ARTIA-Bladder: Daily Online Adaptive Short-Course Radiation Therapy (RT) and Concurrent Chemotherapy for Muscle-Invasive Bladder Cancer (MIBC): A Prospective Trial of an Individualized Approach for Reducing Bowel and Bladder Toxicity

PURPOSE/OBJECTIVE(S)

Concurrent chemo-radiotherapy is commonly prescribed for muscle-invasive bladder cancer (MIBC). Post hoc analysis of two large, randomized trials found that hypofractionation improves loco-regional control (LRC) vs. standard fractionation in this population. A challenge in traditional image-guided radiotherapy of the bladder is that daily changes in bladder position and size requires large margins to ensure target coverage. This makes it difficult to spare uninvolved bladder from high-dose treatment, increases the risk of bowel toxicity, and results in historical rates of acute G3+ toxicity exceeding 20-30%. Daily online adaptive RT (ART) may enable reduced, personalized margins that maintain target coverage while reducing dose to OARs. This prospective clinical trial will test whether: 1) participants undergoing ART for MIBC have a lower rate of acute G3+ GI/GU toxicity compared with the 31% historical control rate (Stage III BC2001 trial), and 2) 2-year LRC with ART will be non-inferior to historical controls (75%).

MATERIALS/METHODS

This multi-national trial will enroll 165 adult subjects with stage cT2-T4aN0M0 urothelial MIBC. Subjects will have undergone an attempt at maximal transurethral resection of bladder tumor. Patients with clinically involved nodes or G2+ GI or G3+ GU symptoms/conditions at baseline are ineligible. Concurrent with chemotherapy, participants will receive (at the discretion of the investigator) either 55 Gy in 20 fx to whole-bladder or 46 Gy in 20 fx to whole-bladder plus simultaneous in-field boost of 55 Gy in 20 fx to tumor bed. A personalized ITV will be derived for each subject based on bladder expansion, as assessed on two CT simulations separated by 30 min. Daily ART will be attempted for all subjects. The primary endpoint is acute G3+ GI/GU toxicity. Secondary endpoints are LRC; quality of life (EORTC QLQ-BLM30, EPIC 26 bowel and urinary); global function (EQ-5D-5L ); 2-year disease-free, bladder intact event-free, and overall survival; 2-year bladder cancer-specific mortality; NTCP model of acute GI toxicity for hypofractionated bladder RT; workflow feasibility of ART; improved target coverage ± reduced dose to critical OARs vs. non-ART dosimetry; acute G3+ GI/GU toxicity rate in subjects with ≥75% of their treatments as ART; and acute G3+ GI/GU toxicity in the cohort treated with partial bladder boost. Exploratory translational and correlative endpoints will also be examined.

RESULTS

This trial opened to enrollment on Feb 2, 2023; the study duration is expected to be 4-5 years.

CONCLUSION

This prospective clinical trial will provide robust clinical data to inform healthcare providers' decisions on the use of daily online ART and hypofractionation as a bladder preservation strategy for this population.

Plain language summary: does treatment with vibegron result in improvements in overactive bladder (OAB) symptoms that are meaningful to people with OAB?

What is this summary about? This is a plain language summary of an article published in the journal Advances in Therapy. In 2020, the US Food and Drug Administration (also called the FDA) approved a medicine called vibegron to treat overactive bladder, also called OAB. The key results used to approve vibegron were from the EMPOWUR study. In the EMPOWUR study, participants who took vibegron had fewer urination episodes, urgency episodes, and bladder leaks each day than those who took a pill containing no medicine, called a placebo. At the end of the study, participants also rated how much their overactive bladder symptoms changed overall during EMPOWUR by responding to a survey. Many participants rated their overactive bladder symptoms as improved overall. This study asked if improvements in the number of urination episodes, urgency episodes, and bladder leaks caused by urgency were associated with feeling better overall. This study also looked at how many participants in the EMPOWUR study had improvements in the number of urination episodes, urgency episodes, and bladder leaks that were big enough to matter. A separate group of people with overactive bladder were asked about the magnitude of improvements that would be important to them. This group had not participated in the EMPOWUR study. What were the results? EMPOWUR participants who reported that taking medicine resulted in their overactive bladder symptoms getting better overall also generally reported fewer daily urinations, urgency episodes, and bladder leaks after treatment. Many had changes in their symptoms that were meaningful. Meaningful was defined for each symptom as: at least 15% fewer urinations, 50% fewer urgency episodes, and 75% fewer bladder leaks. Participants who received vibegron had meaningful reductions in the daily number of episodes of urination, urgency, and bladder leaks more often than those who received the placebo (pill with no active medicine). People with overactive bladder who did not participate in the study were interviewed and said that improvements to those symptoms, similar to those seen in the EMPOWUR study, would be important to them. What do the results mean? This study suggests that the results we measured in the EMPOWUR study may also reflect changes in overactive bladder symptoms that are big enough to be important to people with overactive bladder. Many participants who took vibegron in the EMPOWUR study felt that it helped to improve their individual overactive bladder symptoms. This may also help improve quality of life of participants. Clinical Trial Registration: NCT03492281 (ClinicalTrials.gov).

Plain language summary of safety and symptom improvement with vibegron in people with overactive bladder: results from the EMPOWUR study

What is this summary about? This is a plain language summary of an article originally published in the Journal of Urology. Overactive bladder (also called OAB) has been treated with the same type of medicine for more than 40 years. Vibegron is in a newer class of medicine for treating overactive bladder called beta-3 adrenergic receptor agonists. The EMPOWUR study was a phase 3 clinical trial that looked at whether vibegron was safe and improved symptoms in people with overactive bladder. Vibegron was approved by the US Food and Drug Administration (also called the FDA) based in part on the results of this study. What were the results? Participants of the EMPOWUR study who took vibegron showed an improvement in their overactive bladder symptoms. These symptoms include the number of urinations (peeing), the urgent need to urinate, and accidental urination (bladder leaks). After 12 weeks, participants who took vibegron had significantly greater improvements than participants who took placebo. What do the results mean? This study suggests that vibegron could safely improve symptoms in people with overactive bladder. Clinical Trial Registration: NCT03492281 (ClinicalTrials.gov).

