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Biomedical subjects

D A Jones

Publications and source records attributed to D A Jones.

At least 145 records · Page 8Linked to original sources
PubMed1995

Promoting an awareness of retractions: the Louisiana State University Medical Center in Shreveport experience.

The current mission statement of the Medical Library Association states that it is "dedicated to improving health through professional excellence and leadership of its members in the ... provision of information services and educational programs ..." With this goal in mind, retractions offer medical librarians a professional challenge to become involved in the scientific process. Through results of a survey conducted among the consortium of South Central Academic Medical Libraries (SCAMeL), this paper reveals opinions on the importance of retraction awareness and who is responsible for disseminating this knowledge. The paper also reports what the Louisiana State University Medical Center at Shreveport Library and other SCAMeL member libraries are doing to promote awareness.

Academic Medical Centers↗
PubMed1995

Activation of thromboxane and prostacyclin receptors elicits opposing effects on vascular smooth muscle cell growth and mitogen-activated protein kinase signaling cascades.

Thromboxane A2 stimulation of smooth muscle cells contributes to the development of vascular lesions after percutaneous transluminal coronary angioplasty. In view of this, we examined the signaling pathways stimulated by a thromboxane receptor agonist, U-46619, in cultures of rat aortic smooth muscle cells. Treatment of rat aortic smooth muscle cells with U-46619 induced cellular hypertrophy ([14C]leucine incorporation) without stimulating mitogenesis ([3H]thymidine incorporation). Analysis of signaling pathways elicited by U-46619 revealed enhanced tyrosine phosphorylation and increased enzymatic activity of mitogen-activated protein (MAP) kinase (Erk2). U-46619 also activated signaling proteins upstream of p21-ras, inducing tyrosine phosphorylation on Shc and complex formation between Shc and growth factor receptor binding protein-2 (GRB2). Exposure of cells to a stable prostacyclin analogue, ciprostene calcium, attenuated U-46619-induced cellular hypertrophy and MAP kinase activity. Ciprostene treatment elevated cellular cAMP and inhibited U-46619-induced tyrosine phosphorylation on Shc and Shc/GRB2 complex formation. These results demonstrate that stimulation of thromboxane A2 and prostacyclin receptors have opposing effects on smooth muscle cell hypertrophy and the signaling pathways associated with this process. We conclude that inhibition of Shc/GRB2 complex formation and MAP kinase activity by ciprostene may contribute to its ability to limit restenosis injury.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1995

The importance of pubic pain following childbirth: a clinical and ultrasonographic study of diastasis of the pubic symphysis.

This study aimed to investigate the diagnosis and consequences of pubic symphysis diastasis postpartum, in particular the use of ultrasonography to measure interpubic gap. It was a prospective follow-up study, which included an ultrasonographic comparison between symptomatic mothers and controls, set in Morriston Hospital, Swansea. Nine women presenting with unusual pubic pain post-partum were included: there were no exclusion criteria. Forty-two controls were also studied: the only exclusion criterion was unusual pubic pain. Interpubic gap was measured with ultrasonography. Follow up was undertaken for a median of 37 months (range 2-57). An abnormal interpubic gap was found in all symptomatic women. The incidence of diastasis was found to be at least one in 800 deliveries and significant long-term disability was found in three women. Diastasis is commoner than generally acknowledged and its consequences may be severe. Interpubic gap confirms diagnosis but does not appear to predict outcome. Ultrasonography aids diagnosis and follow up.

Female↗
PubMed1994

Platelet-derived growth factor stimulates phosphorylation of growth factor receptor-binding protein-2 in vascular smooth muscle cells.

