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Biomedical subjects

L Simpson

Publications and source records attributed to L Simpson.

At least 127 records · Page 7Linked to original sources
PubMed1992

Countertransference and clinical choices in public-sector treatment of a patient and her family.

Clinical decision making in the treatment of families of individuals with prolonged mental illness can be affected by countertransference that is stimulated by the context of treatment as well as by the family being treated. For clinicians, psychoeducation, the current intervention of choice for such families, can serve defensive functions that are motivated by counter-transference; a case example illustrates how such defenses led a clinician to avoid deeper therapeutic work. The authors believe that clinicians must strive to understand their motivations for whatever clinical decisions they make; to facilitate this awareness, intensive psychotherapy should be required as an adjunct to training.

Activities of Daily Living↗
PubMed1992

Should we palpate foot pulses?

UNLABELLED: Palpation of foot pulses is traditionally used to evaluate patients with arterial disease. This study investigated observer variation in assessment of pedal vessels by pulse palpation and Doppler auscultation. A series of 33 claudicant patients and five controls were examined by a consultant, registrar, SHO and nurse. Dorsalis pedis (DP) and posterior tibial (PT) pulses were palpated and were then examined by Doppler with measurement of systolic pressures. CONTROL GROUP: No disagreement in DP pulses. However, all observers agreed on the presence of a PT pulse in only 70% of limbs. Claudicants: There was better agreement in palpation of the DP pulse (all observers agreed in 67% of limbs), than the PT pulse (all agreed in 53%). This suggests that the DP pulse is easier to palpate than the PT (P less than 0.05). By contrast there was better agreement on Doppler signals from the PT artery, all agreed in 78% of limbs; compared with the DP artery, all agreed in 58% (P less than 0.01). Pressure measurements by the observers agreed to within +/- 0.15 in 88% of claudicant and 100% of control limbs. Pedal pulse palpation in patients with arterial disease is subject to substantial observer error. Doppler pressure measurement is preferable unless pulses are bounding.

Adult↗
PubMed1991

Leishmania tarentolae minicircles of different sequence classes encode single guide RNAs located in the variable region approximately 150 bp from the conserved region.

The complete sequences of three kinetoplast DNA minicircles (B4, D3 and D12) from Leishmania tarentolae are reported. All L. tarentolae minicircles encode single gRNAs localized within the variable region approximately 150 bp from the conserved region. The 5' termini and tentative 3' termini of the new gRNAs were determined and the gene sequences and flanking sequences of all minicircle gRNA genes compared for conserved motifs of possible transcriptional regulatory significance. All minicircle gRNAs possess 3' oligo-[U] tails of variable length similar to maxicircle gRNAs. A role for the D3 minicircle gRNA in the editing of the 5' pan-edited MURF4 mRNA was suggested by sequence analysis, and a role for the D12 minicircle gRNA in the editing of the COIII mRNA and another minicircle gRNA (Lt154) in the editing of the pan-edited G6 mRNA have been previously reported. The cryptogene mRNAs edited by the B4 and Lt19 minicircle gRNAs are yet undetermined.

Animals↗
PubMed1991

Chimeric gRNA-mRNA molecules with oligo(U) tails covalently linked at sites of RNA editing suggest that U addition occurs by transesterification.

Chimeric RNA molecules were detected by polymerase chain reaction amplification of kinetoplast RNA using a 3' primer specific to mRNA and a 5' primer specific to guide RNA (gRNA), and directly by Northern analysis. Covalent linkage of the 3' oligo(U) tail of the gRNA to the mRNA occurs at editing sites. Chimeric molecules were isolated for NADH dehydrogenase subunit 7 and cytochrome oxidase subunits II and III. We propose that these molecules are intermediates in the editing process and that successive transesterifications result in the transfer of uridine residues from the gRNA 3' oligo(U) tail to an editing site, with the number of uridine residues determined by base pairing with adenine and guanine "guide" nucleotides in the gRNA.

Animals↗
PubMed1991

Polymerase chain reaction amplification of Trypanosoma cruzi kinetoplast minicircle DNA isolated from whole blood lysates: diagnosis of chronic Chagas' disease.

