Taste perception in honeybees: just a taste of honey?

The advent of the genomic era has opened new doors to understand the fundamental organization of living organisms and has therefore promoted a fertile field of comparative research that intends to identify similarities and differences between related and unrelated species at the genomic level. One of the organisms whose genome has been recently decoded is that of the honeybee Apis mellifera, enabling a direct comparison with another well-studied insect, the fruit fly Drosophila melanogaster. It was reported that the honeybee has only ten gustatory receptors and thus a very poor taste perception compared to Drosophila, which presents 68 gustatory receptors, and the mosquito Anopheles gambiae, which presents 76 gustatory receptors. In this forum article, we discuss the implications of these findings taking into account previous and new discoveries on honeybee gustation based on behavioral and neurobiological studies by several authors and us. We conclude that the world of taste of a honeybee might not be as poor as proposed and that further studies should integrate molecular, neurobiological, behavioral and ecological approaches to better characterize taste perception in bees. Handling editor: Lars Chittka     

Taste: independent origins of chemoreception coding systems?

A large family of divergent candidate gustatory receptors has been identified in Drosophila. As with the odorant receptors, one receptor is expressed per sensory neuron, each class of which projects to discrete regions of the brain, allowing a combinatorial coding system for specific recognition of ligands.     

Hot male: can sex in humans be modified by temperature?

Sex determination in many animals has an environmental component, particularly through temperature. In this article, it is argued that some evidence may by seen for this in humans, and it is proposed that the influence of temperature on sex determination may be a reason for the placing of testicles outside the body cavity in most male mammals.     

Genes and environment in arthritis: can RA be prevented?

Understanding of how interactions between genes and environment contribute to the development of arthritis is a central issue in understanding the etiology of rheumatoid arthritis (RA), as well as for eventual subsequent efforts to prevent the disease. In this paper, we review current published data on genes and environment in RA as well as in certain induced animal models of disease, mainly those in which adjuvants only or adjuvants plus organ-specific autoantigens are used to induce arthritis. We refer to some new data on environmental and genetic factors of importance for RA generated from a large case-control study in Sweden (1200 patients, 1200 matched controls). We found an increased risk of seropositive but not of seronegative RA in smokers, and there are indications that this effect may be due to a gene-environment interaction involving MHC class II genes. We also found an increased risk of RA in individuals heavily exposed to mineral oils. This was of particular interest because mineral oils are strong inducers of arthritis in certain rodent strains and because polymorphisms in human genetic regions syntenic with genes predisposing for oil-induced arthritis in rats have now been shown to associate with RA in humans. Taken together, our data support the notion that concepts and data on gene-environment interactions in arthritis can now be taken from induced animal models of arthritis to generate new etiological hypotheses for RA.     

Basal metabolic rate of endotherms can be modeled using heat-transfer principles and physiological concepts: reply to "can the basal metabolic rate of endotherms be explained by biophysical modeling?"

Our recent article (Roberts et al. 2010 ) proposes a mechanistic model for the relation between basal metabolic rate (BMR) and body mass (M) in mammals. The model is based on heat-transfer principles in the form of an equation for distributed heat generation within the body. The model can also be written in the form of the allometric equation BMR = aM(b), in which a is the coefficient of the mass term and b is the allometric exponent. The model generates two interesting results: it predicts that b takes the value 2/3, indicating that BMR is proportional to surface area in endotherms. It also provides an explanation of the physiological components that make up a, that is, respiratory heat loss, core-skin thermal conductance, and core-skin thermal gradient. Some of the ideas in our article have been questioned (Seymour and White 2011 ), and this is our response to those questions. We specifically address the following points: whether a heat-transfer model can explain the level of BMR in mammals, whether our test of the model is inadequate because it uses the same literature data that generated the values of the physiological variables, and whether geometry and empirical values combine to make a "coincidence" that makes the model only appear to conform to real processes.     

Understanding drugs and diseases by systems biology?

