Oversimplification and Overstandardization in Biological Methods: Sperm Bioassays in Ecotoxicology as a Case of Study and a Proposal for Their Reformulation

An interesting toxicological bioassay (fertilization inhibition in sea urchin) uses as assessment criterion a variable (fertilization ratio) whose variation with time creates two types of difficulties. First, it fails to distinguish between the toxic effect and the spontaneous decline in the sperm activity, causing some inconsistencies. Second, the sensitivity of the fertilization ratio to many other variables of the system requires a complex standardization, constraining the achievement of the method without solving its main problem. Our proposal consists of using a parameter (sperm half-life) as the response of the assay, and describing explicitly the behavior of the system as a simultaneous function of dose and time. This new focus is able to solve the problematic character of the results based on the fertilization ratio and by using the same data set which is required by the conventional approach; it simplifies the protocol, economizes experimental effort, provides unambiguous and robust results, and contributes to the detection of an artefactual temperature effect, which is not very evident under the usual perspective. Potential application of this new approach to the improvement of other formally similar bioassays is finally suggested

Revista de Vertebrados de la Estación Biológica de Doñana

Descripción de una nueva subespecie de lagarto ágil (Lacerta agilis garzoni) de los PirineosDiet of the Montagu's Harrier (Circus pygargus) in southwestern Spain SpainObservaciones ornitológicas en la Guayana francesaDaily feeding rhythm of ducks on the marismas of the Guadalquivir and their responses to birds of preyA note on the emetic technique for obtaining food samples from passerine birds.Distribución de contaminantes organoclorados en tejidos de garza imperial (Ardea purpurea) y pato cuchara (Anas clypeata) de la Reserva Biológica de Doñana.Etograma cuantificado del gamo (Dama dama) en libertad.Peer reviewe

Facing the Challenge of Data Transfer from Animal Models to Humans: the Case of Persistent Organohalogens

A well-documented fact for a group of persistent, bioaccumulating organohalogens contaminants, namely polychlorinated biphenyls (PCBs), is that appropriate regulation was delayed, on average, up to 50 years. Some of the delay may be attributed to the fact that the science of toxicology was in its infancy when PCBs were introduced in 1920's. Nevertheless, even following the development of modern toxicology this story repeats itself 45 years later with polybrominated diphenyl ethers (PBDEs) another compound of concern for public health. The question is why? One possible explanation may be the low coherence between experimental studies of toxic effects in animal models and human studies. To explore this further, we reviewed a total of 807 PubMed abstracts and full texts reporting studies of toxic effects of PCB and PBDE in animal models. Our analysis documents that human epidemiological studies of PBDE stand to gain little from animal studies due to the following: 1) the significant delay between the commercialisation of a substance and studies with animal models; 2) experimental exposure levels in animals are several orders of magnitude higher than exposures in the general human population; 3) the limited set of evidence-based endocrine endpoints; 4) the traditional testing sequence (adult animals – neonates – foetuses) postpones investigation of the critical developmental stages; 5) limited number of animal species with human-like toxicokinetics, physiology of development and pregnancy; 6) lack of suitable experimental outcomes for the purpose of epidemiological studies. Our comparison of published PCB and PBDE studies underscore an important shortcoming: history has, unfortunately, repeated itself. Broadening the crosstalk between the various branches of toxicology should therefore accelerate accumulation of data to enable timely and appropriate regulatory action

Oversimplification and overstandardization in biological methods: sperm bioassays in ecotoxicology as a case of study and a proposal for their reformulation

An interesting toxicological bioassay (fertilization inhibition in sea urchin) uses as assessment criterion a variable (fertilization ratio) whose variation with time creates two types of difficulties. First, it fails to distinguish between the toxic effect and the spontaneous decline in the sperm activity, causing some inconsistencies. Second, the sensitivity of the fertilization ratio to many other variables of the system requires a complex standardization, constraining the achievement of the method without solving its main problem. Our proposal consists of using a parameter (sperm half-life) as the response of the assay, and describing explicitly the behavior of the system as a simultaneous function of dose and time. This new focus is able to solve the problematic character of the results based on the fertilization ratio and by using the same data set which is required by the conventional approach; it simplifies the protocol, economizes experimental effort, provides unambiguous and robust results, and contributes to the detection of an artefactual temperature effect, which is not very evident under the usual perspective. Potential application of this new approach to the improvement of other formally similar bioassays is finally suggested

Stimulation of bacteriocin production by dialysed culture media from different lactic acid bacteria

Headline: Stimulation of bacteriocin production by dyalised culture media. Keywords: bacteriocin production; stimulatory effects. *Corresponding author: [email protected] Abstract The cross-effects of dyalised postincubates (with a cut-off at 1,000 Da) on the biomass and bacteriocin production of six strains of lactic acid bacteria were studied, and a predominance of stimulating responses was found, the characteristics of which suggested merely nutritional effects or the presence of precursor fragments of the bacteriocins. Additionally, the cluster analysis of the detected responses provides an approach to define groups of highly (potential consortia) or doubtfully compatible strains of lactic acid bacteria. Such a definition, that does not claim taxonomic value, has practical interest, however, in cases (e.g. silage production) in which it is convenient the use of mixed inocula including strains able to establish positive interactions. J.A. Vázquez et al .-1

The influence of substrate structure on the kinetics of the hydrolysis of starch by glucoamylase

8 páginasIn this research the influence of substrate structure on the kinetics of the enzymatic hydrolysis of starch by glucoamylase was evaluated. For this purpose, two substrates of different form and molecular weight were used. In one case, the kinetics of the hydrolysis corresponds to a typical Michaelis-Menten behavior; in the other, a decrease of the hydrolysis rate occurred once a determined substrate concentration was surpassed. The structural differences between the starches, which caused important differences on the rheological properties of their solutions, justify the observed differences in their behavior. Branching of the substrate exerts two opposite effects on the hydrolysis rate because it allows the increase of the number of available points for the enzymatic attack, although the branching increases the steric hindrances and, consequently, the mass transfer resistances. The balance between these two effects is clearly dependent on the substrate concentration.Peer reviewe

Mass transfer control of enzymatic hydrolysis of polysaccharides by glucoamylase

6 pages, 6 figures, 2 tablesA kinetic study of the enzymatic hydrolysis of starch, amylopectin, and glycogen solutions at several concentrations by a commercial glucoamylase was carried out. The results show a decreasing reaction rate zone when starch and amylopectin are used as substrates, at concentrations higher than 50 and 10 g l−1, respectively. In spite of that, the experimental data can be well fitted to a substrate inhibition model. Additional experiments [(i) working at lower substrate concentrations but keeping the same substrate/enzyme ratio; (ii) in static or shaken conditions; (iii) with/without addition of a thickener agent] led us to conclude that hydrolysis of high viscosity starch and amylopectin solutions is controlled by the mass transfer rate.We acknowledge CAICYT and CICYT for their economic support (Projects 1D87060 and BIO89-0264)Peer reviewe