Feeding behaviour and reproductive biology of Colorado potato beetle adults fed transgenic potatoes expressing the Bacillus thuringiensis Cry3B endotoxin

Colorado potato beetle (Leptinotarsa decemlineata Say) adult longevity and fecundity were studied on transgenic potato clones expressing a Cry3B endotoxin of Bacillus thuringiensis (Bt). Adult longevity and fitness were studied for the first 3 weeks after emergence. Beetle reproductive biology on highly resistant clones, intermediary resistant clones and control potato plants was monitored by dissecting females after 7–15 days of feeding and also by analysing haemolymph protein content after 3 days of feeding. Feeding behaviour on transgenic plants expressing high toxin concentrations and on control plants was monitored individually for 36 newly emerged adult beetles feeding on leaf disks during the first two meals. Lethal Time₅₀ for adult beetles feeding on transgenic clones as the sole source of food was not significantly shorter than for beetles on control clones reared in a growth chamber. Differences tended to be larger when the experiment was conducted in a greenhouse with a less optimal temperature range (LT₅₀ = 9.52 and 10.45 days for two transgenic clones and 13.86 for control). In contrast, female egg production on transgenic plants was almost totally inhibited. Dissection studies indicated that adult males living on high-level Bt-expressing transgenic potatoes were still able to mate and produce mobile sperm, but the females were impaired in their reproductive ability since their ovaries were generally not fully developed. An examination of the haemolymph revealed the protein concentration in females living on transgenic plants to be dramatically reduced ( 50%), and electrophoresis showed a reduced content of vitellogenin in these samples.Feeding behaviour of adult Colorado potato beetles was not affected by the different food plants; this indicates that transgenic potato plants were readily accepted as host plants by beetles. The effects of these findings on the use of transgenic plants as a means of L. decemlineata control are discussed.     

Obese Women Have Lower Monosodium Glutamate Taste Sensitivity and Prefer Higher Concentrations Than Do Normal‐weight Women

The goal of this study was to determine whether obese women exhibit altered umami and sweet taste perception compared to normal‐weight women. A total of 57 subjects (23 obese and 34 normal weight) participated in a 2‐day study separated by 1 week. Half of the women in each group were evaluated using monosodium glutamate (MSG; prototypical umami stimulus) on the first test day and sucrose on the second test day; the order was reversed for the remaining women. We used two‐alternative forced‐choice staircase procedures to measure taste detection thresholds, forced‐choice tracking technique to measure preferences, the general Labeled Magnitude Scale (gLMS) to measure perceived intensity of suprathreshold concentrations, and a triangle test to measure discrimination between 29 mmol/l MSG and 29 mmol/l NaCl. Obese women required higher MSG concentrations to detect a taste and preferred significantly higher MSG concentrations in a soup‐like vehicle. However, their perception of MSG at suprathreshold concentrations, their ability to discriminate MSG from salt, and their preference for sucrose were similar to that observed in normal‐weight women. Regardless of their body weight category, 28% of the women did not discriminate 29 mmol/l MSG from 29 mmol/l NaCl (nondiscriminators). Surprisingly, we found that, relative to discriminators, nondiscriminators perceived less savoriness when tasting suprathreshold MSG concentrations and less sweetness from suprathreshold sucrose concentrations but had similar MSG and sucrose detection thresholds. Taken together, these data suggest that body weight is related to some components of umami taste and that different mechanisms are involved in the perception of threshold and suprathreshold MSG concentrations.     

Reversible inactivation of ribonucleases by ADPribosylation

The activity of purified bovine seminal RNAase and pancreatic RNAase A (EC 3.1.27.5) has been investigated following in vitro ADPribosylation in the presence of nuclear ADPribosyltransferase (EC 2.4.2.30) and NAD+ X ADPribosylation of these enzymes was correlated with a significant decrease in their activities. Approximately three residues of ADPribose were present per mol of enzyme. Removal of the bound ADPribose restored enzyme activity to near normal levels. Similar results were obtained with nuclei isolated from bull seminal vesicles as an endogenous source of seminal RNAase and nuclear ADPribosyltransferase. The findings suggest that in vitro ADPribosylation has a reversible inactivating effect on ribonucleases.     

