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Biomedical subjects

J Turner

Publications and source records attributed to J Turner.

At least 127 records · Page 7Linked to original sources
PubMed1998

The cellular intake kinetics and acute biological effects of various oxovanadium species: a comparative study.

It is well known that different oxovanadium species can have significantly different biopotencies, including hypoglycemic actions. The basis for the observed differences in the biopotency of different oxovanadium species: vanadate, vanadyl, 1,10-phenanthroline bisperoxovanadate (phen-bpv), 4-methyl 1,10-phenanthroline bisperoxovanadate (mpv) and 4,7-dimethyl 1,10-phenanthroline bisperoxovanadate (dpv), was examined in this study. The cellular uptake kinetics for these oxovanadium species was measured. Phen-bpv and vandyl had the most rapid cellular uptake. Mpv, dpv and vanadate exhibited a much slower uptake kinetics. Stimulation of protein tyrosine phosphorylation (PTP), both the time dependency and the dose dependency, was used as an index for biopotency. Although phen-bpv and vanadyl had the same cellular uptake kinetics, they differed markedly in their ability to stimulate PTP. Structurally similar oxovanadium species, phen-bpv, mpv and dpv demonstrated different uptake kinetics and effects on stimulating PTP. Bioavailability, both in term of cellular uptake and migration or transport to the active site, has been shown to be an important factor, in addition to intrinsic activity of the oxovanadium species, in determining the overall biopotency. Finally, this study demonstrates that variation of the chelating ligand has a profound effect on the physiochemical properties and biological effects of the oxovanadium species.

Kinetics↗
PubMed1998

Activity of amoxicillin/clavulanate in patients with tuberculosis.

Some beta-lactam antibiotics are active in vitro against Mycobacterium tuberculosis. There are anecdotal reports of successful treatment of tuberculosis caused by multiple-drug-resistant strains of M. tuberculosis with regimens that included amoxicillin/clavulanate. Reduction of M. tuberculosis in the sputum of patients with pulmonary tuberculosis during administration of amoxicillin/clavulanate was measured by a quantitative culture method to determine the activity in vivo. Patients were randomized to receive isoniazid, ofloxacin, or amoxicillin/clavulanate for 7 days. Isoniazid was the most effective agent, reducing M. tuberculosis after 2 days at a mean rate (+/- standard deviation) of 0.60 +/- 0.30 log10 cfu/mL per day, compared with 0.32 +/- 0.05 and 0.34 +/- 0.03 for ofloxacin and amoxicillin/clavulanate, respectively. The early bactericidal activity of amoxicillin/clavulanate was comparable to that reported for antituberculous agents other than isoniazid. Further studies of beta-lactam antibiotics with in vitro activity against M. tuberculosis are warranted to define their role in treatment of tuberculosis.

Adolescent↗
PubMed1998

Effects of soy protein on renal function and proteinuria in patients with type 2 diabetes.

For > 150 y, clinicians and investigators have observed that high protein intakes accelerate the progression of renal disease and that low protein intakes have beneficial effects. Some studies suggest that the effects of soy-protein intake resemble those of a low-protein diet. The Brenner hypothesis suggests that high protein intakes by diabetic individuals create hyperfiltration and glomerular hypertension eventuating in renal damage. On the basis of the available evidence, we are proposing the soy-protein hypothesis, which states that substituting soy protein for animal protein in diabetes patients results in less hyperfiltration and glomerular hypertension and, therefore, resultant protection from diabetic nephropathy. Furthermore, substituting soy protein for animal protein should have therapeutic value in diabetic nephropathy with resultant slowing of deterioration of renal function and decreasing proteinuria. The preliminary results of the study of 8 type 2 diabetes patients with obesity, hypertension, and proteinuria are reported. Under the conditions of the study, providing soy protein as half of the daily protein intake had no distinct effects on renal function or proteinuria in these subjects. Soy-protein intake was associated with a significant reduction in serum cholesterol and triacylglycerol concentrations. Further studies are required to critically examine the effects of soy-protein intake on the renal function of diabetes patients.

