Biomedical subjects

M V Kinder

Publications and source records attributed to M V Kinder.

7 recordsLinked to original sources

PubMed2001

Demonstration of spontaneous and stretch induced urinary bladder EMG in the living rabbit.

Spontaneous bladder EMG was recorded in the living rabbit from an isovolumetric bladder without chemical or electrical stimulation. Mechanical intervention, either by lifting the bladder out of the abdomen or by rapid filling, resulted in stretch induced bladder EMG. A self made epoxy resin electrode device that embedded 32 EMG recording electrodes in a matrix like pattern, each electrode Ag/AgCl, d = 0.6 mm with an interdistance of 2.3 mm, was used for registration. The recorder used a common average reference technique and a sample frequency of 400 Hz. A signal bandwidth of 0.05 to 108 Hz was available for analysis. Spontaneous EMG consisted of single spikes and bursts (2-20 spikes), but not of continuous activity. The shape of spikes was triphasic. Single spikes appeared with and without burst activity. Small (2-5 spikes) and large bursts (6-20 spikes) were discerned; small bursts not necessarily propagated across electrodes, large bursts did and were able to organize, suggesting that they were under short neuron system control. Spontaneous EMG was probably related to both contraction and relaxation. Stretch induced EMG was characterised by continuous activity on all electrodes, spikes that followed each other immediately, slowly fading away. The spikes had an elongated third phase when compared to the shape of spontaneous activity. Highest activity and amplitudes were found after lifting the bladder out of the abdomen and placing it on the electrode device. A concept is put forward in which the continuous activity is not unequivocally related to muscle shortening, but where the current stress and strain situation of the bladder tissue can cause a muscle fibre elongation upon the appearance of electrical activity. The EMG activity found was in many aspects similar to results of a previous study using mortalized rabbits. Artifact sources like the heart, respiration, or local movement between electrode and bladder could easily be identified due to the new experimental methodology used.

Animals↗

PubMed1999

Validity of a non-invasive determination of the isovolumetric bladder pressure during voiding in men with LUTS.

Invasive pressure flow analysis is the gold standard for discriminating between hypocontractile bladder muscle function and infravesical obstruction in male patients with lower urinary tract symptoms. Here a non-invasive method to determine the isovolumetric bladder pressure to judge contractility is presented. This is based on interruption of urine flow by sudden occlusion of a specially fixed condom catheter. The pressure inside the condom is recorded and used to estimate the isovolumetric bladder pressure. Combined with, for example, home uroflowmetry, this non-invasive method may overcome some of the disadvantages (e.g., invasiveness, cost) of the conventional pressure flow test. To determine the isovolumetric bladder pressure reliably with this non-invasive method, two constraints have to be met. First, the bladder neck and urethra have to remain open after occlusion of the condom catheter. This was tested combining the non-invasive test with radiography in five patients. Second, a steady state has to be reached, i.e., the flow in the urethra, due to the elastic properties of the biological and the condom systems, should come to a stop when the bladder pressure and the condom pressure equilibrate. This was investigated by comparing the non-invasively recorded condom pressure with the simultaneously invasively recorded intravesical pressure in 52 patients. In these patients, three different methods of condom fixation were evaluated. The results show that the bladder neck and urethra remain open during the test. However, a steady state is often not reached. In more than 80% of the cases with the best condom fixation, the bladder pressure has not stabilized, although the condom pressure reached a plateau. Therefore, this method of sudden occlusion is not yet clinically applicable for determining the isovolumetric bladder pressure. Neurourol. Urodynam. 18:477-486, 1999.

Humans↗

PubMed1999

The neuronal control of the lower urinary tract: A model of architecture and control mechanisms.

The human micturition cycle is controlled by central and peripheral nervous structures and connections. In literature, no complete or generally accepted model describes the principles of micturition control. In this paper, the integration of (neuro-)anatomy, (neuro-)physiology and control theory is used to describe and model the neuronal control of the lower urinary tract. Neuroanatomy supplies the most basic information necessary for the modellation of the peripheral pathways and central connections involved in the control of the uropoetic system. It is found that not all the nervous structures and connections have been identified as such yet. The linking up between several nervous structures (e.g., the presence of central and peripheral relay stations) is not completely clear. A s a consequence, each model to describe the micturition cycle from the perspective of control theory is yet of limited physiological value as it cannot exceed a rather general level of modellation. Adding functional considerations (neurophysiology and control theory) to the neuroanatomical skeleton completes the model. Some control mechanisms active during the micturition cycle can still not be revealed in detail. Crucial questions on the neuronal innervation of the human uropoetic system and the control mechanisms active during the micturition cycle remain, like how the supraspinal trigger mechanisms for micturition are organised, or how the voluntary cessation of voiding is realised. A simplified version of the model discussed in this paper can already be used for mathematical modelling, e.g., neural network simulations.

Afferent Pathways↗

PubMed1999

Three dimensional registration of mechanical bladder activity using polystyrene fluorescent spheres: A technical note.

