Calcium channels that are required for secretion from intact nerve terminals of vertebrates are sensitive to omega-conotoxin and relatively insensitive to dihydropyridines. Optical studies with and without voltage-sensitive dyes

Extrinsic absorption changes exhibited by potentiometric dyes have established the ionic basis of the action potential in synchronously activated populations of nerve terminals in the intact neurohypophyses of amphibia and mammals (Salzberg et al., 1983; Obaid et al., 1983, 1985b). Also, large and rapid changes in light scattering, measured as transparency, have been shown to follow membrane depolarization and to be intimately associated with the release of neuropeptides from the nerve terminals of the mouse neurohypophysis (Salzberg et al., 1985; Gainer et al., 1986). We report some experiments that help to define the pharmacological profile of the calcium channels present in intact neurosecretory terminals of vertebrates. For these, we used the peptide toxin omega-conotoxin GVIA (1-5 microM) and the dihydropyridine compounds Bay-K 8644 and nifedipine (2-5 microM), together with the after-hyperpolarization of the nerve terminal action potential. This undershoot depends upon the activation of a calcium-mediated potassium channel, as suggested by its sensitivity to [Ca++]o and charybdotoxin. omega-conotoxin GVIA substantially reduced the after-hyperpolarization in neurosecretory terminals of Xenopus, while neither of the dihydropyridine compounds had any effect under conditions that mimic natural stimulation. The effects of these calcium channel modifiers on the action potential recorded optically from the terminals of the Xenopus neurohypophysis were faithfully reflected in the behavior of the light-scattering changes observed in the neurohypophysis of the CD-1 mouse. omega-conotoxin GVIA (5 microM) reduced the size of the intrinsic optical signal associated with secretion by 50%, while the dihydropyridines had little effect. These observations suggest that the type of calcium channel that dominates the secretory behavior of intact vertebrate nerve terminals is at least partially blocked by omega-conotoxin GVIA and is insensitive, under normal conditions, to dihydropyridines.     

Tissue-specific and age-related variations in repetitive sequences of mouse extrachromosomal circular DNAs

Extrachromosomal circular (ecc) DNA was isolated from mouse brain, liver, and heart tissues at different ages. To determine the abundance of repetitive sequences in eccDNAs, preparations were probed for short-interspersed (B1 and B2), long-interspersed (L1), endogenous retroviral-like (IAP), and tandemly repeated satellite sequences (SAT) of the mouse genome. Together these sequence families comprise approximately 15% of the mouse genome. The hybridization results showed that each tissue had a characteristic pattern of repetitive sequence elements in eccDNAs, and the abundance of repetitive sequences changed as a function of age. Repetitive sequences decreased in liver and brain eccDNAs from 1 month to 8 months of age but appeared to remain stable thereafter. In contrast, repetitive sequence families in heart eccDNAs were constant from 1 month to 16 months of age but declined in 24-month-old mice. The present studies indicate that extrachromosomal sequences exhibit greater flexibility than chromosomal sequences.     

Fine needle aspiration of peripheral neuroepithelioma of soft tissues.

Peripheral neuroepithelioma of soft tissue is a malignant primitive neuroectodermal tumor that appears both in children and adults and usually has a poor outcome. Fine needle aspiration on two patients with tumors in the lower limbs showed small round cells with unipolar processes and a tendency to form Homer-Wright rosettes. The cells had a round to oval nucleus with fine chromatin, up to four small, conspicuous nucleoli and vacuolated, periodic acid-Schiff-positive cytoplasm. The diagnosis was supported by electron microscopic study of the aspirate, which showed features of neuroblastic differentiation (i.e., neurosecretory granules), and by histologic, immunohistochemical and cytogenetic study of the resected tumors.     

Use of the additive main effects and multiplicative interaction model in QTL mapping for adaptation in barley

The additive main effects and multiplicative interaction (AMMI) model has emerged as a powerful analytical tool for genotype x environment studies. The objective of the present study was to assess its value in quantitative trait locus (QTL) mapping. This was done through the analysis of a large two-way table of genotype-by-environment data of barley (Hordeum vulgare L.) grain yields, where the genotypes constituted a genetic population suitable for mapping studies. Grain yield data of 150 doubled haploid lines derived from the Steptoe x Morex cross, and the two parental lines, were taken by the North American Barley Genome Mapping Project (NABGMP) at 16 environments throughout the barley production areas of the USA and Canada. Four regions of the genome were responsible for most of the differential genotypic expression across environments. They accounted for approximately 50% of the genotypic main effect and 30% of the genotype x environment interaction (GE) sums of squares. The magnitude and sign of AMMI scores for genotypes and sites facilitate inferences about specific interactions. The parallel use of classification (cluster analysis of environments) and ordination (principal component analysis of GE matrix) techniques allowed most of the variation present in the genotype x environment matrix to be summarized in just a few dimensions, specifically four QTLs showing differential adaptation to four clusters of environments. Thus, AMMI genotypic scores, when the genotypes constituted a population suitable for QTL mapping, could provide an adequate way of resolving the magnitude and nature of QTL x environment interactions.Ignacio Romagosa was on sabbatical leave from the University of Lleida and the Institut de Recerca i Tecnologia Agroalimentàries, Lleida, Spain, when this study was conducted     

