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Biomedical subjects

A R Thompson

Publications and source records attributed to A R Thompson.

15 recordsLinked to original sources
PubMed1992

Leukotriene B4 receptor antagonists: the LY255283 series of hydroxyacetophenones.

A series of hydroxyacetophenones was prepared for evaluation as leukotriene B4 (LTB4) receptor antagonists, culminating in 1-[5-ethyl-2-hydroxy-4-[[6-methyl-6-(1H-tetrazol-5- yl)heptyl]oxy]phenyl]ethanone (compound 35, LY255283). Using an assay for inhibition of specific [3H]LTB4 binding to human PMN, we found that substitution of a nonpolar substituent in the 5-position was required for activity. Best activity was realized with hydrogen in the 3-position, hydroxyl in the 2-position, short chain alkyl ketone in the 1-position, and a six- or eight-carbon chain linking the oxygen in the 4-position with an unsaturated terminal function. Compound 35, having an IC50 of 87 nM in the binding assay, was chosen for further preclinical evaluation.

Acetophenones↗
PubMed1992

Coagulation factor IX: successful surgical experience with a purified factor IX concentrate.

The use of plasma-derived coagulation factor concentrates has been marked by the transmission of viral agents. Infusions of factor IX complex concentrates have been additionally complicated by inappropriate thrombosis. Use of these concentrates in the neonate, in those with liver disease, and in surgical patients results in increased risk for this complication. Twenty patients have been infused with a purified coagulation factor IX concentrate for fall-off and recovery studies. A two-compartment model indicated an initial phase half-life of 4.06 +/- 2.86 hr and a beta phase half-life of 20.0 +/- 3.8 hr following the administration of AlphaNine, Coagulation Factor IX (Human). In vivo recovery was 62.7% +/- 13.8%, with an average factor IX coagulant level of 73% +/- 16% at 15 min after the infusion of a mean dose of 45 U/kg. Thirteen previously transfused patients with hemophilia B underwent major orthopedic or general or dental surgery using this purified factor IX. Operative outcomes were excellent in all patients. No excessive bleeding was noted. There was no laboratory or clinical evidence for a disseminated intravascular coagulopathy. The excellent surgical outcomes observed in this multitransfused group with biochemical evidence for active liver disease demonstrates the utility and safety of a purified coagulation factor IX concentrate.

Adult↗
PubMed1992

Screening for nonsense mutations in patients with severe hemophilia A can provide rapid, direct carrier detection.

Despite marked genetic heterogeneity in families with hemophilic patients, transition mutations in CG dinucleotides occur frequently. Of 71 CG dinucleotides in the factor VIII cDNA, a C-to-T transition in 12 would lead to a new Stop codon (CGA to TGA). Using restriction enzyme digestion of 11 amplified DNA fragments, seven point mutations were localized among 60 patients with severe hemophilia A. Five were detected as loss of a natural or introduced TaqI site at codons -5, 583, 1941, 2116, and 2209 and were confirmed as CGA (Arg) to TGA (Stop) nonsense mutations by DNA sequencing. A novel C-to-T nonsense mutation was detected as loss of the RsaI site at codon 1966 and confirmed by sequence in two unrelated individuals. Two partial gene deletions were detected as selective failure to amplify exon 1 and exons 15-22, respectively. In an additional (61st) patient who was subsequently found to have mild (instead of severe) hemophilia, digests suggested a mutation in codon 1696. Upon sequencing, this codon contained a novel missense mutation, a C-to-G transversion changing CGA (Arg 1696) to GGA (Gly). In four families with women available for testing, carrier status was rapidly determined by direct screening for the point mutation. In two of three with sporadic occurrences, the mother was a carrier as were two of four sisters. In the other family, the mother and a sister were homozygous for the TaqI cleavage site in their amplified exon 24 fragment, indicating a de novo C-to-T transition in codon 2209 in the patient's factor VIII gene. This final patient's sister was a noncarrier even though by linkage analysis she inherited the same factor VIII gene as her brother.

Base Sequence↗
PubMed1992

Somatic gene transfer in the development of an animal model for primary hyperparathyroidism.

