Kinetic studies of the binding of acridinecarboxamide topoisomerase poisons to DNA: implications for mode of binding of ligands with uncharged chromophores

We have used stopped-flow spectrophotometry and the sodium dodecyl sulfate sequestration technique to study the kinetics of dissociation of DNA complexes of the mixed topoisomerase I/II poison N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (termed DACA) and a range of related linear tricyclic carboxamides with neutral chromophores. Complexes of DACA and related acridine and phenazinecarboxamides bearing an N,N-dimethylaminoethyl side chain dissociate from calf thymus DNA by a kinetic pathway involving four discernible steps in a manner similar to complexes of N-[(2-dimethylamino)ethyl]-9-aminoacridine-4-carboxamide (termed 9-amino-DACA). We infer from these findings that the side chains of DACA, its phenazine homologue, and 9-amino-DACA make comparable interactions with the DNA base pairs. In the case of 9-amino-DACA, a selective topoisomerase II poison, these are known, by crystallographic analysis, to involve hydrogen-bonding interactions between the protonated dimethylammonium group of the side chain and the O6/N7 atoms of guanine and to include a bridging water molecule hydrogen bonded to the carboxamide group and a phosphate oxygen. By contrast, we find that other linear tricyclic carboxamides with neutral chromophores which lack a peri nitrogen atom and are biologically inactive dissociate from DNA by a different mechanism in which it appears their side chains fail to interact with guanine. We conclude that the ability of the carboxamide group to lie preferentially in the plane of the chromophore, so facilitating the dimethylammonium-guanine hydrogen bond and ensuring maintenance of the water-bridged carboxamide-phosphate interaction, is a critical requirement for antitumor activity among ligands of the linear tricyclic carboxamide class. However, unlike the situation for 9-amino-DACA, for ligands with uncharged chromophores containing peri nitrogen atoms such as DACA, this outcome is possible with the 4-carboxamide group rotated cis or trans with respect to the ring nitrogen. This difference may have relevance to the ability of DACA to be a dual poison of both topoisomerases I and II.

Crystal structure of 9-amino-N-[2-(4-morpholinyl)ethyl]-4-acridinecarboxamide bound to d(CGTACG)2: implications for structure-activity relationships of acridinecarboxamide topoisomerase poisons

The structure of the complex formed between d(CGTACG)2 and 9-amino-N-[2-(4-morpholinyl)ethyl]-4-acridinecarboxamide, an inactive derivative of the antitumour agents N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (DACA) and 9-amino-DACA, has been solved to a resolution of 1.8 A using X-ray crystallography. The complex crystallises in the space group P6(4 )and the final structure has an overall R factor of 21.9%. A drug molecule intercalates between each of the CpG dinucleotide steps with its side chain lying in the major groove, and its protonated morpholino nitrogen partially occupying positions close to the N7 and O6 atoms of guanine G2. The morpholino group is disordered, the major conformer adopting a twisted boat conformation that makes van der Waals contact with the O4 oxygen of thymine T3. A water molecule forms bridging hydrogen bonds between the 4-carboxamide NH and the phosphate group of guanine G2. Sugar rings are found in alternating C3'-exo/C2'-endo conformations except for cytosine C1 which is C3'-endo. Intercalation perturbs helix winding throughout the hexanucleotide compared with B-DNA, steps 1 and 2 being unwound by 10 and 8 degrees, respectively, while the central TpA step is overwound by 11 degrees. An additional drug molecule lies at the end of each DNA helix linking it to the next duplex to form a continuously stacked structure. The protonated morpholino nitrogen of this 'end-stacked' drug hydrogen bonds to the N7 atom of guanine G6, and its conformationally disordered morpholino ring forms a C-H...O hydrogen bond with the guanine O6 oxygen. In both drug molecules the 4-carboxamide group is internally hydrogen bonded to the protonated N10 atom of the acridine ring. We discuss our findings with respect to the potential role played by the interaction of the drug side chain and the topoisomerase II protein in the poisoning of topoisomerase activity by the acridinecarboxamides.

