Selenium and mercury are redistributed to the brain during viral infection in mice

As part of the general host response to coxsackievirus B3 (CB3) infection, the concentration of essential and nonessential trace elements changes in different target organs of the infection. Essential (e.g., Se) and nonessential (e.g., Hg) trace elements are known to interact and affect inflammatory tissue lesions induced by CB3 infection. However, it is unknown whether these changes involve the brain. In the present study, the brain Hg and Se contents were measured through inductively coupled plasma-mass spectrometry and their distribution investigated by means of nuclear microscopy in the early phase (d 3) of CB3 infection in normally fed female Balb/c mice. Because of the infection, the concentration of Hg (4.07±0.46 ng/g wet wt) and Se (340±16 ng/g wet wt) in the brain increased twofold for Hg (8.77±1.65 ng/g wet wt, p<0.05) and by 36% for Se (461±150 ng/g wet wt, ns). Nuclear microscopy of brain sections from mice having elevated Se and Hg concentrations failed to find localized levels of the elements high enough to make detection possible, indicating approximately homogeneous tissue distribution. Although the pathophysiological interpretation of these findings requires further research, the increase of Hg in the brain during infection might have an influence on the pathogenesis of the disease.     

Identification and Distribution of m- and p-Hydroxyphenylacetic Acids in the Brain of the Rat

The m and p isomers of hydroxyphenylacetic acid have been identified and quantitated in whole rat brain and in several regions using a capillary column high resolution gas chromatography–mass spectrometry procedure. Their concentrations were: for m-hydroxyphenylacetic acid (mean ± S.E., number of determinations in parentheses)—whole brain, 2.3 ± 0.3 ng/g (7); hypothalamus, 1.2 ± 0.3 ng/g (5); caudate nucleus, 5.5 ± 0.6 ng/g (5); brain stem, 1.8 ± 0.1 ngig (5); cerebellum, 1.2 ± 0.1 ng/g (5) and the “rest,” 1.7 ± 0.1 ng/g (5); and for p-hydroxyphenylacetic acid–whole brain, 10.6 ± 0.7 ng/g (7); hypothalamus, 4.5 ± 0.1 ng/g (4); caudate nucleus, 28.3 ±1.6 ng/g (5); brain stem, 8.6 ± 0.6 ng/g (5); cerebellum, 8.1 ± 0.4 ng/g (9, and the “rest,” 5.3 ± 0.5 ng/g (5). This heterogeneous distribution parallels closely that exhibited by their respective precursor amines, m- and p-tyramine.     

Differential effects of dietary sodium intake on blood pressure and atherosclerosis in hypercholesterolemic mice

The amount of dietary sodium intake regulates the renin angiotensin system (RAS) and blood pressure, both of which play critical roles in atherosclerosis. However, there are conflicting findings regarding the effects of dietary sodium intake on atherosclerosis. This study applied a broad range of dietary sodium concentrations to determine the concomitant effects of dietary sodium intake on the RAS, blood pressure, and atherosclerosis in mice. Eight-week-old male low-density lipoprotein receptor ?/? mice were fed a saturated fat-enriched diet containing selected sodium concentrations (Na 0.01%, 0.1%, or 2% w/w) for 12 weeks. Mice in these three groups were all hypercholesterolemic, although mice fed Na 0.01% and Na 0.1% had higher plasma cholesterol concentrations than mice fed Na 2%. Mice fed Na 0.01% had greater abundances of renal renin mRNA than those fed Na 0.1% and 2%. Plasma renin concentrations were higher in mice fed Na 0.01% (14.2±1.7 ng/ml/30 min) than those fed Na 0.1% or 2% (6.2±0.6 and 5.8±1.6 ng/ml per 30 min, respectively). However, systolic blood pressure at 12 weeks was higher in mice fed Na 2% (138±3 mm Hg) than those fed Na 0.01% and 0.1% (129±3 and 128±4 mmHg, respectively). In contrast, mice fed Na 0.01% (0.17±0.02 mm²) had larger atherosclerotic lesion areas in aortic roots than those fed Na 2% (0.09±0.01 mm²), whereas lesion areas in mice fed Na 0.1% (0.12±0.02 mm²) were intermediate between and not significantly different from those in Na 0.01% and Na 2% groups. In conclusion, while high dietary sodium intake led to higher systolic blood pressure, low dietary sodium intake augmented atherosclerosis in hypercholesterolemic mice.     

