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PubMedDate not supplied

Correlation analysis of pesticide use data and cancer incidence rates in California counties.

California, the leading agricultural state in the United States, has maintained a population-based cancer registry since 1988, and it also maintains a comprehensive, state-wide pesticide reporting system. Data on cancer incidence and pesticide use reporting are available, by county, for all 58 counties in California. Average annual age-adjusted cancer incidence rates (1988-1992), on a county-, sex-, and race/ethnicity-specific basis, were obtained from the California Cancer Registry (CCR), which maintains the population-based cancer registry throughout California. Pesticide use data (i.e., pounds of active ingredient applied annually in each county) were obtained from the California Department of Pesticide Regulation for 1993. Investigators used Pearson product-moment correlation coefficients (r) to correlate age-adjusted incidence rates for selected cancers with the use data for selected pesticides. For most sex- and race/ethnicity-specific groups, the correlation coefficients were very close to zero or negative in sign, indicating no correlation between pesticide use and cancer incidence. There were, however, several exceptions, particularly in Hispanic males for whom the following correlations were observed: leukemia and atrazine (r=.40), leukemia and 2,4-dichlorophenoxyacetic acid (r=.41), leukemia and captan (r=.46), atrazine and brain cancer (r=.54), and atrazine and testicular cancer (r=.41). For black males, we observed the following: atrazine and prostate cancer (r=.67) and Captan and prostate cancer (r=.49). In females, only a few of the correlations were elevated. Although most of the correlations examined in this analysis were not elevated, several of those in the Hispanic and black male populations were. These segments of the population have traditionally been employed as farm workers in California and have had the greatest potential for exposure to pesticides. This was an ecological study for which no data about exposure to pesticides at the individual level were available for analysis. In addition, no latency period was allowed between potential exposure and diagnosis with cancer. However, the results obtained in two minority groups who represented the majority of farm workers in the fields suggested that additional research studies, in which more rigorous study designs are used, should be conducted in those groups.

Age Distribution↗

PubMed2003

Eating behaviour, and preprandial and postprandial correlations in male broiler and layer chickens.

1. It has been suggested that broiler chickens have a disturbed satiety and hunger mechanism. The satiety mechanism for eating can be expressed as the positive correlation between meal length and the length of the preceding (preprandial) interval; the hunger mechanism for eating as the positive correlation between meal length and the length of the succeeding (postprandial) interval. An experiment was conducted to investigate eating behaviour of male broiler and layer chickens by measuring meal and interval lengths. 2. Eight male broilers and 8 male layer chickens were housed individually and visually isolated in floor pens (1 m2/pen) on wood shavings. From 4 to 7 weeks of age, eating behaviour of each bird was recorded for 3 h in two conditions each week. In the first condition, the birds were not deprived from feed. In the second condition, they were 24-h food deprived and feed was provided just before the observation started. Preprandial and postprandial correlations were calculated based on data of the non-deprived condition. Before and after each observation bird and feeder were weighed to measure weight gain and feed consumption during observation. 3. Under the non-deprived condition, the broilers spent initially more, but at a later age less time on eating. The broilers had fewer meals per hour, consumed more feed per hour, and had longer meal and interval lengths than the layer chickens. After 24-h feed deprivation, the broilers had a longer first meal, consumed more feed per hour and spent more time on eating than the layer chickens. Significant preprandial correlations but no postprandial correlations were found in the broilers. In the layer chickens, both significant preprandial and postprandial correlations were found. This indicates that for regulating eating behaviour, the satiety mechanism dominates the hunger mechanism in broilers, and satiety and hunger mechanisms are equally involved in layer chickens. 4. The typical eating behaviour of broilers and the calculated preprandial and postprandial correlations have given new indications that hunger and satiety mechanisms in broilers have changed compared with layer chickens. In broilers, there is no lower set point, but only an upper set point for controlling eating behaviour, which suggests that broilers eat to their maximal physical capacity.

Animals↗

PubMed2004

Chromatin fluorescence characteristics and standard semen analysis parameters: correlations observed in andrology testing among 136 males referred for infertility evaluation.

