Variations of susceptibility to alloxan induced diabetes in the rabbit

The variations of susceptibility to alloxan induced Diabetes in a total of seventeen rabbits was described. Our study was designed to explore dosage schedules which might improve rabbit responsiveness to and survival after alloxan treatment. A wide range of response to intravenously administered alloxan was observed. Permanent diabetes (blood glucose 350 mg/dl) was found in three rabbits after a single injection (60 mg/kg in one, 100 mg/kg in two). This effect has persisted for eight months. By contrast, two other rabbits injected with a single dose of alloxan (60 mg/kg) developed only transient hyperglycemia. Similarly, four other rabbits either did not respond or had an incomplete response after receiving a total dose of 120 mg/kg. These data suggest that there is extreme variability in individual rabbits susceptibility to the diabetogenic affects of alloxan.     

Variations in the microclimate in rabbit warrens in semi-arid New South Wales

Rabbit burrows in three different habitats in an arid area showed characteristic variations and differences. Burrows in stony soil were generally cooler and more humid than burrows in sand and gravel soil. The temperature of the burrows in sand and gravel showed similar characteristics but the humidity in the gravel burrows was almost always significantly less than that of the sand burrows. Air and ground temperatures were significantly correlated but air and ground humidities showed a less significant correlation. Seasonal differences in microclimate within and between the three types of burrows were pronounced and are thought to cause differences in the survival of rabbits in arid areas.     

Variations in rabbit oviduct microvascular architecture after ovulation induced by hCG

Rabbits were induced to ovulate by injection with hCG and vascular corrosion casts of the oviducts were examined by scanning electron microscopy after 24 and 48 h, when the ova would be expected to be at the ampullary-isthmic junction, and traversing the isthmus respectively. At 24 h there was dilatation of the isthmic subserosal venous plexus. It is suggested that venous distension in the isthmic subserosal venous plexus, due to raised venous pressure or to reduced venous wall tone, may occlude the isthmic lumen to ova, and thus explain the known pre-isthmic delay in ovum transport. By 48 h after hCG, distension was no longer evident, consistent with the possibility of ovum transport.     

Variations of mitochondrial DNA sequence in three breeds of rabbit (Oryctolagus cuniculus)

Sequencing of the 300 bp region of the mitochondrial cytochrome b gene was done. Genetic analysis was carried out for the first time in three exotic breeds (Giant White, Soviet Chinchilla, and German Angora) of European rabbit (Oryctolagus cuniculus) to determine intra- and interspecific variability and to measure the genetic distance. The frequencies of types of mutations (transition, transversion, deletion, and insertion) were also determined. This study throws light on matrilineage of breeds that arise due to interbreed crosses and the genetic management of a stocked rabbit breeding population.     

Variations in hepatic progesterone 21-hydroxylase activity reflect differences in the microsomal concentration of rabbit cytochrome P-450 1

A monoclonal antibody specific for cytochrome P-450 1 that extensively (greater than 95%) inhibits the hepatic 21-hydroxylation of progesterone was used in a two-site immunoradiometric assay to estimate the concentration of cytochrome P-450 1 in microsomes prepared from 24 individual, untreated New Zealand White rabbits. The progesterone 21-hydroxylase activities of these microsomes ranged from 0.2 to 5.8 nmol min-1 mg microsomal protein-1. Scatchard analysis revealed similar slopes and thus apparent affinities between the antibody and microsome samples that varied greater than 10-fold in 21-hydroxylase activity. The maximal extent of binding of the antibody to different microsomal preparations was greater for microsomes exhibiting high as compared to low 21-hydroxylase activity, suggesting that the level of binding reflects the microsomal content of P-450 1. Quantitation was based on the extent of binding of the 125I-labeled monoclonal antibody to P-450 1 sequestered from a sample by a heterologous monoclonal antibody adsorbed to the wells of a microtiter plate. These results indicate that the microsomal content of P-450 1 varies from less than 0.05 to 0.5 nmol/mg microsomal protein. The microsomal content of this antigen as determined in the two-site immunoradiometric assay was highly correlated (r = 0.97) with progesterone 21-hydroxylase activity. Linear regression analysis was used to estimate the turnover number for progesterone in situ, yielding a value of 11 nmol deoxycorticosterone formed min-1 nmol microsomal P-450 1(-1). This is similar to the value of 14 nmol deoxycorticosterone formed min-1 nmol-1 obtained for the reconstituted, purified P-450 1 used as a standard in the immunoquantitation assay.