Biomedical subjects

A Wenzel

Publications and source records attributed to A Wenzel.

At least 109 records · Page 6Linked to original sources

PubMed1997

N-methyl-D-aspartate receptors containing the NR2D subunit in the retina are selectively expressed in rod bipolar cells.

N-methyl-D-aspartate receptor subunit messenger RNAs are widely expressed in the retina and several types of second and third order neurons are responsive to N-methyl-D-aspartate. Functional N-methyl-D-aspartate receptors are assembled from the NR1 subunit with at least one of the four NR2 subunit variants (NR2A-2D). We have analysed immunohistochemically the cellular distribution of N-methyl-D-aspartate receptors containing the NR2D subunit in the rat and rabbit retina. Using a subunit-specific NR2D antiserum, exclusively bipolar cells with somata localized close to the outer plexiform layer were labelled in both species. The axons were immunoreactive and arborized in the innermost inner plexiform layer. The morphology and localization of these cells, which were much more numerous in rat than in rabbit, suggested that they are rod bipolar cells. This was confirmed in both species by co-localization of the NR2D subunit immunoreactivity with protein kinase C-alpha, a selective marker for rod bipolar cells. At the subcellular level, a distinct polarization in the distribution of NR2D immunoreactivity was demonstrated by confocal laser scanning microscopy: staining was moderate in dendrites arborizing within the outer plexiform layer, intense at that pole of the soma facing the outer plexiform layer, and low in the portion of the soma embedded in the inner nuclear layer. Proximal axonal segments and axonal end-feet in the inner plexiform layer displayed the strongest NR2D subunit immunoreactivity. The axonal staining suggests that neurotransmission of the rod bipolar cells is modulated within the inner plexiform layer by N-methyl-D-aspartate receptors containing the NR2D subunit.

Animals↗

PubMed1997

Students' attitudes towards and use of computer-assisted learning in oral radiology over a 10-year period.

OBJECTIVE: To compare the attitudes towards CAL of today's dental students with those 10 years ago and to assess the use of CAL over a 10-year period. METHODS: A questionnaire was given to 40 current dental students containing 15 identical questions to those asked 10 years previously. Attitudes were ranked on a scale from 1 (worst) to 5 (best). Over the entire period, 420 students (mean = 42 students/year, range 33-56) used the programs. The material consisted of interactive computer-based teaching programs on: intraoral radiography, X-ray density and sharpness, basic radiation physics, radiation biology, X-ray apparatus and a multiple choice bank. A central computer served the PCs which the students could use as they required. Each program start was recorded at the server. Due to rebuilding and change of server, no data were sampled during 7 months of 1991. RESULTS: Overall, there was no statistically significant difference (P > 0.05) between students' attitudes in 1996 and 1985. Two questions were scored significantly higher in 1996. The programs were run 12,269 times in the 10-year period. Use of the programs increased steadily whereas number of dental students/year decreased. Program runs in each year, expressed as percentage (in brackets) of total runs over the 10-year period, were: 1986 (1), '87 (8), '88 (8), '89 (11), '90 (9), '91 (3), '92 (13), '93 (13), '94 (16), '95 (18). CONCLUSIONS: The favourable attitudes seen 10 years ago when CAL was initiated could not be ascribed to a Hawthorne effect as similarly or more favourable attitudes were recorded in 1996. Though not mandatory, CAL was frequently and increasingly used by dental students over the 10-year period.

Adult↗

PubMed1997

NMDA receptor heterogeneity during postnatal development of the rat brain: differential expression of the NR2A, NR2B, and NR2C subunit proteins.

Changes in the expression of the NMDA receptor subunits (NRs) NR2A, 2B, and 2C were investigated in histo blots of the developing rat brain with subunit-specific antisera. At birth, the NR2B subunit was detected almost ubiquitously, the NR2A subunit staining was faint and restricted to the hippocampus, cerebral cortex, and striatum, and no NR2C subunit immunoreactivity was detected. During the first 3 postnatal weeks, the NR2B subunit became confined to forebrain structures, whereas the NR2A immunoreactivity became abundantly expressed throughout the brain. The NR2C immunoreactivity emerged 5 days after birth in the olfactory bulb, thalamus, and vestibular nuclei and became very intense after 10 days in cerebellar granule cells, its primary site of expression in adulthood. After 3 weeks, NR2A and NR2B immunoreactivity decreased to adult levels, whereas NR2C immunoreactivity remained unchanged. The patterns of distribution of the subunit proteins were in agreement with those of their corresponding mRNAs, as monitored by in situ hybridization histochemistry, although the mRNA translation appeared to be delayed by several days in certain areas. Our results reveal a progressive increase in the heterogeneity of NMDA receptors due to the comparably late onset of NR2A and NR2C subunit expression and by the area-specific rearrangement of NR2B subunit expression following birth.

