OFF-RESPONSE OF GUSTATORY NERVE FOLLOWING TERMINATION OF QUININE STIMULI APPLIED TO THE FROG TONGUE

After a Ringer-adapted frog tongue was stimulated with 0.001M quinine-HCl(Q-HCl) in deionized water, the Ringer rinse ofthe tongue elicited a large gustatory nerve response. Sincethe Ringer-adapted tongue did not respond to Ringer solution,this nerve response after Q-HC1 is termed an off-response. Itwas revealed that the off-response of gustatory nerve to theRinger rinse resulted from the enhancing effect of Q-HCl adaptationupon the response to 111.2 mM NaCl component of Ringer whichwas ineffective for Ringer-adapted tongue. Weaker enhancementof the response to NaCl of Ringer was also produced by adaptingthe tongue to water. Therefore, the enhancing effect of Q-HClin deionized water is the summed effect of Q-HCl solute andwater solvent. Microelectrode study revealed that during theadaptation to Q-HCl the membrance potential of some NaCl-sensitivetaste cells was more hyperpolarized than that of Ringer-adaptedstate. The larger membrane potential maintained under Q-HCladaptation was markedly depolarized by the NaCl component ofthe Ringer. This sufficient depolarization response of the tastecells might be associated with generation of the off-responsein the gustatory nerve.     

ELECTRICAL VARIATIONS DUE TO MECHANICAL TRANSMISSION OF STIMULI

Mechanical stimulation of Nitella often produces responses resembling propagated negative variations but traveling faster and going past a killed spot. They appear to result from a mechanical disturbance traveling along the cell and stimulating each spot it touches (i.e. the stimulus itself travels). They are called mechanical variations to distinguish them from propagated negative variations. A mechanical disturbance may cause an irreversible change (death wave), but in traveling along the cell it may lose intensity and then produce only a reversible response (mechanical variation) which may eventually change to a propagated negative variation. The all or none law does not apply to incomplete mechanical variations, for the response varies with the strength of the stimulus.     

GUSTATORY NEURAL RESPONSE OF THE CHORDA TYMPANI TO LICK-DURATION STIMULI

NaCl solutions were flowed over the anterolateral region ofthe tongue of laboratory albino rats to determine the effectsof stimulus flow duration upon muitiunit chorda tympani nerveresponses. Fifty-five msec flow duration ‘artificial licks’delivered 5µl, while 2000 msec flow duration stimuli delivered650µl. Resonses were summated, A/D converted, and averaged,with time to stimulus presentation onset, ± 1 msec, astrigger. It was found that the latency and slope of the initialsegment of the phasic response were independent of flow duration,but they changed systematically with NaCl concentration. Slopeof both premaximum and postmaximum response was insensitiveto flow duration. In contrast, the magnitude and duration ofall segments of the phasic response were dependent upon bothstimulus flow duration and concentration. The final rising slopeof the phasic response, and the maximum response magnitude attained,were smaller, and were reached sooner, for the shorter flow,lick-duration stimuli. All maximum magnitudes to lick-durationstimuli occurred 170 msec or less after stimulus on-set. Thisis similar to the interval between actual licks. The contributionto the observed response differences of total number of fungiformpapillae stimulated, total number of receptor sites available,and rate of stimulus spread, was estimated.     

TAXIMETRICS AS APPLIED TO THE GENUS LITHOPHRAGMA (SAXIFRAGACEAE)

A taximetric analysis of Lithophragma, a genus endemic to North America containing 10 taxa, reveals a close similarity to the taxonomy proposed by the author in a recent monograph using the traditional intuitive approach. The taximetric method is based on a neo-Adansonian approach utilizing the same characters used in the intuitive study, but arbitrarily giving equal weight to all unit characters. A total of 29 unit characters was employed and although this is fewer than is considered necessary by most taximetrists to ensure reproducible results, the analysis is restricted to but a single small genus. The number of unit characters could be greatly increased by the inclusion of generic characters; however, such characters would be merely redundant and positive. A rearranged similarity matrix and dendogram are included. The conclusion is reached that taximetrics may help place plant taxonomy on an objective basis as is classification in such disciplines as physics and chemistry. Its application, however, must await extensive documentation of plant taxa on a broad basis.     

ON THE RELATION OF DIRECT CURRENTS TO CONDENSER DISCHARGES AS STIMULI

Data on the electrical stimulation of sciatic-gastrocnemius preparations of the frog by both direct currents and condenser discharges at the same time are discussed in relation to the validity of the differential equation See PDF for Equation where p is the local excitatory process, V the stimulating current or voltage, and K and k are constants. It is concluded that the constant k is the same whether it is derived from the data of the one stimulus or the other when the same fibres are being stimulated.     

