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PubMed1990

Transfers to the old, government debt and demographic change.

"In this paper we take the view that policy makers...take the relationship between (explicit) intergenerational transfer systems (including public pension schemes) and government deficits into account. It is assumed that policy makers are behaving altruistically towards past and future generations. Given the behavioral model, an analysis is made of the effects of demographic changes (such as the 'baby-boom' of the 1940s and 1950s and the decline of birth rates in the 1970s) on the decisions to be taken with respect to the tax rate of the public pension system and the size of government debt. From the analysis it appears that, with the assumption of altruistic decision-makers, periods of increasing or decreasing debt can occur alternately in periods of demographic change." The geographical focus is on developed countries.

Behavior↗

PubMed1991

Conjugational transfer of recombinant DNA in cultures and in soils: host range of Pseudomonas putida TOL plasmids.

Recombinant TOL plasmid pWWO-EB62 allows Pseudomonas putida to grow on p-ethylbenzoate. This plasmid can be transferred to other microorganisms, and its catabolic functions for the metabolism of alkylbenzoates are expressed in a limited number of gram-negative bacteria, including members of pseudomonad rRNA group I and Escherichia coli. Transfer of the recombinant plasmid to Erwinia chrysanthemi was observed, but transconjugants failed to grow on alkylbenzoates because they lost catabolic functions. Pseudomonads belonging to rRNA groups II, III, and IV, Acinetobacter calcoaceticus, and Alcaligenes sp. could not act as recipients for TOL, either because the plasmid was not transferred or because it was not stably maintained. The frequency of transfer of pWWO-EB62 from P. putida as a donor to pseudomonads belonging to rRNA group I was on the order of 1 to 10(-2) transconjugant per recipient, while the frequency of intergeneric transfer ranged from 10(-3) to 10(-7) transconjugant per recipient. The profile of potential hosts was conserved when the donor bacterium was Escherichia coli or Erwinia chrysanthemi instead of P. putida. No intergeneric gene transfer of the recombinant TOL plasmid was observed in soils; however, intraspecies transfer did take place. Intraspecies transfer of TOL in soils was affected by the type of soil used, the initial inoculum size, and the presence of chemicals that could affect the survival of the donor or recipient bacteria.

Anti-Bacterial Agents↗

PubMed2004

Phenotypic plasticity in bacterial plasmids.

Plasmid pB15 was previously shown to evolve increased horizontal (infectious) transfer at the expense of reduced vertical (intergenerational) transfer and vice versa, a key trade-off assumed in theories of parasite virulence. Whereas the models predict that susceptible host abundance should determine which mode of transfer is selectively favored, host density failed to mediate the trade-off in pB15. One possibility is that the plasmid's transfer deviates from the assumption that horizontal spread (conjugation) occurs in direct proportion to cell density. I tested this hypothesis using Escherichia coli/pB15 associations in laboratory serial culture. Contrary to most models of plasmid transfer kinetics, my data show that pB15 invades static (nonshaking) bacterial cultures only at intermediate densities. The results can be explained by phenotypic plasticity in traits governing plasmid transfer. As cells become more numerous, the plasmid's conjugative transfer unexpectedly declines, while the trade-off between transmission routes causes vertical transfer to increase. Thus, at intermediate densities the plasmid's horizontal transfer can offset selection against plasmid-bearing cells, but at high densities pB15 conjugates so poorly that it cannot invade. I discuss adaptive vs. nonadaptive causes for the phenotypic plasticity, as well as potential mechanisms that may lead to complex transfer dynamics of plasmids in liquid environments.

Analysis of Variance↗

PubMed1983

An empirical test of the effect of social security on fertility in the United States.

The author attempts to estimate the effects of the social security program on fertility in the United States from 1933 to 1974. A fertility model based on the choice theoretic calculus is presented, "with the distinguishing feature that the childbearing cohort's utility depends on own consumption as well as consumption of their retired parents. In this framework, changes in social security affect household income, and thus fertility, directly, as well as indirectly due to substitution of social security for private intergenerational transfers."

Americas↗

PubMed1992

Living arrangements of the elderly in Poland--evidence from survey Life Course (Family, Occupation and Migratory Biography), 1988.

"The paper presents a structural analysis of the living arrangements of the elderly in Poland based on the results of [a 1988] Polish retrospective survey.... Evaluation of living arrangements includes persons aged 60 and over and concentrates mainly on: family and household composition, intergenerational transfers, occupational activity of retired persons and selected aspects of health and life satisfaction."

Adult↗

PubMed1986

The changing economy and the family.

