Myelin development in infant brain

Myelin was isolated from subcortical areas of ten human brains, with ages ranging from 24 days to 350 days-of-age; samples were subsequently analyzed for lipid composition. Eight infants were victims of Sudden Infant Death Syndrome, and two infants were accident cases. Gray and white matter samples from each brain were also dissected and analyzed. Galactolipids were only 12% of the total lipids in white matter from brains of infants that were 24 days-of-age, a time when myelination was just starting in the subcortical areas. At 175 and 350 days of age, myelination was well underway and galactolipids measured 22% of the total lipids. Total phospholipids decreased (65% to 54%) in white matter during development, with the decrease mostly in phosphatidylcholine (23% to 15%). Even though there was little white matter present at early ages, myelin could be isolated. Surprisingly, the lipid composition of myelin, from the 24-day-infant brain was similar to that from adult brain. Galactolipids were 22% of the total lipids, cholesterol, 23%, and phospholipids, 52%. These results suggest that only subtle remodeling of myelin occurs in humans once myelination commences. All four major gangliosides were present in myelin during this first year of development. Interestingly, the yield of myelin from the 350-day-old infant subcortical white matter was similar to that from an adult. Thus major tracts in this area may have acquired most of the myelin by one year-after-birth. Since the control samples blend quite well into the developmental pattern obtained, it is believed there are no abnormalities in myelin lipids from SIDS infants.     

Isolation and characterization of plasma membrane-associated cortical granules from sea urchin eggs

Cortical granules, which are specialized secretory organelles found in ova of many organisms, have been isolated from the eggs of the sea urchins Arbacia punctulata and Strongylocentrtus pupuratus by a simple, rapid procedure. Electron micropscope examination of cortical granules prepared by this procedure reveals that they are tightly attached to large segments of the plasma membrane and its associated vitelline layer. Further evidence that he cortical granules were associated with these cell surface layers was obtained by (125)I-labeling techniques. The cortical granule preparations were found to be rich in proteoesterase, which was purified 32-fold over that detected in a crude homogenate. Similarly, the specific radioactivity of a (125)I-labeled, surface glycoprotein was increased 40-fold. These facts, coupled with electron microscope observations, indicate the isolation procedure yields a preparation in which both the cortical granules and the plasma membrane-vitelline layer are purified to the same extent. Gel electrophoresis of the membrane-associated cortical granule preparation reveals the presence of at least eight polypeptides. The major polypeptide, which is a glycotprotein of apparent mol wt of 100,000, contains most of the radioactivity introduced by (125)I-labeling of the intact eggs. Lysis of the cortical granules is observed under hypotonic conditions, or under isotonic conditions if Ca(2+) ion is present. When lysis is under isotonic conditions is induced by addition of Ca(2+) ion, the electron-dense contents of the granules remain insoluble. In contrast, hypotonic lysis results in release of the contents of the granule in a soluble form. However, in both cases the (125)I-labeled glycoprotein remains insoluble, presumably because it is a component of either the plasma membrane or the vitelline layer. All these findings indicate that, using this purified preparation, it should be possible to carry out in vitro studies to better define some of the initial, surface-related events observed in vivo upon fertilization.     

The passive transfer of protective immunity against Angiostrongylus cantonensis with immune lymph node cells from different lymphoid tissues in rats

-Yong W. K. and Dobson C. 1982. The passive transfer of proctective immunity against Angiostrongylus cantonensis with immune lymph node cells from different lymphoid tissues in rats. International Journal for Parasitology12: 423–425. Lymph node cells from the posterior cervical and mesenteric lymph nodes of immune rats passively protected syngeneic recipient rats against Angiostrongylus cantonensis better than cells from the spleen, thymic and inguinal lymph nodes either as reduced worms burdens and/or stunted growth. No antibody was detected in the sera of recipient rats after transfer of the cells and before infection which suggested that the protection was cell- rather than antibody-mediated.     

黑胸大蠊（Periplaneta fuliginosa）病毒的分离及某些特性

从黑胸大蠊(Periplaneta fuliginosa)自然罹病的虫尸中分离得到一株非包涵体病毒。将病毒悬液均匀拌入无菌饲料并供食154～169日龄黑胸大蠊健康若虫时,能使其感染、发病,死亡率可达98％以上。在电子显微镜下观察时,病毒为球形二十面体颗粒,直径约23nm。病毒悬液具有典型核蛋白紫外吸收光谱。病毒用DNase和RNase处理并经吖啶橙染色、二苯胺和苔黑酚试验及甲醛反应证明:该病毒含有单链DNA。以上特性与细小病毒科的特征有点类似。     

海三棱藨草种群的物候与分布格局研究

海三棱藨草群落是生长在海岸带滩涂原生裸地上的原生植被,在上海地区分布面积达20多万亩。本项工作研究了上海市南汇县东海农场海堤外侧滩涂上海三棱藨草种群的物候和分布格局。根据滩涂高程以及海三棱藨草种群生长状况,可以划分成三个地带,即地带A,海三棱藨草与芦苇群落交错区;地带B,海三棱藨草种群生长最适的中潮位地带;地带C,梅三棱藨草种群定居地带。由于三个地带内,生境条件不同,海三棱藨草种群的物候有明显差异。从地带A至C,海三棱藨草种群的分布格局依次为随机分布、均匀分布和随机分布或群聚分布。其空间分布格局在随时间变化的同时也在空间上改变其位置。     

Plasmid stability in a recombinant mammalian cell bioprocess

Summary A simple experimental method is devised to determine the fraction of plasmid-harboring cells in a bioprocess employing recombinant mammalian cells. The fraction of plasmid-harboring cells decreased as serum content in the growth medium decreased. The relatively higher increase in the generation time of the plasmid-harboring cell was primarily responsible for this decrease. The mathematical expression obtained for this fraction in terms of the two parameters, i.e. the generation time ratio and the plasmid-loss probability, could represent the experimental data extremely well. The numerical values of these parameters could show the inherent insight of the system. It was found that the data plot against time can draw us to a misleading conclusion of the absence of the effect of serum concentration.     

