SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
"The paper presents a model which shows that the probability of migrants being mobile after migration depends on the number of previous waves. The model concludes that low order waves provide positive externalities to higher order waves. This conclusion is empirically tested by comparing the interindustry mobility of two sequential waves of political migrants to Israel."
A model of urban population density functions is proposed that uses all available data on densities in urban areas. "This model postulates that population density at each census tract in each city is determined by city size, transportation costs, land supply, income and age of city." The model is applied to data on cities in Israel.
"A multinomial logit model focusing on economic and other locational factors is formulated and applied to data on place-to-place migration in Israel. Results indicate the effects of expected industrial wage differentials, in accordance with the hypothesis of Harris and Todaro (1970), and of disparities in the structure of industrial employment, suggesting that perceived risk as well as expected return enter into the decision to migrate, as Stark and Levhari (1982) have argued. Other effects include those associated with regional differentials in amenities and agglomeration associated with urbanization, population mobility by age group, center-periphery migration trends, border security hazards, and the like. Implications of the analysis for the Israeli policy of population dispersion are discussed."
"The author investigates how trends in international labour migration in the Arab world have been paralleled by new directions in migration research....[She] seeks to evaluate why the urban impact of international migration is so great and outlines the considerable potential which exists for pursuing research on this aspect of urban development."
Explore the source record for details and available documents.
The author explores the reasons for the failure of a plan for population exchanges that took place between Jews and Arabs in Palestine in the 1930s. Special focus is given to the success of previous exchanges between Greece and Turkey that took place during the 1920s and why this model failed in Palestine. The author concludes that "the Zionist plans which assumed that one could encourage voluntary transfer by creating attractive economic conditions in the target areas, did not take into account the factors of nationalism, ties to place of residence, religion, etc. These factors carried no less weight than the economic factor and they could effectively prevent any voluntary transfer of the Arab population."
Bos indicus breeds, commonly known as Zebu cattle, have spread from their center of origin in Western Asia into large areas of Asia (including the Asia-Pacific basin), Africa, South and Central America (including the Caribbean islands). The original Zebu genotype, however, has been modified by planned and unplanned cross-breeding programs involving many native and Bos taurus breeds in their new habitats. Though accurate estimates are not available, more than half of the world's cattle population includes a proportion of B. indicus germ plasma. B. indicus native breeds have developed by natural selection over centuries for their ability to survive in rough, harsh tropical environments. Most of these non-described breeds still exhibit high fertility, in terms of calving rates, and disease resistance but they grow very slowly and take well over 3 years to reach puberty and produce only a few liters of milk over a short lactation period. Selection has been carried out in some areas and distinct Zebu breeds have been developed that have moderately high growth rate and milk production. However, they are slow breeders and have extended pre-pubertal and postpartum anestrous periods, compared to their temperate counterparts exposed to similar environment and management. The reproductive biology of B. indicus is similar to that of B. taurus. Most of the proven management, nutritional, hormonal and biotechnological interventions developed through experimentation with B. taurus breeds are equally applicable to B. indicus and their crosses. Zebu breeds predominate in most tropical countries where the majority of the human population lives. If meat and milk production are to be increased in the tropics, Zebu cow productivity, in terms of number of calves produced per lifetime or per unit area of land, must be increased and the time from birth to slaughter must be reduced. This goal could be achieved either by selection within local Zebu populations or through planned cross-breeding with B. taurus breeds. Because the productive and reproductive potentials of Zebu cattle are relatively low, worthwhile gains could only be achieved by selection over many generations. This would require substantial investment in labor, feed and drugs that may not be economic since the return from such investment is relatively low. However, many studies have shown that cross-breeding with B. taurus, which combines additive, dominance and epistatic effects of the two genotypes, ensures high productive and reproductive performance. Therefore, planned cross-breeding with suitable B. taurus breeds, although demanding additional investment in labor, feed and drugs, will still be economic because the return far exceeds the costs.
West Nile (WN) virus is a mosquito-borne flavivirus that is native to Africa, Europe, and Western Asia. It mainly circulates among birds, but can infect many species of mammals, as well as amphibians and reptiles. Epidemics can occur in rural as well as urban areas. Transmission of WN virus, sometimes involving significant mortality in humans and horses, has been documented at erratic intervals in many countries, but never in the New World until it appeared in New York City in 1999. During the next four summers it spread with incredible speed to large portions of 46 US states, and to Canada, Mexico, Central America and the Caribbean. In many respects, WN virus is an outstanding example of a zoonotic pathogen that has leaped geographical barriers and can cause severe disease in human and equine. In Europe, in the past two decades there have been a number of significant outbreaks in several countries. However, very little is known of the ecology and natural history of WN virus transmission in Europe and most WN outbreaks in humans and animals remain unpredictable and difficult to control.
