Flemish Giant Research Articles

Evaluation of meniscal mechanics and proteoglycan content in a modified anterior cruciate ligament transection model.

Post-traumatic osteoarthritis (PTOA) develops as a result of traumatic loading that causes tears of the soft tissues in the knee. A modified transection model, where the anterior cruciate ligament (ACL) and both menisci were transected, was used on skeletally mature Flemish Giant rabbits. Gross morphological assessments, elastic moduli, and glycosaminoglycan (GAG) coverage of the menisci were determined to quantify the amount of tissue damage 12 weeks post injury. This study is one of the first to monitor meniscal changes after inducing combined meniscal and ACL transections. A decrease in elastic moduli as well as a decrease in GAG coverage was seen.

A comparison of selected performance indicators, nutrient digestibility and nitrogen balance parameters in Californian and Flemish Giant rabbits

Medium rabbit breeds such as Californian (CAL) are generally regarded as most suitable for meat production on commercial farms. Despite the increasing scale of production, commercial rabbit breeding has not replaced traditional and organic small-scale farming systems which use various rabbit breeds and hybrids. The Flemish Giant (FG), the largest rabbit breed in the world, is widely used in small household farms. According to researchers, the progeny of FG does have a relatively high weaning weight, and bucks are deemed good paternal components in commercial crossing. The aim of this study was to compare rearing rate, body weight, daily gains, carcass dressing percentage and the percentage of primal cuts in the carcass in CAL and FG rabbits. Nutrient digestibility, nitrogen balance and nitrogen retention parameters were also compared in the studied breeds. In our study, CAL rabbits were characterised by better reproductive performance in comparison with FG rabbits. Despite the above, the observed daily gain values, daily nitrogen balance and retention parameters and carcass dressing percentages of the compared breeds suggest that FGs may be a good alternative to medium breeds such as CAL rabbits.

Intra-articular injection of synovium-derived mesenchymal stem cells and hyaluronic acid promote regeneration of massive cartilage defects in rabbits.

IntroductionThe purpose of this study was to investigate whether intra-articular injection of synovium-derived mesenchymal stem cells (SD MSCs) with low molecular weight hyaluronic acid (HA) could promote regeneration of massive cartilage in rabbits.Material and methodsThe SD MSCs were harvested from the knees of 10 Flemish giant rabbits, expanded in culture, and characterized. A reproducible 4-mm cylindrical defect was created in the intercondylar groove area using a kit for the mosaic chondroplasty of femoral condyle COR (De Puy, Mitek). The defect was made within the cartilage layer without destruction of subchondral bone. Two weeks after the cartilage defect, SD MSCs (2 × 106 cell/0.15 ml) were suspended in 0.5% low molecular weight HA (0.15 ml) and injected into the left knee, and HA solution (0.30 ml) alone was placed into the right knee. Cartilage regeneration in the experimental and control groups were evaluated by macroscopically and histologically at 10, 30, and 60 days.ResultsOn day 10, after intra-articular injection of SD MSCs, we observed an early process of cartilage regeneration in the defect area. Histological studies revealed that cartilage defect was covered by a thin layer of spindle-shaped undifferentiated cells and proliferated chodroblasts. In contrast, an injection of HA did not induce reparation of cartilage in the defect area. At 30 days, macroscopic observation showed that the size of cartilage defect after SD MSC injection was significantly smaller than after HA injection. Histological score was also better in the MSC-treated intercondylar defect. At 60 days after MSC treatment, cartilage defect was nearly nonexistent and looked similar to an intact cartilage.ConclusionThus, intra-articular injection of SD MSCs can adhere to the defect in the intercondylar area, and promote cartilage regeneration in rabbits.

