TAP2-defective RMA-S cells present Sendai virus antigen to cytotoxic T lymphocytes

The murine antigen-processing-defective mutant cell line RMA-S is leaky in the presentation of certain endogenously synthesized minor histocompatibility and viral antigens to major histocompatibility complex (MHC) class I-restricted cytotoxic T lymphocytes (CTL). The viral antigens include influenza virus nucleoprotein, vesicular stomatitis virus (VSV) nucleocapsid and Rauscher murine leukemia virus (MuLV) antigen. Here we demonstrate Sendai virus antigen presentation by the HAM2 (murine TAP2, transporter associated with antigen presentation type 2)-defective RMA-S cell line and compare antigen presentation after restoration of the defect by murine TAP1/2 gene transfection. Kinetic studies revealed that RMA-S cells required 2-3 h longer incubation and approximately 10 times higher doses of Sendai virus to reach the same level of killing as the RMA parental line. After transfection of RMA-S cells with the murine TAP1/2 gene, Sendai virus antigen presentation was restored to levels of the RMA wild-type line with regard to time of virus infection and dose of virus needed for sensitizing target cells. The presentation of Sendai virus antigen in RMA-S cells was sensitive to brefeldin A (BFA), suggesting that the presentation was mediated via the endogenous pathway. Our findings confirmed leakiness of antigen presentation in RMA-S cells and extended it to Sendai virus. The results underscored the role for intact expression of the TAP 1/2 molecules for efficient MHC class I-mediated antigen presentation.

High-field MR microscopy using fast spin-echoes

Fast spin-echo imaging has been investigated with attention to the requirements and opportunities for high-field MR microscopy. Two- and three-dimensional versions were implemented at 2.0 T, 7.1 T, and 9.4 T. At these fields, at least eight echoes were collectable with a 10 ms TE from fixed tissue specimens and living animals, giving an eightfold improvement in imaging efficiency. To reduce the phase-encoding gradient amplitude and its duty cycle, a modified pulse sequence with phase accumulation was developed. Images obtained using this pulse sequence exhibited comparable signal-to-noise (SNR) to those obtained from the conventional fast spin-echo pulse sequences. Signal losses due to imperfections in RF pulses and lack of phase rewinders were offset in this sequence by reduced diffusion losses incurred with the gradients required for MR microscopy. Image SNR, contrast, edge effects and spatial resolution for three k-space sampling schemes were studied experimentally and theoretically. One method of sampling k-space, 4-GROUP FSE, was found particularly useful in producing varied T2 contrast at high field. Two-dimensional images of tissue specimens were obtained in a total acquisition time of 1 to 2 min with in-plane resolution between 30 to 70 microns, and 3D images with 256(3) arrays were acquired from fixed rat brain tissue (isotropic voxel = 70 microns) and a living rat (isotropic voxel = 117 microns) in approximately 4.5 h.

Modulation of cellular immune responses by cold water swim stress in the rat

Alterations of cell-mediated immune responses in the rat produced by 5-day (one 3-min stress session each day for 5 days) and 1-day (three 3-min stress sessions within 12 h) cold water stress administration were investigated. Mitogenic responses to concanavalin A (Con A) and lipopolysaccharide (LPS), interleukin-2 (IL-2) production, CD4+/CD8+ T-cell ratios, and natural killer (NK) cell activity of blood and spleen lymphocytes were increased by the 5-day cold water stress. Responses to Con A and LPS, IL-2 production, and CD4+ and CD8+ percentages of blood and spleen lymphocytes were decreased by the 1-day cold water stress. Corticosterone levels were increased by both the 1-day and 5-day cold water stress. Cold water stress, as a natural stressor, may have its own unique pattern of neuroendocrine changes because of the accompanying body temperature variations that may influence immune functions.

Three-dimensional NMR microscopy of rat spleen and liver

Three-dimensional microscopic NMR images of spleen and liver specimens from rats injected with dextran magnetite particles and from controls were obtained at 4.7 T, using a specially designed probe in conjunction with a 3D filtered back projection reconstruction algorithm. All of the images were reconstructed as 64(3) arrays with (25 microns) 3 isotropic voxels. With the aid of the MR contrast agent, the red pulp and marginal zone of the spleen and the portal triad of the liver could be distinguished from the surrounding tissue in T2-weighted images. For mature rat spleen, natural contrast in T2-weighted images was found to distinguish the same features. Histological examinations of the tissues with and without contrast agent were also performed using an optical microscope. Microscopic NMR images, despite their lower resolution, clearly revealed many features seen in the optical images.

