Acquisition of texture-cued fasting-anticipatory meal-size change in rats with adequate energy intake

To determine if an increase in intake at a meal before a long fast can be conditioned to food texture cues, male Sprague-Dawley rats were given a high- or low-fat diet in one texture (powder or pellet) for 1 h prior to a 12.5-h fast and in the other texture before a 3-h fast. Each group (N = 9) went through a pseudorandom sequence of four duplicates of each texture-fast pairing over 4 experimental days in each of three training trials, followed by one 4-day trial under extinction, i.e. without the difference in fast lengths between textures. Neither the high-fat group nor the low-fat group as a whole gave a clear indication of a learnt texture-cued increase in meal size before the longer fast relative to the shorter fast. However, the rats trained on the high-fat diet that had the highest intakes on the first 4 days of training showed a relative increase in the amount eaten of the texture predicting the longer fast during the third training trial, and this effect also approached statistical significance in the extinction test. These results provide some support for the conclusion that anticipatory hunger/satiety can be differentially conditioned to dietary texture cues, but only if sufficient food is eaten before a short fast to prevent the rise in hunger during longer fasts that reinforces the discriminative increase in meal size.

Effect of quipazine, a selective 5-HT3 agonist, on dietary self-selection of different macronutrient diets in male and female rats

Macronutrient intakes, 2h and 12h, following administration of a selective 5-HT3 agonist, quipazine, N methyl, dimaleate (QUIPAZINE; 2.5, 5.0 and 7.5 mg/kg, i.p.) at dark onset were examined in three groups of adult male and female Wistar rats fed different sources of the three macronutrients: Group 1 (casein, corn starch, safflower oil), Group 2 (egg protein, corn starch/sucrose, lard) and Group S (casein hydrolysate, maltose dextrin, butter). QUIPAZINE decreased total food intake only in female rats from Group 1 (2 h) at a dose of 7.5 mg/kg and Group 2 (2h and 12h) with doses of 2.5 and 7.5 mg/kg. Intakes from corn starch and corn starch/sucrose diet (12h) were reduced in male and female rats, respectively, with doses of 2.5 and 7.5 mg/kg of QUIPAZINE. In conclusion, when provided with different sources of the three macronutrients, quipazine injection reduces specifically carbohydrate ingestion from corn starch-containing diets in male and female rats. Thus, the nature of the macronutrient source is of major importance to assess the effect of a drug on nutrient-specific selection.

Altered lipid profile, lipoprotein composition, and oxidant and antioxidant status in pediatric Crohn disease

BACKGROUND

Growing evidence supports a role for peroxidation in the pathogenesis of Crohn disease (CD). The activation of inflammatory cells, the release of their mediators, and the excessive production of free radicals may affect circulating lipids.

OBJECTIVE

We examined the lipid profile, lipoprotein composition, and oxidant-antioxidant status of children with CD.

DESIGN

We studied 22 pediatric CD patients and 10 healthy control subjects.

RESULTS

The proportion of saturated and monounsaturated fatty acids in plasma of CD patients was higher but that of polyunsaturated fatty acids was lower than in control subjects. This resulted in higher ratios in CD patients of palmitoleic acid to linoleic acid (P < 0. 05) and of eicosatrienoic acid to arachidonic acid (P < 0.04), 2 established indexes of essential fatty acid deficiency. Hypocholesterolemia was noted in CD patients as a result of lower LDL-cholesterol concentrations than in control subjects (P < 0.02). Plasma apolipoproteins B (P < 0.02) and A-I (P < 0.02) were also lower in CD patients, whereas plasma triacylglycerols were higher (P < 0.005). Lipoprotein composition was altered in CD patients, with relative triacylglycerol depletion and protein enrichment in VLDL. In contrast, intermediate-density lipoprotein of CD patients was characterized by an increased percentage of triacylglycerol and protein (P < 0.005) and a reduced proportion of phospholipids (P < 0. 01). Additional abnormalities were observed in the chemical distribution of HDL(2) and HDL(3) moieties. Lipid peroxidation was documented by higher plasma malondialdehyde concentrations in CD patients (P < 0.05), accompanied by lower retinol concentrations (P < 0.02).

