Suppression of acute seizures by theta burst electrical stimulation of the hippocampal commissure using a closed-loop system

This study investigated the effects of electrical stimulation with theta burst stimulation (eTBS) on seizure suppression. Optimal parameters of eTBS were determined through open-loop stimulation experiments and then implemented in a close-loop seizure control system. For the experiments, 4-aminopyridine (4-AP) was injected into the right hippocampus of Sprague-Dawley rats to induce an acute seizure. eTBS was applied on the ventral hippocampal commissure and the effects of eTBS with different combinations of burst frequency and number of pulses per burst were analyzed in terms of seizure suppression. A closed-loop seizure control system was then implemented based on optimal eTBS parameters. The efficiency of the closed-loop eTBS was evaluated and compared to that of high frequency stimulation. The results show that eTBS induced global suppression in the hippocampus and this was sustained even after the application of eTBS. The optimal parameter of eTBS in the open-loop stimulation experiments was a burst frequency at 100Hz with nine pulses in a burst. The eTBS integrated with the on-off control law yielded less actions and cumulative delivered charge, but induced longer after-effects of seizure suppression compared to continuous high frequency stimulation (cHFS). To conclude, eTBS has suppressive effects on 4-AP induced seizure. A closed-loop eTBS system provides a more effective way of suppressing seizure and requires less effort compared to cHFS. eTBS may be a novel stimulation protocol for effective seizure control.

The influence of thought control on the experience of persecutory delusions and auditory hallucinations in daily life

Attempts to control or suppress thoughts are often unsuccessful and may even lead to an increase in the unwanted content. Intrusive thoughts and thought control are influential in the experience of psychosis, although recent findings have arisen from non-clinical samples and data tend to be retrospective in nature. The current study utilised repeated momentary assessments (experience sampling methodology) delivered as part of participants' daily routine to examine the associations between thought control and the experience of persecutory delusions and auditory hallucinations. The findings revealed that thought control was related to the subsequent severity and distress in relation to psychotic symptoms. Moreover, most of these effects persisted over two subsequent monitoring timepoints, although their size was diminished. These findings add weight to models of psychosis that include a role for thought control, and also highlight opportunities for targeted momentary interventions. Future work might seek to elucidate which specific aspects of thought control are important, alongside the use of more multifaceted measures of psychotic experiences.

Suppression of irrelevant activation in the horizontal and vertical Simon task differs quantitatively not qualitatively

The Simon effect is usually explained by the assumption that the irrelevant stimulus location automatically activates the corresponding response. In the case of incongruent stimulus-response assignments automatically activated responses therefore have to be suppressed to ensure correct responses. This account, however, has been called into question for other than horizontally arranged visual Simon tasks. We investigated whether there is a qualitative or quantitative difference in suppression of irrelevant activation between horizontally and vertically arranged Simon tasks, using delta-function analyses. Sequential analyses revealed suppression after incongruent trials in both tasks, supporting the idea of a quantitative rather than a qualitative difference between the tasks. We conclude that automatic response activation is weaker in vertical tasks resulting in lower inhibitory demands as compared to horizontal tasks.

Emotion regulation, physiological arousal and PTSD symptoms in trauma-exposed individuals

OBJECTIVES

Retrospective studies suggest a link between PTSD and difficulty regulating negative emotions. This study investigated the relationship between PTSD symptoms and the ability to regulate negative emotions in real-time using a computerised task to assess emotion regulation.

METHOD

Trauma-exposed ambulance workers (N = 45) completed self-report measures of trauma exposure, PTSD symptoms and depression. Participants then completed a computer task requiring them to enhance, decrease or maintain their negative emotions in response to unpleasant images. Skin conductance responses (SCR) were recorded and participants also made ratings of emotion intensity. Immediately after the computer task, participants were asked to describe the strategies they had used to regulate their negative emotions during the task and recorded spontaneous intrusions for the unpleasant images they had seen throughout the following week.

RESULTS

PTSD symptoms were associated with difficulty regulating (specifically, enhancing) negative emotions, greater use of response modulation (i.e., suppression) and less use of cognitive change (i.e., reappraisal) strategies to down-regulate their negative emotions during the task. More intrusions developed in participants who had greater reductions in physiological arousal whilst decreasing their negative emotions.

LIMITATIONS

PTSD was measured by self-report rather than by a clinician administered interview. The results suggest a relationship between emotion regulation ability and PTSD symptoms rather than emotion regulation and PTSD.

