Search PubMed⌕ Search

Biomedical subjects

Dirk De Ridder

Publications and source records attributed to Dirk De Ridder.

At least 19 recordsLinked to original sources
PubMed2007

Autonomous contractile activity in the isolated rat bladder is modulated by a TRPV1 dependent mechanism.

AIMS: Resiniferatoxin (RTX), a vanilloid compound and agonist of the transient receptor potential channel 1 (TRPV1), is known for its beneficial effects on neurogenic detrusor overactivity. The mainstream rationale for its use is the desensitization of TRPV1 on sensory bladder afferents. However, recent findings showed that TRPV1 is present in other cell types in the bladder. To eliminate the effects of RTX on spinal and central neural circuits, we investigated autonomous contractility in normal and neurogenic rat bladders after treatment with RTX. METHODS: Female Wistar rats were made paraplegic at vertebral level T8-T9. Animals were intravesically pre-treated with vehicle (ethanol 5%) or RTX (100 nM) and sacrificed after 72 hr. Each bladder was excised and placed in a heated organ bath, where intravesical pressures were measured. Effects on contractile parameters of intravesical volume load, the non-selective muscarinic receptor agonist carbachol (CA) and electrical stimulation (ES) of nerves were studied in both groups. RESULTS: In RTX-treated normal bladders we found shorter contractions with higher amplitude than in control bladders (P < 0.05). In RTX-treated neurogenic bladders the amplitude and duration of autonomous contractions were increased compared with controls (P < 0.05). Furthermore RTX induced an increased response to CA and to ES (P < 0.05). CONCLUSIONS: RTX significantly affected the properties of autonomous bladder contractile activity. This provides evidence for local effects of RTX on bladder contractile activity, which are not mediated by afferent neural pathways and which may contribute to the beneficial effects on detrusor overactivity. TRPV1 and TRPV1(+) cells seem to play an important role in (autonomous) bladder contractility.

Animals↗
PubMed2007

Cytokine production following experimental implantation of xenogenic dermal collagen and polypropylene grafts in mice.

AIM: We earlier showed that xenogenic Pelvicol (Bard, Olen, Belgium) implants induce a lesser inflammatory response than Prolene (Johnson and Johnson, Dilbeek, Belgium). The purpose of this study was to determine cytokine profiles in the host immune responses to Pelvicol in a mouse model. The hypothesis was that Pelvicol would induce a "T-helper2" (Th2) rather than T-helper1 (Th1) type of inflammatory response. METHODS: Mice were implanted subcutaneously with Pelvicol or Prolene and the graft sites were harvested at 3 to 28 days. Histopathology was done and cytokine levels were determined by immunohistochemistry and RT-PCR. Flow cytometry was used to identify which cell population contributed to the observed cytokine production profiles. RESULTS: Pelvicol induced a decreased inflammation and displayed an increase in IL-10 and TGF-beta, but reduce of TNF-alpha and IFN-gamma, indicating a Th2 type dominated response as examined by immunohistochemistry and RT-PCR. Flow cytometry showed that the monocytes/maceophages were the main cell population responsible for production of these cytokines. Monocytes/maceophages from Pelvicol explants showed upregulated expression of IL-10 while Prolene explants expressed TNF-alpha. CONCLUSION: Pelvicol induced a Th2 type cytokine-dominated immune response after subcutaneous implantation in mice.

Animals↗
PubMed2006

Posterior intravaginal slingplasty with preservation of the uterus: a modified surgical technique in a young myelomeningocele patient.

We report a case of uterine prolapse in a young woman, treated by posterior intravaginal slingplasty with preservation of the uterus as a feasible and safe surgical procedure. Posterior intravaginal slingplasty is commonly used to correct vaginal vault prolapse, but may be a valuable alternative to correct uterine prolapse. We compare this technique to other techniques to correct uterine prolapse.

Adult↗
PubMed2006

Design and validation of a new screening instrument for lower urinary tract dysfunction: the bladder control self-assessment questionnaire (B-SAQ).

