Summary We describe the use of lectins as specific stabilizing agents for the polysaccharide capsular components of two Gram-positive bacteria,Streptococcus agalactiae andStreptococcus bovis. Treatment of bacterial suspensions with wheatgerm agglutinin and concanavalin A allowed better morphological preservation as well as immunoelectron microscopic localization of a capsular component (lipoteichoic acid) by employing specific antibodies and the protein A-gold technique. Data obtained indicate that lectins are useful agents in preserving highly water-soluble capsular components during the electron microscopy procedures for both unembedded and embedded samples. 相似文献
A statistical analysis was performed on the data resulting from an international collaborative study of the Ames test according to a standardized experimental protocol, which involved the comparative testing of 4NQO (4 doses), in 3 separate experiments for each of the 38 participating laboratories, by using a common reference (R) culture and in-house laboratory (L) cultures of 5 strains of S. typhimurium. Despite some toxicity phenomena recorded at the highest dose of 4NQO, the majority of the dose-response curves in individual laboratories were linear on a bi-log scale and their mean values fitted a linear regression framework. Scattering of data around mean values of laboratories was Gaussian-like even at the highest dose of 4NQO, toxic effects being expressed as a dose-related increase of variance. A weighted least-square analysis could therefore take into account toxic effects without resorting to a sophisticated non-linear model incompatible with log transformation. Various analytical approaches--e.g. the weighted estimates of linear regression parameters, a multifactor (laboratory, experiment, dose, culture of each strain) analysis of variance with all the possible interactions, the assessment of correlations in individual laboratories and of coefficients of variation for induced and spontaneous mutability--could detect some statistically significant differences between L and R cultures. However, at a critical evaluation on an individual basis, only few of these differences, without any peculiar involvement of given strains, were convincing in view of the existence of real phenomena of genetic drift. Therefore, on the whole, the genetic drift of Salmonella tester strains appears to lend a negligible contribution to the considerable inter- and intra-laboratory variability detected in this study. With a background variability between replications averaging 26%, a dose-related variability was evident both between experiments (28-54%) and between laboratories (44-127%). 相似文献
Exosomes are nanovesicles released by normal and tumor cells, which are detectable in cell culture supernatant and human biological fluids, such as plasma. Functions of exosomes released by "normal" cells are not well understood. In fact, several studies have been carried out on exosomes derived from hematopoietic cells, but very little is known about NK cell exosomes, despite the importance of these cells in innate and adaptive immunity. In this paper, we report that resting and activated NK cells, freshly isolated from blood of healthy donors, release exosomes expressing typical protein markers of NK cells and containing killer proteins (i.e., Fas ligand and perforin molecules). These nanovesicles display cytotoxic activity against several tumor cell lines and activated, but not resting, immune cells. We also show that NK-derived exosomes undergo uptake by tumor target cells but not by resting PBMC. Exosomes purified from plasma of healthy donors express NK cell markers, including CD56(+) and perforin, and exert cytotoxic activity against different human tumor target cells and activated immune cells as well. The results of this study propose an important role of NK cell-derived exosomes in immune surveillance and homeostasis. Moreover, this study supports the use of exosomes as an almost perfect example of biomimetic nanovesicles possibly useful in future therapeutic approaches against various diseases, including tumors. 相似文献
When modeling infectious diseases, it is common to assume that infection-derived immunity is either (1) non-existent or (2) perfect and lifelong. However there are many diseases in which infection-derived immunity is known to be present but imperfect. There are various ways in which infection-derived immunity can fail, which can ultimately impact the probability that an individual be reinfected by the same pathogen, as well as the long-run population-level prevalence of the pathogen. Here we discuss seven different models of imperfect infection-derived immunity, including waning, leaky and all-or-nothing immunity. For each model we derive the probability that an infected individual becomes reinfected during their lifetime, given that the system is at endemic equilibrium. This can be thought of as the impact that each of these infection-derived immunity failures have on reinfection. This measure is useful because it provides us with a way to compare different modes of failure of infection-derived immunity.
