AAV1/2-mediated BDNF gene therapy in a transgenic rat model of Huntington's disease

Reduced expression and disrupted corticostriatal transportation of brain-derived neurotrophic factor (BDNF) is proposed to contribute to the selective vulnerability of medium spiny striatal projection neurons (MSNs) in Huntington's disease (HD). We have previously demonstrated that BDNF overexpression in the quinolinic acid lesioned rat striatum attenuates motor impairment and reduces the extent of MSN cell loss. To further investigate the potential therapeutic properties of BDNF for HD, the current study examines the effect of bilateral AAV1/2-mediated BDNF expression in the striatum of a transgenic rat model of HD. Transfer of the BDNF gene to striatal neurons using an AAV1/2 serotype vector enhanced BDNF protein levels in the striatum. Bilateral BDNF expression attenuated the impairment of both motor and cognitive function when compared with AAV1/2-vehicle- or YFP-treated transgenic HD rats. Interestingly, a gender effect was apparent with female transgenic HD rats exhibiting less functional impairment than males. Quantification of NeuN and DARRP32 immunoreactivity and striatal volume revealed limited disease phenotype between wild type and transgenic HD animals. However, AAV1/2-BDNF-treated transgenic HD rats showed evidence of greater striatal volume and increased NeuN+ cell numbers compared with wild-type vehicle- and AAV1/2-vehicle- or YFP-treated transgenic HD rats. We propose BDNF holds considerable therapeutic potential for alleviating behavioral dysfunction and neuronal degeneration in HD, with further work required to examine the role of BDNF-TrkB signaling and the preservation of axonal and synaptic function.

Redirection of doublecortin-positive cell migration by over-expression of the chemokines MCP-1, MIP-1α and GRO-α in the adult rat brain

Inflammation-induced chemoattraction plays a major role in adult subventricular zone (SVZ)-derived precursor cell migration following neural cell loss, in particular through the release of chemokines by activated microglia and macrophages. We previously demonstrated that monocyte chemotactic protein-1 (MCP-1) (chemokine (c-c motif) ligand (CCL)2), macrophage inflammatory protein-1α (MIP-1α) (CCL3) and growth regulatory protein-α (GRO-α) (chemokine (c-x-c motif) ligand (CXCL)1) are up-regulated following neural cell loss in the adult striatum and act as potent chemoattractants for SVZ-derived precursor cells in vitro. Based on these observations, the current study aimed to examine the individual effect of MCP-1, MIP-1α and GRO-α on the migration of adult SVZ-derived neural precursor cells in vivo. To address this without the confounding effects of injury-induced chemotactic cues, adeno-associated viral (AAV)2-mediated in vivo gene transfer was used to ectopically express either MCP-1, MIP-1α or GRO-α, or the control red fluorescent protein (RFP) in the normal adult rat striatum. The extent of doublecortin (Dcx)-positive cell recruitment from the SVZ into the striatal parenchyma was then determined at 4 and 8weeks following AAV2 injection. Ectopic expression either of MCP-1 or MIP-1α in the normal adult rat brain significantly increased the number of Dcx-positive cells and the extent of their migration into the striatum at both 4 and 8weeks after vector injection but did not promote either precursor cell proliferation or neural differentiation. In contrast, while over-expression of GRO-α 4weeks after vector injection induced a significant increase in Dcx-positive cell migration compared to control, this effect was reduced to control levels by 8weeks post injection. Further, direct comparison between MCP-1, MIP-1α and GRO-α at both 4 and 8weeks post vector injection indicated that GRO-α may have a reduced effect in inducing Dcx-positive cell migration when compared to MCP-1. Combined, these results confirm that over-expression of the chemokines MCP-1, MIP-1α and GRO-α can override cues directing precursor cell migration along the rostral migratory stream (RMS) and provides a mechanism by which neural precursor cell migration can be redirected into a non-neurogenic region. Differences in the migratory effect observed between individual chemokine may be due to ligand-binding affinity and/or receptor expression on SVZ-derived precursor cells.

IGF-I redirects doublecortin-positive cell migration in the normal adult rat brain

The migration of subventricular zone (SVZ)-derived neural precursor cells through the rostral migratory stream (RMS) to the olfactory bulb is tightly regulated by local micro-environmental cues. Insulin-like Growth Factor-I (IGF-I) can stimulate the migration of several neuronal cell types and acts as a 'departure' factor in the avian SVZ. To establish whether IGF-I can also act as a migratory factor for adult neuronal precursor cells in vivo, in addition to its well established role in precursor cell proliferation and differentiation, we used AAV2-mediated gene transfer to produce ectopic expression of IGF-I in the normal adult rat striatum. We then assessed whether the expression of IGF-I would recruit SVZ-derived neuronal precursor cells from the RMS into the striatum. Ectopic expression of IGF-I in the normal adult rat brain significantly increased the number of doublecortin (Dcx)-positive cells and the extent of their migration into the striatum 4 and 8 weeks after AAV2-IGF-I injection but did not promote neuronal differentiation. In vitro migration assays confirmed that IGF-I is an inducer of migration and directs SVZ-derived adult neuronal precursor cell migration by both chemotaxis and chemokinesis. These results demonstrate that overexpression of IGF-I in the normal adult rat brain can override the normal cues directing precursor cell migration along the RMS and can redirect precursor cell migration into a non-neurogenic region. Enhanced expression of IGF-I following brain injury may therefore act as a diffusible factor mediating precursor cell migration to areas of neuronal cell damage.

