2007 - Volume 34 - Issue 3

153-156
A Surgery Table with a Mouth Prop for Rodents
by EG Rivaldo & DMP Padilha

Laboratory animal research represents a remarkable source of information. Rodents are often used as an experimental model for studies in the medical field, showing several advantages. The access to the oral cavity allows one to examine it and to perform surgical restorative procedures. The application of topical substances on hard tissues and mucosa is also possible. Literature includes reports on mouth-opening systems for animals, but they are not available on the market. Therefore, researchers must improvise methods that allow access to the oral cavity, but which may compromise the experiment. The purpose of this technical report is to introduce an inexpensive and easy-to-use surgery table containing a device for rodent mouth opening, which facilitates access to the oral cavity, maintaining mouth-opening and spreading the cheeks apart.

159-166
Rod-Through-Plate Fixator for Long Bone Fractures:A Morphological Study on Rabbits
by Vladimir Andrianov, Aleks Lenzner, Peeter Roosaar, Andres Arend & Marina Aunapuu

We study the effect of a new fixator for treatment of diaphyseal bone fractures of small animal. The experiments were performed on 12 New Zealand White rabbits. Transverse osteotomy was made in the central third of the diaphysis of the rabbit’s femur and a rod-through-plate fixator was used to treat the bone fracture. The regeneration of the bone tissue was studied by means of radiography and histomorphology at postoperative weeks 2, 4 and 8. The rod-through-plate fixator gives stable fixation and early mobilisation of the limb. Radiographic images showed that the fractures had repaired well. Morphologically, all the parts of the callus had a typical structure. An immunohistochemical examination showed elevated levels of extracellular matrix proteins collagen type II, osteocalcin and osteopontin in the callus area. The new fixation method gives strong fixation of bone fragments with minimal traumatization of soft tissue during the operation. The construction of the rod-through-plate fixator allows one to reduce pressure in the area of the fracture and the dynamic fixation given by intramedullary rods allows micromotions stimulating callus formation and avoiding implant-induced osteoporosis. The fixator has a simple construction and its use expands the treatment possibilities for diaphyseal fractures of long bones. The rod-through-plate fixator use does not require special training for the surgeon.

173-183
Morphology of G Cells in Hypergastrinemic Cotton Rats
by Marianne Ø. Bendheim, Reidar Fossmark, Helge L.Waldum & Tom C. Martinsen

In a strain of inbred cotton rats, 25-50% of females develop spontaneous gastric hypochlorhydria and hypergastrinemia. Hypergastrinemic animals develop ECL cell derived gastric carcinomas located in the oxyntic mucosa, thus being an interesting animal model for studying the role of gastrin in gastric carcinogenesis. The response to gastric hypoacidity in cotton rats as regards the level of hypergastrinemia is far more pronounced than in the more commonly used laboratory rat. It is unknown whether the pronounced hypergastrinemic response in cotton rats is due to a greater population of G cells or a greater capacity of hormone synthesis in each G cell. The aim of the study was therefore to examine G cell population and ultrastructure in normogastrinemic and hypergastrinemic cotton rats by the use of immunhistochemical methods applied on both light- and electron-microscopy. Five hypergastrinemic vs. five normogastrinemic cotton rats were compared. Cotton rats with gastric hypochlorhydria have a 55-fold increase in serum gastrin levels and a 6-fold increase in G cell number, but this is not accompanied by significant changes in G cell ultrastructure. The lack of ultrastructural changes in these activated G cells indicates that previously reported changes in chronic stimulated G cells are just one of several ways G cells are activated.

189-195
Effect of Cage Density and Sex on Growth, Food Utilization and Some Stress Parameters of Young Rabbits
by E. Ebru Onbasılar & Ílyas Onbasılar

The aim of the experiment was to study the effects of cage density (1, 3 and 5 rabbits per cage) and sex (male and female) on stress parameters of young rabbits. A total of 90 (45 male and 45 female) weaned New Zealand White rabbits aged 35 days old were used in the experiment. Rabbits were allocated as 1, 3 and 5 rabbits, in each of 5 cages, to obtain three different cage density groups: 4200, 1400 and 840 cm2 floor area per rabbit, respectively. Mean values for total body weight gain, food intake, food:gain ratio, the plasma corticosterone level and serum levels of glucose, cholesterol and triglycerides were taken as indicators of stress. The group having 5 rabbits per cage had significantly lower total body weight gain (p<0.001), food intake (p<0,001) and higher food:gain ratio (p<0,01) than other groups during the experiment. The levels of plasma corticosterone and serum glucose were higher (p<0.001) in the group with 5 rabbits per cage than other groups. Values for serum levels of cholesterol and triglyceride were not affected by cage density. Gender effect was detected only in corticosterone level. Male rabbits had higher plasma corticosterone than female rabbits. The results suggest that the allocation of 1 or 3 rabbits per cage had no measurable adverse effects on the welfare of male and female young rabbits, whereas (at our cage densities) 5 ones.

201-210
Oral Bone Grafting in a Rat Model and the Use of Scanning Electron Microscopy for Tissue Morphology Evaluation
by JC Zielak, SA Mathias, AF Giovanini & AL Mathias

Oral bone grafting is a procedure widely performed in current dentistry. Several biomaterials fit this purpose. The aim of this study was to use scanning electron microscopy (SEM) to evaluate the ultrastructural aspects of bone repair in a rat model, with periodontal tissues involved. Two groups (I and II) of 20 animals each were operated on to create a surgical defect with a round carbide burr (3mm) on the right side of their mandible, anterior to the mental foramen. Both groups were evenly divided with 5 animals each to receive the application of either bifasic calcium phosphate bioceramic (B), lyophilized deproteinated bovine bone (L), bifasic bioceramic associated with lyophilized deproteinated bovine bone (BL), or no biomaterial (control or C). Group I was monitored for one week and group II for three weeks prior to euthanasia. Hemi-mandibles were prepared for SEM analysis. Parameters such as exposure of incisive root surface, width of the cross-section of filiform structures and presence of mineralized-like globuli (area) were evaluated. The findings of this study suggested that surgical procedures for introduction or not of biomaterial did not cause problems with normal feeding to the animals. Both of the biomaterials used promoted a periodontal ligament involvement. Fibers (single filiform structures) could be detected in a range from 0.07 to 0.18μm of diameter, except for L that was larger – considered to be due to residual fibers of bovine origin. C bundles (groups of fibers) showed larger width of cross-section than with the use of biomaterials. Globuli areas (mineralization) were smaller to C than with the biomaterials use. B showed larger globuli areas, suggesting slow incorporation. It was concluded that the use of these biomaterials favored maintenance of tissue volume although slowing remodeling, and the combination (BL) presented the best performance.