Isolation and Characterization of Thermus thermophilus Strain ET-1: An Extremely Thermophilic Bacterium with Extracellular Thermostable Proteolytic Activity Isolated from El Tatio Geothermal Field, Antofagasta, Chile

The present study describes the isolation of an extremely thermophilic bacterium from El Tatio, a geyser field in the high planes of Northern Chile. The thermophile bacterium named Thermus thermophilus strain ET-1 showed 99% identity with T. thermophilus SGO.5JP 17-16 (GenBank accession No. CP002777) by 16S rDNA gene analysis. Morphologically, the cells were non-sporeforming Gram-negative rods that formed colonies with yellow pigmentation. This strain is able to proliferate between 55 and 80 °C with a pH range of 6-10, presenting an optimum growth rate at 80 °C and pH 8. The bacterium produces an extracellular protease activity. Characterization of this activity in a concentrated enzyme preparation revealed that extracellular protease had an optimal enzymatic activity at 80 °C at pH 10, a high thermostability with a half-life at 80 °C of 10 h, indicating that this enzyme can be classified as an alkaline protease. The proteolytic enzyme exhibits great stability towards chelators, divalent ions, organic solvents, and detergents. The enzyme was inhibited by phenylmethylsulfonyl fluoride (PMSF), implying that it was a serine protease. The high thermal and pH stability and the resistance to chelators/detergents suggest that the protease activity from this T. thermophilus. strain could be of interest in biotechnological applications.

Unnexin is a protein subunit of a large-pore channel expressed by unicellular organisms

Cells of vertebrate and invertebrate organisms express proteins specialized in membrane channel-based cell-cell communication that are absent in unicellular organisms. We recently described the prediction of some members of the large-pore channel family in kinetoplastids, consisting of proteins called unnexins, which share several structural features with innexin and pannexin proteins. Here, we demonstrated that the unnexin1 protein (Unx1) is delivered to the cell membrane, displaying a topology consisting of four transmembrane domains with C and N termini on the cytoplasmic side and form large-pore channels that are permeable to small molecules. Low extracellular Ca2+/Mg2+ levels or extracellular alkalinization, but not mechanical stretching, increases channel activity. The Unx1 channel mediates the influx of Ca2+ and does not form intercellular dye coupling between HeLa Unx1 transfected cells. Unx1 channel function was further evidenced by its ability to mediate ionic currents when expressed in Xenopus oocytes. Downregulation of Unx1 mRNA with morpholine contains Trypanosoma cruzi invasion. Phylogenetic analysis revealed the presence of Unx1 homologs in other protozoan parasites, suggesting a conserved function for these channel parasites in other protists. Our data demonstrate that Unx1 forms large-pore membrane channels, which may serve as a diffusional pathway for ions and small molecules that are likely to be metabolic substrates or waste products, and signaling autocrine and paracrine molecules that could be involved in cell invasion. As morpholinos-induced downregulation of Unx1 reduces the infectivity of trypomastigotes, the Unx1 channels might be an attractive target for developing trypanocide drugs.

Commonalities between the Atacama Desert and Antarctica rhizosphere microbial communities

Plant-microbiota interactions have significant effects on plant growth, health, and productivity. Rhizosphere microorganisms are involved in processes that promote physiological responses to biotic and abiotic stresses in plants. In recent years, the interest in microorganisms to improve plant productivity has increased, mainly aiming to find promising strains to overcome the impact of climate change on crops. In this work, we hypothesize that given the desertic environment of the Antarctic and the Atacama Desert, different plant species inhabiting these areas might share microbial taxa with functions associated with desiccation and drought stress tolerance. Therefore, in this study, we described and compared the composition of the rhizobacterial community associated with Deschampsia antarctica (Da), Colobanthus quitensis (Cq) from Antarctic territories, and Croton chilensis (Cc), Eulychnia iquiquensis (Ei) and Nicotiana solanifolia (Ns) from coastal Atacama Desert environments by using 16S rRNA amplicon sequencing. In addition, we evaluated the putative functions of that rhizobacterial community that are likely involved in nutrient acquisition and stress tolerance of these plants. Even though each plant microbial rhizosphere presents a unique taxonomic pattern of 3,019 different sequences, the distribution at the genus level showed a core microbiome with a higher abundance of Haliangium, Bryobacter, Bacillus, MND1 from the Nitrosomonadaceae family, and unclassified taxa from Gemmatiamonadaceae and Chitinophagaceae families in the rhizosphere of all samples analyzed (781 unique sequences). In addition, species Gemmatirosa kalamazoonesis and Solibacter usitatus were shared by the core microbiome of both Antarctic and Desert plants. All the taxa mentioned above had been previously associated with beneficial effects in plants. Also, this microbial core composition converged with the functional prediction related to survival under harsh conditions, including chemoheterotrophy, ureolysis, phototrophy, nitrogen fixation, and chitinolysis. Therefore, this study provides relevant information for the exploration of rhizospheric microorganisms from plants in extreme conditions of the Atacama Desert and Antarctic as promising plant growth-promoting rhizobacteria.

