Effect of a hyperlipidic diet on lipid composition, fluidity, and (Na+-K+)ATPase activity of rat erythrocyte membranes

Feeding rats a hyperlipidic diet in which animals were offered daily a variety of high-energy food resulted in a significant increase of serum free fatty acids and a decrease of phospholipids with respect to controls. On the contrary, there were no significant differences in erythrocyte membrane total lipid composition between the two groups. Erythrocyte membranes showed a significant decrease in saturated fatty acid content and a significant increase in (n-6) polyunsaturated fatty acid content; (n-3) polyunsaturated fatty acids significantly decreased. Membrane fluidity, investigated by fluorescence polarization of diphenylhexatriene, significantly increased in the erythrocyte membranes of the experimental group. These results seem compatible with the decreased saturated/unsaturated fatty acid ratio. A significant decrease of (Na+-K+)ATPase activity occurred in erythrocyte membranes of the experimental group rats with respect to the controls.     

2',3'-dideoxycytidine permeation of the human erythrocyte membrane

The mechanism by which 2,3'-dideoxycytidine, an inhibitor of HIV-I infectivity, permeates the cell membrane was investigated. The influx of ddCyd into human erythrocytes was nonconcentrative. The initial velocity of both ddCyd influx and efflux was, in contrast to compounds that permeate the cell membrane via the nucleoside transporter, a linear function of nucleoside concentration in the 1 microM to 10 mM range and relatively insensitive to temperature. Furthermore, potent inhibitors of nucleoside transporter and other nucleosides were found to inhibit ddCyd influx only partially or not at all suggesting that ddCyd permeates the human erythrocyte membrane predominantly by nonfacilitated diffusion. This unusual characteristic seems to be due to the lack of 3'-hydroxyl moiety of ddCyd which appears to be an important determinant for the nucleoside carrier specificity rather than to lipid solubility itself. As far as permeation of the cell membrane is concerned ddCyd shares these properties with 2',3'-dideoxythymidine and 3'-azido-3'-deoxythymidine.     

Conformation and ion binding properties of peptides related to calcium binding domain III of bovine brain calmodulin

The conformational and ion binding properties of the sequences 93-104, 96-104, and 93-98 of domain III of bovine brain calmodulin (CaM) have been studied by CD and Tb3+-mediated fluorescence. In aqueous solution the interaction of all fragments with Ca2+ and Mg2+ ions is very weak and without any effect on the peptide conformation, which remains always random. In trifluoroethanol the interaction is very strong and the different fragments exhibit very distinct binding properties. In particular, the dodecapeptide fragment 93-104, and its N-terminal hexapeptide 98-104, bind calcium and magnesium with a very high binding constant (Kb greater than 10(5) M-1), undergoing a substantial conformational change. The structural rearrangement is particularly evident in the hexapeptide fragment, which tend to form a beta-bend. The C-terminal nonapeptide fragment 96-104 interacts with calcium and magnesium more weakly, and the binding process causes a decrease of ordered structure. These results suggest that, even in the entire dodecapeptide sequence corresponding to the loop of domain III of CaM, the calcium binding site is shifted toward the N-terminal hexapeptide segment. This interpretation is consistent with the results of crystallographic studies of CaM, which show that the calcium ions are located toward the amino terminal portion of the loop.     

Immunophenotyping of acute myeloid leukaemia: relevance of analysing different lineage-associated markers

The immunophenotype of 135 previously untreated patients with FAB defined acute myeloid leukaemia (AML) was studied at diagnosis. The panel of reagents included monoclonal antibodies (MoAb) recognising myeloid-associated determinants (CD11, CD13, CD14, CD33 and others) as well as MoAb directed towards lymphoid antigens (CD7, CD10, CD19) and TdT. The results indicate that CD13 and/or CD33 are consistently expressed in AML and only rarely in ALL blasts (131/135 + ve cases, versus 4/130 in ALL). Lymphoid antigen expression was rarely detected when CD10 and CD19 were investigated in AML (0.9% and 2% + ve cases, respectively), whereas significant positivities were found for TdT and CD7 (20% and 10% respectively). Concerning FAB subtypes, two new MoAb (LAM3 and LAM7) proved very useful in the specific recognition of AML with monocytic features. The phenotype CD13+ and/or CD33+, CD9+, HLA-DR- was found to be almost exclusive for M3 AML. The response to induction chemotherapy was analysed in CD7+ and in TdT+ patients. In the latter group a statistically significant lower response rate was found with respect to TdT-ve-AML patients.     

