Effect of multidrug-resistant P-glycoprotein gene expression on chloroaluminum tetrasulfonate phthalocyanine concentration

The effect of multidrug-resistant P-glycoprotein gene expression (MDR1) in 3T3 cells on cellular concentrations and cytotoxicity induced by the photodynamic agent chloroaluminum tetrasulfonate phthalocyanine (AlSPc) was evaluated. 3T3 cells transfected with a retroviral vector expressing human MDR1 cDNA were resistant to colchicine. Resistant cells incubated with daunomycin accumulated only 40-50% of the quantity of daunomycin accumulated in control cells. Resistant cells incubated with daunomycin in the presence of verapamil had intracellular daunomycin concentrations approximately equal to control cells without verapamil. When these MDR1 3T3 cells were incubated with AlSPc, cellular concentrations of AlSPc did not differ between cells resistant to colchicine and those that were not. Similarly, there was little difference in cytotoxicity demonstrated by 51Cromium release in the two cell lines exposed to AlSPc and light (675 nm; 6 J/cm2). This study suggests photodynamic therapy using AlSPc may be a useful treatment modality for tumors in which the MDR1 P-glycoprotein confers resistance to cancer chemotherapeutics.

Evidence for the regulation of guinea-pig heart microsomal phosphatidylcholine-hydrolysing phospholipase A1 by guanosine 5'-[gamma-thio]triphosphate

We have recently characterized lysophospholipase A2 activities in guinea-pig heart microsomes and postulated that these enzymes act sequentially with phospholipases A1 to release fatty acids selectively from phosphatidylcholine (PC) and phosphatidylethanolamine, thus providing an alternative route to the phospholipase A2 mode of release. In a further investigation of the postulated pathway, we have characterized the PC-hydrolysing phospholipase A1 in guinea-pig heart microsomes. Our results show that the enzyme may have a preference for substrates with C16:0 over C18:0 at the sn-1 position. In addition, although the enzyme cleaves the sn-1 fatty acid, the rate of hydrolysis of PC substrates with C16:0 at the sn-1 position was influenced by the nature of the fatty acid at the sn-2 position. The order of decreasing preference was C18:2 > C20:4 = C18:1 > C16:0. The hydrolyses of the molecular species were differentially affected by heating at 60 degrees C. An investigation into the effect of nucleotides on the activity of the enzyme showed that guanosine 5'-[gamma-thio]triphosphate (GTP[S]) inhibited the hydrolysis of PC by phospholipase A1 activity, whereas GTP, guanosine 5'-[beta-thio]diphosphate (GDP[S]), GDP, ATP and adenosine 5'-[gamma-thio]triphosphate (ATP[S]) did not affect the activity. The inhibitory effect of GTP[S] on phospholipase A1 activity was blocked by preincubation with GDP[S]. A differential effect of GTP[S] on the hydrolysis of different molecular species was also observed. Taken together, the results of this study suggest the presence of more than one phospholipase A1 in the microsomes with different substrate specificities, which act sequentially with lysophospholipase A2 to release linoleic or arachidonic acid selectively from PC under resting conditions. Upon stimulation and activation of the G-protein, the release of fatty acids would be inhibited.

Regulation of Hsp70 function by a eukaryotic DnaJ homolog

We report that a purified cytoplasmic Hsp70 homolog from Saccharomyces cerevisiae, Hsp70SSA1, exhibits a weak ATPase activity, which is stimulated by a purified eukaryotic dnaJp homolog (YDJ1p). Stable complex formation between Hsp70SSA1 and the permanently unfolded protein carboxymethylated alpha-lactalbumin (CMLA) was assayed by native gel electrophoresis. The affinity of Hsp70SSA1 for CMLA appeared to be regulated by YDJ1p. Significant reduction in both CMLA-Hsp70SSA1 complex formation and the release of CMLA pre-bound to Hsp70SSA1 was observed only in the presence of both YDJ1p and ATP. Thus, Hsp70SSA1 and YDJ1p interact functionally in the execution of Hsp70SSA1 chaperone activities in the eukaryotic cell.

