Serum Glutathione Peroxidase Activity and Blood Selenium in Pigs

Blood serum glutathione peroxidase activity and blood selenium concentration were measured in blood samples from pigs subjected to experimentally induced selenium deficiency and dietary selenium supplementation on graded levels. A highly significant correlation between blood selenium and serum GSH-Px activity in pigs, especially in selenium deficient pigs, was demonstrated. There was also a strong relationship between blood selenium concentration and serum GSH-Px activity in pigs receiving dietary selenium at graded levels. Serum GSH-Px activity exhibited an excellent close-response relationship to dietary selenium. Linear regression analysis showed that the increased serum GSH-Px activity was a function of the dietary selenium concentration. The fitness of serum in monitoring slight changes of the selenium status of pigs with help of the estimation of GSH-Px activity was discussed. The measurement of serum GSH-Px activity seems to provide a useful and rapid means for defining selenium requirements and for identifying selenium deficiency in growing pigs.     

Antisense oligonucleotides to crabp I and II alter the expression of TGF-β3, RAR-β, and tenascin in primary cultures of embryonic palate cells

Summary The cellular retinoic acid-binding proteins (CRABPs) are thought to modulate the responsiveness of cells to retinoic acid (RA). We have previously shown that primary cultures of murine embryonic palate mesenchymal (MEPM) cells express both CRABP-I and CRABP-II genes and that this expression is regulated by RA and transforming growth factor β (TGF-β). These cells also express high levels of TGF-β3, which is also regulated by RA and TGF-β. We have used an antisense strategy to investigate the role of the CRABPs in retinoid-induced gene expression. Subconfluent cultures of MEPM cells were treated for several days with phosphorothioate modified 18-mer oligonucleotides antisense to CRABP-I or CRABP-II and then with all-trans-retinoic acid at a concentration of 3.3 μM or 0.33 μM for 5 or 22 h. Total RNA was then extracted and the expression of TGF-β3, retinoic acid receptor β (RAR-β), and tenascin was assessed by northern blot analysis. Antisense oligonucleotides to CRABP-I partially inhibited the RA-induced TGF-β3, RAR-β, and tenascin mRNA expression. The corresponding mis-sense oligonucleotides were without effect. Antisense oligonucleotides to CRABP-II also partially inhibited RA-induced expression of these genes. As with the CRABP-I antisense, mis-sense oligonucleotides to CRABP-II had no effect. These data suggest that both CRABPs modulate the responsiveness of MEPM cells to retinoic acid. Inhibition of endogenous CRABP expression renders MEPM cells less responsive to RA with respect to induction of TGF-β3, RAR-β, and tenascin gene expression. These results have important implications for our understanding of the role of the CRABPs in retinoid teratology.     

The origin of adaptive mutants: Random or nonrandom?

Several recent reports have claimed that adaptive mutants in bacteria and yeast are induced by selective conditions. The results of these reports suggest that mutants can arise nonrandomly with respect to fitness, contrary to what has been widely accepted. In several cases that have received careful experimental reexamination, however, the detection of seemingly nonrandom mutation has been explained as an experimental artifact. In the remaining cases, there is no evidence to suggest that cells have the capacity to direct or choose which genetic variants will arise. Instead, current models propose processes by which genetic variants persist as mutations only if they enable cell growth and DNA replication. Most of these models are apparently contradicted by experimental data. One model, the hypermutable state model, has recently received limited circumstantial support. However, in this model the origin of adaptive mutants is random; the apparent nonrandomness of mutation is merely a consequence of natural selection. The critical distinction between the origin of genetic variation (mutation) and the possible consequence of that variation (selection) has been neglected by proponents of directed mutation.     

Manganese stimulates incorporation of [3H]inositol into an agonist-insensitive pool of phosphatidylinositol in brain membranes

In a particulate preparation from rat brain, manganese ions stimulate the incorporation of [3H]inositol into inositol phospholipids in a concentration-dependent manner. Incubation with CDP-diacylglycerol (0.5 mM) alone had no effect on the incorporation of [3H]inositol but potentiated the stimulatory effect of manganese. Despite the increase in [3H]inositol incorporation into phosphatidylinositol, the carbachol-induced accumulation of [3H]inositol-1-phosphate was unaltered in membranes preincubated with manganese but when coincubated with CDP-diacylglycerol the carbachol-induced accumulation of [3H]inositol-1-phosphate was increased. These data suggest that manganese stimulates the incorporation of [3H]inositol into an agonist-insensitive pool of phosphatidylinositol.     

