Species Rattus Norvegicus Research Articles

Comparative analysis of the intestinal microbiome in Rattus norvegicus from different geographies.

Rat species Rattus norvegicus, also known as the brown street rat, is the most abundant mammal after humans in urban areas, where they co-exist with humans and domestic animals. The reservoir role of R. norvegicus of zoonotic pathogens in cities among rodent-borne diseases that could endanger the lives of humans and other mammals. Therefore, understanding the normal microbiome of R. norvegicus is crucial for understanding and preventing zoonotic pathogen transmission to humans and animals. We investigated the intestinal microbiome of free-living R. norvegicus collected from the Ruili, Nujiang, and Lianhe regions of Yunnan, China, using 16S rRNA gene sequence analysis. Proteobacteria, followed by Firmicutes, and Bacteroidetes were abundant in the intestines of R. norvegicus; however, bacterial compositions varied significantly between samples from different locations. Following a similar trend, Gammaproteobacteria, Bacilli, and Clostridia were among the top bacterial classes in most intestinal samples. The situation differed slightly for the Lianhe and Nujiang samples, although Phyla Bacteroidota and Spirochaetota were most prevalent. The Alpha diversity, Chao1, and Simpson indexes revealed microbial richness among the R. norvegicus samples. A slight variation was observed among the samples collected from Ruili, Nujiang, and Lianhe. At species levels, several opportunistic and zoonotic bacterial pathogens, including Lactococcus garvieae, Uruburuella suis, Bartonella australis, Clostridium perfringens, Streptococcus azizii, Vibrio vulnificus, etc., were revealed in the R. norvegicus intestines, implying the need for a regular survey to monitor and control rodent populations. In conclusion, we explored diverse microbial communities in R. norvegicus intestines captured from different regions. Further, we identified several opportunistic and potential bacterial pathogens, which still need to be tested for their underlying pathogenesis. The findings of our current study should be considered a warning to the health authorities to implement rat control and surveillance strategies globally.

TRFtarget 2.0: expanding the targetome landscape of transfer RNA-derived fragments.

tRFtarget 1.0 (http://trftarget.net/) is a platform consolidating both computationally predicted and experimentally validated binding sites between transfer RNA-derived fragments (tRFs) and target genes (or transcripts) across multiple organisms. Here, we introduce a newly released version of tRFtarget 2.0, in which we integrated 6 additional tRF sources, resulting in a comprehensive collection of 2614 high-quality tRF sequences spanning across 9 species, including 1944 Homo sapiens tRFs and one newly incorporated species Rattus norvegicus. We also expanded target genes by including ribosomal RNAs, long non-coding RNAs, and coding genes>50 kb in length. The predicted binding sites have surged up to approximately 6 billion, a 20.5-fold increase than that in tRFtarget 1.0. The manually curated publications relevant to tRF targets have increased to 400 and the gene-level experimental evidence has risen to 232. tRFtarget 2.0 introduces several new features, including a web-based tool that identifies potential binding sites of tRFs in user's own datasets, integration of standardized tRF IDs, and inclusion of external links to contents within the database. Additionally, we enhanced website framework and user interface. With these improvements, tRFtarget 2.0 is more user-friendly, providing researchers a streamlined and comprehensive platform to accelerate their research progress.

EFFECTS OF DRUG BETAMETHASONE ON HEMATOLOGICAL PARAMETERS OF RATTUS NORVEGICUS (BERKENHOUT 1769) IN VIVO CONDITIONS

Glucocorticoids prevent or suppress the full inflammatory response to the infectious, immunological or physical agents by inhibiting early inflammatory events such as edema or cell exudation. The main effect of glucocorticoids on the inflammatory process is the inhibition or recruitment of neutrophils and monocytes. In this study, the effect of the glucocorticoid betamethasone on the hematological parameters of rats of the species Rattus norvegicus Berkenhout 1769 was examined in vivo. Betamethasone has been shown to affect the values of hematological parameters four hours after application and leads to a significant decrease in the prevalence of lymphocytes and monocytes, but also leads to a statistically significant increase in erythrocyte count, hemoglobin concentration and hematocrit values.

