bluuebunny/crossref_metadata_2025_split huggingface dataset:
The porous plates of coniform chloride cells in mayfly larvae: High-resolution analysis and demonstration of solute pathways
Authors: Komnick H. , Stockem W. 
Published: April 2021

ABSTRACT
The porous plates of coniform chloride cells in mayfly larvae were studied by electron microscopy using carbon replicas, whole-mount cuticles and thin sections. The cuticular skeleton of the porous plates is a local differentiation of the epicuticle forming a structure of extremely high organization. It is composed of cylindrical rods, which measure 20 ran in diameter, and are oriented perpendicular to the cuticular surface. They form an overlapping hexagonal pattern and are interconnected by double rows of transverse bars which are arranged in. a complicated but regular fashion. This spongy skeleton defines a continuous space system which may be characterized as composed of triangular pores, the sides of which measure 20 nm. The pores are arranged in a hexagonal pattern, and interconnected via slit-like communications. The porous plates are covered with a porous lamina which possesses 2·5-nm-wide pores in hexagonal arrangement.
Results obtained from negative staining, infiltration with colloidal lanthanum hydroxide and histochemical precipitation of sodium indicate that the porous system provides pathways for solutes across the cuticle.
The 3-dimensional architecture of the porous plates is reconstructed in a model that also includes morphogenetic aspects.
Pattern formation in the blue-green alga,Anabaena: I. basic mechanisms
Authors: Wilcox Michael , Mitchison G. J. , Smith R. J. 
Published: April 2021

ABSTRACTFilaments of Anabaena have a spaced pattern of differentiated cells called heterocysts, which is maintained as a filament grows by the regular determination of new heterocysts. By following the growth of every cell in a filament, we have identified proheterocysts (prospective heterocysts) at their earliest appearance, and described the sequence of events in the formation of the pattern. The determination of proheterocysts obeys 2 rules: (1) that there are inhibitory zones around pre-existing heterocysts, and (2) that only the smaller daughter of a division can become a heterocyst (all divisions are asymmetrical). There are, however, certain conditions in which these rules are over-ridden, where a pattern consisting of groups of consecutive proheterocysts is seen which resolves into a normal discrete pattern. This process is highly suggestive of interaction between developing cells. We have tested this hypothesis in normal growth conditions by breaking filaments near to early proheterocysts, on the assumption that this will cause a build-up of inhibitory effect of the cell upon itself. It is found that these cells regress, losing their differentiated character and dividing. We therefore propose an interactive model for pattern formation in Anabaena.
capsella embryogenesis: The central cell
Authors: Schulz Patricia , Jensen W. A. 
Published: April 2021

ABSTRACT
The central cell is the binucleate cell of the angiosperm megagametophyte which contains the polar nuclei and participates in double fertilization. The structure of the mature central cell, the fusion of the polar nuclei and the primary endosperm nucleus were studied with the electron microscope. The central cell cytoplasm appears very active and has an extensive ER, many mitochondria, dictyosomes, microbodies, polysomes, chloroplasts with well developed grana and starch and lipid reserves. A single, giant mitochondrion appears in the cytoplasm near the polar nuclei at the time of fertilization, but its origin, fate and function are not known. Cytoplasmic aggregates of dense, granular material are associated with the primary endosperm nucleus and structurally resemble the nucleolus and similar aggregates in the nucleoplasm. It is suggested that these cytoplasmic perinuclear bodies may represent extruded nucleolar material. The central cell cytoplasm does not undergo any notable structural reorganization as a result of fertilization. The relationship of the central cell to the other cells of the mature megagametophyte and its possible role in embryogenesis is discussed.
Prenucleolar bodies of Urechis oocytes
Authors: Das N. K. , Alfert M. 
Published: April 2021

