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Biomedical subjects

A N Hamir

Publications and source records attributed to A N Hamir.

At least 19 recordsLinked to original sources
PubMed2006

Experimental second passage of chronic wasting disease (CWD(mule deer)) agent to cattle.

To compare clinicopathological findings in first and second passage chronic wasting disease (CWD(mule deer)) in cattle, six calves were inoculated intracerebrally with brain tissue derived from a first-passage CWD-affected calf in an earlier experiment. Two uninoculated calves served as controls. The inoculated animals began to lose both appetite and weight 10-12 months later, and five subsequently developed clinical signs of central nervous system (CNS) abnormality. By 16.5 months, all cattle had been subjected to euthanasia because of poor prognosis. None of the animals showed microscopical lesions of spongiform encephalopathy (SE) but PrP(res) was detected in their CNS tissues by immunohistochemistry (IHC) and rapid Western blot (WB) techniques. Thus, intracerebrally inoculated cattle not only amplified CWD PrP(res) from mule deer but also developed clinical CNS signs in the absence of SE lesions. This situation has also been shown to occur in cattle inoculated with the scrapie agent. The study confirmed that the diagnostic techniques currently used for diagnosis of bovine spongiform encephalopathy (BSE) in the US would detect CWD in cattle, should it occur naturally. Furthermore, it raised the possibility of distinguishing CWD from BSE in cattle, due to the absence of neuropathological lesions and to a distinctive multifocal distribution of PrP(res), as demonstrated by IHC which, in this study, appeared to be more sensitive than the WB technique.

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PubMed2006

First and second cattle passage of transmissible mink encephalopathy by intracerebral inoculation.

To compare clinicopathologic findings of transmissible mink encephalopathy (TME) with other transmissible spongiform encephalopathies (TSE, prion diseases) that have been shown to be experimentally transmissible to cattle (sheep scrapie and chronic wasting disease [CWD]), two groups of calves (n = 4 each) were intracerebrally inoculated with TME agents from two different sources (mink with TME and a steer with TME). Two uninoculated calves served as controls. Within 15.3 months postinoculation, all animals from both inoculated groups developed clinical signs of central nervous system (CNS) abnormality; their CNS tissues had microscopic spongiform encephalopathy (SE); and abnormal prion protein (PrP(res)) as detected in their CNS tissues by immunohistochemistry (IHC) and Western blot (WB) techniques. These findings demonstrate that intracerebrally inoculated cattle not only amplify TME PrP(res) but also develop clinical CNS signs and extensive lesions of SE. The latter has not been shown with other TSE agents (scrapie and CWD) similarly inoculated into cattle. The findings also suggest that the diagnostic techniques currently used for confirmation of bovine spongiform encephalopathy (BSE) would detect TME in cattle should it occur naturally. However, it would be a diagnostic challenge to differentiate TME in cattle from BSE by clinical signs, neuropathology, or the presence of PrP(res) by IHC and WB.

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PubMed2006

Abnormal prion protein in ectopic lymphoid tissue in a kidney of an asymptomatic white-tailed deer experimentally inoculated with the agent of chronic wasting disease.

Chronic wasting disease (CWD), a transmissible spongiform encephalopathy (TSE) of deer and elk, is one of a group of fatal, neurologic diseases that affect several mammalian species, including human beings. Infection by the causative agent induces accumulations of an abnormal form of prion protein (PrPres) in nervous and lymphoid tissues. This report documents the presence of PrPres within ectopic lymphoid follicles in a kidney of a white-tailed deer that had been experimentally inoculated by the intracerebral route with CWD 10 months previously. The deer was nonclinical, but spongiform lesions characteristic of TSE were detected in tissues of the central nervous system (CNS) and PrPres was seen in CNS and in lymphoid tissues by immunohistochemistry. The demonstration of PrPres in lymphoid tissue in the kidney of this deer corroborates a recently published finding of PrPres in lymphoid follicles of organs other than CNS and lymphoid tissues in laboratory animals with TSE (scrapie).

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PubMed2006

Abnormal prion accumulation associated with retinal pathology in experimentally inoculated scrapie-affected sheep.

