Influence of pollution on parasites of aquatic animals

We have tried to draw attention to an increasing body of evidence (from several publications) that parasites of fish might be useful indicators of pollution. Several types of pollutants, including domestic sewage, pesticides, polychlorinated biphenyls, heavy metals, pulp and paper effluents, petroleum aromatic hydrocarbons, acid rain, and others, are known to affect aquatic animals. Many of the latter are parasitized and, under natural environmental conditions, most fish parasites are believed to cause little or no harm. However, chronic exposure to pollutants over a period of time causes biochemical, physiological and behavioural host changes that ultimately can influence the prevalence and intensity of parasitism. Some of these changes include host nutrition, growth and reproduction. Macroscopic lesions might not always be apparent, but subtle disorders in several specific tissues and organs might occur. Pollutants might promote increased parasitism in aquatic animals, especially fish, by impairing the host's immune response or favouring the survival and reproduction of the intermediate hosts. Alternatively, decreased parasitism might ensue through toxicity of the pollutant to free-living stages and intermediate hosts or by alteration of the host's physiology. Experimental studies indicate that the numbers of ectoparasites such as trichodinid ciliates and monogeneans increase significantly on the gills following exposure to a pollutant, and this is supported by field data on other ciliates and monogeneans where evidence of pollution has been clearly demonstrated. There is also evidence that endoparasitic protozoons, such as myxozoons, microsporans and haematozoons, all of which are capable of proliferating in their hosts, increase substantially in prevalence and intensity when interacting with pollutants. The period of patency might also be prolonged in haematozoan infections. Most reports of pollution effects on endoparasites suggest increased parasitism in fish hosts. This also applies to fish living in areas which receive thermal effluents. Parasites might in turn enhance their hosts' susceptibility to pollutants, and information in support of this view is accumulating. Finally, immunosuppression represents one of the underlying mechanisms influencing increased parasitism. Thus, while published information suggests more than a casual connection between fish parasites and pollution, further research is needed to establish the cause-and-effect relationship and at the same time take cognizance of histopathological effects of the toxic agents and their concentrations in water. Areas for future research are recommended.

Free-radical-generated F2-isoprostane stimulates cell proliferation and endothelin-1 expression on endothelial cells

BACKGROUND

Free-radical-generated F2-isoprostane stimulates DNA synthesis and endothelin-1 (ET-1) expression on endothelial cells. 8-Iso-prostaglandin F2alpha (8-iso-PGF2alpha) is a member of the recently discovered family of prostanoids, the F2-isoprostanes, produced in vivo by cyclooxygenase-independent, free-radical-catalyzed lipid peroxidation. The goal of our study is to establish the effect of isoprostane on ET-1 production by endothelial cells, as well to determine the receptors responsible for these effects.

METHODS

The proliferative effect of isoprostanes was measured as an increase of viable cell number and [3H]-thymidine uptake. ET-1 gene expression and protein synthesis were determined by Northern blot and radioimmunoassay, respectively. We also determined inositol 1,4,5-trisphosphate synthesis. Thromboxane A2 (TXA2) receptor antagonist SQ29,548 was used to establish the role of TXA2 receptor in isoprostane effect, as well as to determine the type of receptors involved in these effects.

RESULTS

Our results show that physiological concentrations of 8-iso-PGF2alpha stimulated cell proliferation, DNA synthesis, and ET-1 mRNA and protein expression in bovine aortic endothelial cells (BAECs). The proliferative effect was partially abolished by treatment with anti-endothelin antibody. 8-Iso-PGF2alpha also increased inositol 1, 4,5-trisphosphate formation in these cells. These effects were partially inhibited by SQ29,548. In competitive binding assays, two binding sites were recognized on BAECs with dissociation constants (Kd) and binding site densities at equilibrium similar to those previously described in smooth muscle cells and likely represent [3H]-8-iso-PGF2alpha binding to its own receptor (high-affinity binding site) and cross-recognition of the TXA2 receptor (low-affinity binding site).

