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Biomedical subjects

F Schubert

Publications and source records attributed to F Schubert.

At least 19 recordsLinked to original sources
PubMed2006

Association between cerebral glutamate and human behaviour: the sensation seeking personality trait.

INTRODUCTION: Brain imaging studies have linked the anterior cingulate cortex (ACC) to motivation, drive, and personality traits like novelty and sensation seeking. Animal studies have shown glutamatergic neurotransmission to be important in ACC function as well as motivated behaviour. However, the role of glutamate in related personality traits like sensation seeking has not been investigated in humans. METHODS: The associations between sensation seeking personality scores and absolute glutamate concentrations in the ACC and the hippocampal region measured by 3-Tesla proton magnetic resonance spectroscopy (1H-MRS) were investigated. RESULTS: ACC glutamate concentration was negatively correlated with the sensation seeking sum score and the experience seeking subscore. A weak negative correlation was also observed between the hippocampal glutamate and the sensation seeking sum score. The reexamination of the glutamate concentration after 4 weeks revealed a similar relationship with sensation seeking. DISCUSSION: Although preliminary, the results are in line with the key role of the ACC for motivation and executive control and with the impact of glutamate on novelty related behaviour observed in animal experiments. The role of the hippocampus for novelty processing is discussed. Glutamate measurement with 1H-MRS may facilitate the understanding of biological underpinnings of personality traits and psychiatric diseases associated with dysfunctions in motivation and drive.

Adult↗
PubMed2006

Hippocampal glutamate concentration predicts cerebral theta oscillations during cognitive processing.

RATIONALE: Brain waves reflect collective behavior of neurons and provide insight into distributed network processing. Frontal and hippocampal theta oscillations (4-7 Hz) were linked to cognitive tasks and animal studies have suggested an involvement of glutamatergic neurotransmission in integrative frontal-hippocampal processing. Human evidence for such relationships is lacking. METHODS: Here, we studied the associations between glutamate concentrations in the hippocampal region, measured by a 3-T proton magnetic resonance spectroscopy (1H-MRS), and EEG theta activity during an auditory target detection paradigm. RESULTS: A robust relationship between hippocampal glutamate and frontal theta activity during stimulus processing was found. Moreover, frontal theta oscillations were related to response speed. CONCLUSION: The results suggest a functional coupling between the frontal cortex and hippocampal region during stimulus processing and support the idea of the hippocampus as a neural rhythm generator driven by glutamatergic neurotransmission. These preliminary data show, for the first time, a relationship between in vivo measured glutamate and basic cerebral information processing in humans.

Adult↗
PubMed2005

Laparoscopically assisted peritoneal shunt insertion in hydrocephalus: a prospective controlled study.

BACKGROUND: Shunting of cerebrospinal fluid to the peritoneal cavity is standard therapy for the management of hydrocephalus. Common problems, however, are infection and shunt malfunction, which frequently is related to the peritoneal end of the catheter. Laparoscopic revision of distal shunt malfunction has become popular, but endoscopic techniques for primary placement of the peritoneal catheter are not performed often. This study aimed to compare laparoscopically assisted peritoneal catheter placement with the conventional minilaparotomy technique. METHODS: In the prospective arm of the study, 50 patients underwent laparoscopic distal shunt placement. The findings were compared with those for another group of 50 patients who underwent surgery by the standard transrectal or pararectal approach. Both groups were similar with regard to age, gender, American Society of Anesthesiologists (ASA) scores, indications for surgery, and frequency of previous abdominal operations. RESULTS: No intraoperative complications occurred. The mean time for surgery was 59 min in the laparoscopically assisted treatment group and 49 min in the standard group. During follow-up assessment, 3 instances of distal catheter malfunction or infection (2 malfunctions and 1 infection) occurred in the endoscopic group, and 12 instances (6 malfunctions and 6 infections) occurred in the control group. This difference was statistically significant. CONCLUSIONS: The findings from this prospective controlled study indicate that the risk for long-term complications attributable to distal shunt malfunction is reduced when laparoscopic techniques are used to place the peritoneal end of the shunt catheter.

Adolescent↗
PubMed2004

Resonant bar simulations in media with localized damage.