OBJECTIVES: To develop and validate a short patient self-assessment screening questionnaire: bladder control self-assessment questionnaire (B-SAQ) for the evaluation of lower urinary tract symptoms. This first validation study was undertaken amongst women. PATIENTS AND METHODS: Three hundred twenty-nine women attending general gynaecology and urogynaecology clinics completed both the B-SAQ and Kings Health questionnaire prior to medical consultation, and independent physician assessment of the presence of lower urinary tract symptoms (LUTS) and need for treatment. The psychometric properties of the B-SAQ were subsequently analysed. RESULTS: The B-SAQ was quick and easy to complete, with 89% of respondents completing all items correctly in less than 5 min. The internal consistency (Cronbach's alpha score 0.90-0.91), criterion validity (Pearson's correlation values of 0.79 and 0.81, p<0.0001 with the incontinence impact domain of the Kings Health questionnaire), and test-retest reliability of the questionnaire were good. The sensitivity and specificity of the questionnaire to identify patients with bothersome LUTS was 98% and 79%, respectively. CONCLUSIONS: LUTS are commonly underreported. Empowering patients to self-assess their bladder symptoms and the need for treatment will improve treatment-seeking behaviour. The B-SAQ is a psychometrically robust, short screening questionnaire that offers patients the ability to assess their bladder symptoms and the bother they cause, and the potential benefit of seeking medical help.

Adolescent↗
PubMed2006

Tensile strength and host response towards silk and type i polypropylene implants used for augmentation of fascial repair in a rat model.

OBJECTIVE: We compared host response, architectural integration and tensile strength of two different macroporous silk constructs to a polypropylene type I implant in a rat model for augmentation of primary fascial defect repair. MATERIALS AND METHODS: Animals were sacrificed on days 7, 14, 30 and 90 after implantation. The explants were evaluated macroscopically for infections, herniations and adhesions, mechanically for tensile strength, and histopathologically, to evaluate collagen deposition and inflammatory response. RESULTS: The tensile strength of the explants showed a gradual increase for all materials. All implants uniformly shrank around one fifth by 90 days. In the silk implants, the inflammatory reaction showed a remarkable higher number of foreign body giant cells that characteristically spread from the periphery into implants. Collagen deposition was comparable for all the materials. In Silk a higher grade of neovascularisation was observed. CONCLUSION: Silk explants expressed high tensiometric strength, which was associated with a marked fibrotic process. The silk implants induced a strong foreign body reaction accompanied by microscopic signs of architectural degradation at 90 days. Polypropylene explants showed a more moderate foreign body reaction without architectural disturbance.

Abdominal Wall↗
PubMed2006

Tensile strength and host response towards different polypropylene implant materials used for augmentation of fascial repair in a rat model.

We compared inflammatory response, fibrosis and biomechanical properties of different polypropylene materials from one manufacturer (Tyco Healthcare) in a rat model for primary fascial repair. Full-thickness abdominal wall defects were primarily repaired using 'overlay' technique. Multifilament implants were Surgipro SPM and SPMW, the latter a wider-weave type of the former. Monofilament SPMM implants and polypropylene suture repair (Surgipro II) served as controls. Explants were evaluated macroscopically and changes in thickness, shrinkage and tensile strength were measured. Inflammatory and connective tissue response was assessed on haematoxylin-eosin and Movat stains. Immunohistochemistry was done to localise rat macrophages/monocytes. Multifilament materials induced a shorter acute inflammatory response and more pronounced chronic inflammatory reaction compared to monofilament implants. Macrophages could be found deep in interstices 7.5 by 12.5 microm. No difference in collagen deposition and neovascularisation was observed. At 90 days time point, explants reconstructed with tighter woven multifilament SPM were weaker than sutured or SPMM controls. Overall shrinkage of 10% was comparable for all groups.

Abdominal Wall↗
PubMed2006

The presence of Fowler's syndrome predicts successful long-term outcome of sacral nerve stimulation in women with urinary retention.

OBJECTIVES: Sacral nerve stimulation (SNS) is an effective treatment for women with urinary retention. Some women present specific electromyography abnormalities of the external urethral sphincter (Fowler's syndrome). The aim of this study was to evaluate whether Fowler's syndrome and psychologic preimplant screening could be predictive factors for long-term success of SNS in women with urinary retention. METHODS: All patients underwent electrophysiologic and urodynamic studies and voiding charts. A validated psychologic screening questionnaire was used. Women with successful temporary stimulation, received a definitive implant (Interstim Medtronic). They were followed prospectively every 6 months. Failure was defined as recurrent retention needing intermittent or permanent catheterisation. RESULTS: Sixty-two women were implanted, 30 with Fowler's syndrome, 32 with idiopathic retention. In those with Fowler's syndrome, 26.6% screened positive for somatisation, as did 43.8% in the idiopathic group (not significant [ns]). Screening for depression was positive in 30% and 18.8%, respectively (ns). There was no correlation with outcome. Twenty-eight patients failed: 9 with Fowler's syndromes, 19 without (p=0.04). Kaplan-Meier analysis showed that patients with Fowler's syndrome benefitted significantly longer from SNS (log-rank test, p=0.005). CONCLUSIONS: The presence of Fowler's syndrome is a positive predictive factor for SNS in female urinary retention. Idiopathic urinary retention patients can benefit as well, but the success might be less predictable. Preimplant psychologic screening, using the Patient Health Questionnaire, does not correlate with long-term outcome of SNS in this population.

