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1.
D. Cvetkovi N. Tomaevi G. F. Ficetola J. Crnobrnja-Isailovi C. Miaud 《Journal of Zoological Systematics and Evolutionary Research》2009,47(2):171-180
Large‐scale patterns of body size variation are described by well‐known generalizations such as Bergmann’s rule; the generality and underlying causes of these patterns have been much debated. Intraspecific extension of this rule was tested in various ectotherms, and evidence was found for both Bergmann and converse Bergmann clines. In this study, we explored spatial patterns of variation in a widespread amphibian, the Common toad (Bufo bufo), along a 2240 km latitudinal gradient across Europe. We tested for covariation of adult body size, age and growth parameters with latitude, altitude, length of activity period and mean temperature during this period using both original and literature data. We selected 13 European populations, representing a latitudinal range from 43 to 63°N and altitudinal range from 15 to 1850 m a.s.l. The length of activity period (12–33 weeks) and Tmean (6.6–15.6°C) significantly decreased as latitude and altitude of these populations increased. Mean body size decreased as latitude increased (not with altitude), and increased with Tmean (not with length of activity period). Mean and minimal adult age increased with latitude and altitude, longevity increased with altitude only. Age increased as length of activity period decreased (not with Tmean). The growth coefficient (0.32–0.92 in males, 0.18–0.74 in females, available for six populations) decreased as altitude increased, and increased as both length of activity period and Tmean increased; latitudinal trend was non‐significant. Our analysis shows that B. bufo clearly exhibited a converse Bergmann cline along latitudinal gradient, but not along altitudinal gradient; the main effect of elevation was on age. The effects of ecological conditions also differed: body size increased with Tmean, while age parameters were related to the length of activity period. This study highlights that, to identify causal factors underlying general ecogeographical rules, we have to take into account different phases of the life cycle, co‐variation among life history traits and ecological factors acting on each of these traits. In amphibians with complex life cycles, lack of appropriate demographical or ecological data may affect our understanding of the variety of observed body size patterns. 相似文献
2.
Irmeli Vuorela Matti Saarnisto Terttu Lempiäinen Jussi-Pekka Taavitsainen 《Vegetation History and Archaeobotany》2001,10(3):121-138
The village of Pegrema in Karelia may be regarded as a Stone Age innovation centre in the large Lake Onega area. Two pollen
and plant macrofossil diagrams are presented which represent the first contribution to the study of human impact in the area
using anthropogenic pollen indicators. A continuous but sporadic human presence from the Mesolithic onwards is demonstrated.
While there is no archaeological evidence relating to the period 4200–3000 B.P., the pollen data suggest continuous, though
rather sparse human presence. The data do not support any natural catastrophes in Pegrema as has been suggested elsewhere.
Cerealia pollen is recorded earlier than expected (c. 5000 B.P.=. In the Bronce Age and Iron Age, the settlement of the Zaonezhye
peninsula is reflected by a slight increase in herb pollen representation, sporadic Cerealia pollen and several periods of
regression in Picea. The long introductory period of agriculture to the area, as well as the similarities and discrepancies between different
sources of evidence (palaeoecological, archaeological and historical) are discussed at some length. The start of land clearance
for permanent cultivation in the profile Pegrema S was dated to the late 13th century. The beginning of more intensive field cultivation in the 15th century is clearly seen in the pollen succession at both localities. The fluctuation in anthropogenic indicators can be related
to population density based on historical data. The village of Pegrema was depopulated in 1956 which is reflected in a distinct
decline in settlement indicators.
Received February 17 / Accepted May 19, 2000 相似文献
3.
Helga Liese-Kleiber 《Vegetation History and Archaeobotany》1993,2(1):37-46
The Federsee mire in the Alpine Foreland of south-western Germany contains a record of a remarkable archaeological landscape.
