Search Results - (Author, Cooperation:Wanke)

2020-09-05

The study examines how a regional university, having recently overseen a dramatic internationalization, deals with the consequences of COVID-19, and how the students - many of whom are international and coming from the global peripheries - experience the pandemic. The study is informed by the critical theory of late modernity and capitalism - especially the theory of uncertainty and risk (Beck, 1992; Beck, Giddens, & Lash 1994). It explores the power relations of the communicative dynamic between the administrators managing the crisis and the students perceiving and living it. It is an early-stage research report, published days after a pilot study was run. A survey among international students (including local, tuition-fee paying, and exchange students) was distributed to obtain initial responses. The analysis is complemented by insights based on close observation of the unfolding situation and analysis of the documents issued by the university. The findings explain the uncertainty experienced by international students, characteristic of many CE universities. The study covers the topics of attitudes towards epidemics, information imbalance, perception of security, and evaluation of the responses. The paper concludes with an urgent call to recently internationalized universities for a recognition of the complexity of students' fears.

Soziologie, Anthropologie ; Publizistische Medien, Journalismus,Verlagswesen ; Sociology & anthropology ; News media, journalism, publishing ; COVID-19; pandemic; risk; uncertainty; late modernity; critical theory; peripheries; crisis communication ; Medizinsoziologie ; interpersonelle Kommunikation ; Medical Sociology ; Interpersonal Communication ; Epidemie ; Risiko ; Universität ; Student ; Kommunikation ; epidemic ; risk ; university ; student ; communication

Zeitschriftenartikel, journal article

1077-3118

AIP Digital Archive

Physics

We have measured the room-temperature, broad-band, terahertz response of a high-speed In0.53Ga0.47As/AlAs resonant-tunneling diode from 120 GHz to 3.9 THz using the free-electron lasers at UCSB. The "rectified'' response is measured with a conventional probe station by using the tungsten probe tip as a whisker antenna. Normalizing the rectified response in the resonant-tunneling regime with the off-resonant response we remove the extrinsic frequency dependence controlled by the antenna and the RC time constant and measure an intrinsic relaxation time.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Quantum-cascade lasers operating above 20 μm (at λ∼21.5 μm and λ∼24 μm) wavelength are reported. Pulsed operation was obtained up to 140 K and with a peak power of a few milliwatts at cryogenic temperatures. Laser action originates from interminiband transitions in "chirped" superlattice active regions. The waveguides are based on surface-plasmon modes confined at a metal–semiconductor interface. The wavelengths were chosen in order to avoid major phonon absorption bands, which are particularly strong at energies just above the reststrahlen band. We also report on a 21.5-μm-wavelength laser based on a two-sided interface-plasmon waveguide. © 2001 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The longest wavelength III–V semiconductor laser to date has been realized employing a quantum cascade configuration for the active material. It operates at λ∼19 μm on interminiband transitions in graded superlattices. The waveguide is based on surface plasmon modes confined at a metal–semiconductor interface. The devices emit peak output powers of 14 mW per facet at 10 K and laser action is achieved up to the maximum temperature of 145 K. © 2000 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

An "injectorless" quantum-cascade (QC) laser is presented. The requirement of using injector regions to transport electrons from the lower laser level and other low-lying energy levels of one active region to the upper laser level of the next electron-downstream active region was eliminated by using an appropriately designed double-quantum-well "chirped" superlattice active region. The major advantage of the "injectorless" QC laser is the close packing of the active regions and the concomitant large optical confinement factor. Using a cascade of 75 consecutive active regions, designed for emission at λ=11.5 μm, a pulsed peak output power of 270 mW is achieved at 7 K and approximately 10 mW at the maximum operating temperature of 195 K. © 2001 American Institute of Physics.

Electronic Resource

1398-9995

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Sensitization to mould spores was investigated in six patients with hypersensitivity pneumonitis, eight patients with idiopathic lung fibrosis, and six healthy controls by immunodiffusion and immunofluorescent testing of personal spore samples. The new technique of personal spore sampling with the Burkard personal volumetric air sampler and indirect immunofluorescent test for detection of spore-specific IgG and IgM confirmed that five patients with hypersensitivity pneumonitis and four with lung fibrosis were actually exposed and sensitized to moulds. Personal spore sampling and subsequent immunofluorescent tests represent sensitive tools for detection of individual mould sensitization and air quality control.

