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Mass Effect (mass + effect)
Selected AbstractsInsulin resistance in type 2 diabetes: role of fatty acids,DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue S2 2002Peter Arner Abstract Insulin resistance is one of the key factors responsible for hyperglycaemia in type 2 diabetes and can result in a number of metabolic abnormalities associated with cardiovascular disease (insulin resistance syndrome), even in the absence of overt diabetes. The mechanisms involved in the development of insulin resistance are multifactorial and are only partly understood, but increased availability of free fatty acids (FFAs) is of particular importance for the liver and skeletal muscle. The role of FFAs in type 2 diabetes is most evident in obese patients who have several abnormalities in FFA metabolism. Because of a mass effect, the release of FFAs from the total adipose tissue depot to the blood stream is increased and the high concentration of circulating FFAs impairs muscle uptake of glucose by competitive inhibition. In upper-body obesity, which predisposes individuals to type 2 diabetes, the rate of lipolysis is accelerated in visceral adipose tissue. This results in a selective increase in FFA mobilisation to the portal vein, which connects visceral fat to the liver. A high ,portal' FFA concentration has undesirable effects on the liver, resulting in dyslipidaemia, hyperinsulinaemia, hyperglycaemia and hepatic insulin resistance. Recently, a new class of antidiabetic agents, the thiazolidinediones (TZDs) or ,glitazones' has been developed. A prominent effect of these agents is the lowering of circulating FFA levels and it is believed, but not yet proven, that this interaction with FFAs constitutes a major mechanism behind the glucose-lowering effect of the TZDs. Copyright © 2002 John Wiley & Sons, Ltd. [source] An Analysis of Possible Mechanisms of Unexpected Death Occurring in Hydatid Disease (Echinococcosis)JOURNAL OF FORENSIC SCIENCES, Issue 4 2009Roger W. Byard M.B.B.S. Abstract:, Most cases of hydatid disease in human populations are due to Echinococcus granulosus. The hydatid life cycle involves passage between definitive hosts such as dogs and intermediate hosts such as sheep. Humans become accidental intermediate hosts following ingestion of food or water contaminated with eggs or by contact with infected dogs. Although hydatid disease may remain asymptomatic, occasional cases of sudden and unexpected death present to autopsy. Causes of rapid clinical decline involve a wide range of mechanisms including anaphylaxis (with or without cyst rupture), cardiac outflow obstruction or conduction tract disturbance, pulmonary and cerebral embolism, pericarditis, cardiac tamponade, myocardial ischemia, pulmonary hypertension, peritonitis, hollow organ perforation, intracerebral mass effect, obstructive hydrocephalus, seizures, cerebral ischemia/infarction, and pregnancy complications. The autopsy assessment of cases therefore requires careful examination of all organ systems for characteristic cystic lesions, as multiorgan involvement is common, with integration of findings so that possible mechanisms of death can be determined. Measurement of serum tryptase and specific IgE levels should be undertaken for possible anaphylaxis. [source] Giant abdominal tumor of the ovaryJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 1 2008Sachiyo Ueda Abstract A giant abdominal tumor can exert a mass effect on surrounding structures. We report here a 34-year-old single female who presented with an increased abdominal girth and was subsequently found to have a giant abdominal mass. Large volume aspiration (85 L) at a slow rate (1 L/min) was initially performed before surgical resection to prevent the development of severe clinical hypotension after large volume aspiration. The patient underwent left salpingo-oophorectomy. Histology revealed a serous cystadenoma of the ovary. Systemic hemodynamics were sequentially measured during the perioperative period. The patient is now well. [source] Intraoperative magnetic resonance imaging in the surgical treatment of cerebral metastasesJOURNAL OF SURGICAL ONCOLOGY, Issue 5 2010Christian Senft MD Abstract Background and Objectives To report on the value of intraoperative magnetic resonance imaging (iMRI) in the neurosurgical treatment of cerebral metastases (CM). Methods We performed a total of 204 surgical procedures with the use of a mobile ultra-low-field iMRI-unit. Of these, there were 12 craniotomies and 2 minimal-invasive procedures for CM, and 63 craniotomies for glioblastoma (GBM). Results On intraoperative imaging, all tumors could be localized and targeted with the help of the integrated neuronavigation system. Intraoperative imaging resulted in continued tumor resection due to unexpected residual tumor tissue in 13 patients harboring GBM (20.6%), but no patient with a CM (0%). In two patients with cystic CM, iMRI helped to achieve complete collapse of cysts by means of stereotactic aspiration, relieving mass effect and allowing for adjuvant radiotherapy. All patients subsequently received adjuvant treatment according to clinical protocols. Conclusion Surgical resection represents one of several treatment modalities in metastatic brain disease. iMRI is useful for neuronavigation and resection control and as an adjunct in minimal-invasive procedures in patients with CM; however, its exact value is yet to be determined by prospective randomized trials. J. Surg. Oncol. 