Pharmacological blockage of the AHR-CYP1A1 axis: a call for in vivo evidence.

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that can be activated by structurally diverse compounds arising from the environment and the microbiota and host metabolism. Expanding evidence has been shown that the modulation of the canonical pathway of AHR occurs during several chronic diseases and that its abrogation might be of clinical interest for metabolic and inflammatory pathological processes. However, most of the evidence on the pharmacological abrogation of the AHR-CYP1A1 axis has been reported in vitro, and therefore, guidance for in vivo studies is needed. In this review, we cover the state-of-the-art of the pharmacodynamic and pharmacokinetic properties of AHR antagonists and CYP1A1 inhibitors in different in vivo rodent (mouse or rat) models of disease. This review will serve as a road map for those researchers embracing this emerging therapeutic area targeting the AHR. Moreover, it is a timely opportunity as the first AHR antagonists have recently entered the clinical stage of drug development.

Women generating narratives after an unwanted prenatal diagnosis result: randomized controlled trial.

We have defined a psychological intervention based on cognitive narrative therapy and the Ottawa decision framework to reduce adjustment problems following a termination of pregnancy (TOP) after a positive prenatal diagnosis (PND). The intervention is composed of four sessions: decision, subjectivation, metaphorization, and projecting. This study aims to assess the effectiveness of a cognitive narrative intervention to prevent depression and anxiety symptoms after TOP. The intervention was accepted by 24 participants. The outcome is compared with a control group of 67 women who also terminated a pregnancy after PND. Participants were from several Portuguese institutions; 64.4% had a genetic and 35.6% had ultrasound diagnosis; the mean age was 30.0 years and the mean gestational age was 19 weeks. There are two evaluations: a baseline at the 15th day and a sixth month follow-up after TOP, using Beck Depression Inventory, Zung Anxiety Scale, Perinatal Grief Scale, and an instrument capturing participant satisfaction. Six months after TOP, there is a lower mean of anxiety and depression (p < 0.05), between groups, with effect sizes on the follow-up of 0.54 for depression, 0.41 for anxiety, and 0.23 for perinatal grief. This intervention has very positive effects on women mental health, and we emphasize the importance of the meaning-making process in the context of terminating a wanted pregnancy.

Colloid centrifugation of fresh stallion semen before cryopreservation decreased microorganism load of frozen-thawed semen without affecting seminal kinetics.

Freezability of equine semen may be influenced by microorganism population of semen. The objective of this study was to verify the effect of single-layer density gradient centrifugation (SLC) of fresh semen before cryopreservation on semen's microbial load (ML) and sperm cells kinetics after freezing-thawing. For that, one ejaculate was collected from 20 healthy stallions and split into control (C) samples (cryopreserved without previous SLC) and SLC samples (subjected to SLC). Semen cryopreservation was performed according to the same protocol in both groups. Microbial load of each microorganism species and total microbial load (TML) expressed in colony-forming units (CFU/mL) as well as frozen-thawed sperm kinetics were assessed in both groups. Additional analysis of the TML was performed, subdividing the frozen-thawed samples in "suitable" (total motility ≥ 30%) and "unsuitable" (total motility < 30%) semen for freezing programs, and comparing the C and SLC groups within these subpopulations. After thawing, SLC samples had less (P < 0.05) TML (88.65 × 10(2) ± 83.8 × 10(2) CFU/mL) than C samples (155.69 × 10(2) ± 48.85 × 10(2) CFU/mL), mainly due to a reduction of Enterococcus spp. and Bacillus spp. A relationship between post-thaw motility and SLC effect on ML was noted, as only in samples with more than 30% total motility was ML reduced (P < 0.05) by SLC (from 51.33 × 10(2) ± 33.26 × 10(2) CFU/mL to 26.68 × 10(2) ± 12.39 × 10(2) CFU/mL in "suitable" frozen-thawed semen vs. 240.90 × 10(2) ± 498.20 × 10(2) to 139.30 × 10(2) ± 290.30 × 10(2) CFU/mL in "unsuitable" frozen-thawed semen). The effect of SLC on kinetics of frozen-thawed sperm cells was negligible.

