Microtubules are polarized polymers that exhibit dynamic instability, with alternating phases of elongation and shortening, particularly at the more dynamic plus-end. Microtubule plus-end tracking proteins (؉TIPs) localize to and track with growing microtubule plus-ends in the cell. ؉TIPs regulate microtubule dynamics and mediate interactions with other cellular components. The molecular mechanisms responsible for the ؉TIP tracking activity are not well understood, however. We reconstituted the ؉TIP tracking of mammalian proteins EB1 and CLIP-170 in vitro at single-molecule resolution using time-lapse total internal reflection fluorescence microscopy. We found that EB1 is capable of dynamically tracking growing microtubule plus-ends. Our singlemolecule studies demonstrate that EB1 exchanges rapidly at microtubule plus-ends with a dwell time of <1 s, indicating that single EB1 molecules go through multiple rounds of binding and dissociation during microtubule polymerization. CLIP-170 exhibits lattice diffusion and fails to selectively track microtubule ends in the absence of EB1; the addition of EB1 is both necessary and sufficient to mediate plus-end tracking by CLIP-170. Single-molecule analysis of the CLIP-170 -EB1 complex also indicates a short dwell time at growing plus-ends, an observation inconsistent with the copolymerization of this complex with tubulin for plus-end-specific localization. GTP hydrolysis is required for ؉TIP tracking, because end-specificity is lost when tubulin is polymerized in the presence of guanosine 5-[␣,␤-methylene]triphosphate (GMPCPP). Together, our data provide insight into the mechanisms driving plus-end tracking by mammalian ؉TIPs and suggest that EB1 specifically recognizes the distinct lattice structure at the growing microtubule end.ϩTIP ͉ single molecule ͉ total internal reflection fluorescence (TIRF) microscopy ͉ dynamic instability

Recent years have seen renewed interest and research about the use of hallucinogens as possible agents in the treatment of psychiatric disorders. However, we are unaware of studies assessing the current attitudes of American psychiatrists regarding hallucinogens. Therefore, we e-mailed surveys to 1000 members of the American Psychiatric Association-250 resident-fellows and 750 attending psychiatrists. The response rate was 32.4%. Respondents tended to perceive hallucinogens as potentially hazardous and appropriately illegal for recreational purposes. However, a large minority expressed optimism about the potential use of hallucinogens for psychiatric treatment. Male and trainee respondents, as compared with female and attending respondents, reported less concern about the risks of hallucinogens and greater optimism about their therapeutic potential. Younger psychiatrists also seemed more optimistic. Optimism among trainees and younger psychiatrists may possibly reflect greater exposure to recent positive publications about hallucinogens and less awareness of more negative past reports.

No abstract

Background: Patients taking methadone for opioid use disorder may desire transition to buprenorphine for a number of reasons. However, the current recommended approach for this transition generally takes weeks to months as an outpatient, causing considerable discomfort to the patient and a heightened risk of relapse during the transition period. Case: We describe the case of a patient on methadone maintenance who was rapidly transitioned to buprenorphine because of her desire to not return to her methadone clinic. In order to rapidly transition the patient from methadone to buprenorphine, naltrexone was administered to precipitate acute opioid withdrawal, which was followed soon after by buprenorphine induction. Discussion: Rapid transition from methadone maintenance to buprenorphine can be accomplished in inpatients by precipitating acute withdrawal with naltrexone, providing an effective alternative for patients who cannot tolerate the typical protracted methadone taper required prior to buprenorphine induction as an outpatient.