Biomedical subjects

R S Baird

Publications and source records attributed to R S Baird.

At least 19 recordsLinked to original sources

PubMed1990

Determination of the interval during which one application of compound 48/80 to the rat conjunctiva influences the response to a second application.

We studied the effect of one application of compound 48/80 to the conjunctiva of the rat on the response to a subsequent challenge. Rats treated once showed conjunctival edema and marked degranulation of conjunctival mast cells. A second exposure to compound 48/80, applied after an interval of 24 h, produced slight clinical effects but had marked effects on conjunctival mast cells. Approximately 90% of the mast cells could no longer be observed by light microscopy. As the interval between initial challenge and rechallenge was increased, the clinical response returned, mast cells were again observable in normal numbers, and the extent of degranulation returned to approximately 50%. After an interval of 7 days, rats responded clinically as they had to the first application of compound 48/80. Although the number of mast cells in the conjunctiva was normal and extensive degranulation occurred, exocytosis was not observed. Thus some effects of the first application of compound 48/80 persisted for at least 1 week. Whether the effects observed depend upon the continued presence of compound 48/80 in the mast cell or granule membrane remains to be determined.

Analysis of Variance↗

PubMed1989

Ocular anaphylaxis induced in the rat by topical application of compound 48/80. Dose response and time course study.

In the present study we sought to develop a model of ocular anaphylaxis based on the topical application of compound 48/80 to the surface of the rat eye. Doses ranging from 50 to 1000 micrograms were found to produce graded edema of the conjunctiva and swelling of the lid. On histologic examination, 50 microns compound 48/80 produced no changes distinguishable from those in PBS-treated controls, 150 microns produced mild alterations, and 250, 500, and 1000 micrograms compound 48/80 produced a marked increase in degranulated mast cells and a mild influx of neutrophils. The time course of the response to 250 micrograms and 1000 micrograms of compound 48/80 was evaluated over a 72-h period. Both doses elicited epithelial damage. A mild reduction in the number of mast cell was seen at 6 h in rats receiving 250 or 1000 micrograms. The reduction persisted to 72 h in rats receiving 1000 micrograms. The number of neutrophils was increased at 1 and 6 h in eyes treated with 250 micrograms and at 1, 6, and 24 h in eyes treated with 1000 micrograms compound 48/80. The clinical and histologic changes induced by application of 250 micrograms compound 48/80 resemble those seen in patients with allergic conjunctivitis suggesting that a model of ocular anaphylaxis based on the topical application compound 48/80 will be clinically relevant and experimentally practical.

Administration, Topical↗

PubMed1989

Morphologic evidence that compound 48/80-challenged rat eyelid mast cells differ in their states of maximal degranulation.

To determine the uniformity of response by mast cells in the rat eyelid, doses of compound 48/80 ranging from 50 to 1,000 micrograms in a 10-microliters drop were applied to one eye of 30 male Sprague-Dawley rats. Phosphate-buffered saline (PBS) was applied to the other eye. Every mast cell was counted throughout microscopic slides of the tissue of the lower eyelids. Both the position and degree of degranulation of every mast cell in each slide were recorded on schematic representations of the lower eyelid. Before histologic examination, animals were observed for clinical signs of ocular anaphylaxis. Doses of 50 and 150 micrograms had no observable clinical effect. At greater doses, edema of the lids and conjunctiva increased with dose. Doses less than 250 micrograms had no significant effect on the number of mast cells or degree of degranulation. Doses of more than 250 micrograms induced degranulation in approximately 50% of the eyelid mast cells. The degree and pattern of degranulation did not change with doses greater than 250 micrograms. The morphology of degranulated mast cells treated with 1,000 or 250 micrograms of compound 48/80 was indistinguishable. We conclude that once maximal stimulation for degranulation is achieved, higher levels of compound 48/80 will not increase the level or change the type of degranulation. In addition, the maximal level of degranulation varies from one mast cell to the next. Mast cells in close proximity may differ markedly in their level of maximal degranulation, with responses ranging from no degranulation to severe degranulation with exocytosis.

