Growth Development and Aging最新文献

We have previously reported the Ts65Dn (Ts) mouse has impaired intestinal absorptive function and amino acid metabolism. Peptide YY (PYY) has enhanced glucose absorption in mice and turkeys. Other studies have reported that persons with Down syndrome have increased intestinal absorption of aluminum. Alzheimer's-like lesions have been reported in Ts mice. Trial 1 of this study examined brain Al concentrations, plasma metabolites and intestinal metabolism of 40 control and 40 Ts mice administered 300microg PYY/kg body weight or 0.9% saline for 3d. Trial 2 examined nutrient digestibility of 12 C and 12 Ts given PYY or saline for 14d. In Trial 1, PYY lowered (p<0.05) the brain Al pool (mg/g FBW) in both C and Ts mice by 80% compared to saline. Ts mice had increased plasma NH3 (329 vs. 269 microM, p<0.05), decreased plasma glucose (7.4 vs. 8.4 mM, p<0.01), elevated apparent energetic efficiency of jejunal glucose uptake (p<0.01) and elevated brain Al pool (0.41 vs. 0.12 microg, p=0.06) compared to C mice. In Trial 2, PYY increased small intestinal density (mg/cm) 12% in both genotypes (p<0.05), but did not alter nutrient digestibility. Brain Al accretion and hyperammonemia are proposed risk factors for Alzheimer's disease (AD). Ts mice and PYY appear to be suitable models for the study of metabolic and neurological anomalies in Down syndrome and AD.

In this paper, we reported the results obtained from fitting a new growth model to serial height data of 80 Fels children. The model assumed that human height growth curves are due to the combined effects of six macroscopic logistic growth processes, each reaching the same asymptotic height value. It was named the Walker and Walker-Hexaphasic-Logistic-Additive (WWHLA) growth model. An advantage to using this model is that it allowed us to easily fit entire growth curves with 14 biologically interpretable parameters. We tested the model using a computerized nonlinear least squares technique. The results showed that the new model worked extremely well. The fits resulted in high R, R2, and adjusted R2 values, large F values, relatively low residual mean squares, Durbin-Watson statistics that were very close to 2, and relatively small standard error estimates for the model parameters. In addition, the normality and constant variance test passed for more than 95 percent of the children, and the graphs of the residuals essentially showed no model bias. The new model identified the six growth components or processes in both male and female growth curves. The processes were named according to when they reached their peak height velocity: neonatal, infantile, early-childhood, middle-childhood, late-childhood, and pubertal. Preliminary results suggest that the WWHLA model appears to be the best that is currently available at this time for describing the human growth curve.

Reproductive performance was characterized in females of a line of mice homozygous for a recessive mutation with a major effect on growth, the high growth (hg) mutation. Specifically, the age at onset of puberty, length of the estrous cycle, ovulation rate, and gestation length in high growth (HG) mice were determined and compared with control mice. HG females reached puberty at an age similar to control animals, exhibited normal ovulation rates and estrous cycle length, but had a shorter length of estrus. Number of fetuses at Day 17 of gestation was greater and gestation length was longer in HG females. The HG females exhibited a variety of reproductive disorders, including increased incidence of repeated detection of mating plugs without intervening pregnancy ("replug"), increased incidence of repeated detection of mating plugs within an interval of 1-8 days without intervening pregnancy ("recycle"), increased interval between pairing with a male and detection of the first mating plug, increased interval between mating and conception, increased postnatal mortality, decreased litter size, and increased incidence of vaginal septum.

A mathematical model for human embryonic/fetal growth data from implantation to birth is developed. In previous work, it was shown that an unbiased estimate for human fetal growth data from about day 50 post-conception until term could be calculated from the Gompertz equation. This period represents a range of embryonic/fetal weights from one to 3500 g. When the Gompertz equation is extended, with no change of parameters, to the prenatal period before 50 days, the predicted weights have a consistent bias which might have a biological basis. Early embryonic growth immediately following fertilization is exponential; i.e., one cell goes to 2, then 4, then 8... etc., with essentially no decrease in relative growth rate. Except for possible small changes in cell size and cell mitosis cycle time, such exponential growth can be considered as a special case of the Gompertz equation with a, the relative rate of decrease of the relative growth rate, equal to zero. The relative growth rate begins to decrease about 20 days post-conception, at the time of cell differentiation into organ precursors. Although the "Hayflick Limit" of the maximum of 50 to 60 cell divisions for human cells would tend to cause a decrease in growth rate, it can be shown that the effect is insignificant during embryonic/fetal growth. The observed decrease in the growth rate might be a result of a decreasing fraction of cells in the pool of dividing cells. For the Gompertz equation model, a at this time changes from zero to a positive number. Analysis of fetal growth data shows that a rapidly becomes large and then decreases over a period of several days to become a constant positive value for the remainder of the prenatal term. Good fits of empirical embryonic/fetal growth data were obtained by nonlinear regression with calculation of the embryonic/fetal weights through numerical integration of the differential Gompertz equations and the functionality of alpha.