Effect of genotype and sex on meat colour changes in rabbit

Abstract. A study based on 150 carcasses of rabbit crosses of three breeds: Flemish Giant (FG), New Zealand White (NZW) and Californian (CAL) was conducted to determine the changes that occur within the first 24 h post mortem in the meat color parameters, i.e. lightness (L*), redness (a*), yellowness (b*), chroma (C*) and hue (H*), in the rabbits of different genetic groups and sexes. Four groups were formed: FN (FG bucks×NZW does); FC (FG bucks×CAL does); FN×C (FN bucks×CAL does); FN×FN (FN bucks×FN does). Meat colour was measured on the surface of Longissimus dorsi (LD) and biceps femoris (BF), 45 min and 24 h post mortem. The genetic groups differed significantly in the meat colour parameters of the LD and BF muscles at both times after slaughter. After 24 h, a* and b* values of the LD muscle were highest in FC group (18.05 and 6.65, respectively) and the lowest in FN×FN group (16.46 and 4.75, respectively). The greatest color difference (ΔE) of the LD muscle was in FN×FN rabbits (9.85) and the smallest in FC group (5.07). The differences between genetic group in color parameters of the BF muscle were smaller but significant, which indicates that crossbreeding may be used in practice to change meat color. Sex did not influence significantly the color parameters of the muscles at either time, although the a* and C* values of the BF muscle were higher in males than females.

Regional and Zonal Histo‐Morphological Characteristics of the Lapine Menisci

The menisci have crucial weight-bearing roles in the knee. Regional variations in structure and cellularity of the meniscus have only been minimally investigated. Therefore, the goal of this study was to illustrate the regional cell density, tissue area, and structure of healthy lapine menisci. Skeletally mature Flemish Giant rabbits were used for this study. Upon sacrifice, menisci were removed, fixed in formalin, and cryosectioned. Histological analysis was performed for the detection of sulfated glycosaminoglycans (GAG), collagen Types I and II, cellular density, and tissue area. ANOVA and paired t tests were used for testing of statistical significance. Glycosaminoglycan coverage of the medial meniscus significantly varied between regions, with the anterior region demonstrating significantly more GAG coverage than the posterior region. Inter- and intra-meniscal comparisons revealed variations between zones, with trends that outer zones of the medial menisci had less GAG coverage. Collagen Types I and II had marked characteristics and varying degrees of coverage across regions. Tissue area varied between regions for both medial and lateral menisci. Cellular density was dependent on region in the lateral meniscus. This is the first study to illustrate regional and zonal variation in glycosaminoglycan coverage, size, and cellular density for healthy lapine meniscal tissue. This data provides baseline information for future investigations in meniscal injury models in rabbits.

Development of a Traumatic Anterior Cruciate Ligament and Meniscal Rupture Model With a Pilot In Vivo Study

The current study describes the development of a small animal, closed-joint model of traumatic anterior cruciate ligament (ACL) and meniscal rupture. This model can be used in future studies to investigate the roles of these acute damages on the long-term health of an injured knee joint. Forty-two Flemish Giant rabbits received an insult to the left tibiofemoral joint ex vivo in order to document optimal energy and joint orientation needed to generate ACL and meniscal rupture, without gross fracture of bone. Impact energies ranged from 10 J to 22 J, and joint flexion angle ranged from 60 deg to 90 deg. Three in vivo animals were impacted at 13 J with the knee flexed at 90 deg, as this was determined to be the optimal load and joint orientation for ACL and meniscal ruptures, and sacrificed at 12 weeks. Impact data from the ex vivo group revealed that 13 J of dropped-mass energy, generating approximately 1100 N of load on the knee, would cause ACL and meniscal ruptures, without gross bone fracture. Acute damage to the lateral and medial menisci was documented in numerous ex vivo specimens, with isolated lateral meniscal tears being more frequent than isolated medial tears in other cases. The in vivo animals showed no signs of ill health or other physical complications. At 12 week post-trauma these animals displayed marked degeneration of the traumatized joint including synovitis, cartilage erosion, and the formation of peripheral osteophytes. Histological microcracks at the calcified cartilage-subchondral bone interface were also evident in histological sections of these animals. A closed-joint model of traumatic ACL and meniscal rupture was produced, without gross bone fracture, and a pilot, in vivo study showed progressive joint degeneration without any other noticeable physical impairments of the animals over 12 weeks. This closed-joint, traumatic injury model may be useful in future experimental studies of joint disease and various intervention strategies.

