Growth Development and Aging最新文献

Growth hormone secretion is under the control of a pair of hypothalamic factors, growth hormone releasing hormone and somatostatin. The growth hormone secretagogue receptor (GHSR) and its endogenous ligand represent a novel third method regulating the release of growth hormone. Early chicken embryonic development has been proposed to be independent of GH. However, recent evidence shows that peripheral GH secretion has paracrine/autocrine functions during embryonic development. In the current study, we used the reverse-transcriptase polymerase chain reaction to determine the expression pattern of the GHSR during embryonic development and the effects of in ovo recombinant human (rh) IGF-I administration on its expression pattern. Eggs were injected once with 100 ng rhIGF-I in 10 mM acetic acid, and 0.1% BSA per embryo on embryonic day 3. Total RNA was isolated from whole embryos on embryonic day (E) 0-6 (n=6 per day), thoracic/abdominal halves of the embryos on E7- E8 (n= 6 per day) and Pectoralis muscle on E9-E20 (n= 4 per day). We found that GHSR expression was low during E0-E4, followed by an increase on E5 and remained constant through E17. GHSR expression then increased on E18 before reducing on E20. A similar pattern was found in the rhIGF-I treated embryos with the exception of a significant increase in GHSR expression on E8. These data indicate that the GHSR may be active in regulating GH secretion during early embryonic development, and upregulation of the GHSR gene following IGF-I administration may have an important role in the determination of postnatal muscle growth.

The intrauterine growth retardation (IUGR) is a complex phenomenon since it causes variability in postnatal growth responses. The aim of the present study was to analyze the effects of lactational rehabilitation on body and cranial growth and sexual dimorphism in IUGR rats. IUGR model was carried out by means of uterine vessels bending in pregnant rats at the first day of pregnancy. Control and sham-operated animals were also included. During suckling, IUGR and sham-operated pups were cross-fostered to a control dam. The animals were x-rayed every four days, from birth to weaning. Body weight and length, and neural and facial variables were measured. The reduced placental blood flow delayed growth in pups. Facial growth was more impaired than the neural one. An incomplete catch up growth was found, since males reached sham values only in neurocranial height and females--except facial length and width--were similar to sham. Because of sex differences in growth recovery, normal sexual dimorphism in body and craniofacial pattern was not expressed in the IUGR group. This study suggests that reduced uteroplacental blood supply in the rat interferes with the full expression of normal dimorphism based on gender and confirms the impact of IUGR on postnatal growth.

The olfactory epithelium is one of the unique sites in the mammalian nervous system at which there is continual neurogenesis. Constant turnover of primary sensory neurons in the periphery results in remodeling of neuronal circuits and synapses in the olfactory bulb throughout life. Most of the specific mechanisms and factors that control this process are still unknown. Recent studies suggest that growth factors and their receptors may play a significant role in the development and continuous regeneration of olfactory neurons. In this study, standard immunohistochemical methods were used to detect the presence of epidermal growth factor-receptor, transforming growth factor-alpha and nerve growth factor-beta in the human olfactory epithelium of different developmental stages (7 to 30 weeks) in formalin-fixed tissue specimens. Immunoreactivity to epidermal growth factor-receptor was seen in basal cells, supporting cells, neurons, apical cytoplasmic region of olfactory epithelium, lamina propria and gland's cell cytoplasm. Similarly transforming growth factor-alpha immunoreactivity was recognized in basal cells, supporting cells, apical cytoplasmic region of olfactory epithelium, lamina propria and gland's cell cytoplasm but not in neurons. Nerve growth factor-beta detection was restricted on olfactory nerve cells, dentritic knob and basal cell layer. So, this study confirms the development of human olfactory mucosa and shows epidermal growth factor-receptor, transforming growth factor-alpha and nerve growth factor-beta proteins are reliable markers for developing olfactory epithelium.

