The significance of “apolysis” in the moulting of insects

The problem of defining the instars of insects is discussed in the light of observations on the timing of apolysis and on the physiology and behaviour of the insect during the pharate period of development.     

Assessing the “Short Mental Distance” in Eco‐Industrial Networks

Like many economic exchanges, industrial symbiosis (IS) is thought to be influenced by social relationships and shared norms among actors in a network. While many implicit references to social characteristics exist throughout the literature, there have been few explicit attempts to operationalize and measure the concepts. The “short mental distance,”“trust,”“openness,” and “communication” recorded among managers in Kalundborg, Denmark, set a precedent for examining and encouraging social interactions among key personnel in the dozens of eco‐industrial networks around the world. In this article we explore the relationships among various aspects of social embeddedness, social capital, and IS. We develop a conceptual framework and an approach using quantitative and qualitative methods to identify and measure these social characteristics, including social network structure, communication, and similarities in norms and conceptions of waste, and apply them in an industrial network in Nanjangud, South India. The findings suggest that there is a fairly high level of shared norms about dealing with waste—the “short mental distance”—in this network, but by‐product transactions are only weakly correlated with the structure and content of communication among managers. Replication of this approach can increase the understanding and comparability of the role of social characteristics in eco‐industrial activities around the world.     

“Environmental stress” and reproductive success in the common marmoset (Callithrix jacchus jacchus)

The present report documents the breeding success of a new colony of common marmosets (Callithrix jacchus jacchus) and demonstrates a correlation between environmental stress and reproductive success. Environmental conditions ranged chronologically over 40 months, through four periods: I) the initial period, when the colony was formed; II) a phase of relative environmental stability; III) a stage of “environmental stress” (when the colony was disrupted by nearby construction); and IV) a return to a stable environment. Examination of reproductive status during each period indicated that the colony exhibited severe reproductive suppression during the time of the environmental disruption. Parity and the number of live births decreased and the number of spontaneous abortions increased during this period. Reproductive success remained low during period IV. More triplets than twins were born during the period of relative environmental stability.     

The role of “the aquatic” in human evolution: Constraining the aquatic ape hypothesis

Few things show the distinctiveness of human evolution research better than the Aquatic Ape Hypothesis (AAH). On one hand, we have “orthodox” research into human evolution, firmly based on land; on the other, we have the aquatic ape community, convinced not only that our ancestors went through an aquatic phase, but that the professional scientific community ignores their work and keeps it out of the mainstream. How many fields of science have two entirely parallel communities that essentially are hermetically sealed from each other?     

The role of glutathione, membrane sphingomyelin, and its metabolites in oxidative stress-induced calcium “dysregulation” in PC12 cells

Previous research showed that increasing membrane sphingomyelin (SPH) levels in rat pheochromocytoma (PC12) cells to the same extent as that seen in some brain regions with aging dramatically increases the vulnerability to oxidative stress (OS). These increases in vulnerability were determined by assessing deficits in the ability of these cells to extrude and/or sequester Ca²⁺ following 30 mM KCl-induced depolarization (recovery). The purpose of the present experiments was to discern whether increasing the levels of particular SPH metabolite(s), i.e., ceramide (Cer), sphingosine (Ssine), or sphingosine-1-phosphate (SPP), or indirectly increasing the concentrations of these metabolites with sphingomylinase (Sase), would interact with the cell’s sensitivity to OS induced by low (5 μM) or high (nonlethal, 300 μM) H₂O₂. In addition, the OS vulnerability was examined as above under decreased SPH levels by exposing the cells to L-cycloserine (Lcc), which prevents SPH synthesis. Both Sase and SPP significantly decreased Ca²⁺ recovery of PC12 cells after H₂O₂ exposure. Conversely, Lcc-treated cells showed no further OS-induced decrements in recovery below those seen in controls. SPP significantly decreased glutathione levels (GSH) in the absence of OS. Repletion of GSH with 20 mM N-acetylcysteine significantly attenuated the effect of 5 μM H₂O₂ on recovery in SPP-treated cells and decreased sensitivity of SPP-treated cells to low doses of OS. Overall, our results suggest a critical role for GSH and SPP in the regulation of OS vulnerability, especially as it relates to Ca²⁺ homeostasis.     

Polarity of microtubular structures in manchette-like formations: Possible role of the “11th filament”

Bundles of microtubular structures appear in the cytoplasm of spermatids of the African frog Dicroglossus occipitalis. They are observed in the vicinity of axonemes. Natural tubulin polymerization leads to the formation of hooks on microtubular structures. They can be related to experimentally induced tubulin hooks. The direction of curvature of the hooks allows us to define the polarity of the bundles. This is opposite to the polarity of axonemal microtubules: Bundles and axonemes are antiparallel. Under colchicine action, arch-like microtubular structures are shown to open in the same direction as they lock. This enables us to characterize their opening and locking site: It corresponds to the place of the “11th filament” described in microtubular structures such axonemes. The “11th filament” is thus demonstrated to be the most susceptible to natural opening and to the action of colchicine in microtubular structures.     

The possible role of “sibling neurite bias” in the coordination of neurite extension,branching, and survival

In this review we consider a novel mechanism, “sibling neurite bias,” which may explain aspects of the coordination of elongation, branching, and resorption among different neurites growing from the same neuronal cell body. In this model, growing neurites which incorporate structural precursors at higher rates would deplete the cellular pool of precursors available to their “sibling” neurites; neurites would compete for survival, but in addition they would bias each other's behavior during active growth. Evidence is reviewed that “sibling neurite bias” may contribute to the establishment and stabilization of specific neural connections. Specific examples examined include the loss of polyinnervation at the developing neuromuscular junction, contextual mapping in the retino-tectal system, and selective neurite growth patterns and synaptic connections in nerve tissue culture model systems.