Multiple complex congenital malformations in a rabbit kit (Oryctolagus cuniculi)

Congenital malformations may occur during early embryogenesis in cases of genetic abnormalities or various environmental factors. Affected subjects most often have only one or 2 abnormalities; subjects rarely have several unrelated congenital defects. Here we describe a case of a stillborn New Zealand white rabbit with multiple complex congenital malformations, including synophthalmia, holoprosencephaly, gastroschisis, and a supernumerary hindlimb, among other anomalies. There was no historical exposure to teratogens or other known environmental causes. Although not confirmed, this case was most likely a rare spontaneous genetic event.

Sutural bone frequency in synostotic rabbit crania

This study tests the hypothesis that crania with synostosed sutures will have a significantly higher incidence of calvarial sutural bones than normal crania. Sutural bones were counted in seven calvarial sutures and compared among four groups of adult New Zealand white rabbit skulls: normal in-colony (NI) controls (N = 14), normal out-colony (NO) controls (N = 12), skulls with familial delayed onset (DO) coronal synostosis (N = 25), and skulls with experimentally immobilized coronal sutures (EI) (N = 20). Comparisons among groups were made with a Kruskal-Wallis one-way ANOVA and between groups with a Mann-Whitney U-test, using a Bonferroni correction for multiple comparisons. Significant differences (P < 0.05) were noted only in the coronal and sagittal sutures, with EI crania having the greatest number of coronal sutural bones; between group differences were undetectable for sagittal sutural bones. A post hoc two-sample binomial test for equal proportions showed that the distribution of coronal sutural bones among individuals across groups was even, while the distribution of sagittal sutural bones was significantly higher in EI crania. These results suggest that altered sutural forces of the calvaria contribute to an increased occurrence of sutural bones. However, the influence of inheritance on increased occurrence of sutural bones cannot be discounted, as reflected in the equivalent number of individuals across groups that possessed coronal sutural bones.

Two decades of control Himalayan rabbit reproductive parameters and spontaneous abnormalities in Japan

The Himalayan rabbit, Chbb:HM, has been bred in a closed colony at our institute from 1971 through 1991. Cumulative reproductive and teratological data of 514 litters from control does in embryotoxicological Segment II studies carried out over this period are herein reported. If compared with other strains of rabbit, the observed pregnancy rate of 92.2% was high, and spontaneous mortality or abortions were rare. However, the average numbers of corpora lutea, implantation sites and viable fetuses per doe were somewhat low. A total of 30 malformations and 130 variations occurred among 2883 viable fetuses.

Development of a strain of rabbits with congenital simple nonsyndromic coronal suture synostosis. Part I: Breeding demographics, inheritance pattern, and craniofacial anomalies

The lack of an animal model of congenital coronal suture (CS) synostosis has prompted the widespread use of an experimental rabbit model using adhesive immobilization of the CS. Such postnatal models have helped make significant scientific contributions but may still not fully represent all aspects of the human congenital condition. In the March 1993 issue of The Cleft Palate-Craniofacial Journal we reported a female rabbit born in our laboratory with complete bilateral CS synostosis. This follow-up study presents our attempts to breed this animal and establish a strain of craniosynostotic rabbits. To date, we have accomplished 10 back- and intercrosses with these animals and have produced a total of 71 live offspring; 10 animals exhibited complete nonsyndromic unilateral (plagiocephalic) or bilateral (brachycephalic) CS synostotic deformities at birth, and 19 animals exhibited partial CS synostosis that showed more than 75% growth retardation across the CS (well below the 95% confidence interval for normals). Results revealed that gestational time and litter size averages were consistent with those reported for the strain, although the average litter size decreased with increased inbreeding. By 1.5 weeks of age the completely synostosed animals already exhibited brachycephalic cranial vaults and midfacial hypoplasia compared to unaffected siblings. Initial pedigree analysis suggested an autosomal dominant inheritance pattern with incomplete penetrance and variable expressivity. The development of such a congenital rabbit model may prove useful in helping to understand the etiopathogenesis of this condition in human populations.

Congenital bilateral coronal suture synostosis in a rabbit and craniofacial growth comparisons with experimental models

Experimental rabbit models of postnatal coronal suture (CS) synostosis have helped make significant contributions towards the understanding and surgical management of human congenital craniosynostosis. The present study compares craniofacial growth patterns in animals with experimental CS immobilization and in a rabbit born in our laboratory with congenital CS synostosis. The study sample consisted of 10 sham controls, 14 experimental animals with bilateral CS immobilization, and one animal with congenital, bilateral CS synostosis. At 1.5 weeks of age, all animals had amalgam markers placed on either side of the frontonasal, coronal, and anterior lambdoid sutures. At this time, the experimental animals had bilateral CS immobilization using methyl-methacrylate. Serial lateral head x-rays were taken at 1.5, 6, 12, and 18 weeks of age. Results revealed that by 1.5 weeks of age the congenital animal already exhibited changes in the cranial vault, cranial base, midface, and orthocephalic cranial base angles compared to controls. By 6 weeks of age, animals with experimental immobilization showed compensatory growth patterns similar to the congenital animal, particularly at the calvarial sutures and upper midface. This pattern continued through 18 weeks. Results showed that experimental, postnatal CS immobilization produced similar craniofacial growth patterns to those observed for our single congenital animal, but to a lesser degree, and therefore validates, in part, findings from experimental rabbit models of synostosis.

"Nude rabbit" with aplasia of B-lymphoid structures

An original observation of the randombred nude rabbit with aplasia of B-lymphoid structures (absence of the follicles in lymph nodes and spleen, no Peyer's plaques). The thymus gland and the T-dependent structures in the spleen and lymph nodes were-on the contrary-well preserved. The nude skin of this genetic rabbit mutant contained large numbers of hair follicles showing almost intrafollicular retention of hairs with their subsequent dysplasia at the subepidermal and ostiopilar level.

[Tibial aplasia and agenesis in a rabbit (case report)]

The occurrence of a tibial aplasia (left side) and agenesia (right side) in a rabbit (aged 4 weeks) is reported. Apart from extreme distorsions of the fibular bones, there were no other skeletal malformations.

A case of combined hermaphroditism and autofertilisation in a domestic rabbit

A true hermaphrodite rabbit served several females and sired more than 250 young of both sexes. In the next breeding season the rabbit, which was housed in isolation, became pregnant and delivered seven healthy young of both sexes. It was kept in isolation and when autopsied was again pregnant and demonstrated two functional ovaries and two infertile testes. A chromosome preparation revealed a diploid number of autosomes and two sex chromosomes of uncertain configuration.