Vergleichende histologische,histochemische und elektronenmikroskopische Untersuchungen an Tränendrüsen

Zusammenfassung Die menschliche Glandula lacrimalis ist eine tubulo-acinöse Drüse und besitzt mehrere Ausführungsgänge. Ihr fehlen Schaltstücke sowie Sekretrohre; die verzweigten Tubuli münden direkt in intralobuläre Ausführungsgänge. Histologisch und histochemisch sind zwei Zelltypen zu unterscheiden: sog. G-Zellen mit zahlreichen, sehr großen Granula, und sog. K-Zellen, die vorwiegend kleine Sekretkörnchen in geringer Menge enthalten. Alle Drüsenzellen verhalten sich PAS-positiv. Die G-Zellen (Drüsenzellen mit großen Sekretkörnchen) sind außerdem reaktiv auf Alcianblau, Astrablau, Rutheniumrot und nietachromatisch nach Toluidinblau. Hierbei handelt es sich demnach um saure Mucopolysaccharide enthaltende Sekretgranula.Die Feinstruktur zeigt den typischen Bau sekretorischer Zellen. Das basale Ergastoplasma ist stark entwickelt und erinnert an das Zellbild eiweißproduzierender Zellen. Augenfällig ist die Fülle von Golgi-Strukturen, die ohne Bevorzugung bestimmter Zellbezirke überall im Cytoplasma verteilt sind. Die zahlreichen Mitochondrion sind auffällig groß.Die supranucleären und apikalen Zellbezirke sind fast völlig vom kugeligen, ovoiden und häufig stark verformten Sekretvakuolen unterschiedlicher Größe ausgefüllt. Ihr Inhalt ist teilweise hell und strahlendurchlässig, teils fein, teils grob granuliert, teils elektronendicht, osmiophil und homogen. Die luminalen Plasmamembranen sind entweder glatt oder mit kurzen, stummeiförmigen Mikrovilli besetzt.In der menschlichen Tränendrüse wurden zahlreiche Hydrolasen und eine Reihe von Oxydoreduktasen aus der Glykolysekette, dem Zitronensäurezyklus, der Atmungskette und dem Pentosephosphatcyklus histochemisch nachgewiesen. Das Enzymmuster gleicht dem der Kaninchen-Tränendrüse. Die Befunde werden diskutiert.

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Comparative histological, histochemical and electronmicroscopical investigations on lacrimal glandsVI. The human lacrimal gland

Summary The human lacrimal gland is a tubuloacinar organ consisting of three rather distinct compartments: acini, tubuli and excretory ducts. Two of these compartments, the acini and tubuli, are the sites of secretory activity. There are two types of secretory cells: K-cells with large granules and G-cells containing a few of very small granules.Histochemically, acinar cells are uniformly characterized by a basal dense basophilia and PAS-positive material in the apical two thirds of the cytoplasm. In contrast, the granules of the G-cells are positive for Alcian blue, Astra blue, Ruthenium red and Toluidine blue.Electron microscopic studies have demonstrated further dissimilarities between these two cell types. If the vertical axis of an acinar cell is divided into four equal zones, it can be found that the basal zone always contains most of the rough-surfaced endoplasmic reticulum, the nucleus lies within the next zone, and the apical half of the cell is filled with secretory material of varying density and a number of scattered Golgi areas. Golgi profiles are most abundant in the granule-containing apical half of the cell but also occur near the nucleus and occasionally in the lateral areas of the basal zone.Secretory granules are bound by ill-preserved membranes. Their internal structure is partly electron lucent, partly electron dense, occasionally characterized by a flocculent graininess. Plasma membranes take different contours on various surfaces of the cell. Bordering the lumen they are relatively even but form a few microvilli. Acinar cells have many mitochondria, some of which may be rather large.Also the distribution pattern of some hydrolases and of a number of oxydoreductases of the glycolytic chain, the citric acid cycle, the respiratory chain and the hexose monophosphate shunt is reported for the human lacrimal gland. The enzyme patterns were similar to those observed in the rabbit.

