Effect of P-wave timing during supraventricular tachycardia on the hemodynamic and sympathetic neural response

BACKGROUND

Previous studies have shown the importance of the timing of atrial and ventricular systole on the hemodynamic response during supraventricular tachycardia (SVT). However, the reflex changes in autonomic tone during SVT remain poorly understood.

METHODS AND RESULTS

Eleven patients with permanent dual-chamber pacemakers were enrolled in the study. Arterial blood pressure (BP), central venous pressure (CVP), and peripheral muscle sympathetic nerve activity (SNA) were recorded during DDD pacing at a rate of 175 bpm (cycle length 343 ms) with an atrioventricular (AV) interval of 30, 200 and 110 ms, simulating tachycardia with near-simultaneous atrial and ventricular systole, short-RP tachycardia (RP<PR), and long-RP tachycardia (RP>PR). Each pacing run was performed for 3 minutes separated by a 5-minute recovery period. All patients demonstrated an abrupt fall in BP, an increase in CVP, and an increase in SNA regardless of the AV interval. The decreases in SBP, DBP, and MAP and the increase in CVP were significantly less during long-RP tachycardia (AV interval 110 ms) than during the other 2 pacing modes (P:<0.05), and the increase in SNA in 7 of the 11 patients was significantly greater during closely coupled atrial and ventricular systole than during long-RP tachycardia (P:<0.05).

CONCLUSIONS

These data suggest that the superior maintenance of hemodynamic stability during long-RP tachycardia is accompanied by reduced sympathoexcitation, which is primarily mediated by the arterial baroreceptors, with a modest cardiopulmonary vasodepressor effect.

Antifungal activity of extracts from medicinal plants used by First Nations Peoples of eastern Canada

From literature describing medicinal usage of plants by First Nations Peoples in eastern Canada, 18 eastern Canadian plants were selected and tested for their antifungal activities. Eight randomly selected tropical plants were also tested for comparative purposes. Four groups of plants were obtained: popular antimicrobial-remedy (n=6), popular non-antimicrobial-remedy (n=6), random temperate (n=6) and random tropical (n=8). Extracts from these plants were tested in disk assays as growth inhibitors of six fungi known to be opportunistic human pathogens (Saccharomyces cerevisiae, Cryptococcus neoformans, Candida albicans, Aspergillus fumigatus, Microsporum gypseum and Trichophyton mentagrophytes). Of the four plant groups tested, extracts from the popular antimicrobial-remedy group were significantly more effective at inhibiting fungal growth based on both overall antifungal activity and number of fungal species inhibited.

NCCN Practice Guidelines for Breast Cancer

The therapeutic options for patients with noninvasive or invasive breast cancer are complex and varied. In many situations, the patient and physician have the responsibility to jointly explore and ultimately select the most appropriate option from among the available alternatives. With rare exception, the evaluation, treatment, and follow-up recommendations contained within these guidelines were based largely on the results of past and present clinical trials. However, there is not a single clinical situation in which the treatment of breast cancer has been optimized with respect to either maximizing cure or minimizing toxicity and disfigurement. Therefore, patient and physician participation in prospective clinical trials allows patients not only to receive state-of-the-art cancer treatment but also to contribute to the improvement of treatment of future patients.

Antimicrobial activity of extracts of eastern North American hardwood trees and relation to traditional medicine

Wood and bark extracts of 14 eastern North American hardwood tree species which were used traditionally as medicine by First Nation's people were screened for antimicrobial activities with eight strains of bacteria and six strains of fungi. Eighty-six percent of the bark extracts were active against methicillin sensitive Staphylococcus aureus; 71% against Bacillus subtilus and 79% against Mycobacterium phlei. The bark extract of Juglans cinerea was active against Pseudomonas aeruginosa 187, Salmonella typhiumurium, and Klebsiella pneumoniae. The wood extracts were less active: 72% were active against S. aureus (methicillin-sensitive), 36% against B. subtilus and 43% against M. phlei. Results from antifungal tests indicated that 36% of the extracts were active against at least one fungal strain and that bark extracts were more active than wood extracts. The bark extract from Juglans cinerea had the broadest spectrum of activities against Candida albicans, Saccharomyces cerevisiae, Cryptococcus neoformans, Trichophyton mentagrophytes, Microsporum gypseum, and Aspergillus fumigatus. In general, the extracts were more active against gram positive bacteria than gram negative bacteria and against filamentous fungi than yeast-like fungi. The study also demonstrated a correlation between frequency of traditional medicinal use by the First Nations people and antimicrobial activity of extracts indicating that the traditional knowledge encompasses an understanding of aspects of chemical ecology.

