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The evolution of the aging process has long been a biological riddle, because it is difficult to explain the evolution of a trait that has apparently no benefit to the individual. Over 60 years ago, Medawar realized that the force of natural selection declines with chronological age because of unavoidable environmental risks. This forms the basis of the mainstream view that aging arises as a consequence of a declining selection pressure to maintain the physiological functioning of living beings forever. Over recent years, however, a number of articles have appeared that nevertheless propose the existence of specific aging genes; that is, that the aging process is genetically programmed. If this view were correct, it would have serious implications for experiments to understand and postpone aging. Therefore, we studied in detail various specific proposals why aging should be programmed. We find that not a single one withstands close scrutiny of its assumptions or simulation results. Nonprogrammed aging theories based on the insight of Medawar (as further developed by Hamilton and Charlesworth) are still the best explanation for the evolution of the aging process. We hope that this analysis helps to clarify the problems associated with the idea of programmed aging.  相似文献   

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This literature search investigates the amount of fluid that a healthy elderly person drinks if he is able to drink according to his needs. The answer to this physiological question may be used by clinicians if they make decisions about how much fluid they need to administer to their patients. The literature that offered an answer to this question was limited. The total number of patients that were examined, however, was high (2866). It appeared that healthy elderly people drink approximately 2100 ml. of fluid per day. This is (probably) no less than the average fluid intake of young adults. Clinicians often think that healthy elderly persons drink less than healthy young adults. However, there is no evidence to be found in the literature to support this opinion. The tendency to underestimate the fluid intake level of elderly patients should be taken into account when determining the quantity of fluid that should be administered to an individual patient.  相似文献   

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Vegetation History and Archaeobotany - The online Archaeobotanical Literature Database (ArchbotLit) is an important tool for getting targeted access to archaeobotanical publications. It offers the...  相似文献   

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Background  

High-throughput genomic research tools are becoming standard in the biologist's toolbox. After processing the genomic data with one of the many available statistical algorithms to identify statistically significant genes, these genes need to be further analyzed for biological significance in light of all the existing knowledge. Literature mining – the process of representing literature data in a fashion that is easy to relate to genomic data – is one solution to this problem.  相似文献   

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Chronomedicine may be conceptualized as dealing with the prevention, causation, diagnosis, and treatment of diseases in humans with a particular focus on the role "time" [Greek: chrónos] plays in our physiology, endocrinology, metabolism and behavior at many organizational levels. While it has been used as a term and somewhat pursued as a discipline for decades, it appears that chronomedicine has captured a broader interest as a promising specialty only more recently. This commentary addresses roots of chronomedicine in the 1900s and perspectives for chronomedicine in the 21st century. Classical terms of chronobiology, e.g., Zeitgeber, melatonin and circadian, may be traced back to Aschoff, Lerner, and Halberg, respectively, but who actually coined the term "chronomedicine" and used it first in a publication remains unclear. Importantly, it could be(come) rather straightforward to transfer abundant insights gained from chronobiology to strategies in chronomedicine as animal models have been increasingly developed to understand human health and disease. Perspectively, chronomedicine should comprise "clinical chronomedicine" (individual-based) and "preventive chronomedicine" (population-based). Overall, due to the "maturing" of chronomedicine as a field, the near future might bring a section dedicated to chronomedicine in existing journals, or even a "Journal of Chronomedicine" as vectors of ideas and research.  相似文献   

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Proprotein convertase subtilisin kexin like type 9 (PCSK9) has since its discovery been a key protein target for the modulation of LDL cholesterol. The interest in PCSK9 has grown even more with the positive clinical trial outcomes in cardiovascular disease recently reported for two PCSK9 antibodies. Currently, there are no PCSK9 small molecule programs active in clinical development. However, there has been a steady increase in publications and patent applications within the PCSK9 small molecule field. This digest will provide a summary of small molecule and peptide PCSK9 modulators reported both in scientific journals and in patent applications, most of them originating from the last 3–4?years. As such, this digest will serve as an introduction to the field and assist further identification and discovery of small molecule PCSK9 modulators.  相似文献   

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The recognition of biomedical concepts in natural text (named entity recognition, NER) is a key technology for automatic or semi-automatic analysis of textual resources. Precise NER tools are a prerequisite for many applications working on text, such as information retrieval, information extraction or document classification. Over the past years, the problem has achieved considerable attention in the bioinformatics community and experience has shown that NER in the life sciences is a rather difficult problem. Several systems and algorithms have been devised and implemented. In this paper, the problems and resources in NER research are described, the principal algorithms underlying most systems sketched, and the current state-of-the-art in the field surveyed.  相似文献   

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Background

We reported a case of an adult that presented Guillain-Barré syndrome (GBS) after bacterial meningitis which was secondary to chronic suppurative otitis media (CSOM). To our knowledge, this is the first case involving an adult presenting with GBS following bacterial meningitis.

