Confocal Optical Coherence Tomography Research Articles

Functional optical coherence tomography reveals transient phototropic change of photoreceptor outer segments.

Dynamic near infrared microscopy has revealed transient retinal phototropism (TRP) correlated with oblique light stimulation. Here, by developing a hybrid confocal microscopy and optical coherence tomography (OCT), we tested sub-cellular source of the TRP in living frog retina. Dynamic confocal microscopy and OCT consistently revealed photoreceptor outer segments as the anatomic source of the TRP. Further investigation of the TRP can provide insights in better understanding of Stiles-Crawford effect (SCE) on rod and cone systems, and may also promise an intrinsic biomarker for early detection of eye diseases that can produce photoreceptor dysfunction.

Confocal microscopy and optical coherence tomography imaging of corneal dystrophies

AbstractCorneal dystrophies are the group of hereditary, slowly progressive disorders affecting all corneal layers. In the past, histological examination was crucial in proper diagnosis of corneal dystrophies. In recent years, non invasive optical imaging systems such as optical coherence tomography (OCT) and confocal microscopy (CM) along with genetic testing have become a new standard procedures in the diagnostic process. Advances in diagnosis and treatment of corneal dystrophies including genetic analysis and confocal microscopy findings were included in the IC3D classification in 2008. The lecture summarizes the basic principles of the confocal microscopy and optical coherence tomography. It describes the pathological corneal changes revealed by slit lamp and histological examination in relation to non contact imaging techniques. The structural changes observed with the histological methods give an account and provide an explanation for pathological changes demonstrated by the OCT and CM. This may allow for a better understanding of the pathological process involved in the corneal dystrophies progression.

Postoperative Changes in Amniotic Membrane as a Carrier for Allogeneic Cultured Limbal Epithelial Transplantation

To investigate the morphologic changes and outcomes of the amniotic membrane as a carrier for allogeneic cultivated limbal epithelial transplantation. Prospective, noncomparative, interventional study. A total of 16 eyes receiving allogeneic cultivated limbal epithelial transplantation with amniotic membrane as a carrier were enrolled. Morphologic changes in the amniotic membrane were observed by confocal microscopy and RTVue optical coherence tomography. The paired t test was employed to compare the mean best corrected visual acuity (BCVA) and corneal stromal thickness. Of the 16 eyes, 12 had stable ocular surfaces (group A), while the other 4 eyes had failed surgeries due to immune rejection (group B). Confocal microscopy showed residual amniotic membrane tissues in 8 eyes in group A at 1 year. However, the amniotic membrane was not detected in group B at 8-10 months. RTVue optical coherence tomography showed discontinuous amniotic membrane tissues in all eyes in group A at 1 year, while highly reflective opacity was seen in the corneal stroma in group B. There were no statistically significant differences in mean BCVA and corneal stromal thickness in group A at 1 month and 1 year after transplantation (P > 0.05), but the mean BCVA showed a statistically significant difference at 1 month and after the disappearance of the amniotic membrane in group B (P < 0.05). For eyes with stable ocular surfaces after cultivated limbal epithelial transplantation, the amniotic membrane can be present in the cornea for at least 1 year, with no impact on visual acuity or corneal stromal thickness. Chronic inflammation and neovascularization on the ocular surface may accelerate the disappearance of the amniotic membrane.

Altered fundus appearance resulting from autofluorescence imaging with the confocal scanning laser ophthalmoscope (cSLO) in cats.

This paper is to report that imaging the tapetal fundus of cats with the 488 nm laser of the Spectralis(®) HRA+OCT (Heidelberg Engineering Inc., Heidelberg, Germany) can result in a pale appearance of the imaged area. Wild-type and Rdy kittens (CRX mutant heterozygotes-CRX(Rdy+/-) ) (8-20 weeks of age) and adult cats (1-4 years of age) were imaged by confocal scanning laser ophthalmoscope (cSLO) and spectral domain optical coherence tomography (SD-OCT) using the Spectralis(®) HRA+OCT. Color fundus photography (RetCam II(®) , Clarity Medical Systems, Inc., Pleasanton, CA) was performed after imaging using the Spectralis(®) HRA+OCT. Following retinal cSLO imaging using the 488 nm laser (autofluorescence imaging) in both wild-type kittens and adult cats, the imaged region appeared paler than the adjacent retina that had not been imaged. This change was probably due to retinal bleaching and was fully reversible. Imaging CRX(Rdy+/-) kittens or adults, which had very reduced levels of visual pigments, did not induce the altered fundus appearance. Those using autofluorescence imaging by cSLO should be aware that it can induce a characteristic pale appearance of the tapetal fundus in the imaged area of normal cats.