Non-Viral Generation of Neural Precursor-like Cells from Adult Human Fibroblasts

Recent studies have reported direct reprogramming of human fibroblasts to mature neurons by the introduction of defined neural genes. This technology has potential use in the areas of neurological disease modeling and drug development. However, use of induced neurons for large-scale drug screening and cell-based replacement strategies is limited due to their inability to expand once reprogrammed. We propose it would be more desirable to induce expandable neural precursor cells directly from human fibroblasts. To date several pluripotent and neural transcription factors have been shown to be capable of converting mouse fibroblasts to neural stem/precursor-like cells when delivered by viral vectors. Here we extend these findings and demonstrate that transient ectopic insertion of the transcription factors SOX2 and PAX6 to adult human fibroblasts through use of non-viral plasmid transfection or protein transduction allows the generation of induced neural precursor (iNP) colonies expressing a range of neural stem and pro-neural genes. Upon differentiation, iNP cells give rise to neurons exhibiting typical neuronal morphologies and expressing multiple neuronal markers including tyrosine hydroxylase and GAD_65/67. Importantly, iNP-derived neurons demonstrate electrophysiological properties of functionally mature neurons with the capacity to generate action potentials. In addition, iNP cells are capable of differentiating into glial fibrillary acidic protein (GFAP)-expressing astrocytes. This study represents a novel virusfree approach for direct reprogramming of human fibroblasts to a neural precursor fate.

Chemokines influence the migration and fate of neural precursor cells from the young adult and middle-aged rat subventricular zone

We have previously demonstrated a role for the chemokines MCP-1, MIP-1α and GRO-α in directing subventricular zone (SVZ)-derived neural precursor cell migration towards the site of cell death in the adult rodent brain. However the influence of chemokines such as MCP-1, MIP-1α and GRO-α on the differentiation of adult neural precursor cells has not previously been investigated. Further, as the majority of neurological disorders and injuries occur during ageing, it is important to investigate the effect of chemokines on adult neural precursor cell cultures obtained from the ageing brain. This study therefore examined the effect of MCP-1, MIP-1α and GRO-α on SVZ-derived neural precursor cell differentiation in vitro, and assessed whether precursor cells from the middle-aged rat brain (13 months old) follow the same migratory and differential profile as neural precursor cells obtained from the young adult rat brain (2 months old). We observed that each of the chemokines examined generated differing effects in regards to neuronal or glial differentiation. Further, both MIP-1α and GRO-α increased total cell number, suggesting an effect on precursor cell proliferation and/or survival. In agreement with cultures obtained from young adult brains, SVZ-derived neural precursor cells cultured from the middle-aged brain exhibited chemotactic migration in response to a concentration gradient. These results indicate that the chemokines MCP-1, MIP-1α and GRO-α can influence both the migration and fate choice of SVZ-derived neural precursor cells, as well as promoting cell viability. While a response to each of these chemokines is maintained in the middle-aged brain, a distinct age-related alteration in differential fate can be identified.

Doublecortin expression in the normal and epileptic adult human brain

Mesial temporal lobe epilepsy (MTLE) is a neurological disorder associated with spontaneous recurrent complex partial seizures and hippocampal sclerosis. Although increased hippocampal neurogenesis has been reported in animal models of MTLE, increased neurogenesis has not been reported in the hippocampus of adult human MTLE cases. Here we showed that cells expressing doublecortin (Dcx), a microtubule-associated protein expressed in migrating neuroblasts, were present in the hippocampus and temporal cortex of the normal and MTLE adult human brain. In particular, increased numbers of Dcx-positive cells were observed in the epileptic compared with the normal temporal cortex. Importantly, 56% of Dcx-expressing cells in the epileptic temporal cortex coexpressed both the proliferative cell marker, proliferating cell nuclear antigen and early neuronal marker, TuJ1, suggesting that they may be newly generated neurons. A subpopulation of Dcx-positive cells in the epileptic temporal cortex also coexpressed the mature neuronal marker, NeuN, suggesting that epilepsy may promote the generation of new neurons in the temporal cortex. This study has identified, for the first time, a novel population of Dcx-positive cells in the adult human temporal cortex that can be upregulated by epilepsy and thus, raises the possibility that these cells may have functional significance in the pathophysiology of epilepsy.

AAV-BDNF mediated attenuation of quinolinic acid-induced neuropathology and motor function impairment

Maintenance and plasticity of striatal neurons is dependent on brain-derived neurotrophic factor (BDNF), which is depleted in the Huntington's disease striatum due to reduced expression and disrupted corticostriatal transportation. In this study we demonstrate that overexpression of BDNF in the striatum attenuates motor impairment and reduces the extent of striatal damage following quinolinic acid lesioning. Transfer of the BDNF gene to striatal neurons using serotype 1/2 adeno-associated viral vectors enhanced BDNF protein levels in the striatum, but induced weight loss and seizure activity following long-term high-level expression. Lower concentration BDNF expression supported striatal neurons against excitotoxic insult, as demonstrated by enhanced krox-24 immunopositive neuron survival, reduction of striatal atrophy and maintenance of the patch/matrix organization. Additionally, BDNF expression attenuated motor impairment in the forelimb use cylinder test, sensorimotor neglect in the corridor food selection task and reversed apomorphine-induced rotational behaviour. Direct correlations were shown for the first time between BDNF-mediated attenuation of behavioural impairment and the integrity of the globus pallidus, seemingly independent from the severity of striatal lesioning. These results demonstrate that BDNF holds considerable therapeutic potential for alleviating both neuropathological and motor function deficits in the Huntington's disease brain, and the critical role of pallidal neurons in facilitating motor performance.

