Modelling cortical cataractogenesis. 14: Reduction in lens damage in diabetic rats by a dietary regimen combining vitamins C and E and beta-carotene.
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Animals↗
Biomedical subjects
J R Trevithick
Publications and source records attributed to J R Trevithick.
Modelling cortical cataractogenesis. 15: Use of combined dietary anti-oxidants to reduce cataract risk.
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Adenosine Triphosphate↗
A new technique for enhancing luminol luminescent detection of free radicals and reactive oxygen species.
A novel technique is reported which makes use of (1) an improved method for solubilizing luminol at neutral pH along with (2) the addition of dimethyl sulfoxide to stabilize superoxide anion in the solutions in which luminescence is detected. These improvements resulted in (1) very low blank values of luminescence and (2) an approximately 6-fold increase in sensitivity of detection of peroxide and superoxide, as well as stabilizing the superoxide radical anion. The technique can also be used to evaluate the availability of antioxidants in biological homogenates and fluids.
Antioxidants↗
Modelling cortical cataractogenesis. 13. Early effects on lens ATP/ADP and glutathione in the streptozotocin rat model of the diabetic cataract.
A possible contribution to cell toxicity in the diabetic lens due to early ATP loss is not well characterized prior to the appearance of vacuoles in the lens. Changes in lens ATP levels at longer periods of hyperglycaemia (6-8 weeks) have been reported. We used [31P]NMR analysis of lens extracts at three time periods, comparing diabetic to concurrent control groups at 1, 2 and 4 weeks of hyperglycaemia. With this design, significant alterations (> 10%) in the ATP/ADP ratio can be monitored. NMR analysis revealed a decreased ATP/ADP ratio at all time periods, averaging a 38% decrease. Luminescent determination of ATP levels indicates that this decrease is mainly caused by a decrease of 25% in ATP concentration. The early loss of GSH was large and not accompanied by an appearance of GSSG, as monitored by HPLC electrochemical detection. A 1-week experiment with animals receiving daily insulin treatment was carried out to control for effects of STZ on the lens. This treatment resulted in normal lens GSH levels and a near normal [31P]NMR profile.
Adenosine Diphosphate↗
Reduction of sunburn damage to skin by topical application of vitamin E acetate following exposure to ultraviolet B radiation: effect of delaying application or of reducing concentration of vitamin E acetate applied.
The skin of the skh-1 mouse after ultraviolet B (280-320 nm, UVB) irradiation shows the pathological changes typical of sunburn damage: spongiosis (edematous spaces) around some cells, necrosis of keratinocytes, giving rise to sunburn cells, inflammatory infiltration of polymorphonuclear leucocytes, etc. In our previous study, these were accompanied by erythema, increased skin sensitivity, and edematous swelling. The topical application of tocopherol acetate (TA) immediately after the UVB exposure decreased these changes. In this paper, multiple measurements of the skin thickness were made at different locations along the magnetic resonance imaging (MRI) cross-sectional image of the skin. This permits effects to be quantified with (if desired) the contralateral half of the back serving as an internal control, either exposed (positive control) or unexposed (negative control). Topical application of TA resulted in an increase in the concentration of free tocopherol in the skin. No qualitative differences in ultrastructural appearance of the UVB-irradiated, TA-treated skin could be discerned by careful examination. In vivo high resolution video microscopy of blood flow in venules of the irradiated mouse ear revealed a large (tenfold) but not statistically significant decrease in stationary lymphocytes adhering to the venule walls. The delaying of the application of TA up to 8 hours after the termination of UVB irradiation still offered statistically significant protection as did immediate application of 5% TA in diluent Myritol 318 (Delios S, Henkel).
Administration, Topical↗
Topical application and uptake of vitamin E acetate by the skin and conversion to free vitamin E.
Radioactive tocopherol acetate was diluted with either (1) unlabelled tocopherol acetate or (2) Delios S (Henkel, a medium chain triglyceride prepared from fractionated coconut oil), a cosmetic base. These preparations were applied topically to a 2 cm diameter circle of skin. After 24 hours the percent of label which was still removable by swabbing the skin surface was 1.7% for (1) and 11.5% for (2). The central circles contained 2.86% of the label applied in 259 mg skin for (1) and 24.2% of the label applied in 226 mg skin for Delios S for (2). Surprisingly, combined samples of approximately one third of the side skin contained 0.7% of the label applied in 460 mg for (1) and 13.2% of the applied label in one third of the side skin in 523 mg for (2). The percent conversion to tocopherol in the skin central areas was 4.52% by HPLC and 4.13% by TLC for (1) and 5.97% for (2). In the side skin the percent conversion to tocopherol was 5.0% for (1) and 6.01% for (2).
Administration, Topical↗
Topical tocopherol acetate reduces post-UVB, sunburn-associated erythema, edema, and skin sensitivity in hairless mice.
