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Biomedical subjects

D Fisher

Publications and source records attributed to D Fisher.

At least 199 records · Page 11Linked to original sources
PubMed1984

A 4 year follow-up study of alveolar bone height influenced by two dissimilar Class II amalgam restorations.

Fifty-four paired, approximal amalgam fillings, extended (E) versus unextended (NE) were placed in forty-three patients and followed up to 4 years. Yearly measurements between the alveolar crest and (a) the apical margin of the fillings (E, NE), and (b) the cemento-enamel junction of the control group, were performed using bite-wing radiographs joined to a translucent grid magnified ten-fold. The rate of alveolar crest resorption was similar for the control (C) and the unextended filling (NE) and reached 0.45 mm after 4 years of follow-up. The resorption of the alveolar crest under the extended (E) filling was significantly higher and reached 0.80 mm after 4 years (P less than 0.001).

Adolescent↗
PubMed1984

An evaluation of the one-day NBT-PABA/14C-PABA in the assessment of pancreatic exocrine insufficiency.

The one-day NBT-PABA/14C-PABA has been performed on 58 consecutive subjects with suspected or established pancreatic disease. 23 of these were normal subjects, 12 were subsequently shown to have other gastrointestinal disease and 23 had proven pancreatic disease. A PABA excretion index (PEI) has been calculated and, using our lower limit of normality (0.61), the test has shown an overall sensitivity of 83% and specificity of 89%. False positives were a particular problem in the other gastrointestinal disease group (25%). There was a close correlation between PEI and Lundh mean tryptic activity (r = 0.89). These results indicate that this test is a satisfactory screening test for pancreatic exocrine disease and is easier to perform with less likelihood of error than many other non-invasive tests of pancreatic function.

4-Aminobenzoic Acid↗
PubMed1983

Platelet associated IgG and immune thrombocytopenia in lymphoproliferative and autoimmune disorders.

Thrombocytopenia is frequently encountered in patients with lymphoproliferative disorders (LPD) and systemic erythromatosus (SLE) and to a lesser extent in association with other diseases such as rheumatoid arthritis (RA), pernicious anaemia (PA) and autoimmune haemolytic anaemia (AIHA). This report attempts to document the incidence of thrombocytopenia in these disorders, other than that overtly due to malignant infiltration or marrow suppression by drugs and to demonstrate, that in a significant proportion antibody mediated immune destruction of platelets can be confirmed by positive platelet antibody tests. Platelet associated IgG (PAIgG) was measured in all patients by a quantitative enzyme linked assay. Platelet antibodies were found in 11 of 24 (46%) thrombocytopenic patients with LPD, 10 of 16 (62%) patients with SLE and thrombocytopenia, and in all patients with RA and PA who had low platelet counts at the time of study. In addition, elevated PAIgG levels were found in the following non-thrombocytopenic patients: 9 of 43 (21%) patients with LPD, 2 of 12 (17%) with SLE, 2 of 12 (17%) with AIHA, 2 of 39 (5%) with PA and 5 of 61 (8%) patients with RA. The nature and the role of raised PAIgG levels in diseases other than autoimmune thrombocytopenia is controversial. Our reasons for interpreting these as true platelet autoantibodies in this selected group of disorders and the clinical implications of our results are discussed.

Anemia, Hemolytic, Autoimmune↗
PubMed1982

Is purified poly(ethylene glycol) able to induce cell fusion?

Preparations of poly(ethylene glycol) 6000 (PEG) from five different commercial sources have been purified, and their ability to fuse hen erythrocytes has been investigated. Quantitative assessments of cell fusion showed that before purification one of the preparations (PEG Wako), was able to induce limited fusion (5-6%) of erythrocytes with conditions (1 min incubation with 50% w/w PEG) under which the other four unpurified preparations of PEG were inactive. On purification, PEG (Wako) became inactive. By contrast, when erythrocytes were incubated with 45% w/w PEG for 15 min, extensive fusion (23-27%) occurred with all five unpurified preparations of PEG. Under these conditions, the fusogenic properties of four of the preparations of PEG were unaffected by purification: fusion induced by PEG (Wako) was, however, decreased on purification from 27% to 19%. It appears that polymeric poly(ethylene glycol) is itself able to fuse cells, but that some commercial preparations, e.g. PEG (Wako), have enhanced fusogenic properties resulting from the presence of contaminating substances. No relationship between the absorbance at 290 nm of PEG and its fusogenic properties was found in this study. The addition of small quantities of fusogenic lipid-soluble compounds to PEG was, however, observed to enhance cell fusion by up to 50%.

