Detection thresholds for phenyl ethyl alcohol using serial dilutions in different solvents

Detection thresholds are typically obtained by presenting a subject with serial dilutions of an odorant. Many factors, including the solvent used to dilute the odorant, can influence the measurement of detection thresholds. Differences have been reported in detection thresholds for phenyl ethyl alcohol (PEA) when different solvents are used. In this study we used gas chromatography (GC) to investigate further the effect of solvent on odor detection thresholds. We used a single ascending method and serial dilutions of PEA in four different solvents--liquid paraffin (LP), mineral oil (MO), propylene glycol (PG) and dipropylene glycol (DPG)--to determine the PEA thresholds for 31 adult subjects. For each solvent, we prepared eight serial log base 10 step dilutions (1-8), with corresponding liquid PEA concentrations of 6.3 x 10(1)-6.3 x 10(-6) (% v/v). We found that the threshold concentrations for PEA in LP (step 6.5) and PEA in MO (step 5.5) were significantly lower (P < 0.05) than for PEA in PG (step 4.0) and DPG (step 4.0) We then used GC to measure both the liquid and gas PEA concentrations for the dilution steps prepared with LP and PG. Although there were large threshold differences in the liquid concentrations of PEA in LP and PG, the headspace gas concentrations of PEA were the same. These results demonstrate the importance of determining the gas concentration of odorant stimuli when performing odor threshold measurements, in particular when comparing odor detection thresholds obtained using different solvents.     

Olfactory discrimination ability of CD-1 mice for aliphatic aldehydes as a function of stimulus concentration

Using an operant conditioning paradigm, we tested the ability of CD-1 mice to discriminate between members of a homologous series of aliphatic aldehydes presented at four different concentrations. We found that the mice were clearly capable of discriminating between all odorant pairs when stimuli were presented at concentrations of 1, 0.01, and 0.001 ppm (corresponding to four, two, and one log unit above the highest individual detection threshold) with no significant difference in performance between these concentrations. In contrast, the animals generally failed to discriminate above chance level when stimuli were presented at 0.0001 ppm (corresponding to the highest individual detection threshold) although stimuli were clearly detectable. Further, we found a significant negative correlation between discrimination performance and structural similarity of odorants in terms of differences in carbon chain length. These findings suggest that an increase in stimulus concentration of only one log unit above detection threshold appears to be sufficient for recruitment of additional subpopulations of odorant receptors to allow for qualitative recognition of aliphatic aldehydes.     

Multiple feedback loops in the flying cockroach: excitation of the dorsal and inhibition of the ventral giant interneurons

1. In a tethered cockroach (Periplaneta americana) whose wings have been cut back to stumps, it is possible to elicit brief sequences of flight-like activity by puffing wind on the animal's body. 2. During such brief sequences, rhythmic bursts of action potentials coming from the thorax at the wingbeat frequency, descend the abdominal nerve cord to the last abdominal ganglion (A6). This descending rhythm is often accompanied by an ascending rhythm (Fig. 2). 3. Intracellular recording during flight-like activity from identified ascending giant interneurons, and from some unidentified descending axons in the abdominal nerve cord, shows that: (a) ventral giant interneurons (vGIs) remain silent (Fig. 3); (b) dorsal giant interneurons (dGIs) are activated at the onset of the flight-like activity and remain active sporadically throughout the flight sequence (Fig.4); (c) some descending axons in the abdominal nerve cord show rhythmic activity phase-locked to the flight rhythm (Fig. 5). 4. Also during such brief sequences, the cercal nerves, running from the cerci (paired, posterior, wind sensitive appendages) to the last abdominal ganglion, show rhythmic activity at the wingbeat frequency (Fig. 6). This includes activity of some motor axons controlling vibratory cercal movements and of some sensory axons. 5. More prolonged flight sequences were elicited in cockroaches whose wings were not cut and which flew in front of a wind tunnel (Fig. 1B). 6. In these more prolonged flight sequences, the number of ascending spikes per burst was greater than that seen in the wingless preparation (Fig. 8; compare to Fig. 2). Recordings from both ventral and dorsal GIs show that: in spite of the ongoing wind from both the tunnel and the beating wings, which is far above threshold for the vGIs in a resting cockroach, the vGIs are entirely silent during flight. Moreover, the vGIs response to strong wind puffs that normally evoke maximal GI responses is reduced by a mean of 86% during flight (Fig. 9). The dGIs are active in a strong rhythm (Figs. 11 and 12). 7. Three sources appear to contribute to the ascending dGI rhythm (1) the axons carrying the rhythmic descending bursts; (2) the rhythmic sensory activity resulting from the cercal vibration; and (3) the sensory activity resulting from rhythmic wind gusts produced by the wingbeat and detected by the cerci. The contribution of each source has been tested alone while removing the other two (Figs. 13 and 14). Such experiments suggest that all 3 feedback loops are involved in rhythmically exciting the dGIs (Fig. 15).     

