Infection control: principles for practice

This article discusses the general principles of infection control and outlines the role nurses can play in maintaining a safe environment. This article is the third and final part of our 1998 series on infection control.     

Distalless expression in crustaceans and the patterning of branched limbs

The ability of two-dimensional echocardiography to detect and to evaluate the extent of wall motion abnormalities is limited by the use of few selected, nonparallel, views of the whole left ventricle. This leads to an incomplete appreciation of the spatial relationships between various cardiac structures and inaccuracy in quantitative data as a result of using of geometric assumptions. Dynamic volume-rendered three-dimensional echocardiography has the ability to overcome the above limitations. In this article we review the use of volume-rendered three-dimensional echocardiography in the diagnosis and assessment of ischemic heart disease, including complications related to myocardial infarction.     

Neuronal units linked to microvascular modules in cerebral cortex: response elements for imaging the brain

How neuronal activity changes cerebral blood flow is of biological and practical importance. The rodent whisker-barrel system has special merits as a model for studies of changes in local cerebral blood flow (LCBF). Stimulus-evoked changes in neural firing and 'intrinsic signals' recorded through a cranial window were used to define regions of interest for repeated flow measurements. Whisker-activated changes in flow were measured with intravascular markers at the pia. LCBF changes were always prompt and localized over the appropriate barrel. Stimulus-related changes in parenchymal flow monitored continuously with H2 electrodes recorded short latency flow changes initiated in middle cortical layers. Activation that increased flow to particular barrels often led to reduced flow to adjacent cortex. Dye was injected into single penetrating arterioles from the pia of the fixed brain and injected into arterioles in slices of cortex where barrels were evident without stains. Arteriolar and venular domains at the surface were not directly related to underlying barrels. Capillary tufts in layer IV were mainly coincident with barrels. The matching between a capillary plexus (a vascular module) and a barrel (a functional neuronal unit) is a spatial organization of neurons and blood vessels that optimizes local interactions between the two. The paths of communication probably include: neurons to neurons, neurons to glia, neurons to vessels, glia to vessels, vessels to vessels and vessels to brain. Matching a functional grouping of neurons with a vascular module is an elegant means of reducing the risk of embarrassment for energy-expensive neuronal activity (ion pumping) while minimizing energy spent for delivery of the energy (cardiac output). For imaging studies this organization sets biological limits to spatial, temporal and magnitude resolution. Reduced flow to nearby inactive cortex enhances local differences.     

Histomorphometric, physical, and mechanical effects of spaceflight and insulin-like growth factor-I on rat long bones

Pituitary adenylate cyclase activating peptide and vasoactive intestinal peptide belong to the same neuropeptide family. Both peptides are present in nerve fibers in the gastric wall and are thought to be involved in the regulation of inflammatory processes. Experimental ulcers were induced in the rat gastric mucosa by local application of acetic acid. During the healing process we examined the PACAP and VIP innervation by means of immunohistochemistry and in situ hybridization. The ulcer area was examined from day 1 to day 15 after ulcer induction. There was a marked depletion of PACAP in nerve fibers at the ulcer margin from day 1 and onwards. On day 10 and day 15, PACAP-immunoreactive nerve fibers could again be visualized at the ulcer margin. In contrast, VIP immunoreactive nerve fibers were present at the ulcer margin at all time points studied. From day 10 following ulcer induction PACAP- and VIP- immunoreactive nerve fibers were increased in frequency in the smooth muscle beneath the ulcer. An upregulation of VIP and PACAP mRNA was also demonstrated in the myenteric ganglia adjacent to ulcer. The present results indicate that neuronal PACAP and VIP react differently to the inflammation at the ulcer margin but similarly in the smooth muscle during the ulcer healing.     

Mutational analysis of the Mu transposase. Contributions of two distinct regions of domain II to recombination

Mu transposase is a member of a protein family that includes many transposases and the retroviral integrases. These recombinases catalyze the DNA cleavage and joining reactions essential for transpositional recombination. Here we demonstrate that, consistent with structural predictions, aspartate 336 of Mu transposase is required for catalysis of both DNA cleavage and DNA joining. This residue, although located 55 rather than 35 residues NH2-terminal of the essential glutamate, is undoubtedly the analog of the second aspartate of the Asp-Asp-35-Glu motif found in other family members. The core domain of Mu transposase consists of two subdomains: the NH2-terminal subdomain (IIA) contains the conserved Asp-Asp-Glu motif residues, whereas the smaller COOH-terminal subdomain (IIB) contains a large positively charged region exposed on its surface. To probe the function of domain IIB, we constructed mutant proteins carrying deletion or substitution mutations within this region. The activity of the deletion proteins revealed that domains IIA and IIB can be provided by different subunits in the transposase tetramer. Substitution mutations at two pairs of exposed lysine residues within the positively charged surface of domain IIB render transposase defective in transposition at a reaction step after DNA cleavage but prior to DNA joining. The severity of this defect depends on the structure of the DNA flanking the cleavage site. Thus, these data suggest that domain IIB is involved in manipulating the DNA near the cleavage site and that this function is important during the transition between the DNA cleavage and the DNA joining steps of recombination.     

Hospital-acquired infection

There were observed 310 injured persons with mild closed craniocerbral trauma (MCCCT). Of them 110 were healthy before the trauma (1st group), arterial hypertension, dyscirculatory encephalopathy of I-II stage were noted in 100 (2nd group), chronic gastrointestinal diseases--in 100 (3d group). It is mandatory to take into account the peculiarities of the MCCCT consequences in injured persons of the second and third groups in the diagnosis, treatment administration and prophylactic measures conduction.     

基于信息检索课的大学生信息检索行为调查研究

信息检索课程的系统化讲授,对于大学生优化信息检索行为,提高信息检索使用效率具有不容忽视的教学辅助作用。立足问卷调查形成的一系列相关数据,探讨大学生信息检索行为存在问题,最终在课程教学中提出优化大学生信息检索的对策：明确信息检索目的,提升实施效果;有效提升检索行为实施频率,增强综合质量;使得信息获取多元发展,优化成效凸显。     

混凝土坝裂缝变形的不确定性分析模型

混凝土坝裂缝的发生和发展受到不确定因素影响。将大坝系统及其安全监控看作一个受诸多因素影响的不确定性系统,结合裂缝实测资料,应用近似推理模型和信息分配法,建立了裂缝变形的不确定性分析模型。     

基于正交设计的黄池沟退水道弯道体型优化的数值模拟分析

为探求黄池沟退水道弯道的合理体型,采用正交设计与数值模拟相结合的方法研究了体型参数对弯道水流的影响。选取弯道宽度、弯道曲率半径、纵向坡度3个主要影响参数按正交试验设计,确定了9组正交试验方案,利用经水工模型试验结果验证的数学模型对正交试验方案进行模拟,分析了体型参数对弯道及下游陡坡段横向水位差的影响。结果表明,3个体型参数影响作用由大到小依次为纵向坡度、弯道宽度和弯道曲率半径;坡度为显著影响因素,且平坡最佳,弯道曲率半径和弯道宽度影响不显著,据此推荐合理体型参数为坡度取0,弯道宽度和弯道曲率半径采用原设计值。