Correction to: Validation of the Spanish Version of Fear of COVID-19 Scale: its Association with Acute Stress and Coping

[This corrects the article DOI: 10.1007/s11469-021-00615-x.].

Validation of the Spanish Version of Fear of COVID-19 Scale: its Association with Acute Stress and Coping its Association with Acute Stress and Coping

The COVID-19 is a “unique” stressor, which can produce physical and psychological trauma. Coping styles can buffer this psychological impact. Consequently, this paper aims to psychometrically adapt the Fear of COVID-19 scale (FCV-19S) to Spanish and examines the relationships between FCV-19S, stress response, and coping strategies. The sample comprised a convenience sample of 1146 participants (12–83 years), 880 from Spain (76.8%), and 266 from Dominican Republic (23.2%). Overall, the findings support a one-factor structure for FCV-19S, consisting of 7-items, and was invariant across age, sex, occupational status, and cross-national. Therefore, indicating evidences of construct validity. Evidences of reliability were also observed (Cronbach’s α = .86, McDonald’s ω = .86, Guttmann’s λ6 = .86, greatest lower bound = .91, composite reliability = .85, and average variance extracted = .44). Moreover, as regards criterion-related validity, the mediation analysis indicated that the relationship between FCV-19S and acute stress was positive and high, with maladaptive coping styles mediating the relationship, and with a stronger mediation for men. The findings give evidences of the reliability and validity of the Spanish version of FCV-19S among Spanish-speaker participants, which provides the chance of cross-cultural studies.

Microbial Hotspots in Lithic Microhabitats Inferred from DNA Fractionation and Metagenomics in the Atacama Desert

The existence of microbial activity hotspots in temperate regions of Earth is driven by soil heterogeneities, especially the temporal and spatial availability of nutrients. Here we investigate whether microbial activity hotspots also exist in lithic microhabitats in one of the most arid regions of the world, the Atacama Desert in Chile. While previous studies evaluated the total DNA fraction to elucidate the microbial communities, we here for the first time use a DNA separation approach on lithic microhabitats, together with metagenomics and other analysis methods (i.e., ATP, PLFA, and metabolite analysis) to specifically gain insights on the living and potentially active microbial community. Our results show that hypolith colonized rocks are microbial hotspots in the desert environment. In contrast, our data do not support such a conclusion for gypsum crust and salt rock environments, because only limited microbial activity could be observed. The hypolith community is dominated by phototrophs, mostly Cyanobacteria and Chloroflexi, at both study sites. The gypsum crusts are dominated by methylotrophs and heterotrophic phototrophs, mostly Chloroflexi, and the salt rocks (halite nodules) by phototrophic and halotolerant endoliths, mostly Cyanobacteria and Archaea. The major environmental constraints in the organic-poor arid and hyperarid Atacama Desert are water availability and UV irradiation, allowing phototrophs and other extremophiles to play a key role in desert ecology.