Electric Stimulation Therapy↗
PubMed2006

Primary and secondary auditory cortex stimulation for intractable tinnitus.

INTRODUCTION: Recent research suggests tinnitus is a phantom phenomenon based on hyperactivity of the auditory system, which can be visualized by functional neuroimaging, and transiently modulated by transcranial magnetic stimulation (TMS). We present the results of the first implanted electrodes on the primary and secondary auditory cortex after a successful TMS suppression. METHODS AND MATERIALS: Twelve patients underwent an auditory cortex implantation, 10 for unilateral and 2 for bilateral tinnitus, based on >50% suppression applying TMS. Results were analyzed for pure tone tinnitus and white noise tinnitus. RESULTS: TMS results in 77% pure tone tinnitus and 67% white noise reduction. Electrical stimulation via an implanted electrode results in a mean of 97% pure tone tinnitus and 24% white noise suppression. Mean Visual Analogue Scale score decreases from 9.5 to 1.5 for pure tone and from 8.8 to 6.8 for white noise postoperatively. DISCUSSION: Pure tone tinnitus might be the conscious percept of focal neuronal hyperactivity of the auditory cortex. Once visualized, this hyperactivity can be modulated by neurostimulation. CONCLUSION: The preliminary results of the first implantations suggest that patients with unilateral pure tone tinnitus are good surgical candidates for electrode implantation and permanent electrical stimulation of the auditory cortex, provided that the tinnitus is of recent origin and can be suppressed by TMS.

Adult↗
PubMed2006

Comparison study of autonomous activity in bladders from normal and paraplegic rats.

AIM: To identify differences in the pattern of pressure generated by isolated bladders from normal and paraplegic rats. MATERIALS AND METHODS: Nine female Wister rats were made paraplegic by spinal cord transsection at the vertebral level T8-T9 and sacrificed between D21 and D28. A further group (n = 9) was used as a control group. Each bladder was excised and placed in an organ bath where intravesical pressures were measured. Pressure changes were divided in two well-defined groups: macro-transients and spikes. The effects of intravesical volume load and muscarinic (M) agonists were studied. RESULTS: We demonstrated a higher frequency, a longer duration, and a higher variance of duration in macro-transients in the neurogenic group. Intravesical volume load influenced the amplitude and frequency of macro-transients in both groups similarly. The effects of the muscarinic (M(2))-selective agonist arecaïdine were different in neurogenic bladder; the effects of the non-selective muscarinic (M)-agonist carbachol were similar in both groups. CONCLUSION: We showed that the pattern of autonomous activity was significantly different between normal and neurogenic rat bladders. We also found evidence for alterations in the muscarinic response of isolated neurogenic rat bladders. This model offers an exciting new research tool to evaluate the detrusor activity in neurogenic and normal conditions.

Animals↗
PubMed2006

The biology behind fascial defects and the use of implants in pelvic organ prolapse repair.

Implant materials are increasingly being used in an effort to reduce recurrence after prolapse repair with native tissues. Surgeons should be aware of the biology behind both the disease as well as the host response to various implants. We will discuss insights into the biology behind hernia and abdominal fascial defects. Those lessons from "herniology" will, wherever possible, be applied to pelvic organ prolapse (POP) problems. Then we will deal with available animal models, for both the underlying disease and surgical repair. Then we will go over the features of implants and describe how the host responds to implantation. Methodology of such experiments will be briefly explained for the clinician not involved in experimentation. As we discuss the different materials available on the market, we will summarize some results of recent experiments by our group.

Animals↗
PubMed2006

Amygdalohippocampal involvement in tinnitus and auditory memory.

