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At least 19 recordsLinked to original sources
PubMed2000

Ring formation drives invagination of the vulva in Caenorhabditis elegans: Ras, cell fusion, and cell migration determine structural fates.

Directed cell rearrangements occur during gastrulation, neurulation, and organ formation. Despite the identification of developmental processes in which invagination is a critical component of pattern formation, little is known regarding the underlying cellular and molecular details. Caenorhabditis elegans vulval epithelial cells undergo morphological changes that generate an invagination through the formation of seven stacked rings. Here, we study the dynamics of ring formation during multivulva morphogenesis of a let-60/ras gain-of-function mutant as a model system to explore the cellular mechanisms that drive invagination. The behavior of individual cells was analyzed in a let-60/ras mutant by three-dimensional confocal microscopy. We showed that stereotyped cell fusion events occur within the rings that form functional and nonfunctional vulvae in a let-60/ras mutant. Expression of let-60/ras gain-of-function results in abnormal cell migration, ectopic cell fusion, and structural fate transformation. Within each developing vulva the anterior and posterior halves develop autonomously. Contrary to prevailing hypotheses which proposed three cell fates (1 degrees, 2 degrees, and 3 degrees), we found that each of the seven rings is a product of a discrete structural pathway that is derived from arrays of seven distinct cell fates (A, B, C, D, E, F, and H). We have also shown how autonomous ring formation is the morphogenetic force that drives invagination of the vulva.

Animals↗
PubMed1977

Drug migration during drying of tablet granulations I: effect of particle size of major diluent.

Migration of a water-soluble drug, propoxyphene hydrochloride, during drying of tablet granulations was studied. Wet granulations of the drug were prepared using lactose as the major diluent and corn starch as a disintegrant. Particle-size fractions of lactose ranging from 53 to 177 micron in diameter were employed in different granulations to examine the effect of particle size of the major diluent on drug migration. Determination of drug concentration at various depths in a dried granulation bed was accomplished by using a drying cell consisting of four layers. A numerical coefficient of migration was developed to compare the extent of drug migration in the various lactose granulations. Migration increased with decreasing particle size of the major diluent, lactose. Two factors that may contribute to increased migration with smaller particles are increased entry suction due to decreased intragranular capillary size and increased intergranular contact area.

Chemistry, Pharmaceutical↗
PubMed1995

The mortality rate of the province of birth as a risk indicator for lung and stomach cancer mortality among Genoa residents born in other Italian provinces.

This study analyses the relationship between migration and mortality for lung and stomach cancer, these diseases being those considered susceptible to changes in environmental conditions and individual habits that usually follow migration. Mortality rate of the province of birth was used as the index of risk related to migration. Data were analysed using the Poisson regression model for grouped data. Results indicate that migration determines modifications in the mortality rates of the migrant populations for the diseases under study. For lung cancer, the analysis showed a greater risk for migrants originating from areas with high rates and that migrants had a reduced risk in comparison with natives of Genoa. With regard to stomach cancer, the study revealed that migrants originating from high risk areas had higher relative risks than the Genoa natives, even if these were lower than expected when compared to the risks of the populations in the regions from which the migrants originated.

Emigration and Immigration↗
PubMed1985

Complex aphthosis: a forme fruste of Behçet's syndrome?

