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Biomedical subjects

D A Nelson

Publications and source records attributed to D A Nelson.

At least 19 recordsLinked to original sources
PubMed1979

Acute leukemia with unusual cytoplasmic inclusions: a cytochemical and ultrastructural study.

A 76-year-old woman with acute leukemia responded incompletely to prednisone and vincristine. Cytochemistry of the blast cells demonstrated only focal alpha-naphthyl acetate and alpha-naphthyl butyrate esterase activity and focal coarse granular beta-glucuronidase activity, a pattern usually associated with acute lymphocytic leukemia. Electron microscopy demonstrated primitive cells with features usually associated with promonocyte differentiation including prominent parallel arrays of microfilaments and nucleoli of the nucleolonema type. In Wright-stained films, blasts contained oval, pale-blue, yellow tinged cytoplasmic inclusions about 2 to 4 micrometers in diameter which did not stain with any of the cytochemical methods employed. With electron microscopy, these inclusions were nonmembrane bound structures, varying from amorphous electron dense stippling to irregularly arranged short segments of filaments to prominent parallel arrays of filaments. We propose that the inclusions may have arisen from the parallel arrays of microfilaments and are nonspecific.

Aged↗
PubMed1979

Spontaneous remission in acute myelogenous leukemia in the adult.

A spontaneous complete remission of 17 months duration was observed in a patient with acute myelogenous leukemia. Resolution of all clinical and morphologic abnormalities occurred. The remission was apparently associated with an acute pulmonary infection. At relapse, remission induction was accomplished with cystosine arabinoside and daunorubicin therapy. In vitro granulocyte-macrophage agar culture studies (CFU-c) showed an abnormal growth pattern at presentation, which persisted during the period of spontaneous remission. Reports of spontaneous remissions of acute myelogenous leukemia in adults have become increasingly rare, and the remissions themselves are short-lived. Despite the association between spontaneous remissions and acute infections or febrile episodes, attempts at remission induction with infectious agents have been unsuccessful. Spontaneous remissions are an uncommon variant of the natural course of acute myelogenous leukemia in the adult.

Aged↗
PubMed1979

Emergency room misuse by medical assistance patients in a family practice residency.

Four hundred individual Emergency Room records were retrospectively reviewed. Demographic data, complaint, diagnosis, and treatment were tabulated and analyzed by computer assistance. Judgment was not made regarding the necessity of physician consultation, but whether an Emergency Room visit was warranted considering the duration of the presenting complaint. During a time period when 29 percent of the total outpatient visits to the Family Practice Center Model Office were made by recipients of Medical Assistance, the same population accounted for 53 percent of the Emergency Room visits reviewed. Twenty-five percent of the 400 visits were judged to be unnecessary according to the pre-established criteria. Sixty-four percent of the unnecessary visits were by Medical Assistance patients. Of 304 total families represented, 73 were responsible for multiple visits. Thirty-one percent of these visits were unnecessary, whereas 21 percent of the visits made by families with single visits were unnecessary. In this family practice setting, it is concluded that Medical Assistance patients have a greater tendency toward inappropriate use of the Emergency Room when compared to non-Assistance patients.

Adolescent↗
PubMed1979

Two-tone masking and auditory critical bandwidths.

Two-tone masking of 1,000-Hz signals was investigated in 5 normally-hearing listerners. The results indicate a consistent increase in critical bandwidth with level of the two masking tones (approximately 3%/dB). Irregularities in the individual two-tone masking functions led to further investigations with a single listener. For subcritical frequency separations between masking tones, -10 dB/decade masking slopes were demonstrated along with large dips or notches in the two-tone masking functions. Both the -10 dB/decade masking slopes and the large notches were replicated in detail when only the lower-frequency tones of the two-tone masking pairs were employed as maskers. Separate masking bands were then introduced that eliminated the -10 dB/decade masking slope and the large notch. It is concluded that the two-tone masking experiment is really a single-tone experiment, and that the detection of beats, roughness, and combination tones determines the form of single-tone and two-tone masking functions. If critical bnadwidth estimates are to be obtained from these experiments, it is most appropriate to refer to those estimates as "critical bandwidths for tonal interaction".

Acoustic Stimulation↗
PubMed1978

L-Asparaginase-induced coagulopathy during therapy of acute lymphocytic leukemia.

L-Asparaginase-induced coagulation abnormalities were observed in all patients receivng this drug. All patients studied demonstrated low factor IX and fibrinogen levels and most (75%) had low levels of factor XI. Disturbances in other factors were much less frequent. Despite the presence of markedly abnormal coagulation studies, clinical bleeding was not observed.

Adolescent↗
PubMed1978

Frequency discrimination in the chinchilla.

