Structural changes in laser-induced retinopathy examined by adaptive optics optical coherence tomography.

Purpose: We report a case of laser-induced retinopathy that posed diagnostic challenges with conventional spectral domain optical coherence tomography (SD-OCT), but was successfully diagnosed using adaptive optics-optical coherence tomography (AO-OCT). Observations: A 27-year-old man with a history of occupational laser device use presented with central scotoma and visual disturbances in the right eye. Conventional SD-OCT only revealed decreased reflectivity in parts of the foveal ellipsoidal zone band. However, other multimodal observations indicated damage to the retinal pigment epithelium (RPE) and choriocapillaris. Additionally, a well-defined circular, dark lesion, approximately 80 µm in diameter, was identified in the outer retina. AO-OCT demonstrated the absence of the RPE and Bruch's membrane, accompanied by the loss of inner and outer segments of cone photoreceptors and dropout of cone cell nuclei, with Müller cells remaining unaffected. Conclusions and Importance: This case of laser-induced retinopathy advances our understanding of the pathophysiological effect of laser exposure on the retina, suggesting a higher incidence of laser-induced retinopathy than previously diagnosed. It also serves as a crucial reminder for laser users to exercise caution and highlights the necessity for ophthalmologists to carefully observe and examine such cases.

Vitreous hemorrhage in retinal vein occlusion without visible traction from the posterior vitreous membrane: An optical coherence tomography angiography case report study.

Background: We report an unusual case of retinal vein occlusion (RVO) associated with vitreous hemorrhage (VH) without visible traction from the posterior vitreous membrane (PVM) at the bleeding point, challenging our current understanding of VH pathophysiology. Case presentation: A 52-year-old man presented with VH in the right eye. A detailed examination using optical coherence tomography angiography (OCTA) and ultra-widefield fluorescein angiography revealed branch RVO with non-perfused areas (NPAs) extending peripherally and neovascularization elsewhere (NVE). OCTA showed NVE infiltrating the vitreous cavity, leading to substantial bleeding without visible PVM traction at the bleeding point. The NVE was successfully removed following vitrectomy, and visual acuity improved from 20/20 to 20/13 preoperatively, along with a postoperative improvement in floaters. Conclusions: This unique case of RVO suggests the possibility of VH occurring independent of PVM contractions at the bleeding point, challenging the traditional understanding of VH. This finding underscores the potential role of OCTA in diagnosing and managing retinal vascular diseases, underscoring the need for further investigations into the underlying mechanisms, with potential implications for personalized therapeutic strategies.

Pigment Epithelial Detachment and Leak Point Locations in Central Serous Chorioretinopathy.

PURPOSE: To examine the associations between the vortex vein characteristics and locations of the pigment epithelial detachment (PED) and leak point in patients with central serous chorioretinopathy (CSC). DESIGN: Observational case series. METHODS: We evaluated 116 eyes of 104 patients with CSC. The PED and leak point locations were superimposed over the choroidal en face images using widefield swept-source optical coherence tomography and fluorescein angiography. We defined the draining areas of the superior and inferior vortex veins and analyzed their associations with the PED and leak point locations. RESULTS: One of the 116 eyes with a unique irrigation pattern dominated by the nasal vortex vein was excluded from the analysis. Sixty-nine (60%) of the remaining 115 eyes exhibited asymmetry between the superior and inferior vortex veins. PEDs and leak points were in the vortex vein draining area with greater dilation in 66 (96%) of 69 eyes with asymmetry, and none (0%) were in the opposite areas. Both the PEDs and leak points showed significant differences in their distributions (P < .001, respectively). Additionally, 74% of PEDs and 84% of leak points were located upstream of the vortex vein draining areas, whose frequency was significantly higher compared to other areas (P < .001, respectively). CONCLUSION: PED and leak point spatial distributions corresponded with the most terminal part of the dilated vortex veins, suggesting that blood flow disturbances, such as stasis within the affected vortex veins, may be essential in the pathogenesis of CSC.

