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Biomedical subjects

F J van Kuijk

Publications and source records attributed to F J van Kuijk.

At least 19 recordsLinked to original sources
PubMed2001

The color difference in orbital fat.

OBJECTIVE: To identify and quantify carotenoids found in white and yellow orbital fat. METHODS: Specimens of nasal (white) and preaponeurotic (yellow) orbital fat were obtained from patients during upper eyelid blepharoplasty. Carotenoids and retinoids were extracted and subjected to spectral and high-performance liquid chromatography analyses. RESULTS: The chromophore content of extracts from unsaponified fat, as measured by absorbance at 425 nm per gram of fat, was 2- to 4-fold higher in preaponeurotic fat than in nasal fat. High-performance liquid chromatography analysis from enzymatically digested fat revealed large amounts of lutein, beta-carotene, and retinol and small amounts of other unidentified carotenoids. The amount of beta-carotene and lutein in preaponeurotic fat was approximately 4-fold higher than in nasal fat. CONCLUSIONS: The higher carotenoid content of preaponeurotic fat might cause it to be more yellow than other orbital fat, and lutein and beta-carotene might be selectively absorbed from plasma by preaponeurotic fat. CLINICAL RELEVANCE: The results provide baseline information for studies of the physiological features of orbital fat in normal and diseased conditions.

Adipose Tissue↗
PubMed2001

[Macular pigment and age-related macular degeneration].

The present concepts of the pathogenesis of AMD include cumulative light damage by oxidative processes in the macular photoreceptors as environmental co-factor for the development of AMD. The direct causative connection of this hypothesis has still to be established but wide circumstantial evidence from epidemiological and basic scientific investigations are strongly supportive. Macular pigment consisting of lutein and zeaxanthin through there ability to filter light and by direct antioxidative properties, has been proposed as the most effective protective factor in the central retina ("natural sun glasses") and could be important to reduce light induced oxidative retinal damage. The observation, that with age and especially in eyes with AMD lower concentrations of macular pigment could be found, can be interpreted that low macular pigment concentrations may be associated with higher risk for AMD. Through dietary intake and eventually with supplementation the concentration of macular pigment can be increased, and analysis of the correlation between macular pigment and AMD may be important to characterise a possible influenceable AMD risk factor.

Aged↗
PubMed2000

Effect of NADPH on formation and decay of human metarhodopsin III at physiological temperatures.

Difference absorption spectra were recorded during the formation and decay of metarhodopsin III after sonicated membrane suspensions of rhodopsin were bleached at 37 degrees C. The data were analyzed using SVD, spectral decomposition and global exponential fitting. By comparison of the results in the presence or absence of 70 microM NADPH and those for bovine or human rhodopsin, a single comprehensive scheme was fit to all the data, including reduction of retinal to retinol by the intrinsic retinol dehydrogenase. On the time scale studied the mechanism involves two 382 nm absorbing species and two 468 nm, absorbing species, supporting the notion that human metarhodopsin III is not a homogeneous species. The results confirm that metarhodopsin III forms and persists sufficiently long in the human retina under physiological conditions that it could undergo secondary photoisomerization.

Animals↗
PubMed2000

Carotenoid oxidative degradation products inhibit Na+-K+-ATPase.

This study investigates the biological significance of carotenoid oxidation products using inhibition of Na+-K+-ATPase activity as an index. Beta-carotene was completely oxidized by hypochlorous acid and the oxidation products were analyzed by capillary gas-liquid chromatography and high performance liquid chromatography. The Na+-K+-ATPase activity was assayed in the presence of these oxidized carotenoids and was rapidly and potently inhibited. This was demonstrated for a mixture of beta-carotene oxidative breakdown products, beta-Apo-10'-carotenal and retinal. Most of the beta-carotene oxidation products were identified as aldehydic. The concentration of the oxidized carotenoid mixture that inhibited Na+-K+-ATPase activity by 50% (IC50) was equivalent to 10 microM non-degraded beta-carotene, whereas the IC50 for 4-hydroxy-2-nonenal, a major lipid peroxidation product, was 120 microM. Carotenoid oxidation products are more potent inhibitors of Na+-K+-ATPase than 4-hydroxy-2-nonenal. Enzyme activity was only partially restored with hydroxylamine and/or beta-mercaptoethanol. Thus, in vitro binding of carotenoid oxidation products results in strong enzyme inhibition. These data indicate the potential toxicity of oxidative carotenoid metabolites and their activity on key enzyme regulators and signal modulators.

