Krypton Laser Research Articles

Safety and therapeutic efficacy of 577 nm yellow solid krypton laser for retinopathy of prematurity; A prospective pilot study.

To evaluate the outcome of 577 nm yellow solid krypton laser as an independent treatment modality for Retinopathy of Prematurity. Prospective, non-comparative, non-randomized, interventional. A prospective pilot study was conducted on 30 treatment eyes with retinopathy of prematurity (ROP) who underwent treatment with a 577 nm yellow solid state krypton laser. 3nethraNEO pediatric retinal imaging system was used to screen these infants born between March to August 2022. Pre procedure data such as gestational age (weeks), birth weight (g), and exposure to risk factors were recorded. Power (mW), exposure duration (msec), and number of laser spots administered were noted. Pain was assessed using the Neonatal Pain/Agitation and Sedation Scale (N-PASS). Post procedure data such as regression, persistence or reactivation of disease, and adverse effects were looked for. All eyes were followed up for a period of 3 months. Chi-square test, Fisher's exact test. Out of 30 eyes, 09 (30%) had type I and 21 (70%) had non-type I ROP. In type I disease, the mean power used was 88+/-10 mW with exposure duration of 130+/-27 msec and an average number of 890+/-260 burns were administered. In non-type I disease, the mean power used was 87+/-10 mW with an exposure duration of 150 ms and an average number of 900+/-290 burns were administered. The mean pain score calculated was 5 in type I and 6 in non-type I ROP. All eyes showed regression of disease after treatment. 577 nm yellow solid krypton laser was safe and effective in treating retinopathy of prematurity disease.

Demonstration of a diode-pumped dual-wavelength metastable krypton laser

Demonstration of a diode-pumped dual-wavelength metastable krypton laser

Licochalcone A alleviates laser-induced choroidal neovascularization by inhibiting the endothelial-mesenchymal transition via PI3K/AKT signaling pathway

Choroidal neovascularization (CNV) is a hallmark of wet age-related macular degeneration, which severely impairs central vision. Studies have shown that endothelial-mesenchymal transition (EndMT) is involved in the pathogenesis of CNV. Licochalcone A (lico A), a flavonoid extracted from the root of licorice, shows the inhibition on EndMT, but it remains unclear whether it can suppress the formation of CNV. The aim of this study is to investigate the effects of lico A on laser-induced CNV, and EndMT process in vitro and vivo. We established the model of CNV with a krypton laser in Brown-Norway rats and then intraperitoneally injected lico A. Our experimental results demonstrated that the leakage of CNV was relieved, and the area of CNV was reduced in lico A-treated rats. Cell migration and tube formation in oxidized low-density lipoprotein (Ox-LDL)-stimulated HUVECs were inhibited by lico A and promoted by PI3K activator 740Y-P. The protein expressions of snai1 and α-SMA were increased, and CD31 and VE-cadherin were decreased in the model rats of CNV, but partially reversed after treatment with lico A. The expression of CD31 was decreased and α-SMA was increased in OX-LDL-treated HUVECs, which was further strengthened by 740Y-P, while the expression of CD31 was up-regulated and α-SMA was down-regulated in lico A treated HUVECs. Our data revealed that EndMT process was alleviated by lico A. Meanwhile, PI3K/AKT signaling pathway was activated in model rat of CNV and Ox-LDL-stimulated HUVECs, which can be suppressed with treatment of lico A. Our experimental results confirmed for the first time that lico A has the potential to alleviate CNV by inhibiting the endothelial-mesenchymal transition via PI3K/AKT signaling pathway.