Incisional hernia repair in rats: description of the sublay technique under videomagnification system.

To describe the technique of sublay correction of incisional hernia in Wistar rats under videomagnification system. Five male rats of the species Rattus norvegicus, of the Wistar lineage, with body weight between 250-350 g and 60 days old were used. Incisional hernia was inducted in all animals. After that, the incisional hernia was immediately corrected by the sublay method. There were no cases of recurrence of the incisional hernia after placement of the polypropylene mesh using the sublay technique. No postoperative complications were observed. The technique is suitable for execution in Wistar rats.

A study of acute dermal toxicity of Artemisia herba-alba Asso essential oils

Medicinal plants constitute a huge reserve of many therapeutic virtues recognized by their powerful effects since the dawn of time. Our research focused on the study of acute skin toxicity (AST) of Artemisia herba-alba Asso (Aha) essential oils, obtained by hydrodistillation. AST has been evaluated, using rats of the species Rattus norvegicus with reference to a method proposed by the organisation for economic co-operation and development (OECD) guideline. Biochemical parameters, alanine aminotransferase, aspartate aminotransférase, total bilirubin, direct bilirubin, and creatinine were measured in whole blood after animal sacrifices. In parallel, the histological liver and kidney sections were analyzed. The Lethal dose 50 (LD 50 ) value was found greater than 5000 mg/kg. In addition, the biochemical markers of the tested rats did not change during the experiment compared to the control group. No tissue damage has been detected. A. herba alba Asso essential oil was considered non-dangerous, which can be used to heal against all benign or severe illnesses.

Pengaruh Pemberian Hormon Medroxy Progesterone Acetat terhadap Ketebalan Endometrium Rattus Norvegicus Betina Strain Wistar

Based on the National Population and Family Planning Agency (BKKBN) data in 2013, there were 8,500,247 couples of childbearing age who were new KB (family planning) participants with the total number using injection was 4,128,115 (48.56%). Research Objectives to find out The Effect of The Administration OF Medroxy Progesterone Acetate Hormone to Endometrial Thickness of The Female Rattus Norvegicus Wistar Strain. The design of this research is the post test only control group design by having white rats species Rattus Norvegicus Wistar Strain as the poplulation, the samples are taken randomly from all populations that met the following sample criteria: female rats, Aged 12-14 weeks, having body weight of 150 - 200 grams. Based on the calculation of the sample size, the sample size / number of animals r = 10 rats was obtained, with a total sample size for both groups of treatment and control were 20 female rats which included: group 1 amounted to 10 rats that were not given Medroxy Progesterone Acetat hormones as a control group where group 2 amounted to 10 rats which given Medroxy Progesterone Acetat as a treatment group. The results showed the average endometrial thickness in the (P1) Medroxy Progesterone Acetate Hormone group was 493.17 µm ± 114.96, this result was lower than the control group 1192.56 µm ± 428.94. From the ANOVA test table, the P value <0.05 means that there is a very significant difference in the average endometrial thickness between the control group and the treatment group. Based on the results of the Post Hoc Bonfferoni Test, it can be seen that the average endometrial thickness between Control and P1 showed a significant difference (P <0.05). The analysis of the result and discussion of the research can be concluded that: the Medroxy Progesterone Acetate hormone affects the endometrial thickness, and there is a difference in the histological picture of endometrial thickness due to the administration of the Medroxy Progesterone Acetate hormone and without the administration of to the administration of the Medroxy Progesterone Acetate hormone.

