Germ-line transmission and expression of a human-derived yeast artificial chromosome

Introduction of DNA fragments, hundreds of kilobases in size, into mouse embryonic stem (ES) cells would greatly advance the ability to manipulate the mouse genome. Mice generated from such modified cells would permit investigation of the function and expression of very large or crudely mapped genes. Large DNA molecules cloned into yeast artificial chromosomes (YACs) are stable and genetically manipulable within yeast, suggesting yeast-cell fusion as an ideal method for transferring large DNA segments into mammalian cells. Introduction of YACs into different cell types by this technique has been reported; however, the incorporation of yeast DNA along with the YAC has raised doubts as to whether ES cells, modified in this way, would be able to recolonize the mouse germ line. Here we provide, to our knowledge, the first demonstration of germ-line transmission and expression of a large human DNA fragment, introduced into ES cells by fusion with yeast spheroplasts. Proper development was not impaired by the cointegration of a large portion of the yeast genome with the YAC.

A Tsunami About 1000 Years Ago in Puget Sound, Washington

Water surged from Puget Sound sometime between 1000 and 1100 years ago, overrunning tidal marshes and mantling them with centimeters of sand. One overrun site is 10 kilometers northwest of downtown Seattle; another is on Whidbey Island, some 30 kilometers farther north. Neither site has been widely mantled with sand at any other time in the past 2000 years. Deposition of the sand coincided-to the year or less-with abrupt, probably tectonic subsidence at the Seattle site and with landsliding into nearby Lake Washington. These findings show that a tsunami was generated in Puget Sound, and they tend to confirm that a large shallow earthquake occurred in the Seattle area about 1000 years ago.

Schizosaccharomyces pombe mitochondria: morphological, respiratory and protein import characteristics

A technique is described for the isolation and purification of intact, respiratory-competent mitochondria from Schizosaccharomyces pombe. The purified mitochondria are capable of oxidizing NADH and succinate as respiratory substrates, indicating the presence of succinate dehydrogenase and an NADH dehydrogenase located on the outer surface of the inner membrane. Mitochondria display good respiratory control with an ADP/O ratio of < 2. Respiratory activity is linearly dependent upon the redox poise of the quinone pool, suggesting the presence of an unbranched respiratory pathway to molecular oxygen. Immunogold labelling using antisera raised against mitochondrial HSP70 proteins (SSP1, SSC1 and PHSP1) from three different species, namely S. pombe, Saccharomyces cerevisiae and the plant Pisum sativum respectively, has been used to investigate the presence and ultrastructure of the mitochondria isolated by this procedure. The immunocytochemistry was carried out using cells containing wild-type levels of SSP1 protein and cells over-expressing the protein. These results also demonstrate the capacity of mitochondria to import increased levels of protein in vivo. In vitro import experiments using COXIV-DHFR indicate that purified S. pombe mitochondria can efficiently import this precursor, and that protein translocation is dependent upon an oxidizable substrate and a membrane potential.

The regulation and nature of the cyanide-resistant alternative oxidase of plant mitochondria

In addition to possessing multiple NAD(P)H dehydrogenases, most plant mitochondria contain a cyanide- and antimycin-insensitive alternative terminal oxidase. Although the general characteristics of this terminal oxidase have been known for a considerable number of years, the mechanism by which it is regulated is unclear and until recently there has been relatively little information on its exact nature. In the past 5 years, however, the application of molecular and novel voltametric techniques has advanced our understanding of this oxidase considerably. In this article, we review briefly current understanding on the structure and function of the multiple NADH dehydrogenases and consider, in detail, the nature and regulation of the alternative oxidase. We derive a kinetic model for electron transfer through the ubiquinone pool based on a proposed model for the reduction of the oxidase by quinol and show how this can account for deviations from Q-pool behaviour. We review information on the attempts to isolate and characterise the oxidase and finally consider the molecular aspects of the expression of the alternative oxidase.

