Biomedical subjects

B Meyer

Publications and source records attributed to B Meyer.

At least 73 records · Page 4Linked to original sources

PubMed2001

Merkel cell carcinoma: a rare cause of hypervascular nasal tumor.

Cutaneous neuroendocrine carcinoma, first described in 1972, is an aggressive disease usually occurring in sun-exposed skin. Other sites have been described, however; such tumors occasionally occur within the nasal fossa. A high rate of metastasis (>30%) explains the poor prognosis. Descriptions of the imaging features of these tumors, mainly located in cutaneous region, are rare. We therefore present the imaging features of two cases of Merkel cell carcinoma involving the sinonasal region, suggestive of a hypervascular tumor.

Aged↗

PubMed2001

Characterization of a new, dominant V124E mutation in the mouse alphaA-crystallin-encoding gene.

PURPOSE: During an ethylnitrosourea (ENU) mutagenesis screening, mice were tested for the occurrence of dominant cataracts. The purpose of the study was morphologic description, mapping of the mutant gene, and characterization of the underlying molecular lesion in a particular mutant, Aey7. METHODS: Isolated lenses were photographed and histologic sections of the eye were analyzed according to standard procedures. Linkage analysis was performed with a set of microsatellite markers covering all autosomal chromosomes. cDNA was amplified after reverse transcription of lens mRNA. For PCR, cDNA or genomic DNA was used as a template. RESULTS: Nuclear opacity and posterior suture anomaly were visible at eye opening and progressed to a nuclear and zonular cataract at 2 months of age. The opacity as well as the microphthalmia was more pronounced in the homozygotes than in the heterozygotes. The mutation was mapped to chromosome 17 between the markers D17Mit133 and D17Mit180. This position made the alphaA-crystallin-encoding gene (Cryaa) an excellent candidate gene. Sequence analysis revealed a mutation of a T to an A at position 371 in the Cryaa cDNA. The mutation was confirmed by an additional MnlI restriction site in the genomic DNA of homozygous mutants leading to replacement of Val with Glu at codon 124 affecting the C-terminal region of the alphaA-crystallin. CONCLUSIONS: The Aey7 mutant represents the first dominant mouse cataract mutation affecting the Cryaa gene. The mutation leads to progressive opacification of the lens. Compared with the beta- and gamma-crystallin-encoding genes, mutations in the alpha-crystallin-encoding genes are rare.

Amino Acid Sequence↗

PubMed2001

[Fractal dimension of speech].

Fractal dimension (D) quantifies the roughness of a temporal signal and estimates its degree of freedom, allowing a good approach of its fluctuations and roughness. Using a 16 kHz time sampling and the box-counting method, we studied Ds of some of the main French phonemes, i.e. [a], [e], [i], [o], [y], and consonants in a consonant-vowel context pronounced 4 times by 10 males and 10 females. For D measurement of long phonemes we used the dyadic Box Counting method and its 10 points D measurement (10pD). For plosion part of plosives consonants, we designed a Semi Continuous Box Counting method devoted to D measurement of short single dimension temporal signal. In the aim to approach infinitely small time scales, and to appreciate at least the tendency of these 10 points set, we calculated also the slope of the 3 last points (3pD). Our study consistently demonstrates that vowels are not fractal; plosive consonants are not fractal; long fricative consonants are fractal; males Ds are significantly higher females Ds, as far as only vowels and long voiced consonants are concerned; there is a significant difference (p < 0.01) between 3pD values of vowels (couple [a] [y] excepted), and fricative consonants (couple [[symbol: see text]]] [f] excepted). In case of nasal consonants, this categorisation is efficient using both 3pD and 10pD measurements (p < 0.05). These results will be commented and discussed, in the aim of clinical use, i.e. dysphonia follow up and auditory prosthesis speech signal processing.

Female↗

PubMed2000

Conformational preferences of a synthetic 30mer peptide from the interface between the neck and stalk regions of kinesin.

