Biomedical subjects

H B Collin

Publications and source records attributed to H B Collin.

At least 37 records · Page 2Linked to original sources

PubMed1988

Paraproteinemic crystalline keratopathy.

Paraproteinemic crystalline keratopathy is an uncommon complication of multiple myeloma and other plasma cell dyscrasias. A case of 16 years' duration was associated with an IgG kappa monoclonal gammopathy and recurrent uveitis. The corneal changes were unusually extensive and distributed throughout all corneal layers. The deposits consisted of diffuse, small, polymorphic aggregates, which were iridescent in the superficial cornea, mat elsewhere, and associated with a diffuse stromal haze; specular microscopy showed additional features. Both corneas were thickened. The deposits failed to stain histochemically, except patchily with Masson Trichrome. There was extensive immunohistochemical labeling for IgG, kappa, and surprisingly, lambda. Ultrastructurally, pleomorphic deposits were found in every corneal cell; paracrystalline deposits with internal banding were seen only in the basal epithelium. Keratocytes and endothelial cells were damaged and reduced in number. Disease recurred in a corneal graft. Three main types of paraproteinemic keratopathy can be distinguished. The deposits probably represent various metabolic products of the monoclonal protein. This is not necessarily a benign condition; hematologic control may be necessary on purely ophthalmological criteria.

Corneal Opacity↗

PubMed1988

The cornea of the sand lance, Limnichthyes fasciatus (Creeiidae).

The sand lance, Limnichthyes fasciatus, is a small fish, 15-30 mm in length, found on the Great Barrier Reef. The eyes, which are not covered by a spectacle, are externally placed, move independently, and measure about 1 mm in diameter. The cornea, unusual even in the teleost world, is about 0.14 mm thick, which represents one-seventh of the length of the eye. The layers of the cornea include an epithelium with a complex pattern of surface microplicae, a grossly enlarged basal cell layer, and a thick basement membrane. Structures (iridophores), which may represent the vestigial remnants of a secondary spectacle, are present in the peripheral corneal epithelium. The stroma, which has no Bowman's layer, is composed of lamellae of collagen fibrils but contains no keratocytes. Posterior to the stroma is a thick (0.1 mm) cellular layer that may represent the autochthonous layer seen in some teleost species. An iridescent layer consisting of approximately 70 parallel cytoplasmic plates oriented at right angles to the visual axis lies anterior to a thick Descemet's membrane. There is a single layer of endothelial cells on the posterior surface.

Animals↗

PubMed1988

The morphology of the retina and lens of the sandlance, Limnichthyes fasciatus (Creeiidae).

The sandlance, Limnichthyes fasciatus (Creeiidae), is a small teleost (30 mm in length), which lives beneath the sand. It has minute dorsally placed eyes (1.04 mm in diameter), which move independently of one another. The structure of the retina and lens was examined by both light and electron microscopy. A deep convexiclivate fovea lies on the visual axis of the eye, and regional increases in photoreceptor and ganglion cell densities occur within the area surrounding the foveal depression. The sandlance possesses a pure cone fovea, with a regular square mosaic of a single cone bordered by four equal double cones distributed over most of the retina. Rods are rare and are distinguishable from cones on ultrastructural morphology. A pigmented choriocapillaris extends behind the retina, closely apposing the retinal pigment epithelial cell layer and Bruch's membrane. Surrounding the optic nerve, and adjacent to the choriocapillaris, is a vascularised, horseshoe-shaped choroidal gland, or rete mirabile. A small system of vitreal blood vessels from the hyaloid artery near the optic nerve, supplies the large number of ganglion cells, arranged in up to five sub-laminae, within the ganglion cell layer. The retina is jacketed by an uveal argentea within the sclera. This argentea contains plates of guanine crystals, oriented with their flat surfaces approximately perpendicular to the incident light path, and discrete bundles of melanosomes apposing the sclera. A non-spherical lens, previously described only in deep-sea teleosts, was found, and its refractive properties are discussed in relation to the deep pit fovea.

