One-Lung Ventilation and Postoperative Pulmonary Complications After Major Lung Resection Surgery. A Multicenter Randomized Controlled Trial

OBJECTIVES

The effect of one-lung ventilation (OLV) strategy based on low tidal volume (TV), application of positive end-expiratory pressure (PEEP), and alveolar recruitment maneuvers (ARM) to reduce postoperative acute respiratory distress syndrome (ARDS) and pulmonary complications (PPCs) compared with higher TV without PEEP and ARM strategy in adult patients undergoing lobectomy or pneumonectomy has not been well established.

DESIGN

Multicenter, randomized, single-blind, controlled trial.

SETTING

Sixteen Italian hospitals.

PARTICIPANTS

A total of 880 patients undergoing elective major lung resection.

INTERVENTIONS

Patients were randomized to receive lower tidal volume (LTV group: 4 mL/kg predicted body weight, PEEP of 5 cmH2O, and ARMs) or higher tidal volume (HTL group: 6 mL/kg predicted body weight, no PEEP, and no ARMs). After OLV, until extubation, both groups were ventilated using a tidal volume of 8 mL/kg and a PEEP value of 5 cmH2O. The primary outcome was the incidence of in-hospital ARDS. Secondary outcomes were the in-hospital rate of PPCs, major cardiovascular events, unplanned intensive care unit (ICU) admission, in-hospital mortality, ICU length of stay, and in-hospital length of stay.

MEASUREMENTS AND MAIN RESULTS

ARDS occurred in 3 of 438 patients (0.7%, 95% CI 0.1-2.0) and in 1 of 442 patients (0.2%, 95% CI 0-1.4) in the LTV and HTV group, respectively (Risk ratio: 3.03 95% CI 0.32-29, p = 0.372). Pulmonary complications occurred in 125 of 438 patients (28.5%, 95% CI 24.5-32.9) and in 136 of 442 patients (30.8%, 95% CI 26.6-35.2) in the LTV and HTV group, respectively (risk ratio: 0.93, 95% CI 0.76-1.14, p = 0.507). The incidence of major complications, in-hospital mortality, and unplanned ICU admission, ICU and in-hospital length of stay were comparable in both groups.

CONCLUSIONS

In conclusion, among adult patients undergoing elective lung resection, an OLV with lower tidal volume, PEEP 5 cmH2O, and ARMs and a higher tidal volume strategy resulted in low ARDS incidence and comparable postoperative complications, in-hospital length of stay, and mortality.

Postoperative pulmonary complications and mortality after major abdominal surgery. An observational multicenter prospective study

BACKGROUND

Postoperative pulmonary complications (PPCs) significantly contribute to postoperative morbidity and mortality. We conducted a study to determine the incidence of PPCs after major elective abdominal surgery and their association with early and 1-year mortality in patient without pre-existing respiratory disease.

METHODS

We conducted a multicenter observational prospective clinical study in 40 Italian centers. 1542 patients undergoing elective major abdominal surgery were recruited in a time period of 14 days and clinically managed according to local protocol. The primary outcome was to determine the incidence of PPCs. Further, we aimed to identify independent predictors for PPCs and examine the association between PPCs and mortality.

RESULTS

PPCs occurred in 12.6% (95% CI 11.1-14.4%) of patients with significant differences among general (18.3%, 95% CI 15.7-21.0%), gynecological (3.7%, 95% CI 2.1-6.0%) and urological surgery (9.0%, 95% CI 6.0-12.8%). PPCs development was associated with known pre- and intraoperative risk factors. Patients who developed PPCs had longer length of hospital stay, higher risk of 30-days hospital readmission, and increased in-hospital and one-year mortality (OR 3.078, 95% CI 1.825-5.191; P<0.001).

CONCLUSIONS

The incidence of PPCs in patients without pre-existing respiratory disease undergoing elective abdominal surgery is high and associated with worse clinical outcome at one year after surgery. General surgery is associated with higher incidence of PPCs and mortality compared to gynecological and urological surgery.