An Evaluation of the Efficacy and Safety of Vibegron in the Treatment of Overactive Bladder

Pharmacologic treatment for overactive bladder (OAB), which is characterized by bothersome symptoms such as urgency and urge urinary incontinence (UUI), includes anticholinergics and β₃-adrenergic receptor agonists. Anticholinergics are associated with adverse effects including dry mouth, constipation, cognitive impairment, and increased risk of dementia. Therefore, the drug class of β₃-adrenergic receptor agonists may represent an effective, safe treatment option. Vibegron, a β₃-adrenergic receptor agonist, was approved for use in Japan (2018) and the United States (2020). Over the past 3 years, 2 phase 3 trials (EMPOWUR, EMPOWUR extension) have been conducted with once-daily vibegron 75 mg for the treatment of OAB, and additional secondary and subgroup analyses have detailed the efficacy and safety of vibegron. In the international phase 3 EMPOWUR trial, treatment with vibegron was associated with significant improvements compared with placebo in efficacy outcomes of micturition frequency, UUI episodes, urgency episodes, and volume voided as early as week 2 that were sustained throughout the 12-week trial. The 40-week EMPOWUR extension study, following the 12-week treatment period, demonstrated sustained efficacy in patients receiving vibegron for 52 weeks. Treatment with vibegron was also associated with improvements in patient-reported measures of quality of life. Across studies, vibegron was generally safe and well tolerated. A separate, dedicated ambulatory blood pressure monitoring study showed that treatment with vibegron was not associated with clinically meaningful effects on blood pressure or heart rate. Across all studies, vibegron was efficacious, safe, and well tolerated and thus represents a valuable treatment option for patients with OAB. Here, nearly 1 year after US approval, we review the published data on efficacy and safety of vibegron 75 mg for the treatment of OAB.

Interpretation of the Meaningfulness of Symptom Reduction with Vibegron in Patients with Overactive Bladder: Analyses from EMPOWUR

INTRODUCTION

Reductions in bothersome symptoms of overactive bladder (OAB) demonstrate improvement in clinical trials, but patient perception of meaningfulness of such improvement is lacking. In the 12-week phase 3 EMPOWUR trial, vibegron significantly reduced average daily number of micturitions, urgency episodes, and urge urinary incontinence (UUI) episodes vs placebo (P < 0.01 each). This analysis assessed meaningfulness of reductions in clinical endpoints observed in EMPOWUR using patient perception of improvement.

METHODS

An anchor-based approach using Patient Global Impression of Change (PGI-C) applied to phase 2 data allowed predefining phase 3 responder definitions. To confirm in phase 3, median change from baseline at week 12 in average daily number of micturitions, urgency episodes, and UUI episodes was generated for each PGI-C category and pooled across treatments. Based on predefined meaningful responder definitions, percentages of patients achieving ≥ 15% reduction in micturitions (post hoc), ≥ 50% reduction in urgency episodes (predefined), and ≥ 75% (predefined) and ≥ 90% (post hoc) reduction in UUI episodes were determined for patients receiving vibegron or placebo.

RESULTS

Across treatments, for micturitions, urgency episodes, and UUI episodes, median change from baseline to week 12 increased with greater subjective improvement based on PGI-C scores, and median reductions pooled across treatment groups were higher than the responder definitions that patients perceived as improved. Significantly more patients receiving vibegron vs placebo achieved ≥ 15% reduction in micturitions (56.3% vs 44.6%, respectively), ≥ 50% reduction in urgency episodes (39.5% vs 32.8%), ≥ 75% reduction in UUI episodes (49.3% vs 32.8%), and ≥ 90% reduction in UUI episodes (35.2% vs 23.5%) at week 12 (P < 0.05 each).

CONCLUSION

Significantly more patients treated with vibegron vs placebo in EMPOWUR achieved meaningful reductions in micturitions, urgency episodes, and UUI episodes that were associated with patient-perceived improvement. Results of these analyses support the meaningfulness of reductions in clinical endpoints observed in the 12-week EMPOWUR trial.

CLINICAL TRIALS REGISTRATION

ClinicalTrials.gov identifier, NCT03492281.

Concomitant use of oral anticoagulants in patients with advanced prostate cancer receiving apalutamide: A post-hoc analysis of TITAN and SPARTAN studies

Apalutamide, an androgen receptor signaling inhibitor, in combination with androgen-deprivation therapy (ADT), is approved for treatment of patients with nonmetastatic castration-resistant prostate cancer and metastatic castration-sensitive prostate cancer, based on the data from the phase 3 SPARTAN and TITAN studies respectively. Apalutamide is an inducer of cytochrome P450 enzymes and P-glycoprotein, which are involved in the metabolism of oral anticoagulants (OACs) and may thus have potential drug-drug interactions when co-administered with OACs. Concomitant use of certain OACs such as apixaban, rivaroxaban, edoxaban, dabigatran, and warfarin was allowed in the SPARTAN and TITAN studies. A post-hoc analysis was conducted to evaluate the incidence of treatment-emergent thrombotic and embolic adverse events (AEs) in patients receiving concomitant OACs with apalutamide + ADT or placebo + ADT in both the studies. Anticoagulants were identified by WHO Drug Anatomical Therapeutic Chemical level 4 classifications. Thrombotic and embolic AEs were coded using the Medical Dictionary for Regulatory Activities Version 22.1. Data were analyzed from patients receiving concurrent OACs among all treated patients in SPARTAN (apalutamide + ADT: 95/803 [11.8%]; placebo + ADT: 48/398 [12.1%]) and TITAN (apalutamide + ADT: 31/524 [5.9%]; placebo + ADT: 28/527 [5.3%]). No consequential differences were observed in the occurrence of thrombotic and embolic events between apalutamide + ADT and placebo + ADT groups receiving concomitant OACs in SPARTAN (11.6% vs 12.5%) or TITAN (19.4% vs 21.4%). Grade 3/4 thrombotic and embolic AEs observed in patients receiving concomitant OACs with apalutamide + ADT or placebo + ADT were 6 (6.3%) vs 5 (10.4%) in SPARTAN and 3 (9.7%) vs 1 (3.6%) in TITAN. This analysis suggests that when necessary, concomitant OACs can be used with apalutamide with appropriate monitoring.

Vibegron for the Treatment of Patients with Dry and Wet Overactive Bladder: A Subgroup Analysis from the EMPOWUR Trial

BACKGROUND

Overactive bladder (OAB) is characterized by urgency and frequency with (OAB wet) or without (OAB dry) urge urinary incontinence (UUI). In the phase 3 EMPOWUR trial, vibegron-a selective β ₃-adrenergic receptor agonist for the treatment of OAB-significantly improved daily number of urgency episodes and micturitions vs. placebo (P < 0.01). These post hoc analyses aimed to compare the efficacy of vibegron vs. placebo in OAB dry and wet populations.