Nucleolar enlargement, nuclear eccentricity and altered cell body immunostaining characteristics of large-sized sensory neurons following treatment of rats with paclitaxel

Paclitaxel-induced sensory neuropathy is a problematic side-effect of cancer chemotherapy. Previous studies in rodents have shown paclitaxel treatment to have many effects on different parts of the peripheral nervous system, but those responsible for its bothersome clinical side-effects are still unclear. In the current study, we sought to obtain information about the involvement of sensory neurons in paclitaxel neurotoxicity at the level of the dorsal root ganglion. Rats were treated with a clinically relevant dose of paclitaxel (87.5mg/m(2) weekly for a total of nine doses) to induce a sensory neuropathy; then their L5 dorsal root ganglia were studied by morphometry and immunohistochemistry. Paclitaxel treatment was generally well tolerated, and slowed conduction velocity and prolonged conduction latencies in the peripheral sensory nerves without altering conduction in the central or motor pathways of the H-reflex arc. In the L5 dorsal root ganglion, nucleolus size and the number of neurons with eccentric nuclei were increased only in a subpopulation of dorsal root ganglion neurons with cell body cross-sectional areas greater than 1750 microm(2), which made up less than 10% of the total population. Paclitaxel treatment increased immunohistochemical staining for activating transcription factor-3 (ATF-3), c-Jun and neuropeptide Y (NPY) but only in a small percentage of neuronal cell bodies and mainly in those with large cell bodies. In conclusion, we have demonstrated that nucleolar enlargement, nuclear eccentricity, ATF-3, c-Jun and NPY are neuronal markers of paclitaxel-induced sensory neuropathy, however, these axotomy-like cell body reactions are infrequent and occur in mainly large-sized sensory neurons.

Adult neurogenesis in mesial temporal lobe epilepsy: a review of recent animal and human studies

Mesial temporal lobe epilepsy (mTLE) is a neurological condition characterized by the occurrence of spontaneous recurrent seizures originating from mesial structures involving the hippocampus within the temporal lobe. This condition is often associated with pathological features in the hippocampus such as neuronal cell loss, widening of the granule cell layer, astrogliosis and mossy fibre spouting. At present, the mechanisms underlying these pathological features are unclear. However, recent advances in adult neurogenesis studies in mTLE animals and patients suggest that newly generated neurons may contribute to the pathogenesis of ongoing epileptogenesis. This article will review the recent animal and human studies on adult neurogenesis in mTLE and discuss how these results suggests that adult endogenous neurogenesis may not always be reparative in the mTLE and may be targeted in new therapeutic strategies for mTLE.

Temporal profile of subventricular zone progenitor cell migration following quinolinic acid-induced striatal cell loss

A number of studies have demonstrated directed migration of neural progenitor cells to sites of brain injury and disease, however a detailed examination of when a cell is "born" in relation to injury induction and the migratory response of that cell has not previously been determined. This study therefore examined the temporal correlation between progenitor cell proliferation ("birth") and neuroblast migratory response into the damaged striatum following quinolinic acid (QA) lesioning of the adult rat striatum. Retroviral labeling of subventricular zone (SVZ)-derived progenitor cells demonstrated that cell loss in the QA-lesioned striatum increased progenitor cell migration through the rostral migratory stream (RMS) for up to 30 days. In addition, a population of dividing cells originating from the SVZ generated doublecortin positive neuroblasts that migrated into the damaged striatum in response to cell loss invoked by the QA lesion. Quantification of bromodeoxyuridine (BrdU)-labeled cells co-expressing doublecortin revealed that the majority of cells present in the damaged striatum were generated from progenitor cells dividing within 2 days either prior to or following the QA lesion. In contrast, cells dividing 2 or more days following QA lesioning, migrated into the striatum and exhibited a glial phenotype. These results demonstrate that directed migration of SVZ-derived cells and neuroblast differentiation in response to QA lesioning of the striatum is acute and transient. We propose this is predominantly due to a reduced capacity over time for newly generated neuroblasts to respond to the lesioned environment due to a loss or inhibition of migratory cues.

The distribution of progenitor cells in the subependymal layer of the lateral ventricle in the normal and Huntington's disease human brain

The recent demonstration of endogenous stem/progenitor cells in the adult mammalian brain raises the exciting possibility that these undifferentiated cells may be able to generate new neurons for cell replacement in neurodegenerative diseases such as Huntington's disease (HD). Previous studies have shown that neural stem cells in the rodent brain subependymal layer (SEL), adjacent to the caudate nucleus, proliferate and differentiate into neurons and glial cells and that neurogenesis occurs in the hippocampus and the SEL of the caudate nucleus in the adult human brain, but no previous study has shown the extent to which progenitor cells are found in the SEL in the normal and diseased human brain with respect to location. From detailed serial section studies we have shown that overall, there is a 2.7-fold increase in the number of proliferating cell nuclear antigen positive cells in HD (grade 2/3); most notably, the ventral and central regions of the SEL adjacent to the caudate nucleus contained the highest number of proliferating cells and in all areas and regions examined there were more cells in the HD SEL compared with the normal brain. Furthermore, progenitor cells colocalized with betaIII tubulin in a subset of cells in the SEL indicating neurogenesis in the HD brain. There was a 2.6-fold increase in the number of new neurons that were produced in the Huntington's disease SEL compared with the normal SEL; however, the Huntington's disease SEL had many more proliferating progenitor cells; thus, the proportion of new neuron production relative to the number of progenitor cells was approximately the same. This study provides new evidence of the pattern of neurogenesis in the normal and HD brain.

Oxaliplatin causes selective atrophy of a subpopulation of dorsal root ganglion neurons without inducing cell loss

Peripheral neuropathy is induced by multiple doses of oxaliplatin and interferes with the clinical utility of the drug in patients with colorectal cancer. In this study, we sought to determine whether cell loss or selective neuronal damage was the basis for the peripheral neuropathy caused by oxaliplatin. Adult female rats were given 1.85 mg/kg oxaliplatin twice per week for 8 weeks. Nerve conduction and L5 dorsal root ganglia (DRG) were studied 1 week after the completion of all treatment. No mortality occurred during oxaliplatin treatment, but the rate of body weight gain was reduced compared to age-matched vehicle-treated controls. Oxaliplatin slowed conduction velocity and delayed conduction times in peripheral sensory nerves, without affecting central or motor nerve conduction. In L5 DRG, total numbers of neurons were unchanged by oxaliplatin, but there were significant reductions in neuronal size distribution, ganglion volume, average cell size and the relative frequency of large cells. In addition, the relative frequency of small DRG cells was increased by oxaliplatin. Oxaliplatin significantly altered the size distribution and average cell body area of the predominantly large parvalbumin-immunoreactive DRG neurons without affecting the frequency of parvalbumin staining. On the contrary, neither the staining frequency nor the size distribution of the predominantly small substance P-immunoreactive DRG neurons was changed by oxaliplatin. In conclusion, oxaliplatin causes selective atrophy of a subpopulation of DRG neurons with predominantly large parvalbumin-expressing cells without inducing neuronal loss. Because DRG cell body size and axonal conduction velocity are positively correlated, neuronal atrophy may be the morphological basis for the development of decreased sensory nerve conduction velocity that characterizes oxaliplatin-induced peripheral neuropathy.

