Dietary fat influences electric membrane properties of neurons in cell culture

1. SJL/J mice were maintained on semipurified diets which differed in the ratio of polyunsaturated/saturated fatty acid content (P/S). Exposure was from conception and was maintained for periods ranging from 6 to 34 weeks. 2. Neural cell cultures were prepared from dorsal root ganglia (DRG). After 6 and 20 days of culture, neuronal electric membrane properties were determined quantitatively by intracellular recording. 3. A number of significant differences were observed for the two dietary conditions. DRG from mice on the low-P/s diet had an increase in the rate of fall of both phases of repolarization which, in conjunction with the reduced action potential overshoot, led to a reduced action potential duration. This shift to shorter-duration action potentials was accompanied by a shift to more monophasic falling phases. The low-P/S neurons also exhibited a decreased afterhyperpolarization, decreased specific membrane resistance, and decreased membrane electrical time constant compared to high-P/S neurons. 4. It was concluded that the P/S ratio in the diet can have a significant effect on the electric properties of neurons. The high-P/S neurons tended to have action potentials with biphasic repolarizations and longer durations. In contrast, the low-P/S neurons tended to have action potentials with monophasic repolarizations and shorter durations. Moreover, the known ionic dependence of these two types of action potentials suggested that the low-P/S diet resulted in action potentials with a more exclusive Na dependence, while the high-P/S diet resulted in action potentials with both Na and Ca dependence.     

Structure-potential dependence of adsorbed enzymes and amino acids revealed by the surface enhanced Raman effect

Surface enhanced Raman scattering (SERS) of some enzymes (alkaline phosphatase, horseradish peroxidase and lactoperoxidase) and some amino acids (tryptophan, tyrosine and phenylalanine) on silver electrodes has been studied. The spectral band intensities of certain amino acids and amino acid residues were determined by their orientation on the surface and depended on the electrode potential (E).Abbreviations SERS surface enhanced Raman scattering - Trp tryptophan - Tyr tyrosine - Phe phenylalanine - E electrode potential - ORC oxidation-reduction cycle     

云南呈贡梁王山现代花粉雨的研究

本文通过对云南呈贡梁王山5块表土分析,初步研究了主要植物花粉的百分含量与其植物覆盖率之间的数量关系,并用校正系数R值表示。按照R值的大小,分为两组:R>1属于超代表性,包括有松、桤木、马桑、蒿和部分蕨类植物;R<1属于低代表性,包括有油杉、栲和石栎、滇青冈、栎、铁仔。在分析松粉分布特征基础上,认为昆明地区西风急流对松粉的传播是主要因素。     

Flow cytometric screening and isolation of Escherichia coli clones which express surface antigens of the oil-degrading microorganism Acinetobacter calcoaceticus RAG-1

Flow cytometry (FCM) in conjunction with immunocytochemical-labeling was used to analyze and screen a population of Escherichia coli clones containing a genomic library from the oil-degrading microorganism Acinetobacter calcoaceticus RAG-1 for the isolation of clones which expressed specific RAG-1 surface antigens. Reconstruction experiments using mixed populations indicated that RAG-1 cells could be clearly distinguished at a ratio of one RAG-1 cell to 500 Escherichia coli cells. Using this technique two clones, WM143 and WM191, were isolated and shown by restriction endonuclease cleavage and Southern hybridization to contain plasmids carrying inserts of RAG-1 DNA of 9.4 and 9.8 kb respectively.Non-common abbreviations FCM flow cytometry - FITC fluorescein-iso-thiocyanate - LB Luria broth - MM minimal salt medium - PBS phosphate buffered saline - PMSF phenylmethylsulfonyl fluoride     

Measurement of light within thin plant tissues with fiber optic microprobes

Vogelmann, T. C., Knapp, A. K., McClean, T. M. and Smith, W. K. 1988. Measurement of light within thin plant tissues with fiber optic microprobes. - Physiol. Plant. 72: 623–630.
The measurement of light with fiber optic microprobes has been extended to thin (200–300 μm) plant tissue samples. To test the method, light measurements were made in thin aqueous films and paradermal sections from 10-day-old etiolated Cucurbita pepo L. cv. Fordhook cotyledons. The measurements obtained were highly reproducible. Paradermal sections of spongy mesophyll that were irradiated with collimated light scattered light more effectively than the palisade layer of intact cotyledons. These results demonstrate that different plant tissues have different light scattering characteristics. The successful extension of the fiber optic microprobe technique to thin systems makes it possible to examine the optical properties of different cell layers within leaves and other plant organs.     