Effect of breeding activity on the microflora of the external genitalia and in the semen of stallions, and the relationship between micro-organisms on the skin and on the external genitalia.

A possible role of breeding activities in the composition of the microbial population in stallions' external genitalia (EG) and the relationship between micro-organisms colonizing the skin of the abdomen and the ones colonizing the EG have not been studied. In experiment 1, EG microbiological samples were collected from 41 stallions used for both natural cover and semen collection (BST) and from 18 non-breeding stallions (NBST). A higher (p < 0.05) frequency of isolation of potentially pathogenic species was found for BST. Age did not influence number of micro-organism species isolated both in BST and NBST. In experiment 2, the microbial content of the EG and semen was compared in 23 BST. Most micro-organisms isolated from the EG were present in semen, albeit with a numerically lower prevalence. In 7 stallions, six microbial species isolated from semen were absent from the EG cultures, suggesting contamination by the operator. In experiment 3, a numerically higher number of micro-organism species was isolated from the EG of 31 stallions, than from their skin of the ventral abdomen in contact with the penis or from the skin of the thorax. With the sole exception of Escherichia coli, potentially pathogenic bacteria were only isolated from the EG but not from the skin. Results suggest that breeding activity increased the number of species colonizing the EG; most species isolated from the EG were also found in semen even if with a lower frequency, and additional semen contamination seemed to occur during its manipulation. Many micro-organism species of the skin were also isolated from the penis, but independently of being or not in contact with the penis, skin did not seem to provide an adequate environment for the growth of potentially pathogenic bacteria that were isolated from EG, with the sole exception for E. coli.

Effective energy barrier distributions for random and aligned magnetic nanoparticles.

Isothermal magnetic relaxation measurements are widely used to probe energy barriers in systems of magnetic nanoparticles. Here we show that the result of such an experiment can differ greatly for aligned and randomly oriented nanoparticles. For randomly oriented cobalt-doped magnetite nanoparticles we observe a prominent low-energy tail in the energy barrier distribution that is greatly attenuated when the particles are magnetically aligned. Monte Carlo simulations show that this behaviour arises for nanoparticles with both cubic and uniaxial magnetic anisotropy energy terms even though for cubic or uniaxial anisotropy alone the energy barrier distribution is independent of nanoparticle orientation.

Effects of body condition and leptin on the reproductive performance of Lusitano mares on extensive systems.

The aim of this study was to investigate the effects of body condition (BC), BC changes, and plasma leptin concentrations on the reproductive performance of Lusitano broodmares on extensive systems. Data from 119 mares (ranging from 4 to 22 years of age) were collected over a period of four consecutive breeding seasons. Each case was considered as one foaled mare bred in 1 year. Body condition changes at conception (ΔBCScon) showed a strong effect on fertility at the first two postpartum estrous cycles and a significant interaction with body condition score at conception (BCScon) was observed (P < 0.01). The best fertility results were obtained with positive and greater ΔBCScon. The best predictive value of fertility (91%) was achieved when the BCScon was 3.0 and ΔBCScon was 0.375. Global foaling rate for the 4-year period was 74.5%. Mean foaling interval and gestation length were, respectively, 368.0 ± 2.8 and 340.3 ± 1.0 days. Gestation length was influenced by the month of foaling (P < 0.05) and decreased as mares got older (P < 0.01). The number of estimated estrous cycles per live foal was 1.78 ± 0.12, including foal heat ovulation. Leptin was correlated with BCS (0.41; P < 0.001), but in the present study, plasma leptin concentrations on late gestation and early lactation did not influence fertility results. At 90 days of age, lower growth performances were obtained in foals which dams presented negative BCS changes on the first 3 months of lactation (P < 0.05). In conclusion, BC changes at early postpartum period influence the reproductive efficiency of broodmares and the growth of their suckling foals. These findings are important to help breeders on management options concerning feeding strategies in the Lusitano production systems and others under similar conditions.

Elementary properties of Kir2.1, a strong inwardly rectifying K(+) channel expressed by pigeon vestibular type II hair cells.

