SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Explore the source record for details and available documents.
Experiments were conducted with chronically catheterized growing lambs to study the effect of variations in rumen volatile fatty acid (VFA) supply on blood plasma free amino acids (FAA) and insulin. Five male lambs were fed, then fasted for 72 h and refed. In the second experiment 48 mmol of a VFA mixture per kg body weight was infused into the rumen vein of another 5 lambs. Rumen VFA, plasma FAA and immunoreactive insulin (IRI) concentrations were determined over the 72 h postfeeding period and during 24 h after refeeding as well as over 24 h after the VFA infusion. Both postprandial increase of rumen VFA and VFA infusion caused a significant increase of plasma FAA concentrations and an increase in IRI. Feed intake decreased the prefeeding total FAA (TFAA) concentration (2.7 mmol/l) to 1.8 mmol/l at 4 h after feeding. It rose again to 2.5 mmol/l at 24 to 72 h postfeeding. IRI seemed to have the highest concentrations when the TFAA were the lowest. VFA infusion also decreased the plasma TFAA, to about half of the preinfusional value. IRI, however, showed a five-fold increase after infusion. The results of these experiments show that variations in VFA absorption from the rumen due to different nutritional stages result in changes of the plasma FAA concentrations. Insulin seems to have an important role in the control of these changes.
Ruminant liver has a quantitatively unique array of substrates presented to it because of the extensive fermentation of dietary carbohydrate to organic acids in the gastrointestinal tract. The single largest input of dietary energy to the extrasplanchnic tissues is acetic acid derived from fermentation, which is largely unused by hepatic parenchyma. The other volatile fatty acids derived from fermentation, primarily propionate, are cleared extensively, but not completely, by the liver. This results in a marked concentration gradient for these acids across the liver lobule. L-lactate, derived from tissue metabolism, as well as variable amounts from rumen fermentation, is used by the liver at a rate lower than for propionate and below the predicted capacity based on in vitro enzymatic and intact cell capacity data. The net result of this selective utilization by the liver results in peripheral blood containing significant concentrations of L-lactate and acetate, but little of the other organic acids. Propionate carbon metabolized by liver cells is converted to glucose with little true loss of carbon, but the same is not true of lactate carbon. The energetic efficiencies by which propionate and lactate carbon are converted to glucose may be much less than optimal because of extensive cycling through pyruvate kinase, pyruvate carboxylase and phosphoenolpyruvate carboxykinase. Inhibition of this futile cycling may represent one avenue by which energetic costs of maintenance and production can be lowered in ruminants.
The present investigation was carried out in order to obtain better information about the growth requirements of small-sized spirochetes containing one endoflagellum from each cell end. Nine strains of such spirochetes were isolated from subgingival plaque in patients suffering from advanced marginal periodontitis. The strains were maintained in fluid NOS medium with 0.07% Noble Agar. The following environmental factors were studied: Oxygen in the incubation atmosphere and the pH value of the medium. The following nutrient factors were studied: Rabbit serum, heart infusion and trypticase, bovine albumin, human globulin, long-chain fatty acids, volatile fatty acids, steroids, amino acids, carbohydrates, and Na-bicarbonate. Growth was normally determined after 3 days' incubation at 35 degrees C by counting numbers of spirochete cells in a Petroff-Hausser counting chamber. All strains tolerated 3% oxygen in the atmosphere and the pH-optimum was 7.5. Rabbit serum was found not to be an essential nutrient factor. Human globulin stimulated growth, while bovine albumin inhibited growth. Heart infusion and trypticase influenced growth moderately. Of the remaining nutrient factors the long-chain fatty acids inhibited growth and the volatile fatty acids did not affect growth, while certain carbohydrates, especially glucose, stimulated growth. Na-bicarbonate in low concentrations stimulated growth, while higher concentrations inhibited growth.
