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K J Miller

Publications and source records attributed to K J Miller.

At least 73 records · Page 4Linked to original sources
PubMed1991

Diglyceride Kinase Activity in Cell Extracts of Rhizobium meliloti: Evidence for a Diglyceride Cycle during Cyclic beta-1,2-Glucan Biosynthesis.

In this article, we provide evidence for the presence of diglyceride kinase activity in cell extracts of Rhizobium meliloti 1021. Characterization of the rhizobial enzyme revealed that it shares many properties with the diglyceride kinase of Escherichia coli. A possible role for this enzyme during cyclic beta-1,2-glucan biosynthesis is discussed.

Journal Article↗
PubMed1991

A novel membrane-bound glucosyltransferase from Bradyrhizobium japonicum.

Bacteria within the family Rhizobiaceae are distinguished by their ability to infect higher plants. The cell envelope carbohydrates of these bacteria are believed to be involved in the plant infection process. One class of cell envelope carbohydrate, the cyclic beta-1,2-glucans, is synthesized by species within two genera of this family, Agrobacterium and Rhizobium. In contrast, species of the genus Bradyrhizobium, a third genus within this family, appear to lack the capacity for cyclic beta-1,2-glucan biosynthesis. Instead, these bacteria synthesize cyclic glucans containing beta-1,6 and beta-1,3 glycosidic linkages (K.J. Miller, R.S. Gore, R. Johnson, A.J. Benesi, and V.N. Reinhold, J. Bacteriol. 172:136-142, 1990). We now report the initial characterization of a novel membrane-bound glucosyltransferase activity from Bradyrhizobium japonicum USDA 110. Analysis of the product of this glucosyltransferase activity revealed the following: the presence of beta-1,3 and beta-1,6 glycosidic linkages, an average molecular weight of 2,100, and no detectable reducing terminal residues. The glucosyltransferase activity was found to have an apparent Km of 50 microM for for UDP-glucose, and activity was stimulated optimally by Mn2+ ions. On the basis of the structural properties of the in vitro glucan product, it is possible that this membrane-bound glucosyltransferase activity may be responsible for the biosynthesis of cyclic beta-1,6-beta-1,3-glucans by this organism.

Cations, Divalent↗
PubMed1991

Human papillomavirus type 16 DNA in anal cancers from six different countries.

An association between anal squamous cell carcinoma and human papillomavirus (HPV) type 16 DNA has been documented in the UK. If HPV type 16 is an important aetiological factor in the development of this tumour it would be expected to occur in anal cancer tissues from other parts of the world. In this study a series of 173 anal squamous cell carcinoma tissue samples from five centres around the world have been examined by DNA hybridisation for HPV type 16 DNA sequences. HPV type 16 DNA was found in 50 of 173 (29%) of these. The prevalence of HPV associated anal squamous cell carcinoma was significantly lower in tissue from India and South Africa than in the Swiss, Polish, or Brazilian samples. HPV associated anal squamous cell carcinoma does occur in other countries and further investigations of the prevalence of these tumours in association with other HPV types are required.

Anus Neoplasms↗
PubMed1990

Clinical and pathological correlates of HPV type 16 DNA in anal cancer.

The aetiology of anal squamous cell carcinoma (SCC) has recently been associated with a sexually transmissible agent--human papillomavirus (HPV) type 16. In this study clinical and pathological data from a prospective series of 67 anal SCC collected over a three year period were compared with the HPV type 16 DNA content of these tumours to determine whether any of the clinical or histological parameters might predict HPV DNA content in a tumour specimen. Of twelve clinicopathological variables examined none was significantly correlated with HPV DNA content at the p = 0.01 level.

Adult↗
PubMed1990

5-HT1 and 5-HT2 binding profiles of the serotonergic agents alpha-methylserotonin and 2-methylserotonin.

