Study of the polymerization step of the rolling circle replication of peach latent mosaic viroid.

We have developed an in vitro transcriptional assay using Escherichia coli RNA polymerase to initiate the replication of peach latent mosaic viroid (PLMVd). Regardless of the polarity of the PLMVd strand used as template, initiation in vitro occurred at the same hairpin structure. These initiation sites correspond to the 5'-ends of two small (280 nt) PLMVd-related RNAs found in infected peach leaves. Using a series of truncated PLMVd-derived transcripts, we have demonstrated that the viroid domain composed solely of the self-complementary hammerhead sequences is sufficient to trigger polymerase-driven replication in vitro. These data suggest that the bacterial-like RNA polymerase from peach chloroplasts catalyzes PLMVd replication.

You can teach an old dog new tricks: olfaction and responses to novel foods by the elderly.

It can be difficult to document effects of age-related olfactory loss on eating behavior. However, we have reported that elders, especially those with poor olfaction, were more willing to accept novel foods than were younger adults. It was also found that elderly subjects were more willing to accept foods with unpleasant odors than were young subjects. Because there is often confounding between a food's odor pleasantness and its familiarity, the purpose of this study was to separate the effects of familiarity and odor pleasantness on food acceptance by the elderly. There was no evidence for effects of age or olfactory sensitivity on food neophobia. However, elderly subjects with poor olfaction showed less reluctance to try the unpleasantly smelling foods than did other subjects. These results suggest that increased willingness to try novel foods among elderly subjects with poor olfaction in earlier work was due to decreased rejection of foods with unpleasant odors and not due to decreased food neophobia per se.

Sequencing of peach latent mosaic viroid variants from nine North American peach cultivars shows that this RNA folds into a complex secondary structure.

We sequenced 34 new peach latent mosaic viroid (PLMVd) variants isolated from nine different peach cultivars. This study provides the widest view of PLMVd diversity reported to date and includes the original characterization of North American variants, which cannot be differentiated from European sequences. PLMVd appears as a species in which each isolate is a complex mixture of RNAs. Analysis of base-pair covariations supports the hypothesis that PLMVd folds into a complex branched structure with the potential of including three new pseudoknots. The resulting "globular-like" structure is in contrast to the rod-like one adopted by most other viroids.

Dietary monotony and food cravings in young and elderly adults.

Many hypothesized mechanisms for food cravings focus on nutritional deprivation. However, outside of the laboratory, nutritional inadequacy is often confounded with dietary monotony. Therefore, one aim was to examine the effects of a nutritionally adequate, liquid, sweet, monotonous diet on food cravings in young and elderly adults. In addition, previous retrospective questionnaire work has indicated that elderly individuals report fewer food cravings than do young adults. Because there are possible age differences in cognitive capacity, another goal of this work was to develop a prospective method (i.e.. a method that depends less on memory) of studying cravings that permits comparison of adults of different ages. Young adults reported significantly more cravings per day during the monotony manipulation than during the baseline period. Therefore, nutritional deprivation is not a necessary condition for food cravings. There were no gender differences. The increase was due primarily to a greater number of cravings for entrees (i.e., foods that differed in sensory quality from the monotonous diet). Cravings for sweets did not change. In contrast to predictions that liking for the monotonous diet would decline as a result of "repetition revulsion," there was no significant change in liking for the diet over the study period. In contrast to the young adults, elderly subjects were not responsive to the monotony manipulation. Elderly men reported almost no cravings at any time during the study. Elderly women reported as many cravings as did young adults during the baseline period, but did not show an increase in cravings during the monotony period. This lack of response to dietary monotony by the elderly could result in nutritionally inadequate diets.

The database of the smallest known auto-replicable RNA species: viroids and viroid-like RNAs.

This is an online database in order to facilitate research on viroid, viroid-like RNAs and human hepatitis delta virus by presenting a large number of sequences and related data in a comprehensive and user-friendly format (e.g., position of their self-catalytic domains, open reading frame, prediction of the most stable secondary structures, etc.). This online database is available on the WWW at http://www.callisto.si. usherb.ca/jpperra

Aminoacyl-tRNA synthetase genes of Bacillus subtilis: organization and regulation.

