bluuebunny/crossref_metadata_2025_split huggingface dataset:
LACTATION
Authors: FOLLEY S. J. 
Published: January 2008

Summary1. In most species oestrogens mainly stimulate mammary duct growth. In the guinea‐pig and goat they promote complete alveolar development. The mouse is the only animal in which treatment with progesterone has been found to promote mammary duct growth. In other species simultaneous treatment with oestrogens and progesterone is necessary for complete alveolar development. It is difficult to say whether or not oestrogens per se can promote alveolar development, because the adrenal cortex produces progesterone.2. Androgens cause duct and alveolar growth in some species.3. Some now believe that, under the influence of oestrogen, the anterior pituitary produces a “mammogenic” hormone which promotes mammary duct growth.4. The presence of the anterior pituitary is essential for the initiation and maintenance of lactation. The anterior lobe is believed to secrete a specific lactogenic hormone (prolactin), but other anterior lobe hormones probably participate in the control of normal lactation.5. Oestrogens may inhibit lactation during pregnancy, but it is probable that the pregnant uterus is also concerned in the inhibition.6. The adrenal‐cortical hormone is necessary for lactation, since adrenal‐ectomized animals do not lactate, and, further, prolactin will not initiate or maintain lactation in hypophysectomized animals unless corticosterone or adrenotrophic hormone is also given.7. The thyroid gland is essential for normal lactation: thyroxine stimulates nilk secretion in the cow.8. Posterior pituitary extracts cause emptying of the bovine udder but do not affect the formation of milk.9. Oestrogen treatment enriches milk in fatty and non‐fatty solids, and so does thyroxine treatment. Repeated injections of certain prolactin extracts increase the fat content of Cow's milk; certain other prolactin preparations increase the lactose content.10. No true secretory nerves innervate the mammary gland. Lactation is disturbed in the cat if the sympathetic chains are extirpated.11. The extraction of milk from the bovine udder depends on the reflex erection of udder tissues caused by stimulation of the teat, which also appears to cause the release of a lactogenic hormone or hormones from the hypophysis.12. The mammary gland synthesizes lactose from blood glucose and also, probably, lactic acid. It is also possible that blood amino acids are de‐aminated by the mammary gland and used for lactose synthesis.13. The precursor of milk fat is the neutral fat of the blood. The mammary gland probably oxidizes long‐chained fatty acids to the short‐chained acids of milk fat.14. It is improbable that milk protein arises from blood amino acids. Plasma proteins are probably utilized for the synthesis of caseinogen, the phosphorus coming from the blood inorganic phosphate.15. Various enzymes have been detected in active mammary tissue, which is a particularly rich source of the alkaline phosphomonoesterase. Changes in the secretory function of the mammary gland are usually accompanied by striking changes in the phosphomonoesterase content of milk.
THE DEVELOPMENT OF THE AUTONOMIC NERVOUS SYSTEM
Authors: YNTEMA CHESTER L. , HAMMOND WARNER S. 
Published: January 2008