A brief review of Valsalva retinopathy

Background: Valsalva retinopathy is a specific type of retinopathy that appears following an acute rise in intrathoracic or intra-abdominal pressure. This review focuses on current literature and future directions for the diagnosis and management of Valsalva retinopathy.
 Methods: In this brief review, the literature was searched to provide an extensive general and updated description of Valsalva retinopathy, focusing on its management and prognosis. Selected articles are summarized to present the etiology, general pathology, pathophysiology, symptoms, signs, diagnosis, differential diagnosis, treatment, and prognosis of Valsalva retinopathy.
 Results: The main symptom of Valsalva retinopathy is loss of visual acuity following exertion. This is caused by the rupture of small superficial vessels in the macula and perimacular areas, leading to extravasation of blood. No link between age, sex, or race has been found, although fundus vessel abnormalities pose some predisposition to the disease. During fundoscopy, Valsalva retinopathy appears most frequently as well-defined preretinal hemorrhages confined to the sub-internal limiting membrane (ILM) or subhyaloid space. If ILM rupture occurs, hyaloid hemorrhage can appear. Diagnosis is based on the patient’s medical history and a standard examination. Usually, only observation of the patient is required, with the hemorrhage resolving within weeks to months. In cases of large premacular hemorrhage or large sub-ILM/subhyaloid hemorrhage, vitrectomy or Nd:YAG krypton laser membranotomy can be performed.
 Conclusions: Of all the aspects of Valsalva retinopathy that might trouble the physician, the most challenging features are differential diagnosis and the choice of optimal treatment. Therapeutic strategies for Valsalva retinopathy can be either conservative or based on Nd:YAG laser membranotomy and/or vitrectomy. All methods seem to have good outcomes. However, physicians should not be afraid of advancing beyond conservative therapy, especially in the event of persistent premacular hemorrhage, which could lead to permanent retinal damage if valuable time is lost, even after vitrectomy.

Repurposing bortezomib for choroidal neovascularization treatment via antagonizing VEGF-A and PDGF-D mediated signaling

Neovascular age-related macular degeneration (neoAMD) is the leading cause of blindness in AMD and manifests as choroidal neovascularization (CNV). Anti-vascular endothelial growth factor (VEGF) therapies are the mainstay treatments but with limited efficacy and cause detrimental effects on the retina after long-term application. These disadvantages warrant alternative strategy. Herein, we examined the effect on CNV by intravitreal injection of bortezomib, a reversible proteasome inhibitor, and further dissected the mechanism. Krypton red Laser was used to create CNV model in mice. The angiogenesis volume was assessed in choroidal flat-mount with isolectin GS-IB4 labeling and the leakage was examined with fluorescein fundus angiography. Injection of Borsub inhibited angiogenesis in the CNV model which was dose-dependent; the injection significantly inhibited leakage as well. Furthermore, Borsub injection reduced the contents of VEGF-A, macrophage chemotactic factor 1 (MCP-1), and platelet-derived growth factor (PDGF)-D but not PDGF-B, examined by enzyme-linked immunosorbent assay, in choroid/retinal pigment epithelium (RPE) tissue. These injections also reduced phospho-VEGFR-2 and phospho-PDGFRβ in choroid/RPE tissue examined by immunoblotting. Moreover, Borsub inhibited the recruitment of mural cells or macrophages to laser-injured spots. Injection of Borsub indicated negative effect on scotopic and photopic responses recorded by electroretinogram. Altogether, intravitreal injection of Borsub significantly reduced CNV by antagonizing VEGF-A/Flk-1 and PDGF-D/PDGFRβ pathways without impacting electroretinography parameters. Thus, Borsub may offer an invaluable therapy for the prevention and treatment of neoAMD.

Quantitative analysis of visual field loss after 577 nm krypton pan-retinal photocoagulation for diabetic retinopathy

