Bilateral integration in the common chemical sense.

Human participants judged the pungency of various concentrations of carbon dioxide presented to one nostril, the other nostril, or both (dichorhinic stimulation). Perceived magnitude grew sharply with concentration over the range explored. The combinatorial rule of bilateral integration followed the Pythagorean theorem: the effective mass in a bilateral stimulus equalled the square root of the sum of squares of the mass entering each nostril. This simple rule implies a possible mutual inhibitory interaction between the two nostrils, but it also implies partial spatial summation of the sensory impact of bilaterally presented concentrations. When persons inhale a relatively strong irritant, such as the higher concentrations used here, they will exhibit a very brief reflex interruption of inhalation. An experiment on the threshold for the reflex implied that it too followed the Pythagorean rule of integration. This occurred for both males and females, though females displayed a lower threshold for the reflex, whether evoked unilaterally or bilaterally. This reflex may hold promise as an objective indicator of functional status of the nasal common chemical sense.

Relationships between ingestion and gustatory perception of caffeine.

We observed that taste detection thresholds for caffeine (CAF) are elevated in habitual CAF users relative to nonusers. A series of experiments were carried out to explore that relationship and assess the influences of salivary CAF and acute vs. chronic CAF ingestion. A significant correlation between CAF ingestion and taste threshold was noted in two studies of U.S. adults, although this was not observed in a parallel study involving an Argentinean population. Acute CAF ingestion (5.5 mg/kg) had no appreciable effect on taste thresholds. Threshold values greatly exceeded even peak salivary CAF levels, indicating that classical taste adaptation was an unlikely influence. Chronic CAF ingestion (450 mg/day for 3 weeks) also had no consistent effect on taste thresholds for CAF or other taste stimuli. Although a number of explanations are considered, we suggest that the sensory phenomenon may reflect preexisting differences between CAF users and nonusers or perhaps an effect of exposure to other bitter and/or CAF-containing foods and beverages.

Heterotrophic bacterial populations in the mineral waters of thermal springs in Spain.

The microbiological quality and heterotrophic bacterial populations of 26 thermal mineral water springs in Spain were studied. In most of the springs the number of viable aerobes was less than 10(3) cfu ml-1 and the number of sporulated bacteria less than 10(2) cfu ml-1. No significant differences were found in the counts obtained with Plate Count Agar (PCA) and PCA diluted 1:10 and incubated at 22 degrees, 37 degrees and 45 degrees C. Total coliforms were found in 14 springs, faecal streptococci in three, spores of sulphite-reducing Clostridium and Pseudomonas aeruginosa in seven. Neither Escherichia coli nor Staphylococcus aureus were found. A total of 665 strains were isolated and 85.4% of these identified; 329 were Gram-positive and 239 were Gram-negative. The genera most prevalent present in the springs were Pseudomonas (in 92.3%), Bacillus (65.4%), Enterobacter, Micrococcus and Staphylococcus (50%), Acinetobacter (42.3%), Arthrobacter (38.4%), Clostridium (27%) and Xanthomonas (23%). Gram-negative bacteria predominated in the mesothermal springs and Gram-positive bacteria in the hyper- and hypothermal springs. The most common Gram-negative rod species isolated were Ps. fluorescens, Ps. aeruginosa, Ps. putida, Ent. agglomerans, Ent. sakazakii, Ac. calcoaceticus and Ent. amnigenus.

Microbiological quality of pharmaceutical raw materials.

A total of 115 samples of pharmaceutical raw materials (excipients) were analysed: 36 lactose, 27 talc, 19 corn starch, 18 arabic gum, 8 gelatin, 3 gelatinized starch, 3 cellulose and one tragacanth gum. 69.9% of the samples showed less than 10(2) bacteria/g (mean = 23.2 cfu/g) and 95.2% less than 10(2) fungi/g (mean = 4.92 cfu/g). Arabic and tragacanth gum were the most contaminated products by bacteria and fungi, respectively. Pregelatinized starch, cellulose and lactose were the least contaminated excipients. In none of the samples Escherichia coli or Salmonella-Shigella were detected; however, strains of Enterobacter, Serratia and Proteus were isolated from 10 samples of 5 different excipients. Only 5 samples did not comply with the microbiological standards as established by the European Pharmacopoeia and USP.

Electrical activity of the olfactory bulb. Changes induced by lesions of contralateral olfactory areas.

Control values for a) trains of sinusoidal waves, b) slow potentials and c) basal activity, were determined in rabbits whose olfactory bulbs (O.B.'s) had been implanted with chronic electrodes. One olfactory epithelium was destroyed in one group of animals and the activity of the contralateral O.B. was analyzed for 7 days. Then, the olfactory peduncle homolateral to the olfactory epithelium previously destroyed was sectioned and the bulbar activity recorded for 15 days. In another group of animals, the olfactory peduncle was sectioned and the activity of the contralateral O.B. analyzed similarly to the previous group. It was observed that no changes occurred in the contralateral O.B. after the destruction of the receptors. The sectioning of the olfactory peduncle produced a temporary increase in the amplitude and duration of the trains of sinusoidal waves from the contralateral O.B. and, only in few cases, in the amplitude of the slow potentials. These results were related to the various nervous structures that had been damaged during the operations.