MULTIMODAL IMAGING IN DEFEROXAMINE RETINOPATHY

To describe macular lesions in patients with deferoxamine (DFO) retinopathy, and to follow their clinical course using multimodal imaging. The authors retrospectively reviewed charts and multimodal imaging of 20 patients with β-thalassemia diagnosed with DFO retinopathy (40 eyes) after a minimum of 10 years of DFO treatment. Imaging included fundus photography, near-infrared reflectance and fundus autofluorescence imaging on confocal laser scanning ophthalmoscope, and spectral domain optical coherence tomography. Mean age of the 20 patients was 45 years, and mean duration of subcutaneous DFO therapy was 32 years (range, 20-52 years). Ten patients (50%) showed different types of pattern dystrophy-like fundus changes, including butterfly shaped-like (n = 3), fundus flavimaculatus-like (n = 3), fundus pulverulentus-like (n = 3), and vitelliform-like (n = 1) changes. Ten patients (50%) presented only minimal changes in the macula; these patients were significantly younger than patients presenting other patterns (P = 0.023). Confocal laser scanning ophthalmoscope and spectral domain optical coherence tomography showed that these abnormalities were more diverse and widespread than expected by ophthalmoscopy. Abnormal fundus autofluorescence and/or near-infrared reflectance signals corresponded to accumulation of material located within the outer retina or in the Bruch membrane-retinal pigment epithelium (RPE) complex on spectral domain optical coherence tomography. Follow-up examinations during a 40-month period revealed progressive development of RPE atrophy in areas of pattern dystrophy-like changes. DFO retinopathy included a variety of pattern dystrophy-like changes or minimal changes affecting the RPE-Bruch membrane-photoreceptor complex. Multimodal imaging demonstrated that fundus changes were more diverse and widespread than expected from ophthalmoscopy. Consistently with previous histologic description of DFO retinopathy, multimodal imaging confirmed that photoreceptor outer-derived retinoids, various fluorophores, and RPE displacement or clumping are involved in DFO retinopathy, finally leading to frank RPE atrophy in most cases of pattern dystrophy-like changes.

Imaging cilial motion by endoscopic optical coherence microscopy

Endoscopic imaging gives minimally invasive access to the airways and can provide important diagnostic information. We have shown that optical coherence microscopy (OCM), the combination of confocal microscopy and optical coherence tomography is able to image airway tissue with subcellular resolution. Due to its high imaging speed and lack of tissue damage OCM is a promising technique for clinical imaging if it can be integrated into endoscopic imaging devices.

Nicotine Accelerates Diabetes-Induced Retinal Changes

Purpose: To investigate the effects of nicotine on retinal alterations in early-stage diabetes in an established rodent model.Materials and Methods: Sprague–Dawley rats were examined using a combination of confocal scanning laser ophthalmoscopy and spectral domain optical coherence tomography to determine changes in retinal structure in response to nicotine exposure, diabetes and the combined effects of nicotine and diabetes. Diabetes was induced by a single injection of 65 mg/kg streptozotocin and nicotine injections were administered subcutaneously daily. Retinal thickness in the superior, inferior, nasal and temporal quadrants were determined based on the spectral domain optical coherence tomography (SD-OCT) volume scans (20° × 20°) centered on the optic disc. Segmentation of discrete retinal layers was performed on a subset of SD-OCT cross-sections to further examine changes in each treatment group. Survival of neurons within the ganglion cell layer (GCL) was assessed by confocal morphometric imaging.Results: The control group did not experience any significant change throughout the study. The nicotine treatment group experienced an average decrease in total retinal thickness (TRT) of 9.4 µm with the majority of the loss localized within the outer nuclear layer (ONL) as determined by segmentation analysis (p < 0.05). The diabetic group exhibited a trend toward decreased TRT while segmentation analysis of the diabetic retinopathy (DR) group revealed significant thinning within the ONL (p < 0.05). The combination of nicotine and diabetes revealed a significant increase of 8.9 µm in the TRT (p < 0.05) accompanied by a decrease in the number of GCL neurons.Conclusions: We demonstrated significant temporal changes in retinal morphology in response to nicotine exposure, diabetes and with the combined effects of nicotine and diabetes. These findings may have implications in determining treatment strategies for diabetic patients using products containing nicotine, such as cigarettes, smokeless tobacco, electronic cigarettes or smoking cessation products.

