Spatial distribution of mRNA during pre-fertilization ovule development in Capsella bursa-pastoris

Summary In situ hybridization of sections of the ovary and ovule of Capsella bursa-pastoris with ³H-polyuridylic acid [³H-poly(U)] showed the presence of polyadenylic acid-containing RNA [poly(A) + RNA] in the cells of the placenta and nucellus. During megasporogenesis there was a decrease in ³H-poly(U) binding activity of the nucellar cells concomitant with the appearance of poly(A) + RNA in the integuments. As the typical eight-nucleate embryo sac was formed, ³H-poly(U) binding was not apparent around the quartet of nuclei at the chalazal end, while it persisted at the micropylar end. Both the egg and synergids as well as the chalazal proliferating tissue showed high concentrations of poly(A) + RNA in their cytoplasm. The results suggest a role for transient localizations of poly(A) + RNA during female sporogenesis and gametogenesis in C. bursa-pastoris.     

Localization of bindin expression during sea urchin spermatogenesis

Expression of the bindin gene was examined in testicular cells of the sea urchin Strongylocentrotus purpuratus. In situ hybridization studies, using an 35S-labeled antisense RNA probe transcribed from a bindin cDNA, reveal that bindin mRNAs are localized in spermatogenic cells displaced towards the lumens of maturing testicular acini. Little or no hybridization is observed in spermatogenic cells displaced towards the perivisceral epithelium or in somatic cells of the testis. A similar localization of the bindin protein itself is observed using a rhodamine-conjugated polyclonal antibody against bindin, which shows a punctate immunofluorescence pattern in late spermatogenic cells. Immunogold labeling of ultrathin sections and electron microscopy reveal that this punctate immunofluorescence is an apparent result of localized deposits of bindin in intracellular vesicles. Through the terminal stages of spermatogenesis, these bindin-containing vesicles apparently fuse to form the single acrosomal vesicle of the mature spermatozoon. These results indicate 1) that bindin mRNAs are transcribed relatively late in spermatogenesis, 2) that bindin is translated soon after production of its mRNA, 3) that bindin quickly associates with intracellular vesicles during or soon after its synthesis, and 4) that these vesicles fuse to form the single acrosomal vesicle during the terminal stage of spermatogenesis.     

Excitatory amino acids: The involvement of second messengers in the signal transduction process

1. Excitatory amino acids (EAA) can activate second messenger systems in addition to a direct gating of ion channels. A discrete coupling between novel EAA receptor subtypes and second messenger systems has been previously proposed. 2. EAAs have been suggested to activate both adenylate and guanylate cyclases and also to induce phosphoinositide (PI) turnover. The increased PI turnover was observed in both central neurons and glia, and a "quisqualate-type" receptor has been most frequently involved, which may differ from the quisqualate receptor previously defined by electrophysiological studies. 3. The roles of EAA-induced calcium influx into neurons and raised intracellular calcium levels are discussed regarding the activation of phosphoinositide turnover. 4. This review examines the data supporting a link between EAA receptors and second messengers and considers whether there is any need for adopting new EAA receptor subtypes. Also, the use of the Xenopus laevis oocyte for expressing EAA receptors and studying any putative links to second messenger systems is discussed.     

Potential regulatory elements of nematode vitellogenin genes revealed by interspecies sequence comparison

Summary The nematode,Caenorhabditis elegans, has a six-member gene family encoding vitellogenins, the yolk protein precursors. These genes are expressed exclusively in the intestine of the adult hermaphrodite. Here we report the cloning of all five members of the homologous gene family from anotherCaenorhabditis species,Caenorhabditis briggsae. Nucleotide sequence analysis of these genes reveals they are about 85% identical to theC. elegans genes in the coding regions. Oveerall similarity is much reduced in noncoding and flanking regions. However, two repeated heptamers, previously identified in the upstream regions of theC. elegans genes, are largely conserved in both location and sequence inC. briggsae. Conservation of certain of these heptamers suggests that proteins bound at these positions may be especially important to promoter function and/or regulation. Comparative sequence analysis also suggests the possibility that the first 70 bases of the vitellogenin mRNAs can be folded into stable secondary structures. Almost all base differences between the two species occur in sequences predicted to be unpaired, suggesting that the ability to form intrastrand base pairs has been selected duringCaenorhabditis evolution.     

Relative deficiency in interferon-γ-secreting CD4+ T cells is strongly associated with poorer COVID-19 vaccination responses in older adults

Although the two-dose mRNA vaccination regime provides protection against SARS-CoV-2, older adults have been shown to exhibit poorer vaccination responses. In addition, the role of vaccine-induced T-cell responses is not well characterised. We aim to assess the impact of age on immune responses after two doses of the BNT162b2 mRNA vaccine, focussing on antigen-specific T-cells. A prospective 3-month study was conducted on 15 young (median age 31 years, interquartile range (IQR) 25–35 years) and 14 older adults (median age 72 years, IQR 70–73 years). We assessed functional, neutralising antibody responses against SARS-CoV-2 variants using ACE-2 inhibition assays, and changes in B and T-cell subsets by high-dimensional flow cytometry. Antigen-specific T-cell responses were also quantified by intracellular cytokine staining and flow cytometry. Older adults had attenuated T-helper (Th) response to vaccination, which was associated with weaker antibody responses and decreased SARS-CoV-2 neutralisation. Antigen-specific interferon-γ (IFNγ)-secreting CD4+ T-cells to wild-type and Omicron antigens increased in young adults, which was strongly positively correlated with their neutralising antibody responses. Conversely, this relationship was negative in older adults. Hence, older adults' relative IFNγ-secreting CD4+ T cell deficiency might explain their poorer COVID-19 vaccination responses. Further exploration into the aetiology is needed and would be integral in developing novel vaccination strategies and improving infection outcomes in older adults.     