Since the first excavations in the 1920's, botanists and mire geologists have studied the relationship between landscape development
and settlement at this site. In a new study, funded by the Deutsche Forschungsgemeinschaft, various disciplines embracing both archaeology and the natural sciences have come together to address outstanding questions
and problems. Pollen analysis can only be carried out within the Federsee mire since no other suitable mires are found in
the vicinity. Because of the size of the Federsee basin (30 km2 at the end of the last glaciation), the regional pollen component, consisting predominantly of arboreal pollen, prevails
over the herbaceous component which mainly reflects activity associated with settlements. Nevertheless, phases of settlement
are clearly reflected in the radiocarbon-dated pollen diagrams and can be correlated with Neolithic and Bronze Age settlements
that are dated either by dendrochronology or radiocarbon. In addition, some settlement phases were identified for which no
archaeological evidence is yet available. As a consequence of human impact during the Atlantic and Subboreal periods, a gradual
opening-up and change in structure of the forests is recorded. There is evidence for an exceptionally high level of human
impact associated with two Bronze Age settlements that were present in the central part of the Federsee mire. Each of the
five transgressions of the Federsee so far identified occurred at the end of a settlement phase. These may have resulted from
anthropogenic activity rather than climatic change.
A contribution to the 8th IPC, Aix-en-Provence, Sept. 1992 相似文献
4.
Impact of Human Activity on Regional Forest Composition and Dynamics in Central New England 总被引:7,自引:3,他引:4
Historical and ecological data from north-central Massachusetts suggest that widespread and intensive human disturbance after
European settlement led to a shift in forest composition and obscured regional patterns of species abundance. A paleoecological
approach was required to place recent forest dynamics in a long-term context. Pollen and charcoal data from 11 small lakes
in north-central Massachusetts were used to reconstruct local vegetation dynamics and fire histories across the region over
the past 1000 years. The sites are located across an environmental gradient. Paleoecological data indicate that prior to European
settlement, there was regional variation in forest composition corresponding to differences in climate, substrate, and fire
regime. Oak, chestnut, and hickory were abundant at low elevations, whereas hemlock, beech, sugar maple, and yellow birch
were common at high elevations. Fire appears to have been more frequent and/or intense at lower elevations, maintaining high
abundances of oak, and archaeological data suggest Native American populations were greater in these areas. A change in forest
composition at higher elevations, around 550 years before present, may be related to the Little Ice Age (a period of variable
climate), fire, and/or activity by Native Americans, and led to regional convergence in forest composition. After European
settlement, forest composition changed markedly in response to human disturbance and there was a sharp increase in rates of
vegetation change. Regional patterns were obscured further, leading to homogenization of broad-scale forest composition. There
is no indication from the pollen data that forests are returning to pre-European settlement forest composition, and rates
of vegetation change remain high, reflecting continuing disturbance on the landscape, despite regional reforestation.
Received 14 May 1997; accepted 5 August 1997. 相似文献
5.
Gill Plunkett 《Vegetation History and Archaeobotany》2009,18(4):273-295
In Ireland, the Middle to Late Bronze Age (1500–600 cal b.c.) is characterised by alternating phases of prolific metalwork production (the Bishopsland and Dowris Phases) and apparent
recessions (the Roscommon Phase and the Late Bronze Age-Iron Age transition). In this paper, these changes in material culture
are placed in a socio-economic context by examining contemporary settlement and land-use patterns reconstructed from the pollen
record. The vegetation histories of six tephrochronologically linked sites are presented, which provide high-resolution and
chronologically well-resolved insights into changes in landscape use over the Middle to Late Bronze Age. The records are compared
with published pollen records in an attempt to discern if there are trends in woodland clearance and abandonment from which
changes in settlement patterns can be inferred. The results suggest that prolific metalworking industries correlate chronologically
with expansion of farming activity, which indicates that they were supported by a productive subsistence economy. Conversely,
declines in metalwork production occur during periods when farming activity was generally less extensive and perhaps more
centralised, and it is proposed that disparate socio-economic or political factors, rather than a collapse of the subsistence
economy, lie behind the demise of metalworking industries. 相似文献
6.
K. L. Metzger A. R. E. Sinclair Ray Hilborn J. Grant C. Hopcraft Simon A. R. Mduma 《Biodiversity and Conservation》2010,19(12):3431-3444
Human population growth rates on the borders of protected areas in Africa are nearly double the average rural growth, suggesting
that protected areas attract human settlement. Increasing human populations could be a threat to biodiversity through increases
in illegal hunting. In the Serengeti ecosystem, Tanzania, there have been marked declines in black rhino (Diceros bicornis), elephant (Loxodonta africana) and African buffalo (Syncerus caffer) inside the protected area during a period when there was a reduction of protection through anti-poaching effort (1976–1996).
