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Biomedical subjects

S Fonda

Publications and source records attributed to S Fonda.

At least 19 recordsLinked to original sources
PubMed2001

Saccadic eye movements are impaired in Duchenne muscular dystrophy.

Extraocular muscles are generally considered to be spared in Duchenne Muscular Dystrophy (DMD). However, this assumption is based mainly on clinical observations, as systematic eye movement recordings have been performed in a very limited number of cases. Our goal was to analyze several saccade parameters in a higher number of cases, in order to reveal a possible ocular-motor impairment in DMD. Data were collected from a population of 9 subjects with DMD and 9 healthy male subjects of comparable age as controls. We used the electrooculographic (EOG) technique coupled with advanced digital signal processing; saccade duration, amplitude, mean velocity, peak velocity and K factor (ratio mean/peak velocity) were measured. The DMD group showed saccades with significantly longer duration and lower velocity, with respect to controls; these differences were accounted for mainly by the largest movements, whereas there were no significant differences at the smallest eccentricity tested (3 deg). Neither amplitude nor K factor were significantly different from controls for any of the eccentricities tested. To our knowledge. this is the first study to suggest significant impairment of eye movements in Duchenne muscular dystrophy.

Adolescent↗
PubMed1994

[A proposal for the use of tridimensional reconstruction in oncology to better assess tumor stage and response to therapy].

Besides radiation therapy, diagnostic imaging has always been considered the main medical application of three-dimensional (3D) reconstruction. On the contrary, our study focused mainly on the use of 3D reconstruction for both spatial characterization and morphometric evaluation of the reconstructed objects. We aimed at assisting physicians to solve clinical and therapeutic problems. In particular, in oncology, 3D reconstruction may allow the objective and accurate quantification of the volume of neoplastic lesions. Therefore, we decided to focus our attention on the spatial characterization and morphometric assessment of the examined neoplastic masses. Volumetric measurements based on 3D reconstruction may be of great value to assess volume changes after irradiation and/or chemotherapy of neoplastic lesions. This might also allow to compare, on the basis of such changes, the role of different treatment protocols on similar neoplastic lesions and, possibly, to lead to a new TNM staging system no longer based on 2D measurements but on volumes. To meet these clinical requirements, we developed a software system for accurate volume measurements. We believed 3D reconstruction to be suited to this purpose and therefore we implemented a software incorporating 3D reconstruction capabilities of abnormal anatomical structures from 2D images, the rotation of the volume of interest for better assessment of spatial relationships, and finally morphometric evaluation, for accurate volume measurements. Instead of calculating the volume of a neoplastic lesion by means of a 3D reconstruction algorithm considering voxels as indivisible (voxel-based approach), we implemented a surface rendering algorithm using a cell-based approach, because it allowed voxels to be represented as small volume units, which could be further divided by means of linear interpolation. Thus, great flexibility was possible in the determination of surfaces, together with a good approximation of the volume of the neoplastic lesions. To assess the reliability of the developed software system, we used a real phantom. Its known actual volume was compared with the one measured by our system and the difference, expressed as a percentage of the actual volume itself, was compared with the one obtained by using reconstruction algorithms with a voxel-based approach (1.4% vs 4.4%). The error produced by the latter is three times greater than the one produced by our algorithm. This is a major result for the physician: better approximation of the actual volume of a neoplastic lesion means better evaluation of the number of neoplastic cells in the lesion. This may be useful for the clinical management of the patient. In the paper, the first clinical applications of our algorithm are reported.

Algorithms↗
PubMed1993

Intraocular injection of APB decreases the metabolic response of the rat superior colliculus.

