Strains Of Rabbits Research Articles

Effect of time of day and rabbit strain on patterns of aortic wall permeability.

Lipid deposits occur more frequently downstream of branch points than upstream in immature rabbit and human aortas but the opposite pattern is seen in mature vessels. These distributions correlate spatially with age-related patterns of aortic permeability, observed in rabbits, and may be determined by them. The mature but not the immature pattern of permeability is dependent on endogenous nitric oxide synthesis. Although the transport patterns have hitherto seemed robust, recent studies have given the upstream pattern in some mature rabbits but the downstream pattern in others. Here we show that transport in mature rabbits is significantly skewed to the downstream pattern in the afternoon compared with the morning (P < 0.05), and switches from a downstream to an upstream pattern at around 21 months in rabbits of the Murex strain, but at twice this age in Highgate rabbits (P < 0.001). The effect of time of day was not explained by changes in nitric oxide production, assessed from plasma levels of nitrate and nitrate, nor did it correlate with conduit artery tone, assessed from the shape of the peripheral pulse wave. The effect of strain could not be explained by variation in nitric oxide production nor by differences in wall structure. The effects of time of day and rabbit strain on permeability patterns explain recent discrepancies, provide a useful tool for investigating underlying mechanisms and may have implications for human disease.

Circulating levels of glucocorticoid hormones in WHHL and NZW rabbits: circadian cycle and response to repeated social encounter

Social environment influences the progression of atherosclerosis in an important experimental model of disease, the Watanabe Heritable Hyperlipidemic rabbit (WHHL). Although the hypothalamic–pituitary–adrenocortical (HPA) system is likely to play an important role in the behavioral modulation of disease, relatively little is known about the glucocorticoid responses in these animals, or in other strains of rabbits. The purpose of the present study was to: (1) evaluate the rabbit glucocorticoid circadian rhythm, (2) compare plasma cortisol and corticosterone responses to social stress, and (3) examine strain differences (i.e., WHHL vs. New Zealand White (NZW)) in rabbit glucocorticoid responses to assess whether WHHLs have an aberrant HPA system. It was found that male rabbits secrete both corticosterone and cortisol in a circadian rhythm that peaks in the afternoon and reaches a nadir at 0600 h, i.e., approximately 12 h out-of-phase with the human glucocorticoid rhythm. Both glucocorticoids responded similarly to social stress induced by repeated daily 4 h pairings with another male rabbit; after 10 days of pairings, glucorticoid values were significantly correlated with the amount of defensive agonistic behavior exhibited. Finally, there were no significant strain differences in glucocorticoid circadian rhythms, baselines, or responses to social stress. These data suggest that glucocorticoid responses (i.e., circadian rhythms, responses to social stress) in the WHHL are similar to glucocorticoid responses in standard laboratory white rabbits.

Pigment epithelial changes in a strain of pigmented rabbits with low ERG b-wave amplitudes

Retinas from a strain of rabbits with low dark-adapted electroretinographic (ERG) b-wave amplitudes, and declining ERG responses with time, were examined by light and electron microscopy. Seven rabbits from the affected strain (13 months to 5 years old) and six control animals (6–26 months old) were included in the study. Small inclusions with an electron dense border, about 0.2–1.5 μm in diameter, were significantly ( p<0.01) more numerous within the retinal pigment epithelial (RPE) cells in the affected rabbits than in the control animals. No morphological evidence of retinal degeneration was found. Further studies are needed to establish the functional defect in this strain of rabbits.

Cholesterol and copper in the liver of rabbit inbred strains with differences in dietary cholesterol response

In order to investigate whether cholesterol intake influences the hepatic copper content of rabbits, we compared the hepatic copper content of two rabbit inbred strains after feeding the animals a control or a cholesterol-rich diet. One strain was not reactive to dietary cholesterol (IIIVO/JU), whereas the other strain was reactive to dietary cholesterol (AX/JU). The coefficient of inbreeding (F) >0.95 for both strains. Dietary cholesterol-reactive rabbits when compared with their non-reactive counterparts had a higher hepatic copper content. The consumption of a hypercholesterolemic diet decreased liver copper concentration (expressed in μg/g dry weight) in both strains of rabbits, which was (in part) due to dietary-induced hepatomegaly. A decrease in the absolute hepatic copper content was found only in the dietary cholesterol-reactive inbred strain. It is discussed that differences in glucocorticoid levels may be responsible for the strain difference in liver copper content. The cholesterol effect on the hepatic copper content in the reactive strain might be caused by an increased bilirubin secretion.