Administration, Topical↗

PubMed1989

Response of rat conjunctival mast cells to multiple versus single applications of compound 48/80.

A single application of the mast cell secretagogue compound 48/80 to the surface of the rat eye induces significant histologic changes. Ocular anaphylaxis is usually the result of repeated, not single, exposures to allergenic substances. The response of conjunctival mast cells to repeated daily applications of compound 48/80 was, therefore, evaluated. Ninety rats received one dose of compound 48/80 or phosphate-buffered saline almost daily for 17 days. The frequency and degree of mast cell degranulation and the number of mast cells and other inflammatory cells in the subepithelial conjunctiva were determined histologically. The clinical response was most marked after one application of compound 48/80; repeated daily applications markedly reduced the clinical response. In eyes treated with multiple applications, 75% fewer mast cells were observable in the conjunctiva by light microscopy compared with phosphate-buffered saline treated eyes. Most mast cells were granulated; a few showed mild to moderate degranulation. Except for epithelial damage, no tissue injury was associated with multiple applications of compound 48/80. In contrast to conjunctivae subjected to a single application of compound 48/80, conjunctivae receiving multiple applications resembled that of phosphate-buffered saline controls.

Administration, Topical↗

PubMed1988

Dark-staining bodies in the conjunctival epithelium of rats after multiple topical challenges with compound 48/80.

Over a 17-day period, 96 Sprague-Dawley rats received approximately daily topical applications of compound 48/80 to the ocular surface of one eye and phosphate-buffered saline (PBS) to the other eye. On histologic examination, dark-staining bodies appeared in the conjunctival epithelium in all 48/80-challenged eyes after day 3. These epithelial dark bodies (EDBs) rarely appeared in PBS-challenged or in single-dose 48/80-challenged tissues. The EDBs, between two and 15 per 30 fields at x 1000 under light microscopy, were limited to the conjunctiva near the fornix rather than near or over the tarsal plate. We hypothesize that these EDBs are associated with repeated application of secretagogue to the conjunctiva.

Administration, Topical↗

PubMed1987

Effect of multiple applications of compound 48/80 on mast cells of rat conjunctiva.

We sought to determine the effect on rat conjunctival mast cells of chronic exposure to a degranulating agent. Compound 48/80 (250 micrograms in 10 microliter) was applied daily to the ocular surface of rats for a total of 13 treatments administered in 17 days. A single application of compound 48/80 was given to rats for comparison. Four groups of animals (6 in each group) were evaluated 1 or 48 h after the last application of compound 48/80 in both chronic exposure and single exposure studies. Although a single exposure to compound 48/80 induced significant degranulation of mast cells in animals observed 1 h after treatment, no significant degranulation of mast cells was observed 1 h after the last dose of compound 48/80 was given to rats whose conjunctiva had been chronically exposed to this degranulating agent. Thus, multiple applications of compound 48/80 attenuated the mast cell response to compound 48/80. This acquired tolerance to compound 48/80 was reflected in the lessened clinical signs in rats receiving repeated applications compared with those given a single application.

Animals↗

PubMed1986

Worm antigen-induced ocular anaphylaxis in rats infected with Nippostrongylus brasiliensis.

A model of topically induced conjunctival anaphylaxis has been developed. Male Sprague-Dawley rats were immunized by infection with 3000 Nippostrongylus brasiliensis larvae and challenged topically on the eye 4 weeks later. Application of worm antigen alone did not induce clinical (conjunctival edema) or histologic (mast-cell degranulation) signs of anaphylaxis. Topical challenge with antigen 15 min after topical application of dithiothreitol (DTT), a mucolytic agent, elicited conjunctival edema and mast-cell degranulation within the first hour after challenge. At 6 and 24 hr, no clinical change was evident and conjunctival mast cells had again become granulated. At none of the three intervals (1, 6 and 24 hr) was there a significant increase in neutrophils, lymphocytes, eosinophils or macrophages in tissues from DTT-pretreated, antigen-eyes. The present model of ocular anaphylaxis resembles the ocular component of human hay fever in that sensitization prior to challenge is essential, the antigen is presented topically to the ocular tissues, conjunctival edema is the clinical manifestation and mast cell degranulation characterizes the histologic changes.

