Analysis of pharmacologically isolated components of the ERG

AbstractAn harmonic analysis was applied to the electroretinogram (ERG) measured in intact cat eyes in control conditions and after pharmacological isolation of the components attributed to photoreceptors (PIII) and bipolar neurons (PII). The frequency response curves obtained in various conditions showed that the bandwidth of the PII component extends over a range of stimulus frequencies higher than the bandwidth of PIII. The enhancement of the PII response to stimuli of high temporal frequency suggests the presence of a frequency dependent gain control located either pre- and/or post-synaptically in the transmission line between the phototransductive cascade and bipolar neurons. A possible role of these processes is to enhance relevant visual information whilst selectively attenuating low frequency signals originating in the transductive cascade

Combining neuroprotectants in a model of retinal degeneration: no additive benefit

The central nervous system undergoing degeneration can be stabilized, and in some models can be restored to function, by neuroprotective treatments. Photobiomodulation (PBM) and dietary saffron are distinctive as neuroprotectants in that they upregulate protective mechanisms, without causing measurable tissue damage. This study reports a first attempt to combine the actions of PBM and saffron. Our working hypothesis was that the actions of PBM and saffron in protecting retinal photoreceptors, in a rat light damage model, would be additive. Results confirmed the neuroprotective potential of each used separately, but gave no evidence that their effects are additive. Detailed analysis suggests that there is actually a negative interaction between PBM and saffron when given simultaneously, with a consequent reduction of the neuroprotection. Specific testing will be required to understand the mechanisms involved and to establish whether there is clinical potential in combining neuroprotectants, to improve the quality of life of people affected by retinal pathology, such as age-related macular degeneration, the major cause of blindness and visual impairment in older adults.This work was supported by the Australian Research Council Centre of Excellence in Vision Science, by the Sir Zelman Cowen Universities Fund and the Lord Mayor’s Charitable Foundation, by Australian Travel Awards for L’Aquila Researchers (ARIA) to FDM and SR and by a Ministero dell’Istruzione, dell’Universita` e della Ricerca dedicato ai PRIN, Progetti di Ricerca di Interesse Nazionale (MIUR-PRIN) (2010-2011) research grant to SB

Saffron Crudes and Compounds Restrict MACC1-Dependent Cell Proliferation and Migration of Colorectal Cancer Cells

The high mortality rate of colorectal cancer (CRC) patients is directly associated with metastatic dissemination. However, therapeutic options specifically for metastasis are still limited. We previously identified Metastasis-Associated in Colon Cancer 1 (MACC1) as a major causal metastasis-inducing gene. Numerous studies confirmed its value as a biomarker for metastasis risk. We investigated the inhibitory impact of saffron on MACC1-induced cancer cell growth and motility. Saffron crudes restricted the proliferation and migration of MACC1-expressing CRC cells in a concentration- and MACC1-dependent manner. Saffron delays cell cycle progression at G2/M-phase and does not induce apoptosis. Rescue experiments showed that these effects are reversible. Analysis of active saffron compounds elucidated that crocin was the main compound that reproduced total saffron crudes effects. We showed the interaction of MACC1 with the cancer stem cell (CSC) marker DCLK1, which contributes to metastasis formation in different tumor entities. Saffron extracts reduced DCLK1 with crocin being responsible for this reduction. Saffron's anti-proliferative and anti-migratory effects in MACC1-expressing cells are mediated by crocin through DCLK1 down-regulation. This research is the first identification of saffron-based compounds restricting cancer cell proliferation and motility progression via the novel target MACC1

Acquired Resilience: An Evolved System of Tissue Protection in Mammals.

