Single-Use and Reusable Flexible Bronchoscopes in Pulmonary and Critical Care Medicine

Flexible bronchoscopy plays a critical role in both diagnostic and therapeutic management of a variety of pulmonary disorders in the bronchoscopy suite and the intensive care unit. In the set-ting of the ongoing viral pandemic, single-use flexible bronchoscopes (SUFB) have garnered attention as various professional pulmonary societies have released guidelines regarding uses for SUFB given the concern for risk of viral transmission when using reusable flexible bronchoscopes (RFB). In addition to offering sterility, SUFBs are portable, easily accessible, and may be more cost-effective than RFB when considering the potential costs of treating bronchoscopy-related infections. Furthermore, since SUFBs are one time use, they do not require reprocessing after use, and therefore may translate to reduced cleaning and storage costs. Despite these advantages, RFBs are still routinely used to perform advanced diagnostic and therapeutic bronchoscopic procedures given the need for optimal maneuverability, handling, angle of deflection, image quality, and larger channel size for passing of ancillary instruments. Here, we review the published evidence on the applications of single-use and reusable bronchoscopes in bronchoscopy suites and intensive care units. Specifically, we will discuss the advantages and disadvantages of these devices as pertinent to fundamental, advanced, and therapeutic bronchoscopic interventions.

Evaluation of Safety and Short-term Outcomes of Therapeutic Rigid Bronchoscopy Using Total Intravenous Anesthesia and Spontaneous Assisted Ventilation

BACKGROUND

There is a paucity of published data regarding the optimal type of anesthesia and ventilation strategies during rigid bronchoscopy.

OBJECTIVE

The aim of our study is to report the procedural and anesthesia-related complications with rigid bronchoscopy using total intravenous anesthesia and spontaneous assisted ventilation.

METHODS

A retrospective review of patients undergoing therapeutic rigid bronchoscopy at the University of Chicago between October 2012 and December 2014 was performed. Data were recorded relating to patients' demographics, comorbidities, type of anesthesia, need for neuromuscular blockade (NMB), intraoperative hypoxemia, hypotension, perioperative adverse events, and mortality.

RESULTS

Fifty-five patients underwent 79 rigid bronchoscopy procedures; 90% were performed for malignant disease and 90% of patients had an American Society of Anesthesiologists (ASA) class III or IV. The majority (76%) did not require use of NMB. The most common adverse events were intraoperative hypoxemia (67%) and hypotension (77%). Major bleeding and postoperative respiratory failure occurred in 3.8 and 5.1% of procedures, respectively. There was no intraoperative mortality or cardiac dysrhythmias. The 30-day mortality was 7.6% and was associated with older age, inpatient status, congestive heart failure, home oxygen use, and procedural duration. Intraoperative hypoxemia, hypotension, and ASA class were not associated with 30-day mortality. The majority (94%) of patients were discharged home. The use of NMB did not impact outcomes.

CONCLUSIONS

This study suggests that therapeutic rigid bronchoscopy can be safely performed with total intravenous anesthesia and spontaneous assisted ventilation in patients with central airway obstruction, significant comorbidities, and a high ASA class. The only significant modifiable variable predicting the 30-day mortality was the duration of the procedure.

Genomic Heterogeneity as a Barrier to Precision Medicine in Gastroesophageal Adenocarcinoma

