Showing papers on "Low protein published in 1983"

Mechanisms of thermogenesis induced by low protein diets

Abstract: Weanling (22-day-old) rats fed a low protein (8% casein) diet consumed the same amount of energy as controls (22% casein diet), but intake corrected for body size (kJ/kg0.75) was increased in the former group. Weight gain and the efficiency of gain (g gain/MJ) were markedly reduced in low protein fed rats. Resting oxygen consumption (VO2) was elevated by 15% in the low protein group but this difference was completely abolished by beta-adrenergic blockade with propranolol. Interscapular brown adipose tissue (BAT) mass, protein content, mitochondrial yield and GDP binding were increased in low protein fed rats but mitochondrial alpha-glycophosphate shuttle activity of BAT was unaltered, although shuttle activity was elevated in liver mitochondria. Plasma triiodothyronine levels were increased by 64% in the low protein group, whereas insulin levels were markedly reduced in spite of normal blood glucose levels. Resting VO2 and BAT mass were also increased in older (55-day-old) rats fed the low protein diet, but the changes were smaller than in weanling rats. These data suggest that the decreased metabolic efficiency seen in rats fed protein deficient diets involves sympathetic activation of BAT, and is therefore similar to the thermogenic responses seen in cold adapted and cafeteria-fed animals.

Brain proteolipids. Isolation, purification and effect on ionic permeability of membranes.

Abstract: Proteolipid apoproteins have been isolated from a whole bovine brain homogenate by chloroform/methanol extraction, and fractionated by chromatography on modified (lipophilic) Sephadex, followed by ion-exchange chromatography on CM-Trisacryl. The various final, highly hydrophobic, fractions are homogeneous (sodium dodecyl sulfate/polyacrylamide gel electrophoresis). Transmembrane ion transfers were studied by 22Na + flux and electrical conductance measurements. Single channel events were observed at low protein concentrations, in particular with one of the final homogeneous apoproteolipids of molecular mass 24 kDa.

Pancreatic polypeptide responses to protein meal challenges in obese but otherwise normal children and obese children with Prader-Willi syndrome.

Abstract: Children with hyperphagia and obesity of Prader-Willi syndrome (PWS) have previously been shown to have blunted pancreatic polypeptide (PP) response to low protein meal stimulation. To evaluate the effects of various protein challenges on PP release in children with PWS, we administered both a low protein (0.2 g/kg) and a high protein (2.0 g/kg) meal stimulation test to 12 children previously diagnosed as having PWS and to an age- and weight-matched group of 19 obese but otherwise normal children. Serum samples were collected just before and for 3 h after meal ingestion. The mean (±sd) age was 11.7 ± 4.2 yr for the PWS group and 10.3 ± 3.8 yr for the obese group (P = 0.323). The percent ideal body weight for height for the PWS group (mean ± sd 186 ± 48%) was not significantly different from the percent ideal body weight for height for the obese group (174 ± 35%; P = 0.421). Peak PP responses were significantly less for the PWS group than for the obese group for both the low and high protein meal stimulati...

Low protein variability and genetic similarity between populations of the polar bear (Ursus maritimus)

Abstract: Blood samples from a total of 460 polar bears (Ursus maritimus) from various Arctic regions, but excluding the USSR, were collected during the period 1967-1981 to study electrophoretic variation in different proteins. Two hundred and one samples from Alaska, 48 from the Canadian Arctic, 89 from Svalbard, and 21 from Northeast Greenland were collected during the period 1967-1973 and were analysed by vertical polyacrylamide gel electrophoresis to study transferrin and hemoglobin polymorphism, Thirty-one samples collected in 1974 were analysed by starch gel electrophoresis for 14 enzyme systems in serum and red blood cells. Seventy samples collected from Alaska, the Barents Sea, and Canada in 198&81 were studied by starch gel electrophoresis, and further analysed for protein variation by thin-layer isoelectric focusing, horizontal polyacrylamide gel electrophoresis, and two-dimensional electrophoresis. In all, about 75 loci were analysed for variation. The degree of protein and enzyme variation in the polar bear was observed to be relatively low. Starch gel electrophoresis revealed variation of an unidentified serum protein. The distribution of this protein indicates a closer connection between bears in Alaska and Canada compared to those in Greenland and Svalbard, but the differences were not significant. As in many large mammals, the information from protein variation in polar bears has limited use for management purposes. We could not find any simple system usable for identification of discrete populations. On the basis of protein variation as sole criterion, the populations investigated could not be separated. Possible explanations for the uniformity of blood proteins can be exchange of bears between geographical areas and/or a high selective pressure in polar bears.