Animals↗

PubMed1987

The effects of hypertonic salicylate on neutrophil migration and vascularization in the rat cornea.

Thermal cauterization of the center of the rat cornea results in emigration of neutrophils into the extravascular limbal tissue and blood vessel growth into the cornea. In this study, 1.0 M sodium salicylate, 1.0 M sodium chloride, and ointment vehicle were administered to normal and cauterized rat corneas for periods of 6, 48, and 144 h. When applied to the normal cornea, salicylate resulted in a marked increase in neutrophils in the limbal tissue at 6 h, but an inhibition at 48 h. Similarly, for the cauterized corneas, administration of salicylate increased the extent of neutrophil emigration at 6 h, but this effect was not sustained at 48 h. Neither vehicle nor sodium chloride had any effect on the extravascular neutrophil population. After 6 days, administration of the vehicle resulted in a slight increase in vascular growth into the cornea, whereas sodium salicylate caused a decrease. These findings indicate that hypertonic (1 M) sodium salicylate does not inhibit the emigration of neutrophils from limbal vessels of cauterized rat corneas, but does appear to have a cytotoxic effect on the tissues and on blood vessel endothelial cells.

Animals↗

PubMed1987

In vivo effects of thimerosal on the rabbit corneal endothelium: an ultrastructural study.

To assess ultrastructural alterations to the corneal endothelium, eye drops containing vehicle alone or vehicle plus 0.004% thimerosal with or without 0.1% disodium ethylenediaminetetraacetate (Na2EDTA) were administered hourly over a 2-day period to rabbit corneas in vivo. Twenty of the corneas received a 5-mm keratectomy that removed epithelium and superficial stroma and 10 corneas were left intact. The vehicle alone had no effect on the endothelium of normal corneas. Thimerosal drops with or without Na2EDTA caused some clarification of the cytoplasm and dilatation of the endoplasmic reticulum of endothelial cells. The mitochondria had dilated cristae and membrane condensations. After keratectomy and vehicle only drops, the central endothelium showed a marked increase in microvilli and mitochondrial changes. Addition of either thimerosal or thimerosal plus Na2EDTA resulted in a slight decrease in membrane activity but an increase in intracellular edema and dilatation and damage to organelles. The peripheral areas were less affected than the center. Although the endothelium was stressed, most changes were considered reversible.

Animals↗

PubMed1986

Effects of salicylate and steroid on neutrophil migration and corneal blood vessel growth.

Cauterization of the cornea results in emigration of neutrophils from the limbal blood vessels into the corneal tissue. Blood vessel proliferation follows, the stimulus for which is unknown. In this study, 0.1 M sodium salicylate drops administered topically to cauterized rat corneas over a 48-h period had an inhibitory effect on the migration of neutrophils from the limbal vessels 6 h after injury, but this was not maintained at 48 h. After 6 days of treatment, the salicylate had no effect on vessel growth into the cauterized rat cornea. Application of prednisolone disodium phosphate ointment to cauterized corneas also inhibited neutrophil migration at 6 h, but increased the extravascular neutrophils at 48 h. After 6 days of treatment, corneal blood vessel growth was significantly reduced. It was concluded that there is no consistent relation between the number of extravascular neutrophils at the corneal limbus and the extent of corneal blood vessel growth.

Animals↗

PubMed1986

Ultrastructural changes to corneal stromal cells due to ophthalmic preservatives.

Normal and keratectomised rabbit corneas received drops containing preservatives over a two day period. All preservatives investigated caused some change in the morphology of the stromal keratocytes, particularly in the absence of the anterior epithelial barrier. Thimerosal (0.004%) or disodium ethylenediaminetetraacetate (0.1% Na2EDTA) produced only minimum change. Chlorbutanol (0.5%) applied to intact corneas resulted in swelling of the cytoplasm and occasionally breaks in the external cell membrane, whilst in the keratectomised corneas some mitochondria showed swelling and distortion of cristae. In the normal cornea, benzalkonium chloride (0.02% or 0.01% with 0.1% Na2EDTA) resulted in intra and extracellular oedema and contraction of keratocytes. On removal of the superficial layers, there was extensive disruption of mitochondria, other organelles and outer cell membranes resulting in total destruction of some cells. Benzalkonium chloride should not be used on corneas with abnormalities of the epithelium.

