Sunlight exposure and cataract.
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Cataract↗
Biomedical subjects
J Dillon
Publications and source records attributed to J Dillon.
The optical properties of the anterior segment of the eye: implications for cortical cataract.
Epidemiological studies have correlated cortical cataract with exposure to light and have suggested that this is due primarily to relatively short wavelengths of ultraviolet radiation (UV-B). In addition, some cellular and animal models also implicate UV-B. In order to evaluate the likely role of different wavelengths of light in the etiology of cortical cataracts, the optical characteristics of several animal models were ascertained and compared to the primate. This study shows that the mouse model absorbs UV-B almost exclusively whereas other animal models such as the rabbit and the guinea pig also contain chromophores that absorb UV-A. The absorptive characteristics of the human lens varies drastically with age. The young lens absorbs primarily UV-A, whereas with age, there are increases in absorptions at 320 nm and out to wavelengths as long as 550 nm. By sectioning human lenses it was found that these changes in absorption properties increased toward the central and the nuclear regions. These absorptive characteristics were then compared to the amount of light reaching the surface of the lens. It was found that UV-B is a minor component of total energy reaching the surface of the human lens and old human lens proteins absorb 2 orders of magnitude more UV-A and visible light than UV-B. It is concluded that it is premature to exclude UV-A or even visible light in the etiology of human cortical cataracts.
Aged↗
The role of fluoxetine in the treatment of premenstrual dysphoric disorder.
Many women experience psychological and physical symptoms associated with the menstrual cycle, commonly referred to as premenstrual syndrome (PMS). For the 3% to 5% of women who meet Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for premenstrual dysphoric disorder (PMDD), symptoms are severe and impair social and occupational functioning. Although the etiology of PMDD is unknown, symptoms of dysphoria, including depression and anxiety, predominate and indicate a link to serotonergic neurotransmission. Pharmacotherapy trials have shown greater efficacy with serotonergic versus nonserotonergic compounds. We reviewed the published literature and found 7 controlled and 4 open-label clinical trials of fluoxetine, a selective serotonin reuptake inhibitor, in the treatment of PMDD. These trials demonstrate that PMDD symptoms decreased during treatment with fluoxetine. Preliminary findings suggest that intermittent luteal-phase fluoxetine dosing may also be a suitable treatment strategy for selected patients with PMDD. At 20 mg/d, adverse events were usually transient, rarely caused discontinuation, and were consistent with fluoxetine's known safety profile. Fluoxetine 20 mg/d is an effective and well-tolerated treatment for women with PMDD, a severe variant of PMS.
Antidepressive Agents, Second-Generation↗
Oxidation of biological electron donors and antioxidants by a reactive lactoperoxidase metabolite from nitrite (NO2-): an EPR and spin trapping study.
We report that a lactoperoxidase (LPO) metabolite derived from nitrite (NO2-) catalyses one-electron oxidation of biological electron donors and antioxidants such as NADH, NADPH, cysteine, glutathione, ascorbate, and Trolox C. The radical products of the reaction have been detected and identified using either direct EPR or EPR combined with spin trapping. While LPO/H2O2 alone generated only minute amounts of radicals from these compounds, the yield of radicals increased sharply when nitrite was also present. In aerated buffer (pH 7) the nitrite-dependent oxidation of NAD(P)H by LPO/H2O2 produced superoxide radical, O2*-, which was detected as a DMPO/*O2H adduct. We propose that in the LPO/H2O2/NO2-/biological electron donor systems the nitrite functions as a catalyst because of its preferential oxidation by LPO to a strongly oxidizing metabolite, most likely a nitrogen dioxide radical *NO2, which then reacts with the biological substrates more efficiently than does LPO/H2O2 alone. Because both nitrite and peroxidase enzymes are ubiquitous our observations point at a possible mechanism through which nitrite might exert its biological and cytotoxic action in vivo, and identify some of the physiological targets which might be affected by the peroxidase/H2O2/nitrite systems.
Cyclic N-Oxides↗
The photochemical attachment of the O-glucoside of 3-hydroxykynurenine to alpha-crystallin: a model for lenticular aging.
