Diorganotin(IV) antitumor agent. (C2H5)2SnCl2 (phen)/nucleotides aqueous and solid-state coordination chemistry and its DNA binding studies

This contribution reports a solution and solid-state study of the aqueous nucleotide coordination chemistry of the diethyltin(IV) antitumor agent, (C2H5)2SnCl2(phen). [trans-en2Os(eta-H2)] (CF3SO3)2, a versatile 1H NMR probe for biomolecules, is first used to investigate the interaction of (C2H5)2SnCl2(phen) with DGMP in neutral aqueous solution, and then the synthesis of mixed-ligands complexes formulated as (C2H5)2SnCl(phen)(Nu) (Nu is nucleotide) by reactions of (C2H5)2SnCl2(phen) with equimolar nucleotides under biologically relevant conditions is described. The new complexes were characterized by 500 MHz 1H, 31P NMR spectra; these spectroscopic data suggest that one of cis-chloro atoms in (C2H5)2SnCl2(phen) is substituted by nucleotide, and that Sn(IV) is directly coordinated to the phosphate group of the nucleotide. No evidence was found for the coordination via donor atoms of the base. On the basis of the above model studies, absorbance, fluorescence and cyclic voltammetric methods, viscosity determination, as well as agrose gel electrophoresis of superhelical pBR322 plasmid DNA were used to study the interaction of (C2H5)2SnCl2(phen) with DNA. The results indicate that (C2H5)2SnCl2(phen) binds to DNA by double modes. The drug first reacts electrostatically with the sugar-phosphate backbone of DNA; this results in changes of DNA conformation, and then phen ligand can intercalate into double-helix DNA and cause unwinding of the DNA.

Down-regulation of gadd153 by c-myc in rat fibroblasts and its effect on cell growth and radiation-induced apoptosis

Using differential display reverse transcription PCR (DDRT - PCR), we found that a 360 bp cDNA fragment was absent in several c-myc transfected rat fibroblasts: REC:myc, REC:myc + ras and rat1-myc. These cells also showed enhanced sensitivity to gamma ray-induced apoptosis. This cDNA fragment was present in the parental REC (Rat Embryo Cells) and rat1 cells, and in c-Ha-ras transfected REC (REC:ras), all of which were relatively resistant to gamma ray-induced apoptosis. The cDNA fragment was subsequently cloned and used as a probe to screen a rat1 cDNA library, and identified as one of the growth arrest and DNA damaging-inducible genes, gadd153. In addition to the down-regulation of rat gadd153 in all the c-myc transfectants, methyl methanesulfonate (MMS)-induced transcription of the gadd153 was attenuated. The rat1-myc cells, when successfully transfected with and stably expressing the rat gadd153, showed a significantly longer doubling time compared to the parental cells. However, overexpression of gadd153 in rat1-myc cells did not affect gamma ray-induced apoptosis. Thus, the suppression of gadd153 appears to be inversely correlated with that of myc, but not involved in the myc-dependent apoptotic pathway.

Control of daughter cell fates during asymmetric division: interaction of Numb and Notch

During development of the Drosophila peripheral nervous system, a sensory organ precursor (SOP) cell undergoes rounds of asymmetric divisions to generate four distinct cells of a sensory organ. Numb, a membrane-associated protein, is asymmetrically segregated into one daughter cell during SOP division and acts as an inherited determinant of cell fate. Here, we show that Notch, a transmembrane receptor mediated cell-cell communication, functions as a binary switch in cell fate specification during asymmetric divisions of the SOP and its daughter cells in embryogenesis. Moreover, numb negatively regulates Notch, probably through direct protein-protein interaction that requires the phosphotyrosine-binding (PTB) domain of Numb and either the RAM23 region or the very C-terminal end of Notch. Notch then positively regulates a transcription factor encoded by tramtrack (ttk). This leads to Ttk expression in the daughter cell that does not inherit Numb. Thus, the inherited determinant Numb bestows a bias in the machinery for cell-cell communication to allow the specification of distinct daughter cell fates.

