Analysis of pelletizing from corn cob waste.

In recent years, biomass market has constantly increased. Pellet industry has started looking for new products with the potential to be used as biofuels. Among them are agricultural wastes, such as corn cob waste, which presents some characteristics that make its direct use in industrial facilities possible. However, these properties are not enough for its use in domestic stoves and boilers, where higher quality of fuel is needed. For this reason, densification is used. In the present research work a technical and energy analysis of corn cob waste pelletizing was carried out in a semi-industrial pelletizer. Some relationships between variables, such as moisture, bulk density and mechanical durability, were analyzed, as well as their influence on energy use and final productivity. The results were satisfactory, as the pellets manufactured fulfilled with most specifications that were consulted, with higher values than those recorded for similar kinds of pellets. Concerning the energy study, the increase in production justified a higher energy consumption of the process in order to get a higher productivity ratio.

Periodic paralysis in quarter horses: a sodium channel mutation disseminated by selective breeding.

We recently reported on a linkage study within a Quarter Horse lineage segregating hyperkalaemic periodic paralysis (HYPP), an autosomal dominant condition showing potassium-induced attacks of skeletal muscle paralysis. HYPP co-segregated with the equine adult skeletal muscle sodium channel alpha subunit gene, the same gene that causes human HYPP. We now describe the Phe to Leu mutation in transmembrane domain IVS3 which courses the horse disease. This represents the first application of molecular genetics to an important horse disease, and the data will provide an opportunity for control or eradication of this condition.

Recent advances in dystrophin research.

Evidence suggesting that dystrophin is a component of the membrane cytoskeleton of excitable cells continues to accumulate. Whereas the specific mechanisms leading to muscle pathology in Duchenne muscular dystrophy are still being debated it is apparent that the progressive weakness that occurs in this disease is the result of a chronic process that is initiated by dystrophin deficiency.

[Molecular nutrition, role of the PPAR system in lipidic metabolism and its importance in obesity and diabetes mellitus]. / Nutrición molecular, papel del sistema PPAR en el metabolismo lipídico y su importancia en obesidad y diabetes mellitus.

PPARs are transcription factors belonging to the super family of hormonal receptors. Their activity is regulated by fibrates, thiazolidinediones, certain anti inflammatory drugs and fatty acid derivatives, present in food. PPAR isoforms play a central role in lipid homeostasis, regulating anabolic (PPAR gamma) and catabolic (PPAR alpha) pathways of lipid metabolism. Additionally, these receptors participate in glucose homeostasis, influence cellular proliferation and differentiation and participate in inflammatory processes. The effects of PPARs on oxidative substrate partitioning suggests that they have a relevant role in the development of obesity and insulin resistance.

Hyperkalemic periodic paralysis M1592V mutation modifies activation in human skeletal muscle Na+ channel.

Mutations in the human skeletal muscle Na+ channel underlie the autosomal dominant disease hyperkalemic periodic paralysis (HPP). Muscle fibers from affected individuals exhibit sustained Na+ currents thought to depolarize the sarcolemma and thus inactivate normal Na+ channels. We expressed human wild-type or M1592V mutant alpha-subunits with the beta1-subunit in Xenopus laevis oocytes and recorded Na+ currents using two-electrode and cut-open oocyte voltage-clamp techniques. The most prominent functional difference between M1592V mutant and wild-type channels is a 5- to 10-mV shift in the hyperpolarized direction of the steady-state activation curve. The shift in the activation curve for the mutant results in a larger overlap with the inactivation curve than that observed for wild-type channels. Accordingly, the current through M1592V channels displays a larger noninactivating component than does that through wild-type channels at membrane potentials near -40 mV. The functional properties of the M1592V mutant resemble those of the previously characterized HPP T704M mutant. Both clinically similar phenotypes arise from mutations located at a distance from the putative voltage sensor of the channel.

A Met-to-Val mutation in the skeletal muscle Na+ channel alpha-subunit in hyperkalaemic periodic paralysis.

HYPERKALAEMIC periodic paralysis (HYPP) is an autosomal dominant disease that results in episodic electrical inexcitability and paralysis of skeletal muscle. Electrophysiological data indicate that tetrodotoxin-sensitive sodium channels from muscle cells of HYPP-affected individuals show abnormal inactivation. Genetic analysis of nine HYPP families has shown tight linkage between the adult skeletal muscle sodium channel alpha-subunit gene on chromosome 17q and the disease (lod score, z = 24; recombination frequency 0 = 0), strongly suggesting that mutations of the alpha-subunit gene cause HYPP. We sequenced the alpha-subunit coding region isolated from muscle biopsies from affected (familial HYPP) and control individuals by cross-species polymerase chain reaction-mediated complementary DNA cloning. We have identified an A----G substitution in the patient's messenger RNA that causes a Met----Val change in a highly conserved region of the alpha-subunit, predicted to be in a transmembrane domain. This same change was found in a sporadic case of HYPP as a new mutation. We have therefore discovered a voltage-gated channel mutation responsible for a human genetic disease.

Sequence and genomic structure of the human adult skeletal muscle sodium channel alpha subunit gene on 17q.

The amino acid sequence of the sodium channel alpha subunit from adult human skeletal muscle has been deduced by cross-species PCR-mediated cloning and sequencing of the cDNA. The protein consists of 1836 amino acid residues. The amino acid sequence shows 93% identity to the alpha subunit from rat adult skeletal muscle and 70% identity to the alpha subunit from other mammalian tissues. A 500 kb YAC clone containing the complete coding sequence and two overlapping lambda clones covering 68% of the cDNA were used to estimate the gene size at 35 kb. The YAC clone proved crucial for gene structure studies as the high conservation between ion channel genes made hybridization studies with total genomic DNA difficult. Our results provide valuable information for the study of periodic paralysis and paramyotonia congenita, two inherited neurological disorders which are caused by point mutations within this gene.