Vestibular and Oculomotor Physiology

453

TINS - December 1982

harsh external conditions. This behavior may well be a model for other types of plasthese two processes which favor a net mig- ticity since it appears that both the ration in a favorable direction. The classical chemotactic signals and receptors to receive definition for each of these combinations them may be induced at the appropriate was probably important at an earlier des- time, and only at the appropriate time, in criptive phase, but becomes less relevant as the cell cycle. The final aspect which makes the field becomes exposed to molecular mechanisms and detailed analysis of the chemotaxis so attractive is that it can be individual organisms. The motion of the studied in primitive species that can be manpolymorphonuclear leucocytes, described ipulated biochemically and genetically to by Zigmond and Sullivan, is illustrative in elucidate the molecular apparatus. The this regard. A leucocyte seems to move rel- most advanced of these studies occurs in entlessly and slowly upon a path apparently bacteria whose state of the art is percepintegrating gradient information over tively reported by Hazelbauer. But rapid space. However, recent studies suggest that advances are occurring in other systems as pseudopods, constantly shooting out from well. Paramecium which is a large enough the leucocytes, may be responding by tem- organism to allow electrophysiological poral sensing, i.e. a positive gradient tends measurements has chemotactic controls which involve calcium gradients. Methylato make the pseudopod remain extended, whereas a negative gradient will lead to its tion of receptors has been identified in the withdrawal back into the cellular body. The bacterial species and in the leukocytes. The net motion of the cell therefore will appear development of the cell cycle in Myxococas spatial sensing, even though the actual cus xanthus can be short-circuited by adding glycerol; however, the glycerolsensory detection is temporal. The manner in which chemotaxis helps generated myxospores are slightly different the cell adjust to the environmental condi- from the myxospores produced by the fruittions of the cell is perhaps nowhere better ing body thus providing insight into the illustrated than in the responses of slime molecular mechanisms. The focus of this book is largely on sysmoulds and Myxococcus xanthus described in the fascinating chapters of Newell and tems for which some elements of molecular Clark. Under normal conditions with high elucidation have been developed. The nutrients the eucharyotic slime moulds and migration of animals or the chemotaxis of the procharyotic bacteria live a high style cells in development is not described. The vegetative life. However, if the nutrients editors have done a good job in the areas are deprived, both species go through a chosen, presenting chapters with a complicated pattern in which the cells minimum of jargon and a maximum of claraggregate using chemotactic signals and ity. The repetitive and yet individualistic then proceed through a differentiative designs of each chemotactic system is like a process in which a sporulation-type process symphony in which a melody recurs but is utilized in order to preserve the species. each species has its own variations on the This accumulation could be considered a basic theme. DANIELE. KOSHLAND,Jr primitive form of altruism, in which some cells give their bodily constituents to other Professor. Departmentof Biochemistry. Univer~i(v cells, so that some cells will survive the of California, Berkeley, ( A 94720. U.S.A.

Microbial m e l o d i e s - variations on a theme Biology of the Chemotactic

Response

edited by J. M. Lackie and P. C. Wilkinson, Cambridge University Press, 1982. £8.95 (xiii + 177 pages) 1SBN 0 521 29897 0 The chemotactic response is increasingly favored for behavioral studies because it is ubiquitous, can be measured objectively and is susceptible to manipulation at the molecular level. This carefully edited book by Lackie and Wilkinson gives a glimpse of chemotactic response in a variety of sensory systems. That chemotaxis is universal is illustrated in Gooday's interesting chapter on chemotaxis in the eukaryotic microbes. The AUomyces species, for example, produce five different motile cells during their life cycles. Of these only two have a need for attraction to each other, i.e. the female and male gametes. Only the female cells produce the sex attractant sirenin and only the male gametes respond to it. The male microbe comes under the spell of sirenin, proceeds through a series of programmed motions when trying to depart from the female so that he inevitably finds the female gamete and produces the next generation. This clever selection of attractants and receptors to produce a desired response is universal from bacteria to Chanel Number 5. Polymorphic nuclear leucocytes, for example, lucidly described by Wilkinson, respond to formyl peptides excreted by bacteria which they are designed to destroy and to C5a, a large peptide from the complement system, and therefore an indicator of an inflammation condition. In the slime moulds, ably explained by Newell, the chemotactic factor is not only a small molecule emitted by one cell in order to attract other cells, but it has the added interesting property of being emitted in an intermittent fashion, so that its frequency as well as its structure is important in the signalling. The quantitation possible in measurements of the chemotactic responses provides objectivity which is not easy to obtain in assays of behavioral responses. This quantltation can involve observation of the patterns of movements of individual cells and a dissection of the types of locomotion within the cell which produce the overall behavior. Dunn and Keller describe some of these approaches and their relationship to classical definitions of klinoand chemo-kinesis, etc. Organisms can direct their movements by differentially increasing their velocities or altering their frequency of turning or by a combination of

