Meningococcal pilin: a glycoprotein substituted with digalactosyl 2,4-diacetamido-2,4,6-trideoxyhexose

Neisseria meningitidis pili are filamentous protein structures that are essential adhesins in capsulate bacteria. Pili of adhesion variants of meningococcal strain C311 contain glycosyl residues on pilin (PilE), their major structural subunit. Despite the presence of three potential N -linked glycosylation sites, none appears to be occupied in these pilins. Instead, a novel O -linked trisaccharide substituent, not previously found as a constituent of glycoproteins, is present within a peptide spanning amino acid residues 45 to 73 of the PilE molecule. This structure contains a terminal 1-4-linked digalactose moiety covalently linked to a 2,4-diacetamido-2,4,6-trideoxyhexose sugar which is directly attached to pilin. Pilins derived from galactose epimerase ( galE ) mutants lack the digalactosyl moiety, but retain the diacetamidotrideoxyhexose substitution. Both parental (#3) pilins and those derived from a hyper-adherent variant (#16) contained identical sugar substitutions in this region of pilin, and galE mutants of #3 were similar to the parental phenotype in their adherence to host cells. These studies have confirmed our previous observations that meningococcal pili are glycosylated and provided the first structural evidence for the presence of covalently linked carbohydrate on pili. In addition, they have revealed a completely novel protein/saccharide linkage.     

高苯丙氨酸血症大鼠脑内单胺类递质的研究

以3d龄Sprague-Dawley大鼠腹腔注射苯丙氨酸(Phe)诱导高苯丙氨酸血症,荧光法测定大脑皮层及其突触体中去甲肾上腺素(NE)、多巴胺(DA)和5-羟色胺(5-HT)含量;Y型电迷宫法测其学习记忆能力.结果显示:高苯丙氨酸血症大鼠大脑皮层NE、DA及5-HT含量降低38.6%～67.4%,突触体中NE、DA和5-HT含量降低51.9%～70.2%,学习记忆能力明显低于对照组.结果提示,苯酮尿症智力障碍可能与大脑皮层及其突触体中某些单胺类递质含量降低相关.     

多管藻中R－藻蓝蛋自的分离、结晶和初步晶体学研究

从青岛采集的多管藻（Ｐｏｌｙｓｉｐｈｏｎｉａｕｒｃｅｏｌａｔａ）中分离得到的Ｒ－藻蓝蛋白,在ｐＨ＝７．０的０．０５ｍｏｌ／Ｌ磷酸盐－硫酸铵缓冲液中,使用悬滴气相扩散法获得适合Ｘ光衍射分析用单晶。经Ｂｕｅｒｇｅｒ徘循照相和ＸＲＤ—１００面探测仪分析,Ｒ－藻蓝蛋白晶体属于四方晶系,空间群为Ｐ４１（３）２１２,晶胞参数：ａ＝ｂ＝１３７．５ｃ＝２１８．５α＝β＝γ＝９０°。用等比重梯度柱法测定了晶体和母液的比重分别为１．１９和１．０９。根据分子量与晶胞体积估算,一个不对称单位含有一个分子,推测它的分子聚集态形式为（αβ）３。     

催产素在脊髓水平对电针镇痛的影响

采用玻璃微电极胞外记录和脊髓表面给药的方法观察了催产素（ＯＴ）、抗催产素血清（ＡＯＴＳ）以及电针穴位对背角神经元伤害性诱发放电的影响。结果表明：电针穴位或脊髓表面施加ＯＴ可部分抑制脊髓背角神经元的伤害性诱发放电;在电针的基础上施加ＯＴ则明显加强电针的抑制效应;相反,用ＡＯＴＳ预处理后,电针的抑制作用放取消。提示ＯＴ在脊髓水平参与了对痛觉信息的调制,并与一定频率的针刺镇痛有关。     

Occurrence of glycosphingolipids in chicken egg yolk.

Chicken egg yolk was found to contain a unique glycosphingolipid pattern not seen in other types of tissue or cell. These glycosphingolipids were isolated in pure form and their structures established by sequential enzymic hydrolysis and permethylation analysis. The major gangliosides in chicken egg yolk are N-acetylneuraminosylgalactosylceramide, N-acetylneuraminosyl-lactosylceramide and di-N-acetylneuraminosyl-lactosylceramide. The only neutral glycosphingolipid found in chicken egg yolk is galactosylceramide.     