Aged↗
PubMed1998

Aggregation of A beta Alzheimer's disease-related peptide studied by dynamic light scattering.

The aggregation behavior of the major component of Alzheimer's disease-related, amyloid peptides, Abeta-(1-40) and Abeta-(1-42), was studied in solution using dynamic light scattering. With most solvents employed, we found fibrils coexisting with oligomeric Abeta species. Pronounced differences were observed in aggregation of Abeta-(1-40) and (1-42) sequences in acetonitrile-water mixtures. Cofactors such as Zn2+ were found to induce deaggregation of Abeta instead of aggregation. The results indicated that the initial state of the peptide immediately after synthesis is rather poorly defined. Using freezing instead of lyophilization after the final peptide synthesis step, may partially relieve these problems.

Acetonitriles↗
PubMed1998

Activities of LL-37, a cathelin-associated antimicrobial peptide of human neutrophils.

Human neutrophils contain two structurally distinct types of antimicrobial peptides, beta-sheet defensins (HNP-1 to HNP-4) and the alpha-helical peptide LL-37. We used radial diffusion assays and an improved National Committee for Clinical Laboratory Standards-type broth microdilution assay to compare the antimicrobial properties of LL-37, HNP-1, and protegrin (PG-1). Although generally less potent than PG-1, LL-37 showed considerable activity (MIC, <10 microgram/ml) against Pseudomonas aeruginosa, Salmonella typhimurium, Escherichia coli, Listeria monocytogenes, Staphylococcus epidermidis, Staphylococcus aureus, and vancomycin-resistant enterococci, even in media that contained 100 mM NaCl. Certain organisms (methicillin-resistant S. aureus, Proteus mirabilis, and Candida albicans) were resistant to LL-37 in media that contained 100 mM NaCl but were susceptible in low-salt media. Burkholderia cepacia was resistant to LL-37, PG-1, and HNP-1 in low- or high-salt media. LL-37 caused outer and inner membrane permeabilization of E. coli ML-35p. Chromogenic Limulus assays revealed that LL-37 bound to E. coli O111:B4 lipopolysaccharide (LPS) with a high affinity and that this binding showed positive cooperativity (Hill coefficient = 2.02). Circular dichroism spectrometry disclosed that LL-37 underwent conformational change in the presence of lipid A, transitioning from a random coil to an alpha-helical structure. The broad-spectrum antimicrobial properties of LL-37, its presence in neutrophils, and its inducibility in keratinocytes all suggest that this peptide and its precursor (hCAP-18) may protect skin and other tissues from bacterial intrusions and LPS-induced toxicity. The potent activity of LL-37 against P. aeruginosa, including mucoid and antibiotic-resistant strains, suggests that it or related molecules might have utility as topical bronchopulmonary microbicides in cystic fibrosis.

Amino Acid Sequence↗
PubMed1998

Novel method for processing respiratory specimens for detection of mycobacteria by using C18-carboxypropylbetaine: blinded study.

A novel method for processing respiratory specimens to improve culture and acid-fast staining of mycobacteria is introduced. This new method utilized N,N-dimethyl-N-(n-octadecyl)-N-(3-carboxypropyl)ammonium inner salt (Chemical Abstract Service no. 78195-27-4), also known as C18-carboxypropylbetaine (CB-18). In a blinded, five-center study, CB-18-based processing was compared to the standard method combining NALC and NaOH (NALC/NaOH). A total of 573 respiratory specimens were tested. Individual specimens were split approximately equally; the host institutions processed half of each specimen by the NALC/NaOH method, while the other half was processed with CB-18 at Quest Diagnostics--Baltimore. A total of 106 specimens were culture positive for acid-fast bacilli (AFB). Replacement of the primary decontamination agent with CB-18 caused changes in all diagnostic parameters. Aggregate culture sensitivity improved by approximately 43% (P < 0.01), and smear sensitivity improved by approximately 58% (P < 0.01). The sensitivity of smear relative to that of M. tuberculosis isolates exceeded 93% (P < 0.01) when specimens were processed with CB-18. The average times to a positive result were reduced by 7.3 days in liquid culture (P < 0.01) and 5.3 days on solid media (P < 0.05); however, the CB-18 method had a 20.8% contamination rate in liquid culture versus a rate of approximately 7.5% with NALC/NaOH processing. There were also unusual reductions in liquid culture sensitivity and smear specificity among CB-18-processed specimens. The characteristics of the latter parameters suggested that refinement of the CB-18 processing method should allow further improvements in culture sensitivity. This study showed that the CB-18 method has the potential to improve both smear and culture detection for these important human pathogens.

