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Guder S, Sadeghi F, Zittel S, Quandt F, Choe C, Bönstrup M, Cheng B, Thomalla G, Gerloff C, Schulz R. Disability and persistent motor deficits are linked to structural crossed cerebellar diaschisis in chronic stroke. Hum Brain Mapp 2023; 44:5336-5345. [PMID: 37471691 PMCID: PMC10543354 DOI: 10.1002/hbm.26434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Revised: 06/15/2023] [Accepted: 07/07/2023] [Indexed: 07/22/2023] Open
Abstract
Brain imaging has significantly contributed to our understanding of the cerebellum being involved in recovery after non-cerebellar stroke. Due to its connections with supratentorial brain networks, acute stroke can alter the function and structure of the contralesional cerebellum, known as crossed cerebellar diaschisis (CCD). Data on the spatially precise distribution of structural CCD and their implications for persistent deficits after stroke are notably limited. In this cross-sectional study, structural MRI and clinical data were analyzed from 32 chronic stroke patients, at least 6 months after the event. We quantified lobule-specific contralesional atrophy, as a surrogate of structural CCD, in patients and healthy controls. Volumetric data were integrated with clinical scores of disability and motor deficits. Diaschisis-outcome models were adjusted for the covariables age, lesion volume, and damage to the corticospinal tract. We found that structural CCD was evident for the whole cerebellum, and particularly for lobules V and VI. Lobule VI diaschisis was significantly correlated with clinical scores, that is, volume reductions in contralesional lobule VI were associated with higher levels of disability and motor deficits. Lobule V and the whole cerebellum did not show similar diaschisis-outcome relationships across the spectrum of the clinical scores. These results provide novel insights into stroke-related cerebellar plasticity and might thereby promote lobule VI as a key area prone to structural CCD and potentially involved in recovery and residual motor functioning.
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Affiliation(s)
- Stephanie Guder
- Department of NeurologyUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Fatemeh Sadeghi
- Department of NeurologyUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Simone Zittel
- Department of NeurologyUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Fanny Quandt
- Department of NeurologyUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Chi‐un Choe
- Department of NeurologyUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Marlene Bönstrup
- Department of NeurologyUniversity Medical Center Hamburg‐EppendorfHamburgGermany
- Department of NeurologyUniversity Medical Center LeipzigLeipzigGermany
| | - Bastian Cheng
- Department of NeurologyUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Götz Thomalla
- Department of NeurologyUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Christian Gerloff
- Department of NeurologyUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Robert Schulz
- Department of NeurologyUniversity Medical Center Hamburg‐EppendorfHamburgGermany
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Choe C, Schleusener J, Choe S, Ri J, Lademann J, Darvin ME. Stratum corneum occlusion induces water transformation towards lower bonding state: a molecular level in vivo study by confocal Raman microspectroscopy. Int J Cosmet Sci 2020; 42:482-493. [PMID: 32692411 DOI: 10.1111/ics.12653] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 07/15/2020] [Accepted: 07/17/2020] [Indexed: 12/23/2022]
Abstract
OBJECTIVE It is conventionally understood that occlusive effects are the retention of excessive water in the stratum corneum (SC), the increase of SC thickness (swelling) and a decrease of the transepidermal water loss. However, the influence of occlusion on water binding properties in the SC is unknown. METHODS The action of plant-derived jojoba and almond oils, as well as mineral-derived paraffin oil and petrolatum topically applied on human skin, is investigated in vivo using confocal Raman microspectroscopy. To understand the oils' influence on the SC on the molecular level, the depth-dependent hydrogen bonding states of water in the SC and their relationship to the conformation of keratin, concentration of natural moisturizing factor (NMF) molecules and lipid organization were investigated. RESULTS A significant SC swelling was observed only in petrolatum-treated skin. The water concentration was increased in oil-treated skin in the intermediate SC region (40-70% SC depth). Meanwhile, the amount of free, weakly and tightly bound water increased, and strongly bound water decreased in the uppermost SC region (0-30% SC depth). The NMF concentration of oil-treated skin was significantly lower at 50-70% SC depth. The lateral organization of lipids in oil-treated skin was lower at 0-30% SC depth. The secondary structure of keratin was changed towards an increase of β-sheet content in mineral-derived oil-treated skin and changed towards an increase of α-helix content in plant-derived oil-treated skin. CONCLUSION The occlusive properties can be summarized as the increase of free water and the transformation of water from a more strongly to a more weakly hydrogen bonding state in the uppermost SC, although some oils cause insignificant changes of the SC thickness. The accompanied changes in the keratin conformation at the intermediate swelling region of the SC also emphasize the role of keratin in the SC's water-transporting system, that is the water in the SC transports intercellularly and intracellularly in the intermediate swelling region and only intercellularly in the uppermost non-swelling region. Bearing this in mind, almond, jojoba and paraffin oils, which are not occlusive from the conventional viewpoint, have an occlusion effect similar to petrolatum on the SC.
