Summary The use of DNA amplification fingerprinting (DAF) as a tool for monitoring mixed microbial populations in bioreactors was evaluated. Short (8-mer or 10-mer) oligonucleotides were used to prime DNA extracts from various biological reactors during polymerase chain reaction (PCR) amplification. The reactors examined in this study included two sets of anaerobic stirred tank continuous flow bioreactors. One set of anaerobic reactors was operated under methanogenic conditions and one set was operated under sulfate-reducing conditions. The anaerobic reactor communities in the methanol-fed reactors showed extensive DAF homology. DAF was also applied to a fixed-film azo dye degrading reactor to examine the degree of uniformity of colonization of the substratum in representative regions of the reactor. This method is a quick and relatively inexpensive means of monitoring microbial community structure during biological processes. Since no cultivation of the sample is involved, the genetic profile of the community is not biased by outgrowth conditions. DAF profiles may be useful for comparisons of population changes over time or of bench-scale vs pilot-scale reactors but not adequate for assessing community diversity. 相似文献
In order to investigate the role of residues inside and outside the peptide binding cleft of the L2 molecule in peptide presentation to cytotoxic T lymphocytes (CTL), we constructed a series of point mutations in the Ld gene. We determined the effects of the mutations in the Ld molecule on the binding and recognition of an Ld-restricted CTL epitope derived from the nucleoprotein (NP) of the lymphocytic phoriomeningitis virus (LCMV). Each of the mutations within the Ld peptide binding cleft resulted in a complete loss of CTL recognition. Addition of the LCMV NP peptide to cells expressing these mutants did not increase surface Ld expression, suggesting that the mutations altered peptide binding. Mutations involving pockets D and E within the cleft affected LCMV peptide binding and recognition as drastically as those in pocket B, which was predicted to interact with a main anchor residue of the peptide. In striking contrast, the mutations located outside the cleft did not change either recognition or binding. These results demonstrate that the Ld residues in the peptide binding cleft are the main determinants dictating LCMV NP peptide binding, and that the residues in each of the pockets within the cleft play a role in this interaction. Surprisingly, one mutation outside the peptide binding cleft, T92S, abrogated CTL lysis of target cells treated with the LCMV NP peptide, but not virus-infected cells. These data show that this mutation selectively altered the presentation of the LCMV NP peptide introduced to the cell exogenously, but not endogenously. This implies that the pathway by which peptides associate with class I molecules within the cell differs from that of exogenous peptide binding. 相似文献
There is a correlation between the location of early atherosclerotic lesions and the hemodynamic characteristics at those sites. Circulating monocytes are key cells in the pathogenesis of atherosclerotic plaques and localize at sites of atherogenesis. The hypothesis that the distribution of monocyte adhesion to the vascular wall is determined in part by hemodynamic factors was addressed by studying monocyte adhesion in an in vitro flow model in the absence of any biological activity in the model wall.
Suspensions of U937 cells were perfused (Re = 200) through an axisymmetric silicone flow model with a stenosis followed by a reverse step. The model provided spatially varying wall shear stress, flow separation and reattachment, and a three-dimensional flow pattern. The cell rolling velocity and adhesion rates were determined by analysis of videomicrographs. Wall shear stress was obtained by numerical solution of the equations of fluid motion. Cell adhesion patterns were also studied in the presence of chemotactic peptide gradients.
The cell rolling velocity varied linearly with wall shear stress. The adhesion rate tended to decrease with increasing local wall shear stress, but was also affected by the radial component of velocity and the dynamics of the recirculation region and flow reattachment. Adhesion was increased in the vicinity of chemotactic peptide sources downstream of the expansion site. Results with human monocytes were qualitatively similar to the U937 experiments.
