Controlled Feeding Schedules Research Articles

EFFECTS OF CANOLA MEAL ON TISSUE TRACE MINERAL CONCENTRATIONS IN GROWING PIGS

This experiment was conducted to determine if the availability of supplemental trace minerals would be reduced by canola meal (CM) in a cereal grain-based diet for growing pigs. Thirty-two barrows weighing 21.5–23.5 kg were allotted to four dietary treatments: barley-wheat, 2:1, supplemented with (1) soybean meal (SBM); (2) canola meal (CM)-source 1 (CM1); (3) canola meal-source 2 (CM2), all fed according to a controlled feeding schedule; or (4) the CM1 diet fed ad libitum. All diets were supplemented with minerals at levels recommended for 20- to 35-kg pigs. In pigs slaughtered at 57 kg, liver and pancreas zinc (Zn) concentrations (dry basis) were higher (P < 0.05) when the SBM diet was fed compared to the CM diets. Pigs fed CM1 diet by either feeding regime showed lower Zn concentrations than those fed CM2. Treatment effects on tissue concentrations of other minerals were minor. From 23 to 57 kg liveweight, pigs fed CM diets gained less (P < 0.05) than those fed a SBM diet under controlled feeding (0.78 vs. 0.86 kg d−1). Pigs fed CM1 diet ad libitum gained 0.87 kg d−1. These results could not be directly related to a mineral deficiency. Based on tissue Zn concentrations, it was concluded that the dietary Zn was less available from the CM diets compared to the SBM diet. Key words: Trace minerals, zinc, pigs, canola meal

PRODUCTION OF HUMAN ALPHA CONSENSUS INTERFERON IN RECOMBINANT ESCHERICHIA COLI

Abstract Using a defined medium and a multiple-phage resistant AM-7 strain of Escherichia coli containing a temperature sensitive multicopy plasmid under lambda promoter control, a fermentation process has been developed for an analog human IFN-α that is a “consensus” of the known IFN-α subtypes. The gene for this interferon was completely synthetic and codon choices were optimized for expression in E. coli. Yields up to 7.6 × 1012 U of IFN-α-Con1 per liter of fermentation broth were achieved. The combination of a tightly regulated expression system and a controlled feeding schedule were fundamental to the attainment of the high expression levels and cell densities required to reach this concentration of interferon.

Morphological and biochemical observations on hepatic glycogen metabolism in mice on a controlled feeding schedule

Changes in hepatocyte morphology were correlated with chemically measured liver glycogen, blood glucose, and plasma insulin levels in control-fed mice (6 hr fed, 18 hr fasted) sacrificed at various time intervals after initiation of a 6-hr meal. At initiation of feeding hepatic glycogen was low(0.05%) but deposition proceeded rapidly, reaching a maximum of 6.99 +/- 0.13% by the sixth hour. Glycogen was depleted during the subsequent fasting period, reaching the prefeeding levels by 24 hr. A relative hyperglycemia (140-192 mg/100/ ml) predominated during all stages of glycogen deposition and depletion until the 21st hour. Plasma insulin levels were maximum during feeding (63 +/- 7 microU/ml, 3 hr) with mild hyperinsulinemia (insulin greater than 16 microU/ml) occurring during glycogen depletion (9-21 hr). Histochemical determinations (PAS) showed lobular patterns of hepatic glycogen which correlated with chemically measured glycogen levels. Six hours after initiation of feeding, periportal cells showed intensely stained masses of glycogen while centrilobular cells showed relatively diffuse staining. At 24 hours after initiation of feeding (18 hr of fasting), no significant staining was observed in the hepatocytes. Ultrastructurally, during all stages of glycogen deposition and depletion, centrilobular cells were characterized by the presence of dispersed glycogen particles with elements of smooth endoplasmic reticulum (SER) between the particles, while periportal cells showed dense glycogen deposits with SER restricted to the periphery of the glycogen masses.

