Bringing up small oocytes to eggs in pigs and cows

It has been known that the mammalian ovary contains a huge number of non-growing small oocytes, of which only a small number grow to their final size, mature, and are ovulated. Artificial maturation of small oocytes could provide a new source of mature eggs for livestock production and assisted reproduction in humans and in endangered species. Two methods have been used for oocyte growth, in vitro growth (IVG) culture and xenotransplantation. By these methods, oocytes in some species grow up to their final size and acquire developmental competence, although the methods are still at the experimental stage. The experiments remind us of many basic questions in mammalian oogenesis: Does the oocyte require certain stimuli to initiate growth? How are the few oocytes selected to grow to final size? How do they grow up in follicular units? How do they acquire meiotic competence during the growth phase? This paper will give some clues to answer these questions by presenting our recent data from IVG and xenotransplantation experiments, and by illustrating differences between the oocytes of mice and larger animals.     

Regulation of cardiac hypertrophy by intracellular signalling pathways

The mammalian heart is a dynamic organ that can grow and change to accommodate alterations in its workload. During development and in response to physiological stimuli or pathological insults, the heart undergoes hypertrophic enlargement, which is characterized by an increase in the size of individual cardiac myocytes. Recent findings in genetically modified animal models implicate important intermediate signal-transduction pathways in the coordination of heart growth following physiological and pathological stimulation.     

Against Bergmann's rule: fly sperm size increases with temperature

A long-standing school textbook biological rule, Bergmann's rule, asserts that animals (and their constituent parts) grow bigger when it is colder. This seems to hold for many warm-blooded animals, as well as for egg, cell and body size of most cold-blooded animals. A unifying mechanism producing this pattern has not been found. We here provide the first experimental evidence that the size of an important type of cell, namely sperm, increases (rather than decreases) with temperature in a cold-blooded animal, the yellow dung fly. By pointing to an exception, our work either questions the generality of one prominent category of explanation of Bergmann's rule, that of a physiological constraint, or alternatively suggests that sperm differ fundamentally in their physiology from other cells.     

Developmental timing of a sensory-mediated larval surfacing behavior correlates with cessation of feeding and determination of final adult size

Controlled organismal growth to an appropriate adult size requires a regulated balance between nutrient resources, feeding behavior and growth rate. Defects can result in decreased survival and/or reproductive capability. Since Drosophila adults do not grow larger after eclosion, timing of feeding cessation during the third and final larval instar is critical to final size. We demonstrate that larval food exit is preceded by a period of increased larval surfacing behavior termed the Intermediate Surfacing Transition (IST) that correlates with the end of larval feeding. This behavioral transition occurred during the larval Terminal Growth Period (TGP), a period of constant feeding and exponential growth of the animal. IST behavior was dependent upon function of a subset of peripheral sensory neurons expressing the Degenerin/Epithelial sodium channel (DEG/ENaC) subunit, Pickpocket1(PPK1). PPK1 neuron inactivation or loss of PPK1 function caused an absence of IST behavior. Transgenic PPK1 neuron hyperactivation caused premature IST behavior with no significant change in timing of larval food exit resulting in decreased final adult size. These results suggest a peripheral sensory mechanism functioning to alter the relationship between the animal and its environment thereby contributing to the length of the larval TGP and determination of final adult size.     

Wingless promotes cell survival but constrains growth during Drosophila wing development

During animal development, organs grow to a fixed size and shape. Organ development typically begins with a rapid growth phase followed by a gradual decline in growth rate as the organ matures, but the regulation of either stage of growth remains unclear. The Wnt/Wingless (Wg) proteins are critical for patterning most animal organs, have diverse effects on development and have been proposed to promote organ growth. Here we report that contrary to this view, Wg activity actually constrains wing growth during Drosophila melanogaster wing development. In addition, we demonstrate that Wg is required for wing cell survival, particularly during the rapid growth phase of wing development. We propose that the cell-survival- and growth-constraining activities of Wg function to sculpt and delimit final wing size as part of its overall patterning programme.     

The BMP proteins in bone formation and repair.