Subsequently, protection effort has increased and has remained stable. During both periods there were major differences in
population decline and recovery in different areas. The purpose of this paper is to analyse the possible causes of the spatial
differences. We used a spatially structured population model to analyze the impacts of three factors—(i) hunting, (ii) food
shortage and (iii) natural predation. Population changes were best explained by illegal hunting but model fit improved with
the addition of predation mortality and the effect of food supply in areas where hunting was least. We used a GIS analysis
to determine variation in human settlement rates and related those rates to intrinsic population changes in buffalo. Buffalo
populations in close proximity to areas with higher rates of human settlement had low or negative rates of increase and were
slowest to recover or failed to recover at all. The increase in human populations along the western boundary of the Serengeti
ecosystem has led to negative consequences for wildlife populations, pointing to the need for enforcement of wildlife laws
to mitigate these effects. 相似文献
7.
Antisettlement and Narcotic Action of Analogues of Diterpene Marine Natural Product Antifoulants from Octocorals 总被引:2,自引:0,他引:2
Anthony S. Clare Daniel Rittschof Donald J. Gerhart Irving R. Hooper Joseph Bonaventura 《Marine biotechnology (New York, N.Y.)》1999,1(5):427-436
Prevoius studies have determined that the octocorals Renilla reniformis and Leptogorgia virgulata contain diterpenes that are potent inhibitors of barnacle settlement. These antifoulants—the renillafoulins and pukalide—are,
however, comparatively complex and thus are not amenable to commercial exploitation. The present study examined 19 analogues,
based on the functional groups of lactone and furan rings in the parent molecules, for antisettlement activity and toxicity.
The latter parameters are presented as EC50 values for inhibition of cypris settlement and naupliar swimming, respectively. Assays of a subset of the analogues indicated
that they were active in solution rather than when bound to a surface and that at relatively high concentrations they had
a narcotic action. The mechanism whereby some of the analogues were able to inhibit settlement at nontoxic concentrations
has yet to be explained but suggests that there is merit in the present approach to antifoulant development.
Received April 1, 1998; accepted February 4, 1999. 相似文献
8.
Laura I. Kooistra 《Vegetation History and Archaeobotany》2008,17(1):113-125
Botanical investigation of archaeological sites situated in the northwest of the region bounded by the rivers Maas, Scheldt
and Demer (‘MSD region’), west of the city of Breda, has provided a great deal of evidence about the landscape and its use
in the period between 2000 b.c. and a.d. 1500. From pollen analysis, it appears that this cover-sand area gradually lost its woodlands through human activity after
the beginning of the Bronze Age (ca. 2000 b.c.). Patches of woodland did survive there, however, until the early Middle Ages. In contrast to the cover-sand area in the
vicinity of ’s-Hertogenbosch and Oss-Ussen in the northeast of the MSD region, the first large heathlands in the Breda area
did not evolve until the early Middle Ages. In late prehistory, land use in this area was not much different from that in
the micro-region of ’s-Hertogenbosch and Oss-Ussen. In the Bronze Age, Hordeum vulgare ssp. vulgare (hulled six-row barley) and Triticum dicoccon (emmer wheat) were grown. During the Iron Age, Panicum miliaceum (common millet) and T. spelta (spelt wheat) were introduced, but these crops disappeared during the Roman period. The Roman period is remarkable because
of the lack of any Mediterranean culinary herbs or exotic fruits. Only pollen of Juglans regia (walnut), found around the transition from the Roman period to the early Middle Ages, indicates the introduction of an exotic
tree into the region. From the early Middle Ages onwards, Secale cereale (rye) was the most important cereal, which was grown as a winter crop. In the course of the Middle Ages, arable weeds of
the Sclerantho annui-Arnoseridetum plant community appeared, which is associated with the continuous growing of rye. 相似文献
9.