Objective To observe the visual field loss after 577 nm krypton pan-retinal photocoagulation (PRP) in the treatment of diabetic retinopathy (DR). Methods A prospective clinical studies. Forty-six eyes of 26 patients with proliferative DR (PDR) and severe non-proliferative DR (NPDR) diagnosed by clinical examination from No. 306 Hospital of PLA during January 2014 and December 2015 were included in this study. Among them, 21 eyes of NPDR and 20 eyes of PDR; 13 eyes with diabetic macular edema (DME) (DME group) and 28 eyes without DME (non-DME group). All eyes underwent best corrected visual acuity (BCVA), fundus color photography, fundus fluorescein angiography (FFA) and optical coherence tomography (SD-OCT) examinations. The visual field index (VFI) and visual field mean defect (MD) values were recorded by Humphrey-7401 automatic visual field examination (center 30° visual field). The BCVA of DR eyes was 0.81±0.28; the VFI and MD values were (89.8±8.4)% and −7.5±3.85 dB, respectively. The BCVA of the eyes in the without DME group and DME group were 0.92±0.20 and 0.57±0.27, the VFI were (90.86±7.86)% and(87.46±9.41)%, the MD values were −6.86±3.43 and 8.87±4.48 dB. PRP was performed on eyes using 577 nm krypton laser. The changes of VFI, MD and BCVA were observed at 1, 3, and 6 months after treatment. Results Compared with before treatment, the VFI of DR eyes decreased by 12.0%, 12.3% and 14.8% (t=7.423, 4.549, 4.79; P 0.05) and MD value (t=−0.560, −0.337; P>0.05) at different time points after treatment. Compared with before treatment, the BCVA was significantly decreased in DR eyes at 1 month after treatment, the difference was statistically significant (t=2.871, P 0.05) and MD values (t=1.582, 0.776, 0.927, 1.098; P>0.05) between the two groups. Conclusion The range of 30° visual field loss is about 12%-14.8% after 577 nm krypton laser PRP for DR. VFI and MD can quantitatively analyze the and extent of visual field loss after PRP treatment. Key words: Diabetic retinopathy/therapy; Laser coagulation/adverse effects; Visual fields

LXHY formula inhibits choroidal neovascularization development via inhibiting the recruitment and adhesion of BMCs to the retina

Objective: The objective of this study is to investigate the inhibitory effect of LXHY, a Chinese medicine compound formula, on choroidal neovascularization (CNV) and to find the possible working mechanism. Methods: CNV was induced in C57BL/6 mice by krypton laser and bone marrow-derived cells (BMCs) isolated from enhanced green fluorescent protein (EGFP) transgenic mice were injected through tail vein 0.5–1 h after the laser surgery. The BMC-treated mice were randomly divided into two groups gavaged with either distilled water (DW group) or LXHY formula solution from day 1 after laser surgery. On days 7, 14, and 28 after treatment, histopathologic examination, fundus fluorescein angiography, and choroidal flatmount assay were performed to measure the CNV severity and BMC recruitment. CXCR4 levels in peripheral blood were measured by enzyme-linked immunosorbent assay. Stromal cell-derived factor-1α (SDF-1α), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) were detected by immunofluorescent staining. Results: On days 7 and 14 after treatment, CNV lesions in the LXHY-treated mice showed less recruitment of BMCs and were smaller in size compared to DW-treated mice. Histological examination also confirmed less severe CNV lesions in the LXHY group. CXCR4 levels in peripheral blood in the LXHY group were less than that of DW group on days 7 and 14. Moreover, the expression levels of SDF-1α, ICAM-1, and VCAM-1 at the lesion sites in the LXHY group were lower compared with the DW group. Conclusion: This experiment indicated that LXHY formula could inhibit CNV formation and development, probably by inhibiting the recruitment and attachment of BMCs into CNV area.

Application of high-performance liquid chromatography combined with ultra-sensitive thermal lens spectrometric detection for simultaneous biliverdin and bilirubin assessment at trace levels in human serum

We present the applicability of a new ultra-sensitive analytical method for the simultaneous determination of biliverdin and bilirubin in human serum. The method comprises isocratic reversed-phase (RP) C18 high-performance liquid chromatography (HPLC) and thermal lens spectrometric detection (TLS) based on excitation by a krypton laser emission line at 407nm. This method enables the separation of IX-α biliverdin and IX-α bilirubin in 11min with limit of detection (LOD) and limit of quantitation (LOQ) for biliverdin of 1.2nM and 3nM, and 1nM and 2.8nM for bilirubin, respectively. In addition, a step-gradient elution was set up, by changing the mobile phase composition, in order to further enhance the sensitivity for bilirubin determination with LOD and LOQ of 0.5nM and 1.5nM, respectively. In parallel, an isocratic HPLC-DAD method was developed for benchmarking against HPLC-TLS methods. The LOD and LOQ for biliverdin were 6nM and 18nM, and 2.5nM and 8nM for bilirubin, respectively. Additionally, both isocratic methods were applied for measuring biliverdin and free bilirubin in human serum samples (from 2 male and 2 female healthy donors). Combining isocratic HPLC method with TLS detector was crucial for first ever biliverdin determination in serum together with simultaneous free bilirubin determination. We showed for the first time the concentration ratio of free bilirubin versus unbound biliverdin in human serum samples.

