Functional analysis of human T cell subsets defined by monoclonal antibodies. V. Suppressor cells within the activated OKT4+ population belong to a distinct subset

In the present report, we characterize a monoclonal antibody directed at a surface differentiation antigen on human T cells. The monoclonal antibody, OKT17, recognizes a cell surface antigen present on the majority of resting normal peripheral T cells. In contrast, OKT17 is unreactive with normal B cells, B cell lines, T cell lines, or SIg+ CLL. Interestingly, after activation, the antigen recognized by OKT17 is lost from a subset of OKT4+ cells. We took advantage of this finding to explore further the functional heterogeneity within activated OKT4+ cells. Evidence was obtained that the PWM-activated OKT4+ subset remaining after depletion of OKT17-reactive T cells (OKT4+ 17-) contains radiosensitive helperr cells but is devoid of suppressor cells. In contrast, the activated OKT4+ 17+ population contains potent radiosensitive suppressor cells as well as radioresistant helpe cells. Taken together, these studies suggest that the OKT17 monoclonal antibody can differentiate two functionally mature, activated OKT4+ human T cells: OKT4+ OKT17+ radiosensitive suppressor cells and OKT4+ 17- radiosensitive helper cells.     

Isolation and characterization of acetylornithine delta-transaminase of wild-type Escherichia coli W. Comparison with arginine-inducible acetylornithine delta-transaminase.

The enzyme that catalyzes the reversible conversion of N-acetylglutamic γ-semialdehyde and l-glutamate to α-N-acetyl-l-ornithine and α-ketoglutarate, acetylornithine δ-transaminase, has been isolated in homogeneous form and crystallized from both the wild-type and the arginine-inducible strains of Escherichia coli W. The molecular weight of the wild-type transaminase is 119,000 while the molecular weight of the arginine-inducible enzyme is 61,000. However, the arginine-inducible acetylornithine δ-transaminase is not a breakdown product of the wild-type, arginine-repressible transaminase. Analysis of crude extracts of the wild-type and arginine-inducible strains by varying the acrylamide concentration in polyacrylamide disc gel electrophoresis showed that arginine-inducible and wild-type transaminases differed in ionic charge. Immunochemical analysis of the two transaminases showed that neither enzyme would cross-react with antibodies prepared against its counterpart. Treatment of the two enzymes with sodium dodecyl sulfate, followed by disc gel electrophoresis revealed that both transaminases were composed of 31,000-dalton subunits. Tryptic digestion of the two transaminases showed that nearly identical peptides were present. The overall data suggest that the wild-type and inducible transaminases were products of two different structural genes. The two transaminases have different molecular weights, ionic charges, and antigenic determinants, but both are composed of similar molecular weight subunits and show a high degree of similarity in amino acid content and peptide composition.     

Intracellular pH controls the development of new potassium conductance after fertilization of the sea urchin egg

Fertilization of the sea urchin egg leads to a sequence of changes at the egg surface and the interior cytoplasm. Among these changes are the transient elevation of internal calcium levels, alkalization of the cytoplasm and development of new K⁺-conductance. In the series of experiments reported here, we separate the effects on potassium activation of the calcium release and the rise in the intracellular pH. The development of new K⁺-conductance was dependent on alkalization of the egg cytoplasm, and not on a rise of internal calcium levels. The effects of 2,4-dinitrophenol, N-ethylmalemide, antimycin A and oligomycin suggest that the maintenance of the alkaline internal pH of fertilized eggs appears to be dependent on membrane ATPase activity.     

The identification of Tithonia voucher specimens used for sesquiterpene lactone investigations

The identification of Tithonia voucher specimens as T. rotundifolia (Mill.) Blake, used for sesquiterpene lactone chemical investigations, have been found to be T. diversifolia (Hemsl.) A. Gray. The compound Ivalin, also is reported for the first time from T. calva Sch. Bip. in Semann.     

