Biomedical subjects

J M Wood

Publications and source records attributed to J M Wood.

At least 19 recordsLinked to original sources

PubMed1992

Production of catecholamines in the human epidermis.

Cell-free extracts from human full thickness skin (i.e., epidermis and dermis), suction blister roofs (i.e., epidermis) and from human keratinocytes express biopterin-dependent tyrosine hydroxylase a well as phenylethanolamine-N-methyl transferase, both representing key enzymes for the biosynthesis of epinephrine. These enzyme activities could not be detected in cell extracts from human melanocytes and human fibroblasts. Since keratinocytes in the human epidermis, and in cell cultures, express a high density of beta-2-adrenoceptors, and this signal transduction system regulates intracellular calcium homeostasis, it can be concluded that epinephrine production in the epidermis activates calcium transport via the beta-2-adrenoceptor system. Our results show for the first time that the human epidermis has the capacity to independently produce epinephrine.

Biopterins↗

PubMed1992

Calcium transport and regulation in human primary and metastatic melanoma.

Thioredoxin reductase (TR) activity on primary melanomas and in surrounding skin is regulated by calcium and, therefore, TR activity can be used to measure the flux of calcium between primary tumors and their surrounding epidermis. Calcium uptake in human melanotic melanoma cell lines SKmel-23 (metastatic) and BC-PT-1 (primary) is related to the density of beta-2-adrenoceptors. The non-pigmented cell line HT-144 (metastatic), did not express beta-2-adrenoceptors, yielding a slow rate of calcium uptake compared to SKmel-23 and BC-PT-1. Cell extracts from melanotic and amelanotic melanoma tissues did not contain a phenylethanolamine-N-methyltransferase (PNMT) for the biosynthesis of epinephrine from norepinephrine and S-adenosylmethionine. However, human full-thickness skin, epidermis and cell cultures of human keratinocytes contained significant PNMT activities. Taken together, these results indicate that (a), TR can be used to monitor calcium flux between primary melanomas and their surrounding skin and vice versa and (b), calcium uptake may be regulated by stimulation of beta-2-adrenoceptors on melanotic melanomas by epinephrine synthesized in the surrounding skin.

Biological Transport↗

PubMed1992

Rapid screening for taxanes by tandem mass spectrometry.

A highly specific and sensitive method is described for determining taxol, cephalomannine, and baccatin III in crude plant extracts. Radical anions of the taxanes are formed by desorption chemical ionization, and a parent tandem mass spectrometric scan is used to recognize these compounds by their characteristic dissociations. The limit of detection of the individual taxanes in typical plant matrices is less than 500 pg when all three species are screened simultaneously. Because of the sensitivity of the method, extraction times can be shortened to 30 min and crude extracts can be examined at the rate of 6/h. Detection of all three taxanes extracted from a single Taxus cuspidata needle in a combined extraction/analysis time of less than 1 h is demonstrated.

Alkaloids↗

PubMed1992

Redesigned purification yields a fully functional PutA protein dimer from Escherichia coli.

Proline utilization by Escherichia coli and Salmonella typhimurium requires expression of genes putP (encoding a proline transporter) and putA. Genetic data indicate that the PutA protein is both put repressor and a respiratory chain-linked dehydrogenase. We report a redesigned purification procedure as well as the physical characteristics and biological activities of the PutA protein purified from E. coli. The purified protein was homogeneous as determined by electrophoresis performed under denaturing and nondenaturing conditions. Its N-terminal sequence corresponded to that predicted by the DNA sequence. We showed copurification of proline and delta 1-pyrroline-5-carboxylate dehydrogenase activities. Purified PutA protein bound put DNA in vitro in an electrophoretic band-shift assay and it could be reconstituted to inverted membrane vesicles, yielding proline dehydrogenase activity. The Stokes radius and Svedberg coefficient of the protein were determined to be 7.1 nm and 9.9 S, respectively. These hydrodynamic data revealed that the protein in our preparation was dimeric with a molecular mass of 293 kDa and that it had an irregular shape indicated by the friction factor (f/f0) of 1.6.

Bacterial Proteins↗

PubMed1992

High growth reassortant influenza vaccine viruses: new approaches to their control.

When a new strain of an influenza virus is required to be incorporated into influenza vaccine, attempts are made to recombine such strains with laboratory adapted viruses, which will grow to high titre in order to improve the yield of the vaccine strain. It is important that such high growth reassortant vaccine strains are not contaminated with genes coding for the antigenic determinants of the high growth laboratory strain. We describe the characterization of two recent high growth reassortants and the application of the polymerase chain reaction to ensure their genetic identity and purity.

