Chromatin subunits from baker''s yeast: isolation and partial characterization.

The organization of proteins along DNA in chromatin of Saccharomyces cerevisiae (baker's yeast) was examined by analyzing the DNA and nucleoprotein products obtained after digestion of yeast nuclei with staphylococcal nuclease. Yeast DNA is digested in situ at regularly spaced cleavage sites about 160 base pairs apart. Nucleoprotein fragments were resolved and isolated by centrifugation on linear, 5-20% sucrose gradients. The predominant 11S component appears to be identical to chromatin "subunits" or "nucleosomes" isolated from higher eukaryotes, containing a 150-160 base pair length of DNA and approximately equimolar amounts of four proteins that coelectrophorese with calf histones H2A, H2B, H3, and H4, plus small amounts of three proteins that electrophorese similarly to H1 histones. Thus, the structural organization of the yeast genome is similar to that of more developed organisms, except for the smaller total repeat length. None of the yeast subunit proteins, including the possible H1 proteins, contains cysteine.     

Preparation and partial characterization of a pancreatic cancer-associated glycoprotein expressing CA50.

In our previous study, two antigens associated with pancreatic cancer were prepared from ascites of the patients by using a newly developed affinity chromatography technique; one expressed CA19-9, CA50, Span-1, sialyl SSEA-1, and Dupan-2. This report describes the other part of the antigens, which was scarcely found in normal sera. This antigen was a glycoprotein with a high molecular weight of 1,000,000 in its native state, estimated by size exclusion chromatography on Sephacryl S400. After sodium dodecyl sulfate polyacrylamide gel electrophoresis and blotting analysis, the antigenic activity was observed on the 200-Kd band, and monoclonal antibody of CA50 showed intense reactivity to it. By means of an enzyme immunoassay, CA19-9 determinant was also recognized on it to a lesser extent, although sialyl SSEA-1 and Dupan-2 determinants were scarcely observed. From these observations, the present antigen was considered to be a serum glycoprotein carrying type-1 polylactosamine determinant and differs from previously reported glycoprotein carrying CA19-9 in its insolubility in perchloric acid solution because of its lesser degree of glycosilation. Serum levels of the antigen measured by enzyme-linked immunosorbent assay demonstrated that highly positive rates were observed in 78% of pancreatic cancers, 82% of biliary tract cancers, and 96% of hepatocellular carcinomas.     

Preparation and characterization of submitochondrial fractions from adrenal cells

A method for preparing submitochondrial fractions from adrenocortical cells was developed by adapting a procedure that has been successful with yeast mitochondria. The method is based upon osmotic swelling, sonication and centrifugation in sucrose. The preparation yields highly purified fractions of outer membrane, intermembrane space, inner membrane and a less purified fraction of matrix. Recoveries are good so that 10(7) cells yield approximately 170 micrograms of inner membrane protein and 12 micrograms of outer membrane protein. Electron microscopy shows that the outer membrane fraction consists of vesicles (0.2-0.6 micron diameter) while inner membrane appears as densely packed sheets of membranous material. Two-dimensional polyacrylamide gels (isoelectric focusing followed by electrophoresis) of all the fractions give highly reproducible patterns of protein spots with Coomassie staining. Steroidogenic proteins were found only in inner membrane fractions which were shown to contain cytochrome P-450 C27 side-chain cleavage and P-450 11 beta-hydroxylase together with adrenodoxin and adrenodoxin reductase. Inner membrane catalyzes side-chain cleavage of cholesterol (conversions to pregnenolone) and 11 beta-hydroxylation (DOC----corticosterone) when substrate and NADPH are added. The preparation yields highly purified submitochondrial fractions from Y-1 mouse adrenal tumor cells and from porcine and bovine adrenocortical mitochondria. The method has the virtue of yielding highly purified intermembrane fluid which is not true of other methods for fractionation of adrenal mitochondria. The procedure also yields cleaner preparations of the two membranes than two other published methods currently used to prepare submitochondrial fractions from adrenocortical cells.     