Macular retinal circulation in healthy eyes examined by optical coherence tomography angiography extended interscan time analysis.

PURPOSE: To examine whether extended interscan time (IST) on optical coherence tomography angiography (OCTA) can detect slow retinal blood flow, which is undetectable on default IST, in the healthy macula. METHODS: OCTA (OCT-A1, Canon Inc.) scanning of a macular area measuring 4 × 4 mm2 of 14 healthy eyes of 14 healthy volunteers with no history or evidence of systemic and macular diseases was performed. ISTs were set at 7.6 (IST7.6, default setting), 12.0 (IST12.0), and 20.6 msec (IST20.6). Ten OCTA images were acquired at each IST, and an averaged image was created. For each averaged OCTA image obtained at IST7.6, IST12.0, and IST20.6, we defined the area surrounded by the innermost capillary ring as the foveal avascular zone (FAZ). We qualitatively evaluated the delineation of the capillaries consisting of the FAZ and quantitatively measured the FAZ area at each IST. RESULTS: Extensions from IST7.6 to IST12.0 and IST20.6 could newly delineated retinal capillaries that were undetectable at the default IST; new capillaries were detected in 10 (71%) eyes at IST12.0 and 11 (78%) eyes at IST20.0. The FAZ areas were 0.334 ± 0.137 mm2, 0.320 ± 0.132 mm2, and 0.319 ± 0.129 mm2 for IST7.6, IST12.0, and IST20.0, respectively; the FAZ areas at IST12.0 and IST20.0 were significantly decreased compared with that at IST7.6 (p = 0.004 and 0.002, respectively). CONCLUSION: In OCTA for healthy participants, extensions of the ISTs newly detected retinal capillaries with slow blood flow around FAZ. The FAZ shapes varied with different ISTs. Thus, the blood flow dynamics are not physiologically uniform around FAZ. Compared with conventional OCTA, this protocol enables a more detailed evaluation of retinal circulation and provides a better understanding of the physiological circulatory status of the healthy retina, and may enable the assessment of circulation in the very early stages in diseased eyes.

Widefield choroidal vasculature associated with future condition of subretinal fluid in central serous chorioretinopathy.

Purpose: To examine choroidal angiographic features in the posterior pole associated with resolution or persistency of subretinal fluid (SRF) in eyes with central serous chorioretinopathy (CSC). Design: Observational case series. Methods: Twenty-nine patients with treatment-naïve CSC were divided into two groups based on the presence or absence of SRF 3 months after the initial visit (month 3) without any treatment. Using enhanced depth imaging of widefield swept-source optical coherence tomography, the choroidal thickness (CT), vessel density (VD), and vessel diameter index (VDI) in the superotemporal and inferotemporal subfields on the temporal side of the 18-mm circle from the disc were measured at the initial visit. We calculated the vertical difference in CT and other choroidal angiographic parameters and evaluated their association with the SRF condition at 3 months. Results: The SRF-resolved and SRF-persistent groups included 10 and 19 patients, respectively. At the initial visit, sex, age, axial length, symptom duration, the logarithm of the minimum angle of resolution visual acuity, and foveal thickness were not significantly different between the two groups. The SRF status at month 3 was not associated with the vertical difference in CT and choroidal VD (P = .614, .065, respectively). However, the vertical difference in choroidal VDI was positively associated with the future presence of SRF (P = .017). Conclusions: Vertically asymmetric dilation of choroidal vessels in the posterior pole may be a vasculature feature associated with SRF from CSC and may be a good predictor of future SRF status.

Extensive reduction in choroidal thickness after photodynamic therapy in eyes with central serous chorioretinopathy.

