The possible involvement of a peroxidase in prostaglandin biosynthesis

Sheep vesicular gland microsomes have been found to have an unusual peroxidase activity with a wide peroxide specificity and capable of oxidizing cofactors of prostaglandin synthetase. The peroxidase was also similar to the synthetase in its cellular location, its activation by hemin, inhibition by heme ligands and its inactivation by different peroxides. The inhibition by 2,7-naphthalenediol (K_i = 2 μM) also suggests that the peroxidase is an integral part of the synthetase complex.     

Male age and strain affect ejaculate quality in the Mexican fruit fly

Aging in all organisms is inevitable. Male age can have profound effects on mating success and female reproduction, yet relatively little is known on the effects of male age on different components of the ejaculate. Furthermore, in mass‐reared insects used for the Sterile Insect Technique, there are often behavioral differences between mass‐reared and wild males, while differences in the ejaculate have been less studied. The ejaculate in insects is composed mainly of sperm and accessory gland proteins. Here, we studied how male age and strain affected (i) protein quantity of testes and accessory glands, (ii) the biological activity of accessory gland products injected into females, (iii) sperm viability, and (iv) sperm quantity stored by females in wild and mass‐reared Anastrepha ludens (Diptera: Tephritidae). We found lower protein content in testes of old wild males and lower sperm viability in females mated with old wild males. Females stored more sperm when mated to young wild males than with young mass‐reared males. Accessory gland injections of old or young males did not inhibit female remating. Knowledge of how male age affects different ejaculate components will aid our understanding on investment of the ejaculate and possible postcopulatory consequences on female behavior.     

Evidence that up-regulation of the parotid Na+-K+-2Cl- cotransporter by hypertonic shrinkage is not duplicated by isotonic shrinkage

The application of Ca2+ mobilizing secretagogues to rat parotid acini results in a significant decrease in cell volume (15-30%) due to isotonic salt loss. It is often assumed that the effects of such an isotonic volume decrease can be mimicked by anisotonic cell shrinkage. We demonstrate that the Na+-K+-2Cl- cotransporter in these cells is up-regulated by Ca2+ mobilizing secretagogues as well as by cell shrinkage in hypertonic media. However, we find that although the protein kinase inhibitors staurosporine (0.3 M) and K252a (0.6 M) significantly blunt the latter up-regulation, they are without effect on the former. These observations suggest that hypertonic and isotonic shrinkage do not result in the activation of the same intracellular signalling pathways, and indicate that anisotonic volume perturbations may not provide good experimental models of physiologic isotonic volume changes.     

Structure and function of pilosebaceous units on the heads of small mammals (Insectivora, Chiroptera, Rodentia)

Haffner, M. 2000. Structure and function of pilosebaceous units on the heads of small mammals (Insectivora, Chiroptera, Rodentia). —Acta Zoologica (Stockholm) 81 : 195–203 The cranial integument of 32 species was examined for increased sebum production and structures serving sebum storage and expulsion by means of light and scanning electron microscopy. The head is rich in sebaceous glands in all species. Some have no further specializations other than regions with enlarged sebum production. These regions either need extra protection per se or they are situated where they can be used for fur grooming directly or be easily reached by the forepaws. The water shrew stores sebum that it can possibly apply as a water‐repellent lipid coating for the fur if required. All vespertilionid bats not only have huge glandular complexes with storage chambers, but also structures for the retaining and application of sebum. Stabilizing elements reflect the extent of external pressure on the specialized pilary canal during sebum discharge. Originally simple hair follicles evolved highly adapted pilosebaceous complexes that possibly produce scent themselves or at least a carrier substance for scent secreted by the many apocrine glands on the snout.     

Marked variations in patterns of cellulase activity against crystalline- vs. carboxymethyl-cellulose in the digestive systems of diverse, wood-feeding termites

Abstract.  Throughout the history of studies on cellulose digestion in termites, carboxymethyl-cellulose has been preferably used as a substrate for measuring cellulase activity in termites due to its high solubility. However, carboxymethyl-cellulose degradation is not directly related to digestibility of naturally occurring cellulose because many noncellulolytic organisms can also hydrolyse carboxymethyl-cellulose. To address this issue, a comparative study of microcrystalline cellulose digestion is performed in diverse xylophagous termites, using gut homogenates. For those termites harbouring gut flagellates , the majority of crystalline cellulose appears to be digested in the hindgut, both in the supernatant and the pellet. For Nasutitermes takasagoensis , a termite free of gut flagellates, crystalline cellulose is degraded primarily in the midgut supernatant, and partially in the pellet of the hindgut. The fungus-growing termite Odontotermes formosanus , which also does not possess intestinal flagellates, shows only a trace of crystalline cellulose hydrolysis throughout the gut. Comparison of levels of activity against crystalline cellulose with previously reported levels of activity against carboxymethyl-cellulose in the gut of each termite reveals significant differences between these activities. The results suggest that the hindgut flagellates produce commonly cellobiohydrolases in addition to endo-β-1,4-glucanases, which presumably act synergistically to digest cellulose. Preliminary evidence for the involvement of bacteria in the cellulose digestion of N. takasagoensis is also found.     

