Substantial increase in detection efficiency for filter array-based spectral sensors.

A method that significantly increases the detection efficiency of filter array-based spectral sensors is proposed. The basic concept involves a wavelength-dependent redistribution of incident light before it reaches the filter elements located in front of the detector. Due to this redistribution, each filter element of the array receives a spatially concentrated amount of a pre-selected and adjusted spectral partition of the entire incident light. This approach can be employed to significantly reduce the reflection and absorption losses of each filter element. The proof-of-concept is demonstrated by a setup that combines a series of consecutively arranged dichroic filters with Fabry-Perot filter arrays. Experimentally, an efficiency increase by a factor larger than 4 compared to a reference system is demonstrated. The optical system is a non-imaging spectrometer, which combines the efficiency enhancement module with the filter arrays, is compact (17.5mm×17.5mm×7.8mm), and integrated completely inside the CCD camera mount.

Topsoil removal reduced in-situ methane emissions in a temperate rewetted bog grassland by a hundredfold.

Peatland restoration is seen as an effective contribution to help achieve the aims of the Paris Agreement because currently huge amounts of peatlands in Northern Central Europe are under unsustainable drainage-based land use. If net zero greenhouse gas emissions from peatlands shall be reached by 2050, restoration measures have to be done as soon as possible. However, rewetting drained peatlands that were under intensive grassland use frequently results in high methane (CH4) emissions, which is often seen as a counter-argument against rewetting. To find the source of high CH4 emissions after rewetting and to explore the best possible way of peatland restoration (i.e., low CH4 emissions after rewetting) under near-natural conditions, we installed a field trial in a drained bog in north-western Germany. The trial consists of seven plots (~8 × 24 m2) representing the status quo-intensive grassland use- and six restoration approaches with combinations of rewetting either on the original surface or after topsoil removal (TSR), biomass harvesting or spreading Sphagnum spp. to initiate vegetation succession. On all seven plots we measured CH4 fluxes using closed chambers. In addition, we investigated CH4 production potential by incubating soil samples and determining methanogen abundance by quantitative PCR. Compared to rewetting on the original surface, CH4 emissions were reduced on TSR plots by factor 30 to 400. Spreading of Sphagnum spp. had only little effect on CH4 emissions during the first year of establishment. TSR also reduced CH4 production potential and methanogen abundance. Further, the response of CH4 fluxes to methanogen abundance was lower after TSR. This suggests that both reduction in labile substrate and in methanogen abundance contribute to near-zero CH4 emissions after TSR. These are the first field-scale results that demonstrate the efficiency of removing degraded topsoil to avoid high CH4 emissions after rewetting.

Flavanone and isoflavone glucosylation by non-Leloir glycosyltransferases.

Flavonoids possess a wide range of biological activities. Their glycosylation is of considerable interest, as it often positively influences their pharmacokinetic and other molecular properties. We recently showed that two non-Leloir glycosyltransferases that use sucrose as carbohydrate donor, an amylosucrase from Neisseria polysaccharea (Ams-Np) and a glucansucrase from Streptococcus oralis (GtfR-So), were hardly able to glucosylate flavones, but accepted flavanes as substrates. We now examined compounds from two other flavonoid classes, flavanones and isoflavones for glucose transfer by these enzymes. Taxifolin was investigated as a flavanone analogue of both, the accepted pentahydroxyflavane catechin and the non-accepted pentahydroxyflavone quercetin. It was glucosylated by both enzymes, but much better by GtfR-So than by Ams-Np due to apparent strong inhibition of the latter. The acceptance of a collection of isoflavones strongly depended on the substitution pattern of the core. Only two of the 10 compounds examined yielded glucosides in satisfactory amounts. With these substrates, both enzymes catalyzed formation of a range of products, differing in the number of saccharide units. The structures of mono- and diglycosylated compounds obtained in higher amounts were elucidated. While GtfR-So attached glucose to taxifolin in the B ring at O4', both enzymes glucosylated the isoflavones in the A ring at O7. All products were α-glucosides. Interglycosidic linkages formed by Ams-Np were α1-4. To our knowledge, this is the first report of glucosylation of flavanone and isoflavone aglycones by an amylosucrase. All characterized compounds have not previously been described.