Gastroesophageal adenocarcinoma (GEA) is a lethal disease where targeted therapies, even when guided by genomic biomarkers, have had limited efficacy. A potential reason for the failure of such therapies is that genomic profiling results could commonly differ between the primary and metastatic tumors. To evaluate genomic heterogeneity, we sequenced paired primary GEA and synchronous metastatic lesions across multiple cohorts, finding extensive differences in genomic alterations, including discrepancies in potentially clinically relevant alterations. Multiregion sequencing showed significant discrepancy within the primary tumor (PT) and between the PT and disseminated disease, with oncogene amplification profiles commonly discordant. In addition, a pilot analysis of cell-free DNA (cfDNA) sequencing demonstrated the feasibility of detecting genomic amplifications not detected in PT sampling. Lastly, we profiled paired primary tumors, metastatic tumors, and cfDNA from patients enrolled in the personalized antibodies for GEA (PANGEA) trial of targeted therapies in GEA and found that genomic biomarkers were recurrently discrepant between the PT and untreated metastases. Divergent primary and metastatic tissue profiling led to treatment reassignment in 32% (9/28) of patients. In discordant primary and metastatic lesions, we found 87.5% concordance for targetable alterations in metastatic tissue and cfDNA, suggesting the potential for cfDNA profiling to enhance selection of therapy.Significance: We demonstrate frequent baseline heterogeneity in targetable genomic alterations in GEA, indicating that current tissue sampling practices for biomarker testing do not effectively guide precision medicine in this disease and that routine profiling of metastatic lesions and/or cfDNA should be systematically evaluated. Cancer Discov; 8(1); 37-48. ©2017 AACR.See related commentary by Sundar and Tan, p. 14See related article by Janjigian et al., p. 49This article is highlighted in the In This Issue feature, p. 1.

Genome-Wide Methylation Study Identifies an IL-13-induced Epigenetic Signature in Asthmatic Airways

RATIONALE

Epigenetic changes to airway cells have been proposed as important modulators of the effects of environmental exposures on airway diseases, yet no study to date has shown epigenetic responses to exposures in the airway that correlate with disease state. The type 2 cytokine IL-13 is a key mediator of allergic airway diseases, such as asthma, and is up-regulated in response to many asthma-promoting exposures.

OBJECTIVES

To directly study the epigenetic response of airway epithelial cells (AECs) to IL-13 and test whether IL-13-induced epigenetic changes differ between individuals with and without asthma.

METHODS

Genome-wide DNA methylation and gene expression patterns were studied in 58 IL-13-treated and untreated primary AEC cultures and validated in freshly isolated cells of subjects with and without asthma using the Illumina Human Methylation 450K and HumanHT-12 BeadChips. IL-13-mediated comethylation modules were identified and correlated with clinical phenotypes using weighted gene coexpression network analysis.

MEASUREMENTS AND MAIN RESULTS

IL-13 altered global DNA methylation patterns in cultured AECs and were significantly enriched near genes associated with asthma. Importantly, a significant proportion of this IL-13 epigenetic signature was validated in freshly isolated AECs from subjects with asthma and clustered into two distinct modules, with module 1 correlated with asthma severity and lung function and module 2 with eosinophilia.

CONCLUSIONS

These results suggest that a single exposure of IL-13 may selectively induce long-lasting DNA methylation changes in asthmatic airways that alter specific AEC pathways and contribute to asthma phenotypes.

Trunk and hip electromyographic activity during single leg squat exercises do sex differences exist?

PURPOSE/BACKGROUND

Researchers have identified sex-differences in lower extremity muscle activation during functional activities that involve landing and cutting maneuvers. However, less research has been conducted to determine if muscle activation differences occur during rehabilitation exercises. The purpose of this investigation was to determine if sex-differences exist for activation amplitudes of the trunk and hip muscles during four single leg squat (SLS) exercises.

METHODS

Eighteen males and 16 females participated. Surface electromyography (EMG) was used to determine muscle activity of the abdominal obliques (AO), lumbar extensors (LE), gluteus maximus (GMX), and gluteus medius (GM) during four SLS exercises. Data were expressed as a percentage of a maximum voluntary isometric contraction (% MVIC). A 2 X 4 mixed-model analysis of variance with repeated measures was used to determine the interaction between sex and exercise on each muscle's activity.