Case presentation

A 46-year man with type 2 diabetes and otitis media (OM) suffered with fever, headache, and vomiting for 6?days. The patient’s neck stiffness was obvious and the Kernig and Brudzinski signs were produced. The result of cerebrospinal fluid (CSF) analysis and cytological examination of the CSF supported the diagnose of bacterial meningitis. On day 17 the patient felt numbness in both hands and feet, which gradually progressed to weakness of the limbs. Bladder dysfunction occurred, which required catheterization. The patient showed a tetraparesis with emphasis on the legs. The deep tendon reflexes of limbs were absent. The patient had peripheral hypalgesia and deep sensory dysfunction. The symptoms were possibly a result of GBS. Nerve conduction study showed that the F wave latency of the upper and lower limbs was prolonged, particularly the lower limbs. 8?days later the repeated nerve conduction study showed a low compound muscle action potential (3.3?mV) with a normal distal motor latency (14.2?ms) and a low motor nerve conduction velocity (34.3?m/s) in the tibial nerve. The patient still required assistance when walking 3 months after onset.

Conclusions

GBS following bacterial meningitis is rare and limbs weakness in patients with bacterial meningitis was usually considered because of weakness. This case should serve as a reminder for clinical doctors that when a patient with bacterial meningitis complains about limbs numbness or weakness, GBS should be considered, especially when the patient had diabetes mellitus (DM) history.
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European Tissue Banks should carry out a physical examination as a part of the donor selection procedure. This is one of the obligations concerning donation and procurement mentioned in the European Commission directives on tissue banking. As the directives do not give any further specification on the content or on the procedure of the physical examination, a search of literature was done in order to find more information. Although data in literature generally remain quite vague, it was possible to set up a list of items which should be looked at during physical examination. This list can be used temporarily until further information is gathered from an international survey and from a risk assessment analysis.  相似文献   

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Background

Congenital malformations of the seminal vesicle are uncommon, and most of them are cystic malformations. If an insult occurs between the 4th and the 13 h gestational week, the embryogenesis of the kidney, ureter, seminal vesicle, and vas deferens could be altered. Cysts of the seminal vesicle may appear with a mass effect, dysuria, epididymitis, or obstruction of the gastrointestinal and genitourinary tracts. Approximately two thirds of them are associated with ipsilateral renal agenesis, because both the ureteral buds and seminal vesicles originate from the mesonephric (Wolffian) duct. They were first described by Zinner in 1914, and 200 cases of seminal vesicle cysts associated with ipsilateral renal agenesis have been reported in the literature. Most patients with this anomaly are asymptomatic until the third or fourth decade of life. Some cases have nonspecific symptoms such as prostatism, urinary urgency, dysuria, painful ejaculation, and perineal discomfort. Transrectal ultrasonography provides good visualization of the pelvic structures and allows guidance for aspiration of the cysts.

Case presentation

We present two cases of seminal vesicle cyst. The first patient had dysuria, increased frequency of urination, and haematuria. He was operated and benefited from a removal of the cyst with right ureterectomy and left ureteral reimplantation. The second patient had disorder of the digestive transit and he benefited from a laparoscopic removal of the cyst.

Conclusions

Seminal vesicle cysts combined with ipsilateral renal agenesis are rare urological anomalies. Usual symptoms that are caused by the seminal vesicle cysts are bladder irritation and obstruction as well as pain in the perineum and scrotum. Epididymitis is frequently found. Treatment consists to removing the seminal vesicle cyst.
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BACKGROUND: Primary central mucoepidermoid carcinoma of jaws is a rare lesion comprising 2-3% of all mucoepidermoid carcinomas reported in literature. CASE PRESENTATION: The case presented here illustrates the hypothesis that its specific pathogenesis is unknown. CONCLUSIONS: Mucoepidermoid carcinoma of the jaw is a rare tumour of unknown aetiology. Although about a 100 cases has been reported in literature, the speculation on its aetiopathogenesis has mainly centred on the pluripotential capabilities of the epithelial lining of odontogenic cysts.  相似文献   

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Purpose

The Social Life Cycle Assessment guidelines (UNEP-SETAC 2009) distinguish two different SLCA approaches, type I and type II. Few comprehensive and analytical reviews have been undertaken to examine the multiplicity of approaches that have been developed within type I SLCA. This paper takes on the task of exploring the evaluation methods used in type I SLCA methods.

Methods

In order to tackle this work, a critical literature review was undertaken, covering a total of 32 reviewed articles, ranging from 2006 to 2015. Those articles have been selected for they make explicit reference to type I, performance reference points (PRPs), corporate behavior assessment, and social performance assessment or if their assessment methods generated a result located at the same point as the inventory data, with regards to the impact pathway. The selected articles were analyzed with a focus on the inventory data used, the aggregation of inventory data on the functional unit, and the type of characterization and weighting methods used. This analysis allowed to make explicit the often implicit logic underlying the evaluation methods and to identify the common denominators of type I SLCA.

