PSYCHOPHYSICAL CHARACTERIZATION OF MUSK CHEMICALS

The odor intensities of six commercial musks: celestolide, muskolactone,galaxolide, musk 36A^®, tonalid^®, and musk ambrette^*were matched by the method of equal odor intensity. Galaxolidewas arbitrarily used as the reference odorant in order to generatea scale for the determination of relative odor intensities.The odor intensities are expressed in terms of Stevens' psychophysicalpower function with the exponent value, b, ranging from 0.43to 0.73.     

Computerized odor psychophysical testing in mice

An automated odor psychophysical procedure was developed andused to determine absolute sensitivity to n–amyl acetate.Mice were trained to initiate a trial by interrupting a photobeamat the rear of the test chamber, then sample an odor port andindicate the presence or absence of odorant by either quicklywithdrawing from the port or by continuing to sample the port.Once the air dilution olfactometer had been adjusted prior toa training or testing session, a microcomputer was used to recordall responses by the animal, to control the delivery of stimulito the odor port and to control all events in the test chamber.Correct reponses on both odor and control trials were reinforcedand incorrect responses on both types of trials were punishedwith a forced ‘time-out’ period. The odor sensitivityof all mice was estimated, using a tracking procedure, and wasthen studied in detail using schedules in which odor concentrationswere presented in ascending, descending and random order. Withall three schedules, thresholds to n-amyl acetate were between1x10^-12 and 1 x10^-13 M. Threshold estimates obtained from twoof these same animals more than 1 year later were within 0.25log units of the original values. This method should prove valuablein future studies of nasal chemoreception in mice.     

A simple and flexible device to odorize large stimulation areas

This paper describes a flow dilution olfactometer which allowsthe odorization of large stimulation areas and the easy manipulationof several odorants and/or concentrations. Generation of theodorized air is performed by mixing in two steps the odor vaporcontained in Tedlar bags with a pure air stream flowing continuouslyout of a nozzle. Discrete concentration values are obtainedby using pre-adjusted needle valves to change the vapor flowsampled in the bags. This kind of olfactometer was utilizedto study odor coding in the olfactory bulbs of rats and rabbits.Five Odorants were delivered at concentrations ranging from2 x 10^-4 to 1.5 x 10^-2 of the saturated vapor pressure. Measurementsshowed that lower concentrations can be obtained by fillingthe bags with a more diluted odor vapor. Furthermore, the numberof test odorants can be increased at low cost by increasingthe number of Tedlar bags.     

Reconstitution of the Photosystem I Secondary Quinone Acceptor (A1) in the P700-Fx Core Isolated from Synechococcus PCC 6301

By treating a F_A/F_B-depleted P700-F_x core from SynechococcusPCC 6301 with diethylether, most of the phylloquinone was removedwithout loss of P700. The 1 ms decay of P700⁺ in the originalcore was replaced by the 25 ns decay, which was interpretedas the backreaction occurring in a P700⁺     

High resolution 2-deoxyglucose localization in olfactory epithelium

The olfactory epithelium of the salamander and the mouse hasbeen analyzed for patterns of activity elicited by odor stimulation.A high-resolution adaptation of the 2-deoxyglucose (2DG) methodwas used, involving freeze-substitution in anhydrous acetonecombined with nuclear emulsion autoradiography, according toSejnowski et al. (1980). In animals exposed to the odor of amylacetate, the autoradiograms of 2 µg thick sections showedrestricted regions of high [¹⁴C]2DG and [³H]2DG uptake. Withinthese regions, there was a characteristic pattern of diffuselocalization in the superficial supranuclear zone; small clumpsor strands of grains in the receptor cell nuclei layer; andthick clumps of grains in the basal cell layer. The relationof these patterns of differential odorinduced activity in thecells of the epithelium is discussed. ^* Present address: Department of Membrane Research, The WeizmannInstitute of Science, Rehovot, Israel     

Modification of responses of newly hatched snails by exposure to odors during development