Electronic Resource

1398-9995

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The risk factors for sensitization to pets was investigated in 169 male pupils. A recent or former contact with cats. Dogs, and guinea pigs in own home was reported in 52 (30.8%), 42 (24.9%), and 20 (11.8%) study subjects, respectively. Clinically manifested allergy was found in two probands to cat and in two others to guinea pigs, three of them had formerly had pets and one proband with allergic rhinitis to cats had never had any pet. Sensitization to animals and aeroallergens was investigated with Phadezym-RAST. Only owners of cats had a higher incidence of cat sensitization than probands without direct contact (26.9% versus 10.3%, P〈0.01). No statistically significant difference in sensitization to dogs and guinea pigs was found in groups with and without these pets. A strong correlation existed between sensitization to pets and other aeroallergens (house dust mite: P〈0.025 birch pollen: P〈0.0001, mugwort: P〈0.0001, and grass pollens: P〈0.0001). No association was found between sensitization to pets an smoking history, brochial hyperreactivity to methacholine or radiological findings of the paranasal sinus.

Electronic Resource

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1460-9568

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Quail neural crest cells were cultured in a differentiative medium to study the inward K+ channel profile in neuronal precursors at various stages of maturation. Between 12 and 24 h of culture, neural crest-derived neurons displayed, in addition to the previously described outward depolarization-activated K+ currents, an inward current enhanced in high K+ medium. A biophysical and pharmacological analysis led us to conclude that this inward K+ current is identical to that previously demonstrated in mouse and human neuroblastoma cell lines (IIR). This current (quail IIR or qllR), which is active at membrane potentials positive to -35 mV, was blocked by Cs+ and by class Ill antiarrhythmic drugs, thus resembling the K+ current encoded by the human ether-a-go-go-related gene (HERG). At later stages of incubation (〉48 h), neural crest-derived neurons underwent morphological and biochemical differentiation and expressed fast Na+ currents. At this stage the cells lost qllR, displaying instead a classical inward rectifier K+ (IRK) current (quail IIRK= qIIRK). This substitution was reflected in the resting potential (VREST), which became hyperpolarized by 〉20 mV compared with the 24 h cells. Neurons were also harvested from peripheral ganglia and other derivatives originating from the migration of neural crest cells, viz. ciliary ganglia, dorsal root ganglia, adrenal medulla and sympathetic chain ganglia. After brief culture following harvesting from young embryos, ganglionic neurons always expressed qilR. On the other hand, when ganglia were explanted from older embryos (7–12 days), briefly cultured neurons displayed the IRK-like current. Again, in all the above derivatives the qllR substitution by qllRK was accompanied by a 20 mV hyperpolarization of VREST. Together, these data indicate that the VREST of normal neuronal precursors is sequentially regulated by HERG- and IRK-like currents, suggesting that HERG-like channels mark an immature and transient stage of neuronal differentiation, probably the same stage frozen in neuroblastomas by neoplastic transformation.

Electronic Resource

1460-9568

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Although it is widely believed that astrocytes lack excitability in adult tissue, primitive action potential-like responses have been elicited from holding potentials negative to −80 mV, in cultured and injury-induced gliotic rodent astrocytes and in human glia under pathological conditions such as glioblastomas and temporal lobe epilepsy. The present study was designed to investigate the properties of astrocytes (identified by immunoreactivity for glial fibrillary acidic protein) derived from multipotent human embryonic CNS stem cells and cultured for 12–25 days in differentiating conditions. We describe here for the first time that brief (1 ms) current pulses elicit spikes from a resting potential (VREST) of ≈ −37 mV and, more interestingly, that spontaneous firing can be occasionally recorded in human astrocytes. A voltage-clamp study revealed that in these cells: (i) the half-inactivation of the tetrodotoxin (TTX)-sensitive Na+ channels is around VREST; (ii) the delayed rectifier K+ current is very small; (iii) the ever-present transient outward A-type K+ channels are paradoxically capable of inhibiting the action potentials elicited from a negative membrane potential (−55 to −60 mV); and (iv) inwardly rectifying currents are not present. The responses predicted from a simulation model are in agreement with the experiments. As suggested by recent studies, the decrease of Na+ channel expression and the changes of the electrophysiological properties during the postnatal maturation of the CNS seem to exclude the possibility that astrocytes may play an excitable role in adult tissue. Our data show that excitability and firing should be considered an intrinsic attribute of human astrocytes during CNS development. This is likely to have physiological importance because the role of astrocytes during development is different from the [K+]o-buffering role played in adult CNS, namely the glutamate release and/or the guiding of migrating neurons.