By using the patch-clamp technique in the cell-attached configuration, we have investigated the single-channel properties of an inward rectifier potassium channel (Kir) expressed by pigeon vestibular type II hair cells in situ. In high-K(+) external solution with 2 mM Mg(2+), Kir inward current showed openings to at least four amplitude levels. The two most frequent open states (L2 and L3) had a mean slope conductance of 13 and 28 pS, respectively. L1 (7 pS) and L4 (36 pS) together accounted for less than 6% of the conductive state. Closed time distributions were fitted well using four exponential functions, of which the slowest time constant (tau(C4)) was clearly voltage-dependent. Open time distributions were fitted well with two or three exponential functions depending on voltage. The mean open probability (P(O)) decreased with hyperpolarization (0.13 at -50 mV and 0.03 at -120 mV). During pulse-voltage protocols, the Kir current-decay process (inactivation) accelerated and increased in extent with hyperpolarization. This phenomenon was associated with a progressive increase of the relative importance of tau(C4). Kir inactivation almost disappeared when Mg(2+) was omitted from the pipette solution. At the same time, P(O) increased at all membrane voltages and the relative importance of L4 increased to a mean value of 47%. The relative importance of tau(C4) decreased for all open states, while L4 only showed a significantly longer open time constant. The present work provides the first detailed quantitative description of the elementary properties of the Kir inward rectifier in pigeon vestibular type II hair cells and specifically describes the Kir gating properties and the molecule's sensitivity to extracellular Mg(2+) for all subconductance levels. The present results are consistent with the Kir2.1 protein sustaining a strong inwardly rectifying K(+) current in native hair cells, characterized by rapid activation time course and slow partial inactivation. The longest closed state (tau(C4)) appears as the main parameter involved in time- and Mg(2+)-dependent decay. Finally, in contrast to Kir2.1 results described so far for mammalian cells, external Mg(2+) had no effect on channel conductance.

Kvbeta1.1 associates with Kvalpha1.4 in Chinese hamster ovary cells and pigeon type II vestibular hair cells and enhances the amplitude, inactivation and negatively shifts the steady-state inactivation range.

Although A-type potassium currents are found in type II hair cells in the inner ear of most species, the molecular mechanisms for activation and inactivation of the A-type potassium current (I(A)) remain unknown. In frog semicircular canal hair cells, for example, there appear to be two classes of currents having either fast or slow inactivation [Norris CH, Ricci AJ, Housley GD, Guth PS (1992) The inactivating potassium currents of hair cells isolated from the crista ampullaris of the frog. J Neurophysiol 68:1642-1653; Russo G, Calzi D, Martini M, Rossi ML, Fesce R, Prigioni I (2007) Potassium currents in the hair cells of vestibular epithelium: position-dependent expression of two types of A channels. Eur J Neurosci 25:695-704]. It has been suggested that somehow the "ball and chain" mechanism (NH(3) (N) terminus motif) is modified by alternative splicing to account for the two classes of inactivation. To examine other possibilities, we cloned alpha and beta subunits that comprise the A-type potassium channel complex in adult and embryonic pigeon brain, cochlea and labyrinth. By sequence homology, we concluded that the subunits present were Kvalpha1.4 and Kvbeta1.1. The sequence of the open reading frame for Kvalpha1.4 contained the N-terminus, pore and COOH (C) terminus motifs for N-and C-type inactivation. The sequence for Kvbeta1.1 displayed amino acids consistent with assembly and association with Kvalpha1.4 alpha subunits. Kvalpha1.4 and Kvbeta1.1 were transfected either singly or in combination into Chinese hamster ovary (CHO) cells. These cells and native hair cells from the pigeon utricle were patch clamped and the inactivation properties of the A-type current were studied. In the native hair cells, the A-type current was identified by its pharmacological (4-aminopyridine (4-AP); IC(50)=11 microM) and voltage dependent inactivation properties. A comparison of the mean time constants from best-fitted single exponential and sum of two exponential equations to the ionic current inactivation revealed the following. In CHO cells when Kvalpha1.4 was expressed alone, the mean time constant (tau(1)=107 ms+/-19, N=32) was significantly (P<0.001) longer and the mean peak amplitude (2.28 nA+/-0.39, N=32) was smaller than when Kvalpha1.4 and Kvbeta1.1 were expressed in CHO cells. Moreover, the co-transfection of Kvalpha1.4 and Kvbeta1.1 into CHO cells caused a shift in the steady state inactivation curve parameter Vo 30 mV in the hyperpolarized direction relative to CHO cells expressing only Kvalpha1.4. Similarly, Kvalpha1.4-transfected CHO cells produced longer time constants and smaller amplitudes than those found for native utricular hair cells. These data lead us to conclude that while the amino acid motifs are present in Kvalpha1.4 and Kvbeta1.1 to suggest N-and C-type inactivation, co-assembly and association of Kvalpha1.4 and Kvbeta1.1 may also produce changes in the time dependent inactivation properties of vestibular hair cells.