Aldehydes↗
PubMed1999

Lycopene and beta-carotene decompose more rapidly than lutein and zeaxanthin upon exposure to various pro-oxidants in vitro.

Major carotenoids of human plasma and tissues were exposed to radical-initiated autoxidation conditions. The consumption of lutein and zeaxanthin, the only carotenoids in the retina, and lycopene and beta-carotene, the most effective quenchers of singlet oxygen in plasma, were compared. Under all conditions of free radical-initiated autoxidation of carotenoids which were investigated, the breakdown of lycopene and beta-carotene was much faster than that of lutein and zeaxanthin. Under the influence of UV light in presence of Rose Bengal, by far the highest breakdown rate was found for beta-carotene, followed by lycopene. Bleaching of carotenoid mixtures mediated by NaOCl, addition of azo-bis-isobutyronitril (AIBN), and the photoirradiation of carotenoid mixtures by natural sunlight lead to the following sequence of breakdown rates: lycopene > beta-carotene > zeaxanthin > lutein. The slow degradation of the xanthophylls zeaxanthin and lutein may be suggested to explain the majority of zeaxanthin and lutein in the retina of man and other species. In correspondence to that, the rapid degradation of beta-carotene and lycopene under the influence of natural sunlight and UV light is postulated to be the reason for the almost lack of those two carotenoids in the human retina. Nevertheless, a final proof of that theory is lacking.

Animals↗
PubMed1999

Lutein and zeaxanthin are associated with photoreceptors in the human retina.

PURPOSE: Previous studies showed that lutein and zeaxanthin, the major human retinal carotenoids, are concentrated in the macula. In this study, the carotenoids in human macular and peripheral retina and the retinal pigment epithelium (RPE) were analyzed. They were also determined in the rod outer segments (ROS) before and after removal of extrinsic membrane proteins. METHODS: Carotenoids were extracted from the macular and peripheral sections of human retina and RPE with hexane in dim light and analyzed by high performance liquid chromatography (HPLC). ROS samples equivalent to the amount in a single retina were also analyzed. RESULTS: Retinal carotenoid amounts were similar to previous reports, but only low levels were detected in the RPE. Regional ratios of lutein:zeaxanthin were similar in the retina and RPE. Approximately 25% of the total retinal carotenoids were found in the ROS, indicating that a substantial portion of peripheral retinal carotenoids are present in the ROS. However, after removal of the extrinsic membrane proteins and subsequent analysis, carotenoids were not detected. CONCLUSIONS: Most of the carotenoids in the human peripheral retina are present in the ROS. These ROS carotenoids are associated with soluble or salt-dependently bound proteins.

Carotenoids↗
PubMed1998

Reduction of 4-hydroxynonenal and 4-hydroxyhexenal by retinal aldose reductase.

Aldose reductase has been purified to homogeneity from bovine retina. It has an apparent molecular weight of 32,000 daltons and shares immunological and kinetic properties with the much studied aldose reductases purified from various sources. Retinal aldose reductase displays a K(m) of approximately 40 microM with 4-hydroxynonenal and 4-hydroxyhexenal, the oxidation end products of arachidonic and docosahexanoeic acids, respectively. It therefore appears that aldose reductase may constitute a major detoxification route of these toxic aldehydes in the retina.

Aldehyde Reductase↗
PubMed1998

Immunohistochemical localization of xanthine oxidase in human retina.

