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Biomedical subjects

W J Streit

Publications and source records attributed to W J Streit.

At least 37 records · Page 2Linked to original sources
PubMed1998

Cytokine mRNA profiles in contused spinal cord and axotomized facial nucleus suggest a beneficial role for inflammation and gliosis.

We have studied temporal mRNA expression patterns for interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), macrophage colony stimulating factor (M-CSF), and transforming growth factor-beta1 (TGF-beta1) in two rat injury paradigms with very different cellular inflammatory reactions: contussion of the spinal cord and axotomy of the facial nerve. Our comparative analyses using semiquantitative reverse transcription polymerase chain reaction (RT-PCR) show an early and robust upregulation of IL-1beta, TNF-alpha, IL-6, and M-CSF mRNAs in spinal cord after contusion injury. Peak expression of these mRNAs was transient and returned to control levels by 24 h postinjury. In contrast, expression of IL-1beta and TNF-alpha mRNAs in the axotomized facial nucleus was minimal and delayed, and levels of M-CSF mRNA remained unaltered. Similar to injured spinal cord, the axotomized nucleus showed a dramatic and early upregulation of IL-6 mRNA, but unlike spinal cord, IL-6 mRNA levels subsided only gradually. Both injury paradigms showed gradually increasing levels of TGF-beta1 mRNA which were maximal at 7 days postinjury. RT-PCR analyses were also performed on isolated blood-borne mononuclear cells and neutrophils. The results showed that these cells contain high levels of IL-1beta and M-CSF mRNAs, moderate levels of TGF-beta and TNF-alpha mRNAs, and minimal levels of IL-6 mRNA. The RT-PCR analyses together with histological observations indicate that expression of the proinflammatory cytokines IL-1beta, TNF-alpha, and IL-6 is short-lived and self-limited after contusion injury, and that it occurs primarily within endogenous glial cells. Transient expression of these molecules likely triggers secondary events which may be beneficial to wound repair and regeneration.

Animals↗
PubMed1998

Tracing of fluoro-gold prelabeled microglia injected into the adult rat brain.

In light of a recent interest in the transplantation of cultured microglial cells, we have examined the use of the fluorescent dye Fluoro-Gold (FG) as a tracer for these cells. Following injection into the adult rat brain, FG prelabeled microglial cells were readily traceable for up to 2 weeks with minimal labeling of endogenous cell populations. Some of the injected cells differentiated into ramified microglial cells as a result of exposure to the adult CNS environment. Injection of free FG into the adult rat brain resulted in the widespread labeling of neurons and perivascular cells, but not endogenous microglial cells, indicating that perivascular cells, but not resting microglia, are actively pinocytotic cells of the CNS. Our results show that FG is an effective label for the tracing of transplanted microglial cells.

Animals↗
PubMed1997

Grafting of cultured microglial cells into the lesioned spinal cord of adult rats enhances neurite outgrowth.

There is contrasting in vitro and in vivo evidence regarding glial cell involvement in central nervous system (CNS) regeneration. This study has investigated the histological events that follow implantation of either microglia, mixed microglia/astrocytes, or astrocytes into the injured adult rat spinal cord. We have conducted an immunohistochemical characterization of the cellular profiles within and neuritic extension into various grafts consisting of gelfoam (GF) matrices impregnated with cultured microglia and/or astrocytes. After 2-5 weeks, prominent neuritic growth was observed into OX-42-immunoreactive (IR) microglial implants. These grafts were infiltrated by numerous host cellular elements including microvasculature and Schwann cells, and they demonstrated conspicuous laminin IR. Often, the patterns for laminin and OX-42 IR in microglial grafts were overlapping, suggesting partial expression of laminin on transplanted microglial cells. Mixed grafts of microglia and astrocytes demonstrated presence of neurites and laminin-IR elements with similar intensity as microglial grafts, while astroglial implants showed the least amount of neurite ingrowth. Some control implants consisting of cell-free GF showed marginal in-growth of neurites in areas of infiltrating OX-42-IR host cells. Collectively, our findings support a neurite growth-promoting role of activated microglia and suggest that microglia may counteract mechanisms that inhibit CNS regeneration. It remains to be determined whether the observed neurite growth-promoting effects are mediated directly by grafted and/or endogenous microglia, or whether this occurs via the recruitment of host Schwann cells.

Animals↗
PubMed1997

Quinolinate immunoreactivity in experimental rat brain tumors is present in macrophages but not in astrocytes.