Muscarinic acetylcholine receptor subtype expression in avian vestibular hair cells, nerve terminals and ganglion cells.

Muscarinic acetylcholine receptors (mAChRs) are widely expressed in the CNS and peripheral nervous system and play an important role in modulating the cell activity and function. We have shown that the cholinergic agonist carbachol reduces the pigeon's inwardly rectifying potassium channel (pKir2.1) ionic currents in native vestibular hair cells. We have cloned and sequenced pigeon mAChR subtypes M2-M5 and we have studied the expression of all five mAChR subtypes (M1-M5) in the pigeon vestibular end organs (semicircular canal ampullary cristae and utricular maculae), vestibular nerve fibers and the vestibular (Scarpa's) ganglion using tissue immunohistochemistry (IH), dissociated single cell immunocytochemistry (IC) and Western blotting (WB). We found that vestibular hair cells, nerve fibers and ganglion cells each expressed all five (M1-M5) mAChR subtypes. Two of the three odd-numbered mAChRs (M1, M5) were present on the hair cell cilia, supporting cells and nerve terminals. And all three odd numbered mAChRs (M1, M3 and M5) were expressed on cuticular plates, myelin sheaths and Schwann cells. Even-numbered mAChRs were seen on the nerve terminals. M2 was also shown on the cuticular plates and supporting cells. Vestibular efferent fibers and terminals were not identified in our studies. Results from WB of the dissociated vestibular epithelia, nerve fibers and vestibular ganglia were consistent with the results from IH and IC. Our findings suggest that there is considerable co-expression of the subtypes on the neural elements of the labyrinth. Further electrophysiological and pharmacological studies should delineate the mechanisms of action of muscarinic acetylcholine receptors on structures in the labyrinth.

Na+ currents in vestibular type I and type II hair cells of the embryo and adult chicken.

In birds, type I and type II hair cells differentiate before birth. Here we describe that chick hair cells, from the semicircular canals, begin expressing a voltage-dependent Na current (INa) from embryonic day 14 (E14) and continue to express the current up to hatching (E21). During this period, INa was present in most (31/43) type I hair cells irrespective of their position in the crista, in most type II hair cells located far from the planum semilunatum (48/63), but only occasionally in type II hair cells close to the planum semilunatum (2/35). INa activated close to -60 mV, showed fast time- and voltage-dependent activation and inactivation, and was completely, and reversibly, blocked by submicromolar concentrations of tetrodotoxin (Kd = 17 nM). One peculiar property of INa concerns its steady-state inactivation, which is complete at -60 mV (half-inactivating voltage = -96 mV). INa was found in type I and type II hair cells from the adult chicken as well, where it had similar, although possibly not identical, properties and regional distribution. Current-clamp experiments showed that INa could contribute to the voltage response provided that the cell membrane was depolarized from holding potentials more negative than -80 mV. When recruited, INa produced a significant acceleration of the cell membrane depolarization, which occasionally elicited a large rapid depolarization followed by a rapid repolarization (action-potential-like response). Possible physiological roles for INa in the embryo and adult chicken are discussed.

Return of potassium ion channels in regenerated hair cells: possible pathways and the role of intracellular calcium signaling.