alpha-Methyl-5-hydroxytryptamine (alpha-Me-5-HT; 2) and 2-methyl-5-hydroxytryptamine (2-Me-5-HT; 3) are considered to be 5-HT2-selective and 5-HT3-selective agents, respectively. These agents were synthesized and examined at serotonin (5-HT) binding sites because there is relatively little documentation as to their selectivity and because they have not been previously examined at the newly discovered 5-HT1D and 5-HT1E sites. As previously reported, 2-Me-5-HT possesses a low affinity (Ki greater than 500 nM) for 5-HT1A, 5-HT1B, 5-HT1C, and 5-HT2 sites; this agent also displays a low affinity for 5-HT1D (Ki = 1220 nM) and 5-HT1E (Ki greater than 10,000 nM) sites. However, alpha-Me-5-HT displays little selectivity for 5-HT1A, 5-HT1B, 5-HT1C, and 5-HT1D sites (Ki = 42, 85, 150, and 150 nM, respectively) and a very low affinity for 5-HT1E (Ki greater than 10,000 nM) sites. Depending upon the radioligand used to label the sites, alpha-Me-5-HT displays either a low affinity (Ki = 880 nM with [3H]ketanserin) or a high affinity (Ki = 3 nM with [3H]DOB) for 5-HT2 sites. These results suggest that alpha-Me-5-HT is not as selective as previously considered and that caution should be used when employing this agent in pharmacological studies because it may act as mixed 5-HT1/5-HT2 agonist.

Animals↗
PubMed1990

Binding of cis(1,2-diaminocyclohexane)platinum(II) and its derivatives to duplex DNA.

A theoretical study is presented for the binding of RR, SS, SR, and RS isomers 1,2-diaminocyclohexane (DAC) or cis-PtII(DAC) to DNA. cis-PtII(DAC) is ligated to N7(G) on two adjacent intrastrand guanine bases in a kinked pentamer duplex of DNA (AT, CG*, CG*, GC, AT). The relative stability of the complexes is determined by calculating the relative conformational energy of the cis-PtII(DAC)(DNA) complexes with molecular mechanics (MM) and the intrinsic binding or ligation energy with quantum mechanics (QM). The results suggest that the RR and SS isomers of PtII(DAC) adducts with DNA are more stable than the SR/RS isomer by 1.7 kcal/mol relative to the cis-PtII(DAC(H2O)2 aquated species. Calculations on the overall stability of these isomers show that the SS and RR isomers are 6.5-8.2 kcal/mol more stable than the SR/RS isomers when bound to DNA, and this is attributed to differences in the strain energy in the DAC rings. The theoretical analyses of these compounds correlate a small differential activity with the trend in intrinsic binding energies. The RR isomer is more active in B16 melanoma cells, and the SS is most active in L1210 leukemia, and in general the RR and SS isomers are more active than the SR and RS in most cell types. The fact that the activity is DNA dependent suggests that excision or repair mechanisms may be taking place and that additional mechanistic steps beyond molecular modeling and quantum mechanical calculations are required to fully understand the activity. These studies of molecular fit of cis-PtII(DAC) to DNA are used to suggest substituted DAC compounds that may yield similar binding characteristics. Modifications to yield DAC derivatives are recommended in anticipation that they may also exhibit activity.

Antineoplastic Agents↗
PubMed1990

Cell-associated oligosaccharides of Bradyrhizobium spp.

We report the initial characterization of the cell-associated oligosaccharides produced by four Bradyrhizobium strains: Bradyrhizobium japonicum USDA 110, USDA 94, and ATCC 10324 and Bradyrhizobium sp. strain 32H1. The cell-associated oligosaccharides of these strains were found to be composed solely of glucose and were predominantly smaller than the cyclic beta-1,2-glucans produced by Agrobacterium and Rhizobium species. Linkage studies and nuclear magnetic resonance analyses demonstrated that the bradyrhizobial glucans are linked primarily by beta-1,6 and beta-1,3 glycosidic bonds. Thus, the bradyrhizobia appear to synthesize cell-associated oligosaccharides of structural character substantially different from that of the cyclic beta-1,2-glucans produced by Agrobacterium and Rhizobium species.

Glucans↗
PubMed1990

Isolation and characterization of the constitutive acyl carrier protein from Rhizobium meliloti.

Rhizobium species produce an inducible acyl carrier protein (ACP), encoded by the nodF gene, that somehow functions in an exchange of cell signals between bacteria and specific plant hosts, leading to nodulation of plant roots and symbiotic nitrogen fixation, as well as a constitutive ACP needed for the synthesis of essential cell lipids. The periplasmic cyclic glucans of Rhizobium spp. are also involved in specific rhizobium-plant interaction. These glucans are strongly similar to the periplasmic membrane-derived oligosaccharides (MDO) of Escherichia coli. E. coli ACP is an essential component of a membrane-bound transglucosylase needed for the biosynthesis of MDO, raising the possibility that either or both of the rhizobial ACPs might have a similar function. We have now isolated the constitutive ACP of R. meliloti and determined its primary structure. We have also examined its function, together with those of ACPs from E. coli, Rhodobacter sphaeroides, and spinach, in the MDO transglucosylase system and as substrate for the E. coli ACP acylase enzyme. All four ACPs act as acceptors of acyl residues, but only the E. coli ACP functions in the transglucosylase system.