Morphological and biochemical observations on hepatic glycogen metabolism in mice on a controlled feeding schedule. II. Streptozotocin-diabetic mice.

Morphological aspects of hepatic glycogen metabolism in streptozotocin (SZ) diabetic mice on a controlled feeding cycle (6 hr fed, 18 hr fasted) were studied and correlated with plasma glucose and insulin levels at various time intervals after feeding. Hepatic glycogen was low at initiation of feeding (approximately 0.05%) and increased to a maximum of 4.54 +/- 0.30% (N = 8) as compared to 6.90 +/- 0.20% (N = 12) in normal animals. Plasma glucose levels were similar to those of normal mice at initiation of feeding (80 +/- 5 mg/dl) but much higher during the feeding period (diabetic: 540 +/- 15 mg/dl, normal: 150 +/- 10 mg/dl). At the end of the feeding period, plasma glucose levels rapidly declined, reaching lower than normal levels. In contrast to insulin responses to feeding in normal animals, plasma insulin levels in SZ-diabetic mice remained very low, never exceeding 16 muU/ml. At maximum hepatic glycogen deposition, light microscopic studies showed atypical patterns of glycogen distribution with periportal cells having generally smaller-than-normal glycogen masses. Ultrastructural studies indicated that these cells contained more abundant quantities of smooth endoplasmic reticulum (SER) than is characteristically seen. The aberrant distribution patterns of glycogen observed in the diabetic mice provided morphological evidence for the proposal that the SER is involved in hepatic glycogenesis, with insulin deficiency resulting in abnormal functioning of the organelle.

Changes in Liver Lobule Glycogen Zonation During Prolonged Fasting of Rats Previously Fed a 30% Casein Diet and Adapted to a Controlled Feeding Schedule

Changes in the lobular distribution of liver glycogen were studied during the prolonged fasting of young adult male Sprague-Dawley rats that were previously adapted to a 30% casein diet and to the 2 + 22 controlled feeding and lighting schedule. The optical density of glycogen, revealed in fixed liver cryostat sections by the periodic acid-Schiff procedure, was determined in the periportal (P), midlobular (M), and centrilobular (C) regions of the liver lobule at various times during a 196-hour fasting period. The prolonged fast could be divided into 3 phases with respect to liver glycogen variation: initial glycogen depletion, glycogen resurgence, and final glycogen depletion. Glycogen was lost from all regions of the liver lobule during the initial glycogen depletion phase. During the glycogen resurgence phase, a lobular glycogen concentration gradient formed (P > M > C). The simultaneous occurrence of increasing liver glycogen, increasing liver tyrosine aminotransferase activity, and decreasing body fat during glycogen resurgence suggests that the young adult rat does not spare body protein during starvation. During the final glycogen depletion phase, liver glycogen was again present in a lobular gradient (P > M > C) but the absolute amount of glycogen in each region of the lobule was markedly reduced in comparison with rats killed during glycogen resurgence.glycogen zonation starvation liver lobule controlled feeding and lighting

Enhanced liver DNA synthesis in partially hepatectomized rats pretreated with 2,3,7,8-tetrachlorodibenzo- p-dioxin

The effect of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) on liver DNA synthesis was studied in rats after a 1 3 hepatectomy. The rats were maintained on a controlled feeding schedule and were treated with 5 μg/kg of TCDD or acetone/corn oil (control). Five days after treatment a 1 3 hepatectomy was performed and at designated times thereafter liver DNA synthesis was measured by [ 3H]thymidine incorporation into DNA. The main finding was that liver DNA synthesis was increased 8- to 10-fold by TCDD over that which was observed in control rats. This increase occurred after a latency period that was appropriate for the regenerative liver DNA synthesis response. Other experiments showed that increased incorporation of thymidine in TCDD-treated rats could be blocked by hydroxyurea, an inhibitor of semiconservative DNA synthesis, and that the increased incorporation was secondary to increased DNA synthesis and not increased thymidine kinase activity. Thus, hepatocytes in TCDD-treated rats respond in a quantitatively different manner than control rats to the same proliferative signal, 1 3 hepatectomy. Liver DNA synthesis in nonhepatectomized TCDD-treated rats tended to be greater than control, but the difference was not statistically significant.

