Classification of canine malignant lymphomas according to the World Health Organization criteria.

A study was carried out to test the accuracy and consistency of veterinary pathologists, not specialists in hematopathology, in applying the World Health Organization (WHO) system of classification of canine lymphomas. This study represents an initiative of the ACVP Oncology Committee, and the classification has been endorsed by the World Small Animal Veterinary Association (WASVA). Tissue biopsies from cases of canine lymphoma were received from veterinary oncologists, and a study by pathologists given only signalment was carried out on 300 cases. Twenty pathologists reviewed these 300 cases with each required to choose a diagnosis from a list of 43 B and T cell lymphomas. Three of the 20 were hematopathologists who determined the consensus diagnosis for each case. The 17 who formed the test group were experienced but not specialists in hematopathology, and most were diplomates of the American or European Colleges of Veterinary Pathology. The overall accuracy of the 17 pathologists on the 300 cases was 83%. When the analysis was limited to the 6 most common diagnoses, containing 80% of all cases, accuracy rose to 87%. In a test of reproducibility enabled by reintroducing 5% of cases entered under a different identity, the overall agreement between the first and second diagnosis ranged from 40 to 87%. The statistical review included 43,000 data points for each of the 20 pathologists.

Inhibition of cyclooxygenase-2 prevents adverse effects induced by phosphodiesterase type 4 inhibitors in rats.

BACKGROUND AND PURPOSE: Phosphodiesterase type 4 (PDE4) inhibitors such as roflumilast are currently being developed as anti-inflammatory treatments for chronic airway disorders. However, high doses of PDE4 inhibitors have also been linked to several side effects in different animal species, including pro-inflammatory effects in the rat. Here, we analysed PDE4-related toxicological findings in a rat model and how these side effects might be therapeutically prevented. EXPERIMENTAL APPROACH: Wistar rats were treated orally once daily with 10 mg·kg⁻¹ roflumilast for 4 days. Macroscopic changes were monitored throughout the study and further parameters were analysed at the end of the experiment on day 5. In addition, the effects of concomitant treatment with cyclooxygenase (COX) inhibitors were assessed. KEY RESULTS: Supratherapeutical treatment with roflumilast induced marked body and spleen weight loss, diarrhea, increased secretory activity of the harderian glands, leukocytosis, increased serum cytokine-induced neutrophil chemoattractant-1 (CINC-1) levels, and histopathological changes in thymus, spleen, mesentery and mesenteric lymph nodes. All these toxicological findings could be prevented by the non-steroidal anti-inflammatory drug (NSAID) and non-selective COX inhibitor, diclofenac, given orally. Similar protective effects could be achieved by the COX-2 selective inhibitor lumiracoxib, whereas the COX-1 selective inhibitor SC-560 was generally not effective. CONCLUSIONS AND IMPLICATIONS: Treatment with an NSAID inhibiting COX-2 prevents the major effects found after subchronic overdosing with the PDE4-specific inhibitor roflumilast. If this effect translates into humans, such combined treatment may increase the therapeutic window of PDE4 inhibitors, currently under clinical development.

Immunoglobulin-producing tumours in dogs and cats.

Tumours with a plasmacytoid pattern taken from 32 dogs and four cats were examined for the presence of immunoglobulins, which would allow them to be designated as B-cell lymphomas. Within a total of 19 immunoglobulin-positive tumours, three types could be distinguished: extramedullary plasmacytoma (15), multiple myeloma (two) and immunocytoma (two). These tumours occurred in 18 of the dogs, and in one cat (extramedullary plasmacytoma). The characteristics of the immunoglobulin-producing tumours were investigated by light and electron-microscopy as well as by immunohistochemical methods. Seventeen of the 19 tumours expressed lambda-type light chains and one tumour kappa-type light chains. Heavy chains were also synthesized by five tumours.

Demonstration of feline and canine platelet glycoproteins by immuno- and lectin histochemistry.