METHODS

Patients were randomly assigned 5:5:4 to receive once-daily vibegron 75 mg, placebo, or tolterodine 4 mg extended release, respectively, for 12 weeks. Baseline criteria for OAB dry included an average of ≥8 micturitions, ≥3 urgency episodes, and <1 UUI episode per diary day and for OAB wet included an average of ≥8 micturitions and ≥1 UUI episode per diary day. Change from baseline in mean daily number of urgency episodes and micturitions was assessed in both populations.

RESULTS

Of the 1463 patients included in the full analysis set, 336 (23%) had OAB dry (vibegron, N = 123; placebo, N = 115; and tolterodine, N = 98), and 1127 (77%) had OAB wet (vibegron, N = 403; placebo, N = 405; and tolterodine, N = 319). Vibegron was associated with significant reductions (95% CIs of the least squares mean differences [LSMD] does not include 0) from baseline at week 12 vs. placebo in mean daily urgency episodes for the dry (LSMD [95% CI], ‒1.0 [‒2.0, ‒0.1]) and wet (‒0.6 [‒1.0, ‒0.1]) populations. Vibegron was associated with significant reductions from baseline at week 12 vs. placebo in mean daily micturitions for the dry (LSMD [95% CI], ‒0.8 [‒1.5, ‒ 0.1]) and wet (‒0.5 [‒0.8, ‒0.1]) populations. There were no significant differences in either outcome between tolterodine and placebo for either the dry or wet populations in this study.

CONCLUSIONS

In this subgroup analysis from the EMPOWUR trial, vibegron was associated with significant reductions compared with placebo in urgency episodes and micturitions in both the OAB dry and wet populations, suggesting that vibegron is similarly efficacious for these endpoints in patients with and without UUI. This trial is registered with NCT03492281.

Vibegron improves quality-of-life measures in patients with overactive bladder: Patient-reported outcomes from the EMPOWUR study

BACKGROUND

Quality of life (QOL) can be significantly impacted by symptoms of overactive bladder (OAB). Vibegron is a highly selective β₃ -adrenergic receptor agonist that showed efficacy in treatment of symptoms of OAB in the randomised, double-blind, placebo- and active-controlled phase 3 EMPOWUR trial. Here we report patient-reported QOL outcomes from the EMPOWUR trial.

METHODS

Patients were randomly assigned 5:5:4 to receive vibegron 75 mg, placebo or tolterodine 4 mg extended release, respectively, for 12 weeks. Patients completed the OAB questionnaire (OAB-q) at baseline and at week 12 and the patient global impression (PGI) scales for severity, control, frequency and leakage at baseline and at weeks 4, 8 and 12. Change from baseline at week 12 and responder rates (OAB-q: patients achieving a ≥10-point improvement; PGI: patients reporting best possible response) were assessed. Vibegron was compared with placebo, and no comparisons were made between vibegron and tolterodine.

RESULTS

Of the 1518 patients randomised, 1463 (placebo, n = 520; vibegron, n = 526; tolterodine, n = 417) had evaluable data for efficacy measures and were included in the analysis. Mean baseline OAB-q and PGI scores were comparable among treatment groups. At week 12, patients receiving vibegron had greater improvements from baseline in OAB-q subscores of coping, concern, sleep, health-related QOL total and symptom bother (P < .01 each) compared with patients receiving placebo; a greater proportion of patients receiving vibegron vs placebo were responders in the OAB-q coping (P < .05) and symptom bother scores (P < .0001). Compared with placebo, a greater proportion of patients who received vibegron achieved the best response on all PGI end-points at week 12 (P < .05 each) and were classified as responders (P < .05 each).

CONCLUSIONS

In the 12-week EMPOWUR trial, treatment with vibegron was associated with significantly greater and clinically meaningful improvement in OAB-q and PGI scores compared with placebo, consistent with improvements in OAB symptoms.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier number NCT03492281.

Efficacy and Safety of Once-Daily Vibegron for Treatment of Overactive Bladder in Patients Aged ≥65 and ≥75 Years: Subpopulation Analysis from the EMPOWUR Randomized, International, Phase III Study

Background

Overactive bladder (OAB) is common among older adults. The efficacy and safety of vibegron for the treatment of OAB were demonstrated in the international, phase III EMPOWUR trial. This subpopulation analysis from EMPOWUR assessed the efficacy and safety of vibegron in patients aged ≥ 65 and ≥ 75 years.

Methods

In EMPOWUR, patients with OAB were randomly assigned 5:5:4 to receive once-daily vibegron 75 mg, placebo, or tolterodine 4 mg extended release, respectively, once daily for 12 weeks. Coprimary efficacy endpoints were change from baseline at week 12 in average daily number of micturitions and urge urinary incontinence (UUI) episodes; a key secondary efficacy endpoint was change from baseline at week 12 in average daily number of urgency episodes. Safety was assessed through adverse events (AEs). Efficacy analyses compared vibegron with placebo; no efficacy comparisons were made between vibegron and tolterodine.

Results

Of the 1463 patients with evaluable efficacy data, 628 patients were aged ≥ 65 years, and 179 were aged ≥ 75 years. After 12 weeks, patients treated with once-daily vibegron 75 mg in both age subgroups showed significant improvements from baseline versus placebo in all three symptoms of OAB: daily micturitions (≥ 65 years, P < 0.0001; ≥75 years, P < 0.05), UUI episodes (≥ 65 years, P < 0.001; ≥ 75 years, P < 0.0001), and urgency episodes (≥ 65 years, P < 0.01; ≥ 75 years, P < 0.01). Significant reductions from baseline versus placebo in daily micturitions, UUI episodes, and urgency episodes were observed beginning at week 2 for patients aged ≥ 65 years treated with vibegron. In patients aged ≥ 65 years, 50.0% of those receiving vibegron versus 29.8% receiving placebo experienced a ≥ 75% reduction in UUI episodes at week 12 (P < 0.0001). Rates of cardiovascular-associated AEs were low for patients receiving vibegron (<2% of patients in either age subgroup) and similar to rates in patients receiving placebo. In patients aged ≥ 65 years, hypertension was reported by 1.2%, 3.1%, and 2.9% of patients receiving vibegron, placebo, and tolterodine, respectively; in patients aged ≥ 75 years, hypertension was reported by 1.3%, 3.3%, and 2.1%, respectively.

Conclusions

In this subpopulation analysis of patients with OAB aged ≥ 65 and ≥ 75 years from the EMPOWUR study, once-daily vibegron 75 mg showed rapid onset and robust efficacy versus placebo and was generally safe and well tolerated, consistent with results from the overall population.

