Biomedical subjects

D Lawson

Publications and source records attributed to D Lawson.

At least 19 recordsLinked to original sources

PubMed2002

Sequence of Plasmodium falciparum chromosomes 1, 3-9 and 13.

Since the sequencing of the first two chromosomes of the malaria parasite, Plasmodium falciparum, there has been a concerted effort to sequence and assemble the entire genome of this organism. Here we report the sequence of chromosomes 1, 3-9 and 13 of P. falciparum clone 3D7--these chromosomes account for approximately 55% of the total genome. We describe the methods used to map, sequence and annotate these chromosomes. By comparing our assemblies with the optical map, we indicate the completeness of the resulting sequence. During annotation, we assign Gene Ontology terms to the predicted gene products, and observe clustering of some malaria-specific terms to specific chromosomes. We identify a highly conserved sequence element found in the intergenic region of internal var genes that is not associated with their telomeric counterparts.

Animals↗

PubMed2002

Image cytometric bcl-2:bax and bcl-2:bcl-x ratios in invasive breast carcinoma: correlation with prognosis.

BACKGROUND: The bcl-2 family of proteins are important regulators of apoptosis. Some of the members, such as bcl-2 and bcl-x(L), inhibit cell death, whereas others, such as bax and bcl-x(S), promote cell death. We evaluated the ratios of bcl-2:bax and bcl-2:bcl-x expression by image cytometry in invasive breast carcinoma to determine prognostic significance. DESIGN: Five-micron sections of formalin-fixed, paraffin-embedded tissue from 88 invasive breast carcinomas were immunostained using steam antigen retrieval, an avidin biotin-complex technique with automated stainer and primary antibodies against bcl-2 (1/160; Dako, Carpenteria, CA), bax (1/1,500; PharMingen, San Diego, CA), and bcl-x (1/1,500; PharMingen). Positive controls were tonsil (bcl-2) and normal breast (bax and bcl-x) tissue samples. Immunostain was measured in 15 high power fields as percentage positive area (PPA) in nuclei and cytoplasm using the CAS 200 image analyzer (Becton Dickinson, San Jose, CA). RESULTS: Median follow-up was 105 months (range 11-130). Significantly improved disease-free survival was found in patients with a bcl-2:bcl-x ratio > or = 1 by univariate and multivariate analyses. The bcl-2:bax ratio was not predictive of overall or disease-free survival. A significant difference in overall and disease-free survival was found between carcinomas with positive and negative bcl-2 expression by univariate analysis; by multivariate analysis, bcl-2 expression was an independent prognostic factor for disease-free survival. The 5-year survival rates were 77% and 50% in patients with bcl-2-positive and bcl-2-negative carcinomas, respectively. CONCLUSION: A bcl-2:bcl-x ratio > or = 1, assessed by image cytometry, is significantly associated with improved disease-free survival in patients with invasive breast carcinoma. Significantly increased overall and disease-free survival is associated with positive bcl-2 expression.

Adult↗

PubMed2002

Serotonergic system and attention deficit hyperactivity disorder (ADHD): a potential susceptibility locus at the 5-HT(1B) receptor gene in 273 nuclear families from a multi-centre sample.

Attention deficit hyperactivity disorder (ADHD) is a highly heritable and heterogeneous disorder, which usually becomes apparent during the first few years of childhood. Imbalance in dopamine neurotransmission has been suggested as a factor predisposing to ADHD. However, evidence has suggested an interaction between dopamine and serotonin systems in the pathophysiology of the disorder. Studies using selective agonists of the different 5-HT receptors microinjected into selected brain structures have shown a positive modulating effect on the functional activities of the mesotelencephalic dopaminergic system. This suggests that some of the genetic predisposition to ADHD might be due to DNA variation at serotonin system genes. In this study, we investigated polymorphisms in HTR(1B) and HTR(2A) (which encode the serotonin receptors 5-HT(1B) and 5-HT(2A) respectively) in a European ADHD sample. Using haplotype based haplotype relative risk (HHRR) and transmission disequilibrium test (TDT) analyses, we observed significant preferential transmission of the allele 861G of the HTR(1B) in the total sample (for HHRR; chi(2) = 7.4, P = 0.0065 and TDT; (chi(2) = 6.4, P = 0.014). Analysis of HTR(2A) failed to reveal evidence of association or linkage between the His452Tyr polymorphism and ADHD in the total sample. However, a significantly increased transmission of the allele 452His was observed in the Irish sample alone (chi(2) = 4.9, P = 0.026). These preliminary data suggest an important role for the serotonin system in the development of ADHD. Further studies, preferentially including different ethnic groups are required to substantiate these findings.

