Anatomic location and age-related changes in the chinchilla thymus

Thymuses of chinchillas varying from 2 weeks to 8 years of age were studied grossly and histologically and were determined to be entirely intrathoracic. Histologically, the amount of actual thymic tissue in the older chinchillas appeared to be less than that in the younger chinchillas. Lymphocyte concentration within medullary centers of the older chinchillas was significantly (P less than 0.05) less than that of the younger animals. Lymphocytopoietic activity was evident in the oldest animals studied. Body weight and thymic mass (thymus plus adipose tissue) weight were greater (P less than 0.05) in the older chinchillas.     

Congenital lipoblastoma in a neonate calf: first report in veterinary literature

Lipoblastoma is a rare benign tumour of adipose tissue that usually occurs in young children. Although around 100 cases of lipoblastoma have been reported in humans, no report has been previously described in animals. This case report describes the clinical and histopathological findings of a congenital lipoblastoma located at the tail base of a 2-day-old male calf. Grossly, the mass was pink with a partly ulcerated and haemorrhagic surface. The calf showed no neurological deficits. Radiographs of the vertebral column revealed no abnormalities, and surgical excision was performed. Histopathology of the mass was consistent with lipoblastoma. The calf was followed up for 13 months and found to be healthy with no signs of recurrence. To the best of the authors' knowledge, this is the first case of lipoblastoma in the veterinary literature. Lipoblastoma should thus be considered in the differential diagnosis list for congenital adipose tissue tumours in animals.     

Thymic hyperplasia causing right ventricular outflow tract compression following treatment for oesophageal rupture in an Arabian colt

True thymic hyperplasia has been reported sporadically in the human literature as an immunological rebound phenomenon following immunosuppressive treatment or disease. There are limited accounts in domestic species, mainly following vaccination, and thymic hyperplasia has not been a recognised condition in the horse to date. This report details a case of true thymic hyperplasia in a 10-week-old Arabian colt diagnosed by histopathology of core biopsy samples. The colt developed pulmonary stenosis caused by compression due to a space occupying lesion in the cranial mediastinum following a 3-month history of hospitalisation for treatment of traumatic oesophageal rupture with perioesophageal abscess formation. Diagnostic imaging of the cranial mediastinum was indicative of a thymic mass, and histopathology confirmed the mass was normal (hyperplastic) thymic tissue. The colt was treated with a tapering dose of corticosteroids, which led to involution of the hyperplastic tissue and resolution of pulmonary artery compression. Thymic hyperplasia may be an unrecognised sequela to chronic inflammation in horses and was only identified in this case when the size was sufficient to compress right cardiac outflow.     

Pathology of congenital generalized lipodystrophy in Agpat2-/- mice

Congenital generalized lipodystrophy (CGL) comprises a heterogeneous group of rare diseases associated with partial or total loss of adipose tissue. Of these, autosomal recessive Berardinelli-Seip congenital lipodystrophy (BSCL) is characterized by the absence of metabolically active subcutaneous and visceral adipose tissues. Metabolic abnormalities associated with lipodystrophy include insulin resistance, hypertriglyceridemia, hepatic steatosis, and diabetes. One form of BSCL has been linked to genetic mutations affecting the lipid biosynthetic enzyme 1-acyl-sn-glycerol 3-phosphate O-acyltransferase 2 (AGPAT2), which is highly expressed in adipose tissue. Precisely how AGPAT2 deficiency causes lipodystrophy remains unresolved, but possible mechanisms include impaired lipogenesis (triglyceride synthesis and storage), blocked adipogenesis (differentiation of preadipocytes to adipocytes), or apoptosis/necrosis of adipocytes. Agpat2(-/-) mice share important pathophysiologic features of CGL previously reported in humans. However, the small white adipose tissue (WAT) depots consisting largely of amoeboid adipocytes with microvesiculated basophilic cytoplasm showed that adipogenesis with deficient lipogenesis was present in all usual locations. Although well-defined lobules of brown adipose tissue (BAT) were present, massive necrosis resulted in early ablation of BAT. Although necrotic or apoptotic adipocytes were not detected in WAT of 10-day-old Agpat2(-/-), the absence of adipocytes in aged mice indicates that these cells must undergo necrosis/apoptosis at some point. Another significant finding in aged lipodystrophic mice was massive pancreatic islet hypertrophy in the face of chronic hyperglycemia, which suggests that glucotoxicity is insufficient by itself to cause β-cell loss and that adipocyte-derived factors help regulate total β-cell mass.     

