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[The dynamics of melanin-affinitive and non-affinitive antibacterial agents in the iris-ciliary body of rabbit eyes--comparative studies in pigmented and albino rabbits].

The differences between the drug penetration levels in the iris-ciliary bodies of sparfloxacin (SPFX) and cefmenoxime (CMX), which respectively have high and low affinity to melanin, were examined using pigmented and albino rabbit eyes. Each drug was mixed with a homogenate of the iris-ciliary bodies of pigmented and albino rabbit eye, respectively. All CMX was distributed in a water soluble protein of the above homogenate of both pigmented and albino eyes, while all SPFX was detected from the water soluble protein of the tissue homogenate of the albino eye. However, in homogenate of the pigmented eyes, 60% of the drug was detected from water soluble protein and 20% of that was detected from water non-soluble protein. In the in vivo study, each drug was topically administered to pigmented and albino rabbit eyes. The SPFX concentration in the iris-ciliary body was significantly higher in the pigmented than in the albino eyes. The results indicated that the intraocular dynamics of the drug which has a high affinity to melanin showed significant differences between pigmented and albino rabbit eyes. This should be considered in studies of ocular pharmacology as an important factor which influences intraocular drug dynamics.

Animals↗

[Effects of phencyclidine on rabbit basilar artery in vitro and rabbit cerebral blood flow in vivo].

The effect of phencyclidine [1-(1-phenylcyclohexyl)piperidine, PCP] on rabbit basilar arteries was studied with an in vitro model of ring segment arteries. PCP 0.05-500 mumol.L-1 caused vasoconstriction of basilar arteries in a concentration-dependent manner. Its maximal effect (Emax) was 94 +/- 21 mg and the concentration causing half maximal effect (EC50) was 25 +/- 18 mumol.L-1. PCP 0.01-10 mumol.L-1 also concentration-dependently augmented the vasoconstriction induced by electric stimulation in rabbit basilar arteries. Its Emax was 91 +/- 18 mg and EC50 was 0.27 +/- 0.17 mumol.L-1. The effects of PCP on mean arterial blood pressure (MABP) and heart rate (HR) of rabbits were observed. PCP iv 4 mg.kg-1 reduced MABP from 14.3 +/- 0.8 to 12.2 +/- 1.0 kPa and HR from 300 +/- 0 to 278 +/- 5 bpm in 5 min. Using the technique of radionuclide imaging in rabbit brain in vivo, we studied the effect of PCP on cerebral blood flow. After iv PCP 4 mg.kg-1, the tp of radiocerebrogram was increased from 4.5 +/- 1.1 to 6.1 +/- 1.0 s, the tg of radiocerebrogram was increased from 11.7 +/- 0.6 to 18.2 +/- 3.3 s and the rate of clearance was decreased. After iv PCP 2 mg.kg-1, only tg increased from 12.6 +/- 2.1 to 15.9 +/- 0.6 s. Hence PCP increased the transit time of nondiffusible indicators (99mTc) through the cerebral circulation. These results suggest that PCP causes constriction of basilar artery and slows down the cerebral blood flow.

Animals↗

Changes in whole blood and serum components during Francisella tularensis and rabbit pox infections of rabbits.

Rabbits infected with virulent Francisella tularensis strain Schu S4 or rabbit pox virus (Utrecht strain) showed significant early changes in serum levels of trace metals, neutral fat and alkaline phosphatase activity. With F. tularensis infections a marked early leukopenia and a decrease in serum amino acids were also observed; the effect on amino acid levels was less pronounced in rabbit pox infections. In both diseases these changes preceded the appearance of acute phase globulins in the serum. Vaccination with the live vaccine strain of F. tularensis slightly increased survival times but did not delay the onset of metabolic changes in rabbits subsequently infected with the virulent Schu S4 strain.

Alkaline Phosphatase↗

Experimental infection of young rabbits with a rabbit enteric coronavirus.

