Temporal variations in the primary productivity of Eleocharis acutangula (Cyperaceae) in a tropical wetland environment

Wetland vegetation typically includes aquatic macrophytes with high primary production capacities. The present study investigated how hydrological variations affect biomass allocation and primary productivity in the emergent macrophyte Eleocharis acutangula (Roxb.) Schult. Eleocharis acutangula ramets were collected from the Campelo Lagoon flood plain (21°39'S, 41°12'W and 21°37S, 41°11'W) between March/2005 and February/2006. This region experienced an unusually short rainy period between November/2005 and February/2006 that generated atypically high primary production levels (128gDWm-2month-1) and total biomass gains (447gDWm-2) in May and June/2005 respectively. Our data indicated that primary production and biomass allocation were strongly influenced by variations in wetland water levels and that macrophytes quickly invested in biomass accumulation when surface water levels rised.

Variations in gastric emptying of liquid elicited by acute blood volume changes in awake rats

We have observed that acute blood volume expansion increases the gastroduodenal resistance to the flow of liquid in anesthetized dogs, while retraction decreases it (Santos et al. (1991) Acta Physiologica Scandinavica, 143: 261-269). This study evaluates the effect of blood volume expansion and retraction on the gastric emptying of liquid in awake rats using a modification of the technique of Scarpignato (1980) (Archives Internationales de Pharmacodynamie et de Therapie, 246: 286-294). Male Wistar rats (180-200 g) were fasted for 16 h with water ad libitum and 1.5 ml of the test meal (0.5 mg/ml phenol red solution in 5% glucose) was delivered to the stomach immediately after random submission to one of the following protocols: 1) normovolemic control (N = 22), 2) expansion (N = 72) by intravenous infusion (1 ml/min) of Ringer-bicarbonate solution, volumes of 1, 2, 3 or 5% body weight, or 3) retraction (N = 22) by controlled bleeding (1.5 ml/100 g). Gastric emptying of liquid was inhibited by 19-51.2% (P<0.05) after blood volume expansion (volumes of 1, 2, 3 or 5% body weight). Blood volume expansion produced a sustained increase in central venous pressure while mean arterial pressure was transiently increased during expansion (P<0.05). Blood volume retraction increased gastric emptying by 28.5-49.9% (P<0.05) and decreased central venous pressure and mean arterial pressure (P<0.05). Infusion of the shed blood 10 min after bleeding reversed the effect of retraction on gastric emptying. These findings suggest that gastric emptying of liquid is subject to modulation by the blood volume.

Variations in gastric compliance induced by acute blood volume changes in anesthetized rats

The impact of acute volume imbalances on gastric volume (GV) was studied in anesthetized rats (250-300 g). After cervical and femoral vessel cannulation, a balloon catheter was positioned in the proximal stomach. The opposite end of the catheter was connected to a barostat with an electronic sensor coupled to a plethysmometer. A standard ionic solution was used to fill the balloon (about 3.0 ml) and the communicating vessel system, and to raise the reservoir liquid level 4 cm above the animals' xiphoid appendix. Due to constant barostat pressure, GV values were considered to represent the gastric compliance index. All animals were monitored for 90 min. After a basal interval, they were randomly assigned to normovolemic, hypervolemic, hypovolemic or restored protocols. Data were compared by ANOVA followed by Bonferroni's test. Mean arterial pressure (MAP), central venous pressure (CVP) and GV values did not change in normovolemic animals (N = 5). Hypervolemic animals (N = 12) were transfused at 0.5 ml/min with a suspension of red blood cells in Ringer-lactate solution with albumin (12.5 ml/kg), which reduced GV values by 11.3% (P<0.05). Hypovolemic rats (N = 12) were bled up to 10 ml/kg, a procedure that increased GV values by 15.8% (P<0.05). In the restored group (N = 12), shed blood replacement brought GV values back to basal levels in bled animals (P>0.05). MAP and CVP values increased (P<0.05) after hypervolemia but decreased (P<0.05) with hypovolemia. In conclusion, blood volume level modulates gastric compliance, turning the stomach into an adjustable reservoir, which could be part of the homeostatic process to balance blood volume.

