[Video head impulse test or caloric irrigation?. Contemporary diagnostic tests for vestibular schwannoma]. / Video-Kopfimpulstest oder thermische Prüfung? Zeitgemäße Funktionsdiagnostik des Vestibularisschwannoms.

The video head impulse test (vHIT) is a new method for investigating vestibular function that is currently poorly studied in terms of its value for clinical diagnosis in otolaryngology. Both the caloric irrigation and vHIT serve to evaluate the horizontal vestibulo-ocular reflex. In the present study, caloric irrigation and vHIT were compared in 46 patients with vestibular schwannoma. Caloric irrigation exhibits a higher sensitivity than vHIT (72% versus 41%) and both tests show only a moderate correlation. Tumor size and hearing level was significantly correlated with caloric abnormalities but not with vHIT findings. Since caloric irrigation and vHIT measure the hVOR in low and high frequency ranges, respectively, these tests have to be considered complementary and are valuable in both diagnostics and therapeutic decisions.

[The video head impulse test: first clinical experiences]. / Der Video-Kopfimpulstest: Erste klinische Erfahrungen.

BACKGROUND: Side-specific test procedures are mandatory in order to assess the function of peripheral vestibular receptors. Semicircular canals (SCC) and vestibulo-ocular reflex (VOR) can be tested by the Halmagyi and Curthoy head impulse test (HIT) and recently by means of the video head impulse test (vHIT). The vHIT procedure is a new method to measure eye and head velocity during brief and rapid head impulses. This method provides objective information of VOR and detects both overt and covert catch-up saccades. MATERIALS AND METHODS: As clinical experiences with vHIT are limited, in this study the horizontal VOR (hVOR) was examined by means of the vHIT in 142 consecutive patients with acute or chronic vestibular syndrome. RESULTS: A total of 20 healthy volunteers served as a control group and exhibited a normal average VOR gain of 0.97 ± 0.09 without re-fixation saccades. In patients, 47.6% showed a pathological vHIT whereas 52.4% revealed a normal test result. Covert catch-up saccades could be revealed in 13.7% by means of vHIT whereas in 86.3% overt catch-up saccades alone or in combination with covert catch-up saccades were found in the majority of catch-up saccades in peripheral vestibular disorders. CONCLUSIONS: By means of the vHIT it is possible to obtain a side-specific and quantitative assessment of hVOR. Video-head impulse test is a reliable tool for vestibular testing even in bedside examinations of patients suffering from dizziness.

Effect of conventional mouthrinses on initial bioadhesion to enamel and dentin in situ.

AIM: The study aimed to investigate the effect of a customary fluoride solution, containing sodium fluoride and amine fluoride, on initial biofilm formation on enamel and dentin in situ compared directly to chlorhexidine. METHODS: Bovine enamel and dentin specimens were mounted on maxillary splints carried by 9 subjects. After 1 min of pellicle formation, rinses with tap water (control), chlorhexidine (meridol med CHX 0.2%, GABA) and a fluoride mouthrinse (elmex, GABA) were performed for 1 min. Subsequently, the slabs were carried for another 8 h. The adherent bacteria were determined by DAPI staining, live-dead staining and determination of colony-forming units after desorption; glucan formation was visualized with concanavalin A. Additionally, energy-dispersive X-ray spectroscopy (EDX) analysis of the in situ biofilm layers was conducted, and contact angle measurements were performed. Statistical evaluation was performed by means of the Kruskal-Wallis test followed by the Mann-Whitney U test (p < 0.05). RESULTS: In the control group, significantly higher amounts of adherent bacteria were detected on dentin (4.8 × 10(6) ± 5.4 × 10(6) bacteria/cm(2)) than on enamel (1.2 × 10(6) ± 1.5 × 10(6) bacteria/cm(2), DAPI). Chlorhexidine significantly reduced the amount of adherent bacteria (dentin: 2.8 × 10(5) ± 3.4 × 10(5) bacteria/cm(2); enamel: 4.2 × 10(5) ± 8.7 × 10(5) bacteria/cm(2)). Rinses with the fluoride solution also significantly reduced bacterial adherence to dentin (8.1 × 10(5) ± 1.5 × 10(6) bacteria/cm(2)). Fluoride could not be detected by EDX analysis of the biofilms. Fluoride mouthrinsing did not influence the wettability of the pellicle-covered enamel surface. CONCLUSION: In addition to the reduction of demineralization and antibacterial effects, fluorides inhibit initial biofilm formation on dental hard tissues considerably, especially on dentin.

