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Biomedical subjects

B Dietrich

Publications and source records attributed to B Dietrich.

At least 19 recordsLinked to original sources
PubMed2003

Sympatry and allopatry in two desert ant sister species: how do Cataglyphis bicolor and C. savignyi coexist?

Two extremely morphologically similar sister species of desert ants, Cataglyphis bicolor and C. savignyi, exhibit broadly overlapping distributional ranges within Tunisia. In order to analyse the microhabitats of C. bicolor and C. savignyi within the sympatric and allopatric areas of both ant species, the plant species located at 113 different nest sites of the two ant species were determined. In the sympatric area, the two species exhibit a clear-cut nest site segregation. This is not the case in the allopatric areas. Hence the two species differentiate their microhabitat only when they are sympatric. The plant species associated mainly with the nest sites of C. bicolor indicate that this species prefers a type of vegetation that needs irrigation. This is in contrast to the nest sites of C. savignyi, which are usually found around plants that characterize typical dry steppe areas. As the ants' foraging paths recorded in the sympatric area reveal, C. bicolor performs significantly shorter foraging runs with respect to both length and time, and covers a much smaller foraging range than C. savignyi does. This result reflects the fact that the microhabitat occupied by the colonies of C. bicolor is richer in food abundance. When direct interspecific interactions were investigated by placing a bait midway between two heterospecific nests, C. bicolor foragers dominated over those of C. savignyi. The same dominance of C. bicolor over C. savignyi occurred in laboratory experiments. These results suggest that the dominant species drives the subordinate one out of the high quality microhabitats, and that the subordinate species is forced to survive in the less lucrative habitats. In conclusion, coexistence seems to be maintained by the asymmetric competitive relationship between the two species and the fact that the subordinate species has the ability to endure in the less favourable microhabitat.

Animals↗
PubMed2001

Ludwig Rehn (1849-1930)--pioneering findings on the aetiology of bladder tumours.

One hundred and six years ago, the surgeon Ludwig Rehn from Frankfurt am Main held a pioneering lecture in Berlin about the possible origins of bladder tumours. He thereby gave the decisive impulse for cancer research in general and specifically for the investigation of aetiological factors involved in the development of urogenital tract tumours. Thereafter, this resulted in an intensified scientific discussion addressing this issue. Although the detailed evaluation of the causes finally contributing to tumour growth is still ongoing, the work of Ludwig Rehn on bladder tumours among aniline workers considerably promoted the establishment of urology as a specialised field within German clinical medicine and is therefore a milestone in the history of medicine.

Germany↗
PubMed2000

Low-dose high-resolution CT of the petrous bone.

PURPOSE: To show that CT of the petrous bone can be realized using a low-dose technique. MATERIAL: and methods: A high-contrast phantom was scanned with 1.5 mm slice thickness and 60-510 mAs using the reconstruction algorithms standard, bone and edge. In 50 patients, the petrous bone was examined using the standard protocol at 510 mAS. Additionally, selected slices were made at 120 or 210 mAs. The resolution of relevant structures was compared. Phantom studies were repeated on a second CT-device; images of patients scanned with 80 mAs were analyzed in regard to resolution of osseous details. RESULTS: With the first CT-device structures of the phantom up to 0. 5 mm were depicted using 510 mAs and the edge kernel. With 120 mAs and the bone kernel structures of 0.6 mm could be distinguished. Although the same resolution was achieved with 60 mAs and the edge kernel, patient examinations showed a profound image noise. The results achieved with 120 mAs and the bone algorithm, however, were equal to that of 510 mAs. With the second device the same image quality was realized with only 80 mAs. CONCLUSION: CT-examinations of the petrous bone can be effected without loss of diagnostic information using only 15% of the radiation dose used for a standard brain examination.

Humans↗
PubMed1998

Resistance factors in colon cancer tissue and the adjacent normal colon tissue: glutathione S-transferases alpha and pi, glutathione and aldehyde dehydrogenase.

