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91.
92.
The origin of matrix metalloproteinases and their familial relationships 总被引:13,自引:0,他引:13
New computer comparisons of the sequences of mammalian matrix metalloproteinases have established for the first time strong links with bacterial metalloproteinases. We also propose that there are five groups in the family of matrix metalloproteinases, although only three are as yet well-characterized as proteins, and discuss their origin and relationships with other zinc containing proteases. 相似文献
93.
We have investigated the binding of 3-[125I]iododizocilpine ([125I]iodo-MK-801) to the N-methyl-D-aspartate (NMDA) receptor in well-washed rat brain membranes. [125I]Iododizocipline binding was displaced by the following: dizocilpine greater than thienylphencyclidine greater than phencyclidine greater than ketamine. Binding of [125I]iododizocilpine was enhanced by glutamate, glycine, and spermidine, whose actions could be reversed by CGS-19755, 7-chlorokynurenate, and arcaine, respectively. [125I]Iododizocilpine binding was also enhanced by a number of divalent cations, including Ba2+, Ca2+, Mg2+, Mn2+, and Sr2+, and several monovalent cations, including Na+ and K+. These cations enhanced [125I]iododizocilpine binding by an action at the polyamine site. In addition, the inhibitory effects associated with high concentrations of these cations was markedly reduced compared to those found in previous studies with [3H]dizocilpine. Analysis of the ability of spermidine, Mg2+, and Sr2+ to alter the inhibition of [125I]iododizocilpine by arcaine gave pA2 values of 5.41, 4.47, and 4.93, corresponding to EC50 concentrations of 3.9, 34.7, and 12.0 microM, respectively, suggesting that physiological concentrations of Mg2+ may occupy the polyamine site. These results demonstrate that [125I]iododizocilpine is a useful probe for the NMDA receptor. Moreover, its high specific activity and relative insensitivity to the inhibitory actions of divalent cations should make [125I]iododizocilpine a valuable ligand for the study of NMDA receptors in intact cellular systems. 相似文献
94.
K S Moore C L Bevins N Tomassini K M Huttner K Sadler J E Moreira J Reynolds M Zasloff 《The journal of histochemistry and cytochemistry》1992,40(3):367-378
We have characterized a novel peptide-containing cell within the gastric mucosa of Xenopus laevis. The cell is a spherical, multinucleated syncytial structure containing a cytoplasmic space filled with dense rice-shaped granules, and is strikingly similar in morphology to the well-studied granular gland of the amphibian skin. Immunohistochemical and immunogold methods were used to demonstrate that several peptides previously isolated from the granular glands of the skin, including the antimicrobial peptides magainin and PGLa (a peptide with amino-terminal glycine and carboxy-terminal leucinamide), are also stored in granules present in these enteric cells. These data demonstrate that this enteric peptide-producing cell is strikingly similar both morphologically and biochemically to the granular gland, previously considered a highly specialized structure of the amphibian integument. This novel gastric mucosal cell, which we have designated a "granular multinucleated cell," is distinct in its morphology and its diversity of stored peptide products from other well-characterized peptide-containing cells in the vertebrate gastrointestinal tract. 相似文献
95.
Growth and morphological changes in the stomach of newborn pigs during the first three days after birth. 总被引:3,自引:0,他引:3
R J Xu P Tungthanathanich M J Birtles D J Mellor G W Reynolds H V Simpson 《Journal of developmental physiology》1992,17(1):7-14
Growth and morphological changes in the stomach of newborn pigs were examined during the first 3 days after birth. The stomach grew disproportionately faster than the body as a whole during this period. The growth was due to hyperplasia and hypertrophy during the first day and mainly to hyperplasia thereafter as gastric DNA content increased progressively after birth, and the protein:DNA and RNA:DNA ratios increased only on the first day. Histological and morphometric analyses revealed that the growth was more pronounced in the gastric body region than in the cardiac and pyloric regions, and more pronounced in the mucosal layer than in other layers. The percentage of mucosal volume occupied by parietal cells (volume density) and the number of parietal cells per unit volume of gastric mucosa (numerical density) increased significantly 3 days after birth in the cardiac and body regions, but not in the pyloric region, of the stomach. The observed morphological changes coincide with the known pattern of functional maturation during the immediate postnatal period. It is suggested that a high level of circulating gastrin and oral ingestion of milk-derived growth factors in the newborn pig contribute to these changes. 相似文献
96.
