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1.
Ann Oncol ; 34(8): 681-692, 2023 08.
Artículo en Inglés | MEDLINE | ID: mdl-37211045

RESUMEN

BACKGROUND: In the PAOLA-1/ENGOT-ov25 primary analysis, maintenance olaparib plus bevacizumab demonstrated a significant progression-free survival (PFS) benefit in newly diagnosed advanced ovarian cancer patients in clinical response after first-line platinum-based chemotherapy plus bevacizumab, irrespective of surgical status. Prespecified, exploratory analyses by molecular biomarker status showed substantial benefit in patients with a BRCA1/BRCA2 mutation (BRCAm) or homologous recombination deficiency (HRD; BRCAm and/or genomic instability). We report the prespecified final overall survival (OS) analysis, including analyses by HRD status. PATIENTS AND METHODS: Patients were randomized 2 : 1 to olaparib (300 mg twice daily; up to 24 months) plus bevacizumab (15 mg/kg every 3 weeks; 15 months total) or placebo plus bevacizumab. Analysis of OS, a key secondary endpoint in hierarchical testing, was planned for ∼60% maturity or 3 years after the primary analysis. RESULTS: After median follow-up of 61.7 and 61.9 months in the olaparib and placebo arms, respectively, median OS was 56.5 versus 51.6 months in the intention-to-treat population [hazard ratio (HR) 0.92, 95% confidence interval (CI) 0.76-1.12; P = 0.4118]. Subsequent poly(ADP-ribose) polymerase inhibitor therapy was received by 105 (19.6%) olaparib patients versus 123 (45.7%) placebo patients. In the HRD-positive population, OS was longer with olaparib plus bevacizumab (HR 0.62, 95% CI 0.45-0.85; 5-year OS rate, 65.5% versus 48.4%); at 5 years, updated PFS also showed a higher proportion of olaparib plus bevacizumab patients without relapse (HR 0.41, 95% CI 0.32-0.54; 5-year PFS rate, 46.1% versus 19.2%). Myelodysplastic syndrome, acute myeloid leukemia, aplastic anemia, and new primary malignancy incidence remained low and balanced between arms. CONCLUSIONS: Olaparib plus bevacizumab provided clinically meaningful OS improvement for first-line patients with HRD-positive ovarian cancer. These prespecified exploratory analyses demonstrated improvement despite a high proportion of patients in the placebo arm receiving poly(ADP-ribose) polymerase inhibitors after progression, confirming the combination as one of the standards of care in this setting with the potential to enhance cure.


Asunto(s)
Antineoplásicos , Neoplasias Ováricas , Humanos , Femenino , Bevacizumab , Neoplasias Ováricas/tratamiento farmacológico , Neoplasias Ováricas/genética , Neoplasias Ováricas/patología , Antineoplásicos/uso terapéutico , Ftalazinas , Inhibidores de Poli(ADP-Ribosa) Polimerasas , Quimioterapia de Mantención
2.
Ann Oncol ; 33(10): 1021-1028, 2022 10.
Artículo en Inglés | MEDLINE | ID: mdl-35772665

RESUMEN

BACKGROUND: In the SOLO2 trial (ENGOT Ov-21; NCT01874353), maintenance olaparib in patients with platinum-sensitive relapsed ovarian cancer (PSROC) and BRCA mutation significantly improved progression-free survival (PFS) and prolonged overall survival (OS). Following disease progression on olaparib, efficacy of subsequent chemotherapy remains unknown. PATIENTS AND METHODS: We conducted a post-hoc hypothesis-generating analysis of SOLO2 data to determine the efficacy of different chemotherapy regimens following RECIST disease progression in patients who received olaparib or placebo. We evaluated time to second progression (TTSP) calculated from the date of RECIST progression to the next progression/death. RESULTS: The study population comprised 147 patients who received chemotherapy as their first subsequent treatment after RECIST progression. Of these, 69 (47%) and 78 (53%) were originally randomized to placebo and olaparib arms, respectively. In the placebo-treated cohort, 27/69 and 42/69 received non-platinum and platinum-based chemotherapy, respectively, compared with 24/78 and 54/78, respectively, in the olaparib-treated cohort. Among patients treated with chemotherapy (N = 147), TTSP was significantly longer in the placebo than in the olaparib arm: 12.1 versus 6.9 months [hazard ratio (HR) 2.17, 95% confidence interval (CI) 1.47-3.19]. Similar result was obtained on multivariable analysis adjusting for prognostic factors at RECIST progression (HR 2.13, 95% CI 1.41-3.22). Among patients treated with platinum-based chemotherapy (n = 96), TTSP was significantly longer in the placebo arm: 14.3 versus 7.0 months (HR 2.89, 95% CI 1.73-4.82). Conversely, among patients treated with non-platinum-based chemotherapy (n = 51), the TTSP was comparable in the placebo and olaparib arms: 8.3 versus 6.0 months (HR 1.58, 95% CI 0.86-2.90). CONCLUSIONS: Following progression from maintenance olaparib in the recurrent setting, the efficacy of platinum-based subsequent chemotherapy seems to be reduced in BRCA1/2-mutated patients with PSROC compared to patients not previously receiving poly (ADP-ribose) polymerase inhibitors (PARPi). The optimal strategy for patients who relapse after PARPi is an area of ongoing research.