Trial Registration

ClinicalTrials.gov identifier NCT03492281; registered April 10, 2018.

International Phase III, Randomized, Double-Blind, Placebo and Active Controlled Study to Evaluate the Safety and Efficacy of Vibegron in Patients with Symptoms of Overactive Bladder: EMPOWUR

PURPOSE

We assessed efficacy, safety and tolerability of vibegron, a novel, potent, highly selective β3-adrenoceptor agonist, administered 12 weeks at 75 mg once daily to patients with overactive bladder in an international phase III trial with placebo and active control.

MATERIALS AND METHODS

Adult patients with overactive bladder with 8.0 or more micturitions per day were randomized 5:5:4 to 75 mg vibegron, placebo or extended-release 4 mg extended-release tolterodine. Up to 25% of patients could have dry overactive bladder (less than 1.0 urge incontinence episode per day). Patients completed 7-day voiding diaries at baseline and weeks 2, 4, 8 and 12.

RESULTS

Of 1,518 randomized patients 90.4% completed the trial. At 12 weeks micturitions decreased by an adjusted mean of 1.8 episodes per day for vibegron vs 1.3 for placebo (p <0.001, co-primary end point) and 1.6 for tolterodine. Among incontinent patients urge incontinence episodes decreased by an adjusted mean 2.0 episodes per day for vibegron vs 1.4 for placebo (p <0.0001, co-primary end point) and 1.8 for tolterodine. Moreover, vibegron was statistically significantly superior to placebo for key secondary measures of number of urgency episodes, volume per micturition and proportion of incontinent patients with a 75% or greater reduction in urge incontinence episodes (all p <0.01). Among vibegron treated patients 1.7% discontinued treatment because of adverse events vs 1.1% for placebo and 3.3% for tolterodine. Incidence of hypertension was 1.7% for vibegron and for placebo.

CONCLUSIONS

Once daily 75 mg vibegron provided statistically significant reductions in micturitions, urgency episodes and urge incontinence, and increased the volume per micturition. Treatment was well tolerated with a favorable safety profile.

Cardiovascular Safety of the β3 -Adrenoceptor Agonist Mirabegron and the Antimuscarinic Agent Solifenacin in the SYNERGY Trial

There have been concerns that treatment of overactive bladder with β₃ -adrenoceptor agonists may potentially have detrimental cardiovascular (CV) side effects. We evaluated the CV safety of mirabegron, a β₃ -adrenoceptor agonist, alone and in combination therapy with the antimuscarinic agent solifenacin. The SYNERGY trial was a multinational, multicenter, randomized, double-blind, parallel-group, placebo and active-controlled phase 3 trial. Patients were randomized to receive solifenacin 5 mg + mirabegron 50 mg (combination 5 + 50 mg), solifenacin 5 mg + mirabegron 25 mg (combination 5 + 25 mg), solifenacin 5 mg monotherapy, mirabegron 25 mg monotherapy, mirabegron 50 mg monotherapy, or placebo for a 12-week double-blind treatment period. A total of 3398 patients were included in the study. Mean changes from baseline to the end of therapy in ECG parameters were similar across treatment groups, although there was an increase in heart rate of 1 beat/minute in the mirabegron treatment groups. There were no clinically meaningful differences in change from baseline in QTcF between monotherapies and placebo and between monotherapies and combination therapy. There were very few major CV events: 1 of 853 (0.1%) with a nonfatal myocardial infarction in the combination 5 + 25 mg group, 2 of 848 (0.2%) with a nonfatal stroke in the combination 5 + 50 mg group, and no events in the other groups. This CV safety analysis of the combination of mirabegron and solifenacin showed rates of CV events comparable with those for monotherapy treatments based on assessments of vital signs, electrocardiograms, and adjudicated CV events.

Pattern formation in ciliary organelle systems of ciliated protozoa

Genetic, morphometric, and microsurgical investigations of the pattern of ciliary organells in ciliate protozoa support the view that ther are two types of developmental process responsible for the positioning of these organelles. The first is exemplified by the propagation of ciliary rows through localized addition of new ciliary units along the axis of the row, a process which is responsible for the maintenance of the pre-existing number of rows in clonal lineages over a large number of fissions. The second is illustrated by two examples: (1) Ciliary units are distributed among ciliary rows of Euplotes minuta according to an invariant geometrical pattern that is independent both of the total number of units and of the number of rows. (2) Microsurgical alteration of the topographical contours of a related ciliate, Paraurostyla weissei, brings about a shift in the sites of formation of certain specific ciliary rudiments to new positions that are determined in relation to the newly constructed form. The two modes of pattern formation in ciliates are discussed from both genetic and developmental viewpoints. The localized positional mechanisms within the ciliary rows allow for a 'configurational heredity' shich is, however, subject to constraints of nuclear genic control both of the stable range of number of rows and of the positioning mechanism itself. The large-scale systems of pattern determination are probably more closely related to the field properties of developing multicellular organisms. In ciliates such systems are almost certainly located in the cell membrane or in the relatively fixed cytoplasmic layer just beneath the membrane.

Intracellular handedness in ciliates

Ciliated protozoa have intrinsically asymmetrical ciliary structures that are asymmetrically arranged over the cell surface. These structures can be arranged in two enantiomorphic configurations, 'right-handed' (RH) and 'left-handed' (LH). Whereas one of these configurations (arbitrarily, RH) is apparently universal in Nature and predominant in the laboratory, mirror-image (RH-LH) doublets and reverse (LH) singlets have been generated and studied in eight different ciliate genera. In all these, the internal asymmetry of individual ciliary structures remains normal even when the asymmetry of arrangement of these structures is reversed. The individual structures may sometimes become inverted (rotationally permuted). LH forms reproduce themselves if they are able to feed, or reorganize periodically before starving to death if they are not. Changes of cellular handedness depend upon unusual geometric configurations and in most cases are unrelated to genic changes. In hypotrich ciliates changes of handedness can be provoked by artificially generated juxtapositions of anterior and posterior cell regions or of right and left cell margins. Reversal of handedness in ciliates can be visualized as a consequence of (re-)establishment of a normal sequence of normally spaced positional values following geometric disturbances created by the experimenter or by the regulating cell.

Positional information in cells and organisms

The processes of pattern formation are usually considered to be quite different in unicellular and multicellular organisms. The only unifying ideas have been very general, such as those concerning regional differences and organization along a polar axis. Concepts like induction, fields and gradients have generally been applied only to the development of multicellular organisms. Here, Joseph Frankel suggests that pattern formation by multicellular organisms evolved in their progenitors in response to multiplication of cytoplasmic structural units rather than of nuclei. Ciliates provide a living example of complex patterning in a compound uninucleate organism.

