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31.
Ewa Lindstrum Per Lindstrum Andr Berglund Kiell Hansson Mild Erik Lundgren 《Journal of cellular physiology》1993,156(2):395-398
Applied weak magnetic fields have been shown to affect cellular activity on several levels, but the mechanisms involved remain elusive. We have decided to study an early signal transduction event in the human T cell line Jurkat; oscillations of free [Ca2+]i, of the type seen by crosslinking the CD3 complex. Cells were exposed to a 50 Hz, 0.1 mT, sinusoidal magnetic field while intracellular free calcium was measured in individual cells, using fura-2 as a probe. An acute response was observed with oscillatory increases in [Ca2+]i, which subsided when the field was turned off. The effect of the magnetic field on [Ca2+]i was comparable to that achieved by an anti-CD3 monoclonal antibody. © 1993 Wiley-Liss, Inc. 相似文献
32.
Total body burdens of Zn, Pb, Al and Cu were measured in Swedish marine nemerteans sampled from an area close to a major source
of pollution. Accumulation patterns varied both seasonally and spatially. The results suggest that nemerteans may be useful
bioindicator species in environmental monitoring programmes. 相似文献
33.
Per Ola Karis 《Plant Systematics and Evolution》1993,186(1-2):69-93
The relationships within theAsteraceae-Asteroideae are scrutinized by means of cladistic analyses of morphological and chemical data. New data are presented, and novel interpretations of features previously used in cladistic analyses are made. Examples are insertion of anther filaments in the corolla, and morphology of disc floret styles, respectively. The results include a polyphyletic or paraphyleticInuleae s. l., and a paraphyleticHeliantheae s.l. in which theEupatorieae constantly form a subclade. Comparisons are made with previous cladistic analyses of morphological data, and those acquired from molecular data. Speculations about the evolution of certain organs are presented. 相似文献
34.
Per M. Jørgensen 《Nordic Journal of Botany》1989,9(1):89-95
A relatively large Leptogium -like lichen overgrowing mosses in wet paramos has been discovered in the northern Andes and Costa Rica. It has, however, a green photobiont and basidiomycete hyphae. No fruitbodies have been observed, only asexual reproduction by fragmentation of the fragile thallus and by goniocysts formed on the ecorticate lower surface. Some aspects of the taxonomy of Omphalina are briefly discussed. 相似文献
35.
We examined population substructure of bottlenose dolphins ( Tursiops sp). in Shark Bay, Western Australia, using 10 highly polymorphic microsatellite loci, and mitochondrial DNA (mtDNA). For microsatellite analysis, 302 different animals were sampled from seven localities throughout the bay. Analysis of genetic differentiation between sampling localities showed a significant correlation between the number of migrants ( Nm ) calculated from F ST , R ST and private alleles, and distance between localities–a pattern of isolation-by-distance. For mtDNA, 220 individuals from all seven localities were sequenced for a 351 base pair fragment of the control region, resulting in eight haplotypes, with two distinct clusters of haplotypes. Values of F ST and (φ)ST for mtDNA yielded statistically significant differences, mostly between localities that were not adjacent to each other, suggesting female gene flow over a scale larger than the sampled localities. We also observed a significant correlation between the number of female migrants calculated from F ST and φST and the distance of sampling localities. Our results indicate that dispersal in female dolphins in Shark Bay is more restricted than that of males. 相似文献
36.
Stomach contents of 112 bycaught harbor porpoises ( Phocoena phocoena ) collected between 1989 and 1996 in the Kattegat and Skagerrak seas were analyzed to describe diet composition and estimate prey size, to examine sample size requirements, and to compare juvenile and adult diets. Although porpoises preyed on a variety of species, only a few contributed substantially to the diet. Atlantic herring ( Clupea harengus ) was the dominating prey species for both juveniles and adults. Our results, in combination with those from previous studies, suggest that where herring is a dominant food source, porpoises prey primarily on size classes containing mature or maturing individuals. Further, we also show that Atlantic hagfish ( Myxine glutinosa ) may be an important food resource, at least for adult porpoises. Examination of sample size requirement showed that, depending on the taxonomic level used to describe the diet, a minimum of 35–71 stomachs are needed to be confident that all common prey species will be found. 相似文献
37.
