Aldehyde oxidase-dependent marked species difference in hepatic metabolism of the sedative-hypnotic, zaleplon, between monkeys and rats.
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A marked difference in hepatic activity of aldehyde oxidase between rats and monkeys was found to be responsible for the previously reported marked species difference in the metabolism of Zaleplon in vivo. In the postmitochondrial fractions, S-9s, from liver homogenates of these animals, Zaleplon was transformed in the presence of NADPH into the side chain oxidation product, N-desethyl-Zaleplon, and the aromatic ring oxidation product, 5-oxo-Zaleplon. In the rat S-9, N-desethyl-Zaleplon and 5-oxo-Zaleplon were a major and a very minor metabolites, respectively. However, in the monkey S-9, Zaleplon was transformed into 5-oxo-Zaleplon at a much higher rate than that for N-desethyl-Zaleplon formation. N-Desethyl-Zaleplon was formed in the monkey S-9 at a rate almost equal to that in the rat S-9. N-Desethyl-5-oxo-Zaleplon was formed at a minor rate only in the monkey S-9 through N-desethyl-Zaleplon as an obligatory intermediate. The hepatic activity for the formation of 5-oxo-Zaleplon in the monkey and rat was localized in cytosol and did not require NADPH. Sensitivity to various inhibitors and requirement of water as oxygen source, using H218O, strongly suggested that the hepatic cytosolic formation of 5-oxo-Zaleplon was mediated by aldehyde oxidase. N-Desethyl-Zaleplon was formed in the presence of NADPH by microsomes from the liver of rats and monkeys, and its formation was strongly suggested using various cytochrome P-450 inhibitors to be mediated by a number of cytochrome P-450 isoforms, such as 3A, 2C, and 2D subfamilies. (+info)
Comparison of characteristics of the nodX genes from various Rhizobium leguminosarum strains.
(42/42092)
We have analyzed the nucleotide sequences of the nodX genes from two strains of Rhizobium leguminosarum bv. viciae able to nodulate Afghan peas (strains A1 and Himalaya) and from two strains of R. leguminosarum bv. trifolii (ANU843 and CSF). The nodX genes of strains A1 and ANU843 were shown to be functional for the induction of nodules on Afghan peas. To analyze the cause of phenotypic differences of strain A1 and strain TOM we have studied the composition of the lipochitin-oligosaccharides (LCOs) produced by strain A1 after induction by the flavonoid naringenin or various pea root exudates. The structural analysis of the LCOs by mass spectrometry revealed that strain A1 synthesizes a family of at least 23 different LCOs. The use of exudates instead of naringenin resulted only in quantitative differences in the ratios of various LCOs produced. (+info)
Genetic and serological analysis of lipoprotein LppA in Mycoplasma mycoides subsp. mycoides LC and Mycoplasma mycoides subsp. capri.
(43/42092)
The genes encoding the 62-kDa lipoproteins from the Mycoplasma mycoides subsp. mycoides large-colony type (LC) strain Y-goat and the M. mycoides subsp. capri strain PG3 were cloned and analyzed by sequencing. These two lipoproteins have been named LppA[MmymyLC] and LppA[Mmyca], and their corresponding genes have been named lppA[MmymyLC] and lppA[Mmyca], respectively. The nucleotide and deduced amino acid sequences of these two lipoproteins showed a very high degree of similarity between these two mycoplasmas. Given the sequence data, LppA seems to fulfill the same structural functions as the previously described major lipoproteins P72 of M. mycoides subsp. mycoides small-colony type and P67 of the Mycoplasma species bovine group 7. Based on lppA gene sequences of M. mycoides subsp. mycoides LC and M. mycoides subsp. capri type strains, a specific PCR assay was developed so that it amplified this gene in all field strains of the two species analyzed in this study but not in the other members of the M. mycoides cluster. Analysis of the PCR-amplified lppA genes with frequently cutting restriction enzymes showed a certain degree of genetic variability which, however, did not cluster the two subspecies. This PCR therefore allows a rapid identification of M. mycoides subsp. mycoides LC and M. mycoides subsp. capri but does not distinguish between these two closely related subspecies. LppA was expressed in Escherichia coli K-12 and used for the production of polyclonal mouse antiserum. Antibodies against recombinant LppA[MmymyLC] reacted with a 62-kDa protein in all M. mycoides subsp. mycoides LC and M. mycoides subsp. capri type strains and field strains tested but not with the other members of the M. mycoides cluster, thus showing the antigenic specificity of LppA and further supporting the concept that a close relationship exists between these two mycoplasmas. (+info)
The physiological strain index applied to heat-stressed rats.
(44/42092)
A physiological strain index (PSI) based on heart rate (HR) and rectal temperature (Tre) was recently suggested to evaluate exercise-heat stress in humans. The purpose of this study was to adjust PSI for rats and to evaluate this index at different levels of heat acclimation and training. The corrections of HR and Tre to modify the index for rats are as follows: PSI = 5 (Tre t - Tre 0). (41.5 - Tre 0)-1 + 5 (HRt - HR0). (550 - HR0)-1, where HRt and Tre t are simultaneous measurements taken at any time during the exposure and HR0 and Tre 0 are the initial measurements. The adjusted PSI was applied to five groups (n = 11-14 per group) of acclimated rats (control and 2, 5, 10, and 30 days) exposed for 70 min to a hot climate [40 degrees C, 20% relative humidity (RH)]. A separate database representing two groups of acclimated or trained rats was also used and involved 20 min of low-intensity exercise (O2 consumption approximately 50 ml. min-1. kg-1) at three different climates: normothermic (24 degrees C, 40% RH), hot-wet (35 degrees C, 70% RH), and hot-dry (40 degrees C, 20% RH). In normothermia, rats also performed moderate exercise (O2 consumption approximately 60 ml. min-1. kg-1). The adjusted PSI differentiated among acclimation levels and significantly discriminated among all exposures during low-intensity exercise (P < 0.05). Furthermore, this index was able to assess the individual roles played by heat acclimation and exercise training. (+info)
Molecular characterization of two endogenous double-stranded RNAs in rice and their inheritance by interspecific hybrids.