CONCLUSION

Disturbances in the lipid profile, in lipoprotein concentrations and composition, and in oxidant-antioxidant status occur in CD patients.

Temporal modulation of nephrotoxicity, feeding, and drinking in gentamicin-treated rats

Gentamicin-induced nephrotoxicity varies temporally, with a peak being observed when this antibiotic is administered during the resting period and a trough when given during the activity period of rats. These nychthemeral variations are modified by fasting and by restricted feeding schedules. In this study, food and water intakes of adult female Sprague-Dawley rats were measured during pretreatment (Days 1 to 5) and during treatment (Days 6 to 10) with gentamicin (80 mg/kg/day, i.p.) injected at 1300 or 0100h. A significantly higher level of serum creatinine was observed when gentamicin was administered at 1300 h compared to 0100 h, and a significantly lower creatinine clearance was found in rats treated with gentamicin at 1300 h compared to those treated with saline at the same time. Gentamicin treatment at 1300 or 0100 h resulted in a decrease in the 24-h food intake. In addition, in the gentamicin-treated group at 0100 h, the maximal food intake observed at late dark during the pretreatment period decreased during treatment, and early dark rather than late dark maximal intake occurred. Our data demonstrate that gentamicin induces a nephrotoxicity that varies temporally, and that gentamicin treatment inhibits food intake and alters its nocturnal variations.

Modulation of endoplasmic reticulum-bound cholesterol regulatory enzymes by iron/ascorbate-mediated lipid peroxidation

Mammalian sterol regulatory enzymes are integral membrane proteins of the endoplasmic reticulum. They play a critical role in liver cholesterol homeostasis and the maintenance of overall cholesterol balance in different species. Because lipid peroxidation has been implicated in hepatic dysfunction and atherosclerosis, we hypothesized that its occurrence could alter the composition and properties of the bilayer lipid environment, and thereby affect the functions of these membrane proteins. Preincubation of rat liver microsomes with iron (Fe)/ascorbate (50 microM/200 microM), known to induce peroxidation, resulted in a significant inhibition of (i) the rate-limiting enzyme in cholesterol biosynthesis, HMG-CoA reductase (46%, p < .01), (ii) the crucial enzyme controlling the conversion of cholesterol in bile acids, cholesterol 7alpha-hydroxylase (48%, p < .001), and (iii) the central enzyme for cholesterol esterification: Acyl-CoA:cholesterol acyltransferase (ACAT, 80%, p < .0001). The disturbances of these key enzymes took place concomitantly with the high production of malondialdehyde (350%, p < .007) and the loss of polyunsaturated fatty acids (36.19 +/- 1.06% vs. 44.24 +/- 0.41 in controls, p < .0008). While alpha-tocopherol simultaneously neutralized lipid peroxidation, preserved microsomal fatty acid status, and restored ACAT activity, it was not effective in preventing Fe/ascorbate-induced inactivation of both HMG-CoA reductase (44%, p < .01) and cholesterol 7alpha-hydroxylase (71%, p < .0001). These results indicate that Fe/ascorbate alters the activity of the rate-determining steps in liver cholesterol metabolism, either directly or via lipid peroxidation, capable of modifying their membrane environment. The present data also suggest that the three regulatory enzymes respond differently when exposed to Fe/ascorbate or antioxidants, which may be due to dissimilar mechanisms.

Serotonin infusion in the SCN reduces casein ingestion in rats

To compare food and water intakes, adult male Wistar rats were infused during 7 days with serotonin (5-HT, 2.5 nmol/24 h) or artificial cerebrospinal fluid (CSF) in the suprachiasmatic nucleus (SCN) in a three-way selection of macronutrient-rich diets. Nocturnal energy intake from the casein-rich diet was significantly lower during infusion of 5-HT than before infusion. Decrease in nocturnal casein consumption was significant in the middle dark phase. Within the infusion period, water intake was reduced by 5-HT infusion during the early, middle and late light phase. The present results reinforce the hypothesis of a serotonergic control of water intake and provide evidence for SCN 5-HT involvement in casein-specific dietary selection.