Dual signal transduction mediated by a single type of olfactory receptor expressed in a heterologous system

Controversy exists over the relationship between the cAMP and IP3 pathways in vertebrate olfactory signal transduction, as this process is known to occur by either of the two pathways. Recent studies have shown that a single olfactory neuron responds to both cAMP- and IP3-producing odorants, suggesting the existence of an olfactory receptor protein that can recognize both ligands. In this study we found that the rat olfactory receptor I7, stably expressed in HEK-293 cells, triggers the cAMP pathway upon stimulation by a specific odorant (octanal) at concentrations lower than 10(-4) M; however, the receptor triggers both pathways at higher concentrations. This indicates that a single olfactory receptor, stimulated by a single pathway-inducing odorant, can evoke both pathways at high odorant concentrations. Using this heterologous system, both the dose-dependent response and receptor I7 specificity were analyzed. The dose-dependent Ca2+ response curve, which also includes the release of Ca2+ ions from internal stores at high odorant concentrations, was not monotonous, but had a local maximum and minimum with 10(-10) and 10(-7) M octanal, respectively, and reached a plateau at 10(-2) M octanal. The specificity of the I7 receptor was lower when exposed to higher concentrations of odorants.     

Ad libitum mixing in a taste memory task: methodological issues

Ad libitum mixing, an application of the method of adjustment in food research, was investigated and evaluated for the purpose of taste memory research. The difference between ascending and descending runs in mixing was studied using a wide range of prefill concentrations lower and higher than standard. The effect of training was studied by comparing subjects with two or 10 replications in the first session where a standard was present as a reference. Results showing higher reproduced concentrations after a 25 h time interval than those produced immediately are consistent with earlier results from within- subject designs. Thus, the difference in recall performance did not depend on the design of the study. No difference between ascending and descending runs in the mixing was observed, thus the prefill concentrations did not affect the reproduction of a given standard. There was no significant difference between produced concentrations after two and 10 replications, although a non-significant trend towards improved performance following 10 replications was observed after the 25 h time interval.      

Isometric muscle length-tension curves do not predict angle-torque curves of human wrist in continuous active movements

In this study we tested the hypothesis that during steady contractions of human wrist extensors or flexors, the torque-angle relationship during movements imposed about the wrist is predicted by the classical isometric muscle length-tension curve, with ascending, descending and ascending limbs. Angle-torque relationships were measured during steady muscle activation (10% of maximal voluntary contraction: MVC), elicited either by electrical stimulation or voluntary regulation of the electromyogram (EMG). Flexion-extension movements of constant speed (+/-10 degrees /s) were imposed on the subjects' hands with a servo actuator, either through the full physiological range of motion +/-50 degrees, or through +/-10 degrees. During extensor contractions, angle-torque curves in +/-50 degrees movements had ascending, descending and ascending limbs, as in isometric contractions. However, in +/-10 degrees movements, torque always increased with increasing muscle length and decreased with decreasing length, even over angles corresponding to the descending limb of isometric curves. For flexor activation, angle-torque curves had similar properties, though descending limbs were less obvious or absent. During imposed movements, hysteresis was observed in the angle-torque curves. This was attributed to non-linearities of the active muscles. Hysteresis reached a maximum at intermediate wrist angles and declined at maximal muscle length, contradicting the recent hypothesis that sarcomere non-uniformity is responsible for the hysteresis. We conclude that the classical isometric length-tension curve, with its prominent descending limb, does not predict angle-torque curves of human wrist muscles in continuous movements. A more appropriate model is one in which stiffness about the wrist is always positive and hysteresis is a significant factor.     

