Stomach Loads Research Articles

Effects of stomach loading on lung aeration, Fshunt, and oxygenation in adult healthy ponies in dorsal recumbency

Effects of stomach loading on lung aeration, Fshunt, and oxygenation in adult healthy ponies in dorsal recumbency

Contribution of tactile and interoceptive cues to the perception of the direction of gravity

Without relevant visual cues, the Subjective Visual Vertical (SVV) is biased in roll tilted subjects toward the body axis (Aubert or A-effect). This effect is generally ascribed to changes in the vestibular and somatosensory inputs following a body tilt. This study focused on the contribution of interoception and tactile cues in the SVV. The body-cast technology and gastric fullness were used to obtain a diffuse tactile stimulation and an overload stomach stimulation, respectively. Fifteen subjects placed in a tilt-chair were rolled sideways from 0° to 90°. They were asked to adjust a luminous line to the vertical under two body restriction conditions (strapped vs. body-cast) and two stomach load conditions (empty vs. full). Results showed (1) an improvement in the SVV judgment when somaesthetic cues were available in the full stomach condition ( p<0.001), (2) an increased A-effect for the higher body tilt values in the body-cast condition (beyond 45°, p<0.001), and (3) a smaller disrupting effect of the body-cast in the SVV judgment in the full stomach condition ( p<0.05). Since the vestibular system produced the same gravity response in all conditions, it can be stated that somaesthetic cues are involved in the SVV. Tactile mechanoreceptors may have contributed by detecting the changing pattern of pressures generated on the skin that results from changes in body orientation. The stomach load may act through the inertial forces exerted against the gravity load when the stomach is full by the mechanoreceptors in the fundus. Thus, the somaesthetic system can indicate the direction of gravity via patterns of pressure within and at the surface of the body.

Contribution of tactile and interoceptive cues to the perception of the direction of gravity

Without relevant visual cues, the Subjective Visual Vertical (SVV) is biased in roll tilted subjects toward the body axis (Aubert or A-effect). This effect is generally ascribed to changes in the vestibular and somatosensory inputs following a body tilt. This study focused on the contribution of interoception and tactile cues in the SVV. The body-cast technology and gastric fullness were used to obtain a diffuse tactile stimulation and an overload stomach stimulation, respectively. Fifteen subjects placed in a tilt-chair were rolled sideways from 0° to 90°. They were asked to adjust a luminous line to the vertical under two body restriction conditions (strapped vs. body-cast) and two stomach load conditions (empty vs. full). Results showed (1) an improvement in the SVV judgment when somaesthetic cues were available in the full stomach condition (p<0.001), (2) an increased A-effect for the higher body tilt values in the body-cast condition (beyond 45°, p<0.001), and (3) a smaller disrupting effect of the body-cast in the SVV judgment in the full stomach condition (p<0.05). Since the vestibular system produced the same gravity response in all conditions, it can be stated that somaesthetic cues are involved in the SVV. Tactile mechanoreceptors may have contributed by detecting the changing pattern of pressures generated on the skin that results from changes in body orientation. The stomach load may act through the inertial forces exerted against the gravity load when the stomach is full by the mechanoreceptors in the fundus. Thus, the somaesthetic system can indicate the direction of gravity via patterns of pressure within and at the surface of the body.

Bombesin Receptor Antagonists Block the Effects of Exogenous Bombesin but Not of Nutrients on Food Intake

The endogenous, meal-contingent release of bombesin (BN)-like peptides is thought to contribute to the termination of a meal. In the following experiments the potency of BN receptor antagonists to attenuate the ability of nutrients to suppress food intake was tested. First, the effectiveness of BN receptor subtype antagonists was verified by testing their ability to block the effects of exogenous BN on food intake. Rats were administered intraperitoneal (i.p.) injections of either saline or 0.1 mg/kg [ D-Phe 12,Leu 14]BN (binds both GRP and NMB receptors), [ D-Phe 6]BN(6–13) ethyl amide (binds GRP > NMB), and cyclo-SS-octa (BIM-23042; binds NMB > GRP). Five minutes later rats were administered 8 μg/kg BN (i.p.) and milk intake was measured. Injections of [ D-Phe 12,Leu 14]BN and [ D-Phe 6]BN(6–13) ethyl amide reliably attenuated the ability of BN to suppress milk intake whereas BIM-23042 was ineffective. The results show that the antagonists were behaviorally effective and that exogenous BN may exert its effects on food intake primarily through the GRP receptor subtype. Next, the antagonists were administered either 5 min prior to or 5 min after an intragastric nutrient load or no load in both overnight-deprived and nondeprived rats, and milk intake was then measured. Stomach loads reduced intake and this effect was not attenuated by BN receptor antagonists. Finally, rats were allowed to prefeed and the milk was then removed. Rats were then administered a BN receptor antagonist (0.1 and 1.0 mg/kg) or saline either immediately after the prefeed, 10 min later, or 20 min later. Milk diet was then returned and intake was measured. Peripheral injections of the BN receptor antagonist had no effect compared to saline on milk intake. Collectively, the results indicate that the blockade of peripheral BN peptide receptors is not sufficient to attenuate the satiety signals generated by stomach loads or prefeeding.

