A Blog Around The Clock

New and Exciting in PLoS this week

Tuesday – let’s take a look at 4 out of 7 PLoS journals. As always, you should rate the articles, post notes and comments and send trackbacks when you blog about the papers. You can now also easily place articles on various social services (CiteULike, Mendeley, Connotea, Stumbleupon, Facebook and Digg) with just one click. Here are my own picks for the week – you go and look for your own favourites:

Disrupting Circadian Homeostasis of Sympathetic Signaling Promotes Tumor Development in Mice:

Cell proliferation in all rapidly renewing mammalian tissues follows a circadian rhythm that is often disrupted in advanced-stage tumors. Epidemiologic studies have revealed a clear link between disruption of circadian rhythms and cancer development in humans. Mice lacking the circadian genes Period1 and 2 (Per) or Cryptochrome1 and 2 (Cry) are deficient in cell cycle regulation and Per2 mutant mice are cancer-prone. However, it remains unclear how circadian rhythm in cell proliferation is generated in vivo and why disruption of circadian rhythm may lead to tumorigenesis. Mice lacking Per1 and 2, Cry1 and 2, or one copy of Bmal1, all show increased spontaneous and radiation-induced tumor development. The neoplastic growth of Per-mutant somatic cells is not controlled cell-autonomously but is dependent upon extracellular mitogenic signals. Among the circadian output pathways, the rhythmic sympathetic signaling plays a key role in the central-peripheral timing mechanism that simultaneously activates the cell cycle clock via AP1-controlled Myc induction and p53 via peripheral clock-controlled ATM activation. Jet-lag promptly desynchronizes the central clock-SNS-peripheral clock axis, abolishes the peripheral clock-dependent ATM activation, and activates myc oncogenic potential, leading to tumor development in the same organ systems in wild-type and circadian gene-mutant mice. Tumor suppression in vivo is a clock-controlled physiological function. The central circadian clock paces extracellular mitogenic signals that drive peripheral clock-controlled expression of key cell cycle and tumor suppressor genes to generate a circadian rhythm in cell proliferation. Frequent disruption of circadian rhythm is an important tumor promoting factor.

Internet Treatment for Depression: A Randomized Controlled Trial Comparing Clinician vs. Technician Assistance:

Internet-based cognitive behavioural therapy (iCBT) for depression is effective when guided by a clinician, less so if unguided. Question: Would guidance from a technician be as effective as guidance from a clinician? Randomized controlled non-inferiority trial comparing three groups: Clinician-assisted vs. technician-assisted vs. delayed treatment. Community-based volunteers applied to the VirtualClinic (www.virtualclinic.org.au) research program, and 141 participants with major depressive disorder were randomized. Participants in the clinician- and technician-assisted groups received access to an iCBT program for depression comprising 6 online lessons, weekly homework assignments, and weekly supportive contact over a treatment period of 8 weeks. Participants in the clinician-assisted group also received access to a moderated online discussion forum. The main outcome measures were the Beck Depression Inventory (BDI-II) and the Patient Health Questionnaire-9 Item (PHQ-9). Completion rates were high, and at post-treatment, both treatment groups reduced scores on the BDI-II (p<0.001) and PHQ-9 (p<0.001) compared to the delayed treatment group but did not differ from each other. Within group effect sizes on the BDI-II were 1.27 and 1.20 for the clinician- and technician-assisted groups respectively, and on the PHQ-9, were 1.54 and 1.60 respectively. At 4-month follow-up participants in the technician group had made further improvements and had significantly lower scores on the PHQ-9 than those in the clinician group. A total of approximately 60 minutes of clinician or technician time was required per participant during the 8-week treatment program. Both clinician- and technician-assisted treatment resulted in large effect sizes and clinically significant improvements comparable to those associated with face-to-face treatment, while a delayed treatment control group did not improve. These results provide support for large scale trials to determine the clinical effectiveness and acceptability of technician-assisted iCBT programs for depression. This form of treatment has potential to increase the capacity of existing mental health services.

Climate-Driven Evolution:

There are several rather distinct traditions in the contemporary study of human evolution. One is the detailed study of anatomical differences among fossils. A second emphasizes classical ecology with detailed attention to ancient climates and environments and comparative biogeography. A third has a focus on behavioral ecology (i.e., what used to be called sociobiology). It appears to this outsider that these are not so much competing traditions as they are nearly independent and seemingly unaware of each other. They each have much to contribute, they are each prominent in particular current disagreements in the field, and they each have glaring weaknesses.

Where to for Sexual Health Education for Adolescents in Sub-Saharan Africa?:

Sub-Saharan Africa remains the global hub of the HIV epidemic. Seventy percent of new HIV infections occur in the region. And because the sexually transmitted epidemic starts among women and men in their teenage years [1], promoting the sexual health of adolescents is a substantial health priority. In light of this, the findings of the MEMA kwa Vijana trial in Tanzania [2] and the long-term follow up of participants in its school-based intervention, published this week in PLoS Medicine [3], are very disappointing. The key questions we have to ask now are: In light of current knowledge about behaviour change, are these findings surprising? And, what are the implications for the next generation of sexual health interventions?