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Biomedical subjects

R E Nordquist

Publications and source records attributed to R E Nordquist.

At least 37 records · Page 2Linked to original sources
PubMed1991

Effect of oxygen free radicals on corneal collagen.

Corneal collagen was labeled in vivo by injection of 14C-proline into the anterior chamber of rabbit eyes. The isolated corneal collagen was incubated in iron-free phosphate buffered saline (pH 7.4) containing 1 mM ascorbate and 0.1 mM CuSO4 for either 1 hour or 3 hours at 37 degrees. Addition of 2 volumes of 8M urea-1 mM dithiothreitol and heating for 1 min at 100 degrees solubilized virutually all of the collagen in the control incubations but left a significant amount of insoluble collagen in specimens exposed to the hydroxyl radical generating system. This residue amounted to 19% and 38% of the initial radioactivity in samples incubated for 1 h and 3 h, respectively. The chromatographic profiles (gel filtration on CL-4B) of the soluble fraction showed an increase in both aggregation and degradation products of collagen in the 1 h incubation mixture, whereas after 3 h there was an increase only in degradation products. These observations suggest that additional crosslinking of the soluble collagen aggregates observed at 1 h may be responsible for their subsequent disappearance at 3 h, with concomitant increase of the insoluble fraction. Collagen degradation by .OH may play a role in corneal ulceration, whereas hydroxyl radical-mediated crosslinking is consistent with age-dependent increases in insoluble collagen.

Animals↗
PubMed1990

Role of active oxygen species in corneal ulceration. Effect of hydrogen peroxide generated in situ.

Cationic glucose oxidase, prepared by amidation of its free carboxylic groups, has prolonged retention in tissues, resulting in sustained release of hydrogen peroxide generated during oxidation of endogenous glucose. Increased levels of hydrogen peroxide can inhibit superoxide dismutase activity, thereby promoting reduction of transition metal ions, particularly iron and copper, by superoxide anions. Therefore, hydrogen peroxide can generate highly reactive hydroxyl radicals through a superoxide-driven Fenton reaction. Amidated glucose oxidase injected into rabbit cornea produces corneal opacification within 3-4 days and severe corneal damage by 7 days. Ultrastructural studies revealed typical tissue lesions observed in corneal melting. Heat-inactivated amidated glucose oxidase had no effect during the first 3-4 days. However, a gradual opacification occurred thereafter, resulting in some cases, in a severe opacity by 7 days. These results are consistent with an oxidative attack on corneal glycoconjugates by radicals derived from glucose oxidase-generated hydrogen peroxide during the first 3-4 days. Invading phagocytic cells are responsible for lesions observed with the inactive enzyme and for the progression of the initial lesions caused by the active enzyme. Stimulated phagocytic cells not only produce active oxygen species during the respiratory burst, but also release neutral collagenase and acid lysosomal hydrolases that contribute to and amplify the degradation of the extracellular matrix.

Animals↗
PubMed1989

Comparison of endothelial damage produced by control and surface modified poly(methyl methacrylate) intraocular lenses.

Biological studies were performed on control and surface modified (passivated) poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs). In acute corneal touch studies in cats, surface modified IOLs caused little endothelial damage and only single cells or small debris were seen adhering to the IOL. In contrast, control IOLs caused major endothelial damage and large sheets of endothelial cells were seen adhering to the control IOL surface. Use of the surface modified IOLs may help reduce the associated endothelial damage during cataract surgery.

Animals↗
PubMed1988

Topical application of all-trans-retinoic acid. A look at the cornea and limbus.

A 0.1% all-trans-retinoic acid in petroleum-base ointment was applied daily in eight normal rabbit eyes. Epithelial samples were collected from the cornea and limbus of six rabbits by impression cytology at 3- to 4-day intervals. Cytological changes were followed for 21 days and the eyes subsequently harvested for histochemical, scanning electron microscopic (SEM), and transmission electron microscopic (TEM) analysis of corneal and limbal structures. Two rabbits were treated with 0.1% all-trans-retinoic acid for 24 days without impression cytology until the 21st day. On the 24th day these eyes were harvested for similar studies. Impression cytology studies of the corneal epithelium demonstrated perinuclear halos and vacuolization of the cytoplasm. Additionally, vacuolization of the cytoplasm was observed by TEM, with attendant extrusion of the cytoplasmic contents and a subjective increase in surface microvilli as seen by SEM. Histochemical analysis revealed mucinlike staining of the corneal epithelium.

Administration, Topical↗
PubMed1988

Abnormal cutaneous nerves in incontinentia pigmenti.

