Diversificación y desarrollo tecnológico de hongos comestibles cultivados en Chile / Diversification and technological development of edible mushroom cultivated in Chile

La finalidad de este trabajo fue la obtención de basidiocarpos (setas), por lo cual se diversificó el cultivo de hongos comestibles Basidiomycetes, siguiendo los objetivos del proyecto FONDEF D05I10196. Para ello, se utilizaron diferentes sustratos agronómicos y forestales sin valor comercial (paja de trigo, aserrines, astillas de maderas, etc.). Partidas del respectivo sustrato fueron pasteurizadas por 3 horas, luego en forma independiente se depositaron en bolsas de nylon (7 K) y se sembraron con la ®semilla¼ del hongo a ensayar, las bolsas fueron incubadas hasta la obtención de basidiocarpos. Se obtuvieron fructificaciones de: Agrocybe aegerita en aserrín de álamo (pero no el de pino), Flammulina velutipes y Hericium erinaceum en aserrín de Nothofagus spp. y paja de trigo y Pholiota nameko en aserrín de pino y astillas de pino.

The purpose of this paper was to get basidiocarps (mushrooms) that is why the culture of edible Basidiomycete mushrooms became diversified according to the objectives of FONDEF D05110196 project. To achieve this, different agronomic and forest substrate lacking any commercial value (wheat straw, wood sawdusts, chips etc. were used. Pieces of the corresponding substratum were pasteurized for 3h, then they were deposited separatedly (independently) in 7-kg polyethylene bags and they were later on sowed with the ®seed¼ of the fungi under test; bags were incubated until the basidiocarp appearance. Fructifications of Agrocybe aegerita in poplar sawdust (yet not in pine chips), Flammulina velutipes and Hericium erinaceum in Nothofagus spp. sawdust and wheat straw as well as Pholiota nameko in pine sawdust and pine chips were obtained.

Presentación clínica de coartación de aorta, relato de casos: revisión de manejo actual / Clinical presentation of aortic coarctation: review of current management: a case series report

La coartación de Aorta es una cardiopatía congénita que se presenta con insuficiencia cardiaca congestiva precozmente sobre todo en la edad neonatal y que, de no ser diagnosticada oportunamente evoluciona con elevadísima morbi-mortalidad. Cuando sobrevive a la barrera de la primera infancia, cursa con hipertensión arterial sistémica, pudiendo debutar incluso con un accidente cerebrovascular, con resultado fatal para el paciente, ó dejarlo con incapacidades como secuela. Resaltamos la importancia del correcto y detallado examen clínico cardiovascular, que incluya la palpación adecuada de los pulsos periféricos así como la medición de la presión arterial sistémica, debido a que siempre cursa con hipertensión arterial en los miembros superiores y ausencia de pulsos en los miembros inferiores. Tratado correctamente presenta bajo riesgo de complicaciones y de mortalidad.

Aortic coarctation is a congenital heart defect that presents with early congestive heart failure, especially during the neonatal stage, and which if not opportunely diagnosed progresses with a high degree of morbidity and mortality. When patients survive the barrier of early childhood, they continue having such problems as systemic arterial hypertension, and run risks of outcomes such as fatal or incapacitating cerebrovascular accident. We emphasize the importance of a careful and detailed clinical cardiovascular examination, to include adequate taking of the peripheral pulses and measurement of systemic blood pressure, since this always presents with hypertension in the upper limbs and an absence of pulses in the legs. Treated adequately, it presents little risk of complications or mortality.

Influence of degree of hepatic steatosis on graft function and postoperative complications of liver transplantation.