In this research, we hypothesized that, in rats, adaptation to high altitude (2500 m) plus training at low altitude (610 m),
”living high–training low”, improves physical performance at low altitude more than living and training at low altitude (610
m). Rats were divided into four groups: (1) living at low altitude (LL, n=12), (2) living and training at low altitude (LLTL, n=13), (3) living at high altitude (LH, n=12), (4) living at high altitude and training at low altitude (LHTL, n=13). The program for living at high altitude involved raising rats under hypobaric hypoxia (equivalent to 2500 m), and the
training program consisted of running on a tread-mill at low altitude. All groups were raised at each altitude and trained
to run at 35 m/min for 40 min/day, 6 days/week for 6 weeks. During this program, we measured heart rates both at rest and
during exercise, and performed running-time trials. The mean heart rate during exercise was lower in groups with training
than in groups without training, and the groups receiving training could run longer than the untrained groups. The LHTL group
especially showed the lowest mean heart rate during exercise and the longest running time among all groups. After 6 weeks
of the training program, all rats had a catheter implanted into the carotid artery, and the mean systemic arterial pressure
was continuously measured during treadmill running. The rate of increase of this pressure as the running intensity increased
was lower in groups with training than in groups without training, especially in the LHTL group. Finally, we anesthetized
all the rats and extracted both the right and left ventricles, and the triceps surae and liver. Training increased the weight
of the left ventricle, triceps surae, and liver. The increase in weight of the left ventricle and triceps surae was higher
in the LHTL group than in the LLTL group in particular. It appeared that living high– training low may be an effective strategy
to improve performance ability at low altitude.
Received: 16 July 1999 / Revised: 24 January 2000 / Accepted: 25 January 2000 相似文献
10.
Swagatika Dash Cuili Jin On On Lee Ying Xu Pei-Yuan Qian 《Journal of industrial microbiology & biotechnology》2009,36(8):1047-1056
In this study, we screened seven novel sponge-associated marine bacteria for their antibacterial and antilarval-settlement
activity in order to find possible new sources of non-toxic or less toxic bioactive antifoulants. The anti-bacterial-growth
activity of crude extracts of each bacterium was evaluated by the disk-diffusion assay. Extracts of four potent bacteria with
high and broad spectra of antibacterial activity were further separated with solvents of different polarities (hexane and
ethyl acetate). To evaluate their indirect inhibitive effect on larval settlement, we tested for their antibiofilm formation
activity against two of the test bacteria (Vibrio halioticoli and Loktanella hongkongensis) inductive to Hydroides elegans larval settlement. About 60 and 87% of the extracts inhibited biofilm formation by V. halioticoli and by L. hongkongensis respectively. The extracts were also tested for their direct antilarval-settlement activity against the barnacle Balanus amphitrite and the polychaete H. elegans; 87% of the extracts had a strong inhibitive effect on larval settlement of both species. Extracts of two of the isolates
completely inhibited larval settlement of B. amphitrite at 70 μg ml−1 and H. elegans at 60 μg ml−1. The organic extracts of Winogradskyella poriferorum effectively inhibited the larval settlement of both H. elegans and B. amphitrite and the biofilm formation of the two bacterial species. The metabolites present in the active crude extracts were profiled
using GC MS, and the most prevalent metabolites present in all extracts were identified. This study successfully identified
potential new sources of antifouling compounds.
相似文献
Pei-Yuan QianEmail: |
11.
Native species richness commonly declines with increasing altitude, but patterns of introduced species richness across altitudinal
gradients have been less frequently studied. We surveyed introduced roadside weeds along altitudinal transects ranging from
30 to 4,100 m in Hawai’i, with the objectives of (1) testing the hypothesis that a mass effect due to mixing of tropical and
temperate species at mid-elevation promotes a hump-shaped pattern of introduced species richness with altitude, and (2) testing
the potential roles of anthropogenic activity, energy (temperature) and water-energy dynamics (productivity-diversity hypothesis)
in determining introduced weed richness. A total of 178 introduced weeds were recorded. Introduced weed richness does not
decline monotonically with altitude. Rather, mixing of tropical and temperate species helps to maintain high mean richness
up to 2,000 m, suggesting a mass effect, but without a distinct richness peak. Patchy occurrence of a transformer species,
Pennisetum clandestinum, introduced high variance in richness at mid-elevations. General linear models considering estimated actual evapotranspiration
(AET, a measure of energy-water dynamics) together with an index of human activity (distance from urban area or length of
major roads) accounted for more variance in introduced weed richness than models with energy alone (temperature) and human
activity. Native Hawaiian species richness along roadsides was also weakly correlated with AET but negatively associated with
human activity. Our observed association between introduced species richness and AET mirrors patterns reported for native
species richness around the world, indicating that AET-richness patterns can develop on a short time scale (on the order of
100 years). To test the generality of introduced weed richness patterns, we tried using the Hawai’i island model to predict
weed richness on the neighboring island of Maui. Although weed richness on Maui was under-predicted, the same predictors (human
activity and AET) were important on Maui. Scaling for differences in regional human population density or economic activity
(both higher on Maui) may allow more accurate and transferable quantitative predictions of introduced weed richness patterns. 相似文献
12.