Chronic changes in the rabbit tibial plateau following blunt trauma to the tibiofemoral joint

The knee is often a site of injury that can often lead to a chronic disease known as osteoarthritis (OA). The disease may be initiated, in part, by acute injuries to joint cartilage and its cells. In a recent study by this laboratory, using Flemish Giant rabbits, an impact compressive load on the tibial femoral joint was shown to cause significant levels of acute damage to chondrocytes in cartilage of the medial and lateral tibial plateaus. In the current study, using the same model, histological and mechanical data from the plateaus were documented at 6 and 12 months post impact, and compared to the unimpacted control limbs and a limb from unimpacted, control animals. The mechanical properties of cartilage were measured with indentation relaxation tests on the medial and lateral plateaus in regions covered and uncovered by the meniscus. The histological studies on impacted limbs showed surface lesions on both plateaus, thickening of the underlying subchondral bone at 12 months and numerous occult microcracks at the calcified cartilage–subchondral bone interface at 6 and 12 months, without significant changes in cartilage thickness or its mechanical properties versus controls. Yet, there was an increase in both the matrix and fiber moduli and a decrease in the permeability of uncovered, medial plateau cartilage in both limbs of impacted animals between 6 and 12 months post impact that was not documented in control animals.

Traumatic Anterior Cruciate Ligament Tear and its Implications on Meniscal Degradation: A Preliminary Novel Lapine Osteoarthritis Model

Injury patterns of the meniscus following impact trauma resulting in anterior cruciate ligament (ACL) rupture are not well understood. This study explored the spatial and temporal distribution of meniscal tears in a novel in vivo lapine model. Skeletally mature Flemish Giant rabbits were subjected to either tibiofemoral impaction resulting in ACL rupture or surgical ACL transection. Meniscal damage was assessed acutely and after 12 wk for traumatically torn, and after 12 wk in ACL transected animals. Morphological grading was assessed using previously established criteria, and descriptions of meniscal damage were diagnosed by a Board certified orthopedist. Histological assessment was also made on 12 wk traumatically torn and ACL transected animals using Fast-Green/Safranin-O staining. Traumatic ACL rupture resulted in acute tears predominately in the lateral menisci. Animals subjected to both surgical transection and traumatic ACL rupture experienced degradation of the lateral and medial menisci 12 wk after injury. However, traumatic ACL rupture resulted in acute lateral damage and chronic degradation of the menisci, as well as more severe degradation of the menisci 12 wk after injury. This study showed that unconstrained high-intensity impacts on the tibiofemoral joint lead to meniscal damage in conjunction with ACL ruptures. Both acute and chronic changes to the menisci following traumatic impaction were observed. This research has implications for the future use of lapine models for osteoarthritis, as it incorporates traumatic loading as a more realistic mode contributing to the progression of osteoarthritis (OA) compared to surgically transected models.

Estimation of genetic distance of rabbit by morphometric analysis

The observation on morphological body conformation of English Spot (ES), Flemish Giant (FG), New Zealand White (NZW m ), and Rex (Rex m ) from Magelang, Central Java, and New Zealand White (NZW b ), Rex (Rex b ), Satin (Satin) and RS (RS) from Balitnak-Ciawi, were carried out to determine estimation of Mahalanobis genetic distance. This research was held in Magelang (Central Java) and Balitnak-Ciawi (West Java), 237 heads of Rabbits were used. Eleven different body parts were measured, those were head (length and width), ear (length and width), chest (girth, depth, and width), humerus length, radius-ulna length, tibia length and body length. General Linear Models were used in this observation (SAS package program). Simple discriminant analyses as further analyses were done for head (length and width), chest (girth, depth, and width), humerus length, radius-ulna length, tibia length and body length. ES, FG and NZW m rabbits had morphological size bigger than others. Mahalanobis genetic distance showed that NZW m and NZW b , Rex m and Rex b were had differences with genetic distances of 5.89139 and 6.75571 respectively. Rabbits from Magelang and from Balitnak were different on morphometric with mahalanobis distance of that region ranges were 4.89426 to 6.96749. Results from canonical analysis showed that the most discriminant variables were obtained by chest girth, chest width and humerus length on first canonical and head length on second cannonical. Key Words : Rabbit, Genetic Distance, Morphometric

