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Biomedical subjects

D B Chandler

Publications and source records attributed to D B Chandler.

At least 37 records · Page 2Linked to original sources
PubMed1988

Quantitation of corneal neovascularization using computerized image analysis.

We have developed a method for quantitating corneal neovascularization, induced in anesthetized rats by silver nitrate/potassium nitrate cauterization, using a LeMont OASYS video input image analyzer. Corneal vessels are visualized by perfusing the upper half of deeply anesthetized animals with a mixture of 10% india ink, 11% gelatin in lactated Ringer's solution. The eyes are then rapidly cooled using a stream of compressed dichlorodifluoromethane (Freon) to solidify the gelatin mixture. Magnified images of flat preparations of the corneas are acquired using a television camera attached to a dissecting microscope. The images are electronically converted to digital form and the digitized data are stored in the image analyzer. The area of the cornea and blood vessels are independently determined by analyzing the digitized data as discrete values of varying shades of gray (gray-scale analysis). The area and gray scale of the injury and its distance from the corneoscleral limbus can also be measured to determine variability of location and intensity of the injury in different animals. This technique allows the area occupied by new blood vessels during studies on corneal neovascularization in rats to be rapidly quantitated.

Animals↗
PubMed1988

Alveolar macrophage subpopulations' responsiveness to chemotactic stimuli.

Recent data suggest that alveolar macrophages are a heterogeneous group of cells with several subpopulations. This study was undertaken to determine if there is heterogeneity among rat alveolar macrophage subpopulations ability to respond to chemotactic stimuli. Alveolar macrophages were harvested by bronchoalveolar lavage and fractionated into density-defined fractions by centrifugation through a continuous isoosmotic gradient of colloidal silica. Unfractionated and density-defined alveolar macrophages were then characterized as to their ability to migrate towards F-Met-Leu-Phen and zymosan-activated serum. Alveolar macrophages of density 1.083-1.097 gm/ml were found to have the greatest migrational movement toward F-Met-Leu-Phen, which was higher than the unfractionated population. In contrast, 2 peaks in alveolar macrophage subpopulations migrational movement towards zymosan-activated serum were noted that were lower than the unfractionated population. These results demonstrated that alveolar macrophages are heterogeneous in their migrational ability towards the chemotactic stimuli F-Met-Leu-Phen and zymosan-activated serum and that there may be a cooperative interaction between the subpopulations that affects macrophage migrational ability.

Animals↗
PubMed1987

Prostaglandin synthesis and release by subpopulations of rat alveolar macrophages.

Alveolar macrophages are the primary phagocytic cell of lung, but are also capable of a variety of other functions, which include initiating or modulating inflammatory and immune responses through the production of soluble mediators. One such group of mediators is the eicosanoids. Further, recent data indicate that alveolar macrophages are not functionally homogeneous, but are heterogeneous with several subpopulations that differ both morphologically and functionally. Considering the apparent importance of prostaglandin synthesis and release in inflammatory and immune responses, the current study was undertaken to determine whether alveolar macrophage subpopulations differ in their ability to synthesize and release prostaglandin (PG) E, PGI2, and thromboxane A2 after stimulation by calcium ionophore A23187, zymosan, or aggregated IgG. Alveolar macrophages were harvested by bronchoalveolar lavage and were separated into 18 density-defined fractions. Density-defined alveolar macrophages (DD-AM) showed marked heterogeneity in prostaglandin synthesis and release. Maximal PGE synthesis and release was seen as a single peak after calcium ionophore A23187 and zymosan stimulation. In contrast, two peaks in PGE synthesis were seen after aggregated IgG stimulation. PGI2 synthesis was seen as a single peak generated by different DD-AM after calcium ionophore A23187 and zymosan. In contrast, aggregated IgG stimulation of subpopulations exhibited uniform synthesis and release of PGI2. Thromboxane A2 synthesis and release was maximal from a broad range of various DD-AM after calcium ionophore A23187, zymosan, and aggregated IgG stimulation. The results demonstrate that DD-AM are heterogeneous in ability to synthesize and release prostaglandins which is dependent on the stimuli. Therefore, specific subpopulations of alveolar macrophages may be central to the control of the pulmonary inflammatory response through specific eicosanoid synthesis and release.

