Adolescent Expressive Reluctance Exacerbates Risk for Substance Use Following Daily Hassles

Previous research has established a link between adolescent’s perceived daily hassles and subsequent adjustment, but less is known about factors that exacerbate this relationship. The purpose of the present study was to identify if adolescent’s reluctance to express emotions moderated the association between their perceived daily hassles and subsequent substance use (i.e., alcohol, marijuana, tobacco). Cross-sectional data were obtained from a larger study that examined the effects of exposure to community violence among low-income, urban adolescents (N = 260, Mage = 14.14, SD = 1.62 years; 92% African American; 54% female). Linear regression analyses controlling for adolescent age, biological sex, and previous levels of drug use and daily hassles revealed that expressive reluctance moderated the association between perceived daily hassles and adolescent substance use. Specifically, for adolescents who were least likely to express their emotions, increases in perceived daily hassles were associated with significant increases in substance use. Further examination of domain-specific hassles revealed that expressive reluctance moderated the effects of academic, parental, and general neighborhood hassles on drug use, while no significant effects were detected for hassles related to friends or neighborhood danger. The present findings clarify which perceived daily hassles adversely affect adolescents, and how emotional expression can play an integral role in determining risk for poor coping behaviors.https://scholarscompass.vcu.edu/uresposters/1280/thumbnail.jp

The effect of leaf area and crop level on the concentration of amino acids and total nitrogen in 'Thompson Seedless' grapes

20 to 50% of the leaves and 25 to 75% of the clusters on 'Thompson Seedless' vines were removed 12 to 16 days after anthesis. In addition, 25 and 50% of the   leaves on other vines were removed 35 and 58 days after anthesis, with no cluster thinning.Total soluble solids in fruits from vines with less than 5 cm2 of leaf surface per gram of fruits was markedly reduced, while concentration in fruits from vines with a ratio above 10 was considerably higher, compared to the concentration in fruits from vines with ratios intermediate between these two values. The concentrations of arginine, proline, total free amino acids, and total N in berry juice were greatly increased by reducing the crop load. Also, the concentration of each of these substances increased during fruit ripening.A significant correlation between leaf area per vine and level of arginine in the juice was obtained. The concentration of proline in the juice was highly correlated with fruit maturity (°B) and with leaf area per unit weight of fruits. Total nitrogen was also correlated with leaf area per unit weight of fruits. Between 4 and 12 cm2 leaf area per gram of fruits there was a linear increase in the concentration of proline and total nitrogen in berry juice, while above 12 cm2 there was generally little further increase in the level of these substances. The ratio of arginine to proline decreased with fruit maturity and with smaller crop weights per vine. Total free amino acids accounted for 64 to 75% of the total nitrogen in the juice of grapes during the fruit-ripening period. Defoliation within 16 days after anthesis reduced crop yields, while later defoliations did not significantly reduce yields

Changes in the activities of ornithine transcarbarnylase and arginase, and concentrations of nitrogenous substances during germination and seedling development of Vitis vinifera L.

During germination and subsequent growth of seedlings of Vitis vinifera L. cv. Chenin blanc, marked changes occurred in the concentrations of the total nonprotein nitrogen fraction, amino nitrogen, and alnide nitrogen, and in the activities of ornithine transcarbamylase (OTC) and arginase. The level of total nonprotein nitrogen was lower in seeds than in seedlings, with maximum concentration reached at the 3rd stage of seedling growth (10 to 15 d after germination) and thereafter declining rapidly. Changes in the concentration of amino nitrogen and amide nitrogen fractions paralleled that of the total nonprotein nitrogen. The concentration of glutalnine exceeded that of asparagine at all stages of seedling development. The presence of OTC and arginase in seeds and seedlings, as well as the parallel changes between arginase activity and concentration of free arginine, suggested that the biosynthesis and degradation of this amino acid in grapevine tissues occurs through the KREBS-HENSELEIT pathway. The MICHAELIS constant for arginase, calculated from the LINEWEAVER-BURK plot, differed in seedlings at three different stages of seedling development. Veränderungen in der Aktivität der Ornithintranscarbamylase und der Arginase sowie der Konzentration der Stickstoffverbindungen während der Keimung und der Sämlingsentwicklung von Vitis vinifera L.Im Verlauf der Keimung und des anschließenden Wachstums der Sämlinge von Vitis vinifera L., cv . Chenin blanc, traten deutliche Veränderungen in der Konzentration des gesamten nicht-proteingebundenen Stickstoffs, des Amino- und des Amidstickstoffs sowie in der Aktivität der Ornithintranscarbamylase (OTC) und der Arginase auf. Die Samen besaßen einen niedrigeren Gehalt an gesamtem nicht-proteingebundenem Stickstoff als die Sämlinge, wobei die maximale Konzentration im 3. Stadium des Sämlingswachstums erreicht wurd~ (10-15 d nach der Keimung); danach nahm sie rasch ab. Die Verschiebungen in der Konzentration des Amino- und Amidstickstoffs verliefen parallel zu den Konzentrationsänderungen des gesamten nichtproteingebundenen Stickstoffs. In allen Stadien der Sämlingsentwicklung lag die Glutamin- über der Asparaginkonzentration. Das Vorkommen von OTC und Arginase in Samen und Sämlingen sowie die parallelen Veränderungen von Arginaseaktivität und Konzentration des freien Arginins la~sen vermuten, daß die Biosynthese und der Abbau dieser Aminosäure im Rebengewebe über den KREBS-HENSELEIT-Cyklus ablaufen. In den Sämlingsstadien 3, 4 und 5 wurden - nach LINEWEAVER-BURK - unterschiedliche MICHAELIS Konstanten der Arginase ermittelt

