Perivascular Location Research Articles

Expression of toll-like receptor 4 and its associated lipopolysaccharide receptor complex by resident antigen-presenting cells in the human uvea.

To investigate the in vivo expression of toll-like receptor 4 (TLR4) and its associated lipopolysaccharide (LPS) receptor complex in the human eye. Normal human ocular tissues were evaluated for in vivo TLR4, MD-2, and CD14 mRNA and protein expression by RT-PCR and immunohistochemistry, respectively. The distribution patterns and phenotypes of the cells expressing these proteins were further characterized by confocal microscopy and double-label immunofluorescence studies. Normal human uvea, retina, sclera, and conjunctiva constitutively expressed TLR4, MD-2, and CD14 mRNA. The protein expression of these molecules was restricted, however, to resident antigen-presenting cells (APCs) in the normal human uvea, consisting mainly of HLA-DR(+) dendritic cells (DCs). These APCs endowed with the complete LPS receptor complex appeared to be strategically positioned in perivascular and subepithelial locations for surveying blood-borne or intraocular LPS. In contrast, other cell types of the normal human cornea, conjunctiva, retina, and sclera did not express TLR4/MD-2 protein in vivo as detectable by immunohistochemistry. The present study demonstrates for the first time that resident APCs in the normal human uvea express TLR4 and its associated LPS receptor complex. This has significant implications for the understanding of normal ocular immunity as well as unraveling the potential role of Gram-negative bacteria in the pathogenesis of acute anterior uveitis (AAU).

Normolipemic plane xanthoma associated with adenocarcinoma and severe itch

Normolipemic plane xanthomas are yellow-red-colored flat patches or plaques with barely palpable borders, under normolipemic conditions usually involving the eyelids, the lateral sides of the neck, the upper aspect of the trunk, or the flexural folds. Histologically the lesions are characterized by an infiltrate consisting of foamy macrophages in the papillary and middermis with a distinct perivascular localization. Plane xanthoma has been associated with monoclonal gammopathy, cryoglobulinemia, and myeloproliferative disorders. We present a patient in whom plane xanthoma developed on the upper aspect of the back, which was accompanied by severe itch in the affected area. These symptoms started 1 month after resection of an adenocarcinoma of the rectum that was complicated by recurrent abdominal abscesses and, currently, by ongoing inflammatory bowel disease. A hypothetic pathophysiologic scheme of events leading to xanthoma formation in this patient is presented. (J Am Acad Dermatol 2003;49:119-22.)

Origin and turnover of microglial cells in fibrillar plaques of APPsw transgenic mice.

Activated microglial cells are an integral component of fibrillar plaques in brains of subjects with Alzheimer's disease (AD) and in brains of transgenic mice overexpressing amyloidogenic fragments of human amyloid precursor protein (APP). The aim of this ultrastructural study of fibrillar plaques was to characterize the origin of microglial cells involved in cored plaque formation. Computer-aided three-dimensional reconstruction of plaques and microvessels in APPsw transgenic mice shows perivascular development of cored plaques. Perivascular location of almost all examined plaques and the infiltration at the interface between vessels and plaques with cells of monocyte/microglia lineage indicates that plaques are formed by inflammatory cells of blood origin. The increase in the number of microglial cells from 1 or 2 in an early plaque to more than 100 in a several-month-old plaque does not result in plaque degradation, but is associated with amyloid core growth and progression of neuronal degeneration, and suggests that recruitment of inflammatory cells of blood origin sustains plaque growth. Infiltration of the plaque with cells of blood origin and degeneration of 10-46% of inflammatory cells in large plaques, which is especially frequent at the interface between capillary wall and plaque, suggest their accelerated turnover.

Human bone marrow angiogenesis: in vitro modulation by substance P and neurokinin A.

We have previously described a culture system for human bone marrow endothelial cells that organize into capillary tubes associated to pericytes. In the present work, we used this model to assess the angiogenic properties of tachykinins, which have been demonstrated to be involved in neuro-immuno-haematopoietic interactions. The substance P (SP) and neurokinin A (NKA) were similarly potent at increasing in vitro angiogenesis, via NK1 and NK2 receptors respectively. These mediators were not produced by cells in culture, suggesting that in vivo they may be released by nerve fibres in the bone marrow. Therefore, we looked for in situ innervation of the human bone marrow, unknown to date, using immunohistochemistry techniques. As in rodents, arterioles were largely innervated, associated with between one and 10 nerve fibres. Capillary innervation was more restrictive as a unique thin nerve fibre was found in the vicinity of only 6% of these vessels. Finally, no nerve fibres were observed in the vicinity of sinus walls. In conclusion, both in vitro results and the anatomical display of nerve fibres suggest a role in human bone marrow for the vasoactive neuropeptides SP and NKA, which were secreted into a perivascular location. These neural mediators might modulate blood flow in the bone marrow both in the short term by adjusting vascular tone and in the long term by inducing angiogenesis.

