Health implications of high dietary omega-6 polyunsaturated Fatty acids

Omega-6 (n-6) polyunsaturated fatty acids (PUFA) (e.g., arachidonic acid (AA)) and omega-3 (n-3) PUFA (e.g., eicosapentaenoic acid (EPA)) are precursors to potent lipid mediator signalling molecules, termed "eicosanoids," which have important roles in the regulation of inflammation. In general, eicosanoids derived from n-6 PUFA are proinflammatory while eicosanoids derived from n-3 PUFA are anti-inflammatory. Dietary changes over the past few decades in the intake of n-6 and n-3 PUFA show striking increases in the (n-6) to (n-3) ratio (~15 : 1), which are associated with greater metabolism of the n-6 PUFA compared with n-3 PUFA. Coinciding with this increase in the ratio of (n-6) : (n-3) PUFA are increases in chronic inflammatory diseases such as nonalcoholic fatty liver disease (NAFLD), cardiovascular disease, obesity, inflammatory bowel disease (IBD), rheumatoid arthritis, and Alzheimer's disease (AD). By increasing the ratio of (n-3) : (n-6) PUFA in the Western diet, reductions may be achieved in the incidence of these chronic inflammatory diseases.

Early results of laparoscopic biliopancreatic diversion with duodenal switch: a case series of 40 consecutive patients

BACKGROUND

Biliopancreatic diversion with duodenal switch (BPD-DS) is an operation which provides one of the greatest maintained weight losses of any bariatric procedure. We looked at the safety and efficacy of laparoscopic BPD-DS for morbid obesity.

METHODS

A 150-200 ml sleeve gastrectomy was created and anastomosed to the distal 250 cm of divided ileum. The median length of the common channel was 100 cm. All patients were prospectively followed up to 12 months.

RESULTS

40 consecutive patients underwent laparoscopic BPD-DS as a primary procedure for morbid obesity. Median patient body mass index (BMI) was 60 kg/m2 (range 42-85 kg/m2). Mean age was 43 +/- 1 years (+/- SEM), with 12 males and 28 females. One patient was converted to open laparotomy (2.5%). Median operative time was 210 +/- 9 minutes (range 110-360 minutes) with a significant correlation between BMI and operative time (p = 0.04). Median length of stay was 4 days (range 3-210 days). There was one 30-day mortality (2.5%). Major morbidities occurred in 6 patients (15%), including 1 anastomotic leak (2.5%), 1 venous thrombosis (2.5%), 4 staple-line hemorrhages (10%) and 1 subphrenic abscess (2.5%). Median follow-up at 6 months (range 1-12 months) resulted in 46% +/- 2% excess weight loss (EWL) and at 9 months 58% +/- 3% EWL.

CONCLUSION

Laparoscopic BPD-DS is a complex, yet feasible, procedure resulting in effective weight loss with an acceptable morbidity. A BMI >65 was associated with increased morbidity and mortality. A long-term study is needed to confirm efficacy and proper patient selection.

Prevention of premature birth by screening and treatment for common genital tract infections: results of a prospective controlled evaluation

OBJECTIVE

Our purpose was to analyze (1) the effects of prevalent lower reproductive tract infections and (2) the effect of systematic diagnosis and treatment to reduce risks of early pregnancy loss (< 22 weeks), preterm premature rupture of membrances, and overall preterm birth.

STUDY DESIGN

A prospective, controlled treatment trial was conducted on 1260 women. During the first 7 months of the program (observation, phase I), women were examined at initiation of prenatal care for a panel of lower genital tract microorganisms and bacterial vaginosis. Women were followed up with reexaminations at 22 to 29 weeks and after 32 weeks' gestation. The recommended treatments of the Centers for Disease Control (i.e., 300 mg of clindamycin orally twice daily for 7 days for bacterial vaginosis) were used for infected women during the second 8 months of the study (treatment, phase II). Data were analyzed according to intent to treat by means of univariate and multivariate methods.

