Effects of hypoxia on calcium fluxes and force development in the neonatal rat atrium.

The effects of hypoxia on 45calcium fluxes and force development were studied in the resting and stimulated (high potassium/low sodium solutions or Bay K 8644) neonatal rat atrium. Under normoxic conditions, high potassium (100 mmol.litre-1)/low sodium Tyrode solution and Bay K 8644 (2.5 X 10(-5) mol.litre-1) significantly increased calcium uptake above that measured in normal Tyrode solution. High potassium/low sodium Tyrode solution elicited a sustained tonic contracture. Bay K 8644 did not increase resting tension but induced spontaneous phasic contractions in some preparations. Hypoxia failed significantly to alter resting calcium uptake but partially inhibited (50-90%) the high potassium/low sodium and Bay K 8644 induced calcium uptake (that is, the calcium uptake above that measured in normal Tyrode solution). The magnitude of the high potassium/low sodium induced contracture was increased by hypoxia (15 min). Bay K 8644 had no effect on resting tension (in five out of six experiments) after 15 min of hypoxia. Acidosis failed to affect resting (with the exception of the 210 min time point), high potassium/low sodium induced, and Bay K 8644 induced calcium uptakes and had little effect on the high potassium/low sodium induced contracture. It is hypothesised that hypoxia reduces the cells' ability to regulate calcium. Furthermore, it appears that hypoxia's effects on calcium fluxes and the high potassium induced contracture involve other mechanisms besides the associated acidosis.

Uterine sarcoma: twenty-seven years of experience.

PURPOSE: A correlation of treatment for uterine sarcoma with outcome, prognostic importance of pathology, and clinical parameters. PATIENTS AND METHODS: One hundred forty-one patients (median age: 56 years, range: 19-85 years) with a histologically verified uterine sarcoma were identified from a database compiled at the Royal Marsden Hospital and the University of Florence between 1974 and 2001. Seventy-two patients had leiomyosarcoma, 42 had mixed müllerian tumors, 22 had endometrial stromal sarcoma, 1 hemangiopericytoma, 1 rhabdomyosarcoma, and 3 patients had unspecified sarcoma. According to FIGO classification, Stage I, II, III, and IV tumors were identified in 71, 13, 31, and 26 patients, respectively. RESULTS: At the time of analysis, 73.7% of patients were dead, and 26.3% were alive with a median survival of 2 years from initial diagnosis. Univariate analysis for cause-specific survival demonstrated statistical significance for histology (p = 0.02), grade (p = 0.003), stage (p = 0.007), and age (p = 0.02). Multivariate analysis demonstrated significant prognostic values for stage (p = 0.02) and histology (p = 0.05) only. Postoperative radiotherapy with a total dose higher than 50 Gy seems to be significant (p = 0.001) in reducing local recurrence. CONCLUSIONS: Our data favor treatment for Stages I, II, and III of uterine sarcoma with radical surgery plus radical dose irradiation comprising both external beam radiotherapy and brachytherapy.

Design and synthesis of 4-substituted benzamides as potent, selective, and orally bioavailable I(Ks) blockers.

Multiple delayed rectifier potassium currents, including I(Ks), are responsible for the repolarization and termination of the cardiac action potential, and blockers of these currents may be useful as antiarrhythmic agents. Modification of compound 5 produced 19(S) that is the most potent I(Ks) blocker reported to date with >5000-fold selectivity over other cardiac ion channels. Further modification produced 24A with 23% oral bioavailability.

A Ca2+-activated K+ channel from rabbit aorta: modulation by cromakalim.

