Body and organ weights and linear measurements of the adult Mongolian gerbil

Gerbils

The gerbil is usually nonaggressive and is one of the easiest rodents to maintain and handle. Its disposition, curious nature, relative freedom from naturally occurring infectious diseases, and adaptability to its environment have contributed to its popularity as a laboratory animal. Gerbils are found in deserts and semiarid geographical regions of the world. The Mongolian gerbils that are available today originated from 20 pairs of captured animals that were maintained in 1935 in a closed, random-bred colony at the Kitasato Institute in Japan. Gerbils have several unique anatomical and physiological features. Mature gerbils are smaller than rats, but larger than mice. Mongolian gerbils are attracted to saliva and use salivary cues to discriminate between siblings and nonsiblings, and females use oral cues in the selection of sociosexual partners. Gerbils have been used as experimental models in a number of areas of biomedical research. Gerbils are excellent subjects for laboratory animal research as they are susceptible to bacterial, viral, and parasitic pathogens that affect humans and other species. Gerbils may have spontaneous seizures secondary to stress such as handling, cage change, abrupt noises, or changes in the environment. Cystic ovaries are seen commonly in female gerbils over 1 year of age. Gerbils have unique characteristics, which make them appropriate for a number of animal models. Classically, gerbils have been used in research involving stroke, parasitology, infectious diseases, epilepsy, brain development and behavior, and hearing.

Kidney Mass and Relative Medullary Thickness of Rodents in Relation to Habitat, Body Size, and Phylogeny

We tested the hypotheses that relative medullary thickness (RMT) and kidney mass are positively related to habitat aridity in rodents, after controlling for correlations with body mass. Body mass, mass-corrected kidney mass, mass-corrected RMT, mass-corrected maximum urine concentration, and habitat (scored on a semiquantitative scale of 1-4 to indicate increasing aridity) all showed statistically significant phylogenetic signal. Body mass varied significantly among habitats, with the main difference being that aquatic species are larger than those from other habitats. Mass-corrected RMT and urine concentration showed a significant positive correlation (N=38; conventional r=0.649, phylogenetically independent contrasts [IC] r=0.685), thus validating RMT as a comparative index of urine concentrating ability. RMT scaled with body mass to an exponent significantly less than 0 (N=141 species; conventional allometric slope=-0.145 [95% confidence interval (CI)=-0.172, -0.117], IC allometric slope=-0.132 [95% CI=-0.180, -0.083]). Kidney mass scaled to an exponent significantly less than unity (N=104 species; conventional slope=0.809 [95% CI=0.751, 0.868], IC slope=0.773 [95% CI=0.676, 0.871]). Both conventional and phylogenetic analysis indicated that RMT varied among habitats, with rodents from arid areas having the largest values of RMT. A phylogenetic analysis indicated that mass-corrected kidney mass was positively related to habitat aridity.

The Mongolian gerbil in aging research

The authors have explored the suitability of the Mongolian gerbil as a model in aging research and reviewed data on major factors in gerbil morbidity and mortality. The gerbil is a semi-desert rodent, introduced relatively recently into biomedical research. It is moderately prolific, has a maximum survival of about 208 weeks and is easily maintained. Maternal neglect, fighting and epidemic diseases (Tyzzer's disease, salmonellosis, pneumonia) are potential causes of mortality in gerbil colonies. Obese or breeding gerbils may exhibit hyperadrenocorticism, diabetes, non-lipoid arteriosclerosis and secondary lesions in several organs. There is a high prevalence of spontaneous neoplasms in aged gerbils, especially tumors of the adrenal cortex, ovary and skin. The gerbil is a useful model of experimentally-induced stroke, but has proven unsuitable for studies of cholesterol-induced atherosclerosis. The normal and pathological anatomy of periodontal disease in the gerbil is similar in many respects to that of man.

Body composition of the horse

Seventeen horses were dissected and their organs and tissues weighed. The results of these dissections are presented together with comparisons of the data with that already available in the literature. Predictive equations for organs and tissue weights are also given which were derived by comparison of linear and allometric regression models using 4 different body weight indices.

Temperature acclimation in the Mongolian gerbil (Meriones unguiculatus): biochemical and organ weight changes

1. Adult Mongolian gerbils (Meriones unguiculatus) were acclimated to 5 +/- 1, 24 +/- 1 and 34 +/- 1 degrees C for 6-8 weeks. 2. Body weights of temperature acclimated gerbils did not differ significantly from controls. Organ wt/body wt ratios of liver, kidney and heart increased in cold-acclimated and decreased in heat-acclimated gerbils. Adrenal wt/body wt ratio increased in the cold and was unchanged in the heat. Relative weights of brain, spleen, lungs, brown fat and ovaries + uterus did not change with temperature acclimation. 3. Cold acclimation produced significant increases in specific and total activity of brown fat alpha GPO and liver SO and AAO and in total activity of kidney SO; a significant decrease in liver mitochondrial ADP/O ratio with succinate as substrate; and no change in brown fat SO or liver alpha KGO. 4. Heat acclimation produced significant decreases in specific and total activity of liver and kidney SO, and in total activity of brown fat SO and alpha GPO, and liver AAO and alpha KGO. 5. The combined biochemical and organ wt changes seen in temperature-acclimated gerbils suggest that this species is capable of altering its metabolic thermogenic potential in response to a wide range of ambient temperatures.

Succinate dehydrogenase activity in the developing molar of the Mongolian gerbil Meriones unguiculatus

The distribution of succinate dehydrogenase in the odontogenic tissues in the Mongolian gerbil, ranging in age from 18 days prenatal to 8 days postnatal, was studied. Activity levels were designated negative, trace, slight, moderate, strong and very, dependent upon visual observations. The results indicated increased levels of activity as the tissue layers differentiated from the lamina stage through early apposition. The cell layer displaying the most succinate dehydrogenase activity was the ameloblastic layer while the stratum intermedium layer was the next most active cell layer. Succinate dehydrogenase activity appeared to be related to the degree of differentiation and functional competency of the odontogenic tissues in the Mongolian gerbil.