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D R Hoffman

Publications and source records attributed to D R Hoffman.

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

Allergens in Hymenoptera venom. XX. Isolation of four allergens from imported fire ant (Solenopsis invicta) venom.

Commercial Solenopsis invicta (Sol i) venom was fractionated by gel filtration and high-performance cation exchange chromatography. Four proteins were isolated and purified to homogeneity. The four proteins were tested with a panel of sera from patients allergic to fire ant venom; all proteins had significant allergenic activity. These proteins corresponded to four of the bands we previously reported to be allergenic by immunoblot analysis. Sol i I has an apparent molecular weight of 37,000 daltons and yields bands of 18,000, 16,500 and 14,000 daltons in sodium dodecyl sulfate-polyacrylamide gel electrophoresis; cation-exchange chromatography indicates that there are three charge forms. Sol i II has a native molecular weight of 28,000 daltons and appears to be easily cleaved into half molecules; it is a phospholipase structurally unlike either bee or wasp phopholipases. Sol i III has a native and denatured molecular weight of 26,000 daltons. Sol i IV has an apparent native molecular weight of 20,000 daltons and gives a single chain of 15,000 daltons in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Sol i II and III are the major proteins in the venom; there are only small amounts of Sol i I and IV. All are significant allergens, and patients are found who react most strongly with each. Regression analysis of RAST data with highly purified allergens indicated that the IgE responses to the allergens were not related to each other. Amino acid compositions indicated that the four allergens were distinct and that the allergens were structurally different from each other. Four proteins identical to Sol i I to IV were isolated from hand-milked pure venom.

Adult↗
PubMed1988

Allergens in Hymenoptera venom. XXI. Cross-reactivity and multiple reactivity between fire ant venom and bee and wasp venoms.

The relationships between fire ant venom and bee and wasp venoms were explored by studying sera from five groups of subjects. Group 1 included adults not allergic to any venoms and who were not exposed to fire ants. Group 2 included adults with fire ant exposure who were not allergic to venoms. Group 3 included patients with recent systemic reactions to fire ant venom. Group 4 included patients allergic to bee and vespid venoms with no fire ant exposure. Last, group 5 included patients allergic to bee and vespid venoms with fire ant exposure. None of the serum samples from group 1 was RAST reactive to fire ant venom, but 24% of those from group 2 were fire ant positive, as were 100% of those from group 3, 51% of those from group 4, and 87% of those from group 5. The RAST-positive patients in groups 2 and 5 were also skin test positive. RAST inhibition studies demonstrated cross-reactivity in some cases and multiple reactivity in others. The serum samples were further investigated via nondenaturing electrophoretic immunoblot studies and RAST with highly purified allergens. Serum samples from group 4 reacted to a single band on immunoblots and with only one of the four purified allergens from fire ant venom (Solenopsis invicta I, or Sol i I). Serum samples from groups 2, 3, and 5 showed various patterns of allergen reactivity. All serum samples from patients allergic to fire ant venom who also reacted to bee and/or vespid venoms by RAST contained IgE antibodies binding to Sol i I.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Platelet-activating factor acetylhydrolase activity in maternal, fetal, and newborn rabbit plasma during pregnancy and lactation.

The inactivation of the biologically active ether-containing glycerophospholipid platelet-activating factor (PAF) is catalyzed by the enzyme PAF acetylhydrolase (1-alkyl-2-acetyl-sn-glycero-3-phosphocholine acetylhydrolase, EC 3.1.1.48). The specific activity of acetylhydrolase has been assayed in maternal rabbit plasma prior to and throughout pregnancy and after parturition. The specific activity of acetylhydrolase was 131 +/- 8 nmol.min-1.ml-1 of plasma (mean +/- SEM) in the nonpregnant rabbit. Similar specific activities were found throughout the first half of pregnancy; however, on day 15 the acetylhydrolase activity began to decrease and reached a minimum around day 27. Within 24-48 hr following delivery, the specific activity of the enzyme increased to the levels found in the nonpregnant animals. The specific activity of acetylhydrolase in fetuses (gestational ages of 21-30 days) and neonates increased from 22 nmol.min-1.ml-1 of plasma (21-day-old) to 328 nmol.min-1.ml-1 of plasma (35-day-old rabbits). The decrease in enzymatic activity of the pregnant rabbit plasma cannot be accounted for by the presence of an inhibitor as determined by plasma-mixing experiments with nonpregnant and pregnant (27-day) plasma. The properties of this enzyme in the rabbit were consistent with those reported by others, i.e., substrate specificity, inactivation by heat and various inhibitors, and Ca2+ independency. The activity of PAF acetylhydrolase was associated primarily with the high density lipoprotein fraction in rabbit plasma. The decrease of this enzymatic activity during pregnancy may serve to remove the protective effect on myometrium to allow an increased amount of PAF to come in contact with this tissue.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1987

