Contemporary topics in laboratory animal science最新文献

Intravascular catheterization access for injection and sampling is one of the most common experimental surgical procedures. The vascular access port (VAP) was developed as an alternative to externalization of catheters. A VAP typically is implanted subcutaneously, with an attached catheter that is tunneled to a blood vessel for chronic catheterization. Catheters and ports have been designed to reduce the problems of occlusion, venous thrombosis, and infection. Key issues involve the use of meticulous aseptic technique for implantation of the devices and a "locking" solution that prevents clotting and retention of residues within the catheter. There are species-specific differences to be considered when planning the surgical implantation and maintenance of these devices. This manuscript reviews the procedures that have been used in the implantation of VAPs in large animal species and makes recommendations for procedures that will decrease complication rates associated with long-term catheterization.

We have observed decreased size and increased mortality rates in interleukin 5 (IL-5)-deficient mice versus IL-5-heterozygous and wild-type mice and have sought to define these differences. IL-5-deficient mice nursed by IL-5 deficient mothers were notably underweight, with a high percentage of preweaning mortality. In contrast, IL-5-deficient mice nursed by IL-5-sufficient foster mothers from birth were well-developed and robust at weaning, with a relatively low percentage of preweaning mortality. Mammary tissues from IL-5-deficient females at various landmark stages throughout life were prepared for microscopic assessment. When compared with mammary tissue from normal mice, that from IL-5-deficient dams appeared to have fewer terminal end buds, less well-developed branching of the mammary ducts, and lower overall density of mammary gland structures. The molecular and cellular bases for the differences in mammary gland development in IL-5-deficient mice relative to wild-type animals remains unknown. Under consideration are the roles that IL-5 and eosinophil granulocytes (the primary cell responsive to IL-5) may have in mammary gland development.

In this study, we fed a standard NIH-31 diet fortified with vitamin E to C57BL/6 mice and strains of mice with a C57BL/6 background that had spontaneously developed ulcerative dermatitis (UD). In addition to the therapeutic response to increased levels of vitamin E, we also defined the occurrence of UD within our facility in terms of age, sex, coat color, and lesion location on the body. Mice with spontaneous UD were fed a vitamin E-fortified diet (3000 IU/kg) for a period of 8 weeks and entered the study without regard to vendor source, age, sex, coat color, or the site or number of UD lesions. We found that lesions occurred most commonly on the dorsal cervical and scapular regions and spared the ventral abdomen and thorax. No sex or coat color predilection was noted for the development of UD, however males were older than females at the time of lesion development. Of 71 mice, 32 (45%) had complete lesion re-epithelialization with hair regrowth. Complete lesion repair was not influenced by sex, age, or coat color. The average time to complete lesion repair ranged from 2 to 5 weeks, and there was no correlation with sex or coat color. The positive response to vitamin E suggests that protection from oxidative injury may play a role in the resolution of UD lesions and offers veterinarians and investigators a new treatment option with ease of compliance.

Respiratory symptoms related to both endotoxins and animal allergens continue to be an important cause of occupational disease for animal technicians and scientists working with rodents. Better sampling methods for airborne allergens and endotoxin are needed to help standardize compliance with federal occupational health regulations. Using an ion-charging device, we sampled 20 mouse rooms and four rat rooms at the University of Virginia, along with 43 domestic living rooms in houses in the Charlottesville area with at least one cat or dog. The use of filter tops on cages corresponds to a 50-fold reduction in mean levels of both airborne allergens (P < 0.001) and endotoxin (P < 0.001). The use of vented cages with filtered exhaust ports was associated with additional reductions. However, the mean airborne endotoxin level in all rooms using filter tops without a filtered exhaust port on the cages was significantly lower (P = 0.003) than the level in domestic living rooms. Our results for maximum airborne allergens or endotoxin are comparable with previous reports. However, the sensitivity of the technique allows an accurate assessment of low-level exposure, which makes it possible to evaluate the effect of cage designs. In addition, this approach allows direct comparison with results for airborne allergen and endotoxin in domestic homes. The results could allow a more consistent approach to the application of occupational health guidelines.

A safe and efficient method for endotracheal intubation was needed to mechanically ventilate mice and rats for various research projects. We developed an easy, reliable, and expeditious method for intubating these rodents. Inexpensive disposable Teflon intravenous catheters are used as endotracheal tubes. Both mice and rats are anesthetized using a combination of injectable and inhalational anesthetics before intubation. A relatively inexpensive custom-designed fiber-optic light guide and battery-powered light source allows visualization of the oropharynx for quick and easy intubation. The fiber-optic light guide has two functions: 1) the light guide transports light from the illuminator to the tip of the fiber for direct visualization of the larynx, and 2) the fiber is used as a stylet to stiffen the Teflon catheter. Direct illumination of the larynx allows its clear visualization and makes the procedure easier and more efficient and, as a result, less traumatic to the animals. This method has been easy to learn, and it allows repeated intubations, even in debilitated or dyspneic animals, for respiratory-gated, noninvasive imaging procedures. With it, we can acquire higher-quality images with fewer motion artifacts than we could before.

