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Biomedical subjects

W Arnold

Publications and source records attributed to W Arnold.

At least 55 records · Page 3Linked to original sources
PubMed2000

Suppression of tumorigenicity in breast cancer cells by the microfilament protein profilin 1.

Differential display screening was used to reveal differential gene expression between the tumorigenic breast cancer cell line CAL51 and nontumorigenic microcell hybrids obtained after transfer of human chromosome 17 into CAL51. The human profilin 1 (PFN1) gene was found overexpressed in the microcell hybrid clones compared with the parental line, which displayed a low profilin 1 level. A comparison between several different tumorigenic breast cancer cell lines with nontumorigenic lines showed consistently lower profilin 1 levels in the tumor cells. Transfection of PFN1 cDNA into CAL51 cells raised the profilin 1 level, had a prominent effect on cell growth, cytoskeletal organization and spreading, and suppressed tumorigenicity of the stable, PFN1-overexpressing cell clones in nude mice. Immunohistochemical analysis revealed intermediate and low levels of profilin 1 in different human breast cancers. These results suggest profilin 1 as a suppressor of the tumorigenic phenotype of breast cancer cells.

Animals↗
PubMed2000

Multiple ionization and fragmentation of negatively charged fullerene ions by electron impact

Cross sections for the electron-impact multiple ionization and fragmentation of negatively charged fullerene ions C(-)(n) ( n = 60, 70) to C(q+)(n-m) ( q = 1,2,3 and m = 0,2,4) have been measured for electron energies up to 1 keV. In the case of pure ionization all threshold energies are about 10 eV higher than the values expected. This shift, however, is not observed for the fragment ions. The experimental data indicate that there is no strong electron-electron interaction between the incident electron and the attached electron. A novel ionization mechanism is proposed which can be expected to be valid for all negatively charged molecular or cluster ions which are able to shield the attached electron from the incident electron.

Journal Article↗
PubMed2000

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Journal Article↗
PubMed2000

Estrus and estrogen changes in mated and unmated free-living European ground squirrels.

The course of behavioral and vaginal estrus and patterns of circulating estrogens were followed in free-living European ground squirrels (Spermophilus citellus) after their emergence from hibernation. Normally mating females were compared to a second group in an area where males had been removed from the population before female emergence. Both groups showed vaginal estrus, but the patterns differed. Mating shortened vaginal estrus to a 3-day period compared to 8 days in unmated females. The extent (cell number) of cell cornification during estrus and the cellular components (percentage distribution) of metestrus did not differ between the two groups. Females in the area without males had significantly higher estrogen levels during estrus and metestrus compared to those in the control area. European ground squirrels were found to be monestrous, as none of the unmated females reentered estrus after metor diestrus was detected. The prolongation of vaginal estrus in unmated females can be viewed as either a physiological inevitability or an adaptation to low mate availability. The extension is still relatively short compared to other sciurid species and perhaps a product of constraints producing a strict time frame for reproduction.

Animals↗
PubMed2000

Phylogenetic Analysis of Bacterial Communities Associated with Leaves of the Seagrass Halophila stipulacea by a Culture-Independent Small-Subunit rRNA Gene Approach.

The phylogenetic diversity of the bacterial community associated with leaves of the marine plant Halophila stipulacea in the northern Gulf of Elat was examined by 16S rRNA gene (rDNA) sequence analyses of a clone library. For 59 clones corresponding to 51 ARDRA (amplified rDNA restriction analysis) groups, the sequence of approximately 1 kb was determined, and the fraction of the corresponding ARDRA groups of the leaf library was calculated. The class Proteobacteria was represented by 62.6% of the clone sequences. Most sequences originated from members of the gamma-subclass (27.3%), affiliated with members of the genera Pseudomonas, Vibrio, Marinomonas, Oceanospirillum, and other marine groups. Affiliation to the alpha-subclass was determined for 24.2% of the sequences. They were related to the genera Hyphomonas, Roseobacter, Ruegeria, and Rhizobiaceae. Several alpha-proteobacterial sequences were distantly related to known sequences. Only 4% of the clone sequences were related to beta-Proteobacteria. Additionally, 7.1% of the sequences possibly belonged to the class Proteobacteria, but branched deeply from known subclasses. Several sequences were affiliated to members of the orders Verrucomicrobiales and Planctomycetales, the Holophaga/Acidobacterium phylum, and chloroplasts of marine diatoms. </hea

Journal Article↗
PubMed2000

Bilateral papilledema from a massive intracranial epidermoid cyst.