Rumen inoculum was cultured in specially designed fermenters that allowed simultaneous measurement of pH, oxidation-reduction potentials, and gas production. The cultures were maintained at pH 6.8 by addition of 1 M NaHCO3 and continuous infusion of artificial saliva. Gas flow was maintained at 20.0 ml/min with a stream of O2-free N2. Monensin at 7.0 micrograms/ml inhibited CH4 production 49% below control concentrations. The sodium salt of 2-bromoethanesulfonic acid added at an initial concentration of 5 x 10(-5) M inhibited CH4 production by 86% and increased H2 production from less than .5 mumol/min in the control to 24.5 mumol/min in the inhibited fermenter. The redox potentials in the control fermenter remained above -.20 V and did not change with the addition of monensin. Bromoethanesulfonic acid rapidly decreased the redox potential in the fermenter to -.33 V. Volatile fatty acid production was not significantly altered by the addition of 2-bromoethanesulfonic acid. The addition of monensin gave the expected decrease in acetate:propionate ratios, decreased acetate and butyrate production, and increased valerate (but not propionate) production.
The ileal digestibilities of maize starch and native pea starch do not differ. However maize starch is digested faster than pea starch and the ileal amino acid digestibility of a diet containing pea starch is lower. In the present study, the net portal fluxes of glucose, lactate, volatile fatty acids (VFA) and amino acids were measured for diets including 650 g maize starch or pea starch/kg. The diets were fed at a level 870 kJ digestible energy/kg0.75 twice daily (06.00 and 18.00 hours) to four female pigs in a crossover design. Portal vein blood flow did not differ between maize and pea starches (1620 and 1484 ml/min respectively; SED 100; P = 0.23). For maize starch portal glucose flux was significantly higher during the first 6 h after feeding, was not different 8 h after feeding and was significantly lower thereafter. Net portal glucose flux was higher for maize starch than for pea starch (1759 and 1265 mmol/12 h respectively; SED 182; P = 0.054). Net portal lactate flux was not significantly different between maize and pea starches (36.5 and 67.2 mmol/12 h respectively; SED 24.1; P = 0.27) and net portal VFA flux was lower for maize starch than for pea starch (169 and 218 mmol/12 h respectively; SED 18; P = 0.054). Net portal fluxes of valine, isoleucine, phenylalanine, tryptophan, arginine, serine, cystine, tyrosine, lysine, histidine and the sum of essential amino acids tended to be or were higher (P < 0.1 or P < 0.05) and net portal flux of aspartic acid tended to be lower for pea starch (P < 0.1). It can be concluded that, although ileal digestibility of both starches is equal, the rate of appearance of glucose in the portal vein was higher for maize starch, influencing the net portal flux of amino acids.
The in vitro inhibition of Clostridium difficile by volatile fatty acids was correlated with the pH and concentrations of volatile fatty acids in the ceca of hamsters of different ages. The concentrations of cecal volatile fatty acids increased with the age of the animals. Maximum concentrations of individual volatile fatty acids were attained when the animals were ca. 19 days old, with acetic, propionic, and butyric acids occurring in the highest concentrations (72, 16, and 32 microequivalents/g of cecum, respectively). The cecal pH was approximately the same in hamsters of all ages (pH 6.6 to 7.0). Only butyric acid reached a concentration in the ceca of hamsters which was inhibitory to the in vitro multiplication of C. difficile. This inhibitory concentration was attained when the animals were ca. 19 days of age. When mixtures of volatile fatty acids were prepared at concentrations equal to those present in the ceca of hamsters, there was a direct correlation between the in vitro inhibitory activity of the volatile fatty acids and the susceptibility of hamsters 4 days of age or older to C. difficile intestinal colonization. The resistance of hamsters less than 4 days of age to C. difficile intestinal colonization appears to be due to factors other than volatile fatty acids.
