Pair-feeding Experiments Research Articles

Toxicity and Tissue Residues from Diphenylhydantoin Fed to Chickens

Within three experiments with broiler-type crossbred chickens, diphenylhydantoin (DPH) was administered via the diet at levels ranging from 10 to 2500 mg./kg. Feed intake and body weight gain were adversely affected by levels of 1000 mg./kg. or higher. A hemorrhagic syndrome occurred in 16 percent of the chickens fed 100–1000 mg./kg., and 33 percent of those fed 2500 mg./kg. Twenty percent of the chickens fed 1000 mg./kg. were anemic; none of those receiving 250 mg./kg. were anemic. Other toxic manifestations included neurological side effects of a lethargic stupor, excitability to a disturbance, or a characteristic condition referred to as “head under.” Pair-feeding experiments revealed that lowered feed intake was not responsible for any of the clinical signs. All of the toxicity signs were reversible in 3 to 4 weeks following withdrawal of DPH. Muscle samples contained 2.5 to 11.4 mcg. DPH/g. at drug levels of 1000 and 2500 mg. DPH/kg. diet. Dose-response curves revealed that plasma, adipose, kidney and liver had levels which were, respectively, 1.05, 1.51, 2.19, and 2.85 times those of muscle.

Nutritional factors affecting drug-metabolizing enzymes of the rat

Feeding diets rich in thiamin depresses aniline hydroxylase, cytochrome P-450 and cytochrome b 5 within 9–14 days. Pair-feeding experiments suggest that the depression of aniline hydroxylase, cytochrome c reductase and ethylmorphine demethylase is due to the thiamin; however, the depression of cytochrome P-450 and b 5 may be due primarily to the increased amount of carbohydrate ingested by rats fed the enriched diet. When starch was substituted for sucrose, cytochrome P-450 was not lowered by high thiamin ingestion, although cytochrome b 5 and NADPH cytochrome c reductase were depressed similarly to that of rats fed high thiamin levels in a sucrose-based diet. Although aniline hydroxylase and ethylmorphine demethylase activities were significantly depressed by both high thiamin diets, this effect was more pronounced in rats fed the sucrose-based diet.

Studies on rumen metabolism. IX. Contribution of plant lipases to the release of free fatty acids in the rumen.

AbstractThe role of plant lipases in the hydrolysis of dietary lipids in the rumen of pasture‐fed ruminants has been investigated by means of in vitro and in vivo experiments with rumen contents. Lipases present in the leaves of numerous pasture plants remained highly active for at least 5 h in the presence of metabolising rumen microorganisms, leading to the hydrolysis of triglyceride. Parallel experiments showed that the lipase activity of actively metabolising micro‐organisms in rumen fluid was very low. A slight increase in lipolytic activity attributable to micro‐organisms occurred after incubations of about 4 h with plant extract when the metabolic activity of the microbial population had passed its peak.In vivo experiments showed that the lipolytic activity of rumen fluid, obtained 0.5 to 5.0 h after feeding fresh grass, was about twice that of rumen fluid obtained after overnight fasting. Paired feeding experiments showed that lipase activity was higher in rumen fluid obtained from a pasture‐fed, than from a hay‐fed animal. Nevertheless, there was appreciable activity in the rumen contents obtained from the hay‐fed twin, which is consistent with the presence of lipase activity in the extracts of dried grass.Multiple forms of plant esterases and phosphatases were present in the soluble fraction of rumen fluid several hours after feeding.It is concluded that the rapid release of free fatty acids which follows the ingestion of pasture is due mainly to the activity of plant enzymes and that rumen microorganisms have a subsidary role in hydrolysing ingested lipid.

Influence of diet on intestinal cell DNA synthesis in the diabetic rat.

The incorporation of thymidine methyl-3H (3H-TdR) into deoxyribonucleic acid (DNA) was measured in the intestine of diabetic rats. Animals were allowed food ad libitum or were pair-fed. Diabetes was induced with streptozotocin. In the pair-feeding experiment, there was a decrease in 3H-TdR incorporation into DNA in the intestine of diabetic rats, and the mucosal weight did not differ significantly from controls. However, when diabetic rats were allowed food ad libitum, there was a significant increase in DNA synthesis in the intestine. The mucosal weight of the diabetic animal was 62 per cent greater in the jejunum and 31 per cent greater in the ileum than in the control segments. It is concluded that a decrease in proliferative cellular activity occurs in the intestinal mucosa of diabetic rats but hyperphagia leads to a compensatory increase in DNA synthesis in these animals.

