Showing papers in "Journal of Nutrition in 1988"
TL;DR: The doubly labeled water method is a form of indirect calorimetry that has been developed only recently and has a precision of 2-8% depending on the isotope dose and the length of the elimination period.
Abstract: The doubly labeled water method is a form of indirect calorimetry that has been developed only recently to the stage of application to human studies. The method measures integral CO2 production for up to 3 wk from the difference in elimination rates of deuterium and 18O from labeled body water. Validations against near-continuous respiratory gas exchange have demonstrated that the method is accurate and has a precision of 2-8% depending on the isotope dose and the length of the elimination period. Although the method has been validated, there is still some debate on refinements of the kinetic model that may lead to improved accuracy and precision. Because the method only requires periodic sampling of body fluids, it is non-restrictive and ideally suited to use in free-living subjects. Recent applications of the method have included obesity research, determination of energy requirements in both developing and developed countries and studies of human growth.
588 citations
TL;DR: A series of feeding experiments was conducted in aquaria to determine the quantitative requirements of the 10 essential amino acids for growth of young Nile tilapia (Oreochromis niloticus) and weight gains analyzed by the broken line regression method indicated the following requirements.
Abstract: A series of feeding experiments was conducted in aquaria to determine the quantitative requirements of the 10 essential amino acids for growth of young Nile tilapia (Oreochromis niloticus). The test diets contained casein and gelatin supplemented by crystalline L-amino acids to provide an amino acid profile similar to 28% whole egg protein except for the test amino acid. Each set of test diets consisted of seven isonitrogenous diets containing varying levels of the amino acid to be tested. Weight gains analyzed by the broken line regression method indicated the following requirements as a percentage of the dietary protein: lysine, 5.12; arginine, 4.20; histidine, 1.72; valine, 2.80; leucine, 3.39; isoleucine, 3.11; threonine, 3.75; tryptophan, 1.00; methionine with cystine (0.54% of the protein), 3.21; and phenylalanine with tyrosine (1.79% of the protein), 5.54.
468 citations
TL;DR: The fraction of fiber that is resistant to digestion and the rate of digestion and passage of potentially fermentable fiber were identified as constraints on fiber digestion in the rumen.
Abstract: Factors affecting fiber digestion in ruminants were evaluated with the use of simple mathematical models. These models were constructed to define the dynamic processes involved so that constraints on fiber digestion may be elucidated. The fraction of fiber that is resistant to digestion and the rate of digestion and passage of potentially fermentable fiber were identified as constraints on fiber digestion in the rumen. Fermentation lag was shown to have no direct effect on fiber digestibility. Fiber that is resistant to fermentation by rumen microbes represents a significant fraction of forage fiber and accumulates in the rumen relative to potentially fermentable fiber. The digestibility of fiber that is potentially fermentable is a function of the rate at which the fiber is digested and its retention time in the rumen. Selective retention of potentially fermentable fiber in the rumen is necessary for the maximization of fiber digestion.
294 citations
TL;DR: Immune responses result in a variety of metabolic adjustments that are mediated by cytokines of leukocytic origin, and nutrition influences the release of cytokines and consequently affects regulation of the immune response.
Abstract: Immune responses result in a variety of metabolic adjustments that are mediated by cytokines of leukocytic origin. Of the dozens of cytokines released during an immune response, interleukin-1 (IL-1), tumor necrosis factor alpha (TNF alpha) and interleukin-6 (IL-6) are the major mediators of intermediary metabolism. These three cytokines act in concert to decrease food intake, increase resting energy expenditure, gluconeogenesis, glucose oxidation, and hepatic synthesis of fatty acids and acute phase proteins, decrease fatty acid uptake by adipocytes and alter the distribution of zinc, iron and copper. Most of these activities result from direct interactions between the cytokine and the responding cells. IL-1, TNF alpha and IL-6 also affect changes in metabolism by changing levels of circulating insulin, glucagon and corticosterone. The nutritional impact of these metabolic changes is dependent upon age. In growing animals, increases in energy expenditure and oxidation of amino acids are balanced by lower needs associated with growth. In adult animals, energy and amino acid requirements are increased by an amount similar to the increased basal metabolic rate and amino acid oxidation. Nutrition also influences the release of cytokines and consequently affects regulation of the immune response. For example, protein deficiency results in decreased IL-1 release and impaired tissue responses to IL-1.
294 citations
TL;DR: Taurine is a ubiquitous dietary constituent of most mammals and is present in especially high concentrations in the tissues of developing mammals, and its role in the development of the nervous system and the process of migration in particular is indicated.
