PubMed Health⌕ Search

Biomedical subjects

M Lambertz

Publications and source records attributed to M Lambertz.

At least 19 recordsLinked to original sources
PubMed2000

Phase transitions in the common brainstem and related systems investigated by nonstationary time series analysis.

Neuronal activities of the reticular formation (RF) of the lower brainstem and the nucleus tractus solitarii (NTS, first relay station of baroreceptor afferents) were recorded together in the anesthized dog with related parameters of EEG, respiration and cardiovascular system. The RF neurons are part of the common brainstem system (CBS) which participates in regulation and coordination of cardiovascular, respiratory, somatomotor systems, and vigilance. Multiple time series of these physiological subsystems yield useful information about internal dynamic coordination of the organism. Essential problems are nonlinearity and instationarity of the signals, due to the dynamic complexity of the systems. Several time-resolving methods are presented to describe nonlinear dynamic couplings in the time course, particularly during phase transitions. The methods are applied to the recorded signals representing the complex couplings of the physiological subsystems. Phase transitions in these systems are detected by recurrence plots of the instationary signals. The pointwise transinformation and the pointwise conditional coupling divergence are measures of the mutual interaction of the subsystems in the state space. If the signals show marked rhythms, instantaneous frequencies and their shiftings are demonstrated by time frequency distributions, and instantaneous phase differences show couplings of oscillating subsystems. Transient signal components are reconstructed by wavelet packet time selective transient reconstruction. These methods are useful means for analyzing coupling characteristics of the complex physiological system, and detailed analyses of internal dynamic coordination of subsystems become possible. During phase transitions of the functional organization (a) the rhythms of the central neuronal activities and the peripheral systems are altered, (b) changes in the coupling between CBS neurons and cardiovascular signals, respiration and the EEG, and (c) between NTS neurons (influenced by baroreceptor afferents) and CBS neurons occur, and (d) the processing of baroreceptor input at the NTS neurons changes. The results of this complex analysis, which could not be done formerly in this manner, confirm and complete former investigations on the dynamic organization of the CBS with its changing relations to peripheral and other central nervous subsystems.

Action Potentials↗
PubMed2000

Nonstationary time-series analysis applied to investigation of brainstem system dynamics.

Previous investigations of the dynamic organization of the lower brainstem and its relation to peripheral and other central nervous systems were predominantly performed by linear methods. These are based on time-averaging algorithms, which merely can be applied to stationary signal intervals. Thus, the current concept of the common brainstem system (CBS) in the reticular formation (RF) of the lower brainstem and basic types of its functional organization have been developed. Here, we present experiments where neuronal activities of the RF and the nucleus tractus solitarii (NTS, first relay station of baroreceptor afferents) were recorded together with related parameters of electroencephalogram (EEG), respiration, and cardiovascular system. The RF neurons are part of the CBS, which participates in regulation and coordination of cardiovascular, respiratory, and motor systems, and vigilance. The physiological time series, thus acquired, yield information about the internal dynamic coordination of the participating regulation processes. The major problem in evaluating these data is the nonlinearity and nonstationarity of the signals. We used a set of especially designed time resolving methods to evaluate nonlinear dynamic couplings in the interaction between CBS neurons and cardiovascular signals, respiration and the EEG, and between NTS neurons (influenced by baroreceptor afferents) and CBS neurons.

Algorithms↗
PubMed1999

Interbeat interval variability in isolated working rat hearts at various dynamic conditions and temperatures.

This study quantifies the effect of afterload and preload changes and of temperature on interbeat interval variability of the intact isolated heart. Ventricular pressure pulse records were obtained from isolated working rat hearts. The variability of interbeat intervals (BIs) was quantified by C90, the central 90% range of the BIs during 10 min periods; predominant frequencies were searched for by power spectral analysis. At 37 degrees C the BI lengths oscillated pseudo-randomly with BI variability C90< or =4 ms. Alternating signs of consecutive BI differences were predominant, and no peaks. were seen in the power spectra. Changes in end-diastolic and aortic pressure had little effect. From 37 degrees C down to 27 degrees C the variability increased about sevenfold, run phase length became randomly distributed, and individual, time-variant peaks occurred in the power spectra. BI variability vanished during atrial pacing. We conclude that: (1) effective mutual synchronization with minimal fluctuation happens within the sino-atrial node of intact rat hearts at body temperature, and synchronization is not affected even by extreme changes in pre- and afterload, (2) the sino-atrial node is the sole source of BI variability in the intact isolated rat heart, (3) low temperature hampers this functional organization which can be reestablished by sinus node accelerating agents (isoprenaline, theophylline), (4) decreasing frequency by N6-Cyclopentyladenosine at normothermia also increases BI variability but less pronouncedly than hypothermia does.

