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991.
Q Zhang C Domenicucci H A Goldberg J L Wrana J Sodek 《The Journal of biological chemistry》1990,265(13):7583-7589
Demineralizing extracts of porcine bone contain two large 66-80-kDa sialoproteins and smaller 20- and 23-kDa glycoproteins with similar chemical properties. Each protein was characterized following extraction from fetal calvariae and purification under dissociative conditions using Sepharose CL-6B, followed by fast protein liquid chromatography fractionation on hydroxyapatite and Mono Q resins. Unlike the large sialoproteins, the 20- and 23-kDa glycoproteins did not contain sialic acid. Nevertheless, affinity-purified antibodies raised against the 23-kDa protein recognized both the 20-kDa protein and a 67-kDa sialoprotein on immunoblots. These antibodies also immunoprecipitated a 60-kDa [35S]methionine-labeled protein produced by cell-free synthesis of calvarial bone mRNA, indicating that the smaller proteins were derived from the 67-kDa protein. The two sialoproteins were shown by primary sequence analysis to be secreted phosphoprotein I (SPPI, osteopontin, bone sialoprotein I) and bone sialoprotein (BSP, bone sialoprotein II). The SPPI was also characterized by its susceptibility to thrombin which produced a 23-kDa fragment, similar to the glycoprotein isolated, and a 30-kDa fragment. Amino-terminal sequence analysis of the 23- and 20-kDa proteins revealed that these proteins were derived from the carboxyl-terminal half of the SPPI molecule, the proteins showing 58% identity with human and rat, and 50% identity with mouse, SPPI sequences. Both the 23- and 20-kDa proteins appeared to be generated by the activity of an endogenous trypsin-like protease that cleaves at Arg-Ser (residues 155-156) and Lys-Ala (residues 182-183) bonds. Radiolabeling studies performed in vitro showed that the 23-kDa fragment was detectable in mineralized tissue within 4 h. The fragment was phosphorylated but, unlike SPPI, was not sulfated. The rapid generation of the 23-kDa glycoprotein and its presence in different bone tissues at different developmental stages indicate that the fragmentation of SPPI is important in bone formation and remodeling. 相似文献
992.
Growth of Pseudomonas C on C1 compounds: enzyme activites in extracts of Pseudomonas C cells grown on methanol, formaldehyde, and formate as sole carbon sources. 总被引:2,自引:2,他引:0 下载免费PDF全文
Pseudomonas C can grow on methanol, formaldehyde, or formate as sole carbon source. It is proposed that the assimilation of carbon by Pseudomonas C grown on different C1 growth substrates proceeds via one of two metabolic pathways, the serine pathway or the allulose pathway (the ribose phosphate cycle of formaldehyde fixation). This contention is based on the distribution of two key enzymes, each of which appears to be specifically involved in one of the assimilation pathways, glycerate dehydrogenase (serine pathway) and hexose phosphate synthetase (allulose pathway). The assimilation of methanol in Pseudomonas C cells appears to occur via the allulose pathway, whereas the utilization of formaldehyde or formate in cells grown on formaldehyde or formate as sole carbon sources appears by the serine pathway. When methanol is present together with formaldehyde or formate in the growth medium, the formaldehyde or formate is utilized by the allulose pathway. 相似文献
993.
H S Goldberg W Mitzner K Adams H Menkes S Lichtenstein S Permutt 《Journal of applied physiology》1975,38(3):411-417
Quasi-static pressure-volume (P-V) curves in normal seated human subjects were determined with pressure at the airway opening (Pa0) set below (negative pressure), above (positive pressure), or equal to ambient pressure. Dynamic compliance (Cdyn) during controlled continuous negative pressure breathing (CNPB) was also studied. Quasi-static P-V curves at negative pressure were decreased in slope, reflected a decrease in total lung capacity, and intersected the P-V curve obtained at ambient Pa0. At positive pressure the P-V curves showed an increase in slope and an increase in total lung capacity. During CNPB a fall in Cdyn was found. The fall in Cdyn was rapid and persisted for the duration of CNPB. Cdyn promptly returned to control levels when Pa0 was adjusted to ambient pressure. 相似文献
994.
DNA strand scission by the antitumor protein neocarzinostatin 总被引:5,自引:0,他引:5
The antibiotic protein, neocarzinostatin, induces the scission of DNA strands and . HeLa cell DNA prelabelled with [14C] thymidine is cut into large pieces with a peak at 80–90S when cells are incubated with 0.5 to 5.0 μg/ml of highly purified neocarzinostatin. Incubation of the antibiotic (0.5 μg/ml) with [3H] SV40 DNA in the presence of 2-mercaptoethanol results in the conversion of superhelical DNA I to nicked circular duplex DNA II. At high levels of drug, smaller fragments of linear DNA are produced. Strand breaks are detected in both neutral and alkaline sucrose gradients, indicating that drug susceptibility is not due to alkali-labile bonds. 相似文献
995.
