Reduced expression of Tap1 and Lmp2 antigen-processing genes in the nonobese diabetic (NOD) mouse due to a mutation in their shared bidirectional promoter

The MHC is an essential contributor to autoimmunity. Lmp2 and Tap1 are genes located in the MHC class II region, and they encode proteins participating in the generation and transport of endogenous peptides for T cell education. A mutation (T-->A) has now been detected in the shared bidirectional promoter of the Lmp2 and Tap1 genes in the nonobese diabetic (NOD) mouse. The nucleotide substitution (TCATTC-->TCAATC) in NOD mice eliminates an initiator (Inr) element (TCATTC) thought to be important for RNA polymerase II positioning in the Lmp2 orientation. It also created a CAAT-like box and an inverted CAAT-like box in the Lmp2 and Tap1 orientations, respectively. Northern blot revealed reduced amounts of Tap1 and Lmp2 mRNA in NOD mice, and 5'-rapid amplification of cDNA ends revealed the loss of a transcription start site of Lmp2 in these animals. The Tap1-Lmp2 promoter from NOD mice showed reduced transcriptional activity in transient transfection assays with luciferase reporter constructs for both Tap1 and Lmp2 genes. Observed altered substrate specificity of Lmp2 containing proteasomes isolated from NOD mice was consistent with reduced Lmp2 activity. The beneficial influence of non-MHC genes (NOR mice) and gender factors (male NOD mice) influencing the penetrance of the promoter polymorphism further confirmed the essential gender and hormonal context of the mutation. This study identifies the first specific mutation in the MHC of the NOD mouse that specifically impacts the activity of genes involved in peptide presentation, a process essential for T cell education.

Early detection of apoptosis using a fluorescent conjugate of annexin V

Apoptosis of mammalian cells is accompanied by various morphological changes including nuclear condensation, DNA fragmentation and cell surface changes. Methods developed over the past few years have focused on detection of DNA-associated changes that occur rather late in apoptosis. However, detection of apoptosis at early stages, before gross morphological changes, is critical for understanding the pathways of programmed cell death. In this report, we describe a rapid and reliable assay for detecting early stages of apoptosis. This assay is based on the observation that soon after initiating apoptosis, most mammalian cell types translocate phosphatidylserine (PS) from the inner face of the plasma membrane to the cell surface. Once on the cell surface, PS can be specifically detected by staining with fluorescein isothiocyanate (FITC)-labeled annexin V (annexin V-FITC), a protein with a strong, natural affinity for PS. Using this assay, we have detected apoptotic cells in culture, in real time, using fluorescence microscopy and flow cytometry. In combination with vital dye staining, the progressive stages of apoptosis were observed. PS redistribution occurs earlier than DNA-associated changes and membrane leakage. In addition, PS externalization occurs during apoptosis induced by a variety of stimuli. Therefore, the annexin V binding assay provides an excellent indicator for the early stages of apoptosis.

[Effect of extremely low frequency (correction of frenquency) magnetic field on brain ischemic reaction in rats]

The effect of extremely low frequency magnetic field (ELMF, 15 Hz, 18 mT) on ischemic brain produced by ligation of general carotid artery in left side was studied in rats. The results showed that the degree of brain blood vessel dilation was higher in magnetic field group than that in control group at the 1st, 3rd and 6th hour after ligation and the extent of damage of neurocyte was apparently lighter in magnetic field group than that in control group at the 3rd and 6th hour after ischemia. It indicates that ELMF stimulation improves the brain blood circulation after brain ischemia and alleviates the brain ischemic reaction.

[Effect of different Anti-G suits on lower limb blood flow]

To study effects of different Anti-G suits (AGS) and different inflation pressure on human cardiac system, changes in lower limb arterial blood flow (BF), heart rate and blood pressure in 5 male subjects with three bladder coverage AGS and a capstain AGS were observed and recorded until inflation pressure reached to its maximum. The percent of bladder coverage was about 30%, 65% and 90% of lower body for three bladder AGS. All AGS were inflated to maximum pressure in +1Gz seating position. The results showed that calf BF, could be blocked by bladder AGS, and the relationship between the mean pressure for BF block and the percentage of bladder coverage was y = 29.66 - 16.35x. (P < 0.0001, r = -0.9229). While the thigh and calf BF was not blocked in subjects with the capsule AGS. The results indicate that the effect of "the higher bladder coverage AGS + lower IP" is probably equal to that of "the lower bladder coverage AGS + higher IP" in holding calf BF.