A large conductance Ca2+-activated K+ channel from rabbit aorta was incorporated into planar lipid bilayers. This channel had a conductance of 337 +/- 7 pS in symmetrical 250 mM KCl solutions and had a Na+/K+ permeability ratio of less than 0.04. In asymmetrical solutions containing 300 mM KCl cis (intracellular), 100 mM KCl trans (extracellular) or 100 mM KCl cis 500 mM KCl trans, the reversal potentials for the channel were -30 and +46 mV, respectively. This channel possessed voltage-dependent activation and cis (intracellular) Ca2+ sensitivity. Cromakalim (50 nM) added to the trans side of the bilayer significantly increased the Popen by 56% from 0.09 +/- 0.01 to 0.14 +/- 0.01 (P less than 0.01) at -40 mV without altering the single channel conductance. This effect was dose-dependent, increasing at higher cromakalim concentrations. The primary effect of cromakalim was to decrease the tau slow of the channel closed state from 266 +/- 32 to 147 +/- 17 ms which is sufficient to account for the increase in Popen of the channel in the presence of cromakalim.

Functional role of endothelin ETA and ETB receptors in venous and arterial smooth muscle.

The functional importance of endothelin ETA and ETB receptors in selected arterial and venous smooth muscle preparations was characterized. Endothelin-1 induced force in the saphenous and jugular veins is normally mediated by endothelin ETB-like receptors. However, desensitization or pharmacological block of these receptors reveals an endothelin ETA receptor population that is of sufficient size to mediate full endothelin-1-evoked force. Block of either endothelin ETA or endothelin ETB receptors alone is insufficient to antagonize endothelin-1-evoked force in saphenous vein. Endothelin-1-induced force in hamster aorta may also be mediated by activation of both endothelin ETA and ETB receptors. However, activation of endothelin ETB-like receptors alone is insufficient to generate a full endothelin-1 response. Sarafotoxin S6c treatment, to desensitize endothelin ETB receptors, failed to affect the responses of rat aorta and rabbit carotid artery to endothelin-1 or endothelin ETA receptor antagonists. These findings indicate that selective endothelin receptor antagonists will vary enormously in their efficacy against endothelin-induced force in different vascular beds.

The intracellular calcium stores in the rabbit trachealis.

We investigated the role of the intracellular Ca2+ stores in the regulation of the rabbit tracheal smooth muscle contraction. Carbachol (10 microM)- and 80K-induced contractions were reduced by preincubating tissues in Ca2+-free (EGTA-PSS) solution. Contractile amplitude plotted as a function of the duration of EGTA-PSS preexposure was described by a biexponential for carbachol and a monoexponential for 80K. In EGTA-PSS, a prior caffeine (50 mM)-induced contraction prevented any subsequent phasic carbachol response; the converse was also true. In contrast, prior exposure to 80K increased the amplitude of a subsequent carbachol or caffeine contraction measured in EGTA-PSS. Repletion of Ca2+ plus either 80K or a low concentration of carbachol (0.3 microM) resulted in delayed tension development. Preincubation in forskolin (10(-5) M) in PSS also delayed tension development. We propose that the internal stores, most likely the sarcoplasmic reticulum in the airway muscle function both to supply and remove Ca2+ from the cytoplasm.

Identification of [3H]P1075 binding sites and P1075-activated K+ currents in ovine choroid plexus cells.

This study examined the pharmacological characteristics of binding sites for the potent K+ channel opener [3H]P1075, as well as the functional effects of P1075 on ionic currents and membrane potential, in ovine choroid plexus (OCP) cells. [3H]P1075 bound to OCP cells with a Kd of 26 +/- 4 nM and a Bmax of 10400 +/- 480 sites/cell. Labelled sites were stereoselective and inhibited by potassium channel openers with a rank order of potency: P1075 > BMS-182264, ((4-[[9cyanoimino)[(1,2,2-trimethylpropyl)amino]-methyl]amino]benz onitrile) > pinacidil >> nicorandil > diazoxide. The K(ATP) channel antagonist glyburide inhibited [3H]P1075 binding with a Ki of 2 microM. The presence of K(ATP) channels on OCP cells was examined by patch clamp and fluorescent (membrane-potential sensitive dye) techniques. In some cells, P1075 activated an outward potassium current which was blocked by glyburide. P1075 produced a glyburide-sensitive, concentration-dependent, hyperpolarization of OCP cells. Levcromakalim hyperpolarized more strongly than its 3R,4S enantiomer, BRL 38226 ((3R-trans)-3,4-dihydro-3-hydroxy-2,2-dimethyl-4-(2-oxo-1-pyrrolidinyl)- 2H-1-benzopyran-6-carbonitrile) indicating a stereoselective interaction. These data indicate that epithelial OCP cells contain glyburide-sensitive K(ATP) channels.

