Diagnosis of quinolone-induced arthropathy in juvenile dogs by use of magnetic resonance (MR) imaging

Post-treatment of hyaluronan to decrease the apoptotic effects of carprofen in canine articular chondrocyte culture

A major concern associated with the use of drugs is their adverse side effects. Specific examples of the drugs of concern include antibiotic agents and non-steroidal anti-inflammatory drugs. Despite the presence of a high degree of efficacy for specific conditions, these drugs may deteriorate the surrounding tissues that are exposed to them. Often, carprofen is used for joint inflammation; however, it may stimulate cartilage degradation which can then lead to osteoarthritis progression. In this study, hyaluronan was combined with carprofen treatment in three different applications (pre-treatment, co-treatment and post-treatment) on normal canine chondrocytes to determine whether Hyaluronan (HA) is capable of mitigating the degree of chondrotoxicity of carprofen. Our findings revealed that carprofen at IC₂₀ (0.16 mg/mL) decreased viability and increased nitric oxide (NO) production. Importantly, carprofen induced the apoptosis of canine chondrocytes via the up-regulation of Bax, Casp3, Casp8, Casp9 and NOS2 as compared to the control group. Although the co-treatment of HA and carprofen appeared not to further alleviate the chondrotoxicity of carprofen due to the presence of a high number of apoptotic chondrocytes, post-treatment with HA (carprofen treatment for 24 h and then changed to HA for 24 h) resulted in a decrease in chondrocyte apoptosis by the down-regulation of Bax, Casp3, Casp8, Casp9, NOS2, along with NO production when compared with the treatment of carprofen for 48 h (P < 0.05). These results suggest that HA can be used as a therapeutic agent to mitigate the degree of chondrotoxicity of carprofen.

Early Pathophysiologic Feature of Arthropathy in Juvenile Dogs Induced by Ofloxacin, a Quinolone Antimicrobial Agent

Arthropathy in dogs induced by ofloxacin, a quinolone antimicrobial agent, was pathophysiologically investigated. In the in vivo studies, ofloxacin was administered orally once or twice at 20 mg/kg/day to male juvenile (3-month-old, n = 3) or adult (36-month-old, n = 2) dogs, and the humeral and femoral heads were examined pathologically. Unlike adult dogs, fluid-filled vesicles were macroscopically observed on the articular surfaces of one juvenile dog 24 hours after a single treatment with ofloxacin. These lesions were seen in all juvenile dogs by twice dosing. Microscopically, fissures or cavity formations in the middle zone of the articular cartilage were noted only in juvenile dogs. Furthermore, the cartilage matrix from the abnormal area to the articular surface showed a decreased safranin-O staining intensity, suggesting proteoglycan depletion. Ultrastructurally, chondrocytes in the middle zone of juvenile dogs displayed dilatation of the cisternae in the rough endoplasmic reticulum as an initial hallmark. In the in vitro studies, chondrocytes isolated from the articular cartilage of naive juvenile dogs were exposed to ofloxacin at 6.3–100 μg/ml for 24 hours. Although no changes were noted in the deoxyribonucleic acid synthesis, protein synthesis, or proteoglycan release at concentrations of up to 100 μg/ml, the proteoglycan synthesis was evidently decreased in a dose-dependent manner from 12.5 μg/ml. The results obtained suggest that the inhibitory action of ofloxacin on proteoglycan syntheses in the chondrocytes may largely contribute to the early morphologic features in the articular cartilage of the juvenile dog.

Cutaneous infectious diseases: Kids are not just little people

The changes in immune response that occur with age play a significant role in disease presentation and patient management. Evolution of the innate and adaptive immune systems throughout life, influenced partly by hormonal changes associated with puberty, plays a role in the differences between pediatric and adult response to disease. We review a series of manifestations of dermatologic infectious diseases spanning bacterial, viral, and fungal origins that can be seen in both pediatric and adult age groups and highlight similarities and differences in presentation and disease course. Therapeutic options are also discussed for these infectious diseases, with particular attention to variations in management between these population subgroups, given differences in pharmacokinetics and side effect profiles.

