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Biomedical subjects

T Dietrich

Publications and source records attributed to T Dietrich.

At least 19 recordsLinked to original sources
PubMed2006

Brain activation during mental rotation in school children and adults.

Mental rotation is a complex cognitive skill depending on the manipulation of mental representations. We aimed to investigate the maturing neuronal network for mental rotation by measuring brain activation in 20 children and 20 adults using functional magnetic resonance imaging. Our results indicate that brain activation patterns are very similar between children and adults. However, adults exhibit stronger activation in the left intraparietal sulcus compared to children. This finding suggests a shift of activation from a predominantly right parietal activation in children to a bilateral activation pattern in adults. Furthermore, adults show a deactivation of the posterior cingulate gyrus and precuneus, which is not observed in children. In conclusion, developmental changes of brain activation during mental rotation are leading to a bilateral parietal activation pattern and faster performance.

Adult↗
PubMed2006

Processing of autobiographical memory retrieval cues in borderline personality disorder.

BACKGROUND: Affective dysregulation in borderline personality disorder (BPD) in response to both external stimuli and memories has been shown to be associated with functional alterations of limbic and prefrontal brain areas. This study aimed to examine neuronal networks involved in autobiographical memory retrieval using standardized stimuli that gain autobiographical significance by illustrating marked solitary and social situations of human life. METHODS: Using event-related functional Magnetic Resonance Imaging (fMRI), we examined the processing of pictures from the Thematic Apperception Test (TAT) in 14 BPD patients and 14 controls. RESULTS: In both groups, TAT stimuli activated brain areas known to be involved in autobiographical memory retrieval. BPD subjects lacked differential amygdala, orbitofrontal and cingulate activations for TAT versus neutral stimuli. In the TAT condition, compared to controls, BPD subjects displayed increased BOLD responses in the bilateral orbitofrontal and insular regions, in the left anterior cingulate and medial prefrontal cortex, as well as in the parietal and parahippocampal areas, consistent with a more aversive and arousing experience assessed by self-reports. CONCLUSIONS: Increased BOLD responses during TAT processing in BPD subjects were in line with previously reported changes in anterior cingulate and orbitofrontal cortices, which are known to be involved in memory retrieval. However, BPD subjects displayed hyperactivation in these areas for both TAT and neutral stimuli. The deficit of selective activation of areas involved in autobiographical memory retrieval suggests a general tendency towards a self-referential mode of information processing in BPD, or a failure to switch between emotionally salient and neutral stimuli.

Affect↗
PubMed2006

[The dry eye. Current concepts on classification, diagnostics, and pathogenesis].

The etiology of dysfunctional tear syndrome ("dry eye") is multifactorial and complex. Recent evidence suggests an important role of androgens in regulating tear film secretion onto the ocular surface. In addition, inflammatory processes of the ocular surface seem to be the common final pathway of all chronic forms of dry eye. Novel concepts of pathogenesis and state-of-the-art diagnostic tools are discussed. In vivo confocal microscopy allows quantification of ocular surface inflammatory cells. This is of increasing importance for evaluation of anti-inflammatory treatments in dry eye patients.

Dry Eye Syndromes↗
PubMed2006

[Current treatment for dry eye syndrome].

The therapy of dry eye disease as a chronic problem necessitates a long-term therapeutic association between patient and ophthalmologist. The aim of therapy is to relieve symptoms and improve vision as far as possible with an acceptable level of effort on the part of the patient. Therapy of dry eye follows a staged concept including tear replacement, serum eye drops, punctum plugs, novel anti-inflammatory drugs (cyclosporin A), and surgical procedures. Interdisciplinary care, especially of patients with autoimmune disease, is recommended and is best provided in a specialized dry eye outpatient clinic with quality control.

Anti-Inflammatory Agents↗
PubMed2006

Gingivitis susceptibility and its relation to periodontitis in men.

