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At least 235 records · Page 13Linked to original sources

Adenovirus protein VI mediates membrane disruption following capsid disassembly.

In contrast to enveloped viruses, the mechanisms involved in membrane penetration by nonenveloped viruses are not as well understood. In these studies, we determined the relationship between adenovirus (Ad) capsid disassembly and the development of membrane lytic activity. Exposure to low pH or heating induced conformational changes in wild-type Ad but not in temperature-sensitive Ad (ts1) particles that fail to escape the early endosome. Wild-type Ad but not ts1 particles permeabilized model membranes (liposomes) and facilitated the cytosolic delivery of a ribotoxin. Alterations in wild-type Ad capsids were associated with the exposure of a pH-independent membrane lytic factor. Unexpectedly, this factor was identified as protein VI, a 22-kDa cement protein located beneath the peripentonal hexons in the viral capsid. Recombinant protein VI and preprotein VI, but not a deletion mutant lacking an N-terminal amphipathic alpha-helix, possessed membrane lytic activity similar to partially disassembled virions. A new model of Ad entry is proposed based on our present observations of capsid disassembly and membrane penetration.

Adenoviridae↗

Efficient pulse sequence for multisection dual-repetition time MR image acquisition.

A magnetic resonance imaging pulse sequence was developed in which multisection spin-echo image data are simultaneously acquired for two repetition time (TR) intervals (TR1 and TR2) in one imaging sequence. In a conventional multisection image at a single TR, the number of sections is limited to TR/TS, where TS is the readout time. With this new sequence, the number of sections that can be imaged at both TRs in one acquisition is equal to (TR1 + TR2)/(TS1 + TS2), where TS1 and TS2 may be different for the two TRs. Imaging time is equal to that for a single image at a TR of TR1 + TR2. Clinical images were obtained with the new sequence from 15 patients and compared with images acquired at the same TR/TE by means of standard multisection single-TR methods. Relative image quality was assessed by three radiologists in 37 comparisons. In general, the dual-TR results at the long TR were judged equivalent to those from a single-TR image. Dual-TR results at the short TR had a modest reduction in contrast, but in none of 15 cases were any pathologic features missed.

Magnetic Resonance Imaging↗

A role for PS integrins in morphological growth and synaptic function at the postembryonic neuromuscular junction of Drosophila.

A family of three position-specific (PS) integrins are expressed at the Drosophila neuromuscular junction (NMJ): a beta subunit ((betaPS), expressed in both presynaptic and postsynaptic membranes, and two alpha subunits (alphaPS1, alphaPS2), expressed at least in the postsynaptic membrane. PS integrins appear at postembryonic NMJs coincident with the onset of rapid morphological growth and terminal type-specific differentiation, and are restricted to type I synaptic boutons, which mediate fast, excitatory glutamatergic transmission. We show that two distinctive hypomorphic mutant alleles of the beta subunit gene myospheroid (mys(b9) and mys(ts1)), differentially affect betaPS protein expression at the synapse to produce distinctive alterations in NMJ branching, bouton formation, synaptic architecture and the specificity of synapse formation on target cells. The mys(b9) mutation alters betaPS localization to cause a striking reduction in NMJ branching, bouton size/number and the formation of aberrant 'mini-boutons', which may represent a developmentally arrested state. The mys(ts1) mutation strongly reduces betaPS expression to cause the opposite phenotype of excessive synaptic sprouting and morphological growth. NMJ function in these mutant conditions is altered in line with the severity of the morphological aberrations. Consistent with these mutant phenotypes, transgenic overexpression of the betaPS protein with a heat-shock construct or tissue-specific GAL4 drivers causes a reduction in synaptic branching and bouton number. We conclude that betaPS integrin at the postembryonic NMJ is a critical determinant of morphological growth and synaptic specificity. These data provide the first genetic evidence for a functional role of integrins at the postembryonic synapse.