The functional activity of the superior colliculus (SC) following flash stimulation was examined by means of 2-deoxyglucose (2DG) method in monocularly enucleated Long-Evans rats intraocularly injected with a solution of 2-amino-4-phosphonobutyric acid (APB), able to silence the ON retinal activity. After APB injection SC layers recipient of retinal axons suffered a sustained 2DG decrease as compared to controls. Moreover, whereas glucose utilization in normal rat SC appears unevenly distributed and closely related to retinal axon density, by contrast, APB-treated rats showed a rather uniform metabolic activity throughout the SC surface. Furthermore, we calculated the 2DG uptake percentage reduction in 12 SC loci of APB rats in respect to homologous loci of controls: glucose utilization decreases at the loci largely differ from each other, showing that retinal axons carrying ON activity are dispersed over the SC in a mosaic pattern. Thus, the SC metabolic map should be representative of its retinotopic organization which, in turn, depends on the asymmetric distribution in the rat's retina of W-like as well as of other ganglion cell types.

Aminobutyrates↗
PubMed1990

Medical treatment of senile cataract: clinical investigation of bendazac-lysine using objective and subjective methods.

A modified Zeiss slit lamp coupled with a digital image-processing system was used to evaluate objectively changes in lens transparency over 1 year at 4-month intervals in 150 eyes of 92 patients affected by early senile cataract. A total of 59 patients were treated daily with 1.5 g bendazac-lysine, and 33 patients constituted the control group. At follow-up, visual acuity was also tested using Snellen letter charts at variable contrast to provide an additional parameter closer to traditional methods. Results indicate that the minimal angle of resolution at 10% contrast (MAR10) and the mean gray-level value of the lens image obtained by retroillumination (MLR) are sensitive to early changes in lens transparency. Using MAR10 as a parameter, the control group showed a significant, progressive worsening of the lens status over 12 months, whereas the treated group exhibited no significant changes. MRL indicated the same behaviour as MAR10, although lens damage was detected later in the control group. The results show that bendazac-lysine may delay the formation of lens opacities.

Aged↗
PubMed1987

Incremental binocular amplitude of the pattern visual evoked potential during the first five months of life: electrophysiological evidence of the development of binocularity.

The amplitude of the pattern visual evoked potential (VEP) of a binocular stimulus has been shown to be generally larger than the VEP obtained monocularly. There is evidence that this effect can be considered an electrophysiological index of fusion. To study how binocular vision develops in infancy we evaluated the incremental binocular amplitude (IBA) in three infants in a longitudinal investigation during the first five months of life. The stimuli were phase-alternating square-wave gratings with spatial and temporal parameters chosen to be appropriate for neonates. IBA was defined as the percentage increment of the largest binocular response compared with the monocular response. In the first two months of life IBA values were near zero, that is, no summation occurred. Between the second and third month IBA values rose markedly and after the third month its value was greater than 100%, demonstrating binocular facilitation. Thus in the first two months of life the eyes do not seem to cooperate as in adults. By the second and third month the binocular pattern VEP reflects an increasing binocular interaction. Other studies of the development of stereopsis have also found evidence of binocularity at similar ages.

Aging↗
PubMed1986

Active blockage and rest position nystagmus: electromyographic demonstration of two types of ocular induced head-turn.

A differentiation of two types of head-turns due to nystagmus, by means of electromyography (EMG) is demonstrated in this paper. The first type is represented by patients who actively block the nystagmus, by means of an increase of discharge of the extraocular muscles who are synergistic and responsible for the head-turn. This block has the same features of the block of nystagmus in convergence and usually exceeds 10-15 degrees from the primary position. The second type is made out of patients whose head-turn is explained with the null-position of Kestenbaum. Here the nystagmus simply disappears in the position of head-turn, which usually is of no more than 10-15 degrees. Both types of patients show the same electronystagmographic features in the position of head-turn. This differentiation is useful from the clinical standpoint. In fact, only the first type of head-turn may require, besides a classical Anderson or Kestenbaum procedure, also a posterior fixation suture according to Cüppers. This operation would be useless in the second type of head-turn. Clinical signs useful for differentiating these two types of head-turn are presented as well.

Adult↗
PubMed1986

Experimental errors in digital image processing for the determination of geometrical parameters of the human eye.