SummaryEarly workers have found that the peripheral sympathetic neurons arise from mesoderm, neural crest, or neural tube. In recent years various studies on normal embryos have supported each of these contradictory views. Experimental studies have yielded results which indicate an origin from the neural crest or neural tube. We feel that a neural crest origin is most probable in the light of present information.Experimental observations on the chromaffin cells of the suprarenal gland and the abdominal aortic bodies show that these cells have an origin in common with the sympathetic rudiments.The ciliary ganglion, one of the parasympathetic group, can arise independently of the semilunar ganglion. Some evidence indicates an origin for the ciliary ganglion from the neural tube, although most studies on normal embryos indicate at least a partial origin from the semilunar ganglion. Understanding of the sources of the other cranial autonomic ganglia has not been advanced in recent years.Enteric and other visceral ganglia may arise from one or more rudiments. Recent reports indicate as sources: (1) neural crest of the trunk, (2) neural crest or tube from levels of the parasympathetic nuclei in the brain stem and sacral level of the spinal cord. In addition, local differentiation from mesoderm and endoderm has been reported.Observations upon dependent differentiation of the autonomic nerves and ganglia have been made. A formative action of preganglionic fibres upon differentiation of autonomic ganglia has been suggested. Sympathetic ganglia, however, form in the absence of these fibres. The late differentiation of the ciliary ganglion depends upon the condition of its field of distribution.The following stages in the development of the sympathetic ganglia are suggested: (1) formation of the neural crest, (2) migration of crest cells, (3) differentiation of neuroblasts, (4) their incorporation into ganglia. It is presumed for this analysis that the neuroblasts arise from cells of the neural crest. At present methods of analysis are available which could serve to solve some of the problems indicate
AERIAL PLANKTON AND ITS CONDITIONS OF LIFE
Authors: GISLÉN TORSTEN 
Published: January 2008

Summary1. Among animals which can be transported by air currents three main types have been distinguished: (a) large forms, from a length of roughly one decimetre down to a few millimetres; (b) small forms varying between some millimetres and about 1/10 mm.; (c) animals of a microsize, smaller than 1/10; mm.2. Large organisms are usually distributed by wind in typhoon and hurricane areas alone. During the Glacial Period, however, cyclonic disturbances proceeded along other routes, in this way creating distributional paths which are now no longer in use.3. Small organisms have considerable possibilities of distribution by convection air currents and winds at moderate altitudes. Examples are given of such distribution over great distances. But as the animals are often strictly specialized ecologically (herbivores, parasites, etc.) they have particular difficulties to overcome in their new surroundings.4. Numbers of micro‐organisms are constantly being driven up into the air to return again to earth in rain showers or downward air currents.5. Micro‐organisms are very resistant to unfavourable factors met with in the air‐sea. Some may be distributed through the air in an anabiotic stage. Being often hermaphrodite or parthenogenetic, many of them can give rise to progeny from a single individual which happens to arrive in suitable surroundings. Their resistance to low temperature, low barometric pressure and drought is superior to that of all other organisms. Nevertheless, in comparison to larger forms, they are very sensitive to radiations, especially ultra‐violet, which seem to check their distribution more than that of larger forms.6. The explanation of the fact that the microforms do not flourish everywhere is found in their very strict biotopical specialization. But wherever a biotope suitable for a certain micro‐organism exists, that organism will appear there as soon as sufficient time has elapsed to allow it to be transported through the air and to settle in the locality. The numbers which arrive are a factor in the survival and establishment of the invading species.7. No geographical borders or barriers exist for microforms. They are often cosmopolitan, or else regionally distributed around the whole globe in certain climatic belts.8. Under favourable conditions, especially in humid air, the harmful influence of radiation is diminished, and microforms may be transported alive by winds over greater distances than in clear and dry weather.
THE OSTEOCLAST
Authors: HANCOX N. M. 
Published: January 2008

SummaryOsteoclasts, Kölliker's universal agent of bone destruction, must still be regarded as enigmatical structures. It is likely that their life span is limited to a few days. Regarded by some as resulting from fusion of relatively immobile individuals of connective tissue type, and by others of mobile cells such as macrophages, it seems a possibility that they may form from any cell, indifferently, which has assumed the ‘histiocytic state’. Osteoclasts resemble histiocytes in their reaction to supravital neutral red, in their brisk motility and in the differentiation of a superficial ecto‐plasmic layer into an ‘undulating membrane’ in tissue culture. There is no direct evidence that osteoclasts erode bone, but their constant occurrence in zones where absorption is taking place, together with the associated histological picture and especially their striated border, suggest that their presence is more than incidental. A linear orientation of cytoplasmic ultramicrons may be reflected in the striated border, which may thus constitute a cytoplasmic zone adapted for the transfer of material into or out from the cell. There is practically no evidence upon which to base an explanation of how osteoclasts could erode bone. The cells form in response to such a wide variety of normal and experimental stimuli that at least in part a local action on the bone seems likely. Local humoral factors, emanating from the bone, may be responsible for the determination of osteoclasts, and the formation of giant cells under the influence of injected phthioic acid seems to provide a valid analogy. It may be that the factors reside in the ground substance. The process of osteoclastic absorption does not appear to be regulated by the nervous system. Further experiments should be undertaken to test the ability of osteoclasts to erode bone and to ascertain whether bone about to be absorbed differs constitutionally from normal bone.
MUSCLE ACTIVITY and MUSCLE PROTEINS
Authors: DUBUISSON M. 
Published: January 2008

