Donald Yool

Oligodendroglial modulation of fast axonal transport in a mouse model of hereditary spastic paraplegia.

Oligodendrocytes are critical for the development of the plasma membrane and cytoskeleton of the axon. In this paper, we show that fast axonal transport is also dependent on the oligodendrocyte. Using a mouse model of hereditary spastic paraplegia type 2 due to a null mutation of the myelin Plp gene, we find a progressive impairment in fast retrograde and anterograde transport. Increased levels of retrograde motor protein subunits are associated with accumulation of membranous organelles distal to nodal complexes. Using cell transplantation, we show categorically that the axonal phenotype is related to the presence of the overlying Plp null myelin. Our data demonstrate a novel role for oligodendrocytes in the local regulation of axonal function and have implications for the axonal loss associated with secondary progressive multiple sclerosis.

Studies on the inhibition of feline EGFR in squamous cell carcinoma Enhancement of radiosensitivity and rescue of resistance to small molecule inhibitors

This study investigated different methods of EGFR (Epithelial Growth Factor Receptor) targeting in feline squamous cell carcinoma with the ultimate aim of establishing a large animal model of human head and neck cancer. Both small molecule receptor tyrosine kinase inhibitor (TKI) and RNA interference (RNAi) techniques were employed to target the feline EGFR. We demonstrated that the human drug gefitinib caused a reduction in cell proliferation and migration in a feline cell line. However, we also document the development of resistance that was not associated with mutation in the kinase domain. RNAi caused a potent reduction in EGFR activity and was able to overcome acquired gefitinib resistance. In addition, RNAi targeting of EGFR, but not gefitinib, caused an additive effect on cell killing when combined with radiation. These results support the use of feline SCC as a model of head and neck cancer in man in the search for novel and effective treatments for both tumors.

Dogs with congenital porto-systemic shunting (cPSS) and hepatic encephalopathy have higher serum concentrations of C-reactive protein than asymptomatic dogs with cPSS

Hepatic encephalopathy (HE) is a cause of significant morbidity and mortality in patients with liver disorders and a wide range of rodent models of HE have been described to facilitate studies into the pathogenesis and treatment of HE. However, it is widely acknowledged that no individual model perfectly mimics human HE and there is a particular need for spontaneous, larger animal models. One common congenital abnormality in dogs is the portosystemic shunt (cPSS) which causes clinical signs that are similar to human HE such as ataxia, disorientation, lethargy and occasionally coma. As inflammation has recently been shown to be associated with HE in humans, we hypothesised that inflammation would similarly be associated with HE in dogs with cPSS. To examine this hypothesis we measured C-reactive protein (CRP) in 30 healthy dogs, 19 dogs with a cPSS and no HE and 27 dogs with a cPSS and overt HE. There was a significant difference in CRP concentration between healthy dogs and dogs with HE (p < 0.001) and between dogs with HE and without HE (p < 0.05). The novel finding that there is an association between inflammation and canine HE strengthens the concept that HE in dogs with cPSS shares a similar pathogenesis to humans with HE. Consequently, dogs with a cPSS may be a good spontaneous model of human HE in which to further examine the role of inflammation and development of HE.

Gastric disease in the dog and cat

The physiology of the normal gastric defence mechanisms in the dog and cat is reviewed to emphasize the routes by which drugs can be used to protect the gastric mucosa. The action of the main anti-ulcer and pro-kinetic drugs are discussed in relation to the diseases that they may be used to treat. Gastric disease in the form of gastric dilatation/volvulus, chronic vomiting without obstruction and gastric outflow disease are described from the point of view of diagnosis and treatment.

Expression of epidermal growth factor receptor (EGFR) and Ki67 in feline oral squamous cell carcinomas (FOSCC)

The aims of this study were to establish expression of epidermal growth factor receptor (EGFR) and Ki67 in 67 archived biopsy samples of feline oral squamous cell carcinomas (FOSCCs) and to establish if the expression of either markers was predictive of survival. Samples were immunohistochemically labelled for the two proteins and scored. Statistical analyses of data, including Kaplan-Meier survival curves, were performed. All samples expressed both markers although levels differed between samples. Median overall survival was 46 days and 1-year survival was 5%. There was no correlation between Ki67 and EGFR scores (Pearsons correlation coefficient, P = 0.861). Low cellular proliferation (low Ki67 score) was positively correlated with an overall longer survival (Log Rank, P = 0.02) and a trend towards better survival for the high EGFR group was observed (Log Rank, P = 0.076). Ki67 and EGFR immunostaining in FOSCC may be of value as biochemical markers for screening of biopsies from cases of FOSCC.