A new method is presented for measuring geometrical parameters of the anterior segment of human eye. A digital imaging technique is employed in conjunction with a slit lamp and TV camera. A method was developed to analyze images and the problem of minimizing measuring errors was studied. The method was tested using a contact lens to simulate the anterior corneal surface.

Electronic Data Processing↗
PubMed1986

Device for eliminating corneal light reflections during recording of lateral images with a slit lamp.

Corneal reflections produce defects in photographic sections of the lens taken with a slit-lamp biomicroscope for computerized densitometric analysis of cataract opacity. A simple and workable, adjustable antireflection device was built that can be easily adapted to photographic slit lamps, a common instrument in ophthalmology equipment. The slit lamp is a versatile tool for photographing structures in the anterior segment of the eye, particularly the lens. Corneal reflections are eliminated for angles between the light band and a photograph plane ranging from 20 degrees to 90 degrees, with the light band no greater than 0.5 mm and the corneal curvature about 7.6 to 7.9 mm. The device acts by blocking aberrant light rays from the light source that would otherwise be reflected by the mirrorlike surface of the cornea and enter the objective lens. Here we present a prototype designed for the Zeiss slit lamp.

Cornea↗
PubMed1986

Modifications of the slit lamp for digital image processing of the anterior segment of the eye.

The Zeiss slit lamp has been modified in order to extend its use to measurements of lens transparency. Two major modifications have been introduced: (1) a support for a high-sensitivity TV camera that is connected to an image processing system; (2) two potentiometers for recording electrical signals proportional to the rotation angle of the slit-supporting arm with respect to the visual axis and the slit tilting angle. As a result, the slit lamp output consists of three signals; one TV signal for the images and two analog signals for measurement of the angles. With the aid of an image-processing system connected to a minicomputer, software has been developed to enable the operator to acquire reliable digital images of the anterior segment of the eye in real time. The software provides the user with an easy-to-follow menu.

Anterior Eye Segment↗
PubMed1984

Improvements in clinical electronystagmogram analysis.

The authors apply the technique of amplitude histogram analysis to the clinical electronystagmogram (ENG). After a brief survey of the underlying concepts, some typical normal and pathological ENG records are discussed. Comparison of advantages and disadvantages reveals that the quoted technique may be suitable to be profitably introduced in clinical practice.

Electronystagmography↗
PubMed1984

Comparative evaluation of blood viscosity in diabetic retinopathy.

The viscosity of the whole blood, plasma and serum, haematocrit and plasma fibrinogen were studied in diabetic patients with (DR) and without (D) retinopathy and in non-diabetic control subjects (C). Blood viscosity was significantly higher in diabetics than in controls. No significant differences in viscosity of the whole blood were found when various types of retinopathy were compared according to the severity of retinal damage. Plasma viscosity was significantly higher (P less than 0.01) than controls (C) only in diabetic patients with retinopathy (DR). Serum viscosity was significantly increased compared with controls (C) only in diabetic patients affected by proliferative retinopathy. Plasma fibrinogen was significantly higher than controls (C) both in diabetics with retinopathy (DR) and without retinopathy (D). Haematocrit did not show a significant difference in the three groups considered (C, D, DR).

Adult↗
PubMed1984

Computer-assisted analyses of [14C]2-DG autoradiographs employing a general purpose image processing system.

A general purpose image processing system is described including B/W TV camera, high resolution image processor and display system (TESAK VDC 501), computer (DEC PDP 11/23), and monochrome and color monitors. Images may be acquired from a microscope equipped with a TV camera or using the TV in direct viewing; the A/D converter and the image processor provides fast (40 ms) and precise (512 X 512 data points) digitization of TV signal with a 256 gray levels maximum resolution. Computer programs have been developed in order to perform qualitative and quantitative analyses of autoradiographs obtained with the 2-DG method, which are written in FORTRAN and MACRO 11 Assembly Language. They include: (1) procedures designed to recognize errors in acquisition due to possible image shading and correct them via software; (2) routines suitable for qualitative analyses of the whole image or selected regions of it, providing the opportunity for pseudocolor coding, statistics, graphic overlays; (3) programs permitting the conversion of gray levels into metabolic rates of glucose utilization and the display of gray- or color-coded metabolic maps.

