NUCLEOTYPIC EFFECT IN HOMEOTHERMS: BODY-MASS-CORRECTED BASAL METABOLIC RATE OF MAMMALS IS RELATED TO GENOME SIZE

The body-mass-corrected rate of basal metabolism in mammals is found to be negatively correlated with genome size, which is possibly linked to average cell size. The correlation, already significant at the species level (r_sp = –0.61, P < 0.0002), gradually strengthens as mean values for higher taxonomic levels (genera, families, and orders) are substituted in place of the species points (r_gen = –0.65, P < 0.0002; r_fam = –0.71, P < 0.0004; r_ord = –0.81, P < 0.008). This finding suggests that a sizeable part of the mammalian (above 25% of human) genome can be used for evolutionary adjustment of metabolic rate resulting from nucleotypic effect independently of body size. The total variance of mammalian genome-size values is found to be divided into two parts: within genera (43%) and taxonomic levels higher than order (57%), with no tangible variance being added between these taxonomic levels; whereas the body-mass-corrected rate of basal metabolism varies mainly at family (42%) and order (53%) levels. The only order for which there seems to be a necessary minimum of data for intraorder analysis (rodents) shows a not statistically significant correlation at the species level (r_sp = –0.47; P < 0.09), significant at the genus level (r_gen = –0.74; P < 0.04), and very high at the family level (r_fam = –0.98; P < 0.03). The concept of ultimate (distant) characters consolidation is proposed. In birds, with average genome sizes 40% of those of mammals, and similarly narrower ranges both of genome sizes and of body-mass-corrected metabolic rates, the correlation was not significant.     

Low IGF-1 levels are associated with cardiovascular risk factors in haemodialysis patients

Cardiovascular diseases (CVD) constitute a significant risk and may, in part, explain the high morbidity and mortality rates among haemodialysis (HD) patients. Several studies have implicated reduced insulin like growth factor (IGF-1) levels in the development of CVD. However, it is not clear whether IGF-1, and its relationship with other hormones such as leptin, insulin, and growth hormone (GH), as well as anthropometric variables may explain the high incidence of vascular complications in chronic kidney disease (CKD) patients. This study was designed to measure total serum IGF-1, leptin, insulin and GH levels in CKD patients and in age-matched control subjects and to elucidate the relationship between IGF-1 and GH, leptin, and insulin as well as other known aetiological risk factors for CVD including blood pressure, body mass index (BMI), and age. The study consisted of 50 CKD patients [36 M and 14 F; mean age; 41.8 ± 10.3 years) on maintenance haemodialysis and 50 healthy control subjects (36 M and 14 F; mean age 41.6 ± 10.2 years) matched for age and sex. None of the subject among patients and controls reported either smoking or history of diabetes mellitus. The circulating levels of IGF-1 were significantly lower (P < 0.001) in both male and female patients compared to the control subjects. Moreover, IGF-1 was strongly and inversely correlated with both systolic blood pressure (SBP) (r = −0.360; P < 0.01) and diastolic blood pressure (DBP) (r = −0.512; P < 0.001) in the CKD group, and when the two groups were combined SBP (r = −0.396; P < 0.001) and DBP (r = −0.296; P < 0.01). When adjusted for age, the correlation was more significant, however, when adjusted for BMI no significant correlation was observed between IGF-1 and blood pressure. IGF-1 was inversely correlated with age (r = −0.367; P < 0.01) and BMI (r = −0.310; P < 0.05) in the control group, but not the patient group. In controls and patients, respectively, a positive correlation between leptin and BMI (r = 0.358; P < 0.01; r = 0.640, P < 0.001) was observed. The results show that circulating levels of IGF-1 were significantly lower in CKD patients as compared to healthy normal subjects and were inversely correlated with SBP and DBP independent of age, but not BMI indicative of a strong relationship between cardiovascular risk factors and low IGF-1 levels. Although, the data do not clearly indicate low IGF-1 levels as a cause or an effect of these cardiovascular risk factors, they do point to an interesting relationship between low IGF-1 levels and increased cardiovascular risk factors among CKD patients as compared to age-matched healthy control subjects.     