Neurogenesis in the striatum of the quinolinic acid lesion model of Huntington's disease

The presence of ongoing neurogenesis in the adult mammalian brain raises the exciting possibility that endogenous progenitor cells may be able to generate new neurons to replace cells lost through brain injury or neurodegenerative disease. We have recently demonstrated increased cell proliferation and the generation of new neurons in the Huntington's disease human brain. In order to better understand the potential role of endogenous neuronal replacement in neurodegenerative disorders and extend our initial observations in the human Huntington's disease brain, we examined the effect of striatal cell loss on neurogenesis in the subventricular zone (SVZ) of the adult rodent forebrain using the quinolinic acid (QA) lesion rat model of Huntington's disease. Cell proliferation and neurogenesis were assessed with bromodeoxyuridine (BrdU) labeling and immunocytochemistry for cell type-specific markers. BrdU labeling demonstrated increased cell proliferation in the SVZ ipsilateral to the QA-lesioned striatum, resulting in expansion of the SVZ in the lesioned hemisphere. Quantification revealed that QA lesion-induced striatal cell loss produced a significant increase in the area of BrdU-immunoreactivity in the SVZ ipsilateral to the lesioned hemisphere between 1 and 14 days post-lesion compared with sham-lesioned animals, with the greatest increase observed at 7 days post-lesion. These changes were associated with an increase in cells in the anterior SVZ ipsilateral to the lesioned striatum expressing the antigenic marker for SVZ neuroblasts, doublecortin (Dcx). Importantly, we observed Dcx-positive cells extending from the SVZ into the QA-lesioned striatum where a subpopulation of newly generated cells expressed markers for immature and mature neurons. This study demonstrates that loss of GABAergic medium spiny projection neurons following QA striatal lesioning of the adult rat brain increases SVZ neurogenesis, leading to the putative migration of neuroblasts to damaged areas of the striatum and the formation of new neurons.

Quantitative analyses of GFRα-1 and GFRα-2 mRNAs and tyrosine hydroxylase protein in the nigrostriatal system reveal bilateral compensatory changes following unilateral 6-OHDA lesions in the rat

Copy numbers of mRNAs for GFRalpha-1 and GFRalpha-2, the preferred receptors for glial cell line-derived neurotrophic factor (GDNF) and neurturin (NTN) were determined by real-time quantitative RT-PCR (QRT-PCR). Receptor expression was assessed in striatum (ST) and substantia nigra (SN) of normal rats and rats acutely or progressively lesioned by 6-OHDA injected into the medial forebrain bundle or ST, respectively. GFRalpha-1 mRNA was clearly detected in normal ST. In normal SN, significantly higher expression of both receptors was observed. At 4 weeks after acute lesion, GFRalpha-2 mRNA was markedly decreased in SN bilaterally, whereas GFRalpha-1 mRNA in SN and ST was not affected. A progressive lesion resulted in a progressive decrease of GFRalpha1 mRNA in ST bilaterally. In SN, levels of GFRalpha-1 mRNA were not significantly affected by a progressive lesion, whereas GFRalpha-2 mRNA was markedly decreased bilaterally. Quantitative western blotting standardized against tyrosine hydroxylase (TH) protein from PC12 cells revealed the expected decrease in TH protein in lesioned SN, but also significant increases in TH protein in contralateral, unlesioned SNs at 4 weeks after both acute and progressive lesions. These data suggest that previously unrecognized compensatory changes in the nigrostriatal system occur in response to unilateral dopamine depletion. Since the changes observed in receptor expression did not always parallel loss of dopamine neurons, cells in addition to the nigral dopamine neurons appear to be affected by a 6-OHDA insult and are potential targets for the neurotrophic factors, GDNF and NTN.

Hepatitis A booster vaccination: is there a need?

Hepatitis A is one of the most common vaccine-preventable infectious diseases in the world. Effective vaccines against hepatitis A have been available since 1992, and they provide long-term immunity against the infection. However, there is no worldwide consensus on how long protection will last or whether there will be a need for hepatitis A virus (HAV) booster vaccinations in the future. In most countries, booster-vaccination policy is guided by manufacturers' recommendations, national authorities, or both. In June, 2002, a panel of international experts met to review the long-term immunogenicity and protection conferred by HAV vaccine in different population groups. Data have shown that after a full primary vaccination course, protective antibody amounts persist beyond 10 years in healthy individuals, and underlying immune memory provides protection far beyond the duration of anti-HAV antibodies. The group concluded that there is no evidence to lend support to HAV booster vaccination after a full primary vaccination course in a healthy individual. However, further investigations are needed before deciding if boosters can be omitted in special patient-groups.