Attention Deficit Disorder with Hyperactivity↗

PubMed2002

Hepatocellular carcinoma and markers of apoptosis (bcl-2, bax, bcl-x): prognostic significance.

Patients with tumors expressing promoters of apoptosis (bax) versus inhibitors of apoptosis (bcl-2, bcl-x) may have increased survival. The purpose of this study was to determine the frequency of expression of apoptotic markers in hepatocellular carcinoma (HCC) and their relationship with prognosis. Seventy HCC were immunostained for bcl-2, bax, and bcl-x. Staining intensity in tumor cells was graded 0 to 3+. Follow-up data were available for mean survival (57 cases) and death rates (58 cases). These values and clinical parameters were related to prognosis. Staining frequency for bcl-2, bax, and bcl-x was 20%, 66%, and 60%, respectively. Immunostaining intensity of bax correlated with overall survival and death rates: of 57 patients, the 37% with 0 to 1+ intensity had a median survival of 6.6 months, the 63% with 2 to 3+ intensity had a median survival of 31.9 months (P = 0.05); 86% of 19 patients with 0 to 1+ intensity died, and 50% of 36 patients with 2 to 3+ intensity died (P < 0.05). Intensity of bcl-x staining tended to correlate with survival: of the 57 patients with 0 to 1+, 42% had a median survival of 32.7 months compared with 5.8 months in the 58% with 2 to 3+ intensity (P = 0.06). By multivariate analysis, this relationship held for bax (P = 0.011) and bcl-x (P = 0.048). There was no correlation between bcl-2 expression, stage, or gender and prognosis. Patients with bax-expressing HCC experience improved survival compared with those with no or low bax expression, in uni- and multivariate models. Patients with no or low bcl-x tended toward improved survival compared with patients with more bcl-x in their HCC. bcl-2 expression did not correlate with prognosis.

Adult↗

PubMed2001

A nuclear SH3 domain-binding protein that colocalizes with mRNA splicing factors and intermediate filament-containing perinuclear networks.

A protein (SNP70) has been isolated that binds to the Src homology domain 3 of p47(phox), p85alpha, and c-src. Cloning and sequencing of the polypeptide revealed it to be a 70-kDa protein that has a number of potential domains, including Src homology 3 binding motifs and several nuclear localization signals. Immunofluorescence using anti-peptide antibodies revealed SNP70 to be primarily concentrated in the nucleus but excluded from nucleoli, in interphase cells. However, it was distributed throughout the cytoplasm in dividing cells. Extraction and subfractionation experiments indicated that SNP70 did not bind directly to DNA but did bind to poly(G)-rich oligonucleotides and was resistant to extraction with non-ionic detergents but was solubilized by treatment with RNase, high salt, or ammonium sulfate. Double-immunofluorescence experiments showed that SNP70 co-localized with two pre-mRNA splicing factors SC35 and U2B" within the nucleus. A population of SNP70 was found outside the nucleus, and double-immunofluorescence and immunoelectron microscopy demonstrated that it associated with vimentin-containing intermediate filaments, particularly those surrounding the nucleus. The data suggest that SNP70 associates with nuclear or perinuclear filaments and may play a role in the regulation of pre-mRNA processing.

Amino Acid Sequence↗

PubMed2001

Gene discovery in Plasmodium chabaudi by genome survey sequencing.

The first genome survey sequencing of the rodent malaria parasite Plasmodium chabaudi is presented here. In 766 sequences, 131 putative gene sequences have been identified by sequence similarity database searches. Further, 7 potential gene families, four of which have not previously been described, were discovered. These genes may be important in understanding the biology of malaria, as well as offering potential new drug targets. We have also identified a number of candidate minisatellite sequences that could be helpful in genetic studies. Genome survey sequencing in P. chabaudi is a productive strategy in further developing this in vivo model of malaria, in the context of the malaria genome projects.

Amino Acid Sequence↗

PubMed2001

A 6.9-Mb high-resolution BAC/PAC contig of human 4p15.3-p16.1, a candidate region for bipolar affective disorder.

Bipolar affective disorder (BPAD) is a complex disease with a significant genetic component and a population lifetime risk of 1%. Our previous work identified a region of human chromosome 4p that showed significant linkage to BPAD in a large pedigree. Here, we report the construction of an accurate, high-resolution physical map of 6.9 Mb of human chromosome 4p15.3-p16.1, which includes an 11-cM (5.8 Mb) critical region for BPAD. The map consists of 460 PAC and BAC clones ordered by a combination of STS content analysis and restriction fragment fingerprinting, with a single approximately 300-kb gap remaining. A total of 289 new and existing markers from a wide range of sources have been localized on the contig, giving an average marker resolution of 1 marker/23 kb. The STSs include 57 ESTs, 9 of which represent known genes. This contig is an essential preliminary to the identification of candidate genes that predispose to bipolar affective disorder, to the completion of the sequence of the region, and to the development of a high-density SNP map.