Assessment of the incidence of GDV following splenectomy in dogs

OBJECTIVE To establish if splenectomy increases the incidence of gastric dilatation and volvulus (GDV) in dogs. METHODS Two case-series studies of cases and controls were performed. Records of dogs that had undergone splenectomy (37 cases) were compared with records of dogs that had undergone other abdominal surgery (43 cases). Records of dogs that presented for non-elective gastropexy (33 cases) were compared with records of dogs presented to the hospital for unrelated reasons (39 cases). Survival following splenectomy and development of GDV in the first 12 months following surgery were retrieved from the clinical records and by questionnaire-based canvassing of the referring clinician. The incidence of GDV following splenectomy was established and the association between a current episode of GDV and previous splenectomy was assessed. RESULTS There was no evidence that splenectomy was associated with an increased incidence of subsequent GDV (P=0.469). No association between a current episode of GDV and previous splenectomy was found. CLINICAL SIGNIFICANCE Splenectomy is not associated with an increase in the incidence of GDV.

Identification of tumour initiating cells in feline head and neck squamous cell carcinoma and evidence for gefitinib induced epithelial to mesenchymal transition

Feline oral squamous cell carcinoma is considered a highly invasive cancer that carries a high level of morbidity. Despite aggressive surgery, patients often succumb to disease, the tumour having inherent insensitivity to radiation and chemotherapy. In this study we sought to identify cells within the feline SCC1 line that have stem cell properties, including inherent resistance mechanisms. When feline cells were subjected to harsh growth conditions, they formed sphere colonies consistent with a stem cell phenotype. Utilising CD133, we were able to identify a small fraction of cells within the population that had enhanced sphere-forming ability, reduced sensitivity to radiation and conventional chemotherapy and demonstrated resistance to the EGFR-targeting drug, gefitinib. In addition, long-term culture of feline SSC1 cells in gefitinib caused a change in cell morphology and gene expression reminiscent of an epithelial to mesenchymal transition. Taken together, these results suggest that feline SCC may be driven by small subset of cancer stem cells.

Whole Blood Manganese Concentrations in Dogs with Congenital Portosystemic Shunts

BACKGROUND Manganese (Mn) is an essential mineral that is a cofactor for many enzymes required in the synthesis of proteins, carbohydrates, and lipids. Because hepatic clearance is essential in Mn homeostasis, conditions in humans resulting in hepatic insufficiency including cirrhosis and both acquired and congenital portosystemic shunting have been reported to result in increased blood Mn concentrations and increased Mn content in the central nervous system. Because Mn toxicity causes neurologic disturbances, increased Mn concentrations have been implicated in the pathogenesis of hepatic encephalopathy. HYPOTHESES Dogs with congenital portosystemic shunts (cPSS) have significantly higher whole blood Mn concentrations than do healthy dogs or those with nonhepatic illnesses. ANIMALS Eighteen dogs with cPSS, 26 dogs with nonhepatic illnesses, and 14 healthy dogs. METHODS Whole blood Mn was measured by graphite furnace atomic absorption spectrometry. The diagnosis of cPSS was made by ultrasonography or during celiotomy either by visual inspection of a shunting vessel or portovenography. RESULTS Dogs with a cPSS had significantly higher whole blood Mn concentrations than did healthy dogs and dogs with nonhepatic illnesses. Whole blood Mn concentrations were not significantly different between healthy dogs and dogs with non-hepatic illnesses. CONCLUSION AND CLINICAL IMPORTANCE Dogs with a cPSS have significantly increased whole blood Mn concentrations. Additional studies are warranted to investigate the role of Mn in cPSS-associated hepatic encephalopathy.

Epidermal growth factor receptor as a therapeutic target in veterinary oncology

Epidermal growth factor receptor (EGFR) is a tyrosine kinase receptor that stimulates cell proliferation and survival and becomes dysregulated in a range of solid tumours in man. It is recognized as a key oncogenic driver and has become a favoured therapeutic target and a prognostic and predictive marker of cancer in man. In animals, EGFR dysregulation is emerging as a potential factor in the development of a number of naturally occurring tumours including mammary, lung, glial and epithelial cancers. Comparative analyses suggest that these diseases share many features with equivalent diseases in man and EGFR may have value as a prognostic or a biological marker of animal disease. There is still little direct evidence that EGFR is a critical oncogenic driver in naturally occurring animal disease and there are no veterinary trials of EGFR-targeted therapy. These will be critical steps in establishing a role for EGFR in veterinary oncology.

Neurological dysfunction in three dogs and one cat following attenuation of intrahepatic portosystemic shunts

Neurological dysfunction is an uncommon complication following extrahepatic portosystemic shunt ligation. Three dogs and one cat are described that developed neurological signs within 21 to 42 hours of attenuation of intrahepatic portosystemic shunts. None of these cases had biochemical evidence of hepatic encephalopathy postoperatively. Two dogs died during management of status epilepticus following aspiration of food. One dog died six months postoperatively. The cat had persistent neurological dysfunction at discharge, but was alive and had recovered most of its neurological function at the time of writing, 37 months after surgery. This report demonstrates the potential for animals with intrahepatic portosystemic shunts to develop postoperative neurological signs and highlights the difficulty of managing such cases. Two dogs had both intrahepatic and extrahepatic portosystemic shunts. Large intestinal malrotation (partial situs inversus) may have been linked to the development of a portosystemic shunt in the remaining dog.