bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE EVOLUTION AND COMPARATIVE PHYSIOLOGY OF TERRESTRIAL AND FRESHWATER NEMERTEANS
Authors: MOORE JANET , GIBSON RAY 
Published: January 2008

Summary(1) Parallel evolution from separate marine ancestors has given rise to two groups of genera of terrestrial nemerteans, representative of at least two different family stocks. They have colonized land by the direct route, moving up the shore on widely separated oceanic islands. The relationships between the known terrestrial and semi‐terrestrial nemerteans, comprising seven genera and 15 species, are defined and their geographic distribution is discussed.(2) In fresh water, three heteronemertean and nine hoplonemertean species are known. The hoplonemerteans arise from two different families representing two different evolutionary routes to fresh water, one by way of estuaries and the other via land. The distribution of freshwater nemerteans and the characters common to all species are discussed.(3) Very little is known about the comparative physiology of land and freshwater nemerteans. However, information about the physiology of marine forms is combined with morphological differences from them found in terrestrial and freshwater species to suggest profitable lines of future research.(4) Water relations pose a major problem for both terrestrial and freshwater nemerteans. The role of the cerebral organs, the blood and the excretory system in the osmotic physiology of some littoral nemerteans is beginning to be understood. These systems in land and freshwater forms have clearly distinctive features which need to be thoroughly investigated.(5) Suggestions are given for valuable lines of investigation of the mucous glands, digestive physiology and general behaviour of terrestrial and freshwater nemerteans.
THE BIOLOGY OF PUBERTY
Authors: BRONSON F. H. , RISSMAN EMILIE F. 
Published: January 2008

SummaryThe objective of this review was to develop a broader, more biological, overview of puberty, as opposed to the more limited, laboratory‐dominated, view that has emanated from experimental physiology. Three conceptual schemes form the basis for our broader perspective. The first deals with the ways in which genes and environmental factors interact to program the timing of reproductive development. The second focuses on the ways environmental factors interact with each other to influence puberty. The third relates the genetic and environmental controls to specific endocrine and neuroendocrine pathways of action.The more traditional approach of studying domesticated animals under carefully controlled conditions predetermines one's conclusions. One logically will conclude that the final stages of reproductive development are rather rigidly determined genetically and not greatly subject to environmental regulation, except for obviously adaptive pheromonal and photoperiodic regulation. One also will search within the reproductive axis itself for the final developmental step that allows functional fertility. In contrast, a more biological view suggests that for most mammals puberty is a highly labile process subject to several kinds of environmental influences that operate at many times during a mammal's life. Furthermore this perspective suggests that the final developmental step allowing fertility onset normally will occur outside rather than within the reproductive axis proper. This conclusion has a potentially great impact upon the way we look at the organization of the brain and endocrine system and in the way we choose animal models for studying human puberty and the types of controls we study.
NUTRIENT TRANSPORT BY THE CRUSTACEAN GASTROINTESTINAL TRACT: RECENT ADVANCES WITH VESICLE TECHNIQUES
Authors: AHEARN GREGORY A. 
Published: January 2008

Summary1. Techniques are described for producing purified brush‐border membrane vesicles (BBMV) of crustacean hepatopancreas which can be used to examine the characteristics of solute transport at the apical pole of hepatopancreatic epithelial cells.2. Hepatopancreatic BBMV illustrated Na‐dependent, carrier‐mediated sugar transport which was electrogenic and sensitive to pH. Increased proton concentration lowered the Michaelis‐Menten constant for glucose transport and increased the apparent diffusional permeability of the membrane to sugar.3. Transports of L‐alanine and L‐lysine by hepatopancreatic BBMV were Na‐independent, carrier‐mediated, and strongly sensitive to transmembrane electrical potential after protonation at acidic pH. L‐alanine and L‐lysine were competitive inhibitors of each other for influx into BBMV and also illustrated trans‐stimulation, suggesting that both amino acids use the same transfer mechanism. L‐Leucine was a non‐competitive inhibitor of L‐lysine influx and may employ a distinct Na‐independent transport process.4. L‐glutamate transport after protonation at acidic pH was Na‐dependent, suggesting that a different transport mechanism was responsible for its movement across hepatopancreatic BBMV than that facilitating the transfer of alanine or lysine.5. Preliminary experiments indicate the presence of Na/H antiport in hepatopancreatic BBMV, providing, for the first time, a possible mechanism for gastrointestinal luminal acidification in crustaceans.6. A proposed model for nutrient transport by crustacean hepatopancreatic BBMV is presented which suggests that transapical transfers of both sugars and amino acids are strongly influenced by in vivo luminal acidification. Luminal protons have at least two major effects on nutrient transport in these animals: (a) titration of sugar transport proteins with subsequent stimulatory effects on influx kinetic constants; (b) protonation of luminal amino‐acid‐charged moieties and conversion into appropriate substrates for transport by either Na‐dependent or Na‐independent, membrane‐potential‐sensitive carrier proteins.
SPERM THRUSTS AND THE PROBLEM OF PENETRATION
Authors: GREEN D. P. L. 
Published: January 2008