Animals↗

PubMed1997

Periodontal regeneration of intrabony defects with resorbable and non-resorbable membranes: 30-month results.

The aim of this prospective split-mouth-study was to compare the healing results in intrabony defects 12 and 30 months after placement of resorbable (polyglactin-910) and non-resorbable (e-PTFE) GTR-membranes. 11 healthy patients with 30 defects participated. 10 patients with 10 pairs of contralateral lesions, which were treated with both membrane types, were included in the split-mouth-design. Furthermore, in an additional group-design all 30 (16 polyglactin-910 and 14 e-PTFE) treated sites were evaluated. Clinical examinations (PBI, REC, PPD, PAL) and radiographic examinations were carried out under standardized conditions immediately before as well as 12 and 30 months after surgery. Additionally, for the assessment of the effectiveness of the 2 membranes by comparing the regeneration results of different defects, the vertical relative attachment gain (V-rAG) was calculated as a % of the PAL gain related to the maximum possible attachment gain (expressed by the baseline depth of the osseous defect intraoperatively measured). Digital subtraction radiography (DSR) was carried out for the quantitative assessment of bone density changes due to GTR. In the split-mouth-design, both types of membranes provided significant V-rAGs (median) after 12 months (polyglactin: 81.7%; e-PTFE: 100.0%) and after 30 months (polyglactin: 69.1%; e-PTFE: 83.8%) compared to baseline. In 90.0% of the polyglactin and e-PTFE sites, a probing attachment gain of at least 2 mm was maintained over the 30-month period. However, in 2 polyglactin treated sites, and 5 e-PTFE treated sites, a new attachment loss was found between 12 and 30 months. DSR showed bone density gain 12 and 30 months postsurgically. No statistically significant differences could be observed between the 2 membrane materials with regard to clinical and radiographic findings. This was confirmed when considering the total number of defects (group-design). In conclusion, based on this 30-month-study resorbable polyglactin membranes may be regarded as a useful alternative to the well established e-PTFE membranes for the treatment of intrabony defects.

Adult↗

PubMed1997

Effect of exposure time on in vitro caries diagnosis using the Digora system.

The aim of this study was to determine the in vitro diagnostic performance for approximal caries and occlusal dentine caries diagnosis of the Digora system for digital radiography in relation to the exposure time. Radiographs were made of 220 extracted human posterior teeth and cuspids at exposure time levels of 3%, 6%, 10%, 20%, and 78% of the exposure time needed for E-speed film (image sets I, II, III, IV, and V, respectively). The image sets were put in random order (III, I, IV, II, V) and assessed independently by 3 observers using a 5-point confidence scale. True caries status was determined histologically after sectioning of the teeth. Evaluated parameters were: interexaminer kappa, sensitivity, specificity, Dz3/4 (the distance of one operating point to the diagonal in the ROC domain) and area under the ROC curve. The Spearman correlation coefficients between the parameters and both exposure time and order of viewing of the sets were calculated. For approximal surfaces, the ranges of mean parameter values were: sensitivity 26-33%, specificity 93-95%, Dz3/4 0.63-0.84, area 0.61-0.69. For occlusal surfaces, the ranges were: sensitivity 52-60%, specificity 91-95%, Dz3/4 1.03-1.34, area 0.79-0.87. Out of 24 pairwise comparisons between sets V and I, 5 were significant. Out of 24 comparisons between set V and II, only 2 were significant. It was concluded that diagnostic performance is unlikely to be impaired for an exposure time as short as 6% of E-speed film exposure. When reducing the exposure time to 3% of E-speed film exposure, caries diagnosis may be impaired.

