[The protective effects of drugs H and X on liver cold ischemic injury]

Using isolated perfusion rat liver model (IPRL), we studied the protective effects of drugs H and X on rat's liver cold ischemic injury. After the rat's liver was preserved for 12 hours in Collins II solution with the addition of drugs H and X, the necrotic rate of sinusoidal lining cells was significantly lower than that of control group. Within certain range of the dosage of drugs H and X, the necrotic rate of sinusoidal lining cells was in the inverse ratio of the dosage in the Collins II solution. We also found that drugs H and X had obvious protective effect on liver cell redox function. But these drugs could not inhibit tissue from swelling after Collins II solution preservation. The protective mechanisms of the drugs maybe relate to the remoral of free radicals and suppression of Kupffer's cells activity.

Rat tail suspension reduces messenger RNA level for growth factors and osteopontin and decreases the osteoblastic differentiation of bone marrow stromal cells

We previously reported that bone marrow stromal cells produce insulin-like growth factors (IGF-I and -II), and that medium conditioned by marrow stromal cells stimulates osteoblast proliferation in vitro. The present study employed the rat tail-suspension model to unload the hindlimbs. It was designed to test the hypothesis that the development of osteopenia or osteoporosis could be due to a deficit in the osteogenic function of marrow stromal cells. Although tail suspension suppressed body weight during the first 3 days of an 11-day pair-fed study, the overall weight gain recorded by these animals was normal. Nevertheless, bone growth was inhibited by suspension. Similarly, the total adherent marrow stromal cell population harvested from the femurs and tibias was decreased by tail suspension, and only half the normal number of fibroblastic stromal cell colonies grew when they were cultured. The proliferation of alkaline-phosphatase-positive cells in the stroma was also inhibited. Northern hybridization revealed that the messenger RNA level for transforming growth factor-beta 2 and IGF-II in stromal cell was reduced by tail suspension. The production of IGF-II by marrow stromal cells was also decreased. The steady-state level of five different transcript sizes of IGF-I mRNA was altered differentially by tail suspension. Osteopontin mRNA was also reduced in marrow stromal cells from tail-suspended rats compared with the normal rats. These data suggest that skeletal unloading not only alters the mRNA level for growth factors and peptide production, but also affects the proliferation and osteogenic differentiation of marrow stromal cells. These changes may be responsible for the reduced bone formation in osteopenia and osteoporosis.

Structures of cDNAs encoding the muscle-type and non-muscle-type isozymes of lamprey fructose bisphosphate aldolases and the evolution of aldolase genes

Nearly full-length cDNA clones for muscle-type and non-muscle-type aldolase mRNAs were cloned from lambda gt10 cDNA libraries constructed from skeletal muscle and liver mRNAs of lamprey (Entosphenus japonicus). The cDNA-M8 has 2,240 bp carrying an open reading frame of 1,089 bp which encodes 362 amino acids without the amino terminal methionine, while the cDNA-L3 is 1,761 bp in length and has an open reading frame of 1,092 bp, which encodes 363 amino acids without the methionine. We designated the cDNA clones M8 and L3 as the muscle-type and non-muscle-type aldolase cDNAs, respectively. The entire amino acid sequences deduced from cDNA-M8 and -L3 show a high degree of identity to one another (76%) and also to vertebrate aldolases A (74-76%), B (68-70%), and C (71-76%) and Drosophila melanogaster aldolases alpha, beta, and gamma (66-67%). Northern blot analyses using the 3'-noncoding sequences of cDNA-M8 and -L3 as hybridization probes indicated that the muscle-type mRNA is expressed mainly in the skeletal muscle, heart muscle, brain, and some other tissues, but probably not in liver, while the non-muscle-type mRNA is expressed mainly in the liver and also in brain and other tissues, except for the heart muscle. Phylogenetic analyses showed that both muscle-type and non-muscle-type aldolases of lamprey resemble one another and might share a common ancestor with vertebrate aldolases A and C, but they are not direct ancestors of vertebrate aldolases.

Synthesis, conformation and opioid activity of deltorphins

A series of deltorphin analogues was prepared by solid-phase peptide synthesis. Their opioid activity was evaluated in rat opiatic assay and their conformation was determined by two-dimension Nuclear Magnetic Resonance Spectroscopy. The analogues containing D-alanine acid at position 2 were much more potent in the assay than their corresponding isomers containing L-alanine acid at this position. The conformational analysis on NMR study in DMSO showed that C-terminal tetrapeptides of both deltorphin II and its L-alanine analog might form a 3(10) helix, which confirms that the substitution of D-amino acid at position 2 decreased the opioid activity.

Glycine 122 is essential for cooperativity and binding of Mg2+ to porcine fructose-1,6-bisphosphatase

Site-directed mutagenesis of an amino acid residue in the substrate binding site of porcine fructose-1,6-bisphosphatase was carried out based on the crystal structure of the enzyme (Zhang, Y., Liang, J.-Y., Huang, S., Ke, H., and Lipscomb, W. N. (1993) Biochemistry 32, 1844-1857). A mutant enzyme form of fructose-1,6-bisphosphatase, G122A, was purified and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, circular dichroism spectrometry (CD), and initial rate kinetics. There were no discernible differences between the secondary structures of the wild-type and the mutant enzyme on the basis of CD data. Altering Gly-122 to alanine caused a significant decrease in the enzyme's activity and affinity for Mg2+. The kcat for this mutant enzyme was only about 5% of that of wild-type fructose-1,6-bisphosphatase, and the Ka for Mg2+ was about 20-fold higher than that of the wild-type enzyme. The Ki for AMP was increased 77-fold in the case of the mutant enzyme; however, the Hill coefficient was unaltered. Most importantly, it was observed that replacement of Gly-122 with alanine caused the total loss of cooperativity for Mg2+. It is concluded that Gly-122 is essential for Mg2+ cooperativity and important for binding of Mg2+ and AMP as well as for enzyme activity.

Calcium entry blockers and activators: conformational and structural determinants of dihydropyrimidine calcium channel modulators

Dihydropyrimidines 4, 6, and 15, uniquely designed to unambiguously establish structural and conformational determinants for DHP receptor occupation and for modulation of calcium channel function, were prepared and examined for calcium channel modulation. Our results confirm and firmly establish a preference for syn-orientation of an unsymmetrically substituted aryl moiety at the DHP receptor (15d vs 15e). We propose a normal vs capsized DHP boat model to explain structural and conformational requirements for modulation of calcium channel function that requires an obligatory left-hand side alkoxy cis-carbonyl interaction for maximal DHP receptor affinity, the effect of channel function being determined by orientation of the 4-aryl group. Enantiomers having an up-oriented pseudoaxial aryl group (normal DHP boat) will elicit calcium antagonist activity, whereas enantiomers having a down-oriented pseudoaxial aryl group (capsized DHP boat) will elicit calcium agonist activity. Single enantiomers of macrocyclic lactone 15b demonstrate opposite channel activity. Antagonist activity resides in enantiomer 15b-A (S-configuration, left-hand side alkoxy cis-carbonyl with up-oriented pseudoaxial aryl group and normal DHP boat), whereas agonist activity resides in enantiomer 15b-B (R-configuration, left-hand side alkoxy cis-carbonyl with down-oriented pseudoaxial aryl group and capsized DHP boat). Moreover, this model is consistent with and provides a rational explanation of previous literature in this area, most notably the observation of chiral inversion and potency diminution upon replacement of ester by hydrogen in the Bay K 8644 series.