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Affiliation(s)
- C Choe
- Kim Il Sung University, Taesong District, Ryongnam-Dong, Pyongyang, DPR Korea
| | - J Schleusener
- Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Charitéplatz 1, Berlin, 10117, Germany
| | - S Choe
- Kim Il Sung University, Taesong District, Ryongnam-Dong, Pyongyang, DPR Korea
| | - J Ri
- Kim Il Sung University, Taesong District, Ryongnam-Dong, Pyongyang, DPR Korea
| | - J Lademann
- Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Charitéplatz 1, Berlin, 10117, Germany
| | - M E Darvin
- Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Charitéplatz 1, Berlin, 10117, Germany
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Choe C, Niemann L, Englisch C, Petersen E, Buhmann C, Pötter‐Nerger M, Blankenberg S, Gerloff C, Schwedhelm E, Zeller T. Subclinical Cardiac Microdamage, Motor Severity, and Cognition in Parkinson's Disease. Mov Disord 2020; 35:1863-1868. [DOI: 10.1002/mds.28129] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 04/24/2020] [Accepted: 05/12/2020] [Indexed: 12/24/2022] Open
Affiliation(s)
- Chi‐un Choe
- Department of Neurology University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Louisa Niemann
- Department of Neurology University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Catrin Englisch
- Department of Neurology University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Elina Petersen
- Epidemiological Study Center University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Carsten Buhmann
- Department of Neurology University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Monika Pötter‐Nerger
- Department of Neurology University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Stefan Blankenberg
- Clinic of Cardiology University Heart and Vascular Center Hamburg Hamburg Germany
- German Center for Cardiovascular Research, DZHK; partner site Hamburg/Lübeck/Kiel Hamburg Germany
| | - Christian Gerloff
- Department of Neurology University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Edzard Schwedhelm
- German Center for Cardiovascular Research, DZHK; partner site Hamburg/Lübeck/Kiel Hamburg Germany
- Institute of Clinical Pharmacology and Toxicology, University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Tanja Zeller
- Clinic of Cardiology University Heart and Vascular Center Hamburg Hamburg Germany
- German Center for Cardiovascular Research, DZHK; partner site Hamburg/Lübeck/Kiel Hamburg Germany
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Hidding U, Gulberti A, Pflug C, Choe C, Horn A, Prilop L, Braaß H, Fründt O, Buhmann C, Weiss D, Westphal M, Engel A, Gerloff C, Köppen J, Hamel W, Moll C, Pötter-Nerger M. Modulation of specific components of sleep disturbances by simultaneous subthalamic and nigral stimulation in Parkinson's disease. Parkinsonism Relat Disord 2019; 62:141-147. [DOI: 10.1016/j.parkreldis.2018.12.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 11/26/2018] [Accepted: 12/22/2018] [Indexed: 10/27/2022]
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Whittington HJ, Atzler D, Zervou S, Faller KME, McAndrew DJ, Choe C, Isbrandt D, Schneider JE, Neubauer S, Lygate CA. LOSS OF HOMOARGININE IS RESPONSIBLE FOR CARDIAC DYSFUNCTION IN CREATINE-DEFICIENT ARGININE:GLYCINE AMIDINOTRANSFERASE (AGAT) KNOCKOUT MICE. Heart 2014. [DOI: 10.1136/heartjnl-2014-306916.33] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Riant F, Bergametti F, Fournier HD, Chapon F, Michalak-Provost S, Cecillon M, Lejeune P, Hosseini H, Choe C, Orth M, Bernreuther C, Boulday G, Denier C, Labauge P, Tournier-Lasserve E. CCM3 Mutations Are Associated with Early-Onset Cerebral Hemorrhage and Multiple Meningiomas. Mol Syndromol 2013; 4:165-72. [PMID: 23801932 DOI: 10.1159/000350042] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/11/2013] [Indexed: 11/19/2022] Open