Weaning from mechanical ventilation in intensive care units across 50 countries (WEAN SAFE): a multicentre, prospective, observational cohort study

BACKGROUND

Current management practices and outcomes in weaning from invasive mechanical ventilation are poorly understood. We aimed to describe the epidemiology, management, timings, risk for failure, and outcomes of weaning in patients requiring at least 2 days of invasive mechanical ventilation.

METHODS

WEAN SAFE was an international, multicentre, prospective, observational cohort study done in 481 intensive care units in 50 countries. Eligible participants were older than 16 years, admitted to a participating intensive care unit, and receiving mechanical ventilation for 2 calendar days or longer. We defined weaning initiation as the first attempt to separate a patient from the ventilator, successful weaning as no reintubation or death within 7 days of extubation, and weaning eligibility criteria based on positive end-expiratory pressure, fractional concentration of oxygen in inspired air, and vasopressors. The primary outcome was the proportion of patients successfully weaned at 90 days. Key secondary outcomes included weaning duration, timing of weaning events, factors associated with weaning delay and weaning failure, and hospital outcomes. This study is registered with ClinicalTrials.gov, NCT03255109.

FINDINGS

Between Oct 4, 2017, and June 25, 2018, 10 232 patients were screened for eligibility, of whom 5869 were enrolled. 4523 (77·1%) patients underwent at least one separation attempt and 3817 (65·0%) patients were successfully weaned from ventilation at day 90. 237 (4·0%) patients were transferred before any separation attempt, 153 (2·6%) were transferred after at least one separation attempt and not successfully weaned, and 1662 (28·3%) died while invasively ventilated. The median time from fulfilling weaning eligibility criteria to first separation attempt was 1 day (IQR 0-4), and 1013 (22·4%) patients had a delay in initiating first separation of 5 or more days. Of the 4523 (77·1%) patients with separation attempts, 2927 (64·7%) had a short wean (≤1 day), 457 (10·1%) had intermediate weaning (2-6 days), 433 (9·6%) required prolonged weaning (≥7 days), and 706 (15·6%) had weaning failure. Higher sedation scores were independently associated with delayed initiation of weaning. Delayed initiation of weaning and higher sedation scores were independently associated with weaning failure. 1742 (31·8%) of 5479 patients died in the intensive care unit and 2095 (38·3%) of 5465 patients died in hospital.

INTERPRETATION

In critically ill patients receiving at least 2 days of invasive mechanical ventilation, only 65% were weaned at 90 days. A better understanding of factors that delay the weaning process, such as delays in weaning initiation or excessive sedation levels, might improve weaning success rates.

FUNDING

European Society of Intensive Care Medicine, European Respiratory Society.

Combining conventional tree-ring measurements with wood anatomy and strontium isotope analyses enables dendroprovenancing at the local scale

Dendroprovenancing provides critical information regarding the origin of wood, allowing further insights into economic exploitation strategies and source regions of timber products. Traditionally, dendroprovenancing relies on pattern-matching of tree rings, but its spatial resolution is limited by the geographical coverage of species-specific chronologies available for crossdating and, in the case of short-distance trades, by scarce environmental variability. Here, we present an approach to provenance timber with high spatial resolution from forested areas that have been exploited intensively throughout history, with the aim to understand the sustainability of the various woodland management practices used to supply timber products. To this end, we combined tree-ring width (TRW), wood anatomical and geochemical analyses in addition to multivariate statistical validation procedures to trace the origin of living oak trees (Quercus robur) sampled in four stands located within a 30-km radius around the city of Limoges (Haute-Vienne, France). We demonstrate that TRW and wood anatomical variables (and in particular cell density) robustly discriminate the eastern from the western site, while failing to trace the origin of trees from the northern and southern sites. Here, strontium isotopic ratios (⁸⁷Sr/⁸⁶Sr) and Ca concentrations identify clusters of trees which could not be identified with TRW or wood anatomy. Ultimately, our study demonstrates that the coupling of wood anatomy with geochemical signatures allows to correctly pinpoint the origin of trees. Given the small geographic scale of our study and the limited differences in elevation and climate between study sites, our results are particularly promising for future dendroprovenancing studies. We thus conclude that the combination of multiple approaches will not only increase the accuracy of dendroprovenancing studies at local scales, but could also be implemented at much larger scales to identify trends in historic timber supply throughout Europe.

