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B Tiwari

Publications and source records attributed to B Tiwari.

9 recordsLinked to original sources
PubMed2001

CD2F-10: a new member of the CD2 subset of the immunoglobulin superfamily.

The CD2 subset of the immunoglobulin superfamily consists of a rapidly expanding family of leukocyte cell surface receptors, at least five of which (CD2, CD48, CD58, CD150, and CD244) are involved in lymphocyte activation as either receptors or ligands. Completion of the draft sequence of the human genome offers the possibility of systematically identifying the full set of proteins and interactions of this important family. Here we describe the identification and characterization of the first new member of the subset, CD2F-10, found exclusively by genome searching.

Amino Acid Sequence↗
PubMed1999

Virulence and transmission success of the malarial parasite Plasmodium falciparum.

Virulence of Plasmodium falciparum is associated with the expression of variant surface antigens designated PfEMP1 (P. falciparum erythrocyte membrane protein 1) that are encoded by a family of var genes. Data presented show that the transmission stages of P. falciparum also express PfEMP1 variants. Virulence in this host-parasite system can be considered a variable outcome of optimizing the production of sexual transmission stages from the population of disease-inducing asexual stages. Immunity to PfEMP1 will contribute to the regulation of this trade-off by controlling the parasite population with potential to produce mature transmission stages.

Animals↗
PubMed1999

Identification of altered DNA-protein interactions at the lamin A proximal promoter in quiescent hepatocytes.

The nuclear lamina of differentiated cells is composed of A-type and B-type lamins. The expression of the A-type lamins has been shown to be primarily under transcriptional control in proliferating cells. In order to gain insights into the factors involved in downregulation of the promoter in quiescent cells, we have compared the DNA-protein interactions at the rat lamin A proximal promoter in fetal (dividing) hepatocytes and adult (quiescent) hepatocytes by DNase I footprinting analysis, electrophoretic mobility shift assays and UV crosslinking experiments. We have identified proteins from adult hepatocyte nuclear extracts that are bound to sequences within 28 bp downstream of the transcription initiation site (62 and 48 kDa proteins) and within 20 bp upstream of the initiation site (54 kDa protein), which may function as transcriptional repressors of the lamin A proximal promoter.

Adaptor Protein Complex alpha Subunits↗
PubMed1998

Functional analysis of the 5' promoter region of the rat lamin A gene.

The A-type lamins are constituents of the nuclear lamina in differentiated cells and have been proposed to play an important role in nuclear organization. In this study, we isolated and characterized a genomic clone containing the putative promoter region of the rat lamin A gene. Sequence analysis of about 2 kb of this region combined with primer extension data revealed the presence of a TATA box at -33, a GC box at -101, and AP1 motifs at -7, -424, and -1677. Deletion analysis of the promoter fragments in three mammalian cell lines indicated that a 221-bp segment of the proximal promoter containing the GC box and AP1 motif at -7 was sufficient to give high levels of luciferase activity in reporter gene assays. Mutations in these two motifs resulted in considerable loss of reporter gene activity. Analysis by electrophoretic mobility shift assays (EMSAs) has provided evidence for specific binding of the AP1 and Sp1 family of transcription factors to the promoter, a conclusion supported by DNase I footprinting data. This characterization of the 5' promoter region of the lamin A gene should afford a basis for the further clarification of the mechanism of regulation of this important gene during growth and development.

Animals↗
PubMed1997

AgNOR expression in CNS neoplasms.

Silver colloid staining of nucleolar organiser regions (AgNORs) is used for assessing the proliferative potential of tumours. The present study aimed at evaluating the AgNOR indices in normal and reactive CNS tissue, benign and malignant CNS neoplasms. The study group comprised of tissue from 22 controls and 100 cases (53 benign & 47 malignant neoplasms). The mean AgNOR index of controls was 0.95, benign neoplasms 1.25 and malignant neoplasms 2.12. A statistically significant difference was observed in controls and cases (p < 0.001) and between benign and malignant tumours (p = 0.002). Mean indices for low and high grade astrocytoma also significantly differed (p < 0.001). Using ROC curves cut off values were obtained for differentiation of neoplastic from non neoplastic (AgNOR index 1.10), benign from malignant (AgNOR index 1.75) and low grade (I & II) from anaplastic (Gr III & IV) Astrocytomas (AgNOR index 1.62). A spectrum of gradually increasing AgNOR indices from normal, reactive, benign to low and high grade malignancy indicates the usefulness of this simple technique as a proliferative marker.

Astrocytoma↗
PubMed1993

The isolation of molecular genetic markers for the identification of sex.

It is difficult to identify sex in many species of eukaryotic organism. This can considerably impede research into their biology. Fortunately, one sex often possesses a unique chromosome termed Y or W. When DNA markers are available for these chromosomes, then sex identification becomes straightforward. We describe a technique that facilitates the isolation of such markers. The procedure makes use of low-stringency PCR to screen randomly selected primers for their ability to amplify sex-specific loci.

Animals↗
PubMed1992

The identification of sex in the starling Sturnus vulgaris using a molecular DNA technique.

Female birds can be identified through the presence of a W-chromosome. We describe a procedure for amplifying a W-linked DNA marker in the starling (Sturnus vulgaris) by the polymerase chain reaction (PCR) so allowing the diagnosis of sex in this species. The technique is sensitive, allowing even the smallest chicks to be sexed from a blood sample. The method possesses a positive internal control to ensure accuracy. It is also applicable to the spotless starling (S. unicolor) but not to two bird species outside the genus. The nucleotide sequence of the female-specific PCR product is given.

Animals↗