Animals↗
PubMed1987

Improvement in efficacy of corticosteroid therapy in an animal model of proliferative vitreoretinopathy by pretreatment.

Intraocular injection of the corticosteroid triamcinolone acetonide reduces the incidence of retinal detachment in rabbit eyes injected with tissue-cultured fibroblasts. When the steroid was injected simultaneously with the cells, a reduction of retinal detachment from 93% (control) to 75% (treated) was achieved on day 28. When the steroid was injected 24 h preceding cell injection, the reduction of retinal detachment was from 85% (control) to 43% (treated). The development of retinal detachment is caused by proliferation of injected fibroblasts. Reduction of this proliferation is probably achieved partially through direct inhibition of mitosis, but more important may be the reduction of the reactive inflammatory process.

Animals↗
PubMed1987

Classification of the stages of proliferative vitreoretinopathy in a refined experimental model in the rabbit eye.

Eighty-four rabbit eyes injected intravitreously with tissue-cultured fibroblasts following gas compression of the vitreous were examined clinically over a period of 1 month. Detailed clinical descriptions of the extent of retinal changes were recorded. Clinical landmarks were determined and arranged into a new classification of this model of proliferative vitreoretinopathy (PVR). The proposed classification will allow easier communication between research groups using this model to study the treatment and prevention of PVR.

Animals↗
PubMed1987

Effects of dietary fats on bleomycin-induced pulmonary fibrosis.

Bleomycin treatment has been used for the experimental induction of pulmonary fibrosis, but the mechanisms involved are poorly understood. Since alterations in the levels of certain fatty acid metabolites have been associated with bleomycin-induced lung injury, we examined the effects of different dietary fats on the development of bleomycin-induced pulmonary fibrosis. Weanling rats were raised on standard laboratory feed or a diet consisting of a fat-free powder to which was added either coconut oil or beef tallow (25% w/w). After 8 weeks of feeding, animals received either 1.5 units bleomycin or an equivalent volume of saline intratracheally. Bleomycin treatment resulted in significant increases in total lung hydroxyproline content in the groups fed the standard lab diet (p less than 0.001) and beef tallow diet (p less than 0.001), but not in the group receiving the coconut oil diet. Furthermore, the lung hydroxyproline content in bleomycin-treated animals was less with the beef tallow diet compared with standard lab feed (p less than 0.05). Bleomycin treatment resulted in an increase in thiobarbituric acid-reactive products, an index of lipid peroxidation, in lungs from animals fed the standard lab diet, but not in the other diet groups. The percentage of diseased lung, as determined by morphometric analysis, was increased in bleomycin-treated animals from all diet groups (p less than 0.05). We conclude that alterations in dietary fats can reduce the severity of pulmonary fibrosis resulting from bleomycin treatment. Possible mechanisms for this effect include alterations in eicosanoid metabolism or changes in immune or effector cell function.

Animals↗
PubMed1987

Scanning electron microscopy of microcorrosion casts: applications in ophthalmologic research.

In light of the complicated nature of the ocular vasculature, it has been difficult to define the normal ocular anatomy by reference to two-dimensional tissue sections. Since it provides three-dimensional replicas, scanning electron microscopy (SEM) of vascular corrosion casts has therefore been an invaluable addition to the study of ocular vasculature. This technique also often permits identification of a normal vessel's arterial, venous, or capillary nature by its surface features. In addition, this technique is finding increased use in defining anatomical features of human vascular disease and is especially well suited for the study of experimental neovascularization as it relates to the eye. This paper reviews the application of SEM of microscopic casts to the study of normal and diseased ocular vessels, as well as the contribution of this method to studies of experimental ocular neovascularization.

Animals↗
PubMed1986

Fractionation of rat alveolar macrophages by isopycnic centrifugation: morphological, cytochemical, biochemical, and functional properties.

