Effects of age on children's intake of large and self-selected food portions

Objective: Whether developmental periods exist in which children become particularly sensitive to environmental influences on eating is unclear. This research evaluated the effects of age on intake of large and self‐selected portions among children 2 to 9 years of age. Research Methods and Procedures: Seventy‐five non‐Hispanic white children 2 to 3, 5 to 6, and 8 to 9 years of age were seen at a dinner meal in reference, large, and self‐selected portion size conditions in which the size of an entrée was age‐appropriate, doubled, and determined by the child, respectively. Weighed food intake data were collected. Entrée bite size and bite frequency were assessed. Height and weight measurements were obtained. Results: The effect of age on children's intake of the large portion was not significant. Entrée consumption was 29% greater (p < 0.001) and meal energy intake was 13% greater (p < 0.01) in the large portion condition than in the reference condition. Increases in entrée consumption were attributable to increases in average bite size (p < 0.001). Neither child weight nor maternal weight predicted children's intake of large portions. Self‐selection resulted in decreased entrée (p < 0.05) and meal energy (p < 0.01) only among those children who ate more when served the large portion. Discussion: The results of this research confirm that serving large entrée portions promotes increased intake at meals among 2‐ to 9‐year‐old children. These findings suggest that any age‐related differences in children's response to large portions are likely to be smaller than previously suspected.     

Estradiol and progesterone in paternal and non-paternal hamsters (Phodopus) becoming fathers: conflict with hypothesized roles

Phodopus campbelli has an extensive paternal behavior repertoire whereas the closely-related Phodopus sungorus is not paternally responsive to a displaced pup. For the first time in a naturally paternal mammal, male estradiol and progesterone were determined during two critical phases: (1) the transition from sexually naive male to paired, expectant father that occurs in the absence of stimuli from pups (sexually naive males, paired males on G8, G12, G15, or G17 of the 18-day gestation) and (2) after pup stimuli became available to the males (paired males on days L1, L3, L5, or L12 of pup development). Hormone concentrations in naive males and between G17 and L1 (as stimuli from the birth and the pups became available to males) were also compared. Paternal responsiveness was tested on L3-L5 and confirmed species differences. Hormone concentrations in naive males were similar in the two species and males of both species had estradiol concentrations as high as fertile adult females. However, in direct contrast to predictions, estradiol concentrations were stable in P. campbelli males but increased before the birth, fell across the birth, and increased over pup development in P. sungorus males. Progesterone concentrations in P. campbelli males increased from G17 to L1 whereas a decrease had been predicted. Testosterone dynamics were consistent with previous studies. Either hormonal facilitation of paternal behavior is a hyper-variable trait that has evolved differently in different species, or, more probably, peripheral hormone concentrations are inadequate to explain the role of sex steroid hormones in paternal behavior.     

The GM2 Glycan Serves as a Functional Coreceptor for Serotype 1 Reovirus

Viral attachment to target cells is the first step in infection and also serves as a determinant of tropism. Like many viruses, mammalian reoviruses bind with low affinity to cell-surface carbohydrate receptors to initiate the infectious process. Reoviruses disseminate with serotype-specific tropism in the host, which may be explained by differential glycan utilization. Although α2,3-linked sialylated oligosaccharides serve as carbohydrate receptors for type 3 reoviruses, neither a specific glycan bound by any reovirus serotype nor the function of glycan binding in type 1 reovirus infection was known. We have identified the oligosaccharide portion of ganglioside GM2 (the GM2 glycan) as a receptor for the attachment protein σ1 of reovirus strain type 1 Lang (T1L) using glycan array screening. The interaction of T1L σ1 with GM2 in solution was confirmed using NMR spectroscopy. We established that GM2 glycan engagement is required for optimal infection of mouse embryonic fibroblasts (MEFs) by T1L. Preincubation with GM2 specifically inhibited type 1 but not type 3 reovirus infection of MEFs. To provide a structural basis for these observations, we defined the mode of receptor recognition by determining the crystal structure of T1L σ1 in complex with the GM2 glycan. GM2 binds in a shallow groove in the globular head domain of T1L σ1. Both terminal sugar moieties of the GM2 glycan, N-acetylneuraminic acid and N-acetylgalactosamine, form contacts with the protein, providing an explanation for the observed specificity for GM2. Viruses with mutations in the glycan-binding domain display diminished hemagglutination capacity, a property dependent on glycan binding, and reduced capacity to infect MEFs. Our results define a novel mode of virus-glycan engagement and provide a mechanistic explanation for the serotype-dependent differences in glycan utilization by reovirus.     