The overproduction of hormones is associated with a variety of endocrinological disorders. We have used somatic cell gene transfer of human PTH (hPTH) to develop an animal model of hypercalcemia and osteoclastic skeletal resorption. Recombinant retroviruses were used to transduce a functional hPTH gene into cultured rat fibroblasts. The recombinant-derived preproparathyroid hormone peptide was appropriately processed in this ectopic cell, and intact hPTH (1-84) was secreted at a high level (2-5 ng/10(6) cells/24 h). Transplantation of the PTH-secreting cells into syngeneic rat recipients was associated with the development of hypercalcemia mediated by increasing serum concentrations of hPTH. Thyroparathyroidectomy in these hypercalcemic rats producing hPTH did not result in hypocalcemia and tetany, which was observed in control animals undergoing thyroparathyroidectomy. Chronic overproduction of hPTH (60 days) was associated with severe hypercalcemia, metastatic calcification, and histological changes of osteoclastic resorption of bone. This animal model will be useful in studying the pathophysiology of severe hyperparathyroidism in humans and should help in the evaluation of new medical therapies for hypercalcemia.

3T3 Cells↗
PubMed1979

Human plasma P component (protein AP): changes during growth and development and evidence for hepatocellular synthesis.

A monospecific rabbit antibody to human plasma P component was used in a quantitative immunoelectrophoretic system. The assay readily detected levels as low as 0.3 microgram/ml, the equivalent of 0.008 U/ml of a normal plasma pool. he average coefficient of variation of duplicate determinations from five sets of nine dilution points of normal plasma was 6.6%. Among normal individuals, groups of 50 adults, 24 children, and 43 term and preterm newborns were each significantly different (p less than 0.001) and the level was positively correlated with age. Three fetal samples of approximately 20 weeks' gestation were near the lower limit of detection of the assay. P component levels in selected groups of patients demonstrated a 1.5 fold elevation of the mean level in 15 patients with high erythrocyte sedimentation rates, no difference in the mean level of 23 patients on warfarin or 16 patients with plasma cell dyscrasia or chronic lymphocytic leukemia, and a depression of the mean level to one fourth of normal in 14 patients with alcoholic liver disease. Among the latter, the prolongation of the prothrombin time was correlated with the depression of P component (p less than 0.05). Conditioned media, even after 10-fold concentration, and lysed cell fractions of cultured adult fibroblasts, B and T lymphocytes, and endothelial and smooth muscle cells failed to demonstrate P component. Circulating levels of P component increase during growth and development to adult life and the hepatocyte is the most likely site of synthesis. Although homologous in structure, C-reactive protein levels are distinguished by their marked response to inflammation and their elevation in most of the patients with hepatocellular damage.

Adolescent↗
PubMed1977

Factor IX antigen by radioimmunoassay. Abnormal factor IX protein in patients on warfarin therapy and with hemophilia B.

Factor IX, isolated from normal human plasma, was homogenous by polyacrylamide gel electrophoresis in urea and sodium dodecyl sulfate. On the latter, it migrated as a single polypeptide chain with or without reducing agents and had an apparent mol wt of 62,000. After iodination by chloramine-T, a single peak of 125I was found on gels. Immunoelectrophoresis in agarose with rabbit antifactor IX sera gave a single arc against both isolated and partially purified factor IX preparations. The rabbit antibody was specific as it failed to inhibit the activities of prothrombin or factors VII or X in normal plasma. At an additional 20-fold dilution, factor IX activity was inhibited 50%. In a double-antibody radioimmunoassay, excess rabbit anti-human factor IX precipitated 90-95% of the 125I-human factor IX. Control without specific antibody gave 6-8%. Dilutions of a pool of normal human plasma paralleled dilutions of the isolated preparation and were used for the standard curve. Of 39 plasma samples from normal donors, the mean factor IX antigen level was 93% of that of a separate normal pool. The radioimmunoassay detected the abnormal factor IX produced in patients on warfarin therapy. After Al(OH)3 adsorption of warfarin treated patient's plasma, factor IX antigen, but not activity, was present in the supernate. Samples from 28 patients on warfarin gave a mean factor IX clotting activity of 27% with a mean antigen of 69%. The antigen level from the warfarin group was significantly lower than the antigen level of the normal group (P less than 0.001). The factor IX antigen level was then assessed in 36 patients from 29 pedigrees with hemophilia B. The median antigen level was 17% of normal. The distribution of the antigen level was wide with two patients around 100% of normal; only two had levels below the limits of resolution of the radioimmunoassay as currently performed (less than 2%). Within each of the five pedigrees in which more than one affected member was tested, activity and antigen levels were the same. The degree of neutralization of the antibody's inhibition of normal plasma by patient's plasma was highly correlated. Additional evidence for the detection of abnormal protein was provided by immunodiffusion of plasmas concentrated by lyophilization. Reactions of complete identity occurred between normal, a warfarin treated and a hemophilia B subject's plasmas.

Adolescent↗
PubMed1977

Eosinophilia and mast cell hyperplasia induced by parasite phospholipid.

