Environmental noise and population dynamics of the ciliated protozoa Tetrahymena thermophila in aquatic microcosms

Population theory predicts that the reddened environmental noise, especially in combination with high population growth rate, reddens population dynamics, increases population variability and strengthens environment–population correlation. We tested these predictions with axenic populations of ciliated protozoa Tetrahymena thermophila. Populations with low and high growth rate were cultured in a stable environment, and in environments with sublethal temperature fluctuations that had blue, white and red spectra (i.e. negatively autocorrelated, uncorrelated, or positively autocorrelated, respectively). Population size and biomass of individuals were determined at 3-h intervals for 18 days.
Dynamics of all populations were reddened, suggesting that internal mechanisms can redden the population spectra. However, population dynamics were reddest, variability highest, and environment–population correlation strongest in the red environment as predicted. Contrary to theoretical predictions and previous empirical findings, population growth rate (r_max being equal to 0.05 and 0.3 h⁻¹) had no effect on population dynamics.
Mean cell size and variability of cell size were affected by the presence and type of environmental noise suggesting that the physiological consequences of variability depend on colour. Environmental variability decreased mean population size and biomass and the decrease was strongest in rapidly fluctuating blue and white environments. The latter finding implies that rapid fluctuations are physiologically stressful, an effect that is not accounted for in the basic population models.     

Sea urchin spermatozoa generate at least two reactive oxygen species; the type of reactive oxygen species changes under different conditions

Reactive oxygen species (ROS) cause oxidative stress and act as signal transduction molecules in many cells. Spermatozoa from several mammals generate ROS, which are involved in male infertility and signaling during capacitation. In the present study, we investigated ROS generation by sea urchin spermatozoa at the initiation of motility, during dilution with seawater, and following egg jelly treatment. In seawater containing an ROS indicator, 5-(and 6-)chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (CM-H(2)DCFDA), fluorescence increased after the addition of spermatozoa. The ROS generation rate was dependent upon the dilution ratio and respiratory rate of the spermatozoa. Spermatozoa in sodium-free seawater did not increase fluorescence, but fluorescence did increase with the addition of NaCl. Sodium chloride also led to the initiation of sperm motility and respiration. Using the indicator MitoSOX Red, ROS generation was detected from spermatozoa exposed to egg jelly dissolved in seawater, but not in normal seawater. Moreover, the respiratory inhibitor antimycin A prevented CM-H(2)DCFDA-detectable ROS and increased MitoSox-detectable ROS at a higher concentration. These findings revealed that the ROS generated were of different species, possibly hydrogen peroxide (H(2)O(2)) and superoxide anion (O(-)(2)), and their detected levels were altered by egg jelly. We concluded that sea urchin spermatozoa generate at least two species of ROS depending on the physiological conditions to which they are exposed. It is possible that the major ROS from sea urchin spermatozoa changes during the course of fertilization.     

Ruminal ciliated protozoa in bison

Ruminal contents from 79 slaughtered bison and 2 ruminally cannulated bison were collected to obtain information on total numbers and species distribution of ciliated protozoa. The bison originated from numerous herds throughout the Great Plains and were grouped into three dietary categories: (i) only forage; (ii) forage with moderate levels of supplementation; and (iii) feedlot concentrate-silage diet. Total ciliate counts were highest in bison receiving grain supplementation (210.1 x 10(4)/g) and lowest in bison consuming only forage (27.1 x 10(4)/g). All protozoan species found in bison have been reported in domestic livestock, although Ophryoscolex sp., a relatively common protozoan in cattle, was detected at low concentrations in only eight bison. The uncommon holotrich Microcetus lappus was present in five bison in concentrations reaching 8.4% of the total ciliate population. Charonina ventriculi, another infrequently observed species, was present in 18 bison, with the highest concentrations in forage-fed animals. Thirty bison possessed a type B protozoan population, characterized by Epidinium sp., Eudiplodinium maggii, and Eudiplodinium bovis. Thirty-eight bison possessed a mixed A-B population, characterized by Polyplastron sp. coexisting with low numbers of Eudiplodinium maggii or Epidinium sp. or both. Thirteen bison possessed populations lacking any remnant type B ciliate species. At least 29 of the bison possessing Polyplastron sp. were known to have been in contact with cattle, whereas all bison isolated from cattle had type B populations. The reduction of type B populations in bison becomes increasingly likely as bison production expands into areas inhabited by domestic livestock.     