Dual‐energy X‐ray Absorptiometry and Anthropometric Estimates of Visceral Fat in Black and White South African Women

Visceral adipose tissue (VAT) is associated with increased risk for cardiovascular disease, and therefore, accurate methods to estimate VAT have been investigated. Computerized tomography (CT) is the gold standard measure of VAT, but its use is limited. We therefore compared waist measures and two dual‐energy X‐ray absorptiometry (DXA) methods (Ley and Lunar) that quantify abdominal regions of interest (ROIs) to CT‐derived VAT in 166 black and 143 white South African women. Anthropometry, DXA ROI, and VAT (CT at L4–L5) were measured. Black women were younger (P < 0.001), shorter (P < 0.001), and had higher body fat (P < 0.05) than white women. There were no ethnic differences in waist (89.7 ± 18.2 cm vs. 90.1 ± 15.6 cm), waist:height ratio (WHtR, 0.56 ± 0.12 vs. 0.54 ± 0.09), or DXA ROI (Ley: 2.2 ± 1.5 vs. 2.1 ± 1.4; Lunar: 2.3 ± 1.4 vs. 2.3 ± 1.5), but black women had less VAT, after adjusting for age, height, weight, and fat mass (76 ± 34 cm² vs. 98 ± 35 cm²; P < 0.001). Ley ROI and Lunar ROI were correlated in black (r = 0.983) and white (r = 0.988) women. VAT correlated with DXA ROI (Ley: r = 0.729 and r = 0.838, P < 0.01; Lunar: r = 0.739 and r = 0.847, P < 0.01) in black and white women, but with increasing ROI android fatness, black women had less VAT. Similarly, VAT was associated with waist (r = 0.732 and r = 0.836, P < 0.01) and WHtR (r = 0.721 and r = 0.824, P < 0.01) in black and white women. In conclusion, although DXA‐derived ROIs correlate well with VAT as measured by CT, they are no better than waist or WHtR. Neither DXA nor anthropometric measures are able to accurately distinguish between high and low levels of VAT between population groups.     

Species richness of Protozoa in Japanese lakes

The protozoan fauna and species richness in the pelagic zone of 15 Japanese lakes were investigated in 1996 using polyurethane foam (PF) substrates. The most common species were flagellates, such as Cryptomonas erosa, Oikomonas termo, and Pleuromonas jaculans. Cinetochilum margaritaceum and Actinophrys sol were the most common species of the Ciliata and Sarcodina, respectively. The similarity of species occurrence was calculated from presence/absence data, but this revealed no clear trend with respect to the influence of lake properties such as trophic state, surface area, or mean depth. The occurrence pattern of Protozoa was most similar in L. Chuzenji and L. Biwa (north basin), two oligomesotrophic natural lakes. Log species richness was positively correlated with log total phosphorus (r = 0.54, P < 0.05) and negatively with log mean depth (r = −0.58, P < 0.05). The diversity index (Margalef's formula), highly correlated with the total species number (r = 0.85, P < 0.01), was negatively correlated with log lake area (r = −0.71, P < 0.01). The logarithm of Phytomastigophora number was positively correlated with log total nitrogen (r = 0.53, P < 0.05), and the logarithm of Ciliata number was negatively correlated with log lake area (r = −0.55, P < 0.05). The species richness of Protozoa on PF substrates was determined by both the nutrient status of the lake and the distance from the location of the suspended PF substrate to the lake bottom or shore. Received: September 25, 1999 / Accepted: January 6, 2000     

Exercise performance and magnetic resonance imaging-determined thigh muscle volume in children

This study examined the relationships between thigh muscle volume (TMV) and aerobic and anaerobic performance in children. A total of 32 children, 16 boys and 16 girls, aged 9.9 (0.3) years completed a treadmill running test to exhaustion for the determination of peak oxygen uptake (peak V˙O₂) and a Wingate Anaerobic Test (WAnT) for the determination of peak power (PP) and mean power (MP). The volume of the right thigh muscle was determined using magnetic resonance imaging. TMV was not significantly different in boys and girls [2.39 (0.29) l vs 2.18 (0.38) l, P > 0.05]. Peak V˙O₂ and MP were significantly higher in boys than girls (P < 0.01) whether expressed in absolute, mass-related or allometrically scaled terms. Absolute PP was not significantly different in boys and girls but mass-related and allometrically scaled values were higher in boys (P < 0.01). TMV was correlated with absolute peak V˙O₂, PP and MP in both sexes (r = 0.52–0.89, P < 0.01). In boys, mass-related PP was correlated with TMV (r =0.53, P < 0.01), and in girls mass-related peak V˙O₂ was correlated with TMV (r = −0.61, P < 0.01). However, in neither sex were allometrically scaled peak V˙O₂, PP or MP correlated with TMV (P > 0.05). There were no significant differences between boys and girls in terms of peak V˙O₂, PP or MP when expressed in a ratio to TMV or allometrically scaled TMV. In conclusion, this study has demonstrated that, when body size is appropriately accounted for using allometric scaling, TMV is unrelated to indices of aerobic and anaerobic power in 10-year-old children. Furthermore, there appear to be no qualitative differences in the muscle function of boys and girls in respect of aerobic and anaerobic function. Accepted: 4 February 1997     

Paraoxonase and arylesterase levels in autoimmune thyroid diseases

Objective: The aim of this study was to evaluate serum paraoxonase-1 (PON1) activity and its association with oxidative stress in autoimmune thyroid disease (AITD).

