Somatosensory paths proceeding to spinal cord and brain--centripetal and centrifugal control for human movement

The flow of fast-conducting somatosensory information proceeding from the human leg, and entering sensorimotor control processes, is modulated according to the demands of limb movement. Both centripetal (proceeding in from sensory receptor discharge) and centrifugal (proceeding out from motor control centres) convergences can cause modulation, as seen in human, dog, and cat studies. Spinal H-reflexes appear to be strongly centripetally modulated in magnitude, as do initial somatosensory-evoked potentials recorded from the scalp following transmission in fast-conducting afferents from the leg. From the brain and from locomotor pattern-generators, there is also centrifugal control onto fast-conducting somatosensory pathways from the leg, both serving spinal reflexes and ascending to the brain. One expression of the centrifugal control appears to be pattern-generator modulation of cutaneous reflexes. Centrifugal control also can be seen premovement, as spinal H-reflex facilitation. Further, it can be observed as reduction of reception at somatosensory cerebral cortex, when motor learning has occurred or when stimuli are less salient for the task. Fourteen research developments have been identified that involve the generalizability of effects, specific mechanisms, and somatosensory modulation in predictive control.     

An Engineered α1 Integrin-binding Collagenous Sequence

Collagen is an extracellular matrix structural component that can regulate cellular processes through its interaction with the integrins, α1β1, α2β1, α10β1, and α11β1. Collagen-like proteins have been identified in a number of bacterial species. Here, we used Scl2 from Streptococcus pyogenes serotype M28 strain MGAS6274 as a backbone for the introduction of discrete integrin-binding sequences. The introduced sequences GLPGER, GFPGER, or GFPGEN did not affect triple helix stability of the Scl (Streptococcal collagen-like) protein. Using ELISA and surface plasmon resonance, we determined that Scl2_GLPGER and Scl2_GFPGER bound to recombinant human α1 and α2 I-domains in a metal ion-dependent manner and without a requirement for hydroxyproline. We predicted a novel and selective integrin-binding sequence, GFPGEN, through the use of computer modeling and demonstrated that Scl2_GFPGEN shows specificity toward the α1 I-domain and does not bind the α2 I-domain. Using C2C12 cells, we determined that intact integrins interact with the modified Scl2 proteins with the same selectivity as recombinant I-domains. These modified Scl2 proteins also acted as cell attachment substrates for fibroblast, endothelial, and smooth muscle cells. However, the modified Scl2 proteins were unable to aggregate platelets. These results indicate that Scl2 is a suitable backbone for the introduction of mammalian integrin-binding sequences, and these sequences may be manipulated to individually target α1β1 and α2β1.     

Protein kinase C-related kinase targets nuclear localization signals in a subset of class IIa histone deacetylases

Class IIa histone deacetylases (HDACs) -4, -5, -7 and -9 undergo signal-dependent nuclear export upon phosphorylation of conserved serine residues that are targets for 14-3-3 binding. Little is known of other mechanisms for regulating the subcellular distribution of class IIa HDACs. Using a biochemical purification strategy, we identified protein kinase C-related kinase-2 (PRK2) as an HDAC5-interacting protein. PRK2 and the related kinase, PRK1, phosphorylate HDAC5 at a threonine residue (Thr-292) positioned within the nuclear localization signal (NLS) of the protein. HDAC7 and HDAC9 contain analogous sites that are phosphorylated by PRK, while HDAC4 harbors a non-phosphorylatable alanine residue at this position. We provide evidence to suggest that the unique phospho-acceptor cooperates with the 14-3-3 target sites to impair HDAC nuclear import.

Structured summary

MINT-7710106:HDAC5 (uniprotkb:Q9UQL6) physically interacts (MI:0915) with PRK2 (uniprotkb:Q16513) by pull down (MI:0096)     

Genetic analysis of the structure and function of transfer messenger RNA pseudoknot 1

tmRNA rescues stalled ribosomes in eubacteria by forcing the ribosome to abandon its mRNA template and resume translation with tmRNA itself as a template. Pseudoknot 1 (pk1), immediately upstream of this coding region in tmRNA, is a structural element that is considered essential for tmRNA function based on the analysis of pk1 mutants in vitro. pk1 binds near the ribosomal decoding site and may make base-specific contacts with tmRNA ligands. To study pk1 structure and function in vivo, we have developed a genetic selection that ties the life of Escherichia coli cells to tmRNA activity. Mutation of pk1 at 20% per base and selection for tmRNA activity yielded sequences that retain the same pseudoknot fold. In contrast, selection of active mutants from 10(6) completely random sequences identified hairpin structures that functionally replace pk1. Rational design of a hairpin with increased stability using an unrelated sequence yielded a tmRNA mutant with nearly wild-type activity. We conclude that the role of pk1 in tmRNA function is purely structural and that it can be replaced with a variety of hairpin structures. Our results demonstrate that in the study of functional RNAs, the inactivity of a mutant designed to destroy a given structure should not be interpreted as proof that the structure is necessary for RNA function. Such mutations may only destabilize a global fold that could be formed equally well by an entirely different, stable structure.     

