Effects of AMP-activated protein kinase (AMPK) signaling and essential amino acids on mammalian target of rapamycin (mTOR) signaling and protein synthesis rates in mammary cells

Regulation of mammary protein synthesis potentially changes the relationships between AA supply and milk protein output represented in current nutrient requirement models. Glucose and AA regulate muscle protein synthesis via cellular signaling pathways involving mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK). The objective of this study was to investigate the effects of essential AA (EAA) and acetate or glucose on mTOR and AMPK signaling pathways and milk protein synthesis rates. A bovine mammary epithelial cell line, MAC-T, was subjected to different media containing 0 or 3.5 mmol/L EAA concentrations with 0 or 5 mmol/L acetate or 0 or 17.5 mmol/L glucose in 2 separate 2 × 2 factorial studies. In a separate set of experiments, lactogenic bovine mammary tissue slices were subjected to the same treatments except that the low EAA treatment contained a low level of EAA (0.18 mmol/L). Supplementation of EAA enhanced phosphorylation of mTOR (Ser2448) and eukaryotic initiation factor 4E binding protein 1 (4EBP1, Thr37/46), and reduced phosphorylation of eukaryotic elongation factor 2 (eEF2, Thr56) in MAC-T cells. Concentration of ATP and phosphorylation of AMPK increased and decreased, respectively, in the presence of EAA in MAC-T cells. Acetate, EAA, or glucose numerically reduced AMPK phosphorylation by about 16% in mammary tissue slices. Provision of EAA increased phosphorylation of mTOR and 4EBP1, intracellular total EAA concentration, and casein synthesis rates in mammary tissue slices, irrespective of the presence of acetate or glucose in the medium. Phosphorylation of mTOR had a marginally negative association with AMPK phosphorylation, which was positively related to eEF2 phosphorylation. Casein synthesis rates were positively and more strongly linked to mTOR phosphorylation than the negative link between eEF2 phosphorylation and casein synthesis rates. A 100% increase in mTOR phosphorylation was associated with an increase in the casein synthesis rate of 0.74%·h⁻¹, whereas a 100% increase in eEF2 phosphorylation was related to a decline in the casein synthesis rate of 0.33%·h⁻¹. Although AMPK phosphorylation was responsive to cellular energy status and had a negative effect on mTOR-mediated signals in bovine mammary epithelial cells, its effect on milk protein synthesis rates appeared to be marginal compared with the mTOR-mediated regulation of milk protein synthesis by EAA.     

XIIXVI. Yeast sequencing reports. Mapping and sequencing of two yeast genes belonging to the ATP-binding cassette superfamily

ATP-binding cassette (ABC) transporters share significant sequence identity within their ATP-binding domains. Degenerate oligonucleotides based on highly conserved portions of the ATP-binding domain genes were used to clone portions of two members of the ABC gene superfamily from Saccharomyces cerevisiae DNA. These genes were designated MDL1 and MDL2 (for multidrug resistance-like). Each MDL gene is predicted to encode a single set of transmembrane domains and a single ATP-binding domain, thus the MDL gene products are ‘half-molecule’ ABC proteins. The two genes were mapped to precise regions on chromosomes XII and XVI and show a considerable similarity to the mammalian P-glycoprotein/multidrug resistance (MDR) and peptide transporter (TAP) genes. Preliminary analysis of null mutants constructed by gene replacement has indicated that the MDL genes are not essential for viability of yeast. The sequences have been deposited in the GenBank data library under Accession Numbers L16958 (Locus YSCBCSA) and L16959 (Locus YSCBCSB).     

Comparison-level preferences after performance: Is downward comparison theory still useful?

Although often credited with prompting a paradigm shift in social comparison theory, T. A. Wills's (1981) downward comparison (DC) theory has received some criticism recently. In particular, several recent studies have failed to find support for Wills's (1981) contention that threat and accompanying negative affect lead to a desire for DC. These apparent failures have led some investigators to question basic principles of the theory. To resolve this controversy, 5 studies were conducted examining preferred comparison level (PCL) after performance; 4 of the studies also assessed change in this preference. Results supported DC theory, but with modifications. Specifically, individuals who performed poorly lowered their PCLs. Under some circumstances, this "downward shift" included an increased interest in "true" DC-comparing with worse-off others. A reconciliation of these results with those of previous studies is offered. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Improved cure rate in children with B-cell acute lymphoblastic leukaemia (B-ALL) and stage IV B-cell non-Hodgkin's lymphoma (B-NHL)--results of the UKCCSG 9003 protocol

From June 1990 to February 1996, 35 patients with B-cell acute lymphoblastic leukaemia (B-ALL) 13 of whom had CNS disease and 28 patients with stage IV B-cell non-Hodgkin's lymphoma (B-NHL) 22 of whom had CNS involvement were treated with a short, intensive multiagent chemotherapy regimen (UKCCSG 9003 protocol) based on the French LMB 86 regimen. Fifty-five were boys. The age range was 11 months to 16.5 years (median 8.4 years). Chemotherapy included cyclophosphamide, vincristine, daunorubicin, high-dose methotrexate (COPADM) and etoposide/high-dose cytarabine (CYVE) with frequent intrathecal (i.t.) triple therapy (methotrexate, cytarabine and hydrocortisone). Cranial irradiation (24 Gy in 15 fractions) was recommended in patients with overt CNS disease. One patient with Wiskott-Aldrich syndrome was withdrawn after entry and has been excluded from the analysis. Ten patients (16%) have relapsed (CNS, four; BM, two; combined CNS and BM, three; and jaw, one) 4-11 months after diagnosis and two patients never achieved complete remission (CR). All have died. In seven of the patients who relapsed, treatment had been modified or delayed because of poor clinical condition. Seven patients (11%) died of toxicity 11 days to 4 months after diagnosis. The cause of death was sepsis (n = 5) or sepsis with renal failure (n = 2). With a median follow-up of 3.1 years from diagnosis (range 9 months to 6.3 years), 43 patients (69%) survive in CR. This study confirms the effectiveness of this regimen with regard to the relapse rate (16%), although the rate of toxic death is of concern.     

