Noggin signaling from Xenopus animal blastomere lineages promotes a neural fate in neighboring vegetal blastomere lineages.

In Xenopus, localized factors begin to regionalize embryonic fates prior to the inductive interactions that occur during gastrulation. We previously reported that an animal-to-vegetal signal that occurs prior to gastrulation promotes primary spinal neuron fate in vegetal equatorial (C-tier) blastomere lineages. Herein we demonstrate that maternal mRNA encoding noggin is enriched in animal tiers and at low concentrations in the C-tier, suggesting that the neural fates of C-tier blastomeres may be responsive to early signaling from their neighboring cells. In support of this hypothesis, experimental alteration of the levels of Noggin from animal equatorial (B-tier) or BMP4 from vegetal (D-tier) blastomeres significantly affects the numbers of primary spinal neurons derived from their neighboring C-tier blastomeres. These effects are duplicated in blastomere explants isolated at cleavage stages and cultured in the absence of gastrulation interactions. Co-culture with animal blastomeres enhanced the expression of zygotic neural markers in C-tier blastomere explants, whereas co-culture with vegetal blastomeres repressed them. The expression of these markers in C-tier explants was promoted when Noggin was transiently added to the culture during cleavage/morula stages, and repressed with the transient addition of BMP4. Reduction of Noggin translation in B-tier blastomeres by antisense morpholino oligonucleotides significantly reduced the efficacy of neural marker induction in C-tier explants. These experiments indicate that early anti-BMP signaling from the animal hemisphere recruits vegetal equatorial cells into the neural precursor pool prior to interactions that occur during gastrulation.     

Association of the envelope glycoproteins of influenza virus with liposomes--a model study on viral envelope assembly.

Envelope glycoproteins of virus N (an avian influenza virus) were artificially associated with liposomes, using octylglucoside as detergent which could be readily removed by dialysis. The prepared liposomes, about 0.1-1 μm in diameter, contained specific hemagglutinin and neuraminidase activities. The total amounts of proteins incorporated into liposomes were about the same irrespective of the lipid composition. Similarly, the neuraminidase activity of liposomes remained unchanged by altering lipids. However, the hemagglutinating and cell-adsorbing properties of liposomes varied greatly depending on the composition of lipids. As both lipid and protein components can be altered, the present system may be elaborated for the study of protein-lipid interactions and functions of viral membranes.     

Rh proteins vs Amt proteins: an organismal and phylogenetic perspective on CO2 and NH3 gas channels.

Rh (Rhesus) proteins are homologues of ammonium transport (Amt) proteins. Physiological and structural evidence shows that Amt proteins are gas channels for NH(3), but the substrate of Rh proteins, be it CO2 as shown in green alga, or NH3/NH4+ as shown in mammalian cells, remains disputed. We assembled a large dataset generated of Rh and Amt to explore how Rh originated from and evolved independently of Amt relatives. Analysis of this rich data implies that Rh was split from Amt first to emerge in archaeal species. The Rh ancestor underwent divergence and duplication along speciation, leading to neofunctionalization and subfunctionalization of the Rh family. The characteristic organismal distribution of Rh vs. Amt reflects their early separation and subsequent independent evolution: they coexist in microbes and invertebrates but do not in fungi, vascular plants or vertebrates. Rh gene-duplication was prominent in vertebrates: while epithelial RhBG/RhCG displayed strong purifying selection, erythroid Rh30 and RhAG experienced different episodes of positive selection in each of which adaptive evolution occurred at certain time points and in a few codon sites. Mammalian Rh30 and RhAG were subject to particularly strong positive selection in some codon sites in the lineage from rodents to human. The grounds of this adaptive evolution may be driven by the necessity to increase the surface/volume ratio of biconcave erythrocytes for facilitative gas diffusion. Altogether, these results are consistent with Rh proteins not being the orthologue of Amt proteins but having gained the function for CO2/HCO3- transport, with important roles in systemic pH regulation.     

大鼠内毒素休克肝线粒体Ca^2＋,Mg^2＋含量变化与线粒体损伤

本文在大鼠内毒素休克模型上，观察了肝线粒体结构和功能与Ｃａ＾２＋，Ｍｇ＾２＋含量变化的关系。结果发现：休克动物肝组织和线粒体的Ｃａ＾２＋浓度升高，Ｍｇ＾２＋浓度下降与正常对照组相比有非常显著性差异；用图像分析仪定量分析显示线粒体结构明显受损，线粒体标志酶之一－琥珀酸脱氢酶（ＳＤＨ）活性明显下降，本文认为组织和线粒体内Ｍｇ＾２＋／Ｃａ＾２＋比值下降是休克细胞不可逆损伤重要因素之一。     

