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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent reports have shown that it is possible to record extracellular electrograms from the rabbit and dog sinoatrial (SA) node. We applied similar techniques to record SA nodal activity in 23 patients who underwent cardiac surgery for various forms of heart disease. Both a bipolar technique, using pairs of electrodes at various interelectrode distances, and a unipolar technique, using an exploring and an indifferent electrode, were used. To record SA nodal electrograms, polarity was reversed from the conventional electrocardiographic recording; high amplification (100 microV/cm) and low-pass filters (0.15-20 Hz) were used. SA nodal electrograms were recorded from eight of 12 patients using the bipolar method and from nine of 11 patients using the unipolar method. There were no significant differences in the success rate or quality of the recording between the two methods. However, the unipolar method allowed a more accurate localization of the SA node. Human SA nodal electrograms resembled those of the dog and rabbit and showed two distinct slopes: a diastolic slope and an upstroke slope preceding the P wave of the ECG, SA conduction times were 32.4 +/- 2.8 msec (mean +/- SEM) at sinus (PP) cycle lengths of 587.6 +/- 35.6 msec for the bipolar method, and 38.2 +/- 3.2 msec at sinus (PP) cycle lengths of 712.2 +/- 50.7 msec for the unipolar method. These methods for recording of extracellular SA nodal electrograms in man may prove useful in 1) localization of the SA node during open heart surgery and 2) assessment of SA nodal function in health and disease.
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PMID:Methods for recording electrograms of the sinoatrial node during cardiac surgery in man. 736 24

Seventy-three Nigerian men with breast cancer seen over a 20-year period were studied to evaluate the pattern of the disease in one black African population. An annual incidence of 1.2 per 100,000 of the population was calculated; the proportion in relation to the disease incidence in women was 3.75%. Two-thirds of the patients were aged 50-65 years; the mean was 54.1 (SEM 2.3). Three patients linked their disease with trauma while seven had pre-existing gynaecomastia. More than 90% of the patients presented with advanced disease (stages III and IV), with bulky tumours (3.5-13.5 cm diameter), fixation to muscle (76.7%), skin involvement (65.6%) and nodal invasion (91.8%). Carcinomas of no special type (infiltrating ductal and undifferentiated cancers (76.7%)) dominated the histopathology, which included one case of lobular carcinoma.
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PMID:Breast cancer in men in black Africa: a report of 73 cases. 786 87

A meta-analysis has been performed of available retrospective reports concerning the 5-15 year disease-free survival of 5,353 premenopausal breast cancer patients operated on either during the follicular or luteal phases of the menstrual cycle. Patients with surgery performed during the luteal phase (d 14-23+) had an overall mean 5% benefit compared to those operated on the follicular phase determined by date of onset of their last menstrual period p = 0.02 by Wilcoxon 2-tailed test. When nodal invasion was reported, node-negative patients had a 5 +/- 2% SEM benefit. Patients with positive nodes had a 34 +/- 3% SEM increase in survival (p = .05), including both estrogen and progesterone-receptor negative as well as positive neoplasms. In 3 of 4 reports from major cancer treatment centers, each containing 249-1175 cases, risk of recurrent cancer and/or death increased 5 to 6-fold after 10 years for women receiving surgery during d 7-14 of their cycle, compared to those resected during d 21-36. Improvement in prognosis was greatest for patients with the highest risk of recurrence due to node-invasive disease and receptor dysfunction. Several cell-mediated immunologic factors inimical to metastasis are maximal in the luteal phase of the menstrual cycle, including natural killer cell activity. A new drug which augments natural killer cell activity may extend any beneficial survival results to post-menopausal breast cancer patients in the future. We conclude that accurate menstrual histories should be included in the medical record from now on for all premenopausal women receiving any surgical procedure upon the breast, preferably using an objective method of determining the date of last ovulation. Prospective randomized clinical trials are necessary to determine the full extent of survival benefits of late luteal surgical timing.
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PMID:Timing of breast cancer surgery during the luteal menstrual phase may improve prognosis. 890 25

