Embryonic and adult vasculogenesis

Two mechanisms account for the formation of blood vessels, vasculogenesis and angiogenesis. Unfortunately, the terms vasculogenesis and angiogenesis literally have the same meaning, i.e., the genesis of blood vessels, and thus do little to distinguish between the two processes. Despite the nomenclature, the two processes are clearly distinct. Vasculogenesis, the de novo formation of blood vessels from mesoderm, is driven by the recruitment of undifferentiated mesodermal cells to the endothelial lineage and the de novo assembly of such cells into blood vessels. Angiogenesis is the generation of new blood vessels from endothelial cells of existing blood vessels, a process driven by endothelial cell proliferation. Recent years have seen dramatic changes in our understanding of the process of vasculogenesis, expanding the scope of its occurrence beyond the earliest stages of development to include involvement in neovascular processes throughout development as well as in the adult. In this review, emphasis is placed on discussion of emerging perspectives on the process of vasculogenesis in both the embryo and the adult.     

Embryonic stroke volume and cardiac output in the chick

Cine recordings of the hearts of chick embryos of 3 days and 2 hr to 4 days and 21 hr incubation were projected and measured. The measurements were converted to volumes. Stroke volume was determined from the difference in end diastolic and end systolic volume and multiplied by heart rate to yield cardiac output. Mean stroke volume was 0.0058 (±0.00036 SEM) mm³ per mg body wt; mean cardiac output was 0.956 (± 0.061 SEM) mm³/min per mg body wt. Stroke volume and cardiac output rose above their control values after intravascular injection of Ringer's solution, and even more so after the injection of dextran solution. The increases in stroke volume were due to increases in end diastolic volume, in the case of dextran injected embryos they occurred in spite of a simultaneous increase in end systolic volume. It is concluded that the rise in cardiac output with growth of the embryo is in large part due to an increase in stroke volume, and that the increase in stroke volume depends in part on the known increase in embryonic blood volume. The experiments further suggest that a rapid hydrostatic and osmotic equilibrium exists between embryonic blood plasma and an extra vascular compartment.     

Embryonic chick intestine in organ culture: hydrocortisone and vitamin D-mediated processes.

The effects of the glucocorticoid, hydrocortisone (HC), on vitamin D-mediated responses were examined in the organ-cultured, embryonic chick duodenum. In this system tissue responses to vitamin D-steroids in the culture medium include increased cAMP concentration, de novo synthesis of a specific calcium-binding protein (CaBP), enhanced uptake and transmucosal transport of calcium, and increased alkaline phosphatase activity. HC at levels ≥ 27.5 nm increased vitamin D-induced CaBP concentration: This apparently represents the first report of an interaction of HC with another steroid, vitamin D, in the regulation of the concentration of a specific protein. High levels of HC (≥27.5 μm) in the culture medium reduced duodenal calcium uptake and transmucosal transport regardless of the presence of vitamin D. However, at lower concentrations of HC (≤2.75 μm), only vitamin D-independent calcium uptake (basal calcium uptake) was reduced. Actinomycin D had no effect on HC reduction of basal calcium uptake suggesting that new protein synthesis is not involved in this action. In other experiments either HC or vitamin D stimulated phosphate and glucose uptake, and this uptake was potentiated by the presence of both steroids. HC also stimulated alanine uptake. Either HC or vitamin D increased both alkaline phosphatase activity (APA) and cAMP concentration, but together their activities were only additive. The data accumulated thus far indicate that HC directly influences calcium (and other nutrient) uptake by the duodenum and increases the concentration of the vitamin D-induced CaBP. Other vitamin D-mediated responses (APA and cAMP) were influenced by HC but there was no readily discernible relationship to nutrient uptake.     

