The first season of the American television series Marvel's Agents of S.H.I.E.L.D., which is based on the Marvel Comics organization S.H.I.E.L.D. (Strategic Homeland Intervention, Enforcement and Logistics Division), revolves around the character of Phil Coulson and his team of S.H.I.E.L.D. agents, who are assigned to several dangerous cases. The cases are centered on Centipede Project and its leader, The Clairvoyant, while Coulson also searches for answers concerning his mysterious resurrection after dying in Marvel's The Avengers. It is set in the Marvel Cinematic Universe (MCU), sharing continuity with the films of the franchise, and was produced by ABC Studios, Marvel Television, and Mutant Enemy Productions. Jed Whedon, Maurissa Tancharoen, and Jeffrey Bell served as showrunners.
"The Ghost" is the first episode of the fourth season of the American television series Agents of S.H.I.E.L.D. Based on the Marvel Comics organization S.H.I.E.L.D., it follows Phil Coulson and his fellow S.H.I.E.L.D. agents as they deal with the enhanced individuals Quake and Ghost Rider. It is set in the Marvel Cinematic Universe (MCU) and acknowledges the franchise's films. The episode was written by showrunners Jed Whedon and Maurissa Tancharoen, and directed by Billy Gierhart.
Bobbi and Mack are not bad guys and Marvel Comics fans can rejoice. We already went through one double-cross with Bobbi "Mockingbird" Morse since she was introduced as a SHIELD field agent undercover in Hydra earlier this season. As fans know, Bobbi eventually goes on to become an Avenger and that still might be the case. Especially after this episode's reveal...
By considering the complexity and relative invasiveness of such approaches, the in vivo use for allowing optical clearing agent penetration into cells has not been explored so far and the approach was limited to the delivery of genes. In addition, considering that epidermis has a thickness of about 0.1 mm compared with a dermal thickness of about 1-5 mm, targeting dermis is more suitable for obtaining an overall tissue optical clearing for three main reasons: i) dermis accounts for more than 90% of the whole skin thickness; ii) the refractive index mismatch between interstitial fluid and dermal components is high, causing high scattering in dermis; iii) the penetration of exogenous agents within dermis is somewhat easier because of larger interstitial spaces compared to those in epidermis.
For in-vivo application the clearing efficacy depends on the agent used as well as on its concentration, leading generally to a more effective clearing as the agent concentration increases. Anyway, this feature has to be considered together with the speed of the process. In fact, both clearing efficacy and speed are strongly affected by the diffusive behavior of the agent within the tissue to be cleared, with a faster and more effective clearing as the agent diffusion time decreases. In this scenario, the use of chemical enhancers able to facilitate the diffusion of the agent in deep tissue has demonstrated to be a key-to-success for an effective in-vivo optical clearing in a reasonable amount of time. A good example is reported in Fig. 5, where the combination of PEG-400 and thiazone is providing faster and more effective clearing of skin in-vivo with respect to the administration of PEG-400 alone. In particular, even if the latter might in principle provide a better refractive index matching for skin dermis, the long diffusion time causes a clearing effect insufficient for monitoring dermal blood flow through intact mouse skin, unless administered in tandem with a chemical enhancer, as thiazone. Other features, such as chemical aggressiveness, reversibility, and side-effects have to be considered with particular attention, especially for in-vivo applications, whereas these are less important in ex-vivo applications. However, it is difficult to describe the motivations for opting toward an approach rather than another when applying clearing agents in-vivo, as the clearing process has been partially clarified at the microscopic and molecular scale only ex-vivo; the mechanisms for in-vivo optical clearing, on the other hand, are still far from being well understood, considering the major physiological complexity with respect to ex-vivo condition. Anyway, few empirical hints could be provided on the basis of the experimental results obtained up to now; for example, the use of aqueous solutions instead of pure agents could limit side-effects due to the chemical aggressiveness of the agent used, such as edema for glycerol in the skin. In addition, the reversibility of the process has been fully demonstrated for aqueous solutions of the agents, in contrast to irreversible effects, such as tissue swelling and morphological transformation occurring when the clearing agent is administered undiluted (for example the fibrillar rearrangement of collagen fibers following the immersion in 100% glycerol). 2b1af7f3a8