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1.
B. AbdullGaffar
Impact factor in cytopathology journals: what does it reflect and how much does it matter? Objective: To study the trends of impact factor (IF) in four cytopathology journals. To investigate the factors that might influence IF in cytopathology literature and whether IF has any impact on cytopathology practice. Methods: The IFs of four cytopathology journals were searched from 2005 to 2009. The IFs and their relationships with the types and number of publications, publishers, the official societies, readership, the quality of their contents, the topics covered and the levels of evidence were compared. Results: Cancer Cytopathology (CC) had the highest IF. Acta Cytologica (AC) had the lowest IF, which appeared to be in decline. Cytopathology (C) and Diagnostic Cytopathology (DC) had a slow but steady increase in their IF. Components that might influence these differences could include the category and the society of the journal, targeted readers and certain types of publications. Publishers, the number of publications, the types of topics covered and the levels of evidence probably have no major effect on IF. Conclusions: IF has its own benefits and original applications. IF is a quantitative measure that does not reflect the levels of evidence in cytopathology journals. IF should not be abandoned because it might encourage competition between cytopathology journals, but it should not dictate their contents.  相似文献   

2.
Recruits of Lipophrys pholis , Coryphoblennius galerita and Gobius cobitis spend the low tide under water in pools, and in the case of G. cobitis also in channels. The pools used by the two blenniids show greater similarity than those used by G. cobitis. Larger juveniles and adults of C. galerita continue to use the same type of pools, which are temporarily abandoned by the males during the breeding season when they use emersed holes and crevices as nests. The much faster growing L. pholis and G. cobitis leave the pools in their first autumn, when they are c. 7 cm long. Whereas G. cobitis >7 cm move to channels and large upper pools, with a smooth substratum, sand and boulders, L. pholis begin to use emersed crevices where they spend low tide often in large groups. When L. pholis or C. galerita were added or removed selectively from pools, their numbers returned to pre-experimental levels after 2 weeks, suggesting that, although intraspecific competition may be strong, interspecific competition was unlikely to explain these results fully.  相似文献   

3.
Regeneration in the metazoans: why does it happen?   总被引:12,自引:0,他引:12  
Why does regeneration occur? And why, when it manifests itself, does it do so in some but not all metazoan species? Hence, what are the permissive or inhibitory factors operating behind this phenomenon? When it comes to regeneration, many questions, such as these, remain unanswered. In fact, the problem of animal regeneration has withstood the probing of scientific inquiry for over 250 years and still awaits a satisfactory mechanistic explanation. In this essay, I will review the distribution and the modes of regeneration that are found in the different metazoan phyla. Also, I will re-examine ideas on its evolutionary origins, and discuss its possible relationship to both asexual reproduction and embryogenesis. This endeavor has two objectives. First, to bring forward an interpretation of regeneration which integrates evolutionary and developmental considerations into its discussion. And second, to suggest a comparative experimental approach to this problem that may bring us closer to understanding the molecular basis of this long-standing biological problem. BioEssays 22:578-590, 2000.  相似文献   

4.
In the era of evidence-based medicine, new treatment protocols and interventions should be routinely evaluated for their efficacy by reviewing the available evidence. In the cleft literature, nasoalveolar molding has garnered attention over the last decade as a new option for improving nasal form and symmetry before primary surgical repair. Systematic review of the evidence is, however, currently lacking. This review evaluates whether nasoalveolar molding can improve nasal symmetry and form toward the norm, as well as whether nasoalveolar molding demonstrates advantages over other protocols in achieving this goal. A literature search of five databases plus relevant reference lists retrieved 98 articles regarding nasoalveolar molding, 21 of which reported objective outcome measures of nasal symmetry and form, and six of which were able to be given evidence level ratings, all in the unilateral cleft population. Statistical analysis was not possible given the range of techniques and outcomes. Studies of bilateral cleft were not given evidence level ratings, given the inability to separate the effects of nasoalveolar molding from other primary nasal interventions in studies that would have otherwise been rated. In unilateral cleft lip-cleft palate, there was some evidence that nasoalveolar molding may improve nasal outcomes, though comparison with other techniques was limited. Despite a relative paucity of high-level evidence, nasoalveolar molding appears to be a promising technique that deserves further study.  相似文献   

