Human impact on vegetation at the Alpine tree-line ecotone during the last millennium: lessons from high temporal and palynological resolution

Three mires and a small lake in the Swiss and Austrian Alps were studied palynologically at high resolution, covering the last 1,000, 400, 50 and 1,200 years, respectively. Methodological lessons include: (1) Sub-decadal resolution in upper, little-decomposed peat layers reveals recurrent marked fluctuations in both percentages and influx of regional tree-pollen types, reflecting variations in pollen production rather than in plant-population sizes. (2) Intermittent, single-spectrum pollen maxima in samples of sub-decadal resolution indicate pollen transport in clumps. This type of pollen transport may remain unrecognized in sections with lower sampling resolution, which may then lead to inappropriate interpretation in terms of plant-population sizes. (3) The detection of short-lived phases of human impact in decomposed peat requires sampling intervals as close as 0.2 cm. (4) PAR (pollen influx) may reflect vegetation dynamics more faithfully than percentages. Reliable PAR, however, is difficult to achieve in Alpine mires due to past human impact on peat growth, even when complex depth–age modelling techniques are used. Critical comparison of PAR with percentages is therefore essential. (5) Careful consideration of spatial scales in pollen signals (local–regional and subdivisions) is essential for a realistic palaeo-ecological interpretation. Results in terms of past human impact on vegetation are summarized as follows: (1) Trends in pollen types reflecting regional human action are in general agreement with earlier findings for the western Swiss Alps, allowing for regional differences. (2) All mires in the Alps investigated here and in an earlier study experienced human impact during the last millennium. The studied small lake, lying in sub-alpine pasture, records forest dynamics at a lower elevation since a.d. 800.     

Plant regeneration from protoplasts of the monocotyledonous Haworthia magnifica v. Poelln.

Calli were initiated from flower buds, gynoecia and inflorescence segments of Haworthia magnifica v. Poelln. and subcultured on solid medium. Two liquid culture steps were necessary to prepare the calli for the isolation of protoplasts capable of sustained cell divisions. Plants were regenerated from protoplast-derived calli. The influence of both the osmolality of the culture media and exudates on the viability of protoplasts and protoplast-derived cell colonies is briefly discussed.     

Indole-3-ethanol oxidase in Phycomyces blakesleeanus. Is indole-3-ethanol a “storage pool” for IAA?

Indole-3-ethanol (IEt) was extracted from Phycomyces blakesleeanus Bgff. and purified by TLC and HPLC. Identification was performed by mass spectrum. The HPLC-purified compound showed an UV-spectrum typical for indoles, with absorption maxima at 220 and 281 nm. The IEt content varied between 1.5 nmol (g fresh weight)⁻¹ and 5.6 nmol (g fresh weight)⁻¹. The observed variations were strongly correlated with certain developmental stages of the fungus. Furthermore, the decrease of IEt between 60 and 84 h of fungal development coincides with a high IEt oxidase activity. The product of the enzyme reaction was indole-3-acetaldehyde, which was identified by co-chromatography with an authentic standard in several TLC and HPLC systems and by chemical conversion to indole-3-acetaldoxime.     

Ontogeny of hormone-secreting cells of the rat pituitary gland: An immunocytochemical study on dissociated cells

Summary An immunocytochemical study was undertaken in foetal, prepubertal and mature rats to determine the time of differentiation of various types of adenohypophyseal cells during development. Freshly dissociated pituitary cells from foetal (18–21 days postconception), neonatal (from birth up to 30 days) and adult rats (more than 8 weeks) were characterized using immunocytochemical methods. All types of hormone-producing cells were present at day 18 postconception, although only 20% of the cells were immunolabelled. Adrenocorticotropin (ACTH)-secreting cells accounted for the highest number of hormone-positive cells. Growth hormone-secreting cells increased remarkably from day 18 postconception onwards. Prolactin-secreting cells were not seen in the foetal adenohypophysis and did not start to increase until 10 days after birth, whereas by that time the number of ACTH, thyrotropin, follicle-stimulating and luteinizing hormone-secreting cells had stopped increasing. By day 30 after birth, 80–95% of the cells were immunoreactive.     

