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Biomedical subjects

M del Cerro

Publications and source records attributed to M del Cerro.

At least 55 records · Page 3Linked to original sources
PubMed1992

Human immunodeficiency virus type 1 infection of neural xenografts.

Human immunodeficiency virus type 1 (HIV-1) infection is highly specific for its human host. To study HIV-1 infection of the human nervous system, we have established a small animal model in which second-trimester (11 to 17.5 weeks) human fetal brain or neural retina is transplanted to the anterior chamber of the eye of immunosuppressed adult rats. The human xenografts vascularized, formed a blood-brain barrier, and differentiated, forming neurons and glia. The xenografts were infected with cell-free HIV-1 or with HIV-1-infected human monocytes. Analysis by polymerase chain reaction revealed HIV-1 sequences in DNA from xenograft tissue exposed to HIV-1 virions, and in situ hybridization demonstrated HIV-1 mRNA localized in macrophages and multinucleated giant cells. Pathological damage was observed only in neural xenografts containing HIV-1-infected human monocytes, supporting the hypothesis that these cells mediate neurotoxicity. This small animal model allows the study of direct and indirect effects of HIV-1 infection on developing human fetal neural tissues, and it should prove useful in evaluating antiviral therapies, which must ultimately target HIV-1 infection of the brain.

AIDS Dementia Complex↗
PubMed1992

Photoreceptor differentiation in retinal xenografts of fetal monkey retina.

Although the potential of retinal grafts to provide the host eye with rod cells is presently well established, the possibility of grafting cone photoreceptors has not been documented. In this study, the neural retinas of two Cebus apella monkey fetuses were xenografted into immunosuppressed Fischer 344 adult rats. Histological analysis showed intimate apposition between the grafted donor cells and the neighboring host rat retina. The transplanted cells survived well and often overgrew the boundaries of the host retina, expanding into the host vitreous cavity. These cells formed histogenetically differentiated structures predominantly populated by the photoreceptors. When transplanted into a foreign environment, donor cells formed inner segments which exhibited the basic morphology of cells developed in situ. This study demonstrates that embryonic monkey neural retina is a viable source of xenograft material. It also indicates that an advanced embryonic stage is not a deterrent to survival and differentiation of grafted primate neuroretinal cells. The successful transplantation of these cells, especially under the relatively adverse conditions of a xenograft, raises the hope that retinal transplantation may in fact be a useful technique for repairing both rod and cone function in damaged retinas of higher animals including humans.

Animals↗
PubMed1992

Reciprocal retinal transplantation: a tool for the study of an inherited retinal degeneration.

The pathogenesis of retinal degeneration in rd mutant mice has been extensively studied, the gene responsible for the defect has been cloned, and the neural retina has been identified as the primary site for the degeneration. However, the possible contributory role of the ocular environment in this form of retinal degeneration remains undetermined. Retinal transplantation, which provides the opportunity to implant the neural retinal into a genetically defined intraocular environment, was used to examine this possibility. A reciprocal retinal transplantation paradigm was designed based on three experimental groups: (1) normal immature retina transplanted into rd/rd mutant eyes, (2) rd/rd immature retina transplanted into normal eye, and (3) normal immature retina transplanted into normal eyes. The rates of survival and histological characteristics of the grafts were compared between the three groups. At post-transplantation Day 3 (PTD 3), there were no differences between the three groups. Between PTD 10 and 15, the retinal grafts in group 1 showed degeneration. In contrast, the retinal grafts in groups 2 and 3 survived and developed well. At PTD 30, the retinal grafts in both groups 1 and 2 showed degeneration, but the retinal grafts in group 3 survived and remained differentiated well. These results suggest that the retinal degeneration of rd mice may be caused by both a deficit of the neural retina and intraocular environmental changes which are elicited either as a result of mutation or as a sequel to retinal degeneration.

Animals↗
PubMed1992

A new procedure for multiple intraretinal transplantation into mammalian eyes.

A new method of intraretinal grafting is described which avoids opening the globe and allows direct visual control of the transplant by observing placement of the graft through the host pupil. A microsyringe with a bevelled needle partially ensheathed in plastic tubing in order to limit penetration was used to inject dissociated donor cells into 2 to 4 pre-selected points of the sub-retinal space of adult rats. The needle tip was inserted through the scleral and choroidal tissue, and observed through the animal's pupil as it reached into the sub-retinal space. Donor cells were then injected into several sites of the retina. Results, using ophthalmoscopy as well as light and electron microscopy, confirmed the atraumatic nature of this technique and the survival of grafted cells. Intraretinal injection of colloidal carbon visually illustrated the effectiveness of this method in covering an extended portion of the host retina. The procedure, which is virtually free of complications has enabled us to perform multisite intra-ocular grafting in a safe, easy, and reliable fashion, under direct visual control.

