[Prevalence, knowledge and control of arterial hypertension in vulnerable neighborhoods of Argentina: A Cross-sectional Study]. / Estudio de prevalencia, conocimiento y control de la hipertensión arterial en barrios vulnerables de Argentina.

INTRODUCTION: Hypertension (HTN) represents the primary individual risk factor, contributing significantly to the global burden of cardiovascular diseases (CVD). In our country, epidemiological research has highlighted substantial variations in the prevalence of these risk factors across different populations. However, there is a lack of epidemiological studies assessing exclusive cardiovascular risk factors within vulnerable neighborhoods characterized by extremely limited economic resources, sociocultural challenges, and inadequate healthcare access. METHODS: A multicenter cross-sectional observational study was conducted among individuals residing in economically deprived and marginalized communities, including informal settlements and underprivileged neighborhoods. Simple random sampling of households was employed. Blood pressure measurements, anthropometric assessments, and epidemiological, economic, and sociocultural questionnaires were administered. Results encompass prevalence rates, awareness levels, and blood pressure control across diverse regions. Logistic regression was utilized to identify independent variables influencing primary outcomes. RESULTS: A total of 989 participants were analyzed. The overall prevalence of hypertension was 48.2%. About 82% had a body mass index (BMI) >25. Approximately 45.3% had less than 6 years of formal education. Independent association was established between education levels below 6 years and higher hypertension prevalence. Among hypertensive individuals, 44% were unaware of their condition, with only 17.2% achieving control, correlated with having health insurance and a higher educational background. Merely 24% were receiving combined therapy. CONCLUSION: The prevalence of hypertension within vulnerable neighborhoods is alarmingly high, surpassing rates in other social strata. Knowledge, treatment, and control levels of hypertension are suboptimal, comparable to other populations. Inadequate use of combination therapy was observed. This study underscores the urgent need for targeted interventions addressing cardiovascular risk factors in poor areas to mitigate the burden of CVD.

Detection of companion galaxies around hot dust-obscured hyper-luminous galaxy W0410-0913.

The phase transition between galaxies and quasars is often identified with the rare population of hyper-luminous, hot dust-obscured galaxies. Galaxy formation models predict these systems to grow via mergers, that can deliver large amounts of gas toward their centers, induce intense bursts of star formation and feed their supermassive black holes. Here we report the detection of 24 galaxies emitting Lyman-α emission on projected physical scales of about 400 kpc around the hyper-luminous hot dust-obscured galaxy W0410-0913, at redshift z = 3.631, using Very Large Telescope observations. While this indicates that W0410-0913 evolves in a very dense environment, we do not find clear signs of mergers that could sustain its growth. Data suggest that if mergers occurred, as models expect, these would involve less massive satellites, with only a moderate impact on the internal interstellar medium of W0410-0913, which is sustained by a rotationally-supported fast-rotating molecular disk, as Atacama Large Millimeter Array observations suggest.

Normal, dust-obscured galaxies in the epoch of reionization.

Over the past decades, rest-frame ultraviolet (UV) observations have provided large samples of UV luminous galaxies at redshift (z) greater than 6 (refs. 1-3), during the so-called epoch of reionization. While a few of these UV-identified galaxies revealed substantial dust reservoirs4-7, very heavily dust-obscured sources at these early times have remained elusive. They are limited to a rare population of extreme starburst galaxies8-12 and companions of rare quasars13,14. These studies conclude that the contribution of dust-obscured galaxies to the cosmic star formation rate density at z > 6 is sub-dominant. Recent ALMA and Spitzer observations have identified a more abundant, less extreme population of obscured galaxies at z = 3-6 (refs. 15,16). However, this population has not been confirmed in the reionization epoch so far. Here, we report the discovery of two dust-obscured star-forming galaxies at z = 6.6813 ± 0.0005 and z = 7.3521 ± 0.0005. These objects are not detected in existing rest-frame UV data and were discovered only through their far-infrared [C II] lines and dust continuum emission as companions to typical UV-luminous galaxies at the same redshift. The two galaxies exhibit lower infrared luminosities and star-formation rates than extreme starbursts, in line with typical star-forming galaxies at z ≈ 7. This population of heavily dust-obscured galaxies appears to contribute 10-25% to the z > 6 cosmic star formation rate density.

Treatment of peripheral arterial disease in diabetes: a consensus of the Italian Societies of Diabetes (SID, AMD), Radiology (SIRM) and Vascular Endovascular Surgery (SICVE).

