Naturally-occurring neoplasms in the Mongolian gerbil, Meriones unguiculatus.

10 spontaneous tumours were observed. Several had not been previously reported for this species and 1 occurred in the youngest gerbil yet reported to have a spontaneous tumour. 7 of the 10 tumours originated from the female reproductive tract.     

Sister chromatid exchange in the Mongolian gerbil, Meriones unguiculatus

Sister chromatid exchange (SCE) studies have been performed in a variety of animals, both in vitro and in vivo, as well as in plants. To date, no such studies have been performed in any member of the gerbil sub-family (Gerbillinae). A new sister chromatid differential staining method was used with mice in vivo and has now been applied to the Mongolian gerbil, Meriones unguiculatus. With some modifications, this in vivo method was found to be highly reproducible in gerbils, and had consistently produced many metaphase cells with clear sister chromatid differentiation. The method involves subcutaneous implantation of a 50 mg slow-release BrdU pellet, the fluorochrome Hoechst 33258, phosphate buffering at pH 6.8, and incandescent light exposure.     

Innervation of the pineal gland in the Mongolian gerbil (Meriones unguiculatus)

Summary Parasympathetic stimulation of parotid glands has been studied in vivo, a) in normal resting glands, b) 72 h after post-ganglionic sympathectomy and c) after adrenergic degranulation of the acinar cells.Morphological results in each gland were compared with a similarly pretreated, but not parasympathetically stimulated, contralateral gland from the same animal.On parasympathetic stimulation of glands with densely granulated acinar cells (groups a- and b-) a variable, but usually relatively small, tendency for vacuole formation occurred in some cells. After prior degranulation of the cells (group c-) the tendency for vacuole formation was greatly accentuated. This indicates that the pre-existing metabolic state of the cells can influence the responses to stimulation of a single nerve. Dilatation of rough endoplasmic reticulum and nuclear changes were also more prominent after parasympathetic stimulation of previously degranulated acinar cells, and this suggests that parasympathetic impulses may have strong activating effects on resynthesis under these conditions. It is also likely that parasympathetic stimulation induced some, albeit small, degree of degranulation and, since this occurred in the absence of sympathetic nerves (group b-) it was probably the consequence of a direct cholinergic effect. The present results therefore indicate that the concept of an absolute dichotomy between parasympathetic and sympathetic responses is not tenable in this tissue.Analyses of saliva for amylase and peroxidase gave complex results but indicate that the two enzymes are not necessarily secreted in parallel. The morphological results support the idea that some enzyme molecules may have entered the saliva without being prepackaged into secretory granules, but could have passed directly from dilated cisterns of rough endoplasmic reticulum into intra-cellular vacuoles, and this tendency was most apparent after para-sympathetic stimulation of previously degranulated cells.Travel grants from the Wellcome Trust to J.R. Garrett are gratefully acknowledged. This work has been helped by the technical assistance of Mr. P.S.A. RowleyM.R.C. Research Assistant     

Aldehyde dehydrogenase of the Mongolian gerbil, Meriones unguiculatus.

The aldehyde dehydrogenase (Aldehyde:NAD(P) oxidoreductase E.C. 1.2.1.3. and 1.2.1.5) phenotype in several tissues of the Mongolian gerbil, Meriones unguiculatus, has been established. The tissue distribution of gerbil aldehyde dehydrogenase is similar to that of the rat, with liver possessing the majority of the aldehyde dehydrognease activity. Male kidney and testis possess significantly more activity than female kidney and ovary. The substrate and co-enzyme specificity of gerbil liver aldehyde dehydrogenase is also similar to that of rat and mouse liver. Gel isoelectric focusing resolves one major gerbil liver aldehyde dehydrogenase isozyme at pI 5.3. Mouse liver is resolved into two major isozymes at pIs 5.3 and 5.6 and rat liver aldehyde dehydrogenase into one major isozyme at pI 5.4. Gerbil liver aldehyde dehydrogenase is functional over a broad pH range with an optima at pH 9.0. Rat and mouse liver aldehyde dehydrogenase possess sharp pH optima at pH 8.5.     

Carbon tetrachloride-induced liver cell injury in the Mongolian gerbil (Meriones unguiculatus)

1. Male Mongolian gerbils (Meriones unguiculatus) liver activates CCl4 to free radicals that bind covalently to cellular components (CB) and stimulate a lipid peroxidation (LP) process to a larger extent than the rat liver. 2. CCl4 administration results in a less intense necrogenic effect in gerbils than in rats and does not cause fatty liver. 3. CCl4 causes less intense effects on liver ultrastructure or calcium metabolism but more marked depression of glucose 6 phosphatase activity (G6P-ase) in gerbils than in rats. 4. Results suggest that a better ability of gerbil liver to keep calcium homeostasis than rat liver might be the cause of their relative resistance to necrosis. Higher intensity of CB and LP in gerbils than in rats might explain more intense effects on G6P-ase.     

Non-specific resistance to Babesia divergens in the Mongolian gerbil (Meriones unguiculatus)

Inoculation of mature gerbils with BCG gave protection to subsequent infection with B. divergens when inoculated by the intracardiac and intraperitoneal routes, the latter showing a dose dependent relationship. BCG vaccination was most effective in immature gerbils (less than 4 weeks old), which are innately resistant to B. divergens. Vaccination of gerbils with killed Propionesbacterium acne and zymosan A failed to elicit a protective response, which contrasts conspicuously with rodent babesia studies. Incubation of B. divergens-infected gerbil blood with hydrogen peroxide produced parasite inhibition only at the highest concentration and treatment of parasitized gerbils with the oxidative radical inducer, alloxan monohydrate, gave equivocal results so it is evident that, unlike Plasmodium spp., B. divergens is not significantly susceptible to the action of reactive oxygen forms.     

Water balance during saline imbibition in the Mongolian gerbil (Meriones unguiculatus)

1. There were few changes in the water balance of gerbils drinking 0.25 and 0.50 M NaCl solutions for 5 days. 2. Imbibition of 0.75 and 1.0 M saline resulted in some dehydration of the body fluids and considerable depletion of the neural lobe vasopressin store. 3. Although large amounts of NaCl were excreted, the maximum urine osmolality was considerably less than that found following water deprivation. 4. The imbibition of 1.0 M saline caused similar changes in water balance to water deprivation showing that little, if any, water was gained from this solution.     

Lysosomal enzymes in oocytes of the Mongolian gerbil,Meriones unguiculatus

Summary Histochemical investigations reveal that the intact oocytes of the Mongolian gerbil, Meriones unguiculatus, contain numerous acid phosphatase positive granules in every follicular stage. Non-specific esterase is active in early oocytes only in a faint peripheral margin of the ooplasm and in the zona pellucida of large secondary and tertiary follicles.This investigation was supported by the Deutsche Forschungsgemeinschaft (Ko 742/1)     

Craniopharyngioma in the Mongolian gerbil (Meriones unguiculatus): a case report

A case of spontaneously occurring infiltrative craniopharyngioma in a laboratory-reared gerbil is reported. The histopathological and ultrastructural features are described.