Regulation of Alternative Pathway Activity in Plant Mitochondria : Deviations from Q-Pool Behavior during Oxidation of NADH and Quinols

External NADH and succinate were oxidized at similar rates by soybean (Glycine max) cotyledon and leaf mitochondria when the cytochrome chain was operating, but the rate of NADH oxidation via the alternative oxidase was only half that of succinate. However, measurements of the redox poise of the endogenous quinone pool and reduction of added quinones revealed that external NADH reduced them to the same, or greater, extent than did succinate. A kinetic analysis of the relationship between alternative oxidase activity and the redox state of ubiquinone indicated that the degree of ubiquinone reduction during external NADH oxidation was sufficient to fully engage the alternative oxidase. Measurements of NADH oxidation in the presence of succinate showed that the two substrates competed for cytochrome chain activity but not for alternative oxidase activity. Both reduced Q-1 and duroquinone were readily oxidized by the cytochrome oxidase pathway but only slowly by the alternative oxidase pathway in soybean mitochondria. In mitochondria isolated from the thermogenic spadix of Philodendron selloum, on the other hand, quinol oxidation via the alternative oxidase was relatively rapid; in these mitochondria, external NADH was also oxidized readily by the alternative oxidase. Antibodies raised against alternative oxidase proteins from Sauromatum guttatum cross-reacted with proteins of similar molecular size from soybean mitochondria, indicating similarities between the two alternative oxidases. However, it appears that the organization of the respiratory chain in soybean is different, and we suggest that some segregation of electron transport chain components may exist in mitochondria from nonthermogenic plant tissues.

Regulation of Electron Transport in Plant Mitochondria under State 4 Conditions

The regulation of electron transport in pea (Pisum sativum L.) leaf mitochondria under state 4 conditions has been investigated by simultaneously monitoring oxygen uptake, the steady-state reduction level of ubiquinone, and membrane potential. Membrane potentials were measured using a methyltriphenylphosphonium electrode while a voltametric technique was used to monitor changes in the steady-state reduction levels of quinone. It was found that the addition of glycine to mitochondria oxidising malate in state 4 led to a marked increase in the rate of O(2) uptake and increased both the membrane potential and reduction level of the quinone pool. Increases in the state 4 respiratory rate were attributed to both an increase in driving flux, due to increased Q-pool reduction, and in membrane potential. Due to the nonohmic behavior of the inner membrane, under these conditions, an increase in potential would result in a considerable rise in proton conductance. Measurement of dual substrate oxidation, in the presence of n-propylgallate, revealed that the increase in respiratory activity was not mediated by the alternative oxidase. Similar increases in membrane potential and the level of Q-pool reduction were observed even in the presence of rotenone suggesting that the rotenone-insensitive pathway is a constitutive feature of plant mitochondria and may play a role in facilitating rapid state 4 rates even in the presence of a high energy charge.

Phase I trial of intraperitoneal recombinant interleukin-2/lymphokine-activated killer cells in patients with ovarian cancer

