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At least 289 records · Page 16Linked to original sources
PubMed2002

Spatial distribution of leaf morphological and physiological characteristics in relation to local radiation regime within the canopies of 3-year-old Populus clones in coppice culture.

Spatial distributions of leaf characteristics relevant to photosynthesis were compared within high-density coppice canopies of Populus spp. of contrasting genetic origin. We studied three clones representative of the range in growth potential, leaf morphology, coppice and canopy structure: Clone Hoogvorst (Hoo) (Populus trichocarpa Torr. & Gray x Populus deltoides Bartr. & Marsh), Clone Fritzi Pauley (Fri) (Populus trichocarpa Torr. & Gray) and Clone Wolterson (Wol) (Populus nigra L.). Leaf area index ranged from 2.7 (Fri and Wol) to 3.8 (Hoo). The clones exhibited large vertical variation in leaf area density (0.02-1.42 m2 m-3). Leaf dry mass per unit leaf area (DM(A)) increased with increasing light in Clones Hoo and Fri, from about 56 g m-2 at the bottom of the canopy to 162 g m-2 at the top. In Clone Wol, DM(A) varied only from 65 to 100 g m-2, with no consistent relationship with respect to light. Conversely, nitrogen concentration on a mass basis was nearly constant (around 1.3-2.1%) within the canopies of Clones Hoo and Fri, but increased strongly with light in Clone Wol, from 1.4% at the bottom of the canopy to 4.1% at the top. As a result, nitrogen per unit leaf area (N(A)) increased with light in the canopies of all clones, from 0.9 g m-2 at the bottom to 2.9 g m-2 at the top. Although a single linear relationship described the dependence of maximum carboxylation rate (17-93 micromol CO2 m-2 s-1) or electron transport capacity (45-186 micromol electrons m-2 s-1) on N(A), for all clones, Clone Wol differed from Clones Hoo and Fri by exhibiting a higher dark respiration rate at low N(A) (1.8 versus 0.8 micromol CO2 m-2 s-1).

Carbon↗
PubMed1993

Physiological characteristics of spontaneously developed diabetes in male WBN/Kob rat and prevention of development of diabetes by chronic oral administration of synthetic trypsin inhibitor (FOY-305).

The male WBN/Kob rats spontaneously develop diabetes mellitus with age. In this study, we examined how glucose tolerance, potency of insulin release, and histology of the pancreas were changed with age in this model. Furthermore, we examined the effect of FOY-305, a synthetic trypsin inhibitor, on this model. Male WBN/Kob rats were divided into two groups: one group fed on standard pellet diet (STD group) and the other on pellet containing 0.1% FOY-305 (FOY group) for 56 weeks after age 4 weeks. Oral glucose (2 g/kg) tolerance test, histology of the pancreas, and glucose (8.3 mM)- and arginine (10 mM)-stimulated insulin release from the isolated perfused pancreas were examined at 8, 20, 40, and 60 weeks of age in both groups. Pancreatic insulin content was examined at 60 weeks. In the STD group, impairment of glucose tolerance and destruction and fibrosis of pancreatic tissues progressed with age. Glucose-stimulated insulin release was remarkably reduced with age, while arginine-stimulated insulin release was preserved. By contrast, in the FOY group, development of glucose intolerance was delayed and the pancreas showed fewer pathologic changes compared with the STD group. Insulin releases in response to both glucose and arginine were preserved at all ages examined. Total pancreatic insulin content at 60 weeks of age was significantly greater than that of the STD group. The male WBN/Kob rat is a new type of diabetic model that shows a similar pattern of insulin release to that in rat with non-insulin-dependent diabetes mellitus and also shows unique histopathological changes in exocrine pancreas. FOY-305 was effective in preventing the development of diabetes in this model, although its mechanism is still unknown.

Administration, Oral↗
PubMedDate not supplied

Sleep physiological characteristics of exhausted men.

