The extent of complex population changes in nature

Summary Many models of animal populations show complex yet predictable patterns of density changes under simple and plausible assumptions. Yet one previous attempt to determine the extent and importance of complex dynamics concluded that they were likely only in some laboratory populations, but not in field populations. Ecologists have treated changes more complex than a return to a simple equilibrium, such as the cyclical changes in populations of lynx and voles in the arctic, as special cases. Highly variable populations, such as insects, are usually thought to be driven by unpredictable changes in the weather. Here, we assemble 71 populations counted for over 50 years, and suggest that complex yet predictable population changes are more common than previously thought.     

The nature and extent of synaptonemal complex formation in haploid barley

Normal synaptonemal complexes have been found in haploid barley meiotic prophase at stages equivalent to pachytene in diploids. Reconstructions of serially sectioned nuclei have shown that up to 60% of the haploid chromosomes may pair in either intra- or interchromosomal associations. The extent and nature of the synaptonemal complex formation suggest that the chromosome pairing is non-homologous. From the virtual absence of chiasmata in metaphase I stages of the haploids it is inferred that crossing over requires a more precise DNA alignment than is provided by synaptonemal complex formation alone.     

Expression of the human SRY protein during development in normal male gonadal and sex-reversed tissues.

Sex determination in mammals is controlled by the SRY gene located on the Y chromosome. It encodes a protein containing a DNA-binding and DNA-bending domain. In spite of recent advances in the identification of the mechanisms that regulate male sex determination in mammals, the expression profile of the SRY protein in normal and sex-reversed human tissues is not well established. In order to localize the SRY protein and determine its cellular distribution and expression at different stages of development, we prepared monoclonal antibodies (mAb) against the recombinant SRY protein. One of these antibodies, LSRY1.1, recognizes a protein of 27 kDa in total lysates of HeLa SRYB3, a human cell line transfected with the SRY gene under the control of the SV40 promoter. Immunocytochemical analysis in the cell lines shows nuclear localization of the SRY protein. We have studied SRY protein expression in human tissues at different stage of fetal development until adult life and have demonstrated that the SRY protein is located in the nuclei of somatic cells and germ cells in the genital ridge during testis development. After testis determination, it can be detected until the adult stage in both germ cells and Sertoli cells. The presence of the SRY protein was also analyzed in biopsies of gonadal tissues of sex-reversal patients such as SRY-positive 46,XX males or SRY-positive 46,XX true hermaphrodites. SRY protein is detected in the nuclei of Sertoli cells of the testis and in the nuclei of granulosa cells in the ovotestis in these patients and in the nuclei of germ cells of both tissue types. These results suggest a common cellular origin for both Sertoli cells and granulosa cells.     

The nature of the skeleton and skeletogenic tissues in the Cnidaria

Calcification of zooxanthellate and non-zooxanthellate corals from 2 classes and 3 orders of Cnidaria was investigated using scanning and transmission electron microscopy and light microscopy. The ultrastructure of the skeleton and skeletogenic tissues (the calicoblastic ectoderm) from areas of active and non-active skeleton deposition were investigated. The results show that the fundamental cellular mechanism of calcification is similar in all 3 orders, and that the role of endosymbiotic zooxanthellae may be one that is concerned with the removal of waste products of the calcification process. The results are discussed with respect to the concepts of calcification and its evolution in the Cnidaria.     

Regulation of protein tyrosine kinase signaling by substrate degradation during brain development

Disabled-1 (Dab1) is a cytoplasmic adaptor protein that regulates neuronal migrations during mammalian brain development. Dab1 function in vivo depends on tyrosine phosphorylation, which is stimulated by extracellular Reelin and requires Src family kinases. Reelin signaling also negatively regulates Dab1 protein levels in vivo, and reduced Dab1 levels may be part of the mechanism that regulates neuronal migration. We have made use of mouse embryo cortical neuron cultures in which Reelin induces Dab1 tyrosine phosphorylation and Src family kinase activation. We have found that Dab1 is normally stable, but in response to Reelin it becomes polyubiquitinated and degraded via the proteasome pathway. We have established that tyrosine phosphorylation of Dab1 is required for its degradation. Dab1 molecules lacking phosphotyrosine are not degraded in neurons in which the Dab1 degradation pathway is active. The requirements for Reelin-induced degradation of Dab1 in vitro correctly predict Dab1 protein levels in vivo in different mutant mice. We also provide evidence that Dab1 serine/threonine phosphorylation may be important for Dab1 tyrosine phosphorylation. Our data provide the first evidence for how Reelin down-regulates Dab1 protein expression in vivo. Dab1 degradation may be important for ensuring a transient Reelin response and may play a role in normal brain development.     