As a rule, problems of wave propagation in finite media with non-uniform spatial distribution of material properties can only be tackled by numerical models. In addition, the modeling of damage features in a material requires the introduction of locally non-linear and--more important--non-unique equations of state. Using a multiscale approach, we have implemented a non-linear hysteretic stress-strain relation based on the Preisach-Mayergoyz (PM) model, into a numerical elastodynamic finite integration technique program, which has originally been developed for linearly elastic wave propagation in inhomogeneous media. The simulation results show qualitatively good agreement with data of non-linear resonant bar experiments in homogeneously non-linear and hysteretic media. When the PM density distribution of hysteretic units at the mesoscopic level is not uniform and/or confined to a finite area in stress-stress space, the response at high amplitude excitation tend to deviate from the quasi-analytical results obtained in the case of a uniform PM-space density. Localized microdamage features in an intact medium can be modeled by conceiving finite zones with pronounced hysteretic stress-strain relations within a "linear" surrounding. Forward calculations reveal a significant influence of the amplitude dependent resonance behavior on the location (edge versus center of a bar), the extend (width of the zone) and the degree (density of hysteretic units) of damage.

Journal Article↗
PubMed2003

Informatics united: exemplary studies combining medical informatics, neuroinformatics and bioinformatics.

OBJECTIVES: Medical informatics, neuroinformatics and bioinformatics provide a wide spectrum of research. Here, we show the great potential of synergies between these research areas on the basis of four exemplary studies where techniques are transferred from one of the disciplines to the other. METHODS: Reviewing and analyzing exemplary and specific projects at the intersection of medical informatics, neuroinformatics, and bioinformatics from our experience in an interdisciplinary research group. RESULTS: Synergy emerges when techniques and solutions from medical informatics, bioinformatics, or neuroinformatics are successfully applied in one of the other disciplines. Synergy was found in 1. the modeling of neurophysiological systems for medical therapy development, 2. the use of image processing techniques from medical computer vision for the analysis of the dynamics of cell nuclei, and 3. the application of neuroinformatics tools for data mining in bioinformatics and as classifiers in clinical oncology. CONCLUSIONS: Each of the three different disciplines have delivered technologies that are readily applicable in the other disciplines. The mutual transfer of knowledge and techniques proved to increase efficiency and accuracy in a manifold of applications. In particular, we expect that clinical decision support systems based on techniques derived from neuro- and bioinformatics have the potential to improve medical diagnostics and will finally lead to a personalized delivery of healthcare.

Computational Biology↗
PubMed2002

Optical detection of elastodynamic fields of ultrasonic transducers.

By applying diffraction grids to the detection surface the full vector content of the elastic wave field of ultrasonic transducers can be measured using common heterodyne interferometers. The signal to noise ratio is good enough to detect even small edge wave contributions to the elastic wave field. Numerical simulation of the elastic wave propagation by the elastodynamic finite integration technique helps to understand the origin of several field components observed in the measurements.

Journal Article↗
PubMed2001

Neurobiology.

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Journal Article↗
PubMed2001

Neurobiology.

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Animals↗
PubMed2001

[Anastomotic protection with a transanal tube after rectum resection and total mesorectal excision].

Between October 1998 and December 1999 50 patients with a primary cancer of the rectum were treated by sphincter saving anterior resection of the rectum and total mesorectal excision. Eight patients were given a neoadjuvant combined radio-chemotherapy. The anastomoses were performed in the triple-stapling technique with a Premium Plus CEEA stapling device (Fa. Tyco Health Care, Tönisvorst, Germany) or with a Proximate ILS curved stapling device (Fa. Ethicon Endo Surgery, Norderstedt, Germany). The anastomoses were situated in 7 cm or in lower distance from the anal skin. In all patients with complete anastomotic tissue rings the anastomoses were protected with the transanal tube. The integrity of the anastomosis (n = 48) was checked for completeness in the 2nd and 12th postoperative week. The patients were sigmoidoscoped and the anastomoses were controlled by transanal ultrasonography. During the hospital stay 2 patients (4.2 %) with a clinically evident anastomotic leakage were detected. 3 patients (6.2 %) with an asymptomatic anastomotic leakage were detected by computertomography. The anastomoses of 27 patients (56.2 %) were clinically and by ultrasonographical examination intact. In these patients a postoperative radiogram was not indicated. Relaparotomy was necessary in one patient for bleeding, in two patients for anastomotic leaks and in three patients for ileus (12.5 %). Because of low anastomotic leakage rate and low morbidity we find the transanal tube to be at least equivalent to conventional colostoma for anastomotic protection.

Adult↗
PubMed2001

Double dissociations between neglect tests: possible relation to lesion site.