Nutrient digestibility and absorption decline with age in several mammalian species. The aim of this study was to compare apparent fat digestibility of different dietary fats in young and senior cats. Three diets enriched with either beef tallow (high in saturated fatty acids), olive oil (high in monounsaturated fatty acids) or sunflower oil (high in polyunsaturated fatty acids) were fed to 6 young (3.0+/-0.9y) and 6 senior (11.6+/-1.4y) cats at 300kJ metabolisable energy/kgBW0.75/d in a 3*3 Latin square design. Food and faecal samples collected over two consecutive 7d periods were analysed for fat, protein, moisture, ash, gross energy and fatty acid content. Apparent digestibilities of fat and energy were significantly lower (P=0.03) in senior cats compared to young cats (fat: 0.922 compared to 0.944; energy: 0.848 compared to 0.885, for senior and young cats, respectively) in all three diets. Senior cats exhibited a lower apparent digestibility for all fatty acid groups compared to the younger cats (saturated: 0.932 compared to 0.952; monounsaturated: 0.964 compared to 0.982; polyunsaturated: 0.980 compared to 0.987, for senior and young cats, respectively). Saturated fatty acids had the lowest apparent digestibility in both young and senior cats, and shorter chain fatty acids were digested more easily than the longer chain fatty acids. These results suggest that the age-related reduction in apparent fat digestibility was a general phenomenon affecting all fatty acids, and was not due to one particular fatty acid group.

The plasminogen system, in addition to its major role in fibrinolyis, is believed to play a key role in development of the nervous system. The purpose of this study was to directly examine and quantify the importance of plasminogen in physical and behavioral development in plasminogen deficient mice (Plg-/-), plasminogen heterozygous mice (Plg+/-), and wild-type mice (Plg+/+, WT) at 2-21 days of age. Remarkably, little difference in growth and behavioral development was observed between Plg-/- and WT mice. Body weight gain and the milestones of physical development-ear detachment, eye opening and teeth eruption were similar from 2-21 days of age. Differences were found in physical development only after 4 wks of age, body weight gain was less and vaginal patency was delayed in the Plg-/- mice compared to WT mice. Behaviors, assessed during the 2-21 days of age period, developed in the Plg-/- mice in a pattern similar to WT mice. Specifically, no differences were found between Plg-/- and WT mice in the development of reflexes, neuromotor ability, motor coordination, locomotor activity, reaction to gravitational positioning, integration of motor and vestibular systems, olfactory development, and incidence of audiogenic seizure susceptibility. However, Plg-/- mice demonstrated a faster surface righting response and a faster latency for audiogenic seizure susceptibility, as well as an increase in the number of grooming bouts at age 17-21 days. These differences indicate that a plasminogen deficiency alters reactivity and the response to stress. The weight of the pituitary was smaller and pituitary and plasma corticotrophin releasing hormone were elevated in the Plg-/- mice compared to the WT mice. The results of this study suggest a role for the plasminogen system in hormone processing and neuroendocrine regulation.

Body growth, muscle growth, bone growth, and measurements of muscle fiber area and fiber number were made in a line of Japanese quail (Coturnix coturnix japonica) selected for high 4 week body weight for 100 generations (line PP), in the control line from which they were derived (line CC), and in genetically equivalent reciprocal crosses (PC and CP) that develop in eggs that differ greatly in weight. There was no difference in body weight or weight of the P. superficialis of newly hatched CC or PC quail. Weights of PP and CP were equal to each other but greater than those of CC and PC. Body and muscle weights of the crosses were equal by 3 to 4 weeks of age. The number of fibers in the Semimembranosus muscle was lowest in CC quail, intermediate in PC and CP quail, and greatest in PP. Cross-sectional area of Semimembranosus fibers from 7 day old CC and PC were equal to each other and smaller than those of PP or CP quail. By 29 days of age, fibers in CC were smallest, those in PC and CP were intermediate and smaller than those of PP quail. At 7 days, the cross-sectional area of P. superficialis fibers of CP quail was greater than those of the other genotypes, but by 14 days and after fiber area was directly related to the bird's genetic potential for growth. These studies show that fiber hyperplasia is genetically determined whereas fiber hypertrophy in early life is primarily dependent on the dam's genotype and egg environment.