CONCLUSION

These studies expand the potential scope of the pathophysiologic significance of F2-isoprostanes, released during oxidant injury, to include alteration of endothelial cell biology.

First trimester prenatal treatment and molecular genetic diagnosis of congenital adrenal hyperplasia (21-hydroxylase deficiency)

Prenatal treatment of pregnancies at risk for congenital adrenal hyperplasia due to 21-hydroxylase deficiency was carried out in conjunction with chorionic villus sampling (CVS) in the first trimester for analysis of restriction fragment length polymorphisms. Fourteen families of a total of 49 families at risk for this disease elected to undergo both prenatal treatment and diagnosis via CVS. Dexamethasone administration to the pregnant woman was initiated at a mean gestational age of 7 weeks (range, 4-10 weeks) before testing to determine whether the fetus was affected with 21-hydroxylase deficiency, and CVS was performed at a gestational age of 8-10 weeks. Two affected female fetuses were identified by molecular genetic techniques among this group; neonatal physical examination demonstrated amelioration of the degree of genital ambiguity compared with both nonprenatally treated older sisters with 21-hydroxylase deficiency. The duration of unnecessary prenatal dexamethasone treatment for unaffected or male fetuses was substantially reduced in the CVS group compared with that in a cohort of 8 prenatally treated pregnancies in which amniocentesis was performed in the early second trimester. There were no major morbidities observed in the treated pregnancies. Postnatal confirmation of CVS diagnosis was obtained in all cases in which DNA from an affected sibling was available for comparative analysis with the DNA from chorionic villus tissue. We conclude based on these data that the benefit/risk ratio is favorable for prenatal administration of dexamethasone in pregnancies at risk for 21-hydroxylase deficiency. Treatment should be initiated during the first trimester in conjunction with diagnosis by CVS/molecular genetic techniques. Long term postnatal surveillance is recommended for all offspring of dexamethasone-treated pregnancies.

Behçet's syndrome: a report of 41 patients with emphasis on neurological manifestations

Forty one patients with the clinical diagnosis of Behçet's syndrome from two teaching hospitals in Kuwait were studied. There were 34 male and seven female patients. Age at presentation ranged from 14 to 48 years. Neurological manifestations were present in 24 patients. Eleven patients showed evidence of increased intracranial pressure, and 10 of these had radiologically confirmed dural sinus thrombosis. Five patients presented with a meningoencephalitic or meningomyelitic picture, three with a stroke-like picture, and three with primarily brain stem signs. One patient developed trigeminal neuritis, and five patients exhibited (along with other features) variable degrees of psychological manifestations. All patients with neurological involvement were treated with steroids, and some also had courses of other immunosuppressant drugs and colchicine. The disease took a relatively benign course, except those patients with meningoencephalitic and meningomyelitic presentation, one of whom died from the disease. Those treated early had a better prognosis. The incidence of dural sinus thrombosis in this series of patients is unusually high. In most patients, the course of the disease was more favourable than reported in the literature. This may be attributed to early and aggressive treatment.

The suppression of iron release from activated myoglobin by physiological electron donors and by desferrioxamine

Interactions between ferrimyoglobin and hydrogen peroxide have been postulated to lead to the formation of activated ferryl myoglobin. In such systems hydroxyl radical formation has also been demonstrated by its ability to degrade deoxyribose subsequent to the release of iron from the porphyrin ring of the myoglobin. We have investigated the potential for ferrylmyoglobin formation and for iron release from ferrylmyoglobin exposed to hydrogen peroxide; the modulation of the stability of the haem group by membranes and in the presence of desferrioxamine and ascorbate have also been assessed. The results show that iron release from ferrimyoglobin activated by hydrogen peroxide is suppressed in the presence of membranes, apparently by the reduction of the ferryl myoglobin species, and lipid peroxidation occurs. In the presence of desferrioxamine, formation of the ferrylmyoglobin species is suppressed by the electron donating properties of the trihydroxamate moiety, which also functions as a chain-breaking antioxidant when added to peroxidising membranes. The physiological antioxidant ascorbate not only suppresses the formation of the ferryl myoglobin species under the conditions described here, but also reduces the myoglobin iron to the iron II state.

