异落新妇甙的结构研究

从百合科菝葵属植物土茯苓(Smilaxg labra Roxb.)根茎的乙醇提取物中分得一个新的天然化合物(I),命名为异落新妇甙(isoastilbin)。根据元素分析,UV,IR,¹H-NMR,¹³C-NMR,2DNMR及FAB-MS,确定化合物I的结构为5,7,3',5'-四羟基二氢黄酮醇-3-O-α-L-鼠李糖甙。     

一些保肝药物对原代培养大鼠肝细胞糖原合成功能的影响

本文参照PO Seglen的方法并加以修改,建立了原代培养大鼠肝细胞糖原合成功能的测定体系。观察到联苯双酯既能使正常肝细胞合成糖原增加88%,又能保护肝细胞完全拮抗四氯化碳对其功能的损伤;银耳多糖能使四氯化碳对肝细胞糖原合成功能的损伤减轻57%;去甲斑蝥素10μg/ml能增加肝细胞糖原合成,浓度增加到100μg/ml时,此作用减弱,1000μg/ml则明显抑制糖原的合成,而且在10～100μg/ml浓度时,即能加强四氯化碳的损伤作用;100μg/ml CL₁₅₀₀和熊果酸二钠单独应用可增加肝细胞糖原合成,但与四氯化碳同时应用,反而加重对糖原合成的抑制作用。     

Secretion of vascular endothelial growth factor/vascular permeability factor from human luteinized granulosa cells is human chorionic gonadotrophin dependent

Vascularization is a prominent event during corpus luteum formation, providing low density lipoproteins for steroid biosynthesis and enabling transport of secreted steroids. The process of vascularization is controlled by specific regulators. Vascular endothelial growth factor (VEGF), otherwise named vascular permeability factor (VPF), induces endothelial cell proliferation as well as angiogenesis in vivo and increases capillary permeability. Here we report the expression of VEGF/VPF mRNA by cultured human luteinized granulosa cells (GC) for at least 10 days. Without HCG VEGF/VPF expression declined after day 4 and by day 10 was reduced to approximately 30% of the value at day 4. However, after culture in the presence of 1 U/ml human chorionic gonadotrophin (HCG), expression of VEGF/VPF mRNA by GC was four times greater than control experiments by day 10, and increased 100% from day 4 to day 10. Simultaneously, HCG supplementation increased VEGF/VPF secretion by GC. Medium VEGF/VPF on day 3 was 13 pM without and 11 pM with HCG. Medium VEGF/VPF on day 10 was 6 pM without HCG and 29 pM with HCG. These results suggest that vascularization of the corpus luteum is induced by HCG-mediated effects of VEGF/VPF.      

The UTX gene escapes X inactivation in mice and humans

We recently have identified a ubiquitously transcribed mouse Y chromosome gene, Uty , which encodes a tetratricopeptide repeat (TPR) protein. A peptide derived from the UTY protein confers H-Y antigenicity on male cells. Here we report the characterization of a widely transcribed X-linked homologue of Uty , called Utx , which maps to the proximal region of the mouse X chromosome and which detects a human X-linked homologue at Xp11.2. Given that Uty is ubiquitously transcribed, we assayed for Utx expression from the inactive X chromosome (Xi) in mice and found that Utx escapes X chromosome inactivation. Only Smcx and the pseudoautosomal Sts gene on the mouse X chromosome have been reported previously to escape inactivation. The human UTX gene was also found to be expressed from Xi. We discuss the significance of these data for our understanding of dosage compensation of X-Y homologous genes in humans and mice.      

Tissue and lineage-specific variation in inactive X chromosome expression of the murine Smcx gene

To understand how gene expression patterns are established on the inactive X chromosome during development, we have studied the murine gene Smcx, which is expressed from both the active and inactive mouse X chromosomes. In all tissues assayed, Smcx only partially escapes X inactivation, with expression levels from the inactive X allele approximately 30-65% that of the active X allele. Additionally, inactive X expression levels differed between extraembryonic and embryonic tissues and among different tissues from newborn and adult mice. Imprinted extraembryonic tissue had the lowest levels of inactive X Smcx expression, whereas the highest levels were in heart. These data suggest that the chromosomal basis of X inactivation differs among tissues, perhaps reflecting differences in the timing or regulation of inactivation in these cell lineages.      