Experimental Infections with Wild and Mutant Yersinia pseudotuberculosis Strains in Rabbits

Experimental oral infections of rabbits with a wild-type Yersinia pseudotuberculosis strain (pIB102), and two null-mutants (yopK and ypkA) were carried out with the aim to explore the possibility to use mutant strains of Y. pseudotuberculosis as live carrier vaccine strains. The infectious process of the three strains proceed with passing hyperthermia, leucocytosis with granulocytosis, moderate monocytosis and a transient lymphopenia, better demonstrated at mutant strain infections. Short-term bacterial dissemination into the brain and viscera was observed at yopK infection. An augmented resistance to bactericidal activity of leucocytes at the initial phase of infection was followed by an increased sensitivity discovered earlier in case of yopK strain accompanied by at least 70- and 20-fold, respectively, for ypkA lower virulence for mice. The level of attenuation of yopK was accompanied by significant Yersinia specific IgG and IgM antibody response. Inflammatory foci were found by morphological examination in brain, lung and small intestines after infection with the wild-type strain, while such foci were only observed in brain and mesenterial lymph nodes after infection with the yopK mutant. After infection with the ypkA mutant foci were found in brain and spleen of the infected animals. Morphological changes in the lymphatic tissue of rabbits infected with mutant strains were consistent with induction of immunogenesis. The data suggest that genetically constructed yopK null-mutant exhibits characteristics that makes the strain suitable to be used as a live carrier vaccine to deliver heterologous antigens.

Antibody-mediated growth of infectious salmon anaemia virus in macrophage-like fish cell lines.

Infectious salmon anaemia virus (ISAV), a pathogen in marine aquaculture, belongs to the genus Isavirus, family Orthomyxoviridae. There is limited information on how ISAV interacts with host defences. To study ISAV-antibody interactions, virus neutralization (VN) assays were performed in the cell lines CHSE-214, SHK-1 and TO using three strains of ISAV and rabbit or fish anti-ISAV sera. Homologous VN titres of >1 : 1280 in CHSE-214 cells corresponded to titres of only 1 : 80 in the macrophage-like fish cell lines SHK-1 and TO, despite using 1000 and 2000 times less virus, respectively. However, rabbit antiserum to infectious pancreatic necrosis virus (IPNV) had a VN titre of 1 : 10,260 against IPNV in both CHSE-214 and TO cells. Poor ISAV neutralization in TO cells was attributed to Fc receptors mediating virus infectivity, because (1) neutralization by rabbit antiserum to ISAV was increased 48-fold in the presence of staphylococcal Protein A and (2) when using FITC-labelled virus and spectrofluorometry, a significant increase (P=0.018) in the intensity of fluorescence of intracellular virus was observed in assays of virus-antiserum mixtures in the absence of Protein A as compared to those in the presence of Protein A. Neutralization of ISAV with fish antisera was observed only in CHSE-214 cells, as Protein A could not restore neutralization in TO cells. These findings demonstrate for the first time antibody-mediated infection of macrophage-like fish cell lines by a fish virus, ISAV, and, as ISAV in Atlantic salmon targets leukocytic and endothelial cells, this may have implications for ISA pathogenesis and vaccination.

Development of an animal model for spontaneous myocardial infarction (WHHLMI rabbit).

Coronary heart disease is the most common cause of death in developed countries. However, there are no suitable animal models that mimic spontaneous myocardial infarction in humans. In this study, we attempted to obtain a rabbit strain with spontaneous myocardial infarction by selective breeding of coronary atherosclerosis-prone Watanabe heritable hyperlipidemic (WHHL) rabbits, designated as WHHLMI rabbits. WHHLMI rabbits were characterized by the high incidence of fatal myocardial infarction at ages 11 to 35 months, being increased from 23% to 97% after the selective breeding. The ECG on WHHLMI rabbits showed a typical feature of myocardial infarction. Histological examination of hearts from suddenly deceased WHHLMI rabbits revealed old myocardial infarction accompanied by fresh myocardial lesions. The culprit coronary arteries exhibited severe atheromatous plaques (>90% lumen area stenosis), suggesting that coronary atherosclerosis is responsible for myocardial infarction observed in WHHLMI rabbits. In addition, the coronary plaques showed vulnerable features including macrophage-rich thin cap and large necrotic core. To the best of our knowledge, this is the first report of spontaneous myocardial infarction in rabbits, and it is suggested that this WHHLMI rabbit strain will be a useful animal model to study human myocardial infarction.

