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Biomedical subjects

M Viana

Publications and source records attributed to M Viana.

29 records · Page 2Linked to original sources
PubMed1997

Polyhexamethylene biguanide (PHMB) in the treatment of experimental Fusarium keratomycosis.

PURPOSE: We wanted to determine whether topical polyhexamethylene biguanide (PHMB) 0.02% was effective in the treatment of experimental Fusarium keratomycosis in rabbits. METHODS: Fusarium solani keratomycosis was induced in the eyes of 12 New Zealand white rabbits. The rabbits were treated with PHMB 0.02% in one eye and placebo in the other eye for 6 days. The rabbits were evaluated in a masked fashion using a standardized system for clinical progression of the disease. Then the corneas were trephined and growth of F. solani in colony-forming units per milliliter (CFU/ml) determined. RESULTS: Clinical evaluation demonstrated no significant mean difference (p > 0.10) in clinical scores between treated and control eyes on day 6 (0.583 +/- 2.503). There was a significant mean CFU difference (p = 0.06) between treated eyes and control eyes (182.5 +/- 314.44). Seven of 12 eyes (58%) in the PHMB group exhibited no growth, whereas two of 12 (17%) eyes reported no growth in the control group. One of 12 eyes (8%) reported > 100 CFU in the PHMB group, whereas seven of 12 eyes (58%) reported > 100 CFU in the control group. CONCLUSIONS: PHMB 0.02% was effective in significantly reducing the fungal growth in our rabbit model of Fusarium keratomycosis. The future role of PHMB in the treatment of Fusarium keratitis needs to be further evaluated.

Administration, Topical↗
PubMed1996

Teratogenic effects of diabetes mellitus in the rat. Prevention by vitamin E.

We wanted to determine whether administration of vitamin E could reduce the production of free radicals which could play a role in the teratogenic effects of diabetes mellitus. Diabetes was induced in Wistar rats by the intravenous administration of streptozotocin. The animals were divided into six groups: one with no supplement (D) and two, supplemented during pregnancy either with oral vitamin E (150 mg/day) (D + E) or with a placebo (safflower oil) (D + O). Three other groups were kept under the same conditions, but were treated with insulin: D + I, D + I + E and D + I + O. There were three groups of matched controls: C, C + E and C + O. All animals were killed on day 11.5 of pregnancy. In C animals the percentages of reabsorptions and malformations were 1.3 and 2%, respectively, compared with 23.6, 24.3, 6.2 and 13.2%, respectively in D and D + I groups. The crown-rump length, number of somites, and protein and DNA content were higher in C animals than in the diabetic rats, independent of insulin treatment. When vitamin E was administered no changes in these parameters were observed in C and D + I animals; however, in the D mothers it reduced the rate of embryo malformations to 4.6% and increased the crown-rump length and the number of somites. However, vitamin E did not modify the protein and DNA content and the percentage of reabsorptions. In conclusion, administration of vitamin E to diabetic animals decreases the rate of embryo malformations and increases their size and maturation, supporting a role for free radicals in the teratogenic effects of diabetes.

3-Hydroxybutyric Acid↗
PubMed1996

In vitro effects of a flavonoid-rich extract on LDL oxidation.

Flavonoids are phenolic compounds of vegetable origin with antioxidant effects. The present study aimed to determine their properties as LDL antioxidants. LDL were incubated with increasing concentrations of flavonoids (0-16 micrograms/ml) and LDL oxidation was started by adding CuCl2 (2 microM) to the media. When flavonoids were present in the media, vitamin E consumption, the lag phase of conjugated diene formation, LDL electrophoretic mobility in agarose gels and the appearance of thiobarbituric acid reacting substances (TBARS) were delayed in a concentration-dependent manner. To determine whether flavonoids could terminate LDL oxidation once initiated, two sets of experiments were performed. In the first, LDL oxidation was initiated as described above. At 2 or 4 h of incubation, flavonoids were added (4 micrograms/ml) and their effect compared to samples where butylated hydroxytoluene or EDTA were added. At 5 h, in the LDL samples where flavonoids were added, the electrophoretic mobility and TBARS production were the same as those present in LDL samples incubated for the whole period in the absence of flavonoids. However, when either butylate hydroxytoluene or EDTA was added, as would be expected, the LDL oxidation process was completely arrested as shown by a reduction in the appearance of TBARS and a lower LDL electrophoretic mobility. In the second experiment, LDL oxidation was initiated as described above and at 0, 10 and 20 min, flavonoids were added (4 micrograms/ml). When vitamin E was still present in the LDL solution, the flavonoids were able to both increase the lag phase in the formation of conjugated dienes and to delay the consumption of vitamin E. The present results show that in vitro, flavonoids prevent LDL oxidation in a concentration-dependent manner, delaying the consumption of vitamin E, but they cannot terminate or delay LDL oxidation once vitamin E in LDL is consumed.

