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Biomedical subjects

D J Olson

Publications and source records attributed to D J Olson.

34 records · Page 2Linked to original sources
PubMed1993

Effects of response strategy and retention interval on performance of Clark's nutcrackers in a radial maze analogue.

Two groups of Clark's nutcrackers (Nucifraga columbiana) were trained to use either a stay or shift response strategy in a radial maze analogue. Each trial had a preretention stage, a retention interval, and a postretention test. In Experiment 1, acquisition with a 5-min retention interval was studied. Response strategy did not affect the rate at which the task was learned. Performance following longer retention intervals was tested in Experiments 2-4. Changes in retention intervals were presented in trial blocks of increasing duration in Experiment 2 and were randomly presented between trials in Experiment 3. Experiment 4 extended the retention interval to 24 hr. No difference in performance was found between the 2 groups in any of these experiments. These results suggest a flexible relationship between spatial memory and response requirement in food-hoarding birds for at least 1 spatial memory task.

Animals↗
PubMed1992

Xwnt-8 modifies the character of mesoderm induced by bFGF in isolated Xenopus ectoderm.

In Xenopus, growth factors of the TGF-beta, FGF and Wnt oncogene families have been proposed to play a role in generating embryonic pattern. In this paper we examine potential interactions between the bFGF and Xwnt-8 signaling pathways in the induction and dorsal-ventral patterning of mesoderm. Injection of Xwnt-8 mRNA into 2-cell Xenopus embryos does not induce mesoderm formation in animal cap ectoderm isolated from these embryos at the blastula stage, but alters the response of this tissue to mesoderm induction by bFGF. While animal cap explants isolated from non-injected embryos differentiate to form ventral types of mesoderm and muscle in response to bFGF, explants from Xwnt-8 injected embryos form dorsal mesodermal and neural tissues in response to the same concentration of bFGF, even if the ectoderm is isolated from the prospective ventral sides of embryos or from UV-ventralized animals. Our results support a model whereby dorso-ventral mesodermal patterning can be attained by a single mesoderm inducing agent, possibly bFGF, which is uniformly distributed across the prospective dorsal-ventral axis, and which acts in concert with a dorsally localized signal, possibly a Wnt protein, which either alters the response of ectoderm to induction or modifies the character of mesoderm after its induction.

Animals↗
PubMed1992

Distinct effects of ectopic expression of Wnt-1, activin B, and bFGF on gap junctional permeability in 32-cell Xenopus embryos.

A polarity in gap junctional permeability normally exists in 32-cell stage Xenopus embryos, in that dorsal cells are relatively more coupled than ventral cells, as measured by transfer of Lucifer yellow dye. The current study extends our analysis of whether gap junctional permeability at this stage can be modulated by secreted factors, and whether the polarity in gap junctional permeability correlates with the effects of ectopic expression of these secreted factors on the subsequent phenotype of the developing embryo. Following ectopic expression of activin B or Wnt-1, but not bFGF, the transfer of Lucifer yellow between ventral animal pole cells is detected in a greater percentage of 32-cell stage embryos. This increased incidence of dye transfer between ventral cells correlates with axial duplications later in development. However, there are differences in the extent of Lucifer yellow transfer between animal and vegetal hemisphere blastomeres which is dependent on whether activin B or Wnt-1 RNA had previously been injected. These results suggest that enhanced gap junctional permeability between ventral cells of 32-cell Xenopus embryos correlates with subsequent defects in the dorsoventral axis, although there are at present no direct data demonstrating a role for gap junctions in establishment or maintenance of this axis. Moreover, while both activin B and bFGF are mesoderm-inducing growth factors, only activin B has effects on gap junctional permeability in 32-cell embryos following ectopic expression, demonstrating an interesting difference in physiological responses to expression of these factors.

Activins↗
PubMed1992

High-frequency audiometric monitoring for early detection of aminoglycoside ototoxicity.

Treatment with aminoglycosides is known to cause irreversible hearing loss, typically affecting higher-frequency hearing first and progressing to lower frequencies. Standardized methodology has not been developed for early detection of ototoxicity. Serial conventional (0.25-8 kHz) and high-frequency (9-20 kHz) hearing threshold monitoring was done prospectively in 53 hospitalized patients administered aminoglycosides. Hearing loss occurred in 47% of the ears studied, with hearing loss first appearing in the high-frequency range in 71% of ears showing change. Analysis of data on an individual basis revealed a five-frequency range most susceptible to initial ototoxicity. Testing only this range would have resulted in early identification of 82% of ears showing change. Results confirm the critical need for serial auditory threshold monitoring encompassing high frequencies in patients receiving aminoglycosides. A shortened five-frequency monitoring protocol is presented and suggested for use with patients unable to tolerate lengthy audiometric testing procedures.