Photoacoustic computed microscopy.

Photoacoustic microscopy (PAM) is emerging as a powerful technique for imaging microvasculature at depths beyond the ~1 mm depth limit associated with confocal microscopy, two-photon microscopy and optical coherence tomography. PAM, however, is currently qualitative in nature and cannot quantitatively measure important functional parameters including oxyhemoglobin (HbO2), deoxyhemoglobin (HbR), oxygen saturation (sO2), blood flow (BF) and rate of oxygen metabolism (MRO2). Here we describe a new photoacoustic microscopic method, termed photoacoustic computed microscopy (PACM) that combines current PAM technique with a model-based inverse reconstruction algorithm. We evaluate the PACM approach using tissue-mimicking phantoms and demonstrate its in vivo imaging ability of quantifying HbO2, HbR, sO2, cerebral BF and cerebral MRO2 at the small vessel level in a rodent model. This new technique provides a unique tool for neuroscience research and for visualizing microvasculature dynamics involved in tumor angiogenesis and in inflammatory joint diseases.

Image-guided evaluation and monitoring of treatment response in patients with dry eye disease

Dry eye disease (DED) is one of the most common ocular disorders worldwide. The pathophysiological mechanisms involved in the development of DED are not well-understood, and thus treating DED has been a significant challenge for ophthalmologists. Most of the currently available diagnostic tests demonstrate low correlation to patient symptoms and have low reproducibility. Recently, sophisticated in vivo imaging modalities have become available for patient care, namely, in vivo confocal microscopy (IVCM) and optical coherence tomography (OCT). These emerging modalities are powerful and non-invasive, allowing real-time visualization of cellular and anatomical structures of the cornea and ocular surface. Here we discuss how, by providing both qualitative and quantitative assessment, these techniques can be used to demonstrate early subclinical disease, grade layer-by-layer severity, and allow monitoring of disease severity by cellular alterations. Imaging-guided stratification of patients may also be possible in conjunction with clinical examination methods. Visualization of subclinical changes and stratification of patients in vivo allows objective image-guided evaluation of tailored treatment response based on cellular morphological alterations specific to each patient. This image-guided approach to DED may ultimately improve patient outcomes and make it possible to study the efficacy of novel therapies in clinical trials.

Morphologic study of the cornea by in vivo confocal microscopy and optical coherence tomography after bifocal refractive corneal inlay implantation

To evaluate the biocompatibility of the Flexivue Microlens intracorneal inlay based on healing of corneal wounds and analysis of corneal structural features using invivo confocal microscopy (IVCM) and anterior segment optical coherence tomography (AS-OCT). Ophthalmology Department, Misericordia e Dolce Hospital, Prato, Italy. Case series. The intracorneal inlay was inserted in a stromal pocket created in the nondominant eye of emmetropic presbyopic patients using a femtosecond laser. Invivo confocal microscopy and AS-OCT examinations were performed preoperatively and 1, 6, and 12 months postoperatively. The mean follow-up was 7.6 months. In the early postoperative period, IVCM showed intense cellular activity in the stroma around the inlay, edema, inflammation, and degenerative material deposition but normal regularity after 12 months. Anterior segment OCT showed a regular planar shape of the corneal pocket in all eyes. The mean of the side-cut angles was 30.7 degrees. The mean difference between the measured and planned pocket depth was 9.77 μm. At 1 month, hyperreflective areas beneath the inlay and microfolds were observed in 21 of the 52 eyes. After 12 months, the anterior segment profile was regular and interface pocket reflectivity decreased over time. Six patients had inlay removal postoperatively (3 before 6 months; 3 before 12 months); after removal, IVCM and AS-OCT showed clear corneas without signs of irregularity. Invivo confocal microscopy and AS-OCT analysis showed that the inlay elicited a low-level wound-healing response in its immediate vicinity with no alteration in the corneal structures. Dr. M. Fantozzi is a member of the Presbia medical advisory board. No other author has a financial or proprietary interest in any material or method mentioned.

