Opuntia micropropagation by axillary proliferation

Cladode explants of Opuntia amyclaea were cultivated in Murashige and Skoog medium with different supplements. Benzyladenine was necessary for shoot development from pre-existing buds. Axillary proliferation was also stimulated in subsequent subcultures in the presence of benzyladenine and when the apical meristem was not present in the explant. The number of shoots and the total dry weight were maximum with 5% of sucrose in the medium. It was found that satisfactory rooting occurred when 5×10^-5 M indole butyric acid was added to the medium. Vascular contact between roots and shoots was clearly shown by histological observations. The micropropagation system developed here allows the production in 100 days of 25 000 rooted plantlets from a single cladode, by the stimulation of axillary proliferation in the absence of apical dominance.     

Model‐based identifiable parameter determination applied to a simultaneous saccharification and fermentation process model for bio‐ethanol production

In this work, a methodology for the model‐based identifiable parameter determination (MBIPD) is presented. This systematic approach is proposed to be used for structure and parameter identification of nonlinear models of biological reaction networks. Usually, this kind of problems are over‐parameterized with large correlations between parameters. Hence, the related inverse problems for parameter determination and analysis are mathematically ill‐posed and numerically difficult to solve. The proposed MBIPD methodology comprises several tasks: (i) model selection, (ii) tracking of an adequate initial guess, and (iii) an iterative parameter estimation step which includes an identifiable parameter subset selection (SsS) algorithm and accuracy analysis of the estimated parameters. The SsS algorithm is based on the analysis of the sensitivity matrix by rank revealing factorization methods. Using this, a reduction of the parameter search space to a reasonable subset, which can be reliably and efficiently estimated from available measurements, is achieved. The simultaneous saccharification and fermentation (SSF) process for bio‐ethanol production from cellulosic material is used as case study for testing the methodology. The successful application of MBIPD to the SSF process demonstrates a relatively large reduction in the identified parameter space. It is shown by a cross‐validation that using the identified parameters (even though the reduction of the search space), the model is still able to predict the experimental data properly. Moreover, it is shown that the model is easily and efficiently adapted to new process conditions by solving reduced and well conditioned problems. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1064–1082, 2013     

Ion selectivity of the nerve membrane sodium channel incorporated into liposomes

Tetrodotoxin-sensitive sodium channels of lobster nerve membranes were incorporated into soybean liposomes by the freeze-thaw-sonication procedure and their ionic selectivity was studied. Veratridine and grayanotoxin-I were used to activate the sodium channels and the increment of the ionic flux through them was specifically abolished by tetrodotoxin. The drug-sensitive 22Na+, 42K+, 86Rb+ and 137Cs+ influxes were measured. The permeability ratios calculated directly from ion fluxes showed that the channels preferably allow the passage of Na+. No anion influx ([32P]phosphate, [35S]sulfate, 36Cl) sensitive to the drugs was observed. The data reveal that the sodium channels incorporated into liposomes remain cation-selective and discriminate among different cations.     

Early intervention in the 3xTg-AD mice with an amyloid β-antibody fragment ameliorates first hallmarks of Alzheimer disease

The single-chain variable fragment, scFv-h3D6, has been shown to prevent in vitro toxicity induced by the amyloid β (Aβ) peptide in neuroblastoma cell cultures by withdrawing Aβ oligomers from the amyloid pathway. Present study examined the in vivo effects of scFv-h3D6 in the triple-transgenic 3xTg-AD mouse model of Alzheimer disease. Prior to the treatment, five-month-old female animals, corresponding to early stages of the disease, showed the first behavioral and psychological symptoms of dementia -like behaviors. Cognitive deficits included long- and short-term learning and memory deficits and high swimming navigation speed. After a single intraperitoneal dose of scFv-h3D6, the swimming speed was reversed to normal levels and the learning and memory deficits were ameliorated. Brain tissues of these animals revealed a global decrease of Aβ oligomers in the cortex and olfactory bulb after treatment, but this was not seen in the hippocampus and cerebellum. In the untreated 3xTg-AD animals, we observed an increase of both apoJ and apoE concentrations in the cortex, as well as an increase of apoE in the hippocampus. Treatment significantly recovered the non-pathological levels of these apolipoproteins. Our results suggest that the benefit of scFv-h3D6 occurs at both behavioral and molecular levels.     

The role of hyperiid parasites as a trophic link between jellyfish and fishes

The trophic interactions between the scyphozoan medusa Chrysaora plocamia and the palm ruff Seriolella violacea were investigated off northern Chile and showed that large numbers of hyperiid amphipods parasitizing the medusa may channel energy back to the fishes, which feed on the parasites. The biomass of hyperiids eaten by the fish was a function of the biomass of hyperiids parasitizing the medusa. This temporally available food supply may enhance fish recruitment. The large number of hyperiids parasitizing diverse jellyfish species represents a missing trophic link in current efforts to understand the effects of jellyfish blooms on marine food webs.