Muscle growth and protein degradation during early development in chicks of fast and slow growing strains

1. Growth of breast and leg muscles and excretion of N tau methyl histidine in layer (slow growing) and broiler (fast growing) chicks were measured at five time intervals between 2 and 33 days of age. 2. The results indicate that muscles of the broiler chick grow faster than in layer chicks and that breast muscles of both strains grow faster than leg muscles in the first 2 weeks after hatching. 3. N tau methyl histidine excretion by layer chicks is higher than that by broilers relative to body weight, musculature and relative maturity at all ages examined. 4. The results suggest that faster growth of muscles is accompanied by a lower rate of protein degradation although at ages of less than 2 weeks differences in protein synthesis rates may also contribute to muscle growth.     

Comparative analysis of uncoupling protein 4 distribution in various tissues under physiological conditions and during development

UCP4 is a member of the mitochondrial uncoupling protein subfamily and one of the three UCPs (UCP2, UCP4, UCP5), associated with the nervous system. Its putative functions include thermogenesis, attenuation of reactive oxidative species (ROS), regulation of mitochondrial calcium concentration and involvement in cell differentiation and apoptosis. Here we investigate UCP4's subcellular, cellular and tissue distribution, using an antibody designed specially for this study, and discuss the findings in terms of the protein's possible functions. Western blot and immunohistochemistry data confirmed that UCP4 is expressed predominantly in the central nervous system (CNS), as previously shown at mRNA level. No protein was found in heart, spleen, stomach, intestine, lung, thymus, muscles, adrenal gland, testis and liver. The reports revealing UCP4 mRNA in kidney and white adipose tissue were not confirmed at protein level. The amount of UCP4 varies in the mitochondria of different brain regions, with the highest protein content found in cortex. We show that UCP4 is present in fetal murine brain tissue as early as embryonic days 12-14 (E12-E14), which coincides with the beginning of neuronal differentiation. The UCP4 content in mitochondria decreases as the age of mice increases. UCP4 preferential expression in neurons and its developmental expression pattern under physiological conditions may indicate a specific protein function, e.g. in neuronal cell differentiation.     

In vivo protein synthesis from 14C-substrates in porcine tissues during the transition to postnatal development

[2-14C] leucine, [1-14C] alanine, [1-14C] glucose, [1-14C] lactate and [1-14C] pyruvate utilization in the protein synthesis has been studied in vivo at early stages of postnatal development of piglets. It has been established, that during the first 24 hours after birth the protein synthesis intensity, judging by [2-14C] leucine incorporation, in liver, skeletal muscle, duodenal wall and subcutaneous tissue of piglets increases 5, 7, 6.5 and 2.1 times respectively. At the age of 1-2 h the radioactive carbon incorporation from [1-14C] glucose into the brain proteins is more pronounced than into the proteins of liver and skeletal muscle. During the first days of life the intensity of the label incorporation from [1-14C] glucose into liver and skeletal muscle proteins of piglets is enhanced, whereas in brain it remains at the same level. The degree of 14C carbon incorporation from [1-14C]-alanine, [1-14C] pyruvate and [1-14C] lactate into the liver and skeletal muscle proteins of 5-days-old piglets is approximately the same, 14C substrates of protein synthesis in brain and subcutaneous adipose tissue having some peculiarities.     

The nature of robustness in development

A trait is robust to a genetic or environmental variable if its variation is weakly correlated with variation in that variable. The source of robustness lies in the fact that the developmental processes that give rise to complex traits are nonlinear. A consequence of this nonlinearity is that not all genes are equally correlated with the trait whose ontogeny they control. Here we explore how developmental mechanisms determine and alter the correlation structure between genes and the traits that they control. A formula is developed by which the correlation of a gene or environmental variable with a trait can be calculated if the mechanism that gives rise to the trait is known. The nature of robustness and the ways in which robustness can evolve are discussed in the context of the problems that arise in the analysis of inherently nonlinear systems.     