GENETIC TRANSFORMATION OF THE DIATOMS CYCLOTELLA CRYPTICA AND NAVICULA SAPROPHILA

Two species of diatoms were genetically transformed by introducing plasmid vectors containing the Escherichia coli neomycin phosphotransferase II (npt II ) gene. Expression of the bacterial npt II gene in the diatoms was achieved using the putative promoter and terminator sequences from the acetyl-CoA carboxylase gene from the centric diatom Cyclotella cryptica T13L Reimann, Lewin, and Guillard. The vectors were introduced into C. cryptica and the pennate diatom Navicula saprophila NAVIC1 Lange-Bertalot and Bonik by microprojectile bombardment. Putative transformants were selected based on their ability to grow in the presence of the antibiotic G418, and production of the neomycin phosphotransferase protein by the transformed cells was confirmed by western blotting. The foreign DNA integrated into one or more random sites within the genome of the transformed algal cells, often in the form of tandem repeats. This is the first report of reproducible, stable genetic transformation of a chlorophyll c -containing alga .     

Mössbauer spectra of the heme peptide (HP) 1–50 and the heme peptide:non-heme peptide (NHP) non-covalent complex 1–50:51–104 derived from cytochrome c: evidence for cytochrome c iron site solvation in aqueous solution

Mössbauer spectroscopic studies on a heme peptide (HP) derived from cytochrome c and on the HP recombined non-covalently with the remaining cleaved section are reported. The results suggest that the environment of the heme site in the known crystal structure of cytochrome c may differ in detail from the environment of the heme in the working protein.     

Granulocyte-macrophage colony-stimulating factor is a chemoattractant cytokine for human neutrophils: involvement of the ribosomal p70 S6 kinase signaling pathway

GM-CSF stimulates proliferation of myeloid precursors in bone marrow and primes mature leukocytes for enhanced functionality. We demonstrate that GM-CSF is a powerful chemotactic and chemokinetic agent for human neutrophils. GM-CSF-induced chemotaxis is time dependent and is specifically neutralized with Abs directed to either the ligand itself or its receptor. Maximal chemotactic response was achieved at approximately 7 nM GM-CSF, and the EC(50) was approximately 0.9 nM. Both concentrations are similar to the effective concentrations of IL-8 and less than the effective concentrations of other neutrophil chemoattractants such as neutrophil-activating peptide-78, granulocyte chemotactic protein-2, leukotriene B(4), and FMLP. GM-CSF also acts as a chemoattractant for native cells bearing the GM-CSF receptor, such as monocytes, as well as for GM-CSF receptor-bearing myeloid cell lines, HL60 (promyelomonocyte leukemic cell line) and MPD (myeloproliferative disorder cell line), following differentiation induction. GM-CSF induced a rapid, transient increase in F-actin polymerization and the formation of focal contact rings in neutrophils, which are prerequisites for cell migration. The mechanism of GM-CSF-induced chemotaxis appears to involve the cell signaling molecule, ribosomal p70 S6 kinase (p70S6K). Both p70S6K enzymatic activity and T(421)/S(424) and T(389) phosphorylation are markedly increased with GM-CSF. In addition, the p70S6K inhibitor hamartin transduced into cells as active protein, interfered with GM-CSF-dependent migration, and attenuated p70S6K phosphorylation. These data indicate that GM-CSF exhibits chemotactic functionality and suggest new avenues for the investigation of the molecular basis of chemotaxis as it relates to inflammation and tissue injury.     

Origins and plasticity of neural crest cells and their roles in jaw and craniofacial evolution

The vertebrate head is a complex assemblage of cranial specializations, including the central and peripheral nervous systems, viscero- and neurocranium, musculature and connective tissue. The primary differences that exist between vertebrates and other chordates relate to their craniofacial organization. Therefore, evolution of the head is considered fundamental to the origins of vertebrates (Gans and Northcutt, 1983). The transition from invertebrate to vertebrate chordates was a multistep process, involving the formation and patterning of many new cell types and tissues. The evolution of early vertebrates, such as jawless fish, was accompanied by the emergence of a specialized set of cells, called neural crest cells which have long held a fascination for developmental and evolutionary biologists due to their considerable influence on the complex development of the vertebrate head. Although it has been classically thought that protochordates lacked neural crest counterparts, the recent identification and characterization of amphioxus and ascidian genes homologous to those involved in vertebrate neural crest development challenges this idea. Instead it suggests thatthe neural crest may not be a novel vertebrate cell population, but could have in fact originated from the protochordate dorsal midline epidermis. Consequently, the evolution of the neural crest cells could be reconsidered in terms of the acquisition of new cell properties such as delamination-migration and also multipotency which were key innovations that contributed to craniofacial development. In this review we discuss recent findings concerning the inductive origins of neural crest cells, as well as new insights into the mechanisms patterning this cell population and the subsequent influence this has had on craniofacial evolution.