Glutathione S-transferases (GST) alpha and pi, glutathione (GSH) and aldehyde dehydrogenase (ADH) were determined in colorectal cancer tissue specimens and in the adjacent normal colon tissue. The median contents in normal and cancer tissue were 8.1 (2.3-30.3) (5-95% quantiles) and 15.1 (5.3-50.3) microg/mg protein for GST pi (P = 0.035), 0.0 (0.0-1.4) and 0.4 (0.0-3.5) microg/mg protein for GST alpha (P = 0.019), 7.3 (1.3-22.7) and 5.6 (2.3-26.0) microg/mg protein for GSH (P = 0.171) and 30.8 (13.0-42.0) and 23.2 (9.0-32.9) microg/mg protein for ADH (P = 0.0017), respectively. Thus, the mean GST alpha and pi both significantly increased in colon cancer compared to the adjacent normal tissue, which underlines their importance as possible resistance factors. A highly significant correlation was obtained between the GSH content in colon cancer and normal tissue (P = 0.0017). Thus, the constitutive GSH expression seems to be maintained during tumor development. A similar correlation was obtained for ADH (P = 0.0075), but the median ADH was lower in cancer tissue compared to the adjacent normal tissue (P = 0.0017). Contrary to GSH and ADH, GST pi did not correlate between normal and colon cancer tissue. Whereas GSH and ADH correlated in normal colon tissue (P = 0.014), no significant correlation for GSH and ADH was observed in colon cancer tissue (P = 0.109). In conclusion, significant correlations between colon cancer and normal tissue were obtained, suggesting that the expression levels of these resistance factors are maintained during carcinogenesis in most patients.

Aldehyde Dehydrogenase↗
PubMed1998

Pediatric cochlear implantation in cochlear malformations.

OBJECTIVE: This study aimed to present relevant information about pediatric cochlear implantation in malformed cochleas based on the experience gathered with 12 implanted children. STUDY DESIGN: A retrospective analysis was performed. SETTING: All patients were diagnosed and implanted at the Medical University of Hannover. Medical check-ups were performed regularly. The rehabilitation concept was developed by the Cochlear Implant Center of Hannover. PATIENTS: All children were female and were between 2 and 13 years of age at the time of implantation, with the average age being 4 years and 2 months. Only patients who were younger than 14 years of age and implanted between September 1992 and October 1995 were evaluated. INTERVENTION: Diagnostic computed tomographic scans including three-dimensional reconstructions and magnetic resonance imaging images were performed. In all cases, Nucleus devices (Mini 22 or 20 + 2) were implanted. Medical University of Hannover standard surgical technique was used, although in most cases, facial nerve monitoring and electrically evoked auditory brain stem responses were additionally recorded. Total or partial obliteration of the middle ear had occurred in two cases. An anteroposterior approach was used four times. The implantation was followed by the standard rehabilitation procedure for children. RESULTS: No serious complications occurred. All children responded to acoustic stimuli and showed improvement in their speech production. However, one autistic child performed poorly, and for another child suffering from a CHARGE syndrome, results still are pending. CONCLUSIONS: Given suitable preconditions, cochlear implantation is feasible with an acceptable risk of complications. Implantation appears to be beneficial in most cases with cochlear malformations provided that eighth nerve and cochlear lumen are present.

Adolescent↗
PubMed1997

Glutathione, glutathione S-transferase alpha and pi, and aldehyde dehydrogenase content in relationship to drug resistance in ovarian cancer.

Glutathione, glutathione S-transferases alpha and pi, and aldehyde dehydrogenase are associated with resistance to carboplatin and/or cyclophosphamide in cell lines. Therefore, we examined whether the expression of these factors in ovarian cancer tissue specimens is associated with resistance of the patients to combination chemotherapy with cyclophosphamide/carboplatin. Ovarian cancer tissue specimens were taken intraoperatively from 139 patients and frozen in liquid nitrogen, and the contents of glutathione S-transferases alpha and pi, total glutathione, and aldehyde dehydrogenase activity were determined. No association between the levels of glutathione S-transferases alpha and pi or aldehyde dehydrogenase activity in tumor tissue and the survival time was observed in patients with primary ovarian cancer. Significantly higher levels of aldehyde dehydrogenase were observed in FIGO stage I and II compared to FIGO stage III and IV tumors (P = 0.019, Wilcoxon test, two sided). The median survival time was significantly longer in patients with primary ovarian cancer with a tumor glutathione content of <4.9 microg/mg protein compared to patients with a tumor glutathione content of > or =4.9 microg/mg protein (P = 0.047). However, glutathione was not an independent prognostic factor, but was significantly associated with FIGO stage resulting in higher levels in FIGO stage III and IV tumors than in FIGO stage I and II tumors (P = 0.0094, Wilcoxon test, two sided). In conclusion the glutathione content was associated with progression of ovarian carcinomas but neither glutathione nor glutathione S-transferases alpha and pi or aldehyde dehydrogenase were independent factors of resistance to cyclophosphamide/carboplatin.