Fusion of phospholipid vesicles induced by the ribosome inactivating protein saporin

The single chain ribosome-inactivating protein Saporin-S6 (SO-6) induces the fusion of acid phospholipid vesicles. The extent of fusion was measured by resonance energy transfer assay between the N-(7-nitro-2-1,3-benzoxadiazol-4-yl)-dimyristoylphosphatidyl lithanolamine (NBD-PE)(donor) and N-(lissamine rhodamine B sulphonyl)-diacylphoshaidylethanolamine (Rh-PE) (acceptor) incorporated in the vesicle. The saturated lipid/protein molar ratio is approx. 100:1. The time course of fusion of vesicles induced by the protein showed that the process was completed within 10 minutes, and the size of the particles in the medium was enlarged which conforms the occurrence of the fusion occurring. The fusion is temperature dependent and the liquid-crystalline state lipid is more apt to fuse than the gel phase lipid. The effect of SO-6 is also dependent on ionic strength and pH, high salt concentration and basic pH may abolish fusion, which suggests that both electrostatic and hydrophobic components may be involved in the process.

Comparison of effects of 5 and 20 Hz magnetic field on brain responses

Effects of 5 and 20 Hz magnetic field (MF) on brain response were compared in 22 normal subjects during selective response (SRP) and selective mental arithmetic (SMA). It was found that significant changes in event-related potentials and EEG power spectra were induced by 5 Hz MF, but changes induced by 20 Hz MF were only in EEG coherence during SMA. The features of brain response changes suggest that the brain is in a more well being state after 5 Hz MF stimulation.

Comparisons of genetic variability and genome structure among mosquito strains selected for refractoriness to a malaria parasite

Restriction fragment length polymorphism (RFLP) markers were used to evaluate Aedes aegypti genome structure and genetic variability within and between substrains selected for different levels of refractoriness to the malaria parasite, Plasmodium gallinaceum. The MOYO-R substrain was previously selected for complete refractoriness and the MOYO-IS substrain for intermediate susceptibility from the Moyo-In-Dry (MOYO) strain by selective inbreeding (F = 0.5). Eighteen mapped RFLP markers were used to provide coverage of the mosquito genome. The two substrains showed reduced genetic diversity compared with the MOYO strain, including significant reductions in mean heterozygosity, number of alleles per locus, and proportion of polymorphic loci. Genetic differentiation between the two substrains was statistically significant, as reflected by differences in allele frequencies. Significant pairwise linkage disequillbrium among the RFLP loci was detected in all three strains, most evidently in the MOYO strain. This is surprising because the RFLP loci examined are separated by large map distances, and therefore linkage disequilibrium should decay to zero after many generations of laboratory culture. Our hypothesis to explain this phenomena is that lack of recombination, or low recombination rates in some regions of the A. aegypti genome, is a result of chromosome inversions. Finally, we used graphical genotyping, wherein whole genome genotypic information for individual mosquitoes is represented in a simple graphic format, to illustrate genome structure and allelic variation within and among the mosquito strains. Our analysis revealed an apparent chromosomal deletion on chromosome 3 for some individuals in the MOYO strain and MOYO-IS substrain.

Human TAP1 polymorphisms detected by denaturing gradient gel electrophoresis

Presentation of endogenous peptides by major histocompatibility complex class I (MHC) molecules is controlled, in part, by the Tap1 and Tap2 genes in the MHC class II region that encode a heterodimeric peptide transporter. Polymorphisms of human Tap1 in normal individuals have now been investigated systematically by denaturing gradient gel electrophoresis (DGGE) analysis of fragments of genomic DNA generated by the polymerase chain reaction. Polymorphisms identified by distinctive DGGE band patterns were confirmed by DNA sequencing. In addition to four previously described polymorphisms in the open reading frame, DGGE detected three new polymorphisms: a G-->T substitution in the promoter region, a 10-bp insert in intron 9, and a G-->T substitution 80-bp downstream of the translation termination codon.

[Cloning of the NS1 gene of dengue-2 virus and determination of its partial nucleotide sequence]

In this study, RT-PCR product of the NS1 gene of dengue-2 virus isolated in China was inserted into the DNA of T-vector plasmid. DNAs of the positive clones, which were identified by using the blue/white spot and PCR, were digested with enzymes, indicating that the inserted fragments were the same sizes as those of the amplified NS1 genes. The result of the nucleotide sequence determined by dideoxy chain-termination method indicated that 5'-terminal nucleotide sequence of the amplified NS1 fragment was not changed.