An aryl dioxygenase shows remarkable double dioxygenation capacity for diverse bis-aryl compounds, provided they are carbocyclic.

The bacterial dioxygenation of mono- or polycyclic aromatic compounds is an intensely studied field. However, only in a few cases has the repeated dioxygenation of a substrate possessing more than a single aromatic ring been described. We previously characterized the aryl-hydroxylating dioxygenase BphA-B4h, an artificial hybrid of the dioxygenases of the biphenyl degraders Burkholderia xenovorans LB400 and Pseudomonas sp. strain B4-Magdeburg, which contains the active site of the latter enzyme, as an exceptionally powerful biocatalyst. We now show that this dioxygenase possesses a remarkable capacity for the double dioxygenation of various bicyclic aromatic compounds, provided that they are carbocyclic. Two groups of biphenyl analogues were examined: series A compounds containing one heterocyclic aromatic ring and series B compounds containing two homocyclic aromatic rings. Whereas all of the seven partially heterocyclic biphenyl analogues were solely dioxygenated in the homocyclic ring, four of the six carbocyclic bis-aryls were converted into ortho,meta-hydroxylated bis-dihydrodiols. Potential reasons for failure of heterocyclic dioxygenations are discussed. The obtained bis-dihydrodiols may, as we also show here, be enzymatically re-aromatized to yield the corresponding tetraphenols. This opens a way to a range of new polyphenolic products, a class of compounds known to exert multiple biological activities. Several of the obtained compounds are novel molecules.

An approach to "escape from flatland": chemo-enzymatic synthesis and biological profiling of a library of bridged bicyclic compounds.

A major reason for the low success rate in current drug development through chemical synthesis has been ascribed to the large fraction of quasi planar candidate molecules. Therefore, an "escape from flatland" strategy has been recommended for the generation of bioactive chemical entities. In a first attempt to test this recommendation, we synthesized a small collection of bridged bicyclic compounds possessing a rigid spherical core structure by combining a group of cyclic dienes with a collection of dienophiles. We started from planar biphenyl analogues and, by enzymatic dioxygenation, transformed them into hydroxylated diene structures. Using a small library of newly synthesized dienophiles, the dienes were converted into bridged bicycles via the Diels-Alder reaction. The resulting collection of 78 structures was first tested for bioactivity in a generic assay based on interference with the proliferation of mammalian cells. A more mechanism-targeted bioactivity profiling method, exploiting cellular impedance monitoring, was subsequently used to obtain suggestions for the mode of action exerted by those compounds that were the most active in the proliferation assay. Proteasome inhibition could be confirmed for 8 of a series of 9 respective candidates. Whilst 7 of these molecules showed relatively weak interference with proteasome activity, one candidate exerted a moderate but distinct inhibition. This result appears remarkable in view of the small size of the compound library, which was synthesized following a few basic considerations. It encourages the application of diverse synthetic approaches to further investigate the role of spherical shape for the success of compound libraries.

Recent developments in the enzymatic O-glycosylation of flavonoids.

The glycosylation of bioactive compounds, such as flavonoids, is of particular relevance, as it modulates many of their pharmacokinetic parameters. This article reviews the literature between 2010 and the end of 2015 that deals with the enzymatic O-glycosylation of this class of compounds. Enzymes of glycosyltransferase family 1 remain the biocatalysts of choice for glycodiversification of flavonoids, in spite of relatively low yields. Transfers of 14 different sugars, in addition to glucose, were reported. Several Escherichia coli strains were metabolically engineered to enable a (more efficient) synthesis of the required donor during in vivo glycosylations. For the transfer of glucose, enzymes of glycoside hydrolase families 13 and 70 were successfully assayed with several flavonoids. The number of acceptor substrates and of regiospecificities characterized so far is smaller than for glycosyltransferases. However, their glycosyl donors are much cheaper and yields are considerably higher. A few success stories of enzyme engineering were reported. These improved the catalytic efficiency as well as donor, acceptor, or product ranges. Currently, the development of appropriate high-throughput screening systems appears to be the major bottleneck for this powerful technology.