Über Arthropoden-Abwehrstoffe. LVIII Zur Feinstruktur der Pygidialdrüsen des Gelbrandkäfers (Dytiscus marginalis L., Dytiscidae,Coleoptera)

Zusammenfassung Die Pygidialdrüsen von Dytiscus sezernieren eine Emulsion, die p-Hydroxybenzaldehyd, p-Hydroxybenzoesäuremethylester, Benzoesäure und ein Glycoproteid enthält. Ihre Loben sind aus zwei verschiedenen Arten von Drüsenzellen aufgebaut, den Kanalzellen, die die Einzelkanäle und den Sammelkanal umgeben, und den Tracheoblasten. Die chitinigen Einzelkanäle enden mit einer traubigen oder blasigen Anschwellung, die aus einer massiven inneren und einer schwammigen äußeren Wandschicht besteht, in einer Höhle der sekretorischen Zellen. Die Zahl der Blasen - und Trauben-Zellen ist etwa gleich. Die zentrale Höhle ist von Mikrovilli umgeben, die durch Mikrofibrillen in hexagonaler Packung ausgesteift werden. Wie die Untersuchung nach Gefrierätzung zeigt, ist die konvexe Seite der Mikrovilli-Membran dichter mit Partikeln besetzt als die konkave Seite. Beide Zelltypen haben ein ausgedehntes tubuläres glattes endoplasmatisches Reticulum; freie Ribosomen und granuläre Zisternen sind selten. In den Traubenzellen ist der Golgi-Apparat besser als in den Blasenzellen entwickelt. Die zentrale Höhle der Traubenzellen enthält eine fein-flockige Substanz, die der Blasenzellen ein dichtes osmiophiles Material. Die Sekretionsmechanismen, die Beteiligung verschiedener Typen von Vesikeln und anderer Zellorganellen an der Sekretion und die Unterschiede zwischen den beiden Drüsenzelltypen werden diskutiert. Es wird angenommen, daß die Hauptkomponenten des Sekretes eccrin ausgeschieden werden.

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On defense substances of arthropods LVIII the fine structure of the pygidial glands of the water beetle, Dytiscus marginalis L.

Summary The pygidial glands of Dytiscus secrete an emulsion containing p-hydroxybenzaldehyde, p-hydroxybenzoate, benzoic acid, and a glycoproteid (Schildknecht, 1970). Their lobes are composed of two different types of secretory cells, channel cells (which surround a channel, draining the secretory cell, as well as the collecting channel), and of tracheoblasts. The chitinous draining channel ends in the form of either a racemous or a bulbous swelling consisting of a massive inner and a spongy outer wall layer in a cavity of the secretory cell. The number of racemous and bulbous cells is nearly the same. The central cavity is surrounded by microvilli which are stiffened by microfibrils in a hexagonal packing. After freeze etching the convex surface of the microvilli reveals more membrane particles than their concave surface. Both cell types have an extended smooth surfaced tubular endoplasmic reticulum; the amount of free ribosomes and of granular cisternae is low. In the racemous cells the Golgi apparatus is better developed than in the bulbous cells. In the racemous cells the central cavity contains a fine-fluffy substance, in the bulbous cells a dense osmiophilic material. The mode of secretion, the participation of various kinds of vesicles and other cell organelles in this process, and the differences between the two types of secretory cells are discussed. It is assumed that the main components of the secretion are released in the eccrine way.

Wir danken der Deutschen Forschungsgemeinschaft für Sachbeihilfen.     

Effects of metopirone on the structure of endocrine glands in the male lizard,Cnemidophorus l. lemniscatus (L.)

Summary Adrenals, pituitary glands, thyroids, testes and kidneys of metopirone-treated and control male lizards were studied by light microscopy. Pituitary-interrenal axis: A great hypertrophy and hyperplasia of the interrenal cells and the pituitary corticotrophs were found in the experimental group. Pituitary-thyroid axis: Metopirone-treated animals showed a moderate hypertrophy and degranulation of pituitary thyrotrophs, and signs of uneven hyperactivity of the thyroid. Pituitary-testicular axis: By effect of metopirone, a marked regression of pituitary interstitiotrophs and a virtual disappearance of the testicular interstitial gland took place. The second portion of the kidney sexual segments appeared degranulated as in castrated animals. The pituitary folliculotrophs and the seminiferous epithelium of the testis did not show alterations.