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Biomedical subjects

A Wenzel

Publications and source records attributed to A Wenzel.

At least 19 recordsLinked to original sources
PubMed1992

Digital subtraction radiography after stannous fluoride treatment for occlusal caries diagnosis.

The material in this study consisted of 38 fully erupted, extracted third molars without clinical cavitation in the occlusal surface. A radiograph was made of each tooth before and after 5, 10, and 20 minutes of stannous fluoride treatment. The radiographs were digitized and subtraction performed between the images obtained after stannous fluoride treatment and the pretreatment image. Two observers assessed the stannous fluoride treated radiographic and the subtraction images on a monitor: 0 = no change, 1 = intensity increase (white area interpreted as a carious lesion) in dentinoenamel area. Caries was assessed on conventional film radiographs made before treatment: 0 = no caries in dentin, 1 = caries in dentin. The presence of caries in dentin was validated histologically. Sensitivity for intensity increase as a sign of caries was overall higher for the subtraction images based on 20-minute treatment than for the radiographic images (0.025 > p > 0.01) but not significantly higher than for the conventional radiographs. However, neither observer gave false-positive scorings in the subtraction images, whereas observer 1 had five false-positive scorings on the conventional films. Observer 2 had none. The subtraction method did not provide a higher sensitivity for dentinal occlusal caries than conventional film radiography, but the intensity increase could be trusted more than the traditional radiolucency as a sign of a dentinal lesion.

Adolescent↗
PubMed1992

Digital subtraction radiography in assessing bone changes in periodontal defects following guided tissue regeneration.

19 patients with a total of 23 periodontal lesions were selected for the study. Following flap-elevation, an occlusive membrane (Gore Tex) adjusted to the size and shape of the lesion was applied. The membrane was removed 4-6 weeks later by a 2nd operation. Clinical attachment levels were measured and intraoral radiographs taken prior to surgery, and 6 and 12 months postoperatively. The root length and marginal bone level were measured on paper drawings of the teeth magnified (15x) from the conventional radiographs. The radiographs were digitized for analysis of the subtraction images between the preoperative and the 6- and 12-month postoperative images. Clinical attachment gain was seen in 78% of the teeth after 6 months and 70% after 12 months. Bone gain was recorded in 56% and 22% after 6 months and in 44% and 66% after 12 months by conventional and digital subtraction radiography, respectively. The bone level measurements on conventional radiographs differed significantly (p = 0.001) between the preoperative and 6-month postoperative, but not between the 6- and 12-month, (p = 0.29) conventional radiographs. There was no significant relationship between the clinical measurements and the assessments of bone changes on conventional radiographs (r = 0.28, p = 0.25), while a stronger relationship was observed between assessment of clinical attachment gain and assessment of bone changes on the subtraction images (r = 0.58, p = 0.01).

Alveolar Bone Loss↗
PubMed1992

Digital subtraction radiography for assessment of simulated root resorption cavities. Performance of conventional and reverse contrast modes.

A previous study of the sensitivity and accuracy of a standardized radiographic technique for the disclosure of root cavities in a cadaver material indicated that it was not possible to perceive small artificial "resorption" cavities. Using the same material, the aim of the present study was to evaluate whether the use of subtraction radiography would improve the detection of root cavities. In an autopsy material of five mandibular blocks each containing two premolars, small, medium, and large cavities were drilled in the cervical, middle, and apical thirds of the proximal and oral root surfaces. Each jaw block was radiographed before (B) and after (A) cavity preparation with three different exposure times resulting in light, medium, and dark film densities. The radiographs were digitized. Digital subtraction was performed between the A- and B images of varying densities by a computer program developed for dental subtraction radiography. Conventional and reverse contrast modes of the subtraction image were assessed independently by four observers. The results showed small inter- and intraobserver differences in diagnostic accuracy for assessment of total number of root cavities. Original film density did not influence the diagnostic performance in the resulting subtraction image. Contrast mode in the subtraction image influenced diagnostic performance as the majority of observers did best with the reverse contrast mode (p < 0.05). Some of the small root cavities were disclosed by the subtraction technique, but overall accuracy was not increased compared to conventional radiography.

