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PubMed2003

Correlates of helminth community in the red-legged partridge (Alectoris rufa L.) in Spain.

Between 1992 and 1996, 587 wild red-legged partridges (Alectoris rufa) from 16 Spanish provinces were examined to study the variations of helminth communities in this game species across a broad geographical area. The survey revealed 13 species of helminth parasites. Dicrocoelium sp.. Rhabdometra nigropunctata, and Cheilospirura gruweli were the most common species, whereas Raillietina bolivari, Choanotaenia infundibulum, Tetrameres sp., and Capillaria anatis were the most rare. Subulura suctoria, Heterakis gallinarum, Heterakis tenuicaudata, Capillaria contorta, Trichostrongylus tenuis, and Raillietina tetragona occurred with intermediate frequencies. The abundance of C. gruweli, S. suctoria, H. tenuicaudata, T. tenuis, and R. tetragona was inversely correlated to latitude and directly correlated to yearly mean temperature, whereas the abundance of Dicrocoelium sp. was directly correlated to latitude and inversely correlated to yearly mean temperature. The abundance of R. tetragona was inversely correlated to latitude and yearly mean humidity. The number of helminths per partridge and the number of helminth species per partridge were lower in young birds than in adults. Partridge body condition was inversely correlated to abundance of C. contorta. Richer infracommunities were linked to richer component communities. At the infracommunity level, total number of helminths per partridge and number of helminth species per partridge were inversely correlated to latitude and directly correlated to yearly mean temperature. At the component community level, both species richness and diversity (Simpson's index) were inversely correlated to latitude and directly correlated to mean temperature. Across the broad geographical range of the study area, the helminth parasite communities of red-legged partridges had marked geographical variation in their structure. Our results suggest that this variation is determined by the distribution of both intermediate and definitive hosts. We discuss the implications of this variation for the hypothesis that supplementary releases of captive-bred partridges for sport hunting can affect the helminth fauna of wild red-legged partridges.

Analysis of Variance↗

PubMed1986

Heritabilities and genetic correlations of growth and reproductive measurements in Hereford bulls.

Weight, hip height, heart girth, pelvic height, pelvic width and scrotal circumference were measured at 403 and 490 d on 427 Hereford bulls. The bulls were members of a random-selection herd so estimates of genetic parameters should have a minimum of bias due to selection. Heritabilities and genetic correlations were estimated by normal paternal half-sib (PHS) correlation procedures. In addition, 256 son-sire pairs (RSS) were used to estimate heritabilities and genetic correlations by regression and covariance methods. The PHS method produced heritability estimates in the range of .41 to .58 for all measures at both ages, with the exceptions of hip height at 403 d (.24) and pelvic height at 490 d (.23). The estimates derived in the RSS method ranged from .10 to .60. The RSS relationship would contain a portion of any maternal X direct covariance effects. A difference in heritability estimated by the two methods could be a reflection of this covariance. Genetic correlations tended to be larger than phenotypic and, in several cases, were negative. The difference in the correlation between two measurements taken at 403 d vs the same correlation estimated at 490 d was not readily explainable but may be evidence for differences in maturation rates or maternal effects. Scrotal circumference had a positive genetic correlation with weight and heart girth and near 0 or negative genetic correlations with pelvic measures. Hip height had positive genetic correlations with weight and heart girth at 403 and 490 d and with pelvic measurements at 403 d, but the correlations were not as large at 490 d.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Correlations between grasp-reflex strengths and serum thyroid-hormone levels depending upon sex and familial sinistrality in human neonates: importance of genetically predetermined cerebral organization.