Over the past twenty years diverse groups in Northeast Asia, Western Europe, and North America have competed to map, sequence, and characterize the immunoglobulin loci of mouse and man. Now that this work is near completion, it has become evident that the human and mouse germline repertoires share broad similarities in gene composition, organization, and other general principles. In spite of these similarities, the repertoires expressed by adult mice and humans are distinct and differ from each other in detail. In both species the mechanisms used to create repertoire diversity appear designed to generate a random range of antigen binding sites. However, a detailed analysis reveals significant constraints in the sequence and amino acid composition of the third complementarity region of the H chain (CDR-H3), which lies at the center of the antigen binding site. The mechanisms used to regulate the composition of the repertoire, their significance to the development and maintenance of immune competence, and the contribution of violation of normal repertoire boundaries to the development of diseases of immune function remain foci of ongoing investigation.
The caves at Klasies River contain abundant archaeological evidence relating to human evolution in the late Pleistocene of southern Africa. Along with Middle Stone Age artifacts, animal bones, and other food waste, there are hominin cranial fragments, mandibles with teeth, and a few postcranial remains. Three foot bones can now be added to this inventory. An adult first metatarsal is similar in size and discrete anatomical features to those from Holocene burials in the Cape Province. A complete and well-preserved second metatarsal is especially long and heavy at midshaft in comparison to all Holocene and more recent South African homologues. A large fifth metatarsal is highly distinctive in its morphology. In overall size, these pedal elements resemble specimens from late Pleistocene sites in western Asia, but there are some differences in proportions. The fossils support earlier suggestions concerning a relatively high level of sexual dimorphism in the African Middle Stone Age population. Squatting facets on the two lateral metatarsals appear to indicate a high frequency of kneeling among members of this group. The new postcranial material also underlines the fact that the morphology of particular skeletal elements of some of the 100,000-year-old Klasies River individuals falls outside the range of modern variation.
Human brucellosis is now a rare disease in countries where eradication programs (especially vaccination) against brucellosis in cattle, sheep, and goats have been successfully implemented. In France, fewer than 50 brucellosis cases are annually notified to the National Institute for Infection Surveillance. Human brucellosis, however, remains endemic in the Mediterranean basin, Middle East, Western Asia, Africa, and South America. Shortcomings of standard diagnostic methods for brucellosis (variable sensitivity of culture, frequent serological cross reactions) have been only partially resolved by modern molecular biology techniques. There are now 3 new challenges to be faced by the medical and veterinarian community: the expanding wildlife reservoir of brucellosis, with a possible impact on domestic animals; the emergence of Brucella. melitensis infections in cattle, for which prophylactic efficacy of available vaccines has not been established; and recent recognition of a huge animal reservoir of Brucella species in marine mammals, for which the potential virulence in humans remains unknown.
Since 1988, the Sultanate of Oman has experienced three outbreaks of paralytic poliomyelitis. The last outbreak occurred in December 1993 and involved two children aged 10 months and 4 1/2 years. The children had received five and four doses, respectively, of trivalent oral polio vaccine (OPV) and lived in the same village. Serum neutralizing antibody tests suggested that paralytic polio in these children was due to poor antibody response to OPV. Wild poliovirus type 1 was isolated from both patients, as well as from seven of ten close contacts of the older child, and one of eight contacts of the younger child. All contacts had received three to six doses of OPV. Genomic sequence studies indicated that the virus isolates belonged to a genotypic group prevalent in southern and western Asia, but differed markedly from virus isolated during the 1988/89 outbreak, suggesting another importation of poliovirus. In response to the outbreak, supplementary immunization with OPV was given to children <6 years of age, initially in the affected district, and subsequently to children in the whole country. This study demonstrates that immunization with three to six doses of OPV did not prevent infection with wild poliovirus. In those children with sub-optimal response to OPV, infection resulted in paralytic poliomyelitis. The outbreak remained localized in one village, indicating that the outbreak control measures were effective.
