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31.
D L Maxwell R W Fuller C M Dixon F M Cuss P J Barnes 《Journal of applied physiology》1990,68(1):295-301
Animal studies suggest that the neuropeptides, substance P and vasoactive intestinal peptide (VIP), may influence carotid body chemoreceptor activity and that substance P may take part in the carotid body response to hypoxia. The effects of these peptides on resting ventilation and on ventilatory responses to hypoxia and to hypercapnia have been investigated in six normal humans. Infusions of substance P (1 pmol.kg-1.min-1) and of VIP (6 pmol.kg-1.min-1) were compared with placebo and with nitroprusside (5 micrograms.kg-1.min-1) as a control for the hypotensive action of the peptides. Both peptides caused significantly less hypotension than nitroprusside. Substance P and nitroprusside caused significantly greater increases in ventilation and in the hypoxic ventilatory response than VIP. No changes were seen in hypercapnic sensitivity. The stimulation of ventilation and the differential effects on ventilatory chemosensitivity that accompanied hypotension are consistent either with stimulation of carotid body chemoreceptor activity or with an interaction with peripheral chemoreceptor input to the respiratory center, as is seen in animals. The similar cardiovascular but different ventilatory effects of the peptides suggest that substance P may also stimulate the carotid body in a manner independent of the effect of hypotension. This is consistent with a role of substance P in the hypoxic ventilatory response in humans. 相似文献
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Cloning, sequencing, and expression of the structural genes for the cytochrome and flavoprotein subunits of p-cresol methylhydroxylase from two strains of Pseudomonas putida. 总被引:1,自引:0,他引:1 下载免费PDF全文
The structural genes for the flavoprotein subunit and cytochrome c subunit of p-cresol (4-methylphenol) methylhydroxylase (PCMH) from Pseudomonas putida NCIMB 9869 (National Collection of Industrial and Marine Bacteria, Aberdeen, Scotland) and P. putida NCIMB 9866 were cloned and sequenced. The genes from P.putida NCIMB 9869 were for the plasmid-encoded A form of PCMH, and the genes from P.putida NCIMB 9866 were also plasmid encoded. The nucleotide sequences of the two flavoprotein genes from P.putida NCIMB 9869 and P.putida NCIMB 9866 (pchF69A and pchF66, respectively) were the same except for 5 bases out of 1,584, and the translated amino acid sequences were identical. The nucleotide sequences of the genes for the cytochrome subunits of PCMH from the two bacteria (pchC69A and pchC66) varied by a single nucleotide in their 303-base sequences, and the translated amino acid sequences differed by a single residue at position 41 (Asp in PchC69A and Ala in PchC66). Both cytochromes had 21-residue signal sequences, as expected for periplasmic proteins, and these sequences were identical. On the other hand, no signal sequences were found for the flavoproteins.pchF69A and pchC69A were expressed, separately or together, in Escherichia coli JM109 and P.putida RA4007, with active PCMH produced in both bacteria. The E. coli-expressed flavocytochrome was purified. Our studies indicated that the E.coli-expressed subunits were identical to the subunits expressed in P.putida NCIMB 9869: molecular weights, isoelectric points, UV-visible spectra, and steady-state kinetic parameters were the same for the two sets of proteins. The subunits readily associated upon mixing two crude extracts of E.coli, one extract containing PchC69A and the other containing PchF69A. The courses of association of PchC69A and PchF69A were essentially identical for pure E. coli-expressed subunits and pure P. putida 9869-expressed subunits. E. coli-expressed PchC69A and PchF69A contained covalently bound heme and covalently bound flavin adenine dinucleotide, respectively, as the proteins expressed in nature. 相似文献
35.
The effects of acclimatization of microbial populations, compound concentration, and media pH on the biodegradation of low concentration dichloromethane emissions in biofiltration systems was evaluated. Greater than 98% removal efficiency was achieved for dichloromethane at superficial velocities from 1 to 1.5 m(3)/m(3). min (reactor residence times of 1 and 0.7 min, respectively) and inlet concentrations of 3 and 50 ppm Although acclimatization of microbial populations to toluene occurred within 2 weeks of operation start-up, initial dichloromethane acclimatization took place over a period of 10 weeks. This period was shortened to 10 days when a laboratory grown consortium of dichloromethane degrading organism, isolated from a previously acclimatized column, was introduced into fresh biofilter media. The mixed culture consisted to 12 members, which together were able to degrade dichloromethane at concentrations up to 500 mg/L. Only one member of the consortium was able to degrade dichloromethane were sustained for more than 4 months in a biofilter column receiving an inlet gas stream with 3 ppm(v) of dichloromethane acidification of the column and resulting decline in performance occurred when a 50-ppm(v) inlet concentration was used. A biofilm model incorporating first order biodegradation kinetics provided a good fit to observed concentration profiles, and may prove to be a useful tool for designing biofiltration systems for low concentration VOC emissions. (c) 1994 John Wiley & Sons, Inc. 相似文献
36.
