2008 - Volume 35 - Issue 3

141-147
A Model to Study Gland Regeneration/Development in Rat: The Expression of Metalloproteinase- 9 and Extracellular Matrix Proteins
by Simone Peringer, Eduardo José Gaio, Jose Amenábar, Dalva Maria Pereira Padilha &
Anna Christina Medeiros Fossati

A model to study gland regeneration as a similar phenomenon to gland development is proposed. This study evaluated the expression of metalloproteinases (MMPs), laminin (LN) and type I and III collagen in the regeneration of the rat submandibular gland (SMG). Eighteen 30-day-old Wistar male rats were anesthetized, and the lower third of their SMG left lobe was excised. The animals were killed on the 2nd, 3rd, 7th and 15th postoperative days, and their SMG lobes were removed, fixed and processed in paraffin. Immunohistochemistry was used to label type I and III collagen, laminin, and MMP-9. The avidin-biotin technique was used, and the reaction was developed with diaminobenzidine. On the 2nd day, MMP9 expression was intense in the margins of the regenerating area and inside striated duct cells in the preserved gland. On the 3rd day, duct cytoplasm labeling persisted and was more intense than in the surrounding mesenchyme, where labeling increased along time. Concurrently, LN labeling in the basal lamina of epithelial buds was intense and discontinuous. Types I and III collagen were present during the whole process, which showed their importance for the regeneration process. The behavior of extracellular macromolecules observed in this study is similar to their behavior in gland development.

151-158
Micronucleated Erythrocytes in Peripheral Blood of Newborn Rabbits after Exposure to Cyclophosphamide during Pregnancy
by Belinda C. Gómez-Meda, Ana L. Zamora-Perez, María L. Ramos-Ibarra, Cecilia M. Batista-González& Guillermo M. Zúñiga-González

There are ever increasing numbers of new chemicals and pharmaceutical products that have the potential to induce birth defects or to cause damage during the perinatal period in humans. Many genotoxic compounds possess teratogenic potential and induce the formation of micronuclei (MN). Objective: To demonstrate that the New Zealand rabbit may be a useful animal model for the evaluation of transplacental genotoxicity and potential teratogenicity of compounds by quantifying micronucleated erythrocytes (MNE) in the peripheral blood of newborn rabbits following maternal exposure. Method: For each dose, a single pregnant rabbit was injected daily on the 25th to 30th days of pregnancy with 1, 4, or 7 mg/kg cyclophosphamide (CP) with one pregnant rabbit being treated with sterile water as the control. Following the daily intramuscular administrations, a drop of blood was taken from six newborn rabbits from each female for microscopic analyses. Results: When compared with controls, significant differences (p < 0.002) were observed in the number of MNE and micronucleated polychromatic erythrocytes (MNPCE) from newborns of females treated with 4 or 7 mg/kg CP, but not from newborns exposed to 1 mg/kg CP. No cytotoxic effects were observed after the treatments. We concluded that the presence of MNE in newborn rabbits suggests that the rabbit may be useful animal model for the detection and prevention of transplacental genotoxicity and/or potential teratogenicity of compounds in the peripheral blood of newborn rabbits following maternal exposure.

163-167
Guinea Pig and Rat as Carriers of Host-unique and Shared Haemophilus Phenotypes
by R Boot

Infections by V- factor dependent Pasteurellaceae (commonly called Haemophilus sp) frequently occur in colonies of guinea pig and rat. We evaluated possible differences between 185 Haemophilus strains from guinea pig (n=97) and rat (n=88) by API NH biotyping and by cell wall lipid profiling (FAME-analysis). By combining results of both methods we found 28 Haemophilus API-FAME types. Seven API-FAME types were shared and comprised 66% and 76% of the guinea pig and rat Haemophilus strains respectively. The remaining 21 Haemophilus phenotypes were unique to either guinea pig (12 types) or rat (9 types).