Successful tracheal transplantation with fresh allografts in a rabbit model.

Immunogenicity and the restoration of blood supply to the donor graft remains a clinical challenge in tracheal allotransplantation. We conducted a study on 20 rabbits of a genetically similar strain to eliminate the risk of rejection caused by immunogenicity. We examined the histomorphological changes related to revascularization and the immunogenic reaction of the fresh allografts after tracheal transplantation. Histomorphological assessment was conducted by investigating the anastomotic sites, graft necrosis, and epithelization. Cellular changes, including the infiltration of granulocytes, histiocytes, and fibroblast proliferation related to a granulation tissue-like reaction, were also assessed, with lymphocyte infiltration which is an indicator of graft rejection. All of these characteristics, apart from epithelization, were graded semiquantitatively as none (0), mild (1), moderate (2), and severe (3). Epithelization was graded as 0, indicating no epithelization; 1, < or =20%; 2, < or =40%; 3, < or =60%; 4, < or =80; 5, complete epithelization of the entire graft. Morphologic integrity of the trachea was completely retained in 16 (80%) animals. The overall rating score of epithelization was 3.6+/-1.0, while those of the granulation tissue-like reaction and lymphocyte infiltration were 4.8+/-0.6 and 1.5+/-0.7, respectively. These findings demonstrate that tracheal allotransplantation is possible with fresh allografts in genetically similar strains of rabbits.

A genetic description of two selected strains of rabbits

Two strains of rabbits (strains 1077 and 2066) have been selected since 1974 for increased litter size. Each strain is split into a fixed number of reproduction groups. The mating scheme is similar to random non‐sib herd mating. The number of animals per generation is higher in strain 1077 (28 mated bucks and 104 mated does) than in strain 2066 (17 and 59, respectively). The increase of the inbreeding coefficient is higher in strain 2066 than in strain 1077 (27 and 21%, respectively, at generation 20). The mean standard deviation of the individual inbreeding coefficients per generation is low (less than 4%) in both strains. Short‐term inbreeding is stable over generations. The observed inbreeding effective size Nef and the observed familial structure effective size Neh converge to the same value. The number of founder genomes still present in the genetic pool of the generation decreases regularly: from 5.6 to 2.4 between G6 and G20 for strain 1077. It is a bit lower over time for strain 2066 (from 5.7 to 1.9 between G6 and G20). The effective number of founders is nearly twice as small as the total number: 30 for strain 1077 and 15 for strain 2066. The effective number of major ancestors decreases slightly in strain 1077 (13.6 in G6 and 12.9 in G20) and regularly in strain 2066 (13.8 in G6 and 9.4 in G20).

Hypochlorite-Modified (Lipo)Proteins Are Present in Rabbit Lesions in Response to Dietary Cholesterol

Myeloperoxidase (MPO), a heme enzyme secreted by activated phagocytes, generates an array of oxidants proposed to play critical roles in host defense, tissues damage, and foam cell formation. Although neutrophils are the major source for MPO, the enzyme could be identified abundantly in circulating monocytes and monocytes/macrophages in rabbit lesions. MPO is the only enzyme known to generate hypochlorous acid (HOCl) and HOCl-modified lipoproteins have pronounced atherogenic and/or proinflammatory features in vivo and in vitro. Using specific monoclonal antibodies, HOCl-modified (lipo)proteins were detected in atherosclerotic plaques of heterozygous Watanabe heritable hyperlipidemic rabbits and to a lesser extent in a specific strain of New Zealand White rabbits with a high atherosclerotic response to hypercholesterolemia. Colocalization of immunoreactive MPO and HOCl-modified-epitopes in serial sections of rabbit lesions provides convincing evidence for MPO-H2O2-chloride system-mediated oxidation of (lipo)proteins under in vivo conditions. We propose that monocyte-derived MPO could connect chronic inflammatory conditions with arterial lipid/lipoprotein deposition during diet-induced atherogenesis in rabbits.