Detection times and analytical performance of commercial urine opiate immunoassays following heroin administration

The Federal Workplace Drug Testing Program changed urine screening and confirmation cutoff concentrations for opiate testing from 300 to 2000 ng/mL in 1998. Morphine was the designated target compound. An additional heroin metabolite, 6-acetylmorphine (6-AM), was added to the testing procedure with a cutoff concentration > or = 10 ng/mL. Testing of 6-AM was required if morphine was positive to assist in medical review. A comparison of the new opiate cutoff concentrations was made with the older cutoff concentration at 300 ng/mL. Six commercial opiate immunoassays, four with a 300-ng/mL cutoff, ONLINE, EMIT, CEDIA and AxSym, and two with 2000-ng/mL cutoffs, ONLINE and EMIT, were selected to test 920 urine samples collected from 11 male human subjects following single doses of heroin. Eight received intravenous doses of 3, 6, and 12 mg heroin HCl and four smoked 3.5-, 5.2-, 10.5-, or 13.9-mg doses of heroin (base). In addition, 183 urine-based blind quality-control specimens were added to the study set to assess linearity, cross-reactivity, and interference. Total morphine, free morphine, and 6-AM were measured in each sample by gas chromatography-mass spectrometry (GC-MS). Linearity, cross-reactivity, and interference results for each immunoassay are described. Detection times, sensitivity, specificity, and efficiency of each assay were determined using data from the specimens collected after heroin administration. Detection times for morphine using the 300-ng/mL cutoff assays was approximately 12 h for low dose and 24 to 48 h for higher doses of heroin. For the two 2000-ng/mL cutoff concentration assays detection time was about 12 h. This was also the detection time for 6-AM by GC-MS. ONLINE had the lowest sensitivity, 60-74%, highest specificity, 98.8-100%, and least interference from a selection of common over-the-counter drugs and opioids. Increasing the cutoff to 2000 ng/mL from 300 ng/mL increased efficiencies of the assays from 72.7 to 82.6% to over 97%.

Liquid chromatography-electrospray ionization mass spectrometry for the detection of lysergide and a major metabolite, 2-oxo-3-hydroxy-LSD, in urine and blood

A method is presented for the quantitative measurement of lysergide (LSD) and its metabolite 2-oxo-3-hydroxy-LSD (O-H-LSD) in urine and blood. O-H-LSD has been reported to have urinary concentrations many times higher than LSD. Measuring its presence in urine would significantly extend the detection time for confirming LSD abuse. A single-step liquid-liquid extraction was performed on 5-mL urine samples prior to separation by gradient liquid chromatography (LC). Electrospray ionization was used to produce the positively charged ions of O-H-LSD, 2-oxo-3-hydroxy-LAMPA (O-H-LAMPA, internal standard), LSD, and iso-LSD. Varying the orifice voltage in the intermediate-pressure region of the source generated the fragmentation necessary to produce qualifying ions. Selected ion monitoring allowed detection limits of 400 pg/mL and 100 pg/mL for O-H-LSD and LSD, respectively. The method was linear for O-H-LSD from 400 to 8000 pg/mL and for LSD from 100 to 6000 pg/mL. LSD-positive samples (n = 9) analyzed by the liquid chromatography-mass spectrometry method were found to contain mean concentrations of 6378 pg/mL O-H-LSD (332-21371 pg/mL) and 844 pg/mL LSD (177-2456 pg/mL). O-H-LSD urinary concentrations were between 0.9 and 19.8 times higher than LSD (mean = 10.2). Whole-blood samples were also analyzed following additional sample cleanup. LSD was measured in the blood samples, but no O-H-LSD was detected. Enzymatic hydrolysis was carried out on LSD-positive samples (n = 6) to evaluate the existence of conjugated O-H-LSD. Beta-glucuronidase from Helix pomatia was incubated with urine samples at 37 degrees C, pH 5.2 for 24 h. At an enzymatic activity of approximately 4000 units per milliliter of urine, no significant (p = 0.05) difference was seen between hydrolyzed and nonhydrolyzed samples suggesting an absence of O-H-LSD-glucuronic acid conjugation.

