A morphological and stereological study on brain,cerebral hemispheres and cerebellum of New Zealand rabbits

The aim of this research was to determine brain, cerebral hemispheres and cerebellum volume and volume ratios by using stereological methods and investigate morphological differences between female and male New Zealand rabbits. The study was applied on 14-month old (10 male and 10 female) New Zealand rabbits. The materials removed from the cavum cranii using dorsal approach. After following routine histological procedure, paraffin blocks were prepared and cut every seventieth section at 10 μm thickness. Slides were stained with Crossmon's triple stain and photographed. The sectional images obtained were transferred to ImageJ program to estimate grey and white matter volume on cerebral hemispheres and cerebellum with principle of Cavalieri. According to results, there was no asymmetry on the left and right cerebral hemispheres of New Zealand rabbits. In the total hemisphere volume calculated by Cavalieri principle, grey and white matter ratio was 81.57% and 18.43% in female, 82.80% and 17.20% in male. It was found that the white matter was significantly higher in females than males in cerebral hemispheres (p < .05). Also, it was found that grey and white matter ratio in total cerebellum volume was 67.82% and 32.18% in female, 67.94% and 32.06% in male respectively. It was determined that the females' white matter was larger than male rabbits in cerebellum (p < .05). It is thought that morphometric data obtained from this study will contribute to the existing anatomical knowledge and also considered as reference values in the clinical sciences.     

Morphometric analysis of progressive changes in hereditary cerebellar cortical degenerative disease (abiotrophy) in rabbits caused by abnormal synaptogenesis

We previously investigated rabbit hereditary cerebellar cortical degenerative disease, called cerebellar cortical abiotrophy in the veterinary field, and determined that the pathogenesis of this disease is the result of failed synaptogenesis between parallel fibers and Purkinje cells. In this study, longitudinal changes in the development and atrophy of the cerebellum of rabbits with hereditary abiotrophy after birth were morphometrically examined (postnatal day [PD] 15 and 42) using image analysis. Although development of the cerebellum in rabbits with abiotrophy was observed from PD 15 to PD 42, the growth rate of the cerebellum was less than that in normal rabbits. In rabbits with abiotrophy, the number of granular cells undergoing apoptosis was significantly higher at PD 15 and dramatically decreased at PD 42. The number of granular cells did not increase from PD 15 to 42. The synaptogenesis peak at PD 15 occurred when the largest number of apoptotic granular cells in rabbits with abiotrophy was observed. Although 26% to 36% of parallel fiber terminals formed synaptic junctions with Purkinje cell spines, the remainder did not at PD 15 and 42. The rate of failure of synaptogenesis in the present study might be specific to this case of abiotrophy. Morphometric analysis revealed detailed changes in development and atrophy in animals with postnatal cerebellar disease occurring soon after birth.     

萱草根素对家兔中枢神经损害的病理学研究

本研究旨在对萱草根素中毒家兔中枢神经系统进行病理学研究。从北黄花菜根中提取萱草根素，用1％的淀粉溶液配制成2％混悬液，试验组家兔每只每天灌服萱草根素混悬液4mL／kg，对照组灌服等量的1％淀粉溶液。于处理后第4、7、10、13、16、19天进行常规病理学检查。试验第4天大脑、小脑、脊髓和视神经中的神经纤维出现脱髓鞘变化，在小脑从白质中央向两侧进行性扩展，在脊髓从边缘向中央扩展，最终呈丝瓜络样变；第7天起，蒲肯野氏细胞和脊髓神经细胞发生固缩、坏死；第10天，大脑神经细胞出现坏死、凋亡，并且数目逐渐增多，出现噬神经现象，视网膜萎缩，节细胞固缩、溶解消失。超微结构观察显示，髓鞘变薄，板层崩解、断裂、分离，失去原来的致密结构；神经细胞染色体边集，线粒体肿胀、消失并空泡化、粗面内质网扩张，结构模糊。结果表明，萱草根素可引起神经纤维脱髓鞘和神经细胞的广泛性坏死，并最终导致家兔失明和死亡。     