Abstract: Taurine is a ubiquitous dietary constituent of most mammals and is present in especially high concentrations in the tissues of developing mammals. Research to date indicates that taurine plays an important role in the development of the nervous system and the process of migration in particular. It is speculated that taurine uptake and release, in conjunction with glutamate uptake and release, may represent one form of communication between neurons and glial cells. The need of taurine by the body is emphasized by the ability of the kidney to curtail taurine excretion to conserve taurine in the face of a low dietary taurine intake. The evidence for a special role of taurine in development is considered and discussed.
230 citations
TL;DR: The peripheral plasma levels of cholecystokinin (CCK) increased significantly during BSA but not during SPI or RS infusions, Thus, CCK levels were not increased by the inhibition of the proteolytic activity by RS in duodenal juice.
Abstract: The objective of this study was to investigate the effects of high and low inhibitor soybean meals on the duodenal enzyme activities and on the possible regulatory role of gastrointestinal hormones in the pancreatic response. After an overnight fast, 11 healthy volunteers received an intraduodenal infusion of saline for 60 min. This was followed by infusion of either of three test meals: extract of raw soybeans (RS), a low inhibitor soy protein isolate (SPI) or bovine serum albumin (BSA), 10 g/h for 60 min. Then saline was again given intraduodenally for 30 min. Gastric juice was collected continuously and duodenal juice and peripheral blood samples were collected every 10 min. Duodenal chymotryptic activity was severely inhibited by RS, whereas SPI and BSA increased the chymotryptic activity. Tryptic activity showed a transient reduction (55%) during RS infusion, whereas BSA and in particular SPI increased the tryptic activity. No change was seen in amylase activity. The lack of total inhibition of tryptic activity has been studied further and is the subject of the accompanying paper. The peripheral plasma levels of cholecystokinin (CCK) increased significantly during BSA but not during SPI or RS infusions. Thus, CCK levels were not increased by the inhibition of the proteolytic activity by RS in duodenal juice.
189 citations
TL;DR: Overall, bST resulted in an exquisite coordination of metabolism to meet nutrient needs for increased synthesis of milk components and avoid a substantial negative net energy balance.
Abstract: Effects of bovine somatotropin (bST) on irreversible loss rate (ILR) and oxidation rate of glucose and nonesterified fatty acids (NEFA) were examined. Nine lactating cows received bST or excipient in a single reversal design using 14-d periods. Kinetic variables were estimated by compartmental analysis of blood metabolite and expired CO2 specific activity values obtained during infusion of [U-14C]glucose or [1-14C]palmitate. With bST treatment, milk energy yield increased by 31% but feed intake was unchanged. Blood glucose concentrations were not affected by treatment or correlated with any glucose kinetic variables. In the control period, glucose ILR was 12.1 mol/d with 66.5% utilized for milk lactose synthesis and 17.4% oxidized to CO2. Treatment with bST increased glucose ILR (+1.5 mol/d) and reduced glucose oxidation (-0.4 mol/d); this accommodated the additional glucose (+1.3 mol/d) required for the increase in lactose secretion. Increases in milk energy yield with bST treatment caused cows to be in a substantial negative net energy balance (-9.8 Mcal/d). No acute lipolytic response occurred with bST treatment, but plasma NEFA were chronically elevated (+104 mumol/L) and NEFA ILR increased (+2.3 mol/d). Increased NEFA turnover was primarily used for increased oxidation to CO2 (+0.5 mol/d) and 41% increase in milk fat (equal to approximately 1.3 mol fatty acids/d). For NEFA, plasma concentrations were correlated with ILR (r = +0.80), oxidation to CO2 (r = +0.74) and net energy balance (r = -0.78). Overall, bST resulted in an exquisite coordination of metabolism to meet nutrient needs for increased synthesis of milk components.
185 citations
TL;DR: The O2 consumption rate of rat heart mitochondria decreased as the fatty acid composition of the phospholipids changed, and the reduction of the activity of cytochrome c oxidase, which requires cardiolipin for its activity.
Abstract: Phospholipids of heart and liver of rats fed a diet containing sardine oil had more omega 3 polyunsaturated fatty acids and less omega 6 polyunsaturated fatty acids than those of rats fed corn oil, whereas there was little difference in the fatty acid composition of brain phospholipids. The mass of phospholipid classes in rat heart mitochondria was not changed, but their fatty acid compositions were altered. Modification of the fatty acid compositions of mitochondrial phosphatidylcholine and phosphatidylethanolamine reached a plateau after 10 d of feeding, but that of cardiolipin continued for 30 d. The O2 consumption rate of rat heart mitochondria decreased as the fatty acid composition of the phospholipids changed. This may be due to the reduction of the activity of cytochrome c oxidase, which requires cardiolipin for its activity. However, F1F0-ATPase, which also requires cardiolipin, was activated under the same conditions.
162 citations
TL;DR: An in vitro fecal incubation system was used to demonstrate how lactose, lactulose and monosaccharides influence short-chain fatty acid production in colon, and found that isobutyrate, valerate, isovalerate and hexanoate were produced in increased amounts in assays incubated with albumin, but in fact decreased in many incubations with saccharides.