Differences in the adhesion rates of U937 cells occurring solely as a function of the fluid dynamic properties of the flow field were clearly demonstrated in the absence of any biological activity in the model wall. 相似文献
The eukaryotic initiation factor 5A (eIF-5A) has been identified as an essential cofactor for the HIV-1 trans-activator protein Rev. Rev plays a key role in the complex regulation of HIV-1 gene expression and thereby in the generation of infectious virus particles. Expression of eIF-5A is vital for Rev function, and inhibition of this interaction leads to a block of the viral replication cycle. In humans, four different eIF-5A genes have been identified. One codes for the eIF-5A protein and the other three are pseudogenes. Using a panel of somatic rodent—human cell hybrids in combination with fluorescence in situ hybridization analysis, we show that the four genes map to threedifferent chromosomes. The coding eIF-5A gene (EIF5A) maps to 17p12–p13, and the three pseudogenes EIF5AP1, EIF5AP2, and EIF5AP3 map to 10q23.3, 17q25, and 19q13.2, respectively. This is the first localization report for a eukaryotic cofactor for a regulatory HIV-1 protein. 相似文献
Abstract. A qualitative bioassay was adapted and used to determine the ability of the early post-implantation mouse embryo to synthesise interferon. Interferon production was not seen in any embryo tissue in the absence of an inducer and could only be detected in virus-induced tissue from the early 7th day of development. This induced interferon synthesis was initially confined to the trophoblast of the early 7th day embryo. It was then found in tissues of both trophoblast and inner cell mass origin in the early 8th day, and subsequently, in derivatives of the embryonic ectoderm in the 13th-day embryo. 相似文献
We surveyed a French male population for the incidence of missing or reduced upper lateral incisors (ULI). In 5,738 subjects, we observed an incidence of 1.59% with one or two reduced ULI (the other normal) and 1.90% with one or two missing ULI (the other normal or reduced), altogether, 3.49% affected subjects. Furthermore, 250 random controls were observed. Agenesis of other teeth is more frequent in propositi. Missing third molars were 12.4% in controls, 24.0% in propositi with reduced ULI and 39.6% in propositi with two missing ULI. Furthermore, agenesis of incisors, canines and premolars ranges from 0.4% in controls to 1.3% in propositi having reduced ULI and 5.0% in propositi with two missing ULI. So, propositi with reduced ULI are intermediate between the controls and the propositi with missing ULI with respect to the frequency of agenesis of other teeth. On the other hand, a different ranking is observed with respect to the teeth measurements: reduction of tooth size is more marked in propositi with reduced ULI than in propositi with missing ULI. The reduction mainly affects canines, incisors and to a lesser degree, premolars. Arch length and interpremolar diameters are smaller in propositi with missing ULI, compared with controls. 相似文献
Summary Aldolase and pyruvate kinase isozymes were investigated in cultured hepatocytes from fetal, regenerating, and 2-acetyl-aminofluorene-fed
rat liver as well as in some epithelial liver cell lines. Our results show that: (a) cell proliferation and prolonged expression
of specific isozymes were found only in cultured hepatocytes from 17-day old fetuses; (b) the fetal type of pyruvate kinase
expressed in regenerating and carcinogen-treated liver was temporarily lost only in cultured hepatocytes from regenerating
liver; (c) the adult type of aldolase and pyruvate kinase was absent in one epithelial cell line derived from a carcinogen-treated
liver and in the hepatoma tissue cell (HTC) line but was found in the Faza clone of the Reuber H35 cell line during the 50 first passages in vitro; and (d) the isozyme pattern of pyruvate kinase was always more strongly
shifted than that of aldolase.
The observations suggest that: (a) hepatocytes from carcinogen-treated liver exhibit the same lack of ability to proliferate
in primary culture as normal adult hepatocytes; (b) adult hepatocytes can produce fetal isozymes without prior cell division;
(c) pyruvate kinase is a stronger marker of dedifferentiation (retrodifferentiation) than aldolase; and (d) regulatory processes
of isozyme expression are different during ontogenesis, regeneration, and hepatocarcinogenesis.
This work was supported by the “Institut National de la Santé et de la Recherche Médicale” and the “Fondation pour la Recherche
Medicale Fran?aise” 相似文献