Electronic Resource

1460-9568

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Action potentials generated by voltage-dependent Ca2+ conductances were studied at 25°C with the perforated-patch technique, in freshly dispersed adult rat sensory neurons perfused with Na-free solutions containing tetraethylammonium. Brief depolarizing currents from membrane potentials negative to –75 mV always elicited long (〉100 ms) plateau spikes which had different thresholds in different neurons: a low threshold around –60/–50 mV and a high-threshold at –30/–20 mV. Stimulations from potentials positive to –55 mV, on the contrary, elicited spikes originating only in the high threshold region and sensitive to 25 μM Cd2+, designated high-threshold spikes. In neurons which showed spikes with low threshold, addition of 25 μM Cd2+ disclosed a smaller and shorter regenerative response, the low-threshold spike. Moreover, the classical ‘anode-break’ stimulation from –50/–60 mV uncovered isolated low-threshold spikes, indicating a time- and voltage-dependent de-inactivating process. From the properties of the low (LVA) and high (HVA) voltage-activated Ca2+ currents, recorded under the same extracellular conditions, a Hodgkin–Huxley model was derived and used to reconstruct all the features of the recorded spikes. The model was also able to simulate experimental blocking of LVA channels by amiloride, modulation of HVA channels by baclofen and induced oscillatory firing. This agreement between the behaviour of recorded spikes and their mathematical description led us to conclude that the LVA and HVA Ca2+ currents underlie the low- and high-threshold Ca2+ spikes, respectively. Furthermore, our data suggest that complex behaviour known to be typical of central nervous system neurons is also present in sensory peripheral neurons.

Electronic Resource

1460-9568

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

We studied, in rat sensory neurons, the modulation of high voltage-activated Ca2+ currents (ICa mediated by the pertussis toxin-sensitive activation of muscarinic receptors, which were found to be of subtypes M2, or M4. Muscarine reversibly blocked somatic Ca2+ spikes but strong predepolarizations only partially relieved the inhibited Ca2+ current. On the other hand, the putative coupling messenger could not rapidly diffuse towards channels whose activity was recorded from a macro-patch. The perforated patch technique virtually prevented the response rundown present during whole-cell experiments. Both ω-conotoxin GVIA (ω-CgTx)-sensitive channels and ω-CgTx- and dihydropyridine-resistant channels are coupled to the muscarinic receptor, but not the L-channel. When measured in the same neuron, dose - response relationships for the first and subsequent agonist applications differed; maximal inhibition, the reciprocal of half-maximal concentration and the Hill coefficient were always highest in the first trial. Muscarine and oxotremorine exhibited monotone dose - response curves, but oxotremorine-M showed non-linear relationships which became monotonic when cells were intracellularly perfused with inhibitors of protein kinase A (PKA) and C (PKC), suggesting that either PKA or receptor-induced PKC could phosphorylate and thus inactivate G-proteins or other unknown proteins involved in inhibitory muscarinic actions on ICa. In summary, these data provide a preliminary pharmacological characterization of the muscarinic inhibition of the Ca2+ channels in sensory neurons, with implications about agonist specificity and the interplay between signalling pathways.