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Gekürzter Teil einer Arbeit, die der Medizinischen Fakultät der Philipps-Universität Marburg als Habilitationsschrift vorlag.

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Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

What is the best method to remove 2,3-diphosphoglycerate from hemoglobin?

We have compared the efficiency of four methods to remove 2,3-diphosphoglycerate (DPG) from hemoglobin (Hb), comprising dialysis, repeated ultrafiltration, gel filtration, and ion-exchange chromatography. All the methods eventually yielded hemoglobin solutions with a ratio of <0.002 mol of DPG/mol of Hb₄ and identical oxygen-binding properties but differed with respect to duration and versatility. Considering these factors, we found the combination of an ion-retardation resin and a mixed-bed resin to be most satisfactory.     

Gruppen-Gründung und Reproduktion bei Nacktmullen (Heterocephalus glaber) im Zoo Dresden

When establishing a new breeding group of Naked mole-rats three significant hurdles are to overcome: 1. Determination of sex. 2. Get over the group specific smell (between individuals of different groups). 3. Get over the reproductive blockade. This report describes experiences achieving these goals as well as establishes requirements for a successful breeding. The sex determination of nonreproductive Naked mole rats is tainted with great uncertainty, because the anogenital region of both sexes appears quite similar. For a lack of births and a failure of rearing offspring the following reasons seem to be responsible: 1. Incorrect sex determination at the time of group founding. 2. The reproductive blockade could not be overcome because of disadvantageous hierarchical relations within the group. 3. Pregnancy is interrupted due to disturbances from outside the enclosure or social stress within the group. 4. Due to these disturbances the alpha-female is not often enough willing to suckle her youngsters.     

Investigations into the phylogenetic position of Micrognathozoa using four molecular loci

Micrognathozoa is the most recently discovered higher metazoan lineage. The sole known species of the group, Limnognathia maerski, was originally reported from running freshwater in Disko Island (Greenland), and has recently been recorded from the subantarctic region. Because of the presence of a particular type of jaws formed of special cuticularized rods, similar to those of gnathostomulids and rotifers, the three metazoan lineages were considered closely related, and assigned to the clade Gnathifera. A phylogenetic comparison of four molecular loci for Limnognathia maerski and other newly generated sequences of mainly acoelomate animals showed that Micrognathozoa may constitute an independent lineage from those of Gnathostomulida and Rotifera. However, the exact position of Micrognathozoa could not be determined due to the lack of support for any given relationships and due to the lack of stability in the position of Limnognathia maerski under analysis of different loci and of different parameter sets for sequence comparison. Nuclear loci tend to place Micrognathozoa with the syndermatan/cycliophoran taxa, but the addition of the mitochondrial gene cytochrome c oxidase subunit I favors a relationship of Micrognathozoa to Entoprocta.     

The role of protein quality control in mitochondrial protein homeostasis under oxidative stress

Mitochondria contribute significantly to the cellular production of ROS. The deleterious effects of increased ROS levels have been implicated in a wide variety of pathological reactions. Apart from a direct detoxification of ROS molecules, protein quality control mechanisms are thought to protect protein functions in the presence of elevated ROS levels. The reactivities of molecular chaperones and proteases remove damaged polypeptides, maintaining enzyme activities, thereby contributing to cellular survival both under normal and stress conditions. We characterized the impact of oxidative stress on mitochondrial protein homeostasis by performing a proteomic analysis of isolated yeast mitochondria, determining the changes in protein abundance after ROS treatments. We identified a set of mitochondrial proteins as substrates of ROS‐dependent proteolysis. Enzymes containing oxidation‐sensitive prosthetic groups like iron/sulfur clusters represented major targets of stress‐dependent degradation. We found that several proteins involved in ROS detoxification were also affected. We identified the ATP‐dependent protease Pim1/LON as a major factor in the degradation of ROS‐modified soluble polypeptides localized in the matrix compartment. As Pim1/LON expression was induced significantly under ROS treatment, we propose that this protease system performs a crucial protective function under oxidative stress conditions.