Ten patients with ovarian cancer refractory to conventional therapy were treated with intraperitoneal (i.p.) recombinant interleukin-2 (rIL-2) and lymphokine-activated killer cells (LAK). The 28-day protocol consisted of 6 priming i.p. rIL-2 infusions on days 0, 4, 6, 8, 10, and 12. Leukapheresis was performed for mononuclear cell collection on days 15, 16, 17, and 18 and lymphokine-activated killer cells were given i.p. with the rIL-2 on days 19 and 21. Three additional i.p. rIL-2 infusions were given on days 23, 25, and 27. Three dose levels of rIL-2 were tested: 5 X 10(5), 2 X 10(6), and 8 X 10(6) units/m2 body surface area. The dose-limiting toxicity was abdominal pain secondary to ascites accumulation with significant weight gain. Other toxic effects included decreased performance status, fever, nausea and vomiting, diarrhea, and anemia. Peripheral lymphocytosis and eosinophilia were seen at all dose levels. The maximum tolerated dose is 8 X 10(6) units/m2/dose. Peripheral and peritoneal IL-2 levels were measured with a bioassay using an IL-2-dependent cell line. At the highest dose level, serum IL-2 was greater than 10 units/ml for 18 h. After the first infusion, a 2-log dilution of the i.p. IL-2 was measured in the serum. In the postleukapheresis i.p. IL-2-dosing period less IL-2 was detected in the serum than in the earlier i.p. IL-2-priming period. The induction and persistence of LAK activity were studied. Peritoneal LAK activity was detected as early as 4 days after the first i.p. infusion, by day 11 in all evaluable patients, and persisted for the 6-day interval between priming IL-2 and LAK/IL-2 infusion. Peritoneal lytic activity persisted until day 28 in 5 tested patients. These peritoneal cells retained lytic activity 48 h in culture medium without rIL-2 present. Peritoneal LAK activity correlated with the percentage of mononuclear cells and the percentage of CD56-positive mononuclear cells in the peritoneum. The yield of peripheral lymphocytes after the six i.p. priming doses of rIL-2 correlated with the dose level of rIL-2 infused. Peripheral blood LAK activity showed a minimal, however progressive, increase during the treatment protocol. LAK activity could be enhanced if rIL-2 was present during the 4-h assay. These studies indicate that i.p. rIL-2 infusion induced durable regional LAK activity and primes peripheral blood cells for LAK activity if exposed briefly to additional IL-2.

Measurement of the redox state of the ubiquinone pool in Rhodobacter capsulatus membrane fragments

The dependence of the respiratory rate on the redox poise of the quinone pool was investigated in wild type and mutant membranes of Rhodobacter capsulatus. A linear relationship has been found between these two parameters only when succinate was oxidized by the bc1 complex. Conversely, a marked nonlinear relationship was observed between the Q-pool reduction level and the respiratory rate when O2 uptake occurred via the alternative oxidase. In addition, it was found that this latter pathway was not engaged until Q-pool reduction level reached approximately 25%. These results are discussed within the framework of a homogeneous pool regulating both photosynthetic and respiratory fluxes.

Efficient Multistep Photoinitiated Electron Transfer in a Molecular Pentad

A synthetic five-part molecular device has been prepared that uses a multistep electron transfer strategy similar to that of photosynthetic organisms to capture light energy and convert it to chemical potential in the form of long-lived charge separation. It consists of two covalently linked porphyrin moieties, one containing a zinc ion (P(Zn)) and the other present as the free base (P). The metailated porphyrin bears a carotenoid polyene (C) and the other a diquinone species (Q(A)-Q(B)). Excitation of the free-base porphyrin in a chloroform solution of the pentad yields an initial charge-separated state, C-P(Zn)-P(.+).-Q(A)(-)-Q(B), with a quantum yield of 0.85. Subsequent electron transfer steps lead to a final charge-separated state, C(.+)-P(Zn)-P-Q(A)-Q(B)(.-), which is formed with an overall quantum yield of 0.83 and has a lifetime of 55 microseconds. Irradiation of the free-base form of the pentad, C-P-P-Q(A)-Q(B), gives a similar charge-separated state with a lower quantum yield (0.15 in dichloromethane), although the lifetime is increased to approximately 340 microseconds. The artificial photosynthetic system preserves a significant fraction ( approximately 1.0 electron volt) of the initial excitation energy (1.9 electron volts) in the long-lived, charge-separated state.