Allergens in Hymenoptera venom. XVII. Allergenic components of Solenopsis invicta (imported fire ant) venom.

Pure venom from Solenopsis invicta was collected by having the insects sting into a capillary tube. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that three major protein bands were present in the venom. A prototype commercial extract was compared and found to contain the three major venom proteins and additional components as well as high potency and specificity by RAST. Immunoblot studies were performed with sera from allergic individuals with blots prepared from denatured SDS-PAGE gels and from two types of nondenaturing gels. The nondenaturing systems demonstrated the presence of two major allergens and three other allergens, each reacting with a third of the sera. Three of the allergens detected in SDS-PAGE blots were of identical mobility to the three major proteins in the pure venom sample. IgE binding to the SDS-PAGE blots was significantly less than that to nondenaturing blots, suggesting that much of the allergenic activity is conformation dependent.

Allergens↗
PubMed1987

Allergens in Hymenoptera venom. XVIII. Immunoblotting studies of venom allergens.

Pure venoms from yellow jackets and bees were used to evaluate denaturing and nondenaturing immunoblot techniques and to compare results of IgE antibody-stained immunoblots to RAST with highly purified allergens. Significant differences in IgE antibody binding were observed among all three techniques, suggesting that tertiary conformation is a major factor in the allergenic determinants of venom allergens. IgG antibodies from hyperimmunized animals and from specimens obtained from allergic patients before and after venom immunotherapy appeared to exhibit less conformational dependence for binding. The conformational dependence of IgE antibody binding to bee and yellow jacket phospholipases was confirmed by direct and inhibition RAST studies. The allergens studied were all single polypeptide chains.

Allergens↗
PubMed1987

Allergens in hymenoptera venom. XIX. Allergy to Vespa crabro, the European hornet.

The European hornet, Vespa crabro, is a very large insect native to much of Europe and Asia and introduced into eastern North America. Four cases of allergic reactions to V. crabro stings are presented, one of which was fatal. V. crabro venom contains 2% protein and peptide. There are three major proteins: Phospholipase AB, antigen 5 and hyaluronidase. These proteins are structurally and antigenically related to those from other vespid wasps, especially Vespula yellow jackets. IgE antibodies from patients allergic to Vespula usually cross-react with V. crabro venom. In three of the four patients with known reactions to V. crabro venom antigen 5 appeared to be the most important allergen. Serum from one patient was most reactive with hyaluronidase. Phospholipase had relatively little IgE-binding activity, although it was the major protein in the venom. V. crabro venom is at least as closely related to Vespula venoms as Dolichovespula venoms are.

Adolescent↗
PubMed1986

Metabolism and function of platelet-activating factor in fetal rabbit lung development.

