Biomedical subjects

G Fontanesi

Publications and source records attributed to G Fontanesi.

At least 19 recordsLinked to original sources

PubMed1992

Distribution of neuropeptide Y, substance P, and choline acetyltransferase in the developing visual system of the pigeon and effects of unilateral retina removal.

The distribution of three neuroactive substances, neuropeptide Y, substance P, and choline acetyltransferase, was studied by immunocytochemical methods in central visual regions of adult, developing, and ablated pigeon brains. In normal adult brains, neuropeptide Y-positive cells and processes were present in the nucleus pretectalis, the nucleus of the basal optic root, the nucleus of the marginal optic tract, and the visual Wulst. Substance P-positive cells and processes were found in the optic tectum and in the visual Wulst. Stained fibers and terminal-like processes, but no cells, were also observed in several visual thalamic nuclei. Choline acetyltransferase-positive cells and processes were located in the optic tectum, visual Wulst, the nucleus isthmo opticus, nucleus isthmi and certain visual thalamic nuclei. Cholinergic fibers and processes, but no cells, were present in the nucleus principalis precommissuralis, the supraoptic decussation, and the nucleus lentiformis mesencephali, pars magnocellularis. In the course of development, the distribution of immunoreactivity for all three substances was found to vary. These changes often involved either progressive increases or decreases in the density of labeled cells, neuropil and/or terminal-like profiles. Experiments with retina ablated pigeons clearly demonstrated that changes in the normal pattern of immunoreactivity distribution only occurred if the retina was removed immediately after hatching, i.e., before retinofugal connections have been established. The adult pattern of immunoreactivity for all three substances appears to be reached at about the same time that the anatomical and functional maturation of the pigeon visual system is completed. The present results suggest that this temporal correlation reflects the important role that retinal afferents play in the development of these putative peptidergic and cholinergic systems.

Aging↗

PubMed1992

Wulst efferents in the little owl Athene noctua: an investigation of projections to the optic tectum.

The efferent projections from the Wulst were studied in the little owl, Athene noctua, using anterograde migration of wheat-germ-agglutinin conjugated horseradish peroxidase (WGA-HRP). Wulst projections were distributed to telencephalic, diencephalic and mesencephalic targets in a general pattern similar to that previously described in other avian species. Our results on the organization of the Wulst-optic tectum pathway in the little owl reveal well defined and laminarly arranged terminal projections into the superficial tectal layers, with a distribution suggestive of topographical relationships between neurons of origin in the Wulst and termination fields in the optic tectum. In contrast to lateral-eyed birds, the little owl possesses conspicuous contralateral projections to the optic tectum. Ipsilateral and contralateral efferents are restricted to different tectal regions, i.e. ipsilateral projections to the caudo-dorsal and contralateral projections to the rostro-ventral optic tectum. In addition, the anterior and posterior Wulst differentially contribute to the ipsilateral and contralateral projections to the optic tectum. This differential organization of Wulst efferents, as well as the presence of substantial contralateral projections, might be related to the high degree of binocular overlap typical of frontal-eyed birds. At a functional level, electric potentials recorded in the optic tectum and evoked by visual stimulation showed that information from one eye can reach the ipsilateral optic tectum. After Wulst ablation, the amplitude of these potentials was significantly reduced, indicating that Wulst efferents may influence visually-evoked activity in the optic tectum.

Animals↗

PubMed1991

Intertrochanteric valgus osteotomy and sliding compression hip screw in fractures of the femoral neck.

