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Biomedical subjects

S Peeters

Publications and source records attributed to S Peeters.

At least 19 recordsLinked to original sources
PubMed1998

The LAURA Pediatric Cochlear Implant Program in Antwerp: what have we learnt in 5 years?

The LAURA Cochlear Implant Program at the University of Antwerp was initiated 5 years ago. Up to now 50 children have received the LAURA cochlear implant (Philips Hearing Implants). Our accumulated experience in selecting the patients, counselling their parents, implanting and fitting the device allowed us to gradually modify the inclusion/exclusion criteria for cochlear implantation and achieve very rewarding results. The most important change was the gradual shift towards a younger age at implantation, our youngest implantee being 11 months old. In this paper we describe the rationale for this change, as well as the prerequisites for a successful pediatric cochlear implant program.

Belgium↗
PubMed1998

New developments in cochlear implants.

Essential to improve the performance with cochlear implants is a better control of the electrode-nerve interface. The long-term stability of the electrode characteristics has to be guaranteed. Most important herein is to have a low and stable electrical impedance and to prevent fibrosis. Results of electrode coating and fibrosis-inhibiting products are described. To assess the properties of the electrode-nerve interface such as stimulation threshold, spatial selectivity and channel interaction, the electrically evoked compound action potential is measured. The measurement paradigm and the first results are described. Models of auditory nerve response to electrical stimulation can be used as a tool for cochlear implant fitting. A simple model is proposed and its predictions are compared with measured responses.

Cochlear Implantation↗
PubMed1998

Growth factors in tympanic membrane perforations.

OBJECTIVE: Little is known about the arrested healing of chronic central tympanic membrane perforations and the mechanism involved in this process. Some authors have traced the failure to a growth factor deficiency at the perforation margin. In addition, recently, several growth factors have been tried out to improve tympanic membrane (TM) closure in animals. The authors sought to determine the expression of some well-known growth factor peptides in normal human TM and in TMs with a chronic central perforation. MATERIALS AND METHODS: Total TM specimens were obtained from patients with a normal TM (N = 10) soon after death and from patients with a chronic perforation (N = 20) undergoing myringoplasty with use of an allograft TM. Formaldehyde solution-fixed TMs were analyzed after immunohistochemical staining using highly purified monoclonal antibodies to determine whether epidermal growth factor receptor (EGF-r), transforming growth factor-alpha (TGF-alpha), basic fibroblast growth factor (b-FGF), or transforming growth factor-beta 1 (TGF-beta 1) was expressed in the TMs. RESULTS: The distribution pattern for EGF-r, TGF-alpha, and b-FGF was similar in perforated and nonperforated TMs. In contrast to this, TGF-beta 1 staining was markedly different in perforated and nonperforated TMs. No or minimal TGF-beta 1 was observed in normal TMs, whereas TGF-beta 1 staining was prominent in perforated membranes, mostly at the perforation border. CONCLUSIONS: The authors experimental findings imply that EGF-r, b-FGF, and TGF-alpha expression are not significantly different in TMs with and without a central chronic perforation. However, for TGF-beta 1, the authors found an increased staining pattern in perforated TMs when compared with that of normal TMs, and staining at the fibrotic and scarred perforation margin was pronounced. Based on these findings, the authors speculate on the possible role of TGF-beta 1 in the development of the fibrotic scar at the perforation margin explaining the deficient healing pattern of tympanic membranes in chronic otitis media. Possible clinical implications for the future, including growth factor therapy, are discussed.

Antibodies, Monoclonal↗
PubMed1997

Comparisons between stress incontinence in women and sphincter mechanism incompetence in the female dog.

In dogs, sphincter mechanism incompetence most often affects middle-aged spayed bitches and is more prevalent in docked animals, certain breeds and in dogs over 30 kg in weight. It results in urinary leakage, mainly when the animal is recumbent and relaxed. In humans, stress incontinence occurs most often in post-menopausal women who are multiparous, have had difficult deliveries and are obese. They also leak urine, but most often when active stressors increase abdominal pressure. Both women and bitches have shorter functional urethras and lower maximal urethral pressures. In women, the compliance and cross-sectional area of the urethra are increased and power generation is substantially weakened. Many women and most bitches have an intrapelvic bladder neck and a short urethra. Owing to hormonal deficiencies they have an impaired capacity to seal the lumen of the urethra and the urethral sphincter is less sensitive to sympathomimetics. In women partial denervation of the pudendal nerve is also a contributory factor.