CONCLUSION: The preliminary results suggest that in chronic unilateral tinnitus the contralateral amygdalohippocampal complex does seem to be involved in tinnitus perception of pure tones. OBJECTIVES: Functional neuroimaging studies have revealed that the hippocampus and amygdala are involved in tinnitus perception. The amygdala and hippocampus are supplied by the anterior choroidal artery. Selective amobarbital injections in the anterior choroidal artery result in a non-functional amygdalohippocampal area for 10 min. The aim of this study was to assess the influence of this procedure on tinnitus perception. PATIENTS AND METHODS: Amobarbital (80 mg in total) was injected selectively in two sessions in the left and right anterior choroidal artery in six male patients with tinnitus: four with unilateral tinnitus, two with bilateral tinnitus. Of the patients with unilateral tinnitus, three had right-sided tinnitus and one had left-sided tinnitus. The average age was 57.3 years (range 43-69). Average tinnitus duration was 5.3 years (range 1-10). The differences in visual analogue scale (VAS) scores before and after the amytal tests were analysed. RESULTS: Amytal injection ipsilateral to the side where the tinnitus was perceived resulted in a maximum of 30% tinnitus suppression, whereas amytal injection contralateral to the tinnitus side yielded a 60-70% tinnitus suppression in three patients with unilateral chronic tinnitus (>4 years). Only pure tone tinnitus was suppressed, white noise was not. Two patients with bilateral tinnitus had no suppression, irrespective of the tinnitus type. A third patient without clinical tinnitus suppression had tinnitus of more recent origin (1.5 years).

Adult↗
PubMed2006

Activation of cortical and subcortical auditory structures at 3 T by means of a functional magnetic resonance imaging paradigm suitable for clinical use.

OBJECTIVES: Visualization of functional magnetic resonance imaging (fMRI) activation of subcortical auditory structures remains challenging because of the cardiac-related pulsatile movement of both the brainstem and the cerebrospinal fluid and involved, until now, special scanning, pre- and postprocessing techniques, which are not convenient in clinical settings. The aim of this study is to examine the activation in both cortical and subcortical auditory structures by means of an fMRI paradigm, which is suitable for clinical use. MATERIALS AND METHODS: Twenty subjects (13 volunteers and 7 patients) were examined on a 3 T imaging system with binaural musical stimulation. RESULTS: Both cortical and subcortical auditory structures are successfully visualized in volunteers and patients. CONCLUSIONS: Activation of both the cortical and subcortical auditory structures can be visualized by means of an appropriate fMRI setup at 3 T. This paradigm can easily be used in patients with tumors and/or hearing disorders.

Adult↗
PubMed2005

Gastrointestinal stromal tumor of the prostate.

We present a unique case of an atypical prostate tumor in a 49-year-old man with acute urinary retention. Digital rectal examination revealed a large prostate with a parenchymal mass on the left side. Radiologic imaging showed a 14.2 x 9.6 x 14.0-cm prostatic mass and multiple liver metastases. A pathologic diagnosis of a prostatic gastrointestinal stromal tumor was made and was confirmed by molecular analysis. Therapy consisted of a tyrosine kinase inhibitor, resulting in prostate mass reduction. After 100 weeks, the patient was in good physical condition with a continuing partial response with a reduced mass volume and liver nodules.

Acute Disease↗
PubMed2005

Transcranial magnetic stimulation for tinnitus: influence of tinnitus duration on stimulation parameter choice and maximal tinnitus suppression.

OBJECTIVE: Tinnitus is a distressing symptom for which few treatments exist. It leads to an important decrease in quality of life in 2 to 3% of the population. Tinnitus is considered a phantom sound, the result of cortical reorganization. Transcranial magnetic stimulation (TMS) is a noninvasive method to modulate cortical reorganization and has been shown to be able to influence tinnitus perception. STUDY DESIGN: Retrospective analysis. SETTING: Tertiary referral center. PATIENTS: The effect of TMS of the contralateral auditory cortex in 114 patients with unilateral tinnitus is investigated as one of the selection criteria used for surgical implantation of electrodes on the auditory cortex. INTERVENTION: TMS is performed at 90% of motor threshold at 1, 3, 5, 10, and 20 Hz, with each stimulation session consisting of 200 pulses. Results were classified as no effect (0-19% improvement), partial effect (20-79% improvement), and good effect (80-100 suppression). MAIN OUTCOME MEASURES: TMS had a good effect in 25% of the patients studied, partial effect in 28% patients, and no effect in 47%. RESULTS: TMS at 200 pulses is capable of tinnitus suppression for seconds only. The results were influenced by tinnitus duration: the longer the tinnitus exists, the lower the stimulation frequency that yields maximal tinnitus suppression (p < 0.001). The maximal amount of tinnitus suppression decreases in time (p < 0.01), resulting in a 2% decrease of potential tinnitus suppression per year. CONCLUSION: TMS of the auditory cortex is capable of modifying tinnitus perception for a very short time. The maximal amount of suppression and best stimulation frequency depends on the tinnitus duration.

Auditory Cortex↗
PubMed2005

Comparison of host response to polypropylene and non-cross-linked porcine small intestine serosal-derived collagen implants in a rat model.

