Preventative strategies for low anterior resection syndrome.

BACKGROUND: A common and debilitating complication of low anterior resection for rectal cancer is low anterior resection syndrome (LARS). As a multifactorial entity, LARS is poorly understood and challenging to treat. Despite this, prevention strategies are commonly overlooked. Our aim was to review the pathophysiology of LARS and explore current evidence on the efficacy and feasibility of prophylactic techniques. METHODS: A literature review was performed between [1st January 2000 to 1st October 2023] for studies which investigated preventative interventions for LARS. Mechanisms by which LARS develop are described, followed by a review of prophylactic strategies to prevent LARS. Medline, Cochrane, and PubMed databases were searched, 189 articles screened, 8 duplicates removed and 18 studies reviewed. RESULTS: Colonic dysmotility, anal sphincter dysfunction and neorectal dysfunction all contribute to the development of LARS, with the complex mechanism of defecation interrupted by surgery. Transanal irrigation (TAI) and pelvic floor rehabilitation (PFR) have shown benefits in preventing LARS, but may be limited by patient compliance. Intraoperative nerve monitoring (IONM) and robotic-assisted surgery have shown some promise in surgically preventing LARS. Nerve stimulation and other novel strategies currently used in treatment of LARS have yet to be investigated in their roles prophylactically. CONCLUSIONS: To date, there is a limited evidence base for all preventative strategies including IONM, RAS, PFP and TAI. These strategies are limited by either access (IONM, RAS and PFP) or acceptability (PFP and TAI), which are both key to the success of any intervention. The results of ongoing trials will serve to assess acceptability, while technological advancement may improve access to some of the aforementioned strategies.

Comparison of Programmed Intermittent Epidural Boluses With Continuous Epidural Infusion for the Maintenance of Labor Analgesia: A Randomized, Controlled, Double-Blind Study.

BACKGROUND: Programmed intermittent epidural boluses may improve the spread of local anesthetics compared to continuous epidural infusion, improving labor analgesia and obstetric outcomes. However, there are limited data from studies using commercially available pumps capable of coadministering programmed intermittent epidural boluses or continuous epidural infusion with patient-controlled epidural analgesia. Therefore, we performed this prospective, randomized, double-blind study to compare the impact of programmed intermittent epidural boluses versus continuous epidural infusion on labor analgesia and maternal/neonatal outcomes. We hypothesized that programmed intermittent epidural boluses will result in lower patient-controlled epidural analgesia consumption compared to that with continuous epidural infusion. METHODS: Following standardized initiation of epidural labor analgesia, women were randomized to receive 0.1% ropivacaine with 2 µg/mL fentanyl as 6-mL programmed intermittent epidural boluses every 45 minutes or continuous epidural infusion at 8 mL/h in a double-blind fashion with similar patient-controlled epidural analgesia settings in both groups. The primary outcome was patient-controlled epidural analgesia consumption per hour. Secondary outcomes included a need for physician interventions, patterns of patient-controlled epidural analgesia use, motor blockade, number of patients who developed hypotension, pain scores, duration of second stage of labor, mode of delivery, and maternal satisfaction. RESULTS: We included 120 patients (61 in programmed intermittent epidural boluses group and 59 in continuous epidural infusion group) in the analysis. The median (interquartile range) patient-controlled epidural analgesia volume consumed per hour was not significantly different between the groups: 4.5 mL/h (3.0-8.6 mL/h) for the continuous epidural infusion group and 4.0 mL/h (2.2-7.1 mL/h) for the programmed intermittent epidural boluses group (P = .17). The Hodges-Lehmann location shift estimate of the difference (95% CI) from the continuous epidural infusion to the programmed intermittent epidural boluses group is 0.9 mL/h (-0.4 to 2.2 mL/h). There were also no significant differences between the groups in any of the secondary outcomes except for higher median (interquartile range) patient-controlled epidural analgesia attempts per given ratio per hour in the programmed intermittent epidural bolus group (0.17 [0.10-0.30] vs 0.12 [0.08-0.18]; P = .03) and more motor block in the continuous epidural infusion group (those with Bromage score <5, 27.5% vs 50.0%; P = .03). CONCLUSIONS: Under the conditions of our study, we did not find improved outcomes with programmed intermittent epidural boluses compared to continuous epidural infusion except for less motor block with programmed intermittent epidural boluses. Future studies should assess whether smaller but clinically important differences exist and evaluate different parameters of programmed intermittent epidural boluses to optimize analgesia and outcomes with this mode of analgesia.