Twenty-four patients ranging from 28 to 56 years of age with Garden grade III or IV fractures of the femoral neck are reviewed after treatment by intertrocherantic valgus osteotomy and Richards sliding compression hip screw. The rationale behind this treatment, the operative technique, and the choice of internal fixation device are all discussed. All patients were followed up after more than 2 years so that any late complications could be documented. The results were evaluated using both the Merle d'Aubigné procedure and radiographic examination: 12 (50%) were rated excellent, 5 (20.8%) good, 2 (8.4%) fair, and 5 (20.8%) poor. The unsatisfactory results are analyzed in detail, attributable to non-union in 2 cases (due to technical error), avascular necrosis in 4 cases (2 were limited and well-tolerated by the patients; 2 were early and massive and necessitated prosthetic replacement), and infection in one case. Even though valgus osteotomy and internal fixation fill a gap in the treatment of femoral neck fractures in adults by yielding good results with a conservative method, they are very demanding surgical procedures, requiring anatomical reduction, atraumatic technique, precise calculation of the valgus angle, and precise placement of the internal fixation device.

Adult↗

PubMed1991

Immediate multiple osteosynthesis in polytrauma.

Thirty polytraumatized patients underwent immediate osteosynthesis of two or more long bone fractures for a total of 82 operations (plus an additional 14 for pelvis, hand, and foot fractures). Since 1983, according to the modern and rational concepts of "all at one time treatment", open fractures as well as associated closed lesions are stabilized immediately if the patient's general condition permits. This type of procedure requires adequate facilities as well as availability of and collaboration between teams of specialists, but it is inarguably advantageous for the patient (relief of pain, drastic reduction in the rate of embolism, improvement of respiratory and circulatory function, only one anesthesia), the surgeons (operation technically easier and shorter), and the ancillary medical personnel (easier nursing, rapid functional rehabilitation). The methods of osteosynthesis should be carefully selected in order to guarantee stability, rapid application, and low aggressiveness. The use of plates and screws is limited, while external fixation is employed frequently. Interlocked intramedullary nailing is adopted with increasing frequency. Review of cases treated by this method shows considerable improvement in terms of healing, functional recovery, and resumption of social and occupational activity.

Adult↗

PubMed1991

Retention of the posterior cruciate ligament in total knee arthroplasty.

The importance of the preservation of the posterior cruciate ligament in total knee arthroplasty is analyzed from a biomechanical, clinical, and functional standpoint. Using clinical and radiographic criteria, the authors assess posterior cruciate ligament validity in a selected group of 31 of 45 total knee arthroplasties (PCA prosthesis) reviewed at least 18 months after the operation. Sixty-eight percent of the replaced knees, which were divided into two groups on the basis of preoperative deformity, had a functional posterior cruciate ligament. In view of these results the authors are satisfied with the prosthetic model they adopted, which was designed not only to preserve the posterior cruciate ligament, but also, by virtue of its special shape, to compensate in the event of ligament insufficiency.

Activities of Daily Living↗

PubMed1990

Binocularity in the little owl, Athene noctua. I. Anatomical investigation of the thalamo-Wulst pathway.

The efferent projections from the visual thalamus to the Wulst were studied in the little owl, Athene noctua. Cells of origin were identified by retrograde labeling after injections of wheat-germ-agglutinin-conjugated horseradish peroxidase into the Wulst. The labeled-cell distribution was correlated with the distribution of anterogradely labeled retinal terminals as revealed by intraocular injections of horseradish peroxidase. The results demonstrated a bilateral thalamofugal visual pathway ascending from the nucleus dorsolateralis anterior thalami (DLA). Projections from the visual thalamus to the Wulst showed a specific and orderly pattern, and retrogradely labeled cells of DLA were distributed equally, in a complementary fashion, on both sides of the brain, with a small region of overlap. Retinal termination fields in DLA largely overlapped relay neurons projecting to either Wulst, although the overlap was not complete. Despite differences in the organization of avian and mammalian visual pathways, which reflect their separate evolutionary origins, similarities between the DLA in the little owl and the lateral geniculate nucleus in mammals suggest that, during evolution similar selective pressures for binocularity led to a similar morphological organization.

Animals↗

PubMed1990

Binocularity in the little owl, Athene noctua. II. Properties of visually evoked potentials from the Wulst in response to monocular and binocular stimulation with sine wave gratings.