Comparing the Fused Dichotic Words Test and the Intracarotid Amobarbital Procedure in children with epilepsy

The validity of the Fused Dichotic Words Test (FDWT) in predicting the nature of speech representation, as determined by the Intracarotid Amobarbital Procedure (IAP), was examined in a sample of 28 children with epilepsy. Various methods of analysis (difference score, lambda, and lambda(*)), for the FDWT data were calculated and compared. Results showed the validity of the FDWT did not change depending on the method of analysis. The difference scores showed that 18 of the 19 patients with left hemisphere speech obtained right-ear advantages, while the patient with right hemisphere speech showed a left-ear advantage. As a group, patients with left-hemisphere speech obtained a statistically significant right-ear advantage for the lambda and lambda(*) indices, while the patient with right-hemisphere speech showed a left-ear advantage that was also significant for both lambda measures. Patients with bilateral speech, as a group, displayed a non-significant ear advantage. Some of the scores from the left-hemisphere group overlapped with those from patients with bilateral speech representation. Controlling for stimulus dominance effects using the lambda(*) measure did not improve classification accuracy for nature of speech representation based on FDWT scores. Finally, comparison of our data using the laterality index from a similar study, showed scores smaller in magnitude than that found in adults with epilepsy.

Statistical comparison of axon-scaled neurochemical production

Treatments designed to increase neurochemical levels may also result in increases in the numbers of axons that produce the neurochemicals of interest. A natural research question is how does one compare the average neurochemical production per axon between two (or more) experimental groups. Two statistical methods are proposed for this problem. The first method utilizes a delta-method approximation to the variance of a function of random variables while the second method is based on the bootstrap. These methods are illustrated with data obtained from perivascular norepinephrine following intracerebroventricular infusion of neurotrophin nerve growth factor in adult rats and are studied in a small simulation experiment. The delta-method confidence intervals exhibited better coverage properties than the bootstrap alternative.

Biventricular pacing decreases sympathetic activity compared with right ventricular pacing in patients with depressed ejection fraction

BACKGROUND

Although there have been few studies in which the hemodynamic effects of right ventricular (RV) and left ventricular (LV) pacing were compared with those of biventricular (BV) pacing, the autonomic changes during these different pacing modes remain unknown. We hypothesized that BV pacing results in improved hemodynamics and a decrease in sympathetic nerve activity (SNA) compared with single-site pacing.

METHODS AND RESULTS

Thirteen men with a mean ejection fraction of 0.28+/-0.7 were enrolled in the study. Arterial blood pressure (BP), central venous pressure (CVP), and SNA were recorded during 3 minutes of right atrial (RA)-RV, RA-LV, and RA-BV pacing at a rate 10 beats faster than sinus rhythm. BP was greater during LV (151+/-7/85+/-3 mm Hg) and BV (151+/-6/85+/-3 mm Hg) pacing than during RV pacing (146+/-7/82+/-3 mm Hg) (P:<0.05). There were no differences in CVP among all pacing modes (P:=0.27). SNA was significantly less (P:<0.02) during both LV (606+/-35 U) and BV (582+/-41 U) pacing compared with RV pacing (685+/-32 U) (P:<0.02). Although not statistically significant (P:=0. 08 to 0.14), there was a trend for patients with a narrow QRS to have a lower mean BP and higher SNA during LV pacing than during BV pacing (r=0.42 to 0.49).

CONCLUSIONS

LV-based pacing results in improved hemodynamics and a decrease in SNA compared with RV pacing in patients with LV dysfunction regardless of the QRS duration.