In vitro translation of the human insulin proreceptor results in N-linked glycosylation without dimer formation

The heterotetrameric configuration of the cell surface human insulin receptor (hINSR) is important for mediating insulin action. Investigation of proreceptor dimerization, the quaternary processing event during biogenesis, offers the potential to examine interactions between disulfide-linked receptor subunits. Thus, dimer formation of the proreceptor was examined in a cell-free system that utilized a coupled transcription and translation method with rabbit reticulocyte lysate. Translation products were labeled with [35S]methionine and identified by non-reducing SDS-polyacrylamide gel electrophoresis and autoradiography. In vitro synthesis in the presence of oxidized glutathione failed to demonstrate dimerization of the nascent proreceptor. Co-translational processing with the addition of microsomal membranes resulted in N-linked glycosylation of the proreceptor but without dimer formation. Thus, similar to that observed in vivo, insulin proreceptor dimerization does not appear to be a co-translational or early post-translational event.

The endosperm-specific expression of a rice prolamin chimaeric gene in transgenic tobacco plants

The 5' upstream region (-680 to +40), containing the potential promoter and complete signal peptide coding sequence of the rice seed storage prolamin gene was amplified in vitro using the polymerase chain reaction from the genome of Chinese rice cultivar Zhonghua 8. The physical map and DNA sequence analysis show strong homology with the 5' flanking region of the rice prolamin gene published by Kim and Okita (1988a). No change in the signal peptide coding sequence and a long leader sequence with several small open reading frames were found. The chimaeric gene containing the 5' flanking region of the prolamin gene (-680 to -18) was transcriptionally fused with the beta-glucuronidase (GUS) reporter gene and the fusion junction was confirmed by both physical mapping and DNA sequence analysis. The resultant chimaeric gene was used to transform tobacco explants, using the Ti binary system of Agrobacterium tumefaciens LBA4404. Three transgenic tobacco plants with as many as 20 copies of the chimaeric GUS gene (confirmed by dot and Southern hybridization) were analysed further. Histochemical analysis revealed GUS activity in the endosperm tissue of tobacco seed at the developmental stage about 20 days after flowering (DAF). No GUS activity was found in leaves, stems, roots and flowers of the transgenic tobacco plants. Therefore, we conclude that the 5' upstream region from -680 to -18 was sufficient to confer the endosperm-specific expression of the rice prolamin gene.

Evaluation of an automatic cardiac activation detector for bipolar electrograms

The identification of local activation events in bipolar cardiac electrograms, the first step of isochronal map construction, is a time-consuming and difficult process. Owing to the variability among bipolar activation complexes and the lack of practical knowledge concerning the relationship of the bipolar waveform to action potential characteristics, a set of empirical rules to guide the assignment of local activation times have been adopted. A computer program, called AP, has been designed, which implements these rules in the form of a syntactic analyser. Canine epicardial recordings were used to evaluate AP by comparing local activation times, assigned by AP, with times assigned independently by three investigators. The Hermes-Cox model for detector evaluation and a bootstrap statistical method were used in conjunction with ROC analysis to evaluate the ability of AP to detect events. Analysis of discrepancies among investigator-assigned times showed that the reliabilities of AP event detection and AP-assigned times were comparable to those of the investigators. The methods used in system design and evaluation are applicable to a broad range of problems in the detection and localisation of waveform components.

Metabolism of alkyl lysophospholipid in epithelial cancer cell lines and inhibition of cell growth

The mechanism of inhibition of cancer cell growth by alkyllysophospholipids is not known. We have investigated the metabolism of 1-O-octadecyl-2-O-methylglycerophosphocholine (ET-18-OCH3) in MCF7, A427, and A549 cell lines to determine whether there is a correlation between metabolism and sensitivity and whether the growth-inhibitory effects are due to ET-18-OCH3 or its metabolites. After 12 h incubation with ET-18-OCH3, less than 1.5% of ET-18-OCH3 taken up in the cells was converted to 1-O-octadecyl-2-O-methylglycerol (OMG). No correlation was observed between the extent of metabolism and sensitivity to the compound. Incubation of cells with 1 microgram OMG/mL (2.8 microM) for 12 h resulted in cellular quantities of OMG in MCF7, A427, and A549 that were, respectively, 8-, 5-, and 25-fold greater than those in cells incubated with 5 micrograms ET-18-OCH3/mL (9.6 microM). While 12 h incubation with 1 microgram OMG/mL did not significantly inhibit the proliferation of MCF7 or A427 cells, incubation with 5 micrograms ET-18-OCH3/mL inhibited MCF7 and A427 growth by 90 and 15%, respectively. A549 cell growth was inhibited 10% by 1 microgram OMG/mL, but not by 5 micrograms ET-18-OCH3/mL. Incubation of cells for 12 h with 5 micrograms OMG/mL (13.9 microM) inhibited the growth of all three cell lines. Our results indicate that both ET-18-OCH3 and OMG can inhibit cell growth but the low quantities of OMG produced from ET-18-OCH3 are not responsible for the observed inhibition of MCF7 and A427 cell growth.