Visually evoked potentials (VEPs) have been recorded from the Wulst surface of the little owl, Athene noctua, in response to counterphase-reversal of sinusoidal gratings with different contrast, spatial frequency and mean luminance, presented either monocularly or binocularly. Monocular full-field stimuli presented to either eye evoked VEPs of similar amplitude, waveform and latency. Under binocular viewing, VEPs approximately doubled in amplitude without waveform changes. VEPs with similar characteristics could be obtained in response to stimulation of the contralateral, but not ipsilateral, hemifield. These results suggest that a 50% recrossing occurs in thalamic efferents and that different ipsilateral and contralateral regions converge onto the same Wulst sites. The VEP amplitude progressively decreased with increase of the spatial frequency beyond 2 cycles/degree, and the high spatial frequency cut-off (VEP acuity) was under binocular viewing (8 cycles/degree) higher than under monocular (5 cycles/degree) viewing (200 cd/m2, 45% contrast). The VEP acuity increased with increase in the contrast and decreased with reduction of the mean luminance. The binocular gain in both VEP amplitude and VEP acuity was largest at the lowest luminance levels. Binocular VEP summation occurred in the medium-high contrast range. With decreased contrast, both monocular and binocular VEPs progressively decreased in amplitude and tended to the same contrast threshold. The VEP contrast threshold depended on the spatial frequency (0.6-1.8% in the range 0.12-2 cycles/degree). Binocular VEPs often showed facilitatory interaction (binocular/monocular amplitude ratio greater than 2), but the binocular VEP amplitude did not change either by changing the stimulus orientation (horizontal vs. vertical gratings) or by inducing different retinal disparities.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Cemented arthroprosthesis in femoral neck fractures.

Primary total hip replacement in femoral neck fractures is still controversial. This report presents the findings of a study of 42 femoral neck fractures treated with cemented arthroprosthesis with an average follow-up of five years. The patients were divided into two groups according to the type of prosthesis, the reaming and cementing techniques, and the type of operating room. Each group had positive results in about 80% of the cases, testifying to the fact that arthroprosthesis is a valid method of treatment provided that the following procedures are scrupulously carried out: the preparation of the patient, the choice and implantation of the prosthesis, and the functional and psychological rehabilitation of the patient.

Aged↗

PubMed1989

Reorganization of visual pathways following posthatching removal of one retina in pigeons.

Organization of visual pathways was studied in 2-month-old pigeons that underwent unilateral retinal removal on either the day of hatching (ERA, i.e., early retinal ablated) or the 9th day after hatching (LRA, i.e., late retinal ablated). A general size reduction of visual areas contralateral to the removed retina was found in ERA pigeons, which additionally showed an altered differentiation of thalamic visual targets as well as a different cytoarchitectonic arrangement of the superficial layers of the optic tectum. No comparable modifications were found in LRA pigeons. The retinal projections of the remaining eye were studied following intraocular injections of 3H-proline. Both in ERA and LRA pigeons, the distribution of retinofugal afferents to primary visual regions contralateral to the injected eye was similar to that of control pigeons. Anomalous ipsilateral projections from the remaining retina to primary retinorecipient regions were found in ERA pigeons only. Effects of early ablation of one retina on second-order visual connections were also studied. Following injections of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) into the visual Wulst contralateral to the operated eye, a smaller number of ipsilateral projecting thalamo-Wulst neurons was found as compared with control pigeons. In contrast, the contralateral thalamo-Wulst projections were increased. No changes in thalamo-Wulst projections were found following tracer injections into the opposite Wulst, i.e., ipsilateral to the operated eye. The present study demonstrates a substantial anatomical reorganization of both primary and secondary visual pathways following unilateral retinal removal immediately after hatching, when maturation of the visual system is not yet completed.

Animals↗

PubMed1989

The electroretinogram of the little owl (Athene noctua).