OBJECTIVE: To compare the host response, architectural integration and tensile strength of polypropylene and porcine small intestine submucosa-derived implants in a rat model. DESIGN: Experimental study. SETTING: Center for Surgical Technologies, Faculty of Medicine, Katholieke Universiteit Leuven, Belgium. SAMPLE: Forty-eight adult male Wistar rats weighing 220-250 g randomised to receive either implant. METHODS: Full thickness abdominal wall defects were primarily repaired with polypropylene mesh (Marlex) (MX group) or porcine small intestine submucosa (Surgisis) (SIS group). Animals were sacrificed at 7, 14, 30 and 90 days after implantation. MAIN OUTCOME MEASURES: The presence of herniation, infection and intra-peritoneal adhesions. Change in thickness and tensile strength of implant. Histopathological and immunohistochemical appearances of inflammatory response and collagen deposition. RESULTS: Implants from the SIS group showed a short term increase in thickness in the first 14 days. Formation of adhesions was significantly more intense in the MX group at 30 days, and more extensive in the SIS group at 90 days. Tensile strength increased over time in both groups but was significantly lower in the SIS group than the MX group at 30 days. Implants in the MX group showed a more pronounced inflammatory response and more pronounced new vessel formation than the SIS group. Collagen formation was initially more fibrous and better organised in the MX group but became greater in the SIS group at 90 days. CONCLUSIONS: Biologically derived implant material induced a less pronounced inflammatory response and differences in collagen deposition. At 30 days tensile strength was weaker in the biological implant group but was equivalent by 90 days. These differences may have implications for the in vivo performance of the materials.

Abdominal Wall↗
PubMed2005

Pulsatile tinnitus and the intrameatal vascular loop: why do we not hear our carotids?

OBJECTIVE: Pulsatile tinnitus is characterized by hearing the heart beat or respiration in one or both ears. In 15% of patients with pulsatile tinnitus, no cause can be found. Other investigators have suggested that a vascular loop entering the internal auditory meatus can be another cause of arterial, pulse synchronous tinnitus. If so, we should constantly hear the arterial pulsations of the carotid arteries passing through the petrous bone. METHODS: Using magnetic resonance imaging, 17 patients with unilateral pulsatile tinnitus and 46 with non-pulsatile tinnitus were analyzed for the presence of a vascular loop entering into the internal acoustic meatus. Four temporal bones were sectioned to find structural differences between the internal acoustic meatus and the pericarotid area. Four patients with intrameatal vascular loops and ipsilateral pulsatile tinnitus underwent surgery by Teflon interpositioning between the loop and the cochlea. RESULTS: In unilateral pulsatile tinnitus, a statistically highly significant amount of intrameatal vascular loops was noted in comparison to non-pulsatile tinnitus. A well-developed pericarotid venous plexus was found histologically. Three of the four patients who underwent surgery were initially tinnitus free, but pulsations recurred after 3 months in one patient. CONCLUSION: Vascular loops in the internal auditory canal may generate pulsatile tinnitus. It may be treated by placing Teflon between the cochlea and the intrameatal vascular loop. One then does not hear the pulsation of the carotids due to a dampening effect of a pericarotid venous plexus.

Adolescent↗
PubMed2004

Host response after reconstruction of abdominal wall defects with porcine dermal collagen in a rat model.

OBJECTIVE: The purpose of this study was to compare the inflammatory response after implantation of Pelvicol with Prolene in a rat model. STUDY DESIGN: Full-thickness abdominal wall defects were created in 64 Wistar rats, and reconstructed with either Pelvicol or Prolene. Animals were sacrificed on days 7, 14, 30, and 90 to evaluate the presence of herniation, infection, adhesions, and changes in thickness and tensile strength of the implants. Histopathology and immunohistochemistry were performed to evaluate the collagen deposition and the inflammatory response. Statistics were done with unpaired t test and Mann-Whitney rank test. RESULTS: Pelvicol implantation induced infiltration of granulocytes, macrophages, and NK cells, which showed up-regulated expression of surface activation markers ICAM-1 and CD11b. This inflammatory response was significantly milder, and declined faster than in Prolene-implanted rats, and was also associated with fewer adhesions. Moreover, Pelvicol induced a slower, but more orderly collagen deposition, paralleling the surface of the implant. Pelvicol implants showed a slower increase in thickness and tensile strength early on, but this difference disappeared by day 90. CONCLUSION: Pelvicol induces a milder inflammatory response, less adhesion formation, more orderly collagen deposition than Prolene, and reaches a comparable tensile strength only after 90 days.

Abdominal Wall↗