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V Garcia-Martinez

Publications and source records attributed to V Garcia-Martinez.

At least 19 recordsLinked to original sources
PubMed2001

Localization of cells of the prospective neural plate, heart and somites within the primitive streak and epiblast of avian embryos at intermediate primitive-streak stages.

By constructing avian transplantation chimeras using fluorescently-labeled grafts and antibodies specific for grafted cells, we have generated a prospective fate map of the primitive streak and epiblast of the avian blastoderm at intermediate primitive-streak stages (stages 3a/3b). This high-resolution map confirms our previous study on the origin of the cardiovascular system from the primitive streak at these stages and provides new information on the epiblast origin of the neural plate, heart and somites. In addition, the origin of the rostral endoderm is now documented in more detail. The map shows that the prospective neural plate arises from the epiblast in close association with the rostral end of the primitive streak and lies within an area extending 250 microm rostral to the streak, 250 microm lateral to the streak and 125 microm caudal to the rostral border of the streak. The future floor plate of the neural tube arises within the midline just rostral to the streak, confirming our earlier study, but unlike at the late-primitive streak stages when both Hensen's node and the midline area rostral to Hensen's node contribute to the floor plate, only the area rostral to the primitive streak contributes to the floor plate at intermediate primitive-streak stages. Instead of contributing to the floor plate of the neural tube, the rostral end of the primitive streak at intermediate primitive-streak stages forms the notochord as well as the rostromedial endoderm, which lies beneath the prechordal plate mesoderm and extends caudolaterally on each side toward the cardiogenic areas. The epiblast lateral to the primitive streak and caudal to the neural plate contributes to the heart and it does so in rostrocaudal sequence (i.e., rostral grafts contribute to rostral levels of the straight heart tube, whereas progressively more caudal grafts contribute to progressively more caudal levels of the straight heart tube), and individual epiblast grafts contribute cells to both the myocardium and endocardium. The prospective somites (i.e., paraxial mesoderm) lie within the epiblast just lateral to the prospective heart mesoderm. Comparing this map with that constructed at late primitive-streak stages reveals that by the late primitive-streak stages, prospective heart mesoderm has moved from the epiblast through the primitive streak and into the mesodermal mantle, and that some of the prospective somitic mesoderm has entered the primitive streak and is undergoing ingression.

Animals↗
PubMed1997

State of commitment of prospective neural plate and prospective mesoderm in late gastrula/early neurula stages of avian embryos.

We examined the ability of epiblast regions of known prospective fate from the late gastrula/early neurula stage of avian embryos to self-differentiate when placed heterotopically, testing their state of commitment. Three sites were examined: paranodal prospective neural plate ectoderm, containing cells fated to form a portion of the lateral wall of the neural tube at essentially all rostrocaudal levels of the neuraxis; prospective mesoderm from the caudolateral epiblast, containing cells fated to ingress through the primitive streak and to form lateral plate mesoderm; and prospective mesoderm from one level of the primitive streak, containing cells fated to continue ingressing and form paraxial mesoderm. Grafts from all sites exhibited plasticity. Grafts from the prospective neural plate ectoderm could readily substitute for regions of prospective mesoderm, when transplanted to either the epiblast or primitive streak, undergoing an epithelial-mesenchymal transition and, where appropriate, expressing paraxis, a gene expressed in paraxial mesoderm. Similarly, grafts containing prospective mesoderm from the epiblast could readily substitute for regions of the prospective neural plate ectoderm, undergoing convergent-extension movements characteristic of neuroectodermal cells and expressing appropriate genes such as Engrailed-2 and Hoxb-1. Grafts containing prospective mesoderm from the primitive streak could also incorporate into the neural plate and undergo convergence-extension movements of neurulation, although their principal contribution was to mesodermal and endodermal structures. Collectively, our results demonstrate that at the late gastrula/early neurula stage, germ layer-specific properties are not irrevocably fixed for prospective ectodermal and mesodermal regions of the blastoderm. Moreover, the signals responsible for the induction of these two tissue types must still be present and available at these late stages.

Animals↗
PubMed1996

Morphology and significance of programmed cell death in the developing limb bud of the vertebrate embryo.

Cell death constitutes a basic mechanism accounting for many morphogenetic and histogenetic events during normal and abnormal development of embryonic organs and tissues. This article focuses on the major areas of mesodermal cell death occurring during vertebrate limb development. In early stages of limb development, cell death appears to reduce the amount of mesodermal tissue destined to form the anlage of the autopodium. In later stages, cell death plays a role sculpturing the shape of the digits. The morphology of the dying cells corresponds with apoptosis, but internucleosomal DNA fragmentation by endonuclease activation does not appear to be a precocious feature. The cell death program can be inhibited in vivo and in vitro by changing the environmental conditions of the prospective dying cells up to 6-10 h before death. In this review, we survey possible factors controlling the establishment of the cell death program. Information concerning the biochemical basis of cell death in the developing limb is also revised. Finally, the possible role of genes whose pattern of expression is coincident with the dying processes is discussed.