This paper aims to describe the relation between standard semen analysis parameters (concentration, motility and morphology) and sperm chromatin structure assay (SCSA) results among patients referred for infertility evaluation. Healthy males (n=136) seeking infertility consultation were evaluated prospectively by semen analysis and sperm chromatin structure assay (SCSA). Significant inverse correlations were observed between high sperm concentration and DNA fragmentation index (DFI) and high DNA stainability (HDS) (r=- 0.45; P<0.001, and r=- 0.40; P<0.001, respectively). Both progressive motility and normal morphology were also strongly inversely correlated with DFI and HDS. However, in stratified analysis the correlation between concentration < or =20 M/ml and DFI, and concentration < or =20 M/ml and HDS were not significant (P=0.31 and 0.38, respectively). For men with sperm motility < or =40% the correlation between motility and HDS was not significant (P=0.22), but between motility and DFI the correlation remained significant (P=0.04). Although strong correlations between DFI, HDS and semen analysis findings were noted in the overall study population, when oligozoospermic and asthenozoospermic patients were analysed separately the correlation between concentration and sperm chromatin fragmentation was not significant. For such men, SCSA appears to be a diagnostic variable independent of the semen analysis, providing information about nuclear abnormalities not readily apparent from standard semen analysis alone. Additionally, SCSA data may offer explanations for previous miscarriage, providing closure for some couples contemplating future use of anonymous donor sperm.

Adult↗

PubMedDate not supplied

Familial correlation and segregation analysis of forced expiratory volume in one second (FEV1), with and without smoking adjustments, in a Tucson population.

BACKGROUND: Previous researchers have found significant familial aggregation but no evidence of Mendelian inheritance of forced expiratory volume in one second (FEV1) in general population studies. However, the influence of cigarette smoking on familial aggregation of FEV1 has been difficult to assess in these studies. OBJECTIVES: The main objective of our study was to attempt to discern the effects of smoking on familial correlation and segregation models of FEV1. SUBJECTS AND METHODS: In a randomly selected sample of white, non-Mexican American families in Tucson, Arizona, we performed two separate familial correlation and segregation analyses of FEV1, one adjusted for cigarette smoking and one unadjusted for smoking. In both, initial survey measures of FEV1 for 1329 females and 1291 males in 746 families were standardized for gender, age, height and height-squared using piecewise linear regression models. In the smoking-adjusted model, total number of pack-years smoked, current and ex-smoking status, and the interaction between total pack-years and current smoking status were also included. RESULTS: FEV1 was significantly correlated among sibling pairs and parent-offspring pairs (both p < 0.001), regardless of smoking adjustment, but sibling correlation was significantly higher than parent-offspring correlation (p < 0.05), suggesting additional effects beyond common parentage. Spousal correlations were not significant even when both spouses smoked. We found no evidence of major gene segregation of FEV1, with or without smoking adjustment, and all of the segregation models were significantly different from the unrestricted model. CONCLUSIONS: The best-fitting model was an environmental model with three distinct distributions of FEV1 and significant residual familial effects. A significant familial component suggests the presence of polygenic factors and/or effects due to a shared environment (multifactorial). That familial correlations of smoking-adjusted and smoking-unadjusted residuals were not appreciably different suggests that current smoking status and number of pack-years smoked do not account for the observed familial aggregation of FEV1.

Adolescent↗

PubMedDate not supplied

Anthropometric-hormonal correlation patterns in fertile and post-menopausal women from Austria.

Correlations between sex-hormone levels and body dimensions were investigated in a group of women from Vienna. Since sex-hormone concentrations in women are subject to dramatic changes with increasing age, both 124 fertile and 142 postmenopausal women were examined. Twenty-nine anthropometric traits were correlated with oestradiol, the gonadotrophins luteinizing hormone (LH) and follicle-stimulating hormone (FSH), the gestagens progesterone, 17-hydroxyprogesterone and prolactin, and the androgens testosterone, androstenedione and DHEA-S, as well as with the transport protein, sex-hormone binding globulin. It was also found that oestradiol concentration was related to levels of gonadotrophins, prolactin, progesterone and androgens and was equally correlated with metric traits. Statistically significant correlations could be observed between all sex-hormone concentrations and the 29 anthropometric traits. The most striking result is the change in direction of correlations between metric traits and oestrogen, gonadotrophin, prolactin and gestagen levels between both proband groups, which is probably due to changes in sex-hormone concentrations in women after menopause. The direction of correlations with androgens remained the same. In post-menopausal women the great impact of fat tissue for sufficient synthesis of oestrogen is shown by a positive correlation between oestradiol and circumference measures.

