Migrants, refugees and insecurity. Current threats to peace?

Since the early 1980s, international migration has moved beyond humanitarian, economic development, labor market and societal integration concerns, raising complex interactive security implications for governments of migrant sending, receiving and transit countries, as well as for multilateral bodies. This article examines the effects of international migration on varied understandings and perceptions of international security. It discusses why international migration has come to be perceived as a security issue, both in industrialized and developing countries. Questions are raised on the migration-security nexus and the way in which the concepts "security" and "migration" are used. The real and perceived impacts of international migration upon national and regional security, both in industrialized and developing countries, are analyzed. The policies developed by governments and multilateral agencies since the mid-1980s to mitigate the destabilizing effects of certain kinds of international population movement and human displacement are examined. The conclusions stress the need for the establishment of a comprehensive framework of international cooperation among origin and receiving countries and international organizations to address the destabilizing implications of international migration.

Environmentally-induced population displacements and environmental impacts from mass migrations. Conference report.

PIP: The International Organization for Migration (IOM) and the Refugee Policy Group (RPG) organized a meeting during January 1992 in Nyon, Switzerland, on migration and the environment. The meeting called attention to the need for strategies to help people forced to leave their homes because of environmental degradation, to increase the understanding of traditional coping mechanisms for dealing with environmental change, to address the root causes of environmental migration, and to minimize the impact of refugees upon local ecosystems. Building upon problems identified at the Nyon meeting, 60 international experts convened at Chavannes-de-Bogis during April 21-24, 1996, to identify effective, practical measures to prevent, mitigate, and rehabilitate environmentally-induced displacements and the negative environmental impacts resulting from mass migrations. Participants included environmental and migration specialists, government officials, and representatives of international and nongovernmental organizations.^ieng

Resonance Raman and optical transient studies on the light-induced proton pump of bacteriorhodopsin reveal parallel photocycles.

The photocycle of bacteriorhodopsin (bR) was studied at ambient temperature in aqueous suspensions of purple membranes using time-resolved resonance Raman (RR) and optical transient spectroscopy (OTS). The samples were photolyzed, and the fractional concentrations of the retinylidene chromophore in its parent state, BR570, and in the intermediate states L550, M412, N560, and O640 were determined in the time domain 20 microseconds-1 s and in the pH range 4-10.5. Two kinetically different L components could be identified. At pH 7 one fraction of L (approximately 65%) decays in 80 microseconds to M (deprotonation of the Schiff base), whereas the residual part is converted in approximately 0.5 ms to N. The RR spectra reveal only minor structural changes of the chromophore in the L-->N transition. These were attributed to a conformational change of the protein backbone [Ormos, P., Chu, K., & Mourant, J. (1992) Biochemistry 31, 6933]. With decreasing pH the L-->N transition is delayed to > 2 ms following a titration-like function with pKa approximately 6.2. The decay of M412 monitored by OTS can be fitted for each pH value by two different amplitudes and time constants (Mf, tau f; Ms, tau s; f = fast, s = slow). Both Mf and Ms consist of subcomponents which can be distinguished by their different reaction pathways (but not by OTS). Mf occurs in the reaction sequences L-->Mf-->N-->BR and L-->Mf-->O-->BR. The population of the first sequence, in which N is formed with the time constant tau f (approximately 2-4 ms, pH 6-10.5), increases with pH. Ms is also found in two different reaction sequences of the form L-->Ms-->BR. The quantitative analysis reveals that each "titration effect" can be related to a certain fraction of bR. It is proposed that each fraction can be identified with a "subspecies" of bR which undergoes an independent and individual cyclic reaction. A complete reaction scheme is set up which represents the manifold of observed phenomena. It is concluded from the pH dependence of the lifetimes of Ms and N that the reconstitution of BR570 in the reaction steps Ms-->BR and N-->BR requires the uptake of a proton from the external phase. It is argued that this proton catalyzes the reisomerization of retinal, whereas the Schiff base is internally reprotonated from Asp-85. A model for proton pumping is proposed in which the proton taken up from the external phase to catalyze the reisomerization of retinal is the one which is pumped through the membrane during the photocycle of bR.

Measures to facilitate the reintegration of returning migrant workers: international experiences.

