Global phylogenomic assessment of Leptoseris and Agaricia reveals substantial undescribed diversity at mesophotic depths

BACKGROUND

Mesophotic coral communities are increasingly gaining attention for the unique biological diversity they host, exemplified by the numerous mesophotic fish species that continue to be discovered. In contrast, many of the photosynthetic scleractinian corals observed at mesophotic depths are assumed to be depth-generalists, with very few species characterised as mesophotic-specialists. This presumed lack of a specialised community remains largely untested, as phylogenetic studies on corals have rarely included mesophotic samples and have long suffered from resolution issues associated with traditional sequence markers.

RESULTS

Here, we used reduced-representation genome sequencing to conduct a phylogenomic assessment of the two dominant mesophotic genera of plating corals in the Indo-Pacific and Western Atlantic, respectively, Leptoseris and Agaricia. While these genome-wide phylogenies broadly corroborated the morphological taxonomy, they also exposed deep divergences within the two genera and undescribed diversity across the current taxonomic species. Five of the eight focal species consisted of at least two sympatric and genetically distinct lineages, which were consistently detected across different methods.

CONCLUSIONS

The repeated observation of genetically divergent lineages associated with mesophotic depths highlights that there may be many more mesophotic-specialist coral species than currently acknowledged and that an urgent assessment of this largely unstudied biological diversity is warranted.

Deep Learning-Based Feature Extraction of Acoustic Emission Signals for Monitoring Wear of Grinding Wheels

Tool wear monitoring is a critical issue in advanced manufacturing systems. In the search for sensing devices that can provide information about the grinding process, Acoustic Emission (AE) appears to be a promising technology. The present paper presents a novel deep learning-based proposal for grinding wheel wear status monitoring using an AE sensor. The most relevant finding is the possibility of efficient feature extraction form frequency plots using CNNs. Feature extraction from FFT plots requires sound domain-expert knowledge, and thus we present a new approach to automated feature extraction using a pre-trained CNN. Using the features extracted for different industrial grinding conditions, t-SNE and PCA clustering algorithms were tested for wheel wear state identification. Results are compared for different industrial grinding conditions. The initial state of the wheel, resulting from the dressing operation, is clearly identified for all the experiments carried out. This is a very important finding, since dressing strongly affects operation performance. When grinding parameters produce acute wear of the wheel, the algorithms show very good clustering performance using the features extracted by the CNN. Performance of both t-SNE and PCA was very much the same, thus confirming the excellent efficiency of the pre-trained CNN for automated feature extraction from FFT plots.

Conventional versus modern abattoirs in Colombia: Impacts on welfare indicators and risk factors for high muscle pH in commercial Zebu young bulls

The aim of the study was to determine the effects of abattoir type (conventional abattoir -CA- versus modern abattoir -MA-) on stress parameters and risk factors for high muscle pH in Colombia. A total of 522 Zebu young bulls were studied in two groups: 285 at CA, and 237 at MA. Blood samples were taken to measure cortisol, glucose, lactate, creatine kinase, β-hydroxybutyrate, total protein, albumin, creatinine, urea, haematocrit, leukocytes and N/L ratio. Cattle were monitored during the unloading, lairage, handling and stunning. The logistic regression model showed that stocking density, transport time, abattoir type, and inefficient stunning were variables associated with the prevalence of dark cutting carcasses. This study demonstrated that modern improvements at abattoir level, proper infrastructure, and stunning equipment, do not always guarantee quality in terms of animal welfare. As a first attempt in the Colombian beef industry, this research suggested how handling practices could affect cattle welfare and the prevalence of high muscle pH even at MA.

Genetic parameters and genotype-environment interactions for skeleton deformities and growth traits at different ages on gilthead seabream (Sparus aurata L.) in four Spanish regions

One of the most important problems of fish aquaculture is the high incidence of fish deformities, which are mainly skeletal. In this study, genetic parameters on gilthead seabream (Sparus aurata L.) for skeleton deformities at different ages (179, 269, 389, 539 and 689 days) and their correlations with growth traits were estimated, as were as their genotype × environment interactions (G × E) at harvesting age. A total of 4093 offspring from the mass spawning of three industrial broodstocks belonging to the PROGENSA(®) breeding programme were mixed and on-grown by different production systems in four Spanish regions: Canary Islands (tanks and cage), Andalusia (estuary), Catalonia (cage) and Murcia (cage). Parental assignment was inferred using the standardized SMsa1 microsatellite multiplex PCR. From three broodstocks, 139 breeders contributed to the spawn and a total of 297 full-sibling families (52 paternal and 53 maternal half-sibling families) were represented. Heritabilities at different ages were medium for growth traits (0.16-0.48) and vertebral deformities (0.16-0.41), and low for any type of deformity (0.07-0.26), head deformities (0.00-0.05) and lack of operculum (0.06-0.11). The genetic correlations between growth and deformity traits were medium and positive, suggesting that to avoid increasing deformities they should be taken into account in breeding programmes when growth is selected. The G × E interactions among the different facilities were weak for length and deformity and strong for growth rate during this period. These results highlight the potential for the gilthead seabream industry to reduce the prevalence of deformities by genetic improvement tools.

Risk factors influencing bruising and high muscle pH in Colombian cattle carcasses due to transport and pre-slaughter operations

The aim of this study was investigate risk factors as possible causes for bruising and high muscle pH under commercial operating conditions in Colombia. Data was recorded for 86 journeys referring to 1179 animals. Carcasses were analyzed in terms of muscle pH and bruises (site, size, severity and shape). Our results indicate that truck load density, stops during transportation of cattle and the lairage time at the plant increased the risk of bruises appearing on carcasses. A lairage time of 18 to 24h at the plant increased the prevalence of bruises 2.1 times compared to lairage periods of between 12 and 18 h. Furthermore, intermittent stops during transit are a risk factor for the increase in the incidence of bruises. However, the transport time (up to 4h) was not related to the presence of bruises and high muscle pH. Finally, steers were found to have less risk of presenting a high muscle pH.

Spreading of pollutants from alkaline mine drainage. Rodalquilar mining district (SE Spain)

In the Rodalquilar mining district of SE Spain, a total of 46 soil samples that were between 0 and 20 cm in depth were taken from the tailings dump, stream sediments, and surfaces that were presumably were unaffected by mining. In each soil sample, organic carbon content, pH, particle size distribution and total and soluble trace element content were analysed. Pollutants were scattered by runoff from two source areas: tailings from Au mining (Sn, Sb, As and Se) and wastes from Pb mining (Pb, Cu and Zn). Sn, Pb, and Sb were spread mostly in the solid phase of the runoff, while Cu, Zn, As and Se were spread in both the solid and soluble phases of the runoff. The pollutants with the highest soluble concentrations were As and Se, which were scattered at greater distances from the source. Some evidence suggests that tailings from Au mining could also be scattered by wind, but no farther than 1500 m from the source.

