Rederivation of Helicobacter hepaticus-infected Mongolian gerbils by Caesarean section and cross-fostering to rats and mice.

The Mongolian gerbil serves as an animal model for a wide range of diseases. As these animals are extensively used for the study of Helicobacter pylori-induced gastritis, naturally occurring infections with rodent Helicobacter species in gerbils are a possible source of interference in studies of H. pylori-associated disease. The gerbil stock at the Central Animal Facility in Hannover was persistently infected with H. hepaticus. The aim of this study was to derive Helicobacter species-free Mongolian gerbils. Therefore, germfree gerbil pups were obtained by Caesarean section and the pups were transferred to female rats and mice with recently delivered litters. In total, four Ztm:NMRI mice, four Ztm:SPRD rats and one DA/Ztm rat that originated from a specified pathogen-free area were selected to serve as foster mothers. With this approach, it was possible to obtain Helicobacter-free gerbils. Rearing by mice was more successful than by rats, as six of nine gerbils were reared by mice, but only one of 29 gerbils was reared by rats.

Indicators for post-surgery recovery in Mongolian gerbils (Meriones unguiculatus).

Telemetric investigations of various parameters are widely used to estimate an animal's state. However, the implantation of the transmitters includes anaesthesia and surgery and has short and longer lasting impacts on the studied object. The aim of the present paper was to evaluate these effects in Mongolian gerbils, namely the hypothermia caused by the anaesthetic and the enduring disturbance of daily rhythmicity until complete recovery. The surgery associated with the implantation of the transmitters differed both in severity and type of anaesthesia. Whereas normal values of body temperature were restored within hours, restoration of daily rhythm required several days, depending on the severity of the surgical procedure. Also, the sensitivity of the body temperature to activity changes was different until the rhythms were re-established. A method based on the rhythm magnitude and shape was proposed to estimate the time until complete recovery of the animals.

Unilateral carotid artery ligation in the Mongolian gerbil as a model for testing infarction-reducing therapies.

This study evaluates infarct size measurement as an indicator of cerebral ischaemia outcome in a placebo-controlled trial of potential cerebral protection in the unilateral carotid artery ligation in the Mongolian gerbil. Ibuprofen was used in an effort to manipulate infarct size as this agent has been shown to reduce ischaemia in myocardial infarction. Using measurements obtained through an infarct-sizing technique and a statistical power analysis of the method, the sample sizes needed to obtain significant results were projected for this model. In this case, it was not possible to demonstrate an effect of ibuprofen on infarct size although a tendency towards larger infarct size in ibuprofen-treated compared with placebo-treated gerbils was observed (36.1 +/- 10.1% versus 30.0 +/- 17.5%). The sample sizes needed to find significant changes in infarct size indicate that this model finds a practical use in studying therapies which will alter infarct size by at least 50%. For example, to detect a 30% change in infarct size, 33 successfully infarcted gerbils per group would be needed, but a 50% change would require a more tenable 13 infarcted gerbils per group. However, given the 40% infarction rate of occluded gerbils seen in this study, almost 33 gerbils per group would be required to detect a 50% change. In addition, somatosensory evoked potential was compared with neurological examination as a predictor of infarction. It would be helpful to be able to pre-screen for infarcted gerbils immediately after occlusion in order to direct infarcted gerbils into control and treated groups. Somatosensory evoked potential successfully predicted infarction with a 90% accuracy in 21 gerbils compared with neurological evaluation which was 100% accurate. But the somatosensory evoked potential prediction was made within 15 min of occlusion as opposed to the 6 h of observation during which the neurological evaluation was made.

Anatomy and physiology of the gerbil cochlear nucleus: an improved surgical approach for microelectrode studies.

A new, improved surgical approach to the cochlear nucleus is developed in the gerbil. This new approach involves making a small hole in the lateral wall of the temporal bone located within the perimeter of the superior semicircular canal. Microelectrodes are passed through the intact parafloccular lobe of the cerebellum to the cochlear nucleus. One advantage of the new approach is that no removal of any CNS vasculature or neural tissue is necessary. Relations between the bulla, temporal bone and cochlear nucleus are presented in detail. The new approach is demonstrated by making single unit recordings from the cochlear nucleus and classifying response patterns as measured in PST histograms. All of the response types found in cat are found in the gerbil.

An evaluation of tribromoethanol (TBE) as an anaesthetic agent in the Mongolian gerbil (Meriones unguiculatus).

Mongolian gerbils injected i.p. with a 1.25% solution of tribromoethanol (TBE) quickly lost the righting reflex and showed good surgical anaesthesia, the duration of which was positively related to the dose administered. All levels (225-450 mg/kg bodyweight) of TBE injected s.c. resulted in loss of the righting reflex, though surgical anaesthesia was not attained. Following recovery from anaesthesia induced with 2.25% TBE i.p., or high doses of 1.25% TBE i.p., visceral adhesions and deaths occurred. To avoid these TBE-induced fatalities such extreme care must be taken during the preparation, storage and administration of the agent that it is not recommended as a suitable anaesthetic for general use in the gerbil.

A method for intracerebrally implanting crystalline hormones into neonatal rodents.

The advantages of this delivery method are that the weight of each hormonal implant can be accurately assessed, the implant can be accurately placed within the brain, there is no obvious damage to the brain following the operation, and hormones leaking out of the brain from the implants have no stimulatory effects on peripheral organs.

Nonreproductive surgery in small mammals.

The sophistication of soft-tissue surgery techniques in small mammals is increasing rapidly. Exotic animal practitioners must be familiar with the diseases, conditions, and anatomic variations of each small-mammal species. The small size of these patients should not preclude the use of technologic advances available for other small animals. Despite these challenges, successful resolution of surgical problems in small exotic mammals is not only possible but also should be the expected result of veterinarians' efforts in such cases.