Diabetic foot (DF) is a chronic and highly disabling complication of diabetes. The prevalence of peripheral arterial disease (PAD) is high in diabetic patients and, associated or not with peripheral neuropathy (PN), can be found in 50% of cases of DF. It is worth pointing out that the number of major amputations in diabetic patients is still very high. Many PAD diabetic patients are not revascularised due to lack of technical expertise or, even worse, negative beliefs because of poor experience. This despite the progress obtained in the techniques of distal revascularisation that nowadays allow to reopen distal arteries of the leg and foot. Italy has one of the lowest prevalence rates of major amputations in Europe, and has a long tradition in the field of limb salvage by means of an aggressive approach in debridement, antibiotic therapy and distal revascularisation. Therefore, we believe it is appropriate to produce a consensus document concerning the treatment of PAD and limb salvage in diabetic patients, based on the Italian experience in this field, to share with the scientific community.

Combined retrograde-antegrade arterial recanalization through collateral vessels: redefinition of the technique for below-the-knee arteries.

The effectiveness of below-the-knee PTA to obtain successful revascularization in patients with critical limb ischemia (CLI) has been well established, and many centers have adopted endovascular intervention as the first-line treatment in patients with chronic lower-extremity disease. The well-known complex and multilevel arterial disease in patients with CLI have lead to interventionists to continuously implement different technologies and techniques. The aim of the present study was to standardize and redefine a technique characterized for combined retrograde-antegrade recanalization of a native leg artery through a collateral arterial branch by using a single access. This concept has been well described in coronary arteries and recently in pelvic and tibial arteries.

Vascular involvement in diabetic subjects with ischemic foot ulcer: a new morphologic categorization of disease severity.

OBJECTIVES: Arteriographic lesions of diabetic subjects with critical limb ischemia (CLI) and ischemic foot ulcer were reviewed retrospectively, to provide new criteria for stratification of these patients on the basis of their vascular involvement. PATIENTS: In 417 consecutive CLI diabetic subjects with ischemic foot ulcer undergoing lower limb angiography, lesions were defined as stenosis or occlusion, localization, and length (<5 cm, 5-10 cm, >10 cm). In a subgroup of 389 subjects, foot arteries also were evaluated. Patients then were categorized into 7 classes of progressive vascular involvement based on angiographic findings. RESULTS: Of the 2893 found lesions (55% occlusions) 1% were in the iliac arteries, whereas 74% were in below-the-knee (BTK) arteries. Sixty-six % of all BTK lesions were occlusions, and 50% were occlusions >10 cm (p<0.001 vs proximal segments). Occlusions of all BTK were present in 28% of patients, although there was patency of at least one foot artery in 55% of patients. The morphologic Class 4 (two arteries occluded and multiple stenoses of tibial/peroneal and/or femoral/popliteal vessels) was the most common (36%). An inverse correlation between morphologic class and TcPO2 was observed (r=-0.187, p=0.003). CONCLUSIONS: In CLI diabetic subjects with ischemic foot ulcer, the vascular involvement is extremely diffuse and particularly severe in tibial arteries, with high prevalence of long occlusions. A new morphologic categorization of these patients is proposed.

Peripheral angioplasty as the first-choice revascularization procedure in diabetic patients with critical limb ischemia: prospective study of 993 consecutive patients hospitalized and followed between 1999 and 2003.

OBJECTIVE: To evaluate the effectiveness of peripheral angioplasty (PTA) as the first-choice revascularisation procedure in diabetic patients with critical limb ischemia (CLI). DESIGN: Prospective study. METHODS: PTA was employed as first choice revascularisation in a consecutive series of diabetic patients hospitalized for CLI between January 1999 and December 2003. RESULTS: PTA was successful performed in 993 patients. Seventeen (1.7%) major amputations were carried out. One death and 33 non-fatal complications were observed. Mean follow-up was 26+/-15 months. Clinical restenosis was observed in 87 patients. The 5 years primary patency was 88%, 95% CI 86-91%. During follow-up 119 (12.0%) patients died at a rate of 6.7% per year. CONCLUSIONS: PTA as the first choice revascularisation procedure is feasible, safe and effective for limb salvage in a high percentage of diabetic patients. Clinical restenosis was an infrequent event and PTA could successfully be repeated in most cases.

