Biphasic fluence-response curves for phytochrome-mediated kalanchoë seed germination : sensitization by gibberellic Acid

The fluence-response curves for the effect of two red pulses separated by 24 hours on the germination of Kalanchoe blossfeldiana Poelln. cv Vesuv seeds, incubated on gibberellic acid (GA₃) are biphasic for suboptimal concentrations. The response in the low fluence range corresponds with a classical red/far-red reversible phytochrome mediated reaction. GA₃ induces an additional response in the very low fluence range, which is also phytochrome mediated. The sensitivity to phytochrome-far-red absorbing form (Pfr), however, is increased about 20,000-fold, so that even far-red fluences become saturating. Both in the very low and low fluence response range, the maximal responses induced by saturating fluences are modulated by the GA₃ concentration. GA₃ having no direct influence on the phytochrome phototransformations, alters the Pfr requirement and determines the responding seed population fraction in the very low and low fluence range. The effet of GA₃ appears to be on the transduction chain of the phytochrome signal.     

Karyotypie diversity and taxonomic problems in the genus Arvicanthis (Rodentia,Muridae)

The analyses of R- and C-banding patterns of chromosomes of Arvicanthis niloticus originating from two different localities (Egypt and Central African Republic) revealed karyotypic differences caused by one pericentric inversion and three translocations, one being reciprocal and the others Robertsonian. There were also some differences in centromeric heterochromatin patterns.The data indicate that these two forms are distinct species, cytogenetically isolated, and that a revision of the taxonomic status of the genus Arvicanthis is needed.     

Anthropometric data in middle-aged women. The population study of women in G?teborg 1968-1969.

Body weight, body height, skinfolds, circumferences and weight indices in a population sample of 1462 women in ages between 38 and 60 years are presented. Significant age differences were noted. High correlations (r) were found between body weight and triceps and subscapular skinfolds (0.62 and 0.72 respectively) and between body weight and arm, waist and buttock circumferences (0.75-0.88). Age differences were mostly noted between 46 and 50 years of age. After that age there was a comparatively greater increase of the waist circumference than of the buttock circumference, while triceps skinfold seemed to decrease after the age of 50 indicating an altered adipose tissue distribution from the extremities to the trunk with increasing age. When taking data from a previous study of body weight in the same population of women into consideration it seems that the age differences in body weight found in cross-sectional study like the present one may to a large extent depend on differences between different cohorts studied.     

Intraspecific variability in response to stimuli for male and ephippia formation in Daphnia pulex

Natural clones and clones from laboratory crossings of Daphnia pulex have been tested in their response to stimuli for male and ephippia formation. The clones are from ponds in Illinois, USA, an area with both obligate and cyclical clones of D. pulex. The progeny from two types of crosses were studied: 1) crosses between an obligate clone producing males and a cyclical clone producing only females, and 2) self-fertilization within a cyclical clone producing both sexes. Both the natural and the artificial clones showed great variation in response to environmental stimuli for males. Ephippia response seems more equal among the clones, but two of the artificial clones could hardly be stimulated to produce ephippia in the induction experiments. In crowded cultures, however, they produced a few. Crossings between cyclicals and obligates yielded mostly cyclical progeny. Progeny from the selfed clone had low survival and fecundity.     

Allelic Negative Complementation at the Abruptex Locus of DROSOPHILA MELANOGASTER

The mutations of the Abruptex locus in Drosophila melanogaster fall into three categories. There are recessive lethal alleles and viable alleles. The latter can be divided into suppressors and nonsuppressors of Notch mutations. The recessive lethals are lethal in heterozygous combination with Notch. As a rule the recessive lethals are lethal also in heterozygous combination with the viable alleles. Heterozygous combinations of certain viable alleles are also lethal. In such heterozygotes, one heteroallele is a suppressor of Notch and the other is a nonsuppressor. Other heterozygous combinations of viable alleles are viable and have an Abruptex phenotype. The insertion of the wild allele of the Abruptex locus as an extra dose (carried by a duplication) into the chromosomal complement of the fly fully restores the viability of the otherwise lethal heterozygotes if two viable alleles are involved. The extra wild allele also restores the viability of heterozygotes in which a lethal and a suppressor allele are present. If, however, a lethal and a nonsuppressor are involved, the wild allele only partly restores the viability, and the effect of the wild allele is weakest if two lethal alleles are involved. It seems likely that of the viable alleles the suppressors of Notch are hypermorphic and the nonsuppressors are hypomorphic. The lethal alleles share properties of both types, and are possibly antimorphic mutations. It is suggested that the locus is responsible for a single function which, however, consists of two components. The hypermorphic mutations are defects of the one component and the hypomorphic mutations of the other. In heterozygotes their cumulative action leads to decreased viability. The lethal alleles are supposed to be defects of the function as a whole. The function controlled by the locus might be a regulative function.     