Alleles↗

CD4+ CD25+ regulatory T cell repertoire formation in response to varying expression of a neo-self-antigen.

We have examined the development of self-peptide-specific CD4+ CD25+ regulatory T cells in lineages of transgenic mice that express the influenza virus PR8 hemagglutinin (HA) under the control of several different promoters (HA transgenic mice). By mating these lineages with TS1-transgenic mice expressing a TCR that recognizes the major I-E(d)-restricted determinant from HA (site 1 (S1)), we show that S1-specific T cells undergo selection to become CD4+ CD25+ regulatory T cells in each of the lineages, although in varying numbers. In some lineages, S1-specific CD4+ CD25+ regulatory T cells are highly abundant; indeed, TS1xHA-transgenic mice can contain as many S1-specific CD4+ T cells as are present in TS1 mice, which do not express the neo-self HA. In another lineage, however, S1-specific thymocytes are subjected to more extensive deletion and far fewer S1-specific CD4+ CD25+ regulatory T cells accumulate in the periphery. We show that radioresistant stromal cells can direct both deletion and CD4+ CD25+ regulatory T cell selection of S1-specific thymocytes. Interestingly, even though their numbers can vary, the S1-specific CD4+ CD25+ regulatory T cells in all cases coexist with clonally related CD4+ CD25- T cells that lack regulatory function. These findings show that the formation of the CD4+ CD25+ regulatory T cell repertoire is sensitive to variations in the expression of self-peptides.

Animals↗

cDNA cloning, sequence analysis and molecular modeling of a new peptide from the scorpion Buthotus saulcyi venom.

In this study, the cDNA of a new peptide from the venom of the scorpion, Buthotus saulcyi, was cloned and sequenced. It codes for a 64 residues peptide (Bsaul1) which shares high sequence similarity with depressant insect toxins of scorpions. The differences between them mainly appear in the loop1 which connects the beta-strand1 to the alpha-helix and seems to be functionally important in long chain scorpion neurotoxins. This loop is three amino acids longer in Bsaul1 compared to other depressant toxins. A comparative amino acid sequence analysis done on Bsaul1 and some of alpha-, beta-, excitatory and depressant toxins of scorpions showed that Bsaul1 contains all the residues which are highly conserved among long chain scorpion neurotoxins. Structural model of Bsaul1 was generated using Ts1 (a beta-toxin that competes with the depressant insect toxins for binding to Na(+) channels) as template. According to the molecular model of Bsaul1, the folding of the polypeptide chain is being composed of an anti-parallel three-stranded beta-sheet and a stretch of alpha- helix, tightly bound by a set of four disulfide bridges. A striking similarity in the spatial arrangement of some critical residues was shown by superposition of the backbone conformation of Bsaul1 and Ts1.

Amino Acid Motifs↗

Yoga training and motor speed based on a finger tapping task.

A finger tapping task was used to assess motor speed (MS) of both hands in 53 adults and 152 children before and after yoga training and in 38 adults of a non-yoga (control) group. All subjects were right hand dominant. The 30-second tapping speed (TS) test was considered as three time intervals, i.e. 0-10 second (TS1), 10-20 seconds (TS2) and 20-30 seconds (TS3). There was a significant (Student's t-test) increase in all three TS values following 10 days of yoga in children and 30 days of yoga in adults. However for both groups at baseline and final assessments, TS2 and TS3 were significantly lower than TS1. Hence the TS was increased after yoga training during the first 10-seconds of the test but not during the next 20 seconds. These results suggest an increase in motor speed for repetitive finger movements following yoga training, but not in strength or endurance, as the increase was not sustained over 30 sec.

Adolescent↗

[Cloning and characterization of three novel genes encoding transmembrane proteins of Schistosoma japonicum].

