Self-organization of motor-propelled cytoskeletal filaments at topographically defined borders.

Self-organization phenomena are of critical importance in living organisms and of great interest to exploit in nanotechnology. Here we describe in vitro self-organization of molecular motor-propelled actin filaments, manifested as a tendency of the filaments to accumulate in high density close to topographically defined edges on nano- and microstructured surfaces. We hypothesized that this "edge-tracing" effect either (1) results from increased motor density along the guiding edges or (2) is a direct consequence of the asymmetric constraints on stochastic changes in filament sliding direction imposed by the edges. The latter hypothesis is well captured by a model explicitly defining the constraints of motility on structured surfaces in combination with Monte-Carlo simulations [cf. Nitta et al. (2006)] of filament sliding. In support of hypothesis 2 we found that the model reproduced the edge tracing effect without the need to assume increased motor density at the edges. We then used model simulations to elucidate mechanistic details. The results are discussed in relation to nanotechnological applications and future experiments to test model predictions.

Jack Michael's Contributions to the Treatment of Autism.

Jack Michael dedicated his life to teaching behavior analysis. He was passionate about Skinner's works and his enthusiasm was contagious. Jack's primary goal for his students was that they be able to analyze behavior like Skinner analyzed behavior, but with a little bit of Jack Michael sprinkled in here and there. Jack is probably best known to behavior analysts for his conceptual contributions to our field (e.g., his work on motivation), but his contributions to the treatment of autism are perhaps his most socially significant achievement. In our tribute to Jack, we will describe how he advanced the treatment of autism not only through his conceptual work and his teaching, but through his role in the development of applied behavior analysis, and in the application of Skinner's (1957) analysis of verbal behavior to language assessment and intervention for children and adults with language delays.

Standing on the Shoulders of a Giant: Remembrances of Jack Michael, Part 1.

In 1959, Jack Michael and his PhD student Ted Ayllon published "The Psychiatric Nurse as a Behavioral Engineer" (Ayllon & Michael, 1959). That study was Ayllon's doctoral dissertation and was the first empirical demonstration of how the principles of behavior (e.g., reinforcement, extinction, satiation) could be applied to solve clinical problems. That research was the beginning of what would soon be called "behavior modification," and later, "applied behavior analysis." Jack's foundational contributions to behavior analysis continued for 5 decades. In recognition of his life's work, his former students and close associates John Mabry, Grayson Osborne, Jon Bailey, Mark Sundberg, and J. Vincent Carbone offer tributes to Jack. These tributes tell the story of Jack's early teaching career, his students, his work, and how he inspired others to become behavior analysts. Six more tributes will appear in the fall issue of The Analysis of Verbal Behavior and will provide insight into Jack's work and other activities in the later part of his career. Those tributes will be from Jack's former students and close associates Hank Schlinger, Dave Palmer, Carl Sundberg, John and Barb Esch, Anna Petursdottir, and Caio Miguel.

Standing on the Shoulders of a Giant: Remembrances of Jack Michael, Part 2.

In Part 1 of these remembrances of Jack Michael, we briefly described Jack's history in terms of how he became a behavior analyst (Sundberg & Schlinger, 2021). We pointed out that he was one of the first to apply the principles of behavior analysis discovered in the experimental laboratory to the area of rehabilitation. In so doing, Jack was perhaps the first applied behavior analyst. In Part 1, some of his former students and close associates from his early years at the University of Houston, Arizona State University, and Western Michigan University-John Mabry, Grayson Osborne, Jon Bailey, Mark Sundberg, and J. Vincent Carbone-provided their personal tributes to Jack. In Part 2, we offer six more tributes that-with one exception, that of Ted Ayllon-provide insight into Jack's work in the latter part of his career. In addition to Ted Ayllon, these tributes are from Jack's students and close associates Hank Schlinger, Dave Palmer, John and Barb Esch, Carl Sundberg, and Caio Miguel. The authors provide insights not only into their views about Jack but also into their own lives. Collectively, they paint a picture of people from different backgrounds that all found their way to Jack Michael and to behavior analysis. To a person, they describe how their behavior, whether as scientists, practitioners, or both, was radically transformed as a result, and how they attribute that change largely to Jack's influence.

