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Biomedical subjects

R Navarro

Publications and source records attributed to R Navarro.

At least 55 records · Page 3Linked to original sources
PubMed2000

Performance of persons with juvenile-onset amputation in driving motor vehicles.

OBJECTIVE: To study the driving of motor vehicles by persons with juvenile-onset amputation and to compare the percentage of drivers among them with that found in the general population. DESIGN: A follow-up study of subjects who were younger than 18 years of age at amputation and who underwent one-sided amputation, covering the period 1976 to 1996. SETTING: The Prosthesis Service of the Asturias Central Hospital, Spain. SUBJECTS: A total of 236 juvenile amputee patients. RESULTS: The percentage of women with amputations who drive is lower than that of their male counterparts (p<.05). The percentage of drivers with upper limb amputations is greater than that of drivers with amputation of the lower limb (p<.05). Motor vehicle adaptations were used more frequently by people with upper limb amputations (p<.05). The ability to drive was not affected by the etiology or the side of amputation, or by the use of a prosthesis. The level of amputation affected driving ability in cases of amputation of the lower limb, but not in those of amputation of the upper limb. CONCLUSION: The percentage of persons with juvenile-onset amputation who drive (47.4%) is similar to that found in the general population (40.8%), and the use of a prosthesis does not have any influence on the capacity to drive a car--89.2% of drivers and 93.5% of nondrivers used a prosthesis.

Adult↗
PubMed2000

Antioxidant activities of estrogens against aqueous and lipophilic radicals; differences between phenol and catechol estrogens.

Natural estrogens have much greater radical-scavenging antioxidant activity than has previously been demonstrated, with activities up to 2.5 times those of vitamin C and vitamin E. The biological significance of this finding remains to be elucidated. In this work the antioxidant activity of a range of estrogens (phenolic, catecholic and stilbene-derived) has been studied. The activity of these substances as hydrogen-donating scavengers of free radicals in an aqueous solution has been determined by monitoring their relative abilities to quench the chromogenic radical cation 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS*+). The results show that the order of reactivity in scavenging this radical in the aqueous phase is dependent on the precise estrogenic structure, with phenolic estrogens being more potent antioxidants than catecholestrogens or diethylstilbestrol. The ability of the same estrogens to scavenge lipid phase radicals has also been assessed, determined by the ex vivo enhancement of the resistance of low-density lipoprotein (LDL) to oxidation; the order of efficacy is different from that in the aqueous phase, with the phenolic estrogens estriol, estrone and 17beta-estradiol being less potent than 2-hydroxyestradiol, 4-hydroxyestradiol, or diethylstilbestrol. In this lipid-based system, phenolic estrogens were found to be unable to regenerate alpha-tocopherol from LDL subjected to oxidative stress, while at the same time 2- and 4-hydroxyestradiol significantly delayed alpha-tocopherol loss. These results indicate that the various estrogens are good scavengers of free radicals generated in both the aqueous and the lipophilic phases. The antioxidant activity of an estrogen depends not only on the hydrophilic or lipophilic nature of the scavenged radical, but also on the phenol and catechol structures of the estrogen compound.

Antioxidants↗
PubMed2000

[Value of a new first web space reconstruction in congenital hand deformities. A study of 54 patients].

INTRODUCTION: Only a few studies are available in the literature on the specific problem of the congenital contracture or absence of the first web in hand deformities, and first web reconstruction. MATERIAL AND METHODS: Sixty-seven first web plasties in 54 patients were retrospectively analyzed: they included 44 cases of classical plasties, i.e., Z-plasty (21 cases); dorsal flap plasty of the index (19 cases), thumb (1 case), or the hand (10 cases), and 16 cases of' pseudo-kite flap. RESULTS: The results were difficult to assess, as the syndromes were dissimilar and the deformities were not comparable (e.g., Apert syndrome versus Poland syndrome). However, it was found that the 'pseudo-kite' technique which was applicable to certain cases resulted in a web extension of 3.2 cm without any deepening. DISCUSSION: No method of classical assessment can be used to comprehensively evaluate the results of first web reconstruction due to the wide variability in clinical characteristics, the lack of patient cooperation in this young age group, the possible MPJ articular thumb instability, and growth factors. Although 4-flap Z-plasty is an adequate technique for non-severe first web deformities, the 'pseudo-kite' flap approach is useful in more severe cases. In 13 cases, a peroperative measurement before and following plasty was made, and a significant increase (205%) in planimetric and stereotactic gain compared to pre-plasty findings was noted. CONCLUSION: It does not seem logical to have a particular preference for a certain approach when considering first web reconstruction in congenital malformations. Each technique has its advantages and disadvantages, depending on patient age, the type of malformation, the state of the thumb, the extent of the first web deformity and the possible presence of scar tissue.