Heterozygosity-fitness correlations in the gilthead sea bream Sparus aurata using microsatellite loci from unknown and gene-rich genomic locations

Heterozygosity-fitness correlations (HFC) were assessed for a sample of a gilthead sea bream Sparus aurata population. Two hundred and seventy-one fish were genotyped at 22 known and novel microsatellite loci, from which correlations between the multilocus heterozygosity index (I(MLH) ) and various fitness traits (fork length, mass and specific growth rates) were calculated. Significant global HFCs were found in this sample (0·02 ≤r(2) ≤ 0·08). In addition, all the significant correlations found in this work were negative, indicating that heterozygotes had lower fitness than their homozygote counterparts. Marker location could not explain the observed HFCs. Evidence of inbreeding, outbreeding or population and family structuring was not found in this work. The presence of undetected general effects that may lead to the appearance of HFCs, however, cannot be ruled out. These results seem to be best explained by the occurrence of local effects (due to linkage) or even by possible direct locus advantages.

Impact of unconfined sulphur-mine waste on a semi-arid environment (Almería, SE Spain)

Thirty-five soil samples were taken from unconfined mine waste, stream sediments, and surfaces unoccupied by mining and presumably unaffected by it, in a sulphur-mining zone surrounded by carbonate material and characterized by a semi-arid climate with short torrential storms. These samples were analysed and the results compared to estimate the spread of pollution in the landscape and to assess potential environmental risk. The mean concentrations of S, Zn, Cd, Pb, and As in mine waste were between 3.5-fold (As) and 50-fold (S) greater than unaffected soils. Oxidation of S led to a sharp drop in pH, strong weathering of minerals, and solubilisation of the constituent elements, forming a toxic acidic mine drainage with highly concentrated pollutants that were discharged into the drainage channels. Successive acid mine drainage into the soil on the valley floor spreads acidification and pollution downstream. The high carbonate content in surrounding soils played an important role in the increase of the pH and precipitation of S, Pb, and Al of the affected soils. Meanwhile, high mobility of Zn, Cd and As under basic conditions and a low Fe concentration explain the broad spread of these elements, as high concentrations were detected in soil more than 2000 m from the source. Only the soil solutions from near the waste dump (first 500 m) were highly phytotoxic, and moderately phytotoxic from 500 to 1500 m away. The concentration of pollutants in the leachates was clearly higher than in soil solutions, even in the soils located over 2000 m from the source, implying that the size of the polluted area will increase with time.

A novel second instar Gasterophilus excretory/secretory antigen-based ELISA for the diagnosis of gasterophilosis in grazing horses

We have developed a novel enzyme-linked immunosorbent assay (ELISA) based on excretory/secretory antigens of second instar Gasterophilus for the diagnosis of gasterophilosis in grazing horses. Between January 2007 and January 2009, two experiments were carried out on free-ranging horses in northwest Spain. During the first year, monthly blood samples were collected from a herd of 25 horses. In the second year, a monthly serological survey was conducted for a total of 398 different horses. All the sera were analyzed by ELISA using excretory/secretory antigens from Gasterophilus intestinalis (GphiL2ES) and Gasterophilus nasalis second-stage larvae (GphnL2ES). Climatic data were collected between January 2007 and January 2009 from local meteorological automated stations to establish the weather pattern in the study area. Observations of Gasterophilus eggs on the horses' hair and third instars passed in the faeces were also done. The kinetics of IgG response decreased against GphiL2ES from January to July, increased slowly from August and rose up to January. After a slight decrease in January, the absorbances against GphnL2ES reduced from April to August, when the lowest values were observed. The IgG values rose until the end of the study in January. Third instars were observed in the faeces in March to May, and Gasterophilus eggs were seen on the horses' hair from June to September. The highest IgG seroprevalences were achieved in winter (January-February; 100%) against both antigens. The lowest percentages of seropositivity were observed in June (3%) to the GphiL2ES, and in July (9%) to the GphnL2ES. The use of antigens from G. intestinalis second-stage larvae was shown to be suitable for diagnosing infestation by G. intestinalis or G. nasalis. We concluded that under oceanic climate conditions, the egg-laying period occurs from late spring, and eggs and first instars are found in the mouth in early summer. During summer the second instars move into the stomach and intestine, where the third-stage larvae remain until the end of winter, when pupation takes place. The adult horse bot fly emerges in the spring. Two treatments for the control of gasterophilosis are suggested: a curative in the summer to eliminate the first instars and a preventive in the autumn to suppress the second instars.

Effects of feeding schedule on locomotor activity rhythms and stress response in sea bream

Feeding cycles entrain biological rhythms, which enable animals to anticipate feeding times and so maximize food utilization and welfare. In this article, the effect of mealtime was investigated in two groups of sea bream (Sparus aurata): one group received a single daily meal at random times during the light period (random daytime feeding, RDF), whereas the other group received the meal during the light period but at the same time (scheduled daytime feeding, SDF). All the fish showed diurnal behavior, although the SDF group showed a lower percentage of diurnalism (84.4% vs. 79.5% in RDF and SDF respectively) and developed food anticipatory activity some hours before the mealtime. In addition, the mean daily locomotor activity of the RDF group was significantly higher than that of the SDF group (3132 vs. 2654 counts/day, respectively). Although the mean weight differed between both groups on day 30 (115.7 g and 125.6 g in RDF and SDF respectively), these differences had disappeared by day 60. Plasma cortisol and glucose significantly differed in both groups (cortisol: 71.8 vs. 8.7 ng/ml, glucose: 53.7 vs. 43.8 mg/dl in RDF and SDF, respectively), whereas lactate did not differ significantly. The results obtained suggest that altering the feeding time (scheduled vs. random) affects the behavior and physiology of sea bream, indicating that a single daily feeding cycle (compared to random) is beneficial for fish welfare because they can prepare themselves for the forthcoming feed.