Recent electrophysiological studies in pigeon have demonstrated that potassium channels are completely functional in regenerated type II hair cells at 21 days post-treatment (PT) with ototoxic doses of streptomycin. The currents return in the order they appear during development. The mixture of ionic currents in a regenerated type II hair cell in a particular region of the neuroepithelium is the same as in its ancestor in that region. The return of currents in regenerated type I hair cells is more complicated. The dominant conductance gKI is not present until after 70 days PT. Before 70 days, the ionic currents in type I hair cells resemble those of regenerated type II hair cells, suggesting that the ionic currents in type II hair cells might be precursors of the ionic currents in regenerated type I hair cells. New data show that at one year PT, the kinetics and drug sensitivity of the dominant K+ conductance in type I hair cells are identical to gKI. Supporting cells, believed to be the precursors of regenerated type II hair cells, have effectively no voltage-gated outward potassium channels, suggesting that regenerated type II hair cells must develop these channels de novo. The next step is to understand the mechanisms by which the potassium channel protein is synthesized, migrates through the cytosol, and is inserted into the plasmalemma of regenerating hair cells. These mechanisms are unknown. We propose that intracellular calcium is involved in this process, as well as in the differentiation, proliferation, and gene regulation of precursor cells fated to become hair cells.

[Secondary prevention in acute myocardial infarction]. / Prevenção secundária no enfarte agudo do miocárdio.

Myocardial infarction is still one of the main causes of mortality and morbidity in Western countries. The advances made in the last 30 years have made it possible to reduce mortality significantly (which is currently below two digits) as well as morbidity. The subject of secondary prevention of myocardial infarction gains particular significance in this context since 10 to 15% of the patients who survive the hospital phase of myocardial infarction die during the first year following discharge and, of these deaths, half occur in the first three months. Therefore, it is necessary to make an early definition of the risk of another coronary event, that is, to make a risk stratification. This should occur throughout hospitalization and should be complete at the time of discharge, never beyond the first weeks of evolution. Bearing in mind the age, sex, coronary risk factors, ischemia persistence, the degree of left ventricular dysfunction and the presence of malignant disrhythmias, there are three risk levels: high; intermediate; and low. An overall approach to secondary prevention of infarction should take into account that, apart from the factors of such high prognostic value (Chapter II) assessed in the definition of risk groups, the measures to reduce reinfarction and sudden death (Chapter III) and the control of the risk factors for heart disease (Chapter IV) should also be considered. The principal late complications of infarction with significant prognostic influence are described in Chapter III: left ventricular dysfunction; rhythm disturbances and residual ischemia. The diagnostic criteria and therapeutic objectives are considered in each of the groups with relevance to consolidated advances according to the modern concept of evidence based medicine, according to international regulations. The grading of scientific evidence into three distinct categories (A, B and C), based on five levels of evidence classified from I to V, is presented accordingly in relation to the therapeutic proposals. Chapter III deals with a set of therapeutic interventions used in secondary prevention because they reduce reinfarction and sudden death: platelet antiaggregants; anticoagulants; Beta blockers; calcium channel blockers; antioxidants and nitrates. A concept of particular clinical significance is presented for each of these groups of drugs. The last part contains an eminently clinical overall review of the principal advances in coronary risk factor control, new therapeutic acquisitions in atherosclerotic disease with natural relevance to hypolipidemic agents and statins, which apart from controlling the plasmatic levels of cholesterol, also stabilize the atherosclerotic plaque and reduce acute coronary events significantly. Apart from dyslipidemia, the classic risk factors are: smoking; hypertension; obesity; diabetes and sedentary life. In each case, reference is made to the general measures and specific approaches, as well as the pharmacological therapy according to evidence based medicine. The recommended attitudes are pointed out. The role of cardiac rehabilitation and postmenopausal hormone replacement therapy are also discussed in the last part of these recommendations, in which the on-going controversy regarding hormone replacement therapy is pointed out in view of the results of more recent clinical trials.

Response to seasonal drought in three cultivars of Ceratonia siliqua: leaf growth and water relations.

