Vincristine-induced peripheral neuropathy in a dog.

A 12-year-old spayed Golden Retriever with mycosis fungoides was treated by use of a chemotherapy protocol that included vincristine. After 16 weekly vincristine injections, the dog began to have signs of peripheral neuropathy. Results of electromyographic examination were consistent with muscle denervation, and motor nerve conduction velocity was depressed. Histologic examination of a common peroneal nerve biopsy specimen revealed severe nerve fiber degeneration. Clinical response and pathologic evidence of improvement were observed after the drug had been discontinued for 2.5 months.     

Spontaneous ophthalmic lesions in young Sprague-Dawley rats.

Eight hundred eight Sprague-Dawley rats were examined for ophthalmic abnormalities during a pretest period in various preclinical safety assessment studies. Persistent pupillary membrane, corneal crystal, healed minor trauma, synechia, coloboma of the iris, lens luxation, cataract, persistent hyperplastic primary vitreous, vitreous hemorrhage, coloboma of the optic disc or choroid, remnant of hyaloid arterial system, retinal hemorrhage, retinal detachment, retinal folding and choroidal defect were observed. The incidences of corneal crystal, synechia, and nuclear cataract in this survey were higher than those reported previously. On the other hand, retinal folding in this survey was less common than that reported previously. These results suggest that background data of eye problems in albino rats should be accumulated in each own laboratory colony. In addition, since spontaneous eye problems are common in young albino rats, elimination of rats with ophthalmic abnormalities from study groups by an ophthalmic examination during a pretest period would facilitate to evaluate toxicity potential of test compounds in safety assessment studies.     

Prevalence of 5-lipoxygenase expression in canine osteosarcoma and the effects of a dual 5-lipoxygenase/cyclooxygenase inhibitor on osteosarcoma cells in vitro and in vivo

Canine osteosarcoma is an insidious disease with few effective treatment modalities; therefore, use of pharmacologic intervention to improve mortality or morbidity is constantly sought. The use of cyclooxygenase enzyme inhibitors has been an area of interest with limited efficacy based on retrospective examination of tumor expression and in vivo cell proliferation models. Recently, examination of dual cyclooxygenase and 5-lipoxygenase inhibitors in human and canine oncology suggests that 5-lipoxygenase inhibitors may be an effective approach in vitro and during tumor induction in rodent models. Therefore, the authors decided to examine 5-lipoxygenase expression in primary canine osteosarcoma samples and have shown that approximately 65% of osteosarcomas label positive for cytoplasmic 5-lipoxygenase. Further examination of a cell culture and xenograft model shows similar 5-lipoxygenase expression. Surprisingly, a canine 5-lipoxygenase inhibitor (tepoxalin) significantly reduced cell proliferation at physiologic doses in vitro and diminished xenograft tumor growth in nude mice, suggesting that further investigation is needed. Traditionally, 5-lipoxygense leads to production of lipid mediators, such as leukotriene B(4) and 5-oxo-eicosatetraenoic acid, which, when added back to the media of tepoxalin-treated cells, did not recover cell proliferation. The lack of nuclear staining in primary and xenografted tumors and the lack of response to eicoasanoids suggest that lipid mediator production is not the primary means by which tepoxalin acts to alter proliferation. Regardless of the mechanisms involved in retarding cell proliferation, future investigation is warranted.     

Clinical peripheral neuropathy associated with diabetes mellitus in 3 dogs

Clinical and electrodiagnostic findings in 3 spontaneously diabetic dogs with clinical peripheral neuropathy (PN) are reported. Clinical signs of a PN may develop in diabetic dogs with adequate glycemic control. In addition, laryngeal paralysis may develop in association with diabetes mellitus in dogs with clinical PN.     

Inhibition of equine mononuclear cell proliferation and leukotriene B4 synthesis by a specific 5-lipoxygenase inhibitor, A-63162.