Ammonia assimilation in Vitis vinifera L.: II. Leaf and root glutamine synthetase

Glutamine synthetase (GS) activity in Vitis vinifera L. cv. Chenin blanc leaf and root tissues was present in the supernatant and particulate fractions. The percentage distribution of GS activity in leaf and root extracts were respectively 39.5 and 49.2 % in the 10,000 gpellet, 38.6 and 41.1 % in the 2.3,500 gpellet, and 21.9 and 9.7 % in the 23,500 g supernatant fractions. Leaf GS activity was always greater than root enzyme activity. Kinetic studies revealed no significant differences between leaf and root GS from the 10,000 g pellet fraction. The Km values for L-glutamate, ATP and hydroxylamine were respectively 3.2 ± 0.7 mM, 0.8 ± 0.2 mM, and 0.8 ± 0.2 mM. Formation of y-glutamyl hydroxamate was linear for the first 35 min. Optimum in vitro reaction conditions were pH 7.70-8.10, incubation temperature 37 °C, and amount of enzyme equivalent to 75-105 mg of fresh tissue. L-arginine, L-ornithine and carbamyl phosphate at a concentration of 5 mM caused inhibition of 13.6 and 12 %, respectively.Die Ammonium-Assimilation bei Vitis vinifera L.:II. Die Glutaminsynthetase der Blätter und WurzelnBei der Rebsorte Chenin blanc (Vitis vinifera L.) lag nach differenzierter Zentrifugation sowohl in den löslichen wie in den strukturierten Fraktionen Glutaminsynthetase-(GS-)Aktivität vor. Die prozentuale Verteilung der GS-Aktivität auf Blatt- und Wurzelextrakte betrug jeweils 39,5 und 49,2 % im 10 000-g-Sediment, 38,6 und 41,1 % im 23 500-g-Sediment sowie 21,9 und 9,7 % im 23 500-g-Überstand. In den Blättern war die GS-Aktivität stets höher als in den Wurzeln. Untersuchungen der Enzymkinetik erbrachten bei dem 10 000-g-Sediment keine signifikanten Unterschiede zwischen der GS-Aktivität der Blätter und der Wurzeln. Die Km-Werte für L-Glutamat, ATP und Hydroxylamin betrugen 3,2 ± 0,7 mM, 0,8 ± 0,2 mM und 0,8 ± 0,2 mM. Die Bildung von y-Glutamylhydroxamat verlief in den ersten 35 min linear. In vitro waren die optimalen Reaktionsbedingungen ein pH von 7,70-8,10, eine Inkubationstemperatur von 37 °C und eine Enzymmenge, die dem Gehalt von 75-105 mg Frischgewebe entsprach. L-Arginin, L-Ornithin und Carbamylphosphat in Konzentrationen von 5 mM hemmten die Enzymwirkung ·um 13,6 bzw. 12%

Ammonia assimilation in Vitis vinifera L.: III. Glutamate oxaloacetate transaminase from leaf and root tissue