Studies on alveolar macrophages have usually been performed on a single cell suspension obtained by lung lavage. However, recent evidence on the diversity of functions of the alveolar macrophage suggests that the macrophage is not a single population, but one composed of several subpopulations of macrophages. One approach toward determining if alveolar macrophages are heterogeneous would be to separate subpopulations based on density. To accomplish this, we developed a continuous gradient of iso-osmotic colloidal silica (Percoll) that separated alveolar macrophages from Fischer 344 rats into 18 density-defined subpopulations. The density-defined alveolar macrophage subpopulations were then characterized and were shown to be significantly different based on morphological, cytochemical, biochemical, and functional analysis. The results of this study suggest that alveolar macrophages are heterogeneous and that a continuous iso-osmotic gradient of colloidal silica is an efficient and reproducible method for separating subpopulations.

Animals↗
PubMed1986

A refined experimental model for proliferative vitreoretinopathy.

Animal models of proliferative vitreoretinopathy (PVR) in which the intact vitreous is injected with large numbers of tissue cultured fibroblasts do not accurately represent the disease as it is found in humans. A refined model of PVR is presented, in which the vitreous is compressed and partially detached using intravitreally injected perfluorpropane, followed by injection of 25,000 homologous fibroblasts. Proliferation occurred on the retinal surface, causing retinal detachments with the same frequency as models using greater numbers of cells.

Animals↗
PubMed1986

Production of arachidonic acid metabolites by endothelial cells in hyperoxia.

This study investigated the response of bovine pulmonary artery endothelial cells to incubation in hyperoxia (95% O2-5% CO2). Changes in cell number and morphology, release of lactate dehydrogenase, and production of arachidonic acid metabolites were assessed during continuous exposure of confluent endothelial monolayers to air (air-5% CO2, "controls") or O2 (95% O2-5% CO2, "O2-exposed") for periods of 12-72 h. Control monolayer cell numbers remained constant (approximately 2,000,000 cells/flask), whereas the number of cells in O2-exposed monolayers decreased progressively to 30% of controls (P less than 0.01) by 72 h. As assessed by radioimmunoassay, both control and O2-exposed cells produced the prostacyclin metabolite, 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), and prostaglandin F2 alpha (PGF2 alpha), but no thromboxane metabolite (TxB2) was detected. The O2-exposed cells released significantly more 6-keto-PGF1 alpha and PGF2 alpha than control cells when apparent net production rates over the entire 72-h period were compared. In addition, both control and O2-exposed (48 h) endothelial monolayers released immunoreactive leukotriene B4 (LTB4) on stimulation with calcium ionophore (10 microM A23187). As with the cyclooxygenase products, O2-exposed cells released more immunoreactive LTB4 than did controls. Both cyclooxygenase and lipoxygenase metabolites of arachidonic acid are released by cultured endothelial cells during the development of O2 toxicity.

Animals↗
PubMed1986

Studies of membrane receptors and phagocytosis in subpopulations of rat alveolar macrophages.

Recent data suggest that alveolar macrophages may be a heterogeneous group of cells with several subpopulations. This study was undertaken to determine if there is heterogeneity among rat alveolar macrophages with respect to receptors for zymosan, immunoglobulin, and complement. In addition, avidity for the immunoglobulin IgG was defined by opsonizing sheep red blood cells (SRBC) with different amounts of IgG. Alveolar macrophages were harvested by bronchoalveolar lavage and separated into 18 density-defined fractions by centrifugation through a continuous isosmotic gradient of colloidal silica. All density-defined alveolar macrophages exhibited similar abilities to attach zymosan and SRBC opsonized with a high level of IgG. In contrast, macrophages of a density of 1.046 g/ml to 1.075 g/ml exhibited high receptor activity capable of attaching and phagocytizing SRBC opsonized with small amounts of IgG. Similarly, attachment indices for complement-coated SRBC exhibited a peak activity among fractions exhibiting similar high avidity receptors for IgG. These results demonstrate the functional heterogeneity with respect to IgG and complement receptors among density-defined rat alveolar macrophage subpopulations.

Animals↗
PubMed1986

Studies of membrane receptors, phagocytosis, and morphology of subpopulations of rat lung interstitial macrophages.

