PubMed Health⌕ Search

Biomedical subjects

P A Goodwin

Publications and source records attributed to P A Goodwin.

8 recordsLinked to original sources
PubMed1998

In vitro patch-clamp studies in skin fibroblasts.

We have conducted single-channel patch-clamp experiments in skin fibroblasts maintained in culture. Two different cell lines, a mouse 3T3-L1 cell line and a human B17 cell line, were selected for these pilot studies. Recordings were made from both cell-attached and excised inside-out patches at room temperature. In the case of the 3T3-L1 cells, the success rate in obtaining good seals (> 1Gomega) was low, and channel openings in either cell-attached or excised patches were rare. We have, however, identified a channel in a cell-attached configuration with a slope conductance of 39 pS in symmetrical K+ solutions. In the case of the human B17 cells, good quality seals were more readily obtained. One principal type of channel opening was identified. In cell-attached patches, the prevalent type of channel in symmetrical K+ solutions had a conductance of 187 pS. This channel was activated by strong depolarization, and there was usually more than one active channel in the patch. It was blocked by extracellular tetraethylammonium (20 mM), and persisted when external Cl- was replaced by aspartate. In excised inside-out patches bathed in symmetrical K+, this channel was activated by an increase in Ca+ applied to the intracellular face. A large conductance channel (175 pS) was also observed in excised inside-out patches, with a reverse physiological K+ gradient. This channel had a reversal potential > 40 mV and appeared not to be voltage-dependent under these recording conditions (2 mM Ca(2+)i). We conclude that the channel we have identified in these cells belongs to the maxi-K+ channel class.

3T3 Cells↗
PubMed1997

Death with dignity.

Explore the source record for details and available documents.

Emergency Medicine↗
PubMed1994

Superoxide scavenging activity in leukocytes and absence of cellular toxicity of a series of coumarins.

Sixteen synthetic or plant-derived coumarins of dietary importance with different patterns of substitution were tested for their capacity to scavenge superoxide and for their cytotoxicity. Superoxide was generated by human polymorphonuclear leukocytes stimulated by phorbol myristate acetate and was measured using the reduction of ferricytochrome c or of nitrobule tetrazolium (NBT). Eleven of the coumarins, all lacking dihydroxy substitution, did not scavenge superoxide. Of the remaining five, the most potent scavenger was fraxetin (7,8-dihydroxy-6-methoxycoumarin) with an IC50 (concentration producing 50% inhibition) of 2.3 microM in the cytochrome assay and 5.8 microM using NBT. The other four coumarins (all containing ortho-dihydroxy catechol functions, and found previously to be pro-oxidant in cell-free systems by virtue of reduction of ferric to ferrous ions), themselves rapidly reduced cytochrome c. Therefore their effects on superoxide were measured using NBT, yielding IC50 values in the range 8.5 to 82.0 microM. Fraxetin and the other active and inactive coumarins were not directly cytotoxic at 100 microM to leukocytes or to erythrocytes, as shown by their failure to cause release of cytosolic lactate dehydrogenase or to cause haemolysis, respectively. However, all five dihydroxylated pro-oxidant coumarins were toxic to NS20Y neuroblastoma cells in 24 hr culture, whereas the other eleven coumarins were nontoxic. We conclude that 7,8-dihydroxylated coumarins such as fraxetin are agents which are not themselves directly cytotoxic and are capable of direct scavenging of superoxide anion radicals, an action which might be protective at sites of leukocyte activation during inflammation. However, in the presence of free ferric ions they may exert potentially damaging pro-oxidant actions, including cytotoxicity. This series of compounds provides a useful basis for structure-activity studies designed to achieve separation or combination of these properties.

Animals↗
PubMed1988

Prolonged disability from job-related injury.

Workers who do not recover as expected from job-related injuries are frequently disabled not by organic complications of their injuries but by a problem that the patient may not acknowledge and the physician may not recognize and deal with. The family physician should be skilled in detecting nonorganic causes of disability and in intervening appropriately to maintain a therapeutic relationship between the patient and the health care providers.

Accidents, Occupational↗
PubMed1985

Interspecies regulation of the SOS response by the E. coli lexA+ gene.

A plasmid-encoded E. coli lexA+ gene was introduced into 6 species of Enterobacteria. Ultraviolet light-sensitization occurred in all species except P. rettgeri, and 4 organisms showed reduced inducibility of RecA-like proteins. The mechanism of lexA+ control of the SOS response therefore appears common to several species.

Bacterial Proteins↗
PubMed1985

Differences in mutagenic and recombinational DNA repair in enterobacteria.

The incidence of recombinational DNA repair and inducible mutagenic DNA repair has been examined in Escherichia coli and 11 related species of enterobacteria. Recombinational repair was found to be a common feature of the DNA repair repertoire of at least 6 genera of enterobacteria. This conclusion is based on observations of (i) damage-induced synthesis of RecA-like proteins, (ii) nucleotide hybridization between E. coli recA sequences and some chromosomal DNAs, and (iii) recA-negative complementation by plasmids showing SOS-inducible expression of truncated E. coli recA genes. The mechanism of DNA damage-induced gene expression is therefore sufficiently conserved to allow non-E. coli regulatory elements to govern expression of these cloned truncated E. coli recA genes. In contrast, the process of mutagenic repair, which uses umuC+ umuD+ gene products in E. coli, appeared less widespread. Little ultraviolet light-induced mutagenesis to rifampicin resistance was detected outside the genus Escherichia, and even within the genus induced mutagenesis was detected in only 3 out of 6 species. Nucleotide hybridization showed that sequences like the E. coli umuCD+ gene are not found in these poorly mutable organisms. Evolutionary questions raised by the sporadic incidence of inducible mutagenic repair are discussed.

DNA Repair↗