[ECG changes during [correction of dring] high G centrifuge training]

ECG of 47 healthy subjects, during G-training on the human centrifuge were recorded and analyzed. Training consisted of 4 G profiles and carried out in 6 d. Subjects were divided into 3 groups according to different anti-G equipment used. The results showed that: high incidence of arrhythmia (87%) was observed, and it increased with the increase of G level; subjects with R/S < 1 under +Gz environment, or HR sharply dropped immediately after the +Gz load have lower G-tolerance; incidence of arrhythmia is lower when advanced anti-G equipment was used.

Fluorescence spectroscopic study of the interaction of saporin with phospholipid vesicles

Saporin-S6 (SO-6) is a type-1 ribosome-inactivating protein purified from the seeds of Saponaria officinalis. The fluorescence characteristics of SO-6 were studied in the presence and absence of phospholipids. The interaction of SO-6 with DMPG or DMPC vesicles results in a decrease in the fluorescence emission intensity of tryptophan without any shift in the emission maximal wavelength. The results of fluorescence titration indicate that DMPG/SO-6 saturation molar ratio is 100: 1, but the binding of DMPC with SO-6 does not reach a saturating plot. A shielding of the tryptophan fluorescence from quenching by acrylamide on interaction with the phospholipids was observed, and this shielding was more pronounced in the presence of DMPG. The interaction of SO-6 with DMPG vesicles is stronger in the liquid-crystalline phase than in the gel phase. Extrinsic fluorescence studies indicated that the interaction of the protein with DMPG vesicles does not modify the phase transition temperature of the lipid, but decreases the amplitude of the change of fluorescence anisotropy associated with the co-operative melting of 1,6-diphenyl-1,3,5-hexatriene (DPH)-labelled vesicles. These results indicate that both electrostatic and hydrophobic components are involved in the SO-6-lipid vesicle interaction.

IRES bicistronic expression vectors for efficient creation of stable mammalian cell lines

Stable transfection of mammalian cells is a widely used technique for the study of gene expression and protein purification. However, selection of cell lines expressing desired genes from a large number of candidate clones is often labor-intensive and time consuming. To improve the efficiency of stable cell line production, we have used a bicistronic mammalian expression vector, pIRES1hyg, which contains the internal ribosome entry site (IRES) of the encephalomyocarditis virus (ECMV). The IRES element permits the translation of two open reading frames from one messenger RNA: one reading frame encoding the recombinant protein of interest and the other an antibiotic resistant marker (e.g. hygromycin). We demonstrate that the use of the bicistronic vector significantly facilitates the creation of stable mammalian cell lines, because all selected antibiotic-resistant colonies express the recombinant gene of interest. Therefore, the use of the pIRES1hyg bicistronic vector for stable transfection eliminates the need to screen large numbers of colonies to find functional clones. We conclude that the IRES bicistronic vector provides a powerful tool for efficient selection of stable transformants in mammalian cells.

Influence of tapeworm infection on the production of aggregation pheromone and defensive compounds in Tribolium castaneum

Recent studies suggest that parasites affect host development, reproduction, and behavior through alterations of host hormones and pheromones, or other hormone-triggered biochemical events. We previously reported that Hymenolepis diminuta infection affects surface-seeking and cannibalism behaviors, and reduces male sperm precedence of Tribolium castaneum beetles. This study examined the quantitative effects of H. diminuta on the production of aggregation pheromone and 3 defensive compounds in male T. castaneum beetles, using 2 wild-caught, geographically distinct T. castaneum strains. For the c-Madison strain, infected beetles exhibited a 2- to 22-fold increase in defensive compounds; conversely, no changes were observed in strain c-Africa. Parasite infection did not significantly influence aggregation pheromone secretion in either strain. Because defensive compounds function as repellents or deterrents to other insects, parasite-induced increases in the secretion of defensive compounds may be a physiologic clue for the behavioral changes in infected T. castaneum beetles. Significant among-strain variation in defensive compound production seen in infected beetles suggests that caution is needed before generalizing about changes in volatile production and in host behavior induced by a parasite.

