Growth Development and Aging最新文献

Growth of chick embryonic femora, tibiotarsi and first phalanges of digit three were measured at one day intervals from day 6 through 16 of incubation. Normal controls were compared to embryos paralyzed at 5 days of incubation. Over the 10 day study period, length of the paralyzed femora, length and width of the paralyzed tibiotarsi and differences in length of the phalanges were observed. Growth in length of phalanx one of digit three was most affected by paralysis over this period. Changes in shape of these bones also occurred during growth. Normal long bones undergo changes in shape as differential growth in length and width occurs. Such changes in shape can be considered as the bone's normal growth "trajectory". Paralyzed bones displayed a different growth trajectory than normal bones. As expected, the long bones of paralyzed embryos were shorter than age-matched controls. Contrary to expectations, however, paralyzed long bones were relatively more stout than age-matched controls.

It has been reported that the amount of D-aspartic acid in dentin is highly correlated with age. However, further studies are necessary to determine the details of this correlation. We quantitatively determined L- and D-aspartic acids in dentin, and from the data calculated the D/L ratio. We did not find any statistically significant difference in the D/L ratio between the same type of left and right teeth from the same jaw, and between the vestibular and lingual sides of the root dentin. However, the D/L ratio was significantly higher on the lingual side than on the labial side of the dentin. Although the D/L ratio in young subjects was comparatively high in the tooth crown and decreased toward the apex of the root, we did not always observe such a tendency in middle- to advanced-age individuals. These results indicate that the ratio of D/L aspartic acid in dentin varies between the lingual side and vestibular side of the crown dentin. Therefore, it appears that the racemization rate of aspartic acid is not uniform but differs with the region of the dentin, and may be affected by differences in factors such as temperature.

The brushtail possum, Trichosurus vulpecula, produces a single offspring 200 mg in body weight. The young grow slowly during the first half of pouch of life at approximately 1g/day. At day 96 post partum the growth rate increases dramatically and it has been suggested that this change in growth rate may result from the initiation of thyroid function in the young possum. To determine the role of the thyroid gland of the possum on growth, the production of hormones from the thyroid was inhibited by administration of the drug, methimazole. The drug was administered to adult and young possums at day 140 post partum for 28 days and to young at day 100 post partum for 42 days and the effects of this treatment on plasma concentrations of thyroxine and on growth were monitored. Methimazole was found to inhibit thyroxine production in 4 of the 6 adult possums although it had no effect on body weight. Similar treatment administered to nine young possums inhibited growth. The three surviving methimazole possum young treated at 100 days post partum weighed less than control possums after day 163 post partum. The four young treated at 140 days post partum also showed depression in growth rate. However, the depression was not as marked as that of the 100 day treated possums. It is highly likely therefore that the surge in growth rate in the possum at day 96 post partum is initiated by thyroxine produced by the thyroid gland of the young.

Industrially employed PCB has caused wide-spread environmental contamination through improper disposal and has been associated with detrimental physiological states in exposed organisms, including depressed body weight, food consumption, and circulating levels of T4 and T3. Previously, the activity of choline acetyltransferase (ChAT) in the basal forebrain and hippocampus was shown to be depressed in young rats exposed to the PCB diet from the time of conception. The present study measured the neurochemical effects of similar PCB exposure in older (i.e., 60 day old) rats, and examined possible restoration of PCB-induced deficits by removing PCB at weaning (28 days). Possible PCB-induced impairment of memory was also evaluated with a radial arm maze. Findings included a significant depression of circulating levels of T4 in all treatment groups with the most profound depression seen in rats continuously fed PCB. Also, T3 levels and relative thyroid weights were not found to be severely depressed. The ChAT activity in both the basal forebrain and hippocampus was not different from control in all treatment groups. It appears that the effect of PCB on thyroxine is persistent, but its influence on ChAT activity is not. However, modest memory deficits were observed despite normal ChAT activity. Average number of working memory errors per test session in the maze increased in a dose-dependent manner across treatment groups.

The estimation of the parameters of a nonlinear model by means of the maximum likelihood procedure is widely used in the study of growth phenomena. The accuracy with which these parameters are calculated is a function of the number of measures taken and particularly, of their distribution across the growth period. If the growth curve is only partially known, the inaccuracy can increase considerably. However, if we have information on the distribution of the parameters of a model in the population, the empirical Bayes method should be used. In this paper, the principle of this approach for nonlinear modeling was recalled. The method was then applied on data of human height. Four nonlinear models are used and their performances are compared. The results show the importance of information on the quality of estimates of growth parameters and consequently on the prediction of adult height.

