PubMed Health⌕ Search

Biomedical subjects

R Cusack

Publications and source records attributed to R Cusack.

9 recordsLinked to original sources
PubMed1999

Effects of similarity in bandwidth on the auditory sequential streaming of two-tone complexes.

We investigated the perceptual grouping of sequentially presented sounds--auditory stream segregation. It is well established that sounds heard as more similar in quality, or timbre, are more likely to be grouped into the same auditory stream. However, it is often unclear exactly what acoustic factors determine timbre. In this study, we presented various sequences of simple sounds, each comprising two frequency components (two-tone complexes), and measured their perceptual grouping. We varied only one parameter between trials, the intercomponent separation for some of the complexes, and examined the effects on stream segregation. Four hypotheses are presented that might predict the extent of streaming. Specifically, least streaming might be expected when the sounds were most similar in either (1) the frequency regions in which they have energy (maximum spectral overlap), (2) their auditory bandwidths, (3) their relative bandwidths, or (4) the rate at which the two components beat together (intermodulation rate). It was found that least streaming occurred when sounds were most similar in either their auditory or their relative bandwidths. Although these two hypotheses could not be distinguished, the results were clearly different from those predicted by hypotheses (1) and (4). The implications for models of stream segregation are discussed.

Auditory Perception↗
PubMed1991

Preliminary studies for an immunotherapeutic approach to the treatment of human myeloma using chimeric anti-CD38 antibody.

Multiple myeloma is a disease in which conventional chemotherapy has only limited value, but which may be ideal for treatment with passive antibody against a suitable cell surface antigen on the neoplastic plasma cell. The CD38 antigen is known to be present on the majority of neoplastic plasma cells, and this was confirmed by detailed examination of bone marrow aspirates from three patients. Strong expression of CD38 was confined to cells which, by the criteria of light-scattering profiles and possession of cytoplasmic Ig, were plasma cells. The vast majority of neoplastic plasma cells appeared to be involved. Using a cell line as a model, it was found that the CD38 antigen acts as a target for a chimeric antibody prepared from the antibody OKT10. The chimeric antibody consists of the Fab portion of the mouse monoclonal antibody linked by a stable thioether bond to an Fc molecule derived from human IgG1, thereby forming mouse Fab-human Fc. In contrast to the parent antibody, the chimeric molecule mediates antibody-dependent cellular cytotoxicity (ADCC) very efficiently with human blood mononuclear effector cells, and is effective at low concentration. Also, even though the CD38 antigen is present on natural killer cells, there appears to be little deleterious action of the antibody on effector cell function. The antibody also failed to affect the growth of progenitor cells of the granulocyte/macrophage or erythroid lineages present in normal bone marrows, despite the suspicion that these cells express the antigen. Other advantages of the CD38 molecule are that it is not found in the serum of patients with myeloma, and it does not appear to modulate in vitro. Fourteen patients with florid myeloma and on various chemotherapeutic regimes had an undiminished capacity to mediate ADCC with the chimeric antibody, when compared with normal individuals. The maintenance of ADCC activity, coupled with the known suppression of the antibody response in these patients, augers well for treatment with chimeric antibody.

ADP-ribosyl Cyclase↗
PubMed1989

Infrapopulation dispersal of Gyrodactylus colemanensis (Monogenea) on fry of Salmo gairdneri.

Manipulative positioning of Gyrodactylus colemanensis on individually isolated fry of Salmo gairdneri was used to examine the behavior of the parasite during colonization and the influence that site of invasion has on size and spatial distribution of ensuing infrapopulations. The parasite's initial response was to relocate posteriorly on the host's body; those that reached a fin usually end up on or adjacent to the fin's margin. Individuals monitored for up to 15 days postinfection moved both anteriorly and posteriorly on the body surface and relocated to new fins via the body surface. The parasite occurred most frequently on the caudal fin followed by the pectoral and pelvic fins, with length of the fin margin and fin activity appearing to be factors influencing the distribution. Infections originating from the head, flank, and caudal fin similarly rose and fell to extinction or near extinction on the host over 49 days at 10 C. The more posterior the site of invasion, the greater the proportion of parasites carried by the caudal fin. The study concludes that G. colemanensis is restricted in its distribution on the host and that the fin margins may serve as a reliable food source and favor transmission to new hosts.

Animals↗
PubMed1986

Gyrodactylus salmonis (Yin and Sproston, 1948) parasitizing fry of Salvelinus fontinalis (Mitchill).

Fry of brook trout, Salvelinus fontinalis (Mitchill), were infected under controlled conditions with Gyrodactylus salmonis (Yin and Sproston, 1948) and the course of infection followed for 22 days in four groups of 40 fish and for 60 days in a group of 200 fish. Between 15 and 44% mortality occurred among infected groups compared with less than 5% in noninfected control groups. Intensely infected moribund fish were cachexic, lethargic, and often darkened in color. Histologic studies revealed that intensely infected fish had a thinner epidermis with fewer goblet cells than control fish. Internally the only obvious lesions involved the kidney where there was extensive tubular degeneration and necrosis. It is hypothesized that attachment and grazing activity by G. salmonis can lead directly to death of fry through disruption of the osmotic permeability of the epidermis. There was no evidence of secondary invasion by bacteria or fungi.

Animals↗
PubMed1986

Development of infections of Gyrodactylus colemanensis Mizelle and Kritsky, 1967 (Monogenea) and the effect on fry of Salmo gairdneri Richardson.

The development of infections of Gyrodactylus colemanensis Mizelle and Kritsky, 1967 (Monogenea) and their effect on fry of Salmo gairdneri Richardson are examined experimentally. Starting with initial infections of 1 to 10 worms per fry, intensity in 2 replicate groups increased to peaks of 55 and 65 on day 22 post-infection and declined to 0 by days 67 and 85 post-infection. The parasites were numerically aggregated within the host groups and there was a negative correlation between intensity and fish size. Infections did not influence growth or survival of the host and produced no clinical signs of disease.

Animals↗