Seismic signal transmission between burrows of the Cape mole-rat,Georychus capensis

Summary Both seismic and auditory signals were tested for their propagation characteristics in a field study of the Cape mole-rat (Georychus capensis), a subterranean rodent in the family Bathyergidae. This solitary animal is entirely fossorial and apparently communicates with its conspecifics by alternately drumming its hind legs on the burrow floor. Signal production in this species is sexually dimorphic, and mate attraction is likely mediated primarily by seismic signalling between individuals in neighboring burrows. Measurements within, and at various distances away from, natural burrows suggest that seismic signals propagate at least an order of magnitude better than auditory signals. Moreover, using a mechanical thumper which could be triggered from a tape recording of the mole-rat's seismic signals, we established that the vertically-polarized surface wave (Rayleigh wave) propagates with less attenuation than either of the two horizontally-polarized waves. Thus, we tentatively hypothesize that Rayleigh waves subserve intraspecific communication in this species.Abbreviations PPM pulses per min - SB simulated burrow - SD standard deviation - SPL sound pressure level     

Programmable in situ amplification for multiplexed imaging of mRNA expression

In situ hybridization methods enable the mapping of mRNA expression within intact biological samples. With current approaches, it is challenging to simultaneously map multiple target mRNAs within whole-mount vertebrate embryos, representing a significant limitation in attempting to study interacting regulatory elements in systems most relevant to human development and disease. Here, we report a multiplexed fluorescent in situ hybridization method based on orthogonal amplification with hybridization chain reactions (HCR). With this approach, RNA probes complementary to mRNA targets trigger chain reactions in which fluorophore-labeled RNA hairpins self-assemble into tethered fluorescent amplification polymers. The programmability and sequence specificity of these amplification cascades enable multiple HCR amplifiers to operate orthogonally at the same time in the same sample. Robust performance is achieved when imaging five target mRNAs simultaneously in fixed whole-mount and sectioned zebrafish embryos. HCR amplifiers exhibit deep sample penetration, high signal-to-background ratios and sharp signal localization.     

Hepatitis C virus 3′UTR regulates viral translation through direct interactions with the host translation machinery

The 3′ untranslated region (3′UTR) of hepatitis C virus (HCV) messenger RNA stimulates viral translation by an undetermined mechanism. We identified a high affinity interaction, conserved among different HCV genotypes, between the HCV 3′UTR and the host ribosome. The 3′UTR interacts with 40S ribosomal subunit proteins residing primarily in a localized region on the 40S solvent-accessible surface near the messenger RNA entry and exit sites. This region partially overlaps with the site where the HCV internal ribosome entry site was found to bind, with the internal ribosome entry site-40S subunit interaction being dominant. Despite its ability to bind to 40S subunits independently, the HCV 3′UTR only stimulates translation in cis, without affecting the first round translation rate. These observations support a model in which the HCV 3′UTR retains ribosome complexes during translation termination to facilitate efficient initiation of subsequent rounds of translation.     

Motion Noise Changes Directional Interaction between Transparently Moving Stimuli from Repulsion to Attraction

To interpret visual scenes, visual systems need to segment or integrate multiple moving features into distinct objects or surfaces. Previous studies have found that the perceived direction separation between two transparently moving random-dot stimuli is wider than the actual direction separation. This perceptual “direction repulsion” is useful for segmenting overlapping motion vectors. Here we investigate the effects of motion noise on the directional interaction between overlapping moving stimuli. Human subjects viewed two overlapping random-dot patches moving in different directions and judged the direction separation between the two motion vectors. We found that the perceived direction separation progressively changed from wide to narrow as the level of motion noise in the stimuli was increased, showing a switch from direction repulsion to attraction (i.e. smaller than the veridical direction separation). We also found that direction attraction occurred at a wider range of direction separations than direction repulsion. The normalized effects of both direction repulsion and attraction were the strongest near the direction separation of ∼25° and declined as the direction separation further increased. These results support the idea that motion noise prompts motion integration to overcome stimulus ambiguity. Our findings provide new constraints on neural models of motion transparency and segmentation.