Optical marker tracing methods have been applied successfully in recent years to quantify local material deformation of heart tissue, skin and striated muscles. In this study, polystyrene fluorescent spheres (d = 0.6 mm) are glued to the ventral serosal bladder wall in the rabbit. Three dimensional video registration of the polystyrene spheres is used to calculate two directions of principal strain (epsilon (1), epsilon (2) ) on the bladder surface in vivo. The aim is to investigate the feasibility of the technique for this new application in two experimental circumstances: during spontaneous bladder wall activity and after electrical stimulation of bladder innervating nerve fibers. During spontaneous activity, random contraction and relaxation occurred simultaneously and separately across the bladder wall for the two principal strains epsilon (1) and epsilon (2). After extradural electrical stimulation of sacral nerve root S2, the principal strains epsilon ( 1) and epsilon (2) synchronized in time in such a way that epsilon ( 1) and epsilon (2) both represented contraction or both represented relaxation. One and the same bladder wall area passed through phases of contraction followed by relaxation and vice versa. After multiple stimulation periods, the coordination between the two principal strains during stimulation was reduced. This technique allows to identify local areas of contraction and relaxation in the intact bladder wall in vivo. Three dimensional video registration of polystyrene fluorescent spheres to study bladder wall contraction and its relaxation proved to be a feasible technique, with which electrical stimulation effects and spontaneous activity could be measured.

Animals↗

PubMed1998

A non-invasive method for bladder electromyography in humans.

No convincing correlation of bladder EMG in humans to simultaneously measured intravesical pressure has been reported in the literature. In most studies on bladder EMG the electrodes contact the bladder wall itself. This causes problems in the discrimination between very small extracellular signals, reflecting actual membrane potential changes of bladder muscle cells, and large electro-mechanical artefact caused by electrode movement as the tissue contracts. Aim of this study is to investigate whether bladder EMG can be performed non-invasively with Ag-AgCl surface electrodes that are placed on the abdominal skin of healthy volunteers. Bipolar electrode signals are obtained in a diagonal, vertical and horizontal direction of the abdominal electrodes. A conventional urodynamic investigation is performed according to International Continence Society standards simultaneously with bladder EMG. This new method shows that voiding is accompanied by a slow voltage change in bipolar electrode signals. The contribution of abdominal and other striated muscle activity to the bipolar electrode signals can clearly be distinguished from the slow voltage changes related to voiding. Free flowmetry shows that the electrical activity picked up by the abdominal electrodes is related to bladder emptying. In pressure/flow studies a relation between the electrical activity and the detrusor pressure is found. The present results suggest that the slow voltage changes found during bladder contraction are caused by summed membrane potential changes of bladder muscle cells, but this concept needs further testing. Also, validation for clinical use remains to be established.

Electromyography↗

PubMed1997

A method for the electromyographic mapping of the detrusor smooth muscle.

Various methods for detrusor EMG in the living mammal have been described in the literature. These methods do insufficiently take into account signal components that are caused by movement between the electrodes and the bladder wall. Reliable detrusor EMG has not been achieved yet. This study investigates the feasibility of a new experimental set-up, in which the electrical activity of the detrusor smooth muscle can be examined. In six rabbits, after cervical dislocation, laparotomy and after excision of the heart, electrical signals of the detrusor muscle are measured with 240 electrodes. The electrodes are positioned on the serosal surface of the filled and isovolumetric bladder. During the recordings, no bladder contractions are deliberately evoked by any stimulus. Consistent results in all six animals show a repetitive spike pattern on multiple electrodes with a repetition frequency of 1.2 Hz. Spikes are triphasic and have a mean duration of 0.47 s (STD = 0.15 s, n = 40) and a mean amplitude of 0.29 mV (STD = 0.07 mV, n = 40). On adjacent electrodes a time shift between the spikes is found, suggesting the propagation of electrical activity across the detrusor surface. The maximum conduction velocity of an arbitrary spike front in the direction of propagation is approximately 30 mm/s. In two animals slow waves are found on the edge of the highpass filter setting. Extensive control experiments are executed to validate the set-up and to interpret the data obtained by the animal experiments. The bladder is still able to contract thirty minutes post mortem. The heart, as a distant signal source, generates a signal that is present on all electrodes and shows no detectable time shift from one electrode to any other. Motion imposed on the electrodes relative to the bladder wall does not reproduce the slow waves and spikes found in the animal experiments. The control experiments support that the results of the animal experiments show electrical activity originating from the detrusor muscle itself. With the experimental set-up described in this paper, nearly artefact free detrusor EMG can be recorded. An electromyographic map of a considerable detrusor smooth muscle area can be obtained.

Animals↗

PubMed1995

Neuronal circuitry of the lower urinary tract; central and peripheral neuronal control of the micturition cycle.

A new presentation technique is introduce to describe the neuronal circuitry involved in the control of the uropoëtic system and its control mechanisms during the micturition cycle. This method is based on the preparation of flow charts and is applied to the discussion of four qualitative models which are derived from the literature. Opinions concerning the reflex arcs and supraspinal connections said to be involved in micturition and continence are different and sometimes contradictory. Little is known about supraspinal (inter)connections and their function in micturition control is still fragmentary. The control mechanisms which terminate voiding are not totally clear. Moreover, the role of the pelvic floor musculature in the control of the lower urinary tract is probably underestimated. The flow charts presented in this paper contribute to the future design of a single complete qualitative model representing the general central and peripheral nervous connections and control mechanisms. Such a model would provide an approach for future research in neuromodulation and neurostimulation of the uropoëtic system and a reduced version could be used for quantitative modelling, e.g. in neural network simulations.

Humans↗