Images in preventive medicine. Bangladesh "information highway" in the year 2000.
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Bangladesh↗
Biomedical subjects
A Dannenberg
Publications and source records attributed to A Dannenberg.
Investigation of the Heterogeneously Catalyzed Hydrolysis of Organophosphorus Pesticides.
The hydrolysis of four organophosphorus pesticides (demeton S, diazinon, disulfoton, and thiometon) in the presence or absence of three iron oxides (hematite, goethite, and ferrihydrite) and aluminum hydroxide has been investigated. Metal oxide surfaces can catalyze as well as inhibit the hydrolysis of organophosphorus insecticides and thus significantly affect the fate of these compounds in the environment. Adsorption of the organophosphorus pesticides onto the metal oxides seems to take place at specific binding sites, and the fraction adsorbed can be as high as 0.4. Activation parameter studies show that the rate-determining step of the mechanism of surface catalysis is complex formation between the pesticide and the oxide when the catalysis takes place only at low temperatures. Product studies show that hazardous, persistent compounds can be formed. An example is 1,2-bis(ethylthio)ethane, a previously unreported and persistent product of insecticide hydrolysis. The research also shows that different products can be formed depending on the reaction conditions (e.g., dissolved oxygen and pH), especially when the reactants contain alkyl sulfide moieties as their primary leaving group.
Journal Article↗
Synthesis and use of a lysolecithin analog for the purification of UDP-glucuronosyltransferase.
Because of their high cost, lysolecithins are generally not considered useful detergents for the purification of membrane-bound enzymes. Therefore, we have synthesized a structural analog of lysolecithin with similar physical properties for which synthesis is straightforward. This analog is 1-palmitoylpropanediol-3-phosphocholine. To compare the efficacy of the two detergents for the purification of a membrane-bound enzyme, we have purified UDP-glucuronosyltransferase from pig liver microsomes using lysophosphatidylcholine or the synthetic analog. The catalytic properties of UDP-glucuronosyltransferase purified with 1-palmitoylpropanediol-3-phosphocholine or lysolecithin were identical. Sodium dodecyl sulfate-gel electrophoresis indicated that the purity of the UDP-glucuronosyltransferase preparation was the same whether lysophosphatidylcholine or its synthetic analog was used. The advantage of using 1-palmitoylpropanediol-3-phosphocholine in preference to lysophosphatidylcholine is that the former can be synthesized for about 1% the cost of the latter. In addition, the method for synthesis of 1-palmitoylpropanediol-3-phosphocholine is general in that the structural features of the polymethylene chain can be varied, allowing for the inexpensive synthesis of a series of detergents.
Electrophoresis, Polyacrylamide Gel↗
Thermal stability of microsomal glucose-6-phosphatase.
The thermal stability of glucose-6-phosphatase in rat liver microsomes was examined in untreated and cholate-treated microsomes. Activity of the enzyme was measured with both glucose-6-P and mannose-6-P as substrates. Heat treatment did not cause glucose-6-phosphatase activity to decline to zero with a single rate constant in untreated microsomes. Instead, heat treatment produced an enzyme with a small residual activity that was stable. The residual level of activity was not stimulated by addition of detergent. In untreated microsomes the energies of activation for the processes of decay were different for glucose-6-phosphatase and mannose-6-phosphatase activities, suggesting that the rate-limiting steps for the hydrolysis of these compounds were different. Treatment of microsomes with detergent increased the rate constants for the thermal decay of glucose-6-phosphatase by about 150 times, and, in contrast to untreated microsomes, glucose-6-phosphatase and mannose-6-phosphatase decayed to zero with a single rate constant in cholate-treated microsomes. Also, rate constants for thermal inactivation of glucose-6-phosphatase and mannose-6-phosphatase were the same in cholate-treated microsomes. Removal of cholate increased the stability of glucose-6-phosphatase but did not regenerate the form of the enzyme present in untreated microsomes. The data for the stability of glucose-6-phosphatase under different conditions provide evidence that the enzyme can exist in at least five different stable states that are enzymatically active.
Acid Phosphatase↗
Effect of brief treatment at alkaline pH on the properties of UDP-glucuronosyltransferase.