Interventions for central serous chorioretinopathy: a network meta-analysis.

Interventions for central serous chorioretinopathy: a network meta-analysis.

Evaluation of the efficacy of laser peripheral iridoplasty in reversing the darkroom provocative test result in Chinese patients with primary angle closure status post laser iridotomy.

To investigate the efficacy and safety of krypton laser peripheral iridoplasty (LPIP) for Chinese patients with primary angle closure (PAC) or primary angle-closure glaucoma (PACG) status post laser iridotomy in reversing the positive results of the dark room provocative test (DRPT). This study was prospective, noncomparative, interventional case series. Thirty-three patients (thirty-eight eyes) with PAC or PACG status post patent laser iridotomy and maintained normal intraocular pressure (IOP) but with positive DRPT results were enrolled. All the subjects were treated with krypton LPIP. DRPT was repeated after krypton LPIP. Results of DRPT were recorded. The visual acuity, IOP and gonioscopy were analyzed before and after krypton LPIP. A minimum time limit for follow-up was 6mo. Thirty-three patients (thirty-eight eyes) were followed for 17.7±8.37mo (range 7-41mo) after LPIP. Positive results of DRPT decreased from 38 eyes to 9 eyes (23.7%) after LPIP. Peripheral anterior synechiae of angle in 34 of 38 eyes (89.5%) remained unchanged at dynamic gonioscopy throughout the follow-up period after LPIP. LPIP decreased positive rates of the DRPT significantly. The mechanism may be that LPIP minimized contact between the peripheral iris and trabecular meshwork, which is a key factor for developing peripheral anterior synechiae.

Clinical effect of photocoagulation on retinal thickness in eyes with proliferative diabetic retinopathy

Objective To observe the damage and recovecry of panretinal photocoagulation (PRP) by different wavelengths of krypton laser on retina in eyes with proliferative diabetic retinopathy. Methods This was a prospective case-control study of 60 eyes (30 right eyes as krypton green laser group and 30 left eyes as krypton yellow laser group) from 30 patients diagnosed as proliferative diabetic retinopathy. They were treated with panretinal photocoagulation (PRP) by a wavelength of 532 nm of krypton green laser and a wavelength of 561 nm of krypton yellow laser respectively. Baseline and morphological changes of optical coherence tomography (OCT) were evaluated before PRP one hour, one week, two weeks, and four weeks after PRP. The thickness of laser spot on nasal optic area was recorded and compared. The thickness of the laser spot of the same eye at different time points were analyzed by using paired sample t-test, while the thickness of the laser spot of the different eyes at the same time point were analyzed by using independent sample t-test. Results Sixty eyes of 30 patients received krypton green laser and krypton yellow laser for PRP respectively. The retinal thickness before PRP was measured as baseline and compared with that at one hour, one week, two weeks, and four weeks after PRP. OCT showed morphological changes of the same eye after PRP: mean retinal thickness was increased by 8.4% at one hour, and dropped as early as one week by 9.5% while 17.1% at two weeks. It remained stable and unchanging at four weeks compared with the data at two weeks. The difference between different time points was statistically significant. No statistically significant difference was found between different eyes at the same time point. Conclusion Krypton green laser and krypton yellow laser all are effective in treating diabetic retinopathy, and there was no statistically significant difference between them in the effect of pigment epithelium layer of retina. The retinal thickness increased by 10% after PRP and kept stable at two weeks after PRP. Key words: Retinopathy, diabetic; Photocoagulation, laser; Krypton laser; Optical coherence tomography

Thermal lens spectrometric determination of ammonium in water samples based on indophenol formation with sodium salicylate