The lipoxygenase metabolites of arachidonic acid have an important role in lymphocyte activation. We used a specific 5-lipoxygenase inhibitor, A-63162, to examine the role of 5-lipoxygenase (5-LO) in equine blood mononuclear cell (BMC) proliferation and leukotriene B4 (LTB4) synthesis after stimulation with mitogen (phytohemagglutinin, PHA) or calcium ionophore (A23187). The A-63162 inhibited PHA-induced equine BMC proliferation and, at the same concentration, also inhibited A23187-induced LTB4 synthesis. The presence of exogenous interleukin 2 (IL-2) or the cyclooxygenase inhibitor indomethacin, failed to reverse the immunosuppression caused by A-63162. Further, we found that A-63162, at the concentration that inhibited BMC proliferation and LTB4 synthesis, had no effect on BMC viability. The addition of the specific protein kinase C inhibitor, H-7, did not inhibit A23187-induced LTB4 synthesis. Results indicate that 5-lipoxygenase metabolites may have an important role in equine lymphocyte activation and that protein kinase C has no role in regulating LTB4 production after A23187 stimulation.     

Ganglioneuromas of the thyroid gland in a colony of Sprague-Dawley rats.

Ganglioneuromas of the thyroid gland of Sprague-Dawley rats were found in 7.2% of 698 rats used in two, 2-year oncogenicity bioassays. The incidence of the tumor was unrelated to treatment or sex. Of the 52 ganglioneuromas of the thyroid gland identified in 50 animals, 40 (80%) had coincident C cell proliferations in the same or contralateral lobe. Ganglioneuromas were contiguous or commingled with C cell proliferations in 63.5% of the cases. The ganglioneuromas consisted of large ganglion cells and, in a few cases, cells thought to be less differentiated neuronal precursors, in a matrix of neurites and Schwann cells. They grew, infiltrating and expanding in the thyroid parenchyma, and did not metastasize. Immunohistochemical staining for calcitonin, S-100 protein, and neurofilaments, as well as electron microscopy, were used to further characterize the tumors. The close association of ganglioneuromas with C cell tumors supports the theory of neural crest origin of C cells and provides a parallel to the association of ganglioneuromas and pheochromocytomas in the adrenal medulla. This is the first report of ganglioneuromas occurring in the thyroid gland or occurring as a common entity in any species.     

Effect of deoxycorticosterone acetate-salt-induced hypertension on diabetic peripheral neuropathy in alloxan-induced diabetic WBN/Kob rats

The relationship between hypertension and diabetic peripheral neuropathy (DPN) has recently been reported in clinical research, but it remains unclear whether hypertension is a risk factor for DPN. To investigate the effects of hypertension on DPN, we analyzed morphological features of peripheral nerves in diabetic rats with hypertension. Male WBN/Kob rats were divided into 2 groups: alloxan-induced diabetic rats with deoxycorticosterone acetate-salt (DOCA-salt) treatment (ADN group) and nondiabetic rats with DOCA-salt treatment (DN group). Sciatic, tibial (motor) and sural (sensory) nerves were subjected to qualitative and quantitative histomorphological analysis. Systolic blood pressure in the two groups exhibited a higher value (>140 mmHg), but there was no significant difference between the two groups. Endoneurial blood vessels in both groups presented endothelial hypertrophy and narrowing of the vascular lumen. Electron microscopically, duplication of basal lamina surrounding the endothelium and pericyte of the endoneurial vessels was observed, and this lesion appeared to be more frequent and severe in the ADN group than the DN group. Many nerve fibers of the ADN and DN groups showed an almost normal appearance, whereas morphometrical analysis of the tibial nerve showed a significant shift to smaller fiber and myelin sizes in the ADN group compared with DN group. In sural nerve, the fiber and axon-size significantly shifted to a smaller size in ADN group compared with the DN group. These results suggest that combined diabetes and hypertension could induce mild peripheral nerve lesions with vascular changes.     

Differences in adrenal morphology in male Dark Agouti, Sprague-Dawley and Wistar rats.

There is little published information describing the differences in adrenal structure between strains of a single species despite quite well known functional differences. In this paper we report morphological differences in the adrenal glands between three strains of laboratory rat; Dark Agouti (DA), Sprague-Dawley (SD) and Wistar (W). Significant differences in adrenal weights (as a percentage of body weight) were not detected between any of the groups. While there were no significant differences in the volume of medullary or zonae glomerulosa or fasciculata tissue, the volume fraction for the zona reticularis was significantly smaller in DAs compared to the other strains. The functional significance of these differences is unknown. However, it is suggested that the reduced volume of zona reticularis tissue may contribute to a reduced capacity for glucocorticoid synthesis or storage.     