[Isolated functional loss of the lateral semicircular canal in vestibular neuritis]. / Isolierte Rezeptorfunktionsstörung des horizontalen Bogengangs.

Today, modern tools in vestibular testing are feasible to provide information about functional status of all five peripheral vestibular receptors. Isolated or combined loss of crista and macula receptor function can be determined in the diagnostic process. We describe a seldom case of isolated functional loss of lateral semicircular canal receptor function in a 55-year-old patient. Whereas there was no ispilateral caloric response and video head impulse test revealed a catch-up saccade, air-conducted (AC) cervical and ocular vestibular-evoked myogenic potentials (cVEMP, oVEMP), subjective visual vertical and MRI were normal.

Novel combination of orientation measurements and transmission microscopy for experimental determination of grain boundary miller indices in silicon and other semiconductors.

The determination of grain boundary planes in multicrystalline material has only been restricted to transmission electron microscope investigations (Jang et al., 1992; Elgat et al., 1985) or to metallograpical investigations of the grain boundary (Randle et al., 1993). The first method is expensive, and both are complex and time consuming in grain boundary preparation. This paper proposes the determination of grain boundary planes in semiconductor wafer by a combined application of Electron Back Scatter Diffraction and Infrared Transmission Microscopy. In particular, the new method is demonstrated with directional solidificated multicrystalline silicon.

Safety of an amino-acetonitrile derivative ( AAD ), monepantel, in weaned lambs following repeated oral administration.

AIM: To demonstrate the safety in weaned lambs of repetitive oral doses of monepantel, an amino-acetonitrile derivative (AAD), when administered at the proposed maximum recommended dose (MRD) and three and five times the MRD over 24 weeks. METHODS: A randomised controlled blinded study design was used. Fifty-six weaned lambs were randomly allocated into a control group, the MRD (3.75 mg/kg) and three (11.25 mg/ kg) and five (18.75 mg/kg) times the MRD treatment groups (n=7 castrated males plus seven females each). Treatment doses of monepantel were calculated based on the MRD of 3.75 mg/ kg, and administered orally on eight occasions at intervals of approximately 21 days. Detailed recording at multiple time points were made of veterinary examinations, observations for adverse events, bodyweight measurements, faecal scores, and haematology, clinical chemistry and coagulation variables. Gross pathology (including measurement of organ weights) and histopathology were performed at the completion of the study. RESULTS: All lambs treated with monepantel and those in the control group thrived, grew and behaved normally to the end of the study. No treatment-related, toxicologically relevant adverse events, clinical observations or macroscopic or microscopic changes were observed. Furthermore, there were no significant differences in bodyweight or organ weights, and haematological, clinical chemistry or coagulation variables between lambs treated with monepantel and control lambs. CONCLUSIONS AND CLINICAL RELEVANCE: Repeated oral administration of monepantel at the MRD and three and five times the MRD every 3 weeks for eight treatments was not associated with any treatment-related adverse effects and was systemically very well tolerated in weaned, growing lambs. This study demonstrated that this population of lambs could tolerate accidental overdoses of up to five times the MRD of monepantel or prolonged repetitive administration at recommended doses or overdoses.

Reproductive safety of an amino-acetonitrile derivative (AAD), monepantel, in rams following repeated oral administration.

