共查询到20条相似文献,搜索用时 31 毫秒
1.
Valvular nasal obstruction may occur in the postoperative rhinoplasty patient. One may anticipate a dropping of the tip, from residual redundant or inelastic skin, in some older patients with long noses. Measures to correct (or avoid) this may be undertaken at the time of the primary rhinoplasty. However, an overcorrection may be necessary if there is much redundant skin. Discretion may indicate the need for a secondary procedure. Lateral wall valving is unusual-but it may occur in the long, high, thin nose (where a suggestion of this action may be observed preoperatively). Maintenance of continuous cartilage along the alar rim, at the time of alar cartilage resection, appears to be important in prevention of postoperative valvular obstruction in these few patients. 相似文献
2.
Kellomäki S Peltola H Nuutinen T Korhonen KT Strandman H 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2008,363(1501):2341-2351
This study investigated the sensitivity of managed boreal forests to climate change, with consequent needs to adapt the management to climate change. Model simulations representing the Finnish territory between 60 and 70 degrees N showed that climate change may substantially change the dynamics of managed boreal forests in northern Europe. This is especially probable at the northern and southern edges of this forest zone. In the north, forest growth may increase, but the special features of northern forests may be diminished. In the south, climate change may create a suboptimal environment for Norway spruce. Dominance of Scots pine may increase on less fertile sites currently occupied by Norway spruce. Birches may compete with Scots pine even in these sites and the dominance of birches may increase. These changes may reduce the total forest growth locally but, over the whole of Finland, total forest growth may increase by 44%, with an increase of 82% in the potential cutting drain. The choice of appropriate species and reduced rotation length may sustain the productivity of forest land under climate change. 相似文献
3.
Ioannidis JP 《Human heredity》2007,64(4):203-213
Non-replication and inconsistency had been common features in the search for common variants of candidate genes affecting the risk of complex diseases. They may continue to require attention in the current era, when massive hypothesis-free testing of genetic variants is feasible. An empirical evaluation of the early experience with genome-wide association (GWA) studies suggests several examples where proposed associations have failed to be replicated by subsequent investigations. Non-replication and inconsistency is defined here in the framework of cumulative meta-analysis. Ideally, associations exist, GWA finds them, and subsequent investigations should replicate them. However, a number of other possibilities need to be considered. No common genetic variants may associate with the phenotype of interest and GWA may find nothing; or associations may exist, but GWA may miss them. Associations that do not exist may be falsely selected by the GWA and subsequent studies may appropriately refute them or falsely replicate them. Finally, GWA may find true associations that are nevertheless falsely non-replicated in the subsequent studies; or associations may be genuinely inconsistent across study populations. A list of options is presented for consideration in each of these scenarios. 相似文献
4.
Charles L. Brown 《The Western journal of medicine》1952,77(3):172-175
Minor degrees of pancreatic insufficiency may go unrecognized. There is a paucity of symptoms and physical findings in mild and moderate degrees of insufficiency and in such circumstances laboratory methods are necessary to determine the presence of insufficiency. The clinical picture when insufficiency is well established may be characterized by loss in weight; vague indigestion; voluminous, light-colored, glistening stools in which fat globulets may be seen; changes in the concentration of pancreatic enzymes in the blood indicative of lowered pancreatic function; diminished amounts of pancreatic enzymes in the duodenal juice, and the related poor digestion of fat and protein in the food. Lowered tolerance of carbohydrate, as found in diabetes mellitus, may or may not be present. The location and character of the disease in the pancreas causing the insufficiency may or may not be apparent. 相似文献
5.
How does interferon inhibit tumour growth? 总被引:1,自引:0,他引:1
I Gresser 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1982,299(1094):69-76
Interferon can inhibit tumour growth in experimental animals and in some patients with benign and malignant tumours. There is experimental evidence to suggest that several mechanisms may be involved: a direct effect on the tumor or an indirect effect via the host, or both. Thus, interferon may slow the rate of tumour cell multiplication and this may lead to cell death. Interferon may induce changes in the cell surface rendering tumour cells more sensitive to host defence mechanisms. Interferon may induce reversion in the phenotype of tumour cells. Interferon may stimulate specific and non-specific humoral and cellular host mechanisms. The relative importance of these different effects of interferon may vary depending on the host and the particular tumour. 相似文献
6.
