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M del Cerro

Publications and source records attributed to M del Cerro.

87 records · Page 5Linked to original sources
PubMed1980

High resolution optical microscopy of animal tissues by the use of sub-micrometer thick sections and a new stain.

The introduction of 1 micron-thick sections from plastic embedded material represents a great technical improvement for the study of tissues under the optical microscope. However, even sections of this thickness appear too thick when observed with oil immersion objectives of high numerical aperture. The extremely shallow depth of field of these lenses allows them to differentiate several focal planes within a one micron thick section. This in turn results in ghost images being formed from out of focus structures, a problem particularly vexing when photomicrography is attempted. To circumvent this difficulty, we reduced the thickness of the sections down to an optimum of 0.4 micron. These thinner sections do require a very energetic stain to give enough contrast to the cellular structures; Stevenel Blue, a stain recently adapted for plastic sections [del Cerro et al., Microsc. Acta 83, (2), 117--121 (1980)] proved to be the most suitable for this purpose of several stains tested. In summary, submicrometer thick sections stained with Stevenel Blue allow to reach the limits of visibility permitted by the best available objectives and effectively merge the realm of optical microscopy with that of low power electron microscopy.

Animals↗
PubMed1978

Presence of displaced neural elements within rat cerebellar fissures.

Clusters of neural tissue have been observed within the cerebellar fissures of normal and experimentally treated albino rats and hooded rats, between the ages of 5 and 90 days. The observations of these intra-fissural clusters were made in conjunction with several series of experiments dealing with the effects of various treatments on cerebellar morphogenesis. More important is the fact that similar displaced clusters are present in normal, untreated animals. Clusters can show a considerable variation in size, ranging from a few closely packed cells, to clusters with many cells completely occupying the area between the two folial surfaces, The clusters consist of immature or mature granule cells, depending on the age. With increasing age a well-developed neuropil is seen with bundles of parallel fibers coursing among the granule cells, along with occasional Bergmann glial fibers, capillaries and pericytes. Synaptic contacts, possibly granule cells, are present within the cluster. The continued differentiation of the cells in the clusters is exemplified by the observation of a mossy fiber terminal at the base of a cluster. Connecting each cluster with the nearby parenchyma is a stalk consisting of granule cells, Bergmann glial fibers, and neurites. The basal lamina of the folial surface is interrrupted at this point. The presence of these clusters implies a failure of normal morphogenetic and migrational control mechanisms. Importantly, the cells of the clusters continue to differentiate and to make synaptic connections, despite their abnormal location.

Age Factors↗
PubMed1976

Early formation of synapses in the molecular layer of the fetal rat cerebellum.

The initial phase of synaptogenesis in the molecular layer of the albino rat cerebellum has been studied quantitatively and qualitatively with the electron microscope. Using both aldehyde-osmium (AL-OS) and ethanolic phosphotungstic acid (E-PTA) preparations, synapses were observed as early as embryonic day 19 throughout the entire rostro-caudal extent of the vermal molecular layer. The undeveloped nature of the elements participating in the formation of these synapses precluded their identification, for at this stage of cerebellar development, the Purkinje cells have not developed characteristic dendrites and both the massive production of cells within the external granule layer and the migration of neuroblasts through the molecular layer are in their initial phases. Evidence of synapse formation at this early stage of molecular layer development indicates that the rudiments of neuronal systems are present before the bulk of the molecular layer has come into existence and before most of the constituent elements of the cerebellum have differentiated. From embryonic day 19 to embryonic day 22, the number of E-PTA synaptic contacts was always less than the number of AL-OS synapses. This decrepancy and the variations observed in the morphology of the presynaptic components of E-PTA stained synaptic contacts, indicate that E-PTA morphology, and particularly the development of presynaptic dense projections, represents a late stage of synapse formation.

Animals↗
PubMed1975

Pathogenesis of cerebellar hypoplasia produced by lymphocytic choriomeningitis virus infection of neonatal rats. II. An ultrastructural study of the immune-mediated pathology.

Lymphocytic choriomeningitis virus, following inoculation of 4-day-old rats, produces an acute destructive but nonfatal necrosis of the cerebellum which is immunologically mediated. An ultrastructural study of the developing lesion indicated the following sequence of events: first, lymphocytic choriomengitis virions appear in the intercellular spaces of apparently normal neural parenchyma, followed shortly thereafter (5 days after infection) by adherence of monocytes to vascular endothelium with migration into tissue and morphologic transformation into activated macrophages, concomitant with necrosis of neural cells which progresses from 1 to 3 weeks after infection. Removal of debris overlaps with and is followed by astrogliosis, collagen deposition, and vascular changes. Finally, several months after infection, an increasing infiltration of plasma cells occurs, accompanied by gradual disappearance of virus from the neural parenchyma. These morphologic observations suggest that the acut immunopathology is cell-mediated whereas local antibody production may play an important role in clearance of virus from persistently infected tissue.

Animals↗
PubMedDate not supplied

Successful xenografts of second trimester human fetal brain and retinal tissue in the anterior chamber of the eye of adult immunosuppressed rats.

