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H Gould

Publications and source records attributed to H Gould.

At least 19 recordsLinked to original sources
PubMed2000

Clusters and fluctuations at mean-field critical points and spinodals

We show that the structure of the fluctuations close to spinodals and mean-field critical points is qualitatively different from the structure close to non-mean-field critical points. This difference has important implications for many areas including the formation of glasses in supercooled liquids. In particular, the divergence of the measured static structure function in near-mean-field systems close to the glass transition is suppressed relative to the mean-field prediction in systems for which a spatial symmetry is broken.

Journal Article↗
PubMed2000

Local synthesis of epsilon germline gene transcripts, IL-4, and IL-13 in allergic nasal mucosa after ex vivo allergen exposure.

BACKGROUND: The production of epsilon germline gene transcripts (Iepsilon(+)/Cepsilon(+) RNA) precedes class switch recombination to IgE and is induced by IL-4 and/or IL-13. Although Iepsilon and Cepsilon RNA(+) B cells have been identified within nasal tissue after in vivo allergen exposure, suggesting local germline transcription, whether these were resident or infiltrating B lymphocytes was not clear. OBJECTIVE: We sought to examine whether B cells resident to the nasal mucosa undergo epsilon germline transcription. METHODS: Nasal mucosal biopsy specimens were obtained from asymptomatic patients with seasonal allergic rhinitis and exposed to allergen ex vivo. Using immunocytochemistry, B lymphocytes were enumerated; with in situ hybridization, the number of cells expressing Iepsilon, Cepsilon, IL-4, and IL-13 messenger (m)RNA(+) cells was examined. RESULTS: Tissue cultured in medium containing specific allergen exhibited significantly more Iepsilon and Cepsilon RNA(+) cells compared with medium alone (P <.05). IL-4 and IL-13 mRNA synthesis also resulted from ex vivo allergen exposure; there were significantly more cells expressing transcripts for these cytokines within allergic nasal mucosal tissue cultured with allergen than medium alone (P <.05). Within allergen-stimulated tissue obtained from allergic patients, 30% of total B cells were Iepsilon RNA(+), and the majority of IL-4 and IL-13 mRNA(+) cells were T cells (68% and 44%, respectively) and mast cells (32% and 19%, respectively). CONCLUSION: These results demonstrate that the nasal mucosa is a site of epsilon germline gene transcription and suggest that local T cell and mast cell production of IL-4 and IL-13 may regulate this event.

Allergens↗
PubMed2000

Cluster monte carlo study of multicomponent fluids of the stillinger-helfand and widom-rowlinson type

Phase transitions of fluid mixtures of the type introduced by Stillinger and Helfand are studied using a continuum version of the invaded cluster algorithm. Particles of the same species do not interact, but particles of different types interact with each other via a repulsive potential. Examples of interactions include the Gaussian molecule potential and a repulsive step potential. Accurate values of the critical density, fugacity, and magnetic exponent are found in two and three dimensions for the two-species model. The effect of varying the number of species and of introducing quenched impurities is also investigated. In all the cases studied, mixtures of q species are found to have properties similar to q-state Potts models.

Journal Article↗
PubMed1999

Expression of CD21 is developmentally regulated during thymic maturation of human T lymphocytes.

CD21, the C3d/CD23/Epstein-Barr virus (EBV), receptor is expressed at low density on cells of the T lineage. Immature thymocytes express CD21 with high density. In the present study, we have analyzed the expression of CD21 during intrathymic maturation of T cells. An intense staining for CD21 was observed at the double-negative stage and at the stage of early acquisition of CD4. CD21 expression was decreased at the double-positive and single-positive stages, to then reach levels similar to those of peripheral blood T cells. Staining of thymus sections showed a bright fluorescent signal on thymocytes entering the thymus in the cortical region. Taking advantage of the immature phenotype of cells expressing high amounts of CD21 (CD21(++)), we depleted thymocyte suspensions in CD3(+) and CD8(+) cells to study the properties of CD21 on this cell subset. Triggering of CD21 with its ligands iC3b, CD23 and anti-CD21 mAb did not alter the proliferative response of thymocytes to IL-7, and did not induce the differentiation of early cells into CD4(+)CD8(+) thymocytes. Immunoprecipitation did not reveal any molecule associated with CD21 that could play a signaling role in thymocytes. Finally, EBV induced a down-regulation of CD21 and an up-regulation of CD1 in CD21(++) thymocytes. Taken together, our observations demonstrate a regulated expression of CD21 on human thymocytes and suggest that the CD21(++) subset may be a target for EBV. We further suggest that CD21 on early thymocytes acts as a ligand for CD23-expressing cells in the thymus.

Cell Differentiation↗
PubMed1998

Alternate promoters and developmental modulation of expression of the chicken GATA-2 gene in hematopoietic progenitor cells.

