Pathology of captive moustached tamarins (Saguinus mystax)

The pathology of 33 moustached tamarins (Saguinus mystax) previously used in hepatitis A and GB virus studies is reported. Chronic lesions in colon, heart, and kidney were common in the monkeys and appeared not to be due to the experimental exposures. Colitis cystica profunda (CCP), a disease that affects humans and is characterized by the presence of mucin-filled epithelial downgrowths and cysts in the colonic submucosa, was found in 24 of the 33 (72.7%) tamarins. Interstitial myocardial fibrosis was present in 22 (66.6%) animals, and various degrees of membranoproliferative glomerulonephritis occurred in 28 (84.8%) monkeys. In addition, 28 (84.8%) tamarins demonstrated diffuse hepatocellular vacuolation with mild lymphoplasmacytic infiltrates, possibly as a result of the experimental infections, and peliosis hepatis occurred in 7 (21.2%) animals. The etiology of CCP is unknown, and no reliable animal models are available because most cases in animals are reported only sporadically. Myocardial fibrosis in tamarins has not been reported previously, and all current animal models require experimental manipulation of the animal to mimic the human disease. The results from this study suggest that captive S. mystax has high incidence of spontaneous CCP, myocardial fibrosis, and membranoproliferative glomerulonephritis. This species may be a spontaneous animal model for pathogenesis and experimental therapy studies of the analogous human diseases.

Membranoproliferative glomerulonephritis type III in a simultaneous infection of Leishmania infantum and Dirofilaria immitis in a dog

In this report a 9-year-old female German Shepherd dog with a membranoproliferative glomerulonephritis (MPGN) type III associated with concomitant infection of Dirofilaria immitis and Leishmania infantum is presented. Light microscopic evaluation of kidney revealed a diffuse hypercellularity and thickening of glomerular basement membrane. Heavy and coarse granular complement C(3) deposition and a weaker positive reaction to immunoglobulin G were present along peripheral glomerular basement membrane and in the mesangium in the immunofluorescent study. Transmission electron microscopy revealed deposits in the mesangium, subendothelium, and subepithelium. These lesions are compatible with membranoproliferative glomerulonephritis type III in humans.

Detection of maedi-visna virus in the kidneys of naturally infected sheep

Infections with maedi-visna virus (MVV) cause progressive inflammation in different organs, mainly the lung, mammary gland, brain and joints. The aim of the present study was to investigate whether the kidney represents a viral target in natural MVV infection. For this, kidney samples from 13 sheep naturally infected with MVV were examined by histology, polymerase chain reaction (PCR), and immunohistochemistry. The kidneys of nine animals showed membranoproliferative glomerulonephritis and interstitial nephritis. The inflammatory infiltrate consisted of lymphocytes, plasma cells and macrophages. Interestingly, lymphoid follicles resembling those known to occur in other MVV-infected tissues were observed. Lung tissue from the same animals had typical MVV lesions, such as lymphofollicular hyperplasia and interstitial pneumonia. Maedi-visna proviral DNA sequences were detected in renal and lung tissue samples from these nine sheep by PCR, and the specificity of the amplified products was further verified by DNA sequencing. Moreover, MVV-specific immunohistochemistry revealed viral antigen in affected kidneys and lungs. These results suggest that the kidney may be a common target in natural MVV infection, and raise the issue of the role of this organ in the disease.

Glomerulonephritis in water buffaloes (Bubalus bubalis) naturally infected by Fasciola hepatica

Glomerulonephritis caused by Fasciola hepatica was observed in buffaloes. Renal biopsies of 20 buffaloes, 11 with F. hepatica and 9 uninfected buffaloes (controls), were examined by light microscopy, direct and indirect immunofluorescence, and immunohistochemical analysis. The biopsies of seven (63.6%) infected buffaloes revealed membranoproliferative glomerulonephritis, three biopsies (27.3%) showed mesangioproliferative glomerulonephritis, and one kidney presented normal biopsy specimens. In the control group, seven buffaloes (77.8%) presented normal biopsy specimens, while two (22.2%) revealed glomerulonephritis-one with a membranoproliferative pattern, and the other with a mesangioproliferative pattern-with extensive inflammatory cell infiltrate. Our conclusion is that glomerulopathy is associated with fascioliasis and that buffaloes are suitable as a naturally existing experimental model of renal injury by circulating immune complexes.