CONCLUSIONS

Difficulty regulating negative emotions may be a feature of trauma-exposed individuals with PTSD symptoms, which may be linked to the types of strategies they employ to regulate negative emotions.

Reward enhances tic suppression in children within months of tic disorder onset

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We examine a common, yet rarely studied, population: children with recent-onset tics.

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The ability to suppress tics is present within months of tic onset.

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Immediate, contingent reward enhances these children's ability to suppress tics.

Tic disorders are childhood onset neuropsychiatric disorders characterized by motor and/or vocal tics. Research has demonstrated that children with chronic tics (including Tourette syndrome and Chronic Tic Disorder: TS/CTD) can suppress tics, particularly when an immediate, contingent reward is given for successful tic suppression. As a diagnosis of TS/CTD requires tics to be present for at least one year, children in these tic suppression studies had been living with tics for quite some time. Thus, it is unclear whether the ability to inhibit tics is learned over time or present at tic onset. Resolving that issue would inform theories of how tics develop and how behavior therapy for tics works. We investigated tic suppression in school-age children as close to the time of tic onset as possible, and no later than six months after onset. Children were asked to suppress their tics both in the presence and absence of a contingent reward. Results demonstrated that these children, like children with TS/CTD, have some capacity to suppress tics, and that immediate reward enhances that capacity. These findings demonstrate that the modulating effect of reward on inhibitory control of tics is present within months of tic onset, before tics have become chronic.

Immune responses of eastern fence lizards (Sceloporus undulatus) to repeated acute elevation of corticosterone

Prolonged elevations of glucocorticoids due to long-duration (chronic) stress can suppress immune function. It is unclear, however, how natural stressors that result in repeated short-duration (acute) stress, such as frequent agonistic social encounters or predator attacks, fit into our current understanding of the immune consequences of stress. Since these types of stressors may activate the immune system due to increased risk of injury, immune suppression may be reduced at sites where individuals are repeatedly exposed to potentially damaging stressors. We tested whether repeated acute elevation of corticosterone (CORT, a glucocorticoid) suppresses immune function in eastern fence lizards (Sceloporus undulatus), and whether this effect varies between lizards from high-stress (high baseline CORT, invaded by predatory fire ants) and low-stress (low baseline CORT, uninvaded) sites. Lizards treated daily with exogenous CORT showed higher hemagglutination of novel proteins by their plasma (a test of constitutive humoral immunity) than control lizards, a pattern that was consistent across sites. There was no significant effect of CORT treatment on bacterial killing ability of plasma. These results suggest that repeated elevations of CORT, which are common in nature, produce immune effects more typical of those expected at the acute end of the acute-chronic spectrum and provide no evidence of modulated consequences of elevated CORT in animals from high-stress sites.

The chronometry of visual perception: review of occipital TMS masking studies

Transcranial magnetic stimulation (TMS) continues to deliver on its promise as a research tool. In this review article we focus on the application of TMS to early visual cortex (V1, V2, V3) in studies of visual perception and visual awareness. Depending on the asynchrony between visual stimulus onset and TMS pulse (SOA), TMS can suppress visual perception, allowing one to track the time course of functional relevance (chronometry) of early visual cortex for vision. This procedure has revealed multiple masking effects ('dips'), some consistently (∼+100ms SOA) but others less so (∼-50ms, ∼-20ms, ∼+30ms, ∼+200ms SOA). We review the state of TMS masking research, focusing on the evidence for these multiple dips, the relevance of several experimental parameters to the obtained 'masking curve', and the use of multiple measures of visual processing (subjective measures of awareness, objective discrimination tasks, priming effects). Lastly, we consider possible future directions for this field. We conclude that while TMS masking has yielded many fundamental insights into the chronometry of visual perception already, much remains unknown. Not only are there several temporal windows when TMS pulses can induce visual suppression, even the well-established 'classical' masking effect (∼+100ms) may reflect more than one functional visual process.

Tourette patients' misbelief of a tic rebound is due to overall difficulties in reliable tic rating

OBJECTIVE

While in clinical interviews the vast majority of patients with Tourette syndrome (TS) report about a tic rebound after voluntary tic suppression, in recent studies in children no paradoxical tic increase could be found. We hypothesized that in adult patients there is a tic rebound after tic suppression.