The fatty acid composition of backfat from Pietrain and Large White pigs

SUMMARYThe fatty acid composition of backfat from Pietrain and Large White pigs was examined. Both the inner and outer layers of Pietrain backfat had higher concentrations of unsaturated fatty acids and lower concentrations of saturated fatty acids. Pietrains consequently had relatively soft fat.A pair-feeding experiment was conducted with Large White and Pietrain pigs to determine whether these differences could be explained by the lower voluntary feed intake of Pietrains. The results showed that the Large Whites continued to accumulate relatively saturated fatty acids even at the lower level of feeding. It was concluded that the differences in the fatty acid composition of backfat reflect genetic differences in the capacity for fat deposition between the two breeds.

Comparative Effects of Casein and Amino Acid Mixture Simulating Casein on Growth and Food Intake in Rats

In several feeding methods, the effect of the amino acid mixture simulating casein on rat growth was compared with that of intact casein. When diets were provided ad libitum, weight gain and food intake were lower for rats fed amino acid diets than those fed a casein diet at dietary nitrogen levels of 3.2 and 4.8%, whereas no difference was observed between both the nitrogen sources at 0.8 and 1.6% levels. The superiority of casein was also found in pair-feeding experiments in which casein diet was pair-fed with amino acid diet on a daily basis at a nitrogen level of 3.2%. When animals were space-pair-fed for 1 hour twice daily, however, both diets supported identical growth during the 14-day experimental period. Identical growth rates were also obtained by force-feeding the same amounts of both diets. These results indicate that the amino acid mixture simulating casein is nutritionally equivalent with intact casein under conditions of space-feeding twice daily to pair-fed partners.

The effect of hypophysectomy and growth hormone replacement on albumin synthesis and catabolism in the rat.

Albumin synthesis and catabolism were respectively measured by McFarlane's (1963) sodium [(14)C]carbonate method and I-labelled albumin in hypophysectomized rats, both untreated and treated with growth hormone. Hypophysectomy resulted in a decrease in both albumin synthesis and catabolic rates. These changes as shown by pair-feeding experiments could not be ascribed to decreased food intake alone. Growth hormone was shown to partially restore both albumin synthesis and catabolic rates. It is proposed that growth hormone stimulates albumin synthesis and that its effect on albumin catabolism is secondary to changes in the mass of the intravascular albumin pool.

The effect of maternal liver injury and dietary reduction on foetal growth in the rat

The effects on foetal growth of administering allyl formate or aflatoxin B 1 or of feeding a restricted diet to the pregnant rat have been studied. A significant retardation of foetal growth occurred in rats given allyl formate (0·15 ml/kg) by intubation on day 19 of pregnancy and in rats developing grade II liver lesions (extensive fatty infiltration, biliary proliferation and persistent cell necrosis) following similar administration of 5–7 mg aflatoxin B 1/kg on day 16. Paired-feeding experiments with untreated animals demonstrated that the reduction of foetal growth was related primarily to the dietary intake of the pregnant rat and only indirectly to the severity of the maternal liver lesion.

Pair feeding between normal and experimental progeny from mother rats during gestation and lactation.

In earlier study from this laboratory, when fed Commercial Laboratory Chow, less feed efficiency in the progeny of underfed mothers during gestation and lactation was reported accompanying with the high nitrogen level in both the urine and the feces. Using the formulated diet with egg albumin, we have undertaken to measure feed efficiency and the pair feeding between normal and restricted progeny. Although we failed to find any significant difference in feed efficiency between the two groups, the pair feeding revealed the retarded growth in restricted progeny during a pair feeding experiment period, suggesting the presence of some abnormality involved in metabolism, particularly protein metabolism, in restricted progeny even when fed diet containing egg albumin.

Plasmodium cynomolgi: Sources of variation in susceptibility of Anopheles quadrimaculatus, A. balabacensis, and A. stephensi

Plasmodium cynomolgi: Sources of variation in susceptibility of Anopheles quadrimaculatus, A. balabacensis, and A. stephensi. Experimental Parasitology 27, 53–59. In paired feeding experiments Anopheles quadrimaculatus, A. balabacensis, and A. stephensi differed significantly in susceptibility to infection with the B strain of Plasmodium cynomolgi. A strain of A. stephensi originating in Iran differed significantly from strains originating in India, Pakistan, and Iraq. The relative susceptibility of laboratory colonies of A. quadrimaculatus and the India strain of A. stephensi fluctuated repeatedly over the course of a year. Segregated breeding populations of the India strain of A. stephensi drifted independently in relative susceptibility.