AIM: To demonstrate the clinical and reproductive safety in rams of repetitive oral doses of monepantel, an amino-acetonitrile derivative (AAD), when administered at three times the proposed maximum recommended dose (MRD) over an entire spermatogenic cycle and during mating with ewes. METHODS: A randomised controlled blinded study design was used with 28 rams randomly divided into two groups. The control group was treated with saline, and the other group was given three times the MRD (11.25 mg/kg) of monepantel. Treatments were administered orally every 5 days, for 100 days, during an entire spermatogenic cycle and subsequent mating period. Detailed recording at multiple time points were made of veterinary examinations; observations for adverse events; bodyweight measurements; faecal scores; haematology, clinical chemistry and coagulation variables; semen indices; evaluation of serving capacity; and gross pathology (including measurement of organ weights) performed on 10 rams from each group at the completion of the study. RESULTS: All rams treated with monepantel and those in the control group thrived and behaved normally to the end of the study. No treatment-related, toxicologically relevant adverse events, clinical observations or macroscopic changes were observed. Furthermore, there were no significant differences in bodyweight or organ weights, and haematological, clinical chemistry or coagulation variables between rams treated with monepantel and control rams. No significant changes were observed in any semen variable measured in any rams, and the serving capacity of rams mated to ewes was unaffected. CONCLUSIONS AND CLINICAL RELEVANCE: Repeated oral administration of monepantel at three times the MRD every 5 days over an entire spermatogenic cycle and during mating was not associated with any treatment-related adverse effects on the reproductive performance of rams and was systemically very well tolerated. This study demonstrated that this population of rams could tolerate accidental overdoses of up to three times the MRD of monepantel or prolonged repetitive administration at overdoses. Thus, those so treated entering a breeding programme would have normal sperm indices, mating behaviour, and health.

Significant correlation between the breakpoints of rare clonal aberrations in benign solid tumors and the assignment of HMGIY retropseudogenes.

Recently, we described a mechanism by which a retropseudogene, during evolution, becomes an exon of a pre-existing active gene. Similar mechanisms may account for the activation of processed genes by chromosomal rearrangements in neoplasms. Because genes of the high-mobility group protein family HMGI(Y) are known to be involved in the development of a variety of benign solid tumors, it was the aim of the present study to analyze breakpoints of clonal chromosome abnormalities in that group of benign tumors for a possible correlation with retropseudogenes of the HMGIY gene. Whereas the HMGIYL1 retrospeudogene has recently been mapped to Xp22.1, we assigned a further retropseudogene by FISH to 4q13, and database research allowed us to assign a third retropseudogene to 12q24.1. Sequence analyses of these retropseudogenes revealed high-identity indices to the HMGIY gene and no frame-shift divergences. Breakpoint information was obtained from cytogenetic aberrations in uterine leiomyomas, lipomas, pleomorphic adenomas, and pulmonary chondroid hamartomas because, in all of these tumor entities, cytogenetic subgroups involving genes of the HMGI(Y) family exist. Chromosomal bands harboring HMGIY retropseudogenes were affected with a significantly higher frequency than expected under the assumption of purely randomly occurring breakages. These results support our hypothesis that HMGIY-related retropseudogenes can be affected by chromosomal rearrangements in benign human tumors.

Effects of an antihypertensive medication on functional capacity under simulated flight-typical stress-conditions.

A model to investigate the functional capacity (psychomental performance) under stressful conditions was developed. Twenty eight patients with mild hypertension receiving Nitrendipine (20 mg) for 30 days were tested under hypoxic (16% oxygen) and/or orthostatic (-30 mmHg lower body negative pressure) conditions using a subset of the AGARD battery. The main effect was a decreasing performance of the grammatical reasoning task (GRT) under hypoxia or the combination of hypoxia and orthostasis. A simultaneous application of stressors while performing psychometric test batteries may be useful to reveal pharmaceutical influences on human performance and may help to recommend the use of drugs in occupational medicine.

Laser pyrolysis products-genotoxic, clastogenic and mutagenic effects of the particulate aerosol fractions.