Previously, platelet-activating factor (PAF, PAF-acether, 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine) had been identified in association with a lamellar-body-enriched fraction of human amniotic fluid obtained from women in labor. In consideration of the fact that fetal lung is the source of lamellar bodies, we have investigated the capacity of the developing lung to synthesize PAF. The specific activity of the PAF biosynthetic enzyme, 1-alkyl-2-lyso-sn-glycero-3-phosphocholine: acetyl-CoA acetyltransferase, increased from 116 pmol/min per mg protein in day 21 fetal rabbit lung to 332 pmol/min per mg protein by day 31. Although this enzymatic activity in fetal kidney also increased, it never reached the level found in lung. In contrast, the actyltransferase activity decreased by 80% in fetal liver between days 21 and 31. The acetyltransferase activity in lung was primarily localized in the microsomal fraction (105 000 X g pellet); however a significant proportion of the activity was found in the 18 000 X g pellet. The specific activity of acetyltransferase in adult alveolar type II rat pneumonocytes was significantly higher than that of adult rat lung or rat alveolar macrophages, suggesting that type II cells make a significant contribution to the actyltransferase activity of lung tissue. PAF acetylhydrolase remained relatively constant throughout the gestation in all tissues. The concentration of PAF in the fetal lung increased by 3-fold from 12 to 35 fmol/mg protein, between day 21 and day 31 of development. The concentrations of the PAF precursors, 2-lyso-PAF (1-alkyl-2-lyso-sn-glycero-3-phosphocholine) and the 2-acyl derivative, were several orders of magnitude higher than the PAF concentration. The pulmonary glycogen content decreased from 163 at day 21 to 35 micrograms/mg protein at day 31 of gestation. We suggest that the increase in PAF concentration may participate in the regulation of glycogen breakdown in fetal lung as it does in perfused rat liver (Shukla, S.D., Buxton, D.B., Olson, M.S. and Hanahan, D.J. (1983) J. Biol. Chem. 258, 10212-10214). The formation of PAF in the developing lung and its secretion, in association with lamellar bodies, into amniotic fluid is discussed in relation to parturition.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1986

The role of platelet-activating factor in human fetal lung maturation.

The presence of the potent bioactive glycerophospholipid 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor) in a lamellar body-enriched fraction of amniotic fluid from women in labor has prompted the present investigation to examine the fetal lung as the possible tissue source of this platelet-activating factor. The metabolism of platelet-activating factor was assessed in an organ culture system in which human fetal lung tissue (12 to 16 weeks) was incubated for 6 to 7 days. During this period, the type II pneumonocytes differentiate and surfactant glycerophospholipid biosynthesis is greatly enhanced. The initial specific activity of the platelet-activating factor biosynthetic enzyme lyso-platelet-activating factor:acetyl-coenzyme A acetyltransferase is two to three times greater in microsomes prepared from fetal lung than in those from the fetal liver or kidney. The specific activity of acetyltransferase in lung tissue increased twofold after 6 days in organ culture. A similar increase in acetyltransferase activity was found in the lamellar body-enriched (18,000 X g) subcellular fraction of fetal lung. The activity of the major platelet-activating factor-inactivating enzyme platelet-activating factor acetylhydrolase did not change significantly in the lung explants during the incubation period. Associated with the enhanced platelet-activating factor biosynthetic activity in the fetal lung was an increase in the platelet-activating factor concentration, from 17 to 37 fmol/mg of protein between days 0 and 6 of culture. Corresponding increases of 3.3- and 3.8-fold in the concentrations of the platelet-activating factor lipid precursors lyso-platelet-activating factor and the 2-acyl congener were found after 6 days in culture. A reciprocal relationship was found between platelet-activating factor and glycogen content as the lung tissue matured in vitro; specifically, as the platelet-activating factor level increased, glycogen decreased from 340 to 77 micrograms/mg of protein. We suggest that platelet-activating factor may mediate the onset of glycogenolysis in fetal lung tissue similar to that in the isolated, perfused rat liver (Shukla SD, Buxton DB, Olson MS, Hanahan DJ. Acetylglyceryl ether phosphorylcholine. A potent activator of hepatic phosphoinositide metabolism and glycogenolysis. J Biol Chem 1983; 258:10212-4). The increased rate of glycogen degradation may serve as the carbon and energy source for the increased synthesis of glycerophospholipids required for surfactant production.(ABSTRACT TRUNCATED AT 400 WORDS)

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1986

Allergens in Hymenoptera venom. XVI: Studies of the structures and cross-reactivities of vespid venom phospholipases.