COVID-19 free oncologic surgical hub: The experience of reallocation of a gynecologic oncology unit during pandemic outbreak

INTRODUCTION

During the SARS-CoV-2 pandemic, the majority of healthcare resources of the affected Italian regions were allocated to COVID-19 patients. Due to lack of resources and high risk of death, most cancer patients have been shifted to non-surgical treatments. The following reports our experience of a Gynaecologic Oncology Unit's reallocation of resources in a COVID-19 free surgical oncologic hub in order to guarantee standard quality of surgical activities.

MATERIALS AND METHODS

This is a prospective observational study performed in the Gynaecologic Oncology Unit, on the outcomes of the reallocation of surgical activities outside the University Hospital of Bologna, Italy, during the Italian lockdown period. Here, we described our COVID-19 free surgical oncologic pathway, in terms of lifestyle restrictions, COVID-19 screening measures, and patient clinical, surgical and follow up outcomes.

RESULTS

During the lockdown period (March 9th - May 4th, 2020), 83 patients were scheduled for oncological surgery, 51 patients underwent surgery. Compared to pre-COVID period, we performed the same activities: number of cases scheduled for surgery, type of surgery and surgical and oncological results. No cases of COVID-19 infection were recorded in operated patients and in medical staff. Patients were compliant and well accepted the lifestyle restrictions and reorganization of the care.

CONCLUSIONSONCLUSIONS

Our experience showed that the prioritization of oncological surgical care and the allocation of resources during a pandemic in COVID-19 free surgical hubs is an appropriate choice to guarantee oncological protocols.

Sigh in Patients With Acute Hypoxemic Respiratory Failure and ARDS: The PROTECTION Pilot Randomized Clinical Trial

BACKGROUND

Sigh is a cyclic brief recruitment maneuver: previous physiologic studies showed that its use could be an interesting addition to pressure support ventilation to improve lung elastance, decrease regional heterogeneity, and increase release of surfactant.

RESEARCH QUESTION

Is the clinical application of sigh during pressure support ventilation (PSV) feasible?

STUDY DESIGN AND METHODS

We conducted a multicenter noninferiority randomized clinical trial on adult intubated patients with acute hypoxemic respiratory failure or ARDS undergoing PSV. Patients were randomized to the no-sigh group and treated by PSV alone, or to the sigh group, treated by PSV plus sigh (increase in airway pressure to 30 cm H₂O for 3 s once per minute) until day 28 or death or successful spontaneous breathing trial. The primary end point of the study was feasibility, assessed as noninferiority (5% tolerance) in the proportion of patients failing assisted ventilation. Secondary outcomes included safety, physiologic parameters in the first week from randomization, 28-day mortality, and ventilator-free days.

RESULTS

Two-hundred and fifty-eight patients (31% women; median age, 65 [54-75] years) were enrolled. In the sigh group, 23% of patients failed to remain on assisted ventilation vs 30% in the no-sigh group (absolute difference, -7%; 95% CI, -18% to 4%; P = .015 for noninferiority). Adverse events occurred in 12% vs 13% in the sigh vs no-sigh group (P = .852). Oxygenation was improved whereas tidal volume, respiratory rate, and corrected minute ventilation were lower over the first 7 days from randomization in the sigh vs no-sigh group. There was no significant difference in terms of mortality (16% vs 21%; P = .337) and ventilator-free days (22 [7-26] vs 22 [3-25] days; P = .300) for the sigh vs no-sigh group.

INTERPRETATION

Among hypoxemic intubated ICU patients, application of sigh was feasible and without increased risk.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT03201263; URL: www.clinicaltrials.gov.

Airway management in anesthesia for thoracic surgery: a "real life" observational study

Background

One-lung ventilation (OLV) in thoracic anesthesia is required to provide good surgical exposure. OLV is commonly achieved through a double lumen tube (DLT) or a bronchial blocker (BB). Malposition is a relevant issue related to these devices use. No prospective studies with adequately large sample size have been performed to evaluate the malposition rate of DLTs and BBs.

