保护胰岛β细胞的体外研究进展

糖尿病是一种由胰岛素分泌缺陷和（或）胰岛素作用缺陷引起的高血糖症性代谢疾病。自Edmonton临床试验取得成功后,胰岛移植成为一种新型治愈糖尿病的方法。但胰岛β细胞在体外分离过程中极易发生凋亡或死亡,且长期的体外培养或冷冻储存也容易令其胰岛素分泌功能逐渐丧失。因此,有效维持或改善β细胞的成活率及功能对胰岛移植的成功至关重要。对胰岛β细胞的体外保护方法进行阐述,并对其研究前景进行展望。     

Endophytic Colonisation of Opium Poppy, Papaver somniferum, by an Entomopathogenic Beauveria bassiana Strain

Beauveria bassiana strain EABb 04/01-Tip isolated from stem-borer larvae of Timaspis papaveris (Hymenoptera: Cynipidae), a serious pest of opium poppy in Spain, was shown to be able to become established endophytically in this pharmaceutical crop. Microbiological, molecular and light and electron microscopic methods were used to study fungal colonisation and to describe its mode of penetration. After inoculation with a foliar spray of conidia, microbiological methods showed 100% of plants examined 24, 48, 72 and 144 h after treatment to be colonised endophytically by the fungus, although the percentage of previously surface sterilised leaf pieces showing fungal growth was 100% at 24 and 48 h, and 80 and 75% at 72 and 144 h after treatment, respectively. The fungus was also observed in leaf pieces obtained from newly formed leaves, indicating that it could spread from treated leaves to leaves formed after fungal application. For molecular studies, a polymerase chain reaction (PCR) protocol was used to amplify the ITS1-5.8S-ITS2 regions of the rDNA of the plant and the fungus. This procedure allowed the detection of the fungus on the surface of the leaves and also endophytically, but only at 72 h after treatment. A nucleotide BLAST search revealed that the ITS1-5.8S-ITS2 sequence of strain EABb 04/01-Tip showed 100% homology with a similar sequence from Cordyceps bassiana. SEM images revealed that although numerous conidia were observed on the leaf surface, few germinated and penetrated. Intracellular colonisation by B. bassiana was not observed, but hyphae were detected growing into the xylem vessels. The fungus was found to colonise 40.5 ± 4.3% of seedlings (with two cotyledons and the two first real leaves) from seeds dressed with a fungal spore suspension. These results may have implications in the biological control of T. papaveris, including the possible systemic protection of the plant against this cynipid.     

Experimental tests of the role of predation in the population dynamics of voles and lemmings

• 1 Reasons for fluctuating populations of small mammals have been intensively investigated since the early days of modern ecology. Particular interest has been taken in vole populations exhibiting multiannual oscillations. Much empirical and theoretical work has been accomplished to find out the key factor(s) driving these population cycles and many reviews have been written about the results.
• 2 One of the most plausible processes for explaining regular fluctuations in small mammals is predation. Here I review the existing literature on the experimental studies of the role of predation in vole population dynamics in the hope that a critical examination of these studies will help researchers improve the design of future experiments.
• 3 Most predation manipulations have been done in exclosures, but there are also studies that have attempted to reduce or increase predator numbers in non‐fenced areas, islands and enclosures.
• 4 As the number of experimental studies has increased, their quality in terms of replication, use of controls and realistic spatial and temporal scales has also improved.
• 5 Most studies have found population‐level effects of predator manipulations on prey populations. The effects have varied from very weak to very strong, reflecting dissimilar experimental designs and the great variety of predator–prey interactions among different kinds of species in different landscapes. Most of these studies show that predation limits population growth of voles, and in some circumstances even regulate vole population fluctuations, but none of them clearly demonstrates that predation consistently changes fluctuation patterns of voles.
• 6 To be able to assess more reliably the true role of predation on (cyclic) population fluctuations of voles, more competent experiments are still needed not only over the geographical range of cyclic population dynamics, but also in areas of weakly or non‐cyclic populations of voles.