Role of 5-HT3 Receptor on Food Intake in Fed and Fasted Mice

Background

Many studies have shown that 5-hydroxytryptamine (5-HT) receptor subtypes are involved in the regulation of feeding behavior. However, the relative contribution of 5-HT₃ receptor remains unclear. The present study was aimed to investigate the role of 5-HT₃ receptor in control of feeding behavior in fed and fasted mice.

Methodology/Principal Findings

Food intake and expression of c-Fos, tyrosine hydroxylase (TH), proopiomelanocortin (POMC) and 5-HT in the brain were examined after acute treatment with 5-HT₃ receptor agonist SR-57227 alone or in combination with 5-HT₃ receptor antagonist ondansetron. Food intake was significantly inhibited within 3 h after acute treatment with SR 57227 in fasted mice but not fed mice, and this inhibition was blocked by ondansetron. Immunohistochemical study revealed that fasting-induced c-Fos expression was further enhanced by SR 57227 in the brainstem and the hypothalamus, and this enhancement was also blocked by ondansetron. Furthermore, the fasting-induced downregulation of POMC expression in the hypothalamus and the TH expression in the brain stem was blocked by SR 57227 in the fasted mice, and this effect of SR 57227 was also antagonized by ondansetron.

Conclusion/Significance

Taken together, our findings suggest that the effect of SR 57227 on the control of feeding behavior in fasted mice may be, at least partially, related to the c-Fos expression in hypothalamus and brain stem, as well as POMC system in the hypothalamus and the TH system in the brain stem.     

Fasting and refeeding modulate neutral amino acid transport activity in the basolateral membrane of the rat exocrine pancreatic epithelium: fasting-induced insulin insensitivity

The effects of fasting and refeeding on amino acid transport in the perfused rat exocrine pancreas were investigated using a rapid dual tracer dilution technique. Unidirectional amino acid influx (15 s) was quantified (relative to the extracellular tracer d-mannitol) over a wide range of perfusate concentrations in pancreata isolated frm fed and 24 h, 48 h, and 72 h fasted and 72 h fasted and refed (24 h) animals. In fed animals transport of phenylalamine (1–24 mM) and l-serine (1–50 mM) was saturable and weighted non-linear regression analyses of the overall transport indicated an apparent K_t=10±3mM and V_max=7.0±1.0 μmol/min per g (n = 7) for phenylalanine and K_t=16±3 mM and V_max=20.6±2.1 μmol/min per g (n = 5) for serine. Fasting animals for 24 h or 48 h did not change the kinetics of either phenylalanine or serine transport. After a 72 h fast the rate of phenylalanine transport (V_max=15.9±2.9 μmol/min per g, (n = 5) was enhanced whereas the transport affinity (K_t=11±3 mM) remained unaltered. l-Serine transport was essentially unaltered. When 72 h fasted animals were refed for 24 h the V_max for the phenylalanine transport was reduced to values observed in fed animals. In parallel experiments refeeding had no significant effect on serine transport. Perfusion of pancreata isolated from 72 h fasted animals with bovine insulin (1 mU/ml or 1 μU/ml) did not stimulate either phenylalanine or serine transport. The fasting-induced stimulation of transport may provide a mechanism by which the extracellular supply of essential amino acids as phenylalanine is increased to meet the demands of continued proteolytic and lipolytic enzyme synthesis.     

A new mass fragmentographic method for the simultaneous analysis of tryptophan, tryptamine, indole-3-acetic acid, serotonin, and 5-hydroxyindole-3-acetic acid in the same sample of rat brain.

A new method for the concurrent extraction and quantification of tryptophan (Trp), tryptamine (T), indole-3-acetic acid (IAA), serotonin (5-HT), and 5-hydroxyindole-3-acetic acid (5-HIAA) in samples of rat brain is presented. Homogenization is carried out in 0.1 n HCl containing 1 n KCl and 0.2% NaHSO₃. After centrifugation at 100,000g, the supernatant is percolated through a column of XAD-2 resin, eluted with distilled methanol, and the resulting eluate is evaporated to dryness. The dry residue is then derivatized to yield the pentafluoropropionated (PFP) and methylpentafluoropropionated (Me-PFP) derivatives. Identification and quantification is readily achieved by gas chromatography-mass fragmentographic analysis on a OV-17 or Dexsil 300 column. Endogenous levels in whole rat brain established by this method are IAA, 13,1 ± 2.0 ng/g (n = 6); T, less than 380 pg/g (n = 6); Trp, 4.16 ± 0.23 μg/g (n = 6); 5-HIAA, 442 ± 24 ng/g (n = 6); and 5-HT, 526 ± 81 ng/g (n = 5).     