Cytomegalovirus infection accelerates inflammation in vascular tissue overexpressing monocyte chemoattractant protein-1

Cardiovascular disease is the leading cause of mortality in the United States. Atherosclerosis is responsible for most of this pathology and is an inflammatory disease with multiple cytokines and adhesion molecules expressed during atherogenesis. Cytomegalovirus (CMV), monocytes, and monocyte chemoattractant protein-1 (MCP-1) have all been implicated in human atherogenesis. A transgenic mouse overexpressing MCP-1 in the myocardium and pulmonary arteries develops myocarditis and pulmonary vascular inflammation. We infected MCP-1 transgenic mice with a sublethal dose of murine cytomegalovirus (MCMV) to look for evidence of accelerated inflammation in vascular tissues overexpressing MCP-1 to determine if MCMV could interact with monocytes and MCP-1 in a manner similar to what may occur in atherogenesis. MCMV infection of MCP-1 transgenic mice caused ascites, myocarditis, and pulmonary artery inflammation, which was not present in mock-infected MCP-1 or MCMV-infected wild-type mice. Inflammatory infiltrates in these tissues consisted of macrophages and T lymphocytes similar to the infiltrates seen in atherosclerosis. Virus presence in inflamed tissues was demonstrated by infecting transgenic mice with MCMV recombinant virus containing the gene sequence for the enhanced green fluorescent protein (EGFP). Human CMV could be involved in atherogenesis in a similar manner by interacting with monocytes and MCP-1 specifically expressed in vascular walls.

Biotransformation of (S)-(+)-linalool by Aspergillus niger: an investigation of the culture conditions

The biotransformation of (S)-(+)-linalool by different Aspergillus niger strains was studied, using submerged shaken liquid cultures. One strain, A. niger DSM 821, was able to convert the substrate to cis- and trans-furanoid linalool oxide (yield 30% and 5%, respectively) and cis- and trans-pyranoid linalool oxide (yield 14% and 1.5%, respectively). The main metabolites, cis-(2S,5R)-furanoid and cis-(3S,6S)-pyranoid linalool oxide, have a sweet, floral, creamy odor and are used in perfumery. The culture conditions involved, such as the composition of the broth and the type and concentration of cosolvent applied and possible adaptation to the substrate during inoculation, were investigated. It was found that (S)-(+)-linalool was converted much better than (R)-(-)-linalool and that no significant chemical conversion of the substrate occurred in control flasks at pH 3.5. Three cosolvents for improving the solubility of linalool in the culture broths were compared, namely MeOH, EtOH, and acetone. The highest bioconversion yields were obtained when the substrate was applied as a diluted solution in acetone. Screening of the fungi for their biotransformation capacity was performed by solid-phase microextraction.

Effect of macrophages and serum of fish susceptible or resistant to epizootic ulcerative syndrome (EUS) on the EUS pathogen, Aphanomyces invadans