Adenoviral vector-mediated delivery of glial cell line-derived neurotrophic factor provides neuroprotection in the aged parkinsonian rat

1. The long-term delivery of neurotrophic factors to specific regions of the central nervous system via gene therapy offers a new strategy for the treatment of neurodegenerative disorders. 2. The neurotrophic factor glial cell line-derived neurotrophic factor (GDNF) is a potent dopaminergic (DA) trophic factor that ameliorates the behavioural and histological consequences of lesioning DA neurons in rodent and primate models of Parkinson's disease. 3. Glial cell line-derived neurotrophic factor gene therapy may have a potential use in the clinical treatment of Parkinson's disease. 4. We examined whether injection of an adenoviral vector encoding human GDNF preproprotein (Ad GDNF) could protect the rat nigrostriatal DA system from progressive neuronal degeneration. Because Parkinson's disease occurs primarily in the elderly population, we studied the effect of GDNF gene delivery in an aged rat model of Parkinson's disease. 5. In the aged (20 month) Fischer 344 rat, Ad GDNF was injected either near DA cell bodies in the substantia nigra (SN) or at the DA terminals in the striatum. One week following gene delivery, the neurotoxin 6-hydroxydopamine (6-OHDA) was injected unilaterally into the striatum to cause progressive degeneration of the DA neurons. 6. Injection of GDNF vector into either the striatum or the SN provided significant cell protection against 6-OHDA. However, only striatal injection of Ad GDNF protected against the development of behavioural and neurochemical changes that occur in the DA-depleted brain. 7. The results of this study are reviewed here and the behavioural and cellular effects of GDNF gene delivery into striatal versus mesencephalic sites are discussed.

Iron-mediated reactions of polychlorinated biphenyls in electrochemical peroxidation process (ECP)

A study was conducted to explore some of the basic processes of polychlorinated biphenyl (PCB) destruction by a new technology termed electrochemical peroxidation process (ECP). ECP represents an enhancement of the classic Fenton reaction (H2O2 + Fe2+) in which iron is electrochemically generated by steel electrodes. Focus was on the extent of adsorption of a mixture of Aroclor 1248 on steel electrodes in comparison to iron filings. Commercially available zero-valent iron filings rapidly adsorbed PCBs from an aqueous solution of Aroclor 1248. Within 4 h, all the PCBs were adsorbed at 1%, 5%, and 10% Fe0 (w/v) concentrations. Little difference in adsorption was found between acidic (2.3) and unamended solutions (pH 5.5), even though significant differences in iron oxidation state and Fe2+ concentrations were measured in solution. PCB adsorption also occurs on steel electrodes regardless of the pH or electric current applied (AC or DC), suggesting the combination of oxidizing (free radical-mediated reactions) and reducing (dechlorination reactions) iron-mediated degradation pathways may be possible. Extraction of the iron powder after 48 h of contact time yielded the progressive recovery of biphenyl with increasing Fe mass(from 0.4% to 3.5%) and changes of the PCB congener-specific pattern as a consequence of dechlorination. A variety of daughter congeners similar to those accumulated during anaerobic microbial dechlorination of Aroclor 1248 in contaminated sediments indicate preferential removal of meta- and para-chlorines.

Glial cell line-derived neurotrophic factor (GDNF) gene delivery protects dopaminergic terminals from degeneration

Previously, we observed that injection of an adenoviral (Ad) vector expressing glial cell line-derived neurotrophic factor (GDNF) into the striatum, but not the substantia nigra (SN), prior to a partial 6-OHDA lesion protects dopaminergic (DA) neuronal function and prevents the development of behavioral impairment in the aged rat. This suggests that striatal injection of AdGDNF maintains nigrostriatal function either by protecting DA terminals or by stimulating axonal sprouting to the denervated striatum. To distinguish between these possible mechanisms, the present study examines the effect of GDNF gene delivery on molecular markers of DA terminals and neuronal sprouting in the aged (20 month) rat brain. AdGDNF or a control vector coding for beta-galactosidase (AdLacZ) was injected unilaterally into either the striatum or the SN. One week later, rats received a unilateral intrastriatal injection of 6-OHDA on the side of vector injection. Two weeks postlesion, rats injected with AdGDNF into either the striatum or the SN exhibited a reduction in the area of striatal denervation and increased binding of the DA transporter ligand [(125)I]IPCIT in the lesioned striatum compared to control animals. Furthermore, injections of AdGDNF into the striatum, but not the SN, increased levels of tyrosine hydroxylase mRNA in lesioned DA neurons in the SN and prevented the development of amphetamine-induced rotational asymmetry. In contrast, the level of T1 alpha-tubulin mRNA, a marker of neuronal sprouting, was not increased in lesioned DA neurons in the SN following injection of AdGDNF either into the striatum or into the SN. These results suggest that GDNF gene delivery prior to a partial lesion ameliorates damage caused by 6-OHDA in aged rats by inhibiting the degeneration of DA terminals rather than by inducing sprouting of nigrostriatal axons.

Gene transfer for neuroprotection in animal models of Parkinson's disease and amyotrophic lateral sclerosis

Glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor for motoneurons (MN) and dopaminergic (DA) neurons, neurons which selectively die in amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD). GDNF gene delivery has been studied in rodent models of ALS and PD. In a mouse model of ALS, implantation of myoblasts retrovirally transduced with GDNF into hindlimb muscles at 6 weeks of age, i.e. prior to the onset of disease symptoms, increased the number of large MNs that maintained projections to treated muscles at 18 weeks of age. GDNF-treated mice also performed better on tests of motor function and had a delayed onset of disease. In a progressive degeneration rat model of PD, effects of in vivo GDNF gene therapy using an adenoviral vector (AdGDNF) were studied in young and aged rats. AdGDNF protected DA neurons against the neurotoxin, 6-hydroxydopamine (6-OHDA), and was effective whether injected either before or after 6-OHDA damage had commenced. However, if AdGDNF was injected prior to 6-OHDA, it was most effective in protecting against DA-dependent changes in the brain when injected near the terminals of the DA neurons. In contrast, if 6-OHDA damage had already commenced, AdGDNF was most effective if injected near the DA soma. These studies suggest that GDNF gene delivery into specific sites in the CNS or into muscle where MNs have access to secreted GDNF may slow the progression of PD and ALS, respectively. Neurotrophic factor gene therapy offers novel interventions not only for PD and ALS, but also other neurodegenerative diseases and injuries to the nervous system.