Transcriptional induction of the melanocyte-stimulating hormone receptor in brain metastases of murine K-1735 melanoma

Metastatic K-1735 murine melanoma cells are amelanotic in culture or in the subcutis of syngeneic mice. When injected into the internal carotid artery, these cells produce melanotic brain metastases. The production of melanin in tumor cells growing in the brain was directly correlated with induction of melanocyte-stimulating hormone receptor (MSH-R) steady-state mRNA transcripts. K-1735 cells isolated from brain lesions and implanted into the subcutis or grown in culture lose MSH-R transcripts and become amelanotic. In contrast to K-1735 cells, B16-BL6 melanoma cells constitutively produce melanin and express high levels of MSH-R mRNA regardless of the site of growth. Somatic cell hybrids between K-1735 and B16 cells produced melanin and expressed high levels of MSH-R mRNA transcripts, regardless of the site of growth, suggesting the dominance of the B16 phenotype. Treatment with alpha-MSH failed to upregulate MSH-R expression in cultured K-1735 cells or to maintain MSH-R expression in K-1735 cells isolated from brain metastases to be grown in culture. Responsiveness to alpha-MSH as determined by cell proliferation, melanin production, and intracellular accumulation of cyclic AMP directly correlated with MSH-R expression. These data demonstrate that a specific organ environment influences the phenotype of metastatic cells by regulation of specific genes that encode for cell surface receptors.

[My personal idea on authorship of Nanjing (Classic of Questioning)]

It has been a matter of dispute on the authorship, date of writing of Nanjing (Classic of Questioning). This paper mentions 2 evidences based on the Classic's academic idea and its developmental history and 3 collateral evidences from literatures of the Han Dynasty, claiming that Nanjing was written in the period of Warrings States by Qin Yueren. This is of significance in the assessment of the position and influence of Nanjing in the history of TCM.

[Streptococcus pneumoniae-induced pulmonary consolidation prevented with tumor necrosis factor alpha monoclonal antibody in mouse]

Streptococcus pneumoniae stimulate mouse peritoneal macrophages to release tumor necrosis factor alpha (TNF alpha) in vitro. When penicillin was added to lysate bacterium, TNF alpha release was accelerated. 150 Kunming mice were infected with streptococcus pnumoniae through inspiration. Dynamic changes of TNF alpha concentration in serum and bronchoalveolar lavage fluid were detected; pulmonary pathological changes were also observed. It was found that TNF alpha monoclonal antibody significantly attenuates TNF alpha activity in serum and bronchoalveolar lavage fluid, white blood cell chemotaxis, emigation, and infiltration were inhibited. We conclude that streptococcus pneumoniae infection stimulates TNF alpha release, and TNF alpha is probably the major mediator that causes tissue damage during streptococcus pneumoniae infection. As penicillin accelerates TNFa release, single therapy of penicillin may worse tissue damage.

The population association of glucokinase gene with type 2 (noninsulin-dependent) diabetes mellitus in Chinese

The association of gluckinase (GCK) gene with type 2 (non-insulin-dependent) diabetes mellitus was investigated in 168 Chinese subjects (85 unrelated type 2 diabetics and 83 non-diabetic controls). The microsatellite polymorphism marker, GCK-5', was amplified with polymerase chain reaction. Four alleles were observed in Chinese population with length varying from 137bp to 143bp and the most common one being the 139bp allele 3. In comparison with non-diabetics, allele 4 was significantly increased in type 2 diabetes (10% versus 38, respectively; X2 = 6.773, P = 0.009); genotype 44 and 4X (X denotes any allele other than allele 4) were significantly increased in type 2 diabetes (16% versus 6% respectively; X2 = 6.439, P = 0.011). The frequency difference was also shown in overweight/obese subgroup comparison (X2 = 7.718, P = 0.021), but not in lean/normal-weight subgroup comparison. No differences of age of onset and frequency of positive family history were observed between type 2 diabetic patients with genotype 44 or 4X and those with XX. The risk for type 2 diabetes in Chinese with genotype 44 or 4X was about 3.5 times higher than in Chinese with genotype XX. Therefore, GCK gene was associated with Chinese type 2 diabetes.

Hematopoietic development of vav-/- mouse embryonic stem cells

The vav protooncogene product is expressed nearly exclusively in hematopoietic lineages and contains several structural motifs (SH2/SH3 domains and a dbl-oncogene homology region) typical of proteins functioning in signaling pathways. To ascertain if vav expression is required for hematopoiesis we generated vav-negative mouse embryonic stem cells by gene targeting and examined the consequences of loss of vav function on erythroid and myeloid development in vitro and in vivo. In conflict with the conclusions drawn from expression of antisense vav RNA in embryonic stem cells [Wulf, G. M., Adra, C. N. & Lim, B. (1993) EMBO J. 12, 5065-5074], we observed erythroid and myeloid development in the absence of vav. These experiments demonstrate that vav expression is not absolutely required for hematopoietic development.

Heterogeneity of protein kinase C activity in human U-373 and G-26 mice glioma cells

Protein kinase C (PKC) enzyme activity in a mouse glioma cell line G-26 and a human glioma cell line U-373 were compared at similar cell confluency in-vitro to establish if a G-26 in-vivo mouse model would be useful to examine the role of PKC inhibitors in controlling human glioma growth in-vivo. Original crude cytosolic and membrane PKC fractions of both mouse glioma G-26 and human glioma U-373 cells did not display significant PKC activity compared to partially purified PKC. Partial purification of mouse glioma G-26 and U-373 cytosolic and membrane fractions showed different cytosolic and membrane PKC activity profiles. Total PKC activity was higher (rho = 0.0001) in human glioma U-373 (7840 picomoles/mg/min) than in mouse glioma G-26 cells (2890 picomoles/mg/min). Thus, results from trials using nude mice human glioma xenografts may be more valid than those obtained from a G-26 in-vivo mouse model for studying the effects of therapeutic drugs on PKC isozymes.

