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21.
P H Clements D T Yu J Levy C M Pearson 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1976,152(4):664-666
Peripheral blood lymphocytes from pregnant and nonpregnant females were studied for the presence of the following surface receptors: (i) Receptor for heat-aggregated human IgG (AggIgG); (ii) Receptor(s) for complement components; (iii) Receptor for sheep red blood cells (SRBC). Absolute numbers of lymphocytes with receptors for complement and those with receptors for SRBC were present in equal numbers in both groups. However, in the pregnant females there was a significantly lower number of lymphocytes with receptors for AggIgG. It is hypothesized that some of the immunological changes which occur during pregnancy may be mediated partly through changes in the total numbers of certain lymphocyte subpopulations. 相似文献
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FACTORS INFLUENCING BRAIN AND TISSUE LEVELS OF TRYPTAMINE: SPECIES, DRUGS AND LESIONS 总被引:1,自引:1,他引:0
J. W. Sloan W. R. Martin T. H. Clements W. F. Buchwald S. R. Bridges 《Journal of neurochemistry》1975,24(3):523-532
With a modification of the spectrophotofluorometric (SPF) method of HESS & UDENFRIEND (1959) (J. Pharmac. exp. Ther. 127 , 175-177), brain tryptamine levels in the rat (20.9 ng/g) and guinea-pig (20.7 ng/g) were found to be less than those in the dog (32.1 ng/g) and cat (52.2 ng/g). Regional distribution studies in the dog and cat showed that tryptamine was present in all major brain regions with highest concentrations in the spinal cord. Blood levels of tryptamine in the guinea-pig, dog and cat (6-7 ng/ml) were lower than brain levels. Pargyline significantly increased brain tryptamine in both the dog and cat; whereas, isocarboxazid (after 4 h) increased brain tryptamine levels in the dog but decreased brain levels in the cat. Reserpine (0.5-1.0 mg/kg per day for 1-4 days) did not significantly decrease brain, spinal cord or blood tryptamine levels in the dog. Spinal cord transection did not decrease tryptamine levels below the lesion in the chronic spinal dog. 相似文献
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Characterization of the novel protein kinase activity present in the R1 subunit of herpes simplex virus ribonucleotide reductase. 下载免费PDF全文
We have compared the protein kinase activities of the R1 subunits from herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) ribonucleotide reductase following expression in Escherichia coli. Autophosphorylation activity was observed when kinase assays were performed with immunoprecipitated R1 or proteins purified to homogeneity, and the activity was stimulated by the basic protein protamine. Transphosphorylation of histones or calmodulin by purified or immunoprecipitated HSV-1 and HSV-2 R1 was not observed, and our results suggest that the activities of these two proteins are similar. We further characterized the protein kinase activity of HSV-1 R1 by producing insertion and deletion mutants constructed with a plasmid expressing R1 amino acids 1 to 449. C-terminal deletion analysis identified the catalytic core of the enzyme as comprising residues 1 to 292, and this polypeptide will be useful for structural determinations by X-ray crystallography. Insertion of a 4-amino-acid sequence at sites within the protein kinase domain identified regions essential for activity; insertions at residues 22 and 112 completely inactivated activity, and an insertion at residue 136 reduced activity sixfold. Similar insertions at residues 257, 262, 292, and 343 had no effect on activity. The ATP analog 5'-fluorosulfonylbenzoyladenosine, which covalently modifies conventional eukaryotic kinases at an essential lysine residue within the active site, did label HSV R1, but this labelling occurred outside the N-terminal domain. These data indicate that the HSV R1 kinase is novel and distinct from other eukaryotic protein kinases. 相似文献
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Carcharocles megalodon (“Megalodon”) is the largest shark that ever lived. Based on its distribution, dental morphology, and associated fauna, it has been suggested that this species was a cosmopolitan apex predator that fed on marine mammals from the middle Miocene to the Pliocene (15.9–2.6 Ma). Prevailing theory suggests that the extinction of apex predators affects ecosystem dynamics. Accordingly, knowing the time of extinction of C. megalodon is a fundamental step towards understanding the effects of such an event in ancient communities. However, the time of extinction of this important species has never been quantitatively assessed. Here, we synthesize the most recent records of C. megalodon from the literature and scientific collections and infer the date of its extinction by making a novel use of the Optimal Linear Estimation (OLE) model. Our results suggest that C. megalodon went extinct around 2.6 Ma. Furthermore, when contrasting our results with known ecological and macroevolutionary trends in marine mammals, it became evident that the modern composition and function of modern gigantic filter-feeding whales was established after the extinction of C. megalodon. Consequently, the study of the time of extinction of C. megalodon provides the basis to improve our understanding of the responses of marine species to the removal of apex predators, presenting a deep-time perspective for the conservation of modern ecosystems. 相似文献
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A high recovery method for concentrating microgram quantities of protein from large volumes of solution 总被引:4,自引:0,他引:4
A method is presented for the recovery of 40-80% of the protein from a 1 microgram/ml solution. The final protein pellet is free of detergent and other ionic compounds and is thus compatible with any denaturing solution. The primary structure of the protein is unaffected by the procedure, making the final pellet an ideal sample for any analytical procedure to determine protein structure. 相似文献
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Bioinsecticides are important in the control of disease vectors, but data regarding their physiological effects on target insects are incomplete. This study describes morphological changes that occur in the midgut of third instar Aedes aegypti L. (Diptera: Culicidae) following treatment with a methanolic extract of Annona coriacea (Magnoliales: Annonaceae). Dissected midguts were subdivided into anterior and posterior regions and analyzed by light and scanning electron microscopy. Insects exposed to the extract displayed intense, destructive cytoplasmic vacuolization in columnar and regenerative midgut cells. The apical surfaces of columnar cells exhibited cytoplasmic protrusions oriented toward the lumen, suggesting that these cells could be involved in apocrine secretory processes and/or apoptosis. We report that A. coriacea extracts induced morphological alterations in the midgut of A. aegypti midgut larvae, supporting the use of plant extracts for control of the dengue vector. 相似文献
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Stacey Llewellyn Tawin Inpankaew Susana Vaz Nery Darren J. Gray Jaco J. Verweij Archie C. A. Clements Santina J. Gomes Rebecca Traub James S. McCarthy 《PLoS neglected tropical diseases》2016,10(1)