Glial cell line-derived neurotrophic factor (GDNF) as a defensive molecule for neurodegenerative disease: a tribute to the studies of antonia vernadakis on neuronal-glial interactions

Research stemming from interests in neuronal-glial interactions has led to the identification of a number of novel trophic factors, such as the dopaminergic neurotrophic factor glial cell line-derived neurotrophic factor (GDNF). Delivery of the GDNF gene to rat models of Parkinson's disease suggests a potential clinical use of GDNF gene therapy for humans with this disease. This review article briefly summarizes the history of GDNF and the effects of GDNF gene delivery prior to or after a lesion of the rat nigrostriatal system.

Delivery of a GDNF gene into the substantia nigra after a progressive 6-OHDA lesion maintains functional nigrostriatal connections

The effects of delivering GDNF via an adenoviral vector (AdGDNF) 1 week after lesioning dopaminergic neurons in the rat substantia nigra (SN) with 6-hydroxydopamine (6-OHDA) were examined. Rats were unilaterally lesioned by injection of 6-OHDA into the striatum, resulting in progressive degeneration of dopaminergic neurons in the SN. One week later, when substantial damage had already occurred, AdGDNF or a control vector harboring beta-galactosidase (AdLacZ) was injected into either the striatum or SN (3.2 x 10(7) PFU/microl in 2 microl). Rats were examined behaviorally with the amphetamine-induced rotation test and for forelimb use for weight-bearing movements. On day 30 postlesion, the extent of nigrostriatal tract degeneration was determined by injecting a retrograde tracer (FluoroGold) bilaterally into the lesioned striatum. Five days later, rats were sacrificed within 2 h of amphetamine injection to examine amphetamine-induced Fos expression in the striatum, a measure of dopaminergic-dependent function in target neurons. AdGDNF injection in the SN rescued dopaminergic neurons in the SN and increased the number of dopaminergic neurons that maintained a connection to the striatum, compared to rats injected with AdLacZ. Further support that these spared SN cells maintained functional connections to the striatum was evidenced by increased Fos expression in striatal target neurons and a decrease in amphetamine-induced rotation. In contrast to the effects observed in rats injected with AdGDNF in the SN, rats injected with AdGDNF in the striatum did not exhibit significant ameliorative effects. This study demonstrates that experimentally increasing levels of GDNF biosynthesis near the dopaminergic neuronal soma is effective in protecting the survival of these neurons and their function even when therapy is begun after 6-OHDA-induced degeneration has commenced. Thus, GDNF gene therapy may ameliorate the consequences of Parkinson's disease through rescuing compromised dopaminergic neurons.

Evaluation of the BACTEC MGIT 960 system for the recovery of mycobacteria

We evaluated the BACTEC MGIT 960 system, which is a fully automated, non-invasive, continuous monitoring system for the growth and detection of mycobacteria. Including respiratory and other specimens, 1,742 specimens were processed and inoculated into the BACTEC MGIT 960 and the BACTEC 460 TB Systems, as well as onto Lowenstein-Jensen (L-J) media. A total of 104 isolates of mycobacteria were recovered from all culture systems. This included Mycobacterium tuberculosis complex, Mycobacterium avium-intracellulare (MAI) complex and other mycobacteria (MOTT). The isolation rates for M. tuberculosis complex and MAI complex were comparable for the BACTEC 460 (54.8% and 13.5%) and the BACTEC MGIT 960 (51.9% and 13.5%). The overall isolation rate was less for BACTEC MGIT 960 (76.9%) which was due to lesser number of MOTT isolates recovered from this system. The mean times to detection (TTD) for all mycobacteria were 9.3 days for the BACTEC MGIT, 14.6 days for the BACTEC 460 and 21.6 days for L-J. A significant difference was observed when TTD was tested in relation to degree of positivity in smears, with the BACTEC MGIT maintaining the short TTD even with less number of bacilli in the smear. The contamination rates were, 6.4% for BACTEC MGIT, 2.9% for BACTEC 460 and 12.1% for L-J medium. The BACTEC MGIT 960 system shows performances comparable to the BACTEC 460 and seems to be a dependable, user friendly system.

Differential effects of glial cell line-derived neurotrophic factor (GDNF) in the striatum and substantia nigra of the aged Parkinsonian rat

Injection of an adenoviral (Ad) vector encoding human glial cell line-derived neurotrophic factor (GDNF) protects dopaminergic (DA) neurons in the substantia nigra (SN) of young rats. As Parkinson's disease occurs primarily in aged populations, we examined whether chronic biosynthesis of GDNF, achieved by adenovirus-mediated delivery of a GDNF gene (AdGDNF), can protect DA neurons and improve DA-dependent behavioral function in aged (20 months) rats with progressive 6-OHDA lesions of the nigrostriatal projection. Furthermore, the differential effects of injecting AdGDNF either near DA cell bodies in the SN or at DA terminals in the striatum were compared. AdGDNF or control vector was injected unilaterally into either the striatum or SN. One week later, rats received a unilateral intrastriatal injection of 6-OHDA on the same side as the vector injection. AdGDNF injection into either the striatum or SN significantly reduced the loss of FG labelled DA neurons 5 weeks after lesion (P </= 0.05). However, only striatal injections of AdGDNF protected against the development of behavioral deficits characteristic of unilateral DA depletion. Striatal AdGDNF injections also reduced tyrosine hydroxylase fiber loss and increased amphetamine-induced striatal Fos expression. These results demonstrate that increased levels of striatal, but not nigral, GDNF biosynthesis prevents DA neuronal loss and protects DA terminals from 6-OHDA-induced damage, thereby maintaining DA function in the aged rat.

