- Volume 38 - Issue 3
In swimming animal models, weights are added according to some percentage of body weight (%BW) or as a constant load (CL) to equalize the workload of each animal or to reduce the time in swimming-to-exhaustion endurance tests. The objective of the present study was to evaluate the effect of body weight variation on swimming exercise workload through the reliability analysis of swimming-to-exhaustion endurance tests. We examined the reliability by comparing the mean time to exhaustion (TEx) in trials performed on the 30th, 60th, 90th, 120th and 150th days of life of Wistar rats using three %BW and CL workloads (4%, 6% and 8% and 7 g, 11 g and 15 g, respectively). We also examined the within-subject variation of TEx over three trials of a CL test (15 g) within one week (when variability in body weight is minimal). The rats’ body density was maintained during growth (mean (SD) 1.031 (0.026) g/ml – 1.026 (0.005) g/ml) despite their significant increase in body weight (mean(SD) 109.05(13.80) g - 442.92(29.39) g). Thus, the absolute loads in longitudinal %BW tests increased gradually, causing a decrease in TEx under all workloads. The CV confidence limits for TEx in CL tests showed high within subjects variation (17.1-111%) compared to the body weight variation (0.4-2.8%). We conclude that load adjustment based on %BW does not adequately equate to the workload between rats of different sizes. The methodology also showed high within-subject variation between trials (not related to body mass changes) that compromises the significance of small effects.
The objective of this study was to evaluate pain sensitization in rats following the induction of an intracerebral haemorrhage located in the basal ganglia and/or thalamus using the Rosenberg model (intracerebral injection of collagenase). Thirty male Sprague-Dawley rats weighing between 175-300 g were used. In a first experiment, 3 groups of 6 animals were used to evaluate pain threshold using the Hargreaves test (thermal sensitivity). Following 3 days of behavioural testing (baseline values), animals in each group were injected intracerebrally either with 0.5, 1 or 2 μL of a collagenase solution (0.5 U/2 μL Type VII collagenase) which induced a hematoma in the right caudoputamen nucleus and/or thalamus. They were then tested for the next 9 consecutive days. No pain-related behavioural changes were observed following injections with 0.5 and 1 μL of collagenase. However with 2 μL, reaction times were significantly faster on days 3, 4, 5, 6 (p < 0.0001) and 7 (p < 0.006) in the right and left hind paws compared to baseline values. The lesion was localized only in the caudoputamen nucleus for animals receiving 0.5 and 1 μL of collagenase whereas lesions extended in the ipsilateral thalamic nuclei (lateral-dorsal and lateral-posterior nuclei) for animals receiving 2 μL of collagenase. In a second experiment, gabapentin reversed mechanical allodynia, evaluated with von Frey filaments, and hyperalgesia, evaluated with Hargreaves test, in rats (n=6) following a collagenase-induced (3 μL) hematoma. In conclusion, these preliminary results suggest that central pain was induced in rats with a collagenase-induced intracerebral haemorrhage localized in the caudoputamen nuclei most probably associated with lesions to the thalamus, and concurrent allodynia and hyperalgesia were reduced with gabapentin treatment.
To determine the best conditions for superovulation in rabbits, we analyzed the influence of age, season and hormone treatment on the numbers of eggs collected over five years from 509 rabbits aged 4–10 months using follicular stimulating hormone (FSH) or pregnant mare serum gonadotropin (PMSG) hormone stimulation. The number of eggs recovered was significantly higher in younger rabbits in both treated groups (P < 0.01–0.05). The number of eggs collected from rabbits treated with FSH were significantly higher than from rabbits treated with PMSG at all ages (P < 0.01). Seasonal differences were not observed in either hormone treatment group as they were maintained under constant temperature, humidity and light cycle through the year. Thus, younger rabbits are more sensitive to hormonal superovulation treatment with both FSH and PMSG, and FSH offers a better regimen for egg collection.