A meta-analysis has been performed of available retrospective reports concerning the 5-15 year disease-free survival of 5,353 premenopausal breast cancer patients operated on either during the follicular or luteal phases of the menstrual cycle. Patients with surgery performed during the luteal phase (d14-23+) had an overall mean 5% benefit compared to those operated on the follicular phase determined by date of onset of their last menstrual period p=0.02 by Wilcoxon 2-tailed test. When nodal invasion was reported, node-negative patients had a 5 + 2% SEM benefit. Patients with positive nodes had a 34 + 3% SEM increase in survival (p = .05), including both estrogen and progesterone-receptor negative as well as positive neoplasms. In 3 of 4 reports from major cancer treatment centers, each containing 249-1175 cases, risk of recurrent cancer and/or death increased 5 to 6-fold after 10 years for women receiving surgery during d7-14 of their cycle, compared to those resected during d21-36. Improvement in prognosis was greatest for patients with the highest risk of recurrence due to node-invasive disease and receptor dysfunction. Several cell-mediated immunologic factors inimical to metastasis are maximal in the luteal phase of the menstrual cycle, including natural killer cell activity. A new drug which augments natural killer cell activity may extend any beneficial survival results to post-menopausal breast cancer patients in the future. We conclude that accurate menstrual histories should be included in the medical record from now on for all premenopausal women receiving any surgical procedure upon the breast, preferably using an objective method of determining the date of last ovulation. Prospective randomized clinical trials are necessary to determine the full extent of survival benefits of late luteal surgical timing.
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PMID:Timing of breast cancer surgery during the luteal menstrual phase may improve prognosis. 862 49

We have studied the effects of magnesium on atrioventricular (AV) conduction times and surface electrocardiogram during both sinus rhythm and atrial pacing in seven dogs anaesthetized with 1 MAC of sevoflurane. A bolus dose of magnesium sulphate (MgSO4) 30, 60 and 90 mg kg-1 significantly increased plasma magnesium concentrations from 1.3 (SEM 0.1) to 15.3 (1.3) mg dl-1. MgSO4 significantly prolonged A-H (AV nodal conduction time during sinus rhythm), St-H (intra-atrial and AV nodal conduction time during atrial pacing) and H-S (total ventricular conduction time) intervals at doses > or = 30 mg kg-1 ; H-V interval (His-Purkinje conduction time) at doses > or = 60 mg kg-1; RR and PR intervals and QRS duration at doses > or = 30 mg kg-1 in a dose-related manner during both sinus rhythm and atrial pacing. QTc interval remained unchanged during sinus rhythm. The doses of MgSO4 used did not have deleterious effects on AV conduction times and surface electrocardiogram during 1 MAC of sevoflurane anaesthesia. This finding suggests that MgSO4 in high doses was safe and may be indicated for cardiac arrhythmia and hypertension during sevoflurane anaesthesia. However, further study is required to apply these findings to clinical anaesthesia.
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PMID:Effects of magnesium sulphate on atrioventricular conduction times and surface electrocardiogram in dogs anaesthetized with sevoflurane. 905 8

Although it is essential to cardiac conduction, little is known about the biochemistry underlying postreceptor adrenergic, cholinergic and purinergic processes in the AV node. To study these mechanisms, we adapted a new and highly sensitive fluorometric assay for cyclic adenosine monophosphate (AMP) to characterize regional adenylylcyclase activity (cyclic AMP production in pmol/min/mg of protein) in membrane preparations made from 20-50 pieces of freeze-dried, 20-microm thick, microdissected samples of tissue from canine right atrium, the AV nodal region, and left ventricle. Basal and NaF-stimulated adenylylcyclase activity (mean +/- SEM, n = 6) were 7.2 +/- 0.4 and 72.4 +/- 7.5 in atrial, 15.6 +/- 1.3 and 58.8 +/- 4.7 in AV nodal, and 6.4 +/- 0.9 and 66.7 +/- 5.0 in ventricular tissues, respectively. Isoproterenol (10(-7)-10(-4) M) increased adenylylcyclase activity in a dose-dependent fashion in three different regions. The isoproterenol (10(-6) M)-stimulated adenylylcyclase activity (n = 6) was 14.4 +/- 1.3 in atrial, 21.9 +/- 1.6 in AV nodal and 13.4 +/- 1.4 in ventricular tissues. Adenosine (10(-3) M) and carbachol (10(-5) M) inhibited isoproterenol (10(-6) M)-stimulated adenylylcyclase activity to 10.1 +/- 1.1, 12.9 +/- 1.3 in atrial, 15.1 +/- 1.6, 15.5 +/- 1.2 in AV nodal, and 7.5 +/- 0.7, 11.9 +/- 1.2 in ventricular tissues, respectively. The results demonstrate that there are regional differences in adenylylcyclase activity under basal conditions and after adrenergic, purinergic, and cholinergic stimulation in the heart. Unlike adenosine, the inhibitory effects of cholinergic stimulation appear to be more specific for the AV node.
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PMID:Measurement of adenylylcyclase activity in the AV nodal region of the canine heart: evidence for inhibition by adenosine and acetylcholine. 923 53

