Hemoglobin polymorphism in inbred strains of rats (Rattus norvegicus)

Hemoglobin phenotypes A and B were determined by polyacrylamide gel electrophoresis of erythrocyte lysates from 29 inbred strains of rats. Fourteen strains have phenotype A and fifteen have phenotype B, which are characterized by five and six hemoglobin bands, respectively. Breeding studies showed that the phenotypes are codominant and that they segregate in a simple Mendelian fashion in the (A×B) F₁×A backcross. Sex and hemoglobin phenotype assort independently, and the hemoglobin phenotype is not linked to the major histocompatibility complex (RT1) and to two erythrocyte alloantigenic systems (RT2 and RT3).This work was supported by National Institutes of Health Grant CA 18659.     

Polymorphisms detected in actin-related sequences of rats (Rattus norvegicus)

Southern blot hybridization of EcoRI digests of DNAs from 13 rat strains using human cardiac actin gene as a probe revealed polymorphisms in actin-related sequences of rats. EcoRI fragments of 11 kb, 7 kb, 6 kb, 5 kb, 4.5 kb and 4 kb detected in several strains were absent in the remaining strains. The presence of these fragments was suggested to be due to presence of extra sequences homologous to the actin genes, such as processed pseudogenes, in the particular strains. The 13 strains were assigned to each of 7 specific patterns of the polymorphic EcoRI fragments. It was concluded that the polymorphisms of actin-related sequences should be useful for genetic monitoring of laboratory rats.     

Comparative studies on release of enzymes from platelets during blood clotting in Rattus rattus flavitecus and Rattus norvegicus (author's transl)

Increase of lactate dehydrogenase (EC 1.1.1.28) and creatine kinase (EC 2.7.3.2) in serum and plasma level during blood clotting was compared in R. rattus flavitectus (black rat) and R. norvegicus (albino rat). Both the enzyme level increased by the release from platelets in process of clotting in rat as previously described (Emori T., Takahashi M. and Nagase S. (1978) Exp. Animals, 27, 167), but the change in black rat was very slight. Owing to search for the reason to prove the difference in this phenomenon, physiological and chemical properties of blood from both the animals were compared, and it was demonstrated that the content of plasma fibrinogen in black rat is higher than that in albino rat, while the platelet number contained in each ml of blood and the enzyme activities in each platelet are not different between them. The analysis of the membrane proteins from platelets of both the animals by SDS-polyacrylamide gel electrophoresis showed that the fractional value of glycoproteins was found to be different between them.     

Influences of food type on food-carrying behavior in rats (Rattus norvegicus)

It is known that rats tend to eat a smaller/lighter piece of food at the food source but carry a larger/heavier one to the nest for consumption. This could be interpreted well in terms of the trade-off or motivational conflict between "feeding" and "risk avoidance", because eating food immediately satisfies feeding motivation while carrying food has an advantage to avoid predatory risk by keeping time spent outside the nest shorter. In the present study, influences of incentive factors of feeding motivation on food-carrying behavior were evaluated using three different kinds of food that were identical in weight. There was no significant difference in food-carrying tendency among the three kinds of food, though a significant preference was indicated among the food. The results suggest that food-carrying behavior is not influenced by food types.     

The effects of environmental control on cognition in rats (Rattus norvegicus)

The aim of this study was to allow nonhuman animals to control their environment using operant conditioning procedures and to assess the effect of control on cognitive tasks. The study tested 4 predictions: (a) rats (Rattus norvegicus) will control a light stimulus; (b) animals will exhibit preferences for particular stimulus strengths; (c) animals who exert control over environmental stimuli will show improved performance on cognitive tasks compared with animals who lack control; and (d) at the end of the operant phase, experimental subjects will have lower corticosterone levels than animals who lack control. Experimental subjects did show control over a light stimulus and performed significantly better over time in a discrimination task compared with subjects who could not control their environment. There was no difference in corticosterone levels between control and experimental subjects. The results will both contribute to our understanding of how control of environmental stimuli affects the welfare of animals in captive environments and aid in designing experimental conditions that will increase validity and reliability in research.     

Etiological structure of icterohemorrhagic leptospirosis in gray rats (Rattus norvegicus)

In 93 Leptospira strains isolated from Norwegian rats serovar determination was made. As a result, leptospires circulating among Norwegian rats were found to belong mainly to serovar copenhageni, group Icterohaemorrhagiae, while leptospires of serovar icterohaemorrhagiae, even if occurring, were found only in the animals inhabiting pigsties. Leptospirosis epizooty among rats, caused by L. icterohaemorrhagiae, took its course independently of leptospirosis epizooty among mice, caused by L. hebdomadis, and simultaneously with it.     

Genetic differences in milk proteins among laboratory rats (Rattus norvegicus)

Genetic differences in the electrophoretic pattern of milk proteins were observed among different inbred rat strains. The results of segregation analysis made on a limited number of females is consistent with the hypothesis of two codominant autosomal alleles system.     