Independent effects of food intake and insulin status on insulin-like growth factor-I in young pigs

The successful use of proteins in pharmaceutical and other commercial applications requires close examination of their relative fragility. Because of the resultant enhanced stability, proteins are often formulated in the solid state, even though dehydration tends to alter their structure. Even in the solid form, however, proteins may become inactivated due to various deleterious processes, e.g., aggregation. This review focuses on such mechanisms, with an emphasis on case studies conducted in our laboratory. Proteins which have both disulfide bonds and free thiols may aggregate via thiol-disulfide exchange, and this process may be facilitated by lyophilization-induced structural perturbations. For proteins possessing disulfides but not free thiols, aggregation also may occur when native disulfides are beta-eliminated, thus giving rise to thiol species which can catalyze disulfide scrambling. Other deleterious processes have also been uncovered, including a formaldehyde-mediated aggregation of formalinized vaccines. It is illustrated how knowledge of such deterioration pathways makes possible the rational development of stable solid protein formulations.     

Design features of seawater intake,distribution and outfall systems,applied to the Ruwais utilities complex,Abu Dhabi

Design aspects applicable to seawater cooling systems of combined power and desalination plants are discussed in this paper. Preventive measures are proposed on how to assure trouble-free seawater supply for cooling and seawater distillation. Site-specific measures are illustrated with the example of the seawater supply system to the Ruwais Utilities Complex, Abu Dhabi, which consists of a combined power and desalination plant as well as a fertilizer plant.     

Distribution of optical scattering properties in four beef muscles

The objective of this study was to determine the influence of the mechanisms regulating tenderness on optical scattering properties of beef. Optical scattering properties of four beef muscles with different amounts of connective tissue and varying sarcomere lengths across a range of aging periods were determined. The optical scattering coefficient of beef muscles were measured based on a diffusive fitting of spatially resolved reflectance measurements. As a reference to beef tenderness, Warner-Bratzler shear forces were also measured in this study. Variation in muscle composition resulted in a range of optical scattering properties across muscles. Our results implied that connective tissue and sarcomere structure have different effects on the optical scattering properties of muscle. In addition, proteolysis of muscle proteins significantly changes the optical scattering properties. These results provide useful information in understanding the originations of optical scattering in beef.     

Good self-control moderates the effect of mass media on adolescent tobacco and alcohol use: Tests with studies of children and adolescents.

Objective: To investigate whether self-control moderates the effect of media influences on tobacco and alcohol use among youth and if so how this effect occurs. Design: In Study 1, a regional sample of 10-year olds (N = 290) was interviewed in households; attention to tobacco/alcohol advertising was assessed. In Study 2, a national sample of youth ages 10–14 years (N = 6,522) was surveyed by telephone; exposure to tobacco/alcohol use in movies was assessed. Good self-control was measured in both studies. Main Outcome Measures: Willingness to use substances and affiliation with peer substance users (Study 1); involvement in smoking or drinking (Study 2). Results: In Study 1, the effect of tobacco/alcohol advertising on predisposition for substance use was lower among persons scoring higher on good self-control. In Study 2, the effect of movie smoking/alcohol exposure on adolescent tobacco/alcohol use was lower, concurrently and prospectively, among persons scoring higher on good self-control. Moderation occurred primarily through reducing the effect of movie exposure on positive smoking/alcohol expectancies and the effect of expectancies on adolescent use; some evidence for moderation of social processes was also noted. Covariates in the analyses included demographics, sensation seeking, and IQ. Conclusion: Good self-control reduces the effect of adverse media influences on adolescent tobacco and alcohol use. Findings on the processes underlying this effect may be useful for media literacy and primary prevention programs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Computational Homology,Connectedness, and Structure-Property Relations

The effective properties of composite materials are often strongly related to the connectivity of the material components. Many structure metrics, and related homogenization theories, do not effectively account for this connectivity. In this paper, relationships between the topology, represented via homology theory, and the effective elastic response of composite plates is investigated. The study is presented in the context of popular structure metrics such as percolation theory and correlation functions.     

Compound C, an inhibitor of AMP-activated protein kinase, inhibits glycolysis in mouse longissimus dorsi postmortem

Pale, soft, and exudative (PSE) meat has been recognized for decades and causes huge economic loss to the meat industry due to its inferior quality. Although it has been well established that fast and excessive glycolysis combined with high temperature in muscle early postmortem is the cause of PSE meat, the molecular mechanisms associated with this abnormal glycolysis remain poorly defined. Our previous studies with mice and pigs suggest that AMPK regulates muscle glycolysis postmortem. To confirm further the role of AMPK in the regulation of postmortem glycolysis, we investigated the effects of intraperitoneal injection of compound C, a specific AMPK inhibitor, on AMPK activation and glycolysis in postmortem longissimus dorsi (LD) muscle of mice. Data showed that intraperitoneal injection of compound C inhibited AMPK activation in postmortem mouse LD muscle. Simultaneously, injection of compound C inhibited glycolysis and increased muscle pH corroborating of our previous observations that postmortem glycolysis is inhibited in AMPK knockout mice. This study firmly supports that AMPK regulates glycolysis in postmortem skeletal muscle and suggests that AMPK can be a target to control postmortem glycolysis, preventing incidence of PSE meat.