Increased summertime UV radiation in New Zealand in response to ozone loss

Long-term decreases in summertime ozone over Lauder, New Zealand (45 degrees S), are shown to have led to substantial increases in peak ultraviolet (UV) radiation intensities. In the summer of 1998-99, the peak sunburning UV radiation was about 12 percent more than in the first years of the decade. Larger increases were seen for DNA-damaging UV radiation and plant-damaging UV radiation, whereas UV-A (315 to 400 nanometers) radiation, which is insensitive to ozone, showed no increase, in agreement with model calculations. These results provide strong evidence of human-induced increases in UV radiation, in a region where baseline levels of UV radiation were already relatively high.

Neuronal death and survival in two models of hypoxic-ischemic brain damage

Two unilateral hypoxic-ischemia (HI) models (moderate and severe) in immature rat brain have been used to investigate the role of various transcription factors and related proteins in delayed neuronal death and survival. The moderate HI model results in an apoptotic-like neuronal death in selectively vulnerable regions of the brain while the more severe HI injury consistently produces widespread necrosis resulting in infarction, with some necrosis resistant cell populations showing evidence of an apoptotic type death. In susceptible regions undergoing an apoptotic-like death there was not only a prolonged induction of the immediate early genes, c-jun, c-fos and nur77, but also of possible target genes amyloid precursor protein (APP751) and CPP32. In contrast, increased levels of BDNF, phosphorylated CREB and PGHS-2 were found in cells resistant to the moderate HI insult suggesting that these proteins either alone or in combination may be of importance in the process of neuroprotection. An additional feature of both the moderate and severe brain insults was the rapid activation and/or proliferation of glial cells (microglia and astrocytes) in and around the site of damage. The glial response following HI was associated with an upregulation of both the CCAAT-enhancer binding protein alpha (microglia only) and NFkappaB transcription factors.

Co-ordinated and cellular specific induction of the components of the IGF/IGFBP axis in the rat brain following hypoxic-ischemic injury

Insulin-like growth factor 1 (IGF-1) is induced after hypoxic-ischemic (HI) brain injury, and therapeutic studies suggest that IGF-1 may restrict delayed neuronal and glial cell loss. We have used a well-characterised rat model of HI injury to extend our understanding of the modes of action of the IGF system after injury. The induction of the IGF system by injury was examined by in situ hybridization, immunohistochemistry, Northern blot analysis, RNase protection assay and reverse transcriptase-polymerase chain reaction (RT-PCR). IGF-1 accumulated in blood vessels of the damaged hemisphere within 5 h after a severe injury. By 3 days, IGF-1 mRNA was expressed by reactive microglia in regions of delayed neuronal death, and immunoreactive IGF-1 was associated with these microglia and reactive astrocytes juxtaposed to surviving neurones surrounding the infarct. Total IGF-1 receptor mRNA was unchanged by the injury. IGFBP-2 mRNA was strongly induced in reactive astrocytes throughout the injured hemisphere, and IGFBP-3 and IGFBP-5 mRNA were moderately induced in reactive microglia and neurones of the injured hippocampus, respectively. IGFBP-6 mRNA was induced in the damaged hemisphere by 3 days and increased protein was seen on the choroid plexus, ependyma and reactive glia. In contrast, insulin II was not induced. These results indicate cell type-specific expression for IGF-1, IGFBP-2,3,5 and 6 after injury. Our findings suggest that the IGF-1 produced by microglia after injury is transferred to perineuronal reactive astrocytes expressing IGFBP-2. Thus, modulation of IGF-1 action by IGFBP-2 might represent a key mechanism that restricts neuronal cell loss following HI brain injury.

The role of neuronal growth factors in neurodegenerative disorders of the human brain

Recent evidence suggests that neurotrophic factors that promote the survival or differentiation of developing neurons may also protect mature neurons from neuronal atrophy in the degenerating human brain. Furthermore, it has been proposed that the pathogenesis of human neurodegenerative disorders may be due to an alteration in neurotrophic factor and/or trk receptor levels. The use of neurotrophic factors as therapeutic agents is a novel approach aimed at restoring and maintaining neuronal function in the central nervous system (CNS). Research is currently being undertaken to determine potential mechanisms to deliver neurotrophic factors to selectively vulnerable regions of the CNS. However, while there is widespread interest in the use of neurotrophic factors to prevent and/or reduce the neuronal cell loss and atrophy observed in neurodegenerative disorders, little research has been performed examining the expression and functional role of these factors in the normal and diseased human brain. This review will discuss recent studies and examine the role members of the nerve growth factor family (NGF, BDNF and NT-3) and trk receptors as well as additional growth factors (GDNF, TGF-alpha and IGF-I) may play in neurodegenerative disorders of the human brain.

Brain-derived neurotrophic factor is reduced in Alzheimer's disease

Alzheimer's disease may be due to a deficiency in neurotrophin protein or receptor expression. Consistent with this hypothesis, a reduction in BDNF mRNA expression has been observed in human post-mortem Alzheimer's disease hippocampi. To further investigate this observation, we examined whether the alteration in BDNF expression also occurred at the protein level in human post-mortem Alzheimer's disease hippocampi and temporal cortices using immunohistochemical techniques. We observed a reduction in the intensity and number of BDNF-immunoreactive cell bodies within both the Alzheimer's disease hippocampus and temporal cortex when compared to normal tissue. These results support and extend previous findings that BDNF mRNA is reduced in the human Alzheimer's disease hippocampus and temporal cortex, and suggest that a loss of BDNF may contribute to the progressive atrophy of neurons in Alzheimer's disease.

Insulin-like growth factor-I (IGF-I) immunoreactivity in the Alzheimer's disease temporal cortex and hippocampus

IGF-I has been shown to enhance neuronal survival and inhibit apoptosis. IGF-I immunoreactivity was examined in the Alzheimer's disease and normal post-mortem human hippocampus and temporal cortex to determine whether IGF-I protein levels are altered in response to neurodegeneration. IGF-I immunoreactivity was induced in a subpopulation of GFAP-immunopositive astroglia in the Alzheimer's disease temporal cortex. These observations raise the possibility that IGF-I has a neuroprotective role in the Alzheimer's disease brain.