The young human lens contains a small metabolite from tryptophan called the O-glucoside of 3-hydroxykynurenine (3-HKG). Its function is to absorb most radiation between 295 and 400 nm, preventing it from reaching the retina. With age the concentration of this component decreases while the lens crystallins acquire covalently attached chromophores. This study investigates the photochemical attachment of 3-HKG to lens alpha-crystallin. Initial studies showed that alpha-crystallin photolyzed in the presence of 3-HKG developed a fluorescence (emission, 440 nm) and UV-visible spectrum similar to that found in aged human lens proteins. Extensive studies were then performed on the tryptic HPLC maps as monitored by photodiode array and fluorescent detection. Numerous photoproducts with either blue (emission, > 400 nm) or green (emission, > 500 nm) fluorescence were formed in addition to nonfluorescent compounds with absorption maxima above 300 nm. Comparisons were made between these model photoproducts and peptide maps from alpha-crystallin isolated from old human lenses. In terms of retention time and UV-visible spectra at least two of the peptides that appear in the model system are also present in the human samples. It is concluded that one of the aging processes in the human lens is the photochemically induced attachment of 3-HKG to lens proteins.
Aging↗
Electron paramagnetic resonance and spin trapping investigations of the photoreactivity of human lens proteins.
Oxidation of cysteine, glutathione and ascorbate by photoexcited proteins from normal and cataractous lenses was investigated using electron paramagnetic resonance in combination with spin trapping. We report that illumination of these proteins in pH 7 buffer with light > 300 nm in the presence of thiols (RSH) and a spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), afforded DMPO/S-cysteine and DMPO/SG adducts, suggesting the formation of the corresponding thiyl radicals. In a nonbuffered aqueous solution, illumination of the proteins and glutathione also produced superoxide detected as a DMPO/O2H adduct. Irradiation of these proteins in the presence of ascorbate generated ascorbate radical. We conclude that chromophores present in the natural normal and cataractous lenses are capable of initiating photooxidative processes involving endogenous thiols and ascorbic acid. This observation may be pertinent to UV-induced development of cataract.
Crystallins↗
Isolation and one-step preparation of A2E and iso-A2E, fluorophores from human retinal pigment epithelium.
Age-related macular degeneration, a major cause of blindness for which no satisfactory treatments exist, leads to a gradual decrease in central high acuity vision. The accumulation of fluorescent materials, called lipofuscin, in retinal pigment epithelial cells of the aging retina is most pronounced in the macula. One of the fluorophores of retinal pigment epithelial lipofuscin has been characterized as A2E, a pyridinium bis-retinoid, which is derived from two molecules of vitamin A aldehyde and one molecule of ethanolamine. An investigation aimed at optimizing the in vitro synthesis of A2E has resulted in the one-step biomimetic preparation of this pigment in 49% yield, readily producing more than 50 mg in one step. These results have allowed for the optimization of HPLC conditions so that nanogram quantities of A2E can be detected from extracts of tissue samples. By using 5% of the extract from individual aged human eyes, this protocol has led to the quantification of A2E and the characterization of iso-A2E, a new A2E double bond isomer; all-trans-retinol and 13-cis-retinol also have been identified in these HPLC chromatograms. Exposure of either A2E or iso-A2E to light gives rise to 4:1 A2E:iso-A2E equilibrium mixtures, similar to the composition of these two pigments in eye extracts. A2E and iso-A2E may exhibit surfactant properties arising from their unique wedge-shaped structures.
Humans↗
Identification of tryptophan oxidation products in bovine alpha-crystallin.