Enhanced self-pumped phase conjugation from 16 degrees -cut KNSBN:Cu

With the maximum coupling coefficient and high internal reflection conditions, the self-pumped phase-conjugation reflectivity of copper-doped potassium sodium strontium barium niobate (KNSBN:Cu) is increased with 16 degrees -cut samples. The response time is also shortened. The resolution property of 16 degrees -cut KNSBN:Cu is determined and a distorted image is corrected by using the 16 degrees -cut sample.

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.

Ras-induced hyperplasia occurs with mutation of p53, but activated ras and myc together can induce carcinoma without p53 mutation

Using a reconstituted mouse prostate organ, the effects on endogenous p53 expression of the ras oncogene or of the ras + myc oncogenes were investigated. In this system the ras gene alone causes mild hyperplasia, but the combination of ras and myc leads to the formation of carcinomas. Surprisingly, while p53 mutations were found in cells derived from the reconstituted organs containing ras alone, no such mutations were found in the ras + myc-transformed cells. Their growth, unlike that of the cells containing ras alone, was not inhibited by transfection with plasmids encoding wild-type human p53. We suggest that expression of both activated ras and myc genes bypasses the need for p53 mutation by neutralizing the tumor suppressor activity of normal p53.

Differentiation of HT-29 human colonic adenocarcinoma cells correlates with increased expression of mitochondrial RNA: effects of trehalose on cell growth and maturation

The HT-29 human adenocarcinoma cell line has been used extensively in the study of colonic cell differentiation and colon cancer. We report here that substitution of glucose with trehalose (alpha-D-glucopyranosyl-alpha-D-glucopyranoside) depresses growth and promotes mucin-producing, goblet-like maturation of HT-29. An initial characterization of this process was made by analyzing several cDNA clones whose RNA templates were differentially expressed at elevated levels in cells grown in trehalose-containing medium. Seven of the 9 clones examined corresponded to 6 mitochondrial genes whose expression levels, relative to those from glucose-grown cells, ranged from approximately 3-fold for 16S rRNA to 8-23-fold for NADH dehydrogenase subunit 4. On the other hand, levels of mitochondrial DNA copy, measured by using NADH dehydrogenase subunit 4 cDNA as probe, were shown to be unaffected by trehalose treatment. Elevation of cellular NADH dehydrogenase subunit 4 RNA in HT-29 cultures grown in medium containing different components (sodium butyrate, galactose, no-sugar, glucose, cellobiose) generally correlated with depressed growth levels and specifically with increased numbers of mucin-producing cells present. Like butyrate, the sugar, trehalose, is an effective inducer of HT-29 differentiation, and may prove useful as a dietary therapeutic, and as a probe for elucidating mitochondrial involvement in colonic cell differentiation and transformation.

Hsp60/chaperonin gene expression and differentiation of human colon adenocarcinoma and multipotent leukaemic cells

Elevated mitochondrial gene expression is an early event in the switch from proliferation to differentiation of the human colon adenocarcinoma cell line, HT29, promoted by trehalose replacement of exogenous glucose. Here we report the isolation and elevated expression of hsp60, the gene encoding chaperonin, a mitochondrial protein required for assembly of mitochondrial and cellular proteins. In contrast to HT29, leukaemic cells (HL60 and K562) neither differentiated nor altered their mitochondrial gene expression after treatment with trehalose. However, differentiation of these cells, as promoted by 12-O-tetradecanoylphorbol-13-acetate actually resulted in decreased levels of hsp60 mRNA expression as well as mitochondrial RNA expression, suggesting significant differences in involvement of mitochondria in the differentiation of these cell lineages.

Perturbations of cellular acylation processes by the synthetic alkyl-lysophospholipid 1-O-octadecyl-2-O-methylglycero-3-phosphocholine do not correlate with inhibition of proliferation of MCF7 and T84 cell lines

