2006～2010年革兰阴性菌对碳青霉烯类抗生素耐药性分析

目的调查分析我院20ff6～2010年临床分离的革兰阴性菌对碳青霉烯类抗生素的耐药性。方法采用纸片扩散法进行抗菌药物敏感实验,采用WHONET5．4软件及SPSS13．0软件进行数据分析。结果大肠埃希菌和肺炎克雷伯菌对亚胺培南和美罗培南的耐药率呈上升趋势,但最高不超过4．5％。铜绿假单胞菌对亚胺培南的耐药率2006年和2007年监测显示为21．3％和41％。2008年达到44．8％,在2009年下降为12．4％,但2010年爽迅速增加到30．1％。鲍曼不动杆菌对亚胺培南耐药率的逐年上升更为显著,从2006年9．1％上升到2010年的68％,差异具有统计学意义（P〈0．01）。嗜麦芽窄食单胞菌对碳青霉烯类抗生素天然耐药,2006年对亚胺培南耐药率为30％,但自2007年起就增加到80．8％,最高达100％。结论肠杆菌科细菌对碳青霉烯类敏感性高,近年耐药率有上升趋势。铜绿假单胞菌和鲍曼不动杆菌对碳青霉烯类耐药率高,尤其是鲍曼不动杆菌的分离率逐年增加,耐药形势严峻。临床应合理使用抗生素,减少多重耐药株的产生。     

Subjective confidence in forecasts

Forecasts have little value to decision makers unless it is known how much confidence to place in them. Those expressions of confidence have, in turn, little value unless forecasters are able to assess the limits of their own knowledge accurately Previous research has shown very robust patterns in the judgements of individuals who have not received special training in confidence assessment: Knowledge generally increases as confidence increases. However, it increases too swiftly, with a doubling of confidence being associated with perhaps a 50 per cent increase in knowledge. With all but the easiest of tasks, people tend to be overconfident regarding how much they know These results have typically been derived from studies of judgements of general knowledge. The present study found that they also pertained to confidence in forecasts. Indeed, the confidence-knowledge curves observed here were strikingly similar to those observed previously. The only deviation was the discovery that a substantial minority of judges never expressed complete confidence in any of their forecasts. These individuals also proved to be better assessors of the extent of their own knowledge Apparently confidence in forecasts is determined by processes similar to those that determine confidence in general knowledge. Decision makers can use forecasters assessments in a relative sense, in order to predict when they are more and less likely to be correct. However, they should be hesitant to take confidence assessments literally. Someone is more likely to be right when he or she is ‘certain’than when he or she is ‘fairly confident’; but there is no guarantee that the certain forecast will come true.     

Endothelium-derived nitric oxide and vascular physiology and pathology

In 1980, Furchgott and Zawadzki demonstrated that the relaxation of vascular smooth muscle cells in response to acetylcholine is dependent on the anatomical integrity of the endothelium. Endothelium-derived relaxing factor was identified 7 years later as the free radical gas nitric oxide (NO). In endothelium, the amino acid L-arginine is converted to L-citrulline and NO by one of the three NO synthases, the endothelial isoform (eNOS). Shear stress and cell proliferation appear to be, quantitatively, the two major regulatory factors of eNOS gene expression. However, eNOS seems to be mainly regulated by modulation of its activity. Stimulation of specific receptors to various agonists (e.g., bradykinin, serotonin, adenosine, ADP/ATP, histamine, thrombin) increases eNOS enzymatic activity at least in part through an increase in intracellular free Ca²⁺. However, the mechanical stimulus shear stress appears again to be the major stimulus of eNOS activity, although the precise mechanisms activating the enzyme remain to be elucidated. Phosphorylation and subcellular translocation (from plasmalemmal caveolae to the cytoskeleton or cytosol) are probably involved in these regulations. Although eNOS plays a major vasodilatory role in the control of vasomotion, it has not so far been demonstrated that a defect in endothelial NO production could be responsible for high blood pressure in humans. In contrast, a defect in endothelium-dependent vasodilation is known to be promoted by several risk factors (e.g., smoking, diabetes, hypercholesterolemia) and is also the consequence of atheroma (fatty streak infiltration of the neointima). Several mechanisms probably contribute to this decrease in NO bioavailability. Finally, a defect in NO generation contributes to the pathophysiology of pulmonary hypertension. Elucidation of the mechanisms of eNOS enzyme activity and NO bioavailability will contribute to our understanding the physiology of vasomotion and the pathophysiology of endothelial dysfunction, and could provide insights for new therapies, particularly in hypertension and atherosclerosis.     