Bipolar Disorder↗

PubMed2001

Differential modulation of sodium channel gating and persistent sodium currents by the beta1, beta2, and beta3 subunits.

Brain sodium channels are complexes of a pore-forming alpha subunit with auxiliary beta subunits, which are transmembrane proteins that modulate alpha subunit function. The newly cloned beta3 subunit is shown to be expressed broadly in neurons in the central and peripheral nervous systems, but not in glia and most nonneuronal cells. Beta1, beta2, and beta3 subunits are coexpressed in many neuronal cell types, but are differentially expressed in ventromedial nucleus of the thalamus, brain stem nuclei, cerebellar Purkinje cells, and dorsal root ganglion cells. Coexpression of beta1, beta2, and beta3 subunits with Na(v)1.2a alpha subunits in the tsA-201 subclone of HEK293 cells shifts sodium channel activation and inactivation to more positive membrane potentials. However, beta3 is unique in causing increased persistent sodium currents. Because persistent sodium currents are thought to amplify summation of synaptic inputs, expression of this subunit would increase the excitability of specific groups of neurons to all of their inputs.

Animals↗

PubMed2001

Presence of carotenoid, an anticarcinogenic marker, in nipple aspirates postlactation.

Case-controlled studies have identified a protective effect of lactation against breast cancer; however, little is known about the nature of this protective mechanism. The purpose of this study was to examine postweaned, nipple aspirate fluid (NAF) from women, ages 18 to 45, for carotenoid, a known antioxidant and anticarcinogenic marker, and compare carotenoid availability in NAF with that reported in colostrum. Women who had lactated at least 6 months and weaned for at least 6 months were recruited into the study A prestudy and poststudy serum prolactin level was obtained. NAF was obtained through a nipple aspirator method. Total carotenoid ranged from 0.4 to 4.0 microg/mL, with a mean level of 1.9+/-1.2 (SD). Women who had weaned earlier (<12mo) had significantly more carotenoids than those who had lactated longer (>12mo) (P = 0.04). These levels were similar to those known to occur in colostrum. This research elucidates possible mechanisms of the protective effect of lactation on the microenvironment of the breast.

Adolescent↗

PubMed2001

Genomic structure and localisation within a linkage hotspot of Disrupted In Schizophrenia 1, a gene disrupted by a translocation segregating with schizophrenia.

Two overlapping and antiparallel genes on chromosome 1, Disrupted In Schizophrenia 1 and 2 (DISC1 and DISC2), are disrupted by a (1;11)(q42.1;q14.3) translocation which segregates with schizophrenia through at least four generations of a large Scottish family. Consequently, these genes are worthy of further investigation as candidate genes potentially involved in the aetiology of major psychiatric illness. We have constructed a contiguous clone map of PACs and cosmids extending across at least 400 kb of the chromosome 1 translocation breakpoint region and this has provided the basis for examination of the genomic structure of DISC1. The gene consists of thirteen exons, estimated to extend across at least 300 kb of DNA. The antisense gene DISC2 overlaps with exon 9. Exon 11 contains an alternative splice site that removes 66 nucleotides from the open reading frame. The final intron of DISC1 belongs to the rare AT-AC class of introns. We have also mapped marker DIS251 in close proximity to DISC1, localising the gene within a critical region identified by several independent studies. Information regarding the structure of the DISC1 gene will facilitate assessment of its involvement in the aetiology of major mental illness in psychotic individuals unrelated to carriers of the translocation.

Cell Line↗

PubMed2001

Progesterone receptor immunohistochemical quantitation compared with cytosolic assay: correlation with prognosis in breast cancer.