Induction by phenobarbital of ornithine decarboxylase activity in rat liver after initiation with diethylnitrosamine

Dietary administration of 0.1% phenobarbital (PB) for 1–2 weeks increased ornithine decarboxylase (ODC) activity slightly but to a significant extent ( P < 0.05) in livers of rats into which diethylnitrosamine (DEN) (200 mg/kg body wt) had been injected intraperitoneally 2 weeks before phenobarbital feeding. The increase was observed only under the controlled feeding schedule which avoided the effect of food intake.

Variations through the day of hepatic and muscular cathepsin A (carboxypeptidase A; EC 3.4.12.2), C (dipeptidyl peptidase; EC 3.4.14.1) and D (endopeptidase D; EC 3.4.23.5) activities and free amino acids of blood in rats: influence of feeding schedule.

1. Growing rats were fed either ad lib. or with six (equal) meals offered every 4 h (from 10.00 hours). Rats of each group were killed at intervals of 4 h beginning at 11.00 hours. Activities of cathepsin A (carboxypeptidase A; EC 3.4.12.2), C (dipeptidyl peptidase; EC 3.4.14.1) and D (endopeptidase D EC 3.4.23.5) were measured in liver and muscle homogenates and free amino acids in blood were determined. 2. In the rats fed ad lib. activities of carboxypeptidase A and endopeptidase D in liver and muscle showed significant variation, with maximum activity in the light period. In general, meal-feeding only caused minor differences in cathepsin activities; although significant differences occurred for carboxypeptidase A. For the later enzyme a peak in activity occurred in the dark as well as in the light period. 3. Irrespective of the feeding schedule, the lower concentration of free essential amino acids of blood occurred generally during the night period. With the controlled-feeding schedule there is an increase of essential amino acids and a slight decrease of non-essentail amino acids of blood.

Scanning microdensitometry of glycogen zonation in the livers of rats adapted to a controlled feeding schedule and to 30, 60, or 90% casein diets.

The effect of diet composition on diurnal changes in glycogen zonation patterns in rat liver was investigated in individually-caged male Sprague-Dawley rats adapted to the 2 + 22 controlled feeding and lighting schedule and to diets containing 30% casein/55% carbohydrates, 60% casein/25% carbohydrates, or 9.0% casein (30 rats/dietary group). Three rats from each dietary group were killed at the following times relative to the onset of feeding (0 min):--60, --30, 0, 15, 30, 45, 60, 90, 120, and 180 min. Glycogen in cryostat sections from the median and right lateral lobes of the liver was fixed and stained by standard techniques. The optical density of glycogen at points along the path between the central and portal veins of a given lobule was determined, and lobular glycogen gradients of replicate animals were integrated to form a composite lobular glycogen distribution profile. In the period from--60 to 0 min, liver glycogen levels were similar for rats on any of the diets, and the glycogen concentration was similar in periportal (P), midlobular (M), and centrilobular (C) hepatocytes. During the 0- to 45-min period, diet-related glycogen depletion occurred (90 > 60 > 30% casein) by asymmetrical glycogen loss (P > M > C hepatocytes) from the liver lobules. Similar food intake curves occurred for all diets. During the 45- to 180-min period, asymmetrical glycogen accumulation began in lobular parenchymal cells (P > M > C hepatocytes), and rate of accumulation was related to dietary to dietary composition (30 > 60 > 90% casein). The differential responses of parenchymal cells within liver lobules to physiological stimuli resulted in glycogen distribution changes that were rapid and of large magnitude. Our results are consistent with the hypothesis that periportal and midlobular hepatocytes are more metabolically responsive and active than centrilobular hepatocytes

Oscillations in tissue Uptake of 75Se-L-Selenomethionine in Rats and Mice Adapted to Controlled Feeding Schedules