Dosage effects on gene expression in a maize ploidy series

Previous studies on gene expression in aneuploids revealed numerous trans-acting dosage effects. Segmental aneuploidy of each varied chromosomal region exhibited predominantly inverse effects on several target genes. Here, dosage regulation was examined in a maize (Zea mays L.) ploidy series where the complete genomic complement is varied. Total RNA from leaf tissue of monoploid, diploid, triploid, and tetraploid plants (1x, 2x, 3x, and 4x, respectively) was analyzed for the expression of 18 genes. For most tested genes, the transcript level per cell is directly proportional to structural gene dosage; that is, on a per genome basis, there is approximately equal expression among the four ploidies. Exceptional cases show a negative correlation of expression with ploidy or a positive correlation greater than expected from the structural gene dosage. These studies suggest that, in general, as structural gene dosage increases in multiples of the monoploid complement, the absolute level of gene expression per cell increases. In contrast, addition or subtraction of only a single chromosome arm tends to alter gene expression patterns extensively. The combined results of the euploid and aneuploid studies suggest that aneuploid effects result from an altered stoichiometry of the factors contributing to the mechanisms of gene expression.

Mutational studies of conserved residues in the dimer interface of nerve growth factor

An understanding of the structure-function relationship of nerve growth factor (NGF) requires precise knowledge of all the residues and regions that participate in NGF receptor binding, receptor activation, and biological activity. Seven recombinant human NGF mutants having alanine substituted for residues located either in the NGF dimer interface or beta-strand region were studied to determine the role of each amino acid residue in NGF biological activity. F86A, T91A, R100A, and R103A remained nearly full active with 61, 120, 91, and 73% of wild-type activity, respectively, in the PC12 cell bioassay. Hydrophobic core and dimer interface residues Y52, F53, and F54 were studied in more detail. Y52A and F54A were expressed in very low levels, suggesting that these two residues may be important for protein stability. Y52A retained full biological activity (91%). F53A had a 20- and 70-fold reduction in biological activity and TrkA phosphorylation, respectively, with only a 5- to 10-fold effect on TrkA binding and no effect on low-affinity receptor binding. F54A had significantly decreased TrkA phosphorylation and biological activity (40-fold). The results suggest that F53 and F54 may play a structural role in TrkA receptor activation subsequent to binding.

[Wound infection and recurrence after total laryngectomy]

95 patients who received total laryngectomy for laryngeal carcinoma were reviewed. They were divided into two groups, those with postoperative wound infection and those without. The relations between postoperative wound infection and local recurrence were discussed. The results showed that the recurrence rate of postoperative infection group was higher than that of no postoperative infection (P < 0.001), and the patients with gram-negative bacilli infection also had much higher recurrence rates (P < 0.05). For the laryngeal cancer, the development of a wound infection after total laryngectomy may be related to the local tumour recurrence within one year.

[The experimental treatment of laryngeal cancer using local draining lymph node lymphocytes]

In order to know whether laryngeal cancer draining lymph node lymphocytes (INL) have antitumor effects in vivo, we transfered IL-2 activated LNL to nude mice with human laryngeal squamous cell carcinoma line PHC3 xenografts, and observed a suppressive effect on tumor growth. It was also found in the epitype changes of LNL by indirect immunofluorencence method the major composition of freshly isolated LNL was CD3+ T cells in which there were more Th/i cells than Ts/c cells, CD4+/CD8+ ratio was 3.30 +/- 0.653. No evidence of lymphocytes multiplication or CD3+, CD4+, CD8+ epitype changes was found after short term IL-2 culture, but we found more HLA-DR+, CD25+ cells which means there was an increase in activated lymphocytes after culture. The experiment suggests that laryngeal cancer draining lymph node lymphocytes have antitumor effects in vivo after IL-2 short term culture, and can be used in clinical immunotherapy.