Retroviral nucleocapsid proteins possess potent nucleic acid strand renaturation activity

The nucleocapsid protein (NC) is the major genomic RNA binding protein that plays integral roles in the structure and replication of all animal retroviruses. In this report, select biochemical properties of recombinant Mason-Pfizer monkey virus (MPMV) and HIV-1 NCs are compared. Evidence is presented that two types of saturated Zn2 NC-polynucleotide complexes can be formed under conditions of low [NaCl] that differ in apparent site-size (n = 8 vs. n = 14). The formation of one or the other complex appears dependent on the molar ratio of NC to RNA nucleotide with the putative low site-size mode apparently predominating under conditions of protein excess. Both MPMV and HIV-1 NCs kinetically facilitate the renaturation of two complementary DNA strands, suggesting that this is a general property of retroviral NCs. NC proteins increase the second-order rate constant for renaturation of a 149-bp DNA fragment by more than four orders of magnitude over that obtained in the absence of protein at 37 degrees C. The protein-assisted rate is 100-200-fold faster than that obtained at 68 degrees C, 1 M NaCl, solution conditions considered to be optimal for strand renaturation. Provided that sufficient NC is present to coat all strands, the presence of 400-1,000-fold excess nonhomologous DNA does not greatly affect the reaction rate. The HIV-1 NC-mediated renaturation reaction functions stoichiometrically, requiring a saturated strand of DNA nucleotide:NC ratio of about 7-8, rather than 14. Under conditions of less protein, the rate acceleration is not realized. The finding of significant nucleic acid strand renaturation activity may have important implications for various events of reverse transcription particularly in initiation and cDNA strand transfer.

Contamination and ecological risk assessment of trace elements in sediments of the rivers of Sundarban mangrove forest, Bangladesh

In this study, total concentrations of 16 trace elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Sb, Hg, Pb, Th and U) in sediments of the rivers of the Sundarban mangrove forest, after the catastrophic oil spill accident in the Sela river of Sundarban, were determined. The overall mean concentrations of V, Cr, Fe and Cd in surface sediments of the Sundarban are remarkably higher than available literature data of those elements. Trace element contamination assessment, using different environmental contamination indices, reveals that As, Sb, Th and U are low to moderately contaminated while Cd is moderately to severely contaminated in the sediments of this area. The multivariate statistical analyses were applied to reveal the origin and behavior of the elements during their transport in the mangrove ecosystem. High Cr, Ni, Cu and As concentrations suggest the risk of potentially adverse biological effects in the ecosystem.

Increasing prevalence and incidence rates of multiple sclerosis in Kuwait

Background:

Kuwait was considered as low to intermediate risk area for MS.

Objectives:

To determine the prevalence and incidence rates of MS among Kuwaiti nationals based on 2011 population census.

Methods:

This cross-sectional study was conducted between October 2010 and April 2013 using the newly developed national MS registry in Kuwait. Patients with a diagnosis of MS according to 2010 revised McDonald criteria were identified. The crude, age- and sex-specific prevalence and incidence rates among Kuwaiti patients were calculated.

Results:

1176 MS patients were identified of which 927 (78.8%) were Kuwaitis and 249 (21.2%) were expatriates. Among Kuwaiti patients, female to male ratio was 1.8:1 with a mean age of 35.40 ± 10.99 years. The prevalence rate of MS was 85.05 per 100,000 persons (95% CI: 82.80 – 87.04). There was a peak in prevalence among patients aged 30–39 years. The incidence of MS was 6.88 per 100,000 persons (95% CI 5.52–8.55). Between 2003 and 2011, the incidence increased 3.22 and 2.54 times in women and men respectively.

Conclusion:

Kuwait is considered a high-risk area for MS. The significant increase in prevalence and incidence rates may represent a true increase despite the improvement in case ascertainment and case definition.

