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31.
Synopsis A quantitative analysis has been made of the glycoproteins present in the goblet cells of the epidermis, gill filaments and gill lamellae of three species of teleost fish. The glycoproteins have been identified by a combination of techniques, including the use of the enzyme sialidase followed by Alcian Blue staining, at pH 2.6 or I. o, in combination with periodic acid-Schiff. The selected fish were representative of species living in marine, freshwater and estuarine environments.The range of glycoproteins identified in these fish was similar to that found in mammalian tissue in that both neutral and acid glycoproteins were present, the latter included both sialomucins sensitive and resistant to sialidase, and sulphomucin. A single goblet cell contained either neutral or acid glycoproteins alone or in combination. Only the epidermis of the plaice and rainbow trout contained uniform cell populations producing acid glycoproteins, the former sulphomucin and the latter mainly sialomucin. At each site in the flounder and in the gill epithelia of the plaice and rainbow trout, the goblet cell population was mixed, with cells producing each type of glycoprotein. The number of goblet cells producing each type of glycoprotein varied at each tissue site. 相似文献
32.
Nematocysts were extracted from 3 nudibranch species and one sea anemone species, and the ability of several test fluids to promote discharge was examined. Except when isolated in sodium citrate, nudibranch nematocysts did not discharge in response to any test fluids. Nudibranch nematocysts isolated in sodium citrate discharged when tested with EGTA, distilled water, and calcium-free artificial seawater, but there were differences among the 3 nudibranch species. Nematocysts isolated from one nudibranch species and nematocysts isolated from that nudibranch's sea anemone prey differed in the percentage that discharged in response to EGTA and distilled water. These results suggest that nematocysts stored by nudibranchs are altered in some way, resulting in the different discharge responses. 相似文献
33.
Sachs PC Francis MP Zhao M Brumelle J Rao RR Elmore LW Holt SE 《Cell and tissue research》2012,349(2):505-515
The discovery of adipose-derived stromal cells (ASCs) has created many opportunities for the development of patient-specific cell-based replacement therapies. We have isolated multiple cell strains of ASCs from various anatomical sites (abdomen, arms/legs, breast, buttocks), indicating widespread distribution of ASCs throughout the body. Unfortunately, there exists a general lack of agreement in the literature as to their "stem cell" characteristics. We find that telomerase activity and expression of its catalytic subunit in ASCs are both below the levels of detection, independent of age and culturing conditions. ASCs also undergo telomere attrition and eventually senesce, while maintaining a stable karyotype without the development of spontaneous tumor-associated abnormalities. Using a set of cell surface markers that have been promoted to identify ASCs, we find that they failed to distinguish ASCs from normal fibroblasts, as both are positive for CD29, CD73 and CD105 and negative for CD14, CD31 and CD45. All of the ASC isolates are multipotent, capable of differentiating into osteocytes, chondrocytes and adipocytes, while fibroblasts show no differentiation potential. Our ASC strains also show elevated expression of genes associated with pluripotent cells, Oct-4, SOX2 and NANOG, when compared to fibroblasts and bone marrow-derived mesenchymal stem cells (BM-MSCs), although the levels were lower than induced pluripotent stem cells (iPS). Together, our data suggest that, while the cell surface profile of ASCs does not distinguish them from normal fibroblasts, their differentiation capacity and the expression of genes closely linked to pluripotency clearly define ASCs as multipotent stem cells, regardless of tissue isolation location. 相似文献
34.
A subset of genes, known as imprinted genes, is present in the mammalian genome. Genomic imprinting governs the monoallelic expression of these genes, depending on whether the gene was inherited from the sperm or the egg. This parent-of-origin specific gene expression is generally dependent on the epigenetic modification, DNA methylation, and the DNA methylation status of CpG dinucleotides residing in loci known as differentially methylated regions (DMRs). The enzymatic machinery responsible for the addition of methyl (-CH(3)) groups to the cytosine residue in the CpG dinucleotides are known as DNA methyltransferases (DNMTs). Correct establishment and maintenance of methylation patterns at imprinted genes has been associated with placental function and regulation of embryonic/fetal development. Much work has been carried out on imprinted genes in mouse and human; however, little is known about the methylation dynamics in the bovine oocyte. The primary objective of the present study was to characterize the establishment of methylation at maternally imprinted genes in bovine growing oocytes and to determine if the expression of the bovine DNMTs-DNMT3A, DNMT3B, and DNMT3L-was coordinated with DNA methylation during oocyte development. To this end, a panel of maternally imprinted genes was selected (SNRPN, MEST, IGF2R, PEG10, and PLAGL1) and putative DMRs for MEST, IGF2R, PEG10, and PLAGL1 were identified within the 5' regions for each gene; the SNRPN DMR has been reported previously. Conventional bisulfite sequencing revealed that methylation marks were acquired at all five DMRs investigated in an oocyte size-dependent fashion. This was confirmed for a selection of genes using pyrosequencing analysis. Furthermore, mRNA expression and protein analysis revealed that DNMT3A, DNMT3B, and DNMT3L are also present in the bovine oocyte during its growth phase. This study demonstrates for the first time that an increase in bovine imprinted gene DMR methylation occurs during oocyte growth, as is observed in mouse. 相似文献
35.