Stepwise conversion of flavonoids by engineered dioxygenases and dehydrogenase: Characterization of novel biotransformation products.

Flavonoids are a large group of plant secondary metabolites that exert various biological and pharmacological effects. In this context, the generation of derivatives is of considerable interest. The introduction of hydroxy groups is of particular relevance, as they are known to be involved in many of the biological interactions and furthermore enable additional modifications, such as glycosylations. Bacterial aryl-hydroxylating dioxygenases (ARHDOs) have proven to be very useful for the conversion of aromatic structures into versatile building blocks for different kinds of derivatizations. Such enzymes have been used with varying success for the oxidation of flavonoids. In order to find better ARHDOs for the hydroxylation of such substrates, we carried out biotransformation trials with a collection of hybrid ARHDOs of different origin, using resting cells of recombinant strains. This identified enzymes able to transform all of the flavonoids examined, typically in yields above 50%. It also showed that moderately reactive substituents of flavonoids, such as hydroxy or amino groups, can lead to spontaneous follow-up reactions with the dienediol structures generated by dioxygenation. A report of flavanone epoxidation, a reaction never before observed to be catalyzed by an ARHDO, is challenged by our results. All ARHDOs examined converted this substrate into a dehydrogenase-transformable dihydrodiol. All dihydrodiols obtained by dioxygenation of the examined flavonoids were successfully re-aromatized into catechols by a bacterial dehydrogenase. These metabolites were usually stable. However, the catechols formed from flavanone and 2'-hydroxy-chalcone, respectively, were interconvertible under mild conditions. Altogether, we isolated and characterized 13 compounds that have not previously been described. The biotransformations reported here give access to novel flavonoid derivatives that may be applied for biological screens as well as for further modification, such as glycodiversification.

Permissivity of the biphenyl-specific aerobic bacterial metabolic pathway towards analogues with various steric requirements.

It has repeatedly been shown that aryl-hydroxylating dioxygenases do not possess a very high substrate specificity. To gain more insight into this phenomenon, we examined two powerful biphenyl dioxygenases, the well-known wild-type enzyme from Burkholderia xenovorans LB400 (BphA-LB400) and a hybrid enzyme, based on a dioxygenase from Pseudomonas sp. B4-Magdeburg (BphA-B4h), for their abilities to dioxygenate a selection of eight biphenyl analogues in which the second aromatic ring was replaced by aliphatic as well as aliphatic/aromatic moieties, reflecting a variety of steric requirements. Interestingly, both enzymes were able to catalyse transformation of almost all of these compounds. While the products formed were identical, major differences were observed in transformation rates. In most cases, BphA-B4h proved to be a significantly more powerful catalyst than BphA-LB400. NMR characterization of the reaction products showed that the metabolite obtained from biphenylene underwent angular dioxygenation, whereas all other compounds were subject to lateral dioxygenation at ortho and meta carbons. Subsequent growth studies revealed that both dioxygenase source strains were able to utilize several of the biphenyl analogues as sole sources of carbon and energy. Therefore, prototype BphBCD enzymes of the biphenyl degradative pathway were examined for their ability to further catabolize the lateral dioxygenation products. All of the ortho- and meta-hydroxylated compounds were converted to acids, showing that this pathway is quite permissive, enabling catalysis of the turnover of a fairly wide variety of metabolites.

Flavonoid glucosylation by non-Leloir glycosyltransferases: formation of multiple derivatives of 3,5,7,3',4'-pentahydroxyflavane stereoisomers.