Perception of sweetness and bitterness in different vehicles.

In the present study, we investigated taste-taste, taste-vehicle, and simultaneous taste-vehicle-taste mixtures. Subjects made estimates of the sweetness and bitterness of 27 stimuli. Sucrose (292, 585, and 1170 mM), caffeine (13, 26, and 52 mM), and binary mixtures of low (292-13 mM), middle (585-26 mM), and high (1170-52 mM) levels of both components were dispersed in water, carboxymethylcellulose (CMC) 1% w/v, and gelatin 6% w/v. The sweetness and bitterness of the sucrose-vehicle-caffeine combinations were significantly weaker than the respective sucrose-vehicle and caffeine-vehicle combinations. The emerged mutual suppressive effects were asymmetrical and persisted when both tastants were presented in CMC and gelatin. Moreover, the increase in vehicle consistency and the simultaneous addition of another taste reduced the perceived intensity of a taste either presented alone or dissolved in water. For both sweetness and bitterness, the total taste suppression observed was always significant.

Interactions between CO2 oral pungency and taste.

Two experiments are reported in which the perceptual interactions between oral pungency, evoked by CO2, and the taste of each of four tastants--sucrose (sweet), quinine sulfate (bitter), sodium chloride (salty), and tartaric acid (sour)--were explored. In experiment 1 the effect of three concentrations of each tastant on the stimulus-response function for perceived oral pungency, in terms of both rate of change (slope) and relative position along the perceived pungency axis, was determined. In experiment 2 the effect of three concentrations of CO2 on the stimulus-response function for the perceived taste intensity of each tastant was examined. Results show that the characteristics of the mutual effects of tastant and pungent stimulus depend on the particular tastant employed. Sucrose sweetness and CO2 oral pungency have no mutual effect; sodium chloride saltiness or tartaric acid sourness and CO2 oral pungency show mutual enhancement; and quinine sulfate bitterness abates CO2 oral pungency, whereas CO2 has a double and opposite effect on quinine sulfate bitterness--at low concentrations of bitter tastant CO2 enhances bitterness, and at high concentrations of bitter tastant CO2 abates bitterness. It is suggested that the perceptual attributes of saltiness and sourness are closer, from a qualitative point of view, to oral pungency than are the attributes of bitterness and sweetness.

Life-span development of odor identification, learning, and olfactory sensitivity.

In the first of three studies, children (aged 8 to 14 years) were found to perform worse than young and middle-aged adults in unprompted identification of doors, with average performance much like that of elderly adults. Comparisons on other tasks, specifically odor threshold, prompted odor identification, and object naming (Boston Naming Test), across the life span (five groups) revealed that children have the same excellent olfactory sensitivity as young adults and merely lack odor-specific knowledge that accumulates slowly through life. Such knowledge apparently accumulates so slowly that age-associated discriminative losses, measurable by early middle age, begin to wear away gains obtained through experience before odors can become overlearned. In the second study, a novel adaptive psychophysical method, the step procedure, confirmed the equivalent sensitivity of children and young adults. In the third study, a paired-associate task illustrated the sluggish course of odor learning. Young adults outperformed children, though the youngest group, first graders, made up ground relatively fast. For children and adults, common odors facilitated performance relative to novel odors. The outcome highlighted the relevance of semantic factors in odor learning irrespective of age.

Electrical activity of the olfactory bulb. Changes induced by lesions of contralateral olfactory areas

Control values for a) trains of sinusoidal waves, b) slow potentials and c) basal activity, were determined in rabbits whose olfactory bulbs (O.B.’s) had been implanted with chronic electrodes. One olfactory epithelium was destroyed in one group of animals and the activity of the contralateral O.B. was analyzed for 7 days. Then, the olfactory peduncle homolateral to the olfactory epithelium previously destroyed was sectioned and the bulbar activity recorded for 15 days. In another group of animals, the olfactory peduncle was sectioned and the activity of the contralateral O.B. analyzed similarly to the previous group. It was observed that no changes occurred in the contralateral O.B. after the destruction of the receptors. The sectioning of the olfactory peduncle produced a temporary increase in the amplitude and duration of the trains of sinusoidal waves from the contralateral O.B. and, only in few cases, in the amplitude of the slow potentials. These results were related to the various nervous structures that had been damaged during the operations.

Electrical activity of the olfactory bulb. Changes induced by lesions of contralateral olfactory areas.

Control values for a) trains of sinusoidal waves, b) slow potentials and c) basal activity, were determined in rabbits whose olfactory bulbs (O.B.s) had been implanted with chronic electrodes. One olfactory epithelium was destroyed in one group of animals and the activity of the contralateral O.B. was analyzed for 7 days. Then, the olfactory peduncle homolateral to the olfactory epithelium previously destroyed was sectioned and the bulbar activity recorded for 15 days. In another group of animals, the olfactory peduncle was sectioned and the activity of the contralateral O.B. analyzed similarly to the previous group. It was observed that no changes occurred in the contralateral O.B. after the destruction of the receptors. The sectioning of the olfactory peduncle produced a temporary increase in the amplitude and duration of the trains of sinusoidal waves from the contralateral O.B. and, only in few cases, in the amplitude of the slow potentials. These results were related to the various nervous structures that had been damaged during the operations.