Abstract: An invitrofecalincubationsystemwasused to demonstrate how lactose, lactulose and rnonosacchar- ides (mainly constituents of dietary fiber) influence short- chain fatty acid production in colon. Short-chain fatty acids were formed from all mono- and disaccharides tested (ex cept L-glucose): D-glucose, D-galactose, o-fructose, D- mannose, L-rhamnose, o-sorbitol, D-arabinose, o-xylose, D-ribose, D-galacturonate, o-glucuronate, lactose and lac tulose. All saccharides increased acetate formation; pro- pionate production was increased from rhamnose, arabi- nose, xylose, ribose, galacturonic and glucuronic acid, whereas the synthesis of butyrate was elevated in assays incubated with sorbito!, galacturonic and glucuronic acid, and to a lesser degree ribose. Isobutyrate, valerate, iso- valerateand hexanoatewere produced in increased amounts in assays incubated with albumin, but in fact decreased in many incubations with saccharides. It is speculated that saccharide fermentation always results in formation of ace tate, and that the relative production of acetate, propionate and butyrate is related to the monosaccharide composition of dietary fiber available for colonie bacteria. However, the production of isobutyrate, valerate, isovalerate and hex anoate is probably not due to saccharide fermentation, but is rather of polypeptide origin. J. Nutr. 118: 321-325, 1988.
158 citations
TL;DR: The results indicate that the chemical forms of dietary Se can have a marked influence on biological responses, including bioavailability of dietary selenium, as well as in tissues of rats fed SeM rather than selenite.
Abstract: Weanling rats were fed a basal diet or this diet plus 02, 10, 20 or 40 mg/kg selenium (Se) as either selenite or selenomethionine (SeM) Except at the 02 mg/kg Se level, Se accumulated in all tissues at higher levels when SeM was fed than when selenite was given, and the magnitude of difference became more pronounced with increasing levels of dietary Se This was particularly true for muscle and brain Se levels in whole blood, testes, kidney and lungs were not significantly different between rats fed 02 mg/kg Se as selenite or as SeM, but the Se levels in liver, muscle and brain were higher in rats fed SeM Although the tissue Se concentrations differed markedly, there were no differences in the glutathione peroxidase (GPX) activity in tissues of rats fed SeM rather than selenite The percentage of Se associated with GPX was lower in all tissues from rats fed SeM than in those from rats fed selenite These results indicate that the chemical forms of dietary Se can have a marked influence on biological responses, including bioavailability of dietary Se
154 citations
TL;DR: The gut proportions of modern humans, in combination with evidence from the fossil record, indicate that during its evolution the human lineage was able to overcome nutritional constraints imposed on body size increases in the great apes.
Abstract: To investigate the digestive kinetics and fiber digestion of great apes, we conducted digestion trials on chimpanzees (Pan troglodytes) with diets of two fiber levels, one containing 34% neutral detergent fiber (NDF) and the other 14% NDF. Chimpanzees exhibited a response to fiber similar to that of humans. First, increases in the fiber concentration of the diet decreased mean transit time (MTT), hindgut turnover time (T) and the digestibility of fiber. Second, differences in MTT and T between the treatments and animals explained most of the variability in the digestibility of fiber components. Third, consistent with human data, the fiber marker passed more slowly than the liquid marker only when the high fiber diet was consumed. Fourth, individual variability, as in humans, was a significant factor affecting digestion and passage. Fifth, the MTT of chimpanzees was longer than that of humans. This result may be due to the apes' larger hindgut. In comparison with other hominoids, humans have smaller volumes in the gastrointestinal tract and hindgut. The gut proportions of modern humans, in combination with evidence from the fossil record, indicate that during its evolution the human lineage was able to overcome nutritional constraints imposed on body size increases in the great apes. We suggest that this advance was achieved through technological and social innovations that permitted early humans to achieve larger body size without lowering dietary quality.
TL;DR: Mucosalphytase and alakaline phosphatase, if present in the human small intestine, do not seem to play a significant role in phytate digestion in humans, whereas the dietary phytase may be an important factor for phytates hydrolysis.
Abstract: The purpose of this study was to investigate whether dietary phytase is involved in the hydrolysis of phytate in the stomach and small intestine of humans. The digestibility of phytase-deactivated wheat bran was studied on eight occasions and untreated wheat bran on two occasions in healthy ileostomates. Five subjects were studied for two 4-d periods and one subject on two occasions for two 4-d periods while fed a constant low fiber diet. The low fiber diet was supplemented with 16 g/d wheat bran in the second period. Three other subjects fed a low fiber diet were studied for 10 consecutive days, bran being added to the diet on d 5, 6 and 7. Inositol hexaphosphate and its degradation products were analyzed with a recently developed HPLC method. On average, 95% of the ingested phytate from phytase-deactivated wheat bran and 40% of the ingested phytate from untreated wheat bran were recovered in ileostomy contents. These results differ from those of a previous analysis using an iron precipitation method. Mucosal phytase and alakaline phosphatase, if present in the human small intestine, do not seem to play a significant role in phytate digestion in humans, whereas the dietary phytase may be an important factor for phytate hydrolysis. Iron precipitation methods are not adequate for determinations of phytate digestion.