Flavonoids are known to possess a multitude of biological activities. Therefore, diversification of the core structures is of considerable interest. One of nature's important tailoring reactions in the generation of bioactive compounds is glycosylation, which is able to influence numerous molecular properties. Here, we examined two non-Leloir glycosyltransferases that use sucrose as an inexpensive carbohydrate donor, glycosyltransferase R from Streptococcus oralis (GtfR) and amylosucrase from Neisseria polysaccharea (Ams), for the glucosylation of flavonoids. Flavones generally were poor substrates. Several inhibited Ams. In contrast, flavanes were well accepted by both enzymes. All glucose attachments occurred via α1 linkages. Comparison of the three available stereoisomers of 3,5,7,3',4'-pentahydroxyflavane revealed significant differences in glycoside formation between them as well as between the two enzymes. The latter were shown to possess largely complementary product ranges. Altogether, three of the four hydroxy substituents of the terminal flavonoid rings were glycosylated. Typically, Ams glucosylated the B ring at position 3', whereas GtfR glucosylated this ring at position 4' and/or the A ring at position 7. In several instances, short carbohydrate chains were attached to the aglycones. These contained α 1-4 linkages when formed by Ams, but α 1-3 bonds when generated by GtfR. The results show that both enzymes are useful catalysts for the glucodiversification of flavanes. In total, more than 16 products were formed, of which seven have previously not been described.

Biotransformation of phloretin by amylosucrase yields three novel dihydrochalcone glucosides.

Glycosylation is one of the most important tailoring reactions for natural products. It typically exerts profound direct or indirect effects on their biological activity. The dihydrochalcone phloretin and its known sugar derivatives, particularly phlori(d)zin, have been shown to influence various cellular processes. We found that a non-Leloir glycosyltransferase, amylosucrase from Neisseria polysaccharea, is an excellent catalyst for the stereospecific glucosylation of phloretin at the 4' position. Three novel phloretin derivatives were obtained, the first ones in which the sugar-aglycone bond possesses the configuration. A first biological characterization in a cell viability assay showed that each sugar attachment reduced the compound toxicity approximately two-fold.

Non-invasive detection of early retinal neuronal degeneration by ultrahigh resolution optical coherence tomography.

Optical coherence tomography (OCT) has revolutionises the diagnosis of retinal disease based on the detection of microscopic rather than subcellular changes in retinal anatomy. However, currently the technique is limited to the detection of microscopic rather than subcellular changes in retinal anatomy. However, coherence based imaging is extremely sensitive to both changes in optical contrast and cellular events at the micrometer scale, and can generate subtle changes in the spectral content of the OCT image. Here we test the hypothesis that OCT image speckle (image texture) contains information regarding otherwise unresolvable features such as organelle changes arising in the early stages of neuronal degeneration. Using ultrahigh resolution (UHR) OCT imaging at 800 nm (spectral width 140 nm) we developed a robust method of OCT image analyses, based on spatial wavelet and texture-based parameterisation of the image speckle pattern. For the first time we show that this approach allows the non-invasive detection and quantification of early apoptotic changes in neurons within 30 min of neuronal trauma sufficient to result in apoptosis. We show a positive correlation between immunofluorescent labelling of mitochondria (a potential source of changes in cellular optical contrast) with changes in the texture of the OCT images of cultured neurons. Moreover, similar changes in optical contrast were also seen in the retinal ganglion cell- inner plexiform layer in retinal explants following optic nerve transection. The optical clarity of the explants was maintained throughout in the absence of histologically detectable change. Our data suggest that UHR OCT can be used for the non-invasive quantitative assessment of neuronal health, with a particular application to the assessment of early retinal disease.

Measurement of tear film thickness using ultrahigh-resolution optical coherence tomography.

