Abstract: By a phenomenon called primary neural induction, the competent cubic epithelium of the ectoderm becomes the vertebrate nervous system upon contact with the roof of the a r c h e n t e r ~ n . ~ ~ . ~ ~ The simple cubic epithelium of the ectoderm gives origin subsequently to different populations of neurons which acquire such extreme morphologic and functional complexity that generalization about their behaviors requires great caution. Although some of the basic epithelial characteristics are maintained in the adult nervous system,52 the capacity to repair cellular losses is greatly impaired.8y10,34 On the other hand, in a system where specific cell recognition and storageretrieval of information are of paramount importance, anatomic stability of the cellular elements, after development, has been always considered essential. Consequently, the characterization of the neurons as perennial elements, first put forward by Bizzozero' in 1894, has been widely accepted until r e ~ e n t l y . ~ ~ ~ ~ ~ It was also established that in the central nervous system of mammals not only were neurons irreplaceable, but also severed axons could not regrow because of the intrinsic inability of the damaged central perikarya to sustain regeneration of their axons. The inability of the mammalian CNS to sustain recovery has been recently challenged by a number of new observations. Postnatal development of microneurons from the subependymal regions of the brain has been documented in rodent^.^-^-',^^ Transplantation experiments, resumed after the pioneering work done at the beginning of this ~en tu ry ,~* '~* ' ' have shown that lesioned neuronal populations can be substituted in selected brain region^.^.'^,^ 7 , 3 7 The phenomenon of sprouting4o360 and the capacity of the central neurons to regrow their axons when proper environment is provided l , I 7 have challenged the well-established rule proposed by Arnemann6 since 1787 that regrowth of nerve fibers cannot occur in the postnatal central nervous system. Even if reestablishment of new circuitries with recovery of function has not been so far obtained in mammals, the new observations have great practical and theoretical importance and provide hope for unsuspected capacity of repair of the nervous system. Furthermore, these results

Abstract: Taste and smell are considered important influences on food selection and intake. However, the exact nature of the effects of chemical sensory function on dietary habits is still unclear. Future research concerning this interaction should facilitate the development of optimal dietary guidelines concerning the palatability of foods for children. At present, however, some broad generalizations about sensory development and food acceptance can be made. First, sweet preference appears innate, and thus addition of sweet substances is almost certain to increase the palatability of foods. Conversely, aversions to bitterness appear from a very early age, and thus bitter flavors are likely to decrease palatability. Third, saltiness may be aversive or neutral to infants, with adult patterns of salt preference not appearing until about age 2. Fourth, odors, including volatile flavors like cherry, which are perceived via the olfactory receptors, cannot be expected to have much impact on children until about age 5. Even though children can detect such odors, their likes and dislikes are attenuated. Finally, young children probably find strong or irritative sensations in the mouth, e.g., from carbonation or pepper, to be aversive.

Abstract: Olfactory receptor cells of the spruce bark beetle,Ips typographus, and its predator, the clerid beetleThanasimus formicarius, were studied using electrophysiological techniques. Recordings were made of nerve impulses from single cells and of the summated receptor potential (electroantennogram).

Abstract: The vomeronasal organ, a chemosensory structure in the nasal cavity, is important in the detection of mammalian chemosignals, many of which are thought to be large molecules having low volatility. We conducted a series of experiments to determine whether nonvolatile molecules enter the vomeronasal organ during a variety of behavioral contexts in five species. We found that a nonvolatile dye entered the vomeronasal organ during investigation of urine from conspecific donors (experiment 1), during investigation of urine from heterospecific donors (experiment 2), during self-grooming (experiment 3), and during social grooming (experiment 4). In other experiments, we determined that nonvolatile molecules entered the vomeronasal organ during consumatory behaviors. Animals that ate a dye-adulterated familiar food had the nonvolatile marker in their vomeronasal organs (experiment 5). Animals that drank either familiar or novel dye-adulterated solutions also had the nonvolatile marker in their vomeronasal organs (experiment 6). In Experiment 7, large (66,000-dalton) fluorescent molecules were mixed with female urine which was then presented to male animals. We observed that the large molecules were transported to the vomeronasal organ. In the final experiment, we determined that mere contact between the snout of a dead animal and the stimulus resulted in transport of nonvolatile substances to the vomeronasal organ. We conclude that the vomeronasal organ, like the olfactory epithelium, is in continuous contact with the environment, but unlike the olfactory epithelium, the sensory receptors of the vomeronasal organ interact with molecules of low volatility, in addition to more volatile odorants.