The Gompertz law of growth has puzzled scientists for decades: while it successfully described growth kinetics of various biological systems (e.g., tumor growth), its foundation has remained unclear. In this paper I recognize the Gompertzian growth as founded on self-similarity, which is so abundant in natural phenomena that it justifiably represents a fundamental natural paradigm. The self-similarity leads to an allometric principle: the sizes of a given biological system at different times are related by a simple power law. The stated relation can be also viewed as basic functional growth equation with unique nonconstant solutions being the Gompertz and the exponential functions. This equation also provides the description of growth and regression dynamics in terms of a difference equation which already has found practical application in characterizing tumor growth kinetics.

Male chickens from lines divergently selected for fast (FGL) and slow (SGL) growth were compared for the growth of cortical bone. Morphology, histomorphometric, compositional and biomechanical properties of the tibiotarsi were analysed in both lines at 1, 8, 15 and 22 d of age. Tibial morphology (length, volume, cross-section and diameters) was similar in FGL and SGL chickens when compared at an equal body weight. Cortical area was also similar in both lines at an equal body weight but cortex porosity was higher in FGL. Tibial mineral density (ash:volume) was higher in FGL than in SGL at hatching and at 8 d of age. Biomechanical properties were lower in SGL than in FGL at 8 d of age, but then became higher in this line when compared at equal body weight. The very slow growth rate in SGL did not modify bone size when chickens were compared at equal body weight. Bone quality was modified in various ways: in SGL bone structure was strengthened by a lower porosity of the cortex while bone tissue was less mineralized up to 22 d of age. In both lines, cortical growth was slower than in commercial cross-breeds and bone quality (structure and composition) was improved compared to broilers.

A longitudinal study with eighty-six rats (Rattus norvegicus albinus var. Wistar) of both sexes was made. The aim was to express adaptability to malnutrition in terms of Age-of-Fitness Point (AFP) and Trend-to-Fitness Stage (TFS). The AFP means the age in which both control and malnourished animals show the same Relative Food Intake (RFI) value, expressed in mg of food intake per g of body weight. The TFS means the percent of RFI reached by the malnourished animals at a given age stage. A TFS=70 for example, means that the animals have to gain 30% of RFI to reach its AFP. Growing animals were submitted to one of the following treatments: control (fed on a stock diet ad libitum), moderate malnutrition (fed on 1/2 of the daily stock diet of a control of the same age and sex) and severe malnutrition (fed on 1/3 of the mentioned diet). Body weight and food intake of all of the animals were registered every ten days, when they were from 20 to 80 days old. Relative Food Intake (RFI) was calculated dividing the food intake (mg) of each animal/day by its respective body weight (g). The RFI data series belonging to each sex and treatment was obtained. The significance of the three independent variables (age, sex, and nutrition) was tested by multiple regressions. Covariation and degree of linearity between RFI and age were tested by simple correlation and simple regression tests. The intercepts of the regressions were all significant. For both sexes they were greater in controls than in the moderately malnourished group, in the latter being greater than in the severely malnourished group. The slopes were significant and negative in all of the groups. While, in males and females, control and moderately malnourished rats showed little differences, the severely malnourished slopes were, respectively, 3.2 and 2.4 times lower than in controls. In controls there were sexual differences for RFI correlated with age which were not present in the malnourished groups. The AFP was calculated by extrapolation: 80-90 days of age in males, with RFI of 80 mg/g, and 100-110 days of age in females, with RFI of 70 mg/g. In males TFS was 29.5% and 88.6 % in moderate and severe malnutrition, respectively. In females these values were 9.1% and 63.2%, respectively. Sexual dimorphism in TFS was significant in the moderately malnourished animals and nonsignificant in the severely malnourished ones.