Pore formation by the sea anemone cytolysin equinatoxin II in red blood cells and model lipid membranes

Summary The interaction ofActinia equina equinatoxin II (EqT-II) with human red blood cells (HRBC) and with model lipid membranes was studied. It was found that HRBC hemolysis by EqT-II is the result of a colloid-osmotic shock caused by the opening of toxin-induced ionic pores. In fact, hemolysis can be prevented by osmotic protectants of adequate size. The functional radius of the lesion was estimated to be about 1.1 nm. EqT-II increased also the permeability of calcein-loaded lipid vesicles comprised of different phospholipids. The rate of permeabilization rised when sphingomyelin was introduced into the vesicles, but it was also a function of the pH of the medium, optimum activity being between pH 8 and 9; at pH 10 the toxin became markedly less potent. From the dose-dependence of the permeabilization it was inferred that EqT-II increases membrane permeability by forming oligomeric channels comprising several copies of the cytolysin monomer. The existence of such oligomers was directly demonstrated by chemical cross-linking. Addition of EqT-II to one side of a planar lipid membrane (PLM) increases the conductivity of the film in discrete steps of defined amplitude indicating the formation of cation-selective channels. The conductance of the channel is consistent with the estimated size of the lesion formed in HRBC. High pH and sphingomyelin promoted the interaction even in this system. Chemical modification of lysine residues or carboxyl groups of this protein changed the conductance, the ion selectivity and the current-voltage characteristic of the pore, suggesting that both these groups were present in its lumen.     

Construction of an ∼2 Mb contig in the region around 80 cM of Arabidopsis thaliana chromosome 2

A method for construction of bacterial artificial chromosome (BAC) contigs from a yeast artifical chromosome (YAC) physical map is described. An ∼2 Mb contig, consisting of two large BAC contigs linked by a small YAC, has been assembled in the region around 80 cM of Arabidopsis thaliana chromosome 2. Clones from this contig will facilitate gene isolation in the region and can be used directly as substrates for DNA sequencing.     

Variability of NPH Insulin Preparations

In 1968-69 certain juvenile diabetics receiving NPH insulin began having pre-breakfast glucosuria and mid-morning hypoglycemic reactions. A mail survey of our clinic population and a study done at the Quebec camp for diabetic children in 1969 revealed that certain lot numbers were associated with poor control and that a change to new lot numbers or alternate insulin preparations resulted in better control. “Suspect” insulin preparations and non-suspect insulins were given to newly diagnosed diabetics, and plasma insulin and glucose levels were measured over a 24-hour period. The data confirmed that the “suspect” insulins were causing early hypoglycemia and failing to control hyperglycemia during the latter hours of the 24-hour period. The lower glucose levels were associated with higher plasma insulin levels. The “suspect” insulins were further found to have elevated levels of free insulin in the supernatant fluid.The requirements for quality control of modified insulin preparations are reviewed and suggestions are offered for their improvement.     

Impacto del ejercicio físico en variables relacionadas con el bienestar emocional y funcional en adultos mayores

Background and aimThe benefits of the physical exercise in aging, and specially in frailty, have been associated with reduced risk of mortality, chronic disease, and cognitive and functional impairments. Multi-component training, which combines strength, endurance, balance, and gait training, represents the most beneficial kind of physical exercise in older adults.MethodsGiven the effectiveness of the multi-component training, a physical exercise program «Actívate» (based on the methodology Vivifrail), with the focus on «active aging», was conducted in the present study. Forty-nine older adults over 60 years participated in this program.ResultsThe physical exercise intervention led to a reduction in diastolic blood pressure, pain threshold and sleep disturbances (e. g. hypersomnia) (t ≥ 2.72, p < 0.01), as well as an increase of walking speed (t = 7.84, p ≤ 0.001). Further, quality of life factors (GENCAT scale), like emotional well-being, personal development, physical well-being, self-determination, and social inclusion, were greater after intervention (t ≥ ?2.06, p < 0.05).ConclusionsThese findings underline the benefits of multi-component training in functionality of older adults, and further, provide relevant aspects about the modulation of pain perception, sleep disturbances, social factors and physical and emotional well-being. Physical exercise programs such as «Actívate» should be promoted, in order to encourage healthy lifestyle habits, in the older adults’ population.     