PIP: Bilateral and multilateral measures implemented to assist migrants who return to their country of origin have been designed to respond to a number of different but specific situations. 2 bilateral agreements are briefly described: 1) an agreement between the Federal Republic of Germany and the Republic of Turkey signed in the early 1970s, and 2) an agreement between France and Algeria signed in 1980. 3 different types of multilateral activities are described: 1) the operation of the so-called Return of Talent program by the Intergovernmental Committee for Migration, 2) the Transfer of KNow-how Through Expatriate Nationals program of the UN Development Programme, and 3) the elaboration of a model machinery on return migration by the Organization for Economic Cooperation and Development. While the 1st 2 activities are operational programs, by which annually between 1000-2000 professionals are assisted in their permanent return to or temporary sojourn in their developing countries of origin, with the financial support of both the developed and the developing countries concerned, the 3rd initiative is a conceptual effort aimed at assisting governments to implement policy measures designed to make return migration commensurate with national development goals. 3 recent proposals include 1) the proposal for an international labor compensatory facility, 2) an international fund for vocational training, and 3) an international fund for manpower resources. A common factor shared by all these programs is that they have all involved on 1 side industrial receiving countries which feel themselves obliged to observe a number of principles guaranteed by law and which govern employment conditions and working relations. The reintegration measures implemented or proposed in cooperation with them have been adopted in full consideration of the prevailing standards of these countries, as different as they may be from 1 country to another. A common consideration has been that the returning migrant should reintegrate in his country of origin as far as possible in conditions allowing the returnee to attain self-sufficiency and social security coverage. However, this underlying context does not necessarily prevail in all world regions where different forms of labor migration take place. Therefore the measures experienced in the relationship of specific countries cannot be easily copied for implementation in other countries. Multilateral measures benefited a rather limited number of individuals only, in many instances skilled and highly skilled migrants.^ieng

Irregular migration: a rising issue in developing countries.

PIP: The growing concern with illegal, or undocumented, migration in developing countries is described. The author notes that although such migration occurred in the past without causing concern, changing economic, political, and social factors since the 1970s have caused governments to attempt to control such flows. A review of regional trends is included, and the consequences of illegal migration for both countries of origin and destination are examined. (SUMMARY IN FRE AND SPA)^ieng

Oligonucleotide formation catalyzed by mononucleotide matrices.

Pb2+-containing precipitates of mononucleotides form matrices which catalyze the self-condensation of nucleotide 5'-phosphorimidazolides and their condensation with nucleosides. The reactions exhibit base-pairing specificity between matrix nucleotide and substrate, and usually follow the Watson-Crick pairing rules. Although purine polynucleotides do not facilitate the oligomerization of pyrimidine nucleotide monomers in solution, it is interesting that purine-containing matrices do catalyze such a reaction. The significance of the results in the context of the prebiotic evolution of polynucleotides is discussed.

Condensation of activated diguanylates on a poly(C) template.

We have studied the metal-ion catalysis of a number of reactions of the isomers of ImpGpG on a poly(C) template. In the absence of a catalytic metal ion, oligomers at least up to (pG)20 are obtained from the ImpGpG isomers in a 1-methylimidazole buffer. The Pb2+ ion improves the yield of longer oligomers and changes substantially the distribution of linkage isomers. The Pb2+ ion greatly improves the yield of longer oligomers obtained from G and ImpGpG on a poly(C) template. The self-condensation of ImpGpG in a 2, 6-lutidine buffer is much less efficient than in a 1-methylimidazole buffer. The Zn2+ greatly increases the yield of products from the [3'-5']-linked dimer, but fails to catalyze the formation of long oligomers from the [2'-5']-linked dimer. The bonds formed in the Zn2+-catalyzed self-condensation of ImpG3pG on poly(C) are mainly [3'-5']-linked.

Template-directed synthesis and selective adsorption of oligoadenylates on hydroxyapatite.

Polyuridylic acid is adsorbed completely from aqueous solution by hydroxyapatite under conditions that permit template-directed synthesis of oligoadenylates in free solution. The yield of oligoadenylates is enhanced to almost the same extent by poly(U) in the presence or the absence of hydroxyapatite. Under very similar conditions small quantities of hydroxyapatite adsorb higher molecular-weight oligoadenylates selectively from a mixture of oligomers. On the basis of these results we propose a mechanism for prebiotic oligonucleotide formation in which selective adsorption on hydroxyapatite or some other immobilized anion-exchanging material plays a major role. Monomers are released from the surface for reactivation, while oligomers are retained in a protected environment by adsorption to the apatite surface.

Efficient metal-ion catalyzed template-directed oligonucleotide synthesis.

The Pb2+ and Zn2+ ions are efficient catalysts for the polycytidylic acid-directed polymerization of an activated guanylic acid derivative, guanosine 5'-phosphorimidazolide. The products include oligomers of 30 to 40 units in length. The nucleotide residues are predominantly 2'-5' linked when Pb2+ is the catalyst, and predominantly 3'-5' linked in the presence of Zn2+. The significance of these results in the context of the prebiotic evolution of RNA polymerase is discussed.

Self-condensation of activated dinucleotides on polynucleotide templates with alternating sequences.

