Laboratory Animals

Some physiological parameters of the agamid lizard (Agama agama agama) were studied after intramuscular injection of ketamine hydrochloride with or without diazepam. Heart rates and electrocardiograms were recorded. Respiratory rates were also monitored before and during anaesthesia. The study showed that ketamine given at a dose of 20-30 mg/kg body weight intramuscularly provides optimal anaesthesia for surgical procedures on the agamid lizard.

In order to clarify the relationships between five strains of rabbits and to identify the strains, principal component and discriminant analyses were carried out using 12 mandibular measurements of three inbred strains (JW-NIBS/Y (JW/Y), NW-NIBS/Y (NW/Y) and Dutch-NIBS/Y (D/Y)) and two outbred strains (JW-NIBS (JW) and NW-NIBS (NW)) which were maintained at the Nippon Institute for Biological Science. The results obtained were as follows.

(1) Principal component analysis revealed that in the males the mandible of JW was the largest but with considerable variation. D/Y was the smallest of all strains examined. The mandibles of NW and NW/Y were similar to the JW mandibles but had a shape which was shorter and higher. In the females the mandible of NW was the largest of all strains and, as in the males, D/Y was the smallest and JW varied markedly.

(2) Discriminant analysis showed the probability of erroneous discrimination to be 14·8% (34/229) when the inbred and outbred strains were combined. In both sexes erroneous discrimination mostly occurred between NW and NW/Y, which have the same origin, and between JW and NW, which have a common ancestor. However, when the inbreds and outbreds were identified separately by discriminant analysis, the probability of erroneous discrimination was low in both cases (4·5% (5/112) and 7·7% (9/117) respectively). These results indicate that strain differences are found in the size and shape of rabbit mandibles and that mandible analysis is effective for strain identification of laboratory rabbits.

A new preparation process was studied which should allow the implantation of collagen type I in its native structure in reconstructive surgery, in this special case for closure of incisional hernias. As experimental animals we used 30 female Lewis rats. A defect of the anterior abdominal wall measuring 3 cm × 4 cm was closed with our collagen substitute. Biopsies taken after 4, 6 and 8 weeks were examined morphologically. As criteria for revitalization and revascularization we used the type of infiltrating cells, the depth and density of infiltration and the formation of new blood vessels. After 4 weeks the implants were infiltrated by fibroblasts that decreased in density towards the centre. Good revascularization could be seen on the muscle-implant interface. After 6 weeks the density of infiltrating cells had increased markedly even to the centre of the collagen implant. Sporadically small vessels could be seen. Eight weeks after implantation the density of infiltrated cells was at the same high level, and capillary bundles could be seen within the whole implant. We believe that this collagen implant is suitable for the closure of hernias as shown by its physical and morphological properties. In particular it appears to guarantee an earlier and tighter closure of hernias than other materials.

Acholeplasma laidlawii was isolated from the faeces of 23·5% and 24% of groups of 51 conventional and 45 specified-pathogen-free (SPF) rabbits respectively. Isolation of the organism from individual animals could often be repeated, suggesting that infection was not merely transient. Two further acholeplasmas were isolated from two SPF rabbits. One was serologically related to Acholeplasma modicum. The other could not be identified and may be a new species.

A technique of neuroleptanalgesia during which rabbits breathed spontaneously for as long as 6 h without any outward sign of stress and with full recovery within 12 h is described. The method involved the constant infusion of a solution comprising fentanyl (0·05 mg/ml) and droperidol (0·13 mg/ml) in 5% dextrose following an intramuscular dose of fentanyl and droperidol. Hourly measurements of blood gases, lung mechanics, mean arterial blood pressure and heart rate were made to assess changes in ventilation and in these physiological parameters for the length of the study. The animals' tracheas were intubated under direct vision with an uncuffed tube. The animals breathed spontaneously and their cardiovascular and respiratory systems were stable throughout the entire monitoring period. There was no statistical difference between the values for all the parameters measured (P < 0·1). A two-way analysis of variance statistical test was applied to all the measurements.

An economic reliable long-term recirculation anaesthesia system for laboratory fish is described. Anaesthesia of channel catfish (Ictalurus punctatus Rafinesque) was induced within 60 s and was maintained for up to 40 min using tricaine methanesulphonate; recovery occurred within 30-60 s. Various surgical procedures were performed on the fish. No deaths were recorded. All water-quality parameters tested over 19 days use of the system remained stable except for total ammonia nitrogen and, by calculation, un-ionized ammonia which increased to a maximum of 0·23 mg/1.

The pH of the rat intestinal tract was decreased by the presence of a microbial flora, but its influence in the forestomach is less clear. Stomach pH values varied according to the amount of food present at the time of measurement. Fasting increased the pH of the gastrointestinal tract in conventional rats but had little effect in germfree rats. In the conventional rat, feeding a purified diet compared with a commercial diet resulted in a lower pH in the forestomach and a higher pH in the caecal contents. Magnesium trisilicate promoted gastric emptying in conventional rats and its antacid effect was observed only in the caecum and colon.