The clinical signs and lesions caused by the rabbit enteric coronavirus (RECV) were studied in young rabbits orally inoculated with a suspension containing RECV particles. The inoculated animals were observed daily for evidence of diarrhea. Fecal samples and specimens from the small intestine and from the gut associated lymphoid tissue (GALT) were collected from 2 h to 29 days postinoculation (PI) and processed for immune electron microscopy (IEM) and light microscopy. Coronavirus particles were detected in the cecal contents of most inoculated animals from 6 h to 29 days PI. Lesions were first observed 6 h PI and were characterized by a loss of the brush border of mature enterocytes located at the tips of intestinal villi and by necrosis of these cells. At 48 h PI, short intestinal villi and hypertrophic crypts were noted. In the GALT, complete necrosis of the M cells as well as necrosis of the enterocytes lining the villi above the lymphoid follicules with hypertrophy of the corresponding crypts were observed in all the animals. Five inoculated rabbits had diarrhea three days PI. The presence of RECV particles in the feces of the sick animals and the microscopic lesions observed in the small intestine suggested that the virus was responsible for the clinical signs. A few inoculated rabbits remained free of diarrhea. Fecal material collected at postmortem examination contained RECV particles. The results suggest that the virus could also produce a subclinical infection.

Animals↗

Allotypy of the rabbit kappa 2 light chain: evidence that the kappa 2 isotype is expressed by all members of the rabbit species.

The rabbit kappa 2 light chain subtype was described after isolation of the Basilea mutant strain, which does not express the kappa 1 subtype; antibodies raised in domestic rabbits against the Basilea kappa 2 chain recognized antigenic determinants present in Basilea strain rabbits and in some wild Oryctolagus cuniculus individuals. Some authors have proposed that the kappa 2 isotype is expressed in some individuals and is silent in others. The results presented here provide immunochemical and genetic evidence that the kappa 2 isotype presents at least two allotypic forms, bas 1 (equivalent to bas+) and bas 2 (equivalent to the so-called bas-), which are expressed in low levels in all members of the rabbit species. In addition, preliminary data on the expression of the bas 2 allotype in some hares (Lepus capensis) are reported. On the basis of these results, the rules guiding the selection of kappa 1 and kappa 2 isotypic light chain expression in this species may now be approached.

Animals↗

Active immunization of female rabbits with purified rabbit acrosin and effect on fertility.

Acrosin immunogen was purified from rabbit testes by sequential acid extraction, ammonium sulfate fractionation, cation-exchange, and affinity chromatography. Twelve females received intradermal injections of purified acrosin in Freund's complete adjuvant followed by a booster injection 6 weeks later. A radioimmunoassay for rabbit acrosin was developed and used to monitor the immune response of the recipients. The females were mated at the time when serum titers of acrosin antibodies were maximal. Four of the animals did not become pregnant, and three of these had the highest antibody titers in the total group. The remaining eight rabbits delivered normal litters at term. Of four control females (immunized with bovine serum albumin), one did not become pregnant. The pregnancy rates for the control and acrosin-immunized rabbits were 75% and 67%, respectively. It is concluded that, although active immunization with acrosin had no significant effect on fertility, the antibody titer produced may be a factor.

Acrosin↗

Different chromosome banding procedures to distinguish between mouse and rabbit chromosomes in mouse-rabbit somatic cell hybrids.

The discrimination of the parental chromosomes in interspecific somatic cell hybrids, is a powerful tool in gene mapping studies. We report the methods used to distinguish between murine and rabbit chromosomes in mouse-rabbit somatic cell hybrids. By means of G-banding patterns it is possible to determine the murine or rabbit origin of the chromosomes, as well as the single chromosome identification in the same hybrid metaphase. To rapidly establish whether the chromosome are of murine or rabbit origin we use C-banding and Hoechst staining procedures, which staining or elongating respectively and preferentially the centromeric area of the mouse chromosomes allowed indubitable species assignment.

