Interobserver Agreement Using Histological Scoring of the Canine Liver

Background

Grading schemes for the assessment of hepatic fibrosis and necroinflammatory activity in humans previously have been applied to dogs with chronic hepatitis. Interobserver agreement is a desirable characteristic for any histological scoring scheme.

Hypothesis/Objectives

To assess interobserver agreement associated with pathologists using a previously published histological scoring scheme to assess hepatic fibrosis and necroinflammatory activity in dogs and to compare fibrosis scores assigned to serial sections stained with hematoxylin & eosin (H&E) and picrosirius red.

Animals

Histological sections of liver from 50 dogs with variable degrees of hepatic fibrosis and necroinflammatory activity were selected from institutional tissue archives.

Methods

Six board‐certified veterinary anatomic pathologists assigned fibrosis and necroinflammatory activity scores to the histological sections. The multiuser kappa statistic was calculated to assess interobserver agreement. Fibrosis stage assigned to serial sections stained with picrosirius red and H&E was compared using the Wilcoxon signed‐rank test.

Results

Multiuser kappa statistics for assessment of fibrosis and necroinflammatory activity from H&E‐stained sections were 0.35 and 0.16, respectively. There was no difference in median fibrosis scores assigned to serial section stained with H&E and picrosirius red (P = .248).

Conclusions and Clinical Importance

There was fair interobserver agreement when pathologists assessed fibrosis and poor agreement when they assessed necroinflammatory activity. This suboptimal agreement must be taken into account by clinicians making decisions based on histology reports of the liver and in the design of studies evaluating these findings. To decrease this variability, ideally >1 pathologist should evaluate each section.

Use of Serum MicroRNAs as Biomarker for Hepatobiliary Diseases in Dogs

Background

Current biochemical indicators cannot discriminate between parenchymal, biliary, vascular, and neoplastic hepatobiliary diseases. MicroRNAs are promising new biomarkers for hepatobiliary disease in humans and dogs.

Objective

To measure serum concentrations of an established group of microRNAs in dogs and to investigate their concentrations in various types of hepatobiliary diseases.

Animals

Forty‐six client‐owned dogs with an established diagnosis of hepatobiliary disease and stored serum samples and eleven client‐owned healthy control Labrador Retrievers.

Methods

Retrospective study. Medical records of dogs with parenchymal, biliary, vascular, or neoplastic hepatobiliary diseases and control dogs were reviewed. Concentrations of miR‐21, miR‐122, miR‐126, miR‐148a, miR‐200c, and miR‐222 were quantified in serum by real‐time polymerase chain reaction.

Results

No different microRNA concentrations were found in the adenoma and congenital portosystemic shunt groups. In all other diseases, miR‐122 concentrations were elevated with the highest concentration in the mucocele group (267‐fold, CI: 40–1,768, P < .001). In dogs with biliary diseases, miR‐21 and miR‐222 were only increased in dogs with mucoceles (26‐fold, CI: 5–141, P = .005 and 13‐fold, CI: 2–70, P = .025, respectively). Uniquely increased microRNAs were found in the hepatocellular carcinoma group (miR‐200c, 35‐fold increase, CI: 3–382, P = .035) and the chronic hepatitis group (miR‐126, 22‐fold increase, CI: 5–91, P = .002).

Conclusions and Clinical Importance

A microRNA panel consisting of miR‐21, miR‐122, miR‐126, miR‐200c, and miR‐222 can distinguish between parenchymal, biliary, and neoplastic hepatobiliary diseases. Serum microRNA profiling is a promising new tool that might be a valuable addition to conventional diagnostics to help diagnose various hepatobiliary diseases in dogs.

[Malignant melanoma of the pelvis as a possible cause of pelvic limb lameness in two gray mares]

Two grey mares, a 12-year-old Arabian and a 13-year-old Lippizaner cross, were referred for chronic pelvic limb lameness and abduction of the limb during the non supporting phase of the stride. The clinical examination revealed melanomas under the tail and on the perineum, and oedema of the proximal lame limb. A mass in the pelvic area was detected on rectal palpation. Laparoscopy was performed and the provisional diagnosis of malignant melanoma was made. Histological examination of the biopsy taken under laparoscopic control from the mass in the pelvis confirmed the diagnosis of malignant melanoma. In the postmortem examination a large black mass in the pelvis and metastases in several organs were diagnosed. The process under the tail showed microscopically the characteristics of dermal melanomatosis. The metastases showed the appearance of a malignant melanoma. The lameness and abduction during the non supporting phase of the stride were possibly caused by a combination of pain, a mechanical limitation, and paresis/paralysis. When an older grey horse with melanomas on the predilection sites is submitted with pelvic limb lameness and abduction of the limb during the non supporting phase of the stride, a malignant melanoma in the pelvis is one of the differential diagnoses and a rectal examination should be performed. Diagnostic laparoscopy in the standing horse can be useful to confirm the provisional diagnosis.