Ruminal ciliated protozoa in bison

[This corrects the article on p. 2734 in vol. 54.].     

Calcium-dependent mitochondrial extrusion in ciliated protozoa

Here we demonstrate that ciliated protozoa can jettison mitochondria as intact organelles, releasing their contents to the extracellular space either in a soluble form, or in association with membrane vesicles at the cell periphery. The response is triggered by lateral clustering of GPI-anchored surface antigens, or by heat shock. In the first instance, extrusion is accompanied by elevated levels of intracellular calcium and is inhibited by Verapamil and BAPTA-AM arguing strongly for the involvement of calcium in triggering the response. Cells survive mitochondrial discharge raising the interesting possibility that extrusion is an early evolutionary adaptation to cell stress.     

Ruminal ciliated protozoa in bison.

Ruminal contents from 79 slaughtered bison and 2 ruminally cannulated bison were collected to obtain information on total numbers and species distribution of ciliated protozoa. The bison originated from numerous herds throughout the Great Plains and were grouped into three dietary categories: (i) only forage; (ii) forage with moderate levels of supplementation; and (iii) feedlot concentrate-silage diet. Total ciliate counts were highest in bison receiving grain supplementation (210.1 x 10(4)/g) and lowest in bison consuming only forage (27.1 x 10(4)/g). All protozoan species found in bison have been reported in domestic livestock, although Ophryoscolex sp., a relatively common protozoan in cattle, was detected at low concentrations in only eight bison. The uncommon holotrich Microcetus lappus was present in five bison in concentrations reaching 8.4% of the total ciliate population. Charonina ventriculi, another infrequently observed species, was present in 18 bison, with the highest concentrations in forage-fed animals. Thirty bison possessed a type B protozoan population, characterized by Epidinium sp., Eudiplodinium maggii, and Eudiplodinium bovis. Thirty-eight bison possessed a mixed A-B population, characterized by Polyplastron sp. coexisting with low numbers of Eudiplodinium maggii or Epidinium sp. or both. Thirteen bison possessed populations lacking any remnant type B ciliate species. At least 29 of the bison possessing Polyplastron sp. were known to have been in contact with cattle, whereas all bison isolated from cattle had type B populations. The reduction of type B populations in bison becomes increasingly likely as bison production expands into areas inhabited by domestic livestock.     

Mitochondria and xanthine oxidase both generate reactive oxygen species in isolated perfused rat liver after hypoxic injury

Hypoxia caused severe damage in isolated perfused livers from fasted male Fischer rats without evidence of the formation of reactive oxygen species during hypoxia. Reoxygenation caused a significant increase in intracellular oxygen species in the injured liver, as indicated by increases in sinusoidal GSSG efflux and tissue GSSG levels. Both parameters were elevated further by addition of KCN (100 microM) or antimycin A (8 microM). Sinusoidal GSSG efflux was suppressed in part by addition of allopurinol (500 microM) and enhanced by hypoxanthine (250 microM). Xanthine oxidase appears to be a partial source, and damaged mitochondria a continuous and quantitatively greater source, of reactive oxygen as a result of liver injury following hypoxia.     

Antioxidants and reactive oxygen species in plants

Reactive oxygen species, antioxidants and oxygen stress arethe subject of investigation by many research laboratories worldwide.The use of molecular biology techniques is propelling the subjectalong at a fast pace and the number of research papers on thetopic is growing fast. Antioxidants and Reactive Oxygen Speciesin Plants summarizes much recent     

Imaging reactive oxygen species in arthritis

Reactive oxygen species (ROS) have been shown to play a role in the pathogenesis of arthritides. Luminol was used as the primary reporter of ROS and photons resulting from the chemiluminescence reaction were detected using a super-cooled CCD photon counting system. Luminol was injected intravenously into groups of animals with different models of arthritis. Imaging signal correlated well with the severity of arthritis in focal and pan-arthritis as determined by histological measurement of ROS by formazan. Measurements were highly reproducible, sensitive, and repeatable. In vivo chemiluminescence imaging is expected to become a useful modality to elucidate the role of ROS in the pathogenesis of arthritides and in determining therapeutic efficacy of protective therapies.     

