抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Background: Over the last few years, probiotics have been one of the most studied interventions in neonatal medicine. Objectives: </

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The “Golden Age” of Probiotics: A Systematic Review and Meta-Analysis of Randomized and Observational Studies in Preterm Infants

The rat, mouse and human estrogen receptor (ER) exists as two subtypes, ER alpha and ER beta, which differ in the C-terminal ligand-binding domain and in the N-terminal transactivation domain. In this study, we investigated the estrogenic activity of environmental chemicals and phytoestrogens in competition binding assays with ER alpha or ER beta protein, and in a transient gene expression assay using cells in which an acute estrogenic response is created by cotransfecting cultures with recombinant human ER alpha or ER beta complementary DNA (cDNA) in the presence of an estrogen-dependent reporter plasmid. Saturation ligand-binding analysis of human ER alpha and ER beta protein revealed a single binding component for [3H]-17beta-estradiol (E2) with high affinity [dissociation constant (Kd) = 0.05 - 0.1 nM]. All environmental estrogenic chemicals [polychlorinated hydroxybiphenyls, dichlorodiphenyltrichloroethane (DDT) and derivatives, alkylphenols, bisphenol A, methoxychlor and chlordecone] compete with E2 for binding to both ER subtypes with a similar preference and degree. In most instances the relative binding affinities (RBA) are at least 1000-fold lower than that of E2. Some phytoestrogens such as coumestrol, genistein, apigenin, naringenin, and kaempferol compete stronger with E2 for binding to ER beta than to ER alpha. Estrogenic chemicals, as for instance nonylphenol, bisphenol A, o, p'-DDT and 2',4',6'-trichloro-4-biphenylol stimulate the transcriptional activity of ER alpha and ER beta at concentrations of 100-1000 nM. Phytoestrogens, including genistein, coumestrol and zearalenone stimulate the transcriptional activity of both ER subtypes at concentrations of 1-10 nM. The ranking of the estrogenic potency of phytoestrogens for both ER subtypes in the transactivation assay is different; that is, E2 >> zearalenone = coumestrol > genistein > daidzein > apigenin = phloretin > biochanin A = kaempferol = naringenin > formononetin = ipriflavone = quercetin = chrysin for ER alpha and E2 >> genistein = coumestrol > zearalenone > daidzein > biochanin A = apigenin = kaempferol = naringenin > phloretin = quercetin = ipriflavone = formononetin = chrysin for ER beta. Antiestrogenic activity of the phytoestrogens could not be detected, except for zearalenone which is a full agonist for ER alpha and a mixed agonist-antagonist for ER beta. In summary, while the estrogenic potency of industrial-derived estrogenic chemicals is very limited, the estrogenic potency of phytoestrogens is significant, especially for ER beta, and they may trigger many of the biological responses that are evoked by the physiological estrogens.

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Interaction of estrogenic chemicals and phytoestrogens with estrogen receptor beta.

Microorganisms attach to surfaces and develop biofilms. Biofilm-associated cells can be differentiated from their suspended counterparts by generation of an extracellular polymeric substance (EPS) matrix, reduced growth rates, and the up- and down- regulation of specific genes. Attachment is a complex process regulated by diverse characteristics of the growth medium, substratum, and cell surface. An established biofilm structure comprises microbial cells and EPS, has a defined architecture, and provides an optimal environment for the exchange of genetic material between cells. Cells may also communicate via quorum sensing, which may in turn affect biofilm processes such as detachment. Biofilms have great importance for public health because of their role in certain infectious diseases and importance in a variety of device-related infections. A greater understanding of biofilm processes should lead to novel, effective control strategies for biofilm control and a resulting improvement in patient management.

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Biofilms: microbial life on surfaces.