Toxicity of PCB-126 in European flounder ( Platichthys flesus ) with emphasis on histopathology and cytochrome P4501A induction in several organ systems

A series of experiments was set up to elucidate the effects of pollution on marine and estuarine fish health, since the European flounder (Platichthys flesus) has shown a relatively high prevalence of (pre)neoplastic liver lesions and lymphocystis virus disease in Dutch coastal and estuarine waters. The hypothesis of a causal relationship between pollution and the above-mentioned diseases was supported by results from semi-field experiments. Therefore several laboratory experiments were carried out to substantiate causality further and to identify the xenobiotics that may play a major role in the field. The present study focuses on polychlorinated biphenyls (PCBs). European flounders (Platichthys flesus) were orally exposed to a single dose of 0, 0.5, 5 or 50 mg PCB-126/kg body weight under controlled laboratory conditions. The effects on liver, gills, gastrointestinal tract, gonads, spleen and mesonephros were examined histologically after 16 days. Induction and localization of cytochrome P4501A (CYP1A) immunoreactivity, and effects on hepatocyte proliferation were visualized immunohistochemically. Effects on thymus size were examined by morphometric analysis of serial sections. Three out of five animals of the highest dose group showed haemorrhages in the fins and tail after 16 days. All animals showed reduced activity in the later stages of the experiment, and some animals of the highest dose group discontinued feeding 14 days after exposure. Strong and exposure-related induction of CYP1A immunoreactivity was noted in hepatocytes, endothelium in all organs examined, and epithelium of the digestive tract and mesonephros at PCB-126 levels of 0.5, 5 and 50 mg/kg. In addition, the strong induction of CYP1A immunoreactivity in a distinct population of haematopoietic cells in the mesonephros and in circulating blood is remarkable, and has not been described previously in other fish species. Furthermore, a morphometrically determined significant reduction in relative thymus size was noted in animals exposed to 50 mg PCB-126/kg. Although the functional implications for the immune system of this reduction need to be further investigated, an impact on the specific resistance against infectious diseases as observed in the field, e.g. viral lymphocystis disease, is not implausible. In addition, a significant increase in absolute liver weight, in hepatosomatic index, and in number of proliferating hepatocytes [measured as immunoreactivity against proliferating cell nuclear antigen (PCNA)] was noted in animals of the highest dose group. From these findings we suppose that PCB-126 (and related chemicals) may play a role in the promotion of tumour development in the liver of European flounders as observed in the field. The results of the present experiment show relatively stronger effects than effects previously reported from experiments with TCDD, suggesting that the TEF of 0.005 assigned to PCB-126 from early life stage mortality experiments in rainbow trout (Oncorhynchus mykiss), underestimates the toxic potential of PCB-126.

Toxicity of TCDD in European flounder (Platichthys flesus) with emphasis on histopathology and cytochrome P450 1A induction in several organ systems

The present study is part of a series of experiments, set up to elucidate the impact of aquatic pollution on fish health in the marine and estuarine environment. In the Dutch coastal and estuarine waters, European flounder (Platichthys flesus) showed a relatively high prevalence of (pre)neoplastic liver lesions and lymphocystis virus disease. The hypothesis of a causal relationship between pollution and these diseases was supported by semi-field experiments. Therefore a series of laboratory experiments was performed to further substantiate causality and identify the xenobiotics that may play a major role in the field. Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are important environmental pollutants. They are highly persistent, highly lipophilic, and have shown to induce several toxic effects in mammalian and non-mammalian species at relatively low concentrations. This report describes a study in which European flounder were orally exposed to the most toxic PCDD congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or to harbor sludge extract under controlled laboratory conditions. The effects on several organs (liver, gills, gastro-intestinal tract, thyroid gland, gonads, spleen and mesonephros) were examined microscopically. Induction and localization of cytochrome P4501A (CYP1A) immunoreactivity, and effects on hepatocyte-proliferation were visualized immunohistochemically. Effects on thymus size were examined by morphometric analysis. Oral exposure of flounder to 0.0125 or 0.3125 µg TCDD/kg bw, or to 0.3125 µg TEQ/kg bw of a harbor sludge extract, weekly for 8 weeks, induced a significant increase in CYP1A immunoreactivity in hepatocytes. Single administration of higher doses (20, 100 and 500 µg/kg bw) of TCDD also induced a significant increase CYP1A immunoreactivity in the endothelium in all organs examined, and in the epithelium of the digestive tract, liver, and mesonephros. Remarkably, strong immunoreactivity was noted in a distinct cell population of the hematopoietic tissue in the mesonephros and spleen, which has not been described in fish previously. Moreover, oral exposure to 20 µgTCDD/kg bw resulted in an increased mitotic activity, and an increased hepatosomatic index was found after exposure to 500 µgTCDD/kg bw. In the thymus only a trend in size reduction was noted, again in the highest dose group. Nevertheless, no marked pathology was detected even in fish exposed to a single dose of 500 µg TCDD/kg body weight. The present experiments show that, under the actual experimental conditions, European flounder is relatively insensitive to the toxic effects of TCDD. However, we assume that exposure to TCDD (and related substances) may promote the development of tumors in the field.

