痢止蒿化学成分的研究

自云南产痢止蒿(Ajuga forrestii Diels)全草的乙醇提取物中分得5个单体,其中化合物Ⅰ和Ⅱ经波谱分析和化学方法鉴定为新的松香烷型二萜类化合物,分别命名为痢止蒿甲素(ajuforrestin A,I)和痢止蒿乙素(ajuforrestin B,II),其余3个是黄酮类化合物:洋芹素(apigenin)、金合欢素(acacetin)和买麻藤乙素(gnetifolin B)。     

Influence of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced injury of dopaminergic nigrostriatal system on movement components of the instrumental reflex and motor thalamic neurons' reactions in the cat.

Peculiarities of excitation and inhibition in ventral lateral and ventral anterior thalamic neurons were studied in cats with movement disorders (bradykinesia and muscle rigidity) induced by injury of nigrostriatal dopaminergic neurons with neurotoxin N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (5 mg/kg daily, intramuscularly for five days). As was shown in chronic experiments, mean discharge frequency of neurons related to initiation of upper limb movements increased. Excitation of these neurons coincided with movement initiation, flexion and extension becoming more prominent and prolonged as compared with normal animals. In parallel to those changes, bradykinesia developed. In acute experiments performed under ketalar anaesthesia and myorelaxine immobilization it was found that neurotoxin caused a decrease of the inhibition duration and effectiveness in relay and non-relay thalamic motor nuclei neurons. The inhibition deficiency was accompanied by a shortening of latencies of orthodromic responses evoked by red nucleus stimulation. Two days after the last neurotoxin injection, light microscope examination revealed that about 48% of neurons located in the pars compacta of substantia nigra were destroyed. Electron microscopic analysis showed hydropic changes in perykaria and dendrites in most neurons of the substantia nigra pars compacta that are typical of the light type of degeneration. Pathomorphological processes in the synaptic apparatus were also found. The content of dopamine in the caudate nucleus fell to 30% as compared with intact animals. The suggestion is made that the deficiency of inhibition developed in motor thalamic neurons in response to nigrostriatal system destruction results from attenuation of dopamine-modulated direct GABAergic nigrothalamic influences and/or might be connected with increased inhibition of inhibitory interneurons of the same thalamic nuclei conditioned by pallidum disinhibition.     

Changes in the neuronal activity of the ventrolateral thalamic nucleus and in the motor components of an instrumental reaction in cats following the systemic administration of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

Activity of ventrolateral thalamic neurons during performance of instrumental reaction was studied in four cats before (81 neurons) and after (70 neurons) five injections of MPTP (5 mg/kg every day). It was found that MPTP administration was followed by a clear increase of the discharge frequency of the studied neurons correlated with forelimb movements. The duration of their excitation connected with movement initiation, flexion or extension of limb increased as well. Movement disorders that evidenced for the development of bradykinesia were observed simultaneously with an increase of the neuronal activity. Dophamine microinjection into the caudate nucleus led to recovery of movements and neuronal discharge frequency. A conclusion was made that in intact cats activity of ventrolateral thalamic neurons related to forelimb movements was under inhibitory influences coming from the nigrostriatal system.     

Hop2/Mnd1 acts on two critical steps in Dmc1-promoted homologous pairing

Meiotic recombination between homologous chromosomes ensures their proper segregation at the first division of meiosis and is the main force shaping genetic variation of genomes. The HOP2 and MND1 genes are essential for this recombination: Their disruption results in severe defects in homologous chromosome synapsis and an early-stage failure in meiotic recombination. The mouse Hop2 and Mnd1 proteins form a stable heterodimer (Hop2/Mnd1) that greatly enhances Dmc1-mediated strand invasion. In order to elucidate the mechanism by which Hop2/Mnd1 stimulates Dmc1, we identify several intermediate steps in the homologous pairing reaction promoted by Dmc1. We show that Hop2/Mnd1 greatly stimulates Dmc1 to promote synaptic complex formation on long duplex DNAs, a step previously revealed only for bacterial homologous recombinases. This synaptic alignment is a consequence of the ability of Hop2/Mnd1 to (1) stabilize Dmc1-single-stranded DNA (ssDNA) nucleoprotein complexes, and (2) facilitate the conjoining of DNA molecules through the capture of double-stranded DNA by the Dmc1-ssDNA nucleoprotein filament. To our knowledge, Hop2/Mnd1 is the first homologous recombinase accessory protein that acts on these two separate and critical steps in mammalian meiotic recombination.     

Glucose-6-phosphate dehydrogenase variants: reexamination of G6PD Chicago and Cornell and a new variant (G6PD Pea Ridge) resembling G6PD Chicago

Two large and unrelated families were investigated for hereditary nonspherocytic hemolytic anemia associated with deficiency of erythrocyte glucose-6-phosphate dehydrogenase (G6PD). In both families, the kinetic and electrophoretic features of the G6PD variants resembled those of G6PD Chicago. Further investigation revealed that members of one of these families previously had been characterized as having the G6PD variants Chicago and Cornell. However, it is clear that each of these terms has been applied to the same variant in this single large kindred. In the second family, we describe a newly identified variant with unique characteristics, which we have designated G6PD Pea Ridge. G6PD Pea Ridge resembles G6PD Chicago but differs in electrophoretic mobility and in a few kinetic parameters. It exhibits an unusually high Ki for NADPH and thus appears to be insensitive to product inhibition. As other cases previously considered to be the Chicago variant become more fully characterized, this probably will be shown to be a heterogeneous group of variants.     

Demonstration of reversible priming of human neutrophils using platelet- activating factor

Exposure of neutrophils to agents such as lipopolysaccharide, tumor necrosis factor-alpha (TNF-alpha), and the granulocyte-macrophage colony-stimulating factor causes a major upregulation of subsequent agonist-induced NADPH oxidase activation. This priming effect is a prerequisite for neutrophil-mediated tissue damage and has been widely considered to be an irreversible process. We have investigated the potential for neutrophils to recover from a priming stimulus by studying the effects of platelet-activating factor (PAF). PAF did not stimulate respiratory burst activity directly, but caused a rapid (maximal at 10 minutes) and concentration-dependent (EC50 50.2 nmol/L) increase in N-formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated superoxide anion release. At time-points > 10 minutes, this priming effect spontaneously declined, with return to basal levels of fMLP- stimulated superoxide anion generation by 120 minutes. An identical priming time-course was observed with N-methyl carbamyl PAF, a nonmetabolizable analogue of PAF, indicating that the transient nature of PAF-induced priming was not secondary to PAF metabolism. Two structurally diverse PAF receptor antagonists (UK-74,505 and WEB 2086), added 10 minutes after PAF addition, increased the rate of decay of the priming effect. In contrast, TNF-alpha-induced priming, which was of a similar magnitude to that observed for PAF, was slower to evolve (maximal at 30 minutes) and remained constant for at least 120 minutes. The reversible nature of PAF-induced priming was confirmed by demonstrating that PAF-, but not TNF-alpha-, induced cell polarization (shape change) and CD11b-dependent neutrophil binding of albumin-coated latex beads was also transient, with return to basal, unstimulated levels by 120 minutes. Furthermore, cells that had spontaneously deprimed following PAF exposure retained their capacity to be fully reprimed by a subsequent addition of either PAF or TNF-alpha. These data imply that neutrophil priming is not an irreversible event: the demonstration of a cycle of complete priming, depriming, and repriming offers the potential for functional recycling of neutrophils at sites of inflammation.