Stereochemistry of carbon monoxide binding to normal human adult and Cowtown haemoglobins

The structures of carbonmonoxyhaemoglobins A and Cowtown (His146 beta----Leu) have been refined at 2.2 A (1 A = 0.1 nm) and 2.3 A resolution, respectively. The least squares fit to the Fe-C-O line makes an angle to the haem normal of about 6 degrees. The Fe-C-O group is bent from linearity by about 7 degrees. The porphyrins in the CO liganded haemoglobins are ruffled. This deformation of the haem and the distortion of the Fe-C-O group may explain the low CO affinity of haemoglobin. The electron density for the C-terminal residues is low but sufficient to distinguish the histidyl and leucyl residues clearly. The similarity between these two structures, apart from 146 beta, means that the reduced alkaline Bohr effect is due solely to the replacement of histidine by a leucine.     

Embryonic origin of the adult hematopoietic system: advances and questions

Definitive hematopoietic stem cells (HSCs) lie at the foundation of the adult hematopoietic system and provide an organism throughout its life with all blood cell types. Several tissues demonstrate hematopoietic activity at early stages of embryonic development, but which tissue is the primary source of these important cells and what are the early embryonic ancestors of definitive HSCs? Here, we review recent advances in the field of HSC research that have shed light on such questions, while setting them into a historical context, and discuss key issues currently circulating in this field.     

Embryonic expression patterns of the mouse and chick Gas1 genes

Control of cell proliferation is essential to generate the defined form of a multi-cellular organism. While much is known about the regulators for cell cycle progression, relatively little is known about the state of growth arrest. Growth arrest (G0) is defined as a cell in a metabolically active but proliferation-quiescent state (reviewed in Baserga (1985) The Biology of Cell Reproduction), typically induced by serum starvation in vitro. Using subtractive hybridization, Schneider et al. (Cell 54 (1988) 787) identified six genes (Gas1 through Gas6) whose expressions are upregulated in serum-deprived NIH3T3 cells. Among the Gas genes, Gas1 is the only one that can cause growth arrest when expressed in cultured cell (Cell 70 (1995) 595; Int. J. Cancer 9 (1998) 569). Here, we describe for the first time the expression pattern of Gas1 during mouse embryogenesis. Our data reveal that Gas1 is expressed in many regions that the cells are actively proliferating and suggest that it may have other roles during development than negatively regulating cell proliferation. Furthermore, we have cloned the chick GAS1 gene and documented the similarity and divergence of Gas1 gene expression patterns between the two species.     

人胚胎干细胞培养建系及其应用

简要概述了自1998年首次建立hES细胞系以来近6－7年国内外的现况、分离培养建系、鉴定标准和冻存技术发展、定向诱导分化及其应用等方面的研究进展。     

High-performance liquid chromatographic separation of human haemoglobins: Simultaneous quantitation of foetal and glycated haemoglobins

A high-performance liquid chromatographic system, which uses a weak cation exchanger (PolyCATA) together with Bis-Tris buffer (pH 6.47–7.0) and sodium acetate gradients, is described. Samples from adults and newborns were analysed and a clean separation of many minor and major normal and abnormal haemoglobin (Hb) variants was greatly improved. The method allows the separation of minor foetal haemoglobin (HbF) variants and the simultaneous quantitation of HbF and glycated HbA. HbF values correlated well with those obtained by the alkali denaturation method (r=0.997). The glycated haemoglobin (HbAr_Ic) levels measured in patients with high HbF concentrations correlated with the total glycated haemoglobin determined by bioaffinity chromatography (r=0.973). The procedure is useful for diagnostic applications and affords an effective and sensitive way of examining blood samples for haemoglobin abnormalities.     

A comparison of the behaviour of human adult and foetal haemoglobins on oxidation.

The measurements of oxidation-reduction potentials at pH 7.0 and ionic strength of 0.1 revealed only a slight difference between human adult (HbA) and foetal haemoglobin (HbF) (161 and 145 mV), which disappeared on increasing the ionic strength to 2.1. Kinetic data for the reactions with potassium ferricyanide and sodium nitrite of both haemoglobins in oxy- and carbonmonoxi-forms are presented at different excessive molar concentrations of oxidizing agents, in different environments at pH 7.0 and temperature ranging from 10--30 degrees C. The rate of HbF oxidation was considerably higher with both agents, despite vast differences in the reaction mechanisms.     

