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At least 19 recordsLinked to original sources
PubMed1976

[The protozoa population in the rumen of fattening bulls fed varying feed and the effect of artificial transfer of protozoa].

High protozoa concentrations were found in the ruminal fluid of fattening bulls weighing 400 kg which were raised for the first five months of age in a large-size calf-raising plant. The ruminal fluid of these bulls, however, contained no protozoa of the group Holotricha. If the animals were fed a mixture of concentrates and pelleted straw (pH 6, 12.5 mMole of volatile fatty acids per 100 ml) 1 ml of the ruminal fluid was found to contain 827,000 protozoa whereas if the animals received rations rich in concentrates (pH 5.8, 14 mMole of volatile fatty acids) 1 ml of ruminal fluid contained only 578,000. Through protozoa transfer carried out by infusing 41 of a mixture of ruminal fluid from other cows per animal it was possible to settle other species, viz. Isotricha, Dasytricha and Ophryoscolex; this, in turn, produced a concomitant decrease in the number of Entodinium and a noticeable decline in the total protozoa population. Further work will be necessary to find out whether it would be advisable to influence the protozoa population of growing cattle kept in large-size cow plants in similar ways as described above.

Animal Feed↗
PubMed1982

Oxygen affinities of the hydrogenosome-containing protozoa Tritrichomonas foetus and Dasytricha ruminantium, and two aerobic protozoa, determined by bacterial bioluminescence.

Oxygen-dependent bioluminescence of Photobacterium (Vibrio) fischeri was used to measure oxygen affinities of four protozoa. The aerobic organisms Acanthamoeba castellanii and Tetrahymena pyriformis showed apparent Km values for O2 of 0.42 and 2.43 microM respectively. The aerotolerant anaerobe Tritrichomonas foetus, and the more strictly anaerobic rumen ciliate Dasytricha ruminantium, both of which have hydrogenosomes, respired with apparent Km values of 1.08 and 1.70 microM-O2. We conclude that mitochondrial respiration is not the only process conferring on organisms a high affinity for O2.

Amoeba↗
PubMed1991

Parasitic protozoa of cyprinid fishes: protozoa of the roach Rutilus rutilus (Linnaeus, 1758) in Czechoslovakia.

In the years 1985-1988, a total of 254 specimens of the roach, Rutilus rutilus, captured in 23 localities of South Bohemia, were examined for the presence of protozoan parasites. Only 17 specimens (6.7%) were free of infection, whereas the others were infected at least with one parasite species, mixed infections were observed most frequently. The following species were found rarely: Myxidium rhodei Léger, 1905 in the liver and muscles. Pleistophora mirandellae Vaney et Conte, 1901 in ovaries, Trichodina nemachili Lom, 1960 on the skin, Trichodina prowazeki Grupcheva et Lom, 1980 on the skin (the first finding in Czechoslovakia). The data concerning localization of individual parasites and their prevalence are presented and five protozoan species described in detail.

Animals↗
PubMed1994

Signal transduction in host cells mediated by glycosylphosphatidylinositols of the parasitic protozoa, or why do the parasitic protozoa have so many GPI molecules?

Considerable circumstantial evidence indicates that glycosylphosphatidylinositol (GPI) molecules of mammalian origin are able to mediate signal transduction in lymphoid cells. For example, perturbation of GPI-anchored surface proteins, but not transmembrane forms of these molecules, can lead to the activation of T lymphocytes. GPIs appear also to be precursors of pharmacologically active phosphoinositol-glycans which mediate responses to hormones such as insulin, nerve growth factor and IL-2. Nonetheless, the biochemical mechanisms of signal transduction by GPIs remain obscure. We have shown that structurally defined GPIs of protozoal parasite origin are able to mediate signal transduction in host macrophages and lymphocytes, by substituting for the putative endogenous GPI-based signalling mechanisms of the host. Signalling by parasite GPIs appears to involve the activation of protein tyrosine kinase and protein kinase C. Evidence from other sources indicates that structurally variant GPIs may provide anergic signals to down-regulate host cell function. These phenomena may represent mechanisms by which eukaryotic parasites regulate host cell function, and can explain a variety of pathological and immunological features of protozoal infections. Furthermore, protozoal GPIs may prove to be an informative model system for the analysis of GPI-mediated signal transduction in lymphocytes and macrophages.

Animals↗
PubMed1982

Dynamics of protozoa in the rumen of sheep.