Cutaneous nerves showed multiple ultrastructural abnormalities in a patient with incontinentia pigmenti. Fetal nerve bundles were seen both in the dermis and entering the epidermis. A cell with some Schwann cell features was identified above the basal layer amid keratinocytes. Dermal melanophages were in close apposition to Schwann cells. All of these features suggest that neural structures may be abnormal in incontinentia pigmenti and play a role in transfer of melanin from epidermis to dermis.

Biopsy↗
PubMed1987

Rapid and sensitive method for measurement of hyaluronic acid and isomeric chondroitin sulfates using high-performance liquid chromatography.

A high-performance liquid chromatographic method for the separation and analysis of the unsaturated tetrasaccharide and hexasaccharide from Streptomyces hyaluronidase (S.HAase) enzyme digestion products of hyaluronic acid (HA) and standard unsaturated disaccharides 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-D-galactose (delta Di-0S), 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-4-O-sulfo-D-galactose (delta Di-4S) and 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-6-O-sulfo-D-galactose (delta Di-6S) is described. An amino phase chemically bonded to silica with a particle diameter of 6 micron was used as the column. The composition and the pH of the mobile phase were systematically varied to determine the optimal chromatographic conditions for separation and analysis of the compounds. For HA, a complete separation was accomplished in less than 12 min with a practical detection limit of 100 ng. Separation of the disaccharides also required less than 15 min with detection limits of 10 ng for delta Di-0S and 25 ng each for delta Di-4S and delta Di-6S. This chromatographic method represents a significant improvement over existing methods. It allows the simultaneous separation and analysis of HA and chondroitin sulfate isomers (after digestion of the latter with chondroitinase) at a higher speed, and with more sensitivity and efficiency.

Chondroitin↗
PubMed1987

Safety of high-energy neodymium:YAG laser pulses in YAG sclerostomy.

YAG sclerostomy was performed in 15 eyes of nine cynomolgus monkeys. Individual pulse energies ranged between 10 and 135 millijoules. Total pulse energy ranged between 2,000 and 36,000 millijoules in order to test the extreme range of energy that might be required. Both acute effects and chronic effects were studied in the corneal endothelium, the lens capsule, the iris, the ciliary body, the retina, and the sclera. Techniques included flat preparations of the corneal endothelium, paraffin sections for light microscopy, and scanning and transmission electron microscopy. Our conclusion is that individual pulse energies of up to 135 millijoules with a total of up to 36 joules of energy are safe in monkey eyes when performing YAG sclerostomy.

Animals↗
PubMed1987

Silver oxide in YAG sclerostomy.

YAG sclerostomy is a filtering procedure performed entirely with the neodymium:YAG laser through a goniolens as an alternative to trabeculectomy in the treatment of glaucoma. Extremely large pulse powers have been required in the past to complete the procedure. We found that an injection of silver-stabilized protein intrasclerally prior to the procedure makes it possible to perform the procedure with low total power.

Animals↗
PubMed1986

Laser-induced glaucoma in rabbits.

Argon laser energy was applied to the trabecular meshwork of pigmented rabbits in an attempt to develop an animal model of 'glaucoma'. Laser energy was varied to determine the optimal level needed to produce sustained ocular hypertension. An initial response of ocular hypertension followed by hypotension was observed in all of the animals tested. Approximately half of the laser-treated rabbits developed a secondary buphthalmus and sustained ocular hypertension. In these animals outflow facility was decreased by approximately 60%. Histologic examination at 4- and 8 weeks after laser treatment demonstrated a wound-healing response resulting in closure of the intertrabecular spaces and obstruction of outflow to injected carbon particles. Optic nerve cupping and a loss of ganglion cells were also observed. Topical application of L-timolol (0.5%), pilocarpine (2.0%) and forskolin (1.0%) were found to be effective in decreasing intraocular pressure in the laser-treated, hypertensive eye with no significant effect in control non-laser-treated eyes, suggesting that this model can be a useful tool for screening potential antiglaucoma medications.

Animals↗
PubMed1985

Neodymium-YAG laser sclerostomy in primates.

A one-stage sclerostomy procedure was performed "noninvasively" in four cynomolgus monkeys solely with the neodymium-YAG laser. The neodymium (Nd)-YAG laser was focused, for the most part, a few diopters behind the focus of the helium-neon aiming beam. This enabled optical breakdown to occur entirely within the sclera to produce a perforating micropuncture of the scleral tissue. Two monkeys were treated with higher energy (23 and 24 joules) and two were treated at lower energy levels (12 and 14 joules). An immediate reduction of intraocular pressure in the treated eye was associated with a significant increase in outflow facility. The sclerostomy remained patent for more than 180 days, as determined by tonography and histologic examination. Scanning electron microscopic examination of the cornea revealed no significant damage to the central cornea or to tissue adjacent to the visual axis in any of the treated eyes. However, there was some endothelial cell loss at the site of the laser treatment at the peripheral cornea and in the area immediately posterior to the incision; there was also a focal break in Descemet's membrane.