Dietary iron overload and induced lipid peroxidation are associated with impaired plasma lipid transport and hepatic sterol metabolism in rats

Although hemochromatosis is characterized by dramatic morphological and functional alterations in the liver, little is known about the effects of an excess of iron on lipid metabolism. Therefore, we determined the effect of chronic iron overload on plasma lipid profile and lipoprotein composition, as well as on hepatic cholesterol metabolism and biliary sterol output. Rats administered a diet enriched with 3% iron carbonyl for 12 weeks displayed a 30-fold increase in iron (P <.0001) and a 5-fold rise in malondialdehyde (P <.001) in the liver. When compared with pair-fed controls, iron-overload rats showed a significant increase in triglycerides (P <.005), free cholesterol (P <.006), cholesteryl ester (P <.007), and high-density lipoprotein (HDL)-cholesterol (P <. 003). Triglyceride and cholesteryl ester enrichment, protein depletion, size increase, and apolipoprotein composition alterations characterized the very low density lipoprotein (VLDL) and HDL particles of iron-overload rats. Assessment of the activity of intracellular key enzymes for cholesterol homeostasis in these rats disclosed a reduction in 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (66%, P <.005) and cholesterol 7alpha-hydroxylase (58%, P <.0004) with an increment of acyl-CoA: cholesterol acyltransferase (62%, P <.002). The lack of optimal enzymatic activity may be a result of marked membrane lipid peroxidation that brings about fluidity drop (P <.029) in microsomes of iron-overload rats (5.00 +/- 0.013) versus controls (8.20 +/- 0. 03), reflected by polarization. A decline of the pool size of cholesterol and bile acids was noted in iron-overload rats during a 6-hour bile drainage. Our results show that experimental iron overload causes marked perturbations in plasma lipid transport and hepatobiliary sterol metabolism. Given the positive correlation of malondialdehyde with most of the altered parameters, iron-catalyzed lipid peroxidation may well be one of the involved mechanisms.

Macronutrient-specific dietary selection in rodents and its neural bases

The only evidence for nutrient selection comes from baseline or treatment effects on nutrient intakes that are qualitatively similar when sensorily contrasting forms of each macronutrient are investigated and/or dietary compositions and strains of rat or mouse are different within or between laboratories. By that criterion the only potential case of a treatment reliably altering macronutrient selection identified in the present review of the literature is d-norfenfluramine, fluoxetine and paraventricular serotonin (5-HT) reducing the intake of dextrin-containing diets at early dark. The only clear example of reverse effects of an agonist and an antagonist on dietary intake was found with serotonergic agents. Claims for catecholaminergic or opioid involvement in protein intake and peptidergic involvement in carbohydrate intake were not substantiated. There remain the issues of which learnt macronutrient-specific postgastric actions and sensory cues from the affected diet rely on the neural pathway(s) on which the drug is acting to alter dietary selection. Until experiments address these questions, the neural bases of nutrient-specific appetites will remain unknown. Drug effects must be consistent across differently textured and flavoured versions of each macronutrient tested.

Effect of fasting on temporal variation in the nephrotoxicity of amphotericin B in rats

Evidence for temporal variation in the nephrotoxicity of amphotericin B was recently reported in experimental animals. The role of food in these variations was determined by studying the effect of a short fasting period on the temporal variation in the renal toxicity of amphotericin B. Twenty-eight normally fed and 28 fasted female Sprague-Dawley rats were used. Food was available ad libitum to the fed rats, while the fasted animals were fasted 12 h before and 24 h after amphotericin B injection to minimize stress for the animals. Water was available ad libitum to both groups of rats, which were maintained on a 14-h light, 10-h dark regimen (light on at 0600 h). Renal toxicity was determined by comparing the levels of excretion of renal enzyme and the serum creatinine and blood urea nitrogen (BUN) levels at the time of the maximal (0700 h) or the minimal (1900 h) nephrotoxicity after the intraperitoneal administration of a single dose of dextrose (5%; control group) or amphotericin B (50 mg/kg of body weight; treated group) to the rats. The nephrotoxicities obtained after amphotericin B administration at both times of day were compared to the nephrotoxicities observed for time-matched controls. In fed animals, the 24-h urinary excretion of N-acetyl-beta-D-glucosaminidase and beta-galactosidase was significantly higher when amphotericin B was injected at 0700 and 1900 h. The excretion of these two enzymes was reduced significantly (P < 0.05) in fasting rats, and this effect was larger at 0700 h (P < 0.05) than at 1900 h. The serum creatinine level was also significantly higher (P < 0.05) in fed animals treated at 0700 h than in fed animals treated at 1900 h. Fasting reduced significantly (P < 0.05) the increase in the serum creatinine level, and this effect was larger in the animals treated at 0700 h. Similar data were obtained for BUN levels. Amphotericin B accumulation was significantly higher (P < 0.05) in the renal cortexes of fed rats than in those of fasted animals, but there was no difference according to the time of injection. These results demonstrated that fasting reduces the nephrotoxicity of amphotericin B and that food availability is of crucial importance in the temporal variation in the renal toxicity of amphotericin B in rats.

