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At least 919 records · Page 51Linked to original sources
PubMed1990

Sewall Wright (1889-1988).

The genetic contributions of Sewall Wright is briefly reviewed with special reference to J.B.S. Haldane's work. These include his work in population genetics, statistics, and animal breeding.

Animal Husbandry↗
PubMedDate not supplied

Breastfeeding and use of the health care system in Bahia State, Brazil: three multivariate analyses.

Three multivariate methods--deviation from total proportion breastfeeding, polynomial regression, and proportional hazards--are used on current status breastfeeding data to explain an inverse relationship between use of the health care system and breastfeeding in Bahia State, Brazil. Among the intervening variables analyzed--urban/rural residence, educational attainment, age of woman, and place of last live birth--education and place of last live birth are found to have a net effect on breastfeeding by all three methods of analysis. The advantages and disadvantages of each method are described.

Adolescent↗
PubMed1990

Vasectomy and cardiovascular deaths in Korean men: a community-based case-control study.

This community-based case-control study was carried out in four cities in South Korea to examine whether vasectomy is associated with a long-term increased risk of cardiovascular death in Korean men. Our results coincide with those from epidemiological studies conducted in Western countries as well as the one study conducted in China and do not support the vasectomy--atherosclerosis hypothesis originating from animal research.

Adult↗
PubMed1990

A surveillance system for assessing health effects from hazardous exposures.

A statistical procedure for monitoring the health status of a community potentially exposed to a hazardous environment is presented. It utilizes two levels of investigation. Level I studies monitor routinely collected vital statistics and routes of community exposure whereas level II studies require additional data collection and are further distinguished by their design and duration. In a level I study, routine vital statistics for specified end points over a specified period of time are monitored, and the observed number of events is compared with the expected number of events for a given population. The statistical model used with this procedure employs a two-step decision rule based on the standardized mortality ratio for the study community. An "alert status" is invoked when the number of events exceeds a prescribed excess. An "action status" is indicated if the excess noted in the initial period persists or if the observed number of events in the initial period greatly exceeds expectation. Should an "action status" be justified, level II studies to determine the likely explanation for the significant excess are initiated. This could include the conduct of a "case-control" study using the exposure data available from monitoring the community.

Cluster Analysis↗
PubMed2026

Understanding Genomic Landscapes of Differentiation in Round-Tailed Horned Lizards (Phrynosoma modestum).

Population divergence is promoted by divergent selection and inhibited by gene flow, but the mechanisms of and relationship between these two processes remain poorly understood. Developing a well-informed hypothesis of the selective pressures underlying divergence in a natural population requires a thorough understanding of both species structure and demographic history. In this study, we assess whole-genome sequences of round-tailed horned lizards (Phrynosoma modestum) from throughout the species range and combine phylogenetic analyses with genomic landscape scans to understand how current genetic diversity has been influenced by demographic histories and evolutionary pressures. Maximum likelihood (ML) phylogenetic analysis supports two lineages within the species, corresponding to a North/South population divide that developed around 7 million years ago (Ma) and displays little migration. However, intermediate genealogical divergence index values between the two lineages ultimately leave us unable to recommend a full taxonomic distinction. Genome-wide scans of population genetic statistics identified islands of divergence exhibiting differentiation patterns linked to models of reproductive isolation and within-population selection. Significantly negative values of Tajima's D and positive selection statistics in these islands offer support for selection acting on P. modestum, but patterns may also stem from recent population expansions. We posit that selection within populations has played a large role in shaping genomic divergence across the species' range. Taken together, our results provide perspective into how variable selective pressures shape the genomics of two divergent populations currently maintaining species integrity, despite significant signatures of geographic structure and divergence.

Animals↗
PubMedDate not supplied

Decline of tuberculosis mortality in an urban Mexican-origin population, 1935-1984.

