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Biomedical subjects

H K Matthies

Publications and source records attributed to H K Matthies.

12 recordsLinked to original sources
PubMed2002

Interactive PC-based volume rendering of CT datasets.

In radiology, the reading of large CT volumes is a time consuming task. Interactive volume rendering (iVRT) is a promising new technique. Using dedicated hardware (VP1000, Terarecon Inc.) it can now be realized on a standard PC in a cost effective manner. For this purpose, a program built using the Visualization Toolkit with integrated functionality for the VP 1000 is used for almost real-time iVRT (8-9 frames/second). It is possible to embed opaque and translucent polygon surfaces (e.g., segmented structures). By interactively varying the opacity, color and gradient transfer functions as well as using freely placable cutting planes, the visualization can easily be adapted to different diagnostic needs.

Humans↗
PubMed2000

Telemedicine of the future: teleneuropathology.

The chief relevance of telemedicine lies in its capability to link medical practitioners and remote hospitals to larger or specialized facilities in a very fast electronic manner. This may become even more important due to current increase in subspecialization and demand for more precise diagnosis and consultation in difficult cases. A network attaching small clinics or laboratories to larger and more specialized units, and to highly specialized referral centers may improve the professional standard of health care services and education. For a wider use, a technological standardization will be required, since the existence of several types of computer and numerous image manipulation programs, have resulted in a proliferation of file formats. However, every potential user or client of telemedicine should keep in mind, that standardization also includes legal and ethical issues such as patient confidentiality and malpractice avoidance. The adoption of workable guidelines and protocols is required. Telepathology in general and teleneuropathology in particular is the practice of pathology at a distance, viewing digitized images of histological slides on a video monitor rather than directly through a light microscope. For the transmission of the digitized images from a telemicroscope to the remote diagnostic video monitor, different technologies such as ordinary telephone lines, broadband telecommunications channels, and the Internet can be used. The transmitted images may serve for primary neuropathological diagnosis, teleconsultation, quality assurance, proficiency testing, and distance learning. Static-imaging and dynamic-imaging are the two major competing technologies of telemicroscopy. Static-imaging systems appear to have levels of diagnostic accuracy which are not satisfactory for diagnostic neuropathology. On the contrary, high levels of diagnostic accuracy can be achieved using dynamic-imaging systems with the transmission of live video images in real time and by using a robotized telemicroscope with the possibility to examine the entire histological specimen under control of the remote teleneuropathologist.

Diagnostic Techniques, Neurological↗
PubMed2000

Multimedia-based courseware in the Virtual Learning Center at the Hannover Medical School.

The commercial use of the World Wide Web causes an extensive change in information technology. Web browser are becoming the universal front-end for all kinds of client-server applications. The possibilities of telematics offer a base for multimedia applications, for instance telelearning. Learning is not limited by geography and does not cause pressure of time by the user. The development of such multimedia information and communication systems demands cooperative working teams of authors, who are able to master several areas of medical knowledge as well as the presentation of these using different multimedia facilities. A very important part of graphic design in the context of multimedia applications is the creation and interactive use of images (still, moving). The growth and the complexity of medical knowledge as well as the need for continuous, fast, and economically feasible maintenance impose requirements on the media used for medical education and training. Web-based courseware in the Virtual Learning Center at the Hannover Medical School is an innovative education resource for medical students and professionals.

Computer-Assisted Instruction↗
PubMed1999

The interactive use of networking multimedia--innovative education resource for professionals and patients.

The combination of new and rapidly developing interactive multimedia computers and applications with electronic networks will require a restructuring of our traditional approach to strategic planning and organizational structure. Worldwide telecommunication networks (using satellites, cable) are now facilitating the global pooling of healthcare information and medical knowledge independent of location. The development of multimedia information and communication systems demands cooperative working teams of authors, who are able to master several areas of medical knowledge as well as the presentation of these in different multimedia forms. The assemblage of telematics and services offers a base for multimedia applications, for example teleteaching, telelearning, telepublishing, teleconsulting, teleconferencing, telemedicine etc. The expansion of the internet will also lead to the formation of interdisciplinary "Global Education Networks". The theory and practice of education are undergoing dramatic changes. Lifelong learning and adaptation of medical practice to new knowledge and new techniques will be even more important in the future.

