PubMed Health⌕ Search

Biomedical subjects

Robert Peters

Publications and source records attributed to Robert Peters.

8 recordsLinked to original sources
PubMed2006

Bilateral cochlear implants in children: localization acuity measured with minimum audible angle.

OBJECTIVE: To evaluate sound localization acuity in a group of children who received bilateral (BI) cochlear implants in sequential procedures and to determine the extent to which BI auditory experience affects sound localization acuity. In addition, to investigate the extent to which a hearing aid in the nonimplanted ear can also provide benefits on this task. DESIGN: Two groups of children participated, 13 with BI cochlear implants (cochlear implant + cochlear implant), ranging in age from 3 to 16 yrs, and six with a hearing aid in the nonimplanted ear (cochlear implant + hearing aid), ages 4 to 14 yrs. Testing was conducted in large sound-treated booths with loudspeakers positioned on a horizontal arc with a radius of 1.5 m. Stimuli were spondaic words recorded with a male voice. Stimulus levels typically averaged 60 dB SPL and were randomly roved between 56 and 64 dB SPL (+/-4 dB rove); in a few instances, levels were held fixed (60 dB SPL). Testing was conducted by using a "listening game" platform via computerized interactive software, and the ability of each child to discriminate sounds presented to the right or left was measured for loudspeakers subtending various angular separations. Minimum audible angle thresholds were measured in the BI (cochlear implant + cochlear implant or cochlear implant + hearing aid) listening mode and under monaural conditions. RESULTS: Approximately 70% (9/13) of children in the cochlear implant + cochlear implant group discriminated left/right for source separations of <or=20 degrees , and, of those, 77% (7/9) performed better when listening bilaterally than with either cochlear implant alone. Several children were also able to perform the task when using a single cochlear implant, under some conditions. Minimum audible angle thresholds were better in the first cochlear implant than the second cochlear implant listening mode for nearly all (8/9) subjects. Repeated testing of a few individual subjects over a 2-yr period suggests that robust improvements in performance occurred with increased auditory experience. Children who wore hearing aids in the nonimplanted ear were at times also able to perform the task. Average group performance was worse than that of the children with BI cochlear implants when both ears were activated (cochlear implant + hearing aid versus cochlear implant + cochlear implant) but not significantly different when listening with a single cochlear implant. CONCLUSIONS: Children with sequential BI cochlear implants represent a unique population of individuals who have undergone variable amounts of auditory deprivation in each ear. Our findings suggest that many but not all of these children perform better on measures of localization acuity with two cochlear implants compared with one and are better at the task than children using the cochlear implant + hearing aid. These results must be interpreted with caution, because benefits on other tasks as well as the long-term benefits of BI cochlear implants are yet to be fully understood. The factors that might contribute to such benefits must be carefully evaluated in large populations of children using a variety of measures.

Adolescent↗
PubMed2005

Matrix metalloproteinase inhibitor Ro 28-2653 in combination with estramustine: tumor-reducing effects on hormone-sensitive prostate cancer in rats.

Therapeutic efficacy of the novel matrix metalloproteinase (MMP) inhibitor, Ro 28-2653 (5-biphenyl-4-yl-5-[4-(-nitro-phenyl)-piperazin-1-yl]-pyrimidine-2,4,6-trione), has been shown in various models of different tumor entities. The tumor growth-reducing effect has been demonstrated in the orthotopic rat prostate Dunning model (subline MatLyLu). Based on these results we investigated Ro 28-2653 in combination with estramustine on the G subline of the Dunning tumor. This subline is characterized by a low metastatic ability and androgen sensitivity. Efficacy was determined by recording tumor growth in vivo by magnetic resonance imaging (MRI). Tumor cells were injected into the prostates of 81 Copenhagen rats. MRI was performed at day 100 and at day 126 after tumor cell injection. The duration of therapy was 17 days with daily oral application of Ro 28-2653 (100 mg/kg) and four i.p. injections of estramustine (7.5 mg/kg). Histological evaluations were conducted to provide further information about the effects on tumor morphology. Orthotopic tumor induction was successful in 100% of the animals. Tumor volume calculations with MRI showed a significant difference between the control groups, the animals treated with Ro 28-2653, and the animals treated with the combination of Ro 28-2653 and estramustine. The new MMP inhibitor Ro 28-2653 reduces tumor growth and provides a compatible therapeutic alternative for patients with prostate cancer.

Animals↗
PubMed2004

Bilateral cochlear implants in adults and children.

OBJECTIVE: To measure the benefit (ie, sound localization and speech intelligibility in noise) of bilateral cochlear implants (CIs) in adults and in children. DESIGN, SETTING, AND PATIENTS: Seventeen adults and 3 children underwent testing 3 months after activation of bilateral hearing. Adults received their devices in a simultaneous procedure and children in sequential procedures (3-8 years apart). Adults underwent testing of sound localization and speech intelligibility, with a single CI and bilaterally. Children underwent testing of sound localization, right/left discrimination, and speech intelligibility, with the first CI alone and bilaterally. We used computer games to attract the children's attention and engage them in the psychophysical tasks for long periods of time. RESULTS: Preliminary findings suggest that, for adults, bilateral hearing leads to better performance on the localization task, and on the speech task when the noise is near the poorer of the 2 ears. In children, localization and discrimination are slightly better under bilateral conditions, but not remarkably so. On the speech tasks, 1 child did not benefit from bilateral hearing. Two children showed consistent improvement with bilateral hearing when the noise was near the side that underwent implantation first. CONCLUSIONS: Bilateral CIs may offer advantages to some listeners. The tasks described in this study might offer a powerful tool for measuring such advantages, especially in young children. The extent of the advantage, however, is difficult to ascertain after 3 months of bilateral listening experience, and might require a more prolonged period of adjustment and learning. Future work should be aimed at examining these issues.