Humans↗
PubMed1992

Validity of diagnosis of questionable caries lesions in occlusal surfaces of extracted third molars.

This study was to evaluate the accuracy of visual inspection, conventional radiography, and digital radiographic methods for the detection of occlusal carious lesions in third molars from a present-day adolescent population. Seventy-eight third molars, considered clinically to be without occlusal cavities, were extracted from young soldiers. Before extraction, an intra-oral radiograph was obtained. After extraction, the teeth were examined visually as per the criteria: 0 = no caries, 1 = chalky/stained fissure indicative of enamel caries, 2 = chalky and dark-stained fissure considered indicative of a dentinal lesion, and 3 = as per criterion 2, but with small surface defects (microcavities). The radiographs were digitised, and image enhancement with contrast stretch and a filtering procedure was performed, respectively. The three types of radiographic image were assessed as per the criteria: 1 = no caries/caries confined to enamel, 2 = caries involving the outermost dentine, and 3 = deep dentinal caries extending half-way or more to the pulp. Ground sections (500-600 microns in thickness) served as validation for lesion depth. The digital radiographic method with contrast stretch performed overall best of the four methods (greater than 70% detection rate) while visual inspection (53% detection rate) performed better than conventional radiography (48% detection rate). When results from visual inspection and conventional radiography were combined, an increase in the detection rate of 11% was obtained with a 7% increase in false-positive scorings. When digitally contrast-manipulated radiographs were combined with visual inspection, a gain of 33% was obtained with an 11% increase in false positives.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Accuracy of visual inspection, fiber-optic transillumination, and various radiographic image modalities for the detection of occlusal caries in extracted non-cavitated teeth.

Occlusal caries lesions may progress into the dentin without this resulting in a macroscopic breakdown of the enamel surface. Imaging methods may therefore be needed to aid in the visual detection of occlusal caries. It was the aim of this study to evaluate diagnostic accuracy in a laboratory set-up of visual inspection (VI), fiber-optic-transillumination (FOTI), conventional radiography (CR), and two digital radiographic image modalities (DRm and DRr) for detection of occlusal caries in clinically non-cavitated teeth. Eighty-one extracted third molars from 18-20-year-old males were assessed by four observers on a five-rank confidence scale by the five methods. Ground sections (500-600 microns) served as validation for true state of disease: 1 = no caries in dentin, 2 = caries just beyond dentino-enamel junction, or 3 = deep dentinal caries, halfway or more to the pulp. ROC analysis was performed on the basis of the confidence rank scale data on two diagnostic thresholds, T1 = caries in dentin (disease state 2+3) and T2 = caries deep in dentin (state 3). On the T1 level, use of the FOTI method gave on average the most accurate diagnosis, closely followed by VI, both performing better than use of radiography. On the T2 level, all five diagnostic methods performed equally well.

Adolescent↗
PubMed1991

A new variant of glycoprotein CD44 confers metastatic potential to rat carcinoma cells.

Using a monoclonal antibody (MAb1.1ASML) raised against a surface glycoprotein of the metastasizing rat pancreatic carcinoma cell line BSp73ASML, cDNA clones have been isolated that encode glycoproteins with partial homology to CD44, a presumed adhesion molecule. In one of the clones, pMeta-1, the epitope marks an additional extracellular domain of 162 amino acids inserted into the rat CD44 protein between amino acid positions 223 and 247 (by analogy to human and murine CD44). The new variants are expressed only in the metastasizing cell lines of two rat tumors, the pancreatic carcinoma BSp73 and the mammary adenocarcinoma 13762NF; they are not expressed in the non-metastasizing tumor cell lines nor in most normal rat tissues. Overexpression of pMeta-1 in the nonmetastasizing BSp73AS cells suffices to establish full metastatic behavior.

