The importance of carotenoids in signaling during aggressive interactions between male firemouth cichlids (Cichlasoma meeki)

Male firemouth cichlids, Cichlasoma meeki, have red pigmentationcovering large areas of their ventral surface, which is displayedduring aggressive interactions. We manipulated the levels ofred pigmentation by assigning the fish to one of two diets,which were as similar as possible except that one was high incarotenoids while the other was low in carotenoids. During diadictrials under white light, fish kept on the high carotenoid dietwon a higher proportion of contests than fish kept on the lowcarotenoid diet Under green light, where differences in rednesscannot be discriminated, there was no effect of diet on theoutcome of contests. These experiments demonstrate that it isthe effect of the diet on red pigmentation that is importantrather than some confounding variable such as differential growthrates. The weight of the two fish was also important; therewas a tendency for the heavier fish to win more contests. Themass effect was subordinate to color under white light but wasthe dominant factor under green light The nature of the contestsunder the different light conditions also varied; the displayin which the red pigmentation is most obvious was not used undergreen light, but was common under white light This suggeststhat the display strategies are flexible and can be alteredaccording to which displays are most effective in a given environmentPrevious studies of other species of fish and birds have shownthat the degree of redness influences mate choice and is affectedby parasite infestations. We propose that carotenoid pigmentationis likely to reflect a general quality, influenced by severalfactors, rather than a context-specific quality such as fightingability.     

Inhibitory effect of oxygen accumulation on the growth of Spirulina platensis

Summary The growth of Spirulina platensis was studied in a light-limited culture under various dissolved oxygen (DO) concentrations. At high DO concentration, e.g. at 1.25 mM DO, the growth rate was decreased up to 36 % compared with that of 0.063 mM DO. The retarded growth rate at high DO concentrations seemed to be coupled with the degeneration of photosynthetic activity in terms of O₂ evolution. Under higher DO concentrations, superoxide dismutase and ascorbate peroxidase activities tended to increase, while the contents of photosynthetic pigment, such phycocyanin, carotenoid and chlorophyll-a decreased distinctly.     

Water Soluble Pigments Containing Xylose and Glucose in Gametangia of the Green Alga, Bryopsis maxima

Several water-soluble pigments were purified from gametangiaof Bryopsis maxima by liquid chromatography and characterizedby pyridylamination and high-performance anion-exchange chromatography.The structure of the main red pigment is proposed based on thedata of infrared spectrum, Mass spectrum, ¹H and ¹³C NMR spectraand pyridylamino analysis. As a consequence, this pigment containeda tetrapyrrole with phytol and a sugar chain comprised of xyloseand glucose. The sequence of the sugars in the chain was determinedbased on its Mass spectrum. The pigment was similar to chlorophyll-originpigments observed in other plants. No aldehyde group, however,was present at C5 in the open tetrapyrrole chain. (Received August 3, 1994; Accepted November 10, 1994)     

Sensitive force technique to probe molecular adhesion and structural linkages at biological interfaces.

Adhesion and cytoskeletal structure are intimately related in biological cell function. Even with the vast amount of biological and biochemical data that exist, little is known at the molecular level about physical mechanisms involved in attachments between cells or about consequences of adhesion on the material structure. To expose physical actions at soft biological interfaces, we have combined an ultrasensitive transducer and reflection interference microscopy to image submicroscopic displacements of probe contact with a test surface under minuscule forces. The transducer is a cell-size membrane capsule pressurized by micropipette suction where displacement normal to the membrane under tension is proportional to the applied force. Pressure control of the tension tunes the sensitivity in operation over four orders of magnitude through a range of force from 0.01 pN up to the strength of covalent bonds (approximately 1000 pN)! As the surface probe, a microscopic bead is biochemically glued to the transducer with a densely-bound ligand that is indifferent to the test surface. Movements of the probe under applied force are resolved down to an accuracy of approximately 5 nm from the interference fringe pattern created by light reflected from the bead. With this arrangement, we show that local mechanical compliance of a cell surface can be measured at a displacement resolution set by structural fluctuations. When desired, a second ligand is bound sparsely to the probe for focal adhesion to specific receptors in the test surface. We demonstrate that monitoring fluctuations in probe position at low transducer stiffness enhances detection of molecular adhesion and activation of cytoskeletal structure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differential Effects of Hypoxia on Ligand Binding Properties of Nicotinic and Muscarinic Acetylcholine Receptors on Cultured Bovine Adrenal Chromaffin Cells