Successful xenografting of first trimester human fetal CNS tissue and retina has been reported in the literature. We wished to test the feasibility of using the anterior chamber of the rat eye to support the development of more mature human fetal xenografts. Here we report on the successful outcome of human brain and retinal transplants. Adult host rats immunosuppressed with cyclosporin A accepted these xenografts and supported their further development. Periodic examination of the host eyes using a direct ophthalmoscope or an ophthalmic slit lamp permitted direct visual monitoring of the health and growth of the transplants. Histologically it was possible to identify neuronal, macroglial, and microglial (macrophage) cell types within the grafts. Mitotic activity and histogenetic differentiation took place. Blood vessels filled with hematic cells were commonly present within the grafts. The walls of these vessels prevented the leakage of horseradish peroxidase, suggesting the presence of a functional brain-blood barrier in the graft. These results indicate that it is possible to use a small animal model to study normal and pathological phenomena on late fetal human neural tissues. Our group has already taken advantage of the model to achieve HIV infectivity of fetal human brain outside the human body.

Animals↗
PubMedDate not supplied

Neither intraocular grafts of retinal cell homogenates nor live non-retinal neurons produce behavioral recovery in rats with light-damaged retinas.

Previously we have observed that fetal retinal cells grafted to the subretinal space of blind rats produced a functional recovery as determined by testing the visual inhibition of the startle response. Following those studies, we performed experiments to test whether the injection itself, cell by-products, or unrelated neural cells could also produce an effect. Visual function was tested by examining the inhibitory effect of a brief light flash (300 lx) on the acoustic startle response to an immediately following intense noise burst in light blinded Fischer 344 rats. Animals were tested before and after grafts of fetal retinal cell homogenates, dissociated perinatal cerebellar cells, and sham injections in the subretinal space. Behavioral testing continued every 2 wk for 14 wk after the graft. In the pretests, the light flash inhibited the startle response, maximal at intervals of 40-70 ms with recovery thereafter. In contrast, after exposure for 4 wk to fluorescent light (300 lx) and a rest in a normal 12/12 h light/dark environment the rats showed reflex facilitation to the light, maximal at an interval of 110 ms, followed by a late period of reflex inhibition. The light flash had no effect on other rats that had been blinded by bilateral enucleation. Light blinded animals receiving either cerebellar grafts or retinal cell homogenates were no different in performance from their sham injected control animals. The present data suggest that neither subretinal injections of neural cells nor non-specific neurochemical factors are able to elicit a positive behavioral response in visually impaired animals.

Animals↗
PubMedDate not supplied

Storage of human fetal retina in optisol prior to subretinal transplantation.

We have previously reported that Optisol, a commercially available medium (Chiron Vision, Irvine, CA), is a favorable fluid for the storage of neural retina. We now characterize the cell survival and histologic integrity of the tissue following storage and then transplantation. Neural retinas from human fetal eyes obtained within 1 h or pregnancy termination were stored in Optisol-GS medium (containing TC-199 and MEM medium, 2.5% chondroitin sulfate, 1% dextran, HEPES buffer, gentamicin sulfate, 0.1 mmol/L nonessential amino acids, sodium bicarbonate, 1 mmol/L sodium pyruvate, and additional antioxidants), at 4 degrees C for the following time periods: 0, 1, 2, and 7 days, and then tested for viability. Retinas stored for 2 and 7 days were mechanically dissociated and grafted into the eyes of light-damaged Fischer 344 rats (17 animals, 28 eyes). Nontransplanted eyes received injections of vehicle only (5 animals, 6 eyes). All animals were immunosuppressed daily with cyclosporine (10 mg/kg). All experiments were conducted in strict accordance with institutional, federal, and ARVO guidelines. Cell viability averaged 94.8%, 90.2%, 83.2%, and 76.8% at 0, 1, 2, and 7 days storage, respectively. Light microscopy demonstrated that the fetal retina was preserved without evident changes for up to 48 h. Up to 7 days there was a good to very good preservation of the cells in the outer neuroblastic layer. One month after transplantation subretinal grafts of retinal tissue stored for 2 and 7 days in Optisol showed good integration with host retina and initial photoreceptor differentiation. Optisol is a widely used medium for the preservation of human corneas prior to transplantation. Our results show that this medium is also highly suitable for preserving human fetal retinas prior to transplantation.

Animals↗
PubMedDate not supplied

A new procedure for evaluating smoothness of corneal surface following 193-nanometer excimer laser ablation.

BACKGROUND: The routine technique for evaluating the smoothness of an excimer laser keratectomy has been scanning electron microscopy (SEM). However, this method suffers from tissue shrinkage and surface artifacts, and evaluates the surface only in a qualitative manner. In our study, we used a Zygo microscope to quantitatively assess the smoothness of the excimer laser ablated corneas, without complicated tissue processing. METHODS: Five rabbit eyes and five PMMA blocks underwent 193-nanometer excimer laser ablations (5.00-millimeter diameter and 80-micrometer depth). The ablation zones of the corneas were trephined and fixated prior to the measurement. The surface smoothness was measured under the Zygo and characterized by two surface parameters (Ra and RMS). After measurement, the corneal and PMMA samples were processed for SEM. RESULTS: The Ra and RMS (mean +/- SD) for the ablated corneas are 183.33 +/- 20.6 and 240.06 +/- 23.10 nm, respectively; for the PMMA blocks, 79.49 +/- 23.02 and 96.45 +/- 27.16 nm, respectively. There are significant differences of Ra and RMS between the ablated corneas and PMMA blocks (p < .01), indicating the ablated corneal surfaces are rougher than the ablated PMMA surfaces. Qualitatively, SEM correlated well with the results of the Zygo measurements. CONCLUSIONS: We found this technique to be a simple, accurate, and reproducible means of objectively assessing the surface smoothness following excimer laser ablation. Combined use of the Zygo and SEM enables more complete evaluation of the ablated corneal surface.