Heavy meromyosin molecules extending more than 50 nm above adsorbing electronegative surfaces.

In the in vitro motility assay, actin filaments are propelled by surface-adsorbed myosin motors, or rather, myosin motor fragments such as heavy meromyosin (HMM). Recently, efforts have been made to develop actomyosin powered nanodevices on the basis of this assay but such developments are hampered by limited understanding of the HMM adsorption geometry. Therefore, we here investigate the HMM adsorption geometries on trimethylchlorosilane- [TMCS-] derivatized hydrophobic surfaces and on hydrophilic negatively charged surfaces (SiO(2)). The TMCS surface is of great relevance in fundamental studies of actomyosin and both surface substrates are important for the development of motor powered nanodevices. Whereas both the TMCS and SiO(2) surfaces were nearly saturated with HMM (incubation at 120 microg mL(-1)) there was little actin binding on SiO(2) in the absence of ATP and no filament sliding in the presence of ATP. This contrasts with excellent actin-binding and motility on TMCS. Quartz crystal microbalance with dissipation (QCM-D) studies demonstrate a HMM layer with substantial protein mass up to 40 nm above the TMCS surface, considerably more than observed for myosin subfragment 1 (S1; 6 nm). Together with the excellent actin transportation on TMCS, this strongly suggests that HMM adsorbs to TMCS mainly via its most C-terminal tail part. Consistent with this idea, fluorescence interference contrast (FLIC) microscopy showed that actin filaments are held by HMM 38 +/- 2 nm above the TMCS-surface with the catalytic site, on average, 20-30 nm above the surface. Viewed in a context with FLIC, QCM-D and TIRF results, the lack of actin motility and the limited actin binding on SiO(2) shows that HMM adsorbs largely via the actin-binding region on this surface with the C-terminal coiled-coil tails extending >50 nm into solution. The results and new insights from this study are of value, not only for the development of motor powered nanodevices but also for the interpretation of fundamental biophysical studies of actomyosin function and for the understanding of surface-protein interactions in general.

An evaluation of the feedback loops in the poverty focus of world bank operations.

The World Bank Group in 2013 made the elimination of extreme poverty by 2030 a central institutional focus and purpose. This paper, based on an evaluation conducted by the Independent Evaluation Group of the World Bank Group, examines how, and how well, the Bank uses feedback loops to enhance the poverty focus of its operations. Feedback loops are important for every element of the results chain running from data, to diagnostics, to strategy formulation and finally to strategy implementation. The evaluation uses a range of instruments, including surveys of stakeholders and World Bank staff, focus group meetings, country case studies and systematic reviews of Bank lending and non-lending operations. We find that while the Bank generates useful information on poverty reduction from its projects and programs, the feedback loops - from outcomes to data analysis to diagnostics to strategy formulation and implementation - have generally been weak, with sizable variation across countries.

Covert verbal mediation in arbitrary matching to sample.

Covert verbal mediation was examined in an arbitrary matching-to-sample (MTS) preparation with a high-verbal group (college students) and a low-verbal group (adults with intellectual disabilities). Arbitrary relations were established between nonsense words, visual symbols, objects, and hand signs. Task difficulty was balanced for the groups based on errors during acquisition. All participants experienced a hand sign condition, and three MTS conditions each with a unique configuration of the comparison array: fixed location, random location, and all symbols the same. The same symbol condition was designed to impede a participant's ability to label individual symbols. The results showed that disrupting labeling adversely affected MTS performance for high-verbal participants, but not for low-verbal participants. The data suggest that high-verbal participants depended on mediating verbal behavior and joint control to assist them in finding the correct comparison stimulus. Low-verbal participants could not benefit from verbal mediating variables and likely relied on unmediated contingencies, or some form of nonverbal mediation. For the high-verbal group, 19 different putative emergent relations were identified as occurring at various stages of acquisition between the sample stimulus and the selection response. These emergent relations likely provided supplementary sources of stimulus control that participated in evoking MTS selection behavior.

Contact angle measurements by confocal microscopy for non-destructive microscale surface characterization.

