1,720,976 research outputs found
Relocation and Hair Cortisol Concentrations in New Zealand White Rabbits
No full textTo investigate how long relocation modified hair cortisol concentrations in New Zealand white rabbits, 19 rabbits were subjected to a change in their breeding facility at the beginning of the trial and then were kept under stable environmental conditions. Hair samples were collected at the time of arrival to the nonhuman animal facility and at 40-day intervals from the same skin area for up to 440 days after the animals' arrival to the facility. A period effect on the hair cortisol concentration was found (p <.01). The transfer of the rabbits to the new facility might have induced an increase in the hypothalamic-pituitary-adrenal axis activity (p <.01). A second increase in hair cortisol concentration (p <.01) occurred at 320 days, after a change of personnel at the facility that occurred at 280 days, which was the only environmental change. The relocation of rabbits to the facility resulted in a stress response leading to elevated cortisol levels. The effect of relocation on mean cortisol concentrations was exhausted within 120 days when all environmental factors were kept stable. © 2016 Taylor & Francis Group, LLC
Lack of direct effect of moderate hyperleptinemia to improve endothelial function in lean rat aorta: role of calorie restriction.
No full textLeptin stimulates vascular sympathetic activity and NO release. The resulting effect of hyperleptinemia on endothelial function is unknown. Reduction of food intake associated with hyperleptinemia may mediate some of the vascular effects of leptin. This study was designed to assess the relative effects of short-term moderate caloric restriction and hyperleptinemia on vascular function in lean rat. Endothelium-dependent and -independent vasorelaxation, nitric oxide synthase (eNOS) expression and nitrite production were measured in lean rats receiving leptin subcutaneous infusion (-26% caloric intake, -4% body weight versus control) or moderate caloric restriction (pair-feeding) for one week. Plasma leptin was increased (P < = 0.05) by approximately 300% in the leptin-infused group, while it decreased (P < or = 0.05) by approximately 40% in calorie-restricted animals. Both leptin infusion and calorie restriction resulted in improved (P < 0.05) endothelium-dependent vasorelaxation to acetylcholine (EC50: -6.1 +/- 0.2 and -6.2 +/- 0.2 versus -5.4 +/- 0.2 in control) and unaltered endothelium-independent vasodilation to DEA-NONOate. Furthermore, in aortas from leptin-infused and calorie-restricted rats, expression of eNOS and nitrite production were increased (P < = 0.05) to similar extent compared to control animals. These findings suggest that moderate short-term calorie restriction with adaptive hypoleptinemia has independent beneficial effects on endothelial function in lean animals by enhancing eNOS expression and function. In addition, physiological hyperleptinemia does not independently contribute to improved vascular function above and beyond the effect of calorie restrictio
Hyperleptinemia prevents increased plasma ghrelin concentration during short-term moderate caloric restriction in rat.
No full textBACKGROUND & AIMS: Ghrelin is an orexigenic hormone secreted by the stomach. Increased plasma ghrelin concentration was reported during diet-induced weight loss in obese humans, suggesting that ghrelin contributes to adaptive increment in appetite associated with caloric restriction. Leptin reduces spontaneous food intake and body weight in rodents. The current study tested the hypothesis that increased plasma leptin prevents the potential increase in plasma ghrelin concentration during moderate caloric restriction in lean rats.
METHODS: Six-month-old male rats (body weight, 367 +/- 9 grams) were randomly assigned to one of the following treatments (8 rats each) for 1 week: (1) leptin subcutaneous infusion to induce moderate hyperleptinemia and moderate caloric restriction (-26% of ad libitum), (2) vehicle infusion and pair feeding, and (3) vehicle infusion and ad libitum feeding.
RESULTS: Leptin-treated (-19 +/- 5 grams) and pair-fed (-19 +/- 2) rats lost weight compared with ad libitum-fed rats (-3 +/- 1, P 0.8).
CONCLUSIONS: Moderate hyperleptinemia prevents an increase of plasma ghrelin during moderate short-term caloric restriction. Satiety-inducing effects of leptin include suppression of gastric orexigenic signals and disruption of a potential feedback mechanism between body weight changes and plasma ghrelin in lean adult rats
Moderate caloric restriction, but not physiological hyperleptinemia per se, enhances mitochondrial oxidative capacity in rat liver and skeletal muscle--tissue-specific impact on tissue triglyceride content and AKT activation.