SummaryAn equation of Lighthill's is used to calculate sperm thrusts. They have values in the range 5–350 pN, depending on species. The limitations of this approach are discussed and comparison is made with the measured thrust for human sperm. The effect of sperm thrusts of this magnitude on covalent bonds and reversible bonds is discussed. Sperm cannot break covalent bonds, but can reduce the lifetime of reversible bonds.The structure and physical properties of the zona pellucida are examined in relation to sperm penetration. The evidence suggests that sperm cannot penetrate it solely by force. A model for sperm penetration is elaborated in which the conjunctive application of thrust and a soluble enzyme leads to strain‐induced proteolysis and the formation of the penetration slit. The potential mechanism of the zona block is discussed, as is the site of the acrosome reaction. The effects of other mechanical inputs into fertilization such as stirring and swimming are examined briefly. Evidence suggests that sperm penetration of the cumulus oophorus and cervical mucus is mechanical, but that in the case of cervical mucus, it is affected by changes in the physical properties of the mucus.
THE ROLE OF METABOLISM AND CALCIUM IN THE CONTROL OF MITOSIS AND OOPLASMIC MOVEMENTS IN INSECT EGGS: A WORKING HYPOTHESIS
Authors: MEER JITSE. M. VAN DER 
Published: January 2008

SummaryPatterns of mitosis and ooplasmic movements in the plasmodial phase of insect embryogenesis and their supramolecular basis are reviewed. Evidence is provided for both the relative independence and the precise correlation of the nuclear cycle and various cycling movements of the ooplasm. I suggest that the timing of these cycles is controlled by a metabolic cycle. The latter may act via a cyclic rise and fall either of the level of free calcium or of the sensitivity of contractile cytoplasmic proteins to a constant level of free calcium. Thus mitotic patterns may reflect metabolic patterns, which in turn may reflect the distribution and activity of mitochondria and may also be related to egg size and shape by a gradient of surface‐to‐volume ratios. The total number of cycles may depend on a limiting cytoplasmic factor, which together with the number of nuclei in a given cycle defines the nucleo‐cytoplasmic ratio. I also propose that both natural and experimental activation of insect eggs trigger the metabolic cycle either directly, by supplying oxygen or water, or indirectly, via a calcium pulse. Possible molecular mechanisms of control are discussed and applied to mitosis and ooplasmic movements. A brief discussion of various cell cycle models in light of data from insect embryogenesis is included.
HISTORY OF ARIDLAND VEGETATION AND CLIMATE: A GLOBAL PERSPECTIVE
Authors: SINGH GURDIP 
Published: January 2008

Summary1. The origin and history of aridlands and their vegetational cover is closely related to geological history, especially in relation to plate tectonics, mountain building, land‐and sea‐level changes and ice ages, and the arrival of modern humans and their subsequent development.2. A close relationship exists between world temperatures and precipitation. Therefore, the development of present‐day zonal, aridland vegetation and climate cannot be divorced from the history of the latest ice age.3. The combined geological and palaeobotanical evidence demonstrate that whilst the origin of modern openland and aridland vegetation went back to the time of the origin of angiosperms during the Cretaceous, its subsequent expansion went hand in hand with the lowering of world temperatures during the Palaeogene and Neogene, when a series of angiospermous families having dominantly herbaceous and openland taxa, as members, appeared successively in the stratigraphic record.4. The successive lowering of world temperatures had the overall effect of reducing precipitation levels all over the globe. Consequently, high rainfall areas, bearing closed forests, became progressively smaller and smaller and the decreased rainfall promoted the evolution and expansion of low biomass, openland and aridland vegetation.5. The break‐up of regional closed forests had started from the middle Miocene but the main expansion of zonal, aridland vegetation, in low and middle latitudes, appears to have taken place, together with the expansion of tundra vegetation, at high latitudes, from the late Pliocene. Glaciations of a magnitude of at least two‐thirds that of the late Pleistocene glacial maxima started to occur about that time, 25 Ma ago.6. The alternations between cold, glacial and warm, interglacial periods, during the late Neogene, especially with increased amplitude during the last 0.4 Ma, allowed less and less time for forest vegetation to expand and stabilize during the warm intervals, with the result that openland and aridland vegetation was able to expand to unprecedented levels.7. Further, as man increased fire frequencies during the late Pleistocene, the relatively fire‐sensitive and mesophytic taxa were selectively eliminated and more and more forests were opened to invasion by openland taxa in low and middle latitudes. Later on, with the clearance of forests for agriculture, the overall effect on vegetation was to create open landscapes which favoured the expansion of openland taxa at low, middle and high latitudes, during an interglacial, that is, the Holocene, a feature that is unprecedented in the entire earlier geological record.
DO INSECTS REALLY HAVE A HOMEOSTATIC HYPOTREHALOSAEMIC HORMONE?
Authors: Veenstra Jan A. 
Published: January 2008

