Biomedical subjects

S A McCormick

Publications and source records attributed to S A McCormick.

11 recordsLinked to original sources

PubMed1992

The collagen shield as a collagenase inhibitor and clinical indicator of collagenase activity on the ocular surface.

Collagen shields applied to the corneas of patients with bacterial keratitis degrade rapidly, often within a few hours. Once treatment brings the infection under control, subsequently applied collagen shields degrade more slowly. In vitro models were established to evaluate the significance of these observations. Twenty-four and 72-hour collagen shields were incubated with collagenase from Clostridium histolyticum. The in vitro rate of digestion of the shields was directly proportional to the concentration of collagenase, with the rate of digestion of the 24-hour shields being greater than that of the 72-hour shields. Therefore, the rate of collagen shield degradation may be a clinically useful index of collagenase activity on the ocular surface. Ultrastructural studies of collagen shields from patients with acute bacterial keratitis revealed irregular degradation of shield matrix with no evidence of adherence of microorganisms or inflammatory cells. Co-incubation of deepithelialized rabbit corneas and collagen shields resulted in inhibition of the digestion of the rabbit corneas when the weight:weight ratio of collagen shield:rabbit cornea was increased to greater than or equal to 2:1. Collagen shields may inhibit corneal collagen degradation in infectious ulceration and melting disorders by effectively competing for collagenase on the ocular surface.

Animals↗

PubMed1992

Isolation and cultivation of human iris pigment epithelium.

There have been very few attempts to isolate and culture human iris pigment epithelium (IPE). Earlier efforts that used whole iris explant methods did not achieve pure cultures of IPE. We have developed methods for separating the IPE from the iris stroma of post-mortem eyes that avoid contamination by other cell types. Three different isolation methods were studied: direct dissection, enzyme digestion, and enzyme-assisted microdissection. The latter method yielded the best results. After treatment with enzyme solution, the IPE was easily separated from the stroma under the stereomicroscope and subsequently cultured with supplemented F12 medium. With this method, approximately 2.3 x 10(5) cells were isolated from each iris with an average viability of 90.2%. IPE cells isolated from 19 of 24 eyes grew to confluence in primary culture. The IPE could be maintained in pure culture for many generations over several months with up to 20 population doublings. Cultured IPE demonstrated cytokeratin and S-100 protein by immunocytochemistry. Some of these cells also displayed desmin, indicating origin from the anterior IPE. Cultured IPE cells retained most of the characteristics of IPE in vivo, such as apical/basal polarization, microvilli, and many cell junctions. Gradual dilution of pigment occurred in the dividing IPE cells, suggesting an inability to produce melanin in vitro. A subpopulation of the IPE cells contained myofilaments by electron microscopy, also indicating a anterior IPE origin. This method provides a source for large numbers of human IPE cells and could be useful in studies of the biology of IPE and the role of IPE in pathogenesis of several eye diseases, most notably exfoliation syndrome and its associated glaucomas.

Adult↗

PubMed1991

Anatomy of the orbital septum and associated eyelid connective tissues. Implications for ptosis surgery.

The anatomy of the orbital septum and associated eyelid connective tissues was examined using cadaver dissection, histologic sections, surgical observations, and special radiologic imaging. The embryologic development of the eyelid connective tissues was also reviewed. Examination revealed a distinct layer of fibroadipose tissue in the eyelid and eyebrow posterior to the orbicularis and frontalis muscles, and anterior to the orbital septum. Fibrous septa within the submuscular fibroadipose tissue become contiguous with more compact lamellae of the orbital septum posteriorly imparting a multilayered quality to the orbital septum. Fat within the fibroadipose layer anterior to the orbital septum may be mistaken for the preaponeurotic fat pad by the unwary surgeon and may lead to surgical error. The orbital septum and the levator aponeurosis were found to join 2 to 5 mm above the superior tarsal border (average, 3.4 mm). Recommendations for ptosis surgery based on these anatomic principles are given.

Adipose Tissue↗

PubMed1991

Tolerance of the carotid-sheath contents to brachytherapy: an experimental study.

Tumor invasion of the carotid artery is a potential indication for brachytherapy, which delivers a high dose of irradiation to residual tumor while limiting the dose to adjacent healthy tissues. The tolerance of carotid-sheath contents to varying doses of brachytherapy, however, has not been clearly established. In order to evaluate brachytherapy effects on carotid-sheath contents, after-loading catheters were implanted bilaterally in 3 groups of 6 rabbits each (18 rabbits). Iridium 192 brachytherapy doses of either 5000 cGy (rad), 9000 cGy, or 13,000 cGy were delivered unilaterally, with the contralateral neck serving as a nonirradiated control in each animal. There were no carotid ruptures and wound healing was normal. Two animals from each group were killed at 6, 20, and 48 weeks. Even at the highest dose (13,000 cGy), nerve conduction studies performed on the vagus nerve prior to sacrifice revealed no increased latency, histologic changes were minimal, and carotid arteries were patent. These observations suggest that the carotid-sheath contents in healthy rabbits could tolerate high doses (up to 13,000 cGy) of low-dose-rate interstitial brachytherapy without complications.

Animals↗

PubMed1990

Distribution of carbonic anhydrase among human photoreceptors.