Expression of COUP-TFII in metabolic tissues during development

In mammals, the COUP-TF-family consisting of two structurally related proteins, COUP-TFI and COUP-TFII belongs to the orphan member of the steroid/thyroid hormone receptor superfamily. In an attempt to gain insights into the role of COUP-TFII, we examined developmental expression pattern of the mouse COUP-TFII focusing our studies on endoderm-derived tissues, pancreas and liver in particular. Independent lines of transgenic mice expressing Escherichia coli beta-galactosidase driven by the COUP-TFII promoter were generated. Embryonic expression of the beta-gal protein at day 9 of gestation was detected in the notochord, the ventral neural tube and, interestingly, in the gut endoderm, a site where COUP-TFII has not been detected previously. Between 9.5 and 11.5 dpc, beta-gal expression pattern that was established earlier persisted and sections revealed a staining of the common atrial chamber of the heart. At 15.5 dpc, beta-gal activity was found in all endoderm-derived tissues. We found that COUP-TFII mRNA and protein were present in fetal and adult hepatocytes. Finally, COUP-TFII expression was detected in pancreas, as judged by co-expression of the beta-gal in some of the glucagon and PDX1 positive-cells at 12.5 dpc and co-expression with insulin positive-cells at 15.5 dpc. In adult pancreas, COUP-TFII protein was present in the endocrine islet cells.     

Wound-induced vascular occlusions in tissues of the reed Phragmites australis: their development and chemical nature

This work focuses on the development of vascular occlusions, which are gels resealing the wounded vascular systems of injured organs, in the common reed Phragmites australis. Their formation seems to be crucial in keeping the internal environment of the plant stable. Histochemical tests, combined with an extraction series, were used to follow changes in the chemical nature of gels during their development. It was found that the first gel material was secreted by living cells in the vicinity of the incision within 1 or 2 d after wounding. Early gels were colourless and mainly composed of acidic polysaccharides interlinked by Ca2+ bridges. The properties of the gel material gradually changed during maturation. The matrix of polysaccharides in the early gels was later modified and interlinked by other components, resulting in a highly resistant material. Structural proteins were identified as the principal interlocking components of the material, and were responsible for its high resistance.     

Ligandin concentrations in the steroidogenic tissues of the rat during development

Ligandin, a ubiquitous multifunctional cytoplasmic protein which exhibits glutathione S-transferase, glutathione peroxidase and Δ⁵-3-ketosteroid isomerase activities and binds to cortisol metabolites, is present in relatively high concentrations in gonadal and adrenal tissue. In contrast to hepatic ligandin, little is known about the ontogeny of ligandin in steroid-synthesising tissues. We report here the intracellular concentrations of ligandin as well as the serum concentrations of testosterone and progesterone measured by radioimmunoassay at different stages of development in the rat. Ligandin levels in testis, ovary and adrenal tissue were relatively high soon after birth, decreased by day 9 and increased rapidly during puberty to reach adult levels. These changes appeared to be paralleled by changes in the circulating levels of testosterone and progesterone. In contrast, ligandin levels in non-steroidogenically active tissues, such as liver and kidney, were low at birth and rose progressively to reach adult levels. Whereas hepatic ligandin concentration could be increased at all stages of development by phenobarbital induction, no induction occurred in the endocrine tissues.     

The cellular distribution of antifeedant prenylated anthranoids in the tissues ofVismia guianensis during development

Summary Accumulation and distribution of two types of phenolic antifeedant metabolites, vismiones and ferruginins, in specialized cells were investigated inVismia guianensis DC. Chemical, light, and electron-microscope analyses revealed that the two types of compounds were produced in different cells and organs and at different stages of plant development. Vismiones accumulated at various concentrations in the leaf, depending on its developmental stage, as well as in the stem of very young plants. Ferruginins appeared late in the plant's development and accumulated exclusively in secretory ducts in the secondary body of the stem and in secretory cavities of the fruits.