Examining patterns suggestive of acquisition during functional analyses: A consecutive controlled series of 116 cases.

The functional analysis approach described by Iwata et al. (1982/1994) has been used widely to determine the variables evoking and maintaining challenging behavior. However, one potential concern with conducting functional analyses is that repeated exposure to contingencies may induce a novel functional relation. To examine the likelihood of these potential iatrogenic effects, we evaluated social test conditions of the functional analysis for 116 participants and searched for patterns of responding indicative of acquisition. Patterns suggestive of acquisition occurred in 13.70% of tangible reinforcement conditions; however, the prevalence was only slightly lower in the attention condition (8.75%). Much lower prevalence was observed for the escape condition (2.13%). When grouped by quotient score, a pattern of acquisition was just as likely to be observed in the attention condition as in the tangible condition. Additionally, patterns indicative of acquisition were no more likely to be observed with participants who emitted automatically reinforced challenging behavior.

Further evidence of renewal in automatically maintained behavior.

Renewal is a relapse phenomenon that refers to the recurrence of a previously reduced behavior following a change in stimulus conditions. Muething et al. (2022) examined the phenomenology of renewal among individuals with automatically maintained challenging behavior treated at an outpatient clinic. We replicated their findings by retrospectively examining renewal across various topographies of automatically maintained behavior treated at an inpatient hospital, and we extended their work by also examining differences across subtypes of automatically maintained self-injurious behavior. The prevalence of renewal was comparable to that observed by Muething et al., supporting the notion that automatically maintained challenging behavior is susceptible to relapse phenomena. Furthermore, renewal was twice as likely to occur for individuals with Subtype 2 versus Subtype 1 self-injurious behavior, providing additional evidence of behavioral differentiation between subtypes. Our findings suggest that even after apparent stability in treatment, practitioners should remain vigilant for the recurrence of automatically maintained behavior during generalization.

Interhemispheric inhibition is different during arm cycling than a position- and intensity-matched tonic contraction.

Task-dependent changes in inhibition may explain why supraspinal excitability is higher during arm cycling than an intensity- and position-matched tonic contraction. The present study investigated whether interhemispheric inhibition (IHI) associated with biceps brachii activity was different during arm cycling, a locomotor output, compared to a tonic contraction. IHI was quantified using an ipsilateral silent period (iSP) evoked via transcranial magnetic stimulation (TMS) of the ipsilateral motor cortex. TMS was delivered at 120% resting motor threshold during the mid-elbow flexion phase of arm cycling (6 o'clock position, made relative to a clock face) and during a position- and intensity-matched tonic contraction. In total, 36 participants took part in the study. However, only 14 participants demonstrated IHI during arm cycling and 10 participants during tonic contraction. Of these participants, eight displayed clear iSPs during arm cycling and tonic contraction. The iSP duration was longer during arm cycling than tonic contraction (p < 0.05), while iSP EMG amplitude and area were not different between tasks (p > 05 for both comparisons). The main finding from this study is that IHI appears to be stronger during arm cycling than an intensity- and position-matched tonic contraction. This does not support previous findings of higher supraspinal excitability during arm cycling.

Interhemispheric inhibition to the biceps brachii during arm cycling.

This is the first demonstration of interhemispheric inhibition (IHI) during a locomotor output, arm cycling. IHI was quantified by assessing the depth of the ipsilateral silent period (iSP) evoked via transcranial magnetic stimulation of the motor cortex. There was a significant reduction in electromyography (EMG) amplitude of the iSP during cycling compared with the control EMG (16.8% ± 17.1%; p < 0.001). Depth and area for measuring the iSP during arm cycling are discussed. Novelty: This is the first study to demonstrate activation of the cortical circuit, interhemispheric inhibition, during a locomotor output.

Symbiont-derived ß-1,3-glucanases in a social insect: mutualism beyond nutrition.

Termites have had a long co-evolutionary history with prokaryotic and eukaryotic gut microbes. Historically, the role of these anaerobic obligate symbionts has been attributed to the nutritional welfare of the host. We provide evidence that protozoa (and/or their associated bacteria) colonizing the hindgut of the dampwood termite Zootermopsis angusticollis, synthesize multiple functional ß-1,3-glucanases, enzymes known for breaking down ß-1,3-glucans, the main component of fungal cell walls. These enzymes, we propose, may help in both digestion of ingested fungal hyphae and protection against invasion by fungal pathogens. This research points to an additional novel role for the mutualistic hindgut microbial consortia of termites, an association that may extend beyond lignocellulolytic activity and nitrogen fixation to include a reduction in the risks of mycosis at both the individual- and colony-levels while nesting in and feeding on microbial-rich decayed wood.

Selection of dinB alleles suppressing survival loss upon dinB overexpression in Escherichia coli.

Escherichia coli strains overproducing DinB undergo survival loss; however, the mechanisms regulating this phenotype are poorly understood. Here we report a genetic selection revealing DinB residues essential to effect this loss-of-survival phenotype. The selection uses strains carrying both an antimutator allele of DNA polymerase III (Pol III) α-subunit (dnaE915) and either chromosomal or plasmid-borne dinB alleles. We hypothesized that dnaE915 cells would respond to DinB overproduction differently from dnaE(+) cells because the dnaE915 allele is known to have an altered genetic interaction with dinB(+) compared to its interaction with dnaE(+). Notably, we observe a loss-of-survival phenotype in dnaE915 strains with either a chromosomal catalytically inactive dinB(D103N) allele or a low-copy-number plasmid-borne dinB(+) upon DNA damage treatment. Furthermore, we find that the loss-of-survival phenotype occurs independently of DNA damage treatment in a dnaE915 strain expressing the catalytically inactive dinB(D103N) allele from a low-copy-number plasmid. The selective pressure imposed resulted in suppressor mutations that eliminated growth defects. The dinB intragenic mutations examined were either base pair substitutions or those that we inferred to be loss of function (i.e., deletions and insertions). Further analyses of selected novel dinB alleles, generated by single-base-pair substitutions in the dnaE915 strain, indicated that these no longer effect loss of survival upon overproduction in dnaE(+) strains. These mutations are mapped to specific areas of DinB; this permits us to gain insights into the mechanisms underlying the DinB-mediated overproduction loss-of-survival phenotype.

