PubMed Health⌕ Search

Biomedical subjects

A Nygren

Publications and source records attributed to A Nygren.

At least 19 recordsLinked to original sources
PubMed2006

Propagation of the cardiac impulse in the diabetic rat heart: reduced conduction reserve.

Diabetes mellitus is a growing epidemic with severe cardiovascular complications. Although much is known about mechanical and electrical cardiac dysfunction in diabetes, few studies have investigated propagation of the electrical signal in the diabetic heart and the associated changes in intercellular gap junctions. This study was designed to investigate these issues, using hearts from control and diabetic rats. Diabetic conditions were induced by streptozotocin (STZ), given i.v. 7-14 days before experiments. Optical mapping with the voltage-sensitive dye di-4-ANEPPS, using hearts perfused on a Langendorff apparatus, showed little change in baseline conduction velocity in diabetic hearts, reflecting the large reserve of function. However, both the gap junction uncoupler heptanol (0.5-1 mM) and elevated potassium (9 mM, to reduce cell excitability) produced a significantly greater slowing of impulse propagation in diabetic hearts than in controls. The maximal action potential upstroke velocity (an index of the sodium current) and resting potential was similar in single ventricular myocytes from control and diabetic rats, suggesting similar electrical excitability. Immunoblotting of connexin 43 (Cx43), a major gap junction component, showed no change in total expression. However, immunofluorescence labelling of Cx43 showed a significant redistribution, apparent as enhanced Cx43 lateralization. This was quantified and found to be significantly larger than in control myocytes. Labelling of two other gap junction proteins, N-cadherin and beta-catenin, showed a (partial) loss of co-localization with Cx43, indicating that enhancement of lateralized Cx43 is associated with non-functional gap junctions. In conclusion, conduction reserve is smaller in the diabetic heart, priming it for impaired conduction upon further challenges. This can desynchronize contraction and contribute to arrhythmogenesis.

Animals↗
PubMed2005

Actions of emigrated neutrophils on Na(+) and K(+) currents in rat ventricular myocytes.

Interactions between neutrophils and the ventricular myocardium can contribute to tissue injury, contractile dysfunction and generation of arrhythmias in acute cardiac inflammation. Many of the molecular events responsible for neutrophil adhesion to ventricular myocytes are well defined; in contrast, the resulting electrophysiological effects and changes in excitation-contraction coupling have not been studied in detail. In the present experiments, rat ventricular myocytes were superfused with either circulating or emigrated neutrophils and whole-cell currents and action potential waveforms were recorded using the nystatin-perforated patch method. Almost immediately after adhering to ventricular myocytes, emigrated neutrophils caused a depolarization of the resting membrane potential and a marked prolongation of myocyte action potential. Voltage clamp experiments demonstrated that following neutrophil adhesion, there was (i) a slowing of the inactivation of a TTX-sensitive Na(+) current, and (ii) a decrease in an inwardly rectifying K(+) current. One cytotoxic effect of neutrophils appears to be initiated by enhanced Na(+) entry into the myocytes. Thus, manoeuvres that precluded activation of Na(+) channels, for example holding the membrane potential at -80 mV, significantly increased the time to cell death or prevented contracture entirely. A mathematical model for the action potential of rat ventricular myocytes has been modified and then utilized to integrate these findings. These simulations demonstrate the marked effects of (50-fold) slowing of the inactivation of 2-4% of the available Na(+) channels on action potential duration and the corresponding intracellular Ca(2+) transient. In ongoing studies using this combination of approaches, are providing significant new insights into some of the fundamental processes that modulate myocyte damage in acute inflammation.

Action Potentials↗
PubMed2005

Cardiopulmonary bypass in humans--jejunal mucosal perfusion increases in parallel with well-maintained microvascular hematocrit.