Methode zum Nachweis der Dauersporen des Kohlhernieerregers Plasmodiophora brassicae in gärtnerischen Kultursubstraten

Populations of pathogenic Pseudomonas syringae pv. syringae were monitored on apparently healthy leaves, blossoms, and fruit from two apple orchards with known histories of blister bark and a pear orchard with a known history of blossom blast. Populations on blossoms and fruits were higher on pears than on apples. Yellow-pigmented, non-pathogenic bacteria might have suppressed or masked the presence of P. syringae pv. syringae on apple trees. Populations of P. syringae pv. syringae on apple and pear leaves fluctuated sharply but higher levels generally occurred during the 1984/85 growing season than during the drier 1983/84 season. This investigation indicates that the resident phase of P. syringae pv. syringae is probably a major source of inoculum for apple blister bark and pear blossom blast in South Africa.     

Comparison of the enthalpy state of vesicles of different size by their interaction with α-lactalbumin

The characteristics of small unilamellar, large unilamellar and large multilamellar vesicles of dimyristoylphosphatidylcholine and their interaction with α-lactalbumin are compared at pH 4. (1) By differential scanning calorimetry and from steady-state fluorescence anisotropy data of the lipophilic probe 1,6-diphenyl-1,3,5-hexatriene it is shown that the transition characteristics of the phospholipids in the large unilamellar vesicles resemble more those of the multilamellar vesicles than of the small unilamellar vesicles. (2) The size and composition of the lipid-protein complex formed with α-lactalbumin around the transition temperature of the lipid are independent of the vesicle type used. Fluorescence anisotropy data indicate that in this complex the motions of the lipid molecules are strongly restricted in the presence of α-lactalbumin. (3) The previous data and a comparison of the enthalpy changes, $\text{ΔH}$, of the interaction of the three vesicle types with α-lactalbumin allow us to derive that the enthalpy state of the small unilamellar vesicles just below 24°C is about 24 kJ/mol lipid higher than the enthalpy state of both large vesicle types at the same temperature. The abrupt transition from endothermic to exothermic $\text{ΔH}$ values around 24°C for large vesicles approximates the transition enthalpy of the pure phospholipid     

Localisation,structure et genèse des concrétions minérales dans le mésentéron des Collemboles Tomoceridae (Insecta,Collembola)

Résumé Le mésentéron des Collemboles est riche en inclusions minérales appelées sphérites. L'étude de leur genèse nous montre qu'ils se forment dans les citernes du réticulum endoplasmique. Leur croissance et leur évolution se poursuivent dans les mêmes citernes par apport de matériel divers. Les sphérites sont formés de nucléi opaques aux électrons entourés de couches concentriques alternativement claires et sombres. Les critaux âgés sont souvent associés à des enroulements membranaires. Le rôle physiologique est discuté. Ces concrétions apparaissant dès l'éclosion, peuvent s'éliminer de differentes manières: par extrusion apocrine, par dégénérescence cellulaire et surtout par le renouvellement périodique de l'épithélium intestinal qui se fait à chaque mue. Ces sphérites peuvent représenter une voie d'excrétion par accumulation et semblent jouer le rôle des tubes de Malpighi qui font défaut chez les Collemboles.

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Summary The mesenteron of Collembola is rich in mineral inclusions called spherites. The study of their genesis shows us that they are produced in the cisternae of the endoplasmic reticulum. Their growing and evolution occur in the same cisternae by adduction of diverse material. The spherites are composed of dark nuclei surrounded by alternatively clear and dark concentric strata. The aged cristals are often connected with membraneous windings. The physiological role is discussed. These concretions which appear already after hatching, cancel out by apocrine extrusion, by cellular degeneration and especially by periodic renovation of the intestinal epithelium which occurs at each moulting. These spherites could reflect a process of excretion by accumulation and seem to have the same part as the Malpighian tubules which lack in Collembola.