Remediation measures and displacement of pollutants in soils affected by the spill of a pyrite mine

The soils affected by the spill of a pyrite mine were analysed in 100 sampling points at three depths (0-10, 10-30, and 30-50 cm) in 1998 (after the tailings were removed), 1999 (after the cleaning of the highly contaminated areas), and 2004 (after the tilling of the upper 20-25 cm). The comparative study reveals that the removal of the tailings left a heterogeneous distribution pattern of the contaminants, with highly polluted spots alternating with less contaminated areas. The cleanup did not substantially lower the concentration in the highly polluted soils, and the spread of the pollutants increased the concentration in As and Pb in the uppermost 10 cm of 60% of the soils, while the Zn and Cd concentrations increased in only 30% of the soils. Given the high concentration of pollutants in the topsoil (especially As), the tilling of the upper 20-25 cm, despite reducing the average concentration of pollutants in the uppermost 10 cm, did not substantially lower the percentage of soils that exceeded the concentration of 40 mg As kg(-1) dry soil and almost doubled the percentage of soils that surpassed this concentration between 10 and 30 cm. Meanwhile, the displacement of Zn and Cd within the soil supported the reduction in the percentage of soils that in the upper 10 cm exceeded the reference concentrations of these elements (900 mg Zn kg(-1) dry soil and 2 mg Cd kg(-1) dry soil), and the percentage of soils exceeding these concentrations between 10 and 50 cm in depth did not increase. Six years after the spill and at the end of all remediation measures, the intervention levels defined by the Environmental Agency of the Regional Government of Andalusia for natural parks were exceeded in the uppermost 10 cm in 35% of the soils.

Impact of the zoophytophagous plant bug Nesidiocoris tenuis (Heteroptera: Miridae) on tomato yield

Nesidiocoris tenuis Reuter (Heteroptera: Miridae) is one of the most controversial dicyphines because of the injuries it causes to tomato (Solanum esculentum) crops. The aim of this study was to quantify the impact of N. tenuis on fruit yield. Tomato plants were exposed to an average of 0.53 +/- 0.26, 3.4 +/- 1.1, 12.0 +/- 1.4, and 35.2 +/- 7.7 N. tenuis per plant for 3 wk. When fruit were exposed to N. tenuis as flowers, the percentage of aborted fruit was higher in compartments infested with N. tenuis, and this was related directly to the cumulative number of N. tenuis (CNN). However, compartments with the highest abortion rates had heavier and bigger fruit and were not significantly different from the controls. The variation in fruit weight was satisfactorily explained with a logistic equation in relation to the proportion of aborted fruit. To estimate the density thresholds, the variation in truss weight was predicted as a function of fruit weight and aborted fruit. The two latter variables were expressed as a function of the CNN. A maximum of 15% truss weight overcompensation was predicted at 15.8% of fruit abortion. Yield reduction was predicted at fruit abortion rates > or = 27.7%, which corresponded to 566 CNN per plant or 32.11 CNN per leaf. N. tenuis may be considered a useful predator of small pests in tomato crops if kept under these thresholds. Mathematical models predict a yield increase and fruit upgrade that overcompensates for the reduction in the number of fruit below the density threshold.

[Ischemic stroke secondary to left atrial myxoma]

We present the case of a 43-year-old-woman with history of ictal episodes who was admitted to the hospital after suffering a stroke affecting the left middle cerebral artery territory. After initial evaluation, an echocardiography identified a left atrial myxoma as aetiology of the stroke. In view of the surgical need, we asked for a cardiac magnetic resonance in order to obtain further anatomical information about the atrial mass. In the present article we review the neurological manifestations of the cardiac myxoma, considering the ischemic cerebrovascular disease as the most frequent presentation, just as this case illustrates.

Regulation of muscle Cav1.1 channels by long-term depolarization involves proteolysis of the alpha1s subunit

The effects of long-term depolarization on frog skeletal muscle Cav1.1 channels were assessed. Voltage-clamp and Western-blot experiments revealed that long-term depolarization brings about a drastic reduction in the amplitude of currents flowing through Cav1.1 channels and in the levels of the alpha1s subunit, the main subunit of muscle L-type channels. The decline of both phenomena was prevented by the action of the protease inhibitors E64 (50 microM) and leupeptin (50 microM). In contrast, long-term depolarization had no effect on beta1, the auxiliary subunit of alpha1s. The levels of mRNAs coding the alpha1s and the beta1 subunits were measured by RNase protection assays. Neither the content of the alpha1s nor the beta1 subunit mRNAs were affected by long-term depolarization, indicating that the synthesis of Cav1.1 channels remained unaffected. Taken together, our experiments suggest that the reduction in the amplitude of membrane currents and in the alpha1s subunit levels is caused by increased degradation of this subunit by a Ca2+-dependent protease.

Genetic structure of northwestern Spanish brown trout (Salmo trutta L.) populations, differences between microsatellite and allozyme loci

Genetic variation in nine wild brown trout (Salmo trutta L.) populations was studied by means of allozyme and microsatellite markers. All brown trout populations were clearly separated into two clusters that represented the Sil and Duero basins. Although both markers revealed a strong genetic differentiation between basins, microsatellite loci resulted much more accurate when population structure at the intrabasin level was analysed. Also pairwise multilocus FST estimates and assignment tests of individual fish to the set of sampled populations demonstrated a much higher efficiency of microsatellites compared to allozymes. The analysis of both markers provides new insights in defining the conservation units at this local area and confirms the existence of a recognized sub-lineage in the Duero basin. The management implications of these findings are discussed and changes in trout release activity are recommended to avoid mixing of trout gene pools mainly in the Sil basin.

Correlations between fitness and heterozygosity at allozyme and microsatellite loci in the Atlantic salmon, Salmo salar L

The relationship between heterozygosity at genetic markers (six allozyme and eight microsatellite loci), and fluctuating asymmetry (FA), length and weight was investigated in two samples of Atlantic salmon (Salmo salar L.) with different timings of first active feeding (early (EA) and late (LA) salmon). This trait had previously been related to fitness. EA fish show smaller values of FA, are longer, heavier and are more heterozygous at allozyme loci than are conspecific LA fish. Also within both samples, heterozygosity at allozyme loci was inversely related to FA and was positively related to weight and length. However, no significant differences in microsatellite diversity (heterozygosity and mean d2 measurements) were observed between samples (EA vs LA). Furthermore, no association was observed between the variability at microsatellite loci and FA, weight or length within each sample. These results suggest that allozyme loci, in themselves, influence fitness components, rather than associations arising from associative overdominance.