Echocardiographic assessment of aortic elastic properties with automated border detection in an ICU: in vivo application of the arctangent Langewouters model

We studied whether combined pressure and transesophageal ultrasound monitoring is feasible in the intensive care unit (ICU) setting for global cardiovascular hemodynamic monitoring [systemic vascular resistance (SVR) and total arterial compliance (C(PPM))] and direct estimation of local ascending and descending aortic mechanical properties, i.e., distensibility and compliance coefficients (DC and CC). Pressure-area data were fitted to the arctangent Langewouters model, with aortic cross-sectional area obtained via automated border detection. Data were measured in 19 subjects at baseline, during infusion of sodium nitroprusside (SNP), and after washout. SNP infusion lowered SVR from 1.15 +/- 0.40 to 0.80 +/- 0.32 mmHg.ml(-1).s (P < 0.05), whereas C(PPM) increased from 0.87 +/- 0.46 to 1.02 +/- 0.42 ml/mmHg (P < 0.05). DC and CC increased from 0.0018 +/- 0.0007 to 0.0025 +/- 0.0009 l/mmHg (P < 0.05) and from 0.0066 +/- 0.0028 to 0.0083 +/- 0.0026 cm2/mmHg (P < 0.05), respectively, at the descending, but not ascending, aorta. The Langewouters model fitted the descending aorta data reasonably well. Assessment of local mechanical properties of the human ascending aorta in a clinical setting by automated border detection remains technically challenging.     

Intranasal localizability of odorants: influence of stimulus volume

When an odorant is presented to one side of the nose and air to the other, the ability to localize which side received the odorant depends upon trigeminal nerve stimulation. It has been shown that performance on this lateralization task increases as stimulus concentration increases. In this study, we determined the influences of stimulus volume and sex on the ability to localize each of 8 odorants presented at neat concentrations: anethole, geraniol, limonene, linalool, menthol, methyl salicylate, phenyl ethanol, and vanillin. At a low stimulus volume (11 mL), only menthol was localized at an above-chance level. At a high stimulus volume (21 mL), above-chance localization occurred for all odorants except vanillin. Women were significantly better than men in localizing menthol. Stimuli rated as most intense were those that were most readily localized. The detection performance measures, as well as rated intensity values, significantly correlated with earlier findings of the trigeminal detectability of odorants presented to anosmic and normosmic subjects. This study suggests that differences in stimulus volume may explain some discrepant findings within the trigeminal chemosensory literature and supports the concept that vanillin may be a "relatively pure" olfactory stimulus.     

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.     

Odorant binding protein based biomimetic sensors for detection of alcohols associated with Salmonella contamination in packaged beef

Detection of food-borne bacteria present in the food products is critical to prevent the spread of infectious diseases. Intelligent quality sensors are being developed for detecting bacterial pathogens such as Salmonella in beef. One of our research thrusts was to develop novel sensing materials sensitive to specific indicator alcohols at low concentrations. Present work focuses on developing olfactory sensors mimicking insect odorant binding protein to detect alcohols in low concentrations at room temperature. A quartz crystal microbalance (QCM) based sensor in conjunction with synthetic peptide was developed to detect volatile organic compounds indicative to Salmonella contamination in packaged beef. The peptide sequence used as sensing materials was derived from the amino acids sequence of Drosophila odorant binding protein, LUSH. The sensors were used to detect alcohols: 3-methyl-1-butanol and 1-hexanol. The sensors were sensitive to alcohols with estimated lower detection limits of <5 ppm. Thus, the LUSH-derived QCM sensors exhibited potential to detect alcohols at low ppm concentrations.     

Functional expression and characterization of odorant receptors using the Semliki Forest virus system

The human olfactory system can recognize and discriminate a large number of different odorant molecules. The detection of chemically distinct odorants starts with the binding of an odorant ligand to a specific receptor protein on the olfactory neuron cell surface. To address the problem of olfactory perception at a molecular level, we have expressed and characterized different olfactory receptors with several expression systems. Here we provide the first documentation of functional expression of odorant receptors using the Semliki Forest virus system. The human odorant OR 17-40 receptor and the rat 17 receptor were functionally expressed in vertebrate kidney cells (HEK293) using recombinant Semliki Forest viruses. Receptors were expressed as a fusion protein with the N-terminal membrane import sequence of the guinea pig serotonin receptor. Experiments employing the Ca2+-sensitive dye fura-2 revealed a fast, transient increase in the [Ca2+]i after application of the specific agonists helional and octanal to HEK293 cells infected with viruses containing RNA for the human odorant OR 17-40 receptor and the rat 17 receptor, respectively.     