Cerebellar granuloprival degeneration in an Italian hound

A severe atrophy of the cerebellum was observed in a 7-month-old male Italian hound with a history of progressive ataxia and head tremor from the age of 3 months. On clinical examination, signs included severe hypermetric gait, head tremors and proprioception deficits in all limbs. At necropsy, a pronounced symmetrical reduction in size of the cerebellum was the only gross lesion observed. Histological examination of the cerebellum revealed marked thinning of the granular and molecular layers with almost complete loss of granule cells. Purkinje cells had normal morphology and distribution. These findings differ from those of previous reports of cerebellar cortical abiotrophy in dogs, which were mainly characterized by prominent Purkinje cell degeneration and loss.     

Acetylcholinesterase activity in specific regions of rabbit brain: Effect of pentobarbitone anesthesia

Acetylcholinesterase activity was determined in the cerebral cortex, cerebellum, hypothalamus, midbrain and medulla oblongata of a) control mature male rabbits, and b) male rabbits injected i.p. with an anesthetic dose of sodium pentobarbitone (60 mg/kg b.w.). Enzyme activity was highest in the midbrain and lowest in the cerebral cortex in controls. Pentobarbitone anesthesia increased enzyme activity in the cerebral cortex. No significant change in acetylcholinesterase activity occurred in the other brain areas studied following pentobarbitone administration. These findings are compared with the results of previous studies in the rat.     

兔轮状病毒病的诊治

某肉兔养殖场幼兔发生了一起以水样腹泻为主要特征的疫病,通过对病死兔的临床症状和病理剖检观察、RT-PCR检测、动物回归试验等确诊为该兔场发生了兔轮状病毒的感染,通过采取一系列治疗措施,疫情得到了控制。     

Cutaneous Lymphomas in European Pet Rabbits (Oryctolagus cuniculus)

Cutaneous lymphoma is a common skin neoplasm of pet rabbits in Europe but is rarely reported in pet rabbits in North America. These neoplasms have not been previously characterized, nor has the cause for the apparent predilection for cutaneous lymphoma in European pet rabbits compared with North American pet rabbits been investigated. In this retrospective study, the authors morphologically and immunohistochemically characterized 25 cutaneous lymphomas in European pet rabbits according to the World Health Organization classification. Tumors were classified as diffuse large B cell lymphomas, with 14 lymphomas exhibiting a centroblastic/centrocytic subtype and 11 tumors exhibiting a T cell-rich B cell subtype. To investigate a potential viral etiology of these lymphomas, 3 diffuse large B cell and 3?T cell-rich B cell lymphomas were evaluated by polymerase chain reaction for retroviral and herpesviral genes. Neither virus was detected. In contrast to other domestic animals, cutaneous lymphomas in European pet rabbits were highly pleomorphic and frequently contained multinucleated giant cells. Unexpectedly, the second most common subtype was T cell-rich B cell lymphoma, a subtype that is rare in species other than horses. Based on a limited number of samples, there was no support for a viral etiology that would explain the higher incidence of lymphoma in European pet rabbits compared with American pet rabbits. Further investigation into genetic and extrinsic factors associated with the development of these tumors is warranted.     

Atrophic rhinitis in New Zealand white rabbits infected with Pasteurella multocida

Atrophic rhinitis was detected in New Zealand White rabbits when upper respiratory tract disease was evaluated during a vaccine field trial for the prevention of pasteurellosis. Of 52 adult rabbits euthanatized and necropsied, 26 (50%) had evidence of turbinate atrophy. Atrophy was detected in 77% of rabbits with Pasteurella multocida infection only, 71% of rabbits with concurrent P multocida and Bordetella bronchiseptica infections, and 6% of rabbits with B bronchiseptica infection only. Grossly, turbinate atrophy was characterized by a mild to severe loss or diminution in the maxilloturbinates. Histologically, turbinate bones were small and irregular in thickness and had numerous osteoclasts and osteoblasts. A neutrophilic exudate filled the nasal passages, and infiltrates of neutrophils and lymphocytes were detected in the mucosa and submucosa of the nasal turbinates. Rhinitis was significantly (P less than 0.001) associated with turbinate atrophy. Isolates of P multocida from rabbits with turbinate atrophy were serotype A:12.     

