Magnitude Of Hormone Response Research Articles

A Rat Model of Human Lipid Emulsion Digestion.

A better understanding of how dietary lipids are processed by the human body is necessary to allow for the control of satiation and energy intake by tailored lipid systems. To examine whether rats are a valid model of human dietary lipid processing and therefore useful for further mechanistic studies in this context, we tested in rats three lipid emulsions of different stability, which alter satiety responses in humans. Different sets of 15 adult male Sprague Dawley rats, equipped with gastric catheters alone or combined with hepatic portal vein (HPV) and vena cava (VC) catheters were maintained on a medium-fat diet and adapted to an 8 h deprivation/16 h feeding schedule. Experiments were performed in a randomized cross-over study design. After gastric infusion of the lipid emulsions, we assessed gastric emptying by the paracetamol absorption test and recorded in separate experiments food intake and plasma levels of gastrointestinal hormones and metabolites in the HPV. For an acid stable emulsion, slower gastric emptying and an enhanced release of satiating gastrointestinal (GI) hormones were observed and were associated with lower short-term energy intake in rats and less hunger in humans, respectively. The magnitude of hormonal responses was related to the acid stability and redispersibility of the emulsions and thus seems to depend on the availability of lipids for digestion. Plasma metabolite levels were unaffected by the emulsion induced changes in lipolysis. The results support that structured lipid systems are digested similarly in rats and humans. Thus unstable emulsions undergo the same intragastric destabilization in both species, i.e., increased droplet size and creaming. This work establishes the rat as a viable animal model for in vivo studies on the control of satiation and energy intake by tailored lipid systems.

Activation of pituitary axis according to underlying critical illness and its effect on outcome

PurposeCritical illness is a life threatening condition inducing a severe acute physical stress. The aim of the study was to investigate the activation of pituitary axis early after ICU admission in patients with critical illnesses of different etiology and its association with outcome. Materials and methodsPatients admitted for acute respiratory distress syndrome (ARDS), severe traumatic brain injury (TBI), subarachnoid hemorrhage (SAH) and neurocritically ill patients at the moment of brain death (BD) diagnosis were included in the present post-hoc analysis. On day 1, 2–3 and 4–5 after admission the following pituitary axes were assessed: hypothalamic-pituitary-adrenal, hypothalamic-pituitary-thyroid, somatotroph, prolactin and copeptin. ICU mortality was used as outcome measure. ResultsOne hundred-thirteen critical ill patients were studied. Thyroid axis suppression and activation of copeptin axis were the most frequent pituitary hormone alterations, present in almost 60% of patients. Activation of the hypothalamic pituitary adrenal axis was a predictor of ICU mortality independently from the underlying critical illness [OR 3.952 (C.I.95% 1.129–13.838)]. ConclusionsPituitary axis function is frequently altered early after ICU admission, the magnitude of hormonal response being different according to the underlying critical illness. The activation of the hypothalamic pituitary adrenal axis was a strong predictor of ICU mortality.

Comparison of the Ontogenesis of Thyroid Hormones, Growth Hormone, and Insulin-like Growth Factor-I inad Libitumand Food-Restricted (Altricial) European Starlings and (Precocial) Japanese Quail

In this study, we compare the ontogenic patterns for thyroid hormones, growth hormone (GH), and insulin-like growth factor-I (IGF-I) in altricial European starlings and precocial Japanese quail and examine the effects of feed restriction on these species. The most marked difference in development between the altricial and precocial birds was with respect to plasma thyroid hormone patterns. In the starling, circulating concentrations of triiodothyronine (T3) and thyroxine (T4) were very low in embryos, then increased progressively after hatching to peak at 10–11 days of age. In contrast, in quail, in which other studies have shown that most thyroid maturation occurs during the embryonic and perihatch periods, the circulating concentrations of T3and T4showed little posthatch ontogenic change. Plasma concentrations of both GH and IGF-I showed similar patterns in both species with a posthatch rise (peak at 3 days in starlings and 8 days in quail), followed by a decline. Food restriction to maintain body weight resulted in decreased plasma concentrations of T3and IGF-I in both species. After return toad libitumfeeding, plasma T3and IGF-I increased in bothearlyandlaterestricted starlings and inlaterestricted quail. Although both species responded to food restriction with similar patterns of endocrine change, age-related differences in the magnitude of hormonal responses were observed.

Altered expression of GLUT-1 and GLUT-3 glucose transporters in neurohypophysis of water-deprived or diabetic rats.