Ascorbate is a pro-oxidant in chromium-treated human lung cells

The human A549 lung cell line is used in this study as a model to evaluate chromium toxicity and mutagenesis since inhalation exposure of this metal gives rise to an epidemiology that indicates the lung as a target organ of chromium toxicity. Hexavalent chromium is considered the carcinogenic form of chromium, however it must be reductively activated following uptake into cells in order to react with intracellular constituents. We have previously established that the fluorescent dyes, dichlorofluorescein (DCF) and dihydrorhodamine, are effective indicators of the reductive activation of chromium and are sensitive measures of the formation of highly reactive chromium species (RCS) intracellularly. In order to examine the role of the two common intracellular reductants, glutathione and ascorbic acid (Vitamin C) in generating RCS intracellularly, we manipulated their intracellular levels through the use of buthionine sulfoximine (BSO) or by the addition of ascorbate into the culture media. We found that the high levels of glutathione in this cancer cell line lowered endogenous oxidation levels markedly, and that, by decreasing intracellular glutathione, BSO not only generated a higher background level of endogenous intracellular oxidation but the chromium-stimulated oxidation also increased markedly. Contrary to it appellation as an anti-oxidant, ascorbic acid stimulated a strong pro-oxidant response upon chromium treatment and this pro-oxidant response was evident regardless of the levels of glutathione in the cells. Based on these results, we conclude that ascorbic acid acts as a pro-oxidant in chromium-treated cells.     

Growth hormone deficiency and replacement in patients with treated Cushing's Disease, prolactinomas and non-functioning pituitary adenomas: effects on body composition, glucose metabolism, lipid status and bone mineral density

BACKGROUND/AIMS: This study was designed to determine whether previous Cushing's disease (CD) or prolactinoma (PRL) could exert adverse effects additional to those of growth hormone (GH) deficiency as a consequence of variable degrees of prior hypogonadism or hypercatabolism. We report the effects of 5 years GH treatment in 124 GH deficiency adults; 42 patients with non-functioning pituitary adenomas (NFPA), 43 with treated PRL and 39 with treated CD. METHODS: Fasting plasma glucose, HbA(1c), lipoprotein profile, anthropometry and bone mineral density (BMD) were measured at baseline, 6 months and annually up to 5 years. RESULTS: Mean body mass index remained unchanged in the PRL group and tended to increase in the NFPA group. In contrast, body mass index decreased in the CD group. Decreases in waist and waist/hip ratio were seen in all groups at 6 months. Decreases in total cholesterol and low-density lipoprotein cholesterol were seen in all groups and remained sustained at 5 years. Plasma glucose and HbA(1c) increased at 6 months. Subsequently, plasma glucose returned to baseline values at 5 years; in contrast, HbA(1c )remained unchanged at the end of the study. Baseline lumbar spine and hip BMD were lower in the PRL and CD groups than in the NFPA group, decreased over 1 year in all groups and subsequently increased by 2 years in NFPA with a subsequent increase in lumbar spine BMD in PRL and CD groups delayed to 3-5 years. CONCLUSIONS: Baseline characteristics and response to GH replacement are qualitatively similar in NFPA, PRL and CD patients. Because improvements in BMD occur later in PRL and CD patients, an extended trial of GH therapy may be indicated in those patients who were commenced on GH therapy as an additional treatment for reduced BMD.     

Peripheral metabolic responses to prolonged weight reduction that promote rapid, efficient regain in obesity-prone rats

Weight regain after weight loss is the most significant impediment to long-term weight reduction. We have developed a rodent paradigm that models the process of regain after weight loss, and we have employed both prospective and cross-sectional analyses to characterize the compensatory adaptations to weight reduction that may contribute to the propensity to regain lost weight. Obese rats were fed an energy-restricted (50-60% kcal) low-fat diet that reduced body weight by 14%. This reduced weight was maintained for up to 16 wk with limited provisions of the low-fat diet. Intake restriction was then removed, and the rats were followed for 56 days as they relapsed to the obese state. Prolonged weight reduction was accompanied by 1) a persistent energy gap resulting from an increased drive to eat and a reduced expenditure of energy, 2) a higher caloric efficiency of regain that may be linked with suppressed lipid utilization early in the relapse process, 3) preferential lipid accumulation in adipose tissue accompanied by adipocyte hyperplasia, and 4) humoral adiposity signals that underestimate the level of peripheral adiposity and likely influence the neural pathways controlling energy balance. Taken together, long-term weight reduction in this rodent paradigm is accompanied by a number of interrelated compensatory adjustments in the periphery that work together to promote rapid and efficient weight regain. These metabolic adjustments to weight reduction are discussed in the context of a homeostatic feedback system that controls body weight.     

Ascorbate is a pro-oxidant in chromium-treated human lung cells

The human A549 lung cell line is used in this study as a model to evaluate chromium toxicity and mutagenesis since inhalation exposure of this metal gives rise to an epidemiology that indicates the lung as a target organ of chromium toxicity. Hexavalent chromium is considered the carcinogenic form of chromium, however it must be reductively activated following uptake into cells in order to react with intracellular constituents. We have previously established that the fluorescent dyes, dichlorofluorescein (DCF) and dihydrorhodamine, are effective indicators of the reductive activation of chromium and are sensitive measures of the formation of highly reactive chromium species (RCS) intracellularly. In order to examine the role of the two common intracellular reductants, glutathione and ascorbic acid (Vitamin C) in generating RCS intracellularly, we manipulated their intracellular levels through the use of buthionine sulfoximine (BSO) or by the addition of ascorbate into the culture media. We found that the high levels of glutathione in this cancer cell line lowered endogenous oxidation levels markedly, and that, by decreasing intracellular glutathione, BSO not only generated a higher background level of endogenous intracellular oxidation but the chromium-stimulated oxidation also increased markedly. Contrary to it appellation as an anti-oxidant, ascorbic acid stimulated a strong pro-oxidant response upon chromium treatment and this pro-oxidant response was evident regardless of the levels of glutathione in the cells. Based on these results, we conclude that ascorbic acid acts as a pro-oxidant in chromium-treated cells.