Methods

A total of 2,127 patients requiring OLV during thoracic surgery were enrolled. The aim of this multicenter prospective observational study performed across 26 academic and community hospitals is to evaluate intraoperative malposition rate of DLTs and BBs. We also aim to assess: which device is the most used to achieve OLV, the frequency of bronchoscope (BRO) use, the incidence rate of desaturation during OLV and the role of other factors that can correlate to this event, and incidence of difficult airway.

Results

Malposition rate for DLTs was 14%, for BBs 33%. DLTs were used in 95% of patients and BBs in 5%. Mean positioning time was shorter for DLT than BB (156±230 vs. 321±290 s). BRO was used in 54% of patients to check the correct positioning of the DLT. Desaturation occurred in 20% of all cases during OLV achieved through a DLT. Predicting factors of desaturation were dislocation (OR 2.03) and big size of DLT (OR 1.15). BRO use (OR 0.69) and left surgical side (OR 0.41) proved to be protective factors. Difficult airway prevalence was 16%; 10.8% predicted and 5.2% unpredicted.

Conclusions

DLT has a low malpositioning rate and is the preferred device to achieve OLV. BRO use recorded was unexpectedly low. The possibility of encountering a difficult airway is frequent, with an overall prevalence of 16%. Risk factors of desaturation are malposition and increased size of DLT. Left procedures and BRO use could lead to fewer episodes of desaturation.

Ultrasound-guided thoracic paravertebral block for closed loop ileostomy repair in severe COPD: a case report

Background and objectives

Ultrasound-guided thoracic paravertebral block is usually considered a good alternative to epidural thoracic for anesthesia and pain control in thoracic and breast surgery. Furthermore it has also been used during abdominal surgery lately, especially hepatic and renal surgery. However, its role is poorly defined in this context. The purpose of this report was to highlight the role of thoracic paravertebral block in providing effective anesthesia and analgesia during both the abdominal surgical intervention and pain control in post-operative period, avoiding possible complications which general anesthesia may arise, which are fairly common in patients with chronic obstructive pulmonary disease and similar comorbidities.

Case report

The authors present a case of abdominal surgery successfully performed on a woman affected by severe chronic obstructive pulmonary disease requiring closed loop ileostomy repair performed with ultrasound guided thoracic paravertebral block without any complications.

Conclusions

Thoracic paravertebral block may be a safe anesthetic method for abdominal surgery in those patients who would undergo potential severe complications by using general anesthesia.

[Ultrasound-guided thoracic paravertebral block for closed loop ileostomy repair in severe COPD: a case report]

BACKGROUND AND OBJECTIVES

Ultrasound-guided thoracic paravertebral block is usually considered a good alternative to epidural thoracic for anesthesia and pain control in thoracic and breast surgery. Furthermore it has also been used during abdominal surgery lately, especially hepatic and renal surgery. However, its role is poorly defined in this context. The purpose of this report was to highlight the role of thoracic paravertebral block in providing effective anesthesia and analgesia during both the abdominal surgical intervention and pain control in post-operative period, avoiding possible complications which general anesthesia may arise, which are fairly common in patients with chronic obstructive pulmonary disease and similar comorbidities.

CASE REPORT

The authors present a case of abdominal surgery successfully performed on a woman affected by severe chronic obstructive pulmonary disease requiring closed loop ileostomy repair performed with ultrasound guided thoracic paravertebral block without any complications.

CONCLUSIONS

Thoracic paravertebral block may be a safe anesthetic method for abdominal surgery in those patients who would undergo potential severe complications by using general anesthesia.

Peripheral venous catheter fracture with embolism into the pulmonary artery

Peripheral vein catheterization is generally considered a harmless procedure. Venous catheter rupture associated with pulmonary embolism is an unlikely but potentially serious complication. We report a case of a peripheral venous catheter (PVC) fracture with pulmonary artery embolization in the left lower lobe treated successfully by a surgical approach. The positioning of a PVC is not always a harmless procedure. Every time there are difficulties in positioning or in removal of a catheter device, it should be carefully inspected to verify integrity. The advisability of removal of these small foreign bodies is debated; percutaneous retrieval is preferred, while surgery should be discussed case by case.