The objective of the present study was to determine how rats adapt to repeated encounters with an unfamiliar male or group of males and to experimental manipulations. Male rats were instrumented with radiotelemetry transmitters to monitor heart rate (HR), mean arterial blood pressure (MAP), and movements in the home cage as indices of arousal and stress. Groups of eight singly housed rats were exposed in their home cages to encounters with an unfamiliar rat or a group of three rats of the same strain, age, and sex for a period of 18 h (1600 to 1000 h) on four consecutive days. On separate occasions, the instrumented rats were given a subcutaneous injection of sterile saline in the animal room or were transported from the animal room to the laboratory and then injected at 1000 h on four consecutive days. Exposure to an unfamiliar rat or a group of 3 rats induced significant (P < 0.05) increases in HR, MAP, and movement in the first 30 min of exposure, and these responses partially but significantly (P < 0.05) adapted by the second or third day. Nocturnal movement in the home cage also was significantly (P < 0.05) increased on the first night and partially reduced on subsequent nights, but nocturnal HR responses were absent or significantly blunted. Nocturnal MAP was not increased. Subcutaneous injection in the animal room or after transport to the laboratory produced significant (P < 0.05) increases in HR, MAP, and movement in the cage 30 min after the injection, and these responses did not adapt over the four days of the experiment. We concluded that male Sprague-Dawley rats adapted quickly, albeit partially, to social encounters but did not adapt to repeated injections, suggesting selective adaptation depending on the type of stimulus used.

To determine whether a nonsocial enrichment program affects cardiovascular responses of individually housed male Sprague-Dawley (SD) and spontaneously hypertensive (SH) rats under basal conditions and after potentially stressful procedures, we used radiotelemetry to record heart rate (HR), systolic blood pressure (SBP), and activity in the cage. Enrichment comprised a simulated burrow (Rodent Retreat), then a food foraging item ("rat cannoli") 2 days later, and a paper bag of bedding for shredding (Nestpak) after another 2 days. Data were collected under undisturbed conditions and before and after several acute and chronic manipulations mimicking common husbandry, experimental, and stressful procedures. Enrichment often, but not always, reduced HR and SBP in male rats, suggesting decreased arousal and stress, and the effects depended on the parameter measured, strain of rat, and nature of the procedure to which animals were exposed. In general, HR varied more than SBP; enrichment affected SH rats more than SD rats; effects of enrichment were more consistently observed under undisturbed conditions than after manipulations of the rats; moderate responses to acute husbandry and experimental procedures were affected more than the larger changes produced by very stressful procedures; and responses to social interactions were unaffected by the enrichment program. What accounts for these variable effects of enrichment is unclear, and more studies are required to resolve the mechanisms. Whether this enrichment program should be used in an animal facility depends on several factors, particularly the professional judgment of the research, veterinary, and animal care staffs involved.

Newly constructed animal facilities require microbiological evaluation prior to occupation to ensure that all facets of the design not only function accordingly and that the building is ready for introduction of new, healthy animal species and personnel. Our objective was to perform microbiological monitoring to ensure the integrity of systems implemented within our facility, both new and those transferred from existing facilities. This monitoring included environmental sampling of the autoclaves, cage washers, tunnel washers, and water system to ensure operant conditions. A sentinel surveillance program also was conducted using Crl:CD1(ICR) mice, C57BL/6J mice, and Crl:CD(SD) rats to make certain the facility had not been contaminated by any infectious agents that could affect animal health prior to their introduction into the facility. On the basis of these results, we introduced new animals, transferred existing animals, relocated personnel, and implemented new measures for sanitation that previously had not been used in any of our other facilities.

A zebrafish larval rearing system experienced a surge in mortality rates soon after the introduction of new stocks. A comprehensive water analysis of pH, nitrites, nitrates, ammonia, chlorine, carbonate hardness, general hardness, and conductivity identified no anomalies. Observations via light microscopy of affected fry revealed consistent signs of impaired mobility, blood clotting, and eventual heart hemorrhage resulting in the death of 90 to 100% of the fry by the age of 2 weeks. Collection of sufficient tissue samples for a histological investigation proved problematic due to the fry's diminutive size. Because a causal agent could not be isolated satisfactorily, the use of a broad-spectrum antibiotic was deemed necessary. After considering many broad-spectrum antibiotics for treatment, we implemented a two-tiered approach for treatment. The rearing system was treated with a nitrofurazone derivative, whereas the adult populations were treated using multi-antibiotic food pellets. The rearing system was treated for 3 weeks, and the adult population was treated for 2 weeks. After the completion of the antibiotic treatments, the biological filters of all of the medicated systems were seeded with nitrifying bacterial cultures. Upon the maturation of the rearing systems' biological filters, mortality rates returned to pre-outbreak levels. There have been no re-occurrences of the fish mortality since the completion of treatment. This epidemic provided some valuable lessons, lessons that if followed, will ensure faster response to unknown pathogens in the future.