Sodium valproate is often used with phenytoin when epilepsy cannot be controlled by a single drug. Sodium valproate depresses phenytoin protein binding and so invalidates plasma phenytoin monitoring as a means of determining precise phenytoin dosage requirements. Plasma and saliva phenytoin and plasma valproate concentrations were measured in 42 patients with epilepsy receiving both drugs. Phenytoin protein binding was also measured by ultrafiltration in 19 of these patients and 19 patients taking phenytoin alone. Saliva phenytoin concentration bore the same close correlation to unbound (therapeutically active) phenytoin in patients receiving both drugs as it did in patients receiving phenytoin alone, whereas plasma total phenytoin did not. The same therapeutic range for saliva phenytoin (4-9 mumol/1; 1-2 microgram/ml) was therefore valid in both groups. The depression of phenytoin binding was directly related to the plasma concentration of valproate both in random samples taken from the 42 patients and in samples taken throughout the day in two of these patients. This was confirmed in vitro. Even when the concentration of valproate is known the degree of binding cannot be predicted. Saliva rather than plasma monitoring of phenytoin treatment is therefore valuable in the presence of valproate and with reduced phenytoin binding from any cause. 相似文献
97.
98.
Amide and ureide biogenic enzymes were measured in the plant fraction of soybean (Glycine max) nodules during the period 11 to 23 days after inoculation with Rhizobium japonicum (USDA 3I1b142). Enzymes involved in the initial assimilation of ammonia, i.e. glutamine synthetase, glutamate synthase, and aspartate aminotransferase, showed substantial increases in their specific activities over the time course. These increases paralleled the induction of nitrogenase activity in the bacteroid and leghemoglobin synthesis in the plant fraction. The specific activity of asparagine synthetase, however, showed a rapid decline after an initial increase in specific activity. Following the initial increases in the ammonia assimilatory enzymes, there was an increase in the activity of 5-phosphoribosylpyrophosphate amidotransferase, the enzyme which catalyzes the first committed step of de novo purine biosynthesis. This was followed by a dramatic increase in the purine oxidative enzymes, xanthine dehydrogenase and uricase. Smaller increases were observed in the activities of enzymes associated with the supply of metabolites to the purine biosynthetic pathway: phosphoglycerate dehydrogenase, serine hydroxymethylase, and methylene tetrahydrofolate dehydrogenase. 相似文献
99.
Monoclonal antibodies specific to transforming polyproteins encoded by independent isolates of feline sarcoma virus. 总被引:5,自引:1,他引:4 下载免费PDF全文
F Veronese G J Kelloff F H Reynolds Jr R W Hill J R Stephenson 《Journal of virology》1982,43(3):896-904
Hybridomas secreting monoclonal antibodies directed against polyprotein gene products of the Gardner, Snyder-Theilen, and McDonough strain of feline sarcoma virus have been isolated. Antibody produced by one hybridoma recognizes immunological determinants localized within a feline leukemia virus gag gene structural component (p15) common to polyproteins encoded by each feline sarcoma virus isolate while antibody produced by a second is specific for p30 determinants unique to P170gag-fms. Additional hybridomas secrete antibody directed against v-fes specific determinants common to the Gardner and Snyder-Theilen feline sarcoma virus-encoded polyproteins and to v-fms determinants unique to P170gas-fms polyprotein. GA P110gas-fes and ST P85gas-fes immunoprecipitated by antibody directed against p15 exhibit readily detectable levels of protein kinase activity but lack such activity when precipitated by antibody specific for their acquired sequence (v-fes) components. P170gas-fms immunoprecipitated by monoclonal antibody to either p15 or p30 lacks detectable levels of autophosphorylation but represents a substrate for the GA P110gag-fes and ST P85gag-fes enzymatic activities. These findings argue that the v-fes-associated protein kinase represents an intrinsic property of the v-fes gene product and recognizes tyrosine acceptor sites within polyprotein gene products of all three strains of feline sarcoma virus. 相似文献
100.
Abelson murine leukemia virus P120: identification and characterization of tyrosine phosphorylation sites. 总被引:2,自引:1,他引:1 下载免费PDF全文
Tryptic peptides containing two major in vivo P120gag-abl tyrosine phosphorylation acceptor sites were identified, phosphorylated in vitro, and purified to homogeneity. The tyrosine site in peptide a is localized at a position six residues distal to its trypsin cleavage site, whereas the tyrosine acceptor site in peptide b is at residue seven. A third peptide, c, contains an amino-terminal phosphotyrosine residue: phosphorylation of this latter peptide only occurs to a significant extent in vivo. 相似文献