METHODS

We investigated the tic severity, premonitory urges and influence of attention deficit hyperactivity disorder (ADHD) before, during and after tic suppression in 22 adult patients with TS using both an objective video tic rating and subjective patient ratings for tics and premonitory urges.

RESULTS

According to the video rating, tic suppression resulted in a significant tic reduction, but no rebound. Patients also reported no tic rebound. They erroneously believed in an absolute tic reduction 20 and 30 min after suppression, but paradoxically felt no relative tic change. Premonitory urges remained unchanged. There was no correlation between premonitory urges and tic severity. The potency for tic inhibition did not correlate with premonitory urges and tic severity. ADHD did not influence tic inhibition.

CONCLUSION

In adults with TS, there is no tic rebound after voluntary tic suppression. Patients also reported no rebound, but erroneously felt a tic reduction in the later course of the study. This misjudgement as well as patients' often reported (mis-)belief of a tic rebound may be caused by overall difficulties in reliable tic rating. Premonitory urges remained unchanged during tic suppression. Tic suppression was not influenced by attention deficits. Premonitory urges are no prerequisite of tic suppression.

An examination of the incremental contribution of emotion regulation difficulties to health anxiety beyond specific emotion regulation strategies

Given the potential transdiagnostic importance of emotion dysregulation, as well as a lack of research examining emotion dysregulation in relation to health anxiety, the present study sought to examine associations among specific emotion regulation strategies (cognitive reappraisal and expressive suppression), emotion regulation difficulties, and health anxiety in a physically healthy sample of adults (N=482). As hypothesized, results of a series of hierarchical multiple regression analyses showed that emotion regulation difficulties provided a significant incremental contribution, beyond the specific emotion regulation strategies, in predicting each of the three health anxiety variables. Among the six dimensions of emotion regulation difficulties, the dimension representing perceived access to effective emotion regulation strategies was the only emotion regulation difficulty dimension that predicted all three health anxiety variables beyond the effects of the specific emotion regulation strategies. Results indicate that emotion regulation difficulties, and particularly one's subjective appraisal of his/her ability to effectively regulate emotions, may be of importance to health anxiety. Clinical implications are discussed.

Inhibitory effects of thought substitution in the think/no-think task: evidence from independent cues

When people try not to think about a certain item, they can accomplish this goal by using a thought substitution strategy and think about something else. Research conducted with the think/no-think (TNT) paradigm indicates that such strategy leads subsequently to forgetting the information participants tried not to think about. The present study pursued two goals. First, it investigated the mechanism of forgetting due to thought substitution, contrasting the hypothesis by which forgetting is due to blocking caused by substitutes with the hypothesis that forgetting is due to inhibition (using an independent cue methodology). Second, a boundary condition for forgetting due to thought substitution was examined by creating conditions under which the generation of appropriate substitutes would be impaired. In two experiments, participants completed a TNT task under thought substitution instructions in which either words or pseudo-words were used as original cues and memory was assessed with original and independent cues. The results revealed forgetting in both original and independent cue tests, supporting the inhibitory account of thought substitution, but only when cues were words, and not when they were non-words, pointing to the ineffectiveness of a thought substitution strategy when original cues lack semantic content.

Trajectories of change in emotion regulation and social anxiety during cognitive-behavioral therapy for social anxiety disorder

Cognitive-behavioral therapy (CBT) for social anxiety disorder (SAD) may decrease social anxiety by training emotion regulation skills. This randomized controlled trial of CBT for SAD examined changes in weekly frequency and success of cognitive reappraisal and expressive suppression, as well as weekly intensity of social anxiety among patients receiving 16 weekly sessions of individual CBT. We expected these variables to (1) differ from pre-to-post-CBT vs. Waitlist, (2) have differential trajectories during CBT, and (3) covary during CBT. We also expected that weekly changes in emotion regulation would predict (4) subsequent weekly changes in social anxiety, and (5) changes in social anxiety both during and post-CBT. Compared to Waitlist, CBT increased cognitive reappraisal frequency and success, decreased social anxiety, but had no impact on expressive suppression. During CBT, weekly cognitive reappraisal frequency and success increased, whereas weekly expressive suppression frequency and social anxiety decreased. Weekly decreases in social anxiety were associated with concurrent increases in reappraisal success and decreases in suppression frequency. Granger causality analysis showed that only reappraisal success increases predicted decreases in subsequent social anxiety during CBT. Reappraisal success increases pre-to-post-CBT predicted reductions in social anxiety symptom severity post-CBT. The trajectory of weekly changes in emotion regulation strategies may help clinicians understand whether CBT is effective and predict decreases in social anxiety.

