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Biomedical subjects

S Schäfer

Publications and source records attributed to S Schäfer.

At least 19 recordsLinked to original sources
PubMed2001

Immunocytochemical localization of mitochondrial single-stranded DNA-binding protein in mitochondria-rich cells of normal and neoplastic human tissue.

Mitochondrial single-stranded DNA-binding protein (mtSSB) is necessary for mtDNA replication. So far the protein has been studied mainly in Escherichia coli and in cell cultures of lower mammals. In this investigation, the authors studied the expression of mtSSB in normal and neoplastic human tissue by light and electron immunocytochemistry. mtSSB has been detected in various tissues and particularly in mitochondria-rich tissues such as external eye muscles and parietal cells of the stomach and in mitochondria-rich tumors (oncocytomas) of various origins. Ultraimmunocytochemistry disclosed the specific distribution of immunoreactive mtSSB over the mitochondria. The staining intensity was heterogeneous. Forty-five percent had a labeling index (silver grains/microm2) greater than 1 and less than 3, approximately 20% had an index of 3 or greater, and 15% of mitochondria remained unstained. The mean labeling index was 1.83. Immunolabeling showed a linear correlation with the mitochondrial profile area (r = 0.82). In conclusion, mtSSB is regularly expressed in normal and neoplastic human tissue of different origin, function, and differentiation. The heterogeneous staining pattern most probably reflects the functional heterogeneity of mitochondria.

DNA, Mitochondrial↗
PubMed2000

The use of transmigration and spermac stain to evaluate epididymal cat spermatozoa.

Epididymal spermatozoa of domestic cats were diluted with TEST medium and frozen. The parameters - estimated percentage of motile spermatozoa, concentration of spermatozoa, cell morphology and transmigration rate (TMR) - were evaluated before freezing and after thawing. Transmigration is a new method to measure the percentage of spermatozoa that consistently move forward, and has not been investigated with cat spermatozoa until now. Estimated percentage of motile spermatozoa averaged 65%, TMR was 76%, concentration of spermatozoa was 30,000 microl(-1) and the incidence of morphologically abnormal spermatozoa averaged 58% before freezing. After thawing, the estimated number of motile spermatozoa declined by 22%, but TMR remained at 76%. The TMR did not correlate with estimated motility but mostly was higher than the latter, which is postulated to be caused by the mobilizing effect of the countercurrent in the transmigration apparature. The estimated percentage of motile cells in the target chamber of the transmigration apparature was improved by using phosphate-buffered saline (PBS) as transmigration medium. Morphology was assessed both after fixation of spermatozoa in Hancock solution and after staining of smears with Spermac. Spermac did not stain all protoplasmic droplets but proved to be more suitable for the routine examination of acrosomal morphology after thawing.

Animals↗
PubMed2000

Proliferation and programmed cell death of neuronal precursors in the mushroom bodies of the honeybee.

We have studied proliferation and programmed cell death in the brain of the honeybee during metamorphosis. DNA fragmentation detection using the TUNEL method combined with 5-bromodeoxyuridine incorporation experiments reveal that in the mushroom bodies neurogenesis is terminated by extensive apoptosis. Proliferation of mushroom body neuroblasts is active until the fourth day of pupal development, ceasing abruptly within 1 day after the onset of apoptosis in the mushroom body proliferative clusters. Inside the mushroom bodies, apoptosis spreads from the apical ends of proliferative clusters, beneath the brain's surface, toward the basal ones. The distributions of apoptotic cells and those in the S phase of the cell cycle overlap significantly. Electron microscopic analysis gives further evidence that mushroom body neuroblasts themselves undergo programmed cell death. We suggest that programmed cell death may be the main factor controlling the final number of Kenyon cells produced during metamorphosis. The overlap in time and space between proliferation and apoptosis raises the question of whether the neuronal precursors switch to programmed cell death during the progression of the cell cycle, or afterwards.

Animals↗
PubMed2000

Reference electrodes based on conducting polymers.

Several attempts to produce conducting polymer based all-solid-state reference electrodes are presented. Open circuit potential of conducting polymers is redox sensitive and Donan equilibrium dependent. Therefore, more sophisticated constructions are necessary. Most promising were bilayers composed of conducting polymers with different ion-exchanger properties.