Animals↗
PubMed1983

Folate utilization in Friend erythroleukemia cells.

In order to study the generation, factors controlling endogenous folate pools, and their functional importance, Friend erythroleukemia cells were grown in media containing 100; 1,000; and 10,000 ng/ml of tritiated pteroylglutamic acid (3H)PteGlu1 and then studied in unlabeled media with varying amounts of PteGlu1. The intracellular folate pool was directly proportional to the PteGlu1 in which the cells were incubated. At equilibrium, greater than 95% of the labeled intracellular folate pool chromatographed as polyglutamyl folate, regardless of the exogenous folate concentration. The functional importance of the intracellular folate pool was studied by varying the endogenous pool and the exogenous (media) supply. The ability of the cells to replicate in the absence of exogenous folate was directly proportional to the intracellular polyglutamyl folate pool. The maximal rate of replication, however, required exogenous PteGlu1 in addition. The cell doubling time was the most important determinant of intracellular folate turnover; changes in the intracellular pool size and the extracellular folate concentration had no effect on the turnover time. In a rapidly proliferating tissue, the onset of functional folate deficiency will be determined by dilution of intracellular polyglutamates among progeny until a critical level is reached.

Animals↗
PubMed1983

Cellular abnormalities of folate deficiency.

To trace the development of folate-deficient abnormalities of morphology and DNA synthesis, Friend erythroleukaemia cells were grown in media containing 10(2), 10(3) and 10(4) ng of [3H]PteGlu1/ml and then transferred to folate-free media. Parameters examined were: intracellular folate levels; growth potential; morphology; dU suppression; and DNA content by flow microfluorimetry. The most sensitive indicators of folate-deficient cell growth were those related to DNA synthesis (dU and flow microfluorimetry). These became abnormal at intracellular folate levels of 0.2-0.5 ng/10(6) cells and markedly so below 0.1 ng/10(6) cells. Morphological criteria were less sensitive. Cells became megaloblastic at intracellular folate levels below 0.06 ng/10(6). The capacity of the cells to replicate in folate-free media was a function of the intracellular folate (ICF): duplications = 4.01 + ln(ICF)/0.67 (r = 0.993, P less than 0.001). These studies demonstrate that regardless of initial intracellular folate levels, cellular stigmata of folate deficiency appear when cellular folate falls below 3 X 10(5) molecules per cell (dU and flow microfluorimetry) and cells lose the capacity for further replication below 7-10 X 10(5) molecules. The intracellular folate level not only predicts early defects, but also determines the replicative capacity.

Cell Division↗
PubMed1983

Reliability of photometric measurements in the Zeiss fundus camera.

The authors test the hypothesis of systematic errors in photometric and/or densitometric measurements performed by Fundus camera equipment. By means of 2 different methods (reflection and transmission) the non-uniformity of light-distribution on sample surfaces placed in front of the fundus camera is shown. The consequent point by point variability in retinal illumination can be defined as the 'retinal shading problem'. This conclusion must be taken into account when equidensitometric measurements are carried out on eye fundus images with fundus camera, by photographic, cinematographic or TV techniques.

Cineangiography↗
PubMed1981

Vision in the neonate (full-term and premature): preliminary result of the application of some testing methods.

Little information is available on the functionality of the visual system in neonates. Comparison was made between neonates born at full term and prematures equated for conceptional age, using two methods of investigation: the visual evoked potential (VEP) and the "forced preferential looking" (FPL). The results obtained by the FPL method indicate a greater visual acuity in premature subjects, whereas the results obtained by the VEP method point to no significant difference in implicit time between the two groups.

Evoked Potentials↗