Epizootic ulcerative syndrome (EUS) is one of the most destructive diseases of fresh and brackish water farmed and wild fish in the Asia-Pacific region. The in vitro germination and growth of the propagules of the EUS pathogen, Aphanomyces invadans (= A. piscicida), were assessed in the presence of the head-kidney macrophages, serum, and serum heated to inactivate complement proteins, of three EUS-susceptible and one resistant fish species. The susceptible species were: striped snakehead (Channa striata), giant gourami (Osphronemus gouramy) and silver barb [Barbodes (= Puntius) gonionotus], and the resistant species was Nile tilapia (Oreochromis niloticus). Fish of all species were acclimatised to either low temperature (20 degrees C +/- 1.6) at which EUS is known to occur, or to high temperature (32 degrees C +/- 5.0) at which EUS does not occur, except for giant gouramis which were only studied at low temperature. The respiratory burst of the macrophages was assessed in the presence of A. invadans or the stimulant phorbol myristate acetate (PMA), and compared to that of controls. Anti-A. invadans antibody concentrations were assessed in all species except silver barbs. All assays were carried out at the same temperature, regardless of the temperature that the fish were kept at. Macrophages of all species other than snakeheads inhibited fungal germination at both temperatures, though only silver barb and gourami macrophages could inhibit germling growth. PMA increased the respiratory burst in nearly all cases. The respiratory burst in the presence of A. invadans was consistently lower than that of controls, though the difference was only significant in the case of snakeheads. The respiratory burst of all macrophage treatments was higher at a low temperature. Except in the case of PMA-stimulated macrophages, regressions between respiratory burst and inhibitory action were only found in susceptible species, suggesting that the respiratory burst is important in those species, but is unable to prevent the proliferation of A. invadans. Serum inhibited fungal germination in all cases other than low temperature tilapia, indicating that the EUS resistance of tilapia is not due to the serum. Inhibition of germling growth by serum only occurred in silver barbs and gourami. Heated serum did not inhibit germination in any case except that of high temperature snakehead, and in fact stimulated germination in the case of tilapia. Heating serum did not affect the growth inhibiting activity of silver barbs and gouramis, but it stimulated growth in some groups. At high temperatures snakeheads had high anti-A. invadans antibody concentrations, which may explain the inhibitory activity of their heated serum. A role for complement and antibodies in defence against A. invadans in susceptible species is suggested.

Adhesion of the fish pathogen Flavobacterium psychrophilum to unfertilized eggs of rainbow trout (Oncorhynchus mykiss) and n-hexadecane

AIMS

The ability of Flavobacterium psychrophilum, the causative agent of rainbow trout fry syndrome (RTFS) in fish, to attach to unfertilized rainbow trout (Oncorhynchus mykiss) eggs and to hydrocarbon n-hexadecane was examined in the present study.

METHODS AND RESULTS

Five different isolates of Fl. psychrophilum obtained from a variety of origins were compared. The effect of the age of the bacterium and conditions of starvation on the ability of the bacterium to adhere, were also evaluated.

CONCLUSION

The different isolates were found to exhibit a similar ability to attach to both substrates. Increased surface hydrophobicity and a greater ability to attach to the surface of the eggs were observed with bacteria aged for one month, compared to bacteria cultured in Cytophaga agar for only three days.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results provide useful information regarding the pathogenicity of RTFS, especially during the initial steps of infection.

Characterization of Borrelia burgdorferi isolated from erythema migrans lesions: interrelationship of three molecular typing methods

Genetic diversity among Borrelia burgdorferi isolates recovered from the skin of Lyme disease patients was assessed by ribosomal DNA (rDNA) spacer restriction fragment length polymorphism analysis, genomic restriction site polymorphism analysis, and plasmid content analysis. There was a significant association between the three rDNA spacer types, the six pulsed-field gel types, and plasmid content (P < 0.001). The association between distinct chromosomal and plasmid markers implies a clonal origin for each genotype.

Recruitment and derecruitment during acute respiratory failure: an experimental study

We aimed to elucidate the relationships between pleural (Ppl), esophageal (Pes), and superimposed gravitational pressures in acute lung injury, and to understand the mechanisms of recruitment and derecruitment. In six dogs with oleic acid respiratory failure, we measured Pes and Ppl in the uppermost, middle, and most dependent lung regions. Each dog was studied at positive end-expiratory pressure (PEEP) of 5 and 15 cm H2O and three levels of tidal volume (VT; low, medium, and high). For each PEEP-VT combination, we obtained a computed tomographic (CT) scan at end-inspiration and end-expiration. The variations of Ppl and Pes pressures were correlated (r = 0.86 +/- 0.07, p < 0.0001), as was the vertical gradient of transpulmonary (PL) and superimposed pressure (r = 0.92, p < 0.0001). Recruitment proceeded continuously along the entire volume-pressure curve. Estimated threshold opening pressures were normally distributed (mode = 20 to 25 cm H2O). The amount of end-expiratory collapse at the same PEEP and PL was significantly lower when ventilation was performed at high VT. End-inspiratory and end-expiratory collapse were highly correlated (r = 0.86, p < 0.0001), suggesting that as more tissue is recruited at end-inspiration, more remains recruited at end-expiration. When superimposed pressure exceeded applied airway pressure (Paw), collapse significantly increased.