TL;DR: Cortisol showed no meal-related responses to any of the diets within its expected circadian rhythm, and glucose levels did exhibit a circadian rhythm.
Abstract: Two experiments were conducted to determine the response of blood glucose, insulin and cortisol levels to four common equine diets. Experiment 1 was designed to determine the diurnal variation of glucose and two glucoregulatory hormones, insulin and cortisol, in four fasting geldings. No diurnal variation was observed in either glucose or insulin levels during the 24-h sampling period. However, cortisol levels did exhibit a circadian rhythm, with elevated values observed in the morning and low values in the evening. Experiment 2 investigated the response of glucose, insulin, cortisol and selected amino acids to four isoenergetic equine diets. Four 2-yr-old quarter horse geldings were used in a Latin square design. Pelleted isoenergetic diets were composed as follows on a digestible energy basis: 100% alfalfa (diet A), 50% alfalfa and 50% corn (diet AC), 100% corn (diet C) and 90% corn and 10% corn oil (diet CO). A single meal was fed after an overnight fast. Blood samples were taken via a jugular catheter from 0800 to 1700 h. Analysis of variance by repeated measures and mean response area for glucose showed no difference between diets. However, postprandial peak glucose levels were elevated (P less than 0.01) over prefeeding levels in diets AC and C. Analysis of variance by repeated measures and mean response area for insulin showed differences (P less than 0.05) between diets. Cortisol showed no meal-related responses to any of the diets within its expected circadian rhythm.
TL;DR: The most effective protocol to produce experimental FD in rats is to feed a folate-free diet that otherwise supports maximum growth in young animals, and additional modifications such as use of methotrexate or amino acid-imbalanced or protein-deficient diets are unnecessary.
Abstract: Development of folate deficiency (FD) was evaluated in weanling rats fed diets containing mixtures of free amino acids or of vitamin-free casein and gelatin as sources of dietary nitrogen. FD could be produced in 21 d with amino acid diets that promoted maximum growth rate, were completely devoid of folate and contained 1% succinylsulfathiazole. Growth retardation and blood dyscrasia associated with FD could not be demonstrated in rats fed diets containing casein and gelatin as nitrogen sources because the vitamin-free casein contained low but measurable levels of folate. The most effective protocol to produce experimental FD in rats is to feed a folate-free diet that otherwise supports maximum growth in young animals. Additional modifications such as use of methotrexate or amino acid-imbalanced or protein-deficient diets are unnecessary.
TL;DR: There is a strong negative correlation between alcohol consumption and CHD, as might be expected from the effect of alcohol on high density lipoprotein levels, but neither of the simple correlations account for CHD in many countries.
Abstract: It is well known that there is a significant positive correlation between consumption of saturated fat and cholesterol and international mortality from coronary heart disease (CHD). It is less well appreciated that there is a strong negative correlation between alcohol consumption and CHD, as might be expected from the effect of alcohol on high density lipoprotein levels. Neither of the simple correlations, however, account for CHD in many countries. We examined dietary and alcohol consumption data from 18 countries. The simple correlations with CHD are as follows: saturated fat, r = 0.71; polyunsaturated fat, r = -0.34; total alcohol consumption, r = -0.58. A multiple-regression equation incorporating the dietary and alcohol data, however, yields an r of 0.92.
TL;DR: Changes in the enzymatic and nonenzymatic components of the primary free radical defense system could be attributed to the reduction in feed intake by Zn- or Cu-deficient rats and not to a direct effect of the Zn or Cu deficiency per se.
Abstract: The effect of dietary Zn or Cu deficiency on the primary free radical defense system was examined in the lungs and livers of 6-wk-old rats. Enzymatic compo nents (Superoxide dismutase, catalase and glutathione peroxidase) and nonenzymatic components (a-tocoph- erol, ascorbate, glutathione and metallothionein) of the pri mary free radical defense system, as well as tissue con centrations of Cu, Zn and Fe, were measured. LiverCuZn- superoxide dismutase and liver catalase activities were sig nificantly lower (P < 0.05), and lung metallothionein and liver ascorbate concentrations were significantly higher (P < 0.05) in Cu-deficient rats than in either pair-fed or ad libitum-fed controls. Zn-deficient rats had a significantly lower (P < 0.05) concentration of livermetallothionein than either control group. Other changes in the enzymatic and nonenzymatic components of the primary free radical de fense system could be attributed to the reduction in feed intake by Zn- or Cu-deficient rats and not to a direct effect of the Zn or Cu deficiency per se. The primary free radical defense system in lung and liver of severely Zn- or Cu- deficient rats was not seriously compromised. J. Nutr. 118:613-621,1988.
