Identification of two glutaminases inRhizobium etli

We present evidence thatRhizobium etli has two glutaminases differentiated by their thermostability and electrophoretic mobility. The thermostable glutaminase (B) is constitutive, in contrast with the thermolabile glutaminase (A), which is positively regulated by glutamine and negatively regulated by ammonium and by the carbon source. In distinction to glutaminase A, glutaminase B plays a minor role in the utilization of glutamine as a carbon source, but it may play a role in maintaining the balance of glutamine and glutamate. By complementation of theRhizobium etli LM16 mutant that lacks glutaminase A, we have cloned the gene that codes for this enzyme.     

Whisker-mediated plant transformation: An alternative technology

A number of different methods, involving direct DNA delivery are now available for plant transformation. Here we review the most recently developed technique which involves the mixing of silicon carbide whiskers with plant cells and plasmid DNA. Fertile transgenic plants have now been produced using whisker-mediated transformation, and this method can now be considered as a simple, inexpensive alternative for plant transformation. A brief review on transformation of animal cells andChlamydomonas using whiskers technology is also included.     

Advance directives, autonomy and unintended death

This Paper argues that Living wills are typically nebulous and confused documents that do not effectively enable you to determine your future treatment. Worse, signing a living will can end your life in ways you never intended, long before you are either incompetent or terminally ill. This danger is compounded by the fact that those who implement living wills are often themselves dangerously confused, so that, for example, they cannot be relied upon to distinguish living wills from DNR orders. In addition, the Paper argues that advance directives concerning resuscitation are often so confused that they end the lives of healthy, alert people who have not suffered cardiac or pulmonary arrest. Finally, the paper argues that advance directives establishing durable power of attorney for health care often preserve the chief dangers of living wills. Suggestions are offered as to how you can most effectively direct your future treatment without endangering your life.     

A POPULATION MEMETICS APPROACH TO CULTURAL EVOLUTION IN CHAFFINCH SONG: DIFFERENTIATION AMONG POPULATIONS

We investigated cultural evolution in populations of common chaffinches (Fringilla coelebs) in the Atlantic islands (Azores, Madeira, and Canaries) and neighboring continental regions (Morocco and Iberia) by employing a population-memetic approach. To quantify differentiation, we used the concept of a song meme, defined as a single syllable or a series of linked syllables capable of being transmitted. The levels of cultural differentiation are higher among the Canaries populations than among the Azorean ones, even though the islands are on average closer to each other geographically. This is likely the result of reduced levels of migration, lower population sizes, and bottlenecks (possibly during the colonization of these populations) in the Canaries; all these factors produce a smaller effective population size and therefore accentuate the effects of differentiation by random drift. Significant levels of among-population differentiation in the Azores, in spite of substantial levels of migration, attest to the differentiating effects of high mutation rates of memes, which allow the accumulation of new mutants in different populations before migration can disperse them throughout the entire region.     

Sex chromosome polymorphism and heterogametic males revealed by two cloned DNA probes in the ZW/ZZ fish Leporinus elongatus

In order to study the divergence of teleost sex chromosomes, subtractive cloning was carried out between genomic DNA of males and females of the rainbow trout (XX/XY) and of Leporinus elongatus (ZW/ZZ). Inserts cloned in a plasmid vector were individually tested on Southern blots of DNA of males and females for sex specificity. No sex-specific insert was obtained from trout, but two out of ten inserts cloned from L. elongatus showed sex-specific patterns in this species: one corresponds to a sequence present on both Z and W chromosomes, while the other is W specific. Sequences of these two inserts show neither clear homology with other known sequences, nor an open reading frame. They cross-hybridize with the genomic DNA of Leporinus friderici, but without sex-specific patterns. Twenty-four L. elongatus adults were sexed by gonadal observation, chromosomed examination and Southern hybridization with one or the other insert. Ten males and 11 females had chromosomes and hybridization patterns typical of their sex. One ZW female was recognized as a male with the W-specific probe. This was also the case for two unusual ZW males, one having a male hybridization pattern with the other probe. These three atypical individuals may result from single genetic exchanges between four regions of the Z and the W, giving rise to three atypical W chromosomes. Finding males with such atypical heterochromosomes in a female heterogametic species may indicate that a gradual transition occurs between the heterogametic systems.     

