A Rostral Sensory Mechanism in Oikopleura dioica (Appendicularia)

The ventral sense organ, below the mouth, is composed of 30 primary sensory cells situated in a row perpendicular to the long axis of the animal. Each cell carries one long and slender, modified cilium which arises from an apical pocket in the cell. The sensory cells project 15 axons at each side of the pharynx to the brain, which is rostrally paired and terminates in bulb-like swellings. Each of these bulbs contains four cell bodies, which, according to their fine structure, as well as the synaptic connections with receptor and brain fibers, belong to three different types. It is suggested that the sense organ is a chemosensor and that its remarkable similarity to the vertebrate mechanisms for olfaction makes it probable that the appendicularian Oikopleura dioica possesses a ‘protochordate’ counterpart to the craniate olfactory apparatus.     

The Oral Papilla of the Lancelet Larva (Branchiostoma lanceolatum) (Cephalochordata)

The oral papilla is a prominent larval organ in the lancelet, which develops early during ontogenesis and disappears completely at metamorphosis. Electron microscopic studies indicated that the prevailing theories of its function are unlikely. Its cells lack the cytological characteristics of sensory or mucus producing cells, and the organ is not equipped with a tuft of flagella. It was not possible to reveal the function of the papilla, but its cells seem to be involved in a pronounced substance transport through the basal cell membrane as well as in the cytoplasm. Apical specializations indicate exo- or endocytotic activity and vesicles imply some exchange also between papilla cells and the sea water.     

Tissue distribution, inhibition and activation of gelatinolytic activities in Atlantic cod (Gadus morhua)

Gelatinolytic activities in fish tissues with properties like matrix metalloproteinases (MMPs) have been paid little attention. However, they have been proposed to participate in post mortem degradation during storage and the disintegration of pericellular connective tissue during spawning. In this paper the distribution of gelatinolytic activities in liver, heart, muscle, gill, and male and female gonad of Atlantic cod (Gadus morhua) was studied by using gelatin SDS-PAGE, proteinase inhibitors, gelatin and lentil lectin Sepharose affinity chromatography. The amount of gelatin degrading enzymes varied from tissue to tissue. Most of the gelatin binding enzymes were found to be matrix metalloproteinases by adding galardin, a broad range MMP inhibitor, to the incubation buffer. A 72 kDa form of cod gelatin degrading enzyme had properties similar to human proMMP-2, as it could be activated by p-aminophenylmercuric acetate and trypsin. Like the human MMP-2 it did not bind to lentil lectin. An 83 kDa cod gelatin degrading enzyme had properties similar to the 92 kDa progelatinase B (proMMP-9). These properties were also similar to that of the 72 kDa form, except that the 83 kDa cod gelatinase was bound to lentil lectin, showing that it is a glycoprotein like MMP-9.     

Effects of Hydroxyurea On the Mitotic Activity and the G2 Phase In Hairless Mouse Epidermis

Hairless mice were given 5 mg hydroxyurea (HU) intraperitoneally (i.p.) followed by 0.15 mg Colcemid® at various times after HU. the animals were killed at 2 and 4 hr after Colcemid, the epidermal mitotic counts in dorsal skin were determined and the mitotic rates calculated. These were compared with the normal mitotic rates, and the ratios between the results from HU-treated and -untreated animals were calculated. Hydroxyurea caused a considerable reduction in the mitotic rate with a trough at 6 hr, followed by a wave of increased mitotic rate with a peak at 14 hr, followed by a secondary drop at 20 hr, and then a return to normal. Another group of mice were given HU only, and the fraction of epidermal cells in G₂ was measured by flow cytometry. From these animals, without previous injection of Colcemid, we also determined the mitotic counts and calculated the mitotic durations. Cells piled up in G₂ for the first 6 hr after HU injection, then the G₂ compartment was emptied. the results are discussed in relation to previous results from this department showing the effect of the same dose of HU on DNA synthesis in the same mouse strain. It is concluded that HU not only blocks or retards DNA synthesis in epidermal cells, but also affects the movement of cells through G₂ and M. the cell kinetic effects of HU thus seem to be very complex.     