Atrioventricular nodal reentry is a commonly recognized mechanism of supraventricular tachycardia (SVT) in adults, but is only rarely documented in the first year of life. The aim of this study was to elucidate characteristics, management, and outcome in infants with atrioventricular nodal reentrant tachycardia (AVNRT). Electrophysiologic studies performed between January 1988 and June 1996 were reviewed. Fifteen infants with AVNRT at 58 +/- 27 days (mean +/- SEM) were identified. Five had AVNRT detected following palliation of structural cardiac anomalies, including 4 with critical obstructions to left ventricular outflow. Typical AVNRT (ventriculoatrial interval 49 +/- 5 ms) was observed in 14 of 15 patients and atypical AVNRT (ventriculoatrial interval 191 +/- 22 ms) in 4 of 15. All patients received long-term therapy, beginning with digoxin in 13. Eight had symptomatic recurrences on digoxin and 6 of these were given beta blockers, with satisfactory control in 4. Three patients were controlled with class III agents, and 2 underwent slow pathway radiofrequency modification at ages 4.1 and 6.7 years, respectively. AVNRT was still inducible in 6 of 6 asymptomatic patients who underwent follow-up atrial stimulation studies after discontinuation of medical therapy. All 15 patients were alive with either absent or well-controlled AVNRT at age 45 +/- 7 months. We conclude that the course and outcome of AVNRT diagnosed in the first year of life are generally benign, but that a minority of patients have symptoms persisting beyond infancy. Digoxin is of questionable benefit in long-term control. AVNRT often remains inducible in asymptomatic patients, although the significance of this finding remains to be determined by long-term follow-up.
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PMID:Characteristics, management, and midterm outcome in infants with atrioventricular nodal reentry tachycardia. 979 51

The neurophysiological effects of nine neuropathy-associated human anti-ganglioside antisera, three monoclonal antibodies to ganglioside GM1 (GM1) and of the cholera toxin B subunit (a GM1 ligand) were studied on mouse sciatic nerve in vitro. GM1 antisera and monoclonal antibodies from patients with chronic motor neuropathies and Guillain-Barre syndrome, and GQ1b/ disialosyl antisera and monoclonal antibodies from patients with chronic ataxic neuropathies and Miller Fisher syndrome were studied. In vitro recording, for up to 6 h, of compound nerve action potentials, latencies, rise times and stimulus thresholds from isolated desheathed sciatic nerve was performed in the presence of antiganglioside antibodies and fresh human serum as an additional source of complement. No changes were observed over this time course, with 4-6 h values for all electrophysiological parameters being within 15% of the starting values for both normal and antibody containing sera and for the cholera toxin B subunit. Parallel experiments on identically prepared desheathed nerves performed with 0.5 nM saxitoxin led to complete conduction block within 10 min of application. Under identical conditions to those used for electrophysiological recordings, quantitative immunohistological evaluation revealed a significant increase in IgM (immunoglobulin M) deposition at nodes of Ranvier from 5.3+/-3.1% to 28.7+/-8.4% (mean+/-SEM) of desheathed nerves exposed to three normal and three antibody containing sera, respectively (P < 0.03). Complement activation was seen at 100% of normal and 79% of disease-associated IgM positive nodes of Ranvier. These data indicate that anti-ganglioside antibodies can diffuse into a desheathed nerve, bind to nodes of Ranvier and fix complement in vitro without resulting in any overt physiological deterioration of the nerve over 4-6 h. This suggests that the node of Ranvier is relatively resistant to acute antiganglioside antibody mediated injury over this time scale and that anti-ganglioside antibodies and the cholera toxin B subunit are unlikely to have major direct pharmacological effects on nodal function, at least in comparison with the effect of saxitoxin. This in vitro sciatic nerve model appears of limited use for analysing electrophysiologically the effects of anti-ganglioside antibodies on nerve function, possibly because its short-term viability and isolation from circulating systemic factors do not permit the evolution of an inflammatory lesion of sufficient magnitude to induce overt electrophysiological abnormalities. In vivo models may be more suitable for identifying the effects of these antibodies on nerve conduction.
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PMID:Anti-ganglioside antibodies can bind peripheral nerve nodes of Ranvier and activate the complement cascade without inducing acute conduction block in vitro. 1035 65

