Slow freezing versus vitrification for the cryopreservation of zebrafish (Danio rerio) ovarian tissue.

The aim of the present study was to compare the efficiency of vitrification and slow freezing techniques for the cryopreservation of zebrafish ovarian tissue containing immature follicles. In Experiment 1, assessment of cell membrane integrity by trypan blue exclusion staining was used to select the best cryoprotectant solution for each cryopreservation method. Primary growth (PG) oocytes showed the best percentage of membrane integrity (63.5 ± 2.99%) when SF4 solution (2 M methanol + 0.1 M trehalose + 10% egg yolk solution) was employed. The vitrification solution, which presented the highest membrane integrity (V2; 1.5 M methanol + 5.5 M Me2SO + 0.5 M sucrose + 10% egg yolk solution) was selected for Experiment 2. Experiment 2 aimed to compare the vitrification and slow freezing techniques in the following parameters: morphology, oxidative stress, mitochondrial activity, and DNA damage. Frozen ovarian tissue showed higher ROS levels and lower mitochondrial activity than vitrified ovarian tissue. Ultrastructural observations of frozen PG oocytes showed rupture of the plasma membrane, loss of intracellular contents and a large number of damaged mitochondria, while vitrified PG oocytes had intact mitochondria and cell plasma membranes. We conclude that vitrification may be more effective than slow freezing for the cryopreservation of zebrafish ovarian tissue

Biochemistry in the High School Textbook: A Distance Between Content And Students Reality?

Several  contents  have  been  taught  in  a  decontextualized  way  within  the  area  of biology,  one  of  these  contents  is  Biochemistry.  Biochemistry  is  one  of  the  most present subjects in the student’s daily lives, because it can explain a huge number of  processes  that  happens  in  their  routine.  The  textbook  is  the  main  tool  in  the Brazilian  public  high  schools  classrooms,  so  a  huge  number  of  programs  to improve the textbooks were created by the government, like the National Program of the Textbook or PNLD( translated from the Portuguese ‘’Programa Nacional do Livro Didático’’). But despite the efforts to improve the textbook, their quality is still questionable, for such reasons like the distance between contents showed in the textbook and student’s reality. The main objective of this work is to evaluate how the  high  school  textbooks  show  the  content  related  to  biochemistry  and  how  this content is contextualized in the student’s reality.  To achieve this goal we analyzed four  textbooks  that  are  most  frequently  used  in  the  schools  today  and  evaluated parameters  related  with  contextualization  between  the  biochemistry  content  and students  daily  lives  situations.  The  analysis  was  done  on  a  qualitative  way.  We observed  a  lack  of  daily  examples  in  the  biochemical  contents,  an  excess  of scientific terms without clear explanations and also a huge presence of conceptual errors  in  all  four  textbooks.  The  data  showed  here  leads  us  to  conclude  that  the science’s textbooks analyzed in this study are inappropriate to teach biochemistry in an interesting way for the students