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The differentiating sieve element in stem and leaf phloem ofMimosa pudica L. was examined with the electron microscope.The nucleus of a sieve element at first resembles that of acompanion cell, except that its nucleolus is smaller. The firstindication of approaching disintegration is a change in theappearance of the nuclear envelope. With the fixatives used,its profile becomes wider and clearer, giving the impressionof having been dilated. Subsequently, the nuclear contents disintegrateand the envelope breaks apart. No nuclear remnants are discerniblein mature sieve elements. The endoplasmic reticulum (ER) ofyoung sieve elements consists of cisternae-bearing ribosomes.At the beginning of nuclear disintegration ER cisternae becomestacked, with electron-dense material accumulating between thecisternae. The stacking assumes various forms. Some of the stackedER is independent of cell organelles and occurs next to theplasmalemma along the cell wall. Part of the ER becomes stackedagainst the plastids or the nucleus. There is also unstackedER which forms an anastomosing system along the plasmalemma.All of the modified ER bears no ribosomes. The anastomosingER appears to persist longer than the stacked ER. 相似文献
64.
Competitive interactions between insects and microbes and the associated cost of development in bacterially‐dense environments are investigated using the blowfly Lucilia sericata (Meigen) (Diptera: Calliphoridae) as a model. The effects of developing in a bacterially‐dense environment are measured by assessing the fitness consequences of competition using the pathogen Staphylococcus aureus. Fitness is quantified in terms of larval survival, puparial development and adult emergence.The influence of bacteria on larval immune defences is investigated using optical density to assess whether antibacterial potency of the larval excretion/secretion changes in response to the degree of contamination of the larval environment. The results obtained demonstrate that bacterial presence has no detrimental effect on survival of L. sericata from egg to adult eclosion, or on puparial size. Additionally, the level of microbial contamination of larvae has no effect on the antibacterial potency of the larval excretion/secretion. These findings confirm that larval antibacterial activity is not induced by the presence of environmental bacteria but is produced constitutively. 相似文献
65.
The three criteria for resistance by plant carrion‐provisioning: insect entrapment and predator enrichment on Mimulus bolanderi 下载免费PDF全文
1. Many sticky plants provision mutualistic scavenging arthropod predators with carrion, which in turn protect the plant from insect herbivores. While insect entrapment is a common trait across plants, which plants attract these predators and may derive protection is still largely unknown. 2. Three conditions were proposed that must be satisfied for observational data to suggest this defensive strategy: (i) the consistent presence of scavenging predators, (ii) positive correlation between predator numbers and carrion, and (iii) suitability of these predators for controlling known herbivores. 3. As a case study, we examined the fire‐following annual, Mimulus [Diplacus] bolanderi (Phyrmaceae), which is part of a well‐studied radiation of California monkeyflowers. Many monkeyflowers entrap insects, though attraction to predators has not been quantified in this genus. 4. A guild of scavenging arthropod predators on M. bolanderi (condition #1) was found, which correlated positively with carrion abundance (#2) and could consume the primary herbivore (#3), suggesting a carrion‐mediated defensive strategy. Lastly, as M. bolanderi is variable in time and space, these interactions are facultative, and these predators are quick to adopt ephemeral carrion resources on novel host plants. 相似文献
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KATHERINE C. KENDALL JEFFREY B. STETZ DAVID A. ROON LISETTE P. WAITS JOHN B. BOULANGER DAVID PAETKAU 《The Journal of wildlife management》2008,72(8):1693-1705
Abstract: We present the first rigorous estimate of grizzly bear (Ursus arctos) population density and distribution in and around Glacier National Park (GNP), Montana, USA. We used genetic analysis to identify individual bears from hair samples collected via 2 concurrent sampling methods: 1) systematically distributed, baited, barbed-wire hair traps and 2) unbaited bear rub trees found along trails. We used Huggins closed mixture models in Program MARK to estimate total population size and developed a method to account for heterogeneity caused by unequal access to rub trees. We corrected our estimate for lack of geographic closure using a new method that utilizes information from radiocollared bears and the distribution of bears captured with DNA sampling. Adjusted for closure, the average number of grizzly bears in our study area was 240.7 (95% CI = 202–303) in 1998 and 240.6 (95% CI = 205–304) in 2000. Average grizzly bear density was 30 bears/1,000 km2, with 2.4 times more bears detected per hair trap inside than outside GNP. We provide baseline information important for managing one of the few remaining populations of grizzlies in the contiguous United States. 相似文献
68.