The aim of this study was to evaluate the impact on initial graft function of the degree of steatosis detected in the back-table biopsy, and its repercussion on the clinical results of the transplant (early posttransplant mortality and morbidity). We undertook a retrospective analysis of 300 liver transplants performed at our center from 1997 to 2004. A wedge liver biopsy was done routinely during back-table surgery (available in 294 transplants). The degree of steatosis was classified as: S0-no steatosis, 201 transplants; S1-mild steatosis (<30%), 58 transplants; S2-moderate steatosis (30% to 60%), 18 transplants; and S3-severe steatosis (>60%), 17 transplants. The ischemia-reperfusion (I/R) injury, based on the maximum mean peak aspartate transferase in the first 72 posttransplant hours, tended to be greater as the degree of graft steatosis increased: S0, 1316; S1, 1985; S2, 2446; and S3, 2955 (P < .005 between S0 and S3). This greater initial hepatic dysfunction was correlated in the group with severe steatosis with a higher rate of severe renal failure requiring hemofiltration/hemodialysis: S0, 9%; S1, 15%; S2, 11%; and S3, 41% (P < .001); as well as with a higher early mortality (90 days): S0, 10%; S1, 21%; S2, 11%; and S3, 41% (P < .001). The Kaplan-Meier survival curve showed a significant difference (log-rank and Breslow) between the group with severe steatosis and the group with no steatosis (P = .002). We conclude that the degree of liver graft steatosis is an important determinant of I/R injury, although this progressive increase in the I/R injury with the degree of steatosis only had clinical repercussions in the case of severe steatosis.

Interleukin-1 receptor antagonist gene polymorphism and mortality in patients with severe sepsis.

This study aims to determine the influence of the polymorphism within the intron 2 of the interleukin-1 receptor antagonist gene (IL-1RN*) on the outcome of severe sepsis, and to assess its functional significance by correlating this polymorphism with the total production of interleukin-1 receptor antagonist (IL-1Ra) protein determined in stimulated peripheral blood mononuclear cells (PBMC). A group of 78 patients with severe sepsis (51 survivors and 27 nonsurvivors) was compared with a healthy control group of 130 blood donors, and 56 patients with uncomplicated pneumonia. We found a significant association between IL-1RN* polymorphism and survival. Thus, after adjusting for age and APACHE II score, multiple logistic regression analysis showed that patients homozygotes for the allele *2 had a 6.47-fold increased risk of death (95% CI 1.01--41.47, P = 0.04). Besides, compared with patients homozygous or heterozygous for the allele *1, IL-1RN*2 homozygotes produced significantly lower levels of IL-1Ra from their PBMC. Our results suggest that insufficient production of this cytokine might contribute, among other factors, to the higher mortality rate found in severe sepsis patients with the IL-1RN*2 homozygous genotype.

Differential expression of calcium channel subtypes in the bovine adrenal medulla.

This study aimed at determining the distribution and expression levels of different subtypes of Ca(2+) channels in the bovine adrenal medulla, and whether individual subtypes were more abundant in chromaffin cells exhibiting an adrenergic or a noradrenergic phenotype. In situ hybridization using riboprobes specific for the pore-forming Ca(2+) channel alpha(1D) (L-type channel), alpha(1B) (N-type channel), and alpha(1A) (P/Q-type channel) subunits of bovine chromaffin cells showed a broad distribution of the three transcripts in adrenal medulla tissue. However, a tissue-specific expression pattern of individual subunits was found; whereas alpha(1B) mRNA was homogeneously distributed throughout the medulla, alpha(1D) and alpha(1A) transcripts were present at higher densities in the internal medullary area, far away from the adrenal cortex. These results were corroborated by comparative analysis of the alpha(1B), alpha(1D), and alpha(1A) products amplified by RT-PCR from total RNA extracted from small pieces of tissue dissected out from external or internal medullary areas. Interestingly, immunohistochemical experiments performed in adrenal gland sections, using antidopamine-beta-hydroxylase and anti-phenylethanolamine-N-methyltransferase antibodies, indicated a higher density of noradrenergic over adrenergic chromaffin cells in the internal medullary region. These results provide direct evidence in favor of a heterogeneous distribution of Ca(2+) channel subtypes in the adrenal medulla, in agreement with previous functional data showing that blockade of the high K+ -elicited responses by dihydropyridines was greater in noradrenergic than in adrenergic chromaffin cells. These differences may be relevant for the differential release regulation of each catecholamine under physiological and pathophysiological conditions.

Serial MRI findings in the Costa Rican variant of neuronal ceroid-lipofuscinosis.

Widespread cerebral atrophy and basal ganglia involvement are highly suggestive imaging features of the variants of late infantile type neuronal ceroid-lipofuscinosis. In the presence of clinical findings indicative of neuronal ceroid-lipofuscinosis, neuroimaging procedures are highly recommended to differentiate the variants from classic late infantile neuronal ceroid-lipofuscinosis. The clinical features and follow-up magnetic resonance imaging studies in a patient with the Costa Rican variant of late infantile neuronal ceroid-lipofuscinosis is presented. These procedures were of the utmost importance to observe the progression of the neurologic ailment and the extent of the cerebral and cerebellar abnormalities.