A comparison between the effects of BMS-180448, a novel K+ channel opener, and cromakalim in rat and dog.

BMS-180448 [(3S-trans)-N-(4-chlorophenyl)-N'-cyano-N"-(6-cyano-3, 4-dihydro-3-hydroxy-2,2-dimethyl-2H-1-benzopyran-4-yl) guanidine] is a structural analog of cromakalim, which was found to similarly decrease ischemic injury, but was 18- to 100-fold less potent as a vasodilator. In the present study, the vascular and cardiac effects of cromakalim and BMS-180448 were evaluated in both in vitro and in vivo preparations. Cromakalim evoked a concentration-dependent relaxation to a K(+)-induced contracture in rat aorta. BMS-180448 behaved in a similar fashion but was 18-fold less potent than cromakalim. Measurements of ischemic damage made in isolated perfused rat hearts demonstrated that cromakalim and BMS-180448 were equipotent as cardioprotective agents; time to contracture was increased with an EC25 value of 4.8 and 4.7 microM, respectively, and lactate dehydrogenase levels were significantly reduced compared to those in the presence of vehicle. In vivo electrophysiologic studies in anesthetized dogs were conducted at basic cycle lengths of 400, 333, and 286 ms, and showed that BMS-180448 caused no significant effect on electrophysiologic parameters with the exception of decreasing atrial effective refractory periods by 12 +/- 3% and 17 +/- 4% at 3 and 10 mg/kg, respectively. There was also a significant drop in mean blood pressure of 18 +/- 5% and 33 +/- 4% at these doses. In contrast, cromakalim was shown to produce shortening of atrial to His conduction time (20 +/- 7%; basic cycle length = 286 ms), atrial effective refractory period (34 +/- 3%; basic cycle length = 400 ms), ventricular effective refractory period (14 +/- 2%; basic cycle length = 400 ms), wavelength (13 +/- 3%; basic cycle length = 400 ms), PR-interval (14 +/- 3%; basic cycle length = 333 ms) and mean blood pressure (65 +/- 3%; basic cycle length = 400 ms) at a dose of 0.3 mg/kg. No supraventricular or ventricular arrhythmias were observed for either compound tested. Based on the reduced cardiac electrophysiologic and vascular effects of BMS-180448, we suggest that BMS-180448 should provide cardioprotective efficacy similar to cromakalim with reduced risk of hypotension or arrhythmias.

The novel cardioprotective agent BMS-180448 activates a potassium conductance in cardiac and vascular smooth muscle.

The goal of the present study was to further characterize the effects of the novel cardioprotective agent BMS-180448 on potassium fluxes in cardiac and vascular smooth muscle. Exposure of voltage-clamped guinea pig ventricular myocytes to BMS-180448 (300 microM) produced an inhibition of IK followed by the delayed (5.5 +/- 0.5 min) activation of a large time-independent potassium current. At 100 microM, BMS-180448 produced only inhibition of IK. The BMS-180448 activated current was refractory to block by 30 microM glyburide but was largely inhibited by 100 microM alinidine (84 +/- 6% inhibition at +40 mV). Cromakalim (100 microM)-activated currents were fully inhibited by 3 microM glyburide and 79 +/- 4% blocked by 100 microM alinidine. The current responses to BMS-180448 were unaffected by the inclusion of 10 mM UDP (100 microM ATP) in the pipette. BMS-180448 also produced a concentration-dependent increase in 86Rb efflux from aortic strips; efflux responses were increased in low calcium medium and fully antagonized by 3 microM glyburide. Thus, BMS-180448 activates a potassium conductance in both cardiac and smooth muscle. The glyburide sensitivity of the BMS-180448-induced increase in 86Rb efflux from the aortic preparations suggests that this drug activates IKATP in vascular smooth muscle. Moreover, the observation that BMS-180448 (100 microM) partially inhibits the effects of cromakalim in ventricular muscle cells suggests that these drugs interact, directly or indirectly, with a common site in cardiac muscle.