The objective of this cross-sectional study was to evaluate whether gingivitis susceptibility is associated with periodontitis. We analyzed data of 462 men in the VA Dental Longitudinal Study aged 47 to 92 years who had never smoked or had quit smoking 5+ years previously. Multiple logistic regression models, with tooth-level bleeding on probing at sites with attachment loss<or=2 mm as the dependent variable, were derived with adjustment for plaque, calculus, crown coverage, age, income, education, marital status, body mass index, diabetes, and vitamin C intake, and stratification by age (<65, 65+ years). Periodontitis and mean attachment loss were positively associated with bleeding on probing, with stronger associations among men<65 years old (for periodontitis, OR 2.1; 95% CI 1.5, 3.1) than men 65+ years of age (OR 1.2; 95% CI 0.9, 1.6). Our results suggest that among never and former smokers, gingivitis susceptibility is higher among men with periodontitis compared with that in men without periodontitis.

Age Factors↗
PubMed2003

Decline of oropharyngeal cancer in Chiangmai province, Thailand, between 1988 and 1999.

A decline of oropharyngeal cancer has already been predicted for Thailand since the early 1960s. To substantiate these predictions it was the purpose of this study to examine trends in the incidence of oropharyngeal cancer in the province of Chiangmai, (1988-1999). Data on cancer incidence were extracted from the annual reports of the Cancer Registry, Cancer Unit, Faculty of Medicine, Chiangmai University, Thailand (1992-1999) and an IARC report on cancer in Thailand (1988-1991). The age-standardized annual incidence per 100000 of oral cancer in males dropped from 3.6 (1988-1991) to 1.2 in 1999 (P for trend 0.0002) and in females from 2.6 (1988-1991) to 1.1 in 1999 (P for trend 0.007). Similar trends in males and females for cancer of the tongue, oropharynx and hypopharynx were seen. The age-standardized annual incidence for cancer of the lip, salivary gland and nasopharyngeal carcinoma remained unchanged. Changes of traditional oral habits such as betel quid chewing and smoking of traditional cigars seem to have resulted in a marked decrease of oral cancer in both men and women in the recent past.

Age Distribution↗
PubMed2001

Prophylaxis of restenosis with (186)re-labeled stents in a rabbit model.

BACKGROUND: Intraluminal beta-irradiation has been shown to decrease neointimal proliferation after angioplasty in experimental models. The purpose of this study was to test the technical feasibility and biological effects of (186)Re-labeled stents. METHODS AND RESULTS: Thirty-four New Zealand White rabbits were fed a 0.5% cholesterol diet before balloon angioplasty and insertion of Palmaz stents in the infrarenal aorta. The animals were killed 7 weeks after stent implantation. Two of 34 animals died prematurely (aortic leak, pneumonia). Control stents (n=7) were compared with (186)Re stents (2.6 MBq [n=6], 8.1 MBq [n=5], 16.0 MBq [n=6], and 25.3 MBq [n=8]). Stent application was successful in all cases. No thrombus occlusion was observed. After 7 weeks, neointima formation was 2.2+/-0.2 mm(2) in the control group. In the treatment groups, a dose-dependent neointima reduction was detectable (0.5+/-0.5 mm(2) [2.6 MBq], 0.4+/-0.4 mm(2) [8.1 MBq], and 0 mm(2) [16.0 MBq, 25.3 MBq]). No induction of neointimal formation was observed at the edges of the stents. Radiation resulted in delayed reendothelialization. CONCLUSIONS: (186)Re stents were capable of reducing neointima formation in a dose-dependent fashion. (186)Re stents did not cause late thrombosis or neointimal induction at the stent margins in the observation period of 7 weeks.

Animals↗
PubMed2001

Effects of blood estrogen level on cortical activation patterns during cognitive activation as measured by functional MRI.

Modulation of the blood estrogen level as it occurs during the menstrual cycle has a strong influence on both neuropsychological and neurophysiological parameters. One of currently preferred hypotheses is that the menstrual cycle hormones modulate functional hemispheric lateralization. We examined six male and six female subjects by functional magnetic resonance imaging (fMRI) to image cortical activation patterns associated with cognitive and motor activation to determine whether these changes during the menstrual cycle can be visualized. Female subjects, who did not use oral contraceptives, were scanned twice, once during the menses and once on the 11/12 day of the menstrual cycle. A word-stem-completion task, a mental rotation task and a simple motor task were performed by all subjects. Our data provide evidence that the menstrual cycle hormones influence the overall level of cerebral hemodynamics to a much stronger degree than they influence the activation pattern itself. No differences were seen between male subjects and female subjects during the low estrogen phase. During both neuropsychological tasks blood estrogen level had a profound effect on the size but not on the lateralization or the localization of cortical activation patterns. The female brain under estrogen showed a marked increase in perfusion in cortical areas involved in both cognitive tasks, whereas the hemodynamic effects during the motor tasks were less pronounced. This might be due to differences in neuronal or endothelian receptor concentration, differences in synaptic function, or, most likely, changes in the cerebrovascular anatomy in different cortical regions.