Suppression of ovarian oxytocin secretion after intra-luteal administration of the arachidonate 5-lipoxygenase inhibitor BWA4C in the ewe

The effect of an intra-luteal injection of the 5-lipoxygenase (5-LO) inhibitor BWA4C (2 mg in 50 μ1 dmso) on the secretion of oxytocin (OT) from the corpus luteum in response to a close-arterial infusion of prostaglandin (PG)-F_2α (5 ng mint) was examined in anaesthetised sheep. Within 30 minutes of administration both basal (pre-infusion) and PGF_2α stimulated OT release into the posterior vena cava were significantly (P<0·01) reduced. These results are consistent with the proposition that 5-LO products of arachidonic acid may modulate OT secretion from the ovine corpus luteum.     

Effect of the 5-lipoxygenase inhibitor, fenleuton, on antigen-induced neutrophil accumulation and lung function changes in horses with chronic obstructive pulmonary disease

The leukotrienes (LT) LTD₄ and LTB₄ have been shown to cause bronchoconstriction and neutrophil accumulation, respectively, in horse lungs. Such changes are characteristic of the equine allergic respiratory disease, chronic obstructive pulmonary disease (COPD). To further investigate the role of these putative mediators in the pathogenesis of equine COPD the effect of a 5-lipoxygenase inhibitor, fenleuton, on antigen-induced changes in horses with this condition has been examined. Six horses with COPD underwent a series of four antigen challenges, one month apart, with placebo pre-treatment on three occasions and fenleuton (4 days oral dosing 5 mg/kg) pre-treatment on one occasion. Three horses received fenleuton prior to the second challenge and three horses received the drug prior to the fourth antigen challenge. Changes in radiolabelled neutrophil distribution, lung function and peripheral leucocyte counts were monitored on each occasion for 7 h following the start of antigen challenge. Antigen challenge caused an increase in radioactive counts over the lungs and a decrease in peripheral leucocyte count. Neither response was affected by fenleuton pre-treatment. Mean maximal changes in pleural pressure (ΔP_plmax) and respiratory rate were also unaffected by fenleuton pre-treatment. However, in the two horses which responded to antigen-challenge with a particularly marked increase in ΔP_plmax (>15 cm H₂O), prior administration of fenleuton reduced the response by 64 and 63%. These results suggest that 5-lipoxygenase inhibitors warrant further investigation as bronchodilators in equine COPD.     

Doublecortin-immunoreactive neuronal precursors in the dentate gyrus of spontaneously hypertensive rats at various age stages: comparison with Sprague-Dawley rats

Spontaneously hypertensive rats (SHRs) are widely accepted in medical research because this model has been used for studies in neurodegenerative diseases such as vascular dementia and stroke. In the present study, we observed newly generated neuronal precursors using doublecortin (DCX, a marker of neural proliferation and differentiation) in the subgranular zone of the dentate gyrus in SHRs compared to Sprague-Dawley rats (SDRs) at various age stages. DCX immunoreactivity, immunoreactive cell numbers and its protein level in the dentate gyrus of the SHRs were higher than those in the SDRs at postnatal month 1 (PM 1). At PM 8, DCX immunoreactivity, immunoreactive cell numbers and protein levels in both groups were markedly decreased compared to those at PM 1; however, they were higher than those in the SDRs. They were decreased in the both groups with age: DCX immunoreactive cells in the SDRs were few at PM 12. Our results indicate that newly generated neuronal precursors are more abundant in SHRs than in SDRs during their life.     

Effects of vertically transferred 3,3',4,4',5-pentachlorobiphenyl on gene expression in the ovaries of immature Sprague-Dawley rats