PURPOSE: To visualize the precorneal tear film with ultrahigh-resolution spectral domain optical coherence tomography, enabling quantification of tear film thickness in healthy subjects. METHODS: A custom-built spectral domain optical coherence tomography system comprising a broadband titanium:sapphire laser operating at 800 nm and a high-speed charge coupled device (CCD) camera with a read-out rate of 47 kHz was used for measurement of precorneal tear film thickness. The system provides a theoretical axial resolution of 1.2 µm in tissue. The signal-to-noise ratio close to the zero delay was measured with 94 dB. A total of 26 healthy subjects were included in this study. Measurement was started immediately after blinking and averaged over a period of 1 second. In a subset of eight healthy subjects, the reproducibility of the approach was studied by measuring the tear film thickness every 10 minutes over 1 hour. RESULTS: The average central tear film thickness of the measured population was 4.79 ± 0.88 µm. Reproducibility was very high, with an intraclass correlation coefficient of 0.97. A breakup of the tear film was observed in one subject after 14 seconds. CONCLUSIONS: Our data indicate that the human precorneal tear film can be measured with excellent reproducibility using ultrahigh-resolution optical coherence tomography. This technique may be a valuable tool in the management of dry eye syndrome.

Graphics processing unit-based dispersion encoded full-range frequency-domain optical coherence tomography.

Dispersion encoded full-range (DEFR) frequency-domain optical coherence tomography (FD-OCT) and its enhanced version, fast DEFR, utilize dispersion mismatch between sample and reference arm to eliminate the ambiguity in OCT signals caused by non-complex valued spectral measurement, thereby numerically doubling the usable information content. By iteratively suppressing asymmetrically dispersed complex conjugate artifacts of OCT-signal pulses the complex valued signal can be recovered without additional measurements, thus doubling the spatial signal range to cover the full positive and negative sampling range. Previously the computational complexity and low processing speed limited application of DEFR to smaller amounts of data and did not allow for interactive operation at high resolution. We report a graphics processing unit (GPU)-based implementation of fast DEFR, which significantly improves reconstruction speed by a factor of more than 90 in respect to CPU-based processing and thereby overcomes these limitations. Implemented on a commercial low-cost GPU, a display line rate of ∼21,000 depth scans/s for 2048 samples/depth scan using 10 iterations of the fast DEFR algorithm has been achieved, sufficient for real-time visualization in situ.

Dioxygenation of the biphenyl dioxygenation product.

Two biphenyl dioxygenases (BphAs) were shown to catalyze dioxygenation of biphenyldienediol in the nonoxidized ring to form the respective symmetrical biphenyl-bis-dienediol. This novel metabolite served as a growth substrate for both BphA source strains. Its catabolism through the upper bph pathway of Burkholderia xenovorans LB400 was analyzed.

Characterization of biphenyl dioxygenase sequences and activities encoded by the metagenomes of highly polychlorobiphenyl-contaminated soils.

Total extracted DNA from two heavily polychlorobiphenyl-contaminated soils was analyzed with respect to biphenyl dioxygenase sequences and activities. This was done by PCR amplification and cloning of a DNA segment encoding the active site of the enzyme. The translated sequences obtained fell into three similarity clusters (I to III). Sequence identities were high within but moderate or low between the clusters. Members of clusters I and II showed high sequence similarities with well-known biphenyl dioxygenases. Cluster III showed low (43%) sequence identity with a biphenyl dioxygenase from Rhodococcus jostii RHA1. Amplicons from the three clusters were used to reconstitute and express complete biphenyl dioxygenase operons. In most cases, the resulting hybrid dioxygenases were detected in cell extracts of the recombinant hosts. At least 83% of these enzymes were catalytically active. Several amino acid exchanges were identified that critically affected activity. Chlorobiphenyl turnover by the enzymes containing the prototype sequences of clusters I and II was characterized with 10 congeners that were major, minor, or not constituents of the contaminated soils. No direct correlations were observed between on-site concentrations and rates of productive dioxygenations of these chlorobiphenyls. The prototype enzymes displayed markedly different substrate and product ranges. The cluster II dioxygenase possessed a broader substrate spectrum toward the assayed congeners, whereas the cluster I enzyme was superior in the attack of ortho-chlorinated aromatic rings. These results demonstrate the feasibility of the applied approach to functionally characterize dioxygenase activities of soil metagenomes via amplification of incomplete genes.

