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Biomedical subjects

T D Lindquist

Publications and source records attributed to T D Lindquist.

51 records · Page 3Linked to original sources
PubMed1985

Axonal transport of polyamines in intact and regenerating axons of the rat sciatic nerve.

The axonal transport of putrescine or its polyamine derivatives spermidine or spermine is a subject of some debate. We investigated this question by injecting [3H]putrescine into the lumbar spinal cord of the rat and measuring the accumulation of radioactivity central to ligatures placed on intact and regenerating sciatic nerves. In normal nerves, approximately twice as much radioactivity built up proximal to these ligatures 2 or 3 days after injection than at more distal ligatures used to control for accumulation of radioactivity which might be due to tissue damage alone. In regenerating nerves the amount of radioactivity accumulating at the ligature was approximately five times that at the distal ligature and two to three times greater than in intact nerves. The identity of the radioactivity in regenerating nerves, determined on an amino acid analyzer, was found to be primarily spermidine and an unknown compound that migrated as a frontal elution peak. Autoradiographic analysis showed that the radioactivity was largely confined to axons, but a significant amount of the silver grains was associated with Schwann cells and myelin sheaths surrounding labeled axons in both intact and regenerating nerves. The data indicate that polyamine derivatives of putrescine are transported axonally in rat sciatic nerves, and some of this transported material accumulates in Schwann cells surrounding the labeled axons. These processes are apparently augmented during regeneration of the injured axons.

Animals↗
PubMed1981

4S RNA is transported axonally in normal and regenerating axons of the sciatic nerves of rats.

Experiments were designed to determine if following injection of [3H]uridine into the lumbar spinal cord of the rat, [3H]RNA could be demonstrated within axons of the sciatic nerve, and if 4S RNA is the predominant RNA species present in these axons. In one experiment the left sciatic nerve of a rat was crushed. Two days later 170 microCi of [3H]uridine was injected into the vicinity of the lumbar ventral horn cells. Ten days after injection, rats were sacrificed and sciatic nerves were prepared for autoradiography. Photomicrographs were taken of labeled areas of intact and regenerating nerves and grains were counted over Schwann cells, myelin, axons and other unspecified areas. In both intact and regenerating sciatic nerves more than 20% of the silver grains were associated with motor axons and approximately 40% were found over cytoplasm of Schwann cells surrounding these axons. These data indicate an intra-axonal localization of RNA in sciatic nerve axons, as well as an active transfer of RNA precursors from axons to their surrounding Schwann cels. In separate studies, the left sciatic nerve was crushed and 10 days later [3H]uridine was bilaterally injected intraspinally into 6 rats. Four control rats were sacrificed at 14 or 20 days after injection. In the remaining 2 rats the sciatic nerve was cut 14 days after injection and the distal part of the nerve was allowed to degenerate for 6 days before sacrificing the rat. Thus, the distal portion of the nerve contained Schwann cells labeled by axonal transport but lacked intact axons. RNA was isolated from experimental and control nerve segments by hot phenol extraction and ethanol precipitation. RNA species (28S, 18S and 4S) were separated by polyacrylamide gel electrophoresis and radioactivity was measured in a liquid scintillation counter. Control groups had RNA profiles similar to those already described, with greater than 30% of the radioactivity present as 4S RNA. The proximal portions of nerve taken from the group in which nerves were cut, had a similar amount of radioactivity present as 4S RNA. However, in the distal segments of these nerves (in which the axons had degenerated thus creating an 'axon-less' nerve) the amount of radioactivity in the 4S peak decreased to approximately 15% of the total RNA, suggesting that 4S RNA is the predominant if not the only RNA present in these axons. These results strongly indicate that both intact and regenerating sciatic nerves of rats selectively transport 4S RNA along their motor axons.

Animals↗
PubMed1979

Evidence that 4S RNA is axonally transported in normal and regenerating rat sciatic nerves.

