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PubMed1985

Ultrastructure of Candida ingens: a yeast that can assimilate volatile fatty acids.

A defined liquid medium was developed for culture of Candida ingens on either volatile fatty acids or glucose as carbon source. Buffering capacity at pH 5.4 was achieved by inclusion of 50 mM phthalic acid which is not assimilated. The yeast grew on C2-C5 acids, with lags in some cases that were dependent on the cultural history of the inoculum. The cells were notably large for Candida species, or yeasts in general, and were significantly more elongated on glucose substrate compared with butyrate. Traditional aldehyde fixatives and heavy metal staining yielded bland micrographs. However, the periodic acid-thiocarbohydrazide-silver proteinate stain of Thiéry resulted in informative, high contrast electron images for this species. The ultrastructure of the cell envelope was not greatly affected by carbon source or by growth habit except that a slime layer was more prevalent in pellicular cells compared with those grown in submerged culture. The slime layer was apparently stabilized by colloidal iron staining. The other feature of the cell envelope was a microfibrillar zone containing periodic acid reactive constituents. Subcellular organelles were typical of yeast species although there was a propensity for large vacuoles in pellicular cells. When cells were grown on fatty acids there was an increase in the number of microbodies compared with that observed on glucose. Microbodies were best demonstrated by diaminobenzidine-hydrogen peroxide staining of protoplasts, which were generated by dissolution of cell walls with snail digestive enzymes.

Candida↗
PubMed1986

Effects of ammonia and volatile fatty acids produced by oral bacteria on tissue culture cells.

Culture filtrates of several bacterial species isolated from the oral cavity were tested for their effects on two types of tissue culture cells: Vero cells, the continuous cell line of African green monkey kidney cells; and chondrocytes, isolated from 15-day-old chick embryo tibiae. Only a limited number of bacterial species--i.e., the asaccharolytic black-pigmented Bacteroides species and Fusobacterium species--affected the two cell types. The effect on Vero cells, detected by the rounding of the cells, correlated with the butyric acid concentration in the bacterial supernatant, which confirms previous findings. A small enhancement of this effect was found with propionic acid and ammonium ions. The same strains which affected Vero cells also affected chondrocytes, detected by a vacuolization of the cells. However, volatile fatty acids on their own had no visible effect on these cells. Instead, ammonium ion in the culture filtrate, when present in concentrations of 20 to 60 mmol/L, proved to be responsible for vacuolization of the chondrocytes. The volatile fatty acids (butyric and propionic) had a limited additive effect. No effects were visible with cell extracts of the bacteria.

Actinomyces↗
PubMed1999

Response of one-humped camel (Camelus dromedarius) to intravenous glucagon injection and to infusion of glucose and volatile fatty acids, and the kinetics of glucagon disappearance from the blood.

The effects of glucagon injection and infusion of glucose and volatile fatty acids were studied in one-humped camels. Twenty adult male camels were divided into four equal groups. The first group was infused with physiological saline and served as a control. The second group was injected with a single dose of glucagon, the third group was infused with glucose (50%) in sterile saline, and the fourth group was infused with a volatile fatty acid (VFA) mixture. In the first, third and fourth groups, sampling was performed before the beginning of infusions (control time), and at 15, 30, 60 and 120 min post-infusion. Plasma glucagon concentrations were monitored in the second group at 5, 10, 15, 20, 30, 45, 90, 105 and 120 min after injection. For glucagon injection, glucose concentration peaked at 15 min post-injection, and tended to decrease thereafter. Plasma glucose concentrations showed significant rises above the basal value at all times after glucose infusion. VFA infusion had no apparent effect on plasma glucose concentration. After injection of glucagon, the plasma lactate concentration dropped significantly at 15 and 30 min, then increased gradually until it reached the original concentration of lactate at 120 min. However, glucose infusion elevated the plasma lactate concentration only at the end of the infusion period. A decrease in plasma lactate was observed at 60 min after VFA infusion. The present investigation provides evidence that the glucagon level in camels is higher than that in other ruminants and in man, and suggests that this is a probable species specificity, which would explain the higher level of glucose in the blood of camels than in that of other ruminants. The disappearance curve of injected glucagon had, as in other ruminants, an exponential two-compartment function. The hormone was rapidly distributed and was eliminated with a high rate of clearance.

Animals↗
PubMed1989

Concentrations of volatile fatty acids and acetate production rates in the forestomachs of grazing camels.