Effects of a Dietary Potassium Deficiency on Protein Synthesis in the Young Chick ,

The influence of the dietary level of potassium on protein synthesis was investigated with young chicks. Incorporation of intraperitoneally injected L-leucine-1-14C into TCA-precipitable material 4 hours postinjection was used as an index of rate of protein synthesis. The results indicated that chicks fed a semipurified diet deficient in potassium incorporated significantly less L-leucine-1-14C into skeletal muscle protein than chicks receiving an adequate level of potassium. Conversely, the incorporation of L-leucine-1-14C into plasma protein was significantly greater in potassium-deficient chicks than in chicks receiving adequate potassium. Radioactivity in the nonprotein fraction of plasma, presumably in the form of the free amino acid, was also higher in potassium-deficient chicks as compared with control chicks. Dietary potassium was without effect on incorporation of L-leucine-1-14C into liver proteins. It was demonstrated, by pair-feeding experiments, that the effects on incorporation of the labeled leucine into skeletal muscle protein were due to a potassium deficiency per se rather than to reduced feed intake.

Alterations in the Activities of Several Rat Liver Enzymes at Various Times after the Feeding of High Carbohydrate Diets to Rats Previously Adapted to a High Protein Regimen

The effect of high carbohydrate (protein-free) diets on the activities of several rat liver enzymes was studied in rats previously adapted to a 90% casein, carbohydrate-free diet. Both, the 90% glucose and the 90% fructose diet, were found to decrease all the liver constituents and enzyme activities studied, with the exception of pyruvate kinase, the activity of which was increased temporarily by both carbohydrate diets. The possibility of a control system regulating the synthesis of this enzyme at the translation level is discussed. Phosphorylase, glucose 6-phosphatase, fructose 1,6-diphosphatase, L-α-glycerophosphate dehydrogenase, glucose 6-phosphate dehydrogenase and malic enzyme activities were decreased to variable amounts. In some cases glucose 6-phosphate dehydrogenase and malic enzyme activities were increased. Tyrosine-α-ketoglutarate transaminase activity was minimal after 1 day of carbohydrate feeding. Glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase and serine dehydrase activities declined logarithmically. In the glucose-fed animals glutamic-oxaloacetic transaminase declined with a half-life of 4 days, glutamic-pyruvic transaminase with a half-life of 2 days and serine dehydrase with a half-life of 1.7 days. Fructose feeding increased the half-life of both glutamic-oxaloacetic transaminase and glutamic-pyruvate transaminase but not the half-life of serine dehydrase. Pair-feeding experiments showed that the tendency of the fructose diet to increase liver size and the half-lives of the 2 transaminases (glutamic-oxaloacetic transaminase and glutamic-pyruvate transaminase) was not due to an increased consumption of the fructose diet.

Effect of hypophysectomy and adrenalectomy on enzymes concerned with nicotinamide adenine dinucleotide synthesis.

The effect of hypophysectomy and adrenalectomy on hepatic nicotinamide mononucleotide pyrophosphorylase, nicotinate mononucleotide pyrophosphorylase, quinolinate transphosphoribosylase and NAD kinase in the rat has been studied. Nicotinate mononucleotide pyrophosphorylase and quinolinate transphosphoribosylase activity was not affected by either adrenalectomy or hypophysectomy. Nicotinamide mononucleotide pyrophosphorylase activity was significantly decreased by hypophysectomyhypophysectomy and adrenalectomy. NAD kinase activity was decreased by hypophysectomy but was not altered by adrenalectomy. Paired-feeding experiments indicate that dietary restriction does not alter the activities of NMN-pyrophosphorylase or nicotinate mononucleotide pyrophosphorylase. Dietary restriction does, however, appear to duplicate the effects of hypophysectomy on NAD kinase. (Endocrinology 81: 779, 1967)

Weight gains, nitrogen metabolism, and body composition of rats fed one or five meals daily.

Three paired-feeding experiments were conducted to determine the effect on growth, metabolism, and body composition of rats fed one or five meals daily. Each experiment, with six littermate pairs of castrated male rats, lasted 30 days including an 11-day metabolism trial. Rats fed five meals ("multiple-feeders") gained weight at a faster (P < 0.05) rate and yielded heavier (P < 0.05) dry body weights than did those fed one meal daily ("single-feeders"). A higher percentage of fat in the single-feeders resulted in little difference in the weight of carcass fat. A heavier weight of body protein in the multiple-feeders was consistent with their greater (P < 0.001) retention of nitrogen. Water intake and the urinary losses of water and nitrogen were greater (P < 0.001) for the single-feeders.