As far as we know, there is no available information about ontogenic changes of tissue concentrations of IGF-I and II and IGFBPs in large mammals. Serum, liver and kidney levels of IGFs and IGFBPs were examined in fetuses at 90 and 110 days of gestation and in pigs at 1d, 3 wk, 3 mo and 6 mo of age. Ontogeny of mRNA levels of IGFs, IGF type I and type II receptors (IGFI-R and IGFII-R), IGFBP-1 and -3 (IGFBPs) and growth hormone receptor (GHR) were also examined by Northern blot analysis in liver, kidney and skeletal muscle of pig. Serum IGF-I, IGF-II and IGFBP-3 concentrations were low during the fetal life and increased after birth. The highest level of IGF-II mRNA was found in fetuses for all studied tissues. In the liver, IGF-I mRNA level and its protein content peaked at 3 wk of age. The highest IGF-II concentration was found at 1d and 3 wk of age. The IGFII-R mRNA remained at a constant level during the whole development period. The most abundant IGFBP-1 mRNA and its protein content were found at birth. The level of IGFBP-2 was high during fetal and early postnatal life. The IGFBP-3 content was relatively low in fetuses and reached the highest level after 3 wk of age. In the kidney, IGFs, IGFBP-3, IGFI-R and IGFII-R as well as GHR mRNA levels were relatively high during the fetal and early postnatal life. The IGFs concentrations were the highest in newborns. In the skeletal muscle, IGFs, IGFBP-3 and IGFI-R mRNA levels decreased with advancing age. During the postnatal life, the high IGFs concentrations in the liver and the kidney correspond to fast growth periods of these organs.

We hypothesized that abnormal capillary formation, which might be associated with an alteration in extracellular malular matrix (ECM), occurs in the alveoli of growing rat lungs treated with beta-aminopropionitrile (beta APN), a lathyrogen that inhibits lysyl oxidase activity. On scanning electron microscopy, a corrosion cast of alveolar capillaries in lungs treated with beta APN appeared abnormal in configuration; transmission electron microscopy showed extensive morphological changes in interstitial cells and ECMs, including collagen, elastin, and presumably glycosaminoglycans and, in binding water (GBW). Morphometric data revealed an increase in GBW of up to 24.4%, a decrease in the amount of collagen fiber (44.5%), and a decrease in lipid-laden interstitial cells; however, the change in elastin was limited to morphological appearance. From these observations, we conclude that alterations in alveolar capillary formation are associate with extensive changes in ECMs, and that these changes in ECM components might also be involved in the abnormal alveolar formations induced by beta APN.

Growth, glucose levels and body composition of male and female C57BL/6 ob/ob and lean (?/+) mice were examined between 17 days and 1 year of age. Obese mice displayed three distinct periods of growth with each phase characterized by a different pattern of glucoregulation. Until 4 weeks of age, ob/ob mice had slightly higher rates of weight gain and fat accretion than littermate lean mice. Glycemia was in the normal range and insulin levels were elevated. Shortly after the transition to solid food, ob/ob mice displayed several weeks of increased body growth and very high rates of fat deposition. During this period of rapid weight gain, hyperglycemia arose despite progressively increasing IRI concentrations. Examination of individual obese mice at this time revealed that glycemia was highly correlated with the rate of body fat deposition. The final phase of the ob/ob syndrome began at 3 months of age, as rates of fat deposition abruptly slowed to values slightly less than those of lean mice and glucose values declined to normal although hyperinsulinemia and glucose intolerance persisted. The present results show that ob/ob mice, although characterized throughout life by many metabolic and growth disturbances, only display diabetes mellitus and exaggerated fat deposition during a 6 to 8 week period just after weaning.

The racemization ration (D/L ratio) of aspartic acid in the dentin (collagen) of deciduous teeth was studied, using dentin of permanent teeth as a reference. D-aspartic acid in deciduous teeth was found to increase almost linearly with aging. The reaction velocity constant of racemization (kyr-1) in deciduous teeth (1.1915 x 10(-3)yr-1) was approximately double the value for permanent teeth (6.2550 x 10(-4)yr-1). The velocity of the racemization reaction was similar between deciduous teeth and permanent teeth in a dry state. The D/L ratio determined using transverse sections of deciduous teeth tended to be high in the crown and low in the root. The reaction velocity of racemization is considered to be affected to some extent by the tooth material, ambient temperature and salivary pH, but most importantly by physiologic resorption of deciduous teeth at the root associated with age.

The pig was used as a model for the application of dual-energy x-ray absorptiometry (DXA) for measuring changes in total and regional body composition that accompany body growth. Ten pigs were scanned at the beginning of the study (26.3 +/- 8.2 kg) and at 14 day intervals until reaching a final weight of 88.6 +/- 2.3 kg. Final body composition was validated by chemical analysis of the carcass. DXA fat and lean tissue measurements were corrected by using values based on previous calibration studies. From individual growth curves, rates of fat (295 +/- 50 g/d), lean (531 +/- 50 g/d) and bone mineral (16.7 +/- 1.4 g/d) deposition rates were estimated. Furthermore, using regional analysis these tissue deposition rates partitioned into front legs, back legs and body trunk. The final DXA measurements of 87.5 kg for total tissue mass, 27.9% for percent body fat and 24.4 kg for total fat mass were not significantly different (P > .05) from direct or chemical measurements. The DXA measurement of bone mineral content 1912 g (2.18%) was similar to the estimate based on total body ash, 1980 g (2.23%). Also, from the final DXA values for lean tissue mass, it was predicted that the body contained 13.5 kg or 15.4% protein and 45.74 kg or 52.3% water. These results indicate that DXA could be an appropriate method for studies involving sequential measurements of body composition during growth.