Intracellular glutathione deficiency is associated with enhanced nuclear factor-kappaB activation in older non-insulin dependent diabetic patients.

Diabetes mellitus may be associated with intracellular glutathione (GSH) deficiency. Since in vivo studies have shown that plasma intracellular GSH plays a key role in regulating the activation of nuclear factor kappaB (NF-kappaB), we have investigated the relationship between intracellular thiols (GSH, homocysteine, cysteine and cysteinyglycine) and NF-kappaB activity in the peripheral blood mononuclear cells (PBMC) of 63 elderly non-insulin dependent diabetes mellitus (NIDDM) patients (28 microalbuminurics and 35 normoalbuminurics) and 30 healthy age- and sex-matched subjects. In addition, we have measured plasma concentrations of these thiol compounds, serum concentrations of interleukin-6 (IL-6) and vascular cell adhesion molecule-1 (sVCAM-1), that are partly dependent on the NF-kappaB activation, as well as the serum levels of thiobarbituric acid reacting substances (TBARS), as index of lipid peroxidation. Diabetic patients with microalbuminuria (MAB) and normoalbuminuria had NF-kappaB activity 2.1- and 1.5-fold greater, respectively, than the control group. As compared to normoalbuminuric patients, patients with MAB had significantly higher levels of glycemia, plasma homocysteine, and serum concentrations of TBARS, IL-6 and sVCAM-1 (in all cases, p < 0.01), and significantly lower GSH content in the PBMC (p < 0.05). The intracellular GSH in PBMC correlated with NF-kappaB activation (r = -0.82; p < 0.0001), serum TBARS (r = -0.60; p < 0.001), and with fasting glycemia (r = -0.56; p < 0.001) in patients with MAB, whereas a weaker association between GSH levels in PBMC and NF-kappaB activation (r = -0.504, p < 0.001) was seen in patients without MAB. These results suggest that the decrease of intracellular GSH content in elderly NIDDM patients with MAB is strongly associated with enhanced NF-kappaB activation, which could contribute to the development of increased glomerular capillary permeability and its rapid progression.

Enhanced acute-phase response and oxidative stress in older adults with type II diabetes.

OBJECTIVE: To test whether oxidative stress could promote a systemic acute-phase response in elderly patients with type II diabetes. DESIGN AND METHODS: In a group of 30 older diabetic patients with poor glycemic control, serum levels of lipid peroxides, measured as thiobarbituric acid-reacting substances (TBARS); C-reactive protein (CRP); interleukin (IL)-6 and the soluble form of its receptor (slL-6R), were evaluated at baseline and after 2 and 3 months of therapeutic intervention. Thirty asymptomatic, untreated individuals with abnormal fasting glycemia, but otherwise healthy status, of similar age, sex, and weight served as control group. RESULTS: At baseline, glycemia (8.83 +/- 0.67mmol/l), HbA1C (8.66 +/- 0.59%), TBARS (8.68 +/- 1.21 micromol/l), CRP (16.05 +/- 3.81 mg/l) IL-6 (5.39 +/- 1.25 pg/ml) and sIL-6R (1425 +/- 492 pg/ml) were significantly higher in diabetic patients than in asymptomatic hyperglycemic individuals (p<0.001). After treatment, glycemia significantly decreased with respect to baseline values (- 9.82% after 60 days and -13.74% after 90 days), as did serum levels of TBARS (-14.05% and -21.89%, respectively), CRP (-32.71% and -43.86%), IL-6 (-23.75% and -40.63%) and sIL-6R (-34.53% and -48.49%, respectively). In diabetic patients, multiple regression showed, at each time, that TBARS and IL-6 were independently correlated with CRP, considering CRP as the dependent variable. Similar correlations were found in asymptomatic hyperglycemic subjects. CONCLUSION: These results suggest that oxidative stress might be implicated in promoting a state of low-grade systemic inflammation in elderly patients with type II diabetes.

Greater diversity than previously thought of chromaffin cell Ca2+ channels, derived from mRNA identification studies.