Thyroid regeneration: characterization of clear cells after partial thyroidectomy

Although having the capacity to grow in response to a stimulus that perturbs the pituitary-thyroid axis, the thyroid gland is considered not a regenerative organ. In this study, partial thyroidectomy (PTx) was used to produce a condition for thyroid regeneration. In the intact thyroid gland, the central areas of both lobes served as the proliferative centers where microfollicles, and bromodeoxyuridine (BrdU)-positive and/or C cells, were localized. Two weeks after PTx, the number of BrdU-positive cells and cells with clear or faintly eosinophilic cytoplasm were markedly increased in the central area and continuous to the cut edge. Clear cells were scant in the cytoplasm, as determined by electron microscopy; some retained the characteristics of calcitonin-producing C cells by having neuroendocrine granules, whereas others retained follicular cell-specific features, such as the juxtaposition to a lumen with microvilli. Some cells were BrdU-positive and expressed Foxa2, the definitive endoderm lineage marker. Serum TSH levels drastically changed due to the thyroidectomy-induced acute reduction in T(4)-generating tissue, resulting in a goitrogenesis setting. Microarray followed by pathway analysis revealed that the expression of genes involved in embryonic development and cancer was affected by PTx. The results suggest that both C cells and follicular cells may be altered by PTx to become immature cells or immature cells that might be derived from stem/progenitor cells on their way to differentiation into C cells or follicular cells. These immature clear cells may participate in the repair and/or regeneration of the thyroid gland.     

Properties and characterization of vesicles released by young and old human red cells

S ummary We have presently demonstrated morphologic differences between young and senescent red cells following 18 h of metabolic depletion in vitro . Young and old red cells both form echinocytes, whereas only young cells demonstrated myelin forms or microspheres. Furthermore, vesicles were released in greater quantities into the cell-free supernatant from young cells. Isolated vesicles from both young and old red cells contained lipids, intrinsic membrane proteins (especially band 3), and haemoglobin, and they were also enriched in acetylcholinesterase (AChE). Young cells produced more vesicles than old cells but the composition of the low density vesicles was similar except that haemoglobin-spectrin complex was found exclusively in vesicles from young cells. Oxidation of young red cells prior to metabolic depletion prevented both myelin formation and vesicle release.     

Isolation and partial characterization of a cholesterol-requiring mutant of Chinese hamster ovary cells.

A sterol-requiring mutant has been isolated from mutagenized Chinese hamster ovary cells. This mutant grows normally only when cholesterol is present in the medium. Cell lysis occurs within 3 days in the absence of cholesterol. The frequency of reversion of this mutant to prototrophic growth is low (less than or equal to 10(-6). Whole cell pulse experiments with [14C]acetate or [3H]mevalonate indicate that the rate of synthesis of digitonin-precipitable material is greatly diminished in the mutant cells as compared to that in normal Chinese hamster ovary cells. Enzyme assays in vitro with crude cell extracts show that the biosynthetic conversion of mevalonate to squalene and the conversion of squalene to lanosterol are not impaired in the mutant cells. Gas-liquid chromatographic analyses of radioactive sterol composition after whole cell pulse experiments with [3H]squalene and with [3H]anosterol suggest that the fundamental enzymatic defect of the mutant is at the stage of lanosterol demethylation. When cells were grown in serum-free medium, lanosterol and dihydrolanosterol accumulated intracellularly in the mutant cells before cell lysis occurred; neither of these two intermediary sterols was detected in the wild-type cells grown under the same condition.     

Immunoprecipitation and partial characterization of diphtheria toxin-binding glycoproteins from surface of guinea pig cells.