Abstract
Mutations of CCM3/PDCD10 cause 10-15% of hereditary cerebral cavernous malformations. The phenotypic characterization of CCM3-mutated patients has been hampered by the limited number of patients harboring a mutation in this gene. This is the first report on molecular and clinical features of a large cohort of CCM3 patients. Molecular screening for point mutations and deletions was used to identify 54 CCM3-mutated index patients. Age at referral and clinical onset, type of inaugural events and presence of extra-axial lesions were investigated in these 54 index patients and 22 of their mutated relatives. Mean age at clinical onset was 23.0 ± 16 years. Clinical onset occurred before 10 years in 26% of the patients, and cerebral hemorrhage was the initial presentation in 72% of these patients. Multiple extra-axial, dural-based lesions were detected in 7 unrelated patients. These lesions proved to be meningiomas in 3 patients who underwent neurosurgery and pathological examination. This 'multiple meningiomas' phenotype is not associated with a specific CCM3 mutation. Hence, CCM3 mutations are associated with a high risk of early-onset cerebral hemorrhage and with the presence of multiple meningiomas.
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Affiliation(s)
- F Riant
- Service de Génétique Neuro-Vasculaire, Assistance Publique-Hôpitaux de Paris, Paris, France ; Centre de Référence des Maladies Vasculaires Rares du Cerveau et de L'Œil, Groupe Hospitalier Lariboisière - Fernand Widal, Paris, France ; Unité Mixte de Recherche-S-740, Institut National de la Santé et de la Recherche Médicale, Paris, France ; Unité Mixte de Recherche-S-740, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
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Sharp B, Choe C, Simmons S. 151: Development of a Novel Communication Tool Using Patient Focus Group Input. Ann Emerg Med 2010. [DOI: 10.1016/j.annemergmed.2010.06.198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Kang D, Choe C, Kim ES, Yang HY, Hur CG, Kim EJ, Han J. 237 POTASSIUM CONCENTRATION AND mRNA LEVELS OF POTASSIUM CHANNELS DECREASED IN CYSTIC OVARIAN FOLLICLE FLUID. Reprod Fertil Dev 2007. [DOI: 10.1071/rdv19n1ab237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Cystic ovarian follicle (COF) is one of the most frequently diagnosed ovarian diseases and a major cause of reproductive failure in cattle. Despite an abundance of reports on this subject, the exact pathogenesis of COF still remains unclear. It is generally accepted that disruption of the hypothalmo-pituitary-gonadal axis, by endogenous and/or exogenous factors, causes cystic formation. We here examined whether ion concentration and expression of ion channels are altered in the follicle fluid derived from a Korean native cow with COF. In an ovary with a cystic follicle, granulosa cell layers were exfoliated; the theca interna was thinner than that in an ovary without cystic follicle, based on histological examination. Concentrations of K+, Na+, and Cl- in COF fluid (COFF) were 10.4 � 3.5 mM, 138 � 12 mM, and 104.9 � 7.0 mM, respectively. In COFF, K+ concentration showed a significant difference from the value observed in normal follicle fluid (NFF) (P < 0.05; NFF: 10.4 � 3.5 mM vs. COFF: 6.2 � 0.8 mM). The total numbers of follicles observed (normal, 3–5 mm in diameter vs. COF, 20–30 mm in diameter) were 200 and 20 in normal and COF, respectively. To compare mRNA expression of K+ channels, we performed semiquantitative RT-PCR using follicle fluid and ovaries with or without cystic follicles. RT-PCR showed that mRNA levels of TASK channels (TASK-1, TASK-3, and TASK-5) decreased by 50% in COFF and an ovary with cystic follicles compared to NFF and a normal ovary. TASK channels are involved in apoptosis of mammalian cells. Our results suggest that potassium may play an important role in the pathogenesis of COF.
