Sensitive in vitro analysis of HIV-1 Rev multimerization.

Oligomerization of the Rev protein of human immuno-deficiency virus type 1 on its cognate response element is essential for export of the late viral mRNAs from the nucleus. Two regions of the protein, flanking the RNA binding site, have been defined as oligomerization sites after mutants (M4 and M7) had been reported to bind specifically to the response element but not to oligomerize in vivo or in vitro. These mutants are often used as paradigms for studies of Rev multimerization. We have re-examined the in vitro binding of these mutants to model Rev response elements, using improved gel mobility assays. We find that both mutants will form oligomers on the Rev response element, but have somewhat lower affinities for RNA than the wild-type protein. M7 has lower specific affinity, but shows little deficiency in oligomerization once binding starts. In contrast, M4 is multimerization deficient, as previously reported. Therefore, whilethe sites are correctly defined, it is inappropriate to employ the original M7 deletion mutant to study Rev oligomerization.

Flexible regions of RNA structure facilitate co-operative Rev assembly on the Rev-response element.

The oligomerisation of Rev on the Rev-response element (RRE) was studied using a series of model substrates. Only a monomer of Rev is able to bind efficiently to a high affinity site that is flanked by perfect duplex RNA. Addition of a bulge or a second stem structure adjacent to the high affinity site permits the co-operative incorporation of a second Rev molecule to the RNA. Model RREs carrying bulges can bind Rev with a higher degree of co-operativity than the native structure. Oligomerisation was efficient when the bulge was moved to the opposite strand of the duplex, but was severely impaired when the distance between the bulge and the high affinity site was increased by more than 8 bp. Rev can oligomerise at either end of the RNA-protein complex formed at the high affinity site; when the duplex flanking a high affinity site is disrupted by a bulge or a stem, oligomerisation proceeds in the direction of the disruption regardless of the orientation of the high affinity site. The results are consistent with the "molecular rheostat" model for RRE function, which suggests that Rev binding to the RRE is highly distributive and provides a sensitive measurement of intracellular Rev concentrations.

Saving, dependency and development.

PIP: This study examines the impact of dependency on savings between 65 less developed countries (LDCs) and 23 developed countries over time and cross-sectionally since 1960. The study tests a modified Leff model and the Mason life-cycle framework. Empirical estimates address potential simultaneity between savings and output growth. The price indices of Summers and Heston are used because each country's national accounts are converted from nominal into purchasing-power variables. This eliminates the problems with using exchange rates which vary systematically by level of development with a "true" index of purchasing power. Savings (S/Y) is the percentage share of gross national saving in gross domestic product. Ygr is the growth of per capita income. Y/N gr is the growth in the per capita gross domestic product. Analysis is based on ordinary least squares (OLS) and two-stage least squares techniques, treatment for heteroscedascity, aggregation periods, several definitions of savings, different country samples, and aged dependency and youth dependency. Findings support the Mason variable-growth life-cycle framework that shows that changes in demographic factors accounted for a large part of savings. The relationships in the modified Leff-type model were weak, with the exception of the mildly negative youth and elderly dependency impact in the 1980s. The rate of growth of youth dependency was negative and significant in all cross-sections for the full sample, all panel estimates for both LDCs and the full sample, and in the 1980s for LDCs. In the OLS model, life-cycle effects were weaker, but direct dependency effects were stronger. S/Y over time became slightly more sensitive to changes in life cycle impacts but less sensitive to youth dependency. Demography's impact on savings over time is attributed to the increase in the pace of youth dependency decline and secondarily to its increasing sensitivity to life-cycle effects.^ieng

Aggregate population and economic growth correlations: the role of the components of demographic change.

The results of recent correlations showing a negative impact of population growth on economic development in cross-country data for the 1980s, versus "nonsignificant" correlations widely found for the 1960s and 1970s, are examined with contemporaneous and lagged components of demographic change, convergence-type economic modeling, and several statistical frameworks. The separate impacts of births and deaths are found to be notable but offsetting in the earlier periods. In contrast, the short-run costs (benefits) of births (mortality reduction) increase (decrease) significantly in the 1980s, and the favorable labor-force impacts of past births are not fully offsetting.