Composition and predicted functions of the bacterial community in spouting pool sediments from the El Tatio Geyser field in Chile

The El Tatio Geyser Field (ETGF), located in Northern Chile, is the main geyser field in the southern hemisphere. Despite this, details of its microbial ecology are still unknown. Here, we briefly report on  the composition and predicted functions of the bacterial community in spouting pool sediments from the ETGF as revealed by high-throughput sequencing of 16S rRNA genes. Results of this analysis showed that while there were differences in richness and diversity between samples, bacterial communities were primarily dominated by the phyla Proteobacteria, followed Firmicutes, Bacteroidetes, Acidobacteria, and Chloroflexi. Analyses of predicted functional activity indicated that the functions were mostly attributed to chemoheterotrophy and aerobic chemoheterotrophy, followed by sulfur (respiration of sulfur compounds and sulfate) and nitrogen (nitrate reduction, respiration of nitrogen and nitrate) cycling. Taken together, our results suggest a high diversity in taxonomy and predictive functions of bacterial communities in sediments from spouting pools. This study provides fundamentally important  information on the structure and function  predictive functions of microbiota  communities in spouting pools. Moreover, since the ETGF is intensively visited and impacted by tens of thousands of tourists every year, our results can be used to help guide the design of sustainable conservation strategies.

Determining personalized treatment by gene expression profiling in metastatic breast carcinoma patients: a pilot study

PURPOSE

The present study evaluates the massive study of gene expression in metastatic breast carcinoma (MBC) patients using microarray gene expression profiling (MAGE) complemented with conventional sequencing, immunohistochemistry (IHC) and fluorescent "in situ" hybridization (FISH), seeking to optimize the treatment in a subset of heavily pretreated patients and with limited life expectancy.

PATIENTS, MATERIAL AND METHODS

MBC patients in hormone therapy progression with survival expectancy of at least 3 months (m) have been included. The MAGE contains gene probes representing genes known to potentially interact with available drugs as cited in the literature.

RESULTS

Thirty-nine procedures were performed from October 2010 to April 2016. Within the 30 evaluable procedures, considering all hormonal manipulations as a single line, the patients had received a median of 4 treatment lines prior to MAGE (range 1-7). Progression was observed in 6 cases, stable disease (SD) in 7 cases and partial response (PR) in 16 cases, which implies a clinical benefit rate (SD + PR) of 76%. Actuarial median progression-free survival (PFS) was 6 m (95% CI 2.5-9.5) in patients with clinical benefit. The median overall survival (OS) for the entire series was 11 m (95% CI 2.2-19.8).

CONCLUSION

Data presented here indicate that the use of MAGE provides relevant information to establish personalized treatment in frail patients with limited life expectancy in which therapeutic futility is a particularly difficult burden to assume.

[Stability study of oxaliplatin and doxorubicin for intraperitoneal administration with hyperthermia]

OBJECTIVE

To evaluate the in vitro physicochemical stability of oxaliplatin and doxorubicin when the in vivo hyperthermic intraperitoneal conditions are reproduced.

METHODS

Three solutions were prepared, A (oxaliplatin 200 mg/L), B(doxorubicin 15 mg/L) and C (oxaliplatin 200 mg/L with doxorubicin 15mg/L) in glucose 5%. The three solutions were subjected to the maximum temperature reached in vivo (49° C) for two hours. Physical stability was focused on visual control of particles or precipitates in solutions, discharge of gases, odor and color. Samples were taken every 15 minutes and the chemical stability was evaluated by determining the concentration of oxaliplatin and doxorubicin remaining in the samples. Oxaliplatin concentrations were determined by atomic absorption graphite chamber while doxorubicin was determined by high performance liquid chromatography.The chemical stability criteria selected was the one described by the American Pharmacopoeia, which sets a permissible variation range between the 90-110% of the initial concentration.

RESULTS

During the assay there was no appearance of particles, precipitates in the samples, discharge of gases, nor colour changes in the solutions. The samples showed a remaining concentration of oxaliplatin and doxorubicin within the 90-110% limit. The stability of the samples that follow to two cycles of freeze-thaw after hyperthermia was also found within the specified limits.

CONCLUSION

A, B and c solutions in 5% glucose, are physically and chemically stable at 49° C for two hours. Under these conditions, these solutions could be used with guarantees of stability in patients with peritoneal carcinomatosis subsidiary of intraperitoneal hyperthermic chemotherapy based in these antineoplastic agents.

