Evolvability as the proper focus of evolutionary developmental biology

SUMMARY Research conducted under the label of evolutionary developmental biology has tended to revolve around a few central issues such as modularity, integration, and canalization. Yet, as the field has grown, it has become increasingly difficult to define in terms of its central question and relation to broader evolutionary concerns. We argue that these central issues of evo-devo gain their currency from connections to a central question that defines the field, and we propose that this central question is about the nature of evolvability. However, not all research currently carried out under the label of "evo-devo" speaks to this focal concern. The aim of this article is therefore to argue for a precise formulation of evolutionary developmental biology's core question.     

Protein kinase G and focal adhesion kinase converge on Src/Akt/β-catenin signaling module in osteoblast mechanotransduction

Mechanical loading of bone induces interstitial fluid flow, leading to fluid shear stress (FSS) of osteoblasts. FSS rapidly increases the intracellular calcium concentration ([Ca(2+)]) and nitric oxide (NO) synthesis in osteoblasts and activates the protein kinase Akt. Activated Akt stimulates osteoblast proliferation and survival, but the mechanism(s) leading to Akt activation is not well defined. Using pharmacological and genetic approaches in primary human and mouse osteoblasts and mouse MC3T3 osteoblast-like cells, we found that Akt activation by FSS occurred through two parallel pathways; one required calcium stimulation of NO synthase and NO/cGMP/protein kinase G II-dependent activation of Src, and the other required calcium activation of FAK and Src, independent of NO. Both pathways cooperated to increase PI3K-dependent Akt phosphorylation and were necessary for FSS to induce nuclear translocation of β-catenin, c-fos, and cox-2 gene expression and osteoblast proliferation. These data explain how mechanical stimulation of osteoblasts leads to increased signaling through a growth regulatory pathway essential for maintaining skeletal integrity.     

Sperm capacitation induces an increase in lipid rafts having zona pellucida binding ability and containing sulfogalactosylglycerolipid

Sperm gain full ability to bind to the zona(e) pellucida(e) (ZP) during capacitation. Since lipid rafts are implicated in cell adhesion, we determined whether capacitated sperm lipid rafts had affinity for the ZP. We demonstrated that lipid rafts, isolated as low-density detergent resistant membranes (DRMs), from capacitated pig sperm had ability to bind to homologous ZP. This binding was dependent on pig ZPB glycoprotein, a major participant in sperm binding. Capacitated sperm DRMs were also enriched in the male germ cell specific sulfogalactosylglycerolipid (SGG), which contributed to DRMs-ZP binding. Furthermore, SGG may participate in the formation of sperm DRMs due to its interaction with cholesterol, an integral component of lipid rafts, as shown by infrared spectroscopic studies. Since sperm capacitation is associated with cholesterol efflux from the sperm membrane, we questioned whether the formation of DRMs was compromised in capacitated sperm. Our studies indeed revealed that capacitation induced increased levels of sperm DRMs, with an enhanced ZP affinity. These results corroborated the implication of lipid rafts and SGG in cell adhesion and strongly suggested that the enhanced ZP binding ability of capacitated sperm may be attributed to increased levels and a greater ZP affinity of lipid rafts in the sperm plasma membrane.     

A Legacy of Low-Impact Logging does not Elevate Prevalence of Potentially Pathogenic Protozoa in Free-Ranging Gorillas and Chimpanzees in the Republic of Congo: Logging and Parasitism in African Apes

Many studies have examined the long-term effects of selective logging on the abundance and diversity of free-ranging primates. Logging is known to reduce the abundance of some primate species through associated hunting and the loss of food trees for frugivores; however, the potential role of pathogens in such primate population declines is largely unexplored. Selective logging results in a suite of alterations in host ecology and forest structure that may alter pathogen dynamics in resident wildlife populations. In addition, environmental pollution with human fecal material may present a risk for wildlife infections with zoonotic protozoa, such as Cryptosporidium and Giardia. To better understand this interplay, we compared patterns of infection with these potentially pathogenic protozoa in sympatric western lowland gorillas (Gorilla gorilla gorilla) and chimpanzees (Pan troglodytes troglodytes) in the undisturbed Goualougo Triangle of Nouabalé-Ndoki National Park and the adjacent previously logged Kabo Concession in northern Republic of Congo. No Cryptosporidium infections were detected in any of the apes examined and prevalence of infection with Giardia was low (3.73% overall) and did not differ between logged and undisturbed forest for chimpanzees or gorillas. These results provide a baseline for prevalence of these protozoa in forest-dwelling African apes and suggest that low-intensity logging may not result in long-term elevated prevalence of potentially pathogenic protozoa.     