Anti-Yo antibody-positive cerebellar degeneration associated with endometrial carcinoma: case report and review of the literature

Paraneoplastic cerebellar degeneration (PCD) is a rare, severely debilitating disease, often with a rapid onset and progression, which predate the diagnosis of malignancy. Despite characteristic features, diagnosis is commonly difficult and successful therapy, which relies on early instigation of treatment, is rare. Here we present a patient in whom anti-Yo antibody-positive PCD was associated with endometrial carcinoma and an extensive review of the literature outlining the clinical features, pathogenesis and treatment of PCD.

Nuclear and cortical regulation in doublets of Paramecium: II. When and how do two cortical domains reorganize to one?

Homopolar doublets with twofold rotational symmetry were generated in Paramecium tetraurelia and in P. undecaurelia by electrofusion or by arrested conjugation. These doublets underwent a complex cortical reorganization over time, which led to their reversion to singlets. This reorganization involved a reduction in number of ciliary rows, a progressive inactivation and loss of one oral meridian, and a reduction and eventual disappearance of one cortical surface (semicell) situated between the two oral meridians. The intermediate steps of this reorganization included some processes that resemble those previously described in regulating doublets of other ciliates, and others that are peculiar to members of the "P. aurelia" species-group and some of its close relatives. The former included a disappearance of one cortical landmark (a contractile vacuole meridian) and transient appearance of another (a third cytoproct) within the narrower semicell. The latter included a reorganization of the paratene zone and the associated invariant (non-duplicating) region to occupy the entire narrower semicell and a redistribution of zones of most active basal-body proliferation within the opposite, wider semicell. The final steps of reorganization involved anterior displacement, invagination, and resorption of one of the two oral apparatuses and eventual disappearance of the associated oral meridian. An oral meridian deprived of its oral apparatus, either by spontaneous resorption or microsurgical removal, could persist for some time in "incomplete doublets" before regulating to the singlet condition. The phylogenetically widespread events encountered in the regulation of doublets to singlets suggest that Paramecium shares some of the global regulatory properties that are likely to be ancestral in ciliates. The more specific events are probably associated with the complex cytoskeletal architecture of this organism and with the frequent occurrence of autogamy that was described in the preceding study (Prajer et al. 1999).

A witness breaks his silence: the meaning of a therapist's response to an adolescent's self-destruction

I describe the case of a self-mutilating adolescent girl and my dilemma, as her therapist, about telling her parents about her self-abuse. I use two complementary, mutually enhancing relational theories of trauma--Ferenczi's (1933) and Davies and Frawley's (1994)--to help understand the minefield I was in. Davies and Frawley describe certain relational configurations that are typical of trauma victims. I believe that it is not only unavoidable but therapeutically vital for therapists to participate in these configurations so they can know the patient's experience in a personal way. It is also crucial that they be witnesses who provide recognition for the patient's pain and, in so doing, relieve the intolerable feeling of isolation that Ferenczi proposed was the most basic trauma. In addition, I discuss the observation that some people who have not been previously traumatized in any gross way manifest characteristics of trauma.

An evaluation of Hsp90 as a mediator of cortical patterning in Tetrahymena

This study asks two questions: 1) whether Hsp90 is involved in the regulation of cortical patterning in Tetrahymena, and 2) if it is, whether specific defects in this regulation can be attributed to functional insufficiency of the Hsp90 molecule. To address question 1, we compared the effects of a specific inhibitor of Hsp90, geldanamycin, on population growth and on development of the oral apparatus in two Tetrahymena species, T. pyriformis and T. thermophila. We observed that geldanamycin inhibits population growth in both species at very low concentrations, and that it has far more severe effects on oral patterning in T. pyriformis than in T. thermophila. These effects are parallel to those of high temperature in the same two species, and provide a tentative affirmative answer to the first question. To address question 2, we ascertained the base sequence of the genes that encode the Hsp90 molecules which are induced at high temperatures in both Tetrahymena species, as well as corresponding sequences in Paramecium tetraurelia. Extensive comparative analyses of the deduced amino acid sequences of the Hsp90 molecules of the two Tetrahymena species indicate that on the basis of what we currently know about Hsp90 both proteins are equally likely to be functional. Phylogenetic analyses of Hsp90 amino acid sequences indicate that the two Tetrahymena Hsp90 molecules have undergone a similar number of amino acid substitutions from their most recent common ancestor, with none of these corresponding to any known functionally critical region of the molecule. Thus there is no evidence that the Hsp90 molecule of T. pyriformis is functionally impaired; the flaw in the control of cortical patterning is more likely to be caused by defects in mechanism(s) that mediate the response to Hsp90, as would be expected from the "Hsp90 capacitor" model of Rutherford and Lindquist.

The effects of supraoptimal temperatures on population growth and cortical patterning in Tetrahymena pyriformis and Tetrahymena thermophila: a comparison

In this investigation, we compare the multiplication rates and morphogenetic responses of the two most studied Tetrahymena species, T. pyriformis and T. thermophila, at supraoptimal temperatures. Although the upper temperature limits differ greatly in the two species, the pattern of growth responses to high temperature is for the most part similar, with some differences in detail. The transient recovery of cell division at the highest temperature that allows cell division, characteristic of T. pyriformis, is observed in a less distinct form in T. thermophila. Moreover, there is a remarkable difference in developmental response, with drastic abnormalities in patterning of oral structures during the transient recovery of cell division in T. pyriformis, and far more limited abnormalities under similar conditions in T. thermophila. The abnormalities result from spatial disorder in the alignment and orientation of basal body pairs within the early oral primordium, followed by failures in the realignment that normally occurs as oral structures (membranelles and undulating membrane) mature. Both the initial spatial disorder and the failures in realignment are far more severe in T. pyriformis than in T. thermophila.