Xanthine oxidase has been established as an important source of oxygen free radicals in ischemia-reperfusion injury. It has been localized in many different tissues such as heart and intestine, but it has not yet been localized in the eye. Xanthine oxidase was detected using immunohistochemistry on paraformaldehyde/glutaraldehyde fixed cryosections. Antibodies used included rabbit antibovine xanthine oxidase antibody and rabbit antihuman xanthine oxidase antibody. Xanthine oxidase was detected in the capillary endothelium cells of blood vessels in the retina of bovine and post mortem human eyes. Whole mount preparation of human retinas showed xanthine oxidase present throughout the small capillary network. Furthermore, whole mounts showed that xanthine oxidase was present in cones. This was confirmed by using mouse anticalbindin antibody for co-labelling. It is possible that xanthine oxidase can be a source of oxidative damage in the retina following ischemia-reperfusion injury.

Animals↗
PubMed1998

Whole blood selenium in exudative age-related maculopathy.

PURPOSE: We tested whether exudative ARM was associated with low whole blood levels of selenium (Se). METHODS: Blood samples, drawn from 10 exudative ARM patients (61.2-76.1 yr) and 9 healthy-eyed (66.9-75.1 yr) subjects, were analyzed by atomic absorption spectroscopy. RESULTS: Selenium concentration was significantly lower in the ARM group (186.6 microg/l) than in controls (207.0 microg/l). Because many ARM patients took Se supplements, we tested the effect on blood Se of 80 microg per day of sodium selenate. We found no enduring effects of supplementation for healthy-eyed, younger adults. CONCLUSIONS: Significant group differences in this preliminary study indicate a larger-scale study of blood Se concentration in exudative ARM patients is warranted. If the effect of Se supplementation on the progression of exudative ARM is tested in future trials, it will be important to use organic Se, to identify the components of blood affected, and to observe protocol for at least six months.

Adult↗
PubMed1998

Does long-term treatment of renal anaemia with recombinant erythropoietin influence oxidative stress in haemodialysed patients?

BACKGROUND: Patients with end-stage renal failure undergoing haemodialysis (HD) are exposed to oxidative stress. Increased levels of malondialdehyde (MDA) were demonstrated in plasma of uraemic patients, indicating accelerated lipid peroxidation (LPO) as a consequence of multiple pathogenetic factors. The aim of our investigation was to examine the role of renal anaemia in oxidative stress in HD patients. METHODS: MDA and 4-hydroxynonenal (HNE) were measured in three groups of patients undergoing HD: group I comprised eight patients with a blood haemoglobin (Hb) < 10 g/dl (mean Hb = 8.1+/-1.3 g/dl), and group II were eight patients with a Hb > 10 g/dl (mean Hb=12.4+/-1.9g/dl); none of these 16 patients had been treated with human recombinant erythropoietin (rHuEpo). Group III comprised 27 patients with a mean Hb of 10.5+/-1.6 g/dl after long-term rHuEpo treatment. RESULTS: Mean plasma concentrations of both MDA and HNE were significantly higher (P<0.0001) in all 43 HD patients than in 20 healthy controls (MDA 2.85+/-0.25 vs 0.37+/-0.03 microM, HNE 0.32+/-0.03 vs 0.10+/-0.01 microM). Comparing the three groups, it was shown that HD patients with a Hb <10 g/dl had significantly higher plasma levels of LPO products (MDA 3.81+/-0.86 microM, HNE 0.45+/-0.07 microM) than HD patients with a Hb >10g/dl (MDA 2.77+/-0.58 UM, HNE 0.25+/-0.05 microM), and than HD patients treated with rHuEpo (MDA 2.50+/-0.12 microM, HNE 0.29+/-0.03 microM). Furthermore, an inverse correlation between plasma concentration of LPO products and haemoglobin levels was seen (r=0.62, P<0.0001). CONCLUSION: Radical generation in HD patients might be caused in part by renal anemia itself. Treatment with rHuEpo may decrease radical generation effectively in HD patients due to the increase in the number of red blood cells and blood haemoglobin concentration.