Energetics, growth, and body composition of Adélie penguin chicks, Pygoscelis adeliae.

Adélie penguins are very abundant in Antarctica and constitute a large biomass of predatory consumers in the Antarctic ecosystem. Adélies eat almost exclusively krill (Euphausia spp.), and to determine krill requirements by Adélies, information on energetics is needed, including energy intake of the chicks. I measured energy use and growth in Adélie penguin chicks, using both field and laboratory techniques. Field metabolic rate was quite variable, but mass-specific rates were not correlated with body mass. Growth followed the logistic equation: the growth constant was 0.143 d-1, and the asymptote for growth to fledging was 3,200 g. Different body organs had similar energy densities (in kilojoules per gram of dry mass), and total body energy density did not vary with chick mass. However, proportional mass of the skin increased rapidly as chicks grew, making the skin an important energy store in larger chicks. Metabolic efficiency measured in the laboratory averaged 69% and did not vary with chick mass. Total energy ingested over the 50-d development period was 162 MJ, which corresponds to approximately 33.6 kg of fresh krill. Previous studies of Adélie energetics have focused on adult energy balance and have calculated chick energy requirements indirectly on the basis of adults' stomach loads of krill and frequency of feeding chicks. Values from previous studies do not agree with those from the present study. The method used in the present study is more informative and accurate for measuring energy use by chicks, since measurements are made directly from chicks.

Influence of glucose, medium- and long-chain triglyceride gastric loads and forced exercise on food intake and body weight in rats

The purpose of this study was to examine the effect of oesophageal loads of glucose, medium (MCT)-and long-chain (LCT) triglycerides, plus treadmill exercise on food intake and body weight in rats. On test days, male rats were administered a gastric aqueous solution of glucose, MCT, LCT or water via an oesophageal tube. One hour later, the animals were forced to run on a treadmill for two hours at a speed of 20 m/min at 0% grade. At the beginning of the 12-hour dark cycle (at 7 p.m.) runners were returned to their cages. On control days, the same gastric loads were administered, but the animals remained in their cages. Food intake was continuously measured during both the dark and light periods. A reduction in body weight and total food intake was found after exercise. The food intake suppressing effect of exercise was seen in the first hours of the dark period. Following MCT and LCT oil stomach loads FI decrease was comparable but the latency of the effect varied. Stomach loads of MCT oil induced a reduction in FI within the 0–3 h of food availability whereas LCT oil suppressed intake during the 3–6-h dark period. This could be explained by their different metabolite fate.

Central gustatory lesions: II. Effects on sodium appetite, taste aversion learning, and feeding behaviors.

Intake and taste reactivity tests were used to determine the effects of bilateral lesions of the gustatory portions of the nucleus of the solitary tract (NST), the parabrachial nucleus (PBN), and the ventral posteromedial nucleus of the thalamus (VPMpc) on several complex ingestive behaviors. In the 1st experiment, lesions of the PBN and the NST blocked, and VPMpc lesions impaired, the behavioral expression of salt appetite. In the 2nd experiment, alanine was paired with injections of LiCl. Control rats as well as rats with NST and VPMpc lesions acquired the taste aversion, but rats with PBN lesions did not. In the 3rd experiment, all animals increased their food intake after injections of 2 U/kg insulin and 250 mg/kg 2-deoxy-D-glucose, and their food intake was suppressed after nutritive stomach loads.