Asunto(s)
Antineoplásicos , Neoplasias Ováricas , Adenosina Difosfato/uso terapéutico , Antineoplásicos/uso terapéutico , Proteína BRCA1/genética , Proteína BRCA2/genética , Carcinoma Epitelial de Ovario/tratamiento farmacológico , Carcinoma Epitelial de Ovario/genética , Progresión de la Enfermedad , Femenino , Humanos , Quimioterapia de Mantención , Recurrencia Local de Neoplasia/tratamiento farmacológico , Recurrencia Local de Neoplasia/genética , Neoplasias Ováricas/tratamiento farmacológico , Neoplasias Ováricas/genética , Ftalazinas , Piperazinas , Inhibidores de Poli(ADP-Ribosa) Polimerasas/uso terapéutico , Ribosa/uso terapéutico
3.
Regul Toxicol Pharmacol ; 103: 73-85, 2019 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-30634024

RESUMEN

Science peer review plays an important role in the advancement and acceptance of scientific information, particularly when used to support decision-making. A model for science peer review is proposed here using a large, multi-tiered case study to engage a broader segment of the scientific community to support decision making on science matters, and to incorporate many of the design advantages of the two common forms of peer review (journal peer review, science advisory panels). This peer review consisted of a two-tiered structure consisting of seven panels (five review panels in Tier 1, two review panels in Tier 2), which focused on safety data for a modified risk tobacco product (MRTP). Experts from all over the world were invited to apply to one or more positions on seven peer review panels. 66 peer reviewers were selected from available applicants using objective metrics of their expertise, and for some panels based upon a consideration of panel diversity with respect to demographic parameters (e.g., geographic region, sector of employment, years of experience). All peer reviewers participated anonymously in which a third-party auditor was used to provide independent verification of their expertise. Peer reviewers were provided electronic links to all review material which included access to publications, reports, omics data, and histopathology slides, with topic-specific panels focusing on topic-specific components of the review package. Peer reviews consisted either of single-round, or multi-round (e.g., modified Delphi) format. Peer reviewer responses to the charge questions were collected via an online survey system, and were assembled into a database. Responses in the database were subject to analyses to assess the degree of favorability (i.e., supportive of the review material), degree of consensus, reproducibility of replicate panels, hidden sources of bias, and outlier response patterns. Conclusions: By careful consideration of science peer review design elements we have shown that: 1) panel participation can be broadened to include scientists who would otherwise not participate; 2) panel diversity can be managed in an unbiased manner without adverse impacts to panel expertise; 3) results obtained from independent concurrent panels are shown to be reproducible; and 4) there are benefits of collecting input from expert panels via a structured format (i.e., survey) to support characterization of consensus, identification of hidden sources of bias, and identification of potential outlier participants.


Asunto(s)
Consenso , Toma de Decisiones , Ciencia , Humanos
4.
ESMO Open ; 8(3): 101213, 2023 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-37075697