Problems initiating and maintaining sleep, and waking up exhausted have been implicated as precursors of a first nonfatal myocardial infarction. These sleep problems are part of an array of complaints that we have labeled as reflecting a state of 'vital exhaustion.' Excess fatigue, loss of vigor, increased irritability, and feelings of demoralization are also characteristic of this state of vital exhaustion, which has been found to constitute a risk indicator for future myocardial infarction. In the present study, we tested the hypothesis that the sleep of exhausted subjects is characterized by a relative absence of slow wave sleep. To test this hypothesis, all-night recordings of the EEG, EOG, and submental EMG of nine exhausted and eight nonexhausted subjects were made for four nights. Sleep stages were rated according to standard criteria. Because these stages do not adequately reflect the essentially continuous aspect of slow wave sleep (SWS), a more detailed analysis of changes in frequencies of the EEG during sleep was also made, using spectral analysis. It seemed that SWS was significantly diminished in exhausted subjects. This suggests that the normal restoration processes that take place during sleep are impaired in exhausted subjects. Additional studies are required to determine the significance of this finding with respect to cardiovascular control during sleep.

Aged↗
PubMed1983

Behavioral, attitudinal, and physiologic characteristics of smoking and nonsmoking asbestos-exposed shipyard workers.

The smoking characteristics of shipyard workers participating in an Asbestos Medical Surveillance Program (N = 3,991) were assessed. Sources of data were: (1) a self-assessment questionnaire on the smoking history and respiratory symptomatology of the 871 current smokers who participated in the smoking study, and (2) chest roentgenograms and pulmonary function test results and medical records for the entire population. The study population included 1,711 current smokers, 988 former smokers and 1,292 never smokers. The annual "quit rate" for former smokers had increased from less than 1% in 1961 to 4.2% in 1978. Of the 871 current smokers who participated in the smoking study, 19% had resumed smoking after having given up cigarettes for one year or longer. Men in the smoking study were reasonably well informed about the health consequences of smoking. While they perceived themselves to be susceptible to disease, and the disease to be serious, the benefits they saw in quitting were related more to economics and aesthetics than to health. When the results were age adjusted, no differences in rate of pulmonary function abnormalities and chest film abnormalities were found between current smokers who voluntarily participated in the smoking study and those who did not. All pulmonary function testing abnormality and chest film abnormality rates were significantly lower for former smokers and never smokers.

Adult↗
PubMed1986

Physiological characteristics of the Mycobacterium tuberculosis-M. bovis group of organisms with particular reference to heterogeneity within M. bovis.

By examining the abilities of mycobacterial strains to remove amino acids from solution, differences were found between Mycobacterium tuberculosis and other closely related taxa. Heterogeneity was observed in most taxa. Strains of M. bovis were examined in greater detail. By using the amino acid typing method in combination with tests routinely used for differentiating mycobacterial species, and SDS-polyacrylamide gel electrophoresis of whole cell soluble proteins, a great degree of heterogeneity was observed in this taxon.

Amino Acids↗
PubMed2004

Relationship between codon biased genes, microarray expression values and physiological characteristics of Streptococcus pneumoniae.

A codon-profile strategy was used to predict gene expression levels in Streptococcus pneumoniae. Predicted highly expressed (PHE) genes included those encoding glycolytic and fermentative enzymes, sugar-conversion systems and carbohydrate-transporters. Additionally, some genes required for infection that are involved in oxidative metabolism and hydrogen peroxide production were PHE. Low expression values were predicted for genes encoding specific regulatory proteins like two-component systems and competence genes. Correspondence analysis localized 484 ORFs which shared a distinctive codon profile in the right horn. These genes had a mean G+C content (33.4 %) that was lower than the bulk of the genome coding sequences (39.7 %), suggesting that many of them were acquired by horizontal transfer. Half of these genes (242) were pseudogenes, ORFs shorter than 80 codons or without assigned function. The remaining genes included several virulence factors, such as capsular genes, iga, lytB, nanB, pspA, choline-binding proteins, and functions related to DNA acquisition, such as restriction-modification systems and comDE. In order to compare predicted translation rate with the relative amounts of mRNA for each gene, the codon adaptation index (CAI) values were compared with microarray fluorescence intensity values following hybridization of labelled RNA from laboratory-grown cultures. High mRNA amounts were observed in 32.5 % of PHE genes and in 64 % of the 25 genes with the highest CAI values. However, high relative amounts of RNA were also detected in 10.4 % of non-PHE genes, such as those encoding fatty acid metabolism enzymes and proteases, suggesting that their expression might also be regulated at the level of transcription or mRNA stability under the conditions tested. The effects of codon bias and mRNA amount on different gene groups in S. pneumoniae are discussed.

Bacterial Proteins↗
PubMed1984

Differences in water relations and physiological characteristics in leaves of wheat associated with leaf position on the plant.