Amikacin↗
PubMed1992

Comparing laboratory and portable tone-burst auditory brain-stem-response (ABR) systems for monitoring high-frequency (> or = 8 kHz) auditory function.

High-frequency (8-20 kHz) hearing sensitivity is of special interest because of its early warning potential for ototoxicity. Many ill patients, however, are unable to respond behaviorally to auditory test procedures. To objectively monitor high-frequency auditory function in these patients, laboratory instrumentation to evoke the auditory brain-stem response (ABR) with high-frequency (8-14 kHz) tone-burst stimuli was developed and documented. To provide evaluation at bedside, a portable high-frequency tone-burst generator was developed to elicit the ABR. Combined with a portable signal averager, this system was validated by comparison with the laboratory system. Thirty-five normal-hearing subjects were used to compare ABRs to high-frequency tone bursts from each system. Analysis of responses to tone bursts revealed no significant mean latency differences, and no significant intersession reliability differences between systems. These results confirm that the portable system is comparable to the laboratory system in obtaining reliable high-frequency tone-burst responses.

Acoustic Stimulation↗
PubMed1992

Early detection of ototoxicity using high-frequency, tone-burst-evoked auditory brainstem responses.

Subjects receiving treatment with ototoxic agents were evaluated concurrently with conventional and high-frequency (> or = 8 kHz) behavioral threshold measures and with ABR to click and to 8, 10, 12, and 14 kHz tone-burst stimuli. Behavioral threshold data revealed ototoxic change in 51 percent of ears evaluated. Of these ears demonstrating behavioral change, 90 percent revealed concurrent ABR changes. If only ABR monitoring with high-frequency tone-burst stimuli had been used, 87 percent of allears showing behavioral change would have been identified. Three fourths of these would have been identified from wave V responses, with 87 percent identified from the two highest frequencies tested for each individual. This research suggests that behavioral change is reflected accurately in the ABR, that high-frequency tone bursts will identify a majority of initial ototoxic changes, and that monitoring hearing with high-frequency, tone-burst-evoked ABRs during treatment with potentially ototoxic agents is significantly more effective than click-evoked ABRs for early detection of ototoxicity.

Acoustic Impedance Tests↗
PubMed1991

Effect of wnt-1 and related proteins on gap junctional communication in Xenopus embryos.

The proto-oncogene wnt-1 (previously referred to as int-1) is thought to be important in embryonic pattern formation although its mechanisms of action are unknown. Premature and increased expression of the Wnt-1 protein, achieved by injection of synthetic wnt-1 RNA into fertilized Xenopus eggs, enhanced gap junctional communication between ventral cells of the developing embryo. This result is consistent with the hypothesis that Wnt proteins activate a receptor-mediated signal transduction pathway and that gap junctional communication can be a target of this pathway. The effects of two Wnt-1-related proteins on gap junctional communication were also investigated: overexpression of Xwnt-8 increased gap junctional coupling in a manner similar to Wnt-1, whereas Xwnt-5A did not. These findings are consistent with the existence of multiple receptors for Wnt proteins.

Animals↗
PubMed1991

Species differences in spatial memory among Clark's nutcrackers, scrub jays, and pigeons.

An operant nonmatching to sample procedure was used to compare the spatial memory abilities of 3 avian species. A trial consisted of the presentation of a spatially defined sample, a delay interval, and a 2-choice test during which the correct location was the new location. A single spatial location served as the sample in Experiment 1. The delay interval was manipulated using a titration procedure. In Experiment 2, 1, 2, or 3 sequentially illuminated locations served as the sample. The delay was 1 of 4 predetermined intervals. In Experiment 3, sample presentation was the same as Experiment 2, but the delay interval was titrated. In all of the experiments, the performance of nutcrackers was consistently better than the performance of scrub jays and pigeons (Experiment 1) and was correlated with differences in their foraging ecology.

Animals↗
PubMed1991

Immunohistochemical features of Paget's disease of the vulva with and without adenocarcinoma.

Six cases of vulvar Paget's disease (VP) with associated adenocarcinoma and 10 cases of VP without adenocarcinoma were compared immunohistochemically with B72.3, a pan-carcinoma marker developed against human mammary tumor cells, anti-carcinoembryonic antigen (anti-CEA), anti-epithelial membrane antigen (anti-EMA), anti-gross cystic disease fluid protein (anti-GCDFP-15), antihuman estrogen receptors (anti-ER), and anti-S-100 protein (anti-S-100). B72.3 reacted with 15/16 (94%) of the cases, anti-CEA reacted with 15/16 (94%), anti-EMA reacted with 16/16 (100%), anti-GCDFP-15 reacted with 14/16 (81%), and none of the 16 cases reacted with anti-ER or anti-S-100. There was no statistically significant difference in the percentage of cases binding antibodies between VP without adenocarcinoma and VP with adenocarcinoma. However, B72.3 and anti-CEA stained VP without adenocarcinoma significantly more strongly than VP with adenocarcinoma (p less than 0.05 and p less than 0.025). VP without adenocarcinoma tended to bind anti-GCDFP-15 more strongly than VP with adenocarcinoma, but without statistical significance. Paget cells stained differently than the cells in their associated adenocarcinoma in two of six cases. In both of these cases, the Paget cells and adenocarcinoma were noncontiguous. In contrast, three of the remaining four cases contained adenocarcinoma contiguous with Paget cells. Immunocytochemistry with B72.3 seems to be as useful as anti-GCDFP-15 in identifying VP.