Carlo Polidori Pablo Mendiola Josep D. Asís José Tormos Jesús Selfa 《Journal of Ethology》2010,28(2):353-361
Studies which quantitatively analyse how aculeate parasitoids exploit their window of opportunity to find and attack a host
are scarce, despite the recognized importance of parasitic pressure as a driving force that promotes aggregate nesting in
their hosts. We have studied the activity and behaviour of the velvet ant Nemka viduata, an ectoparasitoid of immature stages of the digger wasp Stizus continuus. Due to the resource exploited by the parasitoid (mature larvae and prepupae), and in general agreement with basic optimal
foraging theory, we expected a major activity at late stages of the host seasonal provisioning period, an independence from
the host daily provisioning patterns and a spatial positive association with host nest density. In accordance with these predictions,
during the season, the parasitoid resulted was more active at the end of the host provisioning period, and across the day,
it showed an inverse quadratic pattern of activity, in contrast to the positive one shown by the host. Thus, at both temporal
scales, N. viduata activity was highly asynchronous with that of the host. At a spatial scale, however, the activity of the velvet ants was
correlated with host nest density, although there is weak evidence suggesting that areas of high host density suffered from
a higher rate of parasitism. Multivariate analyses confirmed a number of relevant factors associated with velvet ants’ activity,
including nest density (positive), air temperature and the hour of the day (both negative). In addition, the activity of both
male S. continuus and male N. viduata entered in the models in association with female parasitoid’s activity, probably because of their mating strategy. 相似文献
13.
The Czech Republic is a central European country whose geographical location, natural conditions, history of human settlement,
and present land-use management make it relatively prone to plant invasions, hence it represents a convenient model for their
study. Research in plant invasions, which date to the late 19th century, is reviewed in the present paper. A long-term floristic
tradition allowed for the accumulation of a large body of floristic data on alien plants. During the 1960s–1970s, the main
research focus was on their distribution. In this period, attempts were also made to predict potential invasiveness of weeds
of arable land. The success rate of this prediction was about 39%. Considerable effort was put into a detailed classification
of human-accompanying plants and the terminology associated with the issue. There is a high level of taxonomic research conducted
in the country, and the new Flora of the Czech Republic treats the immigration status of taxa with reasonable care and detail.
A complete, serious catalogue of the alien plants of the country has been published recently: there are currently 1378 alien
plants (33.4% of the total flora). The core of present research in plant invasions is in ecological, biological, and biogeographical
studies, focussed on (i) the history of invasion of particular species since their introduction, (ii) the role and importance
of alien species in vegetation, including their participation in succession, and (iii) the major invasive species of the Czech
flora and comparison of congeners. Reynoutria spp., Heracleum mantegazzianum, Oenothera spp., Pinus strobus, and Bidens frondosa are among the taxa most intensively studied in recent time. A complete list of 69 invasive plants in the Czech flora introduced
after the year 1500 [following the definition of Richardson et al. (2000a) Diversity and Distributions 6: 93–107] is given.
The available legal instruments relevant to the issue are reviewed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Most marine fishes have pelagic larvae that settle to benthic juvenile/adult habitats. Ecologists have argued that mortality rates are particularly high during the settlement transition, but relevant data have been sparse. Recently, researchers have used several novel techniques to estimate the magnitude of predation mortality during the settlement transition. We used meta-analysis to determine that for 24 taxonomically diverse species in geographically widespread locations, an estimated 55.7% (CI: 43.0–65.5%) of juveniles were consumed within 1–2 days of settlement. Such high mortality highlights this brief period as a key phase in the life history of fishes and supports the view that these communities are strongly influenced by predation. Additionally, we argue that because predators have such strong effects on juvenile survival, the population and community dynamics of reef fishes may be linked to human exploitation of reef predators. 相似文献
15.