From recent advances in the fields of bone biology and pattern formation, the first clues to our understanding of embryonic skeletal development are beginning to emerge. This complex process involves an integration of spatial patterning and the differentiation of specialized cells that make up bone and cartilage. The result is a scale model of the mature skeleton which is able to grow in size to fit the adult body plan. In the mature animal, bone repair after injury appears to be similar to bone formation in the embryo, suggesting that analogous mechanisms for the control of bone formation may exist in the adult and embryonic skeletons.     

Animal Welfare in Relation to Standards in Organic Farming

The new EU-regulations on organic farming (1804/1999) are also influencing the animal welfare. A lot of positive regulations is to find, but also regulations that seen to mind more about the general public and customer and their view on organic farming, than the health and welfare of the animals.The paper specially focus on the impact of the regulations and the recommendations that phytotherapeutic essences and homeopathic products take precedence over the so called chemically-synthesised allopatic veterinary medical products, and that the use of the same is prohibited for preventive treatments. Key questions here are the lack of scientific evidence concerning homeopathy in animals, and that Swedish veterinarians are not allowed to work with homeopathy.Differences in interpretation of the regulations between animal owners and veterinarians will also be discussed. What is a disease that needs treatment? Who is to decide about the treatment? Parasitic infections are discussed as an illustrative example.Other consequences of the regulations concerning the animal welfare are problems in certain geographical zones, for instance subarctic areas where necessary crops are impossible to grow.Animal transports and splitting mother-offspring are briefly discussed as future problems to be handled in the regulations, and the paper ends by presenting the need of regulated herd health control programs in organic husbandry, which can detect and focus on welfare and production problems. The organic movement is not static, and must not be so.     

Cell size homeostasis: Metabolic control of growth and cell division

Joint regulation of growth rate and cell division rate determines cell size. Here we discuss how animal cells achieve cell size homeostasis potentially involving multiple signaling pathways converging at metabolic regulation of growth rate and cell cycle progression. While several models have been developed to explain cell size control, comparison of the two predominant models shows that size homeostasis is dependent on the ability to adjust cellular growth rate based on cell size. Consequently, maintenance of size homeostasis requires that larger cells can grow slower than small cells in relative terms. We review recent experimental evidence showing that such size adjustment occurs primarily at or immediately before the G1/S transition of the cell cycle. We further propose that bidirectional feedback between growth rate and size results in cell size sensing and discuss potential mechanisms how this may be accomplished.     

Limitation of size by hypoxia in the fruit fly Drosophila melanogaster

The size of an organism is of fundamental importance in all biological processes. It dictates many of the critical interactions and physical factors that delimit the envelope within which an organism can grow. We investigated the effects of reduced oxygen on size and development in the fruit fly Drosophila melanogaster, and showed that limiting the oxygen in the environment limits both whole animal and cell size. When oxygen levels were reduced from 20% in nitrogen to 15%, 10% and 7.5%, there was a linear decrease in both male and female mass. Both cell size and cell number decreased in low oxygen, but changes in cell size accounted for a larger proportion of the overall change in fly size. Cell numbers decreased by a maximum of 11% between flies reared in 20% oxygen and those reared in 7.5% oxygen, whereas cell surface area decreased by 17%. Low oxygen levels increased development time and mortality, but reduced fecundity. Reducing the level of oxygen available significantly slowed development times, with flies reared in 10% oxygen emerging on average 1.5 days later than those in 20% oxygen. The effect of oxygen on size is reversible during embryonic and larval development up to the pupal stage, when final size is set.     

Dynamic strain similarity in vertebrates; an alternative to allometric limb bone scaling

Galileo (1638) observed that "nature cannot grow a tree nor construct an animal beyond a certain size, while retaining the proportions which suffice in the case of a smaller structure". However, subsequent measurement has shown that limb bone dimensions are scaled geometrically with body size (Alexander et al., 1979a), and that the material properties of their constituent bone tissue are similar in animals over a wide range of body weight (Sedlin & Hirsch, 1966; Yamada, 1970; Burstein et al., 1972; Biewener, 1982). If, as suggested in previous scaling arguments (McMahon, 1973; Biewener, 1982), vigorous locomotion involved the same proportional forces over a wide range of animal size, this would create a paradox since large animals would be in far greater danger of skeletal failure than small ones. However, in vivo strain gauge implantations have shown that, during high speed running, axial force as a proportion of body weight (G) in the limb bones of animals decreases as a function of body size from 6.9 G in a 7 kg turkey to 2.8 G in a small (130 kg) horse. Estimates of axial force in larger animals suggest that this is further reduced to 0.8 G in a 2500 kg elephant. Nevertheless, it appears that, regardless of animal size or locomotory style, the peak stresses in the bones of these animals are remarkably similar. Therefore, throughout the range of animals considered (350 times differences in mass), we suggest that similar safety factors to failure are maintained, not by allometrically scaling bone dimensions, but rather by allometrically scaling the magnitude of the peak forces applied to them during vigorous locomotion.(ABSTRACT TRUNCATED AT 250 WORDS)     

