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Biomedical subjects

D A Nelson

Publications and source records attributed to D A Nelson.

At least 181 records · Page 10Linked to original sources
PubMed1982

Frequency discrimination in regions of normal and impaired sensitivity.

Psychometric functions for frequency discrimination were obtained from both normal-hearing and hearing-impaired listeners at 300, 1200, and 3000 Hz. Difference limens for frequency (DLFs) were derived from those psychometric functions after repeated practice sessions, ensuring that all listener's results represented levels of optimum performance. Practice effects were found to be considerable in many listeners. The psychometric functions for all listeners, both normal-hearing and hearing-impaired, were well described by linear functions of performance level (d') and frequency difference (Hz), which passed through the zero origin. Those listeners with normal sensitivity thresholds at all frequencies exhibited the most acute frequency discriminations. Listeners with sensitivity losses at high frequencies exhibited larger DLFs, even at lower test frequencies where sensitivity thresholds were normal.

Adult↗
PubMed1982

Frequency discrimination at 1200 Hz in the presence of high-frequency masking noise.

To evaluate the possible contribution of high-frequency hearing to frequency discrimination at lower frequencies, pure-tone frequency discrimination tasks at 1200 Hz, with and without high-frequency masking noise, were performed by two highly practiced normal-hearing listeners. Signal levels ranged from 10 to 80 dB SPL. Spectra of the three high-frequency masking noises ranged from 1.8 to 2.1 kHz, from 2.8 to 3.1 kHz, and from 4 to 8 kHz. The frequency difference limen (DLF) intensity functions, describing DLFs as a function of signal level which were obtained in the presence of high-frequency masking noise, were essentially the same as the DLF intensity functions obtained without masking noise. These results indicate that high-frequency hearing is not necessary for acute frequency discriminations at low and at middle frequencies.

Adult↗
PubMed1982

Anterior cruciate ligament reconstruction using one-third of the patellar ligament, augmented by extra-articular tendon transfers.

Eighty patients with persistent clinical and functional instability of the knee due to anterior cruciate ligament insufficiency underwent the operation reported, in which one-third of the patellar ligament substitutes for the cruciate ligament and extraarticular tendon transfers, medial and lateral, augment the substitution. The patients were followed for a minimum of two years, and fifty returned for personal evaluation. The average follow-up was thirty-three months, with a range of two to five years. There were thirty-five male and fifteen female patients. The average age was twenty-three years. The average interval from initial injury to the index operation was two years. Meniscal tears and articular changes were noted in most of the patients. Forty-three (86 per cent) of the fifty patients had at least one torn meniscus, twenty-seven patients (54 per cent) had significant degenerative articular changes, and fourteen (28 per cent) had patellar articular changes. In the procedure described, eccentric placement of the tibial and femoral tunnels for more accurate placement of the patellar ligament substitute is essential. The over-all results were graded as excellent in thirty knees, good in seventeen, fair in one, and a failure in two. One knee that was classified as a failure showed excellent stability, but the patient had significant pain from chondromalacia of the patella, while significant pain and hyperesthesia from a neuroma was the reason for failure in the second patient.

Adolescent↗
PubMed1981

Proteoglycans in the microvasculature. I. Histochemical localization in microvessels of the rabbit eye.

