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Cortisone at 100 and 200 microM concentrations produced a significant increase in both life span and reproduction in the rotifer Asplanchna brightwelli. Two possible mechanisms are discussed to explain these results: (1) cortisone stabilization of lysosomal membranes, or (2) recognition of cortisone as a hormone capable of altering resource allocation by the rotifers.
Linear and non-linear modelling of human acute toxicity (as human lethal concentrations; HLCs) of the 38 organic chemicals from the 50 priority compounds of the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) programme was investigated. The models obtained were derived either from a set of 23 physicochemical properties of the compounds or from their acute toxicities to five aquatic non-vertebrates together with the physicochemical properties. For the linear type, modelling was performed using a partial least square projection to latent structures (PLS) regression method; for the non-linear models, both PLS regression and neural network were utilized. A neural network using a combination of backpropagation and cascade-correlation algorithms was applied in this study. The results generally reveal a slightly better predictive performance of the models obtained from PLS regression than those obtained from neural networks. However, the model composed of physicochemical properties (PC-model) from the trained neural network using a back propagation algorithm with pruning technique proved superior to that trained with a combination of backpropagation and cascade-correlation algorithms after leave-one-out cross-validation. The predictive power of the PC-models, whether linear or non-linear, was comparable with that of the corresponding models consisting of both structural descriptors and the ecotoxicological tests (ECOPC-models), except for the battery (ECOPC-model) from the neural network. The composition of the 'best' PLS and neural network models points to the importance of the combination of physicochemical properties reflecting lipophilicity, size, volume, intermolecular binding forces and electronic properties of the molecule. All the aquatic non-vertebrate tests are shown to be essential in explaining human acute toxicity. However, the degree of contribution differed, with the crustacean (Artemia salina) and the bacterial (Microtox) bioassays being more important to the linear and non-linear PLS models, whereas the crustacean (Artemia salina and Streptocephalus proboscideus) tests, and the rotifer (Brachionus calyciflorus) assay were important to the neural network models. The organochlorine (lindane) and bipyridinium (paraquat) pesticides were common outliers in all the models. Moreover, the latter two compounds and the organophosphate (malathion) pesticide were also common outliers in all ECOPC-models. Other types of pesticides, however, fit the models. The predicted HLCs of a number of non-pesticides, including some chlorinated compounds, also deviated from the observed HLCs by more than one order of magnitude.
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In this study, the effects of different environmental temperatures and of dietary restriction on the lifespan, reproductive cycle, and fecundity of the rotifer Asplanchna brightwelli were examined. When temperature effects were analyzed, it was observed that the mean lifespan and the times at which the reproductive cycle started and ended all increased as environmental temperatures decreased. When dietary restriction was imposed by increasing the interval between feeding times from 12 to 36 hours, there was an increase both in the mean lifespan and in the length of the reproductive period in this rotifer.
An analysis of the mean lifespans among the progeny of the viviparous rotifer Asplanchna brightwelli produced during four generations has revealed that longevity of the offspring is not affected by maternal age of the parent or by the parent's lifespan. The production of viable offspring at any time during the parent's reproductive period may be of importance in assuring the continuity of clones of this short-lived rotifer species.
Groups of rotifers of the species Asplanchna brightwelli were exposed to U.V. irradiation at dosages ranging from 50 to 4800 J/m2. The lifespan of the rotifers was significantly reduced by exposure to U.V. in the range of 200 to 4800 J/m2. A logarithmic decline in lifespan was seen as the U.V. dose increased. Rotifers were most sensitive to U.V. exposure during the prereproductive stage at the beginning of their lifecycle. Exposure of rotifers to visible light following U.V. radiation provided no evidence that photoreactivation could influence lifespan in this species.
