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K Hahn

Publications and source records attributed to K Hahn.

At least 55 records · Page 3Linked to original sources
PubMed2001

In-vivo analysis of the human planum temporale (PT): does the definition of PT borders influence the results with regard to cerebral asymmetry and correlation with handedness?

The aim of our study was to examine whether the degree of planum temporale (PT) asymmetry and the possible correlation of morphological PT asymmetries with handedness are influenced by the definition of PT borders. For this reason, we applied three different anatomical PT definitions formerly used in the literature. The PT total (with the end of the Sylvian fissure (SF) as its posterior border) was separated into anterior and posterior regions. The border between anterior and posterior PT was set according to the following definitions: at the end of Heschl's gyrus (1st definition); at the start of the ascending SF ramus according to the 'knife-cut' method (2nd definition); and at the bifurcation of the SF (3rd definition). Thirty right-handed healthy men were recruited. MRI data sets analyzed with the software program BRAINS were used for in vivo PT volumetry. The Edinburgh Handedness Inventory (EHI) and the Hand Dominance Test were used to determine the degree of handedness. In summary, we detected that the type and the degree of asymmetry between left and right PT were strongly dependent on the definition used for PT borders: a left>right asymmetry was found in all PT regions, except a right>left asymmetry of the anterior PT according to our 1st PT definition (lateral to Heschl's gyrus) and a symmetry of the posterior PT according to our 3rd PT definition (posterior to SF bifurcation). In addition, a significant correlation was found between the degree of handedness measured by the EHI and the right posterior PT (3rd definition). We conclude that the influence of the definition of PT borders on the investigated variables may explain some of the variances between former investigations on PT asymmetry and handedness. The possible implications of the correlation between handedness and the extension of the right parietal PT are discussed and have to be elucidated by further studies.

Adolescent↗
PubMed2001

Regional differences in peptide degradation by rat cerebral microvessels: a potential novel regulatory mechanism for communication between blood and brain.

The blood-brain barrier (BBB), composed of the microvessels of cerebral capillary endothelial cells, regulates the passage of peptides into the brain in several ways, mainly by saturable transport or passive diffusion. Here we describe an additional mechanism by which this regulatory function can occur. Cerebral microvessels were isolated from different regions of the brain and incubated with the mu-opiate selective endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) or the opiate-modulating Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2), both tetrapeptides selectively tritiated at the Pro. Degradation was determined by HPLC. For both peptides, the metabolism by microvessels from the cerebral cortex was much greater than that by microvessels from the hypothalamus or pons. For endomorphin-1, the least degradation was in the pons; for Tyr-MIF-1 there was no difference in metabolism by microvessels from the pons or hypothalamus. The results show a novel mechanism at the BBB by which the BBB can selectively regulate the activity of different peptides in different regions of the brain.

Animals↗
PubMed2001

18F-FDG PET and 99mTc-sestamibi scintimammography for monitoring breast cancer response to neoadjuvant chemotherapy: a comparative study.

Presurgical neoadjuvant chemotherapy has shown promise in the treatment of locally advanced breast carcinoma (LABC). Response assessment by clinical examination and mammography is difficult. This study evaluated and compared fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG-PET) and technetium-99m sestamibi scintimammography (SMM) as potential methods for the early assessment of tumour response to neoadjuvant chemotherapy in patients with LABC. Seven patients underwent PET and SMM [planar and single-photon emission tomography (SPET)] before beginning chemotherapy, after the first and second cycles of chemotherapy and after completing chemotherapy prior to surgery. PET and SMM results were evaluated visually and semi-quantitatively by calculating standardised uptake values (SUV) and tumour/lung ratios in the initial and subsequent studies. The findings were correlated with the initial clinical and mammographic findings and the final histopathological diagnoses. There was a highly significant correlation between SUVmean, SUVmax and the tumour/lung ratio determined with SMM-SPET in the studies performed before and during neoadjuvant chemotherapy. All three patients with complete remission showed decreasing FDG and sestamibi uptake as early as 8 days after therapy. In the presurgical study, increased sestamibi and FDG uptake was no longer evident. Three patients had partial remission with clearly reduced but persisting focal FDG and sestamibi uptake after neoadjuvant therapy. One patient who did not respond to therapy had unchanged intense tracer uptake during chemotherapy that was evident with both techniques. An early decline in glucose metabolism or sestamibi uptake 8 days after beginning therapy did not necessarily predict complete tumour remission in the further course of chemotherapy. On the other hand, increased tracer uptake after the first cycle did not exclude a partial tumour response. After the second chemotherapeutic cycle both techniques were able to distinguish between complete and partial/no response. There was a good correlation between preoperative FDG and sestamibi uptake and the histopathologically determined tumour size. However, small residual invasive tumours in patients with clinically complete remission could not be visualised with either technique. The preliminary data demonstrate that sestamibi SMM is as useful as FDG-PET for the monitoring of tumour response to neoadjuvant chemotherapy.