Induction of Fos-like immunoreactivity in the rat hypothalamus by an endogenous feeding suppressant (2-buten-4-olide)

Central influence of 2-buten-4-olide (2-B4O), an endogenous feeding suppressant, was studied through immunohistochemical detection of Fos expression in the rat hypothalamus. Animals received 2-B4O (100 or 200 mg/kg i.p.) or saline 2 h before perfusion with 4% phosphate-buffered paraformaldehyde. The hypothalamus was removed and cut into vibratome sections. Immunohistochemical analysis revealed that injection of 2-B4O induced Fos-like immunoreactivity significantly in the paraventricular, dorsomedial and arcuate nuclei and the periventricular and lateral hypothalamic areas. These hypothalamic regions may control feeding under the influences of endogenous 2-B4O.

Modulation of streptonigrin cytotoxicity by nitroxide SOD mimics

Nitroxides are cell-permeable, stable radicals that react readily with paramagnetic species such as transition metals or short-lived free radicals, though not generally with diamagnetic molecules. Nitroxides can undergo one-electron selective redox reactions and thereby potentially modify the activity of cytotoxic drugs. Streptonigrin (SN) toxicity requires bioreduction to yield the semiquinone radical, and the toxicity is reportedly mediated by transition metals and oxygen-derived reactive species via redox-cycling of the semiquinone intermediate. The present study shows that (1) nitroxides protected isolated DNA and also aerated or hypoxic bacterial cells from SN toxicity; (2) H2O2 potentiated the hypoxic cytotoxicity of the drug but inhibited the damage to aerated cells; (3) pretreatment of cells with H2O2 conferred some protection, but not when the drug alone was preexposed to H2O2; and (4) desferrioxamine and 2,2-dipyridyl, though neither diethylenetriamino pentaacetate, exogenous catalase, or superoxide dismutase, decreased SN-induced cell killing. The mechanisms by which nitroxides protect from SN toxicity involve both a selective radical-radical reaction with SN semiquinone and the reoxidation of reduced cellular transition metal ions. On the other hand, H2O2 appears to exert two opposing effects: (1) facilitation of cell killing by the Fenton reaction and (2) lowering the cellular level of reducing equivalents, thus inhibiting the bioreductive activation of SN.

[Study on factors affecting vaccination effect of poliomyelitis vaccine]

We carried out this 1:2 matched case-control study in some counties and townships in Guangxi, Henan and Jiangsu provinces from June to October in 1992 to find the risk factors of poliomyelitis incidence among fully vaccinated children. Then we processed the collected data with individual and multiple condition logistic regression analysis and found the risk factors of poliomyelitis incidence among fully vaccinated children included two kinds, the community factors and the individual factors. The community factors which related to the cold chain and health services. They are the special risk factors for fully vaccinated children. The individual factors are the common risk factors for both fully vaccinated and unvaccinated children. In addition, children received five or more doses of TOPV was a favorable factor against poliomyelitis. It was showed that we must improve vaccination quality while rising TOPV coverage continually.

[Chemical studies of Epimedium acuminatum Franch]

Three flavonol glycosides isolated from the aerial parts of Epimedium acuminatum were identified as baohuoside II, epimedoside A and icariin on the basis of spectral data (UV, IR, MS, and 1HNMR) and chemical properties. Baohuoside II was isolated from the species for the first time.

Effects of nitroxide stable radicals on juglone cytotoxicity

Nitroxides stable radicals are unreactive toward most diamagnetic molecules, but readily undergo one-electron redox reactions with paramagnetic species such as free radicals and transition metals, thus serving as cell-permeable antioxidants. The cytotoxicity of juglone (5-hydroxy-1,4-naphthoquinone), like that of other naphthoquinones, requires bioreduction to yield the semiquinone which in turn reduces oxygen to O2.-. Therefore, nitroxides are expected to mitigate cytotoxicity of quinone-based xenobiotics, such as naphthoquinones. In the present study, in vitro scission of isolated DNA was induced upon juglone reduction by glutathione and Fe(II) ions, however, not by xanthine oxidase or cytochrome c reductase. The DNA scission was inhibited by nitroxides, catalase and chelating agents, though not by superoxide dismutase. Juglone was more toxic toward bacterial cells under hypoxia than under air. Nitroxides < or = 2 mM protected bacterial cells from juglone-induced toxicity under both aerobic and hypoxic conditions. The cytoprotective effect of lipophilic nitroxide was greater than that of hydrophilic ones. Catalase and metal chelating agents decreased juglone-induced cell killing, whereas H2O2 increased it. The mechanisms underlying the nitroxides protective effect involve (a) the reoxidation of reduced transition metal ions, (b) the selective radical-radical reaction with juglone semiquinone, and possibly (c) under aerobic condition catalytic removal of extra- and intracellular O2.-. The present results suggest also that the cell membrane rather than DNA is the main target of juglone toxicity.

Limonene chemoprevention of mammary carcinoma induction following direct in situ transfer of v-Ha-ras

Monoterpenes, including limonene and its in vivo rat plasma metabolites, have been shown to be inhibitors of protein isoprenylation of small G proteins, including p21 ras. In addition, dietary limonene has been shown to be capable of preventing the development and causing the regression of chemically induced mammary carcinomas, many of which contain activated ras oncogenes. On the basis of these observations, it was hypothesized that a possible mechanism by which limonene exerts its effects on the chemoprevention and regression of mammary tumors involves the inhibition of protein isoprenylation of the small G protein p21. In the first study, we asked whether dietary limonene was able to prevent the development of mammary carcinomas which were induced using direct retroviral gene transfer of v-Ha-ras into the mammary parenchyma in situ. Limonene modified neither the rate of gene transfer nor the stability of gene expression. However, limonene did greatly inhibit the formation of mammary carcinomas induced by the insertion of activated ras. In a follow-up study, we asked whether chemoprevention by limonene was preferentially effective against a subset of chemically induced mammary carcinomas with activated ras. Rats were fed limonene to prevent the development of N-nitroso-N-methylurea-induced mammary tumors, a majority of which contain the activated Ha-ras oncogene. As expected, limonene administration increased the latency period and lowered the frequency of mammary carcinoma development as compared to controls. However, tumor characterization revealed that limonene treatment did not alter the percentage of carcinomas with activated ras. These studies are consistent with the above studies in that limonene is effective in preventing mammary carcinomas with activated ras. Interestingly, carcinomas without activated ras were prevented to the same extent as those with the activated oncogene.