Electroretinographic responses (ERGs) have been recorded from the cornea of the little owl (Athene noctua) in response to single light flashes and to alternating sinusoidal gratings (pattern) at different levels of light adaptation. Both flash- and pattern-evoked ERGs show scotopic as well as photopic components. The pattern evoked ERG is spatially tuned with tuning functions which shift towards lower frequencies by reducing the mean luminance. The retinal acuity is about 6 c/deg at 2.3 log cd/m2 and decreases progressively by reducing the mean luminance. No pattern ERG can be recorded beyond -6.7 log cd/m2 at any spatial frequency. The pattern ERG amplitude decreases progressively by reducing the contrast. The extrapolated contrast threshold is about 1%. Acuity and contrast sensitivity ERG values are in the range of those obtained by operant techniques in other species with duplex retinae such as owls and cats.

Animals↗

PubMed1989

Changing distribution of GABA-like immunoreactivity in pigeon visual areas during the early posthatching period and effects of retinal removal on tectal GABAergic systems.

The distribution of GABA-like immunoreactivity in the pigeon visual system was studied during the first 9 days after hatching using a mouse monoclonal antibody, mAb 3A12, to glutaraldehyde linked GABA (Matute & Streit, 1986). GABA-like immunoreactivity was seen in cell bodies as well as in neuropil at the level of both the retina and central visual regions at any posthatching age. However, the distribution of putative GABAergic cells and processes varied with age reaching the adult pattern at around 9 days. As a general observation, almost no cell bodies in the retina (except for some perikarya in the ganglion cell layer) were labeled at hatching but densely packed immunostained processes were present in the inner plexiform layer. During the next few days, GABA-immunoreactive amacrine and horizontal cells appeared and the adult distribution of GABA-like immunoreactivity was reached at around 9 days. In the other visual regions examined, the general trend in the variation of GABA-like immunoreactivity included: (1) a progressive decrease in the density of immunostained cell bodies and (2) an almost parallel increase in the concentration of stained neuropil. Since in pigeons the adult organization of visual pathways and the final distribution of putative GABAergic systems are reached at around the same age, we suggest the possibility that incoming ganglion cell axons play a role in regulating the distribution of GABA-like immunoreactivity in visual areas. This hypothesis is supported by the fact that the distribution of GABA-like immunoreactivity in the superficial layers of the optic tectum was altered following ablation of the contralateral retina immediately after hatching.

Animals↗

PubMed1988

The pattern electroretinogram by skin electrodes: effect of spatial frequency and age.

Steady-state (8 Hz) pattern electroretinograms in response to sinusoidal gratings were recorded from 18 elder subjects (mean age 62.7 years) and 22 young subjects (mean age 27 years) by means of skin electrodes. All subjects were free from ocular pathology and their corrected visual acuity was 1.0 or better. In young subjects the second harmonic amplitude as a function of spatial frequency is spatially tuned, with a maximum at around 1.7 c/deg. The response of elder subjects is significantly (P less than 0.05) reduced over the whole range of spatial frequency as compared with that of younger ones. This decrease is more marked (P less than 0.01) at intermediate spatial frequencies, resulting in a shallower tuning. The response phase is not significantly different between young and elder subjects.

Adult↗

PubMed1988

Intercondyloid fractures of the humerus in the adult: surgical treatment and results.

The authors reviewed 14 cases of intercondyloid fracture of the humerus in the adult treated surgically between 1979 and 1989. After critically analysing the results, the surgical procedures, principal complications and their sequelae are discussed. They found a close relationship between the quality of the osteosynthesis and the quality of the results. However, despite the high percentage of favourable results, the authors emphasize the frequency of incomplete recovery of movement in the elbow joint.

Adult↗

PubMed1988

Total P.C.A. knee arthroprosthesis.