Artificial bowel sphincter in severe anal incontinence

OBJECTIVE

The artificial anal sphincter has been suggested as an alternative in the treatment of severe anal incontinence when conventional surgical methods are not possible or have failed. Experience in this procedure is still limited and the results have not yet been sufficiently established. The aim of this study is to evaluate the efficacy of the ACTICON (American Medical Systems, Minneapolis, MN) on patients operated upon in our Unit.

PATIENTS AND METHOD

In this prospective study an ACTICON sphincter was implanted in 10 patients (8 women) with an average age of 56 years and with an average period of severe anal incontinence of 151 months. The origin of incontinence was obstetric injury (n: 4), neuropathy (n: 3) and sphincteral injury from previous anal surgery (n: 3). The degree of continence was measured using the Fecal Incontinence Scoring System (FISS) and the pre- and postoperative anal manometric parameters at 6-month intervals. The average follow-up time for the efficacy of the implanted system was 29 months.

RESULTS

A total of 6 patients [60%] displayed complications in the immediate postoperative period: subaponeurotic reimplantation of the connecting tubes was necessary after infection of the abdominal wound (n:1); superficial dehiscence of the perianal wound (n: 2), infection of the perianal wound (n: 1) and perianal haematoma (n: 2) that were resolved by conservative treatment. For 3 patients [30%] the system was explanted, definitively in one and in 2 of them reimplanted successfully. At the end of the follow-up period, 9 patients [90%] still have an activated artificial sphincter. The score on the Fecal Incontinence System decreased significantly after the system was activated (P < 0.0001) and the pressure with the cuff closed was significantly higher than pre-operative anal pressure (P < 0.0001). All the patients are now continent for solid stool, 56% have occasional involuntary losses of gases and 33% occasionally have involuntary losses of gases and liquid stool. Only 2 patients [22%] have complete continence.

CONCLUSIONS

Our findings indicate that the ACTICON artificial anal sphincter is well tolerated and can be an effective alternative in the treatment of severe anal incontinence. Although complete continence is only achieved in a low percentage of cases, for the rest of the patients the ACTICON neosphincter reduces the symptoms considerably.

Timing of first feeding and life-history strategies in salmon: genetic data

To investigate the relationship between genetic composition and some physiological traits of interest (age at smoltification, precocious maturation in male parr) in early and late first feeding Atlantic salmon, genetic variation at 6 isozyme and 8 microsatellite loci was examined. Early and late first feeding salmon showed different allelic and genotypic distributions at both isozyme and microsatellite loci. A positive relation between enzymatic loci heterozygosity and precocious active alimentation and earlier smoltification (S1 cf. S2) were also found.

Cerebral-buccal pathways in Aplysia californica: synaptic connections, cooperative interneuronal effects and feedback during buccal motor programs

Ingestion of seaweed by Aplysia is in part mediated by cerebral-buccal interneurons that drive rhythmic motor output from the buccal ganglia and in some cases cerebral-buccal interneurons act as members of the feeding central pattern generator. Here we document cooperative interactions between cerebral-buccal interneuron 2 and cerebral-buccal interneuron 12, characterize synaptic input to cerebral-buccal interneuron 2 and cerebral-buccal interneuron 12 from buccal peripheral nerve 2,3, describe a synaptic connection between cerebral-buccal interneuron 1 and buccal neuron B34, further characterize connections made by cerebral-buccal interneurons 2 and -12 with B34 and B61/62, and describe a novel, inhibitory connection made by cerebral-buccal interneuron 2 with a buccal neuron. When cerebral-buccal interneurons 2 and 12 were driven synchronously at low frequencies, ingestion-like buccal motor programs were elicited, and if either was driven alone, indirect synaptic input was recruited in the other cerebral-buccal interneuron. Stimulation of BN2,3 recruited both ingestion and rejection-like motor programs without firing in cerebral-buccal interneurons 2 or 12. During motor programs elicited by cerebral-buccal interneurons 2 or 12, high-voltage stimulation of BN2,3 inhibited firing in both cerebral-buccal interneurons. Our results suggest that cerebral-buccal interneurons 2 and 12 use cooperative interactions to modulate buccal motor programs, yet firing in cerebral-buccal interneurons 2 or 12 is not necessary for recruiting motor programs by buccal peripheral nerve BN2,3, even in preparations with intact cerebral-buccal pathways.

Calciseptine, a Ca2+ channel blocker, has agonist actions on L-type Ca2+ currents of frog and mammalian skeletal muscle

Calciseptine is a natural peptide consisting of 60 amino acids with four disulfide bonds. The peptide is a natural L-type Ca2+-channel blocker in heart and other systems, but its actions in skeletal muscle have not been previously described. The aim of this study is to characterize the effects of calciseptine on L-type Ca2+ channels of skeletal muscle and on contraction. Whole-cell, patch-clamp experiments were performed to record Ca2+ currents (I(Ca)) from mouse myotubes, whereas Vaseline-gap voltage-clamp experiments were carried out to record I(Ca) from frog skeletal muscle fibers. We found that calciseptine acts as a channel agonist in skeletal muscle, increasing peak I(Ca) by 37% and 49% in these two preparations. Likewise, the peptide increased intramembrane charge movement, though it had little effect on contraction. The molecular analysis of the peptide indicated the presence of a local, electrostatic potential that resembles that of the 1,4-dihydropyridine agonist Bay K 8644. These observations suggest that calciseptine shares the properties of 1,4-dihydropyridine derivatives in modulating the permeation of divalent cations through L-type channels.

Mitochondria regulate inactivation of L-type Ca2+ channels in rat heart

1. L-type Ca2+ channels play an important role in vital cell functions such as muscle contraction and hormone secretion. Both a voltage-dependent and a Ca2+-dependent process inactivate these channels. Here we present evidence that inhibition of the mitochondrial Ca2+ import mechanism in rat (Sprague-Dawley) ventricular myocytes by ruthenium red (RR), by Ru360 or by carbonyl cyanide m-chlorophenylhydrazone (CCCP) decreases the magnitude of electrically evoked transient elevations of cytosolic Ca2+ concentration ([Ca2+]c). These agents were most effective at stimulus rates greater than 1 Hz. 2. RR and CCCP also caused a significant delay in the recovery from inactivation of L-type Ca2+ currents (I(Ca)). This suggests that sequestration of cytosolic Ca2+, probably near the mouth of L-type Ca2+ channels, into mitochondria during cardiac contractile cycles, helps to remove the Ca2+-dependent inactivation of L-type Ca2+ channels. 3. We conclude that impairment of mitochondrial Ca2+ transport has no impact on either L-type Ca2+ currents or SR Ca2+ release at low stimulation frequencies (e.g. 0.1 Hz); however, it causes a depression of cytosolic Ca2+ transients attributable to an impaired recovery of L-type Ca2+ currents from inactivation at high stimulation frequencies (e.g. 3 Hz). The impairment of mitochondrial Ca2+ uptake and subsequent effects on Ca2+ transients at high frequencies at room temperature could be physiologically relevant since the normal heart rate of rat is around 5 Hz at body temperature. The role of mitochondria in clearing Ca2+ in the micro-domain near L-type Ca2+ channels could be impaired during high frequencies of heart beats such as in ventricular tachycardia, explaining, at least in part, the reduction of muscle contractility.

