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51.
Primary and first passage rabbit chondrocyte cultures synthesized a "free" form of hyaluronic acid (HA-f) previously characterized in rabbit cartilage. HA-f was isolated from the [3H] glcN/35SO4-labelled cell-associated-fraction (CAF) and from the culture medium by successive equilibrium centrifugations in Cs2SO4/CsCl/Cs2SO4 under low salt conditions. The culture medium HA-f appeared in the void volume of Sepharose CL-2B eluted with low salt, (0.5M sodium acetate), and was susceptible to digestion with Streptomyces hyaluronidase. HA-f aggregated purified rabbit cartilage proteoglycan monomer. These results indicated that HA-f probably subserves hyaluronic acid already complexed with proteoglycan monomer. Newly synthesized HA-f may be required for the continual formation of proteoglycan aggregates. 相似文献
52.
A. S. Paschoa M. E. Wrenn N. P. Singh F. W. Bruenger S. C. Miller M. Cholewa K. W. Jones 《Biological trace element research》1987,13(1):275-282
Several geological formations of the Utah-Colorado mining region mined for uranium ore during and after World War II had been
mined earlier for vanadium. Therefore, most miners and millers from that region were exposed to those metals’ ores or tailings
at one time or another. Preliminary investigation to determine uranium and vanadium retained in the lungs of a former uranium
miner and miller from this region, who died of lung cancer (mesothelioma), showed a high nonuniform distribution of vanadium.
This observation led to the hypothesis that the vanadium content in the lungs could be associated with inhaled particles.
Further examination of spectra of characteristic X-rays obtained by scanning particle-induced X-ray emission (microPIXE) of
an autopsy sample of this lung indicated that vanadium was indeed present in localized sites within the 20-μm spatial resolution
of the proton beam. This work points out that the microPIXE-RBS (Rutherford backscattering) test for vanadium can be used
for site localization of inhaled particles retained in the lungs. Further studies are in progress to: (i) locate uranium-bearing
particles in lung tissues of former uranium miners and millers; and (ii) evaluate the local doses of alpha radiation received
from these particles. 相似文献
53.
L D Foil T R Klei R I Miller G E Church C S Foil D D French J N Smith 《The Journal of parasitology》1987,73(2):320-326
Seasonal changes in density and spatial distribution of Onchocerca cervicalis microfilariae were studied in ventral-midline skin of 15 infected pony mares in southern Louisiana. Triple running mean analysis of data over a 13-mo period indicated that a distinct pattern exists in total microfilariae population density and in microfilariae occurrence in different levels of the dermis. Microfilariae density reaches peak levels in the spring followed by a 58% decrease in the summer, a 19% increase in the fall, and a decrease to the lowest numbers in the winter. Microfilariae were found in all levels of the skin during the spring, summer, and fall but were not found in the superficial layers of the dermis during the winter months. The population density of Culicoides variipennis, a demonstrated vector of O. cervicalis, appeared to have seasonal fluctuations similar to the changes in microfilarial density. Harmonic wave analysis of microfilariae density data in individual ponies showed that all individuals did not follow the population trend. 相似文献
54.
55.
Differences among human immunodeficiency virus strains in their capacities to induce cytolysis or persistent infection of a lymphoblastoid cell line immortalized by Epstein-Barr virus. 总被引:18,自引:12,他引:6 下载免费PDF全文
Four strains of human immunodeficiency virus (HIV) manifest consistent differences in biologic behavior after infection of the X50-7 line of human umbilical cord lymphocytes immortalized by Epstein-Barr virus (EBV). Some dilutions of the first strain examined, human T-cell lymphotropic virus type III B, which is derived from a pool of patient isolates propagated in H9 cells, caused transient cytopathic effects (CPE) followed by recovery of a subpopulation of X50-7 cells which became virus carrier cultures. Other dilutions of the same virus stock completely lysed X50-7 cells. Two other strains, RF2 and YW, both from individual patients with acquired immune deficiency syndrome, always induced complete cytolysis of X50-7 cells at all dilutions which infected the cells. However, RF2 did establish persistent infection of H9 cells. A fourth strain, PH1-MN, from a child with acquired immune deficiency syndrome-related complex, induced only transient CPE in X50-7 and H9 cells, which thereafter always recovered to form carrier cultures. For all four strains, the dilutions of HIV stocks which caused CPE corresponded to dilutions which resulted in the detection of HIV polypeptides by immunoblot. Cytolysis in HIV-infected X50-7 cells was accompanied by a decrease in the amount of EBV nuclear antigen; however, HIV infection did not induce EBV replication. Thus CPE in X50-7 cells is due to replication of HIV per se and not to activation of EBV. The observations indicate that there are differences in the cytolytic properties of HIVs and that these differences are influenced by the target cell. 相似文献
56.