     

Does low nutritional quality act as a plant defence? An experimental test of the slow‐growth,high‐mortality hypothesis

Abstract.  1. The slow-growth, high-mortality hypothesis was experimentally tested in this study by investigating the effects of plant quality and natural enemies on leaf-miner growth, performance, and survivorship. Two leaf miners ( Acrocercops albinatella and Brachys tesselatus ) occurring on the turkey oak Quercus laevis were studied using a factorial design that manipulated predation/parasitism pressure and plant nutritional quality.
2. Forty trees were randomly divided into four treatments: (1) control plants (nutrients and natural enemies unaltered); (2) nutrients added, natural enemies unaltered; (3) nutrients unaltered, natural enemies reduced; and (4) nutrients added and natural enemies reduced. Water content, leaf toughness, tannin concentration, and foliar nitrogen were quantified monthly for each plant, and mine growth and survivorship were assessed by tracing mines on a 2–3-day interval and by following the fates of 50 mines per species per treatment combination.
3. Fertilised plants exhibited significantly higher amounts of nitrogen, but no significant differences among treatments were observed for water content, leaf toughness, and tannin concentration. These results only partially support the slow-growth, high-mortality hypothesis, as mines were significantly smaller and developed faster on fertilised plants, but neither fertilisation nor natural enemy exclusion significantly affected mine survivorship or mortality caused by natural enemies.     

Females competing to reproduce: dominance matters but testosterone may not

The associations among aggression, testosterone (T), and reproductive success have been well studied, particularly in male birds. In many species, males challenged with simulated or real territorial intrusions increase T and levels of aggression, outcomes linked to higher dominance status and greater reproductive success. For females, the patterns are less clear. Females behave aggressively towards one another, and in some species, females respond to a social challenge with increases in T, but in other species they do not. Prior work on female dark-eyed juncos (Junco hyemalis) had shown that experimental elevation of T increases social status and intrasexual aggression. Here, we conducted two experiments designed to answer three questions: Are endogenous concentrations of T associated with dominance status in captive female juncos? Does dominance status influence readiness to breed in female juncos? And do captive females increase T in response to a challenge? In the first experiment, we introduced two females to a breeding aviary, allowed them to form a dominance relationship and then introduced a male. We found that dominant females were more likely to breed than subordinates, but that dominance status was not predicted by circulating T. In the second experiment, we allowed a resident male and female to establish ownership of a breeding aviary (territory) then introduced a second, intruder female. We found that resident females were aggressive towards and dominant over intruders, but T did not increase during aggressive interactions. We suggest that during the breeding season, intrasexual aggression between females may influence reproductive success, but not be dependent upon fluctuations in T. Selection may have favored independence of aggression from T because high concentrations of T could interfere with normal ovulation or produce detrimental maternal effects.     

Effects of social status, age, and season on androgen and cortisol levels in wild male golden lion tamarins (Leontopithecus rosalia)

This study examines factors affecting androgen and cortisol levels in wild, male golden lion tamarins (Leontopithecus rosalia). Golden lion tamarins are a cooperatively breeding species in which groups often contain two potentially breeding males. Brothers frequently emigrate together and develop a clear dominance hierarchy, but interactions between them are primarily affiliative. Duos in which the males are not related are less stable. In addition, reproductive skew theory predicts that dominant males will be less likely to share reproduction with related subordinates. As such, we predicted that both androgens and cortisol would be higher in subordinate males unrelated to the dominant male. We also predicted that androgens in breeding males would be higher during the mating season than the birth/infant care season, as per Wingfield's "challenge hypothesis" (1990). Fecal samples were collected from 24 males in 14 social groups and assayed by enzyme immunoassay. Androgen levels were higher in breeding males during the mating season, thus supporting the challenge hypothesis. However, while subordinate males unrelated to the dominant male had significantly lower androgens than any other group, cortisol levels were not correspondingly higher. These results suggest that unrelated subordinate males show measurable reproductive suppression and may use strategies such as infantilization to avert aggression from dominant males.     