The conformation of a synthetic peptide, consisting of 30 amino acids spanning the neck and hinge regions of rat brain kinesin, was investigated by NMR spectroscopy. The peptide extends from K357 to D386 and has the sequence KSVIQHLEVELNRWRNGEAVPEDEQISAKD. A total of 82 distance range constraints and 23 dihedral angle constraints could be obtained from NOESY and E.COSY spectra, respectively. These were used to calculate 500 structures by applying the REDAC algorithm of the software package DYANA. The first half of the peptide matched the helical structure of the neck determined from an X-ray crystal structure of kinesin. This part normally dimerizes into a coiled-coil by virtue of a leucine zipper interaction, but it is alpha-helical even in the monomeric state. The second half (not visible in the X-ray structure because of disorder) contains locally defined structure elements (extended chain, helical loop) connected by flexible joints. This is consistent with the "hinge" function postulated for this domain which is important for kinesin's motility and orientation.

Amino Acid Sequence↗

PubMed2000

Compositional inversion symmetry breaking in ferroelectric perovskites

Cubic perovskite compounds of the form (A(1/3)A(')(1/3)A(")(1/3))BO3 and A(B(1/3)B(')(1/3)B(")(1/3))O3, in which the differentiated cations form an alternating series of monolayers, are studied using first-principles methods. Such compounds are representative of a possible new class of materials in which ferroelectricity is perturbed by compositional breaking of inversion symmetry. For isovalent substitution the ferroelectric double-well potential becomes asymmetric, so that minority domains may no longer survive. The symmetry breaking is enormously stronger for heterovalent substitution; here the double-well behavior is destroyed. Tuning between these behaviors may allow for the optimization of desired materials properties.

Journal Article↗

PubMed2000

Mapping the active site of angiotensin-converting enzyme by transferred NOE spectroscopy.

The interaction of five furylacryloyl (fa)-amino acid derivatives, fa-Phe, fa-Phe-Phe, fa-Gly-Leu-NH(2), fa-Ala-Lys, and fa-Trp, with angiotensin-converting enzyme (ACE), a protein of MW = 130 kDa, was studied by transferred NOESY experiments. Identification of fa derivatives binding to ACE as well as determination of their relative affinities could be accomplished directly from the compound mixtures. Of the five fa derivatives we found that fa-Phe, fa-Trp, and fa-Gly-Leu-NH(2) bind more strongly to ACE than the other two. The dissociation constant of fa-Phe was determined from NMR spectra to 5 x 10(-4) M. A large excess of dipeptides competitively displaced fa-Trp and fa-Phe-Phe from the receptor pocket, allowing the binding site to be mapped. Also, the relative affinities of the fa-Phe, fa-Ala-Lys, and fa-Gly-Leu-NH(2) changed after addition of the dipeptides with fa-Gly-Leu-NH(2) showing the strongest binding. In addition, the presence of a strong inhibitor of the S1' and S2' sites, namely captopril, resulted in the same transferred NOE intensities of fa-Phe, indicating that it binds solely to the S1 and S2 subsites. A rapid screening of binding specificity from mixtures is possible by using a large excess of ligand(s) in transferred NOE studies, even when relatively small amounts of protein are present.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2000

Seismic hazard in the Marmara Sea region following the 17 August 1999 Izmit earthquake

On 17 August 1999, a destructive magnitude 7.4 earthquake occurred 100 km east of Istanbul, near the city of Izmit, on the North Anatolian fault. This 1,600-km-long plate boundary slips at an average rate of 2-3 cm yr(-1), and historically has been the site of many devastating earthquakes. This century alone it has ruptured over 900 km of its length. Models of earthquake-induced stress change combined with active fault maps had been used to forecast that the epicentral area of the 1999 Izmit event was indeed a likely location for the occurrence of a large earthquake. Here we show that the 1999 event itself significantly modifies the stress distribution resulting from previous fault interactions. Our new stress models take into account all events in the region with magnitudes greater than 6 having occurred since 1700 as well as secular interseismic stress change, constrained by GPS data. These models provide a consistent picture of the long term spatio-temporal behaviour of the North Anatolian fault and indicate that two events of magnitude equal to, or greater than, the Izmit earthquake are likely to occur within the next decades beneath the Marmara Sea, south of Istanbul.

Journal Article↗

PubMed2000

[The mechanisms of hearing and hearing loss].