Glutamate-oxaloacetate transaminase (GOT) activities in Vitis vinifera L. cv. Chenin blanc leaf and root tissues were associated only with the soluble fraction. Mean in vitro enzyme activity of both tissues was 4.3 ± 0.8 μmol oxaloacetate formed per g fresh tissue per hour. Km values of GOT from leaves and roots were (1.9 ± 0.4) · 10-4 M for α-ketoglutarate and (4.7 ± 0.5) · 10-3 M for L-aspartate. Optimum in vitro conditions for GOT activity were pH 7.4-7.8, amount of enzyme equivalent to 95-130 mg fresh tissue and incubation temperature 38-39 °C. Neither leaf nor root GOT responded to exogenous pyridoxal-5' phosphate.Die Ammonium-Assimilation bei Vitis vinifera L.:III. GlutamatcOxalacetat-Transaminase aus Blatt- und WurzelgewebeDie Aktivität der Glutamat-Oxalacetat-Transaminase (GOT) in Blatt- und Wurzelgewebe der Rebsorte Chenin blanc (Vitis vinifera L.) war auf die lösliche Fraktion beschränkt. In vitro betrug die mittlere Enzymaktivität in beiden Organen 4,3 ± 0,8 μmol Oxalacetat je g Frischgewicht und h. Die Km-Werte von GOT aus Blättern und Wurzeln betrugen (1,9±0,4) . 10-4 M für α-Ketoglutarat und (4,7±0,5) · 10-3 M für L-Aspartat. Die optimalen Bedingungen der GOT-Aktivität waren in vitro ein pH von 7,4-7,8, eine Enzymmenge, die dem Gehalt von 95-130 mg Frischmaterial entsprach, und eine Inkubationstemperatur von 38-39 °C. Weder Blatt- noch Wurzel-GOT reagierten auf zugesetztes Pyridoxal-5'-Phosphat

Ammonia assimilation in Vitis vinifera L.: I. Isolation and properties of leaf and root glutamate dehydrogenase

Glutamate dehydrogenase (GDH) activity in Vitis vinifera L. cv. Chenin blanc leaf and root tissues was associated with the particulate and the soluble fractions. In leaf extracts, about 66 % of the NADH-GDH activity was in the 10,000 g pellet and about 34 % was in the 23,500 gpellet fractions, whereas NADPH-GDH activity was associated mainly with the soluble fraction (23,500 g). In root extracts, about 53 % of the NADHGDH activity was in the soluble and 43 % in the 10,000 gpellet fractions, whereas about 47, 37, and 16 % of NADPH-GDH activity were in the soluble, 10,000 g and 23,500 gpellet fractions, respectively. GDH from the 10,000 gpellet of leaf and the soluble fraction of root extracts differed in their affinities to substrates. The Km values of leaf and root GDH were, respectively, 3.9 ± 1.1 and 0.7 ± 0.4 mM for a-ketoglutarate; 35.7 ± 7.1 and 61.3 ± 12.4 mM for NH4Cl; and 100.0 ± 7.4 and 36.2 ± 4.4 μM for NADH. GDH from leaf and root tissues showed Michaelis-Meuten kinetics with all. substrates except NH4Cl, which exhibited a sigmoid relationship in roots. Optimum in vitro reaction conditions were pH 7.90-8.10, incubation temperature of 38-40 °C, and amount of enzyme equivalent to 80-110 mg of fresh tissue. Enzyme from both leaves and roots was inhibited by EDTA and L-glutamate. Activation with Ca2+ was more pronounced in root GDH than in leaf GDH.Die Ammonium-Assimilation bei Vitis vinifera L.:1. Isolierung und Eigenschaften der Glutamatdehydrogenase aus Blättern und WurzelnBei der Rebsorte Chenin blanc (Vitis vinifera L.) wurde die Glutamatdehydrogenase- (GDH-)Aktivität der strukturierten und löslichen Fraktionen von Blattund Wurzelgeweben bestimmt. Die NADH-GDH-Aktivität von Blattextrakten verteilte sich zu ca. 66 % auf das nach Zentrifugation bei 10 000 g erhaltene Sediment und zu ca. 34 % auf das 23 500-g Sediment, während die NADPH-GDH-Aktivität hauptsächlich an die lösliche Fraktion (23 500 g) gebunden war. Bei Wurzelextrakten waren ca. 53 % der NADH-GDH-Aktivität in der löslichen Fraktion und 43 % im 10 000-g-Sediment enthalten, während jeweils 47, 37 und 16 % der NADPHGDH- Aktivität auf die lösliche Fraktion, das 10 000-g-Sediment bzw. das 23 500-g-Sediment entfielen. Die GDH aus dem 10 000-g-Sediment des Blattmaterials und aus der löslichen Fraktion der Wurzelextrakte unterschieden sich in ihrer Substrataffinität. Die Km-Werte der Blatt- und Wurzel GDH betrugen 3,9 ± 1,1 bzw. 0,7 ± 0,4 mM für a-Ketoglutarat, 35,7 ± 7,1 bzw. 61,3 ± 12,4 mM für NH4Cl sowie 100,0 ± 7,4 bzw. 36,2 ± 4,4 μM für NADH. Die GDH aus Blatt- und Wurzelgeweben folgte mit allen Substraten der Michaelis-Menten-Kinetik, ausgenommen mit NH4Cl; hier lag bei Wurzelextrakten eine sigmoide Beziehung vor. In vitro waren die optimalen Reaktionsbedingungen ein pH von 7,90-8,10, eine Inkubationstemperatur von 38-40 °C und eine Enzymmenge, die dem Gehalt von 80-110 mg Frischgewebe entsprach. Durch EDTA und L-Glutamat wurde das Enzym sowohl der Blätter als auch der Wurzeln inhibiert. Wurzel-GDH wurde durch Ca2+ stärker aktiviert als Blatt-GDH