Chinchillas were trained with shock-avoidance procedures to discriminate or detect pure-tone frequency differences. Inital attempts at determining frequency-difference thresholds utilized a complex discrimination paradigm and a go-no-go response. Although discriminations of large frequency differences were obtained from chinchillas after considerable training, discriminations of small frequency differences could not be trained. Therefore, determinations of frequency-difference thresholds could not be made with the complex discrimination paradigm and the go-no-go response task. A simple detection paradigm, involving the detection of frequency alternation in an ongoing train of tone bursts proved to be a more successful technique. Frequency-alternation detection was quickly learned by six chinchillas, and frequency-difference thresholds were obtained with an adaptive sequential procedure. Psychometric functions were reconstructed from the threshold tracking data of chinchillas, and comparisons were made with differential frequency thresholds from cats and humans obtained by previous investigators. Differential frequency thresholds from chinchillas paralleled those from cats and were about twice as large. Differential frequency thresholds from humans were considerably smaller than from chinchillas, especially for low-frequency tones. When a constant detectability index was used to specify differential frequency sensitiviy in chinchillas, chinchilla and human differential sensitivity functions paralleled one another. Human differential sensitivity was about ten times better than that of the chinchilla.

Animals↗
PubMed1977

Chromatin subunits from baker's yeast: isolation and partial characterization.

The organization of proteins along DNA in chromatin of Saccharomyces cerevisiae (baker's yeast) was examined by analyzing the DNA and nucleoprotein products obtained after digestion of yeast nuclei with staphylococcal nuclease. Yeast DNA is digested in situ at regularly spaced cleavage sites about 160 base pairs apart. Nucleoprotein fragments were resolved and isolated by centrifugation on linear, 5-20% sucrose gradients. The predominant 11S component appears to be identical to chromatin "subunits" or "nucleosomes" isolated from higher eukaryotes, containing a 150-160 base pair length of DNA and approximately equimolar amounts of four proteins that coelectrophorese with calf histones H2A, H2B, H3, and H4, plus small amounts of three proteins that electrophorese similarly to H1 histones. Thus, the structural organization of the yeast genome is similar to that of more developed organisms, except for the smaller total repeat length. None of the yeast subunit proteins, including the possible H1 proteins, contains cysteine.

Centrifugation, Density Gradient↗
PubMed1977

The zeta sedimentation ratio (ZSR) and activity of disease in rheumatoid arthritis.

Zeta sedimentation ratios (ZSR) and modified Westergren erythrocyte sedimentation rates (ESR) were compared with an independent clinical assessment of disease activity in 100 patients with rheumatoid arthritis. The correlation between ZSR and ESR was good. Both methods correlated well with disease activity. The ZSR was more frequently elevated than the ESR in each category of disease activity, but the differences were slight. In addition to its practical advantages, the ZSR appears to be a satisfactory method for monitoring the activity of rheumatoid arthritis.

Adult↗
PubMed1977

Histones H2A and H2B are neighbors along DNA in chromatin: characterization of subnucleosomal particles containing H2A+H2B.

Two specific slow sedimenting nucleoprotein particles containing equimolar amounts of histones H2A and H2B and 38 or 49 base pair (bp) lengths of DNA have been isolated by centrifugation on sucrose gradients. The 3.4S particles containing 38 bp DNA and H2A+H2B thermally denature at 61 degrees, considerably higher than Proteinase K treated particles (44 degrees), but lower than 11S nucleosomes (76 degrees). Treatment with Proteinase K increases the circular dichroism of 3.4S particles at 280 nm by 63% and decreases the sedimentation coefficient to 2.1S. These results indicate that H2A and H2B are proximate along DNA in nucleosomes and alone can alter the optical activity and perhaps conformation of local regions of DNA.

Animals↗
PubMed1977

Structural repeat units of Chinese hamster ovary chromatin. Evidence for variations in repeat unit DNA size in higher eukaryotes.

DNA lengths in the structural repeat units of Chinese hamster ovary (CHO) and chicken erythrocyte chromatin were compared by analyzing the sizes of DNA fragments produced after treatment of nuclei with staphylococcal nuclease. The repeat length of CHO chromatin (173 +- 4 BP) is about 20 base pairs (BP) smaller than that of chicken erythrocyte chromatin (194 +- 8 BP). Repeat lengths of rat liver and calf thymus chromatin were found to be about 10 BP shorter than that of chicken erythrocyte chromatin. Thus significant variations occur in repeat units of chromatin of higher eukaryotes. These variations occur in the lengths of "spacer" (or "internucleosomal") DNA segments, not in "core particle" (or "nucleosomal") DNA lengths. The concept of spacer regions and the possible influence of H1 histones is discussed.

Animals↗