Summary1. If it were experimentally possible to examine muscle extracts made during defined phases of the contraction cycle, the relation of muscular work to changes in the composition of such extracts might then be elucidated. The changes of normal muscle proteins in relation to muscular function, could then be considered from a truly physiological point of view.2. Such a study is possible: the technique for making extracts (a) from resting and relaxed muscle, (6) from fatigued muscle, and (c) from contracted muscle, are described. Reasons are given for preferring certain extracting agents. Advantages of the electrophoretic method of analysis are discussed.3. Proteins extractable at μ≪ 0–15 can be assumed to be in solution in the muscle cell. Fatigue and contraction do not modify their qualitative or quantitative distribution in the extracts.4. Proteins appearing in an extract of an ionic strength > 0–15 ≪ 0.5 must be assumed to be fixed in the cell as insoluble complexes; they can be released by strong salt solutions, which break down certain linkages. To this group belong actomyosin, β1 bT2 and γ myosins obtained from normal resting muscle.5. The qualitative and quantitative composition of extracts at μ 0–35‐0‐50 depends on the functional state of the muscle, which influences the protein linkages. Thus, during all kinds of contraction (maximal contraction) or contracture (contracture by monoiodoacetate, strychnine or rigor mortis), β1 and β2 myosins become inextractible, while a new protein, contractin, appears.6. These results are discussed. It appears that the contractile mechanism is characterized by the formation and dissociation of protein complexes whose constituents are numerous and mostly unidentified, practically nothing is known as to the nature of their linkage forces.7. This review deals with an early stage in the physiological study of muscle proteins: the problem is to determine which of the proteins really belong to the structures which take part in muscular contraction and relaxation–by the use of methods which test the strength of the bonds holding these proteins in position. The use of extracting agents of various ionic composition, which may act selectively on these bonds, may be expected in the future to yield important additional information.
THE SPIRAL STRUCTURE OF CHROMOSOMES
Authors: MANTON I. 
Published: January 2008

Summary. i. Sufficient examples of spiral structure of chromosomes are now known from dicotyledons, monocotyledons, pteridophytes and perhaps gymnosperms, together with some animals, to show that the phenomenon is a fundamental one in the plant and animal kingdoms, at least in the higher groups.2. Various methods found to be effective for revealing the spiral are listed, though the spiral itself cannot be an artifact.3. Since 1939, new observations have been made on the following principal topics: (a) chromonema length; (b) direction of coiling, especially in a somatic chromosome; (c) prophase development leading to generalizations about ‘gyre elimination’ as a normal part of the spiralization cycle; (d) geometrical form of the spiral.4. Unification of terminology is recommended by general adoption of the terms plectonemic and par anemic to describe the geometrical form of the spiral. The term ‘standard coil’ is recommended to replace ‘minor spiral’ for contrasting the major spiral with those of other types of division.5. The need is stressed for further evidence on the minor spiral in the strict sense.6. The importance of the interpretation of the ‘telophase split’ and of the origin of relational coiling for an understanding of the functional importance of the whole phenomenon of spiral structure is stressed. The suggestion made in earlier publications is repeated that the functional significance of the spiral might be that of co‐ordinating the component strands of a chromosome so that these may act in a unified manner when outside the resting nucleus.
MALFORMATIONS EMBRYONNAIRES D'ORIGINE CARENTIELLE
Authors: GIROUD Par ANTOINE 
Published: January 2008