Between 1983 and 1986 the authors implanted 36 porous-coated P.C.A. total knee prostheses in 34 patients. Complications included two fatal cases of pulmonary embolism and one deep infection which healed within five months following removal of the prosthesis and arthrodesis. The results obtained in 23 patients after an average follow-up of 18 months were excellent in 87% and fair in 13% (according to the Hungerford evaluation system). Radiographic evaluation showed excellent prosthetic positioning in 70% of the cases, the presence of radiolucent lines in areas 5-6-7-8-11-15-19 (according to Hungerford) in 21% of the cases, and zonal bone resorption in areas 1-2-3-4 in 43% of the cases. The authors report their conclusions with reference to complications, the preservation of the posterior cruciate ligament, and problems related to positioning the prosthesis.

Aged↗

PubMed1988

Lumbosciatic pain due to sacral pathology.

Lesions of the sacrum are a possible, albeit infrequent, cause of low back pain and sciatica. The purpose of this paper is to draw attention to this possibility which, perhaps due to the rarity of sacral pathologies, is often overlooked in the investigation of lumbosciatic pain. This may influence the prognosis because of the consequent delay in diagnosis. Several cases are reported which were initially operated on for radicular disc syndromes with negative results, and only later correctly diagnosed as sacral lesions.

Adult↗

PubMed1987

Morphological and functional changes in the retinotectal system of the pigeon during the early posthatching period.

Anterograde transport of either HRP or wheat germ agglutinin-conjugated HRP was used to study the posthatching development of the retinotectal connection in the pigeon. The functional maturation of the retinotectal system was also investigated by recording electroretinographic (ERG) and tectal evoked (TEP) responses to either flash or pattern stimuli. Two main morphological changes occurred in the retinotectal system during the first 6 days after hatching: an ipsilateral retinofugal component that was present at hatching disappeared and the outer tectal layers were progressively invaded by the contralateral retinofugal axons, which at hatching were limited to the stratum griseum et fibrosum superficiale of the dorsolateral tectal quadrant. During the early posthatching period, at the same developmental stage at which an ERG to unpatterned or patterned stimulation could first be recorded, a visually evoked response could be elicited in the contralateral optic tectum. Therefore, the retina and optic tectum seem to start functioning simultaneously, the limiting factor being the late maturation of photosensitive lamellae in the outer segments of the developing photoreceptors. During the first 20 days posthatching, the retinotectal system undergoes extensive development as revealed by latency and amplitude changes of the visually evoked potentials. We suggest that the pigeon visual system serves as a useful model for studies concerning visual development and plasticity.

Age Factors↗

PubMed1987

Pharmacological dissociation of the b-wave and pattern electroretinogram.

Electroretinographic responses to modulation of either luminance (focal ERG) or spatial contrast (pattern ERG) were recorded from the pigeon eye before and after intravitreal injection of glutamate analogues DL alpha amino adipic acid (DL alpha AA) and 2-amino-4 phosphonobutyric acid (APB). Both toxins reversibly abolished the b-wave. The pattern ERG was still present, however, when the b-wave had been abolished by the toxins. This result demonstrates that the b-wave and the pattern ERG can be pharmacologically dissociated and suggests the possibility that in pigeons the b-wave and pattern ERG reflect the activity of different generators.

2-Aminoadipic Acid↗

PubMed1987

Vascular complications of detachment of the proximal tibial epiphysis. Report of 2 cases.

The authors describe two cases of proximal epiphyseal detachment of the tibia complicated by lesions of the popliteal artery. Following reduction and stabilization by Kirschner wires, vascular repair was done, in one case by the Fogarty method, and in the other by resection and substitution with a vein graft. The outcome was successful only in the second case. In the first case the vascular repair failed, with all the severe sequelae of ischaemic contractures in the ankle and foot. The need for early diagnosis of the arterial lesion is emphasized, as well as early and radical treatment (preferably by vein graft) if a good result is to be obtained. Failure results in severe and disabling contracture and stiffness of the ankle and foot.

Adolescent↗