PubMed Health⌕ Search

Biomedical subjects

M Benz

Publications and source records attributed to M Benz.

At least 19 recordsLinked to original sources
PubMed2007

[On the relation between binaural difference potentials and directional hearing].

BACKGROUND: Central auditory processing disorders (CAPD) are associated with reduced discriminatory abilities of the auditory system. One of these abilities is directional hearing, which is based on the evaluation of interaural signal differences. Since these differences affect also the binaural difference potentials (BDP), these derived evoked potentials could be suitable for the objective detection of disabilities in acoustic localization. METHOD: Auditory brainstem responses (ABR) evoked by monaural and binaural stimulation were recorded in 32 adult normal-hearing volunteers at stimulus levels between 10 and 80 dB nHL and the BDP were derived. Additionally, a test of directional hearing was performed and evaluated. RESULTS: BDP are detectable at all stimulus levels without difficulties, with acceptable examination times and with satisfactory reliability in a routine clinical environment. The electrodes can be positioned at the mastoid (A1 and A2) and vertex (Cz) as for conventional ABR recording. Normal ranges are given for latency and amplitude as well as for their lateral differences. CONCLUSION: The spectrum in directional hearing ability as covered by normal-hearing subjects is not mirrored in the parameters of their BDP. Nevertheless, it cannot be ruled out that a real impairment of directional hearing goes along with significantly altered BDP.

Adult↗
PubMed2006

Exposure to microbial components and allergens in population studies: a comparison of two house dust collection methods applied by participants and fieldworkers.

Dust collection by study participants instead of fieldworkers would be a practical and cost-effective alternative in large-scale population studies estimating exposure to indoor allergens and microbial agents. We aimed to compare dust weights and biological agent levels in house dust samples taken by study participants with nylon socks, with those in samples taken by fieldworkers using the sampling nozzle of the Allergology Laboratory Copenhagen (ALK). In homes of 216 children, parents and fieldworkers collected house dust within the same year. Dust samples were analyzed for levels of allergens, endotoxin, (1-->3)-beta-D-glucans and fungal extracellular polysaccharides (EPS). Socks appeared to yield less dust from mattresses at relatively low dust amounts and more dust at high dust amounts than ALK samples. Correlations between the methods ranged from 0.47-0.64 for microbial agents and 0.64-0.87 for mite and pet allergens. Cat allergen levels were two-fold lower and endotoxin levels three-fold higher in socks than in ALK samples. Levels of allergens and microbial agents in sock samples taken by study participants are moderately to highly correlated to levels in ALK samples taken by fieldworkers. Absolute levels may differ, probably because of differences in the method rather than in the person who performed the sampling. Practical Implications Dust collection by participants is a reliable and practical option for allergen and microbial agent exposure assessment. Absolute levels of biological agents are not (always) comparable between studies using different dust collection methods, even when expressed per gram dust, because of potential differences in particle-size constitution of the collected dust.

Air Pollutants↗
PubMed2004

Hertel exophthalmometry versus computed tomography and optical 3D imaging for the determination of the globe position in zygomatic fractures.

It has been the aim of the present study, to introduce the combination of computed tomography and optical 3D imaging to exophthalmometry and to compare the resulting data to the classic Hertel method. Twenty patients without orbital pathology and 12 patients were included in the study, who were subjected to a preoperative computed tomography. Optical 3D images of the facial surface were assessed and Hertel exophthalmometry was carried out to determine protrusion. In patients with zygomatic fractures the assessment of optical 3D images and Hertel values was repeated 5 days after surgery. Preoperative axial CT slices and postoperative optical contours through the globes were superimposed and the change in protrusion was determined. The protrusion values assessed either by CT, Hertel exophthalmometry or optical 3D imaging for patients without orbital pathology did not show any statistically significant differences between each other. For zygomatic fractures, Hertel exophthalmometry revealed more pronounced protrusion data in four of five cases of a posterolaterally dislocated lateral orbital rim and a higher degree of enophthalmos in cases without dislocation of the lateral orbital rim than it could be proved in the CT slices. The differences between optical measurements and CT data were minimal in patients with zygomatic fractures. The combination of computed tomography as baseline measurement and optical 3D imaging for the follow-up examinations reveal more realistic data in cases of zygomatic fractures than Hertel measurements and should be preferred.