The Effect of Medroxy Progesterone Acetate Hormone Administration to Endometrial Thickness of the Female Rattus norvegicus Wistar strain

Many alternative contraceptives can be used as needed. The most effective type of contraception is injection contraception because it is relatively safe, effective, simple and inexpensive. Contraceptive users must be selective in choosing contraception because there is no method of contraception that is safe and effective for all acceptors. The side effects of Medroxy Progesterone Acetat injection include bleeding disorders such as amenorrhoea, weight gain, high blood pressure, acne, spotting. Medroxy Progesterone Acetat is a progestin contraceptive regimen that is often used and works long-term. The mechanism of action of Medroxy Progesterone Acetate injection is to inhibit gonadotropin secretion so that it will prevent the maturation of primary follicles in the ovary and also prevent ovulation and cause endometrial depletion.The research design is the post test only control group design. The population in this research are the white rats species Rattus norvegicus Wistar strain. The samples are taken randomly from all populations that met the following sample criteria: Female rats, Aged 12-14 weeks, having a body weight of 150 - 200 grams.The results showed that Medroxy Progesterone Acetate hormone affects the thickness of the endometrium, and there is a difference in the histological picture of endometrial thickness due to the administration of the Medroxy Progesterone Acetate hormone and without the administration of the Medroxy Progesterone Acetate hormone

<i>Moringa oleifera</i> Diets Effect on Haematological Parameters of Rat (<i>Ratus norvegicus</i>)

With aim of place at the disposal of the laboratories nonconventional food with food values and which do not have impact on the system haematopoietic of the rats of laboratory in particular the rat of the species Rattus norvegicus, the study of the haematologic parameters of rats nourished with nonconventional food makes containing powder of Moringa oleifera was undertaken. Indeed, analysis of the blood taking away carried out following the administration of five diets container various rates of powder of Moringa oleifera (0% (Control food), 25%, 50%, 75% and 100%) respectively codified L3P, L3P25, L3P50, L3P75 and L3P100. These different food formulations were administered to rats (Ratus norvegicus) during three months. The weight of these animals was daily taken, followed by blood samples every 30 days for the determination of the blood count. The results of the study were shown differences between the various food formulations for each period of blood samples in biological parameters. These differences were more significant for platelets. During the three months of study, the hematocrit, platelets, MCV and outside the control group, were reported a slight progressive increase. The leukocyte parameters of all the rats in the investigation, indicated an increase in the second month. In conclusion, the study shows that during the three months of investigation, the tested foods do not disturb the haematological parameters except for thrombocytes which reveal a modification.

Small rodent species on pig and dairy farms: habitat selection and distribution.

Rodent species are common in livestock production systems, and some of them are considered serious pests because of the sanitary problems and economic losses they cause. Information about microhabitat selection by rodent species in livestock production systems is necessary for understanding rodent requirements and to contribute to effective prevention and development of control measures for pest rodent species. In this work we study microhabitat selection by rodent species that inhabit pig and dairy farms in central Argentina. Rodent trapping was conducted over three years (2008-2011) on 18 livestock farms, each one sampled seasonally during one year. To study habitat selection, microhabitat characterizations were performed describing 22 environmental variables in captured sites and random trap sites without captures. With a trapping effort of 7333 Sherman and 7026 cage live trap-nights, 444 rodents of seven species were captured (including the murine pest species Rattus norvegicus, R. rattus and Mus musculus and four native species). The three murines selected characteristics related to building structure and/or to food sources availability/proximity, while Akodon azarae selected sites with tall herbatious vegetation. We identified microhabitat characteristics that explain habitat distribution of small rodent species in these complex farm systems. This study contributes to broaden the integrated pest management of rodent pest species and could also contribute to the reduction of the use of rodenticides in these systems. © 2018 Society of Chemical Industry.