Adult↗
PubMed2001

Comparison of dynamic MR imaging of the breast and sestamibi scintimammography for evaluation of indeterminate mammographic lesions.

The aim of this study was to compare Tc-99m sestamibi scintimammography and dynamic contrast-enhanced MR imaging for the evaluation of indeterminate mammographic lesions. Forty patients with questionable mammographic findings were included in a prospective study. Thirty lesions were non-palpable. Mean lesion size was 1.6+/-0.7 cm (range 0.5-3.5 cm). Scintigraphy was considered as malignant when focal tracer accumulation was present. In MR imaging, lesions were classified according to their signal intensity time course: no enhancement or steady enhancement with low signal intensity (M0); steady enhancement with high signal intensity (M1); or rapid enhancement with plateau (M2) or washout (M3). Lesions classified as M2 or M3 were considered as suspicious for malignancy. Histopathologic evaluation was performed in 24 lesions. In 16 cases lesions were classified as benign from follow-up examinations (mean 24 months). Malignancies were proven in 14 patients (9 invasive carcinomas, 5 ductal carcinoma in situ). Sensitivity of MR imaging was 12 of 14 (86%) and sensitivity of scintimammography was 8 of 14 (57%). One of 26 benign lesions was false positive at MR imaging. Scintigraphy showed no false-positive results. In conclusion, magnetic resonance imaging provided high accuracy in evaluation of indeterminate mammographic lesions. Sensitivity of scintimammography was too low in detecting small carcinomas.

Adult↗
PubMed2001

The effect of the skull on event-related P300.

OBJECTIVES: Event-related potentials (EP) indicate neuronal processes with a high temporal resolution, while functional magnetic resonance imaging (fMRI) has a high spatial distribution. Information from both techniques may complement each other. However, this combination is fraught with difficulty because of a possible interference of the skull or the scalp with scalp-recorded EP. The aim of the present study was to investigate this influence of skull and scalp thicknesses on event-related P300 potentials. METHODS: Thirty healthy controls were examined using an auditory evoked P300 elicited by a standard oddball paradigm. Skull and scalp thicknesses were determined using coronal T2-weighted magnetic resonance imaging (MRI). RESULTS: P3b-amplitudes were significantly correlated with temporo-parietal skull thickness (r=-0.42; P=0.021; regression slope of -1.14 microV/mm skull thickness), whereas scalp had no influence on P300. The amplitude of the more frontal subcomponent P3a was not related to frontal skull thickness. CONCLUSIONS: Therefore, the utility of P300 as a research tool can be enhanced when adjustment for skull thickness is made.

Adult↗
PubMed2001

The dispositional inference strikes back: situational focus and dispositional suppression in causal attribution.

The authors propose that correction of dispositional inferences involves the examination of situational constraints and the suppression of dispositional inferences. They hypothesized that suppression would result in dispositional rebound. In Study 1, participants saw a video of either a free or a forced speaker. Participants shown a forced speaker later made stronger dispositional inferences about a 2nd, free speaker than control participants did. Study 2 provided evidence for higher rebound among participants who reported trying harder to suppress dispositional inferences during the 1st video. In Study 3, participants were asked to focus on situational constraints or to avoid thinking about the speaker's characteristics. Only the latter instructions led to a dispositional rebound. These data support the view that the correction of dispositional inferences involves 2 processes that lead to distinct consequences in subsequent attribution work.

Adult↗
PubMed2001

[Spiral CT of the abdomen: weight-adjusted dose reduction].