Adult↗
PubMed2001

Hyperexcitatory activity in visual cortex in homonymous hemianopia after stroke.

OBJECTIVES: Damage to and destruction of neural afferents result in a disruption of sensory input, which causes reduced activity in the corresponding cortical areas. Conversely, there is also evidence that lesions in the sensory pathway induce changes in the intracortical connectivity resulting in augmented cortical activity due to disinhibition. As disinhibition is assumed to be involved in the reconfiguration of neural networks, its appearance after brain lesions might be relevant for the restitution of impaired brain functions. METHODS: The effects of lesions in the visual pathway on the activity in visual cortex were studied using magnetoencephalography. In order to compare the neural activity affected by the lesion with the activity associated with intact visual processing, only patients with unilateral, post-chiasmatic lesions resulting in homonymous hemianopia were examined. RESULTS: Stimulation within the scotoma resulted in reduced magnetic activity compared to the stimulation of the intact hemifield. Increased activity was observed when the border region of the scotoma was stimulated. CONCLUSIONS: It is concluded that the magnetic hyperactivity reflects cortical disinhibition induced by lesions in the visual system. Furthermore, the possible role of cortical disinhibition as a basis for cortical reorganization and as a precondition for the recovery of impaired visual functions is discussed.

Hemianopsia↗
PubMed2000

Marginal integrity of large compomer Class II restorations with cervical margins in dentine.

OBJECTIVES: The aim of the present study was to investigate the marginal integrity of total-bond Dyract AP restorations in large Class II restorations with cervical margins in dentine. The efficacy of a new non-rinse conditioner and the effect of beveling the enamel margins were also studied. METHODS: Large MOD cavities with cervical margins located 1mm below the CEJ were prepared in 48 extracted human molars. Six groups (n=8) were filled using a total-bond technique with Spectrum TPH or Dyract AP or a sandwich technique with Dyract in combination with Spectrum TPH. For Dyract AP total-bond restorations, a new non-rinse conditioner was tested vs. a total-etch with 36% phosphoric acid in beveled and butt-joint cavities. After water storage for 21 days and thermocycling (2000x, 5-55 degrees C), replicas were produced for quantitative marginal analysis in the SEM. Afterwards, teeth were immersed in 0.5% basic fuchsin for 24h and dried. Percent dye penetration over the total margin length was analysed in three layers using a sequential grinding technique. Statistical analysis was performed with non-parametric tests and the Bonferroni correction for multiple comparisons at p<0.05. RESULTS: All restoration types showed microleakage. On cervical margins in dentine, Dyract AP restorations showed better marginal adaptation than Spectrum TPH total-bond restorations (marginal openings (MO), median 33.8 vs. 79.6%), but were inferior to Dyract/Spectrum TPH sandwich restorations (MO: 0. 0%). The non-rinse conditioner improved the marginal adaptation of Dyract AP restorations in dentine (MO: 4.7 vs. 38.4%, p=0.0206 for beveled cavities, 12.2 vs. 33.8%, p=0.0238, for butt-joint cavities) and yielded similar results in enamel margins provided that enamel margins were beveled. Beveling of enamel significantly reduced the occurrence of enamel microcracks. CONCLUSIONS: The use of a non-rinse conditioner in combination with Dyract AP may improve the marginal adaptation of Class II restorations compared to composite restorations. The sandwich technique with Dyract results in better marginal adaptation in cervical dentine compared to all other restorative techniques tested in this study. However, microleakage cannot predictably be prevented with the sandwich technique.

Acid Etching, Dental↗
PubMed1999

Models for the description of angioscotomas.

To describe small scotomas in visual field examinations several statistical models are proposed and applied to the evaluation of angioscotoma in 13 ophthalmologically normal subjects. A special perimetric grid is used where thresholds can be estimated along a line of narrow-spaced test points which crosses the predicted location of the retinal vessel. A two-stage analysis employs single estimations to fit a threshold curve by means of a special parametric description of the luminance difference sensitivity threshold as a function of stimulus position. An alternative model incorporates the threshold as a function of position into the probabilistic description of the binary response (stimulus seen/not seen).