Phospholipases (PLs) isolated from the venoms of three species of yellow jackets, white-faced hornets, European hornets, and paper wasps were studied by peptide mapping after limited enzyme hydrolyses and cyanogen bromide cleavage. Significant differences in the primary structures were observed. Cross-reactivities of vespid PLs were studied by precipitation reactions in gel with rabbit antibodies, immunoblots of sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels with rabbit antisera, and RAST inhibition with individual sera from vespid-reactive patients. The cross-reactivities of both human IgE antibodies and rabbit IgG antibodies were variable and not reciprocal between antigen and antibody, suggesting that there are multiple antigenic determinants on the PL molecules and that individuals respond to different determinants. No general patterns of cross-reactivity could be observed.

Allergens↗
PubMed1986

Cytotoxicity and metabolism of alkyl phospholipid analogues in neoplastic cells.

The cytotoxic response of several types of neoplastic cells to analogues of unnatural alkyl phospholipids (e.g., rac-1-hexadecyl-2-methoxy-glycero-3-phosphocholine) has been partially attributed to their accumulation as a result of the low activity of the alkyl cleavage enzyme (a tetrahydropteridine-dependent monooxygenase) in tumor cells. We tested this possibility by comparing the alkyl cleavage enzyme activity in cells that exhibit differences in sensitivity toward the cytotoxic effects of the rac-1-hexadecyl-2-methoxy-glycero-3-phosphocholine. Human promyelocytic leukemia cells (HL-60), a cell line highly sensitive to the cytotoxic alkyl phospholipid analogue, possessed an alkyl cleavage enzyme activity (0.25 pmol/min/microgram protein) similar to that found in three cell types known to be relatively resistant to the cytotoxic activity of the analogue: immature human promyeloblastic leukemia cells (K562) (0.22 pmol/min/microgram protein), human polymorphonuclear neutrophils (0.34 pmol/min/microgram protein), and Madin-Darby canine kidney cells (0.37 pmol/min/microgram protein). Moreover, our results indicate that the cytotoxic rac-1-octadecyl-2-methoxy-glycero-3-phosphocholine analogue is not a substrate for the alkyl cleavage enzyme with an active microsomal preparation of the enzyme from rat liver; cleavage of this analogue was 200-fold less than the rate obtained with 1-octadecylglycerol as substrate. In cultures of either sensitive or resistant type cells, approximately 90% of the added rac-1-[9',10'-3H]octadecyl-2-methoxy-glycero-3-phosphocholine was not metabolized during a 24-h incubation. The amount of radiolabel in fatty acids, a major product of alkyl cleavage activity, was small, and essentially identical amounts were produced in all four cell types [3.1 +/- 0.2% (SD)]. These data indicate that differences in the cellular activities of the alkyl cleavage enzyme are not responsible for the differential cytotoxic responses between normal and specific types of neoplastic cells toward rac-1-octadecyl-2-methoxy-glycero-3-phosphocholine. On the other hand, the cellular uptake of the alkyl phospholipids could be a factor in explaining the cytotoxic response of certain tumor cells, since more radiolabeled 1-octadecyl-2-methoxy-glycero-3-phosphocholine was associated with the susceptible HL-60 cells than with the resistant cell types. Autoradiography revealed that the radiolabeled 2-methoxy analogue accumulates at the periphery of HL-60 leukemia cells, whereas the label was more uniformly distributed in polymorphonuclear neutrophils and K562 cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Platelet-activating factor metabolism in human amnion and the responses of this tissue to extracellular platelet-activating factor.