In this study the pathogenesis of lyme disease was investigated in vivo by means of the wild-type mouse strains C3H/HeN and FVB/N as well as transgenic mouse strains, which are tissue specific modulated in their TGF-▀ or GM-CSF (granulocyte-monocyte colony stimulating factor) activity and sensitivity. The mice were infected intradermally with B. burgdorferi. Progression of lyme disease was monitored using a number of diagnostic tests (recultivation of borrelia from tissue, ELISA, Western blot, histologic analysis). The study confirms the mouse strain FVB/N WT (wild type) to be susceptible to B. burgdorferi infections and that this represents a suitable in vivo model for investigations concerning the progression of a B. burgdorferi infection. We further demonstrate transgenic modification of TGF-▀ or GM-CSF activity, and sensitivity in T cells and epithelium respectively, do not affect the pathogenesis of lyme disease. Our data show a positive linear correlation between antibody response and the severity of arthritic processes due to B. burgdorferi infection. Determination of the increase in antibody titer in sera of infected organisms therefore might be a useful tool to predict the progression of inflammatory processes in the course of lyme disease.
Conventional treatment that eliminates other gastrointestinal nematodes has failed to show adequate efficacy against Trichuris trichura in non-human primates (NHPs). We investigated the efficacy of albendazole and ivermectin against natural infestation of nematodes in non human primates. 18 vervet monkeys (Chlorocebus aethiops) and 21 baboons (Papio anubis) were divided into three treatment groups comprising of 6 vervets and 7 baboons per group. Albendazole (ABZ, 7.5mg/kg) was administered orally, and ivermectin (IVM, 300μg/kg) subcutaneously, each for three consecutive days. Group I animals were treated with a combination of albendazole and ivermectin, Group II ABZ alone, while Group III animals were treated with IVM alone. Faecal samples were collected at 0, 7, 14 and 28 days post treatment (dpt) and analysed for the presence of faecal eggs using the McMaster and formol ether acetyl (FEA) methods. Faecal egg count reduction percentage (FECR (%)) and cure rate (CR (%) i.e. percentage of faecal egg negative individuals after treatment) were used to determine the efficacy of the treatment regimens. The FEA method was found to be a more sensitive assessment method than the McMaster technique. When both methods were used the helminths observed included Trichuris trichura (100% in both NHPs) and strongyles (29.4% in vervets and 28.6% in baboons). In vervets, the FECR of T. trichura at 28 dpt was 100% (Group I), 75% (Group II) and 0% (Group III) while the CR (at the same time point) was 100% (Group I), 60% (Group II) and 0% (Group III). In baboons, the FECR% and CR% of T. trichura at 28dpt, for groups I, II, III was 100%, 100%, 0%, respectively. All the three drug regimens were curative (100%) of strongyles at 28 dpt. It is concluded that a combined ivermectin and albendazole treatment for 3 days is effective in treating T. trichura and strongyles infections in vervet monkeys and baboons. Further trials should be conducted using a bigger sample size as well as in other primates including humans.
Rats are often anesthetized prior to positron emission tomography (PET) brain imaging in order to prevent head movements. Anesthesia can be administered by inhalation agents, such as isoflurane (Forene), or injection mixtures, such as fentanyl-fluanisone-midazolam (Hypnorm-Dormicum). Unfortunately, anesthesia affects a variety of physiological variables, including those in the brain. The aim of this study was to compare the effects of inhalation and injection anesthesia on the binding potential of the dopaminergic D2/3 tracer [11C]raclopride used for PET brain imaging in human and animal studies. Male Lewis rats were assigned to either inhalation (isoflurane; N=4) or injection (fentanyl-fluanisone-midazolam; N=5) anesthesia. Isoflurane was given continuously, and fentanyl-fluanisone-midazolam was supplemented every 30-60 minutes when the tail reflex was positive. Catheters were surgically placed in femoral arteries and veins for blood sampling and tracer injection. After a short attenuation scan, the rats were PET scanned for 90 minutes after injection of [11C]raclopride. We found that rats anesthetized with isoflurane had double the binding potential in the striatum compared with fentanyl-fluanisone-midazolam anesthetized rats. Our results are in agreement with other studies showing that anesthesia may have a major influence on brain imaging studies involving tracer kinetics in rats.