This review brings together observations on the stress-induced regulation of resilience mechanisms in body tissues. It is argued that the stresses that induce tissue resilience in mammals arise from everyday sources: sunlight, food, lack of food, hypoxia and physical stresses. At low levels, these stresses induce an organised protective response in probably all tissues; and, at some higher level, cause tissue destruction. This pattern of response to stress is well known to toxicologists, who have termed it hormesis. The phenotypes of resilience are diverse and reports of stress-induced resilience are to be found in journals of neuroscience, sports medicine, cancer, healthy ageing, dementia, parkinsonism, ophthalmology and more. This diversity makes the proposing of a general concept of induced resilience a significant task, which this review attempts. We suggest that a system of stress-induced tissue resilience has evolved to enhance the survival of animals. By analogy with acquired immunity, we term this system \u27acquired resilience\u27. Evidence is reviewed that acquired resilience, like acquired immunity, fades with age. This fading is, we suggest, a major component of ageing. Understanding of acquired resilience may, we argue, open pathways for the maintenance of good health in the later decades of human life

Organic electronics allows the photo-electric excitation and inhibition of neuronal activity in primary neuronal cultures and acute retinal explants

Interfacing organic electronics and biology offers new possibilities in biotechnology, due to the unique properties exhibited by organic conducting polymers (e.g. biological affinity, mechanical flexibility, ease of functionalization and cost effectiveness). Organic conducting polymers have been exploited as materials for cellular interfaces in several fashions as: (i) passive electrode coatings or culturing substrates, (ii) organic biosensors or (iii) actuators for neurotransmitter release and electrodes for controlled cell seeding, growth and activity detection. Very recently, an organic photovoltaic donor-acceptor blend has been exploited for neuron stimulation by a photo-electric process. With respect to previous examples with inorganic semiconductors, this system has several advantages including flexibility, no power requirement and biocompatibility. Here, we report the novel use of a single component semiconductor organic polymer for the direct control of neuronal activity. This interface, that is more efficient than the classical bulk hetero-junction interface, has the remarkable capability to evoke excitation of neuronal firing in response to illumination. We demonstrate that the polymer layer has the ability to induce action potential firing up to 20 Hz in cultured hippocampal neurons. Moreover, this interface has been exploited to restore visual response in retinal explants obtained from animal models of retinal degeneration (light-blinded albino SD rats). By recording local field potentials in the RGC layer, we demonstrated the ability of the organic conductive polymer to mimic the function of photoreceptors and induce retinal activation of retinal ganglion cells after light illumination. These results paved the way to the development of a new and disruptive technology for interfacing artificial devices with neuronal networks, with applications in neuroprosthesis and brain machine interface research

Biocompatibility of a Conjugated Polymer Retinal Prosthesis in the Domestic Pig

The progressive degeneration of retinal photoreceptors is one of the most significant causes of blindness in humans. Conjugated polymers represent an attractive solution to the field of retinal prostheses, and a multi-layer fully organic prosthesis implanted subretinally in dystrophic Royal College of Surgeons (RCS) rats was able to rescue visual functions. As a step toward human translation, we report here the fabrication and in vivo testing of a similar device engineered to adapt to the human-like size of the eye of the domestic pig, an excellent animal paradigm to test therapeutic strategies for photoreceptors degeneration. The active conjugated polymers were layered onto two distinct passive substrates, namely electro-spun silk fibroin (ESF) and polyethylene terephthalate (PET). Naive pigs were implanted subretinally with the active device in one eye, while the contralateral eye was sham implanted with substrate only. Retinal morphology and functionality were assessed before and after surgery by means of in vivo optical coherence tomography and full-field electroretinogram (ff-ERG) analysis. After the sacrifice, the retina morphology and inflammatory markers were analyzed by immunohistochemistry of the excised retinas. Surprisingly, ESF-based prostheses caused a proliferative vitreoretinopathy with disappearance of the ff-ERG b-wave in the implanted eyes. In contrast, PET-based active devices did not evoke significant inflammatory responses. As expected, the subretinal implantation of both PET only and the PET-based prosthesis locally decreased the thickness of the outer nuclear layer due to local photoreceptor loss. However, while the implantation of the PET only substrate decreased the ff-ERG b-wave amplitude with respect to the pre-implant ERG, the eyes implanted with the active device fully preserved the ERG responses, indicating an active compensation of the surgery-induced photoreceptor loss. Our findings highlight the possibility of developing a new generation of conjugated polymer/PET-based prosthetic devices that are highly biocompatible and potentially suitable for subretinal implantation in patients suffering from degenerative blindnes

