Clearing agents are among the most noxious and hazardous chemicals in histology laboratories. Despite its hazards, Xylene has probably been the most commonly used chemical in the histology laboratory. There have been several laboratory tests to replace xylene as a clearing agent. Still, in some cases, most commercially available substitutes are less effective, more expensive, slightly biodegradable, and not readily available. The present study was aimed at evaluating the clearing and dewaxing effect of Eucalyptus (citrodora oil) and Xylene during histological and histochemical tissue processing and staining of some selected organs of adult Wistar rats. Citrodora oil was used alongside xylene to clear adult Wistar rats’ livers, kidneys, brains, and testicular tissues. The Citrodora oil was extracted from the leaves of eucalyptus plants by hydro distillation method. The oil’s physical properties, phytochemical, Gas Chromatography-Mass Spectroscopy (GC-MS) and Nuclear Magnetic resonance studies were carried out using standard procedures. The tissues were also histologically processed using the standard method. The results showed that Citrodora oil was pale yellow in color. The Citrodora oil and xylene densities were 0.80 g/ml and 0.84 g/ml, respectively. The viscosity of the Citrodora oil was 0.34cp, and that for xylene was 0.45cp. The flash point of Citrodorawas at 350C, while that of xylene was 390C. The refractive indexes ofCitrodora oil and xylene were 1.46 and 1.50, respectively. The GC-MS results of Citrodora oil show that the predominant constituent in Citrodora oil is citronellal, with a relative abundance of 42.20%, followed by β- Citronellol (21.71%). Xylene contains 94% o-xylene, 97% p-xylene, 98% m-xylene and 98%p-xylene. The nuclear magnetic resonance showed that all the chemical shifts are positive to the reference and are mainly triglycerides. Histological, histochemical and immunohistochemical observation showed that the section quality and the cytoplasmic and nuclear staining qualities appeared to give good contrast in Citrodora oil when compared with xylene.
There were statistically significant differences (p≥0.05)in the section quality and staining ability of the liver, kidney, brain and testicular tissues of Wistar rats cleared in Citrodora oil and Xylene compared. This study concludes that Citrodora oil can clear and dewax Wistar rat tissues during tissue and staining processes for histological, histochemical and immunohistochemical tissue processing and staining as xylene.
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