Immunosuppressive properties of chloroquinoxaline sulfonamide

Chloroquinoxaline sulfonamide (CQS), a sulfanilamide derivative with antitumor activity, was found to be toxic to lymphoid tissue during preclinical studies. The mechanism of this toxicity appears to involve profound inhibition of lymphocyte activation. Incubation of human peripheral blood mononuclear cells (PBMNCs) with CQS decreased cellular incorporation of thymidine and deoxyuridine in a dose-dependent manner. Analysis of cell cycle distribution by flow cytometry indicated that CQS blocked movement out of the G0/G1 phase. Drug-treated cells were smaller and expressed fewer receptors for interleukin-2 (IL-2) and transferrin than untreated mitogen-stimulated lymphocytes. These observations support the notion that CQS has cell cycle specificity in regulating lymphocyte proliferation. As little as 10 microM CQS markedly inhibited both human lymphocyte and murine CTLL cell replication in response to IL-2 containing growth factors. However, CQS did not block secretion of IL-2 into culture supernatant fractions by human PBMNCs. Finally, CQS inhibited in vitro production of immunoglobulins G and M by mitogen-stimulated lymphocytes, primarily by causing cytotoxicity. In all of these drug effects, CQS was approximately one to two logs more potent than the parent compound, sulfaquinoxaline (SQ). These studies indicate that CQS inhibits essential basic processes in human lymphocytes. This agent may find use as an immunosuppressive drug.

Role of nonohmicity in the regulation of electron transport in plant mitochondria

The relationship between the respiratory rate and the membrane ionic current on the protonmotive force has been investigated in percoll purified potato mitochondria. The dependence of the membrane ionic current on the membrane potential was monitored using a methyltriphenylphosphonium-sensitive electrode and determining the maximal net rate of depolarization following the addition of a respiratory inhibitor. We have confirmed that a nonohmic relationship exists between the ionic conductance and membrane potential. Addition of ATPase inhibitors markedly increased the initial rate of dissipation suggesting that in their absence the dissipation rate induced by respiratory inhibitors is partially offset by H(+)-efflux due to the hydrolysis of endogenous ATP. This was corroborated by direct measurement of endogenous ATP levels which decreased significantly following dissipation of the membrane potential. Results are discussed in terms of the regulation of electron transport in plant mitochondria in vivo.

Regulation of alternative pathway activity in plant mitochondria: nonlinear relationship between electron flux and the redox poise of the quinone pool

The dependence of respiratory flux via the alternative pathway on the redox poise of the ubiquinone (Q) pool was investigated in soybean cotyledon mitochondria. A marked nonlinear relationship was observed between Q-pool reduction level and O2 uptake via the alternative oxidase. Significant engagement of the alternative pathway was not apparent until Q-pool reduction level reached 35-40% but increased disproportionately on further reduction. Similar results were obtained with electron donation from either Complex 1 or Complex 2. Close agreement was obtained over a range of experimental conditions between the estimated contribution of the alternative pathway to total respiratory flux, as measured with salicylhydroxamic acid, and that predicted from the redox poise of the Q-pool. These results are discussed in terms of existing models of the regulation of respiratory flux via the alternative pathway.

Increased susceptibility to inoculated Lewis lung carcinoma (3LL) but unaltered tumor growth in mice treated with monoclonal antibody to L3T4 on mouse T-helper cells

The importance of different lymphocyte cell populations in early recognition and destruction of tumor cells has not been fully established. Certainly natural killer cells and cytotoxic T lymphocytes are involved. Using a recently developed monoclonal antibody (GK 1.5) that has been shown to have in vivo cytotoxic activity directed at L3T4-bearing T cells, we provide in these experiments evidence that T-helper cells are also important in early antitumor immunity. Development of progressive tumor growth after the subcutaneous inoculation of 10(5) Lewis lung carcinoma (3LL) cells was greater in antibody-treated mice (13 of 20 treated mice vs. 6 of 21 controls). Nevertheless, in those animals that developed tumors, the latentcy period (time from tumor cell inoculation until tumor first palpable) and tumor growth rate were no different in antibody-treated mice when compared with control animals. In subsequent experiments, animals were exposed to irradiated tumor cells in Freund's adjuvant on three occasions and tumor growth was then assessed. Growth was slower in the sensitized group. Administration of GK 1.5, however, did not enhance the tumor growth rates in either the previously sensitized or control groups. The results suggest that T-helper cells might be of greater functional importance in early tumor cell recognition and destruction and of lesser importance in the restraint of tumor growth, once the tumor has become established.