Hypertrophy without increased isometric strength after weight training

Eight men (20-23 years) weight trained 3 days.week-1 for 19 weeks. Training sessions consisted of six sets of a leg press exercise (simultaneous hip and knee extension and ankle plantar flexion) on a weight machine, the last three sets with the heaviest weight that could be used for 7-20 repetitions. In comparison to a control group (n = 6) only the trained group increased (P less than 0.01) weight lifting performance (heaviest weight lifted for one repetition, 29%), and left and right knee extensor cross-sectional area (CAT scanning and computerized planimetry, 11%, P less than 0.05). In contrast, training caused no increase in maximal voluntary isometric knee extension strength, electrically evoked knee extensor peak twitch torque, and knee extensor motor unit activation (interpolated twitch method). These data indicate that a moderate but significant amount of hypertrophy induced by weight training does not necessarily increase performance in an isometric strength task different from the training task but involving the same muscle group. The failure of evoked twitch torque to increase despite hypertrophy may further indicate that moderate hypertrophy in the early stage of strength training may not necessarily cause an increase in intrinsic muscle force generating capacity.     

Antigenic heterogeneity of strains of Saccharomyces cerevisiae and Candida albicans recognised by serum antibodies from patients with Crohn''s disease

Abstract Vitronectin, a serum and extracellular matrix protein involved in immunological reactions, interacts with Helicobacter pylori strains. Of the 20 H. pylori strains tested three strains bound more than 50% of the vitronectin added, five strains bound 25–40%, nine strains bound 10–20% and three strains bound 5–8% vitronectin. Two strains, one with high- and one with low-binding properties, were selected for further characterization of ¹²⁵I-vitronectin binding. Binding to the urea-activated ¹²⁵I-labelled vitronectin was fast, saturable and reversible when an excess of unlabelled vitronectin was added to the bacteria with bound ¹²⁵I-vitronectin. The binding was heat- and protease-sensitive, suggesting that the binding was mediated by bacterial cell-surface proteins. Since components such as fetuin and orosomucoid but not asialofetuin inhibited the binding, sialic-acid specific proteins, related to H. pylori sialic-acid specific haemagglutinins, were probably involved.     

Membrane and cytoplasmic resistivity properties of normal and sickle red blood cells

The cytoplasmic resistivities and membrane breakdown potentials of normal (AA), sickle-cell-trait (AS), and sickle (SS) red blood cells have been measured by the biophysical methodology of resistive pulse spectroscopy over a range of osmolalities. At isotonicity, the average membrane breakdown potentials are virtually identical for the three types of cells occurring at about 1150 V/cm. Average isotonic cytoplasmic resistivities are somewhat higher for the SS cells (166.7±7.49 ohm-cm) compared to the AA (147.6±1.98 ohm-cm) or AS cells (148.7±1.79 ohm-cm). As medium osmolality is varied, the differences in resistive properties become enlarged, especially at very low and very high osmolalities. At high osmolalities, both types of sickle cells show a large increase in internal resistivity compared to the normals; at low osmolality, the SS samples exhibit a distinctly different membrane breakdown characteristic, decreasing in this parameter, whereas the other two groups increase. Of the 15 SS samples tested, three displayed much higher cytoplasmic resistivities at isotonicity: 218.2±5.25 ohm-cm, compared to an average of 153.5±3.46 ohm-cm for the other 12. The relationship between these high resistivities and the subfraction of irreversibly sickled cells in the sample is discussed.     

Comparison of glucokinase in C3H/He and C58 mice that differ in their hepatic activity

Partially purified preparations of the hepatic glucokinase from C3H/He and C58 inbred mice have been used to explore the molecular basis for the observed twofold difference in activity between the strains. The single codominant gene that appears to regulate activity, the alleles of which are designated Gk^a and Gk^b, respectively, for the two strains, could represent a structural gene change. This now seems unlikely because the mouse enzyme, although showing small differences from rat glucokinase, appeared to be identical in the two strains with respect to thermal stability, electrophoretic mobility in agarose gels, and kinetic properties such as the apparent K _m values for MgATP^2– and glucose and the unique cooperative interaction with the latter substrate. The enzymes also reacted identically in a range of immunological tests (double-diffusion, immunoelectrophoresis, immune precipitation and immune inhibition assays) and ELISA immune inhibition assays indicated that the twofold difference in activity was due to a similar difference in antigenically active enzyme. Genetic control over the physiologically significant regulation of enzyme amount is therefore probable.This work has been supported in part by a grant from the British Diabetic Association and a Training Studentship to PAJ from the Medical Research Council (U.K.).