A prospective study of N-acetyltransferase genotype, red meat intake, and risk of colorectal cancer

Carcinogenic heterocyclic amines are activated by N-acetyltransferase (NAT) enzymes, encoded by NAT1 and NAT2, to genotoxic compounds that can form DNA adducts in the colon epithelium. We have examined the relation of polymorphisms in the genes coding for both enzymes to risk of colorectal cancer and the gene-environment interaction with red meat intake among participants in the prospective Physicians' Health Study. Baseline blood samples from 212 men subsequently diagnosed with colorectal cancer during 13 years of follow-up were genotyped, along with 221 controls. NAT genotypes were analyzed by a PCR-restriction fragment length polymorphism method. Effect modification of the relation of red meat intake and risk of colorectal cancer by NAT genotype was assessed using conditional logistic regression. There was no overall independent association of NAT acetylation genotypes and colorectal cancer risk. The relative risks for the rapid acetylation genotype were 0.93 [95% confidence interval (CI), 0.61-1.42] for NAT1, 0.80 (95% CI, 0.53-1.19) for NAT2, and 0.81 (95% CI, 0.52-1.27) for NAT1/NAT2 combined. We observed a stronger association of red meat intake with cancer risk among NAT rapid acetylators, especially among men 60 years old or older. Among those men who were rapid acetylators for both NAT1 and NAT2, consumption of >1 serving of red meat per day was associated with a relative risk of 5.82 (95% CI, 1.11-30.6) compared with consumption of < or = 0.5 serving per day (P, trend = 0.02). These prospective data, which need to be confirmed in other studies, suggest that polymorphisms in the NAT genes confer differential susceptibility to the effect of red meat consumption on colorectal cancer risk.     

Sequence motifs in adenoviral DNA block immune activation by stimulatory CpG motifs

Unmethylated CpG dinucleotides in particular base contexts (CpG-S motifs) are relatively common in bacterial DNA but are rare in vertebrate DNA. B cells and monocytes have the ability to detect such CpG-S motifs that trigger innate immune defenses with production of Th1-like cytokines. Despite comparable levels of unmethylated CpG dinucleotides, DNA from serotype 12 adenovirus is immune-stimulatory, but serotype 2 is nonstimulatory and can even inhibit activation by bacterial DNA. In type 12 genomes, the distribution of CpG-flanking bases is similar to that predicted by chance. However, in type 2 adenoviral DNA the immune stimulatory CpG-S motifs are outnumbered by a 15- to 30-fold excess of CpG dinucleotides in clusters of direct repeats or with a C on the 5' side or a G on the 3' side. Synthetic oligodeoxynucleotides containing these putative neutralizing (CpG-N) motifs block immune activation by CpG-S motifs in vitro and in vivo. Eliminating 52 of the 134 CpG-N motifs present in a DNA vaccine markedly enhanced its Th1-like function in vivo, which was increased further by the addition of CpG-S motifs. Thus, depending on the CpG motif, prokaryotic DNA can be either immune-stimulatory or neutralizing. These results have important implications for understanding microbial pathogenesis and molecular evolution and for the clinical development of DNA vaccines and gene therapy vectors.     

Varicocele scintigraphy: a simplified screening method for the detection of spermatic vein reflux

Forty-three men underwent varicocele scintigraphy to exclude underlying varicocele as a possible cause of decreased semen quality. The total acquisition time for each study amounted to as little as 200 seconds. In four cases retrograde blood flow was seen in the left internal spermatic vein, with subsequent clear visualization of the pampiniform plexus. In three of four of these patients, pregnancy ensued after therapeutic intervention. Seven patients showed only increased scrotal activity locally, in the absence of retrograde blood flow. The remaining 32 patients showed a normal blood flow pattern. The existence of spermatic vein reflux in varicocele-related infertility is thought to be a major factor in proper patient selection for therapeutic ligation or embolization of the internal spermatic vein. It is suggested that this simplified scintigraphic method may be useful in the detection of retrograde blood flow in patients with varicocele, especially in small or subclinical varicocele.     

Puerarin inhibits tetrodotoxin-resistant sodium current in rat dorsal root ganglion neurons