Initial Effects of Amino Acid Imbalance in the Rat

In an attempt to distinguish the initial effects of an amino acid imbalance from the indirect effects of the depressed food intake, several biochemical changes were determined in protein-depleted rats in short-term experiments. The rats were fed for 24 hours an imbalanced diet, made by adding 3.1% of an amino acid mixture lacking threonine to a basal diet containing 10% wheat gluten supplemented with 0.8% of lysine and 0.1% of DL-threonine. In pair-feeding experiments it was observed that the protein, amino acid N and threonine content in liver of rats fed the imbalanced diet was higher than in those fed the basal diet. Relative high levels of liver protein concentration in protein-depleted rats after feeding the imbalanced diet were also observed in ad libitum experiments. These observations support the assumption that the imbalance could act initially, stimulating the liver protein synthesis. An increase in liver weight correlated with a high glycogen content was also observed in protein-depleted rats fed the imbalanced and the corrected diet (imbalanced plus 0.1% DL-threonine) both in ad libitum or in the pair-feeding experiments. These observations indicate the utilization of the excess of amino acids provided by the amino acid mixture for glyconeogenesis. As a consequence of the changes in liver and plasma concentration of threonine and amino acid N, some of the ratios that reflect their relative proportions were markedly altered. The possibility that the depression in food intake characteristic of the imbalance could be related to those changes is discussed.

Pantothenic Acid Deficiency in Pregnant and Non-pregnant Guinea Pigs, with Special Reference to Effects on the Fetus

To study the effects of pantothenic acid deficiency during pregnancy in the guinea pig, it was necessary first to establish the appropriate duration of the deficiency period, by subjecting adult animals to the deficient diet. These experiments showed that the adult guinea pig is sensitive to a deficiency of pantothenic acid. Thirteen non-pregnant adults died within 10 to 41 days after institution of the deficient diet, and 3 pregnant animals survived only 9 to 16 days. Liver pantothenic acid and coenzyme A levels were markedly reduced, and liver fat concentration was greatly increased. Pair-feeding experiments showed that this increase in liver fat was at least partially due to decreased food intake. A transitory dietary deficiency of pantothenic acid during the ninth or tenth weeks of gestation (total period 70 days) resulted in loss of fetuses through abortion, or death of the mother. Deficiency during the tenth week appeared to produce a significant increase in the liver fat of the newborn. Concomitantly, liver pantothenic acid level was lower than normal, both at birth and at 7 days of age. Young whose mothers had received the deficient diet during the ninth, the seventh or the sixth weeks showed no significant changes in liver fat at birth, but liver pantothenic acid concentration was lower than normal. No gross morphological abnormalities were noted. Liver fat concentration in normal newborn guinea pigs was found to be more than 10 times the normal adult level. At 62 days of gestation, it was even higher than at birth, but it decreased after parturition to one-third of the newborn level by 2 days of age. In contrast, liver cholesterol showed only slight changes in the neonatal period. The experiments suggest that the greatest need for pantothenic acid during fetal development of the guinea pig is in the period shortly before birth.

BODY AND MUSCLE WEIGHT DEPRESSING EFFECTS AND THYMOLYTIC POTENCIES OF GLUCOCORTICOIDS IN THE RAT.

SummaryThe effects of hydrocortisone, prednisolone, methylprednisolone, dexamethasone or triamcinolone on body weights, the weights of the rectus femoris, triceps brachialis and gastrocnemius muscles and food consumption were studied in normal male rats, weighing 87–111 g. Subcutaneous administration of the aforementioned glucocorticoids, once a day for 10 consecutive days, elicited a reduction in body weights, muscle weights and food consumption which appeared roughly proportional to the relative thymolytic potency of each glucocorticoid. From pair-feeding experiments, it was apparent that the reduction in food consumption accounted for 53–65% of the total body weight losses. Muscle weight losses were similarly affected. It was concluded that glucocorticoids have similar quantitative effects on body and muscle weights of the rat if administered at equipotent thymolytic doses.

Food restriction and lipid metabolism in pregnancy

In order to study the effects of reduced food intake during pregnancy on tissue and serum lipids, a paired feeding experiment was carried out on pregnant rats in which deprived rats were given 30 per cent of the daily intake of their freely eating controls. When they were sacrificed at term, the deprived rats contained 6 to 8 live young. Dry residue values in liver, kidney, placenta and depot fat were significantly lower in the deprived animals except in the placenta. Total lipid was reduced in all organs except the placenta. In the deprived rats, serum total lipid, triglycerides, phospholipid, free and total cholesterol, and free fatty acids were held to levels previously observed in nonpregnant fully fed rats. Palmitate levels were lower in all organs except liver in the deprived rats; palmitoleate was lower in all tissues; oleate was lower in liver, kidney and serum. Arachidonate levels were higher in all tissues. It was concluded that, during the period of rapid mobilization and utilization of depot fat, palmitate was selectively metabolized. The higher tissue arachidonate levels in the deprived rats were interpreted as an expression of relatively higher phospholipid levels. Evidence is presented that normal pregnancy itself is accompanied by alterations in the triglyceride types found in the depot fat.