Methods: A total of 50 patients with AITD, including 25 with Hashimoto's thyroiditis and 25 with Graves’ disease were enrolled. The control group comprised 27 healthy subjects. Blood samples were obtained in the euthyroid period and 3 months after initiation of medical treatment. Serum samples from patients with AITD and the healthy control group were analyzed for basal PON1, salt-stimulated PON1, and arylesterase (ARE) activities, along with lipid hydroperoxide (LOOH) and total free sulfhydryl (–SH) levels.

Results: Serum PON1 activities and –SH levels were significantly lower (P?<?0.001, for each), whereas LOOH levels were significantly higher (P?<?0.001, for each) in patients with AITD, compared to the control group. We observed no significant differences in ARE levels between the patient and healthy control groups (P?>?0.05). PON1 activity was positively correlated with –SH (r?=?0.522, P?<?0.001) and negatively correlated with LOOH (r?=??0.487, P?<?0.001). PON1 phenotype distribution of the subjects was not significantly different among the three groups (P?=?0.961).

Conclusions: Serum PON1 activity is decreased in patients with AITD, and correlated positively with –SH, a well-known antioxidant, and negatively with LOOH, an index of lipid oxidation.     

Fat mass limits lower-extremity relative strength and maximal walking performance in older women

The purpose of this study was to determine if excess fat negatively affects relative strength and walking gait performance in overweight, older women. Twenty-five older women (65–80 yr) were separated into normal weight (BMI < 25 kg m⁻², n = 11) and overweight groups (BMI ? 25 kg m⁻², n = 14). Strength and rate of torque development (RTD) of the knee extensors and flexors, ankle plantarflexors and dorsiflexors were measured. Participants walked at standard and maximal speeds during which muscle activation, spatiotemporal and kinetic gait variables were measured. Relative to mass, overweight older women had 24% lower maximal torque and 38% lower RTD than normal weight women. Maximal walking speed was slower in overweight (1.25 ± 0.22 vs. 1.54 ± 0.25 m s⁻¹, P = 0.004) and was correlated to strength (r = 0.53, P < 0.01) and fat mass (r = −0.65, P = 0.001). At maximal speed, overweight had 11% lower vertical ground reaction force relative to mass, 8% slower stride rate, 12% shorter strides, 13% longer foot–ground contact times, 21% longer double-limb support times, 65% greater knee extensor and 78% greater plantarflexor activation (P < 0.05). Overweight, older women demonstrated altered gait and reduced walking performance related to poor relative strength and rate of torque development of lower-extremity muscles.     

Adaptations of placental and cord blood ABCA1 DNA methylation profile to maternal metabolic status

In utero environmental perturbations have been associated with epigenetic changes in the offspring and a lifelong susceptibility to cardiovascular diseases (CVD). DNA methylation at the ATP-binding cassette transporter A1 (ABCA1) gene was previously associated with CVD, but whether these epigenetic marks respond to changes in the maternal environment is unknown. This study was undertaken to assess the associations between the maternal metabolic profile and ABCA1 DNA methylation levels in placenta and cord blood. Placenta and cord blood samples were obtained at delivery from 100 women including 26 with impaired glucose tolerance (IGT) diagnosed following a 75 g-oral glucose tolerance test (OGTT) between week 24 and 28 of gestation. ABCA1 DNA methylation and mRNA levels were measured using bisulfite pyrosequencing and quantitative real-time PCR, respectively. We report that ABCA1 DNA methylation levels on the maternal side of the placenta are correlated with maternal high density lipoprotein cholesterol (HDL-C) levels (r < –0.21; P < 0.04) and glucose levels 2 h post-OGTT (r = 0.25; P = 0.02). On the fetal side of the placenta, ABCA1 DNA methylation levels are associated with cord blood triglyceride levels (r = –0.28; P = 0.01). ABCA1 DNA methylation variability on both sides of the placenta are also associated with ABCA1 mRNA levels (r < –0.35; P = 0.05). As opposed to placenta, cord blood DNA methylation levels are negatively correlated with maternal glucose 2 h post-OGTT (r = –0.26; P = 0.02). In conclusion, the epivariations observed in placenta and cord blood likely contribute to an optimal materno–fetal cholesterol transfer. These in utero epigenetics adaptations may also potentially trigger the long-term susceptibility of the newborn to dyslipidemia and CVD.     

