Browsing by Author "Tolessa, Tesfaye"

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    Evaluation of In Vivo Antihypertensive and Ex Vivo V asodepressor Activities of the Seed Extract of Calpurnia aurea (Ait.) Benth.subsp. aurea (Fabaceae)
    (Addis Ababa University, 2014-03) Getiye, Yohannes; Engidawork, Ephrem (PhD); Tolessa, Tesfaye
    Being the most important modifiable risk factor for stroke, renal, vascular and heart diseases; hypertension is still one of the leading causes of disability, morbidity and mortality among the populace worldwide. Consequently, the continued search for alternative antihypertensive agents of natural origin, with fewer side effects but greater effectiveness, necessitated evaluation of Calpurnia aurea for possible antihypertensive potential. In this study, the antihypertensive property of hydro-alcoholic seed extract of Calpurnia aurea was assessed using in vivo and ex vivo techniques. The in vivo antihypertensive efficacy of the crude extracts was evaluated in normotensive and 2K1C rat model of hypertension. The crude extract caused a significant fall in systolic blood pressure (SBP), diastolic blood pressure (DBP)and mean arterial blood pressure (MABP) at the doses of 15, 30 and 45 mg/kg in normotensive anaesthetized rats (p < 0.05, p < 0.01, p< 0.001).The effect on DBP was greater than SBP. In the same manner with the normotensive study, the BP fell dose-dependently and significantly in renal hypertensive rats, induced by renal ischemia. The extract produced 15.4% (p< 0.05), 26.9% (p< 0.01), 33.2% (p <0.01) reduction in SBP at the respective doses of 15, 30 and 45 mg/kg. Similar to the normotensive result, higher DBP effect was observed; 15.1% (p< 0.05), 30.2% (p< 0.01), 36.1% (p <0.01) fall from the control value at the above mentioned doses. Regarding MABP; 15.2% (p< 0.05), 28.8% (p <0.01) and 34.9% (p <0.01) reduction was noted with 15 mg/kg, 30 mg/kg and 45 mg/kg doses of the extract, respectively. The extract also caused a dose-dependent relaxation of guinea pig aorta precontracted with KCl (80mM),at a concentration of 5–250 mg/mL, with a maximum relaxation of 92.1±0.72% (p < 0.001) achieved at 250 mg/mL concentration. The relaxation mechanism was found to be independent of the endothelium system, muscarinic iv receptors, histamine receptors, ATP dependent K+ channels, cyclooxygenase enzymes and cGMP/NO pathway. The relaxation may be correlated with the effect on calcium ion channels, as it shifted the Ca2+ dose response curve (p< 0.05, p< 0.01 and p< 0.001) to the right with suppression of the maximum effect by 37.4% (p < 0.001). In conclusion, the findings suggest that the extract had a promising antihypertensive effect most likely caused by dilation of the blood vessels through Ca++ channel blockade, a confirmation for the folkloric use of the plant. Key words: Hypertension, Calpurnia aurea, hydro-alcoholic seed extract, in vivo, ex vivo, antihypertensive, vasorelaxation.