A 6 M guanidine-HCl/0.2 M EDTA solution was used to lyse and store whole blood specimens. DNA stored in guanidine-EDTA-blood (GEB) lysate was found to be undegraded after incubation at 37 degrees C for 1 month, suggesting that this represents an appropriate reagent for transport of blood samples from the field to a laboratory for analysis. Trypanosoma cruzi kinetoplast DNA in GEB lysate can be cleaved using the chemical nuclease, 1,10-phenanthroline-copper ion (OP-Cu2+). This procedure liberates linearized minicircle molecules from network catenation, distributing them throughout the lysate, and allowing a small aliquot of the original lysate to be analyzed by PCR amplification. This increases the sensitivity of the method dramatically for the detection of small numbers of trypanosomes in a large volume of blood. DNAs isolated from aliquots of T. cruzi-positive GEB lysates were polymerase chain reaction (PCR)-amplified with 3 sets of T. cruzi-specific kDNA minicircle primers, yielding the 83-bp and 122-bp conserved region fragments and the 330-bp variable region fragments. The PCR products were analyzed by gel electrophoresis and/or hybridization. Results indicate that a single T. cruzi cell in 20 ml of blood can be detected by this method. Blood samples from several chronic chagasic patients were tested. Amplification of T. cruzi kDNA minicircle sequences was obtained in al cases, even when xenodiagnosis was negative. This PCR-based test should prove useful as a replacement or complement for xenodiagnosis or serology in clinical and epidemiological studies of chronic Chagas' disease.

Animals↗
PubMed1991

Biomechanical testing of new and old fixation devices for vertical shear fractures of the pelvis.

Malgaigne fractures of the pelvis have been treated with many different methods of fixation. We developed a plate for use on the anterior aspect of the sacroiliac (SI) joint using information obtained from cadaveric dissections and computed tomography (CT) scans of male (50) and female (50) pelvises. We tested each of six pelvises in the Instron, with five different fixation systems. Our results showed that the weakest system was the anterior quadrilateral frame plus two symphyseal plates. When comparing three posterior screws with the SI joint plate, the difference was not statistically significant. However, in both of these systems, a second symphyseal plate added to the overall stability.

Biomechanical Phenomena↗
PubMed1990

Guide RNAs in kinetoplastid mitochondria have a nonencoded 3' oligo(U) tail involved in recognition of the preedited region.

Maxicircle-encoded guide RNAs (gRNAs) for cytochrome b and maxicircle unidentified reading frames 2 and 3 (MURF2 and MURF3) were isolated by hybrid selection and sequenced. All three gRNAs contained nonencoded 3' oligo(U) tails 5-24 nucleotides in length, with a mean length of approximately 15 nucleotides. Secondary structure calculations indicate a functional role of the 3' oligo(U) tail in stabilizing the initial hybrid formed between the gRNA and the preedited mRNA, and allowed the identification of potential mRNA recognition sites for an editing complex. In addition, isolated MURF2 gRNA-II could be 5' capped with [alpha-32P]-GTP and guanylyltransferase, suggesting that at least some gRNAs represent primary transcripts.

Animals↗
PubMed1990

Partially edited mRNAs for cytochrome b and subunit III of cytochrome oxidase from Leishmania tarentolae mitochondria: RNA editing intermediates.

Partially edited mRNAs were selected by the polymerase chain reaction and sequenced. In the case of cytochrome b, 102 out of 106 clones displayed patterns of editing that were consistent with a strictly progressive 3' to 5' editing process, as predicted by the guide RNA model of RNA editing. In the case of cytochrome oxidase subunit III (COIII), 177 out of 304 clones displayed strictly progressive 3' to 5' patterns of editing. However, the remaining 127 COIII clones displayed unexpected patterns in which upstream editing preceded downstream editing, uridines were inserted at sites not normally edited, and purine residues were deleted. We suggest that many of these RNAs are produced by normal 3' to 5' editing of the COIII mRNA with incorrect guide RNA molecules.

Animals↗
PubMed1990

Kinetoplast DNA minicircles encode guide RNAs for editing of cytochrome oxidase subunit III mRNA.

Guide RNAs (gRNAs) for the editing of sites 1-8 of COIII mRNA and an "unexpected" partially edited COIII mRNA are encoded in the variable regions of specific kinetoplast DNA minicircles. The gRNAs can form 37 and 44 nucleotide perfect hybrids (allowing for G-U base pairs) with edited mRNAs. The gRNAs were detected on Northern blots and shown to have unique 5' ends situated close to the beginning of the potential base pairing with the edited mRNAs. We suggest that kinetoplast DNA minicircle molecules in general may encode gRNAs for editing of cryptogene mRNAs by a mechanism similar to that previously proposed for editing by maxicircle-encoded gRNAs.

Animals↗
PubMed1990

A model for RNA editing in kinetoplastid mitochondria: "guide" RNA molecules transcribed from maxicircle DNA provide the edited information.

A class of small RNA molecules possibly involved in RNA editing is present in the mitochondrion of Leishmania tarentolae. These "guide" RNA (gRNA) molecules are encoded in intergenic regions of the mitochondrial maxicircle DNA and contain sequences that represent precise complementary versions of the mature mRNAs within the edited regions. In addition, the 5' portions of several gRNAs can form hybrids with mRNAs just 3' of the preedited region. A model is presented in which a partial hybrid formed between the gRNA and preedited mRNA is substrate for multiple cycles of cleavage, addition or deletion of uridylates, and religation, eventually resulting in a complete hybrid between the gRNA and the mature edited mRNA.