Cellular events and the pattern of p53 protein expression following cyclophosphamide-initiated cell death in various organs of developing embryo

This study was aimed at characterizing the temporal patterns of cell responses and p53 protein expression in the limbs, head, and liver of embryos responding to cyclophosphamide (CP)-induced teratogenic insult. ICR murine embryos were examined 24, 48, or 72 h after injection of 40 mg/kg CP on day 12 of pregnancy. The cellular events and temporal pattern of p53 protein expression were determined by FACS analysis and by TUNEL (apoptosis) in the head, limbs, and liver of the embryos. All tested organs showed apoptosis and a significantly decreased proportion of live cells after 24 h. Subsequent events were organ-dependent. In the liver, there were no dysmorphic events at any time and excessive cell death had been almost compensated for by 48 h. Compensation was preceded by G(1) arrest and accompanied by an increased level of p53 protein in surviving cells. Excessive cell death in the head and the limbs resulted in structural anomalies. In the head, there was an increased level of p53 protein and G(1) arrest after 24 h and the number of live cells at 48 h was equal to that seen in earlier samples, despite apoptosis. In the limbs, however, only isolated viable cells were seen by 48 h, but there was no increased level of p53 protein or G(1) arrest. Results of this study suggest that the differential sensitivity of tested organ systems to CP may be associated with differences in cellular events following CP-initiated cell death. They also suggest that the input of p53 in determining the response of these organ systems to CP-induced teratogenic insult may be different. Teratogenesis Carcinog. Mutagen. 19:353-367, 1999.

Structural requirements for outside-in and inside-out signaling by Drosophila neuroglian, a member of the L1 family of cell adhesion molecules

Expression of the Drosophila cell adhesion molecule neuroglian in S2 cells leads to cell aggregation and the intracellular recruitment of ankyrin to cell contact sites. We localized the region of neuroglian that interacts with ankyrin and investigated the mechanism that limits this interaction to cell contact sites. Yeast two-hybrid analysis and expression of neuroglian deletion constructs in S2 cells identified a conserved 36-amino acid sequence that is required for ankyrin binding. Mutation of a conserved tyrosine residue within this region reduced ankyrin binding and extracellular adhesion. However, residual recruitment of ankyrin by this mutant neuroglian molecule was still limited to cell contacts, indicating that the lack of ankyrin binding at noncontact sites is not caused by tyrosine phosphorylation. A chimeric molecule, in which the extracellular domain of neuroglian was replaced with the corresponding domain from the adhesion molecule fasciclin II, also selectively recruited ankyrin to cell contacts. Thus, outside-in signaling by neuroglian in S2 cells depends on extracellular adhesion, but does not depend on any unique property of its extracellular domain. We propose that the recruitment of ankyrin to cell contact sites depends on a physical rearrangement of neuroglian in response to cell adhesion, and that ankyrin binding plays a reciprocal role in stabilizing the adhesive interaction.

Mutations of alpha spectrin and labial block cuprophilic cell differentiation and acid secretion in the middle midgut of Drosophila larvae

Mutations in Drosophila alpha spectrin cause larval lethality and defects in cell shape and adhesion (J. Lee et al., 1993, J. Cell Biol. 123, 1797-1809). Here we examined the effects of two lethal alpha spectrin alleles (alpha-specrg41 and alpha-specrg35) on development and function of the larval midgut. Homozygous null alpha-specrg41-mutant larvae exhibited a striking defect in middle midgut acidification. In contrast, many homozygous alpha-specrg35 mutants were capable of acidification, indicating partial function of the truncated alpha-specrg35 product. Acidification was also blocked by a mutation in the labial gene, which is required for differentiation of cuprophilic cells in the midgut, suggesting that these cells secrete acid. We found that two isoforms of spectrin (alphabeta and alphabetaH) are segregated within the basolateral and apical domains of cuprophilic cells, respectively. The most conspicuous defect in cuprophilic cells from labial and alpha spectrin mutants was in morphogenesis of the invaginated apical domain, although basolateral defects may also contribute to the acidification phenotype. Acid secretion in vertebrate systems is thought to involve the polarized activities of apical proton pumps and basolateral anion exchangers, both of which interact with spectrin. We propose that the alpha-specrg41 mutation in Drosophila interferes with the polarized activities of homologous molecules that drive acid secretion in cuprophilic cells.

Randomised trial of oral and intravenous methylprednisolone in acute relapses of multiple sclerosis

BACKGROUND

An intravenous rather than oral course of methylprednisolone is often prescribed for treating acute relapses in multiple sclerosis (MS) despite the lack of evidence to support this route of administration. Our double-blind placebo-controlled randomised trial was designed to compare the efficacy of commonly used intravenous and oral steroid regimens in promoting recovery from acute relapses in MS.

METHODS

42 patients with clinically definite relapse in MS received oral, and 38 intravenous, methylprednisolone. Clinical measurements at entry and at 1 week, 4 weeks, 12 weeks, and 24 weeks included Kurtzke's expanded disability status scale (EDSS), Hauser's Ambulatory Index, and an arm-function index. The primary outcome criterion was a difference between the two treatment groups of one or more EDSS grades at 4 weeks.

FINDINGS

There were no significant differences between the two groups at any stage of the study in any measurement taken: the mean difference in EDSS at 4 weeks (adjusted for baseline level) was 0.07 grades more in those taking oral steroids (95% CI -0.46 to 0.60). The most optimistic outcome for intravenous therapy is an average benefit of less than half a grade improvement on EDSS over oral treatment.

INTERPRETATION

Since our study did not show any clear advantage of the intravenous regime we conclude that it is preferable to prescribe oral rather than intravenous steroids for acute relapses in MS for reasons of patient convenience, safety, and cost.

Signal detection and noise suppression using a wavelet transform signal processor: application to ultrasonic flaw detection

The utilization of signal processing techniques in nondestructive testing, especially in ultrasonics, is widespread. Signal averaging, matched filtering, frequency spectrum analysis, neural nets, and autoregressive analysis have all been used to analyze ultrasonic signals. The Wavelet Transform (WT) is the most recent technique for processing signals with time-varying spectra. Interest in wavelets and their potential applications has resulted in an explosion of papers; some have called the wavelets the most significant mathematical event of the past decade. In this work, the Wavelet Transform is utilized to improve ultrasonic flaw detection in noisy signals as an alternative to the Split-Spectrum Processing (SSP) technique. In SSP, the frequency spectrum of the signal is split using overlapping Gaussian passband filters with different central frequencies and fixed absolute bandwidth. A similar approach is utilized in the WT, but in this case the relative bandwidth is constant, resulting in a filter bank with a self-adjusting window structure that can display the temporal variation of the signal's spectral components with varying resolutions. This property of the WT is extremely useful for detecting flaw echoes embedded in background noise. The detection of ultrasonic pulses using the wavelet transform is described and numerical results show good detection even for signal-to-noise ratios (SNR) of -15 dB. The improvement in detection was experimentally verified using steel samples with simulated flaws.