Adolescent↗

PubMed1988

The nature of conformational correlations in alpha- and beta-anomers of nucleic acid components in aqueous solution by nuclear magnetic resonance.

The solution distribution of combinations of the sugar ring puckering domains, C2'endo(S), C3'endo(N), and C4'-C5' rotamers, +sc(g+), ap(t), -sc(g-), in alpha and beta-anomers in ribo- and deoxyribo- pyrimidine nucleic acid components can be determined from vicinal coupling constants (M. Remin, J. Biomol. Str. Dyn. 2, 211 (1984). A general correlation pattern with a conformational constant lambda reflecting an intrinsic physical property of the sugar-side chain ensemble, is developed and expressed in terms of four principles: I) The +sc rotamer contributes to the C3'endo population to a higher extent (1-Yt) than to C2'endo, (1-Yt-Yg-/Xs). II) The ap rotamer contributes to both C2'endo and C3'endo populations to the same extent (Yt). III) The -sc rotamer contributes only to the C2'endo population, (Yg-/Xs). IV) The molar fractions Xs, Yt and Yg- of conformations C2'endo, ap and -sc, respectively, are strongly correlated, lambda = (Yg-/Xs)/Yt approximately 0.5, and therefore Yt is a basic variable parameter which determines all others in the correlation pattern. In alpha-anomers, regardless of the type and conformation of the sugar ring and base, the molar fraction Yt = 0.37 +/- 0.02. This finding means that different alpha-anomers show one correlation pattern free of the influence of the base. In beta-anomers, structure and conformation of the base are important factors which modulate (through Yt) the correlation pattern, conserving its fundamental features. Yt is considerably increased by a syn-oriented pyrimidine base, but decreases when the base is anti. The transition from anti to syn orientation of the base is followed by destabilization of (C2'endo, +sc) in favor of (C3'endo, ap). The principles of conformational correlations rationalize a variety of correlations observed in the past.

Chemical Phenomena↗

PubMed1999

Power of the concentrated changes test for correlated evolution.

The concentrated changes test (CCT) calculates the probability that changes in a binary character are distributed randomly on the branches of a cladogram. This test is used to examine hypotheses of correlated evolution, especially cases where changes in the state of one character influence changes in the state of another character. The test may be sensitive to the addition of branches that lack either trait of interest (white branches). To examine the effects of the proportion of white branches and of tree topology on the CCT probability, we conducted a simulation analysis using a series of randomly generated 100-taxon trees, in addition to a nearly perfectly balanced (symmetrical) and a completely imbalanced (asymmetrical) 100-taxon tree. Using two models of evolution (gains only, or gains and losses), we evolved character pairs randomly onto these trees to simulate cases where (1) characters evolve independently (i.e., no correlation among the traits) or (2) all changes in the dependent character occur on branches containing the independent trait (i.e., a strong correlation among the traits). This allowed us to evaluate the sensitivity of the CCT to type I and type II errors, respectively. In the simulations, the CCT did not appear to be overly sensitive to the inclusion of white branches (low likelihood of type I error with both CCT probabilities < 0.05 and < 0.01). However, the CCT was susceptible to type II error when the proportion of white branches was < 20%. The test was also sensitive to tree shape and was positively correlated to Colless's tree imbalance statistic I. Finally, the CCT responded differently for simulations where only gains were allowed and those where both gains and losses were permitted. These results indicate that the CCT is unlikely to detect a correlation between characters when no such correlation exists. However, when a trait can be gained but not lost, the CCT is conservative and may fail to detect true correlations among traits (increased type II error). Determination of the sampling universe (the taxa included in the comparative analysis) can strongly influence the probability of making such type II errors. We suggest guidelines to circumvent these limitations.

Biological Evolution↗

PubMed2000

A new in vitro/in vivo kinetic correlation method for nitrofurantoin matrix tablet formulations.