5.
Extruded pellets containing activated carbon (AC) can be used to sow native seeds while simultaneously applying herbicide to control invasive species. Incorporating AC in pellets has been demonstrated to protect native seeds; however, there may be unintended detrimental impacts to seedling emergence. We aimed to optimize seed position within pellets to maximize emergence and survival of the perennial shrub Jacksonia furcellata. Seeds were positioned at 2 mm (top), 6 mm (middle), and 12 mm (bottom) within pellets (with or without AC), sown on or below the soil surface, and compared to non-pelleted seeds sown under the soil surface in the equivalent positions (2, 6, and 12 mm depth). Trays were treated with a pre-emergent herbicide (Simazine) or left unsprayed. Emergence (without herbicide) was significantly higher from seeds positioned at the bottom of pellets without AC sown on the soil surface (70%), compared to non-pelleted seeds sown at the bottom (12 mm below the soil surface; 57%). However, emergence was inhibited when seeds were positioned in the middle (6 mm) of pellets with AC (32%). When treated with Simazine, survival was highest from seeds positioned at the bottom of pellets with AC (60%), compared to pellets without AC (15%) and non-pelleted seeds sown at the bottom (12 mm below the soil surface; 15%). Jacksonia furcellata seeds positioned at the bottom of pellets, sown on the soil surface, shows promise to minimize negative impacts to emergence, and maximize herbicide protection. Further testing with additional species is required to refine pellet production (e.g. recipe, extrusion, and shape) for optimal emergence.  相似文献   

6.
Vesicular transport in capillary endothelium: does it occur?   总被引:7,自引:0,他引:7  
A revised picture of the organization of endothelial plasmalemmal vesicles is presented. Three-dimensional reconstructions of endothelial segments from frog mesenteric capillaries and rat heart capillaries based on ultrathin serial sectioning have shown that plasmalemmal vesicles are not true vesicles but parts of an elaborate system of invaginations of the surface membrane. The revised picture probably applies to capillary endothelia in general. The absence of free cytoplasmic vesicles implies that vesicular transport is unlikely to occur. A reinterpretation of previous studies of vesicular transport shows that they are equally compatible with the present view that plasmalemmal vesicles are static elements of invaginations of the endothelial surface membrane.  相似文献   

7.
《Trends in parasitology》2023,39(4):251-259
Treatment failure (TF) jeopardizes the management of parasitic diseases, including leishmaniasis. From the parasite’s point of view, drug resistance (DR) is generally considered as central to TF. However, the link between TF and DR, as measured by in vitro drug susceptibility assays, is unclear, some studies revealing an association between treatment outcome and drug susceptibility, others not. Here we address three fundamental questions aiming to shed light on these ambiguities. First, are the right assays being used to measure DR? Second, are the parasites studied, which are generally those that adapt to in vitro culture, actually appropriate? Finally, are other parasite factors – such as the development of quiescent forms that are recalcitrant to drugs – responsible for TF without DR?  相似文献   

8.
The mechanisms responsible for the preservation of duplicate genes have been debated for more than 70 years. Recently, Lynch and Force have proposed a new explanation: subfunctionalization--after duplication the two gene copies specialize to perform complementary functions. We investigate the probability that subfunctionalization occurs, the amount of time after duplication that it takes for the outcome to be resolved, and the relationship of these quantities to the population size and mutation rates.  相似文献   

9.
Fas ligand (FasL) was first described functionally as an inducible cell surface molecule used by cytotoxic T cells to induce apoptotic cell death in tumor cells and activated lymphocytes. With the identification of Fas as the Ipr gene product, FasL became recognized as a molecule involved in down-regulation of the immune system. While FasL can be used to efficiently kill Fas-expressing tumor cells as well as activated T and B lymphocytes in vitro, attempts to use FasL therapeutically to treat cancer or to prevent transplant  相似文献   