Feeding-Related Circadian Variation in tele-Methylhistamine Levels of Mouse and Rat Brains

Circadian changes in the brain histamine (HA) and tele-methylhistamine (t-MH) levels were studied in mice and rats after adaptation to an alternating 12-h light/dark cycle (lights on at 0600). Although there was no significant circadian fluctuation of the brain HA levels, the levels of t-MH, a major metabolite of brain HA, showed a marked circadian variation. In mice, the t-MH levels were about 80 ng/g from 1200 to 1800 but about two times higher values were obtained from 2400 to 0600 of the next morning. In rats, the t-MH levels ranged from 24 to 28 ng/g at 0600 and 1200, slightly increased at 1800, and reached at 2400 a peak twice as high as the levels seen during the light period. The t-MH levels again rapidly decreased during the subsequent 3 h. In mice fasted from 1200, the t-MH levels did not increase during the period of darkness. When mice were fed at 1200 after a 24-h fast, a significant increase in the t-MH levels was observed at 1800. There was no significant circadian variation of the HA and t-MH levels in the plasma of mice and rats. These results suggest that circadian variation in brain t-MH levels is related to feeding and possible subsequent changes in elimination of t-MH from the brain and/or turnover of HA in the brain. This phenomenon should be given due attention when HA dynamics in the brain are being assessed.     

Biosynthesis of brain 2-phenylethylamine: influence of decarboxylase inhibitors and D-amphetamine

2-Phenylethylamine (PEA) is an endogenous brain amine which probably modulates affective behavior. Using a gas-liquid chromatographic method for the quantification of PEA (as its dinitrophenyl-sulfonic acid derivative), we found in rabbits 340.9 ± 45.8 ng of PEA/g of wet brain. Brain PEA levels were markedly decreased by the ip administration of 200 mg/Kg, 4 hrs before sacrifice, of the L-aromatic amino acid decarboxylase inhibitors α-methyldopa (28.2 ± 5.1 ng/g), L-α-methyldopa hydrazine (MK-486 [66.9 ± 13.0 ng/g]) or a combination of both (30.0 ± 3.3 ng/g). Since MK-486 inhibits only peripheral decarboxylase, brain PEA must be in part of peripheral origin. Another decarboxylase inhibitor, RO 4-4602 mg/Kg, 4 hrs before sacrifice) failed to affect brain PEA content. D-amphetamine (10 mg/Kg) induced a small depletion of PEA after 30 min in untreated animals; when given in combination with RO 4-4602, brain PEA content was markedly decreased. This supports the view that amphetamine releases PEA and stimulates its synthesis.     

Effect of 2-Amino-7-Phosphonoheptanoic Acid on Regional Brain Amino Acid Levels in Fed and Fasted Rodents

Abstract: 2-Amino-7-phosphonoheptanoic acid, an antagonist of excitation caused by dicarboxylic amino acids with a selective action on N -methyl-d-aspartate receptors, has been administered in an anticonvulsant dose (1 mmol/kg i.p.) to fed or fasted rats and mice. The drug impaired motor activity in fasted mice. Glucose and amino acids were determined in dissected regions of brain fixed by microwave irradiation. Glucose content was low in the brains of fasted rats and mice but was restored to normal (fed) concentration 45 min after the administration of 2-amino-7-phosphonoheptanoic acid in fasted mice. In fed animals, 2-amino-7-phosphonoheptanoic acid did not change brain aspartate concentration. In fasted animals, aspartate concentration was raised in most brain regions. In fasted rats and mice, 2-amino-7-phosphonoheptanoic acid significantly increased glutamine in rat cortex and mouse striatum, decreased glutamate content in rat striatum, and decreased aspartate concentration in all regions except mouse cortex and striatum. GABA levels were significantly decreased in rat striatum and hippocampus. These changes are consistent with an increased synaptic release of glutamate and aspartate following blockage of their post-synaptic action at selected sites.     