Plasma micronutrient concentrations in infants undergoing therapy for phenylketonuria

Twenty-seven infants with classical phenylketonuria were evaluated longitudinally for 6 mo while ingesting Phenex^TM -1 Amino Acid Modified Medical Food With Iron as their primary protein source. Intake of selected nutrients and biochemical indices of trace and ultratrace mineral status and plasma retinol and α-tocopherol concentrations were evaluated. The means of iron status indices (complete blood count, plasma ferritin, iron, transferrin saturation, total iron binding capacity) and the plasma concentrations of trace and ultratrace minerals (copper, manganese, molybdenum, selenium, zinc) and plasma retinol and α-tocopherol were in the reference ranges. Vitamin A intakes (r = 0.49,p < 0.05) and plasma retinol-binding protein concentrations (r = 0.42,p < 0.05) were positively correlated with plasma retinol concentrations at 3 mo of study. At 6 mo, concentrations of plasma transthyretin (r = 0.72,p < 0.01) and retinolbinding protein (r = 0.48,p < 0.05) were positively correlated with plasma retinol concentrations. At 6 mo, concentrations of plasma transthyretin (r = 0.52,p < 0.05) were positively correlated with retinol-binding protein concentrations. Phenex-1 supports normal mean iron status indices and mean concentrations of trace and ultratrace minerals, retinol, and α-tocopherol when fed in adequate amounts.     

Assessment of Isolated Wetland Condition in Florida Using Epiphytic Diatoms at Genus, Species, and Subspecies Taxonomic Resolution

Diatoms are useful indicators of aquatic conditions, and metrics based on published autecological indicator values have been developed utilizing their sensitivities to various ambient physical and chemical conditions. The autecological values often differ within genera, and indeed within species taxonomic levels, requiring identification to subspecies taxonomic level for accurate application. This study was conducted to determine if autecological metrics, and ultimately indices of biotic integrity, could be developed using mean autecological values at the genus, species, and subspecies taxonomic levels, and to investigate the potential benefits of increased taxonomic resolution. Sixty-nine isolated herbaceous wetlands in various land use modalities in peninsular Florida were sampled a single time for epiphytic diatoms, and soil/water physicochemical parameters. Thirty genera, 148 species, and 26 subspecies were identified. The proportional matrices at each taxonomic level were highly similar (Mantel’s r > 0.75, P < 0.0001). Autecological metrics and two sensitive or tolerant measures were developed at each taxonomic level. Wetland condition, as determined by summed metric values, was strongly correlated across taxonomic level (r ² > 0.83, P < 0.0001), and no significant difference was found when sites were placed into bins of excellent, good, fair, or poor, based on quartile scoring, for each taxonomic level. Specific conductance, soil pH, soil and water total phosphorous, and water color were significantly related to site non-metric multidimensional scaling (NMDS) ordination scores at each taxonomic level. This study concludes that indices of biotic integrity, when developed using autecological indices, provide similar qualitative conditional information across taxonomic levels for isolated herbaceous wetlands. Electronic supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Interrelations and associations of serum levels of steroids and pituitary hormones with markers of insulin resistance,inflammatory activity,and renal function in men and women aged >70 years in an 8-year longitudinal study of opposite-sex twins

