HCN channels contribute to the intrinsic activity of cochlear pyramidal cells

A hyperpolarization-activated current recorded from the pyramidal cells of the dorsal cochlear nucleus was investigated in the present study by using 150- to 200-m-thick brain slices prepared from 6- to 14-day-old Wistar rats. The pyramidal neurones exhibited a slowly activating inward current on hyperpolarization. The reversal potential of this component was –32 ± 3 mV (mean ± SE, n = 6), while its half-activation voltage was –99 ± 1 mV with a slope factor of 10.9 ± 0.4 mV (n = 27). This current was highly sensitive to the extracellular application of both 1 mM Cs⁺ and 10 M ZD7288. The electrophysiological properties and the pharmacological sensitivity of this current indicated that it corresponded to a hyperpolarization-activated non-specific cationic current (I_h). Our experiments showed that there was a correlation between the availability of the h-current and the spontaneous activity of the pyramidal cells, suggesting that this conductance acts as a pacemaker current in these neurones. Immunocytochemical experiments were also conducted on freshly isolated pyramidal cells to demonstrate the possible subunit composition of the channels responsible for the genesis of the pyramidal h-current. These investigations indicated the presence of HCN1, HCN2 and HCN4 subunits in the pyramidal cells.Received 15 May 2003; received after revision 26 June 2003; accepted 21 July 2003     

Calcium transients and intramembrane charge movement in skeletal muscle fibres

Myoplasmic calcium transients in response to pulse depolarisations have been monitored using the dye antipyralazo III, which provides a linear measure of the change in cytoplasmic free calcium concentration. Intramembrane charge movements were recorded simultaneously with the calcium transients. Except for its initial phase, the calcium transient during each pulse closely followed the time course expected for calcium redistribution between three intracellular compartments with time-independent flux coefficients. The time at which the flux coefficients attained their steady values occurred just after the intramembrane charge movement had been completed. This is the required sequence if charge movement were to control one or more coefficients f or calcium fluxes across the sarcoplasmic reliculum membrane.     

Melanoma cells exhibit strong intracellular TASK-3-specific immunopositivity in both tissue sections and cell culture

Amplification of the kcnk9 gene and overexpression of the encoded channel protein (TASK-3) seems to be involved in carcinogenesis. In the present work, TASK-3 expression of melanoma cells has been studied. For the investigation of TASK-3-specific immunolabelling, a monoclonal antibody has been developed and applied along with two, commercially available polyclonal antibodies targeting different epitopes of the channel protein. Both primary and metastatic melanoma cells proved to be TASK-3 positive, showing prominent intracellular TASK-3-specific labelling; mostly concentrating around or in the proximity of the nuclei. The immunoreaction was associated with the nuclear envelope, and with the processes of the cells and it was also present in the cell surface membrane. Specificity of the immunolabelling was confirmed by Western blot and transfection experiments. As TASK-3 immunopositivity of benign melanocytes could also be demonstrated, the presence or absence of TASK-3 channels cannot differentiate between malignant and non-malignant melanocytic tumours.     

A conserved microRNA module exerts homeotic control over Petunia hybrida and Antirrhinum majus floral organ identity

It is commonly thought that deep phylogenetic conservation of plant microRNAs (miRNAs) and their targets indicates conserved regulatory functions. We show that the blind (bl) mutant of Petunia hybrida and the fistulata (fis) mutant of Antirrhinum majus, which have similar homeotic phenotypes, are recessive alleles of two homologous miRNA-encoding genes. The BL and FIS genes control the spatial restriction of homeotic class C genes to the inner floral whorls, but their ubiquitous early floral expression patterns are in contradiction with a potential role in patterning C gene expression. We provide genetic evidence for the unexpected function of the MIRFIS and MIRBL genes in the center of the flower and propose a dynamic mechanism underlying their regulatory role. Notably, Arabidopsis thaliana, a more distantly related species, also contains this miRNA module but does not seem to use it to confine early C gene expression to the center of the flower.     

Operational and Strategic Decisions in Hospitality. Lessons from an Action Research Process

Systemic Practice and Action Research - The aim of this article is to find measures that reduce personnel costs in a catering company through the optimization of routes and tasks for staff to...     

Demonstration of poliomyelitis virus in homogenates and ureadesoxycholate lysates of cells exhibiting or lacking cytopathogenicity

Zusammenfassung Stark cytolytisch wirkende Urea-Desoxycholatlösung zertört die biologische Aktivität des Poliovirus (Typ I, Mahoney-Stamm)nicht; somit ist dieses Mittel zur Freisetzung infektiösen Materials aus latent oder manifest infizierten Zellkulturen sehr geeignet.     

Renal lesions induced by the simultaneous administration of angiotensin and hexadimethrine bromide

Zusammenfassung Einmalige Verabreichung von Angiotensin oder Hexadimethrin-bromid verursacht bei der Ratte keine signifikante Schädigung der Nierenrinde. Wird zuerst Angiotensin und wenige Minuten später Hexadimethrin-bromid injiziert, so kommt es zu Nierenrindeninfarkten, fokalen glomerulären und tubulären Nekrosen.