The amino acid 75Se-L-selenomethionine was used to study variations in amino acid uptake by various tissues of rats and mice adapted to a schedule of controlled feeding and lighting conditions. Food only became available for an 8-hour period at the beginning of the 12-hour dark period of the 24-hour cycle. Systematic oscillations were observed in the uptake of selenomethionine by the liver, pancreas, blood, kidneys, skeletal muscle, bone and brain of both rats and mice but only very small changes were noted in the spleen, lung and heart. The level of the uptake into the liver and pancreas and possibly the kidney appear to be related to the dietary state of the animals.

Functional modification of liver form-B RNA polymerase activity by a protein fraction from rats accustomed to controlled feeding schedules

A protein fraction extracted from the liver of rats accustomed to eating during the first 8 h of a daily 12 h dark period is able to increase homologous form-B RNA polymerase activity. When the protein factor is added to RNA polymerase extracted at the end of the daily fasted period (0.9:00 h) the sensitivity of enzyme to ionic strength is modified, and resembles that of the enzyme extracted during the eating period (15:00 h) either using liver deproteinized DNA or chromatin as template. The chromatin-bound RNA polymerase activity is also modified in the presence of the factor, showing a modification of enzyme sensitivity to ionic strength similar to the one induced by food intake.

Sequential changes in ornithine decarboxylase, thymidine kinase, and other enzyme activities in regenerating liver in rats on controlled feeding schedules

The changes in activity of five enzymes including ornithine decarboxylase (ODC), tyrosine aminotransferase (TAT), thymidine kinase (TK), ornithine aminotransferase (OAT) and serine dehydratase (SDH) in the early stage of the regenerating rat liver have been studied under a controlled feeding and lighting schedule. The first three enzyme activities were stimulated sequentially by partial hepatectomy. The earliest response was observed in ODC activity. A significant increase in this enzyme activity was observed at 2 hrs and the maximal level was at 4 hrs after the operation. TAT began to increase at 4 hrs and the maximal level was at 8 hrs. The TK activity was induced at about 24 hrs and the highest value was at 48 hrs after partial hepatectomy. A significant decrease in OAT activity was observed at 24 hrs after the operation and subsequently. Although a decrease in SDH activity was also observed this decrease did not seem to correlate directly with the regeneration process, since a lowered level of the enzyme activity was also found in the sham operated group.

Regulation of liver glycogen metabolism by the portal blood glucose concentration in rats adapted to controlled feeding schedules

1. 1. Animals adapted to controlled feeding schedules have been used to investigate the regulation of the diurnal rhythm of hepatic glycogen metabolism. 2. 2. At the onset of feeding the concentration of glucose in the portal blood supply to the liver increases and appears responsible for sequential increases in the activities of glucokinase and glycogen synthetase preceding glycogen deposition. 3. 3. The rate of glycogen deposition is correlated with the activity of glycogen synthetase a.

Food-induced changes in UV-absorption spectra of isolated chromatin from liver of rats under controlled feeding schedules.

We have measured the UV-spectra of liver chromatin extracted at 2 different times of day, corresponding to low or high rate of RNA synthesis from rats maintained under controlled feeding schedules. Results show that food intake does modify the UV-spectra of liver chromatin.

Folate metabolism in the rat liver during regeneration after partial hepatectomy.

1. Folate metabolism was studied during the early phases of liver regeneration after partial hepatectomy in rats accustomed to eating during the first 8h of a daily 12h dark period. 2. The content of 5-CH(3)-H(4)folate was drastically decreased during the first hours of regeneration. 3. The total HCO-H(4)folate coenzymes showed a constant decrease during the first 3 days of regeneration, and a continuous interconversion between 5-HCO-H(4)folate and 10-HCO-H(4)folate. 4. 10-HCO-H(4)folate synthetase, serine hydroxymethyl-transferase and 5,10-CH(2)-H(4)folate dehydrogenase activities were relatively low during the first hours after the operation, and increased only several hours later. 5. The increase in enzyme activities showed a stepwise pattern, apparently due to an interaction between the regeneration process and the controlled feeding schedules.