Long-term depolarization regulates the alpha1s, subunit of skeletal muscle Ca2+ channels and the amplitude of L-type Ca2+ currents

The effects of long-term depolarization on the level of alpha1s and on L-type Ca2+ currents of skeletal muscle were investigated. Long-term depolarization (14 h) caused a 50% decrease of alpha1s, revealed with the Western blot technique. This decline was prevented by preincubation with the Ca2+ channel blocker nifedipine. Electrophysiological experiments using the voltage-clamp technique were performed to measure the actions of long-term depolarization on Ca2+ currents and charge movement. A progressive decline in the amplitude of the Ca2+ currents by depolarizations lasting 0.5-14 h was observed. Similar to Western blot results, the fall in current amplitude was prevented by nifedipine, and it depended on external Ca2+. The nonlinear charge mobilized by step pulses was also significantly reduced (50%) by long-term depolarization. It is suggested that alpha1s subunit is down-regulated by long-term depolarization by a very stringent mechanism and that, in this process, Ca2+ ions permeating through L-type channels play a key role. A new role for the L-type Ca2+ current in skeletal muscle fibers in which the channels are self-regulated is proposed.

[Meningococcal disease in Spain: seasonal nature and recent changes]

BACKGROUND

In this study we built a time series model in the time domain based on the cases of meningococcal disease declared every four weeks in Spain between 1972 and 1998 With the model we analyzed the incidence of the disease and examined whether an epidemic really took place at the beginning of 1997, or whether the values were in the range of expectations. At this time there was widespread social alarm in Spain, because there was considered to be an outbreak of meningitis. We also examined whether the incidence of the disease diminished during 1997 following the measures introduced by the Comisión Interterritorial del Sistema Nacional de Salud.

METHOD

The data on the incidence of the meningococcal disease in Spain were obtained from the Boletín Epidemiológico Semanal, published by the Instituto de Salud Carlos III, declared from 1972 to 1998 and grouped every four weeks. The method corresponds to the time series model in the domain of time: the Box-Jenkins method.

RESULTS

In order to explain the behaviour of the disease during the years of the study we chose a model ARIMA(0,1,1) (0,1,1)13 that shows annual seasonal behaviour, with higher incidence in the winter and the beginning of spring, and lower incidence in summer. An intervention analysis showed that in March 1996 there was a level shift in the incidence of the illness. This lasted until September 1997, at which time the incidence returned to pre-1996.

CONCLUSIONS

The measures of sanitary monitoring against the meningitis in the months of greater incidence, winter and beginning of spring must be intensified. Between spring 1996 and autumn 1997 the incidence of meningitis increased. Thereafter, until the end of 1998, there was a significant decrease in incidence, attributable to the performance of the health authorities.

[Valaciclovir in the treatment of initial infection by genital herpes virus: comparative study]

BASIS

To know the therapeutic efficiency in the genital herpes of two drugs: acyclovir and valaciclovir.

METHODS

There were included in the study 142 patients with diagnostic of clinic first episode by genital herpes in two equal groups of 71 patients each one. The distribution in both groups was random to receive one of the following treatment standards: acyclovir 200 mg by verbal each 5 hours, during 7 days; valaciclovir: 500 mg by verbal each 12 hours during 7 days being valued objective and subjective response to the treatment.

RESULTS

The prevailing symptom was the pain (45% and 46.4%), followed by the warmth or burning sensation. The most frequent lesions in both groups were blisters (39.4% and 46.4%). The analysis response to the treatment in relationship to the symptoms as well as in the lesions it could be appreciated that there are not significant differences in the patients treated in both groups (p = 0.3). The adverse effect communicated by the discussed patients were scarce and similar in both groups.

CONCLUSIONS

Both drugs are suitable for the treatment of the genital herpes. The advantage observed with the valaciclovir is the dosing comfort and the facility of completing the treatment.

Regeneration of cerebral-buccal interneurons and recovery of ingestion buccal motor programs in Aplysia after CNS lesions

In the sea slug Aplysia, rhythmic biting is eliminated after bilateral cerebral-buccal connective (CBC) crushes and recovers within 14 days postlesion (dpl). The ability of cerebral-buccal interneuron-2 (CBI-2) to elicit ingestion buccal motor programs (iBMPs; i.e., fictive rhythmic ingestion) and to regenerate synaptic connections with target buccal neurons was assessed with intracellular recordings and dye injections. Isolated central ganglia were obtained from control animals and from lesioned animals at selected times after bilateral CBC crushes. Within 3 wk postlesion, transected CBI-2 axons sprouted at least 10 fine neurites confined to the core of the CBC that projected across the crush site toward the buccal ganglia. When fired with depolarizing current steps, CBI-2 was not observed to elicit iBMPs in preparations until 14 dpl. Thereafter a progressive enhancement in CBI-2's ability to elicit iBMPs was observed with time postlesion. By 40 dpl, CBI-2-elicited iBMPs were indistinguishable from those of controls. CBI-2 regenerated monosynaptic connections with appropriate buccal premotor- and motorneurons by 14 dpl, and the strength of these connections increased with time postlesion. Dramatic frequency facilitation was exhibited by the regenerating CBI-2 buccal synapses; for instance, at early postlesion times, no observable excitatory postsynaptic potentials (EPSPs) were obtained with 1- Hz stimulation of CBI-2, while at 7 Hz, a dramatic increase in EPSP amplitude was obtained with successive spikes. The present study shows that the time course of axonal and synaptic regeneration by command-like interneuron CBI-2 is correlated with the recovery of ingestion buccal motor programs elicited by CBI-2. These results parallel our previous findings of functional neural regeneration in the feeding system and suggest that functional neural regeneration is at least in part mediated by regeneration of specific synaptic pathways.

