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1.
Kathryn A Belill Timothy L Settle C Roselina Angel Seon-Woo Kim Stephen W Rothwell 《Comparative medicine》2014,64(3):186-192
Rats are a common model for the study of bone healing, with the cranium, femur, and tibia being the bones studied most frequently. This study examines noncritical-sized lesions that would allow rats to continue to bear weight without the need for fixation but that are sufficiently large to enable characterization of the healing process. We compared the femoral bone strength associated with 3 lesion sizes selected for use in future studies. Sprague–Dawley rats (age, 10 to 16 wk) were used to assess the ultimate breaking strength, stress, and break force of normal, unmanipulated femurs. We then created lesions of 3 different sizes in the mid- to distal diaphysis of the left and right femurs and characterized the associated decreases in bone strength. Femurs (n= 85) for this study were collected through tissue sharing from rats used in other acute surgical procedures and were tested by using a 3-point bending flexural materials-testing machine. Our hypothesis was that, as a model for bone healing, 3 induced lesions of different sizes would show incremental and proportional decreases in femoral strength, with the intermediate-sized (1.5-mm) lesion demonstrating a decrease of 20% to 40%. A lesion of 1.5 mm yielded a decrease in strength of 17% for both the left and right femurs. The strength of left femurs carrying intermediate lesions was significantly less than that of control, uninjured femur bones. In addition to providing validation for our own future bone-healing project, these data are a useful baseline for other investigators studying bone healing in a rat femur model.Rodents, particularly rats, represent a reliable and affordable model for conducting basic research involving the skeleton.2 Although biomechanical techniques for testing bone strength have been well documented, few studies define the theory, methods, and experimental procedures for evaluating the fracture toughness of bone (fracture resistance), especially whole-bone testing in small animals.10 This said, femurs are still the ideal rat and mouse bones to use to evaluate the fracture toughness properties in small-animal model studies.4,10 Bending tests are useful to assess the mechanical properties of bones from rodents and other small animals.15 Even though this method of testing is referred to as a ‘bending test,’ the material (in this case, bone) is actually fractured to assess fracture toughness or breaking. For bending tests, long bones are loaded mainly in bending or compression during normal movement of the animals and are subject to both intrinsic and extrinsic large bending forces.4,14 In rodents, locomotion results in alternating tension and compression on the cortex of weight-supporting bones during the gait cycle, with no limit on the magnitude or direction in which these forces can be exerted.8 This makes testing of bending, compression, torsion or any combination of methods potentially applicable. Therefore we chose to conduct 3-point bending testing on rat femurs. Bones were stressed to the point of fracture and the values required were recorded for computer-assisted analysis.In the testing of bone, the fundamental structural properties of greatest importance are stiffness, strength, and toughness.8,10 Measured and calculated values of importance are peak force (ultimate breaking strength), fatigue resistance, stress, strain, break force, and energy to break. We chose to collect and compare peak force (measured data) as well as stress and break force (both calculated data). We made these choices because the most important biomechanical property from a clinical point of view is the peak force, which corresponds to the ability of a patient''s leg to resist high loading before a fracture or irreversible deformation occurs.Strength can be tested as tension, compression, bending, or shear.8,10 Strength as a material parameter is defined as the ultimate stress at which failure occurs, but strength is defined structurally as the ultimate load (or force) when failure of the system occurs.8 In the current study, we tested the strength of rat femurs via 3-point bending. We hypothesized that the 1.5-mm lesion, which involved 39% of the bone circumference, would yield a 20% to 40% decrease in strength. In addition, the femurs with induced lesions showed a consistent decrease in strength, with larger lesions associated with lower peak force on both the right and left sides. 相似文献
2.