RESUMEN

BACKGROUND: Up to 30% of metastatic breast cancer (BC) patients develop brain metastases (BM). Prognosis of patients with BM is poor and long-term survival is rare. Identification of factors associated with long-term survival is important for improving treatment modalities. PATIENTS AND METHODS: A total of 2889 patients of the national registry for BM in BC (BMBC) were available for this analysis. Long-term survival was defined as overall survival (OS) in the upper third of the failure curve resulting in a cut-off of 15 months. A total of 887 patients were categorized as long-term survivors. RESULTS: Long-term survivors compared to other patients were younger at BC and BM diagnosis (median 48 versus 54 years and 53 versus 59 years), more often had HER2-positive tumors (59.1% versus 36.3%), less frequently luminal-like (29.1% versus 35.7%) or triple-negative breast cancer (TNBC) (11.9% versus 28.1%), showed better Eastern Cooperative Oncology Group (ECOG) performance status (PS) at the time of BM diagnosis (ECOG 0-1, 76.9% versus 51.0%), higher pathological complete remission rates after neoadjuvant chemotherapy (21.6% versus 13.7%) and lower number of BM (n = 1, BM 40.9% versus 25.4%; n = 2-3, BM 26.5% versus 26.7%; n ≥4, BM 32.6% versus 47.9%) (P < 0.001). Long-term survivors had leptomeningeal metastases (10.4% versus 17.5%) and extracranial metastases (ECM, 73.6% versus 82.5%) less frequently, and asymptomatic BM more often at the time of BM diagnosis (26.5% versus 20.1%), (P < 0.001). Median OS in long-term survivors was about two times higher than the cut-off of 15 months: 30.9 months [interquartile range (IQR) 30.3] overall, 33.9 months (IQR 37.1) in HER2-positive, 26.9 months (IQR 22.0) in luminal-like and 26.5 months (IQR 18.2) in TNBC patients. CONCLUSIONS: In our analysis, long-term survival of BC patients with BM was associated with better ECOG PS, younger age, HER2-positive subtype, lower number of BM and less extended visceral metastases. Patients with these clinical features might be more eligible for extended local brain and systemic treatment.


Asunto(s)
Neoplasias Encefálicas , Neoplasias de la Mama Triple Negativas , Humanos , Neoplasias Encefálicas/terapia , Neoplasias Encefálicas/secundario , Pronóstico , Encéfalo
5.
ESMO Open ; 7(3): 100495, 2022 06.
Artículo en Inglés | MEDLINE | ID: mdl-35653983

RESUMEN

BACKGROUND: Up to 40% of patients with metastatic human epidermal growth factor receptor 2 (HER2)-positive breast cancer develop brain metastases (BMs). Understanding of clinical features of these patients with HER2-positive breast cancer and BMs is vital. PATIENTS AND METHODS: A total of 2948 patients from the Brain Metastases in Breast Cancer registry were available for this analysis, of whom 1311 had primary tumors with the HER2-positive subtype. RESULTS: Patients with HER2-positive breast cancer and BMs were-when compared with HER2-negative patients-slightly younger at the time of breast cancer and BM diagnosis, had a higher pathologic complete response rate after neoadjuvant chemotherapy and a higher tumor grade. Furthermore, extracranial metastases at the time of BM diagnosis were less common in HER2-positive patients, when compared with HER2-negative patients. HER2-positive patients had more often BMs in the posterior fossa, but less commonly leptomeningeal metastases. The median overall survival (OS) in all HER2-positive patients was 13.2 months (95% confidence interval 11.4-14.4). The following factors were associated with shorter OS (multivariate analysis): older age at BM diagnosis [≥60 versus <60 years: hazard ratio (HR) 1.63, P < 0.001], lower Eastern Cooperative Oncology Group status (2-4 versus 0-1: HR 1.59, P < 0.001), higher number of BMs (2-3 versus 1: HR 1.30, P = 0.082; ≥4 versus 1: HR 1.51, P = 0.004; global P = 0.015), BMs in the fossa anterior (HR 1.71, P < 0.001), leptomeningeal metastases (HR 1.63, P = 0.012), symptomatic BMs at diagnosis (HR 1.35, P = 0.033) and extracranial metastases at diagnosis of BMs (HR 1.43, P = 0.020). The application of targeted therapy after the BM diagnosis (HR 0.62, P < 0.001) was associated with longer OS. HER2-positive/hormone receptor-positive patients showed longer OS than HER2-positive/hormone receptor-negative patients (median 14.3 versus 10.9 months; HR 0.86, P = 0.03), but no differences in progression-free survival were seen between both groups. CONCLUSIONS: We identified factors associated with the prognosis of HER2-positive patients with BMs. Further research is needed to understand the factors determining the longer survival of HER2-positive/hormone receptor-positive patients.