Multimodal photoacoustic and optical coherence tomography scanner using an all optical detection scheme for 3D morphological skin imaging.

A noninvasive, multimodal photoacoustic and optical coherence tomography (PAT/OCT) scanner for three-dimensional in vivo (3D) skin imaging is described. The system employs an integrated, all optical detection scheme for both modalities in backward mode utilizing a shared 2D optical scanner with a field-of-view of ~13 × 13 mm(2). The photoacoustic waves were detected using a Fabry Perot polymer film ultrasound sensor placed on the surface of the skin. The sensor is transparent in the spectral range 590-1200 nm. This permits the photoacoustic excitation beam (670-680 nm) and the OCT probe beam (1050 nm) to be transmitted through the sensor head and into the underlying tissue thus providing a backward mode imaging configuration. The respective OCT and PAT axial resolutions were 8 and 20 µm and the lateral resolutions were 18 and 50-100 µm. The system provides greater penetration depth than previous combined PA/OCT devices due to the longer wavelength of the OCT beam (1050 nm rather than 829-870 nm) and by operating in the tomographic rather than the optical resolution mode of photoacoustic imaging. Three-dimensional in vivo images of the vasculature and the surrounding tissue micro-morphology in murine and human skin were acquired. These studies demonstrated the complementary contrast and tissue information provided by each modality for high-resolution 3D imaging of vascular structures to depths of up to 5 mm. Potential applications include characterizing skin conditions such as tumors, vascular lesions, soft tissue damage such as burns and wounds, inflammatory conditions such as dermatitis and other superficial tissue abnormalities.

Heritability of ocular component dimensions in mice phenotyped using depth-enhanced swept source optical coherence tomography.

The range of genetic and genomic resources available makes the mouse a powerful model for the genetic dissection of complex traits. Because accurate, high-throughput phenotypic characterisation is crucial to the success of such endeavours, we recently developed an optical coherence tomography (OCT) system with extended depth range scanning capability for measuring ocular component dimensions in mice. In order to test whether the accuracy and reproducibility of our OCT system was sufficient for gene mapping studies, we carried out an experiment designed to estimate the heritability of mouse ocular component dimensions. High-resolution, two dimensional tomograms were obtained for both eyes of 11 pairs of 8 week-old outbred MF1 mice. Subsequently, images were obtained when their offspring were aged 8 weeks. Biometric data were extracted after image segmentation, reconstruction of the geometric shape of each surface, and calculation of intraocular distances. The repeatability of measurements was evaluated for 12 mice scanned on consecutive days. Heritability estimates were calculated using variance components analysis. Sets of tomograms took ∼2 s to acquire. Biometric data could be obtained for 98% of the 130 eyes scanned. The 95% limits of repeatability ranged from ±6 to ±16 µm for the axial ocular component dimensions. The heritability of the axial ocular components was 0.6-0.8, except for corneal thickness, which had a heritability not significantly different from zero. In conclusion, axial ocular component dimensions are highly heritable in mice, as they are in humans. OCT with extended depth range scanning can be used to rapidly phenotype individual mice with sufficient accuracy and precision to permit gene mapping studies.

Artefact reduction for cell migration visualization using spectral domain optical coherence tomography.