Radiation-induced apoptosis: effects of cell age and dose fractionation

The cell cycle dependence of radiation-induced apoptosis was measured using mitotically synchronized REC:myc(ch1) and Rat1:mycb cells. Cells in S and G2 phases were more susceptible; the apoptotic fraction was about 0.7-0.8 as compared to about 0.4 for G1 cells at a dose of 10 Gy. Two-dimensional cytofluorimetric analysis of cells, pulsed-labeled with bromodeoxyuridine and then irradiated with 10 Gy, showed both G1 and G2 blocks (6-8 h) for REC:myc(ch1) cells but only G2 block for Rat1:mycb cells. Consistent with these results, wild-type p53 and WAF1 (or p21), known to play a role in G1 delay, was induced by radiation in REC:myc(ch1) but not in Rat1:mycb cells. The cell cycle dependence of radiation-induced apoptosis and the absence of a G1 block for Rat1:mycb cells led to the prediction and observation of the novel "inverse split-dose effect," i.e., a radiation dose given in two equal halves separated by a few hours yielded a higher level of apoptosis relative to that resulting from the same total dose given all at once. This effect is due to cell cycle progression from G1 to the more sensitive S-G2 phase during the interval between the split doses. In contrast, the inverse split-dose effect for apoptosis is absent for REC:myc(ch1), due presumably to the radiation-induced G1 delay. Parallel split-dose experiments, but using clonogenic survival as end points, show recovery for REC:myc(ch1) cells but not for Rat1:mycb cells, reflecting the influence of split-dose, radiation-induced apoptosis.

Localization of sequences required for size-specific splicing of a small Drosophila intron in vitro

Many introns in Drosophila and other invertebrates are less than 80 nucleotides in length, too small to be recognized by the vertebrate splicing machinery. Comparison of nuclear splicing extracts from human HeLa and Drosophila Kc cells has revealed species-specificity, consistent with the observed size differences. Here we present additional results with the 68 nucleotide fifth intron of the Drosophila myosin heavy chain gene. As observed with the 74 nucleotide second intron of the Drosophila white gene, the wild-type myosin intron is accurately spliced in a homologous extract, and increasing the size by 16 nucleotides both eliminates splicing in the Drosophila extract and allows accurate splicing in the human extract. In contrast to previous results, however, an upstream cryptic 5' splice site is activated when the wild-type myosin intron is tested in a human HeLa cell nuclear extract, resulting in the removal of a 98 nucleotide intron. The size dependence of splicing in Drosophila extracts is also intron-specific; we noted that a naturally larger (150 nucleotide) intron from the ftz gene is efficiently spliced in Kc cell extracts that do not splice enlarged introns (of 84, 90, 150 or 350 nucleotides) derived from the 74 nucleotide white intron. Here, we have exploited that observation, using a series of hybrid introns to show that a region of 46 nucleotides at the 3' end of the white intron is sufficient to confer the species-specific size effect. At least two sequence elements within this region, yet distinct from previously described branchpoint and pyrimidine tract signals, are required for efficient splicing of small hybrid introns in vitro.

Structural analysis of the N- and C-termini in a peptide with consensus sequence

We present a structural analysis of a peptide, the sequence of which includes amino acids that show preferences for specific positions near the N- and C-termini in protein helices. This peptide has the sequence ac-YMSEDELKAAEAAFKRHGVP-amide, which includes a strong version of an N-terminal Harper-Rose capping box structure as well as a Gly located close to the C-terminus designed to elucidate its role in C-terminal capping. The sequence of five residues at the middle is inserted to separate effects at the two ends via a helix-stabilizing linker. Application of a simulated annealing procedure using interproton distance constraints derived from 1H NOESY experiments in water reveals the presence of a C-terminal structure in this model. The C-terminus forms a folded back structure in a significant fraction of structures generated by the annealing, in most of which Gly assumes an alpha L conformation. This structure occurs within a highly flexible region of the molecule and hence is occupied only a fraction of the time.

[Inhibitory effect of heparin on glomerular mesangial cell]

The pure mesangial cells (MsC) were isolated from the culture of rat glomeruli. After identification, they were divided into heparin-treatment group and control group. It was found that heparin profoundly inhibited the growth of MsC with 75.9% inhibitory rate by means of direct counting MsC. MTT method proved that the inhibitory effect of heparin on MsC was dose-dependent. Electronmicroscopic observation revealed dilated endoplasmic reticulum and Golgi vesicles, more secondary lysosomes, prominent myelin figures and decreased microfilaments in the cytoplasm of the MsC exposed to heparin. Immunocytochemical studies showed that the amounts of FN and LM in the cytoplasm of MsC decreased after heparin treatment. Immunocytochemical investigation also confirmed that heparin could inhibit the expression of nuclear oncogene c-fos and c-jun in the MsC stimulated by PMA. The significance and possible mechanism of inhibitory effect of heparin on MsC were discussed.