Cellular electrophysiology of coronary artery ligation in chronic pressure overload.

We evaluated ischemia-induced cellular electrophysiologic abnormalities in chronic pressure overload ventricular myocardium in vitro. Left ventricular systolic hypertension was induced in cats via partial supracoronary aortic constriction (overload); at 1 1/2-3 months, resulting pressure overload was accompanied by ventricular hypertrophy (25-35% by weight) and patchy endocardial fibrosis. Two hours of subsequent acute myocardial ischemia (ischemia) was imposed on overload (ischemia/overload) via total occlusion of distal branches of the left coronary artery system. Spontaneous premature depolarizations in vitro were increased in ischemia/overload compared to control, ischemia or overload alone; bursts of spontaneous, repetitive depolarizations were also unique to these preparations. Multiple site recordings of endocardial transmembrane action potentials overlying the borders (interface) of fibrotic areas in ischemia/overload demonstrated numerous electrophysiologic abnormalities, including several not observed in control, ischemia or overload. Unique to the border areas of ischemia/overload preparations was the presence of maintained but depressed resting potential without action potentials; also, the incidence of depolarizations at the onset of the plateau phase was highest in these preparations. In non-fibrotic areas, electrophysiologic properties including resting potential and action potential amplitude and rate of rise were diminished in ischemia/overload compared to ischemia or overload preparations. These data demonstrate that acute myocardial ischemia in the setting of chronic pressure overload leads to additional cellular electrophysiologic abnormalities compared to ischemia or overload alone.

Palliative chemotherapy in recurrent carcinoma of the cervix: an audit of the use of ifosfamide and review of the literature.

A review was conducted on 34 patients treated with intravenous ifosfamide for relapsed, inoperable carcinoma of the cervix between 1988 and 1996. The median age of patients was 44 years. Thirty-two patients had squamous cell carcinoma and 2 had adenocarcinoma. Radiotherapy had been used in primary management in 33, neo-adjuvant platinum chemotherapy in 7, and previous palliative chemotherapy in 11. Symptomatic response was assessed with respect to the symptom requiring palliaton. 25 patients failed to complete 6 cycles of chemotherapy: due to progressive disease in 14, lack of symptom response in 2, and toxicity in 11 of whom 7 had encephalopathy sufficient to abandon treatment. 32 patients were evaluable for objective response. Pathologic complete response (CR) was achieved in 1 patient, and partial response (PR) was achieved in 3 patients. The objective response rate was 11.8%. Symptomatic response throughout treatment occurred in 8 patients (24%); objective response was seen in only 3 (1 CR, 2 PR) of them and progressive disease in the remaining 5. Response duration in the 4 objective responders was 25 months in the patient with CR and 4, 6 and 8 weeks in the 3 patients with PR. In conclusion, ifosfamide, as given, is associated with unacceptable toxicity and insufficient symptomatic efficacy for use as a palliative treatment in patients with relapsed carcinoma of the cervix.

An audit of outcome of adjuvant post-operative radiotherapy for 52 women with stage II carcinoma of the endometrium.