We have investigated the hypothesis that the antiproliferative effect of 1-O-octadecyl-2-O-methylglycero-3-phosphocholine (ET-18-OCH3) is mediated through the inhibition of cellular acylation processes that control the unsaturated fatty acid complement of phospholipids. The effect of ET-18-OCH3 on the incorporation of radiolabeled oleic, linoleic, and arachidonic acids into MCF7 and T84 phospholipids was investigated. Incubation of MCF7 cells with fatty acids and 2.75 micrograms/ml ET-18-OCH3, which inhibited the proliferation of the cells after 8 h, resulted in decreased incorporation of fatty acids into a number of phospholipids, notably phosphatidylcholine; however, increased incorporation of fatty acids into other phospholipids was also observed. After 12 h incubation with the alkyl-lysophospholipid, differences in the distribution of newly incorporated fatty acids into the phospholipid classes were observed without any effect on the total amount of fatty acid incorporated. Incubation of MCF7 cells with 5 micrograms/ml ET-18-OCH3, which caused a cessation in proliferation, had a similar effect on the incorporation of the fatty acids into the phospholipids, but the redistribution of newly incorporated fatty acids in the phospholipids was accompanied by a decrease in the amount of associated radiolabeled fatty acid. Incubation of T84 cells with the labeled fatty acids and 3.5 micrograms/ml ET-18-OCH3, which significantly decreased proliferation after 8 h, resulted in decreased incorporation of oleic acid into phosphatidylcholine and increased incorporation of oleic, linoleic, and arachidonic acids into phosphatidylethanolamine, prior to the decrease in proliferation. After 12 h incubation with alkyl-lysophospholipid, significant increases in the total amount of labeled oleic and arachidonic acids incorporated in the phospholipid fraction were observed. These results clearly indicate that the antiproliferative effect of ET-18-OCH3 in MCF7 and T84 cells is not dependent on inhibition of acylation processes and the above hypothesis may not be applicable to all alkyl-lysophospholipid-sensitive cells.

The differential susceptibility of A427 and A549 cell lines to the growth-inhibitory effects of ET-18-OCH3 does not correlate with the relative effects of the alkyl-lysophospholipid on the incorporation of fatty acids into cellular phospholipids

Proliferation of A427, a lung cancer cell line, was significantly decreased 10 h after incubation with 5 micrograms/ml 1-O-octadecyl-2-O-methylglycero-3-phosphocholine (ET-18-OCH3) while the proliferation of A549, another lung cancer cell line, was unaffected until 15 h after incubation with the alkyl-lysophospholipid (ALP). The relative sensitivity of cells to the antiproliferative effect of ET-18-OCH3 has been postulated to be due to the degree of inhibition of cellular acylation processes. We therefore investigated the effect of 5 micrograms/ml ET-18-OCH3 on the incorporation of fatty acids for up to 12 h, into A427 and A549 phospholipids. Significant changes observed in the incorporation of fatty acids into A427 phospholipids by the ALP were a decreased incorporation of oleic acid into PC after 8 h, an increased incorporation of linoleic acid into PE after 12 h, decreased incorporation of arachidonate into PE after 3 h, and increased incorporation into PA after 5 h. Although the above changes affected the distribution of newly esterified fatty acids in the phospholipids, there was no effect on the total quantity of label incorporated in the phospholipid fraction between the experimental and control cells after 12 h. Incubation of A549 cells with ET-18-OCH3 resulted in decreased esterification of oleic acid into PC, SM, and LPC after 5 h; decreased incorporation of linoleic into PE after 12 h; and a decreased incorporation of arachidonate into SM after 1.5 h. After 12 h incubation with ET-18-OCH3, changes in the distribution of radiolabeled fatty acids were observed in the quantitatively minor phospholipids, SM and LPC. A 20% decrease in the quantity of oleic acid incorporated into the phospholipids was observed in cells incubated with the ALP; however, no differences were observed in the quantity of linoleic or arachidonic acid incorporated into the phospholipids. The lack of common effects of the ALP on the incorporation of fatty acids into A427 and A549 phospholipids, coupled with the absence of changes that were more severe or manifested earlier in the more sensitive A427 cell line, suggests that the effect of ET-18-OCH3 on the acylation processes depends on the cell type and the fatty acid species and is unlikely to be responsible for the relative sensitivities of the cells to the compound. Radiolabeled ET-18-OCH3 was used to examine the correlation between the amount of the compound accumulated in A427, A549, MCF7, T84, and LS174T cells and the relative susceptibilities of the cells to the ALP.(ABSTRACT TRUNCATED AT 400 WORDS)

Structure of HIV-1 reverse transcriptase/DNA complex at 7 A resolution showing active site locations