Reactive oxygen species and airway inflammation 总被引:23,自引:0,他引:23
P J Barnes 《Free radical biology & medicine》1990,9(3):235-243
Reactive oxygen species may be generated by several inflammatory cells which participate in airway inflammation and their production may be increased in asthma. Oxygen metabolites may contribute to the epithelial damage which is characteristic of asthmatic airways and may activate cells such as mast cells in the airway mucosa. Reactive oxygen species may cause bronchoconstriction, mucus secretion, have effects on airway vasculature, and may increase airway responsiveness. The role of reactive oxygen species in airway disease has been largely neglected, but appears to be an important area for future study. It is also possible that antioxidant defenses may be defective in asthma. If reactive oxygen species participate in the inflammatory response in airway disease, then radical scavengers or antioxidants could play a useful role in therapy. 相似文献
7.
Cultural variation may play an important role in human nutrition and must be considered in either clinical or public health intervention particularly in areas with large immigrant populations. Acculturative and environmental change influence the food habits and health of transitional groups. Nutritional assessment may be complicated by cultural variation. The relationship between ethnicity and nutrition may be of evolutionary significance. Food beliefs may have beneficial or detrimental effects on health status. The study of acculturating populations may elucidate the pathogenesis of nutrition-related chronic diseases. Appreciation of the interaction of culture and nutrition may be of benefit to physicians and nutritionists in clinical practice and to those concerned with the prevention of nutrition-related chronic diseases. 相似文献
8.
Possible causes of fever after interferon administration 总被引:2,自引:0,他引:2
V U Bocci 《Biomedicine / [publiée pour l'A.A.I.C.I.G.]》1980,32(4):159-162
Several factors can be responsible for the febrile response evoked by interferon (IF) administration in man. Since different cells and inducers are used for production of IF, the pyrogenic substance may not always be the same. Leucocyte IF (LeIF) may contain endogeneous pyrogen (EP), fibroblast IF (FIF) may contain heterogeneous proteins and/or EP, and lymphoblastoid IF (LyIF) may contain a factor released by the transformed lymphocyte able to induce, in vivo, the release of EP from leucocytes. Finally, IF may be intrinsically pyrogenic and, if this is the case, until homogeneous IF is used, it may potentiate the action of the pyrogenic contaminants. 相似文献
9.
David C. Stolinsky 《The Western journal of medicine》1980,132(3):189-208
Neoplasms can produce a variety of remote effects on the host; these are referred to as paraneoplastic syndromes. The syndromes may affect any of the systems of the body, may precede or follow the diagnosis of the underlying neoplasm, and may or may not parallel the course of the neoplasm in severity. The diagnosis of and therapy for these syndromes can be challenging to a physician, but successful therapy may bring about worthwhile relief for the patient. In addition, the syndromes and the substances that cause them are sometimes useful in diagnosing and in following the course of certain neoplasms. Perhaps of greater importance, study of these remote effects of neoplasia may shed light on the nature of the neoplastic process itself. 相似文献
10.
