A gene, called m‐mb‐1, was isolated from a murine pre‐B‐minus T lymphocyte subtracted library. It was found expressed as mRNA at low to medium abundance in early progenitors of the B lineage, in pre‐B and mature B lineage cell lines, in normal resting B lymphocytes and in polyclonally activated B cell blasts. The gene was not expressed in plasmacytomas, in cell lines of the monocyte/macrophage, the T lymphocyte or the fibroblast lineages, nor in thymus, liver, heart, kidney, lung or brain. The nucleotide sequence of the m‐mb‐1 gene encodes a putative membrane glycoprotein with 220 amino acids, which includes a leader sequence, a putative extracellular domain with two potential N‐glycosylation sites, a transmembrane portion and a putative intracellular domain. The partial sequence of a human homologue, h‐mb‐1, shows nearly 90% homology in nucleotide as well as amino acid sequences to the murine form of a stretch of the putative intracytoplasmic domain. Antibodies raised against a fusion protein of m‐mb‐1 with protein A, affinity purified for their m‐mb‐1 specificity, stained pre‐B and mature B cell lines on their surface, but did not stain T cell lines and fibroblasts. Antibodies raised against a stretch of 20 amino acids of the putative intracellular domain with 90% homology between the mouse and human protein did not stain the surface of any cell lines tested.(ABSTRACT TRUNCATED AT 250 WORDS)
Chlorinated phenols (CP) are frequently found as harmful
soil contaminants. Depending on the environment, CP may
persist for extended periods of time. The influence of
environmental factors on the degradation of 2,6-dichlorophenol
(2,6-DCP) in unsaturated soil was examined using Ralstonia
basilensis RK1 as inoculum for bioaugmentation. The
disappearance of 2,6-DCP in soil microcosms was caused
by bacterial mineralization. This was proved using U-14C-labeled 2,6-DCP. After 5 days of incubation, 61% of the initial
activity was detected as 14CO2, while only 20% of the
radioactivity remained in the soil, and 2,6-DCP was not
detected. The relative importance of individual factors and
possible two-factor interactions was assessed using a
fractional-factorial experimental design. The following
individual factors were identified as important: 2,6-DCP
concentration, temperature, inoculum size, and the presence
of an additional substrate. The strongest factorial
interaction was observed between bacterial inoculation
and 2,6-DCP concentration. For practical reasons, the
influence of oxygen, organic matter, and the age of the
contamination were not included in the factorial design;
however, these factors were analyzed separately and found
to significantly affect the biodegradation of 2,6-DCP. The
findings of this study are important for the design of
bioremediation techniques as well as the prediction of
natural attenuation.
Development of B cells in fetal liver occurs in one synchronous wave and involves probably no more than four critical divisions. This leads us to suggest that the main pool of proliferating progenitors that replenish the peripheral B-cell pool are progenitors before Ig gene rearrangement, that the four Ig gene rearrangements (DH to JH, VH to DHJH, VK to JK, and V lambda to J lambda) might occur in four critical divisions, and that a stromal-cell-dependent phase of pre-B development in which all rearrangements are made is succeeded by a stromal-cell-independent phase of sIG+ pre-B-cell maturation to mature mitogen-reactive B cells. We speculate on the molecular nature of the tightly controlled steps of Ig rearrangements during pre-B-cell development that might involve the pre-B-cell specific genes Vpre-B and lambda 5 and the B-lineage-specific gene mb-1 in interactions with stromal cells.
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