Asunto(s)
Neoplasias Encefálicas , Neoplasias de la Mama , Neoplasias Encefálicas/secundario , Neoplasias de la Mama/tratamiento farmacológico , Femenino , Humanos , Receptor ErbB-2/metabolismo , Receptor ErbB-2/uso terapéutico , Sistema de Registros
7.
Geburtshilfe Frauenheilkd ; 75(6): 566-573, 2015 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-26166837

RESUMEN

A subcutaneous formulation of trastuzumab to treat patients with HER2-positive breast cancer is available since August 2013. The subcutaneous formulation is administered as a fixed dose of 600 mg over a period of up to 5 minutes. The HannaH trial compared subcutaneous with intravenous administration and found comparable pharmacokinetics, efficacy and tolerability for both administration forms of trastuzumab in the neoadjuvant setting. The randomized crossover study PrefHer reported a clear preference from the patient's point of view for subcutaneous over intravenous administration of trastuzumab. The accompanying time-and-motion study reported a reduction concerning the total time spent for the institution as well as for the patient receiving trastuzumab s. c.. The experience of 7 German centers largely corresponded with the results of these studies. Patients expressed a clear preference for subcutaneous trastuzumab administration, with the time saved by the subcutaneous administration route cited as the greatest benefit. Although the existing reimbursement terms mean that centers will receive a lower remuneration, the centers' overall evaluation of the subcutaneous administration route for trastuzumab was overwhelmingly positive. The greatest benefit cited by the centers was the flexibility in scheduling patient appointments. This increased flexibility improved conditions in some centers which were experiencing pressures due to a shortage of staff, particularly at peak times. The general consensus, however, was that the remuneration systems for oncological treatments urgently need to be amended to ensure that the real costs of treatment are covered, even if the administration route has changed.

8.
J Histochem Cytochem ; 23(4): 271-82, 1975 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-47870

RESUMEN

A cytochemical technique for localizing cytochrome oxidase activity, based upon the oxidative polymerization of 3,3-diaminobenzidine (DAB) to an osmiophilic reaction product, has been employed to test the possibility of extramitochondrial cytochrome oxidase in gastric mucosa. Deposition of reaction product was found to be exclusively localized within mitochondris; in particular, no reaction product was observed at the apical plasma membrane. Measurements of the effect of DAB on acid secretion revealed a biphasic action consisting of an initial stimulation followed by inhibition. The stimulation of secretion of DAB is interpreted to indicate that DAB is oxidized via a pathway which is linked to the secretory process. The combined cytochemical and physiological measurements provide evidence that the metabolic energy supply for acid secreation is derived from mitochondrial reactions. The results are discussed in relation to current models for the coupling between acid secreation and oxidative metabolism.


Asunto(s)
Complejo IV de Transporte de Electrones/análisis , Mucosa Gástrica/enzimología , Animales , Bencidinas/farmacología , Mucosa Gástrica/efectos de los fármacos , Mucosa Gástrica/ultraestructura , Histocitoquímica , Humanos , Microscopía Electrónica , Mitocondrias/ultraestructura , Consumo de Oxígeno , Rana catesbeiana , Coloración y Etiquetado
9.
Ann N Y Acad Sci ; 934: 37-51, 2001 May.
Artículo en Inglés | MEDLINE | ID: mdl-11460650

RESUMEN

In this paper, the topic of laminar to turbulent flow transition, as applied to the design of gas turbines, is discussed. Transition comes about when a flow becomes sufficiently unstable that the orderly vorticity structure of the laminar layer becomes randomly oriented. Vorticity with a streamwise component leads to rapid growth of eddies of a wide range of sizes and eventually to turbulent flow. Under "natural" transition, infinitesimal disturbances of selected frequencies grow. "Bypass transition" is a term coined to describe a similar process, but one driven by strong external disturbances. Transition proceeds so rapidly that the processes associated with "natural" transition seem to be "bypassed." Because the flow environment in the turbine is disturbed by wakes from upstream airfoils, eddies from combustor flows, jets from film cooling, separation zones on upstream airfoils and steps in the duct walls, transition is of the bypass mode. In this paper, we discuss work that has been done to characterize and model bypass transition, as applied to the turbine environment.

