Body weight and metabolic level in growing chickens

Body weight and metabolic level in growing chickens. Acta Physiol. Pol., 1977, 28 (6): 575-583. In the investigations carried out on 128 White Rock chicken the metabolic level was determined under standard conditions in chickens characterising by different growth rate resulted from different feeding levels. It was shown that the feeding level of growing chicken has an essential influence on the character of the regression between the metabolic level and body weight. It was also found that this regression is not necessarily ot the character of Kleiber's function H = aWb. The differences in the metabolic level between the chickens maintained on different feeding levels did not disappear even after 4 days of starvation. In the light of the obtained results and recent investigations by other authors the usefulness of the so-called metabolic unit of the body size based on W0.75 in context to growing animals within one species has bee criticized.     

Change in elastin structure in human aortic connective tissue diseases

Summary Biochemical pathogenesis of the aortic connective tissue diseases (such as, Marfan's syndrome, dissecting aneurysm or aortic aneurysm) was examined by estimating glycoprotein, collagen and elastin contents in the aorta and the intramolecular cross-linking component (isodesmosine) and the intermolecular cross-linking components (cystine, histidinoalanine) in comparison with the control samples obtained from subjects with aortic regurgitation. The elastin content in the aorta and isodesmosine content obtained from the extract of the aortic sample found to be decreased. Ratio of cysteine residues (Cys/Cys-Cys) in the elastin fraction in disease increased. Content of histidinoalanine was found to be decreased. It may be suggested that elastin is maintained in its native nature and shape by intra- and inter-molecular cross-linking bridges, and they are readily denatured by various disease conditions. After elastin was solubilized by elastase, immunoreactive elastin content in those aortic diseases was found to be increased in the human connective tissue. Serum elastase and elastase-like activities tend to increase more than those in the control. These findings may suggest that the change in the structure of elastin would make more susceptible to elastase and other proteolytic enzymes. The reasonable hypothesis may be that molecular defect of fibillin or other constitutional structural glycoproteins produce deficient and functionally incompetent elastin associated microfibrils, and the defect of microfibrils cause to insufficient intra- and inter-molecular cross-links in elastin.     

Elastin mRNA levels and insoluble elastin accumulation in neonatal rat smooth muscle cell cultures

Insoluble elastin accumulation, elastin mRNA translational efficiencies, and elastin mRNA levels were evaluated in cultures of neonatal rat aortic smooth muscle cells grown for several days in consecutive passages. When the products of in vitro translation were immunoprecipitated with an anti-alpha-elastin antibody, a single 79,000-Da protein was obtained. Northern blot analysis also indicated an elastin mRNA species corresponding to approximately 4.2 kilobases. Insoluble elastin accumulation increased in cells cultured for 7-21 days in first through fourth passages, while with one exception, relative levels and translational activity of elastin mRNA decreased with time in culture. The data indicated that a simple relationship between elastin accumulation and elastin mRNA levels was not evident.     

Multiple control level governing H10 mRNA and protein accumulation

We have studied the variation of histone H10 and of its coding mRNA during rat liver regeneration after partial hepatectomy. Our data showed that while H10 decreased when cell proliferation was initiated, H10 mRNA accumulated in a proliferation-dependent manner as did H3 mRNA. These results showed two interesting aspects of the regulation of H10 expression in vivo, confirming results we have obtained previously in vitro: first H10 mRNA accumulation is a proliferation-dependent event; second, H10 protein accumulation may be uncoupled from that of its coding mRNA.     

Modelling the mechanical response of elastin for arterial tissue

We compare two constitutive models proposed to model the elastinous constituents of an artery. Holzapfel and Weizsäcker [1998. Biomechanical behavior of the arterial wall and its numerical characterization. Comput. Biol. Med. 28, 377–392] attribute a neo-Hookean response, i.e. $\Psi =c(I_1-3))$, to the elastin whilst Zulliger et al. [2004a. A strain energy function for arteries accounting for wall composition and structure. J. Biomech. 37, 989–1000] propose $\Psi =c(I_1-3{)}^{3/2}$. We analyse these constitutive models for two specific cases: (i) uniaxial extension of an elastinous sheet; (ii) inflation of a cylindrical elastinous membrane. For case (i) we illustrate the functional relationships between: (a) the Cauchy stress (CS) and the Green–Lagrange (GL) strain; (b) the tangent modulus (gradient of the CS–GL strain curve) and linearised strain. The predicted mechanical responses are compared with recent uniaxial extension tests on elastin [Gundiah, N., Ratcliffe, M.B., Pruitt, L.A., 2007. Determination of strain energy function for arterial elastin: experiments using histology and mechanical tests. J. Biomech. 40, 586–594; Lillie, M.A., Gosline, J.M., 2007a. Limits to the durability of arterial elastic tissue. Biomaterials 28, 2021–2031; 2007b. Mechanical properties of elastin along the thoracic aorta in the pig. J. Biomech. 40, 2214–2221]. The neo-Hookean model accurately predicts the mechanical response of a single elastin fibre. However, it is unable to accurately capture the mechanical response of arterial elastin, e.g. the initial toe region of arterial elastin (if it exists) or the gradual increase in modulus of arterial elastin that occurs as it is stretched. The alternative constitutive model ($n=\frac{3}{2}$) yields a nonlinear mechanical response that departs from recent uniaxial test data mentioned above, for the same stretch range. For case (ii) we illustrate the pressure–circumferential stretch relationships and the gradients of the pressure–circumferential stretch curves: significant qualitative differences are observed. For the neo-Hookean model, the gradient decreases rapidly to zero, however, for $n=\frac{3}{2}$, the gradient decreases more gradually to a constant value. We conclude that whilst the neo-Hookean model has limitations, it appears to capture more accurately the mechanical response of elastin.     