BACKGROUND: An imbalance between splanchnic oxygen supply and demand occurs during cardiopulmonary bypass (CPB) in man, which might disrupt the intestinal mucosal barrier function. The aim of the present study was to evaluate the effects of mild hypothermic CPB on intestinal mucosal perfusion in man undergoing cardiac surgery. Additionally we aimed to identify variables, which independently could predict changes of intestinal mucosal microcirculatory variables during CPB. METHODS: Jejunal mucosal perfusion (JMP), jejunal mucosal hematocrit (JMHt), red blood cell (RBC) velocity and arteriolar vasomotion using endoluminal jejunal laser Doppler flow metry were studied in eight cardiac surgical patients before and during CPB at a temperature of 34 degrees C. RESULTS: Cardiopulmonary bypass and the accompanied hemodilution (25-30%) induced a 44% increase in JMP (P < 0.05) and a 42% increase in RBC velocity (P < 0.01), with no change in JMHt. The oscillation amplitude of JMP, at a fundamental frequency of 2.8 cycles min(-1), increased with 175% (P < 0.05) during CPB. Splanchnic oxygen extraction increased by 64% during CPB (P < 0.05). Stepwise multiple regression analysis identified systemic hematocrit, arterial O2 and CO2 tension and splanchnic oxygen extraction as independent predictors of RBC velocity during CPB (R2=0.63, P < 0.001). The oscillation amplitude of JMP was predicted by RBC velocity and splanchnic oxygen extraction (R2= 0.68, P <0.0001). CONCLUSIONS: The increase in RBC velocity and enhanced arteriolar vasomotion, as well as maintained jejunal mucosal hematocrit, are microcirculatory, compensatory mechanisms for the splanchic oxygen supply/demand mismatch seen during cardiopulmonary bypass in humans.

Aged↗
PubMed2003

Two-minute rapid eye movement (REM) density fluctuations in human REM sleep.

Rapid eye movement (REM) density fluctuations during REM sleep were studied in five healthy young adults (23-26 years of age). Appropriate electro-oculographic (EOG) montage and automated EOG analysis enabled the detection of horizontal, vertical, and oblique REMs. REM density time series based on these REMs were formed for all the REM periods of the subjects. Autoregressive (AR) spectral analysis of the REM density time series estimated periodicities in the range of 1.7-2.4 min for 14 of the 16 REM periods analyzed, regardless of duration or number of REMs. Four subjects had such periodicities in each of their REM periods and the fifth subject had such periodicities in half the REM periods. This REM density fluctuation at a periodicity of about 2 min may relate to an important 'rhythmic' component of the REM generating mechanism(s).

Adult↗
PubMed2003

Altered response in renal blood flow and oxygen tension to contrast media in diabetic rats.

PURPOSE: To investigate the effect of the contrast medium (CM) iopromide on renal microcirculation and oxygen tension in non-diabetic control and streptozotocin-diabetic Wistar Furth rats. MATERIALS AND METHODS: Oxygen tension was measured with Clark-type microelectrodes and blood flow with laser-Doppler flow probes. In order to differentiate between an acutely increased blood glucose concentration and a long-term diabetic state, some of the non-diabetic control rats were intravenously infused with glucose. RESULTS: CM decreased the medullary oxygen tension in control (non-diabetic normoglycemic) rats ( approximately 35%) but not in diabetic rats. Medullary blood flow in control rats increased after CM administration and remained elevated, while it was unchanged in the diabetic rats. In response to CM, glucose-infused control rats responded similarly to control animals in medullary oxygen tension, but similarly to diabetic rats in medullary blood flow. Contrary to in control rats, medullary oxygen tension was unchanged in diabetic animals after CM administration. CONCLUSION: Streptozotocin-diabetic rats have an altered response to intravenous injection of the CM iopromide compared to non-diabetic rats. The unaltered medullary oxygen tension, seen in the diabetic group after injection of CM, suggests that non-hemodynamic mechanisms are responsible for the increased frequency of renal failure commonly seen among diabetic patients.

Animals↗
PubMed2003

Et-A receptor antagonist BQ123 prevents radiocontrast media-induced renal medullary hypoxia.