10.
Brain Res ; 678(1-2): 213-24, 1995 Apr 24.
Artículo en Inglés | MEDLINE | ID: mdl-7620891

RESUMEN

Whole cell patch clamping was used to investigate mechanisms of mixture suppression for in situ olfactory receptor neurons (ORNs) of the spiny lobster Panulirus argus. We used a set of single compounds and binary mixtures that have been used in previous biochemical studies of receptor-odorant binding, electrophysiological studies of spiking output from ORNs, and behavioral studies. These odorants were adenosine 5'-monophosphate (AMP), betaine (Bet), L-cysteine (Cys), L-glutamate (Glu), taurine (Tau), ammonium chloride, D,L-succinate, binary mixtures of these compounds, as well as a 33-component artificial oyster mixture (AOM). For the 40 ORNs studied, these stimuli more frequently elicited inward than outward currents. AMP, Glu, Tau and Bet evoked the largest and most numerous inward currents; Cys most commonly evoked outward currents. Na+ was an important charge-carrying ion for the Glu-evoked response in one ORN and the Bet-evoked response in another ORN. Mixture suppression, defined conservatively in this study as cases where the response to a binary mixture was less than the response to the more excitatory component of that mixture, was observed in 6 ORNs. In all 6 cases, neither component of the mixture evoked an outward conductance (i.e. neither was inhibitory). Five of these cases of mixture suppression involved a mixture containing two excitatory compounds (i.e. producing inward conductances): four ORNs were excited by both Glu and AMP, and one ORN was excited by both Tau and Glu. One case of mixture suppression occurred for a compound (Tau) tha did not produce a current when presented alone but which when added to Bet suppressed the inward current generated by Bet. Mechanisms for these suppressions are discussed, including inhibition of receptor binding by the components of a binary mixture and effects on second messengers or ion channels.


Asunto(s)
Nephropidae/fisiología , Neuronas/fisiología , Neuronas Receptoras Olfatorias/fisiología , Adenosina Monofosfato/farmacología , Animales , Electrofisiología , Potenciales Evocados , Ácido Glutámico/farmacología , Técnicas de Placa-Clamp , Sodio/farmacología
11.
Regul Toxicol Pharmacol ; 26(3): 257-70, 1997 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-9441916

RESUMEN

Using the Monte Carlo method and physiologically based pharmacokinetic modeling, an occupational inhalation exposure to trichloroethylene consisting of 7 h of exposure per day for 5 days was simulated in populations of men and women of 5000 individuals each. The endpoint of concern for occupational exposure was drowsiness. The toxicologic condition leading to drowsiness was assumed to be high levels of both trichloroethanol and trichloroethylene. Therefore, the output of the simulation or dose metric was the maximum value of the sum of the concentration of trichloroethylene in blood and the concentration of trichloroethanol within its volume of distribution occurring within 1 week of exposure. The distributions of the dose metric in the simulated populations were lognormal. To protect 99% of a worker population, a concentration of 30 ppm over a 7-h period of the work day should not be exceeded. Subjecting a susceptible individual (the 99th percentile of the dose metric) to 200 ppm (the ACGIH short-term exposure limit or STEL) for 15 min twice a day over a work week necessitates a 2.5-h rest in fresh air following the STEL exposure to allow the blood concentrations of trichloroethylene and trichloroethanol to drop to levels that would not cause drowsiness. Both the OSHA PEL and the ACGIH TLV are greater than the value of 30 ppm derived here. As well as suggesting a new occupational guidance value, this study provides an example of this method of guidance value derivation.


Asunto(s)
Simulación por Computador , Modelos Biológicos , Método de Montecarlo , Exposición Profesional , Solventes/farmacocinética , Solventes/toxicidad , Tricloroetileno/farmacocinética , Tricloroetileno/toxicidad , Administración por Inhalación , Compartimentos de Líquidos Corporales , Relación Dosis-Respuesta a Droga , Etilenclorhidrina/análogos & derivados , Etilenclorhidrina/sangre , Etilenclorhidrina/farmacocinética , Etilenclorhidrina/toxicidad , Femenino , Humanos , Masculino , Sensibilidad y Especificidad , Tricloroetileno/sangre
12.
J Neurophysiol ; 71(2): 454-66, 1994 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-7909838