Immune complex-associated thrombocytopenic purpura syndrome in sexually mature Göttingen minipigs

Eleven cases of thrombocytopenic purpura (TP) in sexually mature male or female Göttingen minipigs occurred sporadically over 3 1/2 years in a closed breeding colony protected by strict barrier conditions. Typical clinical signs of TP, including extensive subcutaneous haemorrhages, were seen in all affected animals. Haematological abnormalities included marked thrombocytopenia and anaemia. A consistent histopathological finding was the presence of membranoproliferative lesions in the renal glomeruli. Immunohistochemically, glomerular deposits were positively labelled for complement factor C1q and often also for immunoglobulins. Bone marrow findings consisting of increased numbers of immature and apoptotic megakaryocytes were compatible with a state of increased platelet consumption. Based on the combined presence of thrombocytopenia and renal immune complexes, it is suggested that the syndrome was related to a type III hypersensitivity reaction. However, further studies are needed to verify this hypothesis.

Supplementation of heterologous complement induces anti-Thy-1.1 nephritis in the Mongolian gerbil (Meriones unguiculatus)

Anti-Thy-1.1 nephritis in the rat is a popular experimental model for mesangial proliferative glomerulonephritis (GN). This model is characterized by direct binding of anti-Thy-1.1 antibody with Thy-1.1 antigen expressed on mesangial cells (MCs) of glomeruli in the rat. A single injection of anti-rat thymocyte serum (ARTS) results in GN with proteinuria and extensive mesangiolysis. Development of mesangiolysis and proteinuria are complement-dependent. We previously demonstrated Thy-1.1 antigen, similar to the rat, in thymocytes, brain cells and MCs of the kidney in the Mongolian gerbil (MG). In this study, we attempted to develop a MG nephritis model, but an injection of ARTS did not induce GN. An additional injection of guinea pig serum as a complement after ARTS injection resulted in anti-Thy-1.1 nephritis in MG. Degeneration of MCs and neutrophil infiltration were observed 1 hr after GP serum injection. Mesangiolysis and fibrin exudation occurred 12 hr after the injection and MC proliferation was apparent 7 days after the injection. In the complement-dependent hemolytic test, MG serum could not hemolyze sheep erythrocytes. These results suggested low activity, or depletion of some factors, in complements of MG serum.

Atypical membranoproliferative glomerulonephritis in a cat

Membranoproliferative glomerulonephritis was observed in a 2-year-old male Japanese domestic cat with clinical renal failure. In the glomeruli, moderate mesangial hypercellularity with an increased mesangial matrix and thickening of the capillary walls were prominent. In addition, frequent duplication of the capillary walls, splitting, and spike formation were observed in the glomerular basement membrane. Granular cat IgG and complement component deposition were detected globally along the glomerular capillary walls and in the mesangium. Transmission electron microscopy revealed dense deposits in the subendothelial and subepithelial regions and the mesangium. Mesangial interposition was also observed. These glomerular lesions are also found in humans with membranoproliferative glomerulonephritis type III, which has not been reported in animals.

Familial glomerulonephropathy in a litter of beagles

Membranoproliferative glomerulonephropathy was diagnosed in 5 of 7 adult Beagles from the same litter. Dogs were raised in more than 1 area of the United States. One died without evidence of renal disease when it was 3 years old. At 8 years of age, 2 dogs developed signs of uremia, including polyuria, polydipsia, and infrequent episodes of anorexia and vomiting. Serum biochemical variables and urine specific gravity values were consistent with renal azotemia. Both dogs had proteinuria. Although healthy, 3 of the 4 remaining Beagles had proteinuria. Of these 3, only 1 was azotemic. Membranoproliferative glomerulonephritis was diagnosed on the basis of results of histologic examination of renal biopsy specimens from 4 of the dogs. Electron microscopy performed on 3 of the renal biopsy specimens revealed identical lesions, consisting of an extremely thickened glomerular basement membrane with multilaminar splitting. Immunoglobulin or amyloid deposits were not detected. On the basis of similar clinicopathologic abnormalities, common genetic background, and identical histopathologic and electron microscopic findings, familial renal disease was diagnosed. Additional studies involving other related Beagles are needed to identify the hereditary nature of membranoproliferative glomerulonephropathy in Beagles.