Electronic Resource

1460-9568

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The voltage-dependent K+ channels belonging to the ether-à-go-go family (eag, erg, elk) are widely expressed in the mammalian CNS. Their neuronal function, however, is poorly understood. Among the elk clones, elk2 is the most abundantly expressed in the brain. We have characterized the human ELK2 channel (HELK2) expressed in mammalian cell lines. Moreover, we have detected helk2 mRNA and ELK2-like currents in freshly dissociated human astrocytoma cells. HELK2 was inhibited by Cs+ in a voltage-dependent way (Kd was 0.7 mm, at −120 mV). It was not affected by Way 123398 (5 µm), dofetilide (10 µm), quinidine (10 µm), verapamil (20 µm), haloperidol (2 µm), astemizole (1 µm), terfenadine (1 µm) and hydroxyzine (30 µm), compounds known to inhibit the biophysically related HERG channel. The crossover of the activation and inactivation curves produced a steady state ‘window’ current with a peak around −20 mV and considerably broader than it usually is in voltage-dependent channels, including HERG. Similar features were observed in the ELK2 clone from rat, in the same experimental conditions. Thus, ELK2 channels are active within a wide range of membrane potentials, both sub- and suprathreshold. Moreover, the kinetics of channel deactivation and removal of inactivation was about one order of magnitude quicker in HELK2, compared to HERG. Overall, these properties suggest that ELK2 channels are very effective at dampening the neuronal excitability, but less so at producing adaptation of action potential firing frequency. In addition, we suggest experimental ways to recognize HELK2 currents in vivo and raise the issue of the possible function of these channels in astrocytoma.

Electronic Resource

1460-9568

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

In this report we studied and compared the biochemical and the electrophysiological characteristics of two cell lines (GT1-7 and GN11) of immortalized mouse LHRH-expressing neurons and the correlation with their maturational stage and migratory activity. In fact, previous results indicated that GN11, but not GT1-7, cells exhibit an elevated motility in vitro. The results show that the two cell lines differ in terms of immunoreactivity for tyrosine hydroxylase and nestin as well as of production and release of 3,4-dihydroxyphenylalanine (DOPA) and of intracellular distribution and release of the LHRH. Patch-clamp recordings in GN11 cells, reveal the presence of a single inward rectifier K+ current indicative of an immature neuronal phenotype (neither firing nor electrical activity). In contrast, as known from previous studies, GT1-7 cells show the characteristics of mature LHRH neurons with a high electrical activity characterized by spontaneous firing and excitatory postsynaptic potentials. K+-induced depolarization induces in GT1-7 cells, but not in GN11 cells, a strong increase in the release of LHRH in the culture medium. However, depolarization of GN11 cells significantly decreases their chemomigratory response. In conclusion, these results indicate that GT1-7 and GN11 cells show different biochemical and electrophysiological characteristics and are representative of mature and immature LHRH neurons, respectively. The early stage of maturation of GN11 cells, as well as the low electrical activity detected in these cells, appears to correlate with their migratory activity in vitro.

Electronic Resource

1460-9568

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

ERG (ether-à-go-go-related gene) K+ channels are crucial in human heart physiology (h-ERG), but are also found in neuronal cells and are impaired in Drosophila‘seizure' mutants. Their biophysical properties include the relatively fast kinetics of the inactivation gate and much slower kinetics of the activation gate. In order to elucidate how the complex time- and voltage-dependent activation properties of ERG channels underlies distinct roles in excitability, we investigated different types of ERG channels intrinsically present in cells or heterologously expressed in mammalian cells or Xenopus oocytes. Voltage-dependent activation curves were highly dependent on the features of the eliciting protocols. Only very long preconditioning times produced true steady-state relationships, a fact that has been largely neglected in the past, hampering the comparison of published data on ERG channels. Beyond this technical aspect, the slow activation property of ERG can be responsible for unsuspected physiological roles. We found that around the midpoint of the activation curve, the time constant of ERG open–close kinetics is of the order of 10–15 s. During sustained trains of depolarizations, e.g. those produced in neuronal firing, this leads to the use-dependent accumulation of open-state ERG channels. Accumulation is not observed in a mutant with a fast activation gate. In conclusion, it is well established that other K+ channels (i.e. Ca2+-activated and M) control the spike-frequency adaptation, but our results support the notion that the purely voltage-dependent activation property of ERG channels would allow a slow inhibitory physiological role in rapid neuronal signalling.

