Evidence for prion protein expression in enteroglial cells of the myenteric plexus of mouse intestine

Transmissible spongiform encephalopathies (TSEs) are slowly progressive and fatal neurodegenerative diseases affecting man and animals. They are caused by pathological isoforms (PrP(Sc)) of the host-encoded cellular prion protein (PrP(C)). There are two crucial factors for the initiation of infection, namely host cells PrP(C) expression and sufficient sequence homology between the PrP(Sc) to which the animal is exposed and its own PrP(C). In acquired TSEs, the gastrointestinal tract (GIT) is the main prion entry site. Hence, it is of paramount importance to an understanding of the early pathogenesis of prion infections, to characterize the GIT cell types constitutively expressing PrP(C). Twenty-three mice were utilized, including wild-type (WT), Prnp knock-out (KO), and PrP(C)-overexpressing (tga20/tga20) animals, of 20-30 g in weight and of either sex. In all three groups of mice, PrP(C)-immunoreactivity (IR), along with glial fibrillary acidic protein (GFAP)-IR and synaptophysin (Syn)-IR were investigated by means of indirect immunofluorescence in wholemount preparations from several gut regions, from duodenum to rectum. In WT mice, PrP(C)-IR and GFAP-IR co-localization was observed in enteric glial cells (EGCs) from all intestinal segments. PrP(C)-overexpressing mice showed a stronger PrP(C)-IR in EGCs, whereas the same cells exhibited no PrP(C)-IR in Prnp-KO mice. Our findings clearly indicate that EGCs of the mouse intestine constitutively express PrP(C); thus they could be a potential target for infectious prions.     

Amyloid precursor protein and amyloid precursor-like protein 2 have distinct roles in modulating myelination,demyelination, and remyelination of axons

The identification of factors that regulate myelination provides important insight into the molecular mechanisms that coordinate nervous system development and myelin regeneration after injury. In this study, we investigated the role of amyloid precursor protein (APP) and its paralogue amyloid precursor-like protein 2 (APLP2) in myelination using APP and APLP2 knockout (KO) mice. Given that BACE1 regulates myelination and myelin sheath thickness in both the peripheral and central nervous systems, we sought to determine if APP and APLP2, as alternate BACE1 substrates, also modulate myelination, and therefore provide a better understanding of the events regulating axonal myelination. In the peripheral nervous system, we identified that adult, but not juvenile KO mice, have lower densities of myelinated axons in their sciatic nerves while in the central nervous system, axons within both the optic nerves and corpus callosum of both KO mice were significantly hypomyelinated compared to wild-type (WT) controls. Biochemical analysis demonstrated significant increases in BACE1 and myelin oligodendrocyte glycoprotein and decreased NRG1 and proteolipid protein levels in both KO brain tissue. The acute cuprizone model of demyelination/remyelination revealed that whereas axons in the corpus callosum of WT and APLP2-KO mice underwent similar degrees of demyelination and subsequent remyelination, the myelinated callosal axons in APP-KO mice were less susceptible to cuprizone-induced demyelination and showed a failure in remyelination after cuprizone withdrawal. These data identified APP and APLP2 as modulators of normal myelination and demyelination/remyelination conditions. Deletion of APP and APLP2 identifies novel interplays between the BACE1 substrates in the regulation of myelination.     

An occasional diagnosis of myasthenia gravis - a focus on thymus during cardiac surgery: a case report

Background  

Myasthenia gravis, an uncommon autoimmune syndrome, is commonly associated with thymus abnormalities. Thymomatous myasthenia gravis is considered to have worst prognosis and thymectomy can reverse symptoms if precociously performed.     

Differential expression and seasonal modulation of VGF peptides in sheep pituitary

The inducible gene vgf and its peptide products are relevant to the neuroendocrine regulation of homeostasis and reproduction in rodents. We show here that in the anterior pituitary of female sheep the somatotrope, gonadotrope, and lactotrope/thyrotrope cell populations each expressed vgf mRNA, but displayed a distinct profile of VGF immunoreactive peptides. ProVGF C-terminus and VGF(443-588) immunoreactivities were found in lactotropes and thyrotropes, often in a subcellular location restricted to the Golgi area and suggestive of rapid peptide (or proVGF) release upon biosynthesis, while high molecular weight bands consistent with proVGF were shown in pituitary extracts. Distinct seasonal changes were revealed, proVGF C-terminus immunoreactive cells being largely identified as lactotropes during the summer (83.7 +/- 2.1% (mean +/-s.e.m.) versus 27.0 +/- 1.9% during the winter), as opposed to thyrotropes during the winter (73.0 +/- 1.9% versus 16.3 +/- 2.1% during the summer). Conversely, antisera to peptides adjacent to the 'Arg-Pro-Arg' cleavage site, and to the VGF(553-555) N-terminus of the proVGF-derived peptide V, selectively labeled gonadotropes, indicating processing to small peptides not retaining the proVGF C-terminus in such cells. Finally, a peptide related to the VGF(4-240) region was immunostained in somatotropes, shown in a Western blot as a band of relative molecular mass of approximately 16,000. In conclusion, a complex, endocrine cell-type-specific processing of proVGF was revealed. Further to the known inducibility of vgf mRNA upon a range of stimuli, discreet, selective modulations of VGF-peptide profile/s are suggested, possibly involved in specific neuro/endocrine or modulatory mechanisms.     