2010; 101:436,441. © 2010 Wiley-Liss, Inc. [source] Properties of ecotones: Evidence from five ecotones objectively determined from a coastal vegetation gradientJOURNAL OF VEGETATION SCIENCE, Issue 4 2003Susan Walker Connor & Edgar (1987) and references therein, and Stace (1997), except where indicated Abstract. Several properties have been suggested to be characteristic of ecotones, but their prevalence has rarely been tested. We sampled five ecotones to seek evidence on seven generalizations that are commonly made about ecotones: vegetational sharpness, physiognomic change, occurrence of a spatial community mosaic, many exotic species, ecotonal species, spatial mass effect, and species richness higher or lower than either side of the ecotone. The ecotones were in a sequence from scattered mangroves, through salt marsh, rush-marsh, scrub, woodland, to pasture. We developed a method to objectively define, by rapid vegetational change, the position and depth of an ecotone, identifying five ecotones. Their positions were consistent across three sampling schemes and two spatial grain sizes. One ecotone is a switch ecotone, produced by positive feedback between community and environment. Another is anthropogenic, due to clearing for agriculture. Two others are probably environmental in cause, and one may be largely a relict environmental ecotone. Sharp changes in species composition occurred. Three ecotones were associated with a change in plant physiognomy. In two, the ecotone was located just outside a woodland canopy, in the zone influenced by the canopy. Community mosaicity was evident at only one ecotone. There were few strictly ecotonal species; many species occurred more frequently within ecotones than in adjacent vegetation, but there were never significantly more ecotonal species than expected at random. There was little evidence for the spatial mass effect reducing ecotonal sharpness, or leading to higher species richness within ecotones. Species richness was higher than in the adjacent habitat in only one ecotone. It seems that supposedly characteristic ecotone features depend on the particular ecological situation, and the ecology of the species present, rather than being intrinsic properties of ecotones. [source] Rare species in communities of tropical insect herbivores: pondering the mystery of singletonsOIKOS, Issue 3 2000Vojtech Novotný The host specificity, taxonomic composition and feeding guild of rare species were studied in communities of herbivorous insects in New Guinea. Leaf-chewing and sap-sucking insects (Orthoptera, Phasmatodea, Coleoptera, Lepidoptera and Hemiptera-Auchenorrhyncha) were sampled from 30 species of trees and shrubs (15 spp. of Ficus, Moraceae, six spp. of Macaranga and nine species of other Euphorbiaceae) in a lowland rain forest. Feeding trials were performed with all leaf-chewers in order to exclude transient species. Overall, the sampling produced 80,062 individuals of 1050 species. The species accumulation curve did not attain an asymptote, despite 950 person-days of sampling. Rare species, defined as those found as single individuals, remained numerous even in large samples and after the exclusion of transient, non-feeding species. There was no difference among plant species in the proportion of rare species in their herbivore communities, which was, on average, 45%. Likewise, various herbivore guilds and taxa had all very similar proportions of rare and common species. There was also no difference between rare and common species in their host specificity. Both highly specialised species and generalists, feeding on numerous plants, contributed to the singleton records on particular plant species. Predominantly, a species was rare on a particular host whilst more common on other, often related, host species, or relatively rare on numerous other host plants, so that its aggregate population was high. Both cases are an example of the "mass effect", since it is probable that such rare species were dependent on a constant influx of immigrants from the other host plants. These other plants were found particularly often among congeneric plants, less so among confamilial plants from different genera and least frequently among plants from different families. There were also 278 very rare species, found as one individual on a single plant species only. Their host specificity could not be assessed; they might have been either very rare specialists, or species feeding also on other plants, those that were not studied. The former possibility is unlikely since monophagous species, collected as singletons at the present sampling effort, would have existed at an extremely low population density, less than 1 individual per 10 ha of the forest. [source] Palmaris profundus: One name, several subtypes, and a shared potential for nerve compressionCLINICAL ANATOMY, Issue 6 2009Elena Pirola Abstract The palmaris profundus is a rare, but known anatomic variation which may lead to compression of the median nerve and/or its branches. Two patients with carpal tunnel syndrome are presented in whom a palmaris profundus was discovered at operation. In these cases, median nerve compression at the wrist was attributed to the course of the extra tendon and its local mass effect on the nerve (i.e., the palmaris profundus and median nerve shared a common sheath); more commonly, the resultant decreased available space for the median nerve within the carpal tunnel due to the presence of an accessory (10th) flexor tendon is thought to be responsible. Postoperative 3 Tesla magnetic resonance imaging (MRI) was performed to demonstrate the full course of the variant muscle; despite variations in the size and longitudinal extent of the accessory musculotendinous unit, an important similarity was noted: the intimate relationship of the median nerve and the palmaris profundus. These two cases and our review of the literature highlight the fact that one name (i.e. palmaris profundus) reflects several anatomic subtypes. However, the close relationship of the palmaris profundus with the median nerve in the forearm and the palm is a common theme which emphasizes the potential pathoanatomic consequences of this relationship: nerve compression. Clin. Anat. 22:643,648, 2009. © 2009 Wiley-Liss, Inc. [source] | |||||||||||||