TL;DR: Determination of fatty acid composition is not a sensitive indicator of diet integrity and Supplementation of fish oil diets with vitamin E to help protect against in vivo peroxidation is discussed.
Abstract: Feeding of purified diets containing fish oil without added antioxidant leads to rapid autoxidation of the oil and the possibility of artifactual results due to the feeding of autoxidation products. Purified diets containing menhaden oil without any added antioxidant deteriorate quickly. Peroxide value of the diet is elevated 5- to 6-fold within 24 h and 12-fold within 48 h when exposed to air at room temperature. Addition of 0.02% t-butylhydroquinone to the fish oil prevents this deterioration for at least 72 h. Determination of fatty acid composition is not a sensitive indicator of diet integrity. Supplementation of fish oil diets with vitamin E to help protect against in vivo peroxidation is discussed.
TL;DR: It is suggested that ingestion of fish oil leads to increased formation of lipoxygenase-derived products of longer-chain n-3 fatty acids, which are abundant in fish oil, and appear to be more effective than 18:3n-3 in suppressing 20:4n-6 levels and the capacity of the tissues to synthesize cyclooxygenasing products.
Abstract: Rats were fed graded amounts of purified 18:3n-3 or fish oil concentrate in the presence of a constant amount of 18:2n-6 to evaluate the ability of 18:3n-3 compared with longer-chain n-3 fatty acids to inhibit 20:4n-6 metabolism in platelets and lungs. Dietary 18:3n-3 at a ratio of 0.28 (n-3 to n-6 fatty acids) suppressed levels of 20:4n-6 in lung and plasma phospholipids and the capacity of the tissues to synthesize cyclooxygenase-derived products in a dose-dependent fashion. At similar ratios of n-3 to n-6 dietary fatty acids, longer-chain n-3 fatty acids, which are abundant in fish oil, appear to be more effective than 18:3n-3 in suppressing 20:4n-6 levels and the capacity of the tissues to synthesize cyclooxygenase-derived products. Much greater amounts of 12-hydroxyeicosapentaenoic acid (12-HEPE) and 5-HEPE than of 12-hydroxyeicosatetraenoic acid (12-HETE) and 5-HETE appeared to be formed in tissues of the group receiving the highest amount of fish oil. These results suggest that ingestion of fish oil leads to increased formation of lipoxygenase-derived products of longer-chain n-3 fatty acids.
TL;DR: Rat liver, kidney, intestine and brain did not respond appreciably to the dietary levels of copper and zinc that were fed, and Chromatography showed that Copper and zinc content of renal metallothionein was directly related to the Dietary levels fed.
Abstract: Regulation of metallothionein gene expression by dietary zinc and copper was examined in rat liver, kidney, intestine and brain using a 3 X 3 factorial design. Purified diets containing 5, 30 and 180 mg Zn/kg and 1, 6 and 36 mg Cu/kg were fed for 2 wk. Serum concentrations of copper and zinc were lower at the lowest intakes of either metal than at normal or supplemental levels. Kidney metallothionein levels were proportional to dietary zinc, being 50% less in the 5 mg Zn/kg group than in those fed the highest zinc intake. Metallothionein mRNA was measured by dot blot hybridization to a 32P-labeled oligonucleotide DNA probe representing the terminal 5' sequence of the metallothionein gene. In kidney the number of metallothionein mRNA molecules per cell increased four- to five-fold (from 4 to 29 molecules per cell) with increasing dietary zinc. A less pronounced effect on metallothionein mRNA was observed in response to dietary copper. At the lowest copper intake level and highest intake of zinc intestinal metallothionein mRNA was sevenfold greater than in any other group. Liver and brain did not respond appreciably to the dietary levels of copper and zinc that were fed. Chromatography showed that copper and zinc content of renal metallothionein was directly related to the dietary levels fed. In kidney, both metallothionein-1 and -2 genes were expressed.
TL;DR: Observations indicate that the diminished expression of immunologic stress in amino acid-deficient chicks is due to an impaired immune response.