Further observations on the sensitive innervation of some bird's proctodeum

The AA. studied the autonomic and sensitive somatic innervation of some female bird's proctodeum, through the properly modified Ruffini's gold chloride method. The vegetative component was constituted by ganglion cells of different size, isolated or grouped to form ganglia, found along the course of nerve trunks or in the concurrent point of different nerve bundles. The sensitive somatic innervation was represented by free and encapsulated endings differently distributed in the thickness of the wall. The former were composed of thin networks, while the latter, located more frequently in the muscular tunica and in the subadventitial connective, were composed of encapsulated receptors classified as Pacini, Pacini-like and Herbst corpuscles. The morphology of these receptors was described and hypotheses were brought up about their probable functional role. The AA, also found, even if very rarely, helicoidal collagen fibres around nerve fascicles.     

On the bulky appliances and artero-venous anastomoses in the vascular district of the base of the brain

It has been studied the vascular territory of the base of the brain and it has been pointed out the presence of characteristical structural arrangements of the vasal wall and artero-venous anastomoses. The just mentioned characteristical structures are placed in points where a vessel divides itself or creates a collateral branch and their functional engagement is target-oriented to control the blood flux.     

Bioaugmentation-Assisted Phytostabilisation of Abandoned Mine Sites in South West Sardinia

Bioaugmentation-assisted phytoremediation implies the administration of selected plant growth promoting bacteria, which significantly improve plant growth and sequestration of heavy metals. In this work, 184 bacterial strains associated with roots of Pistacia lentiscus were isolated from plants spontaneously growing in the abandoned Sardinian mining areas (SW Sardinia, Italy) and phylogenetically characterised. Twenty-one bacterial isolates were assayed for properties relevant for plant growth promotion and metal tolerance. Five different strains, belonging to the genera Novosphingobium, Variovorax, Streptomyces, Amycolatopsis, Pseudomonas, were selected based on their properties for the greenhouse phytoremediation tests. Among the tested inocula, the strain Variovorax sp. RA128A, able to produce ACC deaminase and siderophore, was able to significantly enhance germination and increase length and weight of shoots and roots. Irrespective of the applied treatment, mastic shrub was able to accumulate Cd, Pb and Zn especially in roots.     

Astroglial in vivo response to cocaine in mouse dentate gyrus: a quantitative and qualitative analysis by confocal microscopy

Astrocytes have been proved to play a critical role in neuromodulation, neuroprotection, pH maintenance, axon guidance control during development, homeostasis preservation and blood brain barrier maintenance in the CNS (Kimmelberg and Norenberg, 1989). Quantitative changes in the expression of glial fibrillary acidic protein (GFAP), a cytoskeletal intermediate filament protein exclusively expressed in astrocytes (Bignami et al, 1972), have been observed after administration of alcohol (Framke, 1995), morphine (Beitner-Johnson et al., 1993), amphetamine and its derivates (Aguirre et al., 1999), cannabinoids (Suarez et al., 2000), nicotine (Janson and Moller, 1993), caffeine (Marret et al., 1993) and prenatal exposure to cocaine (Clarke et al., 1996; Nassogne et al., 1998). However, the general astrocytic response to drugs of abuse is still far from being defined. In the present study we examined the in vivo astroglial response to cocaine in mouse dentate gyrus, the hippocampus being a common target of neurotoxic agents (Walsh and Emerich, 1988) which has a prominent effect on learning and memory processes (Eichenbaum et al., 1992). Quantitative changes in immunoreactivity of GFAP were investigated 24 h after acute and repeated daily administration of intraperitoneal cocaine (20 mg/kg). Drug-induced morphological alterations and spatial distribution of astrocytes were evaluated by means of confocal microscope. The results show that, compared to control animals, GFAP expression is two-fold enhanced after a single cocaine injection, still significantly higher after seven consecutive daily administrations, but not statistically different after prolonged (14 days) drug treatment. Moreover, morphological and morphometric analyses reveal significant modifications in astrocytic numbers, cell size and shape complexity. These data demonstrate that in mouse dentate gyrus, cocaine exposure differently affects the expression of GFAP and induces strong changes in astrocytes proliferation rate and cell morphology. Taken together, our findings provide the first in vivo quantitative and qualitative evaluation of astrocytic response to several regimens of cocaine in adult animals brain.     

Prion Protein-Deficient Neurons Reveal Lower Glutathione Reductase Activity and Increased Susceptibility to Hydrogen Peroxide Toxicity

The prion protein (PrP) has a central role in the pathogenesis of transmissible spongiform encephalopathies (TSE). Accumulating evidence suggests that normal cellular PrP (PrP(c)) may be involved in copper homeostasis and modulation of copper/zinc superoxide dismutase (Cu/ZnSOD) activity in neurons. Hydrogen peroxide (H(2)O(2)) is a toxic reactive oxygen species generated through normal cellular respiration, and neurons contain two important peroxide detoxifying systems (glutathione pathway and catalase). To determine whether PrP expression affects neuronal resistance to H(2)O(2), we exposed primary cerebellar granule neuron cultures derived from PrP knockout (PrP(-/-)) and wild-type (WT) mice to H(2)O(2) for 3, 6, and 24 hours. The PrP(-/-) neurons were significantly more susceptible to H(2)O(2) toxicity than WT neurons after 6 and 24 hours' exposure. The increased H(2)O(2) toxicity may be related to a significant decrease in glutathione reductase activity measured in PrP(-/-) neurons both in vitro and in vivo. This was supported by the finding that inhibition of GR activity with 1,3-bis(2-chloroethyl)-1-nitrosurea (BCNU) increased H(2)O(2) toxicity in WT neurons over the same exposure period. The PrP toxic peptide PrP106-126 significantly reduced neuronal glutathione reductase activity and increased susceptibility to H(2)O(2) toxicity in neuronal cultures suggesting that PrP toxicity in vivo may involve altered glutathione reductase activity. Our results suggest the pathophysiology of prion diseases may involve perturbed PrP(c) function with increased vulnerability to peroxidative stress.