A non-arthropathic dose and its disposition following repeated oral administration of ofloxacin, a new quinolone antimicrobial agent, to juvenile dogs

A non-arthropathic dose and disposition of ofloxacin, a potent new quinolone antimicrobial agent, were assessed in male juvenile (3-month-old) dogs, when administered orally at 5, 10 and 20 mg/kg/day once daily for 8 consecutive days. Ofloxacin concentrations in sera and articular cartilages were analyzed by high-performance liquid chromatography (HPLC). Macroscopically, arthropathy characterized by fluid-filled vesicles in articular surface of the humerus and femur was observed in animals receiving 10 and 20 mg/kg/day of ofloxacin, but not in those given 5 mg/kg/day. At 20 mg/kg/day, arthropathy of comparable severity also occurred on day 2. Microscopically, the cavity formation in the middle zone of the articular cartilage was first identified and then necrotic chondrocytes were found numerous around the cavity, followed by appearance of chondrocyte clusters. In pharmacokinetics, peak serum concentration (Cmax) and area under the concentrations (AUC0-24) were increased in a dose-dependent manner. However, no remarkable differences in these two parameters were noted between a single and repeated treatments, suggesting no accumulation of the drug. The articular ofloxacin concentration 2 hr after treatment was approximately 1.8 (day 2) to 2.0 times (day 8) higher than the serum concentration. Based on these results, a non-arthropathic dose of ofloxacin in male juvenile dogs following an 8-day treatment is considered to be 5 mg/kg/ day, and its Cmax, AUC0-24 and articular cartilage concentrations 2 hr after treatment were 3.4 microg/ml, 35.1 microg-hr/m/ and 7.0 microg/g, respectively, under these experimental conditions. Thus, arthropathy due to ofloxacin may be predicted by monitoring serum drug concentration.

Effects of nalidixic acid on hamster knee cartilage morphology and synovial fluid composition

Quinolone-induced changes were studied in the knee joints of 4-wk-old female hamsters given intraperitoneal doses of either nalidixic acid (400 mg/kg body weight) or vehicle on days 0 and 1. After euthanasia on day 4, synovial fluid was collected for cytologic evaluation and for analysis of concentrations of hyaluronan, proteoglycans, total protein, and collagen as hydroxyproline. Slides of formalin-fixed decalcified tissues were stained with hematoxylin-eosin or safranin O for histologic scoring of lesion severity. Nine of 10 hamsters treated with nalidixic acid had fissures within articular cartilage of the femur and reduced safranin O staining of matrix indicative of loss of proteoglycans. Synovial membranes from affected joints, however, were not inflamed. Synovial fluid cell counts and cytomorphology were unaffected by treatment. In synovial fluid from 5 of 10 treated hamsters, proteoglycans were elevated by more than 2 SDs above the control group, and individual animal levels correlated with the histologic severity score (r2 = 0.36; p = 0.02). The hyaluronan content of the synovial fluid from treated hamsters was mildly but significantly elevated (p = 0.005), and the histologic severity score again correlated with individual animal levels (r2 = 0.42; p = 0.01). Hydroxyproline was unaffected by treatment. Although synovial fluid changes and histologic changes were correlated on a group basis, interanimal variability was significant and the magnitude of biochemical changes were far smaller than those that occur during inflammation. Changes in synovial fluid composition are not sufficiently robust to predict cartilage changes in individual animals.

The advantage of magnetic resonance imaging in diagnosis of cauda equina syndrome in dogs

Three dogs were evaluated in our study using magnetic resonance imaging (MRI) to reveal the anatomical deformity and the degree of the lesion of cauda equina. In all dogs, MRI revealed soft tissue, such as cauda equina, epidural fat, and intervertebral disc, at the lumbosacral region clearly without contrast medium. Our results suggest that MRI has some advantages in evaluating cauda equina syndrome in dogs.

Pharmacokinetic disposition and arthropathic potential of oral ofloxacin in dogs

We examined the relation between the pharmacokinetic disposition and arthropathic potential of ofloxacin, a new quinolone antibacterial agent, using both male immature (3-month-old) and mature (18-month-old) beagles. Ofloxacin was orally administered to these dogs at 20 mg/kg once daily for 8 consecutive days, and the animals were killed 2 h after the last treatment. Serum ofloxacin concentrations were repeatedly measured on days 1 and 7 by use of high-performance liquid chromatography (HPLC), and pharmacokinetic parameters were calculated. In addition, on day 8, the drug concentrations in the joint synovial fluid and humeral and femoral condyles were measured. Clinico-pathological tests of blood and serum or histopathological examination of bone specimens were also performed. Arthropathy was macroscopically observed in the cartilage surface of all immature dogs, but not in mature dogs. There were, however, no noticeable differences in pharmacokinetic parameters between the two age groups of dogs or between single and 7-day treatments. In contrast to the occurrence of arthropathic lesions, the synovial fluid and condylar drug concentrations in immature dogs was equal to or lower than those in mature dogs, suggesting that the pharmacokinetic disposition of ofloxacin may not be essential for cartilage lesions.