AIDS, caused by human immunodeficiency virus (HIV), is one of the world's most serious health problems, with current protocols being inadequate for either prevention or successful long-term treatment. In retroviruses such as HIV, the enzyme reverse transcriptase copies the single-stranded RNA genome into double-stranded DNA that is then integrated into the chromosomes of infected cells. Reverse transcriptase is the target of the most widely used treatments for AIDS, 3'-azido-3'-deoxythymidine (AZT) and 2',3'-dideoxyinosine (ddI), but resistant strains of HIV-1 arise in patients after a relatively short time. There are several nonnucleoside inhibitors of HIV-1 reverse transcriptase, but resistance to such agents also develops rapidly. We report here the structure at 7 A resolution of a ternary complex of the HIV-1 reverse transcriptase heterodimer, a monoclonal antibody Fab fragment, and a duplex DNA template-primer. The double-stranded DNA binds in a groove on the surface of the enzyme. The electron density near one end of the DNA matches well with the known structure of the HIV-1 reverse transcriptase RNase H domain. At the opposite end of the DNA, a mercurated derivative of UTP has been localized by difference Fourier methods, allowing tentative identification of the polymerase nucleoside triphosphate binding site. We also determined the structure of the reverse transcriptase/Fab complex in the absence of template-primer to compare the bound and free forms of the enzyme. The presence of DNA correlates with movement of protein electron density in the vicinity of the putative template-primer binding groove. These results have important implications for developing improved inhibitors of reverse transcriptase for the treatment of AIDS.

Conserved residues flanking the thiol/disulfide centers of protein disulfide isomerase are not essential for catalysis of thiol/disulfide exchange

Protein disulfide isomerase (PDI) catalyzes the oxidative folding of proteins containing disulfide bonds by increasing the rate of disulfide bond rearrangements which normally occur during the folding process. The amino acid sequences of the N- and C-terminal redox active sites (PWCGHCK) in PDI are completely conserved from yeast to man and display considerable identity with the redox-active center of thioredoxin (EWCGPCK). Available data indicate that the two thiol/disulfide centers of PDI can function independently in the isomerase reaction and that the cysteine residues in each active site are essential for catalysis. To evaluate the role of residues flanking the active-site cysteines of PDI in function, a variety of mutations were introduced into the N-terminal active site of PDI within the context of both a functional C-terminal active site and an inactive C-terminal active site in which serine residues replaced C379 and C382. Replacement of non-cysteine residues (W34 to Ser, G36 to Ala, and K39 to Arg) resulted in only a modest reduction in catalytic activity in both the oxidative refolding of RNase A and the reduction of insulin (10-27%), independent of the status of the C-terminal active site. A somewhat larger effect was observed with the H37P mutation where approximately 80% of the activity attributable to the N-terminal domain (approximately 40%) was lost. However, the H37P mutant N-terminal site expressed within the context of an inactive C-terminal domain exhibits 30% activity, approximately 70% of the activity of the N-terminal site alone.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo molecular analysis of lymphokines involved in the murine immune response during Schistosoma mansoni infection. II. Quantification of IL-4 mRNA, IFN-gamma mRNA, and IL-2 mRNA levels in the granulomatous livers, mesenteric lymph nodes, and spleens during the course of modulation

Parasite egg-induced granulomas are the primary pathogenic lesions in murine schistosomiasis mansoni. This cell-mediated granulomatous response is specific for soluble egg Ag and appears to be mediated predominantly by CD4+ Th2 cells. As infection progresses from the acute to the chronic phase, the cell-mediated anti-soluble egg Ag responses attenuate in a process termed modulation. In this study the hypothesis that modulation is effected by a chronic phase increase in Th2-inhibiting Th1 cell activity was investigated. Northern blot quantification of mRNA specific for the Th2 lymphokine, IL-4, and the Th1 lymphokines, IFN-gamma and IL-2, in the spleens, mesenteric lymph nodes, and granulomatous livers of mice infected for various lengths of time over the course of modulation was performed. Also, the capacity of mitogen- and Ag-stimulated spleen cells to produce message for these lymphokines was compared. Peak tissue levels of both IL-4 mRNA and IFN-gamma mRNA were seen in acutely infected mice, and levels of both messages declined as infection became chronic. Stimulated spleen cells from acutely infected mice also produced higher levels of IL-4 and IFN-gamma mRNA than cells from chronically infected mice. IL-2 mRNA was never detected in any tissue sample but was detected in the stimulated spleen cells, again with acute phase levels higher than chronic phase levels. Hence, this study shows no evidence for increased Th1 cell activity during chronic infection and suggests that modulation may be effected by a generalized suppression of lymphokine synthesis.

