Synecological comparisons sustained by ecophysiological fingerprinting of intrinsic photosynthetic capacity of plants as assessed by measurements of light response curves

In some literature variations in photosynthetic rates are considered to be of little relevance for individual fitness. This depends among other things on how one defines fitness, i.e. if one takes strictly Darwinian fitness as seed production or if one needs to evaluate particular traits and consider plant establishment. It also matters if one takes the Darwinian "organism individual" as the central entity in evolution ("individual fitness") or the "species individual" in a modified "Structure of Evolutionary Theory" sensu Stephen Jay Gould. A phenotypically expressed trait like photosynthetic rate, even if intra- and interspecific differences may be small, can matter in habitat performance and niche acquisition. Light dependence curves (LCs) of photosynthetic rates are now readily measured under field conditions using miniaturized equipment of pulse amplitude modulated fluorometers. In contrast to actual momentary measurements of quantum yield of photosynthesis under actually prevailing ambient conditions, LC measurements reflect the expressed intrinsic capacity of photosynthesis. In this review we explore the power of LC measurements yielding cardinal points such as maximum apparent electron transport rate of photosystem II (ETRmax) and saturating photosynthetically active radiation (PARsat) in making intra- and interspecific comparisons of plant performance and synecological fingerprinting in ecophysiological studies across species, sites, habitats and ecosystems.

Viscosity of gums in vitro and their ability to reduce postprandial hyperglycemia in normal subjects

Experiments were carried out in vitro with three viscous polysaccharides (guar gum, pectin, and carboxymethylcellulose (CMC)) of similar initial viscosity submitted to conditions that mimic events occurring in the stomach and duodenum, and their viscosity in these situations was compared to their actions on postprandial hyperglycemia in normal human subjects. Guar gum showed greater viscosity than the other gums during acidification and/or alkalinization and also showed larger effects on plasma glucose levels (35% reduction in maximum rise in plasma glucose) and on the total area under the curve of plasma glucose (control: 20,314 ± 1007 mg dl-1 180 min-1 vs guar gum: 18,277 ± 699 mg dl-1 180 min-1, P<0.01). Pectin, which showed a marked reduction in viscosity at 37oC and after events mimicking those that occur in the stomach and duodenum, did not have a significant effect on postprandial hyperglycemia. The performance of viscosity and the glycemia response to CMC were at an intermediate level between guar gum and pectin. In conclusion, these data suggest that temperature, the process of acidification, alkalinization and exposure to intestinal ions induce different viscosity changes in gums having similar initial viscosity, establishing a direct relationship between a minor decrease of gum viscosity in vitro and a reduction of postprandial hyperglycemia

Studies on the intrinsic nervous system of the wild rodent Calomys callosus digestive tract. II: The submucous plexus

The submucous plexus of the normal small and large intestine of Calomys callosus was studied by NADH and AChE histochemical techniques and by transmission and scanning electron microscopy. The plexus contains (mean ± SD) 7,488 ± 293 neurons/cm2 in the duodenum, 5,611 ± 836 in the jejunum, 2,741 ± 360 in the ileum, 3,067 ± 179 in the cecum, and 3,817 ± 256 in the proximal colon. No ganglia or nerve cell bodies were seen in the esophagus, stomach, distal colon or rectum. The neurons are pear-shaped with a round or oval nucleus and the neuronal cell profile areas were larger in the large intestine than in the small intestine. Most of the neurons display intense AChE activity in the cytoplasm. AChE-positive nerve fibers are present in a primary meshwork of large nerve bundles and in a secondary meshwork of finer nerve bundles. At the ultrastructural level, the ganglia are irregular in shape and covered with fibroblast-like cells. The nucleoplasm of the neurons is finely granular with a few condensations of chromatin attached to the nuclear envelope. In the neuropil numerous varicosities filled with vesicles of different size and electron densities are seen. The pre- and post-synaptic membrane thickenings are asymmetric. Characteristic glial cells with oval nuclei and few organelles are numerous. These data provide a detailed description of this submucosal meshwork.