Characterization of production and enzyme properties of an endo-β-1,4-glucanase fromBacillus subtilis CK-2 isolated from compost soil

Bacillus subtilis CK-2, isolated from garden organic waste compost, was found to have high hydrolytic activity against carboxymethylcellulose (CMC) due to the secretion of an endo--1,4-glucanase. Enzyme production was related to the sporulation process, and was regulated by the concentration of readily metabolizable carbohydrate in growth medium. Enzyme production did not require CMC or other cellulose containing materials. The endo--1,4-glucanase activity was optimal at pH 5.6–5.8 and at 65 MoC, and achieved thermal stability up to 55 MoC. The activity was inhibited by Hg²⁺. The purified enzyme gave a single band corresponding to a MW of 35.5 kDa on SDS-PAGE, while the Sephadex G-75 chromatography revealed a molecular weight of the active enzyme around 70 kDa, indicating a dimeric form of the active enzyme. The enzyme activity was irreversibly inhibited by SDS. Native PAGE and IEF revealed three different isoelectric forms of the enzyme, all with an identical N-terminal amino-acid sequence.Abbreviations CMC carboxymethylcellulose - DNS dinitrosalicylic - SDS sodium dodecyl sulfate     

Fine structure of the brain and brain nerves ofOikopleura dioica (Urochordata,Appendicularia)

Summary Each second brain nerve consists of only one single fibre terminating at two different types of touch receptors in the oral region. The two nerves are the dendrites of two perikarya in the forebrain and are the master neurons for ciliary reversal in the stigmata, which is a two-neuron reflex. By axoaxonal synapses they control one motor neuron in the midbrain, i.e. the command neuron for ciliary reversal in both rings. This cell sends one axon branch in each third nerve to the cilia cells. In the left nerve this fibre is closely associated with a coarsely granulated accessory fibre, which apparently regulates the ciliary beat. The third nerves also contain one fibre each from another motor neuron in the hindbrain. These fibres make synaptic contacts at some specialized epidermal cells in the lateral trunk behind the ciliary rings. A few previously unknown nerves in the dorsal forebrain innervate epidermal cells. It is likely that the complicated epidermal motor innervation regulates the secretory activity of the oikoplasts or of the epidermal cells in constructing a new house, including the necessary complicated filters and food trapping mechanisms.     

Cr(III)-Induced polymerization of human albumin

Chromium (III)-albumin complexes that have allergenic properties and induce contact dermatitis are aggregated in solution. This is shown by small-angle X-ray scattering of Cr(III)-albumin solutions at 21°C in a Tris-HCl buffer of pH=7.40. At high concentrations of Cr(III), albumin appears to aggregate to an average molecular weight of an octamer, with an average gyration radius of 116 Å. At low concentration of Cr(III), dimers and also some higher polymers form with an average molecular weight of 135,000 and an average radius of gyration of 57 Å. Analysis of the shapes of the Cr(III)-albumin complexes indicate that they are more elongated than albumin, suggesting that, in the presence of Cr(III), the albumin molecules associate sideways with an expansion mainly of the largest axis.     

Studies on fermentation processes in silage

Zusammenfassung Kohlenhydrat-Zusatzmittel dienen bei der natürlichen Gärfutterbereitung einerseits als Nährstoffe für die Mikroorganismen, andererseits beeinflussen sie die Feuchtigkeit des Gärfutters durch ihr Absorptionvermögen.Bei der Milchsäuregärung kann Zucker vollständig ausgenützt werden, Stärke und Cellulose dagenen nicht, oder nur unbedeutend. Zusatz von Gerstenmalz hat wegen seines höheren Zuckerinhaltes und wegen seiner diastasewirkung einen wesentlich besseren Effekt als Gerstegrütze.Malz, Grütze und Cellulose besitzen ein hohes Absorptionsvermögen und können dadurcheine günstige Wirkung bei der Gärfutterbereitung ausüben.

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These studies are still in progress. We are indebted to the Swedish Foundation: Fonden för främjande av forskinings- och försöksverksamheten på jordbrukets område, for generous financial support.     

Models of ontogenetic allometry in cladoceran morphology studies

Ontogenetic variation of morphological traits in cladocerans is usually analysed by a simple allometry function. We found that common cyclomorphic and inducible traits in Bosmina and Daphnia sometimes deviate from simple allometry, however. Consequently, simple allometric analysis may at times be inadequate since important aspects of the ontogenetic development may not be revealed. We suggest that other allometric models should be used more extensively in ontogenetic studies of cladocerans morphology. Especially, complex allometric functions may help analyse the effects of size-selective predation on morphological defence traits when predators prefer prey of intermediate size. Guest editor: Piet Spaak Cladocera: Proceedings of the 7th International Symposium on Cladocera