Localization of HIV-1 RNA in mammalian nuclei

The Rev protein of human immunodeficiency virus type 1 (HIV-1) facilitates the nuclear export of unspliced and partially spliced viral RNAs. In the absence of Rev, these intron-containing HIV-1 RNAs are retained in the nucleus. The basis for nuclear retention is unclear and is an important aspect of Rev regulation. Here we use in situ hybridization and digital imaging microscopy to examine the intranuclear distributions of intron-containing HIV RNAs and to determine their spatial relationships to intranuclear structures. HeLa cells were transfected with an HIV-1 expression vector, and viral transcripts were localized using oligonucleotide probes specific for the unspliced or spliced forms of a particular viral RNA. In the absence of Rev, the unspliced viral RNAs were predominantly nuclear and had two distinct distributions. First, a population of viral transcripts was distributed as approximately 10-20 intranuclear punctate signals. Actinomycin D chase experiments indicate that these signals represent nascent transcripts. A second, stable population of viral transcripts was dispersed throughout the nucleoplasm excluding nucleoli. Rev promoted the export of this stable population of viral RNAs to the cytoplasm in a time-dependent fashion. Significantly, the distributions of neither the nascent nor the stable populations of viral RNAs coincided with intranuclear speckles in which splicing factors are enriched. Using splice-junction-specific probes, splicing of human beta-globin pre-mRNA occurred cotranscriptionally, whereas splicing of HIV-1 pre-mRNA did not. Taken together, our results indicate that the nucleolus and intranuclear speckles are not involved in Rev regulation, and provide further evidence that efficient splicing signals are critical for cotranscriptional splicing.

Four isolates of Giardia lamblia cultivated axenically in China and the restriction endonuclease analysis of their DNA

Axenic culture of 4 Giardia lamblia isolates, 3 from humans and 1 from a rabbit, have been established in China for the first time. The trophozoites of Giardia used for the initial cultivation were obtained from the purified cysts excysted in suckling gerbil (Meriones unguiculatus) and BALB/c mice. Modified TYI-S-33 medium was used in establishment of the culture. DNA banding patterns were compared using restriction-endonuclease analysis and then followed by Southern blot analysis with genomic DNA as a probe. The 4 isolates showed identical banding patterns after being digested with Hind III, Bgl II, Pts I, Hae III, and Hinf. Two different banding patterns were observed after further digestion with Alu I and southern blot analysis. This indicated that isolates of human and rabbit origins do not have strict host specificity and that cross transmission may occur between humans and rabbits.

[Changes of brain potentials related to visual attention during simulated weightlessness]

To study the possible effect of simulated weightlessness on brain function state, the brain event-related potentials (ERPs) during a simple visual selective response task were compared between head down tilt (HDT) and head up tilt (HUT) in 9 normal subjects. The results were: both the target (T) and non-target (NT) flash signals induced significant slow positive potentials which were supposed to be related to the attention activity; the amplitude of the positive potentials in the frontal regions decreased significantly especially for NT-ERPs during HDT as compared with that during HUT. The data provide new evidence indicating that the ability of brain response declined during simulated weightlessness and more attention should be paid to the study of brain function during space flight.

Microsatellite-centromere mapping in the zebrafish (Danio rerio)

Ten (CA)n microsatellite simple sequence repeat (SSR) markers, 1, 2, 12, 14, 16, 18, 20, 22, 26, and 29, were used to show high chiasma interference and to determine centromere-marker map distances in the zebrafish (Danio rerio). Of these, SSR 12 exhibited no recombinant tetratypes among 175 half-tetrad embryos, placing this marker within 1 cM of the centromere of Linkage Group XVII. Fractions of heterozygous half-tetrads for the remaining nine markers ranged from 0.64 to 0.89. Of these, six recombinant fractions were more than 0.67 (P < 0.05), indicating strong chiasma interference during female meiosis in the zebrafish. Consistent with previous mapping data, SSRs 2 and 20 of Linkage Group VI were tightly linked. Half-tetrad analysis will allow the mapping of the remaining centromeres and may be useful in the mapping of new genes and mutations in the zebrafish.

The effect of head-down tilt on brain potentials related to visual attention

To study the possible effect of simulated weightlessness on brain function state, the brain event-related potentials (ERPs) in a simple visual selective response task were compared between HDT and HUT in 9 normal subjects. The results were: The Target(T) and non-Target(NT) flash signals both induced significant slow positive potentials which were supposed to related to the attention state; the amplitude of the positive potentials in frontal regions decreased significantly especially for NT-ERPs during HDT compared with that during HUT. The data reported provide new evidence indicating that more attention should be paid on the brain function study during space flight.

Alternately spliced NH2-terminal immunoglobulin-like Loop I in the ectodomain of the fibroblast growth factor (FGF) receptor 1 lowers affinity for both heparin and FGF-1