Amino Acid Sequence↗
PubMed1991

The N-Myc oncoprotein is associated in vivo with the phosphoprotein Max(p20/22) in human neuroblastoma cells.

Proteins encoded by the proto-oncogenes c-myc, L-myc, and N-myc contain at their carboxy-terminus a tripartite segment comprising a basic DNA binding region (BR), a helix-loop-helix (HLH) and a leucine zipper motif (Zip), that are believed to be involved in DNA binding and protein-protein interaction. The N-Myc oncoprotein is overexpressed in certain human tumors that share neuroectodermal features due to amplification of the N-myc gene. Using a monoclonal antibody directed against an N-terminal epitope of the N-Myc protein in immunoprecipitations performed with extracts of neuroblastoma cells, two nuclear phosphoprotein, p20/22, forming a hetero-oligomeric complex with N-Myc are identified. Both proteins are phosphorylated by casein kinase II in vitro. By partial proteolytic maps we show that p20 and p22 are structurally related to each other and that p20 is identical with Max, a recently described in vitro binding partner of myc proteins. Time course experiments show the presence of the complex in cellular extracts immunoprecipitated within a 5 min interval after the preparation of the cell extract. While the expression of N-myc is restricted, expression of both Max(p20/22) and the murine homolog Myn(p20/22) was observed in cells of diverse human and murine embryonal lineages as detected by heterologous complex formation. By introduction of expression vectors containing the wild type N-myc gene or N-myc genes with in frame deletions or point mutations into recipient cells and subsequent immunoprecipitation of the resulting N-Myc proteins we show that the HLH-Zip region is essential to the formation of the N-Myc-p20/22 complex.

Animals↗
PubMed1991

Sources of noise in digital subtraction radiography.

In 17 patients, three identical radiographic examinations were performed for the lower premolar-molar region, by two examiners at one visit and by one examiner again approximately 3 months later. Recordings were performed with a newly developed device. The radiographs were converted to digital images in the following way: (1) video camera recording of the radiograph obtained at first visit by the first examiner (A), (2) copying of the numeric image of this radiograph (B), (3) repeated video recording of this radiograph (C), (4) video recording of the radiograph obtained at first visit by the second examiner (D), and (5) video recording of the radiograph obtained after 3 months (E). Subtractions were performed between the images: B - A, C - A, D - A, and E - A. The standard deviation of the histogram for the distribution of gray shades in the subtraction images was used to evaluate noise in the image. The standard deviation was 1.3 between B - A, 2.8 between C - A, 4.0 between D - A, and 4.1 between E - A. Physical noise originating from the video camera and the analog-to-digital conversion process thus constituted the major part of noise seen in subtraction images performed between radiographs recorded with a time interval. This indicates that reproducible recordings could be performed with the present device, which, in combination with a subtraction program able to correct for some geometry and density differences, may aid the use of subtraction radiography in clinical trials.

Adolescent↗
PubMed1991

Radiographic detection of occlusal caries in noncavitated teeth. A comparison of conventional film radiographs, digitized film radiographs, and RadioVisioGraphy.

The aim of this study was to compare the accuracy of conventional film radiographs, digitized radiographs, and RadioVisioGraphy (RVG) for the detection of dentinal caries in occlusal surfaces of noncavitated extracted teeth. Eighty-one fully erupted extracted third molars were assessed by four observers using five radiographic methods: conventional film radiographs, digitized radiographs with contrast enhancement and with a filtering procedure, and RVG with contrast enhancement and with x function. Scoring criteria were dichotomous. Histologic sections (500 to 600 microns thick) served as the validation criterion. The two digital methods with contrast enhancement tended to perform more accurately than, although not significantly different from, the other three methods (p greater than 0.05). Average likelihood ratios (true positive/false positive) were 4.3 (conventional film radiographs), 4.4 (RVG with contrast enhancement), 3.6 (RVG with x function), 4.9 (digitized radiographs with contrast enhancement), and 3.7 (digitized radiographs with filtering procedure). Observers 1 and 2 (oral radiologists) performed better than observers 3 and 4 with all five methods (p less than 0.005).