We examined the effect of reduced fluence (rf)-photodynamic therapy (PDT) of the macular area on the wide-field choroidal thickness in 20 eyes with central serous chorioretinopathy (CSC) and 20 age- and sex-matched control eyes. The choroidal thickness at the posterior pole was measured before and after rf-PDT, using a grid with inner and outer rings, each divided into superotemporal, inferotemporal, superonasal, and inferonasal quadrants, respectively, making up a total of nine subfields including the central 3 mm ring. Before treatment, all eyes showed wide-field choroidal thickening from the dilated vortex vein ampulla to the fovea, along the course of the vein. After rf-PDT of the macular area, the choroidal thickness significantly decreased, not only in the irradiated macular area but also outside the arcade vessels in all quadrants (p < 0.001 for all inner subfields; p = 0.035 and p = 0.024 for the outer superonasal and inferonasal subfields, respectively; p < 0.001 and p = 0.004 for the outer superotemporal and inferotemporal subfields, respectively). For control eyes, the choroidal thickness did not differ between the initial visit and follow-up 1.2 ± 0.7 months after the initial visit (p > 0.05 for all subfields). These findings provide new insights into the pathogenesis of CSC and explain the reasons for the effectiveness of rf-PDT for this condition.

Association of Retinal Pigment Epithelium Reflectivity on Optical Coherence Tomography with Recurrence of Vogt-Koyanagi-Harada Disease: A Retrospective Observational Study.

Purpose: Despite the necessity of optical coherence tomography (OCT) for diagnosis and longitudinal monitoring in patients with Vogt-Koyanagi-Harada (VKH) disease, no studies have identified useful OCT markers for predicting recurrence in these patients. Although the precise reason for this remains unclear, one possibility is that infiltration of inflammatory cells into the choroid attenuates the OCT signal, making it difficult to precisely assess the structure of the choroid. Therefore, this study aimed to investigate changes in retinal pigment epithelium (RPE) reflectivity immediately above the choroid in eyes with acute VKH disease, as well as the association between RPE reflectivity and VKH disease recurrence. Patients and Methods: This single-centered retrospective observational study included 20 treatment-naïve patients with acute VKH disease presenting with serous retinal detachment (SRD) in the posterior pole at the initial visit between October 2015 and January 2020, as well as 15 healthy control eyes. All patients were followed up for at least 6 months and received treatment with intravenous methylprednisolone followed by oral administration of prednisolone. Swept-source OCT images through the fovea were used to measure central retinal thickness, central choroidal thickness, and RPE reflectivity. Results: During an observation period of 37.2 ± 30.8 months, recurrence of inflammation was observed in 11 patients (55.0%). Initial visual acuity was worse in patients who developed recurrence than in those who did not (P=0.024). On initial OCT images, RPE reflectivity differed significantly between patients with and without recurrence (1.75 ± 0.42 vs 1.35 ± 0.20; P=0.018), while there were no significant differences in other chorioretinal parameters, such as central retinal thickness and choroidal thickness. Conclusion: RPE reflectivity on OCT images may be useful for predicting the recurrence of inflammation in patients with VKH disease.

Analysis of widefield choroidal thickness maps of healthy eyes using swept source optical coherence tomography.

We aimed to obtain widefield (WF) swept source optical coherence tomography (SS-OCT) data and examine the features of choroidal thickness maps in healthy eyes. The posterior pole choroidal thickness was examined in 127 eyes using enhanced depth imaging of SS-OCT with a viewing angle of 20 (vertical) × 23 (horizontal) mm, and choroidal thickness maps were generated. For SS-OCT image analysis, we developed a grid with inner and outer rings, each divided into superotemporal, inferotemporal, superonasal, and inferonasal quadrants, comprising a total of nine subfields, including the central 3-mm ring. The posterior pole choroidal thicknesses were significantly lower at the periphery than in the central area, in the inferior field than in the superior field, and in the nasal field than in the temporal field (p < 0.001 for all). We also evaluated the effects of age and axial length (AL) on the WF choroidal thickness. The choroidal thickness in all subfields was negatively associated with advanced age (p < 0.05). The choroidal thicknesses in the central and inferonasal inner and outer subfields were negatively associated with AL (p = 0.042, 0.034, and 0.022, respectively). These findings provide insights into the two-dimensional characteristics of choroidal thickness and its association with age and AL.