Men and family planning: toward a policy of male involvement.

PIP: The stated aim of this discussion is to examine the extent of male use of family planning and the nature of men's role in family planning in developing countries. Case studies are presented which are successful examples of strategies for involving men in family planning. Policies that aim to increase male involvement must be sensitive to cultural values, apply to a decentralized government approach toward information and supplies, include adequate political will, and consider the costs and benefits of changing values. A male family planning policy would not always be compatible with all fertility values in developing countries or traditional values of the older population. A policy should stress the value of male individuals contributing as much as possible for their own and others' welfare. Community participation is considered important in order to create a feeling of mutual support. A sizeable investment will be required for mass distribution of contraceptive information. Schools are viewed as an ideal place for educating youth about the problems of high fertility and about use of family planning methods, such as the condom. Religious organizations should be used to educate people about responsible parenthood and to minimize barriers to use of modern contraception. Comic books on how to use condoms are suggested as a good source. Local authorities who are trusted are useful in influencing acceptance among local populations. Local personnel may be trained as information disseminators. Adequate contraceptive information needs to be supplied to a wide audience. Lack of supply and inadequate information are given as two key reasons for insufficient use of male contraception. Condoms should be priced to be affordable to the average person and free to those with no income. Program strategies that proved successful are cited for Thailand's Mechai Viravaidya program and Bali's grass-roots program. The vasectomy program in Bangladesh is also noted for its success. Low levels of condom use are attributed to factors such as price, education, availability, accessibility, culture, religion, and economic conditions. Male sterilization levels can be enhanced with wider availability of clinics and provision of correct information for challenging beliefs that vasectomy is a form of castration.^ieng

Male college students and family planning use in Zambia.

PIP: The success of family planning depends on attitudes and knowledge about contraception. In this study, the correlation between ever use of contraception and health attitudes among men was assessed. 65 male participants were randomly selected from residence halls on the University of Lusaka campus in Lusaka, Zambia. Students reflected a diverse ethnic mix. The findings indicated that only 37.5% had approval from ethnic traditions for contraceptive use. Chi square tests rejected the null hypothesis that there is no relationship between the variables "ever use" and "ethnic orientation." 52.5% who reported ever use of contraception were juniors or seniors, which indicated little difference by level of education and ever use. Family planning ever use due to health reasons was reported by 70% of participants. These findings support the research of Manda on noncollege populations about use of condoms. College students do have favorable attitudes toward contraception and toward health. This research supports the public education campaign of the Ministry of Health to promote the practice of safe sex for health reasons and the prevention of AIDS, a widespread problem in Zambia.^ieng

Australia: the coming of age.

Current demographic trends in Australia and their implications are assessed. The author concludes that "Australia faces a relatively favourable demographic future: ageing is proceeding at a slower pace here, the pattern of the labour force ageing is conducive to restructuring in the intermediate future, and a well-established immigration policy can be used to accommodate demographics with social and economic goals. The financing of social services for the aged will produce fewer concerns here partly because of less immediate demographic pressures and partly because of the orientation of the age-pension system."

The demographic transition and population policy in Egypt.

PIP: Household-level fertility research was examined with the broader contexts of the demographic transition and public policy. The Easterlin-Crimmins (1982, 1985) model was the framework chosen for the examination. It was modified and applied to a sample of rural Egyptian households. An interesting dimension of the Easterlin-Crimmins framework is the presence of a phase of development where fertility is constrained by supplying factors -- a phenomenon most likely to occur in rural settings in the 3rd world. Thus the data set from rural Egypt offers a good opportunity to explore this aspect of their model. The framework also is useful for delineating the relative importance of behavioral versus family planning factors in explaining changes in the fertility of a population. On average, estimated Cn (surviving natural fertility) approximately equaled Cd (desired surviving family size) for the noncontracepting subpopulation of rural Egypt. These families had little or no motivation for contraception and remain in the premodernization Phase I, i.e., the desired number of surviving children exceeds the number of surviving children under a natural fertility regime. In contrast, the noncontracepting subset of families drawn from both the rural and urban areas of Sri Lanka and Colombia, already had embarked on Phase II, i.e., the supply constraint is released, but contraception is too costly. By applying child survivorship rates (s) to actual fertility for the contracepting subsets of women, on average, actual surviving fertility exceeded Cd by 1.0 children in rural Egypt, 2.0 in Sri Lanka, and 2.9 in Colombia. All 3 of these populations are in Phase III, i.e., contraception becomes increasingly pervasive as the gap between Cn and Cd widens and contraceptive costs decline. The methodology offers promise for identifying the separate influences of family planning and socioeconomic change. The results provided insights into the basic determinants underlying the demographic transition. Duration of marriage was the most single powerful determinant of completed family size in rural Egypt. Prolonged breastfeeding (20 months on average) was only slightly less powerful in reducing fertility in rural Egypt than contraception. The rise in child survivorship inherent in socioeconomic development raised the natural supply of children. Families did respond when family size expectations exceed desired, with the most educated being the most responsive. Contraceptors were more fecund than noncontraceptors in rural Egypt, and their child survivorship rates were higher.^ieng