Antigens, Viral↗

PubMed1992

Effects of the 1989 San Francisco earthquake on frequency and content of nightmares.

In a systematic evaluation of the effects of a natural disaster on nightmares, nightmare frequency was found to be about twice as high among 92 San Francisco Bay area college students as among 97 control subjects in Tucson, Arizona, after the 1989 Loma Prieta earthquake. Subjects in California had not only more nightmares in general but substantially more nightmares about earthquakes. Over a 3-week period, about 40% of those in the San Francisco Bay area reported one or more nightmares about an earthquake, as compared with only 5% of those in Arizona. However, nightmares about earthquakes were not more emotionally intense than other nightmares. These findings support the long-held view that the experience of a potentially traumatic event can result in more frequent nightmares, particularly about the event itself, but contradict the common opinion that nightmares about such events are unusually intense.

Adult↗

PubMed1992

Nightmare prevalence in the healthy elderly.

Fifty-one healthy elderly subjects (median age = 65) gave retrospective estimates of nightmare frequency in questionnaires and recorded the occurrence of nightmares in daily logs over a 2-week period. (a) Mean annual nightmare frequency as estimated from logs was only 65% as high among college student controls. (b) Elderly subjects were about 1/5 as likely as college students to report a problem with nightmares. (c) Frequency estimates on the basis of logs were over 10 times higher than retrospective estimates.

Aged↗

PubMed1992

Evaluation of the efficacy of contrast sensitivity measures for the detection of early primary open-angle glaucoma.

We investigated the relative efficacy of contrast sensitivity (CS) measures for the identification of early primary open-angle glaucoma (POAG) patients. The contrast sensitivity function (CSF) was sampled at five spatial frequencies using a standard oscilloscope technique and measures of CS were also obtained using the Cambridge Gratings, Pelli-Robson CS Charts, Melbourne Edge Test (MET), and the High and Low Contrast Bailey-Lovie Letter Charts. Of the techniques evaluated, the High and Low Contrast Bailey-Lovie Letter Charts and the oscilloscope technique at the peak of the CSF exhibited the highest levels of sensitivity and specificity for differentiating between the POAG patients and normals. However, the relatively low levels of sensitivity and specificity obtained for the oscilloscope and chart tests overall indicate that, regardless of the pass/fail criterion selected, CS is unsuitable for screening for early POAG.

Adult↗

PubMed1992

Could the pharmacological differences observed between angiotensin II antagonists and inhibitors of angiotensin converting enzyme be clinically beneficial?

Over the past several years, angiotensin I converting enzyme (ACE) inhibitors, compounds that block the formation of angiotensin II (ANG II), have become widely used in the treatment of cardiovascular disease. Recently, a new class of orally active, non-peptide inhibitors of the renin-angiotensin system, the ANG II receptor antagonists have also become available. Since both classes of compounds block the renin-angiotensin system, although at different sites, it remains to be determined whether blockade of ANG II receptors will have any specific advantage over inhibition of ACE. The following review assesses the actions of ANG II antagonists and suggests ways in which blockade of ANG II receptors may differ both pharmacologically and clinically from inhibition of ACE.

Angiotensin II↗

PubMed1992

Contrast sensitivity deficits in subjects with glaucoma-like discs using an oscilloscope-based method.

The central visual function of 20 subjects with glaucoma-like discs, normal intraocular pressures and normal visual fields and 20 age-matched normal subjects was assessed by measuring contrast sensitivity using an oscilloscope technique. The subjects with glaucoma-like discs exhibited a significant reduction in contrast sensitivity compared to the age-matched normal; these differences were greatest at spatial frequencies of 2 and 4 cdeg-1.

Aged↗

PubMed1992

Gene products that promote mRNA turnover in Saccharomyces cerevisiae.

We showed previously that the increased rate of mRNA turnover associated with premature translational termination in the yeast Saccharomyces cerevisiae requires a functional UPF1 gene product. In this study, we show that the UPF1 gene codes for a 109-kDa primary translation product whose function is not essential for growth. The protein contains a potential zinc-dependent nucleic acid-binding domain and a nucleoside triphosphate-binding domain. A 300-amino-acid segment of the UPF1 protein is 36% identical to a segment of the yeast SEN1 protein, which is required for endonucleolytic processing of intron-containing pre-tRNAs. The same region is 32% identical to a segment of Mov-10, a mouse protein of unknown function. Dominant-negative upf1 mutations were isolated following in vitro mutagenesis of a plasmid containing the UPF1 gene. They mapped exclusively at conserved positions within the sequence element common to all three proteins, whereas the recessive upf1-2 mutation maps outside this region. The clustering of dominant-negative mutations suggests the presence of a functional domain in UPF1 that may be shared by all three proteins. We also identified upf mutations in three other genes designated UPF2, UPF3, and UPF4. When alleles of each gene were screened for effects on mRNA accumulation, we found that the recessive mutation upf3-1 causes increased accumulation of mRNA containing a premature stop codon. When mRNA half-lives were measured, we found that excess mRNA accumulation was due to mRNA stabilization. On the basis of these results, we suggest that the products of at least two genes, UPF1 and UPF3, are responsible for the accelerated rate of mRNA decay associated with premature translational termination.