Journal Article↗
PubMed2000

Correlation between tapping and inserting of pegs in Parkinson's disease.

BACKGROUND: Various investigators have developed complex quantitative instrumental procedures for objective assessment of parkinsonian motor impairment, since drawbacks of rating scales are interrater variability, subjective impression, and insensitivity to subtle modifications. OBJECTIVES: To determine whether performance of inserting of pegs and tapping (i) correlates with each other (ii) differentiates between parkinsonian subjects and healthy controls and (iii) reflects severity of Parkinson's disease (PD). SUBJECTS AND METHODS: In 157 previously untreated idiopathic parkinsonian patients and healthy controls, we measured (i) the total time taken to insert 25 pegs from a rack into a series of appropriate holes in a Purdue pegboard-like apparatus and (ii) the number of taps on a contact board with a contact pencil for a period of 32 seconds for assessment of fine motor skills. RESULTS: Results of both tests correlated with each other, differed between parkinsonian subjects and controls and reflected scored severity of PD. Better correlation with intensity of PD was noted with the Purdue pegboard-like task. CONCLUSION: Both tapping and inserting of pegs represent useful tools for objective evaluation of severity of PD. Peg insertion correlated better with disease severity. Both approaches may be useful in future clinical studies.

Adult↗
PubMed2000

[Psychiatric complications of pharmacotherapy--a review].

Various commonly used drugs with somatic indications may give rise to a host of partially serious psychiatric side-effects. This overview details important prescribed drugs of daily use and their psychiatric complications. The problems of elderly patients are particularly considered. Also, polypharmacy will be given special attention.

Age Factors↗
PubMed1999

Quantification of extracellular and intracellular adenosine production: understanding the transmembranous concentration gradient.

BACKGROUND: Inhibitors of adenosine membrane transport cause vasodilation and enhance the plasma adenosine concentration. However, it is unclear why the plasma adenosine concentration rises rather than falls when membrane transport is inhibited. We tested the hypothesis that the cytosolic adenosine concentration exceeds the interstitial concentration under well-oxygenated conditions. METHODS AND RESULTS: In isolated, isovolumically working guinea pig hearts (n=50), the release rate of adenosine and accumulation of S-adenosylhomocysteine (after 20 minutes of 200 micromol/L homocysteine), a measure of the free cytosolic adenosine concentration, were determined in the absence and presence of specific and powerful blockers of adenosine membrane transport (nitrobenzylthioinosine 1 micromol/L), adenosine deaminase (erythro-9-hydroxy-nonyl-adenine 5 micromol/L), and adenosine kinase (iodotubericidine 10 micromol/L). Data analysis with a distributed multicompartment model revealed a total cardiac adenosine production rate of 2294 pmol. min-1. g-1, of which 8% was produced in the extracellular region. Because of a high rate of intracellular metabolism, however, 70.3% of extracellularly produced adenosine was taken up into cellular regions, an effect that was effectively eliminated by membrane transport block. The resulting approximately 2.8-fold increase of the interstitial adenosine concentration evoked near-maximal coronary dilation. CONCLUSIONS: We rejected the hypothesis that the cytosolic adenosine concentration exceeds the interstitial. Rather, there is significant extracellular production, and the parenchymal cell represents a sink, not a source, for adenosine under well-oxygenated conditions.

Adenine↗
PubMed1999

[Temporal bone fracture after head trauma causing rhinoliquorrhea and meningitis].

We report our experience in managing a temporal bone fracture after head trauma that had no apparent clinical signs. Recurrent CSF rhinorrhea and meningitis lead to extensive diagnostic procedures. Operative exploration of the temporal bone demonstrated a fracture line along the horizontal part of the carotid artery. The location of the fracture did not cause such typical symptoms as hearing impairment, facial paralysis, vertigo or tinnitus. Only CSF liquorrhea through the Eustachian tube indicated a fracture at the lateral skull base.

Cerebrospinal Fluid Rhinorrhea↗
PubMed1999

[Photorefractive keratectomy. Free-running vs. q-switched Er:YAG laser (scanning mode)].

