insulin synthesis in brain.We previously reported that short-term fasting promotes insulin expression and subsequent activation of insulin receptor in the rat periventricular nucleus. In order to uncover a physiological importance of the fasting-induced insulin expression in hypothalamus, we analyzed the effect of short-term food deprivation on the expression of several participants of PI3K/AKT/mTOR and Ras/MAPK signaling pathways that are typically activated by this hormone.We found that the hypothalamic content of total and activated IRS1, IRS2, PI3K, and mTOR remained unchanged, but phosphorylated AKT1/2/3 was decreased. The levels of activated ERK1/2 were increased after six-hour fasting. Moreover, activated ERK1/2 was co-expressed with activated insulin receptor in the nucleus arcuatus. Our previously published and current findings suggest that the ERK activation in hypothalamus was at least partially initiated by the centrally produced insulin.

Morphological and histological changes in digestive tract development during starvation in the miiuy croaker.

A histological method was used to describe the ontogenetic development of the digestive tract of laboratory-reared miiuy croaker (Miichthys miiuy) and to evaluate the effects of short-term food deprivation on the morphology and histology of the digestive tract. Larvae and juveniles were maintained at 24 °C in a thermostatically controlled system. Three starvation experiments were conducted during different developmental stages: 1-7 days after hatching (dah; prior to benthic swimming); 26-35 dah (during settling); and 42-53 dah (after benthic swimming). According to the structural changes in the ontogenetic development of the digestive tract, three stages were observed. The first stage was from hatching to 3 dah; the digestive tract was undifferentiated in newly hatched larvae and then showed remarkable morphological changes and differentiation. During this period, larvae depended on endogenous nutrition. The second stage (4-20 dah) was a critical period in which larvae transitioned from endogenous feeding to exogenous feeding and the digestive tract fully differentiated into the buccopharynx, oesophagus, stomach, anterior intestine and posterior intestine. Goblet cells and vacuoles appeared in the digestive tract, and pharyngeal teeth and taste buds developed. During the third stage (20-36 dah), the gastric glands developed and the stomach differentiated into the fundic, cardiac and pyloric regions. At 25 dah, pyloric caeca developed and mucosal folds and spiral valves were clearly distinguishable. After 30 dah, the digestive tract did not undergo any noticeable differentiation, indicating the complete development of the digestive system. The wet weight and SGR (specific growth rate) of miiuy croaker larvae and juveniles greatly decreased when they were deprived of food, and compensatory growth was observed in re-feeding juveniles. The livers of starved larvae and juveniles were atrophied and dark coloured, the intestines were transparent and thin, and the stomach cubages were reduced. The histological effects of starvation were mainly evident in the degeneration of cells in digestive organs, as seen in the shrinkage and separation of cells and the loss of intercellular substances in the liver, pancreas, intestine and stomach. These changes became more severe with increased duration of starvation. In addition, the histological structure of the digestive tracts of starved larvae and juveniles partly recovered after re-feeding, and the effects of starvation on miiuy croaker were age dependent.

The effect of fasting and refeeding on mRNA expression of PepT1 and gastrointestinal hormones regulating digestion and food intake in zebrafish (Danio rerio)

In vertebrates, a significant part of ingested protein is absorbed as di- and tripeptides through a brush border membrane proton/oligopeptide transporter protein called PepT1. The aim of the present study was to determine the effect of short-term food deprivation and refeeding in adult zebrafish (Danio rerio) on gastrointestinal mRNA expression of PepT1 as well as on the satiety hormones cholecystokinin (CCK), gastrin-releasing peptide (GRP) and ghrelin (GHR) in order to elucidate a potential mechanism driving compensatory growth. Sixty adult zebrafish were stocked in a 40-L aquarium and fed daily a commercial flake diet to satiation for 10 days where the digestive tracts (DT) of sampled fish (n = 5) were dissected out. Samplings were repeated following 1, 2 and 5 days of food deprivation and after 1, 2 and 5 days of refeeding. The RNA was extracted from all sampled DTs and analyzed by quantitative real-time PCR for the mRNA expression of PepT1, rRNA 18S, CCK, GRP and GHR. PepT1 mRNA expression increased with successive refeedings reaching a level approximately 8 times higher than pre-fast levels. CCK, GRP and GHR mRNA levels also decreased during fasting, but increased only to pre-fasting levels with refeeding. Overall, the results suggest that PepT1 may be a contributing mechanism to compensatory growth that could influence CCK secretion and GRP and GHR activity.

