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Biomedical subjects

M Parafita

Publications and source records attributed to M Parafita.

12 recordsLinked to original sources
PubMed2004

Accuracy and precision of EyeSys and Orbscan systems on calibrated spherical test surfaces.

BACKGROUND: It is important to know how well the surface topography can be measured with current devices for corneal topographic analysis. There are several applications that need an accurate and precise method to measure corneal shape and variations, such as the effect of contact lens wear and the different refractive surgery techniques. PURPOSE: The aim of this study is to compare the accuracy and reproducibility of the measurement of the central curvature on calibrated steel balls using the EyeSys videokeratoscope and the Orbscan corneal topography system. METHODS: The videokeratoscope (EyeSys Corneal Analysis System 2000, version 3.1) and the Orbscan corneal topography system (Orbscan II version 3.0) were used by four trained investigators to measure a series of five uniform and calibrated test surfaces with known radius of curvature ranging from 6.13 to 9.00 mm. RESULT: No statistically significant difference was found between the videokeratoscope and Orbscan systems in relation to accuracy or precision. The 95% confidence limits showed a close agreement between both instruments. The mean bias was less than +/-0.05 mm for both devices. The precision of the instruments was found to be similar. CONCLUSION: The EyeSys seems to measure more accurately, but the accuracy of the Orbscan was also acceptable, suggesting that both instruments are accurate and precise enough for research and clinical purposes. However, further studies of accuracy and repeatability of topographical measurements on human eyes generated by different topographers are necessary.

Cornea↗
PubMed1999

Further information on the knowledge of topographical corneal thickness.

Central and peripheral corneal thickness has been used increasingly to obtain information about physiologic and clinical conditions of the cornea. In this study, a new method based on ultrasonic pachometry for topographical corneal thickness measurement is described. Results suggest that the technique is reliable for clinical determination of global corneal thickness. Measurements taken by one observer on different sessions (intersession variation) and measurements taken by different observers (interobserver variation) are not significant different (p = 0.586 and 0.273, respectively). This new ultrasound topographical pachometric method can be considered a useful tool for determination of topographical corneal thickness. It has implications for the use of topographical ultrasonic pachometry in contact lenses research, refractive surgery, and management of different pathologic conditions.

Journal Article↗
PubMed1993

Pigmented paravenous retinochoroidal atrophy.

Pigmented paravenous retinochoroidal atrophy is a rare disorder that is not well understood or classified. We examined a patient who had chorioretinal atrophy with pigment clusters located in the paravenous areas without macular involvement. Other conditions which may also present retinochoroidal atrophy and/or pigmentary degeneration are discussed. The electroretinography results were subnormal but the evoked potentials were not totally extinguished. Fluorescein angiography and retinography confirmed the relative and absolute scotomas corresponding to the atrophic paravenous areas.

Aged↗
PubMed1992

Oral fluorescein angiography and fluoroscopy: determination of plasma fluorescein levels and clinical application.

One hundred oral fluorescein angiographic explorations were performed in 85 patients of both sexes, mean age 55.57 years, and range 8 to 77 years. Fluorescein was administered as one 250-mg (15 patients) or 500-mg (70 patients) capsule per 15 kg of body weight. In 15 fasting and 15 postprandial patients administered 500-mg capsules, no significant differences by group were found between fluorescein plasma levels. Fundus fluorescence under slitlamp illumination was poor for patients receiving the lower dosage of fluorescein, whereas at the higher dosage it was visible in all but one patient. The best filters were found to be a Kodak-Wratten 47A for the excitation filter and Kodak-Wratten 8 for the barrier filter. With a conventional fundus camera and fluorescein angiography filters, good photographs were achieved in all cases. The integrity of the blood-retina barriers was explored for various chorioretinal pathologies.

Administration, Oral↗
PubMed1989

Effect of carbaryl on the respiration, glycolysis and gluconeogenesis in isolated liver cells.

