EphA5 and ephrin-A2 expression during optic nerve regeneration: a 'two-edged sword'.

During development, gradients of EphA receptors (nasal(low)-temporal(high)) and their ligands ephrin-As (rostral(low)-caudal(high)) are involved in establishing topography between retinal ganglion cells (RGCs) and the superior colliculus (SC). EphA5-expressing RGC axons are repulsed by ephrin-A2-expressing SC neurones. In adult rats RGCs maintain graded EphA5 expression but ephrin-A2 expression is down-regulated in the SC to a weak gradient. At 1 month after optic nerve transection, EphA5 expression is reduced in the few remaining RGCs and is no longer graded; by contrast, SC ephrin-A2 is up-regulated to a rostral(low)-caudal(high) gradient. Here we examined expression in adult rat 1 month after bridging the retina and SC with a peripheral nerve graft, a procedure that enhances RGC survival and permits RGC axon regeneration. Double labelling with cell markers revealed preservation of a nasal(low)-temporal(high) EphA5 gradient in RGCs and establishment of a rostral(low)-caudal(high) ephrin-A2 gradient within neurones of the SC. The results suggest a potential for guidance cues to restore the topography of RGC axons in the SC. However, high ephrin-A2 levels were also found in astrocytes surrounding the peripheral nerve graft insertion site. The repulsive ephrin-A2 environment offers at least a partial explanation for the observation that only a limited number of RGC axons can exit the graft to enter target central nervous system tissue.

Eph/ephrin expression in the adult rat visual system following localized retinal lesions: localized and transneuronal up-regulation in the retina and superior colliculus.

Following unilateral optic nerve section in adult PVG hooded rat, the axon guidance cue ephrin-A2 is up-regulated in caudal but not rostral superior colliculus (SC) and the EphA5 receptor is down-regulated in axotomised retinal ganglion cells (RGCs). Changes occur bilaterally despite the retino-collicular projection being mostly crossed. Here we investigate the dynamics of Eph/ephrin expression using in situ hybridization and semi-quantitative immunohistochemistry after localized retinal lesions. Unilateral krypton laser lesions to dorso-nasal retina ablated contralaterally projecting RGCs (DN group); ventro-temporal lesions ablated contralaterally and ipsilaterally projecting RGCs (VT group). Lesions of the entire retina served as controls (Total group). Results are compared to normal animals in which tectal ephrin-A2 and retinal EphA5 are expressed, respectively, as shallow ascending rostro-caudal and naso-temporal gradients. In both SCs of DN and Total groups, tectal ephrin-A2 was up-regulated caudally; in the VT group, expression remained normal bilaterally. Unilateral collicular ablation indicated that bilateral changes in ephrin-A2 expression are mediated via intercollicular pathways. EphA5 expression in the VT group was elevated in the intact nasal region of experimental retinae. For each experimental group, EphA5 expression was also elevated in nasal retina of the opposite eye, resulting in uniform expression across the naso-temporal axis. Up-regulation of ephrin-A2 in caudal, but not rostral, SC suggests the enhancement of developmental positional information as a result of injury. Bilateral increases in retinal EphA5 expression demonstrate that signals for up-regulation operate interocularly. The study demonstrates that signals regulating guidance cue expression are both localized and relayed transneuronally.

Down-regulation of nitric oxide production by droloxifene and toremifene in human breast cancer cells.

We investigated the effect of tamoxifen, 4-OH tamoxifen, toremifene droloxifene, interferon-alpha2a, interferon-alpha2b and interferon-alpha2c, singly and in combination, for their effect on nitric oxide production by MCF-7 and ZR-75-1 human breast cancer cells. Tamoxifen and 4-OH tamoxifen singly had no effect on nitric oxide production by either cell line. However, treatment with droloxifene or toremifene significantly reduced nitric oxide production by both MCF-7 and ZR-75-1 human breast cancer cell lines. Combination treatment with anti-estrogens and interferon-alpha2a interferon-alpha2b or interferon-alpha2c had no synergistic or additive effect compared to each drug singly.

Identification of the pocket factors in a picornavirus.

Bovine enterovirus (BEV), along with other enteroviruses and the rhinoviruses, has a hydrophobic pocket within structural protein VP1. In the crystal structures of these viruses there is electron density commensurate with a non-protein molecule within the pocket. These molecules, termed pocket factors, have been shown to stabilise the capsid and their removal from the pocket is a necessary prerequisite to uncoating. The pocket factors have been proposed, from the electron densities and uncoating studies, to be short chain fatty acids. In order to identify the pocket factor of BEV, we have grown and purified the virus in an identical manner to that used for the crystal structure determination and have performed a lipophilic extraction. Palmitic acid, C(16:0), was the most abundant accounting for 40.8% by mass of the lipophilic extract (39.3 mol%). Myristic acid C(14:0), was next most abundant at 18.5% by mass (20.0 mol%). In addition, we have identified other fatty acids in smaller proportions. We have therefore shown that BEV contains saturated fatty acid pocket factors of varying chain length. We have also compared the profile of the fatty acyl chain composition of BEV with those for uninfected BHK-21 cell plasma membrane and endoplasmic reticulum extracts.