This study was undertaken to test the hypothesis that relative growth is the same in Japanese quail divergently selected for 4-week body weight for 30 generations, and their control. Relative growth rate is the increase in body weight per unit of body weight per unit of time, and it represents the efficiency of an animal as a producer of new body mass material. The maximum relative growth rate of the divergent and control lines were observed during the first week. Selection for high 4-week body weight has resulted in higher relative growth rate for the first two weeks compared to quail from the low line, but by week 3, quail from the low line had higher relative growth rate compared to quail from the high line. Asymptotic body weight increased by about 100 and 70%, respectively in the male and female high lines and declined by about 25% in the low lines. Absolute growth rate is thought to be related to the cumulative growth already achieved whereas relative growth rate is related to the amount of growth remaining. However, selection on absolute weight basis can elicit a response in relative growth rate in the early part of the developmental period which possibly pre-determines the asymptotic body weight. Since relative growth rate depends on the amount of growth remaining, the rate of decline in relative growth is then set accordingly. Furthermore, it is thought that different sets of genes may operate between the developmental period and maturation period.

The present research has been planned to determine the effects of early polysensorial enrichment on the plastic mechanisms that specify the complex organization of the cortical plate. The basal dendritic field, which is the input side of the neuron, developed increased geometrical complexity in enriched pups. Particularly striking was the specific territorial expansion of dendritic fields, induced by the exposition to a polysensorial enriched environment, observed in the lateral aspect of the parieto-occipital cortex. This implies an interplay involving the lateral aspect of the parieto-occipital cortex with afferents from whiskers and peribucal structures (areas for exploring the habitat). It is evident that during the early postnatal period the cerebral cortex develops a highly sophisticated network, which exhibits a high degree of substrate specificity tightly regulated by environmental cues.

The recovery in body weight (catch-up growth) was studied in juvenile male and female rats either exposed to hypoxia during the first postnatal week (10% inspired O2, Hypoxic) or with limited caloric intake (by growing in large litter size) during the first two postnatal weeks (LowCal). Compared to controls, the experimental rats had a severe stunting in body growth. The effects on the dry and wet weights of the internal organs (kidney, lungs, brain, heart, liver, thymus, skeleton) differed between Hypoxic and LowCal, but were similar between sexes. Catch-up growth during the following weeks was more apparent in females than in males, and accompanied by increased oxygen consumption. At 1 and, especially, 3 months, the organs had almost recovered their original weights, although differences in protein and DNA content (measured in brain, lungs, heart, brown adipose tissue) were still present in some cases. In general, organ recovery was more apparent in LowCal than in Hypoxic, and in females than in males. In the experimental groups the unevenness in weight among organs (coefficient of variation of the individual weights relative to control) at 10 days, 1 month and 3 months correlated with the specific growth rate of the first, second and third month. This finding supports the possibility that inter-organ unevenness may represent an additional factor controlling the rate of catch-up growth.

Background: Reference intervals are a fundamental tool for characterizing the health status in a given population and play a central role in defining diagnostic values in clinical applications. Estimation of the conditional distribution of a variable, as the body mass index (BMI), is necessary for providing reference values when there is a trend as a function of the covariate.

Subjects and method: We studied 1453 boys and young between 5 and 16 years old measured in a study carried out in the schools of Lleida (Spain). BMI conditional distributions with age have been derived using a new parametric method based on the one proposed by Sorribas et al. [Stat. Med. (2000) 19:697-713]. This method is based on S-distributions as a parametric model for the distribution and uses maximum likelihood estimation of the conditional distribution.

Results: The methods commonly used for estimating reference curves are based on a smoothing of sample quantiles using different techniques. However, these methods do not provide information on the conditional distribution of the target variable. Our method provides an estimation of such distribution and the corresponding reference curves for the quantiles as a function of a covariate, in our case age.

Conclusions: The suggested methodology provides appropriate reference quantiles for the BMI. Our results allow characterizing the change in distribution within the age range considered. Besides describing a raise in BMI with age, we observe an increase in dispersion around puberty. This must be considered when using BMI as a diagnostic variable.