Extending food deprivation reverses the short-term lipolytic response to fasting: role of the triacylglycerol/fatty acid cycle

The effects of short-term food deprivation on lipid metabolism are well documented, but little is known about prolonged fasting. This study monitored the kinetics of glycerol (rate of appearance, R(a) glycerol) and non-esterified fatty acids (R(a) NEFA) in fasting rabbits. Our goals were to determine whether lipolysis is stimulated beyond values seen for short-term fasting, and to characterize the roles of primary (intracellular) and secondary (with transit through the circulation) triacylglycerol/fatty acid cycling (TAG/FA cycling) in regulating fatty acid allocation to oxidation or re-esterification. R(a) glycerol (9.62±0.72 to 15.29±0.96 μmol kg(-1) min(-1)) and R(a) NEFA (18.05±2.55 to 31.25±1.93 μmol kg(-1) min(-1)) were stimulated during the first 2 days of fasting, but returned to baseline after 4 days. An initial increase in TAG/FA cycling was followed by a reduction below baseline after 6 days without food, with primary and secondary cycling contributing to these responses. We conclude that the classic activation of lipolysis caused by short-term fasting is abolished when food deprivation is prolonged. High rates of re-esterification may become impossible to sustain, and TAG/FA cycling could decrease to reduce its cost to 3% of total energy expenditure. Throughout prolonged fasting, fatty acid metabolism gradually shifts towards increased oxidation and reduced re-esterification. Survival is achieved by pressing fuel selection towards the fatty acid dominance of energy metabolism and by slowing substrate cycles to assist metabolic suppression. However, TAG/FA cycling remains active even after prolonged fasting, suggesting that re-esterification is a crucial mechanism that cannot be stopped without harmful consequences.

Food Deprivation Sensitizes Pain Perception

While food deprivation has known effects on sympathovagal balance, little is known about hunger’s influence on the perception of pain. Since autonomic activities influence many cognitive and emotional processes, this suggests that food deprivation should interact with the perception of pain. This study analyzed the possible effects of short-term food deprivation on pain sensitivity in healthy female participants. This study was comprised of 32 healthy female participants who underwent a 48-hr inpatient hospital investigation. Prior to testing, heart rate and heart rate variability were assessed. After a standardized breakfast, day 1 measurements were taken. Food intake was then not allowed again until the following evening for 22 participants (experimental group), while 12 participants were served standard meals (control group). Pain threshold and tolerance were assessed at 10:00 a.m. on both days using a pressure algometer. Additionally pain experience was examined. Food deprivation significantly reduced pain thresholds and tolerance scores in the experimental group. Additionally, the sympathovagal balance changed, characterized by a decrease in parasympathetic activation. Higher vagal withdrawal after food deprivation was associated with higher pain sensitivity in the experimental group. Furthermore, perceived unpleasantness and pain intensity increased for threshold and tolerance stimuli in the experimental group. We conclude that short-term food deprivation sensitized pain perception in healthy females. An imbalance in sympathovagal activation evoked by food deprivation accounted for this effect. Our results might be a pathogenic mechanism for the development of emotional difficulties associated with disturbed eating behavior.

Effects of short-term food deprivation on interoceptive awareness, feelings and autonomic cardiac activity

The perception of internal bodily signals (interoception) plays a relevant role for emotion processing and feelings. This study investigated changes of interoceptive awareness and cardiac autonomic activity induced by short-term food deprivation and its relationship to hunger and affective experience. 20 healthy women were exposed to 24h of food deprivation in a controlled setting. Interoceptive awareness was assessed by using a heartbeat tracking task. Felt hunger, cardiac autonomic activity, mood and subjective appraisal of interoceptive sensations were assessed before and after fasting. Results show that short-term fasting intensifies interoceptive awareness, not restricted to food cues, via changes of autonomic cardiac and/or cardiodynamic activity. The increase of interoceptive awareness was positively related to felt hunger. Additionally, the results demonstrate the role of cardiac vagal activity as a potential index of emotion related self-regulation, for hunger, mood and the affective appraisal of interoceptive signals during acute fasting.

Effect of hunger on the response to, and the production of, chemical alarm cues in a coral reef fish

A wide variety of fish species release chemical alarm cues upon mechanical damage to their skin by predator attack. We investigated the effects of short-term food deprivation on the response to, and the production of, chemical alarm cues in the coral reef-dwelling goby Asterropteryx semipunctatus (family Gobiidae). Gobies deprived of food for 4 days did not react with fright when exposed to conspecific skin extracts. However, when the same individuals had been fed ad libitum, they responded with a typical alarm reaction to the skin extracts, including decreased movement and feeding. In a second experiment, gobies were exposed to skin extracts from conspecifics that had been food deprived and from conspecifics fed ad libitum. Damaged skin from food-deprived individuals did not elicit an alarm response in conspecifics, whereas skin from individuals that had been fed ad libitum yielded a typical alarm response. Histological sections of goby skin showed that food-deprived gobies had fewer sacciform cells in their epidermis than did gobies fed ad libitum. Evidence suggests that there may be a trade-off between foraging and antipredator behaviour, and also between the benefits derived from maintaining chemical alarm cue cells and the cost of producing them in A. semipunctatus.