Mammalian peroxisomes and reactive oxygen species

The central role of peroxisomes in the generation and scavenging of hydrogen peroxide has been well known ever since their discovery almost four decades ago. Recent studies have revealed their involvement in metabolism of oxygen free radicals and nitric oxide that have important functions in intra- and intercellular signaling. The analysis of the role of mammalian peroxisomes in a variety of physiological and pathological processes involving reactive oxygen species (ROS) is the subject of this review. The general characteristics of peroxisomes and their enzymes involved in the metabolism of ROS are briefly reviewed. An expansion of the peroxisomal compartment with proliferation of tubular peroxisomes is observed in cells exposed to UV irradiation and various oxidants and is apparently accompanied by upregulation of PEX genes. Significant reduction of peroxisomes and their enzymes is observed in inflammatory processes including infections, ischemia-reperfusion injury, and allograft rejection and seems to be related to the suppressive effect of tumor necrosis factor- on peroxisome function and peroxisome proliferator activated receptor-. Xenobiotic-induced proliferation of peroxisomes in rodents is accompanied by the formation of hepatic tumors, and evidently the imbalance in generation and decomposition of ROS plays an important role in this process. In PEX5^–/– knockout mice lacking functional peroxisomes severe alterations of mitochondria in various organs are observed which seem to be due to a generalized increase in oxidative stress confirming the important role of peroxisomes in homeostasis of ROS and the implications of its disturbances for cell pathology.     

Phagocytic leukocytes and reactive oxygen species

Phagocytic leukocytes, when appropriately stimulated, display a respiratory burst in which they consume oxygen and produce superoxide anions. Superoxide is produced by the phagocyte NADPH-oxidase system which is a multiprotein complex that is dissociated in quiescent cells and is assembled into the functional oxidase following stimulation of these cells. Also associated with the respiratory burst is the generation of other reactive oxygen species. The identity of components of the NADPH-oxidase system and their interactions are known in considerable molecular detail. Understanding of the regulation of superoxide production is less well known. This review also points out the important role of microscopy in complementing biochemical studies to understand better the cell biology of the phagocyte respiratory burst. Presented at the 50th Anniversary Symposium of the Society for Histochemistry, Interlaken, Switzerland, October 1–4, 2008.     

Dynamics of ruminal ciliated protozoa in feedlot cattle

Fluctuations in ciliated protozoan concentrations were monitored in 40 individually fed crossbred heifers that were stepped up to an 85% concentrate diet either slowly (12 days) or rapidly (3 days), with or without monensin (30 ppm). Ruminal fluid was withdrawn from all animals by stomach tube at the start of the study, after each group reached full feed, and at 14-day intervals thereafter throughout the finishing period until termination (day 119). Neither monensin nor speed of step-up affected (P greater than 0.10) total protozoan concentrations, ruminal pH, or lactic acid concentrations. Average protozoan concentrations peaked on day 5, progressively declined until day 56, and then increased (P less than 0.05), suggesting an adaptation to ruminal conditions. Concentrations of Isotricha spp. were higher (P less than 0.05) on the final two sampling dates than at any other time. After day 28, Entodinium, Isotricha, and Polyplastron were the only surviving genera. Protozoa were not detected in 11 heifers on day 42 and day 56, but only two animals were defaunated on day 119, indicating either exogenous or endogenous refaunation. Average protozoan concentrations were not different (P greater than 0.25) between ruminal samples collected by stomach tube the day before slaughter (2.8 x 10(5)/g) and digesta samples collected the next day (1.6 x 10(5)/g). In feedlot cattle, defaunation apparently is transitory and individual animals harbor a dynamic protozoan population that fluctuates in response to changing ruminal conditions.     