Urinary C-peptide: a simple measure of integrated insulin production with emphasis on the effects of body size, diet, and corticosteroids.

Abstract: C-Peptide is secreted from the β-cell in equimolar quantities with insulin. Since a fraction of C-peptide is excreted in the urine, measurement of C-peptide in timed urine collections is a simple indirect measure of integrated insulin production. Normal subjects were studied to determine the effects of diet and oral prednisone on urinary C-peptide excretion. In subjects on a defined diet, there is a positive correlation of urinary Cpeptide with body weight. When insulin production is increased after oral prednisone, there is also a positive correlation with body mass index and percent ideal body weight. Prednisone increases plasma glucose, immunoreactive insulin, and serum and urinary C-peptide levels beginning 8–12 h after oral administration. This effect of prednisone is most marked in the postprandial state. Diets high in carbohydrate and protein result in significantly more insulin production, as measured by urinary Cpeptide, than isocaloric diets with low protein or carbohydrate composition.

Dietary manipulation of plasma albumin concentration.

Abstract: The variation in plasma albumin concentrations of rats fed a wide range of protein- and energy-deficient diets has been investigated. These changes have been correlated with simultaneous effects of the diets on growth rate, carcass composition, protein and energy balance, and plasma concentration of insulin corticosterone and triiodothyronine (T3). Although rats eating diets of low protein content and libitum developed hypoalbuminemia, those fed equivalent amounts of protein at low energy intakes had plasma albumin concentrations nearer, or equal to control values. Data from the balance study showed that for hypoalbuminemia to occur, not only had dietary protein to be inadequate, it was also necessary for energy consumption to be in excess of requirements. It is suggested that in protein-deficient animals, energy consumed in excess of the amount required for maintenance and the protein-limited growth rate initiates a metabolic response which results in inappropriate use of the meagre protein intake. This "dysadapted" state, in the rat, appears to be indicated by elevated plasma T3 values. The implication that kwashiorkor-like symptoms can be generated by a relative as opposed to a total energy excess is discussed in relation to the appearance of this disease in humans.

Purification and molecular characterization of the brain synaptic membrane glutamate-binding protein.

Abstract: A glutamate-binding protein from rat brain synaptic plasma membranes has been purified to apparent homogeneity. This protein has a Mr of 14,300 based on amino acid and carbohydrate analyses. The protein is enriched with tryptophan residues, which contribute substantially to its hydrophobic nature. It also has a relatively high content of acidic amino acids, which determine is low isoelectric point (4.82). The protein exhibits either a single, high-affinity class of sites for L-[3H]glutamate binding (KD = 0.13 microM) when binding is measured at low protein concentrations, or two classes of sites with high (KD = 0.17 microM) and low affinities (KD = 0.8 microM) when binding is measured at high protein concentrations. These observations suggest preferential binding of L-glutamate to a self-associating form of the protein. The displacement of protein-bound L-[3H]glutamic acid by other neuroactive amino acids has characteristics similar to those observed for displacement of L-glutamate from membrane binding sites. Chemical modification of the cysteine and arginine residues results in an inhibition of glutamate binding activity. The possible function of this protein in the physiologic glutamate receptor complex of neuronal membranes is discussed.

Preparation of colorless sunflower protein products: Effect of processing on physicochemical and nutritional properties

Abstract: A comparison was made of the different technological treatments for the preparation of colorless sunflower protein products from the viewpoint of the effect of processing conditions on the extraction yield of nitrogen and lipid, chemical, physicochemical and nutritional properties of the processed products. The technological treatments comprised soaking dehulled seeds in dilute citric acid or sodium bisulfite solution and washing the defatted meal with the respective solution. The defatting process was carried out with hexane or azeotrope (hexane/ethanol). Nitrogen and lipid recovery was slightly greater for hexane defatted products than for azeotrope defatted products. About 21.4% of the phenolic compounds of the sunflower seeds were bound to the proteins of the seeds before processing and therefore could not be eliminated by the aqueous extraction. Aqueous extraction of phenolic compounds was limited for full fat seed. The free phenolic compounds were very stable in acid medium but sensitive to oxidation in alkaline medium and had no significant effect on in vitro enzymatic proteolysis and growth inhibition of rats. Lysine and the bound phenolic compounds were the critical factors responsible for inhibition of enzymatic proteolysis and reduced growth of rats. The diet containing whole seed meal presented a low protein efficiency ratio (PER) value. Citric acid, a chelating agent, proved to be an antioxidant as effective as sodium bisulfite; the products obtained by citric acid treatment had a visually whiter color than those processed by sodium bisulfite.

