Susceptible Escherichia coli cells can actively excrete tetracyclines.

Escherichia coli shows severalfold less susceptibility to tetracyclines when grown in enriched medium than in minimal medium. Transport studies with cells harvested from these media showed different handling of the drugs. Whereas an energy-dependent uptake of tetracycline and minocycline was observed in susceptible K-12 and wild-type E. coli strains grown in minimal medium, an active efflux of minocycline and, to a lesser extent, tetracycline was seen in cells grown in L broth and other enriched media. This efflux was replaced by an active uptake system after treatment of cells grown in L broth with EDTA. When assayed at a lower temperature (27 degrees C), even cells grown in minimal medium showed an efflux of minocycline. Everted membrane vesicles prepared from susceptible cells grown in minimal medium or L broth showed an energy-dependent accumulation of minocycline and tetracycline when supplied with certain divalent cations. These results suggest that an active efflux of tetracyclines occurs in susceptible E. coli but is not detected in cells grown in minimal medium because greater permeability of the outer membrane allows a more rapid active uptake. This efflux system is distinct from that specified by tetracycline resistance determinants. Since the active efflux of minocycline in cells grown in L broth disappeared at external antibiotic concentrations of greater than 100 microM, it may be saturable and so mediated by a membrane carrier.     

Bacterial meningitis in patients with nasopharyngeal carcinoma

Bacterial meningitis was found in 12 patients with nasopharyngeal carcinoma, accounting for 0.65% of the 1850 patients with the tumour diagnosed between 1981 and 1994 in our hospital. In 11 patients, the time-lag between diagnosis of cancer and the appearance of infection ranged from 9 months to 11 years (mean 57 months) whereas in one patient it was only 5 days. Three patients developed mixed bacterial meningitis. Cerebrospinal fluid culture for bacteria was positive in six patients. Three patients (25%) were bacteraemic. Gram-negative bacilli, especially Pseudomonas aeruginosa, were the most common pathogens. Age, sex and histopathology were not risk factors for infection. Conditions predisposing to meningitis included intracranial invasion of the tumor, neutropenia, otitis media, and neurosurgical procedures. All but two patients had intracranial tumour invasion and erosion of the base of the skull. Local spread of micro-organism to the meninges was more important than haematogenous spread. The overall mortality in our patients was 66.7%, much higher than in patients without cancer.      

Transformacion Para Salud: A Patient Navigation Model for Chronic Disease Self-management

Increased cost of chronic illnesses in United States is an urgent call to develop a cost effective approach to improve chronic disease self-management, especially among vulnerable populations. An emerging role for professionals and paraprofessionals is the patient navigator. We present an example of a conceptual framework, Transformation for Health, developed to underpin the training of certified community health workers (CHW) to deliver health care, preventive services, and health education for underserved populations to promote chronic disease self-management. Transformacion Para Salud (TPS), a patient navigation model for chronic disease self-management, was a two year demonstration program to develop a culturally sensitive intervention to facilitate patient behavior changes. Patients involved in the TPS intervention showed improvements in clinical and behavioral outcomes after twelve months of intervention. This article describes the conceptual basis and implementation of the TPS and discusses program evaluation, specific intervention outcomes, and implications for practice. Use of CHWs in the patient navigator role demonstrated a cost effective method to improve access to quality, cost-effective, primary health care services as well as to facilitate chronic disease self-management.     