Luffin-S--a small novel ribosome-inactivating protein from Luffa cylindrica. Characterization and mechanism studies

We purified and characterized a novel RIP (ribosome inactivating protein), Luffin-S from the seeds of Luffa cylindrica. Different from Luffin-A and B, which are RNA N-glycosidases with molecular weights of 27 and 28 kDa, respectively, Luffin-S has an M.W. of only approx. 10 kDa, much smaller than any other RIPs so far investigated. Its abundant resources, toxicity similar to TCS in a cell-free protein synthesis system and unique mechanism as phosphodiesterase, like alpha-sarcin, promisingly make it a potential toxic moiety of immunotoxin.

[Both 987P and F41 fimbriae produced by the same enterotoxigenic Escherichia coli strain isolated from a piglet with diarrhea]

An enterotoxigenic Escherichia coli strain isolated from a piglet with diarrhea was examined for the presence of fimbriea 987P and F41 by a direct agglutination (with MAbs), an indirect immunofluorescence technique (MAbs as first antibodies), SDS-PAGE and Western blots (antisera IgG as probes). Results of these techniques revealed that both 987P and F41 fimbrial adhesins were produced by the same strain, not by separate ones.

[Comparative study of organ storage solutions for rat liver preservation: effects of HX and Collins I solution on sinusoidal lining cells and hepatic functions]

The liver sinusoidal lining cell injury and biochemical function changes were studied with isolated perfusion after rat livers had been preserved in HX solution or in Collins II solution. Seventy inbred Wistar rats were randomly divided into control group (n = 10), group H (preserved with HX solution, n = 30), and group C (preserved with Collins II solution, n = 30). The effects of the storage solutions were assessed by measuring the sinusoidal lining cell mortality (SLCM), Krebs-Henseleit perfusate ketone body ratio (PKBR), the hepatic sugar release (SL), and the number of livers secreting bile during isolated perfusion. The results suggest that the HX solution be much superior to Collins II solution in preventing sinusoidal lining cell injury and maintaining normal hepatic functions.

A novel human homologue of a dead-box RNA helicase family

Putative cDNA clones for a nuclear antigen that cross-reacts with anti-human aldolase A monoclonal antibody MAb1A2 were isolated from the HeLa lambda gt11 cDNA library and a candidate clone (clone 3) was analyzed. The cDNA has an open reading frame (ORF) of 1,317 bp encoding a novel RNA helicase belonging to the DEAD RNA helicase family. The ORF also contains a nuclear targeting signal and the epitope for MAb1A2. The putative RNA helicase has sequence similarity to Escherichia coli RNA helicase DEAD, mouse translation factor eIF-4A, and human p68 and p54.

Absence of transforming growth factor-beta responsiveness in the tamoxifen growth-inhibited human breast cancer cell line CAMA-1

Tamoxifen has been an effective antiestrogen in suppressing breast cancer growth which is estrogen-responsive or dependent. Early studies have provided circumstantial evidence that transforming growth factor-beta (TGF-beta) may be an autocrine mediator of tamoxifen action. Therefore, it is both fundamentally important and clinically relevant to investigate the relationship between tamoxifen and TGF-beta. In this study, we demonstrated that CAMA-1 cells, which are sensitive to tamoxifen inhibition, did not respond to TGF-beta growth inhibition. The type I and II TGF-beta receptors were undetectable by the radio-ligand affinity labeling technique. Despite the presence of a normal TGF-beta type II receptor gene, the mRNA transcript of the gene was undetectable by the extremely sensitive Intron-differential RNA/PCR method. The possibility that the lack of TGF-beta receptors might be intimately linked to the absence of normal retinoblastoma (Rb) gene products, as suggested by previous studies of retinoblastoma cells, was further investigated. The lack of TGF-beta receptor expression was found due to reasons other than the absence, deletion or abnormality of the Rb gene because a normal Rb gene and its hyper- and hypo-phosphorylated protein products were detected in CAMA-1 cells. In conclusion, our results suggest that the TGF-beta system is not obligatory for antiestrogen growth inhibition of CAMA-1 cells.

Z curves, an intutive tool for visualizing and analyzing the DNA sequences

A novel method mapping the DNA or RNA sequence into a folding curve in three dimensional space, the Z curve, has been proposed based on the symmetry of the regular tetrahedrons. There exists a unique Z curve for a given DNA sequence, on the contrary, the DNA sequence can be uniquely determined by the given Z curve. The properties of the Z curves have been studied in great details. The symmetry, the periodicity, the local motif, and the global feather of the distribution of bases of the DNA sequences are reflected by the rich folding structures of the Z curves. The Z curves may be smoothed by the B-spline functions of different orders. Therefore, the Z curves may have any resolution by choosing the suitable spline functions. The higher the order of the B-spline function chosen, the lower the resolution of the Z curve. So, the Z curves are suitable for visualizing and analyzing the DNA sequences with any length. The study of the Z curves develops further a new area to visualizing and analyzing the DNA sequences by a geometrical approach. The method of the Z curves may be strengthened by using the ripe mathematical tools of geometry on the one hand; and by using the powerful technique of the computer graphics on the other hand.

Dihydropyrimidine dehydrogenase activity in human peripheral blood mononuclear cells and liver: population characteristics, newly identified deficient patients, and clinical implication in 5-fluorouracil chemotherapy

Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme in the catabolism of 5-fluorouracil (FUra), one of the most widely used anticancer drugs. Previous studies from our laboratory demonstrated the clinical importance of DPD in cancer patients (G. D. Heggie, J-P. Sommadossi, D. S. Cross, W. J. Huster, and R. B. Diasio. Cancer Res., 47: 2203-2206, 1987; B. E. Harris, R. Song, S-j. Soong, and R. B. Diasio. Cancer Res., 50: 197-201, 1990), particularly in those with DPD deficiency who experience severe FUra toxicity (including death) following FUra treatment [R. B. Diasio, T. L. Beavers, and J. T. Carpenter. J. Clin. Invest., 81: 47-51, 1988; B. E. Harris, J. T. Carpenter, and R. B. Diasio. Cancer (Phila.), 68: 499-501, 1991]. We now suggest that measurement of DPD activity may be useful in routine screening of cancer patients prior to FUra treatment. In this paper, we describe the following serial studies: (a) we developed a sensitive, accurate, and precise DPD assay and a storage method to stabilize DPD activity, permitting large scale DPD screening in cancer patients; (b) we demonstrated a normal distribution (Gaussian distribution) of human DPD activity from peripheral blood mononuclear cells (PBM-DPD) in a population study. Baselines for PBM-DPD with fresh and frozen samples were 0.425 +/- 0.124 (SD) and 0.189 +/- 0.064 nmol/min/mg protein, respectively. The 95% and 99% distribution ranges for both fresh and frozen samples were also determined, providing criteria for detection of DPD-deficient patients; (c) we identified nine new patients with profound or partial DPD deficiency; (d) we determined a baseline for human liver DPD activity, which was shown to be 0.360 +/- 0.182 nmol/min/mg protein (frozen samples); (e) we did a preliminary evaluation of liver DPD from deficient patients. Low liver DPD activity in two deficient patients correlated with low PBM-DPD activity. Using a polyclonal antibody raised against human liver DPD in our laboratory (Z. Lu, R. Zhang, and R. B. Diasio. J. Biol. Chem., 267: 17102-17109, 1992), Western blot analysis demonstrated decreased DPD protein in the liver cytosol from DPD-deficient patients compared to normal subjects. These results may be useful in improving the effectiveness and/or lessening the toxicity of FUra chemotherapy.

