Pharmacological modulation of prostaglandin production by phagocytic cells of the thymic reticulum in relation to immunoregulation

We cultured phagocytic cells derived from the thymic reticulum in order to study the regulation of prostaglandin (PG) production by antiinflammatory or immunostimulating agents. The kinetics of PGE₂, 6-keto-PGF_1α and PGF_2α production were measured by specific radioimmunoassays of the supernatants harvested from cells treated with dexamethasone, a steroidal antiinflammatory drug and by two non steroidal inhibitors (indomethacin and sulindac) or by various immunostimulating agents, one of them, RU 41740 is currently being used in humans. Our results revealed that ech of these drugs exerts a differential effect on the PG production, with a striking action on PGE₂ synthesis, a lesser effect on 6-keto-PGF_1α production and almost no effect on PGF_2α synthesis. The possible mechanisms responsible for this complex regulation of PG production are discussed.     

Differential effects of glutamine and arginine on 7S globulin accumulation during the maturation of oil palm somatic embryos

The low vigour of plantlets resulting from oil palm somatic embryos may be due to insufficient levels of deposited storage proteins. Thus, in order to improve embryonic maturation and the vigour of regenerated plantlets, we investigated the effects of modifying the culture conditions with respect to the accumulation of the major oil palm storage proteins, the 7S globulins. In this study, the effect of arginine and glutamine on globulin accumulation was studied using somatic embryos of two different genotypes. Arginine and glutamine were both found to enhance protein accumulation but in different ways, which were best illustrated by measurements of soluble proteins per embryo and 7S globulin content per dry weight. Arginine increased the level of soluble proteins by 46% irrespective of the clone, and glutamine by 19% and 63% depending on the clone. The clone which accumulated the least protein in the presence of glutamine was that which contained the more protein initially. Only arginine favoured the accumulation of 7S globulin content per dry weight, irrespective of the clone considered (+26%). This study will enable further investigations of specific storage proteins as potential markers for regenerated plantlets vigour. Received: 22 July 1997 / Revision received: 6 January 1998 / Accepted: 1 December 1998     

Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution

In order to study the relationships among mammalian alpha-globin genes, we have determined the sequence of the 3' flanking region of the human alpha 1 globin gene and have made pairwise comparisons between sequenced alpha-globin genes. The flanking regions were examined in detail because sequence matches in these regions could be interpreted with the least complication from the gene duplications and conversions that have occurred frequently in mammalian alpha-like globin gene clusters. We found good matches between the flanking regions of human alpha 1 and rabbit alpha 1, human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and horse alpha 1 and goat II alpha. These matches were used to align the alpha-globin genes in gene clusters from different mammals. This alignment shows that genes at equivalent positions in the gene clusters of different mammals can be functional or nonfunctional, depending on whether they corrected against a functional alpha-globin gene in recent evolutionary history. The number of alpha-globin genes (including pseudogenes) appears to differ among species, although highly divergent pseudogenes may not have been detected in all species examined. Although matching sequences could be found in interspecies comparisons of the flanking regions of alpha- globin genes, these matches are not as extensive as those found in the flanking regions of mammalian beta-like globin genes. This observation suggests that the noncoding sequences in the mammalian alpha-globin gene clusters are evolving at a faster rate than those in the beta-like globin gene clusters. The proposed faster rate of evolution fits with the poor conservation of the genetic linkage map around alpha-globin gene clusters when compared to that of the beta-like globin gene clusters. Analysis of the 3' flanking regions of alpha-globin genes has revealed a conserved sequence approximately 100-150 bp 3' to the polyadenylation site; this sequence may be involved in the expression or regulation of alpha-globin genes.