Studies on ATP-diphosphohydrolase nucleotide-binding sites by intrinsic fluorescence

Potato apyrase, a soluble ATP-diphosphohydrolase, was purified to homogeneity from several clonal varieties of Solanum tuberosum. Depending on the source of the enzyme, differences in kinetic and physicochemical properties have been described, which cannot be explained by the amino acid residues present in the active site. In order to understand the different kinetic behavior of the Pimpernel (ATPase/ADPase = 10) and Desirée (ATPase/ADPase = 1) isoenzymes, the nucleotide-binding site of these apyrases was explored using the intrinsic fluorescence of tryptophan. The intrinsic fluorescence of the two apyrases was slightly different. The maximum emission wavelengths of the Desirée and Pimpernel enzymes were 336 and 340 nm, respectively, suggesting small differences in the microenvironment of Trp residues. The Pimpernel enzyme emitted more fluorescence than the Desirée apyrase at the same concentration although both enzymes have the same number of Trp residues. The binding of the nonhydrolyzable substrate analogs decreased the fluorescence emission of both apyrases, indicating the presence of conformational changes in the neighborhood of Trp residues. Experiments with quenchers of different polarities, such as acrylamide, Cs+ and I- indicated the existence of differences in the nucleotide-binding site, as further shown by quenching experiments in the presence of nonhydrolyzable substrate analogs. Differences in the nucleotide-binding site may explain, at least in part, the kinetic differences of the Pimpernel and Desirée isoapyrases.

Quenching of the intrinsic fluorescence of bovine serum albumin by chlorpromazine and hemin

The binding of chlorpromazine (CPZ) and hemin to bovine serum albumin was studied by the fluorescence quenching technique. CPZ is a widely used anti-psychotic drug that interacts with blood components, influences bioavailability, and affects function of several biomolecules. Hemin is an important ferric residue of hemoglobin that binds within the hydrophobic region of albumin with high specificity. Quenching of the intrinsic fluorescence of bovine serum albumin (BSA) was observed by selectively exciting tryptophan residues at 290 nm. Emission spectra were recorded in the range from 300 to 450 nm for each quencher addition. Stern-Volmer graphs were plotted, and the quenching constant estimated for BSA solution titrated with hemin at 25ºC was 1.44 (± 0.05) x 10(5) M-1. Results showed that bovine albumin tryptophans are not equally accessible to CPZ, in agreement with the idea that polar or charged quenchers have more affinity for amino acid residues on the outer wall of the protein. Hemin added to albumin solution at a molar ratio of 1:1 quenched about 25% of their fluorescence. The quenching effect of CPZ on albumin-hemin solution was stronger than on pure BSA. This increase can be the result of combined conformational changes in the structure of albumin caused firstly by hemin and then by CPZ. Our results suggest that the primary binding site for hemin on bovine albumin may be located asymmetrically between the two tryptophans along the sequence formed by subdomains IB and IIA, closer to tryptophan residue 212.

Loss of resting bradycardia with detraining is associated with intrinsic heart rate changes

The mechanisms underlying the loss of resting bradycardia with detraining were studied in rats. The relative contribution of autonomic and non-autonomic mechanisms was studied in 26 male Wistar rats (180-220 g) randomly assigned to four groups: sedentary (S, N = 6), trained (T, N = 8), detrained for 1 week (D1, N = 6), and detrained for 2 weeks (D2, N = 6). T, D1 and D2 were treadmill trained 5 days/week for 60 min with a gradual increase towards 50% peak VO2. After the last training session, D1 and D2 were detrained for 1 and 2 weeks, respectively. The effect of the autonomic nervous system in causing training-induced resting bradycardia and in restoring heart rate (HR) to pre-exercise training level (PET) with detraining was examined indirectly after cardiac muscarinic and adrenergic receptor blockade. T rats significantly increased peak VO2 by 15 or 23.5% when compared to PET and S rats, respectively. Detraining reduced peak VO2 in both D1 and D2 rats by 22% compared to T rats, indicating loss of aerobic capacity. Resting HR was significantly lower in T and D1 rats than in S rats (313 ± 6.67 and 321 ± 6.01 vs 342 ± 12.2 bpm) and was associated with a significantly decreased intrinsic HR (368 ± 6.1 and 362 ± 7.3 vs 390 ± 8 bpm). Two weeks of detraining reversed the resting HR near PET (335 ± 6.01 bpm) due to an increased intrinsic HR in D2 rats compared with T and D1 rats (376 ± 8.8 bpm). The present study provides the first evidence of intrinsic HR-mediated loss of resting bradycardia with detraining in rats.