Nucleotide sequence relationships of double-stranded RNAs in flax rust, Melampsora lini

Flax rust, Melampsora lini strain SP6, contains 11 double-stranded (ds) RNA molecules with a total length of about 25 kbp. The dsRNAs are inherited in three genetic units: the L unit comprising a single 5.2 kbp dsRNA and contained within a 40-nm virus-like particle, and the A and B units each consisting of five dsRNAs (A1-A5, and B1-B5) ranging in size from 1.2 to 2.7 kbp. This paper reports the isolation of a cDNA library representing 10 of the 11 dsRNAs. By nucleic-acid hybridization techniques it has been shown that all ten sequences are unique showing no detectable cross-hybridization with any other dsRNA present in the rust. A near full-length sequence of 1932 bp of the B3 dsRNA is reported and contains several open reading frames, the largest of which comprises most of the molecule.

Physical Chemistry of the H2SO4/HNO3/H2O System: Implications for Polar Stratospheric Clouds

Polar stratospheric clouds (PSCs) play a key role in stratospheric ozone depletion. Surface-catalyzed reactions on PSC particles generate chlorine compounds that photolyze readily to yield chlorine radicals, which in turn destroy ozone very efficiently. The most prevalent PSCs form at temperatures several degrees above the ice frost point and are believed to consist of HNO(3) hydrates; however, their formation mechanism is unclear. Results of laboratory experiments are presented which indicate that the background stratospheric H(2)SO(4)/H(2)O aerosols provide an essential link in this mechanism: These liquid aerosols absorb significant amounts of HNO(3) vapor, leading most likely to the crystallization of nitric acid trihydrate (NAT). The frozen particles then grow to form PSCs by condensation of additional amounts of HNO(3) and H(2)O vapor. Furthermore, reaction probability measurements reveal that the chlorine radical precursors are formed readily at polar stratospheric temperatures not just on NAT and ice crystals, but also on liquid H(2)SO(4) solutions and on solid H(2)SO(4) hydrates. These results imply that the chlorine activation efficiency of the aerosol particles increases rapidly as the temperature approaches the ice frost point regardless of the phase or composition of the particles.

The time of administration of 3'-azido-3'-deoxythymidine (AZT) determines its host toxicity with possible relevance to AZT chemotherapy

3'-Azido-3'-deoxythymidine (AZT) is the drug most widely used in the treatment of AIDS. Its major drug-related toxicity is bone marrow suppression, which limits the dose of AZT that can be used. It is essential that AZT be phosphorylated for antiviral effect. We have recently demonstrated that thymidine kinase (TK), the initial enzyme in AZT anabolism, follows a circadian pattern in rat bone marrow. The present study was undertaken to determine whether AZT toxicity is related to the time of its administration and whether the variation in toxicity is correlated with the circadian variation in TK activity. Male Sprague-Dawley rats were housed under standardized conditions of light and dark (lights on 0600 to 1800 and lights off 1800 to 0600) for 4 weeks. The animals were randomly divided into seven groups; six groups were administered AZT by intraperitoneal injection at the same dose of 750 mg/kg of body weight at various times (0400, 0800, 1200, 1600, 2000, and 2400), and one group was used as a control. AZT-related toxic effects, including bone marrow toxicity, differed significantly among the treatment groups, depending on the time of AZT administration (by analysis of variance and Cosinor analysis, P < 0.001). The least toxicity was observed in rats receiving AZT at 1600 (10 h after light onset [10 HALO], in late sleep span) and the greatest toxicity was observed in those injected at 0400 (22 HALO, in late activity span). To verify these results, we administered AZT by intraperitoneal injection at an approximately 50% lethal dose (1,500 mg/kg) to two groups of rats, one at 1200 (6 HALO, in the middle of the sleep span) and the other at 2400 (18 HALO, in the middle of the activity span). AZT lethality was significantly higher in rats receiving AZT at 2400 (18 HALO, in the middle of the activity span). Further statistical analysis demonstrated that the variation in AZT toxicity was correlated with the circadian variation in TK activity in bone marrow of the same species (peak activity at 0400 [22 HALO, in late activity span] and trough activity at 1600 [10 HALO, in late sleep span]), suggesting that the circadian variation in TK activity may be the biochemical basis for the observed circadian variation in AZT toxicity. These results may be useful in the design of improved AZT chemotherapeutic regimens.

Comparison of dihydropyrimidine dehydrogenase from human, rat, pig and cow liver. Biochemical and immunological properties

Dihydropyrimidine dehydrogenase (DPD, EC 1.3.1.2) is the initial and rate-limiting enzyme in the catabolic pathway of pyrimidines and has an important role in cancer chemotherapy with fluoropyrimidine drugs. Recently, we purified and characterized this enzyme from human liver and raised a rabbit polyclonal antibody against the purified human enzyme (Lu et al., J Biol Chem 267: 17102-17109, 1992). In the present study, using this purification procedure, DPD was purified to homogeneity from three other mammalian species, i.e. pig, rat, and cow. Comparison of the biochemical properties of these purified enzymes was conducted. Molecular masses of DPD from human, pig, rat, and cow liver were: 210, 204, 210, and 216 kDa, respectively. DPD from all four species appeared to be composed of two subunits. The apparent pI values were 4.6, 4.8, 4.85, and 5.25, respectively. Kinetic studies with uracil, thymine, 5-fluorouracil, and NADPH were carried out with the purified DPD preparation, suggesting species differences in kinetic parameters. Amino acid composition of these purified enzymes also demonstrated slight species differences. In the present study, a rabbit polyclonal antibody against rat liver DPD was raised. Using polyclonal antibodies against human and rat liver DPD, immunoblotting demonstrated cross-reactivity among the four species. In summary, purification and comparison of DPD from different mammalian species will provide a basis for further biochemical and molecular studies of this enzyme.