[Xanthan production by Xanthomonas campestris in a non-conventional culture medium]

Among 3 varieties of Xanthomonas campestris, the variety ocumo (X. campestris pv. ocumo), showed the greatest capacity for producing xanthan. This bacteria grows appropriately and produces this polysaccharide in a wide diversity of carbohydrate sources. However, this strain does not produce xanthan when the carbohydrate comes from lignocellulosic materials. The glucose syrup FAVEPRO was the carbon source that showed the best yield (23 g/l) with the greatest viscosity (7000 cps) of xanthan. The optimum production conditions in 1 L erlenmeyer flasks, with a working volume of 0.2 L and in a 14 L (stirred tank type bioreactor) with a working volume of 10 L, were the following: total sugar 5%, urea 0.05%, di-potassium hydrogen phosphate 0.5%, pH 7.5, inoculum 10%, temperature 30 degrees C, agitation 250-1000 rpm and aereation 0.3-1.0 vvm. This strain of X. campestris pv. ocumo was able to produce xanthan (10 g/l) in a culture medium based on a previously treated agricultural waste, called soluble acid extract of cassava bark. The viscosity of this medium increased up to 1500 cps.

Short-term synaptic enhancement modulates ingestion motor programs of aplysia

Activity-dependent synaptic plasticity regulates the flow of information in neuronal networks and has important implications for the expression of behavior. We find a functional role for short-term synaptic enhancement (STE) such as facilitation, augmentation, and post-tetanic potentiation at central synapses in the sea slug Aplysia californica. Consummatory feeding in Aplysia such as rhythmic biting is controlled by command-like cerebral-buccal interneurons (CBIs) that drive rhythmic motor output in the buccal ganglia. CBI interneuron-2 (CBI-2) makes monosynaptic connections onto buccal neurons, including premotor neurons B31/32 and B34 and motor neurons B61/62. Stimulating CBI-2 at a physiological firing frequency of 10 Hz for 30 sec causes these synapses to increase their EPSP amplitude by approximately 200%. This STE persists for nearly 2 min, during which time there is an increased cycle frequency of rhythmic ingestion buccal motor programs (iBMPs) elicited by CBI-2. This increase does not occur if the contralateral CBI-2 is trained and the test is performed with the ipsilateral CBI-2; therefore, the effect on motor programs only occurs in CBI-2 pathways in which STE is elicited. Furthermore, we find that STE elicited at CBI-2 buccal synapses permits iBMPs to be initiated at lower firing frequencies. Thus, STE of CBI-2 synapses appears to contribute to the initiation or modulation, or both, of buccal motor programs for rhythmic ingestion in Aplysia.

Collagen alpha1(I) gene contains an element responsive to tumor necrosis factor-alpha located in the 5' untranslated region of its first exon

The aims of the present study were to identify the cis-acting element through which tumor necrosis factor-alpha (TNFalpha) inhibits collagen alpha1(I) gene transcription and the trans-acting factors involved in this effect in cultured hepatic stellate cells. Deletion analysis of the collagen alpha1(I) promoter demonstrated that TNFalpha inhibited gene expression through an element located between -59 and + 116 bp relative to the transcription start site. DNase I protection assays revealed a footprint between +68 and +86 bp of the collagen first exon, the intensity of which decreased when the DNA probe was incubated with nuclear protein from TNFalpha-treated hepatic stellate cells. This footprint contained a G+C-rich box. Transfection experiments demonstrated that mutations in this G+C-rich element abrogated the inhibitory effect of TNFalpha on the collagen alpha1(I) promoter. Gel retardation experiments using a radiolabeled oligonucleotide containing sequences of this region confirmed that TNFalpha treatment decreased the formation of two complexes between nuclear proteins and DNA. These complexes were efficiently blocked with an oligonucleotide containing an Spl-binding site and were supershifted with specific Spl and Sp3 antibodies. These results suggest that TNFalpha inhibits collagen alpha1(I) gene expression by decreasing the binding of Spl to a G+C-rich box in the 5' untranslated region of its first exon.

Muscle and motor-skill dysfunction in a K+ channel-deficient mouse are not due to altered muscle excitability or fiber type but depend on the genetic background

The voltage-gated K+ channel Kv3.1 is expressed in skeletal muscle and in GABAergic interneurons in the central nervous system. Hence, the absence of Kv3.1 K+ channels may lead to a phenotype of myogenic or neurogenic origin, or both. Kv3.1-deficient (Kv3.1-/-) 129/Sv mice display altered contractile properties of their skeletal muscles and show poor performance on a rotating rod. In contrast, Kv3.1-/- mice on the (129/Sv x C57BL/6)F1 background display normal muscle properties and perform like wild-type mice. The correlation of poor performance on the rotating rod with altered muscle properties supports the notion that the skeletal muscle dysfunction in Kv3.1-/- 129/Sv mice may be responsible for the impaired motor skills on the rotating rod. Surprisingly, we did not find major differences between wild-type and Kv3.1-/- 129/Sv skeletal muscles in either the resting or action potential, the delayed-rectifier potassium conductance (gK) or the distribution of fast and slow muscle fibers. These findings suggest that the Kv3.1 K+ channel may not play a major role in the intrinsic excitability of skeletal muscle fibers although its absence leads to slower contraction and relaxation and to smaller forces in muscles of 129/Sv Kv3.1-/- mice.

A statistical analysis of the seasonality in pulmonary tuberculosis

The present study examines whether pulmonary tuberculosis (PTB) has an annual seasonal pattern. A mathematical model is also obtained to forecast the pattern of incidence. The data for the study are the cases of PTB reported throughout Spain, published in the Epidemiology Bulletin by the Carlos III Health Center of the Spanish Ministry of Health in a 26-year period, 1971-1996. The analytical results show that the low rates in tuberculosis notifications over the period 1971-1981 have changed, halting in 1982 and reversing with high incidence from 1983 onwards. An annual seasonal pattern was also shown with higher incidence during summer and autumn. With the mathematical model we predicted the disease behaviour in 1997 and the results were compared to the reported cases. In Spain, as in several industrialised countries, the reason for this recent increase in the number of reported cases is, mainly, the human immunodeficiency virus (HIV) infection. The seasonal trend, with higher incidence in winter, can be attributed to the increase in indoor activities, much more common than in a warm climate. The tubercle bacilli expelled from infected persons in a room with closed windows may remain infectious for a long time, increasing the risk of exposure of healthy persons to the bacilli. As the preclinical period, from exposure to clinical onset, may be of several weeks, the high incidence in spring would be explained. Moreover, in winter and spring the infections of viral aetiology, like flu, are more frequent and cause immunological deficiency which is another reason for the seasonal trend observed. An incidence greater than that foreseen by the mathematical model would express a failure in epidemiologic surveillance, and thus the results of this study may be used to assess a quality of the preventive measures.