Oxidation is known to affect the structure, activity, and rate of degradation of proteins, and is believed to contribute to a variety of pathological conditions. Metal-catalyzed oxidation (MCO) is a primary oxidizing system in many cell types. In this study, the oxidative effects of a MCO system (the Fenton reaction) on the structure of the tryptophan residues of alpha-crystallin were determined. Tandem mass spectrometry (MS/MS) was utilized to identify specific tryptophan and methionine oxidation products in the bovine alpha-crystallin sequence. After oxidative exposure, alpha-crystallin was digested with trypsin, and the resulting peptides were fractionated by reverse-phase HPLC. Structural analysis by mass spectrometry revealed that tryptophan 9 of alphaA- and tryptophan 60 of alphaB-crystallin were each converted into hydroxytryptophans (HTRP), N-formylkynurenine (NFK), and kynurenine (KYN). However, only HTRP and KYN formation were detected at residue 9 of alphaB-crystallin. Oxidation of methionine 1 of alphaA- and methionine 1 and 68 of alphaB-crystallin was also detected. The products NFK and KYN are of particular importance in the lens, as they themselves are photosensitizers that can generate reactive oxygen species (ROS) upon UV light absorption. The unambiguous identification of HTRP, NFK, and KYN in intact alpha-crystallin represents the first structural proof of the formation of these products in an intact protein, and provides a basis for detailed structural analysis of oxidized proteins generated in numerous pathological conditions.
5-Hydroxytryptophan↗
Radiolysis-induced oxidation of bovine alpha-crystallin.
Radiolysis of water by ionizing radiation results in the production of pure hydroxyl radicals. This technique, combined with analysis by tandem mass spectrometry (MS/MS), has been used to study the effect of hydroxyl radicals on the intact bovine alpha-crystallin protein. After exposure to gamma-irradiation, the oxidized alpha-crystallin was digested with trypsin and the resulting peptides were fractionated by reverse-phase HPLC. The isolated fractions were analyzed by matrix-assisted laser desorption ionization and by MS/MS to determine the locations and identities of the modifications. Structural analysis revealed that methionine 1 of alpha A- and alpha B-crystallin and methionine 68 of alpha B-crystallin were oxidized to methionine sulfoxide. Hydroxytryptophan was formed from each tryptophan residue in alpha-crystallin, although only tryptophan 9 of alpha A-crystallin was converted into N-formylkynurenine. This study has, for the first time, identified the sites of modification and the structures produced in the intact alpha-crystallin protein by exposure to hydroxyl radicals. By determining the consequences of in vitro exposure of alpha-crystallin to pure hydroxyl radicals, the in vivo contribution of this reactive oxygen species to the overall oxidative stress of the lens will be achieved from the identification of the modifications to alpha-crystallin purified from intact human lenses.
Amino Acid Sequence↗
Identification of photooxidation sites in bovine alpha-crystallin.
Because UV irradiation of proteins can produce reactive oxygen species and exposure to UV light has been implicated in cataractogenesis, the sites of photooxidation of bovine alpha-crystallin, a major lens protein with molecular chaperone activity, were identified using tandem mass spectrometry (MS/MS). Bovine alpha-crystallin was irradiated with UV light (> 293 nm) for 1, 4 and 8 h, digested with trypsin and analyzed by matrix-assisted laser desorption ionization, time-of-flight mass spectrometry (MALDI) to identify the oxidized sequences. Tryptic peptides were purified by reverse-phase HPLC and oxidized peptides were sequenced by MS/MS to determine the sites of oxidation. Tryptophan fluorescence decreased exponentially with increasing time of UV exposure and peptides containing residues 1-11 of alpha A-crystallin and 1-11, 12-22 and 57-69 of alpha B-crystallin were determined to be oxidized by shifts of 16 D or multiples of 16 Da above the mass of the unmodified peptide. The MALDI analysis revealed single oxidation of all four sequences, which increased with increasing time of UV exposure and possible double oxidation of alpha B 12-22. The specific sites of photooxidation indicate that the N-terminal regions of alpha A- and alpha B-crystallin are exposed to an aqueous environment and are in the vicinity of tryptophan residues from neighboring subunits.
Amino Acid Sequence↗
Spontaneous spinal epidural haemorrhage complicating transjugular intrahepatic portosystemic stent shunting.
A patient with chronic liver disease and portal hypertension who developed acute spinal cord compression following transjugular intrahepatic portosystemic stent shunting is described. Radiological and pathological examinations revealed an epidural haematoma.
Epidural Space↗
The nitrite/elastin reaction: implications for in vivo degenerative effects.