Social chemosignals from breastfeeding women increase sexual motivation

Human pheromones, a type of social chemosignal, modulate endocrine function by regulating the timing of ovulation. In animals, pheromones not only regulate ovulation but also female reproductive motivation and behavior. There is no extant evidence that humans produce social chemosignals that affect human sexual motivation or reproductive behavior as occurs in other mammals. Here, we demonstrate that natural compounds collected from lactating women and their breastfeeding infants increased the sexual motivation of other women, measured as sexual desire and fantasies. Moreover, the manifestation of increased sexual motivation was different in women with a regular sexual partner. Those with a partner experienced enhanced sexual desire, whereas those without one had more sexual fantasies. These results are consistent with previous pheromonal effects on endocrine function, and warrant further study of these social chemosignals as candidates for pheromonal processes, including their effects on other aspects of motivation and behavior.     

Psychophysical dissection of genotype effects on human bitter perception

The purpose of this study was to define the effects of individual polymorphisms within the haplotypes of the TAS2R38 taste receptor gene on human bitter taste perception. A racially and ethnically diverse sample of children and adults (N = 980) was phenotyped for thresholds of 6-n-propylthiouracil (PROP) and genotyped for 3 polymorphisms of the TAS2R38 gene (A49P, V262A, I296V). Subjects were grouped according to their diplotype (i.e., specific combinations of haplotypes) and compared for PROP thresholds. By contrasting subjects with particular diplotypes, we found that in addition to A49P, V262A and I296V were related to the ability of the subjects to detect PROP. The V262A variant site affected the ability of subjects to detect mid-range concentrations of PROP, whereas the I296V variant site affected the ability of subjects to perceive PROP at the lowest concentration. These data agree with results from previous studies using cell-based assays for 2 variant sites (A49P and V262A) but not those for the I296V variant site. The reason for the discordant results is not known but it highlights the need for psychophysical as well as cell-based methods to understand the genotype-phenotype relationship for taste receptors. Human PROP sensitivity is determined by the combination of each of these 3 polymorphisms within the TAS2R38 gene.     

In vitro poly(ADP‐ribosyl)ated histones H1a and H1t modulate rat testis chromatin condensation differently

Rat testis H1 proteins were poly(ADP‐ribosyl)ated in vitro. The modifying product, poly(ADP‐ribose), was found covalently bound to each histone variant at various extents and exhibited distinct structural features (linear and short, rather than branched and long chains). Interest was focused on the somatic H1a, particularly abundant in the testis, as compared with other tissues, and the testis‐specific H1t, which appears only at the pachytene spermatocyte stage of germ cell development. These H1s were modified with poly(ADP‐ribose) by means of two in vitro experimental approaches. In the first system, each variant was incubated with purified rat testis poly(ADP‐ribose)polymerase in the presence of [³²P] NAD. In parallel, poly(ADP‐ribosyl)ated H1s were also prepared following incubation of intact rat testis nuclei with [³²P] NAD. In both experiments, the poly(ADP‐ribosyl)ated proteins were purified from the native forms by means of phenyl boronic agarose chromatography. The results from both analyses were in agreement and showed qualitative differences with regard to the poly(ADP‐ribose) covalently associated with H1a and H1t. Comparison of the bound polymers clearly indicated that the oligomers associated with H1a were within 10–12 units long, whereas longer chains (≤20 ADP‐R units) were linked to H1t. Individual poly(ADP‐ribosyl)ated H1s were complexed with homologous H1‐depleted oligonucleosomes (0.5–2.5 kbp) in order to measure their ability to condensate chromatin, in comparison with the native ones. Circular dichroism showed that the negative charges of the oligomeric polyanion, although present in limited numbers, highly influenced the DNA‐binding properties of the analyzed H1s. In particular, the poly(ADP‐ribosyl)ated H1a and H1t had opposite effects on the condensation of H1‐depleted oligonucleosomes. J. Cell. Biochem. 76:20–29, 1999. © 1999 Wiley‐Liss, Inc.