PURPOSE: Renal vasoconstriction with resultant tissue hypoxia, especially in the renal medulla, has been suggested to play a role in contrast media (CM)-induced nephropathy. Endothelin (ET) is released into the blood stream following CM injection and has been proposed as a potential mediator through its vasoconstrictive properties. MATERIAL AND METHODS: To investigate the possible protective influence of ET-receptor antagonists against CM-induced reduction in renal function, we studied the effects of injection of iopromide with and without pretreatment with BQ123 (ET-A antagonist) or BQ788 (ET-B antagonist) on renal superficial cortical flow (CBF), outer medullary blood flow (OMBF) and outer medullary oxygen tension (pO2) in normal rats. RESULTS: Administration of CM (1600 mg I/kg b.w.) did not affect CBF in any of the groups. However, a transient decrease in OMBF occurred, which was unaffected by both BQ123 and BQ788. Also a transient decrease in outer medullary pO2 was induced by CM administration. The pO2 reduction was significantly smaller after pretreatment with BQ123, than after injection of CM alone or together with BQ788, and pO2 returned more rapidly to the control level. Neither receptor antagonist had an effect on CM-mediated increases in electrolyte excretion. CONCLUSION: In the normal rat, activation of ET-A receptors is partly involved in the depression of outer medullary pO2 caused by injection of iopromide. However, the decrease in OMBF after iopromide injection is not mediated by ET receptors. The beneficial effects of the ET-A receptor antagonist on CM-induced changes in outer medullary pO2 seem therefore not primarily mediated on the hemodynamic level but may rather involve tubular transport mechanisms.

Animals↗
PubMed2002

Voltage-sensitive dye mapping in Langendorff-perfused rat hearts.

An imaging system suitable for recordings from Langendorff-perfused rat hearts using the voltage-sensitive dye 4-[beta-[2-(di-n-butylamino)-6-naphthyl]vinyl]pyridinium (di-4-ANEPPS) has been developed. Conduction velocity was measured under hyper- and hypokalemic conditions, as well as at physiological and reduced temperature. Elevation of extracellular [K(+)] to 9 mM from 5.9 mM caused a slowing of conduction velocity from 0.66 +/- 0.08 to 0.43 +/- 0.07 mm/ms (35%), and reduction of the temperature to 32 degrees C from 37 degrees C caused a slowing from 0.64 +/- 0.07 to 0.46 +/- 0.05 mm/ms (28%). Ventricular activation patterns in sinus rhythm showed areas of early activation (breakthrough) in both the right and left ventricle, with breakthrough at a site near the apex of the right ventricle usually occurring first. The effects of mechanically immobilizing the preparation to reduce motion artifact were also characterized. Activation patterns in epicardially paced rhythm were insensitive to this procedure over the range of applied force tested. In sinus rhythm, however, a relatively large immobilizing force caused prolonged PQ intervals as well as altered ventricular activation patterns. The time-dependent effects of the dye on the rat heart were characterized and include 1) a transient vasodilation at the onset of dye perfusion and 2) a long-lasting prolongation of the PQ interval of the electrocardiogram, frequently resulting in brief episodes of atrioventricular block.

Animals↗
PubMed2001

The association between exposure to a rear-end collision and future health complaints.

Different symptoms, together with neck pain, have been attributed to persons with persistent complaints after a previous motor vehicle crash (MVC) and are sometimes referred to as the "late whiplash syndrome." A cohort study was conducted to determine whether exposure to a rear-end collision, with or without whiplash injury, is associated with future health complaints. The results regarding future neck or shoulder pain have previously been described, and the objective of the present report was to focus on outcomes other than neck pain. Included in the study were persons 18 to 65 years of age and covered by traffic insurance at one of the largest insurance companies in Sweden. Claim reports were collected from the period November 1987 to April 1988. Drivers exposed to a rear-end collision were divided into two subgroups: those with reported whiplash injury (n = 232) and those without reported whiplash injury (n = 204). For comparison, 3688 subjects who were unexposed to MVCs were selected, with consideration taken to the age and gender distribution in the exposed subgroups. The prevalence of different health complaints among the study subjects was estimated according to a mailed questionnaire at follow-up in 1994, 7 years after the rear-end collision. When exposed subjects with whiplash injury were compared to unexposed subjects, increased relative risks in the range of 1.6-3.7 were seen for headache, thoracic and low back pain, as well as for fatigue, sleep disturbances and ill health. No corresponding increased risks were found among the exposed subjects without reported whiplash injury. We conclude that rear-end collisions resulting in reported whiplash injuries seem to have a substantial impact on health complaints, even a long time after the collision. There is a need to identify factors that predict a non-favorable outcome in order to improve clinical management.

Accidents, Traffic↗
PubMed2001

Possible reasons for the prognostic value of troponin-T on admission in patients with ST-elevation myocardial infarction.

