The Fertilization and Early Development of Embryo and Endosperm in Stevia rebaudiana Bertani

The mature embryo sac is surrounded by endothelium tapetum. It is composed or an egg apparatus, one central cell with secondary nucleus, and 1–6 antipodal cells. About the 6th hour after pollination, female and male nuclei fuse with each other. The syngamy occurred almost simultaneously with the fusion of an other sperm nucleus and the secondary nucleus, but the velocity of the latter is faster than that of the syngamy. The fertilization of Stevia rebaudiana Bertani belongs to the premitotic type. About the 8th hour after pollination, primary endosperm nucleus is in mitosis, its dividing orientation may parallel or at right angle to the long axis of the embryo sac, and gives rise to two initial endosperm cells. The first five divisions of the endosperm cells are of synchronism. At the stage of heart-shaped embryo, the endosperm cells show the signs of digestion and absorbed. The endosperm development is of the cellular type. About the 10th hour after pollination, zygote divides for the first time. The division of the zygote is always transverse. The embryo development conforms to the Asterad type.     

Protein-ligand interactions measured by 15N-filtered diffusion experiments

NMR diffusion coefficient measurements have been shown to be sensitive to the conformational and oligomeric states of proteins. Recently, heteronuclear-filtered diffusion experiments have been proposed [Dingley et al. (1997) J. Biomol. NMR, 10, 1–8]. Several new heteronuclear-filtered diffusion pulse sequences are proposed which are shown to have superior sensitivity to those previously proposed. One of these new heteronuclear-filtered diffusion experiments has been used to study the binding of an SH3 domain to a peptide. Using this system, we show that it is possible to measure binding constants from diffusion coefficient measurements.     

Jumbled spine and ribs (Jsr): a new mutation on mouse Chromosome 5

Jumbled spine and ribs (Jsr) is an autosomal dominant mutation that results in malformation of the axial skeleton. The vertebrae of mutant mice (Jsr/+) are all shorter than those of normal mice (+/+) in the inbred line and show various abnormalities. In addition, several ribs are fused at their proximal region because of fusion of thoracic vertebrae. In this study, we localized the Jsr mutation on distal Chromosome (Chr) 5 and constructed a high-resolution map. Chromosomal mapping was performed with an inter-subspecific backcross of (CKH-Jsr/+× MOG) F₁ carrying the Jsr allele and CKH-+/+. The predicted gene order around Jsr was determined to be cen–(Epo, Pdgfa, D5Mit31, D5Mit374)–(Jsr, Nfe2u, D5Mit99, D5Mit247, D5Mit284, D5Mit292, D5Mit327)–D5Mit328–tel. Subsequently, high-resolution mapping concluded the Jsr localization to be cen–Nfe2u–1.0cM–Jsr–0.2cM–D5Mit247,292–tel. Jsr/Jsr homozygotes are alive, as the mutation is not lethal. Based on histological analysis of mutant embryos, Jsr is hypothesized to be caused by abnormal development of primordial cells in the axial skeleton. Received: 1 June 1998 / Accepted: 15 October 1998     

河南省封丘农田杂草类型的初步研究

采用聚类分析的方法,研究阐明在气候差异不明显的冲积平原区,农田杂草类型和相应的土壤类型(相当于土属)有明显的相关性。在划分旱地农田杂草类型时,环境条件的差异比栽培作物具有更重要的指示意义。由于杂草多为广布种,采用聚类分析的方法,比单纯用优势种能够更客观地划分杂草类型。 根据实地观测,指出了封丘地区危害严重的主要杂草种类和危害时间,以及不同环境条件下杂草的分布和危害程度,这对于农业生产上杂草的防除工作有一定指导意义。     

Apoptosis during bone-like tissue development in vitro

We present evidence of cell death by apoptosis during the development of bone-like tissue formation in vitro. Fetal rat calvaria-derived osteoblasts differentiate in vitro, progressing through three stages of maturation: a proliferation period, a matrix maturation period when growth is downregulated and expression of the bone cell phenotype is induced, and a third mineralization stage marked by the expression of bone-specific genes. Here we show for the first time that cells differentiating to the mature bone cell phenotype undergo programmed cell death and express genes regulating apoptosis. Culture conditions that modify expression of the osteoblast phenotype simultaneously modify the incidence of apoptosis. Cell death by apoptosis is directly demonstrated by visualization of degraded DNA into oligonucleosomal fragments after gel electrophoresis. Bcl-X_L, an inhibitor of apoptosis, and Bax, which can accelerate apoptosis, are expressed at maximal levels 24 h after initial isolation of the cells and again after day 25 in heavily mineralized bone tissue nodules. Bcl-2 is expressed in a reciprocal manner to its related gene product Bcl-X_L with the highest levels observed during the early post-proliferative stages of osteoblast maturation. Expression of p53, c-fos, and the interferon regulatory factors IRF-1 and IRF-2, but not cdc2 or cdk, were also induced in mineralized bone nodules. The upregulation of Msx-2 in association with apoptosis is consistent with its in vivo expression during embryogenesis in areas that will undergo programmed cell death. We propose that cell death by apoptosis is a fundamental component of osteoblast differentiation that contributes to maintaining tissue organization. J. Cell. Biochem. 68:31–49, 1998. © 1998 Wiley-Liss, Inc.     