The localisation of acids, sugars, potassium and calcium in developing grape berries

Grape berries (Vitis vinifera cv. Chardonnay) were divided into four concentric zones in order to follow the developmental changes in the concentrations of malate, tartrate, glucose, fructose, potassium and calcium within the skin and the fruit flesh. Green berries showed a definite malate gradient, increasing in concentration from the skin towards the seeds; tartaric acid, on the other hand, was highest in concentration at the periphery and lowest in the berry center. With progressing maturity, the ratio between the tartrate concentration in the skin and the corresponding values in the berry core decreased, whereas the reverse was true for malate. In the ripe berry an acid gradient could also be found in the axial direction, decreasing from the pedicel towards the stylar scar. Before the onset of ripening, the highest glucose and fructose concentrations were observed in the skin and the berry center. The accumulation of these sugars in the pulp began without any apparent lag phase at a rate of about 2 mg/ berry · d. After veraison, the highest concentrations were found in the fruit core and the tissue below the peripheral vascular bundles. Both potassium and calcium were mainly localized near the peripheral and central vascular bundles. The potassium content increased during the entire period of berry development at a constant rate of 0.04 mg/berry · d, whereas calcium accumulation stopped about 30 d after anthesis. At this time, the calcium content was approximately 0.1 mg/berry

Leaf age and photosynthesis in Vitis vinifera L.

The photosynthetic activity of individual vine leaves was measured on potted plants grown out doors, using both infrared C02 analysis and 14C02 fixation techniques. Peak photosynthetic activity occurred at the time when the leaf became fully expanded, approximately 40 days after unfolding. Thereafter, photosynthesis declined gradually.The increase in photosynthesis during leaf expansion was not attributable to increased chlorophyll concentration, altered spectral characteristics, or to any outstanding anatomical change. Nevertheless, a sensecent leaf was readily distinguished anatomically from an expanding or mature leaf.Irrespective of leaf age, sucrose was the major 14C02 fixation product. Oligo- saccharides also incorporated label, and accounted for a higher proportion of the 14C fixation products in older leaves. Regardless of leaf age, malic and citric acids became labelled, but the formation of 14C tartaric acid was restricted to the rapidly expanding foliage. The amino compounds serine and aspartic acid showed some incorporation of label in all leaves examined

Magnetic properties of Quantum Corrals from first principles calculations

We present calculations for electronic and magnetic properties of surface states confined by a circular quantum corral built of magnetic adatoms (Fe) on a Cu(111) surface. We show the oscillations of charge and magnetization densities within the corral and the possibility of the appearance of spin--polarized states. In order to classify the peaks in the calculated density of states with orbital quantum numbers we analyzed the problem in terms of a simple quantum mechanical circular well model. This model is also used to estimate the behaviour of the magnetization and energy with respect to the radius of the circular corral. The calculations are performed fully relativistically using the embedding technique within the Korringa-Kohn-Rostoker method.Comment: 14 pages, 9 figures, submitted to J. Phys. Cond. Matt. special issue on 'Theory and Simulation of Nanostructures

Interaction of the Electromagnetic p-Waves with Thin Metal Films

For the first time it is shown that for thin metallic films thickness of which not exceed thickness of skin-layer, the problem allows analytical solution for arbitrary boundary value problems. The analysis of dependence of coefficients of transmission, reflection and absorbtion on angle incidence, thickness of films and coefficient of specular reflection is carried out.Comment: 15 pages, 9 figure