125I-Labeled membrane glycoproteins that specifically interact with diphtheria toxin and CRM197 protein--but not with diphtheria toxoid, fragment A of diphtheria toxin, or cholera toxin--were detected by use of the lactoperoxidase labeling technique followed by an immunoprecipitation system. These glycoproteins, which adhere to lentil lectin-Sepharose columns, are present on the surface of diphtheria toxin-sensitive guinea pig lymph node cells but are completely lacking on the surface of diphtheria toxin-resistant mouse L cells. The major 125I-labeled glycoprotein that interacts with diphtheria toxin exhibits anomalous behavior, characteristic of glycoproteins, when analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. This demonstration of the biochemical nature of specific diphtheria toxin binding membrane components raises the possibility that the detected components are diphtheria toxin receptors.     

Purification and partial characterization of canine angiotensinogen

A procedure is described to isolate angiotensinogen (renin substrate) from canine plasma. The isolation procedure resulted in an 800-fold purification with a rate of recovery of approximately 12%. The purified protein has a specific activity of 24 micrograms of angiotensin I/mg protein. The amino terminal amino acid sequence of canine angiotensinogen was found to be identical to that of the horse but to differ from that of human and rat angiotensinogens. Canine angiotensinogen was heterogeneous with respect to molecular weight and isoelectric point. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of pure angiotensinogen revealed two closely spaced bands with apparent molecular weights of 58,000 and 56,000. Chromatofocusing showed four isoforms: Peaks of pure angiotensinogen eluted at pH levels of 4.32, 4.23, 4.15, and 4.04. Isoelectric focusing confirmed the presence of four isoforms. Thus, the purification procedure identified two molecular weight forms and four isoforms of canine angiotensinogen. Isolation of the four isoforms will allow their characterization and the study of their physiological significance.     

Purification to homogeneity and partial characterization of cytotoxic lymphocyte maturation factor from human B-lymphoblastoid cells

A cytokine that can synergize with interleukin 2 to activate cytotoxic lymphocytes was purified to homogeneity. The protein, provisionally called cytotoxic lymphocyte maturation factor (CLMF), was isolated from a human B-lymphoblastoid cell line that was induced to secrete lymphokines by culture with phorbol ester and calcium ionophore. The purification method, utilizing classical and high-performance liquid chromatographic techniques, yielded protein with a specific activity of 8.5 x 10(7) units/mg in a T-cell growth factor assay. Analysis of the purified protein by sodium dodecyl sulfate/polyacrylamide gel electrophoresis demonstrated that CLMF is a 75-kDa heterodimer composed of disulfide-bonded 40-kDa and 35-kDa subunits. Determination of the N-terminal amino acid sequences of the two subunits revealed that both subunits are not related to any previously identified cytokine. Purified CLMF stimulated the proliferation of human phytohemagglutinin-activated lymphoblasts by itself and exerted additive effects when used in combination with suboptimal amounts of interleukin 2. Furthermore, the purified protein was shown to synergize with low concentrations of interleukin 2 in causing the induction of lymphokine-activated killer cells.     

Purification and partial characterization of hamster placental lactogen

A radioreceptor assay for PRL-like activity was used to monitor the purification of a lactogenic protein, hamster placental lactogen (haPL), from late pregnant hamster placentae. Investigations of the PRL-like activity in placental extracts demonstrated that haPL is subject to disulfide-related aggregation phenomena that are not observed for mouse PL. By inclusion of 2-mercaptoethanol in the buffers used for purification, monomeric haPL was obtained. A 750-fold purification was achieved by ammonium sulfate precipitation and chromatography on phenyl-Sepharose, TSK diethylaminoethyl-650S, hydroxylapatite, and Sephadex G-100. This procedure yielded 6.2 mg (by dry wt) of purified haPL from 286 g 15-day pregnant hamster placentae, with an overall yield of 20%. The purified haPL has a mol wt of 25,200 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and an isoelectric point of 8.8. haPL is lactogenic as judged by its ability to compete for lactogen binding sites on rabbit mammary gland membranes and to stimulate secretion of alpha-lactalbumin by cultured mouse mammary gland epithelial cells.     