Major abdominal surgery and postoperative pain control: are protocols enough?

Suitable postoperative pain control (POPC) requires both the application of appropriate pain therapy and the continuous supervision of its therapeutic effects. In our hospital, POPC was, until recently, limited to the first 48 postoperative hours. The purpose of this retrospective study was to assess, the evolution of POPC at the end of the first postoperative 48 hours among major abdominal surgery patients using the Acute Pain Service (APS) database. Further we sought to establish the indications to extend POPC to the entire postoperative period. Regardless of the type of protocol applied after surgery, 79.6% of cases showed pain control was still needed after the 48(th) hour. In about half of the cases, POPC was perpetuated with only the drug category or by dosage modifications, while in roughly one third of the cases we adopted both drug and administration route changes. These changes were made by the APS after a thorough evaluation of the patients' conditions and needs in terms of analgesia. Interestingly, in approximately 5% of cases the surgeon decided to interrupt pain therapy. When applying evidence-based guideline protocols, organizational issues are important as well as a better definition of the APS role in POPC, at least from the timing point of view.

[Women's health and night work]

The following aspects are taken into consideration: health, work activity, family life, social life. The A. recalls the importance of preventive measures. Therefore must actued prevention activities to protect women health in accomplishment both Community regulation and Italian legislation.

[Mobbing: a problem in occupational health]

Occupational stress may be the cause of psychosomatic and mental disorders. A development of conflicts into a negative direction may trigger a mobbing behaviour at workplace and a mobbing syndrome on the victims. On account of the frequency of mobbing activities at work, it is to assert the need of preventive interventions.

Simultaneous antagonism of interleukin-5, granulocyte-macrophage colony-stimulating factor, and interleukin-3 stimulation of human eosinophils by targetting the common cytokine binding site of their receptors

Human interleukin-5 (IL-5), granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-3 are eosinophilopoietic cytokines implicated in allergy in general and in the inflammation of the airways specifically as seen in asthma. All 3 cytokines function through cell surface receptors that comprise a ligand-specific alpha chain and a shared subunit (beta(c)). Although binding of IL-5, GM-CSF, and IL-3 to their respective receptor alpha chains is the first step in receptor activation, it is the recruitment of beta(c) that allows high-affinity binding and signal transduction to proceed. Thus, beta(c) is a valid yet untested target for antiasthma drugs with the added advantage of potentially allowing antagonism of all 3 eosinophil-acting cytokines with a single compound. We show here the first development of such an agent in the form of a monoclonal antibody (MoAb), BION-1, raised against the isolated membrane proximal domain of beta(c). BION-1 blocked eosinophil production, survival, and activation stimulated by IL-5 as well as by GM-CSF and IL-3. Studies of the mechanism of this antagonism showed that BION-1 prevented the high-affinity binding of (125)I-IL-5, (125)I-GM-CSF, and (125)I-IL-3 to purified human eosinophils and that it bound to the major cytokine binding site of beta(c). Interestingly, epitope analysis using several beta(c) mutants showed that BION-1 interacted with residues different from those used by IL-5, GM-CSF, and IL-3. Furthermore, coimmunoprecipitation experiments showed that BION-1 prevented ligand-induced receptor dimerization and phosphorylation of beta(c), suggesting that ligand contact with beta(c) is a prerequisite for recruitment of beta(c), receptor dimerization, and consequent activation. These results demonstrate the feasibility of simultaneously inhibiting IL-5, GM-CSF, and IL-3 function with a single agent and that BION-1 represents a new tool and lead compound with which to identify and generate further agents for the treatment of eosinophil-dependent diseases such as asthma.