Bicuspid↗

PubMed1997

Influence of oxygen ventilation on Doppler microemboli signals in patients with artificial heart valves.

BACKGROUND AND PURPOSE: The purpose of this study was to evaluate the influence of inhalation of 100% oxygen on microembolic signal (MES) counts in patients with artificial cardiac valves. METHODS: A total of 134 outpatients were examined. Transcranial Doppler baseline monitoring (45-minute duration) was performed in all patients under resting conditions. The first 30 patients subsequently underwent transcranial Doppler monitoring for at least 20 minutes under noninvasive positive pressure ventilation with 100% oxygen and for an additional 30 minutes under resting conditions. The same protocol was applied to all following patients with a baseline MES count > or = 10, while the examination was discontinued in the remaining patients. RESULTS: Baseline MES counts < 10, which remained unchanged during oxygen inhalation and the subsequent resting period, were observed in 26 of 30 initial patients. A total of 46 patients with MES counts > or = 10 were identified. Oxygen application was feasible in 43 patients. An exponential MES decrease was noted in 42 patients during oxygen inhalation (statistically significant in 38 patients), followed by a subsequent increase in 38 of 43 patients (statistically significant in 25 patients) under resting conditions. CONCLUSIONS: The exponential reduction of MES counts observed in this study corresponds to blood denitrogenation, thus strongly arguing for nitrogen bubbles as underlying embolic material in prosthetic valve carriers.

Adolescent↗

PubMed1997

Variations in the expression of the adenomatous polyposis coli (APC) tumor suppressor gene in human cancer cell lines of different tissue origin.

The adenomatous polyposis coli (APC) tumor suppressor gene APC is mutated in familial adenomatous polyposis and in most sporadic colorectal tumors. Through its interaction with beta-catenin the APC protein may play a role in a signal transduction pathway regulating cell proliferation. Despite the fact that APC is ubiquitously expressed, mutations leading to truncated proteins are restricted to tumors of the digestive system. To determine further alterations not resulting in protein truncation, but possibly influencing the signaling, we compared the relative expression level of the APC protein and transcripts in 24 human colorectal cancer cell lines and in additional 17 lines of noncolorectal tissue origins, which have not previously been studied. By Western analysis, the highest levels of full-length APC protein were found in a subset of neuroblastoma and retinoblastoma cell lines. In contrast, in five noncolorectal lines it was not detectable. Truncated APC was exclusively found in 18 of the 24 colorectal cancer cell lines, but was never detected in any cell line derived from other tissues. In most colorectal cancer cell lines the protein level of full-length or mutated APC was reduced. By the more sensitive immunoprecipitation analysis, weak expression of full-length APC could be shown even in those noncolorectal cancer cell lines where it was not detectable by Western blotting. In addition, APC transcript expression was found in all cell lines, the level in colorectal cancer cell lines being reduced.

Adenomatous Polyposis Coli↗

PubMed1996

Conditional expression of N-myc in human neuroblastoma cells increases expression of alpha-prothymosin and ornithine decarboxylase and accelerates progression into S-phase early after mitogenic stimulation of quiescent cells.

To elucidate the contribution of the N-Myc protein to neuroblastomas we have used a synthetic inducible expression system on the basis of the tetracycline repressor of E coli to reversibly express N-myc in a human neuroblastoma cell line in which expression of endogenous N-myc is barely detectable. Like the c-Myc protein, N-Myc up-regulates the expression of both alpha-prothymosin and ornithine decarboxylase. Induction of N-myc increases both the rate of DNA-synthesis and the proliferation rate, and shortens the G1 phase of the cell cycle. A comparison of cell populations in which the presence of N-Myc protein was restricted to different parts of G(zero)/G1 revealed that N-Myc is rate-limiting for cell cycle progression during the first 5 h after serum stimulation of quiescent cells providing direct evidence that Myc-proteins act early after mitogenic stimulation of quiescent cells.

Basic Helix-Loop-Helix Leucine Zipper Transcriptio↗

PubMed1996

The effects of arginine administration on the levels of arginine, other amino acids and related amino compounds in the plasma, heart, aorta, vena cava, bronchi and pancreas of the rat.