Spontaneous hypoxaemia and right ventricular hypertrophy in fast growing broiler chickens reared at sea level

1. At 6 weeks of age, the time of most rapid body growth, fast growing broiler chickens showed more right ventricular hypertrophy than slower growing chickens. 2. The degree of right ventricular hypertrophy was directly related to blood haematocrit and indirectly related to arterial oxygen saturation (estimated in the chickens using an ear oximeter designed for man). 3. When oxygen saturation was estimated sequentially from 6 to 17 weeks of age, mean oxygenation improved with age, partly due to the death of the chickens with the worst saturations, but also because of an improvement in oxygenation of the survivors.     

Regional variations in the nonlinearity and anisotropy of bovine aortic elastin

Arterial walls have a regular and lamellar organization of elastin present as concentric fenestrated networks in the media. In contrast, elastin networks are longitudinally oriented in layers adjacent to the media. In a previous model exploring the biomechanics of arterial elastin, we had proposed a microstructurally motivated strain energy function modeled using orthotropic material symmetry. Using mechanical experiments, we showed that the neo-Hookean term had a dominant contribution to the overall form of the strain energy function. In contrast, invariants corresponding to the two fiber families had smaller contributions. To extend these investigations, we use biaxial force-controlled experiments to quantify regional variations in the anisotropy and nonlinearity of elastin isolated from bovine aortic tissues proximal and distal to the heart. Results from this study show that tissue nonlinearity significantly increases distal to the heart as compared to proximally located regions ( $p<0.05$ ). Distally located samples also have a trend for increased anisotropy ( $p=0.07$ ), with the circumferential direction stiffer than the longitudinal, as compared to an isotropic and relatively linear response for proximally located elastin samples. These results are consistent with the underlying tissue histology from proximally located samples that had higher optical density ( $p<0.05$ ), fiber thickness ( $p<0.05$ ), and trend for lower tortuosity ( $p<0.07$ ) in elastin fibers as compared to the thinner and highly undulating elastin fibers isolated from distally located samples. Our studies suggest that it is important to consider elastin fiber orientations in investigations that use microstructure-based models to describe the contributions of elastin and collagen to arterial mechanics.     

A routine method for contrasting elastin at the ultrastructural level

A reliable, simple, and inexpensive method for ultrastructural investigation of elastin is described. This method uses uranyl acetate dissolved in absolute methanol, followed by an optional lead citrate counterstain. The procedure was tested on a number of animal and human tissues that had been fixed and processed differently.     

Molecular-level characterization of elastin-like constructs and human aortic elastin

This study aimed to characterize the structures of two elastin-like constructs, one composed of a cross-linked elastin-like polypeptide and the other one of cross-linked tropoelastin, and native aortic elastin. The structures of the insoluble materials and human aortic elastin were investigated using scanning electron microscopy. Additionally, all samples were digested with enzymes of different specificities, and the resultant peptide mixtures were characterized by ESI mass spectrometry and MALDI mass spectrometry. The MS² data was used to sequence linear peptides, and cross-linked species were analyzed with the recently developed software PolyLinX. This enabled the identification of two intramolecularly cross-linked peptides containing allysine aldols in the two constructs. The presence of the tetrafunctional cross-link desmosine was shown for all analyzed materials and its quantification revealed that the cross-linking degree of the two in vitro cross-linked materials was significantly lower than that of native elastin. Molecular dynamics simulations were performed, based on molecular species identified in the samples, to follow the formation of elastin cross-links. The results provide evidence for the significance of the GVGTP hinge region of domain 23 for the formation of elastin cross-links. Overall, this work provides important insight into structural similarities and differences between elastin-like constructs and native elastin. Furthermore, it represents a step toward the elucidation of the complex cross-linking pattern of mature elastin.     