Studies in regenerating goldfish optic nerves indicate that RNA may be axonally transported during optic nerve regeneration14,18,19. The present study was performed to determine if the axonal migration of RNA could be demonstrated during regeneration of the rat sciatic nerve. Rats, which had only the left sciatic nerve crushed 10 days earlier, were injected bilaterally with [3H]uridine into the spinal cord at segmental levels L5 and L6, thus labeling ventral horn cells giving rise to the sciatic nerve. Six, 14 and 20 days later rats were sacrificed by cardiac perfusion of saline followed by 10% formaldehyde. Formaldehyde-precipitable radioactivity, identified as [3H]RNA, was 4--5 times greater in the regenerating sciatic nerve compared to the normal nerve and moved without impediment beyond the point of the crush into the regenerating portion of the nerve. The axonal migration of free unincorporated labeled RNA precursors was also demonstrated, raising the possibility that the distribution of [3H]RNA along the sciatic nerve might be entirely extra-axonal; i.e., free [3H]uridine is taken up by Schwann cells from the axon where it is incorporated into [3H]RNA. This interpretation of the data would also result in the appearance of a proximodistal distribution of RNA associated radioactivity. To determine whether any sciatic nerve [3H]RNA was due to axonal transport, rats which had only the left sciatic nerve crushed 10 days earlier were injected bilaterally with [3H]uridine into the spinal cord. Fourteen days after injection, rats were sacrificed and radioactivity present in the nerve was confirmed as RNA by SDS polyacrylamide gel electrophoresis. Radioactivity in the various RNA species 14 days after intraspinal injection showed the following distribution: 28 + 18S RNA--normal 39.3% +/- 2.1; regenerating 45.4% +/- 1.6; 4S RNA--normal 43.0% +/- 1.3; regenerating 46.8% +/- 2.7. Similar characterization of sciatic nerve RNA 1 or 3 days following the intravenous administration of [3H]uridine gave the following distribution: 28 + 18S RNA--normal 72.4% +/- 3.0; regenerating 75.0% +/- 3.6; 4S RNA--normal 7.7% +/- 1.3; regenerating 10.7% +/- 0.8. The intraspinal injection of [3H]uridine would label Schwann cell RNA and, in addition, any species of intra-axonal RNA, while intravenous injections would label Schwann cell RNA and not axonal RNA. If 4S RNA is in the axon, one would predict relatively more labeled 4S RNA following intraspinal injections than following intravenous injections. The data demonstrate an enrichment of 4S RNA in both normal and regenerating rat sciatic nerve following the intraspinal but not following the intravenous injection of labeled precursor. Therefore, we suggest that 4S RNA migrates axonally in both normal and regenerating sciatic nerves of rats.

Animals↗
PubMedDate not supplied

Monoclonal antibodies to intermediate filament proteins: diagnostic specificity in orbital pathology.

Intermediate filaments derived from different cell types are antigenically distinct. Monoclonal antibodies to human intermediate filament proteins can, therefore, be used as tissue-specific reagents capable of distinguishing cell type in poorly differentiated neoplasms. We report a case demonstrating the specificity of antiintermediate filament protein antibodies in establishing a difficult orbital diagnosis of esthesioneuroblastoma.

Antibodies, Monoclonal↗
PubMedDate not supplied

Unsuspected infectious keratitis in host corneal buttons.

Infectious keratitis may be unsuspected preoperatively in patients undergoing penetrating keratoplasty. We have diagnosed five cases of previously unknown corneal infection discovered only after post-keratoplasty histopathologic examination using specific stains. These cases of preoperatively unsuspected infectious keratitis illustrate examples where histopathologic examination using specialized stains may alert the physician to the need for appropriate postoperative antimicrobial therapy. Furthermore, these cases illustrate the ability of soft contact lenses to mask symptoms of infectious keratitis. Additionally, the clinical appearance of advanced bullous keratopathy may mask signs of infectious keratitis.

Acanthamoeba↗
PubMedDate not supplied

Bilateral angle-closure glaucoma associated with uveal effusion: presenting sign of HIV infection.

A 40-year-old homosexual man presented with acute myopia and bilateral angle-closure glaucoma. Recognition of an anterior chamber configuration of a modestly shallowed central chamber with marked peripheral shallowing clinically suggested uveal effusion. B-scan echography provided definitive, confirmatory evidence of diffuse choroidal thickening with ciliochoroidal effusion. Treatment with aqueous suppressants, cycloplegics, and topical steroids resulted in complete resolution of the angle closure and reversal of induced myopia. The patient, who was systemically well without signs of AIDS or AIDS-related complex, was later tested and found to be serologically-positive for the human immunodeficiency virus.