The kinetic distributions of in vitro percentage release and in vivo percentage urinary excretion rates of nitrofurantoin from matrix tablets were plotted using a kinetic program. In vitro release rates were determined using the USP paddle and half-change methods. Urinary excretion curves of the drug were characterized by means of the statistical moments. The individual linear correlations between each in vitro and in vivo kinetic distribution were established, and regression equations were calculated. The application results of the best correlations obtained were evaluated according to in vivo results. A reversed kinetic procedure was applied for transformation of the correlated kinetic values to the drug percentage release rates. The modified Langenbucher kinetic showed excellent linear correlation (r = .9985). The method that is proposed in this study, the kinetic correlation program, is simple, independent of time, and suggests that it is possible to use kinetic distributions in the in vitro/in vivo correlation. This study also suggests using kinetic correlation to investigate the suitability of the in vitro dissolution methods with the in vivo drug dissolution.

Anti-Infective Agents, Urinary↗

PubMed2003

Correlation of exhaled nitric oxide levels and airway inflammation markers in stable asthmatic patients.

Monitoring of inflammation is an important factor in asthma management. The gold standard for measuring direct airway inflammation is bronchial biopsy specimens taken from proximal airways through a fiberoptic bronchoscope. As a noninvasive procedure, the use of exhaled nitric oxide (FENO) for monitoring airway inflammation has been reported in many studies. The aim of this study was to evaluate the correlation of FENO with direct measurements of airway inflammation in biopsy specimens and pulmonary function tests (PFT). Histopathologic features were observed on bronchial biopsy specimens obtained from nine stable mild-moderate asthmatics. Each subject had measurements of PFT, FENO levels, blood eosinophil count, and bronchoscopy with bronchial biopsies and bronchoalveolar lavage. Five subjects with forced expiratory volume in 1 second >80% had methacholine challenge test. None of the subjects had prior anti-inflammatory therapy for asthma. No correlation was found between PFT, blood eosinophil count, and FENO levels. There was a negative correlation between PC20 and FENO. Though there was no correlation between bronchial biopsy eosinophil, monocyte and lymphocyte counts, and FENO, we found a weak positive correlation between total inflammatory cell count in bronchial biopsies and FENO levels. A negative significant correlation was found between FENO levels and epithelial desquamation (p<0.05, r=-0.7). These results suggest that, FENO levels reflect the increased number of activated inflammatory cells in airways and the negative correlation with epithelial desquamation reflects the role of epithelium in NO syntheses. FENO should not be interpreted as a specific inflammation marker for asthma.

Adult↗

PubMed2006

Correlations between frequency-domain HRV indices and lagged Poincaré plot width in healthy and diabetic subjects.

The conventional Poincaré plot for heart rate variability (HRV) analysis is a scatterplot of successive (lag 1) pairs of RR intervals (intervals between heartbeats), and its width (SD1) is considered a measure of short-term variability. It has been shown that SD1 correlates better with HF than with LF (high- and low-frequency bands of the spectrum, respectively). Our aim was to assess how these correlations were affected when SD1 was obtained for longer lags. 10 min ECGs were used to construct Poincaré plots with lags of 1-10 heartbeats in two groups of subjects, one with normal HRV and the other with impaired HRV (control and diabetic groups respectively, N = 15 each). SD1 was quantified for these subjects and HRV spectral indices were estimated. The diabetic group had lower LF, HF and SD1 than the control group (p < 0.05). In both groups, SD1 tended to increase as the lag increased. In the control group, SD1 for lags 1 and 2 was highly correlated with HF (r(s) > 0.9), while SD1 for lags 4 correlated better with LF (r(s) 0.9) than with HF (0.65 <or= r(s) <or= 0.73). However, in the diabetic group, the correlation results did not change in that way for different lags (correlation results between HF and SD1: r(s) 0.95 for lags 1-10). In conclusion, the comparative strength of the correlations between lagged Poincaré widths and spectral indices might be useful to distinguish normal from pathological HRV.

Adult↗

PubMed2002

Continuous cerebral autoregulation monitoring by cross-correlation analysis.