Anesthesia↗
PubMed1992

Impoverished stimulus input does not simulate the slowed visual kinetics of retinal damage.

In the rat with normal sight, the acoustic startle reflex to a sound burst is suppressed when the sound is preceded by a brief light pulse. This effect of light in the rat with retinal damage is reduced and peak suppression is seen at a greater delay. Both observations are expected consequences of the loss of visual sensitivity that should accompany photoreceptor loss. However, in an early stage of retinal damage, the peak of the suppressive effect is so delayed that at long lead times the light flash is a more effective stimulus in the rat with the damaged retina than in the normal rat. Two experiments tested the hypothesis that this crossing over of the two groups is a secondary consequence of a nonspecific loss of visual sensitivity in the visually impaired rat. If the hypothesis is correct, reductions in the intensity or duration of the light flash and the degree of dark adaptation should model the effect in normal rats. The overall amount of reflex suppression was diminished with these manipulations, but none diminished the temporal development of reflex suppression to a degree sufficient to produce the paradoxical crossover effect characteristic of retinal damage. These data indicate that decrements in the speed of visual processing are not secondary to the changes in sensitivity that accompany retinal damage, but should be viewed as a separate and independent form of visual impairment.

Animals↗
PubMed1992

A new model for evaluating corneal wound strength in the rabbit.

Presented in this report is a new model to evaluate corneal wound strength quantitatively by using an Instron 1125 tensiometer with video monitoring. Twenty-six rabbits received full thickness 8 mm central corneal incisions that were marked with sutures at each end and dressed with collagen shields. Animals were killed and corneas were harvested from 3-30 d postoperatively. Tensile test specimens, of rectangular (n = 9) or hourglass (n = 17) planform geometry, were prepared. Uniaxial tension tests were performed on these specimens parallel to the long dimension and perpendicular to the incision. Specimens were processed for light microscopy. Individual specimen load and displacement records were normalized to yield geometry independent stress and strain data sets. Maximum wound strength was determined as peak tissue stress on loading. Maximum tissue stiffness (inverse compliance) was derived from the peak slope of the stress-strain profile. Tissue fracture toughness was calculated as the total area under the stress-strain profile from the onset of loading to total wound failure. Data points at 3, 5, 10, 18, and 30 d show maximum wound strength increasing from 15.2 to 832 kilopascals (KPa), maximum stiffness increasing from 0.20 to 11.4 megapascals, and fracture toughness increasing from 1.82 to 87.7 KPa. Histological observations correlate well with tensiometry deductions. These data suggest enhanced mechanical load bearing with time, indicative of enhanced collagen fiber formation and cross-linking.

Animals↗
PubMed1992

Noncross-linked collagen discs and cross-linked collagen shields in the delivery of gentamicin to rabbits eyes.

Using fluorescent polarization immunoassay, in vitro absorption and elution of gentamicin by noncross-linked collagen discs was measured. This technique was compared with that of cross-linked collagen shields and topical drops to provide adequate gentamicin levels in the cornea and aqueous humor of the rabbit eye. In vitro results showed that the noncross-linked collagen discs absorbed increased gentamicin with prolonged soaking time. All 2-hr presoaked discs completely dissolved within 6 min after being placed in the lower fornix of the rabbit eye. The presoaked discs released most of their gentamicin load within 0.5 hr of elution. Gentamicin levels in the cornea and aqueous humor, using 2-hr presoaked discs, were similar to those obtained with a single drop (P greater than 0.05) of topical solution and significantly lower than those obtained by applying a collagen shield at all intervals (P less than 0.01) and by hourly drops measured at 4- and 6-hr intervals (P less than 0.01). These results suggest that, in their current formulation, the presoaked collagen discs may not be an effective alternative to collagen shields or topical drops for gentamicin delivery because of their rapid dissolution in the eye.

Absorption↗
PubMed1992

Collagen shields as a vehicle for collecting and studying migratory cells on human corneas.

Collagen shields have been studied in the enhancement of the initial healing of epithelial defects, as an adjunct in the treatment of dry eye, and as a reservoir and delivery system for topical ocular medications. The authors used collagen shields to collect information on the numbers and types of free cells populating the normal and postoperative ocular surface. In addition, correlative microscopic techniques were used to study details of the mechanisms responsible for the dissolution of the shields when applied to the human eye. Collagen shields were applied as a bandage lens on the eyes of patients who underwent extracapsular cataract extraction (n = 10) or penetrating keratoplasty (n = 10) and on normal volunteers (n = 10). The shields were collected at the 1-day postoperative examination and fixed in aldehyde mixtures. Specimens then were processed for correlative light (LM), transmission (TEM), and scanning (SEM) microscopy. Cell accumulation was shown by SEM on both anterior and posterior shield surfaces. Cell adherence occurred primarily on the posterior shield periphery for approximately 2 mm, with the central zone relatively clean. Both LM and TEM evaluation revealed cell counts ranging from 0.066 cells/10(4) microns2 (standard deviation, +/- 0.256) in healthy eyes compared with shields placed on postoperative eyes (194.25 +/- 7.32 cells/10(4) microns2). Various correlative microscopy techniques revealed that most cells were polymorphonuclear leukocytes with a low number of other hematogenous (lymphocytes and monocytes) and exfoliated epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Dressings↗
PubMed1991