Anaphylaxis↗

PubMed1986

Conjunctival basophil hypersensitivity in the guinea pig.

We have induced a basophil hypersensitivity reaction in the upper tarsal conjunctiva of the guinea pig by methods that induce a comparable basophil hypersensitivity reaction in the flank. The inflammatory cell infiltrate in this reaction contained large numbers of basophils and eosinophils with accompanying neutrophils and monocytes. Ocular tissue can serve as a priming site for systemic immunization and also for elicitation of a secondary flare after challenge with antigen. Very few inflammatory cells were observed in the cutaneous epithelium of either primary or secondary flares. In contrast, the mucosal stroma and epithelium contained large numbers of inflammatory cells (basophils, eosinophils, and neutrophils), suggesting directed cellular movement onto the ocular surface. The lesion of ocular basophil hypersensitivity in the guinea pig has features in common with two human eye diseases, vernal conjunctivitis and contact lens-associated giant papillary conjunctivitis. We hypothesize that the acute basophil hypersensitivity reactions of the conjunctiva are transformed into chronic inflammatory and proliferative states in vernal conjunctivitis and giant papillary conjunctivitis.

Animals↗

PubMed1985

Effects of eye rubbing on the conjunctiva as a model of ocular inflammation.

We assessed the effects of eye rubbing on the histologic characteristics and inflammatory cell infiltrate of the conjunctiva. The upper eyelids of 20 adult rats were rubbed during a five-minute period, and then the animals were killed immediately, or at four, eight, or 24 hours after trauma. One eye of each animal was rubbed; the unrubbed contralateral eye served as a control. Counts of mast cells, degranulated mast cells, and inflammatory cells (neutrophils, eosinophils, lymphocytes, plasma cells, and macrophages) were recorded from conjunctival samples from the upper eyelid. Immediately after eye rubbing the conjunctival epithelium was histologically disrupted and 50% of the mast cells showed evidence of degranulation. At four hours after trauma the increase in the number of neutrophils was more than 2,300%. Neutrophils were in the margins in the conjunctival vessels, had migrated into the substantia propria, and were aligned subjacent to the epithelial basement membrane; large numbers of neutrophils populated the epithelium. The four-hour stage was the most dramatic phase of inflammation that occurred from the eye rubbing. At 24 hours there was a significant increase in the number of macrophages. The numbers of lymphocytes, plasma cells, and eosinophils were not significantly changed throughout the study. Our findings demonstrate that eye rubbing histologically disrupts the epithelium and induces significant alteration in the inflammatory cell infiltrate of the conjunctiva. These changes may influence the course of ocular disease.

Animals↗

PubMed1985

Anaphylaxis of ocular adnexa induced by infection of anti-IgE antibody.

To examine the role in ocular tissue injury of anaphylaxis alone (as distinct from other mechanisms possibly present in a model involving immunization), a model of anaphylaxis was produced by injection of rabbit anti-rat IgE antibody into ocular adnexal tissues of rats. Adnexal swelling, seen within 15 min, disappeared by 6 hr. Vascular permeability and weight of adnexal tissues were increased at 0.5 hr and had returned to near normal levels by 6 hr. Histologic study revealed extensive degranulation of mast cells at 0.5 hr after injection and a return to normal by 24 hr. Neutrophils reached a level of 7400/mm3 at 6 hr and returned to normal by 24 hr. Macrophages accumulated by 24 hr in all tissues, including control eyes injected with normal serum. The similarity of results from this 'pure' model of anaphylaxis to results from a model produced by injecting antigen into ocular adnexal tissues of immunized rats suggests that anaphylactic mechanisms are responsible for the changes seen in the antigen-injected model.