Nitrite ion is a by-product of nitrogen oxides (nitric oxide and nitrogen dioxide) from cigarette smoke and is used as a preservative for curing meats. Therefore, study of the reaction of nitrite with elastin in vitro was undertaken. By colorimetric assay, reactivity of nitrite with insoluble elastin at neutral pH, 37 degrees C, and physiologic concentration was confirmed. In histochemical studies on in situ human aortic elastin, nitrite-treated sections displayed marked structural disruptions. Determinations of fluorescence and absorbance on nitrite-treated soluble bovine elastin revealed marked alterations of fluorescence, and increased UV and visible absorbance. Amino acid analysis confirmed that it reacted with tyrosine. The findings indicate that non-enzymatic nitration by nitrite may have deleterious effects on elastin in vivo and may provide insights into the pathogenesis of chronic elastin degenerative processes, including aortic aneurysms, pulmonary emphysema, and premature skin wrinkling, all of which have been well known to have associations with cigarette smoking.
Amino Acids↗
Control genes for reverse-transcription-polymerase chain reaction: a comparison of beta actin and glyceraldehyde phosphate dehydrogenase.
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Actins↗
Complete map and identification of the phosphorylation site of bovine lens major intrinsic protein.
PURPOSE: To determine the complete primary structure, including posttranslational modifications, of bovine lens major intrinsic protein (MIP) using a recently developed combination of liquid chromatography and mass spectrometry. METHODS: The MIP was isolated from bovine lenses by sucrose gradient centrifugation and was cleaved with cyanogen bromide (CNBr). A high-performance liquid chromatographic system, developed for hydrophobic protein analysis, was used to separate the cleavage fragments. Matrix-assisted laser desorption ionization and electrospray tandem mass spectrometry were employed to obtain molecular weight and sequence data from bovine MIP CNBr fragments, directly or after subsequent digestion with trypsin. RESULTS: The complete sequence of bovine MIP was mapped by molecular weight measurements of CNBr fragments, confirming the reported DNA sequence. The C-terminal peptide (177 to 263) was fully sequenced and the major site of phosphorylation was determined to be at serine 235 rather than at the previously reported serine 243. The level of phosphorylation in the native protein was determined to be 25%. No other posttranslational derivatizations were observed with the exception of the previously detected deamidation of asparagine 246. CONCLUSIONS: These results represent the first complete MIP sequence map at the amino acid level and identify the single major phosphorylation site at serine 235.
Amino Acid Sequence↗
Free radical reactions photosensitized by the human lens component, kynurenine: an EPR and spin trapping investigation.
We have undertaken electron paramagnetic resonance and spin trapping investigations of the photochemistry of kynurenine (KN), a natural component of the human eye and close analog of the principal chromophore in the young human lens 3-OH-kynurenine O-glucoside (3HKG). 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) was employed as a spin trap. We found that upon UV irradiation (> 300 nm) KN photoreduces oxygen to superoxide radical (in DMSO) and nitromethane (CH3NO2) to a nitromethane radical anion (CH3NO2.-) (in air-free buffers, pH 7 and 9.5). KN also sensitized photooxidation of cysteine, NADH, EDTA, azide, and ascorbate; oxygen greatly accelerated this process. Oxidation of cysteine, NADH, and EDTA was accompanied by superoxide radical formation. Cysteinyl and azidyl radicals were detected as DMPO adducts. We also observed that KN undergoes photodegradation to a product(s) whose photosensitizing capacity is greater than that of KN itself. We postulate that: (i) 3HKG may be able to photoinitiate free radical reactions in vivo, and (ii) oxygen is an important factor determining the yields of free radical processes initiated by lenticular chromophores.
Ascorbic Acid↗
Hypoxemia during diagnostic laparoscopy: a prospective study.
