Growth Development and Aging最新文献

Stress response is a universal mechanism developed by all organisms to deal with adverse changes in the environment, which lead to the synthesis of heat shock proteins (Hsps). In this study, the effect of moderate (41 degrees C) and severe (44 degrees C) heat stress on Hsp70 transcript expression pattern was investigated during chicken embryogenesis. Acute exposure to severe heat stress for one hour resulted in a fifteen-fold increase in Hsp70 mRNA levels. The return of stressed embryos to normal incubation temperature resulted in Hsp70 mRNA levels five-fold higher than control after three hours and normal levels after six hours. Moderate heat stress did not induce enhancements on Hsp70 mRNA levels. The spatial expression of Hsp70 transcripts was detected in embryos under normal incubation conditions. Whole-mount in situ hybridization analysis showed that Hsp70 transcripts were constitutively present in somite and in distinct encephalic domains (predominantly in prosencephalon and mesencephalon areas) of the chicken embryo. These results showed that Hsp70 induction is dependent on incubation temperature conditions, suggesting that early chicken embryos may induce a quick emergence response to cope with severe heat stress by increasing Hsp70 mRNA levels.

The present study examined the influence of dexamethasone (DEX) treatment on preadipocyte differentiation and insulin-like growth factor binding protein (IGFBP) secretion in stromal-vascular (S-V) cell cultures established from subcutaneous adipose tissue obtained from nine 75 day and four 50 day pig fetuses. Cultures of S-V cells from four young pigs (5-7 days old) were also studied. Each fetal S-V cell culture represented 1 pool of S-V cells/dam. Cultures were seeded and plated in 10% FBS from day 0-3 and treated with insulin (ITS) + 10 nM DEX from day 3-6 (late DEX treatment). Alternatively, cultures were seeded and plated in 10% FBS + 80 nM DEX from day 0-3 and treated with insulin alone from day 3-6 (early DEX treatment). Conditioned media was collected on day 6 of culture after 3 days of conditioning, and prepared for subsequent 125I-IGF-I ligand blot analysis for IGFBPs and RIA for IGF-I and IGF-II. Early and late DEX increased (P<0.05) preadipocyte (AD-3+) recruitment but only early DEX increased preadipocyte differentiation (lipid + and C/EBP alpha+) by day 6 in S-V cultures from 75 day fetuses. Levels of IGFBP-2, IGFBP-4, IGF-I and IGF-II in media conditioned by 75 day fetal S-V cultures were not influenced by late DEX. However, late DEX reduced levels of 29 kDa IGFBPs and markedly increased (P<0.05) IGFBP-3 levels in 75 day S-V media. Late DEX also markedly increased (P<0.05) IGFBP-3 levels in 50 day S-V media but had little influence on other IGFBPs. Early DEX treatment increased (P<0.05) IGFBP-4 levels in 75 day S-V media but had little to no influence on levels of IGF-I, IGF-II and other IGFBPs. These studies indicate that IGFBP-4 may regulate local metabolism during preadipocyte differentiation, whereas IGFBP-3 may antagonize preadipocyte differentiation by targeting IGF-I away from differentiating cells and towards growing cells.

This investigation tested the hypothesis that differences in the growth of fore- and hindlimb muscles in the rat are regulated by the pituitary and food intake. Using morphometric techniques, the growth of muscle fibers was compared in two slow-twitch muscles, the flexor carpi ulnaris (FCU) of the forelimb, and the soleus of the hindlimb, in male Wistar rats fed ad libitum, food restricted (FR) or hypophysectomized (hypox) from age 60 days. Growth was defined as an increase in fiber diameter and/or type 1 fiber percentage. The soleus had larger diameter fibers than the FCU in controls and FR, but not hypox rats. The growth in diameter, between 60 and 180 days, of both types 1 and 2 fibers in the soleus and type 2 fibers in the FCU was inhibited by hypox and, to a lesser extent, FR. Neither type 1 fiber diameter nor percentage of type 1 fibers in the FCU increased with age nor was it affected by hypox or FR. The percentage of type 1 fibers was higher in the soleus than the FCU and was further increased in the soleus of hypox rats. Food restriction produced a smaller rise than hypox in type 1 fiber percentage in the soleus. Thus, differences in fore- and hindlimb muscle fiber growth are modulated by pituitary hormones and, to a lesser extent, by food intake.

