Cutaneous Leishmaniasis in the Dorsal Skin of Hamsters: a Useful Model for the Screening of Antileishmanial Drugs

Traditionally, hamsters are experimentally inoculated in the snout or the footpad. However in these sites an ulcer not always occurs, measurement of lesion size is a hard procedure and animals show difficulty to eat, breathe and move because of the lesion. In order to optimize the hamster model for cutaneous leishmaniasis, young adult male and female golden hamsters (Mesocricetus auratus) were injected intradermally at the dorsal skin with 1 to 1.5 x l0⁷ promastigotes of Leishmania species and progression of subsequent lesions were evaluated for up to 16 weeks post infection. The golden hamster was selected because it is considered the adequate bio-model to evaluate drugs against Leishmania as they are susceptible to infection by different species. Cutaneous infection of hamsters results in chronic but controlled lesions, and a clinical evolution with signs similar to those observed in humans. Therefore, the establishment of the extent of infection by measuring the size of the lesion according to the area of indurations and ulcers is feasible. This approach has proven its versatility and easy management during inoculation, follow up and characterization of typical lesions (ulcers), application of treatments through different ways and obtaining of clinical samples after different treatments. By using this method the quality of animal life regarding locomotion, search for food and water, play and social activities is also preserved.     

Characterization of cellulases of fungal endophytes isolated from Espeletia spp.

Endophytes are microorganisms that asymptomatically invade plant tissues. They can stimulate plant growth and/or provide defense against pathogen attacks through the production of secondary metabolites. Most endophyte species are still unknown, and because they may have several applications, the study of their metabolic capabilities is essential. We characterized 100 endophytes isolated from Espeletia spp., a genus unique to the paramo ecosystem, an extreme environment in the Andean mountain range. We evaluated the cellulolytic potential of these endophytes on the saccharification of the oil palm empty fruit bunch (OPEFB). The total cellulolytic activity was measured for each endophyte on filter paper (FPA). In addition, the specific carboxymethyl cellulase (CMCase), exoglucanase, and β-glucosidase activities were determined. We found four fungi positive for cellulases. Of these fungi, Penicillium glabrum had the highest cellulolytic activity after partial purification, with maximal CMCase, exoglucanase and β-glucosidase enzyme activities of 44.5, 48.3, and 0.45 U/ml, respectively. Our data showed that the bioprospection of fungi and the characterization of their enzymes may facilitate the process of biofuel production.     

Persistent antibody and T cell responses induced by HIV-1 DNA vaccine delivered by electroporation

Intramuscular needle injection of HIV-1 DNA vaccines typically elicits weak immune responses in immunized individuals. To improve such responses, the immunogenicity of a vaccine consisting of electroporated DNA followed by intramuscular protein boost was evaluated in rabbits and macaques. In macaques, electroporation of low dose DNA encoding HIV-1 env followed by gp120 protein elicited Th1 cytokines and functional CTL that persisted for over 1 year. In both macaques and rabbits, robust anti-envelope antibodies, elicited by electroporated DNA, were augmented by gp120 protein and such responses neutralized sensitive SHIV isolates. These findings highlight efficient priming of immune responses by electroporated DNA that in conjunction with protein boost may give rise to long-term immunity in immunized hosts.     

A rabbit ventricular action potential model replicating cardiac dynamics at rapid heart rates

Mathematical modeling of the cardiac action potential has proven to be a powerful tool for illuminating various aspects of cardiac function, including cardiac arrhythmias. However, no currently available detailed action potential model accurately reproduces the dynamics of the cardiac action potential and intracellular calcium (Ca_i) cycling at rapid heart rates relevant to ventricular tachycardia and fibrillation. The aim of this study was to develop such a model. Using an existing rabbit ventricular action potential model, we modified the L-type calcium (Ca) current (I_Ca,L) and Ca_i cycling formulations based on new experimental patch-clamp data obtained in isolated rabbit ventricular myocytes, using the perforated patch configuration at 35-37°C. Incorporating a minimal seven-state Markovian model of I_Ca,L that reproduced Ca- and voltage-dependent kinetics in combination with our previously published dynamic Ca_i cycling model, the new model replicates experimentally observed action potential duration and Ca_i transient alternans at rapid heart rates, and accurately reproduces experimental action potential duration restitution curves obtained by either dynamic or S1S2 pacing.     

Effect of pluviosity and sun shine on sperm production and seminal characteristics of the fish Brycon henni (Pisces: Characidae)

Effect of pluviosity and sun shine on sperm production and seminal characteristics of the fish Brycon henni (Pisces: Characidae). In Colombia the fish Brycon henni is a protected endemic species. It inhabits water bodies in coffee producing areas (700-1900 ma.s.l.; 4 degrees 35'56" N - 74 degrees 04'51" W; 18-28 degrees C). Insufficient knowledge of its basic biology and behavior prevent the commercial culture of this promising fish. We studied the production and sperm physiology of captive males. Along a year 20 samples were taken from each of 10 males. The sample was obtained by abdominal cefalo-caudal massage and transported to the laboratory at 4 degrees C. Except for September and October (maximum rainfall), sperm was always obtained in at least 50% of the males. Color, osmolality and pH were similar in all the samples. Volume, concentration, viability, motility and activation time were variable: sunshine had a positive effect on volume (Spearman p < 0.05) and on sperm concentration (Spearman p < 0.05) while pluviosity had a negative effect on volume and viability. The proportion of ions (Na, K, Mg, Ca) was constant along the year; Na being 10-fold higher than K and 100-fold higher than Mg and Ca; however the absolute concentration of all ions was slightly higher in April and in July (with no apparent relation with the other variables analyzed).     

Susceptibility of Colombian Plasmodium falciparum isolates to 4-aminoquinolines and the definition of amodiaquine resistance in vitro

There are wide variations in the threshold used to define in vitro resistance of Plasmodium falciparum to amodiaquine (AQ), probably due to differences in methodology and interpretation. In vitro susceptibility data of Colombian P. falciparum strains to AQ and N-desethylamodiaquine is used to illustrate the need to standardized methodologies and compare inhibitory concentrations, instead of resistant/susceptible phenotypes, when studying the mechanisms of resistance to AQ and monitoring drug susceptibility trends in the field.