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    A History of Oromo Literature and Identity Issues (C. 1840-1991)
    (Addis Ababa University, 2019-06) Tolessa, Tesfaye; Ta’a, Tesema (Prof)
    The purpose of the study is to document the reciprocal relationships between Oromo literature and identity issues in the process of the Oromo struggle against the formation of Ethiopian homogenous nation as the subject has not received proper historical study. In an attempt to fill the gap, the dissertation reconstructs a history of Afaan Oromo literature as a storehouse of Oromo identity, transcript for consciousness creation and instrument of resistance against impositions of Amhara rulers. For the study, pertinent available data were collected, interpreted and analysed qualitatively based on historical research methods using mainly narrative and analysis styles. The research findings depict that before the Oromo were conquered by the Amhara, the main emphasis of Afaan Oromo literature was the socialization of Oromo youths into ethically committed and morally strong Oromo. It was mainly used to teach the Oromo youth what was good and evil, moral and immoral, destructive and constructive, and encourage thought and action with its tales, poems, songs, epics, riddles, demonological legends, ballads, anecdotes, proverbs, lullabies, history and others. It also stored these principles in the forms of values, tension, myths, common experiences, psychological makeup and intellectual curiosity. The first attempt to write in Afaan Oromo might have come from the Muslim scholars whose efforts were to get written Afaan Oromo in a suitable script, which continued until Qubee was adopted in 1991. From c. 1840 onwards, the missionaries saw it as a language spoken by many people over large territorial areas and as a pathway to control the Oromo cultural identity and convert them to Christianity. The missionaries insisted on writing in Afaan Oromo under severe conditions that even cost them heavy prices. Consequently, from 1840 to 1899, they effectively worked on translation of the scriptures into Afaan Oromo, inscription of Afaan Oromo folklores and studies of Afaan Oromo grammar and vocabularies which gave Afaan Oromo a written basis, and from 1900 to the period of Italian conquest on teaching how to read and write in Afaan Oromo. Besides, the determination to write in Afaan Oromo and the increased consciousness of nationalism were paradoxically escalated by the attempts to suppress Afaan Oromo and Oromo cultural identity in favour of the formation of the linguistically, religiously and culturally homogenous Ethiopia from the last quarter of the nineteenth century. The Oromo grievances against the domination were articulated, recorded and passed on vertically from generation to generation and horizontally from one geographical area to another in Afaan Oromo literature. The networking of the grievances by Oromo oral literature and the consolidation of Oromo consciousness of their identity made the Oromo to consider the Italians as liberators when they began to use Afaan Oromo for education, broadcasting and office activities. These linguistic and cultural freedoms that the Oromo tasted under Italian rule made them to pose serious resistance against the restoration of Emperor Haile Sillasie. The Harar and Baalee Oromo uprisings, the Maccaa-Tuulamaa Association, the Afran Qalloo Cultural Movement and other covert movements of the Oromo were what evolved because of the imposed strict language policy and this gradually consolidated Oromo consciousness. The struggle was one factor for the decline of Emperor Haile Sillasie. The struggle to write in Afaan Oromo and the Oromo iv national question continued under the Darg until it was declared that the Oromo were a nation with their own regional state and Afaan Oromo became the written official language of the Oromia Regional State in 1991. The script adopted to write Afaan Oromo passed through intermittent linguistic studies with constant and critical debates until Qubee was adopted as standardized script to write Afaan Oromo. The script in which Afaan Oromo was to be written continued to be the subject of linguistic and political debates of the agencies engaged in issues of written Afaan Oromo throughout the study period until Qubee was officially declared as the script in which Afaan Oromo is now written.
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    A History of Oromo Literature and Identity Issues, (c.1840-1991)
    (Addis Ababa University, 2019-06) Tolessa, Tesfaye; Ta’a, Tesema (Professor)