MACULAR BLOOD FLOW CHANGES IN BRANCH RETINAL VEIN OCCLUSION EXAMINED BY OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY VARIABLE INTERSCAN TIME ANALYSIS.

PURPOSE: To examine the relationship between changes in retinal blood flow and the recurrence of macular edema in eyes with branch retinal vein occlusion. METHODS: This observational study included 32 eyes in 32 patients (18 men and 14 women) with branch retinal vein occlusion who visited the Department of Ophthalmology at Kyoto University Hospital (February 2021-November 2021). At the time of inclusion in the study, each patient underwent optical coherence tomography angiography on a macular area measuring 4 × 4 mm 2 . For variable interscan time analysis, different interscan times were set at 7.6 (IST 7.6 ) and 20.6 ms (IST 20.6 ) for the optical coherence tomography angiography. The parafoveal vessel densities were measured sectorally at IST 7.6 and IST 20.6 , and their relationship with the longitudinal changes evident in the retinal thicknesses during the variable interscan time analysis examination and 2 months later was evaluated. RESULTS: The parafoveal vessel densities in the affected sector was significantly greater at IST 20.6 than at IST 7.6 ( P = 0.011). At 2 months after the variable interscan time analysis examination, 6 patients (19%) showed recurrence of macular edema involving the fovea. The difference in the parafoveal vessel densities (IST 20.6 - IST 7.6 ) in the affected sector was significantly associated with longitudinal retinal thickening in the corresponding parafovea ( P = 0.020) and fovea ( P = 0.014). CONCLUSION: In eyes with branch retinal vein occlusion, optical coherence tomography angiography variable interscan time analysis facilitated the detection of retinal blood flow changes that might be predictive for the recurrence of macular edema.

DETECTION AND CHARACTERISTICS OF UNRUPTURED RETINAL ARTERIAL MACROANEURYSMS.

PURPOSE: To determine the presence of unruptured retinal arterial macroaneurysms (RAMs) and to examine the characteristics of the detected lesions. METHODS: This retrospective observational study included the affected and contralateral eyes of 50 patients (100 eyes) with symptomatic, unilateral, ruptured RAMs who visited the Department of Ophthalmology at the Kyoto University Hospital (April 2014-April 2020) and were followed up for at least 6 months after the onset. The presence and characteristics of unruptured RAMs were examined by reviewing the findings of color fundus photography and infrared scanning laser ophthalmoscopy performed before the onset or during the follow-up period. RESULTS: Unruptured RAMs were detected in six of the 50 patients. Some patients had bilateral or multiple unruptured RAMs, and a total of 12 unruptured RAMs were detected in eight eyes of the six patients. Among the detected lesions, eight exhibited a longitudinal increase in their diameter during the follow-up period, whereas six exhibited ruptures. CONCLUSION: Unruptured RAM is not an uncommon retinal vascular abnormality and can enlarge and progress to ruptured RAM.

Pigmentary lesions in eyes with rhegmatogenous retinal detachment with flap tears: a retrospective observational study.

We included 97 patients with unilateral rhegmatogenous retinal detachment (RRD) with posterior vitreous detachment who underwent vitrectomy, and examined pigmentary lesion (PL) characteristics around the sites of original tears using pre- and postoperative ultra-widefield scanning light ophthalmoscopy, green light fundus autofluorescence (FAF) imaging, and intraoperative digital video. If PL did not involve RRD, we used OCT to preoperatively assess any pathologic changes to the lesion. A total of 116 retinal tears (mean count, 1.2 ± 0.5; range, 1-4 per eye) were observed in the detached retina. Overall, 102 (88%), 63 (54%), 14 (12%), and 25 (22%) tears were accompanied by lattice degeneration (LD) or PL, both LD and PL, only LD, and only PL, respectively. In green FAF images, LD showed normal to mild-hyper fluorescence, whereas all PL showed hypofluorescence. On OCT, PL were located at the RPE level, while choroid abnormalities were unclear. In the retinal areas of 22 eyes, which were not affected by RRD, we observed PL without retinal tears; some were accompanied by vitreous traction and tractional retinal detachment. Pre-, intra-, and post-operative assessments of original flap tears suggested that PL might be a risk factor for RRD, developing alongside or separately from LD.

