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  • 1
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Microplasmodesmata ; Intercellular communication ; Hetorocysts ; Freezefracture ; Plasma membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Structures which may establish cytoplasmic continuity between adjacent cells of filamentous cyanobacteria have been observed by freeze-fracture electron microscopy. They are visible in the septum region of the plasma membrane as pits on the E-face (EF) and corresponding protrusions on the P-face (PF). Between 100 and 250 of these structures, termed microplasmodesmata, were present between adjacent vegetative cells in all four strains of heterocyst-forming filamentous cyanobacteria, Anabaena cylindrica Lemm, A. variabilis (IUCC B377), A. variabilis Kütz. (ATCC 29413) and Nostoc muscorum, examined. Only 30–40 microplasmodesmata were observed between adjacent cells in two species, Phormidium luridum and Plectonema boryanum, that do not form heterocysts. The results suggest that in species that form heterocysts a greater degree of cytoplasmic continuity is established, presumably to facilitate the exchange of metabolites. In species capable of forming heterocysts, the number of microplasmodesmata per septum between two adjacent vegetative cells remained constant whether the filaments were grown in the presence of NH4 and lacked heteroxysts or under N2-fixing conditions and contained heterocysts. When a vegetative cell differentiates into a heterocyst, about 80% of the existing microplasmodesmata are destroyed as the poles of the cell become constricted into narrow necks leaving smaller areas of contact with the adjacent vegetative cells.
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  • 2
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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  • 4
    ISSN: 1432-2323
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé De nombreuses méthodes ont été décrites pour déterminer le siège des parathyroïdes hyperfonctionnelles avant l'intervention. Au cours des deux dernières années 18 malades ont été opérés pour hyperparathyroidisme persistant (14) ou récidivant (4). Une ou plusieurs glandes responsables furent découvertes chez 17 sujets et 16 présentèrent une calcémie normale après l'opération. Dix-huit sujets furent soumis à une exploration par ultra-sons, 17 à une tomodensitométrie et 13 subirent un prélèvement sanguin veineux sélectif pour doser l'hormone parathyroïdienne, ces explorations permettant de localiser la lésion ou les lésions respectivement dans 9 (50%), 8 (47%) et 9 (69%) des cas. Chez 3 sujets la tumeur fut localisée par l'ultrasonographie et confirmée par la biopsie aspiration guidée par l'exploration aux ultra-sons. Tous les opérés présentaient une tumeur parathyroïdienne à l'intervention. La plus petite tumeur détectée par l'ultrasonographie mesurait 0,6×0,6 ×0,6 cm, celle par la tomodensitométrie 0,9×0,9 ×0,8 cm. Au passif de la tomodensitométrie s'inscrit un faux positif, au dosage sanguin un faux positif également. Chez les deux opérés dont le taux de calcémie ne revint pas à la normale, les explorations ne permirent pas d'abord de localiser la tumeur mais chez l'un des deux patients la tomodensitométrie, la résonance nucléaire magnétique et le dosage de l'hormone parathyroïdienne dans le sang permirent ultérieurement de découvrir un adénome (0,6×0,6×0,5 cm) médiastinal qui fut extirpé avec un plein succès. L'angiographie digitalisée s'est montrée utile pour définir la distribution du système veineux parathyroïdien et pour procéder aux prélèvements sanguins électifs. L'ultrasonographie et la tomodensitométrie sont des méthodes complémentaires puisque l'une ou l'autre de ces méthodes s'est montrée positive chez 15 sujets cependant que couplées ces deux explorations furent positives seulement chez 2 sujets. Quand l'une de ces deux explorations s'est montrée positive la tumeur fut toujours découverte au lieu déterminé par le test exploratoire. L'opéré pour adénome parathyroïdien médiastinal développa un syndrome secondaire à la péricardotomie mais tous les autres opérés n'accusèrent aucune complication. Les méthodes qui permettent de déterminer le siège des tumeurs parathyroïdiennes facilitent le traitement chirurgical et diminuent le taux de la morbidité. On peut les considérer comme indispensables, chez les malades qui doivent être ré-opérés pour hyperparathyroidisme.