Relations of grasp-reflex strengths to serum free-thyroid hormone levels were studied in human neonates. In right-dominant (RH) males and females without familial sinistrality (-FS), grasp-reflex strengths from right (R) and left (L) inversely correlated with serum triiodothyronine (T3). In RH, +FS males, grasp-reflex strengths from R and L hands directly correlated with T3 (no correlations in RH, +FS females). There was no significant correlation between grasp reflex and T3 in non-right-handed (NRH), -FS neonates. In NRH +FS neonates, there was a significant negative linear correlation between grasp reflex from left and T3 only in NRH, +FS males. The following correlations were found between grasp reflex and thyroxine (T4): direct relation in RH, +FS males and females; inverse relation in NRH, -FS females only for the right hand; inverse correlations in NRH, +FS females. The R-L grasp reflex directly correlated with T3 in RH, -FS males, and inversely correlated with T3 in RH, -FS females (no significant correlations in others). These results indicated that thyroid hormones may influence cerebral maturation and lateralization differentially according to genetically predetermined cerebral organization. The generalizations of the hormonal effects on, at least, cerebral functioning would be wrong, if the genetically predetermined main features of the brain are neglected.

Brain↗

PubMed2002

Heritability and correlations among body condition score loss, body condition score, production and reproductive performance.

The objectives of this study were to estimate the heritability of body condition score loss (BCSL) in early lactation and estimate genetic and phenotypic correlations among BCSL, body condition score (BCS), production, and reproductive performance. Body condition scores at calving and postpartum, mature equivalents for milk, fat and protein yield, days to first service, and services per conception were obtained from Dairy Records Management Systems in Raleigh, NC. Body condition score loss was defined as BCS at calving minus postpartum BCS. Heritabilities and correlations were estimated with a series of bivariate animal models with average-information REML. Herd-year-season effects and age at calving were included in all models. The length of the prior calving interval was included for all second lactation traits, and all nonproduction traits were analyzed with and without mature equivalent milk as a covariable. Initial correlations between BCS and BCSL were obtained using BCSL and BCS observations from the same cows. Additional genetic correlation estimates were generated through relationships between a group of cows with BCSL observations and a separate group of cows with BCS observations. Heritability estimates for BCSL ranged from 0.01 to 0.07. Genetic correlation estimates between BCSL and BCS at calving ranged from -0.15 to -0.26 in first lactation and from -0.11 to -0.48 in second lactation. Genetic correlation estimates between BCSL and postpartum BCS ranged from -0.70 to -0.99 in first lactation and from -0.56 to -0.91 in second lactation. Phenotypic correlation estimates between BCSL and BCS at calving were near 0.54, whereas phenotypic correlation estimates between BCSL and postpartum BCS were near -0.65. Genetic correlations between BCSL and yield traits ranged from 0.17 to 0.50. Genetic correlations between BCSL and days to first service ranged from 0.29 to 0.68. Selection for yield appears to increase BCSL by lowering postpartum BCS. More loss in BCS was associated with an increase in days to first service.

Animals↗

PubMed2004

Genetic correlations among production, body size, udder, and productive life traits over time in Holsteins.

Genetic correlations among milk, fat, and protein yields; body size composite (BSC); udder composite (UDC); and productive life (PL) in Holsteins were investigated over time. The data set contained 25,280 records of cows born in Wisconsin between 1979 and 1993. The multiple trait random regression (MT-RR) animal model included registration status, herd-year, age group, and stage of lactation as fixed effects; additive genetic effects with random regressions (RR) on year of birth using the first-order Legendre polynomial; and residual effects. Heterogeneous residual variances were considered in the model. Estimates of variance components and genetic correlations among traits from MT-RR were compared with those estimated with a multiple trait interval (MT-I) model, which assumed that every 3-yr interval was a separate trait and included the same effects as in the MT-RR model except for the RR. Genetic correlations estimated with MT-RR and MT-I models over time among all traits were compared with correlations among breeding values predicted with the single trait (ST) model without RR. Correlations among breeding values predicted with MT-RR, ST, and MT models were also calculated. Additive genetic and residual variances for all traits except PL increased over time; those for PL were constant. As a result, heritability estimates had no significant changes during the 15 yr. Genetic correlations of PL with milk, fat, protein, and BSC declined to zero or negative; those with UDC remained positive. Correlations among breeding values predicted with ST, MT, and MT-RR models were relatively high for all traits except PL. Genetic correlations between PL and other traits varied over time, with some correlations changing sign. For accurate indirect prediction of PL from other traits, the genetic correlations among the traits need to be re-estimated periodically.

