Effect of quinolinic acid-induced lesions of the nucleus accumbens core on performance on a progressive ratio schedule of reinforcement: implications for inter-temporal choice

Rationale: The nucleus accumbens core (AcbC) is believed to contribute to the control of operant behaviour by reinforcers. Recent evidence suggests that it is not crucial for determining the incentive value of immediately available reinforcers, but is important for maintaining the values of delayed reinforcers. Objective: This study aims to examine the effect of AcbC lesions on performance on a progressive-ratio schedule using a quantitative model that dissociates effects of interventions on motor and motivational processes (Killeen 1994 Mathematical principles of reinforcement. Behav Brain Sci 17:105-172). Materials and methods: Rats with bilateral quinolinic acid-induced lesions of the AcbC (n=15) or sham lesions (n=14) were trained to lever-press for food-pellet reinforcers under a progressive-ratio schedule. In Phase 1 (90 sessions) the reinforcer was one pellet; in Phase 2 (30 sessions), it was two pellets; in Phase 3, (30 sessions) it was one pellet. Results: The performance of both groups conformed to the model of progressive-ratio performance (group mean data: r 2 >0.92). The motor parameter, δ, was significantly higher in the AcbC-lesioned than the sham-lesioned group, reflecting lower overall response rates in the lesioned group. The motivational parameter, a, was sensitive to changes in reinforcer size, but did not differ significantly between the two groups. The AcbC-lesioned group showed longer post-reinforcement pauses and lower running response rates than the sham-lesioned group. Conclusions: The results suggest that destruction of the AcbC impairs response capacity but does not alter the efficacy of food reinforcers. The results are consistent with recent findings that AcbC lesions do not alter sensitivity to reinforcer size in inter-temporal choice schedules. © 2007 The Author(s)

Transient up- and down-regulation of expression of myosin light chain 2 and myostatin mRNA mark the changes from stratified hyperplasia to muscle fiber hypertrophy in larvae of gilthead sea bream (Sparus aurata L.)

Hyperplasia and hypertrophy are the two mechanisms by which muscle develops and grows. We study these two mechanisms, during the early development of white muscle in Sparus aurata, by means of histology and the expression of structural and regulatory genes. A clear stage of stratified hyperplasia was identified early in the development of gilthead sea bream but ceased by 35 dph when hypertrophy took over. Mosaic recruitment of new white fibers began as soon as 60 dph. The genes mlc2a and mlc2b were expressed at various levels during the main phases of hyperplasia and hypertrophy. The genes myog and mlc2a were significantly up-regulated during the intensive stratified formation of new fibers and their expression was significantly correlated. Expression of mstn1 and igf1 increased at 35 dph, appeared to regulate the hyperplasia-to-hypertrophy transition, and may have stimulated the expression of mlc2a, mlc2b and col1a1 at the onset of mosaic hyperplasia. The up-regulation of mstn1 at transitional phases in muscle development indicates a dual regulatory role of myostatin in fish larval muscle growth

Vasodilators in the treatment of acute heart failure: what we know, what we don’t

Although we have recently witnessed substantial progress in management and outcome of patients with chronic heart failure, acute heart failure (AHF) management and outcome have not changed over almost a generation. Vasodilators are one of the cornerstones of AHF management; however, to a large extent, none of those currently used has been examined by large, placebo-controlled, non-hemodynamic monitored, prospective randomized studies powered to assess the effects on outcomes, in addition to symptoms. In this article, we will discuss the role of vasodilators in AHF trying to point out which are the potentially best indications to their administration and which are the pitfalls which may be associated with their use. Unfortunately, most of this discussion is only partially evidence based due to lack of appropriate clinical trials. In general, we believe that vasodilators should be administered early to AHF patients with normal or high blood pressure (BP) at presentation. They should not be administered to patients with low BP since they may cause hypotension and hypoperfusion of vital organs, leading to renal and/or myocardial damage which may further worsen patients’ outcome. It is not clear whether vasodilators have a role in either patients with borderline BP at presentation (i.e., low-normal) or beyond the first 1–2 days from presentation. Given the limitations of the currently available clinical trial data, we cannot recommend any specific agent as first line therapy, although nitrates in different formulations are still the most widely used in clinical practice