A SURVEY FOR 1,3,6,7-TETRAHYDROXY-C-GLYCOSYLXANTHONES EMPHASIZING THE “PRIMITIVE” LEPTOSPORANGIATE FERNS AND THEIR ALLIES

A survey for 1,3,6,7-tetrahydroxy-C-glycosylxanthones of representative species within the primitive vascular plants, emphasizing the leptosporangiate ferns, has indicated a limited distribution of these compounds within three leptosporangiate families: Hymenophyllaceae, Aspleniaceae and Marsileaceae. In the Hymenophyllaceae the distribution of these compounds appears to be a useful criterion for segregating species of Mecodium from other species of Hymenophyllum (sensu lato) and suggests that the tubulate vs. the valvate indusial condition may not be an ideal character for separating all species of Hymenophyllum (s.l.) from those of Trichomanes (s.l.). These compounds appear useful for delimiting several species of Elaphoglossum section Pachyglossa and support a relationship among the Aspleniaceae, Athyriaceae, and Elaphoglossaceae. Their presence in Marsilea also raises questions as to the origin of this group of plants.     

Effect of a peri fluoro substituent on the conformation of dihydrodiol derivatives of polycyclic aromatic hydrocarbons

$\text{Trans}$-3,4-, 5,6-, 8,9-, and 10,11-dihydrodiols formed from the metabolism of 7-fluorobenz[a]anthracene by rat liver microsomes were isolated by reversed-phase high performance liquid chromatography. Ultraviolet absorption, mass, and NMR spectral analyses indicated that the 5,6- and 8,9-dihydrodiols were preferentially in quasi-diaxial conformations, whereas the 3,4- and 10,11-dihydrodiols were preferentially in quasi-diequatorial conformations. CPK space-filling models suggest that the quasi-diaxial conformation is primarily the result of electronic repulsion between the fluorine and the $\text{peri}$ hydroxyl oxygen. These findings provide a structural basis in the interpretation of the carcinogenic potencies of some fluorinated polycyclic aromatic hydrocarbons.     

心磷脂-细胞色素C体系CD谱的研究

 线粒体内膜中含有特异的心磷脂是细胞色素C氧化酶活性的必需脂。本工作测定了心磷脂脂质体对细胞色素C溶液园二色(CD)谱的影响,发现心磷脂可引起血色素铁的氧化,并使其轴向配位场强的对称性下降。提示心磷脂可能参与酶和底物之间的电子转移过程。     

人白血病细胞癌性促凝物(CP)的分离纯化及其特性的初步研究

用三步纯化法从人M_3型白血病细胞中分离纯化出人类肿瘤癌性促凝物(CP)。促凝活性回收率为24％,CP纯化倍数为2481倍。纯化CP在SDS-PAGE上为单一区带,其理化和酶学特性类似于动物肿瘤CP,分子量约为70 000,PI为4.8,在FVⅡ缺乏血浆中以及在含有组织因子(TF)抑制剂情况下仍能激活FX。CP促凝活性能被半胱氨酸蛋白酶抑制剂HgCl_2抑制,纯化CP能与抗动物肿瘤CP抗体形成免疫沉淀反应。     

Primary sequence of the glucanase gene from Oerskovia xanthineolytica. Expression and purification of the enzyme from Escherichia coli

A 2.7-kilobase fragment of DNA from Oerskovia xanthineolytica containing the gene for a beta-1,3-glucanase has been isolated and its complete nucleotide sequence determined. The sequence was found to contain two large open reading frames. Purification of the mature native enzyme and subsequent amino-terminal sequencing defined the glucanase gene in one reading frame which potentially encodes a protein of 548 amino acids. We have expressed this glucanase gene in Escherichia coli under control of the lacUV5 promoter and found the product to be secreted into the periplasm as a mature enzyme of about the same molecular weight as that of the native protein. The recombinant enzyme was purified to near homogeneity by a single step of high performance liquid chromatography. The ability of the recombinant enzyme to digest beta-glucan substrates and to lyse viable yeast cells was found to be indistinguishable from that of the native protein. Deletion of the cysteine-rich carboxyl-terminal 117 amino acids of the enzyme, which also contain two duplicated segments, abolished the lytic activity but did not significantly affect the glucanase function of the protein. The possible involvement of this domain in interaction with the yeast cell wall is discussed.