Abstract: Experiments were conducted to determine the influence of immunologic stress on methionine and lysine requirements of growing chicks. Immunologic stress was elicited by injection of either Escherichia coli lipopolysaccharide or heat-killed Staphylococcus aureus every other day for 6 d. In the first experiment, diets were formulated to provide methionine levels of 0.30, 0.50 and 0.70%. In the second experiment, diets contained 0.75, 0.90 or 1.2% lysine. In chicks fed amino acid-sufficient diets, those chicks injected with immunogens had slower growth, lower feed intake and poorer efficiency of feed utilization than those injected with saline. The decreases due to immunogens were diminished in chicks fed amino acid-deficient diets. The methionine requirements of saline- and immunogen-injected chicks were above 0.5% and between 0.3 and 0.5%, respectively; the lysine requirements were greater than 0.95% and between 0.7 and 0.95%, respectively. Thus immunogen injection decreased methionine and lysine requirements, probably because of a decreased need of amino acids for growth and tissue accretion. Immunogen-induced depression in serum zinc and increase in serum copper levels were ameliorated by lysine or methionine deficiencies. Compared with saline-injected chicks, immunogen-injected chicks had significantly higher serum interleukin-1 (IL-1) activity by 53% when fed the methionine-sufficient diet, but they did not have significantly greater IL-1 levels when fed the methionine-deficient diet. These observations indicate that the diminished expression of immunologic stress in amino acid-deficient chicks is due to an impaired immune response.
TL;DR: It is concluded that, as the margin between optimal stimulatory concentration and toxic excess is narrow, rumen fermentation should be manipulated cautiously when using minerals.
Abstract: The supply of minerals needed to meet rumen microbe requirements should match the amount of energy available for fermentation. Therefore, we attempt to assess microbial requirements for phosphorus (P), sulfur (S) and magnesium (Mg) in terms of fermentable organic matter at the rumen level (OMF) or in terms of digestible matter in the total tract (OMD). In vivo, about 5 g of P and 1.8 g of S/kg OMD should be available (a) in the rumen. Pa is provided mostly by salivary secretion, which depends on several dietary factors as well as on the physiological state of the animal; dietary S supply with natural diets depends on dietary S availability, which can be particularly low for some roughages. Dietary Mg concentration should be in the range 1.5-2.5 g/kg OMD. The circumstances in which major minerals may be used to manipulate rumen fermentation are discussed. With a high concentrate diet the addition of a mineral buffer may help to maintain an adequate pH for cellulolysis and enhance the efficiency and quantity of the microbes produced. Some inconsistent results are obtained, possibly because of the sensitivity of rumen microbes to high osmolality. It is concluded that, as the margin between optimal stimulatory concentration and toxic excess is narrow, rumen fermentation should be manipulated cautiously when using minerals.
TL;DR: Feeding fish oil appears to prevent both the inhibition of 20:4 omega 6 biosynthesis and the accumulation of cholesterol ester that were apparent when 2% cholesterol was added to either beef tallow or linseed oil diets.
Abstract: Male weanling rats were fed for 28 d a purified diet containing 20% (wt/wt) fat providing high levels of either saturated fat or alpha-linolenic acid or eicosapentaenoic and docosahexaenoic acids with or without 2% (wt/wt) cholesterol supplementation. Effect of diet on rate of desaturation of eicosatrienoic acid (20:3 omega 6) and lipid composition of liver microsomal membranes was examined. The desaturation of 20:3 omega 6 to arachidonic acid (20:4 omega 6) was higher in rats fed linseed oil and lower in rats fed fish oil than in control animals fed the beef tallow diet. The desaturation of 20:3 omega 6 was lower in rats fed beef tallow or linseed oil diets supplemented with cholesterol than in the respective unsupplemented diet. Inclusion of 2% (wt/wt) cholesterol in the fish oil diet failed to affect synthesis of 20:4 omega 6 from 20:3 omega 6. These in vitro changes in delta 5-desaturase activity are consistent with the diet-induced alterations observed in the fatty acid composition of microsomal membranes. Both free cholesterol and cholesterol ester in the microsomal membrane were higher in rats fed beef tallow or linseed oil diets supplemented with exogenous cholesterol than in the respective unsupplemented diet, and only free cholesterol was higher in rats fed the fish oil diet supplemented with cholesterol. Feeding fish oil appears to prevent both the inhibition of 20:4 omega 6 biosynthesis and the accumulation of cholesterol ester that were apparent when 2% cholesterol was added to either beef tallow or linseed oil diets.
TL;DR: In vivo studies of the small intestine in rats showed that the rate of disappearance of fructans was lower than that of mannose, which is known to be absorbed through passive diffusion.