Effect of diet textural characteristics on the temporal rhythms of feeding in rats

To examine whether the diurnal rhythms of protein-rich and carbohydrate-rich diet ingestion can be altered by presenting the diets in different textural forms, adult male Wistar rats were assigned to two dietary groups. One group received a two-way choice between high-protein powder and high-carbohydrate granular (HPP-HCG) diets. In the other group the textures were reversed [high-protein granular and high-carbohydrate powder (HPG-HCP) diets]. Rats fed HPP-HCG diets selected significantly less protein (kcal) vs. rats fed HPG-HCP diets, during the 24-h and 12-h dark phase and during the 4-h early and late dark phases. Carbohydrate intakes of the two dietary groups were not significantly different. Total caloric intake for the HPG-HCP dietary group was significantly higher than that of the HPP-HCG dietary group during the 24-h and 12-h dark phase. Body weight was significantly lower in rats fed HPP-HCG diets. In conclusion, macronutrient-rich diets presented in different textural forms alter protein-rich diet ingestion and total energy intake.

Opposite effects on feeding of suprachiasmatic nucleus neuropeptide Y administration in rats

The effects of injecting or infusing neuropeptide Y (NPY) into the suprachiasmatic nucleus of rats on patterns of individual macronutrient and water intake were examined during the following 2 h and also across 12 and 24 h light/dark cycles. Increased total energy intake (218 and 170%) and energy intake from the dextrin/sucrose diet (499 and 247%) were observed in the 2 h following injection of 100 pmol NPY at early light and early dark, respectively, and in the following 24 h (total energy: 67%, dextrin/sucrose: 73%). Nocturnal casein energy intake was also increased (258%) following NPY injection. Continuous infusion of 10 pmol/h of NPY suppressed nocturnal total energy (36%) and dextrin/sucrose intake (36%) as well as 24 h energy intake from casein (43%). These results demonstrate divergent effects of NPY subsequent to different mode of administration.

Fall and winter hormone concentrations related to stress in pigs identified as normal and carrier for stress susceptibility

Stress is associated with significant losses in the swine industry. Seasonal changes have been shown to affect stress resistance in several species of animals. In the present study, we examined the effect of two seasons (fall or winter) on plasma insulin, cortisol, and adrenocorticotrophin hormone (ACTH) levels from fasted normal and carrier pigs for stress susceptibility when submitted to a blood-sampling stressor between 10:00 and 11:00. Comparisons were made of 10 diurnally active normal (NN) and 8 carrier (Nn) pigs reared in the fall to 9 NN and 10 Nn pigs reared in the winter. The light-dark cycle throughout the period of the experiment was 10 h light/14 h dark, with lights on from 07:00 to 17:00. Feed consisted of the traditional western Canadian swine ration consumed ad libitum. Results revealed significant season-by-genotype interactions for plasma insulin and ACTH concentrations in response to the blood-sampling stressor. The normal pigs displayed a significantly lower plasma insulin level during winter compared to the fall season. Plasma ACTH of normal pigs was 18% lower in the winter compared to the fall season, although this difference was not statistically significant. The carrier genotype, on the other hand, demonstrated higher plasma insulin concentration and lower plasma ACTH concentration in the winter compared to the fall season. Furthermore, there was a main genotype effect in plasma cortisol concentration such that the carrier pigs experienced a greater level compared to the normal genotype. Similarly, the carrier pigs had a more acute ACTH response to the blood-sampling stressor compared to the normal pigs during the fall season. Results have demonstrated that these two seasons of the year affect the response of both genotypes to a blood-sampling stressor, with the carrier genotype experiencing a more intense stress reaction in the fall season. These results further contribute to the recent research indicating that carrier pigs for stress susceptibility have a unique stress response.

