The use of thioesterase II as a rat mammary epithelial cell-specific marker

The avidin-biotin-peroxidase complex immunoperoxidase technique was employed to determine the intercellular distribution of thioesterase II in rat mammary glands. This enzyme is responsible for shifting the product specificity of the fatty-acid synthetase enzyme complex from long to medium chain fatty acids. Thioesterase II was found exclusively in the cells lining the lumen of the ductal and alveolar structures in glands from mature virgin (150 days old) and pregnant rats. The ductal cell staining intensity was considerably less than that of the alveolar cells in the mature virgin rat glands. No immunoreactive thioesterase II was found in the stromal, adipose, vascular, or myoepithelial components of the gland in the developmental stages examined. In the glands from immature virgin rats (40-45 days old) thioesterase II was again found only in the epithelial cells lining the lumen of the ductal and end-bud structures although this layer was usually more than one cell thick. Quantitative determination of thioesterase II activity in cytosol preparations revealed similar levels in mammary fragments from enzymatically-dissociated glands obtained from mature virgins and in end buds derived from immature virgins, but somewhat higher levels in mammary structures derived from late-pregnant animals. These immunohistological and biochemical results demonstrate thioesterase II's usefulness as a mammary epithelial cell-specific marker.     

根结线虫天敌真菌的筛选研究初报

从土壤和病株上分离到10个线虫的天敌真菌菌株,其中有三个菌株较有希望,烛台霉属(Candelabrello sp.)一个。孤孢属(Monacrosporium spp.)两个,菌株代号分别为CN_7;CN_(?)和CN_5。 据试验:CN_7较好,菌丝体生长的温度范围是20～33℃,最适宜的温度范围是25～30℃,以式捕捉环捕食线虫,对培养基选择性不强,最适宜的pH值是6.0～7.5,但在pH4.5～8.0都能进收缩行捕捉,捕捉器官形成量多,捕虫势强且稳定,在水中也能形成捕捉环并捕食线虫。     

自病人气管灌洗物中分离出一株嗜肺性军团杆菌

本文报道了用自制的蓝藻军团杆菌选择性培养基从病人气管灌洗物中分离到一株嗜肺性军团杆菌(Legionella pneumophila)并与BCYE及硝酸铁琼脂平板等培养基作了比较,发现该菌在蓝藻军团杆菌选择性培养基上生长最好。生化、动物试验;细菌学、血清学的鉴定和诊断及临床治疗效果观察均与军团病杆菌(LDB)的鉴定标准相符合,证明经分离得的是一株嗜肺性军团杆菌血清6型菌株。     

A general method for highly selective cross-linking of unprotected polypeptides via pH-controlled modification of N-terminal alpha-amino groups

A method is described for the highly selective modification of the alpha-amino groups at the N-termini of unprotected peptides to form stable, modified peptide intermediates which can be covalently coupled to other molecules or to a solid support. Acylation with iodoacetic anhydride at pH 6.0 occurs with 90-98% selectivity for the alpha-amino group, depending on the N-terminal residue (as shown with a series of model hexapeptides containing a competing Lys residue). Although Cys residues must be protected (reversibly or irreversibly) before the anhydride reaction, there are no detectable side reactions of the alpha-amino moiety--of the reagent or of modified peptide--with the side chains of His, Met, or Lys. The reaction works well in denaturants, so that inhibitory effects of noncovalent structure can be minimized. In a second step the iodoacetyl-peptide can be reacted with a thiol group on a protein, on a solid chromatography matrix, on a spectroscopic probe, etc. This is illustrated by reaction of a series of N alpha-iodoacetyl-peptides with murine interferon-gamma, which contains a C-terminal Cys residue. Data are presented which suggest that this iodoacetic anhydride scheme is superior in selectivity for alpha-amino groups to conventional chemical approaches to cross-linking such as use of 2-iminothiolane or N-hydroxysuccinimide-activated carboxylic acid esters. The reaction is ideally suited for modifying peptide fragments, as pure species or as mixtures, derived from proteolytic or chemical fragmentation of proteins. Furthermore, polypeptides synthesized biosynthetically, for example via recombinant DNA techniques, can be cross-linked in this way.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in lung mechanics and reactivity with age after viral bronchiolitis in beagle puppies