Amino acids and their roles in tumor immunotherapy of breast cancer

Breast cancer is the most commonly diagnosed cancer among women. The primary treatment options include surgery, radiotherapy, chemotherapy, targeted therapy and hormone therapy. The effectiveness of breast cancer therapy varies depending on the stage and aggressiveness of the cancer, as well as individual factors. Advances in early detection and improved treatments have significantly increased survival rates for breast cancer patients. Nevertheless, specific subtypes of breast cancer, particularly triple-negative breast cancer, still lack effective treatment strategies. Thus, novel and effective therapeutic targets for breast cancer need to be explored. As substrates of protein synthesis, amino acids are important sources of energy and nutrition, only secondly to glucose. The rich supply of amino acids enables the tumor to maintain its proliferative competence through participation in energy generation, nucleoside synthesis and maintenance of cellular redox balance. Amino acids also play an important role in immune-suppressive microenvironment formation. Thus, the biological effects of amino acids may change unexpectedly in tumor-specific or oncogene-dependent manners. In recent years, there has been significant progress in the study of amino acid metabolism, particularly in their potential application as therapeutic targets in breast cancer. In this review, we provide an update on amino acid metabolism and discuss the therapeutic implications of amino acids in breast cancer.     

Nitric oxide inducing function and intracellular movement of chicken interleukin-18 in cultured cells

To evaluate the characteristics of chicken interleukin-18 （ChIL-18） in different forms in vitro, the ChIL-18 full-length gene （ChIL-18-F） and the ChIL-18 presumed mature protein gene （ChIL-18-M） were cloned and inserted into the eukaryotic expression vector pCI, to construct recombinant pCI-ChIL-18-F and pCI-ChIL-18-M. The recombinant plasmids were then transferred into chicken splenic lymphocytes （CSLs）. Western blot showed that ChIL-18-F, with a molecular weight of 23.0 kDa, was produced in CSLs transfected by pCI-ChIL-18-F; ChIL-18-M, with a molecular weight of 19.5 kDa, was produced in CSLs transfected by pCI-ChIL-18-M. The nitric oxide （NO） level in the transfected CSLs and the culture medium at different time points was further examined under confocal microscopy using 4,5-diaminofluorescein staining. The results showed that both pCI-ChIL-18-F and pCI-ChIL-18-M groups showed significant increase in intracellular and extracellular NO production compared with pCI transfected control cells. These results suggest that both ChIL- 18-F and ChIL- 18-M could stimulate NO secretion in CSLs. To characterize the intracellular distribution of ChIL-18, ChIL-18-F and ChIL-18-M were each fused to the enhanced green fluorescent protein gene, and expressed in Vero cells. The results showed that the ChIL-18-F tended to the membranous region in Veto cells, while ChIL- 18-M did not. This indicates that the N-terminal 27 amino acid peptide helped ChIL-18 target to Vero cell membranes.     

Southeast Asian biodiversity: an impending disaster

Southeast Asia has the highest relative rate of deforestation of any major tropical region, and could lose three quarters of its original forests by 2100 and up to 42% of its biodiversity. Here, we report on the current state of its biota and highlight the primary drivers of the threat of extinction now faced by much of the unique and rich fauna and flora of the region. Furthermore, the known impacts on the biodiversity of Southeast Asia are likely to be just the tip of the iceberg, owing to the paucity of research data. The looming Southeast Asian biodiversity disaster demands immediate and definitive actions, yet such measures continue to be constrained by socioeconomic factors, including poverty and lack of infrastructure. Any realistic solution will need to involve a multidisciplinary strategy, including political, socioeconomic and scientific input, in which all major stakeholders (government, non-government, national and international organizations) must participate.     

Amylin-induced suppression of ANP secretion through receptors for CGRP1 and salmon calcitonin

Amylin cosecretes with insulin from pancreatic beta-cells and shows high sequence homology with CGRP, adrenomedullin, and salmon calcitonin. This study aimed to investigate the effect of amylin on the atrial hemodynamics and ANP release from rat atria and to identify its receptor subtypes. Isolated perfused left atria from either control or streptozotocin-treated rats were paced at 1.3 Hz. The concentration of ANP was measured by radioimmunoassay and the translocation of ECF was measured by [3H]-inulin clearance. Rat amylin increased atrial contractility and suppressed the release of ANP. Rat CGRP showed similar effects but was approximately 300-fold more potent than amylin. Pretreatment with receptor antagonist for CGRP1 [rat alpha-CGRP (8-37)] or salmon calcitonin [acetyl-(Asn30, Tyr32)-calcitonin(8-32), (AC 187)] blocked the suppressive effect of ANP release and the positive inotropic effect by rat amylin. However, receptor antagonists for amylin [amylin (8-37), acetyl-amylin] did not block those effects. Amylin (8-37), acetyl-amylin, or rat alpha-CGRP (8-37) alone accentuated the release of ANP with no changes in atrial contractility. The effect of rat amylin and rat amylin (8-37) on the ANP release was attenuated in streptozotocin-treated rats. We suggest that amylin suppressed ANP release with increased atrial contractility through receptors for CGRP1 and salmon calcitonin and the attenuation of amylin and its antagonist on ANP release from streptozotocin-treated rat atria may be due to the downregulation of amylin receptor.