bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE ROLE OF THE NERVOUS SYSTEM IN SOME ACTIVITIES OF STARFISHES
Authors: SMITH J. E. 
Published: January 2008

Summary(i) The general disposition of the sensory, association (internuncial) and motor elements of the starfish arm as revealed by intra‐vitam staining is described and figured (Fig. i), and (2) the nature of the nervous arcs responsible for reflex activities is discussed. (3) It is pointed out that the nature of the activities of an organ and the degree of integration of groups of organs are conditioned by the form and properties of the neurones and tracts through which they are innervated. (4) The pedicellariae, papulae and spines which are situated on, or are part of the dorsal body wall of a starfish are innervated through a plexus which has peripheral qualities. (5) There is little evidence of anatomical differentiation within the peripheral plexus except for the presence of groups of transversely running tracts which may correspond to the through‐conduction tracts (vide infra (8)). (6) The properties of the peripheral plexus are those of a nerve net as defined by Pantin (1935a, c) and the movements of the pedicellariae are analysed in relation to these properties. (7) The net shows evidence of differential capacity for facilitation in its various parts, in particular (8), there are transverse through‐conduction tracts in the plexus which, when coupled with the lateral motor systems of neurones (E of Fig. i) are the means of innervating the papulae and muscles of the body wall. (9) The movements and postures of the tube feet are described. (10) Together with the capacity of the feet to be co‐ordinated throughout the entire animal they demonstrate the central nervous properties of the circumoral ring and radial cords through which they are innervated. (11) These central nervous properties derive from the presence of special centres of co‐ordination, from a marked polarity of conduction, and from a certain configuration of the motor neurones within the central nervous system and the tube feet. (12) An account is given of the probable location and functions of the nerve centres and of the disposition of the nerve tracts within the central nervous system. (13) A brief reference is made to the effects of peripheral excitation on the pattern of coordinated movement of the podia.
THE PRESENT STATUS OF THE GERM‐CELL PROBLEM IN VERTEBRATES
Authors: EVERETT N. B. 
Published: January 2008

Summary(i) Morphological studies relating to the origin and differentiation of the definitive germ cells in vertebrates have, as indicated, resulted in conflicting views. In many instances two or more competent investigators who have studied the same form have reached different conclusions. (2) Some contend that the germ cells are set aside from the soma during the early stages of embryonic development, and that these alone serve as the progenitors of the functional sex cells. (3) Others recognize an early differentiation of sex cells but hold that these are supplemented by others produced from the somatic epithelium of the gonad in late embryonic or post‐embryonic stages. (4) Another group recognizes the early differentiated cells as germ cells but contend that these all degenerate and that the definitive ones are formed from the germinal epithelium. These degenerating germ cells are believed by certain authors to be a phylogenetic recapitulation of the condition in lower forms. (5) Finally, yet another group contends that the so‐called primordial germ cells are not germ cells at all but are enlarged cells in some stage of mitosis or in some specific metabolic phase. This group believes that all germ cells are derived from the somatic cells of the germinal epithelium. (6) Experimental work supports the view that the primordial germ cells, which are recognized early, are the progenitors of the definitive sex cells. When these primordial germ cells are prevented from reaching the site of the developing gonad the individual fails to develop sex cells, although a sterile gonad and its associated structures may develop. (7) I suggest that the observed proliferation of germ cells from the germinal epithelium, reported by numerous investigators, can be interpreted in another way by a thorough study of the enlarged germ cells in relation to the epithelium. It seems probable that the cells of the epithelium, which form functional sex elements, are not and never were a part of the mesothelial covering, but are cells which were segregated early, and are merely stored in the epithelium.
THE PHYSIOLOGICAL SIGNIFICANCE OF INORGANIC LEVELS IN THE INTERNAL MEDIUM OF ANIMALS
Authors: CONWAY EDWARD J. 
Published: January 2008