The effect of 7-nitroindazole (7-NI), an inhibitor of neuronal nitric oxide synthase (nNOS) on the dimethylphenylpiperazinium(DMPP)-evoked release of [3H]noradrenaline ([3H]NA) from rat hippocampal slices was studied. The effect of DMPP (20 microM) to increase the basal release of [3H]NA was significantly potentiated by 7-NI (40 microM). In our previous study we showed that the response to DMPP has two components, a nicotinic receptor-mediated, [Ca2+]-dependent exocytosis followed by a [Ca2+]-independent, uptake blocker-sensitive carrier-mediated release. To clarify which part of the response was affected by the inhibition of nNOS, we investigated the effect of 7-NI on the nicotine-evoked NA release (nicotine has only receptor-mediated effect) and on the DMPP-evoked NA release in Ca(2+)-free medium where the receptor-mediated component is abolished. Nicotine (100 microM) significantly increased the basal release of [3H]NA but this release was not affected, whereas in Ca(2+)-free medium the response to DMPP (20 microM) was still potentiated by 7-NI (40 microM). In the presence of the NA uptake blocker desipramine (10 microM) DMPP (20 microM) was unable to provoke NA release independently from the presence or absence of 7-NI (40 microM). Our data show that 7-NI influences the carrier-mediated component of DMPP-evoked [3H]NA release, which indicates that nitric oxide produced by nNOS may play a role in the regulation of the NA uptake carrier.     

Isolation and characterization of tilapia (Oreochromis mossambicus) insulin-like growth factors gene and proximal promoter region

It has been shown that both multidrug resistance-associated protein (MRP1) and canalicular multispecific organic anion transporter (cMOAT/MRP2) have the ability to extrude glutathione conjugates (GS-X pump activity)from cells. Therefore, they play an important role in the detoxification of xenobiotics. Using mrp1-knockout mice, it has recently been shown that MRP1/mrp1 has an important role in the export of leukotriene C4 (LTC4), a mediator of inflammation, and in protecting the body from a number of toxins, including several antitumor drugs. A comparison of the transport properties across the bile canalicular membrane in normal and mutant rats, whose cMOAT function is hereditarily defective, has shown that the physiologic role of cMOAT is to excrete LTC4, bilirubin glucuronides, 171-estradiol-170-D-glucuronide, and reduced folates. In the present review article, we summarize the substrate specificity and mechanism for the transport of these GS-X pumps, focusing on the pharmacologic and physiologic aspects. The transport activity mediated by cMOAT is also discussed in terms of a comparison between membrane vesicles from hepatocytes and cMOAT-transfected cells, and we also briefly examine the possible role of MRPI and cMOAT in the extrusion of reduced glutathione.     

Adverse effects of calcium binding contrast agents in diagnostic cardiac angiography. A comparison between formulations with and without calcium binding additives

RATIONALE AND OBJECTIVES: The authors compared complications and hemodynamic and electrophysiologic effects of two formulations of diatrizoate, one with additives that bind calcium and one without, in diagnostic cardiac angiography. METHODS: Two hundred twenty-three consecutive low-risk patients alternately received Hypaque 76 (group 1, little calcium binding effect), and MD 76 (group 2, significant calcium binding). Electrocardiographic and hemodynamic changes related to coronary angiography and left ventriculography were measured, and complications requiring treatment were recorded. RESULTS: There were more complications in patients in group 2 than in group 1 (18 versus 8, P = 0.04). Arterial pressure fell more, the QT interval increased more, and the heart rate fell more in group 2 after coronary angiography. CONCLUSIONS: Formulations of diatrizoate that minimize calcium binding are advocated for cardiac angiography when using high osmolality contrast media. The more detrimental effects that calcium binding has on myocardial function and cardiac conduction may lead to the higher incidence of complications.     

Vitellin processing and protein synthesis during cricket embryogenesis

At the start of insect embryogenesis most of the protein mass of the egg cytoplasm exists as vitellin (Vt) obtained endocytically during vitellogenesis. Of the new embryo polypeptides (EP) appearing in the egg during embryogenesis, many are synthesized de novo, while, in some species, others derive from developmentally programmed partial proteolysis of Vt. Earlier we showed that by the end of vitellogenesis the two native Vts in Acheta domesticus exist in opposing gradients along the longitudinal axis of the egg. Here we hypothesize that this ooplasmic Vt distribution presents a milieu for Vt processing out of which region-specific regulatory molecules could arise. The metabolic origin and stage-specific patterns of seven predominant EPs (EP 1-7) identified by SDS-PAGE were examined and the results correlated with developmental morphology during the 14 days of embryogenesis. Based on antibody reactivity, peptide mapping and in vitro radiolabeling, we determined that EPs 1-3, 6 and 7 are Vt-derived, while EPs 4 and 5 are produced de novo by the embryo. The five Vt-derived EPs appear during the first 24 h of embryogenesis when migrating cleavage nuclei and associated cytoplasm form the cellular blastoderm, and levels of EPs 4 and 5 increase during days 4-6 of embryogenesis when katatrepsis and yolk mass contraction occur. Positive periodic acid-Schiff staining indicated that EPs 1-3 and their Vt-precursor polypeptides are glycoproteins. This work shows that developmental stage-specific Vt processing occurs during A. domesticus embryogenesis and points next to investigation of the functional significance of Vt cleavage products during development.