BACKGROUND: Examination of morphology in plane corneal ablation (in vitro) induced by an Er:YAG-laser (2.94 microns) in two modes: free-running (50 microseconds) and q-switched (200 ns). METHODS: Sequences of different fluences in each mode were applied to freshly enucleated swine eyes. Parameters of free-running mode: fluences 1.21-4.77 J/cm2, frequency 80 Hz, spot size 500 microns FWHM, hexagonal spot shape. Parameters of q-switched mode: fluences 0.79-2.33 J/cm2, frequency 20 Hz, spot size 500 microns FWHM, round spot shape. RESULTS: Histology showed thermal damage of 10-25 microns in depth caused by the free-running mode compared with 4.5-7.5 microns by the q-switched mode. In both gross photography and scanning electron microscopic examination, the surface was found to be more homogeneous and smoother in the q-switched mode. CONCLUSIONS: Depending on the different application modes, both laser systems could be used for a defined corneal ablation in photorefractive keratectomy. However, at the moment, results using the Er:YAG laser are not as favorable as with the excimer laser.

Animals↗
PubMed1999

Coordination of tRNA nuclear export with processing of tRNA.

Eukaryotic tRNAs are synthesized in the nucleus and need to be exported to the cytoplasm where they function in translation. tRNA export is mediated by exportin-t, which binds tRNA directly and with high affinity. tRNAs are initially synthesized as precursor molecules. Maturation to functional tRNA takes place in the nucleus, precedes export, and includes trimming of the 5' and 3' ends, posttranscriptional addition of the 3' CCA end, nucleoside modifications, and in some cases splicing. Here we address the question of how tRNA maturation is coordinated with export and thus how cytoplasmic accumulation of inactive maturation intermediates is avoided. This could, in principle, be achieved by nuclear retention of immature tRNA or by selective export of the fully mature form. We show that exportin-t has a strong preference for tRNA with correctly processed 5' and 3' ends and nucleoside modification. tRNA recognition by exportin-t can thus be considered as a quality control mechanism for these maturation steps prior to tRNA export. Surprisingly however, exportin-t can efficiently bind unspliced tRNA and intron-containing tRNA is exported when the rate of splicing is slow. During characterization of the exportin-t/tRNA interaction we found that exportin-t recognizes features in the tRNA that are conserved between prokaryotic and eukaryotic tRNAs. Our data suggest that correct tRNA shape, the 5' and 3' terminal ends, and the TpsiC loop are critical for exportin-t binding.

Animals↗
PubMed1999

Exhaled nitric oxide in patients with Wegener's granulomatosis.

In Wegener's granulomatosis (WG), a pathogenic role of infections, in particular of a chronic colonization of the nasal mucosa with Staphylococcus aureus, has been postulated. Nitric oxide (NO), which is thought to play a role in primary host defence and inflammation, is produced endogenously within the respiratory tract, mainly from the paranasal sinuses. In order to further characterize its role in WG, nasal and pulmonary NO excretion in WG patients in comparison to healthy volunteers was measured. Seventeen patients with WG were included in the study. Five patients had active disease (bloody rhinitis with ulceration and crusting) and immunosuppressive therapy (IST), and 12 were in remission (six with, and six without, IST). S. aureus was found in the swabs of all patients with active WG and in three patients in remission. NO was measured in exhaled gas using a chemiluminescence analyser. The NO excretion rate in nasally sampled gas was significantly reduced (p<0.05) in patients with active WG ((mean+/-SD)102+/-100 nL x min(-1)) compared to healthy controls (299+/-13 nL x min(-1)), and patients in remission (281+/-86 nL x min(-1) with IST, 280+/-133 nL x min(-1) without IST). Pulmonary NO excretion in active or nonactive WG patients did not significantly differ from that of healthy volunteers (48+/-21 nL x min(-1)). These results demonstrate a reduced nasal NO excretion in active Wegener's granulomatosis. This may be caused by destruction and/or functional impairment of sinus epithelium. The reduced NO concentration may well compromise host defence in the upper airways, thus contributing to colonization with Staphylococcus aureus and further promoting Wegener's granulomatosis.

Adult↗
PubMed1998

Adenosine is worth trying in patients with paroxysmal supraventricular tachycardia on chronic theophylline medication.