We measured and compared Na-Ca exchanger current (INa-Ca) from rabbit isolated ventricular and atrioventricular (AV) nodal myocytes, using action potential (AP) and ramp voltage commands. Whole cell patch-clamp recordings were made at 35-37 degrees C; INa-Ca was measured as 5 mM nickel (Ni)- sensitive current with major interfering voltage and calcium-activated currents blocked. In ventricular cells a 2-s descending ramp elicited INa-Ca showing outward rectification and a reversal potential (Erev) of -13.1 +/- 1. 2 mV (n = 12; mean +/- SEM). With a ventricular AP as the voltage command, the profile of INa-Ca followed the applied waveform closely. The current-voltage relation during AP repolarization was almost linear and showed an Erev of -38.3 +/- 5.3 mV (n = 6). As INa-Ca depended on the applied voltage waveform, comparisons between the two cell types utilized the same command waveform (a series of AV nodal APs). In ventricular myocytes this elicited INa-Ca that reversed near -38 mV and was inwardly directed during the pacemaker potential. This command was also applied to AV node cells; mean INa-Ca density at all voltages encompassed by the AP (-70 to +30 mV) did not differ significantly from that in ventricular myocytes (P > 0.05, ANOVA). This finding was confirmed using brief (250 ms) voltage ramp protocols (P > 0.1 ANOVA). These data represent the first direct measurements of AV nodal INa-Ca and suggest that the exchanger may be functionally expressed to similar levels in the two cell types. They may also suggest a possible role for INa-Ca during the pacemaker potential in AV node as inward INa-Ca was observed over the pacemaker potential range even with bulk internal Ca buffered to a low level.
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PMID:Na+-Ca2+ exchange current from rabbit isolated atrioventricular nodal and ventricular myocytes compared using action potential and ramp waveforms. 1071 77

The rate of spontaneous diastolic depolarization (DD) of sinoatrial nodal cells (SANCs) that triggers recurrent action potentials (APs) is a fundamental aspect of the heart's pacemaker. Here, in experiments on isolated SANCs, using confocal microscopy combined with a patch clamp technique, we show that ryanodine receptor Ca(2+) release during the DD produces a localized subsarcolemmal Ca(2+) increase that spreads in a wavelike manner by Ca(2+)-induced Ca(2+) release and produces an inward current via the Na(+)-Ca(2+) exchanger (NCX). Ryanodine, a blocker of the sarcoplasmic reticulum Ca(2+) release channel, in a dose-dependent manner reduces the SANC beating rate with an IC(50) of 2.6 micromol/L and abolishes the local Ca(2+) transients that precede the AP upstroke. In voltage-clamped cells in which the DD was simulated by voltage ramp, 3 micromol/L ryanodine decreased an inward current during the voltage ramp by 1.6+/-0.3 pA/pF (SEM, n=4) leaving the peak of L-type Ca(2+) current unchanged. Likewise, acute blockade of the NCX (via rapid substitution of bath Na(+) by Li(+)) abolished SANC beating and reduced the inward current to a similar extent (1.7+/-0.4 pA/pF, n=4), as did ryanodine. Thus, in addition to activation/inactivation of multiple ion channels, Ca(2+) activation of the NCX, because of localized sarcoplasmic reticulum Ca(2+) release, is a critical element in a chain of molecular interactions that permits the heartbeat to occur and determines its beating rate.
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PMID:Sinoatrial nodal cell ryanodine receptor and Na(+)-Ca(2+) exchanger: molecular partners in pacemaker regulation. 1259 47


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