Alternate splicing of a single exon encoding an NH2-terminal immunoglobulin (Ig) disulfide loop in the ectodomain of the fibroblast growth factor receptor (FGFR) types 1 and 2 results in alpha and beta isoforms that exhibit 3- and 2-Ig loops, respectively. Previously we demonstrated that alternately spliced Loop I has no independent ligand binding activity but is sufficiently interactive with the ligand- and heparin-binding site formed by Loops II and III to lower affinity for the same fibroblast growth factor (FGF) ligand. Here we show that a lower affinity of FGFR1 alpha for heparin parallels the lower affinity for FGF-1. A mutant of FGFR1 alpha in which the sequence between Loops I and II was deleted exhibits high affinity for both FGF-1 and heparin and other properties of the FGFR1 beta isoform, which include resistance to degradation by trypsin and display of specific antibody epitopes. This suggests that the interloop sequence facilitates the interaction of Loop I with Loops II and III. Lack of expression of both exons coding for Loop I and the sequence between Loops I and II in the FGFR2 gene characterizes rat prostate tumor cells, which exhibit a loss of the low affinity class of FGF receptors. Although the exon coding for the sequence between Loops I and II is alternately spliced in the FGFR2 beta isoform, coordinate expression with the exon coding for Loop I results in the functional differences between the FGFR alpha and FGFR beta variants.

Ligand-specific structural domains in the fibroblast growth factor receptor

Two tandem immunoglobulin-like disulfide loops (Loops II and III) linked by a short connecting sequence in the ectodomain of the fibroblast growth factor receptor kinase compose the binding sites for glycosaminoglycan and fibroblast growth factor (FGF) ligands. Alternate splicing of exons IIIb and IIIc coding for the COOH-terminal half of Loop III confers high affinity for FGF-7 or FGF-2, respectively, on the fibroblast growth factor receptor ectodomain without effect on the binding of FGF-1. Here we show that a 139-amino acid fragment composed of Loop II, the inter-Loop II/III sequence, and a short segment of the NH2 terminus of Loop III is sufficient and near the minimal requirement for binding of FGF-1, FGF-2, and FGF-7. Extension of the fragment by five additional highly conserved residues (SD(P/A)QP) within a distinct constitutive structural domain (fl1) in Loop III restricts the binding of FGF-7 without effect on FGF-1 and FGF-2. Since the presence of exon IIIc in the full-length ectodomain does not change this ligand binding profile, we suggest that alternately spliced exon IIIc plays no active role in binding of the three ligands. In contrast, exon IIIb actively abrogates the restriction on the binding of FGF-7 and concurrently lowers the affinity for FGF-2.

Infection of Tribolium beetles with a tapeworm: variation in susceptibility within and between beetle species and among genetic strains

Host susceptibility and resistance to parasites are often hypothesized to be genetically variable traits. We tested 2 species of Tribolium flour beetles for among-strain variation in susceptibility to the rat tapeworm Hymenolepis diminuta. Twelve genetic strains of Tribolium confusum and 11 strains of Tribolium castaneum were examined. We found T. castaneum was more susceptible to the tapeworm than T. confusum. There was significant among-strain and between-sex variation for both beetle species in infection intensity and prevalence. Among-vial variation was marginally significant. These results add to evidence that host susceptibility to a parasite is a genetically variable trait. We view these results as important findings for understanding natural selection on host-parasite interactions. Traits that are genetically variable can respond to natural selection. Thus, if a beetle's susceptibility to the tapeworm is correlated with fitness and heritable, susceptibility can evolve. Susceptibility is likely to be pleiotropic and have important consequences on issues ranging from parasite transmission to host species interactions and community structure.

Abnormal class I assembly and peptide presentation in the nonobese diabetic mouse

Presentation of self-antigens by major histocompatibility complex (MHC) class I molecules requires the function of the MHC class II-linked genes Tap-1 and Tap-2. Evidence suggests that interruption of self-peptide presentation results in reduced cell surface expression of MHC class I molecules and the interruption correlates with progression to diabetic autoimmunity in nonobese diabetic (NOD) mice and humans. NOD mice possess a rare Tap-1 allele (Tap-1b); this is associated with reduced Tap-1 mRNA abundance in lymphocytes from diabetes-prone females and decreased conformationally correct class I molecules on the cell surface. In this study, we demonstrate that, similar to lymphoma cell lines with mutations in Tap-1 or Tap-2, the reduced expression of class I molecules on the surface of lymphocytes from diabetes-prone female NOD mice was normalized by incubation at low temperatures or by exposure to class I allele-specific peptides. As would be expected for cells that express surface class I molecules not associated with peptide, female NOD lymphocytes were resistant to lysis by class I-restricted, peptide-specific cytotoxic T lymphocytes. Furthermore, the rate of class I exit from the endoplasmic reticulum of lymphocytes from female NOD mice was delayed as demonstrated by delayed glycosylation. Male NOD mice, which are not prone to diabetes, lacked these functional defects in class I assembly and had near-normal levels of Tap-1 mRNA and exhibited normal density of class I epitopes that were peptide filled. These results are consistent with the possibility that the rare Tap-1b allele is associated with a quantitative defect in Tap-1 expression that influences disease course.