Canine and feline platelet cytocentrifuge preparations (CCPs), cryostat and paraffin-embedded bone marrow sections were used in this study. We evaluated whether platelets, megakaryocytes and megakaryocyte precursor cells could be labelled by monoclonal antibodies (Y2/51, CLB-thromb/1, HPL1) against human platelet membrane glycoprotein GP IIIa and the GP IIb/IIIa complex or by the following 10 biotinylated lectins: concanavalin A (Con A), Lens culinaris agglutinin (LCA), Pisum sativum agglutinin (PsA), wheat germ agglutinin (WGA), peanut agglutinin (PNA), Phaseolus vulgaris lectin (PHA-L), Ricinus communis agglutinin 120 (RCA120), Ulex europaeus agglutinin-I(UEA-1), soybean agglutinin (SBA) and Dolichos biflorus agglutinin (DBA). Monoclonal antibodies Y2/51 and HPL1 cross reacted with platelets and megakaryocytic cells from both species, whereas CLB-thromb/1 was unreactive with canine preparations. Only Y2/51 labelled megakaryocytic cells in paraffin-embedded samples. LCA, PSA, WGA and PHA-L labelled feline and canine platelets and different numbers of morphologically identifiable megakaryocytes and numerous other, mostly myeloid, cells. Immunoblots of dog and cat platelet lysates using Y2/51 visualized a single protein of 95 kDa (unreduced), a mol.wt value within the range of those reported for GP IIIa. Some of the platelet (but not necessarily megakaryocyte) glycoproteins reacting with LCA, PSA and WGA could be identified in lectin blots following one- or two (nonreduced/reduced)-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Thus in dogs and cats, the immunohistochemical detection of GP IIIa (and eventually GP IIb/IIIa) rather than lectin binding patterns could be important for the diagnosis of megakaryoblastic leukaemias.

Increased production of atrial natriuretic peptide in the rat thymus after irradiation.

The rat thymus involutes when exposed to dexamethasone, and this phenomenon is accompanied by a striking increase of ANP localized in thymic macrophages. This study was designed to investigate whether a stimulus, that is X-rays, well known to also cause involution of the thymus, is followed by an elevation of ANP-expression. Rats were irradiated with 4, 6 and 8 Gy, and after 4 days we found a dose-dependent increase (3-, 30- and 40-fold) of mRNA coding for ANP. The corresponding ANP precursor (ANP1-126) has been found elevated 4-, 10-, and 13-fold, respectively. Immunohistochemical analysis of irradiated (6 Gy) tissue revealed heavily IR-ANP positive cells in the cortex, which, due to their morphological and enzyme-histochemical characteristics, were identified as highly phagocytising macrophages. We suggest, thus, that regardless of the stimulus applied (DEX or X-rays) causing the vast cell death in the thymus, the increased ANP-expression is linked to the highly activated phagocytic system of the thymus under these conditions.

Acute megakaryoblastic leukemia in one cat and two dogs.

The clinical, hematologic, and histologic features of acute megakaryoblastic leukemia are described for an 8-year-old female Domestic Shorthair cat, a 3-year-old female mixed-breed dog, and a 3-year-old male German Shepherd Dog. The neoplastic cells were characterized as belonging to the megakaryocytic lineage. The following techniques were used: electron microscopy; detection of antibodies against human von Willebrand factor (vWF) and human platelet glycoprotein GP IIIa using a modified avidin biotin peroxidase complex technique on formalin-fixed paraffin sections; and enzyme histochemical methods on plastic sections for alkaline phosphatase, acid phosphatase, myeloperoxidase, alpha-naphthyl acetate esterase, alpha-naphthyl butyrate esterase, naphthol AS acetate esterase, and naphthol AS-D chloroacetate esterase. In addition, benign megakaryocytic cells, platelets, and neoplastic cells were labeled with lectins that have partially been shown to bind to platelet glycoproteins of other species. In healthy cats and dogs, the megakaryocytes and platelets reacted with lectins PSA, LCA, PHA-L, and WGA. Megakaryocytes and platelets from healthy cats were also labeled by lectin PNA. The lectins PHA-L and WGA reacted with neoplastic cells from the cat and both dogs. Lectin PNA bound to neoplastic cells from the cat, and lectins PSA, LCA, and SBA bound to neoplastic cells from both dogs. For the retrospective examination of paraffin-embedded material, the detection of vWF and GP IIIa appears to be the most reliable method for the identification of megakaryocytic cells.

Synthesis and distribution of atrial natriuretic peptide (ANP) in hearts from normal dogs and those with cardiac abnormalities.

The cardiac distribution of immunoreactive atrial natriuretic peptide (IR-ANP) and ANP-specific mRNA was studied in 35 normal dogs and 44 dogs with primary and secondary heart abnormalities. According to clinical and pathological findings the dogs were assigned to seven groups: Group 1, normal young dogs (< 12 months); Group 2, normal adult dogs (> 12 months); Group 3, low to moderate hypertrophy; Group 4, severe hypertrophy; Group 5, dilated cardiomyopathy; Group 6, renal failure with secondary left ventricular hypertrophy; and Group 7, other heart abnormalities. In comparison with hearts of normal dogs, the amount of IR-ANP and ANP-specific mRNA was reduced in the atria and increased in the ventricles of dogs with hypertrophy and cardiomyopathy. The immunoreactivity in normal canine atria was far lower than in control rats and hamsters. The pattern of ventricular immunoreactivity was faint and patchy. Only in a few ventricular localizations of three dogs of Group 5 and one dog of Group 6 was there a granular pattern suggesting the presence of secretory granules. A state of intense secretory stimulation in cardiomyopathy was indicated by electron microscopy. Due to its low concentration and localized pattern, however, IR-ANP does not seem to be a reliable marker for the presence of hypertrophic or cardiomyopathic changes in dogs.