The evaluation of the rare patient who presents with oral and genital aphthae or almost constant, multiple (greater than 3) oral aphthae, but no systemic signs or symptoms (i.e., complex aphthosis), is difficult because no laboratory test is available to exclude Behçet's syndrome. Six patients with complex aphthosis were evaluated. In addition, patients with simple aphthosis, those with seronegative arthritis, and normal controls were assessed for circulating immune complexes (CIC) by in vitro and in vivo assays and for neutrophil migration by subagarose methods, since these tests have given significant results in patients with Behçet's syndrome. Patient 1, with complex aphthosis, had Raji cell evidence for CIC (51.2 mg aggregated human gamma globulin Eq/ml), C1q, and C3 in dermal blood vessels 4 hours post intradermal histamine injection and had a Sweet's syndrome-like vasculitis 24 hours post histamine injection. In addition, her serum enhanced the migration of patient neutrophils (3.6 +/- 0.6 to 4.6 +/- 0.5; N = 6, p less than or equal to 0.01). All other test and control patients had negative or normal CIC and neutrophil migration determinations. Sixteen-month clinical follow-up has confirmed that Patient 1, but not Patients 2 to 6, has developed overt manifestations of Behçet's syndrome.

Adult↗
PubMed1998

Leucine-rich repeat glycoproteins of the extracellular matrix.

The extracellular matrix plays an integral role in the pivotal processes of development, tissue repair, and metastasis by regulating cell proliferation, differentiation, adhesion, and migration. This review is focused on a family of related glycoproteins represented by at least one member in all specialized extracellular matrices. This family currently comprises nine members grouped together on the basis of their presence in the extracellular matrix and by virtue of a leucine-rich repeat motif that dominates the structure of the core protein. It is likely that most, if not all the members of this group exist as proteoglycans in some tissues, and thus have been termed the Small Leucine-Rich Proteoglycan family, or SLRPs. The leucine-rich repeat (LRR) is usually present in tandem array and has been described in an increasing number of proteins, giving rise to a LRR-superfamily. The LRR domain of the SLRP family is unique within the superfamily in that it is flanked by cysteine clusters, and the 24 amino acid consensus for SLRP members is x-x-I/V/L-x-x-x-x-F/P/L-x-x-L/P-x-x-L-x-x-L/I-x-L-x-x-N-x-I/L, where x is any amino acid. Enormous progress has been made in describing the membership, structure and localization of this family, and recently new insight has emerged into the putative function of these molecules not just as modulators of matrix assembly but also on their intriguing role in regulating cell growth, adhesion, and migration. Determination of membership, structure and putative function of this fascinating class of molecules is summarized in this review.

Amino Acid Sequence↗
PubMed1987

Determinants of interstate migration: differences between elderly and nonelderly movers.

This paper analyzes the determinants of interstate inmigration and outmigration for persons aged 5 to 54 and for persons aged 55 and over. The paper finds several similarities between the sets of migration determinants, but several potentially important differences emerge as well. Perhaps most striking among these are that states with high earnings of workers tend to have high rates of outmigration of elderly adults and that states with high levels of unemployment have high levels of inmigration of elderly people--these relationships are generally the opposite of those found for the nonelderly. This suggests the possibility of continued divergence in the spatial distribution of younger and older populations and offers the potential for the continued reallocation of resources between states (through the federal government) to pay for programs earmarked for the older population.

Age Factors↗
PubMed1985

Effect of vinblastine on the cell cycle and migration of ameloblasts of mouse incisors as shown by autoradiography using 3H-thymidine.

The effects of vinblastine on the cell cycle and the migration of ameloblasts were studied in the lower incisors of mice by labelling the cells with 3H-thymidine ([3H]TdR) and radioautography. A group of mice received 2 micrograms/g of body weight vinblastine intraperitoneally and 6 hr after these animals and those of a control group were injected with 1 microCi/g body weight of [3H]TdR, and sacrificed at time intervals from 0.75 hr to 15 days. The generation time of ameloblasts in the progenitor compartment was 14.8 hr in animals treated with vinblastine and 17 hr in the controls, using the FLM curve method; with the grain dilution method the duration was respectively 29.25 hr and 25.96 hr. The thymidine labelling index of the treated animals was 50% higher than the controls. The velocity of ameloblast migration, determined either by the displacement of the most incisally labelled cell or by the grain dilution method, was lower in the experimental group (2.48 cell positions/hr and 9.18 microns/hr respectively) as compared with the control (3.21 cell positions/hr and 18.88 microns/hr respectively). The results on the ameloblast production rate are contradictory but the slowing down in the velocity of cell migration is compatible with a decrease of the rate of cell production in the progenitor compartment as a vinblastine effect.