Lipoprotein lipase PvuII polymorphism is associated with variations in serum lipid levels in non-diabetic pregnant women

The aim of the present study was to determine if there is an association between the single nucleotide polymorphisms (SNPs) of the lipoprotein lipase (LPL) and apolipoprotein E (apo E) genes and the serum lipid profile in pregnancy and puerperium. Non-diabetic women of European descent in the third semester of pregnancy (N = 120) were selected. Those with diseases or other condition that could modify their lipid profile were excluded from the study (N = 32). Serum lipids were measured by routine laboratory procedures and genomic DNA was extracted by a salting out method. LPL (PvuII and HindIII) and apo E (HhaI) SNPs were detected by the polymerase chain reaction and restriction fragment length polymorphism. Categorical and continuous variables were compared by the chi-square test and Student t-test or ANOVA, respectively. Women carrying the LPL P1P1 genotype had higher serum LDL cholesterol (N = 21; 155 ± 45 mg/dL) than women carrying the P1P2/P2P2 genotypes (N = 67; 133 ± 45 mg/dL; P = 0.032). During the puerperium period, serum levels of triglycerides and VLDL cholesterol were significantly reduced in women carrying the P1P1 (73%, P = 0.006) and P1P2 (51%, P = 0.002) genotypes but not in women carrying the P2P2 genotype (23%, P > 0.05). On the other hand, serum concentrations of lipids did not differ between the LPL HindIII and apo E genotypes during pregnancy and after delivery. We conclude that LPL PvuII SNP is associated with variations in serum lipids during pregnancy and the puerperal period in non-diabetic women.

Liver oxidative stress of the grey mullet Mugil cephalus presents seasonal variations in Ennore estuary

The objective of this study was to determine the liver oxidative stress status of grey mullets living in heavy-metal-rich polluted Ennore estuary compared with unpolluted Kovalam estuary. Fish were collected from both estuaries during the monsoon and summer seasons from October 2004 to September 2006. Fish liver homogenate (N = 20 per group) was prepared for evaluating oxidative stress parameters. Fish living in the polluted estuary had significantly higher lipid oxidation products, conjugated dienes (0.346 ± 0.017 vs 0.141 ± 0.012 DA233/mg protein), lipid hydroperoxides (0.752 ± 0.032 vs 0.443 ± 0.03 nmol/mg protein), and lipid peroxides (3.447 ± 0.14vs 1.456 ± 0.096 nmol MDA/mg protein) than those of the unpolluted estuary during the summer. In contrast, significantly lower levels of superoxide dismutase (20.39 ± 1.14 vs 53.63 ± 1.48 units/mg protein) and catalase (116 ± 6.87vs 153 ± 8.92 units/mg protein) were detected in the liver of fish from the polluted estuary (Ennore) compared to fish from the unpolluted estuary (Kovalam) during the summer. Variations in most of the oxidative stress parameters were observed between the summer and monsoon seasons, indicating the importance of seasonal variation for estuaries and their inhabitants.

Quality time: exploring meaningful mandatory community involvement programs in secondary schools /

The purpose of this study was to explore the experiences of 5 stakeholder groups—students, parents, community organization representatives, guidance counsellors, and secondary school principals—in dealing with a mandatory secondary school graduation requirement in Ontario. The requirement is that students must complete 40 hours of eligible community involvement activities during their high school years in order to graduate. Ten stakeholders were interviewed regarding the nature of the community involvement program, what makes it work, and suggestions for improvement. The study found that although this program has the potential to provide a meaningful experience for students, and students are seen to gain from their experience in multiple ways, it depends substantially on the commitment of students, educators, and community organizations to make it worthwhile. Stakeholders recommended changes to the current program, which included making it a more structured process that would increase the consistency ofhow this program is implemented, finding ways to curb cheating and to reduce the administrative burden on schools, having more support from the Ontario provincial government and Ontario Ministry of Education and Training in the promotion and communication of this program, and developing partnerships between community organizations and schools to enrich the application of this program. This study concludes with a recommendation that the Ontario Ministry of Education and Training consider introducing Service-Learning, a curriculum-based experiential service and learning process, as an enhancement to the current community involvement program.

A cognitive schematic paradigm for expository essay writing in secondary schools

The methodology outlined in this study for teaching exposit ory writing to advanced (five year phase) grade eleven students is based on the assumption that writing as a problem solving strategy is a high level cognitive skill . In adhering to this assumption, a cognitively based schematic organizer known as a cross-classification chart was tested for its effectiveness a t the planning stage of the writing process . Results were not significant in any of the three components that were evaluated; however , a post- hoc analysis undertaken because of recorded observed data indicated a significant difference in the mean score on the Organization component for the treatment subgroup using the cross- classification organizer . Furthermore, the treatment group's positive response from the attitude survey towards planning writing is encouraging enough that replication and extension of the application of schema theory to wri ting should be pursued in cross-section and longitud i nal studies.

