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Biomedical subjects

J Woodcock

Publications and source records attributed to J Woodcock.

At least 19 recordsLinked to original sources
PubMed1994

Identification of residues in the first and fourth helices of human granulocyte-macrophage colony-stimulating factor involved in biologic activity and in binding to the alpha- and beta-chains of its receptor.

Residues within the first and fourth helices of human granulocyte-macrophage colony-stimulating factor (hGM-CSF) were analyzed for their role in biologic activity and interaction with the alpha- and beta-chains of the hGM-CSF receptor. Within the first helix substitution of the surface residues Glu14, Asn17, Gln20, Arg23, Arg24, and Asn27 or the buried residues Ala18, Leu25, and Leu28 did not significantly impair bioactivity or receptor binding. Substitutions at the buried residues Ala22 and Leu26 had intermediate bioactivity. However, substitutions of the surface residue Glu21 or the buried residue Ile19 reduced the relative bioactivity of the analogues to as little as 0.45% and 0.3%, respectively. Substitution of the charged surface residues of the fourth helix showed that substitution at Glu104, Lys107, and Lys111 had no significant effect on bioactivity, but substitution at Glu108 and Asp112 reduced the potency of the analogues to 34% and 7%, respectively. Receptor binding studies showed that, whereas Glu21 is the critical residue for binding to the hGM-CSF-receptor beta-chain, Asp112 is likely to be involved in binding to the GM-CSF-receptor alpha-chain. These results establish the relative contribution of residues in the first and fourth helices for GM-CSF bioactivity and receptor binding, and support a model where the fourth helix of GM-CSF interacts with the alpha-chain, and the first helix with the beta-chain of the GM-CSF receptor.

Amino Acid Sequence↗
PubMed1994

The comparative pharmacokinetics and tissue penetration of single-dose ciprofloxacin 400 mg i.v. and 750 mg po.

The pharmacokinetics of ciprofloxacin following single doses of 400 mg i.v. and 750 mg po were compared in six healthy volunteers. Concentrations of ciprofloxacin were measured in plasma, cantharides induced blister fluid and urine, by microbiological assay and high performance liquid chromatography (HPLC). Mean peak plasma concentration was 6.7 +/- 1.4 mg/L after i.v. and 3.9 +/- 1.7 mg/L after oral administration with mean elimination half-lives of 4.2 and 4.0 h respectively. Mean area under the concentration versus time curve (AUC) was greater following oral administration (19.2 +/- 1.1 mg/L.h versus 14.2 +/- 1.1 mg/L.h). Blister fluid peak concentrations following i.v. and oral administration were 2.6 +/- 1.3 mg/L and 2.28 +/- 1.2 mg/L respectively. The elimination half-life from blister fluid was 4.1 +/- 1.1 h and the AUC 13.8 +/- 1.1 mg/L.h following i.v. administration compared with 4.6 +/- 1.5 h and 20.3 +/- 1.3 mg/L.h for the oral dose. A mean of 50.8% of i.v. administered drug and 39.6% or orally administered drug was excreted in urine in 24 h as measured by HPLC. The corresponding values by microbiological assay were greater, suggesting excretion of active metabolites. Both i.v. and oral doses produced levels in blister fluid concentration above the MICs for most Enterobacteriaceae, Pseudomonas aeruginosa, Haemophilus influenzae and Neisseria spp. at 12 h post dose. The pharmacokinetic data from inflammatory fluid indicate that ciprofloxacin 400 mg i.v. is more equivalent to 750 mg po than the plasma pharmacokinetic data suggest.

Administration, Oral↗
PubMed1994

Concentration of amoxycillin and clavulanate in lung compartments in adults without pulmonary infection.