Predicting Severity of Acute Pain After Cesarean Delivery: A Narrative Review.

Cesarean delivery is one of the most common surgical procedures in the United States, with over 1.3 million performed annually. One-fifth of women who undergo cesarean delivery will experience severe pain in the acute postoperative period, increasing their risk of developing chronic pain and postpartum depression, and negatively impacting breastfeeding and newborn care. A growing body of research has investigated tools to predict which patients will experience more severe pain and have increased analgesic consumption after cesarean delivery. These include quantitative sensory testing, assessment of wound hyperalgesia, response to local anesthetic infiltration, and preoperative psychometric evaluations such as validated psychological questionnaires and simple screening tools. For this review, we searched MEDLINE, the Cochrane database, and Google Scholar to identify articles that evaluated the utility of various tools to predict severe pain and/or opioid consumption in the first 48 hours after cesarean delivery. Thirteen articles were included in the final review: 5 utilizing quantitative sensory testing, including patient responses to pressure, electrical, and thermal stimuli; 1 utilizing hyperalgesia testing; 1 using response to local anesthetic wound infiltration; 4 utilizing preoperative psychometric evaluations including the State-Trait Anxiety Inventory, the Pain Catastrophizing Scale, the Pittsburgh Sleep Quality Index, the Hospital Anxiety and Depression Scale, and simple questionnaires; and 2 utilizing a combination of quantitative sensory tests and psychometric evaluations. A number of modalities demonstrated statistically significant correlations with pain outcomes after cesarean delivery, but most correlations were weak to modest, and many modalities might not be clinically feasible. Response to local anesthetic infiltration and a tool using 3 simple questions enquiring about anxiety and anticipated pain and analgesic needs show potential for clinical use, but further studies are needed to evaluate the utility of these predictive tests in clinical practice.

Cockroach allergen exposure and plasma cytokines among children in a tropical environment.

BACKGROUND: Little is known about the effects of socioeconomic status or cockroach allergen on immune responses in school-age children, particularly in tropical environments. OBJECTIVE: To examine whether cockroach allergen and/or socioeconomic status is associated with plasma cytokine levels in Puerto Rican children. METHODS: This was a cross-sectional study of 532 children (6-14 years old) with (n = 272) and without (n = 260) asthma in San Juan (Puerto Rico). House dust allergens (cockroach [Bla g 2], dust mite [Der p 1], cat dander [Fel d 1], dog dander [Can f 1], and mouse urinary protein [Mus m 1]) were quantified using monoclonal antibody arrays. A panel of 14 cytokines (interleukin [IL]-1ß, IL-4, IL-6, IL-10, IL-17A, IL-17F, IL-21, IL-22, IL-23, IL-25, IL-31, IL-33, interferon-γ, and tumor necrosis factor-α) was measured in plasma samples. Low household income was defined as less than $15,000 per year (below the median income for Puerto Rico in 2008-2009). Linear regression was used for the analysis of cockroach allergen and plasma cytokines. RESULTS: In a multivariable analysis adjusting for low income and other allergen levels, cockroach allergen was significantly associated with decreased IL-17A and with increased levels of 8 cytokines (IL-4, IL-10, IL-17F, IL-21, IL-25, IL-31, interferon-γ, and tumor necrosis factor-α). After stratifying this analysis by cockroach allergy (ie, having a cockroach positive immunoglobulin E reaction), our findings remained largely unchanged for children sensitized to cockroach but became weaker and statistically nonsignificant for non-sensitized children. CONCLUSION: Cockroach allergen has broad effects on adaptive immune responses in school-age children in a tropical environment, particularly in those sensitized to cockroach.

Maternal depressive symptoms, maternal asthma, and asthma in school-aged children.