Summary(i) Proceeding from a consideration of the non‐diffusible constituents of the cells, the sum of the electric charges thereon, the mean intracellular pH, and an optimum or maximum membrane potential, the inorganic levels of Na, K, H, HCO2 and CI can be interpreted as physiological requirements and HCO3 and CI concentrations in turn, assuming a necessary ventilation tension of CO2. (2) Omitting considerations of the membrane potential, or treating them as of secondary importance, the optimum pH value, and in turn the K and HCO3 concentrations, are theoretically deducible by an alternative method of wider implications. (3) Including the effects of contact with the solid bone salts the concentration of the inorganic phosphate ions and minimal values for Ca and Mg ionic concentrations may also be deduced.
ANTIGENS, ANTIBODIES AND GENES*
Authors: IRWIN M. R. 
Published: January 2008

SummaryThis article is a survey of a few pertinent findings about antigens as they occur in one species of bacteria, the pneumococcus, and in the cells and organs of mammals and birds. The main points of general biological interest emphasized are as follows: (1) The fact that carbohydrates, not proteins, are responsible for the specificity of the different types of pneumococci points the way to a comparable concept of specificity in organisms other than bacteria. That is, substances other than proteins, if linked to proteins, may account for some part of known specificities. (2) Changes within each type of pneumococcus may take place from a smooth, capsulated form to a rough, non‐capsulated form, and vice versa. Under certain conditions a rough form of one type may be changed to the smooth form of an entirely different type. The activating principle in one such change has been found to be a nucleic acid. (3) The antigens of the blood cells of man are gene‐determined. There are, however, antigens of the blood cells, tissues or organs of other species which have not yet been explained genetically. (4) It has been possible by immunological techniques to make a sharp distinction between the cells or sera of closely related species. Reagents prepared by absorbing the antisera to the cells or serum of one species by the corresponding antigens of the other were reactive with the homologous antigen, but not with that used in the absorption. From these results it may be deduced that each species possesses ‘species‐specific’ antigens in comparison with a related species, as well as those common to the two species. (5) In bird species which produce viable hybrids the antigens have been found to be gene‐controlled. (6) The cellular antigens are generally thought to be the more or less direct products of their causative genes. However, a few instances are known of cellular antigens which are the result of complementary action of genes. Also, within the group of genes which act directly on the respective antigens there appear to be some which singly are capable of effecting the same combination of antigens as two (or more) alleles may produce.
THE PHYSIOLOGICAL SIGNIFICANCE OF THE PHOSPHOMONOESTERASES
Authors: MOOG FLORENCE 
Published: January 2008

SummaryResearches of the past ten years bearing on the physiological significance of the common acid and alkaline phosphomonoesterases may be summarized in the following facts and concepts, (i) The alkaline phos‐phomonoesterase appears to be a salt‐soluble, the acid a water‐soluble, substance; both consist of a metallic coenzyme and a protein‐like carrier. Neither depends oh sulphydryl groups for activity, but the alkaline phosphatase seems to require amine and phenolic hydroxy! groups; it is affected only by strong oxidizing agents. There is not yet any incontestable evidence that alkaline phosphomonoesterases of different sources are not identical. (2) Phosphatases probably catalyse only hydrolyses, not syntheses. (3) The content of both phosphatases in the blood serum is characteristic of age and physiological state, and is used in the diagnosis of bone and liver disorders; biliary obstruction results in elevation of serum alkaline phosphatase probably because phosphatase is normally excreted by way of liver and gut, but other explanations are possible. Diet influences serum alkaline phosphatase level. (4) The study of phosphatase function has been advanced by the development of techniques for the histochemical demonstration of acid and alkaline phosphatases. (5) It is certain that alkaline phosphatase is indispensable in normal ossification; it is generally instrumental in abnormal calcifications, but in a few cases calcification occurs without it. (6) Glycolysis seems to accompany normal bone formation, but this fact does not clarify all the unsolved problems of ossification. (7) Hormones and vitamins influence both alkaline phosphatase activity and bone formation. (8) In kidney tubules alkaline phosphatase probably functions in dephosphorylating sugar molecules that are removed from the tubular fluid by phosphorylation. The enzyme is present at other sites where it might serve in a similar manner. (9) Phosphatases are commonly found in the cytoplasm of growing, regenerating, and secreting cells in which protein synthesis is being carried on; there appears to be a correlation in such cells between content of pentosenucleic acid and of phosphatase. In dividing nuclei, phosphatase parallels desoxyribonucleic acid. (10) Acid phosphatase is found in seminal fluid, and may help to nourish the sperm. (11) The occurrence of two common phosphomonoesterases with widely different pH optima may indicate a mechanism for allowing two dephosphorylating steps to go on simultaneously in a single cell. In tissues which carry on much traffic in glycogen, acid phosphatase is possibly provided to prevent bone formation. (12) The actual role which the phosphatases play in the physiology of the organism will be understood only with elucidation of the complete enzyme systems of which the phosphatases are a part.
LES AFFINITÉS DES GRAPTOLITHES
Authors: KOZLOWSKI PAR ROMAN 
Published: January 2008

