RIPK1 regulates cytokine signaling and cell death during infection and inflammation. Peterson et al. show that RIPK1 kinase activity triggers apoptosis in response to bacterial pathogen blockade of innate immune signaling and that this pathway of effector-triggered immunity is critical for a successful antibacterial response.

Chronic exposure to intermittent hyperoxia causes abnormal carotid body development and attenuates the hypoxic ventilatory response (HVR) in neonatal rats. We hypothesized that concurrent exposure to intermittent hypercapnic hypoxia would influence this plasticity. Newborn rats were exposed to alternating bouts of hypercapnic hypoxia (10% O 2 /6% CO 2 ) and hyperoxia (30-40% O 2 ) (5 cycles h −1 , 24 h d −1 ) through 13-14 days of age; the experiment was run twice, once in a background of 21% O 2 and once in a background of 30% O 2 (i.e., "relative hyperoxia"). Hyperoxia had only small effects on carotid body development when combined with intermittent hypercapnic hypoxia: the carotid chemoafferent response to hypoxia was reduced, but this did not affect the HVR. In contrast, sustained exposure to 30% O 2 reduced carotid chemoafferent activity and carotid body size which resulted in a blunted HVR. When given alone, chronic intermittent hypercapnic hypoxia increased carotid body size and reduced the hypercapnic ventilatory response but did not affect the HVR. Overall, it appears that intermittent hypercapnic hypoxia counteracted the effects of hyperoxia on the carotid body and prevented developmental plasticity of the HVR.

Human settlement expansion into elephant ranges, as well as increasing elephant populations within confined areas has led to heightened levels of human–elephant conflict in southern African communities living near protected areas. Several methods to mitigate this conflict have been suggested including the use of bees as an elephant deterrent. We investigated whether bee auditory and olfactory cues (as surrogates for live bees) could be used to effectively deter elephants. We evaluated the responses of elephants in the southern section of the Kruger National Park to five different treatments: (1) control noise, (2) buzzing bee noise, (3) control noise with honey scent, (4) honey scent, and (5) bee noise with honey scent. Elephants did not respond or displayed less heightened responses to the first four treatments. All elephants exposed to the bee noise with honey scent responded with defensive behaviours and 15 out of 21 individuals also fled. We concluded that buzzing bees or honey scent as isolated treatments (as may be the case with dormant beehives) were not effective elephant deterrents, but rather an active beehive emitting a combination of auditory and olfactory cues was a viable deterrent. However, mismatches in the timing of elephant raids and activity of bees may limit the use of bees in mitigating the prevailing human–elephant conflict.

We previously observed that chronic intermittent hyperoxia attenuates the hypoxic ventilatory response (HVR) in neonatal rats. In clinical situations, however, intermittent hyperoxia alternates with bouts of hypercapnic hypoxia. In the present study, we exposed rats from birth through 14 days of age to one of three treatments: control (21% O2/0% CO2), intermittent hypercapnic hypoxia (10% O2/6% CO2, 5 episodes h‐1; I21/10), or intermittent hyperoxia + hypercapnic hypoxia (30% O2/0% CO2 to 10% O2/6% CO2, 5 episodes h‐1; I30/10). I30/10 rats exhibited slightly greater baseline ventilation than controls (measured by head‐body plethysmography) at P14, but this corresponded to a greater resting metabolic rate (in both I30/10 and I21/10 vs. controls). Although I21/10 and I30/10 treatments reduced single‐unit carotid chemoafferent responses to hypoxia (measured in vitro), the HVR was not different from that of control rats in either of these groups. Similarly, I21/10 and I30/10 treatments did not alter the hypercapnic ventilatory response. I21/10 and I30/10 rats had larger mass‐specific dry lung weight compared to controls, while continuous hyperoxia (60% O2) decreased lung size. Our results suggest that intermittent hypercapnic hypoxia counteracts the effects of intermittent hyperoxia, either by presenting an opposing stimulus (e.g., carotid body activation vs. inhibition) or by eliciting a more prominent plastic response.