In Bacillus subtilis, 14 of the 24 genes encoding aminoacyl-tRNA synthetases (aaRS) are regulated by tRNA-mediated antitermination in response to starvation for their cognate aminoacid. Their transcripts have an untranslated leader mRNA of about 300 nucleotides, including alternative and mutually exclusive terminator-antiterminator structures, just upstream from the translation initiation site. Following antitermination, some of these transcripts are cleaved leaving at the 5'-end of the mature mRNAs, stable secondary structures that can protect them against degradation. Although most B. subtilis aaRS genes are expressed as monocistronic mRNAs, the gltX gene encoding the glutamyl-tRNA synthetase is cotranscribed with cysE and cysS encoding serine acetyl-transferase and cysteinyl-tRNA synthetase, respectively. Transcription of gltX is not controlled by a tRNA, but tRNA(CyS)-mediated antitermination regulates the elongation of transcription into cysE and cysS. The full-length gltX-cysE-cysS transcript is then cleaved into a monocistronic gltX mRNA and a cysE-cysS mRNA.

Co-transcription of Rhizobium meliloti lysyl-tRNA synthetase and glutamyl-tRNA synthetase genes.

An open reading frame encoding a putative polypeptide very similar to several lysyl-tRNA synthetases was found 10 nucleotides downstream of Rhizobium meliloti gltX encoding glutamyl-tRNA synthetase. Expression of this gene complemented a mutation in lysS of Escherichia coli and led to the overexpression of a polypeptide of the expected mass (62 kDa), thus confirming that it encodes R. meliloti lysyl-tRNA synthetase. Reverse transcription/polymerase chain reaction was used to demonstrate that this lysS gene is co-transcribed with gltX in R. meliloti. This is the first reported case of two immediately adjacent and co-transcribed genes encoding aminoacyl-tRNA synthetases.

In vivo and in vitro processing of the Bacillus subtilis transcript coding for glutamyl-tRNA synthetase, serine acetyltransferase, and cysteinyl-tRNA synthetase.

In Bacillus subtilis, the adjacent genes gltX, cysE, and cysS encoding respectively glutamyl-tRNA synthetase, serine acetyl-transferase, and cysteinyl-tRNA synthetase, are transcribed as an operon but a gltX probe reveals only the presence of a monocistronic gltX mRNA (Gagnon et al., 1994, J Biol Chem 269:7473-7482). The transcript of the gltX-cysE intergenic region contains putative alternative secondary structures forming a p-independent terminator or an antiterminator, and a conserved sequence (T-box) found in the leader of most aminoacyl-tRNA synthetase and many amino acid biosynthesis genes in B. subtilis and in other Gram-positive eubacteria. The transcription of these genes is initiated 45 nt upstream from the first codon of gltX and is under the control of a sigmaA-type promoter. Analysis of the in vivo transcript of this operon revealed a cleavage site immediately downstream from the p-independent terminator structure. In vitro transcription analysis, using RNA polymerases from Escherichia coli, B. subtilis, and that encoded by the T7 phage, in the presence of various RNase inhibitors, shows the same cleavage. This processing generates mRNAs whose 5'-end half-lives differ by a factor of 2 in rich medium, and leaves putative secondary structures at the 3' end of the gltX transcript and at the 5' end of the cysE/S mRNA, which may be involved in the stabilization of these mRNAs. By its mechanism and its position, this cleavage differs from that of the other known transcripts encoding aminoacyl-tRNA synthetases in B. subtilis.

Overproduction of the Bacillus subtilis glutamyl-tRNA synthetase in its host and its toxicity to Escherichia coli.

The Bacillus subtilis glutamyl-tRNA synthetase (GluRS), encoded by the gltX gene, aminoacylates its homologous tRNA(Glu) and tRNA(Gln) with glutamate. This gene was cloned with its sigma A promoter and a downstream region including a rho-independent terminator in the shuttle vector pRB394 for Escherichia coli and B. subtilis. Transformation of B. subtilis with this recombinant plasmid (pMP411) led to a 30-fold increase of glutamyl-tRNA synthetase specific activity in crude extracts. Transformation of E. coli with this plasmid gave no recombinants, but transformation with plasmids bearing an altered gltX was successful. These results indicate that the presence of B. subtilis glutamyl-tRNA synthetase is lethal for E. coli, probably because this enzyme glutamylates tRNA1(Gln) in vivo as it does in vitro.

"Try it; it's good and it's good for you": effects of taste and nutrition information on willingness to try novel foods.