Anaphylaxis↗

PubMed1985

Effect of anaphylaxis on conjunctival goblet cells.

Rats undergoing ocular anaphylaxis induced by systemic or local injection of antigen, topical application of antigen, or topical application of compound 48/80 were evaluated conjunctival goblet cell changes that might be related to anaphylaxis. The number of goblet cells in 1 micron, alkaline Giemsa-stained sections averaged 500/mm2 of epithelium in normal rats; this number was not significantly changed in any of the experimental groups. Goblet cells in control rats occasionally demonstrated evacuation of their contents (less than 1%) or upward displacement of the intracellular bolus of mucus (about 1%); these percentages were not increased in anaphylaxis. Topical application of 2.0 micrograms of histamine induced an intracellular displacement of mucus in both control animals and animals undergoing anaphylaxis. These findings suggest that in ocular anaphylaxis the amount of histamine released may be insufficient to produce such intracellular changes. Our results indicate that in ocular anaphylaxis in the rat, there is no light microscopic evidence of increased mucus discharge from conjunctival goblet cells. Increased mucus in secretions of patients with ocular allergic syndromes may not be attributable to anaphylactic mechanisms alone.

Administration, Topical↗

PubMed1984

Late-phase reactions in ocular anaphylaxis in the rat.

We assessed whether anaphylactic stimulation of rat ocular tissue produces a late-phase reaction at the histologic level. Clinical changes of swelling and redness started within minutes, peaked at about 20 min, and then subsided. Neutrophils increased at 1/2 hr after stimulation, peaked at 6 hr, and subsided to normal at 24 hr. Eosinophils reached a significant increase at 6 hr. Compaction of vessel contents was present at 1/2 hr; vessels were normal thereafter. Extravasated red blood cells and debris in the tissue were prominent at 6 hr. Macrophages had accumulated significantly at 6 hr and maintained that level at 24 hr. Any effect of anaphylaxis on macrophage accumulation was masked because control-injected ocular tissue also showed an accumulation of macrophages at 24 hr. Our results demonstrate that in ocular tissue, as in skin, the early acute phase of immediate hypersensitivity is but one stage of a multiphasic reaction.

Anaphylaxis↗

PubMed1983

Ultrastructure of mast cells in rat ocular tissue undergoing anaphylaxis.

In a study of ocular tissues undergoing anaphylaxis, in uninjected rats most mast cells contained electron-dense granules with no discernible internal structure. A few cells showed varying degrees of swelling of the matrix granules. In rats injected with normal rabbit serum, more mast cells showed swelling of the granule matrix and a few showed extensive swelling of nearly all granules. Mast cells from rats undergoing anaphylaxis by either anti-IgE or antigen injection showed membrane and granule alterations: extensive dendritic processes, fusion of granule membranes, fusion between granule and plasma membranes, and disruption of plasma membranes. Communication was established between the exterior of the cell and contents of individual granules of cisternae formed by several fused granules. The matrix of nearly all granules was extensively swollen.

Anaphylaxis↗

PubMed1983

Macrophages in ocular tissues of rats. Determination of their number after local anaphylaxis and other procedures.

The number of macrophages in rat ocular tissues was determined, with the tip of the eyelid containing about 3,000 macrophages per cubic millimeter, which is similar to the number of mast cells at this site. Fewer macrophages were present in orbital tissues and conjunctiva. Macrophages accumulated in ocular tissues of immunized rats injected locally with antigen, but the number did not exceed that observed in antigen-injected controls. Injection of various fluids into ocular tissues, but not the trauma of needle punctures alone, stimulated a marked accumulation of macrophages. Thus, the response to nonspecific stimuli masked the macrophage response to antigen-induced, ocular anaphylaxis.

Anaphylaxis↗

PubMed1983

Sequence of mast-cell changes in ocular anaphylaxis.

