PubMed Health⌕ Search

Biomedical subjects

N C Nelson

Publications and source records attributed to N C Nelson.

At least 19 recordsLinked to original sources
PubMed1999

The double helix is dehydrated: evidence from the hydrolysis of acridinium ester-labeled probes.

A highly chemiluminescent reporter molecule, acridinium ester (AE), was tethered to single-stranded oligonucleotide probes and hybridized to complementary as well as mismatched target sequences. When tethered to single-stranded probes, AE was readily hydrolyzed by water or hydroxide ion. In contrast, when hybridized to a complementary target, hydrolysis of the AE probe was markedly inhibited. Mismatches near AE eliminated the ability of the double helix to strongly inhibit AE hydrolysis. To establish the molecular basis for these remarkable hydrolysis properties of AE-labeled probes, the binding and hydrolysis mechanisms of AE-labeled probes were examined. When tethered to single- or double-stranded nucleic acids, hydrolysis of AE was found to proceed by generalized base catalysis in which a base abstracts a proton from water and the resulting hydroxide ion then hydrolyzes AE. Analysis of the hydrolysis rates of AE bound to DNA revealed that AE binds the minor groove of DNA and that its hydrolysis is inhibited by low water activity within the minor groove of the helix. Depending upon the sequence of the DNA, the water activity of the minor groove was estimated to be at least 2-4-fold lower than bulk solution. Hydrolysis measurements of AE tethered to RNA as well as RNA/DNA hybrids argued that the grooves of these double helices are also dehydrated relative to bulk solution. Remarkably, mismatched bases, regardless of their structure or sequence context, enhanced hydrolysis of AE by inducing hydration of the double helix that spread approximately five base pairs on either side of the mismatch.

Acridines↗
PubMed1998

Advantages of 2'-O-methyl oligoribonucleotide probes for detecting RNA targets.

We have compared various kinetic and melting properties of oligoribonucleotide probes containing 2'-O-methylnucleotides or 2'-deoxynucleotides with regard to their use in assays for the detection of nucleic acid targets. 2'-O-Methyl oligoribonucleotide probes bound to RNA targets faster and with much higher melting temperatures (Tm values) than corresponding 2'-deoxy oligoribonucleotide probes at all lengths tested (8-26 bases). Tm values of both probes increased with length up to approximately 19 bases, with maximal differences in Tm between 2'-O-methyl and 2'-deoxy oligoribonucleotide probes observed at lengths of 16 bases or less. In contrast to RNA targets, 2'-O-methyl oligoribonucleotide probes bound more slowly and with the same Tm to DNA targets as corresponding 2'-deoxy oligoribonucleotide probes. Because of their greatly enhanced Tm when bound to RNA, 2'-O-methyl oligoribonucleotide probes can efficiently bind to double-stranded regions of structured RNA molecules. A 17 base 2'-O-methyl oligoribonucleotide probe was able to bind a double-stranded region of rRNA whereas the same 17 base 2'- deoxy oligoribonucleotide probe did not. Due to their enhanced Tm when bound to RNA targets, shorter 2'-O-methyl oligoribonucleotide probes can be used in assays in place of longer 2'-deoxy oligoribonucleotide probes, resulting in enhanced discrimination between matched and mismatched RNA targets. A 12 base 2'-O-methyl oligoribonucleotide probe had the same Tm as a 19 base 2'-deoxy oligoribonucleotide probe when bound to a matched RNA target but exhibited a much larger decrease in Tm than the 2'-deoxy oligoribonucleotide probe when bound to an RNA target containing either 1 or 2 mismatched bases. The increased Tm, faster kinetics of hybridization, ability to bind to structured targets and increased specificity of 2'-O-methyl oligoribonucleotide probes render them superior to corresponding 2'-deoxy oligoribonucleotides for use in assays that detect RNA targets.

Aminoacridines↗
PubMed1998

Surgical removal of subfoveal iatrogenic choroidal neovascular membranes.