Adult↗
PubMedDate not supplied

Ketorolac, prednisolone, and dexamethasone for postoperative inflammation.

This 6-week, partially masked, three-arm, multicenter study was conducted to evaluate the postoperative anti-inflammatory efficacy of ketorolac, a cyclooxygenase inhibitor. The study setting was the clinical practice of six ophthalmic surgeons. The study enrolled 157 candidates for routine extracapsular cataract extraction or phaco-emulsification and posterior-chamber intraocular lens implantation. Patients who received any glucocorticoid or cyclooxygenase inhibitor within 1 week of surgery were excluded. All patients were treated with solutions of 0.5% ketorolac, 1% prednisolone acetate, or 0.1% dexamethasone instilled into the operative eye three times daily from 1 day before surgery to 4 weeks after surgery. Efficacy variables included the signs of anterior-segment inflammation, primarily cells and flare in the anterior chamber, as observed by slit-lamp biomicroscopy; fluorescein leakage across the blood-aqueous barrier as measured by fluorophotometry; and the rating of efficacy by the investigator. No significant differences were seen between ketorolac and either glucocorticoid in cells and flare. No significant differences were found in other signs of inflammation, except conjunctival hyperemia and Descemet's folds at week 2. Ketorolac showed significantly greater efficacy than the glucocorticoids against blood-aqueous barrier breakdown at day 5 and week 2, as demonstrated by the difference in fluorescein concentration between the operated and nonoperated eyes. Investigators did not detect any significant difference in rating for overall effectiveness and acceptability. These findings support the use of ketorolac as an alternative to glucocorticoids for the treatment of postoperative inflammation.

Aged↗
PubMedDate not supplied

Cytotoxicity of viscoelastics on cultured corneal epithelial cells measured by plasminogen activator release.

BACKGROUND: Plasminogen activator has been shown to be released by epithelial cells following corneal injury. The demonstration of the release of plasminogen activator from cultured corneal epithelial cells has been used for developing a cytotoxicity test, the Corneal Epithelial Plasminogen Activator test, which compares changes in the level of plasminogen activator in tissue culture media following chemical exposure as an index of chemical injury. METHODS: Cultured rabbit corneal epithelial cells were exposed to varying concentrations of several viscoelastics for 1 hour. Release of plasminogen activator into the tissue culture media following exposure to the viscoelastic agent was studied as an index of chemical injury. RESULTS: The least cytotoxicity to cultured rabbit epithelium was associated with those viscoelastic agents containing methylcellulose. A 1-hour exposure to most concentrations of methylcellulose and chondroitin sulfate (Phacote) and methylcellulose (Occucoat) demonstrated release of greater amounts of plasminogen activator than was seen following a similar exposure to balanced salt solution, suggesting the greatest protective effect of these two viscoelastics. In contrast, sodium hyaluronate and chondroitin sulfate (Viscoat) showed decreased amounts of plasminogen activator release after a 1-hour exposure to cultured corneal epithelial cells demonstrating cytotoxicity. Polyacrylamide (Orcolon) and most diluted preparations of sodium hyaluronate (Healon and Healon Yellow) showed only mild reductions in the release of plasminogen activator, whereas undiluted sodium hyaluronate preparations were nearly as cytotoxic as Viscoat. CONCLUSIONS: This study suggests that viscoelastic agents containing methylcellulose (Phacote and Occucoat) may be most protective of the corneal epithelium during ophthalmic surgery. The clinical success of several dilute viscoelastic solutions as tear substitutes was corroborated by the lack of cytotoxicity seen in this study. Viscoat and undiluted sodium hyaluronate preparations showed the greatest cytotoxicity to cultured rabbit corneal epithelium.

Acrylic Resins↗
PubMedDate not supplied

Open-sky phacoemulsification during corneal transplantation.

A continuous, circular capsulorhexis maintains the integrity of the anterior capsule. During corneal transplantation, a capsulorhexis may be combined with phacoemulsification, allowing the cataractous lens to be delivered in small fragments, thereby maintaining the integrity of the anterior capsular margin. This approach allows stable "in-the-bag" placement of a posterior chamber intraocular lens (PC-IOL) during combined cataract extraction and corneal transplantation. The technique also minimizes the risk of radial anterior capsular tears and subsequent decentration of the PC-IOL.

Cataract Extraction↗