Ameloblasts↗
PubMed1985

A skin chamber technique for leukocyte migration studies; description and reproducibility.

An in vivo skin chamber method, using lesions obtained by suction, was evaluated for studying leukocyte migration. No dyspigmentation or scar was seen after two months. The number of leukocytes accumulated in the collection chamber was 6.9 X 10(7)/cm2 and was correlated to the area of the lesion (r = 0.964). Reproducibility, essentially unchanged over an extended period, was 19% for one skin chamber and 13.6% for determinations with duplicate chambers; by comparison, with an under-agarose technique, the coefficient of variation for migration was low on consecutive days (6%), but much higher (29%) when determined over a longer period. No correlation was found between the skin chamber technique and chemotaxis or random migration determined with the under-agarose technique (r = -0.38 and 0.12 respectively). Zymosan-activated serum attracted a higher number of leukocytes than did fresh serum, whereas heat-inactivated serum attracted a lower number. This attraction seems to be partly caused by C5a, as a higher C5a-concentration was detected in zymosan-activated serum and in fresh serum after 24 hours in a collection chamber than in heat-inactivated serum.

Adult↗
PubMed2000

Ras/Rac-Dependent activation of p38 mitogen-activated protein kinases in smooth muscle cells stimulated by cyclic strain stress

p38, a subfamily of the mitogen-activated protein kinases (MAPKs), is a crucial signal transducer between a variety of extracellular stimuli and gene expression in mammalian cells. This kinase is activated in cultured cells stimulated by heat shock, osmotic stress, and proinflammatory cytokines, but a similar activation of p38 MAPKs in vascular smooth muscle cells (SMCs) stimulated by mechanical stress has yet to be studied. We studied signal pathways leading to time- and strength-dependent p38 activation in rat SMCs in response to cyclic strain stress. p38 phosphorylation in stressed SMCs showed maximal activation at 10 minutes. This activation was significantly inhibited by pretreatment of the SMCs with pertussis toxin, a G-protein antagonist, and enhanced by treatment with suramin, a growth factor receptor antagonist, but opposite effects in the activation of extracellular signal-regulated kinases stimulated by mechanical forces were found. p38 activation was markedly reduced in stressed SMCs after protein kinase C depletion. Interestingly, SMC lines stably expressing dominant-negative ras (ras N17) or rac1 (rac1 N17) almost abolished p38 phosphorylation induced by cyclic strain stress. When p38 activation was inhibited by the specific inhibitor SB 202190, SMC migration, determined in a Boyden chamber in response to stimulation with platelet-derived growth factor-BB, and SMC proliferation, stimulated by cyclic strain stress, were abrogated. Thus, we provide the first evidence that cyclic strain stress rapidly activates p38 MAPKs via activation of protein kinase C ras/rac signal pathways, suggesting that p38 MAPKs are important signal transducers mediating the mechanical stress-induced cell responses essential for SMC migration and proliferation.

Journal Article↗
PubMed1999

Differential expression of thrombospondin and cellular fibronectin during remodeling in proliferative glomerulonephritis.