Antioxidants↗
PubMed1995

Relative effects of age and compromised vision on driving performance.

The aim of this study was to determine the relative effects of age and compromised vision on driving-related skills and on-road accidents. A total of 107 subjects were tested. They represented four groups that varied in age and visual status, as follows: (1) a younger, normally sighted group; (2) an older, normally sighted group; (3) a younger, visually compromised group; and (4) an older, visually compromised group. Driving performance was assessed by self-reported and state-recorded accident frequency and by an evaluation of performance on an interactive driving simulator. The older groups had poorer driving-related skills, as measured with our interactive driving simulator, than had the younger groups, but they did not have significantly higher on-road accident rates than the younger groups. The older subjects and those with compromised vision had reduced risk-taking scores, as measured with a self-report questionnaire. In addition, all older drivers had increased eye movements and had slower simulator driving speeds, which suggests that behavioral compensation is made for visuocognitive/motor deficits. Regression analyses showed that compromised vision and visual field loss predicted real-world accidents in our study population.

Accidents, Traffic↗
PubMed1993

Evaluation of driving performance in patients with juvenile macular dystrophies.

The driving performance of 20 subjects with central vision impairment due to either Stargardt disease or cone-rod dystrophy (visual acuity, 20/40 to 20/70) was compared with that of 29 control subjects with normal vision who had similar driving histories. Driving performance was defined by accident involvement based on self-report and state records and by an evaluation of performance on an interactive driving simulator. The proportion of individuals involved in accidents in the central vision loss group was comparable to that of the control group. For 13 of the 20 subjects with central vision loss who did not restrict their driving to daylight hours, there was a greater likelihood of involvement in nighttime accidents than in the control group. Visual function measures and simulator indexes did not predict accident involvement for the central visual loss group, although these subjects showed longer braking response times and a greater number of lane boundary crossings than the control group. These findings are in contrast to our previously published report of subjects with retinitis pigmentosa, who were more likely to have been involved in both daytime and nighttime accidents than a control group and for whom visual field extent was significantly related to accident involvement.

Accidents, Traffic↗
PubMed1993

Trial 2 in the elevated plus-maze: a different form of fear?

A factor analysis of the scores from rats given two trials in the elevated plus-maze showed that four independent factors emerged. Measures of anxiolytic activity on trial 1 (number of open arm entries and time spent on open arms) loaded on factor 1, measures of anxiolytic activity on trial 2 loaded on factor 2, the measure of general activity (number of closed arm entries) on both trials loaded on factor 3, and a measure of decision time (time spent in central square) for both trials loaded on factor 4. The independence of trials 1 and 2 anxiety measures raises the possibility that the state of anxiety/fear on the second trial in the plus-maze is qualitatively different from that on trial 1. This difference is reflected in the loss of anxiolytic action of diazepam (2 mg/kg) on trial 2. However, this occurs only when the trials are short (5 min); when they are longer (10 min) diazepam retains anxiolytic efficacy. It is concluded that during a brief (5 min) trial in the plus-maze rats acquire a specific phobic anxiety, which is relatively resistant to benzodiazepines. With a longer exposure to the plus-maze this form of fear extinguishes.

Animals↗
PubMed1993

Visual acuity in patients with best vitelliform macular dystrophy.

PURPOSE: Forty-seven patients with Best vitelliform macular dystrophy were evaluated in a cross-sectional fashion for visual acuity loss with age. METHODS: The authors assessed only patients who had at least one eye with a recognizable phenotype of Best vitelliform macular dystrophy. Patients with absent foveal changes or with only minimal foveal pigment mottling and hypopigmentation in each eye were excluded. RESULTS: A significant difference was noted between the visual acuities of the two eyes of the patients (2 lines or greater in the majority [64%] of patients). Nevertheless, for both eyes a significant correlation was noted between patient age and visual acuity, with older patients tending to have worse visual acuities. In the eyes with the best visual acuity, the majority of patients younger than 40 years of age (76%) had a visual acuity of 20/40 or better. In patients older than 30 years of age, a substantial percentage (74%) had a visual acuity of 20/100 or worse in at least one eye. CONCLUSION: The authors' findings indicate that although patients with Best vitelliform macular dystrophy who show characteristic macular lesions may retain good visual acuity in at least one eye, an appreciable number can lose substantial visual acuity, at least monocularly. In this population, no patient older than 50 years of age fulfilled the visual acuity criterion of 20/40 in at least one eye, the requirement in most states for an unrestricted driver's license, and only 20% of patients older than 40 years of age fulfilled this visual acuity criterion.