骨桥蛋白的制备及功能研究

目的　探讨骨桥蛋白 (OPN)对血管平滑肌细胞是否具有促黏附及趋化作用。方法　从大鼠源性血管平滑肌细胞的细胞培养基中纯化OPN ,制备家兔抗OPN多克隆抗体。用酶联免疫吸附及迁移分析方法测定OPN对血管平滑肌细胞的影响。结果　骨桥蛋白能够促进血管平滑肌细胞发生黏附 ,且其促黏附功能呈浓度依赖性。黏附率在实验开始后 90～ 1 2 0min区段达到最高。与对照相比 ,OPN刺激血管平滑肌细胞的迁移距离明显增加。结果　骨桥蛋白是血管平滑肌细胞的黏附、迁移活化因子     

Concentration and partial characterization of human salivary gastrone

Summary An inhibitor of gastric-acid secretion has been purified from human saliva and its activity concentrated 30-fold. Inactive material has been removed from saliva by extraction into phenol, by digestion with protease, by heat precipitation, and by prolonged dialysis. The final preparation contained polysaccharide or mucopolysaccharide of molecular weight in excess of 100,000, as well as traces of sialic acid and protein.The authors wish to record their indebtedness to Drs. D. B. Morell, F. J. Radcliff, and J. Gagolski for their advice and encouragement with this study and to the Postgraduate Medical Foundation in the University of Sydney for generous financial support.Research Fellow of the Royal Australasian College of Physicians.     

Functional regeneration in liver of old rats after partial hepatectomy

This study suggests that changes in liver protein metabolism occurring with age are not due to changes in the genome. Regenerating rat liver in old animals has regained functional properties of young rat liver.Specifically albumin synthesis, which is elevated in old animals, returns to young rat levels in old rats for several weeks after partial hepatectomy. Both in vivo and in vitro studies support this evidence. Old rat liver ferritin also undergoes changes in regenerating liver. The amount of ferritin iron/g liver falls to one half, the amount of iron/mg ferritin protein drops, but the amount of ferritin protein/g liver remains constant in regenerated old rat liver. The half-life of ferritin in regenerated old rat liver (2·3 days) is much shorter than in old rat liver controls (3·9 days) and approaches that of young rat liver ferritin (2·1 days).Determinations were done at a time when liver weight had been fully restored following removal of 67 per cent of the liver. Functional properties of old rat liver are restored by 12 weeks after partial hepatectomy.     

健康老年人活化部分凝血活酶时间参考值与海拔高度的关系

目的为制定中国健康老年人活化部分凝血活酶时间(APTT)参考值标准提供科学依据。方法搜集全国72个市县级医院和有关研究单位测定的10 053例健康老年人APTT参考值,研究其与7项地理指标的关系,通过逐步回归及曲线估计建立并选取最优预测模型,选用克里金法进行插值并绘制健康老年人APTT预测参考值的空间分布图。结果与健康老年人APTT参考值相关系数最大的地理因素是海拔高度,呈显著正相关关系,与海拔高度的最优预测模型为y=30.78+0.002 999X1±0.451。我国健康老年人APTT预测参考值的空间分布规律为西高东低,呈阶梯状分布。结论我国健康老年人APTT预测参考值的空间分布规律与海拔高度的总体分布规律一致,已知中国某地的海拔高度,可通过此模型估算该地健康老年人APTT预测参考值。     

Quantitative characterization of cell synchronization in yeast

Metabolic oscillations in baker's yeast serve as a model system for synchronization of biochemical oscillations. Despite widespread interest, the complexity of the phenomenon has been an obstacle for a quantitative understanding of the cell synchronization process. In particular, when two yeast cell populations oscillating 180 degrees out of phase are mixed, it appears as if the synchronization dynamics is too fast to be explained. We have probed the synchronization dynamics by forcing experiments in an open-flow reactor, and we find that acetaldehyde has a very strong synchronization effect that can account quantitatively for the classical mixing experiment. The fast synchronization dynamics is explained by a general synchronization mechanism, which is dominated by a fast amplitude response as opposed to the expected slow phase change. We also show that glucose can mediate this kind of synchronization, provided that the glucose transporter is not saturated. This makes the phenomenon potentially relevant for a broad range of cell types.