Animals↗
PubMed1995

Expression and signaling specificity of the IFNAR chain of the type I interferon receptor complex.

The IFNAR chain of the type I interferon (IFN) receptor (IFNIR) undergoes rapid ligand-dependent tyrosine phosphorylation and acts as a species-specific transducer for type I IFN action. Using the vaccinia/T7 expression system to amplify IFNAR expression, we found that human HeLa-S3 cells transiently express high levels of cell surface IFNAR chains (approximately 250,000 chains per cell). Metabolic labeling and immunoblot analysis of transfected HeLa cells show that the IFNAR chain is initially detected as 65-kDa and 98-kDa precursors, and then as the 130-kDa mature protein. Due to variation in N-glycosylation, the apparent molecular mass of the mature IFNAR chain varies from 105 to 135 kDa in different cells. IFNIR structure was characterized in various human cell lines by analyzing 125I-labeled IFN cross-linked complexes recognized by various antibodies against IFNIR subunits and JAK protein-tyrosine kinases. Precipitation of cross-linked material from Daudi cells with anti-IFNAR antibodies showed that IFNAR was present in a 240-kDa complex. Precipitation of cross-linked material from U937 cells with anti-TYK2 sera revealed a 240-kDa complex, which apparently did not contain IFNAR and was not present in IFN-resistant HEC1B cells. The tyrosine phosphorylation and down-regulation of the IFNAR chain were induced by type I IFN in several human cell lines of diverse origins but not in HEC1B cells. However, of type I IFNs, IFN-beta uniquely induced the tyrosine phosphorylation of a 105-kDa protein associated with the IFNAR chain in two lymphoblastoid cell lines (Daudi and U266), demonstrating the specificity of transmembrane signaling for IFN-beta and IFN-alpha through the IFNAR chain.

Animals↗
PubMed1995

Morphological changes in the normal pattern of ventricular myoarchitecture in the developing human heart.

BACKGROUND: The aim of the present study was to describe the morphological changes in the normal pattern of ventricular myoarchitecture in the prenatal and adult human heart, to understand the three-dimensional organization of the muscle fibers and their active functional role in valvular dynamics. METHODS: We used dissection and histological techniques in 56 human hearts from fetuses and adults of both sexes. RESULTS: In all hearts, the ventricular wall was arranged in three different layers: superficial (subepicardial), middle, and deep (subendocardial) myocardium. The superficial and deep layers are present in both ventricles, whereas the middle layer is found only in the left ventricle. Age-related differences were noted in the pattern of myoarchitecture of the superficial layer, mainly in the fetal period, and especially in the right ventricle; however, the middle layer always shows a circumferential pattern, which is specially evident in elderly hearts. The ventricular fibers in the superficial and deep layers are anchored in the ventricular orifices. CONCLUSIONS: Our findings reveal that muscle fiber architecture showed age- but not sex-related differences. These variations may reflect a mechanism of adaptation of the heart to functional demands throughout life.

Adolescent↗
PubMed1995

Morphological analysis of the fish heart ventricle: myocardial and connective tissue architecture in teleost species.

Light and scanning electron microscopy were used to study the structure of the heart ventricle in three species of marine teleost fishes: the hake (Merluccius merluccius), the angler fish (Lophius piscatorius) and the sea bream (Pagellus centrodontus). Our findings show the ventricle to be shaped differently in each species: tubular in the hake, saccular in the angler fish and pyramidal in the sea bream. From a structural viewpoint, interest was centered on two aspects: organization of the myocardial fibres and arrangement of connective tissue. In hake and angler fish ventricles, the myocardium was exclusively trabecular in nature, whereas the bream ventricle, in addition to trabecular myocardium, presented a thin compact layer. Muscle fibres showed precise patterns of organization at the level of the ventricular orifices. With the techniques used the intramyocardial connective tissue was detected in the following ventricular zones: i) at the level of subepicardial and subendocardial spaces, ii) surrounding the myocardial fascicles, and iii) surrounding individual myocardial cells. According to this structural study, the pyramidal ventricle of the fish should be considered as a ventricular pump with greater efficiency.

Animals↗
PubMed1995

Cell death in the embryonic developing limb.