A fifth limb, quite independent of the others, was found in a pup born in our colony of Wistar rats. The malformation is described.

To evaluate the efficacy of a commercial bacterial vaccine in protecting Strain 13 guineapigs against fatal Bordetella bronchiseptica pneumonia, it was necessary to establish the infectivity and disease pathogenesis induced by virulent organisms. When guineapigs were exposed to small-particle aerosols of varying concentrations of virulent B. bronchiseptica, a spectrum of disease was produced that ranged from inapparent illness to fulminant bronchopneumonia. Clinical signs began by day 4 after exposure, and were evidenced by anorexia, weight loss, respiratory distress and serous to purulent nasal discharge. Pathological alterations were limited to the respiratory system. Moribund animals exhibited a suppurative necrotizing bronchopneumonia and necrotizing tracheitis. In animals that survived the challenge, the bacteria were eliminated from the lungs by day 28 but continued to persist in the laryngeal area and the trachea. The median infectious dose and the median lethal dose were estimated to be 4 colony-forming units (CFU) and 1314 CFU respectively. These data suggest that the guineapig will be a valuable model system in which to study interactions between Bordetella species and host cells as well as to evaluate potential B. bronchiseptica immunogens.

We use a mutant hairless Sprague Davvley rat to evaluate the capacity of retinoids to inhibit the epidermal ornithine decarboxylase activity induced by sellotape stripping. In order to minimize the variability introduced by the animals in our model we decided to validate the hairless rats used.

A number of animal parameters were examined using a single lot of 50 males and 50 females aged from 4 to 11 weeks and acclimatized to laboratory conditions. The body weight growth curves were established. Nude animals present two periods of hair growth, the first at 6-7 weeks and the second at about 10-11 weeks. Hair development is more pronounced in males. No histological change was observed in the stratum corneum but an increase in epidermal thickness was noted in males aged 9 weeks. Removal of the stratum corneum by sellotape stripping was more effective and reproducible in the females, as determined histologically. Sellotape-stripping induction of ornithine decarboxylase in the epidermis was higher in rats aged 5-6 weeks and reached a plateau in animals aged 6-12 weeks. Individual variations obtained were lower in females (about 5%-10% in females and 10%-20% in males).

The present research suggests that female rats aged about 8 weeks provide maximum reproducibility of response and ease of use.

Spontaneous cardiac and renal lesions in APA hamsters were examined histopathologically. Myocardial degeneration, valvular thickening, coronary arterial degeneration and increase in heart weight were common in old hamsters. These changes, which suggest cardiac failure, seem to be related to cardiac thrombosis which predominantly affected the left atrium and was found in over 40% of each sex over 16 months of age. Neither glomerular amyloidosis nor arteriolar nephrosclerosis was detected. In general the histopathology of renal lesions in APA hamsters resembled that of the condition known as glomerulonephrosis in rats. Renal lesions occurred more frequently and more severely and developed more rapidly in females than in males. There was no apparent correlation between cardiac thrombosis and renal disease.

We have used our laboratory records to compare data on the reproduction and maintenance of common marmosets in different colonies and to provide additional information on the species in captivity. Data are presented for a period of 12 years. This was long enough to allow information on longevity, mortality, aggression and incest. In addition 543 infants were born from a total of 202 births. No seasonality was found and the highest proportion of births overall was that of triplets. A significantly greater proportion of males was born, but perinatal mortality reduced this to a proportion of 52·2% surviving males. The interbirth interval for all normal births ranged from 145 to 382 days, with a median of 158 days. There was no evidence that interbirth intervals increased with age. The proportion of non-breeding pairs was small (4 out of 28) and progesterone assays showed that these females were ovulating.

A technique is described for the intermittent collection of blood from the rat tail. By using commonly available equipment, blood samples can easily be obtained from rats without the need for anaesthesia. The development of this technique makes the rat more readily available as an animal model for repeated withdrawals of small blood samples for pharmacokinetic or bioavailability evaluations.

A technique for endotracheal intubation in rabbits, which eliminates the need for tracheostomies, special devices, laryngoscopes and guide wires, is described. Inhalation anaesthesia with controlled ventilation for major surgical procedures in rabbits is easier to perform than previous reports in the literature suggest.

The new Animals (Scientific Procedures) Act 1986 has significant implications in terms of record keeping. In many designated establishments, however, most of the records are already collected as part of good working practice and the new Act merely formalizes this situation. Recording the required information may be tedious, but it can be carried out using either a paper-based system or its computerized equivalent. The new legislation imposes no additional record-keeping requirements on personal licence holders and the real burden falls on the project licence holder, particularly for large projects involving several personal licence holders. In the case of an animal house operating a computerized system, considerable assistance with project record keeping can be given by the designated establishment and project status reports will be very helpful in this respect. Computerization also enables automatic production of cage labels which ensures uniformity of labelling and compliance with the Home Office guidelines.