Animals↗

PubMed1986

Ultrastructural changes to the corneal endothelium due to benzalkonium chloride.

Ten normal and 20 keratectomised corneas received hourly drops of vehicle with or without benzalkonium chloride (0.02% BAC or 0.01% BAC plus 0.1% disodium ethylenediaminetetraacetate) over the daylight hours of 2 days (18 applications). When applied to the intact cornea, BAC with or without Na2EDTA caused only slight clarification of the endothelial cytoplasm, whilst in a few mitochondria the cristae were displaced. In the keratectomised corneas receiving BAC, the majority of mitochondria of the central endothelial cells were pale and swollen or even disrupted. Many contained aggregations of membranous material either within the mitochondrion or at its outer membrane. The peripheral endothelium was much less affected than the central area of endothelium behind the keratectomy. These results suggest that BAC should not be administered to corneas in which the anterior epithelial barrier is incomplete.

Animals↗

PubMed1982

An accurate in vitro assessment of the corneal endothelium.

This study describes an in vitro preparation of isolated corneal endothelium, in which silver is used to stain the endothelial cell outlines. This permits high-power light microscopy and accurate measurement of individual cell characteristics. The photographed cell areas measured with a planimeter and mean areas and cell densities were calculated. A total of 40 individual cells were measured from each of 11 guinea-pig corneas to give a mean cell area of 293 micro 2 and a mean cell density of 3413 cells/mm2. These figures are similar to findings for young human subjects. The accuracy and repeatability of the method were examined and an analysis of variance was carried out to ascertain the effects to interaction between zones and eyes within individual guinea pigs. Differences between eyes were rarely significant and peripheral cells were not found to be significantly different in area from central cells.

Analysis of Variance↗

PubMed1982

The effect of ophthalmic preservatives on the healing rate of the rabbit corneal epithelium after keratectomy.

Most ophthalmic preparations contain preservatives. Some are toxic to healthy corneal epithelium or retard healing of corneas from which part or all of the epithelium has been removed leaving an intact basement membrane. In this paper, the effect of commonly used concentrations of benzalkonium chloride (BAC), thimerosal, and ethylenediaminetetracetic acid (EDTA) upon the healing of rabbit corneas after partial lamellar keratectomy is investigated. This model has not been used previously for a study of preservative toxicity. Thimerosal (0.004%), BAC (0.01%), or EDTA (0.1%) applied four times per day had no significant effect on the corneal healing or epithelial migration rates. A slight retardation occurred when BAC (0.01%) and EDTA (0.1%) were used together, while healing failed to occur as long as benzalkonium chloride (0.02%) was administered.

Animals↗

PubMed1982

The effect of ophthalmic preservatives on the shape of corneal endothelial cells.

The mean area (293.6 +/- 53.6 micrometers 2) and perimeter (65.5 +/- 5.8 micrometers) of individual cells were determined from the photographed endothelium of a total of 54 guinea pig corneas, after staining with silver nitrate and removal of the epithelium and stroma. In addition a quantitative assessment of cell shape S (= P2/A) was calculated. The mean cell density (3406 +/- 619 cells per mm2) was similar to that for young humans, and the S value (14.76 +/- 0.73) was as expected for slightly irregular hexagonal and pentagonal shapes. Incubation of the corneas in glutathione-bicarbonate-Ringer solution for periods up to 4 h resulted in only slight changes in the endothelial cell shape (S = 15.21 +/- 0.89). However, incubation with thimerosal (0.01%) for 2 h (S = 16.78 +/- 1.79) or with disodium ethylenediaminetetraacetate (Na2EDTA) (0.2%) for 1 h (S = 17.20 +/- 2.36) gave a marked increase in the tortuosity of the cell 'outlines'. Longer periods of contact with Na2EDTA resulted in a rounding up and separation of endothelial cells.

