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A Castellano

Publications and source records attributed to A Castellano.

At least 37 records · Page 2Linked to original sources
PubMed1995

Molecular characterization of renal calcium channel beta-subunit transcripts.

An apical, hormone-regulated, calcium entry channel in the distal convoluted tubule and/or connecting tubule (DCT/CNT) is thought to play an important role in controlling renal calcium excretion. We previously identified a gene transcript encoding the pore-forming alpha 1-subunit of a calcium channel (alpha 1A, or CaCh4) which may be a candidate for such a molecule. The properties of voltage-dependent calcium channels are known to be modulated by their beta-subunits. To identify the accessory beta-subunit of DCT/CNT calcium channels, degenerate primers based on published beta-subunit sequences were used to amplify rat kidney cDNA by the polymerase chain reaction (PCR), and the products were subcloned and sequenced. Alternatively spliced transcripts of three beta-subunit genes (beta 2, beta 3, and beta 4) were identified. Northern blot analysis indicated that beta 4-subunit is preferentially expressed in kidney cortex. Transcripts of all three beta-subunit genes were detected by PCR in microdissected nephron segments, but only beta 4-subunit was found in DCT/CNT. As the beta 4- and alpha 1A-subunits colocalize to the DCT/CNT, we hypothesize that they may be constituent subunits of a renal calcium channel regulated by a hormone(s).

Alternative Splicing↗
PubMed1995

Vulvo-vaginitis and reproduction.

The main micro-organisms able to interfere with the reproductive function have been considered. In particular, the problems concerning the vaginal environment and its interactions with spermatozoa, immunological aspects and contraception. Lastly, reference has been made to methods of prevention and study in the field of diagnostics and of clinical management.

Bartholin's Glands↗
PubMed1994

T-type and N-type calcium channels of Xenopus oocytes: evidence for specific interactions with beta subunits.

We used amplifying effects of calcium channel beta subunits to identify endogenous calcium channels in Xenopus oocytes. Expression of rat brain beta 4 increased macroscopic endogenous current magnitude with a small effect on kinetics. In contrast, expression of rat brain/cardiac beta 2 produced a much larger increase in current magnitude and dramatically slowed current decay. Low concentrations of omega-conotoxin GVIA irreversibly blocked currents in both uninjected and beta 2-injected oocytes. Single channel recordings revealed both T- and N-type calcium channels with conductances of 9 and 18 pS, respectively, in uninjected oocytes and in oocytes expressing either beta subunit. Expression of either beta subunit slowed average current decay of T-type single channels. Slowing of T-type current decay by expression of beta 2 was due to reopening of the channels. N-type single channel average current decay showed little change with expression of beta 4, whereas expression of beta 2 slowed average current decay.

Animals↗
PubMed1994

[The efficacy of the hysteroscopic treatment of menorrhagia associated with uterine fibromyomas].

Objective of our study was to determine the effectiveness of hysteroscopic surgery in the treatment of menorrhagia associated with uterine myomas. 25 women with clinical and ultrasonographic diagnosis of intramural or submucous myomas were treated for menorrhagia by hysteroscopic surgery: 9 by resection and 16 by resection and endometrial ablation. In both groups there was a significant decrease of dysmenorrhea. The mean number of pads used during the heaviest day of menses decreased significantly from 19.5 to 7.4 in women undergoing resection only, and from 20.8 to 2.9 in women treated by resection and endometrial ablation. 2 women of 9 became amenorrheic and no one underwent hysterectomy. 12 of 16 became amenorrheic and 2 underwent hysterectomy. Our study show that menorrhagia can be treated by hysteroscopic surgery of uterine myomas in some selected women.

Adult↗
PubMed1993

Cloning and expression of a neuronal calcium channel beta subunit.

Although pharmacological and electrophysiological studies have demonstrated the existence of multiple types of voltage-dependent calcium channels in neuronal tissue, the subunit composition of these channels is not well known. Here, we report the cloning and expression of a new rat brain beta subunit (beta 4). Northern blot analysis indicates that beta 4 mRNA is expressed almost exclusively in neuronal tissues, with the highest levels being found in the cerebellum. Coexpression studies indicate that rat beta 4 can interact with rabbit cardiac muscle alpha 1, rabbit skeletal muscle alpha 1, and calcium channels endogenous to Xenopus oocytes. beta 4 modulation of alpha 1 activity is similar to the modulation induced by beta 1, beta 2, or beta 3. The most striking effect of beta subunits is their ability to increase functional alpha 1 activity, which can be measured as either increased dihydropyridine binding to membranes from transfected COS cells or increased calcium channel activity in Xenopus oocytes.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1993

Cloning and expression of a third calcium channel beta subunit.