Animals↗

PubMed2004

Correlations among body condition scores from various sources, dairy form, and cow health from the United States and Denmark.

The objectives of this study were to estimate genetic correlations among body condition scores (BCS) from various sources, dairy form, and measures of cow health. Body condition score and dairy form evaluated during routine type appraisal was obtained from the Holstein Association USA, Inc. A second set of BCS was obtained from Dairy Records Managements Systems (DRMS) and was recorded by producers that use PCDART dairy management software. Disease observations were obtained from recorded veterinarian treatments in several dairy herds in the United States. Estimated breeding values for diseases in Denmark were also obtained. Genetic correlations among BCS, dairy form, and cow health traits in the United States were generated with sire models. Models included fixed effects for age, DIM, and contemporary group. Random effects included sire, permanent environment, herd-year season for health traits, and error. Predicted transmitting abilities (PTA) for BCS and dairy form were correlated with estimated breeding values for disease in Denmark. The genetic correlation estimate between BCS from DRMS and BCS from the Holstein Association USA, Inc., was 0.85. The genetic correlation estimate between BCS and a composite of all diseases in the United States was -0.79, and PTA for BCS was favorably correlated with an index of resistance to disease other than mastitis in Denmark (0.27). Dairy form was positively correlated with a composite of all diseases in the United States (0.85) and was unfavorably correlated with an index for resistance to disease other than mastitis in Denmark (-0.29). Adjustment for protein yield PTA had a minimal affect on correlations between PTA for BCS or dairy form and disease in Denmark. Selection for higher body condition or lower dairy form with continued selection for yield may slow deterioration in cow health as a correlated response to selection for increased yield.

Animals↗

PubMed2006

Estimation of genetic correlations among countries in international dairy sire evaluations with structural models.

The increase in the number of participating countries and the lack of genetic ties between some countries has lead to statistical and computational difficulties in estimating the genetic (co)variance matrix needed for international sire evaluation of milk yield and other traits. Structural models have been proposed to reduce the number of parameters to estimate by exploiting patterns in the genetic correlation matrix. Genetic correlations between countries are described as a simple function of unspecified country characteristics that can be mapped in a space of limited dimensions. Two link functions equal to the exponential of minus the Euclidian distance between the coordinates of two countries and the exponential of minus the square of this Euclidian distance were used for the study on international simulated and field data. On simulated data, it was shown that structural models might allow an easier estimation of genetic correlations close to the border of the parameter space. This is not always possible with an unstructured model. On milk yield data, genetic correlations obtained from 22 countries for structural models based on 2 and 7 dimensions, respectively, were analyzed. Only a structural model with a large number of axes gave reasonable estimates of genetic correlations compared with correlations obtained for an unstructured model: 76.7% of correlations deviated by less than 0.030. Such a model reduces the number of parameters from 231 genetic correlations to 126 coordinates. On foot angle data, large deviations were observed between genetic correlations estimated with an unstructured model and correlations estimated with a structural model, regardless of the number of axes taken into account.

Algorithms↗

PubMed1999

Genetic correlations among protein yield, productive life, and type traits from the United States and diseases other than mastitis from Denmark and Sweden.

Sire genetic evaluations for protein yield, productive life, and selected type traits from the US were correlated with sire evaluations for disease from Denmark and Sweden and were then adjusted to approximate genetic correlations. Disease categories from Denmark included reproductive diseases, foot and leg diseases, metabolic and digestive diseases, and all diseases other than mastitis. Genetic evaluations for Denmark were from separate analyses for each disease category using a multiple-trait sire model with first, second, and third lactations handled as multiple traits. Evaluations from Sweden for all diseases other than mastitis were from a single-trait sire model using only first lactations. In addition, Danish and Swedish genetic evaluations were regressed on US type evaluations to test for quadratic relationships. Relationships were based on 104 bulls with US and Danish evaluations (88 with US type) and 84 bulls with US and Swedish evaluations (83 with US type). Genetic correlations between US protein yield and diseases were unfavorable, but correlations were favorable between productive life and disease. Genetic correlations among US type and diseases were around zero, except for correlations with US dairy form (range -0.34 to -0.73). Genetic correlations calculated from residual correlations (adjusted for predicted transmitting abilities for milk) between productive life and diseases were favorable (range 0.29 to 0.51). Genetic correlations calculated from residual correlations (adjusted for predicted transmitting abilities for milk) between dairy form and diseases ranged from -0.10 to -0.53. Selection for increased productive life may reduce disease occurrences, but selection for higher dairy form scores will increase disease occurrences.

