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Biomedical subjects

A Wenzel

Publications and source records attributed to A Wenzel.

At least 73 records · Page 4Linked to original sources
PubMed2000

Normal values of M mode echocardiographic measurements of more than 2000 healthy infants and children in central Europe.

OBJECTIVE: To obtain normal M mode (one dimensional) echocardiographic values in a substantial sample of normal infants and children. DESIGN: Data were obtained over three years from a single centre in central Europe. PATIENTS: 2036 healthy infants and children aged one day to 18 years. METHODS: In line with recommendations for standardising measurements from M mode echocardiograms, and using digital echocardiographic equipment, measurements were obtained of the following: right ventricular anterior wall thickness at end diastole, right ventricular end diastolic dimension, thickness of interventricular septum at end diastole and end systole, thickness of posterior wall of the left ventricle at end diastole and end systole, left ventricular dimension at end diastole and end systole, pulmonary and aortic valve diameter, and left atrial dimension. RESULTS: Measurements are presented graphically on centile charts with respect to body surface area, and as tables with mean and 2 SD values for newborns in relation to body weight, and for infants and children in relation to body surface area. Best fitting regression equations are given for each measured variable, using the 50th centile values. CONCLUSION: In comparison with previously published normal values, the presented charts and tables make it possible to judge echocardiographic measurements of a particular patient as normal or abnormal.

Adolescent↗
PubMed2000

The retina of c-fos-/- mice: electrophysiologic, morphologic and biochemical aspects.

PURPOSE: Mice without a functional c-Fos protein (c-fos-/- mice) do not exhibit light-induced apoptotic cell death of rods in contrast to their wild-type littermates (c-fos+/+ mice). To analyze the consequences of the absence of c-fos in the retina, we investigated whether the retinas of c-fos-/- mice have a reduced capacity to absorb and transduce light compared with c-fos+/+ mice. METHODS: Retinal function was evaluated in dark-adapted mice by full-field electroretinograms (ERGs) over more than 6 log units of intensity. Retinal morphology was studied by light- and electron microscopy. Arrestin and the heat shock protein 70 (Hsp70) were detected by Western blot analysis. The rhodopsin content and the kinetics of rhodopsin regeneration were determined in retinal extracts. RESULTS: Although the configuration of the ERGs was comparable in both groups of mice, c-fos-/- mice showed a marked variability in all quantitative ERG-measures with lower mean amplitudes, longer latencies, and a 0.9-log-unit lower b-wave sensitivity on average. Morphometry showed that c-fos-/- mice have 23% fewer rods on average, whereas the number of cones was comparable among c-fos+/+ and c-fos-/- mice. Arrestin levels appeared slightly reduced in c-fos-/- mice when compared with c-fos+/+ mice, whereas Hsp70 levels were comparable in both genotypes. The kinetics of rhodopsin regeneration were similar, but c-fos-/- mice had a 25% lower rhodopsin content on average. CONCLUSIONS: Compared with c-fos+/+ mice, retinal function in c-fos-/- mice is attenuated to a variable but marked degree, which may be, at least in part, related to the reduced number of rods and the reduced rhodopsin content. However, c-fos does not appear to be essential for the ability to absorb photons, nor for phototransduction or the function of second-order neurons. The resistance to light-induced apoptosis of photoreceptor cells in c-fos-/- mice may result from the acute deficit of c-fos in the apoptotic cascade rather than from developmental deficits affecting rod photoreceptor function.

Animals↗
PubMed2000

Digital imaging for dental caries.

Laboratory studies show that digital intraoral radiography systems are as accurate as dental film for the detection of caries when a good-quality image is obtained, although more re-takes might be necessary because of positioning errors with the digital systems, particularly the charge-coupled device sensors. The phosphor plate is more comfortable for the patient than nondigital systems, and the dose can be further reduced with the storage phosphors. Cross-contamination does not pose a problem with digital systems if simple hygiene procedures are observed.

Cross Infection↗
PubMed2000

The hypoalgesic effect of 3-D video glasses on cold pressor pain: reproducibility and importance of information.