The purpose of this study was to characterize the patterns of PrP(Sc) immunoreactivity in the retinae of scrapie-affected sheep and to determine the extent of retinal pathology as indicated by glial fibrillary acidic protein immunoreactivity (GFAP-IR) of Müller glia. Sections from the retina of 13 experimentally inoculated scrapie-affected and 2 negative control sheep were examined with immunohistochemical staining for PrP(Sc), GFAP, and PrP(Sc)/GFAP double staining. GFAP-IR of Müller glia is suggestive of retinal pathology in the absence of morphologic abnormality detected by light microscopy. Sheep with the least amount of PrP(Sc) in the retina have multifocal punctate aggregates of prion staining in the outer half of the inner plexiform layer and rarely in the outer plexiform layer. In these retinae, GFAP-IR is not localized with prion accumulation, but rather is present in moderate numbers of Müller glia throughout the sections of retina examined. The majority of sheep with retinal accumulation of PrP(Sc) have intense, diffuse PrP(Sc) staining in both plexiform layers, with immunoreactivity in the cytoplasm of multiple ganglion cells and lesser amounts in the optic fiber layer and between nuclei in nuclear layers. This intense PrP(Sc) immunoreactivity is associated with diffuse, intense GFAP-IR that extends from the inner limiting membrane to the outer limiting membrane. This is the first report of a prion disease in a natural host that describes the accumulation of PrP(Sc) in retina associated with retinal pathology in the absence of overt morphologic changes indicative of retinal degeneration.

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PubMed2006

Acute fatal toxoplasmosis in squirrels (Sciurus carolensis) with bradyzoites in visceral tissues.

Acute toxoplasmosis was diagnosed in 3 gray squirrels (Sciurus carolensis) from Louisiana and Pennsylvania. The predominant lesion was multifocal necrosis in several organs, especially of the lymph nodes. Numerous Toxoplasma gondii tachyzoites were seen in lesions, and the diagnosis was confirmed immunohistochemically by reaction with polyclonal T. gondii-specific antibodies. Tissue cysts were seen in several organs, including lung alveoli. The presence of tissue cysts in alveoli of pet squirrels maybe of public health concern if tissue cysts excreted in nasal secretions are swallowed by children.

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PubMed2005

Second passage of sheep scrapie and transmissible mink encephalopathy (TME) agents in raccoons (Procyon lotor).

To determine the transmissibility and pathogenicity of sheep scrapie and transmissible mink encephalopathy (TME) agents derived from raccoons (first passage), raccoon kits were inoculated intracerebrally with either TME (one source) or scrapie (two sources-each in separate groups of raccoons). Two uninoculated raccoon kits served as controls. All animals in the TME-inoculated group developed clinical signs of neurologic dysfunction and were euthanatized between postinoculation month (PIM) 6 and 8. Raccoons in the two scrapie-inoculated groups manifested similar clinical signs of disease, but such signs were observed much later and the animals were euthanized between PIM 12 and 18. Necropsy revealed no gross lesions in any of the raccoons. Spongiform encephalopathy was observed by use of light microscopy, and the presence of protease-resistant prion protein (PrPres) was detected by use of immunohistochemical (IHC) and Western blot analytic techniques. Results of IHC analysis indicated a distinct pattern of anatomic distribution of PrPres in the TME- and scrapie-inoculated raccoons. These findings confirm that TME and sheep scrapie are experimentally transmissible to raccoons and that the incubation periods and IHC distribution for both agents are distinct. Therefore, it may be possible to use raccoons for differentiating unknown transmissible spongiform encephalopathy (TSE) agents. Further studies, with regard to the incubation period and the pattern of PrPres deposition by use of IHC analysis in bovine spongiform encephalopathy and for other isolates of scrapie, chronic wasting disease, and TME in raccoons are needed before the model can be further characterized for differentiation of TSE agents.

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PubMed2004

Failure to detect prion protein (PrPres) by immunohistochemistry in striated muscle tissues of animals experimentally inoculated with agents of transmissible spongiform encephalopathy.