Changes in δ13C and δ15N in different tissues of juvenile sand goby Pomatoschistus minutus: a laboratory diet-switch experiment

Studies on diet or migration of organisms based on stable isotopes require precise estimates of how quickly stable isotope ratios change in the investigated tissues. Isotopic turnover rates in fish, however, are poorly understood. Prior to field applications of the stable isotope technique for investigating sand goby Pomatoschistus minutus migrations, a laboratory diet-switch experiment was conducted to (1) determine C and N isotopic turnover rates in sand goby muscle, liver and heart tissue, and (2) evaluate the relative contribution of growth and metabolic replacement to the total change in isotopic composition. Both time-based and growth-based models adequately described the carbon and nitrogen isotopic change in each tissue. The variation in isotopic turnover rates among the tissues and elements could be attributed to differences in metabolic activity. Muscle tissue had the slowest turnover rates, with half-lives of approximately 25 and 28 d for δ13C and δ15N, respectively. The shortest half-life value for δ15N was in liver tissue (3 d) and for δ13C in heart tissue (6 d). The rate of isotopic change in goby muscle tissue was mainly regulated by somatic growth, but metabolic replacement significantly accelerated the turnover rate for δ13C. In liver and heart tissue, basal metabolism contributed considerably to the isotopic shift. As a result, effects of short-term food deprivation were only found in liver and heart tissue. Although the observed trophic fractionation factors were within reported ranges, they were exceptionally large for δ13C in muscle and liver tissue.

Changes in glucose, glycogen, thyroid activity and hypothalamic catecholamines in tench by starvation and refeeding.

The effects of short-term food deprivation (7 days) and refeeding (2 days) on different biochemical and neuroendocrine parameters were studied in tench. A 7-days fast resulted in a significant reduction of plasma glucose and glycogen hepatic content, supporting the key role of liver glycogen as energy depot for being consumed during fasting. The rapid recovery of normal values of blood glucose and glycogen stores by refeeding indicates a rapid replenishment of liver glycogen stores. The short-term starvation decreased circulating thyroid hormones (both T3 and T4) and T4 release from thyroid, supporting an interaction between nutritional state and thyroid function in tench. All these metabolic and hormonal changes were partial or totally reversed under refeeding conditions. An increase in hypothalamic content of norepinephrine and dopamine was found in fasted fish. This result might be a consequence of stress induced by starvation.

Influence of food deprivation on sympathetic support of blood pressure in the spontaneously hypertensive rat

We examined the effects of short-term food deprivation on directly measured blood pressure and sympathetic support of blood pressure in male (n=7, 231±7 g) and female (n=9, 193±4 g) spontaneously hypertensive rats (SHR, Charles River). Carotid arterial catheters were inserted under halothane anesthesia for direct assessment of cardiovascular function in conscious, unrestrained rats. After several days of recovery, mean arterial blood pressure (MAP) and heart rate (HR) were determined prior to, during, and after food deprivation. Baseline MAP and HR were 170±14 mmHg and 351±13 beats/min in males and 187±6 mmHg and 354±9 beats/min in females. An overnight fast produced significant (P<0.05) reductions in MAP and HR. After 48-hours of food deprivation, MAP was markedly reduced in males (−42±7 mmHg) and in females (−42±9 mmHg). Heart rate was significantly decreased during fasting in both males (−76±10 beats/min) and females (−60±11 beats/min). Caloric deprivation was accompanied by a significant reduction in sympathetic support of blood pressure (−32±8 mmHg in males, −21±7 mmHg in females) as determined by the depressor response to ganglionic blockade produced by hexamethonium/atropine (30.0/0.1 mg/kg). After three days of refeeding, MAP, HR, and sympathetic support of blood pressure returned to values not significantly different from baseline. The results suggest that short-term food deprivation produces rapid reductions in MAP and HR in the SHR, which are mediated, at least in part, by reduced sympathetic tone.