Effect of Neuropeptide Y Injected into the Hypothalamic Suprachiasmatic Nucleus or the Lateral Cerebral Ventricle on Food Intake

The effects of neuropeptide Y (NPY) injected into the hypothalamic suprachiasmatic nucleus (SCN) or the lateral cerebral ventricle (LCV) at four different time points of the day on the subsequent 2h food intake from three macronutrient rich diets were examined. Adult Wistar male rats on 12-12 h light-dark cycles received either saline or NPY (lOOpmol) through chronically implanted guide cannulas into the SCN or the LCV. The results show that NPY was effective at stimulating energy intake from the dextrin/sucrose diet when injected in the SCN after lights-on, and total energy intake when injected in the LCV before and after lights-on. This suggests that NPY is effective at altering nychthemeral variations in total energy and energy from dextrin/sucrose diets, but this modulation is specific to the site of administration.

Time-restricted feeding schedules modify temporal variation of gentamicin experimental nephrotoxicity

The effect of timing of gentamicin dosing relative to food access periods was evaluated in experimental animals. Female Sprague-Dawley rats were treated for 4 and 10 days with gentamicin (40 mg/kg of body weight/day) intraperitoneally at either 0700, 1300, 1900, or 0100 h according to three food presentation schedules: food was available from 0800 to 1600 h in the first group, from 1600 to 0000 h in the second group, and from 0000 to 0800 h in the last group. Animals were thus subjected to a restricted feeding period. Results indicate that time-restricted feeding schedules displace the peak and the trough of gentamicin-induced renal toxicity, as evaluated by changes in the inhibition of sphingomyelinase activity, cellular regeneration (incorporation of [3H]thymidine into DNA of renal cortex), and blood urea nitrogen and serum creatinine levels, as well as histopathological lesions observed after 10 days of treatment. In fact, the toxicity was minimal when gentamicin was injected during the feeding period, while the maximal toxicity was found when gentamicin was administered during the fasting period. It is concluded that the feeding period can modulate aminoglycoside nephrotoxicity. The time of dosing of gentamicin relative to the time of feeding seems to be a more important modulator of gentamicin nephrotoxicity than the light-dark cycle.

Iron-salicylate complex induces peroxidation, alters hepatic lipid profile and affects plasma lipoprotein composition

Iron overload, with its associated toxic effects, has serious health consequences and results in damage to the liver, heart and other organs. Salicylate may be used as the lipophilic carrier, transporting more iron into hepatocytes. In this study, we examined the effect of the combined administration of these compounds on plasma lipid profile and lipoprotein composition, as well as on hepatic lipid concentration. Male Spraque-Dawley rats were injected i.p. with Fe (15 mg/kg weight). This injection was repeated 24 h later with a gavage of sodium salicylate (700 mg/kg). Control rats received 0.9% NaCl only. The peroxidation indices TBARS (P < 0.001) and conjugated dienes (P < 0.05) significantly increased in the blood (50 and 122%, respectively) and liver (333 and 101%, respectively) of Fe salicylate-treated rats. Concomitantly, blood and liver arachidonic acid content was diminished by iron treatment. In parallel, the plasma lipid profile was markedly affected in Fe-salicylate treated-rats. Lower plasma concentrations of total cholesterol (25%, P < 0.0001) cholesteryl ester, (34%, P < 0.001) and high-density lipoprotein-cholesterol (50%, P < 0.001) were observed. Lipoprotein composition analysis revealed enrichment of free cholesterol and depletion of cholesterol ester in very low-density, intermediate-density, low-density and high-density (HDL2, HDL3) lipoproteins. Furthermore, SDS-polyacrylamide gel electrophoresis revealed several alterations in the apolipoprotein distribution of these lipoproteins. The activity of lecithin:cholesterol acyltransferase was unchanged and could not account for the reduction of cholesterol esterification. As for the plasma, the liver exhibited a significant (P < 0.001) decrease in total cholesterol (2.42 +/- 0.07 versus 1.89 +/- 0.06 mg/g liver), essentially due to a reduction in cholesteryl ester (0.93 +/- 0.07 versus 0.51 +/- 0.03 mg/g, P < 0.001). Again, the activity of ACAT (dpm/mg microsomal protein) was not lower (12,700 +/- 1250) than that of controls (9650 +/- 1080). Thus, the iron-salicylate was able to induce peroxidation and to profoundly affect the intravascular and intrahepatic lipid, and plasma lipoprotein metabolism. Additional work is needed to elucidate the mechanisms involved in the underlying lipid and lipoprotein abnormalities.