Oculomotor progress - version 'a' V e s t i b u l a r and O c u l o m o t o r Physiology

edited by Bernard Cohen, The New York Academy o f Sciences, 1981. $175 (xiv + 892pages) I S B N 0 89766 138 9 This volume with almost 75 individual contributions records the proceedings of a conference on Vestibular and Oculomotor Physiology held in September 1980 by the Bfirhny Society and cosponsored by the New York Academy of Sciences. The book is divided in 15 sections which deal in turn with vestibular receptor mechanisms, central oculomotor organization to clinical investigations.

The first three chapters deal with the directional sensitivity of the response to hair bundle displacement, the function of the endolymphatic duct, and the eye muscle geometry in lateral and frontal-eyed animals. Problems of graviception are treated in the next chapter with studies of otolithic function in man on earth and in weightlessness. Eight chapters are devoted to the processing of vestibular, visual, spinal and reticular neural activities in the production of eye movements. About half of these papers deals with studies of the visual-vestibular interactions in different types of bralnstem neurones. Habituation in the vestibular sys-

t INS - Decemh,'r I ~,~¢2

454 tern is studied in monkeys and man. The role of cerebellar nuclei in different types of ocular movements and in the plasticity of vestibulo-ocular reflex is analysed in the remainder papers. There are a few papers that examine auditory-vestibular interactions showing acoustic-induced eye movements and suppression of vestibular nystagmus by fixation of visual and acoustic targets in patients. Three chapters concentrate on clinical work and cover abnormal head-eye interactions and eye movements in patients with different types of CNS disorders. Dynamic changes in the

vestibulo-ocular reflex and studies of visual-vestibular interactions are studied in the diagnosis of vestibular disease. There is no material on eye muscleper se. The work reported is generally very good and many leading investigators are included among the authors. Most of the information has been. or will be, published elsewhere but it is convenient to find such a wide variety of material gathered in one volume. All papers are relatively short and the majority concentrate on recent experimental work reported in the traditional way (Introduction, Methods, etc.). The abun-

JEEM Supplement on pattern formation Growth and the Development of Pattern

edited by R. M. Gaze, V. French, M. Snow and D. Summerbell, Cambridge University Press, 1981. £21.00 (i + 325 pages) ISBN 0 52l 24557 5 At least three symposia dealing with pattern formation have been published in the last several months: 'Growth and the Development of Pattern (Journal o f Embryology and Experimental Morphology, vol. 65 supplement, 1981 ; JEEM); 'Theories of Pattern Formation' (Philosophical Transactions o f the Royal Society o f London, ser. B, vol. 295, no. 1078, 1981; PTRS); and 'Principles and Problems of Pattern Formation in Animals' (American Zoologist, vol. 22, no. 1, 1982; A Z ) . Their titles reflect their respective emphases rather well. All three cover many topics, but the first gives special attention to the problem of how growth and the ultimate size of a structure are regulated in relation to the structure's pattern, the second emphasizes formulation of theories to account for pattern formation, and the last is an eclectic collection which contains discussions of pattern, growth, theory, and more studies on neural systems than the first two. Neither the mechanism(s) by which patterns are established, nor the mechanism(s) by which growth is regulated, are known in any system. The precision of each, however, can be impressive - for example, insects are sometimes classified into species or even genera on the basis of minute details of bristle number, location and morphology; and the two wings of a single chick embryo are matched in length to within 2% in most individuals (Summerbell, J E E M ) . Some workers (e.g. Holder, J E E M ) feel that there is a direct and obligatory link between pattern and size, whereas others (e.g. Maden, J E E M ) lay more emphasis on cases in which the two can be dissociated. An explicit discussion of panem formation and size regulation is

dance of detailed observations does not bring an easily assimilated overview of the fields for the non-specialist. Unfortunately. there is no summary on major points of consensus or conlroversy and the volume does not reflect the modifications of the points of view which may have resulted from discussions between this outstanding international group ~f contributors. S. T'~(-f)UMONT