BACKGROUND: Little is known about the joint effects of maternal asthma and maternal depression on childhood asthma. OBJECTIVE: To examine whether maternal depression and maternal asthma lead to greater risk of childhood asthma than maternal asthma alone. METHODS: Cross-sectional studies of children (6-14 years old) in San Juan, Puerto Rico (n = 655) and Sweden (n = 6,887) were conducted. In Puerto Rico, maternal depressive symptoms were defined using the Center for Epidemiologic Studies Depression Scale (CES-D) questionnaire. In Sweden, maternal physician-diagnosed depression was derived from national registries, and maternal depressive symptoms were defined using an abbreviated CES-D questionnaire. Childhood asthma was defined as physician-diagnosed asthma plus current wheeze (in Puerto Rico) or plus medication use (in Sweden). Logistic regression was used for multivariable analysis. RESULTS: Compared with Puerto Rican children whose mothers had neither asthma nor depressive symptoms, those whose mothers had asthma but no depressive symptoms had 3.2 times increased odds of asthma (95% confidence interval [CI] = 2.1-4.8) and those whose mothers had asthma and depressive symptoms had 6.5 times increased odds of asthma (95% CI = 3.3-13.0). Similar results were obtained for maternal depression and maternal asthma in the Swedish cohort (odds ratio for maternal asthma without maternal depression = 2.8, 95% CI = 2.1-3.7; odds ratio for maternal asthma and maternal depression = 4.0, 95% CI = 1.7-9.6). Although the estimated effect of maternal asthma on childhood asthma was increased when maternal depressive symptoms (Puerto Rico) or maternal depression (Sweden) was present, there were no statistically significant additive interactions. CONCLUSION: Maternal depression can further increase the risk of asthma in children whose mothers have a history of asthma.

Rapid Cycle Deliberate Practice Versus Traditional Simulation for Training Extracorporeal Membrane Oxygenation Specialists in Circuit Air Emergency Management: A Randomized Trial.

INTRODUCTION: Extracorporeal membrane oxygenation (ECMO) is a highly complex therapy used to support critically ill patients. Simulation-based training of ECMO specialists in the management of ECMO emergencies has been described in the literature, but optimal methods are not currently established. The objective of this study was to compare rapid cycle deliberate practice (RCDP) simulation versus traditional simulation (TS) with reflective debriefing for training ECMO specialists in the management of arterial air emergencies. METHODS: A prospective, randomized, pre-post interventional design was used to compare the impact of RCDP training with that of TS training on ECMO specialist performance during a simulated ECMO circuit emergency. Participants were divided into 2 training groups-RCDP and TS. Each participant completed a simulated arterial air emergency scenario before training, immediately after training, and again 3 months later. The primary outcome was the time required by individual participants to complete critical clinical actions. RESULTS: Twenty-four ECMO specialists completed the study. Immediately after the training, the RCDP group had faster times to dissociate the patient from the ECMO circuit (11-seconds RCDP vs. 16-seconds TS, P = 0.03) and times to re-establish ECMO support (59-seconds RCDP vs. 82.5-seconds TS, P = 0.01). Follow-up testing at 3 months showed persistence in faster times to re-establish ECMO support in the RCDP group (114-seconds RCDP vs. 199-seconds TS, P = 0.01). CONCLUSIONS: Rapid cycle deliberate practice simulation provides a superior curriculum and method of training ECMO specialists in the management of arterial air emergencies in comparison with traditional simulation.

Additional sex combs-like 1 belongs to the enhancer of trithorax and polycomb group and genetically interacts with Cbx2 in mice.

The Additional sex combs (Asx) gene of Drosophila behaves genetically as an enhancer of trithorax and polycomb (ETP) in displaying bidirectional homeotic phenotypes, suggesting that is required for maintenance of both activation and silencing of Hox genes. There are three murine homologs of Asx called Additional sex combs-like1, 2, and 3. Asxl1 is required for normal adult hematopoiesis; however, its embryonic function is unknown. We used a targeted mouse mutant line Asxl1(tm1Bc) to determine if Asxl1 is required to silence and activate Hox genes in mice during axial patterning. The mutant embryos exhibit simultaneous anterior and posterior transformations of the axial skeleton, consistent with a role for Asxl1 in activation and silencing of Hox genes. Transformations of the axial skeleton are enhanced in compound mutant embryos for the polycomb group gene M33/Cbx2. Hoxa4, Hoxa7, and Hoxc8 are derepressed in Asxl1(tm1Bc) mutants in the antero-posterior axis, but Hoxc8 expression is reduced in the brain of mutants, consistent with Asxl1 being required both for activation and repression of Hox genes. We discuss the genetic and molecular definition of ETPs, and suggest that the function of Asxl1 depends on its cellular context.

