Electroretinograms (ERGs) of all experimental groups.

<p>A series of ERG traces were elicited by flashes of increasing intensity (denoted on right as value of log cd*s/m² for each trace) under scotopic (<b>a</b>) and photopic (<b>b</b>) conditions. The traces shown are from an animal representative of each experimental group at 16 weeks of age. ZDF-i, insulin-treated ZDFs.</p

Effect of insulin on control Lean rat ERG.

<p>Units for intensity denoted as log cd*s/m²; Data presented are group mean ± SD; Amplitude denoted in µV; Implicit times (IT) denoted in ms; Age denoted in weeks.</p><p>Lean, congenic control rats; Lean-i, insulin treated Lean rats;</p>*<p>p<0.05; n = 8.</p

Number of animals examined by ERG for each time-point.

<p>ZDF, Zucker Diabetic Fatty rats; Lean, congenic control rats; ZDF-i, insulin treated ZDF.</p

Retinal Adaptation to Changing Glycemic Levels in a Rat Model of Type 2 Diabetes

<div><h3>Purpose</h3><p>Glucose concentrations are elevated in retinal cells in undiagnosed and in undertreated diabetes. Studies of diabetic patients suggest that retinal function adapts, to some extent, to this increased supply of glucose. The aim of the present study was to examine such adaptation in a model of type 2 diabetes and assess how the retina responds to the subsequent institution of glycemic control.</p> <h3>Methods</h3><p>Electroretinography (ERG) was conducted on untreated Zucker diabetic fatty (ZDF) rats and congenic controls from 8–22 weeks of age and on ZDFs treated with daily insulin from 16–22 weeks of age. Retinal sections from various ages were prepared and compared histologically and by immunocytochemistry.</p> <h3>Principal Findings/Conclusions</h3><p>Acute hyperglycemia did not have an effect on control rats while chronic hyperglycemia in the ZDF was associated with scotopic ERG amplitudes which were up to 20% higher than those of age-matched controls. This change followed the onset of hyperglycemia with a delay of over one month, supporting that habituation to hyperglycemia is a slow process. When glycemia was lowered, an immediate decrease in ZDF photoreceptoral activity was induced as seen by a reduction in a-wave amplitudes and maximum slopes of about 30%. A direct effect of insulin on the ERG was unlikely since the expression of phosphorylated Akt kinase was not affected by treatment. The electrophysiological differences between untreated ZDFs and controls preceded an activation of Müller cells in the ZDFs (up-regulation of glial fibrillary acidic protein), which was attenuated by insulin treatment. There were otherwise no signs of cell death or morphological alterations in any of the experimental groups. These data show that under chronic hyperglycemia, the ZDF retina became abnormally sensitive to variations in substrate supply. In diabetes, a similar inability to cope with intensive glucose lowering could render the retina susceptible to damage.</p> </div

Average blood glucose and body weight as a function of age.

<p>ZDF rats were hyperglycemic in the fed state at 8 and 10 weeks of age, but measurements were highly variable. Blood glucose (<b>a</b>) in untreated ZDF (<i>dashed line</i>) and Lean (<i>solid line</i>) rats was measured in the fasted state. Treated ZDFs (ZDF-i) could not be fasted, and therefore fed values were obtained (<i>dotted line</i>). Body weights (<b>b</b>) of ZDF (<i>dashed line</i>), Lean (<i>solid line</i>) and ZDF-i rats (<i>dotted line</i>) are shown. Data presented are group mean +SD of 4–14 animals and significant differences (2 way ANOVA LSD; p<0.05) between ZDFs and Leans are denoted by <b>*</b>and between ZDF-i and the other experimental groups by <b>^#</b>ZDF-i, insulin-treated ZDFs.</p

Phosphorylated Akt (pAkt) immunofluorescence.

<p>A phospho-specific antibody was used to detect activated Akt in the retina of Lean (<b>a</b>), ZDF (<b>b</b>) and insulin treated ZDF (<b>c</b>) rats at 16 weeks of age; and of Lean (<b>d</b>), ZDF (<b>e</b>) and insulin treated ZDF (<b>f</b>) rats at 23 weeks of age. ZDF-i, insulin-treated ZDFs; ONL, outer nuclear layer; INL, inner nuclear layer; GCL, ganglion cell layer. Scale bar = 20 µm.</p

Support of Neuronal Growth Over Glial Growth and Guidance of Optic Nerve Axons by Vertical Nanowire Arrays

Neural cultures are very useful in neuroscience, providing simpler and better controlled systems than the <i>in vivo</i> situation. Neural tissue contains two main cell types, neurons and glia, and interactions between these are essential for appropriate neuronal development. In neural cultures, glial cells tend to overgrow neurons, limiting the access to neuronal interrogation. There is therefore a pressing need for improved systems that enable a good separation when coculturing neurons and glial cells simultaneously, allowing one to address the neurons unequivocally. Here, we used substrates consisting of dense arrays of vertical nanowires intercalated by flat regions to separate retinal neurons and glial cells in distinct, but neighboring, compartments. We also generated a nanowire patterning capable of guiding optic nerve axons. The results will facilitate the design of surfaces aimed at studying and controlling neuronal networks

Retinal morphology.

<p>Hematoxylin and eosin stainings are shown for cryostat sections obtained from 31-week-old Lean (<b>a</b>) and ZDF (<b>b</b>) rats and from untreated (<b>c</b>) and insulin treated (<b>d</b>) ZDF rats at 23 weeks of age. The average number+SD of cell rows (<b>e</b>) in ONL and INL at 23 weeks of age were calculated for Lean (n = 4), untreated ZDF (n = 3) and insulin-treated ZDF (n = 6) rats, and no significant differences were detected (one way ANOVA; p>0.05). ZDF-i, insulin-treated ZDFs; ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer. Scale bar = 10 µm.</p

Cell death.

<p>TUNEL staining of cryostat sections obtained from Lean rats at 16 (<b>a</b>) and 23 (<b>d</b>) weeks of age, from ZDF rats at 16 (<b>b</b>), and 23 (<b>e</b>) weeks of age, and from insulin treated ZDF rats at 16 (<b>c</b>) and 23 weeks of age (<b>f</b>)<b>;</b> arrows point to positive cells found in ZDF (<b>b</b>) and Lean (<b>d</b>) rats. The average number of TUNEL positive cells +SD in each retinal layer were calculated (<b>g</b>) for Lean, untreated ZDF and insulin-treated ZDF rats at 16 (n = 4) and 23 weeks of age (n = 4, 3 and 6 respectively), and no significant differences were detected at either age (one way ANOVA; p>0.05). ZDF-i, insulin-treated ZDFs; ONL, outer nuclear layer; INL, inner nuclear layer; GCL, ganglion cell layer. Scale bar = 20 µm.</p

Inner retinal parameters.

<p>Scotopic b-wave amplitudes (<b>a</b>) and b/a ratio (<b>b</b>) for 1 log cd*s/m² are shown. Implicit times for oscillatory potential wavelet 3 (c) and the photopic b-wave (d) are also shown (0 and 1 log cd*s/m², respectively). Data presented are group mean +SD (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0055456#pone-0055456-t001" target="_blank">Table 1</a> for number of animals in each group at various ages) and significant differences (2 way ANOVA LSD; p<0.05) between individual pairs of experimental groups at each age tested are indicated (<b>*</b>) in tables below the graphs. ZDF-i, insulin-treated ZDFs.</p