AbstractThe paper aims to evaluate the effects caused by a Mandibular Advancement Device (MAD) for Obstructive Sleep Apnoea Syndrome (OSAS) treatment. This study is based on Finite Element Method (FEM) for evaluating the load distribution on temporomandibular joint, especially on the mandibular condyle and disc, and on periodontal ligaments. The stress values on condyle and periodontal ligaments lead authors to consider MAD a safe procedure even for a long period. The obtained results also show the relationship between MAD material and load distribution at the periodontal ligaments. The paper is a step toward future analyses for studying and comparing the effects of MAD features, such as material, shape and dimensions, in order to allow the clinician prescribing the most fitting device. 相似文献
Quantitative information on population size, structure and dynamics are urgently needed for assessing species extinction risk and developing monitoring measures, especially for beetles belonging to the threatened guild of saproxylic organisms. Here freshly cut log piles (FCLP) were tested for the monitoring of the longhorn beetle Morimus asper (Sulzer, 1776) (Coleoptera: Cerambycidae). Novel mathematical models based on presence–absence or count data were compared with the most commonly used capture–recapture methods to investigate if less invasive and easier approaches may be suitable for large-scale monitoring of this species and other large saproxylic beetles. The use of FCLP as bait was reliable to detect the presence and abundance of M. asper, and capture events were not influenced by the phenomena of trap-happiness or trap-shyness. In order to obtain accurate presence–absence estimates of M. asper at a reasonable cost piles of at least 0.25 m3 are suggested. Models which take into account the abundance of the species without marking individuals were the best compromise between costs and accuracy of estimation. Therefore, a reliable assessment of the population size of M. asper, can be based on count data without marking individuals. Because FCLP attract adults of M. asper and other saproxylic beetles, they could act also as potential ecological traps if chipped and/or removed after the sampling season. Therefore, if FCLP are used in monitoring as a part of conservation programmes, the piles should be left until completely decayed. 相似文献
Adjuvant chemotherapy (AC) in Stage II Colon Cancer (CC) is still under debate. Choice should be based on patients and disease characteristics. According to guidelines AC should be considered in high-risk T3N0 patients. No data are available for better option in low-risk patients. The aim of the study is to retrospectively evaluate relapse-free survival (RFS) and disease-free survival (DFS) according to treatment received in T3N0 CC.
Methods
RFS and DFS are evaluated with Kaplan-Meier method. Multivariate Cox proportional hazard model was developed using stepwise regression, enter limit and remove limit were p = 0.10 and p = 0.15, respectively.
Results
834 patients with T3N0 CC were recruited. Median age was 69 (29–93), M/F 463/371, 335 low-risk patients (40.2%), 387 high-risk (46.4%), 112 unknown (13.4%); 127 (15.2%) patients showed symptoms at diagnosis. Median sampled lymph nodes were 15 (1–76); 353 (42.3%) patients were treated with AC. Median follow up was 5 years (range 3–24). The 5-years RFS was 78.4% and the 5-years DFS was 76.7%. At multivariate analysis symptoms, lymph nodes, and adjuvant chemotherapy were prognostic factors for RFS. AC is prognostic factor for all endpoints.In low-risk group 5-years RFS was 87.3% in treated patients and 74.7% in non-treated patients (p 0.03); in high-risk group was respectively 82.7% and 71.4% (p 0.005).
Conclusions
Data confirmed the role of known prognostic factors and suggest the relevance of adjuvant chemotherapy also in low-risk stage II T3N0 CC patients. However, the highest risk in low-risk subgroup should be identified to be submitted to AC. 相似文献
The most pervasive macroecological patterns concern (1) the frequency distribution of range size, (2) the relationship between range size and species abundance and (3) the effect of body size on range size. We investigated these patterns at a regional scale using the tenebrionid beetles of Latium (Central Italy). For this, we calculated geographical range size (no. of 10‐km square cells), ecological tolerance (no. of phytoclimatic units) and abundance (no. of sampled individuals) using a large database containing 3561 georeferenced records for 84 native species. For each species, we also calculated body mass and its ‘phylogenetic diversity’ on the basis of cladistic relationships. Frequency distribution of range size followed a log‐normal distribution as found in many other animal groups. However, a log‐normal distribution accommodated well the frequency distribution of ecological tolerance, a so far unexplored issue. Range size was correlated with abundance and ecological tolerance, thus supporting the hypothesis that a positive correlation between distribution and abundance is a reflection of interspecific differences in ecological specialization. Larger species tended to have larger ranges and broader ecological tolerance. However, contrary to what known in most vertebrates, not only small‐sized, but also many medium‐to‐large‐sized species exhibited great variability in their range size, probably because tenebrionids are not so strictly influenced by body size constraints (e.g. home ranges) as vertebrates. Moreover, in contrast to other animals, tenebrionid body size does not influence species abundances, probably because these detritivorous animals are not strongly regulated by competition. Finally, contrary to the assumption that rare species should be mainly found among lineages that split from basal nodes, rarity of a tenebrionid species was not influenced by the phylogenetic position of its tribe. However, lineages that split from more basal nodes had lower variability in terms of species geographical distribution, ecological tolerance and abundance, which suggests that lineages that split from more basal nodes are not only morphologically conservative but also tend to have an ecological ‘inertia’. 相似文献