No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
CCK-8 decreases body weight in Zucker rats
... Moreover, previous concerns about tolerance to the eatinginhibitory effects of GI peptides with chronic administration in animal models and, hence, about their therapeutic potential, may be unwarranted. Thus, CCK administered just prior to each meal in obese Zucker and dietary-induced obese rats adapted to three scheduled meals/day (a feeding paradigm that is presumably more relevant for human eating than continuous ad libitum access to food) persistently reduced meal size and body weight over several weeks of treatment [77,78]. In addition, chronic administration of GLP-1 analogs resulted in significant weight loss in obese humans [79], implying that GLP-1 receptor activation preserves its effectiveness with chronic use and that this is an effective and promising strategy that deserves further exploration [1]. ...
... In a classical study, West and colleagues (232) administered CCK before each spontaneous meal in rats and found that it continued to decrease meal size (i.e., there was no loss of sensitivity to the satiating effect of CCK), but 24-h food intake was not reduced because the rats increased meal frequency to compensate for the CCK effect on meal size. On the other hand, G. P. Smith et al. (35,199) presented evidence for an effect of CCK on body weight; he and his colleagues adapted rats to three scheduled meals/day and injected CCK intraperitoneally before each of these meals. Under these conditions CCK had a substantial effect on body weight in both Zucker and DIO rats. ...
The gastrointestinal tract serves as a portal sensing incoming nutrients and relays mechanical and chemosensory signals of a meal to higher brain centers. Prolonged consumption of dietary fat causes adaptive changes within the alimentary, metabolic, and humoral systems that promote a more efficient process for energy metabolism from this rich source, leading to storage of energy in the form of adipose tissue. Furthermore, prolonged ingestion of dietary fats exerts profound effects on responses to signals involved in termination of a meal. This article reviews the effects of ingested fat on gastrointestinal motility, hormone release, and neuronal substrates. It focuses on changes in sensitivity to satiation signals resulting from chronic ingestion of high-fat diet, which may lead to disordered appetite and dysregulation of body weight.
Although many physiological studies have been reported on the symbiosis between hydra and green algae, very little information from a molecular phylogenetic aspect of symbiosis is available. In order to understand the origin and evolution of symbiosis between the two organisms, we compared the phylogenetic relationships among symbiotic green algae with the phylogenetic relationships among host hydra strains. To do so, we reconstructed molecular phylogenetic trees of several strains of symbiotic chlorella harbored in the endodermal epithelial cells of viridissima group hydra strains and investigated their congruence with the molecular phylogenetic trees of the host hydra strains. To examine the species specificity between the host and the symbiont with respect to the genetic distance, we also tried to introduce chlorella strains into two aposymbiotic strains of viridissima group hydra in which symbiotic chlorella had been eliminated in advance. We discussed the origin and history of symbiosis between hydra and green algae based on the analysis.
Synergism between the Columbia University Appetitive Behavior Seminar and the research program of Smith and Gibbs on the satiating effect of cholecystokinin during the past 40years is described. The Seminar was synergistic with the research program in five ways. First, the steady parade of speakers gave us a window on the varied and interesting work going on in the field. Second, the Seminar was the kind of audience for presentations of the work-in-progress on CCK that scientists hope for and rarely find. Criticism by members of the Seminar was relentless and constructive, and ideas for further experiments or new ways to tackle problematic data poured forth. Third, members of the Seminar did experiments that facilitated the experimental success of the research program. Fourth, members of the Seminar tutored us on topics that we wanted to import into the research program on CCK. Fifth, and probably most important, members of the Seminar gave us the encouragement, good humor, and friendship so necessary for coping with the struggles of the scientific life.
The relative ability of a norleucine substituted cholecystokinin (CCK) analogue, U-67827E, to interact with CCK receptors and to inhibit food intake was examined across a variety of paradigms. U-67827E and CCK had identical in vitro potencies as demonstrated by their ability to induce pyloric contractions or competitively inhibit [125I]CCK-8 binding to type A and B CCK receptors. However, the in vivo potency of U-67827E was significantly greater than that of CCK-8. In rats, U-67827E inhibited food intake with 10-100 times the potency of CCK. In rhesus monkeys, U-67827E produced significantly greater inhibitions of daily food intake and did so in a dose-dependent manner with no evidence of compensation or tolerance. U-67827E also inhibited gastric emptying for significantly longer durations than CCK. Together these results demonstrate that CCK analogues with increased in vivo bioavailability can affect food intake beyond a single meal.
In the past 20 years, the mechanisms of the satiating effect of food that terminate a meal have been investigated intensively in rodents and in humans. This research has revealed that three peptides, cholecystokinin, pancreatic glucagon, and bombesin, released by ingested food from the gastrointestinal tract decrease meal size in a specific, dose-related manner without signs of acute toxicity or tolerance. In humans, the three peptides decrease meal size without decreasing the reported pleasure or satisfaction of the meal. Although their chemical structure and specific effect justify calling these peptides a new class of anorectic agents, not enough work has been done to evaluate their efficacy for weight loss in obese humans or their safety when administered for months.
1. The effect of hibernation on cerebral cortical concentrations of cholecystokinin and vasoactive intestinal peptide was investigated in the golden mantled ground squirrel (Citellus lateralis). 2. During hibernation, cortical brain weight decreased to 83% of the non-hibernating weight. 3. The concentration of the small form of CCK was significantly reduced. The concentration of the large forms of immunoreactive CCK did not significantly change during hibernation. The molecular forms of CCK appeared the same both before and during hibernation. 4. Of note, the concentration of vasoactive intestinal peptide significantly increased during hibernation. 5. Since there was a three-fold reduction in the ratio of large to small forms of CCK during hibernation, this suggests that post-translational processing of the precursor peptides are markedly reduced during hibernation.
