Early and late changes in Pax6 expression accompany eye degeneration during cavefish development.

We have compared Pax6 expression during embryonic development in the eyed surface form (surface fish) and several different eyeless cave forms (cavefish) of the teleost Astyanax mexicanus. Despite lacking functional eyes as adults, cavefish embryos form small optic primordia, which later arrest in development and show various degrees of eye degeneration. The pattern of Pax6 mRNA expression was modified early and late during cavefish development. In early surface fish embryos, two bilateral Pax6 expression domains are present in the anterior neural plate, which extend across the midline and fuse to form the forebrain and optic primordia. In cavefish embryos, these Pax6 domains are diminished in size and remain separated, resulting in an anterior gap in Pax6 expression and presumably the formation of smaller optic primordia. The anterior gap in Pax6 expression was confirmed by double staining for Pax6 and distalless-3 mRNA, which marks the anterior margin of the neural plate and is unaltered in cavefish. Similar anterior gaps in Pax6 expression occurred in independently derived cavefish populations, suggesting that they are important in eye degeneration. Later during surface fish development, Pax6 protein is expressed in the cornea, lens, and ganglion and amacrine cells of the neural retina. Pax6 expression was gradually reduced during cavefish lens development, concomitant with lens arrest and degeneration, and was absent in the corneal epithelium, which does not differentiate in cavefish. In contrast, Pax6 expression in the retinal ganglion and amarcine cells is unmodified in cavefish, despite retarded retinal development. The results suggest that changes in Pax6 expression are involved in the evolution of cavefish eye degeneration.

Myocardial protection of warm blood cardioplegic induction during cardiopulmonary bypass.

In his prospective randomized clinical study, we evaluated the myocardial protection of warm blood cardioplegic induction and cold blood cardioplegic induction, respectively, during cardiopulmonary bypass. Twenty-eight adult patients who underwent valve replacement were randomly divided into two groups: group T (14 cases) received cold (6-8 degrees C) blood cardioplegic induction after ECG showed straight line induced by warm (35-37 degrees C) blood cardioplegia; whereas, group C (14 cases) received cold blood cardioplegic induction only. The effects of myocardial protection of both cardioplegic inductions were evaluated by clinical outcomes, myocardial biochemistry index (cardiac troponin T, cTnT), and myocardial automorphology. The ratio of myocardial auto resuscitation was significantly higher in group T (93%) than that in group C (50%). Only one case in group T (7%) and three cases in group C (21%) needed temporary pacemakers. No case in group T (0%) and five cases (36%) in group C received dopamine. The postoperative mechanical ventilation time and ICU stay time of group T were shorter than those of group C. Myocardial biochemistry indexplasma level of cTnT in group T was lower than that of group C immediately and 6 h after cardiopulmonary bypass. Myocardial morphology-group T had comparably better outcomes than group C. We concluded that warm blood cardioplegic induction during cardiopulmonary bypass, compared with cold blood cardioplegic induction, provides better myocardial protection.