Repeated Evolution of Fungal Cultivar Specificity in Independently Evolved Ant-Plant-Fungus Symbioses

Some tropical plant species possess hollow structures (domatia) occupied by ants that protect the plant and in some cases also provide it with nutrients. Most plant-ants tend patches of chaetothyrialean fungi within domatia. In a few systems it has been shown that the ants manure the fungal patches and use them as a food source, indicating agricultural practices. However, the identity of these fungi has been investigated only in a few samples. To examine the specificity and constancy of ant-plant-fungus interactions we characterised the content of fungal patches in an extensive sampling of three ant-plant symbioses (Petalomyrmex phylax/Leonardoxa africana subsp. africana, Aphomomyrmex afer/Leonardoxa africana subsp. letouzeyi and Tetraponera aethiops/Barteria fistulosa) by sequencing the Internal Transcribed Spacers of ribosomal DNA. For each system the content of fungal patches was constant over individuals and populations. Each symbiosis was associated with a specific, dominant, primary fungal taxon, and to a lesser extent, with one or two specific secondary taxa, all of the order Chaetothyriales. A single fungal patch sometimes contained both a primary and a secondary taxon. In one system, two founding queens were found with the primary fungal taxon only, one that was shown in a previous study to be consumed preferentially. Because the different ant-plant symbioses studied have evolved independently, the high specificity and constancy we observed in the composition of the fungal patches have evolved repeatedly. Specificity and constancy also characterize other cases of agriculture by insects.     

Effects of exercise training on plasma catecholamines and blood pressure in labile hypertensive subjects

Plasma catecholamine concentrations (norepinephrine, NE; epinephrine, E) were measured along with heart rate (HR) and blood pressure (BP) at rest in supine (20 min) and standing (10 min) positions and in response to cycle ergometer exercise (5 min; 60% estimated maximal aerobic power) in 12 hypertensive patients before and after 20 weeks of aerobic training on cycle ergometer (six males, one female) or by jogging (five males). In a control group of labile hypertensive patients (five males, two females), estimated maximal aerobic power as well as HR and BP at rest in the supine and standing positions and in response to exercise were not modified from the first to the second evaluation (43 +/- 4 vs 43 +/- 5 ml.kg-1.min-1). In comparison estimated maximal aerobic power significantly increased in both training groups (cycle: 38 +/- 4 to 43 +/- 4; jogging: 38 +/- 3 to 46 +/- 4 ml.kg-1.min-1). However HR and BP were not modified following training, except for small reductions in systolic (18.9 to 18 kPa: 142 to 135 mmHg) and diastolic pressures (13.3 to 12 kPa: 100 to 90 mmHg) (p less than 0.05) at standing rest in the cycle group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increases of spinal kinin receptor binding sites in two rat models of insulin resistance

An autoradiographic study was conducted to determine whether kinin receptors are altered in the rat spinal cord in two experimental models of chronic hyperglycemia and insulin resistance. Sprague-Dawley rats were given 10% d-glucose in their drinking water alone or with insulin (9 mU/kg/min with osmotic pumps) for 4 weeks. Both groups and control rats were treated either with a normal chow diet or with an alpha-lipoic acid-supplemented diet as antioxidant therapy. After 4 weeks of treatment, glycemia, insulinemia, blood pressure, insulin resistance index, the production of superoxide anion in the aorta and the density of B2 receptor binding sites in the dorsal horn were significantly increased in the two models. These effects were prevented or attenuated by alpha-lipoic acid. In contrast, B2 receptor binding sites of most spinal cord laminae were increased in the glucose group only and were not affected by alpha-lipoic acid. Results show that chronic hyperglycemia associated with insulin resistance increases B1 and B2 receptor binding sites in the rat spinal cord through distinct mechanisms, including the oxidative stress for the B1 receptor.     