Molecular and functional analyses of incompatibility genes at het-6 in a population of Neurospora crassa

Two closely linked genes, un-24 and het-6, associated with the het-6 heterokaryon incompatibility functional haplotype were examined in 40 Neurospora crassa strains from a Louisiana sugarcane field. Partial diploid analyses were used to determine that half of the strains were functionally Oak Ridge (OR) and half were non-OR and indistinguishable from the standard Panama (PA) form. PCR-based markers were developed to identify polymorphisms within both un-24 and het-6. Two common forms of each gene occur based on these molecular markers. Rare forms of both un-24 and het-6 were identified as variants of the non-OR form by a DNA transformation assay. The heterokaryon incompatibility function of haplotypes, based on partial diploid analyses, was perfectly correlated with the PCR-based markers at both loci. This correlation indicates that the two loci are in severe linkage disequilibrium in this population sample and may act as an incompatibility gene complex. Southern hybridizations using OR- and PA-derived cloned probes from the region that spans un-24 and het-6 showed that the apparent absence of recombination in this approximately 25-kbp region is associated with low levels of overall sequence identity between the PA and OR forms.

Antifungal rapamycin analogues with reduced immunosuppressive activity

Several 1,2,3,4-tetrahydro- and 7-N-hydroxycarbamate derivatives of the natural product rapamycin were prepared and assayed for their immunosuppressive and antifungal profiles. Substitutions at the 7-position indicate the possibility of a differentiated immunosuppressive to antifungal profile, whereas 40-position variants of the tetrahydro-analogues did not show similar differentiated activity.

Effects of hypoxia on sympathetic neural control in humans

This special issue is principally focused on the time domain of the adaptive mechanisms of ventilatory responses to short-term, long-term and intermittent hypoxia. The purpose of this review is to summarize the limited literature on the sympathetic neural responses to sustained or intermittent hypoxia in humans and attempt to discern the time domain of these responses and potential adaptive processes that are evoked during short and long-term exposures to hypoxia.

Increased sympathetic activity after atrioventricular junction ablation in patients with chronic atrial fibrillation

OBJECTIVES

The aim of this study was to determine the changes in sympathetic nerve activity (SNA) after atrioventricular junction (AVJ) ablation in patients with chronic atrial fibrillation (AF).

BACKGROUND

Polymorphic ventricular tachycardia (PMVT) has been reported after AVJ ablation in patients paced at a rate of < or =70 beats/min. We hypothesized that AVJ ablation results in sympathetic neural changes that favor the occurrence of PMVT and that pacing at 90 beats/min attenuates these changes.

METHODS

Sympathetic nerve activity, 90% monophasic cardiac action potential duration (APD90), right ventricular effective refractory period (ERP) and blood pressure measurements were obtained in 10 patients undergoing AVJ ablation. Sympathetic nerve activity was analyzed at baseline and during and after successful AVJ ablation for at least 10 min. Data were also collected after ablation at pacing rates of 60 and 90 beats/min. The APD90 and ERP were measured before and after AV block during pacing at 120 beats/min.

RESULTS

Sympathetic nerve activity increased to 134 +/- 16% of the pre-ablation baseline value (p < 0.01) after successful AVJ ablation plus pacing at 60 beats/min and decreased to 74 +/- 8% of baseline (p < 0.05) with subsequent pacing at 90 beats/min. Both APD90 and ERP increased significantly.

CONCLUSIONS

1) Ablation of the AVJ followed by pacing at 60 beats/min is associated with an increase in SNA. 2) Pacing at 90 beats/min decreases SNA to or below the pre-ablation baseline value. 3) Cardiac APD and ERP increase after AVJ ablation. The increase in SNA, along with the prolongation in APD, may play a role in the pathogenesis of ventricular arrhythmias that occur after AVJ ablation.

Sensitivity of cyclin E-overexpressing cells to cisplatin/taxol combinations

Combinations of anticancer drugs, referred to as "combinatorial" chemotherapy, is often used in the treatment of cancer patients. Recent advances in our understanding of cell cycle and cellular stress responses may be viewed in the context of responses to anticancer drugs. A desired outcome is cell death preferentially occurring in cancer cells. We report that cyclin E, an oncogene that is deregulated in breast and other human cancers, can sensitize cancer cells to cisplatin/taxol combinations. The drug combination may selectively induce apoptosis in cyclin E-overexpressing cells.