Acyl Carrier Protein↗
PubMed1988

Phosphoglycerol substituents present on the cyclic beta-1,2-glucans of Rhizobium meliloti 1021 are derived from phosphatidylglycerol.

The synthesis of periplasmic cyclic beta-1,2-glucans is a property unique to species of the family Rhizobiaceae. For this reason, it is generally believed that these molecules may play an important role in the plant infection process. In the present study, we determined that the cyclic beta-1,2-glucans produced by Rhizobium meliloti 1021 were predominantly anionic in character and contained both phosphoglycerol and succinic acid substituents. In addition, we demonstrated that phosphatidylglycerol was the source of the phosphoglycerol substituents present on these oligosaccharides and that greater than 60% of the total phospholipid turnover in this organism involved this substitution reaction.

Glucans↗
PubMed1987

Cyclic glucans produced by Agrobacterium tumefaciens are substituted with sn-1-phosphoglycerol residues.

In a previous study (Miller, K.J., Kennedy, E.P. and Reinhold, V.N. (1986) Science 231, 48-51) it was reported that the biosynthesis of periplasmic cyclic beta-1,2-glucans by Agrobacterium tumefaciens is strictly osmoregulated in a pattern closely similar to that found for the membrane-derived oligosaccharides of Escherichia coli (Kennedy, E.P. (1982) Proc. Natl. Acad. Sci. USA 79, 1092-1095). In addition to the well-characterized neutral cyclic glucan, the periplasmic glucans were found to contain an anionic component not previously reported. Biosynthesis of the anionic component is osmotically regulated in a manner indistinguishable from that of the neutral cyclic beta-1,2-glucan. We now find that the anionic component consists of cyclic beta-1,2-glucans substituted with one or more sn-1-phosphoglycerol residues. The presence of sn-1-phosphoglycerol residues represents an additional, striking similarity to the membrane-derived oligosaccharides of E. coli.

Anions↗
PubMed1987

Transfer of phosphoethanolamine residues from phosphatidylethanolamine to the membrane-derived oligosaccharides of Escherichia coli.

The membrane-derived oligosaccharides (MDO) of Escherichia coli are periplasmic constituents composed of glucose residues linked by beta-1,2 and beta-1,6 glycosidic bonds. MDO are substituted with phosphoglycerol, phosphoethanolamine, and succinic acid moieties. The phosphoglycerol residues present on MDO are derived from phosphatidylglycerol (B. J. Jackson and E. P. Kennedy, J. Biol. Chem. 258:2394-2398, 1983), but evidence as to the source of the phosphoethanolamine residues has been lacking. We now report that phosphatidylethanolamine, exogenously added to intact cells of E. coli, provides a source of phosphoethanolamine residues that are transferred to MDO. The biosynthesis of phosphoethanolamine-labeled MDO is osmotically regulated, with maximum synthesis occurring during growth in medium of low osmolarity.

Cell Membrane↗
PubMed1986

Metabolic activation of the serotonergic neurotoxin para-chloroamphetamine to chemically reactive intermediates by hepatic and brain microsomal preparations.

Para-chloroamphetamine (PCA) is selectively toxic to serotonergic neurons in laboratory animals. Acute, reversible neurotoxicity is followed by long-term effects which include inactivation of tryptophan hydroxylase and destruction of neurons. We have studied the metabolic formation of reactive intermediates that might be involved in long-term PCA neurotoxicity. Incubation of [3H]PCA with rat hepatic microsomes resulted in NADPH-dependent and oxygen-dependent covalent binding of radioactivity to microsomal protein. Addition of SKF-525A and glutathione to incubation mixtures inhibited [3H]PCA covalent binding 30% and 92% respectively. No inhibition of radiolabeled covalent binding was observed in an atmosphere of carbon monoxide/oxygen (80/20). 7,8-Benzoflavone was more effective than metyrapone in inhibiting [3H]PCA covalent binding. The extent of [3H]PCA covalent binding to microsomal protein was unchanged after phenobarbital pretreatment of rats, whereas 3-methylcholanthrene pretreatment increased [3H]PCA covalent binding (175%). NADPH-dependent and oxygen-dependent covalent binding of radioactivity was also observed when [3H]PCA was incubated with rat brain microsomal preparations. Addition of SKF-525A and glutathione to incubation mixtures inhibited covalent binding 10 and 40% respectively. There were no significant differences in total, NADPH-independent or NADPH-dependent covalent binding of radiolabeled R,S(+/-)-, R(-)-, or S(+)-PCA to rat hepatic microsomal protein. Less covalent binding was observed when [3H]amphetamine was incubated with rat liver microsomal preparations as compared to results with [3H]PCA. Minimal covalent binding was observed when [3H]PCA was incubated with liver microsomal preparations from rabbits, a species resistant to PCA neurotoxicity. Results of these metabolism studies are consistent with the hypothesis that oxidative metabolic activation of PCA to reactive and toxic metabolites is related to the long-term neurotoxicity of this agent.