Epidermal growth factor receptor (EGFR) mutations in a series of non-small-cell lung cancer (NSCLC) patients and response rate to EGFR-specific tyrosine kinase inhibitors (TKIs)

INTRODUCTION Epidermal growth factor receptor (EGFR) mutation related to tyrosine kinase inhibitors' (TKIs) responsiveness in non-small cell lung cancer (NSCLC) has become an important issue for therapeutic decision-making in NSCLC patients. MATERIAL AND METHODS Sixty-nine Caucasian NSCLC patients were screened for mutations in the tyrosine kinase (TK) domain of EGFR by direct sequencing from December 2005 to September 2010. RESULTS Activating mutations in the EGFR TK domain were found in 8 of 69 (11.6%) (7 deletions in exon 19 and one L858R mutation in exon 21). Seven of those mutations were found in adenocarcinoma and one mutation in bronchiolo-alveolar carcinoma; five of them in females (one smoker) and three of them in males (one smoker). All patients carrying activating mutations in the TK domain of EGFR were treated with TKIs. Ten patients not carrying an activating mutation in EGFR, who progressed after chemotherapy, were also treated with compassionate use of EGFR-specific TKIs (gefitinib or erlotinib). An objective response (partial response) was observed in all patients carrying an activating mutation in EGFR that received TKIs. Median overall survival for these patients has not been reached, however mean survival has been estimated at 39.5 months (95% CI, 22-57). CONCLUSIONS As previously reported, EGFR TK mutational analysis was a predictive test for response to targeted therapy with EGFR TKIs. The early identification of these patients consistently attains disease response and clearly improves outcomes.

[Population pharmacokinetics of gemcitabine applied to personalize the dosage used in cancer patients]

OBJECTIVE

To develop and internally validate a population pharmacokinetic model for gemcitabine and its metabolite 2',2'-difluorodeoxyuridine (dFdU); and to evaluate its predictive perfomance for personalizing the dosage used in cancer patients.

METHODS

Gemcitabine and dFdU plasma concentrations were determined in 18 cancer patients. A 2-compartment pharmacokinetic model was implemented in the NONMEN VI program to determine the appropriate pharmacokinetic parameters. The power to identify the parameters was assessed by parametric bootstrap, and the internal model validation was performed using nonparametric bootstrap and visual and numerical predictive check methods. The final predictive performance of the model was assessed for accuracy and precision during the first (a priori) and second (a posteriori) chemotherapy cycles.

RESULTS

The mean and interpatient variability of gemcitabine and dFdU clearance was 2.70 L/min (31.0%) and 0.0515 L/min (35.8%), respectively. The estimated distribution volume at steady state was 30 L for gemcitabine and 238 L for dFdU. Internal validation confirmed that the population pharmacokinetic model was appropriate for describing the plasma concentrations of gemcitabine and dFdU over time, as well as its variability in the study population. The accuracy and precision of a posteriori gemcitabine plasma concentrations improved by 67% and 46%, respectively, compared to the a priori prediction.

CONCLUSION

The population pharmacokinetic model adequately characterised the gemcitabine and dFdU plasma concentrations in the study population over time, and can be used to accurately and precisely optimise gemcitabine dosing regimens in cancer patients.

[Populational pharmacokinetics of doxorubicin applied to personalised its dosing in cancer patients]

OBJECTIVE

To develop and internally validate a population pharmacokinetic model for doxorubicin and to evaluate its predictive performance for dose individualization in cancer patients.

METHODS

Doxorubicin plasma concentrations were determined in thirty-three cancer patients treated with intravenous doxorubicin. A three-compartment pharmacokinetic model was implemented in the NONMEN VI programme to determine the doxorubicin pharmacokinetic parameters. The identifiability of the parameters was assessed by parametric bootstrap and model validation was performed using nonparametric bootstrap, visual predictive check, and numerical predictive check. The final model's predictive performance was evaluated in terms of accuracy and precision of plasma concentration predictions during the first and second cycles of chemotherapy.