Population and development: controversy and reconciliation.

PIP: This paper evaluates the 2 most important antinatalist arguments the have dominated the population debate over the last 25 years, drawing heavily on 3 1984 studies -- land and resource scarcity and saving and investment. The extent to which these arguments have successfully included the indirect effects of population growth on an economy in order to determine the net impact of population is assessed an emerging revisionist interpretation of the role of population in development is discussed. It is believed that on scientific grounds, and focusing primarily on economic impact, neither the arguments nor the various models used to support the antinatalist position sufficiently support the strength of the general conclusion that population growth exerts a strong adverse impact on the economy. Population growth reveals sooner the symptoms of underlying problems, but many of the solutions are to be found in areas other than altering the rate of population growth. Population growth is viewed less as a cause of development problems and more as an agent that pushes more fundamental problems to the forefront. Empirical evidence concerning nonrenewable resource constraints is not sufficient to make any strong conclusion about the impact of rapid population growth. With regard to food, the problem is more one of unrealized potential for increasing agricultural output and of the distribution of income than of diminishing returns to land. The results of economic research have failed to provide substantial and convincing empirical evidence to support the strong antinatalist concern about the adverse effect rapid population growth has on savings and investment. Authors of recent literature reviews deemphasized this impact. A revisionist interpretation deemphasizes some of the traditional" hypothesized direct influence of population and assigns population the role of an accomplice in contrast to the leading role of villain in the development story. To this list is added the importance of the pace of population growth and the political response to it. 2 problems commonly attributed to population are noted to illustrate some of the relevant considerations: food imbalance and high unemployment rates. For many countries, a main cause of food shortage is government policy that penalizes agriculture through the imposition of taxes and subsidies that twist the terms of trade against farmers, thereby reducing incentives to produce and innovate. 1 impact of rapid population growth is to bring this problem to a head sooner. It also forces a more rapid response. The critical question is whether such "time pressure" is more or less likely to bring about changes that will address the causes of the problem or the manifestations of problems. For high rates of unemployment or underemployed labor in 3rd world cities, the question is whether the pressure of time results in a resolution of the fundamental causes or just a treatment of the symptoms.^ieng

Population growth, the dependency rate, and the pace of economic development.

Abstract The analysis of population's impact on the economy has frequently been developed in the context of the dependency-rate argument. The dependency rate, typically measured as the proportion of the total population outside the labour force, is a summary statistic which is intended to capture the influence of a population's age structure on the process of economic growth. Unfortunately, there has been substantial confusion surrounding the economic interpretation of the dependency rate. This confusion derives from the fact that the dependency rate has been used as a proxy for several age-specific influences of population on economic growth. Additionally, for anyone of these influences of population, the impact on the economy will be determined by the particular economic model within which the dependency rate is being analysed. In other words, depending on which age-specific economic aspect of the dependency rate is being examined, and depending on which economic model forms the basis of the analysis, it is possible that an increase in the dependency rate may be associated with either an increase or a decrease in the economy-wide growth of output per head. As a result, the widely used dependency-rate statistic may not be a particularly useful predictor of economic - demographic - growth-rate interrelationships unless the analyst makes explicit his underlying economic framework, and unless the particular economic influences for which the dependency rate is taken as a proxy are delineated.