The effects of lithium chloride on pattern formation in Tetrahymena thermophila

Lithium ions have long been known to exert dramatic effects on the specification of cell fates in multicellular systems. We have analyzed the effects of Li+ on intracellular patterning in a complex unicellular organism, the ciliate Tetrahymena thermophila. LiCl does not affect the locations of major structural landmarks in the cortical region of wild-type cells and does not modify the phenotype of pattern-mutant cells. However, in all strains studied LiCl differentially affects early stages of oral development. It initially triggers a slow regression of oral primordia, which is followed by an excessive proliferation of basal bodies that leads to a hypertrophy of the ciliature of the cell's feeding organelle. This hypertrophy mimics the effects of the membranellar-pattern-D mutation, the phenotype of which is enhanced in the presence of LiCl. These effects were partially reversed by myo-inositol; however, neomycin failed to mimic the effects of LiCl. Thus, although lithium ions have major cellular effects on Tetrahymena, they do not influence the specification of the body plan in a manner analogous to that observed in multicellular organisms and may work in part through mechanisms other than the now-classical inositol-phosphate cycle.

Monoclonal antibodies reveal complex structure in the membrane skeleton of Tetrahymena

Twelve monoclonal antibodies were raised that are specific for the membrane skeleton of Tetrahymena. Five were directed against T. pyriformis and seven were directed against T. thermophila. Some cross-reactivity between species was found. Each monoclonal antibody recognized one of the three major components of epiplasm, i.e. the bands A, B, and C identified in electrophoretic separations of epiplasmic proteins. It was found, using these antibodies, that the epiplasmic proteins A, B and C have overlapping but independent distributions within the cell.

Cellular polarity in ciliates: persistence of global polarity in a disorganized mutant of Tetrahymena thermophila that disrupts cytoskeletal organization

Much of the cell surface on the ciliate Tetrahymena thermophila is covered by a polarized lattice of cytoskeletal structures that are associated with basal bodies of the ciliary rows. Unique structural landmarks, including an oral apparatus and contractile vacuole pores, develop before cell division in localized domains located, respectively, posterior and anterior to the transverse fission zone. All of these structures can be visualized by specific monoclonal antibodies. A single-locus recessive mutation, disorganized-A (disA), primarily affects the striated rootlets of the ciliary-row basal bodies and brings about a severe disorganization in the positioning and orientation of these basal bodies and associated cytoskeletal elements. Nonetheless, the new oral apparatus, contractile vacuole pores, and other unique structures appeared at or near their normal sites along the anteroposterior axis of disA cells, indicating that the positioning of these localized structures is not dependent on the integrity of the ciliary rows. Abnormalities were present in the details of construction of some of the localized structures and in aspects of cell shape that may be influenced by these details. In the main, however, analysis of disA mutant cells indicates that intracellular domains near the cell poles develop independently of the vectorial polarity of the ciliary rows.

Efficacy of postoperative 5-FU, high-dose leucovorin, and sequential radiation therapy for clinically resectable rectal cancer

We report the local control and survival in a previously reported phase I dose escalation trial of combined postoperative 5-FU, high dose leucovorin (LV), and sequential radiation therapy followed by maintenance LV/5-FU for the treatment of patients with clinically resectable rectal cancer. Following surgery for stages T3-4N0-2M0 primary (21) or recurrent (4) rectal cancer, 25 patients received 5-FU/LV x 1 cycle. Radiation therapy (5040 cGy) began on day 8. A second cycle of 5-FU/LV was given concurrent with the fourth week of radiation. Patients received an additional 10 cycles of LV/5-FU. The median follow-up was 40 months (range 18-52). The incidence of grade 3+ acute toxicity in the 9 patients who received the recommended dose of 5-FU was 44%. The local failure rate was 28%. Abdominal and distant failure rates were 24%. The 3-year actuarial disease-free survival was 74% and the overall survival was 80%. Our preliminary data reveal reasonable local control and survival rates. However, further follow-up is needed to assess our results at 5 years. Postoperative combined modality therapy with high-dose LV may be an option for the adjuvant treatment of patients with resectable rectal cancer.

"Fenestrin" and conjugation in Tetrahymena thermophila

Certain monoclonal antibodies interact with proteins of Tetrahymena thermophila found in the conjugation junction as well as around the gametic nuclei (pronuclei) of conjugating cells; they also react with the oral primordium and fission zone of vegetative cells and with the cytoproct and contractile vacuole pores of all cells. One of these (FXIX-3A7) was investigated in detail. Immunogold labelling suggests that the material labelled by the 3A7 monoclonal antibody, which we call "fenestrin," is located beneath the epiplasm (membrane skeleton). Immunoblots reveal that the major and perhaps sole antigen is a 64 kDa polypeptide, found in two isoelectric variants. Developmental studies implicate fenestrin in two processes involved in conjugation. The first is "tip transformation." During preliminary starvation ("initiation"), labelling of fenestrin first appeared as a spot at the anterior end of starved mature cells, then after mixing of different mating types ("costimulation") it extended posteriorly along the anterior suture. After pairing, this region spread to form a widened plate. The second process is pronuclear transfer. Fenestrations representing channels between the conjugating cells began to appear 0.5 to 1 h after the conjugants united, and eventually merged to form a small number of temporary large holes during exchange of the transfer pronuclei. A fenestrin envelope also enclosed both the transfer and resident pronuclei; a strand of fenestrin connected the two. Shortly after pronuclear transfer, both transfer and resident pronuclei were released from fenestrin caps and fused to produce a zygotic nucleus (synkaryon) not associated with fenestrin Fenestrin thus appears to be intimately involved in the process of pronuclear exchange.

Preoperative 5-fluorouracil, low-dose leucovorin, and concurrent radiation therapy for rectal cancer

BACKGROUND

A Phase I trial was performed to determine the maximum tolerated dose of concurrent preoperative radiation therapy (5040 cGy) and 2 cycles (bolus daily times 5) of 5-fluorouracil (5-FU) and low-dose leucovorin (LV) (20 mg/m2), followed by surgery and 10 cycles of postoperative 5-FU/LV in patients with primary or recurrent rectal cancer.

METHODS

Twenty-four patients were entered into the study. Preoperatively, the initial dose of 5-FU was 325 mg/m2. 5-FU was escalated 50 mg/m2, while the dose of LV and radiation therapy remained constant. Chemotherapy and radiation began concurrently on day 1. The postoperative chemotherapy was not dose escalated; 5-FU, 425 mg/m2, and LV, 20 mg/m2. The median follow-up was 10 months (range, 4-19 months).