Transmissible spongiform encephalopathies (TSEs) are fatal neurologic diseases. Infection by the causative agent, a prion, induces accumulations of an abnormal form of prion protein (PrP(res)) in tissues of nervous and lymphoid systems. Presence of characteristic histopathologic changes (spongiform encephalopathy) and detection of protease-resistant PrP(res) in neural and lymphoid tissues are the basis of currently available methods for diagnosis of TSEs. In this study, samples of striated muscle tissues (tongue, heart, diaphragm, and masseter muscle) from 20 animals (cattle, sheep, elk, and raccoons) were examined for PrP(res) by immunohistochemistry (IHC). All the animals had developed a TSE after experimental inoculation. PrP(res) was found by IHC in the brain but not in the muscle tissues of all the animals examined. These findings are contradictory to recently published reports of laboratory animals with TSEs, where these altered prion proteins were detected in tongue and other striated muscles. Further testing of muscle tissues is needed to confirm the findings of the present study.

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PubMed2003

Preliminary observations on the experimental transmission of scrapie to elk (Cervus elaphus nelsoni) by intracerebral inoculation.

To determine the transmissibility of scrapie to Rocky Mountain elk (Cervus elaphus nelsoni), six elk calves were inoculated intracerebrally with brain suspension from sheep naturally affected with scrapie. One elk developed a brain abscess and was euthanatized at 7 weeks postinoculation (PI), and two others died at 6 and 15 months PI because of physical injuries. At 25 and 35 months PI, two other elk died after brief terminal neurologic episodes. Necropsy of these revealed moderate weight loss but no other gross lesions. Microscopically, characteristic lesions of spongiform encephalopathy were seen throughout the brains and the spinal cords, and in both cases these tissues were positive for PrP(res) by immunohistochemistry. Brains of both animals were positive for PrP(res) by western blot and for scrapie-associated fibrils (SAFs) by negative stain electron microscopy. PrP(res) and SAFs were not detected in the three elk that died or were euthanatized because of coincidental causes. Over 3.5 years after initiation of this experiment, the one remaining inoculated elk and two uninoculated (control) elk are alive and apparently healthy. These preliminary findings demonstrate that 1) sheep scrapie agent can be transmitted to elk by intracerebral inoculation; 2) the infection can result in severe, widely distributed spongiform change and accumulations of PrP(res) in the central nervous system (CNS); and 3) based on the examination of a limited number of CNS sections from two cases, this condition cannot be distinguished from chronic wasting disease with currently available diagnostic techniques.

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PubMed2002

Severe biliary hyperplasia associated with liver fluke infection in an adult alpaca.

An adult alpaca (Lama pacos) had a locally extensive area of hepatic atrophy involving the right lobe. Grossly, the atrophic lobe was light tan and firm and contained small, raised, white to yellow, partially mineralized circular nodules predominantly at the periphery of the atrophic tissue. Microscopically, viable hepatocytes were not present in the atrophic area, and the tissue consisted of diffuse biliary epithelial proliferation without any evidence of nuclear or cellular atypia or the presence of mitotic figures. The circular mineralized nodules consisted of granulomatous inflammation with intralesional parasitic ova surrounded by fibrous connective tissue. Morphologically, the ova were compatible with those of Fasciola hepatica. The severe biliary hyperplasia was unusual, and it was not clear whether it was caused by an aberrant host response to the parasitic infection or whether it was an unrelated event.

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PubMed2002

Sarcocystis mephitisi n. sp. (Protozoa: Sarcocystidae), Sarcocystis neurona-like and Toxoplasma-like infections in striped skunks (Mephitis mephitis).

Two structurally distinct types (A, B) of microscopic sarcocysts were found in muscles of 4 of 5 feral skunks. Type A sarcocysts had sarcocyst walls of up to 6 microm thick. The villar protrusions (Vp) on the sarcocyst wall were up to 5 microm long. The Vp were constricted at the base, expanded in the middle, and had a blunt tip. Numerous microtubules were present in the Vp and in the granular layer. Bradyzoites were up to 11 microm long and up to 3.2 microm wide. Based on the distinctiveness of the Vp, a new name, Sarcocystis mephitisi is proposed for type A sarcocysts. Type B sarcocysts had a relatively thin (approximately 1-2 microm thick) sarcocyst wall and the Vp were slender and tapered toward the tip. These sarcocysts were structurally similar to S. neurona sarcocysts. A Toxoplasma gondii-like tissue cyst was found in a section of tongue of 1 of the 4 skunks.