Cerebral involvement in benign tertian malaria

Although Plasmodium vivax usually causes benign uncomplicated malaria, it can occasionally result in severe disease with life-threatening, end-organ involvement generally seen with falciparum malaria. We report a case of cerebral malaria caused by P. vivax and review the literature on this subject.

A new Alamar Blue viability assay to rapidly quantify oligodendrocyte death

We developed a rapid fluorometric viability assay for primary cultures of OL precursors (preOLs) or mature OLs that utilized the oxidation/reduction indicator dye Alamar Blue (AB). PreOLs had a lower rate of AB reduction than did mature OLs (0.02 +/- 0.01 units/min per cell versus 0.07 +/- 0.01). The assay was tested under two conditions toxic to preOLs: oxidative stress induced by glutathione depletion or kainate excitotoxicity. When glutathione was depleted by a 24-h exposure to cystine-depleted medium, the EC50 values for the dependence upon cystine for survival did not differ significantly when determined by AB reduction (2 +/- 2 microM), by the trypan blue exclusion method (3 +/- 3 microM) or by MTT histochemistry (1 +/- 0.4 microM). Quantification of preOL viability with AB was unaffected by the presence of free radical scavengers (alpha-tocopherol or idebenone) or the antioxidant enzymes Cu,Zn-superoxide dismutase and catalase. There was no difference in preOL viability as determined by AB or MTT after a 24-h exposure to kainate at concentrations up to 1 mM. AB offers a rapid objective measure of OL viability in primary culture and is a valid means to quantify OL death.

Impact of changes in antibiotic policy on Clostridium difficile-associated diarrhoea (CDAD) over a five-year period in a district general hospital

The impact of changes in antibiotic policy on Clostridium difficile-associated diarrhoea (CDAD), over a five-year period between 1995 and 2000, were studied in the Preston Acute Hospitals Trust. In 1996 the policy was changed in the Preston Acute Hospitals Trust from cefotaxime to ceftriaxone for initial treatment of severe sepsis or pneumonia in medical patients. Over the next nine months the average number of patients with C. difficile toxin-positive stools per quarter increased from 16 to 39. The predicted use of ceftriaxone exceeded by 65% an estimate based on prior use of cefotaxime. A policy of restricted duration of ceftriaxone was introduced, and although this reduced usage by over 50%, CDAD continued at an average of 9.2 cases per month, despite withdrawal of oral cephalosporins in December 1998. In August 1999 levofloxacin was substituted for ceftriaxone in the policy. The incidence of CDAD fell progressively to five cases per month by 2000. It would appear that a short (typically three dose) course of third-generation cephalosporin poses a similar risk for CDAD as a more prolonged course. The six-month delay in the decline of CDAD after virtual withdrawal of cephalosporins may reflect a slowly diminishing environmental reservoir.

Differential S-nitrosylation of proteins in Alzheimer's disease

Numerous studies have provided evidence regarding the involvement of protein S-nitrosylation in the progression of Alzheimer's disease (AD) pathology and its implication in the formation and accumulation of misfolded protein aggregates. The identification of S-nitrosylated proteins can be a major step toward the understanding of mechanisms leading to neuronal degeneration. The present study targeted S-nitrosylated proteins in AD hippocampus, substantia nigra and cortex using the following work-flow that combines S-nitrosothiol-specific antibody detection, classical biotin switch method labeled with fluorescence dye followed by electrospray ionization quadrupole time of flight tandem MS (ESI-QTOF MS/MS) identification. Endogenous nitrosocysteines were identified in 45 proteins, mainly involved in metabolism, signaling pathways, apoptosis and redox regulation as assigned by REACTOME and KEGG pathway database analysis. Superoxide dismutase (SOD2) [Mn], fructose-bisphosphate aldolase C (ALDOC) and voltage-dependent anion-selective channel protein 2 (VDAC2) showed differential S-nitrosylation signal, not previously reported in AD regions. Extensive neuronal atrophy with increased protein S-nitrosylation in AD regions is also evident from immunofluorescence studies using S-nitrosocysteine antibody. A number of plausible cysteine modification sites were predicted via Group-based Prediction System-S-nitrosothiols (GPS-SNO) 1.0 while STRING 8.3 analysis revealed functional annotations in the modified proteins. The findings are helpful in characterization of functional abnormalities and may facilitate the understanding of molecular mechanisms and biological function of S-nitrosylation in AD pathology.