No full textThe study aimed at determining, in lean tissues from nonobese rats, whether physiological hyperleptinemia with leptin-induced reduced caloric intake and/or calorie restriction (CR) per se: 1) enhance mitochondrial-energy metabolism gene transcript levels and oxidative capacity; and 2) reduce triglyceride content. Liver and skeletal muscles were collected from 6-month-old Fischer 344 rats after 1-wk leptin sc infusion (0.4 mg/kg . d: leptin + approximately 3-fold leptinemia vs. ad libitum-fed control) or moderate CR (-26% of those fed ad libitum) in pair-fed animals (CR). After 1 wk: 1) leptin and CR comparably enhanced transcriptional expression of mixed muscle mitochondrial genes (P < 0.05 vs. control); 2) CR independently increased (P < 0.05 vs. leptin-control) hepatic mitochondrial-lipooxidative gene expression and oxidative capacity; 3) hepatic but not muscle mitochondrial effects of CR were associated (P < 0.01) with increased activated insulin signaling at AKT level (P < 0.05 vs. leptin-control); 4) liver and muscle triglyceride content were comparable in all groups. In additional experiments, assessing time course of posttranscriptional CR effects, 3-wk superimposable CR (P < 0.05): 1) increased both liver and muscle mitochondrial oxidative capacity; and 2) selectively reduced muscle triglyceride content. Thus, in nonobese adult rat: 1) moderate CR induces early increments of mitochondrial-lipooxidative gene expression and time-dependent increments of oxidative capacity in liver and mixed muscle; 2) sustained moderate CR alters tissue lipid distribution reducing muscle but not liver triglycerides; 3) mitochondrial-lipid metabolism changes are tissue-specifically associated with hepatic AKT activation; 4) short-term physiological hyperleptinemia has no independent stimulatory effects on muscle and liver mitochondrial-lipooxidative gene expression. Increased lean tissue oxidative capacity could favor substrate oxidation over storage during reduced nutrient availability
Protocol for the study of hepatic bilirubin uptake in the isolated perfused rat liver
Full text linkWe present a protocol for the study of bilirubin uptake in the isolated and perfused rat liver. The liver is
perfused with an albumin-free saline buffered solution supplemented with glucose, pyruvate and lactate,
in the absence of oxygen, at a physiologically low flow rate. Fractions of the venous effluent are collected
and analyzed for bilirubin, bilirubin glucuronide and biomarkers of liver integrity. The liver preparation is
viable and intact for 1 h after isolation from the general circulation, with constant levels of both bilirubin
and bilirubin glucuronide (< 2 nM) in the effluent. Up to 12 boli of 10 nmol bilirubin can be sequentially
injected into the portal vein without and with molecules that target sinusoidal membrane transporters of
organic anions. Selective inhibition of bilirubin or bilirubin glucuronide uptake is detected as transient
peaks in the effluent (Cmax up 6 to 60 nM). This protocol allows collecting repeated observations in the
same liver, thus reducing the animal number by a factor of 10
Myostatin expression is not altered by insulin deficiency and replacement in streptozotocin-diabetic rat skeletal muscles.
No full textBACKGROUND AND AIMS: Insulin is a major post-prandial muscle-anabolic hormone. A substantial loss of skeletal muscle mass occurs in insulin-deprived diabetes and is reversed by insulin treatment. Myostatin is a negative regulator of muscle mass upregulated in several chronic catabolic conditions. Whether myostatin expression is altered in insulin-deprived diabetes is unknown. In spite of opposite effects on muscle mass the potential role of basal circulating insulin in the regulation of myostatin expression is also undetermined.
METHODS: We measured (Northern Blot) myostatin transcript levels in muscle groups with different fiber composition in streptozotocin-diabetic male rats receiving one of the following treatments for eight weeks: (1) control (C); (2) diabetes without treatment (DM); (3) diabetes with once-daily slow-acting insulin treatment (INS).
RESULTS: INS normalized plasma insulin and prevented weight reduction observed in DM. In fast-twitch gastrocnemius muscle myostatin transcript levels were unchanged (P>0.4) in both DM and INS compared to C. Myostatin transcripts were not measurable in any group in slow-twitch soleus muscle.
CONCLUSIONS: Muscle-specific myostatin expression is not increased under catabolic conditions in insulin-deprived diabetes. Insulin treatment also does not change myostatin transcript levels. The data provide the first assessment of potential interplay between insulin and myostatin and they do not support a major role of circulating insulin in the in vivo regulation of myostatin gene expression. A role of myostatin in muscle catabolism in chronic insulin-deprived diabetes is also not indicated by the current results
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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