32 research outputs found
California & Foothill Tunnel Feasibility Project:
Safety on and off campus while attending college is one of the fastest growing concerns around the country. Having a secure path to get to campus is also a large problem to a select number of students here at California Polytechnic State University. The Rape Tunnel at the corner of California and Foothill Boulevard is considered to many to be a danger because of its unpredictable accessibility and the stigma that surrounds it
The geography of recent genetic ancestry across Europe
The recent genealogical history of human populations is a complex mosaic
formed by individual migration, large-scale population movements, and other
demographic events. Population genomics datasets can provide a window into this
recent history, as rare traces of recent shared genetic ancestry are detectable
due to long segments of shared genomic material. We make use of genomic data
for 2,257 Europeans (the POPRES dataset) to conduct one of the first surveys of
recent genealogical ancestry over the past three thousand years at a
continental scale. We detected 1.9 million shared genomic segments, and used
the lengths of these to infer the distribution of shared ancestors across time
and geography. We find that a pair of modern Europeans living in neighboring
populations share around 10-50 genetic common ancestors from the last 1500
years, and upwards of 500 genetic ancestors from the previous 1000 years. These
numbers drop off exponentially with geographic distance, but since genetic
ancestry is rare, individuals from opposite ends of Europe are still expected
to share millions of common genealogical ancestors over the last 1000 years.
There is substantial regional variation in the number of shared genetic
ancestors: especially high numbers of common ancestors between many eastern
populations likely date to the Slavic and/or Hunnic expansions, while much
lower levels of common ancestry in the Italian and Iberian peninsulas may
indicate weaker demographic effects of Germanic expansions into these areas
and/or more stably structured populations. Recent shared ancestry in modern
Europeans is ubiquitous, and clearly shows the impact of both small-scale
migration and large historical events. Population genomic datasets have
considerable power to uncover recent demographic history, and will allow a much
fuller picture of the close genealogical kinship of individuals across the
world.Comment: Full size figures available from
http://www.eve.ucdavis.edu/~plralph/research.html; or html version at
http://ralphlab.usc.edu/ibd/ibd-paper/ibd-writeup.xhtm
Microanatomy of the trophosome region of Paracatenula cf. polyhymnia (Catenulida, Platyhelminthes) and its intracellular symbionts
Marine catenulid platyhelminths of the genus Paracatenula lack mouth, pharynx and gut. They live in a symbiosis with intracellular bacteria which are restricted to the body region posterior to the brain. The symbiont-housing cells (bacteriocytes) collectively form the trophosome tissue, which functionally replaces the digestive tract. It constitutes the largest part of the body and is the most important synapomorphy of this group. While some other features of the Paracatenula anatomy have already been analyzed, an in-depth analysis of the trophosome region was missing. Here, we identify and characterize the composition of the trophosome and its surrounding tissue by analyzing series of ultra-thin cross-sections of the species Paracatenula cf. polyhymnia. For the first time, a protonephridium is detected in a Paracatenula species, but it is morphologically reduced and most likely not functional. Cells containing needle-like inclusions in the reference species Paracatenula polyhymnia Sterrer and Rieger, 1974 were thought to be sperm, and the inclusions interpreted as the sperm nucleus. Our analysis of similar cells and their inclusions by EDX and Raman microspectroscopy documents an inorganic spicule consisting of a unique magnesium–phosphate compound. Furthermore, we identify the neoblast stem cells located underneath the epidermis. Except for the modifications due to the symbiotic lifestyle and the enigmatic spicule cells, the organization of Paracatenula cf. polyhymnia conforms to that of the Catenulida in all studied aspects. Therefore, this species represents an excellent model system for further studies of host adaptation to an obligate symbiotic lifestyle
Suboptimal Activation of Antigen-Specific CD4+ Effector Cells Enables Persistence of M. tuberculosis In Vivo
Adaptive immunity to Mycobacterium tuberculosis controls
progressive bacterial growth and disease but does not eradicate infection. Among
CD4+ T cells in the lungs of M.
tuberculosis-infected mice, we observed that few produced IFN-γ
without ex vivo restimulation. Therefore, we hypothesized that one mechanism
whereby M. tuberculosis avoids elimination is by limiting
activation of CD4+ effector T cells at the site of infection in
the lungs. To test this hypothesis, we adoptively transferred Th1-polarized
CD4+ effector T cells specific for M.
tuberculosis Ag85B peptide 25 (P25TCRTh1 cells), which trafficked
to the lungs of infected mice and exhibited antigen-dependent IFN-γ
production. During the early phase of infection, ∼10% of P25TCRTh1
cells produced IFN-γ in vivo; this declined to <1% as infection
progressed to chronic phase. Bacterial downregulation of fbpB
(encoding Ag85B) contributed to the decrease in effector T cell activation in
the lungs, as a strain of M. tuberculosis engineered to express
fbpB in the chronic phase stimulated P25TCRTh1 effector
cells at higher frequencies in vivo, and this resulted in CD4+ T
cell-dependent reduction of lung bacterial burdens and prolonged survival of
mice. Administration of synthetic peptide 25 alone also increased activation of
endogenous antigen-specific effector cells and reduced the bacterial burden in
the lungs without apparent host toxicity. These results indicate that
CD4+ effector T cells are activated at suboptimal
frequencies in tuberculosis, and that increasing effector T cell activation in
the lungs by providing one or more epitope peptides may be a successful strategy
for TB therapy