Contact angle measurements are of great importance in surface characterization but the practical use has often been limited to macroscopic dimensions (millimeters). Therefore, we have developed a confocal microscopy method that allows non-destructive measurements of both low (<30 degrees ) and high (30 degrees -90 degrees ) contact angles. Low contact angles were measured by reconstructing the drop profile from the interference patterns in droplets condensed from atmospheric humidity. At higher contact angles water droplets with a small amount of fluorescein were sprayed onto the surfaces and 3D-image stacks were recorded and used to extract the contact angle. Suitable drop sizes were between a few up to about 50 mum radius, using a 40x magnification objective. Using drops >10 micrometers radius for microcontact angle measurements a good correlation was obtained between measured micro- and macrocontact angles. After microcontact angle measurements the surfaces were rinsed and heavy meromyosin motor fragments were adsorbed to the surface. Importantly, the sensitive actin propelling function of these motor proteins was not affected by the previous contact angle measurements using fluorescent droplets. This suggests that the methodology should be suitable for non-destructive characterization of different parts of micropatterned surfaces being developed for biological assays.

Recollections of Jack Michael and the Application of Skinner's Analysis of Verbal Behavior.

Jack Michael offered a course on verbal behavior almost every year throughout his teaching career. Jack was also interested in the application of Skinner's work and in 1976 began to offer a graduate course at Western Michigan University titled Verbal Behavior Applications. Jack and his students pursued the application of Skinner's work on verbal behavior with dozens of empirical studies during the 1970s. In honor of the 60th anniversary of the publication of Skinner's book Verbal Behavior, the current paper presents some of my recollections of Jack's work on verbal behavior as his student, graduate teaching assistant, and research collaborator during that time period.

Verbal Stimulus Control and the Intraverbal Relation.

The importance of the intraverbal relation is missed in most theories of language. Skinner (1957) attributes this to traditional semantic theories of meaning that focus on the nonverbal referents of words and neglect verbal stimuli as separate sources of control for linguistic behavior. An analysis of verbal stimulus control is presented, along with its distinction from nonverbal stimulus control and motivational control. It is suggested that there are at least four different types of increasingly complex verbal discriminations relevant to speaker and listener behavior: simple, compound, verbal conditional, and verbal function-altering (Eikeseth & Smith, 2013; Schlinger & Blakely, 1994). Separate but interlocking accounts of how these specific types of verbal stimuli produce different evocative and function-altering effects for the speaker and for the listener are provided. Finally, the effects of weakening verbal stimulus control and the loss of intraverbal behavior are considered, especially as they relate to dementia, aphasia, and traumatic brain injury.

Thirty Points About Motivation From Skinner's Book Verbal Behavior.

Skinner discussed the topic of motivation in every chapter of the book Verbal Behavior (1957), usually with his preferred terminology of "deprivation, satiation, and aversive stimulation." In the current paper, direct quotations are used to systematically take the reader through 30 separate points made by Skinner in Verbal Behavior that collectively provide a comprehensive analysis of his position regarding the role of motivation in behavior analysis. In addition, various refinements and extensions of Skinner's analysis by Jack Michael and colleagues (Laraway, Snycerski, Michael, & Poling, 2003; Michael, 1982, 1988, 1993, 2000, 2004, 2007) are incorporated, along with suggestions for research and applications for several of the points.

Intraverbal behavior and verbal conditional discriminations in typically developing children and children with autism.

Individuals with autism often experience difficulty acquiring a functional intraverbal repertoire, despite demonstrating strong mand, tact, and listener skills. This learning problem may be related to the fact that the primary antecedent variable for most intraverbal behavior involves a type of multiple control identified as a verbal conditional discrimination (VC(D)). The current study is a descriptive analysis that sought to determine if there is a general sequence of intraverbal acquisition by typically developing children and for children with autism, and if this sequence could be used as a framework for intraverbal assessment and intervention. Thirty-nine typically developing children and 71 children with autism were administered an 80-item intraverbal subtest that contained increasingly difficult intraverbal questions and VC(D)s. For the typically developing children the results showed that there was a correlation between age and correct intraverbal responses. However, there was variability in the scores of children who were the same age. An error analysis revealed that compound VC(D)s were the primary cause of errors. Children with autism made the same types of errors as typically developing children who scored at their level on the subtest. These data suggest a potential framework and sequence for intraverbal assessment and intervention.

The multiple control of verbal behavior.