Comparing Optic Nerve Head Analysis Between Confocal Scanning Laser Ophthalmoscopy and Spectral Domain Optical Coherence Tomography

Purpose/aim of the study: Confocal scanning laser ophthalmoscopy, HRT3, and spectral domain optical coherence tomography (OCT), RTVue-100, are able to give 3-dimensional (3D) topography images of optic nerve head (ONH) and to derive stereometric parameters and sectorial analysis. The purpose of the study is to evaluate the agreement of these two devices and their diagnostic accuracy to discriminate eyes with glaucoma from those without.Materials and methods: Glaucoma patients and healthy control subjects were included. All of them underwent a complete ophthalmological examination, including slit lamp evaluation and visual field (VF) test. After pupil dilatation, HRT3 and RTVue-100 were performed. The following stereometric parameters were recorded: disc area, rim area, rim volume, cup volume, cup area, cup/disk ratio, and the following sectors, superotemporal, superonasal, inferotemporal, inferonasal.Results: Forty-six eyes of 46 glaucoma patients and 58 eyes of 58 healthy subjects were included in the study. In both groups, HRT3 rim area and rim volume were statistically higher than RTVue-100 (glaucomas: 0.95 ± 0.38 versus 0.44 ± 0.33 and 0.19 ± 0.13 versus 0.02 ± 0.03, p < 0.01. controls: 1.41 ± 0.30 versus 1.08 ± 0.37 and 0.37 ± 0.13 versus 0.14 ± 0.11, p < 0.01), while cup area was statistically higher by RTVue-100 (glaucomas: 1.42 ± 0.57 versus 1.14 ± 0.58, p < 0.01. controls: 1.05 ± 1.35 versus 0.65 ± 0.48). Bland and Altman plots confirmed the presence of a fixed bias. The parameters with largest AUROC were rim volume, rim area and cup/disk ratio for both instruments. HRT3 inferotemporal sector had the highest sensitivity (80.43%, at 75.9% specificity), while for RTVue-100, the superotemporal sector had the highest sensitivity (76.1%, at 81% specificity). The agreement was moderate for inferotemporal sector and fair for the others.Conclusions: HRT3 and RTVue-100 are not interchangeable for ONH analysis. They both have good diagnostic accuracy, but RTVue-100 shows slightly better performance, at least with regard to rim area volume.

Assessing Sodium Iodate–Induced Outer Retinal Changes in Rats Using Confocal Scanning Laser Ophthalmoscopy and Optical Coherence Tomography

Sodium iodate induces RPE atrophy and photoreceptor degeneration, as seen in the pathogenesis of many retinal diseases. We investigated a new approach of analyzing retinal images using confocal scanning laser ophthalmoscopy (cSLO) that allows longitudinal assessment of sodium iodate-induced lesions in the retina of living rats. A single dose of sodium iodate (25-75 mg/kg) was given intravenously to adult Sprague-Dawley rats. Control animals were given normal saline or sodium iodide. The retina was examined by cSLO and optical coherence tomography (OCT) in living rats, which were then killed for histologic assessments. Confocal scanning laser ophthalmoscopy revealed the appearance of dark patchy blots in planar images of the retina 7 days after intravenous injection of sodium iodate (25-75 mg/kg). This finding coincided with the observations of degenerative changes in the outer retinal layers in OCT images and in histology of the retina. Further analyses showed a concomitant localization of degenerative profiles in histologic preparations of this retina, suggesting that the blots corresponded to the deteriorating photopigments and outer nuclear layer (ONL). In histologic sections, these degenerative profiles appeared as irregular folds or rosettes in the ONL. Quantitative analyses showed that the changes in blot number were dose dependent, which again coincided with results showing a dose-dependent lesion in the photopigment layer and ONL in histologic sections of the retina. Sodium iodate-induced degenerative changes can be assessed quantitatively and reliably by in vivo retinal imaging using cSLO in adult rats, allowing efficient evaluation of lesions in a large area of retina in longitudinal studies.