A modification of the standard midline posterior approach to the intertransverse area of the lumbar spine

A midline approach to the lumbar region is most frequently used for posterior lumbar spine surgery. The exposure of the deeper layer of muscles, however, is imprecise and can entail substantial tissue damage and blood loss. During 10 years of operative surgical experience, we have developed an improved and less traumatic technique for exposure of the lumbar transverse processes and intertransverse region in which the tendons of multifidus and longissimus muscles are isolated at every level and divided laterally to the facet joints. This method eases identification and accurate cauterisation of the subjacent arteries, thereby reducing tissue damage and blood loss. It takes no more time and clarifies the exposure of the lumbar transverse processes and intertransverse region. Cadaveric dissection confirms the muscular and arterial anatomy of the region. We recommend use of this modified approach to improve standard practice

GH overexpression causes muscle hypertrophy independent from local IGF-I in a zebrafish transgenic model

The aim of the present study was to analyse the morphology of white skeletal muscle in males and females from the GH-transgenic zebrafish(Danio rerio) lineage F0104, comparing the expression of genes related to the somatotrophic axis and myogenesis. Histological analysis demonstrated that transgenic fish presented enhanced muscle hypertrophy when compared to non-transgenic fish, with transgenic females being more hypertrophic than transgenic males. The expression of genes related to muscle growth revealed that transgenic hypertrophy is independent from local induction of insulin-like growth factor 1 gene (igf1). In addition, transgenic males exhibited significant induction of myogenin gene (myog) expression, indicating that myog may mediate hypertrophic growth in zebrafish males overexpressing GH. Induction of the a-actin gene (acta1) in males, independently from transgenesis, also was observed. There were no significant differences in total protein content from the muscle. Our results show that muscle hypertrophy is independent from muscle igf1, and is likely to be a direct effect of excess circulating GH and/or IGF1 in this transgenic zebrafish lineage

Physiological Evaluation of Alkali-Salt Tolerance of Thirty Switchgrass (Panicum virgatum) Lines

Soil salt-alkalization is a major limiting factor for crop production in many regions. Switchgrass (Panicum virgatum L.) is a warm-season C4 perennial rhizomatous bunchgrass and a target lignocellulosic biofuel species. The objective of this study was to evaluate relative alkali-salt tolerance among 30 switchgrass lines. Tillers of each switchgrass line were transplanted into pots filled with fine sand. Two months after transplanting, plants at E5 developmental stage were grown in either half strength Hoagland's nutrient solution with 0 mM Na+ (control) or half strength Hoagland's nutrient solution with 150 mM Na+ and pH of 9.5 (alkali-salt stress treatment) for 20 d. Alkali-salt stress damaged cell membranes [higher electrolyte leakage (EL)], reduced leaf relative water content (RWC), net photosynthetic rate (Pn), stomatal conductance (gs), and transpiration rate (Tr). An alkali-salt stress tolerance trait index (ASTTI) for each parameter was calculated based on the ratio of the value under alkali-salt stress and the value under non-stress conditions for each parameter of each line. Relative alkali-salt tolerance was determined based on principal components analysis and cluster analysis of the physiological parameters and their ASTTI values. Significant differences in alkali-salt stress tolerance were found among the 30 lines. Lowland lines TEM-SEC, Alamo, TEM-SLC and Kanlow were classified as alkali-salt tolerant. In contrast, three lowland lines (AM-314/MS-155, BN-13645-64) and two upland lines (Caddo and Blackwell-1) were classified as alkali-salt sensitive. The results suggest wide variations exist in alkali-salt stress tolerance among the 30 switchgrass lines. The approach of using a combination of principal components and cluster analysis of the physiological parameters and related ASTTI is feasible for evaluating alkali-salt tolerance in switchgrass