Amino Acid Sequence↗

PubMed1992

Receptor-mediated effects of angiotensin II on growth of vascular smooth muscle cells from spontaneously hypertensive rats.

This study examines the effects of angiotensin II on hypertrophy and proliferation of aortic smooth muscle cells from spontaneously hypertensive and Wistar-Kyoto rats and the receptor subtypes mediating these effects. In quiescent confluent cells, angiotensin II induced a dose-dependent increase in thymidine and leucine incorporation without stimulating cell proliferation. In nonconfluent cells, angiotensin II stimulated cell proliferation only in combination with a submaximal concentration of fetal calf serum. These effects were enhanced in cells from spontaneously hypertensive rats compared with Wistar-Kyoto rats. The effects of angiotensin II could be blocked by the AT1 receptor antagonist DuP 753 but not by the AT2 receptor ligand PD 123177. In receptor binding studies with cells derived from both rat strains, AT1-typical binding was observed. These data show that the angiotensin II receptors present in vascular smooth muscle cells in culture from both rat strains are of the AT1 receptor subtype. This receptor subtype appears to mediate vascular smooth muscle cell hypertrophy and proliferation as well as vasoconstriction. Although no difference in the receptor profile was detectable between the two rat strains, the affinity for the ligands to the receptor and the receptor density tended to be greater in cells from spontaneously hypertensive rats than in cells from Wistar-Kyoto rats. These results may partly explain the greater hypotensive response to angiotensin II receptor blockade in spontaneously hypertensive rats than in Wistar-Kyoto rats, although both rat strains have the same plasma concentrations of angiotensin II.

Angiotensin II↗

PubMed1992

Effect of restriction of the binocular visual field on driving performance.

The importance of the visual field on driving performance was investigated. This was undertaken by simulating binocular visual field defects for a group of young normal subjects and assessing the impact of these defects on performance on a driving course. Constriction of the binocular visual field to 40 or less, significantly increased time taken to complete the course, reduced the ability to detect and correctly identify road signs, avoid obstacles and to manoeuvre through limited spaces. Accuracy of road positioning and reversing were also impaired. Constriction of the binocular visual field did not significantly affect speed estimation, stopping distance, or the time taken for the reversing and manoeuvring tasks. The monocular condition did not significantly affect performance for any of the driving tasks assessed.

Adult↗

PubMed1992

Regional variations in binocular summation across the visual field.

Binocular summation for a contrast detection task was measured as a function of eccentricity and target size along the horizontal and vertical meridians for ten young normal subjects. Binocular summation at the fovea was of the order of 1.4 for all target sizes, although there was some intersubject variation. Binocular summation was highest along the vertical meridian. With increasing eccentricity from the fovea, binocular summation for target size I (0.108 degrees projected diameter) decreased, remained relatively constant for target size III (0.431 degrees projected diameter) and increased with increasing eccentricity from the fovea for target size V (1.724 degrees projected diameter). For target sizes I and III, binocular summation was present only when interocular differences in sensitivity were under 5 dB, for target size V this relationship did not hold. Influences such as stimulation of corresponding retinal points and cortical representation are considered.

Adult↗

PubMed1991

Prevention of Ca(2+)-induced or thromboxane B2-induced hepatocyte plasma membrane bleb formation by thromboxane receptor antagonists.

Isolated hepatocytes incubated in the presence of either Ca2+ ionophore A23187 or thromboxane B2 develop many plasma membrane blebs which are a characteristic feature of toxic or ischaemic cell injury. When hepatocytes are incubated in the presence of both Ca2+ ionophore A23187 and any one of three thromboxane receptor antagonists (SK and F 88046, B.M. 13505, B.M. 13177), bleb formation is strongly inhibited. Hepatocytes incubated in the presence of both thromboxane B2 and any one of the three thromboxane receptor antagonists are also well protected from the formation of blebs. Treatment of isolated hepatocytes with Ca2+ ionophore A23187 is known to stimulate the production of thromboxanes. The data presented are consistent with thromboxane B2 acting as an intermediary in a proposed mechanism of cell injury and death in which elevated cytosolic free Ca2+ levels activate phospholipase A2 and the arachidonate cascade.