The skeletal muscle dihydropyridine receptor/Ca2+ channel consists of five distinct subunits (alpha 1, alpha 2 delta, beta 1, and gamma). Homologous alpha 1, alpha 2 delta, and beta 2 subunits are expressed in heart and brain. The present study reports the cloning and expression of a third beta subunit, beta 3, which is expressed predominantly in brain. Its open reading frame encodes a protein with 484 amino acids with a predicted molecular mass of 54,571 Da. Coexpression of beta 3 with a cardiac alpha 1 in Xenopus oocytes induces similar changes in Ca2+ channel activity as beta 1 and beta 2, that is, it increases peak currents, modulates the voltage dependence of activation, and accelerates activation. In addition, beta 3 accelerates the rate of inactivation at positive test potentials.

Amino Acid Sequence↗
PubMed1993

Dual modulation of K+ currents and cytosolic Ca2+ by the peptide TRH and its derivatives in guinea-pig septal neurones.

1. We describe a dual effect of the peptide TRH (thyrotrophin-releasing hormone) and its derivatives at concentrations between 0.1 and 1 microM on the K+ currents and cytosolic Ca2+ concentration in enzymatically dispersed septal neurones. 2. In response to membrane depolarization, septal neurones recorded under whole-cell patch clamp can generate two major K+ currents: (i) a fast and transient K+ current (I(t)), that after a maximum at 2-5 ms inactivates completely at all membrane potentials in less than 50 ms; and (ii) a slowly activating current (I(s)), which reaches a maximum in 15-20 ms and does not exhibit appreciable inactivation during short-lasting voltage pulses. 3. In about 70% of the neurones tested (n = 48) TRH induced a reversible, and often transient, increase of I(t), I(s) or both K+ conductaNces. In approximately 10% of the cells the peptide had an opposite effect and caused a more protracted and partially reversible attenuation of the amplitude of I(t) and I(s). 4. The dual action of TRH on the K+ currents was mimicked by its derivatives but the effects varied depending on their structural relationship with the precursor neuropeptide. The physiological metabolite cyclo-His-Pro and the synthetic analogue methyl-TRH, in which the carboxyl terminus of the molecule is conserved, increased the K+ currents, whereas depression of the K+ conductances was predominantly observed in the presence of TRH-OH, in which the amino end of TRH is maintained intact. 5. In fura-2-loaded unclamped cells, TRH induced either release of Ca2+ from internal stores, Ca2+ entry, or both. With TRH-OH we never observed mobilization of internal Ca2+ but this peptide evoked a large Ca2+ influx. 6. The results demonstrate that the physiological metabolites of brain TRH (cyclo-His-Pro and TRH-OH) have biological activity. TRH and its derivatives exert two types of regulatory actions on the voltage-gated K+ channels and cytosolic Ca2+ concentration in central neurones, which can be explained assuming that TRH and TRH-derived products interact with different subtypes of brain receptors recognizing preferentially either the amino or the carboxyl termini of the TRH molecule.

Animals↗
PubMed1993

Stabilizing effect of water/alcohol solvents towards autoxidation of human haemoglobin.

The stabilization of haemoglobin (Hb) in water/alcohol solvents (ethanol, butan-1-ol, ethylene glycol and glycerol) against autoxidation, a major barrier to the successful use of Hb in biological and medical engineering was studied, with these solvents, a large decrease in the autoxidation rate is observed over a range of concentrations. Studies on the effect of Hb concentration on autoxidation showed that, irrespective of the Hb concentration, oxyHb is more stabilized in water/alcohol solvents than in water. In these solvents, at the concentration exhibiting the maximal stabilizing effect, the oxygen affinity of Hb was little disturbed, but the changes in enthalpy and entropy of activation increased with the stabilization effect of alcohol. The impact of alcohols on the thermal denaturation of metHb was studied. We observed that metHb is less stable in ethanol and butan-1-ol than in water, whereas the opposite is observed with glycerol and ethylene glycol. The strong stability of oxyHb observed with these solvents could result both from an increase in water structure and an increase of viscosity. Finally, e.p.r. has shown that alcohols lead to an increase of the global distance between the nitrogens of proximal histidine (F8) and nitric oxide in the nitrosyl Hb.

1-Butanol↗
PubMed1992

Cloning and expression of a cardiac/brain beta subunit of the L-type calcium channel.