BACKGROUND: The efficacy of an antibiotic is usually predicted from serum levels and MIC90 values for likely pathogens, but in the lung tissue concentrations may be more informative. This study compares concentrations of amoxycillin and clavulanate in serum, epithelial lining fluid (ELF), alveolar macrophages, and bronchial mucosa in 15 adults. METHODS: Amoxycillin 500 mg and clavulanic acid 250 mg were given 1-2 hours before diagnostic bronchoscopy for haemoptysis or radiological abnormality. Mucosal biopsy samples were taken from macroscopically normal sites, alveolar macrophages harvested by lavage, and ELF volume derived from urea concentrations in bronchial lavage fluid and blood. Amoxycillin was assayed by inhibition of growth of Micrococcus lutea, and clavulanate (in serum, ELF, and bronchial mucosa) by inhibition of growth of Klebsiella pneumoniae; in macrophages clavulanate was measured by high performance liquid chromatography. RESULTS: The median concentrations in serum were 6.90 mg/l for amoxycillin and 5.25 mg/l for clavulanate. The median bronchial mucosal concentration of amoxycillin was 2.99 mg/l and of clavulanate was 1.65 mg/l; the median concentrations in ELF were 0.89 and 0.96 mg/l, and in macrophages 0 and 0.76 mg/l, respectively. In macrophages amoxycillin levels were undetectable in 10 of 14 subjects (71%); by contrast, only 6 of 14 subjects (43%) had no detectable clavulanate. CONCLUSIONS: Clavulanate levels exceeded quoted MIC90 values (around 0.25 mg/l) for Legionella pneumophila both in ELF and in macrophages. Amoxycillin-clavulanate may therefore have a clinical role in infections with Legionella pneumophila.

Adult↗
PubMed1994

Can observational studies replace or complement experiment?

The therapeutic effects of interventions in patients with rheumatoid arthritis (RA) are frequently modest. In the assessment of treatments effects, variability due to a variety of sources causes problems that are best controlled by randomized clinical trials. Currently most trials give only a short term picture of RA, a chronic disease whose outcome is multidimensional. Inclusion criteria of clinical trials are frequently very strict, raising concern about the external validity of the results. More longterm data is needed to guide clinical practice. Observational studies may contribute to the body of evidence, but have inherent shortcomings. They are liable to bias and supply weaker evidence. There must be creative development of trial designs suitable for evaluating longterm outcomes. Such trials may include many of the positive features of observational studies, but should not omit the principles of randomization and controlled comparison.

Antirheumatic Agents↗
PubMed1992

GM-CSF, IL-3 and IL-5: cross-competition on human haemopoietic cells.

The biological properties of GM-CSF, IL-3 and IL-5 are multiple; initially described as haemopoietic growth factors, they also regulate inflammation, allergic reactions and cell adherence. The receptors for these three cytokines share a common component which may play a key role in their biological activity. This review describes the potential roles of GM-CSF, IL-3 and IL-5 in inflammation and discusses approaches to modulate their function.

Binding, Competitive↗
PubMed1991

Interaction of antibiotics with A- and P-site-specific bases in 16S ribosomal RNA.

We have studied the interactions of the antibiotics apramycin, kasugamycin, myomycin, neamine and pactamycin with 16S rRNA by chemical probing of drug-ribosome complexes. Kasugamycin and pactamycin, which are believed to affect translational initiation, protect bases in common with P-site-bound tRNA. While kasugamycin protects A794 and G926, and causes enhanced reactivity of C795, pactamycin protects G693 and C795. All four of these bases were previously shown to be protected by P-site tRNA or by edeine, another P-site inhibitor. Apramycin and neamine, which both induce miscoding and inhibit translocation, protect A1408, G1419 and G1494, as was also found earlier for neomycin, gentamicin, kanamycin and paromomycin. A1408 and G1494 were previously shown to be protected by A-site tRNA. Surprisingly, myomycin fails to give strong protection of any bases in 16S rRNA, in spite of having an apparently identical target site and mode of action to streptomycin, which protects several bases in the 915 region. Instead, myomycin gives only weak protection of A1408. These results suggest that the binding site(s) of streptomycin and myomycin have yet to be identified.

Aminoglycosides↗
PubMed1991

Commentary concerning demonstration of safety and efficacy of investigational anticancer agents in clinical trials.

Expeditious clinical development and approval of new drugs that are beneficial to patients are matters of high priority. There has been a great deal of discussion within the oncology community about what should constitute evidence of effectiveness of new anticancer agents for purposes of drug approval. This commentary is intended to illustrate a variety of end points that can lead to approval of new anticancer agents for specific clinical situations. Although the ultimate hope of antineoplastic therapy is prolongation of life, there are other effects of anticancer drugs that constitute clear clinical benefit and represent evidence of effectiveness. The guiding principle is that the beneficial effects obtained from a new drug should sufficiently outweigh the adverse effects such that the potential risk:benefit ratio achieved by an individual patient is favorable. The assessment of a new drug should flexibly evaluate safety and efficacy in the context of the specific clinical condition being treated. Early discussions with the Food and Drug Administration (FDA) and the National Cancer Institute (NCI) are recommended to identify prospectively the end points and trial designs needed to demonstrate effectiveness of a new drug. The general principles discussed will likely apply to the drug approval process for other medical disciplines as well.

