The cytology of the vitellogenic stages of oogenesis in Drosophila melanogaster. II. Ultrastructural investigations on the origin of protein yolk spheres

The cytology of the vitellogenic stages in the development of the oocyte of Drosophila melanogaster is described following an electron microscopic study of sections of plastic-embedded ovaries and single egg chambers. One of the first morphological manifestations of yolk deposition is an infolding of the plasma membrane of the oocyte and the abscission of membranous tubules and vesicles. The protein (alpha) yolk spheres originate along the oocyte periphery from membranous sacs to which are attached membranous tubules. It is assumed that the majority of the protein within the alpha sphere is synthesized by neighboring tubular, rough surfaced endoplasmic reticulum. The other organelles in the ooplasm are described, and their origin and possible roles in vitellogenesis are examined. The relative importance of intra- and extra-ovarian synthesis of yolk protein in different insect species is discussed.     

Genetic Variation Stimulated by Epigenetic Modification

Homologous recombination is essential for maintaining genomic integrity. A common repair mechanism, it uses a homologous or homeologous donor as a template for repair of a damaged target gene. Such repair must be regulated, both to identify appropriate donors for repair, and to avoid excess or inappropriate recombination. We show that modifications of donor chromatin structure can promote homology-directed repair. These experiments demonstrate that either the activator VP16 or the histone chaperone, HIRA, accelerated gene conversion approximately 10-fold when tethered within the donor array for Ig gene conversion in the chicken B cell line DT40. VP16 greatly increased levels of acetylated histones H3 and H4, while tethered HIRA did not affect histone acetylation, but caused an increase in local nucleosome density and levels of histone H3.3. Thus, epigenetic modification can stimulate genetic variation. The evidence that distinct activating modifications can promote similar functional outcomes suggests that a variety of chromatin changes may regulate homologous recombination, and that disregulation of epigenetic marks may have deleterious genetic consequences.     

Wildlife hazard assessment for Phoenix Sky Harbor International Airport

We examined wildlife abundance, distribution, and movement patterns at Phoenix Sky Harbor International Airport (PHX) and within an 8-km radius to assess current air-strike hazards, and to provide baseline information for projecting changes in air-strike hazards as land-use patterns around PHX change. We found that water sources at or near PHX especially induced wildlife movement patterns that put air traffic at risk. This was particularly true of the Salt River bed adjacent to the airport, which also is a natural flight corridor for birds. Compounding the problem, air traffic at PHX was the heaviest when bird abundance and activity was the greatest during migration and breeding. We feel that air strike hazards at PHX are likely to increase substantially as the Salt River bed is reclaimed to produce additional lakes and high quality riparian habitat. We offer recommendations to reduce the hazard levels currently found at PHX and to reduce additional hazards as the habitat around PHX is converted and produces more attractive wildlife habitat.     

Integrating Aquatic Metabolism and Net Ecosystem CO2 Balance in Short- and Long-Hydroperiod Subtropical Freshwater Wetlands

Ecosystems - How aquatic primary productivity influences the carbon (C) sequestering capacity of wetlands is uncertain. We evaluated the magnitude and variability in aquatic C dynamics and compared...     

One-channel Cell-attached Patch-clamp Recording

Ion channel proteins are universal devices for fast communication across biological membranes. The temporal signature of the ionic flux they generate depends on properties intrinsic to each channel protein as well as the mechanism by which it is generated and controlled and represents an important area of current research. Information about the operational dynamics of ion channel proteins can be obtained by observing long stretches of current produced by a single molecule. Described here is a protocol for obtaining one-channel cell-attached patch-clamp current recordings for a ligand gated ion channel, the NMDA receptor, expressed heterologously in HEK293 cells or natively in cortical neurons. Also provided are instructions on how to adapt the method to other ion channels of interest by presenting the example of the mechano-sensitive channel PIEZO1. This method can provide data regarding the channel’s conductance properties and the temporal sequence of open-closed conformations that make up the channel’s activation mechanism, thus helping to understand their functions in health and disease.     

Impact of Father Involvement: A Closer Look at Indirect Effects Models Involving Marriage and Child Adjustment

In this article we present a framework for understanding the indirect effects of fathering on child development in the context of the marriage. We discuss three central pathways of influence: through relations between marital quality and fathering, through children's exposure to father expressions of marital discord, and through relations between marital quality and father psychological functioning. We provide corresponding hypotheses and review recent research to support or refute each. A common theme is that fathers, as well as mothers, have important influences in marital contexts, with some evidence for different or even greater impact of fathers in terms of the relations between the marital relationship and parenting, the impact of child exposure to marital conflict expressions, and as a function of parental symptomatology, although these effects are often complex. We discuss the value of including fathers in research on families and child development, and point out some promising directions for future study.