Gravity as an orientation guide during web-construction in the orb spiderAraneus diadematus (Araneae,Araneidae)

summary The effect of gravity on the web building behaviour of the common garden spiderAraneus diadematus was studied in three ways: (i) frames with partially completed vertical webs were swivelled into a horizontal position, (ii) by rotating frames with spiders in a vertical klinostat (1 rpm), and (iii) by vertically rotating a partially completed web treadmill fashion keeping the building animal in a certain position in space.(i) In the horizontal, radial wheels are not constructed, however, a more or less irregular spiral is added to a completed wheel; (ii) in the klinostat the radial wheel lacks the up/down distinction of normal webs, and the spiral is irregular; (iii) in the treadmill the spiral course is abnormal, and the degree of deviation depends on the position of the animal. If the body axis is parallel to gravity the spiral path deviates to both sides of the norm. In ag perpendicular body position the path deviates predominantly to one side, spiralling sharply inwards towards the hub. The observations suggest that the cyclic changes in the body position of spiral-buildingAraneus are an important component of the animal's orientation during this phase of web-construction.     

Ecological effects of lime treatment of acidified lakes and rivers in Sweden

Effects on the aquatic biota of lime (CaCO₃) application in acidified lakes and streams were studied in a number of waters. After treatment, lime-sensitive species of mosses (Sphagnum spp.) decreased, but species such as Potamogeton natans and Myriophyllum alterniflorum seemed to be favoured. A few years after liming species composition and diversity of phytoplankton, zooplankton and benthic insect larvae were almost identical to that found in oligotrophic and non-acid lakes. Molluscs and benthic crustaceans may have difficulties recolonizing. Reproduction of remaining species of fish was successful as soon as pH increased. High survival of larvae and fry can result in some extremely rich year classes with slow individual growth. In most cases restocking of depleted fish stocks was successful.     

Processing of yeast mitochondrial RNA: involvement of intramolecular hybrids in splicing of cob intron 4 RNA by mutation and reversion

Revertants have been obtained from six mutants of the box9 cluster, which are supposed to be defective in RNA splicing as a result of alterations in a splice signal sequence. This sequence is in the 5' part of intron 4 of the cob gene, 330 to 340 bp downstream from the 5' splice site. Sequencing reveals that reversion to splicing competence is achieved by restoration of the wild-type box9 sequence; by creation of novel box9 sequences; and by introduction of a second site or suppressor mutation (sup-) compensating for the effect of the primary box9- mutation. The sup- mutation alters a sequence in intron 4,293 bp upstream from the box9- primary mutation. The box9 sequence and this upstream sequence can base pair to form an intramolecular hybrid in intron RNA in which box9- and sup- are compensatory base pair exchanges (G----A and C----U, respectively). Thus intramolecular hybrid structures of intron RNA are essential for RNA splicing.     

Epitopes of peptide 43-88 of guinea pig myelin basic protein: localization with monoclonal antibodies

Two monoclonal antibodies, one raised by immunization with mouse myelin basic protein (MBP) and the second raised by immunization with peptide 68-88 of guinea pig MBP, were compared with respect to specificity. The former antibody (15.32) cross-reacted completely with rat, guinea pig, human, and bovine MBP. It also reacted with peptide 43-88 from each MBP. The latter antibody (22.17) was nonreactive with MBP, but cross-reacted with peptide 43-88 from rat, human, guinea pig, and bovine MBP. When tested with small peptides derived from peptide 43-88, antibody 22.17 reacted with an epitope in the C-terminal region. Antibody 15.32 reacted with an epitope in the N-terminal half of the peptide. The data show that 22.17 reacted with a unique epitope associated only with free peptide, whereas 15.32 recognized an epitope common to both peptide 43-88 and MBP.     

Structural alterations in fibronectin correlated with morphological changes in smooth muscle cells

Nontransformed cultures of vascular smooth muscle cells proliferate until they form a confluent sheet of cells. Subsequently, the cells become reorganized to form multicellular nodules that are loosely attached to the substrate. The formation of nodules is facilitated by the addition of medium conditioned by nodular cultures. Nodulation is inhibited by the addition of fibronectin. Fibronectins derived from monolayer culture conditioned medium or from plasma are maximally effective while fibronectin isolated from nodular cell conditioned medium is inactive. Analysis by NaDodSO4-polyacrylamide gel electrophoresis reveals that the nodular cell fibronectin has a molecular weight that is about 20-30 kd less than that of monolayer cell fibronectin. Further, nodular cell conditioned medium contains an activity that can convert both plasma fibronectin and monolayer cell fibronectin to the lower molecular weight correlated with the loss of biological activity.     

Transduction and Plasmid Deoxyribonucleic Acid Analysis in a Multiply Antibiotic-Resistant Strain of Staphylococcus epidermidis

A genetic analysis of a multiply antibiotic-resistant strain of Staphylococcus epidermidis was performed. Experiments designed to show reversion of organisms to antibiotic susceptibility, as well as studies of the influence of ultraviolet irradiation of phage on the transduction frequencies of the resistance markers, indicated that determinants of chloramphenicol (cml), tetracycline (tet), and neomycin (neo) resistance are present on separate plasmids, but the streptomycin marker is chromosomal. In 2 to 6% of tetracycline-resistant transductants, co-transduction of cml was also observed. By using CsCl-dye density gradients followed by neutral sucrose gradients, the plasmids carrying cml, tet, and neo could be isolated and their molecular weights could be determined. The tetracycline plasmid is shown to be incompatible with one of the cryptic plasmids of a recipient strain.     

Vegetationsschwankungen in einem Melico-Fagetum

Summary Following the dry year of 1959 considerable damage was done to a number of beeches in a Melico-Fagetum wood in the Drübel area near Brilon (Sauerland). The effects of this damage coupled with the subsequent removal of the affected trees were studied over an 8-year period with a permanent quadrat and revealed the following vegetation cycle: pure or almost pure beechwood — dying or cutting down of single beeches and with it an opening up of the tree canopy — an increase in the abundance and flowering of wild strawberry (Fragaria vesca) and other lightloving species — an increase in the density and growth of sycamore (Acer) and ash (Fraxinus) saplings — a decrease in the amount of wild strawberry and indeed of other light-loving species too because of the increasing shade — development of beech seedlings into young trees under the shadow of the other shrubs and trees — probably a sycamoreash-beech stand — probably a pure or almost pure becchwood again.

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Zusammenfassung Das Dürrejahr 1959 verursachte in einem Melico-Fagetum des Drübels bei Brilon erhebliche Schäden an mehreren Buchen. Diese Schäden und die folgende Abholzung der erkrankten Bäume lösten, wie 8jährige Untersuchungen in einem Dauerquadrat ergaben, folgenden Vegetationsyklus aus: Reiner oder fast reiner Buchen-Hochwald — Absterben bzw. Schlag einzelner Buchen und damit Auflockerung der Baumschicht — Vermehrung bzw. Blüte der Walderdbeere und anderer lichtliebender Arten — Verdichtung und schnelles Emporwachsen des Ahorn- und Eschen-Jungwuchses — Abnahme der Erdbeere, wohl auch anderer licht-liebender Arten infolge wieder zunehmender Beschattung — Heranwachsen von Buchen-Keimlingen zu Jungpflanzen, und zwar im Schatten der anderen Sträucher und Bäume — voraussichtlich Ahorn-Eschen-Buchen-Bestand — voraussichtlich wieder reiner oder fast reiner Buchen-Hochwald.