CLINICALTRIALSGOV IDENTIFIER

NCT00380731; http://www.clinicaltrials.gov/ct2/show/NCT00380731?term=social+anxiety+cognitive+behavioral+therapy+Stanford&rank=1.

Tombusvirus-based vector systems to permit over-expression of genes or that serve as sensors of antiviral RNA silencing in plants

A next generation Tomato bushy stunt virus (TBSV) coat protein gene replacement vector system is described that can be applied by either RNA inoculation or through agroinfiltration. A vector expressing GFP rapidly yields high levels of transient gene expression in inoculated leaves of various plant species, as illustrated for Nicotiana benthamiana, cowpea, tomato, pepper, and lettuce. A start-codon mutation to down-regulate the dose of the P19 silencing suppressor reduces GFP accumulation, whereas mutations that result in undetectable levels of P19 trigger rapid silencing of GFP. Compared to existing virus vectors the TBSV system has a unique combination of a very broad host range, rapid and high levels of replication and gene expression, and the ability to regulate its suppressor. These features are attractive for quick transient assays in numerous plant species for over-expression of genes of interest, or as a sensor to monitor the efficacy of antiviral RNA silencing.

Brain mechanisms underlying the effects of aging on different aspects of selective attention

The ability to suppress irrelevant information declines with age, while the ability to enhance relevant information remains largely intact. We examined mechanisms behind this dissociation in an fMRI study, using a selective attention task in which relevant and irrelevant information appeared simultaneously. Slowing of response times due to distraction by irrelevant targets was larger in older than younger participants. Increased distraction was related to larger increases in activity and connectivity in areas of the dorsal attention network, indicating a more pronounced (re-)orientation of attention. The decreases in accuracy in target compared to nontarget trials were smaller in older compared to younger participants. In older adults we found increased recruitment of areas in the fronto-parietal control network (FPCN) during target detection. Moreover, older adults showed increased connectivity between the FPCN, supporting cognitive control, and somatomotor areas implicated in response selection and execution. This connectivity increase was related to improved target detection, suggesting that older adults engage additional cognitive control, which might enable the observed intact performance in detecting and responding to target stimuli.

Ribosomal protein S14 silencing inhibits growth of acute myeloid leukemia transformed from myelodysplastic syndromes via activating p53

OBJECTIVES

Ribosomal protein S14 (RPS14) plays a key role in erythropoiesis and causes p53 activation in 5q- syndrome. However, the oncogenic potential of RPS14 is not understood in leukemia and high-risk myelodysplastic syndrome (MDS). Here, we investigated the changes of proliferation and apoptosis of SKM-1, an acute myeloid leukemia (MDS/AML) cell line transformed from MDS, and explored the role of RPS14 in them.

METHODS

SKM-1 cells were transfected with recombined lentiviral vector shRPS14. Reverse-transcribed polymerase chain reaction and western blot assay were carried to detect the expression of RPS14 and p53. Cell proliferation was determined by MTT assay. Cell cycle and apoptosis were detected through flow cytometry.

RESULTS

When compared with negative control, the proliferation rate of SKM-1 cells transfected with RPS14 hairpin siRNA dropped by 30%. Transfected SKM-1 cells presented with activation of p53. Transfection also arrested cells in G0/G1 phase and induced apoptosis, indicating that RPS14 is involved in the pathophysiology of MDS/AML.

DISCUSSION

These findings indicate that partial silencing of RPS14 inhibits the proliferation of MDS/AML cells, and RPS14 may negatively regulate p53 activation in MDS/AML cells.

Emotion suppression and mortality risk over a 12-year follow-up

OBJECTIVE

Suppression of emotion has long been suspected to have a role in health, but empirical work has yielded mixed findings. We examined the association between emotion suppression and all-cause, cardiovascular, and cancer mortality over 12 years of follow-up in a nationally representative US sample.

METHODS

We used the 2008 General Social Survey-National Death Index (GSS-NDI) cohort, which included an emotion suppression scale administered to 729 people in 1996. Prospective mortality follow up between 1996 and 2008 of 111 deaths (37 by cardiovascular disease, 34 by cancer) was evaluated using Cox proportional hazards models adjusted for age, gender, education, and minority race/ethnicity.