Using reverse transcription followed by PCR amplification (RT-PCR), we have identified multiple messenger RNAs encoding for the neuronal pore-forming Ca(2+) channel subunits alpha(1A) (P/Q channel), alpha(1B) (N channel), alpha(1D) (neuronal/endocrine L channel), alpha(1E) (R channel), alpha(1G-H) (T channel) and alpha(1S) (skeletal muscle L channel) in bovine chromaffin cells. mRNAs for the auxiliary beta(2), beta(3), beta(4), alpha(2)/delta and gamma(2) subunits were also identified. In agreement with these molecular data, perforated patch-clamp recordings of whole-cell Ca(2+) currents reveal the existence of functional R-type Ca(2+) channels in these cells that were previously undetected with other techniques. Our results provide a molecular frame for a much wider functional diversity of Ca(2+) channels in chromaffin cells than that previously established using pharmacological and electrophysiological approaches.

Changes in the intracellular homocysteine and glutathione content associated with aging.

Since moderate hyperhomocysteinemia is an independent risk factor for vascular disease by mean of its oxidant effect and glutathione plays a main role as intracellular redox-regulating agent, we have studied for the first time the total intracellular content of homocysteine in aging. Plasma homocysteine concentration, total intracellular and plasma glutathione, and other related thiol compounds such as cysteine and the glutathione catabolite cysteinglycine were also studied. Forty three healthy elderly subjects and twenty seven healthy young ones were studied. The total intracellular peripheral blood mononuclear cell content was higher for homocysteine, cysteine and cysteinglycine, whereas that of the total glutathione was greatly decreased in elderly people with respect to young ones. Elderly subjects showed significantly higher levels than young ones of total plasma homocysteine and cysteinglycine, but not cysteine, whereas total plasma glutathione levels were increased. In addition, elderly subjects showed significantly decreased plasma vitamin E levels and increased concentrations of serum lipid peroxides measured as TBARS (reaction product of malondialdehyde with thiobarbituric acid). The intracellular glutathione content presented significantly negative correlation with serum TBARS, and intracellular and plasma homocysteine levels. These findings show an increase of homocysteine synthesis associated with aging, which in turn can produce an augmented oxidant effect on endothelium, and an impaired intracellular antioxidant capacity leading to an enhanced lipid peroxidation and decreased total intracellular glutathione content.

The novel Na(+)/Ca(2+) exchange inhibitor KB-R7943 also blocks native and expressed neuronal nicotinic receptors.

We studied the effects of the novel Na(+)/Ca(2+) exchange inhibitor KB-R7943, 2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea methanesulphonate, on the native nicotinic receptors present at the bovine adrenal chromaffin cells, as well as on rat brain alpha(3)beta(4) and alpha(7) nicotinic acetylcholine receptors (AChRs) expressed in Xenopus oocytes. As expected, KB-R7943 blocked the Na(+)-gradient dependent (45)Ca(2+) uptake into chromaffin cells (IC(50) of 5.5 microM); but in addition, the compound also inhibited the (45)Ca(2+) entry and the increase of cytosolic Ca(2+) concentration, [Ca(2+)](c), stimulated by 5 s pulses of ACh (IC(50) of 6.5 and 1.7 microM, respectively). In oocytes expressing alpha(3)beta(4) and alpha(7) nicotinic AChRs, voltage-clamped at -60 mV, inward currents elicited by 1 s pulses of 100 microM ACh (I(ACh)) were blocked by KB-R7943 with an IC(50) of 0.4 microM and a Hill coefficient of 0.9. Blockade of alpha(3)beta(4) currents by KB-R7943 was noncompetitive; moreover, the blocker (0.3 microM) became more active as the ACh concentration increased (34 versus 66% blockade at 30 microM and 1 mM ACh, respectively). Inhibition of alpha(3)beta(4) currents by 0.3 microM KB-R7943 was more pronounced at hyperpolarized potentials. If given within the ACh pulse (10 microM), the inhibition amounted to 33, 64 and 80% in oocytes voltage-clamped at -40, -60 and -100 mV, respectively. The onset of blockade was faster and the recovery slower at -100 mV; the reverse was true at -40 mV. In conclusion, KB-R7943 is a potent blocker of nicotinic AChRs; moreover, it displays many features of an open-channel blocker at the rat brain alpha(3)beta(4) AChR. These results should be considered when KB-R7943 is to be used to study Ca(2+) homeostasis in cells expressing nicotinic AChRs and the Na(+)/Ca(2+) exchanger.

Predictive value of nuclear factor kappaB activity and plasma cytokine levels in patients with sepsis.