Potential of graphene-based materials to combat COVID-19: properties, perspectives, and prospects

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a new virus in the coronavirus family that causes coronavirus disease (COVID-19), emerges as a big threat to the human race. To date, there is no medicine and vaccine available for COVID-19 treatment. While the development of medicines and vaccines are essentially and urgently required, what is also extremely important is the repurposing of smart materials to design effective systems for combating COVID-19. Graphene and graphene-related materials (GRMs) exhibit extraordinary physicochemical, electrical, optical, antiviral, antimicrobial, and other fascinating properties that warrant them as potential candidates for designing and development of high-performance components and devices required for COVID-19 pandemic and other futuristic calamities. In this article, we discuss the potential of graphene and GRMs for healthcare applications and how they may contribute to fighting against COVID-19.

Binding sites in mammalian genes and viral gene regulatory regions recognized by methylated DNA-binding protein

Methylated DNA-binding protein (MDBP), a ubiquitous mammalian protein, recognizes a variety of related DNA sequences. Some of these sequences require methylation of their CpG dinucleotides for binding and others do not. We report that MDBP binds, in a DNA methylation-independent fashion, to two sites in the mouse polyomavirus enhancer, one in the enhancer of the human hepatitis B virus, and to one in the long terminal repeat of equine infectious anemia proviral DNA. We have also found a number of MDBP sites in human and rodent DNAs which bind much better to MDBP when they are methylated at CpG dinucleotides within the recognition site. These include sites at the beginning of the human genes for hypoxanthine phosphoribosyl transferase, HLA-A2, -A3, and -A25 antigens, and alpha-galactosidase A. In the case of methylation-responsive MDBP sites, changes in their methylation status during differentiation or DNA replication could help drive development by modulating transcription.

First-in-human study of pbi-05204, an oleander-derived inhibitor of akt, fgf-2, nf-κΒ and p70s6k, in patients with advanced solid tumors

BACKGROUND

PBI-05204, a Nerium oleander extract (NOE) containing the cardiac glycoside oleandrin, inhibits the α-3 subunit of Na-K ATPase, as well as FGF-2 export, Akt and p70S6K, hence attenuating mTOR activity. This first-in-human study determined the safety, pharmacokinetics (PK) and pharmacodynamics (PD) of PBI-05204 in patients with advanced cancer. Methods Forty-six patients received PBI-05204 by mouth for 21 of 28 days (3 + 3 trial design). Dose was escalated 100% using an accelerated titration design until grade 2 toxicity was observed. Plasma PK and mTOR effector (p70S6K and pS6) protein expressions were evaluated. Results Dose-limiting toxicities (grade 3 proteinuria, fatigue) were observed at dose level 8 (0.3383 mg/kg/day). Common possible drug-related adverse were fatigue (26 patients, 56.5%), nausea (19 patients, 41.3%) and diarrhea (15 patients, 32.6 %). Electrocardiogram monitoring revealed grade 1 atrioventricular block (N = 10 patients) and grade 2 supraventricular tachycardia (N = 1). The MTD was DL7 (0.2255 mg/kg) where no toxicity of grade ≥ 3 was observed in seven patients treated. Seven patients (15%) had stable disease > 4 months. Mean peak oleandrin concentrations up to 2 ng/mL were achieved, with area under the curves 6.6 to 25.5 μg/L*hr and a half-life range of 5-13 h. There was an average 10% and 35% reduction in the phosphorylation of Akt and pS6 in PBMC samples in 36 and 32 patients, respectively, tested between predose and 21 days of treatment. Conclusions PBI-05204 was well tolerated in heavily pretreated patients with advanced solid tumors. The recommended Phase II dose is 0.2255 mg/kg/day.