    Abstract: Resumen Numerosos métodos de localización preoperatoria de glándulas paratiroides hiperfuncionantes han sido descritos. En el curso de los últimos dos años se han realizado operaciones en 18 pacientes con hiperparatiroidismo persistente (14) o recurrente (4). Una o más glándulas paratiroides hiperfuncionantes fueron identificadas en el curso de la operación en todos los pacientes, con una excepción, y todos los pacientes se convirtieron en normocalcémicos. Se realizó ultrasonografía en 18 pacientes, tomografía computadorizada (TC) en 17 y determinaciones venosas selectivas (DVS) de hormona paratiroidea (PTH) en 13; tales exámenes identificaron correctamente la lesión en 9 (50%), 8 (47%) y 9 (69%) del grupo total de pacientes, respectivamente. En tres casos se identificó la presencia de probables tumores paratiroideos por ultrasonografía y fue confirmada por medio de la citología o biopsia de aspiración bajo guía ultrasonográfica. Todos presentaban tumores paratiroideos que fueron confirmados en la operación. El más pequeño tumor localizado por ultrasonografía medía 0,6×0,6×0,6 cm, y por TC 0,9×0,9× 0,8 cm. Se presentaron un resultado falso positivo en CT y un falso positivo en DVS. En 2 pacientes en quienes no se logró la hipercalcemia, ninguno de los estudios de localización fue positivo. Uno de estos pacientes ulteriormente presentó un adenoma mediastinal de 0,6×0,6×0,5 cm, localizado por medio de TC, resonancia magnética nuclear y DVS; tal tumor fue resecado por vía de una esternotomía mediana, y el paciente se encuentra actualmente normocalcémico. La angiografía digital ha probado recientemente ser de utilidad para delinear el patrón venosa para la DVS. La ultrasonografía y la TC aparecen como estudios complementarios, puesto que el uno o el otro de estos estudios se hallo positivo en 15 pacientes y, sin embargo, sólo dos pacientes exhibieron la ultrasonografía y la TC conjuntamente positivas. Cuando uno de los dos exámenes de localización sugirió la misma ubicación de la lesión paratiroidea, se encontró siempre la presencia de un tumor. Un paciente desarrolló el síndrome de postpericardiotomía después de la esternotomía mediana, pero no hubo otras complicaciones. Los procedimientos de localización hacen más expedito el procedimiento quirúrgico, disminuyen la morbilidad y deben ser vehementemente recomendados en pacientes que requieran reoperación por hiperparatiroidismo.
    Notes: Abstract Numerous techniques have been described for the preoperative localization of hyperfunctioning parathyroid glands. During the past 2 years, 18 patients have had operations for persistent (14) or recurrent (4) hyperparathyroidism. One or more hyperfunctioning parathyroid glands were identified at operation in all but 1 patient and all but 2 patients became normocalcemic. Eighteen patients had ultrasonography, 17 patients had computed tomography (CT) scanning, and 13 patients had selective venous sampling (SVS) for parathyroid hormone (PTH) assay. These studies correctly identified the lesion(s) in 9 (50%), 8 (47%), and 9 (69%) of the patients, respectively. In 3 patients, probable parathyroid tumors were identified by ultrasonography and confirmed by aspiration biopsy cytology under ultrasonic guidance. All had parathyroid tumors confirmed at operation. The smallest tumor localized by ultrasonography was 0.6×0.6×0.6 cm and by CT scanning was 0.9×0.9×0.8 cm. There was 1 false-positive CT scan and 1 false-positive SVS. In the 2 patients who failed to become normocalcemic no localization study was positive. One of these patients subsequently had a 0.6×0.6×0.5 cm mediastinal adenoma localized by CT scan, nuclear magnetic resonance, and SVS. The tumor was removed via median sternotomy and the patient is now normocalcemic. Digital angiography has recently been helpful for “mapping out” the venous pattern for venous sampling for PTH. Ultrasonography and CT scanning complemented each other, since one or the other of these studies was positive in 15 patients, yet only 2 patients had both a positive ultrasound and CT scan. When any 2 localizing tests suggested the same site for the parathyroid lesion, the tumor was found in all cases. One patient developed post-pericardotomy syndrome after a medium sternotomy, but there were no other complications. Localization procedures expedite surgical treatment, decrease morbidity, and are strongly recommended in patients requiring reoperation for hyperparathyroidism.