Arms races between and within species. 总被引:35,自引:0,他引:35
R Dawkins J R Krebs 《Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain)》1979,205(1161):489-511
An adaptation in one lineage (e.g. predators) may change the selection pressure on another lineage (e.g. prey), giving rise to a counter-adaptation. If this occurs reciprocally, an unstable runaway escalation or 'arms race' may result. We discuss various factors which might give one side an advantage in an arms race. For example, a lineage under strong selection may out-evolve a weakly selected one (' the life-dinner principle'). We then classify arms races in two independent ways. They may be symmetric or asymmetric, and they may be interspecific or intraspecific. Our example of an asymmetric interspecific arms race is that between brood parasites and their hosts. The arms race concept may help to reduce the mystery of why cuckoo hosts are so good at detecting cuckoo eggs, but so bad at detecting cuckoo nestlings. The evolutionary contest between queen and worker ants over relative parental investment is a good example of an intraspecific asymmetric arms race. Such cases raise special problems because the participants share the same gene pool. Interspecific symmetric arms races are unlikely to be important, because competitors tend to diverge rather than escalate competitive adaptations. Intraspecific symmetric arms races, exemplified by adaptations for male-male competition, may underlie Cope's Rule and even the extinction of lineages. Finally we consider ways in which arms races can end. One lineage may drive the other to extinction; one may reach an optimum, thereby preventing the other from doing so; a particularly interesting possibility, exemplified by flower-bee coevolution, is that both sides may reach a mutual local optimum; lastly, arms races may have no stable and but may cycle continuously. We do not wish necessarily to suggest that all, or even most, evolutionary change results from arms races, but we do suggest that the arms race concept may help to resolve three long-standing questions in evolutionary theory. 相似文献
11.
Hunting G-quadruplexes 总被引:3,自引:0,他引:3
Huppert JL 《Biochimie》2008,90(8):1140-1148
Whilst DNA spends much of its time in the double-stranded form, frequently in storage, wrapped around histones and packaged as chromatin, it can also form other complex structures, which may play a role in natural regulation and gene control. These alternative structures therefore also present an interesting novel series of targets for artificial intervention, and so may lead to novel therapeutics. In this review, I describe the current understanding of how genomic and bioinformatics studies may be used to understand the roles that one such structure, the four-stranded guanine-rich G-quadruplex, may play in the genome, and outline how these may be considered as targets for intervention. I will also describe recent work looking at RNA G-quadruplexes, and the biological roles they may play. 相似文献
12.
Partnership 总被引:1,自引:0,他引:1
Individuals are called partners when it is in their best interest to help each other, if by doing so they increase the probability of being together in the future when, for similar reasons, they will continue to help each other. Kinsmen or individuals who often face (hedonic) situations in which helping is the dominating strategy are committed to help each other. Partnership may develop among them since the loss of the other means the loss of a guaranteed helper. Thus, they may be willing to take additional risks to help each other. Partnership may occur among unrelated individuals and with no hedonic situations. Partnership creates bonds between partners which may be much stronger than those between kinsmen; an individual may take more risks for his partner than he will ever take for a kin. Partnership may evolve without the sophistication and memory required for reciprocation altruism. Although kin selection, partnership and reciprocation are likely to appear fused as the causes for altruism, we argue that it may be possible to distinguish between them in some situations. We show that as the partners get older partnership may become less important to them. We also show that like cooperation, and for analogous reasons, malice may evolve among partners so that each will be willing to take additional risks in order to eliminate the other. 相似文献
13.
Wahlund B 《Biological signals and receptors》1999,8(1-2):120-125
Altered diurnal secretory patterns, i.e. altered phase and/or amplitude of melatonin have been reported in sleep and affective disorders. The alteration may depend on environmental factors which in vulnerable individuals may cause sleep and/or affective disorders. Early stress in conjunction with development of resistance to corticotropin-releasing hormone may be linked to the low melatonin syndrome in subgroups of depressed patients. Also the seasonal variation in melatonin as well as serotonin may be linked to the seasonal pattern seen in subgroups of affective disorders. Melatonin may be used as a combined marker for proneness to develop affective disorders especially in latent carriers of bipolar disorders. 相似文献
14.
Veiga JP 《Proceedings. Biological sciences / The Royal Society》2003,270(Z1):S87-S89
The killing of genetically unrelated young by males has been viewed as a strategy that forces victimized females to advance the onset of their next fertile period, thus infanticidal males gain a time advantage that may be crucial to maximize reproductive success. Among females that may raise several broods in a year, a failure occurring relatively earlier in the time-course of the previous breeding attempt may result in an increased investment in the next breeding attempt. This female strategy may be exploited by males in their own interest, and may strongly select for male infanticidal behaviour. I demonstrate that, in the house sparrow, females mated with infanticidal males re-laid earlier, initiated more breeding attempts and fledged more offspring than females mated with non-infanticidal males. These results suggest that both the time saving and the manipulation of female investment are independent mechanisms conferring advantages that may have selected for male infanticide in the studied population. 相似文献
15.
