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Biomedical subjects

D Lawson

Publications and source records attributed to D Lawson.

At least 55 records · Page 3Linked to original sources

Characterization of a chromosome-specific chimpanzee alpha satellite subset: evolutionary relationship to subsets on human chromosomes.

Alpha satellite DNA is a tandemly repeated DNA family found at the centromeres of all primate chromosomes examined. The fundamental repeat units of alpha satellite DNA are diverged 169- and 172-bp monomers, often found to be organized in chromosome-specific higher-order repeat units. The chromosomes of human (Homo sapiens (HSA)), chimpanzee (Pan troglodytes (PTR) and Pan paniscus), and gorilla (Gorilla gorilla) share a remarkable similarity and synteny. It is of interest to ask if alpha satellite arrays at centromeres of homologous chromosomes between these species are closely related (evolving in an orthologous manner) or if the evolutionary processes that homogenize and spread these arrays within and between chromosomes result in nonorthologous evolution of arrays. By using PCR primers specific for human chromosome 17-specific alpha satellite DNA, we have amplified, cloned, and characterized a chromosome-specific subset from the PTR chimpanzee genome. Hybridization both on Southern blots and in situ as well as sequence analysis show that this subset is most closely related, as expected, to sequences on HSA 17. However, in situ hybridization reveals that this subset is not found on the homologous chromosome in chimpanzee (PTR 19), but instead on PTR 12, which is homologous to HSA 2p.

Animals↗

Immediate breast reconstruction for stage III breast cancer using transverse rectus abdominis musculocutaneous (TRAM) flap.

BACKGROUND: The management of state III breast cancer is challenging; it often includes multimodal treatment with systemic therapy and/or radiation therapy and surgery. Immediate breast reconstruction has not traditionally been performed in these patients. We review the results of immediate transverse rectus abdominis musculocutaneous (TRAM) flap in 21 patients treated for stage III breast cancer. METHODS: Data have been collected retrospectively on 21 patients diagnosed with stage III breast cancer between 1987 and 1994. All patients had mastectomy and immediate TRAM reconstruction. Thirteen patients received primary systemic therapy, 10 patients received postoperative consolidation radiotherapy to the operative site, and 3 patients received preoperative radiation. RESULTS: Mean follow-up for the group was 26 months. Two patients died with disseminated disease: neither of them developed local disease recurrence in the operative site; 82% of the patients followed for at least two years are free of disease. Sixty-two percent of the patients received preoperative chemotherapy, the remaining patients received postoperative multiagent chemotherapy and/or radiation therapy. Two of the patients received autologous bone marrow transplants after their adjuvant therapy. Ten patients had postoperative radiotherapy for consolidation; three patients received preoperative radiation. CONCLUSIONS: Immediate TRAM reconstruction for stage III breast cancer is not associated with a delay in adjuvant therapy or an increased risk of local relapse. It facilitates wide resection of involved skin without skin grafting. Radiation therapy can be delivered to the reconstructed breast when indicated without difficulty. Breast reconstruction facilitates surgical resection of stage III breast cancer with primary closure and should be considered if the patient desires immediate breast reconstruction.

Breast Neoplasms↗

Rapid bright-field detection of oligonucleotide primed in situ (PRINS)-labeled DNA in chromosome preparations and frozen tissue sections.

We describe a new application of a bright-field microscopic procedure for rapid enzyme cytochemical detection of repeated DNA sequences in metaphase preparations and frozen tissue sections. Various chromosome-specific oligonucleotide primers were used in up to three sequential primed in situ (PRINS) labeling reactions together with Taq DNA polymerase and biotin, digoxigenin and/or fluorescein isothiocyanate (FITC)-modified nucleotides. DNA target sequences were localized simultaneously by the precipitates of the horseradish peroxidase-diaminobenzidine (PO-DAB, brown color), alkaline phosphatase-Fast Red (APase-Fast Red, red color) and horseradish peroxidase-teramethylbenzidine (PO-TMB, green color) reaction in hematoxylin counterstained metaphases and interphase nuclei using a standard bright-field microscope. In addition, a protocol is reported for the application of PRINS to frozen tissue sections from normal colon and bladder epithelium. Methanol/acetic acid fixation in combination with a pepsin digestion before performing the PRINS reaction proved to be critical steps in the total procedure that permits access of the PRINS reactants, while preserving the morphology of the nuclei in the tissue. Quantification of PRINS signals showed the majority of epithelial cells with the expected two chromosome copies. The described procedures can be considered valuable tools for application in molecular cytogenetics, cell biology and pathology.

