Ultrastructural characteristics of primordial germ cells and their amoeboid movement to the gonadal ridges in the tammar wallaby

 The primordial germ cells (PGCs) of tammar wallaby fetuses are large cells with large nuclei. The cytoplasm of the PGCs contains characteristic spherical mitochondria and abundant ribosomes that make the cyoplasm appear dense. No permanent junctional complexes between PGCs and somatic cells were observed, and there were few cytoplasmic inclusions. The majority of migrating PGCs were observed outside the gonad in the dorsal mesentery and in the tissues adjacent to the gonad. The migrating PGCs have many finger-like, blunt pseudopodia, within which microfilament bundles are observed. The numerous dumbell-like PGCs with polarised cytoplasm suggest that the PGCs of this marsupial move to the gonadal ridges by amoeboid movement, but once the PGCs reach the gonadal ridge, they assume their more characteristic ovoid shape. Accepted: 10 January 1997     

Migratory pathways and selective aggregation of the lateral reticular neurons in the rat embryo: a horseradish peroxidase in vitro study, with special reference to migration patterns of the precerebellar nuclei

The migration and ultimate domain invasion of postmitotic lateral reticular nucleus (LRN) neurons were followed in embryonic day 15-20 (E15-E20) rat embryos, by using a horseradish peroxidase (HRP) in vitro axonal tracing method. All of the LRN axons elongate and neuronal somata migrate via the subpial or marginal migratory stream (mms), circumnavigating the ventrolateral aspect of the medulla at the glial endfeet level. They reach the ventral midline at E16, bypass it, and begin to settle in their final territory at E17. At E18 the LRN anlage is fully formed, and at E19-E20 its cells have finished their migration and are rapidly differentiating. Comparison of these sequential steps with their counterparts in the development of the inferior olive (ION) and external cuneatus (ECN) brings to light the essential role of the neuroepithelial cells of the interolivary commissure (the "floor plate"). This zone is likely to act as 1) a chemoattractant for the growth cones of the LRN, ION, and ECN, and 2) a decision-making center, which instructs the somata of these neurons to cross the midline or not, ultimately governing the crossed or uncrossed pattern of their projection to their common target, the cerebellum. Finally, the ontogeny of the LRN and ECN provides a most surprising example, even unique in the central nervous system, of long-distance, neurophilic migration that conveys neuronal cell bodies contralaterally to the side on which they proliferate.     

球囊导管损伤后早期动脉平滑肌细胞的增殖

目的：研究动脉硬化早期中膜与内膜平滑肌细胞的增殖。方法：球囊导管损伤大鼠的颈总动脉后在电镜和光镜下观察其形态和生化指标变化。结果：术后24h 5-溴脱氧尿嘧啶尿苷阳性平滑肌细胞出现,阳性细胞率分别于术后第2,5d出现高峰。术后第2,3d迁移细胞的出现率最高。术后第3d,88.8%迁移细胞增殖细胞核抗原阳性。透射电子显微镜下,术后第3d中膜平滑肌细胞特别是内层的为合成型,并且与细胞外基质连接稀疏,基底膜、胶原纤维和弹性纤维被消失。结论：动脉损伤后,中膜平滑肌细胞呈高增殖性,由收缩型转变为合成型,与细胞外基质的结合性降低,中膜弹性纤维、胶原纤维被消化,增生活跃的细胞向内膜的迁移性增高。迁移至内膜的平滑肌细胞呈高增殖性。     

The NK1 receptor and its participation in the synergistic enhancement of corneal epithelial migration by substance P and insulin-like growth factor-1

1. We have previously shown that substance P (SP) and insulin-like growth factor-1 (IGF-1) act synergistically to enhance the migration of rabbit corneal epithelial cells in an organ culture model. The present study was designed to identify the epithelial cell SP receptor that participates in this synergistic effect.
2. Rabbit corneal blocks were incubated for 24 h, then the length of the path of epithelial migration was measured. Reagents tried in the TC-199 culture medium, in the presence or absence of IGF-1, were: SP, agonists of tachykinin receptors NK₁, NK₂ or NK₃ and antagonists of tachykinin receptors NK₁ or NK₂.
3. The binding characteristics of SP receptors were examined in rabbit cultured corneal epithelial cells by binding assays with [¹²⁵I]-SP in the presence or absence of excess unlabelled SP or ligands of NK₁, NK₂ or NK₃ receptors.
4. As was demonstrated previously, SP and IGF-1 stimulated epithelial migration when they were added to the culture medium together, but individually they had no effect. NK₁ agonists had the same synergistic effect with IGF-1 as did SP, but the NK₂ and NK₃ agonists did not. Furthermore, the NK₁ antagonist abolished the synergistic effect of SP and IGF-1, but the NK₂ antagonist had no effect.
5. SP bound specifically to rabbit cultured corneal epithelial cells. The binding affinity was 0.44 nM and there were 2.43×10⁴ binding sites per cell. The NK₁ ligand competed, in a dose-dependent fashion, with the binding of SP to corneal epithelial cells, but neither the NK₂ nor NK₃ ligand affected binding.
6. We conclude that the SP receptor in rabbit corneal epithelial cells is NK₁ and that this receptor participates in the synergistic enhancement of corneal epithelial migration by SP and IGF-1. The precise mechanism(s) of this interaction requires more study. These findings imply that both neural and humoral factors are essential for the maintenance and healing of corneal epithelium.