RESULTS

Overall, presence of bacterial vaginosis (32.5%) at enrollment was associated with pregnancy loss at < 22 weeks' gestation (relative risk 3.1, 95% confidence interval 1.4 to 6.9). Among women in the observation phase bacterial vaginosis was associated with increased risk of both preterm birth (relative risk 1.9, 95% confidence interval 1.2 to 3.0) and preterm premature rupture of membranes (relative risk 3.5, 95% confidence interval 1.4 to 8.9). Within this population (phase I) 21.9% of preterm birth overall (43.8% premature rupture of membranes) is estimated as attributable to bacterial vaginosis. Among women with bacterial vaginosis phase II (treatment) was associated with reduced preterm birth (relative risk 0.5, 95% confidence interval 0.3 to 0.9); there was a similar reduction for women with preterm premature rupture of membranes (relative risk 0.5, 95% confidence interval 0.2 to 1.4). Women with both bacterial vaginosis and trichomoniasis were at highest risk of preterm birth (28%); treatment of both conditions (phase II) reduced preterm birth (17%) but did not eliminate this risk. Earlier patient enrollment and oral antibiotic treatment were associated with reduced preterm birth.

CONCLUSIONS

This prospective, controlled trial confirms that the presence of bacterial vaginosis is associated with increased risks of pregnancy loss at < 22 weeks, preterm premature rupture of membranes, and preterm birth. Orally administered clindamycin treatment is associated with a 50% reduction of bacterial vaginosis-linked preterm birth and preterm premature rupture of membranes. Women at risk for preterm birth or preterm premature rupture of membranes because of bacterial vaginosis or common genital tract infections should be screened, treated, reevaluated for cure, and re-treated if necessary.

Bacterial vaginosis is associated with prematurity and vaginal fluid mucinase and sialidase: results of a controlled trial of topical clindamycin cream

OBJECTIVE

The pathogenesis of preterm birth and other adverse pregnancy outcomes linked with reproductive tract infection remains poorly understood. Mucolytic enzymes, including mucinases and sialidases (neuraminidase), are recognized virulence factors among enteropathogens and bacteria that cause periodontal infection. Perturbation of maternal cervicovaginal mucosa membrane host defenses by such enzyme-producing microorganisms may increase the risk of subclinical intrauterine infection during pregnancy and thus increase risks of preterm birth.

STUDY DESIGN

We prospectively evaluated vaginal fluid mucinase and sialidase and selected cervicovaginal bacteria along with pregnancy outcomes in 271 women. Within this study, women with bacterial vaginosis (16 to 27 week' gestation) were treated with 2% clinadmycin vaginal cream or placebo. Enzyme, microbial findings, treatment effects, and pregnancy outcomes were compared among drug- and placebo-treated women and control women without bacterial vaginosis.

RESULTS

Presence of bacterial vaginosis at intake was associated with increased risk of preterm birth (relative risk 3.3, 95% confidence interval 1.2 to 9.1, p = 0.02), premature rupture of membranes (relative risk 3.8, 95% confidence interval 1.6 to 9.0, p = 0.002), and preterm premature rupture of membranes. Mucinase and sialidase activities were more commonly identified, and they occurred in higher concentrations, if present, in women with bacterial vaginosis (mucinase: 44.3% with bacterial vaginosis vs 27.4% without, p = 0.007; sialidase: 45% with bacterial vaginosis vs 12% without p < 0.001). Sialidase activity was associated with bacterial vaginosis-linked organisms (Gardnerella vaginalis, Mobiluncus spp, and Mycoplasma hominis) and Chlamydia trachomatis and yeast species; mucinase activity was associated only with bacterial vaginosis-linked microorganisms. Clindamycin, 2% cream, was effective treatment for bacterial vaginosis and temporarily reduced mucinase and sialidase activities. Topical treatment of bacterial vaginosis did not reduce risks of perinatal morbidity. Women with persistent or recurrent sialidase 8 weeks after treatment were at increased risk of preterm birth (15.6% vs 7.4%) premature rupture of membranes (30% vs 15%), and low birth weight (20% vs 3%, relative risk 6.8, 95% confidence interval 1.6 to 28.1).

CONCLUSIONS

Persistence of sialidase-producing vaginal microorganisms in numbers sufficient to increase vaginal fluid sialidase activity may be a risk factor for possibly preventable subclinical intrauterine infection and preterm birth. This study confirms and further informs our understanding of the association of bacterial vaginosis and preterm birth; studies to evaluate whether systemic treatment for bacterial vaginosis can effectively reduce vaginal mucolytic enzymes and risks of prematurity and other morbid outcomes are continuing.