Adult↗
PubMed1998

Fruits and vegetables that are sources for lutein and zeaxanthin: the macular pigment in human eyes.

BACKGROUND: It has been suggested that eating green leafy vegetables, which are rich in lutein and zeaxanthin, may decrease the risk for age related macular degeneration. The goal of this study was to analyse various fruits and vegetables to establish which ones contain lutein and/or zeaxanthin and can serve as possible dietary supplements for these carotenoids. METHODS: Homogenates of 33 fruits and vegetables, two fruit juices, and egg yolk were used for extraction of the carotenoids with hexane. Measurement of the different carotenoids and their isomers was carried out by high performance liquid chromatography using a single column with an isocratic run, and a diode array detector. RESULTS: Egg yolk and maize (corn) contained the highest mole percentage (% of total) of lutein and zeaxanthin (more than 85% of the total carotenoids). Maize was the vegetable with the highest quantity of lutein (60% of total) and orange pepper was the vegetable with the highest amount of zeaxanthin (37% of total). Substantial amounts of lutein and zeaxanthin (30-50%) were also present in kiwi fruit, grapes, spinach, orange juice, zucchini (or vegetable marrow), and different kinds of squash. The results show that there are fruits and vegetables of various colours with a relatively high content of lutein and zeaxanthin. CONCLUSIONS: Most of the dark green leafy vegetables, previously recommended for a higher intake of lutein and zeaxanthin, have 15-47% of lutein, but a very low content (0-3%) of zeaxanthin. Our study shows that fruits and vegetables of various colours can be consumed to increase dietary intake of lutein and zeaxanthin.

Carotenoids↗
PubMed1997

Simultaneous detection of carotenoids and vitamin E in human plasma.

A simplified method for analysis of the antioxidants carotenoids and vitamin E in human plasma is presented. The method is based on high-performance liquid chromatography with a single column, a flow-rate gradient, and detection at 450 and 290 nm with a diode array detector. It gives good separation of the vitamin E isomers and the major carotenoids in plasma, with a 25 min analysis time. It was found that hydrolysis of triglycerides and cholesterol esters is required to obtain good recovery of non-polar carotenoids such as lycopene, alpha-carotene and beta-carotene. Two methods were used for hydrolysis of the non-polar lipids, saponification with ethanolic KOH and digestion with an enzyme mixture of lipase and cholesterol esterase. It was found that the enzymatic digestion gave the best recoveries, better than 94% for all of the antioxidants, and preserved several carotenoids. A plasma pool is used for day to day calibration of the method, which eliminates the need for stock solutions of carotenoids that are stable for only a month due to oxidative breakdown and their tendency to crystallize when stored at -20 degrees C in organic solvents.

Antioxidants↗
PubMed1997

4-Hydroxynonenal interaction with rhodopsin.

4-Hydroxynonenal binds easily to rhodopsin and this was accompanied by a decrease in measurable sulfhydryl groups. Analysis of tryptic digests of the rhodopsin-HNE adduct by high performance liquid chromatography revealed that several peptides present in the digests of rhodopsin disappeared, whereas HNE modified peptides not originally present were found in digests of the rhodopsin-HNE adduct. Matrix assisted laser desorption time of flight mass spectrometry showed that up to ten molecules of HNE bound to rhodopsin.

Aldehydes↗
PubMed1997

Metarhodopsin III formation and decay kinetics: comparison of bovine and human rhodopsin.

Absorbance spectra were recorded at various times after photolysis of hypotonically washed membrane suspensions of human and bovine rhodopsin (pH 7 or 8, T = 20 or 37 degrees C). Global data analysis showed that at 20 degrees C, metarhodopsin III formation was the only process occurring from 1 to 30 min following photolysis. At pH 8, a significant amount of human metarhodopsin I was present before metarhodopsin III formed. At 37 degrees C, two decay processes were seen, formation of metarhodopsin III (lifetime 113 +/- 3 sec bovine, 93 +/- 2 sec human) and formation of a species with the properties of n-retinylidine opsin (lifetime 900 +/- 150 sec bovine, 2000 +/- 350 sec human). A larger fraction of human rhodopsin (approximately 50%) is converted to metarhodopsin III than is the case for bovine rhodopsin (approximately 35%).