The relationship between fluctuating cytokine concentrations in plasma and the outcome of sepsis is complex. We postulated that early measurement of the activation of nuclear factor kappaB (NF-kappaB), a transcriptional regulatory protein involved in proinflammatory cytokine expression, may help to predict the outcome of sepsis. We determined NF-kappaB activation in peripheral blood mononuclear cells of 34 patients with severe sepsis (23 survivors and 11 nonsurvivors) and serial concentrations of inflammatory cytokines (interleukin-6, interleukin-1, and tumor necrosis factor) and various endogenous antagonists in plasma. NF-kappaB activity was significantly higher in nonsurvivors and correlated strongly with the severity of illness (APACHE II score), although neither was related to the cytokine levels. Apart from NF-kappaB activity, the interleukin-1 receptor antagonist was the only cytokine tested whose level in plasma was of value in predicting mortality by logistic regression analysis. These results underscore the prognostic value of early measurement of NF-kappaB activity in patients with severe sepsis.

Multiple calcium pathways induce the expression of SNAP-25 protein in chromaffin cells.

Incubation of bovine adrenal chromaffin cells in high K+ (38 mM) during 24-48 h enhanced 2.5 to five times the expression of SNAP-25 protein and mRNA, respectively. This increase was reduced 86% by furnidipine (an L-type Ca2+ channel blocker) but was unaffected by either omega-conotoxin GVIA (an N-type Ca2+ channel blocker) or -agatoxin IVA (a P/Q-type Ca2+ channel blocker). Combined blockade of N and P/Q channels with omega-conotoxin MVIIC did, however, block by 76% the protein expression. The inhibitory effects of fumidipine were partially reversed when the external Ca2+ concentration was raised from 1.6 to 5 mM. These findings, together with the fact that nicotinic receptor activation or Ca2+ release from internal stores also enhanced SNAP-25 protein expression, suggest that an increment of cytosolic Ca2+ concentration ([Ca2+]), rather than its source or Ca2+ entry pathway, is the critical signal to induce the protein expression. The greater coupling between L-type Ca2+ channels and protein expression might be due to two facts: (a) L channels contributed 50% to the global [Ca2+]i rise induced by 38 mM K+ in indo-1-loaded chromaffin cells and (b) L channels undergo less inactivation than N or P/Q channels on sustained stimulation of these cells.

Relationship of plasma leptin to plasma cytokines and human survivalin sepsis and septic shock.

Leptin production is increased in rodents by administration of endotoxin or cytokines. To investigate whether circulating leptin is related to cytokine release and survival in human sepsis, plasma concentrations of leptin, interleukin (IL)-6, IL-1beta, tumor necrosis factor (TNF)-alpha, soluble TNF receptor type I, IL-1 receptor antagonist (IL-1ra), and the inflammatory modulator IL-10 were measured as soon as severe sepsis (n=28) or septic shock (n=14) developed and every 6 h for 24 h. Patients with sepsis or septic shock had leptin concentrations 2.3- and 4.2-fold greater, respectively, than the control group. There was an independent association for leptin with IL-1ra and IL-10 in both patient groups. By discriminant analysis, leptin and IL-6 were independent predictors of death. These findings suggest that increases in leptin levels may be a host defense mechanism during sepsis.

Differential blockade of rat alpha3beta4 and alpha7 neuronal nicotinic receptors by omega-conotoxin MVIIC, omega-conotoxin GVIA and diltiazem.

Rat alpha3beta4 or alpha7 neuronal nicotinic acetylcholine receptors (AChRs) were expressed in Xenopus laevis oocytes, and the effects of various toxins and non-toxin Ca2+ channel blockers studied. Nicotinic AChR currents were elicited by 1 s pulses of dimethylphenylpiperazinium (DMPP, 100 microM) applied at regular intervals. The N/P/Q-type Ca2+ channel blocker omega-conotoxin MVIIC inhibited alpha3beta4 currents with an IC50 of 1.3 microM; the blockade was non-competitive and reversible. The alpha7 currents were unaffected. At 1 microM, omega-conotoxin GVIA (N-type Ca2+ channel blocker) inhibited by 24 and 20% alpha3beta4 and alpha7 currents, respectively. At 1 microM, omega-agatoxin IVA (a P/Q-type Ca2+ channel blocker) did not affect alpha7 currents and inhibited alpha3beta4 currents by only 15%. L-type Ca2+ channel blockers furnidipine, verapamil and, particularly, diltiazem exhibited a preferential blocking activity on alpha3beta4 nicotinic AChRs. The mechanism of alpha3beta4 currents blockade by omega-conotoxins and diltiazem differed in the following aspects: (i) the onset and reversal of the blockade was faster for toxins; (ii) the blockade by the peptides was voltage-dependent, while that exerted by diltiazem was not; (iii) diltiazem promoted the inactivation of the current while omega-toxins did not. These data show that, at concentrations currently employed as Ca2+ channel blockers, some of these compounds also inhibit certain subtypes of nicotinic AChR currents. Our data calls for caution when interpreting many of the results obtained in neurons and other cell types, where nicotinic receptor and Ca2+ channels coexist.

