rctB mutations that increase copy number of Vibrio cholerae oriCII in Escherichia coli

RctB serves as the initiator protein for replication from oriCII, the origin of replication of Vibrio cholerae chromosome II. RctB is conserved between members of Vibrionaceae but shows no homology to known replication initiator proteins and has no recognizable sequence motifs. We used an oriCII based minichromosome to isolate copy-up mutants in Escherichia coli. Three point mutations rctB(R269H), rctB(L439H) and rctB(Y381N) and one IS10 insertion in the 3'-end of the rctB gene were obtained. We determined the maximal C-terminal deletion that still gave rise to a functional RctB protein to be 165 amino acids. All rctB mutations led to decreased RctB-RctB interaction indicating that the monomer is the active form of the initiator protein. All mutations also showed various defects in rctB autoregulation. Loss of the C-terminal part of RctB led to overinitiation by reducing binding of RctB to both rctA and inc regions that normally serve to limit initiation from oriCII. Overproduction of RctB(R269H) and RctB(L439H) led to a rapid increase in oriCII copy number. This suggests that the initiator function of the two mutant proteins is increased relative to the wild-type.     

Nocturnal vision and landmark orientation in a tropical halictid bee

BACKGROUND: Some bees and wasps have evolved nocturnal behavior, presumably to exploit night-flowering plants or avoid predators. Like their day-active relatives, they have apposition compound eyes, a design usually found in diurnal insects. The insensitive optics of apposition eyes are not well suited for nocturnal vision. How well then do nocturnal bees and wasps see? What optical and neural adaptations have they evolved for nocturnal vision? RESULTS: We studied female tropical nocturnal sweat bees (Megalopta genalis) and discovered that they are able to learn landmarks around their nest entrance prior to nocturnal foraging trips and to use them to locate the nest upon return. The morphology and optics of the eye, and the physiological properties of the photoreceptors, have evolved to give Megalopta's eyes almost 30 times greater sensitivity to light than the eyes of diurnal worker honeybees, but this alone does not explain their nocturnal visual behavior. This implies that sensitivity is improved by a strategy of photon summation in time and in space, the latter of which requires the presence of specialized cells that laterally connect ommatidia into groups. First-order interneurons, with significantly wider lateral branching than those found in diurnal bees, have been identified in the first optic ganglion (the lamina ganglionaris) of Megalopta's optic lobe. We believe that these cells have the potential to mediate spatial summation. CONCLUSIONS: Despite the scarcity of photons, Megalopta is able to visually orient to landmarks at night in a dark forest understory, an ability permitted by unusually sensitive apposition eyes and neural photon summation.     

Tumor necrosis factor and norepinephrine lower the levels of human neutrophil peptides 1-3 secretion by mixed synovial tissue cultures in osteoarthritis and rheumatoid arthritis

Introduction  

Neutrophils and monocytes play an important role in overt inflammation in chronic inflammatory joint diseases such as rheumatoid arthritis (RA). The sympathetic nervous system (SNS) inhibits many neutrophil/monocyte functions and macrophage tumor necrosis factor (TNF), but because of the loss of sympathetic nerve fibers in inflamed tissue, sympathetic control is attenuated. In this study, we focused on noradrenergic and TNF regulation of human neutrophil peptides 1-3 (HNP1-3), which are proinflammatory bactericidal α-defensins.     

High Performance Liquid Chromatography of Molecular Species from Free Sterols and Sterylglycosides Isolated from Oat Leaves and Seeds

Free sterols and sterylglycosides (SG) from oat leaves and seedswere isolated by conventional thin layer chromatography (TLC)and subjected to high performance liquid chromatography (HPLC)for resolution of molecular species. Acylsterylglycosides, isolatedby TLC, were converted to SG by mild alkaline hydrolysis anddetermined as SG. Sterols and SG were injected onto the columnwithout any chemical treatment and the separated species weredetected at 200 nm. The separation of SG-species follows exactlythe separation of free sterols. Though gas liquid chromatography still is the method of choice,advantages of HPLC is to analyse directly the SG-species withouthydrolysis and derivatization as compared to GLC. After TLCthe sterol- and the SG-fraction are injected directly onto thecolumn. This is extremely important for labile sterylglycosidesor sterols, as demonstrated for the avenasterols. ¹ Preliminary reports have been presented on the "4. Arbeitstagung,Pflanzliche Lipide", October 7–8, 1983 in M?nster (FRG)and on the "6th International Symposium on the Structure, Functionand Metabolism of Plant Lipids", Neuchatel, Switzerland, July16–20, 1984. (Received November 12, 1984; Accepted January 14, 1985)     

Structure and function of vertebrate CMP-sialic acid synthetases

Activation of sugars into nucleotide sugars is critical for their entry into biosynthetic pathways. In eukaryotic cells, the activation of the acidic nine-carbon sugar sialic acid to CMP-sialic acid takes place in the cell nucleus, whereas all other nucleotide sugars are made in the cytoplasm. Molecular cloning of vertebrate CMP-sialic acid synthetases confirmed the nuclear localization and introduced new molecular tools for directly exploring the functional mechanisms of the enzymes, as well as the physiological relevance of their nuclear transport. Although major advances have been made in understanding structure-function relationships and defining elements involved in the nuclear transport, the riddle surrounding the physiological relevance of nuclear localization awaits resolution.     

Molecular characterization of the diurnal/circadian expression of the chlorophyll a/b-binding proteins in leaves of tomato and other dicotyledonous and monocotyledonous plant species

Diurnal oscillations of steady-state mRNA levels encoding the chlorophyll a/b-binding proteins were monitored inLycopersicon esculentum, Glycine max, Phaseolus vulgaris, P. aureus, P. coccineus, Pisum sativum, Sinapis alba, Hordeum vulgare, Triticum aestivum andZea mays. In these plant speciescab mRNA accumulation increases and decreases periodically indicating i) that the expression of the genes for chlorophyll a/b-binding proteins (cab genes) is controlled by a circadian rhythm, and ii) that the rhythm is widely distributed among monocotyledonous and dicotyledonous plant species. A detailed characterization of the pattern ofcab mRNA expression in tomato leaves shows that the amplitude of the oscillation is dependent on i) the developmental stage of the leaves, ii) the circadian phase and duration of light and iii) the circadian phase and duration of darkness. In addition to the chlorophyll a/b-binding proteins, genes coding for other cellular functions were examined for cyclic variations of their mRNA levels. The analysis includes genes involved in i) carbon metabolism (e.g. phosphoenolpyruvate carboxylase, pyruvate orthophosphate dikinase, alpha amylase, fructose-1,6-bisphosphate aldolase, triosephosphate isomerase), ii) photosynthesis (large and small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, Q_B-binding protein, reaction-center protein of photosystem I) and iii) other physiological or morphological reactions (e.g. ubiquitin, actin). However, no periodic fluctuation pattern was detected for the mRNA levels of these genes in tomato and maize leaves.