酸敏感离子通道与脑梗死

急性脑梗死约占全部脑卒中的70%,病死率和致残率高,且极易复发。但目前针对急性脑梗死在时间窗内溶栓、抗凝等治疗手段不能从根本上切实有效地修复受损脑组织,且伴有出血等风险。寻找脑梗死形成发展的原因并予以治疗迫在眉睫。酸中毒是引起缺血性脑损伤的重要机制。大量实验研究表明,酸中毒能加重神经元的缺血性损伤,且其梗死面积与酸中毒的程度直接相关。但缺血产生的酸中毒如何引起神经元损伤的确切机制尚不明确。最近研究发现酸中毒能激活一种在中枢及周围神经中广泛存在的膜通道,即酸敏感离子通道,它对Ca2+通透,能引起细胞内Ca2+超载,同时能激活胞内酶引起细胞内蛋白质、脂类及核酸的降解,加重缺血后脑损伤。本文就酸敏感离子通道1a与脑梗死做一综述。     

黑龙江省三江平原丹顶鹤的数量分布

在地面调查的基础上,我们使用Y-11轻型飞机对黑龙江省三江平原地区的丹顶鹤的数量分布近行了调查,调查时飞行高度80米,航速140公里/小时,续航里程共3748公里。调查结果表明,丹顶鹤在三江平原主要分布在8个地区,其中嘟噜河下游、洪河自然保护区、七星河流域和兴凯湖低地是主要繁殖地,总数量共309只。     

Fibrinogen-sepharose interaction with prothrombin, prethrombin 1, prethrombin 2 and thrombin

Binding of prothrombin, prethrombin 1, prethrombin 2 and thrombin to fibrinogen-Sepharose was studied. Thrombin and prethrombin 2 bound to fibrinogen-Sepharose, while prethrombin 1 and prothrombin did not. Bound thrombin and prethrombin 2 were recovered from the column by eluting with 0.1 M NaCl/0.05 M Tris-HCl buffer (pH 7.4). The affinity of thrombin and prethrombin 2 to fibrinogen-Sepharose depended on ionic strength and reached a maximum at 50 mm concentration. Prethrombin 2 interacts with fibrinogen as well as thrombin; and prothrombin fragment 1.2 is not important in the formation of this complex. Thus, prethrombin 2, which is a precursor of thrombin without measurable enzymatic activity and which lacks the single cleavage at Arg-322-Ile-323 present in thrombin, has the same or very similar structural conformation as thrombin and has the same macromolecular substrate recognition site. These results confirm the earlier results that active center is not necessary in fibrinogen-thrombin interaction.     

Effect of aryl 4-guanidinobenzoates on the acrosin activity of human spermatozoa

Certain aryl 4-guanidinobenzoates (AGs; inhibitors of proteinases, including the sperm enzyme acrosin) have been shown to be more potent vaginal contraceptives in rabbits and less toxic than nonoxynol-9, the active ingredient of most marketed vaginal contraceptive formulations. To determine if these AGs can contact sperm and inhibit acrosin when mixed with the entire human ejaculate for a short period of time (roughly imitating clinical conditions), the inhibitors were added to semen at various concentrations for 2 min, after which the seminal plasma and unbound inhibitor were removed from the sperm by Ficoll centrifugation. Subsequently, the total arginine amidolytic activity of the spermatozoa was determined spectrophotometrically after a combined treatment that resulted in extraction, proacrosin activation, and reaction with substrate. Dose-response curves were prepared. All AGs studied were effective inhibitors of the amidolytic activity under these conditions, with ED50 values (the dose levels at which half of the acrosin associated with 10(6) sperm is inhibited) ranging from 10(-5) to 10(-7) M. To determine the effect on the proteolytic activity of individual spermatozoa, the experiment was repeated with 4'-acetamidophenyl 4-guanidinobenzoate (AGB), and the protease released from the sperm was measured by the gelatin-plate assay. The inhibition results were similar to those obtained by extraction of the spermatozoa and measurement of amidolytic activity. Thus, when mixed with the human ejaculate, AGs interact rapidly with spermatozoa to inhibit both their arginine amidolytic and proteolytic activity (probably due primarily or only to inhibition of acrosin) and remain bound even after removal of the seminal plasma. These data encourage further study of the compounds for contraceptive purposes.     

Synthesis of nucleosides labeled with tritium at the 5'-carbon atom of the ribose residue

Chemical and enzymatic syntheses of [5'-3H]adenosine, [5'-3H]guanosine, and [5'-3H]uridine have been developed. The reduction of beta-D-ribo-pentadialdo-1,4-furanosyl derivatives of corresponding bases is used in the chemical synthesis. The maximum molar activity of the labelled products was 220 TBk/mol in reactions with [3H]NaBH4 and 370-740 TBk/mol in reactions with gaseous tritium. The enzymatic synthesis was performed by the rebosylation of heterocyclic bases with nucleoside phosphorylase and [5'-3H]uridine as a ribosyl donor. Nucleoside phosphorylase is proposed to be used in the immobilized form to avoid the decrease of molar activity. Nucleosides labelled with tritium both in ribosyl and heterocyclic moieties were synthesised enzymatically.     