Bacteriological Techniques↗
PubMed1998

Pulse-chase experiments revealed beta-secretase cleavage from immature full-length amyloid precursor protein harboring the Swedish mutation. Implications for distinct pathways.

The molecular mechanisms of the nonamyloidogenic and the amyloidogenic pathways of the amyloid precursor protein (APP) are unknown, but proteolysis of APP is essential for the generation of beta-amyloid. To study the time-course of C-terminal fragment generation by alpha- and beta-secretase, we expressed the APP751 isoform with the Swedish mutation in the human neuroblastoma cell line SY5Y as previously described (Urmoneit et al., 1995). We show in pulse-chase experiments that the C-terminal fragments, CT, generated by alpha-secretase and A4CT, generated by beta-secretase, could be generated from immature full-length APP before O-glycosylation is completed. Thus beta A4 may be generated from immature APP that has not passed through the trans-Golgi-network (TGN), which presents experimental evidence for the intracellular localization of beta-secretase activity in an earlier Golgi complex.

Alzheimer Disease↗
PubMed1998

Discriminating constant from variable angular velocities in structure from motion.

We investigated accuracy in discriminating between constant and variable angular velocities for orthographic projections of three-dimensional rotating objects. The reported judgments of "constant" or "variable" angular velocity were only slightly influenced by the projected angular velocities, but they were greatly affected by the variations of the deformation, a first-order component of the optic flow. When viewing either a rotating ellipsoidal volume or a planar surface that accelerated and decelerated over the course of rotation, observers' tendencies to report a variable angular velocity were increased when the temporal phase of the acceleration pattern increased the range of variation of the median deformation; the tendencies were decreased when the same acceleration pattern was used to decrease the range of variation of the median deformation. These results provide evidence contrary to the hypothesis that the visual system performs a mathematically correct analysis of the optic flow.

Discrimination Learning↗
PubMed1998

Cisplatin- and paclitaxel-induced apoptosis of ovarian carcinoma cells and the relationship between bax and bak up-regulation and the functional status of p53.

We investigated the roles of p53 and Bcl-2 homologues in the induction of apoptosis by cisplatin and paclitaxel in wild-type p53-expressing human ovarian carcinoma cells and cisplatin-resistant derivatives that have lost p53 function. Cisplatin induced apoptosis in parental A2780 but not in cisplatin-resistant A2780/cp70 cells, whereas paclitaxel induced apoptosis in both cell lines. Immunoprecipitation of p53 using antibodies specific for p53 conformation (pAb 1620 and pAb 240) showed that there were no relative changes in p53 conformation before and after cisplatin treatment in either cell line. A2780/cp70 cells have lost p53 function, yet they have wild-type p53 gene sequence. However, A2780/cp70 cells constitutively express more p53 in a form detected by pAb 240, an antibody that also detects mutant conformations of p53 that are transcriptionally inactive. There were no changes in levels of Bcl-2, Bcl-XL, or 24-kDa Bax over 72 hr after exposure to cisplatin or paclitaxel, but each agent led to up-regulation of Bak and 21-kDa Bax in A2780 cells. Paclitaxel, but not cisplatin, increased Bak and 21-kDa Bax levels in A2780/cp70 cells. These data suggest that apoptosis in A2780 and A2780/cp70 is associated with an increased level of Bak and 21 kDa Bax after drug-induced damage and that functional p53 may be required for this effect after cisplatin but not after paclitaxel.