We measured changes with growth in lung function and airway reactivity after acute canine parainfluenza virus type 2 (CPI2, n = 5), canine adenovirus type 2 (CAV2, n = 7), and sequential CAV2-CPI2 (n = 6) infections or no infection (controls, n = 6) in beagle puppies (age approximately 79 days). In the CPI2 and CAV2 groups, a lower respiratory illness developed by day 3 postinfection with clinical recovery by day 14. In the CAV2-CPI2 group, puppies were inoculated initially with CAV2 and 12 days later with CPI2. In this group, illness persisted until day 14 after infection with CPI2. Lung resistance (RL), dynamic (Cdyn) and static (Cst) lung compliance, functional residual capacity (FRC), and responsiveness to aerosolized histamine were measured before infection and at periodic intervals until 239 +/- 43 days of age. Lung function data were analyzed using a longitudinal random effects model. In all groups, FRC, Cst, and Cdyn increased with age. In all infected groups, the regression slopes for Cdyn were steeper than in controls. RL decreased linearly with age without group slope differences. Histamine reactivity increased with age, but there were no differences in slope among groups. Lung pathological studies showed areas of obliterative bronchiolitis and chronic small airways inflammation particularly in the CAV2 and CAV2-CPI2 groups. Thus, viral bronchiolitis produces chronic small airways inflammation in beagle puppies and alters the changes in lung function occurring with growth. Histamine reactivity increases with age and is not modified by viral infection.     

Cloning of the blasticidin S deaminase gene (BSD) from Aspergillus terreus and its use as a selectable marker for Schizosaccharomyces pombe and Pyricularia oryzae

Aspergillus terreus produces a unique enzyme, blasticidin S deaminase, which catalyzes the deamination of blasticidin S (BS), and in consequence confers high resistance to the antibiotic. A cDNA clone derived from the structural gene for BS deaminase (BSD) was isolated by transforming Escherichia coli with an Aspergillus cDNA expression library and directly selecting for the ability to grow in the presence of the antibiotic. The complete nucleotide sequene of BSD was determined and proved to contain an open reading frame of 393 bp, encoding a polypeptide of 130 amino acids. Comparison of its nulceotide sequence with that of bsr, the BS deaminase gene isolated from Bacillus cereus, indicated no homology and a large difference in codon usage. The activity of BSD expressed in E. coli was easily quantified by an assay based on spectrophotometric recording. The BSD gene was placed in a shuttle vector for Schizosaccharomyces pombe, downstream of the SV40 early region promoter, and this allowed direct selection with BS at high frequency, following transformation into the yeast. The BSD gene was also employed as a selectable marker for Pyricularia oryzae, which could not be transformed to BS resistance by bsr. These results promise that the BSD gene will be useful as a new dominant selectable marker for eukaryotes.     

Characterization of a strain of cerebral endothelial cells derived from goat brain which retain their differentiated traits after long-term passage