Orosomucoid expression profiles in liver,adipose tissues and serum of lean and obese domestic pigs,Göttingen minipigs and Ossabaw minipigs

The acute phase protein orosomucoid (ORM) has anti-inflammatory and immunomodulatory effects, and may play an important role in the maintenance of metabolic homeostasis in obesity-induced low-grade inflammation. Even though the pig is a widely used model for obesity related metabolic symptoms, the expression of ORM has not yet been characterized in such pig models. The objective of this study was to investigate the expression of ORM1 mRNA in liver, visceral adipose tissue, subcutaneous adipose tissue (SAT) from the abdomen or retroperitoneal abdominal adipose tissue (RPAT) and SAT from the neck, as well as the serum concentration of ORM protein in three porcine obesity models; the domestic pig, Göttingen minipigs and Ossabaw minipigs.No changes in ORM1 mRNA expression were observed in obese pigs compared to lean pigs in the four types of tissues. However, obese Ossabaw minipigs, but none of the other breeds, showed significantly elevated ORM serum concentrations compared to their lean counterparts. Studies in humans have shown that the expression of ORM was unchanged in adipose tissue depots in obese humans with an increased serum concentration of ORM. Thus in this respect, obese Ossabaw minipigs behave more similarly to obese humans than the other two pig breeds investigated.     

Mixed Thymoma in a Young Cynomolgus Monkey (Macaca fascicularis)

A mass with a diameter of 1.5 cm was found in the thymus of a 4-year and 3-month-old male cynomolgus monkey. Microscopically, the mass consisted of two different patterns of proliferation, dense or fascicular proliferation of elongated spindle cells in a sporadic storiform pattern and dense proliferation of thymic cortex-like lymphoid cells in which the multifocal pale nests resembling the thymic medulla were distributed. In these pale nests, large dendriform cells sometimes forming Hassall's corpuscles were present. The proliferating spindle cells were positive for cytokeratin. The lymphoid cells in the mass were positive for CD3. We concluded that the mass consisted of the neoplastic thymic epithelium with thymocytes proliferation containing medullary differentiation. The mass was diagnosed as a mixed thymoma according to the WHO classification of thymomas in humans. Mixed thymoma is characterized as a mixture of two types of proliferative lesions, spindle-shaped epithelial proliferation and a lymphocyte predominant lesion with or without medullary differentiation. To the best of our knowledge, this is the first report concerning thymoma in monkeys.     

Changes in adipocyte size during post-embryonic growth in the female Aylesbury duck

Mean adipocyte size was determined in inguinal, subcutaneous and peritoneal adipose tissues during the first 8 weeks of postembryonic growth. Increases in adipocyte volume are compared with the overall increases in adipose tissue mass during the same period.     