Animals↗

PubMed1980

Recurrent keratoconus after keratoplasty.

A 35-year-old woman who had undergone bilateral penetrating corneal grafts for keratoconus had keratoconus in the eye that had received a graft 16 years earlier. A second penetrating keratoplasty was performed, and the excised button was examined with light and electron microscopy. Both the light and electron microscopic findings were consistent with the clinical diagnosis of keratoconus. Keratoconus in a graft for the same disease should be added to the list of late complications of successful keratoplasties.

Adult↗

PubMed1979

Prevalence of the Hudson-Stähli line of the cornea.

The prevalence of the corneal Hudson-Stähli line among 400 eyes was found to range from 5.3% of the eyes of patients aged 11-20 years to 100% of eyes of patients aged 81-90 years. In 87.3% of patients over 50 years of age corneas were affected; this percentage is considerably higher than previous estimates. Up to the age of 60 years it occurs more frequently in men than in women.

Adolescent↗

PubMed1979

Bilateral keratoconus posticus circumscriptus: a case report.

The characteristics, clinical appearance, and frequency of the rare corneal condition, keratoconus posticus circumscriptus, are discussed. A bilateral case of this condition, examined by use of techniques not previously employed, is described.

Adult↗

PubMed1979

Epicapsular stars with visual loss.

The presence of epicapsular stars (congenital epicapsular pigmentation) is a common occurrence, but it can become clinically significant when vision is impaired. A case history reporting such a condition is presented.

Adolescent↗

PubMed1978

Conjunctival resection treatment and ultrastructural histopathology of superior limbic keratoconjunctivitis.

Four patients with symptomatic superior limbic keratoconjunctivitis underwent resection of the superior bulbar conjunctiva. One of these patients also underwent a tarsal conjunctival resection in the other eye. Three of the patients had previously been treated by various regimens without resolution; the fourth had had no prior treatment. All four patients had immediate and continued relief of the ocular symptoms after the superior bulbar conjunctiva was excised. The patient who underwent tarsal conjunctival resection experienced only short-term relief. We studied the conjunctival tissue by light and transmission electron microscopy. Both techniques revealed abnormalities related to the bulbar conjunctival surface with keratinization of the epithelium, acanthosis, degeneration of the nuclei, and intracellular accumulation of glycogen. Inflammatory cells were minimally present. The tarsal conjunctiva appeared essentially normal.

Adult↗

PubMed1978

Keratinization of the bulbar conjunctival epithelium in superior limbic keratoconjunctivitis in humans. An electron microscopic study.

A prominent histological feature of superior limbic keratoconjunctivitis is the presence of keratinization of the superior bulbar conjunctiva. Ultrastructurally the affected conjunctival epithelium shows all of the characteristics of keratinization as described in skin. There is a superficial layer of horny cells with reduced organelles and thickened cell membrane. In the intermediate layers, the cells contain an increased number of cytoplasmic filaments which are sometimes aggregated into dense masses, keratohyalin granules, both in the cytoplasm and in the nucleus, membrane coating granules, lysosomes and various other types of membranous structures.

Conjunctiva↗

PubMed1978

The fine structure of nuclear changes in superior limbic keratoconjunctivitis.

Superior limbic keratoconjunctivitis (SLK) is a condition of unknown etiology. Histological signs include acanthosis, dyskeratosis, keratinization, and ballon degeneration of the bulbar conjunctival epithelium. Ultrastructural examination of biopsy material from five eyes of patients with SLK shows numerous nuclear changes in the conjunctival epithelial cells. These include abnormal distribution and aggregation of nuclear chromatin, the presence of filaments within the nucleus, and dense accumulations of cytoplasmic filaments which surround the nucleus, resulting in "strangulation" and the formation of multilobed nuclei or multinucleated cells. These changes do not appear to have been described previously in any cell type.

Cell Nucleus↗