Competition during colonization vs competition after colonization in disturbed environments: A metapopulation approach

How two species interact during and after colonization influences which of them will be present in each stage of succession. In the tolerance model of ecological succession in a patchy environment, empty patches can be colonized by any species, but the ability to tolerate reduced resource levels determines which species will exclude the other. Here, we analyze a meta-population model of the possible roles of competition in colonization and succession, using non-linear Markov chains as a mathematical framework. Different kinds of competition affect the final equilibrial, abundances of the species involved in qualitatively different ways. An explicit criterion is given to determine which interactions have stronger effects on the final equilibrial levels of the weaker, species. Precise conditions are stated for the co-existence of both species. Both species are more likely to co-exist in the presence of an intermediate disturbance frequency.     

Mixed connective tissue disease. A clinico-serological study of 17 cases

Mixed connective tissue disease (MCTD) was described as a distinct clinical syndrome in 1972. Since then many cases have been reported in the literature worldwide. In this study we present our experience with a group of 17 Mexican patients with this syndrome, and we analyze their clinical and serological features, as well as the causes of death in these patients. The patients are Mexican mestizos living in Guadalajara and most of them have been followed-up at Hospital General de Occidente for a period of 1–10 years. The female/male ratio was 16:1, and their age ranged from 14–55 years with a mean of 29 years. The disease duration has ranged from 1–17 years, with a mean of 6 years. Among the clinical manifestations we have found a high frequency of lymphadenopathy when compared with published series (13/17 or 76%), and the laboratory findings in our patients included a very high polyclonal increase of gammaglobulins (93%), lymphopenia (76%), direct immunofluorescence speckled nuclear epidermal deposits in skin biopsies (75%) and positive rheumatoid factor (65%). Other clinical and serological features were similar to those reported in other series of patients with MCTD. Six of the 17 patients have died (35%), and in 3 of them (17.5%) the cause of death was due to an infectious disease that suddenly presented, and apparently was not related to a concomitant high dose of steroids or malnutrition in the patients. It seems that in addition to the already well known autoimmune abnormalities that occur in MCTD, there are other features like the presence of lymphadenopathy, the high polyclonal increase of gammaglobulins, and the lymphopenia, that reflect the profound disturbance of the immune system in this syndrome, possibly contributing to the sudden appearance of a severe infectious disease in some of our patients.Abbreviations ANA antinuclear antibody - CIE counterimmunoelectrophoresis - MCTD mixed connective tissue disease - PHA passive hemagglutination - PM polymyositis - RF rheumatoid factor - SLE systemic lupus erythematosus - SS systemic sclerosis (SS)     

Characterization of multiple circular RNAs derived from a plant viroid-like RNA by sequence deletions and duplications.

Northern blot hybridizations with a probe complementary to a 275-nt circular RNA isolated from carnation plants revealed that this RNA co-exists in vivo with minor amounts of other small circular RNAs. Sequencing of cDNA clones of nine RNA species demonstrated deletions and duplications of the predominant 275-nt RNA. Minor sequence heterogeneities were observed at the crossover sites. Deletions mapped to three arms of the cruciform structure of lowest free energy obtained previously for the parental 275-nt RNA, whereas repeats encompassed mostly regions of the arm where deletions were not found. Some of the deleted and duplicated regions corresponded to sequences forming part of the two hammerhead structures involved in the in vitro self-cleavage of the plus and minus strands of the 275-nt RNA. A copy choice model is proposed for the emergence of deletions and duplications, where the RNA polymerase with the nascent strand dissociates from the template at regions rich in secondary and possibly tertiary structures, and reinitiates synthesis at different upstream and downstream positions.     

The RTX haemolysins ApxI and ApxII are major virulence factors of the swine pathogen Actinobacillus pleuropneumoniae: evidence from mutational analysis

The involvement of the RTX haemolysins (Apxl and ApxII) of the swine pathogen Actinobacillus pleuropneumoniae in virulence was investigated using haemolysin-deficient mutants constructed by a mini-Tn10 mutagenesis procedure. Two types of haemolysin mutant with single insertions of the transposon were obtained from a serotype 1 strain producing both ApxI and ApxII. One presented a complete loss of haemolytic activity because of the absence of ApxI and ApxII production. The other displayed weaker haemolysis than the wild type and produced only ApxII. The chromosomal regions flanking mini-Tn10 were cloned and sequenced. In the non-haemolytic mutant, the transposon had inserted in apxIB, a gene involved in the exportation of ApxI and ApxII toxins. The weakly haemolytic mutant resulted from the disruption of the structural gene for ApxI. Both mutations In the apxI operon were associated with a significant loss of virulence for mice and pigs, demonstrating that haemolysins are involved in A. pleuropneumoniae pathogenicity. The non-haemolytic mutant was apathogenic and the weakly haemolytic mutant retained some virulence for pigs, suggesting that both ApxI and ApxII are needed for full virulence.