217 research outputs found
Thyroid hormone uptake in cultured rat anterior pituitary cells: effects of energy status and bilirubin
Transport of thyroxine (T(4)) into the liver is inhibited in fasting and
by bilirubin, a compound often accumulating in the serum of critically ill
patients. We tested the effects of chronic and acute energy deprivation,
bilirubin and its precursor biliverdin on the 15-min uptake of
[(125)I]tri-iodothyronine ([(125)I]T(3)) and [(125)I]T(4) and on TSH
release in rat anterior pituitary cells maintained in primary culture for
3 days. When cells were cultured and incubated in medium without glucose
and glutamine to induce chronic energy deprivation, the ATP content was
reduced by 45% (P<0. 05) and [(125)I]T(3) uptake by 13% (NS), but TSH
release was unaltered. Preincubation (30 min) and incubation (15 min) with
10 microM oligomycin reduced ATP content by 51% (P<0.05) and 53% (P<0. 05)
under energy-rich and energy-poor culture conditions respectively;
[(125)I]T(3) uptake was reduced by 66% (P<0.05) and 64% (P<0.05). Neither
bilirubin nor biliverdin (both 1-200 microM) affected uptake of
[(125)I]T(3) or [(125)I]T(4). Bilirubin (1-50 microM) did not alter basal
or TRH-induced TSH release. In conclusion, the absence of inhibitory
effects of chronic energy deprivation and bilirubin on thyroid hormone
uptake by pituitary cells supports the view that the transport is
regulated differently than that in the liver
Biogeophysical feedbacks trigger shifts in the modelled vegetation-atmosphere system at multiple scales
Terrestrial vegetation influences climate by modifying the radiative-, momentum-, and hydrologic-balance. This paper contributes to the ongoing debate on the question whether positive biogeophysical feedbacks between vegetation and climate may lead to multiple equilibria in vegetation and climate and consequent abrupt regime shifts. Several modelling studies argue that vegetation-climate feedbacks at local to regional scales could be strong enough to establish multiple states in the climate system. An Earth Model of Intermediate Complexity, PlaSim, is used to investigate the resilience of the climate system to vegetation disturbance at regional to global scales. We hypothesize that by starting with two extreme initialisations of biomass, positive vegetation-climate feedbacks will keep the vegetation-atmosphere system within different attraction domains. Indeed, model integrations starting from different initial biomass distributions diverged to clearly distinct climate-vegetation states in terms of abiotic (precipitation and temperature) and biotic (biomass) variables. Moreover, we found that between these states there are several other steady states which depend on the scale of perturbation. From here global susceptibility maps were made showing regions of low and high resilience. The model results suggest that mainly the boreal and monsoon regions have low resiliences, i.e. instable biomass equilibria, with positive vegetation-climate feedbacks in which the biomass induced by a perturbation is further enforced. The perturbation did not only influence single vegetation-climate cell interactions but also caused changes in spatial patterns of atmospheric circulation due to neighbouring cells constituting in spatial vegetation-climate feedbacks. Large perturbations could trigger an abrupt shift of the system towards another steady state. Although the model setup used in our simulation is rather simple, our results stress that the coupling of feedbacks at multiple scales in vegetation-climate models is essential and urgent to understand the system dynamics for improved projections of ecosystem responses to anthropogenic changes in climate forcing
Effects of interleukin-1 beta on thyrotropin secretion and thyroid hormone uptake in cultured rat anterior pituitary cells
The effects of interleukin-1 beta (IL-1 beta) and tumor necrosis
factor-alpha (TNF alpha) on basal and TRH-induced TSH release, and the
effects of IL-1 beta on the uptake of [125I]T3 and [125I]T4 and on nuclear
binding of [125I]T3 were examined. Furthermore, the release of other
anterior pituitary hormones in the presence of IL-1 beta was measured.