Background: The physiological serum levels of steroids and pituitary hormones in older men and women have been sparsely reported in the literature.Objectives: The aims of this study were to investigate the normal variation and sex differences in steroids and pituitary hormones in those aged >70 years, and to study the interrelation between these hormones and indicators of the metabolic syndrome, inflammatory activity, and renal function.Methods: The investigation comprised a population-based sample of pairs of white opposite-sex twins from the Swedish Twin Registry. At baseline in 1996 and at the 8-year follow-uup in 2004, serum levels of progesterone, cortisol, testosterone, estradiol, follicle-stimulating hormone, luteinizing hormone, prolactin, creatinine, C-reactive protein (CRP), and urea were analyzed. Serum levels of insulin and cystatin were analyzed only at the follow-up.Results: The study sample included 219 men and 183 women aged 71 to 80 years (mean [SD], 74.5 [2.5] years) at baseline in 1996, and 127 men and 135 women at follow-uup in 2004. At baseline, in both men and women, the variation of progesterone in serum was positively correlated with that of estradiol (men: r = 0.226, P < 0.01; women: r = 0.115, P = NS), testosterone (men: r = 0.178, P < 0.01; women: r = 0.315, P < 0.001), and cortisol (men: r = 0.314, P < 0.001; women: r = 0.296, P < 0.001). The values of progesterone and other steroid hormones were associated with markers of insulin resistance (iie, insulin, waist circumference), inflammatory activity (ie, CRP) for progesterone (men: r = 0.267, P < 0.001; women: r = 0.150, P < 0.05), and renal function (ie, creatinine) for progesterone (men: r = 0.424, P < 0.001; women: r = 0.212, P < 0.01). Estradiol and prolactin were associated with insulin resistance, inflammation, and renal function. Furthermore, progesterone was associated with prolactin (men: r = 0.275, P < 0.001; women: r = 0.172, P < 0.05).. Among both men and women, there was a strong correlation between testosterone and estradiol (men: r = 0.753, P < 0.001; women: r = 0.526, P < 0.001); in women, there was also a link between testosterone and cortisol at follow-up (r = 0.340, P < 0.01). For progesterone, there was a significant correlation between the values of the co-twins (in 1996: r = 0.16, P < 0.05; in 2004: r = 0.45, P < 0.001). Higher serum levels of progesterone (2.0 [0.7] nmol/L in men and 1.7 [0.8] nmol/L in women) and prolactin (6 [5] μg/L in men and 8 [10] μg/L in women) were found among those who were deceased at follow-up compared with survivors (progesterone: 1.8 [0.5] nmol/L in men and 1.4 [0.6] nmol/L in women, P < 0.01; prolactin: 4 [3] μg/L in men and 5 [2] μg/L in women, P < 0.001).Conclusions: In this study of opposite-sex Swedish twins aged >70 years, there was a sex difference in the serum levels of steroids and pituitary hormones between men and women. Progesterone and other steroid hormones were associated with markers of insulin resistance, inflammatory activity, and renal function. Progesterone and prolactin levels were associated with increased risk of mortality in this sample.     

Botanical composition and extent of lignification affecting digestibility of wheat and oat straw and paspalum hay

Samples of 1 kg of wheat straw, oat straw and paspalum hay were separated manually into botanical fractions, and the three largest fractions of each forage were analysed chemically for cell-wall constituents, silica and nitrogen. Proportions of digested dry matter, cellulose and hemicellulose, and potential digestibility for each of these major botanical fractions were determined when chaffed samples were placed in nylon bags and incubated for 12, 24, 48, 72 and 96 h in the rumen of sheep fed on lucerno. Cross-sections of botanical fractions were stained with safranin and fast green, and proportions of lignified tissue determined by light-microscopy and planimetry.Large differences in dry-matter digestibility between wheat straw and oat straw were attributed to the different proportions of botanical fractions. Within forages, stem was the largest fraction, the most lignified and had the lowest potential digestibility. Proportions of digested dry matter from botanical fractions at 12 h were poorly correlated with lignin content of dry matter (r = 0.25) but at 72 h were negatively correlated with lignin content of dry matter (r = ?0.84, P<0.01) and with proportions of lignified tissue (r = ?0.67, P<0.05) in the respective botanical fractions. Proportions of cellulose and hemicellulose digested at 72 h were strongly correlated with lignin content of cell walls (r = ?0.90, P<0.01; r = ?0.85, P<0.01, respectively). Proportions of lignified tissues were less closely correlated with all measurements of digestibility than were proportions of lignin in cell walls determined chemically. Development of a technique for measuring intensity of lignification might enhance the value of light-microscopy measurements.     

Fasting Plasma Insulin Modulates Lipid Levels and Particle Sizes in 2‐ to 3‐Year‐Old Children

Objective: Obesity and hyperinsulinemia are associated with dyslipidemia in adults and older children, but little is known about these relationships in very young children. We examined the relation of fasting insulin to lipid levels and lipid particle size in young healthy children. Research Methods and Procedures: Analyses were performed on data from 491 healthy 2‐ and 3‐year old Hispanic children enrolled in a dietary study conducted in New York City, 1992–1995. Obesity measures included BMI, ponderal index, skinfold thickness, and waist circumference. Low‐density lipoprotein (LDL)‐ and high‐density lipoprotein (HDL)‐cholesterol particle size were measured by nuclear magnetic resonance. Results: Fasting insulin level was positively correlated with triglyceride levels (r = 0.24 for boys and r = 0.23 for girls; p < 0.001 for both) and inversely correlated with HDL‐cholesterol level in boys (r = ?0.20; p < 0.01). Higher fasting insulin level was also correlated with smaller mean HDL particle size in both boys (r = ?0.21; p < 0.001) and girls (r = ?0.14; p < 0.05) and smaller mean LDL particle size in boys (r = ?0.13; p < 0.05). The associations of fasting insulin level with triglyceride and HDL‐cholesterol levels and HDL and LDL particle size remained significant after multivariate regression adjustment for age, sex, and BMI or ponderal index. Discussion: Fasting insulin level is associated with relative dyslipidemia in healthy 2‐ and 3‐year‐old Hispanic children.     