Animals↗
PubMed1982

Effects of poly(ethylene glycol) on liposomes and erythrocytes. Permeability changes and membrane fusion.

Poly(ethylene glycol) 6000 induced a concentration-dependent, time-dependent decrease in the latency of the reaction between Arsenazo III sequestered in liposomes and extraliposomal Ca2+. This was mediated by a gross change in liposomal permeability, i.e. by a release of Arsenazo III from liposomes rather than simply by an entry of Ca2+. The loss of latency was strongly temperature-dependent, and it was markedly diminished on increasing the cholesterol content of the liposomes. It was apparently not due to an osmotic stress of the polymer. The high activation energy found (63 kJ . mol-1) is thought to indicate that the loss of latency resulted from local discontinuities in the lipid bilayers, caused by dehydration, rather than from partial or total lysis. Related microscopy experiments indicated that the polymer also caused the liposomes to fuse, and it is suggested that membrane fusion may have occurred at the sites of dehydration-induced discontinuities in adjacent bilayers. In addition, the polymer was found to enhance the permeability of hen erythrocytes of Ca2+ in a manner that was comparable to its effect on liposomal latency, and it is proposed that gel fusion induced by poly(ethylene glycol) may occur at the sites of similarly induced discontinuities in the phospholipid bilayers of two closely adjacent cells.

Animals↗
PubMed1982

The interaction of phospholipid membranes with poly(ethylene glycol). Vesicle aggregation and lipid exchange.

(1) The water soluble polymer, poly(ethylene glycol), causes aggregation of sonicated vesicles of dimyristoylphosphatidylcholine in a manner consistent with a steric exclusion mechanism. (2) Poly(ethylene glycol) promotes the exchange of lipids between multilamellar vesicles of dimyristoylphosphatidylcholine and dipalmitoylphosphatidylcholine when the lipids are in the liquid-crystalline state. (3) 31P-NMR studies demonstrate that the bilayer configuration of smectic mesophases of dipalmitoylphosphatidylcholine is substantially maintained in the presence of poly(ethylene glycol).

Dimyristoylphosphatidylcholine↗
PubMed1982

Interactions of glycerol monooleate and dimethylsulphoxide with phospholipids. A differential scanning calorimetry and 31P-NMR study.

1. A comparative study has been made of the effects of the fusogens glycerol monooleate and dimethyl-sulphoxide on the polymorphic phase behaviour of dipalmitoyl phosphatidylcholine and dipalmitoyl phosphatidylethanolamine by differential scanning calorimetry and 31P-NMR techniques. 2. Glycerol monooleate induces a reduction in the temperature, cooperativity and enthalpy of the gel to liquid-crystal transitions of dipalmitoyl phosphatidylcholine and dipalmitoyl phosphatidylethanolamine, whereas dimethylsulphoxide induces an increase in the temperature and enthalpy and a reduction in the cooperativity of the gel to liquid-crystal transitions for those same phospholipids. 3. Glycerol monooleate induces the formation of isotropic and hexagonal (HII) phases when mixed with either dipalmitoyl phosphatidylcholine or dipalmitoyl phosphatidylethanolamine. By contrast, in the presence of dimethylsulphoxide, those same phospholipids retain the lamellar configuration observed in the absence of fusogen. 4. These results are discussed in terms of the mechanisms of chemically induced cell fusion.