Anencephaly in calves

Anencephaly occurred in four calves and was characterized by cranioschisis, absence of the diencephalon with the cerebral hemispheres and rostral midbrain, various forms of eye defects, and relatively normal development of caudal brain stem, cerebellum and spinal cord. Amorphous dysplastic vestiges of the cerebral tissue protruded into the cranial defects. Morphologic features varied but were essentially similar. The cerebellum was absent in one case. Anencephaly in calves at least those we observed and defined in this study is localized defect confined to the brain, eye and skull. No spinal defect was observed in the calves.     

Pathology of listerial encephalitis in chickens in Japan

Neural signs (torticollis, drowsiness) and mortality were observed in five chickens of a native chicken flock (reared for meat) that included 450 male birds on a farm that had 2300 native chickens and 1120 layers. Histologic lesions were observed in the medulla oblongata, optic lobe, cerebellum, and spinal cord of the affected birds. The lesions, which were most severe in the medulla oblongata, were massive abscesses with rarefaction (demyelination and malacia) of the parenchyma with gram-positive bacteria. The degenerative and necrotic areas were characterized by fibrin thrombosis, hemorrhages, and congestion in the blood vessels. Immunohistochemically, the bacteria positive for L. monocytogenes antigen were observed in the medulla oblongata, cerebellum, and spinal cord. Ultrastructurally, the small rod-shaped and thin-cell-walled bacteria were observed in the parenchyma of the medulla oblongata. Listeria monocytogenes (serotype 4b) was isolated from the medulla oblongata and spinal cord. The pathogenesis of listerial encephalitis in chickens was discussed.     

Fatal toxoplasmosis in domestic rabbits in the USA.

Three rabbits from two sources died after an acute illness characterized by fever, lethargy and diarrhea in one rabbit and no clinical signs in two rabbits. The most striking lesion in all three rabbits was foci of necrosis of the spleen and liver associated with massive presence of multiplying Toxoplasma gondii tachyzoites. The diagnosis was confirmed by specific staining with anti-T. gondii serum in an avidin-biotin complex immunohistochemical stain.     

The morphology and location of atrial specific granules and the demonstration of atrial natriuretic factor in porcine,lapine and bovine heart by immunoelectronmicroscopy

The atrial specific granules (ASGs) were studied in samples collected from the right and left auricles of conventionally slaughtered cows (10), pigs (16) and rabbits (8). In addition, the presence of atrial natriuretic factor (ANF) was detected by immunocytochemistry. Mature ASGs, characterized by the presence of highly osmiophilic and electron-dense material surrounded by a membrane, were present in all atrial myoendocrine cells and their diameters ranged from 100 to 470 nm in pigs, from 100 to 235 nm in cattle, and from 125 to 275 nm in rabbits. Immunoelectronmicroscopical studies revealed the presence of ANF in the ASGs of pigs and cattle, whereas anti-ANF polyclonal serum failed to detect any significative reaction in lapine ASGs. The ultrastructural features of the ASGs of pigs, cattle and rabbits described may be useful in comparing the morphological picture of several cardiac endocrine pathological conditions.     