RESULTS

The 75th vs. 25th percentile on the emotional suppression score was associated with hazard ratio (HR) of 1.35 (95% Confidence Interval [95% CI]=1.00, 1.82; P=.049) for all-cause mortality. For cancer and cardiovascular disease mortality, the HRs were 1.70 (95% CI=1.01, 2.88, P=.049) and 1.47 (95% CI=.87, 2.47, P=.148) respectively.

CONCLUSIONS

Emotion suppression may convey risk for earlier death, including death from cancer. Further work is needed to better understand the biopsychosocial mechanisms for this risk, as well as the nature of associations between suppression and different forms of mortality.

Accepting or suppressing the desire to eat: investigating the short-term effects of acceptance-based craving regulation

Previous studies addressing the long-term impact of acceptance of food cravings have revealed positive effects in terms of reduced craving experience. The present study investigated the short-term (direct) consequences of acceptance-based craving regulation. Hungry participants were exposed to desirable food and were either instructed to accept or suppress food cravings during exposure. Control participants did not regulate cravings and were allowed to eat from the food. Participants who accepted food cravings reported a significant increase in food craving during the course of the experiment. Participants who suppressed their cravings during exposure kept their craving levels constant. In contrast, control participants who were allowed to eat from the food, reported a significant drop in cravings. These findings suggest that although acceptance may entail an effective strategy for reducing food cravings in the long run, it may require repeated practice to overcome the immediate counterproductive effects.

Natural CD8⁺25⁺ regulatory T cell-secreted exosomes capable of suppressing cytotoxic T lymphocyte-mediated immunity against B16 melanoma

Natural CD4(+)25(+) and CD8(+)25(+) regulatory T (Tr) cells have been shown to inhibit autoimmune diseases. Immune cells secrete exosomes (EXOs), which are crucial for immune regulation. However, immunomodulatory effect of natural Tr cell-secreted EXOs is unknown. In this study, we purified natural CD8(+)25(+) Tr cells from C57BL/6 mouse naive CD8(+) T cells, and in vitro amplified them with CD3/CD28 beads. EXOs (EXO(Tr)) were purified from Tr cell's culture supernatants by differential ultracentrifugation and analyzed by electron microscopy, Western blot and flow cytometry. Our data showed that EXO(Tr) had a "saucer" or round shape with 50-100 nm in diameter, contained EXO-associated markers LAMP-1 and CD9, and expressed natural Tr cell markers CD25 and GITR. To assess immunomodulatory effect, we i.v. immunized C57BL/6 mice with ovalbumin (OVA)-pulsed DCs (DC(OVA)) plus Tr cells or EXO(Tr), and then assessed OVA-specific CD8(+) T cell responses using PE-H-2K(b)/OVA tetramer and FITC-anti-CD8 antibody staining by flow cytometry and antitumor immunity in immunized mice with challenge of OVA-expressing BL6-10OVA melanoma cells. We demonstrated that DC(OVA)-stimulated CD8(+) T cell responses and protective antitumor immunity significantly dropped from 2.52% to 1.08% and 1.81% (p<0.05), and from 8/8 to 2/8 and 5/8 mice DC(OVA) (p<0.05) in immunized mice with co-injection of Tr cells and EXO(Tr), respectively. Our results indicate that natural CD8(+)25(+) Tr cell-released EXOs, alike CD8(+)25(+) Tr cells, can inhibit CD8(+) T cell responses and antitumor immunity. Therefore, EXOs derived from natural CD4(+)25(+) and CD8(+)25(+) Tr cells may become an alternative for immunotherapy of autoimmune diseases.

Timing effects of antecedent- and response-focused emotion regulation strategies

Distraction and cognitive reappraisal influence the emotion-generative process at early stages and have been shown to effectively attenuate emotional responding. Inhibiting emotion-expressive behavior is thought to be less beneficial due to later implementation, but empirical results are mixed. Thus, the current study examined the temporal dynamics of these emotion regulation strategies at attenuating the late positive potential (LPP) while participants were shown unpleasant pictures. Results revealed that all strategies successfully reduced the LPP and self-reported negative affect. We confirmed that distraction attenuated the LPP earlier than cognitive reappraisal. Surprisingly, expressive suppression affected emotional responding as early as distraction. This suggests that suppression was used preventively and disrupted the emotion-generative process from the very beginning instead of targeting the emotional response itself. Thus, the obtained results point to the importance of considering the point in time when response-focused emotion regulation strategies are being implemented.