Thereisgrowinginterestinthepossiblehealththreatposedbyendocrine-disruptingchemicals (EDCs), which are substances in our environment, food, and consumer products that interfere with hormone biosynthesis, metabolism, or action resulting in a deviation from normal homeostatic control or reproduction. In this first Scientific Statement of The Endocrine Society, we present the evidence that endocrine disruptors have effects on male and female reproduction, breast development and cancer, prostate cancer, neuroendocrinology, thyroid, metabolism and obesity, and cardiovascular endocrinology. Results from animal models, human clinical observations, and epidemiological studies converge to implicate EDCs as a significant concern to public health. The mechanisms of EDCs involve divergent pathways including (but not limited to) estrogenic, antiandrogenic, thyroid, peroxisome proliferator-activated receptor , retinoid, and actions through other nuclear receptors; steroidogenic enzymes; neurotransmitter receptors and systems; and many other pathways that are highly conserved in wildlife and humans, and which can be modeled in laboratory in vitro and in vivo models. Furthermore, EDCs represent a broad class of molecules such as organochlorinated pesticides and industrial chemicals, plastics and plasticizers, fuels, and many other chemicals that are present in the environment or are in widespread use. We make a number of recommendations to increase understanding of effects of EDCs, including enhancing increased basic and clinical research, invoking the precautionary principle, and advocating involvement of individual and scientific society stakeholders in communicating and implementing changes in public policy and awareness. (Endocrine Reviews 30: 293–342, 2009)

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Endocrine-Disrupting Chemicals: An Endocrine Society Scientific Statement

In a prospective, randomised, double-blind study, 179 patients undergoing retropubic or transurethral prostatectomy were given pre-operatively either 1 g aztreonam or a placebo. In patients treated with aztreonam there was a significant reduction in the number with post-operative bacteriuria and in the number requiring treatment of post-operative bacteriuria. Other differences were not significant. The mean duration of post-operative hospital stay for patients receiving aztreonam was 7.1 days compared with 6.9 days for those receiving placebo. In patients treated with aztreonam there was no increase in the frequency of infections due to Gram-positive bacterial species.

Double-blind study comparing aztreonam with placebo for prophylaxis of infection following prostatic surgery.

BACKGROUND. Chlamydia trachomatis is frequently overlooked as a cause of dysuria and urinary frequency in general practice patients. AIM. This study set out to determine the impact of performing chlamydial antigen detection on sterile pyuria samples from patients aged 16-65 years and which were submitted to a hospital microbiology laboratory by general practitioners in the Winchester health district for routine microbiological investigations. METHOD. Chlamydial antigen detection was performed by enzyme immunoassay and direct immunofluorescence. The cost of performing the test was estimated. In the first year of the study (1991) questionnaires were sent to general practitioners whose patients had a positive test result. RESULTS. A total of 1025 samples of sterile pyuria were received at the laboratory between January 1991 and March 1993. Chlamydial antigen was detected in 54 samples (5%); 22 men and 32 women aged between 16 and 57 years (mean 25 years). The detection rate was highest in the 16-20 years age group (22% of men had a positive sample and 7% of women). Completed questionnaires from 27 general practitioners revealed that 59% of their patients were referred to the genitourinary clinic for treatment and contact tracing. The others were treated by the general practitioner. The cost of the screening programme per cure in this population was estimated to be 246 pounds. CONCLUSION. C trachomatis is a significant pathogen which may go unrecognized and untreated. The cost, medically and financially, of screening for this pathogen and treating infected patients and contacts is likely to be less than ignoring it, particularly if screening is confined to the 16-30 years age group. General practitioners should consider the diagnosis of chlamydial infection in young adult patients with sterile pyuria, and microbiology laboratories should screen sterile pyuria samples for chlamydial antigen.

Michael Millar

Papers

Double-blind study comparing aztreonam with placebo for prophylaxis of infection following prostatic surgery.

Detection of chlamydia trachomatis in general practice urine samples

Inadvertent intravenous infusion of Mucor during parenteral feeding of a neonate.

Identification of transcription factors and coactivators affected by dibutylphthalate interactions in fetal rat testes.

‘Zero Tolerance’ of Avoidable Infection in the English National Health Service: Avoiding the Redistribution of Burdens