Dietary organic chromium supplementation and its effect on the immune response of rainbow trout (Oncorhynchus mykiss)

Recently, there has been an increasing interest in the potential effect of dietary chromium on the health of fish, particularly with respect to their metabolism and growth. Information as to the role of this mineral on their immune response, is limited however, so the aim of this study was to assess the effects of dietary chromium yeast supplementation on the immune response of rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout (56 g average weight) were fed three semipurified diets containing different levels of chromium (1540, 2340 and 4110 ppb), obtained by supplementing a basal diet with 800 or 2570 ppb chromium yeast, for 6 weeks. After this, time differences in their immune response were examined. A positive influence was observed on serum lysozyme activity at this time in fish maintained on the high chromium diet. The respiratory burst of head-kidney macrophages was also examined, and statistical differences were found in the level of respiratory burst elicited by macrophages from both groups of fish fed supplemented chromium after 3 and 6 weeks of feeding (absorbance at 3 weeks: 0.118, 0.166. 0.151 and 6 weeks 0.114, 0.168, 0.151 for the 1540, 2340 and 4110 ppb groups). Macrophages of fish receiving diets supplemented with chromium also had a greater ability to phagocytose yeast after 6 weeks than the control fish (40.5, 48 and 48.5% macrophages phagocytic in the 1540, 2340 and 4110 ppb groups, respectively). The results of the study show that chromium yeast is able to modulate the immune response of rainbow trout, and this effect appears to be both dose- and time-dependent.

Subject and observer-rated quality of life in schizophrenia

OBJECTIVE

We aimed to explore the relationship between objectively rated quality of life and subjective measures of social functioning and life satisfaction.

METHOD

Participants of the Schizophrenia Care and Assessment Program (SCAP) study at Dandenong in Australia were included in this analysis. Subjective ratings of several domains of social functioning and life satisfaction were taken from the SCAP instrument and comparisons made with data from the Quality of Life scale rated by research staff as well as several psychopathology measures.

RESULTS

Subjectively reported life satisfaction was not related to positive or negative symptoms of schizophrenia but did correlate with depressive symptoms. Quality of Life scale measures correlated with negative symptoms on most domains. There was very limited overlap in domain items between the life satisfaction and quality of life measures.

CONCLUSION

Life satisfaction and objectively rated quality of life are not closely related and appear to have different determinants in patients with schizophrenia.

Possible function of IL-6 and TNF as intraadrenal factors in the regulation of adrenal steroid secretion

Interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF alpha) and their mRNAs are present in the human, rat, and bovine adrenal cortex. The release of these cytokines from adrenal cells is regulated by factors that alter adrenal function (e.g., ACTH, angiotensin II, interleukin-1). IL-6 and TNF type 1 receptors are also present on adrenocortical cells. Exposure to IL-6 increases cortisol or corticosterone release from human, bovine, and rat adrenal cells. IL-6 increases basal and ACTH-stimulated aldosterone release, but inhibits angiotensin II-stimulated aldosterone secretion from bovine adrenal cells. IL-6 increases dehydroepiandrosterone (DHEA) release from human cells, but decreases DHEA secretion from bovine cells. TNF alpha inhibits corticosterone release from normal rat adrenal cells or fragments, but increases corticosterone release from cholestatic rat adrenal slices. TNF alpha decreases cortisol release from bovine and fetal human adrenal cells, but increases cortisol release from adult human adrenal cells. TNF alpha inhibits aldosterone secretion from rat and bovine adrenocortical cells. TNF alpha does not affect DHEA secretion from fetal human adrenocortical cells, but inhibits basal and ACTH-stimulated DHEA release from bovine adrenal cell. Because IL-6 and TNF alpha are produced in the adrenal gland and modify adrenal steroid secretion, these cytokines may function as intraadrenal factors in the regulation of adrenal steroid secretion.