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  • 5
    ISSN: 1432-2242
    Keywords: Hordeum ; Amphidiploids ; Chromosome elimination ; Chromosome stability ; Gene balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Both diploid and tetraploid hybrids of Hordeum vulgare x H. bulbosum exhibit chromosome instability during plant development and generally lose the H. bulbosum chromosomes by the next generation. However an amphidiploid involving the cultivar ‘Vada’ was found to retain the bulbosum chromosomes through a sexual cycle. Comparisons were made between this stable amphidiploid and a second, unstable amphidiploid involving the cultivar ‘Emir’. At meiosis there was a wide range of chromosome numbers in the ‘Emir’ amphidiploid but only a narrow range in the ‘Vada’ amphidiploid. Degraded chromosomes were commonly found in the PMCs of the ‘Emir’ amphidiploid but none was found in the stable ‘Vada’ amphidiploid. The two amphidiploids were reciprocally crossed and the chromosome numbers of the progeny checked. The H. bulbosum chromosomes had been retained in many of the progeny and both triploid and tetraploid hybrids were found. It is proposed that a gene(s) exists in ‘Vada’ capable of preventing the elimination of bulbosum chromosomes from H. vulgare x H. bulbosum hybrids.
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  • 6
    ISSN: 1432-2242
    Keywords: Hordeum ; Stable hybrids ; Chromosome elimination ; Chromosome stability ; Gene balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The hybrid progeny from a stable amphidiploid of H. vulgare x H. bulbosum involving the cultivar ‘Vada’ and an unstable amphidiploid involving the cultivar ‘Emir’ were studied. The genotypes examined contained two genomes from ‘Vada’ or one from ‘Vada’ and one from ‘Emir’, with one or two genomes from H. bulbosum. Comparisons between the chromosome numbers in root-tips and anthers revealed that there was no chromosome elimination in most plants, whether there was one or two Vada genomes present. The one plant in which chromosome elimination was positively identified had ‘Emir’ as opposed to ‘Vada’ cytoplasm. It also had a high incidence of degraded or fragmented chromosomes in the PMCs. Differences in stability between a 27 chromosome plant and other hypotetraploids suggest that ‘Vada’ contains both elimination genes and elimination suppressor genes. Upon selfing, again irrespective of the number of ‘Vada’ genomes present, circa triploid hybrids gave rise to diploid H. vulgare offspring while hypotetraploids produced hybrid-like plants. These included diploids, triploids and tetraploids. There was evidence that suggested that H. vulgare as well as H. bulbosum chromosomes had been eliminated.
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  • 7
    ISSN: 1432-0509
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 8
    ISSN: 1432-0509
    Keywords: Ultrasound, diagnosis ; Ultrasound, abdomen ; Gallbladder disease, acute
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Ultrasonography was performed as the first imaging procedure in 100 patients who presented with acute right upper quadrant pain suggestive of cholecystitis or cholelithiasis. In the final analysis 46 patients were found to have gallbladder disease (40 patients with cholelithiasis, 5 with acalculous cholecystitis, and 1 with a cholesterol polyp in the gallbladder). In 22 of 54 patients with a normal gallbladder, other abdominal disease was found. The error rate for ultrasound was 5%, and in 4 patients ultrasound was not the suitable procedure for the diagnosis. In 91 patients the ultrasonographic diagnosis was correct.
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  • 9
    ISSN: 1432-0509
    Keywords: Gastric perforation ; Hepatic artery infusion ; Chemotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Hepatic artery infusion chemotherapy may result in mucosal inflammation and ulceration, gastrointestinal hemorrhage, pancreatitis and catheter-related vascular injury. We report a patient who developed gastric perforation during hepatic artery infusion chemotherapy. The influence of variations of hepatic artery branching and catheter placement in producing this life-threatening complication is discussed.
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  • 10
    Electronic Resource
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    Springer
    Communications in mathematical physics 85 (1982), S. 563-602 
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract This paper develops the Riemannian geometry of classical gauge theories — Yang-Mills fields coupled with scalar and spinor fields — on compact four-dimensional manifolds. Some important properties of these fields are derived from elliptic theory: regularity, an “energy gap theorem”, the manifold structure of the configuration space, and a bound for the supremum of the field in terms of the energy. It is then shown that finite energy solutions of the coupled field equations cannot have isolated singularities (this extends a theorem of K. Uhlenbeck).
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