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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 249 (1987), S. 101-109 
    ISSN: 1432-0878
    Keywords: Eye ; Choriocapillaris ; Angioarchitecture ; Scanning electron microscopy ; Vascular microcorrosion casts ; Rana temporaria ; Rana esculenta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pattern of the vascular supply to the choroid of the frog eye was studied in toto with the use of the injection-replication-SEM technique. The choroid of anuran amphibians is composed mainly of the choriocapillaris. In both species studied (Rana temporaria, Rana esculenta), an independent arterial supply to the choriocapillaris supplemented that from the ciliary arteries. This additional vascular route arises from the optic artery, a separate branch of the arteria infundibularis superficialis. The optic artery, accompanied by its vein within the vascular sheath of the optic nerve, joins the rich arterial capillary network of the choriocapillaris and supplies the posterior pole of the ocular bulb. The superficial capillary network displays a dense collar around the entrance of the optic nerve into the eye and is composed of a circular meshwork of small capillaries, several layers deep. More peripherally, however, it becomes single layered. This capillary network, as a whole, establishes numerous connections with the adjacent choriocapillaris at the posterior pole of the ocular bulb. In anuran amphibians the complex arrangement of both arterial systems supporting the choriocapillaris may be regarded as a more complete equivalent of the short posterior ciliary arteries of mammals.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 250 (1987), S. 465-473 
    ISSN: 1432-0878
    Keywords: Eye ; Angioarchitecture ; Hyaloid ; Scanning electron microscopy ; Vascular microcorrosion casts ; Rana temporaria, Rana esculenta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The angioarchitecture of the superficial vascular hyaloid system (membrana vasculosa retinae) of the frog eye was studied by means of scanning electron microscopy of vascular corrosion casts. The terminal vessels form a single-layered sheath intimately adjacent to the vitreal side of the avascular retina. The hyaloid system is subdivided by the ventral venous trunk into three central areas: the dorsal, the temporo-ventral, and the naso-ventral area. Toward the ora serrata, the hyaloid system is bordered by an arterial ring, and by nasal and temporal venous branches forming more or less complete hemicircles. A vascular zone composed of several tongue-like sectors establishes an inter-connection between the peripheral vascular rings and the central areas of the fundus. The arterial blood is supplied from the arterial ring. The drainage of the hyaloid system is provided via two routes: (1) the Y-shaped ventral trunk collects blood from the central areas, (2) the two peripheral venous branches drain the tongue-like sectors. The vessels within the dorsal area follow preferentially a dorso-ventral meridional direction. This densely capillarized territory corresponds in localization to the area centralis retinae. The ultrastructure of microvessels of the hyaloid system is characterized by features typical for capillaries of the central nervous system.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 419-426 
    ISSN: 0170-2041
    Keywords: Sphingosines ; Azidosphingosines ; Octadec-4-enes ; Enzymes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of 2,4-O-benzylidene-D-threose (3) with the Wittig reagent obtained from 2-bromopentadecane furnished 5-methyloctadec-4-ene derivatives (E,Z)-8. The introduction of the azido group into the 2-position and acid-catalyzed removal of the benzylidene protective group afforded 5-methyl-substituted azidosphingosines (E)-10 and (Z)-10 which were converted via azide reduction into the corresponding sphingosines (E)-1 and (Z)-1, respectively. Reaction of 3 with methylmagnesium bromide, ensuing selective 2-O-mesylation, and then 4-O-oxidation gave ketone 13. The Wittig reaction of 13 with triphenyltetradecylphosphorane afforded exclusively 4-methyloctadec-4-ene derivative (Z)-16 which was transformed into 4-methyl-substituted sphingosine (Z)-2 as described above. For the synthesis of the corresponding E isomer, 3 was converted into carbinols 21h,l. 2-O-Silyl protection and then water elimination furnished 4-methyl-substituted (4E)-octadec-4-ene derivative (E)-23 which was transformed into (E)-2.
    Type of Medium: Electronic Resource
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