Analysis of NADH dehydrogenases from plant [mung bean (Phaseolus aureus)] mitochondrial membranes on non-denaturing polyacrylamide gels and purification of complex I by band excision

The present paper describes the analysis of plant mitochondrial NADH dehydrogenases using a recently developed non-dissociating gradient polyacrylamide-gel-electrophoresis technique [Kuonen, Roberts & Cottingham (1986) Anal. Biochem. 153, 221-226]. Solubilized mung-bean (Phaseolus aureus) submitochondrial particles were analysed on 3-22% (w/v) gradient polyacrylamide gels containing 0.1% Triton X-100 and stained for multiple NADH dehydrogenase activities. A rotenone-sensitive NADH dehydrogenase (Complex I) was identified on the basis of co-migration with the purified mammalian enzyme. The polypeptide composition of the plant enzyme was further analysed by band excision and SDS/polyacrylamide-gel electrophoresis.

Effect of commercial peritoneal dialysis fluids on the lytic function of lymphokine-activated killer cells

Intraperitoneal (ip) immunotherapies are often administered in saline or peritoneal dialysis solutions. In preparation for a Phase I i.p. interleukin-2/lymphokine-activated killer cell (IL-2/LAK) trial in patients with recurrent ovarian cancer, we evaluated the effect of six solutions, including two 1.5% dextrose peritoneal dialysis solutions (PDS), on the lytic function of LAK. In vitro IL-2-activated LAK cells were exposed to solutions, washed with Hanks' balanced salt solution, and lytic activity was measured in a standard 4-h chromium release assay using Daudi as a tumor target. LAK function was abrogated after 2 h of exposure to Inpersol and after only 20 min of exposure to Dianeal PD-2. Five percent dextrose also significantly decreased lytic capabilities of LAK, whereas 0.9% sodium chloride or lactated Ringers had no deleterious effect on function. Adjustment of PDS to pH greater than 6.5 decreased the damaging effect on LAK function, suggesting that the low pH of PDS and 5% dextrose results in a loss of LAK cell viability and therefore lytic function. Based on these data, we have chosen to administer IL-2/LAK i.p. in lactated Ringers.

Immunologic enhancement of B16 melanoma growth

In certain experimental tumor models, tumor growth is less pronounced in immune deficient animals. Characteristically, tumors such as the murine B16 melanoma and Lewis lung carcinoma (3LL) are weakly antigenic. We proposed that with such tumors that are weakly antigenic, growth is enhanced by T-cell factors. Young mice were inoculated with irradiated B16 cells in complete Freunds adjuvant (CFA) on three occasions, each separated by 2 weeks. Specific antibody (IgG) to B16 membrane antigens was detected by an enzyme-linked immunosorbent assay (ELISA) after the first injection, and it continued to rise for 6 weeks. B16 growth was compared in 20 mice that had received irradiated B16 in CFA or CFA alone by the same schedule previously. Despite the previous sensitization, the rates of tumor appearance and growth were similar. In an additional experiment involving 23 mice that had received B16 immunization, the period of time in which a palpable tumor developed after the injection of viable B16 cells did not correlate with anti-B16 antibody level. It appeared that detectable antibody to B16 antigens was of little consequence. To explain why B16 primary growth and metastases were reduced in immune deficient hosts, we proposed that lymphocytes might enhance tumor growth. To demonstrate this, splenic lymphocytes from tumor-bearing (B16 or 3LL) or control mice were injected with B16 cells into young, immune competent hosts. Tumors (B16) developed earlier and growth was more rapid in mice that received spleen cells from tumor-bearing (B16) mice. Subsequent cell depletion experiments to determine the mediator of tumor enhancement implicated a T-cell fraction that was neither of T-helper nor T-suppressor cell type phenotypically. Immune deficiency states that are associated with dysfunction of those cells that account for tumor enhancement might explain the reduced tumor aggressiveness that is observed frequently in these conditions.