In 20 patients who had suffered a first right hemisphere stroke, we examined the prevalence of double dissociations between the results of a star cancellation and a line bisection test. Both are common methods to assess spatial hemineglect. Within the group of neglect patients, we found no significant correlation between the two tasks. Furthermore, 5 patients with impaired performance on one of the tests were within the normal range on the other one. In agreement with experimental studies, we argue that spatial hemineglect is not a unitary syndrome. Furthermore, the findings in one of our patients are compatible with the view that an isolated deficit on cancellation tasks might follow from a lesion in the right anterior cingulate gyrus.

Adult↗
PubMed2001

Regionalisation of anterior neuroectoderm and its competence in responding to forebrain and midbrain inducing activities depend on mutual antagonism between OTX2 and GBX2.

The anterior neural ridge (ANR), and the isthmic organiser (IsO) represent two signalling centres possessing organising properties necessary for forebrain (ANR) as well as midbrain and rostral hindbrain (IsO) development. An important mediator of ANR and IsO organising property is the signalling molecule FGF8. Previous work has indicated that correct positioning of the IsO and Fgf8 expression in this domain is controlled by the transcription factors Otx2 and Gbx2. In order to provide novel insights into the roles of Otx2 and Gbx2, we have studied mutant embryos carrying different dosages of Otx2, Otx1 and Gbx2. Embryos deficient for both OTX2 and GBX2 proteins (hOtx1(2)/hOtx1(2); Gbx2(-/-)) show abnormal patterning of the anterior neural tissue, which is evident at the presomite-early somite stage prior to the onset of Fgf8 neuroectodermal expression. Indeed, hOtx1(2)/hOtx1(2); Gbx2(-/-) embryos exhibit broad co-expression of early forebrain, midbrain and rostral hindbrain markers such as hOtx1, Gbx2, Pax2, En1 and Wnt1 and subsequently fail to activate forebrain and midbrain-specific gene expression. In this genetic context, Fgf8 is expressed throughout the entire anterior neural plate, thus indicating that its activation is independent of both OTX2 and GBX2 function. Analysis of hOtx1(2)/hOtx1(2); Gbx2(-/-) and Otx1(+/-); Otx2(+/-) mutant embryos also suggests that FGF8 cannot repress Otx2 without the participation of GBX2. Finally, we report that embryos carrying a single strong hypomorphic Otx2 allele (Otx2(lambda)) in an Otx2 and Gbx2 null background (Otx2(lambda)/-; Gbx2(-/-)) recover both the headless phenotype exhibited by Otx2(lambda)/- embryos and forebrain- and midbrain-specific gene expression that is not observed in hOtx1(2)/hOtx1(2); Gbx2(-/-) mutants. Together, these data provide novel genetic evidence indicating that OTX2 and GBX2 are required for proper segregation of early regional identities anterior and posterior to the mid-hindbrain boundary (MHB) and for conferring competence to the anterior neuroectoderm in responding to forebrain-, midbrain- and rostral hindbrain-inducing activities.

Animals↗
PubMed2000

Vascular organization in the mesorectum: angiography of rectal resection specimens.

The technical advances in rectal cancer surgery are known as the total mesorectal excision. The resection in an anatomically defined plane under direct vision and with sharp dissection distinguishes it conventional rectal surgery. The result must be a complete mesorectum without deep gouges. We performed specimen angiography to confirm completeness of the removed mesorectum. Thirteen total mesorectal excision specimens were examined by angiography after continence-preserving resection of rectal carcinoma. In 11 of the 13 cases the vascular supply was exclusively via the superior rectal artery. In two cases with hypoplastic left terminating branches of the superior rectal artery there was additional perfusion via a caudally ascending vessel or via smaller vessels connected laterally. In all specimens both arterial supply and venous outflow were located within the mesorectal fascial sheath. There was no radio-opaque substance leaking from the mesorectal surface in the case of a complete mesorectal specimen. Tiny vascular branches running laterally occurred in 7 of the 13 cases. We found no larger vascular connections branching off in the lateral direction. The rectal blood supply comes almost exclusively through the superior rectal vessels. Thus the fascia covering the mesorectum forms, as far as rectal vascularization is concerned, a closed compartment. The mesorectal vessels are enclosed in the fibrous avascular mesorectal fascia. They run close above the fascia. In the case of an incomplete mesorectal excision the specimen angiography shows a stain leaking from the mesorectal fascia. Our method can be used to confirm the completeness of the removed mesorectum.

Aged↗
PubMed2000

Quantitative MRS: comparison of time domain and time domain frequency domain methods using a novel test procedure.