Fuller CA 《Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology》1994,1(1):P1-P4
The physiological system responsible for the temporal coordination of an organism is the circadian timing system (CTS). This system provides two forms of temporal coordination. First, the CTS provides for synchronization of the organism with the 24 hour period of the external environment. This synchronization of the organism with the environment is termed entrainment. Second, this system also provides for internal coordination of the various physiological, behavioral, and biochemical events within the organism. When either of these two temporal relationships are disturbed, various dysfunctions can be manifest within the organism. Homeostatic capacity of other physiological systems may be reduced. Performance is decreased and sleep disorders, mental health impairment (e.g., depression), jet lag syndrome, and shift work maladaptation frequently occur. Over the last several years, several studies have evaluated the potential influence of gravity on this physiological control system by examining changes in rhythmic characteristics of organisms exposed to altered gravitational environments. The altered gravitational environments have included the microgravity of spaceflight as well as hyperdynamic fields produced via centrifugation. 相似文献
37.
Herpes simplex virus type 1 and pseudorabies virus bind to a common saturable receptor on Vero cells that is not heparan sulfate. 总被引:11,自引:10,他引:1 下载免费PDF全文
Herpes simplex virus type 1 (HSV-1) and pseudorabies virus (PRV) infect different natural hosts but are very similar in structure, replicative cycle, and entry into cultured cells. We determined whether HSV-1 and PRV use the same cellular components during entry into Vero cells, which are highly susceptible to each virus but are not from native hosts for either. UV-inactivated virions of either HSV-1 or PRV could saturate cell surfaces to block infection of challenge HSV-1 or PRV. In the presence of saturating levels for infection of either virus, radiolabeled virus bound well and in a heparin-sensitive manner. This result shows that heparan sulfate proteoglycans on Vero cells are not the limiting cellular component. To identify the virus component required for blocking, we used an HSV-1 null mutant virus lacking gB, gD, or gH as blocking virus. Virions lacking gB were able to block infection of challenge virus to the same level as did virus containing gB. In contrast, virions lacking gD lost all and most of the ability to block infection of HSV-1 and PRV, respectively. HSV-1 lacking gH and PRV lacking gp50 also were less competent in blocking infection of challenge virus. We conclude that HSV-1 and PRV bind to a common receptor for infection of Vero cells. Although both viruses bind a heparin-like cell component on many cells, including Vero cells, they also attach to a different and limited cell surface component that is bound at least by HSV-1 gD and possibly gH and to some degree by PRV gp50 but not gB. These results clearly demonstrate binding of both HSV-1 and PRV to a common cell receptor that is not heparan sulfate and demonstrate that several types of attachment occur for both viruses during infectious entry. 相似文献
38.
Difference imaging of adenovirus: bridging the resolution gap between X-ray crystallography and electron microscopy. 总被引:26,自引:6,他引:20 下载免费PDF全文
While X-ray crystallography provides atomic resolution structures of proteins and small viruses, electron microscopy provides complementary structural information on the organization of larger assemblies at lower resolution. A novel combination of these two techniques has bridged this resolution gap and revealed the various structural components forming the capsid of human type 2 adenovirus. An image reconstruction of the intact virus, derived from cryo-electron micrographs, was deconvolved with an approximate contrast transfer function to mitigate microscope distortions. A model capsid was calculated from 240 copies of the crystallographic structure of the major capsid protein and filtered to the correct resolution. Subtraction of the calculated capsid from the corrected reconstruction gave a three-dimensional difference map revealing the minor proteins that stabilize the virion. Elongated density penetrating the hexon capsid at the facet edges was ascribed to polypeptide IIIa, a component required for virion assembly. Density on the inner surface of the capsid, connecting the ring of peripentonal hexons, was assigned as polypeptide VI, a component that binds DNA. Identification of the regions of hexon that contact the penton base suggests a structural mechanism for previously proposed events during cell entry. 相似文献
39.
R W Fuller 《BMJ (Clinical research ed.)》1993,306(6884):1066-1067
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