AIM OF THE STUDY: The influence of weight-adjusted current application in spiral CT of the abdomen on noise was investigated in a clinical study. PATIENTS AND METHODS: In 77 routine abdominal CT investigations (120 kV, 8 mm, pitch 1.5) the patients were divided into three body-weight groups A (< 60 kg), B (60-80 kg), and C (> 80 kg). The tube current was randomized prospectively in low weight group A, either 125 mA or 150 mA, in middle and high weight groups B and C, 150, 175 or 200 mA, with a tube revolution time of one second. The noise was measured in liver, skeleton muscle, fat tissue, and bladder content for evaluation of image quality. RESULTS: The bodyweight groups differ significantly in noise, e.g., in the liver (150 mA): group A: 15.8 HU, group B: 18.9 HU, group C: 21.5 HU. The increase of tube current (150, 175, 200 mA) within a body weight group resulted in a minor decrease of noise (18.9 HU, 17.6 HU, 17.5 HU, respectively, in group B). There is a good correlation of noise with body weight, body mass index and body cross section, but not with body size. CONCLUSION: A body weight adjusted reduction of tube current is possible without an increase of noise.

Adipose Tissue↗
PubMed2001

Advances in energy-filtering transmission electron microscopy.

First experiments using a new energy-filtering microscope (Sub-eV-Sub-A microscope, or SESAM) are shown. They make use of the high transmissivity of the 90 degree filter. This allows the mapping of chemical bonding of large specimen areas, even if narrow energy selecting slits are used. Because large scattering angles are accepted by this filter, energy-filtered diffraction patterns extending to 150 mrad can be recorded by a single exposure. This can be used to determine the reduced density function of amorphous materials and reduces the exposure time of the investigated area by three orders of magnitude as compared with previous approaches.

Journal Article↗
PubMed2001

Clinical impact of differential renal function to indicate and assess pyeloplasty and the significance of coexisting vesicoureteral reflux.

PURPOSE: In patients with ureteropelvic junction obstruction (JPJO) who are conservatively treated, 5% to 10% of them show a deterioration of renal function without recovery after delayed pyeloplasty. Should surgery be indicated based on observed deterioration of differential renal function (DRF)? Can we expect improvement of the DRF after pyeloplasty? What other influencing parameters may affect DRF? MATERIALS AND METHODS: In this study, the authors examined 85 ureterorenal junctions that had undergone the Anderson-Hynes technique for surgical correction of UPJO. Based on the values obtained from the preoperative DRF (Tc-99m mercaptoacetyltriglycine), the cases were separated into three categories: group I had poor DRF (less than 11% of total renal function [TRF]), group II had moderate DRF (11% to 33% of TRF), and group III had adequate DRF (more than 33% of TRF). Twelve months after surgery, renal function was reassessed. The results were correlated with age at surgery, symptoms, coexisting vesicoureteral reflux, and drainage. RESULTS: Seven ureterorenal junctions (8%) comprised group I, 15 (18%) comprised group II, and 63 (74%) comprised group III. After UPJO repair, 13% showed marked improvement in DRF, 86% remained stable, and 1% exhibited diminished function. In 50% of the renal cases with preoperative DRF less than 33%, postoperative improvement was seen. In follow-up renal scans, 30 cases (35%) revealed nonobstructive drainage, whereas the remaining 53 junctions (62%) showed moderate delayed drainage. Both the moderate delayed group (57%) and the nonobstructive group (50%) showed similar DRF improvement. Sixty-six percent of the patients with impaired DRF improved after pyeloplasty performed within the first 3 months of life, compared with 42.8% of patients in whom surgery was performed after 5 years of age. Vesicoureteral reflux was evident in 27.2% of the patients with preoperative impaired DRF compared with 11% with normal DRF. Forty-five percent of the patients with impaired DRF and no improvement after surgery had coexisting vesicoureteral reflux, compared with 9% of those with postoperative improvement. CONCLUSIONS: Sustained renal impairment after pyeloplasty is likely as a result of preexisting renal dysplasia with vesicoureteral reflux. Moderate delayed drainage after surgery does not affect DRF. Surgery for UPJO should be indicated independent of a DRF follow-up (except very low DRF) or the age at the time of diagnosis.

Child↗
PubMed2001

Striatal dopamine transporter binding in early to moderately advanced Parkinson's disease: monitoring of disease progression over 2 years.