Strain-Dependent Differences in the Pattern of Aortic Lipid Deposition in Cholesterol-Fed Rabbits

Spontaneous lesions develop downstream of branch points in immature human and rabbit aortas, but occur more frequently at the sides and upstream of these sites in mature vessels. Cholesterol-induced lesions in mature rabbits, however, have shown the downstream distribution in one trial and the more upstream distribution in another. We tested the hypothesis that this discrepancy reflected a difference in the degree of impairment of the nitric oxide pathway. Mature rabbits were fed cholesterol-enhanced versions of the two base diets used in the previous trials, and some were given additional vitamin E or l-arginine to protect the NO pathway or L-NAME to inhibit it. Unexpectedly, the rabbits developed a lesion pattern intermediate between the two previously described, and this distribution was unaffected by the base diet or supplements. Consequently, an exploratory study was conducted to investigate possible effects of other differences between the two earlier trials. These were the precise age of the mature rabbits and the feeding protocol employed; both base diets again were used. Two different lesion patterns were observed in this trial, but there was no systematic effect of any of the controlled variables. Instead, there appeared to be an influence of the supplier from which the rabbits had been obtained. A multivariate analysis of all four trials confirmed that the pattern of disease was associated with rabbit strain, and not with base diet, cholesterol level, or precise age.

CpG motif identification for veterinary and laboratory species demonstrates that sequence recognition is highly conserved.

Oligodinucleotides containing CpG motifs stimulate vertebrate immune cells in vitro, have proven efficacy in murine disease models and are currently being tested in human clinical trials as therapies for cancer, allergy, and infectious disease. As there are no known immunostimulatory motifs for veterinary species, the potential of CpG DNA as a veterinary pharmaceutical has not been investigated. Here, optimal CpG motifs for seven veterinary and three laboratory species are described. The preferential recognition of a GTCGTT motif was strongly conserved across two vertebrate phyla, although a GACGTT motif was optimal for inbred strains of mice and rabbits. In a subsequent adjuvanticity trial, the in vitro screening methodology was validated in sheep, representing the first demonstration of CpG DNA efficacy in a veterinary species. These results should provide candidate immunostimulant and therapeutic drugs for veterinary use and enable the testing of CpG DNA in large animal models of human disease.

Rabbits possess a serum paraoxonase polymorphism similar to the human Q192R

Serum paraoxonase (PON1) is a high-density lipoprotein (HDL)-associated enzyme that hydrolyses aromatic esters, organophosphates and lactones and can protect low-density lipoprotein (LDL) against oxidation. These properties are influenced by a well-characterized polymorphism (Q192R) in human PON1. We now report the identification and characterization of a phenotypically similar, but genetically distinct polymorphism in rabbit PON1. This polymorphism in rabbits was detected by phenotyping sera obtained from 16 inbred rabbit strains and 20 outbred New Zealand White rabbits by paraoxonase/arylesterase activity. The genetic basis of the rabbit polymorphism was determined by DNA sequencing and found to reside in a region distinct from the human Q192R and M55L polymorphisms. Three variant nucleotides within exon 4 (corresponding to P82S, K93E and S1O1G) were found to segregate with the observed rabbit PON1 phenotypes (rPON1A and rPON1B). The rPON1A and rPON1B proteins were purified and compared to the two human isoforms (192Q and 192R). The human and rabbit PON1s displayed similar characteristics with respect to physical properties and substrate specificity. However, rPON1A and rPON1B hydrolysed a variety of substrates at different rates. The rPON1A was also at least three-fold more efficient at protecting LDL from oxidation than rPON1B. Our characterization of a rabbit PON1 polymorphism provides useful insights into important functional residues in PON1. In addition, due to the observed similarities between the rabbit and human polymorphisms, the rabbit may serve as a good model to examine the effect of human PON1 polymorphisms in disease development.