Animals↗

PubMed2006

[Computer modeling correlation between the entering wound and the final position of the metallic intraocular foreign body].

AIM: The aim of this study was to establish the correlation coefficient between given parameters of the entering wound and final position of the metallic intraocular foreign body. MATERIAL AND METHODS: Fifty patients (50 eyes) with a penetrating injury of the eye and present metallic intraocular foreign body were included in this study. Clinically found data of the entering wound and final position of the intraocular foreign body (IFB) as well were transformed with a computer model into the three-dimensional parameters. Both parameters were statistically evaluated by means of correlation analysis, and correlation coefficient and determination coefficient were calculated. RESULTS: The extent of correlation between two variables is called correlation coefficient. The coefficient values range between -1 to +1. The closer is the calculated value to ranges (to -1 or to +1) the more are the two variables more correlated. The coefficient of determination values range from 0 to +1. The closer the results are to +1, the better the model describes the dependence between the two variables. The results obtained by means of correlation analysis were for the correlation coefficient 0.454, and for the coefficient of determination 0.6411 respectively. CONCLUSION: Results of the correlation analysis show that the knowledge of coordinates of the entering wound has no prediction value for final position of the foreign body in the eye. These two variables are not correlated and so the accurate final position of the foreign body cannot be predicted. The final position of the intraocular metallic foreign body is probably influenced by biophysical factors not included in this study.

Biomechanical Phenomena↗

PubMedDate not supplied

[Six-minute walk work is not correlated to the degree of airflow obstruction in patients with Chronic Obstructive Pulmonary Disease (COPD)].

INTRODUCTION: The six-minute walking test distance, despite being considered the main parameter, does not consider body weight which is known to influence exercise capacity. A body of evidence shows the degree of airflow obstruction does not correlate to walking distance and the body weight affects the work/energy required to perform the walk. OBJECTIVE: To verify if the degree of airflow obstruction correlates to six-minute walk work obtained by weight-walking distance product. PATIENT AND METHODS: A total of 60 patients with chronic obstructive pulmonary disease were evaluated. The physiological and functional variables were correlated to distance and body weight walking distance product (WxW). RESULTS: There were no correlations between six- minute walk work and the degree of airflow obstruction. A positive and significant correlation were observed between the distance and Carbon Monoxide Diffusing Capacity (DLCO) (r=0.6; p<0.01) and between the distance and final SatO 2 (r= 0.3 ; p <0.05). Correlation between distance and Borg scale was negative and significant (r= -0.3; p<0.05). The six-minute walk work was positive and significantly correlated to DLCO (r= 0.7; p<0.01) and negative but significantly correlated to Borg scale in the initial (r= - 0.3; p<0.01) and final of the test (r= -0.4; p<0.05). CONCLUSION: Based on this data, there was no correlation between the degree of airflow obstruction and six-minute walk work test. The DLCO was the only respiratory functional parameter significantly correlated to the distance and to the six- minute walk work.

Aged↗

PubMed1992

The correlation between lupus anticoagulant and autoantibodies.