Immunization with a cannabinoid receptor type 1 peptide results in experimental allergic meningocerebellitis in the Lewis rat: a model for cell-mediated autoimmune neuropathology.

Neuronal elements are increasingly suggested as primary targets of an autoimmune attack in certain neurological and neuropsychiatric diseases. Type 1 cannabinoid receptors (CB1) were selected as autoimmune targets because they are predominantly expressed on neuronal surfaces in brain and display strikingly high protein levels in striatum, hippocampus, and cerebellum. Female Lewis rats were immunized with N-terminally acetylated peptides (50 or 400 microg per rat) of the extracellular domains of the rat CB1 and killed at various time points. Subsequent evaluation using immunohistochemistry and in situ hybridization showed dense infiltration of immune cells exclusively within the cerebellum, peaking 12-16 days after immunization with the CB1 peptide containing amino acids 9-25. The infiltrates clustered in meninges and perivascular locations in molecular and granular cell layers and were also scattered throughout the CB1-rich neuropil. They consisted primarily of CD4(+) and ED1(+) cells, suggestive of cell-mediated autoimmune pathology. There were no inflammatory infiltrates elsewhere in the brain or spinal cord. The results show that neuronal elements, such as neuronal cell-surface receptors, may be recognized as antigenic targets in a cell-mediated autoimmune attack and, therefore, support the hypothesis of cell-mediated antineuronal autoimmune pathology in certain brain disorders.

Th1, Th2 and Th3 cytokines in the pathogenesis of bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune bullous skin disease mediated by autoantibodies against hemidesmosomal proteins. In addition to humoral immunity, the contribute of infiltrating T-helper (Th) autoreactive lymphocytes and their related cytokines to the pathomechanism of blistering is now growing in interest. To investigate T-cell activation markers and the presence of inflammatory and fibrogenic cytokines (i.e. IL2, IL-4, IL-5, IFN-γ, TGF-β) in BP lesional skin, we performed an immunohistochemical study and an in situ hybridization procedure on five BP patients, comparing them with two psoriatic patients and four healthy subjects. Our aim was to expand suitable information about tissutal expression of cytokines, secondly to further investigate the role of TGF-β (a Th3-like or T-regulatory (T-reg) cytokine) in a non-scarring disorder like BP, in order to highlight its pleiotropic activity. The immunohistochemical analysis revealed a moderate to strong staining for IL-4 and IL-5 with a prevalent perivascular localization in the upper dermis. The staining for IFN-γ showed a moderate/focal expression on the dermal perivascular infiltrate. IL-2 protein was observed in four cases. While no positive staining for IL-4 mRNA was detected in all BP subjects with in situ hybridization, IL-5 mRNA was documented in four BP specimens. A focal nuclear staining for IFN-γ was observed in the epidermal layers and on the cellular infiltrate of lesional skin. In all BP cases, a moderate/diffuse positivity for TGF-β 1 mRNA was documented in both cytoplasm and nucleus of the infiltrating perivascular cells of lesional and perilesional skin. Our results suggest a balance between Th1, Th2 and Th3 activity, with quantitatively different impact of the various cytokines on the pathomechanism of blistering, depending on the reciprocal network. The supposed participation of each cytokine analyzed in the pathogenesis of BP is discussed. The newest data obtained consist of TGF-β detection in a non-scarring disease like PB, that had never been documented before, and in the confirmation of a mixed cytokine pattern in the fully developed phase of the disease.

