Teratogenicity of combinations of sodium dichromate, sodium arsenate and copper sulphate in the rat

1. The teratogenicity of sodium dichromate (2 mg Cr/kg), sodium arsenate (5 mg As/kg) and copper sulphate (2 mg Cu/kg) in female Wistar rats was studied following the administration of the test compounds separately and in their various combinations on gestation day 8. 2. The test compounds administered separately and the combination of dichromate plus Cu2+ were non-fetotoxic and either non- or weakly teratogenic, whereas arsenate/Cu2+ was both weakly fetotoxic and teratogenic. 3. Dichromate/arsenate and dichromate/arsenate/Cu2+ caused a marked decrease in mean fetal weight and an increased incidence of fetal resorption and abnormality formation.     

Immunocytochemical analysis of cytocentrifuged fine needle aspirates. A study based on lung tumors aspirated in vitro

The value of Cytospin preparations of fine needle aspiration (FNA) biopsy material for immunocytochemical analysis was investigated using aspirates obtained from 23 resected human lung tumors. The results were compared with those on cryostat sections from the same tumors. The Cytospin preparations of the FNA biopsies gave the best immunostaining reactions and enabled a comprehensive range of monoclonal antibodies (MAbs) to be utilized. The quality of the Cytospin immunostaining compared favorably with that on cryostat sections of the same tumors and generally yielded a similar immunophenotype. However, the Cytospin preparations were not suitable for staining with MAb Ki67, which detects an antigen associated with cellular proliferation. With Ki67, conventionally prepared smears were much superior and enabled an assessment of tumor growth fraction that concurred with the growth fraction calculated from cryostat sections in most cases.     

Activin B: precursor sequences, genomic structure and in vitro activities

We report here the complete amino acid sequence of the human inhibin beta B-subunit as deduced from the sequence of cDNA and genomic clones. The primary translation product of the beta B mRNA predicts a protein of 407 amino acids, containing a prepro region of 292 amino acids separated by basic amino acids from the mature C-terminal 115 amino acids. Mammalian tissue culture cells transfected with a beta B-subunit expression plasmid secreted an activin B homodimer of approximately 22K mol wt. Coexpression of the beta A- and beta B-subunit mRNAs resulted in the secretion of the three forms of activin, A, AB, and B. Purified activin B was shown to elicit FSH release in an in vitro pituitary assay and trigger the accumulation of hemoglobin in K562 cells. The potency of activin B in both of these assays (ED50 approximately 2 ng/ml) was indistinguishable from that observed for activin A.     

Tumor necrosis factor-alpha induces vitamin D-1-hydroxylase activity in normal human alveolar macrophages.

The induction of 1-hydroxylase in alveolar macrophages by tumor necrosis factor-alpha (TNF) was examined in view of recent evidence suggesting that local production of 1,25-(OH)2D3 may play a role in the regulation of immune functions. Incubation of pulmonary alveolar macrophages from normal human subjects with recombinant TNF caused a 2- to 10-fold increase in 25-hydroxyvitamin D3-1-hydroxylase activity. The dose-response curve was linear over the range 0.05-5.0 IU/ml, and no further increase was seen at higher concentrations. The increase in 1-hydroxylase activity was present after 12 h and reached a maximum after 3 days. The effect of TNF was inhibited in a dose-dependent manner by the presence of 1,25(OH)2D3 (10(-10)-10(-8) M) in the incubation media for 5 days but was unaffected by 10(-9) M 1,25(OH)2D3 after 12 h. The enhancement of macrophage 1-hydroxylase activity by TNF was comparable to that induced by gamma interferon (IFN) but the effects of maximal doses of both agents were not additive. The presence of antibody to TNF resulted in a 76% inhibition of TNF-induced 1-hydroxylase but had no significant effect on IFN-induced 1-hydroxylase activity.     

Effect of cytoplasmic acidification on the membrane potential of T-lymphocytes: Role of trace metals

Summary The effect of lowering intracellular pH on the membrane potential (E _m ) of rat thymic lymphocytes was studied using the potential-sensitive dyebis-oxonol. Cells were acid loaded by addition of the electroneutral K⁺/H⁺ exchanging ionophore nigericin. Acidification to pH 6.3 in Na⁺-free solution resulted in a biphasic change inE _m : an early transient hyperpolarization followed by a sustained depolarization. These changes were associated with a rise in cytosolic free Ca²⁺ ([Ca²⁺] _i ). The hyperpolarization was eliminated when the change in [Ca²⁺] _i was prevented using BAPTA, an intracellular Ca²⁺ chelator. Moreover, a similar hyperpolarization was elicited by elevation of [Ca²⁺] _i at physiological pH _i using ionomycin, suggesting involvement of Ca²⁺-activated K⁺ channels. In contrast, the depolarization phase could not be mimicked by raising [Ca²⁺] _i with ionomycin. However, intracellular BAPTA effectively inhibited the acidificationinduced depolarization. Inhibition was also obtained by extracellular addition of EGTA or dithiothreitol, even when the external free Ca²⁺ concentration remained unaltered. These observations suggested a possible role of contaminating trace metals. Cytosolic acidification is envisaged to induce intracellular accumulation of one or more trace metals, which induces the observed changes inE _m . Accordingly, similar changes inE _m can be induced without acidification by the addition of small amounts of Cu²⁺ to the medium. The ionic basis of theE _m changes induced by acidification and the significance of these observations are discussed.     

Spinach chloroplastic carbonic anhydrase: nucleotide sequence analysis of cDNA

We have determined the nucleotide sequence of a cDNA encoding spinach (Spinacia oleracea) chloroplastic carbonic anhydrase (CA). The open reading frame encodes a protein consisting of a transit peptide and a mature CA protein with a predicted mass of 24, 116 daltons. This represents the first report of a nucleotide sequence of a plant CA.     

Addition of telomere-associated HeT DNA sequences "heals" broken chromosome ends in Drosophila

Stocks of D. melanogaster X chromosomes carrying terminal deletions (RT chromosomes) have been maintained for several years. Some of the chromosomes are slowly losing DNA from the broken ends (as expected if replication is incomplete) and show no telomere-associated DNA added to the receding ends. Two stocks carry chromosomes that have become "healed" and are no longer losing DNA. In both stocks the broken chromosome end has acquired a segment of HeT DNA, a family of complex repeats found only at telomeres and in pericentric heterochromatin. Although the HeT family is complex, the HeT sequence joined to the broken chromosome end is the same in both stocks. In contrast, the two chromosomes are broken in different places and have no detectable sequence similarity at the junction with the new DNA. Sequence analysis suggests that the new telomere sequences have been added by a specific mechanism that does not involve homologous recombination.