Adenosine↗
PubMed1998

Simultaneous changes of rhythmic organization in brainstem neurons, respiration, cardiovascular system and EEG between 0.05 Hz and 0.5 Hz.

Several neurons from different regions of the brainstem of anesthetized dogs were simultaneously recorded, together with various parameters of the cardiovascular system, respiration, efferent sympathetic neural activities and cortical activity. Often rhythmic changes of activity in the range 0.05-0.5 Hz could be observed in the simultaneously recorded signals. The rhythms were analysed in time domain and by power spectra and their changes depicted over the time. The most striking rhythms between 0.05 Hz and 0.5 Hz are the respiratory rhythm and those rhythms that originate in reticular neurons of the common brainstem system as well as their respective harmonics, i.e. the ranges around the integer multiple frequencies of these basic rhythms. The observed oscillations can vanish and reappear at times. Frequencies of basic oscillations and harmonics and their amplitudes are subject to distinct slow modulations. These modulations can have irregular as well as regular courses. The different rhythms can appear separately or simultaneously in the single signals. The most important phenomenon to be observed is that the rhythms mutually influence their frequencies, which follows the rules of 'relative coordination' as described by E. v. Holst. Such changes of rhythmic activities generally also concern the ranges of harmonics of the basic rhythms. Rhythmic influences on peripheral functional systems, e.g. the cardiovascular system, are most distinct at times when the different rhythms overlap in their frequency ranges. This holds not only for the ranges of basic frequencies, but also for the ranges of their harmonics. Further it was found that rhythms with the same basic frequencies may not only appear simultaneously, but also at various times in the different functional systems. The temporal course of changes of these rhythms, their interactions and their influence on the processing of cardiac rhythmic neuronal discharge patterns is demonstrated. The meaning of the mutually influencing rhythms for the functional organization of central nervous structures is discussed.

Animals↗
PubMed1997

Influences of mandatory breathing on rhythmical components of electrodermal activity.

We investigated whether rhythmical components of electrodermal activity (EDA) can be influenced by voluntary modification of the respiratory frequency. Fifty-five volunteers participated in an experiment with nine mandatory sections of cycle times between 3.1 s and 12.2 s. The cycle time of the rhythmical EDA components often differed considerably from respiratory cycle time. ANOVA yielded that both cycle time and position within the section had an effect on the EDA power of the mandatory cycles (P < 0.05). No significant interaction between effects of section and of position was discovered (P > 0.1). A separate analysis of the cycle times of the rhythmical EDA components revealed integer relationship with the respiratory cycle times. Thus, voluntary changes in the respiratory frequency can influence occurrence and cycle time of rhythmical EDA components in a way similar to sliding coordination in the sense of E. von Holst.

Adult↗
PubMed1997

[Evaluation of possible measuring errors from overlaying pressure components in invasive blood pressure recording with external transducers].

Invasive arterial blood pressure measurement using external transducers is a routine measure in intensive care medicine and anaesthesiology. Despite the frequency of its use, measuring errors may occur that can strongly affect the significance of the results. The error with the greatest influence on blood pressure measurement arises from an inadequate dynamic behaviour of the measuring chain, and has been investigated in numerous publications. Measuring errors due to hydrostatic and dynamic pressure have not been considered to date. The present investigation describes an analysis of such measuring errors and possible ways of avoiding them. A side-hole catheter permits pressure measurements to be made without the measuring error caused by dynamic pressure behaviour. However, both analytical and experimental studies revealed that, since the velocities involved are small, this error is negligible in blood pressure measurements, and the increased cost of such catheters is therefore not justified. Measuring error due to hydrostatic pressure can be eliminated by using a zero point compensator. Such a compensator that permits vertical changes in the position of the patient without the need for manual resetting of the zero point has now been developed. However, the clinical test showed that the advantages offered by the zero point compensator again do not justify the increased cost. Furthermore, lateral changes in the patient's position during its use can lead to erroneous measurements.

Artifacts↗
PubMed1997

[Incidence of contralateral inguinal hernias in infancy and childhood].

