The convergent trajectories of bird communities along ecological successions in european forests

Summary There is much more variation in the composition of bird communities in the earlier open and semi-open seral stages of ecological successions in forested landscapes of Europe than later on in preforested and forested climactic stages. The demonstration of this trend is achieved from the study of four habitat gradients, two in the mediterranean region (Provence and Corsica) and two in central Europe (Burgundy, France and Poland). A multivariate analysis has been used to illustrate the dynamics of communities along these succession. Displays of the results in bivariate space as well as an illustration of the distributional profiles of some of the most characteristic species show that: i) there is a discrimination between the two mediterranean gradients and the two medioeuropean ones and ii) each succession starts with a very distinct set of species and then the four gradients regularly converge in the last climactic stage where there is almost no discrimination between communities. These results are discussed in the light of the history of European biotas during the Pleistocene. The reason why there is more variation in species composition in the earlier seral stages than in the later forested stages are discussed according to current theories on the role of habitat selection on speciation processes.     

T-DNA length variability in mannopine hairy root: more than 50 kilobasepairs of pRi T-DNA can integrate in plant cells

Independent carrot (Daucus carota) hairy root lines were established by inoculation of discs taken from the same carrot with Agrobacterium rhizogenes 8196 and A. tumefaciens C58C1(pRi8196) carrying pRi8196. Several lines were compared with respect to T-DNA length. One of them was found to have integrated sequences covering more than 50 kbp of the Ri plasmid     

Use of novel objects to enhance environments of captive chimpanzees

A small group of chimpanzees was allowed to manipulate different quantities of novel objects in order to enhance their captive conditions. This procedure led to a general increase in the manipulation frequency by the apes. It decreased their inactivity and their self-grooming, and almost eliminated the abnormal behaviors displayed by one individual. The distribution of novel objects did not affect the total frequency of social interactions and did not increase the aggressivity of the animals, even though dominant individuals secured most of the objects when only a small number of them were available. Following their familiarization with the novel objects, the chimpanzees' manipulation frequency decreased whereas self-grooming and abnormal behaviors were increased. Suggestions are made on how to maximize the use of a limited bank of toys to occupy captive chimpanzees.     

Absence of Turner stigmata in a 46,XYp-female

A 46,XY female patient with streak gonads and a large deletion of Yp is described. The deletion included the Y chromosomal genes SRY, ZFY, and RPS4Y. The patient did not display any Turner stigmata, such as webbing of the neck, cardiac or other abnormalities. The findings argue against an important role of RPS4Y in the prevention of Turner stigmata in males and are consistent with a role of SRY in testis differentiation in humans.     

Survey of human and rat microsatellites

Length variations in simple sequence tandem repeats (microsatellite DNA polymorphisms) are finding increasing usage in mammalian genetics. Although every variety of short tandem repeat that has been tested has been shown to exhibit length polymorphisms, little information on the relative abundance of the different repeat motifs has been collected. In this report, summaries of GenBank searches for all possible human and rat microsatellites ranging from mononucleotide to tetranucleotide repeats are presented. In humans, the five most abundant microsatellites with total lengths for the runs of repeats of greater than or equal to 20 nucleotides contained repeat sequences of A, AC, AAAN, AAN, and AG, in order of decreasing abundance, where N is C, G, or T. These five groups comprised about 76% of all microsatellites. Many other human simple sequence repeats were found at low frequency. In the 745 kb of human genomic DNA surveyed, one microsatellite of greater than or equal to 20 nucleotides in length was found, on average, every 6 kb. Only 12% of the human microsatellites had total lengths greater than or equal to 40 nucleotides. Roughly 80% of the A, AAN, and AAAN microsatellites and 50% of the AT microsatellites, but few of the other human microsatellites, were found to be associated with interspersed, repetitive Alu elements. In rats, the five most abundant microsatellites contained AC, AG, A, AAAN, and AAGG sequences, respectively. Rat microsatellites were generally longer than human microsatellites, with 43% of the rat sequences greater than or equal to 40 nucleotides.     

Novel DNA structures resulting from dTam3 excision in tobacco

A Tam3 two-element system has been designed by combining an immobilized Tam3 element with a non-autonomous dTam3 element inserted into the HPT gene. The phenotypic assay employed, restored hygromycin resistance, indicated thattrans-activation of the non-autonomous dTam3 element occurred. Molecular analyses of the excision sites revealed that the ends of the dTam3 element remain in the empty donor sites. The predominant consequence of this type of excision appears to be that excised fragments fail to re-integrate into the tobacco genome. Only one case of dTam3 re-integration could be detected. The ends of this element had been degraded upon integration into the tobacco genome. Either the altered structure of the Tam3 derivatives or tobacco host factors are influencing thetrans-activation of a dTam3 element, resulting in aberrant excision.     

Bioluminescence Assay for Measuring the Number of Bacteria Adhering to the Hydrocarbon Phase in the BATH Test

A thorough validation of the bacterial adherence to hydrocarbons (BATH) test was performed by means of a bioluminescence assay. Ten different gram-negative strains were subjected to the BATH test. For the calculation of the adhesion index, several factors had to be taken into account: ATP leakage, the action of ATP-hydrolyzing enzymes, the change in the extraction efficiency of Nucleotide-Releasing Reagent for Microbial Cells (NRB; Lumac bv) after vortexing and the difference in light production after the addition of NRB. When the adhesion index values obtained by bioluminescence measurement were used as reference, the total plate count technique appeared to be unreliable in estimating the number of bacteria adhering to the hydrocarbon phase. A highly significant correlation was established, however, between those reference values and the adhesion index values obtained by the optical density reading for octane and especially for hexadecane. With xylene, no correlation was found between the optical density reading values and the total plate count or bioluminescence values.     

Multiple transformation of plant cells by Agrobacterium may be responsible for the complex organization of T-DNA in crown gall and hairy root

Summary Inoculation of carrot discs and Lotus corniculatus plantlets with mixtures of different Agrobacterium rhizogenes or of A. rhizogenes and A. tumefaciens or with Agrobacterium strains harboring both an Ri and a modified Ti plasmid resulted in frequent multiple (pluribacterial) transformation of cells, as revealed by the mixed opine-type of hairy roots arising from them. Multiple transformation may account for the presence of dispersed T-DNA inserts in crown gall and hairy root lines. A plant genetic engineering strategy based on segregation of T-DNA inserts in the progeny of multiple transformants is proposed.     

Natural killer activity of kurloff cells: A direct demonstration on purified kurloff cell suspensions

In order to study their natural killer effect, guinea pig splenic Kurloff cells were fractionated by Percoll discontinuous density gradient centrifugation. Kurloff cells were collected and tested for cytotoxicity in a 24-hr chromium-release test. Comparison of different splenic cellular samples (of males or estrogenized females) with increasing percentage of Kurloff cells, revealed a highly significant positive correlation (r = 0.93, α < 0.01) with the cellular cytotoxicity developed against the K 562 target cells.