Animals↗

In vitro cell response of Treponema pallidum-infected rabbits. II. Inhibition of lymphocyte response to phytohaemagglutinin by serum of T. pallidum-infected rabbits.

Serum inhibitors of lymphocyte response to PHA were found in T. pallidum-infected rabbits. The humoral inhibitors could be detected as early as 10 days after infection and persisted for at least 6 months. The factors also suppressed the allogeneic lymphocyte response. Control, or normal, rabbit sera likewise contain serum inhibitors, but in much lower concentration. The detection of the humoral inhibitors depended on the susceptibility of the indicator lymphocytes. Cells of some rabbits were more sensitive to the inhibitors than others. In addition to serum inhibitors, lymphocytes of T. pallidum-infected animals seem to be impaired and responded to PHA less vigorously than cells of normal rabbits. The inhibitory activity is most likely the result of a complex group of substances with different physicochemical characteristics; some pre-exist and others are newly formed after infection. Problems associated with the detection of such inhibitors are discussed.

Animals↗

Increased concentration of glucocorticoid receptors in rabbit iris--ciliary body compared to rabbit liver.

Dexamethasone binding to both rabbit iris-ciliary body and rabbit liver glucocorticoid receptors was compared by means of a batch assay in which the binding components were adsorbed to hydroxylapatite. The results showed that homogenates of both the rabbit iris-ciliary body and the rabbit liver contained a single class of high-affinity receptors. Binding affinity was virtually identical for the two receptors. A comparison of total binding sites in homogenates of the iris-ciliary body and the liver revealed that the iris-ciliary body glucocorticoid receptor was present in nearly twice the concentration of the hepatic receptor.

Adsorption↗

Structure of a germline rabbit immunoglobulin V kappa-region gene: implications for rabbit V kappa-J kappa recombination.

Rabbit kappa-immunoglobulin chains exhibit diversity in the number of amino acids between the invariant residues Cys 88 and Phe 98; this length diversity is formally similar to that found in the human and mouse heavy chain systems, in which it results from interposition of the D element between V and J. To explore the molecular basis for this length diversity in rabbit kappa-chains we have determined the nucleotide sequence of a rabbit germline V kappa immunoglobulin gene. The spacing between the 7-mer and 9-mer signal elements of this gene suggest that it could recombine with J kappa without a D element. We discuss alternative explanations for the length diversity of rabbit kappa-chains.

Amino Acid Sequence↗

[The pathology of ther reproducing female rabbit: a comparative, descriptive study of morbidity phenomena observed during the reproduction o purebred strains of rabbit].

We analysed the working life of purebred New Zealand, and Californian rabbit breeding does kept in identical conditions. Our study notes the health of the does as well as various factors affecting the survival rate of baby rabbits until weaning. After the first six months of rearing the productivity and the health of the two breeds were very different. The Californian females came through their first two gestations and lactations very well but more than half of them showed signs of respiratory ailments, and many had to be eliminated. Their first two litters were characterised by a low number of baby rabbits weaned as well as a large number of whole litters dead before weaning. The females of the New Zealand breed were in good health but then died suddenly at the end of gestation or in the middle of lactation; the surviving females raised practically their whole litter until weaning. The loss of animals is numerically fairly similar in the two breeds but takes on different farms. This comparative study of the elimination of the does, of their mortality, or of that of the baby rabbits during lactation leads us to the hypothesis that these three phenomena are probably different manifestations of the same pathological phenomena occurring early on, probably from the first gestation onwards.

Animals↗

Experimental endocarditis in rabbits. 5. Results of long-term penicillin or streptomycin treatment of streptococcus faecalis endocarditis and the effect of long-term exposure of healthy rabbits to the same drugs.