Adult↗
PubMed2004

Fusion of computed tomography data and optical 3D images of the dentition for streak artefact correction in the simulation of orthognathic surgery.

OBJECTIVE: To determine the limits of accuracy of fusion of optical three-dimensional (3D) imaging and computed tomography (CT) with and without metal artefacts in an experimental setting and to show the application of this hybrid system in 3D orthognathic surgery simulation. METHODS: Ten plaster casts of dental arches were subjected to a CT scan and optical 3D surface imaging. Subsequently, the first molars in the plaster casts were supplied with metal restorations, bilaterally, and new CT scans and optical surface images were assessed. The registration of the surface data of the two imaging modalities of the study models without and with metal restorations was carried out. The mean distance between the two data sets was calculated. From a patient a CT scan of the skull as well as optical 3D images of plaster casts of the dental arches were acquired. Again the two imaging modalities were registered and virtual orthognathic surgery simulation was carried out. RESULTS: The mean distance between the corresponding data points of CT and optical 3D surface images was 0.1262+/-0.0301 mm and 0.2671+/-0.0580 mm, respectively, for the plaster casts without and with metal restorations. The differences between these data were statistically significant (P<0.0005). For the patient case a mean difference of 0.66+/-0.49 mm and 0.56+/-0.48 mm for mandible and maxilla, respectively, was calculated between CT and optical surface data. CONCLUSION: The accuracy of the fusion of 3D CT surface data and optical 3D imaging is significantly reduced by metal artefacts. However, it seems appropriate for virtual orthognathic surgery simulation, as post-operative orthodontics are performed frequently.

Adult↗
PubMed2001

Iron metabolism in anoxic environments at near neutral pH.

Anaerobic dissimilatory ferric iron-reducing and ferrous iron-oxidizing bacteria gain energy through reduction or oxidation of iron minerals and presumably play an important role in catalyzing iron transformations in anoxic environments. Numerous ferric iron-reducing bacteria have been isolated from a great diversity of anoxic environments, including sediments, soils, deep terrestrial subsurfaces, and hot springs. In contrast, only few ferrous iron-oxidizing bacteria are known so far. At neutral pH, iron minerals are barely soluble, and the mechanisms of electron transfer to or from iron minerals are still only poorly understood. In natural habitats, humic substances may act as electron carriers for ferric iron-reducing bacteria. Also fermenting bacteria were shown to channel electrons to ferric iron via humic acids. Whether quinones or cytochromes released from cells act as electron transfer components in ferric iron reduction is still a matter of debate. Anaerobic ferrous iron-oxidizing phototrophic bacteria, on the other hand, appear to excrete complexing agents to prevent precipitation of ferric iron oxides at their cell surfaces. The present review evaluates recent findings on the physiology of ferric iron-reducing and ferrous iron-oxidizing bacteria with respect to their relevance to microbial iron transformations in nature.

Journal Article↗
PubMed1998

Anaerobic and aerobic oxidation of ferrous iron at neutral pH by chemoheterotrophic nitrate-reducing bacteria.

Nine out of ten anaerobic enrichment cultures inoculated with sediment samples from various freshwater, brackish-water, and marine sediments exhibited ferrous iron oxidation in mineral media with nitrate and an organic cosubstrate at pH 7.2 and 30 degrees C. Anaerobic nitrate-dependent ferrous iron oxidation was a biological process. One strain isolated from brackish-water sediment (strain HidR2, a motile, nonsporeforming, gram-negative rod) was chosen for further investigation of ferrous iron oxidation in the presence of acetate as cosubstrate. Strain HidR2 oxidized between 0.7 and 4.9 mM ferrous iron aerobically and anaerobically at pH 7.2 and 30 degrees C in the presence of small amounts of acetate (between 0.2 and 1.1 mM). The strain gained energy for growth from anaerobic ferrous iron oxidation with nitrate, and the ratio of iron oxidized to acetate provided was constant at limiting acetate supply. The ability to oxidize ferrous iron anaerobically with nitrate at approximately pH 7 appears to be a widespread capacity among mesophilic denitrifying bacteria. Since nitrate-dependent iron oxidation closes the iron cycle within the anoxic zone of sediments and aerobic iron oxidation enhances the reoxidation of ferrous to ferric iron in the oxic zone, both processes increase the importance of iron as a transient electron carrier in the turnover of organic matter in natural sediments.