Widefield Choroidal Thickness of Eyes with Central Serous Chorioretinopathy Examined by Swept-Source OCT.

PURPOSE: To examine widefield (WF) changes in the choroidal thickness of eyes with central serous chorioretinopathy (CSC). DESIGN: An observational study. PARTICIPANTS: Twenty-two patients (20 men and 2 women) with treatment-naïve unilateral CSC and 28 normal eyes of 28 age-matched, healthy participants (21 men and 7 women). METHODS: We performed enhanced depth imaging of swept-source (SS) OCT with a viewing angle of vertical 20 mm × horizontal 23 mm. Moreover, we developed a grid consisting of 9 subfields, with diameters of 3, 9, and 18 mm; the inner and outer rings were enclosed by circles with diameters of 3 and 9 mm and 9 and 18 mm, respectively, which were divided into 4 subfields-superotemporal, inferotemporal, superonasal, and inferonasal. MAIN OUTCOME MEASURES: Widefield changes in choroidal thickness. RESULTS: The mean duration from the presumed onset of CSC was 6.8 ± 3.1 months during the examination. Compared with that in normal eyes, the choroidal thickness in eyes of patients with CSC was significantly greater in all subfields (P < 0.020 for fellow eyes; P < 0.001 for eyes with CSC). Compared with that in fellow eyes, the choroidal thicknesses in eyes of patients with CSC were significantly greater, except for the outer superotemporal and inferonasal subfields (P < 0.001 for all inner subfields; P < 0.001 for the outer superonasal and inferotemporal subfields). In areas with dilated vortex veins, choroidal thickening was observed from the vicinity of the vortex vein ampulla to the macula along the course of the veins. Choroidal thickening on the dominant side was significantly greater than that on the nondominant side (P = 0.015 for the nasal subfield of the inner ring; P = 0.003 and P < 0.001 for the temporal subfields of the inner and outer rings, respectively). CONCLUSIONS: Enhanced depth imaging of SS-OCT facilitated the analysis of WF changes in choroidal thickness in both healthy patients and patients with CSC. The local factors of the affected vortex vein and systemic risk factors may be involved in the pathogenesis of CSC.

Retinal arterial macroaneurysm rupture caused by dissection-like change in the vessel wall.

PURPOSE: To highlight a potential pathogenetic mechanism of retinal arterial macroaneurysm. OBSERVATIONS: A 79-year-old woman presented with a ruptured retinal arterial macroaneurysm in the right eye. One year after treatment, high-resolution multimodal imaging with optical coherence tomography (OCT), OCT angiography, and adaptive optics scanning light ophthalmoscope showed that a narrow passage developed in the vessel wall of the pre-existing retinal arterial macroaneurysm and another macroaneurysm had developed adjacent to the pre-existing one. CONCLUSIONS AND IMPORTANCE: These images suggest the pathogenesis of retinal arterial macroaneurysm (RAM) associated with crack-like changes in the retinal arterial wall, similar to pathologies seen in systemic arteries.

Three-dimensional locations of ruptured retinal arterial macroaneurysms and their associations with the visual prognosis.