Purification of Piscirickettsia salmonis and associated phage particles

Piscirickettsia salmonis was isolated from cell culture using differential centrifugation and purified on a 30% Percol gradient. The purity of the preparation was assessed by transmission electron microscopy and phage-like particles were found to be associated with some of the P. salmonis isolates examined. This is believed to be the first report of a phage associated with rickettsia from fish.

Time required for partial pressure of arterial oxygen equilibration during mechanical ventilation after a step change in fractional inspired oxygen concentration

OBJECTIVE

To determine the time required for the partial pressure of arterial oxygen (PaO2) to reach equilibrium after a 0.20 increment or decrement in fractional inspired oxygen concentration (FIO2) during mechanical ventilation.

SETTING

A multi-disciplinary ICU in a university hospital.

PATIENTS AND METHODS

Twenty-five adult, non-COPD patients with stable blood gas values (PaO2/FIO2 > or = 180 on the day of the study) on pressure-controlled ventilation (PCV). Following a baseline PaO2 (PaO2b) measurement at FIO2 = 0.35, the FIO2 was increased to 0.55 for 30 min and then decreased to 0.35 without any other change in ventilatory parameters. Sequential blood gas measurements were performed at 3, 5, 7, 9, 11, 15, 20, 25 and 30 min in both periods. The PaO2 values measured at the 30th min after a step change in FIO2 (FIO2 = 0.55, PaO2[55] and FIO2 = 0.35, PaO2[35]) were accepted as representative of the equilibrium values for PaO2. Each patient's rise and fall in PaO2 over time, PaO2(t), were fitted to the following respective exponential equations: PaO2b + (PaO2[55]-PaO2b)(1-e-kt) and PaO2[55] + (PaO2[35]-PaO2[55])(e-kt) where "t" refers to time, PaO2[55] and PaO2[35] are the final PaO2 values obtained at a new FIO2 of 0.55 and 0.35, after a 0.20 increment and decrement in FIO2, respectively. Time constant "k" was determined by a non-linear fitting curve and 90% oxygenation times were defined as the time required to reach 90% of the final equilibrated PaO2 calculated by using the non-linear fitting curves.

RESULTS

Time constant values for the rise and fall periods were 1.01 +/- 0.71 min-1, 0.69 +/- 0.42 min-1, respectively, and 90% oxygenation times for rises and falls in PaO2 periods were 4.2 +/- 4.1 min-1 and 5.5 +/- 4.8 min-1, respectively. There was no significant difference between the rise and fall periods for the two parameters (p > 0.05).

CONCLUSION

We conclude that in stable patients ventilated with PCV, after a step change in FIO2 of 0.20, 5-10 min will be adequate for obtaining a blood gas sample to measure a PaO2 that will be representative of the equilibrium PaO2 value.

Generation of an isogenic collection of yeast actin mutants and identification of three interrelated phenotypes

A large collection of yeast actin mutations has been previously isolated and used in numerous studies of actin cytoskeletal function. However, the various mutations have been in congenic, rather than isogenic, backgrounds, making it difficult to compare the subtle phenotypes that are characteristic of these mutants. We have therefore placed 27 mutations in an isogenic background. We used a subset of these mutants to compare the degree to which different actin alleles are defective in sporulation, endocytosis, and growth on NaCl-containing media. We found that the three phenotypes are highly correlated. The correlations are specific and not merely a reflection of general growth defects, because the phenotypes are not correlated with growth rates under normal conditions. Significantly, those actin mutants exhibiting the most severe phenotypes in all three processes have altered residues that cluster to a small region of the actin crystal structure previously defined as the fimbrin (Sac6p)-binding site. We examined the relationship between endocytosis and growth on salt and found that shifting wild-type or actin mutant cells to high salt reduces the rate of alpha-factor internalization. These results suggest that actin mutants may be unable to grow on salt because of additive endocytic defects (due to mutation and salt).

[Intracranial hemangioma]

A case of intracranial hemangioma in a neonate is described by the authors. The rarity of the condition raised differential diagnosis problems.