Antineoplastic Agents↗
PubMed1990

Focusable Doppler ultrasound in mapping dorsal hand flaps.

The dorsal arterial anatomy of 50 normal hands was mapped using high frequency pulsed wave Doppler ultrasound. The findings correlated with previous anatomical studies regarding the variability in the incidence of the arteries. Eight clinical cases were studied preoperatively, seven of whom underwent surgery involving local flaps. Intraoperatively the presence of the mapped vessels was confirmed in each case. This investigation defines the role of high frequency pulsed wave Doppler ultrasound in the mapping of dorsal hand flaps.

Adult↗
PubMed1987

Mutational analysis of upstream sequences required for transcriptional activation of the Klebsiella pneumoniae nifH promoter.

Upstream sequences of the Klebsiella pneumoniae nifH promoter were mutagenised and activation of the mutated promoters by the nif-specific transcriptional activator protein NifA examined in vivo. Of the sixteen mutations analysed, only those within the nifH upstream activator sequence (UAS), characterised by a TGT-N10-ACA motif, influenced nifH promoter activity. Mutations altering the two-fold rotational symmetry of the UAS or the spacing between the TGT and ACA motifs reduced promoter activity, consistent with the UAS functioning as a NifA binding site. The bases flanking the TGT-ACA motif of the UAS also appear to influence activation by NifA. Substituting the nifH UAS with a binding site for the transcriptional activator NtrC resulted in improved NtrC-dependent activation of the nifH promoter demonstrating that the activator specificity of the nifH promoter is dependent upon the presence of the appropriate upstream sequences to which the activator binds.

Base Sequence↗
PubMed1987

Positional requirements for the function of nif-specific upstream activator sequences.

The upstream activator sequence (UAS) found in Klebsiella pneumoniae nif promoters and required for the activation of transcription by nifA, is absent from the nifF-nifL intergenic region, but is present downstream from the nifLA transcription start at +59. To determine whether nif upstream activator sequences can function in a 3' position, the nifH UAS was cloned downstream from the NifH transcription start, but no activation of transcription by nifA dependent upon the UAS in its 3' location could be detected. A mild repressive effect was detectable when the nifH UAS was placed downstream of the nifH promoter, but not when the cat promoter was substituted for the nifLA promoter upstream from the motif at +59 described above. However, deletion analysis showed that the UAS motif located downstream of the nifLA promoter has a role in transcription from the nifF promoter, although it is situated at position -263 with respect to the nifF transcription start, about 100 bp further upstream than previously described occurrences of the activator sequence.

Genes, Bacterial↗
PubMed1987

Transcriptional activation of the Klebsiella pneumoniae nitrogenase promoter may involve DNA loop formation.

Transcriptional activation of nitrogen fixation genes by NifA in Klebsiella pneumoniae requires an upstream NifA binding site. We now report that the introduction of half turns of the DNA helix into the DNA separating the upstream NifA binding site from the downstream promoter element of the nifH promoter decreases NifA-mediated activation to a greater extent than does the introduction of full helical turns. Reducing the spacing between the upstream and downstream elements of the nifH promoter also results in a promoter down phenotype. Introduction of a tight protein-binding site, the lac operator, between the upstream and downstream promoter elements did not render activation of the nifH promoter sensitive to occupancy of this site by the lac repressor. These findings indicate that NifA-mediated activation of transcription requires that NifA is bound upstream, and to the correct face of the DNA helix, in order to interact with downstream transcription factors. This implies that the interaction is brought about by the formation of a DNA loop between upstream and downstream promoter elements rather than by NifA sliding downstream.

DNA Restriction Enzymes↗
PubMed1986

Neovascularization in human cutaneous melanoma: a quantitative morphological and Doppler ultrasound study.

A study of tumour blood flow in 36 patients with 38 malignant melanomas using Doppler Ultrasound flowmetry has shown that tumour blood flow can be detected in most melanomas more than 0.9 mm thick, and is absent in most melanomas less than this thickness. Histological quantitation of blood vessels using lectin staining to delineate vascular endothelium and automated image analysis has shown a high degree of correlation between vascularity at the tumour base and tumour thickness. Since it is likely that the development of a vascular plexus at the tumour base is a prerequisite for dissemination, the development of these blood vessels may prove to be an independent prognostic factor for thin melanomas. This work also provides a new model for dynamic, in vivo investigation of the vascularity of human tumours.

Adult↗
PubMed1986

Rejection of skin grafts and generation of cytotoxic T cells by mice depleted of L3T4+ cells.