Focal atrial fibrillation: experimental evidence for a pathophysiologic role of the autonomic nervous system

INTRODUCTION

Focal paroxysmal atrial fibrillation (AF) was shown recently to originate in the pulmonary veins (PVs) and superior vena cava (SVC). In the present study, we describe an animal model in which local high-frequency electrical stimulation produces focal atrial activation and AF/AT (atrial tachycardia) with electrogram characteristics consistent with clinical reports.

METHODS AND RESULTS

In 21 mongrel dogs, local high-frequency electrical stimulation was performed by delivering trains of electrical stimuli (200 Hz, impulse duration 0.1 msec) to the PVs/SVC during atrial refractoriness. Atrial premature depolarizations (APDs), AT, and AF occurred with increasing high-frequency electrical stimulation voltage. APD/AT/AF originated adjacent to the site of high-frequency electrical stimulation and were inducible in 12 of 12 dogs in the SVC and in 8 of 9 dogs in the left superior PV (left inferior PV: 7/8, right superior PV: 6/8; right inferior PV: 4/8). In the PVs, APDs occurred at 13+/-8 V and AT/AF at 15+/-9 V (P < 0.01; n = 25). In the SVC, APDs were elicited at 19+/-6 V and AT/AF at 26+/-6 V (P < 0.01; n = 12). High-frequency electrical stimulation led to local refractory period shortening in the PVs. The response to high-frequency electrical stimulation was blunted or prevented after beta-receptor blockade and abolished by atropine. In vitro, high-frequency electrical stimulation induced a heterogeneous response, with shortening of the action potential in some cells (from 89+/-35 msec to 60+/-22 msec; P < 0.001; n = 7) but lengthening of the action potential and development of early afterdepolar-izations that triggered APD/AT in other cells. Action potential shortening was abolished by atropine.

CONCLUSION

High-frequency electrical stimulation evokes rapid ectopic beats from the PV/SVC, which show variable degrees of conduction block to the atria and induce AF, resembling findings in patients with focal idiopathic paroxysmal AF. The occurrence of the arrhythmia in this animal model was likely due to alterations in local autonomic tone by high-frequency electrical stimulation. Further research is needed to prove absolutely that the observed effects of high-frequency electrical stimulation were caused by autonomic nerve stimulation.

A review of the literature on the aging adult skull and face: implications for forensic science research and applications

This paper is a summary of findings of adult age-related craniofacial morphological changes. Our aims are two-fold: (1) through a review of the literature we address the factors influencing craniofacial aging, and (2) the general ways in which a head and face age in adulthood. We present findings on environmental and innate influences on face aging, facial soft tissue age changes, and bony changes in the craniofacial and dentoalveolar skeleton. We then briefly address the relevance of this information to forensic science research and applications, such as the development of computer facial age-progression and face recognition technologies, and contributions to forensic sketch artistry.

Molecular cloning of a cDNA of a camptothecin-resistant human DNA topoisomerase I and identification of mutation sites

Camptothecin (CPT), a plant alkaloid with antitumor activity, is a specific inhibitor of eukaryotic DNA topoisomerase I. We have previously isolated and characterized a CPT-resistant topoisomerase I isolated from a CPT-resistant human leukemia cell line, CPT-K5. cDNA clones of topoisomerase I were isolated from the CPT-resistant and the parental CPT-sensitive cell lines, respectively. Sequencing of the clones identified two mutations in the cDNA isolated from the resistant cells, which cause amino acid changes from aspartic acid to glycine at residues 533 and 583 of the parental topoisomerase I. When the CPT-K5 topoisomerase I was expressed in E. coli as a fusion protein with Staphylococcal Protein A fragment, the activity was resistant to CPT at a dose level up to 125 microM, whereas the parental fusion protein was sensitive to CPT as low as 1 microM. The resistance index (greater than 125) of the CPT-K5 fusion topoisomerase I is similar to that of the native CPT-K5 topoisomerase I. These results indicate that either or both of the two amino acid changes identified in the mutant enzyme is responsible for the resistance to CPT.