OBJECTIVE: To clone and analyze novel antigen molecules of Schistosoma japonicum (Sj), and to provide effective vaccine candidate antigens against schistosomiasis japonica. METHODS: Sj adult cDNA library was screened using sera of mice infected with Trichinella spiralis (Ts) and the inserts of positive clones were specifically amplified by PCR. The positive clones were sequenced and the sequence data were analyzed using Nucleotide BLAST software of NCBI and Expert Protein Analysis System of Swiss Institute of Bioinformatics. RESULTS: Nine positive clones were obtained after three rounds of immunoscreening. The size of these inserts ranged from 0.6 kb to 2.1 kb. Among five novel genes, Sj-Ts1, Sj-Ts3 and Sj-Ts5 (GenBank accession number: AY005816, AF299080 and AY024352, respectively) encode trans-membrane proteins with 83, 83 and 233 amino acids, respectively. Sj-Ts1 protein predicted contains one possible trans-membrance helix, one N-myristoylation site, two phosphorylation sites for protein kinase C and one for tyrosine kinase, Sj-Ts3 protein contains two possible transmembrance helices and one casein kinase II phosphorylation site, whereas Sj-Ts5 protein has five possible transmembrance helices, one N-glycosylation site, one N-myristoylation site, two phosphorylation sites for cAMP- and cGMP-dependent protein kinase and four for protein kinase C and one for casein kinase II. CONCLUSION: Three novel genes encoding three transmembrane proteins might be developed as new vaccine candidates against Sj infection.

Amino Acid Sequence↗

[Early diagnosis and staging of pancreatic cancer].

Case of pancreatic cancer have increased in number, and the number of deaths from that disease has reached 20,000 in recent years in Japan. Only a few patients with pancreatic cancer can be cured. However, the prognosis in small pancreatic cancer such as TS1 less than 2 cm is relatively good if radical surgical resection is performed. Therefore early diagnosis of pancreatic cancer is important to improve the dismal prognosis. Although clinical symptoms are not reliable for the diagnosis of pancreatic cancer, 30% of TS1 patients have abdominal or back pain. Recent epidemiologic studies have shown that familial history of pancreatic cancer, chronic pancreatitis, diabetes, obesity, and smoking are possible high-risk factors for pancreatic cancer. Serum pancreatic enzyme and tumor markers in terms of CA19-9 and CEA are measured first. Ultrasonography (US) should be performed as soon as possible. Not only tumors but also slightly dilated main pancreatic ducts and/or small simple cysts that may represent indirect changes due to pancreatic cancer can be detected with US. Enhanced computed tomography, magnetic resonance cholangiopancreatography and endoscopic US are also useful. Endoscopic retrograde cholangiopancreatography yields more detailed images of branch ducts, and the cytology of pancreatic juice can be determined following examination. Unfortunately, position-emission tomography is not a reliable method for the diagnosis of small tumors in the pancreas. Finally, TNM staging of pancreatic cancer is performed based on the results of these imaging examinations.

Amylases↗

Inhibition of growth of HeLa cell tumours in nude mice by 125I-labeled anticytokeratin and antiPLAP monoclonal antibodies.

The radiommunotherapeutic potential of 125I-labeled monoclonal antibodies was investigated in 48 nude mice (BALB/c, nu/nu) inoculated s.c. with the HeLa Hep 2 human adenocarcinoma cell line. This isotope, 125I, which is not commonly used for therapeutic purposes caused significant decrease in tumour growth from day 10 to day 42, when coupled to monoclonal antibodies directed against placental alkaline phosphatase (H7) or cytokeratins (TS1). The average growth rate was approximately 50-60% of that observed in the untreated control group after 42 days. The specific radioactivity in each organ 42 days after injection of radiolabeled monoclonal antibodies, indicated that these target antigens retain significant amounts of radiolabeled antibody in the tumours for at least 6 weeks after injection. No weight loss was seen in the animals during this experiment. By use of autoradiographic techniques, the labeled monoclonal antibodies were visualized deep in tumours in characteristic patterns representative of viable tumour cells (H7) and necrotic areas (TS1). The therapeutic approach using 125I labeled antibodies is encouraging and may offer new dimensions in radioimmunotherapy.

