Rigoberto Oros-Pantoja

Nasal IgA secretion in a murine model of acute stress. The possible role of catecholamines.

Stress stimuli affect the immune system of the mucosa, and in particular IgA secretion. It is well documented that intense psychological and physical stress can increase susceptibility to infection by diverse pathogens in the upper respiratory tract. Our workgroup reported that chronic stress caused by immobilization elicits a decrease in nasal IgA levels in mice. Here, we explore how acute stress (caused by 4h of immobilization) affects IgA secretion in the nasal mucosa, and the possible role of the sympathetic nervous system in this effect. Nine-week-old male CD1 mice were divided into four groups: control, chemical sympathectomy (with 6-OHDA) and treatment with nadolol (5mg/kg) or phentolamine (15mg/kg). All these groups were subdivided into stressed and unstressed animals. The parameters evaluated included plasma corticosterone and epinephrine (only in control groups), SIgA levels (by ELISA) and SIgA expression (by Western Blot) in nasal fluid, percentage of IgA+ plasma cells, and mRNA expression of heavy alpha chain, pIgR, TNFα and TGFβ in nasal mucosa. Acute stress reduced the percentage of IgA+ cells while increasing the levels of IgA, the two hormones, and the mRNA expression of heavy alpha chain, pIgR, TNFα and TGFβ, which resulted in greater synthesis and transport of IgA. The treatments with 6-OHDA and α- and β-adrenergic receptor blockers suggest that sympathetic innervation by both types of adrenergic receptors is important for the control of SIgA secretion in nasal mucosa during acute stress. The increase in this parameter depended on the cytokines involved in IgA synthesis and transport.

New track-structure Monte Carlo code for 4D ionizing photon transport

ABSTRACT Radiodiagnosis and radiation treatment, in each of their areas such as imaging, radiotherapy and nuclear medicine, require precise calculations about the energy deposited and scattering of the ionizing radiation used. In healthcare applications, it is required to know the penetration and amount of energy deposited in the biological tissue irradiated by ionizing photons; these parameters are function of the photon interaction processes with matter, which can be analyzed experimentally or by Monte Carlo simulation. Purpose: The aim of this work was to develop a new Monte Carlo code for ionizing photon transport in water with the track structure technique, that allows to discriminate primary and secondary photons, and to determine the energy deposited, interaction coordinates, path length and time of flight (TOF) inside of scatter volume. Methods: C++ programming language was used. In the Compton scattering, the polar angle was sampled by methods: Kahn and EGS. Water spheres centered at the origin with different radius were used, where the isotropic point source was placed at (0, 0, 0) for different energies to compute the energy lost by photons and TOF inside spherical volume. Results: It was determined that the best sampling method for the polar angle generation in each Compton interaction was the EGS method. Energy deposited in target region filled with water was compared with MCNPX 2.6 and others’ results from literature. Mean TOF and pathlength inside region of interest was obtained for 4 radii and 5 energies. Conclusions: Quantities computed with the new code are, according to reported data, and so, the new code is reliable for photon transport in water using the track structure method; this will allow the new code to become a useful tool in the areas of radiology and radiation dosimetry. Also, TOF inside scatter volume was reported.

Effects of astaxanthin in mice acutely infected with Trypanosoma cruzi

During Trypanosoma cruzi infection, oxidative stress is considered a contributing factor for dilated cardiomyopathy development. In this study, the effects of astaxanthin (ASTX) were evaluated as an alternative drug treatment for Chagas disease in a mouse model during the acute infection phase, given its anti-inflammatory, immunomodulating, and anti-oxidative properties. ASTX was tested in vitro in parasites grown axenically and in co-culture with Vero cells. In vivo tests were performed in BALB/c mice (4–6 weeks old) infected with Trypanosoma cruzi and supplemented with ASTX (10 mg/kg/day) and/or nifurtimox (NFMX; 100 mg/kg/day). Results show that ASTX has some detrimental effects on axenically cultured parasites, but not when cultured with mammalian cell monolayers. In vivo, ASTX did not have any therapeutic value against acute Trypanosoma cruzi infection, used either alone or in combination with NFMX. Infected animals treated with NFMX or ASTX/NFMX survived the experimental period (60 days), while infected animals treated only with ASTX died before day 30 post-infection. ASTX did not show any effect on the control of parasitemia; however, it was associated with an increment in focal heart lymphoplasmacytic infiltration, a reduced number of amastigote nests in cardiac tissue, and less hyperplasic spleen follicles when compared to control groups. Unexpectedly, ASTX showed a negative effect in infected animals co-treated with NFMX. An increment in parasitemia duration was observed, possibly due to ASTX blocking of free radicals, an anti-parasitic mechanism of NFMX. In conclusion, astaxanthin is not recommended during the acute phase of Chagas disease, either alone or in combination with nifurtimox.

67Ga as a biosensor of iron needs in different organs: Study performed on male and female rats subjected to iron deficiency and exercise

The aim of the present study was to determine the iron needs in different organs and tissues using 67Ga as a biosensor in males and females rats subjected to iron deficiency (ID) and voluntary exercise (EX). 67Ga citrate was injected i.p. to female and male Wistar rats (n=5/sex/group). Groups: Control (sedentary conditions), Control+EX, ID and ID+EX. To determine the 67Ga uptake, samples from the following regions of interest (ROIs) were extracted 12h post-injection: blood, liver, gonads, bone marrow, heart, adrenal glands, skeletal muscle, stomach, kidney, eyeball, sciatic nerve, small intestine and peritoneum. The total 67Ga uptake was 412% higher in ID subjects than in control subjects, being 1011% higher in ID-males than ID-females. In ID-females, the ROIs with the greater 67Ga uptake were blood, kidney and bone marrow, while in ID-males they were sciatic nerve, eyeball and adrenals, which demonstrates that the biodistribution differed between sexes in sedentary conditions but when subjected to EX, the biodistribution was similar in each sex group although females had a greater 67Ga uptake. In ID+EX subjects, the ROIs that showed the highest uptake were sciatic nerve, eyeball and adrenal glands. Using 67Ga as a biosensor, it is possible to identify the needs of iron that each organ requires to perform their functions in normal physiological conditions. In addition, a higher or lower 67Ga uptake in a specific organ may indicate its malfunction or show damage.