Imaging reactive oxygen species in asthma

Inflammatory processes in asthma are characterized by an infiltration of inflammatory cells including mononuclear phagocytes. It has been observed that mononuclear phagocytes, alveolar macrophages and blood monocytes, release higher quantities of reactive oxygen species in asthmatic patients than in healthy subjects. Chemiluminescence assays were developed to measure the superoxide anion and the other reactive oxygen species. The chemiluminescence response was first analysed with a luminometer, which made it possible to study cells in suspension before and after PMA-stimulation. Secondly a video-imaging camera was used in experiments on adherent cells before and after stimulation with PMA and/or specific stimulus IgE/anti-IgE. Both techniques showed that human alveolar macrophages, blood monocytes, PMN and lymphocytes were spontaneously primed in vivo and were more easily stimulated in asthma. Analysis of adherent cells in vitro may provide give information on the physiological condition of adherent cells in vivo.     

Heavy metals in aquatic macrophytes drifting in a large river

Macrophytes drifting throughout the water column in the Detroit River were collected monthly from May to October 1985 to estimate the quantities of heavy metals being transported to Lake Erie by the plants. Most macrophytes (80–92% by weight) drifted at the water surface. Live submersed macrophytes made up the bulk of each sample. The most widely distributed submersed macrophyte in the river, American wildcelery (Vallisneria americana), occurred most frequently in the drift. A total of 151 tonnes (ash-free dry weight) of macrophytes drifted out of the Detroit River from May to October. The drift was greatest (37 tonnes) in May. Concentrations of heavy metals were significantly higher in macrophytes drifting in the river than in those growing elsewhere in unpolluted waters. Annually, a maximum of 2 796 kg (eight heavy metals combined) were transported into Lake Erie by drifting macrophytes. The enrichment of all metals was remarkably high (range: 4 000 × to 161 000 × ) in macrophytes, relative to their concentration in water of the Detroit River. Detroit River macrophytes are thus a source of contaminated food for animals in the river and in Lake Erie.Contribution 734 of the National Fisheries Research Center-Great Lakes, U.S. Fish and Wildlife Service, 1451 Green Road, Ann Arbor, MI 48105.     

Defence against reactive oxygen species

As part of the European Commission Concerted Action on Functional Food which was managed by the International Life Sciences Institute (Europe) a series of Theme Papers was produced which examined the ‘state of the art’ with respect to the subject matter and made recommendations for research. This paper is a summary of the paper concerned with Defence Against Reactive Oxygen species. Having reviewed the scientific literature the authors concluded that certain stringent criteria, which they identified, would need to be satisfied in order to be able to conclude that free radical events are involved in certain human diseases, and that antioxidants are capable of modulating these events and thus reducing the risk of disease. Although there is some evidence that would lead to this conclusion the authors demonstrated that there is at present insufficient evidence available on which to base a firm conclusion that antioxidants are capable of reducing risk of disease, and very little evidence that addresses the important question as to how much of the nutrients concerned are required in the diet to achieve the objective of reducing risk. Research priorities address the need in particular for the development and validation of cellular markers of oxidative damage which are required before there can be new human studies that address the question. There is also a need for more information as to the pharmacokinetics of uptake from diet, distribution and cellular concentration of the antioxidants.     

Defense against reactive oxygen species

As part of the European Commission Concerted Action on Functional Food which was managed by the International Life Sciences Institute (Europe) a series of Theme Papers was produced which examined the 'state of the art' with respect to the subject matter and made recommendations for research. This paper is a summary of the paper concerned with Defence Against Reactive Oxygen species. Having reviewed the scientific literature the authors concluded that certain stringent criteria, which they identified, would need to be satisfied in order to be able to conclude that free radical events are involved in certain human diseases, and that antioxidants are capable of modulating these events and thus reducing the risk of disease. Although there is some evidence that would lead to this conclusion the authors demonstrated that there is at present insufficient evidence available on which to base a firm conclusion that antioxidants are capable of reducing risk of disease, and very little evidence that addresses the important question as to how much of the nutrients concerned are required in the diet to achieve the objective of reducing risk. Research priorities address the need in particular for the development and validation of cellular markers of oxidative damage which are required before there can be new human studies that address the question. There is also a need for more information as to the pharmacokinetics of uptake from diet, distribution and cellular concentration of the antioxidants.