ABSTRACT
The immature oocyte and unfertilized eggs of Urechis caupo, a marine echiuroid worm, contain many nuclear bodies and a main nucleolus. These bodies are similar to prenucleolar bodies of other materials with respect to their origin, structure, cytochemical and biochemical characteristics. They are formed in large numbers during the diffuse diplotene stage, perhaps by an aggregation of nucleolar materials which had been associated with chromosomes. They are fibrillar in structure, made up mainly of some nucleolar proteins, and are inactive in RNA synthesis. Biochemical analyses suggest the possibility that these structures contain a small amount of ribosomal RNA precursors which may have originated from the main nucleolus. An accumulation of prenucleolar bodies in Urechis oocytes may result from the lack of formation of multiple functional nucleoli, such as those found in amphibian oocytes.
Studies on contact inhibition of growth in the mouse fibroblast, 3t3: I. changes in cell size and composition during ‘unrestricted’ growth
Authors: Meisler A. I. 
Published: April 2021

ABSTRACT
Growth of the contact-inhibited 3T3 and its SV40-transformed derivative, 3T3T is unbalanced. Despite obvious exponential increase in cell number, cell volume, RNA and protein show a marked decrease with increasing population density in both cell types, greater in 3T3 than 3T3T. Daily medium change does not correct this growth pattern but merely seems to equalize initial growth rates of the 2 cell types and prolong the period during which the cell number continues to increase. The evidence suggests that the lag period that ensues following plating of the cells is a period of intense metabolic activity during which a large proportion of cellular protein and RNA is synthesized in preparation for exponential growth.
Studies on contact inhibition of growth in the mouse fibroblast, 3t3: II. effects of amino acid deprivation and serum on growth rate
Authors: Meisler A. I. 
Published: April 2021

ABSTRACT
The effect of amino acid concentration on the initial growth rate of the contact-inhibited mouse fibroblasts 3T3 and its SV40-transformed derivative 3T3T has been studied. In medium in which the serum had been passed through a Sephadex column, and the concentration of amino acids lowered 1000-fold, one acid at a time, the growth rate constants were computed. For most of the 16 amino acids studied, the initial growth rate of 3T3 decreased more profoundly than that of 3T3T. The presence in serum of a factor which stimulates amino acid uptake and growth rate of 3T3T is described.
The localization of trypsin in cultured mammalian cells
Authors: Hodges Gisele M. , Livingston D. C. , Franks L. M. 
Published: April 2021

ABSTRACT
The localization of trypsin in HeLa and CBM 17 baby mouse kidney cells was studied using fluorescent and electron-microscope autoradiographical techniques. Intracellular uptake of trypsin, as well as cell surface localization, was demonstrated by the use of direct FITC- and tritium acetylated-labelled trypsin and immunoreactive procedures. Intracellular penetration of the enzyme was temperature dependent and while evident at 37 and 25 °C was negligible at 4 °C. Higher proteolytic activity could be demonstrated in the supernatants from disrupted trypsin-treated cells than in supernatants from disrupted PBS-treated cultures. Treatment of trypsin with serum, whilst depressing enzyme protease activity, did not modify intracellular uptake of the enzyme and intracellular localization of trypsin persisted in cultured cells for up to about 48 h. The results, while not accounting for the primary event in cell alteration following exposure to trypsin, clearly suggest that consideration must be given to the fact that intracellular penetration of the enzyme may affect certain intrinsic processes of the cell.
The effects of fasting and feeding on the protein synthesis rate and polyribosomal profile of frog pepsinogenic cells
Authors: Van Venrooij W. J. , Poort C. , Geuze J. J. 
Published: April 2021

ABSTRACT
1. The rate of [14C]leucine incorporation into the protein of frog pepsinogenic cells was measured in both fasted and fed animals. The incorporation rate increases after feeding, becoming maximal after 2 h. 2. In the oesophagi of fasted frogs, only monoribosomes and dimers are present. The absence of polyribosomes is not due to autolysis in the homogenate. After feeding, heavy polyribosomal aggregates appear. 3. It is concluded that feeding stimulates protein synthesis in frog pepsinogenic cells.
Dissecting the PRSS37 interactome and potential mechanisms leading to ADAM3 loss in PRSS37-null sperm
Authors: Xiong Wenfeng , Shen Chunling , Li Chaojie , Zhang Xiaohong , Ge Haoyang , Tang Lingyun , Shen Yan , Lu Shunyuan , Zhang Hongxin , Han Mi , Zhang Aijun , Wang Jinjin , Wu Youbing , Fei Jian , Wang Zhugang 
Published: April 2021