Ropivacaine and Ketorolac Wound Infusion for Post-Cesarean Delivery Analgesia: A Randomized Controlled Trial.

OBJECTIVE: To evaluate the efficacy of wound infusion with ropivacaine plus ketorolac compared with placebo for post-cesarean delivery analgesia in women who received a multimodal analgesic regimen including intrathecal morphine. METHODS: In a randomized double-blind study, women undergoing scheduled cesarean delivery under spinal or combined spinal epidural anesthesia were randomized to wound infusion with ropivacaine 0.2% plus ketorolac, or saline placebo using an elastometric pump for 48 hours. The primary outcome was pain score with movement at 24 hours after surgery (0-10 scale, 0=no pain and 10=worst possible pain). Secondary outcomes included pain scores at rest at 24 hours, pain scores at rest and with movement at 2 and 48 hours, opioid consumption, and time to first rescue analgesic. A sample size of 35 per group (n=70) was planned. RESULTS: From November 8, 2016, to May 17, 2019, 247 women were screened, and 71 completed the study per protocol: 38 in the placebo group and 33 in the ropivacaine plus ketorolac group. Patient demographics and intraoperative characteristics were comparable between the groups. There was no significant difference between the groups in the primary outcome of pain score with movement at 24 hours (difference in median score 0, 95% CI -1 to 2, P=.94). There were also no significant differences between the placebo and ropivacaine plus ketorolac groups in pain scores at other time points, in total opioid consumption (difference in median consumption -12.5 mg, 95% CI -30 to 5, P=.11), or in time to rescue analgesics (median [interquartile range] 660 [9-1,496] vs 954 [244-1,710] minutes, hazard ratio 0.69, 95% CI 0.41 to 1.17, P=.16). CONCLUSION: There was no benefit of wound infusion with ropivacaine and ketorolac in women who received intrathecal morphine and a multimodal analgesic regimen. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, NCT02829944. FUNDING SOURCE: The study was supported in part by Avanos Medical Inc.

Development of Validated Checklists to Evaluate Clinical Specialists in Pediatric ECMO Emergencies Using Delphi Method.

Extracorporeal membrane oxygenation (ECMO) is a low-volume, high-risk modality of care. Clinical specialists (CS) who manage ECMO circuit emergencies vary in background and approach to circuit emergencies based on institutional training standards, leading to variation that may impact the quality of care. Validated checklists to assess CS performance are crucial to eliminate disparities and improve efficiency. This study focused on the development and validation of checklists to evaluate the clinical performance of ECMO CS in three ECMO circuit emergencies. A research team with diverse clinical background from our institution developed the first iteration of three ECMO emergency checklists: (1) venous air, (2) arterial air, and (3) oxygenator failure. A modified Delphi technique with a panel of 11 national content experts in ECMO was used to develop content validity evidence. Rating scales from 1 to 7 were used to evaluate each checklist item. The response rate for three rounds of Delphi was 100%. Items with mean score >4 were kept, and new item recommendations were added based on comments from the panel. The venous air, arterial air, and oxygenator failure checklists were revised from 10, 13, and 9 items to 12, 12, and 10 items, respectively. A Cronbach's α of 0.74 during the second round of responses indicated an acceptable degree of agreement. This study demonstrated content validation of three ECMO emergency checklists to assess performance of ECMO CS using a consensus-based Delphi technique. Future validity evidence should be acquired by implementing these checklists in the simulation environments.

The Polycomb group--no longer an exclusive club?