Laser therapy has gained wide acceptance and application in many medical disciplines. Nevertheless, during surgical procedures, the thermal destruction of tissue creates a smoke plume. Recent research data indicate that pyrolysates liberated during vaporisation of tissue induce DNA damage. However, assessing potential health hazards during medical laser treatment requires comprehensive insight into the cytotoxic, genotoxic, clastogenic and mutagenic capacity of laser pyrolysis products (LPP). Therefore, the aim of this study was to evaluate the cytotoxic, genotoxic, clastogenic and mutagenic potential of substances resulting from laser irradiation. Four different types of porcine tissues were irradiated with a surgical CO2 laser, the aerosols were sampled under defined conditions and subjected to the SCE test, micronucleus test and the HPRT test. The results showed that the pyrolysis products are strong inducers of cytotoxic effects. The pyrolysis products induced positive effects in the SCE test, micronucleus test and the HPRT test. The ability and extent to induce genotoxic and mutagenic effects turned out to be dependent on the type of tissue that had been irradiated. In general, the effects were most pronounced with liver pyrolysate. In all test systems, a clear dose relationship could be established. In conclusion, we were able to prove that the particulate fraction of laser pyrolysis aerosols originating from biological tissues undoubtedly have to be classified as cytotoxic, genotoxic, clastogenic and mutagenic. Therefore, they could be potential health hazards for humans.

DNA effects in repair-deficient V79 Chinese hamster cells studied with the comet assay.

Using the alkaline comet assay (single cell gel electrophoresis), we studied the induction and persistence of DNA damage induced by methyl methanesulfonate (MMS) and neocarzinostatin (NCS) in the repair-deficient Chinese hamster cell lines V-E5 and XR-V15B. Effects in the comet assay were analyzed directly after treatment as well as after a postincubation period in mutagen-free medium to gain insight into the DNA repair capacities of the mutant cell lines in relation to different primary DNA lesions. Both mutagens caused a concentration-related increase in DNA strand breakage in both mutant cell lines and in the normal parental cell lines. Repair of MMS-induced DNA damage during postincubation was similar in normal and mutant cell lines, while diminished repair was seen after NCS treatment in XR-V15B cells. Our data show that XR-V15B cells only repaired about 30% of NCS-induced DNA damage within 1 h, while the parental V79 cell line repaired about 70%. Since this cell line is defective in the repair of DNA double-strand breaks (DSB), the results indicate that NCS-induced DSB significantly contribute to the genotoxic effects seen in the comet assay. However, compared to previously studied induction of gene mutations and chromosome aberrations, detection of NCS-induced DNA effects with the comet assay was less sensitive and increased DNA migration only occurred under strong cytotoxic conditions.

A comparative investigation of DNA adducts, DNA strand breaks and gene mutations induced by benzo[a]pyrene and (+/-)-anti-benzo[a]pyrene-7,8-diol 9,10-oxide in cultured human cells.

Genotoxic effects of benzo[a]pyrene (BP) and its reactive metabolites (+/-)-anti-benzo[a]pyrene-7,8-diol 9,10-oxide ((+/-)-anti-BPDE) were comparatively investigated in vitro with the permanent human fibroblast cell line MRC5CV1. Induced DNA adducts were measured by 32P-postlabeling, DNA strand breakage was determined by the comet assay and the HPRT gene mutation test was used to detect cytotoxicity and mutagenicity. Treatment of MRC5CV1 cells with S9 mix-activated BP or with (+/-)-anti-BPDE resulted in a concentration-dependent increase in DNA adducts and strand breaks. Genotoxic effects of BP and (+/-)-anti-BPDE were detected by 32P-postlabeling and the comet assay with similar sensitivity. However, under the same experimental conditions, a clear induction of gene mutations was only found after (+/-)-anti-BPDE treatment. The relationship between the induction of primary DNA alterations like DNA strand breaks and DNA adducts and the induction of gene mutations is discussed.

Micronucleus induction by neocarzinostatin and methyl methanesulfonate in ionizing radiation--sensitive Chinese hamster V79 cell mutants.