Exposure of the skin of the back of skh-1 hairless mice to UVB (310 nm peak) irradiation at doses of 0.115-0.23 J/cm2 results after 24-48 h in an erythema which can be quantified using an erythema meter, providing a useful model of sunburn. Application of pure d-alpha-tocopherol acetate, a thick oil, to the skin immediately following the exposure to UVB significantly reduces the increase in erythema index, by 40-55%. At the lower dose (0.115 J/cm2), skin thickness (associated with edematous swelling of the sunburned skin) was measured by a novel non-invasive technique not previously reported for this purpose--magnetic resonance imaging (MRI). In two experiments the UVB-induced increase in skin thickness was significantly reduced at 24 hr by 29 and 54%, and at 48 hr by 26 and 61%. After 8 days the untreated irradiated mouse skin still showed a significant increase in thickness (24%) compared to the untreated unirradiated control, while the treated irradiated control was not significantly thicker than the unexposed control. Skin sensitivity was tested using a modification of the technique of esthesiometry, by observing rapid avoidance responses of the mouse to a pressure of 0.96 g/cm2 exerted by applying to the skin the tip of a nylon esthesiometer fiber extended to 60 mm in length. The untreated irradiated mice were more sensitive (p less than 0.07, Wilcoxon test) than the treated irradiated mice, and also significantly different from the untreated unirradiated control mice (p less than 0.04, Wilcoxon test), but the treated irradiated mice were not significantly differently sensitive when compared to the unirradiated controls (p less than 0.32). Taken together these data indicate that the erythema, edema, and skin sensitivity commonly associated with UVB-induced sunburn are significantly reduced by topical application of tocopherol acetate even after the exposure has occurred. This observation suggests that treatment of sunburn may be possible even after the irradiation has stopped, by a derivative of d-alpha-tocopherol which is stable to autooxidation.
Animals↗
Modelling cortical cataractogenesis. XII: Supplemental vitamin A treatment reduces gamma-crystallin leakage from lenses in diabetic rats.
Normal and streptozotocin diabetic female Wistar rats were given normal diets with the following additions: 0, or 12,500 iu/kg food vitamin A (retinyl palmitate). At the end of 6 weeks, the rats were examined for weight gain or loss, general body condition, and cataracts. At sacrifice, blood was collected for measurement of serum glucose. gamma-Crystallin levels were determined in aqueous and vitreous humours using a radioimmunoassay. One lens (the right) was homogenized in 8 M guanidinium chloride for ATP analysis. In normal rats, gamma-crystallin was detected in both aqueous and vitreous humours, with a greater concentration found in the vitreous. Diabetes caused a 4-5 fold increase in gamma-crystallin in both aqueous and vitreous humours. Diabetes also led to a significant loss of body weight, and decrease in lens ATP levels. Addition of vitamin A to the diet resulted in reduction in gamma-crystallin leakage into the aqueous and vitreous humours. Vitamin A at 12,500 iu/kg food resulted in an increase in lens ATP for the diabetic rats. Neither streptozotocin diabetes nor vitamin A in the diet appeared to affect the weight of the lenses after 6 weeks. It is suggested that childhood vitamin A deficiency leading to latent fiber cell damage may be an important factor contributing to the high incidence of cataracts in the third world.
Adenosine Triphosphate↗
A possible relationship between cataract, increased levels of the major heat shock protein HSP 70 and decreased levels of S-antigen in the retina of the RCS rat.
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Animals↗
A possible role for vitamins C and E in cataract prevention.
Biochemical evidence suggests that oxidative stress caused by accumulation of free radicals is involved in the pathogenesis of senile cataracts. If so, appropriate amounts of the antioxidant vitamins C and E might be expected to prevent or retard the process. Such activity has been observed in several in vitro and in vivo studies of experimentally-induced cataracts. A recent epidemiologic study found that cataract patients tended to have lower serum levels of vitamins C, E, or carotenoids than did control subjects. The present investigation, which compared the self-reported consumption of supplementary vitamins by 175 cataract patients with that of 175 individually matched, cataract-free subjects, revealed that the latter group used significantly more supplementary vitamins C and E (P = 0.01 and 0.004, respectively). Because the results suggested a reduction in the risk of cataracts of at least 50%, a randomized, controlled trial of vitamin supplementation in cataract prevention may be warranted.
Aged↗
Modelling cortical cataractogenesis. XI. Vitamin C reduces gamma-crystallin leakage from lenses in diabetic rats.