恶性疟原虫抗原基因在鼠伤寒沙门氏菌中的表达及免疫原性的初步鉴定

将人工合成的恶性疟原虫杂合７４肽抗原基因克隆到表达载体ｐＷＲ４５０－１中，获得了重组质粒ｐＷＲＣ，将其先转化到减毒伤寒沙门氏菌ＬＢ５０００修饰后，再转化到ＳＬ３２６１，得到重组减毒鼠伤寒沙门氏菌ＳＬ３２６１（ｐＷＲＣ）。ｐＷＲＣ在ＳＬ３２６１中以β－半乳糖苷酶－杂合多肽抗原Ｃ融合蛋白（ＧＺ－Ｃ）形式表达，表达量约占菌体蛋白总量的１１．３％．Ｗｅｓｔｅｒｎｂｌｏｔ及免疫双扩散显示ＧＺ－Ｃ可与兔抗ＧＺ－Ｃ抗原的免疫血清发生特异反应。ＧＺ－Ｃ识别兔抗ＧＺ－Ｃ及鼠抗恶性疟原虫抗血清的ＥＬＩＳＡ滴度分别为１：３２００及１：５１２０。初步结果表明ＳＬ３２６１（ｐＷＲＣ）表达的ＧＺ－Ｃ具有抗原性。连续传代ＳＬ３２６１（ｐＷＲＣ）未见质粒ｐＷＲＣ丢失及对宿主有明显的毒性。     

Reconstruction of 4-MV bremsstrahlung spectra from measured transmission data

Transmission data for 4-MV bremsstrahlung beams have been measured with a combination of lead and aluminum attenuators. From these data, the original energy spectra have been reconstructed using an iterative least-squares technique, previously evaluated by simulation studies. The spectra on the central axis for three similar 4-MV linear accelerators indicated no significant differences. When studying the spectra at 5 degrees and 9 degrees off the central axis, that at 9 degrees showed the expected increase of low-energy photons. All these spectra showed a maximum photon energy of 4.5 +/- 0.2 MeV. When the magnetron power was reduced, the spectrum on the central axis shifted to lower energies and the maximum photon energy decreased to 3.5 +/- 0.2 MeV. The result of this experimental study confirms the conclusions from the previous stimulation, that the numerical technique for analysis of transmission data can accurately represent 4-MV bremsstrahlung spectra and detect differences in energy distribution with changes in machine tuning and position in the radiation field for a 4-MV bremsstrahlung beam.     

A new haplogroup pattern displayed in Fujian Han in China

Human Y-chromosomal binary polymorphisms have been considered to preserve the paternal genetic legacy and provide evidence on human evolution and the genetic relationships among and demographic history of different populations. To reveal the genetic origin and immigration of the Fujian Han, 13 binary markers on the Y chromosome were used to screen Fujian Han by allele-specific polymerase chain reaction. The results indicated that the M₉G marker was highly prevalent (96.20%), suggesting a significant genetic drift. In addition, M₁₂₂C frequency was only 22.78%, and M₄₅A and M₁₀₃T were default. The distinctive haplogroup frequencies (H₁, H₅, and H_6/7/8) imply that the haplogroup pattern is a relatively ancestral and interim type. Received: October 13, 2001 / Accepted: December 3, 2001     

Covalent crosslinking of myosin subfragment-1 and heavy meromyosin to actin at various molar ratios: Different correlations between ATPase activity and crosslinking extent

Summary This paper describes a systematic study of crosslinking of skeletal muscle myosin subfragment-1 (S1) and heavy meromyosin (HMM) to F-actin in the rigor state with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). We followed the time courses of S1 or HMM head crosslinking at various actin:S1 or actin:HMM head molar ratios and the resulting superactivation of ATPase activity. The ATPase activity of the covalent complexes was measured at 0.5 M KCl, where the covalent complexes retain superactivated ATPase activity but the activity of uncrosslinked myosin heads is not activated by actin. S1 crosslinking was slowest at the actin:S1 molar ratio of 11, but faster at larger molar ratios, where more than 80% of added S1 could be crosslinked to actin. In spite of the dependence of crosslinking rate on actinS1 ratio, there were two linear correlations between ATPase activity and the extent of S1 crosslinking to actin: one for S1 crosslinked to actin at actinS1 molar ratios more than 2.71 and the other for S1 crosslinked at a molar ratio of 11. Extrapolation of the former correlation line to 100% crosslinked S1 gave an ATPase activity of 39 s^–1 for actin-S1 covalent complex at 25 °C, whereas that of the other correlation line gave 21 s^–1. The latter smaller activity suggests that the interface between actin and S1 in their rigor complexes at a molar ratio of 11 is different from that at molar ratios of more than 2.71. The acto-HMM crosslinking rate depended on the ratio of actin to HMM head, like that of S1 crosslinking to actin. The ATPase activity of crosslinked actin-HMM was, unlike that of actin-S1 covalent complexes, bell-shaped as a function of the crosslinked heads, but chymotryptic conversion of HMM to S1 in the covalent complexes made the bell-shaped characteristics disappear and increased the activity close to that of actin-Sl covalent complexes. These results indicate that some physical constraint imposed on myosin heads suppresses the actin-activated ATPase activity of HMM crosslinked to actin.