Animals↗
PubMed1985

Design of new contact lens for YAG laser filtering procedures.

A contact goniolens has been developed specifically for YAG laser filtering procedures both for use in unblocking failed surgical filtering procedures and for performing two-stage or one-stage YAG filtering procedures. The design concentrates the YAG energy and maintains a constant small angle with the cornea.

Contact Lenses↗
PubMed1984

Acute intraocular pressure elevation produced by argon laser trabeculoplasty in the cynomolgus monkey.

The short-term effect of argon laser trabeculoplasty (ALT) was studied in a nonhuman primate model. The ALT treatment produced a consistent intraocular pressure elevation in the treated eye for eight hours. A statistically significant indomethacin-resistant increase in aqueous humor protein concentration was also observed. Morphologic observations using light microscopy and scanning and transmission electron microscopy revealed evidence of a fibrinous material covering the trabecular openings four hours after ALT. Cells and tissue debris appeared to be trapped in this fibrinlike net and may be the cause of the acute rise in IOP. Twenty-eight hours after ALT, the fibrin net was shown to be discontinuous, with fewer cells and less debris present. These acute morphologic alterations were not seen in control eyes or the laser-treated eyes observed later.

Animals↗
PubMed1984

Experimental YAG laser sclerostomy.

A Q-switched neodymium-YAG laser was used to produce a corneoscleral perforation in human cadaver eyes. A through-and-through incision could be created solely with the YAG-laser at peak pulse energies of 16 millijoules (mJ). The minimal total energy required for perforation was 3,312 mJ. However, "optimal" perforation, producing splitting along natural scleral cleavage planes, required 26,676 mJ. Scanning electron microscopy showed the perforations to be clean holes with little debris.

Cornea↗
PubMed1984

Model of epithelial downgrowth: II. Scanning and transmission electron microscopy of corneal epithelialization.

We present a cat model of prolific epithelial downgrowth reviewing the scanning and transmission electron microscopy data. The cat model of posterior corneal epithelialization closely mimics the human clinical condition in the following areas: uneven epithelial spread over the endothelial surface on scanning electron microscopy, prominence of intercellular desmosomes and hemidesmosomes, and attachment of the latter to a basement membrane overlying a newly formed posterior collagenous layer. Cell layering is attenuated during the centripetal spread of cells down the center of the cornea. Adjacent endothelial cells show signs of cytotoxicity by increased microvilli and eventual plasma membrane retraction. Endothelial cells are covered by the advancing epithelium with subsequent endothelial cell death. The density of subepithelial collagen attachments would suggest that removal of Descemet's membrane would be required to guarantee total epithelial cell removal.

Animals↗
PubMed1983

Sialic acid metabolism in rat liver: effect of carbon tetrachloride.

Sialic acid metabolism was investigated in the livers of control rats and of rats treated with a single oral dose (1.5 ml/kg body weight) of carbon tetrachloride. The main change observed during the necrotic stage of CCl4 poisoning (18 h after treatment) was a highly significant reduction in sialyltransferase activity. Slight reciprocal changes in neuraminidase activities, i.e., a small decrease in cytosolic neuraminidase and a small increase in the membrane bound enzyme were also observed. At 72 h after CCl4 treatment, during the stage of liver regeneration, the main change was a marked elevation in membrane-bound neuraminidase (two fold above control values). Moderate increases in the specific activities of CMP-N-acetylneuraminic acid synthetase and sialyltransferase were also observed. A considerable decrease in the sialic acid content of the isolated smooth endoplasmic reticulum (one half of control values) was detected at 72 h after CCl4 administration. The sialic acid content of the rough endoplasmic reticulum, on the other hand, remained at control levels.

Animals↗
PubMed1983

Gamma-glutamyltranspeptidase levels as an aid in the management of human cancer.

Plasma gamma-glutamyltranspeptidase (GGTP) levels were measured in 435 cancer patients, 120 healthy controls, 15 patients with systemic lupus erythematosis, and 10 patients with rheumatoid arthritis. The mean GGTP activity of all cancer patients studied, with the exception of malignant lymphoma, was significantly elevated compared to control values. Several patient groups were retrospectively analyzed to determine whether GGTP levels correlated with clinical status. Patients who were disease-free had GGTP levels in the normal range, whereas patients with metastases had elevated levels. Serially increasing GGTP levels were associated with disease progression and death. Persons who remained free of disease had serial GGTP levels within the normal range. Furthermore, decreasing levels were associated with response to therapy. These results indicate that GGTP levels may have prognostic value in various human malignancies.

Arthritis, Rheumatoid↗