Progressive dehydration due to water deprivation and streptozotocin diabetes both produce increased activity of the hypothalamoneurohypophysial system and enhanced vasopressin secretion. To determine whether enhanced metabolic activity affects glucose transporter protein expression, this study examined the effect of these conditions on 45-kDa GLUT-1 and the neuronal glucose transporter, GLUT-3, which mediate glucose transport in the rat neurohypophysis. Progressive water deprivation increased hematocrit, plasma electrolytes Na+ and Cl-, and vasopressin over 3 days, relative to the severity of dehydration. Plasma vasopressin increased threefold by 24 h, reaching 4.5-fold by 72 h. These changes were reflected in a 56 and 75% decrease in neurohypophysial vasopressin content by 48 and 72 h, respectively. Significant changes in glucose transporters were also observed at 48 and 72 h, with GLUT-1 increasing by 18 and 44% and GLUT-3 increasing by 42 and 55%, respectively. Streptozotocin-induced diabetes produced increases in hematocrit, plasma Cl-, and vasopressin, although the magnitude of these changes was less than with dehydration. There was a twofold increase in plasma vasopressin by 3 days, commensurate with the onset of overt diabetes, and a threefold increase by 2 wk. These changes were reflected in a 30 and 40% decline in neural lobe vasopressin content, respectively. Despite the difference in the magnitude of hormone response, GLUT-3 increased by the same amount (53%) as in dehydration. GLUT-1, however, was decreased 16% by 3 days and 25% by 1 and 2 wk of diabetes. Although the opposite effects on GLUT-1 may relate to differences in circulating insulin or glucose, this study is the first demonstration of increased expression of GLUT-3 in response to a common hypothalamic signal in these two conditions.

Specific steroid response from a nonspecific DNA element

A fundamental dilemma of steroid hormone regulation is how specific transcription is attained in vivo when several receptors recognize the same DNA sequence in vitro. We have identified an enhancer of the mouse sex-limited protein ( Slp) gene that is activated by androgens but not by glucocorticoids in transfection. Induction requires a consensus hormone response element (HRE) and multiple auxiliary elements within 120 base pairs. Androgen specificity relies on a dual function to augment androgen but prevent glucocorticoid action from a site that both receptors can bind. The nonreceptor factors are the dominant force in transcriptional specificity, although HRE sequence variations can affect the stringency and magnitude of hormonal response. The effect of HRE variations suggests that receptor position is altered relative to the other factors. Thus protein interactions that elicit specific gene regulation are established by the array of DNA elements in a complex enhancer and can be modulated by subtle sequence differences that may influence precise protein contacts.

Uptake of Benzyladenine by Excised Watermelon Cotyledons

The uptake of 8-[(14)C]N(6)-benzyladenine (BA) was studied in excised watermelon (Citrullus vulgaris Schrad.) cotyledons 24 hours after the start of imbibition. The passive nature of this uptake is suggested by the following evidence: (a) no sign of saturation on increasing external concentration of BA; (b) no decrease in uptake under conditions that inhibit ATP synthesis; (c) no change in amount of radioactivity absorbed when cotyledons are frozen and thawed before the uptake test. About two-thirds of the radioactivity taken up is released after 12 hours of washing. If the washing is performed at 2 C very little radioactivity is released.There seems to be a correlation between the level of radioactivity (i.e. of BA + derivatives) present in the cotyledons and the magnitude of hormonal responses that are observed four days after uptake. This relationship holds regardless of whether a given level of radioactivity has been reached after a short period of uptake or after a long period of uptake followed by washing.

Induction of ovalbumin mRNA by estrogen in the chick oviduct

To study the induction of mRNA ov in chick oviduct tissue, two experimental designs were developed: oviduct tissue incubated in vitro with hormone, and an in vivo system involving hormone injection into the lumen of anesthetized chicks. The magnitude of hormone response in oviduct tissue suspension was shown to depend on the conditions of the incubation medium and on the previous hormonal treatment of the chicken. When animals were withdrawn from estrogen treatment (48–72 h), restimulation of oviduct minces with 10 −8M estradiol in vitro induced-rapidly the synthesis of mRNA ov. The rate of synthesis reached its peak in the first two hours of incubation, when approximately 0.2% of the mass of the newly synthesized RNA was mRNA ov. A marked decrease in the level of mRNA ov synthesis and a gradual appearance of a lag period was observed when the estrogen withdrawal time was extended beyond 86 h. A nuclear precursor to ovalbumin mRNA could be shown to be processed into mature mRNA ov in this oviduct tissue suspension system. In vivo experiments were performed in chickens after various intervals of time following hormone withdrawal (2–13 days). Estradiol (10 −8M) was injected into the oviduct lumen of anesthetized chicks. Within two hours a nearly maximal rate of mRNA ov synthesis was observed. These two systems have proven to be efficient for the assay of the estrogen-mediated induction of mRNA ov synthesis and serve to support the hypothesis that in the chick oviduct system, estrogen regulation of gene expression is primarily at the transcriptional level.