Organic electronics allows the photo-electric excitation of neuronal activity in primary neuronal cultures and acute retinal explants

Interfacing organic electronics and biology offers new possibilities in biotechnology, due to the unique properties exhibited by organic conducting polymers (e.g. biological affinity, mechanical flexibility, ease of functionalization and cost effectiveness). Organic conducting polymers have been exploited as materials for cellular interfaces in several fashions as: (i) passive electrode coatings or culturing substrates, (ii) organic biosensors or (iii) actuators for neurotransmitter release and electrodes for controlled cell seeding, growth and activity detection. Very recently, an organic photovoltaic donor-acceptor blend has been exploited for neuron stimulation by a photo-electric process. With respect to previous examples with inorganic semiconductors, this system has several advantages including flexibility, no power requirement and biocompatibility. Here, we report the novel use of a single component semiconductor organic polymer for the direct control of neuronal activity. This interface, that is more efficient than the classical bulk hetero-junction interface, has the remarkable capability to evoke neuronal firing in response to illumination. We demonstrate that the polymer layer has the ability to induce action potential firing up to 20 Hz in cultured hippocampal neurons. Moreover, this interface has been exploited to restore visual response in retinal explants obtained from animal models of retinal degeneration (light-blinded albino SD rats). By recording local field potentials in the RGC layer, we demonstrated the ability of the organic conductive polymer to mimic the function of photoreceptors and induce retinal activation of retinal ganglion cells after light illumination. These results paved the way to the development of a new and disruptive technology for interfacing artificial devices with neuronal networks, with applications in neuroprosthesis and brain machine interface research

A fully organic retinal prosthesis restores vision in a rat model of degenerative blindness

The degeneration of photoreceptors in the retina is one of the major causes of adult blindness in humans. Unfortunately, no

Blockade of glutamate-mediated activity in the developing retina perturbs the functional segregation of ON and OFF pathways

The dendrites of ganglion cells initially ramify throughout the inner plexiform layer of the developing retina before becoming stratified into ON or OFF sublaminae. This ontogenetic event is thought to depend on glutamate- mediated afferent activity, because treating the developing retina with the glutamate analog 2-amino-4-phosphonobutyrate (APB), which hyperpolarizes ON cone bipolar cells and rod bipolar cells, thereby preventing their release of glutamate, effectively arrests the dendritic stratification process. To assess the functional consequences of this manipulation, extracellular recordings were made from single cells in the A laminae of the dorsal lateral geniculate nucleus and from the optic tract in mature cats that had received intraocular injections of APB during the first postnatal month. Such recordings revealed that stimulation of the APB-treated eye evoked both ON as well as OFF discharges in 37% of the cells tested. (As expected, when the normal eye was activated, virtually all cells yielded only ON or OFF responses). The proportion of ON-OFF cells found here corresponds closely to the incidence of multistratified dendrites observed previously in anatomical studies of APB-treated cat retinas. This suggests that the ganglion cells with multistratified dendrites receive functional inputs from ON as well as OFF cone bipolar cells. This interpretation is further supported by the finding that the proportion of ON-OFF cells was very similar in the geniculate layer innervated by the treated eye and in the optic tract. The cells activated by the APB-treated eye were also found not to show response suppression when flashing stimuli of increasing size were used. This suggests that exposing the developing retina to APB perturbs the neural circuitry mediating the antagonistic center-surround organization found in normal receptive fields. The functional changes evident after treating the developing retina with APB suggest that it should now be feasible to assess how the segregation of ON and OFF retinal pathways relates to organizational features at higher levels of the visual system, such as orientation selectivity in cortical cells