Gamma-aminobutyric acid-producing lactobacilli positively affect metabolism and depressive-like behaviour in a mouse model of metabolic syndrome

Metabolic and neuroactive metabolite production represents one of the mechanisms through which the gut microbiota can impact health. One such metabolite, gamma-aminobutyric acid (GABA), can modulate glucose homeostasis and alter behavioural patterns in the host. We previously demonstrated that oral administration of GABA-producing Lactobacillus brevis DPC6108 has the potential to increase levels of circulating insulin in healthy rats. Therefore, the objective of this study was to assess the efficacy of endogenous microbial GABA production in improving metabolic and behavioural outcomes in a mouse model of metabolic dysfunction. Diet-induced obese and metabolically dysfunctional mice received one of two GABA-producing strains, L. brevis DPC6108 or L. brevis DSM32386, daily for 12 weeks. After 8 and 10 weeks of intervention, the behavioural and metabolic profiles of the mice were respectively assessed. Intervention with both L. brevis strains attenuated several abnormalities associated with metabolic dysfunction, causing a reduction in the accumulation of mesenteric adipose tissue, increased insulin secretion following glucose challenge, improved plasma cholesterol clearance and reduced despair-like behaviour and basal corticosterone production during the forced swim test. Taken together, this exploratory dataset indicates that intervention with GABA-producing lactobacilli has the potential to improve metabolic and depressive- like behavioural abnormalities associated with metabolic syndrome in mice.

Why do dolphins carry sponges?

Tool use is rare in wild animals, but of widespread interest because of its relationship to animal cognition, social learning and culture. Despite such attention, quantifying the costs and benefits of tool use has been difficult, largely because if tool use occurs, all population members typically exhibit the behavior. In Shark Bay, Australia, only a subset of the bottlenose dolphin population uses marine sponges as tools, providing an opportunity to assess both proximate and ultimate costs and benefits and document patterns of transmission. We compared sponge-carrying (sponger) females to non-sponge-carrying (non-sponger) females and show that spongers were more solitary, spent more time in deep water channel habitats, dived for longer durations, and devoted more time to foraging than non-spongers; and, even with these potential proximate costs, calving success of sponger females was not significantly different from non-spongers. We also show a clear female-bias in the ontogeny of sponging. With a solitary lifestyle, specialization, and high foraging demands, spongers used tools more than any non-human animal. We suggest that the ecological, social, and developmental mechanisms involved likely (1) help explain the high intrapopulation variation in female behaviour, (2) indicate tradeoffs (e.g., time allocation) between ecological and social factors and, (3) constrain the spread of this innovation to primarily vertical transmission.

Differential response of mesoderm- and neural crest-derived smooth muscle to TGF-beta1: regulation of c-myb and alpha1 (I) procollagen genes

Previously, we demonstrated that avian vascular smooth muscle cells (VSMC) derived from embryonic abdominal and thoracic aorta grow differently in the presence of transforming growth factor beta (TGF-beta1) and platelet-derived growth factor (PDGF-BB) (Wrenn et al., In Vitro Cell. Dev. Biol. 29, 73-78, 1992). The thoracic VSMC (N-VSMC) are derived from neural crest, and therefore differentiate from ectoderm; the abdominal VSMC (M-VSMC) are derived from mesoderm. The present study was designed to identify factors that mediate the differential responses of the VSMC to TGF-beta1. We found that TGF-beta1 increased DNA synthesis by approximately sevenfold in N-VSMC. Levels of both alpha1 (I) procollagen and c-myb mRNAs were markedly induced in N-VSMC treated with TGF-beta1. Chimeric plasmids containing up to 3.5 kb of alpha1 (I) procollagen 5' flanking DNA were induced to equivalent levels as procollagen mRNA in N-VSMC. However, TGF-beta1 increased DNA synthesis by threefold in M-VSMC; there was no effect on alpha1 (I) procollagen expression, and c-myb was not expressed, as demonstrated by immunohistochemistry staining and RNA analyses. Antisense c-myb oligodeoxynucleotides blocked the TGF-beta1 induction of alpha1 (I) procollagen and the growth of N-VSMC. The increase in DNA synthesis by M- and N-VSMC was correlated with the secretion of PDGF-AA, and staurosporine and antibodies directed against PDGF-AA suppressed DNA synthesis. Our results demonstrate that TGF-beta1 activity and c-myb expression modulate the expression of alpha1 (I) collagen and cell proliferation in neural crest-derived smooth muscle. The regulation of these events by TGF-beta1 may be important during morphogenesis of blood vessels and vascular diseases.

