A new method for comparative light and electron microscopic studies of individual cells, selected in the living state

A simple and efficient method for preparation of isolated ovarian follicles for transmission electron microscopy

OBJECTIVE

A simple method for preparation of isolated ovarian follicles for transmission electron microscopy (TEM) using transwell inserts is described.

MATERIALS AND METHODS

Pre-antral follicles were enzymatically isolated from mouse ovaries and cultured overnight on transwell insert polyester membranes. The following day, isolated ovarian follicles were processed for TEM by moving the transwell insert through successive wells containing the fixation and embedding reagents. After polymerization of the resin, the polyester membrane with the follicles embedded in the resin was disengaged from the transwell unit. The resin was sectioned. Semi-thin sections were stained with toluidine blue while ultra-thin sections were stained by uranyl acetate and examined by light microscopy and TEM, respectively.

RESULTS

Isolated ovarian follicles were easily processed in groups for TEM. Follicles were well embedded and there appeared to be no loss of tissue during processing. The ultra-structure of processed isolated ovarian follicles was well preserved with little evidence of processing artifacts.

CONCLUSIONS

In situ processing and preparation of isolated ovarian follicles by first allowing attachment on transwell insert membranes was shown to be a simple, rapid and effective method for TEM.

A simple and cheap method for removing glass coverslips from neuronal cultures and relocating identified cells

A simple and cheap method is described for removing glass coverslips from neuronal cultures grown on collagen and embedded into Epoxy resins for electron microscopy. The method involves scoring the coverslip with a scalpel and rubbing an ice block over the scored coverslip. A thin film of water then runs between the glass and the resin, which expands during cooling and causes the coverslip to spring away. This method is superior to the application of liquid nitrogen, which often causes damage of the embedded tissue.

A procedure for selecting specific areas of sections for comparative light and electron microscopic studies

The paper describes a method which enables correlative light and electron microscopical studies to be made of specific tissue structures or of individual cells. For this purpose a new specimen marker has been constructed. The device, which is attached to the objective of a light microscope, permits the operator to examine and exactly encircle the selected area without changing the objective. The technique is illustrated by two examples using immunoelectronmicroscopy.

Concerning the nature of the cryosectioning process

Intentional melting of frozen-thin-sections induces ultrastructural alterations. Cross sections through frozen dried and embedded cryosections revealed that even at the surface of such a section no melting artefacts are visible. One surface of the cryosection (obtained at 168 K) has a saw-teeth appearance whereas the other surface is rather smooth. The rate of freeze-drying in the cryochamber of the microtome was estimated to be in order 3.3 nm/min at 183 K and 22.5 nm/min at 193 K for sections, about 120 nm thick, of rat kidney frozen in freon 22 without any chemical fixation of cryoprotection. Although freeze-drying will normally not interfere with the cryo-sectioning process itself, it is a process which cannot be neglected during handling of sections. The available evidence indicated that frozen-thin-sections represent the frozen tissue with respect to the ultrastructure an probably also with respect to the chemical composition.

A teflon culture and embedding device for the study of cells by light and electron microscopy

A method is described which permits continuous light microscopic observation of cell cultures under sterile conditions. Moreover, cells or groups of cells selected in such cultures may be processed for electron microscopy, without disturbance of possible cellular interactions, in such a way that these selected cells may be observed in the electron microscope. The method is based on the use of a transparent Teflon film in culture chambers.

Vertical plane serial sectioning of identified tissue culture cells

Identifying marks can be made around specific cells on the culture surface of plastic tissue culture dishes. When the cultures are embedded in situ and the plastic dish is split away, the marks are reproduced around the cells. The marks permit trimming and complete serial sectioning of specific cells in the vertical plane.

Autoradiographic detection of mucopolysaccharide accumulation in single fibroblasts

A method is described for localizing acid mucopolysaccharides autoradiographically in cultured cells. Normal fibroblasts and fibroblasts, from patients suffering from Mucopolysaccharidosis II disease (MPS II), were cultured for six days in the presence of 35SO4 and one day in unlabelled medium. The cultured cells were transferred to plastic film dish and, after settling, they were rapidly quenched, freeze-dried, fixed in osmium tetroxide vapour and embedded in Epon. Grain counting after autoradiography in 2 mum sections revealed a significant difference (P greater than 0.001) in 35SO4 incorporation in the perinuclear cytoplasm of MPS II cells and control cells grown under the same conditions. Autoradiography was also performed after mixing MPS II cells and control fibroblasts in a ratio 1:1-8 prior to freezing and the same ratio was found between labelled and unlabelled fibroblasts. These results demonstrate the feasibility of the present autoradiographic technique for the detection of the acid mucopolysaccharide storage at the single cell level.