Arginine (0.8g/kg, ip) or a vehicle was administered to rats and the levels of arginine and a large number of related amino compounds++ were measured in plasma, heart, aorta, vena cava, pancreas and bronchi at specified time intervals. Arginine levels (nmol/ml) increased in the plasma from 237 to 3172 at 15 min, 1236 at 30 min and 509 at 120 min. Peak concentrations (nmol/g) of arginine are reached in the tissues at 15 or 30 minutes with control and postinjection values of 500 and 1769 in the heart, 314 and 1563 in the aorta, 575 and 2976 in the vena cava, 760 and 1943 in the bronchi, and 234 and 3638 in the pancreas. Arginine injection also affects a number of amino acids and related compounds in the plasma and tissues most notably ornithine, isoleucine, phosphoserine, leucine and ethanolamine. However, plasma level changes do not predict tissue level changes which are highly specific for an individual compound and tissue. There was no general indication that arginine injection stimulates nitric oxide (NO) formation in any tissue. Thus, arginine is rapidly absorbed from the abdominal cavity into the blood stream, is quickly taken up by the tissues studied and disappears after about 2 to 3 hours. The effects seen after arginine administration could be caused by arginine per se and/or changes in one or more of the related amino compounds but not by NO.

Amino Acids↗

PubMed1996

Impact of lossy image compression on accuracy of caries detection in digital images taken with a storage phosphor system.

Image compression may reduce storage needs whether in the lossless (reversible) or lossy (irreversible) form. The aims of the study were to evaluate (1) storage needs, (2) subjective image quality, and (3) accuracy of caries detection in digital radiographs compressed to various levels by a lossy compression method. The material consisted of 116 extracted human premolars and molars. The teeth were mounted three in a line and radiographed by the Digora system (Sorodex Medical Systems, Helsinki, Finland). The images were exported in tagged image file format and compressed with the Lempel-Ziv-Welch reversible and the Joint Photographic Experts Group irreversible compression algorithm on four levels. The total of 580 images were assessed by five observers on a 5-rank confidence scale for caries diagnosis. The observers subjectively judged image quality on an 11-point rank scale. With the reversible compression, images could be compressed to less than 50% of the original storage needs whereas the four irreversible compression factors compressed to 20%, 8%, 5%, and 3%, respectively. For occlusal surfaces, when receiver operating characteristic curve areas were increasingly smaller and the compression rate was higher. The difference between the original and the most compressed images was 14% (p = 0.1). The median quality score was above middle on the 11-point rank scale for all except the most compressed images (median score = 1). In conclusion, for caries diagnosis, compression ratio rates of 1:12 can be justified before accuracy and image quality is significantly affected.

Dental Caries↗

PubMed1996

In vitro comparison of Kodak Ultra-speed, Ektaspeed, and Ektaspeed Plus, and Agfa M2 Comfort dental x-ray films for the detection of caries.

The aim of this study was to compare the diagnostic accuracy of two new dental x-ray films, Kodak Ektaspeed Plus (Plus) and Agfa M2 Comfort (M2), respectively, with the current Kodak Ultra-speed (Ultra) and Ektaspeed (Ekta) films for the detection of caries. A total of 103 occlusal and 224 proximal surfaces were examined independently by three observers. A histologic examination performed after the teeth were sectioned served as the validation method for lesion depth. Receiver operating characteristic curve areas were calculated to express the diagnostic accuracy. In the occlusal surfaces the receiver operating characteristic curve areas ranged from 0.764 (in Ultra films) to 0.800 (in Ekta films). In the proximal surfaces the receiver operating characteristic curve areas ranged from 0.550 (in Ultra films) to 0.696 (in Plus films). No statistically significant differences were found between the different film types.

Dental Caries↗

PubMed1996

Developmental and regional expression of NMDA receptor subtypes containing the NR2D subunit in rat brain.