Vegetative incompatibility in the het-6 region of Neurospora crassa is mediated by two linked genes

Non-self-recognition during asexual growth of Neurospora crassa involves restriction of heterokaryon formation via genetic differences at 11 het loci, including mating type. The het-6 locus maps to a 250-kbp region of LGIIL. We used restriction fragment length polymorphisms in progeny with crossovers in the het-6 region and a DNA transformation assay to identify two genes in a 25-kbp region that have vegetative incompatibility activity. The predicted product of one of these genes, which we designate het-6(OR), has three regions of amino acid sequence similarity to the predicted product of the het-e vegetative incompatibility gene in Podospora anserina and to the predicted product of tol, which mediates mating-type vegetative incompatibility in N. crassa. The predicted product of the alternative het-6 allele, HET-6(PA), shares only 68% amino acid identity with HET-6(OR). The second incompatibility gene, un-24(OR), encodes the large subunit of ribonucleotide reductase, which is essential for de novo synthesis of DNA. A region in the carboxyl-terminal portion of UN-24 is associated with incompatibility and is variable between un-24(OR) and the alternative allele un-24(PA). Linkage analysis indicates that the 25-kbp un-24-het-6 region is inherited as a block, suggesting that a nonallelic interaction may occur between un-24 and het-6 and possibly other loci within this region to mediate vegetative incompatibility in the het-6 region of N. crassa.

Clinical governance: principles into practice

This paper describes the early development of clinical governance in an acute NHS Trust. Three Trust-wide workshops and 17 individual departmental workshops were held between 1998-1999. The discussions in these workshops were used to define the key founding principles of clinical governance and the operational structure. The philosophy behind clinical governance, to improve quality of services, was recognised as being part of mainstream trust business, not an optional add-on. The authors found that teamwork and multidisciplinary collaboration are essential components of future quality improvement. Effective leadership skills need to be supported and developed, with responsibilities shared between a core group within each department rather than one individual. Contributions should be recognised and rewarded. Collaboration with primary care and involvement of patients are prerequisites. Specific objectives should be agreed by each department and used to monitor progress. More effective use of existing resources (staff, time, IT and training) can be made.

Intelligence profiles in children and adolescents with left temporal lobe epilepsy: relationship to language laterality

Pre- and postoperative IQ profiles were examined in children and adolescents with left temporal-lobe epilepsy. Participants were grouped according to their pattern of speech dominance, as indicated by the intracarotid sodium amobarbital procedure. Seven participants with typical (left hemisphere) speech representation were matched for age and sex to seven participants with atypical (bilateral or right hemisphere) speech representation. The group with atypical speech representation tended to perform worse pre- and postoperatively on several verbal and nonverbal subtests. Unlike Strauss et al.'s (1990) sample, however, the groups did not differ significantly on pre- or postoperative Performance IQ. The results suggest that when individuals are matched closely for age and sex, there may only be limited support for a nonverbal "crowding" hypothesis. Atypical speech representation in children and adolescents with early temporal-lobe epilepsy appears to be associated with lowered performance on both verbal and nonverbal IQ subtests.

Controlling for stimulus dominance effects in the Fused Dichotic Words Test when predicting speech lateralization in children

A log-linear analysis (Grimshaw et al., 1994) of Fused Dichotic Words Test data was examined in a sample of 28 children with epilepsy who had undergone the intracarotid amobarbital procedure to determine the nature of speech representation. The analysis yields a measure of ear dominance (lambda*) that controls for stimulus dominance confounds. Most patients with unilateral speech obtained statistically significant ear advantages, whereas most with bilateral speech displayed no significant ear advantage. Despite controlling for stimulus dominance confounds, some of the scores from patients with left-hemisphere speech overlapped with those from patients with bilateral speech representation.

Morally managing medical mistakes

Mistakes and errors happen in most spheres of human life and activity, including in medicine. A mistake can be as simple and benign as the collection of an extra and unnecessary urine sample. Or a mistake can cause serious but reversible harm, such as an overdose of insulin in a patient with diabetes, resulting in hypoglycemia, seizures, and coma. Or a mistake can result in serious and permanent damage for the patient, such as the failure to consider epiglottitis in an initial differential diagnosis, resulting in a chronic vegetative state for a seven-year-old boy. Or a mistake can be an error in judgment that leads to a patient's death.