Membrane Transport in Isolated Vesicles from Sugarbeet Taproot: III. Effects of Fluoride on ATPase Activity and Transport 下载免费PDF全文
The effects of fluoride on the tonoplast type ATPase and transport activities associated with sealed membrane vesicles isolated from sugarbeet (Beta vulgaris L.) storage tissue were examined. This anion had two distinct effects upon the proton-pumping vesicles. When ATP hydrolysis was measured in the presence of gramicidin D, significant inhibition (approximately 50%) only occurred when the fluoride concentration approached 50 millimolar. In contrast, the same degree of inhibition of proton transport occurred when the fluoride concentration was about 24 millimolar. Effects on proton pumping at this concentration of fluoride could be attributed to an inhibition of chloride movement which serves to dissipate the vesicle membrane potential. Valinomycin could partially restore ATPase activity in sealed vesicles which were inhibited by fluoride and this restoration occurred with a reduction in the membrane potential. Fluoride demonstrated a competitive interaction with chloride-stimulation of proton transport and inhibited the uptake of radioactive chloride into sealed vesicles. When the vesicles were allowed to develop a pH gradient in the absence of KCl, and KCl was subsequently added, fluoride reduced enhancement of the existing pH gradient by KCl. The results are consistent with a chloride carrier that is inhibited by fluoride. 相似文献
57.
Low birth weight (LBW) is associated with a large number and variety of risk conditions during pregnancy. The number and types of risk conditions per pregnancy were determined in 1,864 white and 872 black mothers delivered at the University of Kansas Medical Center between 1975 and 1978. The incidence of LBW infants increased steadily among white and black mothers as the number of risk factors increased from none to three or four per pregnancy. Among pregnancies without spontaneous premature rupture of membranes (PROM), 51 percent of the LBW infants were born to mothers who had multiple risk factors associated with their pregnancies, even though only 18 percent of these pregnancies were associated with multiple risk factors. Among pregnancies with PROM, 72 percent were associated with multiple risk conditions, and 31 percent resulted in LBW infants. About 90 percent of LBW infants from PROM pregnancies had mothers with multiple risk factors. For all numbers of risk conditions, black mothers had a higher incidence of LBW infants than white mothers. Among black mothers without spontaneous premature rupture of membranes (PROM), the incidence of LBW infants increased from 3.2 percent (10/308) in low (zero)-risk condition pregnancies to 33 percent (16/49) among mothers with three or four risk conditions during the pregnancy. Among white mothers without PROM, the incidence of LBW infants increased from 1.7 percent (12/708) in low (zero)-risk condition pregnancies to 30 percent (19/64) in pregnancies with three or four risk conditions.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
58.
Summary This workshop was an impromptu event, but the fact that a number of interesting problems were identified by the participants from the floor may indicate that it is worth repeating. If it is to be repeated, however, it is important that notice be given, and that the scope of the workshop be defined in advance, so that participants can be better informed and bring supporting data. The best approach would be to identify a convenor and define the scope of the workshop prior to the first circular for the next Seaweed Symposium; invitations could then be issued by the convenor for specific topics and data, and a very brief program could be issued with the third circular. Such a procedure may very well allow the identification of new areas for research. 相似文献
59.
60.
Contraction of filaments of Escherichia coli after disruption of cell membrane by detergent. 总被引:7,自引:5,他引:2 下载免费PDF全文
The osmotic pressure within a living bacterium creates stresses in the peptidoglycan that stretch the sacculus. We measured the amount of stretch by monitoring the shrinkage of growing cells of Escherichia coli after removal of the osmotic pressure by disruption of the phospholipid membranes with sodium dodecyl sulfate. Because the rods of the wild type are so short, length changes of filaments of longer than 7 microns were measured on phase-contrast micrographs. The filaments were prepared by growing ftsA and ftsI strains under permissive conditions in rich medium and then shifting them to 42 degrees C for 40 to 180 min. During this time, the mutant cells became elongated but did not divide. The growing filaments were mounted on a glass surface that had been treated with poly-L-lysine or RNase. The filaments were photographed before being treated with sodium dodecyl sulfate. The filaments were rephotographed at the time when the first change in phase contrast was noted. Some filaments were also measured at 10-min time intervals from 0 to 60 min. The reduction in phase contrast signaled the leakage of solutes and the loss of turgor pressure. The average length of the filaments decreased 17%. If the circumference were stretched to the same degree, then the surface area in vivo would be 45% greater than in the relaxed state. For comparison, a fully cross-linked monolayer of E. coli peptidoglycan in its most compact conformation could stretch up to 300% in achieving the most extended conformation possible without splitting covalent bonds. 相似文献