Lectin-gene expression in pea (Pisum sativum L.) roots

The expression of a lectin gene in pea (Pisum sativum L.) roots has been investigated using the copy DNA of a pea seed lectin as a probe. An mRNA which has the same size as the seed mRNA but which is about 4000 times less abundant has been detected in 21-d-old roots. The probe detected lectin expression as early as 4 d after sowing, with the highest level being reached at 10 d, i.e. just before nodulation. In later stages (16-d- and 21-d-old roots), expression was substantially decreased. The correlation between infection by Rhizobium leguminosarum and lectin expression in pea roots has been investigated by comparing root lectin mRNA levels in inoculated plants and in plants grown under conditions preventing nodulation. Neither growth in a nitrate concentration which inhibited nodulation nor growth in the absence of Rhizobium appreciably affected lectin expression in roots.Abbreviation cDNA copy DNA - poly(A)⁺RNA polyadenylated RNA     

Nucleotide sequence of the fixABC region of Azorhizobium caulinodans ORS571: similarity of the fixB product with eukaryotic flavoproteins, characterization of fixX, and identification of nifW.

Summary The nucleotide sequence of a 4.1 kb DNA fragment containing the fixABC region of Azorhizobium caulinodans was established. The three gene products were very similar to the corresponding polypeptides of Rhizobium meliloti. The C-terminal domains of both fixB products displayed a high degree of similarity with the -subunits of rat and human electron transfer flavoproteins, suggesting a role for the FixB protein in a redox reaction. Two open reading frames (ORF) were found downstream of fixC. The first ORF was identified as fixX on the basis of sequence homology with fixX from several Rhizobium and Bradyrhizobium strains. The second ORF potentially encoded a 69 amino acid product and was found to be homologous to a DNA region in the Rhodobacter capsulatus nif cluster I. Insertion mutagenesis of the A. caulinodans fixX gene conferred a Nif^– phenotype to bacteria grown in the free-living state and a Fix^– phenotype in symbiotic association with the host plant Sesbania rostrata. A crude extract from the fixX mutant had no nitrogenase activity. Furthermore, data presented in this paper also indicate that the previously identified nifO gene located upstream of fixA was probably a homologue of the nifW gene of Klebsiella pneumoniae and Azotobacter vinelandii.     

四川省西部鱼类寄生粘孢子虫——1.粘体虫属六新种(粘孢子纲:双壳目)

本文报导四川省西部鱼类寄生粘孢子虫粘体虫属六新种,即异型粘体虫,新种Myxosoma disparis sp.nov.,四川粘体虫,新种Myxosoma sichuanensis sp.nov.,光唇粘体虫,新种Myxosoma acrossochilusi sp.nov.鳅粘体虫,新种Myxosoma nemachilusi sp.nov.斜囊粘体虫,新种Myxosoma obliqua sp.nov.,雅安粘体虫,新种Myxosoma yaanensis sp.nov.。     

Temporal events of gypsy moth vitellogenesis and ovarian development

Abstract The vitellogenic period of gypsy moth ovarian development starts on day 3 of the pupal stage and continues through adulthood. During this period, rapid increases occur in follicle size, protein content, and wet weight of the ovary. Patency is observed on day 3 of the pupal stage.
Pre-vitellogenic follicles are formed in the last larval stadium. Newly formed follicles detach from the germarium on day 4, and increase rapidly to 140 per ovariole at the end of the last larval stadium. The pre-vitellogenic follicles are uniformly around 50 um in diameter. No vitellogenin is incorporated into the oocytes until the pupal stage.
Polyacrylamide gel electrophosesis (PAGE) in the presence of sodium dodecylsulphate (SDS) analysis of male and female haemolymph samples and vitellogenic ovaries demonstrates the presence of two female-specific subunits of vitellogenin of 180 kD and 160 kD. These proteins are detected only in haemolymph and ovarian extracts of vitellogenic females. The molecular weight of the native protein determined by size exclusion chromatography is approximately 400–420 kD.
A highly sensitive double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed to monitor the temporal changes in vitellogenin titre in haemolymph. Vitellogenin production starts on day 2 of the last larval stadium, reaching a maximum level by day 6 of the last larval stadium, and decreasing in the late pupal stage as vitellogenin was internalized into the oocytes. This is the first report of vitellogenin production occurring in the larval stage of a holometabolous insect. The fact that vitellogenin production and uptake occur during different stages of development in the gypsy moth, opens up some interesting questions concerning the underlying regulatory mechanisms controlling each process.