Phospholipid preparations from the nematode Ascaris suum or cysts of Echinococcus granulosus (hydatid cysts) induced an eosinophilia when injected into the peritoneal cavity of rats. Peritoneal eosinophilia persisted throughout 21 days of daily injections of Ascaris lipid and was accompanied by blood eosinophilia, mast cell granule lysis and mast cell hyperplasia. The active material consisted of lecithin and lecithin plasmalogen, and in aqueous suspension had a membrane-like appearance. Electron microscopy revealed that the phospholipid was ingested by all types of cells in the peritoneal cavity, including mast cells, and was rapidly broken down by eosinophils. Phagocytosis was found to be complement dependent. The lipid combined with properdin in human serum and stimulated complement breakdown via the alternative complement pathway.

Animals↗
PubMed1977

X-linked syndrome of platelet dysfunction, thrombocytopenia, and imbalanced globin chain synthesis with hemolysis.

An unusual family is described with a congenital bleeding disorder present in four males belonging to three generations. Of the three surviving affected males, all had splenomegaly and petechiae. The three had moderate thrombocytopenia (55-90 X 10(9)/liter) and markedly prolonged Ivy-template bleeding times (greater than 30 min). They were also noted to have reticulocytosis and, upon further investigation, imbalanced globin chain synthesis resembling that of beta-thalassemia minor. Studies on nine additional family members in four generations were normal except for slight elevations of reticulocyte counts in female members, one of whom had the abnormal globin chain synthesis ratio. In male members, the bleeding tendency and clinical signs always occurred in the presence of the globin chain synthesis defect and reticulocytosis. This previously undescribed condition was apparently transmitted as an X-linked disorder.

Blood Group Antigens↗
PubMed1976

High affinity binding of human and bovine thrombins to p-chlorobenzylamido-epsilon-aminocaproyl agarose.

Human thrombin (EC 3.4.21.5) binds tightly to p-chlorobenzylamido-epsilon-aminocaproyl agarose, and is not eluted by 2 M NaCl at pH 8. Its zymogen, human prothrombin, does not bind to the same absorbent. 2 M NaCl partially elutes DFP-treated thrombin. For native human and bovine thrombins, protein and activity are quantitatively eluted by 25% dioxane, and upon rechromatography the active human enzyme exhibits the same binding properties. Equally tight binding of human thrombin occurs with derivatives of the m- and p-chlorobenzylamines. With the o-chloro derivative or benzylamine itself insolubilized to epsilon-aminocaproyl agarose, thrombin is eluted by high ionic strength. Bovine trypsin and bovine factor Xa bind less tightly than thrombin to p-chlorobenzylamido-epsilon-aminocaproyl agarose, being eluted by high ionic strength. It is proposed that the specific thrombin adsorption is related to a secondary binding site of high affinity and with hydrophobic properties. This site is not available in the zymogen. Furthermore, the less specific protease, trypsin, and the more specific protease, factor Xa, lack this binding site.

Animals↗
PubMed1976

Removal of heparin and protamine from plasma.

A simple chromatographic technique for rapid adsorption of heparin and protamine from plasma samples is described, allowing accurate interpretation of coagulation screening tests and specific clotting factor assays. With the use of columns of ECTEOLA-cellulose, up to 300 U. of heparin could be completely adsorbed from a 1 ml. plasma sample. When citrated nonheparinized plasma was passed over the ECTEOLA-cellulose columns, the thrombin, prothrombin, and partial thromboplastin times were unaffected. Levels of fibrinogen, prothrombin, and factors V, VII, VIII, IX, and XI average within 90 per cent of control, nonchromatographed samples. When heparinized plasma samples (0.1 and 1.0 U. per milliliter) were passed over columns, heparin was completely removed and the results of the screening tests and the specific factor assays were the same as for the chromatographed nonheparinized samples. In addition, heparinized samples with decreased factor VIII activity maintained their pretreatment factor VII activities after heparin removal. Blood samples containing heparin were obtained from two patients during open-heart surgery. Following heparin adsorption on ECTEOLA-cellulose columns, factor VIII activity levels remained above 60 per cent during cardiopulmonary by-pass. The presence of protamine sulfate in plasma samples prolonged the prothrombin and partial thromboplastin times while slightly shortening the thrombin time. The protamine effect persisted after ECTEOLA-cellulose, but could be removed by a similar column of carboxymethyl-cellulose. The latter resin had no effect on screening tests or on assays of factors VIII or IX activity. The combination of the two resins was then used to remove the separate inhibitory effects from heparinized plasma samples to which protamine had been added.

Adsorption↗