Breed differences in macrophage infiltration and senescence state in adipose tissues of Wagyu and Holsteins

Obesity stimulates the macrophage infiltration and senescence state in adipose tissues of humans and rodents. The adipogenesis capacity of Japanese Black cattle (Wagyu) is higher than that of Holsteins. We hypothesized that breed differences between Wagyu and Holsteins may affect the level of macrophage infiltration and senescence state in adipose tissues. The macrophage infiltration, senescence marker gene expression and activity of senescence‐associated β‐galactosidase (SA‐βgal) in visceral and intramuscular adipose tissue of Wagyu were higher than those of Holsteins. In contrast, there were no differences in macrophage infiltration, senescence marker gene expression and activity of SA‐βgal in subcutaneous adipose tissue between the breeds. Expression of p53 gene, the master regulator of macrophage infiltration and senescence state, in visceral and intramuscular adipose tissue of Wagyu was higher than that of Holsteins. In contrast, there was no difference in the expression of p53 gene in subcutaneous adipose tissue between the breeds. These results suggest that breed differences in macrophage infiltration and senescence state in adipose tissues of Wagyu and Holsteins are affected by p53 expression.     

Signals of adiposity

Adipose tissue, a reserve of energy, has played an essential role in mammalian evolution. Adipose tissue differs from other tissues in that its mass has considerable capacity to expand, which while beneficial in decreasing the risk of starvation, increases the risk of predation. Adipose tissue mass is thus under tight control in nondomestic species. Adipose tissue secretes a variety of factors, some of which (leptin, tumor necrosis factor (TNF) , resistin) are thought to be involved in modulation of adipose mass. Leptin has a variety of functions, primarily targetting the hypothalamus where it acts to decrease appetite and increase energy expenditure. Leptin is also involved in the adaptations to fasting, and leptin is also required for normal reproductive and immune function. TNF and resistin appear to have key paracrine roles, attenuating the anabolic effects of insulin on adipose tissue metabolism.     

Recurrent bilateral exophthalmos associated with metastatic thymic carcinoma in a pet rabbit

A five-year-old, castrated, male chinchilla rabbit was presented for evaluation of recurrent bilateral exophthalmos. Besides a transient and stress-related exophthalmos with protrusion of both third eyelids, the ophthalmological examination was unremarkable. Plain radiography of the thorax revealed a large precardial mass of soft tissue density. Cytological preparations from the thoracic mass were dominated by small, mature lymphocytes with approximately 10 to 20 per cent lymphoblasts. Computed tomography of the head showed a symmetrical laterodorsal deviation of both eyes without evidence of retrobulbar masses. On necropsy a large cystic mass was present in the cranial thorax associated with severe hydrothorax, hydropericardium and ascites. Histology identified the precardial mass as thymic carcinoma with metastases in the kidneys. This case illustrates the difficulty of diagnosing thymic tumours based on cytological or histological features of the primary tumour alone. To the authors' knowledge, this is the first case of recurrent bilateral exophthalmos associated with a metastatic thymic carcinoma in a pet rabbit.     

The potential role of leptin and adiponectin in obesity: a comparative review

Leptin and adiponectin are adipokines produced by the white adipose tissue. The adipokines have been shown to be valuable quantitative markers of adiposity in dogs. Leptin positively correlates with body condition score (BCS) in dogs, regardless of age, sex and breed, and is influenced by feeding state, pharmacological treatment and thyroid gland activity. Conversely, adiponectin negatively correlates with body fat mass and is therefore more abundant in lean animals. The implication of leptin and adiponectin in the pathogenesis of metabolic syndrome is well established in humans, but currently lacking in dogs. Additional studies are necessary to demonstrate their potential usefulness for monitoring the progression of obesity-related diseases and response to treatment. To date, measurement of canine leptin and adiponectin has been used in experimental studies only, whereas bodyweight and BCS are considered the first-approach parameters for the routine assessment of body fat content in obese dogs.     