RésuméL'article contient un exposé succinct de principaux faits qui plaident en faveur d'une parentéétroite entre Ies Graptolithes et les Ptérobranches. Un examen critique est tout d'abord fait des arguments sur lesquels s'appuyaient différents auteurs pour attribuer les Graptolithes soit aux Hydroídes, soít aux Bryozoaires. On conclut que ces opinions ne reposaient pas sur des fondements solides. A l'attribution des Graptolithes aux Hydroídes s'oppose leur symétrîe nettement bilatérale, la présence à l'intérieur de leurs thèques d'un stolon à parois chitineuses ainsi que leur faculté dépaissir leurs thèques à l'extérieur. L'hypothèse, soutenue par Ulrich et Ruedemann, de la parentéétroite entre les Graptolithes et les Bryozoaires est également écartée et les arguments mis en avant par ces auteurs à l'appui de leur thèse sont considerés comme non convaincants. La théorie de l'affinité entre les Graptolithes et les Ptérobranches, développée entre 1905 et 1910 par Schepotieff et qui n'a pas trouvé d'accueil bienveillant des specialistes, est reconnue comme étant juste dans son essence, malgré l'argumentation souvent erronée de cet auteur. Une interpretation nouvelle est donnée des similitudes entre les particularités de structure des constructions chitineuses dans ces deux groupes d'animaux, appuyée surtout sur des faits nouveaux mis en évidence par létude des Graptolithes du Tremadoc de Pologne. Les rhabdosomes des Graptolithes, surtout ceux de l'ordre des Dendroidea, sont construits essentiellement de la même façon que le sont les cæneciums de Cephalodiscus et surtout le tubarium de Rhabdopleura. Tous ils se composent d'un assemblage de petits segments chitineux ou fusellus. En outre le stolon des Graptolithes est, quant à sa structure et son rôle biologique, identique à celui de Rhabdopleura. Le mode de bourgeonnement des individus de la colonie de Rhabdopleura est le même que celui de la première thèque des Graptolithes. Si Ton considère que toutes ces similitudes concernent des caractères bien spéciaux, ne se retrouvant que chez les Graptolithes parmi les animaux fossiles et chez les Ptérobranches parmi les animaux actuels, on ne peut pas échapper à la conclusion de l'existence d'une étroite liaison génétique entre ces deux groupes d'animaux, dont l'un s'est éteint aux temps paléozoïques et l'autre, qui y était également représenté, s'est continué jusquà nos jours.
THE CLASSIFICATION OF FERNS
Authors: HOLTTUM R. E. 
Published: January 2008