Quantitation of estrogen and progesterone receptors (PR) represents the standard of care in the treatment of patients with breast cancer. Historically this was performed by cytosolic assay; current methods utilize immunohistochemical staining, which may be quantitated visually or by image cytometry. Formalin-fixed paraffin embedded sections from 95 breast carcinomas were immunostained with an avidin-biotin complex technique. steam antigen retrieval, and a monoclonal PR antibody (1/40 Biogenex). Nuclear immunostain was quantitated visually as the percentage of immunopositive nuclei, scored as 0 to 4. By image cytometry, the percentage of positively staining nuclear area (PPNA) was determined in 15 hpf using the CAS 200 Image Analyzer. Dextran-coated charcoal (DCC) ligand binding assay data were divided into negative (<10 fmol), low positive (10-50), or positive (>50). A statistically significant correlation was found between stage (P = 0.0001), the presence of nodal metastases (P = 0.0001), cytosolic assay (P = 0.036), image cytometry (P = 0.01), and disease-free survival. Only stage (P = 0.0001) and PR quantitation per cytosolic assay (P = 0.0001) correlated with overall survival. The method of choice for the assessment of PR hormone status in breast carcinomas is the DCC ligand binding assay. This method correlates with both survival and disease-free survival. Image cytometric quantitation of PR immunohistochemical staining correlates only with disease-free survival. The commonly used method of visual quantitation of PR immunostaining fails to relate either to survival or disease-free survival.

Breast Neoplasms↗

PubMed2000

Two residues in the T-loop of GlnK determine NifL-dependent nitrogen control of nif gene expression.

X-ray crystallographic analysis of the Escherichia coli P(II) protein paralogues GlnB and GlnK has shown that they share a superimposable structural core but can differ in conformation of the T-loop, a region of the protein (residues 37-54) that has been shown to be important for interaction with other proteins. In Klebsiella pneumoniae GlnK has been shown to have a clearly defined function in regulating NifL-mediated inhibition of NifA activity in response to the nitrogen status, and GlnB, when expressed from the chromosome, does not substitute for GlnK. Because the T-loops of K. pneumoniae and E. coli GlnB and GlnK differ at just three residues, 43, 52, and 54, we have used a previously constructed heterologous system, in which K. pneumoniae nifLA is expressed in E. coli, to investigate the importance of GlnK residues 43, 52, and 54 for regulation of the NifLA interaction. By site-directed mutagenesis of glnB we have shown that residue 54 is the single most important amino acid in the T-loop in the context of the regulation of NifA activity. Furthermore, a combination of just two changes, in residues 54 and 43, allows GlnB to function as GlnK and completely relieve NifL inhibition of NifA activity.

Amino Acid Substitution↗

PubMed2000

An evolutionarily conserved germ cell-specific hnRNP is encoded by a retrotransposed gene.

The gene encoding heterogeneous ribonucleoprotein (hnRNP) G recently has been mapped to the X chromosome. All mammals have a Y chromosome-encoded homologue of HNRNP G called RBMY, which is implicated with a role in male fertility and is a candidate for the azoospermia factor gene. We have identified a new member of this gene family, HNRNP G-T, and have mapped it as a single-copy gene on chromosome 11. This gene contains an uninterrupted open reading frame and no introns, consistent with derivation from a retroposon. However, unlike many retroposon-derived genes, HNRNP G-T is not a pseudogene. An antiserum raised to the conceptual reading frame of HNRNP G-T showed that it encodes a protein that is highly expressed in germ cells and in particular in the nuclei of meiotic spermatocytes. Surprisingly, although this antiserum was raised against human hnRNP G-T protein, it can also detect a similar protein in the testis of several mammals. This suggests that the protein is highly conserved and that the retrotransposition event generating the HNRNP G-T gene pre-dated at least the common ancestor of mouse and man. The existence of an additional testis-specific hnRNP G family member provides evidence for the importance of these proteins in normal germ cell development.

Amino Acid Sequence↗

PubMed2000

Long-term (three years) effect of estrogen replacement therapy on major adverse cardiac events in postmenopausal women after intracoronary stenting.

This study examined whether estrogen replacement therapy (ERT) in postmenopausal women impacts intermediate and long-term outcome after successful coronary stenting. Our findings offer evidence that ERT significantly reduces target lesion revascularization after intracoronary stenting in postmenopausal patients who are on ERT before the intervention.

Angioplasty, Balloon, Coronary↗

PubMed2000

A novel nervous system beta subunit that downregulates human large conductance calcium-dependent potassium channels.

The pore-forming alpha subunits of many ion channels are associated with auxiliary subunits that influence channel expression, targeting, and function. Several different auxiliary (beta) subunits for large conductance calcium-dependent potassium channels of the Slowpoke family have been reported, but none of these beta subunits is expressed extensively in the nervous system. We describe here the cloning and functional characterization of a novel Slowpoke beta4 auxiliary subunit in human and mouse, which exhibits only limited sequence homology with other beta subunits. This beta4 subunit coimmunoprecipitates with human and mouse Slowpoke. beta4 is expressed highly in human and monkey brain in a pattern that overlaps strikingly with Slowpoke alpha subunit, but in contrast to other Slowpoke beta subunits, it is expressed little (if at all) outside the nervous system. Also in contrast to other beta subunits, beta4 downregulates Slowpoke channel activity by shifting its activation range to more depolarized voltages and slowing its activation kinetics. beta4 may be important for the critical roles played by Slowpoke channels in the regulation of neuronal excitability and neurotransmitter release.