A giant step towards artificial life?

Step by step, the components of an artificial form of cellular life are being assembled by researchers. Lipid vesicles the size of small bacteria can be prepared and under certain conditions are able to grow and divide, then grow again. Polymerase enzymes encapsulated in the vesicles can synthesize RNA from externally added substrates. Most recently, the entire translation apparatus, including ribosomes, has been captured in vesicles. Substantial amounts of proteins were produced, including green fluorescent protein used as a marker for protein synthesis. Can we now assemble a living cell? Not quite yet because no one has produced a polymerase that can be reproduced along with growth of the other molecular components required by life. But we are closer than ever before.     

粤北南岭无斑肥螈的种群结构及食性

南岭山区的无斑肥螈 (Pachytritonlabiatus)主要分布于海拔 85 0m以上的山区溪流中 ,当雌性头体长 >5 5mm ,雄性头体长 >4 5mm时 ,卵巢和精巢分别开始明显发育 ;生殖时期为每年 9～ 1 0月份 ;数量呈明显下降趋势 ;主要食饵为环节、软体、节肢动物类。     

Assessing dinosaur growth patterns: a microscopic revolution

Some of the longest standing questions in dinosaur paleontology pertain to their development. Did dinosaurs grow at slow rates similar to extant reptiles or rapidly similar to living birds and mammals? How did some forms attain gigantic proportions? Conversely, how did birds (avian dinosaurs) become miniaturized? New data on dinosaur longevity garnered from bone microstructure (i.e. osteohistology) are making it possible to assess basic life-history parameters of the dinosaurs such as growth rates and timing of developmental events. Analyses of these data in an evolutionary context are enabling the identification of developmental patterns that lead to size changes within the Dinosauria. Furthermore, this rich new database is providing inroads for studying individual and population biology. All in all, paleohistological research is proving to be the most promising avenue towards gaining a comprehensive understanding of dinosaur biology.     

Lipid composition of the liver oil of deep-sea sharks from the Chatham Rise, New Zealand

Deep-sea sharks approach neutral buoyancy by means of a large liver that contains large amounts of low-density lipids, primarily squalene and diacyl glyceryl ether (DAGE). As an animal increases in size and matures sexually, many biochemical changes take place within the animal. It was hypothesized that maintenance of neutral buoyancy in deep-sea sharks involves fine-scale changes in the chemical composition of the liver oil as individual sharks grow and develop. To test this hypothesis, the lipid composition of liver oil for individuals of different size and sex of deep-sea sharks from the Chatham Rise, New Zealand was compared. The composition of liver oil varied within and among species. Several species contained large amounts of squalene and DAGE, whereas only traces of these lipids were present in other species. The amounts of squalene and DAGE in liver oil were inversely related, and squalene content tended to decrease as sharks increased in size. Species with high squalene levels (>80%) in liver oil were not abundant on the Chatham Rise, although levels of DAGE (a lipid of increasing commercial interest) were elevated in many species. Maintenance of neutral buoyancy in deep-sea sharks appears to involve changes in the composition of low-density liver lipids as the sharks increase in size and mature.     