Adenocarcinoma↗

Comparison of two double labeling techniques to measure cell cycle kinetics in myeloid leukemias.

Five patients with acute myeloid leukemia (AML) received a one hour infusion of iododeoxyuridine (IUdR) 100 mg/M2 to label S-phase cells in vivo. The aspirate was labeled in vitro either with tritiated thymidine (3HTdr) or bromodeoxyuridine (BrdU) to measure the duration of S-phase (Ts). The mean Ts using 3HTdr (Ts1) was 15.9h (13.1-19.8h) and using BrdU (Ts2) was 17.1h (14.5-20.6h). Total cell cycle time (Tc) ranged between 44.7h to 158.8h using Ts1 and 54.0h to 170.5h using Ts2. Based on this close approximation between the results, we confirm the reliability of the newly developed method that relies purely on immunohistochemical reaction.

Bromodeoxyuridine↗

cAMP promotes the synthesis in early G1 of gp115, a yeast glycoprotein containing glycosyl-phosphatidylinositol.

The glycoprotein gp115 (Mr = 115,000, pI 4.8-5) is localized in the plasma membrane of Saccharomyces cerevisiae cells and maximally expressed during G1 phase. To gain insight on the mechanism regulating its synthesis, we have examined various conditions of cell proliferation arrest. We used pulse-labeling experiments with [35S]methionine and two-dimensional gel electrophoresis analysis, which allow the detection of the well characterized 100-kDa precursor of gp115 (p100). In the cAMP-requiring mutant cyr1, p100 synthesis is active during exponential growth, shut off by cAMP removal, and induced when growth is restored by cAMP readdition. The inhibition of p100 synthesis also occurs in TS1 mutant cells (ras1ras2-ts1) shifted from 24 to 37 degrees C. During nitrogen starvation of rca1 cells, a mutant permeable to cAMP, p100 synthesis is also inhibited. cAMP complements the effect of ammonium deprivation, promoting p100 synthesis, even when added to cells which have already entered G0. Experiments with the bcy1 and cyr1bcy1 mutants have indicated the involvement of the cAMP-dependent protein kinases in the control of p100 synthesis. Moreover, the synthesis of p100 was unaffected in A364A cells, terminally arrested at START B by alpha-factor. These results indicate that the switch operating on p100 synthesis is localized in early G1 (START A) and is one of the multiple events controlled by the cAMP pathway.

Cell Cycle↗

Down-regulation of suppressor cell induction.

A unidirectional cascade of cell interactions has been described previously that involves at least three distinct populations of suppressor T cells (Ts) that interact in appropriate succession to mediate suppression of delayed hypersensitivity responses to the 4-hydroxy-3-nitrophenylacetyl hapten (NP). The present work focuses on the potential bidirectional effects of one suppressor factor and how it can regulate the homeostatic mechanisms that maintain this suppressor cell cascade. Specifically, the effects of prior administration of mice with a transducer suppressor factor (TsF2) on the generation of NP-specific TS1 suppressor cells were evaluated. It was observed that the TSF2 given 2-14 days prior to administration of the tolerogen (NP-coupled splenic-adherent cells) interfered with the development of inducer TS1 suppressor cells. This down-regulation of suppressor cell induction is mediated by a population of cells that have the following characteristics: NP-binding, Lyt-1+2-, L3T4+, I-J+, and Vicia villosa (VV)-adherent T cells (for convenience these cells are termed anti-suppressor cells). Furthermore, there are genetic restrictions (both H-2 and IgH) between TSF2 and host which control the generation of anti-suppressor cells. The results suggest that TSF2 may have a role in homeostatic mechanisms that regulate the NP-specific suppressor cell cascade. The relationship of anti-suppressor and contra-suppressor cells is discussed.