Predatory marine snail larvae and embryos were exposed to preyodors (oyster, mussel and barnacle) during development. Whenjuvenile snails hatched they were tested by bioassay to determineeffects of this prior odor exposure. Juvenile snails were testedwith oyster, mussel and barnacle odors and with partially purifiedbarnacle odor of known attractiveness. Independent of priorodor exposure, only solutions containing barnacle odor wereattractive. Snails exposed during development to prey odorsnot in themselves attractive were more responsive to barnacleodors than snails that developed in barnacle odors. Snails notexposed to prey odors during development were intermediate intheir responsiveness. Field bioassays showed detectable attractantlevels in an environment containing barnacles. Attractant activitywas not detected in an environment where barnacles were absent.Responses of snails that developed in field odor conditionswere similar to those of snails that developed in the presenceof barnacles. Odor exposure during development is importantin determining future responses of these predatory snails toprey odors. ¹Duke University Marine Laboratory, Pivers Island, Beaufort,NC 28516, USA ²University of Miami RSMAS/MAC 4600 Rickenbacker Causeway, Miami,FL 33149, USA ³Suffolk University, Department of Biology, Beacon Hill, Boston,MA 02114, USA     

Perceptive performance and feeding behavior of calanoid copepods

The goal of this study was to determine variables associatedwith calanoid feeding behavior, and thus, to improve our understandingof the basics of calanoid feeding rates. These variables includedperiods and frequency of appendage motion, rates of cell clearance,distance at which a copepod first reacts to a cell which iseventually captured, and rate of water flow through the areacovered by the motions of a copepod's feeding appendages. Theeffects of these variables on feeding rates were determinedfor copepodids and adult females of the calanoid copepod Eucalanuspileatus at phytoplankton concentrations covering the rangeencountered by this species on the south-eastern shelf of theUSA. Our results indicate that the distance at which E.pileatusperceives phytoplankton cells increases {small tilde}2-foldas food concentrations decrease from 1.0 to 0.1 mm³ l^–1.These results lead us to hypothesize that this is due to increasedsensitivity of chemosensors on the copepods' feeding appendages.This 2-fold increase in perceptive distance amounts to a near4-fold increase in perceived volume which is close to the 6-foldincrease in volume swept clear (VSC) from 1.0 to 0.1 mm³ l^–1of Thalassiosira weissflogii. We assume that the increases inVSC by planktonic copepods, when food levels are below satiation,are largely a function of the sensory performance of the individualcopepod.     

Calcium transients in single fibers of low-frequency stimulated fast-twitch muscle of rat

Ca²⁺transients were investigated in single fibers isolated from ratextensor digitorum longus muscles exposed to chronic low-frequency stimulation for different time periods up to 10 days. Approximately 2.5-fold increases in resting Ca²⁺ concentration([Ca²⁺]) were observed 2 h after stimulationonset and persisted throughout the stimulation period. The elevated[Ca²⁺] levels were in the range characteristicof slow-twitch fibers from soleus muscle. In addition, we noticed atransitory elevation of the integral[Ca²⁺] per pulse with a maximum (~5-fold)after 1 day. Steep decreases in rate constant of[Ca²⁺] decay could be explained by an immediateimpairment of Ca²⁺ uptake and, with longer stimulationperiods, by an additional loss of cytosolic Ca²⁺ bindingcapacity resulting from a decay in parvalbumin content. A partialrecovery of the rate constant of [Ca²⁺] decayin 10-day stimulated muscle could be explained by an increasing mitochondrial contribution to Ca²⁺ sequestration.

     

Bioluminescence of the solitary spumellarian radiolarian, Thaiassicolla nucleate (Huxley)

Bioluminescence of the solitary spumellanan radiolanan, Thaiassicollanucltata(Huxley), was investigated with photon-counting radiometryand intensified videography Light emission originated from numerousmicrosouices distributed throughout the extracapsulum and propagatedat a rate of 0 5 cm s^–1. The central capsule was not asource of bioluminescence A single brief mechanical stimulusproduced a flash with a simple waveform, mean duration of 5s,and maximum photon flux of 7 x 10⁸ photons s^–1. Totalmechanically stimulable luminescence was 5x10⁹ photons per organism.Maintained mechanical stimulation caused summation of lightemission that persisted for 18 s at a stirring speed of 2000r.p.m. Lower rates of stimulation increased the period overwhich luminescence was expressed. The response to electricalpulses involved minimal excitation during stimulation, a flashwas produced only after the cessation of stimulation and includedadditional flashes superimposed on the decay of luminescenceThe night-time vertical distribution of T nudeata during May1987 in the northern Sargasso Sea had a subsurface maximum ata depth of 45 m.     