Two biological determinants of anterior cruciate ligament graft strength: A review

Introduction: 1. A major long-term determinant of anterior cruciate ligament (ACL) graft strength is the biological remodeling process to which the ACL graft collagen matrix is subjected immediately after surgical implantation. The collagen matrix provides the tensile strength of ligaments. Previous quantitative ultrastructural studies have shown that both human and goat anterior cruciate ligament patellar tendon (ACL-PT) autografts contain mainly small diameter collagen fibrils (< 100 nm) at 3–20 years post-surgery irrespective of the tissue of origin of the graft. Similar observations have recently been reported for human ACL allografts over an 8 year period.1 2. Parry and Craig (1988) suggested there was a strong correlation between large collagen fibrils and the ultimate tensile strength and modulus of ligaments/tendons. This part of the study was designed to test the hypothesis that there was a positive correlation between large collagen fibrils and the tensile modulus and the area-normalized ultimate load of patella tendon preparations subjected to loading and unloading conditions. Methods: Two studies are presented in review. 1. This part of the study examined goat ACL-PT autografts up to 3 years post-surgery for collagen fibril size, collagen type and hydroxypyridinium (HP) cross-link density. Twenty-two mature female goats received an ACL-PT autograft to the right knee and were tested at 6 weeks (n = 5), 12 weeks (n = 4), 24 weeks (n = 5), 1 year (n = 5) and 3 years (n = 3). Two in each group were assigned for HP analyses and the rest for collagen fibril quantitation. The fibrils of five left control ACL’s and two PT’s were also quantitated. Two normal animals served as controls for HP analyses. 2. Experimental design. Nineteen Flemish giant rabbits (average weight 5.2 ± 0.6 kg) were used in this second study. Three experimental conditions were tested in which the right limbs were used as the experimental side and the left as the control side. 1. A central window of 40% of the width of the patella tendon was removed and the animals (n = 4) sacrificed immediately (T = 0), 2. Same surgery as in 1. but sacrificed at 7 weeks (n = 6), 3. Same surgery as in 2. but a stress shielding device implanted to unload the tendon (n = 6) and sacrificed at 7 weeks. Groups 2. and 3. were allowed 1 week cage activity and were then exercised on a treadmill for 6 weeks and then sacrificed at 7 weeks post-surgery (T = 7). The patella tendons were tested mechanically for area-normalized ultimate load, tensile stiffness and corresponding modulus from the linear range of response were determined for each tendon. Tranverse sections of the same tendons were prepared for computerized quantitative collagen fibril analyses after tensile testing. The mean of the area weighted mean collagen fibril diameters was determined from four tissue blocks obtained from the central region of each control and experimental patella tendon mechanically tested. These mean fibril diameters were then used in regression correlation analyses vs modulus, stiffness and ultimate load at T = 0 and T = 7 for both the control and experimental tendons. Results: 1. The collagen fibril profile for each time group was compared to the control ACL and PT with Kolomogorov–Smirnov analyses. Differences were found between the PT collagen profile with the 12, 24 and 52 week groups (P = 0.005, 0.07 and 0.1, respectively). All the grafts except the 6 week group contained mainly small fibrils ( 100 nm with Young’s modulus of the grafts which was tested in a separate study. The HP density was low in the 6, 12 and 24 week groups, but increased in the 1 and 3 year groups. Significant correlation (r = 0.75, P = 0.01) was found between the HP density and Young’s modulus.1 2. Strong positive correlations were found between the area weighted mean fibril diameter and the tensile modulus (r = 0.74, P < 0.05) and the normalized ultimate load (r = 0.72, P < 0.05) for the whole rabbit control tendons and the experimental tendons. Discussion: 1. This first study shows that the poor long term strength of goat ACL-PT autografts is probably due to the lack of large fibrils and the low cross-link density determined in the predominantly small collagen fibril populations in these grafts even at 3 years post-surgery.2 2. This is the first study to successfully correlate area weighted mean collagen fibril diameters with biomechanical parameters such as ultimate load, tensile stiffness and modulus of the patella tendon.3 References 1Shino K , Oakes BW et al. (1995) Am J Sports Med 23, 203–9. 2Ng GYF , Oakes BW , Deacon OW , McLean ID , Eyre D (1996) J Orthop Res 14, 851–6. 3Oakes BW , Singleton C , Haut R (1998) TORS, New Orleans, USA 23, 24–4.