In vivo molecular analysis of lymphokines involved in the murine immune response during Schistosoma mansoni infection. II. Quantification of IL-4 mRNA, IFN-gamma mRNA, and IL-2 mRNA levels in the granulomatous livers, mesenteric lymph nodes, and spleens during the course of modulation

Parasite egg-induced granulomas are the primary pathogenic lesions in murine schistosomiasis mansoni. This cell-mediated granulomatous response is specific for soluble egg Ag and appears to be mediated predominantly by CD4+ Th2 cells. As infection progresses from the acute to the chronic phase, the cell-mediated anti-soluble egg Ag responses attenuate in a process termed modulation. In this study the hypothesis that modulation is effected by a chronic phase increase in Th2-inhibiting Th1 cell activity was investigated. Northern blot quantification of mRNA specific for the Th2 lymphokine, IL-4, and the Th1 lymphokines, IFN-gamma and IL-2, in the spleens, mesenteric lymph nodes, and granulomatous livers of mice infected for various lengths of time over the course of modulation was performed. Also, the capacity of mitogen- and Ag-stimulated spleen cells to produce message for these lymphokines was compared. Peak tissue levels of both IL-4 mRNA and IFN-gamma mRNA were seen in acutely infected mice, and levels of both messages declined as infection became chronic. Stimulated spleen cells from acutely infected mice also produced higher levels of IL-4 and IFN-gamma mRNA than cells from chronically infected mice. IL-2 mRNA was never detected in any tissue sample but was detected in the stimulated spleen cells, again with acute phase levels higher than chronic phase levels. Hence, this study shows no evidence for increased Th1 cell activity during chronic infection and suggests that modulation may be effected by a generalized suppression of lymphokine synthesis.

Thermal Conductivity of Monolithic Organic Aerogels

The total thermal conductivity lambda of resorcinol-formaldehyde aerogel monoliths has been measured as a function of density rho in the range from rho = 80 to 300 kilograms per cubic meter. A record-low conductivity value in air at 300 K of lambda approximately 0.012 watt per meter per kelvin was found for rho approximately 157 kilograms per cubic meter. Caloric measurements under variation of gas pressure as well as spectral infrared transmission measurements allowed the determination of solid conductivity, gaseous conductivity, and radiative conductivity as a function of density. The development of such low conductivity materials is of great interest with respect to the substitution of environmentally harmful insulating foams made from chlorofluorocarbons.

Functions of hepatitis B surface proteins

HBV surface proteins play a number of functional roles in cellular infection, viral synthesis and in immune responses of the host. Three coterminal proteins of differing sizes and three subdomains of the individual molecules can be recognized. In this brief review, functions of the various proteins and domains are described and their significance as potential immunogens is discussed. Although it is apparent that the surface proteins are involved in the development of persistent HBV infections, the underlying mechanisms of liver involvement remain unknown.

Stimulated Raman scattering and four-wave mixing from a mixture of carbon disulfide and phenylethanol in a hollow optical fiber

We observe, for what is to our knowledge the first time, stimulated Raman scattering and four-wave mixing in a liquid-core optical fiber filled with a mixture of carbon disulfide and phenylethanol pumped by the frequencydoubled output of a Q-switched YAG laser (lambda = 532.1 nm). The frequencies of the stimulated Raman scattering and four-wave mixing spectra are specified, and theoretical interpretations are also given.

High-order stimulated Raman scattering and nonlinear red-shifted broadening in benzyl alcohol core optical fiber

Six orders of Stokes lines and the first-order anti-Stokes line were observed we believe for the first time, in a benzyl alcohol liquid core optical fiber. All the Stokes lines were asymmetrically broadened favoring the lower frequencies. The blue-shifted broadening was only a few percent of the amount of the red-shifted broadening, and the broadening of the fifty-order Stokes line was so broadened to exceed the characteristic Raman frequency shift, 1000 cm(-1), to connect with the sixth-order Stokes line. The asymmetric broadening was discussed to be mainly due to the effect of the stimulated Rayleigh wing scattering.