RESULTS

Doxorubicin clearance was 58.8 L/h, with interpatient variability of 29.2% and intrapatient variability of 18.9%. The estimated volume of distribution at steady state was 2294 L, with inter-and intrapatient variability of 7.3% and 26.1%, respectively. Internal validation confirmed that the population pharmacokinetic model is appropriate to describe the time course of the doxorubicin plasma concentrations and its variability in this population. The accuracy and precision of an a posteriori prediction of doxorubicin plasma concentrations improved by 63% and 41% compared to the a priori prediction.

CONCLUSION

The Bayesian population pharmacokinetic model characterised the time course of doxorubicine plasma concentrations and can be accurately and precisely used to optimise doxorubicine dosing regimens in cancer patients.

Conductivity anisotropy in the antiferromagnetic state of iron pnictides

Recent experiments on iron pnictides have uncovered a large in-plane resistivity anisotropy with a surprising result: The system conducts better in the antiferromagnetic x direction than in the ferromagnetic y direction. We address this problem by calculating the ratio of the Drude weight along the x and y directions, D(x)/D(y), for the mean-field Q=(π,0) magnetic phase diagram of a five-band model for the undoped pnictides. We find that D(x)/D(y) ranges between 0.2<D(x)/D(y)<1.7 for different interaction parameters. Large values of the orbital ordering favor an anisotropy opposite to the one found experimentally. On the other hand, D(x)/D(y) is strongly dependent on the topology and morphology of the reconstructed Fermi surface. Our results point against orbital ordering as the origin of the observed conductivity anisotropy, which may be ascribed to the anisotropy of the Fermi velocity.

Low magnetization and anisotropy in the antiferromagnetic state of undoped iron pnictides

We examine the magnetic phase diagram of iron pnictides using a five-band model. For the intermediate values of the interaction expected to hold in the iron pnictides, we find a metallic low moment state characterized by antiparallel orbital magnetic moments. The anisotropy of the interorbital hopping amplitudes is the key to understanding this low moment state. This state accounts for the small magnetization measured in undoped iron pnictides and leads to the strong exchange anisotropy found in neutron experiments. Orbital ordering is concomitant with magnetism and produces the large zx orbital weight seen at Γ in photoemission experiments.

UGT1A1,A7 and A9 genotyping and pharmacokinetics of irinotecan-containing chemotherapy in patients with advanced cancer

e14563

Background: To the best of our knowledge only one previous report in asian lung cancer patients (pts) assesed UGT1A1, A7 and A9 genotypes along with irinotecan pharmacokinetics (Han et al. JCO 2006; 24: 2237–44). We set out to evaluate UGT1A1, A7 and A9 genotypes in caucasian cancer patients and their relationship with both irinotecan toxicity and irinotecan pharmacokinetics. Methods: UGT1A1, A7 and A9 genotypes were obtained from blood genomic DNA by direct sequencing. The area under the time-concentration curve (AUC) of SN-38 and SN-38G were calculated. The ratio between these AUCs (AUC SN-38G /AUC SN-38) was also calculated. Associations between pharmacokinetics parameters and the UGT1A genotypes were assessed by univariate analysis. Toxicity was collected using standard NCI grading criteria. Statistical correlation between presence of grade III and IV toxicity and UGT1A1,A7 and A9 genotypes was done by Pearson's Chi square. At least 80 patients (with both genotype and pharmacokinetics) are needed to achieve enough statistical power. Results: At the time of writing this abstract, complete genotyping and toxicity data from 59 patients were available. Sex (females 17, males 42). Median age 60 (range 25–88). Pathology (no. pts): lung (26), colon (17), others (16). 21 pts. (35.59%) had received previous chemotherapy. All but 5 pts received doses of irinotecan between 120 and 150 mg/m2. Median no. of cycles 6 (range 1–15). The frequencies of the different UGT1A1, A7 and A9 genotypes are similar to those previously reported. At least one episode of grade III or IV leukopenia was present in 19 pts. (32.2%), and grade III diarrea in 11 pts (18.6%). No statistically significant correlation was found between presence of leukopenia grades III and IV, and the genotypes UGT1A1,A7, and A9 (P=0.687, P=0.156 and P=0.476, respectively). Diarrea grade III was not statistically significantly associated with UGT1A1 (P=0.318), A7 (P=0.318) and A9 (P=0.158). 21 out of 59 pts. had pharmacokinetics (PK) data available. In genotype-PK association analysis, UGT1A1,A7 and A9 were not statistically associated with AUC SN-38G / AUC SN-38 ratios (P=0.844, P=0.911, P=0.431, respectively). Conclusions: Patients are still being accrued to achieve the targeted size.

