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31.
Characterization of the alanine racemases from two mycobacteria 总被引:2,自引:0,他引:2
D-Alanine is a necessary precursor in the biosynthesis of the bacterial peptidoglycan. The naturally occurring L-alanine isomer is racemized to its D-form through the action of a class of enzymes called alanine racemases. These enzymes are ubiquitous among prokaryotes, and with very few exceptions are absent in eukaryotes, making them a logical target for the development of novel antibiotics. The alanine racemase gene from both Mycobacterium tuberculosis and M. avium was amplified by PCR and cloned in Escherichia coli. Overexpression of the proteins in the E. coli BL21 system, both as native and as His-tagged recombinant products, has been achieved. The proteins have been purified to electrophoretic homogeneity and analyzed biochemically. A D-alanine requiring double knock-out mutant of E. coli (alr, dadX) was constructed and the cloned genes were able to complement its deficiencies. 相似文献
32.
A Capetti S Landonio P Meraviglia A Di Biagio S Lo Caputo G Sterrantino A Ammassari B Menzaghi M Franzetti GV De Socio G Pellicanò E Mazzotta A Soria M Meschiari M Trezzi L Sasset BM Celesia P Zucchi S Melzi E Ricci G Rizzardini 《PloS one》2012,7(7):e39222
Background
Long term efficacy of raltegravir (RAL)-including regimens in highly pre-treated HIV-1-infected patients has been demonstrated in registration trials. However, few studies have assessed durability in routine clinical settings.Methods
Antiretroviral treatment-experienced patients initiating a RAL-containing salvage regimen were enrolled. Routine clinical and laboratory follow-up was performed at baseline, week 4, 12, and every 12 weeks thereafter. Data were censored at week 96.Results
Out of 320 patients enrolled, 292 (91.25%) subjects maintained their initial regimen for 96 weeks; 28 discontinued prematurely for various reasons: death (11), viral failure (8), adverse events (5), loss to follow-up (3), consent withdrawal (1). Eight among these 28 subjects maintained RAL but changed the accompanying drugs. The mean CD4+ T-cell increase at week 96 was 227/mm3; 273 out of 300 patients (91%), who were still receiving RAL at week 96, achieved viral suppression (HIV-1 RNA <50 copies/mL). When analyzing the immuno-virologic outcome according to the number of drugs used in the regimen, 2 (n = 45), 3 (n = 111), 4 (n = 124), or >4 (n = 40), CD4+ T-cell gain was similar across strata: +270, +214, +216, and +240 cells/mm3, respectively, as was the proportion of subjects with undetectable viral load. Laboratory abnormalities (elevation of liver enzymes, total cholesterol and triglycerides) were rare, ranging from 0.9 to 3.1%. The mean 96-week total cholesterol increase was 23.6 mg/dL.Conclusions
In a routine clinical setting, a RAL-based regimen allowed most patients in salvage therapy to achieve optimal viral suppression for at least 96 weeks, with relevant immunologic gain and very few adverse events. 相似文献33.
Thomas D Alcock Catherine L Thomas Seosamh
Lochlainn Paula Pongrac Michael Wilson Christopher Moore Guilhem Reyt Katarina Vogel-Miku Mitja Kelemen Rory Hayden Lolita Wilson Pauline Stephenson Lars
stergaard Judith A Irwin John P Hammond Graham J King David E Salt Neil S Graham Philip J White Martin R Broadley 《Plant physiology》2021,186(3):1616
Magnesium (Mg) and calcium (Ca) are essential mineral nutrients poorly supplied in many human food systems. In grazing livestock, Mg and Ca deficiencies are costly welfare issues. Here, we report a Brassica rapa loss-of-function schengen3 (sgn3) mutant, braA.sgn3.a-1, which accumulates twice as much Mg and a third more Ca in its leaves. We mapped braA.sgn3.a to a single recessive locus using a forward ionomic screen of chemically mutagenized lines with subsequent backcrossing and linked-read sequencing of second back-crossed, second filial generation (BC2F2) segregants. Confocal imaging revealed a disrupted root endodermal diffusion barrier, consistent with SGN3 encoding a receptor-like kinase required for normal formation of Casparian strips, as reported in thale cress (Arabidopsis thaliana). Analysis of the spatial distribution of elements showed elevated extracellular Mg concentrations in leaves of braA.sgn3.a-1, hypothesized to result from preferential export of excessive Mg from cells to ensure suitable cellular concentrations. This work confirms a conserved role of SGN3 in controlling nutrient homeostasis in B. rapa, and reveals mechanisms by which plants are able to deal with perturbed shoot element concentrations resulting from a “leaky” root endodermal barrier. Characterization of variation in leaf Mg and Ca accumulation across a mutagenized population of B. rapa shows promise for using such populations in breeding programs to increase edible concentrations of essential human and animal nutrients.“Leaky” root Casparian strips lead to accumulation of two-fold greater magnesium and ∼35% greater calcium concentrations in leaves of a Brassica rapa mutant. 相似文献
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36.