This study is concerned with the impact of changes in economic conditions on the family. "Three issues are considered in this paper. First, the reasons why the family is not fading away as an economic entity are discussed. The argument of this paper is that, despite the declines in various economic functions of the family and the increases in divorces and in other failures, the survival capacity of the family is both strong and robust." Second, the author contends that the economic approach should be extended to deal with the effects of the life-span revolution, shifts in prices and incomes, and the ability of the family to cope with these changes. Third, the hypothesis is put forward that intergenerational transfers are less important than increases over time in real per capita incomes and changes in income composition, its permanent and temporary components, and the sources of income. The geographical focus is worldwide.

Costs and Cost Analysis↗

PubMed1988

America's elderly.

The older population in the US has grown twice as fast as the rest of the population in the last 20 years. This growth is expected to accelerate early in the next century as the large baby boom cohorts move through middle age and become elderly. Today, about 1 in 8 Americans is 65 years of age or older. By 2030, 1 out of every 4 persons will be in older person. Substantial improvements in life expectancy at all ages, particularly at extreme old age, mean that not only will there be a greater proportion of elderly in the population, but the more will be the "oldest-old," over 85. By 2050, they will be more than 1/4 of the population. As people live longer, many are active and healthy well past retirement. However, many individuals living into their 80s have to cope with chronic disabilities affecting their capacity to perform day-to-day activities. Modern medicine has made great inroads against mortality from such illnesses as heart disease and stroke, but has not eliminated all the effects of these diseases. As the population ages, the issues of health care funding and availability, particularly long-term care, increase in importance. Contrary to widespread belief, the elderly are not abandoned by their families to nursing home care. The vast majority--95%--live in the community. Those needing assistance generally receive help from family and friends. This has created a tremendous demand for federal subsidies to support community-based long-term care services. 1/4 of the federal budget is now spent on the elderly--$270 billion in 1986. Medicaid and Medicare are among the government's success stories, but these programs are threatened by their very success. Economists estimate that government expenditures are 3 times greater for the elderly than for children, raising the issue of "intergenerational equity"--how to balance the amount of care society provides to those who have already contributed with what is provided to those who will contribute in the future. The view that the young and old simply compete for fixed resources is misleading. It ignores the interdependence among generations, and the burdens and benefits of intergenerational transfers at all stages of the life course.

Adult↗

PubMed1991

[[Coresidence with parents and marriage in modern Japan]].

Marriage trends and parental coresidence in Japan are analyzed using data on 9,000 couples from the 1987 Ninth National Fertility Survey. Consideration is given to age at marriage, residence characteristics, birth order, family size, and intergenerational transfers related to birth order. The author finds that "the percentage of children coresiding with parents at marriage has hardly changed and continued to be about 30 percent...since [the] 1960s." Comments on these findings by Kiyomi Morioka, Nobuyoshi Toshitani, and Makoto Atoh are included in Japanese (pp. 71-3). (SUMMARY IN ENG)

Asia↗

PubMed1994

Evidence for natural horizontal transfer of tetQ between bacteria that normally colonize humans and bacteria that normally colonize livestock.

Though numerous studies have shown that gene transfer occurs between distantly related bacterial genera under laboratory conditions, the frequency and breadth of horizontal transfer events in nature remain unknown. Previous evidence for natural intergeneric transfers came from studies of genes in human pathogens, bacteria that colonize the same host. We present evidence that natural transfer of a tetracycline resistance gene, tetQ, has occurred between bacterial genera that normally colonize different hosts. A DNA sequence comparative approach was taken to examine the extent of horizontal tetQ dissemination between species of Bacteroides, the predominant genus of the human colonic microflora, and between species of Bacteroides and of the distantly related genus Prevotella, a predominant genus of the microflora of the rumens and intestinal tracts of farm animals. Virtually identical tetQ sequences were found in a number of isolate pairs differing in taxonomy and geographic origin, indicating that extensive natural gene transmission has occurred. Among the exchange events indicated by the evidence was the very recent transfer of an allele of tetQ usually found in Prevotella spp. to a Bacteroides fragilis strain.

Animals↗

PubMed1995

Transfer of macrolide-lincosamide-streptogramin B (MLS) resistance in Clostridium difficile is linked to a gene homologous with toxin A and is mediated by a conjugative transposon, Tn5398.

An MLS resistance gene designated ermBZ, from a toxigenic Clostridium difficile strain (630) could be transferred between C. difficile strains, and to and from Bacillus subtilis. The intergeneric transfer occurred in the absence of any detectable plasmid DNA and the element responsible for gene transfer entered the recipient's chromosome, behaviour which is characteristic of a conjugative transposon. The element was designated Tn5398 and was found in six C. difficile strains. Tn5398 could be transferred to the non-toxigenic strain C. difficile CD37 which lacks the genes for toxins A and B. Transconjugants from both C. difficile and B. subtilis that had received the ermBZ gene also acquired a sequence of DNA that was homologous to the part of the toxin A gene that coded for the C-terminal repeat region.