Aerobiosis↗
PubMed1998

Humic acid reduction by propionibacterium freudenreichii and other fermenting bacteria

Iron-reducing bacteria have been reported to reduce humic acids and low-molecular-weight quinones with electrons from acetate or hydrogen oxidation. Due to the rapid chemical reaction of amorphous ferric iron with the reduced reaction products, humic acids and low-molecular-weight redox mediators may play an important role in biological iron reduction. Since many anaerobic bacteria that are not able to reduce amorphous ferric iron directly are known to transfer electrons to other external acceptors, such as ferricyanide, 2,6-anthraquinone disulfonate (AQDS), or molecular oxygen, we tested several physiologically different species of fermenting bacteria to determine their abilities to reduce humic acids. Propionibacterium freudenreichii, Lactococcus lactis, and Enterococcus cecorum all shifted their fermentation patterns towards more oxidized products when humic acids were present; P. freudenreichii even oxidized propionate to acetate under these conditions. When amorphous ferric iron was added to reoxidize the electron acceptor, humic acids were found to be equally effective when they were added in substoichiometric amounts. These findings indicate that in addition to iron-reducing bacteria, fermenting bacteria are also capable of channeling electrons from anaerobic oxidations via humic acids towards iron reduction. This information needs to be considered in future studies of electron flow in soils and sediments.

Journal Article↗
PubMed1997

pH-dependent regulation of leukocyte 5-lipoxygenase activity in inflammatory exudates by albumin.

OBJECTIVE AND DESIGN: In order to study the regulation of cellular 5-lipoxygenase activity under inflammatory conditions, the effects of inflammatory exudates on rat leukocyte 5 lipoxygenase activity were investigated. MATERIALS: Peritoneal leukocytes and inflammatory exudates were collected from glycogen treated rats. TREATMENT: Glycogen (1 g/kg body weight, in a final volume of 3 ml PBS) was injected intraperitoneally into male Wistar rats. After 4 h, the inflammatory exudate was collected. METHODS: Rat peritoneal leukocytes were isolated and the cellular 5-lipoxygenase activity was determined by HPLC after cell stimulation with calcium ionophore A23187. RESULTS: Inflammatory exudates from glycogen treated animals strongly inhibited cellular 5-lipoxygenase activity of ionophore challenged leukocytes. Albumin was identified as the inhibitor in exudates. Inhibition of cellular 5-lipoxygenase activity by albumin was pH-dependent and was strongly increased by the alkaline pH (7.9-8.0) of the exudate. The albumin effect increased in the range of pH 7.4-8.2 where albumin undergoes a conformational change called neutral to base (N-B) transition. S-Carboxymethyl-albumin had a similar activity to that of albumin, which indicated that the free SH-group at Cys-34 of albumin is not necessary for the effect. The albumin dimer showed a significantly higher inhibition than albumin and it suppressed cellular 5-lipoxygenase activity by 98%. Peptic and tryptic fragments of albumin which comprise domains I, II and II, III, respectively, were less active or inactive. Thus, an intact albumin molecule or the dimer are required for efficient inhibition of cellular 5-lipoxygenase activity. CONCLUSIONS: Our data suggest that during inflammation, albumin extravasation and changes in pH-value are involved in the regulation of the inflammatory reaction by suppression of leukotriene release.

Animals↗
PubMed1996

Determinants of plasma anti-oxidant vitamin levels in a population at high risk for stomach cancer.

