Publications by authors named "Olav Sand"

My interest in fish bioacoustics was ignited more than 50 years ago and resulted in a zigzag time travel between various interesting problems that were unsettled at the time. The present paper gives a brief overview of the main topics I have worked on in the field of fish hearing, i.e.

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Synthesis and release of FSH and LH are differentially regulated by GnRH, but the mechanisms by which this regulation is achieved are not well understood. Teleost fish are powerful models for studying this differential regulation because they have distinct pituitary cells producing either FSH or LH. By using pituitary cultures from Atlantic cod (Gadus morhua), we were able to investigate and compare the electrophysiological properties of fshb- and lhb-expressing cells, identified by single-cell quantitative PCR after recording.

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We have characterized the response to gonadotropin-releasing hormone 2 (GnRH2) in luteinizing hormone producing cells from gfp-transgenic medaka. Teleosts have separate cells producing the two types of gonadotropins, enabling us for the first time to study the intracellular signaling that controls secretion of each gonadotropin separately. Pituitary cell cultures were prepared, and lhb-producing cells were selected by their GFP expression.

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Polymorphic ciliates, like Tetrahymena vorax, optimize food utilization by altering between different body shapes and behaviours. Microstome T. vorax feeds on bacteria, organic particles, and solutes, whereas the larger macrostome cells are predators consuming other ciliates.

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Lactobacillus plantarum C11 releases plantaricin A (PlnA), a cationic peptide pheromone that has a membrane-permeabilizing, antimicrobial effect. We have previously shown that PlnA may also permeabilize eukaryotic cells, with a potency that differs between cell types. It is generally assumed that cationic antimicrobial peptides exert their effects through electrostatic attraction to negatively charged phospholipids in the membrane.

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Ciliates feed by phagocytosis. Some ciliate species, such as Tetrahymena vorax, are polymorphic, a strategy that provides more flexible food utilization. Cells of the microstomal morph of T.

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Protocols for primary cultures of teleost cells are commonly only moderately adjusted from similar protocols for mammalian cells, the main adjustment often being of temperature. Because aquatic habitats are in general colder than mammalian body temperatures and teleosts have gills in direct contact with water, pH and buffer capacity of blood and extracellular fluid are different in fish and mammals. Plasma osmolality is generally higher in marine teleosts than in mammals.

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The swimming behaviour of ciliates is mainly determined by membrane potential and transmembrane fluxes. In a chemical gradient, swimming ciliates may approach or move away from the source. Based on experiments on Paramecium, it is generally assumed that chemical attractants and repellents affect the swimming behaviour of ciliates by specific changes in the membrane potential.

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The amplitude histogram of spontaneously occurring miniature synaptic currents (mSCs) is skewed positively at developing Xenopus neuromuscular synapses formed in culture. To test whether the quantal size of nerve-evoked quanta (eSCs) distributes similarly, we compared the amplitude histogram of single quantum eSCs in low external Ca(2+) with that of mSCs and found that nerve stimulation preferentially released large quanta. Depolarization of presynaptic terminals by elevating [K(+)] in the external solution or by direct injection of current through a patch pipette increased the mSC frequency and preferentially, but not exclusively, evoked the release of large quanta, resulting in a second broad peak in the amplitude histogram.

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The nonhemolytic enterotoxin (Nhe) produced by Bacillus cereus is a pore-forming toxin consisting of three components, NheA, -B and -C. We have studied effects of Nhe on primate epithelial cells (Vero) and rodent pituitary cells (GH(4)) by measuring release of lactate dehydrogenase (LDH), K(+) efflux and the cytosolic Ca(2+) concentration ([Ca(2+)](i)). Plasma membrane channel events were monitored by patch-clamp recordings.

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Certain antimicrobial peptides from multicellular animals kill a variety of tumor cells at concentrations not affecting normal eukaryotic cells. Recently, it was reported that also plantaricin A (PlnA), which is a peptide pheromone with strain-specific antibacterial activity produced by Lactobacillus plantarum, permeabilizes cancerous rat pituitary cells (GH(4) cells), whereas normal rat anterior pituitary cells are resistant to the peptide. To examine whether the preferential permeabilization of cancerous cells is a general feature of PlnA, we studied its effect on primary cultures of cells from rat liver (hepatocytes, endothelial, and Kupffer cells) and rat kidney cortex, as well as two epithelial cell lines of primate kidney origin (Vero cells from green monkey and human Caki-2 cells).

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Antimicrobial peptides produced by multicellular organisms protect against pathogenic microorganisms, whereas such peptides produced by bacteria provide an ecological advantage over competitors. Certain antimicrobial peptides of metazoan origin are also toxic to eukaryotic cells, with preference for a variety of cancerous cells. Plantaricin A (PlnA) is a peptide pheromone with membrane permeabilizing strain-specific antibacterial activity, produced by Lactobacillus plantarum C11.

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Plantaricin A (PlnA) is a 26-mer peptide pheromone with membrane-permeabilizing, strain-specific antibacterial activity, produced by Lactobacillus plantarum C11. We investigated the membrane-permeabilizing effects of PlnA on cultured cancerous and normal rat anterior pituitary cells using patch-clamp techniques and microfluorometry (fura-2). Cancerous cells displayed massive permeabilization within 5 s after exposure to 10-100 microM PlnA.

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The aim of the present study was to explore the electrophysiological properties of pituitary cells from Atlantic cod (Gadus morhua), as a basis for future studies of the signaling pathways involved in the control of pituitary secretion in this species. Primary cultures of pituitary cells from maturing Atlantic cod were prepared by trypsin treatment and mechanical dispersion. Electrophysiological recordings were performed using the perforated patch clamp method.

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Acoustic stimuli within the sonic range are effective triggers of C-type escape behaviours in fish. We have previously shown that fish have an acute sensitivity to infrasound also, with acceleration thresholds in the range of 10(-5) m s(-2). In addition, infrasound at high intensities around 10(-2) m s(-2) elicits strong and sustained avoidance responses in several fish species.

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