Modulation by acute stress of chloride permeation across microdissected vestibular neurons membranes: different results in two rabbit strains and CRF involvement

Free hand isolation of adult rabbit vestibular Deiters’ neurons and dissection of their single membranes allows the study of their ionic permeability characteristics in a microchambers device. In the case of hare-like rabbits, the dissection of such membranes presents evidence of a high basal permeation of labelled chloride, possibly related to mechanical disturbance of the plasma membrane-related cytoskeleton and activation of chloride channels. This did not apply to the laboratory strain of white New Zealand rabbits. However, membranes from hare-like rabbits which were stressed by being rotated on a platform before the experiment, behaved like those from the New Zealand strain. Vice versa, habituation to handling day after day of New Zealand rabbits resulted in a chloride permeation equal to that of unstressed hare-like rabbits. We propose that the stressful conditions result in the release of neurochemical messages to the vestibular Deiters’ cells which influence their electrophysiological behavior. The corticotropin releasing factor (CRF), a stress-related peptide present in the climbing fibers, actually blocks the basal chloride permeation across the Deiters’ membranes and this effect is partially reversed by its receptor antagonist, α-helical CRF [9–41].

Tyrosinase gene variants in different rabbit strains.

Tyrosinase gene variants in different rabbit strains.

Rabbit strain affects patterns of aortic permeability and lipid deposition

Rabbit strain affects patterns of aortic permeability and lipid deposition

Discovering the role of the major histocompatibility complex in the immune response.

The discovery that genes in the major histocompatibility complex (MHC) play an important role in the immune response depended on the chance interaction of several unrelated events. The first, and most important, was the decision by Michael Sela to synthesize a series of branched, multichain, synthetic polypeptides based on a backbone of poly-l-lysine. The prototype compound, (T,G)-A-L, was tipped with short random sequences of tyrosine and glutamic acid. This resulted in a restricted range of antigenic determinants composed of only two or three amino acids with a variable length-ideal for binding to the peptide binding groove of MHC class II molecules. The second was the decision by John Humphrey to immunize various strains of rabbits with this synthetic polypeptide. Two of these rabbit strains showed very large quantitative differences in antibody response to (T, G)-A-L. In transferring this system to inbred mouse strains, the third bit of good fortune was the availability at the National Institute of Medical Research, in Mill Hill (London), of the CBA (H2(k)) and C57 (H2(b)) strains. The H2(b) haplotype is the only one mediating a uniform high antibody response to (T,G)-A-L. The fourth critical ingredient was the availability of numerous congenic and H2 recombinant inbred strains of mice produced earlier by Snell, Stimpfling, Shreffler, and Klein. A search for congenic pairs of mice expressing the responder and nonresponder H2 haplotypes on the same background revealed that these strains responded as a function of their H2 haplotype, not of their inbred background. Extensive studies in a variety of inbred strains carrying recombinant H2 haplotypes, as well as a four-point linkage cross, mapped immune response to (T,G)A-L within the murine MHC, between the K and Ss loci. The demonstration that stimulation in the mixed lymphocyte reaction (MLR) mapped to the same region quickly led to attempts to produce antisera in congenic H2 recombinant strain combinations. These antisera identified I-region associated (Ia) antigens. Immunoprecipitation and blocking studies showed that the gene products controlling specific immune responses, the mixed lymphocyte reaction, and the structure of Ia antigens were one and the same-now designated as the I-A MHC class II molecules. These antisera and inbred strains enabled Unanue to demonstrate the peptide binding function of class II MHC molecules.

CYP2E1 expression in bone marrow and its intra- and interspecies variability: approaches for a more reliable extrapolation from one species to another in the risk assessment of chemicals.