Normal and streptozotocin diabetic female Wistar rats were given vitamin C (VC) at 0.3% or 1.0% (w/w) in the diet: 1% dietary VC resulted, in 12-24 hr, in significant increases in serum ascorbate levels and lens ascorbate concentrations in normal rats. The increase was biphasic, with VC concentrations falling to a lower level which was still significantly elevated compared to controls in the period of 1.7-4 days for serum and 1.7-5 days for lenticular VC. At the end of 10 weeks the rats were examined for weight gain or loss, general body condition and cataracts. At the time of killing, blood was collected for measurement of serum glucose. Alpha-crystallin levels were determined in vitreous and aqueous humours using a radioimmunoassay. One lens from each rat was fixed for either scanning electron microscopy or light microscopy; the other lens was homogenized in 8 M guanidinium chloride for adenosine triphosphate analysis. In normal rats, a small amount of gamma-crystallin was found in the vitreous humour, and an even smaller amount in the aqueous humour. Diabetes caused a five-fold increase in the vitreous humour and a 2.5-fold increase in gamma-crystallin in the aqueous humour. Diabetes also led to a significant worsening in general body condition, loss of body weight, formation of cataracts, and decrease in lens adenosine triphosphate levels. Addition of VC to the diet of diabetic animals resulted in reduction in cataracts and a decrease of gamma-crystallin leakage into the aqueous and vitreous humours. VC had no effect on lens adenosine triphosphate levels.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Radiation cataractogenesis induced by neutron or gamma irradiation in the rat lens is reduced by vitamin E.
Although cataract of the eye lens is a known late effect of ionizing radiation exposure, most of the experimental work to date has concentrated on single, acute high doses or multiple, fractionated, chronic exposures. Many papers have dealt with biochemical alterations in metabolism and cellular components, with microscopic and electron microscopic lesions to the epithelial and cortical layers, and with clinical cataract formation. However, the minimum cataractogenic dose for rats has for many years been considered to be about 2 Gy for a single, acute dose of low LET radiation. Our purpose in designing this pilot study was three fold: firstly, to determine whether any physical damage could be detected after low, acute exposure to neutron radiation (10 and 100 cGy); secondly, to compare the relative effectiveness of fast (14 MeV) neutrons with gamma-rays; and thirdly, to investigate the possibility that vitamin E could protect the lenses from radiation damage. The results revealed that morphological damage was already discernible within minutes after exposure to neutrons or gamma-rays, that it became greater after 24 hours, that neutrons were more damaging than gamma-rays, and that vitamin E could effectively reduce the cataractogenic damage induced by ionizing radiation. Control, non-irradiated lenses with or without vitamin E, either in vivo or in vitro, showed no damage. Also, it appeared that in vitro irradiation was more damaging to lenses than in vivo irradiation, so this culture technique may prove to be a sensitive tool for assessing early damage caused by ionizing radiation.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Modeling cortical cataractogenesis: IX. Activity of vitamin E and esters in preventing cataracts and gamma-crystallin leakage from lenses in diabetic rats.
Normal and streptozotocin diabetic female Wistar rats were given vitamin E in the diet as the tocopherol, acetate, or succinate form (2,850 IU/kg food). At the end of 6 weeks, the rats were examined for weight gain or loss, general body condition, and cataracts. At sacrifice, blood was collected for measurement of serum glucose, and gamma-crystallin levels were measured in aqueous and vitreous humors using a radioimmunoassay. One lens was homogenized in 8 M guanidinium chloride for ATP analysis. In normal rats, gamma-crystallin was detected in both aqueous and vitreous humors, with the higher concentration in the vitreous humor. Diabetes caused a sixfold increase in gamma-crystallin in both the aqueous and vitreous humors. Diabetes also led to a significant worsening in general body condition, loss of body weight, formation of cataracts, and decrease in lens ATP levels. Addition of vitamin E and vitamin E succinate, but not vitamin E acetate, to the diet resulted in reduction of gamma-crystallin leakage into the vitreous humors and an increase in body weight. There was no improvement noted for the lens ATP levels, the general body condition, or visual cataract score. Neither streptozotocin-induced diabetes nor vitamin E in the diet appeared to affect the weight of the lenses.
Adenosine Triphosphate↗
Vitamin E intake and risk of cataracts in humans.
Experimental evidence suggests that oxidative stress due to the accumulation of free radicals plays a role in the pathogenesis of cataracts and that the process can be prevented or ameliorated by antioxidants. In addition, a recent study found that cataract patients tended to have lower serum levels of vitamins C, E, or carotenoids than did control subjects. This investigation, which compared the self-reported consumption of supplementary vitamins by 175 cataract patients with that of 175 individually matched, cataract-free subjects, revealed that the latter group used significantly more supplementary vitamins C and E (p = 0.01 and 0.004, respectively). Inasmuch as the observed reduction in risk of cataracts was at least 50%, a randomized, controlled trial of vitamin supplementation in cataract prevention seems justified.
Aged↗
51Cr release and oxidative stress in the lens.