Toxicology of environmental chemicals in the flounder (Platichthys flesus) with emphasis on the immune system: field, semi-field (mesocosm) and laboratory studies

European flounder (Platichthys flesus) has shown an increased prevalence of liver tumors and lymphocystis disease (a viral infection) that correlated with pollution in field research in Dutch coastal and estuarine waters. Semi-field or mesocosm experiments confirmed the supposed causality. Although these types of research are highly relevant for the feral population, laboratory experiments are necessary to establish causal relationships between specific chemical pollutants and disease. Therefore, the effects on flounder of some of the potentially causative chemicals such as benzo[a]pyrene (BaP), dimethyl-benz[a]anthracene (DMBA), 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD), 3,3',4,4',5 pentachlorobiphenyl (PCB-126), and bis(tri-n-butyltin)oxide (TBTO) were examined in several laboratory experiments. These effects were evaluated using general toxicological parameters and histopathology. For immune function assessment, attempts to develop an infection model with the lymphocystis virus were made, but appeared unsuccessful and immune function tests are not fully operational at the moment. Flounder has been successfully maintained and exposed to toxic substances in captivity in our laboratory. Short-term aqueous exposure to high levels of BaP or DMBA did not induce marked effects under our experimental conditions. Results of oral exposure of flounder to low levels of TCDD, PCB-126 or harbor sludge extract show significant induction of cytochrome P4501A (CYP1A) in hepatocytes. Oral exposure to high levels of TCDD or PCB-126 also significantly induced CYP1A immunoreactivity in epithelium in mesonephros and digestive tract and in endothelium in several organs. Remarkable was the induction of CYP1A in a distinct population of mononuclear cells in the mesonephros. Moreover, oral exposure to TCDD resulted in an increased mitotic activity and an increase of the hepatosomatic index in the 20 and 500 microgram TCDD/kg group respectively. Therefore, exposure to TCDD and related substances may promote the development of liver tumors in the field. Exposure to PCB-126 also significantly reduced the relative thymus volume, but other results indicate that flounder is relatively insensitive to this type of chemicals. Short-term aqueous exposure of flounder to TBTO, in concentrations that were in the same order of magnitude as upper TBT levels measured in the field, caused mortality after 7-12 days associated with gill lesions, and induced reduction of the non-specific resistance and decrease of the relative thymus volume. From these results we therefore conclude that TBTO might play a causal role in, for instance, increased prevalence of lymphocystis virus infections in the field

Controlled dose confirmation study of a 2% moxidectin equine gel against equine internal parasites in The Netherlands

The efficacy of a 2% moxidectin equine gel at a dosage rate of 0.4 mg kg-1 was evaluated in a controlled trial at Utrecht University. Twelve yearling castrated male Shetland ponies grazed a pasture of 2 ha from May 1994 until housing in November. Six ponies were treated with moxidectin, whereas the others served as non-treated controls. Necropsy was carried out 35 days after treatment. Greater than 99% efficacy of moxidectin was observed on faecal egg output. No effect of moxidectin was observed on mucosal inhibited early cyathostome L3 (EL3) or on the total numbers of mucosal developing stages. However, a 89.6% reduction was observed on large mucosal fourth stage larvae (L4). Moxidectin treatment probably triggered resumption of development of EL3. Moxidectin appeared to be highly effective (95-100%) on lumenal L4 cyathostomes, adult strongylids, Strongylus vulgaris larvae from the arteries, S. edentatus larvae from the abdominal wall and Trichostrongylus axei. Moxidectin had relatively poor efficacy against Gasterophilus intestinalis and had no effect on Anoplocephala perfoliata. No side-effects of moxidectin treatment were observed.

Monoclonal gammopathy in a Dutch warmblood mare

A 15-year-old Dutch warmblood mare was presented because of lethargy, which had been present for several weeks, and severe anaemia. Total protein was high and serum electrophoresis revealed a monoclonal peak in the alpha-2 region. Monoclonal immunoglobulin, IgG(T), was detected by immuno-electrophoresis in serum and urine. Postmortem examination revealed a relatively large number of plasmacytoid cells in the bone marrow and a monotonous population of plasmacytoid cells in the spleen. These findings are suggestive of a plasma cell myeloma.

[A horse with chronic eosinophilic enteritis]

A three-year-old pregnant Dutch Warmblood mare was referred to the Department of Large Animal Medicine and Nutrition, Faculty of Veterinary Medicine, because of weight loss for 1 month. The main clinical features were (beside weight loss) moderate ventral oedema, enlarged mesenteric lymph nodes, and uniform thickening of the wall of the jejunum. Haematological evaluation revealed leukocytosis (15.9 G.l-1 with 18% lymphocytes and 1% eosinophils) and a decreased total serum protein and albumin concentration (35 g.l-1 and 36.3% albumin). At necropsy transmural eosinophilic enteritis was found in combination with macrophages. There was an abnormal (11% increase) absorption of glucose in the small intestine.