Electronic Resource

1365-2958

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Medicine

Amino acid limitation results in impaired sexual fruit body formation in filamentous fungi such as Aspergillus nidulans. The starvation signal is perceived by the cross-pathway regulatory network controlling the biosynthesis of translational precursors and results in increased expression of a transcriptional activator encoded by a c-Jun homologue. In the presence of amino acids, the gene product of the mammalian RACK1 homologue cpcB is required to repress the network. Growth under amino acid starvation conditions permits the initiation of the sexual developmental programme of the fungus, but blocks fruit body formation before completion of meiosis. Accordingly, arrest at this defined control point results in microcleistothecia filled with hyphae. Addition of amino acids results in release of the block and completion of development to mature ascospores. The same developmental block is induced by either overexpression of c-Jun homologues or deletion of the RACK1 homologue cpcB of A. nidulans in the presence of amino acids. Therefore, the amino acid starvation signal regulates sexual development through the network that also controls the amino acid biosynthetic genes. Expression of the RACK1 gene suppresses the block in development caused by a deletion of cpcB. These data illuminate a connection between metabolism and sexual development in filamentous fungi.

Electronic Resource

1365-2958

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Medicine

The role of mild oxidative stresses elicited by diethylmaleate (DEM)-induced glutathione depletion in the progression of the yeast cell cycle has been investigated. We found that different wild-type strains are sensitive to oxidative stresses induced by similar DEM doses: ≈ 1 mM on YPD plates, 5–10 mM in shaken flasks. At lower doses, DEM caused a transient decrease in growth rate, largely because of a decreased G1-to-S transition. Treatment with higher DEM doses leads to complete growth arrest, with most cells found in the unbudded G1 phase of the cell cycle. DEM treatment resulted in transcriptional induction of stress-responsive element (STRE)-controlled genes and was relieved by treatment with the antioxidant N-acetyl cysteine. Reciprocal shift experiments with cdc25 and cdc28 mutants showed that the major cell cycle arrest point was located in the Start area, at or near the CDC25-mediated step, before the step mediated by the CDC28 cyclin-dependent kinase. The DEM-induced G1 arrest requires a properly regulated RAS pathway and can be bypassed by overexpressing the G1-specific cyclin CLN2. However, cells with either a deregulated RAS pathway or overexpressing CLN2 failed to grow and arrested as budded cells, indicating that a second DEM-sensitive cell cycle step exists.

Electronic Resource

1365-2958

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Medicine

The general control transcriptional regulator gene cpcA of Aspergillus niger was cloned by complementation of a Saccharomyces cerevisiaeΔgcn4 mutant strain. The encoded protein conferred resistance to amino acid analogues when expressed in yeast. Disruption of cpcA in A. niger resulted in a strain which is sensitive towards 3-aminotriazole and fails to respond to amino acid starvation. cpcA encodes a transcript of ≈2400 nucleotides in length that includes a 5′ leader region of 900 nucleotides. The 5′ leader region contains two small open reading frames, suggesting translational control of gene expression. Steady-state mRNA levels of cpcA increase by a factor of three upon amino acid starvation. The coding region of cpcA is interrupted by a 57 bp intron and the deduced amino acid sequence displays an ≈30% overall identity to yeast GCN4p and Neurospora crassa cpc-1p. Critical amino acid residues of the transcriptional activation domains of GCN4p are conserved in cpcAp. The basic DNA-binding domain shows up to 70% amino acid sequence identity to other basic zipper (bZIP)-type transcriptional activators. cpcAp binds specifically to a GCN4p recognition element in gel retardation experiments. The C-terminal dimerization domain encodes a leucine zipper with only a single leucine residue.

Electronic Resource

1398-9995

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Respiratory allergies and subclinical sensitization to aeroallergens were investigated in 129 rural and in 222 urban probands. The incidence of respiratory allergies was not significantly higher in the urban residents. Sensitization to aeroallergens was investigated with Phadezym RAST (house dust mite, Cladosporium, orchard grass, birch pollens) and the Phadiatop multi RAST and found to be significantly more frequent in polluted than in unpolluted areas. Allergen-specific IgE was detected n 37.8% of urban probands and in 25.6% of rural probands with Phadezym RAST (P 〈 0.025) and a positive Phadiatop multi RAST was found in 43.7% versus 32.6 (P 〈 0.05).

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