(45/42092)
We completely sequenced 13,936 nucleotides (nt) of a double-stranded RNA (dsRNA) of wild rice (W-dsRNA). A single long open reading frame (13,719 nt) containing the conserved motifs of RNA-dependent RNA polymerase and RNA helicase was located in the coding strand. The identity between entire nucleotide sequence of W-dsRNA and that of the dsRNA of temperate japonica rice (J-dsRNA, 13,952 nt) was 75.5%. A site-specific discontinuity (nick) was identified at nt 1,197 from the 5' end of the coding strand of W-dsRNA. This nick is also located at nt 1,211 from the 5' end in the coding strand of J-dsRNA. The dsRNA copy number was increased more than 10-fold in pollen grains of both rice plants. This remarkable increase may be responsible for the highly efficient transmission of J-dsRNA via pollen that we already reported. J-dsRNA and W-dsRNA were also efficiently transmitted to interspecific F1 hybrids. Seed-mediated dsRNA transmission to F2 plants was also highly efficient when the maternal parent was wild rice. The efficiency of dsRNA transmission to F2 plants was reduced when the maternal parent was temperate japonica rice; however, the reduced rates in F2 plants were returned to high levels in F3 plants. (+info)
Both group IB and group IIA secreted phospholipases A2 are natural ligands of the mouse 180-kDa M-type receptor.
(46/42092)
Snake venom and mammalian secreted phospholipases A2 (sPLA2s) have been associated with toxic (neurotoxicity, myotoxicity, etc.), pathological (inflammation, cancer, etc.), and physiological (proliferation, contraction, secretion, etc.) processes. Specific membrane receptors (M and N types) for sPLA2s have been initially identified with snake venom sPLA2s as ligands, and the M-type 180-kDa receptor was cloned from different animal species. This paper addresses the problem of the endogenous ligands of the M-type receptor. Recombinant group IB and group IIA sPLA2s from human and mouse species have been prepared and analyzed for their binding properties to M-type receptors from different animal species. Both mouse group IB and group IIA sPLA2s are high affinity ligands (in the 1-10 nM range) for the mouse M-type receptor. These two sPLA2s are expressed in the mouse tissues where the M-type receptor is also expressed, making it likely that both types of sPLA2s are physiological ligands of the mouse M-type receptor. This conclusion does not hold for human group IB and IIA sPLA2s and the cloned human M-type receptor. The two mouse sPLA2s have relatively high affinities for the mouse M-type receptor, but they can have much lower affinities for receptors from other animal species, indicating that species specificity exists for sPLA2 binding to M-type receptors. Caution should thus be exerted in avoiding mixing sPLA2s, cells, or tissues from different animal species in studies of the biological roles of mammalian sPLA2s associated with an action through their membrane receptors. (+info)
Cdc42: An essential Rho-type GTPase controlling eukaryotic cell polarity.
(47/42092)
Cdc42p is an essential GTPase that belongs to the Rho/Rac subfamily of Ras-like GTPases. These proteins act as molecular switches by responding to exogenous and/or endogenous signals and relaying those signals to activate downstream components of a biological pathway. The 11 current members of the Cdc42p family display between 75 and 100% amino acid identity and are functional as well as structural homologs. Cdc42p transduces signals to the actin cytoskeleton to initiate and maintain polarized gorwth and to mitogen-activated protein morphogenesis. In the budding yeast Saccharomyces cerevisiae, Cdc42p plays an important role in multiple actin-dependent morphogenetic events such as bud emergence, mating-projection formation, and pseudohyphal growth. In mammalian cells, Cdc42p regulates a variety of actin-dependent events and induces the JNK/SAPK protein kinase cascade, which leads to the activation of transcription factors within the nucleus. Cdc42p mediates these processes through interactions with a myriad of downstream effectors, whose number and regulation we are just starting to understand. In addition, Cdc42p has been implicated in a number of human diseases through interactions with its regulators and downstream effectors. While much is known about Cdc42p structure and functional interactions, little is known about the mechanism(s) by which it transduces signals within the cell. Future research should focus on this question as well as on the detailed analysis of the interactions of Cdc42p with its regulators and downstream effectors. (+info)
Mechanisms of arthropod transmission of plant and animal viruses.
(48/42092)
A majority of the plant-infecting viruses and many of the animal-infecting viruses are dependent upon arthropod vectors for transmission between hosts and/or as alternative hosts. The viruses have evolved specific associations with their vectors, and we are beginning to understand the underlying mechanisms that regulate the virus transmission process. A majority of plant viruses are carried on the cuticle lining of a vector's mouthparts or foregut. This initially appeared to be simple mechanical contamination, but it is now known to be a biologically complex interaction between specific virus proteins and as yet unidentified vector cuticle-associated compounds. Numerous other plant viruses and the majority of animal viruses are carried within the body of the vector. These viruses have evolved specific mechanisms to enable them to be transported through multiple tissues and to evade vector defenses. In response, vector species have evolved so that not all individuals within a species are susceptible to virus infection or can serve as a competent vector. Not only are the virus components of the transmission process being identified, but also the genetic and physiological components of the vectors which determine their ability to be used successfully by the virus are being elucidated. The mechanisms of arthropod-virus associations are many and complex, but common themes are beginning to emerge which may allow the development of novel strategies to ultimately control epidemics caused by arthropod-borne viruses. (+info)