Chemical composition and ultrastructural changes in Scots pine needles in a forest decline area in southwestern Finland

Tree decline and deaths have been observed among 15 to 20-year-old Scots pines (Pinus sylvestris L.) in a dry heath forest in southwestern Finland. The sudden decline in height growth, the dieback of leading shoots and the yellowing of needles in young shoots in the upper part of the tree are typical symptoms of the decline of these young pines. Needle ultrastructure and chemical composition of Scots pines with or without decline and fluctuations of them in different seasons were studied. Afflicted trees were found to suffer from a deficiency in calcium and magnesium with low concentration of foliar nitrogen and phosphorus observed in all the trees studied. Ultrastructural study revealed changes characteristic of different seasons and measured nutrient status of needles. A clear reduction of membrane system in chloroplasts, especially related to Mg deficiency, was observed in most samples. The symptoms related to N deficiency, the translucent appearance of the cytoplasm and chloroplast stroma, and the elongated chloroplasts, as well as swelling of mitochondria, indicating P deficiency, were also found in the needles sampled from this forest decline area. The present study showed that it is possible to detect specific nutrient deficiency symptoms in needle ultrastructure in field samples and for use as sensitive indicators of unbalanced nutrient status.     

Studies on well-coupled Photosystem-I-enriched subchloroplast vesicles. Electron transfer by b- and c-type cytochromes in relation to the origin of the ‘slow’ electric potential component

Cytochrome redox changes and electric potential generation are kinetically compared during cyclic electron transfer in Photosystem-I-enriched and Photosystem-II-depleted subchloroplast vesicles (i.e., stroma lamellae membrane vesicles) supplemented with ferredoxin using a suitable electron donating system. In response to a single-turnover flash, the sequence of events is: (1) fast reduction of cytochrome b-563 (t_0.5 ≈ 0.5 ms) (2) oxidation of cytochrome c-554 (t_0.5 ≈ 2 ms), (3) slower reduction of cytochrome b-563 (t_0.5 ≈ 4 ms), (4) generation of the ‘slow’ electric potential component (t_0.5 ≈ 15–20 ms), (5) re-reduction of cytochrome c-554 (t_0.5 ≈ 30 ms) and (6) reoxidation of cytochrome b-563t_0.5 ≈ 90 ms). Per flash two cytochrome b-563 species turn over for one cytochrome c-554. These b-563 cytochromes are reduced with different kinetics via different pathways. The fast reductive pathway proceeds probably via ferredoxin, is insensitive to DNP-INT, DBMIB and HQNO and is independent on the dark redox state of the electron transfer chain. In contrast, the slow reductive pathway is sensitive to DNP-INT and DBMIB, is strongly delayed at suboptimal redox poising (i.e., low $\text{NADPH}\text{NADP}{}^{\mathrm{+}}$ ratio) and is possibly coupled to the reduction of cytochrome c-554. Each reductive pathway seems obligatory for the generation of about 50% of the slow electric potential component. Also cytochrome c-559_LP (LP, low potential) is involved in Photosystem-I-associated cyclic electron flow, but its flash-induced turnover is only observed at low preestablished electron pressure on the electron-transfer chain. Data suggest that cyclic electron flow around Photosystem I only proceeds if cytochrome b-559_LP is in the reduced state before the flash, and a tentative model is presented for electron transfer through the cyclic system.     

Preparation of isolated liver endothelial cells and Kupffer cells in high yield by means of an enterotoxin

A new method for preparing non-parenchymal rat liver cells (NPC) is described. The liver cell suspension, prepared by perfusing the liver with collagenase, was treated with enterotoxin from Clostridium perfringens for 15 min. The enterotoxin made the parenchymal cells leaky, and these cells could be separated from the NPC by centrifugation in a solution containing Nycodenz (20%, w/v). During the centrifugation, the NPC floated, while the parenchymal cells sedimented. The yield of NPC per liver (200 g rat) was about 250 X 10(6) cells. The NPC were further separated into endothelial cells, Kupffer cells and stellate cells by centrifugal elutriation. This method was particularly useful for preparing endothelial cells in high yield (100 X 10(6) cells per liver). Intravenously injected formaldehyde-treated albumin was selectively taken up by the endothelial cells. Isolated endothelial cells in suspension as well as in surface culture maintained their ability to endocytose this ligand.     

The binding of human milk lactoferrin to immunoglobulin A

To define the step at which translational initiation factor IF1 exercises its stimulation, initial rate kinetic analyses of 30 S initiation complex formation were carried out in the presence and absence of this factor. It was shown that, without affecting the affinity of the ribosomes either for the initiator tRNA or for the poly(AUG) used as template, IF1 increases approximately 2.5-fold the limiting Vmax of the 'pre-ternary complex'----ternary complex transition which represents the rate-limiting step in 30 S initiation complex formation. This kinetic effect titrates with the 30 S ribosomal subunit which must therefore represent the target of IF1 action.     