Renal pathology in working dogs in the South African National Defence Force

Urine analysis, serum biochemical profile and a cortical wedge biopsy for histopathological examination was performed on 42 South African National Defence Force (SANDF) dogs from around the country. The only significant finding on urine analysis and serum biochemistry was a relatively large number (16/42) of dogs with elevated serum inorganic phosphate levels. Histopathology revealed that only 9 of the animals had normal kidneys reflected in the wedge biopsy material, with over 50% of them showing signs of glomerular pathology (primarily mesangioproliferative glomerulonephritis). Other conditions detected histopathologically were haemosiderosis (47% of animals), focal nephrosis (2.4%), membranoproliferative glomerulonephritis (2.4%), focal interstitial nephritis (4.7%) and acute tubular nephrosis (4.7%). The lesions observed were of limited distribution and extent; this histopathological finding may account for the absence of significant abnormalities on urine analysis or serum biochemistry profiles. It appears from these results that a large percentage of the SANDF population would be expected to have mild renal lesions, but that these lesions are not severe enough to lead to clinical signs. The findings of this study are similar to those of randomly selected populations of non-military dogs performed in other areas of the world, which also demonstrated an unexpectedly high incidence of histopathological renal pathology in dogs considered healthy. These lesions may well, however, play a role in later life, and it is recommended that military veterinarians maintain an index of suspicion for renal disease, particularly glomerular disease. The aetiology of the histopathological lesions is unknown.

Immune-mediated thrombocytopenia associated with Angiostrongylus vasorum infection in a dog

A three-year-old weimaraner was presented with lethargy, anorexia, neck pain and a soft fluctuant swelling in the thoracic inlet. A cough had been noted previously. Clinical examination revealed tachycardia, tachypnoea, pallor and a large subcutaneous swelling, with bruising, suggestive of a haematoma in the thoracic inlet. Thoracic radiographs revealed a cranial mediastinal mass which had the ultrasonographic appearance of fluid, and there was also a marked generalised interstitial lung pattern. Routine haematology revealed severe anaemia and thrombocytopenia, although coagulation tests were within normal limits. A diagnosis of immune-mediated thrombocytopenia was however made on the basis of a positive antiplatelet antibody test and a rapid response to prednisolone therapy. Furthermore, a tentative diagnosis of Angiostrongylus vasorum infection was suggested on the basis of clinical and radiographic findings, although no lungworm larvae were identified on faecal analysis. Despite initiating treatment with fenbendazole, the dog died suddenly. Postmortem examination revealed myocarditis, thrombosing arteritis, pneumonia and chronic membranoproliferative glomerulonephritis associated with A vasorum infection.

Complement regulation

Because of its strong potential for generating inflammation and causing tissue destruction the complement system has to be kept strictly under control. Cells of the host need special protection against the cytolytic complement system. This paper will describe how inappropriate activation of complement in the fluid phase is prevented and how viable human blood cells defend themselves against being destroyed and cleared away by the complement system. Since disturbances in complement regulation occasionally result in disease a brief reference will be made to two of the syndromes caused by complement regulator deficiency, hereditary angioedema (HAE) and paroxysmal nocturnal hemoglobinuria (PNH).

Alteration of anionic sites in renal glomerular basement membrane of pigs

Ultrastructural alteration of anionic sites (ASs) in the glomerular basement membrane (GBM) was studied in 10 cases of swine mesangial proliferative glomerulonephritis using a cationic ultrastructural tracer, 0.5% polyethyleneimine (M.W. = 1,800). Glomerular ASs were seen as discrete electron-dense particles in the GBM, mesangial matrix and epithelial cell surfaces by electron microscopy. In the lamina rara externa (LRE) of the normal GBM, ASs were distributed regularly in a single layer. In those areas of the LRE that contained electron dense deposits or clusters of spherical microparticles (SMPs), however, a distinct reduction or loss of ASs was observed in all the pigs. Quantitative assessment of ASs in the LRE over 1,000 nm of the GBM revealed a significant reduction in ASs in one case with diffuse global thickening of the GBM as compared with the remaining nine pigs without GBM thickening (P < 0.001, Mann-Whitney's U-test). There were no ASs in the lamina densa (LD) of the normal GBM, but an irregular distribution of ASs was seen within the LD of the pig showing diffuse global thickening of the GBM. These results suggest that a disturbance of the charge-selective barrier in the GBM may be induced by electron-dense deposits or SMPs, in the LRE as well as thickening of the GBM in swine glomerulonephritis.