Visualization of cell migration during chemotaxis using spectral domain optical coherence tomography (OCT) requires non-standard processing techniques. Stripe artefacts and camera noise floor present in OCT data prevent detailed computer-assisted reconstruction and quantification of cell locomotion. Furthermore, imaging artefacts lead to unreliable results in automated texture based cell analysis. Here we characterize three pronounced artefacts that become visible when imaging sample structures with high dynamic range, e.g. cultured cells: (i) time-varying fixed-pattern noise; (ii) stripe artefacts generated by background estimation using tomogram averaging; (iii) image modulations due to spectral shaping. We evaluate techniques to minimize the above mentioned artefacts using an 800 nm optical coherence microscope. Effect of artefact reduction is shown exemplarily on two cell cultures, i.e. Dictyostelium on nitrocellulose substrate, and retinal ganglion cells (RGC-5) cultured on a glass coverslip. Retinal imaging also profits from the proposed processing techniques.

Mapping choroidal and retinal thickness variation in type 2 diabetes using three-dimensional 1060-nm optical coherence tomography.

PURPOSE: To map choroidal (ChT) and retinal thickness (RT) in healthy subjects and patients with diabetes with and without maculopathy using three dimensional 1060-nm optical coherence tomography (3D-1060nm-OCT). METHODS: Sixty-three eyes from 42 diabetic subjects (41-82 years of age; 11 females) grouped according to a custom scheme using Early Treatment Diabetic Retinopathy Study definitions for pathology within 1 disc-diameter of fovea (without pathology [NDR], microaneurysms [M1], exudates [M2], clinically significant macular edema [CSME]) and 16 eyes from 16 healthy age matched subjects (38-79 years of age; 11 females) were imaged by 3D-1060nm-OCT performed over a 36° × 36° field of view. Axial length, 45° fundus photographs, body mass index, plasma glucose, and blood pressure measurements were recorded. The ChT at the subfoveal location and ChT maps between RPE and the choroidal-scleral interface were generated and statistically analyzed. RESULTS: RT maps show thinning in the NDR group but an increase in thickness with increasing maculopathy in the temporal and central regions (unpaired t-test; P < 0.05). ChT mapping of all diabetic patients revealed central and inferior thinning compared to healthy eyes (unpaired t-test; P < 0.001). Subfoveal ChT (mean ± SD) for healthy eyes was 327 ± 74 µm, which was significantly thicker than all diabetic groups (214 ± 55 µm for NDR, 208 ± 49 µm for M1, 205 ± 54 µm for M2, and 211 ± 76 µm for CSME (ANOVA P < 0.001; Tukey P < 0.001). CONCLUSIONS: 3D-1060nm-OCT has shown that the central choroid is thinner in all type 2 diabetic eyes regardless of disease stage. The choroidal thinning may exceed the magnitude of possible choriocapillaris atrophy. In contrast to the conventional assessment of pathologic thickness change in several locations, thickness maps allow investigation of the choroid over the extent of affected areas.

Selective breeding for susceptibility to myopia reveals a gene-environment interaction.

Purpose. To test whether the interanimal variability in susceptibility to visually induced myopia is genetically determined. Methods. Monocular deprivation of sharp vision (DSV) was induced in outbred White Leghorn chicks aged 4 days. After 4 days' DSV, myopia susceptibility was quantified by the relative changes in axial length and refraction. Chicks in the extreme tails of the distribution of susceptibility to DSV were kept and paired for breeding (high- and low-susceptibility lines). A second round of selection was then performed. The third generation of chicks, derived from the selected parents, was assessed after either monocular DSV (4 or 10 days) or lens wear. Results. After two rounds of selective breeding, the chicks from the high-susceptibility line developed approximately twice as much myopia in response to 4 days' DSV as did those from the low-susceptibility line (P < 0.001). All ocular component dimensions differed significantly (P < 0.001) between the two selected lines, both before treatment and in the responses of the treated eye. When DSV was conducted for 10 days, the relative changes in axial length and refractive error were still significantly different between the high and low lines (P < 0.001). The chicks bred for high or low susceptibility to DSV also showed significantly different responses to minus lens wear, but not to plus lens wear. Additive genetic effects explained ∼50% of the interanimal variability in response to DSV. Conclusions. Genes and environment interact to shape refractive development in chicks.