RESULTS

No interaction effect existed between sex and exercise. A main effect for sex existed for the GM and LE. On average, females generated 39% greater GM (27.6 ± 10.4 % MVIC versus 19.8 ± 10.5 % MVIC) and 40% greater LE (8.0 ± 2.8 % MVIC versus 5.7 ± 2.8 % MVIC) activity than males. All subjects, regardless of sex, demonstrated similar GMX and AO activity. Overall EMG values ranged from 11.0 % MVIC to 14.7 % MVIC for the GMX and 5.7 % MVIC to 8.8 % MVIC for the AO.

CONCLUSIONS

None of the subjects generated sufficient EMG activity for strength gains. Females generated a moderate level of GM activity appropriate for neuromuscular re-education/endurance. Males generated a low level of GM activity that may not necessarily be sufficient to improve GM function. Subjects exhibited low levels of EMG activity for the other muscles. These findings suggest that clinicians modify and/or prescribe different exercises than those studied herein for the purpose of improving GM, GMX, AO, and LE function.

LEVEL OF EVIDENCE

3b.

Endoscopic treatment of native lung hyperinflation using endobronchial valves in single-lung transplant patients: a multinational experience

BACKGROUND

Hyperinflation of the native lung (NLH) is a known complication to single-lung transplantation for emphysema. The hyperinflation can lead to compression of the graft and cause respiratory failure. Endobronchial valves have been used to block airflow in specific parts of the native lung, reducing the native lung volume and relieving the graft.

OBJECTIVE

We report short-term follow-up and safety from 14 single-lung transplant patients with NLH treated with bronchoscopic lung volume reduction using endobronchial valves.

METHODS

Retrospective clinical information related to endobronchial valve treatment was obtained from four centres. All patients were treated with IBV(TM) Valve System (Spiration, Olympus Respiratory America, Redmond, WA, USA). All patients had evidence of severe NLH with mediastinal displacement.

RESULTS

A total of 74 IBV valves were placed in 14 patients, with an average of 5.3 (range 2-10). Five patients had two procedures with staged treatment. Eleven patients reported symptom relief, and nine had lung function improvements. There was a significant increase in forced expiratory volume in 1 s of 9% (P = 0.013) and forced vital capacity of 15% (P = 0.034) within the first months after treatment. There were no reported device-related adverse events nor reports of migration. Two patients had pneumothorax. One patient had pneumonia in the location of the valve placement, and another had infection within days. Three other patients were hospitalised with infection 2 months after treatment.

CONCLUSIONS

Treating NLH with IBV endobronchial valves leads to clinical improvement in the majority of patients, and the treatment has an acceptable safety.

Bronchial thermoplasty: Long-term safety and effectiveness in patients with severe persistent asthma

BACKGROUND

Bronchial thermoplasty (BT) has previously been shown to improve asthma control out to 2 years in patients with severe persistent asthma.

OBJECTIVE

We sought to assess the effectiveness and safety of BT in asthmatic patients 5 years after therapy.

METHODS

BT-treated subjects from the Asthma Intervention Research 2 trial (ClinicalTrials.govNCT01350414) were evaluated annually for 5 years to assess the long-term safety of BT and the durability of its treatment effect. Outcomes assessed after BT included severe exacerbations, adverse events, health care use, spirometric data, and high-resolution computed tomographic scans.

RESULTS

One hundred sixty-two (85.3%) of 190 BT-treated subjects from the Asthma Intervention Research 2 trial completed 5 years of follow-up. The proportion of subjects experiencing severe exacerbations and emergency department (ED) visits and the rates of events in each of years 1 to 5 remained low and were less than those observed in the 12 months before BT treatment (average 5-year reduction in proportions: 44% for exacerbations and 78% for ED visits). Respiratory adverse events and respiratory-related hospitalizations remained unchanged in years 2 through 5 compared with the first year after BT. Prebronchodilator FEV₁ values remained stable between years 1 and 5 after BT, despite a 18% reduction in average daily inhaled corticosteroid dose. High-resolution computed tomographic scans from baseline to 5 years after BT showed no structural abnormalities that could be attributed to BT.