Vaccinia viruses isolated from skin infection in horses produced cutaneous and systemic disease in experimentally infected rabbits

The susceptibility of rabbits to two isolates of Vaccinia virus (VACV) recovered from cutaneous disease in horses in Southern Brazil was investigated. Rabbits were inoculated in the ear skin with both VACV isolates, either in single or mixed infection. All inoculated animals presented local skin lesions characterized by hyperaemia, papules, vesicles, pustules and ulcers. Infectious virus was detected in the lungs and intestine of rabbits that died during acute disease. Histological examination of the skin revealed changes characteristic of those associated with members of the genus Orthopoxvirus. These results demonstrate that rabbits develop skin disease accompanied by systemic signs upon intradermal inoculation of these two equine VACV isolates, either alone or in combination, opening the way for using rabbits to study selected aspects of the biology and pathogenesis of VACV infection.     

Latent infection by bovine herpesvirus type-5 in experimentally infected rabbits: virus reactivation, shedding and recrudescence of neurological disease.

Latent infection with bovine herpesvirus type-5 (BHV-5) was established in rabbits inoculated with two South American isolates (EVI-88 and 613) by intranasal or conjunctival routes. Nine rabbits (613, 8/27; EVI-88, 1/34) developed neurological disease and died during acute infection and other three (613, n=2; EVI-88, n=1) developed a delayed neurological disease, at days 34, 41 and 56 post-inoculation (p.i.). Between days 56 and 62 p.i., the remaining rabbits were submitted to five daily administrations of dexamethasone (Dx) to reactivate the infection. Twenty-five out of 44 rabbits (56.8%) shed virus in nasal or ocular secretions after Dx treatment. Virus shedding was first detected at day two post-Dx and lasted from one to 11 days. The highest frequencies of virus reactivation were observed in rabbits inoculated conjunctivally (10/15 versus 15/29); and among rabbits infected with isolate 613 (12/16 versus 13/28). Virus reactivation upon Dx treatment was accompanied by neurological disease in nine rabbits (20.4%), resulting in six deaths (13.6%). Virus in moderate titers and mild to moderate non-suppurative inflammatory changes in the brain characterized the neurological infection. Three other rabbits showed severe neurological signs followed by death after 31 to 54 days of Dx treatment. Virus, viral nucleic acids and inflammatory changes were detected in their brains. The late-onset neurological disease, after acute infection or Dx treatment, was probably a consequence of spontaneous virus reactivation. These results demonstrate that BHV-5 does establish a latent infection in rabbits and that clinical recrudescence may occur upon reactivation.     

Anterior corneal dystrophy of American Dutch belted rabbits: biomicroscopic and histopathologic findings

Spontaneously occurring anterior corneal opacities were present in related, juvenile American Dutch belted rabbits. Slit lamp biomicroscopy revealed focal opacities of epithelium, basement membrane, and subepithelial corneal stroma. Lesions were characterized histologically by thin and disorganized surface epithelium, thickened and intensely staining epithelial basement membrane, fimbriated and irregular basement membrane-stromal juncture, and disorganized subepithelial stroma. Biomicroscopic and histopathologic features of anterior corneal dystrophy of American Dutch belted rabbits appear similar to those of human anterior corneal dystrophies.     

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.     

Molecular detection and genotype identification of E. cuniculi from pet rabbits

Encephalitozoon cuniculi is a microsporidian which is frequently reported from rabbits. This microorganism can either ravage rabbit farms or transmit to humans from pet rabbits. This study aimed to investigate the prevalence and the genotype distribution of E. cuniculi among pet rabbits. In this study urine samples were collected from 50 pet rabbits, aged 2 months to 3 years, admitted to teaching veterinary hospital. Four races Lop, Dutch, Mix, and Angora were screened for E. cuniculi. The clinical symptoms were recorded and total DNA was extracted from urine samples. E. cuniculi was identified using amplification of the small subunit ribosomal RNA (ssu rRNA) gene and its genotypes were characterized using PCR/sequencing of the polar tube protein (PTP) gene. Phylogenetic tree was drawn to confirm the characterized genotypes. Out of 50 samples, 41 (82 %) of rabbits were asymptomatic, while nine (18 %) had at least one of symptoms including head-tilt, circling, and ataxia. A statistical correlation was seen between mean age + SD and symptoms (P-value = 0.039). The presence of E. cuniculi was confirmed in 16/50 (32 %) rabbits and all of them were identified as the genotype I. Our findings represented no consistency between E. cuniculi PCR – positive and the presence of symptoms (P-value = 0.318). Our results showed positive correlation between symptoms and age; however, the lack of correlation between PCR results with age may signify the latent infection in younger rabbits. All identified E. cuniculi were the genotype I, which is reported from rabbits and humans, highlighting the zoonotic concern for this genotype, particularly among subjects who keep pet rabbits.     