Adenocarcinoma↗
PubMed1991

Reliability of evoked responses to high-frequency (8-14 kHz) tone bursts.

Instrumentation to evaluate the auditory brainstem response to high-frequency (8-14 kHz) tone bursts has been developed in the Auditory Research Laboratory, Portland, Oregon VA Medical Center. This system is intended to monitor the audition of patients receiving ototoxic drugs who are unresponsive to behavioral test procedures. The reliability of responses obtained with the high-frequency tone-burst system was studied in 30 normal ears. Intrasubject variability of intersession data from response waves I, III, and V to tone bursts of frequencies 8, 10, 12, and 14 kHz was not significantly different from click response variability. The results of this study demonstrate the reliability of the ABR to these high-frequency tone-burst stimuli. This technique may provide early identification of hearing loss in unresponsive subjects receiving treatment with potentially ototoxic agents, thus allowing alternative treatments to minimize or prevent communicative handicap.

Acoustic Stimulation↗
PubMed1990

Reliability and validity of high-frequency (8-20 kHz) thresholds obtained on a computer-based audiometer as compared to a documented laboratory system.

A Macintosh computer-based audiometer (Virtual 320) was evaluated for reliability and validity of high-frequency (8-20 kHz) thresholds by comparison with a well documented laboratory high-frequency evaluation system (PARVA-HF). High-frequency earphones originally provided with the V320 for high-frequency testing required modification to improve reliability in calibration and in subject threshold testing. Twenty normal-hearing adults were evaluated in the 8-20 kHz frequency range on both testing systems. Results of intrasubject multiple-session testing were evaluated to determine the reliability of high-frequency thresholds obtained. The V320 produced reliable results comparable to the PARVA-HF. Validity of high-frequency thresholds was inferred by comparing V320 responses to those obtained with the PARVA-HF. Comparable findings between systems imply validity of thresholds obtained with the V320. Conventional frequency (0.25-8 kHz) threshold evaluation with the V320 and a Grason-Stadler 1701 audiometer also yielded comparable results.

Adult↗
PubMed1983

Characteristics of spatial memory in pigeons.

Pigeons learned a delayed-alteration (DA) task in a T-maze. Very few trials were needed prior to accurate performance. Similarly, after little training the birds performed accurately with delays of 8-16 min. End-of-delay cues, possibly provided by the experimenter, response-based cues, and intramaze cues were all experimentally examined and rejected as bases for the birds' performances; pigeons appear to rely on spatial (extramaze) cues. Long-delay performances were undisturbed by changes in delay-interval stimuli (illumination shifts and transportation around the laboratory). Finally, birds were shown to acquire DA so quickly because of a potent tendency to avoid recently visited locations (i.e., a preexisting "win-shift" tendency). Characteristics of pigeon spatial memory thus include temporal persistence, resistance to retroactive interference, and a win-shift bias. In these respects spatial memory of pigeons parallels spatial memory of rats.

Animals↗
PubMed1976

The application of xeroradiography in diagnosis of maxillofacial problems.

The evaluation of maxillofacial pathology was undertaken using xeroradiography. The edge enhancement and wide image latitude were shown to give additional information, especially in areas of bony overlap, such as the temporomandibular joint, without resorting to tomography. Other areas of possible utilization are also discussed, including sialography.

Adult↗
PubMed1975

Amyloidosis: a rational approach to diagnosis by intraoral biopsy.

Amyloidosis and its oral manifestations are briefly described. The techniques for antemortem tissue diagnosis of amyloidosis are reviewed and evaluated. In screening for amyloidosis, biopsy of specific oral lesions (when present) is recommended instead of the traditional biopsy of normal-appearing gingiva. This approach is illustrated with four cases. Although rectal biopsy is generally accepted as the screening technique of choice, it is suggested that intraoral biopsy be considered as an easier, safer, more comfortable, and possibly more fruitful technique. It is advocated that in cases of both documented and suspected amyloidosis both intraoral and rectal biopsies should be performed in order to help provide documentation of the most useful technique for routine screening.

Aged↗