Showing papers by "National University of Cuyo published in 1975"

On spin-orbit coupling

Abstract: It is shown that the well-known spin-orbit interaction term contained in Dirac's theory of the electron is, in the relativistic approximation, a pure quantum phenomenon and cannot be derived from relativistic point mechanics.

Domestikation und Migration vonSolanum tuberosum L.

Abstract: In der vorliegenden Studie fassen wir Beobachtungen zusammen, die wir im Laufe von zwei Jahrzehnten in zahlreichen L/tndern Lateinamerikas, in Sfidafrika und in Indien machen konnten. Unsere Befunde an ,,ReliktKartoffeln" wurden einerseits mit dem lebenden Material des S o l a n u m (Tuberarium)-,,Gen-Pools" in Sfidamerika verglichen, andererseits aber auch mit den Beschreibungen frfiher europ/iischer Kartoffel-Erwerbungen, die zum Tell mehrere Jahrhunderte zurfickliegen und fast in Vergessenheit geraten sind. Als verl/iBliche frfihe Urkunden fiber den Kartoffel-Anbau in Mitteleuropa erwiesen sich die Sortenbeschreibungen bei HOPPE (1747), SIMON (1782), GERIVIERSHAUSEN (1786), KRONITZ (1785), BURGER (1818) und PUTSCHE (1819). Unsere Studien wurden von der Absicht geleitet, die auf drei Kontinenten heute noch existierenden primifiven Klone von S o l a n u m tuberosum bevor sie durch moderne Zuchtsorten endgfiltig verdr/ingt werden und infolgedessen aussterben zur Aufkl/irung des immer noch undurchsichtigen Ursprungs dieser wichtigen Kulturpfianze heranzuziehen. Unentschieden ist noch immer, ob die tetraploide Kulturkartoffel direkt yon wildwachsenden Arten abstammt, ob sie alloploiden Ursprungs ist, oder ob sie sich dutch einfache Genomverdopplung aus einer diploiden primitiven Indianerkartoffel entwickelt hat (vgl. : BURTON, 1966; DODDS, 1965; BR/JCHER, 1964; HOWARD, 1970; LAMM, 1944; UGENT, 1970; SWAIvlINATHAN & MAGOON, 1961 u.a.) . SchlieBlich wird auch noch diskutiert, ob S o l a n u m tuberosum monophyletischen Ursprungs ist, oder ob es auBer dem ,,andinen Dispersionsbogen" (urn den Begriff ,,Genzentrum zu vermeiden) noch ein weiteres hypothetisches, insulates ,,Genzentrum Chilo6" der Kartoffel gibt (ZHUKOVSKI, 1959).

Electron microscopic studies on the pineal organ of the antarctic penguin, (Pygoscelis papua).

Abstract: The pineal organ of the migratory antarctic penguin, Pygoscelis papua, has a lobular structure. Clusters formed by different types of parenchymal cells are separated by connective tissue septa containing blood vessels. The predominant cell type displays a well-developed Golgi complex, free ribosomes, clear and granular vesicles (secretory granules), and lysosomes. Other cell types found in the gland are supporting and ependymal-like cells. The former contain dense bodies and filament bundles, the latter possess abundant cilia and clusters of ribosomes. Typical photoreceptor elements are lacking. Blood vessels are located within a perivascular space bordered by basal laminae. This perivascular space extends between the basal protrusions of the parenchymal cells. The presence of pinocytotic vesicles, secretory granules and cytoplasmic processes in the vicinity of these spaces suggests active sites of transport and exchange of substances. Intercellular canaliculi-like spaces are surrounded by parenchymal cells rich in microvilli. These canaliculi are continuous with the cavities (invaginations) of secretory and other parenchymal cells.

Role of the blood-brain barrier in the anticholinergic differential effects on LH and prolactin release in proestrous rats.

Abstract: The effects of homatropine and atropine on plasma LH and prolactin (PRL) levels during the afternoon of pro-oestrus were investigated. Homatropine methylbromide was unable to block the spontaneous increase of LH but prevented the prolactin surge in pro-oestrous rats at doses of 450 and 700 mg/kg s.c. Atropine sulphate blocked both LH and PRL at doses of 450 and 700 mg/kg s.c. These two anticholinergics when injected into the 3rd ventricle (250μg/rat) blocked the pro-oestrus increase of LH and inhibited PRL. Pharmacological experiments were performed in parallel and the injection of either homatropine or atropine (450 mg/kg s.c.) resulted in the abolishment of peripheral toxic signs induced by pilocarpine (50 mg/kg s.c.) whereas its central toxic signs were prevented by atropine but not by homatropine. Our findings suggest that the difference in action of systemic injections of atropine and homatropine on LH and PRL release is explained by a relatively low permeability of homatropine to the brain. Therefore, cholinergic LH-controlling mechanisms may be situated above the median eminence and those related to PRL placed outside the blood-brain barrier.

Reversible ultrastructural changes of arcuate neurons after vinblastine injection into the median eminence of the rat

Abstract: The ultrastructural effects of vinblastine on the arcuate neurons and median eminence were studied in the rat. The animals were stereotaxically injected with solutions of 1 mM and 5 mM vinblastine into the median eminence and killed 3, 8 and 21 days after injection. Eight days after injection of 1 mM vinblastine the neurons of the arcuate nucleus showed marked changes. The Golgi complex was more distinct and considerable increases in the populations of dense bodies, granulated vesicles and coated vesicles were observed. Changes in the axo-somatic synapses and degenerating fibers in the surrounding neuropil were also characteristic of the experimental animals. The outer zone of the median eminence showed numerous degenerated nerve fibers and fibers engulfed by glial cell processes. Eight days after injection of 5 mM vinblastine arcuate neurons and median eminence showed similar changes, but quantitative differences were noted. A striking ultrastructural recovery of the arcuate neurons and axons in the outer zone of the median eminence was observed 21 days after injection of either 1 mM or 5 mM vinblastine. The results are discussed in relation to axoplasmic transport and axonal degeneration.

Structure of the ρ-singularity in a multicluster model

Abstract: We construct a multicluster model for\(\pi {\mathcal{N}}_{CEX} \) amplitude in the forward direction which, in contrast to conventional ρ-Regge models, reproduces within error bars the data for\(\sigma _{\pi ^ - p}^{tot} - \sigma _{\pi ^ + p}^{tot} \) and\(d\sigma _{CEX} /dt|_{t - 0} \) for 3 ≤plab ≤ 60 GeV/e and fairly agrees with preliminary Batavia results. The model for the imaginary part shows an oscillation around a traditional ρ-pole value due to the onset of one large rapidity gap intermediate states. We propose that this oscillation, which fits well into Serpukhov enhancement, is the counter-part of similar threshold effects in\(\sigma _{\pi {\mathcal{N}}}^{tot} \) and\(\sigma _{{\mathcal{N}}{\mathcal{N}}}^{tot} \) arising at much higher energies. Absorptive corrections between clusters are considered to add consistency to the model.