[Perforated gastric ulcer: an increasing neonatal ICU disease? Report of 4 cases]

Between november 1994 and september 1995, there were 4 cases of premature infants in our Neonatal Intensive Care Unit (NICU) who developed gastrointestinal perforation and bleeding due to peptic ulcer and 3 died of this complication. In the first case, the neonate developed pneumoperitonium when weaning from the ventilator and was submitted to the operation with clinical diagnosis of Necrotizing Enterocolitis. Surprisingly, during the procedure, a perforated gastric ulcer was disclosed. Ever since, this NICU is aware of this diagnosis and try to better identify the possible risks factors. Asphyxia, prematurity, stress and situations where low gastrointestinal flow (asphyxia, exchange transfusion, pneumothorax, hemodynamic shock, cardiac arrest) were observed in almost every case. Treatment with dexamethasone or aminophilline was used in 3 of 4 cases and this potential serious side effect should be considered in all babies treated with steroids. The association of ranitidine (2 mg/kg 12/12 h) could not prevent the perforation in cases 1 and 3. Better understanding of physiopathology of the ulcer in this period of life and a effective preventable drug is still lacking.

Improving chest pain evaluation within a multihospital network by the use of emergency department observation units

BACKGROUND

Since 1993 the 13 VHA Southern New England (VHA-SNE) hospitals have been engaged in a regionally sponsored initiative to analyze and improve selected clinical processes. Nine of these hospitals have chosen to participate in an initiative in which observation units were postulated to offer a tool for improving the care of patients with chest pain-the VHA initiative to Implement Chest Pain Treatment in Observation Units.

THE FIVE PHASES

In phase 1 of the initiative, the VHA-SNE's Clinical Benchmarking Work Group reviewed the medical literature, which confirmed longstanding systemic and pervasive problems in the evaluation of chest pain patients. The work group's preferred practice was the outpatient "rule out myocardial infarction [MI] evaluation" program during monitored observation; serial testing can accurately diagnose low- and moderate-probability patients with MI. In Phase 2 the study group surveyed the emergency departments in the nine hospitals, discovering significant variation in admission rates and practice patterns. During phase 3 the work group identified a health care organization demonstrating best-practice performance--one of the few hospitals in the nation with an operational outpatient "rule out MI evaluation" program. A team site-visited that organization and recorded information about its structure and processes. VHA-SNE then published a monograph that identified its current performance, described the best-practice approach, offered strategies to implement the model program, and analyzed the financial implications and return on investment. In phase 4 a pilot hospital implemented the model program, which in phase 5 is being extended to the other hospitals represented in the work group. Information regarding protocols, lessons learned, and barriers to implementation was freely provided.

Activating point mutations in the common beta subunit of the human GM-CSF, IL-3 and IL-5 receptors suggest the involvement of beta subunit dimerization and cell type-specific molecules in signalling

We have combined retroviral expression cloning with random mutagenesis to identify two activating point mutations in the common signal-transducing subunit (h beta c) of the receptors for human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-3 and IL-5 by virtue of their ability to confer factor independence on the haemopoietic cell line, FDC-P1. One mutation (V449E) is located within the transmembrane domain and, by analogy with a similar mutation in the neu oncogene, may act by inducing dimerization of h beta c. The other mutation (I374N) lies in the extracellular, membrane-proximal portion of h beta c. Neither of these mutants, nor a previously described mutant of h beta c (FI delta, which has a small duplication in the extracellular region), was capable of inducing factor independence in CTLL-2 cells, while only V449E could induce factor independence in BAF-B03 cells. These results imply that the extracellular and transmembrane mutations act by different mechanisms. Furthermore, they imply that the mutants, and hence also wild-type h beta c, interact with cell type-specific signalling molecules. Models are presented which illustrate how these mutations may act and predict some of the characteristics of the putative receptor-associated signalling molecules.