Anti-Bacterial Agents↗

PubMed1993

In vivo transfer of pR68.45 from Pseudomonas aeruginosa into indigenous soil bacteria.

The release of genetically engineered organisms (GEMs) into the environment could result in novel gene sequences becoming transferred to, and established in, the indigenous soil biota. The potential for recombination in nonsterile soil is difficult to determine due to problems isolating transconjugants of indigenous microbes, while concurrently suppressing introduced donors. We have developed a system that allows us to detect the transfer of the plasmid R68.45 from Pseudomonas aeruginosa strain PA025 into the indigenous soil bacterial population. Transconjugants were selected by plating on minimal media containing antibiotics and were verified by DNA-DNA hybridization. The observed maximum transfer frequency was approximately 10(-6). Fatty acid analysis of transconjugants showed that intergeneric transfer was occurring between the introduced organism and genetically dissimilar species.

Conjugation, Genetic↗

PubMedDate not supplied

[Distribution and diversity of conjugative plasmids among some multiple antibiotic resistant E.coli strains isolated from river waters].

In natural bacterial communities the microbial structure and functions are subjected to dynamic environmental and genetic adaptation. Plasmid-mediated horizontal genes transfer has a major impact on the adaptability of bacteria, exemplified by the interspecific and intergeneric transfer of antibioresistance genes in a variety of aquatic media. The high incidence of resistant bacteria has been documented for fresh waters, marine waters and chronically polluted waters. The aim of this study was to establish the distribution and diversity of plasmids and to study the transfer of plasmids harboring multiple antimicrobial-resistance determinants (R plasmids) belong to 12 multiple antibiotic resistant E. coli strains isolated from river waters. Antimicrobial resistance patterns were performed for aminoglycosides (gentamycin, kanamycin), beta-lactams (ampicillin), cephalosporins (ceftazidime and cefotaxime), tetracycline, nalidixic acid and chloramphenicol by disk diffusion method following NCCLS recommendations. Minimum inhibitory concentrations (MICs) were performed using dilution method in Mueller-Hinton broth with a 0.06-64 micrograms/ml concentration range for all antimicrobials and bacterial inoculum corresponding to 0.5 standard of the McFarland scale. For the data analysis NCCLS breakpoints for resistance and sensitivity were used. Bacterial plasmid isolation was performed by an alkaline lysis method. Genetic characterization was performed by agarose gel electrophoresis and spectrophotometric analysis. R-plasmid transfer frequencies were estimated by conjugation of drug-resistant E. coli strains used as donors with E. coli DH5 alpha F recipient marked with chromosomal resistance to nalidixic acid (Nal). The drug resistance markers possessed by a particular donor strain were sequentially used to screen for R+ transconjugants by incorporation the particular drug in the selective media. All E. coli strains are multiple antibiotic resistant, 65% of them being resistant to all 8 antibiotics tested. Plasmid profile analysis revealed the presence of several plasmids ranging from 3.8 kpb to more than 50 kpb. All aquatic R+ strains transferred two or more of their resistance markers to E. coli DH5 alpha F, transfer of resistance to ampicillin and tetracycline being the most frequent and having a frequency of 10(-4) or greater (expressed as transconjugants/donor). The phenotypic data shows the frequency and dynamic flow of multiple antibioresistant E. coli strains in aquatic media. Electrophoretic patterns analysis reflects the high incidence and diversity of plasmids in aquatic E. coli strains. Plasmid-harboring E. coli strains transferred antibiotic resistance and, hence, possessed conjugative R plasmids. Of these, 80% transferred drug resistance at a frequency of about 10(-4).

Anti-Bacterial Agents↗

PubMed1979

Transfer of drug resistance factors to the dimorphic bacterium Caulobacter crescentus.

The P-type drug resistance factors RP4, RK2, R702, R68.45, and the N-type drug resistance factor R46 are transferred to Caulobacter crescentus at high frequencies. They are stably maintained and their antibiotic resistances are expressed. Experiments with RP4 have shown that intergeneric transfer of RP4 occur at a frequency of 10(-1). C. crescentus strains maintain RP4 as a plasmid, are sensitive to RP4-specific phage, and segregate phage-resistant cells at a frequency of 10(-4) to 10(-5). The RP4 plasmid can be used in several ways: (1) the RP4 plasmid will promote chromosomal exchange between C. crescentus strains at frequencies ranging from 10(-6) to 10(-8); (2) RP4 will promote the transfer of nonconjugative colE1 plasmids from E. coli to C. crescentus; once transferred, the colE1 plasmid is stably maintained under nonselective conditions, can be transferred serially, and segregates independently from RP4; and (3) RP4 can be used to introduce transposons into the C. crescentus chromosome, providing the basis for additional genetic techniques.