Intrinsic bent DNA sites in the chromosomal replication origin of Xylella fastidiosa 9a5c

The features of the nucleotide sequences in both replication and promoter regions have been investigated in many organisms. Intrinsically bent DNA sites associated with transcription have been described in several prokaryotic organisms. The aim of the present study was to investigate intrinsic bent DNA sites in the segment that holds the chromosomal replication origin, oriC, of Xylella fastidiosa 9a5c. Electrophoretic behavior analyses, as well as in silico analyses of both the 2-D projection and helical parameters, were performed. The chromosomal segment analyzed contains the initial sequence of the rpmH gene, an intergenic region, the dnaA gene, the oriC sequence, and the 5' partial sequence of the dnaN gene. The analysis revealed fragments with reduced electrophoretic mobility, which indicates the presence of curved DNA segments. The analysis of the helical parameter ENDS ratio revealed three bent DNA sites (b1, b2, and b3) located in the rpmH-dnaA intergenic region, the dnaA gene, and the oriC 5' end, respectively. The chromosomal segment of X. fastidiosa analyzed here is rich in phased AT tracts and in CAnT motifs. The 2-D projection indicated a segment whose structure was determined by the cumulative effect of all bent DNA sites. Further, the in silico analysis of the three different bacterial oriC sequences indicated similar negative roll and twist >34.00° values. The DnaA box sequences, and other motifs in them, may be associated with the intrinsic DNA curvature.

Intrinsic denervation of the colon is associated with a decrease of some colonic preneoplastic markers in rats treated with a chemical carcinogen

Denervation of the colon is protective against the colon cancer; however, the mechanisms involved are unknown. We tested the hypothesis that the denervated colonic mucosa could be less responsive to the action of the chemical carcinogen dimethylhydrazine (DMH). Three groups of 32 male Wistar rats were treated as follows: group 1 (G1) had the colon denervated with 0.3 mL 1.5 mM benzyldimethyltetradecylammonium (benzalkonium chloride, BAC); G2 received a single ip injection of 125 mg/kg DMH; G3 was treated with BAC + the same dose and route of DMH. A control group (Sham, N = 32) did not receive any treatment. Each group was subdivided into four groups according to the sacrifice time (1, 2, 6, and 12 weeks after DMH). Crypt fission index, ß-catenin accumulated crypts, aberrant crypt foci, and cell proliferation were evaluated and analyzed by ANOVA and the Student t-test. G3 animals presented a small number of aberrant crypt foci and low crypt fission index compared to G2 animals after 2 and 12 weeks, respectively. From the second week on, the index of ß-catenin crypt in G3 animals increased slower than in G2 animals. From the 12th week on, G2 animals presented a significant increase in cell proliferation when compared to the other groups. Colonic denervation plays an anticarcinogenic role from early stages of colon cancer development. This finding can be of importance for the study of the role of the enteric nervous system in the carcinogenic process.