Zinc,copper and selenium in reproduction

Of the nine biological trace elements, zinc, copper and selenium are important in reproduction in males and females. Zinc content is high in the adult testis, and the prostate has a higher concentration of zinc than any other organ of the body. Zinc deficiency first impairs angiotensin converting enzyme (ACE) activity, and this in turn leads to depletion of testosterone and inhibition of spermatogenesis. Defects in spermatozoa are frequently observed in the zinc-deficient rat. Zinc is thought to help to extend the functional life span of the ejaculated spermatozoa. Zinc deficiency in the female can lead to such problems as impaired synthesis/secretion-of (FSH) and (LH), abnormal ovarian development, disruption of the estrous cycle, frequent abortion, a prolonged gestation period, teratogenicity, still-births, difficulty in parturition, pre-eclampsia, toxemia and low birth weights of infants. The level of testosterone in the male has been suggested to play a role in the severity of copper deficiency. Copper-deficient female rats are protected against mortality due to copper deficiency, and the protection has been suggested to be provided by estrogens, since estrogens alter the subcellular distribution of copper in the liver and increase plasma copper levels by inducing ceruloplasmin synthesis. The selenium content of male gonads increases during pubertal maturation. Selenium is localized in the mitochondrial capsule protein (MCP) of the midpiece. Maximal incorporation in MCP occurs at steps 7 and 12 of spermatogenesis and uptake dereases by step 15. Selenium deficiency in females results in infertility, abortions and retention of the placenta. The newborns from a selenium-deficient mother suffer from muscular weakness, but the concentration of selenium during pregnancy does not have any effect on the weight of the baby or length of pregnancy. The selenium requirements of a pregnant and lactating mother are increased as a result of selenium transport to the fetus via the placenta and to the infant via breast milk.     

Antoni van Leeuwenhoek and measuring the invisible: The context of 16th and 17th century micrometry

This article explores the impact of 16th and 17th-century developments in micrometry on the methods Antoni van Leeuwenhoek employed to measure the microscopic creatures he discovered in various samples collected from his acquaintances and from local water sources. While other publications have presented Leeuwenhoek's measurement methods, an examination of the context of his techniques is missing. These previous measurement methods, driven by the need to improve navigation, surveying, astronomy, and ballistics, may have had an impact on Leeuwenhoek's methods. Leeuwenhoek was educated principally in the mercantile guild system in Amsterdam and Delft. He rose to positions of responsibility within Delft municipal government. These were the years that led up to his first investigations using the single-lens microscopes he became expert at creating, and that led to his first letter to the Royal Society in 1673. He also took measures to train in surveying and liquid assaying practices existing in his time, disciplines that were influenced by Pedro Nunes, Pierre Vernier, Rene Descartes, and others. While we may never know what inspired Leeuwenhoek's methods, the argument is presented that there were sufficient influences in his life to shape his approach to measuring the invisible.     

Genotypic variation in foraging responses to environmental stimuli by honey bees,Apis mellifera

We experimentally tested a model predicting that colony-level genotypic diversity contributes to colonylevel foraging flexibility in honey bees. We established a colony into which we placed individually marked workers from three genetically distinct groups. The colony was placed in an enclosure that contained feeding stations with pollen and sugar syrup. Foraging resources, stores of pollen and the quantity of brood within the colony were varied temporally. Individual foragers switched between resource types in response to changes in relative resource quality and colony need, demonstrating flexibility in resource choice at the individual level. However, genetic groups within the colony varied in their tendency to collect pollen versus nectar, and in lability of response to changes in foraging stimuli. Our data suggest that within-colony genotypic diversity contributes to a resilient foraging response to environmental variation.     

Circular proteoglycans from sponges: first members of the spongican family

Species-specific cell adhesion in marine sponges is mediated by a new family of modular proteoglycans whose general supramolecular structure resembles that of hyalectans. However, neither their protein nor their glycan moieties have significant sequence homology to other proteoglycans, despite having protein subunits equivalent to link proteins and to proteoglycan monomer core proteins, and glycan subunits equivalent to hyaluronan and to the glycosaminoglycans of hyalectans. In some species, these molecular components are assembled into a structure with a circular core formed by the link protein- and hyaluronan-like subunits. Besides their involvement in cell adhesion, these sponge proteoglycans, for which we propose the term spongicans, participate in signal transduction processes and are suspected to play a role in sponge self-nonself recognition. Their in vivo roles and the mild methods used to purify large amounts of functionally active spongicans make them ideal models to study the functions and possible new applications of proteoglycans in biomedical research. Received 21 May 2002; received after revision 5 July 2002; accepted 10 July 2002 RID="*" ID="*"Corresponding author.     