     

Elektronenmikroskopische Untersuchungen über die Innenversilberung der Sehnenfibrillen

Zusammenfassung 1. Die Behandlung der nativen und formolfixierten Sehnenfibrillen mit einer ammoniakalischen Silberlösung führt immer zu einer Einlagerung von Silberpartikeln in den D-Teilen der Fibrillen.2. Bei den nativen Fibrillen liegen die Silberkörner in einem, zwei oder drei Streifen im D-Teil.3. In den formolfixierten Fibrillen ist das Silber nur in einem Streifen vorhanden.4. Die Behandlung der nativen und formolfixierten Sehnenfibrillen mit anderen Silbersalzen führt zu keiner Versilberung der Fibrillen.5. Die Behandlung der nativen Sehnenfibrillen mit neutraler Kochsalzlösung oder Trypsin und anschließender Versilberung führt zu keiner wesentlichen Änderung des Silberbildes.6. Hyaluronidase-, Citratpuffer- und Perjodateinwirkung auf native Sehnenfibrillen mit anschließender Versilberung führt zu keiner Innenversilberung der D-Teile.7. Acetylierung und Behandlung mit Bisulfit der nativen Fibrillen und anschließender Versilberung mit ammoniakalischer Silberlösung verhindert eine Innenversilberung der D-Teile.8. Die formolfixierten Fibrillen zeigen eine Innenversilberung der D-Teile nach einer Vorbehandlung mit einer neutralen Kochsalzlösung, Citratpuffer, Hyaluronidase, Trypsin und Perjodat. Nur die Acetylierung und die Behandlung mit Bisulfit verhindert eine Innenversilberung.9. Die Innenversilberung der Sehnenfibrillen durch eine ammoniakalische Silberlösung wird weder durch Licht noch durch Chloride oder lichtempfindliche Silbereiweißverbindungen hervorgerufen.10. Die Versilberung in den D-Teilen wird durch Stoffe in den Fibrillen bewirkt, die Silber aus einer ammoniakalischen Silberlösung ausfällen können.11. Die reduzierenden Stoffe haben enge Beziehungen zur citratlöslichen Fraktion und sind perjodat- und hyaluronidaseempfindlich. Formalinfixierung beeinflußt diesen Versilberungsmodus durch ein vermehrtes Auftreten von Querbindungen.12. Die Sonderstellung der ammoniakalischen Silberlösung für die Innenversilberung wird diskutiert. Sie kann stereochemische Gründe haben oder durch die große Beständigkeitskonstante erklärt werden.13. Das Ausfallen von metallischem Silber in den D-Teilen der Sehnenfibrillen kann nicht mit dem photographischen Prozeß in Verbindung gebracht werden. Das gilt auch für die Bindegewebsversilberung nachGömöri.14. Die Silberorte in den D-Teilen lassen sich nur teilweise mit den bekannten Querstreifungsbildern nach Osmium- oder Phosphorwolframsäurefixierung in Beziehung setzen.

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Summary 1. After treatment of native or formalin-fixed tendon fibrils with an ammoniacal silver solution, silver particles are deposited in the D-bands of the fibrils. In the native fibrils these are arranged in one, two or three striae per band, but after formalin fixation they lie in one stria only.2. No external reducing agent is necessary for the production of the particles.3. Pretreatment of native fibrils with neutral salt solution or with trypsin has no effect on subsequent silvering. On the other hand, silvering is abolished by treatment with hyaluronidase, citrate buffer or periodate and also by acetylation and bisulphite.4. Formalin-fixed fibrils show the silvering effect after all these procedures except acetylation or bisulphite treatment.5. It is postulated that silvering of the D-bands is due to reducing substances which can precipitate silver from ammonical solutions and that formalin influences the process by the production of cross linkages.

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Mit 6 Textabbildungen

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Durchgeführt mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Principles and applications of luminescence spectrometry coupled to liquid chromatographic techniques

An overview is presented of the physicochemical basis of luminescence, and its application to the detection of chemicals (drugs, biomedically important compounds, environmentally active substances) in liquid chromatographic systems.