Epistemological views about vicious epigenetic circles due to aging

Aging is not a disease. Age changes occur in every adult animal. They take place in all species. Yet, malignant tumours and neurodegenerative diseases grow with age. Nobody dies from aging. Death results from age-associated diseases. Muscular and digestive atrophies rise with age. But should it be said that digestive atrophy leads to malnutrition, or is it the contrary? Where is the chicken and where is the egg? We are enclosed in a vicious circle. A vicious circle is not a simple cycle. It is an irreversible phenomenon that happens when a system of objects is acting on itself. Vicious circles now reach the molecular level. This paper tries to show that the destruction of elastin and of fibronectin in connective tissues produces a self destruction effect. Von Neumann showed that a model of self reproduction with the help of reproductive automata could be imagined. We attempt now to show that nature has imagined a model to produce self destruction, trough degradation products of fibronectin and of elastin. This self destruction process is neither purely stochastic, nor genetically programmed. It is an epigenetical process. It is not present in the beginning, as an a priori instruction, it emerges. We try to give here a unusual specific philosophical definition of the word "emergence".     

Seed Size and Dispersal Systems of Early Cretaceous Angiosperms from Famalicão, Portugal

Seeds and fruits of Early Cretaceous (Barremian-Aptian) angiosperms from the Famalic?o locality in Portugal were analyzed to establish seed and fruit size (volume) distributions and to infer the proportion of animal-dispersed fruits. On the basis of a sample of 106 angiosperm fruit and seed taxa, the average seed size was 0.78 mm3 (range 0.02-6.86 mm3), whereas the average fruit size was 2.06 mm3 (range 0.12-8.34 mm3). Variation in seed size among taxa is smaller than in modern plant communities, but within-taxon variation is similar to that known for extant plants. No significant difference in the size of "fleshy" versus other fruits was observed. The proportion of fleshy fruits was 24.5%. This high figure was surprising and indicates that the significance of animal dispersal during an early stage in angiosperm evolution has been underestimated. We suggest that reptiles and multituberculates, and perhaps other mammals and birds as well, were the likely seed dispersers and that the early angiosperms from Famalic?o probably were herbs or small shrubs that inhabited a semiopen coniferous woodland.     

Mycobacteria from leprous tissue of an armadillo cultivated on a hyaluronic acid based medium.

Mycobacteria were isolated from pooled leprous tissues of an armadillo. The suspensions of acid fast bacilli obtained were inoculated into a culture medium composed of umbilical cord extract, supplemented with yeast extract powder and glycerol with sheep serum added. Incubation temperature was 34 degrees C. An abundant growth of mycobacteria was observed in the primo culture in four weeks. The culture was easily sub-cultured on the homologous media. The primo culture did not grow on Lo?wenstein medium. The identity of the cultures of mycobacteria obtained is not yet established. The same strain of mycobacteria was cultured in media inoculated with suspensions of M. leprae decontaminated with sodium hydroxide-citrate solution. We confirm the findings of Skinsnes et al. (1975) that mycobacteria from human and animal leprous tissue can be cultured repeatedly on a hyaluronic based medium.     

The Effects of Experimentally Induced Adelphophagy in Gastropod Embryos

Adelphophagy, development where embryos grow large by consuming morphologically distinct nutritive embryos or their own normal siblings is widespread but uncommon among animal phyla. Among invertebrates it is particularly common in some families of marine gastropods and segmented worms, but rare or unknown in other closely related families. In calyptraeid gastropods phylogenetic analysis indicates that adelphophagy has arisen at least 9 times from species with planktotrophic larval development. This pattern of frequent parallel evolution of adelphophagy suggests that the embryos of planktotrophic species might be predisposed to evolve adelphophagy. Here we used embryos of three species of planktotrophic calyptraeids, one from each of three major genera in the family (Bostrycapulus, Crucibulum, and Crepidula), to answer the following 3 questions: (1) Can embryos of species with planktotrophic development benefit, in terms of pre-hatching growth, from the ingestion of yolk and tissue from experimentally damaged siblings? (2) Does ingestion of this material from damaged siblings increase variation in pre-hatching size? and (3) Does this experimentally induced adelphophagy alter the allometry between the velum and the shell, increasing morphological similarity to embryos of normally adelphophagic species? We found an overall increase in shell length and velum diameter when embryos feed on damaged siblings within their capsules. There was no detectable increase in variation in shell length or velum diameter, or changes in allometry. The overall effect of our treatment was small compared to the embryonic growth observed in naturally adelphophagic development. However each embryo in our experiment probably consumed less than one sibling on average, whereas natural adelphophages often each consume 10–30 or more siblings. These results suggest that the ability to consume, assimilate, and benefit from yolk and tissue of their siblings is widespread across calyptraeids.