The rotifer Asplanchna brightwelli could be exposed to concentrations of neutral red at 0.1 to 0.75 microgram/ml for two consecutive generations with no adverse effect on the lifespan or fecundity of either generation. Chronic exposure to higher concentrations of neutral red caused reductions in both lifespan and fecundity of the rotifers. Because neutral red stains the Paramecium which serve as a food source for the rotifers, the extent of red coloration in each rotifer's gut gave an approximation of how much food that rotifer had consumed. The Paramecium concentration had to be reduced to 100 per ml before pale gut coloration provided clear evidence of reduced food intake or dietary restriction. The group of rotifers with reduced food intake had a significantly longer lifespan than any other group. Their lifespan was 14.2% longer than that of control rotifers.
Rotifers were maintained in various light conditions for at least 20 generations. In the first set of experiments lifespan and fecundity data were compared for groups of rotifers maintained under LL (continuous light), DD (continuous dark) or LD 12:12 (control, 12 hr. light 12 hr. dark). The mean lifespan of the rotifers cultured in DD conditions was significantly increased as compared to the LL or LD 12:12 groups but there were no fecundity differences. There was no alteration in lifespan or fecundity of the LL group as compared to the LD 12:12 control. In a second set of experiments, an LD 6:18 cycle was imposed to determine whether a shift in the circadian cycle would influence lifespan. Rotifers exposed to the LD 6:18 cycle and to the DD conditions showed an 18% and 22% increase in mean lifespan respectively. The results are interpreted to demonstrate that lifespan is influenced by the circadian cycle.
Supplementation with vitamin E at a concentration of 25 micrograms/ml significantly increased the mean lifespan of the rotifer Asplanchna brightwelli. Of the three life stages, the prereproductive, reproductive and postreproductive, only the prereproductive stage was significantly extended by vitamin E supplementation. Vitamin E supplemented rotifers were larger than control rotifers in their early stages of life, but both groups attained the same size by the end of their lifespan.
The rotifer Asplanchna brightwelli shows a continuous decline in swimming activity through the course of its 5-day life span. This activity loss occurs at a slower rate when rotifers are treated with very low dosages (0.00025% to 0.0005%) curare. Rotifers treated with these low dosages of curare have a significantly longer life span than that of untreated control rotifers.
Norepinephrine (NE) induces three pharmacological effects in Brachionus plicatilis. As a result of excitation the rate of ciliary motion and swimming increases, and the animals flip their foot constantly at a rapid rate. This rapid foot flipping was used as a specific model to measure adrenergic effects in B. plicatilis. Phenylephrine induces the same effect at identical efficacy, while isoproterenol and salbutamol, two beta-agonists, show one-half and one-tenth NE efficacy. The beta blocker propranolol and the alpha blocker tolazoline both antagonize foot flipping induced by NE. However, propranolol shows antagonism because it causes foot paralysis by itself. Timolol, another beta blocker but without the membrane effect of propranolol, does not antagonize the alpha receptor mediated NE effect, nor does it cause foot paralysis. Propranolol, timolol and tolazoline also show agonist activity, inducing foot flipping. NE does not antagonize the foot paralysis induced by propranolol, only its anesthetic effect by delaying its onset. These results indicate that the foot flipping induced by NE is a receptor-mediated alpha adrenergic effect, while the foot paralysis is caused by membrane phenomena.
1. The acute toxicity of endosulfan was determined for the freshwater rotifer Brachionus calyciflorus. 2. The mean 24 hr LC50 value for endosulfan was 5.15 ppm with a coefficient of variation of 14.7%. 3. Rotifers were exposed at two sublethal concentrations (1.5-2.0 ppm) of endosulfan for bioaccumulation experiments, for an exposure time of 24, 48, 72 and 96 hr. The rotifers were fed with Nannochloris oculata (5 x 10(5) cell/ml). 4. The highest accumulation of endosulfan was found 24 hr after the start of the exposure to 1.5 ppm of the toxicant. A steady-state concentration in rotifer was reached between 24-48 hr, followed by a gradual decrease until 96 hr.