Macrohistone Variants Preserve Cell Identity by Preventing the Gain of H3K4me2 during Reprogramming to Pluripotency

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Highlights? Macrohistone variants are regulated during reprogramming and differentiation ? The levels of macrohistone variants modulate the efficiency of reprogramming ? MacroH2A.1 occupies pluripotency and differentiation genes in keratinocytes ? MacroH2A.1 occupancy prevents the gain of H3K4me2 during reprogramming     

Spatially and temporally-restricted expression of two T-box genes during zebrafish embryogenesis

T-box genes are conserved in all animal species. We have identified two members of the T-box gene family from the zebrafish, Danio rerio. Zf-tbr1 and zf-tbx3 share high amino acid identity with human, murine, chick and Xenopus orthologs and are expressed in specific regions during zebrafish development.     

Molecular basis of left-right asymmetry

In vertebrates visceral asymmetry is conserved along the left-right axis within the body. Only a small percentage of randomization (situs ambiguus), or complete reversal (situs inversus) of normal internal organ position and structural asymmetry is found in humans. A breakdown in left-right asymmetry is occasionally associated with severe malformations of the organs, clearly indicating that the regulated asymmetric patterning could have an evolutionary advantage over allowing random placement of visceral organs. Genetic, molecular and cell transplantation experiments in humans, mice, zebrafish, chick and Xenopus have advanced our understanding of how initiation and establishment of left-right asymmetry occurs in the vertebrate embryo. In particular, the chick embryo has served as an extraordinary animal model to manipulate genes, cells and tissues. This chick model system has enabled us to reveal the genetic pathways that occur during left-right development. Indeed, genes with asymmetric expression domains have been identified and well characterized using the chick as a model system. The present review summarizes the molecular and experimental studies employed to gain a better understanding of left-right asymmetry pattern formation from the first split of symmetry in embryos, to the exhibition of asymmetric morphologies in organs.     

Triatoma infestans in Greater Buenos Aires, Argentina

The Health Administration Agencies of many municipalities in Greater Buenos Aires (GBA) receive frequent reports on triatomines in houses. The aim of this work was to identify and describe the dispersal foci of Triatoma infestans in an urban neighborhood of GBA, and contribute to the knowledge of the epidemiological situation in the region. In June 1998, potentially infested places were entomologically evaluated. T. infestans was only detected in a hen building for egg production, which housed approximately 6,000 birds. A total of 2,930 insects were collected. Density was about 9 triatomines/m(2). The proportions of fifth instar nymphs and adults were significantly higher than those of the other stages (p<0.001). The number of triatomines collected largely exceeded the highest domestic infestation found in one house from rural endemic areas of Argentina. Though triatomines were negative for Trypanosoma cruzi, they could acquire the parasite by coming in contact with infected people living in GBA. Besides, the numerous and widely distributed places housing hens and chickens, would favor the settlement of the vector. Together, both facts may constitute a risk of parasitic vectorial transmission. It is recommended to intensify systematic activities of vector search and case detection in GBA.     

Effect of a moderate intensity exercise training protocol on the metabolism of macrophages and lymphocytes of tumour-bearing rats

It is commonly accepted that moderate intensity exercise is beneficial to the immune system. We tested the influence of a moderate intensity training protocol (8 weeks) upon immune system function in Wistar tumour-bearing (TB) rats. The metabolism of glucose and glutamine in lymphocytes and macrophages was assessed, together with some functional parameters (hydrogen peroxide production and lymphocyte proliferative response). These substrates were chosen since they represent the most important energetic and synthetic metabolites for these cellular types. The training protocol caused a decrease of 17.4 per cent in the production of H(2)O(2) by macrophages, as well as a decrease in glucose consumption (25 per cent) and lactate production (47.1 per cent), and an increase in the production of labelled CO(2) from the oxidation of [U-(14)C]-glucose, in TB rats. The training protocol was also able to induce changes in the maximal activity of some key enzymes in the metabolism of glucose and glutamine, a reduction of hexokinase (68.8 per cent) activity and an increase in the activity of citrate synthase (10.1 per cent) in TB rats. The training protocol increased the proliferative response of lymphocytes cultivated in the absence of mitogens (75 per cent), of those cultivated in the presence of ConA (38.2 per cent) and in the presence of LPS (45.0 per cent). These cells also showed an increase in the maximal activity of some key enzymes of the glycolytic and glutaminolytic pathways. Our data demonstrated that the training protocol was able to induce an increase in aerobic utilisation of both substrates in lymphocytes and macrophages. The training protocol was also able to prevent several changes in glucose and glutamine metabolism that are normally present in sedentary TB rats. These changes in immune cell metabolism induced by the training protocol were able to increase TB rat survival.