Gene expression in autumn leaves

Two cDNA libraries were prepared, one from leaves of a field-grown aspen (Populus tremula) tree, harvested just before any visible sign of leaf senescence in the autumn, and one from young but fully expanded leaves of greenhouse-grown aspen (Populus tremula x tremuloides). Expressed sequence tags (ESTs; 5,128 and 4,841, respectively) were obtained from the two libraries. A semiautomatic method of annotation and functional classification of the ESTs, according to a modified Munich Institute of Protein Sequences classification scheme, was developed, utilizing information from three different databases. The patterns of gene expression in the two libraries were strikingly different. In the autumn leaf library, ESTs encoding metallothionein, early light-inducible proteins, and cysteine proteases were most abundant. Clones encoding other proteases and proteins involved in respiration and breakdown of lipids and pigments, as well as stress-related genes, were also well represented. We identified homologs to many known senescence-associated genes, as well as seven different genes encoding cysteine proteases, two encoding aspartic proteases, five encoding metallothioneins, and 35 additional genes that were up-regulated in autumn leaves. We also indirectly estimated the rate of plastid protein synthesis in the autumn leaves to be less that 10% of that in young leaves.     

Control of Plasmid R1 Replication: Kinetics of Replication in Shifts Between Different Copy Number Levels

Plasmid R1 replication was studied in shifts between two steady states of copy number. The copy number was varied in two ways. First, we utilized the fact that it decreases with increasing growth rate. To minimize the metabolic effects of changes in the growth rate, the downshifts were obtained by adding α-methylglucoside to cultures growing in glucose-minimal medium, and the upshifts were obtained by adding glucose to cultures growing in the presence of glucose plus α-methylglucoside. Second, we used a temperature-dependent copy mutant of plasmid R1 (pKN301). Plasmid pPK301 shows a threefold higher copy number at 40 than at 30°C. In both types of shift, plasmid replication immediately adjusted to the postshift differential rate. The copy number asymptotically adjusted to the new steady state. Hence, the system that controls plasmid R1 replication sets the frequency of replication without measuring the actual copy number. It has been suggested that plasmid R1 replication is under negative control by an R1-mediated repressor protein. Among the replication control models that involve negative control, the Pritchard inhibitor dilution model, the Sompayrac-Maaløe autorepressor model, and the plasmid λdv system all predict gene dose-independent copy number control.     

Molecular characterization of two deletion events involving Alu-sequences, one novel base substitution and two tentative hotspot mutations in the hypoxanthine phosphoribosyltransferase (HPRT) gene in five patients with Lesch-Nyhan syndrome

Mutations identified in the hypoxanthine phosphoribosyltransferase (HPRT) gene of patients with Lesch-Nyhan (LN) syndrome are dominated by simple base substitutions. Few hotspot positions have been identified, and only three large genomic rearrangements have been characterized at the molecular level. We have identified one novel mutation, two tentative hot spot mutations, and two deletions by direct sequencing of HPRT cDNA or genomic DNA from fibroblasts or T-lymphocytes from LN patients in five unrelated families. One is a missense mutation caused by a 610C→T transition of the first base of HPRT exon 9. This mutation has not been described previously in an LN patient. A nonsense mutation caused by a 508C→T transition at a CpG site in HPRT exon 7 in the second patient and his younger brother is the fifth mutation of this kind among LN patients. Another tentative hotspot mutation in the third patient, a frame shift caused by a G nucleotide insertion in a monotonous repeat of six Gs in HPRT exon 3, has been reported previously in three other LN patients. The fourth patient had a tandem deletion: a 57-bp deletion in an internally repeated Alu-sequence of intron 1 was separated by 14 bp from a 627-bp deletion that included HPRT exon 2 and was flanked by a 4-bp repeat. This complex mutation is probably caused by a combination of homologous recombination and replication slippage. Another large genomic deletion of 2969 bp in the fifth patient extended from one Alu-sequence in the promoter region to another Alu-sequence of intron 1, deleting the whole of HPRT exon 1. The breakpoints were located within two 39-bp homologous sequences, one of which overlapped with a well-conserved 26-bp Alu-core sequence previously suggested as promoting recombination. These results contribute to the establishment of a molecular spectrum of LN mutations, support previous data indicating possible mutational hotspots, and provide evidence for the involvement of Alu-mediated recombination in HPRT deletion mutagenesis. Received: 21 April 1998 / Accepted: 16 July 1998     

Synthesis of alkyne derivatives of a novel triazolopyrazine as A(2A) adenosine receptor antagonists

A novel [1,2,4]triazolo[1,5-a]pyrazine core was synthesized and coupled with terminal acetylenes. The structure-activity relationship of the alkynes from this novel template was studied for their in vitro and in vivo adenosine A(2A) receptor antagonism. Selected compounds from this series were shown to have potent in vitro and in vivo activities against adenosine A(2A) receptor. Compound 12, in particular, was found to be orally active at 3mg/kg in both a mouse catalepsy model and a 6-hydroxydopamine-lesioned rat model.