Two mutant V79 Chinese hamster cell lines (V-E5, XR-V15B) which show hypersensitivities to DNA damage and their two parental cell lines (V79-LE, V79-B) were used for micronucleus studies. The characteristics of V-E5 strongly resemble those of cells derived from patients suffering from the genomic instability syndrome ataxia telangiectasia, whereas XR-V15B has a decreased ability to rejoin double-strand breaks. The two cell lines V-E5 and XR-V15B showed increased spontaneous micronucleus frequencies and higher sensitivity for micronucleus induction by methyl methanesulfonate (MMS) and neocarzinostatin (NCS) both with and without the use of cytochalasin B in the micronucleus assay. Thus, defects in cellular responses to DNA damage are modulating factors in micronucleus formation.

Detection of DNA effects in human cells with the comet assay and their relevance for mutagenesis.

The single cell gel test (SCG-test or comet assay) is a rapid and sensitive method for measuring DNA damage and repair in individual cells. A wide variety of mutagens have been shown to cause DNA alterations detectable with the comet assay, but it is not yet clear whether a relationship exists between the DNA effects and the induction of mutations. We are therefore investigating in a cell culture system with human cells (MRC5CV1) the induction of DNA damage by environmental mutagens and the formation of mutations at the HPRT gene. In the present study we investigated benzo[a]pyrene (BP), an environmental mutagenic and carcinogenic polycyclic aromatic hydrocarbon, and its reactive metabolite (+)-anti-benzo[a]pyrene-7,8-diol 9, 10-oxide ((+)-anti-BPDE). S9 mix activated BP and the direct acting mutagen (+)-anti-BPDE caused a concentration-related increase in DNA migration in the comet assay. Postincubation experiments indicated that induced DNA effects are eliminated by DNA repair within 24 h. BP-treatment caused a strong genotoxic effect in the comet assay but had only a marginal effect on the frequency of gene mutations. When cells were treated with BP in the presence of cadmium sulphate, a clear increase in genotoxicity was observed while the effect on mutations was unchanged. Our results indicate that DNA alterations detected with the comet assay do not necessarily relate to mutagenesis. The absence of a close relationship between DNA migration in the comet assay and mutagenesis may be explained by the fact that some effects seen in the comet assay occur as a consequence of an error free DNA repair process.

The pattern of adriamycin-induced mutations in V-E5 Chinese hamster cells with chromosomal instability.

The V-E5 cell line, a mutant V79 Chinese hamster cell line, was used to study the effect of chromosomal instability on the spectrum of gene mutations and chromosome aberrations induced by the anthracycline antibiotic adriamycin (AM). V-E5 cells showed hypersensitivity to the cytotoxic effects of AM when compared to the parental cell line. AM caused both, chromosome-type aberrations and chromatid-type aberrations in V-E5 cells. Under the same experimental conditions, gene mutations were induced at the hprt locus which mainly represented deletion mutations. The spectrum of AM-induced chromosomal aberrations and gene mutations did not show any peculiarities in comparison to normal V79 cells. It is concluded that the genomic instability in V-E5 cells does not influence the pathways leading to chromosome aberrations and gene mutations after AM treatment.

The effect of defective DNA double-strand break repair on mutations and chromosome aberrations in the Chinese hamster cell mutant XR-V15B.

The radiosensitive Chinese hamster cell line XR-V15B was used to study the effect of decreased rejoining of DNA double-strand breaks (DSBs) on gene mutations and chromosome aberrations. XR-V15B cells are hypersensitive to the cytotoxic effects of neocarzinostatin (NCS) and methyl methanesulfonate (MMS). Both mutagens induced more chromosome aberrations in XR-V15B cells than in the parental cell strain. The clastogenic action of NCS was characterized by the induction of predominantly chromosome-type aberrations in cells of both strains, whereas MMS induced mainly chromatid aberrations. The frequency of induced gene mutations at the hprt locus was not increased compared to the parental V79 cells when considering the same survival level. Molecular analysis by multiplex polymerase chain reaction (PCR) of mutants induced by NCS revealed a high frequency of deletions in cells of both cell lines. Methyl methane-sulfonate induced mainly mutations without visible changes in the PCR pattern, which probably represent point mutations. Our findings suggest a link between a defect in DNA DSB repair and increased cytotoxic and clastogenic effects. However, a decreased ability to rejoin DNA DSBs does not seem to influence the incidence and types of gene mutations at the hprt locus induced by NCS and MMS.