Identification and characterization of a novel rodent bocavirus from different rodent species in China

Members in the genus Bocaparvovirus are closely related to human health and have a wide host range. The diverse hosts raise the possibility of crossing species barrier, which is a feature of emerging viruses. Among the mammalian hosts, rodents are generally acknowledged to be important reservoirs of emerging viruses. Here, rodent samples collected from six provinces and autonomous regions of China (Liaoning, Inner Mongolia, Tibet, Xinjiang, Guangxi and Yunnan) were used to investigate the prevalence and distribution of bocaparvoviruses. By using next-generation sequencing first, a partial non-structural protein 1 (NS1) gene belonging to a possible novel bocaparvovirus was discovered. Following this, PCR-based screening of NS1 gene was conducted in 485 rodent samples, with 106 positive results found in seven rodent species (Rattus norvegicus, Mus musculus, Apodemus agrarius, Cricetulus barabensis, Rattus flavipectus, Rattus rattus and Rhombomys opimus). Finally, six nearly full-length genomes and three complete CDS were obtained and the newly identified bocaparvovirus was tentatively named rodent bocavirus (RoBoV). RoBoV has three ORFs: NS1, NP1, and VP, which are characteristics of bocaparvoviruses. Phylogenetic analyses revealed that porcine bocavirus isolate PBoV-KU14, a member of Ungulate bocaparvovirus 4, was the most related virus to RoBoV, with 92.1–92.9% amino acid identities in NS1 protein. Alignments of RoBoV-related sequences showed RoBoV isolates could be classified into two clades, demonstrating an inter-host genetic diversity. The results indicate a potential interspecies transmission of RoBoV between rodents and swine and expand our knowledge on bocaparvoviruses in rodent populations.

Spatial modeling of rat bites and prediction of rat infestation in Peshawar valley using binomial kriging with logistic regression.

In this study, we propose to develop a geostatistical computational framework to model the distribution of rat bite infestation of epidemic proportion in Peshawar valley, Pakistan. Two species Rattus norvegicus and Rattus rattus are suspected to spread the infestation. The framework combines strengths of maximum entropy algorithm and binomial kriging with logistic regression to spatially model the distribution of infestation and to determine the individual role of environmental predictors in modeling the distribution trends. Our results demonstrate the significance of a number of social and environmental factors in rat infestations such as (I) high human population density; (II) greater dispersal ability of rodents due to the availability of better connectivity routes such as roads, and (III) temperature and precipitation influencing rodent fecundity and life cycle.

Detection and genetic characterization of diverse Bartonella genotypes in the small mammals of Singapore.

Bartonella species are arthropod-borne bacterial pathogens that infect numerous mammalian species. Small mammals play an important role as natural reservoirs of many Bartonella species, maintaining the greatest diversity of Bartonella described to date. Although Bartonella research has been conducted in Southeast Asia, no studies have been undertaken on small mammals in Singapore. Here, we report the detection and description of Bartonella in small mammals in Singapore during the period of November 2011 to May 2014. BartonellaDNA was detected in 20.8% (22/106) of small mammal spleens with a PCR amplifying the beta subunit of bacterial RNA polymerase (rpoB) gene. Commensal species Rattus norvegicus and Rattus tanezumi had the highest prevalence, 75% (3/4) and 34,5% (10/29), followed by Suncus murinus 30% (6/20), Tupaia glis 16,7% (1/6) and Mus castaneus 13.3% (2/15). Phylogenetic analysis of 18 rpoB gene sequences revealed five Bartonella genotypes circulating in the small mammals of Singapore. Bayesian tip-significance testing demonstrated strong structuring in the geographical signal, indicating that distribution of Bartonella species is correlated to the distribution of their hosts. Major deforestation and fragmentation in Singapore favour synanthropic species that traverse habitats and increase the possibility of spillover to incidental hosts.

SEROPREVALENCE OF TOXOPLASMA GONDII AMONG COMMENSAL RODENTS FROM GIZA GOVERNORATE, EGYPT

Toxoplasma gondii is an obligate intracellular zoonotic parasite that infects a large spectrum of warm-blood animals, including humans. Congenital toxoplasmosis is a worldwide problem. Rodents are intermediate hosts and serve as food for felids, the definitive hosts. A serological survey for antibodies to T. gondii was ca-ried out among two species of commensal rodent species Rattus norvegicus and R. rattus, trapped from different localities within Abu-El- Nomros center, Giza Governorate. Of 125 rats, 5 (4.0%) had anti-Toxoplasma antibodies. Of 79 R. nor- vegicus 3 (3.8%), and 46 R. rattus 2 (4.3%). The results showed that mature and immature of males and females of both sp'ecies had anti-toxoplasmal. This result was not sta- tistically significant between two species of R. norvegicus and R. rattus and also between the two sexes of each species.