For the first time, a thermal lens spectrometric (TLS) detection was applied for the determination of ammonium based on indophenol blue reaction. The blue–coloured indophenol was detected following excitation by a krypton laser at 647 nm. The achieved limit of detection (LOD) and limit of quantification (LOQ) were 8 ng/mL and 25 ng/mL, respectively. This represents an improvement of 20 times when compared to the spectrophotometric detection. The results obtained by TLS were benchmarked by ammonium determination using the ion exchange chromatography (IC). It was demonstrated that for the analysed samples the developed TLS method offers slightly lower LOD in comparison to IC (LOD = 12 ng/mL). The ammonium levels in all water samples determined by TLS were in good agreement with the concentrations determined by IC. A sample throughput of 12 samples per hour was provided by TLS, which is about three times higher when compared to the IC.

Red Laser Cyclophotocoagulation in the Treatment of Secondary Glaucoma in Eyes With Uveal Melanoma

To evaluate retrospectively the usefulness of the red diode and krypton laser for transscleral contact cyclophotocoagulation (CPC) in the treatment of secondary glaucoma in eyes with uveal melanoma. Twenty-seven eyes of 27 patients (mean age, 66 y; range, 33 to 85 y) with a uveal melanoma and secondary glaucoma were treated with a transscleral 670-nm diode (40 treatments) and 647-nm krypton (5 treatments) laser CPC; 25 eyes had been or were subsequently treated with brachytherapy. The energy used was 420 mW at the tip of the probe (exposure time, 10 s). Seventeen eyes were treated once, 6 eyes twice, and 4 eyes 3 to 6 times. The aim was to preserve vision in 21 patients and to relieve pain in 6 patients. Fourteen patients (52%) died during follow-up. With ≥1 CPCs, the intraocular pressure decreased from a median of 40 mm Hg at baseline to 28 mm Hg at 12 months (n=18) and 23 mm Hg at 24 months (n=10). Hypotony developed in 6 eyes. Before CPC, 12 eyes had a best corrected visual acuity (BCVA) of 20/400 or better. At 12 months, 5 of 18 eyes had BCVA 20/400 or better, and at 24 months 4 of 10 eyes. Four eyes were removed. At the latest visit, 15 of 23 eyes had no light perception, but were preserved. All patients whose aim of treatment was to relieve pain achieved pain relief. CPC lowered intraocular pressure and the number of medications needed for secondary glaucoma in eyes with uveal melanoma, also providing pain relief.

An Experimental Study on Choroidal Neovascularization Induced by Krypton Laser in Rat Model

The purpose of this work was to study the efficacy and safety of choroidal neovascularization (CNV) formation induced by Krypton laser in Brown Norway (BN) rats, and observe the trend of the change of CNV after laser photocoagulation. Twenty-five male BN rats were involved in this study. Two eyes of one rat without any laser photocoagulation were randomly selected as the control group, and the other 48 eyes of 24 rats were selected as the experimental group. Eight eyes of four rats were randomly selected to receive the examinations of fundus fluorescein angiography (FFA), histopathology, and transmission electron microscopy 3, 7, 14, 21, 28, and 56 days after laser photocoagulation. After laser photocoagulation, the leakage appeared in burns on day 7 (59%), reached the peak on day 21 (84%), (p<0.01), and remained stable after day 21, proven by FFA and histopathology (p>0.05). The thickness of CNV increased from day 7 to day 21 (p<0.01), and remained stable after day 21 (p>0.05). The experimental model of CNV can be successfully induced by Krypton laser in rats with a stable, long-lasting, and high success rate. After laser photocoagulation, the leakages appear on day 7, reach the peak on day 21, and remain stable after day 21.