Jialiang Lin Xiangxiang Pan Chongan Huang Mingbao Gu Ximiao Chen Xuanqi Zheng Zhenxuan Shao Sunli Hu Ben Wang Hao Lin Yaosen Wu Naifeng Tian Yan Wu Weiyang Gao Yifei Zhou Xiaolei Zhang Xiangyang Wang 《Journal of cellular and molecular medicine》2020,24(1):671-685
Inflammation and neuronal apoptosis contribute to the progression of secondary injury after spinal cord injury (SCI) and are targets for SCI therapy; autophagy is reported to suppress apoptosis in neuronal cells and M2 polarization may attenuate inflammatory response in microglia, while both are negatively regulated by mTORC1 signalling. We hypothesize that mTORC1 suppression may have dual effects on inflammation and neuronal apoptosis and may be a feasible approach for SCI therapy. In this study, we evaluate a novel inhibitor of mTORC1 signalling, Astragaloside IV (AS‐IV), in vitro and in vivo. Our results showed that AS‐IV may suppress mTORC1 signalling both in neuronal cells and microglial cells in vitro and in vivo. AS‐IV treatment may stimulate autophagy in neuronal cells and protect them against apoptosis through autophagy regulation; it may also promote M2 polarization in microglial cells and attenuate neuroinflammation. In vivo, rats were intraperitoneally injected with AS‐IV (10 mg/kg/d) after SCI, behavioural and histological evaluations showed that AS‐IV may promote functional recovery in rats after SCI. We propose that mTORC1 suppression may attenuate both microglial inflammatory response and neuronal apoptosis and promote functional recovery after SCI, while AS‐IV may become a novel therapeutic medicine for SCI. 相似文献
16.
José M. Gómez Adela González-Megías Cristina Armas Eduardo Narbona Luis Navarro Francisco Perfectti 《Ecology letters》2023,26(Z1):S47-S61
Plasticity-mediated changes in interaction dynamics and structure may scale up and affect the ecological network in which the plastic species are embedded. Despite their potential relevance for understanding the effects of plasticity on ecological communities, these effects have seldom been analysed. We argue here that, by boosting the magnitude of intra-individual phenotypic variation, plasticity may have three possible direct effects on the interactions that the plastic species maintains with other species in the community: may expand the interaction niche, may cause a shift from one interaction niche to another or may even cause the colonization of a new niche. The combined action of these three factors can scale to the community level and eventually expresses itself as a modification in the topology and functionality of the entire ecological network. We propose that this causal pathway can be more widespread than previously thought and may explain how interaction niches evolve quickly in response to rapid changes in environmental conditions. The implication of this idea is not solely eco-evolutionary but may also help to understand how ecological interactions rewire and evolve in response to global change. 相似文献
17.
Laboratory dialysis, one of the most widely used techniques in biological research is truly a ' gateway technology' . The analogy is to that of a ' gate' of a building through which everybody has to pass, even though they may wish to go to different departments. Similarly, researchers may be working in altogether different areas but all may need to use laboratory dialysis at one stage or the other during the course of their research. Biochemists may use it to purify enzymes, an immunologist may use it to purify monoclonal antibodies from culture supernatants, a chemist may use it as a step in the crystallography process or for purification of ionic liquids, a biotechnologist may use it to study the effectiveness of enzyme immobilization and a drug discovery scientist may use it for determining drug-protein interaction. The present article reviews patents in the field of laboratory dialysis from inception till date, focusing on the various developmental and innovation related milestones during evolution of the technique. It captures the full panorama of a very interesting technique which continues to be as relevant today as it was in 1866 when the term ' dialysis' was first coined. 相似文献
18.