SummarySince trehalose in insects, in contrast to glucose in mammals, does not enter the haemolymph directly from the digestive tract, but is all synthesized by the insect itself, and furthermore an increased trehalose synthesis during stress and flight does not lead to significant increases in haemolymph trehalose, there seems to be no physiological need for an insect homeostatic hypotrehalosaemic hormone. Experiments in which tissue extractions were found to lower haemolymph trehalose can not prove the existence of such a hormone, while all insect species which so far have been submitted to a trehalose‐tolerance test, decrease their haemolymph trehalose concentrations at a rate which can be accounted for by the metabolic use of trehalose. These results therefore indicate the absence, and not the presence, of a homeostatic hypotrehalosaemic hormone. This is also true for blowflies, from which an insulin‐like immunoreactive peptide has been isolated. It seems therefore unlikely that this insulin‐like peptide is a homeostatic hypotrehalosaemic hormone. The physiological mechanism by which this insulin‐like peptide would have to act to function as a hypotrehalosaemic hormone is also an unlikely one. It therefore seems justified to conclude that so far, homeostatic hypotrehalosaemic hormones have not been demonstrated in insects. Furthermore, it may well be that they do not exist.
FLUCTUATING ASYMMETRY: AN EPIGENETIC MEASURE OF STRESS
Authors: PARSONS P. A. 
Published: January 2008

Summary(1) Fluctuating asymmetry (FA) is a useful trait for monitoring stress in the laboratory and in natural environments.(2) Both genomic and environmental changes can increase FA which represents a deterioration in developmental homeostasis apparent in adult morphology. Genetic perturbations include intense directional selection and certain specific genes. Environmental perturbations include temperature extremes in particular, protein deprivation, audiogenic stress, and exposure to pollutants.(3) There is a negative association between FA and heterozygosity in a range of taxa especially fish, a result consistent with FA being a measure of fitness.(4) Scattered reports on non‐experimental populations are consistent with experiments under controlled laboratory conditions. FA tends to increase as habitats become ecologically marginal; this includes exposure to environmental toxicants.(5) In our own species, FA of an increasing range of traits has been related to both environmental and genomic stress.(6) Domestication increases FA of the strength of homologous long bones of vertebrate species due to a relaxation of natural selection.(7) FA levels are paralleled by the incidence of skeletal abnormalities in stressful environments.(8) Increased FA is a reflection of poorer developmental homeostasis at the molecular, chromosomal and epigenetic levels.
THE SINGER AND THE SONG: ON THE RECEIVING END OF BIRD SONG
Authors: McGREGOR PETER K. 
Published: January 2008

SummaryVariation in singing behaviour between males can involve fixed differences such as the song type composition of repertoires, as well as more flexible effects such as matched counter‐singing (Krebs & Kroodsma, 1980; Section III. 4), differences in bout length (the number of songs in a period of song) and changes in strophe length. Short‐term strophe length changes seem to be related to the willingness and ability of males to respond strongly to playback. Whether this is because strophe length indicates motivation or the degree of exhaustion of the neuromuscular song‐production system, or both, is currently unclear.
STUDY OF THE VERTICAL AUTOROTATION OF A SINGLEWINGED SAMARA
Authors: SETER D. , ROSEN A. 
Published: January 2008