Experimental tumors of the central nervous system were investigated with antibodies to quinolinate to assess the cellular distribution of this endogenous neurotoxin. In advanced F98 and RG-2 glioblastomas and E367 neuroblastomas in the striatum of rats, variable numbers of quinolinate immunoreactive cells were observed in and around the tumors, with the majority being present within tumors, rather than brain parenchyma. The stained cells were morphologically variable, including round, complex, rod-shaped, and sparsely dendritic cells. Neuroblastoma and glioma cells were unstained, as were neurons, astrocytes, oligodendrocytes, ependymal cells, endothelial cells, and cells of the choroid plexus and leptomeninges. Glial fibrillary acidic protein immunoreactivity was strongly elevated in astrocytes surrounding the tumors. Dual labeling immunohistochemistry with antibodies to quinolinate and glial fibrillary acidic protein demonstrated that astrocytes and the cells containing quinolinate immunoreactivity were morphologically disparate and preferentially distributed external and internal to the tumors, respectively, and no dual labeled cells were observed. Lectin histochemistry with Griffonia simplicifolia B4 isolectin and Lycopersicon esculentum lectin demonstrated numerous phagocytic macrophages and reactive microglia in and around the tumors whose distribution was similar to that of quinolinate immunoreactive cells, albeit much more numerous. Dual labeling studies with antibodies to quinolinate and the lectins demonstrated partial codistribution of these markers, with most double-labeled cells having the morphology of phagocytes. The present findings suggest the possibility that quinolinate may serve a functional role in a select population of inflammatory cell infiltrates during the immune response to brain neoplasms.

Animals↗
PubMed1997

Activation of microglia in the brains of humans with heart disease and hypercholesterolemic rabbits.

Activated microglial cells are concentrated in senile plaques characteristic of Alzheimer's disease. Such accumulations of activated microglia may contribute towards neurodegeneration via production of cytokines and free radicals. Studies suggesting a link between Alzheimer's disease and heart disease led us to study microglia immunohistochemically, using monoclonal antibody LN-3, in age-matched nondemented humans with and without heart disease. Using a qualitative staging system for assessing morphological changes occurring in microglia, we found higher microglial activation in the brains of subjects with heart disease than in those without it. Lectin histochemical examination of brains from rabbits maintained on a high-cholesterol diet also revealed increased microglial activation and leukocyte infiltration. Collectively our observations from humans and rabbits suggest that hypercholesterolemia and heart disease accelerate brain aging, and that the formation of senile plaques may be the end result of progressive microglial activation that occurs with aging.

Aged↗
PubMed1997

Oral feeding of interferon tau can prevent the acute and chronic relapsing forms of experimental allergic encephalomyelitis.

IFN tau is a member of the type I IFN family but unlike IFN alpha and IFN beta, IFN tau lacks toxicity at high concentrations. Recently, ovine IFN tau was shown to prevent acute induction and superantigen reactivation of experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis (MS). In this report, we examined the ability of IFN tau when administered by oral feeding to block development of EAE. Oral feeding of INF tau prevented paralysis in the acute form of EAE in NZW mice and chronic-relapsing EAE in SJL/J mice. In addition, oral feeding of IFN tau at 10(5) U/dose was as effective as intraperitoneal (i.p.) injection in preventing chronic-relapsing EAE, and both forms of IFN tau administration resulted in IL10 production. Histological examination revealed no inflammatory lymphocytic infiltration to the CNS in IFN tau treated animals as compared to controls. Prolonged treatment of IFN tau was shown to be necessary for chronic-relapsing EAE since removal of IFN tau treatment by either oral feeding or i.p. injection resulted in onset of disease. Lastly, sera from SJL/J mice which received prolonged IFN tau treatment by oral feeding exhibited little to no development of anti-IFN tau antibodies. Thus, oral feeding of ovine IFN tau may be a successful form of IFN tau administration for treatment of autoimmune diseases such as MS and may circumvent potentially debilitative antibody responses.

Acute Disease↗
PubMed1997

Localization of unmyelinated axons in rat skin and mucocutaneous tissue utilizing the isolectin GS-I-B4.

The alpha-D-galactose specific isolectin I-B4 from Griffonia simplicifolia (GS-I-B4) labels CNS microglia and certain peripheral neurons, including a subpopulation of small dark, type B dorsal root ganglion cells, some post-ganglionic sympathetic axons, and nearly all peripheral gustatory axons. The innervation patterns of GS-I-B4 reactive sensory ganglion cells are unknown for many peripheral target tissues, including their probable primary target, the skin. The present study describes the distribution of GS-I-B4 reactive axons in hairy and glabrous hindpaw skin and in the glans penis of rats, using both single and double-labelling histochemical techniques. Neuronal processes were identified using (1) histochemistry with horseradish peroxidase conjugated GS-I-B4 or (2) immunohistochemistry against PGP 9.5 to identify all axons, and biotinylated lectin histochemistry with avidin-FITC to identify the subpopulation of GS-I-B4 reactive axons. GS-I-B4 strongly labelled unmyelinated cutaneous sensory afferents, as well as some sympathetic efferents and visceral afferents. lectin reactive axons were seen to innervate the upper hair shaft epidermis in hairy skin, and were abundant in the shallow dermis in hairy and glabrous skin and glans penis. Lectin reactive axons were also abundant in the lamina propria and distal urethral epithelium of the penis. These results provide new evidence for the cutaneous sensory role of GS-I-B4 reactive primary afferents, as well as evidence to support the contention that the lectin is a specific marker for a subpopulation of unmyelinated axons and not simply a marker for the myelination state of an axon.