Through a series of life table analyses, this paper describes the natural history of tuberculosis mortality in a Mexican-origin community over five decades (1935-84) during which the disease underwent a transition from a major underlying cause of death to a disease conditioned mentioned more often on death certificates as contributing to death than causing death. The decline in death rates from 1940 to 1950 was especially remarkable. Successive birth cohorts of Mexican Americans, separated by as little as five years of age, experienced distinctly lower risk of death from tuberculosis as they entered young adulthood. There was a rapid convergence in age-specific patterns of tuberculosis death rates in Mexican Americans toward those of non-Hispanic whites, so that by 1960 tuberculosis was primarily a cause of death in old age rather than young adulthood. The impact of changing environment, both through improvements of conditions within neighborhoods and through residential mobility, on birth cohorts at risk of tuberculosis needs to be examined in further research.

Adolescent↗
PubMed2004

3D-T1rho-relaxation mapping of articular cartilage: in vivo assessment of early degenerative changes in symptomatic osteoarthritic subjects.

RATIONALE AND OBJECTIVES: To determine the in vivo feasibility of quantifying early degenerative changes in patellofemoral joint of symptomatic human knee using spin-lattice relaxation time in the rotating frame (T(1rho)) magnetic resonance imaging (MRI). MATERIALS AND METHODS: All the MRI experiments were performed on a 1.5 T whole-body GE Signa clinical scanner using a custom built 15-cm diameter transmit-receive quadrature birdcage radiofrequency coil. The T(1rho)-prepared magnetization was imaged with a three-dimensional gradient-echo pulse sequence pre-encoded with a three-pulse cluster consisting of two hard 90 degrees pulses and a low power spin-lock pulse. Quantitative T(1rho) relaxation maps of asymptomatic (n = 8 males), and six symptomatic human volunteers (four men, two women) were computed using a appropriate signal expression. RESULTS: All six symptomatic volunteers showed elevation in T(1rho) relaxation times when compared with asymptomatic subjects. In symptomatic population, the T(1rho) relaxation times varied from 63 +/- 4 ms to 95 +/- 12 ms (mean +/- standard deviation) depending on the degree of cartilage degeneration. The increase in T(1rho) of symptomatic population was statistically significant (n = 6, P <.002) when compared with corresponding asymptomatic population. However, in asymptomatic population the relaxation times varied only from approximately 45 to 55 ms (n = 8, age range 22-45 years). CONCLUSION: Preliminary results demonstrated the in vivo feasibility of quantifying early biochemical changes in symptomatic osteoarthritis subjects employing T(1rho)-weighted MRI on a 1.5 T clinical scanner. This study on limited number of symptomatic population shows that T(1rho)-weighted MRI provides a noninvasive marker for quantitation of early degenerative changes of cartilage in vivo. However, further studies are needed to correlate early osteoarthritis determined from arthroscopy with T(1rho) in a large symptomatic population.

Adult↗
PubMed1980

[Problems of statistical evaluation of stereological data from single cells].

A definition of morphometrical parameters of single cell populations is given. Methods for estimating these quantities (confidence estimation included) are described. For the comparison of equivalent parameters of 2 cell populations 2 statistical test procedures replacing the common t-test, are discussed. In addition, a homogeneity test is proposed for comparing the distributions of morphometrical data.

Cell Nucleus↗
PubMed2006

Moxonidine improves glycaemic control in mildly hypertensive, overweight patients: a comparison with metformin.