Losartan inhibits the post-transcriptional synthesis of collagen type I and reverses left ventricular fibrosis in spontaneously hypertensive rats.

OBJECTIVE: Previous studies have shown that as well as left ventricular hypertrophy, myocardial fibrosis develops early in rats with spontaneous hypertension (SHR). The present study was designed to investigate whether chronic treatment with the angiotensin II type 1 (AT1) receptor antagonist losartan modifies collagen type I metabolism and reverses left ventricular fibrosis in young SHR with left ventricular hypertrophy. DESIGN: The study was performed in 30-week-old normotensive Wistar-Kyoto (WKY) rats, untreated SHR and SHR treated with losartan (20 mg/mg per day, orally) for 14 weeks before they were killed. METHODS: Ventricular pro-alpha 1 (I) collagen messenger RNA was analyzed by Northern blot. Serum levels of the carboxy-terminal propeptide of procollagen type I (PIP) and the pyridoline cross-linked telopeptide domain of collagen type I (CITP) were determined by specific radioimmunoassays as markers of collagen type I synthesis and degradation, respectively. Collagen volume fraction was determined in the left ventricle by quantitative morphometry. RESULTS: Compared with WKY rats, SHR exhibited increased (P < 0.05) mean arterial pressure, pro-alpha 1 (I) collagen messenger RNA, PIP and left ventricular collagen volume fraction, and similar CITP values. After the treatment period, mean arterial pressure was higher (P < 0.05) in losartan-treated SHR than in WKY rats. Compared with untreated SHR, treated SHR showed no left ventricular hypertrophy and diminished (P < 0.05) values of mean arterial pressure, PIP and left ventricular collagen volume fraction. No changes in pro-alpha 1 (I) collagen messenger RNA and CITP values were observed with treatment in SHR. No significant differences in the left ventricular collagen volume fraction were observed between treated SHR with normal blood pressure and treated SHR with abnormally high blood pressure at the end of the treatment period. CONCLUSIONS: These results suggest that chronic AT1 blockade with losartan decreases the post-transcriptional synthesis of fibril-forming collagen type I molecules in young SHR. This effect may be involved in the ability of this drug to reverse left ventricular fibrosis in young rats with genetic hypertension. Apart from its antihypertensive action, other mechanisms may mediate the antifibrotic effect of losartan in this animal model.

Unmasking the functions of the chromaffin cell alpha7 nicotinic receptor by using short pulses of acetylcholine and selective blockers.

Methyllycaconitine (MLA), alpha-conotoxin ImI, and alpha-bungarotoxin inhibited the release of catecholamines triggered by brief pulses of acetylcholine (ACh) (100 microM, 5 s) applied to fast-superfused bovine adrenal chromaffin cells, with IC50s of 100 nM for MLA and 300 nM for alpha-conotoxin ImI and alpha-bungarotoxin. MLA (100 nM), alpha-conotoxin ImI (1 microM), and alpha-bungarotoxin (1 microM) halved the entry of 45Ca2+ stimulated by 5-s pulses of 300 microM ACh applied to incubated cells. These supramaximal concentrations of alpha7 nicotinic receptor blockers depressed by 30% (MLA), 25% (alpha-bungarotoxin), and 50% (alpha-conotoxin ImI) the inward current generated by 1-s pulses of 100 microM ACh, applied to voltage-clamped chromaffin cells. In Xenopus oocytes expressing rat brain alpha7 neuronal nicotinic receptor for acetylcholine nAChR, the current generated by 1-s pulses of ACh was blocked by MLA, alpha-conotoxin ImI, and alpha-bungarotoxin with IC50s of 0.1 nM, 100 nM, and 1.6 nM, respectively; the current through alpha3 beta4 nAChR was unaffected by alpha-conotoxin ImI and alpha-bungarotoxin, and weakly blocked by MLA (IC50 = 1 microM). The functions of controlling the electrical activity, the entry of Ca2+, and the ensuing exocytotic response of chromaffin cells were until now exclusively attributed to alpha3 beta4 nAChR; the present results constitute the first evidence to support a prominent role of alpha7 nAChR in controlling such functions, specially under the more physiological conditions used here to stimulate chromaffin cells with brief pulses of ACh.