CONCLUSIONS

These data demonstrate the 5-year durability of the benefits of BT with regard to both asthma control (based on maintained reduction in severe exacerbations and ED visits for respiratory symptoms) and safety. BT has become an important addition to our treatment armamentarium and should be considered for patients with severe persistent asthma who remain symptomatic despite taking inhaled corticosteroids and long-acting β₂-agonists.

Magnetic resonance imaging criteria to predict complete excision of parasellar pituitary macroadenoma on postoperative imaging

Purpose To evaluate preoperative magnetic resonance imaging (MRI) criteria for their ability to predict the complete removal of parasellar pituitary macroadenoma on the 3-month postoperative MRI. Methods Dedicated pre- and postoperative pituitary MRI studies were reviewed in 49 patients who had undergone transsphenoidal surgery for macroadenomas with potential unilateral parasellar involvement. Twelve preoperative MRI findings and postoperative MRI outcomes were statistically compared. Results Depiction of the inferolateral (positive predictive value [PPV]: 0.6; negative predictive value [NPV], 0.92) and lateral (PPV: 0.65; NPV: 0.85) compartments of the cavernous sinus and the percentage of intracavernous carotid artery encasement (PPV: 0.63; NPV, 1.0 for <50% encasement) were the only criteria significantly predictive of parasellar tumor complete resection. The odds ratios indicated that depiction of the lateral venous or inferolateral venous compartments increased the likelihood of a complete resection by 6 times, whereas for every 25% reduction in intracavernous carotid artery encasement, the chance of a complete resection increased 3.4 times. Conclusion The preoperative MR imaging features that are useful in predicting the complete removal of the parasellar component of a pituitary adenoma as assessed by postoperative MRI are (1) depiction of the lateral and inferolateral compartment of the cavernous sinus and (2) decreasing encasement of the intracavernous carotid artery.

The clinical and immunologic features of pulmonary fibrosis in sarcoidosis

Sarcoidosis is a multisystem, granulomatous disease that most often affects the lungs. The clinical course is highly variable; many patients undergo spontaneous remission, but up to a third of patients progresses to a chronic disease course. The development of pulmonary fibrosis (PF) in a subset of patients with chronic disease has a negative impact on morbidity and mortality. While sarcoidosis-associated PF can be progressive, it is often referred to as "burnt out" disease, a designation reflecting inactive granulomatous inflammation. The immune mechanisms of sarcoidosis-associated PF are not well understood. It is not clear if fibrotic processes are active from the onset of sarcoidosis in predisposed individuals, or whether a profibrotic state develops as a response to ongoing inflammation. Transforming growth factor β (TGF-β) is an important profibrotic cytokine, and in sarcoidosis, distinct genotypes of TGF-β have been identified in those with PF. The overall cytokine profile in sarcoidosis-associated PF has not been well characterized, although a transition from a T helper 1 to a T helper 2 signature has been proposed. Macrophages have important regulatory interactions with fibroblasts, and the role of alveolar macrophages in sarcoidosis-associated PF is a compelling target for further study. Elucidating the natural history of sarcoidosis-associated PF will inform our understanding of the fundamental derangements, and will enhance prognostication and the development of therapeutic strategies.

Interstitial lung disease and gastroesophageal reflux disease: key role of esophageal function tests in the diagnosis and treatment

CONTEXT

Gastroesophageal reflux disease (GERD) is common in patients with respiratory disorders and interstitial lung fibrosis from diverse disease processes. However, a cause-effect relationship has not been well demonstrated. It is hypothesized that there might be more than a coincidental association between GERD and interstitial lung damage. There is still confusion about the diagnostic steps necessary to confirm the presence of GERD, and about the role of effective control of GERD in the natural history of these respiratory disorders.

