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Biomedical subjects

P Allen

Publications and source records attributed to P Allen.

At least 19 recordsLinked to original sources
PubMed1992

Spectral pattern discrimination by children.

This research measured the ability of 47 children, aged 4-9 years, to use spectral shape cues to discriminate among random-intensity sounds. The children were tested in forced-choice paradigms that were embedded in a video game format. Two classes of sounds were studied: tonal complexes with sinusoidally rippled amplitude spectra, and synthetic speech sounds (isolated vowels and consonants). The discriminability of the sounds was measured both in quiet and in a background of wide-band noise. Although the intersubject variability in performance was high, especially among the youngest children, the results revealed a substantial age effect. For both classes of sounds, the performance of the younger children was significantly poorer than the performance of an adult control group. However, there was no evidence in the data that the masking effect of the noise was greater for the children than for the adults.

Adolescent↗
PubMed1992

Differences in cardiac calcium release channel (ryanodine receptor) expression in myocardium from patients with end-stage heart failure caused by ischemic versus dilated cardiomyopathy.

The molecular basis for the systolic and diastolic dysfunction characteristic of end-stage heart failure in humans remains poorly understood. It has been proposed that both abnormal calcium handling and defects in the contractile apparatus may contribute to the myocardial dysfunction. Two channels, the calcium release channel (CRC) or ryanodine receptor of the sarcoplasmic reticulum (SR), and the slow calcium channel or dihydropyridine receptor (DHPR) of the transverse tubule, play key roles in regulating intracellular calcium concentration and in excitation-contraction (E-C) coupling in the heart. The DHPR serves as the voltage sensor and plasma membrane calcium channel resulting in activation of the CRC during E-C coupling in heart muscle. In this study, we investigated the levels of CRC expression in several forms of end-stage heart failure in humans. A cardiac CRC cDNA was cloned from rabbit and used as a probe for Northern blot analyses to determine mRNA levels in the left ventricles of normal (n = 4) and cardiomyopathic (n = 34) human hearts from patients undergoing cardiac transplantation. Compared with normal patients, patients with ischemic cardiomyopathy (n = 18) showed a 28% decrease in CRC mRNA levels (p less than 0.025) and patients with idiopathic dilated cardiomyopathy (n = 14) a nonsignificant 12% increase. In these same hearts, alpha-actin levels were unchanged in end-stage heart failure, as has been previously reported. This is the first report indicating that the expression of the CRC mRNA is abnormal in end-stage human heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Autoimmune disease of the ovary induced by a ZP3 peptide from the mouse zona pellucida.

We describe a novel experimental system in mice for the study of ovarian autoimmune disease, a condition encountered in women with premature ovarian failure. The ovarian autoimmune disease is induced in B6AF1 mice by a 15-amino acid peptide (Cys-Ser-Asn-Ser-Ser-Ser-Ser-Gln-Phe-Gln-Ile-His-Gly-Pro-Arg) from mouse ZP3, the sperm-binding component of the zona pellucida that surrounds growing and mature oocytes. Whereas the peptide induces both T cell and antibody responses, adoptive transfer of CD4+ T cell lines derived from affected animals causes oophoritis without observable antibodies to the zona pellucida peptide. The primacy of the T cell response in the pathogenesis of disease is further substantiated by defining oophoritogenic peptides as small as eight amino acids (Asn-Ser-Ser-Ser-Ser-Gln-Phe-Gln) that do not elicit an antibody response to the full-length ZP3 peptide. The identification of a well characterized peptide as a causative agent of autoimmune oophoritis should facilitate understanding of the pathogenesis of this T cell-mediated autoimmune disease. Because the proteins of the zona pellucida are conserved among mammals (the mouse and human ZP3 proteins are 67% identical), this murine model may lead to better understanding of the pathogenesis of human autoimmune oophoritis.

Amino Acid Sequence↗
PubMed1991

Stage I-II low-grade lymphomas: a prospective trial of combination chemotherapy and radiotherapy.

Between 1984-1989, 44 patients with stage I-II low grade lymphoma were treated prospectively with sequential chemotherapy and involved-field radiotherapy. The chemotherapy was cyclophosphamide, vincristine, prednisone, and bleomycin (COP-Bleo); doxorubicin was included (CHOP-Bleo) for patients with adverse prognostic features (high LDH; extranodal sites; bulky nodes). Of the 44 patients, 37 had measurable disease and all have responded. With a median follow-up of 32 months, the 5-year survival and failure-free survival were 89% and 74%, respectively. Compared to past experience with involved-field radiotherapy alone, the failure-free survival is significantly better with COP-Bleo plus radiotherapy. The potentially cured fraction has risen from 40% to 74%.

Adult↗
PubMed1990

Growth, feed efficiency and carcass composition of finishing Friesian steers fed the beta-adrenergic agonist L-644,969.

The beta-adrenergic agonist L-644,969 was evaluated to determine its effects on growth performance and carcass composition of Friesian steers. L-644,969 is the R,R isomer of 6-amino [[(1-methyl-3-phenylpropyl) amino] methyl]-3-pyridine methanol dihydrochloride. Four groups of 18 steers, averaging 380 kg body weight, were individually given ad libitum access to a pelleted concentrate diet that contained either 0, .25, 1.0 or 4.0 ppm L-644,969 for the final 12 wk of the finishing period. Live weight gain was not affected by L-644,969, but feed consumption was linearly reduced (5.5, 6.3 and 15.7%; P less than .01) and feed conversion efficiency was linearly increased (16, 25 and 31%; P less than .01) relative to unmedicated controls, respectively. In addition, L-644,969 quadratically increased carcass weight (3.7, 9.3 and 8.5%; P less than .01) and dressing percentage (2.7, 7.9 and 7.9%; P less than .001). The proportion of trimmed fat in the carcass was quadratically reduced (14.5, 29 and 36%; P less than .001) and yield of lean meat quadratically increased (6.7, 13 and 15.6%; P less than .001). beta-adrenergic agonist treatment altered the distribution of lean meat such that a greater (P less than .001) proportion of the total lean was in the hind portion of carcasses from treated animals. Based on these findings, we suggest that L-644,969 may have utility as an agent to improve efficiency of production of lean beef.

Adrenergic beta-Agonists↗
PubMed1979

The expression of Ia antigenic determinants on macrophages required for the in vitro antibody response.

A subpopulation of antigen-presenting macrophages required for an in vitro antibody response to burro erythrocytes was deleted by pretreating the splenic macrophages with anti-Ia serum and complement (C). The in vitro response of the macrophage depleted T-B cell population could not be restored by the addition of macrophages resistant to anti-Ia antibodies and C (Ia-). The response of Ia- macrophages and the macrophage-depleted T-B cells was only reconstituted by the addition of Ia+ macrophages. Macrophages pretreated with anti-Ia antibodies restricted to react with determinants of one I subregion could not support the in vitro antibody response when added to cultures whose macrophages were pretreated with anti-Ia serum and C specific for the I-J subregion. These results confirmed that Ia determinants of the I-A, the I-E, and the I-C subregions were all expressed on the I-J+ macrophage required for an in vitro antibody response.

Animals↗