Paving the way. Outcome planner for the orthopaedic patient at home

The home care nurse often spent more time documenting than actually caring for the patient. The decision was made to streamline documentation, and our road to outcome planners began.

Association of an exon 3 mutation (Trp66-->Gly) of the LDL receptor with variable expression of familial hypercholesterolemia in a French Canadian family

The ligand-binding domain of low-density lipo-protein (LDL) is composed of seven 40-amino-acid repeats encoded by exons 2-6. Previous studies identified a missense mutation in codon 66 of exon 3, which resulted in the production of LDL receptor protein that is not processed to its mature form. In the current investigation, we documented the presence of two identical mutant LDL receptor alleles (Trp66-->Gly) in two familial hypercholesterolemia (FH) probands, II-1 and II-2, associated with markedly elevated plasma LDL cholesterol (17.22 +/- 0.78 and 11.95 +/- 0.24 mmol/liter, respectively). Functional assays of their fibroblast LDL receptor showed inefficient binding (39 and 50%), internalization (33 and 37%), and degradation (32 and 37%) compared with controls. The contribution of the apo B gene to variation in LDL levels was virtually eliminated given the normal ligand interaction with cell surface receptors and the absence of the mutation occurring in codon 3500 of the apo B gene. Similarly, the homozygous apo E3/E3 wildtype phenotype excluded any genetic contribution of apo E to the lipoprotein abnormalities. Furthermore, the LPL mutations commonly observed in French Canadians could not account for the observed lipid alterations. Several alterations in lipoprotein composition characterized VLDL, IDL, LDL, HDL2, and HDL3 fractions. Moreover, defective intestinal fat transport was observed in both probands (II-1 and II-2). Thus, the disturbance of lipoprotein concentration, composition, size, and metabolism may in part be related to the exon 3 mutation (Trp66-->Gly) of the LDL receptor gene. The biochemical phenotype was more severe in the father (I-1) than in the mother (I-2), and in the younger homozygous proband (II-1) than in the older (II-2). The greater severity was associated with a higher LDL cholesterol/HDL cholesterol ratio. Whether the differences between the two probands are due to polygenic factors or to a metabolic consequence of a major nonallelic trait is unknown. Nevertheless, the present biochemical findings stress the extent of the lipid abnormalities associated with homozygous FH and the importance of the phenotypic variability encountered even among subjects carrying the same mutation.

Insulin modulation of newly synthesized apolipoproteins B-100 and B-48 in human fetal intestine: gene expression and mRNA editing are not involved

We investigated insulin's effect on intestinal lipid, transport and, particularly, the biogenesis of apolipoproteins crucial to lipoprotein secretion. Adding insulin (3 mU) to the serum-free medium of cultured jejunal explants from human fetuses (17-20 weeks) reduced triglyceride and chylomicron production and inhibited apo B-48 and apo B-100 secretion. When apo B mRNA was assayed by RT-PCR and its editing by primer extension, no change was detectable following the addition of insulin. HDL lipid content, apo A-1 synthesis and RNA level were unaffected by insulin. Collectively, these results suggest that the insulin-stimulated decline in intestinal chylomicron output may involve apo B co- or post-translational modifications.

