Phototoxicity evaluation--Tetrahymena thermophila as an alternative model

Interest in utilizing an alternative to animal method for toxicological evaluation has received considerable attention due to cost effectiveness and the ethical issues involving animal experimentation. Alternative methods for phototoxicity evaluation are significant because of growing concern over increasing health effects due to stratospheric ozone depletion resulting in an increasing penetration of ultraviolet light-B radiation (UVB, 290-320 nm) which contributes to activation of chemical and biological molecules to potential phototoxic agents. The classic rabbit eye-irritancy test referred to as Draize test has been the subject of severe criticism by animal welfare groups. Dermal toxicity test using guinea pigs and mouse tail phototoxicity test is time consuming and requires a large number of laboratory animals. In photohaemolysis assay some of the phototoxic agents (such as riboflavin) react with the membrane proteins of the erythrocyte. However, in vitro test system using protozoa offers a promising alternative means of phototoxicity evaluation. Our previous studies have demonstrated that synergistic action of photochemically reactive agents and sunlight produces lethal effects to Paramecium but the protozoan has not received serious consideration for use as an alternative model for phototoxicity evaluation. In the present communication we have described the potential application of Tetrahymena as an alternative model to study the radiation-induced changes both in the presence or absence of photoreactive chemical agents. This model is likely to provide scope for studying the biological effects of environmental UVB radiation, DNA damage and defence against oxidative stress.     

Towards an alternative evolution model

Lamarck and Darwin agreed on the inconstancy of species and on the exclusive gradualism of evolution (nature does not jump). Darwinism, revived as neo-Darwinism, was almost generally accepted from about 1930 till 1960. In the sixties the evolutionary importance of selection has been called in question by the neutralists. The traditional conception of the gene is disarranged by recent molecular-biological findings. Owing to the increasing confusion about the concept of genotype, this concept is reconsidered. The idea of the genotype as a cluster of genes is replaced by a cybernetical interpretation of the genotype. As nature does jump, exclusive gradualism is dismissed. Saltatory evolution is a natural phenomenon, provoked by a sudden collapse of the thresholds which resist against evolution. The fossil record and the taxonomic system call for a macromutational interpretation. As Lamarck and Darwin overlooked the resistance of evolutionary thresholds, an alternative evolution model is needed, the first to be constructed on a palaeontological and taxonomic basis.Progress emerges from error, far more than from chaos. (Gray, 1963)     

Development of a gut perfusion model as an alternative to the use of live fish

An alternative fish model with the principal aim of studying the interaction between fish pathogens and the intestinal tissue was developed. The preparation consisted of an excised gut tractus from rainbow trout (Oncorhynchus mykiss), perfused through cannulation of the aorta intestinalis ventralis with filtered and heparinized Cortland+dextran 1% as the perfusion fluid. This perfusion fluid was delivered by means of a drip. The perfused gut tractus was suspended in a circular bath filled with Ringer solution, which was aerated and kept at a constant temperature of 12 degrees C. Unperfused gut placed in Ringer solution at the same temperature served as the negative control. Perfusion was effective in maintaining the gut in a healthy condition for at least 60 min with only slight oedema and sloughing of the epithelium. Conversely, the unperfused gut revealed excessive tissue degeneration and severe necrosis.     

Xenopus as a model to study alternative splicing in vivo

An increasing number of genes are being identified for which the corresponding mRNAs contain different combinations of the encoded exons. This highly regulated exon choice, or alternative splicing, is often tissue-specific and potentially could differentially affect cellular functions. Alternative splicing is therefore not only a means to increase the coding capacity of the genome, but also to regulate gene expression during differentiation or development. To both evaluate the importance for cellular functions and define the regulatory pathways of alternative splicing, it is necessary to progress from the in vitro or ex vivo experimental models actually used towards in vivo whole-animal studies. We present here the amphibian, Xenopus, as an experimental model highly amenable for such studies. The various experimental approaches that can be used with Xenopus oocytes and embryos to characterize regulatory sequence elements and factors are presented and the advantages and drawbacks of these approaches are discussed. Finally, the real possibilities for large-scale identification of mRNAs containing alternatively spliced exons, the tissue-specific patterns of exon usage and the way in which these patterns are modified by perturbing the relative amount of splicing factors are discussed.     

Cardiac telerehabilitation as an alternative to centre-based cardiac rehabilitation

Netherlands Heart Journal - Multidisciplinary cardiac rehabilitation (CR) reduces morbidity and mortality and increases quality of life in cardiac patients. However, CR utilisation rates are low,...     