A previously described model of experimental Streptococcus faecalis endocarditis in rabbits without an indwelling catheter during the infectious processes was used to study the effect of long-term treatment with antibiotics. Groups of animals infected with six different strains were treated for four weeks and the following parameters were determined: survival rate, bacterial concentration in blood and vegetations, signs at autopsy indicating congestive heart failure. Before the therapeutic experiments, the tolerance of the rabbit to long-term exposure of the drugs penicillin and streptomycin was considered in a group of non-infected animals. Two out of 20 rabbits died with enteritis during the penicillin exposure, and a general weight reduction was observed. Streptomycin was apparently completely harmless. There was no therapeutic effect of streptomycin on S. faecalis endocarditis due to strains all designated resistant to streptomycin by MIC, except in rabbits infected with a strain, which showed partial susceptibility to the drug by IC50. Regardless of the therapeutic effect, evidence was obtained for rapid development of increased resistance of the infecting strains towards streptomycin. After long-term treatment with penicillin in either low or high dose some of the animals survived and the valves were sterilized in 37% of the animals after low-dose and in 39% after high-dose. It was observed that congestive heart failure occurred with the greatest frequency and intensity after infection with proteolytic strains.

Animals↗

The binding of rabbit basophil-derived platelet-activating factor to rabbit platelets.

The platelet binding characteristics of platelet-activating factor (PAF), a basophil-derived lipid that causes aggregation and secretion in rabbit platelets, were studied. In an assay in which binding was quantitated by loss of PAF activity, suspensions of washed rabbit platelets rapidly removed PAF from solution. Rabbit erythrocytes, lymphocytes, and neutrophils also bound PAF, but their binding capacity was less than that of the platelets. PAF binding to rabbit platelets was saturable and dependent on temperature and concentration of PAF and platelets but not on the presence of extracellular Ca2+. Initial rates of PAF binding and platelet secretion were identical, although temperature dependence studies suggested that binding was not the rate-controlling step in PAF-induced platelet secretion. Analysis of binding kinetics suggested that a PAF concentrations saturable for platelet secretion, only some of the available platelet binding sites were occupied.

Animals↗

A homologue of the rabbit kappa-chain allotype b9 ON IgG from a cottontail rabbit.

Eight out of 12 anti-b9 antisera tested strongly bound 125IgG of only one of four individual cottontail rabbits (Sylvilagus floridanus). In addition to this apparent polymorphism of a b9 homologue in cottontail rabbits, a polymorphism defined by some anti-b5 antisera was found. Three of 15 anti-b5 antisera reacted with IgG from only two of the four cottontail rabbits. Reactions with anti-b4 and anti-b6 were similar to those with hare IgG. Most anti-b4 and anti-b6 antisera bound the IgG from each animal. The cottontails we tested also resembled the hare with respect to their weak reactivity with some anti-a2 antisera (Vh allotype) and strong reactivity with anti-15 (an allotype localized in the Fc portion of rabbit gamma-chains).

Animals↗

Morphological and biochemical features affecting the antithrombotic properties of the aorta in adult rabbits and rabbit pups.

We hypothesised that there are important physiologic differences in arterial wall structure and function with respect to antithrombotic activity in the very young (pre-puberty) compared to adults. Electron microscopy, gel electrophoresis, and activity assays were used to examine differences in aorta structure and function comparing prepubertal rabbits (pups) to adult rabbits. Differences in endothelial function, extracellular matrix structure, proteoglycan (PG) distribution and glycosaminoglycan (GAG) content and function were shown. In both intima and media, total PG, chondroitin sulfate (CS) PG and heparan sulfate (HS) PG content were significantly increased in pups compared to adult rabbits. These findings corresponded to increased concentrations by mass analyses of CS GAG and DS GAG in aortas from pups. There was also a significant increase in antithrombin activity in pups due to HS GAG. In conclusion, differences in both structure and antithrombin activity of aortas from pups compared to adult rabbits suggest that young arteries may have greater antithrombotic potential that is, at least in part, related to increased HS GAG.

Aging↗

Idiotypic specificities of rabbit anti-Salmonella abortus-equi antibodies produced by spleen cell clones involved in successive transfers in irradiated rabbits.