Adult↗
PubMed1999

Marginal adaptation of direct composite and sandwich restorations in Class II cavities with cervical margins in dentine.

OBJECTIVES: The aim of this study was to evaluate the marginal adaptation of direct Class II sandwich restorations with resin-modified glass-ionomer cements and compomers in comparison to base and total bond restorations. For sandwich restorations with a triple cure resin-modified glass-ionomer cement the influence of different light curing techniques was also evaluated. METHODS: Large butt-joint class II cavities with cervical margins 1 mm below the cemento-enamel junction were cut into 120 extracted human molars. The cavities (15 groups, n = 8) were filled using a sandwich, base or total bond technique with materials from five different manufacturers. A three-sited light curing technique was used in 13 groups. For the material combination Vitremer/Z100 two additional groups with a different wand positioning and a metal matrix were evaluated. After water storage for 21 days and thermocycling (2000x, 5-55 degrees C), replicas were quantitatively analysed in the SEM. Statistical analysis was performed with the Kruskal-Wallis test and the Bonferroni test at p < 0.05. RESULTS: The marginal adaptation of vertical enamel margins was not dependent on the restorative technique. For margins in dentine, marginal adaptation was significantly better with the sandwich technique than with a base or total bond technique for all materials. There were no significant differences between the base and total bond technique. Overall, resin-modified glass-ionomer cements showed somewhat better results than compomers in sandwich restorations, though differences were not significant for some criteria. Vitremer/Z100 sandwich restorations applied with a metal matrix showed the highest mean percentage of excellent margins of all experimental groups. CONCLUSIONS: Both resin-modified glass-ionomer cements and compomers can improve the marginal quality when used in a sandwich technique. Further research is necessary to determine the ideal material combination for sandwich restorations.

Compomers↗
PubMed1993

Anti-peripheral nerve myelin antibodies and terminal activation products of complement in serum of patients with acute brachial plexus neuropathy.

OBJECTIVE: To determine if complement-fixing antibodies to peripheral nerve myelin (anti-PNM antibodies) and terminal complement activation products were increased in serum of patients with brachial plexus neuropathy compared with normal controls. DESIGN: Case series. SETTING: University medical center. PATIENTS: Three patients (aged 6, 39, and 51 years) with acute brachial plexus neuropathy were studied during the acute and recovery phase of their disease. METHODS: Anti-PNM antibodies were measured in serum samples obtained from three patients and 25 normal controls with the C1 fixation and transfer assay. Soluble terminal complement activation products, SC5b-9, were measured by enzyme-linked immunosorbent assay (ELISA) in serum samples of one patient with brachial plexus neuropathy and of five normal controls. RESULTS: Both serum anti-PNM antibodies and soluble terminal complement activation products were increased in the acute phase of brachial plexus neuropathy compared with normal control values and decreased several months later during clinical recovery. CONCLUSION: Complement dependent, antibody-mediated demyelination may participate in the peripheral nerve damage of brachial plexus neuropathy.

Acute Disease↗
PubMed1986

[Classification of the germinal epithelium in Java monkeys (Macaca cynomolgus) using digital image processing].

Testicular tissue of two adult crab-eating macaques was used to investigate the distribution of the spermatids in the seminiferous tubules. For this purpose, morphological criteria for distinction among the various degrees of development of these cells were elaborated. Subsequently, based upon analyses of serial sections, three-dimensional reconstructions of the cellular distribution pattern were generated by means of digital image processing. In these reconstructions it became evident that the spatial extension of a single differentiation stage can vary considerably. Large tubular portions that contained a single differentiation stage alternated with those exhibiting several differentiation stages which occupied only small patch-like areas of the seminiferous epithelium. Particularly in the latter portions of the tubule a helical continuity of subsequent stages in the sense of a wave of spermatogenesis became immediately obvious. Transitory changes in the direction of the wave (modulations) occurred frequently. The present findings support the suggestion that an uniform kinetic principle of mammalian spermatogenesis exists, which is subjected to slight modifications during the evolution of primates.

Animals↗