Regulation of nonphosphorylating electron transport pathways in soybean cotyledon mitochondria and its implications for fat metabolism

The respiration of mitochondria isolated from germinating soybean cotyledons was strongly resistant to antimycin and KCN. This oxygen uptake was not related to lipoxygenase which was not detectable in purified mitochondria. The antimycin-resistant rate of O(2) uptake was greatest with succinate as substrate and least with exogenous NADH. Succinate was the only single substrate whose oxidation was inhibited by salicyl hydroxamic acid alone, indicating engagement of the alternative oxidase. Concurrent oxidation of two or three substrates led to greater involvement of the alternative oxidase. Despite substantial rotenone-resistant O(2) uptake with NAD-linked substrates, respiratory control was observed in the presence of antimycin, indicating restriction of electron flow through complex I. Addition of succinate to mitochondria oxidizing NAD-linked substrates in state four stimulated O(2) uptake substantially, largely by engaging the alternative oxidase. We suggest that these properties of soybean cotyledon mitochondria would enable succinate received from the glyoxysome during lipid metabolism to be rapidly oxidized, even under a high cytosolic energy charge.

Pyruvate transport by thermogenic-tissue mitochondria

1. Mitochondria isolated from the thermogenic spadices of Arum maculatum and Sauromatum guttatum plants oxidized external NADH, succinate, citrate, malate, 2-oxoglutarate and pyruvate without the need to add exogenous cofactors. 2. Oxidation of substrates was virtually all via the alternative oxidase, the cytochrome pathway constituting only 10-20% of the total activity, depending on the stage of spadix development. 3. During later stages of spadix development, pyruvate oxidation was enhanced by the addition of aspartate. This was caused by acetyl-CoA condensing with oxaloacetate, produced from pyruvate/aspartate transamination, and so decreasing feedback inhibition of pyruvate dehydrogenase. 4. Pyruvate oxidation was inhibited by the long-chain acid maleimides AM5-11, but not by those with shorter polymethylene side groups, AM1-4. 5. The alpha-cyanocinnamate derivatives UK5099 [alpha-cyano-beta-(1-phenylindol-3-yl)acrylate] and CHCA [alpha-cyano-4-hydroxycinnamate] inhibited pyruvate-dependent O2 consumption and the carrier-mediated uptake of pyruvate across the mitochondrial inner membrane. Characteristics of non-competitive inhibition were observed for CHCA, whereas for UK5099 the results were more complex, suggesting a very low rate of dissociation of the inhibitor-carrier complex. 6. A comparison of the values of Vmax. and Km for oxidation and transport suggested that it was the latter which controls the overall rate of pyruvate oxidation by mitochondria from both tissues.

Tumor vasculature in young and old hosts: scanning electron microscopy of microcorrosion casts with microangiography, light microscopy and transmission electron microscopy

Tumor growth in vivo is dependent upon new blood vessel formation. When B16-F10 melanoma cells are implanted subcutaneously in young (3 mo) and old (24 mo) C57BL/6 mice the rate of growth is dependent on the age of the mice. This study involved a wide range of histological and microscopic techniques but was limited primarily to the initial phase of tumor growth. Stereological point counting from light microscopy (LM) of standard histological sections has been used to yield data regarding blood content. Tumor-bearing mice were perfused through the aorta with a fixation solution and were infused with a low-viscosity radiopaque gel (Microfil) or resin (Mercox). Soft x-rays of the whole animal were used for identifying the feeding vessels to the tumor. Tumors with Microfil were sliced and used for microangiography and light-microscopic observation while those with resin were used to make corrosion casts for scanning electron microscopy (SEM). The different characteristics of the tumor blood vessels in different aged mice were most obvious through SEM of vascular corrosion casts. In comparison with tumors in young mice those of similar size in old hosts had more necrosis, reduced presence of angiogenic features, decreased vessel density, reduced penetration into the tumor, and enhanced tortuosity of the vessel lumen. Transmission electron microscopy (TEM) revealed incompletely developed wall structure of the vessels regardless of host. The above results are consistent with the hypothesis that retarded angiogenesis may be responsible in part for the limited growth of tumors in old hosts.