Antineoplastic Agents↗
PubMed1997

Activation of c-Src by receptor tyrosine kinases in human colon cancer cells with high metastatic potential.

Recent data suggest that signal transduction may have a critical role in the development and regulation of the metastatic phenotype. Here, we investigated the role of c-Src activation in the process of human colon cancer metastasis to the liver. Our data, derived from two different sets of human colon cancer cell line metastatic variants, suggest that not only do highly-metastatic cells display constitutively elevated c-Src protein kinase activity when compared to poorly metastatic cells, but also that receptor tyrosine kinases participate in the ligand-activation of c-Src above basal levels. Specifically, the epidermal growth factor receptor (EGFR), p185HER2/Neu and the hepatocyte growth factor receptor (c-Met) appear to be linked to the process because they preferentially activate c-Src in highly-metastatic cells. EGFR was found to associate with c-Src in colon cancer cells and specific inhibitors of the EGFR resulted in a reduction of c-Src activity to basal levels. In addition, c-Src transfectants displayed partially-activated EGFRs, suggesting a feedback role for c-Src in the regulation of the EGFR. p185HER2/Neu was also identified in immunocomplexes of c-Src following ligand activation of the EGFR, but only in highly-metastatic cells. Collectively, these observations suggest a paradigm whereby c-Src interacts with multiple cell-surface growth factors in a catalytic fashion for the development of tumor cells with metastatic potential.

Colonic Neoplasms↗
PubMed1997

Effectiveness of a regional trauma system in reducing mortality from major trauma: before and after study.

OBJECTIVE: To assess the effect of the development of an experimental trauma centre and regional trauma system on the survival of patients with major trauma. DESIGN: Controlled before and after study examining outcomes between 1990 and 1993, spanning the introduction of the system in 1991-2. SETTING: Trauma centre in North Staffordshire Royal Infirmary and five associated district general hospitals in the North West Midlands regional trauma system, and two control regions in Lancashire and Humberside. SUBJECTS: All trauma patients taken by the ambulance services serving the regions or arriving other than by ambulance with injury severity scores > 15, whether or not they had vital signs on arrival at hospital. MAIN OUTCOME MEASURES: Survival rates standardised for age, severity of injury, and revised trauma score. RESULTS: In 1990, 33% of major trauma patients in the experimental region were taken to the trauma centre, and by 1993 this had risen to only 39%. Crude death rates changed by the same amount in the control regions (46.5% in 1990-1 to 44.4% in 1992-3) as in the experimental region (44.8% to 41.3%). After standardisation, the estimated change in the probability of dying in the experimental region compared with the control regions was -0.8% per year (95% confidence interval -3.6% to 2.2%); for out of hours care, the change was 1.6% per year (-2.3% to 5.6%), and, for multiply injured patients, the change was -1.6% (-6.1% to 2.6%). CONCLUSION: Any reductions in mortality from regionalising major trauma care in shire areas of England would probably be modest compared with reports from the United States.

Adolescent↗
PubMed1997

Fidelity of Escherichia coli DNA polymerase III holoenzyme. The effects of beta, gamma complex processivity proteins and epsilon proofreading exonuclease on nucleotide misincorporation efficiencies.