Inflammation near the nerve cell body enhances axonal regeneration

Although crushed axons in a dorsal spinal root normally regenerate more slowly than peripheral axons, their regeneration can be accelerated by a conditioning lesion to the corresponding peripheral nerve. These and other observations indicate that injury to peripheral sensory axons triggers changes in their nerve cell bodies that contribute to axonal regeneration. To investigate mechanisms of activating nerve cell bodies, an inflammatory reaction was provoked in rat dorsal root ganglia (DRG) through injection of Corynebacterium parvum. This inflammation enhanced regeneration in the associated dorsal root, increasing 4-fold the number of regenerating fibers 17 d after crushing; peripheral nerve regeneration was not accelerated. A milder stimulation of dorsal root regeneration was detected after direct injection of isogenous macrophages into the ganglion. It is concluded that changes favorable to axonal regeneration can be induced by products of inflammatory cells acting in the vicinity of the nerve cell body. Satellite glial cells and other unidentified cells in lumbar DRG were shown by thymidine radioautography to proliferate after sciatic nerve transection or injection of C. parvum into the ganglia. Intrathecal infusion of mitomycin C suppressed axotomy-induced mitosis of satellite glial cells but did not impede axonal regeneration in the dorsal root or the peripheral nerve. Nevertheless, the similarity in reactions of satellite glial cells during 2 processes that activate neurons adds indirect support to the idea that non-neuronal cells in the DRG might influence regenerative responses of primary sensory neurons.

[Trace elements in the aqueous extract of twenty Chinese drugs before and after charring]

Our study on the variation of trace element contents in the aqueous extract of 20 Chinese drugs before and after charring has shown that after charring Ca ions increase noticeably in the extract of 6 drugs, increase slightly in another 6 and decrease in varying degrees in the remaining 8. In all the charred drugs no rise has been observed in the contents of trace elements, but instead, in most of them the contents tend to drop.

Retrovirus-mediated transgenic keratin expression in cultured fibroblasts: specific domain functions in keratin stabilization and filament formation

With retrovirus-mediated gene transfer, we used intact and deleted keratin proteins to investigate the molecular basis of intermediate filament function. Three levels of assembly show a different stringency for the involvement of individual keratin domains: protein accumulation requires the alpha helix domains; stable filament formation additionally requires both N- and C-terminal domains of either one of the two interacting keratins, suggesting that head to tail homotypic interaction is important for effective elongation; and higher order organization of the cytoplasmic network depends on correct type I-type II pairing of keratins. The presence of two distinct interaction sites along potentially different axes may explain the characteristic morphology of keratin intermediate filament networks.

[The isolation and structure of tripchlorolide (T4) from Tripterygium wilfordii]

A new compound named tripchlorolide was isolated from Total Glucosides (T II) extracted from the woody part of the root of Tripterygium wilfordii Hook. f. Tripchlorolide (T4) was obtained as white needle-like crystals, mp 256-258 degrees C. Its molecular formula is C20H25O6Cl. The structure of T4 was elucidated on the basis of spectral (UV, IR, MS, FTMS/SCI, 1H-NMR, 13C-NMR, 1H-1H cosy, 13C-1H cosy) analyses, X-ray and chemical evidence. In preliminary pharmacologic assay, tripchlorolide showed definite anti-inflammatory actions and strong immunosuppressive and antifertile activities, the potency of the latter being 100 times stronger than that of T II.

Cloning, characterization, and expression of the gene for the catalytic subunit of cAMP-dependent protein kinase in Caenorhabditis elegans. Identification of highly conserved and unique isoforms generated by alternative splicing

