The effects of mercaptoethanol-formaldehyde on tissue fixation and protein retention.
The study compared the effects of mercaptoethanol-formaldehyde and formaldehyde alone, on tissue fixation and protein retention in human and mouse tissues. Shrinkage of tissues and the penetration rate of the fixatives were assessed. The cross-linking ability of the fixatives was determined by viscometry, sodium dodecyl sulphate-polyacrylamide gel electrophoresis, and spectrophotometry, using bovine serum albumin and human haemoglobin. Tissues fixed in buffered 0.0025% mercaptoethanol-4% formaldehyde showed good nuclear and cytoplasmic detail, better than those fixed in buffered 4% formaldehyde. There was no significant difference in shrinkage. A mixture of 0.0025% mercaptoethanol-4% formaldehyde penetrated faster into adult liver than 4% formaldehyde. The mean penetration rate (+/-SE) or coefficient of diffusibility of 0.0025% mercaptoethanol-4% formaldehyde into adult liver was 1.32 +/- 0.01 and that of 4% formaldehyde was 1.12 +/- 0.06 (p < 0.04). Both fixatives diffused more rapidly into mouse liver than into human liver. The cross-linking ability of mercaptoethanol-formaldehyde depends on the concentration of the fixative and the time of fixation. Bovine serum albumin (15%) and 0.1% mercaptoethanol alone formed a gel, whilst electrophoresis showed monomers in the supernatant. Mercaptoethanol (0.1%) also rapidly decreased the absorption at 420 nm, suggesting denaturation. It seems that mercaptoethanol increases the number of thiol groups available to form cross-links with formaldehyde. This study demonstrated that mercaptoethanol-formaldehyde fixed and cross-linked tissues better than formaldehyde at 3 h and 4 h, but not at 1 h and 2 h. The most effective concentration of mercaptoethanol for tissue fixation in 4% formaldehyde is 0.0025%.
Durgun-Yücel
B
B
Department of Anatomy, Faculty of Medicine, Cukurova University, Balcah, Adana, Turkey.
Hopwood
D
D
Yücel
A H
AH
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D005404:Fixatives / Q000737:chemistry*; D005557:Formaldehyde / Q000737:chemistry*; D006801:Humans; D008623:Mercaptoethanol / Q000737:chemistry*; D051379:Mice; D011506:Proteins / Q000187:drug effects* / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D016707:Tissue Fixation / Q000379:methods*; D014783:Viscosity
D005404:Fixatives; D011506:Proteins; D005557:Formaldehyde; D008623:Mercaptoethanol