ABSTRACT
A disintegrin and metalloproteinase 3 (ADAM3) is a sperm membrane protein critical for sperm migration from the uterus into the oviduct and sperm-egg binding in mice. Disruption of PRSS37 results in male infertility concurrent with the absence of mature ADAM3 from cauda epididymal sperm. However, how PRSS37 modulates ADAM3 maturation remains largely unclear. Here, we determine the PRSS37 interactome by GFP immunoprecipitation coupled with mass spectrometry in PRSS37-EGFP knock-in mice. Three molecular chaperones (CLGN, CALR3 and PDILT) and three ADAM proteins (ADAM2, ADAM6B and ADAM4) were identified to be interacting with PRSS37. Coincidently, five of them (except ADAM4) have been reported to interact with ADAM3 precursor and regulate its maturation. We further demonstrated that PRSS37 also interacts directly with ADAM3 precursor and its deficiency impedes the association between PDILT and ADAM3. This could contribute to improper translocation of ADAM3 to the germ cell surface, leading to ADAM3 loss in PRSS37-null mature sperm. The understanding of the maturation mechanisms of pivotal sperm plasma membrane proteins will pave the way toward novel strategies for contraception and the treatment of unexplained male infertility.
On the Physiology of Amoeboid Movement
Authors: Pantin C. F. A. 
Published: April 2021

ABSTRACTIt was shown in the first paper of this series 15 that amoeboid activity was affected by certain changes in the conditions of the medium in the same way as certain other forms of contractility. This suggested that some fundamental mechanism of contractility was similar in all these cases.Like the majority of biological processes, contractility is affected in a characteristic manner by temperature, and if there really is a fundamental similarity between amoeboid and other forms of contractility, the effect of temperature should be similar in both cases.
Skin Grafts in the Lizard, Anolis Carolinensis, Cuv
Authors: May Raoul M. 
Published: April 2021

ABSTRACT
Autotransplants of pigmented (melanophore-bearing) skin on a white region, and of white skin on a pigmented region both exhibit a strict specificity. There is no migration of the melanophores in any case of transplantation. Transplants of pigmented skin lose their colour-changing power immediately on being completely disconnected from neighbouring tissues, and regain it slowly as nerves regenerate. The melanophores are supplied largely by nerves which reach them directly through the underlying tissues. If these nerves are cut from a given area of skin, without separating the area from the surrounding skin, it at first loses the power of colour change, but the neighbouring integument appears able, after a delay of a few days, to control the denervated area. Areas of melanophore-bearing skin, isolated by incision from surrounding skin, but with their subcutaneous connections intact, can act normally with the rest of the animal in the colour-changes. Adrenalin, in producing the green state in pigmented grafts which have regained the colour-changing function, acts as it does upon normal integument. The action is indirectly through the sympathetic nervous system, and not directly upon the melanophores. Homoiotransplants, either pigmented or white, are absorbed. The absorption occurs after the grafts have well healed in place. The scutes disappear, leaving the area covered by thin scaleless integument. New scutes regenerate wherever there are areas barren of them. Scute regeneration progresses centripetally, suggesting some formative influence exerted by the surrounding normal integument.
The Permeability and Haemolytic Action of the Fatty Acids and Some of their Halogen Derivatives
Authors: Bodansky M. 
Published: April 2021

ABSTRACT
A critical discussion of the methods of studying the permeability of erythrocytes is contained in a recent review by Jacobs (1). In this review the procedures based upon the osmotic volume changes are considered and the unique advantages of the haemolysis method are pointed out in particular. By this method, the behaviour of enormous numbers of cells is made easily visible to the naked eye, through mere changes in the turbidity of the cell suspension. This procedure may therefore be employed as a gross statistical method. Appropriate modifications and improvements in the technique, depending on the nature of the problem, make possible fairly quantitative results. A second advantage of the method is its great delicacy. A third is that by means of certain refinements (2) it may be adapted to experiments whose total duration is only a few seconds.
The Vapour Pressure of the Blood of the Edible Snail
Authors: Kamada Takeo 
Published: April 2021