Sites in the brain at which cholecystokinin octapeptide (CCK-8) acts to suppress feeding in rats: A mapping study

In this study, an examination was made of the sites in the brain of the rat at which the injection of cholecystokinin octapeptide (CCK-8) would alter food intake. Rats fasted for 24 hr received intracerebral injections of CCK-8 (1 nmol) or an equal volume of saline (0.5 μl), into various sites in the brain through permanently implanted stainless steel cannulae. After prior acclimatisation to individual plexiglass compartments, latency to feed, as well as consumption of food and water during 0–20, 20–40 and 40–60 min after the injection, were recorded. The available food was the standard rat pellets, to which the animal otherwise had constant daily access. With this paradigm, active sites at which CCK-8 suppressed feeding were defined as sites at which consumption of food for 0–20 min was reduced by 25% or more, or the latency to feed was increased by 3 min or more after the injection of CCK-8, as compared to the effect of the injection of saline, made at the same site. Such active sites were most densely distributed in the rostral diencephalon, e.g. hypothalamus, the medial pontine area and lateral medulla, in the vicinity of the nucleus tractus solitarii (NTS). By grouping data for injections according to histologically identified sites, statistical analysis of groups of injections confirmed that these three major areas of the brain were active with regard to the suppression of feeding by CCK-8. These data suggest that CCK may not only initiate satiety messages, as a circulating hormone at peripheral sites, but also participate in the conduction of such information to the target in the brain by serving as a neurotransmitter in the lateral medulla (e.g. NTS), medial pontine area (e.g. relay station between the NTS and hypothalamus) and the lateral hypothalamus, where local release of CCK-8 after stomach loading has been observed.

Comparison of the interoceptive sensory consequences of CCK, LiCl, and satiety in rats.

In three experiments we assessed the degree to which ad lib feeding, injection of cholecystokinin (CCK), and injection of lithium chloride (LiCl) produce states with similar sensory consequences. In each experiment, two groups of rats were trained to use cues arising from food deprivation and satiation as discriminative signals for shock. One group was shocked when deprived but not when nondeprived. The other group received the reversed discrimination. Testing began when incidence of freezing was greater under the shocked deprivation than under the nonshocked deprivation condition. In Experiment 1, the rats were tested under 24-hr food deprivation after injections of CCK, LiCl, and saline (in counterbalanced order). We reasoned that if either CCK or LiCl induce satiety-like states, they should promote patterns of responding different from those produced by saline but similar to those produced by ad lib feeding. The effects of CCK on freezing did not differ from those of saline, whereas both CCK and LiCl had effects that were different from ad lib feeding. This pattern of results was also obtained when deprivation level during training and testing was reduced to 8 hr (Experiment 1A) and also when rats received small amounts of food in conjunction with CCK (Experiment 2). The intubation of a high-calorie stomach load (Experiment 1A) produced a response profile like that observed after free feeding. Freezing after LiCl treatment differed from that observed after free feeding and from that found after injection of CCK. The results indicate that rats can differentiate between the sensory consequences of the states produced by CCK, by LiCl, and by ad lib feeding.

The rate and amount of food intake as determinants of vomiting

AbstractVomiting of nonmedical origin by retarded persons has been found to be greatly influenced by reinforcement procedures. To explicate the possible influence of the rate and amount of food intake, a satiation procedure and a spaced‐eating procedure were provided to three profoundly retarded adults with this problem. Vomiting was found to double or triple after satiation for each subject, and to decrease during spaced eating for each subject; the decrease was especially great for the two subjects who learned to eat most slowly after extended spaced eating training. These results suggest that vomiting is caused in large part by excessive stomach loading and can be effectively treated by reducing the eating rate and/or amount of food intake. This generalization may also apply to infants and to the bulimic binge‐purge cycle of nonretarded adults.

Effects of acute and short-time antibiotic treatment on renal lithium elimination and serum lithium levels in the rat.

Male Wistar rats received a single stomach load (10 ml/kg) of a 150 mmol LiCl solution, either alone or together with tetracycline (33.5 mg/10 ml), ampicillin (33.5 mg/10 ml), or metronidazole (15 mg/10 ml). Urine was collected 1-5 hours after administration and blood samples were drawn after 1, 6, and 24 hours. All antibiotics caused a reduction in urinary lithium excretion but did not affect renal lithium clearance. Serum lithium levels were reduced by tetracycline and metronidazole 6 hours after administration but increased after 24 hours. Additional experiments including frequent mapping of serum lithium levels confirmed these findings. Tetracycline, also reduced renal sodium clearance and increased distal sodium reabsorption. Short-term daily treatment during one week with tetracycline or metronidazole showed that these initial changes were only transient, since after treatment for one week no differences could be observed between antibiotic-treated rats and control rats. The results indicate that antibiotics may cause a delay but no decrease of the gastrointestinal absorption of lithium and that they do not affect renal lithium clearance. Signs of lithium intoxication during combined use of lithium and antibiotics are therefore probably not caused by a renal interaction mechanism affecting the renal lithium clearance.