The distribution of carbonic anhydrase (CA) among human photoreceptors has been a topic of dispute. In our experiments, by modifying an established enzyme histochemical technique, reproducible staining was observed. Of the cones in the peripheral retina, 91% were positive for CA. The CA-negative (CA-) cones were absent within approximately 8 arc min of the foveal center and their density peaked at 2 arc deg. No CA activity was found in the rods. Morphologic differences were noted between the CA-positive (CA+) and CA- cones. Compared to the CA+ cones, the CA- cones had longer and more nearly columnar inner segments, more nearly spherical nuclei, and more generous amounts of perikaryal cytoplasm. In the peripheral retina, the distance between CA+ to CA+ nearest neighbors were larger compared to CA- to CA+ nearest neighbors (P less than 0.0001). The frequency distribution and morphology of the CA- cones suggest that they are the blue-sensitive cones. As such, this study demonstrates a biochemical similarity between blue cones and rods that may provide insight into the function and phylogeny of the blue cones.

Adult↗

PubMed1989

Bilateral bifid mandibular condyles. Report of three cases.

Bilateral bifid mandibular condyles are a rare anomaly that had previously been described only by Hrdlicka in material from skull collections. We present here three cases of bilateral bifid mandibular condyles in patients who sought treatment for other reasons. The radiographic appearance of this anomaly and its embryology are discussed.

Adult↗

PubMed1989

Transscleral and transconjunctival diathermy.

The authors developed a new diathermy electrode that can be used with simultaneous indirect ophthalmoscopic control. The electrode uses the same source and handle as the conventional diathermy but can be used transconjunctivally or transsclerally through full thickness sclera. Chorioretinal scars were successfully induced in 30 rabbit eyes (with or without retinal detachment). Long-term follow-up revealed normal maturation of the scars, with firm adhesion of the retina to the choroid but no gross or histopathologic evidence of permanent scleral damage.

Animals↗

PubMed1988

Histopathology of nasolacrimal duct obstruction compatible with localized sarcoidosis.

We report a case of nasolacrimal duct obstruction with histopathology compatible with localized sarcoidosis, in a patient with no evidence of systemic disease. Excisional biopsy of the nasolacrimal duct revealed multiple noncaseating granulomas. Previously reported cases of sarcoidosis involving the lacrimal drainage system all had systemic disease, and these case are reviewed. Our case illustrates the potential value of nasolacrimal duct biopsy during dacryocystorhinostomy.

Dacryocystorhinostomy↗

PubMed1987

The anatomy of the lateral canthal tendon.

This report documents the anatomy of the lateral canthus using gross dissection, histologic examination, computed tomography, magnetic resonance imaging, and clinical measurement. Lateral canthal dissections of 16 cadaver orbits demonstrated a well-defined attachment of the tarsal plates to the orbital rim, averaging 10.6 mm in length and 10.2 mm in width at their insertion on Whitnall's tubercle, 1.5 mm behind the orbital rim and 9.7 mm inferior to the frontozygomatic suture. Histologic examination showed a band of dense fibrous tissue attached to the tarsal plates, with intermingled muscle fibers from the pretarsal orbicularis oculi muscle. A small pocket of fat was identified posterior to the orbital septum and anterior to the lateral canthal tendon. Clinical measurements of normal adults revealed 2 mm of lateral movement of the canthal angle during abduction, apparently caused by posterior fibrous attachments to the check ligament of the lateral rectus muscle.

Adult↗

PubMed1986

Primary acquired nasolacrimal duct obstruction. A clinicopathologic report and biopsy technique.

Primary acquired nasolacrimal duct obstruction (PANDO) of adults is a clinical syndrome of unknown cause, and the histopathology of the nasolacrimal duct has not been substantially studied. A technique of excisional biopsy of the soft tissue contents within the nasolacrimal canal during external dacryocystorhinostomy (DCR) is presented. No complications were associated with the biopsy technique in 14 cases. Two cases of lacrimal obstruction secondary to sarcoidosis and leukemia were discovered in biopsies of patients with the clinical syndrome of PANDO, demonstrating the value of routine biopsy during DCR. Biopsies revealed a spectrum of changes that correlated with duration of symptoms. Early cases revealed active chronic inflammation along the entire length of the narrowed nasolacrimal duct. Intermediate cases revealed focal resolution of the inflammatory process with fibrosis, while late cases showed fibrous obliteration of the entire duct. Although the first event in primary acquired nasolacrimal duct obstruction remains uncertain, clinicopathologic correlation suggests that compression of the duct by inflammatory infiltrates and edema precedes clinical chronic dacryocystitis.

Adult↗

PubMed1985

Ocular chrysiasis.

Thirty-four patients who had received over 1 gram of gold compounds for rheumatoid arthritis were examined for ocular chrysiasis. Ninety-seven percent of the patients receiving continuous chrysotherapy at the time of their ocular examination exhibited corneal chrysiasis. With few exceptions, corneal gold deposits were limited to the posterior one-half of the corneal thickness. Deposits tended to concentrate inferiorly and to spare the superior and peripheral cornea. Duration of chrysotherapy correlated positively with the clinically graded density of deposits. In this series, 55% (16/29) of these patients receiving gold therapy for three years or more had lenticular chrysiasis, although this has previously been considered rare. Our data suggest that gold is deposited in the cornea and lens from the anterior chamber aqueous fluid.

Adolescent↗