The pattern of mutations induced by neocarzinostatin and methyl methanesulfonate in the ataxia telangiectasia-like Chinese hamster cell line V-E5.

The Chinese hamster cell line V-E5 is a mutant cell line isolated from V79 cells. The phenotypic characteristics of V-E5 strongly resemble those of cells from patients suffering from the genomic instability syndrome ataxia telangiectasia. In order to further characterize the mutant cell line and to get insight into the underlying genetic defect we compared the clastogenic and mutagenic effects of neocarzinostatin (NCS) and methyl methanesulfonate (MMS) in V-E5 and V79 wild-type cells (V79-LE). V-E5 cells were 2-3 times more sensitive to the cytotoxic effect of NCS or MMS. The clastogenic action of NCS was characterized by the predominant induction of chromosome breaks and dicentrics in both cell lines, whereas MMS mainly induced chromatid-type aberrations. The frequency of mutations induced by NCS as well as MMS was slightly enhanced in V-E5 cells compared to V79 cells treated with the same dose. However, the mutant cell line was found to be hypomutable when considering the same survival level as in the parental cell line. Molecular analysis of mutants induced by NCS revealed a high frequency of total deletions of the hprt gene in both cell lines. In contrast, among MMS-induced mutations only 11% deletion mutations were found in V79-LE, whereas in V-E5 MMS-induced deletions were seen in 52% of the hprt-deficient mutants. These results are discussed with respect to a possible relation between genomic instability, cell cycle control and mutational spectra.

Differences in the response to mutagens between two V79 sublines.

Two V79 Chinese hamster sublines (V79-UL and V79-MZ) which differed markedly with respect to their spontaneous pattern of mutations at the HPRT locus were comparatively investigated in genotoxicity tests with ethyl methanesulphonate (EMS). EMS-induced frequencies of HPRT mutations and sister chromatid exchanges (SCEs) were much higher in V79-MZ than in V79-UL. V79-MZ were not hypersensitive against EMS and had normal frequencies of spontaneous gene mutations and chromosome aberrations. Baseline SCE frequencies at various BrdUrd concentrations were slightly increased compared to V79-UL. EMS induced a similar amount of chromosome aberrations in both cell lines but exchange figures occurred with lower frequency in V79-MZ. The results indicate that specific and significant differences in the response to mutagens may exist between 'normal' Chinese hamster cell lines which might be relevant for genotoxicity testing.

The molecular nature of mutations induced by adriamycin at the hprt locus of V79 cells.

Adriamycin (AM), a widely used chemotherapeutic drug, induced a broad spectrum of gene mutations at the hprt locus of V79 cells. The frequency and distribution of AM-induced deletions was analyzed with multiplex polymerase chain reaction in two V79 cell lines, which differed considerably in their spontaneous deletion frequency. Among AM-induced mutants, deletions predominated in both cell lines. Apart from total deletions of the hprt gene, partial deletions were found which were distributed all over the hprt gene with breakpoints in nearly all introns. Under the same experimental conditions, chromosome aberrations were induced by AM which mainly represented chromatid-type aberrations. Neither the induction of gene mutations nor the induction of chromosome aberrations was enhanced by the repair inhibitor 3-aminobenzamide. These results are discussed in the context with our earlier findings on bleomycin-induced mutations and it is suggested that at least two mechanisms lead to the formation of gene deletions. One of them seems to be associated with a misrepair process of frank DNA double-strand breaks and related to chromosome aberrations while the other is not.