Vitreous Pharmacokinetics and Retinal Safety of Intravitreal Preserved Versus Non-preserved Triamcinolone Acetonide in Rabbit Eyes

Purpose: To compare the intravitreal pharmacokinetic profile of a triamcinolone acetonide formulation containing the preservative benzyl alcohol (TA-BA) versus a preservative-free triamcinolone acetonide formulation (TA-PF), and evaluate potential signs of toxicity to the retina. Methods: A total of 60 New Zealand male white rabbits, divided into two groups, were studied. In the TA-BA group, 30 rabbits received an intravitreal injection of TA-BA (4 mg/0.1ml) into the right eye. In the TA-PF group, 30 rabbits received an intravitreal injection of TA-PF (4 mg/0.1ml) into the right eye. The intravitreal drug levels were determined in 25 animals from each group by high-performance liquid chromatography (HPLC). The potential for toxicity associated with the intravitreal triamcinolone injections was evaluated in five randomly selected animals from each group by electroretinography (ERG) and by light microscopy. Results: Median intravitreal concentrations of TA-BA (mu g/ml) were 1903.1, 1213.0, 857.8, 442.0, 248.6 at 3, 7, 14, 21 and 28 days after injection. Intravitreal concentrations of TA-PF (mu g/ml) were 1032.9, 570.1, 516.6, 347.9, 102.8 at 3, 7, 14, 21 and 28 days after injection. The median intravitreal triamcinolone concentration was significantly higher in the TA-BA compared to the TA-PF group at 7 days post-injection (p < 0.05). There was no significant difference between the two groups in median triamcinolone concentration at the other time points evaluated. There was no evidence of toxic effects on the retina in either group based on ERG or histological analyses. Conclusions: Following a single intravitreal injection, the median concentration of triamcinolone acetonide is significantly higher in the TA-BA compared to the TA-PF group at 7 days post-injection. No toxic reactions in the retina were observed in either group.

Restoration of the rabbit corneal surface after total epithelial debridement and complete limbal excision

How is the corneal epithelium restored when all of it plus the limbus have been eliminated? This investigation explored the possibility that this may be achieved through the conjunctival epithelium. The corneal epithelium of the right eye of 12 rabbits (Oryctolagus cuniculus) was totally scraped followed by surgical excision of the limbus plus 1.0-1.5 mm of the adjacent conjunctiva. Antibiotics and corticosteroids were applied for 1 week after surgery. Histological and immunohistochemical techniques were used to monitor the events taking place on the eye surface 2 weeks and 1, 3 and 6 months thereafter. Initially, the corneal surface was covered by conjunctival-like epithelium. After 1 month and more prominently at 3 and 6 months an epithelium displaying the morphological features of the cornea and reacting with the AE5 antibody was covering the central region. It is likely that the corneal epithelium originated from undifferentiated cells of the conjunctiva interacting with the corneal stroma.

DETERMINATION OF DICLOFENAC SODIUM IN RABBIT PLASMA BY HPLC/UV: EVALUATION AND CHARACTERIZATION OF ITS CRYSTALLINE FORMS, ANHYDROUS AND HYDRATE, ON THE ANTIPYRETIC EFFECT

Diclofenac sodium (DS) is a non-steroidal anti-inflammatory drug that is widely prescribed for the treatment of rheumatoid arthritis and post-surgery analgesia. The active pharmaceutical ingredient is the anhydrous form; however, it can also exist in hydrate form. In this context, knowing the properties of the solid state is important and relevant in the pharmaceutical area because they have a significant impact on the solubility, bioavailability, and chemical stability of the drugs. In the present study, data from XRPD, FTIR spectroscopy, and thermal analysis were used for the identification and characterization of DS forms (anhydrous and hydrate). An HPLC method was optimized to evaluate the plasma concentration of DS in rabbits. The optimized method exhibited good linearity over the range 0.1-60 mu g/mL with correlation coefficients of >0.9991. The mean recovery was 100%. Precision and accuracy were determined within acceptable limits. Finally, to compare the pharmacological properties of anhydrous and hydrate DS forms, we investigated their effects in the febrile response induced by lipopolysaccharide from E. coli in rabbits. The results show that the antipyretic effect of anhydrous and hydrate DS forms are similar.

The protective effect of cilostazol on isolated rabbit femoral arteries under conditions of ischemia and reperfusion: the role of the nitric oxide pathway

OBJECTIVES: The clinical significance of ischemia/reperfusion of the lower extremities demands further investigation to enable the development of more effective therapeutic alternatives. This study investigated the changes in the vascular reactivity of the rabbit femoral artery and nitric oxide metabolites under partial ischemia/reperfusion conditions following cilostazol administration. METHODS: Ischemia was induced using infrarenal aortic clamping. The animals were randomly divided into seven groups: Control 90 minutes, Ischemia/Reperfusion 90/60 minutes, Control 120 minutes, Ischemia/Reperfusion 120/90 minutes, Cilostazol, Cilostazol before Ischemia/Reperfusion 120/90 minutes, and Ischemia 120 minutes/Cilostazol/Reperfusion 90 minutes. Dose-response curves for sodium nitroprusside, acetylcholine, and the calcium ionophore A23187 were obtained in isolated femoral arteries. The levels of nitrites and nitrates in the plasma and skeletal muscle were determined using chemiluminescence. RESULTS: Acetylcholine- and A23187-induced relaxation was reduced in the Ischemia/Reperfusion 120/90 group, and treatment with cilostazol partially prevented this ischemia/reperfusion-induced endothelium impairment. Only cilostazol treatment increased plasma levels of nitrites and nitrates. An elevation in the levels of nitrites and nitrates was observed in muscle tissues in the Ischemia/Reperfusion 120/90, Cilostazol/Ischemia/Reperfusion, and Ischemia/Cilostazol/Reperfusion groups. CONCLUSION: Hind limb ischemia/reperfusion yielded an impaired endothelium-dependent relaxation of the femoral artery. Furthermore, cilostazol administration prior to ischemia exerted a protective effect on endothelium-dependent vascular reactivity under ischemia/reperfusion conditions.