Thrombospondin-1 (TSP-1) and an alternatively spliced fibronectin (Fn)-EIIIA isoform are adhesive proteins associated with embryogenesis and tissue remodeling. We compared, by immunohistochemistry and in situ hybridization, the course of TSP-1 and Fn-EIIIA expression in a model of glomerulonephritis induced by Habu snake venom (HV) and characterized by mesangial cell migration, proliferation, and extracellular matrix (ECM) synthesis. At 24 hr after HV, TSP-1 and Fn-EIIIA proteins localized in the central aspects of lesions associated with platelets and macrophages and at the margins of lesions coinciding with mesangial cell migration (determined by Thy-1 staining). Mesangial cells at this time expressed TSP-1 but not Fn-EIIIA mRNA. TSP-1 protein and mRNA peaked in lesions at 48 hr and were associated with cell proliferation (determined by PCNA, alpha-smooth muscle actin phenotype, and expression of beta-PDGF receptor mRNA). TSP-1 expression declined at 72 hr when expression of ECM synthesis peaked, as determined by increased expression of collagen Type IV, laminin, and TGF-beta1 protein and mRNA. Mesangial cell expression of Fn-EIIIA was first observed at 48 hr and was most abundant at 72 hr after HV. Therefore, platelet- and macrophage-derived Fn-EIIIA and TSP-1 in early lesions are associated with mesangial cell migration. Mesangial cell upregulation of TSP-1 is associated with migration and proliferation but not maximal ECM accumulation, whereas mesangial cell expression of Fn-EIIIA is associated with proliferation and ECM accumulation. These results suggest distinctive temporal and spatial roles for TSP-1 and Fn-EIIIA in remodeling during glomerular disease. (J Histochem Cytochem 47:533-543, 1999)

Animals↗
PubMed1993

Effect of shear stress upon localization of the Golgi apparatus and microtubule organizing center in isolated cultured endothelial cells.

Despite substantial evidence to suggest that directed cell migration is dependent upon positioning of the Golgi apparatus (GA) and the microtubule organizing center (MTOC), some controversy exists about whether such a relationship is relevant to endothelial cells under flow. The present study was undertaken to provide an indepth investigation of the relationship between shear stress, GA/MTOC localization, cell migration and nuclear position. Bovine carotid endothelial cells were exposed to 22 or 88 dynes/cm2 for 0.5, 2, 8 or 24 h, and localization of their GA/MTOCs was determined relative to the direction of flow. In no-flow control specimens, (0, 0.5, 2, 8 and 24 h) there was no change in the equally distributed GA/MTOCs. In contrast, during the first 8 h at 88 dynes/cm2 and by 2 h at 22 dynes/cm2 there was a significant increase in the number of cells with GA/MTOCs localized upstream to flow direction. The effect was temporary, however, and by 24 h there was no significant difference between the no-flow, 22 and 88 dynes/cm2 specimens. Analysis of GA/MTOC localization with respect to the direction of cell migration determined that 72.5% of no-flow cells possessed GA/MTOCs localized to the sides of nuclei nearest the direction of migration. In contrast, 64% of the specimens shear stressed over the same time period had GA/MTOCs localized to the sides of nuclei opposite the direction of migration. These results suggest that positioning of the GA/MTOC in endothelial cells is not dependent completely upon the direction of migration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Variations in interstate migration of men across the early stages of the life cycle.

The results reported here show that the stage of an individual's life cycle not only has direct effects on the likelihood of migration, but also establishes a context within which the motives to migrate are evaluated and acted upon. One contextual impact of the life cycle concerns the effects of length of residence on migration. The results show that the probability of migrating declines more rapidly over time for married males with children than for singles males--i.e., the difference between the likelihood of migration for single males and married males with children widens with increasing length of residence. Much of this difference may be due to the greater number and strength of community ties for individuals who are married with children. These ties are not well developed at the beginning of a residence but continue to strengthen over the course of a residence. In addition, there are variations in the levels of job rewards and location-specific resources across the life cycle and there are two variations across the early life cycle in the effects of independent variables on the initial rate of migration. One resource (self-employment) and one job reward (prestige) have different effects for single individuals than for either group of married males. If the span of the life cycle considered in this analysis were broadened to include older men, additional differences in the effects of independent variables might be uncovered. In research with cross-sectional data containing a wider range of ages than the data used here, Heaton et al. (1981) found that economic variables were more important in determining the migration of younger individuals than that of older individuals, whereas noneconomic factors were more important determinants of the migration of older than of younger individuals. The results of this paper and Heaton's results suggest that at different stages of life people use a somewhat different "subjective cost-benefit calculus" in making migration decisions. The importance of certain migration determinants may vary significantly depending on whether an individual is married, whether he or she has children, and/or whether he or she is in the labor force or retired. Additional research on these issues could greatly contribute to our understanding of migration.