Inhibition of oyster drill chemotaxis

A bioassay was developed by Rittschof el al. (1983) to examinedistance chemoreception in the predatory marine gastropod, Urosalpinxcinerea. This bioassay was used to test the effect of a senesof low mol. wt. organics on the ability of newly hatched oysterdrills to detect a prey odor released from barnacles, Balanusbalanoides. Two series of low mol. wt. organics were testedusing methanol as the reference compound. In one series, R-OH,the carbon chain length was varied from 1 to 4. In the secondseries, CH³-R, the chain length was held constant while thefunctional group, R, was varied. When these compounds were presentin the rnM range, they inhibited the creeping response of oysterdrills towards barnacle prey odor. In the CH₃-R series, inhibitionincreased in the following order: sodium acetate > ethylacetate > acetonitnle > methanol; and, in the alcoholseries C₁ to C₄, inhibition increased with increasing chainlength. No creeping response was observed when these compoundswere tested in the absence of prey odor.     

Direct block of cloned hKv1.5 channel by cytochalasins, actin-disrupting agents

The action of cytochalasins, actin-disrupting agents on human Kv1.5 channel (hKv1.5) stably expressed in Ltk^– cells was investigated using the whole cell patch-clamp technique. Cytochalasin B inhibited hKv1.5 currents rapidly and reversibly at +60 mV in a concentration-dependent manner with an IC₅₀ of 4.2 µM. Cytochalasin A, which has a structure very similar to cytochalasin B, inhibited hKv1.5 (IC₅₀ of 1.4 µM at +60 mV). Pretreatment with other actin filament disruptors cytochalasin D and cytochalasin J, and an actin filament stabilizing agent phalloidin had no effect on the cytochalasin B-induced inhibition of hKv1.5 currents. Cytochalasin B accelerated the decay rate of inactivation for the hKv1.5 currents. Cytochalasin B-induced inhibition of the hKv1.5 channels was voltage dependent with a steep increase over the voltage range of the channel's opening. However, the inhibition exhibited voltage independence over the voltage range in which channels are fully activated. Cytochalasin B produced no significant effect on the steady-state activation or inactivation curves. The rate constants for association and dissociation of cytochalasin B were 3.7 µM/s and 7.5 s^–1, respectively. Cytochalasin B produced a use-dependent inhibition of hKv1.5 current that was consistent with the slow recovery from inactivation in the presence of the drug. Cytochalasin B (10 µM) also inhibited an ultrarapid delayed rectifier K⁺ current (I_K,ur) in human atrial myocytes. These results indicate that cytochalasin B primarily blocks activated hKv1.5 channels and endogenous I_K,ur in a cytoskeleton-independent manner as an open-channel blocker. voltage-gated K⁺ channel; heart; open channel block     

Canonical Discriminant Analysis Applied to the Headspace GC Profiles of Coffee Cultivars

Chemometric methods were applied for analyzing the relationship between the classification of coffee cultivars and their volatile components. Six typical cultivars were selected from Coffea arabica L., and their headspace profiles were analyzed by GC and GC/MS. A canonical discriminant analysis, with GC peaks as the variables, suggested the existence of a relationship between the sensory characteristics and canonical variables.

The six coffee cultivars were divided into three groups, respectively having a roasted note, sweet aroma and fermented odor. It is suggested that Brazil and Mandheling varieties had a roasted note derived from methylpyrazine, while Mocha coffee had a fermented odor derived from 2,3-butanedione.     

Lipid Metabolism in Fucus serratus as Modified by Environmental Factors

The effect of changes in the environment on lipid metabolismhas been studied in the brown alga, Fucus serratus L. Lightstimulated the incorporation of radioactivity from /{^I4C/}acetateinto oleic and, especially, into linoleic acid. The same effectwas caused by lowering the incubation temperature from 15 °Cto 4 °C. Incubations in the presence of Cd ^{+ +}, Pb ^{+ +} orZn^{+ +} had no effect on the total uptake of /{¹⁴C/}acetate intothe frond tip samples, but lowered the labelling of total lipidsrelative to aqueous-soluble components. However, pre-exposureof the algae to heavy metal cations caused changes in the uptakeof radioactivity but had less effect on the relative labellingof lipids than incubations in the presence of heavy metal cations.Algae collected from sites where the dissolved levels of heavymetals were elevated, showed a decrease in the relative labellingof lipids from /{¹⁴C/}acetate. Concentrations of Cd^{+ +}, Pb⁺⁺ or Zn^{+ +} at 10 x levels found at the collection site had littleeffect on the pattern of fatty acids made by Fucus serratus. Key words: Lipid metabolism, Fucus serratus L., Environmental changes     