We have isolated and characterized the chicken GATA-2 (cGATA-2) gene. We show that, as in the case of some other members of the GATA gene family, the gene is expressed from alternative first exons. One of the resulting mRNAs represents only a minor form of the GATA-2 mRNA in the cells and tissues we analyzed; the other is ubiquitously expressed. We have defined the minimal promoter that controls expression of this most abundant mRNA and that is necessary for full activity in hematopoietic progenitor cells. The activity of this promoter in transient assays is consistent with developmental differences of expression levels in these cells. We identify within the promoter a previously unrecognized extended CCAAT motif essential for its activity. The organization of the cGATA-2 gene, with alternative first exons and a CCAAT box in the proximal promoter, is similar to that recently described for mouse GATA-2, and the proximal promoter also resembles the only promoter so far described in Xenopus. Nonetheless, the roles of the promoters in development and tissue-specific expression are quite different in these organisms, most strikingly in the mouse, which assigns developmental roles to its proximal and distal promoters that are quite different from those in the chicken. We suggest that although the overall organization may remain the same, the role assigned to each promoter varies among organisms. We identify distant upstream regulatory elements in the cGATA-2 gene that modulate expression from the proximal promoter and that may be responsible for this variation.

Animals↗
PubMed1994

[Value of computerized tomography in diagnosis of small intestine injuries after blunt abdominal trauma].

Intestinal injury is increasing in frequency among persons sustaining blunt abdominal trauma, and the consequences of delayed recognition of intestinal injuries are serious. This critical retrospective analysis evaluates the role for CT in the diagnosis of blunt abdominal trauma, including hollow visceral injury. CT scan, when used in conjunction with a history emphasizing the mechanism of injury and a careful physical examination, is highly accurate in detecting small bowel injuries. CT is less helpful in distinguishing between different types of small bowel injury. Intestinal wall thickening with low-density fluid in the abdominal cavity strongly suggests rupture. Until further experience is gained with CT, free intraperitoneal fluid in the absence of solid organ injury should be regarded as an indication for exploratory laparotomy.

Abdominal Injuries↗
PubMed1993

Tube thoracostomy for occult pneumothorax: a prospective randomized study of its use.

Occult pneumothorax is defined as a pneumothorax that is detected by abdominal computed tomographic (CT) scanning, but not routine supine screening chest roentgenograms. Forty trauma patients with occult pneumothorax were prospectively randomized to management with tube thoracostomy (n = 19) or observation (n = 21) without regard to the possible need for positive pressure ventilation, to test the hypothesis that tube thoracostomy is unnecessary in this entity. Eight of the 21 patients observed had progression of their pneumothoraces on positive pressure ventilation, with three developing tension pneumothorax. None of the patients with tube thoracostomy suffered major complications as a result of the procedure. Hospital and ICU lengths of stay were not increased by tube thoracostomy. Patients with occult pneumothorax who require positive pressure ventilation should undergo tube thoracostomy.

Adolescent↗
PubMed1992

Developmental regulation of globin gene expression.

We have used the globin family of genes in chicken to study developmental regulation of gene expression, both at the level of individual interaction of trans-acting factors with local promoters and enhancers, and at the level of chromatin structure. Regulation of all members of the alpha- and beta-globin clusters is affected by the erythroid regulatory factor GATA-1. Separate mechanisms exist for regulation of individual members of the family. As an example, we describe the control mechanisms that play a role in the expression of the rho-globin gene, which is expressed only in primitive lineage erythroid cells. In addressing the involvement of chromatin structure in gene activation, we have examined the role of locus control elements, and also considered the way in which RNA polymerase molecules might accommodate to the presence of nucleosomes on transcribed genes.

Animals↗
PubMed1991

Structure and promoter activity of the gene for the erythroid transcription factor GATA-1.

We have cloned the gene for the chicken erythroid transcription factor GATA-1 (formerly Eryf1, NF-E1, or GF-1). The gene is composed of six exons, two of which encode the two finger domains of the protein. Transcription of GATA-1 in chicken embryonic erythroid cells initiates from multiple sites clustered approximately 200 base pairs upstream from the start of protein-coding sequence. A number of sequence motifs for known DNA-binding proteins are found to be protected in DNase I-footprinting experiments by either erythroid or brain nuclear extracts or by both. Notably, a cluster of three GATA-1 sites is protected by the erythroid extract, as well as by purified GATA-1. We find that the upstream region of the gene functions as a powerful promoter when transfected into embryonic erythroid cells. In primary chicken embryo fibroblasts the promoter exhibits lower activity, which is increased when the cells are cotransfected with a second plasmid expressing the GATA-1 cDNA. The results suggest that GATA-1 protein plays an autoregulatory role in its own expression.

Animals↗
PubMed1991

Purification and characterization of Ku-2, an octamer-binding protein related to the autoantigen Ku.

The octamer motif (ATTTGCAT) is an important regulatory element in eukaryotic gene expression. A previously unidentified protein that recognizes this motif has been isolated from the human B cell line, Daudi. The protein, which we term Ku-2, bears a close resemblance to the DNA-binding autoantigen Ku. Like Ku, it is a heterodimer with subunits of 83 and 72 kDa; antisera raised against either subunit of Ku cross-react with Ku-2. Two peptides have been sequenced and show a strong similarity to regions in the corresponding subunits of Ku. The sequences are not identical, however, suggesting that Ku-2 may be a B cell homologue of Ku. Both Ku and Ku-2 bind to the termini of DNA duplexes, but Ku-2 also binds to an internal octamer motif. It is not known whether Ku shares the latter property or whether the octamer binding is a consequence of sequence differences between the two proteins. Ku-2 does not react with antisera against the POU domain of the octamer-binding protein Oct-2, indicating that the DNA binding domains of the two proteins are dissimilar despite the ability of both to bind to the octamer motif. We discuss the evidence for the existence of a family of octamer-binding proteins related to Ku.

Amino Acid Sequence↗