Abstract: Hypoxia is known to disturb neuronal signal transmission at the synapse. Presynaptically, hypoxia is reported to suppress the release of neurotransmitters, but its postsynaptic effects, especially on the function of neurotransmitter receptors, have not yet been elucidated. To clarify the postsynaptic effects, we used cultured bovine adrenal chromaffin cells as a model of postsynaptic neurons and examined specific binding of l -[³H]nicotine (an agonist for nicotinic acetylcholine receptors: nAChRs) and ²²Na⁺ flux under control and hypoxic conditions. Experiments were performed in media preequilibrated with a gas mixture of either 21% O₂/79% N₂ (control) or 100% N₂ (hypoxia). Scatchard analysis of the specific binding to the cells revealed that the K_D under hypoxic conditions was twice as large as that under control conditions, whereas the B _max was unchanged. When the specific [³H]nicotine binding was kinetically analyzed, the association constant ( k ₁) but not the dissociation constant ( k ₋₁) was decreased to 40% of the control value by hypoxia. When the binding assay was performed using the membrane fraction, these changes were not observed. Nicotine-evoked ²²Na⁺ flux into the cells was suppressed by hypoxia. In contrast, specific [³H]quinuclidinyl benzilate binding to the intact cells was unaffected by hypoxia. These results demonstrate that hypoxia specifically suppresses the function of nAChRs (and hence, neuronal signal transmission through nAChRs), primarily by acting intracellularly.     

Block by 5-hydroxytryptamine of neuronal acetylcholine receptor channels expressed inXenopus oocytes

Summary 1. Effects of 5-hydroxytryptamine (5-HT) on neuronal nicotinic acetylcholine (ACh) receptor channels were investigated by expressing cloned channel subunits inXenopus oocytes.2. When channels were expressed with a combination of ₃ and ₄ subunits, 5-HT (10 to 300 µM) reversibly inhibited an inward current activated by 100 µM ACh in a concentration-dependent manner. The inhibition was also observed when ₃ subunit was combined with ₂ subunit instead of ₄ subunit, or ₄ subunit was combined with ₂ or _4–1 subunit instead of ₃ subunit to express channels.3. Compounds known to antagonize at 5-HT receptors (LY53857, metoclopramide and propranolol) exhibited an agonistic effect: they inhibited the ACh-activated current.4. The results suggest that 5-HT inhibits recombinant neuronal nicotinic receptor channels through a binding-site distinct from conventional 5-HT receptors. The binding-site may not be attributed to a unique type of channel subunits.     

Effects of surfactant proteins SP-B and SP-C on dynamic and static mechanics of immature lungs

Kobayashi, Tsutomu, Katsumi Tashiro, Ken Yamamoto, ShunichiNitta, Shigeo Ohmura, and Yasuhiro Suzuki. Effects of surfactant proteins SP-B and SP-C on dynamic and static mechanics of immature lungs. J. Appl. Physiol. 83(6):1849-1856, 1997.To investigate the effects of surfactantproteins B (SP-B) and C (SP-C) on lung mechanics, we compared tidal andstatic lung volumes of immature rabbits anesthetized with pentobarbitalsodium and given reconstituted test surfactants (RTS).With a series of RTS having various SP-B concentrations (0-0.7%)but a fixed SP-C concentration (1.4%), both the tidal volume with25-cmH₂O insufflation pressure and the static volume deflated to5-cmH₂O airway pressure increased, significantly correlating with the SP-B concentration: the former increased from 6.5 to 26.0 ml/kg (mean), and the latter increased from6.4 to 31.8 ml/kg. With another series of RTS having afixed SP-B concentration (0.7%) but various SP-C concentrations(0-1.4%), the tidal volume increased from 5.1 to 24.8 ml/kg,significantly correlating with the SP-C concentration, whereas thestatic volume increased from 3.4 to 32.0 ml/kg, the ceiling value, inthe presence of a minimal concentration of SP-C (0.18%). Inconclusion, certain doses of SP-B and SP-C were indispensable foroptimizing dynamic lung mechanics; the static mechanics, however,required significantly less SP-C.

     

Localization of flagellin genes on the physical map of Methanococcus voltae

Methanococcus voltae DNA, digested individually with the restriction enzymes ApaI, SacII, BamHI, or EagI, was resolved by pulsed-field gel electrophoresis reproducing the previously published digestion patterns. Hybridization of a flagellin gene-specific probe to such gels dried down (unblots) resulted in the identification of one band per enzyme harboring the flagellin genes. These bands all overlapped, revealing that an approximately 15-kb BamHI/EagI DNA fragment should harbor the flagellin genes. Double digestion with BamHI and EagI resulted in the resolution of two bands in the 15-kb region of the gel. Separation of these two fragments prior to blotting and probing with a flagellar gene-specific probe revealed that one of these fragments possessed the flagellar sequences. The presence of an EagI restriction site in flaB3 localized the flagellin genes precisely at the junction of EagI fragments Ea2 and Ea5 at approximately the 1800-kb position of the physical map.