ABSTRACTIt is an interesting fact that the water content of the edible snail, Helix pomatia, varies with the physiological condition of the animal. Duval (1930) showed that the osmotic pressure of the blood varied from Δ = − 0·37° to ‒ 0·43° in hibernating animals, and from — 0-30° to — 0-40° in active summer animals. Cardot and Troussier (1929) found that the blood volume was considerably greater in active than in hibernating animals, and Brand (1931) showed the same to be true of the water content of the whole body. In the present paper, the observations of Duval (1930) on the osmotic pressure of the blood are repeated, using the very accurate thermo-electric method described by A. V. Hill (1930 a).
The Energy Sources in Ontogenesis
Authors: Needham Joseph 
Published: April 2021

ABSTRACTThe study of the respiratory quotient during embryonic development is of particular interest and importance in view of the body of evidence which has accumulated indicating that the characteristic source of energy changes with time as animal embryos develop from fertilised egg cell to mobile self-supporting organism. This evidence (brought together by Needham (24)) points to an association of carbohydrate catabolism with the earliest stages of development, and to a later appearance of protein and fat catabolism successively. The respiratory quotients which have been obtained in the past on embryonic material form, indeed, a part of this evidence, but a discussion of them will be deferred until the experimental data of the present communication have been dealt with. Up to the present no respiratory measurements of any kind have been made on crustacean embryos, although many of them appear to offer an extremely attractive material to the general physiologist. The eggs of many decapod Crustacea are carried by the females for the whole of their incubation period, and it is therefore only necessary to collect a sufficient number of individual adults, in order to obtain masses of eggs in all developmental stages; and these masses, moreover, will be quite uniform embryologically, since the eggs in them were all fertilised at the same time.
Studies in Animal Locomotion
Authors: Gray J. 
Published: April 2021

ABSTRACT
When a body is moving in water it encounters a resistance in the direction of its motion, and consequently the body must be supplied with energy if motion is to occur at a uniform speed. A study of the mechanism of propulsion of a fish falls therefore into two parts, (1) a study of the forces resisting motion through the water, and (2) a study of the mechanism whereby the fish utilises the energy liberated by its muscles for overcoming the forces of resistance. To some extent these two aspects of the problem are interdependent and involve considerable hydrodynamical difficulties, but in the present paper an attempt will be made to show that the movements of a fish’s body1 are such as to generate forces capable of opposing the forces of resistance whatever be the nature or magnitude of the latter. The problem was attacked two centuries ago by Borelli and by Pettigrew in 1873 since then comparatively little attention has been devoted to the subject except by Breder (1926), whose results will be considered later.
On the Cephalopod Phosphagen
Authors: Baldwin Ernest 
Published: April 2021

ABSTRACT
Cephalopod tissues contain a hitherto undescribed phosphagen compound. The rate of acid hydrolysis is comparable with those of creatine and arginine phosphates, but is minimal in N/10 acid, while the retardation produced by the molybdate ion is only about 3 − 4 times. The finding of a new compound in the Cephalopoda, the Lamellibranchiata being already known to contain arginine phosphate, is possibly of evolutionary significance.
Is Cleavage Rate a Function of the Cytoplasm or of the Nucleus?
Authors: Moore A. R. 
Published: April 2021

ABSTRACT
There are two views of the relative roles which the nucleus and the cytoplasm play in forming the embryo. One view is the working hypothesis of the geneticist according to which the cytoplasm of the fertilised egg is a passive and plastic substrate on which the chromosomes of the nucleus work to mould the form of the new being. In its extreme form this hypothesis ignores the facts of segregation and localisation of formative substances in the egg. The other view holds that the cyto-plasm is characteristic of the species and therefore determines the general form and pattern of the embryo, that in the early stages of development the cytoplasm is supreme in this respect, and only later do the chromosomes induce superficial modifications in the developing individual.
The Temperature and Humidity Relations of the Cockroach (Blatta Orientalis)
Authors: Gunn D. L. 
Published: April 2021