Comparative anatomical studies of thyroid and thymic arteries: I. Rat (Rattus norvegicus albinus)

The thyroid and thymic arteries were investigated in 50 male and 50 female rats. In more than 70% of the animals, on both sides the cranial thyroid artery forms a common trunk with the ascending pharyngeal artery. The caudal thyroid artery arises not from the deep cervical but from the pericardiacophrenic artery. It may be replaced, however, by a branch of some other artery, such as the brachiocephalic, subclavian, vertebral, or ascending cervical, suggesting a shift of its origin from the internal thoracic artery to the thyrocervical trunk as in man. All the thoracic lobes of the thymus are supplied directly by a thymic branch of the internal thoracic artery or indirectly by a branch of the pericardiacophrenic artery. More than half of the specimens have a cervical thymic lobe of variable size, which is supplied by a branch of the cranial thyroid, external carotid, and/or occipital arteries. Some of these thymic arteries, except those from the external carotid and occipital arteries, reach the thoracic lobe. The thoracic lobes lacking a cervical lobe may be supplied by the thymic branch arising only from the cranial thyroid artery. Other anomalous arteries supplying the thoracic lobe are derived from the superficial cervical and/or the right common carotid arteries. These results show that the thymic arteries of rats are basically similar to those of man, although they display a clear difference in their frequency and origin.     

Evidence for linkage between four esterase loci in the rat (Rattus norvegicus)

Two new esterase polymorphisms have been described in tissue homogenates of the four rat strains August/Orl, LEW/Orl, Long Evans/Orl, and WAG/Orl. Independent expression of these polymorphisms in the different strains and in various tissues of a particular animal agrees with the separate genetic control hypothesis; the gene symbols Es-4 and Es-5 have been assigned to the loci. Transmission of both genes follows a normal autosomal recessive Mendelian pattern; preliminary data indicate tight linkage between these loci and the previously described Es-2 and Es-3 loci.     

Nucleotide sequence variants of Rattus norvegicus mitochondrial DNA

The mitochondrial DNA (mtDNA) molecules of different albino, domesticated rats (Rattus norvegicus) of the SASCO colony are of two kinds (SASCO-1 and SASCO-2) in regard to their sensitivity at certain sites to a number of restriction enzymes. MtDNA molecules from Utah wild R. norvegicus (Wild-UT) have sensitivities to restriction enzymes which differ at some sites from either SASCO-1 or SASCO-2 mtDNA molecules. Four single nucleotide differences were found among the HindIII F fragments (169 nucleotides) of SASCO-1, SASCO-2, and Wild-UT mtDNAs. Arguments are presented in favor of the interpretation that each variant nucleotide is the third nucleotide of the codon containing it, and that none of the four differences would result in a difference in the respective amino acid translated.Dedicated to Professor W. Beermann on the occasion of his 60th birthday     

Leptospira interrogans biofilm formation in Rattus norvegicus (Norway rats) natural reservoirs

Rattus norvegicus (Norway rat) is the main reservoir host of pathogenic Leptospira, the causative agent of leptospirosis, in urban environments. Pathogenic Leptospira forms biofilms in the environment, possibly contributing for bacterial survival and maintenance. Nonetheless, biofilms have not yet been studied in natural animal reservoirs presenting leptospiral renal carriage. Here, we described biofilm formation by pathogenic Leptospira inside the renal tubules of R. norvegicus naturally infected and captured in an urban slum endemic for leptospirosis. From the 65 rats carrying Leptospira in their kidneys, 24 (37%) presented biofilms inside the renal tubules. The intensity of leptospiral colonization in the renal tubules (OR: 1.00; 95% CI 1.05–1.1) and the type of occlusion pattern of the colonized renal tubules (OR: 3.46; 95% CI 1.20–9.98) were independently associated with the presence of Leptospira biofilm. Our data showed that Leptospira interrogans produce biofilms during renal chronic colonization in rat reservoirs, suggesting a possible role for leptospiral biofilms in the pathogenesis of leptospirosis and bacterial carriage in host reservoirs.     

Effect of dietary protein on zinc phosphide toxicity in albino rats (Rattus norvegicus)

Adult male and female albino rats (R. norvegicus) were administered rodenticide, zinc phosphide ranging from 4, 2, 1, 0.5, 0.25 and 0.125% in the diet containing 10(A), 17(B) and 24%(C) protein. Zinc phosphide induced 100% mortality at 4, 2, 1, 0.5% in diet A; 4 and 2% in diet B; and 4% in diet C. The results reveal influence of dietary protein in modulating the toxicity of zinc phosphide, suggesting that greater caution should be exercised while formulating its baits for effectiveness. The results also suggest that baits having 10% protein are more suitable to carry the rodenticide from view point of acceptability and efficacy towards the target species.     

The influence of females upon aggression in domesticated male rats (Rattus norvegicus)

The aggression of adult male Long-Evans rats (Rattus norvegicus), toward males of the same strain, was tested before and after a 1-week period of cohabitation with a pair of intact females, ovariectomized females, or intact males, comparable to the females in size. Only cohabitation with intact females increased the aggression of resident males against unfamiliary male intruders. Female enhancement of aggression does not appear to be caused by sexual frustration of males, or a function of dominance-subordinance relations, per se. Increased aggression may be mediated by elevated testosterone production associated with mating.