Trehalose, the insect blood sugar, inhibits loading of diacylglycerol by lipophorin from the fat body in locusts

Trehalose, the insect blood sugar, was found to inhibit diacylglycerol uptake by lipophorin from the fat body in vitro. Trehalose inhibited diacylglycerol uptake by about 40%-50% at various physiological concentrations. This suggests that trehalose may play a dual role in the hemolymph, i.e. serving as the insect's fuel and as a regulator in lipid transport.     

Virulence studies on chromosomal α-toxin and Θ-toxin mutants constructed by allelic exchange provide genetic evidence for the essential role of α-toxin in Clostridium perfringens-mediated gas gangrene

The pathogenesis of clostridial myonecrosis, or gas gangrene, involves the growth of the anaerobic bacterium Clostridium perfringens in the infected tissues and the elaboration of numerous extracellular toxins and enzymes. The precise role of each of these toxins in tissue invasion and necrosis has not been determined. To enable genetic approaches to be used to study C. perfringens pathogenesis we developed an allelic exchange method which involved the transformation of C. perfringens cells with a suicide plasmid carrying a gene insertionally inactivated with an erythromycin-resistance determinant. The frequency with which double reciprocal crossover events were observed was increased to a workable level by increasing the amount of homologous DNA located on either side of the inactivated gene. Allelic exchange was used to isolate mutations in the‘chromosomal pfoA gene, which encodes an oxygen-labile haemolysin known as Θ-toxin or perfringolysin O. and in the chromosomal pic gene, which encodes the α-toxin or phospholipase C. The resultant mutants failed to produce detectable Θ-toxin or α-toxin activity, respectively, and could be complemented by recombinant plasmids that carried the respective wild-type genes. The resultant strains were virulence tested in a mouse myonecrosis model. The results showed that the pic mutants had demonstrably reduced virulence and therefore provided definitive genetic evidence for the essential role of α-toxin in gas gangrene or clostridial myonecrosis.     

Can Newts Cope with the Heat? Disparate Thermoregulatory Strategies of Two Sympatric Species in Water

Many ectotherms effectively reduce their exposure to low or high environmental temperatures using behavioral thermoregulation. In terrestrial ectotherms, thermoregulatory strategies range from accurate thermoregulation to thermoconformity according to the costs and limits of thermoregulation, while in aquatic taxa the quantification of behavioral thermoregulation have received limited attention. We examined thermoregulation in two sympatric newt species, Ichthyosaura alpestris and Lissotriton vulgaris, exposed to elevated water temperatures under semi-natural conditions. According to a recent theory, we predicted that species for which elevated water temperatures pose a lower thermal quality habitat, would thermoregulate more effectively than species in thermally benign conditions. In the laboratory thermal gradient, L. vulgaris maintained higher body temperatures than I. alpestris. Semi-natural thermal conditions provided better thermal quality of habitat for L. vulgaris than for I. alpestris. Thermoregulatory indices indicated that I. alpestris actively thermoregulated its body temperature, whereas L. vulgaris remained passive to the thermal heterogeneity of aquatic environment. In the face of elevated water temperatures, sympatric newt species employed disparate thermoregulatory strategies according to the species-specific quality of the thermal habitat. Both strategies reduced newt exposure to suboptimal water temperatures with the same accuracy but with or without the costs of thermoregulation. The quantification of behavioral thermoregulation proves to be an important conceptual and methodological tool for thermal ecology studies not only in terrestrial but also in aquatic ectotherms.     

Characterization of Biofilm Formation by Borrelia burgdorferi In Vitro

Borrelia burgdorferi, the causative agent of Lyme disease, has long been known to be capable of forming aggregates and colonies. It was recently demonstrated that Borrelia burgdorferi aggregate formation dramatically changes the in vitro response to hostile environments by this pathogen. In this study, we investigated the hypothesis that these aggregates are indeed biofilms, structures whose resistance to unfavorable conditions are well documented. We studied Borrelia burgdorferi for several known hallmark features of biofilm, including structural rearrangements in the aggregates, variations in development on various substrate matrices and secretion of a protective extracellular polymeric substance (EPS) matrix using several modes of microscopic, cell and molecular biology techniques. The atomic force microscopic results provided evidence that multilevel rearrangements take place at different stages of aggregate development, producing a complex, continuously rearranging structure. Our results also demonstrated that Borrelia burgdorferi is capable of developing aggregates on different abiotic and biotic substrates, and is also capable of forming floating aggregates. Analyzing the extracellular substance of the aggregates for potential exopolysaccharides revealed the existence of both sulfated and non-sulfated/carboxylated substrates, predominately composed of an alginate with calcium and extracellular DNA present. In summary, we have found substantial evidence that Borrelia burgdorferi is capable of forming biofilm in vitro. Biofilm formation by Borrelia species might play an important role in their survival in diverse environmental conditions by providing refuge to individual cells.     

A mixed-valence Cu(I)-Cu(II) and metal-metal bond containing coordination polymer obtained from an in situ oxidation reaction route

A new mixed-valence copper coordination polymer with copper-copper metal bonds in a two-dimensional network was generated from an in situ oxidation reaction route under hydrothermal conditions. The synthesis of this coordination polymer demonstrated that the novel compounds that may not be accessible using the known methods could be synthesized via an oxidation reaction route. The reaction conditions are mild enough to keep the building blocks intact during the oxidation and self-assembly process under hydrothermal conditions.     