We have previously shown that 3,3',4,4',5-pentachlorobiphenyl (PCB-126) vertically transferred from dams potentially exerts a direct effect on the ovaries of offspring and adversely affects female puberty. To investigate its toxicological targets in ovarian tissues, mRNAs encoding representative peptides that regulate follicular development in granulosa cells, theca cells, and oocytes were quantified using ovaries collected on postnatal days (PND) 5, 15, and 24 from the offspring of dams administered oral doses of 0, 1 or 3 microg/kg PCB-126 starting 2 weeks prior to mating and continuing until 20 days after delivery. Quantification using the real-time RT-PCR method revealed that PCB-126 lowered the amounts of mRNAs that encoded the inhibin alpha- and inhibin/activin beta A-subunits from PND 15 onwards; the amounts of mRNAs for inhibin/activin beta B-subunit, follicle-stimulating hormone (FSH) receptor, and aromatase on PND 15; and the amounts of luteinizing hormone receptor mRNA on PND 24 compared with those of the age-matched controls. In contrast, no differences were noted for mRNAs encoding c-kit, growth differentiation factor-9, bone morphogenetic protein-15, or kit ligand for any of the age groups examined. The serum FSH level on PND 24 was higher than that in the control. Since the earliest effects on the mRNAs in the rat ovaries were observed in those expressed in the granulosa cells of the growing follicles after the antral follicles had developed, molecules in granulosa cells but not in oocytes during the early stages of the antral follicles might be the primary targets of vertically transferred PCB-126.     

Cytomorphologic differentiation of benign and malignant mammary tumors in fine needle aspirate specimens from irradiated female Sprague-Dawley rats.

BACKGROUND: Fine needle aspiration (FNA) offers a rapid and minimally invasive means to distinguish malignant from benign neoplasms. However, few studies have been published regarding the cytopathology of mammary tumors in rats despite widespread use of the rat model for breast cancer formation and inhibition. OBJECTIVE: The purpose of this study was to determine the diagnostic accuracy of FNA cytology and to develop distinguishing cytologic criteria for the diagnosis of radiation-induced benign and malignant mammary tumors in rats. METHODS: In a study of radiation-induced mammary carcinogenesis, 100 Sprague-Dawley rats with cutaneous masses were randomly chosen for FNA. The aspirates were smeared, fixed, and stained with a modified Papanicolaou procedure for diagnostic evaluation. Cytologic and histologic diagnoses (benign vs malignant) were compared, and diagnostic accuracy was calculated using the histologic diagnosis as the criterion standard. FNA smears were scored semiquantitatively on a scale of 1-4 for cellularity, atypia, nuclear size, chromatin pattern, nuclear membrane thickness, nucleoli, and mitoses. The background was evaluated for necrosis, hemorrhage, inflammation, and mucosecretory material. Cytomorphologic features were compared statistically between benign and malignant tumors, based on the histologic diagnosis. RESULTS: The sensitivity of FNA was 92.3% and specificity was 89.4% for the detection of malignancy. However, 14% of specimens, all fibroadenomas by histology, had insufficient cells for cytologic evaluation, for an overall accuracy rate of 78.0%. Malignant tumors had significantly higher scores for all cytomorphologic features, and were significantly more likely to contain cell clusters and necrotic debris. CONCLUSIONS: FNA is an accurate method for differentiating benign and malignant rat mammary tumors.     

Single-injection method for evaluation of renal function with 3H-inulin and 14C-tetraethylammonium bromide in conscious unrestrained Sprague-Dawley rats

A single-injection, double-isotope method for simultaneously determining glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) in conscious, unrestrained rats was evaluated. 3H-inulin and 14C-tetraethylammonium bromide were used to determine GFR and ERPF, respectively. Using a modified, single exponential, 1-compartment, mathematical model, solute clearance was estimated, using a plasma radioactivity disappearance curve constructed from samples collected during a 60-minute period. In 12 healthy, conscious, adult male Sprague-Dawley rats, the mean (+/- SEM) GFR, ERPF, and filtration fraction were 5.65 +/- 0.40 ml/min/kg, 13.92 +/- 0.82 ml/min/kg, and 0.41 +/- 0.03, respectively. In 7 adult male Sprague-Dawley rats that had undergone a three-quarter nephrectomy 6 weeks prior to study, the mean GFR, ERPF, and filtration fraction were 2.69 +/- 0.36 ml/min/kg, 7.02 +/- 0.90 ml/min/kg, and 0.39 +/- 0.03, respectively. In 37 adult male rats in various stages of renal disease, the mean GFR and ERPF correlated significantly (r = 0.85, P less than 0.001 and r = 0.83, P less than 0.001, respectively) with the reciprocal of plasma creatinine. The single-injection, double-isotope technique yielded functional values similar to those reported for healthy rats in which other clearance methods were used. Using this technique, we were able to detect alterations associated with various degrees of renal functional loss. The technique enabled us to evaluate conscious, unrestrained rats, eliminated the need to collect urine, and required short blood collection times (60 min) and small volumes (0.1 ml) of plasma.     