The effect of the level of dietary fat on the toxicity of phenolic antioxidants.

SUMMARYA study was made of the effect of two antioxidants, butylated hydroxy anisole (BHA) and butylated hydroxy toluene (BHT), with variation in the type and quantity of dietary fat, on growth, food consumption, reproduction, mortality, organ weights and post‐mortem pathology of the rat.The normal cellular behaviour of experimental animals fed diets containing one hundred times the amount of the antioxidant normally expected to be present in human foods (normal testing dose, NTD), is the conventional yardstick of non‐toxicity.The NTD of BHA produced no apparent changes in any of the parameters measured. When BHT was fed at a dietary level of 0·1 p.c. (the NTD) in conjunction with a 20 p.c. lard supplement, it significantly reduced the initial growth rate and mature weight of male rats. No such significant effect was noted in female rats or in male rats with a 10 p.c. lard supplement. A paired feeding experiment showed that this inhibition of growth was a direct toxic effect of BHT and could not be explained by a reduction in the palatability of the diet.At the NTD, BHT produced a significant increase in the weight of the liver relative to the body weight. The mean absolute weight of the liver was also increased.A significant loss of hair on the top of the head occurred in animals whose diet contained the NTD of BHT. This effect was only noted in animals under conditions of increased stress and was enhanced by an increase in the lard content of the diet. Anophthalmia occurred in 10 p.c. of the litters born of parents fed BHT.Even when present in the diet at a concentration of 0·5 p.c., BHA and BHT had no effect on one reproductive cycle of the rat, or the histology of the spleen, kidney, liver, testes or skin, or the ratio to total body weight of the weight of the heart, spleen and kidney.If the conventional NTD be accepted, BHA fulfilled the requirements of non‐toxicity. BHT, at the NTD, on the other hand, produced deleterious deviations from normal cellular behaviour which cast doubt on the advisability of permitting this antioxidant in foodstuffs for human consumption.

The Effects in Rats of Vitamin B12, with and without Ethyl Alcohol, on Nitrogen Balance, Serum Albumin, Liver Nitrogen and Fat

Female rats were maintained on a soybean meal diet containing 12% of protein. The effect of supplementing the diet by injecting 7.5 μg of vitamin B12 daily was studied in both ad libitum and paired-feeding experiments. A 15% solution of ethyl alcohol was the only drinking solution for sub-groups of both the vitamin B12-treated and the control rats fed ad libitum. The rats receiving vitamin B12 and eating the deficient diet ad libitum grew more rapidly, ate more of the diet and retained more nitrogen than their controls. Vitamin B12 was also associated with increased growth, food intake and nitrogen balance in the alcohol treated rats. In the pair-fed rats, vitamin B12 did not significantly increase either growth or nitrogen retention. Caloric intake was essentially the same for the ad libitum rats on the diet alone as for rats on diet plus alcohol. In the rats receiving vitamin B12, the total caloric intake was considerably greater than in the deficient rats and did not differ significantly between the group on vitamin B12 plus water and the group on vitamin B12 plus alcohol. Alcohol per se was associated with decreased growth, food intake and nitrogen balance. In both the paired feeding and the ad libitum experiments, the administration of vitamin B12 was associated with lower levels of liver fat and higher levels of liver nitrogen. Drinking 15% ethanol for the period of the experiment did not further alter the liver composition with respect to total fat and nitrogen. Administration of vitamin B12 led to a decrease in the plasma albumin expressed as percentage of the total plasma proteins in the ad libitum-fed rats. Alcohol further decreased plasma albumin. Total plasma proteins at sacrifice were not affected by any regimen tried; vitamin B12 had no effect on plasma albumin levels of the pair-fed rats. Adrenal weight per 100 gm of body weight was not affected by the administration of vitamin B12 or alcohol. Adrenal cholesterol was decreased in the ad libitum-fed rats on vitamin B12 regardless of whether or not they had ingested ethyl alcohol. Vitamin B12 did not affect the adrenal cholesterol concentration of the pair-fed rats. Microscopic sections of the livers from animals treated with vitamin B12 showed much less fat than did the sections from deficient rats. This was also the case when alcohol and vitamin B12 were given.