In amniote vertebrates, the development of form and structure of the limb bud is accompanied by precise patterns of massive mesodermal cell death with morphological features of apoptosis. These areas of cell death appear to eliminate undifferentiated cells which are required only for a limited time period of limb development. Predictable skeletal and morphological anomalies of the limb occur when the pattern of cell death is modified in mutant species or under experimental conditions. Most evidence points to the occurrence of local triggering mechanisms to account for the establishment of the areas of cell death and the subsequent activation of cell death genes. Modifications of the extracellular matrix and diminution in the contribution of growth factors by neighbouring tissues appear as the most likely potential candidates for triggering the cell death program. Information on the genetical basis of cell death in the developing limb is very scarce. Among the increasing number of cell death genes identified in other cell death systems, such as p-53 and the ced-3/ICE and ced-9/ bcl-2 gene families, only bcl-2 has been studied in detail during limb development and yet, the information obtained is contradictory. Bcl-2 is not expressed in the areas of cell death of the developing limb, but normal limbs develop in mice with disruption of the bcl-2 gene. Obviously, the clarification of the role of the cell death genes constitute a major task in future studies of cell death in the developing limb.

Animals↗
PubMed1995

Primitive-streak origin and state of commitment of cells of the cardiovascular system in avian and mammalian embryos.

Early events of cardiovascular development have received renewed interest in recent years. The cardiovascular system is the first major organ system to become functional during early embryogenesis. Cells fated to form the cardiovascular system can be identified as early as during stages of gastrulation of avian and mammalian embryos. In the present brief summary, we describe the primitive-streak origin of the avian cardiovascular system and examine the state of commitment of prospective cardiogenic and vasculogenic areas of the primitive streak. In addition, we describe initial experiments aimed at elucidating the primitive-streak origin of the heart in mouse embryos. Finally, we consider the possible roles of Hensen's node and the "cardiac" endoderm in determination of cell fate and patterning of the avian developing heart tube. Although recent studies have shed considerable light on the origin, migration, and determination of the cardiovascular system, much still remains to be learned about mechanisms underlying cardiovascular patterning in the early embryo.

Animals↗
PubMed1994

Spatial arrangement of the heart muscle fascicles and intramyocardial connective tissue in the Spanish fighting bull (Bos taurus).

The spatial arrangement of the muscle fascicles and intramyocardial connective tissue was examined in the ventricles of the heart of the Spanish fighting bull (Bos taurus). In both ventricles, the muscle fascicles of the myocardium are arranged in 3 main directions, forming 3 muscle layers within the ventricular wall. The preferentially vertical arrangement of the muscle fascicles in the superficial and deep layers at the level of the fibrous aortic rings and the base of the semilunar valve leaflets suggests that these fascicles are actively involved in valvular dynamics. After controlled digestion of myocytes and elastic fibres with NaOH, a 3-dimensional arrangement of the scaffolding of connective tissue that supports the muscle fascicles and myocytes was observed. The arrangement and structure of this scaffolding may influence the order of contraction of muscle fascicles in different layers of the ventricle. In addition, differences were observed between the connective tissue scaffolding surrounding the myocytes of the 2 ventricles; these variations were correlated with the different biomechanical properties.

Animals↗
PubMed1994

Age-dependent dystrophic calcification of the aortic valve leaflets in normal subjects.

The aortic valves of 43 subjects (14 females and 29 males, mean age 48.9 +/- 22.2 years, range 3-88 years), dying from accidental causes and without any previous record of cardiovascular disease, were studied. The whole aortic root was removed and morphological features recorded. Calcium content was determined by atomic absorption spectrophotometry. Calcium content sustained a positive significant correlation (p < 0.001) with age. Comparison of regression lines from subjects of different age groups disclosed a significantly greater slope in the regression line of persons older than 50 years than in those of the younger population (p < 0.05). The increase with age of calcium content displayed no significant differences between male and female nor between any of the three aortic cusps. The presence of Lambl's excrescences on the aortic leaflets became more frequent with age and was associated with a higher calcium content.

Adolescent↗
PubMed1993

Locations of the ectodermal and nonectodermal subdivisions of the epiblast at stages 3 and 4 of avian gastrulation and neurulation.

A prospective fate map of the avian epiblast at late gastrula and early neurula stages has been generated through the construction of quail/chick transplantation chimeras. This map shows the subdivisions of the prospective ectoderm, mesoderm, and endoderm, both within the epiblast prior to their ingression and within the primitive streak. The map demarcates the locations and extents of the prospective surface ectoderm, otic placodes, neural crest, and neural plate--including its postnodal levels--in prospective ectoderm of the epiblast; prospective foregut, within the prospective endoderm of the epiblast and primitive streak; and prospective notochord, somites, intermediate mesoderm, lateral plate mesoderm, and extraembryonic mesoderm in the prospective mesoderm of the epiblast and/or primitive streak. Prospective cardiogenic cells are apparently absent from the primitive streak at these stages, and contributions of the epiblast to the heart are relatively scant and inconsistent with the expected timing and directions of migrations of prospective cardiogenic cells. Mapping of the primitive streak at earlier stages in another study (García-Martinez and Schoenwolf: Developmental Biology, in press) reveals that the ingression of cardiogenic cells through the primitive streak occurs prior to late gastrula stages, suggesting that contributions of epiblast to the heart at later stages are artifactual. Tests of prospective potency, based on the projected locations of origin of various cell groups provided by the new prospective fate map, are underway.