Anterior pituitary cells from male Wistar rats were cultured for 3 days in
medium containing 10% FCS. Incubation were performed at 37 C in medium
with 0.5% BSA for measurement of [125I]T3 uptake and with 0.1% BSA for
measurement of [125I]T4 uptake. Exposure to IL-1 beta (1 pM-1 nM) or TNF
alpha (100 pM) for 2-4 h resulted in a significant decline in TSH release,
which was almost 50% (P < 0.05) for 1 nM IL-1 beta and 24% (P < 0.05) for
100 pM TNF alpha. Measurement of other anterior pituitary hormones (FSH,
LH, PRL, and ACTH) in the same incubation medium showed that IL-1 beta did
not alter their release. When the effects of IL-1 beta (1 pM-1 nM) and TNF
alpha (100 pM) on TRH-induced TSH release were measured in short term
experiments, the inhibitory effects had disappeared. The addition of 1-100
nM octreotide, a somatostatin analog, resulted in a decrease in
TRH-induced TSH release up to 33% of the control value (P < 0.05).
Exposure to dexamethasone (1 nM to 1 microM) affected basal and
TRH-induced TSH release similar to the effect of IL-1 beta. The 15-min
uptake of [125I]T3 and [125I]T4, expressed as femtomoles per pM free
hormone, was not affected by the presence of IL-1 beta (1-100 pM). When
IL-1 beta (100 pM) was present during 3 days of culture, TSH release was
reduced to 88 +/- 2% of the control value (P < 0.05). This effect was not
associated with an altered [125I]T3 uptake (15 min to 4 h) or with any
change in nuclear T3 binding. We conclude that 1) IL-1 beta decreases TSH
release by a direct action on the pituitary; 2) this effect is not due to
elevated thyroid hormone uptake or increase T3 nuclear occupancy; 3) IL-1
beta does not affect TRH-induced TSH release or the release of other
anterior pituitary hormones; and 4) TNF alpha affects basal and
TRH-induced TSH release in the same way as IL-1 beta
Naming a phantom – the quest to find the identity of Ulluchu, an unidentified ceremonial plant of the Moche culture in Northern Peru
The botanical identification of Ulluchu, an iconic fruit frequently depicted in the art of the pre-Columbian Moche culture that flourished from A.D. 100–800 on the Peruvian north coast, has eluded scientists since its documentation in ceramics in the 1930s. Moche fine-line drawings of Ulluchu normally depict seed-pods or seeds floating in the air in sacrificial scenes, associated with runners and messengers or intoxicated priests. It is a grooved, comma-shaped fruit with an enlarged calyx found mainly in fine-line scenes painted on Moche ceramics. The term first appeared without linguistic explanation in the work of pioneer Moche scholar Rafael Larco Hoyle, and the identification of the plant was seen as the largest remaining challenge in current archaebotany at the Peruvian North coast. The name Ulluchu seems to have been coined by Larco. According to his description, the name originated in the Virú River valley, and is supposedly of Mochica origin. However, there is no linguistic evidence that such a term indeed existed in the Mochica or Yunga language
Wetscapes : Restoring and maintaining peatland landscapes for sustainable futures
Peatlands are among the world's most carbon-dense ecosystems and hotspots of carbon storage. Although peatland drainage causes strong carbon emissions, land subsidence, fires and biodiversity loss, drainage-based agriculture and forestry on peatland is still expanding on a global scale. To maintain and restore their vital carbon sequestration and storage function and to reach the goals of the Paris Agreement, rewetting and restoration of all drained and degraded peatlands is urgently required. However, socio-economic conditions and hydrological constraints hitherto prevent rewetting and restoration on large scale, which calls for rethinking landscape use. We here argue that creating integrated wetscapes (wet peatland landscapes), including nature preserve cores, buffer zones and paludiculture areas (for wet productive land use), will enable sustainable and complementary land-use functions on the landscape level. As such, transforming landscapes into wetscapes presents an inevitable, novel, ecologically and socio-economically sound alternative for drainage-based peatland use
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