Ethanol metabolism in guinea pig: In vivo ethanol elimination,alcohol dehydrogenase distribution,and subcellular localization of acetaldehyde dehydrogenase in liver

Guinea pig ethanol metabolism as well as distribution and activities of ethanol metabolizing enzymes were studied. Alcohol dehydrogenase (ADH; EC 1.1.1.1) is almost exclusively present in liver except for minor activities in the cecum. All other organ tissues tested (skeletal muscle, heart, brain, stomach, and testes) contained only negligible enzyme activities. In fed livers, ADH could only be demonstrated in the cytosolic fraction (2.94 μmol/g liver/min at 38 °C) and its apparent K_m value of 0.42 mm for ethanol as substrate is similar to the average K_m of the human enzymes. Acetaldehyde dehydrogenase (ALDH; EC 1.2.1.3) of guinea pig liver was measured at low (0.05 mm) and high (10 mm) acetaldehyde concentrations and its subcellular localization was found to be mainly mitochondrial. The total acetaldehyde activity in liver amounts to 3.56 μmol/g/ min. Fed and fasted animals showed similar zero-order alcohol elimination rates after intraperitoneal injection of 1.7 or 3.0 g ethanol/kg body wt. The ethanol elimination rate of fed animals after 1.7 g ethanol/kg body wt (2.59 μmol/g liver/min) was inhibited by 80% after intraperitoneal injection of 4-methylpyrazole. Average ethanol elimination rates in vivo after 1.7 g/kg ethanol commanded only 88% of the totally available ADH activity in fed guinea pig livers. Catalase (EC 1.11.1.6), an enzyme previously implicated in ethanol metabolism, is of 3.4-fold higher activity in guinea pig (10,400 U/g liver) than in rat livers (3,100 U/g liver), but 98% inhibition by 3-amino-1,2,4-triazole did not significantly alter ethanol elimination rates. After ethanol injection, fed and fasted guinea pigs reacted with prolonged hyperglycemia.     

Effects of a Longitudinal Training Program on Responses to Exercise in Overweight Men

Objective: The aim of this study was to determine how training modifies metabolic responses and lipid oxidation in overweight young male subjects. Research Methods and Procedures: Eleven overweight subjects were selected for a 4‐month endurance training program. Before and after the training period, they cycled for 60 minutes at 50% of their Vo ₂max after an overnight fast or 3 hours after eating a standardized meal. Various metabolic and endocrine parameters, and respiratory exchange ratio values were evaluated. Results: Exercise‐induced plasma norepinephrine concentration increases were similar before and after training in fasted or fed conditions. After food intake, exercise promoted a decrease in plasma glucose and a higher increase in epinephrine than in fasting conditions. The increase in epinephrine after the meal was more marked after training (264 ± 32 vs. 195 ± 35 pg/mL). Training lowered the resting plasma nonesterified fatty acids. During exercise, changes in glycerol were similar to those found before training. Lipid oxidation during exercise was higher in fasting than in fed conditions (15.5 ± 1.4 vs. 22.3 ± 1.7 g/h). Training did not significantly increase fat oxidation when exercise was performed in fed conditions, but it did in fasting conditions (18.6 ± 1.4 vs. 27.2 ± 1.8 g/h). Discussion: Endurance training decreased plasma nonesterified fatty acids, cholesterol, and insulin concentrations. Training increased lipid oxidation during exercise, in fasting conditions, and not when exercise was performed after the meal. During exercise in overweight subjects, the fasting condition seems more suited to oxidizing fat and maintaining glucose homeostasis than a 3‐hour wait after a standard meal.     

Bicarbonate measurements in rat liver, brain, heart, and skeletal muscle.

A method is described for measuring total CO₂ and HCO₃^? in tissues rapidly frozen in liquid nitrogen. The method is a modification of the procedure of D. D. Van Slyke and J. M. Neill (1924, J. Biol. Chem.61, 523–573) for use with freeze-clamped tissue where anoxic changes have not occurred. The HCO₃^? content exclusive of tissue CO₂ in fed rats was found to be: liver, 19.4 ± 1.0; brain, 20.2 ± 0.9; thigh, 16.2 ± 0.8; and heart, 15.4 ± 1.4 μmol/g.     