Adolescent↗
PubMed1991

Fixation characteristics in macular disease. Relationship between saccadic frequency, sequencing, and reading rate.

The relationship between reading rate and saccadic frequency in patients with macular degeneration was studied to determine if this simple measure of eye movements would be helpful in explaining the reduction in reading rates. Nineteen subjects and five controls were tested for visual acuity, reading rate, and saccadic frequency for intended stationary, simple left-to-right, and sequencing step tasks. Eye movements were recorded using an electro-oculography technique. Absolute eye position was not known. The results demonstrated that, using a 2 degree threshold for a stationary target, patients refixated a mean of 42.7 times per min, and controls refixated 0.00 times per min. For a two-letter left-to-right task, patients averaged 3.57 times more saccades than an ideal response, and controls had 1.14 times more saccades than ideal (P less than 0.01). For a five-letter left-to-right sequencing task, patients refixated a mean of 2.10 times more than ideal, and controls refixated 1.15 times more than ideal (P less than 0.05). Regression analysis demonstrated that sequencing task scores of saccadic frequency and visual acuity were the best predictors of reading rate (r2 = 0.705). These results indicate that higher saccadic frequencies are associated with lower reading rates and that there appears to be a relationship between the sequencing of visual information and reading rate.

Aged↗
PubMedDate not supplied

Stereoacuity testing in patients with retinal and optic nerve disorders.

A study comparing the relative sensitivity for detecting abnormal stereoacuity in patients with retinal or optic nerve disease on clinically used stereoacuity tests is not available. It is also not apparent from the ophthalmic literature if optic nerve or retinal diseases are likely to have a greater impact on stereoacuity performance. We were also interested in determining a level of visual acuity loss that would likely results in an impairment of stereoacuity on these clinical tests. Forty-two patients with various retinal and optic nerve disorders and eighteen normal subjects were evaluated for stereoacuity using three tests: Titmus Stereoacuity Test (TST), Randot Stereoacuity Test (RST), and TNO Stereoacuity Test (TNO). The performance on these three stereoacuity tests was compared with the normal subjects. Additionally, TST scores from our patients were compared to predicted TST scores derived from a previously published nomogram. For patients with retinal and optic nerve disease, an abnormal score on one clinical test of stereoacuity was likely to predict an abnormality on the other tests. Performance on the TST relative to the predicted value derived from a nomogram was not significantly different for patients with retinal vs. optic nerve disease. With some exceptions, patients with visual acuities of 20/30 or worse in at least one eye were likely to show abnormal stereoacuity.

Adolescent↗
PubMedDate not supplied

Effect of acipimox on plasma lipids and glucose/insulin in pregnant rats.

To determine how a reduction in maternal hypertriglyceridemia during late pregnancy may affect glucose/insulin relationships, pregnant and virgin rats were orally treated with acipimox, a potent antilipolytic agent. In 20-day pregnant rats receiving 80 mg of acipimox, plasma triglycerides (TG), free fatty acids (FFA), and glycerol decreased more than in virgin rats shortly after the drug (up to 7 hours), when compared with animals treated with distilled water, whereas plasma glucose level was unaffected by the treatment in either group of rats. When acipimox was given every 12 hours from day 17 to day 20 of pregnancy, plasma TG, FFA, and glycerol levels progressively increased, whereas they either decreased or did not change in virgin rats receiving the same treatment, with no effect in plasma glucose levels in either group. Fetal body weight was lower than in controls in 20-day pregnant rats that received acipimox for 3 days. On day 20 of pregnancy, 3 hours after receiving acipimox or distilled water, rats received a 2 g glucose/kg oral load and it was found that the change in plasma glucose was similar in both groups, whereas the increase in plasma insulin was greater in pregnant rats treated with acipimox. However, no difference was found in either variable after the oral glucose load in virgin rats receiving acipimox or distilled water. No differences in plasma glucose levels were found after intravenous (i.v.) administration of insulin in pregnant rats treated or not treated with acipimox. In conclusion, present results show that administration of acipimox during the last days of gestation inhibited lipolysis and decreased fetal weight. Over a short period of time, in pregnant rats, reductions of plasma FFA and TG after acipimox treatment improved the glucose-induced insulin release, but did not seem to have any effect in peripheral insulin resistance.

Animals↗