Animals↗

In vitro generation of suppressor T cells. Induction of CD3+, IgH-restricted suppressor cells.

Previous studies of the immune response of C57BL/6 mice to the 4-hydroxy-3-nitrophenyl acetyl (NP) hapten determined that challenge with antigenic forms of hapten induces both immunity and suppression. The anti-NP plaque-forming cell response can be down regulated by an Ag-induced cascade consisting of three suppressor T cell subsets. These three populations, termed Ts1, Ts2, and Ts3 have been characterized to have inducer, transducer and effector functions, respectively. Although the functions of each of these subsets have been examined in vivo, the cellular requirements for in vitro Ts induction have only been investigated for the Ts3 population. The present study characterizes the cellular events that lead to the induction of the Ts2, suppressor transducer population. Culture of naive C57BL/6 spleen cells with Ts1-derived suppressor factor in the absence of exogenous Ag leads to the generation of Ts2 cells that mediate Ag-specific suppression of NP plaque-forming cell responses. Phenotypic analyses demonstrate that a CD3+, CD4-, CD5+, CD8+, and I-J+ precursor population is stimulated by TsF1 to become mature Ts2 cells that express CD3, CD8, and I-J but not CD5. Although previous studies have reported an essential role for B cells in the induction of other Ts populations, depletion of B cells from Ts2 induction cultures had no effect on Ts2 generation. Despite the absence of B cells in these cultures, the mature Ts2 cells were functionally IgH restricted. Studies with IgH congenic B.C-8 mice suggest that this restriction specificity was imposed by the idiotype-related determinants expressed on the TsF1, not the T cell genotype.

Animals↗

Purification and analysis of an antigen-specific suppressor factor from a T cell hybridoma specific for phenyltrimethylamino hapten.

The synthetic monovalent antigen L-tyrosine-p-azophenyltri-methylammonium (tyr (TMA)) induces in A/J mice, a cascade of regulatory T cells in the absence of any detectable effector function (e.g., CTL, delayed-type hypersensitivity, etc.). An important component of the activated T cells is a first order suppressor T cell or Ts1 that is Ly-1+2-, functions only at the afferent limb of the anti-TMA response, binds the TMA ligand and bears cross-reactive idiotypes associated with anti-TMA antibodies. This Ts1 produces a suppressor factor (TsF1) that binds the TMA ligand, bears the cross-reactive idiotypes and I-J determinants and functions to induce an idiotype-specific Ts2 population. To study the biochemistry of this TsF, use was made of T cell hybridomas that constitutively produce TMA-TsF1 (8A.1 and 8A.3). The TsF1 was purified from culture supernatant or cell extracts by (NH4)2SO4 precipitation, reverse phase HPLC and either affinity chromatography or by preparative IEF. The TsF1 has an isoelectric point of 6.5 and a m.w. of 26,000 or 62,000 as analyzed by SDS-PAGE or high performance molecular sieve chromatography. Its precipitation in 30 to 40% (NH4)2SO4; elution pattern from reverse phase high performance columns; its capacity to bind to a mAb specific for L-glutamic acid 60L-alanine30-L-tyrosine10 (GAT)-TsF1 strongly suggest that this protein belongs to the same family of proteins as do the GAT-TsF1 described previously. Most noteworthy is that although these TsF1 proteins show remarkable similarities, they are absolutely specific in their biologic activity; TMA-TsF1 will not suppress the response to GAT-BA-TNP and GAT-TsF1 will not suppress the response to TMA-BA-TNP. Thus the TMA-TsF1 represents a second example of a unique group of Ag-specific proteins whose function is to induce or activate other suppressor T cells in the primary immune response to Ag.

Ammonium Sulfate↗

Macrophage transmission of suppressor signal for suppression of delayed hypersensitivity and humoral response in JEV-infected mice.