Animals↗
PubMed1997

Exposure to in utero irradiation produces disruption of radial glia in rats.

In utero exposure of fetal rats to gamma-irradiation produces diffuse cortical dysplasia and neuronal heterotopia. This study examined the effects of in utero irradiation on radial glia and astrocytes in the perinatal period in order to better understand the specific mechanisms which produce cortical dysgenesis in this model. Fetal rats were exposed to 225 cGy of gamma-irradiation on embryonic day 17. Vibratome sections were processed for cresyl violet staining and immunohistochemistry with Rat-401 and an antibody for glial fibrillary acidic protein (GFAP) on E20, P0, P2, and P4. In utero irradiation produced a profound disruption of the radial glia which lasted throughout the perinatal period. This injury coincided with the location of the most severe cortical dysplasia in this model. In addition, there was increased GFAP immunoreactivity in the cortex and the striatum when compared to nonirradiated controls on P0, P2, and P4. Our results demonstrate that in utero irradiation has a lasting, injurious effect on radial glia and also incites a reactive astrocytic response. This suggests that disruption of radial glial fibers by gamma-irradiation is a major factor in the pathogenesis of cortical dysgenesis in this model.

Animals↗
PubMed1996

Differential activation of microglia and astrocytes following trimethyl tin-induced neurodegeneration.

We have investigated the response of astrocytes and microglia to trimethyl tin intoxication in the septum, hippocampus, olfactory bulb, and pyriform cortex of the rat. Microglia were studied qualitatively using lectin histochemistry, and astrocytes were examined both qualitatively with immunohistochemistry, and quantitatively using an immunoassay for glial fibrillary acidic protein. Our results show that activated microglia first appeared 2 days after trimethyl tin intoxication in the lateral septum and hippocampus. Four days after trimethyl tin intoxication, the same regions revealed a most intense microglial reaction characterized by microglial hypertrophy and the formation of phagocytic clusters. By day 7, microglial activation in the septum and hippocampus had lessened, suggesting that the cells were reverting to the resting phenotype. The microglial response in the pyriform cortex and olfactory bulb, while being later in onset than in the septum and hippocampus, showed a similar progression of microglial changes reaching maximal intensity 7 days after trimethyl tin intoxication. Significant increases in the expression of glial fibrillary acidic protein were observed in all regions examined and typically occurred after microglial activation was already underway. We conclude that microglial and astroglial reactions which occur in response to trimethyl tin-induced neuronal necrosis are separated in time, with microglial activation preceding astrogliosis. In addition, our study stresses the importance of microglia as an endogenous source of CNS macrophages, and illustrates the merit of histochemical analysis with microglial markers for the early delineation of neurotoxicant-induced brain damage.

Animals↗
PubMed1995

Analysis of TGF-beta 1 gene expression in contused rat spinal cord using quantitative RT-PCR.

We have used northern blot analysis and quantitative reverse transcription polymerase chain reaction (RT-PCR) to determine the postinjury expression profile of the transforming growth factor-beta 1 (TGF-beta 1) gene in the contused rat spinal cord. Spectrophotometric estimates of total sample RNA and quantitative analyses of cyclophilin mRNA using RT-PCR served as controls for comparisons between samples. No changes in cyclophilin gene expression were found at any postinjury survival times. The results of the TGF-beta 1 analyses, which were carried out on spinal cord samples taken at postinjury intervals ranging from 6 h to 10 days, show that the amount of TGF-beta 1 mRNA present in spinal cord increases rapidly following injury, reaching maximum levels 7 days postinjury. Unoperated control samples contained approximately 2 x 10(8) molecules of TGF-beta 1 mRNA/0.5 microgram total RNA. By 1 day postinjury, the amount of TGF-beta 1 mRNA in the cord had increased by a factor of 2.5 to 5 x 10(8) molecules/0.5 microgram total RNA. At 7 days postinjury, there were approximately 15 x 10(8) molecules of TGF-beta 1 mRNA/0.5 microgram total RNA. By 10 days postinjury the amount of TGF-beta 1 mRNA present in the spinal cord had declined to 8 x 10(8) molecules of TGF-beta 1 mRNA/0.5 microgram total RNA, a value similar to that observed at 3 days postinjury. The roles that TGF-beta 1 might play in modifying cellular responses in injured spinal cord are discussed.