Bacteria↗

PubMed2002

Transfers from older parents to their adult children in Taiwan and the Philippines.

This study examines the extent to which older parents provide material resources and services to their children in the Philippines and Taiwan, and the influence of coresidence on reported transfers between parents and their adult children. The data used in the analyses are from two nationally representative household surveys of persons aged 60 and older in the Philippines and Taiwan. Results show that almost half of older parents in the Philippines provide resources to non-coresident children and only 4 percent of older Taiwanese parents currently make such transfers. When transfers with coresident children are included, older parents show much greater involvement in family support: 69 and 14 percent of older parents in the Philippines and Taiwan, respectively, say they make transfers to children. The difference between the two measures diminishes with age, however, as overall levels of giving decline. Results from multivariate models show that while both measures are associated in similar ways with key factors such as age, health, gender, and economic resources, the association between living arrangements and intergenerational transfers varies across measures. These results suggest that older adults' in these countries tend to exhibit a preference for transfers to the children with whom they live, and that coresidence with grandchildren may be an indirect transfer of services to non-coresident adult children.

Journal Article↗

PubMed1996

Repeated horizontal transfer of P transposons between Scaptomyza pallida and Drosophila bifasciata.

Two distinct P element subfamilies, designated M-type and O-type, reside in the genome of D. bifasciata. PCR-screening of 65 Drosophila species revealed that only D. bifasciata and its closest relative D. imaii possess O-type elements. Outside the genus, O-type elements were detected in Scaptomyza pallida. Restriction analyses show that the general structure of the O-type elements from S. pallida and D. bifasciata is the same. Sequence divergence turned out to be extremely low (0.43%). These results suggest that the O-type subfamily of D. bifasciata has been received by horizontal transfer from an external source, most probably from the genus Scaptomyza, as has been previously suspected for the M-type family. Since the sequence divergence between M-type elements from S. pallida and D. bifasciata is eighteen-fold higher than that between O-type elements, two independent intergeneric transfer events have to be postulated. In order to re-examine the taxonomic status of S. pallida, a partial sequence (489 bp) of the Adh gene was analysed. The data clearly prove that S. pallida has to be placed far outside the D. obscura group.

Alcohol Dehydrogenase↗

PubMed2001

Demonstration that the group II intron from the Clostridial Conjugative transposon Tn5397 undergoes splicing In vivo.

Previous work has identified the conjugative transposon Tn5397 from Clostridium difficile. This element was shown to contain a group II intron. Tn5397 can be conjugatively transferred from C. difficile to Bacillus subtilis. In this work we show that the intron is spliced in both these hosts and that nonspliced RNA is also present. We constructed a mutation in the open reading frame within the intron, and this prevented splicing but did not prevent the formation of the circular form of the conjugative transposon (the likely transposition intermediate) or decrease the frequency of intergeneric transfer of Tn5397. Therefore, the intron is spliced, but splicing is not required for conjugation of Tn5397.

Bacillus subtilis↗

PubMed1999

Transfer of a conjugative transposon, Tn5397 in a model oral biofilm.

A tetracycline resistance profile was established from a microcosm dental plaque in a constant depth film fermenter. The fermenter was inoculated with a Bacillus subtilis strain which contained the conjugative transposon, Tn5397, which confers tetracycline resistance upon its host. After 6 hour and 24 hour the tetracycline resistance profile of the biofilm was redetermined and a tetracycline resistant Streptococcus species was isolated. A molecular analysis of this strain confirmed that Tn5397 was present in the genomic DNA of the isolate. These data represent the first report, to our knowledge, of intergeneric transfer of a conjugative transposon in a mixed species biofilm and demonstrates the ability of conjugative transposons to disseminate antibiotic resistance genes in a mixed species environment.

Bacillus subtilis↗

PubMed1995

Old age security and inheritance in Nepal: motives versus means.

This paper documents expectations of old age support in rural Nepal. Current living arrangements of the elderly have been analysed with a focus on the ownership of land holdings. It is argued that the intergenerational transfer of property through inheritance from the older to the younger generation, especially among sons, together with the Nepali normative prescription that sons care for their aged parents, provides a mechanism for old age support. However, land is becoming a scarce resource, cultural traditions are breaking down through modernisation and the living conditions of the elderly are likely to deteriorate as this process continues.

Adolescent↗