The presence of a positive lupus anticoagulant (LA) has recently been associated with reproductive failure. LA positivity and reproductive failure have also been associated with autoantibody abnormalities, especially antiphospholipid autoantibodies. Because the correlation between LA and autoantibody positivity has remained controversial, we retroactively investigated 326 sera of patients with reproductive failure for correlation between lupus anticoagulant and 15 autoantibodies separately for IgG, IgM, and IgA isotypes. LA by TTI and APTT correlated significantly (p less than 0.0001). Among 18 antiphospholipid isotypes, 6 (33%) correlated significantly with TTI, 5 (28%) with APTT, and 3 (17%) both with TTI and APTT. Among 15 isotypes to histone subfractions, 4 (27%) correlated significantly to TTI, 3 (20%) to APTT, and 2 (13%) to both LA assay methods. Of 12 isotypes to antipolynucleotide antibodies, 2 (17%) correlated significantly to TTI, 1 (8%) to APTT, and none to both assay methods. The correlation between LA and autoantibodies was less striking among LA-positive than LA-negative sera. LA by both TTI and APTT was primarily found to correlate with IgG and IgA autoantibodies. This occurs in decreasing frequency to phospholipids, histones, and polynucleotides. At abnormal levels of LA (by either method) the correlation with autoantibody levels is less pronounced and appears closer with IgM autoantibodies to histones and polynucleotides than antibodies to phospholipids. We conclude that the correlation between LA and autoantibodies, especially antiphospholipid antibodies, is less pronounced than often reported in the literature. Patients suspected to suffer from reproductive failure due to abnormal autoimmunity have to be screened not only with LA and/or selected antiphospholipid autoantibodies, but with a more comprehensive autoantibody profile.

Autoantibodies↗

PubMed1995

Transition zone index as a method of assessing benign prostatic hyperplasia: correlation with symptoms, urine flow and detrusor pressure.

PURPOSE: Prostate volume has been poorly correlated to various parameters used to assess benign prostatic hyperplasia (BPH), including symptoms, peak urine flow and detrusor pressure at peak urine flow. The purpose of this study was 2-fold: 1) to determine if transrectal ultrasound measurement of the transition zone of the prostate served as a better proxy for determining prostate size and correlated better with American Urological Association symptom score, peak urine flow and detrusor pressure, and 2) if the parameter transition zone index (the ratio between transition zone volume and prostate volume) was useful in evaluating clinical prostatism. MATERIALS AND METHODS: We prospectively evaluated 61 men with symptomatic BPH (age 64.6 +/- 9.7 years) according to symptoms, peak urine flow, pressure/flow analysis, transrectal ultrasound volume of the entire prostate and the transition zone, and calculation of the transition zone index. RESULTS: Age correlated with symptoms (r = 0.31, p = 0.01) and peak urine flow correlated negatively with symptoms and age (p = 0.002). Age also correlated with prostate volume (r = 0.54 and p = 0.03) and transition zone (r = 0.31, p = 0.05). There was a weak correlation between prostate volume and symptoms, peak urine flow and detrusor pressure at peak urine flow; a stronger correlation between transition zone and symptoms (r = 0.48, p = 0.03), and peak urine flow (r = -0.34, p = 0.05), and a significant correlation (p = 0.001) between transition zone index and symptoms (r = 0.75), peak urine flow (r = -0.71) and detrusor pressure at peak urine flow (r = 0.43). A transition zone index of greater than 0.50 was a useful cutoff point and highly significant (p = 0.002) for delineating patients with more severe abnormalities of symptoms, peak urine flow and detrusor pressure at peak urine flow. CONCLUSIONS: Transition zone index is a parameter that correlates significantly with evaluated parameters of BPH and may serve as a useful proxy for evaluating worsening obstruction. Studies are underway to determine if transition zone index can be used prospectively to predict and correlate response with therapies designed to ablate prostatic tissue medically or surgically.

Age Distribution↗

PubMed1993

Cardiac performance and thyroid function. The correlation between systolic time intervals, heart rate and thyroid hormone levels.

UNLABELLED: In the search for a clinical correlate to thyroid function, correlations were sought between the plasma level of thyroid hormones and the cardiac function, assessed by heart rate and the systolic time intervals. The present study is the first to 1) use a curvilinear correlation and 2) do so in the entire hormone range. A third degree Chebychew's regression equation was used to enable curvilinear correlation. In a population of 10 hypothyroid, 14 euthyroid, and 25 hyperthyroid patients a statistically significant curvilinear correlation was found between the thyroid hormone levels and the systolic time intervals. The correlation coefficients showed the heart rate equally correlated to the thyroid hormone levels as the best correlated of the systolic time intervals. The correlation between the heart rate and T3 was almost linear, with a heart rate increase of 4 beats/minute with each increase in plasma T3 of 1 nmol/l. CONCLUSION: The thyroid function reflects in the cardiac function in a curvilinear regression between T3 and systolic time intervals and in an almost linear regression between T3 and heart rate. The variation, however, is too great and the slope too low, to suggest the use of the heart rate as a clinical correlate to thyroid function.