Lipid composition of the peripheral nerves in malnutrition: an experimental study in young rhesus monkeys

An experimental model of protein calorie malnutrition (PCM) was created in young rhesus monkeys. Ulnar and tibial nerves from six monkeys with PCM, six rehabilitated and 12 control monkeys were studied for lipid composition and activity of myelin marker enzyme. Total lipids, myelin marker lipids and activity of myelin marker enzyme, 2', 3'-cyclic nucleotide 3' - phosphohydrolase were decreased, while esterified cholesterol and free fatty acids were increased in PCM as compared to controls. There was partial recovery in myelin marker lipids and complete restoration of other lipids on nutritional rehabilitation.     

Rat liver membrane secretory component is larger than free secretory component in bile: evidence for proteolytic conversion of membrane form to free form

Secretory component is a receptor for polymeric immunoglobulins on epithelial cells and hepatocytes that facilitates transport of polymeric immunoglobulins into external secretions. Little is known about the transcellular migration of secretory component-polymeric IgA complexes or the membrane forms of secretory component. We therefore examined rat bile and liver membranes to identify and compare the various molecular species of secretory component. Bile or liver membrane proteins were electrophoresed in sodium dodecyl sulfate-polyacrylamide gels and electrophoretically transferred to nitrocellulose membranes. Protein profiles on blots were probed with antisecretory component antiserum, and the immunoreactive bands were visualized by indirect immunoperoxidase staining. Bile collected in the presence of proteolytic inhibitors showed an immunoreactive doublet band (Mr = 82,000 and 78,000) in the molecular weight range of free secretory component. By contrast, free secretory component in bile collected in the absence of proteolytic inhibitors and purified by affinity chromatography migrated as a single protein with an Mr = 70,000. Both components of the free secretory component doublet bound dimeric IgA when blots were probed with human dimeric IgA. Crude liver membranes prepared in the presence of proteolytic inhibitors showed two immunoreactive secretory component-containing bands, Mr = 107,000 and 99,000, whereas membranes prepared without proteolytic inhibitors showed two smaller immunoreactive bands; one of these proteolytically severed proteins comigrated with the 82,000-dalton free secretory component in bile. These results indicate that membrane forms of secretory component are present in rat liver. The observations that the membrane secretory component is larger than biliary free secretory component and yields biliary SC-like forms of secretory component upon proteolysis support the hypothesis that free secretory component in bile is a proteolytic product of larger liver membrane-associated secretory component.     

Studies on the damage to Escherichia coli cell membrane caused by different rates of freeze-thawing

Freeze-thawing of Escherichia coli cells caused a release of cell membrane components such as protein, phospholipids and lipopolysaccharides. A greater amount of release and a lesser extent of cell survival were seen in slow freeze-thawing than in rapid freeze-thawing. Several dehydrogenases in the cells were also freed. The mode of release was also dependent on the rate of freeze-thawing.The materials released by slow freeze-thawing were found to be mostly composed of outer membrane components, whereas the materials released by rapid freeze-thawing contained cytoplasmic as well as outer membrane components. The chemical composition of these fragments differed significantly from that of the original membranes. The relative content of cytoplasmic membrane-bound enzymes in these fragments also differed from that of the cytoplasmic membrane.The fragmentation was assumed to have resulted mainly from the crystallization of external water. In slow freeze-thawing, it was considered that the phase separation of the membrane phospholipid bilayer increased the possibility of outer membrane fragmentation. Rapid freeze-thawing caused cytoplasmic membrane damage to the cells as well as to the outer membrane. In rapid freeze-thawing, the effect of phase separation appeared to be small because of rapid passage through the transition temperatures.The presence of 10% glycerol completely inhibited the release of cellular materials and enzymes. Cell survival was maintained at a high level in the glycerol-treated samples whether freeze-thawed slowly or rapidly.     

Trypanosoma brucei: Maintenance of concentrated suspensions of bloodstream trypomastigotes in vitro using continuous dialysis for measurement of endocytosis

A continuous dialysis technique capable of maintaining concentrated suspensions of bloodstream Trypanosoma brucei (up to 4 × 10⁸/ml) at 25 C for 2 hr without loss of viability has been developed in order to measure endocytosis under controlled conditions in vitro. Using this technique, the kinetics and mechanism of uptake of the metabolically inert macromolecule, ¹²⁵I-labelled polyvinylpyrrolidone (¹²⁵I-PVP), have been investigated. Binding to the plasma membrane and the rate of uptake of ¹²⁵I-PVP from the extracellular medium by the trypanosome are both decreased by the addition of unlabelled PVP and human serum albumin. A mechanism for uptake of ¹²⁵I-PVP by a combination of fluid-phase and adsorptive endocytosis from the flagellar pocket of the trypanosome is proposed. In the presence of serum albumin and unlabelled PVP, endocytosis of ¹²⁵I-PVP occurs in the fluid phase only, with endocytic indices of 14.5 ± 0.9 and 54.1 ± 11.3 nl/hr/mg protein in vitro at 25 C and in vivo at 37 C, respectively.     

降脂红曲的菌学性质及化学成分的分析

本文对No.4降脂红曲的生理特性进行了分析,测定了其一般的化学成分,将No.4红曲米的色调和色价与其它红曲米进行了对比,确定了该红曲的最适培养条件,制定了No.4红曲米的质量标准,并验证了它可作为糖化酶的生产菌。