The sulfated octapeptide of cholecystokinin (CCK-8) was infused intraperitoneally into 7 free-feeding male Sprague Dawley rats over a 6-day period. Infusions were given near the end of each free-feeding meal (1.87 microgram/meal/rat), and also during the intermeal interval in gradually increasing doses (0.10-0.63 microgram/5 min/rat). Food intake was continuously monitored and the infusions were controlled by microcomputer. Meal patterns, total food intake, and body weights during drug infusion were compared with data collected during a baseline period when only saline was infused. Meal-contingent CCK-8 infusion produced a significant 29.9% decrease in meal size which persisted throughout the drug-infusion period. Intermeal infusion of CCK-8 failed to prolong the intermeal interval (IMI) but it did initially prevent the compensatory decrease in IMI and increased feeding frequency expected after meal size was reduced. By the last day of drug infusion, total daily food intake recovered to baseline levels due to increased feeding frequency. Body weight was only transiently reduced by CCK-8 infusion. These findings show that tolerance does not develop to the action of CCK-8 to suppress meal size, and the administration of exogenous CCK-8 to free-feeding rats does not persistently prolong the intermeal interval.
The purpose of this study, in part, was to determine the ability of cholecystokinin (CCK-33/39 and CCK-8) to penetrate the blood cerebrospinal fluid (CSF) barrier in dogs by measuring these forms of CCK in plasma and in CSF. In addition, the effectiveness of centrally administered bombesin in releasing brain CCK-33/39 and CCK-8 was evaluated. Six groups of five dogs each were studied. Each group received one of the following: (1) intravenous infusion of CCK-33/39 (1.3 micrograms/kg/hr); (2) intravenous infusion of CCK-8 (0.4 micrograms/kg/hr); (3) intrathecal infusion of CCK-33/39 (1.3 micrograms/kg/hr); (4) intrathecal infusion of CCK-8 (0.5 micrograms/kg/hr); (5) intravenous infusion of bombesin (1 micrograms/kg/hr); and (6) intrathecal infusion of bombesin (1 microgram/kg/hr). Plasma concentrations of CCK-33/39 significantly increased during intravenous infusion of CCK-33/39 (from basal of 84 +/- 8 to 142 +/- 2 pg/ml) or bombesin (from basal of 78 +/- 13 to 325 +/- 87 pg/ml); however, CSF perfusate concentrations of CCK-33/39 did not increase. CCK-33/39 levels of the CSF perfusate increased significantly (P less than .05) from 211 +/- 84 to 9,873 +/- 3,368 pg/ml during intrathecal infusion of CCK-33/39, but failed to rise simultaneously in the systemic circulation. Similarly, intravenous infusion of CCK-8 caused a fivefold elevation in plasma CCK-8 levels and no change in CSF perfusate levels of CCK-8; moreover, intrathecal infusion of CCK-8 failed to elevate peripheral CCK-8 levels, despite CSF perfusate CCK-8 levels of 92,300 +/- 18,598 pg/ml. Intrathecal concentrations of neither CCK-33 nor CCK-8 were affected by intravenous or intrathecal administration of bombesin. We conclude that CCK-33/39 and CCK-8 do not penetrate the blood-cerebrospinal fluid barrier in dogs, and centrally administered bombesin is ineffective in causing release of cholecystokinin from brain tissue into the CSF.
Since the discovery of the satiety effect of CCK in 1973, progress has been made and problems have been encountered. The progress has included the accumulation of strong, indirect evidence that exogenous CCK acts in the abdomen to activate vagal afferent fibers and that exogenous CCK may be useful in the treatment of bulimia and obesity in humans. The most pressing problem is the current lack of evidence for the hypothesis that the satiety effect of exogenous CCK reveals a physiological function of endogenous CCK released by food entering the small intestine during a meal. Since clarification of this problem and exploitation of the current progress seem possible with current ideas and techniques, the satiety effect of CCK should continue to receive considerable experimental attention.
Among the earliest diverging animal phyla are the Cnidaria. Freshwater polyps of the genus Hydra (Cnidaria, Hydrozoa) have long been of general interest because different species of Hydra reveal fundamental principles that underlie development, differentiation, regeneration and also symbiosis. The phylogenetic relationships among the Hydra species most commonly used in current research are not resolved yet. Here we estimate the phylogenetic relations among eight scientifically important members of the genus Hydra with molecular data from two nuclear (18S rDNA, 28S rDNA) and two mitochondrial (16S rRNA, cytochrome oxidase subunit I (COI)) genes. The phylogenetic trees obtained by maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI) methods were generally compatible with present morphological classification patterns. However, the present analysis also bears on several long-standing questions about Hydra systematics and reveals some characteristics of the phylogenetic relationships of this genus that were unknown so far. It indicates that Hydra viridissima, the only species in Hydra, which contains symbiotic algae, might be considered as the sister group to all other species within this genus. Analyses of both nuclear and mitochondrial sequences support the view that Hydra oligactis and Hydra circumcincta are sisters to all other Hydra species. Unexpectedly, we also find that in contrast to its initial description, the strain used for making transgenic Hydra, Hydra vulgaris (strain AEP) is more closely related to Hydra carnea than to other species of Hydra.
ResearchGate has not been able to resolve any references for this publication.