Summary1. Autorotation of a single‐winged samara is a highly nonlinear phenomenon that represents a delicate equilibrium between gravity, inertia and aerodynamic effects. Therefore, in order to analyse this phenomenon, an accurate detailed model is necessary. Such a model has not been presented in the past. Recently the authors derived a detailed model which is briefly described in the paper.2. The aerodynamic contributions present the most complicated part of the phenomenon. These contributions are treated using the blade‐element/momentuin method, with certain improvements and additions. These improvements are necessary due to inherent differences between samara wings and other rotary wing systems (aircraft propellers, helicopter rotors, etc.).3. The cross‐sectional aerodynamics of the samara is characterized by relatively small Reynolds numbers, high angles of attack and rough surfaces. While these characteristics are different from other rotary wings, they are typical of the wing cross‐sections of insects and birds. Therefore the lift and drag coefficients, which are necessary for the analysis, are obtained using available data for insect and bird wings.4. The results of the theoretical model are compared with experimental results of tlvo kinds. The first kind includes results for a samara of an Acer platanoides that were reported in the literature. In addition, a special experimental model of a samiira was built and tested. This model offers a simple way of varying the configuration in order to study (experimentally) the effect of different geometric parameters on the autorotation.5. In the light of the uncertainty in the aerodynamic coefficients, it can be concluded that there is quite a good agreement between the theoretical and experimental results. Thus, after LTalidation, the theoretical model is used for a parametric study to find the influence of different parameters on the autorotation. The important results of this study are outlined below.6. The spanwise flolv component and the tangential component of the induced velocity have a very small influence and thus can be neglected.7. It is important to include in the analysis the effects of the axial induced velocity, the tip effect, and the drag of the root region.8. Since chordwise variations of the centre of pressure location, as a function of the angle of attack, were seen in the past (based on over simplified analyses) as the mechanism which is responsible for the samara stability, this effect is also added to the model. While the influence of this effect on the pitch angle is large and small on the sinking rate, it results in an increase in the deviation between the theoretical and experimental results.9. Autorotation is sensitive to the cross‐sectional aerodynamic coefficients. This sensitivity is critical since the available data on these coefficients is, to say the least, unsatisfactory and require significant improvement.
Life History AND BIOECONOMY OF THE House Mouse
Authors: BERRY R. J. , BRONSON F. H. 
Published: January 2008

Summary1. More is known about the western European house mouse, Mus (musculus) domesticus than any other non‐human mammal. If laboratory and field information is combined, an extremely valuable understanding of the species' bioeconomy could be obtained.2. The seven stages of mouse life‐history are surveyed (up to birth, nest life, sex life, social structure, population statics and stability, senescence, and death), and the interactions between the changing phenotype and the environment are described.3. These interactions can be used to build up a model of the opportunities and compromises which result in the fitness of individual mice. It is not yet possible to quantify such a model, but this should in principle be achievable.
CELLULAR BIOLOGY OF BONE RESORPTION
Authors: ZAIDI MONE , ALAM A. S. M. TOWHIDUL , SHANKAR VIJAI S. , BAX BRIDGET E. , BAX CHRISTOPHER M. R. , MOONGA BALJIT S. , BEVIS PETER J. R. , STEVENS CLIFFORD , BLAKE DAVID R. , PAZIANAS MICHAEL , HUANG CHRISTOPHER L. H. 
Published: January 2008

SummaryPast knowledge and the recent developments on the formation, activation and mode of action of osteoclasts, with particular reference to the regulation of each individual step, have been reviewed. The following conclusions of consensus have emerged.1. The resorption of bone is the result of successive steps that can be regulated individually.2. Osteoclast progenitors are formed in bone marrow. This is followed by their vascular dissemination and the generation of resting preosteoclasts and osteoclasts in bone.3. The exact pathways of differentiation of the osteoclast progenators to mature osteoclasts are debatable, but there is clear evidence that stromal cells support osteoclast generation.4. Osteoclasts are activated following contact with mineralized bone. This appears to be controlled by osteoblasts that expose mineral to osteoclasts and/or release a factor that activates these cells.5. Activated osteoclasts dissolve the bone mineral and digest the organic matter of bone by the action of agents secreted in the segregated microcompartments underlying their ruffled borders. The mineral is solubilized by protons generated from CO, by carbonic anhydrase and secreted by an ATP‐driven vacuolar H+‐K+‐ATPase located at the ruffled border. The organic matrix of the bone is removed by acid proteinases, particularly cysteine‐proteinases that are secreted together with other lysosomal enzymes in the acid environment of the resorption zone.6. Osteoclastic bone resorption is directly regulated by a polypeptide hormone, calcitonin (CT), and locally, by ionized calcium (Ca2+) generated as a result of osteoclastic bone resorption.7. There is new evidence that osteoclast activity may also be influenced by the endothelial cells via generation of products including PG, NO and endothelin.
THE EVOLUTION OF CONSCIOUSNESSWILLIAM JAMES'S UNRESOLVED PROBLEM
Authors: GLYNN IAN M. 
Published: January 2008

SummaryPart I of this article shows that, for different reasons, neither traditional interactionist dualism nor more modern theories of the mind/body relationship — including functional‐state identity theory — provide a satisfactory explanation of the evolution of consciousness. Interactionist dualism leaves us with a philosophical impasse; the more modern theories have not yet succeeded in providing adequate answers to the difficulties that were raised by William James in 1879.Part II of the article disputes Kripke's claim that identity theories are, anyway, untenable because the relevant identities would have to be necessary rather than contingent.