Computer-Assisted Instruction↗
PubMed1999

The electronic patient records of the Hannover Medical School.

In this paper, the successful introduction of a commercially available electronic patient record archiving system at the Hannover Medical School is described. Since 1996, more than 11 million document sheets of 130,000 patient records have been stored electronically. Currently, 100,000 sheets are stored each week.

Data Collection↗
PubMed1990

Posttetanic long-term potentiation in the dentate gyrus of freely moving rats is accompanied by an increase in protein synthesis.

In rats, the incorporation of L-[U-14C]leucine into proteins of cytosolic (soluble proteins) and of the 100,000 x g pellet fraction from ipsilateral hippocampus subregions (CA1, CA3 and CA4/area dentata) and visual cortex was studied from 5 min to 65 min after electrical tetanization of the right perforant path. The rates of protein synthesis were estimated calculating the relative specific radioactivity of proteins (RSA). The stimulation parameters used were identical to those of previous experiments inducing post-tetanic long-term potentiation (LTP) of both the amplitude of population spike and the slope function of the excitatory post-synaptic potential (EPSP) in the area dentata. Under these conditions, RSA-values of both fractions evaluated in the CA4/area dentata were found to be about two times higher in tetanized rats compared to either stimulated or passive controls (p less than 0.05). In all the other brain regions studied, no differences between tetanized and control animals were observed. These results provided evidence for an LTP-induced augmentation of protein synthesis in the ipsilateral dentate area which might be an essential prerequisite for those structural changes realizing the long-lasting enhanced efficacy of synaptic transmission at the perforant path-granular cell connections within this hippocampus subfield.

Animals↗
PubMed1989

N-methyl-D-aspartate receptor activation is required for the induction of both early and late phases of long-term potentiation in rat hippocampal slices.

The possible involvement of N-methyl-D-aspartate (NMDA) receptors in mechanisms enabling the maintenance of long-term potentiation (LTP) was investigated in rat hippocampal slices. The action of the specific NMDA receptor antagonists (-)-2-amino-7-phosphonoheptanoic acid (D-APH) and 2-amino-5-phosphonovaleric acid (DL-APV) as well as of the inactive isomer L-APH was tested on orthodromic population excitatory postsynaptic potential (EPSP) and population spike (PS) responses recorded extracellularly from CA1 pyramidal cells. If the active D-isomer of APH (10 microM) or DL-APV (50 microM), but not if L-APH was present during tetanization, both EPSP and spike potentiation were markedly reduced or even blocked for the whole recording period (8 h after tetanization). It is concluded that the NMDA receptor component expressed during tetanization is a necessary step not only for initiation but also for subsequent mechanisms enabling late phases of synaptic LTP. Some remaining potentiation of the population spike may be related to a second, NMDA-independent mechanism.

2-Amino-5-phosphonovalerate↗
PubMed1986

Low frequency perforant path stimulation as a conditioned stimulus demonstrates correlations between long-term synaptic potentiation and learning.

Stimulation of the perforant path with impulse trains of 15 cps and 670 msec duration was used as a conditioned stimulus in a two-way shuttle box avoidance on rats. Field potentials in the dentate area evoked by test stimuli were measured after the training sessions until the 7th day. Foot-shock and unconditioned escape elicited only a transient slight depression of the population spike amplitude (P) and increased also slightly the slope function (SF) of the population EPSP of the evoked test potentials. The control stimulation of the perforant path without pairing with foot-shock as in conditioning did only slightly increase SF of test potentials, but produced a strong transient inhibition followed by a long lasting moderate depression of P. After conditioning, all animals exhibited the same initial inhibition of P as shown in control stimulation of the perforant path. However during the following 4 hours, good learners with a relearning index greater than 30% developed a significant potentiation of P lasting until the second training session 24 hours later, which resulted in a further enhancement. SF of the evoked test potentials increased in good learners with a similar time course after conditioning but without initial depression. After 7 days P showed still enhanced but non-significant values. Poor learners with a relearning index less than 10% did not develop a potentiation of P after conditioning and initial inhibition, but a long-term depression. Also SF of test potentials decreased in poor learners during 4 hours after conditioning and returned almost to baseline until the following day. After 7 days, P and SF did not differ from baseline. The analysis of the observed synaptic changes by E-S curves demonstrated the post-tetanic LTP seems to differ in some ways from post-conditioning LTP in good learners. The latter exhibits a clear tendency of a right shift contrary to the left shift commonly occurring after tetanization. Furthermore poor learners do not only fail to produce long-term potentiation, but fail to show a change in the opposite direction with a left shift of the E-S curves. The observed correlation of LTP in the conditioning pathway with the learning ability suggests an involvement of LTP at least in the acquisition and early retention of this learned behavior. The results do however not finally clarify the role of LTP in long-term retention.