Christopher Vollmers Iwijn De Vlaminck Hannah A. Valantine Lolita Penland Helen Luikart Calvin Strehl Garrett Cohen Kiran K. Khush Stephen R. Quake 《PLoS medicine》2015,12(10)
Background
It remains difficult to predict and to measure the efficacy of pharmacological immunosuppression. We hypothesized that measuring the B-cell repertoire would enable assessment of the overall level of immunosuppression after heart transplantation.Methods and Findings
In this proof-of-concept study, we implemented a molecular-barcode-based immune repertoire sequencing assay that sensitively and accurately measures the isotype and clonal composition of the circulating B cell repertoire. We used this assay to measure the temporal response of the B cell repertoire to immunosuppression after heart transplantation. We selected a subset of 12 participants from a larger prospective cohort study (ClinicalTrials.gov NCT01985412) that is ongoing at Stanford Medical Center and for which enrollment started in March 2010. This subset of 12 participants was selected to represent post-heart-transplant events, with and without acute rejection (six participants with moderate-to-severe rejection and six without). We analyzed 130 samples from these patients, with an average follow-up period of 15 mo. Immune repertoire sequencing enables the measurement of a patient’s net state of immunosuppression (correlation with tacrolimus level, r = −0.867, 95% CI −0.968 to −0.523, p = 0.0014), as well as the diagnosis of acute allograft rejection, which is preceded by increased immune activity with a sensitivity of 71.4% (95% CI 30.3% to 94.9%) and a specificity of 82.0% (95% CI 72.1% to 89.1%) (cell-free donor-derived DNA as noninvasive gold standard). To illustrate the potential of immune repertoire sequencing to monitor atypical post-transplant trajectories, we analyzed two more patients, one with chronic infections and one with amyloidosis. A larger, prospective study will be needed to validate the power of immune repertoire sequencing to predict rejection events, as this proof-of-concept study is limited to a small number of patients who were selected based on several criteria including the availability of a large number of samples and the absence or presence of rejection events.Conclusions
If confirmed in larger, prospective studies, the method described here has potential applications in the tailored management of post-transplant immunosuppression and, more broadly, as a method for assessing the overall activity of the immune system. 相似文献37.
Induction of RelB participates in endotoxin tolerance 总被引:3,自引:0,他引:3
Yoza BK Hu JY Cousart SL Forrest LM McCall CE 《Journal of immunology (Baltimore, Md. : 1950)》2006,177(6):4080-4085
38.
Juris E. Shvinka Lolita M. Pankova Ineta N. Mežbårde Leons J. Licis 《Applied microbiology and biotechnology》1989,31(3):240-245
Summary The anaerobic aerotolerant bacterium Zymomonas mobilis 113 produced superoxide (O
2
-
) and hydrogen peroxide (H2O2) under aerobic conditions. The main generators of H2O2 were glucose oxidase and superoxide dismutase (SOD). The O
2
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generation was probably related to minor alternative reduced nicotinamide adenine zinucleotide (NADH)-oxidation reactions in the electron transport chain. An increase in medium pO2 was observed during growth of Z. mobilis 113 in a batch culture. The maximum pO2 increase correlated with glucose oxidase and SOD activities. An decrease in medium pO2 value coincided with an increase in catalase activity in batch culture. Medium deoxygenation reduced the pO2 effect, yet the culture still responded with a pO2 increase after inoculation and addition of the feeding medium. We conclude that the apparent pO2 effects are related to changes in H2O2 concentration in the culture liquid. 相似文献
39.
The importance of boron nutrition for brain and psychological function 总被引:12,自引:0,他引:12
Penland JG 《Biological trace element research》1998,66(1-3):299-317
Boron (B) nutriture has been related to bone, mineral and lipid metabolism, energy utilization, and immune function. As evidence
accumulates that B is essential for humans, it is important to consider possible relationships between B nutriture and brain
and psychological function. Five studies conducted in our laboratory are reviewed. Assessments of brain electrical activity
in both animals and humans found that B deprivation results in decreased brain electrical activity similar to that observed
in nonspecific malnutrition. Assessments of cognitive and psychomotor function in humans found that B deprivation results
in poorer performance on tasks of motor speed and dexterity, attention, and short-term memory. However, little support was
found for anecdotal reports that supplementation with physiologic amounts of B helps alleviate the somatic and psychological
symptoms of menopause. Parallels between nutritional and toxicological effects of B on brain and psychological function are
presented, and possible biological mechanisms for dietary effects are reviewed. Findings support the hypothesis that B nutriture
is important for brain and psychological function in humans.
Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the US Department
of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable. The US Department
of Agriculture, Agricultural Research Service, Northern Plains Area, is an equal opportunity/affirmative action employer,
and all agency services are available without discrimination. 相似文献
40.
FACTORS INFLUENCING THE FREQUENCY OF MESOSOMES OBSERVED IN FIXED AND UNFIXED CELLS OF STREPTOCOCCUS FAECALIS 总被引:7,自引:0,他引:7 下载免费PDF全文
Mesosomes of Streptococcus faecalis (American Type Culture Collection 9790) were seen about 92% less frequently in freeze fractures of unfixed cells than in freeze fractures and sections of fixed cells. This difference in frequency was not related to any period of unbalanced macromolecular synthesis induced by chemical fixation. All measured synthetic processes (DNA, RNA, and protein synthesis, and glycerol incorporation) were halted with either osmium tetroxide (OS) or glutaraldehyde fixation. That fewer mesosomes were seen in freeze fractures of unfixed cells was probably due to the difficulty of observing cross-fractured mesosomes in this organism in the unfixed state. Unfortunately, mesosomes probably preferentially cross fracture in the unfixed state and therefore are usually only observed, infrequently, in those cases where the freeze fracture follows the surface layer of a mesosomal membrane. However, the addition of glycerol to unfixed cells, especially in the chilled state, greatly increased the frequency of observation of cytoplasmic mesosomes in freeze fractures. It is thought that glycerol, like chemical fixation, increases the number of surface-fractured mesosomes, which in turn increases the frequency of mesosome observation. It was also observed that cellular autolysis occurring during OS fixation seemingly reduced the number of mesosomes observed in thin sections and freeze fractures of OS-fixed cells. 相似文献