Adenosine is widely used to terminate paroxysmal supraventricular tachycardia. However, it is usually considered of no value in patients on theophylline, for methylxanthines completely antagonize the A(1) -receptor mediated negative dromotropic adenosine effect. We report a case of a 69 year old man who had chronic obstructive lung disease and spontaneous pneumothorax. Supraventricular tachycardia with a heart rate of 200 bpm persisted even after a pleural drain was inserted and the lung became fully inflated. Although the patient was on theophylline medication with effective serum plasma levels, adenosine terminated the supraventricular tachycardia after three repeated doses of 3, 6 and 9 mg, respectively. This observation further nourishes previous hypotheses that chronic administration of an A1-receptor antagonist leads to up-regulation of the adenosine receptor number.

Adenosine↗
PubMed1998

[Neonatal hearing screening with the Echosensor automated device for otoacoustic emissions. A comparative study].

Following the recommendations of the United States National Institutes of Health Consensus Conference in 1993, otoacoustic emissions (OAE) are now used internationally for hearing screening. The use of recording systems as well as the interpretation of results requires specially trained personnel although measurements are easier to perform than other recording methods available. To date, no objective method for general hearing screening, has been introduced in Germany, for neonates or children at risk, even though it would be desirable to detect and rehabilitate children with congenital hearing loss as early as possible (incidence, 1-6 per 1000). The Echosensor provides the means for carrying out OAE recordings within a short period of time and includes an automatic evaluation of results. Recordings can also be made by trained personnel. As a comparison test, audiologically trained staff recorded otoacoustic emissions in 111 new-born children in order to compare the results of the Echosensor with the results of a conventional OAE measurements device (the ILO88). The aim of this pilot study was to determine the reliability and validity of the recordings in comparison with available standards in brainstem audiometry. Our study showed that the results of the Echosensor corresponded well with the ILO88 results. Consequently, an OAE measuring method is now available is also provides high sensitivity and specificity and is easy to use. Our findings show that the Echosensor can meet the demands of systematic hearing screening in Germany.

Acoustic Impedance Tests↗
PubMed1998

The application of a biotin-anti-biotin gold technique providing a significant signal intensification in electron microscopic immunocytochemistry: a comparison with the ultrasmall immunogold silver staining procedure.

A three-step biotin-anti-biotin gold-detection system (method A) has been applied for ultraimmunocytochemistry using ultrasmall colloidal gold (0.8 nm) linked to anti-biotin antibodies which were visualized and enhanced by silver reduction. The reactivity for glucagon in human pancreatic islets and for cytochrome-c oxidase in heart mitochondria has been compared to a two-step ultrasmall immunogold technique (method B). For both antigens, method A provided significantly higher labelling indices (P<0.001): the labelling density for cytochrome-c oxidase was 223/microm2 using method A and 78/microm2 using method B. For glucagon, the labelling density was 1455/microm2 with method A and 322/microm2 with method B. The results demonstrate that the silver-intensified biotin-anti-biotin gold-detection system is a valuable immunocytochemical method for signal enhancement. The method utilizes biotinylated antibodies from different species, allowing its broad application at the electron microscopic level.

Animals↗
PubMed1998

Immunohistochemical detection of human mtDNA polymerase gamma and of human mitochondrial transcription factor A in cytochrome-c-oxidase-deficient oxyphil cells of hyperfunctional parathyroids.

Immunohistochemical studies were performed in 18 hyperfunctional parathyroids with oxyphil cell aggregates for the detection of cytochrome-c-oxidase (complex IV of the respiratory chain), mitochondrial DNA polymerase gamma and human mitochondrial transcription factor A (h-mtTFA). Seventy-three oxyphil areas exhibiting a defect of cytochrome-c-oxidase were found. The defect involved both the mitochondrially coded subunits II/III and the nuclear derived subunits Vab. There was no loss of mtDNA polymerase gamma or of h-mtTFA in these foci, corresponding to a high content of mtDNA revealed by in situ hybridization. Isolated defects of h-mtTFA were also not found. In contrast, isolated defects of mtDNA polymerase gamma were present in 22 oxyphil foci. These results show that defects of cytochrome-c-oxidase in oxyphil cells are not due to altered expression of h-mtTFA or DNA polymerase gamma, indicating that other nuclear factors involved in the generation of the respiratory chain may be impaired. The low incidence of defects of mtDNA polymerase gamma and the absence of alterations of h-mtTFA and cytochrome-c-oxidase in these foci suggest that defects of mtDNA polymerase gamma are of minor pathogenetic significance.

Cytochrome-c Oxidase Deficiency↗