Dieter Schäfer

Arteriovenous anastomoses in the cat carotid body

SummaryIn artery surrounding areas in the periphery of the carotid body of the cat we found arteriovenous anastomoses differing in respect to their character. So far, it is not yet to decide the frequency of their occurrence and their functional significance. The anastomoses were demonstrated by light microscopy of serial sections and by scanning electron microscopy with a more developed corrosion casting technique.ZusammenfassungIn den arteriennahen, peripheren Bereichen des Glomus caroticum der Katze wurden arteriovenöse Verbindungen nachgewiesen, die ihrem Charakter nach unterschiedlich sind. Es ist allerdings noch nicht zu entscheiden, ob derartige Anastomosen regelmäßig vorkommen und wie sie funktionieren. Die beschriebenen Gefäßverbindungen konnten lichtmikroskopisch anhand von histologischen Serienschnitten und mit Hilfe einer weiterentwickelten Korrosionstechnik im Rasterelektronenmikroskop dargestellt werden.

Fine structure of chemosensitive cells (glomus caroticum) in tissue culture

SummaryCells of the carotid body of both embryonic and 1 to 2-d-old rabbits were cultured in monolayer in primary tissue culture. The cells grew in their original association of type I and type II cells. The fine structure of both cell types was similar to that in vivo. Even after one week in culture their morphological characteristics, such as the dense-cored vesicles, were preserved. The prolonged synthesis of catecholamines in culture and the formation of new granular vesicles is discussed.

The element distribution in ultrathin cryosections of cultivated fibroblast cells

SummaryA preparation method for measurements of the intracellular distribution of elements in tissue culture cells is described which is based on cryofixation, cryoultramicrotomy, cryotransfer and X-ray microanalysis in a scanning transmission electron microscope. Dry weight concentrations of phosphorus, sulfur, chlorine and potassium in the nucleus, the cytoplasm and the mitochondria of L929 fibroblast cells of the mouse are reported. The preparation and quantitation procedures are discussed with respect to present limitations and possible improvements of the method.

Cytochemical localization of alkaline phosphatase in the cell membrane of Dictyostelium discoideum amebae

SummaryWe demonstrated that alkaline phosphatase was localized on the cell membrane ofDictyostelium discoideum amebae and on isolated plasma membranes. The enzyme activity was specifically inhibited by 0.01 M KCN or cysteine. The same method could also be applied to bakers yeast and MDCK cells (dog kidney cells in vitro).

Der Einfluß acht verschiedener Aldehyde und des pH-Wertes auf die Darstellbarkeit der Glukose-6-Phosphatase in kultivierten Zellen

SummaryEight different aldehydes were tested regarding their use for fixation and following demonstration of glucose-6-phosphatase in cultured chicken heart calls. Since a perfect fixation of structure does not imply a sufficient preservation of enzyme activity and vice versa compromises were necessary. Glutaraldehyde and hydroxyadipaldehyde permit an excellent, methacrolein, glyoxal and acetaldehyde a limited, acrolein, „para“formaldeyhde and crotonaldehyde no demonstration of glucose-6-phosphatase. In the endoplasmic reticulum the nuclear envelope and the dictyosomes of cultured chicken heart cells the optimal pH for cytochemical demonstration ranges between pH 5.8 and 6.2. In the nucleus reaction product was noted only at a pH 6.8.ZusammenfassungAcht verschiedene Aldehyde wurden auf ihre Brauchbarkeit als Fixierungsmittel und für den anschließenden Nachweis der Glukose-6-phosphatase bei kultivierten Hühnerherzzellen geprüft. Gute Strukturerhaltung und schonende Enzymerhaltung stimmen nicht überein, so daß Kompromisse notwendig sind. Glutaraldehyd und Hydroxyadipinaldehyd ermöglichen eine gute, Methacrolein, Glyoxal und Acetaldehyd eine nur bedingt brauchbare, Acrolein, „Para“formaldehyd und Crotonaldehyd keine Glukose-6-phosphatase-Darstellung. Das pH-Optimum zum cytochemischen Nachweis dieses Enzyms liegt für das endoplasmatische Retikulum, den perinuklearen Spalt und die Dictyosomen kultivierter Hühnerherzzellen im Bereich pH 5,8 und 6,2. Die Reaktion tritt im Kern ausschließlich bei pH 6,8 auf.

Autophagosomen in gezüchteten Hühnerherzzellen

SummaryThe appearance of autophagosomes can be induced within embryonic chicken heart cells in vitro by means of sublethal X-ray treatment. Under these conditions small parts of cytoplasm which are surrounded by two membranes can be observed. These membranes are formed by parts of the endoplasmic reticulum. Within the two surrounding boundaris of young autophagosomes glucose-6-phosphatase can be demonstrated cytochemically. Most of the autophagosomes contained acid phosphatase. During the cell regeneration the autophagosomes are extruded by exocytosis into the culture medium. There is some evidence that contractile elements participate in this mechanism.ZusammenfassungBei embryonalen Hühnerherzzellen in vitro lassen sich Autophagosomen durch subletale Röntgenbestrahlung (1200 R, 2400 R) induzieren. Kleine Bereiche des Cytoplasmas werden dabei von Membranen umgeben, die dem endoplasmatischen Retikulum entstammen. Bei jungen Autophagosomen läßt sich zwischen den beiden umgebenden Membranen Glucose-6-phosphatase nachweisen. Von wenigen Ausnahmen abgesehen, enthalten alle saure Phosphatase. In der Regenerationsphase werden dann die Autophagosomen exocytotisch in das Kulturmedium abgestoßen. Es gibt Hinweise dafür, daß an diesem Vorgang kontraktile Elemente beteiligt sind.

The Oxygen Barrier in the Carotid Body of Cat and Rabbit

After a careful preparation of the carotid body of the cat the surface Po2 has been measured by means of a Pt needle electrode with a Pt diameter of 3/u fixed within Araldite to increase the outer diameter to 700/u. We found that the surface Po2 almost reached the arterial Po2.