The nematode Caenorhabditis elegans expresses substantial amounts of several forms (Mr values = 39,000-41,000) of the catalytic subunit (C) of cAMP-dependent protein kinase. Approximately 65% of the total cAMP-dependent phosphotransferase activity is recovered in particulate fractions of homogenates prepared from asynchronous populations of C. elegans. The C subunit is expressed at a low level in cytosolic and particulate compartments during embryogenesis. As the nematodes progress from late embryonic stages to the newly hatched, first larval (L1) stage, C subunit content increases 15-fold. High levels of C subunits are observed in several subsequent larval and adult stages of development. Since the relative abundance of C subunit mRNA changes little with development, it appears that control of C expression is exerted the translational and/or post-translational levels. cDNAs for two types of C have been cloned and sequenced. The derived amino acid sequence of a major isoform (CeCAT alpha, 358 residues) is highly homologous (82% identical) with the murine C alpha subunit. A second, novel C subunit (CeCAT alpha', 374 residues) has a unique 56-residue carboxyl-terminal region that is generated by the alternative splicing of the C pre-mRNA. The splicing process that yields CeCAT alpha' is unusual because it converts the central portion of an apparent 1-kilobase (kb) intron to an exon. The alternative exon introduces the novel carboxyl terminus and a new translation stop signal, while simultaneously converting the coding sequence for 40 carboxyl-terminal residues in CeCAT alpha into 3'-untranslated nucleotides. The 5' end of the C. elegans C subunit mRNA is produced by the trans-splicing of the C gene transcript to a 22-base pair C. elegans leader sequence originally described by Krause, M., and Hirsh, D. [1987) Cell 49, 753-761). The 20-kb C. elegans C gene is divided into seven exons by introns ranging in size from 54 to 8000 bp. The sizes of the C. elegans C subunit gene, cytoplasmic mRNA (2.5 kb), and subunit protein are similar to the sizes of the murine C alpha gene, mRNA, and polypeptide. However, the nematode and murine C genes differ significantly in the organization of their introns and exons.

Differential screening of murine ascites cDNA libraries by means of in vitro transcripts of cell-cycle-phase-specific cDNA and digital image processing

Cell-cycle-phase-specific cDNA libraries were prepared in the lambda gt10 vector and in the in vitro transcription vector, pBluescript. Plaques of the cDNA libraries prepared in the lambda gt10 vector were differentially screened with (a) in vitro transcripts of the cell-cycle-phase-specific cDNAs cloned in the transcription vector and (b) with first-strand cDNA of mRNA from phase-synchronous cells. The results suggest that first-strand cDNA can be replaced, at least in prescreening experiments, by in vitro transcripts of representative cDNA libraries prepared in in vitro transcription vectors. The fractions of differential clones detected with in vitro transcripts (1.2%) and with first-strand cDNA (1%) were in the same order. Individual clones selected by differential hybridization with in vitro transcripts could be verified by differential hybridization with cell-cycle-phase-specific first-strand cDNA. This indicates that the pattern of stage-specific prevalences of cDNA clones is essentially retained during careful amplifications of large cDNA libraries. The application of in vitro transcripts of stage-specific cDNA for differential screening experiments is of interest in cases where the amount of biological material is either limited or difficult to prepare. It also allows standardization of the probes in repeated screening experiments. Three clones reflecting cell-cycle-phase-specific mRNA prevalences were chosen and analyzed on the sequence level. Two sequences with S-phase prevalences were identified. They code for elongation factor EF1 alpha and for glyceraldehyde-3-phosphate dehydrogenase, respectively. The third sequence reflects the first cDNA of a mRNA with significant prevalence in G2-phase cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effects of xamoterol and isoprenaline on rat cardiac beta-adrenoceptors: studies of function and regulation

1. The effects of the beta 1-selective partial agonist xamoterol and the full agonist isoprenaline on rat cardiac beta-adrenoceptors were compared in functional studies of heart rate response in vivo and in vitro. In addition, the ability of both agents to cause receptor down-regulation in the rat heart following chronic (6 days) subcutaneous infusions was assessed by radioligand binding with [125I]-pindolol. 2. In the functional studies, xamoterol produced a maximal effect equivalent to approximately 65% of that of isoprenaline and was overall less potent than the full agonist. 3. Compared to saline control, the density of beta-adrenoceptors was reduced approximately 39% in ventricular membranes prepared from animals after 6 days of isoprenaline infusion but was unaffected by xamoterol. The relative proportions of the beta-adrenoceptor subtypes were unchanged by either active treatment. 4. Plasma xamoterol level at the end of the infusion period was equivalent to that associated with maximum tachycardia in vivo and to the concentration producing maximal stimulation of the rat isolated atrium in vitro. Thus suggesting 100% beta-adrenoceptor occupancy during the period of xamoterol infusion. 5. These results indicate that in this animal model xamoterol does not induce cardiac beta-adrenoceptor down-regulation during chronic treatment, with doses that produce a maximal functional response both in vitro and in vivo.