10.
The sexual selection hypothesis explains infanticide by males in many mammals. In our 11-year study, we investigated this hypothesis in a herd of Przewalski's horses where we had witnessed infanticidal attacks. Infanticide was highly conditional and not simply linked to takeovers. Attacks occurred in only five of 39 cases following a takeover, and DNA paternity revealed that, although infanticidal stallions were not the genetic fathers in four cases out of five, stallions present at birth did not significantly attempt to kill unrelated foals. Infanticide did not reduce birth intervals; only in one case out of five was the infanticidal stallion, the father of the next foal; mothers whose foals were attacked subsequently avoided associating with infanticidal stallions. Therefore, evidence for the sexual selection hypothesis was weak. The “human disturbance” hypothesis received some support, as only zoo bred stallions which grew up in unnatural social groups attacked foals of mares which were pregnant during takeovers.  相似文献   

11.
Asymmetric development of the vertebrate embryo has fascinated embryologists for over a century. Much has been learned since the asymmetric Nodal signaling cascade in the left lateral plate mesoderm was detected, and began to be unraveled over the past decade or two. When and how symmetry is initially broken, however, has remained a matter of debate. Two essentially mutually exclusive models prevail. Cilia-driven leftward flow of extracellular fluids occurs in mammalian, fish and amphibian embryos. A great deal of experimental evidence indicates that this flow is indeed required for symmetry breaking. An alternative model has argued, however, that flow simply acts as an amplification step for early asymmetric cues generated by ion flux during the first cleavage divisions. In this review we critically evaluate the experimental basis of both models. Although a number of open questions persist, the available evidence is best compatible with flow-based symmetry breakage as the archetypical mode of symmetry breakage.  相似文献   

12.
13.
14.
OBJECTIVE--To evaluate children''s and parents'' perceptions of hospital doctors'' attire. DESIGN--Questionnaire study asking children and parents to assign positive and negative attributes to five photographs of a male or female doctor dressed formally and informally. SETTING--Outpatient department, Children''s Hospital, Birmingham. SUBJECTS--203 consecutive child-parent pairs attending outpatient clinics over three months. MAIN OUTCOME MEASURES--Children''s and parents'' preferences, assessed by comparing proportions. RESULTS--70% (286/406) of children and parents rated doctors'' dress as important; more children rated it "very important" (27% (54/203) v 14% (29/203), P < 0.01, 95% confidence interval for difference 5% to 21%). Of the 99 children responding, 44 regarded the man in white coat as most competent (44% v 20% expected by chance, P < 0.01, 34% to 54%) and most concerned (32% v 20%, P < 0.01, 23% to 41%). Children also regarded the woman in white coat as most competent; however, male and female doctors in white coats rated lower for friendliness. Asians and regular surgical attenders preferred doctors in white coats. The man in polo shirt and trousers was rated as most friendly (40% v 20% expected by chance, P < 0.01, 30% to 50%) and most gentle (37% v 20%, P < 0.01, 27% to 46%). The woman in tee shirt and slacks also rated most friendly and gentle; however, both casually dressed doctors rated lower for competence. Parents preferred more casual dress but expressed preferences less strongly, and they poorly predicted which outfits their children preferred. CONCLUSIONS--Children regard formally dressed doctors as competent but not friendly; they regard casual dress as friendly but not competent.  相似文献   

15.
The mechanism of action of F(1)F(0)-ATP synthase is controversial. Some favor a tri-site mechanism, where substrate must fill all three catalytic sites for activity, others a bi-site mechanism, where one of the three sites is always unoccupied. New approaches were applied to examine this question. First, ITP was used as hydrolysis substrate; lower binding affinities of ITP versus ATP enable more accurate assessment of sites occupancy. Second, distributions of all eight possible enzyme species (with zero, one, two or three sites filled) as fraction of total enzyme population at each ITP concentration were calculated, and compared with measured ITPase activity. Confirming data were obtained with ATP as substrate. Third, we performed a theoretical analysis of possible bi-site mechanisms. The results argue convincingly that bi-site hydrolysis activity is negligible, and may not even exist. Effectively, tri-site hydrolysis is the only mechanism. We argue that only tri-site hydrolysis drives subunit rotation. Theoretical analyses of possible bi-site mechanisms reveal serious flaws, not previously recognized. One is that, in bi-site catalysis, the predicted direction of subunit rotation is the same for both ATP synthesis and hydrolysis; a second is that infrequently occurring enzyme species are required.  相似文献   