Dihydropyridine-sensitive ion currents and charge movement in vesicles derived from frog skeletal muscle plasma membranes

1. Whole-cell voltage clamp experiments were performed in vesicles derived from frog skeletal muscle plasma membranes to characterize the electrophysiological properties of dihydropyridine (DHP) receptors. This preparation allows control of the composition of the internal medium and the recording of currents, without the influence of the sarcoplasmic reticulum (SR). 2. In solutions containing Ba2+, Bay K 8644-sensitive, L-type inward currents were recorded. Peak Ba2+ currents (IBa) averaged 3.0 microA microF-1 and inactivated in a voltage-dependent manner. Half-maximal steady-state inactivation occurred at -40 mV. No major facilitation of tail currents was observed. 3. The time course of activation of L-type Ca2+ channels was voltage dependent and 10 times faster than that in muscle fibres; the current density values were also much lower. 4. Lowering [Mg2+]i from 2 to 0.1 mM shifted the time to peak of IBa versus voltage relation by -13 mV. 5. In solutions that contained mostly impermeant ions, non-linear capacitive currents were recorded. Charge movement with properties resembling charge 1 was observed in polarized vesicles. The charge movement depended on voltage with Boltzmann parameters: Qmax (maximum charge), 45.6 nC microF-1; V (potential at which Q = 0.5 Qmax), -58.4 mV; and k (slope factor), 22. 3 mV. There was no indication of the presence of Qgamma (the 'hump' component of charge movement). 6. In depolarized vesicles, non-linear currents were observed during hyperpolarizing pulses. The currents produced an excessive charge during 'on' transients only. Charge during 'off' transients was linear from -180 to +60 mV. There was no evidence of the presence of charge 2.

Microcomputer decision support system for intensive care

This article describes a computer system to support decisions in Intensive Medicine developed for a multipurpose Intensive Care Unit (13 beds and about 700 yearly patients). The system is used in a microcomputer (486DX4). Works done in this area are mentioned; and the different programs which integrate the system, the advantages of its use and the results accomplished are described. Some of the most important results are the quality increment of the medical care given, physicians' possibilities of dedicating more time to their patients, cost reductions, and improvements in the development of teaching and in the conditions to carry out research work in the Intensive Care Unit (ICU). An analysis is made of the system requirements that guarantee its integration to the Unit work, and the easy and safe use of it by the physicians and nurses.

Combined Assessment of Genetic Variability in Populations of Brown Trout (Salmo trutta L.) Based on Allozymes, Microsatellites, and RAPD Markers

: Genetic variability within and among four Spanish natural populations of Salmo trutta L. was evaluated on the basis of 25 enzyme loci, 3 microsatellite loci, and 9 randomly amplified polymorphic DNAs (RAPDs). A total of 21 allelic markers were found, 12 of which were reported by microsatellites, whereas enzyme and RAPD accounted only for 6 and 3, respectively. Genetic variation within samples was significantly higher for microsatellites and RAPD than for enzyme loci. Although all methods reported a high degree of allelic heterogeneity among samples, also revealing a high degree of gene diversity, genetic relationships depicted by UPGMA dendrograms closely agreed for all kinds of data. Microsatellite loci appeared to be the most feasible technique when searching for specific alleles for a population or an area, owing to the higher number of allelic variants found.

Axonal regeneration in the central nervous system of aplysia californica determined by anterograde transport of biocytin

Rhythmic biting, a component of consummatory feeding behavior in the sea hare Aplysia californica, is eliminated following bilateral cerebral-buccal connective (CBC) crushes and recovers within 14 days postlesion. To assess axonal regeneration after CBC lesions, we used biocytin backfills of CBCs followed by fluorescence labeling with streptavidin-lissamine rhodamine. Anterograde transport of biocytin showed up to 1 mm of outgrowth by regenerating axons at 3 days postlesion. At 7 days postlesion, the regenerated axons approached or had entered the ipsilateral buccal neuropil and exhibited numerous varicosities; the average rate of axonal growth was 326 microm/day for the longest, most rapidly growing axons labeled in the CBC. The number of varicosities on labeled axons, suggestive of intercellular interactions, was increased dramatically at all times postlesion. At 14 and 20 days postlesion, regenerated axons branched extensively in the ipsilateral buccal neuropil, entered the contralateral buccal neuropil, and entered peripheral nerves on both sides of the midline. At these later times postlesion, some labeled axons encircled unlabeled buccal cell bodies and exhibited branches containing numerous varicosities, indicative of axosomatic contacts. Some regenerating axons were observed in the sheath of the CBC, but the vast majority of labeled axons remained confined to the connective core, as in control preparations. The bilateral projections within the buccal ganglia of labeled cerebral-to-buccal axons and the large number of varicosities present on these processes are indicative of regenerating axons and synapses that likely contribute to the functional recovery of rhythmic biting.

A long-term blockade of L-type calcium currents upregulates the number of Ca2+ channels in skeletal muscle

The effects of a long-term blockade of L-type Ca2+ channels on membrane currents and on the number of dihydropyridine binding sites were investigated in skeletal muscle fibers. Ca2+ currents (ICa) and intramembrane charge movement were monitored using a voltage-clamp technique. The peak amplitude of ICa increased by more than 40% in fibers that were previously incubated for 24 hr in solutions containing the organic Ca2+ channel blocker nifedipine or in Ca2+-free conditions. A similar incubation period with Cd2+, an inorganic blocker, produced a moderate increase of 20% in peak ICa. The maximum mobilized charge (Qmax) increased by 50% in fibers preincubated in Ca2+-free solutions or in the presence of Cd2+. Microsomal preparations from frog skeletal muscle were isolated by differential centrifugation. Preincubation with Cd2+ prior to the isolation of the microsomal fraction doubled the number of 3H-PN200-110 binding sites and produced a similar increase in the values of the dissociation constant. The increase in the number of binding sites is consistent with the increase in the peak amplitude of ICa as well as with the increase in Qmax.