Growth factor receptor-binding protein-2 (GRB2) couples growth factor receptor activation to the p21ras nucleotide exchange factor son-of-sevenless (SOS). Son-of-sevenless can serve as a substrate for mitogen-activated protein kinases and may be subject to feed back regulation in mitogen-stimulated cells. Herein, we demonstrate phosphorylation on GRB2 in rat A10 vascular smooth muscle cells exposed to platelet-derived growth factor (PDGF). Lysates from smooth cells stimulated with PDGF revealed a shift in the electrophoretic mobility of GRB2. Further investigation confirmed that phosphorylation on GRB2 accompanied this mobility shift. Phosphorylation on GRB2 was time-dependent and correlated with PDGF receptor activation. The time-course for phosphorylation of GRB2 and subsequent decay corresponded with other events characteristic of platelet-derived growth factor signaling. GRB2 was not phosphorylated in cells treated with phorbol 12-myristate 13-acetate, and down-regulation of protein kinase C failed to attenuate phosphorylation on GRB2 in response to growth factor. Analysis of GRB2 immune complexes revealed a kinase activity capable of phosphorylating GRB2 in vitro and demonstrated that the kinase activated in response to PDGF may physically associate with GRB2 signaling complexes.

Adaptor Proteins, Signal Transducing↗
PubMed1994

Platelet-derived growth factor stimulates growth factor receptor binding protein-2 association with Shc in vascular smooth muscle cells.

Platelet-derived growth factor (PDGF) stimulates smooth muscle cell proliferation and migration in vascular disorders such as atherosclerosis and restenosis. Growth factor receptor binding protein-2 (GRB2) and Shc have been shown to link growth factor receptor activation with guanine nucleotide exchange on p21-ras. We have examined this pathway in cultures of rat A10 vascular smooth muscle cells. Our data demonstrate that PDGF stimulates tyrosine phosphorylation on Shc in a concentration- and time-dependent manner that parallels PDGF beta-receptor activation. Immunoprecipitates of Shc from cells exposed to PDGF revealed Shc.GRB2 complexes. Shc immune complexes also contained PDGF beta-receptors. Complex formation was maximal with 30 ng/ml PDGF and peaked within 10 min of exposure. Although PDGF beta-receptors contain a putative GRB2 binding site, activated receptors failed to bind GRB2 directly. Evaluation of Shc from membrane and cytosolic fractions of A10 cells showed little redistribution of Shc following PDGF exposure. Cytosolic Shc bound only GRB2, whereas, membrane-associated Shc complexed with GRB2, the PDGF beta-receptor, Src, and additional tyrosine phosphorylated proteins. We conclude that Shc serves as a primary docking protein for GRB2 in smooth muscle cells and is critical for proliferation in response to PDGF.

Adaptor Proteins, Signal Transducing↗
PubMed1994

Isolation of the tomato Cf-9 gene for resistance to Cladosporium fulvum by transposon tagging.

The tomato Cf-9 gene confers resistance to infection by races of the fungus Cladosporium fulvum that carry the avirulence gene Avr9. The Cf-9 gene was isolated by transposon tagging with the maize transposable element Dissociation. The DNA sequence of Cf-9 encodes a putative membrane-anchored extracytoplasmic glycoprotein. The predicted protein shows homology to the receptor domain of several receptor-like protein kinases in Arabidopsis, to antifungal polygalacturonase-inhibiting proteins in plants, and to other members of the leucine-rich repeat family of proteins. This structure is consistent with that of a receptor that could bind Avr9 peptide and activate plant defense.

Amino Acid Sequence↗
PubMed1994

Chloroplast targeting of spectinomycin adenyltransferase provides a cell-autonomous marker for monitoring transposon excision in tomato and tobacco.

Antibiotic resistance genes can act as either cell autonomous or non-cell autonomous genetic markers with which to monitor the excision of plant transposons. To convert spectinomycin resistance from a non-cell autonomous resistance to cell autonomous resistance, a transit peptide for chloroplast localization from a petunia ribulose bisphosphate carboxylase (rbcS) gene was fused in-frame to the aadA gene, which confers spectinomycin and streptomycin resistance. Constructs were generated in which the expression of this chimeric gene was prevented by the presence, in the 5' untranslated leader, of the maize transposons Activator (Ac) or Dissociation (Ds). When progeny of tobacco or tomato plants transformed with these constructs were germinated on spectinomycin-containing medium, germinally revertant and somatically variegated individuals could be distinguished.

Base Sequence↗
PubMed1994

Analysis of the chromosomal distribution of transposon-carrying T-DNAs in tomato using the inverse polymerase chain reaction.

