The Nude Mouse

The nude mouse is ham without a thymus.In most vertebrates the thymus constitutes a vital part of the immune system. If the thymus is surgically removed from adult mice, no immediate changes can be observed in immune responses, - even if present day refined laboratory techniques can demonstrate alterations in the function of lymfjhocytes of such animals. If the thymus 2's surgically removed from mice within 24 hours of birth, however, there is rapid marked impairment in the animals’ cell—mediated immune responses, and in the formation of humoral antibodies to a number of antigens. Now, the nude mouse is born without a thymus. This would make one suppose that the made mouse does represent a base line for study of thymic function in the immune system. And furthermore, that the absence of the thymus could be exploited in studies of other biological systems, e.g. malignant tumour tissue, transplanted in the nude mouse. In the following we summarize some of the evidence in favour of this

Doses for Laboratory Animals based on Metabolic Rate

The differences in metabolic rates (M) of different mammals often make it difficult to estimate the dose of e.g. anaesthetics from one species to another. It is well known that the mammalian metabolic rate is correlated to the body weight (W), and the relationship between body weight and metabolic rate kan be expressed using the equation:(1) M = 3.8 x W-25Using the assumption, that the dose of e.g. an anaesthetic only depends on the metabolic rate of the animal, a simple mathematic equation can be used in scaling the dose from one species to another: As an example the equation is employed for the calculation of the doses of pentobarbital for a series of different mammals of different size. The calculated doses agree well with the doses reported in the literature. The equation may be of generel usefulness for a quick calculation of a suitable dose level, when the dose level of another species is known

Regulation and Function of FTO mRNA Expression in Human Skeletal Muscle and Subcutaneous Adipose Tissue

OBJECTIVE-Common variants in FTO (the fat mass- and obesity-associated gene) associate with obesity and type 2 diabetes. The regulation and biological function of FTO mRNA expression in target tissue is unknown. We investigated the genetic and nongenetic regulation of FTO mRNA in skeletal muscle and adipose tissue and their influence on in vivo glucose and fat metabolism. RESEARCH DESIGN AND METHODS-The FTO rs9939609 polymorphism was genotyped in two twin cohorts: 1) 298 elderly twins aged 62-83 years with glucose tolerance ranging from normal to type 2 diabetes and 2) 196 young (25-32 years) and elderly (58-66 years) nondiabetic twins examined by a hyperinsulinemic-euglycemic clamp including indirect calorimetry. FTO mRNA expression was determined in subcutaneous adipose tissue (n = 226) and skeletal muscle biopsies (n = 158). RESULTS-Heritability of FTO expression in both tissues was low, and FTO expression was not influenced by FTO rs9939609 genotype. FTO mRNA expression in skeletal muscle was regulated by age and sex, whereas age and BMI were predictors of adipose tissue FTO mRNA expression. FTO mRNA expression in adipose tissue was associated with an atherogenic lipid profile. In skeletal muscle, FTO mRNA expression was negatively associated to fat and positively to glucose oxidation rates as well as positively correlated with expression of genes involved in oxidative phosphorylation including PGC1 alpha. CONCLUSIONS-The heritability of FTO expression in adipose tissue and skeletal muscle is low and not influenced by obesity-associated FTO genotype. The age-dependent decline in FTO expression is associated with peripheral defects of glucose and fat metabolism. Diabetes 58:2402-2408, 200

Dietary carbohydrate source influences molecular fingerprints of the rat faecal microbiota

BACKGROUND: A study was designed to elucidate effects of selected carbohydrates on composition and activity of the intestinal microbiota. Five groups of eight rats were fed a western type diet containing cornstarch (reference group), sucrose, potato starch, inulin (a long- chained fructan) or oligofructose (a short-chained fructan). Fructans are, opposite sucrose and starches, not digestible by mammalian gut enzymes, but are known to be fermentable by specific bacteria in the large intestine. RESULTS: Animals fed with diets containing potato starch, or either of the fructans had a significantly (p < 0.05) higher caecal weight and lower caecal pH when compared to the reference group, indicating increased fermentation. Selective cultivation from faeces revealed a higher amount of lactic acid bacteria cultivable on Rogosa agar in these animals. Additionally, the fructan groups had a lower amount of coliform bacteria in faeces. In the inulin and oligofructose groups, higher levels of butyrate and propionate, respectively, were measured. Principal Component Analysis of profiles of the faecal microbiota obtained by Denaturing Gradient Gel Electrophoresis (DGGE) of PCR amplified bacterial 16S rRNA genes as well as of Reverse Transcriptase-PCR amplified bacterial 16S rRNA resulted in different phylogenetic profiles for each of the five animal groups as revealed by Principal Component Analysis (PCA) of band patterns. CONCLUSION: Even though sucrose and cornstarch are both easily digestible and are not expected to reach the large intestine, the DGGE band patterns obtained indicated that these carbohydrates indeed affected the composition of bacteria in the large gut. Also the two fructans resulted in completely different molecular fingerprints of the faecal microbiota, indicating that even though they are chemically similar, different intestinal bacteria ferment them. Comparison of DNA-based and RNA-based profiles suggested that two species within the phylum Bacteroidetes were not abundant in numbers but had a particularly high ribosome content in the animals fed with inulin