Molecular and functional mapping of regional differences in P2Y receptor expression in the rat lens.

Extracellular ATP has been shown to mobilize intracellular Ca(2+) in cultured ovine lens epithelial cells and in human lens epithelium, suggesting a role for purines in the modulation of lens transparency. In this study, we characterized the expression profiles of P2Y receptor isoforms throughout the rat lens at both the molecular and the functional levels. RT-PCR indicated that P2Y(1), P2Y(2), P2Y(4) and P2Y(6) are expressed in the lens, while P2Y(12), P2Y(13) and P2Y(14) are not.

A focus on the human lens in vitro.

The lens is a unique organ in that it is avascular and non-innervated, obtaining all nutrients from the aqueous and vitreous humours that bathe the lens. All lenses attempt to achieve the same goal, namely to maintain transparency and focus light on to the retina. However, the mechanisms by which these processes are maintained, or disrupted leading to a loss of transparency, are likely to differ in some cases between animals and humans.

Potentiation of ATP-induced Ca2+ mobilisation in human retinal pigment epithelial cells.

Interaction of signalling pathways directs the functional output of many cells. This study investigated the consequences of activating adenosine and adrenergic receptors on ATP-induced Ca2+ responses in human retinal pigment epithelial (RPE) cells. Intracellular Ca2+ concentration ([Ca2+]i) of human RPE cells in primary culture was monitored using Fura-2.

Characterization and functional activity of thrombin receptors in the human lens.

Purpose: To investigate the expression of thrombin receptors in the human lens, the activation of downstream signaling pathways, and the ability of thrombin to regulate lens cell growth.

Methods: Thrombin receptor function in the human lens was determined first by measuring changes in intracellular calcium in response to thrombin and protease-activated receptor-activating peptides (PAR-APs). In the human capsular bag model, cell growth was assessed by phase microscope inspection of the cell coverage of the posterior capsular surface.

Regional differences in tyrosine kinase receptor signaling components determine differential growth patterns in the human lens.

Purpose: The lens epithelium can be separated into two regions, the nondividing central zone and the equator, the site of all division in the normal lens. In the present study, the distribution of epithelial growth factor (EGF)/epithelial growth factor receptor (EGFR) signaling components was investigated and related to mitotic distribution in the lens.

Methods: Anterior and equatorial regions of the native epithelium were prepared separately from donor lenses.

Spatial characteristics of receptor-induced calcium signaling in human lens capsular bags.

Purpose: Despite recent improvements in intraocular lens (IOL) design, posterior capsule opacification (PCO) arising from lens cell growth remains a major problem. Calcium signaling has been shown to play a major role in driving human lens cell growth, and therefore it is necessary to understand the underlying mechanisms.

Methods: Calcium signaling was studied in capsular bags (ex vivo) removed from donors who had undergone earlier cataract surgery.

Calcium activates SK channels in the intact human lens.

Purpose: Apamin-sensitive, calcium-activated SK potassium channels have been implicated in schizophrenia and myotonic dystrophy (MD), and both conditions carry an increased risk of cataract. The presence and functional activity of SK channels were therefore investigated in the human lens.

Methods: The expression of all three members of the SK channel family was quantified by PCR.

Pterygial derived fibroblasts express functionally active histamine and epidermal growth factor receptors.

Pterygia are characterised by a fleshy outgrowth of altered conjunctival tissue over the cornea and are most common in tropical regions. Pterygial fibroblasts are characteristically distinct from normal conjunctival fibroblasts, and therefore the aim of this study was to determine the presence and functional significance of histamine and epidermal growth factor (EGF) receptors in these cells. Pterygial specimens were cultured in vitro and cellular outgrowths were phenotypically characterised as fibroblasts using vimentin and cytokeratin staining.