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121.
Retinal hemodynamics can be quantified from videoangiographic image sequences by digital image processing. Intensity changes of dye dilution curves provide dynamics parameters of the local retinal blood flow. The measuring points of dye dilution curves have to be fixed on identical image contents in each image of a complete image sequence. To obtain measurements for every pixel on the retinal surface a motion-compensated image sequence is required. A new method adapted to the compensation of eye motion and movement artifacts in Scanning Laser Ophthalmoscopy in long image sequences (300-500 images) is presented in this paper. To inhibit error propagation of time sequential motion estimation, the eye movement is divided into two dynamic movements components. The method presented permits compensation for eye motion in retinal fluorescein angiographic sequences. Owing to the short calculation times, this algorithm can be used in clinical routine. 相似文献
122.
The structure of the influenza-virus-matrix-protein (IMP) 58-66 nonapeptide, bound to the major-histocompatibility-complex-encoded human leukocyte antigen (HLA) A2 protein was studied by molecular dynamics simulation. Starting from the extra electron density map of peptides co-crystallized with HLA-A2, the nonapeptide IMP58-66 was docked residue by residue in the protein binding cleft. The complex was simulated for 100 ps in a shell of 1372 water molecules. The averaged simulated HLA-A2 conformation was found to be similar to the crystal structure (0.182 nm RMS deviation, for the backbone atoms of the alpha 1-alpha 2 domain). Nine out of the 14 hydrogen bonds observed in the antigen-binding site were reproduced in the simulation. The IMP58-66 peptide exhibits an extended conformation with kinks at positions 3 and 5. The side chains of residues 2, 3 and 9 develop van der Waals' interactions with hydrophobic pockets of HLA-A2, corresponding to polymorphic residues of the major-histocompatibility-complex-encoded proteins. Both the N-terminus and C-terminus of the nonapeptide were anchored in the antigen-binding groove by hydrogen bonds with conserved amino acids. The N-terminus was more flexible and contacts four HLA-A2 conserved tyrosines (Tyr7, Tyr59, Tyr159 and Tyr171) and Glu63 by direct or water-relayed hydrogen bonds. Water intercalation occurred only around the N-terminus of the peptide, the C-terminal carboxylate forming strong hydrogen bonds with polar residues (Tyr84 and Thr143) and a salt bridge with Lys146 all over the molecular dynamics simulation. This model is fully compatible with the recently published crystal structure of the HLA-B27 protein, complexed by a mixture of self nonapeptides. 相似文献
123.
S Jung S Kr?mer H J Schluesener T Hünig K Toyka H P Hartung 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(12):3768-3775
The mAb R73 directed to the TCR-alpha/beta of rat lymphocytes was tested for its therapeutic potential during the effector phase of experimental autoimmune neuritis (EAN) in Lewis rats. EAN can be actively induced by immunization with bovine peripheral nerve myelin, bovine P2 protein, or a peptide containing its neuritogenic epitope and serves as a model of the human Guilain-Barré syndrome. Adoptive transfer of activated P2-specific T lymphocytes also produces the monophasic disease (AT-EAN) characterized by inflammation and demyelination of peripheral nerves and highlights the central role of T lymphocytes in the pathogenesis of EAN. A single administration of the mAb R73 immediately after injection of activated P2-specific T line cells completely prevented the development of clinical and electrophysiologic signs of EAN in most animals and greatly alleviated the disease in the others. In further experiments mAb R73 was applied after the appearance of first clinical signs of EAN actively induced by immunization with a neuritogenic peptide or bovine peripheral nerve myelin. In both cases the anti-TCR-alpha/beta mAb reversed clinical signs of EAN and prevented the development of peripheral nerve dysfunction. In vivo and in vitro data suggest that impairment of Ag recognition and T cell function by occupancy of the TCR and R73-induced TCR-modulation rather than depletion of TCR-alpha/beta-bearing lymphocytes is the decisive mechanism underlying suppression of EAN that is apparent already within 48 h of the first R73 injection. 相似文献
124.