Systems biology aims to provide a holistic and in many cases dynamic picture of biological function and malfunction, in case of disease. Technology developments in the generation of genome-wide datasets and massive improvements in computer power now allow to obtain new insights into complex biological networks and to copy nature by computing these interactions and their kinetics and by generating in silico models of cells, tissues and organs. The expectations are high that systems biology will pave the way to the identification of novel disease genes, to the selection of successful drug candidates—that do not fail in clinical studies due to toxicity or lack of human efficacy—and finally to a more successful discovery of novel therapeutics. However, further research is necessary to fully unleash the potential of systems biology. Within this review we aim to highlight the most important and promising top-down and bottom-up systems biology applications in drug discovery.     

Pathways and mechanisms of N-acylethanolamine biosynthesis: can anandamide be generated selectively?

Long-chain N-acylethanolamines (NAEs) and their precursors, N-acylethanolamine phospholipids, are ubiquitous trace constituents of animal and human cells, tissues and body fluids. Their cellular levels appear to be tightly regulated and they accumulate as the result of injury. Saturated and monounsaturated congeners which represent the vast majority of cellular NAEs can have cytoprotective effects while polyunsaturated NAEs, especially 20:4n-6 NAE (anandamide), elicit physiological effects by binding to and activating cannabinoid receptors. It is the purpose of this article to review published data on the pathways and mechanisms of NAE biosynthesis in mammals and to evaluate this information for its physiological significance. The generation and turnover of NAE via N-acyl PE through the transacylation-phosphodiesterase pathway may represent a novel cannabinoid receptor-independent signalling system, analogous to and possibly related to ceramide-mediated cell signalling.     

Marine microbial diversity: can it be determined?

Estimates of the order of magnitude for the total number of microbial species on Earth range from 10(3) to 10(9). Despite global dispersal of microorganisms, this number is probably rather large. The total biodiversity of an ecosystem is composed of two elements: first, a set of abundant taxa that carry out most ecosystem functions, grow actively and suffer intense losses through predation and viral lysis. These taxa are retrievable with molecular techniques but are difficult to grow in culture. Second, there is a seed bank of many rare taxa that are not growing or grow extremely slowly, do not experience viral lysis and predation is reduced. Such taxa are seldom retrieved by molecular techniques but many can be grown in culture, which explains the dictum 'everything is everywhere'.     

Cancer therapy: can the challenge be MET?

The deregulation of tyrosine kinase receptors (RTKs) is frequent in human tumors and is often associated with the acquisition of an aggressive phenotype. The Met oncogene, encoding the RTK for hepatocyte growth factor (HGF), controls genetic programs leading to cell growth, invasion and protection from apoptosis. The deregulated activation of Met is crucial not only for the acquisition of tumorigenic properties but also to achieve an invasive phenotype. The involvement of MET in human tumors has been definitively established and can be achieved through several mechanisms, including MET interaction with unrelated membrane receptors, such as integrins, plexins, CD44, FAS and other RTKs. Interfering with Met activation is thus a new and challenging approach to hamper tumorigenic and metastatic processes.     

Human cloning: can it be made safe?

There are continued claims of attempts to clone humans using nuclear transfer, despite the serious problems that have been encountered in cloning other mammals. It is known that epigenetic and genetic mechanisms are involved in clone failure, but we still do not know exactly how. Human reproductive cloning is unethical, but the production of cells from cloned embryos could offer many potential benefits. So, can human cloning be made safe?     

Taste perception with age: generic or specific losses in supra-threshold intensities of five taste qualities?

The influence of ageing on supra-threshold intensity perception of NaCl, KCl, sucrose, aspartame, acetic acid, citric acid, caffeine, quinine HCl, monosodium glutamate (MSG) and inosine 5'-monophosphate (IMP) dissolved in water and in 'regular' product was studied in 21 young (19-33 years) and 21 elderly (60-75 years) persons. While the relative perception (intensity discrimination) seems to be remarkably resistant to the effect of ageing, the absolute perception (intensity rating) decreased with age for all tastants in water, but only for the salty and sweet tastants in product. When assessed while wearing a nose clip, only the perception of salty tastants was diminished with age. The slopes of the psychophysical functions were flatter in the elderly than in the young for the sweet, bitter and umami tastants in water, and for the sour tastants in product only. The age effects found were almost exclusively generic and never compound-specific within a taste. This study indicates that the relevance of determining intensities of tastants dissolved in water for the 'real life' perception of taste in complex food is rather limited.