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PubMed1980

Study of kinetics of epithelial cell populations in normal tissues of the rat's intestines and in carcinogenesis. II. Peculiarities of kinetics of enterocyte populations in experimental tumours of the colon.

Cell proliferation in adenocarcinomas induced in the rat's colon by parenteral injection of 1,2-dimethylhydrazine was compared with that in normal colonic epithelium by means of autoradiographs. The distinct zone of proliferation, typical of the intestines, was not observed in the tumours, and cells replicated nearly in all segments of neoplasms. Tumour enterocytes were found to have a longer short mitotic cycle (16 instead of 11 hrs), due, chiefly, to an extension of G1-period duration. They were also characterized by a more pronounced heterogeneity as far as the values of ts and tG2 are concerned, and, probably, by the formation of an R2-population. Both the index of S-phase (29%) and labelled cell fraction (87%) after 6 injections of 3H-thymidine spaced at six-hour intervals, were lower in adenocarcinomas than in the zone of maximum proliferation in the descending colon (45 and 100%, respectively) and yet higher than the same parameters calculated for the whole population of the intestinal epithelium (17 and 60%, respectively). As far as proliferation parameters go, adenocarcinoma cells highly resemble those of the crypt bottom population in control animals, which was found to consist of several subpopulations with a varying mean duration of the mitotic cycle, and where stem enterocytes are likely to occur. When enterocytes become malignant, disturbances in their differentiation decrease cell shedding into the intestinal lumen and, thus, cause tumours to arise and develop.

Adenocarcinoma↗
PubMed1991

Marketing to the mature population, Part 1: Evaluating the attractiveness of the mature population.

The mature population represents a major market force for the 1990s and the 21st century. Individuals age 65 and older make up a sizable percentage of the population and spend billions of dollars on health-related products and services. Despite the size and apparent attractiveness of this market, it may not be an easy one to penetrate. Pharmacists must recognize the vast differences within this group in terms of what its members want and expect from pharmacies. Only by understanding the unique attributes of the specific subgroups can pharmacists develop an effective marketing plan to serve their needs profitably. Specific marketing techniques for attracting segments of the mature population are described in Part 2.

Aged↗
PubMed1999

Spatial population dynamics: analyzing patterns and processes of population synchrony.

The search for mechanisms behind spatial population synchrony is currently a major issue in population ecology. Theoretical studies highlight how synchronizing mechanisms such as dispersal, regionally correlated climatic variables and mobile enemies might interact with local dynamics to produce different patterns of spatial covariance. Specialized statistical methods, applied to large-scale survey data, aid in testing the theoretical predictions with empirical estimates. Observational studies and experiments on the demography of local populations are paramount to identify the true ecological mechanisms. The recent achievements illustrate the power of combining theory, observation and/or experimentation and statistical modeling in the ecological research protocol.

Journal Article↗
PubMed2002

Haematological malignancies in a general population, based on information collected from a population study, hospital records, and the Cancer Registry of Norway: the Tromsø Study.

OBJECTIVES: To investigate the prevalence and incidence of haematological malignancies, and to compare the rates found with those reported from the Cancer Registry of Norway. METHODS: Three sources of information were used: (1) automated blood cell counts from 27 145 persons older than 24 yr (72% of those invited), participating in a population study (the Tromsø Study 1994-95); (2) patient medical records at the University Hospital of Tromsø during 1991-96; (3) the Cancer Registry of Norway. RESULTS: (1) In the population study, 13 new cases of haematological malignancies were diagnosed. For five of these the early detection was probably beneficial. (2) From the hospital records another 59 participants and 36 non-participants to the population study were found to have haematological malignancies. (3) Additionally, six cases were identified from the Cancer Registry. Totally, we thus identified 114 period prevalent cases, of which 86% had been reported to the Cancer Registry. Age-adjusted period prevalence of haematological malignancies was 4.7 per thousand in men and 2.9 per thousand in women. The prevalence increased with age. There were 84 cases with leukaemia, lymphoma, or multiple myeloma diagnosed at any time and still alive at 31 December 1996 (point prevalence 2.2 per thousand). Our estimated incidence of haematological malignancies did not differ significantly from that reported from the Cancer Registry. CONCLUSION: We found approximately the same rates of haematological malignancies as the Cancer Registry, although an underreporting of 14% to the Cancer Registry was detected. The point prevalence of leukaemia, lymphoma, and multiple myeloma was 2.2%.