Expression of atrial natriuretic peptide in thymic macrophages after dexamethasone treatment of rats.

The rat thymus represents a site of synthesis of atrial natriuretic peptide (ANP); the immunosuppressor dexamethasone strikingly increases ANP-expression in this immune organ. The presented data suggest that this increase can be attributed to macrophages. By means of immunohistochemistry and Northern blot analysis these immune cells were found to express ANP-immunoreactivity as well as mRNA coding for ANP. In contrast, macrophages of control thymi displayed only weak ANP-immunoreactivity. Thus, ANP appears to be a constituent of rat thymic macrophages, and its synthesis in the thymus is strongly elevated by acute exposure of the animals to glucocorticoids.

AA-like amyloid deposits confined to arthritic joints in two dogs with rheumatoid arthritis.

Two dogs with clinical, serological, radiographic and pathological changes similar to those of rheumatoid arthritis of man and a previously undescribed pattern of amyloid deposits are described. As revealed by light and electron microscopical investigations, amyloid fibrils were found exclusively in articular tissue structures of arthritic joints and in one tonsil of one dog. Based on our immunohistochemical results, the amyloid protein is believed to be of a local AA type.

[Significance and detection of different mast cell populations in the dog]. / Bedeutung und Nachweis verschiedener Mastzellpopulationen beim Hund.

Mast cell heterogeneity in dogs, possible roles of recognized mast cell populations in health and disease, and histochemical, enzyme and lectin histochemical studies for their demonstration in paraffin embedded tissues are described.

[Pathological changes of the endocrine pancreas in dogs and cats in comparison with clinical data]. / Pathologische Veränderungen des endokrinen Pankreas bei Hund und Katze im Vergleich mit klinischen Daten.

In a retrospective study concerning the functional morphology of the endocrine pancreas the files of the Institute for Veterinary Pathology, University of Munich, of the last 12 years were reviewed. Cases of diabetes mellitus as well as developmental disorders and tumors of the endocrine pancreas were examined by routine histological and immunohistological methods. Cases are discussed together with clinical data and the relevant literature. The forms of diabetes mellitus were categorized according to the classification used in human pathology.

Origin and characterization of atrial natriuretic peptide in the rat parotid gland.

The heart atria represent the major site of synthesis for atrial natriuretic peptide (ANP) which exerts potent natriuretic, diuretic and vasoactive functions. Recently, ANP-immunoreactivity has been detected in extracardial organs involved in water and electrolyte homeostasis, such as the intestine and certain exocrine glands. The present study investigates ANP in the parotid gland. It was found by immunohistochemical techniques that the peptide is localized in ductal cells of the gland. An analysis of the immunoreactive material by high-pressure liquid chromatography and radioimmunoassay revealed the prohormone of ANP (ANP 1-126) and the biologically active fragment (ANP 99-126). Furthermore, Northern blot hybridization disclosed the presence of mRNA coding for ANP. It is suggested that ANP is synthesized and released from the parotid gland and functions in the control of saliva production.

Immunohistochemical demonstration of various antigens in tissues embedded in plastic.

In the course of a chronic experimental study of polyarthritis in rats, we have established a plastic embedding technique which allows the processing not only of soft tissues but also of tissues such as cartilage, intraarticular ligaments, and even undecalcified whole rat joints and provides broad survival of enzymes and antigens. Preservation of morphological details and the precision of antigen localization are superior to those seen in cryostat and paraffin sections. The method seems to have much diagnostic and investigative value, especially in arthritis research.

Ia antigens in plastic-embedded tissues: a post-embedding immunohistochemical study.

The aim of the present study was to establish a plastic embedding technique that makes possible the immunohistochemical demonstration of class II major histocompatibility complex (MHC) antigens (Ia antigens) in undecalcified joint tissues. Therefore a series of fixatives and dehydrating agents was tested for saving Ia immunoreactivity by post-embedding immunostaining of thin sections (2 microns) of rat tissues that had been embedded in glycol methacrylate (GMA), and by comparing with cryostat sections. An indirect immunoperoxidase and the avidin-biotin complex (ABC) technique were used. Combined with fixation by 4% formaldehyde, dehydration with GMA was found to give the best preservation of Ia antigenicity, followed by dehydration with ethylene glycol. The thinness of tissue sections facilitated the association of Ia antigens with different subcellular compartments in distinct cell populations. These various patterns are described.