Amphetamine↗
PubMed1986

Osmotic adaptation by gram-negative bacteria: possible role for periplasmic oligosaccharides.

The cyclic (1----2)-beta-D-glucans produced by species of Agrobacterium and Rhizobium resemble the membrane-derived oligosaccharides of Escherichia coli in their periplasmic localization, intermediate size, and (1----2)-beta-D-glucan backbones. The regulation of the biosynthesis of cyclic (1----2)-beta-D-glucan by Agrobacterium tumefaciens is now shown to parallel the osmotic regulation of membrane-derived oligosaccharide biosynthesis in Escherichia coli. This result suggests a general role for periplasmic oligosaccharides in the osmotic adaptation of Gram-negative bacteria as ecologically diverse as enteric and soil bacteria.

Adaptation, Physiological↗
PubMed1986

Effect of the method of biopsy on the prognosis of and reliability of receptor assays in patients with operable breast cancer.

A comparison has been made of the survival of contemporary patients treated by mastectomy in whom the original diagnosis was made by either Tru-cut biopsy or by excision biopsy. After a minimum of 5 years of follow-up there was no difference in survival between those biopsied by either method. When subdivided by tumour size again no differences emerged. Among those patients in whom the original Tru-cut biopsy was false negative there was no difference in survival compared with those treated by excision biopsy. This suggests that Tru-cut biopsy is a safe method for obtaining a histological diagnosis in operable breast cancer. Furthermore, when the receptor status of the tumours from the two groups was determined, there was no difference in the percentage of oestrogen receptor positive tumours, nor in the mean receptor value. However, there were more progesterone receptor positive tumours among the Tru-cut group, suggesting that a better tumour sample could have been submitted for analysis. This may be yet another advantage for the use of Tru-cut biopsy for the diagnosis of breast cancer.

Biopsy↗
PubMed1986

Effects of monovalent and divalent salts on the phospholipid and fatty acid compositions of a halotolerant Planococcus sp.

The phospholipid headgroup and fatty acid compositions of a halotolerant Planococcus sp. (strain A4a) were examined when cells were grown in the presence of high concentrations of a variety of salts. The fatty acid composition of Planococcus sp. strain A4a was altered primarily as a function of the osmolality of the growth medium. The phospholipid headgroup composition was influenced by both the osmolality of the growth medium and the nature of the cation species present. An increase in the cardiolipin/phosphatidylglycerol molar ratio was detected when cells were grown in the presence of high concentrations of monovalent cations.

Calcium Chloride↗
PubMed1985

High-performance liquid chromatographic assay and preclinical pharmacological studies of pibenzimol (bisbenzimidazole).

A sensitive and selective high-performance liquid chromatographic assay with ultraviolet or fluorescence detection has been developed for the experimental antitumor agent pibenzimol. Drug is isolated from plasma or other aqueous solutions with reversed-phase C18 disposable extraction columns and chromatography afforded with a deactivated reversed-phase C18 column and phosphate buffer--methanol mobile phase. Plasma standard curves are linear for concentrations for pibenzimol from 0.01 to 5.0 micrograms/ml. Pibenzimol is stable in fresh human plasma and whole blood. Pibenzimol appears to bind to plasma proteins; however, drug adsorption to glass, plastic, membranes, and filters precludes accurate determination of pibenzimol plasma protein binding. Plasma concentrations of pibenzimol fall rapidly following rapid intravenous administration to rabbits, but parent drug is detectable in plasma 24 h after drug administration. The 24-h urinary recovery of pibenzimol is 10-20%.

Animals↗