Excess rumen product anions in cattle. II. Toxic and lethal effects with butyrate.

Toxicity to butyrate was observed in 100-250 kg male Holstein calves following intravenous injection of 0.7-3.6 mmole/kg body weight, intravenous infusion with 0.12-0.53 mmole/min/kg body weight and intraruminal dosage with 19.4 mmole/kg body weight butyrate. Lower doses produced ataxia and serous nasal discharge. Higher doses produced sudden flaccid paralysis and death from asphyxia. No postmortem lesions, gross or histological, were observed. Plasma K+ was reduced to 2.2-2.5 mEq/L. When infusions were stopped, rapid recovery preceded clearance of butyrate and low K+ remained. Nerve depolarization in the central nervous system may be the cause of the toxic effects. Butyrate acidosis is suggested as a factor in unexplained sudden deaths in ruminants.     

In vitro inhibition of 5-lipoxygenase metabolite, leukotriene B4, in bovine mononuclear cells by bovine viral diarrhea virus.

Bovine viral diarrhea (BVD) virus inhibited phytohemagglutinin (PHA)-, PHA plus phorbol-12-myristate-13 acetate (PMA)- or PHA plus calcium ionophore (A23187)-stimulated bovine peripheral blood mononuclear cell (PBMC) proliferation. Further, BVD-virus inhibited A23187-stimulated leukotriene B4 (LTB4) synthesis into the culture supernatants. Presence of exogenous LTB4 failed to reverse the BVD virus-induced immunosuppression. Our results suggest that BVD virus-induced immunosuppression is due to a factor that may be necessary to induce LTB4 synthesis for normal mononuclear cell proliferation.     

Erythrocyte dysplasia in peripheral blood smears from 5 thrombocytopenic dogs treated with vincristine sulfate

Secondary dyserythropoiesis has been associated with vincristine administration in dogs. Evaluation of bone marrow aspirates for the presence of morphologic abnormalities in the erythroid lineage aids in the diagnosis. However, morphologic features of circulating erythroid precursors in these cases have not been described previously. The purpose of this report was to describe the cytologic features of dyserythropoiesis in peripheral blood and also bone marrow smears in a case series of dogs with immune‐mediated thrombocytopenia (IMT) treated with vincristine sulfate. Nineteen dogs receiving vincristine for treatment of IMT were identified by retrospectively searching a computerized medical record system. There were 5 dogs that had dysplastic erythroid precursors in peripheral blood smears within 7 days of vincristine treatment. Two of those 5 dogs also had evidence for erythrodysplasia in modified Wright's‐stained bone marrow smears obtained postvincristine administration. Morphologic changes included bizarre or inappropriate mitotic figures, abnormal nuclear configurations (fragmentation, elongation, indentation, and binucleation), atypical nuclear remnants (Howell‐Jolly bodies), or nuclear and cytoplasmic asynchrony within the erythroid precursors. A brief review of the literature with discussion of the etiologies for dyserythropoiesis is provided. The dyserythropoiesis was clinically insignificant in all 5 cases and resolved. However, pathologists and clinicians should be aware of these potential findings to prevent misdiagnosis of other conditions.     

Toxic hepatopathy in sheep associated with the ingestion of the legume Tephrosia cinerea.

A disease known as water belly (barriga d'água), characterized by chronic progressive ascites, affects sheep in the semiarid region of northeastern Brazil. The objectives of this investigation were to study the disease and to determine its cause. Only sheep grazing for long periods in pastures where Tephrosia cinerea represents 80% to 100% of the available forage are affected. Most animals die after a clinical manifestation period of some weeks or months, but others recover when they are withdrawn from the pastures or after the first rains. At necropsy, large amounts of liquid were found in the abdominal cavity, and the liver was hard, with an irregular surface. On histology examination, the main liver lesion was chronic periportal and subcapsular fibrosis with bridging. The disease was produced experimentally in 1 sheep by the administration of large amounts of T. cinerea for 232 days. Another sheep, recovered from the spontaneous disease, had clinical signs after the ingestion of large amounts of the plant for 40 days. Seeds and leaves of the plant were examined by gas chromatography-mass spectrometry for the presence of pyrrolizidine alkaloids with negative results. It is concluded that the disease is caused by the ingestion of T. cinerea.