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1.
Larval hemolymph tyrosinase activity in Drosophila melanogaster was detected with high performance liquid chromatography with electrochemical detection. The enzyme hydroxylated L-tyrosine, and oxidized the diphenol substrates L-dopa and dopamine. In larvae of a selected immune-reactive strain the rates of tyrosine hydroxylation, dopa oxidation, and dopamine oxidation were markedly increased during the early stages of melanotic encapsulation of the eggs of the parasitic wasp Leptopilina boulardi. Tyrosinase activity was not modified in parasitized larvae of a selected susceptible strain of D. melanogaster, in which hosts the parasitoids developed unmolested. During the same period of parasitization, the amount of free tyrosine in immune reactive larvae was approximately three times higher than in susceptible hosts. These data indicate that the tyrosinase system of the immune reactive strain is activated during parasitization, and this results in the synthesis of some precursors which ultimately produce a melanotic and sclerotic capsule around the eggs of the parasite. Based on known genetic information of the enzyme system in Drosophila, it appears that at least two genes may be involved in the activation process, one associated with the proenzyme for monophenol oxidase activity, and the second with the proenzyme for diphenol oxidase activity. 相似文献
2.
Ritanserin, a serotonin-S2 receptor antagonist, does not prevent 5-hydroxytryptophan-induced beta-EP, beta-LPH and cortisol secretion 总被引:1,自引:0,他引:1
F Facchinetti E Martignoni G Nappi S Marini F Petraglia G Sandrini A R Genazzani 《Hormone research》1987,27(1):42-46
Ritanserin, a new serotonin antagonist selective upon S2 receptor subclass is available. Thus, in order to better define the positive control of serotoninergic pathway on proopiomelanocortin (POMC)-related peptide release, a group of 7 healthy male volunteers has been submitted to a 5-hydroxytryptophane (5-OH-TP) test (200 mg p.o.) before and after 4 days Ritanserin pretreatment. Plasma beta-endorphin (beta-EP), beta-lipotropin (beta-LPH) and cortisol levels were measured hourly for 4 h after each 5-OH-TP loading. Hormonal levels were measured by specific RIAs on extracted (cortisol) and chromatographed (beta-EP and beta-LPH) plasma samples. Basal plasma concentrations of the three hormones were unchanged by Ritanserin pretreatment. Similarly, the integrated areas of beta-LPH, beta-EP and cortisol release in response to 5-OH-TP remained unaffected by the receptor blockade. These data confirm that serotonin-acting drugs are able to stimulate POMC-related peptide release and indicate that such interaction is not mediated through S2 receptor subclass. 相似文献
3.
4.
Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews
(genus Sorex) for the region between the tRNA(Pro) and the conserved
sequence block-F revealed variable numbers of 79-bp tandem repeats. These
repeats were found in all 19 individuals sequenced, representing three
subspecies and one closely related species of the masked shrew group (Sorex
cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an
outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an
adjacent 76-bp imperfect copy of the tandem repeats. One individual was
heteroplasmic for length variants consisting of five and seven copies of
the 79-bp tandem repeat. The sequence of the repeats is conducive to the
formation of secondary structure. A termination-associated sequence is
present in each of the repeats and in a unique sequence region 5' to the
tandem array as well. Mean genetic distance between the masked shrew taxa
and the pygmy shrew was calculated separately for the unique sequence
region, one of the tandem repeats, the imperfect repeat, and these three
regions combined. The unique sequence region evolved more rapidly than the
tandem repeats or the imperfect repeat. The small genetic distance between
pairs of tandem repeats within an individual is consistent with a model of
concerted evolution. Repeats are apparently duplicated and lost at a high
rate, which tends to homogenize the tandem array. The rate of D- loop
sequence divergence between the masked and pygmy shrews is estimated to be
15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid
sequence evolution in shrews may be due either to their high metabolic rate
and short generation time or to the presence of variable numbers of tandem
repeats.
相似文献
5.
6.