Animals↗
PubMedDate not supplied

Hypersensitivity following excimer laser ablation through the corneal epithelium.

BACKGROUND: From our preliminary study, we found corneal hypersensitivity after excimer laser. To study the effects of corneal epithelial wound healing on corneal sensitivity, we investigated the recovery of corneal sensitivity following excimer laser and manual epithelial debridement. METHODS: The corneal epithelium of the right eye of New Zealand white rabbits (n = 19) was manually debrided and the left eye was ablated with the excimer laser (5 Hz, 160 mJ/cm2, 47-micrometer depth). The wound-healing rate was measured up to 46 hours. Corneal sensitivity was measured for 10 weeks. RESULTS: There was no significant difference in the wound-healing rate, but at 36 hours there was a reduction in wound-healing rate of the excimer ablated corneas. In the laser-ablated cornea, sensitivity rapidly increased to a normal level by day 5, and then it continued to increase gradually and reached a maximum at day 42. Thereafter, it retained a higher level than normal up to 10 weeks. There were significant differences in the recovery of sensitivity following excimer ablation and manual debridement. CONCLUSIONS: These results show the development of a lasting enhanced sensitivity in the cornea after excimer laser ablation, suggesting the need to conduct further studies of neural plasticity and sensory thresholds following interventions on the corneal surface.

Animals↗
PubMedDate not supplied

Corneal sensation following excimer laser photorefractive keratectomy in humans.

BACKGROUND: For the correction of myopia, small amounts of corneal tissue--including corneal nerves--are removed, resulting in flattening of the central cornea. METHODS: We studied the changes in corneal sensation in five regions of the cornea following photorefractive keratectomy at varying depths. We examined and compared the recovery of sensation in 17 sighted myopic eyes, with preoperative refractive ranges from -1.00 to -7.25 D. Eyes were divided into shallow (0 to 30 microns) or deep (31 to 70 microns) ablation groups depending on the attempted laser correction. Corneal sensation was measured in the central ablated area and the temporal, inferior, nasal, and superior unablated regions preoperatively and at 1, 3, and 6 months postoperatively. RESULTS: Central and inferior sensation were significantly reduced in the deep ablations at 1 month and continued in the central cornea 6 months postoperatively. There were no overall differences in the sensations in the unablated nasal, temporal, and superior regions between either group or over time. There was a significant second order trend (p = .034) in these three regions, indicating a sharper increase in sensation from baseline in the deeper group at 1 month than the gradual upward trend of the shallow group. CONCLUSIONS: Corneal sensation of both the central ablated area and the unablated peripheral cornea is decreased after deep anterior stromal excimer laser ablations and does not recover within 1 month. Although the deeper group showed isolated areas in the periphery of significant second order trends in sensation, the overall trends were not large, indicating no significant anesthetic effect. Fluctuations in sensation can be detected in the five regions even 6 months after excimer laser keratectomy. The clinical importance of these data remain to be defined.

Adult↗
PubMedDate not supplied

Topical diclofenac following excimer laser: effect on corneal sensitivity and wound healing in rabbits.

BACKGROUND: Diclofenac is a nonsteroidal antiinflammatory drug (NSAID) that is widely used systemically and topically. We studied the effect of diclofenac on corneal reepithelialization and corneal sensitivity after excimer laser treatment in rabbits. METHODS: Twelve New Zealand white rabbits were divided into four groups (A, B, C, and D). Groups A and B received diclofenac four times and eight times daily, respectively, following a central 5-millimeter epithelial debridement. Groups C (control) and D (diclofenac four times daily) underwent excimer laser ablation (30-micrometer depth) following manual debridement. Wound healing was compared between groups A and B and groups C and D. Sensitivity was recorded preoperatively and postoperatively 1 to 5 and 14 days in groups C and D until normal values were reestablished. RESULTS: Total time for corneal wound healing and epithelial migration rates was not delayed in any group receiving diclofenac (A, B, and D). Sensitivity after laser ablation reached a minimum of 15% to 20% in both groups C and D by day 2 and returned to normal (100%) by day 8. The decrease in sensitivity between group C, the controls, and group D, receiving diclofenac four times daily, was not statistically significant. CONCLUSIONS: Diclofenac can be used up to eight times daily in the rabbit without causing changes in corneal wound healing or epithelial migration rate. There was no significant, long-term reduction of sensitivity, and recovery was not affected by diclofenac.

Administration, Topical↗