Classification trees as an alternative to linear discriminant analysis

Linear discriminant analysis (LDA) is frequently used for classification/prediction problems in physical anthropology, but it is unusual to find examples where researchers consider the statistical limitations and assumptions required for this technique. In these instances, it is difficult to know whether the predictions are reliable. This paper considers a nonparametric alternative to predictive LDA: binary, recursive (or classification) trees. This approach has the advantage that data transformation is unnecessary, cases with missing predictor variables do not require special treatment, prediction success is not dependent on data meeting normality conditions or covariance homogeneity, and variable selection is intrinsic to the methodology. Here I compare the efficacy of classification trees with LDA, using typical morphometric data. With data from modern hominoids, the results show that both techniques perform nearly equally. With complete data sets, LDA may be a better choice, as is shown in this example, but with missing observations, classification trees perform outstandingly well, whereas commercial discriminant analysis programs do not predict classifications for cases with incompletely measured predictor variables and generally are not designed to address the problem of missing data. Testing of data prior to analysis is necessary, and classification trees are recommended either as a replacement for LDA or as a supplement whenever data do not meet relevant assumptions. It is highly recommended as an alternative to LDA whenever the data set contains important cases with missing predictor variables.     

Biogas plant slurry as an alternative to chemical fertilizers

The effectiveness of biogas plant slurry in combination with chemical fertilizers was studied for the production of various crops. Replacement of nitrogenous fertilizer with slurry decreased the yields of major crops, i.e. wheat, bajra, jawar and mustard. Application of slurry to replace half the nitrogenous fertilizer gave better yields in vegetable crops while replacement of the total nitrogenous fertilizer gave better yields in fodder crops.     

Transgenic oilseed crops as an alternative to fish oils

Growing evidence suggests that omega-3 long chain polyunsaturated fatty acids (VLC-PUFAs), especially eicosapentaenoic acid (EPA; 20:5Δ5,8,11,14,17) and docosahexaenoic acid (DHA; 22:6Δ4,7,10,13,16,19) play critical roles in human health and development. VLC-PUFAs are mainly found in fish, some fungi, marine bacteria and microalgae. Currently, the predominant dietary sources of VLC-PUFAs are marine fish and seafood. However, the increasing demand for fish and fish oils is putting enormous pressure on marine ecosystems leading to a depletion of fish stocks while commercial cultivation of marine microorganisms and aquaculture are not sustainable and cannot compensate for the shortage in fish supply. Therefore, there is an obvious requirement for an alternative and sustainable source for VLC-PUFAs. Over the last decade, many genes encoding the primary VLC-PUFAs biosynthetic activities became available providing a toolkit for the “reverse-engineering” of transgenic plants to produce fish oils. In this review, we will describe the recent advances in this field and the insights they give us into the complexities of metabolic engineering of oil-seed crops producing VLC-PUFAs.     

Simple life-history traits explain key effective population size ratios across diverse taxa

Effective population size (N_e) controls both the rate of random genetic drift and the effectiveness of selection and migration, but it is difficult to estimate in nature. In particular, for species with overlapping generations, it is easier to estimate the effective number of breeders in one reproductive cycle (N_b) than N_e per generation. We empirically evaluated the relationship between life history and ratios of N_e, N_b and adult census size (N) using a recently developed model (agene) and published vital rates for 63 iteroparous animals and plants. N_b/N_e varied a surprising sixfold across species and, contrary to expectations, N_b was larger than N_e in over half the species. Up to two-thirds of the variance in N_b/N_e and up to half the variance in N_e/N was explained by just two life-history traits (age at maturity and adult lifespan) that have long interested both ecologists and evolutionary biologists. These results provide novel insights into, and demonstrate a close general linkage between, demographic and evolutionary processes across diverse taxa. For the first time, our results also make it possible to interpret rapidly accumulating estimates of N_b in the context of the rich body of evolutionary theory based on N_e per generation.     

Evaluation of alternative hypotheses to explain temperature-induced life history shifts in Daphnia

Negative correlations between environmental temperature andbody size are widespread in planktonic organisms, and ectothermsgenerally, but remain poorly understood. Here we evaluate experimentallytwo alternative hypotheses suggested to explain life historyshifts induced by raised temperature using parthenogenetic clonesfrom two Daphnia species. Explanation 1 proposes that the lifehistory shifts could be adaptive if increased temperature isused as an indirect cue to indicate increased risk from size-selectivepredators. Explanation 2 proposes that at larger body size energybecomes more limiting as temperature increases because of aless favourable assimilation: metabolism balance. In a factoriallaboratory experiment we examine the effects of three rearingtemperatures on the growth and reproductive traits of Daphniaraised in water with fish kairomone, Chaoborus kairomone, orin uncontaminated water. None of the three predictions of explanation1 were met by the data. In both D. pulex and D. curvirostris,and some other published studies, data suggested that at largerbody sizes the sum of growth and reproduction was lower at hightemperature, supporting our prediction from explanation 2. However,we propose a novel third explanation based on new evidence oftemperature-dependence in both reproductive effort and costin D. pulex.     