KATHERINE A. HALMI 《World psychiatry》2009,8(3):150-155
Eating disorders are challenging and difficult to treat, because of the necessity of a multidisciplinary treatment team for effective outcomes and the high mortality rate of anorexia nervosa. An adequate initial assessment and evaluation requires a psychiatric assessment, a medical history and medical examination, a social history and an interview of family members or collateral informants. A comprehensive eating disorder treatment team includes a psychiatrist coordinating the treatment and appropriate medical physician specialists, nutritionists, and psychotherapists. An adequate outpatient eating disorder clinic needs to provide individual psychotherapy with cognitive behavioral techniques specific for anorexia nervosa and bulimia nervosa, family therapy, pharmacological treatment and the resources to obtain appropriate laboratory tests. Eating disorder patients requiring inpatient care are best treated in a specialized eating disorder inpatient unit. A cognitive behavioral framework is most useful for the overall unit milieu. Medical management and nutritional rehabilitation are the primary goals for inpatient treatment. Various group therapies can cover common core eating disorder psychopathology problems and dialectical behavior therapy groups can be useful for managing emotional dysregulation. Residential, partial hospitalization and day treatment programs are useful for transitioning patients from an inpatient program or for patients needing some monitoring. In these programs, at least one structured meal is advisable as well as nutritional counseling, group therapy or individual counseling sessions. Group therapies usually address issues such as social skills training, social anxiety, body image distortion or maturity fears. Unfortunately there is s paucity of evidence based randomized control trials to recommend the salient components for a comprehensive service for eating disorders. Experienced eating disorder clinicians have come to the conclusion that a multidisciplinary team approach provides the most effective treatment. 相似文献
69.
Abstract: We fitted radiotransmitters to 68 lilac-crowned parrot (Amazona finschi) fledglings from 1996 to 2003 to determine the survival and development of juveniles during their first year after leaving the nest. Overall, first-year survival was 73% (CI = 53–94%) and all mortalities occurred within 5 weeks of fledging, with highest mortality in the first week postfledging. Survival varied between years, influencing recruitment of independent young in the population. Nesting lilac-crowned parrots produced 0.70 independent young per egg-laying pair during 1996–2003. Lowest productivity of 0.25 independent young per pair occurred in 2003, with 40% postfledging survival. Juvenile development after fledging was characterized by variations in mobility, distance from the nest, and separation distance between siblings. Mobility and distance of young birds from the nest increased linearly with months postfledging. The first 2–3 weeks after fledging were characterized by low mobility and survival of young parrots, making this the most critical phase postfledging. The dependency period for young parrots extended to 4–5 months postfledging and was characterized by increased mobility and low separation between siblings, as juveniles traveled in family groups. Independence occurred in month 5 and was marked by a significant increase in mobility and separation between siblings, indicating the break-up of family groups. The first weeks after leaving the nest were crucial for survival and highlight the need for secure habitats where fledglings can improve flight and locomotory skills. The 4–5-month dependency of young parrots may be a key period for development, enhancing survival, and establishment in the breeding population. Release programs need to replicate learning and development acquired during the postfledging dependency phase to enhance survival of captive-reared psittacines. Researchers should conduct surveys of parrot group sizes during the dependency period 1–4 months after the end of nesting to provide reliable demographic data on annual recruitment of wild populations. 相似文献
70.
Since the publication of DSM-III in 1980, the official position of American
psychiatry has been that the presence of bereavement is an exclusion criterion
for the diagnosis of a major depressive episode (MDE). However, the empirical
validity of this exclusion has not been well established. As DSM-V is now
being planned, it is timely to reexamine the bereavement exclusion, particularly
in the light of new evidence since the last reviews of this subject. This
paper evaluates the relative validity of two competing hypotheses: 1) the
bereavement exclusion for the diagnosis of MDE is not valid because, using
validating criteria, bereavement related depression (BRD) within the first
two months after the death of a loved one resembles non-bereavement related
depression (SMD); 2) the bereavement exclusion for the diagnosis of MDD is
valid because, using validating criteria, BRD within the first two months
after the death of a loved one does not resemble SMD. The prevailing evidence
more strongly supports Hypothesis 1 than Hypothesis 2. Thus, the bereavement
exclusion for the diagnosis of MDE may no longer be justified. 相似文献