Imaging of striatal dopamine transporter binding allows differentiation between patients with Parkinson's disease and controls. We investigated the use of this technique to monitor disease progression. We used N-(3-iodopropen-2-yl)-2beta-carbomethoxy-3beta-(4-chlorophenyl) tropane (IPT) and single photon emission computed tomography (SPECT) to determine dopamine transporter function in eight patients with Parkinson's disease Hoehn and Yahr stage I to III over time. Patients were recruited from the movement disorder clinic and were studied at entry and after a follow-up period of 1 and 2 years. Specific striatal IPT binding was measured with a manual region of interest technique. At entry, all patients showed a reduction of striatal IPT uptake of approximately 50% compared to controls, with a mean striatum to background ratio of 3.61 +/- 0.72 (controls, 7.34 +/- 1.18). Putamen to background ratios were initially measured as 2.42 +/- 0.74 and caudate to background ratios as 5.00 +/- 0.73 (controls, 6.46 +/- 1.22 for putamen and 8.58 +/- 1.36 for caudate). Specific striatal IPT binding decreased by a mean of 6.6% in the first year and another 5.3% in the second year. Changes of specific IPT binding over time were similar in caudate and putamen. In patients with clinically asymmetric disease, differences between the rate of decline in the ipsilateral and contralateral sides could not be detected. The findings suggest that IPT SPECT can quantify the reduction of dopamine transporter binding over time. This technique seems to be a useful tool in monitoring the intra-individual progression of dopaminergic cell loss in patients with Parkinson's disease and may help to follow the effects of putative neuroprotective drugs in future clinical trials.

Adult↗
PubMed2001

Association of an interleukin-1beta genetic polymorphism with altered brain structure in patients with schizophrenia.

OBJECTIVE: This study investigated the effect on brain morphology of an interleukin-1beta genetic polymorphism (C-->T transition at position -511) in patients with schizophrenia. METHOD: In vivo magnetic resonance imaging and genotype analysis were used in the examination of 44 male schizophrenic patients and 48 healthy male comparison subjects. RESULTS: No association between the interleukin-1beta polymorphism and schizophrenia was detected. Within the patient group, bifrontal-temporal gray matter volume deficits and generalized white matter tissue deficits in allele 2 carriers (genotype T/T or C/T) were found. In contrast, the interleukin-1beta polymorphism had no influence on brain morphology within the healthy subjects. CONCLUSIONS: The data suggest that allele 2 within the promoter region of the interleukin-1beta gene at position -511 contributes to structural brain alterations in patients with schizophrenia.

Adolescent↗
PubMed2001

Genetics of acid adaptation in oral streptococci.

A growing body of information has provided insights into the mechanisms by which the oral streptococci maintain their niches in the human mouth. In at least one case, Streptococcus mutans, the organism apparently uses a panel of proteins to survive in acidic conditions while it promotes the formation of dental caries. Oral streptococci, which are not as inherently resistant to acidification, use protective schemes to ameliorate acidic plaque pH values. Existing information clearly shows that while the streptococci are highly related, very different strategies have evolved for them to take advantage of their particular location in the oral cavity. The picture that emerges is that the acid-adaptive regulatory mechanisms of the oral streptococci differ markedly from those used by Gram-negative bacteria. What future research must determine is the extent and complexity of the acid-adaptive systems in these organisms and how they permit the organisms to maintain themselves in the face of a low-pH environment and the microbial competition present in their respective niches.

Acids↗
PubMed2001

Spiritual care: bridging the disciplines in congregational health ministries.

These materials describe the professional, legal, relational, and theological roles of parish nurses, health care chaplains, and community clergy. It illustrates these roles by discussing two case studies of how these professionals can work together. It then provides examples of role violations for each profession and recommends some simple rules that will enable them to work together productively.

Chaplaincy Service, Hospital↗
PubMed2001

Thyroid cancer after diagnostic administration of iodine-131 in childhood.

Hahn, K., Schnell-Inderst, P., Grosche, B. and Holm, L-E. Thyroid Cancer after Diagnostic Administration of Iodine-131 in Childhood. Radiat. Res. 156, 61-70 (2001). To determine the carcinogenic effects of diagnostic amounts of (131)I on the juvenile thyroid gland, a multicenter retrospective cohort study was conducted on 4,973 subjects who either had been referred for diagnostic tests using uptake of (131)I (n = 2,262) or had had a diagnostic procedure on the thyroid without (131)I (n = 2,711) before the age of 18 years. Follow-up examinations were conducted after a mean period of 20 years after the first examination in 35% of the exposed subjects (n = 789) and in 41% of the nonexposed subjects (n = 1,118). Iodine-131 dosimetry of the thyroid was carried out according to ICRP Report No 53, and the median thyroid dose was 1.0 Gy. In the exposed group, two thyroid cancers were found during 16,500 person-years, compared to three cancers in the nonexposed group during 21,000 person-years. The relative risk for the exposed group was 0.86 (95% CI: 0.14-5.13). The study did not demonstrate an increased risk for thyroid cancer after administration of (131)I in childhood.

Adolescent↗