It was found previously that platelet-activating factor (PAF, 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is undetectable in human amniotic fluid obtained before labor but is present in the majority of samples of amniotic fluid obtained after labor. In the present investigation, the amount of PAF in amnion tissue and the ability of this tissue to produce PAF and respond to PAF were investigated. Amounts of PAF in amnion obtained either during the second trimester of gestation or at term (before labor) were similar. After labor, however, the amount of PAF in amnion increased to 2.5-times that in amnion before labor without any discernible changes in the amounts of two related glycerophospholipids viz., 1-0-alkyl-sn-glycero-3-phosphocholine and 1-0-alkyl-2-acyl-sn-glycero-3-phosphocholine. The Ca2+-ionophore A23187, in the presence of Ca2+, caused an increase in the amount of PAF in amnion tissue disks but PAF did not appear to be released into the incubation medium. The stimulation of PAF formation by A23187 and Ca2+ was not affected by the addition of indomethacin. Addition of PAF to disks of amnion tissue resulted in an increase in the concentration of prostaglandin E2 in the incubation medium. An increase in prostaglandin E2 formation of similar magnitude was induced by A23187. Based on these results it is concluded that PAF can be synthesized in amnion tissue and net production is stimulated by Ca2+. In addition, amnion is receptive to extracellular PAF and exhibits, as one response, an increased production of prostaglandin E2.

Amnion↗
PubMed1985

Allergens in Hymenoptera venom XIII: Isolation and purification of protein components from three species of vespid venoms.

Pure venoms were collected from individual insects of the species Dolichovespula maculata, white-faced hornet, Vespula squamosa, southern yellow jacket, and Polistes exclamans, paper wasp (one species). The venoms were first fractionated by high-resolution gel filtration on a 1.6 m column of Sephadex G-75 superfine, and the components were then purified by high-performance, ion-exchange chromatography on a Mono-S cation exchange column followed by a further gel filtration step. The isolated components were evaluated for purity by sodium dodecyl sulfate polyacrylamide gel electrophoresis by use of two different types of silver stains, by assays for enzyme activities, and by immunodiffusion with the use of rabbit antisera. The protein components were isolated in highly purified states by these techniques. Only three significant proteins were found in V. squamous venom: phospholipase (PL) A and B, hyaluronidase (HYAL), and antigen 5 (Ag 5). D. maculata venom contained HYAL, Ag 5, two isozymes of PL A and B, a high-molecular-weight protein, and several trace proteins. No significant amounts of proteases were found in D. maculata venom. P. exclamans venom contained HYAL, PL A and B, Ag 5, a high-molecular-weight protein, and several minor proteins. In all three venoms the PL A and B activities were found to be in the same molecule and did not separate. Trace components with apparent PL A activity were observed in the venoms. The venoms were screened for a variety of esterases, proteases, peptidases, glucosidases, and phosphatases, and none were detected in more than trace amounts. Vespid venoms do not appear to contain significant amounts of acid phosphatases as bee venoms do.

Allergens↗
PubMed1985

Allergens in Hymenoptera venom XIV: IgE binding activities of venom proteins from three species of vespids.

RAST disks were prepared with purified proteins from the venoms of Vespula squamosa, Dolichovespula maculata, and Polistes exclamans and tested against a panel of sera obtained from patients allergic to each of the venoms. By the use of several criteria, IgE binding was strongest to antigen 5 of V. squamosa and phospholipase of P. exclamans. Hyaluronidase from Polistes had little IgE binding activity. All five proteins tested from D. maculata bound IgE antibodies strongly. Linear correlation analysis suggested that all of the proteins were distinct allergens in each of the venoms. A variety of patterns of response were observed for individual sera with each of the venoms.

Allergens↗
PubMed1985

Allergens in Hymenoptera venom XV: The immunologic basis of vespid venom cross-reactivity.

RAST-inhibition studies were performed by use of whole venom sac extracts to inhibit binding to purified venom allergens from various vespid wasps. Immunodiffusion studies were also performed with rabbit antisera raised against purified venom proteins. Immunologic cross-reactivity was demonstrated among the hyaluronidases, phospholipases, and antigen 5 s from both subgenera of yellow jackets, white-faced hornets, and paper wasps. The paper wasp hyaluronidase and antigen 5 were less related to those of the other three species than those of yellow jackets and hornets. It appears that immunologic cross-reactivity is the major mechanism of multiple allergic sensitivity to vespid venoms. Therapy with only the primary venom should be sufficient to protect against reactions from cross-reacting venoms.

Allergens↗