Glycogen-rich and glycogen-depleted astrocytes in the oedematous human cerebral cortex associated with brain trauma, tumours and congenital malformations: an electron microscopy study

Primary objective: The anaerobic mobilization of astrocyte glycogen in anoxic-ischemic regions of the oedematous human cerebral cortex is analysed. Methods and procedures: Seventeen cortical biopsies of patients with brain trauma, brain tumours and congenital malformations were examined by conventional transmission electron microscopy. Results: Glycogen-rich and glycogen-depleted, clear or dense astrocytes cell bodies were observed in anoxic ischaemic regions of different brain cortical areas in perineuronal, neuropilar and perivascular localization. Glycogen-rich astrocytes showed clear or moderately dense cytoplasm and accumulation of both g -type or monogranular glycogen granules and f -type or multigranular glycogen particles. Focal regions of translucent cytoplasm were observed in areas of glycogen degradation. Glycogendepleted astrocytes exhibited a clear cytoplasm and scarce amount or absence of g -type glycogen granules. Coexisting glycogen-rich and glycogen-depleted neuropilar astrocytic processes were observed in the vicinity of degenerated myelinated axons and degenerated axodendritic contacts. Glycogen-rich and glycogen-depleted perivascular astrocytic processes were also found surrounding injured and collapsed cerebral capillaries. Conclusion: The findings suggest astrocytic glycogen mobilization during anoxic and ischaemic conditions, revealing the important contribution of astrocytes on neuronal survival under conditions of energy substrate limitations.

Distribution of adoptively transferred, tumor-sensitized lymphocytes in the glioma-bearing rat.

For adoptively transferred lymphocytes to exert anti-tumor effects in vivo, they must traffic or initiate the migration of endogenous immune cells to the site of tumor. Using a rat model, we examined the trafficking of tumor-sensitized lymphocytes to an intracerebral glioma. By labeling the cells with 111Indium oxine (111In) prior to intravenous injection, we were able to quantify the relative number of lymphocytes that traveled to the tumor site. There was no difference in lymphocytic influx between the tumor-bearing and non-tumor-bearing cerebral hemispheres in 3-day rat glioma models. However, in 7-day models, significantly greater numbers of 111In-labeled lymphocytes resided in the tumor-bearing hemisphere at 12 h post-administration. This number increased more than two-fold by 24 h post-adoptive transfer. Using fluorescent-labeled lymphocytes and microscopy, we confirmed that the detection of radioactivity within the brain was truly due to tumor infiltrating 111In-labeled lymphocytes. Adoptively transferred cells were found in perivascular and peritumoral locations. These data demonstrate that tumor-sensitized lymphocytes traffic to an intracerebral target site where they can exert an effect, further supporting adoptive immunotherapy as a treatment for glioma.

Syntrophin-dependent expression and localization of Aquaporin-4 water channel protein.

The Aquaporin-4 (AQP4) water channel contributes to brain water homeostasis in perivascular astrocyte endfeet where it is concentrated. We postulated that AQP4 is tethered at this site by binding of the AQP4 C terminus to the PSD95-Discs large-ZO1 (PDZ) domain of syntrophin, a component of the dystrophin protein complex. Chemical cross-linking and coimmunoprecipitations from brain demonstrated AQP4 in association with the complex, including dystrophin, beta-dystroglycan, and syntrophin. AQP4 expression was studied in brain and skeletal muscle of mice lacking alpha-syntrophin (alpha-Syn(-/-)). The total level of AQP4 expression appears normal in brains of alpha-Syn(-/-) mice, but the polarized subcellular localization is reversed. High-resolution immunogold analyses revealed that AQP4 expression is markedly reduced in astrocyte endfeet membranes adjacent to blood vessels in cerebellum and cerebral cortex of alpha-Syn(-/-) mice, but is present at higher than normal levels in membranes facing neuropil. In contrast, AQP4 is virtually absent from skeletal muscle in alpha-Syn(-/-) mice. Deletion of the PDZ-binding consensus (Ser-Ser-Val) at the AQP4 C terminus similarly reduced expression in transfected cell lines, and pulse-chase labeling demonstrated an increased degradation rate. These results demonstrate that perivascular localization of AQP4 in brain requires alpha-Syn, and stability of AQP4 in the membrane is increased by the C-terminal PDZ-binding motif.

Induction of type 1 immune pathology in the brain following immunization without central nervous system autoantigen in transgenic mice with astrocyte-targeted expression of IL-12.

