Nitric oxide prevents human platelet adhesion to fiber membranes in whole blood

During cardiopulmonary bypass or long-term extracorporeal life support, foreign surface induced platelet deposition in the oxygenator causes deterioration of gas exchange. In this study, the authors evaluated the effectiveness of nitric oxide (NO) in reducing the adhesion of platelets in whole blood to the surface of hollow fiber membranes. For this purpose, a test chamber was designed consisting of a gas exchanger with ten mitsubishi multi-layered composite hollow fibers (MHF: 257 mm OD; 203 mm ID; 70 mm length) and a polypropylene tube (16 mm OD; 100 mm length). Pure N2 (control) or nitric oxide (NO) (100 ppm, 200 ppm in N2) were delivered into the test chamber previously filled with 13 ml human whole blood. Platelet counts and platelet factor 4 (PF4), as a measure of platelet activation, were measured before and after either 1 or 2 hr of testing, and fibers were observed under scanning electron microscopic study (SEM) after each experiment. In the control and 100 ppm NO groups, platelet counts decreased and the level of PF4 increased during the 1 hr period. In the 200 ppm NO group, almost no platelet deposition could be observed on the surface of fibers under SEM. In conclusion, NO flow through hollow fiber membranes can markedly reduce platelet adhesion. Additional quantitative studies should define the optimal concentration for this effect and determine if this finding could improve oxygenator function, especially under conditions of long-term support.     

Risk factors for the development of oesophageal cancer as a second primary tumour

Exposure to irradiation or chemotherapy as well as prolonged exposure to risk factors, such as alcohol and tobacco, may induce a second primary carcinoma of the oesophagus. To estimate the potential risk of previous treatment regimens, we performed a case-control study. In the Tumour Registry of The Netherlands Cancer Institute, from 1955, 27 cases of squamous cell carcinoma of the oesophagus were identified following treatment for malignant lymphoma (n = 11), breast cancer (n = 8) and lung cancer (n = 8). The median interval was 6.6 years (range 1-16). Preferably 3 controls from the same tumour registry were matched to each case on the basis of sex, age, primary tumour, location of primary treatment (academic or general hospital), calendar year at diagnosis of primary tumour and duration of follow-up. Clinical data and details of treatment were obtained from the medical records. In patients who had smoked for more than 5 years, there was a 3.2-fold increased risk of oesophageal carcinoma (P = 0.04); for those with a regular alcohol intake the relative risk was 3.3 (P = 0.01). There was no significant relationship between irradiation of the mediastinum and subsequent risk for oesophageal cancer. The number of chemotherapy-treated patients was too small to calculate the relative risk associated with cytostatic drugs. In conclusion, oesophageal cancer as second primary cancer is extremely rare. Risk factors include the well known abuse of alcohol and tobacco. No significant relationship with previous mediastinal irradiation could be demonstrated.     

The biosynthesis of mycolic acids in Mycobacterium tuberculosis. Enzymatic methyl(ene) transfer to acyl carrier protein bound meromycolic acid in vitro

A closely related family of enzymes from Mycobacterium tuberculosis has been shown by heterologous expression to catalyze the modification of mycolic acids through the addition of a methyl (or methylene) group derived from S-adenosyl-L-methionine (SAM). Overproduction of all six of these enzymes in Escherichia coli and subsequent in vitro reactions with heat-inactivated acceptor fractions derived from Mycobacterium smegmatis in the presence of [methyl-3H]SAM demonstrated that the immediate substrate to which methyl group addition occurs was a family of very long-chain fatty acids. Inhibitors of methyl transfer, such as S-adenosyl-L-homocysteine and sinefungin, were shown to inhibit this reaction but had no effect on whole cells of either M. smegmatis or M. tuberculosis. Purified mycolic acids from M. tuberculosis were pyrolyzed, and the resulting meroaldehyde was oxidized and methylated to produce full-length methyl meromycolates. These esters were shown to comigrate with a fraction of the acceptor from the in vitro reactions, suggesting that methyl group addition occurs up to the level of the meromycolate. Protease and other treatments destroyed the activity of the acceptor fraction, which was also found to be extremely sensitive to basic pH. Antibody to the acyl carrier protein AcpM, which has recently been shown to be the carrier of full-length meromycolate produced by a unique type II fatty acid synthase system, inhibited the cell-free methyl(en)ation of these acids. These results suggest that mycolate modification reactions occur parallel with the synthesis of the AcpM-bound meromycolate chain.     