Biotin↗

Prophylactic aspirin and risk of peptic ulcer bleeding.

OBJECTIVE: To determine the risks of hospitalisation for bleeding peptic ulcer with the current prophylactic aspirin regimens of 300 mg daily or less. DESIGN: A case-control study with hospital and community controls. SETTING: Hospitals in Glasgow, Newcastle, Nottingham, Oxford, and Portsmouth. SUBJECTS: 1121 patients with gastric or duodenal ulcer bleeding matched with hospital and community controls. RESULTS: 144 (12.8%) cases had been regular users of aspirin (taken at least five days a week for at least the previous month) compared with 101 (9.0%) hospital and 77 (7.8%) community controls. Odds ratios were raised for all doses of aspirin taken, whether compared with hospital or community controls (compared with combined controls: 75 mg, 2.3 (95% confidence interval 1.2 to 4.4); 150 mg, 3.2 (1.7 to 6.5); 300 mg, 3.9 (2.5 to 6.3)). Results were not explained by confounding influences of age, sex, prior ulcer history or dyspepsia, or concurrent non-aspirin non-steroidal anti-inflammatory drug use. Risks seemed particularly high in patients who took non-aspirin non-steroidal anti-inflammatory drugs concurrently. CONCLUSION: No conventionally used prophylactic aspirin regimen seems free of the risk of peptic ulcer complications.

Anti-Inflammatory Agents, Non-Steroidal↗

Actin, its associated proteins and metastasis.

In this short article we have overviewed the effect of transformation on AAPs. We have not dealt with molecules indirectly associated with actin which are modified by transformation, such as the catenins, cadherins, vinculin, and integrins [Tsukita et al., 1993], although their relationship with and importance to the transformed phenotype cannot be overemphasised. Similarly, alterations in polyphosphoinositide metabolism that occur in transformed cells may also promote or induce alterations in the microfilament cytoskeleton via interactions with proteins such as gelsolin, alpha-actinin, and MARCKS [Bretscher, 1993]. At present, there are no clear-cut rules regarding the effect that oncogenesis has on AAPs, since the expression level of one oncogenically modified AAP can vary from one tumour to another, even within the same type of tumour [Yamamoto et al., 1993]. This apparent inconsistency may well be because we are "playing with an incomplete pack of cards" [Pollard, 1993], or it may reflect this highly complex control mechanism in which any perturbation of the normal expression levels of actin/AAPs unbalances the delicate equilibrium which controls normal cell behaviour [Bray and Vasiliev, 1989]. For example, it is possible that oncogenically induced alterations to actin isoform expression [Lin et al., 1985] exert a downstream effect on actin-associated protein expression. Oncogenically induced actin based cell movements may be activated by alterations to either a single AAP or a synergistic functional unit of these molecules [Shapland et al., 1993; Vandekerckhove et al., 1990].(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗

Multi-PRINS: multiple sequential oligonucleotide primed in situ DNA synthesis reactions label specific chromosomes and produce bands.

A fast method for identifying several chromosomes with chromosome-specific oligonucleotide primers directing an in situ labeling reaction is described. Up to three reactions distinguished by different fluorochromes (fluorescein isothiocyanate, rhodamine/Texas red, p-amino-methyl-cyclohexane carboxylic acid) can currently be performed. Prospects for increasing this up to seven colors, and for the future of the process in prenatal diagnosis are discussed.

Base Sequence↗

Human repeat-mediated integration of selectable markers into somatic cell hybrids.

We describe a strategy to introduce preferentially the dominant selectable marker neoR into the human chromosome within a monochromosome hybrid cell line. Integration of a construct containing the marker is mediated by human-specific repeat elements that promote multilocus human-specific integration with a single targeting vector. We tested two classes of repeat elements: the Alu family of SINE repeats and the Line1 repeat family. We show that Alu sequences alone are insufficient to direct human-specific integration but when used in combination with a Line1 element, or when only Line1 elements are included, integration of the vector into the human component of a monochromosome somatic cell hybrid is favored. The vectors also carry sequences that facilitate mapping and selective cloning of the targeted region. This strategy provides a means to generate selectable human subchromosomal fragments that can be used for localization of genes through positional cloning and, more important, for the identification of functional units through DNA transfer.