IL-12, a cytokine produced by microglia, may regulate cellular immunity at a localized level in the CNS. To investigate this further, we examined the consequences of peripheral immune stimulation without specific autoantigen in wild-type or transgenic (termed GF-IL12) mice with astrocyte production of the bioactive IL-12 p75 heterodimer. Active immunization with CFA and pertussis toxin, a procedure known to stimulate a robust type 1-biased immune response, produced CNS immune pathology from which GF-IL12 but not wild-type mice developed signs of clinical disease consisting of loss of activity, piloerection, mild tremor, and motor change. All immunized mice had some degree of mononuclear cell infiltration into the brain; however, the severity of this was markedly increased in GF-IL12 mice where leukocytes accumulated in perivascular and parenchymal locations. Accumulating cells consisted of CD4(+) and CD8(+) T cells and macrophage/microglia. Moreover, expression of cytokines (IFN-gamma and TNF), chemokines (IFN-inducible protein-10 and RANTES), the immune accessory molecules, MHC class II, B7.2, ICAM-1 and VCAM-1, and NO synthase-2 was induced in the CNS of the GF-IL12 mice. Therefore, peripheral immunization of GF-IL12 but not wild-type mice can provoke active type 1 immunity in the brain-a process that does not require CNS-specific immunizing autoantigen. These findings indicate that the cytokine milieu of a tissue can dramatically influence the development of intrinsic immune responses and associated pathology.

CD1d is Expressed on Dermal Dendritic Cells and Monocyte-Derived Dendritic Cells

CD1 proteins are a family of cell surface molecules that present lipid antigens to T cells. We investigated skin dendritic cells and monocyte-derived dendritic cells for expression of CD1 molecules using a panel of 10 different monoclonal antibodies focusing on the recently described CD1d molecule. By immunohistochemical analysis, CD1d expression in normal human skin was restricted to dendritic appearing cells in the papillary dermis mainly located in a perivascular localization. Langerhans cells did not show detectable CD1d expression in situ. Epidermal/dermal cell suspensions analyzed by flow cytometry demonstrated distinct subpopulations of HLA-DR positive dermal dendritic cells expressing CD1a, CD1b, and CD1c. CD1d was expressed on HLA-DRbright dermal antigen-presenting cells in dermal suspensions (16% +/- 3.6%), as well as on highly enriched dermal dendritic cells migrating out of skin explants (60.5% +/- 8.0%). Migrated mature dermal dendritic cells coexpressed CD83 and CD1d. Western blot analysis on microdissected skin sections revealed the presence of a 50-55 kDa CD1d molecule in dermis, suggesting that CD1d is highly glycosylated in skin. Both immature and mature monocyte-derived dendritic cells cultured in autologous plasma expressed CD1d molecules. In contrast, culture in fetal bovine serum downregulated CD1d expression. In conclusion, antigen-presenting cells in skin express different sets of CD1 molecules including CD1d and might play a role in lipid antigen presentation in various skin diseases. Differential expression of CD1 molecules depending on culture conditions might have an impact on clinical applications of dendritic cells for immunotherapy.

Apoptosis of endothelial cells precedes myocyte cell apoptosis in ischemia/reperfusion injury.

Apoptosis contributes to cell loss after ischemia/reperfusion injury in the heart. This study describes the time course and level of apoptosis in different cell types in the intact heart during ischemia/reperfusion injury. Isolated Langendorff-perfused rat hearts were subjected to perfusion alone (control) or to 35 minutes of regional ischemia, either alone or followed by 5, 60, or 120 minutes of reperfusion. Sections were stained by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and propidium iodide and with anti-von Willebrand factor, anti-desmin, or anti-active caspase 3 antibodies; they were then visualized by confocal microscopy. Sections were also examined by electron microscopy. No TUNEL-positive cells were seen in control hearts or hearts exposed to ischemia alone. Early in reperfusion, TUNEL staining was colocalized with endothelial cells from small coronary vessels. Endothelial apoptosis peaked at 1 hour of reperfusion and, at this time, there was clear perivascular localization of apoptotic cardiac myocytes, whose number was inversely proportional to their distance from a positive vessel. After 2 hours of reperfusion, apoptotic cardiac myocytes assumed a more homogeneous distribution. Active caspase 3 labeling was seen independent of DNA fragmentation during ischemia alone, but it colocalized with TUNEL staining over the 3 time points of reperfusion. Immunocytochemical findings were confirmed by electron microscopy and Western blotting. In the very early stages of reperfusion, apoptosis is first seen in the endothelial cells from small coronary vessels. The radial spread of apoptosis to surrounding cardiac myocytes suggests that reperfusion induces the release of soluble pro-apoptotic mediators from endothelial cells that promote myocyte apoptosis.