The influence of protein:energy value of the ration and level of feed intake on the energy and nitrogen metabolism of the growing pig. 2. N metabolism at two environmental temperatures.

Abstract: 1. The nitrogen balances of thirty-six individually-housed, entire male pigs (body-weight range 19–50 kg) were measured over 7 d periods when the animals were kept initially at an environmental temperature of 22° and then at 10° while fed on rations containing 153, 201 and 258 g crude protein (N × 6·25; CP)/kg dry matter (DM). The respective metabolizable energy (ME) contents were 16·29, 16·96 and 17·24 MJ/kg DM. Each ration was given at three levels, 20, 35 and 50 g feed/kg body-weight per d. The animals fed on the 20 and 35 g/kg feeding level were catheterized and blood samples withdrawn on two consecutive days within the N-balance periods for the determination of blood urea (BU) concentration both before and at hourly intervals for 7 h following the morning feed.2. An increase in feed intake resulted in a significant increase in N retention (NR) at each environmental temperature. However, NR as a proportion of N intake was higher the lower the protein content of the ration. With the exception of the animals fed on the low-protein ration, NR at any given feed intake was lower at 10° than at 22° and these differences were reflected in the animal's body-weight gain.3. Values for the fasting N metabolism (Nf), calculated from the relationship between NR and intake of digestible N (IDN), were temperature-dependent. At 22°, a constant Nf value of 0·255 g N/kg body-weight0·75 per d was found appropriate, while at 10° Nf increased with increase in protein content of the ration from 0·380 on the low protein ration to 0·533 and 0·753 g N/kg body-weight0·75 per d on the medium- and high-protein rations respectively.4. The efficiency of N utilization (kN) reflected the differences in the relationships between NR and IDN. At 22° the relationship was curvilinear so that kN decreased with increase in both the level of feed intake and the protein content of the ration. At 10° the relationship was linear, hence kN was independent of feed intake within rations. However, it decreased from 0·909 to 0·679 as the protein content of the ration was increased.5. The concentration of BU attained a maximal value some 3–5 h after the ingestion of the feed, with the values at 10° being higher than those at 22°. BU increased as the level of protein in the ration increased but decreased with the level of feed intake when dietary protein concentration was held constant. There was a significant correlation between BU and kN, indicating that BU is a useful criterion for assessing the efficiency of N utilization.

Failure to secrete immunoreactive insulin by rats fed a low protein diet.

Abstract: Rats fed a 6% protein diet for 14 weeks showed a normal glucose tolerance but failed to release immunoreactive insulin (IRI), following iv glucose. Furthermore the isolated perfused pancreas of the rats fed the 6% protein diet secreted eleven times less IRI than the isolated pancreas prepared from the rats reared on an 18% protein diet when both were subjected to the same glucose challenge. This difference occurred despite the fact that the total IRI content of the pancreas' was not significantly different between the two groups. In the protein-malnourished rats it is suggested that the normal glucose tolerance response, despite the failure to release a concommitant amount of IRI, may indicate increased sensitivity to IRI or may be due to the secretion in these animals of a biologically active insulin, which shows no immunological cross-reactivity with pancreatic insulin. Alternately there may be increased peripheral glucose utilisation in the low protein rats.

Growth and development of rats artificially reared on a high or a low plane of nutrition.

Abstract: In order to exclude the possibility of differences in maternal care which are known to result from typical methods of undernutrition during the suckling period, rat pups were reared artificially on different planes of nutrition away from their mothers. Artificial rearing was accomplished by fitting infant rats with a gastric cannula through which a milk substitute was infused intermittently. Rats were fed thus from 4 to 21 d on a high (ARHI) or a low (ARLO; 44% of ARHI level) plane of nutrition. Underfeeding of the ARLO group was continued till 25 d, after which all rats were given a good-quality pelleted diet qd lib. Compared with mother-reared (MR) litter-mates, ARHI rats showed advanced eye-opening and, at 21 and 25 d, they resisted restraint more strongly. Growth in body-weight of ARHI and MR rats was similar but, when autopsied at 32 weeks, the ARHI rats were shorter (nose-rump length) and had lighter gastrocnemius muscles, adrenals and brains, but heavier epididymal-fat pads. ARLO rats had deficits at 32 weeks compared with ARHI rats in whole body, kidney and epididymal-fat-pad weights, and in tibia length. In a second experiment, ARHI and MR rats were killed at 21 d. All the differences found at 32 weeks were already present at 21 d. In addition, the ARHI pups had enlarged livers and intestines but shorter tibias. The milk substitute, which is one commonly used in such studies, has a low protein and high carbohydrate content compared with rats' milk. This difference probably caused the abnormal organ growth of ARHI rats.