Anti-Bacterial Agents↗

Instant PRINS: a rapid method for chromosome identification by detecting repeated sequences in situ.

We describe a method for labeling specific chromosomes in situ by oligonucleotide-primed synthesis and incorporation of fluorochrome-labeled dUTP, together with an accelerated protocol for the reaction. The combination of the two developments produces extremely rapid results, in some cases taking less than 5 min for the complete process. The significance of this development for clinical diagnosis is discussed.

Base Sequence↗

Is myosin a "back door" enzyme?

ATP has been modeled into the active site of chicken skeletal myosin subfragment-1 using the adenylate kinase.Ap5A structure as a starting reference. The resulting docked ATP.S1 structure is justified in that it rationalizes the photolabeling data from several ATP analogs. The gamma-phosphate of ATP sits at the bottom of the active site pocket and is partially visible via a view along the prominent 50-kDa cleft of S1 but not when viewed from above the active site. It is postulated that actin binding promotes the movement of the P-loop and Arg-245 to allow Pi from ATP to leave via a "back-door" in the 50-kDa fragment while ADP is still bound at the active site. Such a mechanism can explain a number of experimental observations, including the kinetics of ATP hydrolysis, the nucleotide dependence of Pi exchange into ATP, and the formation of stable myosin.ADP.vanadate complexes in muscle fibers.

Adenosine Triphosphate↗

Power spectrum of the fast Fourier transform for measurement of standing balance.

Power spectrum of the force moment generated from the fast Fourier transform (FFT) was utilised to evaluate standing balance on a force platform. The principles on generating and analysing an FFT spectrum from the output of the force platform are illustrated. Test-retest reliability of twelve healthy young people (age = 26 +/- 4 years) was performed with the preferred leg stance. The intraclass correlation coefficient (ICC), R, of mean power (P), spectral area (Sx) and maximum power (Px) were 0.89, 0.85 and 0.89 respectively, indicating that the spectral parameters are reliable quantitative measures of balance. Pearson product moment (PPM), r, of these spectral parameters were 0.95, 0.85 and 0.95 respectively showing that these spectral parameters are significantly correlated (p < 0.01). A comparison was made with respect to the one legged stance and two legged stance steadiness. The one legged stance (Sx = 95.75 cm.Hz) was significantly less stable than the two legged stance (Sx = 41.58 cm.Hz) with a value of 9.37. Moreover, the one legged stance was highly correlated to the two legged stance (r = 0.84), indicating that, in general, a subject who has a stable one legged stance should have a stable two legged stance.

Adolescent↗

Cloning and sequencing of cDNAs encoding the actin cross-linking protein transgelin defines a new family of actin-associated proteins.

We have used degenerate oligonucleotides, derived from the amino acid sequence of transgelin peptides [Shapland et al., 1993: J. Cell Biol. 121:1065-1073], to isolate and sequence overlapping cDNA clones encoding this actin gelling protein. Primers with 5' restriction enzyme sites directed against the N and C terminal amino acids present in these clones were then used to amplify and clone the entire transgelin coding region from reverse transcribed rat small intestine cDNA (RT-PCR). These studies have shown that transgelin is the product of a single gene which is conserved between yeast, Drosophila, molluscs, and humans. Transgelin is expressed as a single message that is regulated at the level of transcription in SV40 transformed 3T3 cells. Our data have shown that transgelin and several other proteins of unknown function, SM22 alpha [Pearlstone et al., 1987: J. Biol. Chem. 262:5985-5991], mouse p27 [Almendral et al., 1989: Exp. Cell Res. 181:518-530], and human WS3-10 [Thweatt et al., 1992: Biochem. Biophys. Res. Commun. 187:1-7], share extensive homology. More limited regions of homology shared between transgelin and other proteins such as rat NP25 (unpublished), chicken calponins alpha and beta [Takahashi and Nadal-Ginard, 1991: J. Biol. Chem. 266:13284-13288], and Drosophila mp20 [Ayme-Southgate et al., 1989: J. Cell Biol. 108:521-531] suggest that all of these proteins may be classified as members of a new transgelin multigene family.

Amino Acid Sequence↗