Characteristics of chimpanzee (Pan troglodytes) ejaculates collected by rectal probe electrostimulation and by artificial vagina

This study compares characteristics of ejaculates collected from 16 adult male chimpanzees using rectal probe electrostimulation (RPE) and from 10 adult male chimpanzees trained to use an artificial vagina (AV). Ejaculate weight, semen volume, and sperm number were significantly lower (P < 0.01) and percentage liquefaction was significantly higher (P < 0.01) in ejaculates collected by RPE. Percentages of motile sperm and of live sperm in semen did not differ significantly between the two collection methods. Total amounts of protein and of α-glucosidase activity were significantly lower (P < 0.01) in seminal fluid from RPE samples. For ejaculates collected by RPE, semen volume correlated positively with protein (r = 0.8640, P < 0.001), fructose (r = 0.6976, P < 0.001), and citrate (r = 0.6976, P < 0.001); sperm number correlated positively with α-glucosidase activity (r = 0.6547, P < 0.001); and protein correlated positively with fructose (r = 0.5906, P < 0.002), citrate (r = 0.5926, P < 0.002) and α-glucosidase activity (r = 0.6006, P < 0.001). For ejaculates collected by AV, semen volume correlated positively with percentage liquefaction (r = 0.6058, P < 0.001), protein (r = 0.8055, P < 0.001), fructose (r = 0.6606, P < 0.001), and citrate (r = 0.8272, P < 0.001); sperm number correlated positively with percentage of motile sperm (r = 0.4196, P 0.004); percentage of motile sperm correlated positively with percentage of live sperm (r = 0.4388, P < 0.002); and, protein correlated positively with fructose (r = 0.6947, P < 0.002) and with citrate (r = 0.5926, P < 0.002). These data show that there is a significant difference in semen parameters and in biochemical parameters of ejaculates obtained by RPE and by AV. © 1995 Wiley-Liss, Inc.     

THE EVOLUTION OF TRACHEID DIAMETER IN EARLY VASCULAR PLANTS AND ITS IMPLICATIONS ON THE HYDRAULIC CONDUCTANCE OF THE PRIMARY XYLEM STRAND

A cumulative correlation analysis of the maximum diameter of primary xylem tracheids recorded for 41 tracheophyte fossils, plotted against their ages (ranging from the Upper Silurian to the Lower Devonian), yields a Spearman rank coefficient (r_sp) of 0.696 (P < 0.01). Data for specimens taxonomically referable to zosterophyllophytes and lycopods reveal an increase in the range and maximum diameter of tracheids from the Siegenian to the Emsian. Correlation analysis of these data yields an r_sp value of 0.95 (P < 0.02). The mean and maximum tracheid diameters recorded for rhyniophytes, when correlated against stratigraphic occurrence, yield r_sp values of 0.81 (P < 0.05) and 0.85 (P < 0.02), respectively. A correlation analysis of the data for rhyniophytes, trimerophytes and progymnosperms yields an r_sp value of 0.87 (P < 0.01). Therefore, despite a relatively small sample size of early Paleozoic plants, the available data show a surprising level of statistical robustness. The data are interpreted to indicate that during the early evolution of tracheophytes, both the range and maximum tracheid diameter of the primary xylem increased, while in some plant lineages (zosterophyllophytes) there is evidence for a plateauing of maximum tracheid diameters by the Middle Devonian. The statistical trends in the data are interpreted within the context of the evolution of the hydraulic conductance of tracheophyte primary xylem.     

The repeatability of feed intake and feed efficiency in beef cattle offered high-concentrate,grass silage and pasture-based diets