The effect of dietary protein source on biochemical indices of stress in stress-susceptible pigs

The porcine stress syndrome (PSS) is responsible for major economic losses to the swine industry. The present study was performed to determine if 8-wk-old pigs representing each of three genotypes (NN = homozygous noncarrier, Nn = heterozygous carrier, nn = homozygous carrier) with respect to the PSS, differ in selected biochemical indices related to stress (exp. 1), and to examine if these indices are affected during 5 wk of dietary adaptation to a cereal-based swine diet (control diet) or to a feed containing casein, a higher quality protein (exp. 2). The first experiment demonstrated that nn and Nn 8-wk-old female pigs have a significantly greater glycemic response to a blood sampling stressor than do NN female pigs. In contrast, no genotype differences in glycemic response were observed within young male pigs. Pigs of nn genotype also demonstrated a significantly greater plasma dopamine-β-hydroxylase (DBH) activity than did the NN pigs. Results of the second experiment revealed that pigs of the nn and Nn genotypes experienced a greater glycemic response to the initial blood sampling stressor than did the NN pigs. Compared with initial levels, upon the sixth weekly blood sampling stressor the nn and Nn pigs experienced reduced plasma glucose concentration irrespective of diet, while no change in glycemic response was observed in the pigs of the NN genotype. Finally, the DBH activity of the Nn pigs adapted for 2 wk to the casein diet was found to be reduced when compared to control-adapted Nn pigs. This study suggests that in addition to genotype differences, regular exposure to stress combined with dietary adaptation to feed containing a higher quality protein (casein) may confer increased resistance to stress in pigs of the Nn genotype. Key words: Pigs, stress, dietary protein, glycemia, dopamine-β-hydroxylase

Day-night treatment difference of tobramycin serum and intrarenal drug distribution and nephrotoxicity in rats: effects of fasting

The effects of short-term food deprivation on the serum and renal distribution and nephrotoxicity of tobramycin were studied in female Sprague-Dawley rats maintained on a 14-h light/10-h dark cycle (light on: 06:00). For the distribution study, a single injection of tobramycin (40 mg/kg, i.p.) was administered at 14:00 or 02:00 to normally fed animals or to animals fasted for 12 h before tobramycin injection; these treatment times correspond to the peak and trough of tobramycin nephrotoxicity as previously determined in other studies. The serum and cortical levels of tobramycin were significantly higher 60, 120, and 240 min after the injection in fasted animals treated at 02:00 compared with normally fed animals treated at the same time (p < 0.05). In animals injected at 14:00, similar levels of tobramycin were measured in both fasted and fed rats. In the nephrotoxicity study, female Sprague-Dawley rats were fasted for 12 h before and 24 h after the timed single injection of tobramycin (150 mg/kg, i.p.). The 24-h urinary excretion of beta-galactosidase was significantly higher in fasted animals treated at 02:00 than in fed rats treated at the same time of day. Seventy-two hours following tobramycin injection, serum creatinine levels and cortical levels of tobramycin were significantly higher in fasted rats treated at 14:00 than at 02:00 and in fed rats treated at 14:00. These data suggest that a short period of food deprivation modulates the temporal variations of tobramycin nephrotoxicity.

Lipid processing and lipoprotein synthesis by the developing human fetal colon

Despite significant progress in the elucidation of the ontogeny of gastrointestinal function, little attention has been given to colonic lipid processing during development. The major purpose of this study was to explore the intracellular phase of fat absorption, lipid synthesis, and secretion in the human fetal colon compared with the jejunum originating from the same fetuses. The synthesis of lipids and major apolipoproteins was examined using cultured fetal colonic explants incubated with [14C]oleic acid and [36S]methionine, respectively. Fetal colonic explants demonstrated substantial ability to incorporate [14C]oleic acid (dpm/mg protein) into phospholipids (48,743 +/- 4,783), triglycerides (25,687 +/- 2,469), and cholesteryl esters (6,751 +/- 1,227). The total amount of radiolabeled lipids was much higher within the tissue (87,472 +/- 9,142) than in the medium (51,916 +/- 4,970), indicating a limited capacity of the fetal colon to export newly synthesized lipids. The limited colonic lipid secretory process was even more evident when compared with homologous fetal jejunal de novo synthesized lipids in tissue (133,975 +/- 13,836) and medium (279,858 +/- 1,610), respectively. Similar to the jejunum, the colon was able to elaborate all the phospholipid classes, with phosphatidylcholine accounting for > 70% of tissue phospholipids. However, their individual levels were present in lesser amounts in the colon (P < 0.001). Colonic explants elaborated most of the major lipoprotein classes but were less efficient than jejunal explants in exporting chylomicrons (33-fold), very low density lipoprotein (1.5-fold), and high-density lipoprotein (9-fold) into the medium. Apolipoprotein (apo) B synthesis and apo B mRNA editing were comparable in colonic and jejunal explants; thus they are not responsible for the defective lipoprotein secretion in the fetal large bowel. These results establish for the first time te capability of the human fetal colon to form, but not to efficiently transport, lipids, lipoproteins, and apoproteins.