An Ultrastructural Investigation on Vitellophage Invasion of the Yolk Mass during and after Germ Band Formation in Embryos of the Stick Insect Carausius morosus Br.

Developing embryos of the stick insect Carausius morosus were examined ultrastructurally with a view to studying vitellophage invasion of the yolk mass during and after germ band formation. Newly laid eggs in C.morosus have a unique yolk fluid compartment surrounded by a narrow fringe of cytoplasm comprising several small yolk granules. Vitellophages originate mainly from a thin layer of stem cells, the so-called yolk cell membrane, interposed between the germ band and the yolk mass. Throughout development, a thin basal lamina separates the yolk cell membrane from the overlying embryo.
Vitellophages extend from the yolk cell membrane with long cytoplasmic processes or filopodia to invade the central yolk mass. Along their route of entrance, filopodia engulf portions of the yolk mass and sequester it into membrane-bounded granules. As this process continues, the yolk mass is gradually partitioned into a number of yolk granules inside the vitellophages.
Later in development, the yolk cell membrane is gradually replaced by the endodermal cells that emerge from the anterior and posterior embryonic rudiments. From this stage of development onwards, vitellophages remain attached to the basal lamina through long filopodia extending between the endodermal cells. Yolk confined in different vitellophagic cells appears heterogeneous both in density and texture, suggesting that yolk degradation may be spatially differentiated.     

Molecular cloning of the dog homologue of the lymphocyte antigen CD28

The nucleotide data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number L22178.     

Elemental microanalysis of fibroblasts by a scanning proton microprobe and application to Menkes’ disease

A scanning proton microprobe has been used for the elemental microanalysis of individual fibroblast cells. Both normal fibroblasts and fibroblasts cultured from patients with Menkes' disease, an X-linked genetic disorder known to be associated with defective copper metabolism, were examined by the probe. The cells were cultured on a thin ultra-clean nylon foil and retained on that surface for analysis. The focused high-energy proton beam was used to irradiate selected individual cells and elemental information was derived from X-ray and backscattered proton data. The sensitivity of the scanning proton microprobe to trace concentrations of heavy elements has allowed this elemental information to be used to identify individual cells as being either normal or a Menkes' mutant. The cell identification was based on the application of discriminate analysis to a data set formed from the ratios of copper to each of the macroelements present in the cell. This method of cell identification offers the promise of rapid diagnosis of Menkes' disease.     

Gene transfer to inflorescence and flower meristems using ballistic micro-targeting

Direct gene transfer to floral meristems could contribute to cell-fate mapping, to the study of flower-specific genes and promoters, and to the production of transgenic gametes via the transformation of sporogenic tissues. Despite the wide potential of its applications, direct gene transfer to floral meristems has not been achieved so far because of the lack of suitable technology. We show in this paper that ballistic micro-targeting is the technique of choice for this purpose, and in this way, we were able to transfer genes efficiently into excised wheat immature spikes. Particle size was adjusted for optimal penetration into the L1 and L2 cell layers of the spikes with limited cell damage. Spikes at different developmental stages were shot either with a plasmid containing two genes involved in anthocyanin biosynthesis or with a plasmid bearing the uidA (-glucuronidase) gene. The transient expression of these marker genes was observed in the different developmental stages tested and in cells of both the L1 and the L2 layers. The transient expression of the uidA gene was significantly increased when the sucrose concentration in the culture medium was increased from 0.06 to 0.52 M. At the highest concentration, 100% of the targeted spikes expressed the uidA gene, with an average of 69 blue cells per spike. Twelve days after microtargeting, multicellular sectors showing transgene expression and containing up to 17 cells were found in 85% of the shot immature inflorescences. This indicated that targeted cells survived particle bombardment. Sectors were found in primordia of both vegetative and reproductive organs.