Kynurenine 3-mono-oxygenase activity and neurotoxic kynurenine metabolites increase in the spinal cord of rats with experimental allergic encephalomyelitis

Kynurenine 3-mono-oxygenase, one of the key enzymes of the “kynurenine pathway”, catalyses the formation of 3-hydroxykynurenine and may direct the neo-synthesis of quinolinic and kynurenic acids. While 3-hydroxykynurenine and quinolinic acid have neurotoxic properties, kynurenic acid antagonizes excitotoxic neuronal death. Here we report that the expression and activity of kynurenine 3-mono-oxygenase significantly increased in the spinal cord of rats with experimental allergic encephalopathy, an experimental model of multiple sclerosis. As a consequence of this increase, the spinal cord content of 3-hydroxykynurenine and quinolinic acid reached neurotoxic levels. We also report that systemic administration of Ro 61-8048, a selective kynurenine 3-mono-oxygenase inhibitor, reduced the increase of both 3-hydroxykynurenine and quinolinic acid, and caused accumulation of kynurenic acid. In the brain and spinal cord of the controls, kynurenine 3-mono-oxygenase immunoreactivity was located in granules (probably mitochondria) present in the cytoplasm of both neurons and astroglial cells. In the spinal cord of rats with experimental allergic encephalopathy, however, cells with a very intense kynurenine 3-mono-oxygenase immunoreactivity, also able to express class II major histocompatibility complex and inducible nitric oxide synthase, were found in perivascular, subependymal and subpial locations. These cells (most probably macrophages) were responsible for the large increase in 3-hydroxykynurenine and quinolinic acid found in the spinal cords of affected animals. The results show that cells of the immune system are responsible for the increased formation of 3-hydroxykynurenine and quinolinic acid, two neurotoxic metabolites that accumulate in the central nervous system of rats with experimental allergic encephalomyelitis. They also demonstrate that selective kynurenine 3-mono-oxygenase inhibitors reduce the neo-synthesis of these toxins.

Increased density of lymphocytes bearing γ/δ T-cell receptors in recurrent aphthous ulceration (RAU)

Lymphocytes bearing the T-cell receptor (TCR) γ/δ are increased in the peripheral blood of patients with recurrent aphthous ulcers (RAU) and Behçet's disease. In this study, we examined whether the density of TCR- γ/δ bearing lymphocytes was also increased locally in RAU lesions. Ten RAU lesions from ten patients were compared with ulcer-free mucosa from sites contralateral to the lesions, and with 10 samples of clinically healthy oral mucosa taken from 10 healthy volunteers. Samples were labeled with a panel of monoclonal antibodies specific to CD3, α/β TCR and γ/δ TCR in avidin-biotin-peroxidase complex (ABC) staining. Lymphocytes expressing γ/δ TCRs were very low in non-lesional mucosa and clinically healthy mucosa. By contrast, γ/δ T-cells were numerous and observed in all RAU lesions especially within the epithelium, inflammatory infiltrates and at perivascular locations. The count of γ/δ T-cells was high in connective tissue of RAU (200±126 cells/mm 2) compared with connective tissue of controls (4±4 cells/mm 2; P<0.0001) or non-lesional mucosa (5±7 cells/mm 2). Interestingly, the density of γ/δ T-cells was also high in the epithelium of RAU (70±34 cells/mm 2) compared with the epithelium of non-lesional mucosa (2.8±06 cells/mm 2; P<0.0001) or epithelium of healthy controls (1.2±1.5 cells/mm 2; P<0.0001). Moreover, the mean percentage of γ/δ+ T-cells among total CD3+ lymphocytes was increased in the connective tissue area from 4% and 5% in controls and non-lesional mucosa, respectively, to 19% in RAU. In epithelial areas, the average percentage was increased from 2% and 6% in controls and non-lesional mucosa, respectively, to 36% in RAU. These data showed that γ/δ T-cells are more numerous in RAU lesions and such an increase was purely restricted to RAU inflammatory areas.

