Perchlorate remediation technologies: A systematic review of solely biodegradation versus a combination of ion-exchange and biodegradation technologies

A systematic review was performed in order to evaluate perchlorate remediation technologies. The two included technologies were ion-exchange concerted with biodegradation and solely biodegradation. A meta-analysis was completed and subsequently, a regression model was formed to conduct a degradation rate analysis and to depict the association between rate and various dependent variables (salinity/sali, nitrate concentration/nitc and carbon source concentration/csou). The outcome of the model analysis suggested that salt concentration did have an effect on the degradation rate in the ion-exchange process and that with a salt concentration greater than or equal to 18.6 g/L, the biodegradation process will produce a greater reduction of perchlorate than ion-exchange concerted with biodegradation. However, when a t-test examined the difference in perchlorate degradation rate between the two cleanup methods, there was no significant difference seen (p=0.7351, α = 0.05).^

DRUG METABOLISM IN LIVER TUMORS: PURIFICATION AND CHARACTERIZATION OF NADPH-CYTOCHROME-P450 REDUCTASE AND THE RESOLUTION OF MULTIPLE FORMS OF CYTOCHROME P-450

The hydroxylation of N- and O-methyl drugs and a polycyclic hydrocarbon has been demonstrated in microsomes prepared from two transplantable Morris hepatomas (i.e., 7288C. t.c. and 5123 t.c.(H). The hydroxylation rates of the drug benzphetamine and the polycyclic hydrocarbon benzo {(alpha)} pyrene by tumor microsomes were inducible 2 to 3-fold and 2-fold, respectively by pretreatment of rats with phenobarbital/hydrocortisone. Hepatoma 5123t.c.(h) microsomal hydroxylation activities were more inducible after these pretreatments than hepatoma 7288C.t.c. Two chemotherapeutic drugs (cyclophosphamide and isophosphamide) were shown to be mutagenic after activation by the tumor hemogenate with the TA100 strain of Salmonella typhimurium bacteria. NADPH-cytochrome P-450 was purified from phenobarbital/hydrocortisone treated rat hepatoma 5123t.c.(H) microsomes 353-fold with a specific activity 63.6 nmol of cytochrome c reduced per min per mg of protein. The purified enzyme, has an apparent molecular weight of 79,500 daltons, and contained an equal molar ratio of FMN and FAD, with a total flavin content of 16.4 nmol per mg of protein. The purified enzyme also catalyzed electron transfer to artificial electron acceptors with the K(,m) values of the hepatoma reductase similar to those of purified liver reductase. The K(,m) value of the hepatoma reductase (13 uM) for NADPH was similar to that of purified liver reductase (5.0 uM). In addition the purified hepatoma reductase was immunochemically similar to the liver reductase.^ Hepatoma cytochrome P-450, the hemeprotein component of the hepatoma microsomes of rats pretreated with phenobarbital/hydrocortisone. The resolution of the six forms was achieved by the DE-53 ion-exchange chromatography, and further purified by hydroxyapatite. The six different fractions that contained P-450 activity, had specific contents from 0.47 to 1.75 nmol of cytochrome P-450 per mg of protein, and indicated a 2 to 9-fold purification as compared to the original microsomes. In addition, difference spectra, molecular weights and immunological results suggest there are at least six different forms of cytochrome P-450 in hepatoma 5123 t.c.(H). ^

DIAGNOSTIC ANTIGENS FOR SCHISTOSOMIASIS MANSONI: PRODUCTION, CHARACTERIZATION AND PURIFICATION OF MONOCLONAL ANTIBODIES, AND AFFINITY PURIFICATION OF ANTIGENS

Attempts have been made in this dissertation to develop a purified antigen with high sensitivity and specificity for diagnosis of Schistosoma mansoni (Sm) infection by using the hybridoma technique.^ Spleen cells, obtained from mice immunized by infection with Sm and boosted by cercarial antigens, or by injection of circulating antigen (CA) in serum from infected mice, were fused with Sp2/0 myeloma cells. The active infection resulted a higher number of hybridomas (100%) than by CA (20%), and higher levels of antibody reactivity as measured by ELISA.^ The IgM and IgG monoclonal antibodies (MCAbs) were purified respectively by gel filtration, DE 52 ion exchange column and proteinase A affinity column. The cercarial and egg antigens were purified by affinity chromatography through MCAb/affi-gel column. The reactivity of the purified antigens were then monitored by ELISA, SDS-PAGE silver stain and EITB.^ The respective MCAbs recognized varying antigenic determinants (AD) present in adult, cercaria and egg stages. By EITB the MCAbs IgM and IgG, when reacted with nine antigens from the various stages, revealed identical bands, suggesting that the two MCAb classes originated from identical AD. By ELISA and COPT, the MCAbs from thirteen cell lines gave same results. But by CHR, two MCAbs showed negative results while eleven other MCAbs showed strong positive. It is assumed that the AD in the immunogen that ilicited the MCAbs were immunochemically closely related.^ One egg purified by immunoaffinity indicated that the epitopes recognized by MCAb were present on four antigenic components with molecular weights (Mr) of approximately 19, 25, 60 and >224 kd, respectively. By EITB the Mr 19 doublet appeared to be species specific; the Mr 25 kd genus specific. They reacted with mouse serum from 13-16 weeks after infection. In monkey serum Mr 19 doublet appeared 8-10 weeks after infection and disappeared at 8-12 weeks after Droncit treatment, paralleled to the disappearance of fecal egg. The Mr 60 and >224 kd bands were also demonstrated with S. japonicum, S. haematobium and Trichinella spiralis infection sera and may be the cause of cross-reaction in conventional serological test. ^