肿瘤坏死因子-α在脂肪组织中的作用

作为一种由脂肪细胞产生和分泌的多功能细胞因子,肿瘤胚死因子-α(TNF-α)除了在免疫系统中发挥作用外,其在脂肪组织中也具有重要的调控作用,如促进脂肪分解、抑制脂肪合成、抑制脂肪细胞分化、诱导脂肪细胞凋亡等。综合起来看,TNF-α可抑制动物的脂肪沉积。     

Atypical thymoma in a horse: Diagnostic approach and application of an alternative histological classification system

Thymoma is a rare condition in horses. This case of a 24-year-old Warmblood gelding that was presented with oedema and signs of vascular congestion of the left forelimb caused by a thoracic mass is described. The diagnostic work-up included blood chemistry, cytology of pleural effusion, ultrasonography, radiography and the visualisation and collection of a tissue sample by thoracoscopy. Finally, post-mortem findings and histopathology revealed thymic epithelial neoplasia with histomorphologic features previously unreported in horses. The unique mixture of spindle-shaped and epithelioid tumour cells in combination with clear features of malignancy suggested the application of the Moran and Suster histological classification system for thymomas in humans (Moran and Suster, 2008, Curr. Treat. Options Oncol., 9, 288), which has not been reported in an equine case before and fits well to the present case.     

Assessment of feline abdominal adipose tissue using computed tomography

Obesity is a common nutritional disorder in cats and it increases the risk factors for various diseases. The aim of this study is to suggest a method for the evaluation of feline obesity using computed tomography. The attenuation range from -156 to -106 was determined as the range of feline abdominal adipose tissue. With this range, total (TAT), visceral (VAT) and subcutaneous (SAT) adipose tissues were measured. The best correlation between the adipose tissue in cross-sectional image and entire abdomen volume was obtained at the L3 and L5 levels. The mean VAT/SAT ratio was 1.18±0.32, which was much higher than in humans. The cats with an overweight body condition had a significantly lower VAT/SAT ratio than cats with an ideal body condition. This technique may contribute to both the clinical diagnosis and the experimental study of feline obesity.     

Spontaneous adenolipoma of the mammary gland in the male F344 rat

A 110-week-old male F344 rat from the high-dose group of a 104-week carcinogenicity study, exhibited a spontaneously occurring subcutaneous mass in the left axilla extending to the chest. Histologically, the mass was well-demarcated from the adjacent mammary tissue and slightly encapsulated without evidence of infiltration into the surrounding tissues. The mass contained both epithelial and adipose components. The epithelial component consisted of ductal structures of various sizes lined by a single layer of flattened to cuboidal epithelial cells with relatively clear or vacuolated cytoplasm. These ductal structures were well-intermingled with an adipose component that consisted of a uniform monomorphic cell population of mature adipocytes. Both cell types were well-differentiated and did not exhibit cellular atypia. Within the mass, fibrous connective tissue was found in the stroma with infiltration of numerous mast cells. Based on these findings, the mass was diagnosed as an adenolipoma of the mammary gland.     

Cellularity of developing subcutaneous adipose tissue in Landrace and Meishan pigs: Adipocyte size differences between two breeds

Experiments were designed to compare the adipocyte cellularity of subcutaneous adipose tissue between growing Landrace (low backfat) and Meishan (high backfat) pigs at 1 week, 3 weeks, 6 weeks, 3 months and 5 months of age. As pigs aged, body weight and backfat thickness of both breeds significantly increased. When compared at equal ages, backfat thickness adjusted to equal body weight was greater for Meishan pigs. The mean diameter of fat cell size also increased with age, and by 6 weeks adipocytes from both outer and inner layers of subcutaneous adipose tissue were larger in Meishan pigs. At 5 months, approximately 80% of the adipose tissue mass in Meishan pigs was attributable to adipocytes measuring 95–165 µm in diameter, whereas adipocytes of 75–145 µm comprised most of the tissue mass in the Landrace. Although the contribution of smaller adipocytes (25–45 µm) to the tissue volume was negligible, both breeds showed a biphasic diameter distribution at all ages, suggesting that adipocyte hyperplasia is still active. Our results demonstrate that cellularity differences exist between the subcutaneous adipose tissues of Landrace and Meishan pigs, and adipocyte hypertrophy is the most overwhelming contributor to the greater backfat deposition for Meishan pigs.