PURPOSE: To report an unusual case of bilateral papilledema from a large intracranial epidermoid cyst. METHODS: Case report. RESULTS: A 26-year-old man presented with visual loss, bilateral papilledema, and only a few neurological symptoms. Magnetic resonance imaging disclosed such a large lesion that his right cerebral hemisphere was compressed to one half its normal size. Histopathologic examination of the completely removed tumor revealed an epidermoid cyst. CONCLUSION: This unique case involved a patient with bilateral papilledema caused by a huge intracranial epidermoid cyst. Epidermoid tumors should be considered in the differential diagnosis of papilledema.

Adult↗
PubMed2000

Assessment of the adhesion quality of fusion-welded silicon wafers with nonlinear ultrasound

Diffusion bonded silicon wafers are employed in the semiconductor industry. Their bonding quality must be monitored by a nondestructive testing technique. We present an ultrasonic technique allowing us to monitor the quality of the diffusion bond by measuring the anharmonic content of a transmitted ultrasonic wave. The anharmonicity is caused by weak bonds and manifests itself at high dynamic strains exerted by the ultrasonic wave. The source of nonlinearity is located in the rim of delaminations in the interface.

Journal Article↗
PubMed2000

Quantitative determination of contact stiffness using atomic force acoustic microscopy

Atomic force acoustic microscopy is a near-field technique which combines the ability of ultrasonics to image elastic properties with the high lateral resolution of scanning probe microscopes. We present a technique to measure the contact stiffness and the Young's modulus of sample surfaces quantitatively, with a resolution of approximately 20 nm, exploiting the contact resonance frequencies of standard cantilevers used in atomic force microscopy. The Young's modulus of nanocrystalline ferrite films has been measured as a function of oxidation temperature. Furthermore, images showing the domain structure of piezoelectric lead zirconate titanate ceramics have been taken.

Journal Article↗
PubMed2000

The effect of blood flow promoting drugs on cochlear blood flow, perilymphatic pO(2) and auditory function in the normal and noise-damaged hypoxic and ischemic guinea pig inner ear.

The effect of blood flow promoting drugs, such as hydroxyethyl starch (HES) either of low or high molecular weight (HES 70, HES 200), pentoxifylline, ginkgo biloba, naftidrofuryl and betahistine, and various combinations of the drugs was studied in unexposed and noise-exposed (broad-band noise, bandwidth 1-12 kHz, 106 dB SPL, 30 min) guinea pigs. The results were compared without therapy and placebo (isotonic saline, NaCl). The cochlear blood flow (CoBF) and the partial pressure of oxygen in the perilymph (PL-pO(2)) were continuously and simultaneously recorded over a period of 210 min. In addition, cochlear microphonics (CMs), compound action potentials of the auditory nerve (CAPs) and auditory brain stem responses (ABRs) were registered. Noise-induced hearing loss (NIHL) paralleled a decrease of PL-pO(2). Both were found to occur before evidence of reduced CoBF. PL-pO(2) and CoBF declined progressively post-exposure, while CMs, CAPs and ABRs showed no further deterioration or signs of recovery up to 180 min after cessation of noise. Treatment started 60 min post-exposure, respectively after 90 min, without manipulation in unexposed animals, and was then studied for a further 120 min. In unexposed animals, CoBF increased significantly during infusion of HES 70, HES 200, pentoxifylline and betahistine. NaCl, ginkgo biloba and naftidrofuryl did not alter CoBF. PL-pO(2) decreased significantly during infusion of all administered drugs and combinations, except for NaCl. CMs, CAPs and ABRs remained constant, with the exception of increased ABRs after infusion of HES 70 and HES 200. In noise-exposed animals, a sustained therapeutic effect on cochlear ischemia was achieved only by HES 200 and pentoxifylline. HES 70, betahistine and ginkgo biloba compensated cochlear ischemia only during infusion; however, 30-60 min after termination of therapy, no significant difference of values for CoBF was observed compared to the untreated noise-exposed groups. NaCl and naftidrofuryl showed no effect on CoBF. None of the applied drugs had a sustained compensatory effect on cochlear hypoxia. CMs, CAPs and ABRs improved significantly after HES 70, HES 200 and betahistine, resulting in partial recovery of CMs, and partial (betahistine) or even full (HES 70 and HES 200) recovery of CAPs and ABRs. In contrast, NaCl, pentoxifylline, ginkgo biloba and naftidrofuryl had no therapeutic effect on NIHL.