The seasonal change in leaf water potential and its components, stomatal resistance, specific leaf weight, photosynthesis rate, the activities of ribulose-1,5-bisphosphate carboxylase and nitrate reductase, and soluble proteins were measured in flag leaves (ninth from base in position), seventh and fifth leaves of wheat Triticum aestivum L. cv Kalyansona. Flag leaves had a lower water and solute potential and lower or equal turgor pressure than seventh and fifth leaves. These differences were found to be independent of environment. The rate of photosynthesis and nitrate reductase activity were always lower in fifth and seventh leaves than in flag leaf. The photosynthetic efficiency in flag leaves appeared to be associated with lower stomatal resistance and higher specific leaf weight. The relations between leaf water potential and relative water content showed a change with leaf position. This change possibly allows flag leaf to maintain its functional efficiency despite its lower water potential.

Journal Article↗
PubMed1990

Physiological Characteristics of Fe Accumulation in the ;Bronze' Mutant of Pisum sativum L., cv ;Sparkle' E107 (brz brz).

The pea (Pisum sativum L.) mutant, E107 (brz, brz) accumulated extremely high concentrations of Fe in its older leaves when grown in light rooms in either defined nutrient media or potting mix, or outdoors in soil. Leaf symptoms (bronze color and necrosis) were correlated with very high Fe concentrations. When E107 plants were grown in nutrient solutions supplied 10 mum Fe, as the Fe(III)-N,N'-ethylenebis[2-(2-hydroxyphenyl)glycine] chelate, their roots released higher concentrations of Fe(III) reducing substances to the nutrient media than did roots of the normal parent cv, ;Sparkle.' Reciprocal grafting experiments demonstrated that the high concentrations of Fe in the shoot was controlled by the genotype of the root. In short-term (59)Fe uptake studies, 15-day-old E107 seedlings exhibited higher rates of Fe absorption than did ;Sparkle' seedlings under Fe-adequate growth conditions. Iron deficiency induced accelerated short-term Fe absorption rates in both mutant and normal genotypes. Iron-treated E107 roots also released larger amounts of both protons and Fe(III) reductants into their nutrient media than did iron-treated ;Sparkle' roots. Furthermore, the mutant translocated proportionately more Fe to its shoot than did the parent regardless of Fe status.

Journal Article↗
PubMed1999

Morphological and physiological characteristics of discontinuous linear atrial ablations during atrial pacing and atrial fibrillation.

INTRODUCTION: Linear atrial ablations are thought to be necessary to accomplish successful catheter ablation of atrial fibrillation. In order to investigate the conduction characteristics of atrial myocardium in regions of linear lesion discontinuity (gaps), we performed activation sequence mapping in gap regions during atrial pacing and atrial fibrillation. METHODS AND RESULTS: In seven dogs, a linear epicardial ablation was created on the right atrial free wall with a discontinuous segment (gap) in the mid-portion of the lesion. A plaque electrode was used to measure conduction across the gap. Conduction was assessed during (1) atrial pacing from the edge of the plaque electrode during sinus rhythm, and (2) during atrial fibrillation. After each series of measurements, the lesion gap was decreased by creating additional radiofrequency ablations and repeat conduction maps were obtained. The process was repeated until conduction block was observed during atrial pacing. Gap lengths ranged from 0 to 25 mm. During atrial pacing, gaps as narrow as 2 mm demonstrated normal conduction and gaps as large as 5 mm demonstrated block during pacing. Although conduction block was never present across gaps greater than 5 mm, the ability to predict conduction block as a function of gap width was difficult for lesions < or = 5 mm due to a significant degree of overlap between normal conduction and conduction block in this gap range. During atrial fibrillation, 1/175 (0.6%) mapped wavelets conducted across gaps that demonstrated block during pacing; whereas, 411/600 (68.5%; P < 0.0001) wavelets conducted across gaps that did not demonstrate block during pacing (P = NS compared to preablation measurements). Histologically normal atrial myocytes were observed within gaps exhibiting conduction block. CONCLUSIONS: Visible gaps > 5 mm rarely demonstrate conduction block during atrial pacing and atrial fibrillation; whereas, gaps < or = 5 mm in length may demonstrate block. Lesion gaps that do not demonstrate conduction block during atrial pacing have no higher rate of functional conduction block during atrial fibrillation than fibrillating atria without ablation lesions.

Animals↗