RESULTS

The resectability rate with negative margins in the 23 patients who underwent surgery was 100%. One patient refused surgery. The pathologic complete response rate was 13% (3 of 23). An additional four patients had negative nodes and a microscopic foci of tumor in the bowel wall. Therefore, the total clinical complete response rate was 30% (7 of 23). The maximum tolerated dose of 5-FU for the preoperative combined modality segment was 375 mg/m2; therefore, the recommended Phase II dose level is 325 mg/m2. The incidence of Grade 3+ toxicity for the 22 patients treated at the recommended 5-FU dose level (325 mg/m2) during the preoperative combined modality segment was as follows: diarrhea, 14%; erythema, 5%; hematologic, 10%; and total, 18%. The median nadir counts were leukocyte count, 3.7 (range, 1.5-5.9); hemoglobin count, 12.2 (range, 10.2-14.3); and platelet count (times 1000), 165 (range, 92-237).

CONCLUSIONS

With this regimen, the recommended doses of chemotherapy in the combined modality segment are slightly higher than those recommended in arm 2 of the Intergroup postoperative adjuvant rectal trial 0114. This regimen will serve both as the preoperative arm of the Intergroup randomized trial of preoperative versus postoperative combined modality therapy for resectable rectal cancer (INT R9401) as well as the basis for the combined modality segment of NSABP RO-3.

Total lymphoid irradiation in multiple sclerosis

Following a report of the efficacy of total lymphoid irradiation (TLI) in the treatment of chronic progressive multiple sclerosis a further randomised double-blind placebo-controlled study was undertaken with the intention of entering 56 patients. In the event it was possible to recruit only 27 patients in a 2.5 year period. Three patients received active treatment openly and 24 were randomised to either active (14) or sham (10) treatment. Treatment was 1980 cGy to the lymphoid system and spleen or sham treatment after full simulation. The primary outcome measure was a comparison of the mean rates of change between treatment groups on the expanded Kurtzke disability scale (EDSS) over the two year follow up period. Patients were also assessed on other clinical outcome measures, psychometry, and serial MRI of the brain. Active treatment resulted in a profound and prolonged fall in T lymphocytes especially those with the CD4 marker and a reversal in CD4:CD8 ratio. No significant benefit was demonstrated on the rate of clinical disease progression (EDSS). A small but significant benefit was found on a score of bladder function. No significant benefit was demonstrated on other clinical or psychometric indices or on subjective visual analogue scales. There was a small but significant difference in the rate of accumulation of lesions on brain MRI favouring the treatment group. The treated group had a higher incidence of clinically relevant side effects, notably amenorrhoea and infections: three deaths (one in the TLI group, two in the sham treated group) occurred. A post hoc calculation indicates that the study had a possible 35% risk of a false negative result using the principal outcome measure. The study fails to confirm the previously reported clinical benefit of TLI although there may be a minor benefit on disease progression as indicated by MRI lesion counts. It is concluded that TLI cannot be recommended for the routine treatment of chronic progressive multiple sclerosis but the beneficial effect on MRI lesions, though modest, suggests that further research into immune modulation of this condition may be worthwhile.

Preoperative 5-fluorouracil, low-dose leucovorin, and concurrent radiation therapy for rectal cancer

BACKGROUND

A Phase I trial was performed to determine the maximum tolerated dose of concurrent preoperative radiation therapy (5040 cGy) and 2 cycles (bolus daily times 5) of 5-fluorouracil (5-FU) and low-dose leucovorin (LV) (20 mg/m2), followed by surgery and 10 cycles of postoperative 5-FU/LV in patients with primary or recurrent rectal cancer.

METHODS

Twenty-four patients were entered into the study. Preoperatively, the initial dose of 5-FU was 325 mg/m2. 5-FU was escalated 50 mg/m2, while the dose of LV and radiation therapy remained constant. Chemotherapy and radiation began concurrently on day 1. The postoperative chemotherapy was not dose escalated; 5-FU, 425 mg/m2, and LV, 20 mg/m2. The median follow-up was 10 months (range, 4-19 months).

RESULTS

The resectability rate with negative margins in the 23 patients who underwent surgery was 100%. One patient refused surgery. The pathologic complete response rate was 13% (3 of 23). An additional four patients had negative nodes and a microscopic foci of tumor in the bowel wall. Therefore, the total clinical complete response rate was 30% (7 of 23). The maximum tolerated dose of 5-FU for the preoperative combined modality segment was 375 mg/m2; therefore, the recommended Phase II dose level is 325 mg/m2. The incidence of Grade 3+ toxicity for the 22 patients treated at the recommended 5-FU dose level (325 mg/m2) during the preoperative combined modality segment was as follows: diarrhea, 14%; erythema, 5%; hematologic, 10%; and total, 18%. The median nadir counts were leukocyte count, 3.7 (range, 1.5-5.9); hemoglobin count, 12.2 (range, 10.2-14.3); and platelet count (times 1000), 165 (range, 92-237).

CONCLUSIONS

With this regimen, the recommended doses of chemotherapy in the combined modality segment are slightly higher than those recommended in arm 2 of the Intergroup postoperative adjuvant rectal trial 0114. This regimen will serve both as the preoperative arm of the Intergroup randomized trial of preoperative versus postoperative combined modality therapy for resectable rectal cancer (INT R9401) as well as the basis for the combined modality segment of NSABP RO-3.

Hypoangular: a gene potentially involved in specifying positional information in a ciliate, Tetrahymena thermophila

In Tetrahymena, two unique cell-surface structures, the oral apparatus and the cytoproct, are formed at opposite ends of one ciliary row, the reference meridian, which is propagated longitudinally during clonal growth. A third set of unique structures, the contractile vacuole pore(s) (CVP), is located at a nearly constant proportion of the cell circumference to the cell's right of the reference meridian. Three allelic recessive temperature-sensitive mutations, collectively named hypoangular (hpo), alter both the geometry of propagation of the reference meridian and the location of the CVPs. In mutant cells, the reference meridian typically undergoes a steady rightward shift in successive cell generations ("cortical slippage"); concomitantly, CVP sets come to lie closer to the reference meridian. Although CVP location is still proportional to the cell circumference, the constant of proportionality (the "CVP angle") is reduced. Another effect is an alteration in the widths of morphogenetic domains within the cortex. As the temperature is raised (made more restrictive), these effects are accentuated and the CVP angle becomes reduced further. At the extreme, the CVP angle collapses to zero and less, i.e., there is a topological switch such that CVPs come to lie to the left of the reference meridian, and the direction of cortical slippage reverses from rightward to leftward. These observations are hard to reconcile with existing formal models of pattern specification in this system and suggest that the hpo locus might specify a key component of the intracellular positional system.