The ear is constituted of an apparatus for transmission, the external ear and the middle ear, and of an apparatus for perception, the inner ear or cochlea and the acoustic nerves. A disorder can occur at each of these levels, leading to different types of hearing loss: defective transmission through a disorder of the external canal and/or by disorder of the tympanic-middle ear bone apparatus; endocochlear hearing loss through disorder of the ciliary cells of the Corti ganglion and/or by metabolic disorder or by pressure modification (such as Meniere's disease) of the endolymph compartment of the inner ear; retrocochlear hearing loss through disorders of the 8th nerve; central hearing loss through disorder of the temporal cortex.

Auditory Perception↗

PubMed2000

[Tumor surgery of the upper cervical spine].

Our own series of tumors of the upper cervical spine was analyzed retrospectively. The standard treatment strategies were reevaluated. A total of nine patients (mean age 61 years, metastasis 4, plasmocytoma 3, chordoma 1, histiocytosis 1) were treated between 1/92 and 2/99. A total of 12 operations were carried out. One-step procedures (6): Three extraoral, one transoral, one dorsal and in one case combined dorsal and extraoral tumor removal were performed. Three dorsal occipitocervical or atlantoaxial stabilizations, one ventral plating and two combined ventral plating plus dorsal three-point fixations, and four vertebral body replacements were carried out. Two-step procedures (3): three extraoral tumor removals with ventral plating plus dorsal three-point fixation, in combination with vertebral body replacement in two cases. The neurological status and the quality of life (Karnofsky performance status, pain levels) were analyzed preoperatively and at the follow-up outpatient examinations (mean follow-up: 18 months). Flexion-extension radiographs were performed at the follow-up. There was no operative mortality. The transient morbidity was 11%. The operative intervention improved the quality of life in all patients. Three patients died within 27 months of operation. Tumor resection at the upper cervical spine using individually modified surgical strategies over an approach corresponding to the tumor location, stabilization and vertebral body replacement increases significantly the time of survival and quality of life with an acceptable surgical risk for complications.

Atlanto-Axial Joint↗

PubMed2000

Differential treatment in acute upper cervical spine injuries: a critical review of a single-institution series.

BACKGROUND: A single-institution series of injuries of the upper cervical spine are analyzed retrospectively and the literature relevant to the topic is reviewed. METHODS: Seventy patients (34 female, 36 male, mean age 47 years) were admitted during a 5-year period for injuries of the upper cervical spine. Sixty-five were followed for a mean time of 18 months. Three isolated ligamentous instabilities, 6 isolated C1 fractures, 3 complex C2 fractures, 10 combined C1/C2, and 48 C2 fractures (17 hangman's, 31 odontoid) were diagnosed. Twenty-nine patients were treated conservatively and for 41 patients surgery was the primary treatment. Twenty-three ventral odontoid screw fixations, 8 ventral platings and 10 dorsal stabilizations were performed. Stability was evaluated using flexion-extension radiography. Pain levels and neurological outcome were assessed. RESULTS: Operative mortality and neurological morbidity were 0%. Two wound infections and 3 instabilities (17%) in odontoid Type II fractures primarily treated with ventral odontoid screw fixation needed dorsal restabilization. During follow-up examinations the neurological status of three patients was improved. In 62 patients preoperative status was attained. Six patients evaluated their pain as severe, two as disabling. CONCLUSIONS: Candidates for surgery as the primary treatment include those with isolated ligamentous instabilities, Type III hangman's fractures and Type II odontoid fractures with dislocation more than 5 mm. In combined C1/C2 fractures the axis fracture dictates the treatment strategy. Patients who undergo dorsal procedures and have involvement of C1 have a greater chance of developing persistent pain.

Acute Disease↗

PubMed2000

Social support and self-esteem predict changes in bipolar depression but not mania.

INTRODUCTION: Our own and other research has suggested that social support predicts course of bipolar disorder, with particularly strong effects on depressive symptoms. Within this paper, we examine which components of social support appear most powerful. METHODS: Thirty-one individuals with Bipolar I disorder were followed longitudinally for 9 months. Participants completed a standardized symptom severity interview monthly, and at a 2-month follow-up, they completed the Interpersonal Support Evaluation List. At a 6-month follow-up, they completed the Rosenberg Self-Esteem Inventory. RESULTS: Self-esteem support appeared to the most important predictor of change in depression across a 6-month follow-up, and multiple regression analyses suggested that social support effects were mediated through self-esteem. LIMITATIONS AND IMPLICATIONS: Although the small sample size suggests a need for replication, current results highlight the importance of psychosocial variables in the course of bipolar depression. Self-esteem may be a particularly important target for clinical interventions.