Animals↗
PubMed2000

Optimal L(1)-L(2) primary tone level separation remains independent of test frequency in humans.

Previous studies described a systematic asymmetry of the level of the 2f(1)-f(2) distortion product otoacoustic emission (DP) in the space of the primary tones levels L(1) and L(2) in normal-hearing humans. Optimal primary tone level separations L(1)-L(2), which result in maximum DP levels, were close to L(1)=L(2) at high levels, but continuously increased with decreasing stimulus level towards L(1)>L(2) (Gaskill and Brown, 1990, J. Acoust. Soc. Am. 88, 821-839). At these optimal L(1)-L(2), however, not only DP levels in normal hearing were maximal, but also trauma-induced DP reductions. A linear equation that approximates optimal L(1)-L(2) level separations thus was suggested to be optimum for use in clinical applications (Whitehead et al., 1995, J. Acoust. Soc. Am. 97, 2359-2377). It was the aim of this study to extend the generality of optimal L(1)-L(2) separations to the typical human test frequency range for f(2) frequencies between 1 and 8 kHz. DPs were measured in 22 normal-hearing human ears at 61 primary tone level combinations, with L(2) between 5 and 65 dB SPL and L(1) between 30 and 70 dB SPL (f(2)/f(1)=1.2). It was found that the systematic dependence of the maximum DP level on the L(1)-L(2) separation is independent on frequency. Optimal L(1)-L(2) level separations may well be approximated by a linear equation L(1)=a L(2)+(1-a) b (after Whitehead et al., 1995) with parameters a=0.4 and b=70 dB SPL at f(2) frequencies between 1 and 8 kHz and L(2) levels between 20 and 65 dB SPL. Below L(2)=20 dB SPL, the optimal L(1) was found to be almost constant. Following previous notions (Gaskill and Brown, 1990), an analysis of basilar membrane response data in experimental animals (after Ruggero and Rich, 1991, Hear. Res. 51, 215-230) is further presented that relates optimal L(1)-L(2) separations to frequency-selective compression of the basilar membrane. Based on the assumption that optimal conditions for the DP generation are equal primary tone responses at the f(2) place, a linear increase of the optimal L(1)-L(2) level separation is graphically demonstrated, similar to our results in human ears.

Acoustic Stimulation↗
PubMed2000

Ovine adenovirus vectors mediate efficient gene transfer to skeletal muscle.

Ovine adenovirus (OAV) vectors represent a promising tool for human gene therapy since these vectors overcome the problem of pre-existing immunity against human adenovirus vectors. In this report we investigated the in vivo characteristics of this novel vector system with respect to its potential for gene transfer into skeletal muscle. We found that moderate doses of an OAV-derived vector expressing the human alpha1-antitrypsin gene (OAVhaat) infected skeletal muscle in mice very efficiently resulting in high serum hAAT levels. The infection was restricted to skeletal muscle, but gene expression was transient and vector DNA was rapidly cleared. Vector clearance was also observed with a vector that lacked the transgene. The loss of vector DNA was accompanied by a cellular immune response in the infected muscle but was not connected with detectable expression of early or late genes of the viral backbone as analyzed by RT-PCR. A very low dose of OAVhaat (3x 10(7) infectious particles) was sufficient to produce reasonable amounts (>100 ng/ml) of serum hAAT, and this was accompanied by a weak immune response to the vector. Under these conditions, a second intramuscular injection of the same recombinant OAV vector was successful. Our study expands the known tissue tropism of OAV-derived vectors in vivo and points to the possible utility of the vector for muscle gene transfer and vaccination.

Animals↗
PubMed2000

Non-invasive measurement of intracranial pressure changes by otoacoustic emissions (OAEs)--a report of preliminary data.

