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Biomedical subjects

D A Nelson

Publications and source records attributed to D A Nelson.

At least 163 records · Page 9Linked to original sources
PubMed1985

Anthralin therapy for alopecia areata.

Topical anthralin application producing a brisk irritant contact dermatitis has been reported to have therapeutic benefit in alopecia areata. A pilot clinical study was undertaken to determine whether topical anthralin application in doses low enough to produce only minimal contact dermatitis would produce a similar therapeutic response. None of the patients in the study received any benefit from this low-dose regimen. If anthralin is of benefit in the therapy of alopecia areata, a significant irritant contact dermatitis is apparently required.

Administration, Topical↗
PubMed1985

Extension of a temporal model of frequency discrimination: intensity effects in normal and hearing-impaired listeners.

The effects of intensity on the difference limen for frequency (DLF) in normal-hearing and in hearing-impaired listeners are incorporated into the temporal model of frequency discrimination proposed by Goldstein and Srulovicz [Psychophysics and Physiology of Hearing, edited by E. F. Evans and J.P. Wilson (Academic, New York, 1977)]. A simple extension of the temporal mode, which includes the dependence of phase locking on intensity, is sufficient to predict the effects of intensity on the DLF in normal-hearing listeners. To account for elevated DLFs in hearing-impaired listeners the impairment is modeled as a reduction in the synchrony of the discharge from VIIIth-nerve fibers that innervate the region of hearing loss. Constraints on the optimal processor and the validity of the temporal model at high frequencies are discussed.

Hearing Loss↗
PubMed1984

Endoscopic variceal sclerotherapy: experience with 30 patients.

Endoscopic sclerotherapy is used to obliterate esophageal varices in an attempt to decrease bleeding episodes. First reported in the 1940s, sclerotherapy has recently enjoyed renewed interest because surgical shunting procedures, though effective in preventing rebleeding, are associated with significant mortality and provide no increase in long-term survival. Sclerotherapy, using a flexible endoscope, has been used in 30 patients at Vanderbilt University and the VA Medical Center, Nashville, Tenn. We present our clinical experience, compare our results with those of other groups, and discuss other approaches to the management of bleeding varices.

Adolescent↗
PubMed1984

Angiolymphoid hyperplasia with eosinophilia.

Angiolymphoid hyperplasia has become a well-recognized entity in adults. Kimura's disease is a similar and possibly identical disease occurring in Oriental children. This is a case report of angiolymphoid hyperplasia with eosinophilia occurring in a 12-year-old Caucasian boy with elevated levels of serum IgE. The condition responded to intralesional triamcinolone. A brief review of the literature is presented and various modes of therapy are discussed.

Angiolymphoid Hyperplasia with Eosinophilia↗
PubMed1984

Broadened forward-masked tuning curves from intense masking tones: delay-time and probe-level manipulations.

Forward-masked psychophysical tuning curves were obtained from normal-hearing listeners under two conditions: lengthened delay time between masker and probe, and increased probe level. Both conditions required higher-level masking tones and both conditions resulted in broader tuning curves. Comparisons were made of tuning curves obtained with different probe-level and delay-time combinations that were chosen to require equivalent masker levels at the probe frequency. Nearly identical tuning-curve shapes were obtained when masker level at the probe frequency was the same. The results are predicted by a two-process model, consisting of a nonlinear filter followed by an exponential decay. Tuning-curve shapes in forward masking appear to be largely dependent upon the masker level (filter output level) at which one attempts to measure them.

Auditory Perception↗
PubMed1983

Extraction of histones H2A, H3 and H4 from yeast nuclei. Measurement of the extent of yeast histone acetylation following one-dimensional gel electrophoresis.

Yeast histones H2A, H3 and H4 were specifically extracted from purified nuclei using a 2% NaCl/75% ethanol solution. The extraction resulted in the complete removal of H2A, H3 and H4 from the nuclear pellet, as monitored by SDS-polyacrylamide gel electrophoresis of the protein. The relative absence of nonhistone proteins from this histone subset simplifies the determination of the extent of histone modification in yeast. Levels of H4 acetylation were measured directly on Coomassie blue-stained Triton acid-urea gels and the levels verified by gel fluorography of the [3H]acetate-labeled histone.

Acetylation↗
PubMed1983

The in vitro effects of vincristine on peripheral blood leukocyte progenitor cells (CFU-C) in patients in blast crisis of chronic granulocytic leukemia: correlation with clinical response.