Projections of excitatory and inhibitory motor neurones to the circular and longitudinal muscle of the guinea pig colon

The aim of this study was to identify myenteric pathways to the circular and longitudinal muscle of the guinea pig proximal colon. To identify excitatory and inhibitory muscle motoneurones, we applied the neuronal retrograde tracer DiI onto the circular or longitudinal muscle layer and performed additional immunohistochemistry for nitric oxide synthase (NOS) and choline acetyltransferase (ChAT). On average 166 +/- 81 circular muscle motoneurones (CMMN) and 100 +/- 74 longitudinal muscle motoneurones (LMMN) were labelled by DiI tracing. Myenteric pathways innervating the muscle were either ascending (DiI-labelled neurones with oral projections) or descending (DiI-labelled neurones with anal projections). The circular muscle was preferentially innervated by ascending pathways (66.0 +/- 9.1%). Most ascending CMMN were ChAT-positive (87.2 +/- 8.5%), whereas descending CMMN were mainly NOS-positive (82.3 +/- 14.6%). Most ascending (62.2 +/- 11.1%) and descending (82.0 +/- 12.5%) CMMN had circumferential projection preferences (circumferential projections were longer than projections along the longitudinal gut axis). In contrast to the polarised projections to the circular muscle, the longitudinal muscle was equally innervated by ascending (46.2 +/- 15.1%) and descending (53.9 +/- 15.1%) neurones. Ascending and descending pathways to the longitudinal muscle consisted predominantly of ChAT-positive neurones (98.1 +/- 1.9% and 68.0 +/- 8.5%, respectively), and both pathways had prominent longitudinal projection preferences. Only 25.5% of the descending LMMN were NOS-positive. In conclusion, the circular muscle in the proximal colon is innervated by descending inhibitory (NOS-positive neurones) and ascending excitatory (ChAT-positive neurones) pathways. In contrast, the longitudinal muscle is primarily innervated by ascending and descending excitatory motoneurones, and only a small proportion of the descending pathway consisted of inhibitory motoneurones.     

Parameters of delay discounting assessment: number of trials, effort, and sequential effects.

Procedural variants in estimating delay discounting (DD) have been shown to yield significant within-subject differences in estimated degree of delay discounting as well as variations in the patterns of choice. The purpose of this study was to evaluate the effect of subject control over the number of trials in a delay discounting task, on degree of delay discounting. Participants were assessed with two computerized DD assessments: the full-length method presented participants with a fixed set of 240 trials, and the abbreviated task, where once participants had shown indifference between the immediate and delayed rewards, the remaining trials for that delay value were omitted. While the full-length and abbreviated methods did not differentially affect patterns of choice or estimated delay discounting, the order of presentation (ascending or descending) of immediate rewards produced differences in each measure: rate of delay discounting was significantly lower when estimated with the descending sequence; a larger proportion of area under the discounting curve was concentrated around the indifference point trial with the descending sequence; and a lower correlation was observed between estimates obtained across methods with the descending sequence.     

Intranasal Odorant Concentrations in Relation to Sniff Behavior

Knowledge on how odorants are transported through the nasal cavity to the olfactory epithelium is limited. One facet of this is how the sniffing behavior affects the abundance of odorants transferred to the olfactory cleft and in turn influences odor perception. A novel system that couples an online mass spectrometer with an odorant pulse delivery olfactometer was employed to characterize intranasal odorant concentrations of butane‐2,3‐dione (or butanedione, commonly known as diacetyl) at the interior naris and the olfactory cleft. Volunteers (n=12) were asked to perform different modes of sniffing in relation to the sniff intensity that were categorized as ‘normal’, ‘rapid’ and ‘forced’. The highest concentrations of butanedione at both positions in the nose were observed during normal sniffing, with the lowest concentrations correlating with periods of forced sniffs. This corresponded to the panelists' ratings that normal sniffing elicited the highest odor intensities. These feasibility assessments pave the way for more in‐depth analyses with a variety of odorants of different chemical classes at various intranasal positions, to investigate the passage and uptake of odorants within the nasal cavity.     

Cloning, functional expression and characterization of a human olfactory receptor.