Animals↗
PubMed1994

Antithrombin-Gly 424 Arg: a novel point mutation responsible for type 1 antithrombin deficiency and neonatal thrombosis.

Inherited type 1 antithrombin (AT) III deficiency is characterized by a decrease of immunoreactive and functional protein levels to about 50%. The disorder is associated with a significantly increased risk of thromboembolism. We have investigated the molecular basis of type 1 AT deficiency in a Belgian family. The diagnosis of the disease was primarily made in a newborn girl with unusually severe thrombotic complications. Using the polymerase chain reaction and single-strand conformation polymorphism analysis, followed by direct sequencing of AT gene fragments, we identified a novel point mutation in exon 6. We detected a G to C substitution in the first position of codon 424 leading to a glycine to arginine substitution. The modification at this highly conserved position in the serine protease inhibitor gene family probably leads to an unstable mutant-gene product. The mutation creates a unique restriction site for the enzyme Hha I in exon 6. This change permitted a rapid and accurate screening of the kindred with identification of the molecular defect in five other family members.

Adult↗
PubMed1994

Contribution of endoscopy to early diagnosis of hypertrophic pyloric stenosis.

The diagnostic accuracy of ultrasonography and gastrointestinal endoscopy was compared in 63 infants who were operated on for infantile hypertrophic pyloric stenosis. Endoscopy was far more accurate than ultrasonography, the diagnosis being made in 97 and 81% of the cases, respectively. The difference between the techniques was even more obvious in the younger patients and in those with a short history of vomiting. The ability to detect coexistent or other causes of vomiting with endoscopy appeared advantageous. The endoscopic procedure is easily done without general anesthesia and was without complications in our series. We recommend endoscopy as an important tool in very young patients with few clinical signs other than vomiting, allowing for appropriate treatment without delay.

Endoscopy↗
PubMed1993

Asymptomatic autoimmune chronic active hepatitis in a male adolescent.

We report a 12-year-old boy presenting with smooth muscle antibody-positive auto-immune chronic active hepatitis. Suspicion of the diagnosis arose after a routine blood test which revealed abnormal liver function tests. In spite of the presence of cirrhosis and patchy necrosis on liver biopsy, our patient never showed any clinical feature of impaired liver function. This observation demonstrates that auto-immune hepatitis may exist for a long time before clinical symptoms appear and probably explains why some cases of auto-immune hepatitis finally present as fulminant liver failure.

Autoimmune Diseases↗
PubMed1993

A digital speech processor and various speech encoding strategies for cochlear implants.

We distinguish two main categories in the speech decoding strategies: those based on feature extraction and those based on time information of the filtered incoming signal. In the first group only those electrode pairs corresponding to the localisation of the four or more, maximum spectral peaks or the formants of the speech signal are stimulated. The second category is essentially based on the timing information that is included in the filter outputs of the filtered speech signal. The Laura implant has the capability to be programmed to the different decodings-strategies. To understand the potential possibilities the main features of the implant are discussed.

Acoustic Stimulation↗
PubMed1993

The prevalence of Helicobacter pylori-positive serology in asymptomatic children.

Epidemiologic data are presented about the prevalence of Helicobacter pylori positivity as determined by serology in a large series of asymptomatic children (n = 466). Serology is now generally accepted as a valid noninvasive screening method for the detection of Helicobacter pylori infection. Blood samples were taken from 466 apparently healthy children (ages 2-14 years) who were admitted to our pediatric 1-day clinic for elective surgery. The children originated from different ethnic backgrounds. All were born in Belgium and have been living there ever since. Thirty-four (7.3%) had positive titers for Helicobacter pylori. There was a significant increase in the number of positive patients with advancing age (5.4% in the age group 2-8 years and 13.4% in the age group 8-14 years; p < 0.001). We also found a significant difference in the prevalence of Helicobacter pylori positivity between Caucasian Belgian children and non-Caucasian children of different ethnic backgrounds. This relatively high prevalence of positive serology in asymptomatic older children (13.4%) should be considered in studies on the incidence or causative role of Helicobacter pylori in children with chronic abdominal complaints.