The aim of this retrospective, observational study was to examine the intraretinal locations of ruptured retinal arterial macroaneurysms (RMAs) and investigate the associations with the visual prognosis. Fifty patients (50 eyes) with untreated RMA rupture who visited the Department of Ophthalmology at Kyoto University Hospital (April 2014-July 2019) were included. The intraretinal position of the ruptured RMAs relative to the affected retinal artery was examined using optical coherence tomography (OCT) and color fundus photography (CFP). The relative RMA positions were anterior to (anterior type, 44%), at the same level as (lateral type, 20%), or posterior to (posterior type, 34%) the affected artery. At the initial visit, the posterior type showed greater subretinal hemorrhage thickness than did the lateral and anterior types (P = 0.016 and 0.006, respectively), and poorer visual acuity (VA) than did the anterior type (P = 0.005). At the final visit, the length of the foveal ellipsoid zone band defect was longer (P = 0.005) and VA was poorer (P < 0.001) for the posterior type than for the anterior type. The intraretinal positions of ruptured RMAs vary, affect the thickness of foveal subretinal hemorrhage and predict future damage to the foveal photoreceptors. The visual prognosis may be poor for posteriorly ruptured RMAs.

Human Foveal Cone and Müller Cells Examined by Adaptive Optics Optical Coherence Tomography.

Purpose: The purpose of this study was to image and investigate the foveal microstructure of human cone and Müller cells using adaptive optics-optical coherence tomography. Methods: Six healthy subjects underwent the prototype adaptive optics-optical coherence tomography imaging, which allowed an axial resolution of 3.4 µm and a transverse resolution of approximately 3 µm. The morphological features of the individual retinal cells observed in the foveola were qualitatively and quantitatively evaluated. Results: In the six healthy subjects, the image B-scans showed hyper-reflective dots that were densely packed in the outer nuclear layer. The mean number, diameter, and density of hyper-reflective dots in the foveola were 250.8 ± 59.6, 12.7 ± 59.6 µm, and 6966 ± 1833/mm2, respectively. These qualitative and quantitative findings regarding the hyper-reflective dots were markedly consistent with the morphological features of the foveal cone cell nuclei. Additionally, the images showed the funnel-shaped hyporeflective bodies running vertically and obliquely between the inner and external limiting membranes, illustrating the cell morphology of the foveal Müller cells. Conclusions: Using adaptive optics, we succeeded in visualizing cross-sectional images of the individual cone and Müller cells of the human retina in vivo. Translational Relevance: Adaptive optics-optical coherence tomography would help to improve our understanding of the pathogenesis of macular diseases.

Segmentation of the Four-Layered Retinal Vasculature Using High-Resolution Optical Coherence Tomography Angiography Reveals the Microcirculation Unit.

Purpose: To differentiate the four layers of the retinal vessel network in the human macula and examine their morphologic features using high-resolution optical coherence tomography angiography (HR-OCTA). Methods: Macular areas measuring 464 × 464 pixels of 10 right eyes of 10 healthy subjects without ocular disease were scanned 10 times using a HR-OCTA device. Averaged OCTA images were created. Based on clear decorrelation signals, four vascular slabs were segmented, comprising one each in the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), and top and bottom of the inner nuclear layer (INL). Qualitative features and quantitative measurements in each slab were compared with those in conventionally segmented slabs. Results: HR-OCTA isolated four layers of vascular plexuses in the macula that followed the corresponding anatomic layers. Segmentations for the RNFL revealed that radial peripapillary capillaries (RPCs) extended to the central macular area. The RPCs followed relatively straight and long paths, with few apparent feed points and anastomoses. The GCL slab enhanced visualization of the capillary-free zones around the arteries and arterioles and helped to differentiate arterial and venous systems. The arterioles and venules were linked by capillaries that were arranged in a mesh-like fashion, with multiple arteriolar feed points and anastomoses. Vascular plexuses in the top and bottom of the INL consisted of capillaries in a vortex arrangement. The center of these vortex arrangements was consistent with the venules in the GCL. Conclusions: HR-OCTA can differentiate the four layers of vascular plexuses in the human macula and elucidate their angiographic features.

Kinetic Study of the Aroxyl-Radical-Scavenging Activity of Five Fatty Acid Esters and Six Carotenoids in Toluene Solution: Structure-Activity Relationship for the Hydrogen Abstraction Reaction.