Inguinal hernia is a frequent surgical disease during infancy, occurring in 1 to 2% of all mature newborns and rise up to 30% of all premature babies. In 9.5% a contralateral hernia is found after unilateral operation. In our own patients this rate was 5.6%. The development of a contralateral hernia was significantly more often found in boys than in girls. If the hernia occurred during the first two months of life, a contralateral hernia developed later highly significant (p > 0.0001). Within the first two postoperative years the second hernia arose in 84.9%. We recommended to routinely operation for a contralateral hernia in all children younger than two months.

Adolescent↗
PubMed1996

Relationship between rhythmic discharge patterns of neurons in the central nucleus of the amygdala, blood pressure fluctuations and cortical activity.

In the discharge sequences recorded from single neurons in the central nucleus of the amygdala of chronically instrumented awake cats, rhythmical patterns with period durations of 5-12 s were observed. At the same time blood pressure and the degree of synchronisation of the EEG showed similar period fluctuations with positive correlation to neuronal activity. It is proposed that the central amygdaloid nucleus uses rhythmic patterns to coordinate somatomotor and vegetative systems.

Amygdala↗
PubMed1996

Electrodermal activity reveals respiratory and slower rhythms of the autonomic nervous system.

Electrodermal Activity (EDA) was measured in 55 subjects during (1) an alarm reaction, (2) mental load, and (3) physical load. In 34 subjects, not only was a transient response observed, but also, oscillatory patterns characterizing short term variations of EDA. The durations of these oscillations varied between 3-16 s. Most commonly, they were approximately within the frequency range of respiration, or lower, at about 0.1 Hz. The EDA-rhythms were also related to the arterial blood pressure. They were, however, not strictly synchronized with respiration or with the blood pressure waves. We conclude that assessment of EDA in combination with fluctuations of the heart rate, and also, if possible, arterial blood pressure, may turn out to be a useful tool in the evaluation of the interaction between different regulatory processes that are realized by the common brainstem system.

Acoustic Stimulation↗
PubMed1995

Cardiac rhythmic patterns in neuronal activity are related to the firing rate of the neurons: I. Brainstem reticular neurons of dogs.

Cardiac rhythmic discharge patterns (CRDP) of brainstem reticular neurons in anesthetized dogs were estimated by ECG-triggered post-event-time histograms (PETH). Modulations of the CRDP occur, whenever the firing levels of the neurons slowly change with periods longer than the cardiac cycle. Therefore, in the activity of one and the same neuron different types of CRDP can occur interlaced in time. 'Partial' PETHs calculated according to the discharge level of the neurons make these various CRDP obvious. On the other hand, the CRDP are not always so clear in the 'total' PETHs, taken from the continuous periods of activity. The meaning of these different CRDP for regulatory processes of the organism is discussed. We study the processing of the easily identifiable signal in neuron activity, i.e., cardiac rhythm, to illustrate how signal processing depends on the momentary activity level of the neurons which is influenced by other afferent signals and by inflows from central structures reaching the neurons.

Animals↗
PubMed1995

Cardiac rhythmic patterns in neuronal activity related to the firing rate of the neurons: II. Amygdala neurons of cats.

Neurons of the central and basal part of the amygdala complex were recorded in conscious, freely moving cats. These neurons have various cardiac rhythmic discharge patterns (CRDPs) which are estimated by post-event-time histograms (PETH). When the firing level of the neurons changed, the CRDPs were modulated. These modulations became obvious, when 'partial' PETHs of the neuronal activity were constructed according to the discharge level of the neurons. With changes of the neuronal discharge level different types of CRDPs were observed, interlaced in time during recordings of the same neuron. In 'total' PETHs, taken from the continuous periods of neuronal activity, cardiac rhythm was hidden or often was not so clearly visible as in 'partial' PETHs, taken at different discharge levels. As in case of neurons of the nucleus tractus solitarii (NTS) and for brainstem reticular neurons, amygdala neurons exhibited modulations of CRDPs as their activity level changed. The results indicate that the processing of activity patterns in these neurons depends on their activity level and functional organization, which is essentially dependent on afferent signals and influences from central structures reaching these neurons.

Amygdala↗
PubMed1994

Urethral lengthening with anterior bladder wall flap for urinary incontinence: a new approach.