Detection of Trichomonas vaginalis in pregnant women with the InPouch TV culture system

Trichomonas vaginalis causes a common genitourinary infection which is frequently asymptomatic. At present, pregnant women are not usually screened for the infection unless they are symptomatic. In the present study, we screened and obtained samples for culture from all pregnant women attending a prenatal clinic with the InPouch TV culture system and compared results with those of standard culture in Diamond's medium and slide wet mount examination. The InPouch TV culture system was as reliable as Diamond's medium in detecting T. vaginalis and may be useful and effective in a pregnancy clinic setting.

A review of unmet needs in obesity management

The prevalence of obesity continues to escalate in the USA; however, there is no consensus regarding the optimal therapy for obesity. For the vast majority of severely obese patients, conventional medical therapies (i.e., diet, exercise, behavioral counseling) often fail over the long term. Existing pharmacotherapy adjunctive to behavioral therapy has limited effectiveness and an imperfect safety record. In contrast, bariatric surgery has a high degree of weight loss efficacy, yet only a small fraction of the qualifying obese population undergoes these procedures because of the associated perioperative risks and potential late complications. In addition, the role of bariatric surgery is unclear in certain patient populations, such as patients with lower body mass index (BMI, 30-35 kg/m(2)), the high-risk super-super obese patients (BMI > 60), the morbidly obese adolescent, and obese patients requiring weight reduction in preparation for other procedures, such as orthopedic, transplant, or vascular surgeries. In these circumstances, there is a need for an effective but less invasive treatment to bridge the gap between medical and surgical therapy. This review examines current treatment outcomes, identifies prominent areas of unmet clinical needs, and provides an overview of two minimally invasive "temporary procedures for weight loss" that may eventually address some of the unmet needs in obesity management.

The microRNA expression changes associated with malignancy and SDHB mutation in pheochromocytoma

Currently, the diagnosis of malignant pheochromocytoma can only be made when there is clinical evidence of metastasis or extensive local invasion. Thus, there is a need for new diagnostic marker(s) to identify tumors with malignant potential. The purpose of this study was to identify microRNAs (miRNAs) that are differentially expressed between benign and malignant pheochromocytomas and assess their diagnostic accuracy. Toward this aim, we analyzed miRNA expression in benign and malignant pheochromocytoma tumor samples using whole genome microarray profiling. Microarray analysis identified eight miRNAs that were significantly differentially expressed between benign and malignant pheochromocytomas. We measured a subset of these miRNAs directly by RT-PCR and found that miR-483-5p, miR-183, and miR-101 had significantly higher expression in malignant tumors as compared to their benign counterparts. Area under the receiver operating curve (AUC) analysis indicated that miR-483-5p, miR-101, and miR-183 could be useful diagnostic markers for distinguishing malignant from benign pheochromocytomas. In addition, these miRNAs could be detected in pheochromocytoma patient serum. Overall our data suggest that misexpression of miR-483-5p, miR-101, and miR-183 is associated with malignant pheochromocytoma.

Accelerated thrombolysis and reperfusion in a canine model of myocardial infarction by liposomal encapsulation of streptokinase

The aim of thrombolytic therapy for acute myocardial infarction with plasminogen activators such as streptokinase is to lyse the coronary thrombus and reestablish blood flow as quickly as possible so that heart tissue loss is minimized and mortality rates are improved. Streptokinase has been encapsulated in large unilamellar phospholipid vesicles and tested in an animal model of acute myocardial infarction. The time required to restore vessel patency has been reduced more than 50% when compared with findings for free streptokinase. The total dosage of streptokinase required was lower, and smaller remnant thrombi were observed with the encapsulated agent. Results from this initial unoptimized study may have significant implications for further reduction in mortality from heart attacks by therapy with plasminogen activators.