Stability and activity of a thermostable malic enzyme in denaturants and water-miscible organic solvents

A study was made of the effects of common protein denaturants and water-miscible organic solvents on both the stability and activity of the malic enzyme [(S)-malate:NADP+ oxidoreductase (oxaloacetate-decarboxylating); EC 1.1.1.40] from the extreme thermoacidophilic archaebacterium Sulfolobus solfataricus. At 25 degrees C, the enzyme was not inactivated in 4 M urea or 0.05% SDS over 24 h, while the half-life was 30 min in 6 M guanidine hydrochloride and 5 h in 0.075% SDS. The enzyme stability in water-miscible organic solvents at 25 degrees C is somewhat surprising: after a 24-h incubation, the enzyme was completely active in 50% dimethylformamide; it lost 15% of its initial activity in 50% methanol or 15% ethanol. However, the resistance to organic solvents was greatly reduced at higher temperatures. The enzyme was able to catalyze the malate conversion even in the presence of 1.5% Triton X-100 or sodium deoxycholate. A number of solvents were found to stimulate the malic activity independent of time. Studies with 50% methanol revealed that the activation was reversible and inversely related to the temperature; moreover, the solvent was demonstrated to exclusively affect the maximal velocity of catalysis, the Km values for both substrates being unchanged. Investigation was made to find out whether there was a correlation between enzyme stability, as well as activation, and hydrophobicity of the organic medium. The residual malic activity after incubation in the water/organic medium correlated inversely with the logarithm of the partition coefficient in octanol/H2O of the mixture used as a hydrophobicity index. On the other hand, the extent of activation depended directly on the logarithm of the molar concentration of the organic solvent required for maximal enzymatic activation. Because of its remarkable resistance to organic solvents required for maximal enzymatic activation. Because of its remarkable resistance to organic solvents and protein denaturants in general, the malic enzyme from Sulfolobus solfataricus can be considered suitable for biotechnological applications.     

Characterization and molecular cloning of Bifidobacterium longum cryptic plasmid pMB1

The small cryptic plasmid pMB1 (1.9 kb), previously isolated from Bifidobacterium longum, has been characterized by physical mapping. Two cloning vectors, pMR3 and pDG7, carrying chloramphenicol and ampicillin resistances derived from pJH101, have been electroporated in Escherichia coli.     

Fatty acids of pulmonary surfactant phosphatidylcholine from fetal rabbit lung tissue in culture. Biosynthesis of n-10 monoenoic fatty acids

We have previously reported that fetal rabbit lung tissue in organ culture produces a lamellar body material (pulmonary surfactant) with a lower percentage of disaturated phosphatidylcholine than is typically found in rabbit lung in vivo (Longmuir, K.J., C. Resele-Tiden, and L. Sykes. 1985. Biochim. Biophys. Acta. 833: 135-143). This investigation was conducted to identify all fatty acids present in the lamellar body phosphatidylcholine, and to determine whether the low level of disaturated phosphatidylcholine is due to excessive unsaturated fatty acid at position sn-1, sn-2, or both. Fetal rabbit lung tissue, 23 days gestation, was maintained in culture for 7 days in defined (serum-free) medium. Phospholipids were labeled in culture with [1-14C]acetate or [U-14C]glycerol (to follow de novo fatty acid biosynthesis), or with [1-14C]palmitic acid (to follow incorporation of exogenously supplied fatty acid). Radiolabeled fatty acid methyl esters obtained from lamellar body phosphatidylcholine were first separated by reverse-phase thin-layer chromatography (TLC) into two fractions of 1) 14:0 + 16:1 and 2) 16:0 + 18:1. Complete separation of the individual saturated and monoenoic fatty acids was achieved by silver nitrate TLC of the two fractions. Monoenoic fatty acid double bond position was determined by permanganate-periodate oxidation followed by HPLC of the carboxylic acid phenacyl esters. Lamellar body phosphatidylcholine contained four monoenoic fatty acids: 1) palmitoleic acid, 16:1 cis-9; 2) oleic acid, 18:1 cis-9; 3) cis-vaccenic acid, 18:1 cis-11; and 4) 6-hexadecenoic acid, 16:1 cis-6. In addition, 8-octadecenoic acid, 18:1 cis-8, was found in the fatty acids of the tissue homogenate. The abnormally low disaturated phosphatidylcholine content in lamellar body material was the result of abnormally high levels of monoenoic fatty acid (principally 16:1 cis-9) found at position sn-2. Position sn-1 contained normal levels of saturated fatty acid. The biosynthesis of the unusual n-10 fatty acids was observed from the start of culture throughout the entire 7-day culture period, and was observed in incubations of tissue slices of day 23 fetal rabbit lung. This is the first report of the biosynthesis of n-10 fatty acids (16:1 cis-6 and 18:1 cis-8) in a mammalian tissue other than skin, where these fatty acids are found in the secretory product (sebum) of sebaceous glands.     

灭幼脲引起两种幼虫表皮组织病变的显微观察

本文研究了灭幼脲引起黄粉(虫甲)(Tenebrio mclitor)和粘虫(Mythimna separata)幼虫的中毒征象和组织学病变.低剂量能引起幼虫蜕皮障碍,但看不到明显的组织学病变.高剂量处理,不仅引起了严重的中毒征象,而且伴有明显的组织学病变:内表皮生长停滞,真皮细胞排列异常,在内表皮和真皮细胞之间出现附加层和球状颗粒.对这些现象进行了较细致的讨论.     

蚤数量与宿主数量关系

无论在自然条件下或在人为条件下,蚤指数和染蚤率的高低与宿主密度的高低是一致的.宿主密度的升降,会导致其寄生蚤指数和染蚤率的升降. 本文讨论了宿主数量下降导致其寄生蚤数量下降的原因,仅是分析推测,提出几方面的看法.