Michael R. Goldberg Paul D. Joiner Stanley Greenberg Albert L. Hyman Philip J. Kadowitz 《Prostaglandins & other lipid mediators》1975,9(3):385-390
In order to determine whether the venoconstrictor response to BK was dependent on prostaglandin (PG) synthesis, effects of indomethacin (INDO) on responses to bradykinin (BK) and norepinephrine (NE) were studied in canine lateral saphenous vein. Cumulative dose-response curves (10−9-10−6M BK or NE) were done in the presence and absence of INDO (10−6M). In the presence of INDO, responses to BK were markedly enhanced while responses to NE were unchanged. After prolonged periods in the bath, responses to BK were enhanced in control strips while responses of strips which had been treated with INDO were depressed. These results suggest that BK does not normally cause venoconstriction by stimulating synthesis of a venoconstrictor PG and that the increase in response to BK after prolonged periods in the bath may be related to changes in PG synthetase. 相似文献
996.
The dynamic state of liver nucleolar proteins as reflected by their changes during administration of thioacetamide 总被引:4,自引:0,他引:4
During the nucleolar hypertrophy produced by thioacetamide treatment, a series of rapid changes occur in nucleolar proteins, some of which are markedly decreased and others, associated with synthesis of preribosomal ribonucleoprotein particles, are markedly increased in amount. These changes were studied by one- and two- dimensional polyacrylamide gel electrophoresis of the 0.4 N H2SO4 soluble nucleolar proteins, which showed an overall increase in the ratio of nonhistone proteins to histones following thioacetamide treatment. Most spots that increased in size and density had electrophoretic mobilities of proteins of the preribosomal ribonucleo-protein particles. One spot (A25) remained constant in size and density during the course of the treatment. Interestingly, marked decreases were found very early in two protein spots (A11 and A24) while two other protein spots (C13 and C14) decreased slowly with time. These results indicate that the nucleolus rapidly exhibits multifaceted changes during alterations in cell function. 相似文献
997.
This study investigated intrascrotal and deep body temperatures, reproductive ability, and histological patterns in the testes of heat-acclimatized rats. Albino rats aged 100-110 days were acclimatized to 35 degrees C. and a relative humidity of 25-40% for at least 3 months. There was free access to food and water and 14 hours of light daily. A control group was kept at an ambient temperature of 22 degrees C. and relative humidity of 35-50%. Deep-body temperature was measured with a thermistor probe inserted 4 cm into the rectum. Intrascrotal temperatures were measured with a thermocouple contained in a 27-gauge hypodermic needle inserted into the scrotum after the testes had been displaced. Readings were taken on alternate days for 30 days. Deep-body and intrascrotal temperatures were higher in experminetal than in control animals. Both groups maintained differences between body and intrascrotal temperatures. The intrascrotal temperatures of heat-acclimatized rats resembled the deep-body temperatures of the controls and, therefore, were similar to the environmental temperatures of cryptorchid testes. The mating rate of heat-acclimated males was lower than that of controls and fewer females conceived when mated with experimental males. However, in females which did conceive the type of male had no effect on implantation, pregnancy loss, or number of young. In about 20% of the experimental animals seminiferous tubules showed necrobiosis of germinal epithelium. Slight hyperplasia of Leydig cells was noted. The epididymal epithelium was intact and normal spermatozoa were present in the lumen. It is suggested that the gradient between the internal body termperature and the termperature of the testes is essential for spermatogenesis. Similar temperatures without the gradient, as in cryptorchid testes or heated scrotum, have been shown to be detrimental to spermatogenesis. 相似文献
998.
Abstract— In any assay for the determination of acetylcholine based on the conversion of choline to a product, the immediate problem is the removal of endogenous choline. Other published enzymatic assays have taken advantage of electrophoresis to accomplish this goal. In the assay to be described, this is accomplished by the enzymatic phosphorylation of endogenous choline by choline kinase. Once this reaction is complete, endogenous acetylcholine is simultaneously hydrolysed and then phosphorylated with [32 P]ATP. The labelled product [32 P]phosphorylcholine is separated from the labelled substrate by precipitation of the ATP and further separation is accomplished on microcolumns of ion exchange resin. Using this methodology, picomole amounts of acetylcholine, derived from tissue, can be measured. 相似文献
999.
1000.
Tissue distribution of ia antigens: Ia on spermatozoa,macrophages, and epidermal cells 总被引:2,自引:2,他引:0
Direct cytotoxic tests and absorption studies demonstrated thatI-region associated antigens (Ia) are not restricted to lymphocytes. Ia was found on spermatozoa, macrophages, and on epidermal cells, whereas Ia was absent from brain, liver, kidney, and fibroblasts. The possible biological meaning of these observations is discussed. 相似文献