171-176
The Effect of Spironolactone on the Pathogenesis of Ligature-induced Alveolar Bone Loss in Wistar Rats
by G. N.Verzeletti, E.J. Gaio & C.K. Rösing

Tumor necrosis factor (TNF) is a pro-inflammatory cytokine that has a straight relationship with tissue destruction in the pathogenesis of periodontitis. Inhibitory effects of TNF production have been attributed to spironolactone. The aim of this study was to evaluate the effect of spironolactone on the pathogenesis of ligature-induced alveolar bone loss in rats. Experimental periodontitis was induced in 38 Wistar rats by ligature placement in the left second maxillary molar. The contra-lateral maxillary molar served as intragroup control. Animals were randomly divided into 4 groups and treated with spironolactone (50, 100, 200 mg·kg-1) or saline. Morphometrical registration of maxillary alveolar bone was performed after 28 days of experimental periodontitis. Intra-group comparisons showed significantly higher alveolar bone loss mean values in maxillary sides with ligature (paired sample t test, p<0.05). Mean alveolar bone loss was not significantly different between groups, independently of the dosage (range: 0.63 – 0.66 mm, one-way ANOVA, p>0.05). Although spironolactone has recognized TNF-inhibitory properties, the possibility of its use on modulation of host immune-inflammatory response in periodontal disease was not confirmed.

181-190
Hematological and Morphological Analysis of the Erythropoietic Regenerative Response in Phenylhydrazine-induced Hemolytic Anemia in Mice
by Marta Roque, Cecilia D´Anna, Christian Gatti & Tania Veuthey

In this study we developed a mouse model of Phenylhydrazine (PHZ) -induced hemolytic anemia to study erythropoietic regenerative response through clinical, pathological, and morphological studies. Hemolytic anemia was induced in female mice (CF1) using PHZ at a wide range of doses (up to 100 mg/Kg) on days 0 and 2. Hemolytic anemia was observed at 60 mg/kg PHZ on day 4 and was evidenced by decreased HCT (34.3±0.28%), reticulocytosis (51.6±2.10%), anisocytosis, poikilocytosis, leukocytosis, and increased Heinz body count. A time-course and dose-dependence analysis of the regenerative response was performed. HCT decreased on days 2 and 4 in a dose-dependent manner, returning to basal levels on day 8. PHZ only induced reticulocytosis (day 4) at the highest doses tested (60-100 mg/kg). Heinz body formation was dose-dependent. These changes were accompanied by splenomegaly and splenic erythroid hyperplasia. Results revealed that the presence of erythroblastic islands was most clear in the spleen, followed by the liver and kidney. SEM showed Heinz body-containing erythrocytes and spherocyte-like erythrocytes. Anemia recovery results from coordinated action of extramedullary tissues depending on the time post injection and the dose applied. In conclusion, this mouse model allowed us a better understanding of murine erythropoietic regenerative response.

191-196
Effect of Treatment with DL-carnitine after Acute Alcoholization in Rats
by Guilherme Vannucchi Portari, José Simon Camelo, Estela Iraci Rabito, Júlio Sérgio Marchini & Alceu A. Jordao

Acute ethanol consumption leads to the formation of free radicals. Among other functions, carnitine has an important antioxidant role and chronic ethanol use leads to carnitine deficiency. The objective of the present study was to determine the variation in the carnitine pool (free cernitine plus its acylated derivates) and the hepatic oxidative stress occurring in the presence of acute ethanol administration followed by treatment with carnitine in rats. Male Wistar rats weighing approximately 60 g were divided at random into four groups of 7 animals each, i.e., group receiving carnitine, group receiving carnitine plus ethanol, group receiving ethanol alone, and untreated control. Acute administration of ethanol and/or carnitine did not change the total amount of carnitine and its derivates in plasma but did alter their profile with the free carnitine increasing to over 75%, while the mean percentage of free carnitine in the control group was 33.2%. There was marked carnitine excretion in the groups treated with DL-carnitine. Higher lipid peroxidation was detected in the groups receiving carnitine, with the maintenance of vitamin E. We conclude that the administration of DL-carnitine after an episode of alcohol intoxication has no beneficial effect in terms of hepatic oxidative stress.

199-201
Probiotic Biotherapy for Eradication of a Potential Pathogen in a Commercial Rat Breeding Facility
by Eje Collinder, Johannes Bergstedt, Anna-Karin Persson, Elisabeth Norin, Tore Midtvedt

This study defined a model for biotherapeutic eradication of beta-haemolytic streptococci, group G, in a rat breeding unit (3100 rats) by use of a strain of Lactobacillus reuteri. The microbe was added to the rats’ drinking water and the genitals of all rats were swabbed three times with a solution of the microbe. After this procedure undesirable streptococci were not recognized in any animal of this breeding farm.