Protozoa were labelled by incubating 100 ml rumen fluid with [14C]choline for 1 h. The protozoa were concentrated by centrifugation and then washed with rumen fluid. This reduced residual 14C in the fluid medium to insignificant amounts while still retaining the viability of the labelled protozoa. Washing procedures using formal saline (40 g formaldehyde/1 saline (9 g sodium chloride/1)) and saline were developed to isolate protozoa for estimation of specific radioactivity. 2. The protozoal pool in freshly-collected rumen fluid incubated in vitro retained 90% of the radioactivity for up to 6 h following addition of 14C-labelled protozoa produced as indicated previously. The specific radioactivity of protozoa did not change during the incubation period. 3. Protozoa labelled with [14C]choline and then stored until they died rapidly lost 14C to methane when they were incubated in rumen fluid or were injected into the rumen. Some [14C]choline was salvaged under these conditions by the live protozoa present as they apparently incorporated up to 13% of the label from the dead protozoa. However, protozoal debris from the injected solution could also have been present in the isolated protozoa. 4. The in vitro results suggested that the protozoal preparations were viable, and that the incorporated choline did not have a turnover in excess of the turnover of nitrogen (i.e. specific radioactivity remained constant with time in vitro) suggesting that the dilution of specific radioactivity of protozoa following mixing of a 14C-labelled dose of protozoa represented the rate of irreversible loss and also replacement of protozoa in the rumen. 5. 14C-labelled protozoa had a half-life in the rumen which was greater than that of rumen fluid and in six animals the protozoal replacement rate was 1-4.1 mg N/min. 6. Losses of 14C from labelled protozoa in the rumen in methane or via abomasal digesta were 65 and 35% respectively. 7. The results suggest that protozoal growth may be as high as 32% of the total microbial protein synthesis in the rumen but that 65% of the protozoa die and are degraded in the rumen.

Abomasum↗
PubMed1981

Kinetics of large ciliate protozoa in the rumen of cattle given sugar cane diets.

1. Experiments were undertaken to examine the kinetics of large ciliate protozoa in the rumen of cattle on sugar-cane diets. 2. Three Zebu bulls were fed once daily on a diet of sugar cane and wheat bran. The diurnal patterns of volatile fatty acids and ammonia concentrations, and the numbers of protozoa in rumen fluid were determined. The numbers of protozoa reached values of 5 X 10(4)/ml for holotrichs (large ciliates) mainly Isotricha and Dasytricha spp and 4 X 10(5) for smaller protozoa, mainly Entodinia (small ciliates). 3. A method was developed which allowed large ciliate protozoa in rumen fluid to be separated from plant material and bacteria and concentrated in a relatively uncontaminated form. Analysis of these protozoa indicated that 1.8 X 10(5) large ciliates contained 1 mg nitrogen and approximately 32 mg dry matter. 4. A labelled preparation consisting mainly of large ciliates (principally Isotricha spp.) was obtained by incubating isolated protozoa in rumen fluid (free of plant materials) containing [14C-methyl]choline and then isolating them by sedimentation and differential centrifugation. 5. A portion of the preparation containing labelled protozoa was incubated in vitro with rumen fluid to determine the turnover of 14C-labelled metabolites. There was no apparent dilution of the label in the protozoa over a 22 h period. 6. A major portion of the preparation containing labelled protozoa was returned to the rumen of each of the donor cattle as a single injection. The specific radioactivity in the large protozoa (microCi/mg N) was monitored frequently for over 30 h, and thereafter daily for a further 12 d. The kinetics of tracer dilution were analyzed to give estimates of the size of the pool of these large ciliates in the rumen (24-46 g N), and of their apparent rate of turnover. 7. In contrast to the slow turnover of the large ciliates, the rate of turnover of the rumen fluid pool (approximately 54 1), estimated from the rate of dilution of polyethylene glycol, was considerably faster. Large ciliates were therefore selectively retained within the rumen.

Ammonia↗
PubMed1988

Dynamics of protozoa in the rumen of cattle.

1. The dynamics of protozoa were studied in two groups of rumen-fistulated cattle fed on a basal diet of molasses ad lib., with oaten chaff given at 6 or 18 g/kg live weight. This diet resulted in different mixtures of protozoal species in the populations in the rumen. 2. The rumen protozoa were studied by intrarumen injections of protozoa labelled in vitro with [14CH3]choline. An indication of protozoal death and fermentation of protozoal cell residues was obtained by measuring 14C loss via the methane pool. 3. After a single injection of labelled protozoa, the decline in the specific radioactivity (microCi/g nitrogen) of the protozoal pool in the rumen indicated that first-order kinetic processes applied. Conversely the specific radioactivity of protozoa, incubated in rumen fluid, remained constant indicating no growth in vitro, presumably owing to a rapid exhaustion of essential nutrients. 4. The protozoal populations in the rumen of cattle fed on the diet with the low level of oaten chaff were mainly small ciliates; but on the higher level of chaff in the diet, the large ciliates were a higher proportion of the total protozoal population present. 5. The mean pool size of protozoa in the rumen was significantly larger and the protozoal half-life tended to be longer for cattle fed on the higher level of chaff in the diet. The apparent production rate of protozoa in cattle fed on each diet was not significantly different and there were no differences in the production rate of methane. The percentage losses of label from protozoa in the rumen via the methane pool were not significantly different on the two diets and indicated that 74% of the protozoa that were apparently irreversibly lost from the rumen could be accounted for by death and lysis in the rumen and therefore only 26% of protozoa apparently entered the lower digestive tract.