The influence of axial length on confocal scanning laser ophthalmoscopy and spectral-domain optical coherence tomography size measurements: a pilot study

To investigate the influence of axial length on SD-OCT and cSLO size measurements from the Heidelberg Spectralis. In this pilot study, eight emmetropic pseudophakic eyes with subretinal visual implant were selected. The axial length was measured in three short (<22.5 mm), three medium (22.51-25.50 mm) and two long (>25.52 mm) eyes. The known size of subretinal implant sensor field (2800 × 2800 μm) was measured on 15 images per eye with cSLO and SD-OCT. The mean axial length was 20.8 ± 0.8 mm in short eyes, 23.3 ± 0.4 mm in medium eyes, and 26.3 ± 0.5 mm in long eyes respectively. We found in short eyes, in medium eyes and in long eyes a mean value of sensor field size measurements from cSLO of 3327 ± 9 μm, 2800 ± 9 μm and 2589 ± 12 μm and from SD-OCT of 3328 ± 9 μm, 2800 ± 12 μm and 2585 ± 19 μm respectively. The size measurements decreased in SD-OCT and cSLO measurements with longer axial lengths significantly (p < 0.0001). The present findings demonstrate accuracy of the scaling in cSLO and SD-OCT measurements of the Heidelberg Spectralis for emmetropic medium eyes. The size measurements from SD-OCT to those from cSLO were approximately equal. Caution is recommended when comparing the measured values of short and long eyes with the normative database of the instrument. Further studies with larger sample sizes are needed to confirm findings.

About the optic disc size

Aim. To compare the dependence of retinal nerve fibre layer thickness on the optic disc size in confocal scanning laser ophthalmoscopy and optical coherence tomography. Methods. 201 outpatient’s cards with verified diagnosis of glaucoma or with suspicion of glaucoma were retrospectively analyzed. The mean age of the patients was 64 (56; 72) years [Me, (Q1; Q3)]. A group of patients who underwent confocal scanning laser ophthalmoscopy (181 eyes), and a group who underwent optical coherence tomography (183 eyes), were separated. Besides, all the groups were twice divided into 3 subgroups each, by means of cluster analysis and on the basis of size classification: large, medium and small. Results. According to the data of confocal scanning laser ophthalmoscopy, the bigger is the optic disc, the thinner is retinal nerve fibre layer (Rs=-0.22; р=0.001). In optical coherence tomography, different correlation was observed, the bigger is the optic disc, the thicker is the retinal nerve fibre layer (Rs=0.15; р=0.03). Conclusion. The size of the optic disc was related to the retinal nerve fibre layer thickness in both examination modes: there was an inverse relation found in confocal scanning laser ophthalmoscopy - the bigger the optic disc, the thinner is the retinal nerve fibre layer), and there was a direct dependence found in optical coherence tomography (the bigger is the optic disc, the thicker is retinal nerve fibre layer), thus it is important to consider the size of the optic disc while estimating the retinal nerve fibre layer thickness.