The present study provides baseline data for a number of mandibular growth dimensions, specially on bone mass and bone strength, that were collected between the 21st and the 180th days of postnatal life, which are intended as a reference for researchers designing experimental studies, specially on mandibular catch-up growth, and as an aid for clinicians who must evaluate results from published animal studies for validity and potential extrapolation to the human clinical situation. Fifty weanling female Wistar (Hsd:Wi) rats were fed ad libitum a diet previously shown to allow normal, undeformed mandibular growth. Five of them were randomly selected at different times between 21 and 180 d of life. Mandibular growth was estimated directly on the right hemimandible by taking measurements between anatomical points; mandibular bone mass (calcium mass) was estimated from the mg of calcium, determined by atomic absorption spectrophotometry, present in the ashes of the left hemimandible; and mechanical properties of the right hemimandible were determined using three-point bending mechanical test. Dimensions, bone calcium mass and bone strength of the female rat mandible increased linearly from day 21 to approximately day 90. Bone growth, as expected, was more than twice when assessed from bone weight than when derived from mandibular area, length or height when the parameters were expressed as the relative increase from the mean infant condition. The growth rate of the posterior part of the mandible (behind the third molar) was almost five times greater than that of the anterior part. The rates of growth of the studied parameters showed a marked decline after day 90. ANOVA indicated that no statistical differences were found between day 90 and day 120 values. It could be concluded that the female rat mandible attains its adult size, peak bone calcium mass and bone structural mechanical properties at some point between 90 and 120 d of postnatal life. Because of the extremely high positive correlation between mandibular bone calcium mass and both mandibular area and mandibular weight, it was possible to calculate the mandibular peak bone mass from the relations 7.69 mgCa/cm2 and 0.19 mgCa/mg bone.

Two data-sets containing the anthropometric measurements of Estonian schoolgirls aged 7-18 were analysed, one (set A) from the late sixties, size 1627 and the other (set K) from the late nineties, size 1546. In all data sets 8 measurements--three height, three breadth measures, chest circumference and mass--were measured using the same methodology, as well as BMI was calculated. The means of all the characteristics in age groups (size 100-150 individuals) were calculated and growth curves of means were approximated using polynomial least squares approximation. The maximal velocity points were found and the growth intensities in different body build groups were compared. It was proved that the usage of cross-sectional data for estimating growth curves is suitable for estimating the velocity of acceleration in different age groups. We found that the height of Estonian girls has increased during the last 30 years by about 4-5%, the breadth measurements--by about 1-2%, chest circumference up to 8% and BMI has decreased by 3-5%. The changes are quite modest in pre-puberty, most significant for girls aged 12-16 and smaller again for girls aged 17 and more. The maximal growth velocity has shifted for all characteristics to the earlier time. Comparison of different body build groups showed that the small girls of the sixties are quite similar to small girls in the nineties, but the differences are greater in the case of large and pycnomorphic girls.

This work was designed to characterize the appetite kinetics and growth of male C57BL/6J (lit) mice. Those variables were assessed with Parks' function of ad libitum feeding and growth. Heterozygous mice (lit/+) attained their mature weight at 12-15 weeks of age, peak growth rate (3.5 g/week) at 5 weeks and displayed the normal decay of food conversion efficiency as a function of age. The homozygous genotype has a chronic defect in the synthesis and secretion of growth hormone (GH). Homozygous mice could not be assessed with Park's function. From the 4th to the 15th week of age, body weight increased linearly and exhibited constant food conversion efficiency. Food intake of both genotypes was commensurate with their body weights. Lit/lit mice became progressively obese. At 40 weeks of age, body fat of lit/lit mice was fivefold that of lit/+ and their body weight was similar to their heterozygous controls. The chronic deficiency of growth hormone produced a lower bone mass (compared to heterozygous controls). Bone mass of both genotypes attained maturity at 12-15 weeks with a maximum growth rate at 5 weeks. Body weight and bone mass grow harmoniously in lit/+ but not in lit/lit mice.