The first aim of the study was to evaluate whether it was possible to manipulate the distraction effect induced by 3-D video glasses on the perceived pain and unpleasantness of the subjects by giving them different information about the expected effect. Second, the study aimed to determine the reproducibility of the effect. Forty-five students enrolled, 39 students participated in the study (24 women and 15 men, median age 23 years, range 19-28 years) because 6 did not show up for the first trial, and 37 completed the study because 2 subjects did not show up for the second trial. The subjects were randomized into 3 groups, balanced with respect to age and sex, that received different information about the effect of 3-D video on pain and unpleasantness: the first group received positive information, the second group received neutral information, and the third group received negative information. Once assigned to a group, there were no crossovers between the groups. A cold pressor stimulus was used to induce experimental pain, and the volunteers rated the intensity of pain and unpleasantness on 100-mm visual analogue scales. A new generation of video glasses were used in the study. Each volunteer was exposed to the cold pressor test in 2 randomized trials (video and control) after the information was given, and the 2 trials were repeated in a second session after 4 weeks. There was no significant difference in the effect of video glasses on perceived pain (P = .74) nor on the perceived unpleasantness (P = .84) among the 3 information groups. The data were therefore pooled. The results of the pooled data showed a significant effect of 3-D video on perceived pain (P = .03) but not on unpleasantness (P = .18). After 4 weeks, the study was repeated, and there were no significant changes in the effect of video glasses. The median visual analogue scale scores were reduced in both the video and the control trials compared with the first session.

Adult↗
PubMed1999

Differential DNA binding activities of the transcription factors AP-1 and Oct-1 during light-induced apoptosis of photoreceptors.

The activity of transcription factors like AP-1 and Oct-1 is critical for the regulation of gene expression. Whereas Oct-1 mainly regulates the expression of housekeeping genes, AP-1 is often involved in cellular responses to external stimuli and plays an essential role in the regulation of light-induced apoptosis of mouse retinal photoreceptors. In this study, we investigated AP-1 and Oct-1 DNA binding activity and AP-1 complex composition in the mouse retina during light-induced photoreceptor apoptosis. AP-1 DNA binding activity was low in dark-adapted animals but was transiently elevated within 12 h after exposure of mice to apoptosis-inducing levels of white fluorescent light. Maximal AP-1 activity was found 6 h after light-exposure. Antibody interference analysis at 6 h after damaging light exposure and under normal light conditions revealed that the major fraction of AP-1 consists of c-Fos/JunD heterodimers in both situations. In contrast to AP-1, Oct-1 DNA binding activity was maximal in dark-adapted animals and was reduced during photoreceptor apoptosis. Transient induction of AP-1 (c-Fos/JunD) and inactivation of Oct-1 may be crucial events for light-mediated apoptosis of retinal photoreceptors.

Animals↗
PubMed1999

Patient discomfort and cross-infection control in bitewing examination with a storage phosphor plate and a CCD-based sensor.

OBJECTIVES: The aim was to compare a CCD-based sensor and a storage phosphor plate with respect to patient discomfort and the efficacy of a simple cross-infection control procedure in connection with a posterior bitewing examination. METHODS: 130 patients accepted to have one posterior bitewing of the left and right side taken with two digital radiography systems, the Digora phosphor plate and the Trophy RVG XL, CCD-based sensor system. The patients assessed their feeling of discomfort after the examination on a 100-mm. Visual Analogue Scale (VAS). Microbiological samples were taken from the RVG sensor and cord and from the Digora envelope, plate and scanner during examination of 14 patients. The samples were plated and incubated anaerobically, and the colony-forming units counted. RESULTS: Median VAS score for discomfort was 20 min for Digora and 32 min for the RVG sensor (P < 0.001). Median total counts of cultivable bacteria were low (< 20), the majority being catalase-positive, Gram-positive cocci and Gram-positive rods, presumably skin bacteria. Only the samples taken from the enveloped Digora plate and the rubber tube coated RVG sensor immediately after exposure yielded large numbers of oral bacteria. CONCLUSION: The phosphor plate was less unpleasant than the CCD sensor. Cross-contamination posed a minor problem for both systems when a simple, standard hygiene procedure was followed.

Colony Count, Microbial↗
PubMed1999

Long-term stability of jaw bone tuberosities formed by "guided tissue regeneration".