Mechanisms of sex determination and X-chromosome dosage compensation

Abnormalities in chromosome number have the potential to disrupt the balance of gene expression and thereby decrease organismal fitness and viability. Such abnormalities occur in most solid tumors and also cause severe developmental defects and spontaneous abortions. In contrast to the imbalances in chromosome dose that cause pathologies, the difference in X-chromosome dose used to determine sexual fate across diverse species is well tolerated. Dosage compensation mechanisms have evolved in such species to balance X-chromosome gene expression between the sexes, allowing them to tolerate the difference in X-chromosome dose. This review analyzes the chromosome counting mechanism that tallies X-chromosome number to determine sex (XO male and XX hermaphrodite) in the nematode Caenorhabditis elegans and the associated dosage compensation mechanism that balances X-chromosome gene expression between the sexes. Dissecting the molecular mechanisms underlying X-chromosome counting has revealed how small quantitative differences in intracellular signals can be translated into dramatically different fates. Dissecting the process of X-chromosome dosage compensation has revealed the interplay between chromatin modification and chromosome structure in regulating gene expression over vast chromosomal territories.     

Kinetics and persistence of cellular and humoral immune responses to SARS‐CoV‐2 vaccine in healthcare workers with or without prior COVID‐19

SARS‐CoV‐2 vaccines are highly efficient against severe forms of the disease, hospitalization and death. Nevertheless, insufficient protection against several circulating viral variants might suggest waning immunity and the need for an additional vaccine dose. We conducted a longitudinal study on the kinetics and persistence of immune responses in healthcare workers vaccinated with two doses of BNT162b2 mRNA vaccine with or without prior SARS‐CoV‐2 infection. No new infections were diagnosed during follow‐up. At 6 months, post‐vaccination or post‐infection, despite a downward trend in the level of anti‐S IgG antibodies, the neutralizing activity does not decrease significantly, remaining higher than 75% (85.14% for subjects with natural infection, 88.82% for vaccinated after prior infection and 78.37% for vaccinated only). In a live‐virus neutralization assay, the highest neutralization titres were present at baseline and at 6 months follow‐up in persons vaccinated after prior infection. Anti‐S IgA levels showed a significant descending trend in vaccinated subjects (p < 0.05) after 14 weeks. Cellular immune responses are present even in vaccinated participants with declining antibody levels (index ratio 1.1–3) or low neutralizing activity (30%–40%) at 6 months, although with lower T‐cell stimulation index (p = 0.046) and IFN‐γ secretion (p = 0.0007) compared to those with preserved humoral responses.     

胜红蓟化感作用研究Ⅶ.胜红蓟素类似物的合成及其对植物与微生物的抑制作用

合成了5种胜红蓟素的结构类似物,将它们与胜红蓟素在对植物和微生物的抑制活性上进行了比较。结果表明,在100mg/l浓度时,对于萝卜和黑麦草两种受体,类似物6－甲酰基－7－甲氧基2,2－二甲基－2H－苯并吡喃和7－羟基－6－甲酰基－3,4－二氢－2,2－二甲基－2H－苯并吡喃较胜红蓟素有更强的抑制作用,尤其是对受体 根长的抑制作用达到显著,这两种类似物同时也具有较强的抗菌活性,在400mg/l浓度下,它们对两种真菌：水稻纹枯病菌和辣椒疫霉病菌的抑制率达到100％;在2000mg/l浓度下,7－羟基－6－甲酰基－3,4－二氢－2,2－二甲基－2H－苯并吡喃还对两种细菌：水稻白叶枯病菌和水稻基腐病菌有较强的抑制作用。研究揭示了构成胜红蓟素基本结构的2,2－二甲基－2H－苯并吡喃对植物无明显抑制作用,对微生物的抑制作用也不强,但当其6位或7位带有活性取代基后,对植物和微生物抑制作用都显著增强。     

寻找mRNA的选择性剪接

在真核生物的基因中,mRNA选择性剪接现象十分普遍。mRNA选择性剪接导致一个基因多转录本的产生,被认为是高等生物增加蛋白质多样性的主要机制,且已发现与许多人类疾病密切相关。发现这些转录本的选择性剪接位点、新的外显子和外显子组合,乃至获得这些剪接变异体的完整克隆,对于基因功能的深入研究十分必要。简要介绍了几种在mRNA水平探索选择性剪接的方法。