Herbivory in holometabolous and hemimetabolous insects: contrasts between Orthoptera and Lepidoptera

Summary Adaptation to a phytophagous diet involves physiological compromises that may be influenced by developmental constraints. In this review, we compare patterns of hostplant utilization with respect to nutrition and allelochemistry in representative holometabolous (lepidopteran) and hemimetabolous (orthopteran) species in order to identify those potential constraints. Overall in Lepidoptera greater molting efficiency and gut permeability, which enhance nutritional efficiency, result in higher exposure to allelochemicals and are associated with greater activity and inducibility of cytochrome P450 monoxygenase detoxication enzymes. In contrast, in Orthoptera, relative impermeability to allelochemicals due to the peritrophic membrane and cuticular sclerotization is associated with reduced nutritional efficiency and lower detoxication enzyme activity.     

Objectivity in confirmation: Post hoc monsters and novel predictions

The aim of this paper is to put in place some cornerstones in the foundations for an objective theory of confirmation by considering lessons from the failures of predictivism. Discussion begins with a widely accepted challenge, to find out what is needed in addition to the right kind of inferential–semantical relations between hypothesis and evidence to have a complete account of confirmation, one that gives a definitive answer to the question whether hypotheses branded as “post hoc monsters” can be confirmed. The predictivist view is then presented as a way to meet this challenge. Particular attention is paid to Worrall’s version of predictivism, as it appears to be the most sophisticated of the lot. It is argued that, despite its faults, his view turns our heads in the right direction by attempting to remove contingent considerations from confirmational matters. The demand to remove such considerations becomes the first of four cornerstones. Each cornerstone is put in place with the aim to steer clear of the sort of failures that plague various kinds of predictivism. In the process, it becomes obvious that the original challenge is wrongheaded and in need of revision. The paper ends with just such a revision.     

Spermatogenesis is extraordinarily accelerated in metamorphosis-arrested larvae of a salamander,Hynobius retardatus

Laboratory experiments were conducted to induce neoteny inHynobius retardatus, which had been reported to propagate in larval forms like axolotl. A large number of newly hatched larvae were reared in an aqueous solution of thiourea (TU) and sodium perchlorate (SPC) in order to arrest the metamorphosis. Gonadal development in the metamophosis-arrested larvae was compared with that in normally metamorphosing and metamorphosed controls. Metamorphosis-arrested male larvae produced morphologically mature spermatozoa approximately 4 months after hatching, when the gonads in the controls began to differentiate into testes, or to show the premeiotic proliferation of germ cells. Possible endocrine controls of these phenomena are discussed.     

The effects of environmental hormones on reproduction

Considerable attention has been given in the past few years to the possibility that man-made chemicals (xenobiotics) in the environment may pose a hazard to human reproductive health. The endocrine-disrupting effects of many xenobiotics can be interpreted as interference with the normal regulation of reproductive processes by steroid hormones. Evidence reviewed here indicates that xenobiotics bind to androgen and oestrogen receptors in target tissues, and to androgen-binding protein and to sex hormone-binding globulin. Although environmental chemicals have weak hormonal activity, their ability to interact with more than one steroid-sensitive pathway provides a mechanism by which their hazardous nature can be augmented. A given toxicant may be present in low concentration in the environment and, therefore, harmless. However, we are not exposed to one toxicant at a time, but, rather, to all of the xenobiotics present in the environment. Therefore, numerous potential agonists/antagonists working together through several steroid-dependent signalling pathways could prove to be hazardous to human reproductive health. Received 25 March 1998; received after revision 15 June 1998; accepted 15 June 1998     

Prediction in context: On the comparative epistemic merit of predictive success

The considerations set out in the paper are intended to suggest that in practical contexts predictive power does not play the outstanding roles sometimes accredited to it in an epistemic framework. Rather, predictive power is part of a network of other merits and achievements. Predictive power needs to be judged differently according to the specific conditions that apply. First, predictions need to be part of an explanatory framework if they are supposed to guide actions reliably. Second, in scientific expertise, the demand for accurate predictions is replaced with the objective of specifying a robust corridor of estimates. Finally, it is highly uncertain to predict the success of research projects. The overall purpose of the paper is to enlarge the debate about predictions by addressing specifically the roles of predictions in application-oriented research.     