The aim of the present study was to evaluate whether bone tuberosities produced by GTR on the lateral surface of the mandibular ramus in rats are stable on a long-term basis. Thirty male 6-month-old albino rats of the Wistar strain were used in the study. Tissue flaps were elevated on the lateral aspect of the mandibular ramus. The periosteum was preserved (P+) on one side of the jaw while the bone was denuded (P-) on the other. A rigid, non-porous oval-shaped teflon capsule was placed on both sides with its opening facing the ramus. Six months following surgery, 10 rats were sacrificed and prepared for histology while the remaining 20 rats were subjected to a second operation during which the capsules were removed. Standardized radiographs, taken immediately before and after removal of the capsule and after 3, 6, 9 and 12 months, were subjected to planimetric measurements and subtraction radiography. Ten animals were sacrificed and prepared for histological analysis after 6 months following removal of the capsules and the remaining 10 animals after 12 months. Histology revealed that at 6 months after the placement of the capsules, 17 were completely filled with new bone. The remaining 3 capsules which were displaced exhibited only partial bone fill. The radiographic analysis revealed that after 6 months 98.6 +/- 7.6% (mean +/- SD) in average of the cross-sectional area created by the capsules was filled with new bone. Within 3 months after removal of the capsules a slight resorption of the new bone had occurred, thereby reducing the area of the bone tuberosities by 4 to 8%. No further resorption of the bone tuberosities took place from 3 to 12 months. These observations indicating that new bone produced by GTR is stable on a long-term basis, may question the general belief that non-functional bone will resorb over time.

Animals↗
PubMed1999

Dental students' ability for three-dimensional perception of two-dimensional images using natural stereopsis: its impact on radiographic localization.

OBJECTIVES: To investigate the ability of dental students to perceive 2D images in 3D using natural stereopsis and to evaluate whether the use of stereovision influences their interpretation of radiographic depth, with particular reference to intra-oral radiographs of third molars compared with scanograms. METHODS: Seventy-two dental students (37 from sixth semester and 35 from fourth semester) who had all completed a course in the use of the buccal-object rule participated in the study. Lectures in 3D perception were given to the sixth semester students. They were trained in 3D perception using a 'single image colour field' stereogram and classical stereograms of circles. Both semester students diagnosed nine scanograms and nine intra-oral radiographs for: (1) the position of the crown of an impacted third molar in relation to the second molar and (2) root deviations in the bucco-lingual plane. The sixth semester students recorded whether they were able to achieve a 3D image in these cases. RESULTS: Five students could not achieve a depth image from the training stereograms. Fifty-six per cent agreed on which two objects in the circles were nearest to the viewer and which were most distant, whereas 38% agreed on the opposite. Root deviation was a more difficult diagnostic task than crown position, and the sixth semester students made significantly more correct diagnoses than the fourth semester students (P < 0.001). Irrespective of semester, there was no significant difference between number of correct diagnoses of crown alignment in intra-oral radiographs and scanograms (P = 0.57), whereas root deviations were diagnosed significantly more accurately from the intra-oral radiographs (P < 0.001). CONCLUSIONS: Most dental students can be taught to use natural stereovision to achieve a 3D image from two radiographs at different angles. 3D image is achieved equally well from intra-oral radiographs with a free-hand tube shift and scanograms. Those students who achieved a 3D image in a particular case, made more correct diagnoses than those who could not.

Adult↗
PubMed1999

Development of a system for craniofacial analysis from monitor-displayed digital images.

OBJECTIVES: To develop a program for clinical craniofacial analysis directly on monitor-displayed digital images. METHODS: The program was developed in VisualBasic (Microsoft, Redwood WA, USA), using Access (Microsoft) database, for landmark identification analysis and data storage. It runs on Windows95 (Microsoft). RESULTS: The following established cephalometric analyses were included in the program: Bjork, Down, Frontal, Jarabak, Occlusogram, Rickett and Tweed. In addition, an orthodontist can simply define his own analyses. If he wants to identify a particular landmark, he clicks on its name at the top of the screen, and the definition including a drawing will be shown. If specified in the analysis selected, reference lines or templates are drawn using the identified landmarks. Soft tissues can be drawn either freehand or using the 'soft tissue detection' that generates an outline from the grey-level histogram. The program has been implemented at the Royal Dental College and at the Department of Maxillofacial Surgery and at the Cleft Palate Centre, Aarhus University Hospital. CONCLUSION: A program (PorDiosW) has been developed which has facilitated cephalometric analysis from digital lateral and frontal skull radiographs and digital photographs. The program has been successfully applied in patients with cleft lip and palate and other developmental craniofacial anomalies before and after surgery.

