Search PubMed⌕ Search

Biomedical subjects

E Evans

Publications and source records attributed to E Evans.

At least 91 records · Page 5Linked to original sources
PubMed1988

Structure and mechanical properties of giant lipid (DMPC) vesicle bilayers from 20 degrees C below to 10 degrees C above the liquid crystal-crystalline phase transition at 24 degrees C.

We have used micromechanical tests to measure the thermoelastic properties of the liquid and gel phases of dimyristoylphosphatidylcholine (DMPC). We have found that the rippled P beta' phase is only formed when a vesicle is cooled to temperatures below the main acyl chain crystallization transition, Tc, under zero or very low membrane tension. We also found that the P beta' surface ripple or superlattice can be pulled flat under high membrane tension into a planar structure. For a ripple structure formed by acyl chains perpendicular to the projected plane, the projected area change that results from a flattening process is a direct measure of the molecular crystal angle. As such, the crystal angle was found to increase from about 24 degrees just below Tc to about 33 degrees below the pretransition. It was also observed that the P beta' superlattice did not form when annealed L beta' phase vesicles were heated from 5 degrees C to Tc; likewise, ripples did not form when the membrane was held under large tension during freezing from the L alpha phase. Each of these three procedures could be used to create a metastable planar structure which we have termed L*beta' since it is lamellar and plane-crystalline with acyl chains tilted to the bilayer plane. However, we show that this structure is not as condensed as the L beta' phase below 10 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Crystallization↗
PubMed1988

Thermomechanical and transition properties of dimyristoylphosphatidylcholine/cholesterol bilayers.

Mixtures of dimyristoylphosphatidylcholine (DMPC) and cholesterol (Chol) have been used to examine the effects of cholesterol on the chain crystallization transitions and thermomechanical properties in phospholipid bilayer membranes. The mechanical properties--elastic moduli and level of tension at membrane rupture--were derived from micropipet pressurization of giant single-walled vesicles. Also, the micropipet method allowed temperature-dependent area transitions to be measured at constant membrane tension. X-ray diffraction measurements were made on selected lipid/cholesterol mixtures. Wide-angle patterns and electron density profiles were used to measure bilayer thickness as an indication of chain tilt and fluidity. Vesicle area versus temperature plots showed that the main acyl chain crystallization transition of DMPC broadened and shifted to higher temperatures. Both above and below the broad transition, the elastic area compressibility modulus, K, was greatly increased with cholesterol addition. The value for the 1:1 DMPC/Chol complex was found to be approximately 700 dyn/cm, comparable to that for DMPC in the L beta' phase. However, for all concentrations above 12.5 mol % (which was weakly solid), vesicle bilayers behaved as surface liquids with no surface shear rigidity even at temperatures well below the DMPC phase transition. Area changes over the broadened transitions were reduced by cholesterol and disappeared with the addition of 50 mol % to leave the thermal area expansivity at 1.3 X 10(-3)/degrees C. These area changes are consistent with separate formation of a 1:1 DMPC/Chol complex that does not condense plus residual free lipid and lipid loosely associated with the 1:1 complex that freezes normally.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol↗
PubMed1988

Interleukin 2 activation of natural killer cells rapidly induces the expression and phosphorylation of the Leu-23 activation antigen.

IL-2 potentiates both growth and cytotoxic function of T lymphocytes and NK cells. Resting peripheral blood NK cells can respond directly to rIL-2, without requirement for accessory cells or cofactors, and enhanced cytotoxicity can be measured within a few hours after exposure to this lymphokine. In this study, we describe an activation antigen, Leu-23, that is rapidly induced and phosphorylated after IL-2 stimulation of NK cells and a subset of low buoyant density T lymphocytes. Previously, it has been uncertain whether all NK cells or only a subset are responsive to IL-2. Since within 18 h after exposure to IL-2, essentially all NK cells express Leu-23, these findings indicate that all peripheral blood NK cells are responsive to stimulation by IL-2. The Leu-23 antigen is a disulfide-bonded homodimer, composed of 24-kD protein subunits with two N-linked oligosaccharides. Appearance of this glycoprotein on NK cells is IL-2 dependent and closely parallels IL-2-induced cytotoxicity against NK-resistant solid tumor cell targets.