Our objective was to identify the determinants of plasma levels of anti-oxidant vitamins which have been linked with decreased risk of cancer and other chronic diseases. Correlation analyses were performed between baseline plasma levels of ascorbic acid, alpha- and beta-carotenes, cryptoxanthin, lycopene and alpha- and gamma-tocopherols and baseline information on dietary and other demographic and life-style factors among 1,364 subjects 35-69 years of age, who are participants in a chemoprevention trial on pre-cancerous lesions of the stomach in Venezuela. Males had lower levels of ascorbic acid, alpha- and beta-carotene and cryptoxanthin and higher levels of alpha-tocopherol than females. This finding was confirmed in non-smokers and non-drinkers. In females, but not in males, age was positively associated with levels of ascorbic acid, cryptoxanthin, alpha- and beta-carotene and gamma-tocopherol. Male tobacco users had lower plasma levels of ascorbic acid, alpha- and beta-carotene and cryptoxanthin than nonusers, and regular alcohol drinkers had a decreased plasma levels of beta-carotene compared with non-drinkers. Female tobacco users had lower levels of ascorbic acid and cryptoxanthin than non-users, and regular alcohol drinkers had lower levels of ascorbic acid and lycopene than non-drinkers. Frequencies of consumption of fresh fruits, fruit juice, raw vegetables and plantains showed weak positive associations with plasma levels of several vitamins studied in both sexes. Sex, age in females, tobacco and alcohol use and dietary consumption affected plasma anti-oxidant vitamin levels in this population significantly. These factors may influence the effect of anti-oxidant treatment in intervention trials.

Adult↗
PubMed1996

Anaerobic, nitrate-dependent microbial oxidation of ferrous iron.

Enrichment and pure cultures of nitrate-reducing bacteria were shown to grow anaerobically with ferrous iron as the only electron donor or as the additional electron donor in the presence of acetate. The newly observed bacterial process may significantly contribute to ferric iron formation in the suboxic zone of aquatic sediments.

Journal Article↗
PubMed1996

Stromal nodules in benign prostatic hyperplasia.

OBJECTIVE: Stromal nodules from benign prostatic hyperplasia (BPH; n = 375 from autopsy, n = 100 from biopsy specimens) were investigated with regard to cytoskeletal components, topography, vascularization, leukocytic infiltrates, and proliferative activity. METHODS: The nature of stromal nodules was studied by histopathology and immunohistochemistry, using antibodies against alpha-actin, desmin, myosin, vimentin, BMA-120, factor VIII, CD3, CD4, CD20, CD34, CD45RO, CD68, PCNA, and MiB1. RESULTS: The findings lead to an extended classification of stromal nodules in BPH: immature mesenchymal (IM; 8.8%), fibroblastic (FB; 65.2), fibromuscular (FM; 21.6), and smooth muscular (SM; 4.4%). The different types occurred in all age decades in a similar distribution (FB > FM > IM > SM). Topographical studies (modified zonal subdivision of McNeal) revealed stromal nodules predominantly in the transitional zone (n = 286), less in the central zone (n = 78), occasionally in the peripheral zone (n = 11), and predominantly in the periurethral (n = 287) and less in the intermediate (n = 84) and subcapsular (n = 4) regions. The different types of nodules presented a distinct vascular pattern. FB, FM, and SM nodules showed significantly increased diffuse infiltrates of T lymphocytes-mainly T helper cells (mean 73%)-and an increase of B lymphocytes. Proliferative activity in the nodules was not observed. Stromal nodules were not observed in normal nonhyperplastic prostates; they only occurred in combination with hyperplastic nodular glandular proliferates. CONCLUSIONS: The findings are suggestive of a maturational sequence of stromal nodules in BPH and of a possible significance of immunocompetent cells in the development of stromal nodules and further suggest that both stroma and epithelium of the prostate respond with nodular hyperplasia to the stimulus, which causes BPH.

Adult↗
PubMed1996

Antioxidants, Helicobacter pylori and stomach cancer in Venezuela.