3,5-dihydroxyphenylglycine is a highly selective agonist for phosphoinositide-linked metabotropic glutamate receptors in the rat hippocampus

Metabotropic glutamate receptors (mGluRs) are a heterogeneous family of G protein-coupled glutamate receptors that are linked to multiple second messenger systems in the CNS. In this study the selectivity of mGluR agonists for different mGluR second messenger effects was characterized in slices of the rat hippocampus. The mGluR agonists (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid and (2S,3S,4S)alpha-(carboxycyclopropyl)glycine produced multiple effects on second messengers that included enhanced phosphoinositide hydrolysis in both adult and neonatal rat hippocampus, inhibition of forskolin-stimulated cyclic AMP (cAMP) formation in adult tissue, and increases in basal cAMP formation in the neonatal hippocampus. In contrast, 3,5-dihydroxyphenylglycine was potent and effective in increasing phosphoinositide hydrolysis in both adult and neonatal hippocampus but unlike the other mGluR agonists did not inhibit forskolin-stimulated cAMP formation (in the adult) or substantially enhance basal cAMP formation (in the neonate). Thus, in the rat hippocampus mGluR agonist-mediated increases or decreases in cAMP formation are not secondary to mGluR-mediated changes in phosphoinositide hydrolysis. Furthermore, 3,5-dihydroxyphenylglycine can be used to activate subpopulations of mGluRs coupled to phosphoinositide hydrolysis with minimal effects on cAMP-mGluR second messenger systems.     

Synthesis and in vitro antitumor activity of some amino-deoxy 7-hexofuranosylpyrrolo[2,3-d]pyrimidines

7-(6-amino-6-deoxy-beta-D-glucofuranosyl)-5-cyanopyrrolo[2,3 -d]pyrimidine (22) and 7-(3-amino-methyl-3-deoxy-beta-D-allofuranosyl)-5- cyanopyrrolo[2,3-d]pyrimidine (28) were synthesized by sequentially coupling silylated 4-amino-6-bromo-5- cyanopyrrolo[2,3-d]pyrimidine with the corresponding protected sugars 9 and 17, followed by deblocking and catalytic hydrogenation. Conversion of the 5-nitrile in 22 and 28 into a carboxamide gave the corresponding sangivamycin derivatives 23 and 29. Whereas 5'-aminomethyl nucleosides 22 and 23 inhibited the growth of four different human tumor cell lines at microM concentrations, the 3'-aminomethyl analogs 28 and 29 were much less active against these cells.     

The molecular genetics of endocrine tumours

The molecular genetics of endocrine tumours is an area of great interest, due to the heterogeneity of endocrine tumour types, the association of hormone over-production in some cases, and the wide variation in tumour behaviour. Genes implicated fall into functional categories such as oncogenes, in which mutations tend to cause activation, and tumour suppressor genes, in which mutations lead to loss of function. Oncogenes include the receptor tyrosine kinases such as RET, signal transduction proteins and other molecules such as cell cycle regulators and nuclear proteins. Tumour suppressor genes include cell cycle regulators such as p53 and other molecules such as the MEN 1 gene. Loss of heterozygosity studies help in the initial localisation of the latter. Endocrine tumours, as with other tumours, develop as a result of a combination of genetic events, and in the paediatric age group they often occur in the setting of familial cancer syndromes. In this review we analyse the main genetic lesions which have been described in endocrine tumours. There has been an explosion of knowledge in the last 5 years including the identification of the causative genes for MEN 2 and most recently for MEN 1. Characterisation of such genes also aids in the study of somatic mutations in sporadic versions of the same tumour types as occur in the familial syndromes. Identification of a genetic predisposition to a certain tumour has management implications that are still to be clarified in most cases, although in the case of MEN 2 the guidelines for prophylactic thyroidectomy are generally well accepted.     

A role for interleukin-6 in host defense against murine Chlamydia trachomatis infection

Interleukin-6-deficient (IL-6(-/-)) knockout mice had significantly increased Chlamydia trachomatis levels in lung tissue and increased mortality compared to B6129F2/J controls early after intranasal infection. Gamma interferon production and chlamydia-specific antibody levels were consistent with a decreased but reversible Th1-like response in IL-6(-/-) mice. IL-6 is needed for an optimal early host response to this infection.     

Pollutant transport during a regional O3-episode in the mid-Atlantic states

Ozone (O3) concentrations in the Baltimore-Washington (B-W) metropolitan area frequently exceed the National Ambient Air Quality Standard (NAAQS) in the summer months. The most extreme O3 events occur in multi-day high O3 episodes. These events can be regional in scale, with O3 concentrations exceeding the NAAQS at numerous locations along the eastern U.S. seaboard, and are typically associated with slow-moving or stagnant high pressure systems. In the B-W region, the most extreme events typically occur with surface high pressure overhead or just west of the region and an upper air high-pressure area (ridge) to the west or northwest. Besides providing conditions conductive to local O3 production (subsidence and strong low-level inversions, weak horizontal winds, little cloud cover), this weather pattern may also result in transport of O3 and its precursors from heavily industrialized areas west and north of the B-W region. In this paper, observations and back trajectories made during the severe regional O3 event of July 12-15, 1995, are used to confirm the hypothesis that significant regional-scale transport of O3 and its precursors occur during extreme O3 events of the standard type in the B-W area.