Four fistulated Holstein cows were arranged in a 4 x 4 Latin square design to study the effects of level and type of energy source on milk yield and composition. Treatments consisted of a basal diet fed alone (low energy treatment) or with 3.3 Mcal of net energy for lactation from extra nutrients perfused either into the rumen (either propionic acid or a mixture of volatile fatty acids) or into the duodenum (glucose). Increasing the energy input without changing the volatile fatty acid profile improved milk yield and slightly increased milk protein and fat yields. Compared with the isoenergetic mixture of volatile fatty acids, both propionic acid and glucose infusions significantly decreased fat content (-4.5 g/kg) and yields (respectively, -111 and -160 g/d), but affected fatty acid proportion and yield differently (more elongation process and less C18 with glucose infusion). Protein yield was slightly increased by propionic acid infusion but not by glucose because of the counterbalanced effects on milk yield (-1.3 kg/d) and protein content (1.5 g/kg). The coagulating properties of milk were directly linked to variations in protein, casein and mineral contents. In conclusion, propionic acid or glucose scarcely affected milk protein content, but induced a similar decrease in milk fat content probably through different metabolic pathways.
Volatile fatty acids (VFAs) represent the major organic constituent of landfill leachate and provide the greatest potential for leachate induced organic contamination of groundwater (e.g. as represented by an increase in the concentration of dissolved organic carbon and chemical oxygen demand). Long-term diffusion tests were performed for laboratory-compacted clayey soil plugs exposed to continuous supply of synthetic leachate containing VFAs. Significant microbial activity developed upon exposure of the soil's indigenous microorganisms to these degradable contaminants. The growth of heterotrophic aerobic bacteria (HAB, which include facultative anaerobes), sulfate reducing bacteria (SRB) and methanogenic bacteria carrying out fermentation and mineralization of the VFAs became evident after 30-50 days of testing. The maximum microbial counts of (2-8) x 10(8) and (0.1-1) x 10(8) cfu/g for HAB and SRB were localized in the soil layer at the interface with the source of organic and inorganic nutrients. Regardless of this rapid growth in microbial population, the VFA consumption was small and measurable only after a lag of 140-180 days. It is considered that this lag of otherwise readily degradable organic compounds (such as VFAs) persisted due to a combination of the effects of a high initial concentration of these acids (2.4 g/l as dissolved organic carbon, DOC) applied to carbon starved soil microorganisms and the small pore size of the compacted clay. Once the significant amounts of gas were generated from fermentation, conditions developed for improved mass transport and exchange of the nutrients and bacteria and the outcome of the intrinsic degradation was more apparent. The breakdown of VFAs that followed after the lag was localized near the top of the soil and was characterized by a short half-life of 0.75-5 days for DOC (total VFAs as dissolved organic carbon).
The determination of free volatile fatty acids (FVFA) is of interest in the analysis of cheeses. As these compounds are components of taste and flavor, they give indications on metabolic reactions taking place during cheese ripening and can provide an evaluation of cheese defects and their causes. One of the most widely used methods for the determination of FVFA in cheese involves preliminary recovery from the matrix by steam distillation, followed by gas chromatography separation. Relatively high distillate volumes must be collected to achieve a quantitative yield of all the compounds of interest, so that, as a result, the solution is too diluted to achieve good instrumental sensitivity. In this paper, an alternative method for the determination of C2-C6 free carboxylic acids in cheeses involving the use of a Nukol capillary column and crotonic acid as internal standard is described. This method is quick and cheap, as the sample preparation is a simple extraction with water. The underivatized FVFA are then directly separated by gas chromatography. Using this method, all FVFA in cheeses can be quantified with good repeatability and excellent recovery.