Animals↗

PubMed1991

Studies on the reactions between human tyrosinase, superoxide anion, hydrogen peroxide and thiols.

Human tyrosinase (5.5 mg) has been purified from a single human melanotic melanoma metastasis (50.5 g). In the presence of dioxygen, L-tyrosine proved to be a very poor substrate for this enzyme with barely detectable activity compared to L-dopa. However, saturating superoxide anion (i.e., greater than 5 x 10(-3) M) enhanced the oxidation rate of L-tyrosine to dopachrome 40-fold. Hydrogen peroxide was shown to be a competitive inhibitor of tyrosinase when L-tyrosine was the substrate. This reversible inhibition is based on a slow pseudocatalase activity for tyrosinase. Monothiols and dithiols inhibit tyrosinase by different mechanisms. Reduced human thioredoxin and 2,3-dithiopropanol are allosteric inhibitors of tyrosinase yielding bis-cysteinate complexes with one of the copper atoms in the enzyme active site. Bis-cysteinate tyrosinase activity is down-regulated to 30% of native enzyme activity in the L-dopa assay; suggesting a true regulatory role for dithiols. Monothiols such as reduced glutathione and beta-mercaptoethanol are much less reactive with tyrosinase although 10(-3) M monothiol totally inhibits enzyme activity. Reduced thioredoxin inhibits tyrosinase 23-fold more than reduced glutathione under the same experimental conditions.

Anions↗

PubMed1991

Sensitivity and resistance in human metastatic melanoma to the new chloroethylnitrosourea anti-tumor drug Fotemustine.

Fotemustine is a novel chloroethylnitrosourea derivative currently used in Phase III clinical trials for disseminated metastatic melanoma. This drug has been shown to inhibit enzymes in the ribonucleotide reduction pathway (i.e., thioredoxin reductase, glutathione reductase and ribonucleotide reductase). 14C chloroethyl-labelled Fotemustine covalently labels the thiolate active sites of thioredoxin reductase and glutathione reductase yielding 14C chloroethyl-thioether enzyme-inhibitor complexes. Enzyme activities can be restored by a reduced thioredoxin or reduced glutathione mediated beta-elimination of the chloroethyl group. 14C Fotemustine has been used to determine its reactivity and metabolism in drug sensitive and resistant melanoma metastases and in cultures of sensitive and resistant clones of human melanoma cells. Melanoma metastases from four different patients who were treated with Fotemustine could be labelled with radioactive drug only under reducing conditions with NADPH as electron donor and DTNB as substrate. FPLC analysis of these extracts revealed two radioactive proteins (I) glutathione reductase and (II) an unidentified protein with 95 and 50 kDa subunits. A similar labelling pattern was also found in extracts of Fotemustine sensitive melanoma cells (Cal 1). Fotemustine resistant tumors were melanotic and contained more glutathione reductase than thioredoxin reductase, whereas sensitive tumors were clinically amelanotic with more thioredoxin reductase than glutathione reductase. Fotemustine resistant melanoma cells (Cal 7) showed a slower uptake of 14C-label with 34% less isotope intracellularly in 1 h compared to sensitive melanoma cells (Cal 1). These results strongly indicate (I) the induction of alternate electron donors thioredoxin reductase or glutathione reductase for ribonucleotide reduction determines tumor and melanoma cell responses to the drug and (II) Fotemustine transport and the intracellular redox status seems to regulate resistance in melanoma cells and tissues.

Antineoplastic Agents↗

PubMed1991

Thioredoxin reductase activity at the surface of human primary cutaneous melanomas and their surrounding skin.

Plasma membrane-associated thioredoxin reductase activities have been determined on primary melanoma tissues and their surrounding skin in 29 patients. Compared to patient's normal skin, enzyme activities in melanoma were higher in some patients (n = 24) and lower in others (n = 5). Those melanomas with high TR activities yielded low activities in the adjacent epidermis, reaching normal activity 3 to 5 cm away from each primary site (n = 4). Tumors with low activities showed higher than normal activities on the immediate surrounding skin (i.e., 1 cm away from the tumor) compared to the normal skin (n = 3). Earlier it was shown that in both keratinocytes and melanoma cells, calcium regulates thioredoxin reductase activity by an allosteric mechanism. The differences in TR activities within the high and low groups may be caused by a calcium flux between the primary tumor and the surrounding epidermis, and vice versa. A comparison of TR activities to tumor invasiveness (Breslow level) in 28 primary melanomas showed a significant correlation using regression analysis (p = 0.031). A 4-fold difference in TR activity corresponds to a one-unit change in Breslow determination. These preliminary results suggest that TR activity may be another useful and sensitive assay for melanoma spread.

Biomarkers, Tumor↗