The human olfactory system can recognize and discriminate a large number of different odorant molecules. The detection of chemically distinct odorants begins with the binding of an odorant ligand to a specific receptor protein on the olfactory neuron cell surface. To address the problem of olfactory perception at a molecular level, we have cloned, functionally expressed and characterized the first human olfactory receptor (OR 17-40). Application of a mixture of hundred different odorants elicited a transient increase in intracellular calcium at HEK 293-cells which were transfected with a plasmid containing the receptor encoding DNA and a membrane import sequence. By subdividing the odorant mixture in smaller groups we could identify a single component which represented the only effective substance: helional. Testing some structurally closely related molecules we found only one other compound which also could activate the receptor: heliotropyl acetone. All other compounds tested were completely ineffective. These findings represent the beginning of molecular understanding of odorant recognition in humans.     

Distinguishing fall activities from normal activities by velocity characteristics

The purpose of this study was to identify unique features of the velocity profile during normal and abnormal (i.e., fall) activities so as to make the automatic detection of falls during the descending phase of a fall possible. Normal activities included walking, rising from a chair and sitting down, descending stairs, picking up an object from the floor, transferring in and out of a tub, and lying down on a bed. The fall activities included tripping, forward and backward falls from standing. The horizontal and vertical velocities (V(h) and V(v)) at various locations of the trunk was measured. It was found that the V(h) and V(v) of the trunk during normal activities were within a well-controlled range, and that when the velocity in one direction increased, the velocity in the other direction usually did not. In contrast, the V(h) and V(v) demonstrated two different characteristics for the fall movement. Firstly, the magnitude of both V(h) and V(v) of the trunk increased dramatically during the falling phase, reaching up to 2-3 times that of normal velocities. Secondly, the increase of V(h) and V(v) magnitude usually occurred simultaneously, and usually about 300-400 ms before the end of the fall. These two velocity characteristics, that is, the magnitude change and the timing of the magnitude change of both V(h) and V(v), could be used to distinguish fall movements from normal activities during the descending phase of the fall. It is hoped that the application of these two velocity characteristics could lead to potentially preventing or degrading fall-related injuries in the elderly population when connected with other devices.     

Prominent roles for odorant receptor coding sequences in allelic exclusion

Mammalian odorant receptors (ORs) are crucial for establishing the functional organization of the olfactory system, but the mechanisms controlling their expression remain largely unexplained. Here, we utilized a transgenic approach to explore OR gene regulation. We determined that although olfactory sensory neurons (OSNs) are capable of supporting expression of multiple functional ORs, several levels of control ensure that each neuron normally expresses only a single odorant receptor. Surprisingly, this regulation extends beyond endogenous ORs even preventing expression of transgenes consisting of OR-coding sequences driven by synthetic promoters. Thus, part of the intrinsic feedback system must rely on elements present in the OR-coding sequence. Notably, by expressing the same transgenic ORs precociously in immature neurons, we have overcome this suppression and established a generic method to express any OR in approximately 90% of OSNs. These results provide important insights into the hierarchy of OR gene expression and the vital role of the OR-coding sequence in this regulation.     

顺式藁苯内酯口服给药在大鼠血浆和脑内的药动学特性(英文)

建立大鼠血浆和脑中Z-槀苯内酯(LIG)浓度测定的高效液相色谱法。采用Agilent Hypersil ODS C18色谱柱(150mm×4.6mm,5μm),流动相为甲醇-5%异丙醇水溶液(60:40,v/v),流速为1.0mL/min,检测波长为280nm。血浆与脑中槀苯内酯浓度线性检测范围分别为93.75~3750ng/m(r=0.9999)和93.75~3750ng/g(r=0.9997),日内及日间精密度RSD10%。本法适用于大鼠口服LIG后血浆及脑中药物浓度的研究。     

The mechanisms of the influence of the anterior and posterior hypothalamus on the electrical activity of the large hemispheres of the forebrain and on autonomic reactions in hens

Studies have been made of the effect of stimulation of the anterior and posterior hypothalamus on the electrical activity of the hemispheres, arterial blood pressure, heart and respiration rates. Mainly desynchronizing mechanisms were revealed in the ascending influences from both the anterior and posterior hypothalamus. Concerning the descending influences, it was found that stimulation of the anterior hypothalamus evokes depressor reactions, whereas stimulation of the posterior hypothalamus results in pressor reactions. Peculiarities of evolutionary development of the ascending and descending mechanisms of the posterior and anterior hypothalamus are discussed.