Acceleration of the Decay of Membrane Potential after Energization of Chloroplasts in Intact Zea mays Leaves

The relationship between dissipation of the flash-induced membranepotential across the thylakoid membrane and the high energystate was studied in Zea mays leaves. The dark decay of theflash-induced 515-nm absorbance change was accelerated by shortpreillumination of the leaf. No acceleration of the decay bypreillumination was observed when leaves were incubated in argonor CO² gas or treated with DCMU. These effects of preilluminationand incubation were reversible. The delayed fluorescence from chlorophyll a was reversibly decreasedby incubating leaves in argon or CO² gas, though the modes ofdepression were somewhat different from each other. In leavesincubated in argon or CO² gas, the phase of slow decrease ofthe intensity of prompt fluorescence during illumination reversiblydisappeared. The results suggested that the dissipation of membrane potentialgenerated by a flash was accelerated after the energizationof chloroplasts in leaves, probably by increased H^– permeabilityof the thylakoid membrane. O2 was important in maintaining (indarkness) and forming (under illumination) the high energy statein chloroplasts in intact leaves. (Received October 1, 1980; Accepted December 15, 1980)     

Cyclopiazonic acid-induced changes in the contraction and Ca2+ transient of frog fast-twitch skeletal muscle

The effects ofcyclopiazonic acid (CPA) were investigated on isolated skeletal musclefibers of frog semitendinosus muscle. CPA (0.5-10 µM) enhancedisometric twitch but produced little change in resting tension. Athigher concentrations (10-50 µM), CPA depressed twitch andinduced sustained contracture without affecting resting and actionpotentials. In Triton-skinned fibers, CPA had no significant effect onmyofibrillar Ca²⁺ sensitivity butdecreased maximal activated force at concentrations >5 µM. Inintact cells loaded with the Ca²⁺fluorescence indicator indo 1, CPA (2 µM) induced an increase inCa²⁺-transient amplitude (10 ± 2.5%), which was associated with an increase in time to peak and inthe time constant of decay. Consequently, peak force was increased by35 ± 4%, and both time to peak and the time constant of relaxationwere prolonged. It is concluded that CPA effects, at a concentration ofup to 2 µM, were associated with specific inhibition of sarcoplasmicreticulumCa²⁺-adenosinetriphosphatase inintact skeletal muscle and that inhibition of the pump directlyaffected the handling of intracellularCa²⁺ and force production.

     

Excitation, inhibition, and suppression by odors in isolated toad and rat olfactory receptor neurons

Vertebrate olfactoryreceptor neurons (ORNs) exhibit odor-induced increases in actionpotential firing rate due to an excitatory cAMP-dependent current. Fishand amphibian ORNs also give inhibitory odor responses, manifested asdecreases in firing rate, but the underlying mechanism is poorlyunderstood. In the toad, an odor-induced Ca²⁺-activatedK⁺ current is responsible for the hyperpolarizing receptorpotential that causes inhibition. In isolated ORNs, a third manner bywhich odors affect firing is suppression, a direct and nonspecificreduction of voltage-gated and transduction conductances. Here we showthat in whole cell voltage-clamped toad ORNs, excitatory or inhibitory currents were not strictly associated to a particular odorant mixture.Occasionally, both odor effects, in addition to suppression, wereconcurrently observed in a cell. We report that rat ORNs also exhibitodor-induced inhibitory currents, due to the activation of aK⁺ conductance closely resembling that in the toad,suggesting that this conductance is widely distributed amongvertebrates. We propose that ORNs operate as complex integrator unitsin the olfactory epithelium, where the first events in the process ofodor discrimination take place.