Adolescent↗
PubMed1991

Predictive QSAR models for estimating ecotoxic hazard of plant-protecting agents: target and non-target toxicity.

Quantitative structure-activity relationships (QSARs) are evaluated for predicting pesticides' effects on non-target and target organisms: aquatic biota, mammals, soil micro-organisms, and plants. Satisfactory estimates of pesticides' fish toxicity are obtained from log POW-dependent QSARs derived using chemicals of similar polarity and reactivity. Algal toxicity of herbicidal compounds reflects interactions with the electron transport chain in photosystem II and can be modelled by QSARs describing the Hill reaction inhibition. The ranking in effects on soil micro-organisms is evaluated from models derived using in-vitro bacteria systems. Mammalian toxicity can be estimated by QSARs using the partition coefficient log POW and electronic terms derived by MNDO quantum mechanical calculations. In general, the targets are more susceptible than the non-target species towards phenylurea herbicides. Plants and algae constitute the most sensitive populations, corresponding to the same mode of action. Differences in mode of action towards bacteria, rats, and fish, which are similarly sensitive organisms, are revealed by QSAR analyses.

Animals↗
PubMed1991

Alterations of hyoid bone position and pharyngeal depth and their relationship after surgical correction of mandibular prognathism.

The present investigation studied changes of hyoid bone position and pharyngeal depth at the levels of the second and fourth cervical vertebrae and their relationships in mandibular prognathism patients who received combined orthodontic-surgical treatment. The material consisted of presurgical and 1-year postsurgical profile cephalograms of 52 adult orthognathic surgery patients (40 females and 12 males) who initially had mandibular prognathism and had undergone bilateral vertical ramus osteotomy through an extraoral incision in the retroangular area. Hyoid bone position and pharyngeal depth were assessed on the profile radiographs with 10 cephalometric variables. Paired t tests were used to evaluate the operative changes in all cephalometric parameters. The relationships between pairs of variables describing hyoid bone position and pharyngeal depth were assessed by means of Pearson's product-moment correlation analysis. Significant differences (p less than 0.01) were observed for the distances of the hyoid bone to the maxilla and the mandible. The distances of the hyoid bone with the anterior cranial base, the vertebral column, and the anterior pharyngeal wall, and the measurements representing pharyngeal depth exhibited no significant changes (p greater than 0.05). Moderate correlations were seen between (1) the depth of the pharynx at the fourth cervical vertebra and the hyosymphyseal distance (r = 0.34) and the distance between the point of the projection of the hyoid bone to the mandibular line with its posterior border (r = -0.34), and (2) the depth of the pharynx at the second cervical vertebra and the distance of the hyoid bone with the anterior pharyngeal wall at the level of the fourth cervical vertebra (r = -0.33).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Approximal caries diagnosis using fiber-optic transillumination: a mathematical adjustment to improve validity.

Several studies were conducted recently to evaluate the use of Fiber-Optic Trans-Illumination (FOTI) in the diagnosis of approximal carious lesions. All these studies utilized radiographic readings to validate the FOTI diagnoses. Other investigations studied the value of radiographic readings using more solid validating techniques, which made it possible to judge the true state of decay, such as histology, cavity preparation and microradiography. In this study, data from both types of studies were used to estimate the validity of FOTI diagnosis of approximal caries relative to the true status of decay through correction for radiographic misclassification. The results indicate that particularly the sensitivity of FOTI diagnosis has yet to be determined.

Dental Caries↗
PubMed1991

Performance for obtaining maximal gain from a program for digital subtraction radiography.

