CROSS-MODAL ADDITIVITY OF TASTE AND SMELL

Subjects were simultaneously given subthreshold levels of taste and odor stimuli, delivered orally, for both a commonly paired and an uncommonly paired taste–odor combination. Results indicate cross‐modal summation of subthreshold concentrations of both taste–odor pairs when the olfactory stimulus is delivered orally. Results of control studies suggest that the summation was indeed across modalities, and not due to the taste of the odor compound or the smell of the taste compounds. Furthermore, results indicate that regardless of taste–odor pair commonness, taste and smell can combine in a completely additive fashion (i.e., at threshold detectability when both stimuli are presented simultaneously at 50% threshold level) if the taste–odor pair is presented orally. In several instances, but not all, measured probabilities exceeded those predicted by probability summation, indicating that hyperadditive mixing often occurs, but there do seem to be individual differences. Cross‐modal summation, regardless of taste–odor pair commonness, has broader implications for the development of foods, beverages and pharmaceuticals, especially in masking undesirable tastes and smells.     

THE EFFECT OF ELECTRICAL STIMULATION UPON THE ACCUMULATION OF ADENOSINE 3'',5''-PHOSPHATE IN ISOLATED CEREBRAL TISSUE

The application of electrical pulses to slices of guinea pig cerebral cortex led to an increase in the levels of adenosine 3′,5′-phosphate (cyclic 3′,5′-AMP) of more than 11-fold within 10 min. This effect of electrical pulses was severely reduced in the presence of theophylline. Cyclic 3′,5′-AMP accumulation in slices was increased in the presence of norepinephrine and histamine about 1·5-fold and six-fold, respectively; the effect of electrical pulses was augmented in the presence of maximal amounts of either amine. For these and other reasons, the accumulation of cyclic 3′,5′-AMP induced by electrical stimulation cannot be ascribed to the release and action of either histamine or norepinephrine.     

THE EFFECT OF PORTA-CAVAL ANASTOMOSIS UPON THE ENERGY STATE AND UPON ACID-BASE PARAMETERS OF THE RAT BRAIN

Abstract— In order to evaluate the influence of porta-caval anastomosis upon the energy state of the brain, lightly anaesthetized rats were studied either 1 or 5 weeks after the shunting procedure and the brains (frontal lobe, cerebellum and brainstem) were analysed for carbohydrate substrates and organic phosphates. The ammonia contents of arterial blood, cerebrospinal fluid (CSF) and tissue increased progressively in the shunted groups and at 5 weeks the increases were three- to six-fold. In all brain structures studied there were decreases in the glucose and in the aspartate contents but regional differences existed for glucose-6-phosphate, α-ketoglutaratc and glutamate. In the brainstem the tissue contents of glucose-6-phosphate and α-ketoglutarate fell while glutamate was unchanged. Calculation of the cytoplasmatic redox state from the lactate dehydrogenase (LDH) and the malate dehydrogenase (MDH) equilibria indicated that the NADH/NAD⁺ ratio increased in the shunted groups. However, since there was no significant fall in the calculated adenylate energy charge, it is concluded that porta-caval anastomosis, and the accompanying hyperammonemia, do not disrupt the balance between production and utilization of energy in the brain.     

THE EFFECT OF OXIDANTS AND REDUCTANTS UPON THE BIOELECTRIC POTENTIAL OF NITELLA

Nitella cells were exposed to various oxidants and reductants, to determine their effect upon the bioelectric potential. These included five systems, with an E_h range from +0.454 v. to –0.288 v., a total range of 0.742 v. When proper regard was given to buffering against acidity changes, and concentration changes of Na or K ions in the oxidized and reduced forms, no significant effect upon the bioelectric potential was found: 1. When an oxidant or reductant (K ferri- or ferrocyanide) was applied instead of an equivalent normality of an "indifferent" salt (KCl). 2. In changing from a given oxidant to its corresponding reductant (ferri- to ferrocyanide; oxidized to leuco-dye, etc.). 3. When a mixture of 2 dyes, (indophenol with positive E''₀, and safranin with negative E''₀) was oxidized and reduced, to give better poising at the extremes. It is conduded that the outer surface of this cell is not influenced by the state of oxidation or reduction of the systems employed; at least it does not respond with a manifest change of bioelectric potential to changes in oxidation-reduction intensity of the medium. The cells continued to show, however, at all times their usual response to concentration changes of KCl, NaCl, etc., and to electrical stimulation.     

EVIDENCE FOR A COMMON MECHANISM OF SMELL STIMULATION IN MAN AND INSECT

The far-infrared vibrational frequencies of organic moleculeswhich given rise to specific olfactory responses in man andin insects are found to form a common linear sequence. Thisis associated with a common pattern of receptors of narrow bandwidthand implies a sensory mechanism shared by vertebrates and invertebrates.     

TASTE THRESHOLDS, TASTE SENSITIVITY AND THE EFFECTS OF ADRENALECTOMY IN RATS

A number of behavioral experiments have attempted to measurethe absolute taste thresholds in the rat. Certain aspects ofthe procedures and methods of data analysis used in these experimentsare reviewed with the suggestions that: (1) Although comparisonshave commonly been made between the taste threshold values reportedin different experiments, these are not valid because of theabsence of a common definition of threshold. (2) The high thresholdmodel on which these experiments are based may be inappropriate.(3) It is possible to measure taste sensitivity rather thantaste thresholds, and (4) Had these points been considered inprevious experiments different conclusions might have resultedregarding the effects of adrenalectomy on NaCl sensitivity.     

顺铂和噪声联合作用对听觉器官的影响

研究了顺铂与噪声联合作用对耳蜗的毒性,发现联合作用后听阈偏移大于单独顺铂作用后阈移和单独噪声作用后阈移的总和。此外,联合作用后听觉脑干诱发电位振幅下降非常明显。结果表明,顺铂与噪声联合作用对内耳的毒性有协同作用。