A randomized chemoprevention trial on precancerous lesions of the stomach is being conducted in Tachira State, Venezuela. The aims of the study are to evaluate the efficacy of vitamin supplementation in preventing the progression rate of precancerous lesions. Here we report on the pilot phase of the study in which two antioxidant preparations were evaluated on their ability to raise antioxidant levels in plasma and in gastric juice. The study aimed also to determine the antibiotic sensitivity profiles of Helicobacter pylori isolates prevalent in the area. Forty-three subjects with precancerous lesions (chronic gastritis, chronic atrophic gastritis, intestinal metaplasia and dysplasia) of the stomach were randomized to one of two antioxidant treatments. Treatment 1 (250 mg of standard vitamin C, 200 mg of vitamin E and 6 mg of beta-carotene three times a day) or treatment 2 (150 mg of standard vitamin C, 500 mg of slow release vitamin C, 75 mg of vitamin E and 15 mg of beta-carotene once a day) for 7 days. Blood levels of total vitamin C, beta-carotene and alpha-tocopherol and gastric juice levels of ascorbic acid and total vitamin C were measured before and after treatment on day 8. Both treatments increased the plasma levels of total vitamin C, beta-carotene and alpha-tocopherol/cholesterol but not those of ascorbic acid or total vitamin C in gastric juice. Treatment 1 was the best choice and resulted in a greater increase in the plasma levels of beta-carotene and alpha-tocopherol. H. pylori was cultured from 90% of the gastric biopsies; 35 isolates were identified which were highly resistant to metronidazole, a front-line antibiotic recommended against H. pylori in other settings.

Adult↗
PubMed1995

The sap47 gene of Drosophila melanogaster codes for a novel conserved neuronal protein associated with synaptic terminals.

Proteins expressed specifically in neurons and transported to synaptic terminals are likely to constitute important molecular elements of nervous system function. In an effort to characterize synapse-associated proteins (SAPs) of Drosophila, we have isolated from a hybridoma library several monoclonal antibodies (MABs) that selectively stain synaptic terminals in immunohistochemical preparations. MAB nc46 binds to most but not all synaptic terminals of the Drosophila nervous system, it also recognizes a protein with homologous distribution in other dipteran flies and binds to large parts of fish CNS. In Western blots the antibody labels a Drosophila brain protein of 47 kDa and cross-reacts with brain proteins from several species including insects, fish, mouse and man. From these data we conclude that the corresponding gene has been conserved in evolution at least among diptera. Using MAB nc46 and expression cloning we have identified the 'sap47' gene coding for the 'synapse-associated protein of 47 kDa' of Drosophila melanogaster. Sequence analysis of genomic and cDNA clones reveals the intron-exon structure of the gene and characterizes the complete open reading frames of two alternatively spliced transcripts. The sap47 gene is located in 89A8-B3 on chromosome 3R and codes for two almost identical inferred polypeptides of 347 and 351 amino acids with no significant sequence homology to known proteins.

Amino Acid Sequence↗
PubMed1995

Hot and cold mate drinking and esophageal cancer in Paraguay.

A hospital-based case-control study, including 131 cases of esophageal cancer and 381 controls, was carried out in Paraguay to investigate the role of hot and cold mate drinking in esophageal cancer risk. Detailed information on mate drinking and on tobacco smoking, alcohol consumption, and dietary habits was obtained by interview. Amount and duration of cold or hot mate drinking were not associated with esophageal cancer risk. However, temperature at which mate was drunk was significantly associated with risk. As compared to drinkers of warm or hot mate, drinkers of very hot mate had an increased risk for esophageal cancer even after adjusting for the strong effects of alcohol and tobacco consumption (adjusted odds ratio = 2.4; 95% confidence interval = 1.3-4.3). This effect seemed to be mainly due to the temperature at which mate cocido (one of the two ways in which hot mate is prepared) was drunk (odds ratio = 6.5; 95% confidence interval = 3.2-12.2). As expected, very strong dose-response associations were found for alcohol consumption and cigarette smoking. After correcting for these and the consumption of other food groups, diets rich in fats and red meats, especially beef, were associated with esophageal cancer risk. In conclusion, the findings from this study suggest that cold mate drinking does not increase the risk of esophageal cancer. This study identifies the very hot temperature at which mate is drunk, and not the amount or the duration, as an important risk factor for esophageal cancer in this population. Alcohol drinking and tobacco smoking remain, nevertheless, the main risk factors for esophageal cancer in Paraguay.