The kinetic properties of UDP-glucuronosyltransferase were measured after brief treatment of liver microsomes at alkaline pH, followed by assay with p-nitro-phenol as aglycone, at pH 7.5. Enzyme activity increased in a graded fashion as the pH of pretreatment was increased above 8.0, with apparent maximal activation of eight-fold for a pretreatment pH of 11.1. The pH for half maximal activation was 10.6. Brief treatment at alkaline pH prior to assay at pH 7.5 was associated too with a graded conversion of the kinetics of the enzyme from non-Michaelis-Menten to Michaelis-Menten at pH 11.7. Sensitivity to the allosteric modulator, UDP-N-acetylglucosamine decreased as the pH increased. A fifty percent loss of sensitivity to UDP-N-acetylglucosamine-induced activation occurred at pH 10.6. Thus, pretreatment at alkaline pH had irreversible effects on the properties of UDP-glucuronosyltransferase in microsomes. In order to establish the cause for the irreversibility of the changes induced by alkaline pH, microsomes were treated at pH 11.6 prior to purifying UDP-glucuronosyltransferase. Enzyme purified from alkali-treated and untreated microsomes had approximately the same specific activity. More importantly, responses to activation by lipids, and regeneration of allosteric properties were the same for both purified enzymes (from alkali-treated and control microsomes). Pure enzyme was not activated by pretreatment at alkaline pH. We interpret these data to mean that the irreversible effects of alkaline pH on the properties of UDP-glucuronosyltransferase in microsomes were not due to direct effects on the enzyme, but to how the enzyme interacted normally with molecules within the plane of the membrane.
Animals↗
Regulation of UDP-glucuronosyltransferase by lipid-protein interactions. Comparison of the thermotropic properties of pure reconstituted enzyme with microsomal enzyme.
The temperature dependence of two kinetic properties of the GT2P isoform of microsomal UDP-glucuronosyltransferase was studied for enzyme in intact microsomes and for pure enzyme reconstituted into different types of lipid bilayers. The properties studied were the non-Michaelis-Menten kinetics of the enzyme and activity at Vmax(app). For enzyme in intact microsomes, the pattern of non-Michaelis-Menten kinetics was seen at all temperatures in the range tested (23 to 48 degrees C), and the slopes of the Hill plots of the data were constant across this range of temperatures. Although non-Michaelis-Menten kinetics were present for pure enzyme in bilayers of 1,2-dimyristoylphosphatidylcholine or 1,2-dipalmitoylphosphatidylcholine only in the gel phase (Hockman, Y., Kelley, M., and Zakim, D. (1983) J. Biol. Chem. 258, 6509-6519), it was not possible to reconstitute this pattern of kinetics for enzyme at T greater than 40 degrees C. For example, GT2P displayed Michaelis-Menten kinetics in bilayers of 1,2-distearoylphosphatidylcholine at 44 degrees C. For enzyme in microsomes, activities at Vmax(app) increased with increasing temperature in the range 23 to 48 degrees C, with a discontinuity in the slope of the Arrhenius plot at 34 degrees C. This thermotropic property also could not be reconstituted with pure GT2P. Instead, activities at Vmax(app) for GT2P reconstituted in 1,2-dioleoylphosphatidylcholine, 1,2-distearoylphosphatidylcholine, or 1,2-stearoyl oleoylphosphatidylcholine increased in the range 23 to 37 degrees C, but then decreased at T greater than 37 degrees C. The fall in activity at T greater than 37 degrees C was reversible, indicating that GT2P undergoes a reversible change at 37 degrees C to a less active form of the enzyme. The differences between pure, reconstituted GT2P and microsomal GT2P indicate that the thermotropic properties of the microsomal enzyme are not properties of the enzyme per se but depend on interactions between it and other components in the microsome. The data suggest, therefore, that the properties of GT2P in microsomes results in part from an organization of components in the microsomal membrane.
Animals↗
Multifocal adenocarcinoma of the proximal small intestine in a patient with celiac sprue.
Adenocarcinoma of the small intestine is a known complication of celiac sprue. We report a 63-year-old man with a history of celiac disease who developed anemia, guaiac-positive stools, and jaundice. Five discrete adenocarcinomas of the proximal small intestine were identified over a 9 year period. Endoscopic retrograde cholangiopancreatographic (ERCP) and radiographic evaluation of the small bowel were helpful in diagnosing adenocarcinoma involving the ampulla of Vater and jejunum. This case demonstrates for the first time the multifocal, malignant potential of sprue. It also illustrates the importance of an aggressive, systematic work-up of patients whose course has changed despite dietary restriction.
Adenocarcinoma↗
Abdominal actinomycosis: evaluation by computed tomography.
Actinomycosis causes disease in multiple organ systems and involves the abdomen approximately 20% of the time. We report a case of a 48-yr-old woman with a large abdominal mass secondary to actinomycosis. The patient demonstrates the clinical and pathologic features of this disease, as well as the role of evaluation by barium examination and computed tomography (CT). A discussion of abdominal actinomycosis is included.
Actinomycosis↗
Effects of prochlorperazine on the function of integral membrane proteins.