BACKGROUND: Laparoscopic liver biopsy can be safely performed using local anesthesia and intravenous sedation, but the frequency of hypoxemia is unknown. METHODS: We prospectively studied 68 patients undergoing diagnostic laparoscopy and liver biopsy managed by a standard protocol. RESULTS: The mean duration of laparoscopy was 27 +/- 5.53 minutes; the mean dose of diamorphine administered was 6.9 +/- 2.7 mg; diazepam, 7.05 +/- 3.52 mg. The baseline arterial oxygen saturation was 95.6% +/- 2.5% and trough was 85% +/- 5.1%. A fall of greater than 4% saturation from the baseline occurred in 64 out of 68 patients (94%). The mean decrease in saturation was 10.1% +/- 5.4%. An arterial oxygen saturation of less than 85% was seen in 32 patients (47%). There was no correlation between the fall in oxygen saturation and the dose of diamorphine or diazepam, the duration of procedure, body mass index, hemoglobin, or volume of pneumoperitoneum induced. One-way analysis of the variance failed to show a significant relationship between the degree of oxygen saturation and Child's class, etiology of liver disease, or smoking habit. CONCLUSIONS: In this study, we demonstrated that significant desaturation is common in diagnostic laparoscopy with liver biopsy and is likely due to a combination of different pharmacologic and physiologic effects. We recommend continuous monitoring of both arterial oxygen saturation and supplemental oxygen for all patients throughout laparoscopy.
Analysis of Variance↗
Effect of the UV modification of alpha-crystallin on its ability to suppress nonspecific aggregation.
Recent studies have shown that structural modifications of alpha-crystallin during lens aging decrease it's effectiveness as a molecular chaperone. Some of these posttranslational modifications have been linked to UV radiation, and this study was undertaken to investigate the effect of UV irradiation on the ability of alpha-crystallin to suppress nonspecific aggregation. The effect of 3-hydroxykynurenine (3-HK) was also investigated as a model for its glucoside (3-HKG), a main lens chromophore that has been linked to photochemical changes in the human lens. Alpha- and gamma-crystallin solutions (1 mg/mL, 1:0.125 wt/wt) were photolyzed (transmission above 295 nm) for various time intervals. Thermal denaturation of gamma-crystallin with or without alpha-crystallin was carried out at 70 degrees C and increases in light scattering were measured at 360b nm. We found that (1) irradiation of gamma-crystallin increased its susceptibility to heat-induced scattering. The addition of alpha-crystallin protects it against thermal denaturation, although its ability to do so decreases the longer gamma-crystallin is irradiated and (2) irradiation of alpha-crystallin decreases its ability to suppress nonspecific aggregating and the presence of of 3-HK during irradiation decreases it further. Our results indicate that posttranslational modifications of alpha-crystallin due to UV irradiation affect the sites and mechanisms by which it interacts with gamma-crystallin. The kinetics of gamma-crystallin unfolding during thermal denaturation were also analyzed. We found that a simple two state model applies for nonirradiated gamma-crystallin. This model does not hold when gamma-crystallin is irradiated in the presence or absence of alpha-crystallin. In these cases, two step or multistep mechanisms are more likely.
Animals↗
The photochemistry of the retinoids as studied by steady-state and pulsed methods.
The retina and retinal pigment epithelium contain a number of retinoids in a metabolic pathway that eventually forms the visual pigments. This study investigates the photochemistry of those retinoids that may contribute to light-induced damage to the retina. These include retinal (RAL), retinol (ROL), retinylpalmitate (ROLpal) and the protonated Schiff-base of retinal (RALsb). Their photochemistry was followed by both EPR spin-trapping techniques and the direct detection of singlet oxygen via its luminescence at 1270 nm. Irradiation (> 300 nm) of RAL, ROL in methanol (MeOH) or RALpal in dimethylformamide, produces free radicals from both solvents. Illumination of RALsb in MeOH containing NADH with light above 400 nm (and even above 455 nm) generates the superoxide radical. We also determined that the quantum yields for singlet oxygen sensitization by RAL, ROL or RALpal in MeOH are 0.05, 0.03 and < 0.01, respectively. These values are at least 75% less than those previously found using chemical methods. These observations indicate that a major photochemical process for these retinoids may be an electron (or hydrogen) process that will lead to radical products, and that the singlet oxygen mechanism is of relatively minor importance in protic solvents. These results may explain the action spectra obtained from light-induced damage to the retina.
Diterpenes↗