Determination of trace levels of fatty acid metal salts by high-performance liquid chromatography with fluorescence prelabeling

A simple method is described for picomole determinations of fatty acid metal salts. Fatty acid salts are directly labeled with 4-bromomethyl-7-methoxycoumarin in the presence of excess ethylenediaminetetraacetic acid tripotassium salt without any solvent extractions. The fluorescence derivatives of fatty acids are separated by reverse-phase high-performance liquid chromatography followed by fluorometric detection. The response of each fatty acid (C8-C18) calcium salt is linear from 1 to 50 micrograms/ml of samples. The detection limit is about 7 pmol. Good recoveries are obtained for the calcium salts of myrystic acid and soap (C8-C18, C18:1,2). The new method is successfully applied to the study on biodegradation of fatty acids in river water.     

Granulocyte colony-stimulating factor synergistically augments 1,25-dihydroxyvitamin D3-induced monocytic differentiation in murine bone marrow cell cultures.

In a series of studies, we have reported that 1,25-dihydroxyvitamin D (3), a known stimulator of monocytic differentiation, primes bone marrow progenitor cells or promyelocytic HL-60 cells to the actions of several factors involved in both monocytic and granulocytic differentiation. In the present study, we have further examined the combinational effects of 1,25-dihydroxyvitamin D (3) and the other inducer of granulopoiesis, granulocyte colony-stimulating factor, on non-fractionated native murine bone-marrow cell culture. Over 6 days of treatment, human granulocyte colony-stimulating factor sustained cell viability, increased the size of small rounded non-adherent cells, and induced granulocytic differentiation, while 1,25-dihydroxyvitamin D (3) decreased cell viability, promoted the development of large adherent flattened cells, and upregulated some monocytic differentiation markers. Combining these two factors over 6 days synergistically upregulated phagocyte activity, membrane-bound interleukin-1alpha, NAD(P)H oxidase, monocytic Mac-1, and non-specific esterase. Similar effects were observed in successive treatment with granulocyte colony-stimulating factor followed by 1,25-dihydroxyvitamin D (3), but successive treatment in reverse order was somewhat less effective. No combinational treatment upregulated granulocytic lactate dehydrogenase, Gr-1, or chloroacetate esterase to as great an extent as was obtained with granulocyte colony-stimulating factor alone, indicating that granulocytic differentiation is attenuated by addition of 1,25-dihydroxyvitamin D (3). Therefore, in contrast to our previous data, the present findings suggest that granulocyte colony-stimulating factor synergistically augments 1,25-dihydroxyvitamin D (3)-induced monocytic differentiation in our murine bone-marrow cell cultures. Considering previously published data, we also suggest that these synergistic effects may be mainly due to the combination of two distinct effects such as the primary proliferative effects of granulocyte colony-stimulating factor on multipotent stem cells and the subsequent differentiative effects of 1,25-dihydroxyvitamin D (3) on proliferating cells.     

Identification of I:A mismatch base-pairing structure in DNA

Deoxyoligonucleotides containing deoxyinosine residues at positions corresponding to ambiguous nucleotides derived from an amino acid sequence have been successfully used as hybridization probes. It is assumed that the hypoxanthine residue can make base pairs with multiple bases. In order to obtain direct evidence for I:A base-pairing, a self-complementary deoxyoligonucleotide, d(G-G-I-A-C-C), was synthesized and its properties were examined by NMR spectroscopy. Three hydrogen-bonded imino proton resonances are observed at low temperatures in H2O suggesting the formation of a self-duplex with complete base pairing. Nuclear Overhauser effect (NOE) experiments showed that a signal at 15.1 ppm originated from the imino proton (H1) of the dI residue (I3) which is hydrogen-bonded to the dA residue (A4). Both the I3 and A4 residues were assumed to have taken an anti glycosidic conformation since irradiating the H1 of I3 gave NOEs both to its own H2 and to that of A4, an NOE also being observed between the H2 protons of I3 and A4. Comparison of the 31P NMR spectra of d(G-G-I-A-C-C) and d(G-G-I-C-C-C) showed the backbone structure of d(G-G-I-A-C-C) to have been disturbed by the presence of purine:purine base pairs in the middle of the hexamer duplex.     

Localization of cytochrome P-450 in the colonic mucosa of 3-methylcholanthrene-pretreated and untreated rats An immunohistochemical study

Summary Immunohistochemical localization of cytochrome P-450 in the colonic mucosa of 3-methylcholanthrene-pretreated and untreated rats was studied by indirect fluorescent antibody staining technique. A polyclonal antibody for cytochrome P-450_MC purified from hepatic microsomes of 3-methylcholanthrene-pretreated rats was used for this experiment. A strong immunofluorescence was found to be localized in the cytoplasm of the surface epithelium of the mucosa in the colon of 3-methylcholanthrene-pretreated rats. A faint immunofluorescence was also observed in the epithelium of untreated rats. 7-Ethoxycoumarin O-deethylase activity of colonic microsomes was significantly enhanced by 3-methylcholanthrene-pretreatment in parallel with an increase in the intensity of immunostaining for cytochrome P-450_MC in Western blotting analysis. This is the first report on the localization of cytochrome P-450 in the colonic mucosa.     