OBJECTIVES

To determine the prevalence of GERD in patients with respiratory disorders and lung involvement; the sensitivity of symptoms in the diagnosis of GERD; and the role of esophageal function tests (manometry and 24- hour pH monitoring) in the diagnosis and treatment of these patients.

METHODS

Prospective study based on a database of 44 patients (29 females) with respiratory disorders: 16 patients had idiopathic pulmonary fibrosis, 11 patients had systemic sclerosis associated interstitial lung disease, 2 patients had polymyositis associated interstitial lung disease, 2 patients had Sjögren associated interstitial lung disease, 2 patients had rheumatoid artrithis associated interstitial lung disease, 1 patient had undifferentiated connective tissue diseases associated interstitial lung disease and 10 patients had sarcoidosis. The average forced vital capacity (% predicted) was 64.3%. All patients had esophageal function tests.

RESULTS

Thirty patients (68%) had pathologic reflux (average DeMeester score: 45, normal <14.7). The average number of reflux episodes recorded 20 cm above the lower esophageal sphincter was 24. Sensitivity and specificity of heartburn were 70% and 57%, of regurgitation 43% and 57%, and of dysphagia 33% and 64%. Twelve patients with GERD underwent a laparoscopic fundoplication which was tailored to the manometric profile: three patients in which peristalsis was normal had a total fundoplication (360°) and nine patients in which the peristalsis was absent had a partial anterior fundoplication (180°).

CONCLUSIONS

The results of our study show that: (a) abnormal reflux was present in about 2/3 of patients with respiratory disorders (idiophatic pulmonary fibrosis, connective tissue disorders and sarcoidosis), and it extended to the upper esophagus in most patients; (b) the sensitivity and specificity of reflux symptoms was very low; and (c) esophageal function tests were essential to establish the diagnosis of abnormal reflux, to characterize the esophageal function and guide therapy. Long term follow-up will be necessary to determine if control of reflux alters the natural history of these respiratory disorders.

Rheumatologic manifestations of sarcoidosis

Sarcoidosis is a systemic, clinically heterogeneous disease characterized by the development of granulomas. Any organ system can be involved, and patients may present with any number of rheumatologic symptoms. There are no U.S. Food and Drug Administration-approved therapies for the treatment of sarcoidosis. Diagnosing sarcoidosis becomes challenging, particularly when its complications cause patients' symptoms to mimic other conditions, including polymyositis, Sjögren syndrome, or vasculitis. This review presents an overview of the etiology of and biomarkers associated with sarcoidosis. We then provide a detailed description of the rheumatologic manifestations of sarcoidosis and present a treatment algorithm based on current clinical evidence for patients with sarcoid arthritis. The discussion will focus on characteristic findings in patients with sarcoid arthritis, osseous involvement in sarcoidosis, and sarcoid myopathy. Arthritic conditions that sometimes coexist with sarcoidosis are described as well. We present two cases of sarcoidosis with rheumatologic manifestations. Our intent is to encourage a multidisciplinary, translational approach to meet the challenges and difficulties in understanding and treating sarcoidosis.

Abstract A22: Spirometric surveillance for premalignant and malignant bronchial lesions

Background: Chronic obstructive pulmonary disease (COPD) and lung cancer (LC) are diseases that share common risk factors. It has been reported that more than half of the patients diagnosed with LC also suffer from COPD. Although COPD is a well known risk factor for LC, the relationship between impaired lung function (LF) and the incidence and progression of pre-malignant lesions (PMLs) in the central airways is still unclear.

Methods: The study included 217 high-risk patients from a hospital-based lung cancer surveillance cohort who underwent bronchoscopy with endobronchial biopsy of suspicious lesions, at the Roswell Park Cancer Institute, Buffalo, New York. All patients had lung function measurement within 6 months preceding their baseline biopsy. Baseline histopathology diagnoses included 91squamous metaplasia (SM), 25 squamous dysplasia (SD), 1 in-situ carcinoma and 5 invasive bronchial carcinoma. Follow-up bronchoscopy and biopsy were performed on 69 patients. Sixteen patients had a progression of the baseline lesion to a higher grade. The relationship between the baseline LF measures and the incidence and progression of PMLs were examined using regression models.