In order to validate cross-correlation analysis between spontaneous slow oscillations of arterial blood pressure (aBP) and intracranial pressure (ICP) or flow velocity as a means to assess the status of cerebral autoregulation continuously, we compared its results with different autoregulation bedside tests. The second aim was to check the method's stability over longer time periods. aBP, ICP, and flow velocity in the middle cerebral artery (FV(MCA)) was measured continuously in 13 critically ill comatose patients. Cross-correlation analysis was performed online and offline between aBP and ICP (CC [aBP --> ICP]) and aBP/FV(MCA) (CC [aBP --> FV(MCA)]). Three different autoregulation bedside tests (cuff deflation, transient hyperemic response, orthostatic hypotension) were performed immediately before a 29-min cross-correlation test period. In addition, continuous cross-correlation autoregulation monitoring was performed over multiple hours (in order to analyze for stability and to assess the influence of other factors). Cluster analysis revealed two main clusters. Cluster 1 (indicative for disturbed autoregulation) showed a centroid at t = -0.21 +/- 3.32 sec, r = 0.43 +/- 0.18 for CC [aBP --> ICP], and t = 0 +/- 3.14 sec, r = 0.44 +/- 0.18 for CC [aBP --> FV(MCA)]. Cluster 2 (indicative for normal autoregulation) revealed a centroid at t = 4.94 +/- 3.74 sec, r =- 0.4 +/- 0.16 for CC [aBP --> ICP], and t = 3.38 +/- 4.44 sec, r = -0.38 +/- 0.18 for CC [aBP --> FV(MCA)]. Comparison between the cross-correlation test results and the bedside tests showed a sensitivity of 44-73% for CC [aBP --> FV(MCA)], whereas CC [aBP --> ICP] was more specific (60-80%). Long-term monitoring revealed stable cross-correlation tests in about 45% of the measurement time. It is concluded that cross-correlation between aBP, ICP, and FV(MCA) is a valid means to monitor the autoregulation status continuously, although further improvement of sensitivity and specificity is needed to make it reliable for clinical decision making.

Adult↗

PubMed2004

Bayesian models for the analysis of genetic structure when populations are correlated.

MOTIVATION: Population allele frequencies are correlated when populations have a shared history or when they exchange genes. Unfortunately, most models for allele frequency and inference about population structure ignore this correlation. Recent analytical results show that among populations, correlations can be very high, which could affect estimates of population genetic structure. In this study, we propose a mixture beta model to characterize the allele frequency distribution among populations. This formulation incorporates the correlation among populations as well as extending the model to data with different clusters of populations. RESULTS: Using simulated data, we show that in general, the mixture model provides a good approximation of the among-population allele frequency distribution and a good estimate of correlation among populations. Results from fitting the mixture model to a dataset of genotypes at 377 autosomal microsatellite loci from human populations indicate high correlation among populations, which may not be appropriate to neglect. Traditional measures of population structure tend to overestimate the amount of genetic differentiation when correlation is neglected. Inference is performed in a Bayesian framework. CONTACT: fur@ohsu.edu.

Bayes Theorem↗

PubMed1998

Improved correlation between scores on the expanded disability status scale and cerebral lesion load in relapsing-remitting multiple sclerosis. Results of the application of new imaging methods.

We hypothesized that a better correlation between MRI and clinical measures of neurological disability using the expanded disability status scale (EDSS) in multiple sclerosis could be obtained by assessing lesion load only in and around the corticospinal tracts, since the EDSS is weighted towards motor and ambulatory deficits. Multiple sclerosis lesions in cerebral MRIs from 39 patients with relapsing-remitting multiple sclerosis were manually painted using a three-dimensional computer display tool and mapped into a standardized three-dimensional coordinate space. Total lesion load was then measured. A mask to expose only the corticospinal tract was extracted from an MRI atlas and used to measure lesion load in the corticospinal tract. To account for the residual anatomical variability among the different MRI volumes after stereotaxic transformation, the corticospinal tract mask was dilated to various degrees and the lesion load remeasured. Spearman's rank correlation coefficient was used to calculate the correlation between the EDSS and total lesion load and corticospinal tract lesion load and between the EDSS subscores and total lesion load and corticospinal tract lesion load. Spearman's rank correlation coefficient between the EDSS and total lesion load was 0.6, probably reflecting the rather broad EDSS range represented in the study. The highest correlation of 0.67 was between the EDSS and corticospinal tract lesion load, dilated with a blurring kernel of 8-10 mm. The pyramidal subscore alone showed a weaker correlation with total lesion load, and with corticospinal tract lesion load, than did the overall EDSS, possibly reflecting the narrow range of disability in these subscores in patients with EDSS scores of 1-6.5. The imperfect correlation between the EDSS and corticospinal tract lesion load suggests that factors other than cerebral T2-weighted lesion volume are important determinants of disability.