Suppression of CD3/CD28 antibody stimulated responses by human granulocytic myeloid-derived suppressor cells: fact or artefact?

T cell responses to CD3/CD28 antibodies are widely used to demonstrate the immunosuppressive activity of added human granulocytic myeloid-derived suppressor cells (G-MDSC). Granulocytic populations have the well established capability to chemically modify antibody structure and/or, phagocytose stimulatory CD3/CD28 antibody coated beads. However the possibility that the suppression observed in CD3/CD28 antibody based assays may result from the effects of the G-MDSC on the stimulatory antibodies rather than the T cells is not routinely controlled for experimentally. In the absence of controls to evaluate potential antibody associated artefacts considerable caution should be applied to the use and interpretation of this assay system as a means of defining suppressive G-MDSC populations.

Proton magnetic resonance spectroscopy: technique for the neuroradiologist

Magnetic resonance spectroscopy (MRS) provides information on neuronal and axonal viability, energetics of cellular structures, and status of cellular membranes. Proton MRS appeals to clinicians and scientists because its application in the clinical setting can increase the specificity of MR imaging. The objective of this article is to provide descriptive concepts of the technique and its application in vivo for a variety of patient populations. When appropriately incorporating MRS into the neuroradiologic evaluation, this technique produces relevant information to radiologists and clinicians for their understanding of adult and pediatric neurologically based disease processes.

Combating antibiotic resistance in bacteria

Combinations of certain antibiotics select against resistant strains of bacteria. This finding may provide a strategy of combating antibiotic resistant bacteria.

The role of suppression in figurative language comprehension

In this paper, we describe the crucial role that suppression plays in many aspects of language comprehension. We define suppression as a general, cognitive mechanism, the purpose of which is to attenuate the interference caused by the activation of extraneous, unnecessary, or inappropriate information. We illustrate the crucial role that suppression plays in general comprehension by reviewing numerous experiments. These experiments demonstrate that suppression attenuates interference during lexical access (how word meanings are 'accessed'), anaphoric reference (how referents for anaphors, like pronouns, are computed), cataphoric reference (how concepts that are marked by devices, such as spoken stress, gain a privileged status), syntactic parsing (how grammatical forms of sentences are decoded), and individual differences in (adult) language comprehension skill. We also review research that suggests that suppression plays a crucial role in the understanding of figurative language, in particular, metaphors, idioms, and proverbs.

lnterleukin-2 Stimulates the Development of Anergy via the Activation of Nonspecific Suppressor T Cells

We have previously demonstrated that incubation of splenic lymphocytes from an unimmunized mouse with IL-2 IFN-α or γ resulted in the development of a population of nonspecific regulatory cells (Ts). These cells were shown to block the ability of lymphocytes to generate mixed-lymphocyte responses in vitro. In the studies reported here, we have investigated the cell populations involved in this phenomenon. The Ts cells develop over a period of 2 or more days in culture with IL-2. Antibody to the 55-kD chain of the IL-2 receptor blocks Ts generation while stimulating T-cell proliferation. Although NK activity develops in these cultures, the mechanism of suppression is not via a lytic mechanism. Generation of the Ts in culture in the presence of IL-2 requires adherent cells as well as CD8+ cells. In studies using Con-A as the stimulus, the generation of Ts clearly requires both CD4+ T cells as well as CD8+ T cells and adherent cells. The evidence suggests that the CD4+ T cells serve as a source of IL-2 that is necessary in the activation of the IL-2-responsive CD8+, nonspecific Ts.

Developmental genetics of a P element induced allele of suppressor-of-forked in Drosophila melanogaster

In this paper we describe a new allele of suppressor of forked, su(f) ^hd37, referred to as hd37, which was isolated in a hybrid dysgenesis mutation screen and is shown to be P induced by its high frequency of reversion in hybrid dysgenic crosses, and by in situ hybridization. hd37 suppresses forked and fails to complement the forked suppression of known su(f) alleles. However, it complements the recessive lethality of alleles in both of the su(f) lethal complementation groups. We also describe a new phenotypic effect of su(f) alleles, the enhancement of Minute(3)i ⁵⁵. Recessive lethal alleles enhance the lethal effects of this Minute, but hd37 does not. The temperature sensitive period for forked bristle suppression by hd37 was found to be very narrow, consisting of a short interval (12-18 h) immediately before bristle formation. These results suggest that the several genetic functions associated with this locus may be genetically separable.