We measured the age-related changes in the D/L-aspartic acid ratio (D/L ratio) of cranial bones in two different sublines of senescence-accelerated mice (SAM/Iw): SAMP2/Iw (SAM, prone 2/Iwate) and SAMR1/Iw (SAM, resistant 1/Iwate). In SAM/Iw under 9 months of age, the D/L ratio in SAMP2/Iw was higher than that in SAMR1/Iw (p<0.001). However, in all 12-month old SAM/Iw, whether SAMP2/Iw or SAMR1/Iw, the D/L ratio was higher in males than in females. There were minor differences in the age-related changes in the D/L ratios between different types of cranial bone. In 1-month old SAM/Iw the rectal temperature was similar in both males and females. However from the age of 2 months, there was a divergence, with the rectal temperature measurement in SAMP2/Iw reaching a peak 2 months of age, whereas SAMR1/Iw had the highest temperature readings at 6 months of age. In both SAMP2/Iw older than 2 months, and SAMR1/Iw older than 6 months, the temperature readings tended to gradually decrease with age in both males and females. These results suggest that the differences in D/L-aspartic acid ratios were dependent on the age, gender, and strain of SAM/Iw, but were not dependant on the type of cranial bone studied. It seems likely that these differences may be related mainly to changes in body temperature.

We evaluated in pups of Akodon azarae both the growth pattern from birth to 48 days of age and the effect of litter size on growth pattern and homeothermy acquisition from birth to weaning age. Individual pups gained weight as expected by a Gompertz growth pattern. Until weaning, litter size affected both the slope of the relationship between body temperature and age and the rate of growth of pups. Pups from small litters increased both body temperature and weight until body temperature and body weight of adults at higher rates than those from large litters.

In most tissues, various cell membrane ion transporting systems are not fully developed and/or maximally active at the prenatal and early postnatal stage. Their progressive development and expression are a function of growth and maturity. We performed a multiple time-point study, in order to investigate the ability of a variety of tissues to maintain appropriate Ca++ and Mg++ homeostasis at different stages of postnatal development. Total intracellular Ca++ in one-week-old rat liver, brain and spinal cord tissues was significantly elevated, compared to mature animals. It increased further through the first three weeks of gestation. Intracellular Ca++ gradually and significantly declined in adult and mature animal groups. Alterations in total intracellular Mg++ of the same tissue samples, although not so profound, paralleled changes in total intracellular Ca++. We conclude that a developmental switch in intracellular Ca++ and Mg++ homeostasis occurs one to three weeks following birth. It might be related to the incomplete development of Ca++ and Mg++ transmembrane transporting systems, previously reported as being only partially expressed at the early postnatal stage. These developmental alterations in total intracellular Ca++ and Mg++ content might serve as a regulatory mechanism, adjusting cell activities to the physiological requirements of the growing and maturing animal.

The objective of the study was to evaluate the impact of in ovo administration of recombinant human insulin-like growth factor-I (rhIGF-I) on myostatin and transforming growth factor-beta2 (TGF-beta2) gene expression during chicken embryogenesis with emphasis on skeletal muscle development. Eggs were injected once with 100 ng rh IGF-I in 10 mM acetic acid, 0.1% BSA per embryo on day 3 of embryonic development. Total RNA was isolated from whole embryos on each of embryonic days (E) 0 to 6 (n = 6 per day/per treatment), from thoracic/abdominal halves of the embryo at E 7 to 8 (n = 6 per day/per treatment), and from pectoralis muscle tissues at E 9 to 20 (n = 4 per day/per treatment). Reverse-transcription polymerase chain reaction (RT-PCR) was used to synthesize cDNAs. Myostatin mRNA isolated from pectoralis muscles of the rhIGF-I treated group increased on E 10 (approximately 2.5 fold) and remained high through E 13, whereas myostatin mRNA from control pectoralis muscles increased at E 9 and remained high until E 12. TGF-beta2 gene expression from in ovo rhIGF-I treated pectoralis muscles dramatically increased at E 13 (approximately 2.5 fold), in contrast to E 14 from control pectoralis muscle, and gradually declined through E 16. Our results demonstrate that in ovo administration of rhIGF-I on E 3 may alter developmental expression patterns of myostatin and TGF-beta2 genes.