Animals↗
PubMed1993

Regulative ability of the prospective cardiogenic and vasculogenic areas of the primitive streak during avian gastrulation.

Four types of microsurgical experiments were conducted to analyze heart and blood vessel development during gastrula stages of avian embryos, stages during which prospective cardiogenic and vasculogenic cells reside within the primitive streak. Experiments addressed whether cells not normally destined to form heart could form heart when given the opportunity to do so and vice versa; cells destined to form rostral levels of the heart (or, alternatively, head blood vessels) could form caudal levels of the heart (or, alternatively, trunk blood vessels) and vice versa; the early endoderm imparts rostrocaudal organization to the heart and associated blood vessels; and ingression of cells from the primitive streak and their subsequent migration into the mesodermal mantle is a cell-autonomous event for migrating cells. Our results demonstrate the lability of prospective cardiogenic and vasculogenic cells of the primitive streak, both in terms of the type of mesodermal structures they are capable of forming (or of being formed from) and in terms of the rostrocaudal patterning of the cardiovascular system. In addition, our results show that cell ingression and migration is directed by environmental cues and is not a cell-autonomous process for migrating cells. Finally, our results suggest that patterning of the cardiovascular system occurs after cells enter the mesodermal mantle, presumably through cell-cell inductive interactions. However, the early endoderm is not the primary source of the patterning influence. What is the source remains to be established.

Animals↗
PubMed1993

Primitive-streak origin of the cardiovascular system in avian embryos.

The origin of the avian cardiovascular system from the primitive streak has been mapped by the construction of quail/chick transplantation chimeras, the use of QH-1 (an antiquail endothelial/endocardial cell marker), and injections of a vital fluorescent dye (DiI) into the primitive streak. Our studies reveal that the prospective heart, including its endocardial and myocardial layers and the adjacent parietal pericardium, occupies much of the rostral half of the primitive streak at early primitive-streak stages of gastrulation. The heart originates from the primitive streak in roughly rostrocaudal sequence (i.e., the prospective bulbus cordis arises more rostrally in the streak than does the prospective ventricle, which in turn arises more rostrally than does the prospective sinus venosus), and all layers of the heart at each of its rostrocaudal subdivisions originate in concert from the same level of the primitive streak. Moreover, all rostrocaudal levels of the primitive streak at gastrula and neurula stages contain prospective endothelial cells. Again, these cells are rostrocaudally ordered within the streak, such that head blood vessels (both arteries and veins) arise at more rostral streak levels than do trunk blood vessels. Ingression of cardiogenic cells is complete by midprimitive-streak stages, and the position formerly occupied by prospective cardiogenic cells within the streak becomes occupied by ingressing prospective somitic cells. Additional studies on the state of commitment of prospective cardiogenic and endothelial cells during their ingression through the primitive streak are underway.

Animals↗
PubMed1993

Internucleosomal DNA fragmentation and programmed cell death (apoptosis) in the interdigital tissue of the embryonic chick leg bud.

In this work we have attempted to characterize the programmed cell death process in the chick embryonic interdigital tissue. Interdigital cell death is a prominent phenomenon during limb development and has the role of sculpturing the digits. Morphological changes in the regressing interdigital tissue studied by light, transmission and scanning electron microscopy were correlated with the occurrence of internucleosomal DNA fragmentation, evaluated using agarose gels. Programming of the cell death process was also analyzed by testing the chondrogenic potential of the interdigital mesenchyme, in high density cultures. Our results reveal a progressive loss of the chondrogenic potential of the interdigital mesenchyme, detectable 36 hours before the onset of the degenerative process. Internucleosomal DNA fragmentation was only detected concomitant with the appearance of cells dying with the morphology of apoptosis, but unspecific DNA fragmentation was also present at the same time. This unspecific DNA fragmentation was explained by a precocious activation of the phagocytic removal of the dying cells, confirmed in the tissue sections. From our observations it is suggested that programming of cell death involves changes before endonuclease activation. Further, cell surface changes involved in the phagocytic uptake of the dying cells appear to be as precocious as endonuclease activation.

Animals↗