Polycomb group (PcG) proteins maintain silencing at target loci in higher eukaryotes but recent evidence suggests that about half of these proteins are also required for maintenance of activation at homeotic loci. We suggest that PcG and trithorax group response elements should acquire a new name, 'maintenance elements', to reflect the dual function of regulatory elements that bind both groups of proteins. New data suggest that there might be a functional link between PcG repression and cell-cycle regulation.

Population Structure, Chemotype Diversity, and Potential Chemotype Shifting of Fusarium graminearum in Wheat Fields of Manitoba.

This study was to investigate the variation of acetyl ester derivative of DON at 15-position oxygen (15ADON) and acetyl ester derivative of DON at 3-position oxygen (3ADON) chemotypes and potential chemotype shifting of Fusarium graminearum based on the population structure of this species in Manitoba. The study was conducted in 15 locations with wheat cvs. Superb and AC Barrie in Manitoba from 2004 to 2005. Percentages of chemotypes 3ADON and 15ADON of F. graminearum ranged from 0 to 95.7 and 4.3 to 100%, respectively. The 3ADON chemotype was distributed in the southern part of Manitoba and predominant in Morris and Horndean. The two chemotypes almost shared the same percentage in Portage la Prairie. The 15ADON chemotype was predominant in the other locations. Significant gene flow was found among the populations from Sanford, Portage la Prairie, Hamiota, Plumas, Rapid City, and Virden; the populations from Cartier, Rivers, Killarney, and Souris; and the populations from Morris, Kenville, and Dauphin. There were no differences between the populations from two wheat cultivars and two chemotypes. The great variation of chemotype likely resulted from the great genetic diversity of F. graminearum. Sexual recombination, population age, and cropping system could result in genetic and chemotypic diversities. Wheat seed shipment and long-distance spore transportation of F. graminearum potentially caused the genetic migration and chemotype shifting in Manitoba.

The Drosophila polycomb group protein Psc contacts ph and Pc through specific conserved domains.

The Polycomb group proteins are transcriptional repressors that are thought to act through multimeric nuclear complexes. We show that ph and Psc coprecipitate with Pc from nuclear extracts. We have analyzed the domains required for the association of Psc with ph and Pc by using the yeast two-hybrid system and an in vitro protein-binding assay. Psc and ph interact through regions of sequence conservation with mammalian homologs, i.e., the H1 domain of ph (amino acids 1297 to 1418) and the helix-turn-helix-containing region of Psc (amino acids 336 to 473). Psc contacts Pc primarily at the helix-turn-helix-containing region of Psc (amino acids 336 to 473), but also at the ring finger (amino acids 250 to 335). The Pc chromobox is not required for this interaction. We discuss the implication of these results for the nature of the complexes formed by Polycomb group proteins.

Site-specific recognition of a 70-base-pair element containing d(GA)(n) repeats mediates bithoraxoid polycomb group response element-dependent silencing.

Polycomb group proteins act through Polycomb group response elements (PREs) to maintain silencing at homeotic loci. The minimal 1.5-kb bithoraxoid (bxd) PRE contains a region required for pairing-sensitive repression and flanking regions required for maintenance of embryonic silencing. Little is known about the identity of specific sequences necessary for function of the flanking regions. Using gel mobility shift analysis, we identify DNA binding activities that interact specifically with a multipartite 70-bp fragment (MHS-70) downstream of the pairing-sensitive sequence. Deletion of MHS-70 in the context of a 5.1-kb bxd Polycomb group response element derepresses maintenance of silencing in embryos. A partially purified binding activity requires multiple, nonoverlapping d(GA)(3) repeats for MHS-70 binding in vitro. Mutation of d(GA)(3) repeats within MHS-70 in the context of the 5.1-kb bxd PRE destabilizes maintenance of silencing in a subset of cells in vivo but gives weaker derepression than deletion of MHS-70. These results suggest that d(GA)(3) repeats are important for silencing but that other sequences within MHS-70 also contribute to silencing. Antibody supershift assays and Western analyses show that distinct isoforms of Polyhomeotic and two proteins that recognize d(GA)(3) repeats, the TRL/GAGA factor and Pipsqueak (Psq), are present in the MHS-70 binding activity. Mutations in Trl and psq enhance homeotic phenotypes of ph, indicating that TRL/GAGA factor and Psq are enhancers of Polycomb which have sequence-specific DNA binding activity. These studies demonstrate that site-specific recognition of the bxd PRE by d(GA)(n) repeat binding activities mediates PcG-dependent silencing.