Male reproductive toxicity of trichloroethylene: sperm protein oxidation and decreased fertilizing ability

The objective of the present study was to characterize and investigate potential mechanisms for the male reproductive toxicity of trichloroethylene (TCE). Male rats exposed to TCE in drinking water exhibited a dose-dependent decrease in the ability to fertilize oocytes from untreated females. This reduction in fertilizing ability occurred in the absence of treatment-related changes in combined testes/epididymides weight, sperm concentration, or sperm motility. In addition, flow cytometric analysis showed that there were no treatment-related differences in sperm mitochondrial membrane potential or acrosomal stability. TCE caused slight histological changes in efferent ductule epithelium, coinciding with the previously reported ductule localization of cytochrome P450 2E1. However, no alterations were noted in the testis or in any segment of the epididymis. Because there were no treatment-related changes to sperm indices and no clear pathological lesions to explain the reduced fertilization, the present study investigated TCE-mediated sperm oxidative damage. Oxidized proteins were detected by immunochemical techniques following the derivatization of sperm protein carbonyls with dinitrophenyl hydrazine. Immunochemical staining of whole, intact sperm showed the presence of halos of oxidized proteins around the head and midpiece of sperm from TCE-treated animals. The presence of oxidized sperm proteins was confirmed by Western blotting using in vitro-oxidized sperm as a positive control. Thiobarbituric acid reactive substances analyses showed a dose-dependent increase in the level of lipid peroxidation in sperm from treated animals, as well. Oxidative damage to sperm may explain the diminished fertilizing capacity of exposed animals and provide another mechanism by which TCE can adversely affect reproductive capabilities in the male.     

A diabody that dissociates to monomer forms at low concentration: effects on binding activity and tumor targeting

A human scFv, 15-9, was selected from a phage display library for binding to murine laminin-1. A diabody was made from the scFv by shortening the linker from 15 to 5 amino acids between the VH and VL sequence. Radioiodinated scFv and diabody were analyzed for size, binding to laminin, and biodistribution in tumor bearing mice. Diabody preparations at concentrations greater than 10 nM were largely dimer forms (approximately 60 kDa) as judged by gel filtration, but diluted diabody was eluted as a monomer (approximately 30 kDa). At low concentrations the radiolabeled diabody did not bind well to laminin. The (125)I diabody had significantly lower accumulation in tumors than did the scFv when injected at lower concentrations. These data indicate that the diabody dimer dissociates at concentrations of about 10nM resulting in monomers with no binding activity for laminin and poor tumor homing properties.     

Comparison of the ability of progesterone and heat solubilized porcine zona pellucida to initiate the porcine sperm acrosome reaction in vitro

It has been previously shown that progesterone can initiate the acrosome reaction (AR) of capacitated human and hamster sperm in vivo. We report here that progesterone can initiate a morphologically normal AR in porcine sperm that have undergone capacitation in a Hepes-buffered medium in vitro. In addition, we have compared the abilities of progesterone and heat-solubilized porcine zona pellucida (zona) to initiate the porcine sperm AR. Capacitated porcine sperm were treated with 1 m?g/ml progesterone, 150 m?g/ml porcine zona, or solvent control for 10 min. After treatment, sperm were incubated with the supravital dye Hoechst 33258, fixed and the acrosomal status determined in the previously viable sperm by fluorescence microscopy with fluorescein isothiocyanate-labeled Pisum sativum agglutini (FITC-PSA). There was no significant difference between the percentage of AR initiated by zona compared to that initiated by progesterone. In order to determine whether there was a synergistic interaction between the two AR initiators, both were added simultaneously to capacitated porcine sperm at optimal (1 m?g/ml progesterone, 150 m?g/ml zona) and suboptimal (75 ng/ml progesterone and 75 m?g/ml zona) concentrations. Simultaneous addition of the two AR-initiators at the two concentrations stimulated an additive AR-initating response, rather than a synergistic one. Several possible explanations for the additive results are discussed. © 1994 Wiley-Liss, Inc.