Rodents (1996) / Chapter Skim
Currently Skimming:
8 RODENTS THAT REQUIRE SPECIAL CONSIDERATION
8 RODENTS THAT REQUIRE SPECIAL CONSIDERATION
Pages 121-158
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 121... ...
, some strains of mice that carry the homozygous mutation nu (nude) , and rodents exposed to sublethal irradiation are so severely immunodeficient that contact with infectious agents of even low pathogenicity can cause severe illness and death, and they require isolation for survival (NRC, 1989~.
|
From page 122... ...
Husbandry In general, the cages or other implements used to house immunodeficient rodents should be capable of being adequately disinfected or sterilized on a regular basis. The housing systems should be capable of eliminating airborne contamination of the animals and should be capable of being manipulated without exposing the animals to microbiologic contamination during experimentation and routine husbandry procedures.
|
From page 123... ...
Moreover, only minimal mechanical safeguards are built into this system, and success depends absolutely on technique. A major drawback to using plastic cages with filter tops is that there is a low rate of air exchange between the cage and the room.
|
From page 124... ...
HEPA-Filtered Airflow Systems These systems have a variety of forms, including modular chambers, hoods, and racks that are designed to hold cages under a positive flow of HEPA-filtered air. In some instances, plastic cages with filter tops have been used in laminar airflow racks that supply a steady stream of HEPAfiltered air across the cage tops to facilitate air diffusion through the filters.
|
From page 125... ...
In addition, because housing of immunocompromised animals generally requires systems that restrict airflow and heat transfer, temperatures in the animal cages tend to be higher than ambient temperature; therefore, increasing the room temperatures is generally not necessary. Humidity and ventilation should be consistent with recommendations in the Guide (NRC, 1996 et seq.~.
|
From page 126... ...
Health monitoring of animals maintained in individual plastic cages with filter tops is complicated by the potential for contamination of individual cages, as opposed to large groups of cages, with a particular microorganism. Because frequent screening of every cage is not economically feasible, statistical schemes for sampling or batching soiled bedding for exposure of sentinel animals is often required.
|
From page 127... ...
A search of the literature will locate investigators who maintain feral rodents in a laboratory environment; however, these scientists usually do not maintain enough animals to permit distribution of more than a few. Colonies of wild rodents are listed in the International Index of Laboratory Animals (Festing, 1993)
|
From page 128... ...
; solid-bottom cages with wood shavings or other bedding are preferred (Dewsbury, 1984~. Most small wild rodents are much quicker than domesticated rodents and can easily escape if the handler is not careful.
|
From page 129... ...
can be maintained with the same husbandry procedures as laboratory mice. A maximum of seven can be housed in 7 x 10 inch plastic cages.
|
From page 130... ...
AGING COHORTS Mice and rats have been favored by mammalian gerontologists as experimental models because of their relatively short and well-defined life spans, small size, comparatively low cost, and the large and growing store of information on their genetics, reproductive biology, physiology, biochemistry, endocrinology, neurobiology, pathology, microbiology, and behavior. However, the term comparatively low cost is used advisedly.
|
From page 131... ...
Survivorship in any colony used for gerontologic research should be determined repeatedly. Survival curves for SPF mice and rats should exhibit a classic "rectangularization pattern," that is, a survival curve should nearly parallel the X axis close to the 100-percent survival level for a prolonged period and then decline sharply as the population nears the species' maximum life span (MxLS)
|
From page 132... ...
For a discussion of the specific uses and relative values of inbred, congenic, recombinant inbred, and nongenetically defined populations, see Gill (19801. Eight SPF mouse strains, commonly used for gerontologic studies are available from the NIA: inbred strains A/HeNNia, BALB/cNNia, CBA/ CaHNNia, C57BL/6NNia, and DBA/2NNia and hybrid strains BALB/cNNia x C57BL/6NNia F1 (CB6F1)
|
From page 133... ...
The prevalence of specific kinds of neoplasms varies among strains. Infectious diseases, including a chronic respiratory complex associated with Mycoplasma pulmonis, can also affect life span.
|
From page 134... ...
Caloric intake for CR rats was 60 percent of that for AL-fed rats. Calories were reduced gradually between 12 and 16 weeks of age and then continued at reduced level for remainder of life span.
|
From page 135... ...
When CR animals are being compared with AL-fed controls, it is desirable to regulate the light cycle so that both groups will begin eating simultaneously, and activity, cell division, hormone concentrations, and other characteristics will be measured in both groups at similar times on the blood-glucose and -insulin curves. Mice and rats are essentially nocturnal, and AL-fed animals naturally begin feeding shortly after the dark cycle begins.
|
From page 136... ...
Record-Keeping Record-keeping is discussed in Chapters 4 and 5. Some special considerations apply in aging rodent colonies.
|
From page 137... ...