No significant financial relationships to disclose.

Phenomenological description of the two energy scales in underdoped cuprate superconductors

Raman and angle-resolved photoemission spectroscopy experiments have demonstrated that in superconducting underdoped cuprates nodal and antinodal regions are characterized by two energy scales instead of the one expected in BCS theory. The nodal scale decreases with underdoping while the antinodal one increases. Contrary to the behavior expected for an increasing energy scale, the antinodal Raman intensity decreases with decreasing doping. Using the Yang-Rice-Zhang model, we show that these features are a consequence of the nonconventional nature of the superconducting state in which superconductivity and pseudogap correlations are both present and compete for the phase space.

Modelling intestinal absorption of salbutamol sulphate in rats

The objective was to develop a semiphysiological population pharmacokinetic model that describes the complex salbutamol sulphate absorption in rat small intestine. In situ techniques were used to characterize the salbutamol sulphate absorption at different concentrations (range: 0.15-18 mM). Salbutamol sulphate at concentration of 0.29 mM was administered in presence of verapamil (10 and 20 mM), grapefruit juice and sodium azide (NaN3) (0.3, 3 and 6 mM). Different pharmacokinetic models were fitted to the dataset using NONMEM. Parametric and non-parametric bootstrap analyses were employed as internal model evaluation techniques. The validated model suggested instantaneous equilibrium between salbutamol sulphate concentrations in lumen and enterocyte, and the salbutamol sulphate absorption was best described by a simultaneous passive diffusion (ka = 0.636 h(-1)) and active absorption (VMax = 0.726 mM/h, Km = 0.540 mM) processes from intestinal lumen to enterocyte, together with an active capacity-limited P-gp efflux (V'max = 0.678 mM/h, K'm = 0.357 mM) from enterocyte to intestinal lumen. The extent of salbutamol sulphate absorption in rat small intestine can be improved by NaN3, grapefruit juice and verapamil.

The influence of active secretion processes on intestinal absorption of salbutamol in the rat

Salbutamol was perfused in the small intestine of rat using a standard rat gut "in situ" preparation: (1) in inhibitor-free solution at seven different concentrations (0.15, 0.29, 1.20, 5.0, 9.0, 13.0 and 18.0mM); (2) at a 0.29mM concentration - thought to be close to the allometric dose in man - in the presence of a non-specific enzyme inhibitor, sodium azide (0.3, 3.0 and 6.0mM); and (3) at 0.29mM in the presence of a selective secretion inhibitor, verapamil (10.0 and 20.0mM). In free solution, the mixed-order rate constants, k'(a), of salbutamol increase as the solute concentration increases until an apparent asymptotic value is reached. This could be due to the saturation of enzymatic systems responsible for the secretion of the drug from the enterocyte to the luminal fluid, a process that could explain the poor absorption of salbutamol. In the presence of sodium azide, the k(a) values increased about 1.5-fold, whereas in the presence of verapamil they increased two- to three-fold. These results indicate that salbutamol can act as a substrate of an intestinal secretory transport, which probably includes--at least in part--the enzyme P-glycoprotein, since verapamil has been shown to inhibit this enzyme by dose-dependent competition. This leads to a secretion-limited peroral absorption of salbutamol, which contributes to the poor oral bioavailability of the drug. The possible options for improving salbutamol absorption are discussed.