Pedigree analysis and inbreeding depression on growth traits in Brazilian Marchigiana and Bonsmara breeds

The study of population structure by pedigree analysis is useful to identify important circumstances that affect the genetic history of populations. The intensive use of a small number of superior individuals may reduce the genetic diversity of populations. This situation is very common for the beef cattle breeds. Therefore, the objectives of the present study were to analyze the pedigree and possible inbreeding depression on traits of economic interest in the Marchigiana and Bonsmara breeds and to test the inclusion of the individual inbreeding coefficient (F-i) or individual increases in inbreeding coefficient (Delta F-i) in the genetic evaluation model for the quantification of inbreeding depression. The complete pedigree file of the Marchigiana breed included 29,411 animals born between 1950 and 2003. For the Bonsmara breed, the pedigree file included 18,695 animals born between 1988 and 2006. Only animals with at least 2 equivalent generations of known pedigree were kept in the analyses of inbreeding effect on birth weight, weaning weight measured at about 205 d, and BW at 14 mo in the Marchigiana breed, and on birth weight, weaning weight, and scro-tal circumference measured at 12 mo in the Bonsmara breed. The degree of pedigree knowledge was greater for Marchigiana than for Bonsmara animals. The average generation interval was 7.02 and 3.19 for the Marchigiana and Bonsmara breed, respectively. The average inbreeding coefficient was 1.33% for Marchigiana and 0.26% for Bonsmara. The number of ancestors explaining 50% of the gene pool and effective population size computed via individual increase in coancestry were 13 and 97.79 for Marchigiana and 41 and 54.57 for Bonsmara, respectively. These estimates indicate reduction in genetic variability in both breeds. Inbreeding depression was observed for most of the growth traits. The model including Delta F-i can be considered more adequate to quantify inbreeding depression. The inclusion of F-i or Delta F-i in the genetic evaluation model may not result in better fit to the data. A genetic evaluation with simultaneous estimation of inbreeding depression can be performed in Marchigiana and Bonsmara breeds, providing additional information to producers and breeders.

Biventricular structural and functional responses to aortic constriction in a rabbit model of chronic right ventricular pressure overload

Objectives: Chronic right ventricular (RV) pressure overload results in pathologic RV hypertrophy and diminished RV function. Although aortic constriction has been shown to improve systolic function in acute RV failure, its effect on RV responses to chronic pressure overload is unknown. Methods: Adjustable vascular banding devices were placed on the main pulmonary artery and descending aorta. In 5 animals (sham group), neither band was inflated. In 9 animals (PAB group), only the pulmonary arterial band was inflated, with adjustments on a weekly basis to generate systemic or suprasystemic RV pressure at 28 days. In 9 animals, both pulmonary arterial and aortic devices were inflated (PAB+AO group), the pulmonary arterial band as for the PAB group and the aortic band adjusted to increase proximal systolic blood pressure by approximately 20 mm Hg. Effects on the functional performance were assessed 5 weeks after surgery by conductance catheters, followed by histologic and molecular assessment. Results: Contractile performance was significantly improved in the PAB+AO group versus the PAB group for both ventricles. Relative to sham-operated animals, both banding groups showed significant differences in myocardial histologic and molecular responses. Relative to the PAB group, the PAB+AO group showed significantly decreased RV cardiomyocyte diameter, decreased RV collagen content, and reduced RV expression of endothelin receptor type B, matrix metalloproteinase 9, and transforming growth factor beta genes. Conclusions: Aortic constriction in an experimental model of chronic RV pressure overload not only resulted in improved biventricular systolic function but also improved myocardial remodeling. These data suggest that chronically increased left ventricular afterload leads to a more physiologically hypertrophic response in the pressure-overloaded RV. (J Thorac Cardiovasc Surg 2012;144:1494-501)

Effects of Hepatocyte Growth Factor Injection and Reinjection on Healing in the Rabbit Vocal Fold

Objectives/Hypothesis. Hepatocyte growth factor (HGF) is a multifunctional polypeptide that plays various roles in embryogenesis and tissue regeneration and exhibits marked antifibrotic activity. The present study sought to assess the effects of HGF injection and reinjection coinciding with its peak of activity on collagen density, vessel density, inflammatory reaction in the lamina propria, and mean epithelial thickness in the injured rabbit vocal fold. Study Design. Prospective, controlled, experimental animal study. Methods. Fourteen rabbits were subdivided into two groups and underwent injury of the vocal folds. Immediately after injury, animals in group 1 received HGF injections into the right vocal fold (RVF), whereas those in group 2 received bilateral HGF injections and a single reinjection into the RVF 10 days after the first, to coincide with the peak of HGF activity. The left vocal folds (LVFs) served as controls in both groups. Histological assessment of laryngeal specimens was performed at 30 and 40 days, respectively. Results. In both groups, collagen density was lower in the right (treated) vocal folds than in the left (control) folds (P = 0.018). Vessel density was higher in the RVFs in group 2 (P = 0.018). Differences were found in mean epithelial thickness and inflammatory reaction in the lamina propria but did not reach statistical significance. Conclusions. In the scarred rabbit vocal fold, HGF injection is associated with decreased collagen density in the lamina propria, whereas reinjection after 10 days produces decreased collagen density and higher vessel density.