Evaluation of the Effects of Aqueous Extract of Psidium Guajava Leaves on Lead Acetate-induced Neurotoxicity in Adult Wistar Rats
CHAPTER ONE
Aim of the study
The aim of the study was to evaluate the effects of aqueous extract of Psidium guajava leaves on lead induced changes in brain tissues mainly cerebellum, cerebrum and hippocampus, behaviour, biochemical and haematological parameters of adult Wistar rats.
Objectives of the study
The objectives of the study were to:
- Evaluate the effects of Psidium guajava aqueous leaves extract on lead induced changes in spatial learning, memory and motor coordination in adult Wistar
- Study the effects of the extract on lead induced alterations in haematological and biochemical parameters of adult Wistar
- Determine the effects of the extract on lead induced changes in brain tissues mainly cerebellum, cerebrum and hippocampus of adult Wistar
CHAPTER TWO LITERATURE REVIEW
FORMS IN WHICH LEAD EXIST
Lead is a poisonous metal which occurs in both inorganic and organic forms (Shalan et al., 2005). Inorganic lead is the form of lead found in old paint, soil, dust and various consumer products. The colour varies, depending on the chemical form, and the most common forms are white lead (a lead carbonate compound), yellow lead (lead chromate, lead monoxide) or red lead (lead tetraoxide) and lead acetate has a sweetish taste (WHO, 2010).
Organic leads are tetra-ethyl lead and are used in leaded gasoline. Organic forms of lead are extremely dangerous, as they are absorbed through the skin and are highly toxic to the brain and central nervous system. Organic lead can be more toxic than inorganic lead (WHO, 2010) because the body more readily absorbs it and as such potential exposures to organic lead should be taken very seriously (Shalan et al., 2005).
CHAPTER THREE MATERIALS AND METHODS
MATERIALS
Materials used in the study included the followings; experimental animals, lead acetate, fresh leaves of Psidium guajava, digital weighing balance, cages, water bottles, dissecting set, orogastric tubes, beakers, syringes, plastic pipette, glass slides, normal saline, etc.
CHAPTER FOUR RESULTS
GENERAL OBSERVATION
Physical changes in the Rats
There were no visible physical changes observed in the Control Group (Group 1) and Group 2 after administration of distilled water and extract, respectively, all the rats were very active. Scratching of the nose was observed in rats from Groups 3, 4, 5 6 and 7 immediately after administration of lead acetate from the1st to the 3rd weeks of the experiment. Five hours after administration, there were restlessness, reduction in physical activities, gnawing, exophthalmus, frequent urination and watery faeces in the rats administered with lead acetate.
CHAPTER FIVE
DISCUSSION
HISTOPATHOLOGY
The present study has shown that lead acetate induced neuronal degeneration in the Purkinje cell layer at various stages. The cerebellar degeneration in lead exposed rats resulted to decrease in number of the Purkinje cells in Purkinje cell layer. These could have caused the observed interference with the motor activity such as loss of movement, grasping, maintenance of equilibrium and regulation of muscle tone which are modulated by the spinal cord and brain stem mechanism involved in postural control. Sohair et al. (2010), had similarly reported marked degeneration due to chronic lead exposure at prenatal period and loss of Purkinje neurons in the adult cerebellum evidenced by decrease in the number of neurons. Such degeneration of Purkinje cells is a common feature of lead exposure (Xu et al., 2005; Villeda et al., 2006; Macauley et al., 2008). The degeneration was characterized by abnormal mitochondria with rarified matrix and ill- defined cristae in the cytoplasm of Purkinje neurons of lead exposed rats (Sohair et al., 2010), which were earlier speculated to have been due to inhibition of mitochondrial oxidative activity (Michaelson and Sauerhoff, 1974). Mitochondria are important organelles for energy production within a neuron and any change in their function may damage the cells. Thus, chronic mitochondrial alterations in cerebellum could be involved in the occurrence of depression in rats (Rezin et al., 2008).
CHAPTER SIX
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
From the observations in the present study, we concluded that:
- The present study observed that there were deficits in Spatial learning, memory and motor activities in adult Wistar rats exposed to lead
- Lead acetate induced oxidative stress and changes in haematological indices in adult Wistar rats.
- There were histological changes in hippocampus, cerebellar and cerebral cortices of adult Wistar rats exposed to lead
- The study has shown that aqueous extract of Psidium guajava leaves ameliorated the changes induced by lead acetate in behaviour, oxidative stress markers, haematological indices and histopathological in adults Wistar rats.
- Thus, aqueous extract of Psidium guajava leaves may be useful therapy in lead exposed patients, especially in lead poisoning endemicarea
RECOMMENDATIONS
From the present study, we recommended that:
- The consumption of Psidium guajava leaves should be encouraged especially the population who may be exposed to increased risk of lead
- The actual underlying mechanism of Psidium guajava leaves extract in neuropathology is still unclear and further research
- Further study should be carried out using immunohistochemical methods to elucidate the deposits of lead in respective tissues of the brains exposed animals treated with Psidium guajava leaves Phytochemical analysis of Psidium guajava leaves needs to be done
- Fractionating the extract and using the various fractions so as to determine the mechanism involved in its amelioration.
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