For quantitative analysis of in vivo MR spectra, a state-of-the-art time domain method was compared with a recently reported time domain frequency domain method which uses wavelets for background characterization. The comparison was made on the basis of results for simulated test problems that were constructed by combining measured and simulated MRS data at different signal-to-noise ratios in order to simultaneously reflect real world difficulties, in particular the overlapping background problem, and to allow for quantitative judgment of a method's accuracy. Incorporating prior knowledge was also considered. The results obtained give insight into the accuracy of the methods when applied to measured MRS data. Due to the improved background characterization, the time domain frequency domain method outperformed the time domain method in some of the test cases. Both methods were also applied to serial brain MR spectra of a healthy volunteer on 10 occasions.

Brain↗
PubMed2000

[Methods for postoperative evaluation of complete excision of the mesorectum].

This study aimed at a more objective evaluation of the specimen after total mesorectal excision [14]. For this reason, a method yielding a simple stained preparation of the totally excised mesorectum was developed. By postoperative injection of 10 ml of an ink solution into the A. rectalis superior of 15 specimens, the arterial mesorectal vascular tree was filled. All specimens had been collected by means of total mesorectal excision. In two specimens, in wich the mesorectal sheath fascia had been injured due to the surgical manipulation, we observed the leakage of ink from the mesorectum even during the injection. In three further specimens, some ink leakage in the form of dots occurred from small opened arterioles after the injection was performed. No ink leakage was observed in the remaining specimens. Prior to the ink injection, thirteen specimens were macroscopically tested and found intact. Three of the fifteen specimens exhibited minor lesions of the mesorectum that would not have been detected macroscopically without ink tagging. The comparison of the findings provided by the surgeon with the histopathological evaluation showed that those specimens in which no ink leakage occurred had an unimpaired mesorectal sheath fascia. These specimens coorespond to the complete excision of the mesorectum and the removal of the tumor in a cancer-sealed package as long as the circumferential rim of the specimen has not been infiltrated by the tumor.

Coloring Agents↗
PubMed1999

The UVA light used during the fluorescence microscopy assay affects the level of intracellular calcium being measured in experiments with electric-field exposure.

In the present paper, the induction of calcium signals in neuroblastoma cells, cells of T-cell leukemia, and osteogenic sarcoma cells were investigated in relation to the UVA irradiation used in fluorescence microscopy. Methods were developed to measure both the mean UVA irradiance and the intensity profile in the UVA-illuminated area of the microscope. This allowed us to calculate the applied UVA radiant exposure of the cells during each experiment. This investigation was undertaken because of the conflicting results in the literature on the effects of electromagnetic fields on the signals of the calcium-sensitive fluorescence probe FURA-2 in lymphocytes. Taking into account that each group used a different system with different optics and lamps, these conflicting results are now at least partially understandable. Our measurements indicate that in a typical experiment with FURA-2 the cells were irradiated with up to 776 kJ m(-2) during 25 min of exposure to UVA light. This causes changes in intracellular free Ca(2+) concentrations ([Ca(2+)](i)). Designating cells in which the [Ca(2+)](i) was distinctly increased during the experiment as "responding", we found Hill-type dependences on the irradiance. Jurkat cells showed a 50% response even at 10 kJ m(-2) and osteosarcoma cells at about 60 kJ m(-2), whereas neuroblastoma cells even at the maximum possible dose responded only minimally. In the case of neuroblastoma cells, we found a dependence of this effect on the CO(2) partial pressure during the preincubation. An electrical treatment with an a.c. field (5 kHz sinusoidal, amplitude modulation 16 Hz 100%, 800 V m(-1), 5 min) had a significant effect on intracellular calcium in neuroblastoma cells only in the case of cells that were not pretreated with CO(2) with high fluences of UVA irradiation. In conclusion, these results indicate that the possibility of UVA artifacts must be considered in all experiments using fluorescence microscopy. Furthermore, our results lead to the hypothesis that oxidative stress could be the link between UVA and electric-field effects.

Animals↗
PubMed1997

'Duplication' of the clavicle or ossification in coracoclavicular ligament.

A case is presented in which plain films revealed a short band of ossification adjacent to the inferior aspect of the lateral part of the clavicle. CT findings indicated that the ossification was situated in the coracoclavicular ligament and was not a manifestation of clavicular 'duplication'.

Acromioclavicular Joint↗
PubMed1997

Rapid destructive osteo-arthritis of the hip.

A case of an unusual destructive hip osteo-arthropathy with a plain-film record of rapid joint destruction is reported. In the absence of any laboratory or pathological support for other pathology this is thought to be an uncommon example of erosive or inflammatory osteo-arthritis in a large joint.

Female↗