Behavior of Colonial Orb-weaving Spiders during a Solar Eclipse

The behavior of colonial orb-weaving spiders (Metepeira incrassata) in tropical Veracruz, Mexico was studied during the total solar eclipse on July 11, 1991. Spiders behaved in a manner typical of daily activity until totality, when many began taking down webs. After solar reappearance, most spiders that had begun taking down webs rebuilt them. There was no significant difference in the overall activity patterns of spiders during totality across a range of colony sizes. Experimental illumination of part of a colony during totality altered web takedown behavior. While spiders in the darkness of totality began to take down webs, those spiders which were artificially illuminated did not. These observations suggest that the primary environmental cue responsible for the daily rhythm of web building behavior in this species is light level.     

Genetic variation in North Africa and Eurasia: Neolithic demic diffusion vs. paleolithic colonisation

The hypothesis that both genetic and linguistic similarities among Eurasian and North African populations are due to demic diffusion of neolithic farmers is tested against a wide database of allele frequencies. Demic diffusion of farming and languages from the Near East should have determined clines in areas defined by linguistic criteria; the alternative hypothesis of cultural transmission does not predict clines. Spatial autocorrelation analysis shows significant gradients in three of the four linguistic families supposedly affected by neolithic demic diffusion; the Afroasiatic family is the exception. Many such gradients are not observed when populations are jointly analyzed, regardless of linguistic classification. This is incompatible with the hypothesis that major cultural transformations in Eurasia (diffusion of related languages and spread of agriculture) took place without major demographic changes. The model of demic diffusion seems therefore to provide a mechanism explaining coevolution of linguistic and biological traits in much of the Old World. Archaeological, linguistic, and genetic evidence agree in suggesting a multidirectional process of gene flow from the Near East in the neolithic. However, the possibility should be envisaged that some allele frequency patterns can predate the neolithic and depend on the initial spread of Homo sapiens sapiens from Africa into Eurasia. © 1994 Wiley-Liss, Inc.     

Fixation requirements for the immunohistochemical reactivity of PCNA antibody PC10 on cryostat sections

Summary In contrast to that in paraffin-embedded tissue, the reactivity of monoclonal PCNA antibody PC10 on cryostat sections requires a special fixation procedure as the target epitope is seemingly not accessible to its antibody. A panel of 18 fixation protocols was investigated. Chilled methanol or acetone, or PLP (paraformaldehyde-lysine-periodate) was found to be unsuitable for skin preparations. A two-step fixation protocol was developed for normal skin and basal cell carcinomas. They were fixed first in 3.4% buffered formaldehyde, followed by fixation in 2:1 v/v ethanol-acetic acid. Following this fixation regime, cryostat sections displayed the same PCNA/PC10 labelling pattern as paraffin sections of formalin-fixed tissue.     

Paleolirnnological records of carotenoids and carbonaceous particles in sediments of some lakes in Southern Alps

Stratigraphic analyses of organic carbon, organic nitrogen and algal and bacterial carotenoids in short cores of profundal sediments of four alpine lakes (Tovel, Leit, Paione superiore and Tom) were used to reconstruct their trophic history. In addition, depth distribution of carbonaceous particle concentrations provided information on lake contamination from atmospheric deposition. In three lakes (Tovel, Leit and Tom), sedimentary carotenoids unique to sulfur photosynthetic bacteria (okenone and isorenieratene) provide evidence of changes in the oxygen, light and sulfide conditions in the water column. All the lakes are oligotrophic or moderately productive, and the algal community is dominated by Chlorophyta, Pyrrhophyta and Cryptophyta. Cyanobacteria are rather poorly represented. The steep increase of carbonaceous particles in the uppermost sediment layers of all the lakes suggests that lake contamination by atmospheric transport of pollutants began in the 1940s to 1950s. These data, coupled with those from a parallel study on Chrysophycean scale-inferred pH, indicate recent acidification in those which are poorly buffered (Paione superiore and Leit).     

Ein Vogelruf, dessen Form sich im Jahresablauf ?ndert: der Verbeugungstriller bei der Brandente (Tadorna tadorna)

Zusammenfassung Der Verbeugungstriller männlicher Brandenten, eine epigame Lautäußerung, weist sowohl in syntaktischen wie auch phonetischen Parametern zyklische jahreszeitliche Veränderungen auf. Die Gesamtdauer der Lautäußerung vergrößert sich allmählich im Laufe des Frühjahrs. Dafür sind eine Verlängerung des tonalen Eingangselements und eine Vermehrung der Elemente der abschließenden Phrase verantwortlich. Dagegen verkürzt sich das 2. Element gleichzeitig. In allen untersuchten Elementen erhöht sich die Tonhöhe parallel zur Verlängerung des Rufes. Diese Veränderungen des Ausdrucksverhaltens geben vermutlich Änderungen innerer Zustandsgrößen wieder.

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Seasonally changing bird call: the trill call of male Shelducks (Tadorna tadorna)

Both syntactic and phonetic features of the trill call accompanying the whistle-shake in adult male Shelducks are subject to cyclic annual changes. In the course of spring, the duration of the whole call increases gradually. This is caused by a prolongation of the first call element and insertion of additive elements in the final phrase. In contrast the second element is shortened by about 10 ms. At the same time, the pitch of all measured elements is raised. These findings are discussed in the framework of hormonal regulation and communicative function.