Results: Patients with forced expiratory volume in 1 second percent predicted (FEV1%) of &lt;50% had 4.5 times greater risk of being diagnosed with PML/cancer, when compared to patients with FEV1% ≥80. Increased risk was noted for all grades of PMLs and cancers, with the risk being almost 8 times for squamous dysplasia [Odds ratio = 7.95; 95%confidence interval (CI) =1.77–35.6]. Similarly, FEV-1/FVC ratio of &lt;50% was associated with 3 times greater risk of detecting a PML/cancer. When COPD was classified based on GOLD criteria, the patients with severe COPD had 2.7 times and 4.8 times greater risk of being detected with SM and SD, respectively. The risk persisted for SD even when an age standardized classification was used to define COPD. COPD patients also had a non-statistically significant 2.5 times greater risk of their baseline lesion progressing to a higher grade [Hazard Ratio 2.48 (95% CI 0.65 – 9.41), p-value - 0.18)]. The mean time to progression from a lower grade lesion to a higher grade was 27 months for patients with COPD and 50 months for patients without COPD.

Conclusion: Impaired LF can be a good predictor of occurrence and progression of PMLs in central airways of high risk patients. Spirometric measurement of lung function can be used as an additional tool for identifying target populations in need of more aggressive LC surveillance.

Citation Information: Cancer Prev Res 2010;3(1 Suppl):A22.

Abstract A21: Lung cancer surveillance with CT scan and autofluorescence bronchoscopy

Background: More than 75% of lung cancer patients are diagnosed at an advanced stage, when the survival rate is less than 15%. Sputum cytology, x-ray and CT scan have been evaluated as screening tools for early lung cancers, without much success. Auto-fluorescence bronchoscopy (AFB) has been recently shown to be effective in diagnosing central bronchial cancers. Combined surveillance with both spiral CT scan and AFB might help to increase the detection rate of the both central and peripheral lung cancers.

Methods: The study included 205 patients who were enrolled in the High Risk Lung Cancer Surveillance Cohort at Roswell Park Cancer Institute (RPCI) with at least 2 of the following risk factors: (1) radiographically documented pulmonary asbestosis or; (2) a history of previously treated aero-digestive cancer or; (3) &gt; 20 pack years smoking history or; (4) COPD with an FEV1 &lt; 70% of predicted. Patients underwent spirometry testing, chest X-ray, sputum cytology, non-enhanced low dose spiral CT scan of the chest, and conventional white light/AF bronchoscopy with biopsy.

Results: A total of 20 invasive cancers/CIS were diagnosed in the 205 patients. Seven were diagnosed at baseline, 4 within 1 year of enrollment and 9 on follow up of more than 1 year. Between them, AFB and CT scan diagnosed all baseline cancers. Only 3/7 cancers were detected on x-ray screening and only 1/7 patients demonstrated atypia on sputum cytology. Overall, 17 invasive cancers and 3 CIS were diagnosed during the surveillance study. All the 3 CIS were identified only on AFB. Of the 17 invasive cancers, CT scan detected 15 cancers (88%) and AFB detected 5 of these cancers (30%). CT scan showed a 67% relative increase in sensitivity for detecting prevalent cancers and 3 times greater sensitivity for incident and prevalent cancers compared to x-ray screening. CT scan and AFB detected 19 of the 20 CIS/cancers (95%), whereas x-ray and sputum cytology together detected only 5/20 CIS/cancers (25%). The sensitivity of CT scan and AFB in diagnosing pre-malignant lesions and cancers improved by almost two and half times relative to x-ray and sputum.

