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991.
A measure of the N-status of phytoplankton at natural cell densitiesmay be made by determining the ratio of intracellular glutamine:glutamate(GLN:GLU). The intracellular pool of free amino acids from 104–106cells is extracted in ultraclean conditions and analysed byreverse phase HPLC. A GLN:GLU ratio of >0.5 indicates N-repleteand <0.2 N-deplete cells.  相似文献   
992.
Screening of a compound library against endothelin receptors (ETA and ETB) revealed PD 102566 (compound 1) as an ETA selective antagonist. Synthesis and structure-activity relationships (SAR) of a series of analogs are described.  相似文献   
993.
Ovaries of neonatal rats are not endowed with specific LH/hCG receptors up to 6–8 days of age. Treatment of ovarian membranes of the neonatal rat with neuraminidase results in a specific binding of radioactively labeled hCG, while an increase of hormone binding is observed after neuraminidase treatment of ovarian membranes of the 21-day-old rat. These changes in hormone receptor sites in the ovary are dependent on the neuraminidase concentration used and are due to a receptor with a dissociation constant (KD) of about 10−9 M. The KD of the receptor in the LH/hCG sensitive ovary without neuraminidase treatment is about 10−10 M. These results indicate the presence of two different LH/hCG receptors in the ovarian membrane. The unmasking effect of neuraminidase onto LH/hCG receptors indicate that ganglioside-like structures are responsible for the masking of receptors in the neonatal, insensitive rat ovary and also in the 21-day-old sensitive ovary. Ganglioside preparations are able to inhibit the binding, and the fractionation of ovary gangliosides results in a fraction with a rather high inhibition potency of LH/hCG binding to the receptor. It is hypothesized that the masked receptors in the sensitive period represent a store of receptors for the reconstitution of the ovarian cells with active receptors after internalization of the hormone-receptor complex. Thus the masking of the receptors in the early postnatal rat ovary could be a prerequisite for the female differentiation of hypothalamic centers. The observed neuraminidase effect in vitro could reflect a physiologic situation. Neuraminidase was found in the ovary, and during early postnatal development the neuraminidase activity pattern coincides with that of the ovarian LH/hCG receptor changes.  相似文献   
994.
The paralytic shellfish poison prducing dinoflagellate Gymnodiniuncatemrum was subjected to changes in salinity, phosphate, ammoniumand nitrate using continuous culture and batch culture methods.In contrast with other algae, this species showed very slowchanges in the concentration of intracellular amino acids, inthe Gln:Glu ratio, and, in contrast with Alrsandnum spp., onlyslow changes in toxin content, during such events as N-feedingof Ndeprived cells or during nutrient deprivation. This organismwas found to be very susceptible to disturbance; maximum growthrates around 0.25–0.3 day–1 with a minimum C:N massratio of 5.5, were attained when cultures were only disturbedby sampling once a day. P-deprived cells were larger (twicethe usual C content of 4 ng C cell–1 and volume of 20pl). The content of free amino acids was always low (5% of cell-N),with low contributions made by arginine (the precursor for paralyticshellfish toxins). Cells growing using ammonium had the lowestC:N ratios and the highest proportion of intracellular aminoacids as arginine. The toxin profile (equal mole ratios of dcSTX,GTX5, dcGT2/3 C1 and C2, and half those values for C3 and C4)was stable and the toxin concentration varied between 0.2 and1 mM STX equivalents (highest when ammonium was not limiting,lowest in P-deprived cells, though as the latter were largertoxin per cell was not so variable). Decreased salinity didnot result in increases in toxin content. Significant amountsof amino acids (mainly serine and glycine, with a total oftenexceeding 4 µM) accumulated in the growth medium duringbatch growth even though the cultures were not bacteria free. 4Present address: Instituto Español de Oceanografia,Apdo 1552, 36280, Vigo, Spain  相似文献   
995.
Full-thickness sections of upper and lower eyelids were obtained from patients who had eyelid pigment implantation performed by one surgeon. These four patients represented eyelid pigment implantation at varying postoperative stages ranging from 6 months to 4 years. Light microscopic evaluation revealed pigment within dermis and superficial orbicularis muscle. Light and electron microscopic evaluation revealed the vast majority of the pigment to be located intracellularly, primarily within macrophages. No foreign-body reaction was seen around the implanted material. Electron probe analysis of the pigment showed only the presence of iron. Analysis of the unused pigment revealed small amounts of silica and magnesium. These substances could not be identified by electron probe analysis in the eyelid tissues.  相似文献   
996.
997.
Human antibody Fc deamidation in vivo   总被引:1,自引:0,他引:1  
Protein and peptide deamidation occurs spontaneously in vitro under relatively mild conditions. For antibodies and other therapeutic proteins, great effort is placed in manufacturing and storage to minimize this form of degradation. Concern has been especially great in cases where deamidation has been shown to impact protein activity. Here we monitored asparagine deamidation from a recombinant human antibody in humans and found that among the conserved sites, only Asn 384 deamidated at an appreciable rate. Under physiological temperature and pH conditions, in vitro antibody deamidation followed similar kinetics, indicating that simple incubation reactions may be used to model in vivo behavior. Endogenous IgG isolated from human serum possessed 23% deamidation at this site, further demonstrating that this modification is naturally occurring. Thus, deamidation generated in manufacturing and storage does not fully determine the patient exposure to the attribute. Instead, pharmacokinetic data along with the deamidation kinetics are combined to predict patient exposure. The deamidation rate can also be used to estimate the serum lifetime of antibodies. This approach could potentially be used to estimate turnover for other cellular or extracellular proteins.  相似文献   
998.
Snu13p is a highly conserved RNA binding protein from Saccharomyces cerevisiae required for both eukaryotic pre-mRNA splicing and pre-rRNA processing. The 1H, 13C, and 15N assignments were determined from multidimensional, multinuclear NMR experiments conducted at 25°C.  相似文献   
999.
1000.
Arterial plasma concentrations of PGF2alpha and 15-keto-PGF2alpha were determined in sham shock and splanchnic artery occlusion shock dogs. Arterial PGF2alpha concentrations (expressed as percentage of control) increased significantly in the SAO group when compared to the sham group during postrelease sampling periods. Similarly, 15-keto-PGF2alpha, a major metabolite of PGF2alpha also increased significantly in arterial blood in SAO shock. Comparison of 15-keto-PGF2alpha and PGF2alpha at each sampling period suggest that the efficiency of 15-hydroxyprostaglandin dehydrogenase is not impaired during SAO shock in the dog. However, the ability of the kidney and other organs to remove 15-keto-PGF2alpha from the circulation during SAO shock does appear to be significantly reduced. Although the changes in circulating concentrations of PGF2alpha are significant, the role of the increased prostaglandin is not clearly understood. We found no basis for any toxic effect of the PGF2alpha nor of any beneficial action. Others, however, have found exogenous PGF2alpha to improve survival in circulatory shock.  相似文献   
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