Efficacy of krypton laser photodynamic therapy for oral mucosa dysplasia in 9,10-dimethyl-1,2-benzanthracene-treated hamsters

The present study aimed to evaluate the efficacy of krypton laser photodynamic therapy (PDT) with PsD-007 for the treatment of oral mucosa dysplasia in 9,10-dimethyl-1,2-benzanthracene (DMBA)-treated hamsters. A DMBA-induced hamster cheek pouch model of precancerous lesions was created and the resultant 25 hamsters were divided into five groups. The right side was treated with PDT and the left side was used as the positive control. Following systemic anesthesia, an incision was made in the groin area to expose the femoral vein. PsD-007 was administered intravenously through the femoral vein. Various doses of photosensitizer were used to treat groups A–E. Subsequent to closing the incision, the right side of the buccal mucosa was irradiated with light using the krypton laser at a wavelength of 413 nm, a power density of 150 mW/cm2 and an irradiation time of 20 min. At six weeks post-surgery, the response was analyzed using histological examinations of the buccal pouch mucosa. A total of 24 hamsters completed the six-week observation period, as one hamster from group C died in the second week following the PDT. Of all 24 irradiated sides, 15 formed normal mucosal tissues and nine demonstrated mild dysplasia. Of the total control sides, six developed moderate dysplasia, five developed severe dysplasia and 13 progressed to carcinoma in situ or squamous cell carcinoma (SCC). The results revealed a significant difference between the two sides (P<0.01) and the various doses of the PsD-007 groups. When the PsD-007 dose was >10 mg/kg, there was no statistical difference (P>0.05). PsD-007-mediated krypton laser PDT is effective for the treatment of oral mucosa dysplasia in hamsters.

Heparanase-1 activities in the development of laser induced choroidal neovascularization.

To investigate the role of heparanase-1 in laser-induced choroidal neovascularization (CNV). Experimental CNV was induced by krypton laser photocoagulation in 15 male Brown Norway rats. Fundus fluorescein angiography and histopathological examination were performed in observing the CNV development. The expression and distribution of heparanase-1 protein in the laser lesions were determined by immunohistochemistry and western blotting analysis. The success rate of laser induced CNV was approximately 75% on 3-4 weeks after laser photocoagulation. The protein levels of heparanase-1 increased significantly in the retina-choroidal complex of CNV models when compared to normal rat eyes (P<0.01). Immunostaining confirmed strong heparanase-1 expressions in all laser lesions, and it displayed to be highest at the newly formed blood vessels within the fibrovascular complex in the subretinal space. Heparanase-1 is closely involved in the development of laser induced CNV.

Effect of a Chinese Herbal Preparation-Mingjing Granule on the recruitment and adhesion of bone-marrow derived cells to choroidal neovascularization in mice induced by laser photocoagulation

Objective To observe the effect of Chinese Herbal Preparation-Mingjing Granule on the recruitment and adhesion of bone-marrow derived cells (BMCs) to choroidal neovascu1arization (CNV) in mice induced by laser photocoagulation.Methods A total of 75 C57BL/6 mice were divided into treatment group (30 mice),control group (30 mice) and normal control group (15 mice).CNV was induced by krypton laser in the mice of treatment group and control group.BMCs from GFP-transgenic mice were injected through tail vein to those mice 0.5-1.0 hours after laser surgery.On day one after laser surgery,the mice of treatment group were gavaged with 0.3 ml Mingjing Granule solution every day[30 g/(kg · d)],while the control group mice were gavaged with distilled water.The mice of normal group fed with normal cereals.7,14,28 days after treatment,choroidal flatmount were prepared to measure the CNV severity and BMCs recruitment.The choroidal histopathological change was observed by optical microscope.CXCR4 level in peripheral blood was measured by enzyme-linked immuno sorbent assay (ELISA).Stromal cell derived factor-1α (SDF-1α),vascular cell adhesion molecule-1 (VCAM-1),intercellular adhesion molecule 1 (ICAM-1) were detected by immunofluorescent staining.Results Choroidal flatmount showed that CNV developed in treatment group and control group,but not in normal group.On day seven and 14,CNV lesions in the treatment group showed less incorporation of BMCs and smaller CNV in size compared with the control group (t=10,9; P=0.007,0.024),histologic sections also showed less severe lesions in the treatment group.CXCR4 level in peripheral blood in the treatment group was less than that in the control group and normal control group on day seven and day 14(t=8.107,2.747; P＜0.05).The expression of SDF-1α,ICAM-1 and VCAM-1 in the treatment group was lower compared with the control group.Conclusions Mingjing Granule could inhibit the recruitment and adhesion of BMCs in peripheral blood to CNV at the early stage.The mechanism may be related with the action of Mingjing Granule in lowing chemokines levels in peripheral blood and expression of adhesion molecules around CNV. Key words: Herba ecliptae/drug effects; Astragalus membranaceus/drug effects; Choroidal neovascularization; Animal experimentation