The effects of 1-naphthyl-N-methylcarbamate (carbaryl) upon respiration, glycolysis and gluconeogenesis in isolated rat hepatocytes was studied. The carbaryl at 0.01; 0.1 and 1.0 mM were dissolved in 1% dimethylsulphoxide. Concentrations of carbaryl at 1.0 mM reduces oxygen consumption. The decrease in the metabolic production of CO2 is significant at even the lowest of the concentrations. The utilization of glucose and the endogenous production of lactic is unaffected by treatment with carbaryl. The net glycolytic flux is decreased. On the other hand, the carbaryl inhibits lactate-gluconeogenesis at all concentrations of substrate studied. Gluconeogenesis from fructose or pyruvate or alanine is also inhibited by carbaryl 1 mM. Carbaryl decreases the lactic dehydrogenase activity but this diminution is only significant for the greatest concentration assayed. The activity of glucose-6-phosphatase is enhanced by carbaryl, but the increase is only significant for 1 mM carbaryl. The glutamic-oxalacetic transferase cytoplasmic and mitochondrial activities are inhibited by 0.1 mM and 1.0 mM carbaryl. Carbaryl decreases glucose production by hepatic cells, and suggests that the carbaryl-induced hyperglycemia in the fasted animal would be due to deficiencies in the peripheral utilization of the glucose.

Animals↗
PubMed1986

Effect of lindane on brain monoamine metabolism.

The effect of the oral administration of the organochlorinate pesticide Lindane (gamma-hexachlorociclohexane) in doses of 30, 60 and 120 mg/kg on the cerebral metabolism of 5-HT and catecholamines in female rats was studied 24 hr after the administration of the pesticide. All the doses tested caused a decrease in the concentration of cerebral and free serum tryptophan, with no significant change in the cerebral levels of 5-HT, although its rate of synthesis was inhibited at the lowest dose. The variations in the levels of 5-HIAA appears to be linked to its elimination from the brain. The higher doses cause increases in NA levels and turnover rates.

Animals↗
PubMed1984

[Effect of ethanol in the pre-ovulatory period on the ovarian cycle, progesterone and estradiol in the rat].

The effect of high doses of ethanol (2 and 4 g/kg) administered to rats in pre-ovulatory periods (18th hour of diestrus) was studied. Plasma levels of estradiol and progesterone were measured at 10 hours of oestrus and changes in the ovarian cycle and the number of mature follicles were recorded. Compared with the control group, the receptive phase of estrus of the treated animals was longer lasting over 2 to 3 days. There was also an increase in the number of mature follicles as well as an increase in the plasma level of estradiol on the morning of estrus. Progesterone values showed no significant variations. Ethanol administered at the 18th hour of diestrus inhibits ovulation but not follicle development and allows the maintenance of high levels of estrogens on the morning of estrus. As a result the keratinization of the vaginal epithelium and the estrus phase are prolonged by 2 or 3 days.

Animals↗
PubMed1983

Influence of dimethylsulphoxide on the functional state of isolated rat hepatocytes.

The effect of dimethylsulphoxide upon respiration, glycolysis and gluconeogenesis in isolated rat hepatocytes was studied. The results show that the glycolysis pathway is strongly inhibited by the action of dimethylsulphoxide in the hepatocytes, with increased glucose uptake and reduced net flux. However, the alterations in respiration and the gluconeogenesis pathway are less pronounced, the only significant change being an increase in respiratory activity during the first 10 min of incubation with dimethylsulphoxide.

Animals↗
PubMed1980

[Effect of gamma-hexachlorocyclohexane (Lindane) on the brain and serum tryptophan (author's transl)].

The effect of convulsant doses of gamma-hexachlorocyclohexane (Lindane) on the brain and serum tryptophan contents as well as on the serum FFA contents was studied. The results indicate a possible correlation between the fluctuations in the FFA, free serum and brain tryptophan concentrations. The total tryptophan concentrations increase as well as the brain tryptophan/free tryptophan ratio, with both experimental doses.

Animals↗
PubMedDate not supplied

Measurement of corneal thickness by videopachymetry: preliminary results.

Corneal thickness measurements find applications in areas such as diagnosis and management of corneal disorders and corneal surgery. We present a technique for the measurement of corneal thickness using a CCD camera mounted on a slit-lamp biomicroscope and common image processing software. Thickness measurements were performed on three RGP contact lenses of known thickness with an average error of 5 microm, SD of 8 microm. Measurements of a living cornea yielded a thickness of 505 microm and a SD of 8 microm for 10 consecutive measurements; this is an acceptable value.

Cornea↗