SUBCELLULAR LOCALIZATION, PURIFICATION AND PROPERTIES OF A CDP-DIACYLGLYCEROL - DEPENDENT PHOSPHATIDYLSERINE SYNTHASE IN BACILLUS LICHENIFORMIS

A CDP-diacylglycerol dependent phosphatidylserine synthase was detected in three species of gram-positive bacilli, viz. Bacillus licheniformis, Bacillus subtilis and Bacillus megaterium; the enzyme in B. licheniformis was studied in detail. The subcellular distribution experiments in cell-free extracts of B. licheniformis using differential centrifugation, sucrose gradient centrifugation and detergent solubilization showed the phosphatidylserine synthase to be tightly associated with the membrane. The enzyme was shown to have an absolute requirement for divalent metal ion for activity with a strong preference for manganese. The enzyme activity was completely dependent upon the addition of CDP-diacylglycerol to the assay system; the role of the liponucleotide was rigorously shown to be that of phosphatidyl donor and not just a detergent-like stimulator. This enzyme was then solubilized from B. licheniformis membranes and purified to near homogeneity. The purification procedure consisted of CDP-diacylglycerol-Sepharose affinity chromatography followed by substrate elution from blue-dextran Sepharose. The purified preparation showed a single band with an apparent minimum molecular weight of 53,000 when subjected to SDS polyacrylamide gel electrophoresis. The preparation was free of any phosphatidylglycerophosphate synthase, CDP-diacylglycerol hydrolase and phosphatidylserine hydrolase activities. The utilization of substrates and formation of products occurred with the expected stoichiometry. Radioisotopic exchange patterns between related substrate and product pairs suggest a sequential BiBi reaction as opposed to the ping-pong mechanism exhibited by the well studied phosphatidylserine synthase of Escherichia coli. Proteolytic digestion of the enzyme yielded a smaller active form of the enzyme (41,000 daltons) which appears to be less prone to aggregation.^ This has been the first detailed study in a well-defined bacillus species of the enzyme catalyzing the CDP-diacylglycerol-dependent formation of phosphatidylserine; this reaction is the first committed step in the biosynthetic pathway to the major membrane component, phosphatidylethanolamine. Further study of this enzyme may lead to understanding of new mechanisms of phosphatidyl transfer and novel modes of control of phospholipid biosynthetic enzymes. ^

MINERALOCORTICOID REGULATION OF ION CONDUCTIVE PATHWAYS OF THE CORTICAL COLLECTING DUCT

Mineralocorticoids (DOCA) are known to increase Na('+) absorption and K('+) secretion in the rabbit cortical collecting duct (CCD). However, the mechanism of regulation of the apical and basolateral cell membranes and tight junction ion conductive pathways (G('a), G('b), and G('tj), respectively) by mineralocorticoids are only partially understood. Using electrophysiological techniques and microelectrodes it was demonstrated that the apical cell membrane contained a dominant Ba('2+) sensitive K('+) conductive pathway, G(,K)('a), and an amiloride sensitive Na('+) conductive pathway, G(,Na)('a). The basolateral membrane contained a dominant Cl('-) conductive pathway, G(,Cl)('b), and a significant Ba('2+) sensitive K('+) conductive pathway, G(,K)('b). Upon elevating the mineralocorticoid levels of rabbits with intact adrenal glands it was found that V('te) was significantly increased after 1 day with a further increase after 13-16 days. These results indicated both primary and secondary effects of mineralocorticoid elevation. After 1 day of DOCA treatment, G(,Na)('a), I(,Na)('a) and I(,K)('a) increased by more than 2-fold and were maintained at high levels after 13-16 days of DOCA treatment. Secondary (chronic) effects of mineralocorticoids were evident after 4 days or more of DOCA treatment. These included a significant increase in G(,K)('a) from 4.0 to 10.2 mS.cm('-2) and a hyperpolarization of V('b) by -20 mV after 4 days of treatment. After 13-16 days of DOCA treatment V('b) remained hyperpolarized at -98.1 mV and G('tj) decreased from 5.6 to 4.2 mS.cm('-2). The hyperpolarization of V('b) was due to an increase in electrogenic Na('+) pump activity as the pump current, I(,act)('b), increased significantly from 35.7 to 195.2 (mu)A.cm('-2). Whereas net passive K('+) current across the basolateral membrane, I(,K)('b), was near zero in the control group of animals, i.e., K('+) near equilibrium, I(,K)('b) was approximately -40 (mu)A.cm('-2) in chronic DOCA treated animals. These results demonstrate that the initial effect of mineralocorticoid elevation is to increase G(,Na)('a). The ensuing depolarization of the apical membrane increases the driving force for K('+) exit into the lumen. Between 1 and 4 days of elevation, G(,K)('a) more than doubles in magnitude and at the same time the electrogenic activity of the Na('+) pump increases. This results in a hyperpolarization of V('b) which increases the driving force for K('+) uptake from the bath to the cell through a basolateral membrane conductive pathway. After 13-16 days G('tj) decreases thereby serving to maintain high electrochemical gradients across the epithelium. Therefore, the long term effects of mineralocorticoid elevation on the CCD appear to be adaptive mechanisms that serve to maintain high levels of K('+) secretion and Na('+) absorption. ^