186 research outputs found
Phytoecdysteroids: understanding their anabolic activity
No full textPhytoecdysteroids, polyhydroxylated ketosteroids, are the plant analogues of insect growth hormones. Although their role in insect molting is well characterized, their function in plants is less clear. Lacking the properties of classic plant hormones, phytoecdysteroids may be involved in plant growth and defense. One of the main benefits of phytoecdysteroids may be their therapeutic effects on mammals, including humans. Their claimed medicinal properties include anabolic, adaptogenic, hepatoprotective, and hypoglycemic activity. Although ethnobotanical use has been supported by some evidence, the research is quite limited, lacking the scientific rigor necessary to be convincing.
Two ecdysteroid containing plants, Ajuga turkestanica, and Spinacia olearaceae (Spinach), were selected as beneficial sources of phytoecdysteroids. Cultivation, analysis of ecdysteroid content, and characterization of anabolic activity were performed to support future medicinal use.
Phytoecdysteroids' anabolic activity, one of their most interesting properties due to the claimed lack of androgenic effect, was studied. Anabolic activity was confirmed in animal studies and a cellular model of skeletal muscle. The cellular model was used to characterize ecdysteroids' effect on protein incorporation and to elucidate the signal transduction pathway involved. Ecdysteroid's lack of androgenic activity was confirmed in vivo and in vitro, with ecdysteroids showing no specific binding to the androgen receptor.
Identification of mammalian nuclear receptors homologous with the insect nuclear ecdysone receptor led to binding and activation assays of potential receptors using ecdysteroids. The discovery of a lesser known membrane bound G Protein Coupled Receptor (GPCR) insect ecdysone receptor, DoEcR, suggested the existence of a hypothetical mammalian membrane bound GPCR ecdysone receptor.
Use of specific inhibitors supported the involvement of G protein signaling, Phospholipase C (PLC), Inositol Phosphate 3 Receptor (IP3R), and Akt. Ecdysteroid stimulated activation of Akt confirmed its role in the anabolic effect. Ecdysteroid generated increases in intracellular calcium were also characterized, with the rapid flux in Ca2+ linked with Akt activation and anabolic activity. The evidence produced suggests the involvement of a putative mammalian GPCR ecdysteroid receptor mediating the anabolic effect through the rapid activation of the PLC/IP3R pathway, generating Ca2+ flux which leads to activation of the Phosphoinositide 3 Kinase/Akt pathway, eventually causing increases in protein incorporation.Ph.D.Includes bibliographical references (p. 131-142)by Jonathan Isaac Gorelick-Feldma
Privacy and Security
No full textIn this Fred Friendly Seminar moderated by Harvard Law School's Arthur Miller, panelists such as U.S. Supreme Court Justice Stephen Breyer; Nadine Strossen, president of the ACLU; Jamie Gorelick, of the U.S. Department of Justice; Professor Stephen Carter, of Yale Law School; and others examine the fine balance between the power of the government and the rights of the individual in a fictional community called Unity. Discussion points include government initiatives such as Megan's Law, Internet privacy, mandatory fingerprinting, and the encryption of privileged information—and whether these actions are constitutional. A Discussion Guide and other resources are located online at www.fredfriendlyseminars.org/federalist. (57 minutes
The impact of climate change on the flowering and fruiting phenology of Arctic plants in Nunavut, Canada
No full textPhenology is the timing of nature’s seasonal events. Ambient temperature plays a key role in phenology and hence, as the climate warms, phenology will likely change. This thesis studied the impact of Arctic climate change on Arctic plant flowering and fruiting phenology in Nunavut, Canada. To establish a baseline for current plant phenology, the first question asked was ‘How does flowering phenology vary across Nunavut?’. Contrary to what might be expected, plants at a more northerly location flower earlier or at the same time and for a shorter duration than conspecifics at a more southerly location. Observations of vast differences in flower abundance in three consecutive and climatically-contrasting years highlighted the challenges of reproductive success with weather extremes associated with contemporary climate change given that Arctic plants require three plus years to complete the sexual reproductive cycle. Finally, three methods, employing long-term phenology monitoring, historical phenological records and an elevation gradient, combined with temperature records, were used to ask the questions: ‘How have temperatures in Nunavut changed?’, ‘How have Nunavut Arctic flowering and fruiting times responded to climate change?’ and ‘What is the predicted temperature-sensitivity of Arctic plants to rising temperatures of climate change?’. Annual temperatures in Nunavut are rising faster than the global average. However, in contrast to temperate regions where spring temperatures are rising the most, monthly temperatures in late summer, autumn and winter are rising significantly in Nunavut. Later-flowering species have advanced flowering times more than early-flowering species and seed dispersal times have advanced more than flowering times. Flowering time temperature-sensitivity is species specific and Nunavut region specific with mid-summer-flowering species more sensitive than early- and late-flowering species and Nunavut Arctic archipelago plants more sensitive than Nunavut mainland conspecifics. That Arctic plants’ reproductive phenological events are temperature-sensitive is a good news story suggesting that they will respond to climate change and possibly experience greater reproductive success. Interspecific and inter-regional variation in phenological temperature-sensitivity suggests Arctic plant ecological community structure will alter with climate change but differentially across Nunavut
Acute pancreatitis: pathogenesis and emerging therapies
No full textAcute pancreatitis is a severe inflammatory disorder with limited treatment options. Improved understanding of disease mechanisms has led to new and potential therapies. Here we summarize what we view as some of the most promising new therapies for treating acute pancreatitis, emphasizing the rationale of specific treatments based on disease mechanisms. Targeted pharmacologic interventions are highlighted. We explore potential treatment benefits and risks concerning reducing acute injury, minimizing complications, and improving long-term outcomes. Mechanisms associated with acute pancreatitis initiation, perpetuation, and reconstitution are highlighted, along with potential therapeutic targets and how these relate to new treatments
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Ovariectomy Affects Acute Pancreatitis in Mice
No full textBackgroundSerum estradiol levels in severe acute injury are correlated with in hospital mortality. In acute pancreatitis, serum estradiol levels are strong predictors of disease severity. Studies of whether changes in estradiol levels play a causative role in acute pancreatitis severity are limited. The ovariectomized mouse model has been used to study the effects of estradiol in health and disease.AimsWe assessed whether the ovariectomized mouse model could be used to assess the effects of estradiol on pancreatitis severity.MethodsC57BL/6 mice with their ovaries removed were used to simulate low circulating estradiol conditions. Ovariectomized mice were treated with six hourly injections of cerulein to induce mild acute pancreatitis and compared to ovariectomized mice pre-treated with subcutaneous estradiol injections.ResultsFindings suggest ovariectomized model is a problematic preparation to study pancreatitis. At baseline, ovariectomy leads to prominent acinar cell ultrastructure changes as well as changes in other select morphologic and biomarkers of pancreatitis. In addition, ovariectomy changed select acute pancreatitis responses that were only partially rescued by estradiol pre-treatment.ConclusionsThese findings suggest that the ovariectomized mouse as a model of estradiol depletion should be used with caution in pancreatic studies. Future studies should explore whether derangements in other female hormones produced by the ovaries can lead to changes in pancreatic studies
Exocrine Pancreas (Structure)
No full textBook description: This comprehensive three-volume encyclopedia is a comprehensive study of the entire digestive pathway, with nearly 500 focused articles. Each specific anatomical site such as the esophagus, stomach, liver, and pancreas is covered in its own subject area. The biology of gastroenterology is dealt with in areas such as anatomy and development, cell biology, and hormones, while clinical issues are also thoroughly covered in sections such as surgery, cancer, parasitology, and radiology and endoscopy
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