tramtrack acts downstream of numb to specify distinct daughter cell fates during asymmetric cell divisions in the Drosophila PNS

Asymmetric cell divisions allow a sensory organ precursor (SOP) cell to generate a neuron and its support cells in the Drosophila PNS. We demonstrate a role of tramtrack (ttk), previously identified as a zinc finger-containing putative transcription factor, in the determination of different daughter cell fates. Both loss of function and overexpression of ttk affect the fates of the SOP progeny. Whereas loss of ttk function transforms support cells to neurons, ttk overexpression results in the reverse transformation. ttk is expressed in support cells but not in neurons. It has been shown that numb, a membrane-associated protein asymmetrically distributed during the SOP division, confers different daughter cell fates. Loss of ttk or numb function results in reciprocal cell fate transformation. Epistatic studies suggest that ttk acts downstream of numb. We propose that ttk executes the command dictated by asymmetrically localized numb to specify distinct daughter cell fates during multiple asymmetric divisions.

Catecholamine-induced mechanical sensitization of cutaneous nociceptors in the rat

C-Fiber mechanoheat (C-MH) nociceptors from the saphenous nerve were studied, in control rats and in rats that underwent surgical sympathectomy. Intradermal injection, alone, of either norepinephrine (NE) or the calcium ionophore, A23187, did not affect mechanical threshold. The combination of A23187 and NE, however, significantly decreased mechanical threshold. In the presence of the alpha 2-adrenergic antagonist, yohimbine, or the cyclooxygenase inhibitor, indomethacin, C-MHs were not sensitized by the combination of NE + A23187. One week after surgical sympathectomy, the number of C-MHs sensitized by NE + A23187 was significantly reduced. In summary, NE appears to sensitize nociceptors indirectly. These data are compatible with the suggestion that a sympathetic postganglionic neuron-dependent release of prostaglandins mediates the sensitization. NE appears to act at an alpha 2-adrenergic receptor, only in the presence of an increased intracellular Ca2+.

Na(+)-K(+)-ATPase activity: role in the impaired sodium excretion of experimental nephrosis in rats

Using the model of adriamycin-induced nephrotic syndrome in rats, we studied the relationship between urine electrolyte excretion rates and proteinuria and determined the activity of Na(+)-K(+)-ATPase in the renal tissue of nephrotic rats. No relationship was found between the increased sodium reabsorption and proteinuria. But the impaired salt excretion was inversely related to the increase of Na(+)-K(+)-ATPase activity in the renal inner medulla. It is proposed that direct effect of adriamycin on renal tubule cells is the primary events, that the increased Na(+)-ATPase activity on basolateral membrane of renal tubule cells be an intrarenal factor which mediates the action of retention of salt by the kidney and that inner medullary collecting ducts might be one of the sites of the sodium retention in nephrotic rats.

RFLP analysis of preferential transmission in interspecific hybrids of Phaseolus vulgaris and P. coccineus

The inheritance of RFLP markers in interspecific hybrids of Phaseolus vulgaris and P. coccineus was analyzed. Of 280 cDNA probes used, 70%-85% revealed polymorphism between species while intraspecific RFLP ranged from 8% to 37%. Segregation of 63 clearly scorable markers was examined in 177 P. vulgaris x P. coccineus F2's maintained as callus. Preferential transmission of the P. vulgaris alleles was observed for 24 of the 28 loci exhibiting non-Mendelian ratios. Although the segregation ratios at 17 loci fit gametic selection, also other factors such as nuclear-cytoplasmic or embryo-endosperm interactions may be involved. In the reciprocal F2, a relatively high frequency of maternal alleles was recovered for several loci, while the paternal allele was favored at others. The cDNA clone detecting the most extreme segregation, with no P. coccineus type detected among 165 P. vulgaris x P. coccineus F2 progeny, showed high homology to histone H2A genes. The markers were mapped to nine linkage groups. Aggregation of markers with preferential maternal transmission was observed, which could be due to selection of individual chromosomes, although false linkage detection cannot be excluded. The results obtained with RFLPs may explain the skewed distribution of phenotypic traits following interspecific hybridization.