The fidelity of Escherichia coli DNA polymerase III (pol III) is measured and the effects of beta, gamma processivity and epsilon proofreading subunits are evaluated using a gel kinetic assay. Pol III holoenzyme synthesizes DNA with extremely high fidelity, misincorporating dTMP, dAMP, and dGMP opposite a template G target with efficiencies finc = 5.6 x 10(-6), 4.2 x 10(-7), and 7 x 10(-7), respectively. Elevated dGMP.G and dTMP.G misincorporation efficiencies of 3.2 x 10(-5) and 5.8 x 10(-4), attributed to a "dNTP-stabilized" DNA misalignment mechanism, occur when C and A, respectively, are located one base downstream from the template target G. At least 92% of misinserted nucleotides are excised by pol III holoenzyme in the absence of a next correct "rescue" nucleotide. As rescue dNTP concentrations are increased, pol III holoenzyme suffers a maximum 8-fold reduction in fidelity as proofreading of mispaired primer termini are reduced in competition with incorporation of a next correct nucleotide. Compared with pol III holoenzyme, the alpha holoenzyme, which cannot proofread, has 47-, 32-, and 13-fold higher misincorporation rates for dGMP.G, dTMP.G, and dAMP.G mispairs. Both the beta, gamma complex and the downstream nucleotide have little effect on the fidelity of catalytic alpha subunit. An analysis of the gel kinetic fidelity assay when multiple polymerase-DNA encounters occur is presented in the "Appendix" (see Fygenson, D. K., and Goodman, M. F. (1997) J. Biol. Chem. 272, 27931-27935 (accompanying paper)).

Catalysis↗
PubMed1997

Sonic hedgehog promotes rod photoreceptor differentiation in mammalian retinal cells in vitro.

The hedgehog gene family encodes secreted proteins important in many developmental patterning events in both vertebrates and invertebrates. In the Drosophila eye disk, hedgehog controls the progression of photoreceptor differentiation in the morphogenetic furrow. To investigate whether hedgehog proteins are also involved in the development of the vertebrate retina at stages of photoreceptor differentiation, we analyzed expression of the three known vertebrate hedgehog genes. We found that Sonic hedgehog and Desert hedgehog are expressed in the developing retina, albeit at very low levels, whereas Indian hedgehog (Ihh) is expressed in the developing and mature retinal pigmented epithelium, beginning at embryonic day 13. To determine whether hedgehog proteins have activities on developing retinal cells, we used an in vitro system in which much of retinal histogenesis is recapitulated. N-terminal recombinant Sonic Hedgehog protein (SHH-N) was added to rat retinal cultures for 3-12 d, and the numbers of retinal cells of various phenotypes were analyzed by immunohistochemistry. We found that SHH-N caused a transient increase in the number of retinal progenitor cells, and a 2- to 10-fold increase in the number of photoreceptors differentiating in the cultures when analyzed with three different photoreceptor-specific antigens. In contrast, the numbers of retinal ganglion cells and amacrine cells were similar to those in control cultures. These results show that Hedgehog proteins can regulate mitogenesis and photoreceptor differentiation in the vertebrate retina, and Ihh is a candidate factor from the pigmented epithelium to promote retinal progenitor proliferation and photoreceptor differentiation.

Animals↗
PubMed1997

Cytokine gene therapy of cancer using gene gun technology: superior antitumor activity of interleukin-12.

We compared the antitumor effect of several transgene expression plasmids encoding specific cytokines, including interleukin-2 (IL-2), IL-4, IL-6, IL-12, interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and granulocyte-macrophage colony-stimulating factor (GM-CSF), following gene gun-mediated DNA delivery into the epidermis overlying an established intradermal murine tumor. IL-12 gene therapy was much more effective than treatment with any other tested cytokine gene for induction of tumor regression. Strong activation of antitumor immunity in response to IL-12 gene therapy was evidenced by an augmented CD8+ T cell-mediated cytolytic activity in the draining lymph nodes of tumor-bearing mice. Furthermore, following the IL-12 gene therapy protocol, test mice were able to eradicate not only the treated but also the untreated solid tumors at distant sites. This systemic antitumor effect of IL-12 gene therapy was not associated with visible signs of toxicity or significantly elevated systemic levels of IFN-gamma. These results show that gene gun-mediated in vivo delivery of IL-12 cDNA clearly distinguishes itself from the other cytokine gene therapy approaches tested in parallel, suggesting that this delivery system may be employed as an efficient model for comparative studies of in vivo cytokine gene therapy. The results also suggest that the current IL-12 gene therapy strategy may provide a safer alternative to IL-12 protein therapy for clinical treatment of cancers.

Animals↗