Acrocephalosyndactylia↗
PubMed2000

[Classification and treatment of symbrachydactyly. A series of 117 cases].

In the present study, a modification has been proposed of the Blauth and Gekeler classification, aimed at a more accurate definition of appropriate surgical treatment. An analysis was made of a series of 120 cases of symbrachydactyly (117 patients); however, surgery was only performed in 86 cases (51 toe transfers in 49 patients; mean age at surgery 12 months). Type I included the separation of short and sometimes stiff fingers; type II, the 'pseudo-cleft', could be subdivided into three groups. Type IIA included those hands with more than two long and frequently hypoplastic digits, regarding which a decision had to be made between removal of rudimentary fingers or their stabilization. In type IIB, hand function was good and surgery was rarely needed. Type III (monodactylous) could also be subdivided into two categories, i.e., normal thumb in type IIIA and hypoplasia in IIIB. Finally, in type IVA, toe transfer surgery was performed on condition that wrist mobility was sufficient to compensate for the insufficient mobility of the artificial thumb on the anterior aspect of the radius. In all cases, a weak but useful pincer movement was obtained, with poor cosmetic results. In the case of toe transfers, surgery was advocated before the age of one year; and although mobility was disappointing (35 degrees active motion), good growth and excellent discrimination (5 mm on average) was observed. Symbrachydactyly is a fairly frequent congenital malformation; its diverse clinical features require a precise classification to better determine adequate treatment management.

Adolescent↗
PubMed2000

Laser Ray Tracing versus Hartmann-Shack sensor for measuring optical aberrations in the human eye.

A comparison and validation study of Laser Ray Tracing (LRT) and Hartmann-Shack wave-front-sensor (to be referred to as H-S) methods was carried out on both artificial and human eyes. The aim of this work was double. First, we wanted to verify experimentally the equivalence of single- and double-pass measurements for both H-S and LRT. This interest is due to the impossibility of making single-pass measurements in human eyes. In addition, we wanted to validate the LRT technique by comparing it with the H-S wave-front sensor, currently used in many physiological optics laboratories. Comparison of the different methods and configurations carried out in the artificial eye yielded basically the same results in all cases, which means a reciprocal validation of both LRT and H-S, in either single- or double-pass configurations. Other aspects, such as robustness against speckle noise or the influence of the size of the entrance (H-S) or exit (LRT) pupil were studied as well. As a global reference, the point-spread function (PSF) of the artificial eye was recorded directly on a CCD camera and compared with simulated PSF's computed from the experimental aberration data. We also applied these two methods to real eyes (double pass), finding again a close match between the resulting aberration coefficients and also between the standard errors for two normal subjects. However, for one myopic eye with an especially low optical quality (RMS wave-front error >2 microm) and asymmetric aberrations, the array of spots recorded with the H-S sensor was highly distorted and too difficult to analyze.

Adult↗
PubMed2000

[Pollicization, remains of the past or current operation].