Cephalometry↗
PubMed1999

Comparison of microscopy and radiography as gold standards in radiographic caries diagnosis.

OBJECTIVES: To compare the effect of the choice of gold standard on the diagnostic outcome of approximal caries detection in original and compressed digital radiographs. METHODS: 116 extracted teeth radiographed with a storage phosphor system constituted the original images. These images were compressed at 1:20 and 1:33 with the JPEG irreversible compression standard. Five radiologists scored the three sets of images for the presence of approximal caries on a five-rank confidence scale. The radiographic scores were validated by stereomicroscopy (the true gold standard). The individual ROC areas for the five observers were used to select the worst (obsworst) and the best (obsbest) performer: Their scores in the original images were used as the second and third 'gold standards' for the remaining observers. Mean ROC areas for the three observers with the three types of images were calculated using these two new 'gold standards'. Differences between the ROC areas when using microscopy, obsworst, and obsbest as the 'gold standard' were compared. RESULTS: The mean ROC areas in the original images were 0.66, 0.74 and 0.91 using the true gold standard and obsbest and obsworst as the 'gold standards' respectively. The difference between the true gold standard and obsworst was statistically significant (P < 0.001). The mean ROC areas using the true gold standard decreased with increasing compression whereas they were constant or increased using obsworst and obsbest as 'gold standards', respectively. CONCLUSIONS: Accuracy in approximal caries diagnosis was significantly higher when an observer was the 'gold standard' than when the true gold standard was obtained by microscopy. Paradoxically, the compressed, degraded images were more accurate than the originals when an observer was the 'gold standard' while they were less accurate with the true gold standard. Thus, results obtained using observers' scores from the radiographs which are being evaluated, as validation for the presence of caries may mislead the clinician.

Bicuspid↗
PubMed1999

Dot probe performance in two specific phobias.

OBJECTIVES: The present study applied MacLeod, Mathews & Tata's (1986) dot probe attentional deployment methodology to individuals with specific phobias. DESIGN: Attentional deployment towards spider-related, blood-related, positive, negative, and neutral words was examined. METHOD: Individuals with either spider phobia (N = 13) or blood/injury phobia (N = 14) and non-anxious controls (N = 14) completed the dot probe attentional deployment task. RESULTS: Individuals with specific phobias did not demonstrate an attentional bias towards phobia-related stimuli relevant to their particular fears. CONCLUSION: Semantic-based information processing paradigms may not be sufficiently potent to demonstrate biased performance towards threatening stimuli in individuals with mild specific phobias who are otherwise healthy.

Adult↗
PubMed1999

The effect of a new type of video glasses on the perceived intensity of pain and unpleasantness evoked by a cold pressor test.

The aim of the study was to evaluate whether distraction induced by a new generation of video glasses (I-Glasses, Virtual i-O, Seattle, WA) has an effect on the perceived intensity of pain and unpleasantness. The effects of three-dimensional video, two-dimensional video, and no video glasses (control) were compared in two groups of healthy volunteers (13 males and 11 females) in a randomized, controlled trial. A cold pressor stimulus (1-2 degrees C chilled water) was used to induce experimental pain, and the volunteers rated the intensity of pain and unpleasantness on 100-mm visual analogue scales. The ratings were statistically compared using the Wilcoxon signed-rank test. Between the groups (males and females), there was a significant difference (P < .01) in the rating of unpleasantness in the three-dimensional video condition, while there were no significant differences between the genders in the other conditions (two-dimensional, control). Three-dimensional video provided a significant reduction in both pain and unpleasantness (P < .01) compared with the control condition in the male group. However, in the female group, there was a significant reduction in unpleasantness with two-dimensional video compared with the control (P < .05). This suggests that the use of distraction by means of video glasses is able to reduce the perceived intensity of pain and unpleasantness.

Adult↗
PubMed1998

Synapse-specific localization of NMDA and GABA(A) receptor subunits revealed by antigen-retrieval immunohistochemistry.

