Biomedical subjects
J L Baum
Publications and source records attributed to J L Baum.
Collagen synthesis by cultures of stromal cells from normal human and keratoconus corneas.
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Mass culture of human corneal endothelial cells.
Human corneal endothelial cells have been grown in mass culture for the first time to our knowledge. Cultures from donors who were under 20 years of age grew well. Cells from older donors were difficult to grow or did not grow at all. Initial outgrowth usually began one week after explantation. After an initial lag phase, mass increased by 15% weekly, and confluency was approached in eight to nine weeks. The lag phase of growth correlated with the age of the donor. A basal lamina was secreted by human corneal endothelial cells in culture. Chromosomal counts demonstrated a modal number of 46. With this technique, sufficient human corneal endothelial cells may be obtained for biochemical investigation.
Origin of the retrocorneal membrane in the rabbit.
Electron microscopic studies have offered presumptive evidence that the origin of both cellular and extracellular components of the retrocorneal membrane (RCM) derive from corneal endothelial cells. In an attempt to demonstrate conclusively the origin of the cell in the RCM, we performed 8-mm exchange, penetrating keratoplasties between male and female rabbits. After allowing for complete healing and using only clear corneas, we produced central RCM by freezing the central cornea after inducing intraocular inflammation. Care was taken to ensure that the membrane was surrounded by normal donor endothelium and Descemet's membrane was intact. Sex chromatin counts of the cells in the RCM of a female host with a male graft showed an average of 2% Barr bodies. Cells in the membrane of a male host with a female graft showed an average of 40% Barr bodies. The experimental and control sex chromatin counts were almost identical. This study provides conclusive evidence that central retrocorneal, fibroblast-like cells and membranes in rabbits are derived from corneal endothelial cells.
Postlenticular membrane associated with Smith-Lemli-Opitz syndrome.
A 6-day-old boy with Smith-Lemli-Opitz syndrome developed bilateral cataracts, posterior synechiae, and a dense postlenticular membrane. No other signs of inflammation were noted that could account for the development of either the posterior synechiae or membrane. To our knowledge, this is the first published report of such an associated membrane.
Ocular findings in Bell's palsy.
Thirty-three patients with Bell's palsy underwent ophthalmic examination, including Schirmer testing, corneal sensitivity measurement, and electromyography. Sixteen patients returned for follow-up after one year. Sixty-one percent of the patients initially showed punctate fluorescein staining of the inferior cornea. Electromyographic studies demonstrate a high correlation between orbicularis function and the presence of corneal epithelial staining. Our results demonstrate a high frequency of minor corneal involvement in the acute phase of Bell's palsy. Healing of the epithelial defects follows improvement in orbicularis function.
The synthesis of glycosaminoglycans by cultures of corneal stromal cells from patients with keratoconus.
Keratoconus is a disease that results in thinning and ectasia of the central cornea. Cultures of corneal stromal cells from patients with keratoconus were established and the synthesis of glycosaminoglycans compared with the synthesis of glycosaminoglycans by normal human corneal stromal cells in culture. Keratoconus and normal control cell cultures were incubated with sodium [(35)S]sulfate and [(3)H]glucosamine for 4 h. After incubation, the labeled glycosaminoglycans were isolated from the medium fractions and cells. Keratoconus and normal control cultures synthesized similar amounts of sulfated glycosaminoglycans independent of the age of donors and(or) the number of subcultures. In contrast to normal control cultures, most of the newly synthesized glycosaminoglycans produced by keratoconus cells were found in the growth medium and much less were in the cell layer. Treatment with glycosaminoglycan-degrading enzymes followed by paper chromatography showed that keratoconus cells, as normal control cells, produced hyaluronic acid and various sulfated glycosaminoglycans. The production of cell layer-related heparan sulfate was markedly reduced in keratoconus cultures. Because heparan sulfate has been shown to be associated with cell surfaces, the decreased heparan sulfate content could reflect changes at this location.
Intraocular levels of cefamandole compared with cefazolin after subconjunctival injection in rabbits.
We compared the intraocular pharmacokinetics of cefazolin with those of cefamandole, a recently marketed cephalosporin with enhanced activity against gram-negative bacilli. Following subconjunctival injection of 12.5 mg into infected eyes (S. aureus endophthalmitis) of pigmented rabbits, both drugs reached peak concentrations greater than 100 microgram/gm in cornea, sclera, and choroid-retina. The half-life was markedly shorter in sclera and choroid-retina than in cornea. Levels in the aqueous humor rose and fell more slowly than those in ocular tissues, reaching a maximum of only 5 to 10 microgram/ml. The pharmacokinetics of the two drugs were virtually identical in most intraocular sites. When cefazolin, which was less irritating than cefamandole by the subconjunctival route, was given in a dosage of 100 mg, levels in ocular tissues were increased by twofold to fourfold and in aqueous humor by 15-fold, compared to the concentrations produced by the 12.5 mg dosage. Levels in the vitreous humor were exceedingly low with both drugs; mean peak concentrations were 0.24 microgram/ml after the 12.5 mg dosage of cefamandole and less than 1.6 microgram/ml after the 100 mg dose of cefazolin.