Abstract: The bioavailability of cereal fructans (fructooligosaccharides) was investigated both in vitro and in vivo In vitro studies indicated very slow hydrolysis by human gastric juice and by homogenate of the intestinal mucosa (rat) After intubation of fructans into the stomachs of rats, the recovery of fructans in the small intestine and colon was approximately the same as that of an unabsorbed marker (polyethylene glycol), indicating no or very low disappearance of fructans in the small intestine In vivo studies of the small intestine in rats showed that the rate of disappearance of fructans was lower than that of mannose, which is known to be absorbed through passive diffusion In addition the cariogenic effect of cereal fructans was compared to that of glucose Acid formation from low molecular-weight fructans was found in human dental plaque in vitro A mouth rinse with unfractionated fructans, containing some quantities of sucrose, fructose and glucose, resulted in relatively low pH values in human plaque in vivo, even if the decrease in pH was somewhat less pronounced when compared with a mouth rinse with glucose
TL;DR: A critical literature review summarizes and discusses information concerning the role of carnitine in the oxidation of long-chain fatty acids and other areas of in vivo metabolism as discussed by the authors, as well as its transport and homeostasis.
Abstract: A critical literature review summarizes and discusses information concerning the role of carnitine in the oxidation of long-chain fatty acids and other areas of in vivo metabolism. Dietary and endogenous sources of carnitine are described, as well as its transport and homeostasis. Attention also is given to: potential causes of cellular carnitine deficiency and the consequences of impaired carnitine function; primary congenital carnitine metabolic disorders; the potential carnitine insufficiency of vegetarians; and human studies of the characteristics of a variety of non-congenital carnitine-deficient clinical states.(wz)
TL;DR: The results indicate that the dietary methionine level can modulate the availability of Se from dietary [ Se]Met and from stored tissue [Se]Met; the inability of stored Se to provide Se for GSH-Px synthesis over a prolonged period of time suggests that [Se?]Met may not be an optimum form for Se supplementation.
Abstract: To study the effect of dietary methionine on the bioavailability of Se from selenomethionine ([Se]Met), weanling rats were first loaded with Se by feeding 05 mg Se as [Se]Met per kg diet of a low methionine (017% by analysis) torula yeast-based diet for 21 d, and then were fed an Se-deficient diet (less than 002 mg Se/kg) supplemented with 0, 04 or 09% methionine for 28 d Plasma, liver and muscle Se increased 26-, 25- and 22-fold, respectively, during [Se]Met supplementation, and then the tissue Se declined exponentially during the Se-deficient diet period Plasma, liver and muscle glutathione peroxidase (GSH-Px) activities decreased 43-50% during the [Se]Met supplementation period in spite of the increase in tissue Se When these [Se]Met-loaded rats were fed the Se-deficient diet and supplemented with methionine, tissue GSH-Px activities increased significantly within 3 to 7 d, but then decreased for the remainder of the experiment Calculation of the percentage of tissue Se present as Se in GSH-Px indicated that substantial Se from dietary [Se]Met was stored in tissues in a form different from GSH-Px when a low methionine diet was fed These results indicate that the dietary methionine level can modulate the availability of Se from dietary [Se]Met and from stored tissue [Se]Met; the inability of stored [Se]Met to provide Se for GSH-Px synthesis over a prolonged period of time suggests that [Se]Met may not be an optimum form for Se supplementation
TL;DR: Vit.
Abstract: Natural killer cell (NK) activity decreases and prostaglandin E2 (PGE2) level increases in aged mice. Because PGE2 is involved in control of NK activity this study was conducted to investigate whether or not decreasing PGE2 level by changing the type of dietary fat or increasing the level of vitamin E (vit. E) modulates NK activity of young and old mice. Mice were fed either a corn oil (CO) or a fish oil (FO) diet supplemented with 30 or 500 mg/kg diet of vit. E for 6 wk. To study the effect of vit. E during active immune response and oxidative stress, groups of old mice fed CO and either 30 or 500 mg/kg diet of vit. E were injected with sheep red blood cells (SRBC) prior to assessment of their NK activity. As reported by others regarding mice fed a nonpurified diet, the old mice in all dietary groups had significantly less NK activity and tended to synthesize more PGE2 than young mice. FO-fed mice synthesized less PGE2 than CO-fed mice; however, their NK activity was not higher than that of CO-fed mice. By contrast young mice fed FO had a moderately lower NK activity than those fed CO. Vit. E supplementation did not change NK activity in nonimmunized mice but was effective in preventing SRBC-induced decrease in NK activity of old mice.
TL;DR: In individual rats the degree of nephrocalcinosis and the concentrations of minerals in kidney were positively correlated.