The aim of this study was to evaluate the effect on subtraction image quality of number of a) gray shades sampled during camera recording, and b) reference points positioned in the two images to be subtracted. Intraoral radiographs were obtained in each of 12 patients, one at 0 degrees and one at 15 degrees horizontal angulation in a standardized recording procedure. The radiographs were videorecorded twice sampling 1) 160-180 and 2) 200-220 shades of gray. The 0 degrees radiographic image was digitally copied. Subtractions were performed between the identical (0 degrees/0 degrees) and the non-identical (0 degrees/15 degrees) radiographs from both gray shade samples after positioning 5, 10, 15, and 20 reference points, respectively, in each of the images to be subtracted. The standard deviation in the subtraction image histogram was used as the test parameter for image quality. No differences existed between image quality obtained from the radiographs sampled using 160-180 and 200-220 shades of gray (P greater than 0.05). The standard deviation fell continuously, the more reference points were positioned in the images. For the 0 degrees/0 degrees images the difference was statistically significant between the 5 and 10 point images (P = 0.045) while for the 0 degrees/15 degrees images differences existed between 5 and 10 point images (P = 0.077) and the 10 and 15 point images (P = 0.048). The precision of reference point positioning as evaluated in the two identical images was satisfactory, the divergence being on average 1.4 pixels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Detection of occlusal caries without cavitation by visual inspection, film radiographs, xeroradiographs, and digitized radiographs.

The study compared visual inspection, conventional film radiographs, xeroradiographs, and digitized radiographs for the detection of caries in occlusal surfaces without cavitation. 166 extracted premolars and permanent molars without macroscopic cavitation were included. Eight observers assessed five grades of occlusal caries by visual inspection and by the three imaging techniques. Histologic sections (700-1,000 microns) served as validating criterion for the presence and depth of carious lesions, 82 teeth being found carious (27 with deep dentinal involvement) and 84 being scored as sound. Approximately 20% of the dentinal carious lesions were detected by visual inspection and 40% by conventional film radiography (both with a minimal number of false-positive observations). By xero- and digital radiography, an increasing number of false-positive scorings was seen. By digital radiography the true-positive detection rate was similarly increased to 60%. The predictive values of a positive test were, on average, 0.85 for visual inspection, 0.89 for film, 0.78 for xero-, and 0.82 for digital radiography and for a negative test 0.56, 0.61, 0.61, and 0.69, respectively. However, digital radiography was able to detect over 70% of deep dentinal lesions in contrast to 45% by the other two imaging methods, without an increase in false-positive diagnoses of truly caries free teeth, compared with the other techniques.

Bicuspid↗
PubMed1991

The MYCN protein of human neuroblastoma cells is phosphorylated by casein kinase II in the central region and at serine 367.

The MYCN gene has been implicated in certain neuronal tumours, such as neuroblastomas and retinoblastomas. These tumours express high levels of mRNA and protein of MYCN as a result of amplification. MYCN encodes a short-lived nuclear phosphoprotein whose function has not yet been elucidated. This study was undertaken to determine the pattern of MYCN protein (pMYCN) phosphorylation in human neuroblastoma cells. We report that pMYCN is phosphorylated in vitro by purified casein kinase II (CK-II). Two-dimensional phosphopeptide maps showed that most of the phosphopeptides of pMYCN phosphorylated in vitro by CK-II correspond to those phosphorylated in vivo. Fine mapping of the phosphorylation sites was performed using two synthetic MYCN peptides corresponding to pMYCN CK-II consensus sequences. Both peptides were found to be phosphorylated by CK-II and competitively inhibited CK-II phosphorylation of pMYCN in vitro. Thus, we have localized two major CK-II phosphorylation sites in pMYCN, one to the highly acidic central region and the second to serine 367 proximal to the C-terminus. Our data demonstrate that pMYCN is a physiological substrate for CK-II and, since CK-II activity is stimulated in response to mitogens, CK-II phosphorylation of pMYCN may, therefore, represent one signal transduction pathway used by neuroblastoma cells.

Amino Acid Sequence↗