Antigens, CD↗
PubMed1988

Sp1, a CAAT-binding factor, and the adenovirus major late promoter transcription factor interact with functional regions of the gamma-fibrinogen promoter.

To study the factors which influence the coordinately and developmentally regulated expression of the three adjacent fibrinogen genes, we have defined the functional regions of the gamma-fibrinogen promoter and the proteins which bind to them. Using a series of 5' and internal deletion mutations, we found that sequences between 88 and 43 base pairs (bp) upstream of the gamma-fibrinogen transcription initiation site functioned in cis to direct properly initiated mRNA accumulation in transfected hepatocytes. The efficient function of these sequences was highly distance dependent, since transcriptional activity decreased by 92% when they were moved 32 bp upstream of the TATA box. We demonstrated that two known and one putative transcriptional factors interacted with this 47-bp sequence. The transcription factor Sp1 interacted with sequences between -51 and -46 as demonstrated by protection from DNase I digestion with the purified protein. Directly adjacent to the Sp1 site, between nucleotides -66 and -53, there was a sequence which bound a CAAT-binding factor. Finally, sequences just 5' to the CAAT factor-binding site interacted with the adenovirus major late transcriptional factor as previously demonstrated. Internal deletion mutations which disrupt these interactions diminished the activity of the promoter in vivo. One consequence of the interaction of these proteins is that a bend is placed in the DNA at or near their sites of interaction.

Base Sequence↗
PubMed1987

Induction of fibrinogen and a subset of acute phase response genes involves a novel monokine which is mimicked by phorbol esters.

We have investigated the requirements for the induction of the acute phase response to inflammation using the FAZA rat hepatocyte cell line which can be induced to activate the acute phase response genes with supernatants from human or rat monocytes. Using ribonuclease mapping of fibrinogen transcripts, we find that the tumor promoter 12-O-tetradecanoylphorbol-13-acetate can induce a 10-20-fold increase in properly initiated and spliced fibrinogen mRNA. This response is likely to be mediated by protein kinase C (Ca2+/phospholipid-dependent enzyme) since the synthetic diacylglycerol, 1-oleoyl-2-acetylglycerol, can also induce fibrinogen mRNA. In addition to the alpha, beta, and gamma chains of fibrinogen, other acute phase response mRNAs are induced by 12-O-tetradecanoylphorbol-13-acetate including alpha 2-macroglobulin. The active agent capable of inducing the fibrinogen mRNAs in the monocyte supernatants is clearly not interleukin 1 (IL-1) or tumor necrosis factor. The FAZA cell line does not have detectable IL-1 receptors and does not respond to either murine or human IL-1 or the 30-kDa precursor for IL-1. In addition, fibrinogen cannot be induced by tumor necrosis factor alpha in this cell line, and the active agent in monocytes supernatants cannot be neutralized with polyclonal or monoclonal antibodies to tumor necrosis factor alpha. We conclude that a third as yet uncharacterized agent is responsible for the induction of fibrinogen during the acute phase response and that this agent transduces its signal to the fibrinogen genes by a mechanism involving protein kinase C.

Acute-Phase Proteins↗
PubMed1987

Factors influencing prognosis in gastric cancer.

In a group of 322 patients with adenocarcinoma of the stomach, 158 underwent resection. The only 5 year survivors came from the resection group. Increasing age, lymph node metastases and increasing depth of invasion of the gastric wall were all adverse prognostic features. There was a high incidence (19%) of resected patients who had suture line involvement. In spite of this there were 5 year survivors among those patients with suture line involvement and also those with lymph node involvement. The judicious implementation of an aggressive resection policy will give patients with favourable tumours the chance of a 5 year cure without involving patients with widespread neoplasm in radical surgery. Patients who had undergone previous gastric surgery for any cause had an extremely bad prognosis. Improvement in 5 year survival rates in patients undergoing resection for gastric cancer could be attributed to the increase in the number of patients with early gastric cancer.

Adenocarcinoma↗
PubMed1987

Molecular genetic analysis of a vaccinia virus gene with an essential role in DNA replication.