猪源性异种骨支架材料的生物相容性

目的:异种骨来源广泛,价格低廉,经过适当处理既能保留骨诱导作用,并作为骨支架使其具有骨传导作用。检测猪源性骨支架材料与人源性骨支架材料的生物相容性有无明显差异,为猪源性骨支架材料取代人源性骨支架材料提供实验依据。方法:实验于2006-08/2007-03在南方医科大学人体解剖学系实验室(广东省组织构建与检测重点实验室)完成。①实验材料:人源性、猪源性骨支架材料(为课题组前期制备);脂肪源间充质细胞(前期培养)。②实验方法及评估:体外细胞毒性实验:提取人源性、猪源性骨支架材料浸提液,用此浸提液培养脂肪源间充质细胞,并用无浸提液的DMEM培养基做对照,镜下观察细胞生长状况,流式细胞术检测细胞生长周期;人源性、猪源性骨支架材料皮下植入试验:于8只新西兰大白兔皮下,脊柱左侧植入异种骨支架材料,右侧植入同种异体骨支架材料。分别于4,8,12,16周将植入材料连同周围组织取出,进行组织切片观察及电镜观察。对动物处置符合动物伦理学标准。结果:①体外细胞毒性实验结果:在同一时间点,浸提液组、正常培养组细胞生长状况均良好,未见明显细胞抑制;流式细胞术检测细胞周期,3组细胞G1、G2、S期细胞百分率差异无统计学意义(P>0.05)。②皮下植入实验结果:组织切片光镜及电镜观察,4周两种植入材料周围均见结缔组织包绕,有大量巨噬细胞、浆细胞、中性粒细胞、单核细胞浸润,材料表面光滑,与结缔组织界限清楚;8周时炎症反应减轻,可见部分材料开始降解,材料表面稍显粗糙,有少量结缔组织长入材料内部;12周炎症反应基本消失、材料降解明显、异位成骨趋势明显,材料表面更加粗糙,周围有大量结缔组织长入材料;16周均无炎症反应,两种材料大部分降解,并且猪源性骨支架材料降解更为迅速,均有新骨形成,材料表面粗糙程度较12周时为甚,骨支架材料基本消失。结论:猪源性异种骨支架材料有良好的生物相容性,与人源性异种骨支架材料无明显差别。     

Prior Calcium Channel Blockade and Short-Term Survival Following Acute Myocardial Infarction

There is concern over the safety of calcium channel blockers (CCBs) in acute coronary disease. We sought to determine if patients taking calcium channel blockers (CCBs) at the time of admission with acute myocardial infarction (AMI) had a higher case-fatality compared with those taking beta-blockers or neither medication. Clinical and drug treatment variables at the time of hospital admission predictive of survival at 28 days were examined in a community-based registry of patients aged under 65 years admitted to hospital for suspected AMI in Perth, Australia, between 1984 and 1993. Among 7766 patients, 1291 (16.6%) were taking a CCB and 1259 (16.2%) a betablocker alone at hospital admission. Patients taking CCBs had a worse clinical profile than those taking a beta-blocker alone or neither drug (control group), and a higher unadjusted 28-day mortality (17.6% versus 9.3% and 11.1% respectively, both P < 0.001). There was no significant heterogeneity with respect to mortality between nifedipine, diltiazem, or verapamil when used alone, or with a beta-blocker. After adjustment for factors predictive of death at 28 days, patients taking a CCB were found not to have an excess chance of death compared with the control group (odds ratio [OR] 1.06, 95% confidence interval [CI]; 0.87, 1.30), whereas those taking a beta-blocker alone had a lower odds of death (OR 0.75, 95% CI; 0.59, 0.94). These results indicate that established calcium channel blockade is not associated with an excess risk of death following AMI once other differences between patients are taken into account, but neither does it have the survival advantage seen with prior beta-blocker therapy.     

Variability in morphology, hygroscopicity, and optical properties of soot aerosols during atmospheric processing

The atmospheric effects of soot aerosols include interference with radiative transfer, visibility impairment, and alteration of cloud formation and are highly sensitive to the manner by which soot is internally mixed with other aerosol constituents. We present experimental studies to show that soot particles acquire a large mass fraction of sulfuric acid during atmospheric aging, considerably altering their properties. Soot particles exposed to subsaturated sulfuric acid vapor exhibit a marked change in morphology, characterized by a decreased mobility-based diameter but an increased fractal dimension and effective density. These particles experience large hygroscopic size and mass growth at subsaturated conditions (<90% relative humidity) and act efficiently as cloud-condensation nuclei. Coating with sulfuric acid and subsequent hygroscopic growth enhance the optical properties of soot aerosols, increasing scattering by ≈10-fold and absorption by nearly 2-fold at 80% relative humidity relative to fresh particles. In addition, condensation of sulfuric acid is shown to occur at a similar rate on ambient aerosols of various types of a given mobility size, regardless of their chemical compositions and microphysical structures. Representing an important mechanism of atmospheric aging, internal mixing of soot with sulfuric acid has profound implications on visibility, human health, and direct and indirect climate forcing.     