     

Modulation of cardiac Ca2+ channels by isoproterenol studied in transgenic mice with altered SR Ca2+ content

Phospholamban(PLB) ablation is associated with enhanced sarcoplasmic reticulum (SR)Ca²⁺ uptake and attenuation of thecardiac contractile responses to -adrenergic agonists. In thepresent study, we compared the effects of isoproterenol (Iso) on theCa²⁺ currents(I_Ca) ofventricular myocytes isolated from wild-type (WT) and PLB knockout(PLB-KO) mice. Current density and voltage dependence ofI_Ca were similarbetween WT and PLB-KO cells. However, I_Ca recorded fromPLB-KO myocytes had significantly faster decay kinetics. Iso increasedI_Ca amplitude inboth groups in a dose-dependent manner (50% effective concentration,57.1 nM). Iso did not alter the rate ofI_Ca inactivationin WT cells but significantly prolonged the rate of inactivation inPLB-KO cells. When Ba²⁺ was usedas the charge carrier, Iso slowed the decay of the current in both WTand PLB-KO cells. Depletion of SRCa²⁺ by ryanodine also slowed therate of inactivation ofI_Ca, and subsequent application of Iso further reduced the inactivation rate ofboth groups. These results suggest that enhancedCa²⁺ release from the SR offsetsthe slowing effects of -adrenergic receptor stimulation on the rateof inactivation ofI_Ca.

     

Intracellular ATP slows time-dependent decline of muscarinic cation current in guinea pig ileal smooth muscle

The effects ofintracellular nucleotide triphosphates on time-dependent changes inmuscarinic receptor cation currents (I_cat) wereinvestigated using the whole cell patch-clamp technique in guinea pigileal muscle. In the absence of nucleotide phosphates in the patchpipette, I_cat evoked every 10 min decayedprogressively. This decay was slowed dose dependently by inclusion ofmillimolar concentrations of ATP in the pipette. This required acomparable concentration of Mg²⁺, was mimicked by UTP andCTP, and was attenuated by simultaneous application of alkalinephosphatase or inhibitors of tyrosine kinase. In contrast, a suddenphotolytic release of millimolar ATP (probably in the free form) causeda marked suppression of I_cat. Submillimolarconcentrations of GTP dose dependently increased the amplitude ofI_cat as long as ATP and Mg²⁺ were inthe pipette, but, in their absence, GTP was ineffective at preventingI_cat decay. The decay ofI_cat was paralleled by altered voltage-dependentgating, i.e., a positive shift in the activation curve and reduction inthe maximal conductance. It is thus likely that ATP exerts tworeciprocal actions on I_cat, throughMg²⁺-dependent and -independent mechanisms, and that theenhancing effect of GTP on I_cat is essentiallydifferent from that of ATP.

     

Effect of creatine on contractile force and sensitivity in mechanically skinned single fibers from rat skeletal muscle

Increasing the intramuscular stores of total creatine [TCr = creatine (Cr) + creatine phosphate (CrP)] can result in improved muscle performance during certain types of exercise in humans. Initial uptake of Cr is accompanied by an increase in cellular water to maintain osmotic balance, resulting in a decrease in myoplasmic ionic strength. Mechanically skinned single fibers from rat soleus (SOL) and extensor digitorum longus (EDL) muscles were used to examine the direct effects on the contractile apparatus of increasing [Cr], increasing [Cr] plus decreasing ionic strength, and increasing [Cr] and [CrP] with no change in ionic strength. Increasing [Cr] from 19 to 32 mM, accompanied by appropriate increases in water to maintain osmolality, had appreciable beneficial effects on contractile apparatus performance. Compared with control conditions, both SOL and EDL fibers showed increases in Ca²⁺ sensitivity (+0.061 ± 0.004 and +0.049 ± 0.009 pCa units, respectively) and maximum Ca²⁺-activated force (to 104 ± 1 and 105 ± 1%, respectively). In contrast, increasing [Cr] alone had a small inhibitory effect. When both [Cr] and [CrP] were increased, there was virtually no change in Ca²⁺ sensitivity of the contractile apparatus, and maximum Ca²⁺-activated force was 106 ± 1% compared with control conditions in both SOL and EDL fibers. These results suggest that the initial improvement in performance observed with Cr supplementation is likely due in large part to direct effects of the accompanying decrease in myoplasmic ionic strength on the properties of the contractile apparatus. ergogenic aid; muscle contraction; fatigue