     

Bicyclic carbo- and heterocycles from an allylidene complex and cyclic 1,3-dienes by tandem cyclopropanation/cope rearrangement

The allylidene complex (CO)₅W=CH---C(Ph)=C(Ph)H (4) reacts with cyclopentadiene by stereospecific transfer of the carbene ligand to one of the two double bonds of cyclopentadiene to give a cis-divinylcyclopropane complex 5. The divinylcyclopropane ligand coordinates to the metal via the unsubstituted double bond. Addition of bromide to solutions of 5 gives rise to the formation of [(CO)₅WBr]⁻ and a bicyclo[3.2.1]octadiene (6), the Cope rearrangement product of the free divinylcyclopropane. Thermolysis of 5 affords 6 and its (CO)₅W complex. The reaction of 4 with furan (8a), 2-methylfuran (8b) and 3-methylfuran (8c) affords the (CO)₅W(bicyclo[3.2.1]oxahepta- diene) complexes (9a–c), The formation of 9a–c which is chemo-, regio- and stereospecific is explained by a tandem cyclopropanation/Cope rearrangement sequence. The bicyclic ligands 10a–c are liberated from the metal either by thermolysis of solutions of 9a–c or by addition of bromide.     

Subunits of forming pollen exine and Ubisch bodies as seen in freeze substitutedLedebouria socialis Roth (Hyacinthaceae)

Summary High-pressure freezing/freeze substitution/TEM was employed to investigate anthers of the monocotyledonous angiospermLedebouria socialis Roth (Hyacinthaceae) during early tetrad stage. The initials of the outer sporopollenous pollen wall stratum (=sexine) and of the homologous tapetal products (=Ubisch bodies) are composed of highly regular subunits: clustered globules with a constant diameter of approximately 28 nm. The clusters develop within diffuse accumulations of electron-dense material. This process, interpreted as sporopollenin polymerization, does not necessarily depend on the presence of membrane-bound enzymes. Immunogold labeling with JIM 5 and JIM 7 antibodies revealed that the primexine as well as the dissolving tapetal cell walls, the sites of sexine and Ubisch body formation, respectively, contain un-esterified and methyl-esterified pectins.Abbreviations E-PTA ethanolic phosphotungstic acid - PA periodic acid - UA/Pb uranyl acetate/lead     

Binding of epidermal growth factor and transforming growth factor-alpha in mammalian preimplantation embryos

Preimplantation embryos of the pig (Days 11 to 15), cow (Days 14 to 16), sheep (Day 14) and pony (Day 16) bind epidermal growth factor (EGF) specifically. Binding was not detected in embryos of the rabbit at Day 5 or 6 or the hamster at Day 3. Transforming growth factor-alpha displaced [(125)I] EGF in pig, cow and pony embryos almost as much as unlabeled EGF. The binding affinities of EGF ranged from 12 to 233 pM in pig and cow embryos. The range of species and binding features indicate that the EGF family may play a significant role in mammalian preimplantation development.     

Effect of oxygen concentration in the incubator's gas phase on the development of cultured preimplantation rabbit embryos

Development of rabbit preimplantation embryos cultured under 20, 5 or 1% oxygen was studied. Three-day-old morulae were cultured in a protein-free medium (BSM II supplemented with 5 mg PVP/ml medium) for 24 and 48 h. Embryonic development was evaluated by gross morphology and by incorporation of tritiated thymidine as an indicator of cell proliferation. The lower oxygen concentrations yielded significantly better embryo development at 24 and at 48 h than the 20% concentration. There was no significant difference in development between 5% and 1% oxygen. Addition of the radical scavanger superoxiddismutase (SOD), either alone or in combination with catalase or reduced glutathione, did not improve embryo development even in the 20% oxygen group. Our data suggest the need to reduce in vitro oxygen levels from 20% to more physiological concentrations.     

Physiologic target of the Air-1 trans-activator revealed by stable transfection assay

RJ 2.2.5 is a human B cell mutant, derived from Raji cells, which has lost expression of major histocompatibility complex (MHC) class II genes because of a defect in the AIR1 locus function. The MHC class II-positive phenotype can be restored by introducing an active AIR1 locus or its mouse equivalent, Air-1. An example of the latter is the H4 cell hybrid, derived by somatic cell fusion between RJ 2.2.5 and mouse class II-positive spleen cells. H4 contains a single mouse chromosome, autosome 16, in which the Air-1 locus maps, and an entire RJ 2.2.5-derived genome. In the present study we show that the physiologic target of the Air-1 locus product is contained within a limited HLA-DRA promoter sequence of 300 base pairs, encompassing the crucial Y, X, and W cis-acting elements. A plasmid construct, pDRA300neo, containing the HLA-DRA promoter sequence which drives the expression of the neomycin resistance gene, has been stably integrated in the genome of the H4 hybrid. Transfectants selected in the presence of G418 retain mouse chromosome 16 and express the DR genes. On the other hand, transfectants grown in a non-selective medium segregate mouse chromosome 16; this is accompanied by a loss of DRA gene expression and G418 resistance, although pDRA300neo is still integrated in the genome. These results offer scope for using this experimental model to clone the Air-1 gene in a straightforward way. Correspondence to: R. S. Accolla.