大鼠胼胝体内神经肽Y免疫反应阳性纤维的发育 总被引:1,自引:0,他引:1
本实验用免疫组织化学ABC法研究了大鼠胼胝体内神经肽Y免疫反应阳性(NPY-IR)纤维的生后发育。结果发现,许多NPY-IR纤维在大鼠出生时便存在于胼胝体内。NPY-IR胼胝体纤维的密度在生后1周内继续逐渐增高,在第2周内达到最高峰。之后,NPY-IR胼胝体纤维的密度逐渐下降,至第3周末时接近成年时的水平,即仅有少量NPY-IR纤维存在于胼胝体内。这些结果提示在大鼠早期生后发育过程中许多NPY-IR胼胝体纤维是暂时性的,其作用可能与大脑皮质的机能发育有关。 相似文献
7.
8.
Immunogenetic aspects of the cellular immune response of Drosophila against parasitoids 总被引:3,自引:0,他引:3
Host-parasite relationships represent integrating adaptations of considerable complexity involving the host's immune capacity to both recognize and destroy the parasite, and the latter's ability to successfully invade the host and to circumvent its immune response. Compatibility in Drosophila-parasitic wasp (parasitoid) associations has been shown to have a genetic basis, and to be both species and strain specific. Studies using resistant and susceptible strains of Drosophila melanogaster infected with virulent and avirulent strains of the wasp Leptopilina boulardi demonstrate that the success of the host cellular immune response depends on the genetic status of both host and parasitoid. Immunological, physiological, biochemical, and genetic data form the bases of a two-component model proposed here to account for the observed specificity and complexity of two coevolved adaptations, host nonself recognition and parasitoid virulence. 相似文献
9.
Multiple transmembrane amino acid requirements suggest a highly specific interaction between the bovine papillomavirus E5 oncoprotein and the platelet-derived growth factor beta receptor 下载免费PDF全文
The bovine papillomavirus E5 protein activates the cellular platelet-derived growth factor beta receptor (PDGFbetaR) tyrosine kinase in a ligand-independent manner. Evidence suggests that the small transmembrane E5 protein homodimerizes and physically interacts with the transmembrane domain of the PDGFbetaR, thereby inducing constitutive dimerization and activation of this receptor. Amino acids in the receptor previously found to be required for the PDGFbetaR-E5 interaction are a transmembrane Thr513 and a juxtamembrane Lys499. Here, we sought to determine if these are the only two receptor amino acids required for an interaction with the E5 protein. Substitution of large portions of the PDGFbetaR transmembrane domain indicated that additional amino acids in both the amino and carboxyl halves of the receptor transmembrane domain are required for a productive interaction with the E5 protein. Indeed, individual amino acid substitutions in the receptor transmembrane domain identified roles for the extracellular proximal transmembrane residues in the interaction. These data suggest that multiple amino acids within the transmembrane domain of the PDGFbetaR are required for a stable interaction with the E5 protein. These may be involved in direct protein-protein contacts or may support the proper transmembrane alpha-helical conformation for optimal positioning of the primary amino acid requirements. 相似文献
10.
Black AP Bhayani H Ryder CA Pugh MT Gardner-Medwin JM Southwood TR 《Arthritis research & therapy》2003,5(5):R277-R284
The aim of this research was to determine whether all memory T cells have the same propensity to migrate to the joint in patients
with juvenile idiopathic arthritis. Paired synovial fluid and peripheral blood mononuclear cell proliferative responses to
a panel of antigens were measured and the results correlated with a detailed set of laboratory and clinical data from 39 patients
with juvenile idiopathic arthritis. Two distinct patterns of proliferative response were found in the majority of patients:
a diverse pattern, in which synovial fluid responses were greater than peripheral blood responses for all antigens tested;
and a restricted pattern, in which peripheral blood responses to some antigens were more vigorous than those in the synovial
fluid compartment. The diverse pattern was generally found in patients with a high acute phase response, whereas patients
without elevated acute phase proteins were more likely to demonstrate a restricted pattern. We propose that an association
between the synovial fluid T cell repertoire and the acute phase response suggests that proinflammatory cytokines may influence
recruitment of memory T cells to an inflammatory site, independent of their antigen specificity. Additionally, increased responses
to enteric bacteria and the presence of αEβ7 T cells in synovial fluid may reflect accumulation of gut associated T cells
in the synovial compartment, even in the absence of an elevated acute phase response. This is the first report of an association
between the acute phase response and the T cell population recruited to an inflammatory site. 相似文献