A domain shared by the Polycomb group proteins Scm and ph mediates heterotypic and homotypic interactions.

The Sex comb on midleg (Scm) and polyhomeotic (ph) proteins are members of the Polycomb group (PcG) of transcriptional repressors. PcG proteins maintain differential patterns of homeotic gene expression during development in Drosophila flies. The Scm and ph proteins share a homology domain with 38% identity over a length of 65 amino acids, termed the SPM domain, that is located at their respective C termini. Using the yeast two-hybrid system and in vitro protein-binding assays, we show that the SPM domain mediates direct interaction between Scm and ph. Binding studies with isolated SPM domains from Scm and ph show that the domain is sufficient for these protein interactions. These studies also show that the Scm-ph and Scm-Scm domain interactions are much stronger than the ph-ph domain interaction, indicating that the isolated domain has intrinsic binding specificity determinants. Analysis of site-directed point mutations identifies residues that are important for SPM domain function. These binding properties, predicted alpha-helical secondary structure, and conservation of hydrophobic residues prompt comparisons of the SPM domain to the helix-loop-helix and leucine zipper domains used for homotypic and heterotypic protein interactions in other transcriptional regulators. In addition to in vitro studies, we show colocalization of the Scm and ph proteins at polytene chromosome sites in vivo. We discuss the possible roles of the SPM domain in the assembly or function of molecular complexes of PcG proteins.

Initial and mid-term results of a 4F compatible self-expanding low strut profile nitinol stent in the superficial femoral artery.

PURPOSE: To evaluate the initial and mid-term results of a new self-expanding low strut profile nitinol stent for treatment of atherosclerotic lesions stenoses and occlusions in the superficial femoral artery (SFA). MATERIALS AND METHODS: In 8 patients (4 male, 4 female, mean age 74.8 +/- 8.8 years) with SFA lesions and non-satisfying results after PTA treatment alone, 10 self-expanding nitinol Xpert stents were deployed via a 4 F sheath. Stent characteristics and handling were graded by the interventionalist. Fontaine classification, duplex flow measurements and ankle brachial index (ABI) at rest and stress were taken prior and one day after stent placement. Patients were followed 3, 6 and 12 months after the procedure obtaining the same parameters at each appointment. RESULTS: Initial stent treatment was successful in all patients. Stent handling and positioning were rated very good and safe. All patients improved clinically by at least one Fontaine stage (range before treatment: stage IIb to IV). The mean ABI at rest (stress) improved initially from 0.68 (0.70) to 1.07 (0.99). During a mean follow-up period of 8.3 months no case of clinically relevant in-stent stenosis was observed with stable values of ABI at rest and stress. CONCLUSION: Treatment of SFA lesions using the 4F-compatible self-expanding nitinol Xpert stent is technically simple, safe and shows good initial and mid-term results.

Location of the LSP-1 Genes in Drosophila Species by IN SITU Hybridization.

The locations of the larval serum protein one (LSP-1) alpha, beta and gamma genes were determined in Drosophila melanogaster and in 14 other species of Drosophila by in situ hybridization to polytene chromosomes. The LSP-1 alpha gene mapped to bands 11B on the X chromosome, the LSP-1 beta gene mapped to bands 21D-E on chromosome 2L, and the LSP-1 gamma gene mapped to band 61A in all the melanogaster subgroup species. In eight other species, both the LSP-1 alpha and beta genes mapped to one site on Muller's element E which corresponds to chromosome 3R of D. melanogaster. No hybridization of LSP-1 gamma was detected in these eight species. Restriction enzyme digestion and analysis of genomic DNA by filter transfer hybridization confirmed the presence of LSP-1 alpha-like and beta-like genes in seven of these species. These results are discussed with respect to conservation of the chromosomal elements in the genus Drosophila.

