Unfixed tissue for electron immunocytochemistry: a simple preparation method for colloidal gold localization of sensitive epitopes using ethanediol dehydration

Immunogold localization of TGF beta 1 protein and mRNA in human skin using a colloidal gold/digoxygenin system

Tissue preservation, and immunogold cytochemical and in-situ hybridization labelling intensities vary according to the preparatory protocols used. We wished to determine which preparative protocols produce optimal preservation, protein and mRNA labelling. Nine combinations of fixative and embedding resin were therefore studied using postembedding immunoelectron microscopy and a novel immunogold digoxygenin in situ hybridization (ISH) system, to quantitate the presence of transforming growth factor beta 1 (TGF beta 1) protein and message in human skin. The best preservation was observed in tissue fixed in 1% glutaraldehyde and embedded in LR White resin or low acid glycolmethacrylate resin (LA-GMA). Preservation was poor in tissue fixed with 1% glutaraldehyde and fair in 4% paraformaldeyde, when embedded in Unicryl. Ethanediol dehydration coupled with LA-GMA embedding resulted in reasonable preservation. Based on quantitative measures of the labelling density for TGF beta 1 protein and mRNA, immunogold labelling was adequate with 1% glutaraldehyde fixation coupled with LR White or LA-GMA resins, and also with 4% paraformaldehyde and LR White resin, but was best with ethanediol dehydration and LA-GMA embedding. ISH labelling under basal conditions was best in LA-GMA with 1% glutaraldehyde or 4% paraformaldehyde. The ISH label in tissue fixed with 1% glutaraldehyde and embedded in LA-GMA was significantly increased by treatment with proteinase K. Overall, ethanediol dehydration was associated with a good immunoelectron microscopic (IEM) label while LA-GMA with 1% glutaraldehyde or 4% paraformaldehyde resulted in a consistently detectable ISH label. LA-GMA embedding with 1% glutaraldehyde fixation gave a good result with both IEM and ISH labelling.

The determination of comparable labeling densities in quantitative immunoelectron microscopic double labeling studies

In quantitative ultrastructural studies using colloidal gold immunocytochemical techniques, labeling intensities vary according to the size of the probe used. Using postembedded indirect two-sided double labeling and single labeling protocols, the labeling characteristics of four antigens were studied using two probe sizes commonly used in double labeling studies. It was determined that the labeling intensity variation resulting from the use of different probe sizes was unpredictable after correcting for the increased probe size alone. It was possible, however, to obtain comparable labeling densities by first determining the labeling intensities for each probe size with its antigen in single label studies on serial sections and using the same procedure as the double labeling studies. A probe size correction factor for each antigen was calculated from these data. This factor was used to obtain comparable measurements of the relative abundance of each label.

Role of chondroitin sulfate glycosaminoglycans in mineralizing osteoblast-like cells: effects of hormonal manipulation

A monoclonal anti-chondroitin sulfate antibody (CS-56) that recognizes native chondroitin sulfate glycosaminoglycans (CSGAG) was used to quantify changes in CSGAG labeling levels in mineralizing human fetal osteoblast-like cell multilayers up to 40 days postconfluence. In control cultures, mean labeling of CSGAG increased in nonmineralized areas from around eight gold probes per micron 2 (gpm) at 20 days to 26 gpm at 40 days. Labeling was markedly increased in the mineralized tissue, to 560 gpm at 30 days and 580 gpm at 40 days. In beta-glycerophosphate-treated cultures, the mineralized areas were increased and appeared earlier (20 days) than in the control cultures. In these cultures, mean CSGASG labeling increased in nonmineralized areas from around 5 gpm at 20 days to 26 gpm at 30 days and was further increased in mineralized areas to 270 gpm at 20 days and 298 gpm at 30 days. Mineralization was not noted in cultures treated with 10(-8) M 1,25-dihydroxyvitamin D, and CSGAG labeling remained low (< 5 gpm) during the study period. These results indicate that an increase in immunoreactive CSGAG is associated with mineralization in this culture system. One possible interpretation of these findings is that proteoglycan molecules or at least their CSGAG side chains may be involved in the mineralization process.

Use of frozen biologic material for combined light and electron microscopy

A simple and rapid method that enables the use of unfixed frozen material for light and electron microscopic purposes is described. At the light microscopic (LM) level, unfixed cryostat sections were used for enzyme histochemistry. When electron microscopic (EM) inspection was needed, tissue blocks, which were stored at -80 degrees C, were fixed at 4 degrees C and prepared for EM according to standard procedures. Ultrastructural analysis of this material demonstrated that most morphologic aspects of normal (human pancreas and rat liver) and pathologic (human pancreatic adenocarcinoma and rat colon carcinoma metastases in liver) tissue were rather well retained. Cryostat sectioning at -25 degrees C did not appear to have damaging effects on the morphology. The method was applied to correlate enzyme histochemical (LM) data with ultrastructural (EM) aspects of mineralization of stroma in explants of human pancreatic adenocarcinoma grown in nude mice and of nonparenchymal cells around metastases of colon carcinoma in rat liver.