The regional and developmental expression of NMDA receptors containing the NR2D subunit was analyzed on the level of the subunit mRNA and protein in rat brain. RNase protection experiments indicated that among two proposed splice variants of the NR2D subunit, only the NR2D-2 subunit is expressed. The regional distribution of the NR2D subunit protein was visualized with a newly developed NR2D-2 subunit-specific antiserum on brain sections using the histoblot technique. In adult brain, NR2D immunoreactivity was mainly restricted to diencephalic, mesencephalic, and brainstem structures. During postnatal development, the NR2D subunit was detected transiently in certain regions, such as the ventrobasal complex of the thalamus, hippocampus, inferior colliculus, and brainstem reticular formation, suggesting that NR2D subunit-containing receptors play a role in these brain areas only during development. The level of NR2D subunit mRNA and protein decreased during late postnatal development. However, significant levels of NR2D subunit mRNA and protein were present in adulthood, in particular, in the globus pallidus, thalamus, subthalamic nuclei, and superior colliculus. These results indicate a functional relevance for NMDA receptors containing the NR2D subunit in the developing and adult brain, although its expression in the adult brain is less prominent and restricted to a few brain areas.

Aging↗

PubMed1996

Radiographic detection of cavitation in approximal surfaces of primary teeth using a digital storage phosphor system and conventional film, and the relationship between cavitation and radiographic lesion depth: an in vitro study.

The need for operative treatment of approximal carious lesions may depend on whether or not the surface is cavitated. The aims of this in vitro study were to compare the accuracy of cavity detection in approximal surfaces of primary molars using a storage phosphor system (Digora) and Ektaspeed Plus film, and to relate radiographic lesion depth to the presence or absence of cavitation in the tooth surface. The material consisted of 72 approximal surfaces in 46 exfoliated/extracted primary molars. The teeth were radiographed using Ektaspeed Plus film and then the Digora system with 10% of the film exposure dose. Three examiners independently scored the radiographs for the presence or absence of cavitation on a 5-point confidence scale and for lesion depth on a four-category disease severity scale. Validation of the radiographic diagnosis of cavitation was done by inspecting the dried and cleaned surfaces in direct light using a sharp probe. The surfaces were scored: 0 = sound, 1 = discoloration without cavitation, 2 = cavitation. Diagnostic accuracy of the two radiographic methods was evaluated by ROC curve analysis. There was no statistically significant difference between the accuracy of the two methods for detection of cavitation. There was also no significant difference in the proportion of lesions in outer enamel, inner enamel and dentine detected by the two methods. The majority of lesions diagnosed radiographically to be in dentine were cavitated.

Chi-Square Distribution↗

PubMed1996

Quantitative digital subtraction radiography for assessment of bone density changes following periodontal guided tissue regeneration.

OBJECTIVES: The quantitative assessment of alveolar bone density changes in periodontal defects following guided tissue regeneration (GTR). METHODS: Twelve patients with 30 intrabony lesions and 16 furcation defects took part. Standardized radiographic and clinical examinations were carried out immediately before and then 5 and 13 months after surgery. Intra-oral radiographs were evaluated by means of digital subtraction radiography (DSR). Within the subtraction images, a window ('experimental region') was defined covering the visible density changes in the defect area. Background noise was measured by using a similarly sized window ('control region') located in an area not affected by GTR. Bone density changes were quantitatively evaluated by calculation of the mean, standard deviation and maximum and minimum values of the grey-level histogram within these windows. RESULTS: DSR revealed significant bone density gain after GTR in intrabony and furcation defects. While a continuous increase was observed over the 13 month period in intrabony defects, changes in furcation defects occurred mostly in the 5-13 month period. Clinically, a distinct vertical and horizontal attachment gain was found. The correlation coefficients between changes in radiographic density and clinical parameters were low, indicating a difference in the information obtained by the two diagnostic methods. CONCLUSION: Quantitative DSR is a valuable, non-invasive, objective method to obtain information on density changes in intrabony and furcation defects treated by GTR. However, a full assessment of soft and hard tissue changes requires both clinical evaluation and DSR.

Alveolar Bone Loss↗

PubMed1996

Observers' use of image enhancement in assessing caries in radiographs taken by four intra-oral digital systems.