When characterizing the health risks for man by exposure to chemicals, species-specific differences have to be taken into consideration, otherwise extrapolation from animal data to the human situation would be inadequate. The site-specific toxicity of chemicals may be explained by the following alternatives: (1) reactive metabolites are generated in the liver and subsequently transported to the target tissue(s); (2) metabolism of the parent compound occurs in the target tissue, a pathway by which the enzymes necessary for activation must be expressed in the target tissue. Cytochrome P450 2E1 (CYP2E1) is an important phase-I enzyme activating several chemicals. In the study described in this paper, myeloid intra- and interspecies variability in the expression of CYP2E1 has been investigated in rats, rabbits and man, because the bone marrow represents an important target organ for toxic effects of several chemicals, e.g. benzene. CYP2E1 at the protein level was detected by Western blotting and enzyme activities were determined by CYP2E1-dependent hydroxylation of chlorzoxazone (CLX). In the bone marrow of Wistar rats, the CLX hydroxylase activities were within the same order of magnitude (range: 0.1-0.4 pmol/mg protein per min) as previously described for mice (range 0.2-0.8 pmol/mg protein per min), whereas the CYP2E1 activities in two strains of rabbits were significantly higher (range: 1.7-4.7 pmol/mg protein per min) than in the rodents (P < 0.05). In human CD34+ bone marrow stem cells, CYP2E1 could also be detected on the protein level by Western blotting. The data demonstrate a presence of CYP2E1 in the bone marrow of all species investigated, thus supporting the hypothesis of CYP2E1-dependent local metabolism of several chemicals as a factor possibly contributing to their myelotoxicity and haematotoxicity. The data show that intraspecies/intrastrain variability of CYP2E1 activity in rodents is small. However, CYP2E1 activity between rodents and a non-rodent species was quite different indicating considerable interspecies variability.

Decreased turnovers of glutathione and ascorbic acid in watanabe heritable hyperlipidemic rabbits.

Oxidative stress has been postulated to play important roles in the pathogenesis of various diseases such as atherosclerosis in hyperlipidemic subjects. Although the possible role of oxidation of low-density lipoprotein (LDL) in the etiology of atherosclerosis has been studied extensively, the turnover of endogenous antioxidants, which is an important protection system against oxidative stress, remains to be elucidated. The aim of our study was to determine the change of the turnover of endogenous antioxidants such as glutathione and ascorbic acid in case of hyperlipidemia, using Japanese white rabbits (JW) and Watanabe heritable hyperlipidemic rabbits (WHHL). The levels of total glutathione and low molecular weight thiols in the liver, kidney, and other organs in both strains of rabbits were similar. However, a kinetic analysis using L-buthionine-(S,R)-sulfoximine revealed that the rate of glutathione turnover in the liver and kidney of WHHL was about 50%) lower than that of JW. Furthermore, intravenously administered ascorbic acid disappeared more slowly in WHHL than in JW. These results indicate that the turnovers of both glutathione and ascorbic acid in WHHL are depressed in comparison with that in JW. These changes would be closely related to the increased oxidizability of lipids in the circulation of hyperlipidemic subjects.

Trigonocephaly in rabbits with familial interfrontal suture synostosis: the multiple effects of premature single-suture fusion.

Previous studies from our laboratory have characterized the craniofacial morphology and growth patterns of an inbred strain of rabbits with autosomal dominant coronal suture synostosis. A number of rabbit perinates from this colony have been collected sporadically over a 5-year period with premature interfrontal suture synostosis. The present study describes the very early onset of craniofacial dysmorphology of these rabbits and compares them to similar-aged normal control rabbits. A total of 40 perinatal New Zealand White rabbits were used in the present study. Twenty-one comprised the sample with interfrontal suture synostosis and ranged in age from 27 to 38 days postconception (term = 31 days) with a mean age of 33.53 days (+/-2.84 days). Nineteen rabbits served as age-matched, normal controls (mean age = 33.05 days +/-2.79 days). Lateral and dorsoventral radiographs were collected from each rabbit. The radiographs were traced, computer digitized, and 12 craniofacial measurements, angles, and indices were obtained. Mean measures were compared using an unpaired Student's t-test. All synostosed rabbits were stillborn or died shortly after birth. Grossly, these rabbits exhibited extreme frontal bossing, trigonocephaly with sagittal keeling, and midfacial shortening. No somatic anomalies were noted. Radiographically, rabbits with interfrontal suture synostosis had significantly (P < 0.05) narrower bifrontal widths, shorter cranial vault lengths, kyphotic cranial base angles, and different cranial vault indices (shapes) compared to controls. Results reveal severe and early pathological and compensatory cranial vault changes associated with premature interfrontal suture synostosis in this rabbit model. The 100% mortality rate noted in this condition may be related to the inheritance of a lethal genetic mutation or to neural compression from reduced intracranial volume. Results are discussed in light of current pathogenic hypotheses for human infants with premature metopic suture synostosis.