1. Exposure of the rotifer Brachionus plicatilis to elevated temperature resulted in the synthesis of a number of proteins, including a prominent one of 58,000 Da (SP58). 2. This protein is immunologically crossreactive with the 65,000 Da heat shock protein of the moth Heliothis virescens, which is a member of a highly conserved family of mitochondrial proteins. 3. Exposure of rotifers to sublethal doses of CuSO4 leads to a 4-5-fold increase in abundance of SP58, with maximum increase occurring at a dose that is approximately 5% of the LC50 for that compound. 4. A similar response was seen with tributyl tin (TBT). Kinetics of induction were sigmoidal, with induction occurring in the range of 20-30 micrograms/l. 5. No response was observed when rotifers were exposed to aluminum chloride, mercury chloride, pentachlorophenol, sodium arsenite, sodium azide, sodium dodecyl sulfate, or zinc chloride. 6. These results indicate that changes in stress protein abundance may prove useful as a biomarker of exposure to particular toxicants.
We have previously found that the methanol extract prepared from Heterocapsa circularisquama, a harmful red rid dinoflagellate, showed light-dependent hemolytic activity toward rabbit erythrocytes. Interestingly, the cytotoxicity of the extract against HeLa cells was also strictly light-dependent, and no significant toxic effect was observed even at very high concentration in the dark. In this study, the hemolytic agents present in the extract were purified by several chromatographic procedures. Final HPLC analysis revealed that there are at least two hemolytic toxins with different retention times (H2-a and H3-a), which have similar absorption spectra. Although H3-a fraction was contaminated by a trace amount of H2-a, H2-a fraction gave a single peak on a three-dimensional chromatogram. The results of fast atom bombardment (FAB)-mass spectrometry (MS) and electrospray ionization quadrupole time-of-flight (ESI Q-TOF) mass spectrometry analyses suggested that the molecular weight of H2-a was 566. Since nuclear magnetic resonance analysis indicated the presence of a pyrrole ring in H2-a molecule, H2-a may be a porphyrin derivative with similar structure of pyropheophorbide a methyl ester, a well-known photosensitizing hemolytic compound. However, some structural and physicochemical differences were observed between H2-a and pyropheophorbide a methyl ester. Since H2-a showed potent photosensitizing cytotoxicity toward HeLa cells in a concentration-dependent manner as well as hemolytic activity, H2-a may be a novel porphyrin derivative with photosensitizing hemolytic cytotoxicity.
The recent discovery of the production of anti-proliferative aldehydes in a variety of microalgal species has lead to considerable investigation into the effects of these toxins on aquatic invertebrates. Studies have, however, rarely considered the impact pollutants may have on grazer responses to algal toxins. In this study, the acute toxicities of five aldehydes to the rotifer Brachionus plicatilis and nauplii of the brine shrimp Artemia salina are examined using immersion assays. In addition, the effect of a representative of these aldehydes in the presence of sub-lethal levels of heavy metals was examined. B. plicatilis generally showed greater sensitivity to the aldehydes than A. salina. The polyunsaturated 2-trans,4-trans-decadienal was the most toxic to both species having 24h LD(50) values of 7 and 20 microM for B. plicatilis and A. salina, respectively. The remaining aldehydes had different orders of toxicity for the two species with a stronger relationship observed between mortality and aldehyde carbon-chain length for A. salina whereas B. plicatilis mortality showed a stronger dependence on the presence of carbon-carbon double bonds in the aldehydes. The presence of 1 microM of copper sulphate in solutions of decadienal resulted in the reduction of the 24h LD(50) of decadienal by approximately a third for both species. 1 microM of copper chloride in solutions of decadienal reduced the 24h LD(50) of decadienal to A. salina nauplii by approximately 11% and 1 microM zinc sulphate caused a reduction of only 3%. Pre-exposure of the organisms to 1 microM copper sulphate had no significant impact on their subsequent mortality in decadienal. The ecological implications and the possible mechanisms for the action of copper sulphate on the response of organisms to decadienal are discussed.