Management of peripheral vascular disease.

The management of patients with peripheral arterial occlusive disease (PAD) has to be planned in the context of natural history, epidemiology, and apparent risk factors that predict deterioration. The ankle-brachial index to date has proved to be the most effective, accurate, and practical method of PAD detection. Given that PAD is a powerful indicator of systemic atherosclerosis and (independent of symptoms) is associated with an increased risk of myocardial infarction and stroke, as well as a six times greater likelihood of death, the prevalence and demographic distribution of measurable PAD becomes particularly relevant. Reliable information on interventions to confer symptom relief is much weaker and reflects discrepancies between published reports from centers of excellence and the experience of patients routinely treated in communities around the world. The impact of newer treatment modalities, such as complex endovascular procedures and therapeutic angiogenesis, has been a subject of recent controversy.

Extensive use of peripheral angioplasty, particularly infrapopliteal, in the treatment of ischaemic diabetic foot ulcers: clinical results of a multicentric study of 221 consecutive diabetic subjects.

OBJECTIVE: To evaluate the feasibility, technical effectiveness and limb salvage potential of percutaneous transluminal angioplasty (PTA), particularly infrapopliteal, in diabetic subjects with ischaemic foot ulcer. DESIGN: Intervention study with PTA in consecutive series. SETTING: Six Diabetology Foot Centres and one Cardiovascular Catheterization Laboratory in Italy. SUBJECTS: Two hundred and twenty-one consecutive diabetic subjects hospitalized for ischaemic foot ulcer. INTERVENTION: Peripheral arterial occlusive disease (PAOD) was investigated by means of foot pulses assessment, ankle-brachial-index (ABI), transcutaneous oxygen tension (TcPO2) and duplex scanning. If non-invasive parameters suggested PAOD, angiography was performed and a PTA was carried out during the same session. MAIN OUTCOME MEASURES: PTA feasibility, improvement of ABI and TcPO2, limb salvage rate, clinical recurrence. RESULTS: On angiography, two patients had stenoses which were <50% of the vessel diameter. PTA was performed in 191 (85.3%) of the 219 subjects with stenoses >50%, even when longer than 10 cm and/or multiple/calcified. In 11 patients (5.8%) PTA was performed in the proximal axis exclusively, in 81 (42.4%) patients in the infrapopliteal axis exclusively and in 99 (51.8%) in both the femoropopliteal and infrapopliteal axis. Both ABI and TcPO2 improved significantly after PTA (P < 0.0001). Clinical recurrence occurred in 14 subjects: 10 of whom underwent a second successful PTA. Of the 191 patients who underwent PTA, 10 (5.2%) underwent an above-the-ankle amputation. CONCLUSIONS: PTA, including infrapopliteal, is feasible in most diabetic subjects with ischaemic foot ulcer and is effective for foot revascularization. Clinical recurrence was infrequent and the procedure could successfully be repeated in most cases. In subjects treated successfully with PTA the above-the-ankle amputation rate was low. PTA should be considered as the revascularization treatment of first choice in all diabetic subjects with foot ulcer and PAOD.

Neonatal electroencephalogram does not predict cognitive and academic achievement scores at early school age in survivors of neonatal extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation is an effective rescue treatment for severe cardiorespiratory failure in term or near-term neonates, although a wide range of neurologic sequelae have been noted in a substantial minority of survivors. The objective of the present study was to determine the value of the neonatal electroencephalogram (EEG) for predicting Wechler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R), Wide Range Achievement Test, and Wide Range Assessment of Memory and Language scores at early school age in 66 testable survivors of extracorporeal membrane oxygenation who were not severely brain damaged. Technically satisfactory EEG recordings were obtained at least twice following admission to our nursery and prior to discharge. The EEGs were classified and graded according to standard criteria. The developmental test results of those who had only normal or mildly abnormal neonatal EEGs (group 1, n = 9) were compared with those who had at least one moderately or markedly abnormal recording (group 2, n = 57). School-age test and subtest scores were not statistically significantly worse in group 2 versus group 1 infants. No child in group 1 and five children in group 2 had WPPSI-R Full-Scale IQ scores of less than 70. Of the nine children in group 2 who had at least one markedly abnormal neonatal EEG recording (graded as burst suppression or as electrographic seizure), only two had abnormally low WPPSI-R Full-Scale IQ scores. We conclude that EEG recordings obtained during the neonatal course of neonates treated with extracorporeal membrane oxygenation do not predict cognitive and academic achievement test results in survivors at early school age who were testable and not severely brain damaged.