Ocular anaphylaxis was produced in rats by the injection of egg albumin into ocular adnexal tissues of immunized animals. Mast cells in the tip of the eyelid from normal, antigen-injected control and antigen-injected immunized rats were examined at 1/2, 1, 6 and 24 hr. The number of cells and their morphology was determined. All three groups had the same number of mast cells at all time intervals. Extensive mast-cell degranulation was observed at 1/2 and 1 hr in lid tips of immunized, antigen-challenged rats. By 24 hr, the mast cells appeared to have 'healed' and regranulated, although it was possible to distinguish these cells from mast cells of normal animals. We conclude that under certain conditions, mast cells participating in ocular anaphylaxis are not destroyed but survive and regenerate granules within the first 24 hr.

Anaphylaxis↗

PubMed1981

Density of goblet cells in vernal conjunctivitis and contact lens-associated giant papillary conjunctivitis.

Using light microscopy, the density of goblet epithelial cells was determined in the conjunctival epithelium of ten patients with vernal conjunctivitis, ten patients with contact lens-associated giant papillary conjunctivitis, and ten normal subjects. The median density was 13,000/cu mm for vernal conjunctivitis, 11,000/cu mm for giant papillary conjunctivitis, and 11,000/cu mm for normal subjects, a statistically insignificant difference. Increased mucus in vernal conjunctivitis and contact mucus in vernal conjunctivitis and contact lens-associated giant papillary conjunctivitis is not accounted for by an increased density of goblet cells per cubic millimeter. It is probably caused by the greater surface area and thickness of epithelium, with a concomitant increase in the total number of goblet cells and increased mucus from nongoblet epithelial cells.

Adolescent↗

PubMed1981

Percentage of degranulated mast cells in vernal conjunctivitis and giant papillary conjunctivitis associated with contact-lens wear.

Using light microscopy, we determined the percentage of granulated and degranulated mast cells in sections of tissue from ten persons with vernal conjunctivitis, ten with giant papillary conjunctivitis associated with contact-lens wear, and ten normal subjects. Tissues from both groups of patients had a significantly higher percentage of degranulated mast cells (greater than 80%) than did normal tissue (less than 25%). The fully granulated mast cells in the three groups did not appear morphologically different, nor did the degranulated mast cells in the three groups. The percentage of degranulated mast cells in vernal conjunctivitis did not differ significantly from that in giant papillary conjunctivitis associated with contact-lens wear. The histamine level in the tears of patients with vernal conjunctivitis, which is four times higher than that of normal subjects and that of patients with giant papillary conjunctivitis associated with contact-lens wear, cannot be explained by a difference in the percentage of degranulated cells detectable by light microscopy.

Adolescent↗

PubMed1981

Ocular anaphylaxis: induction by local injection of antigen.

A model of local ocular anaphylaxis has been developed in the rat. Erythema, oedema, and enhanced retention of radioiodinated rat serum albumin ([125I]-RSA) were noted in ocular adnexal tissues of immunized rats within 5 min of injection of antigen; these changes reached a maximum 15 min after antigen injection. Erythema, oedema, and retention of [125I]-RSA subsided to baseline levels 1--6 hr after challenge. A significant increase in weight of ocular adnexal tissues was seen within 15 min after challenge. The weight increase reached a maximum at 45 min and persisted through 6 hr. Weight approached baseline values by 24 hr. Although antigen was injected into the ocular adnexa and not directly into the globe, the globes of the antigen-injected eyes of immunized rats underwent anaphylaxis, possibly because of absorption of antigen through the sclera. In addition, the adnexa and globes of the contralateral eyes, which did not receive antigen, also underwent anaphylactic changes. These changes were not as marked as those observed in the antigen-injected tissues, but followed the same time-course of development. We conclude that anaphylaxis can be locally induced in ocular tissues, that the onset of anaphylaxis is within minutes, and the effects last for at least 24 hr.

Anaphylaxis↗