Multinuclear and magic-angle spinning NMR investigations of molecular organization in phospholipid-triglyceride aqueous dispersions

The supramolecular organization of multi-bilayers formed by aqueous egg phosphatidylcholine-triolein (PC-TO) mixtures has been investigated using 31P, 13C, and 1H nuclear magnetic resonance (NMR). For these emulsions, which mimic substrates in the early hydrolytic stages of fat digestion, the NMR spectra obtained with magic-angle spinning (MAS) exhibit resolution comparable to that of sonicated vesicles and integrated peak intensities consistent with their chemical composition. Both 31P line shapes and MAS sideband patterns from the phosphocholine group indicate that mixing with triolein produces a PC bilayer which remains predominantly liquid crystalline in its organization; nevertheless, anomalous spectral features in MAS spectra may be attributed to additional phases in which the headgroups adopt a different orientation with respect to the bilayer normal, and tight packing enhances phosphorus-phosphorus interactions. 13C and 1H line widths monitored as a function of PC mole fraction, spinning speed, and decoupling strength show that the choline headgroups and glycerol backbones are anchored preferentially in the phospholipid-triglyceride assemblies, whereas all acyl chains become very fluid. The average degree of chain order also decreases for the mixed dispersions, as judged from spinning-sideband intensities in 1H MAS NMR spectra. The absence of proton spin-diffusion effects in the PC-TO multilayers is demonstrated by examination of their spinning sidebands and relaxation times, making it possible to use MAS-assisted two-dimensional NMR to assign overlapped 1H resonances and to identify proximal interactions between the two constituents. The usefulness of these NMR strategies in mechanistic studies of gastric fat digestion is also discussed.

Suppression of autoimmune disease by dietary n-3 fatty acids

Previous studies have demonstrated that dietary fish oil preparations have anti-inflammatory effects in humans and in experimental animals, but the individual components of fish oils that are responsible for their anti-inflammatory effects have not been documented. We therefore investigated in (NZB x NZW)F1 mice, a model for human systemic lupus erythematosus, the effects of diets containing ethyl esters of two purified n-3 fatty acids, eicosapentaenoic acid (EPA-E) and docosahexaenoic acid (DHA-E), a refined fish oil triglyceride (FO) which contained 55% n-3 fatty acids, and beef tallow (BT) which contains no n-3 fatty acids. The diets were initiated prior to the development of overt renal disease at age 22 weeks, and continued for 14 weeks. The extent of the renal disease was quantified by light microscopy and by proteinuria. Diets containing either 10 wt% FO, 10% EPA-E, or 6% or 10% DHA-E alleviated the severity of the renal disease, compared to the BT diet, whereas diets containing either 3% or 6% EPA-E or 3% DHA-E were less effective. Two diets containing approximately 3:1 mixtures of EPA-E and DHA-E alleviated the renal disease to a greater extent than expected for either of these fatty acids given singly. We believe that these experiments provide the first demonstration of anti-inflammatory effects of individual dietary n-3 fatty acids. The results also indicate that the anti-inflammatory effects of fish oils depend on synergistic effects of at least two n-3 fatty acids.

Novel neurite growth-inhibitory properties of an astrocyte proteoglycan

Conditioned medium (CM) of primary cultures of GFAP-positive adherent astrocytes from neonatal rat neocortex contained a chondroitin sulphate/dermatan sulphate proteoglycan (CDSPG) that co-eluted with a heparan sulphate proteoglycan (HSPG) by ion-exchange chromatography. The CDSPG was resolved from the HSPG by molecular sieve chromatography, which indicated that the molecular mass of the HSPG was greater than 300 kDa, while that of the CDSPG was approximately 50 kDa. Specific lyase digestion and urea/polyacrylamide gel electrophoresis established the homogeneity of the CDSPG and suggested molecular masses of the core protein and glycosylated protein as 54 kDa and 58 kDa respectively. Virtually all of the poly-D-lysine substrate-bound proteoglycan-associated neurite growth-promoting activity of astrocyte CM was accounted for by the HSPG. On poly-D-lysine the immobilized CDSPG displayed little neurite growth-stimulatory activity relative to the HSPG. However, the CDSPG inhibited the potent growth-promoting activity of the HSPG by displacing it from the poly-D-lysine substrate. Differential cellular regulation of production of growth-modulatory proteins with different binding avidity for the substrate of growth may determine the success of a regenerative axonal response by fully competent neurons.