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Biomedical subjects

C C Nelson

Publications and source records attributed to C C Nelson.

At least 37 records · Page 2Linked to original sources
PubMed1994

Drill guide for hydroxyapatite implants.

A drill guide to facilitate the second drilling of hydroxyapatite orbital implants is presented. The drill guide is adaptable to various drill types. It is nontraumatic and provides excellent, one-handed fixation, eliminating the need for an assistant. It allows for consistent, straight drilling to a predetermined depth and, because it is encased, it protects the patient from injury. The drill guide has been used on 30 patients and is without untoward effects.

Durapatite↗
PubMed1994

Effects of maternal hospitalization in early childhood: anticipated anxiety associated with an analog separation for childbirth and surgery.

Assessed early childhood anticipation of anxiety in response to analog 3-day maternal hospitalization for surgery or childbirth. Reaction to analog nonhospital separation was also assessed. Within each condition, gender effects were examined. Participants were 120 first-grade children at four elementary schools. Between-groups comparisons showed maternal separation for surgery was anticipated as more anxiety provoking, whereas anxiety associated with separation for childbirth and nonhospital separation was anticipated as similar. In general, within each separation situation, girls and boys anticipated similar levels of anxiety.

Anxiety, Separation↗
PubMed1994

The effects of P-box substitutions in thyroid hormone receptor on DNA binding specificity.

Three "P-box" amino acids within the DNA recognition alpha-helix of members of the steroid hormone and thyroid hormone families of nuclear receptors are known to determine the identity of two of the six base pairs within the half-sites of cognate DNA elements. We introduced P-box substitutions derived from different members of the thyroid hormone/estrogen receptor (T3R/ER) family into the beta-isoform of human thyroid hormone receptor (hT3R beta) and tested the DNA binding and transactivation activities of these mutants using thyroid hormone response elements (TREs) with half-sites composed of different sequences and arranged in different orientations. Different P-box sequences derived from the T3R/ER family resulted in distinct DNA binding specificities determined by the fourth base pair of the half-site. Thyroid hormone receptor mutants containing EGA, EAA, EGS substitutions for the wild type EGG P-box bound with wild type affinity to consensus AGGTCA half-sites, regardless of orientation. TREs composed of AGGACA half-sites bound hT3R beta s with an EGG or EAA P-box sequence, but not those with EGA or EGS P-box sequence. A reversal of this specificity was observed on a direct repeat TRE with AGGGCA half-sites. Additionally, an ESG P-box substitution in hT3R beta prevented the receptor from binding to a direct repeat as a homodimer, but this mutant could bind as a heterodimer with retinoid X receptor or to the everted repeat TRE from the chicken lysozyme promoter.

Amino Acid Sequence↗
PubMed1994

Basic research in orbital and oculoplastic surgery.

This review summarizes basic research in orbital and oculoplastic surgery during the past year. Innovative and exciting projects have been undertaken elucidating microscopic anatomy of the orbital septum, orbital lymphatics, and levator elastic fiber network. Eyelid anatomy as assessed by magnetic resonance imaging has been beautifully demonstrated. In the realm of orbital disease, several studies have provided potential alternative therapeutic modalities in the management of the anophthalmic socket. These particular studies range from the use of demineralized bone in the rabbit anophthalmic socket, to the use of bone graft to reconstruct the monkey orbital floor. Further elegant studies outline the velocity of ophthalmic artery flow, and potential applications of ocular thermography.

Animals↗
PubMed1993

Gradual loss of synaptic cartels precedes axon withdrawal at developing neuromuscular junctions.

We have studied the spatial deployment of synapses arising from different axons that converge on the same developing neuromuscular junctions. Labeling the competing synaptic "cartels" with different dyes in mouse muscle showed that, perinatally, each axon adds similar terminal areas, whereas later, areas occupied by the competing cartels diverged by gradual elimination of one axon's synapses and ongoing addition of synaptic area by the other. Activity-dependent labeling of synapses capable of vesicle recycling in snake muscle also revealed a gradual change in territories occupied by competing inputs, implying that an axon maintained some functional synapses even as others in its cartel were being eliminated. Thus the process of synapse elimination is gradual, with loss of one viable synapse after another, until an axon is left with no synaptic territory and withdraws.

Animals↗
PubMed1993

Gas chromatography/tandem mass spectrometry measurement of delta 9-tetrahydrocannabinol, naltrexone, and their active metabolites in plasma.

The combination of gas chromatography and mass spectrometry (GC/MS) is generally recognized as offering the best sensitivity and specificity for the detection and measurement of drugs and their metabolites in biological specimens. This finding has resulted in the widespread use of GC/MS in many areas of pharmacology and toxicology. However, a GC/MS assay can be performed in many ways, depending upon the specific requirements of the analytical tasks. For example, pharmacokinetic studies generally employ chemical ionization and single-ion monitoring to obtain optimum sensitivity, whereas GC/MS methods for confirmation of the presence of drugs of abuse in urine most often use electron ionization and multiple-ion monitoring to obtain conclusive results. Another example is the increasing use of the combination of gas chromatography and tandem mass spectrometry (GC/MS/MS) for analyses requiring sensitivities better than nanograms per milliliter. Examples of the application of GC/MS and GC/MS/MS methods for the detection of delta 9-tetrahydrocannabinol, naltrexone, and their active metabolites are described and compared in terms of sensitivity, specificity, and unique features.