BACKGROUND: In patients with acute myocardial infarction and ST-segment elevation, increased troponin-T (TnT) on admission implies an increased mortality. OBJECTIVE: To elucidate the underlying mechanisms of the prognostic value of TnT. METHODS AND RESULTS: One hundred and one patients were included and all received thrombolytic treatment. The patients were compared according to TnT level on admission (cut-off 0.1 microg/l). Elevation of TnT was associated with long-term mortality and also with longer delay, more episodes of chest pain during the last 24 h and fewer noninvasive signs of reperfusion at 90 min. In the group with elevated TnT, the coronary angiography at 24 h showed a strong trend towards lower patency in the infarct-related artery. TnT was also associated with increased infarct size if a higher cut-off level (0.43 microg/l) was used. In univariate analysis, elevated TnT, longer delay, repeated chest pain, Q-waves on admission and reduced left ventricular (LV) function were significantly associated with long-term mortality. In multivariate models, only reduced LV function and less than TIMI (thrombolysis in myocardial infarction) grade 3 flow turned out to be significant independent risk factors. CONCLUSIONS: The prognostic value of TnT level on admission regarding long-term mortality was confirmed and seems mainly to be explained by its association with longer delay and recent myocardial damage, but its association with reduced effect of thrombolytic treatment, larger infarct size and impaired LV function might also be of importance.

Adult↗
PubMed2001

Myocardial Doppler tissue velocity improves following myocardial gene therapy with VEGF-A165 plasmid in patients with inoperable angina pectoris.

BACKGROUND: Myocardial tissue velocity and perfusion were studied in patients with severe angina pectoris following gene therapy by intramyocardial injection of phVEGF-A165 via thoracotomy. Plasma concentrations of VEGF-A increased postoperatively. Two months after treatment anginal status and myocardial tissue velocity improved and perfusion showed a tendency to improve. Tissue velocity imaging appears to be a sensitive, objective method for detecting changes in myocardial function following gene therapy. OBJECTIVE: To study effects on myocardial tissue velocity and perfusion in patients with angina pectoris following intramyocardial injection of phVEGF-A165 via thoracotomy. DESIGN: Open label, phase I/II. METHODS: Six patients with Canadian Cardiovascular Society (CCS) angina pectoris functional class III - IV and with major defects at adenosine stress single-photon emission computerized tomography (SPECT) were studied. In addition to SPECT, coronary angiography and dobutamine stress echocardiography with tissue Doppler velocity imaging were performed before and two months after gene transfer. RESULTS: Plasma concentrations of VEGF-A increased 2 to 3 times (P < 0.04) over baseline from 2 to 14 days after injection with normalization after 4 weeks. The CCS class improved about 40%, from 3.3 +/- 0.2 to 2.0 +/- 0.3 (P < 0.02) and nitroglycerine consumption decreased 30 - 40%, from 44 +/- 17 to 15 +/- 5 tablets per week (P < 0.05). The maximal systolic myocardial tissue velocity increased in all patients about 25% (P < 0.02) but did not reach the reference range. Myocardial perfusion at SPECT improved in four of the six patients. CONCLUSIONS: Anginal status, myocardial tissue velocity and perfusion can be improved by phVEGF-A165 intramyocardial injection. Tissue velocity imaging appears to be a sensitive, objective method for detecting changes in myocardial function following gene therapy.

Aged↗
PubMed2000

Assessing the needs of patients in pain: a matter of opinion?

STUDY DESIGN: A prospective cohort study including patients with nonspecific spinal pain was performed. OBJECTIVES: To investigate whether the use of expert judgment in routine practice can provide a basis for reliable decision making concerning the need for intervention in patients with spinal pain and their ability to benefit from treatment. SUMMARY OF BACKGROUND DATA: A wide range of instruments and techniques are used to assess and treat patients with spinal pain. Many instruments are used without being clinimetrically tested. METHODS: A questionnaire concerning the patients' need of treatment and their potential to assimilate it was sent to experts in the health care arena: physicians, physical therapists, social insurance officers. The experts included were those connected with patients participating in a larger outcome study. Two cohorts of patients (sample 1, n = 217; sample 2, n = 257) were followed for 6 and 12 months, during which time the patients' health and work status were mapped. RESULTS: No acceptable agreement was found between any of the experts' ratings of patients' needs and potential for rehabilitation. Logistic regression showed that the experts' judgments were based almost solely on the age of the patient. The prediction analyses showed that the most consistent predictor of the patients' status at the 6-month follow-up assessment was the patients' own belief in the existence of effective treatments and their perceived ability for learning to cope with the condition. CONCLUSIONS: Expert judgment as exercised in routine practice cannot be used as basis for reliable decision making concerning the need of the patient with spinal pain for intervention and the patient's ability to benefit from treatment.