How do addictive drugs hijack the brain's reward system? This review speculates how normal, physiological reward processes may be affected by addictive drugs. Addictive drugs affect acute responses and plasticity in dopamine neurons and postsynaptic structures. These effects reduce reward discrimination, increase the effects of reward prediction error signals, and enhance neuronal responses to reward-predicting stimuli, which may contribute to compulsion. Addictive drugs steepen neuronal temporal reward discounting and create temporal myopia that impairs the control of drug taking. Tonically enhanced dopamine levels may disturb working memory mechanisms necessary for assessing background rewards and thus may generate inaccurate neuronal reward predictions. Drug-induced working memory deficits may impair neuronal risk signaling, promote risky behaviors, and facilitate preaddictive drug use. Malfunctioning adaptive reward coding may lead to overvaluation of drug rewards. Many of these malfunctions may result in inadequate neuronal decision mechanisms and lead to choices biased toward drug rewards. 相似文献
19.
S Rosaspina G Salvatorelli A K Zekaria D Anzanel 《Bollettino della Società italiana di biologia sperimentale》1990,66(1):21-27
The morphology of differentiated and differentiating cells of the red and white series in Lutjanus herenbergi and in Lutjanus flaviflammus is described. Early stages of red and white blood cells may be found only in smears of hemopoietic organs. Polychromatic erythroblasts, myelocytes and lymphoblasts may also occasionally be found in blood smears. Mature blood cells may be found both in blood smears and in hemopoietic organs. Differential white cell counts seem to demonstrate that the granulocytic series elements are the most common leukocytes in blood smears. Almost all granulocytes may be classified in the first three Arneth classes. An analysis of hemopoietic organs in these species was also performed. It was found that the only organs carrying on a hemopoietic function are the kidney and the spleen. The kidney is essentially a site of granulocytic differentiation while the spleen is a lymphopoietic organ. An erythropoietic activity may generally be observed in the kidney although weak erythropoietic activity may at times be found in the spleen. 相似文献
20.
WILLIAM LOUIS STERN FLS WALTER S. JUDD 《Botanical journal of the Linnean Society. Linnean Society of London》1999,131(4):353-382
Vanilla is a pantropical genus of green-stemmed vines bearing clasping (aerial) and absorbing (terrestrial) roots. Most vanillas bear normal, thick foliage leaves; others produce fugacious bracts. Seventeen species, including both types were studied. Foliage leaves of Vanilla are glabrous, have abaxial, tetracytic stomatal apparatuses, and a homogeneous mesophyll. Species may or may not have a uniseriate hypodermis. Crystals occur in the foliar epidermises of some species, but all species have crystalliferous idioblasts with raphides in the mesophyll. Vascular bundles in leaves are collateral and occur in a single series alternating large and small. Sclerenchyma may or may not be associated with the vascular bundles. Scale leaves may be crescent or C-shaped and usually have abaxial stomatal apparatuses. A hypodermis may or may not be present; the mesophyll contains raphide bundles in idioblasts. Vascular bundles are collateral and occur in a single row sometimes aligned close to the adaxial surface. They may or may not be associated with sclerenchyma. Stems of leafy vanillas show a sclerenchyma band separating cortex from ground tissue; stems of leafless vanillas do not show a sclerenchyma band. Ground tissue of the stem may consist solely of assimilatory cells or mixed assimilatory and water-storage cells. In some species centrally located assimilatory cells are surrounded by layers of water-storage cells. A uniseriate hypodermis is present in all stems. Sclerenchyma may completely surround the scattered collateral vascular bundles, occur only on the phloem side, or be absent. Both aerial and terrestrial roots are notable for their uniseriate velamen the cell walls of which may be unmarked or ornamented with anticlinal strips. Exodermis is uniseriate; the cells vary from barely thickened to strongly thickened. Only the outer and radial walls are thickened. Cortical cells of aerial roots generally have chloroplasts that are lacking from the same tissue of terrestrial roots. Raphide bundles occur in thin-walled cortical idioblasts. Endodermis and pericycle are uniseriate; pericycle cells are all ?-thickened opposite the phloem. Cells of the endodermis are either ?- or ∪-thickened opposite the phloem. Vascular tissue may be embedded in thin- or thick-walled sclerenchyma or in parenchyma. Metaxylem cells are always wider in terrestrial than in aerial roots of the same species. Pith cells are generally parenchymatous but sclerotic in a few species. 相似文献