When combined, early bedside head ultrasound and electroencephalography predict abnormal computerized tomography or magnetic resonance brain images obtained after extracorporeal membrane oxygenation treatment.

Definitive neuroimaging of the brain using computerized tomography (CT) or magnetic resonance imaging (MRI) in extracorporeal membrane oxygenation (ECMO)-treated infants must be delayed until after this therapy is completed. Bedside head ultrasound (HUS) and electroencephalography (EEG) studies during ECMO, if highly correlated with later definitive neuroimaging, might be used to affect the acute clinical care and early parental counseling of infants with severe cardiorespiratory failure. One hundred and sixty ECMO-treated patients had both bedside EEG and HUS studies performed during ECMO, as well as a later CT or MRI study prior to hospital discharge. There was a significant difference in CT or MRI findings among patients having normal studies on both the HUS and EEG, compared to those having an abnormality on either the HUS or the EEG, and compared to those having abnormalities on both studies. In ECMO-treated infants, the combination of a normal bedside HUS and an EEG without marked abnormalities is highly predictive of normal post-ECMO CT and MRI neuroimaging studies.

[Percutaneous treatment of peripheral obstructive arteriopathy: the reasons for a choice]. / Il trattamento percutaneo delle arteriopatie ostruttive periferiche: i perché di una scelta.

Progressive aging of the Italian population is a relevant fact and this increases the occurrence of peripheral vascular disease in this subset of the population. At the same time, due to the national demographic decline, more and more aged people are going to live on their own. In this category the problem of self-caring is becoming highly relevant considering that only 12-13% of patients who had a limb amputation will walk with an artificial leg. This implies relevant social costs which are somewhat hidden because of their distribution in society (hospital, home care, individuals). Undoubtedly, there will be a dramatic reduction in the quality of life for these people. New technological progress and the development of new treatment modalities in the last decade have had a profound impact on the care of these patients. The role of peripheral vessel arteriography as a gold standard for the final evaluation of the disease and for the possibility of endovascular treatment has been widely accepted. Percutaneous transluminal intervention has proven to be more efficient economically with less morbidity and mortality than traditional vascular surgery, mainly in the limb salvage subgroup of patients. Health organization authorities should take these changes into account and modify their attitude towards the treatment of this pathology in order to provide better care for patients and to better allocate the economical resources of the National Health System.

The possible role of magnesium in protection of premature infants from neurological syndromes and visual impairments and a review of survival of magnesium-exposed premature infants.

The survival rate of very preterm, low birth weight infants (weighing less than 1500 g) is 85 per cent in the USA and is ever increasing, while 42 to 75 per cent of extremely premature infants (weighing 751-1000 g) survive. Of great concern is the lack of consistent decrease in neurological syndromes and associated visual impairments. Because of short gestations, these infants have not had time to accrue up to 80 per cent of magnesium normally present at term. These very preterm infants are at highest risk for cerebral hypoxia/ischemia (H/I), intracranial hemorrhage (ICH), periventricular leukomalacia (PVL) or cystic PVL (CPVL), and possible sequelae, cerebral palsy (CP) and mental retardation (MR). These syndromes are associated with damage to optic structures and the visual pathways which traverse the brain. Visual defects are common in surviving preterm infants. Increased levels of harmful neurochemical mediators that have been reported in these conditions include oxygen free radicals, excitatory amino acids, tumor necrosis factor-alpha (TNF-a), and thromboxane A2 (TXA2) which are aggravated in magnesium deficiency and may be ameliorated by magnesium. We review the published data concerning the effects of prenatal magnesium supplementation on ICH, CPVL, CP and MR and available reports concerning survival. Further considerations on the safety and efficacy of magnesium sulphate administration given prenatally to the preterm neonate await the outcome of three trials that are continuing for more than a year on three continents.

Five-year follow-up of neonates with reconstructed right common carotid arteries after extracorporeal membrane oxygenation.