Embryonic and adult neural stem cell research in China

Neural stem cells(NSCs) are one specific type of multipotential stem cells that have the ability to proliferate for a long time and to differentiate into neural cells,including neurons,astrocytes and oligodendrocytes.These NSCs exist in both the embryonic and adult central nervous system(CNS) of all mammalian species.Progress has been made in the understanding of the developmental regulation of NSCs and their function in neurogenesis.This review discusses recent progress in this area,with emphasis on work d...     

Embryonic development of pineal gland vesicles: a morphological and morphometrical study in chick embryos.

Pineal cell aggregates in 5, 10 and 15 day-old chick embryos have been studied. Cell aggregates were classified into rosettes or vesicles and spheroid and ellipsoid vesicles distinguished. The number of pineal vesicles per unit of surface (vesicle density) was determined in three pineal portions: apical, anterior and posterior. By day 5, only cellular rosettes were found, mainly in the apical portion. After 10 and 15 days, the presence of rosettes was occasional. The posterior wall showed only small spheroid vesicles, while in the apical and anterior areas ellipsoid vesicles were also observed. Moreover, the spheroid/ellipsoid vesicle ratio increased from the 10th to the 15th day of incubation. The vesicle density decreased between the 10th and 15th day because of the increase in both vesicle and pineal size, without changes in the total number of vesicles. The results suggest that changes in vesicle morphology and density could be related to the functional activity of the pineal gland during embryonic development.     

Detection of sex-specific proteins in chick embryo gonads and mesonephros: effects of estradiol benzoate or tamoxifen on their expression

Gonadal and mesonephric protein patterns from 19 day old normal chick embryos were investigated by two-dimensional polyacrylamide gel electrophoresis. Under these conditions, several sex-specific polypeptides were detected. As concerns gonadal extracts, four sex-specific polypeptides, all restricted to the cytosol, were present in the testis, whereas three sex-specific polypeptides, two localized in the cytosol, the other being membrane-bound, were identified in the ovary. Among the ovary-specific polypeptides two proved to be estrogen-dependent. They appeared in the left testis of embryos after early estradiol benzoate treatment and their expression was reduced in the ovary after early exposure to the antiestrogen, tamoxifen. Mesonephros extracts of both sexes also differed in their protein composition since three additional polypeptides (one in both the cytosolic and membrane fractions, the others in the cytosol) not found in females were found to be present in males. None appeared to be affected after either estradiol or tamoxifen treatment.     

Embryonic and adult isoforms of XLAP2 form microdomains associated with chromatin and the nuclear envelope

Laminin-associated polypeptide 2 (LAP2) proteins are alternatively spliced products of a single gene; they belong to the LEM domain family and, in mammals, locate to the nuclear envelope (NE) and nuclear lamina. Isoforms lacking the transmembrane domain also locate to the nucleoplasm. We used new specific antibodies against the N-terminal domain of Xenopus LAP2 to perform immunoprecipitation, identification and localization studies during Xenopus development. By immunoprecipitation and mass spectrometry (LC/MS/MS), we identified the embryonic isoform XLAP2??, which was downregulated during development similarly to XLAP2??. Embryonic isoforms XLAP2?? and XLAP2?? were located in close association with chromatin up to the blastula stage. Later in development, both embryonic isoforms and the adult isoform XLAP2?? were localized in a similar way at the NE. All isoforms colocalized with lamin B2/B3 during development, whereas XLAP2?? was colocalized with lamin B2 and apparently with the F/G repeat nucleoporins throughout the cell cycle in adult tissues and culture cells. XLAP2?? was localized in clusters on chromatin, both at the NE and inside the nucleus. Embryonic isoforms were also localized in clusters at the NE of oocytes. Our results suggest that XLAP2 isoforms participate in the maintenance and anchoring of chromatin domains to the NE and in the formation of lamin B microdomains.