Abstract: The effects of dietary calcium (Ca) concentration and calcium: phosphorus (Ca:P) ratio on mineral balance and nephrocalcinosis were studied in female rats. In the first experiment there were two dietary Ca concentrations (0.25 and 0.50%, wt/wt) at two different Ca:P ratios (0.6 and 1.3). In the second experiment the diets were formulated to contain 0.40% P and either 0.13, 0.25, 0.50 or 0.75% Ca. The diets contained 0.03% magnesium (Mg). The fecal outputs of Ca, P and Mg were lower (P less than 0.01) after feeding low Ca diets than after feeding high Ca diets. Urinary excretion of P decreased with increasing dietary Ca and increased with increasing P intake. In rats fed the 0.25% Ca diets whole-body retentions of Ca and P were lower than in the rats fed 0.50% Ca. Both increases in dietary Ca from 0.13 to 0.50% and P from 0.20 to 0.40% elevated Ca and P content of kidneys as well as the degree of nephrocalcinosis. However, after feeding the highest Ca concentration (0.75%) nephrocalcinosis was essentially absent while kidney concentrations of Ca and P were relatively low. When compared with 0.50% Ca in the diet, 0.75% Ca increased group mean whole-body retention of Ca but lowered that of P. In individual rats the degree of nephrocalcinosis and the concentrations of minerals in kidney were positively correlated.
TL;DR: Overall, the results demonstrated that bST treatment increased yield of milk and milk components even when cows were in negative nitrogen and energy balance, and heat loss did not differ from predicted heat loss.
Abstract: Effects of exogenous bovine somatotropin (bST) on energy and nitrogen utilization by high producing dairy cows were examined. Nine cows received bST (51.5 IU/d) or exipient (control) in a single reversal design involving 14-d treatment periods. Energy and nitrogen balances were measured in open-circuit respiration chambers. Yield of 4% solids-corrected milk was increased by 22% with bST treatment. Dry matter intake and the apparent digestibilities of dry matter, energy and nitrogen were not altered by treatment. The only significant component of nitrogen utilization that was altered by bST treatment was an increase in milk nitrogen secretion. Cows were in negative tissue nitrogen balance during the control period (-21 g/d) and tended to become more negative during the bST treatment period (-34 g/d). Heat energy loss and milk energy secretion were increased with bST treatment. Tissue energy balance was -1.1 Mcal/d during the control treatment period and the use of energy reserves with bST treatment decreased tissue energy balance to -9.8 Mcal/d. Changes in heat production with bST treatment were equal to those predicted from the changes in milk and body tissue. Overall, the results demonstrated that bST treatment increased yield of milk and milk components even when cows were in negative nitrogen and energy balance. Effects of bST were predominantly associated with nutrient partitioning, and observed heat loss (associated with maintenance and partial efficiencies of milk synthesis and tissue utilization) did not differ from predicted heat loss.
TL;DR: A particular strategy of moving acid-resistant cellulose genes into noncellulytic, but acid- resistant, rumen bacteria is described.
Abstract: Rumen microbiologists are beginning to use genetic engineering techniques, and researchers should carefully consider both the potentials and limitations of using this technology to manipulate the rumen microbial ecosystem. Despite encouraging rhetoric, it is difficult to identify specific examples where genetic engineering would enhance ruminal performance. Many practical problems (lactic acidosis, deamination, etc.) might be better served by genetic engineering approaches that delete rather than add genes. The difficulty with this approach is that a highly selective means of preventing wild types from recolonizing the rumen would be needed. The addition of specific genes is confounded by 1) the fact that the rumen microorganisms are already adapted to the rumen, 2) the diversity of species inhabiting the rumen and 3) the complexity of interactions among these species. Aspects such as increased rates of cellulose digestion and changes in amino acid composition of the microflora are particularly sensitive to these biological constraints. Genetic engineering has, however, the potential to alleviate new limitations that humans have imposed on the rumen (detoxification, resistance to low pH, the digestion of novel feed materials, etc). A particular strategy of moving acid-resistant cellulose genes into noncellulytic, but acid-resistant, rumen bacteria is described.
TL;DR: Within a tissue, regardless of the subcellular distribution of aminotransferase activity, the relative rates of transamination with subsaturating or "saturating" concentrations of KIV or isoleucine were similar, and amino acid preference was also similar within a tissues, but not necessarily between or among different tissues.
Abstract: The activity of branched-chain aminotransferase in mitochondria isolated from rat tissues was examined, and the mitochondrial contribution to total tissue branched-chain aminotransferase activity was calculated using the mitochondrial marker enzyme citrate synthase. Mitochondrial aminotransferase activity was highest in heart followed by skeletal muscle, kidney and brain. In heart muscle all of the aminotransferase activity was accounted for by the mitochondrial fraction. Activity was found to be mitochondrial in skeletal muscle with high red fiber content and also in kidney cortex. Activity was predominantly cytosolic in brain and muscles with high white fiber composition. Thus, the distribution of branched-chain aminotransferase activity in skeletal muscle was dependent on fiber type. No branched-chain aminotransferase activity was detected in liver mitochondria, and in liver tissue activity was too low to be relevant at physiological concentrations of branched-chain amino acids. Within a tissue, regardless of the subcellular distribution of aminotransferase activity, the relative rates of transamination with subsaturating or "saturating" concentrations of KIV or isoleucine were similar. Finally, amino acid preference was also similar within a tissue, but not necessarily between or among different tissues.