Discovery of Novel Alphacoronaviruses in European Rodents and Shrews.

Eight hundred and thirteen European rodents and shrews encompassing seven different species were screened for alphacoronaviruses using PCR detection. Novel alphacoronaviruses were detected in the species Rattus norvegicus, Microtus agrestis, Sorex araneus and Myodes glareolus. These, together with the recently described Lucheng virus found in China, form a distinct rodent/shrew-specific clade within the coronavirus phylogeny. Across a highly conserved region of the viral polymerase gene, the new members of this clade were up to 22% dissimilar at the nucleotide level to the previously described Lucheng virus. As such they might represent distinct species of alphacoronaviruses. These data greatly extend our knowledge of wildlife reservoirs of alphacoronaviruses.

Morphological Changes in the Testis of Rattus norvegicus Exposed to Cigarette Smoke

Smoking has become a major cause of diseases worldwide. Cigarette smoking is associated with an increase in the development of a number of conditions which represent significant impact on public health. In this light the problem arises: Does exposure to cigarette smoke cause morphological changes in the testicles of rats? The present study is justified because of the growing importance of pathological conditions caused by exposure to substances in the cigarette and the scarcity of literature to correlate exposure to cigarette smoke to the emergence of testicular diseases that can promote infertility. The objective of this study was to analyze the morphology of the rat testicles exposed or not to cigarette smoke by checking the cell area of the germinal epithelium and comparison of histomorphometry of the seminiferous tubules. The study was approved by the “Comite de Etica em Uso de Animais” (Ethics Committee on Animal Use) - CEUA / FACID under protocol 038/13. A total of 14 animals of the species Rattus norvegicus were selected, males, with 60 days of age and weighing 300 g, divided into two groups (G1 and G2), with seven animals each group. The G1 animals were exposed to smoke produced by the combustion of four cigarettes for 30 minutes, twice a day, six days a week for 60 days. The G2 animals were not exposed. After 60 days, animals in both groups were euthanized and samples of the testicles were dissected and sent for routine processing for further microscopy light analysis. In each testicle sample was randomly calculated the cell area of the germinal epithelium of the seminiferous tubules, with the help of “ImageJ” software. Then the mean areas and standard deviations of each group of animals were calculated, for later histomorphometric comparison between groups. The results were statistically analyzed. Student T test was used, and the level of significance was 5% (p

Beyond an AFLP genome scan towards the identification of immune genes involved in plague resistance in Rattus rattus from Madagascar

Genome scans using amplified fragment length polymorphism (AFLP) markers became popular in nonmodel species within the last 10 years, but few studies have tried to characterize the anonymous outliers identified. This study follows on from an AFLP genome scan in the black rat (Rattus rattus), the reservoir of plague (Yersinia pestis infection) in Madagascar. We successfully sequenced 17 of the 22 markers previously shown to be potentially affected by plague-mediated selection and associated with a plague resistance phenotype. Searching these sequences in the genome of the closely related species Rattus norvegicus assigned them to 14 genomic regions, revealing a random distribution of outliers in the genome (no clustering). We compared these results with those of an in silico AFLP study of the R. norvegicus genome, which showed that outlier sequences could not have been inferred by this method in R. rattus (only four of the 15 sequences were predicted). However, in silico analysis allowed the prediction of AFLP markers distribution and the estimation of homoplasy rates, confirming its potential utility for designing AFLP studies in nonmodel species. The 14 genomic regions surrounding AFLP outliers (less than 300 kb from the marker) contained 75 genes encoding proteins of known function, including nine involved in immune function and pathogen defence. We identified the two interleukin 1 genes (Il1a and Il1b) that share homology with an antigen of Y. pestis, as the best candidates for genes subject to plague-mediated natural selection. At least six other genes known to be involved in proinflammatory pathways may also be affected by plague-mediated selection.

