Maturation-related Changes Research Articles

Maturation-related changes in mass and elemental contents of secretory granules as measured by electron-microprobe

The relationship between granule density, protein content, and Ca and S contents were studied in two secretory granule fractions, from parotid glands of the rat, previously shown to constitute different stages in granule maturation. The density of the lighter fraction was between 1.133 and 1.142 g/ml, while that of the heavier fraction was greater than 1.142 g/ml. The mean protein content of the denser granules was 12% greater than that of the lighter granules (P less than 0.03), while the dry-mass elemental concentrations in the two granule fractions were unchanged. These results indicate that protein is added to granules during the maturation process (presumably by vesicular traffic), and that the resulting increase in granule density is not driven simply by decrease in water content and/or increased concentrations of inorganic Ca or S in the granules. The elemental concentration values also indicate that the diffusible elements permeate the granule membrane during the fractionation procedures.

Maturation-related changes in the expression of Fc gamma RII and Fc gamma RIII on mouse mast cells derived in vitro and in vivo.

The expression and function of Fc gamma RII and Fc gamma RIII on three mouse mast cell populations that differ in maturity as assessed by secretory granule constituents were analyzed by cellular and immunochemical approaches. As quantified by flow cytometric analysis of the binding of the rat 2.4G2 anti-Fc gamma RII/III mAb, mouse serosal mast cells (SMC) purified from the peritoneal cavity expressed more receptors per cell than did mouse IL-3-dependent, bone marrow culture-derived mast cells (BMMC), which are progenitors of SMC. Coculture of BMMC with mouse 3T3 fibroblasts for 2 wk, which alters the secretory granule composition toward that of SMC, also increased receptor epitope expression to a level equivalent to that of SMC. As assessed by rosette assays with mouse mAb to SRBC, all three mast cell populations bound IgG1, IgG2a, and IgG2b, essentially all binding was inhibited by 2.4G2 antibody, and greater quantities of the antibody were required to block immune adherence by cocultured mast cells and SMC as compared with BMMC. Immunoprecipitation and SDS-PAGE analysis of Fc gamma RII and Fc gamma RIII from BMMC, cocultured mast cells, and SMC that were surface radiolabeled with Na125I revealed predominant native forms of 62, 57, and 56 kDa, respectively, and an additional surface form of 43 kDa in SMC. Removal of N-linked carbohydrate from immunoprecipitates demonstrated that BMMC expressed peptide cores of 38 kDa (Fc gamma RII-1 gene product) and 31 kDa (Fc gamma RII-2 gene product), and barely detectable amounts of a 28-kDa (Fc gamma RIII gene product) core. The expression of all three was increased by coculture with 3T3 fibroblasts, consistent with the increased expression of their common epitope by cytofluorographic analysis. SMC expressed primarily the Fc gamma RII-1 and some Fc gamma RIII gene product. Thus, the three populations of mast cells express different amounts and ratios of the Fc gamma RII and Fc gamma RIII gene products, and maturation of BMMC during coculture with fibroblasts in vitro and in the peritoneal cavity in vivo augments cell-surface expression of the receptors and immune adherence function.

Maturation in Larch

The effect of maturation on the morphological and photosynthetic characteristics, as well as the expression of two genes involved in photosynthesis in the developing, current year foliage of Eastern larch (Larix laricina [Du Roi]) is described. These effects were observed on foliage during the third growing season after grafting of scions from trees of different ages onto 2 year old rootstock. Specific leaf weight (gram dry weight per square meter), leaf cross-sectional area (per square millimeter), and chlorophyll content (milligram per gram dry weight) all increase with increasing age in long shoot foliage from both indoor- and outdoor-grown trees. Net photosynthesis (NPS) (mole of CO(2) per square millimeter per second) increases with age on indoor- but not outdoor-grown trees. NPS also increases with increased chlorophyll content, but outdoor-grown scions of all ages had higher chlorophyll content, and chlorophyll does not appear to be limiting for NPS outdoors. To extend these studies of maturation-related differences in foliar morphology and physiology to the molecular genetic level, sequences were cloned from the cab and rbsS gene families of larch. Both cab and rbcS gene families are expressed in foliage but not in roots, and they are expressed in light-grown seedlings of larch but only at very low levels in dark-grown seedlings (~2% of light-grown seedlings). Steady-state cab mRNA levels are relatively higher (~40%) in newly expanding short shoot foliage from juvenile plants compared to mature plants. Unlike cab, the expression of the rbcS gene family did not seem to vary with age. These data show that the maturation-related changes in morphological and physiological phenotypes are associated with changes in gene expression. No causal relationship has been established, however. Indeed, we conclude that the faster growth of juvenile scions reported previously (MS Greenwood, CA Hopper, KW Hutchison [1989] Plant Physiol 90: 406-412) is not due to increased NPS or cab expression. Long shoot foliage is the dominant foliar type on young trees and its lower specific leaf weight will permit production of more photosynthetic surface area per unit of leaf biomass.