ABSTRACTIn a series of studies, of which this is the first, I propose to bring experimental methods to bear upon the relation between a convenient insect—Blatta orientalis— and some of the physical factors in the environment—namely temperature and humidity. The cockroach is very susceptible to desiccation (Zabinski, 1929; Gunn, 1931), and this paper is concerned with the relation between the speed of desiccation and the dryness of the air1 at various temperatures.
Control of the Foetal Circulation
Authors: Mott J. C. 
Published: April 2021

ABSTRACT
Foetal cardiac output is high, and the heart has not been shown to have the sustained reserves demonstrated in the adult heart. About 40% (∼ 200 ml. kg body weight−1. min−1) of the combined output of both ventricles (CVO) in unanaesthetized foetal lambs in late gestation is directed to the umbilical circulation. At least one-half of the systemic flow (∼ 300 ml. kg body weight−1. min−1) goes to skin and carcass. About 50 % of the remainder (10% CVO) is shared by brain, heart and kidney and the rest by other viscera; less than 6% CVO perfuses the lungs. Hypoxaemia, acidaemia and various vasomotor agents influence the partition of cardiac output between systemic and umbilical circulations, with or without relatively small changes of blood pressure, which is low by adult standards. In general, the conductance of systemic circuits is more susceptible to change than that of the umbilical. Both cerebral and myocardial blood flow increase several-fold during hypoxaemia. The additional volume flow of blood demanded by such vasodilatation in organs forming a relatively small proportion of body weight is more than accounted for by concurrent vasoconstriction in muscle (which contributes a substantial fraction of body weight) and other tissues. Both humoral and reflex neural mechanisms are involved in these adjustments.
The Control of Respiration and Circulation in Fish During Exercise and Hypoxia
Authors: Randall David 
Published: April 2021

ABSTRACT
Gas exchange across fish gills is reviewed and the respiratory and cardio-vascular changes associated with exercise and hypoxia described.
Heart rate is controlled by inhibitory vagal cholinergic activity which increases during hypoxia and decreases during exercise. Stimulation of receptors on the first gill arch during hypoxia initiates bradycardia. The increase in stroke volume during hypoxia in dogfish appears to be related to cardiac slowing rather than β-adrenergic stimulation of the heart.
Stimulation of cardiac β-adrenergic receptors causes positive inotropic and chronotopic responses in many fish, whether these are operative during exercise and hypoxia is not clear.
Gill water flow is inversely related to arterial oxygen content in resting fish and there is probably an arterial oxygen content receptor coupled to gill ventilation. Little is known of the control of breathing during exercise, the switch from rhythmic to ram ventilation at high water velocities may be initiated by mechanoreceptors on the gill surface.
Respiratory Gas Exchange at Lungs, Gills and Tissues: Mechanisms and Adjustments
Authors: Piiper Johannes 
Published: April 2021

ABSTRACT
A general model for external gas exchange organs of vertebrates is presented, in which the main parameters are the ventilatory, diffusive and perfusive conductances for O2 and CO2. The relevant properties of the exemal medium (air or water) and of the internal medium (blood) are analysed in terms of capacitance coefficients (effective solubilities) for O2 and CO2. The models for the main types of gas exchange organs (fish gills, amphibian skin, and avian and mammalian lungs) are compared in terms of their intrinsic gas exchange efficacy. The adjustments to increased metabolic rate or to hypoxia are achieved by increasing the conductances. The gas exchange at tissue level is analysed using the Krogh cylinder and a simplified model containing a diffusive and a perfusive conductance. The adjustments to increased load (exercise, hypoxia) consist in both increased local blood flow and in improvement of diffusion conditions (enlargement and recruitment of capillaries). Some particular features of respiration in transitional (unsteady) states, such as occurring at the beginning of exercise and of hypoxia, are examined. The additional physical variables are the O2 (and CO2) stores acting according to their capacitances and partial pressure changes. Delayed increase in O2 uptake at the beginning of exercise is due to the limited speed of physiological adjustments. The ensuing O2 debt is energetically covered by anoxidative energy releasing processes (hydrolysis of high-energy phosphates and anaerobic glycolysis). Finally, the reduction of metabolic rate as adjustment to hypoxia is discussed.