Animals↗
PubMed1986

Calcium-induced long-term potentiation in the hippocampal slice: characterization of the time course and conditions.

A transient increase in extracellular calcium concentration causes a long-lasting enhancement of radiatum fibers evoked excitatory postsynaptic potential and population spike responses of CA1 pyramidal neurons which resembles long-term potentiation (LTP). The duration of this potentiation is much longer than described previously and is probably limited by the survival of the preparation itself (greater than 8 hr). Therefore, Ca-induced LTP can be used for the investigation of a postulated late phase of LTP. Ca effects were activity-independent, since the subsequently evoked responses were facilitated even when the presynaptic fibers were not concurrently stimulated during or immediately after superfusion with the high Ca medium. In contrast, if too frequent testing of the synaptic input was done during the high Ca pulse, a short lasting depression instead of potentiation was observed. A lower extracellular magnesium concentration in the standard medium (1.3 instead of 2.0 mM MgSO4) prevents the potentiation of the EPSP at least for the first few hours. Presumably, both tetanus- and Ca-induced LTP share some common mechanisms, since an additional tetanization after Ca induction was not followed by an additional LTP. Compared to the potentiation following tetanization, the Ca-induced LTP was, however, not accompanied by a potentiation of the EPSP/spike ratio within the range of the population spike threshold intensity.

Animals↗
PubMed1984

Effect of the memory-improving substance methylglucamine orotate on paradoxical sleep in rats.

The effects of methylglucamine orotate (MGO) were studied on polygraphic sleep recordings in rats for 8 h per day between 8 a.m. and 4 p.m. MGO (225 mg/kg) was injected intraperitoneally immediately prior to the onset of recording. In the acute experiment, the effect of MGO was compared to pre- and post-drug control days. In the chronic experiment, a sequence of 5 control days, 10 days of MGO treatment, and a further 8 control days was tested. Both acute and chronic administration of MGO resulted in increased paradoxical sleep (PS) latency and a small, but significant, decrease in PS during the first 4 h after injection. This effect seems to be specific to PS, as no effects of MGO on waking or total sleep were found. With chronic administration, no PS rebound occurred within the 8-h recording time during the 8-day post-treatment control period. How the RNA precursor can decrease PS and whether this effect may play a role in the memory-improving action of the substance is discussed in terms of an interrelationship between macromolecular synthesis, sleep, and memory, respectively.

Animals↗
PubMed1983

PAGE-autoradiography of fucose incorporation into rat hippocampal glycoproteins after acquisition of a brightness discrimination.

Male rats aged 8 weeks received intraventricular injections of 100 microCi (3.7 MBq) L-[1-3H] fucose each, 7 h after acquisition of a brightness discrimination task. Two, 8 and 24 h as well as 16, 29 and 60 days after injection of labelled fucose hippocampal tissue was prepared to obtain Tris-soluble, Triton-soluble and Triton-resistant fractions. Two and 8 h after application of [3H]fucose, the trained animals revealed an increased incorporation of fucose mainly into the Triton-soluble glycoproteins. However, it is considered that also material from the Tris-soluble fraction may be used as an additional precursor for Triton-soluble glycoproteins. Quantitative analysis of autoradiographic densitograms obtained after SDS-polyacrylamide gel electrophoresis showed the occurrence of a training-related increase in fucose incorporation predominantly into the slow-moving Triton-soluble glycoproteins. The latter exhibited a higher turnover rate than the faster-moving glycoproteins. For the longer incorporation times (days) after injection of labelled fucose, no differences were observed between trained animals and corresponding active and passive controls.

Animals↗