Catecholamine release and ventricular arrhythmias during coronary occlusion and reperfusion in the dog

In anesthetized dogs, 60-min occlusions of either the proximal (n = 14), distal (n = 8) left circumflex (LCX), or left anterior descending (LAD, n = 10) arteries were followed by reperfusion. Coronary sinus and aortic norepinephrine and epinephrine plasma concentrations were measured. The ventricular arrhythmias were ventricular premature depolarizations (VPDs), unsustained ventricular tachycardia (VT) (greater than or equal to 3 and less than 20 VPDs), sustained VT (greater than or equal to 20 VPDs), and ventricular fibrillation (VF). A gradual twofold increase (p less than 0.05) in myocardial norepinephrine overflow followed occlusion in all three groups. The increases in the amounts of norepinephrine released in the coronary sinus blood during reperfusion were significant and proportional to the size of the occluded area: proximal LCX, from 0.236 +/- 0.038 to 1.528 +/- 0.490 ng/mL of plasma (p less than 0.001); LAD, from 0.180 +/- 0.027 to 0.795 +/- 0.286 ng/mL (p less than 0.05); distal LCX, from 0.215 +/- 0.039 to 0.404 +/- 0.110 ng/mL (p less than 0.05). Aortic epinephrine concentrations were significantly increased only by LAD occlusion; at 15 min, the value had increased to 0.187 +/- 0.053 ng/mL from an initial value of 0.069 +/- 0.029 ng/mL (p less than 0.001). Two phases of ventricular arrhythmias followed both occlusion and reperfusion. Phase 1 postocclusion was characterized by VPDs and phase 2 by VPDs and unsustained VT. Sustained VT was seen only in phase 1 postreperfusion, whereas unsustained VT was seen in phase 2. VF was seen in 50, 35, and 25% of the dogs with proximal LCX, LAD, and distal LCX occlusion and reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Corelease of neuropeptide Y like immunoreactivity with catecholamines from the adrenal gland during splanchnic nerve stimulation in anesthetized dogs

The release of neuropeptide Y like immunoreactivity (NPY-li) from the adrenal gland was studied in relation to the secretion of catecholamines (CA: NE, norepinephrine; E, epinephrine) during the left splanchnic nerve stimulation in thiopental-chloralose anesthetized dogs (n = 16). Plasma concentrations of NE, E, and NPY-li were determined in the left adrenal venous and aortic blood. Adrenal outputs of NPY-li, NE, and E were 2.4 +/- 0.4, 1.4 +/- 0.2, and 7.3 +/- 1.7 ng/min, under basal conditions, respectively. These values increased significantly (p less than 0.05; n = 8) in response to a continuous stepwise stimulation at frequencies of 1, 3, and 10 Hz given at 3-min intervals during 9 min, reaching a maximum output of 4.6 +/- 0.9 (NPY-li), 240.2 +/- 50.2 (NE), and 1412.5 +/- 309.7 ng/min (E) at a frequency of 10 Hz. Burst electrical stimulation at 40 Hz for 1 s at 10-s intervals for a period of 10 min produced similar increases (p less than 0.05) in the release of NPY-li (4.8 +/- 1.0 ng/min, n = 8), NE (283.5 +/- 144.3 ng/min, n = 8), and E (1133.5 +/- 430.6 ng/min, n = 8). Adrenal NPY-li output was significantly correlated with adrenal NE output (r = 0.606; n = 24; p less than 0.05) and adrenal E output (r = 0.640; n = 24; p less than 0.05) in dogs receiving the burst stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ant assemblage structure on cocoa trees in smallholder farms in the Centre Region of Cameroon

We investigated the ant community structure in cocoa farms in the Centre Region of Cameroon. Ants were collected on the cocoa trees during the years 2006 and 2007 using chemical knock‐down. We tested the hypothesis of the existence of deterministic factor in the structuration of ant mosaic using C‐Score; we assessed the relationship between the numerical dominant and subdominant ant species using Spearman correlation test and discussed on the influence of vegetation structure and farm management on the ant community structure. A total of 53 ant species belonging to 20 genera and five subfamilies were identified from a set of 51,525 workers collected. C‐score analysis supported the hypothesis that ant community were structured by competition. Negative relationships were found between dominant ant species. Farming practices which were mainly pruning, chemical treatment and habitat structure appeared to influence the ecological status and distribution of dominant ant species.