Fine structure of hepatocytes from fasted and fed rats.

The fine structure of hepatocytes from rats maintained on a controlled feeding schedule are described. Liver samples were processed for electron microscopy, histochemistry and chemical determinations of glycogen at precise time-intervals following a 30-hour fast and a 2-hour meal. Hepatocytes from 30-hour-fasted rats with extremely low hepatic glycogen levels were devoid of glycogen particles. Centrilobular cells showed areas of the cytoplasm rich in vesicles of smooth endoplasmic reticulum (SER) while periportal hepatocytes contained less extensive regions of SER. Soon after feeding the fasted rats, glycogen particles appeared in regions of the cell rich in SER. Centrilobular hepatocytes contained numerous glycogen areas which were infiltrated with tubules of SER, while periportal cells showed dense glycogen deposits with SER restricted to the periphery of the masses of glycogen. Throughout glycogen deposition each glycogen particle was closely associated with membranes of SER until maximum glycogen deposition was achieved 12 hours after initiation of feeding. At this point SER was reduced to the lowest amounts of the time-periods studied. During stages of glycogen depletion SER proliferated and reached the highest concentration measured in this study. Tubules of SER were present throughout the glycogen masses of centrilobular hepatocytes, whereas in periportal cells the organelle was restricted to the periphery of the glycogen masses. It is concluded that SER is associated with glycogen particles in rat hepatocytes during both deposition and depletion of glycogen.

Ornithine Decarboxylase Activity in Regenerating Liver from Rats Adapted to Controlled Feeding Schedules

Ornithine Decarboxylase Activity in Regenerating Liver from Rats Adapted to Controlled Feeding Schedules

Modification of the template capacity of liver chromatin for form-B ribonucleic acid polymerase by food intake in rats under controlled feeding schedules.

Nuclei from liver of rats accustomed to eating during the first 8h of a daily 12h dark period demonstrate an increased capacity to synthesize RNA 6H after the beginning of the feeding period. 2. This increase is accompanied by a higher yield of extractable form-B DNA-dependent RNA polymerase activity. 3. The endogenous RNA polymerase activity associated with nuclear chromatin is also stimulated by food intake. Both purified and chromatin-associated form-B enzyme activities exhibit different ionic strength requirements after food intake. 4. The sensitivity of exogenous (added) form-B-enzyme to changes in ionic strength changes after feeding when chromatin is used as template. 5. Chromatin extracted from the liver of fed rats is a better template for form-B-enzyme than chromatin extracted from starved rats.

Effect of controlled feeding on the isoenzymes of pyruvate kinase, hexokinase and aldolase in liver during development

Controlled feeding schedules have been used to maintain rats during the first thirty days following birth to investigate the role of food in determining the course of liver development. Use of the ‘8 + 16’ feeding schedule and a new ‘16 + 8’ suckling schedule allowed rats to be reared through the neonatal period without access to solid food until the day they were weaned. Food-independent increases in Pyruvate kinase type I isoenzyme, glucokinase and aldolase B take place in the late suckling period. Thus it appears that the change in the nutritional status of the animal at weaning is not a major factor in liver development.

Diurnal variations of liver folate metabolism in rats maintained under controlled feeding schedules.

SummaryRats maintained under controlled feeding schedules exhibit daily rhythms of the enzyme activities involved in folate metabolism. Tetrahydrofolate dehydrogenase and serine hydroxymethyl transferase show only small variations in their activity in the range of the 24-hr cycle. The 5,10-CH2-H4folate dehydrogenase shows a peak of activity at 6 PM (18:00), while the 5,10-CH2-H4folate synthetase activity reaches its lowest level between 3:00 PM (15:00) and 3:00 AM (3:00). The liver content of folate coenzymes does not change significantly during the whole day.