Long term (from the Mesolithic to the Bronze Age) habitation of the Akali settlement on a clearly defined bog-island in East Estonia is used as an example of transitional development from a prosperous foragers’ habitation centre to a hinterland of established farming cultures, taking place through availability, substitution and consolidation phases of crop farming in the boreal forest zone. The pre-Neolithic finds of Triticum and Cannabis t. pollen at c. 5600 b.c. are interpreted as possible indications of the acquaintance of foragers with farming products, through contacts with central European agrarian tribes during the availability phase. The substitution phase is marked by more or less scattered pollen finds of various cereals and hemp and, at Akali, is connected with Neolithic period 4900–1800 b.c. An increasing importance of crop farming in the economy is characteristic of the consolidation phase, but because natural conditions are unfavourable for arable land-use, a regression of human presence is recorded during the second part of the Neolithic. The settlement was abandoned during the Bronze Age at the time when crop farming become the basis of the economy in Estonia. The re-colonisation of the area, traced to ca. a.d. 1200, took place for political reasons rather than through increasing suitability of the landscape.Editorial responsibility: Felix Bittmann 相似文献
16.
雪岭云杉(Picea schrenkiana)是天山特有树种,也是天山森林优势种;研究其种群结构动态的海拔梯度变化有助于保护、管理这一重要的森林资源。本研究以东天山北坡江布拉克景区的雪岭云杉种群为研究对象,利用便携式背包雷达(LiBackpack)扫描与手测验证相结合的方法,在1800-2600 m的海拔梯度上设置了27个30 m×30 m(共24300 m2)的样方进行调查测量,基于树木胸径数据,制作了雪岭云杉的静态生命表和存活曲线,计算其种群数量动态变化指数和时间序列预测模型,分析不同海拔高度雪岭云杉种群结构动态特征。结果表明:1)整体来看,江布拉克景区雪岭云杉种群结构现状良好,但幼苗(DBH<5 cm)储备明显不足。低、高海拔雪岭云杉种群径级结构表现为"倒J型",中海拔段为"稳定型"。雪岭云杉种群在不同海拔高度存在幼龄树死亡率高的共性。2)中海拔雪岭云杉种群动态变化指数最低;低海拔种群危险率最低;表明中海拔树木存活能力最强,雪岭云杉种群在中海拔生长状况最好。3)时间序列预测模型表明,研究区雪岭云杉种群未来动态更新趋势良好,未来2、4、6、8径级时,低海拔段Ⅱ-Ⅶ径级、高海拔段Ⅱ、Ⅳ-Ⅷ径级个体数量呈现增加的趋势;中海拔不同径级个体数量变化较小。建议对低、高海拔雪岭云杉种群个体采取抚育、间伐措施,中海拔砍伐过多的区域应移栽原生苗而促进雪岭云杉种群发育更新;同时加大管理力度,减少人为干扰。 相似文献
17.
The objective of this study was to analyze the spatial and temporal dynamics of Chironomidae larvae assemblages in a subtropical
mountain river basin of northwestern Argentina. We hypothesized that they would respond to (1) environmental changes along
the altitudinal gradient in the Yungas forests; (2) environmental changes caused by spates (e.g., increased discharge or sediment transportation). We sampled five
sites along an altitudinal gradient of ca. 1,500 m (from 680 to 2,170 m) during low-water and high-water period for 2 years.
The Chironomidae larvae assemblages varied along the altitudinal gradient and between sampling periods based on an indicator
species analyses and an ordination analyses (NMDS). The best indicator for high altitude sites was “Genus X” followed by Onconeura sp.2, “Genus 9”, “Genus 10”, and Rheotanytarsus sp.2; while Rheotanytarsus lamellatus, Oliveiriella sanjavieri, and Thienemanniella sp. were good indicators for low altitude sites. O. sanjavieri and R. lamellatus were the best indicators for high-water period. The most relevant environmental variables influencing their spatial and temporal
distribution were altitude, water temperature, conductivity, and pH. This study is the first to analyze and describe in detail
the spatial and temporal distribution of Chironomidae larvae assemblages in northwestern Argentina, and most of the taxa reported
here are new records for the region. 相似文献
18.
