Activation of murine T cells by toxic shock syndrome toxin-1. The toxin-binding structures expressed on murine accessory cells are MHC class II molecules

Toxic shock syndrome toxin-1 (TSST-1)-binding structures present on murine lymphoid tissues were investigated by using 125I-TSST-1. T-depleted C57BL/6 spleen cells incubated with TSST-1 for 3 h at 0 degree C were mitogenic to splenic T cells, indicating that the former cells bind and present TSST-1 to T cells. TSST-1-binding activity was observed in C57BL/6 splenic B cells and L cells transfected with I-Ab genes, but not in splenic T cells and control L cells. Scatchard plot analysis showed that these B cells and transfectants bound TSST-1 with similar binding affinity. SDS-PAGE analysis showed that lysates of C57BL/6 spleen cells and the I-Ab-positive transfectants contain a single band which bound TSST-1 and comigrated with I-Ab heterodimers. TSST-1-binding activity observed clearly in C57BL/6. BALB/c, and C3H/HeN spleen cells and L cells transfected with I-Ab or I-Ak genes was not reduced by paraformaldehyde fixation. Binding of 125I-TSST-1 to the three spleen cells was markedly reduced by anti-I-A antibodies, but not by anti-I-E antibodies. C57BL/6, C3H/HeN, and (C3H/HeN x C57BL/6) F1 T cells were activated by TSST-1 to proliferate and produce IL-2 in the presence of FT6.2 cells, LT1-30-3 cells and either of them, respectively, but not in the presence of control L cells. These results indicate that I-A molecules function as the structures via that accessory cells directly bind TSST-1 on the cell surface and present a triggering signal of TSST-1 to T cells.     

心肌细胞间的电耦联

心脏是由无数个独立的心肌细胞通过缝隙连接形成的一个功能性合胞体。心肌细胞间的电耦联是心脏“全或无”性动作电位传导和机械收缩的先决条件。缺氧、缺血、药物、细胞内外离子浓度的改变以及激素等因素可直接或间接地影响心肌细胞间的电耦联,从而导致心脏功能的改变。     

向日葵离体孤雌生殖的超微结构研究

本文是研究未受精胚珠培养诱导的孤雌生殖过程超微结构变化的首次报道。向日葵(Heliaanthus annuus L.)的卵细胞在离体条件下被激活,发生细胞核移位、极性丧失、细胞器增多并转变成活动状态、液泡化程度增大、合点端形成细胞壁等一系列变化,预示即将启动孤雌生殖。孤雌生殖的原胚具有若干显著特征,如极性颠倒、有自体吞噬活动、壁的自由生长、游离核分裂等。对这些现象作了初步的讨论。     

Characterization of a 56-kb plasmid of Erwinia amylovora Ea322: its noninvolvement in pathogenicity

A plasmid from Erwinia amylovora strain Ea322, pCPP60, was studied for its involvement in the phytopathogenicity of this strain. Eviction through incompatibility and curing with acridine orange did not affect the pathogenic capability of Ea322. The plasmid was characterized as self-transmissible with a narrow host range. Hybridization of its origin of replication with plasmids of different incompatibility groups revealed affiliation with IncF. The exact subgroup was not determined, although it does not belong to IncFI, IncFII, IncFIV, or IncFV. A sequence of 800 bp, required for conjugation in cis, was cloned in pUC9. A "miniplasmid" containing the origin of replication in a 1.2-kb sequence was constructed. Its high copy number was in contrast with the stringently controlled copy number of the native plasmid of one to three copies per chromosome equivalent.     

Variability of entrainment of cohesive sediments in freshwater

Estimates of sediment entrainment are required for models of particle transport in lakes and estuaries but are difficult to make because of the multiplicity of factors affecting cohesiveness of surficial sediments. We present results of sediment resuspension studies performed in an annular flume calibrated with laser-Doppler velocimetry. In our experiments, using sediments collected from two sites in the R. Raisin which flows into L. Erie and from one site in the western basin of L. Erie near the mouth of the R. Raisin, we applied shear stresses at the sediment-water interface in steps from 2 to 12 dyne/cm². Percent water content at the surface of the sediments was either 77 or 74%, and trials were run with and without oxygenating the water overlying the sediments. Entrainment rates as a function of shear stress at the sediment-water interface were best described by a power-law relationship. All but 14% of the variability in the power law expression was due to shear stress and percent water content; the variability not accounted for was due to differences in particle size distributions, chemical properties, and biological activity in the sediments.     