Eradication of porcine factor H deficiency in Norway

In pigs a hereditary deficiency of the complement-inhibitory protein factor H consistently leads to the development of lethal membranoproliferative glomerulonephritis type II. This autosomal recessive disease has been a common cause of early losses of piglets in the Norwegian Yorkshire breed, but has not been reported in the Norwegian Landrace breed. The aim of the present work was to identify carriers of factor H deficiency and to eradicate the disease from commercial pig populations. Factor H in plasma was measured by an enzyme immunoassay. Sixteen known carriers of the disease (parents of factor H-deficient offspring) had half the level of factor H (median 110, range 87 to 156 mg/litre) recorded in 17 homozygous healthy Yorkshire pigs (median 212, range 183 to 293 mg/litre) and 20 Landrace pigs (median 227, range 200 to 255 mg/litre). Factor H analysis in 397 piglets produced by the mating of known carriers revealed an approximately 1:2:1 distribution of individuals with very low, half-normal and normal levels of factor H representing homozygous deficient, heterozygous and homozygous healthy individuals. Thus, carriers could be identified reliably by measuring the plasma concentration of factor H. Most of the population of Norwegian Yorkshire breeding pigs (490 pigs) was therefore examined, and a half-normal factor H level consistent with the carrier state was found in 13.5 per cent. These animals were prevented from breeding and since then no losses of piglets suspected of being due to factor H deficiency have been reported. No carrier was identified among 102 Norwegian Landrace boars, almost excluding the existence of factor H deficiency in this breed.

Porcine membranoproliferative glomerulonephritis type II: an autosomal recessive deficiency of factor H

Hypocomplementaemic hereditary membranoproliferative glomerulonephritis (MPGN) type II is a common cause of the early loss of piglets in the Norwegian Yorkshire breed. The disease is associated with extensive complement activation due to a deficiency of factor H, a plasma protein which regulates complement. To investigate its mode of inheritance, 33 litters were bred from healthy animals associated with the disease, and a total of 385 recorded offspring were produced. The examination of renal tissue from the hypocomplementaemic piglets consistently revealed diagnostic signs of MPGN type II, including thickening of the glomerular capillary wall and proliferation of mesangial cells, dense intramembranous deposits, and massive glomerular deposits of complement component C3 and the terminal complement complex. No such glomerular lesions were detected in 20 normocomplementaemic littermates. The 88 affected piglets were present in 27 litters containing a total of 317 piglets, and there were approximately equal numbers of each sex. Retrospective immunoblot analysis and enzyme immunoassay of plasma samples from the MPGN-affected piglets and their healthy littermates revealed that the affected piglets were deficient in factor H, whereas the healthy piglets were not. It is concluded that porcine factor H deficiency is inherited as a simple autosomal recessive trait with complete penetrance, and consistently results in hypocomplementaemia and lethal membranoproliferative glomerulonephritis type II.

Familial nephropathy in Bernese mountain dogs

Between January 1988 and March 1992 nephropathies were frequently diagnosed in Bernese Mountain Dogs. During this period, 20 animals (16 females, four males), ages 2-5 years (average age at time of diagnosis = 3.3 years) presented with clinically renal insufficiency. Morphologic diagnosis of the renal lesions was identical in all cases, i.e., membranoproliferative glomerulonephritis (MPGN) with concomitant interstitial nephritis. Deposits of immunoglobulin-M (IgM) and of the third complement component were regularly demonstrated immunohistochemically in the glomeruli; deposits of immunoglobulin-A (IgA) and immunoglobulin-G (IgG) were found only in isolated cases. Reduplication of glomerular basement membranes, mesangial interposition, and subendothelial deposits of the immunocomplex type were also detected by electron microscopy. A pedigree analysis indicated that the MPGN in these 20 Bernese Mountain Dogs of approximately the same age was of hereditary genesis. Thus, MPGN should be allocated to the group of familial nephropathies. Serologically, high IgG titers against Borrelia burgdorferi were found in 17 dogs. These findings are discussed in relation to familial nephropathies in humans.