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Choe C, Son DS, Choi SH, Cho SR, Kim HJ, Yeon SH, Han MH. 291 EFFECTS OF ANTIOXIDANT AND CULTURE MEDIUM ON THE DEVELOPMENT OF PORCINE IN VITRO-MATURED - IN VITRO-FERTILIZED EMBRYOS. Reprod Fertil Dev 2007. [DOI: 10.1071/rdv19n1ab291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Most cells cultured in vitro are exposed to the risk of injury by free oxygen radicals (FOR). However, some of FOR-induced injury could be reduced by the antioxidants and culture medium used for in vitro embryos. This study was undertaken to examine the effects of the antioxidant and culture medium on the development of porcine in vitro-matured–in vitro-fertilized embryos. In Experiment 1, we treated the porcine oocytes in NCSU23 medium with various concentrations of β-mercaptoethanol (β-ME) to determine the effective concentration of antioxidants during IVM of porcine oocytes. In Experiment 2, we tested different culture media to find the proper culture conditions for in vitro porcine embryos. The porcine oocytes that were matured in NCSU23 medium and then fertilized in mTBM medium were cultured in NCSU23 or porcine zygote medium-5. All steps (maturation, fertilization, and development) were carried out in vitro. Differences were analyzed among treatments using the general linear model (GLM) procedure in the Statistical Analysis System (SAS Institute, Inc., Cary, NC, USA). The results were summarized as follows. Various concentrations of β-ME showed different developmental rates in porcine embryos. The rates of blastocyst formation at Day 7 after IVF were 9.2 � 1.8 (n = 65), 10.0 � 4.2 (n = 80), 17.5 � 1.1 (n = 63), 20.7 � 1.7 (n = 82), and 14.6 � 1.4 (n = 82) in oocytes treated with β-ME at 0, 10, 25, 50, and 100 �M during IVM, respectively. Of the concentrations of β-ME tested, 50 �M β-ME markedly increased the rates of blastocyst formation at Day 7 (P < 0.05). The rates of blastocyst formation at Day 7 in the NCSU23 and PZM-5 culture media of porcine IVF-derived embryos were 18.8 � 2.6 (n = 96) and 15.6 � 7.1 (n = 77), respectively. The developmental rates were slightly increased in NCSU23, compared with those in PZM-5, but there were no significant differences (P < 0.05) between the NCSU23 and PZM-5 media. In conclusion, these results suggest that the addition of 50 �M β-ME in the IVM medium can improve developmental the rates of porcine embryos in vitro.
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Kim HJ, Chakravarti N, Oridate N, Choe C, Claret FX, Lotan R. N-(4-hydroxyphenyl)retinamide-induced apoptosis triggered by reactive oxygen species is mediated by activation of MAPKs in head and neck squamous carcinoma cells. Oncogene 2006; 25:2785-94. [PMID: 16407847 PMCID: PMC1458365 DOI: 10.1038/sj.onc.1209303] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
N-(4-hydroxyphenyl)retinamide (4HPR), a synthetic retinoid effective in cancer chemoprevention and therapy, is thought to act via apoptosis induction resulting from increased reactive oxygen species (ROS) generation. As ROS can activate MAP kinases and protein kinase C (PKC), we examined the role of such enzymes in 4HPR-induced apoptosis in HNSCC UMSCC22B cells. 4HPR increased ROS level within 1 h and induced activation of caspase 3 and PARP cleavage within 24 h. Activation of MKK3/6 and MKK4, JNK, p38 and ERK was detected between 6 and 12 h, increased up to 24 h and preceded apoptosis. 4HPR-induced activation of these kinases was abrogated by the antioxidants BHA and vitamin C. SP600125, a JNK inhibitor, suppressed 4HPR-induced c-Jun phosphorylation, cytochrome c release from mitochondria and apoptosis. Suppression of JNK1 and JNK2 using siRNA decreased, whereas overexpression of wild type-JNK1 enhanced 4HPR-induced apoptosis. PD169316, a p38, inhibitor suppressed phosphorylation of Hsp27 and apoptosis. PD98059, an MEK1/2 inhibitor, also suppressed ERK1/2 activation and apoptosis induced by 4HPR. Likewise, PKC inhibitor GF109203X suppressed ERK and p38 phosphorylation and PARP cleavage. These data indicate that 4HPR-induced apoptosis is triggered by ROS increase, leading to the activation of the mitogen-activated protein serine/threonine kinases JNK, p38, PKC and ERK, and subsequent apoptosis.