Adult↗
PubMed1992

The alcohol dehydrogenase polymorphism in natural populations of Drosophila melanogaster: restriction map variation in the region of the Adh locus in populations from two hemispheres.

Restriction endonuclease variation in the 12 kb region surrounding the Adh locus was measured in seven Australian and six Chinese populations of Drosophila melanogaster. There is a higher level of nucleotide-substitution variation in the Australian populations than in the Chinese, which is possibly a reflection of their origins. None of the restriction site polymorphisms, nor any of the insertions, showed a significant association with latitude. A 0.2 kb deletion varied with latitude in the Chinese populations. In accordance with previous studies, a majority of the insertions were located in a region 1.5-3.5 kb 3' from the Adh coding region, and a majority of the deletions were at a site 3 kb 5' to the Adh coding region. Two of the insertions shared homologies with known mobile elements. Overall, the data suggest that restriction endonuclease variation in the Adh region is not related to the cline in Adhs frequencies.

Alcohol Dehydrogenase↗
PubMed2003

Prevalence, clinical spectrum and health care utilization of gastro-oesophageal reflux disease in a Chinese population: a population-based study.

BACKGROUND: Population-based data on gastro-oesophageal reflux disease in Chinese are lacking. The prevalence, clinical spectrum and health care-seeking behaviour of subjects with gastro-oesophageal reflux disease were studied. METHODS: Ethnic Chinese (3605) were invited to participate in a telephone survey using a validated gastro-oesophageal reflux disease questionnaire and the Hospital Anxiety and Depression Scale. RESULTS: A total of 2209 subjects (58% female; mean age, 40.3 years) completed the interview. The annual, monthly and weekly prevalence rates of gastro-oesophageal reflux disease were 29.8%, 8.9% and 2.5%, respectively. Gastro-oesophageal reflux disease symptoms were associated with non-cardiac chest pain [odds ratio (OR), 2.3; 95% confidence interval (95% CI), 1.7-3.1], dyspepsia (OR, 1.9; 95% CI, 1.4-2.5), globus (OR, 1.8; 95% CI, 1.2-2.7), acid feeling in the stomach (OR, 5.8; 95% CI, 4.5-7.5) and the use of non-steroidal anti-inflammatory drugs (OR, 2.3; 95% CI, 1.5-3.6), but not with dysphagia, bronchitis, asthma, hoarseness and pneumonia. Patients with gastro-oesophageal reflux disease had a significantly higher anxiety and depression score and required more days off work when compared with subjects without. The frequency of heartburn (P = 0.032), female gender (P < 0.001), degree of depression (P = 0.004) and social morbidity (P < 0.001) were independent factors associated with health care-seeking behaviour. CONCLUSION: The prevalence of gastro-oesophageal reflux disease was lower than that in Western populations, but carried a significant socio-economic burden in the studied Chinese population. The frequency of heartburn, female gender and psychosocial factors were associated with health care utilization in gastro-oesophageal reflux disease.

Adult↗
PubMed1999

Population structure delineated with microsatellite markers in fragmented populations of a tropical tree, carapa guianensis (Meliaceae)

Deforestation and selective logging in the tropics may have serious consequences on genetic processes in tropical tree populations, affecting long-term survival of a given species as well as tropical forest communities. Because understanding the effects of human-induced changes on genetic processes is of utmost importance in formulating sound conservation and management plans for tropical forest communities, we developed microsatellite or simple sequence repeat (SSR) markers for the tropical tree Carapa guianensis (Meliaceae) and assessed the polymorphism of SSRs in adult and sapling populations in a large contiguous forest and in selectively logged and fragmented forests. The number of alleles in polymorphic loci ranged between 4 and 28. No inbreeding was detected in saplings or adult cohorts, but the allelic richness was lower in the sapling cohort of the isolated fragment. Genetic distances, Nei's D and (delta&mgr;)2, and RST values among saplings were greater than among adult cohorts, suggesting restriction of gene flow due to deforestation and habitat fragmentation. These SSR loci may be used to address many related questions regarding the population and conservation genetics of tropical trees.

Journal Article↗
PubMed2000

Population genetics of Escherichia coli in a natural population of native Australian rats.