Animals↗
PubMed1995

Griffonia simplicifolia II lectin labels a population of radial glial cells in the embryonic rat brain.

Staining with the Griffonia simplicifolia II lectin (GSL II), a marker for adult rat oligodendrocytes, was studied in rat brain at embryonic (E) days E14, E16, E18, and E20. At E14, only two regions of the CNS showed labeling--the hippocampal primordium and the ventromedial floor of the mesencephalic aqueduct and fourth ventricle. Labeling in these areas was confined to cells with bipolar processes which spanned from the ventricular lumen to the pial surface. At E16, GSL II+ radial glia were present in the hippocampus, septal area, cerebral peduncle, thalamus, tegmentum, and throughout much of the midbrain. At E16, E18, and E20, GSL II strongly labeled two midline radial glial raphes--dorsal to the mesencephalic aqueduct and ventral to the mesencephalic aqueduct and fourth ventricle. Comparison of GSL II lectin labeling with nestin immunostaining, using Rat-401, showed that GSL II labeled a distinct population of radial cells different from nestin-positive radial glia. GSL II also labeled a group of neurons at E16 and E18 in the hypothalamus and basal striatum. We suggest that GSL II+ radial glia represent a population of oligodendroglial precursors present in the embryonic brain, and that GSL II reactivity could serve as a differentiation marker for cells committed to the oligodendroglial lineage. This work supports the possibility that some oligodendroglia, like astrocytes, are derived from radial glial precursors.

Animals↗
PubMed1994

Astrocytes but not microglia express NADPH-diaphorase activity after motor neuron injury in the rat.

The purpose of this study was to identify cellular sources of nitric oxide (NO) after injury to rat facial motor neurons using NADPH-diaphorase histochemistry. We employed intraneural injections of either saline or toxic ricin, followed by nerve crush, in order to produce regeneration or degeneration of facial motor neurons (FMNs), respectively. Reactive astrocytes responding to ricin-induced degeneration of FMNs showed increased NADPH-diaphorase activity while reactive astrocytes responding to axotomy (saline injection) did not. Reactive microglial cells were found not to express NADPH-diaphorase in either one of these two paradigms. We conclude that irreversible neuron injury resulting in neurodegeneration causes increased production of NO by reactive astrocytes.

Animals↗
PubMed1994

In situ detection of transforming growth factor-beta mRNA in experimental rat glioma and reactive glial cells.

Malignant gliomas are associated with a state of systemic immunosuppression which appears to be partially mediated by transforming growth factor beta (TGF-beta) secreted from glioma cells. In a recently described animal model of malignant glioma, massive activation of local microglial cells and formation of microglia-derived macrophages has been observed in the absence of detectable tumour regression. We have investigated the in situ expression of TGF-beta in rat glioma as a possible cause of ineffective tumour destruction. Two weeks following unilateral injection of glioma cells, large tumours were observed in the affected hemisphere. In situ hybridization for TGF-beta 1 mRNA revealed an intense signal over the entire tumour area. In the peritumoural area, at sites of glial activation, a lower signal was obtained over cellular profiles containing nuclei typical for microglia, as well as other unidentified cellular profiles. No signal was obtained over the contralateral unaffected hemisphere. Northern blot analysis revealed a strong expression of TGF-beta 1 mRNA in tumour tissue, a lesser signal in the peritumoural reactive brain tissue and virtually no signal in normal tissue. Our data indicate that the experimental rat glioma has the potential to secrete TGF-beta in vivo which might render the microglial infiltration ineffective. TGF-beta expressed by activated microglial cells themselves might further inhibit their tumoricidal potential, thus contributing further to unrestrained tumour growth.

Animals↗
PubMed1994

Oligodendrocytes produce low molecular weight glycoproteins containing N-acetyl-D-glucosamine in their Golgi apparatus.

Lectin histochemistry using the Griffonia simplicifolia II lectin (GSL II) has revealed a novel group of glycoproteins containing terminal N-acetyl-D-glucosamine (GlcNAc) residues in oligodendrocytes. The GlcNAc-containing glycoproteins were not present in other types of glial cells, but were expressed by some neuronal cell populations. Within oligodendrocytes their localization was confined to the Golgi apparatus, as determined ultrastructurally. Biochemical analyses using tricine/SDS-polyacrylamide gel electrophoresis and western blotting with GSL II showed the GlcNAc-containing glycoproteins to be insoluble, with molecular masses ranging from 15 to 30 kDa. Our study provides a first account of insoluble, GlcNAc-rich 15-30 kDa glycoproteins in oligodendroglia. The findings are discussed in the context of the functional significance of other known oligodendrocyte glycoproteins.

Acetylglucosamine↗