Chronic changes in rabbit retro-patellar cartilage and subchondral bone after blunt impact loading of the patellofemoral joint

Animal models of acute joint injury are useful for study of changes in joint tissues that may eventually lead to degradative disease. Our laboratory has developed a joint trauma model using a single blunt impact to the patellofemoral joint of rabbits and documented softening of retro-patellar cartilage and thickening of its underlying bone out to 12 months post-trauma. In the present study, we examined changes in these joint tissues out to 36 months post-impact. Forty-nine Flemish giant rabbits were impacted on the right patellofemoral joint and sacrificed at one of six times: 0, 4.5, 7.5, 12, 24, and 36 months post-impact. A 30% reduction in the compressive modulus of traumatized retro-patellar cartilage occurred at 4.5 months versus the contralateral, non-impacted limb and remained at this reduced level out to 36 months. The fluid permeability of traumatized cartilage also increased over time from baseline and versus the non-impacted limb. Tissue thickness increased slightly at 4.5 months and then decreased over time to a 45% difference from baseline at 36 months post-trauma. While impacted cartilage revealed a significantly greater length of surface fissuring than contralateral, non-impacted cartilage, no time-dependent changes were evident in this study. Moreover, the number and depth of these impact surface lesions did not change as a function of time. Finally, the histological analyses indicated that the thickness of underlying subchondral bone increased over time from baseline and versus that in the non-impacted limb. This long-term study suggested an association between a decrease in the characteristic time constant of traumatized cartilage and thickening of the underlying subchondral bone. Any potential cause and effect relationship, however, must be investigated in future studies.

Polysulphated glycosaminoglycan treatments can mitigate decreases in stiffness of articular cartilage in a traumatized animal joint.

A single, blunt impact to the rabbit patellofemoral joint has been shown to decrease the stiffness of retropatellar cartilage and increase the thickness of the underlying bone. Polysulphated glycosaminoglycan treatments, on the other hand, have been shown to inhibit the degradation of articular cartilage and possibly increase synthesis of collagen and glycosaminoglycans in experimental studies on diseased joints. The aim of the current study was to examine the effect of early treatments with polysulphated glycosaminoglycans on cartilage using an in vivo post-trauma animal model. The study used 24 Flemish Giant rabbits in three groups: control, impacted, and impacted with treatment. Treatment consisted of intramuscular injections the day of insult and every 4 days thereafter for 6 weeks. At 30 weeks after trauma, mechanical tests were performed on the retropatellar cartilage to determine its mechanical stiffness. The patellae were also grossly evaluated for surface lesions on the retropatellar cartilage and histologically processed to measure the thickness of the subchondral bone. The rabbits that received no treatment had a statistically significant decrease in stiffness (modulus) for the cartilage of the impacted patellae compared with that of the contralateral, unimpacted patellae and compared with the cartilage of rabbits in the control group. The degradation in mechanical stiffness, however, was not observed in patellae of rabbits in the group receiving treatment. There was also a significant increase in the underlying thickness of the subchondral plate on the impacted patellae compared with that on the contralateral, unimpacted sides for rabbits in both the treated and nontreated groups. In conclusion, the polysulphated glycosaminoglycan treatments minimized a decrease in mechanical stiffness (modulus) of retropatellar articular cartilage 30 weeks after trauma. The mechanism by which the mechanical stiffness of the cartilage was preserved is unknown.