Rabbits irradiated with 750 rad were reconstituted with different amounts of spleen cells from the same donor previously immunized against Salmonella abortus-equi (S. a. e.). Two limited numbers of spleen cell clones producing anti-S. a. e. antibodies were respectively expressed in two recipients of the smallest amount (5 x 10(6)) of donor spleen cells. We tried to propagate these spleen cell clones in two new sets of irradiated recipients. We prepared antiidiotypic sera with the anti-S. a. e. serum of respectively (1) the initial donor of the cells, (2) the two intermediate recipients in which a restricted number of spleen cell clones were expressed and (3) one rabbit from each of the second two sets of recipients in which it seemed, as judged by the anti-S. a. e. antibody spectrotypes, we succeeded in propagating these spleen cell clones. With these antiidiotypic sera, we looked for the spleen cell donor idiotypes in the anti-S. a. e. serum of the diverse recipients and vice versa. Recipients of 1 x 10(8) or 2.5 x 10(7) spleen cells produced anti-S. a. e. antibodies with a spectrotype as heterogeneous as the spectrotype of antibodies produced by the donor. These antibodies carried the idiotypic pattern of the donor's antibodies, which was revealed by a given antiidiotypic serum, and the donor's allotypic patterns. The two recipients of 5 x 10(6) spleen cells which were used as intermediate spleen cell donors for the two new sets of irradiated rabbits produced antibodies of restricted heterogeneity which carried donor's allotypic patterns but not the idiotypic pattern of the donor's antibodies (revealed by a given antiidiotypic serum). We observed during these two successive spleen cell clone transfers the expression, in the irradiated recipients, of several idiotypes of anti-S. a. e. antibodies which were not detected in the anti-S. a. e. serum of the spleen cell donor and sometimes even not in the anti-S. a. e. serum of the intermediate donor. The antibodies we studied were produced by the donor's spleen cells as they carried donor allotypic patterns and came from bleedings made one week after transfer, a time which is not sufficient for irradiated rabbits used as controls to recover their aptitude to mount an antibody response after the damages caused by the irradiation. Presumably, spleen cell clones which did not produce antibodies in the donor were recruited to produce antibodies during the successive transfers. These spleen cell clones might have been kept silent in the donor by the clonal dominance phenomenon, this dominance being broken or totally changed during the transfers.

Animals↗

Antibody responses to rabbit haemorrhagic disease virus in predators, scavengers, and hares in New Zealand during epidemics in sympatric rabbit populations.

AIM: To test for antibodies to rabbit haemorrhagic disease (RHD) virus (RHDV) in sera from mammals and birds associated with rabbit populations infected with RHDV. METHODS: Sera from feral and domestic cats, feral ferrets, stoats, hedgehogs, hares, harrier hawks, and black-backed gulls were taken (apart from some of the hares) from areas in New Zealand where RHD was active among rabbit populations. The presence of antibodies to RHD was investigated using a competition enzyme-linked immunosorbent assay (ELISA). RESULTS: Some individual animals of all species were seropositive. Thirty eight of 71 feral cats, but only 1/80 domestic cats were seropositive at a 1:40 dilution. The latter had not been exposed to RHDV. Also reactive in the ELISA were 2/8 stoats; 11/115 ferrets, with significantly more females having antibodies than males; 4/73 hedgehogs; 2/18 hawks, and 1/30 gulls. Three of 66 hares, comprising 3/14 from one population, were seropositive. CONCLUSIONS: Apart from the hares, all these species are known to prey upon rabbits or scavenge their carcasses, a possible means of exposure to RHDV. The possibility that the positive test reactions were due to cross-reactions with other caliciviruses cannot be ruled out, especially for the hares. Nor could the study differentiate whether the positive results were due to an antigenic reaction to ingestion of RHDV, as suggested by overseas work, or to infection of new species by RHDV. These possibilities are being investigated further.

Journal Article↗