Modulation of retinal differentiation by oncogenes: effect of the v-src gene on expression of choline acetyltransferase and glutamine synthetase.

Expression of the protooncogene c-src in chick neural retina is developmentally regulated and associated with neural differentiation. In the present study, chick neural retina (NR) cell cultures from 7 day embryos were exposed to the exogenous src oncogene, the c-src counterpart, to establish the effect of expression of v-src on specific retinal cellular differentiation. NR cells from 7 day chick embryos were placed in monolayer or rotation culture and infected with Rous sarcoma virus (RSV) containing a single transforming gene. Other cultures were infected with a transforming defective mutant of RSV which still possesses mitogenic activity for NR cells. While control cultures showed typical neuronal and Muller cell morphologies at the light and electron microscopic level, NR cells infected with RSV exhibited dramatic morphological alterations in monolayer culture and cell aggregates. However, the mutant src gene induced mitosis without accompanying transforming properties. When aggregate cultures were treated with hydrocortisone to induce glutamine synthetase (GS) expression in Muller cells, control cultures showed the typical immunofluorescence pattern of GS staining, while RSV infected cultures showed no GS fluorescence. Cultures infected with mutant RSV showed some staining for GS. In contrast, choline acetyltransferase activity was shown to increase in both monolayer and aggregate cultures of retinal cells following v-src expression. These data indicate that the presence of excess v-src in differentiating cultures of NR inhibits the expression of some neural specific enzymes and enhances the presence of other specific proteins. Moreover, continually growing cultures of oncogene-altered retinal cells may be useful as models to study gene expression in development of the nervous system.

Animals↗
PubMed1991

Intraretinal grafting restores visual function in light-blinded rats.

In seeing rats light flashes inhibit acoustic startle reflexes at short lead times. In contrast, visually impaired (light-blinded) rats show an early phase of exaggerated reflex expression, revealing the presence of pathological visual processing, and then an aberrant late phase of delayed inhibition. Grafting fetal retinal cells into the damaged retina entirely removed reflex facilitation and restored a modest degree of properly timed and statistically significant reflex inhibition. This restoration of visually-mediated behaviour, observed in two independent groups, reveals that intraretinal grafts provide useful information to blinded hosts.

Acoustic Stimulation↗
PubMed1990

Intraocular transplantation of cell layers derived from neonatal rat retina.

The goal of this study was to determine whether cell layers derived from either the inner or outer regions of the neonatal rat retina had the capacity to grow and differentiate when transplanted into the adult retina of the same species and, if so, whether there would be differences between the grafts originated from the two different cell populations. Two different tracers were used to label donor cells and to identify them following transplantation. Firstly, at postnatal day (PND) 2, the pups received bilateral injections of rhodamine-labeled microspheres in the superior colliculus in order to label retrogradely the retinal ganglion cells. From the day of birth until the day of sacrifice (PND 4), the donors received daily injections of [3H]thymidine to label the nuclei of dividing cells. At PND 4 the animals were sacrificed and the retinas isolated. Following brief enzymatic treatment, the inner and outer retinal regions were separated from each other using filter membranes. Cells derived from each of the two moieties were transplanted separately into the eyes of adult host animals of the same strain. After survival times ranging from 3 to 44 days, the host eyes were enucleated and prepared for examination using both light and electron microscopic methods. Both retinal regions gave viable transplants. Unexpectedly, the transplants derived from the inner zone of the retina survived better than those derived from the outer zone, despite the fact that the highest number of undifferentiated and mitotically active cells occurred in the latter.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

In vivo staining of the mammalian retina by means of a simple fluorescent method.

Intraocular injections of microliter volumes of a solution containing the fluorescent stain Fluoro-Gold produces an intense and long-lasting in vivo stain of the cells forming the neural retina of rats and mice. The label is incorporated by the neuro-retinal cells, while other intraocular structures such as the lens, iris, ciliary processes and even the optic nerve head exclude it. The fluorophore can be easily demonstrated under epi-illumination by means of commonly used fluorescence filter combinations. The stain has proven to be compatible with cryostat sectioning and with plastic embedding. Furthermore, electron dense lysosomal and lamellar bodies in retinal neurons which have incorporated the stain may provide a means for identification of Fluoro-Gold labeled cells at the electron microscopic level which is consistent with previous results. Intraocular injection of Fluoro-Gold fills the need for a reliable, simple, and robust in vivo and in toto stain of the neural retina.