Characterization of the mechanical properties of soft biological tissues is important for establishing the mechanical tolerances of the tissues, and for input to computational models. In this work, the viscoelastic properties of bovine liver tissue in shear loading have been measured using relaxation and constant shear rate loading. The tissue is nonlinearly viscoelastic for strains greater than 0.2%, has a yield strain of approximately 10, and shows moderate strain-rate sensitivity. The response can be modelled using a nonlinear viscoelastic differential model previously developed for brain tissue. 相似文献
36.
Krützen M Sherwin WB Connor RC Barré LM Van de Casteele T Mann J Brooks R 《Proceedings. Biological sciences / The Royal Society》2003,270(1514):497-502
Male bottlenose dolphins (Tursiops sp.) in Shark Bay have one of the most complex male societies outside humans. Two broad mating strategies have been identified in males. In the first strategy, there are two types of alliances: stable 'first-order' pairs and trios that herd individual females in reproductive condition, and 'second-order' teams of two first-order alliances (five or six individuals) that join forces against rivals in contests for females. In the alternative strategy, a 'super-alliance' of ca. 14 individuals, males form pairs or trios to herd females, but in contrast to the stable alliances, these pairs and trios are highly labile. Here, we show that males in stable first-order alliances and the derived second-order alliances are often strongly related, so that they may gain inclusive fitness benefits from alliance membership. By contrast, members of the super-alliance are no more closely related than expected by chance. Further, the strength of the association of alliance partners within the super-alliance, as measured by an index of joint participation in consorting a female, was not correlated with their genetic relatedness. Thus, within one population and one sex, it appears that there may be simultaneous operation of more than one mode of group formation. 相似文献
37.
Oldfield C Bonella H Renwick L Dodson HI Alderson G Goodfellow M 《Antonie van Leeuwenhoek》2004,85(4):317-326
Rhodococcus equi is a facultative pathogen of foals. Infection causes an often fatal pulmonary pneumonia. The organism has also been isolated from pigs, cattle, humans and the environment. Equine virulence has a high positive correlation with the expression of a 17.4 kD polypeptide of unknown function, VapA, the product of the plasmid-encoded vapA gene. More recently an isogene of vapA, referred to as vapB and encoding an 18.2 kDa polypeptide, has been identified among pig and human isolates. The two genes share > 80% sequence identity, yet their host strains apparently exhibit different pathogenicity profiles (for example by reference to virulence in mouse model system and host specificity). In this study, a polymerase chain reaction (PCR) technique was developed that permits the selective amplification of vapA and vapB. Using this technique the distribution of the two genes among 35 randomly selected isolates of Rhodococcus equi from various animal and environmental sources was determined. Using this technique the genotype of each isolate could be unambiguously assigned as vapA+, vapB+ or vap- (i.e., scoring negative for both vapA and vapB). No isolate scored positive for both vapA and vapB. 100% of equine isolates scored vapA+, confirming the status of vapA as a reliable marker of equine virulence. All three genotypes were found among human isolates; porcine isolates scored either vapB+ or vap- and no vapA+ isolates were present in this sample. Rigorous statistical analysis using the Fisher Exact test confirmed that the high frequency of vapA+ among equine isolates is significant; however the sample size was too small to draw statistically significant conclusions regarding the distribution of genotypes among within other animal groups. 相似文献
38.
Enzymatic Recovery of Elemental Palladium by Using Sulfate-Reducing Bacteria 总被引:9,自引:2,他引:9 下载免费PDF全文
Worldwide usage of platinum group metals is increasing, prompting new recovery technologies. Resting cells of Desulfovibrio desulfuricans reduced soluble Pd2+ to elemental, cell-bound Pd0 supported by pyruvate, formate, or H2 as the electron donor without biochemical cofactors. Pd reduction was O2 insensitive, opening the way for recycling and recovery of Pd under oxic conditions. 相似文献
39.
40.
Anthony Johns K. Rewers-Felkins P. Devesly Gabor M. Rubanyi Lynne H. Parker-Botelho 《Neurochemistry international》1991,18(4):575-580
Specific receptor-induced signal transduction mechanisms for the endothelin-2 isoform (ET-2), a potent vasoconstrictor of vascular smooth muscle, were examined in Swiss 3T3 cells. Half-maximal binding (EC50) and maximal, saturable binding (Bmax) were estimated from Scatchard analyses and were found to be 24.2 ± 3.3 pM and 56500 ± 1700 sites/cells, respectively. A saturating concentration of ET-2 (100 nM) increased intracellular free calcium (measured by Fura-2 fluorescence) from a resting level of 100 nM to a peak level of 600–800 nM. The initial increase in intracellular free calcium was transitory and was followed by a smaller maintained elevation (250 nM). In the absence of extracellular calcium, ET-2 induced a transitory response equal in size to the peak in the presence of extracellular calcium, but the maintained response was absent. ET-2 increased intracellular free calcium in a concentration-dependent manner with an EC50 of 1 nM. In calcium free solution (2 mM EGTA), ET-2 increased the efflux of 45Ca from cells loaded to isotopic equilibrium (3 h) with 45Ca. The intracellular second messenger, IP3, also increased the calcium efflux from saponin permeabilized 3T3 cells loaded with 45Ca (pCa 6) in the presence of MgATP. In the presence of extracellular calcium, ET-2 significantly increased calcium uptake into 3T3 cells by 92 ± 36.6 pmoles/million cells/2 min (n = 8). It is suggested that ET-2 binds to specific, high affinity receptors in 3T3 cells and that this receptor interaction increases the intracellular free calcium by IP3-induced mobilization of calcium from cellular stores and by increasing influx of extracellular calcium. 相似文献