Heterogeneity of tubulin epitopes in mouse fetal tissues

A panel of six monoclonal antibodies against alpha (TU-01, TU-03, TU-04, TU-05, TU-09) or beta (TU-13) subunits of tubulin was used to study expression of tubulin epitopes in 14-day-old mouse embryos. Specificity of antibodies was confirmed by immunoblotting experiments. Monoclonal antibodies TU-01, TU-09 and TU-13, like the polyclonal antibody reacted essentially with all tissues, whereas other antibodies displayed differential reactivity. Most notably, TU-03 reacted very strongly with simple epithelia and basal layer of stratified epithelial layers. TU-04 recognized maturation related changes in spinal cord. Reactivity of TU-05 was restricted to central nervous system and peripheral nerves. Present results document immunohistochemical heterogeneity of tubulin in fetal tissues and suggest the existence of maturation and tissue specific epitopes of tubulin in developing organs.

Maturation-related change of the protein kinase activity in the rabbit red blood cells

The protein kinase activity of rabbit reticulocyte and erythrocyte hemolysate is due to multiple forms (casein kinases and histone kinases) which have been partially purified by Sepharose 6B filtration followed by phosphocellulose chromatography in the presence of 0.2% Triton X-100. The casein kinase activity is resolved by such a procedure into two form different in catalytic proterties: i.e. the casein kinase TS phosphorylates both serine and threonine residues of casein, while the casein kinase S phosphorylates only serine residues. The comparative results indicate that during differentiation and maturation of rabbit red blood cells multiple cytosol protein kinase acitivities markedly decrease, while the casein kinase S does not change significantly.

Maturation-related changes in proteoglycans of fetal articular cartilage

Proteoglycans of the articulating and growing zones of maximum and minimum contact of bovine fetal articular cartilage were studied and compared to proteoglycans of immature calf and adult steer. During fetal maturation, localized changes were observed as early as the second trimester of fetal life but were restricted to the most superficial zones. Proteoglycans extracted from the growing zones were purified by density-gradient ultracentrifugation. The majority of proteoglycan monomers were able to interact with endogenous hyaluronate to form aggregates. Monomers had, at all fetal stages, similar elution profiles on Sepharose 2B and similar ratios of chondroitin sulfate chains/keratan sulfate chains/ O-glycosidically linked oligosaccharides. Keratan sulfate chains were of similar size at all stages, but chondroitin sulfate chain size decreased markedly with fetal maturation. In the first and second trimesters of fetal life, the proteoglycans were poorly substituted with glycosaminoglycans. A major increase in the absolute number of glycosaminoglycans and oligosaccharides attached to core protein was detected during the third trimester of fetal life. No further changes in substitution occurred in early postnatal life. Enzymatic digestion of proteoglycan monomer demonstrated that the increase in substitution with keratan sulfate occurred to the same extent in the main polysaccharide attachment region and in the keratan sulfate-rich region.

Maturation-related changes in catecholamine-dependent cyclic AMP and protein kinase in the rabbit myocardium.