We are developing a system for isolating tomato genes by transposon mutagenesis. In maize and tobacco, the transposon Activator (Ac) transposes preferentially to genetically linked sites. To identify transposons linked to various target genes, we have determined the RFLP map locations of Ac- and Dissociation (Ds)-carrying T-DNAs in a number of transformants. T-DNA flanking sequences were isolated using the inverse polymerase chain reaction (IPCR) and located on the RFLP map of tomato. The authenticity of IPCR reaction products was tested by several criteria including nested primer amplification, DNA sequence analysis and PCR amplification of the corresponding insertion target sequences. We report the RFLP map locations of 37 transposon-carrying T-DNAs. We also report the map locations of nine transposed Ds elements. T-DNAs were identified on all chromosomes except chromosome 6. Our data revealed no apparent chromosomal preference for T-DNA integration events. Lines carrying transposons at known map locations have been established which should prove a useful resource for isolating tomato genes by transposon mutagenesis.

Base Sequence↗
PubMed1994

An evaluation of different protocols for measuring the force-velocity relationship of the human quadriceps muscles.

A modified Cybex II isokinetic dynamometer was used to evaluate the problems associated with measuring the concentric force-velocity characteristics of human knee extensor muscles. Three contraction protocols were investigated, simple voluntary contractions (VC); releases from maximal voluntary isometric contractions (VR) and releases from isometric femoral nerve stimulated contractions (FNR). Percutaneous stimulation of the quadriceps was unsuitable for dynamic contractions as the proportion of the muscle activated varied with the angle of knee flexion. Isometric length-tension relationships and isokinetic contractions at seven angular velocities between 0.5 and 5.2 rad.s-1 were recorded in five subjects. During isometric and slow dynamic contractions the voluntary forces were often greater than those obtained by femoral nerve stimulation, probably due to subjects stretching the rectus femoris during voluntary manoeuvres. It was found that the VC protocol produced acceptable isokinetic force recordings only at velocities below 3.1 rad.s-1 in most subjects whilst VR contractions resulted in unexpectedly low forces at velocities below 1.57 rad.s-1. Of the three techniques employed, FNR, although uncomfortable for subjects, provided the most accurate and reliable method of measuring force-velocity characteristics of knee extensor muscles. FNR contractions produced a force-velocity curve which showed a smooth decline in force with increasing velocity up to 5.2 rad.s-1. VC contractions appear to be an acceptable alternative for testing the muscles provided the angular velocity is less than 3.1 rad.s-1 and the subjects can be prevented from stretching the rectus femoris during the movement.

Adult↗
PubMed1994

Post-junctional excitatory adenosine A1 receptors in the rat vas deferens.

1. At concentrations between 1 nM and 1 microM, the A1-selective agonists N6-cyclopentyladenosine (CPA) and (R)-N6-phenylisopropyladenosine (R-PIA) each enhanced contractions of the rat vas deferens induced by ATP (10 microM), and this enhancement was blocked by an A1-selective concentration (1 nM) of the antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). 2. No such enhancement was observed with the non-selective agonists adenosine and 5'-N-ethylcarboxamidoadenosine (NECA) at concentrations between 1 nM and 100 microM, which instead inhibited the contractions. 3. These results show that in addition to the previously demonstrated inhibitory A1 and A2 adenosine receptors, the rat vas deferens also possesses post-junctional excitatory A1 adenosine receptors.

Adenosine↗
PubMed1994

Risk factors for hepatitis C virus infection. A case-control study of blood donors in the Trent Region (UK).

The introduction of screening for hepatitis C virus (HCV) by the National Blood Transfusion Service identified donors who had acquired HCV infection. We undertook a case-control study amongst blood donors in the Trent Region to determine risks for HCV infection. A total of 74 blood donors confirmed positive for hepatitis C infection and 150 age, sex and donor venue matched controls were included in the study. Fifty-three percent of hepatitis C infected blood donors reported previous use of injected drugs compared to no controls; relative risk (RR) not estimatable (lower limit 95% CI = 20). Other risk factors were a history of: receipt of a blood transfusion or blood products RR = 3.6 (95% CI 1.5-8.3), having been a 'health care worker' RR = 2.8 (95% CI 1.1-7.6), tattooing RR = 3.3 (95% CI 1.2-8.7), and an association with having been born abroad RR = 3.2 (95% CI 1.1-9.5). No risk was shown for a history of multiple sexual partners, ear piercing or acupuncture. Injecting drug use explains more than 50% of hepatitis C infections in blood donors, a group who are less likely to have injected drugs than the general population.