16.
The literature on apoptosis has grown tremendously in recent years, and the mechanisms that are involved in this programmed cell death pathway have been enlightened. It is now known that apoptosis takes place starting from early development to adult stage for the homeostasis of multicellular organisms, during disease development and in response to different stimuli in many different systems. In this review, we attempted to summarize the current knowledge on the circumstances and the mechanisms that lead to induction of apoptosis, while going over the molecular details of the modulator and mediators of apoptosis as well as drawing the lines between programmed and non-programmed cell death pathways. The review will particularly focus on Bcl-2 family proteins, the role of different caspases in the process of apoptosis, and their inhibitors as well as the importance of apoptosis during different disease states. Understanding the molecular mechanisms involved in apoptosis better will make a big impact on human diseases, particularly cancer, and its management in the clinics.  相似文献   

17.
A gradual alteration in the mechanisms underlying reproduction and fertility characterizes the aging process in human females. These changes culminate in menopause, conventionally defined as a cessation of menstrual cycles that marks the end of reproductive capacity. In fact, a central and defining event in menopause is the discontinuation of ovulation, which is correlated with a number of structural and functional changes in the reproductive axis. Despite several decades of research, a degree of uncertainty remains as to whether nonhuman primates undergo menopause, and whether they are suitable models of human reproductive senescence. We review some of the controversies that have clouded our understanding of reproductive aging in nonhuman primates, including issues of definition, timing, comparability of data from wild versus captive populations, and cross-species comparisons. The existing data support the view that menopause occurs in a number of primate species and is not unique to humans.  相似文献   

18.
19.
Immunostimulation in crustaceans: does it really protect against infection?   总被引:10,自引:0,他引:10  
There is a growing need to control, prevent or minimise the devastating effects of disease in crustacean culture without recourse to toxic chemicals or antibiotics. In keeping with approaches to disease control in fish and higher mammals, interest is developing in compounds that confer protection and/or enhance immune reactivity to likely pathogens in shellfish (sometimes, erroneously, referred to as as "shellfish vaccines"). The agents currently under scrutiny for crustaceans include glucans, lipopolysaccharides and killed bacterial cells. They are thought to act as "immuno-stimulants" because of their known effects on the crustacean immune system in vitro. A number of papers are now appearing in the literature claiming to demonstrate their positive impact on immunity and immunity and disease resistance. This review article considers the problem of disease and its control in crustacean farming, describing the types of capability in cultured species. Analysis of the validity of the results of many of the published studies raises questions about the value of these compounds for cost-effective control of infection in aquaculture, especially for long lasting protection in both adults and juveniles. This review further discusses the potential risks to the wellbeing of the stock animals from repeated use of these agents and makes the case for rigorous testing of putative stimulants, at the gene, protein and functional levels, as well as for the need to consider alternative strategies and approaches to disease control.  相似文献   

20.
Abscisic acid in the xylem: where does it come from, where does it go to?   总被引:19,自引:0,他引:19  
Abscisic acid is a hormonal stress signal that moves in the xylem from the root to the different parts of the shoot where it regulates transpirational water loss and leaf growth. The factors that modify the intensity of the ABA signal in the xylem are of particular interest because target cells recognize concentrations. ABA(xyl), will be decreased as radial water flow through the roots is increased, assuming that radial ABA transport occurs in the symplast only. Such dilutions of the plant hormone concentration can be compensated in different ways, which help to keep the ABA-concentrations in the xylem constant: (i) apoplastic bypass flows of ABA, (ii) ABA flows between the stem parenchyma and the xylem during transport and (iii) the action of beta-D-glucosidases that release free ABA from its conjugates to the root cortex and the leaf apoplast. The significance of reflection coefficients (sigma(ABA)), permeability coefficients of membranes (P(S)(ABA)) and apoplastic barriers for ABA is discussed.  相似文献   

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