Animals↗
PubMed1990

Zygotic activity of the nullo locus is required to stabilize the actin-myosin network during cellularization in Drosophila.

Cellularization of the Drosophila embryo requires the establishment of a hexagonal network of actin and myosin filaments that are interconnected around the nuclei in the cortex of the syncytial blastoderm. This cytoskeletal network provides the framework and possibly the contractile force for the membrane invaginations that synchronously subdivide the syncytial embryo into individual cells. Zygotic expression of the nullo locus is essential for the preservation of an intact actin-myosin network. Embryos deleted for the nullo locus have a disrupted network, resulting in the formation of many multinucleate cells. We show that nullo is not required for the initial formation of the actin-myosin network, but is necessary for the maintenance of its hexagonal shape during cellularization. The phenotype of embryonic mosaics is nonautonomous, indicating that nullo does not have to be expressed in every nucleus for proper cellularization. Examination of nullo mutant clones in adults reveals that nullo activity is not required for cell division in imaginal discs. Furthermore, germline clone experiments suggest that maternal expression of the nullo locus is not essential for either germline proliferation or the cellularization of progeny. We propose a model in which nullo functions specifically at cellularization to stabilize the actin-myosin network during contraction.

Actins↗
PubMed1989

The Leishmania kinetoplast-mitochondrion contains terminal uridylyltransferase and RNA ligase activities.

Purified mitochondria of Leishmania tarentolae contain 3'-terminal uridylyltransferase and RNA ligase activities which can be solubilized by detergent lysis of the organelle. Run-off transcription of maxicircle and minicircle DNA also occurs in intact and Triton-lysed mitochondria, using [32P]GTP as the labeled precursor. Heparin inhibits the solubilized terminal uridylyltransferase activity but does not affect the labeling of endogenous RNAs in intact mitochondria with [32P]UTP. Clarification of the mitochondrial Triton lysate causes an increase in terminal uridylyltransferase activity with exogenous substrates. These two activities are candidates for involvement in a post-transcriptional RNA editing process of mitochondrial transcripts.

Animals↗
PubMed1989

Kinetoplastid mitochondria contain functional tRNAs which are encoded in nuclear DNA and also contain small minicircle and maxicircle transcripts of unknown function.

The mitochondrion of Leishmania tarentolae contains approximately 35-40 tRNAs many of which comigrate with cytoplasmic tRNAs. Both mitochondrial (KtRNA) and cytoplasmic (CtRNA) tRNAs are functional, as they could be acylated either by mitochondrial or cytoplasmic synthetase extracts. There are two methionyl tRNA species in the cytoplasmic and mitochondrial fractions, one of which is unique to each fraction, indicating that the KtRNA fraction is free of CtRNA contamination. Leucyl and glycyl tRNAs were identified by hybridization with a genomic clone from Trypanosoma brucei. KtRNA hybridizes with nuclear chromosomes, but not with minicircle or maxicircle DNA. KtRNA isolated by DEAE chromatography or agarose gel electrophoresis contains additional small RNAs which hybridize with both minicircle and maxicircle DNA. These transcripts do not migrate like tRNAs in acrylamide gels and their functions is unknown. We suggest that most if not all mitochondrial tRNAs in L. tarentolae are nuclear-encoded and imported into the mitochondrion.

Amino Acyl-tRNA Synthetases↗
PubMed1989

Detection and characterization of a B cell stimulatory factor (BSF-TC) derived from a bone marrow stromal cell line.

Stromal cell lines derived from murine bone marrow support the growth of immature pre-B cells and produce cytokines that affect the growth and differentiation of other hematopoietic precursors. Conditioned medium (CM) from one such line (TC-1) stimulated marked proliferation of B cells previously activated by anti-Ig (anti-Ig blasts). Proliferation of anti-Ig blasts was not induced by purified cytokines known to be produced by TC-1 (CSF-1, GM-CSF, or G-CSF) or by IL-1, IL-2, IL-3, IL-4, IL-5, or IL-6. Furthermore, IL-2, IL-4, and IL-5, alone or in combination, failed to support proliferation or differentiation of anti-Ig blasts. TC-1 CM enhanced proliferation of B cells that were co-cultured with LPS, anti-Ig, or dextran sulfate; co-stimulation with anti-Ig was unaffected by the presence of monoclonal anti-IL-4. Proliferation of low, but not high, density B cells isolated from spleen was directly stimulated by TC-1 CM. These results suggest that bone marrow stromal cells produce a novel B cell stimulatory factor (BSF-TC) that induces proliferation of activated B cells.

Animals↗