To determine whether volatile fatty acids (VFA) are involved in the regulation of plasma concentrations of insulin of glucagon in the goat, VFA, separately or in combination, were administered into the jugular vein, the portal vein or the rumen, and their effect on pancreatic hormones as well as on VFA measured in venous blood. Propionate, n-butyrate and n-valerate, but not acetate, injected in pharmacological doses, were potent stimuli not only of the secretion into the plasma of insulin but also of glucagon. As regards insulin, the response to VFA was probably not mediated to an appreciable extent by glucose or glucagon. Beta-Hydroxybutyrate did not mediate the effect of n-butyrate on insulin and glucagon. The effects of VFA appear to be peculiar to the ruminant since in the rat injection of similar doses resulted in either no changes or very small changes of plasma insulin and glucagon. Intraportal infusions over 4h of mixtures of VFA, resulting in less extreme, more physiological blood concentration of VFA, elicited sudden transient increases in insulin and to a lesser extent in glucagon. After these peaks insulin and glucagon declined to preinfusion levels and remained virtually unaltered during the remainder of the infusion in spite of sustained, raised concentrations of VFA in the peripheral circulation. These results suggest that under these conditions the rate of increase of VFA is a signal for the secretion of pancreatic hormones. Intraruminal infusions, representing a more physiological route of administration, of single VFA at high rates resulted in a small increase in insulin for propionate infusion only, whereas a mixture of VFA at a physiological rate induced barely any change in insulin or glucagon. It is concluded that under physiological conditions the rate of increase of VFA may contribute to the insulin secretion in the free-feeding goat, but it is unlikely that VFA are the sole controlling agents of insulin release. It is even less probable that the release of glucagon is governed by VFA in the free-feeding goat.
A trial was conducted with wethers to study the effect of the administration of a synthetic diet (composition: 30.125% starch, 30.125% sucrose, 25% cellulose, 5.25% urea, 8.125% mineral supplement, 1.25% maize oil and 0.125% cholinechloride) upon rumen fermentation. The adaptation to the synthetic diet lasted three months, the proportion of the synthetic diet increasing every week (by 10%) to the detriment of a traditional diet (composition: 0.5 kg meadow hay, 0.3 kg barley, 0.2 kg wheat bran, salt and straw ad libitum). In the 10th week the animals consumed 0.5 kg granular synthetic diet, 0.2 kg cellulose flakes and 0.01 kg polystyrene. After three weeks of the administration of the fully synthetic diet, the rumen fluid was sampled after morning feeding in intervals of 0, 1, 3, 5 and 7 hours. In the dynamics of fermentation, statistically significant differences were found only in isobutyric and isovaleric acid between the 0th and 1st and between the 5th and 7th hours (P less than 0.05--P less than 0.001). The data for all the time intervals were recalculated to average values. These were as follows: total volatile fatty acids 63.03 mmol/l, acetic acid 51.00 mol%, propionic acid 26.75 mol%, butyric acid 19.43 mol%, isobutyric acid 0.91 mol%, isovaleric 1.27 mol%, valeric acid 0.62 mol%, energy efficiency of VFA production 78.23%. The obtained data are confronted with literary data on synthetic diets which contained urea and various energy sources.
Explore the source record for details and available documents.
Short-chain fatty acids are a major by-product of anaerobic metabolism and can be detected in gingival fluid from periodontal pockets. Since most T cells are present subjacent to the pocket epithelium in conjunction with the plasma cells, it is important to know how these T cells are affected by short-chain fatty acids produced by subgingival plaque. The purpose of this study is to examine the effects of extracellular metabolites from periodontopathic bacteria on the proliferation and cytokine production of mouse splenic cells as a potential mechanism of imbalance among host-microbial interactions. A low-molecular-weight, heat-stable agent present in the two-day culture filtrate of Porphyromonas gingivalis, Prevotella loescheii, and Fusobacterium nucleatum significantly depressed Con A- and LPS- induced cell proliferation. To determine whether short-chain fatty acids present in the filtrate could account for the depression, we tested extracted volatile and non-volatile fatty acids for their effects on mitogenic activity. The volatile fatty acids extracted from immunosuppressive supernatants greatly inhibited T- and B- cell proliferation. Among these volatile fatty acids, butyric, propionic, valeric, and isovaleric acids impaired cell proliferation dose-dependently. From gas-liquid chromatographic analysis data, it is suggested that immuno-inhibitory activities in culture filtrates are mainly attributable to butyric and isovaleric acids in P. gingivalis, to propionic, butyric, and isovaleric acids in P. loescheii, and to butyric acid in F. nucleatum. Furthermore, these fatty acids significantly depressed interleukin 2 (IL-2), IL-4, IL-5, IL-6, and IL-10 production by Con A-stimulated splenic-T cells dose-dependently.(ABSTRACT TRUNCATED AT 250 WORDS)