74As-Arsenate Metabolism in Flemish Giant Rabbits with Renal Insufficiency

The metabolic management of carrier-free 74As-arsenate (As(V)) by uremic rabbits of the strain Flemish Giant was studied. Renal insufficiency was induced by nephrectomy of respectively 1 kidney (3/6 nephrectomy) and 1 kidney + 2/3 remaining kidney (5/6 nephrectomy). Marginal renal insufficiency developed in the 3/6 nephrectomized group, while animals of the 5/6 group became severely uremic. Renal excretion of 74As was reduced by 90% in 5/6 nephrectomized animals 4 h after intraperitoneal injection (i.p.) of the animals. The associated uremic syndrome caused a strong decrease in methylation capacity of inorganic arsenic (Asi). The second methylation step from monomethylarsonic acid (MMA) to dimethylarsinic acid (DMA) was more strongly affected than the first one, from arsenite (As(III)) to MMA. The increased availability of Asi led to more extensive binding to insoluble tissue constituents after 5/6 nephrectomy. The decreased renal reduction of As(V) led to a decrease in As(III) and an increase of As(V) and the associated As(V)-transferrin binding in plasma. Uptake of 74As-transferrin by the bone marrow might contribute to uremic anemia.

Mechanisms of improvement in pulmonary gas exchange during isovolemic hemodilution.

Severe anemia is associated with remarkable stability of pulmonary gas exchange (S. Deem, M. K. Alberts, M. J. Bishop, A. Bidani, and E. R. Swenson. J. Appl. Physiol. 83: 240-246, 1997), although the factors that contribute to this stability have not been studied in detail. In the present study, 10 Flemish Giant rabbits were anesthetized, paralyzed, and mechanically ventilated at a fixed minute ventilation. Serial hemodilution was performed in five rabbits by simultaneous withdrawal of blood and infusion of an equal volume of 6% hetastarch; five rabbits were followed over a comparable time. Ventilation-perfusion (VA/Q) relationships were studied by using the multiple inert-gas-elimination technique, and pulmonary blood flow distribution was assessed by using fluorescent microspheres. Expired nitric oxide (NO) was measured by chemiluminescence. Hemodilution resulted in a linear fall in hematocrit over time, from 30 +/- 1.6 to 11 +/- 1%. Anemia was associated with an increase in arterial PO(2) in comparison with controls (P < 0.01 between groups). The improvement in O(2) exchange was associated with reduced VA/Q heterogeneity, a reduction in the fractal dimension of pulmonary blood flow (P = 0.04), and a relative increase in the spatial correlation of pulmonary blood flow (P = 0. 04). Expired NO increased with anemia, whereas it remained stable in control animals (P < 0.0001 between groups). Anemia results in improved gas exchange in the normal lung as a result of an improvement in overall VA/Q matching. In turn, this may be a result of favorable changes in pulmonary blood flow distribution, as assessed by the fractal dimension and spatial correlation of blood flow and as a result of increased NO availability.