Pollicization is a long time honored operation but more recent introduction of microsurgical techniques allowing toe to thumb transfers has changed the indications in trauma and congenital malformations. We reviewed two series of patients to assess the long-term result in both traumatized and malformed hands. Twenty-seven pollicized mutilated fingers were reviewed with a mean follow up of 9.5 years; the longest follow up published in the literature. Despite the age quite advanced of the population and multidigital amputations (more than two fingers were amputated in 16 cases), 21 patients had a good or fair result on a global score including mobility, sensibility, daily use, cortical integration, cold intolerance or pain and appearance. In congenital malformations, hypoplasia or aplasia of the thumb in presence of long fingers remains one of the best indication of pollicization. Out of 35 operated children, 27 were reviewed with a sufficient follow up (mean 6 years) to assess the result. Sensibility and growth were excellent (3 cases need some secondary shortening) mobility was close to normal in 61% of cases but the main concern was the strength which reached only 42% of the standard.

Adolescent↗
PubMed1999

The depth-of-field of the human eye from objective and subjective measurements.

The depth-of-field (DOF) measured through psychophysical methods seems to depend on the target's characteristics. We use objective and subjective methods to determine the DOF of the eye for different pupil diameters and wavelengths in three subjects. Variation of image quality with focus is evaluated with a double-pass technique. Objective DOF is defined as the dioptric range for which the image quality does not change appreciably, based on optical criteria. Subjective DOF is based on the accuracy of focusing a point source. Additional DOFs are obtained by simulation from experimental wavefront aberration data from the same subjects. Objective and subjective measurements of DOF are only slightly affected by pupil size, wavelength and spectral composition. Comparison of DOF from double-pass and wavefront aberration data allows us to evaluate the role of ocular aberrations and Stiles-Crawford effect.

Adult↗
PubMed1999

A new approach to the study of ocular chromatic aberrations.

We measured the ocular wavefront aberration at six different visible wavelengths (between 450 and 650 nm) in three subjects, using a spatially resolved refractometer. In this technique, the angular deviation of light rays entering the pupil at different locations is measured with respect to a target viewed through a centered pupil. Fits of the data at each wavelength to Zernike polynomials were used to estimate the change of defocus with wavelength (longitudinal chromatic aberration, LCA) and the wavelength-dependence of the ocular aberrations. Measured LCA was in good agreement with the literature. In most cases the wavefront aberration increased slightly with wavelength. The angular deviations from the reference stimulus measured using a magenta filter allowed us to estimate the achromatic axis and both optical and perceived transverse chromatic aberration (TCA), (including the effect of aberrations and Stiles-Crawford effect). The amount of TCA varied markedly across subjects, and between eyes of the same subject. Finally, we used the results from these experiments to compute the image quality of the eye in polychromatic light.

Adult↗
PubMed1999

Homeopathic effect on heart rate variability.

We record ECGs from healthy human subjects during 24-h long intervals, using ambulatory equipment. We calculate from the data various parameters, searching for those that change in a clear and systematic way under a homeopathic stimulus, (Strophantus hispidus 30c). The energy fraction at high frequencies in the power spectrum of heart rate variability fulfills this condition, and we are able to interpret our results in a way consistent with the information on this medicine in the homeopathic Materia Medica.

Adolescent↗
PubMed1999

Comedolytic effect of topical retinaldehyde in the rhino mouse model.

BACKGROUND: Retinaldehyde is a key molecule in the metabolism of vitamin A by keratinocytes. In order to evaluate its range of topical activity in acne, its comedolytic effect was compared to that of retinoic acid in the same vehicle, in the rhino mouse model. METHODS: The animals were treated on the back daily for 5 consecutive days per week for 3 weeks. At the end of this period, histological slides were analyzed in order to quantify the features of comedones and epidermal thickness. RESULTS: Topical treatment with a retinaldehyde (0.05% w/w) and a retinoic acid formulation (0. 025% w/w) induced comedolysis and increased the epidermal thickness with the same intensity. CONCLUSION: These data indicate that retinaldehyde exerts a significant comedolytic activity.

Acne Vulgaris↗
PubMed1999

Off-axis aberrations of a wide-angle schematic eye model.