Calorimetry, Differential Scanning↗
PubMed1982

A continuous-flow (AutoAnalyzer II) procedure for measuring erythrocyte transketolase activity.

In this semiautomated method, an AutoAnalyzer II is used to measure the enzymic production of glyceraldehyde 3-phosphate in hemolysates, to assay erythrocyte transketolase (EC 2.2.1.1) activity. Hemolysate and indicator reactions are separated by dialysis to eliminate hemoglobin interference and increase sensitivity. Internal standards of glyceraldehyde 3-phosphate in hemolysate carriers were quantitatively measured with good precision and accuracy in the presence or absence of the transketolase substrate, ribose 5-phosphate. Chart-recorder values for these standards were used to calibrate the AutoAnalyzer output in IUB units (U) of transketolase activity. Substrate-product relationships were examined to characterize reaction kinetics and optimize assay conditions. AutoAnalyzer transketolase results correlated well with those from two manual procedures.

Autoanalysis↗
PubMed1981

Effects of retinol, fatty acids and glycerol monooleate on the fusion of chick embryo myoblasts in vitro.

Cell fusion of embryonic chick myoblasts has been studied in the presence of fat-soluble agents that induce erythrocytes to fuse. Retinol inhibited myoblast fusion but the cells recovered their ability to fuse within 48 h of removal of the retinol from the medium. Myristic acid, oleic acid, glycerol monooleate, linolenic acid and arachidonic acid similarly prevented fusion in myogenic cultures. By contrast, linoleic acid moderately enhanced the fusion of chick skeletal myoblasts. In addition, stearic acid, which does not fuse erythrocytes, inhibited myoblast fusion whereas the saturated, non-fusogenic fatty acid, arachidic acid, was without effect.

Animals↗
PubMed1981

Three cDNA clones encoding mouse transplantation antigens: homology to immunoglobulin genes.

We constructed cDNA libraries from poly(A)+ RNA isolated from cell lines of two different inbred strains of mice, and screened the libraries with a cDNA clone encoding a human transplantation antigen. Three cDNA clones were identified, sequenced and found to encode amino acid sequences highly homologous to portions of a known mouse transplantation antigen. Comparison of the cDNA sequences of mouse transplantation antigens with the constant region domains of the mouse immunoglobulin mu gene reveals a striking homology, which suggests that the two genes share a common ancestor. Antibody genes undergo DNA rearrangement during B cell differentiation that are correlated with their expression. In contrast, DNA blots with these cDNA probes suggest that the genes for the transplantation antigens are not rearranged in the genomes of liver or embryo cells, which express these antigens, as compared with sperm cells, which do not express these antigens. In Bam Hl-digested liver DNAs from different inbred strains of mice, 10-15 bands of hybridization were found. Accordingly, the genes encoding the transplantation antigens appear to constitute a multigene family with similar gene numbers in different mice.

Amino Acid Sequence↗
PubMed1980

Partition of rat erythrocytes in aqueous polymer two-phase systems.

The partition of rat erythrocytes between the top phase and inferface of aqueous poly(ethylene glycol)-dextran two-phase systems containing 0.15 M NaCl and 0.01 M sodium phosphate depends on the association of the cells with microscopic globules of dextran that persist in the poly(ethylene glycol)-rick top phase after the horizontal interface between the two phases has formed.

Animals↗
PubMed1980

Cell fusion, haemolysis and mitochondrial swelling induced by retinol and derivatives.

A comparative study has been made of the abilities of retinol and its derivatives to induce cell fusion and haemolysis of hen erythrocytes and to cause swelling of rat liver mitochondria. Retinol, retinaldehyde, alpha-retinoic acid, iso-13-retinol and to a lesser extent retinyl acetate were active in all three systems. Iso-13-retinoic acid was extremely membranolytic but did not produce stable fused cells. By contrast retinoic acid, its cyclopentyl derivative RO8-7699, and the long chain fatty acid esters of retinol, viz. the oleate, linoleate and palmitate esters, were neither fusogenic nor haemolytic, nor did they affect mitochondria.

Animals↗