Abstract: In Experiment 1, rats with posterior lateral olfactory tract/anterior amygdala lesions or with control neocortical lesions were tested for retention of a preoperatively learned odor detection task and for learning on new odor discrimination problems. All rats had perfect or near-perfect retention of the detection task, and there were no discernible differences between groups in learning on the new odor discrimination problems. In Experiment 2, an intensity-difference threshold for olfaction was determined in 4 rats before and after lesions of the posterior lateral olfactory tract and anterior amygdala. There were no apparent differences between pre- and postoperative performances on this psychophysical test. These results indicate that lateral olfactory tract projections to the amygdala and posterior olfactory cortex are not essential for normal performance on simple olfactory discrimination tasks.

Abstract: 1. The electrical activity of the two olfactory receptor neurons in individual pheromone-sensitive sensilla on the antennae of male cabbage looper moths (Trichoplusia ni) was monitored extracellularly. Responses to single and multiple component stimuli containing up to three of the seven behaviorally active compounds for this species were obtained at several different stimulus intensities. 2. Neurons which produced large amplitude action potentials (A neurons) were more responsive to (Z)7-dodecenyl acetate, a major component of the female pheromone gland, than were their companion B receptor neurons. B receptor neurons were more responsive to (Z)7-dodecenol, a behavioral inhibitor of male orientation to calling females. Neither neuron was particularly responsive to stimuli containing only dodecyl acetate, a minor component of female glands, which has powerful synergistic effects on male behavior. 3. Some blends of these three compounds elicited responses which were not readily predicted from a knowledge of the cells' responses to individual components of the blend. 4. The average A receptor neuron was significantly more responsive to the blend containing (Z)7-dodecenyl acetate and 10% dodecyl acetate than it was to either component alone or, for that matter, to the algebraic sum of their individual responses. These enhancements were intensity-dependent, occurring to a significant extent only in the middle portion of a neuron's dose-response function. Although A recpetor neurons are not particularly responsive to either (Z)7-dodecenol or dodecyl acetate, a binary mixture of these components elicited significantly smaller responses than expected. Blends which contained all three compounds elicited responses in A receptor neurons which were also significantly smaller than those expected. These reductions were dose-dependent and occurred most reliably at the middle of the dose-response function. 5. The responses of B receptor neurons to blends were more variable than those obtained simultaneously in A receptor neurons. Although all of the various alterations in discharge magnitude observed in the typical A receptor neuron response to blend stimulation were seen in some fraction of the B receptor neurons sampled, only the trinary blend elicited responses which were significantly different from those expected. These reductions in the response of B receptor neurons were also intensity-dependent because they were more reliably observed in the middle portion of the neurons' dose-response function. 6. The sensory processing of complex chemical signals by the insect olfactory system has been postulated to involve a set of narrowly tuned, highly specific olfactory receptor neurons, one for each of the behaviorally relevant component compounds in the pheromone blend. Here we show that olfactory receptor neurons may also be responsive in unique ways to multiple component stimuli even in cases where an individual behaviorally relevant pheromone component is not processed by a separate class of receptor neuron.

Abstract: Electroantennograms (EAGs) were recorded fromTrirhabda bacharides Le Conte (Coleoptera: Chrysomelidae) females to 28 odorants and volatiles emanating from leaves of 26 plant species including three known host plants,Baccharis halimifolia L.,B. neglecta Britt, andB. salicina T. & G. (Compositae: Asterae). Antennal receptors were highly responsive to components of the green leaf volatile complex, especially 6-carbon saturated and monounsaturated alcohols andtrans-2-hexenal. EAGs elicited by heptanal were greater than those elicited by any other saturated aldehyde. Oxygenated monoterpenes were more active than monoterpene hydrocarbons. β-Bisabolol was the most active sesquiterpene. In general, EAGs to volatiles emanating fromBaccharis and other composite species were greater than those elicited by species from other families. Furthermore, when one considers only plants occurring in the environs ofT bacharides hostB. neglecta, EAGs elicited by its host plant were at least two times greater than those elicited by other coinhabiting plants.

Abstract: Adult male rats (Rattus norvegicus) were trained in a Y-maze to discriminate the presence of a littermate from its absence. Transfer of training in subsequent tests indicated that (a) the animals were capable of distinguishing among individuals when relatedness and familiarity were held constant, (b) this ability was not due to training, and (c) their performance was based solely on odor cues. The results are discussed in relation to social behavior in rats.

