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181.
Marcelo R Risk Vasilios Lirofonis Ricardo L Armentano Roy Freeman 《Journal of applied physiology》2003,95(3):1207-1215
Compliance is not linear within the physiological range of pressures, and linear modeling may not describe venous physiology adequately. Forearm and calf venous compliance were assessed in nine subjects. Venous compliance was modeled by using a biphasic model with high- and low-pressure linear phases separated by a breakpoint. This model was compared with a linear model and several exponential models. The biphasic, linear, and two-parameter exponential models best represented the data. The mean coefficient of determination for the biphasic model was greater than for the linear and exponential models in the calf (biphasic 0.94 +/- 0.04, exponential 0.81 +/- 0.16, P = not significant; and linear 0.54 +/- 0.05, P < 0.05) and forearm (biphasic 0.83 +/- 0.17, exponential 0.79 +/- 0.15, P = not significant; and linear 0.51 +/- 0.06, P < 0.05). The breakpoint pressure in the biphasic model was higher in the calf than the forearm, 34.4 +/- 3.9 vs. 29.1 +/- 4.5 mmHg, P < 0.05. A biphasic model can describe limb venous compliance and delineate differences in venous physiology at high and low pressures. The steep low-pressure phase of the compliance curve extends to higher pressures in the calf than in the forearm, thereby enlarging the range of pressures over which hemodynamic regulation by the calf venous circulation occurs. 相似文献
182.
Inflorescence meristems and vegetative tissues, excised from noninduced Bougainvillea ‘San Diego Red’ plants, were cultured in vitro in media containing either 3% fructose, glucose or sucrose as carbon sources. Growth and development of young leaves were equivalent whether sucrose or fructose was used whereas floret initiation on inflorescence meristems was much greater when fructose or glucose was the carbon sources. Brief (1-3 days) exposure of inflorescence meristems to fructose at the beginning of culture and subsequent transfer to sucrose did not increase development over continuous culture in sucrose. Longer exposures (4-7 days) to fructose with subsequent transfer to sucrose did, however, increase the percentage of meristems developing florets, but such treatment did not increase development to the same level as those exposed to fructose for the entire period in vitro. During the first 18 days of culture, growth of meristems in sucrose was linear while that in fructose was exponential. There was no difference in carbohydrate requirements for floret initiation on meristems excised from short-day induced or noninduced plants, suggesting that induction does not enhance the ability of meristems to utilize sucrose. 相似文献
183.
A. Bhattacharya B. Bhattacharyya S. Roy 《Protein science : a publication of the Protein Society》1996,5(10):2029-2036
9-(Dicyanovinyl) julolidine (DCVJ) is a fluorescent probe, which binds to a unique site on the tubulin dimer and exhibits different properties that are dependent upon its oligomeric state (Kung & Reed, 1989). DCVJ binds to tubulin, the tubulin-colchicine complex, and the tubulin-ruthenium red complex equally well, but binds tighter to the ANS-tubulin complex than to tubulin alone. The energy transfer studies indicate a small amount of energy transfer with colchicine, but a significant energy transfer with ANS. It was shown previously that ruthenium red binds near the C-terminal tail region of the alpha-subunit. Ruthenium red causes major quenching of fluorescence of the tubulin-DCVJ complex, suggesting proximity of binding sites. The derived distances are consistent with DCVJ binding near the alpha beta interface, but on the opposite face of the colchicine binding site. Location of the binding site correlates with the observed effect of a different polymerized state of tubulin on the DCVJ spectroscopic properties. The effect of dimer-dimer association on DCVJ binding, at high protein concentrations (Kung & Reed, 1989), suggests that such an association may occur through lateral contacts of the elongated tubulin dimer, at least in a significant fraction of the cases. Transmission of ANS-induced conformational change to the DCVJ binding site, which is near important dimer-dimer contact sites, makes it possible that such conformational changes may be responsible for polymerization inhibition by anilino-naphthalene sulfonates. 相似文献
184.