Dietary methionine effects on plasma homocysteine and HDL metabolism in mice

The effects of dietary manipulation of folate and methionine on plasma homocysteine (Hcy) and high-density lipoprotein cholesterol (HDL-C) levels in wild-type and apolipoprotein-E-deficient mice were determined. A low-folate diet with or without folate and/or methionine supplementation in drinking water was administered for 7 weeks. Fasted Hcy rose to 23 microM on a low-folate/high-methionine diet, but high folate ameliorated the effect of high methionine on fasted plasma Hcy to approximately 10 microM. Determination of nonfasted plasma Hcy levels at 6-h intervals revealed a large diurnal variation in Hcy consistent with a nocturnal lifestyle. The daily average of nonfasted Hcy levels was higher than fasted values for high-methionine diets but lower than fasted values for low-methionine diets. An acute methionine load by gavage of fasted mice increased plasma Hcy 2.5 h later, but mice that had been on high-methionine diets had a lower fold induction. Mice fed high-methionine diets weighed less than mice fed low-methionine diets. Based on these results, two solid-food diets were developed: one containing 2% added methionine and the other containing 2% added glycine. The methionine diet led to fasted plasma Hcy levels of >60 microM, higher than those with methionine supplementation in drinking water. Mice on methionine diets had >20% decreased body weights and decreased HDL-C levels. An HDL turnover study demonstrated that the HDL-C production rate was significantly reduced in mice fed the methionine diet.     

The metabolic cost of subcutaneous and abdominal rewarming in king penguins after long-term immersion in cold water

Marine endotherms in the polar regions face a formidable thermal challenge when swimming in cold water. Hence, they use morphological (fat, blubber) adjustment and peripheral vasoconstriction to reduce demands for heat production in water. The animals then regain normothermia when resting ashore. In the king penguin (Aptenodytes patagonicus) metabolic rate is lower in fed than in fasted individuals during subsequent rewarming on land. This has been suggested to be a consequence of diversion of blood flow to the splanchnic region in fed birds, which reduces peripheral temperatures. However, peripheral temperatures during recovery have never been investigated in birds with different nutritional status. The aim of this study was, therefore, to measure subcutaneous and abdominal temperatures during the rewarming phase on land in fasted and fed king penguins, and investigate to which extent any different rewarming were reflected in recovery metabolic rate (MR_R) after long term immersion in cold water. We hypothesized that fed individuals would have a slower increase of subcutaneous temperatures compared to fasted penguins, and a correspondingly lower MR_R. Subcutaneous tissues reached normothermia after 24.15 (back) and 21.36 min (flank), which was twice as fast as in the abdomen (46.82 min). However, recovery time was not affected by nutritional condition. MR_R during global rewarming (4.56 ± 0.42 W kg⁻¹) was twice as high as resting metabolic rate (RMR; 2.16 ± 0.59 W kg⁻¹). However, MR_R was not dependent on feeding status and was significantly elevated above RMR only until subcutaneous temperature had recovered. Contrary to our prediction, fed individuals did not reduce the subcutaneous circulation compared to fasted penguins and did not show any changes in MR_R during subsequent recovery. It seems likely that lower metabolic rate in fed king penguins on land reported in other studies might not have been caused primarily by increased circulation to the visceral organs.     

Histamine paw edema of mice was increased and became H2-antagonist sensitive by co-injection of nitric oxide forming agents,but serotonin paw edema was decreased

Nitric oxide (NO) suprisingly caused the opposite effect on histamine and serotonin edema. The local injection of acidified nitrite (0.3–30 μg /paw which correspond to 10 μg−1mg/kg) increased histamine edema of mice up to 45±4% and suppressed serotonin edema to 90±3%. Other NO-generators (nitroprusside sodium and hydroxylamine) showed similar effects. These results were in accordance with our previous data on endogenous NO. Methylene blue (MB, 30ng/paw which corresponds to 1 μg/kg) suppressed histamine edema (62±3%) and increased serotonin edema (43±3%) in normal mice, being reversed by acidified nitrite. This suggests the involvement o of guanosine 3′, 5′ -cyclic monophosphate (cGMP) formation for the action of NO. Histamine edema became sensitive to H₂-antagonist, cimetidine, by co-injection of 30 μg/paw (which corresponds to 1mg/kg) acidified nitrite (ED₅₀=30 μg/kg versus ⪢ 1mg/kg). NO seemed to modify the histamine receptor(s) or tautomeric form of histamine. NO, O₂⁻ and other oxyradicals might finely control the vascular permeability together with inflammatory mediators.     