Ammonia↗
PubMed1983

Association of methanogenic bacteria with rumen protozoa.

Methanogenic bacteria superficially associated with rumen entodiniomorphid protozoa were observed by fluorescence microscopy. A protozoal suspension separated from strained rumen fluid (SRF) by gravity sedimentation exhibited a rate of methane production six times greater (per millilitre) than SRF. The number of protozoa (per millilitre) in the protozoal suspension was three times greater than that of SRF; however, the urease activity of this fraction was half that of SRF. The methanogenic activity of SRF and the discrete fractions obtained by sedimentation of protozoa correlated with the numbers of protozoa per millilitre in each fraction. Gravity-sedimented protozoa, washed four times with cell-free rumen fluid, retained 67-71% of the recoverable methanogenic activity. Thus it is evident from our observations that many methanogens adhere to protozoa and that the protozoa support methanogenic activity of the attached methanogens. When protozoa-free sheep were inoculated with rumen contents containing a complex population of protozoa, methanogenic activity of the microflora in SRF samples was not significantly enhanced.

Animals↗
PubMed2001

The effects of sequential inoculation of mixed rumen protozoa on the degradation of orchard grass cell walls by anaerobic fungus Anaeromyces mucronatus 543.

The effects of protozoa on the degradation of plant cell walls (CW) during different growth stages of the fungus Anaeromyces mucronatus have been investigated. Since fungi show a marked lag in their in vitro cultures and many protozoa rapidly die during a prolonged incubation time, the effects of protozoa may vary according to the growth phase of the fungi. Therefore, the approach adopted was (i) to inoculate CW with fungus monoculture, (ii) to inoculate CW with fungus-protozoa coculture, or (iii) to sequentially inoculate fungal cultures that had been grown in CW for 24 (initial stage of growth), 48, and 72 h (late stage of growth) with mixed protozoa. When a fungus was associated with protozoa, a growth phase dependent effect was observed. Ruminal protozoa adversely affected the growth and activity when introduced in the initial growth stage of A. mucronatus, but a synergetic interaction was detected when added to late growth stage cultures. Although there is no immediate explanation for these results, the data suggested that protozoa can engulf the fungal zoospores, which are in ruminal fluids and (or) attached to small feed particles, but cannot engulf the fungal thallus that is tightly attached to feed particles by a rhizoidal system. Our data indicated that the protozoa did not influence cellulolysis by the fungi in exponential and (or) stationary phase, but they had a marked inhibitory effect on fungi that were in lag phase. Inhibition during lag phase could result from the protozoal predation of fungal zoospores that had failed to attach to substrates.

Anaerobiosis↗
PubMed1987

Relative contributions of ruminal bacteria and protozoa to the degradation of protein in vitro.

Mixed ruminal microorganisms from a cow fed timothy hay and concentrate supplement (50:50) were incubated with various protein sources for 15 h (no carbohydrates or growth), and deamination was studied under enzyme-limiting substrate-excess conditions (n = 3). Addition of amphotericin (10 micrograms/ml) killed protozoa and decreased (P less than .05) ammonia production from killed bacteria but it had no effect (P greater than .05) on casein deamination. Monensin (5 micrograms/ml) also killed protozoa; however, it decreased (P less than .05) casein deamination to a much greater extent than amphotericin. Antibacterial antibiotics (penicillin G, polymixin B, cephalosporin C and streptomycin) greatly reduced (P less than .05) ammonia formation from casein. Isolated bacteria always produced more ammonia than isolated protozoa, but the difference was less with heat-treated, particulate proteins. Heated soybean protein was as soluble as heated casein but it was deaminated (P less than .05) at a faster rate by bacteria. Nonammonia-nonprotein N accumulation was greater (P less than .05) with the protozoa than bacteria. When incubations containing bacteria or protozoa were compared with combinations of protozoa and bacteria, the combinations always caused a synergistic increase in ammonia and decrease (P less than .05) in nonammonia-nonprotein N. These results suggest: soluble proteins were primarily degraded by bacteria; protozoa could contribute to the degradation of insoluble, particulate proteins; protozoa were limited in their ability to assimilate peptides (or amino acids); low molecular weight products could be fermented more readily by bacteria and monensin was toxic to protozoa, but decreases in ammonia were primarily due to action of monensin on bacteria.

Animals↗