Influence of GABA and GABA-producing Lactobacillus brevis DPC 6108 on the development of diabetes in a streptozotocin rat model

The aim of this study was to investigate if dietary administration of γ-aminobutyric acid (GABA)-producing Lactobacillus brevis DPC 6108 and pure GABA exert protective effects against the development of diabetes in streptozotocin (STZ)-induced diabetic Sprague Dawley rats. In a first experiment, healthy rats were divided in 3 groups (n=10/group) receiving placebo, 2.6 mg/kg body weight (bw) pure GABA or L. brevis DPC 6108 (~10(9)microorganisms). In a second experiment, rats (n=15/group) were randomised to five groups and four of these received an injection of STZ to induce type 1 diabetes. Diabetic and non-diabetic controls received placebo [4% (w/v) yeast extract in dH2O], while the other three diabetic groups received one of the following dietary supplements: 2.6 mg/kg bw GABA (low GABA), 200 mg/kg bw GABA (high GABA) or ~10(9) L. brevis DPC 6108. L. brevis DPC 6108 supplementation was associated with increased serum insulin levels (P<0.05), but did not alter other metabolic markers in healthy rats. Diabetes induced by STZ injection decreased body weight (P<0.05), increased intestinal length (P<0.05) and stimulated water and food intake. Insulin was decreased (P<0.05), whereas glucose was increased (P<0.001) in all diabetic groups, compared with non-diabetic controls. A decrease (P<0.01) in glucose levels was observed in diabetic rats receiving L. brevis DPC 6108, compared with diabetic-controls. Both the composition and diversity of the intestinal microbiota were affected by diabetes. Microbial diversity in diabetic rats supplemented with low GABA was not reduced (P>0.05), compared with non-diabetic controls while all other diabetic groups displayed reduced diversity (P<0.05). L. brevis DPC 6108 attenuated hyperglycaemia induced by diabetes but additional studies are needed to understand the mechanisms involved in this reduction.

The influence of rosuvastatin on the gastrointestinal microbiota and host gene expression profiles

Statins are the most widely prescribed medications worldwide for the treatment of hypercholesterolemia. They inhibit the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-R), an enzyme involved in cholesterol synthesis in higher organisms and in isoprenoid biosynthesis in some bacteria. We hypothesized that statins may influence the microbial community in the gut through either direct inhibition or indirect mechanisms involving alterations to host responses. We therefore examined the impact of rosuvastatin (RSV) on the community structure of the murine gastrointestinal microbiota. RSV was orally administered to mice and the effects on the gut microbiota, host bile acid profiles, and markers of inflammation were analyzed. RSV significantly influenced the microbial community in both the cecum and feces, causing a significant decrease in α-diversity in the cecum and resulting in a reduction of several physiologically relevant bacterial groups. RSV treatment of mice significantly affected bile acid metabolism and impacted expression of inflammatory markers known to influence microbial community structure (including RegIIIγ and Camp) in the gut. This study suggests that a commonly used statin (RSV) leads to an altered gut microbial composition in normal mice with attendant impacts on local gene expression profiles, a finding that should prompt further studies to investigate the implications of statins for gut microbiota stability and health in humans.NEW & NOTEWORTHY This work demonstrates that rosuvastatin administration in mice affects the gastrointestinal microbiota, influences bile acid metabolism, and alters transcription of genes encoding factors involved in gut homeostasis and immunity in the gastrointestinal tract.

Australian hospital generalist and critical care nurses' perceptions of doctor-nurse collaboration

Previous researchers have indicated that collaborative practice between doctors and nurses results in positive effects on patient care, health-care costs and provider satisfaction. Despite these benefits, collaborative practice appears to be the exception, rather than the dominant pattern, within health care. A collaborative relationship cannot evolve if individuals do not value and respect others' competencies. This study, a mailed survey, used the Collaboration with Medical Staff Scale to compare the perceptions of doctor-nurse collaboration held by critical care nurses and generalist hospital nurses. The hypothesis that critical care nurses perceive there to be greater collaboration with doctors than their generalist nurse colleagues was supported even after taking into consideration education and experience. These results suggest that critical care is an area that might be useful when trying to understand the dimensions and implications of collaboration among health professionals.

Evidence for multiple atrio-AV nodal inputs in the normal dog heart

INTRODUCTION

Complete AV block after combined fast pathway (FP) and slow pathway (SP) ablation is uncommon. The purpose of this study was to interrupt activation of these and additional inputs by placing a radiofrequency lesion across the interatrial septum between the FP and SP ablation sites.