Adolescent↗
PubMed1993

The nutritional value of a whey hydrolysate formula compared with a whey-predominant formula in healthy infants.

Forty-five healthy infants were included in a double-blind randomized prospective study comparing the nutritional value of two formulas. One group received a whey-predominant formula (n = 20); the other group received a whey hydrolysate formula (n = 25). Four infants of the whey hydrolysate group were dropped because they refused the formula. Although the mean daily volume intake was smaller with the whey hydrolysate formula compared with the whey-predominant formula (p < 0.001), the weight gain in the two groups after 13 weeks was identical (27.2 g/day in both groups; the mean difference in weight gain between the groups after 13 weeks was only 8 g). Length gain at 13 weeks was 10.4 cm in the whey-predominant formula group and 10.8 cm in the whey hydrolysate formula group (p = NS). After 13 weeks, blood was sampled for hemoglobin, hematocrit, red blood cell count, white blood cell count, lymphocytes, glycemia, proteins, albumin, prealbumin, calcium, phosphorus, urea, creatinine, iron, iron-binding capacity, zinc, and vitamins A and E. Except for the iron-binding capacity, zinc, urea (in plasma as well as in urine) (all three were higher in the whey hydrolysate group), no significant differences were found. According to these results, exclusive feeding of the whey hydrolysate formula from birth to 3 months of age to healthy infants appears to result in an adequate nutritional status, as assessed at 3 months of age.

Double-Blind Method↗
PubMed1992

[Helicobacter pylori infections in children].

In our patient population with chronic aspecific abdominal complaints Helicobacter pylori gastritis is no rarity. This entity has been diagnosed in 10 children out of 48 (mean age: 8 years 11 months) who underwent an endoscopy of the upper gastrointestinal tract. After treatment with amoxicillin and colloidal bismuth subcitrate during a period of 2 weeks the complaints disappeared and an eradication was obtained in 7. Histology of the antral mucosa demonstrated a type B chronic active gastritis in all patients. A Helicobacter pylori specific serology was positive in all 10 patients. This test was also positive in 17 out of 35 asymptomatic first degree family members; this is an illustration for the high family prevalence of Helicobacter pylori.

Adolescent↗
PubMed1991

Lack of ciprofloxacin ototoxicity after repeated ototopical application.

The possible side effects of ototopically applied ciprofloxacin on inner ear function were investigated. The hearing function of pigmented guinea pigs was evaluated by daily frequency-specific evoked response audiometry after repeated application of the drug to both ears. Ciprofloxacin appeared to have no statistically significant effect on the hearing thresholds of the experimental animals.

Administration, Topical↗
PubMed1986

Acoustic simulation experiments with preprocessed speech for an 8-channel cochlear implant.

A speech processor for simulation of preprocessed speech in cochlear implantation has been developed. An acoustic simulation of spectrally reduced speech was presented to 169 normally hearing subjects. Several perceptual tests with 9 different filter conditions were carried out. The intelligibility of sentences and the discrimination of phonemes in nonsense syllables were measured. It was established that even within one test session, an important learning effect occurred.

Cochlear Implants↗
PubMed1985

Information transmission with an eight channel bipolar cochlear implant. Acoustic simulation experiments.

In order to find the best stimulus parameters for the processing of a speech signal for cochlear implant applications, a speech processor was developed. The information which can be transmitted by means of an eight channel implant is simulated. The results indicate that identification and forced choice discrimination of (CV) and (VC) syllables is possible. The perception of consonants is more affected than that of vowels. Within one test session an effect of learning was established which remained restricted to the trained filter condition.

Acoustics↗