Suppression of feeding by sodium depletion in food-deprived rats

Food-deprived rats were depleted of sodium peritoneal dialysis (pd) against 5.0% glucose solution and offered food 24 h later. Food intake was suppressed compared with fasting sham-dialyzed controls, or controls dialyzed against Ringer-Tyrode. Sodium depletion by subcutaneous formalin also suppressed feeding. Measurements of osmolality and sodium chloride (NaCl) concentrations of the ascitic fluid showed that osmolality increased 19% mainly due to NaCl diffused 96.2 +/- 7.23 mEq/l. Consequently serum sodium concentration fell significantly (5.5% below control value). Serum potassium concentration did not change. Measurements of blood glucose levels showed that 1.87 g/l of glucose had been absorbed while it was in the peritoneum. Twenty four hours after sodium depletion, blood glucose levels of fasting sodium-depleted animals did not differ from nondepleted controls. Stomach load of glucose, in the same amount given for pd, did not suppress feeding in fasting rats 24 h later. Fasting sodium-depleted rats, offered 0.3 M NaCl to drink instead of food, drank as much as non-fasting sodium-depleted controls, ruling out the possibility of impaired behavior. Suppression of feeding was reversed in fasting sodium-depleted animals which were allowed to replace their sodium deficit by free-drinking or by stomach loading of sodium solutions. These results provide the first demonstration that depletion of sodium suppresses feeding in food-deprived rats.

Water intake after stomach loads of NaCl in Mongolian gerbils.

Sixty mongolian gerbils (Meriones unguiculatus), 30 male and 30 female, were stomach loaded (2% b.w.) with either water or .9, 2, 6, 10, or 12% NaCl (wt x vol.). Unlike male rats, male gerbils did not lose weight. Female gerbils, like female rats, did not lose weight. However, female gerbils did not increase their water intake at any concentration, whereas males increased their water intake only at the 10 and 12% levels. These data are very much unlike those for the rat (male and female) which show an increase in water intake in response to NaCl solutions above isotonicity.

Acute effects of aldosterone on water and electrolyte transport in the colon and coprodeum of the domestic fowl (Gallus domesticus) in vivo.

White Leghorn laying hens were maintained on commercial poultry food (medium-Na+ diet) and fresh water. High-Na+ diet birds received, in addition, 10 ml 9% (w/v) NaCl/kg by stomach load for 2 days before perfusion experiments. The lumen of the coprodeum and colon of anaesthetized birds was perfused with a hyperosmotic solution resembling ureteral urine. Transmural solute and water fluxes and potential difference (p.d.) values were measured for 2.5 h before and for 8 h after i.v. injection of aldosterone (120 microgram/kg). After administration of aldosterone, the lag, increasing and stabilized plateau phases were identified for Na+, K+ and Cl- fluxes (which together formed an electroneutral ion-exchange system); plateau flux values were significantly greater than preinjection values and were comparable to values for birds maintained on low-Na+ diets in parallel experiments. Ammonium, phosphate and water fluxes were unresponsive to aldosterone and p.d. values showed a transient increase in medium-Na+ diet birds only. In parallel experiments on birds on low sodium diets the ammonium flux and p.d. increased but the osmotic flow and phosphate transfer did not respond. Therefore acute injection of aldosterone reproduced some but not all of the responses to dietary Na+ restriction in fowls.

CHRONIC ALDOSTERONE THERAPY AND THE CONTROL OF TRANSEPITHELIAL TRANSPORT OF IONS AND WATER BY THE COLON AND COPRODEUM OF THE DOMESTIC FOWL (GALLUS DOMESTICUS) IN VIVO

White Leghorn laying hens were maintained on commercial poultry food (medium-Na+ diet) and fresh water. Birds maintained on a high-Na+ diet received, in addition, 10 ml 9% (w/v) NaCl/kg by stomach load for 2 days before the perfusion experiments. Some birds on each dietary Na+ level also received aldosterone injections (60 micrograms/kg per day, i.m.) for 2 days before the perfusion experiments. The lumen of the coprodeum and colon of anaesthetized birds was perfused with solutions resembling ureteral urine, with systematically varied Na+, NH4+, Cl- and osmotic concentrations. Aldosterone enhanced net Na+ absorption (JNa) and associated net Cl- absorption and K+ secretion, and induced (in birds on medium- but not on high-Na+ diets) the appearance of a saturable JNa component dependent on the luminal concentration of Na+. Aldosterone enhanced net absorption of NH4+ and decreased the transmural potential difference in birds on a high-Na+ diet only; water and phosphate fluxes were not affected. Disparities between aldosterone- and Na+-depletion-induced effects suggested that one or more factors (in addition to aldosterone) are involved in the normal mediation of the responses of the lower intestine of the domestic fowl to varied Na+ intake.