Adult↗
PubMed1994

Intestinal metaplasia types and the risk of gastric cancer: a cohort study in Slovenia.

Between 1967 and 1976, 1,525 Slovenian patients with a histological diagnosis of intestinal metaplasia (IM) were classified according to subtype of IM based on morphology and mucin staining; 518 cases were diagnosed with type I, 197 with type II and 275 with type III, but in 291 the diagnosis of IM was not confirmed. Patients who had developed cancer or died up to 1986 were identified by record linkage at the Slovenia Cancer Registry and the Central Population Registry in Slovenia. A total of 34 incident cases of gastric cancer occurring at least 6 months after the diagnosis of IM were identified. The standardised incidence ratio (SIR) for stomach cancer was 2.23 in the whole cohort. It was highest for IM type III, followed by type II and IM-unconfirmed, but not increased for type I. The relative risk (RR) of developing gastric cancer based on Cox's proportional hazards model was 2.14 for type II and 4.58 for type III, compared with type I. The RR was especially increased for a subgroup of type III secreting sulphomucins in their goblet cells in comparison with types I-II negative to sulphomucins. Our results confirm that subtyping of IM is useful for identifying individuals at high risk for gastric cancer.

Adult↗
PubMed1994

Difficulty in eradicating Helicobacter pylori in a population at high risk for stomach cancer in Venezuela.

The bacterium Helicobacter pylori (HP) has been implicated in the etiology of precancerous lesions of the stomach and there is evidence suggesting that it may influence the efficacy of chemoprevention of gastric cancer with vitamin C. Eradication seldom has been attempted in populations from developing countries, with a high prevalence of HP frequently resistant to metronidazole. A randomized, double-blind, controlled trial to evaluate the efficacy of colloidal bismuth subcitrate (120 mg q.i.d.) and amoxycillin (500 mg q.i.d.) in eradicating HP was conducted in 220 subjects drawn from a population with a high prevalence of metronidazole-resistant HP in Tachira state, Venezuela. One month after completion of two weeks' treatment, eradication rates of 6.5 percent in the treatment group and two percent in the placebo group were estimated on the basis of HP diagnosis in biopsies, and of 13.9 percent compared with 3.9 percent on the basis of a 14C-urea breath test, although the negative predictive value of the breath test was very low compared with HP diagnosis in biopsies. In the treatment group, particularly among males, a significant decrease in bacterial load was detected. Reasons for failure of treatment in high HP-prevalence areas are discussed, and it is suggested that primary prevention of HP infection may be the optimal approach to reducing levels of stomach cancer in these high-risk groups.

Adult↗
PubMed1994

Monoclonal antibody KS1/4-methotrexate immunoconjugate studies in non-small cell lung carcinoma.

The antigen reactive with murine monoclonal antibody (MAb) KS1/4 is expressed on epithelial malignancies and some normal epithelial tissues. Studies were undertaken to evaluate KS1/4-methotrexate (KS1/4-MTX) immunoconjugate in patients with advanced non-small cell carcinoma of the lung. Eleven patients in two different groups received KS1/4-MTX in two different escalating dose infusion schedules with a maximal tolerated dose of 1,750 mg/M2 and a cumulative dose of MTX of 40 mg/M2. Toxicities were similar in both groups and included fever, anorexia, nausea, vomiting, diarrhea, abdominal pain, guaiac positive stool, and hypoalbuminemia. Two patients had an associated aseptic meningitis. One patient had a 50% decrease in two lung nodules without a change in lymphangitic infiltrates. This patient received a second course of treatment and developed an immune complex-mediated arthritis and serum sickness. Four patients mounted a human antimouse antibody response. Post-treatment tumor biopsies documented binding of MAb KS1/4. These studies document the feasibility and potential usefulness of a MAb directed against tumor-associated antigens with the targeting of chemotherapeutic drugs in patients with non-small cell lung carcinoma.

Aged↗