Infectious agents of particular concern to gerontologists are mouse hepatitus virus, Sendai virus, rotavirus, and Mycoplasma pulmonis in mice and Sendai virus, Kilham rat virus, rat corona/sialodacryoadenitis virus, and Mycoplasma pulmonis in rats (Lindsey, 1986; NRC, 19911. Those agents are of concern because they affect either immune function or general health.
|
From page 138... ...
has been somewhat neglected by gerontologists because of its comparatively large size, relatively long life span, and relatively high cost of maintenance. Although published survival curves have indicated an MxLS of around 80 months (Rust et al., 1966)
|
From page 139... ...
Guinea pigs are highly susceptible to a variety of infectious diseases; therefore, it is important to maintain them under SPF conditions for gerontologic research. Several such colonies have been established.
|
From page 140... ...
Several outbred, inbred, and mutant stocks have been developed, but they are not as readily available as some other rodents. The life span characteristics of this species have not been rigorously investigated; however, although typical survival curves have been demonstrated for females, the curves for males, which usually live longer, are atypical.
|
From page 141... ...
. Although it is recognized that the imposition of selection criteria can delay achieving inbred status, the goals of any breeding strategy must include preservation of the desired phenotypic characteristics (e.g., the development of diabetes mellitus)
|
From page 142... ...
Blood samples should be obtained from the tail within 2 hours of the urine test and tested with an appropriate technique. Animals testing 4+ for glycosuria and having blood glucose concentrations greater than 250 mg/dL are considered diabetic.
|
From page 143... ...
. ~ _ course of action depends on the ratio of insulin to "ideal" body weight TABLE 8.2 Starting Doses of Insulin for BB/Wor Rats That Become Diabetic After the Age of 65 Days Initial Blood Glucose Concentration, m: /dL 250 300 350 400 450 500+ Body weight, ga Starting Dose of Insulin,b U 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 0.4 0.4 0.6 0.8 1.0 1.2 1.4 1.4 1.4 1.6 1.6 1.8 2.0 _.
|
From page 144... ...
Use of Spleen Cells to Reduce Frequency of Diabetes and Improve Breeding Efficiency Diabetes-prone rat strains are profoundly T-cell lymphopenic. Injections of neonatal bone marrow, fresh spleen cells, or concanavalin-A-stimu
|
From page 145... ...
Fresh spleen cells are obtained from diabetes-resistant rats, which are histocompatible with diabetes-prone rats but are not lymphopenic. Spleens are prepared with standard techniques (Burstein et al., 1989~.
|
From page 146... ...
or plasma glucose concentration is increased. This determination can be made by measuring blood glucose directly or by measuring urinary glucose with a glucose test strip.
|
From page 147... ...
RODENTS THAT REQUIRE SPECIAL CONSIDERATION 147 diets, including standard, commercially available mouse feed, promote a high incidence of diabetes (Coleman et al., 1990~. NOD is an inbred strain and should be maintained by brother x sister mating.
|
From page 148... ...
Flexible-film or rigid isolator systems, however, permit the most complete control of the physical and microbiologic environment. Microbiologic status should be monitored regularly and should include testing for standard murine infectious agents.
|
From page 149... ...
Pronuclear embryos are generally collected 14-17 hours after the beginning of the dark cycle. For example, if the dark cycle begins at 10 p.m., PMSG would be administered between 1 and 3 p.m.
|
From page 150... ...
150 RODENTS: LABORATORYANIMAL MANAGEMENT of DNA extracted from tissue taken from the tip of the tail; approximately 1 cm of tissue is sufficient. Rarely, it is possible to identify transgenic mice by detecting gene products from the introduced DNA.
|
From page 151... ...
Data Management A large amount of data accumulates in a transgenic colony and must be managed efficiently. ~ ~ ~ Daily or weekly records Include data on oreeolng birth, weaning, death, and laboratory analyses; they also include documentation of observations on such things as characteristics that are possibly related to gene manipulation, pathologic conditions, and unusual behaviors.
|
From page 152... ...
1979. Survival characteristics of mouse strains.
|
From page 153... ...
1979b. Inbred and Genetically Defined Strains of Laboratory Animals.
|
From page 154... ...
Pp. 114-185 in Genetics and Probability in Animal Breeding Experiments: a primer and reference book on probability, segregation, assortment, linkage and mating systems for biomedical scientists who breed and use genetically defined laboratory animals for research.
|
From page 155... ...
1978. Revi¢w of disease patterns and life span in aging mice: Genetic and environmental interactions.
|
From page 156... ...
, Institute of Laboratory Animal Resources' Committee on Infectious Diseases of Mice and Rats.
|
From page 157... ...
1992. Survival curves, reproductive life span and age-related pathology of Mus carol)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.