The mouse Mid1 gene: implications for the pathogenesis of Opitz syndrome and the evolution of the mammalian pseudoautosomal region

We have recently reported isolation of the gene responsible for X- linked Opitz G/BBB syndrome, a defect of midline development. MID1 is located on the distal short arm of the human X chromosome (Xp22. 3) and encodes a novel member of the B box family of zinc finger proteins. We have now cloned the murine homolog of MID1 and performed preliminary expression studies during development. Mid1 expression in undifferentiated cells in the central nervous, gastrointestinal and urogenital systems suggests that abnormal cell proliferation may underlie the defect in midline development characteristic of Opitz syndrome. We have also found that Mid1 is located within the mouse pseudoautosomal region (PAR) in Mus musculus , while it seems to be X- specific in Mus spretus. Therefore, Mid1 is likely to be a recent acquisition of the M. musculus PAR. Genetic and FISH analyses also demonstrated a high frequency of unequal crossovers in the murine PAR, creating spontaneous deletion/duplication events involving Mid1. These data provide evidence for the first time that genetic instability of the PAR may affect functionally important genes. In addition, we show that MID1 is the first example of a gene subject to X-inactivation in man while escaping it in mouse. These data contribute to a better understanding of the molecular content and evolution of the rodent PAR.      

Topographic organization of somatosensory corticotectal influences in cat

Using electrophysiological techniques, the present study demonstrated that substantial direct somatosensory cortical influences on the superior colliculus (SC) originate from three areas: a) SIV, b) para-SIV (the cortex adjacent to SIV but deeper in the anterior ectosylvian sulcus (AES) and for which no topography has yet been described), and c) the rostral suprasylvian sulcus. Influences also appeared to originate from SI and SII, but these may have been indirect. Detailed examination of the AES revealed that these corticotectal projections are topographically organized, and stimulation of a given cortical locus was observed to affect only those cells in the SC whose receptive fields overlapped those of cells at the stimulation site. A similar receptive-field register was found between the suprasylvian sulcus and the SC. Within this topographic pattern, considerable convergence was evident and an individual SC cell could be influenced from a surprisingly large cortical area. This was particularly evident within the representation of the forelimb. Thus, an SC cell with a receptive field covering the forelimb and paw could receive convergent input from many cortical cells with receptive fields covering all or restricted portions of this body region. Considerable corticotectal divergence also was observed within this general topographic scheme. For example, a given corticotectal site representing the digits sent projections to many different SC cells that included the digits within their receptive fields. These data are more consistent with a block-to-block than a point-to-point corticotectal projection. Somatosensory corticotectal projections excited only those SC cells that could also be activated by peripheral somatosensory stimuli. Similarly, the caudal AES, which contains auditory cells, excited only those SC cells activated also by peripheral auditory stimuli. Yet convergent influences from both auditory and somatosensory regions of the AES were observed in the SC cells that could be activated by both auditory and somatosensory stimuli. These data indicate that the AES is a major source of excitatory input to cells of the deep laminae of the SC. Since it is these deep laminae cells that project to premotor regions of the brain stem and the spinal cord, it is reasonable to suppose that the AES has a significant impact on the output signals of the SC that initiate the orientation responses to peripheral sensory stimulation.     

Effects of cooling somatosensory cortex on response properties of tactile cells in the superior colliculus

The corticotectal influences of somatosensory cortex were investigated by using reversible deactivation of cortex by cooling. More than half of the somatosensory superior colliculus (SC) cells studied exhibited a response depression (often not apparent qualitatively) or an elimination of responses to somatosensory stimuli during the period in which cortex was rendered inactive. Responses were restored to their initial levels by cortical rewarming. Hyperresponsiveness was never observed as a consequence of cortical cooling. Susceptibility to cooling-induced depression was not invariably linked to a specific cell type, location in the SC, or receptive-field size. Yet cells that had small receptive fields and were activated by hair displacement had the highest probability of being affected by this procedure. In some cells a contraction of the receptive field was induced by cortical cooling. This observation is consistent with previous experiments that showed that SC somatosensory receptive fields are constructed by the convergence of ascending and descending inputs and indicates that the responsiveness of specific receptive-field regions may depend on the functional integrity of cortex. Two cortical regions were found to produce cooling-induced effects in somatosensory SC cells: 1) SIV (and para-SIV), located in the anterior ectosylvian sulcus, and 2) the cortex within the rostral suprasylvian sulcus. These results indicate that somatosensory cortex, like visual cortex, plays a critical role in modulating the responses of SC cells. Apparently, the ability of both somatosensory and visual SC cells to code the presence of peripheral stimuli depends largely on the functional influences of their respective cortices. However, in contrast to previous observations on visual corticotectal influences, no specific receptive-field properties could be shown to be impressed on SC cells by somatosensory cortex.