Carbohydrate, Amino acid, Phenolic and Mineral Nutrient Contents of Pepper Plants in Relation to Age-Related Resistance to Phytophthora capsici

The relationship between age-related resistance of peper plants to Phytophthora capsici and contents of carbohydrates, amino acids, phenolics and mineral nutrients in pepper stems was studied using two pepper cultivars, Hanbyul (susceptible) and Kingkun (resistant). With increasing age of pepper plants, the two cultivars, which differ in their susceptibility to Phytophthora blight, became gradually resistant to the disease. The cultivar Kingkun distinctly showed the age-related resistance to Phytophthora blight at the second branch stage. The weight of dry matter in healthy stems of pepper plants at the second branch stage was twice that at the six leaf stage. The resistant cultivar Kingkun contained lower levels of fructose, glucose and sucrose in stems than the susceptible cultivar Hanbyul at the different developmental stages. No consistent differences between the developmental stages of the plants were recognized with regard to their glucose content. However, the contents of fructose and sucrose in the cultivar Hanbyul greatly increased at the second branch stage. The levels of inositol reduced in both pepper cultivars during plant development. In view of the fact that there were only slight changes in the amount of total amino acids, it seems unlikely that there is a relationship between the amino acid metabolism and the retardation of Phytophthora infection during plant development. The amounts of total phenolic compounds in pepper stems were relatively low at the later growth stages of the plants and also in the resistant cultivar Kingkun. The contents of macroelemental nutrients such as nitrogen, phosphorus, potassium, calcium and magnesium were drastically reduced in pepper stems at the later plant growth stage. No significant differences between the cultivars or the plant growth stages were found in the silicon and microelemental nutrients such as sodium, iron, zinc and manganese. These results suggest that the expression of age-related resistance of pepper plants may be due to the morphological and nutritional changes in tissues of pepper stems during ageing, i.e. the pronounced increase in weight of dry matter, the significant decrease in amounts of mineral nutrients such as nitrogen, phosphorus, potassium, calcium and magnesium, and the tow contents of fructose, glucose and sucrose in the stem tissues.     

The distribution and localization of the stage-specific GP31 antigen from infective Ostertagia circumcincta larvae.

The 31,000 mol. wt glycoprotein (GP31) antigen of infective third-stage (L3) Ostertagia circumcincta larvae was shown, by surface labelling experiments and immunofluorescent antibody staining of whole larvae and larval sections, to be distributed internally. When transverse sections of L3 O. circumcincta, taken from the anterior pharyngeal region, were further examined by electron microscopy, after immunogold staining with rabbit anti-GP31 antiserum, the GP31 antigen was found to be specifically located in 'secretory organelles' within the cells of the oesophageal glands. By in vitro culturing L3 O. circumcincta in medium supplemented with 35S-methionine and then analysing the excretory-secretory material released by the larvae, it was found that the GP31 molecule was one of the major components of the excretory-secretory complex. The purified GP31 molecule had no detectable proteolytic activity in protein degradation assays. On examination of Triton X-100 extracts of infective larvae from other nematode parasite species, a predominant antigen similar to GP31 was found in Trichostrongylus colubriformis and Haemonchus contortus, but in Toxocara canis a minor component corresponding in mol. wt to GP31 was also detected. Based on these results the possible role of GP31 as a candidate antigen for a broad spectrum molecular vaccine against gastrointestinal nematode parasites in sheep is discussed.     

Aggregation-dependent turnover of flagellar adhesion molecules in chlamydomonas gametes

Previous studies on flagellar adhesion in chlamydomonas (Snell, W. and S. Roseman. 1979. J. Biol. Chem. 254:10820-10829.) have shown that as gametes adhere to flagella isolated from gametes of the opposite mating type, the adhsiveness of the added flagella but not of the gametes is lost. The studies reported here show that the addition of protein synthesis inhibitors (cycloheximide [CH] or anisomycin) to the medium of such cell- flagella mixtures causes the cells to lose their adhesiveness. This loss, however, occurs only after the cells have interacted with 4-8 flagella/cell and does not occur if the cells are kept in CH (7 h) without aggregating. The availability of an impotent (imp) mating type plus (MT(+)) mutant (provided by U.W. Goodenough), which adheres but is unable to undergo the fusion that normally follows adhesion, made it possible to determine whether a similar loss of adhesiveness occurs in mixtures of matting type minus (mt(-)) and imp mt(+) gametes. In the absence of inhibitor, mt(-) and imp mt(+) gametes adhered to each other (without fusing) for several hours; however, in the presence of CH or anisomycin, the gametes began to de-adhere 35 min after mixing, and, by 90 min, 100 percent of the cells were single again. This effect was reversible, and the rapid turnover of cells were single again. This effect was reversible, and the rapid turnover of molecules involved in adhesion occurred only during adhesion inasmuch as gametes pretreated for 4 h with CH were able to aggregate in CH for the same length of time as nonpretreated cells aggregated in CH. By the addition of CH at various times after the mt(-) and imp mt(+) gametes were mixed, measurements were made of the “pool size” of the molecules involved in adhesion. The pool reached a minimum after 25 min of aggregation, rapidly increased for the next 25 min, and then leveled off at the premixing level. These results suggest that flagellar adhesion in chlamydomonas causes modification of surface molecules (receptors, ligands), which brings about their inactivation and stimulates their replacement.