Adult↗
PubMed2004

Seasonal variation of mortality in the Antiarrhythmics Versus Implantable Defibrillators (AVID) study registry.

OBJECTIVES: We postulated that the pattern of death would be nonrandom with respect to temporal variables. BACKGROUND: Previous studies have demonstrated increased sudden death is associated with periods of relative stress, and overall mortality is associated with temporal variables. METHODS: In the Antiarrhythmics Versus Implantable Defibrillators (AVID) registry, vital status was obtained for 4,450 patients (who had a recent episode of sustained ventricular arrhythmias or unexplained syncope and inducible ventricular tachycardia) through the National Death Index Service as of December 31, 1997 (follow-up 25.5 +/- 13.7 months). RESULTS: Mortality was not associated with the day of the week or with holidays but was associated with season (P = .033). Seasonal variation was present both in northern and southern sites. Mortality was higher during the winter months compared to the remaining months (111.2% in winter vs 96.5% in other months, P = .036). In addition, increased mortality was associated with a high-risk season variable defined (prior to evaluation of treatment arm associations) as spring in the north and winter in the south (P < .001). The hazard ratio for death associated with this "high-risk season" measured 1.25 (P = .001) compared to the other seasons in each region. A test of interaction between "high-risk" season and implantable cardioverter-defibrillator (ICD) status suggested that the group with ICDs experienced reduced mortality during the "high-risk season" compared to the group without ICDs (P = .047). CONCLUSIONS: Mortality was higher in the winter months and in the respective regional "high-risk" seasons. Furthermore, seasonal variation in mortality may have been due to variation in sudden arrhythmic death, and associated increases in mortality were reduced by ICD therapy.

Anti-Arrhythmia Agents↗
PubMed2004

Laparoscopic radical cystectomy with continent urinary diversion (rectosigmoid pouch) performed completely intracorporeally: an intermediate functional and oncologic analysis.

OBJECTIVES: To present our experience with the first series of rectosigmoid pouch creation performed completely laparoscopically for continent urinary diversion after radical cystectomy to treat transitional cell carcinoma of the bladder. We evaluated the intermediate functional and oncologic outcomes. METHODS: Between April 2000 and January 2004, 20 patients underwent laparoscopic radical cystectomy with urinary diversion for transitional cell carcinoma at the Department of Urology, Charite Hospital, Campus Mitte. Of the 20 patients, 12 received a rectosigmoid pouch for urinary diversion. The procedures were performed completely laparoscopically, including free-hand laparoscopic suturing and in situ knot tying techniques. The mobilized specimens were removed in an endoscopy bag by way of the rectum or vagina. RESULTS: All operations were completed laparoscopically by two surgeons without conversion to open surgery. The median operating time was 485 minutes. One patient needed a blood transfusion of 2 U. All specimens had negative surgical margins. Two patients required reoperation. The median follow-up was 33 months. All patients were continent during the day, and 11 patients were continent at night. One patient developed unilateral hydronephrosis with loss of kidney function. No patient developed local recurrence, but 3 patients had systemic progression. Two of the three died of metastatic disease. CONCLUSIONS: This is the first series of laparoscopic radical cystectomy using an intracorporeal rectosigmoid pouch. Our functional data for continence and upper urinary tract obstruction were comparable with those of open rectosigmoid pouch studies. We were able to demonstrate an oncologic outcome similar to that achieved by the open surgical approach.

Adult↗
PubMed2004

Laparoscopic anatrophic nephrolithotomy.

Management of staghorn calculi is still a challenge. To combine the surgical principles of treatment with the minimal invasive access we performed a laparoscopic anatrophic nephrolithotomy in a female patient successfully. Patient was discharged free of stone on fifth postoperative day. No complications occurred.

Adult↗
PubMed2003

Detection of early secretory antigenic target-6 antibody for diagnosis of tuberculosis in non-human primates.

Tuberculosis is one of the most economically devastating, zoonotic infections of captive non-human primates. The limitations of the tuberculin skin test, which is currently used to diagnose tuberculosis in living non-human primates, make it necessary to find new, simple, and economical diagnostic methods. We describe use of an enzyme-linked immunoassay to detect IgG antibodies against early secretory antigenic target (ESAT)-6, a small protein secreted by virulent tubercle bacilli, in paired (pre- and post-outbreak) sera from 57 non-human primates involved in an outbreak of Mycobacterium bovis infection in a research colony. Of 25 animals with tuberculosis lesions at necropsy, 22 (88%) had high serum levels of the ESAT-6 antibody. The ESAT-6 antibody was found in 16% (5/32) of post-outbreak sera from animals in which tuberculosis could not be confirmed at necropsy. The strong association between the ESAT-6 antibody and tuberculosis in non-human primates documented in this study, together with the robustness of the serologic assay, make the ESAT-6 ELISA a valuable tool for diagnosis of tuberculosis in captive non-human primates.

Animals↗