In an attempt to understand the effects of information on willingness to taste foods, we presented college students with a variety of familiar and novel foods of animal and vegetable origin. Participants received one of four types of information about the foods: none, they tasted good, they were high in vitamins, or they were high in vitamins and might soon be available in the college cafeteria. The information manipulation had no effect on willingness to taste familiar foods. Willingness to taste novel non-animal foods was increased by both taste and vitamin-plus-availability information, while willingness to taste animal foods was not affected by information. Willingness to taste novel foods was also predicted by a measure of trait neophobia. The results suggest that (a) emotional reactions to animal foods may block information effects, and (b) nutrition information is more effective in a context where the food is believed to be available.

Food cravings in young and elderly adults.

Fifty young-adult and 48 elderly Ss participated in a structured interview study on food cravings (defined as an intense desire or longing to eat a particular food). Elderly Ss were less likely than young Ss to report cravings and reported craving a smaller number of different foods. In contrast to a number of other researchers, we found a relationship between dietary restrictions and cravings. Types of food craved differed by gender and age. Women reported significantly more cravings for chocolate and for sweets than did men. However, craving for sweets declined with age among women. Cravings were not evenly distributed throughout the day, but tended to occur in the late afternoon and early evening.

"Try it. You'll like it." Effects of information on willingness to try novel foods.

Three experiments are reported on the effects of "taste" or nutrition information on willingness to try novel foods. "Taste" information improved responses to four out of the five foods examined. There was a consistent, but not statistically significant, trend for nutritional information to be effective. In experiment I, conducted with 3- to 8-year-old children in a laboratory setting, and in experiment II, conducted with 10- to 20-year-olds in a cafeteria, there were strong age effects. Older subjects responded more positively to novel foods than did younger subjects. There were no significant interactions between information and age and there were no sex differences. It is commonly assumed that novel foods are rejected because they are thought to be dangerous. However, the fact that dangerous foods are good tasting should be irrelevant to willingness to taste them. Our results are consistent with the idea that, in settings like laboratories and cafeterias, culture has already defined foods as being safe. Perhaps rejection in such settings is based on fear of a negative sensory experience.

Clustering and co-transcription of the Bacillus subtilis genes encoding the aminoacyl-tRNA synthetases specific for glutamate and for cysteine and the first enzyme for cysteine biosynthesis.

The Bacillus subtilis cysE and cysS genes encoding, respectively, the serine acetyltransferase and the cysteinyl-tRNA synthetase were found downstream from the gltX gene encoding the glutamyl-tRNA synthetase. This gene organization is also conserved in Bacillus stearothermophilus where the cysE and cysS genes show high amino acid identity with those of B. subtilis. In both organisms the coding sequences of cysE and cysS overlap, suggesting a translational coupling. B. subtilis cysE and cysS were expressed in Escherichia coli using the inducible trc promoter; they functionally complement mutants of E. coli affected in those genes. Overproduction of B. subtilis CysRS in E. coli has a toxic effect on cell growth. Disruption of gltX and cysS by Campbell-type insertion is lethal for the cell, indicating that these genes code for an essential and unique function in B. subtilis. S1 mapping analysis shows that the transcription of gltX is under the control of a sigma A promoter located 43 base pairs upstream of the initiation codon. A T-box sequence and a rho-independent terminator known to regulate expression of other aminoacyl-tRNA synthetase genes and of some amino acid biosynthetic operons in Bacillus sp., were found between gltX and cysE. No sigma A promoter was detected upstream of cysE, which is consistent with the lethality of a Campbell-type insertion using a plasmid that interrupts transcription coming from the gltX promoter, and suggests that gltX, cysE, and cysS constitute an operon. This is the first case where genes implicated in the biosynthesis of an amino acid and its cognate aminoacyl-tRNA synthetase are shown to be co-transcribed.

Reduction of neophobia in humans by exposure to novel foods.

In the first part of a two-part study we attempted to determine whether individuals consider novel foods (in comparison to familiar foods) to be dangerous and expect to dislike their tastes, and, if so, whether willingness to eat them is systematically related to the degree of perceived danger and expected disliking. A series of multiple regression analyses revealed that disliking and danger are both good predictors of willingness to try novel foods while willingness to try familiar foods is predicted only by disliking. In the second part of the study we examined experimentally the effect of "forced" exposure to novel foods on subsequent neophobia. Some subjects were required to taste seven novel foods while others tasted seven similar familiar foods; all subjects were then given the task of selecting for tasting one member of each of 11 pairs of foods. The pairs were comprised of one novel and one familiar food (different from those used in the exposure to novelty manipulation), and number of novel choices was the measure of neophobia (with fewer choices indicative of greater neophobia). The results were discussed in terms of the usefulness of considering food neophobia as a phobia in the sense in which clinical psychologists use the term.