Conventional immunohistochemistry provides little evidence for the synaptic localization of ionotropic neurotransmitter receptors, suggesting that their epitopes are not readily accessible in situ. Here, we have adapted antigen retrieval procedures based on microwave irradiation to enhance the immunohistochemical staining of gamma-aminobutyric acid type A (GABA[A]) and N-methyl-D-aspartate (NMDA) receptor subunits in rat brain tissue. Microwave irradiation of fixed tissue produced a marked reduction of nonspecific staining, allowing an improved detection of GABA(A) receptor subunits. However, staining of NMDA receptor subunits remained suboptimal. In contrast, microwave irradiation of cryostat sections prepared from fresh tissue resulted in a major enhancement of both NMDA and GABAA receptor subunit staining. The diffuse, partially intracellular signals were largely replaced by numerous, intensely immunoreactive puncta outlining neuronal somata and dendrites, highly suggestive ofsynaptic receptors. In hippocampus CA1-CA3 fields, the NR2Aand NR2B subunit positive puncta exhibited an extensive colocalization in the stratum oriens and radiatum, whereas pyramidal cell bodies, which receive no excitatory synapses, were unstained. In addition, the NR2A subunit, but not the NR2B subunit, was selectively detected on pyramidal cell dendrites in the stratum lucidum of CA3, suggesting a selective targeting to sites of mossy fiber input. For the GABAA receptor subunits, the most striking change induced by this protocol was the selective staining of the axon initial segment of cortical and hippocampal pyramidal cells. The alpha2 subunit immunoreactivity was particularly prominent in these synapses. In control experiments, the staining of cytoskeletal proteins (neurofilaments, glial fibrillary acid protein) was not influenced by prior microwave irradiation. The enhancement of cell-surface-associated staining is therefore strongly suggestive of an 'unmasking' of subunit epitopes by the microwave treatment. These results reveal a remarkable specificity in the synaptic targeting of NMDA and GABAA receptor subunits in hippocampal and neocortical neurons, suggesting that individual neurons can express multiple receptor subtypes in functionally distinct synapses.

Animals↗
PubMed1998

In vitro analysis of the accuracy of subtraction radiography and computed tomography scanning for determination of bone graft volume.

PURPOSE: This study evaluated the accuracy of digital subtraction radiography (DSR) and three-dimensional computed tomography (3D CT) for determination of bone graft volume in the maxillofacial region. MATERIALS AND METHODS: Standardized bone defects were made on the top of the alveolar ridge in 10 dry pig mandibles. To resemble the clinical situation, a bone block was harvested from the symphyseal region of the mandible and fixed in the defect. True bone graft volume was determined by the water displacement technique (VOL I) and correlated to direct measurements by calipers (VOL II). The mean gray value of the bone graft as imaged by DSR was correlated to the directly measured thickness. Furthermore, VOL I was correlated to the 3D CT of the bone graft (VOL III) and to the 3D CT with the bone graft fixed in the defect (VOL IV). RESULTS: There was a strong correlation between VOL I and VOL II (r = .95), whereas there was a poorer correlation between mean gray level in DSR and measured bone thickness (r = .63). A strong correlation was also registered between VOL I and VOL III (r = .97) and VOL I and VOL IV (r = .97).

Alveolar Bone Loss↗
PubMed1998

Quantitative digital subtraction radiography for the determination of small changes in bone thickness: an in vitro study.

OBJECTIVE: The objective of this study was to determine the ability of quantitative digital subtraction radiography to detect small changes in bone thickness adjacent to tooth roots. STUDY DESIGN: A series of cortical or cancellous bone slices with a 50 microm-stepwise increasing thickness were attached to 4 porcine mandible sections covering buccal and interproximal "defect" regions. Standardized radiographs were quantitatively evaluated for radiographic density changes with the use of digital subtraction radiography. Furthermore, all radiographs were conventionally evaluated by 10 clinicians. The Wilcoxon signed-rank test and the Mann-Whitney U test were used for statistical analysis (alpha = 0.05). RESULTS: A high linear correlation was found between the actual thickness of bone slices and radiographic density changes (cortical bone: r2 = 0.89 to 0.99; cancellous bone r2 = 0.61 to 0.86, p < or = 0.001). A certain increase in bone thickness caused a 3 times higher increase in radiographic density for cortical bone than for cancellous bone (p < or = 0.05). The detection limits of digital subtraction radiography were 200 microm for cortical and 500 microm for cancellous bone, whereas the detection limits of conventional radiography were 600 microm and 2850 microm, respectively. CONCLUSIONS: This in vitro study demonstrated a very high correlation between the objective, quantitative assessment of subtle changes in alveolar bone by digital subtraction radiography and the true changes in bone thickness.

Absorptiometry, Photon↗