Biomedical subjects

D C Dees

Publications and source records attributed to D C Dees.

4 recordsLinked to original sources

PubMed1997

Cutinase A of Botrytis cinerea is expressed, but not essential, during penetration of gerbera and tomato.

The plant pathogen Botrytis cinerea can infect undamaged plant tissue directly by penetration of the cuticle. This penetration has been suggested to be enzyme-mediated, and an important role for cutinase in the infection process has been proposed. In this study the expression of the cutinase encoding gene cutA of B. cinerea was analyzed using a cutA promoter-GUS reporter gene fusion. Transformants containing the fusion construct were examined for GUS expression on gerbera flowers and tomato fruits. High GUS activity was detected from the onset of conidial germination and during penetration into epidermal cells, indicating that cutA is expressed during the early stages of infection. To determine the biological relevance of cutinase A for successful penetration, cutinase A-deficient mutants were constructed by gene disruption. Pathogenicity of two transformants lacking a functional cutA gene was studied on gerbera flowers and tomato fruits. Their ability to penetrate and cause symptoms was unaltered compared to the wild-type strain. These results exclude an important role for cutinase A during direct penetration of host tissue by B. cinerea.

Base Sequence↗

PubMed1996

An improvement in hearing sensitivity following hearing-aid fitting in a child with an apparent sensorineural hearing impairment.

This case describes an apparent improvement in hearing sensitivity in a young girl over a period of 12 months, after she was fitted with binaural hearing-aids. Discrepancies between objective and subjective test results are highlighted. Even if the underlying reason for the conflicting test results was due to poor listening skills or test error, this child behaved like a hearing-impaired child and her performance improved after hearing-aid use. The case also illustrates the application of earphone testing from six months of age. The importance of closely monitoring all children who are fitted with hearing-aids is highlighted.

Female↗

PubMed1996

A new concept for Cochlear implant speech processing.

OBJECTIVE: A new speech processing concept and its implementation cochlear implant neural net, simulation and stimulation (CINSTIM), for cochlear implant systems is currently under investigation. The main objectives of this new strategy are to improve speech perception within the early rehabilitation period for prelingually deaf cochlear implant users and to improve speech perception in noise for all implant users. The advantage of this approach is the capability to assess and compare entirely different speech processing methods within the existing implant hardware. DESIGN: The processing concept is based on discrete sequences of distinguishable stimulus patterns, robust speech processing, and a classifier. The embedded Kohonen classifier employs unsupervised neural net algorithms. RESULTS: Initial experimental results have validated the general processing scheme as well as the development of this complex software. In addition, a limited alphabet of distinguishable stimulus patterns was achieved and assessed with experienced users of a conventional cochlear implant system. Test subjects were able to learn and recognize up to 60% of these artificial patterns after a few training sessions. Currently this speech processing strategy is being evaluated through the Cochlear MSP system; however, it is compatible with the other computer driven digital cochlear implant systems.

Cochlear Implants↗

PubMed1991

Otoacoustic emissions and auditory brainstem responses in the newborn.

The auditory function of 370 infants, drawn from both low and high risk groups, was tested before postnatal discharge using three tests: standard auditory brain stem responses (ABR), automated analysis of ABR, and automated analysis of evoked otoacoustic emissions (OAE). All infants failing any neonatal test had further audiological evaluation. Follow up information was also available on those who passed neonatal tests. Automated OAE testing of both ears was quickest (median 12.5 minutes) and least invasive (no scalp electrodes). Bilateral failure rates (and upper 95% confidence limits) with a stimulus 35-36 dB above normal hearing threshold level (nHL) were 3.0% (4.6) with automated OAE, 3.2% (5.1) with ABR, and 2.7% (4.4) with automated ABR. Automated OAE was the test most sensitive for subsequently confirmed hearing impairment. Sequential testing with automated OAE followed, in those failing this test, by automated ABR would have provided a screening test for substantial hearing impairment with a specificity greater than 99% in this population. Possible application as a universal screen is discussed.

Audiometry, Evoked Response↗