Nodal is a novel TGF-beta-like gene expressed in the mouse node during gastrulation

During gastrulation, the three germ layers of the embryo are formed and organized along the anterior-posterior body axis. In the mouse, gastrulation involves the delamination of ectodermal cells through the primitive streak and their differentiation into mesoderm. These processes do not occur in embryos homozygous for a retrovirally induced recessive prenatal lethal mutation, the strain 413-d insertional mutation. Instead of giving rise to mesoderm, embryonic ectoderm in 413-d mutants overproliferates and then rapidly degenerates, although extraembryonic lineages remain viable. Here we isolate a candidate for the mutated gene which encodes a new member of the transforming growth factor-beta (TGF-beta) superfamily. Expression is first detected in primitive streak-stage embryos at about the time of mesoderm formation. It then becomes highly localized in the node at the anterior of the primitive streak. This region is analogous to chick Hensen's node and Xenopus dorsal lip (Spemann's organizer), which can induce secondary body axes when grafted into host embryos (reviewed in refs 5 and 6). Our findings suggest that this gene, named nodal, encodes a signalling molecule essential for mesoderm formation and subsequent organization of axial structures in early mouse development.

Epicardial mapping of ventricular defibrillation with monophasic and biphasic shocks in dogs

To study the mechanism of defibrillation and the reason for the increased defibrillation efficacy of biphasic waveforms, the potential gradient in a 32 x 30-mm region of the right ventricle in 15 dogs was progressively lowered in four steps while a strong potential gradient field was maintained throughout the rest of the ventricular myocardium. The volume of right ventricle beneath the plaque was 10 +/- 2% of the total ventricular mass. A 10-msec monophasic (eight dogs) or 5/5-msec biphasic (seven dogs) truncated exponential shock 30% above the defibrillation threshold voltage was given via electrodes on the left ventricular apex and right atrium to create the strong potential gradient field. Simultaneously, a weaker shock with the same waveform but opposite polarity was given via mesh electrodes on either side of the small right ventricular region to cancel part of the potential difference in the region and to create one of the four levels of potential gradient fields. Shock potentials and activations were recorded from 117 epicardial electrodes in the small region, and in one dog global epicardial activations and potentials were recorded from a sock containing 72 electrodes. Each gradient field was tested 10 times for successful defibrillation after 10 seconds of electrically induced fibrillation. For both monophasic and biphasic shocks, the percentage of successful defibrillation attempts decreased (p < 0.05) as the potential gradient decreased in the small region. Defibrillation was successful approximately 80% of the time for a mean +/- SD potential gradient of 5.4 +/- 0.8 V/cm for monophasic shocks and 2.7 +/- 0.3 V/cm for biphasic shocks (p < 0.05). No postshock activation fronts arose from the small region for eight waveform when the gradient was more than 5 V/cm. For both waveforms, the postshock activation fronts after the shocks were markedly different from those just before the shock and exhibited either a focal origin or unidirectional conduction.(ABSTRACT TRUNCATED AT 400 WORDS)

Mechanisms of rubidium permeation by rabbit cortical collecting duct during potassium restriction

To examine the pathways of K permeation in the cortical collecting duct (CCD) from K-restricted rabbits, we studied the effects of the following three maneuvers: 1) luminal amiloride addition; 2) luminal Ba addition; and 3) luminal Na removal. Luminal addition of amiloride (1 mM) significantly increased the 86Rb lumen-to-bath efflux coefficient (KRb), and this effect was fully blocked by the presence of 2 mM luminal Ba. Addition of 2 mM luminal Ba reduced KRb both in the absence of luminal Na and in the presence of luminal Na. In contrast to the effect of amiloride addition, removal of luminal Na significantly increased KRb, but neither 2 mM luminal Ba nor 4 mM luminal Ba totally abolished this effect. However, simultaneous addition of luminal Ba and Sch 28080 (10 microM) fully inhibited the increase in KRb upon luminal Na removal, indicating that luminal Na removal enhances Rb efflux in part via H-K-adenosinetriphosphatase (H-K-ATPase). To test whether Na acts as a partial agonist for cation efflux via the H-K-ATPase we examined the effect of Sch 28080 on the 22Na lumen-to-bath efflux coefficient (KNa). These studies were conducted in the presence of 0.1 mM luminal amiloride to block fully apical conductive Na efflux, and the effect of Sch 28080 on KNa was examined at two different ambient K concentrations. In the presence of 0.5 mM K, Sch 28080 (10 microM) significantly inhibited KNa from 47.6 +/- 4.8 to 35.0 +/- 6.8 nm/s (P < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