Adherence Patterns and DNA Probe Types of Escherichia coli Isolated from Diarrheal Patients in China

One hundred and seventy-two strains of Escherichia coli isolated from diarrheal patients in Beijing, P. R. China, were analyzed for plasmid DNA profile, HEp-2 cell adherence ability and reactivity to 10 previously described DNA probes. They had not been recognized as pathogenic E. coli in China. Of the 110 strains tested, 76 (69%) contained one or multiple large plasmids. Of the 71 strains with the large plasmids 64 could adhere to HEp-2 cells. Of the 172 strains, 102 (59.3%) were hybridized with at least one of the 10 probes. Of those, seven strains hybridized with enteroaggregative E. coli (EAggEC) probe. Their serotypes were O128 (two strains), O6 (one strain), and O111 (one strain). Three strains were untypable. Six and three strains were hybridized with enteropathogenic E. coli (EPEC) attaching and effacing genes (eae) or EPEC adherence factor (EAF) probe, respectively. Two non-O157: H7 strains hybridized with enterohemorrhagic E. coli (EHEC) probe. Seventy-two strains (41.9%) hybridized with shiga-like toxin 2 or 1 (SLT2 or SLT1) probes. Among the SLT1 or SLT2 probe-positive strains, 54 hybridized with invasive (INV) plasmid probe developed for identification of enteroinvasive E. coli (EIEC) and Shigella species. The INV and SLT probe-positive strains might represent a new variety of verotoxin-producing E. coli (VTEC).     

Elongation factor 1α genes of the red alga Porphyra purpurea include a novel, developmentally specialized variant

The life cycle of the red alga Porphyra purpurea alternates between two morphologically distinct phases: a shell-boring, filamentous sporophyte and a free-living, foliose gametophyte. From a subtracted cDNA library enriched for sporophyte-specific sequences, we isolated a cDNA encoding an unusual elongation factor 1 (EF-1) that is expressed only in the sporophyte. A second EF-1 gene that is expressed equally in the sporophyte and the gametophyte was isolated from a genomic library. These are the only EF-1 genes detectable in P. purpurea. The constitutively expressed gene encodes and EF-1 very similar to those of most eukaryotes. However, the sporophyte-specific EF-1 is one of the most divergent yet described, with nine insertions or deletions ranging in size from 1 to 26 amino acids. This is the first report of a developmental stage-specific EF-1 outside of the animal kingdom and suggests a fundamental role for EF-1 in the developmental process.     

Characterization of a Kinesin-Related Gene ATSV, within the Tuberous Sclerosis Locus (TSC1) Candidate Region on Chromosome 9Q34

In the search for candidate genes for the tuberous sclerosis (TSC1) disease locus on chromosome 9q34, we have isolated an overlapping series of 22 plasmid and phage cDNA clones covering nearly 7 kb and with an open reading frame of 5070 bp encoding a protein of 1690 amino acids. The putative protein product is a member of the kinesin superfamily and is homologous to the mouse KIF1A and theCaenorhabditas elegansunc-104 genes. Both KIF1A and unc-104 function in the anterograde axonal transport of synaptic vesicles. The human homolog is therefore termed H-ATSV (axonal transporter of synaptic vesicles, HGMW-approved nomenclature ATSV) Screening of DNA from 107 tuberous sclerosis patients and 80 unaffected individuals with H-ATSV cDNA probes by pulsed-field gel electrophoresis/Southern blotting following digestion by rare-cutting methylation-sensitive restriction enzymes showed variant banding patterns in three patients with tuberous sclerosis. However, further analysis indicated that these variant fragments represent a rare polymorphism probably associated with methylation of clustered restriction sites. There is no evidence to support H-ATSV as a candidate gene for TSC1.