OBJECTIVE: To present the cases of two patients with laser-induced iatrogenic subfoveal choroidal neovascular membranes (CNVMs) who underwent surgical removal of the membranes with favorable outcomes. DESIGN: Interventional case reports. PARTICIPANTS: Two patients with iatrogenic subfoveal CNVM. One case developed after laser treatment for macular edema due to branch retinal vein occlusion, and the second case developed after focal laser photocoagulation for diabetic retinopathy. INTERVENTION: Surgical removal by pars plana vitrectomy. MAIN OUTCOME MEASURES: Visual acuity, scotoma, retinal examination with fundus photography, and fluorescein angiography before surgery and during the postoperative period. RESULTS: Both patients underwent surgical removal after progression of the membrane with severe visual loss of 20/200 was noted. At present follow-up, there is a significant improvement in visual acuity and a reduction in the size of the scotoma. No recurrence of CNVM is noted. CONCLUSION: Both patients with laser-induced iatrogenic subfoveal CNVM achieved a good visual outcome after surgical removal of the membrane. The reasons for a good surgical result are thought to be twofold. First, the origin of the CNVM is extrafoveal at the site of laser application. The chance for foveal cone cell damage during the surgery is reduced. Second, the degree of cellular destruction in iatrogenic CNVM is usually focal without extensive retinal photoreceptor cell and retinal pigment epithelial damage. Therefore, a better chance of postoperative visual recovery is anticipated.

Choroid↗
PubMed1998

Rapid detection of genetic mutations using the chemiluminescent hybridization protection assay (HPA): overview and comparison with other methods.

The detection of genetic mutations is of paramount importance for the study, diagnosis, and treatment of human genetic disease. Methods of detection generally fall into one of two categories: those to scan for unknown mutations and those to detect known mutations. This review focuses on methods for the detection of known mutations. The hybridization protection assay (HPA) is described in detail. The HPA method utilizes short oligonucleotide probes covalently labeled with a highly chemiluminescent acridinium ester (AE). The assay format is completely homogeneous, requiring no physical separation steps, and can rapidly and sensitively detect all single-base mismatches as well as multiple mismatches, insertions, deletions, and genetic translocations. When very low copy number targets are assayed, HPA is coupled with transcription-mediated amplification (TMA), an isothermal method that amplifies DNA or RNA targets. Other methods that are described for the detection of known mutations include hybridization with sequence-specific oligonucleotides, hybridization to oligonucleotide arrays, allele-specific amplification, ligase-mediated detection, primer extension, and restriction fragment analysis. The advantages and limitations of each of these methods are discussed. Methods to scan for unknown mutations are briefly described.

Base Pair Mismatch↗
PubMed1996

Detection of all single-base mismatches in solution by chemiluminescence.

A rapid in-solution method for the detection of all 12 single-base mismatches is described. The technique is based on the hybridization protection assay (HPA) format that utilizes oligonucleotide probes labeled with a highly chemiluminescent acridinium ester (AE). Hydrolysis by weak base renders AE permanently non-chemiluminescent. When an AE-labeled probe hybridizes to an exactly complementary target, AE is protected from hydrolysis relative to the unhybridized conformation. Single-base mutations in the duplex adjacent to the site of AE attachment disrupt this protection resulting in rapid AE hydrolysis and loss of chemiluminescence. The discrimination effect was seen in both DNA and RNA. Studies of Tm values revealed that this effect is not due to a decrease in the overall stability of the duplex, suggesting the AE is responding to local structural changes in the double helix induced by mismatches. Using this principle all 12 single mismatches were clearly discriminated from the corresponding matched sequences. The assay is homogeneous, simple, sensitive, applicable to both amplified and non-amplified targets, and is completed in 30-60 min. An example showing discrimination between wild-type and mutant sequences corresponding to the reverse transcriptase coding region of HIV-1 is given.

Acridines↗
PubMed1996

Simultaneous detection of multiple nucleic acid targets in a homogeneous format.