A schematic eye model based on anatomical data, which had been previously designed to reproduce image quality on axis, has been transformed into a wide-angle model by simply adding a spherical image surface that plays the role of the retina. This model captures the main features of the wide-angle optical design of the human eye with minimum complexity: four conic optical surfaces plus a spherical image surface. Seidel aberrations (spherical aberration, coma, astigmatism, field curvature, and distortion), longitudinal and transverse chromatic aberrations, and overall monochromatic spot diagrams have been computed for this eye model and for field angles ranging from 0 degree to 60 degrees by both finite and third-order ray tracing. The modulation transfer function for each field angle has been computed as well. In each case our results have been compared with average experimental data found in the literature, showing a reasonably good agreement. The agreement between the model and experimental data is better off axis, mainly at moderate (10 degrees-40 degrees) field angles, than on axis. The model has been applied to simulate a variety of experimental methods in which image aberrations are estimated from measurements taken in the object space. Our results suggest that for some types of aberration, these methods may yield biased estimates.

Astigmatism↗
PubMed1999

Incidence of factor IX inhibitor development in severe haemophilia B patients treated with only one brand of high purity plasma derived factor IX concentrate.

Fifteen previously untreated patients (Pups) with severe haemophilia B (factor IX activity < or = 2 U/dl) only treated with one brand of plasma-derived high purity factor IX concentrate (FIX LFB) were studied. Age at first injection varied from 1 to 137 months and follow-up since this first injection from 21 to 86 months (median: 35). Cumulative exposure days (CED) were from 4 to over 100 (median: 26). Among these 15 Pups only one developed an inhibitor. Mutation analysis performed in all patients showed total gene deletion in the patient with inhibitor, partial gene deletion in another one, and missense mutations in 9 families. Mutation was not found in one patient. Actually, according to the data already published, only two patients were at high risk for inhibitor development in our population. Our study, although rather small, confirms the previously reported low incidence of inhibitors in haemophilia B. Large studies on incidence of FIX inhibitors are indeed difficult to perform, due to both the overall small number of severe haemophilia B patients and the low incidence of FIX inhibitors. Consequently, the impact of bias, such as prevalence of different types of gene defects in a given population, is major. Therefore, any study, dealing with incidence of FIX inhibitors in severe haemophilia B should report, for each patient, the type of gene defect.

Antibodies↗
PubMed1998

Objective measurement of the off-axis longitudinal chromatic aberration in the human eye.

Longitudinal chromatic aberration (LCA) of the human eye has been studied repeatedly, but only at the fovea. Poor visual acuity prevents its subjective determination beyond a few degrees eccentricity. Consequently, we have used an objective approach, similar to that of Charman and Jennings [(1976). Vision Research 16, 999-1005], to measure ocular LCA across the visual field. To determine the validity of our double-pass approach, a direct comparison between objective and subjective results was established where possible, namely at the fovea and parafoveally (2.5 deg). In both cases we focused a monochromatic point source at four different wavelengths (458, 501.8, 543.5 and 632.8 nm). At the fovea, for a 3 mm pupil, we found a close match between subjective and objective results. However, as the subjective task became harder (off-axis or larger pupils), subjective results tended to yield slightly more myopic eyes than the results for objective refraction. In all cases, the offset was virtually independent of the wavelength used. Therefore, we have not found evidence of any biased estimates of the LCA, as determined objectively. Our foveal results show reasonable agreement with previous findings, except for slightly smaller amounts of LCA. Starting at the fovea, LCA tends to gradually increase with eccentricity, up to 40 deg, although such an increase is small, just approaching statistical significance. Computation of the LCA using a model eye predicts a slightly smaller increase with eccentricity.

Adult↗
PubMed1998

Monochromatic aberrations and point-spread functions of the human eye across the visual field.