Infanticide as an alternative male reproductive strategy in langurs: A mathematical model

This paper makes explicit some of the assumptions underlying the view that infanticide is one of two (or more) alternative reproductive strategies utilized by adult male langur monkeys (genus Presbytis). A mathematical model has been developed from these assumptions, and formulae derived which give the equilibrium proportion of infanticidal males expected in langur populations under any given set of reproductive and demographic conditions. Together with estimates of adult male reproductive success obtained from a previous analysis of langur infanticide, these formulae were then used to calculate the precise proportion of infanticidal males expected in natural populations of langurs characterized by specific average male tenures. Further, the number of generations required for such populations to reach their predicted equilibrium was estimated using a simple computer model of langur population dynamics. The present work has thus produced several quantitative predictions which are directly falsifiable with observational data obtainable from wild populations of langur monkeys. With only slight modification, the present model may also be applied to the numerous other primate and non-primate species whose mating systems include many of the same general features as that of langurs.     

Natural cavity restoration as an alternative to nest box supplementation

Nest box supplementation is widely used to increase nest‐site availability for cavity nesting animals but the analysis of its effects on individuals breeding in natural cavities is often neglected. This study offers a novel restoration technique to revert abandonment of natural breeding sites by a secondary cavity avian bird, the European roller (Coracias garrulus), and other ecologically similar species. We found that, after a program of nest box supplementation with ensuing monitoring, rollers gradually abandon nesting in natural and seminatural cavities in favor of nest boxes because the latter are of higher quality. We examine whether reducing the entrance size of natural and seminatural cavities improves their suitability for rollers. A 6‐year program reduced the diameter of the entrance of sandstone cavities and cavities in bridges. This led to a high occupancy (59%) of manipulated nest‐sites. Manipulated sites were most frequently occupied by rollers and little owls (Athene noctua) (31 and 18% of sites, respectively). Manipulation did not affect clutch size or fledgling success. We suggest that nest‐site diversity and nesting in natural cavities should be preserved to reduce nest box dependence. Our study illustrates the value of nest boxes when used alongside restoration of natural breeding sites and provides insights for the management of natural cavities.     

Peracetic acid as an alternative wastewater disinfectant to chlorine dioxide

AIMS: The aim of this study was to compare the efficiency of peracetic acid with that of chlorine dioxide in the disinfection of wastewater from a sewage treatment plant (serving about 650 000 inhabitants) that has been using peracetic acid as a disinfectant since 1998. METHODS AND RESULTS: A total of 23 samplings were made, each consisting of three samples: from secondary effluent, effluent disinfected with 2 mg l(-1) of peracetic acid and effluent disinfected with 2.2 mg l(-1) of chlorine dioxide (contact time 20 min). For each sample, measurements were made of the heterotrophic plate count at 36 degrees C, total and faecal coliforms, Escherichia coli, enterococci, pH, suspended solids and chemical oxygen demand (COD). During the first phase of the experiment the peracetic acid was seen to be less efficient than chlorine dioxide. To improve the disinfectant action a system of mechanical agitation was added which led to a greater efficiency in the inactivation of bacteria of faecal origin. CONCLUSIONS: Both products were found to be influenced by the level of microbial contamination, the amount of suspended solids and COD but not by the pH of the effluent before disinfection. The immediate mixing of the wastewater and disinfectant caused a greater reduction in enterococci. SIGNIFICANCE AND IMPACT OF THE STUDY: Since peracetic acid was seen to produce a high abatement of micro-organisms, it can be considered as a valid alternative to chlorine dioxide in the disinfection of wastewaters.     

Defining quantitative stream disturbance gradients and the additive role of habitat variation to explain macroinvertebrate taxa richness

Most studies dealing with the use of ecological indicators and other applied ecological research rely on some definition or concept of what constitutes least-, intermediate- and most-disturbed condition. Currently, most rigorous methodologies designed to define those conditions are suited to large spatial extents (nations, ecoregions) and many sites (hundreds to thousands). The objective of this study was to describe a methodology to quantitatively define a disturbance gradient for 40 sites in each of two small southeastern Brazil river basins. The assessment of anthropogenic disturbance experienced by each site was based solely on measurements strictly related to the intensity and extent of anthropogenic pressures. We calculated two indices: one concerned site-scale pressures and the other catchment-scale pressures. We combined those two indices into a single integrated disturbance index (IDI) because disturbances operating at both scales affect stream biota. The local- and catchment-scale disturbance indices were weakly correlated in the two basins (r = 0.21 and 0.35) and both significantly (p < 0.05) reduced site EPT (insect orders Ephemeroptera, Plecoptera, Trichoptera) richness. The IDI also performed well in explaining EPT richness in the basin that presented the stronger disturbance gradient (R² = 0.39, p < 0.001). Natural habitat variability was assessed as a second source of variation in EPT richness. Stream size and microhabitats were the key habitat characteristics not related to disturbances that enhanced the explanation of EPT richness over that attributed to the IDI. In both basins the IDI plus habitat metrics together explained around 50% of EPT richness variation. In the basin with the weaker disturbance gradient, natural habitat explained more variation in EPT richness than did the IDI, a result that has implications for biomonitoring studies. We conclude that quantitatively defined disturbance gradients offer a reliable and comprehensive characterization of anthropogenic pressure that integrates data from different spatial scales.