In the past decade, the Sultanate of Oman has experienced three outbreaks of paralytic poliomyelitis--a widespread polio type 1 epidemic in 1988/1989, four cases of polio type 3 in three different regions in 1991, and a localized type 1 outbreak in 1993. The lessons learnt from each of these epidemics have guided us to modify and improve our polio eradication activities. Currently, these activities include administration of five primary and three booster doses of trivalent oral polio vaccine, yearly national immunization campaigns (NIDs) since 1995 with coverage of >90%, localized immunization campaigns, acute flaccid paralysis (AFP) surveillance which involves reporting of all cases by facsimile to the Department of Surveillance within 24 h of detecting a case and weekly zero reporting from 22 sentinel sites, and virological testing of stool specimens of all AFP cases and their close contacts at the national, World Health Organization accredited laboratory. The cumulative success of these activities has resulted in Oman being free from polio for the past 6 years. However, the possibility of importation of wild poliovirus, particularly from southern and western Asia still exists.
HLA-DQA1 and polymarker (LDLR, GYPA, HBGG, D7S8, and GC) genotypic and allelic frequencies are determined for a population sample of 102 unrelated Basque individuals using PCR-based methodology. All six loci met Hardy-Weinberg expectations in at least two of the three analyses performed (HLA-DQA1 failed to meet Hardy-Weinberg requirements in the heterozygote deficiency test). Three linkage analysis programs (GDA, GENEPOP and LINKDOS) detected possible linkage disequilibrium between LDLR and HBGG and results from one (GDA) indicated a possible non-random association between HBGG and HLA-DQA1 as well. Allelic data for the six loci are compared to that previously established for other populations (18 for polymarker alone, 16 for polymarker plus HLA-DQA1) to determine homogeneity between the Basque sample and these groups. According to the results of G-tests based on these loci, the Tadjik, a nomadic Caucasian group from western Asia, and the Basque residents are the only sample populations surveyed that are homogenous with the Basque sample. Phylogenetic analysis places the Basque sample correctly within the Caucasian cluster.
It was only in 1980 that the first human retrovirus, HTLV-1, was isolated. Since then, HTLV-2, HIV-1 and HIV-2 have been identified. All four viruses are transmitted with varying efficiency sexually, vertically from mother to infant, and through blood by transfusion or contamination. HTLV-1 is endemic in populations in south-west Japan, Taiwan, sub-Saharan Africa, the Caribbean, southern USA, central and south America, Australia, Papua New Guinea, Solomon Islands and western Asia. There is now epidemic spread amongst IVDUs in north and south America and southern Europe. HTLV-1 is the aetiological agent of adult T-cell leukaemia/lymphoma (ATL) and tropical spastic paraparesis/HTLV-1 associated myelopathy (TSP/HAM). Other associations which may be causative are with polymyositis, infective dermatitis, gastrointestinal malignant lymphoma and chronic lymphatic leukaemia. ATL appears to be due to malignant transformation of HTLV-1 infected cells, and TSP/HAM to chronic activation of these cells. The epidemiology of HTLV-2 is being separated only recently from HTLV-1 through the application of PCR. It has a low level of endemicity in populations of central Africa, and central and south America. It is being spread epidemically amongst IVDUs in north America and southern Europe. Its association with any pathology in man remains uncertain. HIV-1 is epidemic and spreading rapidly throughout the world. In areas where homosexual contact was the predominant mode of transmission, heterosexual spread is becoming increasingly important. The areas where heterosexual contact is the predominant mode of transmission include the worst affected populations in the world, for example sub-Saharan Africa and some of the Caribbean. There have been recent and explosive increases of HIV-1 seroprevalence in IVDUs and female prostitutes in Asia, especially Thailand and India. Of the diverse pathology following infection, only the haematological consequences are reviewed in detail: these include anaemia, leucopenia, thrombocytopenia, disorders of coagulation and lymphomas. HIV-2, compared to HIV-1, is less infectious and causes less immunosuppression with more slowly progressive disease. It is prevalent in west Africa, but is spreading, albeit slowly, far beyond.
"The main purpose of this paper is to present some basic information about the population of Turkey.... This paper looks primarily at the time sequences of the outcomes for key demographic variables....A brief account is given in the last part of this paper of the theoretical frameworks that are employed to explain the decline of birth rates from very high to low levels in Turkey."
"The principal objective of this paper...is to estimate the number of Kurds in Turkey and their spatial distribution.... The ethnically Kurdish component of the population has increased from 3.132 million in 1965 to 7.046 million in 1990. This very substantial increase has been due to high fertility, which is a characteristic of agrarian or recently agrarian societies...,coupled with falling mortality, a typical case of demographic transition.... Perhaps more importantly, the massive population movements during the last two decades have spatially redistributed the Kurds."