Brain↗

PubMed1985

Genetic and molecular mechanisms of the in vitro transformation of Syrian hamster embryo cells by the carcinogen N-ethyl-N-nitrosourea II. Correlation of morphological transformation, enhanced fibrinolytic activity, gene mutations, chromosomal alterations and lethality to specific carcinogen-induced DNA lesions.

The stability of N-ethyl-N-nitrosourea (ENU)-induced DNA damage in Syrian hamster embryo (SHE) cells was determined to study correlations with ENU-induced mutation and transformation. Confluent cultures were treated with ENU and after 0, 3 or 6 days holding in low serum medium to inhibit cell proliferation, the extent of ethylation at different sites in the DNA was determined with h.p.l.c. The amounts of dTp(Et)dT-triester, and O4- and O2-EtThy remained constant during the 6-day period. O6-EtGua slowly decreased (t1/2: 14 days); the initial level was lower than expected from in vitro data, suggesting that Syrian hamster embryo cells contain alkyl transferase. Evidence for active removal was also obtained in the case of 7-EtGua (t1/2: 59 h), O2-EtCyt (t1/2: 96 h) and possibly 3-EtGua (t1/2: 102 h). As expected, the promutagenic O6-EtGua was found to correlate with gene mutations. In addition, however, we have found that the likewise promutagenic O4- and O2-EtThy also correlate with gene mutations. Furthermore, our data suggest that sister chromatid exchange (SCE) and cytotoxicity (clonal survival) have a similar molecular basis. Both correlate with O2-EtCyt and 3-EtGua which are located in the narrow groove and are therefore expected to block DNA replication. Chromatid aberrations and micronuclei could not be correlated to specific DNA lesions, but were found to correlate mainly to N-ethylations. The same holds for morphological transformation, but in this case there is also a small contribution of DNA O-ethylation. In contrast, enhanced fibrinolytic activity did correlate only with stable O-ethylations, including O6-EtGua.

Alkylation↗

PubMed2005

Mobilization of CD34(+), CD117(+), CXCR4(+), c-met(+) stem cells is correlated with left ventricular ejection fraction and plasma NT-proBNP levels in patients with acute myocardial infarction.

AIMS: The aim of the study was to assess the correlation between the number of CD34(+), CD117(+), c-met(+), CXCR4(+) stem cells mobilized into peripheral blood, left ventricular ejection fraction (LVEF), NT-proBNP levels, and myocardial necrosis markers in patients with acute myocardial infarction (AMI). METHODS AND RESULTS: 43 patients with STEMI were enrolled. Stem cells number was measured using flow-cytometer and concentrations of NT-proBNP, SDF-1, G-CSF, VEGF, IL-6, and HGF were measured using ELISA kits. The number of stem cells mobilized early (<12 h) in AMI was significantly, positively correlated with LVEF: r=0.49 (P=0.0012) for CD34(+) cells, r=0.48 (P=0.0018) for CXCR4(+) cells, r=0.45 (P=0.0043) for CD117(+) cells, and r=0.41 (P=0.01) for c-met(+) cells and negatively correlated with NT-proBNP levels on admission r=-0.35 (P=0.024) for CD34(+) cells, r=-0.42 (P=0.007) for CXCR4(+) cells, r=-0.33 (P=0.04). In patients with LVEF </=40%, the peak number of CD34(+), CXCR4(+), CD117(+), and c-met(+) stem cells was significantly lower when compared patients with LVEF >40%. The number of CXCR4(+) cells on admission and after 24 h was negatively correlated with respective cardiac Troponin I levels (r=-0.37; P=0.029 and r=-0.45, P=0.02) and maximum activity of CK-MB (r=-0.37; P=0.021). No significant correlations between levels of haematopoietic cytokines and LVEF were found. CONCLUSION: The mobilization of CD34(+), CD117(+), CXCR4(+), c-met(+) stem cells into peripheral blood early in STEMI is positively correlated with LVEF and negatively correlated with NT-proBNP levels and myocardial necrosis markers.