Adult↗

PubMed2000

Coping and medication adherence in bipolar disorder.

BACKGROUND: Effective treatment of bipolar disorder depends on medication adherence, yet few correlates of adherence have been identified. The pleasure experienced during some manic episodes may render some individuals reluctant to adhere to medications that reduce these 'highs'. Clinical observers identify denial of the severity or existence of illness as common to both bipolar disorder and addiction. The Alcoholics Anonymous model promotes acceptance as a pathway to abstinence adherence. This report hypothesized that acceptance coping would correlate positively and denial coping would correlate inversely with adherence to mood-stabilizing medication among individuals with bipolar disorder. METHODS: Thirty-two participants diagnosed with bipolar I disorder were administered scales from the Brief COPE and an adherence self-report measure. RESULTS: Consistent with hypotheses, curvilinear relationships between acceptance and denial with adherence were detected, suggesting that low levels of acceptance and high levels of denial undermine medication adherence. LIMITATIONS: Given the cross-sectional, naturalistic design of the study, no causal inferences can be made. CONCLUSIONS: The results uncover links between coping styles and adherence in a psychiatric population. The link between acceptance-denial coping, and mature, self-supportive behavior may point the way towards more effective psychosocial interventions.

Adaptation, Psychological↗

PubMed2000

Increases in manic symptoms after life events involving goal attainment.

Bipolar disorder has been conceptualized as an outcome of dysregulation in the behavioral activation system (BAS), a brain system that regulates goal-directed activity. On the basis of the BAS model, the authors hypothesized that life events involving goal attainment would promote manic symptoms in bipolar individuals. The authors followed 43 bipolar I individuals monthly with standardized symptom severity assessments (the Modified Hamilton Rating Scale for Depression and the Bech-Rafaelsen Mania Rating Scale). Life events were assessed using the Goal Attainment and Positivity scales of the Life Events and Difficulties Schedule. As hypothesized, manic symptoms increased in the 2 months following goal-attainment events, but depressed symptoms were not changed following goal-attainment events. These results are congruent with a series of recent polarity-specific findings.

Achievement↗

PubMed2000

Responsiveness to threats and incentives, expectancy of recurrence, and distress and disengagement: moderator effects in women with early stage breast cancer.

Models of neurobiological systems linking personality, motivation, and emotion can be integrated with the expectancy construct to suggest hypotheses about distress and giving up in response to adversity. In 220 women with breast cancer, threat responsiveness-sensitivity of the behavioral inhibition system (BIS)-and incentive responsiveness-sensitivity of the behavioral activation system (BAS)-and expectancies about cancer recurrence were measured. It was predicted and found that high BIS sensitivity interacted with recurrence expectancy to predict elevated distress and disengagement. Low BAS sensitivity (reward responsiveness) also interacted with expectancy of recurrence to predict elevated disengagement. In contrast, high BAS sensitivity (fun seeking) interacted with recurrence expectancy to predict elevated distress. Discussion centers on theoretical implications and possible applications.

Adaptation, Psychological↗

PubMed2000

[Diagnostic methods for the quantification of radiation injuries of the lungs].

PURPOSE: The aim of this paper is to find techniques for quantifying radiation lung injury after irradiation with lung involvement to improve an early diagnosis. METHODS: The case of a patient with NSCLC was used to demonstrate different methods in order to quantify a developing pneumopathy after radiation treatment. By means of HRCT studies in the follow-up, a procedure was developed by defining a test-ROI in high-dose areas of the lung and evaluating the corresponding HU-histogramm for the parameters of the lung peak. Changes during the follow-up can be derived from the differential HU-histogram by the determination of a parameter called delta HUrel, which quantifies the shift to higher HU values. Alternatively, a Fourier analysis of the lung pattern within the test-ROI results in a Fourier amplitude distribution, which reacts sensitively to changes during the follow-up. Furthermore, a Fourier-frequency histogram can be derived which is independent of the spatial orientation of the density pattern. RESULTS: From the HRCT follow-up study, values for delta HUrel can be derived to be 0.24, 0.44, and 0.50 (56, 100 and 422 days after beginning the treatment). The differential Fourier frequency-histogram presentations demonstrate pronounced pattern changes. CONCLUSION: The presented methods demonstrate possibilities to quantify radiation lung injury. The proven sensitivity can possibly be improved after the introduction of a breath triggered HRCT technique.