1. Concentration profiles of volatile fatty acids (VFA), fluid volumes and turnover rates, and acetate production rates were measured in two different seasons in the forestomachs of four fistulated dromedary camels grazing in the Kenyan thornbush savannah. 2. VFA profiles and average concentrations were similar under both feeding conditions but, due to a smaller fluid turnover, VFA outflow to lower gastric sections in the dry season was reduced by almost 50%. 3. The mean acetate production rate fell from 2234 mmol/hr in the green season to 816 mmol/hr in the dry season, i.e. by approximately 64%.

Acetates↗
PubMed1978

A model for the estimation of volatile fatty acid production in the rumen in non-steady-state conditions.

A method of estimating volatile fatty acid (VFA) production in the rumen in non-steady-state conditions was proposed. Laboratory models indicated that good estimates of total production over a complete feeding cycle could be obtained even when a wide range of production rates and volume changes occurred during the experiment. But estimates of instantaneous production rates might have contained large errors unless some attempt was made to match the infusion rate of labelled VFA to the rate at which VFA was produced in the rumen.

Animals↗
PubMed1975

[Distribution of volatile fatty acids in digestive tract contents of rabbit. II.--Rabbits subjected to fasting (author's transl)].

Volatile fatty acids (VFA) were measured by gas chromatography in the digestive material of Rabbits subjected to:--alimentary fast for 48 hours;--stercoral fast for 96 hours. A 48 hour alimentary fast caused a substantial drop in VFA in the digestive tract, butyric acid was the most affected, its concentration falling below that of propionate. Fasting for 48 hours did not cause a total cessation of fermentation. Stercoral fasting did not diminish the quantity of VFA in the digestive tract. VFA production was even augmented in the posterior parts (caecum and colon).

Animals↗
PubMed2004

The effect of volatile fatty acids on the nitrification of a saline effluent.

Anaerobically produced volatile fatty acids (VFA) may affect the nitrification yield. The effect of the type of VFA (acetic, propionic and butyric acid) on nitrification of a saline (24 g NaCl l(-1)) medium was studied. Nitritation (40 mg N-NH4+ l(-1)) and nitratation (100 mg N-NO2- l(-1) were assessed in batch cultures fed with different VFA (32 mg TOC l(-1)). The effect of increasing VFA concentrations on nitrification was studied in batch reactors fed with an initial concentration of 40 mg N-NH4+ l(-1) and C/N ratios of 0, 2, 4, 8 and 16 as well as in a continuous mixed flow reactor operated at 30 degrees C and pH 7.5 and fed with 500 mg N-NH4+ l(-1) and 500, 1000, 2000, and 4000 mg TOC l(-1). Nitritation and nitratation rates were decreased by organic matter; inhibition increased with the VFA size. A non-competitive inhibition model fitted the experimental data on nitrification rate reduction at increasing acetic add concentrations; inhibition constants were 685 mg acetic acid l(-1) for ammonia oxidation and 74.3 mg acetic acid l(-1) for nitrite oxidation. The continuous reactor's nitrifying ability decreased from 82% to 40% at C/N ratios 1 and 4, respectively. Loss of nitrification, but a 50% ammonia removal was found at a C/N of 8. It was concluded that the nitrification rate reduction is proportional to the VFA molecular weight and that an increase in VFA concentration diminishes the nitrifying ability due to kinetic limitations.

Acetates↗
PubMed1975

Volatile fatty acid metabolism by rumen mucosa from cattle fed hay or grain.

Effects of an all-grain versus an all-hay diet on metabolic activity of rumen mucosa of cattle were investigated. After diets had been fed for 3 to 4 mo, rumen papillae were collected at slaughter from the dorsal rumen sac and incubated with one of various volatile fatty acids. Rates of substrate utilization were in the order: n-butyrate greater than n-valerate approximately propionate greater than iso-butyrate approximately iso-valerate. Over-all, papillae from hay-fed steers utilized greater amounts of volatile fatty acids. Dietary treatment did not significantly affect extent of conversion of volatile fatty acids to lactate and to ketone bodies. Lactate was the major metabolite from propionate and n-valerate. Ketone body formation accounted for more than 90% of n-butyrate uptake by papillae. Ketone formation from n-valerate was restricted to beta-hydroxybutyrate while that from iso-valerate was essentially acetoacetate plus acetone. Metabolic systems in rumen mucosa of physiologically mature ruminants seem to adapt little to varying individual volatile fatty acids available for absorption in vivo.

Acetoacetates↗