SURGERY FOR ASYMPTOMATIC CAROTID ARTERY STENOSIS

SUMMARY The recent European Carotid Surgery Trial (ECST) and North American Symptomatic Carotid Endarterectomy Trial (NASCET) have clearly defined a population who benefit from carotid artery endarterectomy (CAE). However these trials used different criteria to identify >70% stenosis of the internal carotid artery (ICA). The role of CAE in asymptomatic ICA stenosis has been investigated by the Carotid Artery Stenosis with Asymptomatic Narrowing Operation Versus Aspirin (CASANOVA) study, the Veterans Administration Asymptomatic Carotid Study (VAACS) and the Asymptomatic Carotid Artery Stenosis (ACAS) trials, all of which have design limitations. The Asymptomatic Carotid Stenosis Trial (ACST) is still recruiting patients but until the natural history of asymptomatic ICA disease is understood, the role of surgical intervention will continue to be controversial.     

Delivery of primary percutaneous coronary intervention for the management of acute ST segment elevation myocardial infarction: summary of the Cardiac Care Network of Ontario Consensus Report

Tremendous debate has developed over the efficacy of primary percutaneous coronary intervention (PCI) compared with fibrinolysis as the preferred treatment for acute ST segment elevation myocardial infarction (STEMI). In 2002, the Ontario Ministry of Heath and Long-Term Care commissioned the Cardiac Care Network of Ontario to develop consensus recommendations regarding the provincial coordination and provision of urgent PCI for STEMI patients. The panel's work has provided important insights into the acute treatment of STEMI that may be useful to other jurisdictions and may provide a reference for other regions considering the implementation of primary PCI for the management of STEMI patients in their community. In the present report, the evidence for primary PCI is reviewed, the important barriers to implementing this strategy are summarized and several recommendations and models of care for the delivery of primary PCI for STEMI on a wide scale are presented.     

Imaging of follicular dendritic cell tumours of the liver

Follicular dendritic cell tumour of the liver is a recently recognized entity. To date, only two cases have been described, both in the pathology literature. Histologically, it resembles an inflammatory pseudotumour and immunohistochemical and ultrastructural studies are required for its diagnosis. The ultrasound, computed tomography and angiographic features of two cases of follicular dendritic cell tumour of the liver are described in detail. One of the patients had multiple recurrences of this tumour. The imaging features are very similar to those of hepatocellular carcinoma. As follicular dendritic cell tumour is considered to be of low-grade malignant potential, in contrast to the dismal prognosis for hepatocellular carcinoma, it is important to be able to accurately distinguish between the two types of tumour prior to initiating definitive therapy.     

Acid–base chemical reaction model for nucleation rates in the polluted atmospheric boundary layer

Climate models show that particles formed by nucleation can affect cloud cover and, therefore, the earth''s radiation budget. Measurements worldwide show that nucleation rates in the atmospheric boundary layer are positively correlated with concentrations of sulfuric acid vapor. However, current nucleation theories do not correctly predict either the observed nucleation rates or their functional dependence on sulfuric acid concentrations. This paper develops an alternative approach for modeling nucleation rates, based on a sequence of acid–base reactions. The model uses empirical estimates of sulfuric acid evaporation rates obtained from new measurements of neutral molecular clusters. The model predicts that nucleation rates equal the sulfuric acid vapor collision rate times a prefactor that is less than unity and that depends on the concentrations of basic gaseous compounds and preexisting particles. Predicted nucleation rates and their dependence on sulfuric acid vapor concentrations are in reasonable agreement with measurements from Mexico City and Atlanta.