Urethral irregularity (impeding catheterization) and failure to achieve continence are common complications in surgery for urinary incontinence. We describe a surgical technique using an anterior bladder wall flap that is sutured to the posterior wall in an onlay fashion creating a flap valve mechanism. Experimental work in dogs demonstrated a significant increase in the leak point pressure in the surgical group when compared to controls (p = 0.019). Voiding cystourethrography and bladder inspection demonstrated an anterior flap valve with no fistula formation in all animals. Histological examination showed a viable anterior bladder wall flap in all cases. This technique was then applied to 6 patients with neurogenic bladder and low urethral resistance that failed to resolve with medical treatment. Urinary continence was achieved in 4 patients. In 1 patient a vesicourethral fistula developed 3 months postoperatively, since the mother failed to catheterize for 12 hours. This technique is a useful alternative in the treatment of urinary incontinence.

Adolescent↗
PubMed1993

A transpulmonary contrast medium enhances the transcranial Doppler signal in humans.

BACKGROUND AND PURPOSE: Transtemporal insonation in transcranial Doppler sonography is often impaired by an insufficient signal-to-noise ratio, especially in elderly patients. A transpulmonary stable air microbubble suspension was injected intravenously in humans as an intracranial ultrasonic contrast agent. METHODS: In a clinical phase II study, 20 patients (15 women, 5 men; mean age, 65.5 +/- 11.5 years) presenting with clinical indications for transcranial Doppler investigation were examined. A total of 97 intravenous injections with different concentrations (200, 300, and 400 mg/mL of suspension) of air microbubbles bound to galactose microparticles as a carrier were performed. The signal enhancement of color-coded pulse curves of basal cerebral arteries was evaluated off-line in comparison to an integrated color-coded decibel scale, considering quality, quantity, and time course of enhancement requiring a 3-dB level above the native signal. The overall diagnostic information was assessed according to a reliability score. RESULTS: The first acoustic signal increase was registered after an average of 21 seconds. Time intervals for a dose-dependent peak intensity and maximal duration were 41.3 +/- 17.1 seconds and 118.0 +/- 69.8 seconds (200 mg/mL); 55.5 +/- 27.7 seconds and 237.0 +/- 112.3 seconds (300 mg/mL); and 66.1 +/- 31.8 seconds and 293.0 +/- 122.0 seconds (400 mg/mL), respectively. Duration of signal enhancement increased significantly (P < .05) with higher concentrations. The extent of signal enhancement during the whole pulse curve reached an average of 9.1 +/- 5.0 dB for 200 mg/mL, 12.0 +/- 5.4 dB for 300 mg/mL (significant on P < .05 level), and 13.1 +/- 5.6 dB for 400 mg/mL concentration (P = NS). Respective maximal intensity spots reached 17.5 +/- 6.0, 20.7 +/- 5.5, and 22.7 +/- 5.9 dB for increasing concentrations, respectively. Overall visual assessment of enhanced pulse curves for diagnostic reliability showed a sufficient result in 38.1% of all injections with 200 mg/mL, in 88.6% with 300 mg/mL, and in 84.2% with 400 mg/mL concentration. Minimal side effects occurring in 12.4% of all injections were all reversible. CONCLUSIONS: Transpulmonary stable air microbubbles bound to a galactose carrier represent a useful and safe contrast agent in case of an insufficient native signal in transcranial Doppler investigation.

Adult↗
PubMed1993

Reevaluation by image analysis of the effects of fibroblasts, fibronectin or laminin upon colony formation in mouse lungs by B16 melanoma cells.

A recently described personal method based on image analysis of histological sections was used in order to quantify lung colony formation by B16 melanoma cells injected intravenously into the mouse. These tumor cells were preincubated in vitro either with fibronectin (FN), laminin (LN) or fibroblasts (FB), which are implicated in the process of invasion and metastasis. Thanks to this method, a more accurate analysis of lung colonies (section area and number) formed by tumor cells was realized. By image analysis, we show that when FB were mixed with B16 cells, a drastic increase of tumor sections number and area was induced. LN increased the tumor sections area, but not their number. No effect of FN on B16 cells was observed. LN and FN promoted tumor anchorage in the depth of the lungs while FB reduced the latter. These facts could explain the contradictory results obtained by simply counting macroscopically superficial lung colonies. When cultured in vitro, these B16 melanoma cells did not produce any type of IV collagenase, either alone or in the presence of LN or FN, but in cocultures (B16 with 3T3) and in fibroblasts cultures, this enzyme was present. This could explain, among other factors, why the rate of invasiveness exerted by B16 cells is higher when the latter are coinjected with FB.