The skeletal muscle dihydropyridine receptor/Ca2+ channel is composed of five protein components (alpha 1, alpha 2 delta, beta, and gamma). Only two such components, alpha 1 and alpha 2, have been identified in heart. The present study reports the cloning and expression of a novel beta gene that is expressed in heart, lung, and brain. Coexpression of this beta with a cardiac alpha 1 in Xenopus oocytes causes the following changes in Ca2+ channel activity: it increases peak currents, accelerates activation kinetics, and shifts the current-voltage relationship toward more hyperpolarized potentials. It also increases dihydropyridine binding to alpha 1 in COS cells. These results indicate that the cardiac L-type Ca2+ channel has a similar subunit structure as in skeletal muscle, and provides evidence for the modulatory role of the beta subunit.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1991

Sodium and calcium currents in dispersed mammalian septal neurons.

Voltage-gated Na+ and Ca2+ conductances of freshly dissociated septal neurons were studied in the whole-cell configuration of the patch-clamp technique. All cells exhibited a large Na+ current with characteristic fast activation and inactivation time courses. Half-time to peak current at -20 mV was 0.44 +/- 0.18 ms and maximal activation of Na+ conductance occurred at 0 mV or more positive membrane potentials. The average value was 91 +/- 32 nS (approximately 11 mS cm-2). At all membrane voltages inactivation was well fitted by a single exponential that had a time constant of 0.44 +/- 0.09 ms at 0 mV. Recovery from inactivation was complete in approximately 900 ms at -80 mV but in only 50 ms at -120 mV. The decay of Na+ tail currents had a single time constant that at -80 mV was faster than 100 microseconds. Depolarization of septal neurons also elicited a Ca2+ current that peaked in approximately 6-8 ms. Maximal peak Ca2+ current was obtained at 20 mV, and with 10 mM external Ca2+ the amplitude was 0.35 +/- 0.22 nA. During a maintained depolarization this current partially inactivated in the course of 200-300 ms. The Ca2+ current was due to the activity of two types of conductances with different deactivation kinetics. At -80 mV the closing time constants of slow (SD) and fast (FD) deactivating channels were, respectively, 1.99 +/- 0.2 and 0.11 +/- 0.03 ms (25 degrees C). The two kinds of channels also differed in their activation voltage, inactivation time course, slope of the conductance-voltage curve, and resistance to intracellular dialysis. The proportion of SD and FD channels varied from cell to cell, which may explain the differential electrophysiological responses of intracellularly recorded septal neurons.

Animals↗
PubMed1991

Molecular diversity and function of G proteins and calcium channels.

General features of signal transduction by G proteins and structural properties of G-protein-modulated calcium channels are described. Recent results on roles of beta gamma dimers in signal transduction, on the kinetic properties of Gi alpha subunits and structural diversity of Go alpha subunits are discussed, as are the background and current state of our knowledge of the modulation of calcium channels by G proteins.

Amino Acid Sequence↗
PubMed1990

Molecular diversity of L-type calcium channels. Evidence for alternative splicing of the transcripts of three non-allelic genes.

The diversity of L-type calcium channels was probed using the polymerase chain reaction and primers based on regions conserved in the L-type skeletal muscle (CaCh 1) and cardiac calcium channels (CaCh 2). Related sequences were amplified from human heart, hamster heart, rabbit heart, mouse ovary, mouse BC3H1 cells, and hamster insulin-secreting (HIT) cells. Sequencing of various clones revealed the presence of alternate splicing in gene products coding for CaCh 1, CaCh 2, and a related calcium channel. This related gene product, which we refer to as neuroendocrine or CaCh 3, is expressed in brain and endocrine cells. The diverse products can be explained by the use of alternate exons of equal size, which account for changes in amino acid composition, in combination with an alternate splice acceptor site or an exon skipping event, which produces channels of variable length. Four variants were defined for the gene 3 product, subtypes 3a, 3b, 3c, and 3d that differed in both the sequence of the third membrane spanning segment of the fourth repeat unit (IVS3) and in the size of the linker between this and the fourth membrane spanning segment (IVS4). Three CaCh 2 variants were cloned, subtypes 2a, 2c, and 2d, that are homologous to the a, c, and d variants of CaCh 3. For the skeletal muscle calcium channel only two variants were isolated. They are homologous to those of the a and c subtypes of CaCh 2 or 3, in that they differ only in the size of the IVS3 to IVS4 linker. These results demonstrate that calcium channel diversity is created by both the expression of distinct genes and the alternate splicing of these genes.