Japanese encephalitis virus (JEV) infection induces suppressor T-cells (Ts1) which suppress both the humoral (Ts-PFC) and cell mediated (Ts-DTH) immune response by producing soluble suppressor factors. This study shows that in the JEV model, both TS-PFC and Ts-DTH mediate suppression by recruiting a second subpopulation of suppressor T-cells, the Ts2-PFC and Ts2-DTH. The signal between Ts1 and Ts2 is transmitted by macrophages (M phi). The suppressor factors are adsorbed by peritoneal or splenic M phi. Both heat-killed and live M phi are capable of adsorbing suppressor factors but only live M phi are capable of presenting the signal to T-cells. Thus these are at least two generations of suppressor T-cells in the JEV-specific suppressor pathway and the presence of M phi is obligatory for transmission of the signal.

Adsorption↗

Induction of immune responses by schistosome granuloma macrophages.

In mice, granuloma formation after Schistosomiasis mansoni infection is known to be a T cell-dependent response to schistosome eggs that peaks at 6 to 8 wk after infection (early) then regresses to a minimum by 20 to 32 wk (late). This decline in host responsiveness, termed modulation, has been attributed to T cell-mediated suppression. We now have investigated the macrophages from either Early or Late schistosome granulomas phenotypically and found no difference in expression of I-A subregion encoded antigens. We also tested granuloma macrophage (Gm) populations in their capacity to induce positive and negative antigen-specific immune responses to the hapten 4-hydroxy-3-nitrophenyl acetyl (NP). As few as 10(3) to 10(4) NP-coupled Early or Late Gm given s.c. were equally capable of inducing MHC-restricted NP-specific delayed-type hypersensitivity (DTH) responses and this DTH-inducing capability was equivalent to that of splenic adherent cell (SAC) controls. Further, both Early and Late Gm were able to generate NP-specific induction-phase suppressor cells (Ts1) when as few as 10(2) NP-coupled Gm were given i.v., the same as NP-SAC controls. Finally, NP-specific effector-phase suppressor cells (Ts3) were equally induced by Early Gm, Late Gm, or SAC controls. Therefore, macrophages derived from Early or Late schistosome granulomas or normal spleens are apparently phenotypically indistinguishable and equally capable, in extremely small quantities, of inducing NP-specific DTH, Ts1, and Ts3 immune responses.

Animals↗

Regulation of the immune response to tumor antigens. X. Activation of third-order suppressor T cells that abrogate anti-tumor immune responses.

The experiments described further define the suppressor T cell pathway in the S1509a tumor system. We demonstrated previously that S1509a-induced Ts1, TsF1, and Ts2 specifically suppress in vivo Ly1+2- T cell-dependent responses to S1509a and that Ts1 suppress in vivo Ly-1+2- T cell-mediated proliferative responses to S1509a. We have now shown that in vivo administration of either S1509a-induced TsF1 or TsF2 suppresses both in vivo and in vitro Ly-1+2- T cell-mediated responses to S1509a. Furthermore, we revealed the existence of Ts3, which are activated by S1509a tumor antigen and TsF2, in this murine tumor system. Finally, we demonstrated that cyclophosphamide abrogates the suppressive effect of TsF2 but not that of Ts3. These results are discussed with respect to T cell-mediated suppression in other murine tumor systems and the possible pivotal role for a tumor antigen-presenting cell in activating Ts3 in the S1509a tumor system.

Animals↗

Differential cyclophosphamide sensitivity of T lymphocytes of the dengue virus-induced suppressor pathway.

Dengue type 2 virus (DV) induces a suppressor pathway in mice which involves sequential participation of three subpopulations of T lymphocytes viz. Ts1, Ts2 and T3 cells. In the present study cyclophosphamide (CY) sensitivity of these cells have been investigated. The findings of the present study demonstrate that Ts1 and Ts2 cells are CY-insensitive while T3 cells are CY-sensitive. This supports our earlier conclusion that T3 may be the inducer cells of suppression.

Animals↗