METHODS AND RESULTS

In eight anesthetized open chest dogs, FP ablation induced significant A-H prolongation (deltaA-H: 51 +/- 14 msec; P < 0.001) and a shift of earliest retrograde atrial activation from the anterior septum to the region of the coronary sinus (CS) os. Subsequently, ablation of the interatrial septum across the fossa ovalis was successful in 5 of 8 dogs, changing the sequence of atrial activation (A) so that A at the His-bundle electrogram, which initially preceded A at the CS os (18 +/- 4 msec vs 46 +/- 7 msec, P < 0.01), now followed CS os A (81 +/- 31 msec vs 59 +/- 20 msec, P < 0.05). Additional ablation of the SP caused a type II Mobitz AV block or complete AV block in 5 of 8 dogs. The four dogs with complete AV block showed a stable, high junctional escape rhythm at a rate of 64 +/- 16 beats/min. Pacing between the ablation lesions and the AV node in one dog showed 1:1 AV conduction and Wenckebach-type AV block indicating preserved AV nodal function. Histology showed necrotic changes in the FP and SP transitional cell zones and in the atrial tissue of the interatrial septum. However, the compact AV node, His bundle, and adjacent atria and transitional cells were undamaged.

CONCLUSION

There are additional AV nodal inputs in the interatrial septum in addition to the anterior FP and posterior SP inputs. Ablation of all of these may be required, if the aim is production of complete AV block proximal to the AV node with a high junctional escape rhythm.

Early and delayed afterdepolarizations associated with cesium chloride-induced arrhythmias in the dog

Monophasic action potentials (MAPs) were utilized to examine the basis for cesium-induced arrhythmia in the dog. Cesium chloride (1 mmol/kg i.v.) produced an immediate prolongation of MAP (250 +/- 11 to 396 +/- 34 ms, p less than 0.05). Coupled premature ventricular beats (345 +/- 46 ms) and polymorphic ventricular tachycardia developed in association with early afterdepolarizations during the first 1-3 min after cesium administration. A slowing of the sinus heart rate with vagus nerve stimulation exacerbated the arrhythmia. During the subsequent 7 min, the MAP duration decreased from 396 +/- 34 to 316 +/- 19 ms. At 8-10 min, the premature ventricular beats were associated with delayed afterdepolarizations in the MAP recordings. However, there was no change in the coupling intervals of the premature ventricular beats (351 +/- 29 ms). Ventricular arrhythmias and delayed afterdepolarizations during this phase were exacerbated by increasing the heart rate with atrial pacing. T wave alternans and U wave formation in the ECG were associated with early or delayed afterdepolarizations in MAP. Cesium chloride (1 mmol) injected into the left anterior descending coronary artery produced local MAP prolongation and ventricular bigeminy. Although the MAP duration returned to predrug values after intracoronary cesium injection, the severity of ventricular arrhythmia increased with succeeding doses. These data suggest that early and delayed afterdepolarizations, T wave alterations, and ventricular beats can be dissociated from the initial action potential prolongation with cesium and closely resemble altered calcium transients observed in vitro.

Distributed intraclot thrombolysis: mechanism of accelerated thrombolysis with encapsulated plasminogen activators

BACKGROUND

The delivery of encapsulated plasminogen activators has demonstrated enhanced thrombolysis in vivo in several models. The mechanism of such improvement has not previously been established.

OBJECTIVES

We explored in vitro the mechanism by which microencapsulation of streptokinase in polymeric microparticles accelerates clot digestion and reduces reperfusion times by as much as an order of magnitude in vivo.

METHODS

The efficacy of microencapsulated streptokinase (MESK) was directly compared with identical dosages of unencapsulated streptokinase (FREE SK) at three initial pressure drops using clots formed of plasma or whole blood in 0.2-cm inner diameter glass capillary tubes.

RESULTS

MESK demonstrated accelerated flow restoration compared with FREE SK for each condition in plasma (23.8 +/- 4.5% faster) and whole blood clots (17.2 +/- 9.2% faster). Images collected by light microscopy show sites of thrombolysis internal to the clot only with MESK while the spatial distribution of fluorescently labeled streptokinase by confocal microscopy confirms greater penetration of the encapsulated agent compared with unencapsulated streptokinase. Digestion thus proceeds in three dimensions rather than restricted to a two-dimensional lysis front.

CONCLUSIONS

The improved clot penetration with MESK establishes enhanced transport with encapsulation and the concept of distributed intraclot thrombolysis as a basis for the accelerated dissolution observed with encapsulated plasminogen activators in vivo.