Expression of Fos, Jun, and Krox family proteins in Alzheimer's disease

Apoptosis is an active process of cell death characterized by distinct morphological features and is often the end result of a genetic program of events, i.e., programmed cell death (PCD). There is growing evidence supporting a role for apoptosis and/or PCD in Alzheimer's disease (AD), based on DNA fragmentation studies and recent findings of increased levels of inducible transcription factors (ITFs) such as c-Jun in AD brains. We have characterized the expression of a large range of ITFs (c-Fos, Fos B, Fos-related antigens, c-Jun, Jun B, Jun D, Krox20, and Krox24) using multiple antisera in AD postmortem hippocampi and compared this with human control hippocampi as well as Huntington's disease hippocampi and human epilepsy biopsy tissue. We found little evidence of nuclear expression of any ITF except c-Jun in the human postmortem tissue, compared with nuclear staining in biopsy tissue. We found some evidence for increased levels of c-Jun and Krox24 protein and krox24 mRNA in the CA1 region of AD hippocampi, suggesting that PCD may be involved in the pathogenesis of AD. In general, staining characteristics of ITFs varied with different antisera directed against the same protein, indicating the need for caution when interpreting results.

Apoptosis, neurotrophic factors and neurodegeneration

Apoptosis is an active process of cell death characterized by distinct morphological features, and is often the end result of a genetic programme of events, i.e. programmed cell death (PCD). There is growing evidence supporting a role for apoptosis in some neurodegenerative diseases. This conclusion is based on DNA fragmentation studies and findings of increased levels of pro-apoptotic genes in human brain and in in vivo and in vitro model systems. Additionally, there is some evidence for a loss of neurotrophin support in neurodegenerative diseases. In Alzheimer's disease, in particular, there is strong evidence from human brain studies, transgenic models and in vitro models to suggest that the mode of nerve cell death is apoptotic. In this review we describe the evidence implicating apoptosis in neurodegenerative diseases with a particular emphasis on Alzheimer's disease.

Bax expression in mammalian neurons undergoing apoptosis, and in Alzheimer's disease hippocampus

Recent studies indicate that the proto-oncogene Bax, and other related proteins (eg Bcl-2) may play a major role in determining whether cells will undergo apoptosis under conditions which promote cell death. Increased expression of Bax has been found to promote apoptosis, while over-expression of Bcl-2 can inhibit apoptosis. To investigate the role of Bax in nerve cell death in the rat brain we examined the level of Bax expression in cells undergoing apoptosis, using a hypoxic-ischemic stroke model. We found that Bax was expressed at high levels in the nuclei of neurons in the hippocampus, cortex, cerebellum, and striatum on the control side, and that Bax levels increased in hippocampal neurons undergoing apoptosis on the stroke side, and then declined (correlating with cell loss). In the Alzheimer's disease hippocampi we found a concentrated localisation of Bax in senile plaques, which correlated with the localisation of beta-amyloid protein in adjacent sections from the same brains. beta-Amyloid positive plaques are thought to contribute to the Alzheimer's disease process, possibly via an apoptotic mechanism, and this may occur via an increase in Bax in these areas. Bax was also strongly stained in tau-positive tangles in Alzheimer's disease hippocampi, suggesting Bax may play a role in tangle formation. In addition, we observed a loss of Bax expression in the dentate granule cells of Alzheimer's disease hippocampi compared with moderate Bax expression in control hippocampi, and this loss may be related to the survival of these neurons in Alzheimer's disease. Finally, we observed substantially different staining patterns of Bax using three different commercially available antisera to Bax, indicating the need for caution when interpreting results in this area.

Trk receptor alterations in Alzheimer's disease

The expression of trk receptors in postmortem normal, Huntington's disease and Alzheimer's disease human brains was investigated using immunohistochemistry, in-situ hybridisation and Western blotting. Alzheimer's disease hippocampi displayed an increase in trkA receptor levels in astrocytes in the CA1 region, some of which were associated with beta-amyloid-positive plaques. Truncated trkB receptors were found in high levels in senile plaques, while the full-length receptor was expressed in glial-like cells in the hippocampus of Alzheimer's disease brains. In-situ hybridisation studies indicated that trk receptor mRNA was also elevated in Alzheimer's. The appearance of trkA and trkB receptors in astrocytes and plaques in Alzheimer's disease might be related to beta-amyloid deposition and could be implicated in the development of Alzheimer's disease.

Age, atheroma and actualisation

General practice involves continuing and comprehensive care. Nowhere is this more important than with elderly patients who present with multiple and long-term problems. In these situations the family doctor can act as a guide and friend in order to assist their patients realise their maximum functional potential.

Nonsyndromic cleft lip and palate: no evidence of linkage to HLA or factor 13A

Nonsyndromic cleft lip with or without cleft palate (CLP) is a common craniofacial anomaly, the etiology of which is not known. Population studies have shown that a large proportion of cases occur sporadically. Recently, segregation analyses applied to CLP families have demonstrated that an autosomal dominant/codominant gene(s) may cause clefting in cases. Associations of autosomal dominant CLP and nonsyndromic cleft palate (CP) with HLA and F13A genes on chromosome 6p have been suggested previously. Linkage to these two areas on chromosome 6p were tested in 12 autosomal dominant families with CLP. With a LOD score of -2 or less for exclusion, no evidence of linkage was found to four chromosome 6p markers. Multipoint analysis showed no evidence of a clefting locus in this region spanning 54 cM on chromosome 6p in these CLP families.

Cutaneous mercury granuloma

Mercury poisoning arising from cutaneous mercury deposition is highly unusual. The diagnosis is difficult to make when no history of a penetrating injury is given. We report such a case and discuss investigation and management. Other cutaneous manifestations of mercury exposure are outlined.