Adult↗
PubMed1994

Failure of the revised pre-donation guidelines to prevent people with a history of high-risk behaviour from donating blood.

We have evaluated the effectiveness of the alteration in the literature aimed at the self-exclusion of blood donors with a history of high-risk behaviour. Since the introduction of anti-HCV screening on 1 September 1991 all HCV-positive donors in the Trent Region have been invited for interview by Blood Transfusion medical staff to ascertain risk factors for HCV infection. We have compared the 5-month periods before (1 September, 1992 to 31 January, 1993) and after (1 February, 1993 to 30 June, 1993) the introduction of the amended literature on 1 February, 1993. No differences between the two time periods were noted for the prevalence rate of HCV infection amongst new or repeat donors, or history of risk factors or specific exclusion criteria. The new literature is failing to exclude people with a history of high-risk behaviour from donating blood and further study of this problem is urgently required.

Adult↗
PubMed1994

Effects of length and stimulation frequency on fatigue of the human tibialis anterior muscle.

It has been suggested that the reduced fatigability of muscles exercised at short length may result from a decrease in the metabolic cost of contractions in the shortened position. We compared the fatigue properties and metabolic cost of stimulated isometric tetanic contractions in the tibialis anterior of 10 normal subjects at the optimum length (Lo) for force production and when the muscle was shortened (Ls). Six 15-s ischemic contractions at Ls caused force to decline to 53% of the fresh value when tested at Lo, whereas muscles exercised and tested at Lo declined to 40% of fresh force. However, the extent of fatigue was proportionately greater if the muscle was exercised and tested at Ls. The apparent fatigue resistance of short muscles was found to be a consequence of recovery occurring under ischemic conditions while the muscle was changed from Ls to Lo-. 31P-nuclear magnetic resonance spectroscopy showed similar metabolic changes associated with 5-s stimulated contractions at Lo and Ls, indicating that any differences in fatigability at the two lengths were not caused by altered metabolic costs. The similarity between the force profiles of muscles fatigued at Ls and those fatigued by high-frequency stimulation supports the hypothesis that an enhanced activation failure occurs at Ls, possibly resulting from failure of sarcolemmal action potential propagation in the transverse tubules.

Adult↗
PubMed1994

A two-step adhesion cascade for T cell/endothelial cell interactions under flow conditions.

Neutrophil adherence to endothelial cells (ECs) under conditions of flow occurs in successive steps, including selectin-dependent primary adhesion and CD18-dependent secondary adhesion. We used a parallel-plate flow chamber to assess the steps in T cell adherence in vitro. On monolayers of L cells transfected with the EC adhesion molecules E-selectin, vascular cell adhesion molecule-1 (VCAM-1), or intercellular adhesion molecule-1 (ICAM-1), E-selectin was capable of mediating only primary adhesion, ICAM-1 was capable of mediating only secondary adhesion, and VCAM-1 was capable of mediating both primary and secondary adhesion. Studies using human umbilical vein EC monolayers stimulated for 24 h with IL-1 also revealed distinct primary and secondary steps in T cell adhesion under flow, and the secondary adhesion was inhibited > 90% by blocking both VCAM-1/alpha 4 beta 1 integrin and ICAM-1/CD18 integrin pathways. However, the primary adhesion under conditions of flow could not be attributed to any of the mechanisms known to support adhesion of leukocytes to ECs. Alone, this pathway was shown to mediate T cell rolling and was a necessary prerequisite for engagement of the two integrin pathways in this system. Thus, T cell adherence to 24-h IL-1-stimulated human umbilical vein ECs at venular wall shear stresses involves at least two successive steps, with clear molecular distinctions from the mechanisms accounting for neutrophil/EC adhesion.

Animals↗