Amid the novel terms and original analyses in Skinner's Verbal Behavior, the importance of his discussion of multiple control is easily missed, but multiple control of verbal responses is the rule rather than the exception. In this paper we summarize and illustrate Skinner's analysis of multiple control and introduce the terms convergent multiple control and divergent multiple control. We point out some implications for applied work and discuss examples of the role of multiple control in humor, poetry, problem solving, and recall. Joint control and conditional discrimination are discussed as special cases of multiple control. We suggest that multiple control is a useful analytic tool for interpreting virtually all complex behavior, and we consider the concepts of derived relations and naming as cases in point.

Diffusion dynamics of motor-driven transport: gradient production and self-organization of surfaces.

The interaction between cytoskeletal filaments (e.g., actin filaments) and molecular motors (e.g., myosin) is the basis for many aspects of cell motility and organization of the cell interior. In the in vitro motility assay (IVMA), cytoskeletal filaments are observed while being propelled by molecular motors adsorbed to artificial surfaces (e.g., in studies of motor function). Here we integrate ideas that cytoskeletal filaments may be used as nanoscale templates in nanopatterning with a novel approach for the production of surface gradients of biomolecules and nanoscale topographical features. The production of such gradients is challenging but of increasing interest (e.g., in cell biology). First, we show that myosin-induced actin filament sliding in the IVMA can be approximately described as persistent random motion with a diffusion coefficient (D) given by a relationship analogous to the Einstein equation (D = kT/gamma). In this relationship, the thermal energy (kT) and the drag coefficient (gamma) are substituted by a parameter related to the free-energy transduction by actomyosin and the actomyosin dissociation rate constant, respectively. We then demonstrate how the persistent random motion of actin filaments can be exploited in conceptually novel methods for the production of actin filament density gradients of predictable shapes. Because of regularly spaced binding sites (e.g., lysines and cysteines) the actin filaments act as suitable nanoscale scaffolds for other biomolecules (tested for fibronectin) or nanoparticles. This forms the basis for secondary chemical and topographical gradients with implications for cell biological studies and biosensing.

Effects of surface adsorption on catalytic activity of heavy meromyosin studied using a fluorescent ATP analogue.

Biochemical studies in solution and with myosin motor fragments adsorbed to surfaces (in vitro motility assays) are invaluable for elucidation of actomyosin function. However, there is limited understanding of how surface adsorption affects motor properties, e.g., catalytic activity. Here we address this issue by comparing the catalytic activity of heavy meromyosin (HMM) in solution and adsorbed to standard motility assay surfaces [derivatized with trimethylchlorosilane (TMCS)]. For these studies we first characterized the interaction of HMM and actomyosin with the fluorescent ATP analogue adenosine 5'-triphosphate Alexa Fluor 647 2'- (or 3'-) O-(N-(2-aminoethyl)urethane) hexa(triethylammonium) salt (Alexa-ATP). The data suggest that Alexa-ATP is hydrolyzed by HMM in solution at a slightly higher rate than ATP but with a generally similar mechanism. Furthermore, Alexa-ATP is effective as a fuel for HMM-propelled actin filament sliding. The catalytic activity of HMM on TMCS surfaces was studied using (1) Alexa-ATP in total internal reflection fluorescence (TIRF) spectroscopy experiments and (2) Alexa-ATP and ATP in HPLC-aided ATPase measurements. The results support the hypothesis of different HMM configurations on the surface. However, a dominant proportion of the myosin heads were catalytically active, and their average steady-state hydrolysis rate was slightly higher (with Alexa-ATP) or markedly higher (with ATP) on the surface than in solution. The results are discussed in relation to the use of TMCS surfaces and Alexa-ATP for in vitro motility assays and single molecule studies. Furthermore, we propose a novel TIRF microscopy method to accurately determine the surface density of catalytically active myosin motors.

Actin filament guidance on a chip: toward high-throughput assays and lab-on-a-chip applications.