We have studied the effects of prochlorperazine on the activities of UDP-glucuronosyltransferase and glucose-6-phosphatase (glucose-6-P'ase) in rat liver microsomes. The activity of UDP-glucuronosyltransferase was increased in a graded fashion by addition of prochlorperazine. Maximal stimulation occurred at 1 mg prochlorperazine to 2 mg microsomal protein, which resulted in a 6-fold increase in activity. However, with smaller concentrations of drug, there was a time-dependent increase in the activity of UDP-glucuronosyltransferase. Sensitivity of UDP-glucuronosyltransferase to activation by UDP-N-acetylglucosamine was lost after treatment of microsomes with prochlorperazine. These results indicate that prochlorperazine causes a profound reorganization of the interactions between lipids and enzyme since the activity and allosteric properties of UDP-glucuronosyltransferase are known to depend on interactions with lipids in a gel phase. Glucose-6-P'ase also was activated in a graded fashion by prochlorperazine; 1 mg of drug/2 mg microsomal protein resulted in a 60% increase in activity. The temperature-dependent instability of glucose-6-P'ase was increased by treatment of microsomes with prochlorperazine and could be prevented only partially by substrate. We conclude that prochlorperazine disrupts the structural organization between lipids and proteins in microsomal membranes, altering thereby the activity and regulation of at least two different integral membrane proteins.
Animals↗
A damage-specific DNA binding protein. Large scale purification from human placenta and characterization.
A new large scale purification procedure for a human damage-specific DNA binding protein is described. Physical characterization suggests that the protein can dissociate into active subunits. A maximum molecular weight of 400,000 was obtained using gel exclusion chromatography, while electrophoresis through a pH 8 polyacrylamide gradient gel suggested a minimum molecular weight for the active protein of 120,000. Binding to UV-irradiated DNA revealed a broad pH optimum, no temperature dependence between 0 and 37 degrees C, and inhibition by intercalating agents. The use of 254 nm irradiation and of 313 nm irradiation in the presence of a triplet state sensitizer with alternating copolymers indicated that the protein was recognizing singlet-state-derived thymine lesions as well as triplet-state-derived adenine lesions. Inhibition of protein binding by pyridoxal 5'-phosphate and NaBH4 suggested a role for lysine at the DNA binding site, while sulfhydryl group involvement was indicated by the sensitivity of the protein to p-hydroxymercuribenzoate inhibition.
Carrier Proteins↗
Proteoglycans in the cartilage of the turkey chondrodystrophy mutant.
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Animals↗
Passage of phenotypes of chemically transformed cells via transfection of DNA and chromatin.
DNA was prepared from 15 different mouse and rat cell lines transformed by chemical carcinogens in vitro and in vivo. These DNAs were applied to NIH3T3 mouse fibroblast cultures by using the calcium phosphate transfection technique. DNAs of five donor lines were able to induce foci on the recipient monolayers. Ten other donor DNAs yielded few or no foci. DNAs from control, nontransformed parental cell lines induced few or no foci. Chromosomes were transfected from one donor whose naked DNA was unable to induce foci, and morphologic transformation of recipients was observed. These experiments prove that in five of these cell lines the chemically induced phenotype is encoded in DNA, and the sequences specifying the transformed phenotype behave as a dominant allele in the NIH3T3 recipient cells. The sequences encoding the transformation are likely found on a single fragment of DNA.
Alleles↗
Cyclooxygenase-2 expression in the developing human kidney.
Cyclooxygenase (COX) exists in two related but unique isoforms, COX-1 and COX-2, and is suggested to have specific functions in different segments of the nephron. COX-2 knockout mice develop fatal nephropathy, which implies that this isoform is important during nephrogenesis. The histologic changes seen in the COX-2 knockout mice are similar to those observed in the kidneys of human fetuses exposed to non-steroidal anti-inflammatory drugs (NSAIDs) in the third trimester of pregnancy. However, only minimal amounts of COX-2 mRNA or protein have been reported in the adult human kidney. We hypothesized that expression of COX-2 is significant in the fetal human kidney and that it is involved in the development of the nephron. To characterize the presence of COX-2 in the human fetal kidney, we used immunohistochemistry to evaluate its expression in 23 fetal kidneys ranging between 15 and 23 weeks of gestational age. Strong expression of COX-2 was localized primarily in the macula densa and the thick ascending limb of the loop of Henle, and in rare glomerular podocytes and vascular endothelial cells. There was a progressive decrease in COX-2 immunoreactivity from the most immature nephrons adjacent to the metanephric regions to the well-developed nephrons in the middle to inner cortex. In contrast to the adult human kidney, this temporal and spatial expression of COX-2 in the fetal kidney suggests that this enzyme may be involved in nephrogenesis, and its inhibition by NSAIDs during the third trimester may be responsible for fetal renal syndromes.
Cyclooxygenase 2↗