Adult↗

PubMed1998

Functional dental correlates of food properties in five Malagasy lemur species.

Biomechanical explanations are fundamental to studies of functional dental morphology. Until recently foods were not classified in mechanical categories amenable to a rigorous examination of the fundamental physical relationship between teeth and foods. Fruit, insect and leaf categories, although descriptive, are mechanically heterogeneous. The diets of five Malagasy lemur taxa were described in terms of two mechanical properties, hardness and shear strength, in an earlier study (Yamashita, 1996b). In the present study, correlations between these two physical food properties and second molar tooth features of two lemur families are examined. Several relationships are hypothesized: 1) crest length is expected to be positively correlated with food shear strength; 2) the radius of curvature (r) of cusps is expected to be positively correlated with food hardness; and 3) basin area should increase relative to cusp radius as food hardness increases, and cusp-to-basin ratios should decrease with increasing food hardness. Two additional hypotheses address the debate concerning the relative influences of the most frequently eaten foods versus the most stressful foods in determining tooth form. The results of the predicted relationships are equivocal. 1) Crest length is negatively instead of positively correlated with strong foods. Crest lengths are correlated with quantities of leaf consumption, which are related to leaf shape more than to material composition. 2) As expected, r is positively correlated with food hardness and negatively with shear strength, but this applies to upper molar cusps only. Lower molar cusps complicate simple generalizations of relationships. 3) Hard foods are correlated with a tight fit of occluding cusps and basins instead of the expected loose fit. The most stressful foods eaten (hardest and strongest) have higher correlations with tooth features than the most frequently eaten foods. Several functional complexes can be identified. Hard food items are correlated with short cusps in lemurids, tight occlusal fit, small trigon and large talonid areas, and deep, acute basins. Large, shallow trigons, shallow, unrestricted talonids, and large upper molar basins are indicative of a diet of strong foods. These results demonstrate that some variation in tooth features is explicable with reference to mechanical properties of diet, although the relationships are complex.

Animal Feed↗

PubMed1999

Comparisons of measures of interclass correlations: the general case of unequal group size.

A problem often encountered in epidemiology is the evaluation of the validity of a short questionnaire for diet or physical activity administered to large numbers of subjects, where the gold standard is a diet record or physical activity diary. It is well known that random measurement error can attenuate the interclass correlation coefficient (validity coefficient) between these two variables. Several authors have proposed a de-attenuated (or corrected) correlation coefficient which is an estimate of the true correlation between the two variables after removing the effect of random measurement error. By true correlation we mean the correlation between the questionnaire and the mean of a large or 'infinite' number of diaries (representing the truth). In this paper the authors propose three methods (two ad hoc methods, the pairwise and weighted sib-mean estimators, and the maximum likelihood with confidence limits computed using the Wald statistic and profile likelihood approaches) to estimate the true correlation between a single questionnaire and the mean of an infinite number of follow-up diaries, in the general case where an unequal number of diaries are available for each individual. A simulation study is done under the assumption that the measured variables are normally distributed. Under the null hypothesis of no correlation between the questionnaires and the diaries, all methods had negligible biases. In cases closer to what is usually seen in practice (true correlation between 0.4 and 0.6), the degree of bias and coverage probability depends heavily on the reliability (intraclass correlation) of the diaries. The maximum likelihood estimator with confidence intervals computed by the profile likelihood approach, while not systematically outperforming the other methods, is shown to be the best of the three proposed approaches.

Bias↗

PubMed1999

Correlations among polychlorinated biphenyls, dioxins, and furans in humans.