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Affiliation(s)
- H-J Kim
- Department of Thoracic/Head and Neck Medical Oncology, University of Texas, MD Anderson Cancer Center, Houston, TX, USA and
| | - N Chakravarti
- Department of Thoracic/Head and Neck Medical Oncology, University of Texas, MD Anderson Cancer Center, Houston, TX, USA and
| | - N Oridate
- Department of Thoracic/Head and Neck Medical Oncology, University of Texas, MD Anderson Cancer Center, Houston, TX, USA and
| | - C Choe
- Department of Thoracic/Head and Neck Medical Oncology, University of Texas, MD Anderson Cancer Center, Houston, TX, USA and
| | - F-X Claret
- Department of Molecular Therapeutics, University of Texas, MD Anderson Cancer Center, Houston, TX, USA
| | - R Lotan
- Department of Thoracic/Head and Neck Medical Oncology, University of Texas, MD Anderson Cancer Center, Houston, TX, USA and
- Correspondence: Dr R Lotan, Department of Thoracic/Head and Neck Medical Oncology-Unit 432, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA. E-mail:
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Lee JB, Kim JS, Choe C, Seong GJ, Kim EK. Comparison of two procedures: photorefractive keratectomy versus laser in situ keratomileusis for low to moderate myopia. Jpn J Ophthalmol 2001; 45:487-91. [PMID: 11583670 DOI: 10.1016/s0021-5155(01)00406-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
PURPOSE A prospective study was conducted to compare the effectiveness, safety, and stability of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for correction of low to moderate myopia. METHODS Forty-five patients with a manifest refraction (PRK, -4.54 +/- 0.80; LASIK, -4.82 +/- 1.10) from -1.50 to -6.00 diopters (D) were treated and followed-up for 6 months. In each case, 1 eye received PRK and the other LASIK. The first eye treated, and the surgical method used in the first eye, were randomized. Uncorrected and corrected visual acuity, manifest refraction, corneal haze, and topographic analysis of ablation decentration were examined. RESULTS The uncorrected visual acuity was 20/20 or better in 35 PRK eyes (77.8%) and 28 LASIK eyes (62.2%) at 6 months (P =.107). At 6 months, 28 eyes (62.2%) that received PRK showed a spherical equivalent of within +/-0.5 D as compared with 24 eyes (53.4%) that received LASIK (P =.393). The amount of ablation decentration was 0.37 +/- 0.25 mm in PRK eyes and 0.49 +/- 0.38 mm in LASIK eyes at 3 months (P =.36). CONCLUSIONS In our study, PRK and LASIK were found to be similarly effective and predictive of correction in low to moderate myopia. PRK has the advantage of less ablation decentration and is safer than LASIK, so we recommend PRK for eyes with low to moderate myopia.
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Affiliation(s)
- J B Lee
- Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
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Abstract
The polyamines, and especially putrescine, play an integral role in the physiological response of cells to varying extracellular osmotic conditions. Ornithine decarboxylase (ODC) synthesis and stability, as well as the activity of the polyamine transporter, had all been reported to be very sensitive to media osmolarity in different cells and tissues, yet the mechanism of this complex, co-ordinated response was not known. In this study we have determined that all these aspects of osmotic-shock response may be mediated by the common regulatory protein, ODC-antizyme. HTC cells were induced for antizyme and then exposed to media of reduced osmotic strength. Both antizyme activity and protein decreased rapidly, under these conditions, to new steady-state levels that depended upon the degree of reduction in media tonicity. This antizyme reduction was found to be due to a rapid increase in antizyme degradation, with a half-life decrease from 75 min down to 45 min occurring immediately upon exchanging media. In complementary experiments, increased media tonicity induced elevated antizyme levels and stability. The sensitivity of antizyme turnover to osmotic conditions was also observed in DH23b cells, which contain elevated levels of more stable antizyme. Interestingly, the two main antizyme proteins, AZ-1 and AZ-2 (presumably products from the first and second translational start sites), differed in their responses to these changing osmotic conditions. Just as feedback regulation of antizyme synthesis provides an effective mechanism for maintaining stable polyamine levels, these studies suggest that alteration in the rate of antizyme degradation may be the mechanism whereby cells adjust steady-state polyamine levels in response to stimulation or stress.
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Affiliation(s)
- J L Mitchell
- Department of Biological Sciences, Northern Illinois University, DeKalb 60115, USA
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