[Construction of an EB virus based shuttle vector plasmid pZH32]

The shuttle vector can replicate in both bacteria and eukaryotic cells. We have constructed a shuttle vector pZH32 based on the EB virus. Three component parts of the plasmid come from pSV2gpt, pS189 and pMCi5. An E. coli tyrosine suppressor tRNA gene, supF, was used as a mutagenic target in this plasmid, and a gpt gene was used as a selectable marker gene for transformed cells. This pZH32 based on EBV replicates autonomously in the nuclei of human cells. It has a low background mutation frequency. The plasmid can be used to examine the mutagenic mechanism of potential mutagens and carcinogens in mammalian cells.

In vivo priming of cytotoxic T lymphocyte responses in relation to in vitro up-regulation of major histocompatibility complex class I molecules by short synthetic peptides

Cytotoxic T lymphocytes (CTL) recognize target antigens as short peptides presented by major histocompatibility complex class I molecules (MHC-I). Externally added peptides can sensitize target cells by binding directly to MHC-I without any need for internal processing. Those which are similar in length to endogenously processed peptides are more potent in this respect than slightly longer peptides. Peptide MHC-I interactions can also be reflected as up-regulation of MHC-I in vitro on certain cells. We have compared the capacity of Db, Kb- and Ld-binding peptides, which are slightly different in length, to up-regulate MHC-I in vitro with their immunogenicity in vivo, in relation to generation of CTL responses. A clear correlation between these two different functions was found. We have also modified a 9-mer Db-binding peptide by adding cystein to the amino terminus and lysine to the amino- or carboxy terminus and studied the effects on MHC-I up-regulation and in vivo immunogenicity. Cystein and lysine contain reactive groups which are likely to influence the binding of modified peptides into the antigen-binding groove of Db. These small modifications of the optimal 9-mer peptide strongly influenced their functions but still there was a correlation between MHC-I up-regulation and CTL responses. Up-regulation of MHC-I in vitro may reflect a capacity of peptides to accumulate on the surface of particular antigen-presenting cells in vivo.

The relationship between cellular ether glycerophospholipid content and sensitivity of cancer cells to 1-O-octadecyl-2-O-methyl-glycerophosphocholine

Cancer cells are more susceptible to the growth-inhibitory effects of alkyl lysophospholipids than normal cells, but the mechanism of this selectivity is unknown. In this study we have investigated the hypothesis that the sensitivity of cells to alkyl lysophospholipids is related to the cellular ether lipid content. The order of decreasing sensitivity of the cells to the growth-inhibitory effect of 1-O-octadecyl-2-O-methyl-glycerophosphocholine (ET-18-OCH3) was MCF 7 > T84 > Malme 3M > A427 > A549, while the order of decreasing ether phospholipid content as a proportion of the total phospholipid was T84 > A427 = A549 = Malme 3M > MCF7. There was also no correlation between ET-18-OCH3-sensitivity and the proportion of ether lipid in the cholineglycerophospholipid or ethanolamineglycerophospholipid classes. Our results clearly indicate that the postulated relationship between ether phospholipid content and ET-18-OCH3-susceptibility may have very limited applicability and is unlikely to be the underlying reason for the selective effects of alkyl lysophospholipids.

In vivo primary induction of virus-specific CTL by immunization with 9-mer synthetic peptides

A primary cytotoxic T lymphocyte (CTL) response in vivo requires antigen presentation by cytosolic processing and can not in general be obtained by vaccination with soluble proteins. In the present work we have found that vaccination of mice with pre-processed synthetic peptides, corresponding to endogenous 9-mers produced in influenza A virus-infected cells, resulted in strong primary CTL responses. The generated CTL efficiently killed virus-infected target cells with preference for viral strains having the identical amino acid sequences to the peptides used for immunization. The optimal conditions for a primary in vivo CTL response was obtained with 100 micrograms peptide dissolved in incomplete Freund's adjuvant and injected s.c. at the base of tail. Spleen cells which had been primed 7-10 days earlier were restimulated for 5 days in vitro, using an optimal low peptide concentration (0.05 microM) and tested against virus-infected and peptide-treated target cells. The peptide-induced CTL were major histocompatibility complex class I restricted and CD8 positive.