SummaryThe early development of an organism is a critical stage which many factors may influence unfavourably. Maternal nutritional deficiencies, especially vitamin deficiencies, can disturb the development and bring about the most diverse malformations, affecting the nervous system, eye, vascular system, kidneys, limbs, etc. The teratological effects of deficiencies in vitamin A, vitamin B2, pantothenic acid and folic acid are firmly established.Deficiencies not only produce malformations in the embryo. They may merely retard development, but they can also cause various lesions, and among others lesions which are analogous to those brought about in the adult by nutritional deficiencies.The gravity of the result of deficiencies varies greatly. It may be negligible or it may end in the death of the embryo or sterility of the mother. The effect is a function of the intensity of the deficiency, as shown by chemical estimations of the vitamin in question.A slight deficiency may produce a malformation. It may therefore occur readily, the more so as it may result from various causes, such as an insufficient exogenous or endogenous supply, a disequilibrium of the ration, imperfect utilization, etc.Deficiencies act on the embryo as on the adult, by a disturbance of metabolism, for it is known that many vitamins are essential constituents of enzymatic systems. The results of the deficiencies depend upon the tissues or cells with which these systems are specially concerned. At an early stage such metabolic disturbances may affect organizers and so cause anomalies in development, that is, deformities.Here, as elsewhere, genetical factors may intervene in restraining or facilitating the effect of a deficiency.It is probable that these phenomena, observed in several types of birds and mammals, are of general occurrence, to be found also in man and in domestic animals.From the practical point of view it follows that maternal nutrition should be closely supervised.
BIOLOGICAL ASPECTS OF SENESCENCE
Authors: COMFORT ALEX 
Published: January 2008

Summary1. Senescence is treated as a generic term for the processes in certain organisms which lead to a decreasing power of homoeostasis with increasing age.2. The presence of these processes in a species can be inferred from life‐tables prepared and interpreted with suitable precautions. It cannot be inferred from the desultory examination of anatomical changes in species of unknown life cycle. Secondary criteria of senescence, e.g. decline of reproductive capacity are of value in judging the degree of age change in individuals of well‐studied species.3. Decreasing homoeostasis with increasing age is known to arise from different causes in different phyla. No single general or ‘inherent’ process can be invoked to explain all types of senescence.4. Senescence occurs only rarely in the wild state, and except in large or social animals regularly occurring senescence is a feature of domestication.5. Susceptibility to senescence is apparently not universal in Metazoa, and may not be so in vertebrates. Probable exceptions to its occurrence are among forms where somatic cells are continually replaced, where there is no limiting size, or where virtual attainment of a limiting size is accompanied by a persisting capacity for growth.6. The ‘senescence’ of asexually reproducing protozoan stocks is not a phenomenon directly analogous to metazoan senescence.7. The specific age of invertebrates and of mammals can be modified by factors modifying the rate of development. The evidence in mammals indicates that senescence results from the attainment of a developmental stage, or from the exhaustion of developmental ‘programme’ not from the cessation of growth per se.8. The specific age varies widely between inbred stocks. Longevity is most readily produced by heterosis, and is probably a correlate of heterozygosity.9. The role of postponed lethal genetic effects, and of the reduction of the selection value of the individual with increasing age, in the evolution of senescence is discussed.The materials for this article were collected during the tenure of a personal grant from the Nuffield Foundation for study and research on the biology of senescence. I am also very grateful to many colleagues who have furnished me with facts and criticisms, without bearing any responsibility for the uses to which I have put them, and to Miss Rosemary Birbeck, for her work in preparing the manuscript.
THE TRANSPORT OF CALCIUM and OTHER CATIONS IN SUBMERGED AQUATIC PLANTS
Authors: LOWENHAUPT BENJAMIN 
Published: January 2008