Escherichia coli, a normal inhabitant of the intestinal tract of mammals and birds, is a diverse species. Most studies on E. coli populations involve organisms from humans or human-associated animals. In this study, we undertook a survey of E. coli from native Australian mammals, predominantly Rattus tunneyi, living in a relatively pristine environment in the Bundjalung National Park. The genetic diversity was assessed and compared by multilocus enzyme electrophoresis (MLEE), sequence analysis of the mdh (malate dehydrogenase) gene and biotyping using seven sugars. Ninety-nine electrophoretic types were identified from the 242 isolates analysed by MLEE and 15 sequences from the mdh genes sequenced from 21 representative strains. The Bundjalung isolates extend the diversity represented by the E. coli reference (ECOR) set, with new MLEE alleles found in six out of 10 loci. Many of the Bundjalung isolates fell into a discrete group in MLEE. Other Bundjalung strains fell into the recognized E. coli ECOR set groups, but tended to be at the base of both the MLEE and mdh gene trees, implying that these strains are derived independently from ancestral forms of the ECOR groups and that ECOR strains represent only a subset of E. coli adapted to humans and human-associated animals. Linkage disequilibrium analysis showed that the Bundjalung population has an 'epidemic' population structure. The Bundjalung isolates were able to utilize more sugars than the ECOR strains, suggesting that diet plays a prominent role in adaptation of E. coli.

Animals↗
PubMed2001

Optimal risk factors in the population: prognosis, prevalence, and secular trends; data from Göteborg population studies.

AIMS: To assess the prognosis and prevalence of optimal risk factors in the population. METHODS AND RESULTS: Data from several Göteborg population studies were used. Optimal risk factors were defined as serum cholesterol <5 mmol x l(-1), blood pressure <140/90 without treatment and being a non-smoker. In a 20-year follow-up of 7130 men aged 47 to 55 at baseline a group of 117 men who were optimal with respect to cholesterol, blood pressure and smoking were identified. In this group there was only one death from coronary disease, corresponding to 0.4 deaths per 1000 years, whereas the overall risk of coronary death in the study was 4.8 per 1000 years. Among men and women aged 25 to 34 in the Göteborg MONICA study 1995, less than half were optimal on all three scores, and in men and women aged 55 to 64, only 7% and 6%, respectively, were optimal. If body mass index below 25 was included only 34% and 37%, respectively, of men and women aged 25 to 34 were optimal, and 11% and 22% among men and women aged 35 to 44. In an analysis of secular trends over 30 years in four successive cohorts of men aged 50 the prevalence of optimal risk factors with respect to cholesterol, blood pressure and smoking increased from 1963 to 1993 but was still only 11% in 1993. CONCLUSIONS: As expected, optimal risk factors with respect to serum cholesterol, blood pressure and smoking confers a very low risk of coronary death. However, the prevalence of optimal risk factor status in the Swedish population is still low.

Adult↗
PubMed1972

The relationship between the firing rate of a single neuron and the level of activity in a population of neurons. Experimental evidence for resonant enhancement in the population response.

A quantitative comparison is made between experiment and the theoretically predicted dynamics of a neuron population. The experiment confirms the theoretical prediction that under appropriate conditions an enlarged resonant response should appear in the activity of the neuron population, near the frequency at which there is minimum modulation in the instantaneous rate of a single neuron. These findings bear on the relationship between the firing rate of a single neuron and the firing rate of a population of neurons.

Animals↗
PubMed1991

Population perspectives on the prevention and treatment of obesity in minority populations.

Possible causes of population differences in obesity prevalence are discussed: biologic susceptibility, treatment availability or effectiveness, and shared behavior patterns leading to caloric imbalance. It is argued that obesity in minority groups in the United States is best understood as a variation on a larger cultural theme, the creation of an environment in which highly palatable foods are accessible to all at low cost and physical activity is not required. Inequities in access to health education, treatment services, and environmental opportunities are probably responsible for the exacerbation of obesity and its attendant health conditions in some minority groups. Programs for the prevention of obesity in minority populations need to address these inequities and also to consider ways to counteract the historical trends in the United States toward nutritional excess in the population as a whole.

Cultural Characteristics↗
PubMed1999

Fatness and body mass index from birth to young adulthood in a rural Guatemalan population.