The acridinium ester 4-(2-succinimidyloxycarbonylethyl)phenyl-10-methylacridinium 9-carboxylate trifluoromethane sulfonate (AE), which reacts rapidly with alkaline hydrogen peroxide to produce light, has been used as a detection label in a number of assay procedures, including nucleic acid probe-based systems [Nelson et al. (1995) in Nonisotopic Probing, Blotting and Sequencing (Kricka, L. J., Ed.) pp 391-428, Academic Press, Inc., San Diego, CA]. We have synthesized a number of derivatives of this AE and characterized their chemiluminescent properties. These derivatives display significant differences in the kinetics of the chemiluminescence reaction as well as optimal pH for light production. These differences allow two or more derivatives to be simultaneously detected and quantitated in a single reaction vessel. Several of these derivatives have been covalently linked to nucleic acid probe molecules and have been further characterized in regard to chemiluminescence properties as well as hydrolysis of the ester bond in both single- and double-stranded conformations. On the basis of these properties, homogeneous assay formats utilizing DNA probes labeled with various AE derivatives were developed. Simultaneous detection and quantitation of Chlamydia trachomatis and Neisseria gonorrhoeae, the gag and pol regions of HIV, and wild-type and mutant HIV sequences was achieved with high sensitivity and discrimination.

Acridines↗
PubMed1994

Using an integrated point of care system: a nursing perspective.

Nurses at LDS Hospital, Salt Lake City, Utah, have had the ability to document patient data and nursing care on a bedside computer for over nine years. This ability has had numerous ramifications for the medical record, nursing practice, and clinical decision making. This article is an effort to describe how and why certain decisions were made, the implications of these decisions, mistakes that were made and their solutions, and the tremendous impact on clinical decision making and improved patient outcomes that is only beginning to be realized by computerization of the medical record.

Computer Security↗
PubMed1993

Management of giant retinal tears with perfluoroperhydrophenanthrene (Vitreon).

Giant retinal tears in 10 eyes were repaired with the perfluorocarbon liquid Vitreon (perfluoroperhydrophenanthrene). The mean patient follow-up period was 9.2 months; retinas remained attached in all eyes at the last examination. Visual acuity improved in 9 eyes and could not be measured in one eye. One patient (mentally retarded) required a second operation for reattachment of the retina, which redetached from trauma after initial successful repair. Vitreon, unlike other perfluorocarbon liquids, may also be used as a short-term intraocular tamponade with the patient remaining in a supine position postoperatively. Vitreon was used as a short-term postoperative intraocular tamponade in 6 eyes. In 4 eyes, Vitreon was used as an intraoperative tool to reposition the retina and, when necessary, to unfold an inverted flap.

Adolescent↗
PubMed1992

Internal choroidectomy of posterior uveal melanomas under a retinal flap.

Local excision of uveal melanoma is an intriguing therapeutic modality in selected cases. An internal choroidectomy under a retinal flap has been developed as an alternative to retinochoroidectomy in managing posterior pole melanomas. This technique offers more adequate preservation of retinal architecture, thus potentially enhancing central visual function in patients with tumors located close to the fovea.

Adult↗
PubMed1992

Use of perfluoroperhydrophenanthrene in the management of suprachoroidal hemorrhages.

BACKGROUND: Suprachoroidal hemorrhage may cause the expulsion of intraocular contents. Generally, cases of nonexpulsive suprachoroidal hemorrhage have a better outcome than their expulsive counterparts. Those cases with massive nonexpulsive suprachoroidal hemorrhage do better with treatment than without. Treatment modalities have included suprachoroidal hemorrhage drainage with or without intraocular volume reformation, and vitrectomy. METHODS: The authors used the liquid perfluorocarbon perfluoroperhydrophenanthrene in the treatment of three patients with nonexpulsive suprachoroidal hemorrhage. The perfluorocarbon was injected into the vitreous cavity while the suprachoroidal blood was drained through anterior sclerotomies. RESULTS: With 5 months of follow-up, complete resolution of the suprachoroidal blood was noted in all patients. All three patients had attached retinas, and postoperative visual acuities were improved over preoperative visual acuities. CONCLUSION: Perfluoroperhydrophenanthrene and other perfluorocarbon liquids may be beneficial in the treatment of certain cases of nonexpulsive suprachoroidal hemorrhages.

Aged↗
PubMed1992

Vitreon, a short-term vitreoretinal tamponade.