Responses of leaf growth and leaf water relations to seasonal drought were monitored during two successive years in three cultivars (Galhosa, Espargal and Mulata) of Ceratonia siliqua L. growing in the field in southern Portugal. Leaf water relations of fully expanded leaves were characterized by pressureâ volume analysis, and morphometric measurements of petiolar xylem were made. The three cultivars differed with respect to onset of leaf initiation. In Galhosa, there was a sharp peak of leaf initiation in June that was immediately followed by a period when leaf expansion rates were highest. The onset of leaf growth occurred earlier in Espargal and Mulata than in Galhosa, and both cultivars continued producing new leaves throughout the summer period. The diurnal pattern of water relations in recently expanded leaves indicated that, during midsummer, Galhosa was the only cultivar in which leaf water potential did not fall below the turgor loss point and leaf relative water content remained above 90%. The occurrence of osmotic adjustment in recently expanded leaves of Galhosa was not demonstrated conclusively. However, during the dry season following leaf formation, a seasonal decrease in osmotic potential sufficient to maintain turgor was detected in 1-year-old leaves of Galhosa but not in 1-year-old leaves of the other cultivars. Among cultivars, Galhosa petioles had the widest xylem conduits, which may partly explain why midday leaf water potential in Galhosa never decreased below -2.0 MPa even at the end of the summer drought.

[Can blood homocysteine explain the family history of vascular diseases?]. / Poderá a homocisteinemia explicar a história familiar da doença vascular?

INTRODUCTION AND AIMS: Family history of vascular disease is an important risk factor for vascular disease, independent of conventional risk factors. Homocysteinemia, a newly defined risk factor, is caused by genetics, such as cystathionine beta synthase deficiencies, and metabolic deficiencies. With the present work we intend to study the influence of family history of vascular disease in homocysteinemia. METHODS: We studied 204 normal persons (153 males), average age 38.7 +/- 10.9 years, in terms of family history of vascular disease (death due to myocardial infarction or a stroke), conventional risk factors, routine laboratory tests, fasting homocysteinemia and after oral methionine loading (0.1 g/Kg body weight). We compared laboratory results, conventional risk factors and homocysteinemia levels in persons with and without a family history of vascular disease. We performed covariance analysis to evaluate, in a multivariate model, factors that were related to basal or after methionine loading homocysteinemia. RESULTS: 35% of persons presented a family history of vascular disease (FHVD). Persons with FHVD presented higher age (45.6 +/- 8.9 versus 35.0 +/- 10.1, p < 0.001), and higher prevalence of hypertension (p = 0.002), dyslipidemia (p = 0.001), obesity (p = 0.03), and physical inactivity (p = 0.03). They presented a tendency, without statistical significance, to have a higher prevalence of diabetes and of hyperhomocysteinemia, and to present higher levels of basal and afterload homocysteinemia. Performing covariance analysis, basal homocysteinemia did not present any relation to FHVD. After methionine load homocysteinemia was strongly influenced by basal homocysteinemia (p = 0.0000), and significantly related to FHVD (p = 0.039). CONCLUSIONS: Homocysteinemia cannot explain most of the risk of family history of vascular disease, not explained by conventional risk factors. The only significant relationship between homocysteinemia and FHVD was observed with afterload homocysteinemia in the multivariate model. FHVD is clearly related to conventional risk factors.

Effects of KCNQ channel blockers on K(+) currents in vestibular hair cells.

Linopirdine and XE991, selective blockers of K(+) channels belonging to the KCNQ family, were applied to hair cells isolated from gerbil vestibular system and to hair cells in slices of pigeon crista. In type II hair cells, both compounds inhibited a slowly activating, slowly inactivating component of the macroscopic current recruited at potentials above -60 mV. The dissociation constants for linopirdine and XE991 block were <5 microM. A similar component of the current was also blocked by 50 microM capsaicin in gerbil type II hair cells. All three drugs blocked a current component that showed steady-state inactivation and a biexponential inactivation with time constants of approximately 300 ms and 4 s. Linopirdine (10 microM) reduced inward currents through the low-voltage-activated K(+) current in type I hair cells, but concentrations up to 200 microM had little effect on steady-state outward K(+) current in these cells. These results suggest that KCNQ channels may be present in amniote vestibular hair cells.