Biological molecular motors that are constrained so that function is effectively limited to predefined nanosized tracks may be used as molecular shuttles in nanotechnological applications. For these applications and in high-throughput functional assays (e.g., drug screening), it is important that the motors propel their cytoskeletal filaments unidirectionally along the tracks with a minimal number of escape events. We here analyze the requirements for achieving this for actin filaments that are propelled by myosin II motor fragments (heavy meromyosin; HMM). First, we tested the guidance of HMM-propelled actin filaments along chemically defined borders. Here, trimethylchlorosilane (TMCS)-derivatized areas with high-quality HMM function were surrounded by SiO(2) domains where HMM did not bind actin. Guidance along the TMCS-SiO(2) border was almost 100% for filament approach angles between 0 and 20 degrees but only about 10% at approach angles near 90 degrees . A model (Clemmens, J.; Hess, H.; Lipscomb, R.; Hanein, Y.; Bohringer, K. F.; Matzke, C. M.; Bachand, G. D.; Bunker, B. C.; Vogel, V. Langmuir 2003, 19, 10967-10974) accounted for essential aspects of the data and also correctly predicted a more efficient guidance of actin filaments than previously shown for kinesin-propelled microtubules. Despite the efficient guidance at low approach angles, nanosized (<700 nm wide) TMCS tracks surrounded by SiO(2) were not effective in guiding actin filaments. Neither was there complete guidance along nanosized tracks that were surrounded by topographical barriers (walls and roof partially covering the track) unless there was also chemically based selectivity between the tracks and surroundings. In the latter case, with dually defined tracks, there was close to 100% guidance. A combined experimental and theoretical analysis, using tracks of the latter type, suggested that a track width of less than about 200-300 nm is sufficient at a high HMM surface density to achieve unidirectional sliding of actin filaments. In accord with these results, we demonstrate the long-term trapping of actin filaments on a closed-loop track (width < 250 nm). The results are discussed in relation to lab-on-a-chip applications and nanotechnology-assisted assays of actomyosin function.

Selective spatial localization of actomyosin motor function by chemical surface patterning.

We have previously described the efficient guidance and unidirectional sliding of actin filaments along nanosized tracks with adsorbed heavy meromyosin (HMM; myosin II motor fragment). In those experiments, the tracks were functionalized with trimethylchlorosilane (TMCS) by chemical vapor deposition (CVD) and surrounded by hydrophilic areas. Here we first show, using in vitro motility assays on nonpatterned and micropatterned surfaces, that the quality of HMM function on CVD-TMCS is equivalent to that on standard nitrocellulose substrates. We further examine the influences of physical properties of different surfaces (glass, SiO(2), and TMCS) and chemical properties of the buffer solution on motility. With the presence of methylcellulose in the assay solution, there was HMM-induced actin filament sliding on both glass/SiO(2) and on TMCS, but the velocity was higher on TMCS. This difference in velocity increased with decreasing contact angles of the glass and SiO(2) surfaces in the range of 20-67 degrees (advancing contact angles for water droplets). The corresponding contact angle of CVD-TMCS was 81 degrees. In the absence of methylcellulose, there was high-quality motility on TMCS but no motility on glass/SiO(2). This observation was independent of the contact angle of the glass/SiO(2) surfaces and of HMM incubation concentrations (30-150 microg mL(-)(1)) and ionic strengths of the assay solution (20-50 mM). Complete motility selectivity between TMCS and SiO(2) was observed for both nonpatterned and for micro- and nanopatterned surfaces. Spectrophotometric analysis of HMM depletion during incubation, K/EDTA ATPase measurements, and total internal reflection fluorescence spectroscopy of HMM binding showed only minor differences in HMM surface densities between TMCS and SiO(2)/glass. Thus, the motility contrast between the two surface chemistries seems to be attributable to different modes of HMM binding with the hindrance of actin binding on SiO(2)/glass.

The search for the etiology of autism.

This special section on autism etiology began with the paper submitted to The Analysis of Verbal Behavior by Drash and Tutor, who propose that autism is a contingency-shaped disorder of verbal behavior. The five papers that follow the Drash and Tutor paper provide reactions to their analysis by several behavior analysts working in the autism field. Only one of the five (Malott) is fully supportive of Drash and Tudor's analysis of autism as a completely contingency-shaped disorder. The other four authors recognize the importance of environmental variables in the development and maintenance of autistic behavior, but caution against the neglect of genetic and other variables such as environmental intrusion, and insist that a complete behavioral theory of the etiology of autism must involve all three variables. The series ends with Drash and Tutor's response to the five papers.