The effect of various hunger manipulations on self-stimulation and the feeding elicited by it

Out of 16 rats self-stimulating in the lateral hypothalamic feeding area, 11 ingested a liquid food consisting of chocolate milk (stimulation-bound feeding) during self-stimulation even though they had been satiated, while the other five did not. The first group was called “feeders” and the second “non-feeders.” In “feeders,” adrenaline (0.1–0.2 mg/kg) injected intraperitoneally and stomach loading (20–25 ml) with either 30% glucose or a liquid food (egg-nog) produced a similar marked reduction in the rate of self-stimulation at all but the highest stimulus intensity and an even greater reduction of stimulation-bound feeding. No effect or even an increase in self-stimulation was observed in “non-feeders.” Therefore, the anorexigenic effects of adrenaline appear similar to natural satiation by stomach loading. On the other hand, amphetamine (2 mg/kg) increased the self-stimulation of “non-feeders” and produced a peculiar effect in “feeders”: the threshold was higher, but once they started to self-stimulate the rates were higher and they continued even when the stimulus intensity was decreased below the basal threshold. This was interpreted as a mixture of anorexia and a central excitatory effect. Insulin (8–12 U/kg) and 24 hr fasting increased self-stimulation of “non-feeders.” However, in “feeders” fasting increased self-stimulation, while insulin decreased it markedly.

The Effects of Stomach Loads of Hypertonic Nacl on Thyroidectomized Prepubescent Rats

Prepubescent male and female rats (N = 56) were surgically thyroidectomized and given stomach loads of .9% or 6.0% NaCl. The 6.0% NaCl, thyroidectomized S s responded by decreasing food intake and losing weight 24 hours after loading. Normal S s did not, and no sex difference was found. The .9% NaCl thyroidectomized S s drank significantly less than the normals. The results were interpreted in terms of thyroid hormone activity which affects renal function.

Inhibition of food deprivation induced hypovolemia by saline consumption in rats

Food deprivation hypovolemia has been observed in a variety of mesic and desert adapted rodents. Xeric adapted rodent species appear to lose intravascular volume in proportion with body weight loss during food restriction, while mesically adapted rodent species lose intravascular volume at a rate much in excess to body weight loss. The laboratory rat was chosen as a representative mesically adapted rodent species for the purpose of investigating this phenomenon. Acute isotonic saline stomach loads had no appreciable influence upon intravascular volume reparation induced by either 2 or 4 days of food deprivation. Free and forced choice saline solutions presented during starvation were noted to significantly inhibit hypovolemia, however, there was no evidence for reparation of carcass water losses. It is suggested that the availability of only water during fasting results in the premature termination of drinking due to cellular over-hydration. When water and a source of sodium are available the food deprived rat can more adequately maintain ad lib intravascular volume. There is presently no explanation for the absence of repaired carcass water.

Inhibition of food intake in the rat following complete absorption of glucose delivered into the stomach, intestine or liver.

1. Solutions of glucose or other carbohydrates were administered during the dark or light period of the circadian cycle to rats which had been only briefly deprived of food. 2. food was restored to the animals at various times after administration of a glucose load by stomach tube. With delays between loading and access to food of up to 3 hr by night and 2 hr by day, subsequent food intake was less than intake after non-nutritive loads. 3. measurement of the glucose content of the gastrointestinal tract at various times after glucose loading showed that this depression of intake was still apparent even when the rat was offered food some time after complete absorption of the stomach load. 4. infusion of a glucose solution into the duodenum or the hepatic protal vein also inhibited subsequent food intake. 5. in all cases, the inhibition of food intake was expressed as a decrease in the size of the first meal after restoring access to food. 6. these results provide the first demonstration that the entry of normal amounts of carbohydrate into the body by the physiological route is followed by depression of food intake which lasts until after absorption is complete.

Caloric compensation in rats with combined lesions in lateral and ventromedial hypothalamus

Compensatory adjustment of caloric intake in response to stomach loading of glucose or vegetable oil was studied in rats with lateral hypothalamic (LH) or with combined lateral and ventromedial hypothalamic (VMH) lesions. The LH lesioned rats as well as the sham operated controls compensated the loaded calories by an adequate reduction of oral intake, but those bearing both LH and VMH lesions tended to undercompensate with increased total caloric intake and body weight during some but not all periods of loading. Some of the rats with combined LH and VMH lesions displayed characteristics of the respective syndrome, such as thirst deficit and hyperphagia.