Evidence for sodium metasilicate receptors on the human osteoblast cell surface; spatial localization and binding properties.

We report details of the interaction of sodium metasilicate with osteoblast cellular membranes using Fluoresceinphosphatidylethanolamine (FPE) as a fluorescent indicator of membrane interactions. Fluorescence imaging studies of the FPE-based indicator system revealed areas of localized binding that would be consistent with the presence of a structure with 'receptor-like' properties. From these results, it seems unlikely that silica binds 'non-specifically' to the osteoblast surface. Moreover, the receptors are localized into membrane domains. Such regions of the cell membrane could well be structures such as 'rafts' or other such localized domains within the membrane. The binding profile of silica with the osteoblast cell surface takes place with all the characteristics of a receptor-mediated process best represented by a cooperativity (sigmoidal) binding model with a Hill coefficient of 3.6.

Purification of annexin V and its use in the detection of apoptotic cells.

Cell death by apoptosis has been studied for many years using fluorescently labeled annexin V. Annexin V shows high affinity for the phosphatidylserine that becomes enriched in the outer leaflet of the plasma membrane during apoptosis, but not necrosis, allowing differentiation between the two types of cell death. In this chapter we detail two methods for the purification of annexin V. The first is an untagged recombinant protein using a three step Fast Protein Liquid Chromatography (FPLC) method, and the second using a single step purification protocol via a glutathione S-transferase (GST) tag. Labeling of the resulting annexin V with a fluorescent dye to allow visualization of the protein is also explained. Finally, two methods are described in which a fluorescently labeled derivative of annexin V is used to detect apoptosis, namely the in vitro method of fluorescence-activated cell sorting (FACS) where fluorescent annexin V is used to differentiate apoptotic and necrotic cells within a population; and detection of apoptosing retinal cells (DARC) allowing the identification of apoptotic cells in the retina in vivo.

Dendritic changes in visual pathways in glaucoma and other neurodegenerative conditions.

Visual information is sent from the retina to central visual targets through the optic nerve formed of retinal ganglion cells' (RGCs) axons. In rodents, the superior colliculus (SC) is the major site of termination of retinal axons, whilst in primates and felines, it is the lateral geniculate nucleus (LGN). Glaucoma is a progressive optic neuropathy characterized by RGC death. There is increasing evidence that neuronal changes occur both in retina and central visual targets in glaucoma and other neurodegenerative diseases such as Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS). Dendrites are fine neuronal processes which support postsynaptic contact elements and are responsible for receiving synaptic signals. The morphology of dendrites has a profound impact on integrating neuronal input to the central nervous system from peripheral targets. This review summarizes different dendritic changes that have been recorded in neurodegenerative processes including those occurring in development, ageing and diseases. The findings suggest dendritic pathology is an early sign in disease and underline the importance of synapto-dendritic structure, providing new insights into therapeutic strategies.

Neuroprotection in glaucoma - Is there a future role?

In glaucoma, the major cause of global irreversible blindness, there is an urgent need for treatment modalities that directly target the RGCs. The discovery of an alternative therapeutic approach, independent of IOP reduction, is highly sought after, due to the indirect nature and limited effectiveness of IOP lowering therapy in preventing RGC loss. Several mechanisms have been implicated in initiating the apoptotic cascade in glaucomatous retinopathy and numerous drugs have been shown to be neuroprotective in animal models of glaucoma. These mechanisms and their potential treatment include excitotoxicity, protein misfolding, mitochondrial dysfunction, oxidative stress, inflammation and neurotrophin deprivation. All of these mechanisms ultimately lead to programmed cell death with loss of RGCs. In this article we summarize the mechanisms involved in glaucomatous disease, highlight the rationale for neuroprotection in glaucoma management and review current potential neuroprotective strategies targeting RGCs from the laboratory to the clinic.

Functional imaging of microdomains in cell membranes.

The presence of microdomains or rafts within cell membranes is a topic of intense study and debate. The role of these structures in cell physiology, however, is also not yet fully understood with many outstanding problems. This problem is partly based on the small size of raft structures that presents significant problems to their in vivo study, i.e., within live cell membranes. But the structure and dynamics as well as the factors that control the assembly and disassembly of rafts are also of major interest. In this review we outline some of the problems that the study of rafts in cell membranes present as well as describing some views of what are considered the generalised functions of membrane rafts. We point to the possibility that there may be several different 'types' of membrane raft in cell membranes and consider the factors that affect raft assembly and disassembly, particularly, as some researchers suggest that the lifetimes of rafts in cell membranes may be sub-second. We attempt to review some of the methods that offer the ability to interrogate rafts directly as well as describing factors that appear to affect their functionality. The former include both near-field and far-field optical approaches as well as scanning probe techniques. Some of the advantages and disadvantages of these techniques are outlined. Finally, we describe our own views of raft functionality and properties, particularly, concerning the membrane dipole potential, and describe briefly some of the imaging strategies we have developed for their study.