Developmental variations in the peripheral erythrocytic system of the rainbow trout, Salmo gairdneri

The peripheral circulating erythrocytic system of the rainbow trout, l3 almo gairdner , was examined in vitro in relation differences in the morphology and multiple hemoglobin system organization of adult and juvenile red cells. Cells were separated by velocity sedimentation under unit gravity, a procedure requiring red cell exposure to an incubation medium for periods of at least three hours. Therefore , this must provide an environment in which red cells remain in a condition approximaing normalcy. Previous studies having demonstrated commonly employed media to be ineffective in this regard , a medium was developed through modification of Cortl and saline. One of the principal additions to this me dium , norepinephrine, altered cell regulation of intracellular calcium, magnesium and chloride concentrations. Catecholamine involvement was also suggeste d in the synthes is of hemoglobin . The procedure was found to separtate cells primarily by density and, to a lesser extent, by shape. Characterization of red cells revealed two subpopulations to exist . The first comprised the bulk of the cell population, and were of greater l ength, width, volume and major:minor axis ratio than the smaller population; these were adult cells. The later, juvenile cells were of smaller overall size and were more spherical in shape . Juvenile cells also possessed fewer electrophore tpically distinguishable isomorphs than did adults with only eight of eleven hemoglobin component s typically found With maturation,hemoglobin complement with the development of three more bands. The total complement of the adult cell contained 7 cathodal bands and four anodal hemoglobin isomorphs. Bands acquired with maturation comprised the smallest percentage of the cells hemoglobin. each averaging less than one-percent of the total. Whether these additional bands are derived through degradation and reaggregation of existing components or are the product of pe gQy2 synthesis is not yet known.

Thermoacclimatory variations in the activities of enzymes implicated in ion transport in the rainbow trout, salmo gairdneri

Two groups of rainbow trout were acclimated to 20 , 100 , and 18 o C. Plasma sodium, potassium, and chloride levels were determined for both. One group was employed in the estimation of branchial and renal (Na+-K+)-stimulated, (HC0 3-)-stimulated, and CMg++)-dependent ATPase activities, while the other was used in the measurement of carbonic anhydrase activity in the blood, gill and kidney. Assays were conducted using two incubation temperature schemes. One provided for incubation of all preparations at a common temperature of 2S oC, a value equivalent to the upper incipient lethal level for this species. In the other procedure the preparations were incubated at the appropriate acclimation temperature of the sampled fish. Trout were able to maintain plasma sodium and chloride levels essentially constant over the temperature range employed. The different incubation temperature protocols produced different levels of activity, and, in some cases, contrary trends with respect to acclimation temperature. This information was discussed in relation to previous work on gill and kidney. The standing-gradient flow hypothesis was discussed with reference to the structure of the chloride cell, known thermallyinduced changes in ion uptake, and the enzyme activities obtained in this study. Modifications of the model of gill lon uptake suggested by Maetz (1971) were proposed; high and low temperature models resulting. In short, ion transport at the gill at low temperatures appears to involve sodium and chloride 2 uptake by heteroionic exchange mechanisms working in association w.lth ca.rbonlc anhydrase. G.l ll ( Na + -K + ) -ATPase and erythrocyte carbonic anhydrase seem to provide the supplemental uptake required at higher temperatures. It appears that the kidney is prominent in ion transport at low temperatures while the gill is more important at high temperatures. 3 Linear regression analyses involving weight, plasma ion levels, and enzyme activities indicated several trends, the most significant being the interrelationship observed between plasma sodium and chloride. This, and other data obtained in the study was considered in light of the theory that a link exists between plasma sodium and chloride regulatory mechanisms.