The braincase of the Late Devonian tristichopterid sarcopterygian Mandageria fairfaxi , from Canowindra, NSW, Australia, differs radically from the conservative pattern present in other 'osteolepiforms' (stem–group tetrapodomorph fishes) and non–dipnoan sarcopterygian fishes in general. The basioccipital region is short, displaced anteriorly, and either unossified or loosely articulated to the exoccipital, leaving most or all of the notochordal tunnel open ventrally. The exoccipital complex, which is developed into a large saddle that would have rested on top of the notochord, carries large, triangular articular facets on its posterior face and appears to have formed part of a functional neck joint, a synovial articulation between the skull and vertebral column that allows the former to rotate against the latter. Such a joint is characteristic of post–Devonian tetrapods, but unknown in other sarcopterygians. We infer that the ventrally open notochordal tunnel allowed gentle flexion of the cranial notochord during (predominantly vertical) rotational movement at the occiput; this is a mechanically unique solution to the problem of creating a mobile neck. Other unusual features of Mandageria include a posteriorly located lateral commissure, and structures on the entopterygoid and lateral commissure that may have been associated with an elaborate spiracular tract. 相似文献
38.
Thomas Ljung Bjrn Andersson Bengt-ke Bengtsson Per Bjrntorp Per Mrin 《Obesity (Silver Spring, Md.)》1996,4(3):277-282
In this study, dexamethasone (dex) was administered in random order in doses of 0.05, 0.125, 0.25 and 0.5 mg at 10 p.m. with measurements of serum Cortisol in the morning (8 a.m.) of this and the following day. The test was performed on 22 apparently healthy men, 40 to 60 years of age, recruited from laboratory personnel, outpatient clinics or advertisements in a newspaper. Eight had a body mass index (BMI) (kg/m2) of <25 and 14 of >25. Twelve men had a waist hip ratio (WHR) of <1.0 and 10 men had a WHR of<1.0. Cortisol values at baseline were correlated inversely with WHR and were usually lower in men with a high (>1.0) rather than a low than low (<1.0) WHR after dex inhibition. There was apparently no inhibition by dex at 0.05 and 0.125 mg on average in men with a WHR of >1.0. In addition, the inhibition at 0.5 mg dex correlated negatively with the WHR and was significantly lower (p<0.05) in men with a WHR of >1.0 than in men with a WHR of <1.0. None of these differences or relationships was found to be dependent on BMI. It is concluded that men with an elevated WHR experience a decrease in the inhibition of Cortisol secretion by dex. It is suggested that this could explain or contribute to the elevated sensitivity of their HPA axis. Furthermore, lower morning Cortisol concentrations suggest a change in diurnal secretion patterns. 相似文献
39.
The results of pollen analysis, magnetic measurements (SIRM), and archaeological and historical investigations, in the Axlarp area are presented. With respect to natural conditions and the distribution of prehistoric features, this area is typical of the higher parts of the Småland uplands, which, agriculturally, is a marginal region of southern Sweden. The study shows that farming in the Axlarp area began at ca. 700 B.C. (dates in calibrated/calendar years). The period 700 B.C.-A.D. 500 was characterized by shifting cultivation of Hordeum and Triticum and much pasture. Between A.D. 500 and A.D. 1200 farming declined but some pasturage was still practised, possibly on a seasonal basis. Two farms were established in the Middle Ages, probably between A.D. 1200–1300. Cereals were sown in stone-cleared fields and pastoral farming and hay making was carried out. One farm was deserted during the 15th or early 16th century and the other developed into the hamlet Axlarp whose farmers practised a three-course cropping system. Land-use history as recorded in the pollen diagram can be related to activities associated with these farms. Cereals grown after A.D. 1200 included Hordeum and Avena, and possibly Triticum and Secale. There are no indications of slash-and-burn cultivation in the area. 相似文献
40.
Earlier studies on social behaviour in the domestic pig have only been performed on groups housed artificially. The present study was undertaken to investigate the social behaviour of free-ranging sows in a well-established flock, so that it could be compared with the behaviour of sows housed indoors that had been studied earlier. The free-ranging flock, which contained 13 animals, 5 of which were sows, lived in an enclosure, approximately 1.1 ha in area. The interaction sequences were registered during 1 h after feeding and during foraging in the enclosure. With sequence analysis, the effect of different behaviours on the behaviour of the receiver animal was measured. This allowed the behaviour patterns to be classed after function. “Aiming”, a behaviour pattern not previously seen, was interpreted as a threat behaviour, being “statistically strongly directive” towards submissive and flight behaviour. The functions of the other 7 behaviours included in the study were found to be the same as in the indoor groups studied earlier. The dominance order was not found to be better established than in the most extensively housed indoor group, but the level of aggression was very low, indicating that a stable dominance order does not automatically lead to a low level of aggression. It was found that the dominance order was mainly maintained through the behaviour of the subordinate animals, supporting the use of an “avoidance order” instead of an “aggression order” as a measurement of social dominance. On the whole, no dramatic differences were found between the behaviour of the free-ranging sows and that of the most extensively housed of the indoor groups studied earlier, although great differences were found between free-ranging sows and sows kept in confinement indoors. 相似文献