Effects of pyridinium chlorochromate adulterant (urine luck) on testing for drugs of abuse and a method for quantitative detection of chromium (VI) in urine

Pyridinium chlorochromate (PCC) as an adulterant is popular for concealing drug-positive results. When 11-nor-delta9-THC-9-carboxylic acid (THC-acid) in urine was treated with 2 mmol/L of PCC (Cr6+ 104 microg/mL), 58-100% of the THC-acid was lost. The loss increased with decreasing pH and increasing reaction time (0-3 days). Free codeine and free morphine remained unaffected by PCC at pH within the physiological range of the urine (pH 5-7). At lower pH, the loss of free morphine varied from 0 to 100%. Amphetamine, methamphetamine, benzoylecgonine, and PCP remained unaffected by PCC when exposed to the oxidant for three days in urine pH of 3-7. Chromium (VI) from PCC in a urine solution was detected by a color reaction with 1,5-diphenylcarbazide (DPC). When the reagent was added to the urine, an immediate red-violet color appeared. The chromium-DPC complex showed a characteristic absorption peak at wavelength 544 nm with a shoulder at wavelength 575 nm. The ratio of absorption was used to identify the chromium compound. The concentration of chromium (VI) was determined by measuring absorption at wavelength 544 nm and was linear over 0.5-20 microg/mL. The limit of detection of the procedure was 0.37 microg/mL.

p53-mediated DNA repair responses to UV radiation: studies of mouse cells lacking p53, p21, and/or gadd45 genes

Human cells lacking functional p53 exhibit a partial deficiency in nucleotide excision repair (NER), the pathway for repair of UV-induced DNA damage. The global genomic repair (GGR) subpathway of NER, but not transcription-coupled repair (TCR), is mainly affected by p53 loss or inactivation. We have utilized mouse embryo fibroblasts (MEFs) lacking p53 genes or downstream effector genes of the p53 pathway, gadd45 (Gadd45a) or p21 (Cdkn1a), as well as MEFs lacking both gadd45 and p21 genes to address the potential contribution of these downstream effectors to p53-associated DNA repair. Loss of p53 or gadd45 had a pronounced effect on GGR, while p21 loss had only a marginal effect, determined by measurements of repair synthesis (unscheduled DNA synthesis), by immunoassays to detect removal of UV photoproducts from genomic DNA, and by assays determining strand-specific removal of CPDs from the mouse dhfr gene. Taken together, the evidence suggests a role for Gadd45, but relatively little role for p21, in DNA repair responses to UV radiation. Recent evidence suggests that Gadd45 binds to UV-damaged chromatin and may affect lesion accessibility. MEFs lacking p53 or gadd45 genes exhibited decreased colony-forming ability after UV radiation and cisplatin compared to wild-type MEFs, indicating their sensitivity to DNA damage. We provide evidence that Gadd45 affects chromatin remodelling of templates concurrent with DNA repair, thus indicating that Gadd45 may participate in the coupling between chromatin assembly and DNA repair.

Mild hyperthermia-induced apoptosis is dependent on p53 in human lymphoid cells

Mild hyperthermia is known to enhance apoptosis. The p53 tumor-suppressor gene product has been shown to function in apoptosis in response to genotoxic stress. However, there is little information regarding the mechanism of p53-dependent apoptosis induced by heat stress. In present study, a p53 contribution in mild hyperthermia-induced apoptosis was investigated in human lymphoid system. After 30-minute exposure at 44 degrees C, the accumulation of p53 protein was clearly observed in TK6 and ML-1 cells. Using comet assay, the more significant sensitivity to hyperthermic apoptosis was found in TK6 (wild-type p53) than in WI-L2-NS (mutated in p53). Furthermore, the significantly rapid shifting from early apoptotic phase to late apoptotic was observed in heat-induced p53 TK6 cells. These findings suggest that p53-dependent apoptosis is efficaciously induced by mild hyperthermia as non-genotoxic stress in human lymphoid system.