Overexpression of the Saccharomyces cerevisiae MET17/MET25 gene in Escherichia coli and comparative characterization of the product with O-acetylserine.O-acetylhomoserine sulfhydrylase of the yeast

The Saccharomyces cerevisiae MET17/MET25 gene encoding O-acetyl-L-serine (OAS).O-acetyl-L-homoserine (OAH) sulfhydrylase (EC 4.2.99.10) was overexpressed in Escherichia coli and the gene product was purified to homogeneity, using three steps, with a recovery of 28% from the total cell extract. The gene product has been compared with OAS.OAH sulfhydrylase purified from the yeast cells. These two protein preparations were indistinguishable with respect to their behavior in polyacrylamide gel electrophoresis, both with and without sodium dodecyl sulfate, their specificity for substrate amino acids, Michaelis constant (Km) value for OAH, sensitivity to carbonyl reagents, absorption spectrum, isoelectric point, behavior in HPLC (both ion-exchange chromatography and gel filtration), sensitivity to heat treatment, susceptibility to trypsin digestion, and their N-terminal amino acid sequence. The results obtained imply that the gene product is properly processed in E. coli, and the technique developed in this study to overexpress the gene in bacterial cells provides us with a large amount of the purified preparation of the enzyme. In contrast to a previous report we found that cystathionine gamma-lyase of S.

Molecular characterisation of the Polycomblike gene of Drosophila melanogaster, a trans-acting negative regulator of homeotic gene expression

The Polycomblike gene of Drosophila melanogaster, a member of the Polycomb Group of genes, is required for the correct spatial expression of the homeotic genes of the Antennapaedia and Bithorax Complexes. Mutations in Polycomb Group genes result in ectopic homeotic gene expression, indicating that Polycomb Group proteins maintain the transcriptional repression of specific homeotic genes in specific tissues during development. We report here the isolation and molecular characterisation of the Polycomblike gene. The Polycomblike transcript encodes an 857 amino acid protein with no significant homology to other proteins. Antibodies raised against the product of this open reading frame were used to show that the Polycomblike protein is found in all nuclei during embryonic development. Antibody staining also revealed that the Polycomblike protein is found on larval salivary gland polytene chromosomes at about 100 specific loci, the same loci to which the Polycomb and polyhomeotic proteins, two other Polycomb Group proteins, are found. These data add further support for a model in which Polycomb Group proteins form multimeric protein complexes at specific chromosomal loci to repress transcription at those loci.

Identification of homeobox genes expressed in human haemopoietic progenitor cells

Homeodomain (HD)-containing proteins have been shown to regulate cellular commitment and differentiation in fungal, invertebrate and vertebrate systems. Bone marrow cells synthesizing the CD34 antigen are a complex mix of early, stem and progenitor cells at various stages of commitment to the many haemopoietic lineages. Here, we report the cloning and sequencing of 31 homeobox (HB) sequences, identified using degenerate oligodeoxyribonucleotide primers, in a polymerase chain reaction with cDNA derived from a purified CD34+ population of human haemopoietic cells. Of these sequences, 16 correspond to previously identified genes, and 13 are located within the HOX A, B and C clusters. Ten of the clones most likely represent human homologues of genes identified previously in other species. Five of the clones reported here represent novel HD sequences. The identification of five new genes using a subclass-specific 5' primer, designed from the engrailed and Xanf1 sequences, suggests that there still remain several uncharacterized HB genes in the human genome. Haemopoietic cells purified on the basis of CD34 antigen synthesis are a rich source of regulatory genes consistent with their ability to differentiate into diverse haemopoietic cell types.

A mutation of the common receptor subunit for interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor, and IL-5 that leads to ligand independence and tumorigenicity

The cytokines interleukin-3, interleukin-5, and granulocyte-macrophage colony-stimulating factor bind with high affinity to a receptor complex that contains a ligand-specific alpha-chain and a common beta-chain, h beta c. We report here the isolation of a mutant form of h beta c, from growth factor-independent cells, that arose spontaneously after infection of a murine factor-dependent hematopoietic cell line (FDC-P1) with a retroviral h beta c expression construct. Analysis of this h beta c mutation shows that a small (37 amino acid) duplication of extracellular sequence that includes two conserved sequence motifs is sufficient to confer ligand-independent growth on these cells and lead to tumourigenicity. Because this is a conserved region in the cytokine receptor superfamily, our results suggest that the large family of cytokine receptors has the capacity to become oncogenically active.