A retrospective review was undertaken of the medical records of 52 women with stage II carcinoma of the endometrium who received adjuvant radiotherapy following surgery. The information was obtained from medical notes and a hospital database. Actuarial disease-free survival was 68% at 5 years for those women with stage IIA disease, and 70% at 5 years for those women with stage IIB disease. 6 of the women (11.5%) had side effects from treatment. In contrast to the literature, the only statistically significant prognostic factor in this study was histological differentiation; patients with poorly differentiated tumours fared worse (p = 0.05). This may indicate that a greater number than 52 women is needed to demonstrate weaker prognostic factors such as substage. A larger review is being undertaken of the remaining women recorded on the database, with stage I, III and IV disease.

Stage IV endometrial carcinoma: a 10 year review of patients.

Stage IV endometrial cancer is uncommon, often occurs in elderly patients and has a poor prognosis, which makes the choice of treatment difficult. 18 patients with stage IV endometrial cancer presenting over a 10 year period, between 1987 and 1997, were reviewed with regard to mode of treatment and response. The mean age was 65 years. Five had disease confined to the pelvis and 13 had extra pelvic disease. 15 of 18 patients had a total abdominal hysterectomy (TAH). One patient received radiotherapy alone and five received post-operative radiotherapy. Overall freedom from pelvic symptoms was achieved in seven of 18 patients. All seven had undergone TAH and two had received post-operative radiotherapy. Progestogens were given to 13 patients. Six received progestogens alone, without radiotherapy or chemotherapy. Of these, two responded, one for 9 months and one with verified lung metastases, who had a complete response, is still alive at 6.5 years. Eight patients received chemotherapy, with single agent cisplatin or carboplatin AUC 6. Three patients responded, one for 4.5 years. The overall median survival was 12 months from diagnosis. Actuarial 5 year survival was 15% (CI 3-36). There was no significant survival difference for, hormone therapy or chemotherapy. Stage IV endometrial cancer has a poor prognosis but durable response can be achieved in some patients.

Calcium entry through receptor-operated channels in bovine pulmonary artery endothelial cells.

The activation of endothelial cells by endothelium-dependent vasodilators has been investigated using bioassay, patch clamp and 45Ca flux methods. Cultured pulmonary artery endothelial cells have been demonstrated to release EDRF in response to thrombin, bradykinin, ATP and the calcium ionophore A23187. The resting membrane potential of the endothelial cells was -56 mV and the cells were depolarized by increasing extracellular K+ or by the addition of (0.1-1.0 mM)Ba2+ to the bathing solution. The electrophysiological properties of the cultured endothelial cells suggest that the membrane potential is maintained by an inward rectifying K+ channel with a mean single channel conductance of 35.6 pS. The absence of a depolarization-activated inward current and the reduction of 45Ca influx with high K+ solution suggests that there are no functional voltage-dependent calcium or sodium channels. Thrombin and bradykinin were shown to evoke not only an inward current (carried by Na+ and Ca2+) but also an increase in 45Ca influx suggesting that the increase in intracellular calcium necessary for EDRF release is mediated by an opening of a receptor operated channel. High doses of thrombin and bradykinin induced intracellular calcium release, however, at low doses of thrombin no intracellular calcium release was observed. We propose that the increased cytosolic calcium concentration in endothelial cells induced by endothelium dependent vasodilators is due to the influx of Ca2+ through a receptor operated ion channel and to a lesser degree to intracellular release of calcium from a yet undefined intracellular store.

Safety of lasalocid in turkeys and its compatibility with tiamulin.

An investigation involving 640 turkeys demonstrated that the inclusion of lasalocid continuously from day-old to 16 weeks of age, at levels up to 375 ppm in the feed, produced no adverse effects; furthermore, the inclusion of 125 ppm lasalocid in the feed was compatible with the administration of 250 ppm tiamulin in the drinking water continuously for five days to turkeys over the same age range.

Mechanism of calcium activation in vascular smooth muscle.