Subtle signs of neural impairment are appearing in children exposed to "low levels" of lead. How does this metal exert its effect on the developing nervous system? The salient features of five mechanisms likely involved are discussed in this review.

Seven day old male broiler chickens were fed diets containing 12, 18 or 24% crude protein + 0 or 1 g methimazole/kg diet for 21 days to examine the interaction of the birds' thyroid status and crude protein levels on metabolism. Methimazole (1-methyl-2-mercaptimidazole) inhibits thyroidal production of thyroid hormones and results in hypothyroidism. Birds were fed a diet containing 18% crude protein for an additional 21 days to determine the carry over effects of treatments. Birds were killed at 28 and 49 d. In vitro lipogenesis was inversely related (P < 0.05) to dietary protein levels in control birds at 28 d. Dietary methimazole attenuated (P < 0.05) this effect, resulting in a common rate similar to that attained in the birds fed the highest level of protein without methimazole. Birds fed methimazole for an initial 21-day period (7 to 28 d of age) had greater lipogenic rates (P < 0.05) at 49 d than did their control counterparts. In contrast, methimazole increased (P < 0.05) abdominal fat pad (AFP) lipoprotein lipase (LPL) at both age periods, indicating increased ability by the AFP to remove triglycerides from systemic circulation. Observations at 49 d suggest that perturbations in the thyroid of the young bird may substantially change metabolism in later life. Results also show that obesity in hypothyroid birds cannot be explained by increases in de novo lipogenesis, but probably relates to changes in LPL activity.

The present study examined the influence of fetal age and thyroxine (T4) and growth hormone (GH) treatment, on the expression of insulin-like growth factor binding proteins (IGFBPs) in fetal pigs. On day 70 of gestation fetuses were either hypophysectomized (hypox), hypox and implanted with T4 pellets, or left intact, and were recovered 5, 10, 15 and 20 days following hypox and T4 pellet placement. Intact fetuses were also recovered from several dams at 50 days of gestation. In additional dams, hypox fetuses (day 70) were implanted with GH loaded Alzet mini-pumps on day 90, and control, untreated, and GH-treated hypox fetuses were recovered on day 105 of development. Subcutaneous adipose tissue, serum and other fetal tissues were collected at the time of recovery and prepared for subsequent ligand blot analysis with 125I -IGF-1 and immunoblot analysis with IGFBP antibodies. The main effect of IGFBP was significant (P <0.01) for age associated changes in serum IGFBP percentages. Between 50 and 75 days of fetal development the levels of 29 kDa IGFBPs in adipose tissue and serum markedly increased. In contrast, IGFBP-2 levels decreased and IGFBP-4 levels increased in adipose tissue while IGFBP-2 levels increased and levels of IGFBP-4 and -3 decreased in serum. Fetal hypox decreased adipose tissue IGFBP levels in a time and IGFBP-dependent manner. For instance, IGFBP-2 and 29 kDa IGFBP levels decreased much faster after fetal hypox than did IGFBP-3 levels whereas IGFBP-4 levels did not decrease. The main effect of IGFBP was significant (P<0.01) for T4-induced changes in adipose tissue IGFBP levels. T4 treatment increased adipose tissue levels of 29 kDa IGFBPs but did not influence IGFBP-2,-3 and -4 levels. GH treatment had no influence on adipose tissue or serum IGFBP levels. These studies indicate that IGFBP-1 (one of the 29 kDa IGFBPs) may be the major IGFBP mediator of the influence of T4 on fetal development.