     

Reproductive outcomes among Mexico-born women in San Diego and Tijuana: testing the migration selectivity hypothesis

Mexican immigrants to the United States have better reproductive outcomes than do U.S.-born non-Latina whites. Explanations offered for this epidemiologic paradox include (1) poor outcomes among Mexican women may be hidden by their return to Mexico; (2) Mexican women may have a higher fetal death rate that alters the pattern of live birth outcomes; (3) Mexican women may have socioeconomic characteristics which, if properly measured, would explain the outcome; (4) Mexican women may have personal characteristics which would explain the outcome, if properly measured; (5) there may be ameliorative or salutogenic protective effects of culture; and (6) migration may be selective of healthier women who are thus more prone to positive outcomes. We test these explanations, with an emphasis on the last one, using a data set that combines reproductive histories and birth outcomes for Mexico-born women delivering in San Diego, California and Mexican women delivering in Tijuana, Mexico. These data are compared with U.S.-born Latinas and U.S.-born non-Latina Whites. Multivariate logistic regression analysis suggests that when controlling for birth history (stillbirths and miscarriages), socioeconomic characteristics (education and prenatal visits), personal characteristics (age, parity, time in area, history of family problems), and health characteristics (history of smoking, alcohol use, drug use, anemia, vaginal bleeding, urinary infection), the adjusted odds of a positive birth outcome (measured as a live birth of 2500 grams or more) is highest for women delivering in Tijuana, implying that migrants may not be so selective when compared to the country of origin. The number of prenatal visits was an important explanatory variable.     

Infiltrative capacity of T leukemia cell lines: A distinct functional property coupled to expression of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinases-1 (TIMP-1)

Infiltrative capacity was found to distinguish separate T leukemia cell lines. Of seven T-cell lines four exhibited capacity to infiltrate Matrigel. Analysis of infiltration was performed at the single-cell level throughout the Matrigel using a depth meter. Further, we examined differences in migration capacity and metalloproteinase production between infiltrating and non-infiltrating T-cell lines. The capacity to infiltrate was not directly correlated to the capacity to adhere to the Matrigel or to migrate on/to extracellular matrix components. It is concluded that infiltration capacity does not simply reflect capacity to migrate but represents a distinct functional property. The production of metalloproteinases and their inhibitors by the separate T-cell lines was analyzed using rt PCR, biosynthetic labelling, zymography, immunoprecipitation and ELISA. All T-cell lines with capacity to infiltrate produced matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) while non-infiltrating cell lines did not express MMP-9. Expression of MMP-1, 2, 3, 10, 14 and 17 showed no correlation to capacity to infiltrate. Analysis of infiltration in the presence of a metalloprotease inhibitor showed an increased number of cells within the gel. This enhancement of infiltration suggests that the function of MMPs and/or their inhibitors in lymphocyte infiltration is more complex than previously thought. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cellular dynamics of corneal wound re-epithelialization in the rat. I. Fate of ocular surface epithelial cells synthesizing DNA prior to wounding

The fate of ocular surface epithelial cells in response to injury of the cornea was examined. Corneal epithelial cells were labeled during DNA synthesis with [3H]thymidine 1 h prior to wounding. A 3-mm diameter epithelial defect was made in the center of the rat cornea, with the basement membrane remaining intact. Within 12 h of abrasion, labeled cells were detected in the regenerating surface. At 18 h, there was a 2.7- and 17-fold increase of labeled basal and suprabasal cells, respectively, in the epithelium adjacent to the wound, and at 24 and 30 h there was an excessive number of cell layers (up to 7) at the margin of the abrasion. Re-epithelialization progressed as a gradient of cell layers that became diminished towards the center of the wound. Completion of layers 1, 2, 3, and 4 were recorded at 24, 30, 36, and 72 h, respectively. No changes in the labeling index of the limbus or conjunctiva were noted. These results suggest that processes of centripetal and vertical migration, as well as events related to cell division, in the uninjured corneal surface are not impeded by wounding of the corneal epithelium. However, wound healing appears to require cells with a basal phenotype, presumably because of this cell type's migratory capability.     