Animals↗
PubMed1997

Absorbance changes of carotenoids in different solvents.

Carotenoids are typically measured in tissues with the high performance liquid chromatography (HPLC) and quantitation is usually done by calibrating with stock solutions in solvents. Four carotenoids including lutein, zeaxanthin, lycopene and beta-carotene were dissolved in hexane and methanol respectively, and their absorbance characteristics were compared. Lutein shows absorbance spectra that are almost independent of solvents at various concentrations. Spectra of zeaxanthin, lycopene and beta-carotene were found to be more solvent-dependent. The absorbance of zeaxanthin at lambda max is about approximately 2 times larger in methanol than in hexane at the higher concentrations, and increased non-linearly with increasing concentration in hexane. The absorbance of lycopene at lambda max in hexane is approximately 4 fold larger than in methanol, but the absorbance of the methanol sample can be recovered by re-extracting this sample in hexane. The absorbance of beta-carotene in hexane is larger than in methanol, and increased linearly with increasing concentration. But beta-carotene showed a non-linear concentration effect in methanol. There are very small variations in lambda max for all four carotenoids between hexane and methanol, due to differences in molar extinction coefficients. The non-linear concentration effects for these carotenoids are probably due to differences in solubility leading to the formation of microcrystals. Thus, care should be taken with quantitation of tissue carotenoid values, when they depend on measurement of concentrations in stock solutions.

Carotenoids↗
PubMed1996

Elimination of n-butylated hydroxytoluene methylation during fatty acid analysis by gas chromatography.

An improved method for fatty acids analysis with optimum recovery of highly polyunsaturated fatty acids methyl esters in biological systems is presented. The method is based on transesterification of phospholipid and triacylglycerols to fatty acid methyl esters using a commercially available reagent, Methyl-Prep II. Without proper precautions, as much as 50% of n-butylated hydroxytoluene (BHT) added to prevent oxidation of polyunsaturated fatty acids, could be methylated during the transesterification step. Methylated BHT elutes close to 14:0 (myristic acid) and no longer functions as an antioxidant, but the modified conditions virtually eliminate the methylation of BHT. Sample extraction and methylation was completed in 30 min at room temperature. A chelator (diethylenetriamine-pentaacetic acid; DTPA) is also added to prevent peroxidation of metal catalyzed free radical chain reactions. The standard deviations of the major fatty acids from multiple human plasma samples prepared on different days were less than 5%. The recovery of arachidonic acid, 20:4, from plasma was improved using the new method, and the recovery for docosahexaenoic acid, 22:6, spiked to human plasma was found to be 99%.

Butylated Hydroxytoluene↗
PubMed1996

4-hydroxynonenal inhibits Na(+)-K(+)-ATPase.

4-Hydroxynonenal binds rapidly to Na(+)-K(+)-ATPase, and this was accompanied by a decrease in measurable sulfhydryl groups and a loss of enzyme activity. The I50 value for Na(+)-K(+)-ATPase inhibition by 4-hydroxynonenal was found to be 120 microM. Although the sulfhydryl groups could be completely restored with beta-mercaptoethanol during the reaction of the Na(+)-K(+)-ATPase-HNE-adduct, the Na(+)-K(+)-ATPase activity was only partially restored by this reducing agent. A combination of hydroxylamine and beta-mercaptoethanol yielded the greatest recovery of enzyme activity, 85% of original. Thus, 4-hydroxynonenal binding to Na(+)-K(+)-ATPase led to an irreversible decrease of enzyme activity under the conditions employed. It is hypothesized that 4-hydroxynonenal reacts with sulfhydryls at sites on the enzyme that are inaccessible by beta-mercaptoethanol. Furthermore, evidence was obtained that 4-hydroxynonenal reacts with other amino acids such as lysine to form adducts that also interfere with protein function.

Aldehydes↗