Thermoaclimatory variations in the microenvironment of hemoglobin in the rainbow trout, Salmo gairdneri and the carp, Cyprinus carpio

Several inorganic substances (e.g., C£ , Mg , Ca , H ) are potent negative modulators of hemoglobin-oxygen affinity. To evaluate the possibility that potentially adaptive changes in the red cell ionic environment of hemoglobin may take place during acclimation of fishes to increased environmental temperature, hematological status (hemoglobin, hematocrit, red cell numbers, mean erythrocytic volume and hemoglobin content), plasma + + 2+ 2+ and packed red cell electrolyte levels (Na , K , Ca , Mg , C£ ) were evaluated in summer and winter populations of the stenothermal rainbow trout, Salmo gairdneri, following acclimation to 2°, 10°, 18°C, and in a spring population of eurythermal carp, Cyprinus carpio, held at 2°, 16° and 30°C. From these data cell ion concentrations and ion:hemoglobin ratios were estimated. In view of the role of red cell carbonic anhydrase in the reductions of blood C02 tensions and the recruitment of Na and C£~ lost by fishes, a preliminary investigation of thermoacclimatory changes in the activity of this system in rainbow trout erythrocytes was conducted. Few changes in hematological status were encountered following acclimation. There was, however, some evidence of weight-specific differential hematological response in carp. This lead to markedly greater increases in hemoglobin, hematocrit and red cell numbers in smaller rather than in larger specimens at higher temperatures; variations which were 2+ well correlated with changes in plasma Ca . Plasma composition in summer trout was not altered by acclimation. In winter trout plasma Na and K increased at higher temperatures. Carp were characterized by increases in plasma calcium, and reductions in sodium and magnesium under these conditions. Several significant seasonal differences in plasma ion levels were observed in the trout. (n) In trout, only erythrocytic K and K :Hb were altered by acclimation, rising at higher temperatures. In carp Na , Na :Hb, C£~ and C£~:Hb in- 2+ 2+ creased with temperature, while Mg and Mg :Hb declined. Changes in overall ionic composition in carp red cells were consistent with increases in H content. In both species significant reciprocal variations in C£~ 2+ - + and Mg were found. In mammalian systems increases in C£ and H reduce hemoglobin-oxygen affinity by interaction with hemoglobin. Reduction in 2+ 2+ Mg maximizes organophosphate modulator availability by decreasing ATP»Mg complex formation. Thus, the changes observed may be of adaptive value in reducing hemoglobin-oxygen affinity, and facilitating oxygen release to cells at higher temperatures. Trout appear to maintain a high chloridelow magnesium state over the entire thermal tolerance zone. Carp, however, achieved this state only at higher temperatures. In both species mean erythrocytic volume was decreased at higher temperatures and this may facilitate branchial oxygen loading. Since mean erythrocytic volume was inversely related to red cell ion content, it is hypothesized that reductions in cell volume are achieved by export of some unidentified solute or solutes. Variations in the carbonic anhydrase activity that could be attributed to the thermoacclimatory process were quite modest. On the other hand, assays performed at the temperature of acclimation showed a large temperature effect where under in vivo conditions of temperature fish acclimated to higher temperatures might be expected to have higher activities. Furthermore, since hematocrit increased with temperature in these fish, while carbonic anhydrase is present only in the erythrocyte, the whole blood levels of this enzyme are expected to increase and further augment the temperature effect. This, in turn, could aid in the reduction of C02 (111) tension and increase the production of H and HC0~~ used in the active uptake of Na and C£ at higher temperatures.

Can business & monetary conditions predict variations in expected stock returns?

Rapport de recherche

Regional Variations in Political Ideology in Canada

Il est reconnu que les résultats électoraux au Canada varient grandement selon la région. Afin de trouver des explications à ce phénomène, il convient d’étudier comment les grandes régions du Canada se distinguent les unes des autres sur le plan politique. La présente recherche amorce cette étude sous l’angle de l’idéologie. Elle tente de déterminer en quoi l’idéologie politique diffère d’une région à l’autre du pays. Elle s’appuie sur les données des études électorales canadiennes de 2008. On a recours à des questions évaluant les préférences des répondants par rapport à plusieurs enjeux politiques pour répondre à la question de recherche. On conduit en premier lieu une analyse factorielle, qui identifie six facteurs qui ont structuré l’opinion publique lors de l’élection de 2008. Ensuite, des tests T sont conduits pour vérifier si les moyennes de ces facteurs idéologiques sont statistiquement différentes d’une région à l’autre. Les résultats montrent que les différences régionales sont souvent significatives et suivent les hypothèses. Toutefois, les résultats touchant à la privatisation de la santé ainsi qu’au Manitoba et à la Saskatchewan vont à l’encontre des attentes.