Amino Acid Sequence↗

PubMed2000

Mutational analysis of the Wolfram syndrome gene in two families with chromosome 4p-linked bipolar affective disorder.

Bipolar affective disorder (BPAD) is a complex disease with a significant genetic component. Heterozygous carriers of Wolfram syndrome (WFS) are at increased risk of psychiatric illness. A gene for WFS (WFS1) has recently been cloned and mapped to chromosome 4p, in the general region we previously reported as showing linkage to BPAD. Here we present sequence analysis of the WFS1 coding sequence in five affected individuals from two chromosome 4p-linked families. This resulted in the identification of six polymorphisms, two of which are predicted to change the amino acid sequence of the WFS1 protein, however none of the changes segregated with disease status. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:158-160, 2000.

Bipolar Disorder↗

PubMed2000

Bcl-2: bax and bcl-2: Bcl-x ratios by image cytometric quantitation of immunohistochemical expression in ovarian carcinoma: correlation with prognosis.

Bcl-2 is a proto-oncogene which is involved in prolonging cell survival by inhibiting programmed cell death. Bax and bcl-x are members of the bcl-2 family; when overexpressed, they can counteract the ability of bcl-2 to inhibit apoptosis. This suggests a model in which the ratios of bcl-2 to bax and bcl-x can be used to determine response to therapy and prognosis. The expression of bcl-2, bax and bcl-x was studied in 50 ovarian carcinomas. The percentage of positive area immunostained (PPA) in the nucleus and cytoplasm of each ovarian carcinoma was quantitated in 15 high power fields by image cytometry. The ratios were obtained by dividing the PPA of bcl-2 by the PPA of bax and bcl-x. 17 of 50 ovarian carcinomas (34%) stained positively for bcl-2, 39 for bax (78%) and 47 for bcl-x (94%). Although there is no significant statistical correlation between expression of bcl-2, bax or bcl-x and grade (P = 0.15; P = 0. 47; P = 0.56), stage (P = 0.71; P = 0.6; P = 0.42), and overall or disease-free survival (P = 0.26; P = 0.55; P = 0.16), increased bcl-2 expression was demonstrated in patients with shortened overall and disease-free survival. Also, increased expression of bax and bcl-x was associated with increased overall and disease-free survival. Bcl-2:bax and bcl-2:bcl-x ratios less than 1 are associated with survival advantage, although not statistically significant (P = 0.83; P = 0.93). Image cytometric measurement of bcl-2, bax, and bcl-x expression is feasible. There is a tendency for their expression to correlate with prognosis in ovarian carcinomas.

Carcinoma↗

PubMed2000

Use of a novel marker, calponin, for myoepithelial cells in fine-needle aspirates of papillary breast lesions.

Benign and malignant papillary lesions of the breast (PBL) can be difficult to distinguish in fine-needle aspirates (FNA). This study evaluates the use of smooth muscle actin (SMA) and a new smooth muscle-specific protein, calponin, for identifying myoepithelial cells (MEC) by immunohistochemical methods in paraffin-embedded cell blocks of FNA of PBL. Formalin-fixed, paraffin-embedded cell blocks of 40 cases of PBL were stained using SMA and calponin, steam heat-induced epitope retrieval, and an avidin biotin-complex technique. Staining was evaluated in MEC, epithelial, and stromal cells. The diagnosis of benign vs. malignant papillary lesion was made by using cytomorphological criteria and the presence/absence of MEC in the cell block. These results were compared to the original cytologic and subsequent histologic diagnoses. Of 40 cases of FNA diagnosed as PBL, there were 27 intraductal papillomas (IP), 6 papillary lesions with atypical features (PLAF), and 7 papillary carcinomas (PC). In all of the IP, MEC stained both with SMA and calponin. None of the PC cases was positive for MEC with calponin, and 2 out of 7 cases were weakly positive by SMA. In 6 cases of PLAF, 2 were negative for MEC, both by SMA and calponin, and a malignant papillary lesion was confirmed by histology. The remaining 4 cases were positive for MEC with both markers and were confirmed to be benign by histology. SMA stained stromal cells strongly in all of the cases where stroma was present (18 of a total of 40 cases of PBL), while calponin stained stroma focally in only 7 cases. More than half of all cases had nuclear staining of epithelial cells with SMA; calponin did not show any nuclear staining.

Actins↗