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排序方式: 共有145条查询结果,搜索用时 15 毫秒
1.
Incidence of Clostridium botulinum Type E in Salmon and Other Marine Fish in the Pacific Northwest 总被引:4,自引:3,他引:1
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Salmon, sole, cod, oysters, clams, and crabs from ocean waters along the coast of Oregon and Washington were examined for the presence of Clostridium botulinum type E. The organism was detected by identification of the type E toxin in enrichment cultures of the viscera of individual fish. Of 369 salmon specimens, 48 yielded cultures containing toxin lethal to mice, and almost half of the toxic cultures were shown to contain botulinal toxin, chiefly type E. Eighteen of 113 sole and cod specimens, 4 of 22 Dungeness crab specimens, 5 of 16 oyster specimens, and 27 of 115 clam specimens gave rise to cultures containing botulinal toxin which was usually type E, although types A and B were occasionally encountered. 相似文献
2.
The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix 总被引:27,自引:0,他引:27
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Brian K. Pilcher Jo Ann Dumin Barry D. Sudbeck Stephen M. Krane Howard G. Welgus William C. Parks 《The Journal of cell biology》1997,137(6):1445-1457
We have shown in a variety of human wounds that collagenase-1 (MMP-1), a matrix metalloproteinase that cleaves fibrillar type I collagen, is invariably expressed by basal keratinocytes migrating across the dermal matrix. Furthermore, we have demonstrated that MMP-1 expression is induced in primary keratinocytes by contact with native type I collagen and not by basement membrane proteins or by other components of the dermal or provisional (wound) matrix. Based on these observations, we hypothesized that the catalytic activity of MMP-1 is necessary for keratinocyte migration on type I collagen. To test this idea, we assessed keratinocyte motility on type I collagen using colony dispersion and colloidal gold migration assays. In both assays, primary human keratinocytes migrated efficiently on collagen. The specificity of MMP-1 in promoting cell movement was demonstrated in four distinct experiments. One, keratinocyte migration was completely blocked by peptide hydroxymates, which are potent inhibitors of the catalytic activity of MMPs. Two, HaCaTs, a line of human keratinocytes that do not express MMP-1 in response to collagen, did not migrate on a type I collagen matrix but moved efficiently on denatured type I collagen (gelatin). EGF, which induces MMP-I production by HaCaT cells, resulted in the ability of these cells to migrate across a type I collagen matrix. Three, keratinocytes did not migrate on mutant type I collagen lacking the collagenase cleavage site, even though this substrate induced MMP-1 expression. Four, cell migration on collagen was completely blocked by recombinant tissue inhibitor of metalloproteinase-1 (TIMP-1) and by affinity-purified anti–MMP-1 antiserum. In addition, the collagen-mediated induction of collagenase-1 and migration of primary keratinocytes on collagen was blocked by antibodies against the α2 integrin subunit but not by antibodies against the α1 or α3 subunits. We propose that interaction of the α2β1 integrin with dermal collagen mediates induction of collagenase-1 in keratinocytes at the onset of healing and that the activity of collagenase-1 is needed to initiate cell movement. Furthermore, we propose that cleavage of dermal collagen provides keratinocytes with a mechanism to maintain their directionality during reepithelialization. 相似文献
3.
Further characterization of the binding of human recombinant interleukin 2 to heparin and identification of putative binding sites 总被引:1,自引:1,他引:1
We have previously provided compelling evidence that human recombinant
interleukin 2 (IL-2) binds to the sulfated polysaccharides heparin, highly
sulfated heparan sulfate and fucoidan. Here we show that IL-2 binding is
dependent on heparin chain length, but with fragments as small as 15-mers
retaining binding activity. The addition of exogenous heparin has no effect
on the in vitro biological activity of IL-2. In addition soluble IL-2
receptor alpha and beta polypeptides do not compete with heparin for the
binding of IL-2. IL-2 bound by heparin is still recognized by two IL-2
specific monoclonal antibodies, 3H9 and H2- 8, whose epitopes lie in the
amino terminal region. Murine IL-2 unlike its human counterpart fails to
bind to heparin. Human IL-2 analogs with single amino acid substitutions at
positions Lys43, Thr51, and Gln126 analogs no longer bind to heparin. By
contrast the Arg38Ala analog retains heparin full heparin binding activity.
These experimental findings together with molecular modeling studies
suggest two putative heparin binding sites on human IL-2, one involving
four basic residues, Lys48, Lys49, Lys54, and His55, and the other being a
discontinuous site comprising Lys43, Lys64, Arg81, and Arg83. Neither of
these two clusters is completely conserved in murine IL-2. Overall our data
suggest that the binding of human IL-2 to heparin and heparan sulfate does
not interfere with IL-2/IL-2 receptor interactions. Therefore, binding to
glycosaminoglycan may be a mechanism for retaining the cytokine in an
active form close to its site of secretion in the tissue, thus favoring a
paracrine role for IL-2.