INTERFERENCE OF SEX-RELATED FACTORS IN THE RESPONSE OF LIVER CELLS TO EXPERIMENTAL MITOTIC STIMULI

Stimulation of liver cell multiplication was obtained under two different experimental conditions.

• 1 A single injection of casein solution resulted in (a) an identical synchronized mitotic wave response in 10-day old male and female rats and (b) a significantly lower response in adult male rats compared to females, a difference which was reduced by castration of males at birth but essentially maintained if animals were operated when 10 days old.
• 2 Partial hepatectomy shortly after puberty resulted in active hepatocyte multiplication occurring 3 hr earlier in females than in males. This difference was suppressed when females were ovariectomized at birth and significantly reduced when they were spayed at a later age. Hepatocytes of castrated females entered actively into S phase 2 hr later than the sham-operated controls. Unilateral ovariectomy on the other hand indicated that during compensatory and/or hyper-compensatory activity of the single ovary there was a maximum difference between the male and female rate of [³H]thymidine uptake in liver nuclei 20 hr after hepatectomy. A further kinetic study (t= 25, 30, 40, 65, 90 hr) indicated no significant sex-related difference in the number of S phases per 10,000 cells.

The DNA content of regenerating versus control livers was comparable in both sexes at t= 22 and 90 hr but higher in females at t= 40 and 65 hr. A possible early postnatal interference of certain hormonal mechanisms in the receptivity to mitotic stimuli is postulated and discussed.     

猫外膝体神经元对光栅刺激方位倾向性的一种分布特性

我们检测了猫外膝体(LGN)神经元对闪烁方波光栅的反应与光栅方位的关系。对一定对比度和空间频率的光栅,26个记录到的神经元的反应均随方位不同而变化,其最大反应和最小反应的比值平均为3.0±0.3(S.E.)。神经元的最优方位(即引起最大反应的光栅方位)随其感受野中心在视网膜上的位置而异,具有平行于其各自感受野中心与视网膜中央区(area cen-sralis)的连接线的倾向。     

CONFIDENCE ELLIPSES APPLIED TO THE COMPARISON OF SENSORY PROFILES

Our experiment involved seven panels and six chocolates – five dark chocolates and one milk chocolate. The aim of the study was to compare the sensory profiles of the chocolates. A natural question to ask is “Did the panelists detect any differences among the five dark chocolates or did they systematically contrast them with the milk chocolate?” The scatter plot of the chocolates obtained by principal component analysis was useless to answer that question, because of the proximity of the points. To overcome that, we used confidence ellipses calculated using bootstrap. The originality of the study lies in the fact that we applied those ellipses to hierarchical multiple factor analysis (HMFA): among the seven panels, six were composed of trained professionals and the last one was composed of untrained students, and through that method, we managed to compare the two types of panels and balance the role of each trained panel. HMFA provides in a single scatter plot a representation of the six chocolates for each panel, the trained panels and all the panels. Confidence ellipses around each chocolate show that the combined panels – the six trained panels and also the untrained panel – differentiate the five dark chocolates. They also show how much larger the untrained panel's variability is than that of the trained panels, and how comparable are the trained panels' variability to each other.     

THE RELATION OF REPERTORY GRID/GENERALIZED PROCRUSTES ANALYSIS SOLUTIONS TO THE DIMENSIONS OF PERCEPTION: APPLICATION TO MUNSELL COLOR STIMULI

The repertory grid method (RGM) was initially devised to determine how individuals construe their worlds. There have been many attempts to extend this principle to look at relationships amongst objects, as seen by groups of individuals. However, to derive the implied consensus representation of the objects, poses conceptual and mathematical problems because of the idiosyncratic nature of constructs elicited using RGM. Generalized Procrustes analysis (GPA) offers a solution since there is no assumption of common interpretation of constructs. It is an implicit but apparently untested assumption of GPA, that mathematical and perceptual structure are analogous. To test this, combined RGM/GPA was applied to color. Using the method of triads, 24 subjects independently described constructs to characterize 26 Munsell color chips differing in Hue, Value and Chroma. Subjects then rated the colors on their own construct scales. The first six dimensions of the consequent color space were interpreted as brightness, greenness, lightness, purple/blueness, redness and yellowness. This differs from expectation only in that the colors were recovered on uni-polar dimensions rather than red-green and blue-yellow continua. However, since the main perceptual attributes of color were recovered the analogy assumption of GPA is supported, as is application to repertory grids.