It has been shown that the sensitivity to isoproterenol of myocardial inotropic response increases with growth in rabbits. In the present study we attempted to delineate the biochemical mechanisms involved in this maturation-related change. We investigated cyclic AMP generation and protein kinase activation by isoproterenol in the ventricular myocardium of rabbits aged 1 day, 1 week, and 1 month. In contrast to an increase in inotropic response, both the sensitivity to isoproterenol of cyclic AMP generation and the sensitivity to exogenous cyclic AMP of protein kinase activation decreased with maturation from 1 day to 1 month of age. ED50 of isoproterenol (mean +/- SE) on cyclic AMP generation in myocardial slices was 1.83 +/- 0.42 x 10(-7) M for 1-day-old, 3.70 +/- 0.61 x 10(-7) M for 1-week-old, and 8.32 +/- 1.20 x 10(-7) M for 1-month-old rabbits. Likewise, the ED50 of isoproterenol on adenylate cyclase activation was 0.65 +/- 0.11 x 10(-7) M, 2.04 +/- 0.32 x 10(-7), and 15.2 +/- 2.5 x 10(-7) M in 1-day, 1-week- and 1-month-old rabbits, respectively. The ED50 of cyclic AMP on protein kinase activation was 1.50 +/- 0.64 x 10(-8) M for 1-day-old and 7.08 +/- 1.52 x 10(-8) M for 1-month-old rabbits. This apparent discrepancy between inotropic response and biochemical response in the sensitivity to isoproterenol indicates that the biochemical mechanism of the maturation-related change in inotropic response was at a step or steps distal to protein kinase activation.

When is it justified to stop the pill?

<h3>Aim</h3> To provide an evidence-based review of muscle metabolism changes with sex-, age- and maturation with reference to the development of youth sport performance. <h3>Methods</h3> A narrative review of data from both invasive and non-invasive studies, from 1970 to 2015, founded on personal databases supported with computer searches of PubMed and Google Scholar. <h3>Results</h3> Youth sport performance is underpinned by sex-, age- and maturation-related changes in muscle metabolism. Investigations of muscle size, structure and metabolism; substrate utilisation; pulmonary oxygen uptake kinetics; muscle phosphocreatine kinetics; peak anaerobic and aerobic performance; and fatigue resistance; determined using a range of conventional and emerging techniques present a consistent picture. Age-related changes have been consistently documented but specific and independent maturation-related effects on muscle metabolism during exercise have proved elusive to establish. Children are better equipped for exercise supported primarily by oxidative metabolism than by anaerobic metabolism. Sexual dimorphism is apparent in several physiological variables underpinning youth sport performance. As young people mature there is a progressive but asynchronous transition into an adult metabolic profile. <h3>Conclusions</h3> The application of recent developments in technology to the laboratory study of the exercising child and adolescent has both supplemented existing knowledge and provided novel insights into developmental exercise physiology. A sound foundation of laboratory-based knowledge has been established but the lack of rigorously designed child-specific and sport-specific testing environments has clouded the interpretation of the data in real life situations. The primary challenge remains the translation of laboratory research into the optimisation of youth sports participation and performance.

Maturation- and species-related differences in inotropic response to isoproterenol

1. Maturation-related changes in the response of atrial myocardium to beta-adrenergic stimulation were investigated in 1-day, 1-week, 1-month and 4-month old rabbits and guinea pigs. 2. A trial myocardium of 1-day and 1-week old rabbits were significantly less sensitive to isoproterenol than the two older groups. No such relationship was found with atrial myocardium of the guinea pig. 3. Isoproterenol-sensitive inotropic effect was also maturation-related in rabbit atrial myocardium, being significantly less in the 1 day and 1 week groups than the two older groups, while no such relationship was found in the guinea pig.

Alpha- and beta-adrenergic mechanisms in the aorta of newborn rabbits and guinea-pigs

1. 1. Maturation-related changes in alpha- and beta-adrenergic mechanisms of the aorta were investigated in 1 day, 1 week, 1 month and 4 month old rabbits and guinea-pigs. 2. 2. Aortic strips from newborn rabbits were equally as sensitive to phenylephrine as strips from the older rabbits. 3. 3. Aortic strips from newborn rabbits did not relax as well in response to isoproterenol as did the strips from adult rabbits, although relaxation to sodium nitrite was comparable in both groups. 4. 4. Aortic strips from 4 month old guinea-pigs had less sensitivity to phenylephrine than did the three younger age groups. 5. 5. Relaxing ability of newborn guinea-pig aorta to isoproterenol and sodium nitrite was equal to that of adult guinea-pig aorta.