Aldehyde Dehydrogenase↗
PubMed1997

Polysomnography in drug development.

Polysomnography in drug development is used to detect desirable and undesirable effects of drugs on normal and disturbed sleep. Although this method is essential for the approval of new hypnotic drugs, it is quite often neglected in the development of drugs that show unwanted side effects on normal sleep. In this review, the requirements for qualified polysomnography are described, the strong and weak points of the method are discussed, and its importance for the drug development process is pointed out.

Animals↗
PubMed1997

Pharmacokinetics of prostaglandin E1 and its main metabolites after intracavernous injection and short-term infusion of prostaglandin E1 in patients with erectile dysfunction.

PURPOSE: Alprostadil (prostaglandin E1) is the preferred monotherapy for intracavernous injection in the diagnosis and treatment of erectile dysfunction. Our study was designed to evaluate whether there is a difference in the pharmacokinetics of prostaglandin E1 and its main metabolites after intracavernous injection or short-term intravenous infusion. In addition, we also investigated the influence of the erectile response on prostaglandin E1 kinetics after intracavernous injection. MATERIALS AND METHODS: A total of 24 patients with erectile dysfunction received, in a randomized order at an interval of 5 hours, an intracavernous injection or a 30-minute intravenous infusion of 20 microg. of alprostadil alfadex (prostaglandin E1). Venous blood samples were obtained 5 minutes before and at various times after the applications. We used highly sensitive gas chromatography/double-mass spectrometry method to measure prostaglandin E1 and its metabolites in plasma. RESULTS: We demonstrated the presence of relevant systemic blood levels of prostaglandin E1 and its metabolites immediately after intracavernous injection. We found significantly lower systemic prostaglandin E1 concentrations between 7 and 20 minutes after intracavernous injection in patients with an erectile response compared with those without. CONCLUSIONS: We found significant systemic concentrations of prostaglandin E1 and its metabolites after intracavernous injection. The systemic presence did not lead to significant changes in vital signs.

Alprostadil↗
PubMed1996

[Cochlear implant in inner ear abnormalities and footplate malformation].

BACKGROUND: Malformations of the cochlea can cause deafness and otogenic meningitis. Cochlear implantation in children with such malformations, which are sometimes quite complex, require special attention before, during and after surgery. PATIENT: The concept developed for these patients at Hannover Medical School is illustrated in a patient with severe bilateral inner ear malformation and bilateral stapes defect. Implantation of a cochlear implant was performed in this 2-year-old girl. A large endostal sack originating from the inner ear, which had caused meningitis twice, was observed in the right middle ear. Both ears had to be obliterated to prevent recurrent meningitis. RESULTS: The child had no post-operative problems and the initial rehabilitation efforts have been successful. The immediate and differentiated reactions to stimulation are very encouraging. This article briefly summaries all diagnostic and therapeutic procedures established over the last three years at Hannover Medical School in cases of implantation into a malformated cochlea. In particular, we describe perioperative radiology (CT scans, MRI and plain radiographs), facial nerve monitoring and intraoperative screening for "hearing sensations", details of surgical technique, and possible postoperative complications. CONCLUSIONS: Based on experience with 13 of these cases, we discuss the different aspects of implantation into a malformated cochlea. Given certain preconditions implantation into a malformated cochlea may be recommended.

Child, Preschool↗
PubMed1995

Memory and attention test performance of young and elderly subjects after retest practice.

The effects of training on two memory and two attention tasks were investigated in 24 healthy elderly and 23 young subjects. Two training periods, each consisting of four sessions, were performed, and the effects of training were assessed during two test sessions 1 week thereafter. Significant age-related effects at the pretraining test session were found for reaction times to a simple visual stimulus, retrieval time of information from long-term storage, and the speed of focusing attention. In both age groups, performance of the first two tasks was significantly improved by training; however, the age-related effect remained significant after training. In the focused attention task, the age difference at baseline disappeared after training due to an opposite learning trend in young and elderly subjects. Thus, the cognitive performance of elderly subjects could be trained to a large extent. Significant age differences, however, could be decreased only if the test performance of young subjects did not improve.

Adult↗