The analgesic and acute anti-inflammatory effect of the ethanolic extract of the leaves of Paederia foetida (EEPF) on experimental animal models

Objective:To study the analgesic and acute anti-inflammatory effect of the ethanolic extract of the leaves of Paederia foetida (EEPF) on experimental animal models. Materials and Methods: Fresh leaves were collected, air-dried, powdered, and percolated in 95% ethanol. Acute toxicity test was done according to OECD guidelines. Healthy albino rats (150-200 gm) of either sex were taken and divided into five groups with six animals in each group for central analgesic activity by tail flick method. Peripheral analgesic activity by 1% glacial acetic acid induced writhing test by taking albino mice (20-30 gm) of either sex which were divided into three groups with six animals in each. EEPF was used in a dose of 500 mg/kg bodyweight subcutaneously for tail-flick method and orally for writhing test. In tail-flick method the basal reaction time was taken and a cut-off period of 10 sec was observed. Reaction time were recorded at predrug, 15, 30, 60, 90, 120, 150 and 180 minutes after administration of drug . The standard drug used for central analgesic activity was pethidine 5 mg/kg bw, naloxone 1mg/kg as antagonist and naloxone 1mg/kg bw with 500mg/kg bw of EEPF to study the central mechanism of action. The standard drug used for peripheral analgesic activity was aspirin 100mg/kg bw orally. A control group was maintained in all the models. For anti-inflammatory study, three groups of animals of either sex (n = 6), weighing 150-200g of the species Rattus norvegicus were taken for the study. Group A was taken as control (Normal salie, 10 mL/kg body weight), Group B as test group (EEPF 500 mg/kg body weight), and Group C as standard (Aspirin 100 mg/kg body weight). The animals were studied for acute inflammation by Carrageenan-induced rat paw edema. Statistical analysis was done by one-way analysis of variance followed by multiple comparison tests.Results: EEPF significantly increased the reaction time in tail-flick method (p<0.05) whereas the combination of naloxone and EEPF decreased the reaction time indicating that naloxone inhibits the analgesic effect of EEPF. In 1% glacial acetic acid induced writhing EEPF reduced writhing significantly In acute inflammation, there was significant inhibition of paw edema in Groups B, C in comparison with Group A (P < 0.05). Conclusion:The ethanolic extract of Paederia foetida has significant analgesic and anti-inflammatory activity. DOI: http://dx.doi.org/10.3329/bjms.v11i3.11723 Bangladesh Journal of Medical Science Vol. 11 No. 03 July’12

Genetic characterization of seoul hantavirus originated from norway rats (Rattus norvegicus) captured in Belgium

Hantaviruses (genus Hantavirus, family Bunyaviridae) cause hemorrhagic fever with renal syndrome (HFRS) in Eurasia and hantavirus (cardio)pulmonary syndrome (HCPS) in the Americas. So far, in Europe, four pathogenic hantaviruses have been found, often in co-circulation: Puumala virus (PUUV), Dobrava virus (DOBV), Saaremaa virus (SAAV), and Seoul virus (SEOV). Of those, only PUUV was found in Belgium. Recently, in our search for hantaviruses in the Flanders region of Belgium we collected genetic and serological evidence for the presence of SEOV virus in local brown rats. In this article, the results of (phylo)genetic analysis of wild-type SEOV strain from the Flanders are presented. The analysis based on the complete S segment sequence and also partial M- and L-segment sequences revealed that the Belgian SEOV strain was related most closely to strains from France, Indonesia, Japan, Singapore, Cambodia (those associated with the species Rattus norvegicus) and Vietnam. Such a clustering was in perfect agreement with the results of direct sequence comparison and suggested the same evolutionary history for all three genome segments of the Belgian SEOV strain (i.e., no reassortment of genome segments). So far, SEOV has been found in two European countries, France and Belgium, and there is every reason to believe that the area of the virus distribution in Europe is not restricted to those countries.