We have identified a gene encoded by vaccinia virus which is essential for DNA replication. The gene, located in the HindIII D fragment of the viral genome, is transcribed early after infection into two transcripts of 3.0 and 3.7 kilobases which share a 3' terminus. The lesions of three temperature-sensitive DNA replication mutants with defects in this gene have been localized by marker rescue with progressively smaller DNA fragments. We have determined by hybrid selection that the gene encodes an 82-kilodalton protein. An antibody has been prepared against this polypeptide and used to quantitate expression of the protein after infection with wild-type virus or with a viral mutant whose lesion maps within this gene. The temporal pattern of expression in the mutant is unaffected, but the product encoded by the mutant is significantly more thermolabile than the wild-type protein.

Animals↗
PubMed1986

Cushing's disease with intermittent hypercortisolism.

In a patient with proved pituitary-dependent Cushing's syndrome (Cushing's disease), 24-hour urinary excretion of free cortisol fluctuated between normal (69 percent of the time, often in the low range and for several days in sequence) and high values. Increased urinary free cortisol excretion occurred unpredictably within the context of a persistent, progressive clinical picture. This case stands in contrast with previous reports of urinary steroid levels varying in a periodic infradiem pattern. Even with normal baseline cortisol indexes, control of the hypothalamic-pituitary axis (as indicated by the suppression test and by the circadian cortisol pattern in plasma) remained abnormal. This patient emphasizes the fact that abnormal control regulation, more than cortisol hypersecretion, is at times indicative of Cushing's disease. Hence, sensitive accurate screening requires not only urinary free cortisol measurement (the usefulness of which may be improved by assay of more than one, possibly nonsequential, 24-hour urine sample), but also dexamethasone suppression testing and late-evening plasma cortisol determination, even if baseline indexes are within the range of normal.

17-Ketosteroids↗
PubMed1986

Membranolytic effects of monosodium urate monohydrate: influence of grinding.

The effect of grinding on the membranolytic interaction between monosodium urate monohydrate (MSUM) crystals and intact erythrocyte membranes was studied. Crystals were ground for between 1-72 h, and percent hemolysis and zeta potentials determined. A cationic amphiphilic probe (CAT12) was incorporated into the erythrocyte membrane and incubated with MSUM. Increasing grinding times caused a decrease in both the crystallinity and zeta potential of the samples, a decrease in percent hemolysis values and a change in the distribution of free and bound spin label populations. The probe redistribution is thought to be due to an electrostatic interaction between negatively charged MSUM and the CAT12 probe.

Crystallization↗
PubMed1986

Developments in red cell rheology at the Institut de Pathologie Cellulaire.

The present day rheological approximation, which has been used successfully to quantitate the deformability properties of red cells, is based on the view that the cell has a liquid interior encapsulated by a viscoelastic solid membrane shell. A review of historical developments in this field shows that determination of intrinsic red cell membrane properties has not come from simple mathematical analysis of experiments. On the contrary, considerable insight has been required to bring together physical and biological methods to rationalize the unique deformability characteristics of the red blood cell. Key developments at the Institut de Pathologie Cellulaire (IPC) in the early 1970s played a role in our improved understanding of red cell rheology. In this article, we describe the material concepts of the red cell membrane held before 1970, discuss the seminal developments at Bicetre, and, finally, outline the contemporary view of red cell deformability.

Biophysics↗
PubMed1985

Early gastric cancer.

Thirty patients with early gastric cancer were studied as part of a consecutive series of 308 gastric cancers, giving a proportion of 9.7%. Twenty-eight of the early gastric cancer patients were symptomatic, pain being the most common symptom. Endoscopy proved more effective than barium studies as a first investigation but the diagnosis rate at first examination was still only 69%. Seven patients with early gastric cancer had lymph node spread at the time of presentation. Five patients eventually died of cancer metastases. There was a high incidence of benign peptic ulceration (50%) and this with lymph node metastasis was an unfavourable prognostic feature. Only four of the 26 patients submitted to standard surgical resections died of cancer. This study supports the concept that early gastric cancer does indeed occur in Western man and the five year survival rate (65%) is much higher than for late gastric cancer (13%). The high incidence of metastasis at the time of presentation may account for the difference between our survival rate for early gastric cancer, and that reported from Japan.

Adenocarcinoma↗