Body mass index (BMI; wt in kg/ht2 in m) has been proposed as a simple and valid measure for monitoring fatness. Using data from a 25-y longitudinal study of rural Guatemalans, we found that, as children, this population was stunted (mean height-for-age z = -2.6) and had low triceps skinfold thicknesses ( approximately 10% of reference medians), yet had mean BMIs above US reference medians. As young adults, mean BMIs were at the 50th and 20th percentiles for women and men, respectively. BMIs between ages 1 and 5 y were moderately correlated (r = 0.2-0.3) with those in young adulthood. BMI was correlated with subscapular (r = 0.5-0.8) and triceps (r = 0.2-0.7) skinfold thicknesses at all ages and with predicted percentage body fat in adolescence (r = 0.65) and adulthood (r = 0.8). Fatness was highly centralized, with ratios of subscapular to triceps skinfold thicknesses at the 50th-90th percentiles of reference medians at all ages. BMI was a poor indicator of central fat; the correlation between BMI and waist-to-hip ratio in 14-17-y-old males was -0.21). In stunted populations in developing countries, BMI alone should be interpreted with caution. In stunted children, BMIs may be high despite small extremity skinfold thicknesses; BMI alone may overestimate the prevalence of fatness in these children. In adults, measures in addition to BMI may be required to identify centralized adiposity in these populations.

Journal Article↗
PubMed1995

The inbreeding effective population number in dioecious populations.

The inbreeding effective population number in a dioecious population with discrete, nonoverlapping generations is investigated for both autosomal and X-linked loci. The recursion relations for the probabilities of genic identity, and the effective population numbers are analyzed and compared in two cases: (i) the offspring identified by sex in the calculation of the probability of common parentage and (ii) the offspring not so identified. Case i gives the correct evolution of the probabilities of identity, but case ii has been more widely studied and applied. A general symmetric framework that reduces the number of parameters is developed and used to examine a wide variety of models of panmixia and monogamy. Cases i and ii agree in many, but not all, models.

Animals↗
PubMed1974

The genetic structure of natural populations of Drosophila melanogaster. XI. Genetic variability in a local population.

Six hundred and ninety-one second chromosomes were extracted from a Raleigh, North Carolina population, and the following experimental results were obtained: (1) Salivary gland chromosomes of all lines were observed and the number of inversion-carrying chromosomes was 130, among which 76 carried In(2R)NS, 36 carried In(2L)t, 4 carried In(2L)t and In(2R)NS, and 14 carried different kinds of rare inversions. (2) Viabilities of homozygotes and heterozygotes were examined. The frequency of lethal-carrying chromosomes was 275/691 (or 0.398):70/130 (or 0.538) in inversion-carrying chromosomes and 205/561 (or 0.365) in inversion-free chromosomes. The former is significantly higher than the latter. The average homozygote viability was 0.4342 including lethal lines and 0.7163 excluding those, the average heterozygote viability being 1.0000. The detrimental load to lethal load ratio (D:L ratio) was 0.334/0.501 = 0.67. The average viability of lethal heterozygotes was less than that of lethal-free heterozygotes, significantly in inversion-free individuals but not significantly so in inversion-carrying individuals. Inversion heterozygotes seem to have slightly better viability than the inversion-free heterozygotes on the average, but not significantly so. (3) The average degree of dominance of viability polygenes was estimated to be 0.293 +/- 0.071 for all heterozygotes whose component chromosomes had better viabilities than 0.6 of the average heterozygote viability, 0.177 +/- 0.077 for inversion-free heterozygotes and 0.489 +/- 0.082 for inversion heterozygotes. (4) Mutation rates of viability polygenes and lethal genes were estimated on the basis of genetic loads and average degrees of dominance of lethal genes and viability polygenes. Estimates were very close to those obtained by direct estimation. (5) Possible overdominance and epistasis were detected, but the magnitude must be very small. (6) The effective size of the population was estimated to be much greater than 10,000 by using the allelism rate of lethal-carrying chromosomes (0.0040) and their frequency.-On the basis of these findings and the comparison with the predicted result (Mukai and Maruyama 1971), the mechanisms of the maintenance of genetic variability in the population are discussed.

Adaptation, Biological↗
PubMed1974

Enzyme variability in natural populations of Daphnia magna. II. Genotypic frequencies in permanent populations.