Bonny Breckinridge DiNovo Richard Doan Roy B. Dyer Samuel Baron Norbert K. Herzog David W. Niesel 《FEMS immunology and medical microbiology》1996,15(2-3):149-158
Abstract Pathogenesis mediated by Shigella flexneri requires invasion of the gastrointestinal epithelium. It has been previously shown that HeLa cells challenged with S. flexneri show alterations in their phosphotyrosine-containing protein profile. In this report, we demonstrated that bacterial water extracts (WE) abrogated the invasion of HeLa cells by S. flexneri in a dose-dependent manner. A proteinaceous component of S. flexneri was shown to be responsible for this inhibitory activity. Proteins encoded on the 140-MDa plasmid were not responsible for the observed inhibition. WE from other Gram-negative bacteria also inhibited Shigella invasion of HeLa cells. HeLa cells pretreated with WE showed changes in the profile and the intensity of phosphotyrosine-containing protein bands. These data were consistent with a surface protein component in WE which initiated aberrant host cell signaling at the membrane which may account for the inhibition of bacterial entry. 相似文献
185.
186.
Roy RR Hodgson JA Aragon J Day MK Kozlovskaya I Edgerton VR 《Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology》1996,3(1):11-15
Electromyograms were recorded from the soleus and medial gastrocnemius muscles and tendon force from the medial gastrocnemius muscle of 2 juvenile Rhesus monkeys before, during and after Cosmos flight 2229 and of ground control animals. Recording sessions were made while the Rhesus were performing a foot pedal motor task. Preflight testing indicated normal patterns of recruitment between the soleus and medial gastrocnemius, i.e. a higher level of recruitment of the soleus compared to the medial gastrocnemius during the task. Recording began two days into the spaceflight and showed that the media gastrocnemius was recruited preferentially over the soleus. This observation persisted throughout the flight and for the 2 week period of postflight testing. These data indicate a significant change in the relative recruitment of slow and fast extensor muscles under microgravity conditions. The appearance of clonic-like activity in one muscle of each Rhesus during flight further suggests a reorganization in the neuromotor system in a microgravity environment. 相似文献
187.
The final modifications that the spermatozoa undergo correspond with the destabilization of their plasma membrane. This indispensable step facilitates the fusion of membranes and primes the signal transduction during fertilization. This destabilization is composed of a series of changes and modulation of the lipids in membranes such as cholestérol, phospholipids and glycolipids. Several differences exist in the lipid composition of the plasma, acrosome, nuclear and mitochondrial membranes of spermatozoa. The principal membrane phospholipids are phosphatidyl choline, phosphatidyl ethanolamine and sphingomyelin. Plasma membrane of sperm is also rich in polyunsaturated fatty acids (PUFA) linked to phospholipids. Such as C18∶2n?6, C20∶4n?6 and large amounts of docosahexaenoic acid (C22∶6n?6). The amount of membrane lipids in human sperm varies considerably between patients. This variation, could influence certain functional properties of the sperm cells such as their ability to undergo capacitation, the acrosome reaction and the fusion between sperm and oocyte membranes. The lipid composition of the human sperm cell can be altered during the process of freezing-thawing. A significant decrease in phospholipids (phosphatidyl choline, phosphatidyl ethanolamine), and PUFA in particular docosahexaenoic acid and arachidonic acid was observed. Human spermatozoa have a molar cholestérol/phopholipid ratio ≤1.0, and reduces during capacitation due to loss of cholestérol. In addition, the decrease in the levels of cholestérol and the methylation of phospholipids is involved in the modification of membrane fluidity and in the maturation of the sperm plasma membrane receptors. Therefore it seems that the methylation is important for the fusion between sperm and oocyte membranes. Intrinsic sperm phospholipase A2 also plays a role in the destabilization of the plasma membrane by producing of lysophospholipid. Therefore this enzyme and free fatty acids are believed to play a role in the acrosome reaction, an indispensable event facilitating the fusion between sperm and oocyte membranes. 相似文献
188.