Pancreatic secretion after secretin and cholecystokinin stimulation in chronic alcoholics with and without cirrhosis

Abstract: We have studied the volume, protein concentration, total protein, and chymotrypsin and trypsin outputs in pure pancreatic juice (PPJ) following endoscopic cannulation of the pancreatic duct in 11 male and 2 female patients with advanced alcoholic cirrhosis (AC). Results were compared to those obtained from 21 nonalcoholic volunteers (NAV) and 26 chronic alcoholic (CA) patients without cirrhosis. Intravenous stimulation with secretin followed 10 min later by intravenous cholecystokinin-pancreozymin (CCK-PZ) resulted in highly significant increases in volumes during both phases of pancreatic stimulation in AC compared to NAV and CA. Protein concentration and total output during secretin stimulation was not different among the three groups. During CCK-PZ stimulation, CA exhibited a significant elevation in protein concentration and total output compared to NAV and AC. Although total chymotrypsin output was lower in secretin-stimulated CA than other groups, no other differences between the groups were observed in either of the hormone-stimulation phases. Marked elevations in trypsin output were observed in secretin-stimulated AC and in CCK-PZ-stimulated AC and CA. The high PPJ volume and the relatively low protein concentration observed in AC may effect a washout phenomenon resulting in a decreased tendency for ductal protein precipitation in these patients.

Excess energy intake promotes the development of hypoalbuminaemia in rats fed on low-protein diets.

Abstract: 1. A group of rats were given ad lib, a diet with a protein-energy: total energy (P:E) value of 0 . 03. Other animals received the same protein intake (g/kg body-weight per d) as this group, but had their energy consumption reduced to either 90, 80, 70, 60 or 50% of the ad lib. value. 2. The restricted growth rate of rats fed on the P:E--0 . 03 diet ad lib. has been shown to be due entirely to their insufficient protein consumption. In contrast, energy intake was far in excess of that required for maintenance and the limited amount of growth. 3. Carcass analysis demonstrated that some of the excess energy intake was stored as fat, but a greater part had been dissipated, presumably by diet-induced thermogenesis. 4. The plasma concentration of triiodothyronine (T3) was elevated in all animals consuming excess energy and was significantly related to both the total surplus and the amount of energy dissipated. 5. In the group of animals restricted to 50% of the ad lib. intake, energy rather than protein appeared to be the factor limiting growth. Energy intake was below estimated requirements for maintenance and was associated with values for plasma T3 that were lower than those found in well-fed control rats. 6. Although all the animals had similar protein intakes, plasma albumin concentration differed between the groups and was found to be inversely proportional to the energy intake. Thus it was lowest in animals receiving food ad lib. and rose to near normal values in the most-severely-restricted rats. 7. It is suggested that hypoalbuminaemia, and perhaps other features of protein deficiency, seen in animals fed on low-P:E diets may occur as an undesirable consequence of the metabolic response required to deal with excess energy consumption.

The effects of human milk and low-protein formulae on the rates of total body protein turnover and urinary 3-methyl-histidine excretion of preterm infants.

Abstract: 1. The effects of human milk and two low-protein formulae on the protein metabolism of 30 preterm appropriate for gestational age infants, birth weight 1.5-2.0 kg, were studied. The compositions of the two formulae were identical except for the protein source, with either casein or whey predominant. 2. The three diet groups all received similar nitrogen (390 mg of N day-1 kg-1) and energy intakes (500 kJ day-1 kg-1). 3. Growth rates for length and weight were comparable and approximated to intrauterine growth. Nitrogen absorption and net nitrogen utilization were enhanced in the human-milk-fed group. However, there were no differences in nitrogen retention, which averaged 274 mg day-1 kg-1 and approximated to intrauterine accretion rates. 4. Rates of whole-body nitrogen flux, protein synthesis and breakdown in the human-milk group were increased by 43-54% over the values seen in either of the two formula-fed groups (P less than 0.01). No differences were seen between the two formula groups. 5. No differences were seen in urine 3-methylhistidine excretion between the three study groups. 6. Our results suggest significant differences in the whole-body protein metabolism of formula-fed infants compared with human-milk-fed infants.