Adult↗
PubMed1982

Biochemistry of the cervical and endometrial content for the study of spermatic migration in sterile women.

We have reviewed the action of various substances contained in the cervix and endometrium, which are normally present and which can stimulate spermatic migration. We consider that the investigation is fundamental in certain pathological cases, especially concerning the study of the cervical factor and of certain cases of sterility without apparent cause, since they can indicate the etiology of sterility. The application of certain pharmacological substances, both of hormonal and non hormonal nature, can reestablish this balance and, with the recovery of spermatic migration, determine the ascent of the male gamete and render its encounter with the female gamete possible.

Ascorbic Acid↗
PubMed1994

The role of guided tissue regeneration and guided bone regeneration.

The goal of periodontal therapy includes not only the halting of the progressive loss of connective tissue attachment but also the restitution of those parts of the supporting apparatus which have been destroyed. The cells which repopulate this area may originate from any number of the different tissue components of the periodontium: the dentogingival epithelium, the gingival connective tissue, the alveolar bone, and the periodontal ligament (PDL). The size and shape of the wound and the potential of the different types of tissues cells to migrate, determines the type of healing. Previous studies have revealed that root resorption was found to occur when granulation tissue derived from the gingival connective tissue or alveolar bone was proliferating into contact with the root surface, while re-epithelialization of the surface prevented both connective tissue attachment and root resorption. The only cells which appear to have the capacity to form a new attachment were cells originating from the PDL. Based on this knowledge of the biological behaviour of the different periodontal tissues during wound healing, the principle of Guided Tissue Regeneration (GTR) was introduced and tested. A membrane section was placed over the debrided root surface in such a way that all periodontal tissues except the PDL cells were prevented from reaching contact with the root. Healing resulted in extensive amounts of new connective tissue attachment, that is, the formation of new cementum with inserting collagen fibres. The objective was, and is, assessment of how predictably new attachment may form when treatment included GTR.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar Bone Loss↗
PubMed1998

Migration of electrons and holes in crystalline d(CGATCG)-anthracycline complexes X-irradiated at 4 K.

Electrons and holes generated in irradiated DNA migrate to stable trapping sites. Protonation and deprotonation reactions at these sites promote the trapping of electrons and holes, thereby inhibiting further migration. The extent of migration determines the final distribution of damage in irradiated DNA. In this study, electron and hole migration is investigated in a crystalline DNA hexamer intercalated with an anthracycline drug. The intercalator is no further than 2 base pairs away from any DNA base. From EPR measurements, there is no evidence of DNA-centered radicals in the irradiated DNA hexamer. The aromatic region of the anthracycline intercalator evidently sequesters most or all of the electrons and most of the holes. Further hole trapping and radical stabilization appear to occur on the anthracycline's amino sugar group, which is nestled in the minor groove of the hexamer. The relatively large yield of this proposed amino sugar radical suggests that holes generated in the DNA solvation shell migrate to the amino sugar, where they become trapped. This would be the first observation of a radical formed by the direct effect of low-dose, low-LET radiation that is trapped within the DNA helix, yet lies outside of the stacked bases. With respect to holes generated in the DNA bases at 4 K, we conclude that most, if not all, are capable of migrating to an intercalator < or = 2 base pairs away. With respect to dry electrons, we conclude that anthracycline competes effectively for electron trapping over a region of at least 2 base pairs; our experiments cannot distinguish between electron attachment to the bases followed by transfer to the intercalator and direct attachment to the intercalator.

Animals↗