A Genetic and Cytogenetic Analysis of the Region Surrounding the Lsp-1 beta-Gene in DROSOPHILA MELANOGASTER.

The region surrounding the gene coding for the beta-polypeptide (21D-22C) of the major Drosophila melanogaster larval serum protein, LSP-1, has been studied in detail. Seven new gamma-ray-induced deficiencies of the region have been used, together with the two extant deficiencies, to map the position of the beta-gene and of the 55 newly induced ethyl methanesulfonate mutants uncovered by one of the largest deficiencies. No lethal mutation of the beta-gene was found.

Interactions of polyhomeotic with Polycomb group genes of Drosophila melanogaster.

The Polycomb (Pc) group genes of Drosophila are negative regulators of homeotic genes, but individual loci have pleiotropic phenotypes. It has been suggested that Pc group genes might form a regulatory hierarchy, or might be members of a multimeric complex that obeys the law of mass action. Recently, it was shown that polyhomeotic (ph) immunoprecipitates in a multimeric complex that includes Pc. Here, we show that duplications of ph suppress homeotic transformations of Pc and Pcl, supporting a mass-action model for Pc group function. We crossed ph alleles to all members of the Polycomb group, and to E(Pc) and Su(z)2 to look for synergistic effects. We observed extragenic noncomplementation between ph503 and Pc, Psc1 and Su(z)2(1) in females, and between ph409 and Sce1, ScmD1 and E(z)1 mutations in males, suggesting that these gene products might interact directly with ph. Males hemizygous for a temperature-sensitive allele, ph2, are lethal when heterozygous with mutants in Asx, Pc, Pcl, Psc, Sce and Scm, and with E(Pc) and Su(z)2. Mutations in trithorax group genes were not able to suppress the lethality of ph2/Y; Psc1/+ males. ph2 was not lethal with extra sex combs, E(z), super sex combs (sxc) or l(4)102EFc heterozygotes, but did cause earlier lethality in embryos homozygous for E(z), sxc and l(4)102EFc. However, ph503 did not enhance homeotic phenotypes of esc heterozygotes derived from homozygous esc- mothers. We examined the embryonic phenotypes of ph2 embryos that were lethal when heterozygous or homozygous for other mutations. Based on this phenotypic analysis, we suggest that ph may perform different functions in conjunction with differing subsets of Pc group genes.

Rapid spread of transposable p elements in experimental populations of Drosophila melanogaster.

The invasion of P elements in natural populations of Drosophila melanogaster was modeled by establishing laboratory populations with 1%, 5% and 10% P genomes and monitoring the populations for 20 generations. In one experiment, the ability of flies to either induce or suppress gonadal sterility in different generations was correlated with the amount of P element DNA. In a second experiment, the percentage of genomes that contained P elements, and the distribution of P elements among individual flies was monitored. The ability to induce gonadal dysgenesis increased rapidly each generation. However, the increase in P cytotype lagged behind by five to ten generations. The total amount of P element DNA and the frequency of flies containing P elements increased each generation. The number of P elements within individual genomes decreased initially, but then increased. Finally, the distribution of P elements within the genomes of individuals from later generations varied considerably, and this pattern differed from the parental P strain. These results suggest that the interaction between the assortment and recombination of chromosomal segments, and multiplicative transposition could result in the rapid spread of P elements in natural populations.

Genetic analysis of the additional sex combs locus of Drosophila melanogaster.

Additional sex combs (Asx) is a member of the Polycomb group of genes, which are thought to be required for maintenance of chromatin structure. To better understand the function of Asx, we have isolated nine new alleles, each of which acts like a gain of function mutation. Asx is required for normal determination of segment identity. AsxP1 shows an unusual phenotype in that anterior and posterior homeotic transformations are seen in the same individuals, suggesting that AsxP1 might upset chromatin structure in a way that makes both activation and repression of homeotic genes more difficult. Analysis of embryonic and adult phenotypes of Asx alleles suggests that Asx is required zygotically for determination of segment number and polarity. The expression pattern of even-skipped is altered in Asx mutant embryos, suggesting that Asx is required for normal expression of this gene. We have transposon-tagged the Asx gene, and can thus begin molecular analysis of its function.