SummaryIntensive morphological studies have been devoted to the more primitive ferns, which represent a small minority of living species, but too little is yet known about the vast majority of other ferns, with the result that recent attempts at a natural classification show considerable differences of treatment.The problem is complicated by convergent evolution in the characters of almost all parts of a fern plant. Not only similar soral form, but also similar frond form, types of venation, scales, etc. have been developed on different evolutionary lines.To illustrate the nature of the problem an attempt has been made to state the probable characters of a primitive leptosporangiate fern, and the kinds of ways in which existing ferns have developed from this condition. Evolutionary change in different parts of the plant has proceeded in different ways and to different degrees in the many genera of existing ferns. Primitive characters of one kind or another are shown by a great number of ferns, along with highly advanced characters of other kinds.Recent schemes of classification are briefly compared, and a summary is given of the author's own scheme, with notes on evolutionary trends in the various groups as he sees them.Much more information is needed on which to establish a really satisfactory scheme. The present one is put forward in the hope that others will take up the work. With modern facilities for travel, it is to be hoped that more botanists will come to the tropics and see ferns and other too‐little‐known plants in their native habitats. Morphological study needs to be undertaken with an understanding of the living plant and of its environment.
STRUCTURE and FUNCTION OF NEURONES IN RELATION TO MENTAL ACTIVITY
Authors: MONNÉ LUDWIK 
Published: January 2008

Summary1. The properties, structural, physiological and colloidal, of the cytoplasm of resting and stimulated neurones differ greatly. Jin this respect resting neurones are similar to mature unfertilized sea‐urchin eggs, which are in a depressed condition, and strongly stimulated neurones resemble fertilized sea‐urchin eggs, which are in a highly stimulated condition. The importance of this comparison for understanding the functioning of neurones is stressed.2. The ground substance of cytoplasm is a texture of fibrils. These fibrils consist of ribonucleic‐acid‐containing chromidia and ribonucleic‐acid‐free interchromidia, which regularly alternate with one another. The structure of cytoplasm is coarse when the fibrils are agglutinated together. The chromidia, which are intensely stainable with basic dyes, aggregate with each other simultaneously with the agglutination of the cytoplasmic fibrils. The structure of cytoplasm is fine when the fibrils are separated from each other and the chromidia are consequently dispersed.3. The structure of the cytoplasm coarsens rapidly when resting neurones of warm‐blooded animals are excised. This change does not occur when strongly stimulated neurones are excised. Coarse cytoplasmic structure and the aggregated condition of chromidia are correlated with decrease in the rate of respiration, narcosis, hibernation, sleep, and in general with inhibition of cellular activities. Fine cytoplasmic structure and the dispersed condition of chromidia are the characteristic features of chromatolysis, which occurs upon stimulation.4. Solidifying (clotting) and liquefying enzyme systems control the properties of cytoplasm. The former enzyme system is responsible for the coarsening of cytoplasmic structure and may be activated by narcotics. Stimulation and chromatolysis are brought about when the latter enzyme system is activated. It is probable that clotting enzymes are activated in case of concussion of the brain, and liquefying enzymes upon recovery.5. It is suggested that mental activities are depressed when the structure of the cytoplasm of neurones is coarse and that these activities are increased when this structure becomes fine.6. Synthesis of new specific proteins may be the mechanism underlying memory. The structural changes in cytoplasm associated with thinking are probably due to protein synthesis.
CONTRACTILE and PACEMAKER MECHANISMS OF THE HEART OF TUNICATES
Authors: KRIJGSMAN B. J. 
Published: January 2008

SUMMARYThe contractile mechanism of the tunicate heart is situated in the delicate single layer of muscle fibres of the heart wall. The subsequent contraction of these fibres produces a peristaltic wave passing along the tube‐shaped heart, resulting in a true circulation. The mechanism of refilling is not yet understood.The pacemaker system is of a diffuse nature. This basic automatism is controlled by two more powerful pacemakers, one at each end of the heart.The peripheral pacemakers are possibly myogenic, and stimulated to contract rhythmically. These local contractions release peristaltic waves. The cause of the rhythmic activity of the pacemakers may be a metabolite which stimulates their sensory mechanism. The active pacemaker adapts itself to this stimulus, which results in a temporary arrest after a period of activity.The fact that after such a pause the opposite pacemaker becomes active, thus causing regular reversal of pulsation, cannot be understood in terms of increasing back‐pressure. Periodic fatigue (adaptation) and subsequent restoration of the pacemakers offer a more plausible explanation of the phenomena.Very probably the tunicate heart does not possess extrinsic regulation.The tunicate heart is not very sensitive to ions or hypotonicity.There is evidence that the heart possesses a special conductive system.It has been pointed out that a number of features of the heart mechanism need further investigation.
ANTARCTIC AQUATIC ECOSYSTEMS AS HABITATS FOR PHYTOPLANKTON
Authors: PRIDDLE J. , HAWES I. , ELLIS‐EVANS J. C. , SMITH T. J. 
Published: January 2008