Alleles↗
PubMed1990

Thyrotropin-releasing-hormone (TRH) and its physiological metabolite TRH-OH inhibit Na+ channel activity in mammalian septal neurons.

The interaction of thyrotropin-releasing hormone (TRH) and its physiological metabolite TRH-OH with Na+ channels was studied in enzymatically dissociated guinea pig septal neurons by using the whole-cell variant of the patch-clamp technique. In about 60% of the cells tested, the neuropeptides at concentrations between 0.01 and 2.5 microM produced a dose-dependent reversible attenuation of Na+ currents. With 2 microM TRH-OH, peak Na+ current amplitude was reduced by 20-50% (27 +/- 8%, mean +/- SD; n = 16), whereas at the same concentration TRH was approximately half as effective as TRH-OH. In the presence of the tripeptides, the voltage-dependent parameter of the Na+ current were unaltered. TRH-induced reduction of Na+ current amplitude was transient and recovered almost completely during maintained exposure to the peptides. In addition, the response to either TRH-OH or TRH decreased with repeated treatment. Our results demonstrate that neuronal Na+ channels can be modulated by naturally occurring neuropeptides.

Animals↗
PubMed1989

Potassium currents in dissociated cells of the rat pineal gland.

The properties of K currents of pineal cells were studied using the whole-cell variant of the patch-clamp technique. The total K current could be separated in two distinct components: a fast, transient current (It) and a slow current (Is). The activation threshold of It was at -35 to -30 mV. On depolarization to +50 mV it reaches a peak in 2-3 ms and inactivates almost completely in 50 ms. Half steady state inactivation occurs at -45 mV. Inactivation of It is voltage-dependent and is well fitted by single exponentials with time constants between 17.2 ms at +50 mV and 27.2 ms at -10 mV. Inactivation is removed with time and the recovery period shortened by membrane hyperpolarization. The slow K current has a threshold at -20 to -15 mV. It reaches a maximum in about 30-40 ms and inactivates slightly, to about 80% of the peak value at the end of pulses lasting 200 ms. With 80 mM external K, tail currents recorded after short (1-2 ms) depolarizations were about 2.5 times faster than the tails recorded at the end of 50 ms pulses. The fast tails were removed by depolarizing prepulses but the slow tails remained unaltered. Thus, the fast and slow tails are probably a reflection of the closing of the transient and slow K channels. The transient K current of pineal cells has general characteristics similar to transient currents recorded in non-secretory cells, but also has particular kinetic properties.

Animals↗
PubMed1988

Bicycle ergometer and echocardiographic study in healthy subjects and patients with angina pectoris after administration of L-carnitine: semiautomatic computerized analysis of M-mode tracing.

The discovery tha carnitine takes an active part in the transportation of long-chain acyl residues across the inner mitochondrial membrane dates back to 1958. It has been shown experimentally tha a reduction in myocardial carnitine content takes place after 15-30 min of ischemia. L-carnitine was administered orally in doses of 3 g/day for 30 days to 16 subjects with effort-induced angina and to 14 healthy subjects. A bicycle ergometer exercise test revealed a 1.5 mm (mean) depression of the ST-T segment in the angina subjects after pharmacological wash-out and a 1 mm depression in the same subjects after carnitine treatment. M-code echocardiography showed positive changes in a number of ventricular function parameters in the angina subjects and also, to a lesser extent, in the healthy controls.

Adult↗
PubMed1987

Ca2+- and voltage-dependent K+ conductance in dispersed parathyroid cells.

The membrane ionic conductances of dispersed parathyroid cells kept in primary culture were studied using the "whole-cell" and "inside-out excised patch" variants of the patch-clamp technique. The major component of the total current was a voltage-dependent outward K+ current without an appreciable inward current. The amplitude of the K+ current was markedly reduced when free internal Ca2+ was buffered by addition of 10 mM EGTA. Recordings of single-channel current in excised membrane patches revealed the presence of K+ channels with large unitary conductance (200 pS in symmetrical 130 mM K+ solutions) which were also activated by depolarization when internal Ca2+ concentration was about 10(-5)-10(-6) M. At any membrane voltage these channels were closed most of the time at internal Ca2+ concentrations lower than 10(-10) M. These results demonstrate the existence of a Ca2+- and voltage-dependent K+ permeability in parathyroid cells which may participate in the unusual membrane potential changes induced by alterations of external Ca2+ and, possibly, in the regulation of parathormone secretion.

Animals↗