Increased density of lymphocytes bearing gamma/delta T-cell receptors in recurrent aphthous ulceration (RAU)

Lymphocytes bearing the T-cell receptor (TCR) γ/δ are increased in the peripheral blood of patients with recurrent aphthous ulcers (RAU) and Behçet’s disease. In this study, we examined whether the density of TCR-γ/δ bearing lymphocytes was also increased locally in RAU lesions. Ten RAU lesions from ten patients were compared with ulcer-free mucosa from sites contralateral to the lesions, and with 10 samples of clinically healthy oral mucosa taken from 10 healthy volunteers. Samples were labeled with a panel of monoclonal antibodies specific to CD3, α/β TCR and γ/δ TCR in avidin-biotin-peroxidase complex (ABC) staining. Lymphocytes expressing γ/δ TCRs were very low in non-lesional mucosa and clinically healthy mucosa. By contrast, γ/δ T-cells were numerous and observed in all RAU lesions especially within the epithelium, inflammatory infiltrates and at perivascular locations. The count of γ/δ T-cells was high in connective tissue of RAU (200±126 cells/mm2) compared with connective tissue of controls (4±4 cells/mm2; P<0.0001) or non-lesional mucosa (5±7 cells/mm2). Interestingly, the density of γ/δ T-cells was also high in the epithelium of RAU (70±34 cells/mm2) compared with the epithelium of non-lesional mucosa (2.8±06 cells/mm2; P<0.0001) or epithelium of healthy controls (1.2±1.5 cells/mm2; P<0.0001). Moreover, the mean percentage of γ/δ+ T-cells among total CD3+ lymphocytes was increased in the connective tissue area from 4% and 5% in controls and non-lesional mucosa, respectively, to 19% in RAU. In epithelial areas, the average percentage was increased from 2% and 6% in controls and non-lesional mucosa, respectively, to 36% in RAU. These data showed that γ/δ T-cells are more numerous in RAU lesions and such an increase was purely restricted to RAU inflammatory areas.

Immunohistochemical analysis for neural markers of the lateral retinaculum in patients with isolated symptomatic patellofemoral malalignment. A neuroanatomic basis for anterior knee pain in the active young patient.

We evaluated 13 lateral retinacula excised at the time of Insall proximal realignments or isolated lateral retinacular releases performed in patients with isolated symptomatic patellofemoral malalignment recalcitrant to nonoperative treatment. Evaluation was performed by means of conventional histologic and immunohistochemical analysis for neural markers (S-100 protein, neurofilament protein, substance P, and neural growth factor). The observations reported here provide a neuroanatomic basis for anterior knee pain syndrome in active young patients with isolated symptomatic patellofemoral malalignment and support the clinical observation that the lateral retinaculum may have a key role in the origin of this pain as a result of increased neural growth factor production, which induces proliferation of nociceptive axons, mainly in a perivascular location.

Pericyte Migration from the Vascular Wall in Response to Traumatic Brain Injury

Any perturbation of the blood brain barrier, whether from changes in cell physiology or from direct injury, may result in microvascular dysfunction and disease. We examined, at the ultrastructural level, microvascular pericyte responses in a well-defined model of traumatic brain injury in the rat. In areas close to the site of impact cortical pericytes underwent a number of changes within the first hour. Approximately 40% of pericytes migrated from their microvascular location. Migration occurred concomitant with a thinning of the abluminal surface of the basal lamina and an accumulation of the receptor for the urokinase plasminogen activator on the leading surface of the migrating cell. Migrated pericytes appeared viable and remained in a perivascular location in the adjacent neuropil. Nonmigrating pericytes in the same section displayed cytoplasmic alterations and nuclear chromatin changes consistent with a rapid degenerative process.

GFAP-positive and myelin marker-positive glia in normal and pathologic environments.

The data herein demonstrate that in addition to the well-characterized myelin marker-positive, glial fibrillary acidic protein (GFAP)-negative, membrane sheet-bearing oligodendrocytes, another type of myelin marker-positive, process-bearing glia exists in normal and pathologic conditions. This second type of myelin marker-positive glia expresses GFAP, and therefore these cells have been referred to as mixed phenotype glia. Although mixed phenotype glia have been documented previously, their identity and function have remained a mystery. The goal of this immunocytochemical study was to further characterize these cells. Using the MBPlacZ transgenic mouse in which beta-galactosidase is under the control of the myelin basic protein (MBP) gene promoter, GFAP-positive/beta-galactosidase-positive and myelin/oligodendrocyte-specific protein (MOSP)-positive/beta-galactosidase-positive cells were detected in subcortical white matter and in perivascular locations within cerebral white and gray matter. In cultures prepared from highly enriched myelin marker-positive immature glia, mixed phenotype glia were detected that were GFAP-positive and either MOSP-, MBP-, O1-, and O4-positive. The expression of multiple myelin markers by mixed phenotype glia may suggest that these cells are of oligodendrocyte origin. Increased numbers of MOSP-positive/GFAP-positive mixed phenotype glia were detected in sections from adult hypomyelinated brain from shiverer, quaking, and PKU mice compared to myelinated control adult mouse brain. Similarly, cultures from control brain exposed to elevated pH for 2-3 weeks showed dramatically increased numbers of mixed phenotype glia (80%) compared to control (<10%). Increased numbers of mixed phenotype glia also were detected in shiverer cultures (40%). Since increases in the number of mixed phenotype glia occur in shiverer, quaking, and PKU mouse brain, these data suggest that mixed phenotype glia contribute to gliosis in pathologic white matter.