Histamine H2-receptor antagonists stimulate proliferation but not migration of human gastric mucosal cellsin vitro

Gastric mucosal cell migration and proliferation are crucial events in the repair of gastric mucosal erosions. This study was designed to test the hypothesis that the H₂ blockers roxatidine and ranitidine might stimulate migration and proliferation of gastric mucous cells derived from a human well-differentiated gastric adenocarcinoma cell line (MKN 28 cells)in vitro, in conditions independent of systemic factors and of acid inhibition. Confluent monolayers of MKN 28 cells were wounded with a razor blade and were then incubated with roxatidine or ranitidine. The number of cells migrating to the damaged area was determined 24 hr later. Cell proliferation was assessed by means of [³H]thymidine uptake and cell counts after incubation with roxatidine or ranitidine. Neither H₂ antagonist significantly stimulated cell migration. On the other hand, cell proliferation was dose-dependently and significantly enhanced by incubation with roxatidine and ranitidine. Exogenous administration of TGF- significantly stimulated MKN 28 cell division. However, incubation with roxatidine or ranitidine did not increase the steady-state mRNA expression of TGF- or EGFR as assessed by northern blot analysis. Based on thesein vitro findings, we postulate that the ulcer healing effect of these H₂ antagonistsin vivo might be due in part to stimulation of gastric mucosal cell proliferation.Data from this paper have been presented in part at the 1995 meeting of the American Gastroenterological Association and published in abstract form in Gastroenterology 108:A72, 1995.     

Formation of “neo-cortex” in a congenital human teratoma

Summary A congenital human teratoma contained a neuroectodermal mass with architectonic features similar to those of the normal developing neo-cortex. Surrounding a central cavity, a germinal, an intermediate and a cortical zone were clearly distinguishable from innermost to outermost. Glial fibers coursed radially through the intermediate and cortical zones. In the cortical plate neuronal elements were oriented radially with an inside out gradient of differentiation. Mesothelial tissue covered the outer surfaces of the cortex. Over limited sectors a gap in the integrity of the meso-glial barrier were associated with neuroglial ectopias.The following points are of neurobiologic importance: the formation of the miniature cerebral cortex occurred in the absence of any influence of afferent subcortical fibers. The radial alignment of glial fibers between the germinal pseudostratified epithelium and the outer surface occurred only in sectors of the neuro-ectodermal mass where a neo-cortex was present, and may therefore have been a critical determinant in the formation of the cortical plate. The integrity of the outer glial mesenchymal barrier may be necessary for the normal arrangement of cortical neurons.     

Adhesion molecules in lymphoma metastasis

Summary Recently, many surface proteins of lymphoid cells that mediate adhesion to other cells and extracellular matrix have been identified. Several of these cellular adhesion molecules (CAM) are also expressed by metastatic lymphoma cells and may mediate adhesion to tissue components during the metastatic process. Correlations observed between expression of certain CAM, like MEL-14 and CD44, and particular patterns of spread, support this notion, but conclusive evidence is scarce.We have used T-cell hybridomas to study the mechanisms of wide-spread lymphoid metastasis. The results obtained with this model are reviewed here. The advantages are that a large number of genetically similar cell lines can be generated, which can be grouped in large panels of highly invasive and non-invasive cells. Invasiveness of these cells in hepatocyte and fibroblast monolayers correlates with exprimental metastasis.Lymphoid CAM that are potentially involved in metastasis are reviewed. Several of these CAM are not, or not consistently, expressed by the invasive T-cell hybridomas, indicating that they are not indispensable. Notably, some of the CAM involved in the onset of an immune response or in migration into inflamed tissues, like ICAM-1 and VLA-4, and the homing receptors MEL-14 and LPAM-1 do not seem to be involved. CAM that are consistently expressed by the T-cell hybrids include LFA-1, the beta-1 integrin subunit CD29, CD31 (PECAM-1) and CD44 (Hermes homing receptor).We have generated considerable evidence that LFA-1 is required for efficient metastasis of T-cell hybrids, based on the behavior of LFA-1-deficient mutants and revertants. High levels of LFA-1 are required. The relevant counterstructure is probably ICAM-2 rather than ICAM-1. Preliminary results suggest that also a beta-1 integrin, possibly VLA-5, plays a role. Finally, we summarize evidence indicating that CD31 and CD44 are primary candidates for involvement in metastatic spread of T-cell hybridomas.