Results and discussion

The analysis highlighted the multiplicity of approaches that are comprised within type I SLCA today, both in terms of the data collected (in particular, its positioning along the impact pathway); the presence of some optional steps, such as the scaling of inventory data on the functional unit (FU); and in terms of the different characterization and weighting steps. With regards to data collection, this review has highlighted that the furthest indicators are positioned along the impact pathway, the hardest it is to justify the link between them and the activities of companies in the product system. The analysis also suggested that an important differentiating factor among type I SLCA methods lies in “what the inventory data is assessed against” at the characterization step and how it is ultimately weighted. To illustrate this, a typology of six characterization methods and five types of weighting methods was presented.

Conclusions

It is interesting to identify which approaches are most appropriate to respond to the various questions that SLCA aims to respond to. A question that arises is what approaches are most likely to tell us anything about the impact of a product system on social well-being? This question is particularly relevant in the absence of well-documented impact pathways between activities within product systems and impact on social well-being.
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Background

Spinal fusion surgery is currently recommended when curve magnitude exceeds 40–45 degrees. Early attempts at spinal fusion surgery which were aimed to leave the patients with a mild residual deformity, failed to meet such expectations. These aims have since been revised to the more modest goals of preventing progression, restoring 'acceptability' of the clinical deformity and reducing curvature. In view of the fact that there is no evidence that health related signs and symptoms of scoliosis can be altered by spinal fusion in the long-term, a clear medical indication for this treatment cannot be derived. Knowledge concerning the rate of complications of scoliosis surgery may enable us to establish a cost/benefit relation of this intervention and to improve the standard of the information and advice given to patients. It is also hoped that this study will help to answer questions in relation to the limiting choice between the risks of surgery and the "wait and see – observation only until surgery might be recommended", strategy widely used. The purpose of this review is to present the actual data available on the rate of complications in scoliosis surgery.

Materials and methods

Search strategy for identification of studies; Pub Med and the SOSORT scoliosis library, limited to English language and bibliographies of all reviewed articles. The search strategy included the terms; 'scoliosis'; 'rate of complications'; 'spine surgery'; 'scoliosis surgery'; 'spondylodesis'; 'spinal instrumentation' and 'spine fusion'.

Results

The electronic search carried out on the 1st February 2008 with the key words "scoliosis", "surgery", "complications" revealed 2590 titles, which not necessarily attributed to our quest for the term "rate of complications". 287 titles were found when the term "rate of complications" was used as a key word. Rates of complication varied between 0 and 89% depending on the aetiology of the entity investigated. Long-term rates of complications have not yet been reported upon.

Conclusion

Scoliosis surgery has a varying but high rate of complications. A medical indication for this treatment cannot be established in view of the lack of evidence. The rate of complications may even be higher than reported. Long-term risks of scoliosis surgery have not yet been reported upon in research. Mandatory reporting for all spinal implants in a standardized way using a spreadsheet list of all recognised complications to reveal a 2-year, 5-year, 10-year and 20-year rate of complications should be established. Trials with untreated control groups in the field of scoliosis raise ethical issues, as the control group could be exposed to the risks of undergoing such surgery.  相似文献   

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Environmental flow releases are a tool for wetland restoration, but there has been no systematic evaluation of their success. We systematically assessed 102 published studies from a wide range of wetland ecosystems across the globe to determine whether releasing environmental flows could maintain or promote biodiversity and increase ecosystem services, and which strategies were most effective. We found that environmental flow releases remarkably increased regulating services (sediment regulation and water purification) and supporting services (primary production and habitat maintenance), and maintained biodiversity and provisioning services. Biodiversity responses were positive only in river wetlands, and were negative in coastal, lake, and marsh wetlands; the overall delivery of ecosystem services responded positively in all ecosystem types except artificial wetlands. The effects were positive for ecosystem services under all environmental flow regimes, and seasonal minimum flow releases could maintain biodiversity and improve ecosystem services. We also found that long‐term environmental flow releases (years to decades) maintained biodiversity. Values of a change‐in‐flow parameter (D) ranging from 0 to 10% improved both biodiversity and ecosystem services. In summary, long‐term implementation, a high‐flow regime, and D ranging from 0 to 10% for the environmental flows promoted biodiversity and improved ecosystem services around the world, particularly in river wetlands. Regional‐level conclusions might be applicable to guide the implementation of environmental flow releases, but small sample sizes reduce their reliability. We also found that the effect sizes of environmental flow release projects for biodiversity and ecosystem services were significantly and positively correlated in rivers, but not in other wetlands.  相似文献   

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