Antigens, CD34↗

PubMed1973

Effects of population size and selection intensity on correlated responses to selection for postweaning gain in mice.

Correlated responses to selection for postweaning gain in mice were studied to determine the influence of population size and selection intensity. Correlated traits measured were three-, six- and eight-week body weights, litter size, twelve-day litter weight, proportion infertile matings and two indexes of reproductive performance. In general, the results agreed with observations made on direct response: correlated responses in the body weight traits and litter size increased as (1) selection intensity increased and (2) effective population size increased. Correlated responses in the body weight traits and litter size were positive in the large population size lines (16 pairs), as expected from the positive genetic correlation between these traits and postweaning gain. However, several negative correlated responses were observed at small population sizes (one and two pairs). Within each level of selection intensity, traits generally associated with fitness tended to decline most in the very small populations (one and two pairs) and in the large populations (16 pairs) for apparently different reasons. The fitness decline at the small effective population sizes was attributable to inbreeding depression. In contrast, it was postulated that the fitness decline at the large effective population size was due to selection moving the population mean for body weight and a trait positively correlated genetically with body weight (i.e., percent body fat) away from an optimum.

Age Factors↗

PubMed1980

Genetic variance and correlation after selection for two traits by index, independent culling levels and extreme selection.

Three two-trait selection methods were analyzed for their effects on genetic variance and correlation by multivariate methods, two-locus methods and computer simulation. The two-trait selection methods studied were independent culling levels (ICL), index (IND) and extreme (EXT) selection. The effects of the selection methods on genetic variance and correlation were partitioned into permanent effects due to changes in gene frequencies and temporary effects due to nonrandom association of alleles at different loci. Multivariate methods were used to predict temporary effects from a single generation of selection by each method and from several generations of index selection. Two-locus theory was used to determine the stability and rank of temporary effects on genetic correlation for all three methods. Predictions were compared to computer simulation results. When selection increased the means of both traits, EXT had the lowest (closest to -1.0) genetic correlation and highest variances, while ICL tended to have the highest (closest to 1.0) genetic correlation. When selection increased the mean of one trait and decreased th mean of the other, EXT had the highest genetic variances and correlation, while ICL had the lowest genetic variance and correlation.

Alleles↗

PubMed2002

Apoptosis in human sperm: its correlation with semen quality and the presence of leukocytes.

BACKGROUND: Apoptosis plays an important role in regulating spermatogenesis. However, the biological significance of apoptosis in ejaculated sperm is not yet clear. This study set out to investigate how apoptosis correlates with semen quality and the presence of seminal leukocytes. METHODS: Fifty-seven semen samples from the male partners of infertile couples were classified as normal or abnormal according to World Health Organization guidelines. Flow cytometry was used to evaluate sperm populations and seminal leukocytes. Preliminary flow cytometry analysis using 6-carboxyfluoresceindiacetate (6-CFDA), which identifies live cells, and propidium iodide (PI), which stains only dead cells, was performed in order to pinpoint the sperm region accurately. Having thus gated the sperm population, bivariate Annexin V/PI analysis was then carried out in order to measure the percentage of apoptotic and necrotic sperm and the apoptotic index (the ratio between apoptotic:live sperm). Leukocytes were counted by the standard peroxidase test and by flow cytometry using monoclonal antibody (mAb) anti-CD45 or anti-CD53. RESULTS: No significant differences in the apoptotic index and the percentage of live and apoptotic sperm were detected between the subjects with normal and abnormal semen. A significant inverse correlation between sperm concentration and the apoptotic index was observed only in the normal sperm group. There was no correlation between the concentration of leukocytes, detected either by peroxidase or by mAb anti-CD45 or anti-CD53, either with the percentage of apoptotic sperm or with the apoptotic index. In contrast, the ratio between CD45 positive leukocytes and sperm showed a significant correlation with the apoptotic index. A weaker correlation was found when leukocytes were counted by peroxidase, while no correlation was observed using mAb anti-CD53. CONCLUSIONS: Sperm apoptosis did not seem to be correlated with semen quality. In the absence of genito-urinary infection, one of the main functions of seminal leukocytes is probably to provide for the removal of apoptotic sperm.

Adult↗