Bovine enterovirus as an oncolytic virus: foetal calf serum facilitates its infection of human cells.

Many viruses have been investigated for their oncolytic properties and potential use as therapeutic agents for cancer treatment. Most of these replication-competent viruses are human pathogens. We investigated the oncolytic properties of an animal virus which is non pathogenic for both its natural host and humans. Bovine enterovirus has previously been shown to exhibit a very wide tissue tropism for cell types in vitro. We compare the ability of bovine enterovirus to replicate in and to cause cytopathic effect in freshly isolated human monocytes and monocyte derived macrophages with the monocyte-like U937 tumour cell line. We also include the adherent ZR-75-1 human breast cancer cell line. We have also carried out infections of bovine enterovirus in the presence and in the absence of serum of bovine origin. Our study shows that the virus will replicate in and produce cytopathic effect in the U937 and ZR-75-1 cell types to the same extent as the cells (BHK-21) in which the virus is routinely propagated. We believe bovine enterovirus to be a worthwhile candidate for further study as an anti-tumour agent.

Synergistic antitumour effect of a combination of toremifene and interferon-alpha on ZR-75-1 human breast cancer cells: dependence on interferon-alpha subtype.

We investigated the effect of toremifene, interferon-alpha2a, interferon-alpha2b and interferon-alpha2c, singly and in combination for their effect on the growth of ZR-75-1 human breast cancer cells. Median effect analysis was used to determine synergistic or additive effects. Anti-proliferative studies showed that the growth of ZR-75-1 cells was inhibited to a greater extent by combination treatment with toremifene plus interferon-alpha2a, resulting in a synergistic interaction (CI <1) for all concentrations tested. A combination of toremifene plus interferon-alpha2b resulted in a synergistic interaction (CI <1) for the two highest concentrations of toremifene (10(-6) and 10(-7) M) and an additive effect (CI approximately equal to 1) for the lower concentrations (10(-8) to 10(-10) M). When toremifene was combined with interferon-alpha2c no additive or synergistic interaction was determined.

Reinnervation of the superior colliculus delays down-regulation of ephrin A2 in neonatal rat.

Although the adult mammalian optic nerve does not regenerate following lesion, in the neonatal rat, retinal ganglion cell (RGC) axons retain the capacity to grow across lesion sites in the brain. Following a brachial lesion at postnatal day 2 (P2), some RGC axons, together with ingrowing cortico-tectal axons, cross the lesion to reinnervate the superior colliculus (SC). Here we use immunohistochemistry to examine expression of the guidance cue ephrin A2 following a brachial lesion. Normal animals show a steady decrease in ephrin A2 immunoreactivity between P5 and P31, with a low rostral to high caudal gradient being evident only at P5. By contrast, after brachial lesion, values are significantly elevated rostrally at P5 and caudally at P12; moreover, a steep rostro-caudal gradient is present at both ages. By P31 values fall to normal levels. Following unilateral enucleation at P2, levels are not significantly different from normal. Our results show that innervation but not denervation triggers increased ephrin A2 expression after a brachial lesion.

Divergent effects of paracetamol on reactive oxygen intermediate and reactive nitrogen intermediate production by U937 cells.

We investigated the effects of paracetamol on reactive oxygen intermediate and reactive nitrogen intermediate production by U937 cells. Cells which had been treated with paracetamol (0.01 microM - 10 microM) exhibited a significant (p<0.001) increase in hydrogen peroxide production and a significant (p<0.001) increase in phorbol 12-myristate 13-acetate induced superoxide production. Conversely, paracetamol (0.01 microM - 10 microM) caused a significant (p<0.001) decrease in the amount of nitrite secreted into the culture medium. Our results indicate divergent effects of paracetamol on ROI and RNI production.

Violence against women--the myth of masochism.

Women have been victims of violence throughout history. Freud's theory of masochism stated that women enjoyed suffering, and until very recently the mental health profession went along with this universal human tendency to blame the victim. In this paper a new understanding of the dynamics of abused wives and violence-prone husbands is being presented indicating that the explanation lies in the new field of the study of psychological reactions of victims of violence and catastrophe.