The effects of aging on the human sense of smell and its relationship to food choice.

Olfaction plays a significant role in the perception of foods. For the most part, taste is limited to sweet, sour, bitter, and salty. The sensory experiences during consumption of complex foods and drinks cannot be constructed from these units. Indeed, much of the taste of a meal derives from olfactory stimulation. Hence, factors that influence olfactory perception should affect treatment of food-related odors. This article initially reviews previously published observations on the effects of age on olfaction and food preferences and then presents the results of original analyses of data derived from a substantial database formed as a result of the National Geographic Smell Survey. Included in the Survey form were topics relevant to the present article. They include the following question: Would you eat something that smelled like this? Two of the odors in the Survey were food related and two were fragrance related. Hence, in addition, we assessed responses to the following question: Would you apply something that smelled like this to your body? Answers were affected in part by the age and gender of the respondent and by the perceived pleasantness and intensity of the odor.

A possible genetic association between PROP-tasting and alcoholism.

Fifty-five young adult subjects and their parents were classified as alcoholic or nonalcoholic based on a standardized questionnaire (the MAST) filled out by the subjects. Subjects' thresholds for detection of 6-n-propylthiouracil (PROP; a PTC-like compound) were determined with the experimenter blind to MAST responses. There was a significantly higher proportion of nontasters of PROP among children of alcoholics than among children of nonalcoholics. There was no relationship between the child's alcoholism status and ability to taste PROP. These results are inconsistent with the view that excessive use of alcohol causes the association between nontasting and alcoholism and are consistent with the view that there is a genetic association between PROP/PTC-tasting and alcoholism.

[Spiritual support in HIV seropositivity or AIDS]. / L'accompagnement spirituel de la personne séropositive ou sidéenne.

Acute life experiences ("expériences limites de l'existence") have long been considered the exclusive domain of religion. Until recently in Québec, the Catholic Church was noted for overseeing these symbolic events. Although the religious reference has not completely disappeared, the author argues that it has now undergone two changes, in terms of privatization and diversification. As such, several systems of belief, whether religious or secular, are being suggested to provide meaning to our lives. Yet, can these approaches provide any relevant support to patients in general, and to HIV-infected persons in particular, including the various organizations and individuals that provide care and assistance? The author points out that genuine support for seropositive persons or AIDS patients in their search for meaning and their fight against the negative forces in life, must involve a person's spiritual dimension. The outcome of this indispensable process does not necessarily have to lead to a traditional religious creed. However, in considering the issue of spiritual support in the context of illness and suffering, the author concludes that "belief in the search for meaning" is an imperative for all those who are concerned by AIDS.

Neophobia in humans and the special status of foods of animal origin.

Research from the anthropological, psychological, and animal behavior literatures suggests that foods of animal origin have a special status. In two studies we explored the question of whether individuals are more neophobic with respect to animal foods than non-animal foods. In the first study male and female subjects, after reading descriptions, rated their willingness to taste ten "novel" foods, which were actually fictitious. Foods in meat/fish/poultry and dairy/egg categories received lower ratings than those in fruit, vegetable, and grain categories. In the second study subjects were exposed to real foods, some of which were named and described accurately and were, therefore, familiar and some of which were named and described fictitiously and were, therefore, novel. There were no food category differences in subjects' willingness to taste familiar foods, but subjects were less willing to eat novel flesh foods than foods in the other categories. The results are discussed in terms of Rozin & Fallon's (1980) taxonomy of motivations for rejecting foods.

Sapid savvy in sucklings: the effect of quinine hydrochloride on intraoral negative pressure and intake by 11-13-day-old rat pups.

Three experiments describe the consummatory behavior of 11-13-day-old rat pups during and following experience with a model aversive taste, quinine hydrochloride. Pups were observed while away from the dam and while suckling. Results show that pups actively reject quinine adulterated solutions in both situations. They do so by spitting the solution from the mouth when away from the nipple and by leaving the nipple and/or decreasing their sucking effort when with the dam.