Abstract: Visual and acoustic cues may serve as aposematic signals that warn predators of poisonous foods. Olfactory aposematism, the use of innocuous odors as warning signals for toxic foods, is another possible means of alerting an animal that a potential food item is unpalatable. Although it has been suggested that olfactory aposematism might be the principle mode of warning utilized by plants in their defense against herbivores, experimental evidence is lacking. This study demonstrates that the opossum,Didelphis virginiana, can utilize an innocuous volatile compound found naturally in a mushroom as a warning signal for a delayed illness caused by mushroom toxin. This supports the contention that characteristic odors of toxic plants may serve a warning function, protecting herbivores from being poisoned and plants from being consumed.

Abstract: Following unilateral olfactory bulbectomy in rats the ipsilateral olfactory neuroepithelium undergoes degeneration. Subsequently, the receptor neuron complement of the tissue is restored by the proliferation and differentiation of immature neuroblasts. However, as noted by other workers, in the absence of a target organ the dynamics of neuron regeneration is altered such that there is an overall reduction in the number of cells positive for the olfactory marker protein when cellular equilibrium is re-established. Immunocytochemical staining of the olfactory epithelium of unilaterally bulbectomized rats with a series of anti-neuronal monoclonal antibodies reveals an attenuation of binding of some antibodies to the neurons of the ipsilateral epithelium. In contrast, other anti-neuronal monoclonal antibodies show no difference in staining intensity when ipsilateral and control contralateral epithelia are compared. These data suggest that the expression of some neuronal antigens is subject to control by the target olfactory bulb, whereas others are independent of such putative regulation. Besides altering the expression of some antigenic determinants, olfactory bulbectomy also results in certain organizational changes in epithelium. First, bulbectomy produces an increase in the incidence of a cell type that appears to span the neuroepithelium. Although the morphology of these cells is more akin to a sustentacular cell than to a receptor neuron, they are not immunoreactive with antibodies to sustentacular cells. The cells are stained, however, by an anti-neuronal antibody, NEU-9. The second aspect of altered organization is the appearance of novel olfactory marker protein-positive structures in the olfactory mucosa.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract: Morphological investigation of tongue, olfactory epithelia, trachea and inner ear in vitamin A deficiency are reported. The results support assumptions concerning the loss of sensory function as been at least a secondary effect of alterations of the neighbourhood of the sensory cells caused by vitamin A deficiency. Taste buds are hindered in function by a dense layer of squamous cells and olfaction is decreased by atrophy of the surrounding respiratory epithelium. Inner ear functionality seems to be affected by vitamin A status via a stabilizing effect on the endolymph-perilymph barrier.

Abstract: Olfactory bulbectomy unmasks photoperiodic responsiveness in normally nonphotoperiodic rats. We assessed whether the photoperiodic effects of bulbectomy reflect disruption of chemosensory input. At 26–28 days of age, male Sprague-Dawley rats were subjected to removal of their vomeronasal organ (VNO) complex, a sham-VNO ablation or large electrolytic lesions aimed at the pyriform cortex or corticomedial nuclei of the amygdala. Other rats were infused with (1) 7.5% ZnSO4, a treatment that destroys the olfactory neuroepithelium, (2) 0.09% saline, or (3) air in each external nare every 4 days; rats from each treatment condition were assigned either to a long (LD 14:10) or short (LD 8:16) day lighting regimen and were autopsied at 90 days of age. Seminal vesicle and paired testes weights did not differ significantly among long-day groups. Mean seminal vesicle and paired testes weights were decreased only in short-day rats treated with ZnSO4. These results indicate that the VNO does not mediate the effects of photoperiod on rat reproduction. Olfactory information, not transduced by the amygdala, or nonsensory components of the olfactory bulbs appear to mask photoperiodism in intact rats.

Abstract: Olfactory bulbectomy is known to potentiate the antigonadal effects of light deprivation. However, the physiological interpretation of the effects of bulbar ablation is complex, since it simultaneously implies sequelae like: a) the loss of olfactory sensitivity (anosmia), b) the suppression of the accessory olfactory system (AOS), and c) the suppression of nonsensorial functions of the bulbs. To study the participation of these three mechanisms in the effects of bulbectomy + light deprivation, we compared, in 28-day-old male rats, the effects of olfactory bulb deafferentation (peripheral anosmia) with those induced by either olfactory bulbectomy or blocking the AOS, alone or associated with blindness. As compared to the intact or blinded animals, both blinded deafferented (EA) and blinded bulbectomized (EB) rats showed various reductions in weights of body, testes, accessory sexual glands, and prostates; serum testosterone levels were also depressed. Testes of EA rats showed various degrees of alterations in spermatogenesis. The only difference between EA and EB groups was in the pituitary weight, significantly lower in EA rats.