The in vitro sensitivity of circulating progenitor cells (CFU-C) of 20 patients in blast crisis of chronic granulocytic leukemia (CGL) to vincristine was correlated with the clinical response to vincristine in vivo. Eleven patients who achieved either a good or partial clinical response displayed a reduction in the number of colonies or clusters formed by their peripheral blood leukocytes in a double layer agar culture assay following incubation with vincristine. The CFU-C of five of six patients who failed to respond clinically to vincristine and prednisone were not suppressed following incubation with up to 12 microM vincristine. Three additional patients were not evaluable due to early post-treatment deaths. In vitro assay of the effects of vincristine on CFU-C appears to have predictive value for in vivo response in blast crisis of CGL.

Adult↗
PubMed1983

An analysis of psychophysical tuning curves in normal and pathological ears.

Simultaneous psychophysical tuning curves were obtained from normal-hearing and hearing-impaired listeners, using probe tones that were either at similar sound pressure levels or at similar sensation levels for the two types of listeners. Tuning curves from the hearing-impaired listeners were flat, erratic, broad, and/or inverted, depending upon the frequency region of the probe tone and the frequency characteristics of the hearing loss. Tuning curves from the normal-hearing listeners at low-SPL's were sharp as expected; tuning curves at high-SPL's were discontinuous. An analysis of high-SPL tuning curves suggests that tuning curves from normal-hearing listeners reflect low-pass filter characteristics instead of the sharp bandpass filter characteristics seen with low-SPL probe tones. Tuning curves from hearing-impaired listeners at high-SPL probe levels appear to reflect similar low-pass filter characteristics, but with much more gradual high-frequency slopes than in the normal ear. This appeared as abnormal downward spread of masking. Relatively good temporal resolution and broader tuning mechanisms were proposed to explain inverted tuning curves in the hearing-impaired listeners.

Adult↗
PubMed1983

Pure tone pitch perception and low-frequency hearing loss.

Pitch perception for pure tones was investigated in a group of listeners with low-frequency sensorineural hearing loss. Pitch judgments from each listener were compared with results from psycho-acoustic tasks which provide information on the "place" of cochlear response. The pitch measures employed were: (1) binaural pure-tone pitch matching in a listener with unilateral hearing loss, (2) octave judgments in listeners with musical ability, and (3) pitch-intensity functions in other listeners. Cochlear place of response was inferred from psychophysical tuning curves (PTC's). Two distinct types of PTC's for low-frequency probe tones were observed. Three listeners demonstrated "abnormally tuned" PTC's. For these listeners the frequencies that were most effective at masking the probe were considerably higher than the probe frequency. The three remaining listeners demonstrated "normally tuned" PTC's. Listeners with abnormally tuned PTC's were suspected of having an extremely abnormal place of response for low-frequency tones; this response pattern being located more toward the base of the cochlea than in the listeners with normally tuned PTC's. Sensitivity thresholds measured in the presence of high-pass masking noise supported this hypothesis. Small pitch-frequency irregularities were observed in many listeners, although they were not consistently related to the inferred place of response for that frequency. The individual listeners' pitch judgments failed to distinguish between two types of PTC's. In particular, listeners who demonstrated abnormally tuned PTC's did not exhibit correspondingly large pitch irregularities. These results are difficult to explain on the basis of a classical "place" theory of pitch perception.

Adult↗
PubMed1983

A general equation describing frequency discrimination as a function of frequency and sensation level.

Frequency-discrimination thresholds, for a wide range of stimulus frequencies and stimulus levels, were obtained from three normal-hearing listeners. Linear regression analyses of the present data, and of data from two previous studies, indicate that an SL-1 transformation of stimulus level and a square root F transformation of stimulus frequency yield linear dimensions that allow accurate predictions of frequency-discrimination thresholds from normal-hearing listeners over a wide range of stimulus frequencies (125-8000 Hz) and stimulus levels (5-8 dB SL) with a single prediction equation.

Humans↗
PubMed1983

Chronic neutropenia: diagnostic approach and prognosis.