Unite de Recherches Neurobiologiques. INSERM

U-6, 280 Bird Sainte-Marguerite. 13000 Marseille, France.

development fit models of this kind? Anderson (JEEM) gives a lucid account of central projections from sensory neurons given by Cooke (AZ). developing at ectopic sites in several differMost of the papers in all three symposia ent insect systems, with the conclusion that make use of the concept of 'positional the developmental history of a sensory cell information'. This term was introduced matters but its (ectopic) location does not almost 15 years ago by Wolpert to encapsu- the new positional information, if it indeed late the idea that a cell differentiates on the exists, does not exert an effect on the cell's basis of two distinct factors: its genetic con- projection in the CNS. Other authors make stitution and developmental history on the greater or lesser use of the positional inforone hand, and the location in which it finds mation framework. Morris-Kay (JEEM) itself on the other. In this model cells from discusses the morphogenesis of the cranial the toe-to-be region of the foot grafted to the neural epithelium during neurulation in elbow-to-he region of the ann would dif- rats. Diamond (AZ) reviews the distribuferentiate into knee structures; they would tion and behaviour of peripheral sensory maintain their hindlimb identity, but they endings in vertebrate skin. Summerbell and would form structures according to their Stifling (AZ) describe the development of new position in the forelimb. The co- the innervation of chick limbs. Finally, ordinate systems which convey information Hunt et al. ( A Z ) describe some ambitious about location are believed to be common at studies on eye development in amphibians. least to all the appendages of an individual This last paper raises, in a neurobiologi(hence leg cells can read ann positional cat context, the issue of compartments. information), among individuals of a These are regions, best known in insect species, and across related species. In fact, bodies, which have boundaries across they might be universal, at least among which cell migration does not occur so that animals (e.g. Summerbell, A Z ) . discrete cell populations are established. Many questions can he asked about posi- Ideas about the origin and significance of tional information. Is it conveyed to cells compartments are discussed by Karlsson by some diffusible material(s) with mor- (JEEM), Kauffman (PTRS), Lawrence phogenetic effects (Gierer, PTRS; McWil- and Wright (PTRS), French (,4 Z), Morata liams. A Z ) ? Is the co-ordinate system a (AZ), Meinhardt ( A Z ) and, in a mampolar rather than a Cartesian one (Holder, malian context, by Snow (JEEM). The J E E M ; French, PTRS; several authors in related and perhaps more general problem A Z ) ? Are there electrical currents whose of segmentation is discussed by Cooke distribution gives a positional information (PTRS and A Z ) . Lawrence and Wright (Jaffe, PTRS)? Could positional informa- (PTRS), Schubiger and Newman (AZ) tion be a matter of history, given by the time and French (AZ). which a cell spends in a critical zone before It would be impossible to summarize, let its place there is taken by another cell alone evaluate, the papers in even one of (Wolpert, PTRS ) ? these symposia. Taken together, however, Positional information is believed to he they convey a sense of the dynamism which interpreted by cells, with differentiation pervades the field of pattern formation, the being the outcome of this interpretation. A difficulties with general concepts like posinumber of authors consider the possible tional information or the polar co-ordinate role of cell lineage in the interpretation model, and the never-ending string of surprocess (Simpson, J E E M ; Snow, J E E M ; prises from new experiments. Kauffman, PTRS ; Kimble, PTRS ; J. PALKA Morata, A Z: Hunt, et al.. A Z; Meinhardt, AZ), Department of Zoology, Universityof Washington. To what extent do data on neural Seattle, WA 98195, U.S.A