Examination of the opaque areas of human cortical cataracts has shown that a large portion of the opacity could be attributed to the globules found there. We tested models involving globule formation as a result of oxidative damage to rat lens cells in culture and whole chick embryo lenses. When cell monolayers from a lens cell line were exposed to oxidizing conditions they developed globules on the cell surface. The cells were protected from damage by the addition of glutathione and vitamin C. Thirteen-day chick embryo lenses were also incubated in oxidizing conditions and the amount of cellular damage was assessed using a chromium-51 release assay we have developed. After 24 hr the percent 51Cr in the medium increased by an average of 20% as a result of 10 mM hydrogen peroxide treatment. The addition of the 10 mM vitamin C to the hydrogen peroxide significantly reduced the 51Cr leakage to the control level. Light microscopy of sections of the lens showed a breakdown of the equatorial fibre arrangement in the presence of H2O2, while addition of vitamin C restored the fibre organization to almost normal. The findings suggest that oxidative stress is an important step in cataractogenesis and point towards the use of water soluble antioxidants as protective agents.
Animals↗
Modelling cortical cataractogenesis. X. Evaluation of lens optical function by computer based image analysis using in vitro rat lens elevated glucose model.
As a model system rat lenses (Wistar) were isolated and cultured intact in medium M199 or M199 with 55 mM glucose. Glucose-stressed lenses developed opacities within 20 hours while control lenses remained clear. The comparative functionality of lenses was examined by two different video/computer-based imaging systems: one based on image analyses of laser light after transmission through the lens (Scanning Lens Monitor), and the other based on image analyses of the projection of white light transmitted through the lens (Kevex Image Analysis System). The combination of both methods detect changes in focal length and light scattering. On the basis of these results, these techniques can be used in animal studies for grading lenses by functional properties to complement morphologically based grading (slit-lamp) of cataracts provided by a veterinary pathologist.
Animals↗
Esthesiometric evaluations of corneal anesthesia and prolonged analgesia in rabbits.
Esthesiometry was used to evaluate prolonged corneal analgesia, induced by repeated intramuscular injections in New Zealand White rabbits of 2.3 to 4.9 kg body weight of two analgesics: meperidine (10 mg/kg) or buprenorphine (200 micrograms/kg) following short term anesthesia induced by ketamine (35 mg/kg) and xylazine (5 mg/kg). The surface pressure was calculated, using data supplied by the manufacturer, for the fiber length just sufficient to elicit the corneal reflex. Thus the corneal reflex was used as a proxy for pain. For the 12 injections of meperidine, at 2 hr intervals, the surface pressure peaked one hour after each injection of meperidine, and subsequently declined at the next hour when the injection was repeated resulting in a saw-tooth pattern of responsiveness. For the 5 injections of buprenorphine, at 5 hr intervals, the surface pressure to elicit the corneal reflex rose after a second injection to overlap the pressures generated by meperidine. The consistent analgesia continued until after 24 hours. Accordingly long-term analgesia may be conveniently measured using a quantitative technique, esthesiometry. Comparison of the two regimens suggests buprenorphine is preferred over meperidine in experiments that require sustained analgesic coverage for periods of 24 hours.
Analgesia↗
In vitro studies of microwave-induced cataract. II. Comparison of damage observed for continuous wave and pulsed microwaves.
Depth of damage caused by pulsed (PU) and continuous wave (CW) microwaves was estimated by scanning electron microscopy in rat lenses fixed immediately, after irradiation in vitro in circulating thermostatically controlled buffered saline. Pulses of 10 microseconds width and 24 kW peak power were delivered to the lens at different repetition rates in order to permit the same total energy to be delivered during 6, 20 or 60 min of irradiation at specific absorption rate (SAR) values of 0, 5.75, 11.5, 23, 69, 231 and 750 mW g-1; total energy [power (pow) x time] deposited in the lens was 0, 0.23, 0.46, 1.38, 4.6, and 15 W min g-1. Damage (granular degeneration of cells at the lens equator) was measured at the apex of penetration of the degeneration. The depth of degeneration (dep) of Pu or CW was compared either: (1) by a one-way analysis of variance (ANOVA) for the CW data alone and the 11 combinations of (pow x time); or (2) by using two alternative models to fit the data, to permit experimental distinguishment between: (a) reciprocal effects of pow x time; and (b) separate effects. Using the ANOVA analysis, the Pu mode of irradiation resulted in more damage at the same average power for every combination tested except one (23 mW g-1, 6 min). Although the separate-effects models explained more of the variation in depth of damage, the reciprocal effects model may provide an adequate fit for practical purposes and has the advantage of greater simplicity. For both models, the pulsed irradiation mode produced 4.7 times the depth of damage caused by CW irradiation. These results are discussed in relation to previous Pu-CW comparisons. It is proposed that this additional damage at the same average power is caused by thermoelastic expansion (TEE).
Animals↗