Chromosomal evolution in Rattini (Muridae, Rodentia)

The Rattini (Muridae, Murinae) includes the biologically important model species Rattus norvegicus (RNO) and represents a group of rodents that are of clinical, agricultural and epidemiological importance. We present a comparative molecular cytogenetic investigation of ten Rattini species representative of the genera Maxomys, Leopoldamys, Niviventer, Berylmys, Bandicota and Rattus using chromosome banding, cross-species painting (Zoo-fluorescent in situ hybridization or FISH) and BAC-FISH mapping. Our results show that these taxa are characterised by slow to moderate rates of chromosome evolution that contrasts with the extensive chromosome restructuring identified in most other murid rodents, particularly the mouse lineage. This extends to genomic features such as NOR location (for example, NORs on RNO 3 are present on the corresponding chromosomes in all species except Bandicota savilei and Niviventer fulvescens, and the NORs on RNO 10 are conserved in all Rattini with the exception of Rattus). The satellite I DNA family detected and characterised herein appears to be taxon (Rattus) specific, and of recent origin (consistent with a feedback model of satellite evolution). BAC-mapping using clones that span regions responsible for the morphological variability exhibited by RNO 1, 12 and 13 (acrocentric/submetacentric) and their orthologues in Rattus species, demonstrated that the differences are most likely due to pericentric inversions as exemplified by data on Rattus tanezumi. Chromosomal characters detected using R. norvegicus and Maxomys surifer whole chromosome painting probes were mapped to a consensus sequence-based phylogenetic tree thus allowing an objective assessment of ancestral states for the reconstruction of the putative Rattini ancestral karyotype. This is thought to have comprised 46 chromosomes that, with the exception of a single pair of metacentric autosomes, were acrocentric in morphology.

Effect of the leaves of Psidium guajava Linn. on experimentally induced colitis in animal models

The aim of this study is to evaluate the effect of the ethanolic extract of the leaves of Psidium guajava (PGE) on experimentally induced colitis in animal models. Fresh tender leaves of the plant were collected, air-dried, powdered and percolated in 95% ethanol. Acute toxicity test was done according to Organization for Economic Cooperation and Development guidelines. Five groups of animals of the species Rattus norvegicus, of either sex, weighing 150–200 g, were taken for the study (n=6). Group A and Group B consisted of normal and experimental control animals (3% gum acacia, 10 ml/kg body weight), respectively. Group C and Group D were test groups (PGE 250 mg/kg body weight and PGE 500 mg/kg body weight, respectively) and Group E was administered standard [5-amino salicylic acid (5-ASA) 100 mg/kg body weight]. All animals were pretreated with the respective drugs for 5 days. Colitis was induced next morning in Groups B, C, D and E by administration of 1 ml of 4% acetic acid transrectally. All the animals were sacrificed 48 hours after colitis induction and distal 10 cm of the colon was resected. Colon was weighed for Disease Activity Index (DAI), and scored macroscopically and microscopically. Biochemical assessment included myeloperoxidase (MPO), tissue catalase (CAT), glutathione (GSH) and superoxide dismutase (SOD) estimation. Statistical analysis was done by one way analysis of variance, followed by multiple comparison tests. Groups C, D, and E showed a significant (P<0.05) decrease in DAI, and macroscopic and microscopic lesion score, as well as a significant improvement (P<0.05) in MPO, CAT, GSH and SOD levels as compared to Group B. The ethanolic extract of P. guajava leaves showed significant amelioration of experimentally induced colitis, which may be attributed to its anti-inflammatory and anti-oxidant property. Key words: Acetic acid, antioxidant, colitis, Psidium guajava