Conclusion: The addition of AFB exam to yearly spiral CT scan of the chest could be a more efficient surveillance tool to identify early stage lung cancers, both in the central and peripheral lung. A greater efficiency and cost effectiveness can be achieved by limiting the use of the combination of AFB and CT scan in very high risk patients, selected based on their exposures and risk factors.

Citation Information: Cancer Prev Res 2010;3(1 Suppl):A21.

Gβγ-mediated Prostacyclin Production and cAMP-dependent Protein Kinase Activation by Endothelin-1 Promotes Vascular Smooth Muscle Cell Hypertrophy through Inhibition of Glycogen Synthase Kinase-3

Endothelin-1 (ET1) is a vasoactive peptide that stimulates hypertrophy of vascular smooth muscle cells (VSMC) through diverse signaling pathways mediated by G(q)/G(i)/G(13) heterotrimeric G proteins. We have found that ET1 stimulates the activity of cAMP-dependent protein kinase (PKA) in VSMC as profoundly as the G(s)-linked beta-adrenergic agonist, isoproterenol (ISO), but in a transient manner. PKA activation by ET1 was mediated by type-A ET1 receptors (ETA) and recruited an autocrine signaling mechanism distinct from that of ISO, involving G(i)-coupled betagamma subunits of heterotrimeric G proteins, extracellular signal-regulated kinases ERK1/2, cyclooxygenase COX-1 (but not COX-2) and prostacyclin receptors. In the functional studies, inhibition of PKA or COX-1 attenuated ET1-induced VSMC hypertrophy, suggesting the positive role of PKA in this response to ET1. Furthermore, we found that ET1 stimulates a Gbetagamma-mediated, PKA-dependent phosphorylation and inactivation of glycogen synthase kinase-3 (GSK3), an enzyme that regulates cell growth. Together, this study describes that (i) PKA can be transiently activated by G(i)-coupled agonists such as ET1 by an autocrine mechanism involving Gbetagamma/calcium/ERK/COX-1/prostacyclin signaling, and (ii) this PKA activation promotes VSMC hypertrophy, at least in part, through PKA-dependent phosphorylation and inhibition of GSK3.

Functional significance of protein kinase A activation by endothelin-1 and ATP: negative regulation of SRF-dependent gene expression by PKA

Endothelin-1 (ET1) and ATP stimulate contraction and hypertrophy of vascular smooth muscle cells (VSMC) by activating diverse signalling pathways. In this study, we show that in VSMC, ET1 and ATP stimulate transient and sustained activation of protein kinase A (PKA), respectively. Using a dominant negative PKA mutant (PKA-DN), we examined the functional significance of PKA activation in the signalling of ET1 and ATP. Overexpression of PKA-DN did not alter the ET1- or ATP-induced phosphorylation of the extracellular signal-regulated protein kinase, Erk2. ATP stimulated a profound, PKA-dependent activation of cAMP-response element (CRE), whereas the effect of ET1 was negligible. Both ET1 and ATP stimulated serum response factor (SRF)-dependent gene expression. Overexpression of PKA-DN potentiated the effects of ET1 and ATP on SRF activity, whereas stimulation of PKA by isoproterenol, forskolin or by overexpression of the PKA catalytic subunit decreased SRF activity. These data demonstrate that (i) PKA negatively regulates SRF activity and (ii) ET1 and ATP stimulate opposing pathways, whose balance determines the net activity of SRF.

Protein synthesis and germ plasm in cleavage embryos of Xenopus laevis

(3H) leucine was injected into unfertilized eggs, fertilized eggs, and Stage 2-12 embryos of X. laevis. Incorporation of the leucine into protein by blastomeres containing germ plasm was studied autoradiographically. Eggs, both fertilized and unfertilized, actively synthesized protein, ad did embryos from Stage 2 onwards. Probably all blastomerers containing germ plasm were labelled. In embryos from Stages 4-12, the germ plasm itself was also labelled, and this result suggests that the germ plasm is metabolically active during cleavage.