Sniffing a human sex-steroid derived compound affects mood and autonomic arousal in a dose-dependent manner

The effects of sniffing different concentrations of the human sex-steroid derived compound 4,16-androstadien-3-one (AND) on autonomic nervous system function and mood were measured in 60 subjects. The effects were sex-specific and concentration-dependent. Only high concentrations of AND (0.00625 M) increased positive mood (p < 0.03) and decreased negative mood (p < 0.05) in women compared to men, and had sympathetic-like effects in women (p < 0.003), and parasympathetic-like effects in men (p < 0.05). These findings further implicate AND in chemical communication between humans, but pose questions as to the path by which AND is transduced, whether through chemical sensing or transdermal diffusion.

Dissociated representations of irritation and valence in human primary olfactory cortex

Irritation and negative valence are closely associated in perception. However, these perceptual aspects can be dissociated in olfaction where irritation can accompany both pleasant and unpleasant odorants. Whereas the sensation of odor reflects transduction at olfactory receptors, irritation reflects concurrent transduction of the odorant at trigeminal receptors. Thus a stimulus can be either a pure olfactant activating the olfactory receptors only or a bimodal odorant activating both types of receptors. Using event-related functional magnetic resonance imaging and a 2 x 2 experimental design contrasting odorant valence (pleasant/unpleasant) and odorant type (pure olfactant/bimodal) we found activity in piriform cortex to be associated with valence, and not type, of odors. In contrast, activity in the olfactory tubercle was associated with type, and not valence, of odors. Importantly, this was found when perceived intensity was held equal across odorants. These findings suggest that dissociable neural substrates subserve the encoding of irritation and valence in olfaction.

Dynamic 4D MRI for Characterization of Parathyroid Adenomas: Multiparametric Analysis

BACKGROUND AND PURPOSE

The hypervascular nature of parathyroid adenomas can be explored by proper dynamic imaging to narrow the target lesions for surgical exploration. The purpose of this study was to establish MR perfusion characteristics of parathyroid adenomas to differentiate them from their mimics, such as subjacent thyroid tissue and cervical lymph nodes.

MATERIALS AND METHODS

Preoperative high-spatial and -temporal resolution dynamic 4D contrast-enhanced MR imaging in 30 patients with surgically proved parathyroid adenomas was evaluated retrospectively. Using coregistered images, we placed ROIs over the parathyroid adenoma, thyroid gland, and a cervical lymph node (jugulodigastric) to obtain peak enhancement, time-to-peak, wash-in, and washout in each patient. Data were analyzed by logistic regression and analysis of variance. Receiver operating characteristic analysis was performed to determine the optimal parameters for determination of parathyroid adenomas versus thyroid tissue and cervical lymph nodes.

RESULTS

Parathyroid adenomas showed significantly (P < .05) faster time-to-peak, higher wash-in, and higher washout compared with cervical lymph nodes and significantly (P < .05) higher peak enhancement, faster time-to-peak, higher wash-in, and higher washout compared with thyroid tissue. Logistic regression analysis indicated significant contribution from time-to-peak (P = .02), wash-in (P = .03), and washout (P = .008) for differentiation of parathyroid adenomas from thyroid and cervical lymph nodes. Using receiver operating characteristic analysis, we obtained the best diagnostic accuracy from a combination of time-to-peak/wash-in/washout in the differentiation of parathyroid adenomas versus lymph nodes (area under the curve, 0.96; sensitivity/specificity, 88%/90%) and in distinguishing parathyroid adenomas versus thyroid tissue (area under the curve, 0.96; sensitivity/specificity, 91%/95%).

CONCLUSIONS

Dynamic 4D contrast-enhanced MR imaging can be used to exploit the hypervascular nature of parathyroid adenomas. Multiparametric MR perfusion can distinguish parathyroid adenomas from subjacent thyroid tissue or lymph nodes with diagnostic accuracies of 96%.