3T3 Cells↗
PubMed1992

Ultrastructural and autoradiographic study of preimplantation rabbit embryos grown in conventional or uterine flushing-supplemented culture media.

Rabbit morulae and blastocysts were cultured in conventional culture media [Ham's F10 or BSM II supplemented with bovine serum albumin (BSA) or serum] or in Ham's medium supplemented with synchronous or asynchronous uterine flushings, mostly for 2 days, and afterwards investigated by light and electron microscopy and by autoradiography. Ultrastructure and cell proliferation differed considerably between cultured embryos and noncultured controls. Cultured embryos displayed more dead cells. They were developmentally retarded (predominance of smooth endoplasmic reticulum rather than the age-specific rough endoplasmic reticulum, mitochondria still round to ovoid shaped) and showed nonspecific signs of cells damage (swollen mitochondria and Golgi complex vesicles, increased number of lysosomes). All these features were also present in embryos grown in uterine flushing-supplemented media, but were less pronounced. Cell damage and impaired cell proliferation had affected trophoblast cells more than embryoblast cells. Endoderm could be differentiated only if culture had been started with blastocysts--not with morulae--and seems to require uterine secretions. No significant ultrastructural differences were observed between embryos cultured in synchronous or in asynchronous uterine flushings. Present results indicate that cultured preimplantation rabbit embryos deviate clearly from those grown in vivo and maintain, for some time, a better cellular structure--and probably function--in the presence of uterine flushings than in conventional culture media. Specific abnormal morphologic features related to a particular medium could not be identified.

Animals↗
PubMed1992

Different modes of dampening influence from baroreceptors are determined by the functional organization of the NTS neuronal network.

Simultaneous recordings of several neurones of the first relay station of baroreceptor afferents show that its general activity-dampening influence is realized via the common brainstem system (CBS) which itself controls the processing on the neurones of the nucleus of the solitary tract (NTS). This feedback system maintains the degree of activity which is necessary for the ongoing behaviour as long as it fits to the environmental situation. The output of the NTS is determined partly by the CBS, partly by the properties of the peripheral afferent input, partly by the dynamic functional organization of the local circuits and partly by influences from other brain areas.

Action Potentials↗
PubMed1991

The dynamic structure of rabbit blastocyst coverings. III. Transformation of coverings under non-physiological developmental conditions.

Under physiological conditions the zona pellucida disappears in the rabbit between Day 3 and early Day 4 post coitum (p.c.) and is replaced by a new layer, the neozona. The dissolution of the zona pellucida and the formation of the neozona was investigated in three different experimental approaches, all of them characterized by non-physiological developmental conditions for the embryo: Prevention of embryo migration from the oviduct into the uterus by postcoital (48 h p.c.) tubal ligation, in vitro culture, and asynchronous embryo transfer into uteri of recipient rabbits. Embryos of age 2 1/2, 3, 4 and 4 1/2 days p.c. were cultured for 12 to 72 h. The media used for in vitro culture were supplemented with BSA, serum or with uterine secretions that were collected either synchronously or asynchronously to the developmental stage of the cultured embryos. Three-day-old embryos were transferred into uteri of pseudopregnant foster rabbits of either synchronous (Day 3) or asynchronous stages (Day 0, 2, 4, 5, 6) and were recovered 24 to 72 h after transfer. The transformation of the coverings was evaluated by light and transmission electron microscopy. The dissolution of the zona pellucida was greatly disturbed in tube-locked embryos, and in cultured embryos if standard protein supplements (BSA or serum) had been used for in vitro culture. In many cases the zona was still completely preserved after 2 or 3 days in culture, at a time when it normally would have already been replaced by the neozona in vivo. The dissolution in vitro, however, progressed incomparably better if the culture medium had been substituted with synchronous or asynchronous uterine secretions. The formation of the neozona could not be verified in cultured blastocysts. After embryo transfer, the dissolution of the zona pellucida was completed in most cases by 2 days after transfer, irrespective of the recipients' progestational stage. Present results indicate that uterine components are essential for the dissolution of the rabbit zona pellucida. These components appear to be present in the uterine cavity constitutively, i.e. independently of the uterine progestational transformation, and need not be in synchrony with the embryo's developmental stage for dissolution of the zona. Normal formation of the neozona does not take place under the non-physiological developmental conditions of in vitro culture.

Animals↗