OBJECTIVE: Serial Doppler ultrasonography and long-term neurodevelopmental follow-up outcomes were evaluated prospectively in neonates whose right common carotid artery (RCCA) was reconstructed after extracorporeal membrane oxygenation (ECMO). METHODS: Children with RCCA reconstruction (n = 34) were monitored for 3.5 to 4.5 years by Doppler ultrasonography for arterial patency, and 28 had IQ testing by 5 years. A comparison group consisted of 35 infants who had RCCA ligation after ECMO. Neonatal electroencephalograms and computed tomography/magnetic resonance imaging scans were also compared. RESULTS: Reconstructions were successful (<50% RCCA stenosis by Doppler ultrasonography) in 26 (76%) of 34 children, 3 (9%) had >/=50% stenosis, and 5 (15%) had occlusion. No significant differences were seen between reconstructed and ligated groups in neonatal complications or ECMO courses. Occurrence of marked neonatal electroencephalographic abnormalities did not differ between groups. Abnormalities on computed tomography/magnetic resonance imaging scans (4 of 31 vs 11 of 29, P =.025) and cerebral palsy (0 of 34 vs 5 of 35, P =.054) were more common in infants with RCCA ligation. No differences were seen in developmental or IQ scores between the 2 groups, and 4 in each group had cognitive handicaps (at least 1 IQ score <70). CONCLUSIONS: Most RCCA reconstructions remained patent, with 24% showing significant stenosis or occlusion. Compared with a historical control group, patients with RCCA reconstruction had fewer brain scan abnormalities and tended to be less likely to have cerebral palsy. RCCA reconstruction after venoarterial ECMO may improve outcome.

Adverse neurodevelopmental outcome after extracorporeal membrane oxygenation among neonates with bronchopulmonary dysplasia.

OBJECTIVE: The relationship between bronchopulmonary dysplasia (BPD) and neurodevelopmental outcome after extracorporeal membrane oxygenation (ECMO) has not been extensively reported. We compared the outcomes in a large series of infants with and without BPD after ECMO. STUDY DESIGN: Hospital charts and follow-up records of 145 infants treated with ECMO (1985 through 1990) were reviewed. Complete long-term respiratory and follow-up outcome data were available in 64 infants. BPD occurred in 17 survivors; the remaining 47 did not have BPD. RESULTS: Babies with BPD were more likely to have had respiratory distress syndrome. Mean (+/- SD) age at ECMO initiation was later for the BPD group (127+/-66 vs 53+/-39 hours, p < 0.001), and the duration of ECMO treatment was longer (192+/-68 vs 119+/-53 hours, p < 0.001). Bayley Scales of Infant Development scores at <30 months were lower in infants with BPD (p < 0.001), as were three of four Mullen Scales of Early Learning scores (> or = 30 months, p < 0.001 or p = 0.01). At 57+/-16 months 11 (64%) patients with BPD had mild neurologic disabilities, and 3 (18%) had severe disabilities. At a similar age (53+/-16 months, p = NS) 16 (34%) patients without BPD had mild disabilities, whereas 2 (4%) had severe disabilities (p < 0.01). CONCLUSIONS: The occurrence of BPD after ECMO is associated with adverse neurodevelopmental outcome. Patients with BPD after ECMO merit close long-term follow-up.

Cerebrovascular complications and neurodevelopmental sequelae of neonatal ECMO.