Effects of food deprivation on white muscle energy reserves in rainbow trout (Oncorhynchus mykiss): the relationships with body size and temperature

The relationship between body size and the depletion of white muscle metabolites (e.g., PCr, ATP, glucose and glycogen) was examined in two sizes (30 or 700 g) of rainbow trout deprived of food for one, four or seven days at either 5 or 15 °C. Following 7 days of food deprivation at 15 °C, the levels of muscle glycogen decreased by approximately 50% in small fish relative to control values (i.e., day 1). In comparison, small fish acclimated to cold temperatures did not exhibit a significant reduction of muscle glycogen over the seven day fasting regime. In contrast to small fish, the levels of white muscle glycogen in large fish remained unchanged after food deprivation, regardless of acclimation temperature. A seven day deprivation of food also resulted in a 50% depletion of white muscle glucose concentrations in small and large fish acclimated to warm temperatures, but there were no significant changes in this variable in fish acclimated to cold temperatures. In contrast to the negative effects of food deprivation on white muscle glycogen and glucose levels, the concentrations of white muscle PCr and ATP were not greatly affected by food deprivation under any of the experimental conditions. Taken together, these results clearly show that food deprivation can have an important influence on the storage of energy metabolites for anaerobic energy production, particularly in small fish at warm temperatures. In the future, it may be very important to consider the physiological effects of short-term food deprivation when interpreting results from studies in which fish have been fasted prior to treatments such as exercise.

Development of Enzyme Immunoassays for 3,5,3′-Triiodo-l-thyronine andl-Thyroxine: Time-Course Studies on the Effect of Food Deprivation on Plasma Thyroid Hormones in Two Marine Teleosts, Sea Bass (Dicentrarchus labraxL.) and Sea Bream (Sparus aurataL.)

The effects of short-term food deprivation and photoperiod on plasma thyroid hormone levels of sea bass and sea bream were studied. Animals were acclimated under constant photoperiod regime (15L/9D) and feeding times (2 hr after light onset and 2 hr before light offset). Time-course studies involved monitoring plasma hormone levels every 4 hr throughout 1.5 24-hr cycles. Plasma 3,5,3′-Triiodo-l-thyronine (T3) andl-thyroxine (T4) were assayed using a newly developed competitive enzyme immunoassay, utilizing acetylcholinesterase as a label of enzymatic tracers. Enzyme immunoassays had sensitivities of 1.25–0.02 and 62.5–0.2 ng/ml for T3and T4, respectively, and reproducibilities of 3.7 and 5.6% intraassay variation for T3and T4, respectively; interassay variations for T3and T4assays respectively were 1.6%, 11% and 6.6%, 8% for sea bass and sea bream plasma similar to RIA. In sea bass, 3 days of food deprivation resulted in depressed plasma T3and T4, overriding significant diel variations seen during the second day of starvation. Sea bream displayed a slight decrease of T4plasma levels while T3levels remained constant for the whole sampling period. Both thyroidal systems responded to photoperiod with a significant increase in plasma T4level at the time of light onset. In addition, sea bass also displayed increased T3levels and decreases in both hormone levels coinciding with “lightoff.” Data show different responses of the sea bass and sea bream thyroidal systems to both nutritional state and photoperiod in that the latter state is influenced by the former. Data suggest plasma thyroid levels can be used as a rapid indicator of nutritional status.

The Effect of Short-term Food Deprivation on the Reinforcing Value of Coffee in Bulimic and Control Women

The effect of short-term food deprivation on the reinforcing value of coffee was examined, utilising behavioural choice methodology. Four women with bulimia nervosa and six healthy controls underwent one food-deprivation day (19 hours) and one nondeprivation day. Subjects made significantly more attempts to earn coffee, earned more points toward coffee, and drank more grams of coffee when food deprived than when nondeprived. The effect was observed in both bulimic and control women. There was a significant diagnosis-by-deprivation interaction with reference to grams of coffee consumed, with bulimic women consuming over twice as much coffee when deprived than nondeprived. The results are discussed with reference to the role of food deprivation in the pathogenesis of substance abuse.

Lack of effect of short-term fasting on cognitive function

In a study designed to assess the effects of short-term food deprivation on cognitive function, a sample of female subjects ( N = 21) was tested on a number of measures of cognitive function after three levels of food deprivation (miss one meal, miss two meals or miss all food for 24 h prior to testing) and a condition in which they ate normally for 24 h prior to testing. There was found to be no significant effects of food deprivation on sustained attention, attentional focus, simple reaction time or immediate memory. However, performance on a low processing load tapping task was significantly poorer when the subjects were deprived of food for 24 h prior to testing, and heart rate was significantly higher when they were non-deprived. These results stand in contrast to the impairments in cognitive function previously found to be associated with spontaneous dieting behaviour (using essentially the same task battery).