We have prepared substantial quantities of the alternating polymers poly(U-G) and poly(C-A) and have used them as templates for the self-condensation of ImpApC, ImpCpA, ImpGpU and ImpG. We find that the condensation of ImpGpU and ImpUpG on poly(C-A) is efficient, the condensation of ImpCpA on poly(U-G) is moderately efficient, while the condensation of ImpApC on poly(U-C) proceeds poorly. In many cases, the product is predominantly 3'-5'-linked. These reactions demonstrate unequivocally, for the first time, that template-directed reactions occur in double-helical structures. Furthermore, they describe for the first time a pair of reactions in which each of two complementary polymers facilitates the synthesis of the other. The prebiotic significance of these findings is discussed.

Template-directed synthesis of oligoadenylates catalyzed by Pb2+ ions.

The Pb2+ ion is an effective catalyst for the template-directed condensation of ImpA on poly(U). This reaction generates up to 35% of oligomers 5 or more units long. Furthermore, the product is predominantly 3'-5'-linked (75%) unlike that from the uncatalyzed reaction which is more than 90% 2'-5'-linked. The significance of metal-ion catalysis for prebiotic polynucleotide formation is discussed.

Studies of oligoadenylate formation on a poly (U) template.

We have studied a variety of condensation reactions involving poly (U) as template and isomeric adenosine dinucleotides as substrates. We find that [3'-5']-linked dinucleotides such as A3pA and pA3pA are better acceptors than the corresponding [2'-5']-linked compounds, while ImpA2pA is a better donor than ImpA3pA. The reaction between A2pA and ImpA3pA, for example, yields only 4% of product while the reaction of A3pA with ImpA2pA yields 86% of product. The more efficient condensation reactions of dimers are about as efficient as the self-condensation of ImpA. They yield a few percent of material in which five or more substrate molecules are linked together. The percentage of the natural [3'-5']-linkage in the product varies greatly, from as little as 1% to as much as 45%.

Formation of the imidazolides of dinucleotides under potentially prebiotic conditions.

Imidazolides of dinucleotides such as ImpApA can be formed from the corresponding dinucleotides in a two-stage process, which gives up to 15% yields under potentially prebiotic conditions. First a solution of the dinucleotide and sodium trimetaphosphate is dried out at constant temperature and humidity. This produces polyphosphates such pnApA in excellent yield (greater than or equal to 80%). The products are dissolved in water, imidazole is added, and the solution is dried out again. This yields the 5'--phosphorimidazolides.

Formation of P1, P2-dinucleoside 5'-pyrophosphates under potentially prebiological conditions.

Organic pyrophosphates such as UppA and NAD are formed when a solution containing a nucleotide, a nucleoside 5'-polyphosphate, Mg2+ and imidazole are allowed to dry out. We suggest that this synthesis may have occured concurrently with oligonucleotide formation.

Formation of nucleoside 5'-phosphoramidates under potentially prebiological conditions.

Adenosine 5'-phosphoramidates form when solutions containing adenosine 5'-polyphosphates pnA (n greater than or equal to 3) or P1, P2-diadenosine 5'-diphosphate and amines are allowed to dry out. Mg ions catalyze these reactions. We have studied systems containing ammonia, imidazole, glycine, ethylenediamine and histamine. The yields of adenosine 5'-phosphoramidates range from 10-50% based on the nucleotide. The prebiotic significance of the reactions is discussed.

Template-directed reactions of aminonucleosides.

We have studied the reactions between adenosine 5'-phosphorimidazolide and 9-(2-amino-2-deoxyxylofuranosyl) adenine (I) or 3'-methylamino-3'-deoxy-adenosine (II), both with and without a poly (U) template. We find that both amino compounds react much more rapidly than does adenosine, in the absence of a template. The rate of reaction is greatly enhanced by a poly (U) template in the case of I, but the enhancement is slight in the case of II.

Formation of nucleoside 5'-polyphosphates under potentially prebiological conditions.

Aqueous solutions of linear inorganic polyphosphates incubated in presence of Mg ions depolymerize to give trimetaphosphate. The presence of a nucleoside 5'-phosphate has little influence upon the reaction. Drying the products obtained by incubating a linear polyphosphate with Mg ions in the presence of a nucleoside 5'-phosphate yields nucleoside 5'-polyphosphates. The prebiological relevance of the reactions is discussed.

Polymerization of nucleotide analogues I: reaction of nucleoside 5'-phosphorimidazolides with 2'-amino-2'-deoxyuridine.

2'-Amino-2'-deoxyuridine reacts efficiently with nucleoside 5'-phosphorimidazolides in aqueous solution. The dinucleoside monophosphate analogues were obtained in yields exceeding 80% under conditions in which little reaction occurs with the natural nucleosides. In a similar way, the 5'-phosphorimidazolide of 2'-amino-2'-deoxyuridine undergoes self-condensation in aqueous solution to give a complex mixture of oligomers. The phosphoramidate bond in the dinucleoside monophosphate analogues is stable for several days at room temperature and pH 7. The mechanisms of their hydrolysis under acidic and alkaline conditions are described.