This investigation of the liquid perfluorocarbon, perfluorophenanthrene (Vitreon), establishes its safety and efficacy as a short-term vitreoretinal tamponade. We utilised Vitreon as an intraoperative tool and postoperative vitreoretinal tamponade in 16 patients. Proliferative vitreoretinopathy (PVR) (six), giant retinal tear (four), rhegmatogenous retinal detachment (three), retinal detachment with keratoprosthesis (two), and submacular and vitreous haemorrhage (one) were successfully repaired. Vitreon was left in the eye and removed 5 days to 4 weeks postoperatively. Complications encountered included proliferative PVR (five), limited peripheral retinal detachment (three), macular pucker (two) cataract (three), hypotony (two), excessive fibrin reaction (one), and elevated intraocular pressure (one). At the latest evaluation, all retinas are attached with a follow-up of 1.25 to 12 months (mean 6.8 months).

Adolescent↗
PubMed1992

Posterior relaxing retinotomies: analysis of anatomic and visual results.

Fifteen eyes with complicated retinal detachments--11 with proliferative vitreoretinopathy (C3 D3), 2 with posterior segment trauma, and 2 with inflammatory retinopathy--were treated with vitrectomy, membrane peeling, and large posterior retinotomy. All posterior relaxing retinotomies were circumferential, including temporal quadrants in all cases. With a minimum follow up of 6 months, 12 eyes (80%) were attached posterior to the retinotomy. Reproliferation resulted in redetachment in 3 eyes (20%). Visual acuity improved in 53%, remained unchanged in 20%, and decreased in 27%. Of the 11 eyes that achieved stable or improved visual acuity, 5 (45%) achieved 20/400 to 20/25 vision, 5 achieved counts fingers perception, and 1 patient remained stable at hand motion perception. Of all the eyes undergoing surgery, hypotony (intraocular pressure < 5 mm Hg) occurred in 6 eyes (40%); 3 of these were among the 12 eyes with attached retinas.

Adolescent↗
PubMed1992

Orbital extension of sinus lymphoma in AIDS patient.

A case of a 27-year-old white male with acquired immunodeficiency syndrome (AIDS) who had a maxillary sinus tumor with secondary orbital involvement was reported. Marked proptosis and distortion of the globe were present. Biopsy by the Caldwell-Luc approach disclosed an immunoblastic lymphoma of B-cell origin. To the best of our knowledge, this is the first reported case of a maxillary sinus lymphoma extending into the orbit in a patient with AIDS.

Adult↗
PubMed1991

Tissue plasminogen activating factor assisted removal of subretinal hemorrhage.

We used tissue plasminogen activator (tPA) to aid in the surgical evacuation of subretinal hemorrhages. Subretinal hemorrhage secondary to a ruptured retinal macroaneurysm was treated in two patients. The surgical technique involved using a micropipette to fashion a small retinotomy through which tPA was injected into the subretinal space and through which the dissolved clot was removed. Visual acuity improved from counts fingers to 20/50 in one patient and from counts fingers to 20/70 in the other. Three additional patients, with massive subretinal hemorrhages secondary to age-related macular degeneration, were similarly treated. In one, visual acuity improved from counts fingers to 20/400; in two others, visual acuity was stabilized; in the first patient, at 20/300, and in the second patient at 20/400. The use of tPA minimizes surgical manipulation of the sensory retina and greatly reduces the size of the retinotomy required for evacuation of subretinal blood.

Aged↗
PubMed1991

A technique for retinal pigment epithelium transplantation for age-related macular degeneration secondary to extensive subfoveal scarring.

We describe the surgical excision of submacular scar in end-stage age-related macular degeneration and transplantation of autologous and homologous retinal pigment epithelial (RPE) cells. The technique involves the preparation of a large retinal flap encompassing the macula and the arcades, removal of the submacular scar, and replacement of the RPE cells, using either an autologous pedicle graft or homologous RPE cells and Bruch's membrane. Fourteen months following the procedure, visual acuity in a patient with a pedicle graft had improved from counts fingers to 20/400 and the patient fixated over the transplanted RPE cells. After 10 months, a homologous graft in a second patient had become encapsulated with a fine subretinal membrane without neovascular tissue; visual acuity had not improved. No intraoperative or postoperative complications resulting from the surgery occurred in either patient.

Aged↗