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PubMed2002

Experimental toxoplasmosis in budgerigars (Melopsittacus undulatus).

The susceptibility of budgerigars (Melopsittacus undulatus) to graded doses of Toxoplasma gondii oocysts was studied. Sixteen budgerigars were divided into 4 groups (A-D) of 4 each. Birds in groups A-C were fed 100,000, 1,000, or 100 infective oocysts of the VEG strain of T. gondii, respectively. Budgerigars in group D were not fed oocysts and served as controls. All 4 birds in group A died (or were killed) because of acute severe enteritis 5 or 6 days after feeding oocysts (DAFO). Three of the 4 birds in group B were killed (or died) because of toxoplasmosis 9 or 14 DAFO. One budgerigar in group C and the 4 budgerigars in group D remained healthy and were killed 35 or 39 DAFO. Toxoplasma gondii was demonstrated in tissues of all budgerigars fed oocysts. The control budgerigars remained clinically normal and showed no evidence of T. gondii exposure. These results indicate that, compared to other passerines, budgerigars are relatively resistant to clinical toxoplasmosis.

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PubMed2001

Sarcocystis neurona infections in raccoons (Procyon lotor): evidence for natural infection with sarcocysts, transmission of infection to opossums (Didelphis virginiana), and experimental induction of neurologic disease in raccoons.

Equine protozoal myeloencephalitis (EPM) is a serious neurologic disease of horses in the Americas and Sarcocystis neurona is the most common etiologic agent. The distribution of S. neurona infections follows the geographical distributions of its definitive hosts, opossums (Didelphis virginiana, Didelphis albiventris). Recently, cats and skunks were reported as experimental and armadillos as natural intermediate hosts of S. neurona. In the present report, raccoons (Procyon lotor) were identified as a natural intermediate host of S. neurona. Two laboratory-raised opossums were found to shed S. neurona-like sporocysts after ingesting tongues of naturally-infected raccoons. Interferon-gamma gene knockout (KO) mice fed raccoon-opossum-derived sporocysts developed neurologic signs. S. neurona was identified immunohistochemically in tissues of KO mice fed sporocysts and the parasite was isolated in cell cultures inoculated with infected KO mouse tissues. The DNA obtained from the tongue of a naturally-infected raccoon, brains of KO mice that had neurological signs, and from the organisms recovered in cell cultures inoculated with brains of neurologic KO mice, corresponded to that of S. neurona. Two raccoons fed mature S. neurona sarcocysts did not shed sporocysts in their feces, indicating raccoons are not likely to be its definitive host. Two raccoons fed sporocysts from opossum feces developed clinical illness and S. neurona-associated encephalomyelitis was found in raccoons killed 14 and 22 days after feeding sporocysts; schizonts and merozoites were seen in encephalitic lesions.

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PubMed2001

Characteristics of a recent isolate of Sarcocystis neurona (SN7) from a horse and loss of pathogenicity of isolates SN6 and SN7 by passages in cell culture.

An isolate of Sarcocystis neurona (SN7) was obtained from the spinal cord of a horse with neurologic signs. The parasite was isolated in cultures of bovine monocytes and equine spleen cells. The organism divided by endopolygeny and completed at least one asexual cycle in cell cultures in 3 days. The parasite was maintained by subpassages in bovine monocytes for 10 months when it was found to be non-pathogenic to gamma interferon knockout (KO) mice. Revival of a low passage (10th passage) of the initial isolate stored in liquid nitrogen for 18 months retained its pathogenicity for KO mice. Merozoites (10(6)) of the late passage (22nd passage) were infective to only one of four KO mice inoculated. Similar results were obtained with SN6 isolate of S. neurona. No differences were found in Western blot patterns using antigens from the low and high passage merozoites of the SN7 and SN6 isolates. These results suggest that prolonged passage in cell culture may affect the pathogenicity of some isolates of S. neurona.

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