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H Witte

Publications and source records attributed to H Witte.

106 records · Page 6Linked to original sources
PubMedDate not supplied

High-frequency and low-frequency heart-rate fluctuation analysis in newborns--a review of possibilities and limitations.

Respiratory sinus arrhythmia (RSA) has been traditionally defined as the high-frequency component of heart-rate fluctuations (HRF) synchronous with the respiratory movements (RM), i.e., the frequency of RSA corresponds to the respiration rate. It can be shown that at defined relations of mean heart and respiration rate some essential effects must be taken into consideration in studies using RSA parameters. The relevance of these effects is shown and a new strategy of RSA quantification demanded, at least in neonates. The diagnostic importance, physiological background and future application of the low-frequency components of the neonatal HRF are reviewed on the basis of our own results. Nonrespiratory cardiovascular HRF cannot always be detected in the neonate by power spectral analysis. Movement-related HRF have a potential diagnostic importance per se, but may also artefactually disturb the quantification of other HRF components. Long-term trends can be used to describe sleep-state related trends and their disturbances.

Arrhythmia, Sinus↗
PubMedDate not supplied

Quantification of transient quadratic phase couplings within EEG burst patterns in sedated patients during electroencephalic burst-suppression period.

The time dynamics of the quadratic phase coupling within burst patterns during electroencephalic burst-suppression has been quantified. It can be shown that a transient quadratic phase coupling (QPC) exists between the frequency ranges 0 to 2.5 and 3 to 7.5 Hz and between the frequency ranges 0 to 2.5 and 8 to 12 Hz. The QPC can be explained by an amplitude modulation, where the slow rhythm modulates the rhythmic activities with a higher frequency. By means of time-variant bicoherence analysis, a strong phase-locking between the modulating and the modulated component can be identified. The phase-locking is demonstrable within the first 250 ms after the burst onset and comes up to the maximum between 750 and 1250 ms. The effect is maintained over the whole first part of the burst (2 s) with a decreasing tendency after 1250 ms. All these effects cannot be found in the EEG before entering the burst suppression period (BSP). The transient coupling phenomena in the EEG bursts during BSP can be regarded as indicators for short-term interrelations between the underlying electrophysiologic processes.

Brain↗
PubMedDate not supplied

Microevolutionary analysis of the nematode genus Pristionchus suggests a recent evolution of redundant developmental mechanisms during vulva formation.

To identify the mechanisms by which molecular variation is introduced into developmental systems, microevolutionary approaches to evolutionary developmental biology have to be taken. Here, we describe the molecular and developmental characterization of laboratory strains of the nematode genus Pristionchus, which lays a foundation for a microevolutionary analysis of vulva development. We describe 13 laboratory strains of the Pristionchus genus that are derived from natural isolates from around the world. Mating experiments and ITS sequence analysis indicated that these 13 strains represent four different species: the gonochoristic species P. Iheritieriand three hermaphroditic species, P. pacificus, P. maupasi, and an as yet undescribed species Pristionchus sp., respectively. P. pacificus is represented by five different strains isolated from California, Washington, Hawaii, Ontario, and Poland. Developmental differences during vulva formation are observed between strains from different species but also between strains of P. pacificus, like the strains from California and Poland. In particular, redundant developmental mechanisms present during vulva formation in P. pacificus var. California are absent in other strains. Amplified restriction fragment length polymorphism (AFLP) analyses of the P. pacificus strains revealed that the American strains are highly polymorphic. In contrast, the developmentally distinct strain from Poland is identical to the Californian strain, suggesting that the developmental differences rely on a small number of changes in developmental control genes rather than the accumulation of changes at multiple loci.

Animals↗
PubMedDate not supplied

[The lumbar ligamentum flavum. Anatomic characteristics with reference to microdiscotomy].