RESUMEN

1. We examined high-threshold synaptic transmission between oscillatory pairs of leech heart interneurons. Inhibitory postsynaptic currents (IPSCs) could be reliably evoked by depolarizing the presynaptic neuron in voltage clamp from a holding potential of -35 mV. At this presynaptic potential, the Ca2+ currents underlying graded transmission are completely inactivated, and we conclude that a high-threshold Ca2+ current is extant in heart interneurons. Further evidence for this was that inhibitory postsynaptic currents were blocked when Co2+ replaced Ca2+ in the saline and thus high-threshold transmission was dependent on the presence of external Ca2+. 2. When IPSCs were evoked by a 200-ms duration voltage step from a holding potential of -35 mV in the presynaptic neuron, the time course of turn-on of the IPSC consisted of a fast (time-to-peak = 17.5 +/- 1.93 (SE) ms [n = 7]) and a slow (time-to-peak = 250 +/- 28.5 ms [n = 8]) component. FMRF-NH2 reduced the amplitude of the fast component but did not affect the slow component. When the presynaptic voltage step was ended the IPSC turned off with a single exponential time course. FMRF-NH2 slowed the time course of turn-off of the IPSC. 3. When IPSCs were evoked by a 1500-ms duration voltage step from a holding potential of -35 mV in the presynaptic neuron, these IPSCs peaked around 300 ms. Following the peak, the IPSC decayed with a single exponential time course. FMRF-NH2 accelerated the time course of this decay. At potentials of 0 mV and +5 mV, FMRF-NH2 produced a significant decrease in the peak current and at potentials of -5 mV and 0 mV, produced a significant decrease in the current integral. 4. High-threshold IPSCs could also be evoked by a spike in the presynaptic neuron. Bath application of 1 microM FMRF-NH2 decreased the amplitude of the spike-evoked IPSC and slowed the time course of its falling phase. 5. We examined the effect of FMRF-NH2 on the quantal synaptic transmission. Bath-application of FMRF-NH2 increased binomial p, the probability of release, and decreased binomial n, the number of units available for release. FMRF-NH2 had no effect on q, the unit size, when calculated from the distributions of PSPs, and increased the coefficient of variation (CV). 6. The lack of a change in q and the increase in CV suggested that FMRF-NH2 acted at a presynaptic location.(ABSTRACT TRUNCATED AT 400 WORDS)


Asunto(s)
Calcio/fisiología , Corazón/inervación , Interneuronas/efectos de los fármacos , Neuropéptidos/farmacología , Neurotransmisores/farmacología , Sinapsis/efectos de los fármacos , Transmisión Sináptica/efectos de los fármacos , Animales , FMRFamida , Ganglios de Invertebrados/efectos de los fármacos , Ganglios de Invertebrados/fisiología , Frecuencia Cardíaca/efectos de los fármacos , Frecuencia Cardíaca/fisiología , Interneuronas/fisiología , Sanguijuelas , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Inhibición Neural/efectos de los fármacos , Inhibición Neural/fisiología , Neuropéptidos/fisiología , Neurotransmisores/fisiología , Umbral Sensorial/efectos de los fármacos , Umbral Sensorial/fisiología , Sinapsis/fisiología , Transmisión Sináptica/fisiología
13.
J Neurosci ; 12(2): 525-37, 1992 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-1346805

RESUMEN

Using single-electrode voltage clamp, heart interneurons of the medicinal leech were shown to possess both a rapidly inactivating outward current, IA, and a more slowly inactivating outward current, IK. IA and IK could be separated by their voltage sensitivity and kinetic properties. FMRF-NH2 (Phe-Met-Arg-Phe-NH2) modulates IK by shifting both steady state activation and inactivation to more hyperpolarized potentials, but it does not affect the time constants. IA and IK appear to use K+ as a charge carrier; a change in the external [K+] produced a shift in the apparent reversal potential in the direction predicted with potassium as the charge carrier. Both IA and IK are sensitive to tetraethylammonium (TEA) and 4-aminopyridine (4-AP), and TEA and 4-AP both interfere with the effects of FMRF-NH2 on IK. The biophysical properties of IA and of IK in the presence and absence of FMRF-NH2 were incorporated into a Hodgkin-Huxley model of these currents that could reproduce voltage-clamp data. FMRF-NH2 produces two apparently dissimilar effects on the heartbeat rhythm--acceleration and disruption. We suggest that both effects could result from the hyperpolarizing shifts in steady state activation and inactivation of IK.


Asunto(s)
Interneuronas/fisiología , Neuropéptidos/farmacología , Neurotransmisores/farmacología , 4-Aminopiridina/farmacología , Animales , Calcio/farmacología , Cobalto/farmacología , Ácido Egtácico/análogos & derivados , Ácido Egtácico/farmacología , Conductividad Eléctrica/efectos de los fármacos , Potenciales Evocados/efectos de los fármacos , FMRFamida , Ganglios/fisiología , Sistema de Conducción Cardíaco/efectos de los fármacos , Técnicas In Vitro , Interneuronas/efectos de los fármacos , Hormonas de Invertebrados/farmacología , Cinética , Sanguijuelas , Sodio/farmacología , Tetraetilamonio , Compuestos de Tetraetilamonio/farmacología
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