Maintenance of mydriasis with topical indomethacin during and after penetrating keratoplasty in the rabbit.
The use of indomethacin eyedrops, 0.5%, in combination with topical atropine and phenylephrine, prior to and immediately following an 8-mm penetrating keratoplasty in rabbits maintains maximal pupillary dilation. With this technique, we achieved clear grafts without synechiae in virtually every instance.
Current concepts in ophthalmology. Ocular infections.
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Cryosurgical iridocyclectomy.
A new surgical technique, cryosurgical iridocyclectomy, was used in the excision of an iris melanoma encroaching on the ciliary body. Iris-tumor-anterior ciliary body segment was removed en bloc. The elucidate the mechanical basis for the success of the procedure, similar operations were performed on three enucleated eyes. It was confirmed that traction on the iris by a cryoprobe resulted in forward movement of the ciliary body without iridodialysis. The iceball that formed prevented iridodialysis at its usual plane of cleavage. Cryosurgical iridocyclectomy is recommended for excision of small discrete iris tumors that encroach on the anterior ciliary body.
Peripheral corneal infiltrates following intravenous injection of diatrizoate meglumine.
A 66-year-old white man developed bilateral peripheral corneal infiltrates on two separate occasions after intravenous injections of a radiopaque dye containing iodide. To our knowledge this is the first case of drug-induced ocular hypersensitivity reaction associated with the administration of these dyes and manifesting with peripheral corneal infiltrates.
The treatment of bacterial endophthalmitis.
Restoration of good visual acuity following bacterial endophthalmitis is dependent on prompt diagnosis, immediate treatment, proper selection of antibiotics, high-dose parenteral and periocular antibiotic therapy, and systemic and periocular corticosteroids. Antibiotic selection should be based on the statistical incidence of pathogens rather than on the result of a Gram stain from the aqueous or vitreous humor. Recent experimental studies in the primate eye suggest that there is little to choose between the subconjunctival and retrobulbar routes of antibiotic administration. The role of intravitreal injection of antibiotic, although promising, requires further definition.
Aspects of corneal wound healing in health and disease.
The paper reviews current aspects of repair processes of the epithelial, stromal, and endothelial layers for both the normal and diseased cornea.
Synthesis of glycosaminoglycans by cultures of normal human corneal endothelial and stromal cells.
Monolayer cultures of normal human corneal endothelial and stromal cells were incubated with [35S]sulfate and [3H]glucosamine for 4 hr. The labeled glycosaminoglycans resulted from this incubation were isolated from the cell layer and the growth medium and further characterized. Both endothelial and stromal cell cultures synthesized a variety of sulfated glycosaminoglycans, with chondroitin 6-sulfate as the major product. Chondroitin 4-sulfate, dermatan sulfate, and heparan sulfate were present in smaller amounts. Keratan sulfate was produced only in minimal amounts. Both cell types also synthesized hyaluronic acid. The hyaluronic acid production in stromal cell strains derived from donors of different ages was similar. The demonstration that the endothelial cell strain derived from a 1-day-old baby contained more hyaluronic acid than cultures from older donors suggests a possible age-related phenomenon as seen in developing tissues.
Late spontaneous clearing of corneal grafts.
Three cases of graft rejection or primary donor failure after penetrating keratoplasty failed to respond to treatment. After cessation of therapy, these edematous corneas all cleared spontaneously in six to 17 months with the return of excellent vision. It is suggested that repeated keratoplasty be delayed up to 18 months in certain instances.
Washout effect vs drug interaction.
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Comparing radioactive and trephine-disk bioassays of dicloxacillin and gentamicin in ocular tissues in vitro.
Trephined disks of tissue (6 mm diameter) from fresh rabbit eyes were immersed overnight in solutions of radioactive carbon (14C)-dicloxacillin or gentamicin, then assayed by one of two methods: agar-diffusion bioassay, using filter-paper disks immersed in known concentrations of antibiotic as standards, or radioactive assay. The bioassay underestimated the concentrations of antibiotic in sclera and iris by 38 to 72%, and slightly overestimated those in the cornea. A corrected bioassay was calculated, based on the differences in fluid mass between tissue specimens and filter-paper disks; this value was within 20% of the radioactive assay in 18 of 24 experiments with dicloxacillin, and in 14 of 24 with gentamicin. There was evidence of pronounced binding of gentamicin to ocular tissues (iris greater than sclera greater than cornea); this appeared to be a saturable and reversible phenomenon. Less marked binding of dicloxacillin to iris and sclera was noted. The results indicated that, depending on the degree of accuracy required, the corrected trephine-disk agar-diffusion bioassay provides a reasonable estimate of the antibiotic content of ocular tissues.