Conserved Organization of γ-Aminobutyric AcidAReceptor Genes: Cloning and Analysis of the Chicken β4-Subunit Gene

A series of genomic clones containing DNA that encodes the chicken gamma-aminobutyric acidA (GABAA) receptor beta 4 subunit have been isolated. These have been restriction mapped and partially sequenced to determine the structural organization and the size of the beta 4-subunit gene. This gene, which comprises nine exons, spans more than 65 kb. The organization of the chicken GABAA receptor beta 4-subunit gene has been compared to that of the murine GABAA receptor delta-subunit gene and to those of the genes that encode other members of the ligand-gated ion-channel superfamily, namely muscle and neuronal nicotinic acetylcholine receptors (AChRs). Although the positions of the intron/exon boundaries of GABAA receptor subunit genes are seen to be highly conserved, there are significant differences between the genes that encode GABAA receptor and AChR subunits. These results are discussed in relation to the proposal that this superfamily of ligand-gated ion-channel receptor genes arose by duplication of an ancestral receptor gene.     

Long-term changes in the phytoplankton of large lakes in response to changes in nutrient loading

In Sweden the recovery process of the four largest lakes (<500 km²) has been followed since the mid-1970's when the phosphorus loading was reduced by approximately 50%. A ten-year investigation period before that acts as a basis of comparison. The response of the dominating species in the phytoplankton communities in the eutrophic Lake Mälaren and the oligotrophic Lake Vättern is discussed also in relation to a pristine state of the lakes. The long-term investigations with monthly sampling make a natural phytoplankton biomass variation range possible to establish - a range that is mainly due to effects of weather fluctuations. In order to get a tool for water management where disturbing and highly disturbing total phytoplankton volumes can be anticipated from a certain phosphorus concentration, a model is suggested based on experiences from more than 50 Swedish lakes investigated during a series of years.     

Histological characterization of in vitro regenerated structures of Panax ginseng

Callus was induced from mature leaf lamina, petiole, stem, and main and branch root of Panax ginseng and maintained under different nutrient and light conditions. Heterogenous callus cultures differentiated organoids and/or embryoids. Embryoids that arose from callus cultures of leaf origin germinated into shoots. The occurrence of the early stages of different regenerated structures was proved on histological level.     

A new homeobox-leucine zipper gene from Arabidopsis thaliana

We have isolated a homeobox-containing gene from Arabidopsis thaliana using a degenerate oligonucleotide probe corresponding to the most conserved region of the homeodomain. This strategy has been used previously to isolate homeobox-containing genes from Caenorhabditis, and recently from A. thaliana. The Arabidopsis genes have an unusual structure in that they have a leucine zipper motif adjacent to the carboxy terminal region of the homeo domain, a feature not found in homeobox-containing genes isolated from animals. We report the isolation and primary structure of a new member of this Arabidopsis homeobox-leucine zipper gene family. This new member has the homeodomain and leucine-zipper motif similar to the two genes previously identified, but differs from these genes in the part corresponding to the carboxy terminus of the polypeptide, as well as in size and isoelectric point of the protein.     

TWO NEUTRALITY TESTS OF Y-LINKED RDNA VARIATION IN DROSOPHILA MELANOGASTER

The evolutionary significance of Y-chromosomal ribosomal DNA sequence variation was tested by two different means. A single sample of males and females was collected from a peach orchard in central Pennsylvania. Wild-caught males and sons of wild-caught, wild-inseminated females were crossed to virgin females having an X-linked rDNA deficiency. Genomic DNA from male progeny of these crosses was extracted and digested with the single restriction endonuclease, DraI. Southern blots of these digestions, when probed with the complete rDNA probe, revealed 10 distinct patterns of restriction fragments. A chisquare test for the homogeneity of the frequency distributions of the sample of wild males and sons of wild females failed to reject a neutral null hypothesis. The allele frequency configuration was tested with the Ewens-Watterson test, and the departure from the infinite alleles neutral model was not significant. Simulations were performed to test the sensitivity of the tests to misclassification and to quantify the power of the two tests.     

Sprunghafter Anstieg von Brutst?rungen bei H?hlenbrütern

Summary From 1986 onwards increasing numbers of Great Tits (Parus major) and Blue Tits (Parus caeruleus) were registered breeding on empty nests. In 1987 and 1988 up to 4% of all found sitting on nests did not lay any egg. The rate of breeding failures might be considerably higher because many individuals breeding on empty nests could have been overlooked by weekly checks of the nest boxes.     

Oxidized and reduced glutathione,ascorbate and glutathione reductase inmatricaria recutita L. Callus cultures

In the long-term cultivated callus cultures ofMatricaria recutita L. the identical concentration changes in the biosynthesis of glutathione, glutamate, aspartate, total thiols and proteins were detected within the subculture. The level of oxidized glutathione during the growth of callus culture was low with the highest value 10.66 nmol g^-1 on the 13th day of subculture. The ratio GSH/GSSG which significantly influences the redox processes in a cell, and the activity of glutathione reductase increased from the 8th day. Ascorbate formation was detected on the 17th day, although no relation between the ascorbate synthesis and the concentration of glutathione and glutathione reductase was found.     

Human T-cell cultures with selective autotumor reactivity

Summary T-cell cultures derived from the blood of 14 patients with solid tumors were propagated with T-cell growth factor (TCGF). The cultures were initiated from lymphocytes exposed to autologous tumor-biopsy cells. TCGF was added either immediately or 3–10 days later. In the former culture type the cell yield on day 7 was considerably higher. The cytotoxic potential of the cultured cells was assayed on two occasions, between days 7 and 10 and between weeks 5 and 8. Cells of all but two cultures had the potential to lyse autologous tumor-biopsy cells.On the population level, cytotoxicity was specific for autologous tumor in those cultures that were driven to growth with TCGF after the 3rd day. These lymphocytes did not lyse allogeneic tumor-biopsy cells. In contrast, all five cultures initiated in the presence of TCGF exhibited a broader cytotoxic potential, i.e., in addition to the stimulator autologous-tumor cells, they also lysed other targets. Another difference between the two culture types was their behavior toward K562. Tested on the 7th day they all lysed K562; however, this function declined in strength or disappeared later in the cultures exposed to TCGF after the 3rd day.Reexposure of the lymphocytes to autologous tumor-biopsy cells after 2 weeks of culture period, but not on the 7th day, induced DNA synthesis. This secondary response was specific inasmuch as allogeneic tumor cells had little or no effect.One of the autotumor restimulated cultures was tested for cytotoxic potential. It increased against the autologous but not against other tumors or K562 cells.