OBJECTIVES: To evaluate observers' use of image-enhancement facilities and time consumption in assessing caries in radiographs taken with four digital systems. METHODS: In total, 131 extracted human premolars and molars were mounted three in a line. Radiographs were taken using four digital systems: Digora (DIG), Radio VisioGraphy (RVG), Sens-A-Ray (SAR) and Visualix (VIX), and imported into a programme with routines for adjustment of brightness, contrast and gamma curve. Sixteen images from each digital system were compressed (JPEG, irreversible compression). The 588 images were scored by six observers for approximal and occlusal caries on a five-point confidence scale using enhancement as they pleased. The programme automatically recorded any enhancement made without the observers knowing this. RESULTS: Some form of digital enhancement was used in almost all images, with the gamma curve being the most frequent. The VIX images were enhanced most followed by SAR, DIG and RVG images. The differences were significant (p < 0.01) except between DIG and SAR images. The compressed images were enhanced significantly more than their uncompressed counterparts (p = 0.02). The average time spent recording one image was 24 s. On average, significantly less time was spent with the DIG images than the other systems (p < 0.01), while there were no significant differences between the CCD-based systems (p > 0.2). There was no relationship between time spent and number of manipulations performed. CONCLUSIONS: The observers took advantage of the facilities available for enhancement of density and contrast in digital images. The potential of gamma curve manipulation requires further investigation.

Dental Caries↗

PubMed1996

Radiographic evaluation of the effect of orthodontic retraction on the root of the maxillary canine.

OBJECTIVES: To evaluate possible apical root resorption following orthodontic retraction of the maxillary canine quantitatively and qualitatively. METHODS: Twenty maxillary canines in 12 patients were retracted using a prefabricated orthodontic spring. Twenty non-treated mandibular canines from the same patients served as controls. Standardized radiographs were taken of all upper and lower canines before (T0) and after (T2) retraction. Root length and tooth length were measured on the radiographs at T0 and T2, and the root length/tooth length ratio was calculated. Ten orthodontists assessed blind the root apex of the pairs of radiographs taken at T0 and T2 for resorption. Digital subtraction was performed between the pairs of radiographs taken at T0 and T2 and the mean density and the standard deviation of the grey shades of the root apex calculated. RESULTS: There were no significant differences between root length/tooth length ratio at T0 and T2 for either the maxillary (p = 0.45) or the mandibular canines (p = 0.79). There was considerable variation between observers judgements of root resorption: nine out of ten observers agreed that a resorption had taken place in only one tooth. There were no significant differences between the mean density values in the subtraction images of the upper and lower canines (p = 0.3). CONCLUSIONS: Quantitative assessment with conventional and subtraction radiography failed to demonstrate root resorption in the maxillary canines. Root resorption could be shown qualitatively in only one tooth. The standardized orthodontic force system used for canine retraction appeared to cause no resorption, or only a small degree of resorption of no clinical relevance.

Adult↗

PubMed1996

Image homogeneity and recording reproducibility with 2 techniques for serial intra-oral radiography.

The present study compared recording reproducibility and image homogeneity after applying two techniques for recording of serial intra-oral radiographs: 1) a technique previously described in 1990 based on mechanical fixation between the patient, the film holder, and the x-ray tube; and 2) a newly developed technique which operates with an optical alignment provided by a light beam. Twenty adults participated in the study. Two intra-oral radiographs were taken with a 30-minute time interval of the mandibular premolar/molar and the incisor region in each individual with either of the methods. All radiographs were scanned and digitized. Subtractions were performed between the two radiographs taken of the same individual and region with the same method. The standard deviation (SD) of the histogram defining the distribution of the grey shades in the subtraction image was used as the statistical test parameter. Subtractions were performed with an automated method and using a reference point-based program in order to test recording reproducibility and image homogeneity, respectively. Paired t-tests revealed that the average SDs obtained by the mechanical fixation method and the optical method were not statistically significantly different neither when applying the automated nor the reference point-based subtraction method (P > 0.05). The SDs increased significantly when the automated method was used compared to the reference point-based method (P = 0.001). In conclusion, the optical method and the mechanical method provided images of similar recording reproducibility and homogeneity.

Humans↗

PubMed1996

An image plate system for digital intra-oral radiography.

Direct image acquisition of intra-oral images using digital, filmless, techniques has been possible only since the late 1980s, although indirect methods have been available since the late 1970s. The techniques possible so far have had a number of limitations, making them cumbersome to use. A new system, the Digora system, has recently been developed in Finland, which overcomes many of these shortcomings. The principles and uses of this system are described here.

Equipment Design↗