Growth performance,carcass characteristics and bioavailability of isoflavones in pigs fed soy bean based diets

A growth trial with 38 weaners (castrated male pigs) was designed to compare the growth performance and carcass quality of pigs fed diets containing either soy bean meal or soy protein concentrate in a pair-feeding design. Soy bean meal (SBM) and soy protein concentrate (SPC) differed in isoflavone (daidzein plus genistein) content (782?μg/g in SBM and 125?μg/g in SPC, respectively). During the experiment, all pigs were fed four-phases-diets characterized by decreasing protein concentrations with increasing age (weaner I, weaner II, grower, finisher diets). Rations of control and experimental groups were isoenergetic, isonitrogenous, and isoaminogen. The weanling pigs with an initial live weight of 8.4?±?1.1?kg were allotted to flat deck boxes. During the growing/finishing period (days 70?–?170 of age), the pigs were housed in single boxes. Both, the weaning and the grower/finishing performances (daily body weight gain, feed intake, feed conversion ratio) were similar in both groups. No differences were found between the groups in carcass composition (percentages of cuts, tissues, and protein/fat), and meat quality of pigs. Moreover, the IGF-1R mRNA expression in longissimus muscle was not influenced by the kind of soy product. However, circulating levels of isoflavones were clearly different between pigs fed SBM (genistein 239?±?44; daidzein 162?±?42; equol 12?±?4?ng/ml plasma) and animals fed SPC (genistein 22?±?9 and daidzein 8?±?3, and equol 10?±?3?ng/ml plasma). The results confirm the expected differences in the bioavailability of soy isoflavones, yet, there were no significant differences in performance of pigs fed either soy bean meal or soy protein concentrate.     

A RAPID AND SIMPLE METHOD FOR THE DETERMINATION OF PICOGRAM LEVELS OF SEROTONIN IN BRAIN TISSUE USING LIQUID CHROMATOGRAPHY WITH ELECTROCHEMICAL DETECTION

A rapid and simple technique using solvent extraction and high pressure liquid chromatography with electrochemical detection has been developed for the determination of serotonin in small brain tissue samples (1-20 mg). The method has a reasonably good specificity and a very low experimental error (less than 3%s.e ., calculated from six samples processed and analysed from the same brain homogenate). The recovery of authentic 5-HT added is 80-90%. The 5-HT levels of rat whole brain was found with the present technique to be 690 ± 17.5 ng/g and of mouse neocortex 304 ± 16 ng/g. Monoamine oxidase inhibition with pargyline (2 h) increased 5-HT levels in mouse neocortex to 194 ± 15% (N = 5) of control, while reserpine depleted 5-HT to 13 ± 4% of control. The method has a sensitivity level of about 20 pg (0.1 pmol) per brain sample.     

Effect of fasting on nychthemeral concentrations of plasma growth hormone (GH), insulin-like growth factor I (IGF-I), and cortisol in channel catfish (Ictalurus punctatus)

This experiment was conducted to characterize the effect of fasting versus satiety feeding on plasma concentrations of GH, IGF-I, and cortisol over a nychthemeron. Channel catfish fingerlings were acclimated for two weeks under a 12L:12D photoperiod, then fed or fasted for 21 d. On day 21, blood samples were collected every 2 h for 24 h. Weight of fed fish increased an average of 66.2% and fasted fish lost 21.7% of body weight on average. Average nychthemeral concentrations of plasma GH were not significantly different between fed (24.7 ng/mL) and fasted (26.8 ng/mL) fish, but average nychthemeral IGF-I concentrations were higher in fed (23.4 ng/mL) versus fasted (17.8 ng/mL) fish. An increase in plasma IGF-I concentrations was observed in fasted fish 2 h after a peak in plasma GH, but not in fed fish. Average nychthemeral plasma cortisol concentrations were higher in fed (14.5 ng/mL) versus fasted (11.0 ng/mL) fish after 21 d. Significant fluctuations and a postprandial increase in plasma cortisol were observed in fed fish and there was an overall increase in plasma cortisol of both fasted and fed fish during the scotophase. The present experiment indicates little or no effect of 21-d fasting on plasma GH levels but demonstrates fasting-induced suppression of plasma IGF-I and cortisol levels in channel catfish.     

