The function of function

Contemporary analyses of biological function almost invariably advocate a naturalistic analysis, grounding biological functions in some feature of the mind-independent world. Many recent accounts suggest that no single analysis will be appropriate for all cases of use and that biological teleology should be split into several distinct categories. This paper argues that such accounts have paid too little attention to the way in which functional language is used, concentrating instead on the types of situation in which it is used. An example of the role of teleology in science is examined and, on the basis of conclusions drawn from this, an alternative unifying analysis is proposed. It is suggested that, contrary to naturalistic accounts, teleology in biology carries no ontological commitment whatsoever to any class of mind-independent entities or properties. Instead, it is best regarded as a methodological device which is used to focus interest, formulate research perspectives and facilitate the structuring of certain questions or types of question that are pertinent in a given context of interest.     

Towards a pluralistic concept of function function statements in biology

The meaning of function statements is not clear. Several authors have come up with different explications. By interviewing biologists I tried to get a picture of how they think about function. Two explications of Feature X of organism S has function F came to the fore: (1) X contributes to F and F contributes to survival/reproduction of S and (2) X does F and that contributes to the evolutionary development of X in S via natural selection. Most biologists also related function to adaptation. Gould and Vrba criticize the ordinary use of adaptation in biology. They propose to use it only in the sense of features developed by natural selection for their current role and to use exaptation for features enhancing fitness, but not developed for this by natural selection. This, however, leaves a terminological gap, because as a consequence only effects of adaptations are functions. Effects of exaptations and effects which are not beneficial, like the production of heart sounds, are placed on the same level. That is not in accordance with the practice of biology. That is why a distinction is made between general, adaptive and exaptive functions: function as a pluralistic concept.Revised version of an earlier paper, published in Dutch in Kennis en Methode, November 1988.     

Hypothalamic-pituitary-adrenal function

Basal hypothalamic-pituitary-adrenal (HPA) function is characterised by pulses of corticosterone secretion followed by a transient refractory period when the axis appears to be inhibited. In females pulses of corticosterone secretion occur approximately once per hour with variation in pulse amplitude underlying a diurnal rhythm. Males show smaller pulses of secretion which become widely spaced during the early light phase nadir. Pulsatility is altered by genetic programming, early life experiences and reproductive status. Activation of the HPA axis during adjuvant induced arthritis results in an increase in the pulse frequency. This is associated with a marked change in hypothalamic gene expression with a diminution of CRH mRNA and a marked increase of AVP mRNA which becomes the predominant HPA secretagogue.     

Vomeronasal function

This contribution briefly explores some unanswered questions about vomeronasal organ function, and introduces other contributions from the symposium 'Vomeronasal Function', presented at the XVII Meeting of the Association for Chemoreception Sciences (1996). Key publications appearing since the symposium are also listed.      

Cardiorespiratory function

ACCURATE EVALUATION OF THE DEGREE OF IMPAIRMENT OF PULMONARY FUNCTION IN PERSONS WITH FIBROSIS AND EMPHYSEMA REQUIRES: (1) ventilatory measurements from rapid spirogram tracings (vital capacity, maximal breathing capacity and the time required to blow the air from the lungs); (2) determination of the degree of bronchospasm present; (3) determination of the degree of pulmonary emphysema (residual air expressed quantitatively as percent of total lung volume); (4) determination of the arterial blood oxygen saturation at rest and immediately after step-up exercise; (5) measurement of the oxygen extraction from inspired air (per cent of oxygen removed) during rest and exercise; (6) determination of the oxygen up-take during exercise; and (7) observation of the duration of dyspnea after step-up exercise. No single physiologic test is adequate in evaluating impairment of pulmonary function, and roentgenograms of the chest are unreliable as a sole basis for appraisal of disability. In industrial medicine, pulmonary function studies make possible (a) more accurate diagnosis and evaluation of pulmonary disability; and (b) earlier detection and thus prevention of prolonged exposure by susceptible individuals to environmental hazards.     

Gene function

The problem of gene function--of the relationships between hereditary material and the characteristics of organisms--preceded the rediscovery of Mendel's laws and accompanied the development of genetics in the XXth century. Molecular biologists replaced the simple gene-character relationship by two relationships: the first, between genes and proteins, was well defined, whereas the second between proteins and the complex structural and functional characteristics of organisms remained unknown. I will describe in this article the experimental approaches which helped to characterize during the last twenty years the relationships between proteins and characters. Four principles of macromolecular organization emerged from these studies: conservation of the elementary components during evolution, existence of pathways and networks, pleiotropy and redundancy. These principles are the explanation of the surprising experimental observations that have been made in recent years. The existence of these principles makes problematic any prediction on the consequences of gene modification. It both sounds the death-knell of the simplistic reductionist approach of many biologists, whereby genes were considered as responsible for specific functions, and definitely prevents the distribution of genes in separate, well defined categories.     

Presynaptic function

Changing the strength of synapses is key to the adaptive modifications of what neuronal circuits compute. Unsurprisingly, many different mechanisms have evolved to alter synaptic strength. Some of these mechanisms depend on the history of synaptic use, others reflect the activity of modulatory neurons that are controlled through neural computations, and still others involve more global measures of neural activity. The molecular machinery synapses use to convey information from one neuron to the next not only plays an essential part in brain function but also is at the basis of processes that are vital to all cells. Because membrane fusion events at synapses are so precisely controlled, synapses offer an especially favorable system in which to study these basic processes. Here, I review some of the recent progress that has been made in understanding both how synaptic strength is regulated and how fundamental cell biological mechanisms are used to accomplish neuronal intercommunication.     

Assessment of spermatozoal function

Different procedures have been developed to assess the functions of spermatozoa in terms of their motility as well as their fertilizing potential. The procedures for assessment of motility are either qualitative or quantitative, subjective or objective, while the procedures for assessment of fertilizing potential are either direct or indirect. In this review, the information available on the procedures are compiled and analysed including the procedures forin vitro penetration of zona-free hamster eggs by human or non-human primate spermatozoa.     

Binary function of mRNA

Since the discovery of messenger RNA (mRNA) over half a century ago, the assumption has always been that the only function of mRNA is to make a protein. However, recent studies of prokaryotic and eukaryotic organisms unexpectedly show that some mRNAs may be functionally binary and have additional structural functions that are unrelated to their translation product. These findings imply that some of the phenotypic features of cells and organisms can also be binary, that is, they depend both on the function of a protein and the independent structural function of its mRNA. In this review, we will discuss this concept within the framework of multifunctional RNA molecules and the RNA World Hypothesis.