Disulfide bond assignments and secondary structure analysis of human and murine interleukin 10

Interleukin 10 (IL-10), which was first discovered by its ability to inhibit the synthesis of various cytokines, most notably gamma interferon, from Th1 helper cells, displays pleiotropic immunoregulatory properties. Human and murine IL-10 have a high amino acid sequence identity (ca. 73%) which includes the conservation of all four cysteine residues in human IL-10 and the first four out of five cysteine residues for murine IL-10. Chemical analysis was used to determine that both recombinant human and recombinant murine IL-10 contain two disulfide bonds. The disulfide pairs for each were determined by mass spectrometric and reversed-phase HPLC analysis of trypsin-derived polypeptide fragments. The disulfide bond assignments for both species were similar in that the first cysteine residue in the sequence paired with the third and the second paired with the fourth. The fifth cysteine in murine IL-10 was determined by chemical modification to be unpaired. Far-UV circular dichroism analysis indicated that the secondary structure of recombinant human and murine IL-10 are composed of ca. 60% alpha-helix. Reduction of the disulfide bonds structurally destabilized the protein and led to a structure containing only 53% alpha-helix. The reduced protein displayed no in vitro biological activity in a mast cell proliferation assay. These studies indicate that IL-10 is a highly alpha-helical protein containing two disulfide bonds, either one or both of which are critical for its structure and function. In addition, these properties suggest that this interesting cytokine may belong to the alpha helical cytokine class of hematopoietic ligands.

Phase I trial of low-dose, prolonged continuous infusion fluorouracil plus interferon-alfa: evidence for enhanced fluorouracil toxicity without pharmacokinetic perturbation

PURPOSE

To determine the maximum-tolerable dose (MTD) of fluorouracil (5-FU) administered as a low-dose, prolonged continuous intravenous infusion (PCI) plus interferon-alfa (IFN-alpha) that would permit treatment for at least 28 consecutive days, and to determine the effect of IFN-alpha on 5-FU pharmacokinetics.

PATIENTS AND METHODS

Twenty-six assessable patients with advanced cancer received low-dose PCI 5-FU (150, 200, 250, and 300 mg/m2/d) plus IFN-alpha, 5 x 10(6) IU/m2 administered subcutaneously (SC) at hour 48 of the 5-FU infusion, then thrice weekly thereafter in cohorts of at least three patients. Treatment continued until treatment-limiting toxicity (TLT) developed, such as mucositis, diarrhea, or fatigue. Escalation to the next 5-FU dose level occurred if none of three or zero to two of six patients developed TLT before day 28. Quantitation of plasma 5-FU concentration by high-performance liquid chromatography was performed in 15 patients. Data were standardized using the Cosinor method and compared before and after IFN-alpha administration using the paired t test.

RESULTS

The mean number of days of continuous 5-FU therapy for patients receiving 150, 200, 250, and 300 mg/m2/d of 5-FU plus IFN alfa-2a (IFN-alpha 2a) was 75, 54, 37, and 22 days, respectively. The MTD of PCI 5-FU by our criteria that could be combined with IFN-alpha was 250 mg/m2/d. Comparison of the standardized pharmacokinetic data showed no significant effect of IFN-alpha on plasma 5-FU concentration, and no alteration of the normal circadian variation in plasma 5-FU concentration that was evident before IFN-alpha administration. Objective response occurred in patients with adenocarcinoma of the pancreas (n = 3), kidney (n = 2), and lung (n = 1).

CONCLUSION

IFN-alpha substantially enhanced the gastrointestinal toxicity of low-dose PCI 5-FU without affecting 5-FU pharmacokinetics, contrary to previous reports using alternative 5-FU schedules in which IFN-alpha-related enhancement of 5-FU toxicity was attributable to reduced 5-FU clearance. Our findings suggest that under certain conditions, mechanisms other than altered 5-FU pharmacokinetics may be responsible for the ability of IFN-alpha to enhance the toxic effects of 5-FU.

Acquired amegakaryocytic thrombocytopenic purpura with a Philadelphia chromosome

A 30-year-old Chinese man with acquired amegakaryocytic thrombocytopenic purpura (AATP) and a Ph chromosome is reported. At presentation, he had severe thrombocytopenia resulting in epistaxis, gingival bleeding, and ecchymoses, while other hematologic values were within the normal range. Bone marrow aspiration showed no megakaryocytes, with a normal appearance of erythroblastic and granulopoietic series. He failed to respond to prednisone treatment, and underwent a progress from isolated thrombocytopenia to full pancytopenia. At last he died of spontaneous intracranial hemorrhage. An in vitro culture for granulocyte-macrophage precursors showed very few colonies. Karyotypic analysis revealed a standard Ph chromosome translocation, t(9;22)(q34;q11), in the majority of bone marrow cells. Southern blot analysis using a 3' bcr-HE probe didn't detect a rearrangement within the bcr DNA sequence. This patient, in fact, was a myelodysplastic disorder, initially presenting as AATP. The diagnosis of chronic myelogenous leukemia was excluded on the basis of clinical and hematologic findings. The heterogeneity of Ph chromosome in myelodysplastic syndrome is discussed.

Relationship between circadian-dependent toxicity of 5-fluorodeoxyuridine and circadian rhythms of pyrimidine enzymes: possible relevance to fluoropyrimidine chemotherapy

Previous studies in experimental animals and patients have suggested a circadian variation in host toxicity following administration of 5-fluorodeoxyuridine (FdUrd) although the biochemical mechanisms are not fully understood. Thymidine kinase (TK; EC 2.7.1.21), the initial enzyme in the thymidine-phosphorylation pathway, is the first enzyme in the anabolism of FdUrd. Dihydropyrimidine dehydrogenase (DPD; EC 1.3.1.2), is the rate-limiting enzyme in the pyrimidine catabolic pathway and has been shown to be the key enzyme in FdUrd catabolism. The present study examined the relationship between the suggested circadian variation in FdUrd toxicity and potential circadian variations in the activity of these enzymes. Initial studies in Sprague-Dawley rats confirmed that the time of FdUrd administration affected death rate and other drug-related toxicities including loss of body weight, diarrhea, and bone marrow suppression, with the least toxicity and highest survival rate being observed in rats receiving FdUrd at 12:00 noon and 4:00 p.m. and the greatest toxicity and lowest survival rate at 12:00 midnight and 4:00 a.m. Statistical analysis revealed a circadian pattern in FdUrd toxicity (Cosinor analysis, P < 0.001). In subsequent studies with the same species, we simultaneously measured TK and DPD activities in several tissues at various times over 24 h. Under standardized light conditions (lights on, 6:00 a.m. to 6:00 p.m.; lights off, 6:00 p.m. to 6:00 a.m.), with sampling at 4-h intervals (4:00 and 8:00 a.m.; 12:00 noon; 4:00 and 8:00 p.m., and 12:00 midnight), a circadian variation in TK activity was observed (P < 0.0001, Cosinor analysis) in bone marrow, intestinal mucosa, liver, and spleen. In the same group of animals, a circadian pattern of DPD activity in liver and bone marrow was also observed (Cosinor analysis, P < 0.0001) that was inverse compared to the circadian variation in TK activity (Pearson correlation analysis, P < 0.05). Further statistical analysis indicated that the observed circadian variation in FdUrd toxicity was correlated with the circadian variation of TK activity and inversely correlated with DPD activity (Pearson correlation analysis, P < 0.05). Based on the above data, we conclude that the circadian pattern of TK and DPD activity may explain the observed circadian variation in toxicity as the time of FdUrd administration is varied. These results may be useful in the design of improved chemotherapeutic regimens using time-modified administration of FdUrd.