Multiple endocrine neoplasia type 2A. Study of a family.

INTRODUCTION: Pheochromocytomas (Pheo) can occur sporadically, isolated or in association with other neuroendocrine lesions. In multiple endocrine neoplasia type 2A (MEN-2A), Pheo is associated to medullary thyroid carcinoma (MTC) or its precursor, C-cell hyperplasia (CCH) and parathyroid hyperplasia. Genetic screening provides early diagnosis and preventive treatment. In order to validate DNA analysis as a reliable method of early identification of gene carriers, we compared the results of genetic screening with clinical, biochemical, imaging and pathological findings in the members of an affected family. POPULATION AND METHODS: The diagnosis of a bilateral necrotic Pheo in a female patient led to the study of a family with four generations, aged 3 to 78 years (mean = 30.3 yrs). The study included a clinical examination; basal and pentagastrin stimulated calcitonin values; urinary catecholamines and their metabolites; serum calcium and a genetic study (direct sequence of PCR products from genomic DNA isolated from leucocytes using specific primers in exon 11 of the RET protooncogene of chromosome 10). The radiologic study, gammagraphic study (131I-MIBG) and magnetic resonance study were performed in members with clinical suspicion of Pheo. RESULTS: Seven out of nine patients had a mutation on codon 634 of exon 11 of RET (TGC-CGC), leading to cysteine arginine substitution in the codified protein; all gene carriers had biochemical markers of MTC/CCH and four of Pheo. The Pheo patients underwent adrenalectomy (bilateral in three) and all the gene carriers underwent prophylactic thyroidectomy. The pathologic findings were: MTC in four (metastasized in one); CCH in three and parathyroid hyperplasia in one. CONCLUSIONS: Phenotypic penetration of RET mutation was 100% for MTC/CCH, but only 57% of the gene carriers had Pheo. Genetic screening allowed early prophylactic treatment in four out of seven patients; pathologic findings revealed several evolutionary stages of the disease. Patients not yet showing Pheo are under close clinical and laboratory surveillance.

Extra-adrenal pheochromocytoma (paraganglioma).

The authors describe the case of a 19-year-old female patient with an abdominal paraaortic extra-adrenal pheochromocytoma (paraganglioma), presenting arterial hypertension. The predominant catecholamine produced by the tumor was norepinephrine (4110 pg/ml; normal < 450 pg/ml). 131I metaiodobenzylguanidine (131I-MIBG), computed tomography and magnetic resonance imaging allowed location and characterization of the tumor. Histologically the tumor (weight = 34.2 g; 5.8 x 4 x 3 cm) was a typical pheochromocytoma.

Effects of cationic substitutions on delayed rectifier current in type I vestibular hair cells.

The resting potassium current (I(KI)) in gerbil dissociated type I vestibular hair cells has been characterized under various ionic conditions in whole cell voltage-clamp. When all K(+) in the patch electrode solution was replaced with Na(+), (Na(+))(in) or Cs(+), (Cs(+))(in), large inward currents were evoked in response to voltage steps between -90 and -50 mV. Activation of these currents could be described by a Hodgkin-Huxley-type kinetic scheme, the order of best fit increasing with depolarization. Above approximately -40 mV currents became outward and inactivated with a monoexponential time course. Membrane resistance was inversely correlated with external K(+) concentration. With (Na(+))(in), currents were eliminated when K(+) was removed from the external solution or following extracellular perfusion of 4-aminopyridine, indicating that currents flowed through I(KI) channels. Also, reduction of K(+) entry through manipulation of membrane potential reduced the magnitude of the outward current. Under symmetrical Cs(+), 0 K(+) conditions I(KI) is highly permeable to Cs(+). However, inward currents were reduced when small amounts of external K(+) were added. Higher concentrations of K(+) resulted in larger currents indicating an anomalous mole fraction effect in mixtures of external Cs(+) and K(+).