Glial fibrillary acidic protein and cartilage

Assessment of glial fibrillary acidic protein and anti-glial fibrillary acidic protein autoantibody concentrations and necrotising meningoencephalitis risk genotype in dogs with pug dog myelopathy

BACKGROUND

Pugs commonly present with thoracolumbar myelopathy, also known as pug dog myelopathy (PDM), which is clinically characterised by progressive signs involving the pelvic limbs, no apparent signs of pain and, often, incontinence. In addition to meningeal fibrosis and focal spinal cord destruction, histopathology has confirmed lymphohistiocytic infiltrates in the central nervous system (CNS) in a considerable number of pugs with PDM. Lymphohistiocytic CNS inflammation also characterises necrotising meningoencephalitis (NME) in pugs. This study aimed to investigate the potential contribution of an immunological aetiology to the development of PDM.

METHODS

The concentrations of glial fibrillary acidic protein (GFAP) in serum and CSF and of anti-GFAP autoantibodies in CSF were measured with an ELISA. In addition, a commercial test was used for genetic characterisation of the dog leukocyte antigen class II haplotype, which is associated with NME susceptibility.

RESULTS

This study included 87 dogs: 52 PDM pugs, 14 control pugs, four NME pugs and 17 dogs of breeds other than pugs that were investigated for neurological disease (neuro controls). Anti-GFAP autoantibodies were present in 15 of 19 (79%) of the PDM pugs tested versus six of 16 (38%) of the neuro controls tested (p = 0.018). All 18 PDM pugs evaluated had detectable CSF GFAP. Serum GFAP was detected in two of three (67%) of the NME pugs and in two of 11 (18%) of the control pugs but not in any of the 40 tested PDM pugs. Male pugs heterozygous for the NME risk haplotype had an earlier onset of clinical signs (70 months) compared to male pugs without the risk haplotype (78 months) (p = 0.036).

LIMITATIONS

The study was limited by the lack of healthy dogs of breeds other than pugs and the small numbers of control pugs and pugs with NME.

CONCLUSIONS

The high proportion of PDM pugs with anti-GFAP autoantibodies and high CSF GFAP concentrations provide support for a potential immunological contribution to the development of PDM.

Glial fibrillary acidic protein in tumor types with cartilaginous differentiation

Glial fibrillary acidic protein (GFAP) is a member of the intermediary filament protein family. It is an important component of astrocytes and a known diagnostic marker of glial differentiation. GFAP is expressed in other neural tumors and pleomorphic adenoma and, less frequently, in cartilage tumors, chordomas, and soft tissue myoepitheliomas. The aim of this study was to evaluate the role of GFAP and its reliability in nonglial tumors as an immunohistochemical marker. We evaluated GFAP gene and protein expression using Q-PCR and immunohistochemistry, respectively, in 81 and 387 cases of soft tissue, bone tumors, and salivary pleomorphic adenomas. Immunohistochemistry staining for GFAP was observed in all osteosarcomas (8 cases), all pleomorphic adenomas (7 cases), in 5 of 6 soft tissue myoepitheliomas, and in 21 of 76 chondrosarcomas. By Q-PCR, GFAP was highly expressed in pleomorphic adenomas and, to a lesser extent, chondrosarcomas, soft tissue myoepitheliomas, and chondroblastic osteosarcomas. The results that we obtained by immunohistochemistry and Q-PCR were well correlated. GFAP is a potential marker for tumors with cartilaginous differentiation, supported by evidence that GFAP is expressed in certain cases of myoepithelial tumors by immunohistochemistry, including soft tissue myoepitheliomas, which are related to cartilaginous differentiation. These findings contribute significantly to the diagnosis of soft tissue myoepitheliomas with cartilaginous differentiation and chondroblastic osteosarcoma in mesenchymal tumors.