One important step in lumbar discotomy is the safe penetration and exact partial removal of the Lig. flavum. This is a crucial prerequisite for the selective and gentle removal of prolapsed and sequestrated intervertebral disc tissue. Extensive lancing of the Lig. flavum should be avoided, to minimize intraoperative and postoperative complications, such as injuries to the nerves and the Dura mater, instabilities, bleeding and scarring. As there has up to now been insufficient information on the anatomy of the Lig. flavum especially regarding microdiscotomy, an analysis of the Ligg. flava L2/L3 to L5/S1, guided by this aim, was carried out on 36 corpses kept in formaline (16 f, 20 m; 52-78 y). Preparations showed the lumbar Ligg. flava to be embodied in the Foramina interarcualia in a characteristic configuration. There also proved to be defined insertion areas on the laminae of the vertebral arches, which must be taken into consideration during the operative exposure. The Lig. flavum rises from the cranial vertebral arch from the ventral surface of the lamina (6.8 mm) whilst the insertion area on the caudal lamina covers the dorsal and the ventral surface. The extent at the ventral surface is 2.2 mm in average. Taking the insertion proportions into account we would suggest the Lig. flavum to be divided as follows: Pars interspinalis, which clearly differs from the Lig. interspinale (and from the M. interspinalis), and which houses venous anastomoses in its dorsal, ridge-shaped extension. Pars interlaminaris, which starts at the laminae and constitutes the target area for flavotomy in its lateral section, and Pars capsularis, which merges into the capsular structures of the facets. In all levels examined, there proved to be dorso-ventrally a typical change in the direction of the course of the fibres in the Pars interlaminaris. Whilst the direction of the fibres dorsally is oriented cranio-medially to caudo-laterally at an angle between 15 degrees and 30 degrees to the median line, the ventral fibres of the Lig. flavum are strictly aligned cranio-caudally. The changes in the directions of the fibres are continuous with the fibres being very closely intertwined, without there being any spatium at all. The texture of the Lig. flavum is, therefore, a mirror image of that of the autochthonuous muscular system of the back, even if the overlapping angle area is considerably smaller. The different segment levels show a segment-specific thickness profile. The analysis has provided anatomic information about the Ligg. flava L2/L3 to L5/S1. These data represent important prerequisites for a selective, gentle and safe intraoperative procedure for discotomy.

Aged↗
PubMedDate not supplied

[Shape transformations of the lumbar spine in relation to passive extension of the lower extremities in the sagittal level].

PROBLEM: The interdependencies between movements of the thighs and the lumbar vertebral shape are of high practical interest. Which are the normals of this phenomenon? METHOD: In an experiment on 107 volunteers without before known spinal disorders and complaints of back pain (47 f, 60 m, 17 a-30 a), the interdependencies between movements of the thighs in the sagittal and the lumbar back profile were analysed. Hip joint movements were provoked by a lift jack, elevating the feet to the volunteers, which sat on a bicycle chair. The hip joint flexion was measured by a Zebris CMS 50. The sagittal profile of the lower back was sensed by a comb of steel needles with low friction support. RESULTS: At 30 degrees of hip flexion, 68% of the volunteers demonstrated a kyphotic, 17% a straight and 15% a lordotic lumbar shape. Starting at 90 degrees of hip flexion, "definitively kyphosating movements" of the lumbar motion segments occur. At the end of the motion, 89% of the volunteers had a kyphotic, 3% a straight and 8% a lordotic lumbar configuration. Each 2 degrees of additional hip joint flexion caudo-cranially one more lumbar motion segment is recruited for the definitive kyphosation of the lumbar spine. CONCLUSIONS: Instead of a "physiological shape of the lumbar spine" its "physiological function" or its "physiological interaction between shape und function" should be in the focus of future discussions. In the sitting, hip joint flexion leads to a coupled motion of the thighs, the pelvic girdle and the lumbar vertebral column with the consequence of a kyphosation of the lumbar back shape.

Adolescent↗
PubMedDate not supplied

[Landing after jumps--wrong technique promotes spondylolysis].

The double-S-shape of the vertebral column usually is explained to be an adaptation to the functional requirements of axial shock absorption. We investigated the effects of axial impacts on the coupled motions of the pelvic girdle and the vertebral column. In contrast to the predictions of the bending spring model, in the first few miliseconds after impact induction the vertebral column shows a tendency of lumbal straightening. This effect may be one reason for high stresses in the vertebral arches, promoting spondylolysis and spondylolisthesis. In sports, high axial impact loads, especially provoked by wrong landing techniques after jumps, should be avoided.

Adaptation, Physiological↗
PubMedDate not supplied

A model for evaluating the stressed patient in the family practice setting.

Family physicians frequently encounter patients with stress-induced medical and psychological problems. When the symptoms are severe, or the mechanisms are vague, it is often useful to perform a detailed medical, behavioral, and psychological evaluation in order to initiate effective therapy. This paper illustrates a model for evaluating stress-related and other psychosomatic problems in a family practice.

Adult↗
PubMedDate not supplied

[Epiduroscopy with access via the sacral canal. Some constructional equipment requirements from the anatomic and biomechanical viewpoint].

To ensure optimal mechanical functioning of the vertebral column, intact symmetry of its bony and muscular elements is mandatory. With this in mind, the need to reduce the invasiveness of spinal surgery is even greater than that applying to surgery in general. To avoid bony or muscular damage during surgery, in particular in the case of the segments L4/L5 and L5/S1-which are particularly prone to intervertebral disc rupture-laser discotomy procedures, with introduction of instruments via the sacral canal during epiduroscopy are presently being developed. Preliminary experiments on human corpses have demonstrated the practicability of the technique, but specially designed instruments have yet to be developed for use in patients. In an attempt to define the conditions of important for the design of the instrument, we have carried out a morphometric analysis of 100 sacral bones (56 females; 44 males). The configuration of the sacral canal is described in quantitative terms, and the results used to determine the diameters and curvatures of the instruments needed for laser discotomy.

Aged↗