In Vitro Methylation of Arsenite by Rabbit Liver Cytosol: Effect of Metal Ions, Metal Chelating Agents, Methyltransferase Inhibitors and Uremic Toxins

ABSTRACTThe methylation of carrier-free 74As-arsenite by liver cytosol of Flemish Giant rabbits is highly susceptible to additions of trace elements. in vitro supplementation of essential trace elements like zinc (Zn2+), vanadium (V5+), iron (Fe2+), copper (Cu2+) and selenate was shown to increase the methylation efficiency. Trivalent metal ions (e.g. Al3+, Cr3+ and Fe3+), Hg2+, Tl+ and SeO32- had a deleterious effect. The inhibitory effect of EDTA, oxime and many divalent cations (Ca2+, Mg2+, Sr2+,.) suggest a co-factor role for a specific divalent metal ion, possibly Zn2+. Chelating agents used in clinical treatment of acute and chronic inorganic arsenic poisoning lower the methylation capacity of cytosol by rendering the trivalent arsenic unavailable for the methyltransferase enzymes. S-adenosylhomocysteine and periodate-oxidized adenosine, inhibitors of s-adenosylmethionine dependent methylation pathways, inhibit the methylation of arsenite. Pyrogallol, a catechol-O-methyltransferase inhibitor, blocks the action of arsenite- and monomethylarsonic methyltransferase enzymes, suggesting a close structural relationship between the active sites of the different enzymes. Some uraemic toxins, namely oxalate, p-cresol, hypoxanthine, homocysteine and myo-inositol, inhibit arsenic methylation.

Basal metabolism of intraperitoneally injected carrier-free 74As-labeled arsenate in rabbits.

The time-dependent occurrence of [74As]arsenate metabolites in Flemish Giant rabbits was investigated. As absorbed rapidly, reaching maximal concentrations in plasma and packed cells after 30 min and 2 hr, respectively. The [74As]arsenate in plasma and packed cells was reduced to [74As]arsenite, to 35 and 50% of the total 74As, respectively. The concentration of methylated As species in plasma and packed cells increased rapidly after 30 min. About 18% of total plasma 74As maximally bound to transferrin. Two-thirds of total 74As in packed cells bound to hemoglobin. Whereas little or no [74As]monomethylarsonic acid, one of the main As metabolites in humans, could be found in other animals, it is present in measurable amounts in the Flemish Giant. Furthermore, the plasma clearance rate of 74As species is lower than that in other rabbits and more similar to that of humans. The tissue 74As distribution varied widely with the highest concentrations in kidneys, liver, and lungs. 74As accumulated in bone whereas other tissues and blood showed rapid clearance rates. In muscle and heart an important part of arsenic was associated with components insoluble in phosphate-buffered isotonic saline. Binding of arsenic to soluble tissue proteins was most important in the kidneys, liver, and spleen. [74As]Arsenate metabolites were detected in all tissues. The relative amounts of [74As]arsenite or [74As]monomethylarsonic acid seldom exceeded 15% of total tissue 74As. The proportion of [74As]dimethylarsenic acid in the low molecular 74As fraction increased steadily. Substantial amounts of [74As]monomethylarsonic acid were found in the tissues..

Basal Metabolism of Intraperitoneally Injected Carrier-Free 74As-Labeled Arsenate in Rabbits

The time-dependent occurrence of [74As]arsenate metabolites in Flemish Giant rabbits was investigated. As absorbed rapidly, reaching maximal concentrations in plasma and packed cells after 30 min and 2 hr, respectively. The [74As]arsenate in plasma and packed cells was reduced to [74As]arsenite, to 35 and 50% of the total 74As, respectively. The concentration of methylated As species in plasma and packed cells increased rapidly after 30 min. About 18% of total plasma 74As maximally bound to transferrin. Two-thirds of total 74As in packed cells bound to hemoglobin. Whereas little or no [74As]monomethylarsonic acid, one of the main As metabolites in humans, could be found in other animals, it is present in measurable amounts in the Flemish Giant. Furthermore, the plasma clearance rate of 74As species is lower than that in other rabbits and more similar to that of humans. The tissue 74As distribution varied widely with the highest concentrations in kidneys, liver, and lungs. 74As accumulated in bone whereas other tissues and blood showed rapid clearance rates. In muscle and heart an important part of arsenic was associated with components insoluble in phosphate-buffered isotonic saline. Binding of arsenic to soluble tissue proteins was most important in the kidneys, liver, and spleen. [74As]Arsenate metabolites were detected in all tissues. The relative amounts of [74As]arsenite or [74As]monomethylarsonic acid seldom exceeded 15% of total tissue 74As. The proportion of [74As]dimethylarsenic acid in the low molecular 74As fraction increased steadily. Substantial amounts of [74As]monomethylarsonic acid were found in the tissues..