Adult↗
PubMed2000

Effect of eliminating compensation for pain and suffering on the outcome of insurance claims for whiplash injury.

BACKGROUND AND METHODS: The incidence and prognosis of whiplash injury from motor vehicle collisions may be related to eligibility for compensation for pain and suffering. On January 1, 1995, the tort-compensation system for traffic injuries, which included payments for pain and suffering, in Saskatchewan, Canada, was changed to a no-fault system, which did not include such payments. To determine whether this change was associated with a decrease in claims and improved recovery after whiplash injury, we studied a population-based cohort of persons who filed insurance claims for traffic injuries between July 1, 1994, and December 31, 1995. RESULTS: Of 9006 potentially eligible claimants, 7462 (83 percent) met our criteria for whiplash injury. The six-month cumulative incidence of claims was 417 per 100,000 persons in the last six months of the tort system, as compared with 302 and 296 per 100,000, respectively, in the first and second six-month periods of the no-fault system. The incidence of claims was higher for women than for men in each period; the incidence decreased by 43 percent for men and by 15 percent for women between the tort period and the two no-fault periods combined. The median time from the date of injury to the closure of a claim decreased from 433 days (95 percent confidence interval, 409 to 457) to 194 days (95 percent confidence interval, 182 to 206) and 203 days (95 percent confidence interval, 193 to 213), respectively. The intensity of neck pain, the level of physical functioning, and the presence or absence of depressive symptoms were strongly associated with the time to claim closure in both systems. CONCLUSIONS: The elimination of compensation for pain and suffering is associated with a decreased incidence and improved prognosis of whiplash injury.

Accidents, Traffic↗
PubMed2000

Neck injuries in frontal impacts: influence of crash pulse characteristics on injury risk.

AIS1 neck injuries are the most frequent disabling injuries among car occupants in road traffic accidents. Although neck injury is mostly regarded as resulting from rear end collisions, almost one third of all neck injuries occur in frontal impacts. The injury mechanisms in both rear-end and frontal impacts are still not known, although different hypotheses exist. Since 1992, approx. 100,000 vehicles on the Swedish market have been equipped with crash recorders to measuring frontal impacts. This paper analyses the influence of different characteristics derived from the acceleration time history on the risk of short- and long-term disability to the neck in frontal impacts. The study includes injury outcomes from 187 restrained front seat occupants in 143 frontal collisions with an overlap exceeding 25%, where the crash pulses have been recorded using crash pulse recorders. The results show that the shape of the crash pulse influences the risk of long-term disability to the neck. The vehicle accelerations in the mid and last third of the crash pulse seem to be important. It is also shown how change of velocity and mean and peak accelerations influence the neck-injury risk. It is suggested that the risk of sustaining an AIS1 neck injury in frontal impacts could be reduced by using more effective pretensioners and more advanced belt-load limiters. These results may also have implications for neck injury mechanisms in rear-end impacts.

Acceleration↗
PubMed2000

The association between exposure to a rear-end collision and future neck or shoulder pain: a cohort study.

Neck pain is the most frequently reported feature in connection with whiplash injury, but it is also a common complaint in the general population. Therefore it is crucial to include an unexposed comparison group when evaluating the association between neck pain and a previous motor vehicle crash (MVC). To determine whether exposure to a rear-end collision, without or with whiplash injury, is associated with future neck or shoulder pain, a cohort study was conducted. The study population consisted of persons covered by traffic insurance at one of the largest insurance companies in Sweden. Claim reports were collected from the period November 1987 to April 1988. Drivers exposed to a rear-end collision were divided into two subgroups, without reported whiplash injury (n = 204) and with reported whiplash injury (n = 232). Two comparison groups, unexposed to MVCs, consisting of 1599 and 2089 persons, were selected with consideration taken to the age and gender distribution in the exposed subgroups. A questionnaire concerning neck or shoulder pain and other subjective health complaints was mailed to all the study subjects at follow-up in 1994, 7 years after the rear-end collision. The relative risk of neck or shoulder pain at follow-up was 1.3 (95% CI 0.8-2.0) in the exposed subjects without whiplash injury compared with the unexposed. The corresponding relative risk in subjects with whiplash injury was 2.7 (95% CI 2.1-3. 5). We conclude that there is no increased risk of future neck or shoulder pain in drivers who did not report whiplash injury in connection with a rear-end collision 7 years earlier. In drivers with reported whiplash injury, the risk of neck or shoulder pain 7 years after the collision was increased nearly three-fold compared with that in unexposed subjects.