Animals↗
PubMed1989

Peptidergic and catecholaminergic fibers in the human corneal epithelium. An immunohistochemical and electron microscopic study.

Innervation of the clinically normal human corneal epithelium was investigated utilizing immunohistochemical and electron microscopic techniques. All corneal epithelial sheets examined demonstrated neuron specific enolase (NSE: a non-specific marker for neural elements), calcitonin gene-related peptide (CGRP: a putative marker for sensory fibers), and tyrosine hydroxylase (TH: a marker for catecholaminergic nerves) immunoreactive fibers. NSE, CGRP, and TH fibers formed a dense basal epithelial plexus. The CGrp fibers tended to have beaded profiles, while TH fibers were smooth. Numerous free nerve endings originating from the basal epithelial plexus og NSE and CGRP fibers terminated throughout the thickness of epithelium. The densities of fibers in the basal epithelial nerve plexus were: NSE greater than CGRP greater than TH. Transmission electron microscopy demonstrated two types of epithelial nerve fibers, one containing large dense-core vesicles and another small dense-core vesicles. Both types contained clear vesicles. These large and small dense-core vesicle fibers appeared to correspond to the CGRP and TH immunoreactive fibers, respectively. These results provide morphological baseline data on the normal sensory and sympathetic corneal epithelial innervation.

Adult↗
PubMed1989

Intraretinal transplantation for rod-cell replacement in light-damaged retinas.

Blindness from retinal disease is often the consequence of extensive damage to the photoreceptor cell population, while other cell types which form the neural retina are relatively spared. In this setting, transplantation of photoreceptor cells could offer hope for the restoration of some degree of visual function. We tested the feasibility of this approach by transplanting immature retinal cells into the eyes of adult rats affected by late stage phototoxic retinopathy, which are almost totally devoid of photoreceptor cells. Dissociated neuroretinal cells from newborn rats were injected into the hosts' retinas. These cells were labelled with the fluorescent tracer Fast-blue for identification within the host eye. Survival time ranged from 3 to 100 post-transplantation days. Fundus examination of light-irradiated eyes showed pallor caused by a considerable reduction of the retino-choroidal vascular bed after light irradiation. Histologically the hosts exhibited decimation of the elements forming the outer layers throughout the entire retina. As visualized by light and electron microscopic procedures, we report the differentiation of clusters of transplanted photoreceptor cells, and the integration of these cells within the adjacent areas of the host retina. Fluorescence microscopy showed these clusters to be formed by fluorescently labelled cells developing in intimate contact with the unlabelled host retina. Electron microscopically it was possible to determine that these photoreceptors had established synaptic contacts. These observations indicate that successful transplantation of immature retinal cells is feasible into adult eyes that have suffered extensive retino-choroidal damage. These findings also support the concept that retinal transplantation is a procedure which may open new avenues into the study of retinal repair.

Animals↗
PubMed1989

Corneal and conjunctival changes in congenital erythropoietic porphyria.

Penetrating keratoplasty and conjunctival resection were performed on a 53-year-old woman with confirmed congenital erythropoietic porphyria. Corneal and conjunctival tissue samples, studied by light and electron microscopy, revealed inflammatory cells and a reduced keratocyte population. Vessels within the conjunctival and corneal stroma displayed a thickened basement membrane. Microfibrillar material was seen in the extracellular spaces of the conjunctival stroma. These changes are similar to those reported for ultraviolet light-exposed skin of porphyria patients. The Descemet's membrane lacked the normal fetal and postnatal banding. It presented as a homogeneous layer, consisting of uniform, densely packed collagen fibers, which suggests endothelial damage in utero. The corneal endothelium was severely damaged.

Conjunctiva↗
PubMed1988

Intraretinal transplantation of fluorescently labeled retinal cell suspensions.

Dissociated cell suspensions of neonatal neural retina, labeled with the fluorescent dyes Fast blue or Fluoro-gold, were transplanted into the retina of normal adult rats or of rats affected by late stage phototoxic retinopathy. Light microscopy showed good survival, differentiation, and integration of the transplants, as well as permanence of the label up to 100 days. The results indicate that the transplantation of dissociated, fluorescently labeled retinal cells has a number of advantages over the transplantation of solid fragments of retinal tissue, previously performed by ourselves and others. The following are some of the most immediate procedural advantages: the number of transplanted cells can be assessed, the transplanted cells are in a more intimate contact with the host tissue and therefore integrate better with the host, and the fluorescent tags permit precise determination of the survival and distribution of the transplanted cells.

Amidines↗