Dronabinol↗
PubMed1993

Tissue specificity and serologic reactivity of an autoantigen associated with autoimmune thyroid disease.

A recent report has identified a new autoantigen called D1 that appears to be associated with Graves' ophthalmopathy and is expressed in the thyroid and eye muscle. To better characterize the tissue specificity and disease relevance of this antigen, we evaluated the expression of D1 RNA in various human tissues using a reverse transcriptase polymerase chain reaction assay. These studies indicate a wide tissue distribution of the messenger RNA for this antigen, including the thyroid, eye muscle, parathyroid, spleen, skeletal muscle, and uterus. There were variations in the relative amounts of specific message for D1 in the different tissues, with the uterus, thyroid, and eye muscle having the greatest amount of product per microgram of total RNA. A maltose binding protein-D1 fusion protein was expressed in Escherichia coli, purified, and used to assess serologic reactivity to D1 by Western blot. Autoantibodies to this antigen were noted in 19 of 24 (78%) of Hashimoto's disease patients, 26 of 41 (63%) of Graves' disease patients, and in 9 of 17 (53%) of normal controls. Sixty percent of Graves' disease patients with clinical ophthalmopathy had antibodies to D1, as did 63% of Graves' patients without signs or symptoms of clinical ophthalmopathy. There was no correlation between reactivity to D1 and either clinical measures of hyperthyroidism or antibody titers to thyroid peroxidase or thyroglobulin. The presence of autoantibodies to this antigen in patients with Hashimoto's disease, in Graves' disease patients without ophthalmopathy and in normal controls indicate that serologic recognition of this antigen is not restricted to patients with ophthalmopathy. In addition, the expression of messenger RNA for this antigen in multiple types of cells questions the tissue specificity of this autoantigen.

Adult↗
PubMed1993

Functional analysis of the amino acids in the DNA recognition alpha-helix of the human thyroid hormone receptor.

The roles in DNA binding and transcriptional activation of individual amino acids in the putative recognition alpha-helix of the first zinc finger of the beta-isoform of the human thyroid hormone receptor (hT3R beta) have been probed by site-directed mutagenesis. Alanine substitutions of highly conserved residues involved in the folding of this zinc finger abolished the binding of hT3R beta to various thyroid response elements. A similar effect was observed for alanine substitutions of those conserved residues in hT3R beta that were expected to make specific contacts to DNA bases common to all hormone response elements. The three P-box amino acids have previously been shown to be essential for discrimination of the base pairs that differ between the DNA binding sites for related steroid/thyroid hormone receptors. In hT3R beta, the P-box residues are E, G, and G; the results of this study show that alanine substitution of the glutamic acid dramatically reduces DNA binding activity by hT3R beta, while the substitution of either glycine has little or no effect on DNA binding. The effects of alanine substitutions on hT3R beta transcriptional activation properties were consistent with the effect of these substitutions on DNA binding properties, with the exception of the second P-box amino acid. T3R beta substituted with alanine at this position is substantially more defective in transcriptional activation than it is in specific DNA binding. These results indicate that there are two separate mechanisms of response element discrimination by P-box amino acids of steroid/thyroid hormone receptors, one which operates at the level of DNA recognition and a second which operates at the level of transcriptional activation.

Amino Acid Sequence↗
PubMed1992

Chromatographic and mass spectrometric methods for determination of lysergic acid diethylamide (LSD) and metabolites in body fluids.

Continued illicit use of the potent psychedelic drug lysergic acid diethylamide (LSD) has stimulated efforts to develop effective analytical methods for detection of the drug and its metabolites in body fluids from suspected LSD users. Recently reported methods based on gas and liquid chromatography, combined with single- and multiple-stage mass spectral analysis, now permit accurate detection and quantitation of LSD at sub-nanogram/milliliter concentrations.

Body Fluids↗
PubMed1992

Determination of lysergic acid diethylamide (LSD), iso-LSD, and N-demethyl-LSD in body fluids by gas chromatography/tandem mass spectrometry.