Modulation of reconstituted ATP-sensitive K(+)-channels by GTP-binding proteins in a mammalian cell line

1. The action of GTP-binding proteins on ATP-sensitive potassium (KATP) channels was investigated. KATP channels were expressed in a mammalian cell line (COS-1 cells) by cotransfecting vectors carrying the sulphonylurea receptor (SUR1) and BIR (Kir6.2), a member of the inward rectifier K+ channel family. G proteins were also tested on KATP channels composed of an isoform of SUR1, SUR2A, in combination with Kir6.2. 2. The alpha and beta gamma subunits of the GTP binding protein G1 were tested separately in inside-out patches under continuous recording. G alpha-11 increases the activity of SUR1-Kir6.2 and SUR2A-Kir6.2 channels by 200 and by 30%, respectively. 3. G alpha-12 does not increase the activity of SUR1-Kir6.2 channels, but increase the activity of SUR2A-Kir6.2 channels by 30%. 4. Control experiments showed that GTP gamma S, a specific activator of G proteins, and heat-inactivated G alpha-11 do not increase the single channel activity. 5. No effects of the other subunits (beta gamma) from either G11 or G12 on the single channel activity were observed. 6. The protein kinase C inhibitors H7 and an inhibitory peptide (FARKGALRQKNV) had no effect on the modulatory action of G alpha-11 on SUR1-Kir6.2 channels. 7. We conclude that both types of reconstituted KATP channels are modulated by G proteins.

G proteins are involved in the suppression of collagen alpha 1 (I) gene expression in cultured rat hepatic stellate cells

We analyse the role of the G proteins in regulating collagen gene expression by measuring collagen alpha 1(I) mRNA levels in cultured hepatic stellate cells in basal conditions and after stimulating or inhibiting the major intracellular signalling pathways. Stimulation of Gs protein and adenylyl cyclase or the addition of 8Br-cAMP to the cells led to a decrease in collagen alpha 1(I) mRNA levels, while blocking protein kinase A abolished this effect. Blocking Gi protein, phospholipase A2 and C, calcium channels and calmodulin resulted in a significant increase in collagen mRNA levels. PKC stimulation led to a marked decrease in these levels. These results suggest that collagen gene expression is inhibited by a number of intracellular pathways. A Gs and a pertussis toxin-sensitive G protein seem to initiate cellular response. Transcription factors, acting in these pathways, must be identified. However, it seems that they do not need to be synthesised.

Sexual determination of the femur using discriminant functions. Analysis of a Spanish population of known sex and age

Until present, functions for sexual discrimination of a Spanish population from series of known sex and age were not available. In this work, we present a sample of 132 femora (72 females and 60 males) belonging to a Spanish population of adult individuals of known filiation deposited in the Complutense University of Madrid. The ten mathematical functions which yield a higher sexual discrimination in each part of the femur, were selected. The resulting percentages of correspondence varied between 84 and 97% when each variable was considered independently, and a 99% is obtained with two variables of the epiphyses combined.

Modulation of Ca2+ channels, charge movement and Ca2+ transients by heparin in frog skeletal muscle fibres

This study is an investigation into the modulatory effects of heparin, a component of the extracellular matrix that binds to dihydropyridine receptors, on contraction and Ca2+ channels in frog skeletal muscle. Using tension and Ca2+ signal measurements in single intact skeletal muscle cells we have found that heparin (100-200 micrograms ml-1) substantially potentiates twitch and tetanic tension (55% and 28%, respectively). In contrast, heparin reduces the amplitude of K+ contractures. Heparin most likely potentiates twitch tension by prolonging action potentials. The ionic basis of this effect was investigated in voltage-clamp experiments. Membrane currents were monitored in voltage-clamped segments of single fibres using the triple Vaseline gap technique. We found that heparin partially blocks delayed rectifier potassium channels. The depressive effects of heparin on K+ contractures prompted us to investigate the effects of heparin on charge movement and Ca2+ currents (ICa) under voltage-clamp. Charge movement was measured using a subtraction procedure that employed a -20 mV control pulse from a holding potential of -100 mV. Heparin depresses the total charge by 25%. We propose that the reduction in the amplitude of potassium contractures is related to a partial blockade of charge movement. Extracellular heparin shifts the ICa-V relation toward more negative voltages and delays the deactivation of tail currents. Double pulse experiments revealed that conditioning depolarizations speed the activation of ICa during test depolarizations. Heparin does not affect this process. The primary action of heparin is to accelerate the activation of ICa during pulses not preceded by conditioning depolarizations. Overall, the kinetic effects of heparin on ICa would increase the Ca2+ influx associated with action potentials. However, mechanical and optical experiments performed in Ca(2+) -free solutions and in the presence of Ca2+ channel blockers revealed that twitch and tetanic potentiation occur even in the absence of Ca(2+) -influx.

Protein and microsatellite single locus variability in Salmo salar L. (Atlantic salmon)

We describe genetic variation at three microsatellite single loci and six allozyme loci of seven natural Atlantic salmon populations from Ireland and Spain. A comparison of genetic variability detected at both types of loci is performed. Also, the relative value of microsatellite single locus variability with regard to the identification of individual salmon populations is assessed. Microsatellite loci are shown to display higher levels of variation than allozyme loci. Mean number of alleles (6 +/- 1.53) and heterozygosity (0.46 +/- 0.04) at microsatellite loci are greater than those found for allozymes (1.85 +/- 0.05 and 0.21 +/- 0.03, respectively), and some microsatellite alleles appear to be specific for a location or geographical area. Allozyme and microsatellite variation show the same pattern of differentiation between populations with Irish and Spanish populations grouped into different clusters. However, greater values of genetic distance were found among microsatellite (D = 0.0747 +/- 0.011) rather than among allozyme loci (D = 0.0449 +/- 0.008). These results provide evidence that microsatellite-based analysis of genetic variation will be useful in the identification of individual populations of Atlantic salmon.

Transient outward K+ channels in vesicles derived from frog skeletal muscle plasma membranes

Whole-cell voltage-clamp experiments were performed in vesicles derived from frog skeletal muscle plasma membranes. Capacitance measurements showed that these vesicles lack invaginations. In solutions containing K+, transient outward currents with reversal potentials close to EK were recorded with a maximum potassium conductance of 0.3 mS/cm2. These currents inactivated in a voltage-dependent manner with a time constant of decay that reached a limiting value of 26 ms at large depolarizations. The steady-state inactivation reached half-maximum values at -66 mV. Transient currents were completely blocked with 5 mM 4-aminopyridine. Single-channel recordings made in inside-out excised patches from the vesicles had ensemble averages with characteristics similar to those of the macroscopic currents, although with significantly faster inactivation time constants. The single-channel chord conductance was 21 pS when the pipette and bath solutions contained 2.5 mM and 120 mM KCl, respectively. It is concluded that these vesicles contain potassium channels that are very similar to A channels found in neurons and other cells.