A new familial glomerulonephropathy in Bernese mountain dogs

Between 1989 and 1992, 22 Bernese mountain dogs (18 females and four males) aged between two and seven years, which had been suffering for some weeks from weight loss, anorexia, apathy, vomiting, polydipsia and polyuria, were examined. All of them had high blood urea nitrogen and serum creatinine concentrations, and many had hyperphosphataemia, hypercholesterolaemia, hypoproteinaemia and nonregenerative anaemia. All the dogs had very high protein: creatinine ratios in the urine, and macroproteinuria was identified by sodium dodecyl sulphate gel electrophoresis. The immunofluorescent titres against Borrelia burgdorferi, measured in 19 of the dogs, ranged between 256 and 32,768. In all cases, membrano-proliferative glomerulonephritis with concomitant interstitial nephritis was diagnosed. From an analysis of the dogs' pedigree it was concluded that the glomerulonephritis of these Bernese mountain dogs was inherited as an autosomal recessive trait and that its expression was influenced by a second gene locus with a sex-linked dominance exchange.

Absence of glomerulonephritis in guinea pigs deficient in the fourth component of complement

Genetically determined deficiencies of the early components of the classical complement pathway (C1, C4, C2) or of the third component of complement (C3) in both human beings and experimental animals are known to be associated with renal disease, including glomerulonephritis. The current study was performed to examine the C4-deficient (C4D) guinea pig for the presence of renal disease. Eighteen C4D animals and 17 control animals (Crl:Hartley) (divided by sex into four age categories) were examined. Light microscopic examination revealed no differences in mesangium, glomerular cellularity, thickness of capillary loops, or presence of epithelial crescents in the kidneys of C4D guinea pigs as compared with control animals. Electron microscopic examination did not reveal glomerular or tubular immune complex deposits in either C4D or control animals. C4D guinea pigs apparently do not demonstrate glomerulonephritis.

Porcine membranoproliferative glomerulonephritis with intramembranous dense deposits (porcine dense deposit disease)

A membranoproliferative glomerulonephritis (MPGN) was diagnosed in 10 Yorkshire piglets, aged between 33 and 73 days, that had been submitted for routine autopsy. Matings of animals related to these piglets subsequently produced 15 offspring that had a membranoproliferative glomerulonephritis when examined at between 5 and 48 days of age. The principal light microscopic changes in all examined glomeruli of all affected piglets were thickening of the glomerular capillary walls and a conspicuous mesangial cell proliferation. The glomerular capillary walls of the affected piglets possessed a weak but distinct autofluorescence when stained with thioflavine T and a strong reactivity for complement factor 3 as demonstrated with immunohistochemical techniques. Ultrastructural examination revealed intramembranous dense deposits in the glomerular basement membranes of kidneys from all affected piglets. On the basis of the initial matings and the morphological observations, it is concluded that the described MPGN in Yorkshire piglets represents an inherited renal disease that is comparable to human MPGN type II-dense deposit disease.

Canine IgA glomerulonephropathy

Three young intact male dogs housed together in a canine blood donor facility developed immune complex glomerulonephropathy within 2 years of each other. All three had membranoproliferative glomerulonephritis with varying clinical presentation and progression. Two dogs had subendothelial, and one dog subepithelial, electron microscopic dense deposits. Immunoperoxidase staining indicated that the primary antibody involved in the glomerular disease of these three dogs was IgA. The nature of the electron dense deposits was further studied by eluting and identifying immunoglobulin from affected kidneys of one dog. The primary antibody identified had a molecular weight greater than 300,000 Da and was determined to be IgA. Although IgA glomerulonephropathy is a common cause of glomerular disease in humans, this study represents the first documentation of the clinical syndrome of IgA glomerulonephropathy in the dog.

Mesangioproliferative glomerulonephritis in mink with encephalitozoonosis

Renal specimens from 6 mink with encephalitozoonosis were studied by light and electron microscopy and immunohistochemistry. The glomeruli of affected kidneys had a mesangioproliferative glomerulonephritis which was characterized by an increase in mesangial cells and matrix in most glomeruli. Some glomeruli were partially or completely sclerosed. There were protein or granular casts in the cortical and medullary tubules. Interstitial nephritis, vasculitis and tubular cysts were found. Electron microscopy demonstrated extensive matrix and increased cellularity in the mesangial areas. Glomeruli showed segmentally thickened or wrinkled capillary basement membranes. Electron dense deposits were found in the glomerular basement membranes and mesangium. Peroxidase-anti-peroxidase immunohistochemistry demonstrated that IgG and IgM positive material was present as granular deposits in the glomerular basement membrane and occasionally in the mesangium.