To understand the roles of two well known tumour suppressor genes.l(2)gl andl(2)gd in normal imaginal disc development inDrosophila, we have initiated a study to examine effect of mulations of these genes on the expression of genes involved in the patterning
of the imaginal discs. In this study we show that the expression ofwingless, theDrosophila orthologue of the mammalian oncogeneWnt, is affected in the imaginal discs ofl(2)gl
4
andl(2)gd
1
mutant individuals. In the tumourous wing imaginal discs froml(2)gl mutant larvae, the pattern ofwingless expression was progressively disrupted with an increase in the area of expression, Tumourous wing imaginal discs froml(2)gd homozygous individuals exhibited progressive broadening and extension of the wingless expressing domains. We suggest thatl(2)gl andl(2)gd might be involved in regulating post embryonic expression ofWingless. 相似文献
189.
E-cadherin is a tumour/invasion suppressor gene mutated in human lobular breast cancers. 总被引:33,自引:0,他引:33
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G Berx A M Cleton-Jansen F Nollet W J de Leeuw M van de Vijver C Cornelisse F van Roy 《The EMBO journal》1995,14(24):6107-6115
Compelling experimental evidence exists for a potent invasion suppressor role of the cell-cell adhesion molecule E-cadherin. In addition, a tumour suppressor effect has been suggested for E-cadherin. In human cancers, partial or complete loss of E-cadherin expression correlates with malignancy. To investigate the molecular basis for this altered expression we developed a comprehensive PCR/SSCP mutation screen for the human E-cadherin gene. For 49 breast cancer patients the occurrence of tumour-specific mutations in the E-cadherin gene was examined. No relevant DNA changes were encountered in any of 42 infiltrative ductal or medullary breast carcinoma samples. In contrast, four out of seven infiltrative lobular breast carcinomas harboured protein truncation mutations (three nonsense and one frameshift) in the extracellular part of the E-cadherin protein. Each of the four lobular carcinomas with E-cadherin mutations showed tumour-specific loss of heterozygosity of chromosomal region 16q22.1 containing the E-cadherin locus. In compliance with this, no E-cadherin expression was detectable by immunohistochemistry in these four tumours. These findings offer a molecular explanation for the typical scattered tumour cell growth in infiltrative lobular breast cancer. 相似文献
190.
Abstract: Microsomal fractions of cerebral cortices of 15-day-old rabbits were used to study the 1-alkyl- sn -glycero-3-phosphate (AGP) acetyltransferase that generates 1-alkyl-2-acetyl- sn -glycero-3-phosphate in the de novo path of platelet-activating factor synthesis. The AGP acetyltransferase activity was inhibited by small concentrations of medium-long chain fatty acyl-CoA thioesters. In contrast, the AGP acyltransferase used oleoyl-CoA as substrate and was not inhibited by the presence of acetyl-CoA in high molar excess. The inhibition of AGP acetyltransferase was seen at concentrations of oleoyl-CoA as low as 0.5 µ M using 12.5 µ M AGP and 200 µ M acetyl-CoA. The inhibition by oleoyl-CoA was noncompetitive for the acetyl-CoA substrate. However, there was evidence that the oleoyl-CoA was competing with AGP in the acetyltransferase reaction, as the inhibition was lessened by increasing the AGP substrate concentration. Several acyl-CoA thioesters were effective as inhibitors of the AGP acetyltransferase, including oleoyl-, palmitoyl-, lauroyl-, and octanoyl-CoA. Propionyl- and butyryl-CoA were less effective as inhibitors, and propionyl-CoA was found to be a competitive inhibitor for acetyl-CoA. We have noted earlier that MgATP is an effective inhibitor of the AGP acetyltransferase and here we show that the inhibition by oleoyl-CoA can be increased by the presence of 0.1 m M MgATP. In brain ischemia, a decline in ATP levels would likely lead to a corresponding fall in acyl-CoA concentrations, thereby relieving the inhibition of AGP acetyltransferase and permitting the flow of AGP into the de novo pathway of platelet-activating factor synthesis. 相似文献