Recent data suggest that pulmonary macrophages may be heterogeneous. Several studies have demonstrated that alveolar macrophages are functionally and biochemically heterogeneous. In addition, interstitial macrophages, which are believed to be the precursors to alveolar macrophages, have been suggested to be heterogeneous. Therefore, this study was undertaken to determine if density-defined interstitial macrophages (DD-IM) are heterogeneous with respect to receptors for zymosan, immunoglobulin, and complement as well as morphologically. Furthermore, avidity for IgG was defined by opsonizing sheep red blood cells (SRBC) with different amounts of IgG. Interstitial macrophages were harvested and separated into 18 DD-IM subpopulations by centrifugation through a continuous iso-osmotic gradient of colloidal silica. Interstitial macrophages showed marked heterogeneity in cellular volume. Furthermore, macrophages of density 1.046 to 1.075 g/ml exhibited higher receptor activity capability of attaching and phagocytizing SRBC opsonized with small amounts of IgG and towards zymosan. All DD-IM exhibited similar abilities to attach complement-coated SRBC. These results demonstrate the functional heterogeneity of interstitial macrophages with respect to IgG and zymosan.

Animals↗
PubMed1986

Glio-vascular architecture in the rabbit retina.

Differences between the rabbit and human retinal circulation, and the use of the rabbit eye in a model of experimental retinal neovascularization, necessitates a complete description of the normal vascular structure in the rabbit and its relationship to adjacent tissue, particularly the glia. The gliovascular relationships in the rabbit were studied by scanning and transmission electron microscopy. Utilizing gas compression of the vitreous to clear the wings of overlying vitreous, the authors were able to make detailed observations of retinal surface by scanning electron microscopy. Glial sheaths surrounding a large number of medium size and smaller vessels were observed. The glial sheaths contained cells which were ultrastructurally similar to Müller cells. No isolated glial tufts were observed in avascular areas. Finally, small, smooth-surfaced cells were found adjacent to many vessels. The exact nature and function of these cells remains unknown.

Animals↗
PubMed1985

The effect of triamcinolone acetonide on a refined experimental model of proliferative vitreoretinopathy.

Animal models of proliferative vitreoretinopathy in which the intact vitreous body is injected with large numbers of fibroblasts do not resemble the human situation. Using a refined rabbit model of proliferative vitreoretinopathy in which the vitreous is compressed and partially detached from the retinal surface and small amounts of tissue-cultured homologous fibroblasts (25,000) are scattered over the vascularized part of the retina, we reevaluated the effect of intravitreally injected triamcinolone acetonide. We found that 2 mg of the corticosteroid reduced the incidence of retinal detachments from 90% to 56%. The effect was less than in previous models with intact vitreous. Large doses of the corticosteroid had no additional effect on the reduction of retinal detachments, indicating an optimal dosage of 2 mg. The effect of the corticosteroid on neovascularization was considerable; with 8 mg it could almost be prevented (reduction from 74% to 8%).

Animals↗
PubMed1985

Intraocular cyclophotocoagulation. Histopathologic evaluation in primates.

Intraocular cyclophotocoagulation with endoscopic visualization, following lensectomy and anterior vitrectomy, was performed on 14 eyes of eight rhesus monkeys. Two eyes received lensectomy and vitrectomy without laser treatment. One eye of each animal was studied one to eight months postoperatively, while the contralateral eyes were enucleated for study immediately after surgery. Histopathologic changes in the treated ciliary processes immediately after therapy included variable degrees of disruption in the epithelial layers and bleeding, while the late changes ranged from partial disruption of the epithelium and intrastromal pigment clumping to replacement of the processes by a fibrotic mass. The degree of these structural changes correlated reasonably well with the level of laser energy used and especially with the immediate, visible tissue alteration. These data may be useful in the development of clinical protocol for intraocular cyclophotocoagulation.

Animals↗
PubMed1985

Subretinal strands: ultrastructural features.

This report describes the histologic and ultrastructural features of 13 subretinal strands removed during vitreous surgery for retinal detachment with proliferative vitreoretinopathy. On the surface of the subretinal strands, retinal pigment epithelial cells were found that maintained their cellular characteristics. Inside the strand were modified pigment epithelial cells, fibroblasts, fibrocytes, myofibroblasts, macrophages, basal lamina material, fibrin, and often large amounts of collagen. In some strands, the basal lamina material was similar to the types found in Drusen and in the inner layer of bruch's membrane. Glial cells were rarely found in these strands.

Basement Membrane↗