Role of ascorbic acid in procollagen expression and secretion by human intestinal smooth muscle cells

The role of ascorbate in the production and secretion of procollagen by human intestinal smooth muscle cells and the conditions in culture for optimal ascorbate bioefficacy were studied. Procollagen synthesis and secretion were determined by the incubation of cells with L-[5-³H]proline, and the quantitation of radiolabelled procollagen bands in the cell layer and the culture medium by polycrylamide slab gel electrophoresis and densitometry. When cells were cultured without ascorbate in the culture medium, procollagen secretion into the medium was 75% less than in cells receiving fresh ascorbate daily. In the cell layer, in contrast, procollagen accumulation was fourfold greater in the scorbutic cells than in the ascorbate-replete cells. These findings contrasted with those in a control line of scorbutic human dermal fibroblasts in which a 95% decrease in procollagen secretion was not associated with any procollagen accumulation in the cells. In the intestinal smooth muscle cells, the absence of ascorbate resulted in a 25 and 50% decrease in steady-state levels of procollagen I and III mRNA, respectively, compared to a 40 and 75% decrease in fibroblasts. Heat inactivation of the serum in the culture medium augmented the promotion of procollagen secretion by ascorbate two- to fourfold. L-ascorbate phosphate did not increase the activity of L-ascorbate when replaced in medium either daily or every 4 days, and its efficacy was not augmented by serum heat inactivation. The changing of culture medium induced collagen secretion in the absence of ascorbate, but this process was markedly enhanced by ascorbate and induced a transient decrease in the steady-state levels of both procollagen and nonprocollagen mRNAs. The predominant action of L-ascorbate on HISM cells in vitro is to promote procollagen secretion and not procollagen synthesis. L-ascorbate-phosphate is not an adequate substitute for L-ascorbate in this cell line. © 1995 Wiley-Liss, Inc.     

Disease-driven reduction in human mobility influences human-mosquito contacts and dengue transmission dynamics

Heterogeneous exposure to mosquitoes determines an individual’s contribution to vector-borne pathogen transmission. Particularly for dengue virus (DENV), there is a major difficulty in quantifying human-vector contacts due to the unknown coupled effect of key heterogeneities. To test the hypothesis that the reduction of human out-of-home mobility due to dengue illness will significantly influence population-level dynamics and the structure of DENV transmission chains, we extended an existing modeling framework to include social structure, disease-driven mobility reductions, and heterogeneous transmissibility from different infectious groups. Compared to a baseline model, naïve to human pre-symptomatic infectiousness and disease-driven mobility changes, a model including both parameters predicted an increase of 37% in the probability of a DENV outbreak occurring; a model including mobility change alone predicted a 15.5% increase compared to the baseline model. At the individual level, models including mobility change led to a reduction of the importance of out-of-home onward transmission (R, the fraction of secondary cases predicted to be generated by an individual) by symptomatic individuals (up to -62%) at the expense of an increase in the relevance of their home (up to +40%). An individual’s positive contribution to R could be predicted by a GAM including a non-linear interaction between an individual’s biting suitability and the number of mosquitoes in their home (>10 mosquitoes and 0.6 individual attractiveness significantly increased R). We conclude that the complex fabric of social relationships and differential behavioral response to dengue illness cause the fraction of symptomatic DENV infections to concentrate transmission in specific locations, whereas asymptomatic carriers (including individuals in their pre-symptomatic period) move the virus throughout the landscape. Our findings point to the difficulty of focusing vector control interventions reactively on the home of symptomatic individuals, as this approach will fail to contain virus propagation by visitors to their house and asymptomatic carriers.     

Adding Years to Your Life (or at Least Looking Like It): A Simple Normalization Underlies Adaptation to Facial Age

Adaptation has been widely used to probe how experience shapes the visual encoding of faces, but the pattern of perceptual changes produced by adaptation and the neural mechanisms these imply remain poorly characterized. We explored how adaptation alters the perceived age of faces, a fundamental facial attribute which can uniquely and reliably be scaled by observers. This allowed us to measure how adaptation to one age level affected the full continuum of perceived ages. Participants guessed the ages of faces ranging from 18–89, before or after adapting to a different set of faces composed of younger, older, or middle-aged adults. Adapting to young or old faces induced opposite linear shifts in perceived age that were independent of the model''s age. Specifically, after adapting to younger or older faces, faces of all ages appeared 2 to 3 years older or younger, respectively. In contrast, middle-aged adaptors induced no aftereffects. This pattern suggests that adaptation leads to a simple and uniform renormalization of age perception, and is consistent with a norm-based neural code for the mechanisms mediating the perception of facial age.     

Composition and stability of the vervet monkey milk microbiome

The human milk microbiome is vertically transmitted to offspring during the postnatal period and has emerged as a critical driver of infant immune and metabolic development. Despite this importance in humans, the milk microbiome of nonhuman primates remains largely unexplored. This dearth of comparative work precludes our ability to understand how species‐specific differences in the milk microbiome may differentially drive maternal effects and limits how translational models can be used to understand the role of vertically transmitted milk microbes in human development. Here, we present the first culture‐independent data on the milk microbiome of a nonhuman primate. We collected milk and matched fecal microbiome samples at early and late lactation from a cohort of captive lactating vervet monkeys (N = 15). We found that, similar to humans, the vervet monkey milk microbiome comprises a shared community of taxa that are universally present across individuals. However, unlike in humans, this shared community is dominated by the genera Lactobacillus, Bacteroides, and Prevotella. We also found that, in contrast to previous culture‐dependent studies in humans, the vervet milk microbiome exhibits greater alpha‐diversity than the gut microbiome across lactation. Finally, we did not find support for the translocation of microbes from the gut to the mammary gland within females (i.e., “entero‐mammary pathway”). Taken together, our results show that the vervet monkey milk microbiome is taxonomically diverse, distinct from the gut microbiome, and largely stable. These findings demonstrate that the milk microbiome is a unique substrate that may selectively favor the establishment and persistence of particular microbes across lactation and highlights the need for future experimental studies on the origin of microbes in milk.