Nest sanitation through defecation: antifungal properties of wood cockroach feces.

The wood cockroach Cryptocercus punctulatus nests as family units inside decayed wood, a substrate known for its high microbial load. We tested the hypothesis that defecation within their nests, a common occurrence in this species, reduces the probability of fungal development. Conidia of the entomopathogenic fungus, Metarhizium anisopliae, were incubated with crushed feces and subsequently plated on potato dextrose agar. Relative to controls, the viability of fungal conidia was significantly reduced following incubation with feces and was negatively correlated with incubation time. Although the cockroach's hindgut contained abundant ß-1,3-glucanase activity, its feces had no detectable enzymatic function. Hence, these enzymes are unlikely the source of the fungistasis. Instead, the antifungal compound(s) of the feces involved heat-sensitive factor(s) of potential microbial origin. When feces were boiled or when they were subjected to ultraviolet radiation and subsequently incubated with conidia, viability was "rescued" and germination rates were similar to those of controls. Filtration experiments indicate that the fungistatic activity of feces results from chemical interference. Because Cryptocercidae cockroaches have been considered appropriate models to make inferences about the factors fostering the evolution of termite sociality, we suggest that nesting in microbe-rich environments likely selected for the coupling of intranest defecation and feces fungistasis in the common ancestor of wood cockroaches and termites. This might in turn have served as a preadaptation that prevented mycosis as these phylogenetically related taxa diverged and evolved respectively into subsocial and eusocial organizations.

A single residue unique to DinB-like proteins limits formation of the polymerase IV multiprotein complex in Escherichia coli.

The activity of DinB is governed by the formation of a multiprotein complex (MPC) with RecA and UmuD. We identified two highly conserved surface residues in DinB, cysteine 66 (C66) and proline 67 (P67). Mapping on the DinB tertiary structure suggests these are noncatalytic, and multiple-sequence alignments indicate that they are unique among DinB-like proteins. To investigate the role of the C66-containing surface in MPC formation, we constructed the dinB(C66A) derivative. We found that DinB(C66A) copurifies with its interacting partners, RecA and UmuD, to a greater extent than DinB. Notably, copurification of RecA with DinB is somewhat enhanced in the absence of UmuD and is further increased for DinB(C66A). In vitro pulldown assays also indicate that DinB(C66A) binds RecA and UmuD better than DinB. We note that the increased affinity of DinB(C66A) for UmuD is RecA dependent. Thus, the C66-containing binding surface appears to be critical to modulate interaction with UmuD, and particularly with RecA. Expression of dinB(C66A) from the chromosome resulted in detectable differences in dinB-dependent lesion bypass fidelity and homologous recombination. Study of this DinB derivative has revealed a key surface on DinB, which appears to modulate the strength of MPC binding, and has suggested a binding order of RecA and UmuD to DinB. These findings will ultimately permit the manipulation of these enzymes to deter bacterial antibiotic resistance acquisition and to gain insights into cancer development in humans.

An active site aromatic triad in Escherichia coli DNA Pol IV coordinates cell survival and mutagenesis in different DNA damaging agents.

DinB (DNA Pol IV) is a translesion (TLS) DNA polymerase, which inserts a nucleotide opposite an otherwise replication-stalling N(2)-dG lesion in vitro, and confers resistance to nitrofurazone (NFZ), a compound that forms these lesions in vivo. DinB is also known to be part of the cellular response to alkylation DNA damage. Yet it is not known if DinB active site residues, in addition to aminoacids involved in DNA synthesis, are critical in alkylation lesion bypass. It is also unclear which active site aminoacids, if any, might modulate DinB's bypass fidelity of distinct lesions. Here we report that along with the classical catalytic residues, an active site "aromatic triad", namely residues F12, F13, and Y79, is critical for cell survival in the presence of the alkylating agent methyl methanesulfonate (MMS). Strains expressing dinB alleles with single point mutations in the aromatic triad survive poorly in MMS. Remarkably, these strains show fewer MMS- than NFZ-induced mutants, suggesting that the aromatic triad, in addition to its role in TLS, modulates DinB's accuracy in bypassing distinct lesions. The high bypass fidelity of prevalent alkylation lesions is evident even when the DinB active site performs error-prone NFZ-induced lesion bypass. The analyses carried out with the active site aromatic triad suggest that the DinB active site residues are poised to proficiently bypass distinctive DNA lesions, yet they are also malleable so that the accuracy of the bypass is lesion-dependent.

SOE-LRed: A simple and time-efficient method to localize genes with point mutations onto the Escherichia coli chromosome.

We use a powerful method to replace wild-type genes on the chromosome of Escherichia coli. Using a unique form of PCR, we generate easily constructible gene fusions bearing single point mutations. Used in conjunction with homologous recombination, this method eliminates cloning procedures previously used for this purpose.