Capacitative Ca2+ entry into Xenopus oocytes is sensitive to omega-conotoxins GVIA, MVIIA and MVIIC.

We have studied capacitative Ca2+ entry into Xenopus oocytes by depleting intracellular Ca2+ stores with inositol 1,4,5-trisphosphate or thapsigargin. Capacitative Ca2+ entry was evoked by hyperpolarisation and monitored via the Ca(2+)-activated Cl- current. Hyperpolarisation-evoked currents increased with extracellular [Ca2+] in the range 0.9-5 mM, and were reversibly inhibited by extracellular Mg2+ (0.1-10 mM) by up to 60%. Currents were decreased by the voltage-gated Ca2+ channel antagonists omega-conotoxin GVIA, MVIIA and MVIIC (0.3-10 microM) and the inhibition of Ca2+ entry in individual oocytes by omega-conotoxins GVIA and MVIIA was highly heterogeneous, but not additive. Flunarizine (10 microM) and the imidazoles SK&F 96365 (10 microM), miconazole (40 microM) and econazole (40 microM) partly blocked Ca2+ entry. Ca2+ entry was unaffected by calciseptine (300 nM) or alpha-bungarotoxin (1 microM). The possibility that these compounds might inhibit the Ca(2+)-activated Cl- current rather than capacitative Ca2+ entry itself was examined by recording the Cl- current activated by the increase in [Ca2+]i activated by the flash photolysis of caged Ca2+. Eicosatetraynoic acid (2-10 microM) markedly inhibited, and La3+ (1 mM but not 100 microM) potentiated the increase in Ca(2+)-activated Cl- current. In contrast, omega-conotoxins and Mg2+ had no effect on the Ca(2+)-activated Cl- current itself. These findings support the hypothesis that capacitative Ca2+ entry into Xenopus oocytes occurs through channels with a pharmacology similar to that of neuronal non-L type voltage-gated Ca2+ channels.

Serotonergic effects of dotarizine in coronary artery and in oocytes expressing 5-HT2 receptors.

In strips of pig coronary arteries incubated in oxygenated Krebs-bicarbonate solution at 37 degrees C, dotarizine blocked the phasic contractions evoked by 5-HT (0.5 microM) or K+ depolarization (35 mM K+) with an IC50 of 0.22 and 3.7 microM, respectively. Flunarizine inhibited both types of contractions with IC50 values of 1.7 microM for 5-HT and 2.4 microM for K+ responses. In Xenopus oocytes injected with in vitro transcribed RNA encoding for 5-HT2A or 5-HT2C receptors, 5-HT (100 nM for 20 s) applied every 10 min caused, in both cases, a reproducible inward current through Ca2(+)-activated Cl- channels (ICl). Dotarizine inhibited the 5-HT2A response in a concentration-dependent manner, with an IC50 of 2.2 nM. In contrast, the 5-HT2C response was unaffected by 1 microM dotarizine and blocked around 62% by 10 microM of this drug. The ICl activated either by intracellular injection of inositol 1,4,5-trisphosphate (IP3) in oocytes or by direct photorelease of Ca2+ in DM-nitrophen-injected oocytes was unaffected by 10 microM dotarizine. It is concluded that dotarizine blocks 5-HT2A receptors with a high affinity; the compound is devoid of intracellular effects on any further steps of the transduction pathway (i.e., IP3 receptor). Contrary to flunarizine that blocks equally well the serotonergic and the K+ vascular responses, dotarizine exhibits 17-fold higher affinity for vascular 5-HT receptors. These findings might be relevant to an understanding of the mechanism involved in the use of dotarizine and flunarizine as prophylactic agents in migraine.