Carcinoma, Non-Small-Cell Lung↗

PubMed2000

A fractal approach to normal and pathological voices.

Using the box-counting method, we demonstrated recently that the stationary signal of vowels is not fractal, but provides the opportunity to design in the smallest scale a kind of signature for each vowel. This fractal approach to these components of speech allows us to quantify the roughness of the voice, between I (sinusoidal complex signal) and 2 (white noise). We used this method to compare these values in normal and pathological voices. We studied the speech of 10 normal speakers, 6 patients suffering from unilateral vocal fold palsy and 6 suffering from various other dysphonias. The meaning of this fractal measurement is discussed and compared with electroglottogram and spectrographic analysis.

Adult↗

PubMed2000

Capillary oxygen saturation and tissue oxygen pressure in the rat cortex at different stages of hypoxic hypoxia.

The objective of this study was to generate data that allow for estimation of the validity of oxygen saturation (SO2) values in superficial cortical capillaries as calculated by a microreflectometric system (EMPHO II). Capillary SO2 and tissue oxygen pressure (PtO2) were measured simultaneously in the cortex of n = 13 Wistar rats under normocapnic (PaCO2 = 36 mmHg) arterial normoxia (PaO2 = 92 mmHg), moderate (paO2 = 53 mmHg) and severe hypoxic hypoxia (PaO2 = 31 mmHg) with microreflectometry and multiwire surface electrodes. Values were pooled according to arterial oxygenation levels, displayed as frequency histograms and compared via ANOVA (p < 0.05). In a Hill-plot (log PtO2 versus log SO2/(100 - SO2)) an in vivo tissue oxygen dissociation curve was obtained and a linear regression/correlation analysis performed. Mean +/- SD values of SO2 respectively PtO2 decreased from 45.6% +/- 14.6% resp. 26.8 +/- 8.2 mmHg during arterial normoxia to 32.6% +/- 10.2% resp. 20.2 +/- 6.6 mmHg during moderate and to 12.3% +/- 11.1% resp. 8.7 +/- 5.0 mmHg during severe hypoxic hypoxia. Linear regression analysis in the Hill-plot of values between 1% and 65% SO2 and 0.1 and 41 mmHg PtO2 revealed an excellent correlation (r2 = 0.88) with an increase of scatter below 10% SO2 or 1.5 mmHg PtO2. We conclude that SO2 values calculated by the algorithm of the applied microreflectometric system reflect very accurately cortical oxygen supply over a very wide range of oxygenation levels when compared to a gold standard reference. Only at extremely low levels (e.g. below 10% SO2) did we find possible inaccuracies with regard to truly absolute saturation values.

Animals↗

PubMed2000

MADS-Box gene diversity in seed plants 300 million years ago.

MADS-box genes encode a family of transcription factors which control diverse developmental processes in flowering plants ranging from root development to flower and fruit development. Through phylogeny reconstructions, most of these genes can be subdivided into defined monophyletic gene clades whose members share similar expression patterns and functions. Therefore, the establishment of the diversity of gene clades was probably an important event in land plant evolution. In order to determine when these clades originated, we isolated cDNAs of 19 different MADS-box genes from Gnetum gnemon, a gymnosperm model species and thus a representative of the sister group of the angiosperms. Phylogeny reconstructions involving all published MADS-box genes were then used to identify gene clades containing putative orthologs from both angiosperm and gymnosperm lineages. Thus, the minimal number of MADS-box genes that were already present in the last common ancestor of extant gymnosperms and angiosperms was determined. Comparative expression studies involving pairs of putatively orthologous genes revealed a diversity of patterns that has been largely conserved since the time when the angiosperm and gymnosperm lineages separated. Taken together, our data suggest that there were already at least seven different MADS-box genes present at the base of extant seed plants about 300 MYA. These genes were probably already quite diverse in terms of both sequence and function. In addition, our data demonstrate that the MADS-box gene families of extant gymnosperms and angiosperms are of similar complexities.

Amino Acid Sequence↗