MEDICAL AND MOLECULAR BIOLOGY
Microscopes are optical devices which allow observation of objects of microscopic size (less than 70µm) and which are invisible for human eye. The main information about types and design of microscopes, as well as about principles of work and the use of microscopic techniques in the biomedical disciplines. The first microscope was probably constructed in 1590 by Dutch sunglasses manufacturer Zacharias Jansen. Another pioneer of microscopy was Robert Hook, who described the construction of microscope with separated objective, eyepiece and a source of light in his book “Micrographic” (1665). He observed and depicts several organisms – e.g. fungi, mosses and small insects. Moreover, he introduced a biological term – cell (cellular). A simple microscope was also designed and constructed in 1676 by Antoine van Leeuwenhoek. He was able to observe many micro-organisms, as well as blood cells, sperm and muscle fibers. During the next two centuries, microscopes and microscopic techniques improved. The mass production of microscopes was initiated by the German company Carl Zeiss in 1847. Another significant milestone of microscopy was construction of first electron microscope in 1933. Recently, microscopes belong to standard laboratory equipment in the biomedicine.
Stereomicroscopes, also called dissecting microscopes belong to two light microscopes which focus on the same point from slightly different angles. This allows the specimen to be observed in three dimensions. Stereomicroscopes are relatively low power compared with light microscopes – useful magnification is usually below 100 times. They can have a single fixed magnification, several discrete magnifications, or a zoom magnification system. Working distance is much longer than with a typical microscope as well. It allows work to be done on the specimen while it is being observed through the microscope. Stereomicroscopes are usually used in diagnostics (e.g. in gynecology) and for various types of surgery (e.g. in neurosurgery, vascular surgery, ophthalmology and otolaryngology).
Permanent slides allow detailed observation of cell morphology. The preparation of permanent slides consists from fixation and following staining of cells or tissue slices. Fixation terminates any ongoing living and autolytic biochemical processes in cells. Chemical or physical fixation is possible. During a physical fixation, used mostly for smears and touch preparations, biological sample is heated and dried at laboratory temperature or above a burner flame. Chemical fixation requires a liquid chemical fixative (e.g. formol, methanol, ethanol etc.). Fixation is followed by staining in different types of solutions which is based on affinity interactions between cell structures and stain components. They are informative (e.g. Nile Blue) or specific stains (e.g. Giemsa stain for chromatin visualization). Some dyes have both fixative and staining effect (e.g. Lugol’s solution, orcein).
Journal of Biochemistry & Biotechnology