Neuroprotection in a Novel Mouse Model of Multiple Sclerosis

Multiple sclerosis is an immune-mediated, demyelinating and neurodegenerative disease that currently lacks any neuroprotective treatments. Innovative neuroprotective trial designs are required to hasten the translational process of drug development. An ideal target to monitor the efficacy of strategies aimed at treating multiple sclerosis is the visual system, which is the most accessible part of the human central nervous system. A novel C57BL/6 mouse line was generated that expressed transgenes for a myelin oligodendrocyte glycoprotein-specific T cell receptor and a retinal ganglion cell restricted-Thy1 promoter-controlled cyan fluorescent protein. This model develops spontaneous or induced optic neuritis, in the absence of paralytic disease normally associated with most rodent autoimmune models of multiple sclerosis. Demyelination and neurodegeneration could be monitored longitudinally in the living animal using electrophysiology, visual sensitivity, confocal scanning laser ophthalmoscopy and optical coherence tomography all of which are relevant to human trials. This model offers many advantages, from a 3Rs, economic and scientific perspective, over classical experimental autoimmune encephalomyelitis models that are associated with substantial suffering of animals. Optic neuritis in this model led to inflammatory damage of axons in the optic nerve and subsequent loss of retinal ganglion cells in the retina. This was inhibited by the systemic administration of a sodium channel blocker (oxcarbazepine) or intraocular treatment with siRNA targeting caspase-2. These novel approaches have relevance to the future treatment of neurodegeneration of MS, which has so far evaded treatment.

Retikuläre Drusen über die Zeit mittels SD-OCT

The aim of the study was the analysis of reticular drusen (RDR) in patients with age-related macular degeneration using simultaneous confocal scanning laser ophthalmoscopy (cSLO) and spectral domain optical coherence tomography (SD-OCT) at different time points. Included in this retrospective analysis were 47 eyes from 32 patients (median age 80.1 years, range 66-89 years) with RDR at baseline and at least one follow-up visit. Registration of the cSLO near-infrared reflectance image and the SD-OCT B-scan (Spectralis HRA + OCT, Heidelberg Engineering, Heidelberg) at different time points was carried out using the AutoRescan tool. While either no alterations or increase in the RDR area (n=19 eyes) or RDR density (n=15) were seen by cSLO imaging, the analysis of the SD-OCT B-scans at different time points revealed a more complex picture. An increase in two well visible lesions at the baseline visit was detected in 8 eyes at the first follow-up and in 3 eyes at the second follow-up examination. A regression was seen in 5 eyes at the first follow-up and in 3 eyes at the second follow-up visit. In most eyes (n=23), an increase of one with a parallel decrease of the second RDR lesion in the identical B-scan was identified at the first follow-up visit, whereas individual RDR showed an increase at the second follow-up examination that had initially shown a decrease in size at the first follow-up visit. The results indicate underlying dynamic processes in the development and changes of RDR over time. For a more accurate analysis, the exact registration of SD-OCT B-scans at different time points and the use of high-resolution very dense volume scans would be helpful in order to assess such discrete changes of miniscule intraretinal lesions over time.

Confocal laser scanning microscopy and optical coherence tomography for the evaluation of the kinetics and quantification of wound healing after fractional laser therapy

Information on the course of wound healing after fractional carbon-dioxide laser therapy has so far been gathered by histopathology. Confocal laser scanning microscopy (CLSM) and optical coherence tomography (OCT) allow the visualization of the upper layers of the skin invivo over time. The aim of this study was to determine whether CLSM and OCT can be used to quantify the kinetics of the dynamic wound-healing process. Twenty healthy probands were treated with fractional carbon-dioxide laser with 8- and 16-W laser power, respectively. Optical follow-ups using CLSM and OCT were performed right after laser application and during the next 3 weeks. Although wound healing seems to be completed after day 7 to 14 clinically, on day 21 in 89.5% of the 8 W-treated areas and in 100% of the 16 W-treated areas subepidermal skin damage was still visible using CLSM and OCT imaging. The maximal penetration depth of CLSM is limited to the papillary dermis, whereas OCT can visualize deeper but with lower resolution. Invivo CLSM and OCT are able to visualize changes after fractional laser treatment noninvasively. They allow especially the detection and quantification of substance defects and thereby help to elucidate the therapeutic effects.