The dynamics of reason and its elusive object in Kant, Fichte and Schelling

Kant used transcendental reflection to distinguish in judgment what belongs to its form and what to its material. Regarding the form of judgment, Buchdahl’s work highlights the analogies between the different levels of judgment in Kant’s transcendental ontology. He uses the explicit contingency of judgments of the system of nature to illuminate the contingency of judgments of objects in general. In the Critique of pure reason, Kant had left much of the work of judgment to the unconscious imagination. Fichte and Schelling attempted to make conscious and determinate the work of the unconscious imagination, but found themselves unable to avoid a reflexive regress in trying to objectify and provide a foundation for the activity of the self in judgment. Buchdahl also clarifies the role Kant gave to the object in judgment, as the indeterminate ‘thinghood’ remaining once all forms of cognition are abstracted. Fichte represented this objective side of consciousness as the not-I, as the limit of the activity of the I, as an unconscious, alien element within consciousness. Schelling struggled to illuminate this unconscious object in judgment, to provide a construction of nature, without dissolving its positive presence into abstract formulations. In pursuing relentlessly Kant’s critique of judgment, Fichte and Schelling exposed its opaque points and problematized the ambition to build a complete system of philosophy.     

The methodological defense of realism scrutinized

I revisit an older defense of scientific realism, the methodological defense, a defense developed by both Popper and Feyerabend. The methodological defense of realism concerns the attitude of scientists, not philosophers of science. The methodological defense is as follows: a commitment to realism leads scientists to pursue the truth, which in turn is apt to put them in a better position to get at the truth. In contrast, anti-realists lack the tenacity required to develop a theory to its fullest. As a consequence, they are less likely to get at the truth.My aim is to show that the methodological defense is flawed. I argue that a commitment to realism does not always benefit science, and that there is reason to believe that a research community with both realists and anti-realists in it may be better suited to advancing science. A case study of the Copernican Revolution in astronomy supports this claim.     

Re-situating fieldwork and re-narrating disciplinary history in global mega-geomorphology

In 1985, more than thirty geomorphologists, planetary scientists, and remote sensing specialists gathered at a conference center in Oracle, Arizona, to discuss an emerging area of research that they called “mega-geomorphology.” Building on a conference of the same name held in London in 1981, they argued that new techniques of remote sensing and insights emerging from the study of extraterrestrial planets had created opportunities for geomorphology to broaden its spatial and temporal scope. This new approach was, however, neither unproblematic nor uncontested. In the discussions around mega-geomorphology that took place in the mid-1980s, the perceived conflict between the use of remote-sensing techniques to observe phenomena on vast spatial scales, on one hand, and the disciplinary centrality of fieldwork and field experience to geomorphology, on the other, was a recurrent theme. In response, mega-geomorphologists attempted to re-situate fieldwork and re-narrate disciplinary histories in such a way as to make remote sensing and planetary science not only compatible with geomorphological traditions but also means of revitalizing them. Only partially successful, these attempts reveal that the process of adopting a planetary perspective in geomorphology, as in other earth sciences, was neither straightforward nor inevitable. They also show how the field and fieldwork could remain central to geomorphology while also being extensively revised in light of new technical possibilities and theoretical frameworks.     

Arsenite transport in plants

Arsenic is a metalloid which is toxic to living organisms. Natural occurrence of arsenic and human activities have led to widespread contamination in many areas of the world, exposing a large section of the human population to potential arsenic poisoning. Arsenic intake can occur through consumption of contaminated crops and it is therefore important to understand the mechanisms of transport, metabolism and tolerance that plants display in response to arsenic. Plants are mainly exposed to the inorganic forms of arsenic, arsenate and arsenite. Recently, significant progress has been made in the identification and characterisation of proteins responsible for movement of arsenite into and within plants. Aquaporins of the NIP (nodulin26-like intrinsic protein) subfamily were shown to transport arsenite in planta and in heterologous systems. In this review, we will evaluate the implications of these new findings and assess how this may help in developing safer and more tolerant crops.     

Adenine nucleotide metabolism during anoxia and postanoxic recovery in insects

Severe hypoxia (anoxia), if maintained for more than a few minutes, causes irreversible damage in humans and other mammals. Why mammals are so vulnerable to anoxia is not fully understood. It is therefore of interest to study animals that are more tolerant of anoxia in order to identify physiological and metabolic properties that are correlated with a high tolerance of anoxia. Insects have high metabolic rates and their energy metabolism is dependent on aerobic ATP production. In insects, as in mammals, anoxia causes a rapid breakdown of physiological function, resulting in a state similar to rigor mortis. This is accompanied by a precipitous decrease in metabolic rate. In contrast to mammals, however, insects can survive anoxia for many hours and recover spontaneously and completely when air is again available. We have followed the metabolism of adenine nucleotides in locust tissues (mainly in the flight muscle) over 3 h of anoxia and during recovery from 1 h of anoxia. The content of ATP in the flight muscle dropped to 1% of normal during 2 h of anoxia. The main product was AMP which increased in content more than 20-fold. Some of the AMP was deaminated to IMP and this was further dephosphorylated to inosine. Altogether less than 30% of the total adenine nucleotides were degraded during 3 h of anoxia and this may contribute to the amazing ability of insects to recover from prolonged anoxia.