Tandem communication improves ant foraging success in a highly competitive tropical habitat

Tropical ants experience intense intra- and interspecific competition for food sources, which influences their activity pattern and foraging strategies. Even though different ant species can coexist through spatial and temporal niche partitioning, direct competition for food cannot be avoided. Recruitment communication is assumed to help colonies to monopolize and exploit food sources successfully, but this has rarely been tested under field conditions. We studied if recruitment communication helps colonies of the Neotropical ant Pachycondyla harpax to be more successful in a highly competitive tropical environment. Additionally, we explored if temporal and spatial niche differentiation helps focal colonies to avoid competition. Pachycondyla harpax competed with dozens of ant species for food. Mass-recruiting competitors were often successful in displacing P. harpax from food baits. However, when foragers of P. harpax were able to recruit nestmates they had a 4-times higher probability to keep access to the food baits. Colonies were unlikely to be displaced during our observations after a few ants arrived at the food source. Competition was more intense after sunset, but a disproportionate increase in activity after sunset allowed focal colonies to exploit food sources more successfully after sunset. Our results support the hypothesis that recruitment communication helps colonies to monopolize food sources by helping them to establish a critical mass of nestmates at large resources. This indicates that even species with a small colony size and a slow recruitment method, such as tandem running, benefit from recruitment communication in a competitive environment.

CLINICAL TRIAL ON CHEMOPROPHYLAXIS OF BREAST CANCER WITH AROMATASE INHIBITOR LETROZOLE IN WOMEN WITH A HIGH RISK OF DEVELOPING BREAST CANCER. PART I: SELECTION OF PATIENTS, THE FREQUENCY OF PRECANCEROUS STATES

In 2004 - 2010, in the Research Institute of Clinical Oncology of the N.N. Blokhin National Medical Research Center of Oncology there was implemented a prospective randomized clinical trial on chemoprophylaxis of breast cancer with letrozole in women with precancerous states of the breast epithelium. The hypothesis of the study supposed letrozole to be capable to eliminate or at least halt the progression of breast precancerous changes, represented by atypical hyperplasia or hyperplasia without atypia. The study included women with a potentially high risk of developing breast cancer: female patients with validated risk factors for the disease or a risk of contralateral breast cancer with a personal history of the disease. The ultimate goal of the examination was to identify patients with morphologically proven precancerous changes in the mammary gland with positive expression of estrogen receptors. To obtain a morphological material, periareolar fine-needle puncture of the mammary gland was performed. The effectiveness of the developed method of sampling happened to be high, allowing the diagnosis in 172 (96.6%) of 178 patients. Hyperplasia without atypia was detected in 69 (38.8%) women, atypical hyperplasia - in 81 (45.5%) patients, in 22 (12.3%) women no pathological changes in the epithelium were detected. The study has failed to be completed due to the slow recruitment of patients. Despite the incompleteness of the study, new data on the prevalence of breast precancerous changes in the postmenopausal women in the Russian population and significant experience in the organization and implementation of studies on chemoprophylaxis of breast cancer have been obtained.

Mistletoe Preparation Iscador: Are there Methodological Concerns with Respect to Controlled Clinical Trials?

In Europe many cancer patients use complementary therapies, particularly mistletoe. Only a few controlled clinical trials have been performed with the mistletoe preparation Iscador as a complementary treatment for cancer, many of them with medium to low quality due to methodological shortcomings. Reasons for some quality concerns, particularly discontinuation of treatment and/or participation and premature termination are analyzed. Analysis is based on controlled clinical trials dealing with Iscador. Data stem from the archive of published and ongoing research of the «Verein für Krebsforschung» (Society for Cancer Research) in Arlesheim, Switzerland. Controlled clinical studies with cancer patients that were started after 01.01.1990 or were not completed by then have been evaluated. Fifty-six controlled studies are documented, 24 of them randomized and 32 non-randomized. Nine of the randomized studies were done by matched-pair design, the others by conventional parallel group design; six of the last were terminated prematurely primarily for slow recruitment due to patient preferences and compliance of physicians. Patient and physician preference seem to be important factors limiting recruitment for randomized trials and hence implementation. This adds to the overall unwillingness of participation by patients with serious diseases. A well-balanced mix of designs using different research methods and outcomes is suggested combined with analyses, in countries where mistletoe therapy in general or Iscador in particular is unknown or not available.

Mechanism of Spontaneous and Receptor-Controlled Electrical Activity in Pituitary Somatotrophs: Experiments and Theory

Cultured pituitary somatotrophs release growth hormone in response to spontaneous Ca2+ entry through voltage-gated calcium channels (VGCCs) that is governed by plateau-bursting electrical activity and is regulated by several neurohormones, including GH-releasing hormone (GHRH) and somatostatin. Here we combine experiments and theory to clarify the mechanisms underlying spontaneous and receptor-controlled electrical activity. Experiments support a role of a Na+-conducting and tetrodotoxin-insensitive channel in controlling spontaneous and GHRH-stimulated pacemaking, the latter in a cAMP-dependent manner; an opposing role of spontaneously active inwardly rectifying K+ ( Kir) channels and G-protein-regulated Kir channels in somatostatin-mediated inhibition of pacemaking; as well as a role of VGCCs in spiking and large conductance (BK-type) Ca2+-activated K+ channels in plateau bursting. The mathematical model is compatible with a wide variety of experimental data involving pharmacology and extracellular ion substitution and supports the importance of constitutively active tetrodotoxin-insensitive Na+ and Kir channels in maintaining spontaneous pacemaking in pituitary somatotrophs. The model also suggests that these channels are involved in the up- and downregulation of electrical activity by GHRH and somatostatin. In the model, the plateau bursting is controlled by two functional populations of BK channels, characterized by distance from the VGCCs. The rapid activation of the proximal BK channels is critical for the establishment of the plateau, whereas slow recruitment of the distal BK channels terminates the plateau.

Effect of annual pasture composition, plant density, soil fertility and drought on vulpia (Vulpia bromoides (L.) S.F. Gray)

Vulpia is a widespread weed of temperate Australian pastures, and readily replaces more productive species. Short-term management of vulpia is possible with herbicides but densities rapidly increase in poorly competitive pastures after herbicide application. A field experiment at Wagga Wagga, NSW, examined the effect of 2 fertility levels and 4 pasture types [subterranean clover sown at 1, 25, 100 kg/ha, and subterranean clover (25 kg/ha) + annual ryegrass (20 kg/ha)] on 2 densities of vulpia (50,5 500 plants/m2) from 1990 to 1994. Initially vulpia plant density was inversely related to sowing rate of subterranean clover, but over time this effect declined as the subterranean clover populations converged. Presence of annual ryegrass always resulted in lower vulpia plant, panicle and seed densities compared with treatments where subterranean clover only was present. Respective densities per m2 in 1993 for the average of the subterranean clover monocultures and for annual ryegrass plus subterranean clover were: plant 1315 v. 265; panicle 6700 v. 130; seed 542 400 v. 3460. The effect of drought in 1994 and presence of annual ryegrass were shown to significantly lower the sustainable population of vulpia at Wagga Wagga from 5000–6000 to <1000 plants/m2. The short-term nature of herbicide application for control, and the need to ensure that competitive species were present to slow recruitment of vulpia in any long-term management strategy, were highlighted.