Neuronal Elements in the Testis of the Rhesus Monkey: Ontogeny, Characterization and Relationship to Testicular Cells

Intrinsic neuron-like cells expressing the catecholamine-biosynthetic enzyme tyrosine hydroxylase (TH) were recently identified in the testis of the prepubertal rhesus monkey. In this study, we characterized the neuron-like nature of these cells and examined distribution and frequency of neuronal elements in the testes of monkeys during postnatal development, puberty and adulthood. Using immunohistochemical methods, we detected both nerve fibers and cell bodies, immunoreactive for the neuronal markers neurofilament 200 (NF-200) and synaptosomal associated protein of 25 kDa (SNAP-25), TH and neuropeptide Y (NPY) in perivascular locations, intermingled with interstitial cells and close to the wall of seminiferous tubules. Marked age-related differences in the numbers of these neuronal elements became apparent, when we quantified NF-200-immunoreactive neuronal elements. Thus, intrinsic neuron-like cell bodies were found only in the testes from immature animals (i.e., until about 3 years of age). Conversely, nerve fibers, presumably representing mainly the extrinsic innervation, were observed at all ages although they became more prominent after the pubertal increase in LH and testosterone levels. Interestingly, another testicular cell type known to contain potent regulatory substances, mast cells, was found to be in close anatomical proximity to nerve fibers. The number of these cells, positively identified with an antibody to tryptase, increased significantly after puberty following the same pattern as nerve fibers. These results confirm that the testicular nervous system of the monkey is composed of two components, intrinsic nerve cells and extrinsic fibers, both of which are catecholaminergic and peptidergic in nature. Furthermore, both components show a marked degree of plasticity during development, especially around the time of puberty. The intratesticular locations of neuron-like cells and fibers suggest that catecholamines and neuropeptides are likely to have multiple sites of actions, and may affect Leydig cells, cells of the tubular wall and vascular cells directly and/or indirectly via intermediation of mast cells.

Filamentous tau pathology in nerve cells, astrocytes, and oligodendrocytes of aged baboons.

Intracellular filamentous inclusions containing abnormally phosphorylated tau protein are hallmarks of several human neurodegenerative disorders. This study reveals tau-positive cytoskeletal abnormalities in neurons and glial cells of aged baboons. The brains of four baboons (Papio hamadryas, 20-30 yr of age) were examined using the Gallyas silver technique for neurofibrillary changes and phosphorylation-dependent anti-tau antibodies (AT8, AT100, AT270, PHF-1, TG-3). Conspicuous changes were noted in two animals, 26 and 30 yr of age. In both animals, a combination of neuronal and glial cytoskeletal pathology was seen preferentially affecting limbic brain areas, including the hippocampal formation. In the 30-yr-old animal, numerous tau-positive inclusions were seen in the granule cells of the fascia dentata. These cells even exhibited an accumulation of argyrophilic neurofibrillary tangles. The glial changes affected both astrocytes and oligodendrocytes. Tau-positive astrocytes were seen in perivascular, subpial, and subependymal locations. Tau-positive oligodendrocytes preferentially occurred in limbic fiber tracts including the entorhinal perforant path. Ultrastructurally, tau-positive straight filaments (10-14 nm) in both neurons and glial cells were revealed by anti-tau immunoelectron microscopy. This study thus indicates the potential usefulness of aged baboons for experimental investigation of neuronal and glial filamentous tau pathology. This nonhuman primate species may provide valuable information pertinent to the broad spectrum of human tauopathies.