Summary A strain of cerebral endothelial cells was established from isolated cortical microvessels of caprine brain. These cells, which are referred to as ECl cells, can be routinely subcultured to 32 passages without the loss of differentiated morphologic and immunologic traits. The ability to routinely subculture ECl cells is an important asset, given that isolated cerebral endothelial cells in mammals generally lose their differentiated traits after only 2 to 3 passages. ECl cells were shown to contain Factor VIII-related antigen, which is a specific marker for cells of endothelial origin. ECl cells morphologically demonstrated a scarcity of pinocytotic vesicles on their apical surfaces, a lack of trans-cytoplasmic vesicles, and the ability to form in culture confluent monolayers with tight junctional complexes. Therefore, ECl cells possess specific antigenic and ultrastructural features which classify them as being small vessel endothelial cells of the blood-brain barrier type. Cytogenetic evaluation of ECl cells demonstrated a normal female goat 60,XX karyotype and confirmed the apparent non-transformed nature of ECl cells due to the lack of chromosome abnormalities or rearrangements. Using scanning electron microscopy, ECl cells were also shown to form confluent monolayers on mixed nitrocellulose filters, a feature that will enable the development of an in vitro system to study trans-endothelial transport. Given that ECl cells are readily subcultured and grow well on nitrocellulose filters, and that they resemble cerebral endothelium in vivo, it seems evident that ECl cells can be used as a versatile model for the study of blood-brain barrier function, regulation, and pathology.     

Asymmetric effects of daytime and nighttime warming on alpine treeline recruitment

Trees at their upper range limits are highly sensitive to climate change, and thus alpine treelines worldwide have changed their recruitment patterns in response to climate warming. However, previous studies focused only on daily mean temperature, neglecting the asymmetric influences of daytime and nighttime warming on recruitments in alpine treelines. Here, based on the compiled dataset of tree recruitment series from 172 alpine treelines across the Northern Hemisphere, we quantified and compared the different effects of daytime and nighttime warming on treeline recruitment using four indices of temperature sensitivity, and assessed the responses of treeline recruitment to warming-induced drought stress. Our analyses demonstrated that even in different environmental regions, both daytime and nighttime warming could significantly promote treeline recruitment, and however, treeline recruitment was much more sensitive to nighttime warming than to daytime warming, which could be attributable to the presence of drought stress. The increasing drought stress primarily driven by daytime warming rather than by nighttime warming would likely constrain the responses of treeline recruitment to daytime warming. Our findings provided compelling evidence that nighttime warming rather than daytime warming could play a primary role in promoting the recruitment in alpine treelines, which was related to the daytime warming-induced drought stress. Thus, daytime and nighttime warming should be considered separately to improve future projections of global change impacts across alpine ecosystems.     

国产7种乌头属植物的核型研究

本文报道了国产7种乌头属植物（两色乌头（Aconitum alboviolaceum Kom.,牛扁 A.barbartum var.puberulum Ledeb.,蔓乌头A.volubile Pall.,展毛蔓乌头 A.ciliare DC.,北乌头 A.kusnezoffii Reichb.,蒿叶乌头 A.artemisiaefolium Bar.et Skv.,细叶乌头 A.macrorhgnchum Turcz.）的核型。其中展毛蔓乌头、蒿叶乌头和细叶乌头的核型为首次报道。本文还首次指出乌头属中具多年生根状茎的牛扁亚属植物的核型没有明显的二型性,而具二年生块根的乌头正属植物的核型的二型性十分明显。此外还讨论了细叶乌头及展毛蔓乌头的系统位置,认为它们与蔓乌头有较近的亲缘关系。     

新型冠状病毒及泛β冠状病毒广谱中和单抗的研究进展

新型冠状病毒的全球大流行,给人类的生命健康和社会秩序带来了巨大的危害。疫苗、小分子药物及各类抗体药物的研发在遏制新型冠状病毒感染传播、降低重症率和死亡风险上发挥了积极的作用。然而,由于新冠病毒庞大的感染基数及自身易突变的特征,当前已经演化出多种能逃逸疫苗及中和抗体的变异株,显著削弱了抗体的保护效果。研发新型冠状病毒广谱甚至泛β冠状病毒广谱的中和抗体对于未来新冠变异株及其他高致病性β冠状病毒的防治具有重要意义。本文从新型冠状病毒中和抗体的筛选制备策略、作用机制、中和效果及广谱性等方面进行了系统综述,并对当前面临的挑战和未来的发展方向进行了讨论和展望,以期为后续相关研究提供参考。