Protective effects of sodium selenite on experimental myocardial infarction

The present study compares the protective effects of sodium selenite (Se), hyaluronidase (Hy) and anisodamine (An) on infarct size, left ventricular myocardial contractility (LVMC) and relaxation (LVMR) and myocardial hypertrophy on the 3rd, 9th and 21st days after the ligation of left main coronary artery in the rats. The results showed that Se could reduce the infarct size, so could Hy and An. However, Se could relevantly improve LVMC and LVMR at the acute phase of infarction, while Hy and An could not. On the 21st day (healing phase) of infarction the indexes of the LVMC and LVMR in Se-, Hy- or An-treated rats were significantly better than those in the control rats. Se could enhance the extent of hypertrophy in non-infarcted myocardium, while Hy and An could not. On the 21st day of this experiment the total natural mortality in the Se-treated rats was significantly lower than that in the control or in the An-treated rats. These data suggest that Se is superior to Hy and An in the treatment of acute myocardial infarction.

Construction and quality of cDNA libraries prepared from cytoplasmic RNA not enriched in poly(A)+RNA

Poly(A)+RNA and cytoplasmic RNA of Ehrlich ascites tumor cells grown in vivo were used to study the quality and efficiency of cDNA synthesis. It was found that the rates of oligo(dT)-primed and unprimed reverse transcription were very similar in both cases. The size distributions of the cDNA strands prepared from unfractionated RNA reflected the size of cytoplasmic mRNA populations including a significant fraction of long molecules up to 6 kb. The fraction of cDNAs primed on rRNAs by oligo(dT) was found to be as low as 2-3%. Following second-strand synthesis by means of RNase H-induced nick translation by DNA polymerase I the overall yields in double-stranded cDNA were slightly higher when unfractionated cytoplasmic RNA was used as starting template. In repeated experiments we obtained an average yield of 2.2 micrograms of double-stranded cDNA when 70 micrograms of unfractionated cytoplasmic RNA was used as starting material. This amount of cDNA synthesized in one assay was sufficient to construct representative cDNA libraries in different vectors. Southern hybridizations of DNA isolated from cDNA libraries with various radiolabelled probes show that the libraries constructed from cDNA synthesized from cytoplasmic RNA not enriched in poly(A)+RNA contain a high ratio of full-length cDNA clones. The results suggest that representative cDNA libraries of high quality can be constructed without pre-isolation of poly(A)+RNA fractions.

Cell cycle phase-specific cDNA libraries reflecting phase-specific gene expression of Ehrlich ascites cells growing in vivo

Asynchronous populations of Ehrlich ascites tumor cells grown in vivo were separated by centrifugal elutriation into fractions of G1-, S-, and G2/M-phase cells with less than 10% cross-contamination. Cytoplasmic mRNA from phase-synchronous cells was used to prepare cDNA which was ligated with bacteriophage lambda gt10 arms and amplified in Escherichia coli C600 hfl-. EcoRI digests of DNA isolated from the sublibraries (G1, S, G2/M) were submitted to Southern hybridizations with radiolabeled probes either (a) for genes whose phase-specific expression is clearly documented, thymidine kinase, dihydrofolate reductase, and thymidylate synthase, or (b) for genes whose change of expression during the cell cycle is likely, lamin C, beta-actin, alpha- and beta-tubulin, c-myc, c-fos, p53. The cDNA sequences for genes of group (a) were found to be significantly enriched in DNA of the S-phase library indicating that the cell cycle phase-specific patterns of the respective mRNA levels are conserved in the sublibraries. Sequences belonging to group (b) were also found to be enriched in DNA isolated from the sublibraries: c-fos in G1 phase, lamin C, beta-actin, tubulins, c-myc in S phase, and p53 in G1/S phase. The unexpected prevalence of c-myc and alpha-tubulin in the S-phase library is supported by Northern analysis of RNA from phase-synchronous cells. Non-phase-specific, randomly chosen sequences hybridized equally strong with DNA isolated from the different sublibraries. No significant changes of the patterns of hybridization signals were observed with DNA from different amplifications of the sublibraries when analyzed with the same DNA probe indicating that the cDNA complexities are well conserved during amplifications. Consequently, the sublibraries are useful to obtain information about the cell cycle phase-specific expression of mRNAs for other genes of interest. Since the sublibraries reflect mRNA levels of the cells growing in vivo they supply data on the physiological in vivo pattern of gene expression undisturbed by potentially unphysiological in vitro conditions.