The primary stimulus for activation of vascular smooth muscle is an increase in the cytosolic free Ca2+ concentration. The level of activating Ca2+ is determined by a variety of Ca2+ homeostatic mechanisms. Ca2+ entry from the extracellular space occurs through the resting Ca2+ leak and the excitable Ca2+ channels: viz. voltage-gated, receptor-operated and stretch-activated channels. Ca2+ release from sarcoplasmic reticulum is induced by inositol triphosphate (IP3) and, possibly, by Ca2+ itself. Activating Ca2+ binds to calmodulin, forming a complex which induces myosin light chain phosphorylation and initiates smooth muscle contraction. The continuous Ca2+ entry together with the higher Ca2+ sensitivity of the contractile apparatus can then maintain smooth muscle tension. Ca2+ buffering by the sarcoplasmic reticulum and Ca2+ extrusion by Ca2+ pumps serve to lower the cytosolic free Ca2+ concentration. These Ca2+-lowering mechanisms are possibly regulated by cyclic nucleotides.

The identified needs of ethnic minority groups with cancer within the community: a review of the literature.

The literature suggests that healthcare provision for ethnic minority groups is poorer than for the majority population. The intention of this paper is to review the literature available on healthcare provision for ethnic minority groups to see if this is the case for those with cancer. The introduction in the UK of monitoring of ethnic origins in the general population and healthcare service is recent and means that there are few data available. At present, cancer mortality is lower among ethnic minority groups than the majority population in the UK, which may partly be explained by a younger than average age within the ethnic minority groups and the fact that some members of ethnic groups retire to their country of origin. However, the mortality rates are expected to increase as the population ages. Breast and lung cancers are the most common cancers among ethnic minority groups in the UK. Traditional intervention strategies have been aimed at the majority white population and have not taken into account the needs identified by the ethnic communities themselves. Intervention strategies include advice on stopping smoking and chewing tobacco, increasing use of screening services by ethnic minority groups, targeted health promotion messages and education on cancer specifically for these groups. More data are required on cancer among ethnic minority groups in the UK. There are many similarities in the use of cancer services between ethnic minority groups and individuals with lower socioeconomic status in the UK.

Ca2+ transport systems mediating the high K+/low Na+-induced uptake of Ca2+ into rat atrium.

The effect of high K+/low Na+-Tyrode's solution on Ca2+ uptake into neonatal rat atrium was studied using 45Ca2+. Substitution of 60-129 mM Na+ in Tyrode's solution by equimolar concentrations of K+ or choline, significantly (with the exception of 60 mM choline substitution) increased Ca2+ uptake above control. Furthermore, the Ca2+ uptake stimulated by K+ substitution was significantly greater than that stimulated by choline substitution at the corresponding concentrations. The choline/low Na+-induced Ca2+ uptake (i.e. that above the Ca2+ uptake measured in normal Tyrode's solution) was increased by pre-exposure to either ice-cold Tyrode's solution for 1 h (approximately 36% increase) or to K+-free Tyrode's solution for 3 h (approximately 100% increase). The choline/low Na+-induced Ca2+ uptake was abolished by the hypertonic addition of NaCl (returning the bathing Na+ concentration to normal), increased (approximately 140%) by the addition of 1.8 mM PO4(3-)-free Hepes buffered choline/low Na+ media, but unaffected by 0.2 mM cadmium. The high K+/low Na+-induced Ca2+ uptake (i.e. that above the Ca2+ uptake measured in normal Tyrode's solution) was relatively insensitive to pre-exposure to cold (0% change) or K+-free media (11% increase) and only 50% inhibited by the hypertonic addition of NaCl (returning the bathing Na+ concentration to normal). However, the high K+/low Na+-induced Ca2+ uptake was 57% inhibited by 0.2 mM cadmium and approximately 30% inhibited by the addition of 1.8 mM PO4(3-) to HCO3-/PO4(3-)-free Hepes buffered high K+/low Na+ media.(ABSTRACT TRUNCATED AT 250 WORDS)