[Juvenile myoclonic epilepsy. Life difficulties and response to treatment]

Juvenile myoclonic epilepsy (JME) may have different forms of clinical expression and produces different kinds of life difficulties. Both eventualities have not been sufficiently described in the literature. Treatment with valproic acid is useful but requires strict compliance of medical instructions. Thirty two patients with this disease, are presented in order to describe their presenting forms, associated life handicaps and the results of their treatment. The disease may first present as tonic-clonic, complex absence or complex partial seizures, followed months or years later, by typical myoclonic crisis or as JME to which other kinds of epileptic crisis may or not be added after some time. Twenty four (75%) patients had 38 life difficulties, these being, mainly, objects dropped from hand, burns and parental aggression. Eighteen (56.25%) patients had relapses during treatment. In 14 cases (77.77%) relapses were due to noncompliance, 8 (57.19%) patients couldn't afford the cost of valproic acid. Knowledge of the presenting forms of the disease may favor opportune diagnosis and treatment, which would prevent life difficulties. Relapses are mainly due to noncompliance and economic reasons.

[Juvenile myoclonic epilepsy: Janz' syndrome]

Thirty two patients with juvenile myoclonic epilepsy are described. The most relevant aspects of the disease are the following: it starts at nearly 12 years of age or before; it is frequently associated with generalized tonic-clonic seizures; myoclonic and tonic-clonic seizures occur at time of awaking or shortly after; no pathological findings occur at the central nervous system; a large number of relatives show generalized seizures and the interictal electroencephalogram is usually disturbed by generalized epileptic activity. Valproic acid, preferably alone, is probably the treatment of choice for these patients.

[Follow-up of infants with birth weight under 1,500 g]

A prospective study of 199 children with birth weight less than 1,500 g was done. 86 boys and 113 girls, 141 (71%) adequate for gestational age and 58 (29%) small for gestational age. At follow-up 43 (21.6%) infants were lost to control, 17 (7%) moved to other places and 7 (3.5%) died in the first year of life. In the first year of life, infants whose birthweights were adequate for gestational age had been hospitalized more frequently and the small for dates showed higher percentage of undernutrition. After the second year of life, it was possible to know the impairment. It was found 7.4% of cerebral palsy, 2.9% of hipoacusia and 2.2% of retinopathy of prematurity, these diagnosis were most frequent in children that were adequate for gestational age. We concluded that small for dates infants are at risk of undernutrition and that those adequate for gestational age are at risk of permanent sequelae.

The early development of the atrioventricular node and bundle of His in the embryonic chick heart. An electrophysiological and morphological study

The development of the atrioventricular node and bundle of His of embryonic chick hearts was studied by electrophysiological and morphological techniques. The dorsal wall of the AV canal and the interatrial septum were explored to determine if they contribute to the formation of the AV node and bundle of His. The resting membrane and action potentials of the interatrial septum cells were systematically analyzed and found to undergo progressive differentiation with development. The earliest identification of the AV node and upper bundle of His group of cells was achieved at 5 1/2–6 days of development by the electrical recording of their corresponding characteristic action potentials, from a circumscribed area located in the lowest and dorsal segment of the interatrial septum. The morphological and anatomical characterization of the cells was made following electrical recording and labelling with charcoal particles. The earlier AV node and bundle of His responses had similar characteristics to those of the adult heart. It is concluded that the AV node and upper bundle of His cells derive from the low interatrial septum. The possibility that AV canal cells contribute to this event was discarded. The functional relationship of the Av node and bundle of His with other cardiac tissues during the early development of the heart is discussed.

Electrophysiological and ultrastructural study of the atrioventricular canal during the development of the chick embryo

The development of the atrioventricular canal (A-V canal) of embryonic chick hearts (35 to 120 h) was studied by morphological and electrophysiological techniques. The earliest identification of the A-V canal action potentials was at 45 to 49 h of incubation coinciding with the atrium formation and the appearance of its corresponding distinctive action potential. At that time the first atrioventricular delay was recorded and its action potentials showed a low rate of rise, particularly at the initiation of the upstroke and a long duration. The conduction velocity was the lowest in the A-V canal. As the development proceeded from 45 to 120 h, the cardiac cells of the A-V canal showed scanty membrane to membrane contacts and large intercellular spaces filled with abundant extracellular matrix components, in striking contrast to the paucity of these components in the atrium and ventricle. The morphological and electrophysiological characteristics described for the A-V canal cells, could help to explain their slow conduction properties and the atrioventricular delay.