Hepatic lesions in rabbits infected with Encephalitozoon cuniculi administered per rectum.

Microsporidia have been recognized recently as opportunistic pathogens in acquired immunodeficiency syndrome patients. In an attempt to develop an animal model of enteric microsporidiosis, adult (5 to 6 months old) male Flemish Giant rabbits from a closed New York colony were administered 5 x 10(3), 5 x 10(5), and 5 x 10(7) Encephalitozoon cuniculi per rectum. Rabbits given 5 x 10(5) and 5 x 10(7) E. cuniculi had moderate granulomatous periportal infiltrates, characterized by the presence of numerous macrophages, epithelioid cells and a few multinucleated giant cells, lymphocytes, and plasma cells. Inflammatory cells also were seen infiltrating the tunica adventitia and tunica media of hepatic portal veins and branches of the hepatic artery. This study demonstrates that administration of E. cuniculi per rectum to rabbits results in infection that is characterized by high frequency and severity of hepatic lesions.

Early detection of osseointegration using scanning electron microscopy and the interfacial biopsy chamber: a pilot study.

This pilot project attempted to demonstrate microscopic evidence of osseointegration in a controlled environment as originally presented by Brånemark. The Interfacial Biopsy Chamber was developed to collect titanium/tissue serial biopsies of the implant-tissue interface at various stages of wound healing. It was surgically placed in two Flemish giant rabbits and titanium/tissue biopsies were collected at 35 and 70 days. The biopsies were examined using scanning electron microscopy (x2000, x3200, and x7500) and light microscopy (x230). Osseous tissue was found in intimate contact with the titanium implant surface with no evidence of an intervening fibrous layer. Cells with the morphological characteristics of osteoblasts were observed covering the titanium surface. Processes extending from the main body of these cells were in intimate contact with the titanium surface, following the machining striations. The photomicrographs were similar to those presented earlier by Brånemark. The project also suggested the use of the Interfacial Biopsy Chamber as a research instrument for the collection of implant/tissue interface serial biopsy samples.

Prediction of carcass merit from live body measurements in rabbits of four breed-types

The objective of the investigation was to evaluate certain live body measurements taken on rabbit fryers as predictors of carcass merit. Four breed-types were involved: two purebred (Californian (CAL) and New Zealand White (NZW)) and two crossbred (CAL sire × NZW dam and Flemish Giant (FG)) groups, giving a total of 226 rabbit fryers. Live mensuration characters (recorded at 70 days of age) as independent variables included body weight and length, loin width and length, femur length, and half-rump circumference. Carcass traits as dependent variables were hot carcass weight, dressing percentage, loin lean cut weight, and lean-to-bone ratio of the loin primal cut. Models including breedtype, season, parity and sex main effects with the inclusion of live mensuration characters as linear covariates were used in multiple regression analyses. Regression equations were most reliable ( R 2≥79.7%) for prediction of hot carcass and loin lean cut weights, as opposed to percentage or ratio traits. Live body weight and loin width measurements yielded modest to high ( R 2=34.1 and 79.7%) determination, respectively, in loin lean-to-bone ratio and lean cut weight. Individual breed-type regressions often varied ( P<0.05), suggesting genetic and (or) physiological differences in maturity at a constant age of 70 days. This investigation demonstrates the applicability of regression equations to predict certain carcass merit traits in the meat rabbit industry.