In permanent habitats populations of the cyclical parthenogen, Daphnia magna, reproduce by continued parthenogenesis and are subject to only sporadic sexual recruitment. The genetic effects of this breeding system have been investigated by analyzing allozyme frequencies in thirteen populations of D. magna.-Genotypic frequencies at polymorphic loci characteristically deviated markedly from Hardy-Weinberg proportions and gametic phase imbalance between loci was frequent. Genotypic frequencies were subject to violent, selectively determined oscillations over short periods of time. These observations suggest that permanent populations of D. magna ordinarily consist of a limited number of highly structured genotypes. The adaptational advantages offered by such structuring may have been a major selective factor favoring the evolution of cyclical parthenogenesis.

Animals↗
PubMed1974

Enzyme variability in natural populations of Daphnia magna. 3. Genotypic frequencies in intermittent populations.

In temporary habitats populations of the cyclical parthenogen, Daphnia magna, are re-established each year from sexual eggs and reproduce parthenogenetically for two or at most three generations. The genetic effects of this breeding system have been investigated by analyzing allozyme frequencies in nineteen intermittent populations.-Genotypic frequencies at polymorphic loci were ordinarily found to be in good agreement with Hardy-Weinberg proportions and disequilibria between loci were not observed. Although significant changes in gene frequencies were observed both during and between successive cycles, there was no evidence of the marked instability of genotype frequencies characteristic of permanent populations. The recombinational degradation of genotypes at the end of each annual cycle in temporary habitats effectively prevents the genotypic structuring which develops when continued parthenogenesis is possible.

Animals↗
PubMed1980

Population impact of mortality reduction: the effects of elimination of major causes of death on the 'saved' population.

In this paper we examine the effects on life expectancy of elimination of 4 major causes of death. Methodologically, we compare the results of cause elimination under assumptions of pattern of failure elimination and assumptions of underlying cause elimination in a modified multiple-decrement life table framework for the segment of the population impacted. The 4 diseases selected for analysis are cancer, ischaemic heart disease, stroke, and diabetes, major killers among the elderly population. The degree to which life expectancy changes occur within the population from elimination of a given cause if a function of 3 factors: 1) distribution of age at death by cause for persons who die of that cause, 2) the gain in person years lived for those 'saved' from dying from that cause which has been eliminated, and 3) the proportion of all deaths which are due to the specific cause which is eliminated. Mortality data from the 1969 U.S. multiple cause mortality tapes from NCHS are analysed to determine the impact of life expectancy for males and females of both races when one of these 4 specific causes of death is eliminated.

Adolescent↗
PubMed1990

Boys from populations with high-carbohydrate intake have higher fasting triglyceride levels than boys from populations with high-fat intake.

Experimentally, high-carbohydrate diets have been shown to elevate triglycerides, but it has not been established whether this rise is permanent or transient. The authors approached this question by studying 719 boys from worldwide populations with marked differences in long-term carbohydrate intake. Fasting serum triglycerides, total cholesterol and high density lipoprotein (HDL) cholesterol concentrations were measured in boys aged 8 and 9 years from 12 countries--eight in Europe, three in Africa, and one in Asia. A standardized protocol was used for obtaining fasting blood and for the preparation, storage and transport of serum, and all measurements were made in one laboratory. Published values were used for the United States. Mean values for lipid levels per country were compared with the percentage of daily energy intake consumed as carbohydrate or fat, as determined by survey. Boys from populations with higher carbohydrate and lower fat intake had lower low density lipoprotein (LDL) cholesterol levels (univariate regression coefficient (+/- standard error, -0.028 +/- 0.009 mmol/liter for each percent of energy from carbohydrate; p less than 0.01, n = 13), but they also had higher fasting triglycerides (0.010 +/- 0.002 mmol/liter for each percent of energy from carbohydrate; p less than 0.01, n = 13) and lower HDL cholesterol levels (-0.022 +/- 0.003 mmol/liter for each percent of energy from carbohydrate; p less than 0.001, n = 13). These trends agree with results from epidemiologic studies within populations and from controlled dietary trials, and suggest that in normolipidemic healthy subjects, high-carbohydrate, low-fat diets cause higher triglyceride levels than diets that are higher in fats and oils.

Africa↗