Testosterone levels of free-ranging resident mantled howler monkey males in relation to the number and density of solitary males: a test of the challenge hypothesis

The challenge hypothesis asserts that testosterone levels and aggression in male adult animals are closely associated with one another in the context of intense reproductive competition, particularly when males challenge one another for the access to females. For mantled howler monkeys (Alouatta palliata), the presence of a solitary male in the vicinity of a social group can be considered a threat for the reproductive success of the resident males, as group takeovers by solitary males are followed by a reestablishment of the access to females among group males and sometimes by infanticide. Therefore, these episodes should be accompanied by an increase in testosterone secretion according to the challenge hypothesis. In order to test our prediction, we relate different group and subpopulation variables to the testosterone levels measured in feces collected from 10 groups living in 6 forest fragments, at Los Tuxtlas, Mexico. Our results suggest that resident A. palliata males regard solitary individuals as potential contesters for their reproductive success and that they respond to interactions with them with an increase in testosterone levels, that is increasing their aggressiveness. Our results also suggest that in the studied groups all males have at least certain access to mates and that the entrance of a new male would affect their reproductive success negatively. Finally, the negative effects of chronically high testosterone levels may be negatively affecting the fitness of our study groups living in high population densities and small fragments.     

Testing "species pair" hypotheses: evolutionary processes in the lichen-forming species complex Porpidia flavocoerulescens and Porpidia melinodes

Pairs of taxa are commonly found in lichen-forming ascomycetes that differ primarily in their reproductive modes: one taxon reproduces sexually, the other vegetatively. The evolutionary processes underlying such "species pairs" are unknown. The species pair formed by Porpidia flavocoerulescens (sexual) and Porpidia melinodes (vegetative) was chosen to investigate four previously proposed hypotheses. These hypotheses posit that species pairs are either two monophyletic, independently evolving species with contrasting reproductive mode; a single outcrossing species polymorphic with regard to its reproductive modes; a sexual mother lineage frequently giving rise to asexual spin-offs; or a complex of cryptic species. The phylogenetic patterns observed within the species pair in the present study were analyzed using stringent hypothesis testing and visualizations of relationships and conflict based on tree and network reconstructions. DNA sequences at the three analyzed loci revealed the same four to five deeply divergent lineages. A detailed analysis of DNA-sequence variability revealed closely linked gene loci, but high levels of conflict within each of the gene fragments, as well as between observed genetic lineages. The observed patterns of phylogenetic relationships, linkage, and conflict are not congruent with any of the previously proposed species pair hypotheses. Rather, it is proposed that the observed results can be explained by conflicting reproductive and nutritional requirements imposed by an obligate symbiotic lifestyle. These interacting constraints produce recurring selective sweeps within predominantly vegetatively reproducing lineages and are the main forces that shape the evolution within the investigated species pair.     

Enterobacterial 38-kDa outer membrane protein is an age-dependent molecular marker of innate immunity and immunoglobulin deficiency as results from its reactivity with IgG and IgA antibody

In earlier studies on an animal model we observed protective properties of outer membrane proteins (OMPs) of Shigella, Hafnia, and Escherichia coli strains. In order to investigate human sera for reactivity with OMPs we subjected these proteins to immunoblotting with umbilical cord plasma and sera from children and adults. The IgG and IgA antibodies interacted primarily with a 38-kDa protein, in similar way for several enterobacterial strains, but different for Pseudomonas aeruginosa. This observation prompted us to determine the reactivity with the purified 38-kDa OMP in the sera of several groups of children. The reactivity of the protein from Shigella flexneri serotype 3a with sera in ELISA was age dependent, increasing from low reactivity in infants to the adult antibody level. The IgG and IgA antibody specific response thus revealed the normal pattern of immunity. The level of IgA and IgG antibody was significantly low in child patients with IgA and/or IgG immunoglobulin deficiencies, but was at the healthy control level in children with recurrent respiratory tract inflammation. These data correlated with total IgA and IgG levels in immunoglobulin-deficient children. The results indicate that this protein may serve as an immunodiagnostic marker, but also as an antigen carrier in vaccines.