Class I restricted CTL recognition of a soluble protein delivered by liposomes containing lipophilic polylysines

CD8+ cytotoxic lymphocytes recognize peptides derived from endogenous antigens complexed with class I major histocompatibility complex while CD4+ helper cells recognize peptides from exogenous antigens bound to class II MHC molecules. A soluble protein can be introduced into the class I pathway of antigen processing and presentation using an appropriate vehicle to deliver the antigen into the cytosol. Cationic liposomes containing lipophilic polylysine readily form complexes with an anionic, soluble protein ovalbumin. Mouse thymoma EL4 cells incubated with such complexes can be sensitized for killing by OVA-specific CTL effector cells. This method of target sensitization by a soluble antigen is more sensitive than the osmotic loading method previously reported.

Improved procedures for the determination of lipid phosphorus by malachite green

We have developed two procedures for the measurement of lipid phosphorus based on interaction between phosphomolybdenum and malachite green. One method, the "micro" assay uses 50-200 microliters of HClO4 and has a sensitivity range of 0.01-1.5 micrograms phosphorus. The second method, the "macro" assay, has a sensitivity range of 0.03-5.0 micrograms phosphorus with 100-500 microliters HClO4. Both assays are very reproducible with day to day standard deviations of less than 6% between triplicates irrespective of the HClO4 content used. At different concentrations of HClO4, each method was successfully used to determine the phosphorus content in phosphatidylethanolamine and sphingomyelin standards that covered the proposed sensitivity ranges. The increased range, sensitivity and greater volumes of HClO4 permitted in the procedures represent significant improvements over existing methods.

Ethanol inhibits C6 cell growth: fetal alcohol syndrome model

Maternal consumption of ethanol produces a pattern of malformations, including nervous system abnormalities, in the developing fetus, a state called Fetal Alcohol Syndrome. We report the dose-dependent inhibition by ethanol of the growth of a glioma derived cell line, C6 cells; the effects occur at ethanol concentrations commonly encountered in the blood during human intoxication. The effects occur with different morphological subtypes of the cell line and do not occur when the cells are exposed to iso-osmolar concentrations of other chemicals. The results demonstrate that C6 cells are a model for the study of the effects of ethanol on nervous system cell growth.

Sexuality in a natural population of bacteria– Bacillus subtilis challenges the clonal paradigm

Reproduction by binary fission necessarily establishes a clonal genotypic structure in bacterial populations unless a high rate of genetic recombination opposes it. Several genetic properties were examined for a wild population of Bacillus subtilis in the Sonoran Desert of Arizona to assess the extent of recombination in a natural population. These properties included allozyme variation revealed by multilocus enzyme electrophoresis, phage and antibiotic resistance, and restriction fragment length polymorphism with Southern hybridization. Evidence of extensive genetic recombination was found along with evidence of modest clonal structure. Recombination must be frequent relative to binary fission in this population. This mixed population structure provides broader options for bacterial evolution than would a purely clonal structure.

H-K-ATPase enhancement of Rb efflux by cortical collecting duct

Previous studies suggest that enhancement of rubidium tracer (86Rb) lumen-to-bath efflux following removal of luminal Na is mediated in part by a Ba-insensitive pathway. To determine the role of a primary active K pump in this response, we examined the action of known inhibitors of H-K-ATPase (Sch 28080) and Na-K-ATPase (ouabain) on the 86Rb lumen-to-bath efflux coefficient (KRb). Luminal Sch 28080 (10 microM) significantly reduced KRb by 39 +/- 8.0% (P less than 0.05), whereas luminal ouabain (0.1 mM) reduced KRb by 10 +/- 14% (P = not significant), suggesting that a luminal H-K-ATPase mediates Rb efflux. To examine whether H-K-ATPase mediates Rb in KRb following removal of luminal Na, additional experiments were conducted to examine the effect of Sch 28080 on KRb in the presence and the absence of luminal Na. In the presence of luminal Na, 10 microM Sch 28080 reduced KRb by 15 +/- 5.0%. However, in the absence of luminal Na, 10 microM Sch 28080 decreased KRb by 48 +/- 8.2%. The percentage inhibition of KRb by Sch 28080 was significantly greater in the absence of luminal Na than in its presence (P less than 0.01), suggesting that the enhancement of KRb following removal of luminal Na is mediated in part by an H-K-ATPase pathway. In either case transepithelial voltage was not significantly altered. In contrast to the lack of effect of luminal ouabain, addition of 0.1 mM ouabain to the bath increased KRb (69.8 +/- 11.1 vs. 95.9 +/- 18.7 nm/s, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)