Treatment of membranoproliferative glomerulonephritis and nephrotic syndrome in a dog with a thromboxane synthetase inhibitor

A 2-year-old spayed female Whippet with membranoproliferative glomerulonephritis and nephrotic syndrome was treated with a specific thromboxane synthetase inhibitor (3-methyl-2[3-pyridyl]-1-indoleoctanoic acid), resulting in decreased proteinuria and resolution of ascites and edema. Glomerular histology, however, appeared unaffected by treatment. Discontinuation of treatment for 10 weeks resulted in increased proteinuria and decreased serum albumin concentrations that were again attenuated when treatment was reinitiated. Thromboxane synthetase inhibitors have been used successfully to treat experimentally induced glomerulonephritis in several species and this treatment appears to hold promise for naturally occurring glomerulonephritis in dogs.

Ovine mesangiocapillary glomerulonephritis type I and crescent formation

Morphologic examination of four Finnish Landrace mixed-breed lambs, 27 to 35 days of age, affected with mesangiocapillary glomerulonephritis type 1, demonstrated a progressive glomerulonephritis. By 27 days of age, three lambs had crescents in 58 to 93% of glomeruli. These three lambs were also uremic. The accelerated rate of crescent formation was attributed to infiltrating polymorphonuclear leukocytes and monocytes, the result of discontinuities (gaps) in the glomerular basement membrane, and to the loss of the integrity of Bowman's capsule. In the three lambs, platelets were identified adjacent to the endothelium or denuded glomerular basement membrane. Two distinctly different types of crescents were noted, apparently dependent on the integrity of Bowman's capsule. One type resulted from the influx of inflammatory cells and dissociation of parietal epithelial cells from Bowman's capsule. The other type was more extensive and contained collagen and was associated with damage to Bowman's capsule resulting in cellular infiltration from the interstitium and sclerosis. Based on morphologic similarities, ovine mesangiocapillary glomerulonephritis is a suitable model for studying the pathogenesis and treatment of mesangiocapillary glomerulonephritis type 1 in human beings.

Analysis of renal immune-deposits in canine leishmaniasis. Preliminary results

Previous studies carried out on 34 dogs spontaneously infected by Leishmania infantum showed the presence of kidney lesions characterized by immunologically mediated glomerular and tubular damage. Glomerular immune-deposits were studied in 13 of these dogs. Immunoglobulins were isolated from kidney tissues by acid elution; IgG fractions from eluates, obtained by ammonium sulfate precipitation, were subjected to clonotypic analysis by autoradiography after isoelectrofocusing (IEF) using 125I radiolabelled goat IgG fraction-anti Fab2 of dog IgG. Idiotypic characterization of IgG eluted from kidney tissues was performed by IEF and autoradiography using both 125I radiolabelled membrane antigens of L. infantum extracted by Triton x 100 and 125I radiolabelled dog IgG for rheumatoid or anti-idiotypic activity. The IgG deposited in the kidney tissues of examined dogs were polyclonal and a specific activity against Leishmania membrane antigens was revealed. Meanwhile an anti-IgG activity of deposited immunoglobulins was not observed.

[Electron microscopic structure of mesangioproliferative glomerulonephritis (MesPGN) in animals]

In a murine lupus model, the kidneys of 42 MRL mice of different age groups (substrains MRL/Mp-lpr/lp and -+/+) were studied by light and transmission electron microscopy. The results demonstrate the ultrastructural feature of the mesangial-proliferative glomerulonephritis which is one of the observed forms of glomerulonephritis. The most important alterations are a severe proliferation of mesangial cells (with an increase in rough endoplasmic reticulum and mitochondria) and electron dense deposits in different sites of the glomerular basement membrane (subepithelial, subendothelial, intramembranous). These deposits are proposed to be immune complexes. Osmiophilic intracytoplasmic inclusions of the mesangial cells are indications of an altered renin production. Alterations of the glomerular epithelial cells are characterized by fusions of the epithelial pedicles, an increase of microvilli and intracytoplasmic concentrations of electron dense material which are also proposed to be immune complex deposits. The morphological feature of the mesangial-proliferative glomerulonephritis is completed by an activation and focal edema of endothelial cells. The described alterations are discussed and compared with findings in other species.