SUMMARYPhotosynthetic bicarbonate assimilation and cation transport by aquatic plants are reviewed. It is suggested that these two processes stand in a causal relation to one another. A number of observations of cation transport not directly associated with photosynthesis are also reviewed, and are related to current concepts of active transport in the plant kingdom.These characteristics of cation transport have been observed in many submerged aquatic plants:

Cations are transported through the leaves in the light but not in the dark.
Cations are accumulated at the abaxial leaf surface from the contiguous external medium and are excreted from the adaxial surface into the medium. Therefore accumulation and excretion can be studied separately.

A new theory of cation transport in bicarbonate‐assimilating aquatic plants is presented. The theory entails the following propositions:

Two active membranes pump cations through the leaf in the light. The membrane on the abaxial leaf surface pumps cations into the leaf; that on the adaxial surface pumps cations out of the leaf.
The cell plasma membranes on the abaxial and adaxial leaf surfaces form these two active membranes.
In the light–i.e. when the transport mechanism is functioning–the biochemical reactions of transport reach steady‐state levels. These levels are determined by the rates of reaction between the constituents. One can therefore alter the steady‐state levels by suitably altering the conditions of one or more of these reactions.
In the dark–i.e. when the transport mechanism is not functioning–the biochemical constituents reach equilibrium levels. The equilibria can be altered by changing the environment of the leaf.
The reactions of transport supply links of a respiratory chain.
The reactions of transport synthesize a bicarbonate‐accepting compound at the plasma membrane.

Evidence for each of these propositions is discussed.The theory is considered applicable, with appropriate modification, to cation transport in a variety of cells.
PHOTORECEPTOR ORGANELLES IN ANIMALS
Authors: MOODY M. F. 
Published: January 2008

Summary1. The relatively high refractive index of rod and cone outer segments causes them to show wave‐guide properties.2. Rod outer segments have a positive intrinsic birefringence and a negative form birefringence. The former results from oriented lipid molecules, the latter from the disk structure of the outer segment.3. Electron microscopy of outer segments shows that the disks are formed from infoldings of the surface membrane, each disk consisting of two folds adhering together on their outer surfaces. Studies of other cell membranes have suggested that their lipid molecules form a continuous or discontinuous bimolecular leaflet which is sandwiched between protein layers, and this structure probably applies to each of the disk membranes.4. From the lipid content of rod outer segments a rough estimate of the thickness of a continuous lipid layer in each disk membrane can be made. This is only a little smaller than the requirements of a bimolecular leaflet.5. Rhodopsin is a lipoprotein whose lipid content forms a considerable fraction of the total outer‐segment lipid. This and other data suggest that rhodopsin may be a structural component of the disk membrane.6. The initial effect of light on rhodopsin is probably to isomerize II‐cis to all‐trans retinene, and various thermal rearrangements follow which eventually cause the detachment of retinene from opsin. The absorption spectrum of rhodopsin is similar in situ and in solution, but the absorption spectra of the photoproducts are somewhat different.7. Rhodopsin is strongly dichroic in the rod, indicating that the retinene molecule lies mainly in the plane of the disks.8. Rhabdomeres, the photoreceptor organelles of many higher invertebrates, are formed from close‐packed microvilli. They show a negative birefringence which probably results from the lipid molecules within the microvillar membrane.9. All well‐authenticated rhabdomere visual pigments have a retinene chromophore, and in many features the photochemical processes resemble those of vertebrate rhodopsin. The extraction processes for vertebrate and invertebrate rhodopsins are also similar.10. The question of whether insect rhabdomeres show dichroism is still open, but there is good evidence for dichroism in some cephalopod rhabdomeres. This is probably the physiological basis for the polarized light discrimination shown by octopus.11. Some possible mechanisms for the transmission of the light stimulus within photoreceptor organelles are discussed.