Chronic neutropenia is a term used to describe a group of disorders characterized by a persistent neutrophil count of less than 1500 cells/microliters. We studied seven children and three sets of parents. We separated patients into a group with good prognosis and a group at higher risk of infection by using a combination of tests, including bone marrow aspiration and biopsy, steroid stimulation of bone marrow reserve, and in vitro CFU-GM and CSA assays. Children with a normal number of myeloid elements in their bone marrow and a normal bone marrow response to steroid stimulation had a benign course. CFU-GM and CSA assays helped to classify these children's neutropenia when their bone marrow had decreased numbers of myeloid elements. Family studies in three children were consistent with an inherited neutropenia, even when their parents were hematologically normal.

Adult↗
PubMed1982

The presence of Burkitt-like cells in non-Burkitt's neoplasms.

In four cases, the morphology of neoplastic cells from the peripheral blood and bone marrow suggested the diagnosis of American Burkitt's lymphoma or acute lymphocytic leukemia (French--American--British--Classification; FAB-L3). Cytochemical and immunologic studies, however, indicated that the neoplastic cells in one case were characteristic of acute lymphocytic leukemia (non-B, non-T-cell type); in another case, metastatic carcinoma; and in two two cases acute myelomonocytic leukemia. We conclude that cytochemical and immunologic cell markers are necessary for the diagnosis of American Burkitt's lymphoma. In addition, neoplastic cells simulating lymphoblasts of acute lymphocytic leukemia, FAB-L3 may derive from non-B lymphocytic lineage.

Adult↗
PubMed1982

Histone acetylation in baker's yeast. Maintenance of the hyperacetylated configuration in log phase protoplasts.

The extent and rates of histone acetylation in the yeast Saccharomyces cerevisiae were investigated. The yeast histones are highly acetylated during log phase. The modification examined is not a function of polypeptide synthesis, but rather occurs on the histones subsequent to deposition. The log phase yeast histones are neither rapidly acetylated nor rapidly deacetylated. Acetylation and deacetylation rates for histones H3 and H4 are on the order of hours, indicating that, during log phase, these histones are maintained in the hyperacetylated form. The acetate turnover rate for H2B is somewhat increased over that observed for H3 and H4.

Acetates↗
PubMed1982

Predictive value of the CFU-C assay in acute nonlymphocytic leukemia.

A double-layer agar culture assay for granulopoietic progenitor cell (CFU-C) was employed to study the in vitro growth pattern of bone marrow or peripheral blood cells from 37 patients at diagnosis of acute nonlymphocytic leukemia. The patients were classified as having type A growth if there were greater than 50 colonies (A1), or greater than one colony and greater than 50 clusters was observed after 14 days in culture (A2). Type B growth was defined as no growth (B1), less than 50 colonies and less than 50 clusters (B2) or cluster growth only (B3). Agar cultures containing marrow cells from 10 patients were stained in situ, and the colonies and clusters revealed abnormal cellular maturation. Treatment with cytosine arabinoside and an anthracycline resulted in a complete remission of leukemia in one of 15 patients with type A growth and 17 of 22 patients with type B growth. The subtype of growth pattern did not correlate with the mechanism (i.e., drug resistance versus kinetic resistance) for the failure to achieve a complete remission. The subtype of type B growth (B1, B2 or B#) did not correlate with the duration of complete remission. Nonetheless, the growth patterns observed in cultures of cells obtained from patients with acute nonlymphocytic leukemia appear to be excellent predictors of the success of achieving complete remission with induction therapy.

Acute Disease↗
PubMed1982

Kanamycin and bumetanide ototoxicity: anatomical, physiological and behavioral correlates.

Severe hair-cell degeneration and cochlear dysfunction was observed in chinchillas examined at 60 days (or longer) after administration of a single injection of 150 mg/kg kanamycin, followed 2 h later by a single injection of 20 mg/kg bumetanide. Outer hair cells in the cochlear base were most severely affected. While inner and outer hair-cell loss was common, some animals showed large regions along the basilar membrane where almost all inner hair cells were present and almost all outer hair cells were absent. Wherever areas of complete degeneration of the organ of Corti occurred, a small, diffuse population of nerve fibers within the spiral lamina was always present. Single-unit tuning curves correlated best with anatomical observations, compared with the other functional measures of auditory sensitivity that were obtained (behavioral audiogram and compound action potential thresholds). Results indicated that behavioral detection of auditory stimuli is relatively independent of innervation density as long as a few inner hair cells are present. Thus, the cross-fiber threshold envelope of the single-unit tuning curves appeared very similar to the behavioral audiogram.

Animals↗