Backscattering Mueller matrix measurement scheme using the same polarizing–analyzing optics

Mueller matrix measurements are most commonly performed using a set of polarization state generating (PSG) optics and an independent set of polarization state analyzing (PSA) optics. However, for polarized confocal microscopy and polarization sensitive optical coherence tomography it would be advantageous if the same set of polarization optics could be used for both PSG as well as PSA. This has not been possible because, in this configuration, a complete set of incident and analyzer states cannot be generated using polarizers and waveplates alone. In an earlier attempt to address this issue it was shown that by using two Faraday rotators, with independently variable circular retardance, in the polarization optics, complete Mueller matrix measurement can be performed. However, a practical implementation of this approach has proved to be difficult due to the requirement to vary the circular retardance. In this paper we show that by incorporating only one Faraday rotator in the polarization optics, one can generate the complete set of incident and analyzer states required for Mueller matrix measurements without the need to vary the circular retardance of the Faraday rotator.

Assessing the Safety of a Replacement Chemical: Nongenomic Activity of Bisphenol S

Suspected links between bisphenol A (BPA) and adverse human health effects have spurred a search for replacement chemicals for use in common applications such as polycarbonate plastics, food can linings, and thermal papers. Bisphenol S (BPS) has been adopted for some uses. A new study now shows that low doses of BPS can disrupt nongenomic signaling pathways in cultured pituitary cells [EHP 121(3):352–358; Vinas and Watson]. Nearly 93% of U.S. residents over age 6 carry measurable amounts of BPA in their bodies. The compound is suspected to contribute to the development of diseases such as diabetes, asthma, and cancer, and animal studies have shown it adversely affects reproduction. In contrast to genomic regulation, which involves receptors in the cell nucleus, nongenomic regulation involves receptors in the cell membrane. Since BPA can interact with cell-membrane estrogen receptors, researchers explored whether structurally similar BPS might likewise influence nongenomic pathways. Treatments included various low doses of BPS alone and paired with estradiol, an endogenous estrogen. Measured responses included activation of ERK and JNK, mitogen-activated protein kinases involved in cell growth, proliferation, and apoptosis (programmed cell death); activation of caspases 8 and 9, enzymes that also are involved in apoptosis; and release of prolactin, a hormone that helps regulate hundreds of biological functions, including metabolism, reproduction, and lactation. BPS has been adopted as a replacement for BPA in applications such as thermal receipt paper. BPS appeared to interact predominantly with the cell-membrane estrogen receptor ER〈. Estradiol and BPS each increased cell proliferation, but following exposure to both compounds there were fewer cells than in control cultures. This can result from decreased proliferation or increased cell death, which is why the investigators also looked at caspase 8 and caspase 9. The former was activated by BPS alone and when combined with estradiol, but caspase 9 was less affected, consistent with an increase in apoptosis. The lowest concentrations of BPS triggered the strongest ERK response; however, ERK activation was not as strong in the presence of both compounds. BPS alone did not activate JNK, but in combination with estradiol it increased JNK activation more than the estrogen alone. The quality and timing of ERK and JNK responses to activation by estradiol were often altered by BPS. By itself, BPS did not affect prolactin secretion, but it significantly suppressed estradiol-induced secretion at most concentrations. Based on these results, low concentrations of BPS appear to affect nongenomic signaling in estrogen-responsive cells, with potential consequences for cell function. The results emphasize the need to screen compounds for estrogenic activity prior to their use in manufacturing.

Photoacoustic Microscopy.

Photoacoustic microscopy (PAM) is a hybrid in vivo imaging technique that acoustically detects optical contrast via the photoacoustic effect. Unlike pure optical microscopic techniques, PAM takes advantage of the weak acoustic scattering in tissue and thus breaks through the optical diffusion limit (~1 mm in soft tissue). With its excellent scalability, PAM can provide high-resolution images at desired maximum imaging depths up to a few millimeters. Compared with backscattering-based confocal microscopy and optical coherence tomography, PAM provides absorption contrast instead of scattering contrast. Furthermore, PAM can image more molecules, endogenous or exogenous, at their absorbing wavelengths than fluorescence-based methods, such as wide-field, confocal, and multi-photon microscopy. Most importantly, PAM can simultaneously image anatomical, functional, molecular, flow dynamic and metabolic contrasts in vivo. Focusing on state-of-the-art developments in PAM, this Review discusses the key features of PAM implementations and their applications in biomedical studies.