Chelsea G. Himsworth David M. Patrick Sunny Mak Claire M. Jardine Patrick Tang J. Scott Weese 《Applied and environmental microbiology》2014,80(4):1299-1305
Clostridium difficile is an important cause of enteric infections in humans. Recently, concerns have been raised regarding whether animals could be a source of C. difficile spores. Although colonization has been identified in a number of domestic species, the ability of commensal pests to serve as a reservoir for C. difficile has not been well investigated. The objective of this study was to determine whether urban rats (Rattus spp.) from Vancouver, Canada, carry C. difficile. Clostridium difficile was isolated from the colon contents of trapped rats and was characterized using ribotyping, toxinotyping, and toxin gene identification. Generalized linear mixed models and spatial analysis were used to characterize the ecology of C. difficile in rats. Clostridium difficile was isolated from 95 of 724 (13.1%) rats, although prevalence differed from 0% to 46.7% among city blocks. The odds of being C. difficile positive decreased with increasing weight (odds ratio [OR], 0.67; 95% confidence interval [CI], 0.53 to 0.87), suggesting that carriage is more common in younger animals. The strains isolated included 9 ribotypes that matched recognized international designations, 5 identified by our laboratory in previous studies, and 21 “novel” ribotypes. Some strains were clustered geographically; however, the majority were dispersed throughout the study area, supporting environmental sources of exposure and widespread environmental contamination with a variety of C. difficile strains. Given that urban rats are the source of a number of other pathogens responsible for human morbidity and mortality, the potential for rats to be a source of C. difficile for humans deserves further consideration. 相似文献
3.
Pitipat Kitpipatkun Akira Yairo Konosuke Kato Katsuhiro Matsuura Danfu Ma Seijirow Goya Akiko Uemura Ken Takahashi Ryou Tanaka 《Comparative medicine》2020,70(6):499
The goal of this study was to evaluate diastolic intraventricular pressure gradients (IVPG) and 2-dimensional tissue tracking (2DTT) patterns during diabetes and cardiomyopathy. Rats (n = 60) were induced to become diabetic (DM group, n = 15) by using streptozotocin, to become cardiomyopathic (CM group, n = 15) by using isoproterenol, and to become both diabetic and cardiomyopathic (DMCM group, n = 15); control rats (CT group, n = 15) were injected with saline. Two months after induction, all rats underwent conventional echocardiography, IVPG, and 2DTT and then were euthanized for microscopic examination of cardiac fibrosis. Compared with the controls, all 3 treated groups showed diastolic dysfunction and delayed cardiac relaxation. DMCM rats showed the most pronounced cardiac abnormalities. In addition, CM and DMCM groups had showed decreased middle IVPG, whereas DMCM rats had decreased midapical IVPG. Although the overall IVPG of the CM group was normal, the middle segment was significantly decreased. 2DTT results showed that the DMCM group had a delay in relaxation compared with other groups. IVPG and 2DTT can be used to overcome the limitation of conventional echocardiographic methods and reveal diastolic dysfunction. DM worsened diastolic function during cardiac disease.Diabetes mellitus (DM) is a chronic disease identified by hyperglycemia.1 DM and associated insulin abnormalities result in hypertension, cardiovascular disease, and multiple organ dysfunction.18 Diabetic cardiomyopathy is defined as abnormal myocardial structure and performance in the absence of other cardiac risk factors, such as coronary artery disease, hypertension, and significant valvular disease, in patients with DM.3 A previous study showed that diastolic dysfunction could result from DM; and cardiac fibrosis in the interstitial and perivascular areas was a hallmark of long-term DM.23 Cardiac fibrosis in DM rats results from myocardial infarction.Cardiomyopathy can be induced in rats by using isoproterenol.17 Cardiomyopathy refers to the cardiac disorder in which myocardial abnormalities result from myocyte injury. Cardiomyopathy has several etiologies, including chronic hypertension, valvular abnormality, and toxin.15 Both DM and cardiomyopathy are fibrotic heart diseases, but their pathogenesis differs. Moreover, DM and CM cause fibrosis in different heart locations.The diastolic function of the left ventricle (LV) can be defined as the pull of blood into the LV under low filling pressure. Two groups have described the pressure differences that pull the blood through the mitral valve into the ventricle during diastole.6,16 The difference of pressure between the LV and aorta during systole and the importance of regional pressure differences within the ventricle during relaxation has recently gained attention.9,29 The diastolic intraventricular pressure gradient (IVPG) in the LV is closely related to LV relaxation. Deterioration of the IVPG is associated with abnormal LV blood flow patterns.22D tissue tracking (2DTT) echocardiography is a promising technique that quantifies myocardial deformation by tracking the ultrasonographic speckle pattern of the cardiac cycle.13 Because of the importance of measuring diastolic function, we used conventional echocardiography, IVPG and 2DTT to evaluate the diastolic impairment without altering systolic function. We studied the relationship between mild (DM rats) and moderate (CM rats) cardiac fibrosis due to myocardial injury and infarction together with the severe fibrosis that develops due to the combination of DM and cardiomyopathy.Streptozotocin and isoproterenol were used to induce DM and cardiomyopathy, respectively. Both cause cardiac fibrosis, but the pathogenesis and affected location are different. Our study was designed to evaluate diastolic IVPG and 2DTT as diastolic indices. Our goal was to delineate IVPG and 2DTT patterns in DM, CM, and very severe fibrotic heart disease induced by combining DM and cardiomyopathy. 相似文献
4.
