The characteristics of an atypical group of the family Enterobacteriaceae resembling Enterobacter cloacae were studied. The urinary tract was the most common source of these organisms, and most strains represented infections of secondary clinical significance. In contrast to typical Enterobacter strains, the atypical strains were highly susceptible to the cephalosporins; otherwise, there was a high degree of susceptibility to five other antibiotics and resistance to ampicillin except in very high concentration.

Ampicillin↗

PubMed1969

Evaluation of a reagent-impregnated strip for detection of nitrate reduction by bacterial isolates.

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Bacteria↗

PubMedDate not supplied

Quantitative MR relaxometry study of muscle composition and function in Duchenne muscular dystrophy.

Magnetic resonance imaging and maps of T1 and T2 values were used to study muscle composition in Duchenne muscular dystrophy (DMD). The mean T2 of anterior tibial muscle was 27 msec in healthy control subjects and 43 msec with increased fatty infiltration in DMD patients. In stronger DMD patients, the distribution of muscle T2 values was narrow, centered at 27 msec as in the controls, with a nonoverlapping fat peak centered at 49 msec. In weaker DMD patients, the width of the muscle T2 peak increased and the peak shifted toward the fat peak. Mean muscle T1 decreased from 1.7 to 0.6 second with increasing fatty infiltration. These results show that quantitative T1 and T2 maps may be used to assess muscle status and monitor DMD progression.

Adipose Tissue↗

PubMedDate not supplied

Porcine endogenus retrovirus transmission from pig cell line to mouse tissues but not human cells in nude mice.

The continuous shortage of human donor organs for transplantation has led to new interest in the application of pig organs. However, reports of pig endogenous retroviruses (PERV), which are able to infect human cells in vitro, have raised concerns about the transmission of PERV to the recipients or even to other community members. In this study, PK15 and human 7721 cell lines were implanted into each flank of nude mice and tumors appeared several weeks postimplantation. PERV infection was detected by PCR, using cytochrome oxidase B sequences as the specific marker for pig DNA. The results showed that PERV gag sequence were positive in mice livers, kidneys, hearts, and lungs, but no cytochrome oxidase B sequences detected, which indicates the absence of pig-mouse microchimerism. The results also showed that PERV did not infect human 7721 tumors in mice. This study confirmed the presence of PERV transmission from pig-to-mouse tissue and strengthened the concern of the risk of transmitting PERV through pig cells xenotransplantation.

Animals↗

PubMedDate not supplied

Long-term effects on HEK-293 cell line after co-culture with porcine endogenous retrovirus.

Xenotransplantation of pig organs, tissues, and cells bears the risk of interspecies transmission of porcine endogenous retrovirus (PERV). To evaluate the long-term effect of PERV infection on human cells, human embryonic kidney cell line HEK-293 cells were co-cultured with PERV produced by the porcine kidney PK15 cell line for 24 hours and the infected HEK-293 cells were continually cultured for 6 months. PERV-gag, pol gene and gag protein were detected in infected HEK-293 cells by PCR and immunofluorescent staining. PERV from the supernatant of infected HEK-293 cells was same as that from PK15 in morphology. The concentration of reverse transcriptase in the supernatant of infected HEK-293 cells was almost 200 times lower than that of PK15 cells. Except that infected HEK-293 cells doubled a little earlier than the control and infected cells grew in serum-free medium poorly, further study for cell morphology and growth showed no significant difference between infected HEK-293 cells and uninfected control. These results suggested although PERV from PK15 could infect human cells in vitro, there was no significant acute effect attributable to PERV infection on the growth of HEK-293 cells by 6 months culture.

Animals↗

PubMedDate not supplied

Protein release in recombinant Escherichia coli using bacteriocin release protein.

The effect of induction level of the bacteriocin release protein (BRP) on cell growth characteristics, protein expression, and protein release in a recombinant strain of Escherichia coli RR1 was investigated. Mitomycin C, the inducing agent, when added to the growth medium in moderate amounts (up to 200 ng/mL) was observed to enhance the release of periplasmic proteins from the cell to the fermentation broth substantially. The percentages of release of the proteins alpha-amylase and beta-lactamase were increased by factors of about 7 and 3, respectively, upon induction of the BRP. The percentage of alpha-amylase released into the broth increased from only about 5% to almost 50% with the aid of BRP. The cell growth curve and low extracellular activity of the cytoplasmic protein beta-galactosidase were indicative that cell lysis did not occur in an appreciable amount at a low induction level, with a mitomycin C concentration of less than 300 ng/mL.