Breeding values for feed intake and feed efficiency in beef cattle are generally derived indoors on high-concentrate (HC) diets. Within temperate regions of north-western Europe, however, the majority of a growing beef animal’s lifetime dietary intake comes from grazed grass and grass silage. Using 97 growing beef cattle, the objective of the current study was to assess the repeatability of both feed intake and feed efficiency across 3 successive dietary test periods comprising grass silage plus concentrates (S+C), grazed grass (GRZ) and a HC diet. Individual DM intake (DMI), DMI/kg BW and feed efficiency-related parameters, residual feed intake (RFI) and gain to feed ratio (G : F) were assessed. There was a significant correlation for DMI between the S+C and GRZ periods (r = 0.32; P < 0.01) as well as between the S+C and HC periods (r = 0.41; P < 0.001), whereas there was no association for DMI between the GRZ and HC periods. There was a significant correlation for DMI/kg BW between the S+C and GRZ periods (r = 0.33; P < 0.01) and between the S+C and HC periods (r = 0.40; P < 0.001), but there was no association for the trait between the GRZ and HC periods. There was a significant correlation for RFI between the S+C and GRZ periods (r = 0.25; P < 0.05) as well as between S+C and HC periods (r = 0.25; P < 0.05), whereas there was no association for RFI between the GRZ and HC periods. Gain to feed ratio was not correlated between any of the test periods. A secondary aspect of the study demonstrated that traits recorded in the GRZ period relating to grazing bite rate, the number of daily grazing bouts and ruminating bouts were associated with DMI (r = 0.28 to 0.42; P < 0.05 - 0.001), DMI/kg BW (r = 0.36 to 0.45; P < 0.01 - 0.001) and RFI (r = 0.31 to 0.42; P < 0.05 - 0.001). Additionally, the number of ruminating boli produced per day and per ruminating bout were associated with G : F (r = 0.28 and 0.26, respectively; P < 0.05). Results from this study demonstrate that evaluating animals for both feed intake and feed efficiency indoors on HC diets may not reflect their phenotypic performance when consuming conserved forage-based diets indoors or when grazing pasture.     

Oxidation of low-density lipoproteins: effect of antioxidant content,fatty acid composition and intrinsic phospholipase activity on susceptibility to metal ion-induced oxidation

The oxidative modification of low-density lipoprotein (LDL) may play an important role in atherogenesis. Our understanding of the mechanism of LDL oxidation and the factors that determine its susceptibility to oxidation is still incomplete. We have isolated LDL from 45 healthy individuals and studied the relationship between LDL fatty acid, vitamin E and β-carotene composition, intrinsic phospholipase A₂-like activity and parameters of LDL oxidation. LDL was exposed to a copper ion-dependent oxidising system and the kinetics of oxidation studied by monitoring formation of fatty acid conjugated dienes. The length of the lag phase of inhibited lipid peroxidation was measured as well as the rate of lipid peroxidation during the propagation phase. There was no significant correlation between LDL antioxidant vitamin or fatty acid composition and lag time to LDL oxidation. Oleic acid was negatively correlated with the rate of LDL oxidation (r = −0.41, P < 0.01) whilst linoleic acid was significantly correlated with the extent of LDL oxidation measured by the production of total dienes (r = 0.34, P < 0.05). Interestingly, LDL vitamin E content was positively correlated with both the rate (r = 0.28, P < 0.05) and extent of LDL oxidation (r = 0.43, P < 0.01). LDL isolated from this group of subjects showed significant intrinsic phospholipase-like activity. The phospholipase activity, whilst not correlated with lag time, was significantly correlated with both rate (r = 0.43, P < 0.01) and total diene production (r = 0.44, P < 0.01) of LDL oxidation. We conclude that antioxidant content, fatty acid composition and intrinsic phospholipase activity have little influence on the lag time of Cu-induced LDL oxidation. These components do however, significantly influence both the rate and extent of LDL oxidation, with increased vitamin E, linoleic acid content and phospholipase activity associated with faster and more extensive oxidation. The possible pro-oxidant effect of vitamin E has interesting implications for the postulated ‘protective’ effects of vitamin E on atherogenesis.     

Nitrogen partitioning and isotopic discrimination are affected by age and dietary protein content in growing lambs