Chronic plumbism in rabbits: a comparison of three diagnostic tests.

Three groups of rabbits (A, B, and C; 6 rabbits/group) were fed a lead supplement of 25, 50, and 100 mg of Pb/kg of live weight/day for 87 days to compare the efficacies of 3 diagnostic tests--whole blood lead concentration, urinary delta-aminolevulinic acid (UALA), and fluorescent erythrocyte test (FET)--and to determine the clinicopathologic changes of experimentally induced lead poisoning in rabbits. All rabbits given lead had whole-blood lead concentrations greater then the maximum value (0.030 mg/dl) for control rabbits (group D), indicating that this measurement is a reliable indicator of lead ingestion. All group A rabbits (fed 25 mg of Pb/kg) and 66% negative UALA test results, with values less than the maximum value (0.12 mg/dl) for group D (control) rabbits. Only group C rabbits (fed 100 mg of Pb/kg) had consistently positive UALA FINDINGS. The test was therefore considered unreliable for detecting daily lead intakes less than 100 mg/kg of live weight of rabbits. All rabbits given lead had erythrocytes which fluoresced red when exposed to light rays with wavelenghts from 320 to 400 nm; fluorescence was not observed in erythrocytes of control rabbits. The FET appears to be a convenient and reliable diagnostic test for lead ingestion. In groups B and C, clinical signs of lead poisoning were mild, nonpersistent anemia characterized by the presence of poikilocytes, hupochromic erythrocytes, target cells, erythroblasts, erythrocytes with punctate basophilic stippling, reduced mean corpuscular hemoglobin concentrations, and relative lymphocytosis, neutropenia, and eosinopenia. One rabbit from the group fed the largest dose displayed partial anorexia.     

Experimental infection of eastern cottontail rabbits Sylvilagus floridanus) with infectious bovine rhinotracheitis virus.

Experimental infection of eastern cottontail rabbits (Sylvilagus floridanus) with infectious bovine rhinotracheitis virus caused acute keratoconjunctivitis and a fatal systemic infection. The clinical syndrome was characterized initially by blepharospasm and ocular discharge. The rabbits were markedly depressed on post-exposure day (PED) 5 and were dead or moribund on PED 6. The virus was readily recovered from liver and adrenal gland tissue on PED 6 and from conjunctival swabs on PED 1 to 6. Histopathologic studies revealed a few necrotic foci in the liver and multiple focal to diffuse necrosis of the adrenal glands. Viral isolation and immunofluorescence tests were used to demonstrate a direct association between infectious bovine rhinotracheitis viral antigens and the lesions.     

猪伪狂犬病病毒的分离鉴定及免疫原性初步研究

采集浙江某猪场疑似猪伪狂犬病发病仔猪的脑、脾脏等组织病料,经PCR检测为猪伪狂犬病病毒(pseudorabies virus,PRV)野毒感染,用BHK-21细胞进行病毒的分离培养,结果显示该病毒能引起典型的细胞病变,第4代病毒液毒价达10^7.0 TCID_50/mL;PCR和动物回归试验结果表明该分离株为PRV,并将其命名为PRV ZJ株。将第4代病毒液制备成油乳剂灭活苗,免疫2 kg左右家兔,免疫后28 d采血并攻毒,测定其免疫原性,结果显示血清中和指数为13490,保护率为100%。本试验结果表明PRV ZJ株有很好的免疫原性,为进一步开展疫苗研究奠定基础。