Effects of fasting on temporal variations in nephrotoxicity of gentamicin in rats

Evidence for temporal variations in the nephrotoxicity of low doses of aminoglycosides were recently shown by using specific and sensitive parameters of renal toxicity. The aim of the present study was to evaluate the effect of a short period of fasting on the temporal variations in the renal toxicity of gentamicin. Twenty-eight normally fed (i.e., food and water were available ad libitum throughout the experiment) female Sprague-Dawley rats (weight, 175 to 220 g) and 28 fasted rats (i.e., only water was available during a 12-h fast before and a 24-h fast after gentamicin injection) were used. The animals were synchronized on a 14-h light, 10-h dark cycle (lights on at 0600 h) for 1 week before gentamicin administration. In July 1993, each group of animals was treated with a single intraperitoneal injection of saline (NaCl, 0.9%) or gentamicin (150 mg/kg of body weight) at either the peak (1400 h) or the trough (0200 h) of the previously determined toxicity. On day 1, the 24-h urinary excretion of beta-galactosidase, N-acetyl-beta-D-glucosaminidase, and gamma-glutamyltransferase was significantly higher in normally fed animals treated with gentamicin at 1400 h than in their time-matched controls and in normally fed animals treated at 0200 h (P < 0.01), which had normal levels of these enzymes. By contrast, the urinary excretion of these enzymes was significantly higher in both groups of gentamicin-treated, fasted rats than in their time-matched control groups (P < 0.01), reaching levels similar to those measured in normally fed rats treated at 1400 h. The accumulation of gentamicin was significantly lower in the renal cortex of normally fed rats treated at 0200 h than in rats treated at 1400 h (P < 0.05), but this time-dependent difference was not found in fasted rats treated at 0200 and 1400 h. Immunogold labeling done on ultrathin sections and observed by electron microscopy showed a similar subcellular localization of gentamicin in normally fed and fasted rats treated at either 1400 or 0200 h. These results suggest that the feeding period is of crucial importance in the temporal variations of the nephrotoxicity of gentamicin in rats.

Effect of central glucagon infusion on macronutrient selection in rats

Compared were the light-dark pattern of absolute energy intake and macronutrient selection of male Wistar rats intracerebroventricularly infused with glucagon (5 ng/h) or saline for 7 days in a three-way selection of macronutrients. Glucagon infusion induced a decrease in 24 h and nocturnal energy intake, whereas no significant change in kcal intake accompanied vehicle infusion. The decrease in kcal intake was due to a suppression of nocturnal ingestion of carbohydrate. This parameter was left unaffected with central vehicle infusion. Glucagon-infused rats had a significantly lower body weight gain than those infused with vehicle. Our study supports the hypothesis of central glucagon's suppressive effect on food intake, but reveals that the latter reflects a lower disposition to eat carbohydrate during the dark phase. The present work emphasizes the role of glucagon in the circadian regulation of carbohydrate intake.

Effect of sucrose and fructose macronutrient diets on feeding behavior of rats

Different carbohydrate sources in animal diets can affect feeding behavior. The absence of a diet standard, thus, has the potential to introduce a confounding factor into experiments. The main objective of this study, therefore, was to determine if the choice of either sucrose or fructose as the pure carbohydrate in a carbohydrate diet ration would affect feeding behavior in rats. It was found that during the light and dark phases: 1) fructose-fed rats selected significantly less energy from carbohydrate than sucrose fed rats, 2) fructose-fed rats selected more protein and lipid energy than sucrose fed rats, and 3) the total caloric intakes of the two groups were not significantly different. Differing postingestive effects of sucrose and fructose with subsequent compensatory intake may explain these results. Two different carbohydrate sources resulted in different macronutrient selection patterns, thus demonstrating the importance of the nature of dietary carbohydrate in the regulation of feeding behavior in rats.