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. 相似文献
5.
Necropsy and histopathologic examination of a rat (Rattus norvegicus) revealed megaesophagus and gangrenous bronchopneumonia. The esophageal dilitation, mural atrophy with persistence of neural structures, regurgitation and bronchopneumonia seen in this case were similar to findings in other animals with megaesophagus. 相似文献
6.
Jesús A. Panti-May Ticiana S. A. Carvalho-Pereira Soledad Serrano Gabriel G. Pedra Josh Taylor Arsinoê C. Pertile Amanda Minter Vladimir Airam Mayara Carvalho Nivison N. Júnior Gorete Rodrigues Mitermayer G. Reis Albert I. Ko James E. Childs Mike Begon Federico Costa 《PloS one》2016,11(3)
The Norway or brown rat (Rattus norvegicus) is among the most ubiquitous of rodents. However, the lack of studies describing Norway rat populations from tropical areas have limited our understanding regarding their demography and seasonal dynamics. In this study, we describe seasonal pattern in the abundance, reproductive parameters, and morphometrics of Norway rat populations in Salvador, Brazil. Rodents were trapped over four seasonal trapping periods (2013–2014) from three valleys. A total of 802 Norway rats were trapped over the course of the study over 7653 trap-nights. Norway rat abundance was high, but there was no significant differences between seasons. The reproductive parameters (e.g. frequency of pregnant and lactating females) did not show statistical differences between seasons. Female rats collected in the rainy season were heavier and older than females from the dry season. Salvador rats had a high incidence of pregnancy and birth rate (estimated birth rate of 79 young per year) compared to previous studies. The information generated is critical for the understanding of the ecology of Norway rat, the main reservoir of Leptospira in Salvador. However, future studies examining the effect of rodent control programs aimed at reducing populations, and determining rates of recovery, will further clarify our understanding of population dynamics. 相似文献
7.
W. J. Moore 《Journal of Zoology》1966,149(2):137-144
A longitudinal study of growth in the rat skull, based on serial radiographs, has shown that by the age of one month after birth, the braincase attains some 93% of its adult (fifth-month) size whilst the facial skeleton and mandible attain but 75% of their adult size. By the third month, growth in the braincase has virtually ceased, whereas significant facial growth continues until the age of five months. 相似文献
8.
JAMES BRODIE 《Journal of Zoology》1981,195(4):542-546
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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. 相似文献
12.