Up to now changes of intracranial pressure can only be objectively assessed by invasive measurement tools e.g. epidural transducers or intraventricular or intraparenchymatous catheters. Changes of intracranial pressure (ICP) are known to influence the inner ear since the subarachnoid space is linked to the perilymphatic space of the inner ear via the cochlear aquaeduct. A new method for assessing cochlear disorders is based on otoacoustic emissions (OAE) which are generated by the outer hair cells (OHCs) of the inner ear. The aim of the present study was to find out whether changes of intracranial pressure can be monitored by spontaneous otoacoustic emissions (SOAEs), transient evoked otoacoustic emissions (TEOAEs) and distortionproduct otoacoustic emissions (DPOAEs). SOAEs, TEOAEs and DPOAEs were measured in 12 young normally hearing subjects (volunteer group) in different body postures (horizontal, -30 degrees and +30 degrees supine position). In 5 patients undergoing continuous intraventricular pressure monitoring for the assessment of normal pressure hydrocephalus (NPH), DPOAEs were measured simultaneously in different body postures as well (patient group). At an increase of ICP the SOAE-level of the volunteer group decreased by -3.3 dB SPL (sound pressure level) and the TEOAE-level by -2.1 dB SPL. The DPOAEs showed a frequency dependent reduction of its level with maximal changes at the lowest frequency tested (f2 = 1 kHz; -7.9 dB SPL). In the patient group the ICP amounted to 19.2 cm H(2)0 and the DPOAE-level also decreased particularly at lower frequencies (-2.0 dB SPL). In conclusion otoacoustic emissions, particularly DPOAEs, may provide a new clinical tool for non-invasive monitoring of ICP.

Environmental Monitoring↗
PubMed2000

Glutamate is the afferent neurotransmitter in the human cochlea.

Glutamate, the most important afferent neurotransmitter in the auditory system, is thought to be the afferent transmitter between the cochlear inner hair cells and afferent neurons, hitherto visualized only in the cochlea of animal species. It has been identified for the first time in sections from the human inner ear. L-glutamate, NMDAR2B and the enzyme glutamine synthetase were identified by using monoclonal antibodies. The distribution pattern of the transmitter L-glutamate in the human cochlea is similar to that observed in other mammals. L-glutamate was identified adjacent to outer and inner hair cells and in the spiral ganglion. Similar distributions were found for glutamine synthetase and the ionotropic NMDA receptor subunit NMDAR2. The identification of neurotransmitters and their receptors in the human cochlea has implications for the pharmacotherapy of inner ear diseases.

Adolescent↗
PubMed2000

Alpha and beta subunits of acetylcholine receptors in the human inner ear.

The localization and distribution of nicotinic acetylcholine receptors (n-ACh-r) was characterized by studying alpha and beta subunits in the adult human inner ear by FITC fluorescence technique. In the cochlea, distinct fluorescence staining occurred for beta subunits in outer hair cells (OHCs), but no alpha subunits were identified. Beta subunits differ quantitatively between the three rows of OHCs, decreasing along a base-to-apex gradient in the cochlea. Both alpha and beta subunits were identified on spiral ganglion cells, adjacent nerve fibres and in vestibular hair cells (HCs). It would appear that they form an active complex in n-ACh-r at these locations.

Adolescent↗
PubMed2000

An immunodominant, cross-reactive B-cell epitope region is located at the C-terminal part of the hamster polyomavirus major capsid protein VP1.

The VP1 represents the major capsid protein of the hamster polyomavirus (HaPV). Here we describe the mapping of epitopes along the VP1 using Escherichia coli-expressed VP1-dihydrofolate reductase (DHFR) fusion proteins and PepScan analysis. By use of DHFR fusion proteins an immunodominant region was localized in the C-terminal part of VP1 between amino acids 320-384. Further epitopes are located in the regions amino acids 1-133 and amino acids 133-320, respectively. There were no obvious differences in the reactivity between sera of tumor-bearing and papilloma-free naturally HaPV-infected hamsters. In contrast, PepScan analysis revealed linear epitopes in the regions amino acids 79-97 and amino acids 353-367 for tumor-bearing animals and amino acids 101-113 and amino acids 165-179 for papilloma-free animals. The region between amino acids 320-384 of HaPV-VP1 was found to be involved in cross-reactivity of VP1 from HaPV and other polyomaviruses. Previously we have demonstrated that heterologous expression of HaPV-VP1 allowed the formation of virus-like particles (VLPs). From epitope mapping data and structural predictions it has been suggested that HaPV-VP1-VLPs may tolerate foreign peptides in the region amino acids 81-88 and the C-terminal part of VP1.

Amino Acid Sequence↗