It is difficult to separate an age-dependent fall in nitrogen use efficiency (NUE; N balance/N intake) in growing ruminants from a progressively decrease in animal protein requirements over time. This study examined the effect of dietary protein content on N partitioning, digestibility and N isotopic discrimination between the animal and its diet (Δ¹⁵N_animal-diet) evaluated at two different fattening periods (early v. late). Twenty-four male Romane lambs (age: 19 ± 4.0 days; BW: 8.3 ± 1.39 kg) were equally allocated to three dietary CP treatments (15%, 17% and 20% CP on a DM basis). Lambs were reared with their mothers until weaning, thereafter housed in individual pens until slaughter (45 kg BW). During the post-weaning period, lambs were allocated twice (early fattening (30 days post-weaning) and late fattening (60 days post-weaning)) to metabolic cages for digestibility and N balance study. When diet CP content increased, the average daily gain of lambs increased (P < 0.05) while the age at slaughter decreased (P = 0.01), but no effect was observed on feed efficiency (P > 0.10). Diet CP content had limited effect on lamb carcass traits. Higher fibre digestibility was observed at the early v. late fattening period (P < 0.001). The N intake and the urinary N excretion increased when diet CP content increased (P < 0.001) and when shifting from early to late fattening period (P < 0.001). Faecal N excretion (P = 0.14) and N balance (P > 0.10) were not affected by diet CP content. Nitrogen digestibility increased (P < 0.001) as the diet CP content increased and on average it was greater at late v. early fattening period (P = 0.02). The NUE decreased (P = 0.001) as the diet CP content increased and as the lamb became older (P < 0.001). However, the age-dependent fall in NUE observed was lower at high v. low dietary CP content (CP × age interaction; P = 0.04). The Δ¹⁵N_animal-diet was positively correlated (P < 0.05) with N intake (r = 0.59), excretion of faecal N (r = 0.41), urinary N (r = 0.69) and total manure N (r = 0.64), while negatively correlated with NUE (r = −0.57). Overall, the experiment showed NUE was lower in older lambs and when lambs were fed high diet CP content, and that Δ¹⁵N_animal-diet was a useful indicator not only for NUE but also for urinary N excretion, which is a major environmental pollution factor on farm.     

Effect of Lysine Addition on Growth of Black Iguana (Ctenosaura pectinata)

The effects of the addition of lysine to commercial feed given to captive black iguana (Ctenosaura pectinata) were evaluated in terms of growth and feed digestibility. Twenty‐eight‐day‐old black iguana with an initial weight of 5.5 ± 0.3 g were housed individually in cages measuring 45 × 45 × 45 cm. The experiment lasted 150 days. The ambient temperature ranged from 28 to 35°C with a relative humidity of 60 to 95%. Treatments consisted of the addition of different percentages of lysine to the feed (0.0, 0.1, 0.2, and 0.3%, dry matter [DM] base). There was a linear response (P < 0.01) in daily gain (68, 112, 118, and 151 mg/d) and daily intake (251, 289, 297, and 337 mg/d) for levels from 0 to 0.3%, respectively, as well in the growth in head size, snout–vent length, and total length. The digestibility of DM, neutral detergent fiber, and acid detergent fiber were reduced linearly (P < 0.01) as lysine levels increased. Intake and digestibility were negatively correlated (r = –0.74; P < 0.001). It is concluded that the addition of lysine to the black iguana diet in the first months of life is important to stimulate growth and intake. Zoo Biol 32:277–280, 2013. © 2012 Wiley Periodicals, Inc.     

Visceral Adipose Tissue and Markers of the Insulin Resistance Syndrome in Obese Black and White Teenagers

Objective: To determine the relationships between visceral and general adiposity, cardiovascular fitness, and markers of the insulin resistance syndrome in obese black and white teenagers. Research Methods and Procedures: Cross‐sectional survey of 81 obese 13‐ to 16‐year‐old youths. Visceral adipose tissue was measured with magnetic resonance imaging, and percentage body fat was measured with dual‐energy X‐ray absorptiometry. Cardiovascular fitness was assessed with a submaximal treadmill test. Fasting blood samples were analyzed for lipids/lipoproteins and insulin. Resting blood pressure was obtained using an automated cuff. Results: Visceral adipose tissue was significantly correlated with unfavorable levels of: triacylglycerol (r = 0.27, p < 0.05), total cholesterol (r = 0.27, p < 0.05), high‐density lipoprotein cholesterol (r = ?0.26, p < 0.05), the ratio of total cholesterol/high‐density lipoprotein cholesterol (r = 0.42, p < 0.01), low‐density lipoprotein cholesterol (r = 0.27, p < 0.05), apolipoprotein B (r = 0.38, p < 0.01), and systolic blood pressure (r = 0.30, p < 0.01). Multiple regression analyses revealed that visceral adipose tissue was more powerful than percentage body fat for explaining variance in lipoproteins (e.g., for the ratio of total cholesterol/high‐density lipoprotein cholesterol, r² = 0.13, p < 0.01, and for systolic blood pressure, r² = 0.07, p < 0.05). Ethnicity was the most powerful of the demographic predictors for blood lipids (r² = 0.15 for triacylglycerol with lower levels in blacks; r² = 0.10 for high‐density lipoprotein cholesterol with higher levels in blacks; r² = 0.06 for the ratio of total cholesterol/high‐density lipoprotein cholesterol with lower levels in blacks). Cardiovascular fitness was not retained as a significant predictor of markers of the insulin resistance syndrome. Discussion: Some of the deleterious relationships between visceral adiposity and markers for the insulin resistance syndrome seen in adults were already present in these obese young people.