OBJECTIVE: To compare concentrations of acetic, propionic, butyric, and i- and n-valerianic acids in digesta samples obtained from the rumen, cecum, proximal loop of the ascending colon (PLAC), and rectum of healthy cows and cows with cecal dilatation or dislocation (CDD). ANIMALS: 20 cows with CDD and 20 healthy cows. PROCEDURE: Samples were collected from all sites during surgical correction of CDD and also from the rectum 1, 2, and 3 days after surgery (group CDD). Samples from healthy (control) cows, matched on the basis of diet and milk yield, were obtained at a slaughterhouse. Concentrations of volatile fatty acids (VFA) were analyzed by use of gas chromatography. Absolute concentration of each VFA was additionally corrected for pH to allow calculation of the concentration of undissociated VFA. RESULTS: Absolute concentration and concentration of the undissociated form of all analyzed VFA were significantly increased in samples collected from the cecum and PLAC of cows in group CDD, compared with concentrations for control cows. Within 3 days after surgery, significant decreases of the absolute concentration of butyric, i- and n-valerianic acids, and undissociated i- and n-valerianic acids were evident in samples obtained from the rectum of group-CDD cows. Concentrations of VFA in samples obtained from the rectum during surgery correlated with corresponding VFA concentrations in samples obtained from the PLAC. CONCLUSIONS: Concentrations of VFA are increased in the cecum and PLAC of cows with CDD. However, the role of increased concentrations of VFA in the etiopathogenesis of CDD is unknown.
Swabs were able to absorb enough extractable volatile fatty acids from broth cultures of anaerobic organisms for detection and analysis by gas-liquid chromatography (GLC). Similarly, volatile fatty acids were often detected in swabs dipped into liquid pus. Fifty-three liquid pus specimens were then investigated fully to determine if GLC analysis of swab samples gave the same result as microbial culture of the specimens and GLC analysis of the liquid pus. Anaerobic bacteria failed to grow from 36 and volatile fatty acids were not extracted from swabs of 31 of these pus samples but were extracted from swabs of five. Anaerobic bacteria were isolated from 17 of the specimens, and in 15, volatile fatty acids were also detected in the swab samples; in two, volatile fatty acids were absent from both swab samples and liquid pus. In this study, results by culture and GLC analysis of swabs were similar in 87% of specimens.
Species of Avena differ markedly in their levels of pre- and post-harvest dormancy. These species offer the opportunity of determining if dormancy is related to the endogenous level of growth inhibitor. Germinability in two species of differing levels of dormancy, common oat Avena sativa L., and wild oat Avena fatua L. was assessed as were the contents of abscisic acid and volatile fatty acids of chain length C(6)-C(10). In A. sativa which did not possess postharvest dormancy there was no correlation between germination and inhibitor levels but in A. fatua the relationship between the content of fatty acid and dormancy was good. The loss of these fatty acids in dry storage by evaporation could explain after ripening.
The effects of concentrations of volatile fatty acids on an anaerobic, glucose-limited, and pH-controlled growing culture of Salmonella enterica serovar Enteritidis were studied. Suddenly increasing volatile fatty acids to the concentrations representative of the ceca of 15-day-old broiler chickens caused washout of serovar Enteritidis. In contrast, a sudden increase to the volatile fatty acid concentrations representative of the ceca of younger broiler chickens caused a reduction in the biomass but not washout. Gradually increasing volatile fatty acids caused a gradual decrease in the biomass of serovar Enteritidis. We conclude that the concentrations of volatile fatty acids present in the ceca of broilers with a mature microflora can cause washout of serovar Enteritidis in an in vitro system mimicking cecal ecophysiology.