BACKGROUND: Correlations among human levels of polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans potentially complicate interpretation of studies of their individual health effects. Outcomes attributed to one may, in fact, be due to another. METHODS: We present correlations among dioxins, furans, and PCBs in blood collected in 1991-1992 from 44 American Vietnam veterans from Michigan. RESULTS: Correlations among specific dioxins and furans ranged from 0.26 to 0.80, with the higher-chlorinated congeners being more highly correlated. Correlations among PCBs ranged from 0.06 to 0.94, with those occurring at highest concentrations being more highly correlated. Correlations of PCBs with dioxins and furans ranged from -0.09 to 0.59. Correlations of individual chemicals with total dioxin toxic equivalents ranged from 0.31 to 0.76. DISCUSSION/CONCLUSIONS: If confirmed in other populations, such correlations may allow the use of simpler assays but may also raise issues of confounding and calibration.

Adult↗

PubMed1981

Correlation of glycosphingolipids and sialic acid in YAC-1 lymphoma variants with their sensitivity to natural killer-cell-mediated lysis.

Sialoglycoconjugates and glycosphingolipids were quantitated in a series of variants derived from the YAC-1 lymphoma, known to be highly sensitive to natural killer (NK)-cell-mediated lysis. The variants, which had widely diverging sensitivities to NK cells, were obtained by a number of methods, including selection in the presence of NK cells, antibody to H-2, or antibody to the murine leukemia-virus-induced antigen, and by fusion of sensitive cells with an NK-resistant cell line, A9HT. The sensitivities of these cells to NK-cell-mediated lysis did not correlate with their sensitivities to anti-H-2a cytotoxic T cells. While no correlation could be made between the NK-sensitivity of these variants and their total cellular sialic acid, a statistically significant inverse correlation was observed between the levels of percentage neuraminidase releasable surface sialic acid of total labelled sialyl components and sensitivity to NK cells. This correlation with cell surface sialic acid was observed with either endogenous or lymphocytic choriomeningitis virus-induced activated NK cells as effectors. Neuraminidase treatment of insensitive target cells caused a moderate increase in sensitivity but failed to render the resistant targets as sensitive as YAC-1. Analysis of glycosphingolipids among the variants revealed a strong positive correlation between the total cell neutral glycolipid with chromatographic migration of asialo-GM2 and sensitivity to endogenous or activated NK-cell-mediated lysis. Significant correlations were not found with any other neutral glycolipids. However, ganglioside homologues with chromatographic mobility of GM1, GD1a, GD1b, And GT also showed a positive correlation with both endogenous and activated NK-cell-mediated lysis. The ratio of asialo-GM2 to GM2 had a highly significant positive correlation with sensitivity. These correlative results suggest that asialo-GM2 and certain gangliosides could be involved in binding or lytic events in NK cell:target cell interactions, and that high levels of sialic acid and sialylation on the surface may inhibit and/or modify such interactions. Further studies with these YAC variants should be useful for examining the biochemical bases of target cell-effector cell interactions in the NK-system.

Animals↗

PubMed1992

Correlating magnetic resonance imaging with the biochemical content of the normal human intervertebral disc.

Magnetic resonance imaging was used to determine the T2 relaxation times of prepared proteoglycan solutions and of normal human intervertebral disc tissue from the annulus fibrosus (AF) and nucleus pulposus (NP). The collagen, proteoglycan, and water contents of the disc tissue samples were determined by biochemical assays after they were scanned. Correlations among 1/T2, collagen, proteoglycan, and water contents of the tissue samples and among 1/T2, water, and proteoglycan contents of the proteoglycan solutions were calculated. A moderate negative correlation between 1/T2 and water content was noted for the tissue samples, and a very high negative correlation was found between 1/T2 and water content for the proteoglycan solutions. The very high positive correlation between 1/T2 and proteoglycan content of the proteoglycan solutions is probably due to this negative correlation between 1/T2 and water content. There was no significant correlation between 1/T2 and proteoglycan content of the tissues. The moderate positive correlation between 1/T2 and collagen content is probably due to the high negative correlation between collagen content and water content. No significant correlation was found between the collagen and proteoglycan contents of the tissues. Thus it appears that the data confirm previous reports in the literature that the collagen of the disc tissue functions to control its water content.

Adult↗