Thymosin treatment: Serum corticosterone and lymphocyte mitogenesis in moderately and severely protein-malnourished mice

Abstract: The present studies were performed to determine the levels of serum corticosterone (SC) and the proliferation of lymphocytes in response to phytohemag- glutinin (PHA) in mice that were injected with thymosin fraction V and fed low protein diets. We found that protein-malnourished mice had consistently higher SC values than the control animals. This result confirms the existence of nutritional stress, which stim ulates the adrenal glands increasing the release of corticosteroid hormones. No changes were observed in the SC level in controls whether or not thymosin was injected. However, in mice fed a protein-deficient diet, there was a significant decrease in SC levels after thymosin treatment, as compared to those of groups not treated with thymosin. Addi tionally, the thymosin effect on the SC levels was correlated with the cell-mediated immune changes. A significant increase in both PHA and lipopolysaccharide-induced lymphocyte transformation was observed in spleen cells from malnourished mice treated with thymosin fraction V. Thus, stress-induced glucocorticoid immunosuppression was demonstrated in malnourished mice. Our results suggest that components of thymosin fraction V may be involved in the mechanism of the restoration of lymphocyte trans formation that was suppressed by glucocorticoid in protein-malnourished mice. J. Nutr. 113: 483-493, 1983.

Low protein diets in uraemia.

Abstract: La deterioration de la fonction renale peut etre retardee considerablement au moyen d'un regime contenant 35 a 45 g de proteines et 19 a 23 mmol de phosphore par jour. Le mecanisme de cet effet n'est pas connu. Les malades peuvent eviter ainsi la malnutrition proteique (albuminemie, rapport uree/creatinine). L'application precoce du regime permet de retarder la necessite des dialyses

Low protein fish vs low protein animal diet enhances the propensity for stroke in stroke-prone/SHR.

Abstract: Weanling male and female, stroke-prone, spontaneously hypertensive rats (SHR/SP) were fed: 1) regular commercial rat chow, 2) low protein fish diet, 3) low protein fish diet + 1% saline, 4) low protein animal diet, and 5) low protein animal diet + 1% saline. The blood pressure of all of the SHR/SP rose rapidly reaching 240 mmHg at 90 days of age; blood pressure of low protein fish diet + 1% saline-fed SHR/SP rose most rapidly, reaching levels ranging from 258 to 300 mmHg. All of these animals developed acute strokes by 90 days of age; none of the other diet-fed SHR/SP manifested cerebral damage. The protein poor diets prevented normal growth, caused hypogonadism, and severely reduced pituitary and adrenal gland weights. The low protein diets were stressful causing significantly increased secretion of adrenocorticotrophic hormone and marked increases in triglyceride, free fatty acid, cholesterol, glucose, and B.U.N. levels. The mixed hemorrhagic-thrombogenic cerebral lesions occurred ipsilaterally in the parietal lobe, involved basal ganglia, and appeared in areas of brain tissue nourished by the middle cerebral artery. It is concluded that the inclusion of 1% saline drinking water with a low protein diet of fish tissue origin specifically, was synergistic in enhancing the propensity of SHR/SP rats to develop their genetically-programmed hypertension and stroke.

Effect of sodium bicarbonate on nitrogen utilization and feed intake by lambs

Abstract: Eight wether lambs, four equipped with rumen cannulae and four intact, were assigned to four high-concentrate diets according to a 4 × 4 double latin square with 27-day periods. The basal diet consisted of barley and corn silage, the latter representing 30% of the dry matter (DM), and was either unsupplemented (9% dietary protein) or supplemented (15% protein) with brewers' dried grains. To each of the low protein (LP) and high protein (HP) diets, sodium bicarbonate (NaHCO3) was either not added or added at the level of 4% of the diet DM. There was a marked, though not statistically significant, improvement in nitrogen retention due to NaHCO3 inclusion, particularly when protein intake was low. Voluntary feed intake increased by 11% as a result of NaHCO3 addition but the effect was nonsignificant. Bicarbonate-induced changes in feed intake were unrelated to changes in rumen pH. A maximum ruminal osmolality of 303 mOsm/kg elicited by NaHCO3 addition did not appear to restrict feed intake. Rumen ammonia con...

Protein and energy metabolism in two lines of chickens selected for growth on high or low protein diets.

Abstract: 1. Genetic adaptation was investigated in broilers selected for seven generations on a normal (A) or a low (B) protein diet. 2. Protein and energy metabolism were studied in males from these selected lines fed on a diet of intermediate protein content. 3. All selected birds retained more nitrogen than those studied 10 years previously. 4. There was no difference in nitrogen retention between groups, although relative growth rate of group B birds was higher. 5. Heat productions relative to gross energy intake were 0.38 (group B) and 045 (group A). Energy retentions relative to gross energy intake were 0.39 (group B) and 0.35 (group A); the difference being primarily due to higher fat retention in group B. 6. Using a common maintenance requirement for metabolisable energy, group B utilised metabolisable energy for growth (0.78) better than did group A (0.71). 7. At 53 d of age plasma glucose (10%) and insulin (50%) were higher in group B than in group A.