Two contiguous residues in human interleukin-3, Asp21 and Glu22, selectively interact with the alpha- and beta-chains of its receptor and participate in function

We have previously reported that the predicted first helix of human interleukin (IL)-3 contains a hydrophilic region encompassing residues Asp21, Glu22, and Thr25 that is crucial for biological activity and IL-3 receptor binding. Using single amino acid substitution mutagenesis, we have now determined that Asp21 and Glu22, but not Thr25, were crucial for full IL-3 activity. Mutant D21R was 30-fold less potent than wild type IL-3 in the stimulation of biological activity. It also exhibited a similar reduction in its ability to bind to the cloned high affinity IL-3 receptor complex (alpha- and beta-chains) or to the receptor alpha-chain alone, indicating that residue 21 is involved in contacts with the alpha-chain. Mutant E22R was approximately 20,000-fold less potent than wild type IL-3 in the stimulation of biological activity and in binding to the IL-3 receptor high affinity complex. However, the binding of E22R to the IL-3 receptor alpha-chain alone was similar to that of wild type IL-3, suggesting that this mutant was defective in interactions with the receptor beta-chain. These results show that two contiguous residues in the N-terminal region of IL-3 mediate binding to the two different chains of the IL-3 receptor and emphasize the functional significance of the conserved Glu in the first helix of the IL-3, granulocyte-macrophage colony-stimulating factor, and IL-5 cytokine subfamily.

Molecular genetics of met 17 and met 25 mutants of Saccharomyces cerevisiae: intragenic complementation between mutations of a single structural gene

We cloned the MET 17 gene of Saccharomyces cerevisiae by functional complementation after transformation of a yeast met 17 mutant. Restriction mapping and nucleotide sequencing of the MET 17 clones revealed that these were from the same genomic region as clones isolated previously and shown to contain the MET 25 gene encoding the enzyme O-acetylhomoserine, O-acetylserine sulphydrylase (OAH-OAS sulphydrylase). Transformation studies with MET 25 clones showed that the MET 17 and MET 25 functions were both endoced in a single transcription unit. We conclude that met 17 and met 25 are both mutations in the structural gene for the OAH-OAS sulphydrylase subunit and that each affects a different functional domain of the enzyme allowing subunit complementation in the met 17 X met 25 diploid. Enzyme assays indicated that the diploid, although not requiring methionine, had a low OAH-OAS sulphydrylase activity (10% of wild type). This is consistent with MET 17 and MET 25 being the same gene. We found that both met 17 and met 25 mutants were devoid of 3' phospho-adenosine 5' phospho-sulphite (PAPS) reductase activity and that this activity was fully restored in the met 17 X met 25 diploid. The possible interactions between OAH-OAS sulphydrylase and PAPS reductase are discussed.

The chicken H5 gene is unlinked to core and H1 histone genes

An H5 cDNA clone was used to select H5 genomal recombinants from a chicken Charon 4A library. DNA sequence analysis shows that the H5 gene contains no introns. Putative 5' promoter elements and a 3' polyadenylation site are present within the 1.8 kb of DNA examined. Analysis of 41 kb of DNA surrounding the H5 gene shows that it is not closely linked to either H1 or core histone genes.Images

Vertebrate histone genes: nucleotide sequence of a chicken H2A gene and regulatory flanking sequences

The DNA sequence of a chicken genomal fragment containing a histone H2A gene has been determined. It contains extensive 5' and 3' flanking regions and encodes a protein identical in sequence to the histone H2A protein isolated from chicken erythrocytes. In the 5' flanking region, a possible "TATA box" and three possible "cap sites" can be recognised upstream from the initiation codon. To the 5' side of the "TATA box" is found an unusual sequence of 21 A's interrupted by a central G residue. It occupies the same relative position as the P. miliaris H2A gene-specific 5' dyad symmetry sequence and the "CCAAT box" seen in other eukaryotic polymerase II genes but is clearly different from both. A significant feature of the 3' non-coding region is the presence of a 23 base-pair sequence that is nearly identical to a conserved region found in sea urchin histone genes. The coding region is extremely GC rich, with strong selection for these bases in the third position of codons. Not a single coding triplet ends in U. No intervening sequences were found in this gene.