相似文献
4.
5.
Larry M. Palato Shannon Pilcher Alissa Oakes Arleen Lamba Jaris Torres Litza I. Ledesma Monjaraz Crystabel Munoz Edward Njoo Dillon J. Rinauro Kate Alexandra Menefee Angela Tun Betssy L. Jauregui Sarah Shapiro Olivia H. Nossiff Eileen Olivares Kevin Chang Viviane Nguyen Luiza A. Nogaj David A. Moffet 《Journal of peptide science》2019,25(8)
The aggregation of the 37‐amino acid polypeptide human islet amyloid polypeptide (hIAPP), as either insoluble amyloid or as small oligomers, appears to play a direct role in the death of human pancreatic β‐islet cells in type 2 diabetes. hIAPP is considered to be one of the most amyloidogenic proteins known. The quick aggregation of hIAPP leads to the formation of toxic species, such as oligomers and fibers, that damage mammalian cells (both human and rat pancreatic cells). Whether this toxicity is necessary for the progression of type 2 diabetes or merely a side effect of the disease remains unclear. If hIAPP aggregation into toxic amyloid is on‐path for developing type 2 diabetes in humans, islet amyloid polypeptide (IAPP) aggregation would likely need to play a similar role within other organisms known to develop the disease. In this work, we compared the aggregation potential and cellular toxicity of full‐length IAPP from several diabetic and nondiabetic organisms whose aggregation propensities had not yet been determined for full‐length IAPP. 相似文献
6.
If endogenous, morphine-like substances have physiological functions, narcotic antagonists should have effects even in the absence of exogenous, narcotic agonists. This hypothesis was supported by studies of taste aversions conditioned with narcotic antagonists; rats drank smaller amounts of distinctively flavoured solutions when their consumption on previous occasions preceded injections of naloxone (1–10 mg/kg), naltrexone (3.2 mg/kg), Mr 1452 (10 mg/kg) or (-)-BC-2860 (10 mg/kg). Stereoisomers (i.e. Mr 1453, (+)-BC-2860) which were inactive as narcotic antagonists did not induce significant taste aversions. It was suggested that the consistency and stereospecificity of aversion with the antagonists gave some support to interpretations in terms of antagonist actions at receptors for endogenous opioids. 相似文献
7.
Uxmal and Tulum are two important Mayan sites in the Yucatan peninsula. The buildings are mainly composed of limestone and grey/black discoloration is seen on exposed walls and copious greenish biofilms on inner walls. The principal microorganisms detected on interior walls at both Uxmal and Tulum were cyanobacteria; heterotrophic bacteria and filamentous fungi were also present. A dark‐pigmented mitosporic fungus and Bacillus cereus, both isolated from Uxmal, were shown to be acidogenic in laboratory cultures. Cyanobacteria belonging to rock‐degrading genera Synechocystis and Gloeocapsa were identified at both sites. Surface analysis previously showed that calcium ions were present in the biofilms on buildings at Uxmal and Tulum, suggesting the deposition of biosolubilized stone. Apart from their potential to degrade the substrate, the coccoid cyanobacteria supply organic nutrients for bacteria and fungi, which can produce organic acids, further increasing stone degradation. 相似文献
8.
In this protocol, we present a standard method for extracting DNA from cells of the social amoeba Dictyostelium discoideum. While this procedure is similar to other phenol:chloroform-based purification methods, it is modified to account for the high level of carbohydrate and nucleases found in Dictyostelium cells. Genomic DNA can be isolated from wild-type and genetically modified cells using the described protocol, allowing molecular genetic analyses to be performed. Following cell lysis, nucleic acid extraction, and precipitation, the isolated DNA is suitable for digestion by restriction enzymes, amplification by PCR and Southern blotting. This procedure takes approximately 3 h to complete. 相似文献
9.
Here we present a protocol for the extraction of RNA from Dictyostelium discoideum. Dictyostelium is a social amoeba that undergoes a basic developmental program, and therefore analysis of RNA levels over a time course is a commonly used technique. This procedure is similar to other guanidine thiocyanate-based methods; however, it has been adjusted because of the large quantities of carbohydrate and nucleases found in Dictyostelium cells. After cell lysis and phenol:chloroform extraction, the resulting high-quality RNA isolated with the described protocol allows the molecular genetic analysis of wild-type and genetically modified cells. The purified RNA can be used for analyses such as northern blotting, RT-PCR and microarrays. This procedure requires approximately 2 h to complete. 相似文献
10.
Novak V Yang AC Lepicovsky L Goldberger AL Lipsitz LA Peng CK 《Biomedical engineering online》2004,3(1):39