The STP-C488 open reading frame of herpesvirus saimiri encodes an oncoprotein that has transforming and tumor-inducing activities independent of the rest of the herpesvirus genome. STP-C488 protein has an unusual, membrane-associated, fibrous structure and is located primarily in perinuclear compartments. We now report that STP-C488 is phosphorylated in vivo. The phosphorylated form, which accounted for about 15% of STP-C488 in transformed cells, migrated slightly more slowly through sodium dodecyl sulfate-polyacrylamide gels than unphosphorylated STP-C488. A serine residue near the amino terminus was shown to be the site of phosphorylation. However, phosphorylation was not required for transformation of Rat-1 cells by STP-C488. 相似文献
125.
The effects of oryzalin and cytochalasin B (CB) on microtubule and actin microfilament arrays and on cell shaping were investigated in developing wheat mesophyll. Excised immature leaf sections capable of differentiating were incubated with the drugs. The behavior of the cytoskeleton was monitored by fluorescence microscopy after labeling with fluorescent dyes. Brief incubation with oryzalin (40 min, 10 microM) caused disassembly of microtubules. Recovery of microtubule arrays was comparatively slow after removal of the drug. Cells failed to establish transverse cortical bands of microtubules and transverse hoops of wall reinforcement. They expanded isodiametrically rather than longitudinally without forming lobes typical of wheat mesophyll cells. Brief treatment with CB (60 min, 20 micrograms ml-1) appeared to disrupt the microfilament arrays. Filaments recovered rapidly after removal of CB, and cells were able to shape in an apparently normal fashion. Continuous incubation at comparatively low concentration of CB (4 micrograms ml-1) appeared to cause selective loss of the fine transverse cortical microfilament arrays. Cortical transverse microtubule arrays persisted, but failed to form distinct bands in the majority of the cells. Cells were able to elongate in an almost normal fashion, but no lobes were formed. 相似文献
126.
Controlling Wine Malolactic Fermentation with Nisin and Nisin-Resistant Strains of Leuconostoc oenos 总被引:8,自引:4,他引:4
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The polypeptide nisin (100 U/ml) prevented malolactic fermentation in wines by indigenous or intentionally added lactic acid bacteria. Nisin (100 U/ml)-resistant mutants of Leuconostoc oenos were obtained and used with nisin in wine to carry out a pure-culture malolactic fermentation in the presence or absence of other lactic acid bacteria. Nisin degradation by mutants was not observed, and residual nisin was detectable in wines 4 months after it was added. Results indicated that nisin or nisin with resistant bacterial starter cultures can be used to control malolactic fermentation in wines. 相似文献
127.
Ischemia decreases the content of the adenine nucleotide translocator in mitochondria of rat kidney 总被引:2,自引:0,他引:2
The activity of the adenine nucleotide translocator is decreased at ischemia. Studies were undertaken to elucidate changes in the adenine nucleotide translocator by determining its content in mitochondria of ischemic rat kidney. After 60 min of ischemia, the content of the adenine nucleotide translocator amounted only to about 55%, of that measured in control mitochondria. At the same time, the flux control coefficient was increased. These changes paralled the well-known effects of ischemia: the decrease in oxidative phosphorylation and in adenine nucleotides. It is supposed that the decrease in the adenine nucleotide translocatar content accounts, at least partially, for the ischemia-induced impairment of mitochondria. 相似文献
128.