AIM: To compare the effects of moxonidine and metformin on glycaemic control in patients with impaired glucose tolerance and signs of the metabolic syndrome. METHODS: A multicentre, prospective, randomized, open-label study design was adopted with blinded endpoint evaluation. Patients > or =40 years old, with impaired glucose tolerance (or diabetes mellitus treated with diet alone) and a body mass index (BMI) of at least 27 kg/m2 were treated twice daily with moxonidine 0.2 mg or metformin 500 mg for 16 weeks. Oral glucose tolerance test (OGTT) was performed at baseline and end-of-study; plasma insulin and plasma glucose levels were measured at 0, 60, 120 and 180 min after administration. RESULTS: With regard to effects on insulin [mean area under the curve (AUC) for insulin], the primary efficacy endpoint of the study, both drugs did not show equivalence. On the contrary, in the per protocol (PP) population, moxonidine statistically significantly (p = 0.025) decreased the AUC for insulin from baseline in the PP population; for metformin, the treatment effect on insulin was a small, net increase resulting in a statistically significant between-group difference of 16.2% (95% CI = 0.1-35.0). The change in mean insulin AUC was most marked in the subgroup of patients with higher sympathetic activity (heart rate >80 bpm). Mean fasting plasma glucose (FPG) levels and HbA1c levels were largely unchanged by moxonidine treatment but significantly decreased by metformin treatment. The difference between the groups was 14.7% (p = 0.0523) in the intent-to-treat (ITT) sample. By study end, both treatments had significantly increased the Matsuda Insulin Sensitivity Index (ISI) from baseline to a comparable extent: moxonidine by reducing plasma insulin after a glucose challenge, metformin by reducing FPG. BMI fell significantly in both groups and blood pressure normalized; both drugs were well tolerated. CONCLUSIONS: Moxonidine improved insulin sensitivity in response to glucose challenge in patients with evidence of metabolic syndrome. This improvement resulted from a reduction in plasma insulin levels and was most marked in patients with high sympathetic drive at baseline. By enhancing insulin sensitivity, moxonidine treatment may help prevent the development of diabetes and thereby ameliorate the risk for cardiovascular disease.

Adult↗
PubMed2005

Effective size of populations under partial inbreeding and selection on a set of linked additive genes.

The prediction theory of effective population size (Ne) is extended to cover selection on a set of linked additive genes and partial inbreeding (partial selfing or partial full-sib mating). Ne under selection is generally expressed as a function of the cumulative change in frequency of a neutral gene due to the random association between the neutral and selected genes generated by finite sampling. In this study, the association under partial selfing was classified into two types, the association between the neutral and selected genes on the same gamete, and the association between the neutral and selected genes each on the different gametes in the same parent. For partial full-sib mating, an additional association, i.e., the association between the neutral and selected genes each in the different parents in the same family, was included in the model. According to this classification of the association, the coefficient accounting for the cumulative change in frequency of the neutral gene was partitioned into two or three components. A method for computing the partitioned coefficients was obtained from the transition matrix approach, in which the joint effect of linkage, selection and partial inbreeding was taken into account. To assess the joint effects of linkage, selection and partial inbreeding on Ne, numerical computations with the obtained expressions were carried out. The effect of linkage on Ne was generally small, except for an extremely small genome size, while the partial inbreeding resulted in a drastic reduction in Ne. For a given genome size, Ne was essentially independent of the length and number of chromosomes. Some of these results were verified by stochastic simulations.

Animals↗
PubMed1997

Study of bone mineral density in lumbar spine and femoral neck in a Spanish population. Multicentre Research Project on Osteoporosis.

The aim of this study was to generate standard curves for bone mineral density (BMD) in a Spanish population using dual-energy X-ray absorptiometry (DXA), at both lumbar spine and femoral neck sites. The total sample size was 2442 subjects of both sexes aged 20-80 years, stratified according to survival rates, demographic distribution by local regions and sex ratio in the Spanish population. Subjects with suspected conditions affecting bone metabolism or receiving any treatment affecting bone mineralization were excluded. The study was carried out in 14 hospitals and bone density measurements were performed, using a QDR/ 1000 Hologic device. In the female population, the highest value for lumbar spine BMD was found within the 30-39 years age group, being significantly lower after the age of 49 years. In the male population, the highest values for lumbar spine BMD are found one decade earlier than in the female population and become significantly lower after the age of 69 years. The highest values for femoral neck BMD in men and women was found in the 20-29 year age group. Values for femoral neck BMD in the female population become statistically lower after the age of 49 years, while in the male population this effect was seen after the age of 69 years. Values for femoral neck BMD were higher in men than women at all ages.

Absorptiometry, Photon↗