Tomoyuki Kawamoto Mieko Nishi Kojiro Takahashi Toshio Nishiyama J. Denry Sato Shigehiko Taniguchi 《In vitro cellular & developmental biology. Plant》1989,25(10):965-970
Summary The stimulatory effects of transforming growth factor β (TGF-β) on epidermal growth factor (EGF)-dependent growth of adult
and newborn human fibroblasts were investigated. EGF-stimulated growth in low serum of dermal fibroblasts from a 41 year-old
adult (HSF-41) was less than half that of newborn foreskin fibroblasts (HFF). The EGF-stimulated growth of HFF after 55 population
doublings (HFF-55) was similarly reduced. The decreased growth response to EGF of fibroblasts, agedin vivo andin vitro appeared to result principally from a decreased sensitivity to EGF due to a decreased number and affinity of high affinity
EGF receptors (H-EGFR). Pre-incubation of HSF-41 and HFF-55 with 25 pM TGF-β enhanced the growth responses of these cells
to EGF and increased the levels of high affinity EGF-binding by these cells Thus, the stimulation by TGF-β of EGF-dependent
growth of human fibroblasts agedin vivo orin vitro is mediated by increased levels of high affinity EGF binding.
This research was supported in part by a grant-in-aid for scientific research (61480388) and a special project research grant
to Okayama University from the Japanese Ministry of Education, Science and Culture.
Editor's statement TGF beta interaction with its receptor is known to affect EGF receptors. In this paper a functional biological
association is established. 相似文献
19.
In previous research, it was determined that the altitude of origin altered the parameters of photic entrainment and free‐running rhythmicity of adult locomotor activity of the high‐altitude Himalayan (haH) strain (Hemkund‐Sahib, 4121 m above sea level) of Drosophila helvetica compared to the low‐altitude Himalayan (laH) strain (Birahi, 1132 m above sea level) of the same species. The present study investigated whether the altitude of origin also affects the parameters of the light pulse phase response curve (PRC) of the adult locomotor activity rhythm of the haH strain. Light pulse PRCs were determined for both strains against the background of constant darkness. Although both were “weak” or type 1 PRCs, the PRC for the haH strain differed from that of the laH strain in three basic parameters. The PRC for the haH strain was of low amplitude, had a protracted dead zone, and showed a ratio of the advance to delay region (A/D>1), while the PRC of the laH strain was characterized by high amplitude, absence of dead zone, and a A/D ratio<1. The asymmetric PRCs of these strains might explain the process of photic entrainment to 24 h light‐dark cycles, as the long period of the free‐running rhythm (τ) of the haH strain is complemented with a larger advance portion of its PRC (A/D>1), whereas the short τ of the laH strain is matched with a larger delay portion of its PRC (A/D<1). Prolonged dead zone and low amplitude in the PRC of the haH strain imply that the photic sensitivity of this strain has been drastically diminished as an adaptation to environmental conditions at the altitude of its origin. While adults of this strain begin activity in very bright light in the forenoon due to non‐permissible low temperature in the morning, the converse is true for the laH strain. 相似文献
20.
Insular ecosystems have been subjected to severe hardship during the last millennia. Large numbers of insular bird species
have undergone local disappearances and full extinctions, and a high number of insular birds are currently categorised as
endangered species. In most of these cases, extinction—or endangerment—is in direct relation to the arrival of ‘aboriginal’
and/or imperialist waves of human settlement. Insular bird extinction events have been documented to have occurred at times
corresponding to aboriginal settlement at many archipelagos and isolated islands, such as the Hawaiian Islands, New Zealand,
the West Indies or the tropical Pacific Islands. However, no bird extinctions could be attributed to the first settlers of
the Canary Islands—until now. The first accelerator mass spectrometer radiocarbon (14C) dating of collagen from a bone of the Dune Shearwater Puffinus holeae (3395 ± 30 year BP), an extinct bird from the Canary Islands, indicates a late Holocene extinction event. This relatively
recent date, together with some features of this bird (large body size, breeding areas situated at very accessible places)
and the absence of its bones from the entire archaeological record suggests that the extinction occurred close to the time
that the first human settlement occurred on the islands. 相似文献