Integument and sensory nerve differentiation ofDrosophila leg and wing imaginal discs in vitro

Summary An ultrastructural analysis is presented of the cuticular and neural structures formed by the prothoracic leg and wing imaginal discs of maleDrosophila melanogaster larvae during culture in vitro with 0.2 g/ml of -ecdysone. A pupal cuticle, and subsequently an imaginal cuticle with a well-defined epicuticle and a laminated endocuticle is formed. The ultrastructure of the epidermis and of cuticular structures such as bristles, trichomes, apodemes, and tracheoles is very similar to that found in situ. Dendrites and nerve cell bodies are formed in vitro, and sensory axons form nerve bundles similar to those of normal appendages in situ, despite their isolation from the central nervous system. It is concluded that at the ultrastructural level, differentiation in vitro closely parallels the normal course of development.     

Indole alkaloid biosynthesis: Partial purification of “ajmalicine synthetase” from Catharanthus roseus

The “ajmalicine synthetase” system of $\text{Catharanthus roseus}$ has been partially purified from callus, seedlings and mature plants. On gel filtration of the cell-free extract, four β-D-glucosidase isozymes were observed in seedlings and plants. Only two were present in the callus. A protein peak at 55,000 daltons in all three materials was capable of synthesizing ajmalicine from tryptamine and secologanin in the presence of NADPH. This “ajmalicine synthetase” rapidly lost its ability to synthsize ajmalicine, but retained the β-glucosidase activity.     

The nuclear matrix: Three-dimensional architecture and protein composition

The structural filament network of the nucleus is prepared while still connected to the cytoskeleton. The relatively gentle procedure removes about 98% of the DNA and at least 86% of the histones. The matrix is bounded by an outer nuclear lamina connected to the cytoskeletal framework, as well as the inner filaments. The filaments range in diameter from 3 to 22 nm, and are organized in a three-dimensional anastomosing network in which nucleoli are enmeshed. The nuclear matrix is separated from the cytoskeletal framework by a double detergent and then partitioned into a chromatin fraction and a matrix fraction by nuclease and high salt. Two-dimensional gel electrophoresis shows that the proteins of the cytoskeleton, chromatin and nuclear matrix are very different. A major protein found in all fractions cofocuses with actin. Vimentin is largely associated with the nuclear matrix, probably as a corona external of filaments.     

Enzymatic formation of the bisfuran structure in aflatoxin biosynthesis.

A relatively stable enzyme system that converts versiconal hemiacetal acetate to versicolorin A was isolated from the soluble fraction of the homogenized cells of Aspergillus parasiticus ATCC 15517. The cell-free preparation did not require oxygen or oxidized nicotinamide adenine dinucleotide phosphate for activity, nor did it require dithiothreitol, polyclar (polyvinyl pyrrolidone), or glycerol for stabilization of activity. It was susceptible to inhibition by dichlorvos and cysteine. Isotope tracer studies revealed involvement of several intermediates in the conversion of versiconal hemiacetal acetate to versicolorin A. These findings confirm the biogenetic relationship of versiconal hemiacetal acetate and versicolorin A, and they confirm that the bisfuran ring structure in aflatoxins and related fungal metabolites is derived from the hemiacetal structure of versiconal hemiacetal acetate.     

Evaluation of antibody inhibition assays of melanoma antigens in sera to monitor tumor growth in melanoma patients

Summary It was reported previously that melanoma leukocyte-dependent antibody (LDA) in the sera of melanoma patients was inhibited by small-molecular-weight (small-mol.-wt.) glycoproteins which were similar to cell surface antigens identified in cell membrane extracts of melanoma cells. The present study was to determine whether measurement of the levels of these factors in sera may be a useful monitor of tumor growth in melanoma patients. Small-mol.-wt. fractions were obtained by gel filtration or membrane chromatography of acidified sera and tested for their ability to inhibit LDA in ⁵¹Cr release cytotoxic assays. A panel of LDA was used, consisting of three antisera from melanoma patients, which appeared relatively specific for melanoma, and three non-melanoma antisera against carcinoembryonic antigen, ₂ microglobulin, and fetal antigens. The results showed that in patients with melanoma, approximately 70% had melanoma LDA-inhibitory activity detected in the small-mol.-wt. fractions of their sera when these were tested against the panel of melanoma LDA. The specificity of the inhibitory activity for melanoma LDA was shown by failure of the serum fractions to inhibit non-melanoma LDA and by absence of inhibitory activity in equivalent serum fractions from non-melanoma carcinoma patients for melanoma LDA. The levels of melanoma LDA-inhibitory activity in the serum fractions appeared to correlate with tumor growth, as shown by clearance of the inhibitory activity after surgical removal of melanoma and reappearance in the serum of patients who subsequently developed recurrent melanoma. The 30% false-negative rate indicated that the assays could not be used to reliably exclude melanoma, but the close correlation with tumor growth and the low number of false-positive results suggested that in 70% of patients detection of these small-mol.-wt. antigens would be of value to detect recurrence from melanoma and to monitor the effectiveness of therapy.