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1.
Muscles are formed by fusion of individual postmitotic myoblasts to form multinucleated syncytial myotubes. The process requires a well-coordinated transition from proliferation, through migratory alignment and cycle exit, to breakdown of apposed membranes. Connexin43 protein and cell-cycle inhibitor levels are correlated, and gap junction blockers can delay muscle regeneration, so a coordinating role for gap junctions has been proposed. Here, wild-type and dominant-negative connexin43 variants (wtCx43, dnCx43) were introduced into rat myoblasts in primary culture through pIRES-eGFP constructs that made transfected cells fluoresce. GFP-positive cells and vitally-stained nuclei were counted on successive days to reveal differences in proliferation, and myotubes were counted to reveal differences in fusion. Individual transfected cells were injected with Cascade Blue, which permeates gap junctions, mixed with FITC-dextran, which requires cytoplasmic continuity to enter neighbouring cells. Myoblasts transfected with wtCx43 showed more gap-junctional coupling than GFP-only controls, began fusion sooner as judged by the incidence of cytoplasmic coupling, and formed more myotubes. Myoblasts transfected with dnCx43 remained proliferative for longer than either GFP-only or wtCx43 myoblasts, showed less coupling, and underwent little fusion into myotubes. These results highlight the critical role of gap-junctional coupling in myotube formation.  相似文献   
2.
Abstract Concentrations of oxalate-degrading anaerobes in ruminal contents of sheep were determined from counts of colonies producing clear zones on a calcium oxalate medium (D agar with 7 mM CaCl2). Viable counts of oxalate degraders from a 55-kg sheep fed a diet containing 32% halogeton (4.6% oxalate) averaged 2.6 × 106/ g (dry weight). When the halogeton concentration in the diet was reduced to 16%, counts of oxalate degraders decreased nearly 300-fold. Oxalate-degrading isolates from this sheep were similar to OxB, the type strain of Oxalobacter formigenes . When a 45-kg sheep was fed diets containing 2.2, 1.5, and 0.8% oxalate, viable counts of oxalate degraders (enumerated on D agar with 14 mM CaCl2 and 20% filter-sterilized ruminal fluid) represented 0.85, 0.52, and 0.06% of the total viable population, respectively; total viable counts were essentially unchanges by these concentrations of dietary oxalate. Similar percentages of oxalate degraders were also observed when a 23-kg sheep was fed diets containing 1.5 or 0.8% oxalate. This report presents the first direct measurements of the concentrations of oxalate-degrading bacteria in the rumen and supports the concept that the availability of oxalate in the diet influences the proportion of oxalate-degrading bacteria in the rumen  相似文献   
3.
    
The cyprinid Barbodes gonionotus (Bleeker) is a commercially important fish in both capture fisheries and aquaculture in Southeast Asia. Five polymorphic microsatellite loci from B. gonionotus are described. Four are highly variable, with 9–30 alleles observed per locus in four populations sampled from Thailand (HO = 0.694–0.808). These will be of use in studies of population genetic structure and in pedigree analyses.  相似文献   
4.
  总被引:3,自引:0,他引:3  
Evaluation of analogs of the blocked insect myotropic neuropeptide leucopyrokinin (LPK) has demonstrated its relative insensitivity to amino acid substitution in the N-terminal in contrast to the C-terminal region. Truncated analogs of LPK without the first, second, and third N-terminal amino acids retain a significant 144%, 59% and 30% of the activity of the parent octapeptide, respectively. The [2-8]LPK analog is the first fragment of an insect neuropeptide to exhibit greater activity than the parent hormone. In contrast, truncated analogs of the insect myotropic, proctolin, exhibit little or no activity. The pentapeptide fragment Phe-Thr-Pro-Arg-Leu-NH2 has been identified as the active core of LPK.  相似文献   
5.
6.
    
A study was conducted to determine which bud (terminal or lateral) breaks first, and thereby exerts primigenic dominance, on ‘Granny Smith’ and ‘Golden Delicious’, 1-year-old apple (Malus × domestica Borkh.) shoots grown in two locations in the Western Cape, South Africa, with differing degrees of chilling. Primigenic dominance of laterals was more common in a warm area than a cool area, and more common in ‘Granny Smith’ than ‘Golden Delicious’. Laterals rarely broke before the terminal in ‘Golden Delicious’, and so differences in lateral development due to position of first bud to break were only analyzed in ‘Granny Smith’ shoots from this point on in the study. In ‘Granny Smith’, lateral budbreak and growth was influenced by the position of the first bud to break on the shoot, but did not differ between locations. On ‘Granny Smith’ shoots with primigenic dominance of the terminal, lateral budbreak and growth was suppressed, in accordance with the typical ‘delayed foliation’ commonly observed in warm winter climates. However, when at least one lateral broke before the terminal, lateral budbreak and growth were similar to previous observations in cold winter areas.  相似文献   
7.
Rhizoremediation of petroleum contaminants is a phytoremediation process that depends on interactions among plants, microbes, and soils. Trees and grasses are commonly used for phytoremediation, with trees typically being chosen for remediation of BTEX while grasses are more commonly used for remediation of PAHs and total petroleum hydrocarbons. The objective of this review was to compare the effectiveness of trees and grasses for rhizoremediation of hydrocarbons and address the advantages of each vegetation type. Grasses were more heavily represented in the literature and therefore demonstrated a wider range of effectiveness. However, the greater biomass and depth of tree roots may have greater potential for promoting environmental conditions that can improve rhizoremediation, such as increased metabolizable organic carbon, oxygen, and water. Overall, we found little difference between grasses and trees with respect to average reduction of hydrocarbons for studies that compared planted treatments with a control. Additional detailed investigations into plant attributes that most influence hydrocarbon degradation rates should provide data needed to determine the potential for rhizoremediation with trees or grasses for a given site and identify which plant characteristics are most important.  相似文献   
8.
    
Phylogenies are increasingly prominent across all of biology, especially as DNA sequencing makes more and more trees available. However, their utility is compromised by widespread misconceptions about what phylogenies can tell us, and improved \"tree thinking\" is crucial. The most-serious problem comes from reading trees as ladders from \"left to right\"--many biologists assume that species-poor lineages that appear \"early branching\" or \"basal\" are ancestral--we call this the \"primitive lineage fallacy\". This mistake causes misleading inferences about changes in individual characteristics and leads to misrepresentation of the evolutionary process. The problem can be rectified by considering that modern phylogenies of present-day species and genes show relationships among evolutionary cousins. Emphasizing that these are extant entities in the 21(st) century will help correct inferences about ancestral characteristics, and will enable us to leave behind 19(th) century notions about the ladder of progress driving evolution.  相似文献   
9.
Fungal growth was quantified during Indonesian rice tapé fermentation using an agar-film technique following sample homogenization for 1 min at 25000 rev/min. After 72 h fermentation, mould hyphal length was 0·68 km/g, yeast hyphal length 2·1 km/g and the numbers of mould chlamydospores and single yeast cells were 14 times 105/g and 5·1 times 107/g respectively. The estimated fungal biomass in rice tapé after 72 h was 25 mg/g dry weight with 62% of this being mould hyphae, 24% mould chlamydospores, 13% yeast hyphae and 1% yeast cells.  相似文献   
10.
Neurochemical Research - Dopamine is an important neuromodulator in the brain that binds to dopamine D1-like receptors (D1, D5) as well as dopamine D2-like receptors (D2, D3, D4). The D2 receptor...  相似文献   
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