Accidents, Traffic↗
PubMed2000

Direct and indirect time spent on care of dental trauma: a 2-year prospective study of children and adolescents.

The aim was to account for the total time spent by professional care-givers (direct time) and by patients and companions engaged as support and help (indirect time) to treat and otherwise attend to children and adolescents with dental trauma to primary and permanent teeth. The study was based on a random sample of 192 children and adolescents with dental traumas reported to an insurance company and prospectively followed up by telephone interviews over a period of 2 years after the trauma episode. On average, direct time represented 16% of total time for all visits for dental trauma to permanent teeth and 11% for trauma to primary teeth. The most extensive type of indirect time was transport time, which took up 30% of the total time spent on injuries to permanent teeth and 36% for injuries to primary teeth. Multiple regression analysis of the impact of dental and demographic injury variables on the time variables showed that complicated trauma was associated with extended time, direct as well as indirect, for permanent and primary teeth injuries. Our estimate of the average relative increase in total time spent by patients and companions in cases of complicated injury to permanent teeth was 117% (95% confidence interval [CI], 52-211) for patients and 112% (95% CI, 42-217) for companions. For transport time a strong predictor was access to a dental clinic near the place of residence. Lack of access could extend the average transport time by 180% (95% CI, 80-335) for patients and 163% (95% CI, 67-317) for their companions in cases of injuries to primary teeth.

Absenteeism↗
PubMed2000

Is asthma underestimated as a cause of sick leave?

Public interest needs to be focused on the economic burden of asthma on society because of the increasing prevalence of the condition. Asthma is common in individuals of working age and sick leave is an important health-economic issue. In the present study we looked at the prevalence of asthma in a sick leave register. Individuals on sick leave due to asthma, individuals on sick leave due to any other respiratory disorder or symptom and individuals on sick leave due to non-respiratory conditions were included in a questionnaire based study. Individuals in the register diagnosed with asthma could be classified as current asthmatics or possible asthmatics in respectively 94% and 99% of the cases. They were also ex-smokers to a greater extent than the other groups, which was more pronounced in males. However, individuals on sick leave due to 'any other respiratory disorder' could be classified as current asthmatics or possible asthmatics in respectively 19% and 30% of the cases. The corresponding figures in the group on sick leave due to 'other diagnoses' were 7% and 10%. Hence, there is evidence that asthma is an under-reported diagnosis and this must be taken into consideration when sick leave registers are used in health-economic studies.

Adolescent↗
PubMed2000

Mathematical simulation of slowing of cardiac conduction velocity by elevated extracellular.

We have studied the dependence of conduction velocity (theta) on extracellular potassium concentration ([K+]o) in a model of one-dimensional conduction using an idealized strand of human atrial cells. Elevated [K+]o in the 5-20 mM range shifts the resting potential (Vrest) in the depolarizing direction and reduces input resistance (Rin) by increasing an inwardly rectifying K+ conductance, I(Kl). Our results show that in this model: (1) theta depends on [K+]o in a "biphasic" fashion. Moderate elevations of [K+]o (to less than 8 mM) result in a small increase in theta, whereas at higher [K+]o (8-16 mM) theta is reduced. (2) This biphasic relationship can be attributed to the competing effects of (i) the smaller depolarization needed to reach the excitation threshold (Vthresh-Vrest) and (ii) reduced availability (increased inactivation) of sodium current, INa, as the cell depolarizes progressively. (3) Decreasing Rin reduces theta due to the increased electrical load on surrounding cells. (4) The effect on theta of [K+]o-induced changes in Rin in the atrium (as well as other high-Rin tissue, such as that of the Purkinje system or nodes) is likely to be small. This effect could be substantial, however, under conditions in which Rin is comparable in size to gap junction resistance and membrane resistance (inverse slope of the whole-cell current-voltage relationship) when sodium channels are open, which is likely to be the case in ventricular tissue.

Action Potentials↗