Procedures for detection and quantitation of lysergic acid diethylamide (LSD), iso-LSD, and N-demethyl-LSD by capillary chromatography/tandem mass spectrometry (GC/MS/MS) are presented. Several methods for derivatization, sample introduction, and ionization, in combination with mass spectrometry/mass spectrometry (MS/MS), have been evaluated for overall ionization efficiency and product-ion sensitivity and specificity. Fragmentation pathways derived from low-energy collision-induced dissociation (CID) spectra of protonated LSD, and the protonated trimethylsllyl derivatives of LSD (LSD-TMS) and deuterium-labeled analogs of LSD, have been proposed. Principal dissociations primarily involve the amide and piperidine-ring moieties in which losses of CH3 radical, CH3NH2, CH3NCH2, diethylamine, diethylformamide, and N,N-diethylpropenamide from MH+ are observed. Positive-ion ammonia chemical ionization and subsequent MS/MS analysis of the protonated molecules (MH+) of the trimethylsilyl (TMS) derivatives of LSD, iso-LSD, and N-demethyl-LSD provide a high degree of specificity for identification of these compounds in urine or blood at low-pg/mL concentrations. Negative-ion chemical ionization and GC/MS/MS analysis of the molecular anion (M-) of the trifluoroacetyl (TFA) derivative is well suited for trace-level identification of N-demethyl-LSD, a metabolite of LSD.

Body Fluids↗
PubMed1992

Extrascleral malignant melanoma.

We present two cases of anterior extrascleral extension of malignant melanoma in eyes previously blind from other causes. In both cases, the tumor was not detected by the physician but rather by the patient himself (case 1) or his wife (case 2). In one case, the tumor became manifest more than 60 years after the eye became blind from trauma. Although blind eyes may harbor lethal tumors and, therefore, need regular examinations, this simple part of the physical examination frequently remains neglected by ophthalmologists as well as by primary care physicians. We wish to emphasize the potential life-saving importance of regular examinations of blind eyes.

Aged↗
PubMed1992

Acute dacryoadenitis and Crohn's disease: findings and management.

Concurrent orbital pseudotumor and Crohn's disease, although rare, have been described. To the best of our knowledge, pseudotumor isolated to the lacrimal gland (dacryoadenitis) with concurrent Crohn's disease has never been reported. We present the clinical course and ultrasonographic and radiologic findings of an acute case of isolated bilateral lacrimal gland pseudotumor in a patient with Crohn's disease. The treatment and review of the literature are discussed.

Acute Disease↗
PubMed1992

Tension pneumoorbitus.

Posttraumatic tension orbitus developed in a young man causing subconjunctival emphysema and proptosis. Intraocular pressures were monitored as a means of indirectly measuring intraorbital pressure. The patient was serially examined for evidence of compressive optic neuropathy. Because of the possibility of orbital pressure increasing several hours from the time of injury, we recommend monitoring of these patients through intraocular pressure measurement and evaluation of the optic nerve for evidence of compression. Our findings, however, do support previous documentation that the intraocular pressure rise following orbital trauma with orbital emphysema is usually not of sufficient severity or duration to result in visual compromise.

Adult↗
PubMed1992

Orbital diagnosis and imaging.

A myriad of imaging modalities now exists to aid in the diagnosis of orbital disease. Most of the recent advances in orbital diagnosis are based on refinements of established techniques, although several represent the application of new technology. Invasive techniques, such as orbital arteriography and venography, have been supplanted with computed tomography, which has become the mainstay of orbital diagnosis. The use of magnetic resonance imaging in the assessment of orbital pathology has also increased. Color Doppler, a recent development in ultrasonography, has now been applied to the eye and orbit.

Biopsy↗
PubMed1992

Oculocardiac reflex in the anophthalmic socket.

The oculocardiac reflex occurred in a patient with an anophthalmic socket undergoing surgery for inferior fornix shortening and laxity of the lower lid. This reflex occurs only rarely in anophthalmia; it has not been previously reported during socket surgery.

Aged↗
PubMed1991

Eyelid lipogranuloma after hydraulic oil injury.

The cytopathology of a lipogranuloma of external origin is reported in the eyelid of a 32-year-old man excised 1 year following regional exposure to an explosion of hydraulic oil under high pressure. The foreign lipids were still present in chronic lipogranulomas with intercellular lipid-filled cysts surrounded by macrophages and giant cells containing intracellular lipid-filled vacuoles. These indicate efforts in storage and very slow digestion. Secondary fibrosis in the region of the lipogranuloma was an important associated process. In view of the widespread technical use of hydraulic oily fluids under high pressure, it is recommended that these fluids be biodegradable.

Accidents, Occupational↗
PubMed1991

Argon laser versus thermal cautery for punctal occlusion. An animal study.

A subset of the dry-eye patient group manifests their problem so severely that permanent punctal occlusion is required. The technique most often used today is thermal cautery. In this prospective study, an animal model was developed, and the effectiveness of the argon laser as a primary alternative therapy to thermal cautery was evaluated. Dogs were found to have a punctum similar in shape and location to humans; therefore, they were deemed to be a more appropriate animal model for punctal studies than cats. Both laser and thermal cautery are similarly effective in completely occluding puncta in animals. There was a trend toward greater stenosis with the laser in those puncta that were only partially occluded. In addition, laser punctal occlusion appeared to be less painful than thermal cautery.

Animals↗