The cytotoxicity of methacryloxylethyl cetyl ammonium chloride, a cationic antibacterial monomer, is related to oxidative stress and the intrinsic mitochondrial apoptotic pathway

Antibacterial monomers incorporated in dentin bonding systems may have toxic effects on the pulp. Thus, the cytotoxicity of antibacterial monomers and its underlying mechanisms must be elucidated to improve the safety of antibacterial monomer application. The influence of an antibacterial monomer, methacryloxylethyl cetyl ammonium chloride (DMAE-CB), on the vitality of L929 mouse fibroblasts was tested using MTT assay. Cell cycle progression was studied using flow cytometry. Production of intracellular reactive oxygen species (ROS) after DMAE-CB treatment was measured using 2,7-dichlorodihydrofluorescein diacetate staining and flow cytometry analysis. Loss of mitochondrial membrane potential, disturbance of Bcl-2 and Bax expression, as well as release of cytochrome C were also measured using flow cytometry analysis or Western blot to explore the possible involvement of the mitochondrial-related apoptotic pathway. DMAE-CB elicited cell death in a dose-dependent manner and more than 50% of cells were killed after treatment with 30 µM of the monomer. Both necrosis and apoptosis were observed. DMAE-CB also induced G1- and G2-phase arrest. Increased levels of intracellular ROS were observed after 1 h and this overproduction was further enhanced by 6-h treatment with the monomer. DMAE-CB may cause apoptosis by disturbing the expression of Bcl-2 and Bax, reducing the mitochondrial potential and inducing release of cytochrome C. Taken together, these findings suggest that the toxicity of the antibacterial monomer DMAE-CB is associated with ROS production, mitochondrial dysfunction, cell cycle disturbance, and cell apoptosis/necrosis.

Rhein induces apoptosis of human gastric cancer SGC-7901 cells via an intrinsic mitochondrial pathway

Rhein is a primary anthraquinone found in the roots of a traditional Chinese herb, rhubarb, and has been shown to have some anticancer effects. The aim of the present study was to investigate the effect of rhein on the apoptosis of the human gastric cancer line SGC-7901 and to identify the mechanism involved. SGC-7901 cells were cultured and treated with rhein (0, 50, 100, 150, and 200 µM) for 24, 48, or 72 h. Relative cell viability assessed by the MTT assay after treatment was 100, 99, 85, 79, 63% for 24 h; 100, 98, 80, 51, 37% for 48 h, and 100, 97, 60, 36, 15% for 72 h, respectively. Cell apoptosis was detected with TUNEL staining and quantified with flow cytometry using annexin FITC-PI staining at 48 h after 100, 200 and 300 µm rhein. The percentage of apoptotic cells was 7.3, 21.9, 43.5%, respectively. We also measured the mRNA levels of caspase-3 and -9 using real-time PCR. Treatment with 100 µM rhein for 48 h significantly increased mRNA expression of caspase-3 and -9. The levels of apoptosis-related proteins including Bcl-2, Bax, Bcl-xL, and pro-caspase-3 were evaluated in rhein-treated cells. Rhein increased the Bax:Bcl-2 ratio but decreased the protein levels of Bcl-xL and pro-caspase-3. Moreover, rhein significantly increased the expression of cytochrome c and apoptotic protease activating factor 1, two critical components involved in mitochondrial pathway-mediated apoptosis. We conclude that rhein inhibits SGC-7901 proliferation by inducing apoptosis and this antitumor effect of rhein is mediated in part by an intrinsic mitochondrial pathway.

Effects of a physical fitness program on memory and blood viscosity in sedentary elderly men

The aim of this study was to investigate the effects of a 6-month exercise program on cognitive function and blood viscosity in sedentary elderly men. Forty-six healthy inactive men, aged 60–75 years were randomly distributed into a control group (n=23) and an experimental group (n=23). Participants underwent blood analysis and physical and memory evaluation, before and after the 6-month program of physical exercise. The control group was instructed not to alter its everyday activities; the experimental group took part in the fitness program. The program was conducted using a cycle ergometer, 3 times per week on alternate days, with intensity and volume individualized at ventilatory threshold 1. Sessions were continuous and maximum duration was 60 min each. There was significant improvement in memory (21%; P<0.05), decreased blood viscosity (−19%; P<0.05), and higher aerobic capacity (48%; P<0.05) among participants in the experimental group compared with the control group. These data suggest that taking part in an aerobic physical fitness program at an intensity corresponding to ventilatory threshold-1 may be considered a nonmedication alternative to improve physical and cognitive function.