    The purpose of the study is to document the reciprocal relationships between Oromo literature and identity issues in the process of the Oromo struggle against the formation of Ethiopian homogenous nation as the subject has not received proper historical study. In an attempt to fill the gap, the dissertation reconstructs a history of Afaan Oromo literature as a storehouse of Oromo identity, transcript for consciousness creation and instrument of resistance against impositions of Amhara rulers. For the study, pertinent available data were collected, interpreted and analysed qualitatively based on historical research methods using mainly narrative and analysis styles. The research findings depict that before the Oromo were conquered by the Amhara, the main emphasis of Afaan Oromo literature was the socialization of Oromo youths into ethically committed and morally strong Oromo. It was mainly used to teach the Oromo youth what was good and evil, moral and immoral, destructive and constructive, and encourage thought and action with its tales, poems, songs, epics, riddles, demonological legends, ballads, anecdotes, proverbs, lullabies, history and others. It also stored these principles in the forms of values, tension, myths, common experiences, psychological makeup and intellectual curiosity. The first attempt to write in Afaan Oromo might have come from the Muslim scholars whose efforts were to get written Afaan Oromo in a suitable script, which continued until Qubee was adopted in 1991. From c. 1840 onwards, the missionaries saw it as a language spoken by many people over large territorial areas and as a pathway to control the Oromo cultural identity and convert them to Christianity. The missionaries insisted on writing in Afaan Oromo under severe conditions that even cost them heavy prices. Consequently, from 1840 to 1899, they effectively worked on translation of the scriptures into Afaan Oromo, inscription of Afaan Oromo folklores and studies of Afaan Oromo grammar and vocabularies which gave Afaan Oromo a written basis, and from 1900 to the period of Italian conquest on teaching how to read and write in Afaan Oromo. Besides, the determination to write in Afaan Oromo and the increased consciousness of nationalism were paradoxically escalated by the attempts to suppress Afaan Oromo and Oromo cultural identity in favour of the formation of the linguistically, religiously and culturally homogenous Ethiopia from the last quarter of the nineteenth century. The Oromo grievances against the domination were articulated, recorded and passed on vertically from generation to generation and horizontally from one geographical area to another in Afaan Oromo literature. The networking of the grievances by Oromo oral literature and the consolidation of Oromo consciousness of their identity made the Oromo to consider the Italians as liberators when they began to use Afaan Oromo for education, broadcasting and office activities. These linguistic and cultural freedoms that the Oromo tasted under Italian rule made them to pose serious resistance against the restoration of Emperor Haile Sillasie. The Harar and Baalee Oromo uprisings, the Maccaa-Tuulamaa Association, the Afran Qalloo Cultural Movement and other covert movements of the Oromo were what evolved because of the imposed strict language policy and this gradually consolidated Oromo consciousness. The struggle was one factor for the decline of Emperor Haile Sillasie. The struggle to write in Afaan Oromo and the Oromo national question continued under the Darg until it was declared that the Oromo were a nation with their own regional state and Afaan Oromo became the written official language of the Oromia Regional State in 1991. The script adopted to write Afaan Oromo passed through intermittent linguistic studies with constant and critical debates until Qubee was adopted as standardized script to write Afaan Oromo. The script in which Afaan Oromo was to be written continued to be the subject of linguistic and political debates of the agencies engaged in issues of written Afaan Oromo throughout the study period until Qubee was officially declared as the script in which Afaan Oromo is now written.
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    Trace Enrichment and Selective Extraction of Residue of Atrazine and Its Major Metabolites in Environmental Waters and Human Urine Utilizing a Hollow Fiber Supported Liquid Membrane Extraction
    (Addis Ababa Universty, 2010-06) Tolessa, Tesfaye; Megersa, Negussie (PhD)
    A simple sample preparation technique using a hollow fiber membrane in conjunction with high performance liquid chromatography has been developed for the extraction and determination of s-triazine herbicides and their major metabolites from environmental water and human urine samples. Optimum extraction conditions have been evaluated with respect to solvent type, acceptor and sample pH, extraction time, shaking speed and salt content as well as humic acid effect. The extraction method has been validated for matrices such as reagent water, tap water, river water and human urine samples, indicating that regent water can be selected as representative matrix for routine analysis of these environmental water samples and human urine samples. A high level of detection linearity with regression coefficients (r2) ranged from 0.994 to 0.999 was obtained for herbicides over a range of analyte concentrations between 50 and 100 μg/L, using peak area as a response variable. The repeatability and reproducibility of the method were less than 11 and 17% for concentration of 50 μg/L, respectively. Limits of detection of the method ranged from 0.03 to 1.12 μg/L and the limits of quantification from 0.10 to 3.73 μg/L, which were low enough to determine all the herbicides residues except desisopropylatrazine at concentrations below or equal to the maximum residue levels (MRLs) specified by European Union. The method was finally applied to the determination of the herbicides in tap water, river water and human urine samples and the concentrations found in these samples were always lower than the MRLs except desisopropylatrazine in tap water