Effect of food deprivation on glutathione and amino acid levels in brain and liver of young and aged rats

The effect of short-term food deprivation on glutathione (GSH) and amino acid levels in brain regions of young and aged rats was compared with changes observed in liver. Animals aged 3 months and 24 months were deprived of food for 48 h. GSH and amino acid levels from cerebral cortex, cerebellum, pons medulla, and liver were assayed and compared with levels in animals of the same age fed normal diets. In liver in both young and old rats, GSH levels fell 30%, from 13 μmol/g tissue to 8/7 μmol/g tissue. Significant changes were observed in other amino acids, including an increase of 30–50% in methionine, glycine, and glutamine, and a decrease of 30–50% in alanine in liver of both young and aged rats, and a 4-fold increase in taurine in young. In brain, little change was observed upon food deprivation. No decrease was observed in GSH, and only small changes were observed in other amino acids. In the aged animal aspartate, glutamate, and alanine levels were slightly lower; tyrosine in cerebellum was reduced by 30%, and both glycine and tyrosine in the pons medulla were reduced by 20–30%. In the brain areas examined, levels of GSH ranged from 1–2 μmol/g in young and 0.8–1.4 μmol/g in old; with levels in pons medulla being lower than those in cerebral cortex. In brain, in contrast to liver, levels were scarcely affected by short-term food deprivation. The relative stability of amino acids paralleled that of brain proteins, which did not significantly decrease even under conditions in which protein content of most other tissues was greatly reduced, indicating specific control of cerebral protein metabolism in protection in malnutrition.

Effects of Short-Term Food Deprivation on Growth of Hand-Reared American Kestrels

Sudden prey reductions were simulated to examine their impact on growth parameters of nestling American Kestrels (Falco sparverius) hand-reared in captivity. The experimental design consisted of three treatments: (1) 15 nestlings fed ad libitum (control individuals), (2) 15 nestlings that were starved for 24 hr when 7 days old, and for 36 hr when 21 days old, and (3) 15 nestlings that were starved for 36 hr when 14 days old and for 48 hr when 28 days old. Fitting biometrical data to the logistic model (body mass and the length of antebrachium, tarsus and beak) or linear models (length of the ninth primary and the central rectrix), no significant differences were found for the growth parameters of each trait between control and starved birds. This revealed no long-term effects caused by temporary starvation. Although starved individuals suffered a significant weight loss following the periods of food deprivation, they recovered mass in 2-4 days by increasing food ingestion when the ad libitum diet was restored. This flexibility of the growth of mass can be seen as an adaptive mechanism to permit compensation in day to day fluctuations of the food supply. Although American Kestrels show reversed sexual size dimorphism prior to fledging, males and females responded similarly to starvation.

Effects of recombinant human insulin-like growth factor I on glomerular dynamics in the rat.

This study was undertaken to investigate the mechanisms by which an infusion of recombinant human insulin-like growth factor I (rhIGF-I) increases GFR and renal plasma flow (RPF) in rats. Glomerular micropuncture studies were carried out in 14 nonstarved Munich Wistar rats and in 12 rats deprived of food for 60-72 h. Animals were given an intravenous injection and infusion of either rhIGF-I or vehicle. In both nonstarved and starved animals, the IGF-I injection and infusion increased the serum IGF-I levels, left kidney GFR, single nephron glomerular filtration rate (SNGFR), single nephron blood flow rate (SNBF), and single nephron plasma flow rate (SNPF). The increase in SNPF and SNGFR was in part due to a fall in efferent arteriolar resistance (RE); there was a tendency, not significant, for afferent arteriolar resistance (RA) to fall in comparison to controls. The increase in SNGFR was partly caused by a rise in SNPF but was primarily due to an increase in glomerular ultrafiltration coefficient (LpA) to twice the control values. The increase in LpA resulted in an increase in SNGFR because the rats operated at ultrafiltration pressure disequilibrium. Control starved as compared with nonstarved rats had lower SNGFR, SNBF, and SNPF. This reduction was due to a tendency, not significant, for both RA and RE to be higher. Decreased SNGFR in food-deprived rats resulted from a reduced SNPF, a lower glomerular transcapillary hydrostatic pressure difference (delta P), and possibly a somewhat reduced LpA. These data indicate that IGF-I increases SNGFR, SNPF, and SNBF primarily by increasing LpA and also by decreasing RE without affecting delta P. Short-term starvation lowers SNGFR, SNPF, and SNBF primarily by decreasing delta P and possibly by lowering LpA and increasing RA and RE. IGF-I reverses some of the glomerular hemodynamic effects of short-term food deprivation.