[Studies on gap junction formation and junctional communication between cultured endothelial cells and smooth muscle cells]

Gap junction (GJ) between two contacted cells is the structural basis of intercellular communication. Gap junction transfer plays an important role in regulation of cell proliferation. Cultured endothelial cells (EC) and smooth muscle cells (SMC) were injected with fluorescein Lucifer Yellow by iontophoretic injection, and examined under fluorescein microscope. We have demonstrated that there existed homologous and heterologous GJ and contact mediated dye transfer between cultured EC and SMC. LDL and insulin which promote SMC proliferation may inhibit the junctional communication between SMC and EC. Tumor promoter TPA induced almost complete inhibition of junctional communication between EC and SMC. The results indicate that normally regulative signals of metabolism and growth are transferred between EC and SMC via junctional communication to maintain the vessel wall homeostasis. High dosage LDL and insulin may keep SMC away from normal growth control and induce their proliferation by means of inhibiting junctional communication. It may be one of important mechanisms of atherogenesis.

[A survey on enteroviruses-carrying status among healthy population in Changle and Wucheng counties of Shandong Province. Shandong Collaborative Group of Poliomyelitis]

Four-hundred and fourty-six faecal specimens sampled from healthy carriers between 0 and more than 20 year-old age groups in Changle and Wucheng counties of Shandong Province were collected from June to Sept. of 1991. From them, 142 (31.84%) isolates of enteroviruses were obtained. There was no significant difference in the enteroviruses isolation rate between Changle and Wucheng. No poliovirus was isolated. Among other enterovirus isolates, 85 were echoviruses, 6 coxsackieviruses, 9 enterovirus type 70 and 2 enterovirus type 71. Other 40 isolates were positive for cytopathogenic effect (CPE) in cell culture, but they could not be identified by antisera to poliovirus and enteroviruses. The results showed that the infection by non-polio enteroviruses which could cause polio-like paralysis should be paid attention in the poliomyelitis eradication program.

[The stimulatory effect of dorsal vagal complex injection of pentagastrin on gastric motility in rats]

Changes in antral motility induced by pentagastrin (G5) microinjected into the dorsal vagal complex (DVC) were investigated in fasting conscious rats. Antral motility was monitored by using chronically implanted force transducer sutured to the antrum. DVC injection of G5 markedly stimulated the amplitude of gastric contraction in a dose-dependent manner. The effect, being rapid in onset and long lasting, could not be mimicked by intravenous administration of G5 but could be markedly inhibited by microinjection of antigastrin serum into DVC. Atropine (100 micrograms.kg-1.h-1) and vagotomy could also abolish the G5 induced antral motility. No significant changes in plasma motilin were observed in portal venous blood after administration of G5 in DVC. These results suggested that DVC is an important site of action for G5 induced stimulation of gastric contraction as mediated by vagal cholinergic pathway.

A mathematical model of the kinetics and tissue distribution of 2-fluoro-beta-alanine, the major catabolite of 5-fluorouracil

2-Fluoro-beta-alanine (FBAL) is the major metabolite of 5-fluorouracil (FUra), one of the most widely used anticancer drugs. It has been suggested previously that FBAL and/or its metabolites may have a role in the hepatotoxicity, neurotoxicity and cardiotoxicity resulting from FUra chemotherapy. Studies in patients and experimental animals have demonstrated that FBAL has a prolonged elimination compared with the parent drug, FUra. In the present manuscript, a mathematical model is developed for the kinetics and tissue distribution of FBAL. This model is based on recently published data from a study of the pharmacokinetics and disposition of FBAL in rats (Zhang et al., Drug Metab Dispos 20: 113-119, 1992). Satisfactory agreement was achieved between predicted and measured values, permitting an accurate evaluation of the kinetic and distribution parameters for FBAL. This model indicates that: (1) FBAL accumulates in several tissues including brain, heart, spleen, and enterohepatic system; and (2) enterohepatic circulation of FBAL and its bile acid conjugates has an important role in FBAL kinetics and distribution as demonstrated by a model in which enterohepatic circulation parameters were deleted.

Functional properties of an H,K-ATPase/Na,K-ATPase chimera

Cultured pig kidney epithelial cells were transfected with a chimeric P-type ATPase catalytic subunit composed of the NH2-terminal half of the rat gastric H,K-ATPase and the COOH-terminal half of the rat Na,K-ATPase (alpha 1 isoform). Low concentrations of ouabain (< or = 0.2 mM) were used to inhibit completely the endogenous pig Na,K-ATPase and high concentrations (5 nM) to test the sensitivity of the chimeric rodent pump. In the presence of a low concentration of ouabain, a small but significant inhibition of residual Rb+(K+) influx by 5 mM ouabain was observed in only the transfected cells. Conditions were found in which a similar component of Rb+ influx was inhibited by the gastric H,K-ATPase inhibitor SCH28080, consistent with SCH28080 binding to the extracellular H1-H2 loop of this enzyme. These experiments demonstrate that this chimera behaves as a functional ion pump and indicate that the protein domains involved in cardiac glycoside binding are not confined to the amino-terminal half of the Na,K-ATPase.

Inducible removal of UV-induced pyrimidine dimers from transcriptionally active and inactive genes of Saccharomyces cerevisiae

The prior UV irradiation of alpha haploid Saccharomyces cerevisiae with a UV dose of 25 J/m2 substantially increases the repairability of damage subsequently induced by a UV dose of 70 J/m2 given 1 h after the first irradiation. This enhancement of repair is seen at both the MAT alpha and HML alpha loci, which are, respectively, transcriptionally active and inactive in alpha haploid cells. The presence in the medium of the protein synthesis inhibitor, cycloheximide in the period between the two irradiations eliminated this effect. Enhanced repair still occurred if cycloheximide was present only after the final UV irradiation. This indicated that the first result is not due to cycloheximide merely blocking the synthesis of repair enzymes associated with a hypothetical rapid turnover of such molecules. The enhanced repairability is not the result of changes in chromatin accessibility without protein synthesis, merely caused by the repair of the damage induced by the prior irradiation. The data clearly show that a UV-inducible removal of pyrimidine dimers has occurred which involves the synthesis of new proteins. The genes known to possess inducible promoters, and which are involved in excision are RAD2, RAD7, RAD16 and RAD23. Studies with the rad7 and rad16 mutants which are defective in the ability to repair HML alpha and proficient in the repair of MAT alpha showed that in rad7, preirradiation enhanced the repair at MAT alpha, whereas in rad16 this increased repair of MAT alpha was absent. The preirradiation did not modify the inability to repair HML alpha in either strain. Thus RAD16 has a role in this inducible repair.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of chain tilt angle in fully hydrated bilayers of gel phase lecithins