The effects of repeated physical stress or fasting on catccholamine storage and release in the rainbow trout, Oncorhynchus mykiss

Rainbow trout, Oncorhynchus mykiss, were subjected to either physical stress (twice daily chasing to exhaustion for 5 days) or a period of 2 months of fasting. Following these treatments, the levels of catecholamines, adrenaline and noradrenaline, stored within the kidney and posterior cardinal vein (PCV) were determined. The ability of the catecholamine-storing chromaffin cells to release catecholamines in response to cholinergic stimulation was measured using an in situ saline-perfused PCV preparation. In the physically stressed fish, the concentration (μg catecholamine g^?1 tissue) of noradrenaline within the anterior and middle thirds of the kidney increased; the concentration of adrenaline was unchanged in all tissues. The content (μg) of noradrenaline or adrenaline, within the various tissues, was similar in both groups of fish with the exception of a higher noradrenaline content in the middle third of the kidney in the physically stressed fish. The total catecholamine content (μg catecholamine) of these tissues (kidney+PCV) was unaffected by physical stress. With the exception of a lower concentration of adrenaline in the middle third of the kidney, the concentrations of catecholamines were unaffected by fasting. There was a trend towards a greater content (μg) of noradrenaline within all of the tissue regions of the fed fish, however, a significant difference was only observed in the anterior third of the kidney. The content of adrenaline in the fed fish was greater in all regions of the kidney as well as the middle third of the PCV. The total catecholamine content (kidney + PCV) was lower in the fasted fish owing to significantly lower PCV and kidney masses. Prolonged physical stress caused a decrease in the responsiveness of the chromaffin cells to the cholinoceptor agonist carbachol (10^?8 to 10^?4mol). The ED₅₀ (the dose of carbachol required to elicit a half maximal response) for catecholamine release was 0·96 ± 10^?6mol carbachol in the physically stressed fish and 0·84 ± 10^?7 in the control fish. Fasting did not alter the pattern of catecholamine release. The ED₅₀ values were 0·96 ± 10^?7 and 1·24 ± 10^?7 mol for fasted and fed fish, respectively. Thus, a physical stress affected both catecholamine storage and release whereas fasting affected only storage and not the release process.     

Application of Physiologically Based Absorption Modeling to Formulation Development of a Low Solubility,Low Permeability Weak Base: Mechanistic Investigation of Food Effect

Physiologically based pharmacokinetic (PBPK) modeling has been broadly used to facilitate drug development, hereby we developed a PBPK model to systematically investigate the underlying mechanisms of the observed positive food effect of compound X (cpd X) and to strategically explore the feasible approaches to mitigate the food effect. Cpd X is a weak base with pH-dependent solubility; the compound displays significant and dose-dependent food effect in humans, leading to a nonadherence of drug administration. A GastroPlus Opt logD Model was selected for pharmacokinetic simulation under both fasted and fed conditions, where the biopharmaceutic parameters (e.g., solubility and permeability) for cpd X were determined in vitro, and human pharmacokinetic disposition properties were predicted from preclinical data and then optimized with clinical pharmacokinetic data. A parameter sensitivity analysis was performed to evaluate the effect of particle size on the cpd X absorption. A PBPK model was successfully developed for cpd X; its pharmacokinetic parameters (e.g., C _max, AUC_inf, and t _max) predicted at different oral doses were within ±25% of the observed mean values. The in vivo solubility (in duodenum) and mean precipitation time under fed conditions were estimated to be 7.4- and 3.4-fold higher than those under fasted conditions, respectively. The PBPK modeling analysis provided a reasonable explanation for the underlying mechanism for the observed positive food effect of the cpd X in humans. Oral absorption of the cpd X can be increased by reducing the particle size (<100 nm) of an active pharmaceutical ingredient under fasted conditions and therefore, reduce the cpd X food effect correspondingly.