Organization of medial elastin at aortic junctions in sheep and lambs

Aortas from four sheep and three fetal lambs were fixed at physiological pressure in 10% neutral buffered formalin. The regions with branches were serially sectioned in either cross or longitudinal section at 7-micron intervals and stained for elastin with Gomori-aldehyde-fuchsin. A large model of one aortointercostal junction was made from Plexiglas to show that bundles of elastin appeared to be continuous from the aorta into the branch. These bundles were then studied from large photomicrographs of the other junctions. At the intercostals and lumbars, the elastin lamellae ran continuously from the outer third of the media into the branch. There was often an added "pad" of elastin and other acellular material on the flow divider (distal lip). The large muscular branches which arose from the abdominal aorta have much less elastin than the intercostals. In them the aortic elastin appears to merge into a raphe on the proximal and lateral sides of the junction, with a very abrupt transition. A "tongue" of muscle from the branch often penetrated into the media of the aorta distally. Occasionally a small acellular cap was seen on the apex of the flow divider. There were few significant differences between the lambs and the sheep, probably because embryologically the arteries develop very early. The proximal and distal lips of all junctions were easily distinguished from each other, and the small and large branches were also different. We suspect these regions may respond differently to pressure, but we did not test this hypothesis.     

Structure of the bovine elastin gene and S1 nuclease analysis of alternative splicing of elastin mRNA in the bovine nuchal ligament

Genomic clones encompassing all the translated sequences, the 3' untranslated sequence, and 1 kb flanking the ATG translation initiation codon of bovine tropoelastin have been obtained and characterized by restriction enzyme analysis and extensive DNA sequencing. These analyses demonstrated that functionally distinct hydrophobic and cross-linking domains of the protein are segregated into separate exons throughout the gene. The putative promoter region lacks a TATA box, has an extremely high G+C content, and contains several SP1 binding sites. Comprehensive S1 analyses using probes covering the entire mRNA and RNA isolated from the nuchal ligament of bovine fetuses of different ages, neonate calves, and adult cows demonstrated that while only a single exon is alternatively spliced at high frequency, many exons are alternatively spliced at limited, variable frequencies. The results also suggest that such limited splicing is increased in the adult tissue relative to fetal and neonate tissues.     

Isolation and translation of elastin mRNA from chick aorta.

mRNA was isolated from 15-day chick embryo aortae by digestion of the tissue at 40° with Proteinase K in 1% sodium dodecyl sulfate followed by chromatography on oligo(dT)-cellulose columns. The mRNA was translated using a reticulocyte lysate system and the tropoelastin immunoprecipitated using a specific antiserum prepared against insoluble elastin. The precipitated product was characterized by polyacrylamide gel electrophoresis and a major peak corresponding to a molecular weight of approximately 70,000 daltons was observed. No higher molecular weight product was observed.     

Biosynthesis of lysine-derived elastin crosslinks in aortic cell culture.

Culture of an established line of aortic medial cells in the presence of L-[¹⁴C] lysine for 72 hours, beginning on the twenty-first day after transfer, has resulted in the incorporation of label into a residue, insoluble after autoclaving. Acid hydrolysates of this residue with or without reduction by NaBH₄ were subjected to ion exchange chromatography. Several radioactive lysine-derived residues were identified, by comparison to standards, as the distinctive crosslinks of elastin, isodesmosine, desmosine, merodesmosine and lysinonorleucine. This confirms the synthesis of elastin in aortic cell culture and establishes the formation of insoluble crosslinked elastin. Differences in the heights of the peaks in the reduced and nonreduced elastin indicate the probable occurrence of dehydromerodesmosine and dehydrolysino-norleucine as well and suggest that these may be intermediates in crosslink formation.     

Palladium chloride as a stain for elastin at the ultrastructural level.

Palladium chloride in aqueous solution stains elastic fibers in thin sections of Epon-embedded tissues. When palladium chloride is used with a lead citrate counterstain, high contrast sections with gray to black elastic fibers are obtained. The stain was tested on newborn and adult mammalian tissues and on adult tissues from lower animals. Sections were mounted on stainless steel grids, stained with 1% palladium chloride solution for 5 to 15 min, rinsed thoroughly, and counterstained with lead citrate for 7 min. Palladium chloride staining solution is stable for several months at room temperature and if the stain is filtered immediately before use, contamination of sections is not a problem. Chemical studies indicate that palladium binds directly to purified bovine ligamentum nuchae elastin and that this binding is not affected by glutaraldehyde fixation or by sodium borohydride reduction of elastin. Osmium post-fixation of glutaraldehyde-fixed elastin did significantly lower the amount of palladium bound. Palladium was shown to be chemically bound to sites on the elastin and not weakly associated. The nature of these sites is discussed.