Latropathic injuries of peripheral nerves

This is a retrospective study of 612 cases of iatropathic injury to peripheral nerves seen in one tertiary referral unit between 1991 and 1998. A total of 291 patients was subsequently operated on to explore the nerve lesion. The most common presenting symptom was pain, which often masked underlying loss of function. The delay in diagnosis was up to 40 months. The findings at operation were analysed according to the type of nerve damaged, the nature of the injury and the referring specialty. Some of the more common causal operations and procedures are discussed. Preventive measures are listed, and early diagnosis and treatment are recommended.

Methylated DNA-binding protein from human placenta recognizes specific methylated sites on several prokaryotic DNAs

Methylated DNA-binding protein (MDBP) from human placenta recognizes specific DNA sequences containing 5-methylcytosine (m5C) residues. Comparisons of binding of various prokaryotic DNAs to MDBP indicate that m5CpG is present in the recognition sites for this protein but is only part of the recognition sequence. Specific binding to MDBP was observed for bacteriophage XP12 DNA, which naturally contains approximately 1/3 of its residues as m5C, and for Micrococcus luteus DNA, M13mp8 replicative form (RF) DNA, and pBR322 when these three DNAs were methylated at CpG sites by human DNA methyltransferase. Five DNA regions binding to MDBP have been localized by DNase I footprinting or restriction mapping in methylated pBR322 and M13mp8 RF DNAs. A comparison of their sequences reveals a common 5'-m5CGRm5CG-3' element or closely related sequence in which one of the m5C residues may be replaced by a T. In addition to this motif, one upstream and one downstream m5CpG as well as other common residues over an approximately 20-bp long region may be recognized by MDBP.

Identifying and understanding the role of pulmonary vein activity in atrial fibrillation

The perception of atrial fibrillation development has changed drastically over the last decade. The pulmonary veins have been targeted as the source of arrhythmogenic activity involved in the initiation of atrial fibrillation. This activity appears to be localized in the myocardial sleeves of the vessels. Extensive study of cells within this tissue has helped create a new model for atrial fibrillation. This review attempts to show how the development, architecture and electrophysiologic properties of the pulmonary veins influence the initiation and perpetuation of atrial fibrillation. It also examines the potential long-term effects of pulmonary vein activity on arrhythmia development.

Simultaneous anterograde fast-slow atrioventricular nodal pathway conduction after procainamide

Three patients with paroxysmal supraventricular tachycardia underwent electrophysiologic studies that included His bundle recordings, incremental atrial and ventricular pacing and extrastimulation before and after intravenous infusion of 500 mg of procainamide. In all three patients the tachycardia was induced during atrial pacing or premature atrial stimulation, or both. Two of the three patients had discontinuous atrioventricular (A-V) nodal curves with induction of a slow-fast tachycardia during failure in anterograde fast pathway conduction and one patient had a smooth A-V nodal curve with induction of a slow-fast tachycardia at critical A-H interval delays. After procainamide: (1) in all three patients atrial pacing induced A-V nodal Wenckebach periodicity (cycle length 300 to 400 ms) resulting in simultaneous anterograde fast and slow pathway conduction (one atrial beat resulting in two QRS complexes) and retrograde fast pathway conduction initiating an echo response or a slow-fast tachycardia, or both; (2) in all three patients there was enhanced conduction and shortening of refractoriness of the anteriograde fast pathway and depressed conduction and lengthening of refractoriness of the retrograde fast pathway; and (3) in two patients there was inability to sustain tachycardia because of selective block within the retrograde fast pathway.

IN CONCLUSION

(1) procainamide altered conduction and refractoriness of the anterograde fast and slow pathways so that simultaneous conduction could occur during atrial pacing, resulting in a double ventricular response and a slow-fast echo or tachycardia, or both; and (2) the differential effects of procainamide on anterograde fast and retrograde fast pathways suggests two functional A-V nodal fast pathways, oine for anterograde and the other for retrograde conduction.