Polymorphic microsatellite loci of the rat (Rattus norvegicus) 总被引:4,自引:0,他引:4
Tetsuo Kunieda Eiji Kobayashi Motokazu Tachibana Hiroshi Ikadai Tomonori Imamichi 《Mammalian genome》1992,3(10):564-567
The EMBL and GenBank DNA databases were searched for microsatellite sequences of the rat containing dinucleotide repeats of (CA)n and (GA)n. Among those obtained, 23 sequences were analyzed by polymerase chain reaction to examine the size variation of the amplified fragment in inbred rat strains. All of the 23 microsatellite sequences varied in size among the strains tested. The 23 microsatellite loci in a pair of substrains separated from the same progenitor strain were then analyzed. Fragments identical in size were observed in all loci of the two substrains, indicating the stability of the microsatellite over a large number of generations. The microsatellite loci, therefore, should be useful markers for linkage analyses in the rat. 相似文献
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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. 相似文献
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Chelsea G. Himsworth Julie Bidulka Kirbee L. Parsons Alice Y. T. Feng Patrick Tang Claire M. Jardine Thomas Kerr Sunny Mak John Robinson David M. Patrick 《PLoS neglected tropical diseases》2013,7(6)
Background
Leptospira interrogans is a bacterial zoonosis with a worldwide distribution for which rats (Rattus spp.) are the primary reservoir in urban settings. In order to assess, monitor, and mitigate the risk to humans, it is important to understand the ecology of this pathogen in rats. The objective of this study was to characterize the ecology of L. interrogans in Norway rats (Rattus norvegicus) in an impoverished inner-city neighborhood of Vancouver, Canada.Methodology/Principal Findings
Trapping was performed in 43 city blocks, and one location within the adjacent port, over a 12 month period. Kidney samples were tested for the presence of L. interrogans using PCR and sequencing. A multivariable model was built to predict L. interrogans infection status in individual rats using season and morphometric data (e.g., weight, sex, maturity, condition, etc.) as independent variables. Spatial analysis was undertaken to identify clusters of high and low L. interrogans prevalence. The prevalence of L. interrogans varied remarkably among blocks (0–66.7%), and spatial clusters of both high and low L. interrogans prevalence were identified. In the final cluster-controlled model, characteristics associated with L. interrogans-infection in rats included weight (OR = 1.14, 95% CI = 1.07–1.20), increased internal fat (OR = 2.12, 95% CI = 1.06–4.25), and number of bite wounds (OR = 1.20, 95% CI = 0.96–1.49).Conclusions/Significance
Because L. interrogans prevalence varied with weight, body fat, and bite wounds, this study suggests that social structure and interactions among rats may influence transmission. The prevalence and distribution of L. interrogans in rats was also highly variable even over a short geographic distance. These factors should be considered in future risk management efforts. 相似文献17.
18.
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. 相似文献
19.
Electromyographic studies of mammalian locomotion have concentrated on cursorial species. Since these may not be typical of mammals in general, the present study has been made on the relatively non-cursorial rat.
Electromyography has been performed on 20 muscles or muscle groups of the hind-limb in decerebrate rats, moving at from one to eight steps per second. All muscles were active in discrete bursts, with fixed phase relations in the step cycle. They can be categorized as flexors–active just before and during swing, extensors/adductors–active just before and during stance, muscles controlling the foot, and some double joint muscles. The latter, represented by semitendinosus and rectus femoris, tend to be active twice in each step cycle. There is a distinct reciprocity in the activities of these two muscles. The duration of the extensor/adductor activity decreases with increase of stepping speed.
The pattern of muscle activity during the step cycle is very similar in both cursorial species and the rat. This suggests that central nervous mechanisms controlling the timing of single limb motor output in mammals may be very conservative. 相似文献
Electromyography has been performed on 20 muscles or muscle groups of the hind-limb in decerebrate rats, moving at from one to eight steps per second. All muscles were active in discrete bursts, with fixed phase relations in the step cycle. They can be categorized as flexors–active just before and during swing, extensors/adductors–active just before and during stance, muscles controlling the foot, and some double joint muscles. The latter, represented by semitendinosus and rectus femoris, tend to be active twice in each step cycle. There is a distinct reciprocity in the activities of these two muscles. The duration of the extensor/adductor activity decreases with increase of stepping speed.
The pattern of muscle activity during the step cycle is very similar in both cursorial species and the rat. This suggests that central nervous mechanisms controlling the timing of single limb motor output in mammals may be very conservative. 相似文献
20.
Radim Brdi;ka 《Animal genetics》1977,8(1):175-177
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. 相似文献