Bacterial Proteins↗

PubMedDate not supplied

Continuous production of cell-free recombinant proteins using Escherichia coli.

Continuous production of extracellular recombinant protein using a previously reported periplasmic protein-release system was successfully demonstrated. The performance of the protein-releasing system was studied using two types of reactor configuration: a conventional chemostat and a chemostat with a cell-recycle system. The constitutively expressed alpha-amylase was used as a model protein. In the chemostat experiments, the total alpha-amylase activity increases with decreasing dilution rate--from 135.5 units/mL at a dilution rate of 0.05 h-1 to 2.06 units/mL at a dilution rate of 0.491 h-1. However, the percentage release of alpha-amylase remained relatively constant, at approximately 29%, in the range of dilution rates investigated. The reactor productivity of the target protein reached a maximum of 8.14 units/mL/h at a dilution rate of 0.1 h-1. Application of the releasing system for the continuous production of cell-free recombinant proteins in a cell-recycle fermentor was also studied. The reactor performance is significantly better than that of either the chemostat or the batch mode. A total productivity of alpha-amylase at 13.2 units/mL/h with 42% recovery of proteins in the cell-free form was obtained at a dilution rate of 0.397 h-1 and a bleeding rate of 9.8%.

Biotechnology↗

PubMedDate not supplied

Digital light-directed synthesis. A microarray platform that permits rapid reaction optimization on a combinatorial basis.

Solution reactions using photogenerated reagents (Gao, X.; Yu, P.; LeProust, E.; Sonigo, L.; Pellois, J. P.; Zhang, H. J. Am. Chem. Soc. 1998, 120, 12698) are a potentially powerful means for combinatorial parallel synthesis of addressable molecular microarrays. In this report, we demonstrate that this chemistry permits combinatorial screening of reaction conditions on a microarray platform. Using this method of optimization and our reaction apparatus, efficient photogenerated acids and reaction conditions suitable for removal of the acid labile protection group on 5'-O of nucleotides are identified in a short period of time. The chemistry platform demonstrated opens new avenues for rapid, simultaneous investigation of multiple reactions using different reagents and reaction parameters directly on a solid support (e.g., a glass plate). The combinatorial screening method described may be extended to include general organic reactions employing photogenerated and conventional reagents as well as a microarray reaction device. This should be especially valuable for efficient synthesis of addressable organic compound libraries.

Chemistry, Organic↗

PubMedDate not supplied

Rate of tendon gap closure in an in vitro collagen gel matrix.

Tendon gap closure was examined in a tissue culture model and found to have a similar time course as skin wound closure. Foot tendons from White Rock chickens were mounted in a collagen gel matrix and maintained with the use of Dulbecco's modified Eagle medium, containing fetal calf serum and antibiotics, for 4 weeks at 37 degrees C in an incubator. Gap distances between tendons were measured every 1 to 3 days and plotted against time as the contraction curve. After an initial lag period of 4 to 8 days, gap distance showed a progressive decrease. Gap closure rate was defined as the slope of the contraction curve, and it was found to be a function of initial gap distance (r = 0.643, p 0.045). The time necessary to reduce the initial gap distance by half had a significant correlation with the initial gap distance (r = 0.986, p < 0.001). Fibroblast migration began on days 2 to 3 after a 1- to 2-day lag period. Fibroblasts were visible in the tendon gap region before the start of collagen gel contraction. At this time, the fibroblast migration rate was 0.33 mm/day. A critical density of fibroblasts was necessary to start collagen gel contraction. Once the gap distance began to diminish, fibroblast migration measurements were hampered because the measurable area was decreasing. Collagen gel contraction reduced the measurable fibroblast migration rate by nearly half to 0.18 mm/day. A linear correlation was found between fibroblast distance traveled and time in culture during both the gel lag and gel contraction time periods. This tendon culture model may be potentially useful for wound healing studies because it allows for studies of fibroblast activity in the early lag phase when the cells populate the collagen lattice but before contraction of the gel occurs.

Journal Article↗