Ultrastructure of oesophageal appendages ("peptonephridia") in enchytraeids (Annelida: Clitellata)

Abstract. Although the oesophageal appendages in the four enchytraeids Enchytrueus crypticus, Fredericia strinta, Buchholzia appendiculata , and Achaeta sp. are quite different from one another in shape and position, their histology and ultrastructure are basically the same. These are intestinal appendages, the lumina of which distally end blind and proximally open into the oesophagus. Almost all of the few cells in their single-layered epithelium have a microvillous, cilia-free border at the apex, facing towards the lumen, and basally comprise an extremely extensive labyrinth. The presence of the latter, composed of very thin cell processes, and of numerous mitochondria identifies the organs as energy-producing and -consuming, transport-active structures. Their possible function as a food-moistening organ or osmoregulatory organ is discussed, and they are compared with other intestinal appendages in enchytraeids and other oligochaetes.     

Dot-blot assays and their use as a direct antigen-binding method to screen monoclonal antibodies to 1,4-beta- and 1,3-beta-glucan synthases

A rapid method has been developed to assay beta-glucan synthases spotted on a nitrocellulose sheet. The sensitivity of this method allows screening of hybridoma-making monoclonal antibodies in a direct antigen-binding assay by measurement of the activity of the enzymes retained by the antibodies previously fixed on nitrocellulose.     

Chromosomal evolution withinPiperaceae

Chromosome numbers for 26 different species of the generaPiper, Peperomia andPothomorphe (Piperaceae) are reported. The basic chromosome numbers are 2n = 26, x = 13 (Piper, Pothomorphe) and 2n = 22, x = 11 (Peperomia), polyploid series are characteristic forPiper andPeperomia. Piper has the smallest chromosomes and prochromosomal interphase nuclei,Peperomia the largest ones and mostly reticulate to euchromatic nuclei.Pothomorphe is intermediate in both characters. The karyomorphological differences betweenPothomorphe andPiper underline their generic separation. Interspecific size variation of chromosomes occurs inPiper andPeperomia. Infraspecific polyploidy was observed inPiper betle. C-banding reveals different patterns of heterochromatin (hc) distribution between the genera investigated. The genome evolution is discussed.     

Konstruktionsprinzipien des Schnabelskeletts beim schlupfreifen Jungvogel

Zusammenfassung Unter Einsatz einer neuartigen, direkt vergrößernden Röntgentechnologie wurde die Konstruktion des Schnabelskeletts von schlupfreifen Jungvögeln untersucht. Wie die bei Verwendung sog. Mikrofokus-Röntgengeräte erzielten Röntgenaufnahmen erkennen lassen, weist das Schnabelskelett der Schlüpflinge — unabhängig vom Entwicklungsmodus — bei allen untersuchten Formen einen recht einheitlichen Bau auf. Sowohl der Ossifikationsgrad der Kiefer als auch die spezifische Osteoarchitektur der Knochenelemente des Schnabelapparates, insbesondere im Bereich der Substantia spongiosa des Os praemaxillare können als anatomische Anpassungen an die beim Sprengen der Eischale auftretenden mechanischen Belastungen des Kieferskeletts gewertet werden.

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Construction principles of the beak skeleton in the hatchling

Summary The structure of the beak skeleton of hatchlings was analysed using a new direct magnifying X-ray technique. The application of these microfocus X-ray systems reveals a quite uniform construction of the beak skeleton in the hatchlings, independent from the mode of development of the bird species groups studied (precocial, altricial etc.). The amount of ossification as well as the specific osteoarchitecture of the jaw bones of the beak apparatus — especially in the region of Substantia spongiosa of the Os praemaxillare — may be considered as an anatomical adaptation to mechanical stress of the jaw bones during picking of the eggshell.

     

Amino acid transport in the rat exocrine pancreas

Summary Amino acid transport and incorporation have been studied in vitro in rat pancreatic lobules after maximal and supramaximal hormonal stimulation with caerulein. Incorporation into proteins was increased already after 30 and 120 min of maximal stimulation, but was decreased after the infusion of a supramaximal dose. Uptake of neutral amino acids was monitored using labeled leucine and -aminoisobutyric acid (AIB). In the case of leucine the free pool was consistently reduced after maximal stimulation, while supramaximal doses led to an increase which could be potentiated by the addition of 2mM tetracaine. Using AIB, a significant increase in the intracellular pool was observed after maximal stimulation, conversely a decrease after supramaximal stimulation. Release of labeled leucine and AIB from preloaded lobules during incubation in the cold was significantly reduced after maximal secretory stimulation, but was found enhanced by 200 to 300 percent after supramaximal stimulation. No fine structural alterations at junctional complexes or at both the lateral and luminal plasma membranes were observed after maximal stimulation except an increased number of exocytotic figures at the luminal face. However, supramaximal stimulation led to progressive rarefaction of the tight junctional network and disintegration of the gap junctions. Concomitantly, an equal distribution of membrane particles on both faces of the plasma membrane together with a random occurrence of exocytotic figures were observed.Supported by a grant from the Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg (SFB 122, project C 5). Dedicated to Professor Dr. Gerhard Petry, Marburg, on the occasion of his 65th birthday     

Internally elongated rodent α-crystallin A chain: Resulting from incomplete RNA splicing?

αA^Ins, an elongated α-crystallin A chain previously observed in rat, was present beside the normal αA chain in mouse, gerbil and hamster, which places its origin at least 30 million years ago. Like in rat the sequences of golden hamster αA^Ins and αA were found to be identical, apart from the internal insertion of 22 residues in αA^Ins. The hamster chains only differed from the rat chains by a single substitution in the inserted sequence of αA^Ins. The origin of αA^Ins, by insertion of 22 residues in an otherwise unchanged αA chain, and its rigid evolutionary conservation are most easily explained by assuming the incomplete removal of a putative intervening sequence from the precursor mRNA of αA, leaving an intracistronic insert of 66 nucleotides in part of the eventually translated mRNA.