The tilt angle theta tilt of the hydrocarbon chains has been determined for fully hydrated gel phase of a series of saturated lecithins. Oriented samples were prepared on glass substrates and hydrated with supersaturated water vapor. Evidence for full hydration was the same intensity pattern of the low angle lamellar peaks and the same lamellar repeat D as unoriented multilamellar vesicles. Tilting the sample permitted observation of all the wide angle arcs necessary to verify the theoretical diffraction pattern corresponding to tilting of the chains towards nearest neighbors. The length of the scattering unit corresponds to two hydrocarbon chains, requiring each bilayer to scatter coherently rather than each monolayer. For DPPC, theta tilt was determined to be 32.0 +/- 0.5 degrees at 19 degrees C, slightly larger than previous direct determinations and considerably smaller than the value required by recent gravimetric measurements. This new value allows more accurate determinations of a variety of structural parameters, such as area per lipid molecule, A = 47.2 +/- 0.5 A2, and number of water molecules of hydration, nw = 11.8 +/- 0.7. As the chain length n of the lipids was increased from 16 to 20 carbons, the parameters A and nw remained constant, suggesting that the headgroup packing is at its excluded volume limit for this range. However, theta tilt increased by 3 degrees and the chain area Ac decreased by 0.5 A2. This behavior is explained in terms of a competition between a bulk free energy term and a finite or end effect term.

A point mutation at cysteine 189 blocks the water permeability of rat kidney water channel CHIP28k

CHIP28k is an important water-transporting protein in the kidney proximal tubule and the thin descending limb of Henle [Zhang, Skach, Hasegawa, Van Hoek, & Verkman (1993) J. Cell Biol. 120, 359-369] that is homologous to human erythrocyte CHIP28 [Preston & Agre (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 11110-11114]. Oligonucleotide-directed mutagenesis was used to identify the cysteine(s) involved in inhibition of the water-transporting function of CHIP28k by the mercurial HgCl2. Each of the four cysteines (at positions 87, 102, 152, and 189) were mutated to serine individually, or in combinations. In vitro transcribed cRNA was expressed in Xenopus oocytes for measurement of osmotic water permeability (Pf) in the absence or presence of 0.3 mM HgCl2. Pf (in cm/s x 10(-4) measured at 10 degrees C) was 7 +/- 1 in water-injected oocytes. In wild-type CHIP28k, Pf was 58 +/- 7 (-HgCl2) and 12 +/- 1 (+HgCl2). Mutation of cysteine 87, 102, or 152, individually or in combinations, had little effect on oocyte Pf or on the inhibition by HgCl2. Mutation of cysteine 189 to serine or glycine gave similar Pf values of 49-56 (-HgCl2); however, Pf was not inhibited up to 1 mM HgCl2. Mutation of cysteine 189 to the larger amino acid tryptophan gave a low Pf of 9 +/- 1; coexpression with wild-type CHIP28k indicated that the tryptophan mutation was not dominant negative. Mutation of the asparagine 42 and 205 glycosylation sites to threonine had little effect on Pf.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of total polyamines in tumor cells by high-performance capillary zone electrophoresis with indirect photometric detection

Tumor cells contain much higher levels of common polyamines such as putrescine, spermidine, and spermine than normal cells. Our previous work demonstrated that high-performance capillary zone electrophoresis with indirect photometric detection was suitable for the determination of underivatized free polyamines in tumor cells. We now report improved sensitivity (7-fold), greater quantitative reproducibility, and quantitation of both bound and free, underivatized polyamines in PC 12 tumor cells. 1,7-Diaminoheptane was used as an internal standard for quantification. Femtomoles of three polyamines and simple cations such as K+ and Na+ were easily separated in less than 10 min. The quantitations for total spermidine and spermine (bound and free) were found to be 2-fold higher than the quantitation for free, unbound polyamines using our previous method. The signal response was linear over 2 orders of magnitude. The method described here provides a fast and simple technique for quantitation of bound, unbound, and total polyamines for use in the study of the biological role of polyamines.

Circadian rhythm of rat spleen cytoplasmic thymidine kinase

The activity of thymidine kinase (TK, EC 2.7.1.21), the first enzyme of the thymidine phosphorylation pathway, was measured at various times over a 24-hr period in the spleens of Sprague-Dawley rats that had been housed under standardized conditions of light and dark for at least 4 weeks before the study. Spleen cytoplasmic TK activity was assayed with [2-14C]thymidine as substrate. Under "normal" light conditions (lights on 6:00 a.m.-6:00 p.m. and lights off 6:00 p.m.-6:00 a.m.), a circadian variation of TK activity was observed (P < 0.0001), Cosinor analysis) with peak activity (1.98 nmol product/hr/mg protein) at 1:00 a.m. (19 hr after light onset, HALO) and trough activity (0.40 nmol product/hr/mg protein) at 1:00 p.m. (7 HALO). Maximum enzyme activity exceeded minimum activity by approximately 5-fold. Reversing the light-dark cycle resulted in a corresponding shift in TK activity. Under these "reverse" conditions (lights on 6:00 p.m.-6:00 a.m. and lights off 6:00 a.m.-6:00 p.m.), a circadian variation in TK activity was also observed (P < 0.0001, Cosinor analysis) with peak activity (1.14 nmol product/hr/mg protein) at 12:00 noon (18 HALO) and trough activity (0.32 nmol/hr/mg protein) at 12:00 a.m. (6 HALO). Maximum enzyme activity exceeded minimum activity by approximately 4-fold. In summary, this study demonstrated for the first time that TK activity varies over a 24-hr period in association with the light-dark cycle.

Structure and expression of the S locus-related genes of maize

The extracellular of the putative receptor-like protein kinase, ZmPK1, is related to the self-incompatibility locus (S-locus) genes of Brassica. We have isolated and characterized a genomic DNA clone of ZmPK1 and three additional genes from maize that are highly related to ZmPK1. These three S-locus related genes do not appear to have the protein kinase catalytic domain that is found in ZmPK1. One or more of these genes are expressed specifically in the silks. This initial description of S-locus related genes in monocotyledonous plants suggests that the S-locus domain may be involved in several different cellular functions in a wide variety of plants.