Viscosity of egg white from hens of different strains fed with commercial and natural additives

Yolk color and egg white (albumen) cleanliness and viscosity are important parameters by which consumers judge the quality of eggs. This study aimed to investigate changes in albumen viscosity during storage of eggs for up to 36 days from two different commercial laying hen strains (Carijo Barbada and Isa Brown) fed a diet containing annatto (1.5 and 2.0%) or a synthetic additive without synthetic colorants (control). Analyses of humidity, albumen height, pH, viscosity, foam formation, and stability were carried out on eggs. Carijo Barbada strain had smaller albumen, lower humidity and higher egg white viscosity than Isa Brown strain; however, with storage, viscosity lowered significantly on both strains. Initially, the addition of 2.0% of annatto or a synthetic additive increased viscosity in both strains, but with storage only the control maintained longer viscosity. Lower viscosity did not change foam density and stability.

Wellspring: an intrinsic case study of community-based education for adults living with cancer /

This paper presents education research as vital to addressing the issues faced by adults living with cancer. This qualitative study looked at philosophies of practice for cancer patient education. It was about understanding how values and beliefs shape the way program planners and managers operationalize their knowledge of adult education and how this has significant impact on meeting the needs of those touched by cancer. Improved technology has extended life expectancy, so that Canadians living with cancer, or even dying with cancer now spend less time in direct medical care. The notion of cancer as simply a medical concern is outdated. This study found that informational and support needs of adults living with cancer are often unmet, ignored or unknown. This research investigated a community-based education initiative that is inviting, accessible, and promotes a sense of hope. More specifically, this case study uncovered factors contributing to the success of Wellspring, a grass-roots cancer patient support centre which has been recognized nationally for its ability to effectively meet the diverse non-medical supportive care needs of as many cancer patients and caregivers as possible. Therefore, Wellspring was selected as a case study. Educating people to take charge of their own lives and supporting them in making informed decisions about their lifestyle choices made Wellspring part of a social action movement that focused on improving social attitudes toward people living with cancer. Results of this descriptive inquiry and philosophical inquiry evolved into data that was used to devise an organic model of community-based education that encompasses Adler's (1993) four dimensions of philosophy within a socio-cultural context.

A possible role for intrinsic calcium buffers in the long- term adaptation of crayfish neurons

Increasing the impulse activity of neurons in vivo over 3 or more days causes a reduction in transmitter release that persists for days or weeks (eg. Mercier and Atwood, 1989). This effect is usually accompanied by decreased synaptic fatigue. These two changes involve presynaptic mechanisms and indicate "long-term adaptation" (LTA) of nerve terminals. Previous experiments have shown that LTA requires extracellular calcium and protein synthesis (eg. Hong and Lnenicka, Soc. Neurosci. Abstr. 17:1322) and appears to involve communication between the cell body and the nerve terminals. The present study examines the possibility that the reduction in transmitter release is caused by an -increase in the calcium buffering ability within the nerve terminals. It examines the responses of adapted and control nerve terminals to exogenously applied calcium buffer, BAPTA-AM, which decreases transmitter release (Robitialle and Charlton, 1992). If LTA increases intrinsic Ca2+-buffering, the membrane permeant form of BAPTA should have less effect on adapted nerve terminals than on controls. Experiments are performed on the phasic abdominal extensor motor neurons of the crayfish, Procambarns clarkii. BAPTA-AM decreases excitatory postsynaptic potentials (EPSP's) of the phasic extensor muscles in a dosedependent manner between 5 and 50 JLM. LTA is elicited by in vivo stimulation at 2.5 Hz for 2-4 h per day over 3 days, which reduces EPSP's by over 50%. Experiments indicate that BAPTA-AM produces no significant change in EPSP reduction in adapted neurons when compared to controls. These results do not support the hypothesis that increased daily activity alters rapid intrinsic calcium buffers, that are able to reduce transmitter output in the same manner as BAPTA.