C-terminal analogues of neuropeptide Y (NPY) of small molecular size have been synthesized. The influence of chain length, single or multiple amino acid substitution, and segment substitutions on receptor binding, pre- and postsynaptic biological activity, and conformational properties have been investigated. Receptor binding and in vivo assays revealed biological activity for NPY Ac-25-36 that increased with increasing alpha-helicity. In attempts to stabilize the alpha-helical content, three independent types of modified NPY Ac-25-36 analogues were synthesized. Strong agonistic activities could be detected in a series of discontinuous analogues, which are constructs of N-terminal parts linked via different spacer molecules to C-terminal segments. One of the most active molecules was NPY 1-4-Aca-25-36 (Aca, epsilon-aminocaproic acid). For the first time conformational properties of a series of small NPY analogues have been investigated by CD, and correlated with biological activity and receptor binding. A C-terminal dodecapeptide segment of NPY with an amount of 50% substitution to the native C-terminal sequence of NPY was found to exhibit significant receptor binding. 相似文献
129.
D Wessels J Murray G Jung J A Hammer D R Soll 《Cell motility and the cytoskeleton》1991,20(4):301-315
Cellular and intracellular motility are compared between normal Dictyostelium amoebae and amoebae lacking myosin IB (DMIB-). DMIB- cells generate elongated cell shapes, form particulate-free pseudopodia filled with F-actin, and exhibit an anterior bias in pseudopod extension in a fashion similar to normal amoebae. DMIB- cells also exhibit a normal response to the addition of the chemoattractant cAMP, including a depression in cellular and intracellular particle velocity, depolymerization of F-actin in pseudopodia, and a concomitant increase in cortical F-actin. DMIB- cells do, however, form lateral pseudopodia roughly three times as frequently as normal cells, turn more often, and exhibit depressed average instantaneous cell velocity. DMIB- cells also exhibit a decrease in the average instantaneous velocity of intracellular particle movement and an increase in the degree of randomness in particle direction. These findings indicate that if there is functional substitution for myosin IB by other myosin I isoforms, it is at best only partial, with myosin IB being necessary for maintenance of the normal rate and persistence of cellular translocation, suppression of lateral pseudopod formation and subsequent turning, rapid intracellular particle motility, and the normal anterograde bias of intracellular particle movement. Furthermore, it is likely that the behavioral abnormalities observed here for DMIB- cells underlie the delay in the onset of chemotactic aggregation, the increase in the time required to complete streaming, and the abnormalities in morphogenesis exhibited by DMIB- cells. 相似文献
130.
C A Hales S W Musto S Janssens W Jung D A Quinn M Witten 《Journal of applied physiology》1992,72(2):555-561
The pulmonary edema of smoke inhalation is caused by the toxins of smoke and not the heat. We investigated the potential of smoke consisting of carbon in combination with either acrolein or formaldehyde (both common components of smoke) to cause pulmonary edema in anesthetized sheep. Seven animals received acrolein smoke, seven animals received a low-dose formaldehyde smoke, and five animals received a high-dose formaldehyde smoke. Pulmonary arterial pressure, pulmonary capillary wedge pressure, and cardiac output were not affected by smoke in any group. Peak airway pressure increased after acrolein (14 +/- 1 to 21 +/- 2 mmHg; P less than 0.05) and after low- and high-dose formaldehyde (14 +/- 1 to 21 +/- 1 and 20 +/- 1 mmHg, respectively; both P less than 0.05). The partial pressure of O2 in arterial blood fell sharply after acrolein [219 +/- 29 to 86 +/- 9 (SE) Torr; P less than 0.05] but not after formaldehyde. Only acrolein resulted in a rise in lung lymph flow (6.5 +/- 2.2 to 17.9 +/- 2.6 ml/h; P less than 0.05). Lung lymph-to-plasma protein ratio was unchanged for all three groups, but clearance of lymph protein was increased after acrolein. After acrolein, the blood-free extravascular lung water-to-lung dry weight ratio was elevated (P less than 0.05) compared with both low- and high-dose formaldehyde groups (4.8 +/- 0.4 to 3.3 +/- 0.2 and 3.6 +/- 0.2, respectively). Lymph clearance (ng/h) of thromboxane B2, leukotriene B4, and the sulfidopeptide leukotrienes was elevated after acrolein but not formaldehyde.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献