A kinetic study of the reaction between an aroxyl radical (ArO•) and fatty acid esters (LHs 1-5, ethyl stearate 1, ethyl oleate 2, ethyl linoleate 3, ethyl linolenate 4, and ethyl arachidonate 5) has been undertaken. The second-order rate constants (ks) for the reaction of ArO• with LHs 1-5 in toluene at 25.0 °C have been determined spectrophotometrically. The ks values obtained increased in the order of LH 1 < 2 < 3 < 4 < 5, that is, with increasing the number of double bonds included in LHs 1-5. The ks value for LH 5 was 2.93 × 10-3 M-1 s-1. From the result, it has been clarified that the reaction of ArO• with LHs 1-5 was explained by an allylic hydrogen abstraction reaction. A similar kinetic study was performed for the reaction of ArO• with six carotenoids (Car-Hs 1-6, astaxanthin 1, ß-carotene 2, lycopene 3, capsanthin 4, zeaxanthin 5, and lutein 6). The ks values obtained increased in the order of Car-H 1 < 2 < 3 < 4 < 5 < 6. The ks value for Car-H 6 was 8.4 × 10-4 M-1 s-1. The ks values obtained for Car-Hs 1-6 are in the same order as that of the values for LHs 1-5. The results of detailed analyses of the ks values for the above reaction indicated that the reaction was also explained by an allylic hydrogen abstraction reaction. Furthermore, the structure-activity relationship for the reaction was discussed by taking the result of density functional theory calculation reported by Martinez and Barbosa into account.

Glycosylceramides from marine green microalga Tetraselmis sp.

Glycosylceramides are ubiquitous and important components of the plasma membrane in most eukaryotic cells and a few bacteria. They play significant roles in a variety of cellular functions. Their molecular structures are well recognized in animals, higher plants, and fungi, but are poorly characterized in lower plants. In this study, a high glycosylceramide-producing microalgal strain Tetraselmis sp. NKG 400013 was found. TLC and MS analyses established the presence of glycosylceramides, GT1 and GT2, in this strain. Their chemical structures were determined by NMR spectroscopy and GC/MS, and were identified as glycosylceramides consisting of the typical botanical sphingoid base ([4E, 8E]-sphinga-4, 8-dienine) and 2-hydroxy-Δ3-unsaturated fatty acyl chains, respectively. To our knowledge, the occurrence of glycosylceramides in microalga of the class Prasinophyceae was previously unknown.

Auto-oxidation products of astaxanthin.

The auto-oxidation products of astaxanthin were investigated. Astaxanthin was allowed to react with atmospheric oxygen at 55°C in the dark for 35 days. A series of oxidative cleavage products, 7-apoastaxanthinal (1), 9-apoastaxanthinone (2), 11-apoastaxanthinal (3), 13-apoastaxanthinone (4), 15-apoastaxanthinal (5), 14'-apoastaxanthinal (6), 12'-apoastaxanthinal (7), 10'-apoastaxanthinal (8), and 8'-apoastaxanthinal (9), were identified. Among them, 3 and 6 were isolated and characterized for the first time. Cleavage of the double bond in astaxanthin was discussed on the basis of the calculation of the stable molecular energy.

[Single and 13-week oral toxicity study of fucoxanthin oil from microalgae in rats].

Single oral dose and 13-week oral subchronic toxicity studies of fucoxanthin-containing oil extracted from microalga, Chaetoseros sp., were conducted in rats. In the single oral dose study, no mortality and no change related to the test material were observed. Thus, the 50% lethal dose of microalgal fucoxanthin oil is more than 2,000 mg/kg body weight. In the 13-week oral dose study, 0, 20 or 200 mg/kg body weight of microalgal fucoxanthin oil was administered. The fucoxanthin-administered groups, showed no mortality and no abnormalities. This result suggested that the no-observed-adverse-effect level of fucoxanthin-containing oil extracted from microalga Chaetoseros sp. was 200 mg/kg body weight under the tested subchronic dose condition.