Summary1. The Southern Ocean is a large‐scale, relatively homogeneous upwelling ecosystem whose phytoplankton apparently grows suboptimally over much of its area. By contrast there is a wide variety of freshwater habitats in the Antarctic and in some of these phytoplankton growth efficiency is very high. The two habitats share similar temperature and irradiance regimes, but differ markedly in availability of inorganic nutrients, in grazing pressure and in the time‐ and space‐scales on which various physical processes act.2. Concentrations of inorganic nutrients in the marine ecosystem have been represented as being in excess of phytoplankton requirements, but the ionic composition of some nutrient pools may not conform to phytoplankton preferences.3. Nutrient‐limitation determines phytoplankton production in Antarctic lakes and gives rise to gross differences between lakes.4. Irradiance in the water column varies greatly over the year in both marine and freshwater ecosystems. Most algae are shade‐adapted, with the ability to utilize low irradiance but with sub‐optimal response to high irradiance. However, local phytoplankton maxima may attain very high carbon fixation and growth rates.5. Consistently low temperatures characterize both systems. Their effects on photo‐synthetic carbon uptake mirror shade‐adaptation. Division rates of marine phytoplankton may however be very much higher than predicted for ambient temperatures.6. Vertical mixing is important in both ecosystems and influences the environment experienced by phytoplankton cells. This appears to have little effect on the average performance of phytoplankton in the strongly mixed surface water column of the Southern Ocean, where the mixed depth may exceed 100 m. This can be related partly to the shade‐adapted photosynthetic response. Euphotic depths range from 20 to 100 m.7. Strong vertical mixing under ice‐free conditions in lakes may maximize photosynthetic efficiency, whilst distinct vertical stratification in permanently ice‐covered lakes gives rise to segregation of nutrient uptake and regeneration.8. Physical removal of phytoplankton biomass by grazing is locally important in the Southern Ocean, in contrast to the estimated mean mesoscale impact of grazing. Vertical sedimentation losses appear important in the context of mixing depth and generation time, and may be modified by vertical circulation of water.9. Loss of phytoplankton biomass from lakes during the ice‐free period is dominated by physical removal via the lake outflow. Grazing is generally unimportant, except where larvae of otherwise nektobenthic zooplankton hatch in synchrony with a phytoplankton maximum. Sedimentation is important under ice‐cover.
γ‐AMINOBUTYRIC ACID AND POSTGANGLIONIC SYMPATHETIC TRANSMISSION IN THE PULMONARY ARTERY OF THE RABBIT
Authors: STARKE K. , WEITZELL R. 
Published: January 2008

The effect of γ‐aminobutyric acid (GABA) on postganglionic sympathetic neurotransmission was studied in strips of the rabbit pulmonary artery. The strips were preincubated with 3H‐noradrenaline and then superfused with 3H‐amine‐free medium. They were stimulated either electrically at 2 Hz, or by 60 mM potassium, or by 1 μM tyramine.
GABA (1 – 1000 μM) did not change the basal outflow of tritium, but decreased the electrically evoked overflow as well as the contractile response. GABA 1 μM decreased the evoked overflow by 12%, and GABA 1000 μM, by 42%. The effect of GABA was not changed by yohimbine, propranolol, cocaine, corticosterone, or indomethacin. It was not antagonized by picrotoxin or bicuculline methiodide. GABA 100 μM also slightly reduced the potassium‐evoked overflow of tritium but did not change the tyramineevoked overflow.
The results show that, in the pulmonary artery of the rabbit, GABA inhibits the release of noradrenaline. Its effect is independent of α‐ and β‐adrenoreceptors and is not mediated by prostaglandins. The effect may be due to activation of presynaptic receptors which appear to differ from conventional GABA receptors inasmuch as they are insensitive to blockade by either picrotoxin or bicuculline.