The ultrastructural organization of ruthenium red (RR) stainable material within small blood vessels located in the limbus of the rabbit eye was studied. Proteoglycans were identified in this material by digesting tissues with Streptomyces hyaluronidase, testicular hyaluronidase, chondroitinase ABC, or heparinase before ruthenium red staining. Neuraminidase digestion enabled separate identification of sialoglycoprotein. The luminal surface of endothelial cells demonstrates an RR-stained glycocalyx containing both sialoglycoprotein and proteoglycans, which are removed by testicular hyaluronidase and crude heparinase. The basal coat of endothelial cells and small granules (10-20 nm in diameter) located within the basal lamina stain with RR and are removed only by crude heparinase. The surface coat of smooth muscle cells and small granules (10-20 nm) within their basal laminas are also digested by crude heparinase. Large proteoglycan granules (20-50 nm), which are completely removed by testicular hyaluronidase and partially digested by Streptomyces hyaluronidase, are deposited between the connective tissue fibers of the media and adventitia. Other large granules that are attached to collagen fibers contain enzyme-resistant anionic materials. The surface coat of adventitial fibroblasts is removed only by crude heparinase. Thin filaments (3-5 nm in diameter) interconnect the cell coat material, basal lamina granules, and large connective tissue granules, to form a network of proteoglycans that traverses the intima, media, and adventitia. The highly ordered arrangement of proteoglycans in the microvascular wall suggests that these macromolecules play several roles in microvascular function.

Animals↗
PubMed1981

Proteoglycans in the microvascular. II. Histochemical localization in proliferating capillaries of the rabbit cornea.

The ultrastructural distribution of proteoglycans around capillaries growing in the cornea of the rabbit eye was determined after staining with ruthenium red (RR). Proteoglycans were identified by digesting tissues with glycosaminoglycan-degradative enzymes. Sialoglycoproteins were differentiated from proteoglycans by neuraminidase digestion. The capillary sprouts demonstrated a luminal glycocalyx containing testicular hyaluronidase-sensitive proteoglycans but little or no sialoglycoprotein. At the capillary tips, where mitosing and migrating endothelial cells are located, the basal cell surface displayed a network of small RR-stained granules (8 nm in diameter), which was partially removed by streptomyces hyaluronidase but not by testicular hyaluronidase. Thin filaments connected the granules to the endothelial cell plasmalemma and to a similar network of granules that is normally present in the corneal stroma. The stroma granules were partially digested by testicular hyaluronidase. In older capillary regions, where endothelial cells ceased proliferation, the basal network of proteoglycan granules was gradually infiltrated by fibrillar material until a basal lamina was formed. The proteoglycan granules were then arranged on both sides of the lamina densa, and a thin glycocalyx covered the basal endothelial cell surface. Thus, proteoglycans and anionic materials associated with growing capillaries serve to link proliferating and migrating endothelial cells to the extracellular matrix, help to organize the capillary basal lamina, form an anionic surface along the luminal front of capillaries, and probably help stabilize the structure of the capillary wall after proliferation ceases.

Animals↗
PubMed1980

Blood colony and cluster-forming activity during various stages of chronic granulocytic leukemia.

The colony and cluster-forming capacity of peripheral blood cells obtained from 25 patients who had chronic granulocytic leukemia (CGL) was evaluated in a double-layer agar culture. Increased numbers of colonies (mean, 264) and clusters (mean, 908) were obtained from the blood cells of nine of ten patients when first examined. The blood cells from 19 patients whose diseases were in the control phase formed normal or nearly normal numbers of colonies and clusters. During the aggressive phase, elevated blood colonies and clusters were observed in the 12 patients studied. Two to four times as many clusters as colonies were observed during these phases of CGL. At the time of blastic crisis, at least eightfold more blood clusters than colonies were observed in the eight patients studied. These studies indicate that the evaluation of blood colony and cluster-forming cells may provide a useful characterization of various clinical phases of CGL in individual patients.

Cell Aggregation↗
PubMed1980

Rapid in situ cytochemical classification of CFU-C colonies in soft agar culture: permanent whole culture preparations.

Soft agar culture CFU-C (colony-forming units in culture) are rapidly classified in situ as eosinophil, macrophage, and neutrophil-monocyte types by whole culture staining with luxol fast blue for eosinophil specific granules and acetoorcein for nuclei. Stained colonies may be picked and examined individually as wet mount cover slip preparations, or the agar culture may be air dried and mounted permanently. The whole culture stain has been variously modified for the enzyme markers alpha-naphthyl acetate esterase and peroxidase and for nuclear staining alone with acetoorcein.

Agar↗
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↗