In mice, "helper/inducer" T cells can be depleted by treatment with a rat monoclonal antibody to the cell surface antigen, L3T4, which is homologous to the human antigen T4 (CD4). In order to examine the contribution of "helper/inducer" T cells to cellular immunity, C57BL/6 (H-2b) mice were treated weekly with 1 mg i.v. of a monoclonal antibody to L3T4. Three days after the first injection, the mice received skin grafts from BALB/c (H-2d) mice. The mice were then examined for skin graft rejection and for the development of cytotoxic cells. Treatment with anti-L3T4 prolonged skin graft survival from 9 to 18 days. Graft rejection was associated with the development of cellular cytotoxicity against H-2d targets. Cytotoxicity developed despite greater than or equal to 90% depletion of splenic L3T4+ cells. Allospecific cytotoxic T cells could also be generated in vitro from C57BL/6 spleen cells depleted of L3T4+ cells, when these were exposed in a mixed leukocyte culture to irradiated, T-cell-depleted, BALB/c spleen cells. In a mixed leukocyte culture using responder spleen cells from untreated C57BL/6 mice, both proliferation and interleukin 2 production were inhibited in the presence of antibody to L3T4 and, to a lesser extent, by antibody to Lyt-2. Complete inhibition was achieved by the presence of both antibodies. In a mixed leukocyte culture using responder spleen cells from C57BL/6 mice that had been treated with anti-L3T4, both proliferation and interleukin 2 production were inhibited largely by antibody to Lyt-2, although the presence of both anti-Lyt-2 and anti-L3T4 was most inhibitory. These findings indicate that graft rejection and cellular cytotoxicity can be generated in mice depleted of L3T4+ cells by methods that have previously been shown to abrogate humoral immunity. Cellular immunity appears to require few, if any, L3T4+ cells. These findings have implications for the clinical use of antibodies to "helper/inducer" T cells.

Animals↗
PubMed1985

Inhibition of humoral immunity in vivo by monoclonal antibody to L3T4: studies with soluble antigens in intact mice.

Monoclonal antibody (MAb) to the mouse "helper" T cell antigen L3T4 inhibits the T cell response to class II major histocompatibility antigens on antigen-presenting cells in vitro and in thymectomized mice. To examine the effect of MAb to L3T4 on humoral immunity in euthymic mice, we treated BALB/c mice with 1 mg of anti-L3T4 i.p. at the time of immunization with either bovine serum albumin (BSA) or chicken egg ovalbumin (OA) in complete Freund's adjuvant. Administration of MAb to L3T4 selectively depleted greater than 90% of L3T4+ cells from the blood, spleen, and lymph nodes, but it had little effect on thymocytes. Mice treated with anti-L3T4 were unable to generate an IgG response to either BSA or OA. Treatment with anti-L3T4 also prevented the antigen-specific IgM response to these antigens, although it did not prevent nonspecific stimulation of IgM anti-BSA and anti-OA antibodies induced by adjuvant in the absence of antigen. Humoral immunity was inhibited even when treatment was delayed until 48 hr after immunization. These findings indicate that T cell help for humoral immunity can be abrogated in intact mice by MAb to L3T4.

Animals↗
PubMed1984

Human and murine natural killer cell activity may require lipoxygenation of arachidonic acid.

Natural killing (spontaneous cell-mediated cytotoxicity) by either human blood cells or mouse spleen cells is reversibly inhibited by nordihydroquaiaretic acid or BW755C, agents that antagonize the lipoxygenation of arachidonic acid. Cultured mouse natural killer cells are similarly inhibited. These studies suggest that natural killing may be dependent on the lipoxygenation of arachidonic acid.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1982

Solvent abuse from a health education perspective.

1 The development of health education and preventive strategies for solvent abuse requires the adaptation of findings and data from other fields and other countries. Experience with illicit drugs suggests that simply denying access to a particularly abused substance may only serve to shift abusers towards other substances. It is, therefore, necessary to acquire evidence on which to judge the relative harmfulness of different substances. Data from the USA on the overall mortality from solvent abuse and on the relative involvement of different solvents is summarized. 2 Findings from health education researches lead to the conclusion that (a) health education is not an effective way of preventing experimentation with solvents, but (b) health education can be effective in modifying abusers' choices of substance and styles of use. 3 Combining these different types of information led to the production of a leaflet suggesting health education strategies that might reduce the likelihood of physical harm befalling solvent abusers. 4 Finally, a plea is made for reports of toxic effects from abused substances to include the kind of data that would assist the development of preventive strategies.

Health Education↗