NaF-induced Ca2+ mobilization is dependent upon the culture density in a parathyroid hormone-responsive osteoblast-like cell line

The effect of NaF on cytosolic free Ca2+ concentrations [( Ca2+]i) was examined in a clonal osteoblast-like cell line (MOB 3-4) loaded with Fura 2. MOB 3-4 cells in a sparse culture, which exhibited neither alkaline phosphatase (ALP) activity nor the response to parathyroid hormone (PTH), responded to NaF (0.1-10 mM) to increase [Ca2+]i transiently. In contrast, the cells in a dense culture, which exhibited both ALP activity and the response to PTH, responded to NaF (above 4 mM) to increase [Ca2+]i slowly. [Ca2+]i in osteoblasts in primary culture slowly increased in response to both NaF (above 4 mM) and PTH (3 U/ml). Thus, the sensitivity and the response of MOB 3-4 cells to NaF and PTH varied with the culture density, and high culture density matured the cells like osteoblasts in primary culture. These NaF-induced Ca2+ mobilizations were not dependent upon external Ca2+ and were enhanced by Al3+ (1 microM), whereas the PTH-induced Ca2+ mobilizations were due to Ca2+ influx. These results suggest that the maturation of MOB 3-4 cells, dependent upon the culture density, modulates intracellular signal transduction pathways and thereby alters the NaF-induced Ca2+ mobilization, and that the culture density must be taken into consideration in studying Ca2+ mobilization in such an osteoblast-like cells line as MOB 3-4 cell line.     

Correlation of activity with phenotypes of Escherichia coli partial function mutants of rnh, the gene encoding RNase H

Summary The rnh gene of Escherichia coli encodes RNase H. rnh mutants display at least two phenotypes: (1) they require functional RecBCD enzyme for growth; thus rnh-339::cat recB270 (Ts) and rnh-339::cat recC271 (Ts) strains are temperature sensitive for growth; (2) rnh mutants permit replication that is independent of the chromosomal origin, presumably by failing to remove RNA-DNA hybrids from which extra-original replication can be primed. We report here that manifestation of these two phenotypes occurs at different levels of RNase H function; we have examined partially functional rnh mutants for their in vitro RNase H activity, their ability to rescue viability in recB or recC cells and their ability to permit growth of mutants incapable of using oriC [dnaA (Ts)].     

NMR studies for identification of dI:dG mismatch base-pairing structure in DNA.

One- and two-dimensional NMR experiments have been undertaken to investigate deoxyinosine:deoxyguanosine (dI:dG) base pairing in a self-complementary dodecadeoxyribonucleotide, d(C1-G2-C3-I4-A5-A6-T7-T8-G9-G10-G11-G12) (designated IG-12), duplex. The NMR data indicate formation of a dI(syn):dG(anti) base pair in a B-DNA helix. This unusual base pairing results in altered NOE patterns between the base protons (H8 and H2) of the I4 residue and the sugar protons of its own and the 5'-flanking C3 residues. The dI(syn):dG(anti) base pair is accommodated in the B-DNA duplex with only a subtle distortion of the local conformation. Identification of the dI:dG base pairing in this study confirms that a hypoxanthine base can form hydrogen-bonded base pairs with all of the four normal bases, C, A, T, and G, in DNA.     

Two monoclonal antibodies against small-cell lung cancer show existence of synergism in binding

Summary Murine IgG1 monoclonal antibodies (mAbs), ITK-2 and ITK-3, were generated against a small-cell lung cancer (SCLC) cell line. Enzyme-linked immunosorbent assay using a variety of established cell lines as substrates, immunoperoxidase staining of freshly frozen tissue sections, and fluorescence-activated cell sorter analysis of peripheral blood leukocytes showed that these mAbs recognize a part of the SCLC-associated cluster 1 antigen. In immunoprecipitation studies, both ITK-2 and ITK-3 bound to a 145-kDa glycoprotein of SCLC cell membrane extracts, as did MOC-1 and NKH-1, which both recognize the cluster 1 antigen. However, because the binding of¹²⁵I-labeled ITK-2 to SCLC cells was not inhibited by MOC-1 or NKH-1, the binding site of ITK-2 on SCLC cells appeared to be different from that of either MOC-1 or NKH-1. Unexpectedly, binding of¹²⁵I-labeled ITK-2 to SCLC cells increased in the presence of ITK-3. This ITK-3-induced increase in ITK-2 binding was due partly to an increase in the number of binding sites for ITK-2 on SCLC cells. Addition of ITK-3 may, therefore, improve the effectiveness of ITK-2-based tumor detection or therapy.