Programmable color tuning of a multiline laser by means of a twisted nematic liquid crystal display

An optical system useful to tune in a controlled way the color of a triline argon krypton (Ar-Kr) laser by means of a twisted nematic liquid crystal display (TNLCD) is presented. The optical setup employs a 4f system and two blazed gratings to first separate and then recombine the spectrum of the light beam. The TNLCD is included in the intermediate focal plane operating in the amplitude modulation mode to control the relative transmission of each spectral line. The resulting color is accurately predicted by using a previously developed physical model of the spectral and voltage dependence of the TNLCD birefringence. By simply changing the gray level image addressed to the display, the Ar-Kr laser is color modulated at a video rate, thus becoming an interesting, reconfigurable, coherent light source for applications such as multicolor holography or color inspection.

Role of the Iron Axial Ligands of Heme Carrier HasA in Heme Uptake and Release

The hemophore protein HasA from Serratia marcescens cycles between two states as follows: the heme-bound holoprotein, which functions as a carrier of the metal cofactor toward the membrane receptor HasR, and the heme-free apoprotein fishing for new porphyrin to be taken up after the heme has been delivered to HasR. Holo- and apo-forms differ for the conformation of the two loops L1 and L2, which provide the axial ligands of the iron through His(32) and Tyr(75), respectively. In the apo-form, loop L1 protrudes toward the solvent far away from loop L2; in the holoprotein, closing of the loops on the heme occurs upon establishment of the two axial coordination bonds. We have established that the two variants obtained via single point mutations of either axial ligand (namely H32A and Y75A) are both in the closed conformation. The presence of the heme and one out of two axial ligands is sufficient to establish a link between L1 and L2, thanks to the presence of coordinating solvent molecules. The latter are stabilized in the iron coordination environment by H-bond interactions with surrounding protein residues. The presence of such a water molecule in both variants is revealed here through a set of different spectroscopic techniques. Previous studies had shown that heme release and uptake processes occur via intermediate states characterized by a Tyr(75)-iron-bound form with open conformation of loop L1. Here, we demonstrate that these states do not naturally occur in the free protein but can only be driven by the interaction with the partner proteins.

Study of krypton laser-induced choroidal neovascularization in a Guinea pig model of high anisometropia.

To investigate the association between high anisometropia and the area of choroidal neovascularization (CNV) induced by krypton laser in guinea pigs and better understand the pathogenesis and prevention of myopic CNV. Nine 3-week old male guinea pigs with anisometropia >6.00D were randomly assigned to three groups according to examination date after laser photocoagulation (7d, 14d and 28d). All animals underwent refraction. The eye with higher myopia was used as the experimental eye, and the other as the control eye. All eyes received repeated multi-wavelength krypton laser photocoagulation treatments (wavelength: 532nm; laser power: 400mW; spot diameter: 50μm; exposure time: 0.1s). Fundus photography and indocyanine green angiography (ICGA) were performed. Afterwards, the animals were sacrificed immediately, and the eyes were enucleated and processed for histopathologic examination and flat mounts. CNV appeared at 7d after laser treatment. The area of CNV peaked at 14d, and decrease in area and the presence of scarring was noted at 28 d. CNV was present in 66.7% of eyes by ICGA at 14 d. CNV could be observed under light microscopy at all three time points. At 14d, flat mount showed the neovascular plexus around the lesion. Semi-quantitative analysis revealed that the area of CNV in treated eyes was greater than that of control eyes. Since the mechanism of CNV in this study resembles that of CNV in pathological myopia, this model can be used to investigate the etiology, pathogenesis and treatment of CNV in pathological myopia.