A refined model on flow and oxygen consumption in the human cornea depending on the oxygen tension at the interface cornea/post lens tear film during contact lens wear.

The study of oxygen consumption rate under" in vivo" human cornea during contact lens wear has been technically a challenge and several attempts have been made in the last 20 years to model the physiology of the human cornea during contact lens wear. Unfortunately, some of these models, based on a constant corneal oxygen consumption rate, produce areas on the cornea where the oxygen tension is negative, which has no physical sense. In order to avoid such inconsistency, different researchers have developed alternative models of oxygen consumption, which predict the likely oxygen metrics available at the interface cornea/post lens tear film by determination of oxygen flux, oxygen consumption, and oxygen tension through the different layers (endothelium, stroma, and epithelium). Although oxygen deficiency produces corneal edema, corneal swelling, hypoxia, acidosis, and other abnormalities, the estimation of the oxygen distribution below the impact of a contact lens wear is interesting to know which lens transmissibility was adequate to maintain the cornea and avoid epithelial and stromal anoxia. The estimation of minimum transmissibility for a lens for extended wear applications will be very useful for both clinicians and manufacturers. The aim of this work is to present a complete discussion based on Monod kinetics model that permits give an estimation of oxygen partial pressure distribution, the profile distribution of corneal flux and oxygen consumption rate, and finally the estimation of the relaxation mechanism of the cornea depending on the oxygen tension at the interface cornea/post lens tear film. Relaxation time in this context can quantify the capability of the corneal tissue to adapt to increasing concentrations of oxygen. It is proposed this parameter as a biological meaningful indicator of the interaction between contact lens polymers and living tissues such as the corneal cellular layer.

Cambios morfológicos, proteicos, glicoproteicos y antigénicos de Trypanosoma cruzi cultivado en medio axénico con tensiones de oxígeno diferentes / Morphological, protein, glycoprotein and antigenic changes of Trypanosoma cruzi cultured in axenic medium with different oxygen tensions

Se ha reportado cultivo axénico de amastigotas de Trypanosoma cruzi derivados de epimastigotas. Se cuestiona si formas redondas en cultivos axénicos son verdaderos amastigotas. Aquí se compararon los cambios biológicos y moleculares de epimastigotas creciendo en alta y baja tensión de oxígeno. T. cruzi (EPm6) se creció en frascos con diferentes alturas de medio LITB (condición horizontal 3 mm y vertical 83 mm). Se colectaron masas de parásitos de diferentes tiempos de crecimiento para análisis proteico, glicoproteico y antigénico. Se estudiaron los cambios morfológicos, incremento de inóculo y resistencia al complemento por microscopia de fases y tinción con Giemsa. Los cambios proteicos y glicoproteicos se compararon por SDS-PAGE. Los cambios antigénicos se analizaron por Western blot con suero de conejo y anticuerpos IgY contra formas amastigotas. En condición vertical, los epimastigotas mantuvieron su morfología típica a lo largo de la curva de crecimiento y no mostraron cambios moleculares significativos. En condición horizontal al 4to y 6to día predominaron formas redondas con capacidad de resistir la lisis por complemento. A partir del 4to día se observaron cambios en los perfiles proteicos y glicoproteicos, concomitantemente con los cambios morfológicos. El suero anti-amastigotas reveló un antígeno amastigota-específico transitorio de 55 kDa en parásitos de 4 días en la condición horizontal, mientras el anticuerpo IgY anti-amastigotas no reveló diferencias entre parásitos creciendo en ambas condiciones. Estas evidencias sugieren que epimastigotas de T. cruzi condicionados a sobrevivir en alta tensión de oxígeno puede mimetizar propiedades biológicas y antigénicas propias del estadio amastigota.

Axenic culture of epimastigote-derived amastigotes of Trypanosoma cruzi has been reported. Have been inquired why round forms appear in culture media and if are true amastigotes. Our proposal was study molecular and biological changes in epimastigotes growing in high and low oxygen tension. T. cruzi (EPm6) were grown in flasks with different height of LITB medium (horizontal condition 3 mm and vertical 83 mm). Parasites were collected masses of different times of growth for proteins, glycoproteins and antigenic analysis. Morphological changes, increase of inoculum and resistance to complement lyses were studied in phase’s microscopy and Giemsa-stained smears. Protein and glycoprotein changes were compared by SDS-PAGE. Antigenic changes were analyzed by Western blot with rabbit serum and IgY antibody against amastigote forms. In vertical condition, the epimastigote maintained its typical morphology along the growth curve and not showed significant molecular changes. In horizontal condition round forms prevailed at 4 and 6 days with capacity to resist lyses by complement. From the 4th day changes in proteins and glycoproteins profiles were observed, concomitantly with the morphological changes. Anti-amastigotes serum revealed a 55 kDa transitory amastigote-specific antigen in four day parasites’ from horizontal condition, while IgY antibody anti-amastigotes don’t revealed differences between parasites grown in both conditions. These evidences suggest that epimastigotes of T. cruzi conditioned to survive in high oxygen tension can mimic biological and antigenic properties own the amastigote-stage.