The monochromatic aberrations of the human eye along the temporal meridian are studied by a novel laser ray-tracing method. It consists of delivering a narrow laser pencil into the eye through a given point on the pupil and recording the aerial image of the retinal spot with a CCD camera. The relative displacement of this image is proportional to the geometrical aberration of the ray (laser pencil) at the retina. We scanned the pupils of four observers in steps of 1 mm (effective diameter, 6.7 mm) and for five field angles (0 degree, 5 degrees, 10 degrees, 20 degrees, and 40 degrees). In addition, the aerial image for each chief ray is a low-pass-filtered version of the retinal point-spread function corresponding to a fully dilated pupil. The resulting spot diagrams, displaying the distribution of ray aberrations, are highly correlated with these point-spread functions. We have estimated the wave-front error by fitting Zernike polynomials (up to the fifth order). Despite the large variation found among observers, the overall rms wave-front error is relatively homogeneous. At the fovea, the average rms value was 1.49 microns when the second-order terms (defocus and astigmatism) were considered; this was reduced to 0.45 micron when the second-order terms were ignored. The rms values increase slowly, in a roughly linear fashion with eccentricity, such that at 40 degrees they are approximately double. These results are consistent with previous findings on the off-axis optical quality of the eye.

Adult↗
PubMed1998

Association of Venezuelan equine encephalitis virus subtype IE with two equine epizootics in Mexico.

Two outbreaks of encephalitis consistent with an etiology of Venezuelan equine encephalitis (VEE) virus occurred in equines on the Pacific coast of southern Mexico in 1993 (Chiapas State) and in 1996 (Oaxaca State). In Chiapas, there were 125 cases, of which 63 were fatal and in Oaxaca, there were 32 cases and 12 fatalities. Virus was isolated from two horses from each outbreak, including three brain isolates and one from blood. Virus isolates (93-42124, ISET-Chi93, Oax131, and Oax142) were shown by indirect immunofluorescence, hemagglutination inhibition, monoclonal antibody ELISA, and nucleotide sequencing to be VEE virus, subtype IE, a type previously thought to be equine-avirulent. Genetic characterization and phylogenetic analysis indicated that the outbreak viruses were identical or nearly identical to one another and that they were closely related to equine-avirulent IE strains from Guatemala and the Gulf coast of Mexico. In a plaque-reduction neutralization test, sera collected from healthy horses in Chiapas and Oaxaca reacted significantly better with isolate 93-42124 than with Guatemala IE isolate 68U201, suggesting that subtle genetic changes may have resulted in alteration of neutralization domains. It is not clear whether these differences may also influence equine virulence. However, renewed VEE virus subtype IE activity in Mexico, and its apparent conversion to equine virulence, underscores the need for increased surveillance, additional laboratory and epidemiologic studies in VEE-endemic regions, and possibly new vaccines.

Amino Acid Sequence↗
PubMed1997

Cholesterol biosynthesis in normocholesterolemic patients after cholesterol removal by plasmapheresis.

Plasmapheresis and low-density lipoprotein (LDL)-apheresis are recognized procedures for the treatment of hyperlipidemia resistant to diet and lipid-lowering drugs and provide information on cholesterol synthesis in hypercholesterolemic patients. However, cholesterol synthesis after acute cholesterol removal from plasma has never been investigated in normocholesterolemic patients. In this study, cholesterol synthesis was evaluated in three normocholesterolemic patients by determination of plasma lathosterol, lathosterol-to-cholesterol ratio, and plasma mevalonic acid. In a short-term kinetic study, samples were collected before and after plasmapheresis and every 6 hours during 24 hours. In the second part of the study, cholesterol synthesis was evaluated daily for 3 days. In normocholesterolemic patients, cholesterol returns to basal levels in 3 days. However, cholesterol removal did not result in a significant increase in lathosterol-to-cholesterol ratio or in plasma mevalonic acid, despite a slight increase in lathosterol. In contrast, when repeated plasma exchanges induced a dramatic hypocholesterolemia (< 1 mmol/liter), an acute but transient stimulation of cholesterol synthesis was observed (lathosterol/cholesterol ratio and MVA, respectively, increase from 8.2 to 22.3 and from 28 nmol/liter to 98 nmol/liter). This study shows that cholesterol synthesis is not stimulated by plasmapheresis in normocholesterolemic patients but is enhanced in dramatic hypocholesterolemic patients (< 1 mmol/liter).

Cholesterol↗