A total of 355 infants have been treated with ECMO at our hospital between 1985 and 1996, 271 of whom have been enrolled in an ongoing prospective study; of the 271 infants enrolled, 223 (82%) survived, and most function within the normal range of development. Nevertheless, handicapping sequelae, including spastic forms of CP, hearing loss, and cognitive deficiencies at school age, have been noted in a significant minority of ECMO-treated survivors. The need for RCCA cannulation during venoarterial ECMO may increase the risk of a cerebrovascular injury, and lateralized CBF abnormalities have been noted on CDI and pulsed Doppler ultrasound studies during and after venoarterial bypass; however, post-ECMO CT scans, HUS, MR images, or clinical evaluations have not indicated selective or greater injury to the right, compared with the left, cerebral hemisphere in our survivors, nor was there a significant predilection for right, rather than left, cerebral hemispheric EEG abnormalities during or following venoarterial bypass. Although we routinely repair the RCCA following venoarterial ECMO, the long-term consequences of a permanently ligated artery have not as yet been demonstrated. We have noted the ominous predictive value of two or more recordings that disclose ES and BS EEG abnormalities before or during venoarterial ECMO and found that the need for vigorous CPR before or during RCCA cannulation significantly increased the risk of these two markedly abnormal bioelectric patterns. Because 85% of infants with severe respiratory failure have moderate to marked EEG abnormalities (including 23% who have BS or ES patterns) before ECMO, we believe that fetal and neonatal complications related to the occurrence and treatment of severe cardiorespiratory failure are responsible in large part for the neurologic sequelae in ECMO survivors. The risk for CP was significantly increased in survivors of neonatal venoarterial ECMO treated at our hospital who required CPR or who independently had a systolic BP below 39 mm Hg before or during ECMO. We also noted that the risk for hearing loss was increased significantly in surviving neonates who had a PaCO2 below 14 mm Hg before ECMO. The possibility that undetected confounding variables were, in part, responsible for the neurologic, audiologic, and cognitive sequelae in ECMO survivors could not be excluded entirely by our data analyses. Although the pathogenesis of severe brain damage has not been defined fully in neonates treated with ECMO, focal, multifocal, or diffuse cerebral ischemia is the most likely final common pathway; thrombosis, infarction, or hemorrhage may follow and contribute to the brain injury. The cause of isolated SNHL is unknown in most affected ECMO survivors, but in some very likely is associated with the complications and treatment of severe cardiorespiratory failure, including profound hypocarbia prior to ECMO. The results of our studies to date are consistent with the following conclusions: (1) hypotension before or during ECMO and the need for CPR before ECMO contribute to the pathogenesis of CP, probably through the mechanism of cerebral ischemia; (2) profound hypocarbia before ECMO and delayed ECMO treatment are associated with a significantly increased risk of hearing loss; (3) hypoxemia without hypotension does not result in CP; (4) the type and severity of neurologic and cognitive sequelae in ECMO survivors depends, in part, on the primary cause of the neonatal cardiorespiratory failure; (5) early neurodevelopment, except for severe deficits, may not predict school-age performance; and (6) abnormally low or borderline WPPSI-R IQ scores and academic deficiencies at early school age, without evidence of a congenital abnormality of brain or CP or SNHL, remain unexplained. The criteria for initiating ECMO in the neonate with severe cardiorespiratory failure include decreasing oxygenation despite mechanical hyperventilation with 100% oxygen. (ABSTRACT TRUNCATED)

Clinical antecedents of neurologic and audiologic abnormalities in survivors of neonatal extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation is an effective rescue treatment for severe cardiorespiratory failure in term or near term neonates, although cerebral palsy, mental retardation, and sensorineural hearing loss are observed in 10 to 20% of survivors. The objective of the present study was to identify potential risk factors that may explain the neurologic and audiologic sequelae noted in 19% of 181 survivors of neonatal extracorporeal membrane oxygenation from our hospital. Our results suggest the following findings in survivors of severe cardiorespiratory failure treated with neonatal extracorporeal membrane oxygenation: (1) hypotension or the need for cardiopulmonary resuscitation before extracorporeal membrane oxygenation significantly increases the risk of spastic cerebral palsy, (2) profound hypocarbia before extracorporeal membrane oxygenation is associated with a significantly increased risk of hearing loss, (3) mental retardation in the absence of spastic cerebral palsy is unexplained except when due to abnormal fetal brain development, and (4) hypoxemia in the absence of hypotension does not increase the risk of neurologic or audiologic sequelae.

The interaction between the AsiA protein of bacteriophage T4 and the sigma70 subunit of Escherichia coli RNA polymerase.

The AsiA protein of bacteriophage T4 binds to the sigma70 subunit of Escherichia coli RNA polymerase and plays a dual regulatory role during T4 development: (i) inhibition of host and phage early transcription, and (ii) coactivation of phage middle-mode transcription, which also requires the T4 DNA binding transcriptional activator, MotA. We report that the interaction between AsiA and sigma70 occurs with a 1:1 stoichiometry. When preincubated with RNA polymerase, AsiA is a potent inhibitor of open complex formation at the lac UV5 promoter, whereas it does not perturb preformed open or intermediate promoter complexes. DNase I footprinting and electrophoretic mobility shift analyses of RNA polymerase-DNA complexes formed at the T4 early promoter P15.0 show that AsiA blocks the initial RNA polymerase binding step that leads to the formation of specific closed promoter complexes. A contrasting result is obtained on the T4 middle promoter PrIIB2, where AsiA stimulates the formation of both closed complexes and open complexes. Therefore, we propose that AsiA modulates initial DNA binding by the RNA polymerase, switching promoter usage at the level of closed complex formation.