A system for automatic temperature-programmed recording of circular dichroism and optical rotatory dispersion

The effect of temperature on the circular dichroism (CD) and the optical rotatory dispersion (ORD) of macromolecules, and particularly nucleic acids, provides useful information regarding macromolecular conformation (1–3). Instruments which can perform this function, however, are not commercially available. The dependence of CD upon temperature is usually measured by manual variation of the temperature of a jacketed-cell assembly positioned within the spectropolarimeter. We wish to report a modification of the Beckman T_m Analyzer ¹, which is designed to record temperature-optical density profiles, permitting the use of this instrument in conjunetion with a Durrum-Jasco recording spectropolarimeter ². This assembly provides for automatic recording of CD or ORD versus temperature at wavelengths between 190 and 700 mμ. We recently employed this system in studies of the temperature dependence of CD in DNA-ethidium bromide complexes (4,5).     

Can some microbes promote host stress and benefit evolutionarily from this strategy?

Microbes can influence host physiology and behavior in many ways. Here we review evidence suggesting that some microbes can contribute to host stress (and other microbes can contribute to increased resilience to stress). We explain how certain microbes, which we call “stress microbes,” can potentially benefit evolutionarily from inducing stress in a host, gaining access to host resources that can help fuel rapid microbial replication by increasing glucose levels in the blood, increasing intestinal permeability, and suppressing the immune system. Other microbes, which we term “resilience microbes,” can potentially benefit from making hosts more resilient to stress. We hypothesize that “stress microbes” use a fast life history strategy involving greater host exploitation while “resilience microbes” use a slow life history strategy characterized by more aligned evolutionary interests with the host. In this paper, we review the evidence that microbes affect host stress and explain the evolutionary pressures that could lead microbes to manipulate host stress, discuss the physiological mechanisms that are known to be involved in both stress and microbial activity, and provide some testable predictions that follow from this hypothesis.     

Another step towards understanding the slit‐limpets (Fissurellidae,Fissurelloidea, Vetigastropoda,Gastropoda): a combined five‐gene molecular phylogeny

Aktipis, S. W., Boehm, E. & Giribet, G. (2010). Another step towards understanding the slit‐limpets (Fissurellidae, Fissurelloidea, Vetigastropoda, Gastropoda): a combined five‐gene molecular phylogeny. —Zoologica Scripta, 40, 238–259. Fissurellids, commonly known as slit or keyhole limpets, are limpet‐shaped gastropods that typically possess a hole, slit or notch in their bilaterally symmetrical shells and usually occur on rocky marine substrates. Competing classifications for Fissurellidae have been circumscribed using various morphological characters such as radular, shell and mantle features; two to five different subfamilies have been recognized. Although fissurellid species are frequently included in larger vetigastropod phylogenies, relatively few phylogenetic studies of the group have been performed. This study presents a phylogenetic investigation of the relationships amongst slit‐limpets in the vetigastropod superfamily Fissurelloidea, representing the first molecular phylogeny of this clade. In this study, the monophyly of Fissurelloidea and Fissurellidae varied depending on the analytical method used, but clades compatible with the subfamilies Diodorinae and Fissurellinae were recovered with high bootstrap support in all analyses. Species traditionally classified in Emarginulinae formed two groups identified in this study as Hemitominae (Puncturella, Cranopsis and Hemitoma) and Emarginulinae sensu stricto (Emarginula, Montfortula, Tugali, Scutus and Nannoscutum), but Hemitominae was only monophyletic in the maximum likelihood analysis. The results of this study contradict traditional fissurellid classifications as well as theories about the evolution of key fissurellid shell characters. The placement of Puncturella, Cranopsis and Hemitoma sister to all remaining fissurellids suggests that the presence of an anteriorly placed foramen or notch is plesiomorphic, and that an anterior notch or slit evolved multiple times in Fissurellidae.     

Inclusive fitness effects can select for cancer suppression into old age

Natural selection can favour health at youth or middle age (high reproductive value) over health at old age (low reproductive value). This means, all else being equal, selection for cancer suppression should dramatically drop after reproductive age. However, in species with significant parental investment, the capacity to enhance inclusive fitness may increase the reproductive value of older individuals or even those past reproductive age. Variation in parental investment levels could therefore contribute to variation in cancer susceptibility across species. In this article, we describe a simple model and framework for the evolution of cancer suppression with varying levels of parental investment and use this model to make testable predictions about variation in cancer suppression across species. This model can be extended to show that selection for cancer suppression is stronger in species with cooperative breeding systems and intergenerational transfers. We consider three cases that can select for cancer suppression into old age: (i) extended parental care that increases the survivorship of their offspring, (ii) grandparents contributing to higher fecundity of their children and (iii) cooperative breeding where helpers forgo reproduction or even survivorship to assist parents in having higher fecundity.     

Need-Based Transfers Enhance Resilience to Shocks: An Agent-Based Model of a Maasai Risk-Pooling System

Human Ecology - Maasai and other Maa-speaking pastoralists in Kenya and Tanzania have a risk-pooling system that they refer to by their word for the umbilical cord (osotua). Gifts from one osotua...     

Need-based transfer systems are more vulnerable to cheating when resources are hidden

Need-based transfer systems pool risk among interdependent individuals. Such arrangements are bound by two simple rules: Ask for help only when in need and, if you are able, give help to others who ask. But there may be a temptation for individuals to break these rules for short-term personal profit. Here, we study one factor that may enforce honesty in need-based transfer relationships: the visibility of resources. Across three experiments employing a novel experimental economic game, breaking of both need-based transfer rules increased when resources were hidden rather than visible (Experiment 1: n = 82, online convenience sample from the US; Experiment 2: n = 80, student sample from the US; Experiment 3: n = 42, online convenience sample from the US). Participants with hidden resources were (1) more likely to request help when not actually in need (greediness), and (2) more likely to not fulfill requests from others for help, even when they had sufficient resources available to help (stinginess). These findings highlight the visibility of resources as one potential limitation of cooperative risk pooling systems.