Hyperammonemia in urea cycle disorders: role of the nephrologist

Hyperammonemia associated with inherited disorders of amino acid and organic acid metabolism is usually manifested by irritability, somnolence, vomiting, seizures, and coma. Although the majority of these patients present in the newborn period, they may also present in childhood, adolescence, and adulthood with failure to thrive, persistent vomiting, developmental delay, or behavioral changes. Persistent hyperammonemia, if not treated rapidly, may cause irreversible neuronal damage. After the diagnosis of hyperammonemia is established in an acutely ill patient, certain diagnostic tests should be performed to differentiate between urea cycle defects and other causes of hyperammonemic encephalopathy. In a patient with a presumed inherited metabolic disorder, the aim of therapy should be to normalize blood ammonia levels. Recent experience has provided treatment guidelines that include minimizing endogenous ammonia production and protein catabolism, restricting nitrogen intake, administering substrates of the urea cycle, administering compounds that facilitate the removal of ammonia through alternative pathways, and, in severe cases, dialysis therapy. Initiation of dialysis in the encephalopathic patient with hyperammonemia is indicated if the ammonia blood level is greater than three to four times the upper limit of normal. Hemodialysis is the most effective treatment for rapidly reducing blood ammonia levels. Continuous hemofiltration and peritoneal dialysis are also effective modalities for reducing blood ammonia levels. An improved understanding of the metabolism of ammonia and neurological consequences of hyperammonemia will assist the nephrologist in providing optimal care for this high-risk patient population.

Histochemistry and immunocytochemistry of the developing ependyma and choroid plexus

The adult human ependyma expresses no intermediate filament proteins or secretory proteins; the fetal ependyma shows strong immunocytochemical (ICC) expression of vimentin, glial fibrillary acidic protein (GFAP), cytokeratins (CKs) of high molecular weight, glycoproteins, and S-100beta protein. Each has a precise and specific spatial distribution within the developing ependyma and a predictable time of appearance and regression in each region of the ventricular system. Several are coexpressed, but some appear earlier or persist longer than others. Secretory proteins of ependymal cells are important in several developmental processes such as the guidance of axonal growth cones. GFAP is not expressed in the floor plate ependyma at any stage of development, unlike vimentin and CK. The choroid plexus epithelium is a specialized ependyma, with an ICC profile that differs from the surface ependyma: vimentin, CK, and S-100beta protein continue to be expressed throughout fetal and adult life, but GFAP is not expressed. Certain cerebral malformations are associated with specific ICC abnormalities: ependymal S-100beta protein continues to be immunoreactive in disorders of neuroblast migration; ependymal vimentin is focally upregulated in Chiari malformations and congenital aqueductal stenosis. Other mammalian and nonmammalian species have characteristic profiles of ependymal immunoreactivity to the same proteins expressed in humans but exhibit interspecific differences.

Glial fibrillary acidic protein immunoreactivity in adrenocortical and Leydig cells of the Syrian golden hamster (Mesocricetus auratus)

In an immunocytochemical investigation of the expression of glial fibrillary acidic protein (GFAP) in non-nervous system tissues ten anti-GFAP antibodies were used on a range of normal adult organs from different species. All four polyclonal and six monoclonal antibodies revealed the expression of GFAP in cells of the zona fasciculata and reticularis of the adrenal cortex and Leydig cells of the Syrian hamster. The Chinese hamster, mole, rat, mouse, guinea pig, rabbit, pig, duck and man were negative. Co-expression of immunoreactivity for GFAP and vimentin was observed in adrenocortical and Leydig cells of the Syrian hamster but there were differences in the staining patterns of these intermediate filament proteins. Expression of GFAP in adrenal cortex of Syrian hamster is confirmed by immunoblot and limited proteolysis analysis which reveal a light form which is immunochemically indistinguishable from its counterpart in the central nervous system. The results presented here suggest a new model for the study of the possible role of GFAP expression in cells known to be sites of steroid synthesis.

Primary intracerebral osteosarcoma

A 64-year-old man was admitted because of a rapidly progressive left side hemiparesis. A computed tomography scan showed a right side intrathalamic mass, partially calcified. Surgical specimen proved to be an osteosarcoma. The patient died 3 days later from an acute myocardial infarct. Autopsy failed to discover any other significant lesion. A review of the literature disclosed that this case might be the second published primary intracerebral osteosarcoma and the first with immunocytochemical analysis.