How does morphine work on colonic motility? An electromyographic study in the human left and sigmoid colon

The effect of morphine on colonic motility was investigated by recording the colonic myoelectric spiking activity by means of a 50 cm long silastic tube equipped with 4 bipolar AgAgCl ring electrodes fixed at 10 cm intervals that was introduced into the left colon in 8 healthy subjects by flexible sigmoidoscopy. Tracings were obtained for 1 hour in the fasting state and for another 1 hour after i.m. injection of morphine sulphate 0.15 mg/kg. The different types of spike bursts were compared before and after morphine injection. The control tracings showed that the spiking activity of the colon was made of 2 types: 1)- Rhythmic Stationary Spike Bursts (RSB), that were seen at only one electrode site; 2)- Sporadic Bursts, that were either propagating over all 4 electrodes (SPB) or non propagating (SNPB). Injection of morphine was followed by 1)- a considerable increase in the number of RSB from 107 +/- 43 bursts/hour (mean +/- SEM) to 491 +/- 23 bursts/hour; 2)- the complete disappearance of the SPB dropping from 7.3 +/- 2.0 bursts/hour to 0.3 +/- 0.2 bursts/hour; 3)- no significant change in SNPB (from 52 +/- 4 bursts/hour to 57 +/- 5 bursts/hour). These results indicate that 1)- stimulation of colonic smooth muscle activity by morphine seems to result from an increase in the number of rhythmic stationary bursts; 2)- however inhibition of colonic transit may be related to the decrease in the number of sporadic propagating bursts.     

Excess amino acid polymorphism in mitochondrial DNA: contrasts among genes from Drosophila, mice, and humans

Recent studies of mitochondrial DNA (mtDNA) variation in mammals and Drosophila have shown an excess of amino acid variation within species (replacement polymorphism) relative to the number of silent and replacement differences fixed between species. To examine further this pattern of nonneutral mtDNA evolution, we present sequence data for the ND3 and ND5 genes from 59 lines of Drosophila melanogaster and 29 lines of D. simulans. Of interest are the frequency spectra of silent and replacement polymorphisms, and potential variation among genes and taxa in the departures from neutral expectations. The Drosophila ND3 and ND5 data show no significant excess of replacement polymorphism using the McDonald-Kreitman test. These data are in contrast to significant departures from neutrality for the ND3 gene in mammals and other genes in Drosophila mtDNA (cytochrome b and ATPase 6). Pooled across genes, however, both Drosophila and human mtDNA show very significant excesses of amino acid polymorphism. Silent polymorphisms at ND5 show a significantly higher variance in frequency than replacement polymorphisms, and the latter show a significant skew toward low frequencies (Tajima's D = -1.954). These patterns are interpreted in light of the nearly neutral theory where mildly deleterious amino acid haplotypes are observed as ephemeral variants within species but do not contribute to divergence. The patterns of polymorphism and divergence at charge-altering amino acid sites are presented for the Drosophila ND5 gene to examine the evolution of functionally distinct mutations. Excess charge-altering polymorphism is observed at the carboxyl terminal and excess charge-altering divergence is detected at the amino terminal. While the mildly deleterious model fits as a net effect in the evolution of nonrecombining mitochondrial genomes, these data suggest that opposing evolutionary pressures may act on different regions of mitochondrial genes and genomes.      

Correlation between precolonization of trigeminal ganglia by attenuated strains of pseudorabies virus and resistance to wild-type virus latency.

We compared the levels of latent pseudorabies virus (PRV) DNA in trigeminal ganglia (TG) of pigs after intranasal inoculation of different PRV strains by using quantitative DNA PCR. The extent of colonization attained in each case varied significantly according to the type of strain and inoculum dose, wild-type (WT) PRV being the most efficient strain in colonizing TG. When groups of pigs representing different levels of precolonization of TG with an attenuated PRV strain were challenged with WT PRV, it became evident that there is a statistically significant inverse correlation between the extent of precolonization attained by an attenuated PRV strain in TG and the level of establishment of latency by superinfecting WT PRV. The protection against WT PRV latency did not correlate with the extent of WT PRV replication at the portal of entry.     

Pharmacological cyclin-dependent kinase inhibitors inhibit replication of wild-type and drug-resistant strains of herpes simplex virus and human immunodeficiency virus type 1 by targeting cellular,not viral,proteins

Pharmacological cyclin-dependent kinase (cdk) inhibitors (PCIs) block replication of several viruses, including herpes simplex virus type 1 (HSV-1) and human immunodeficiency virus type 1 (HIV-1). Yet, these antiviral effects could result from inhibition of either cellular cdks or viral enzymes. For example, in addition to cellular cdks, PCIs could inhibit any of the herpesvirus-encoded kinases, DNA replication proteins, or proteins involved in nucleotide metabolism. To address this issue, we asked whether purine-derived PCIs (P-PCIs) inhibit HSV and HIV-1 replication by targeting cellular or viral proteins. P-PCIs inhibited replication of HSV-1 and -2 and HIV-1, which require cellular cdks to replicate, but not vaccinia virus or lymphocytic choriomeningitis virus, which are not known to require cdks to replicate. P-PCIs also inhibited strains of HSV-1 and HIV-1 that are resistant to conventional antiviral drugs, which target viral proteins. In addition, the anti-HSV effects of P-PCIs and a conventional antiherpesvirus drug, acyclovir, were additive, demonstrating that the two drugs act by distinct mechanisms. Lastly, the spectrum of proteins that bound to P-PCIs in extracts of mock- and HSV-infected cells was the same. Based on these observations, we conclude that P-PCIs inhibit virus replication by targeting cellular, not viral, proteins.     

Lipid phosphate phosphatase-2 activity regulates S-phase entry of the cell cycle in Rat2 fibroblasts

Lipid phosphates are potent mediators of cell signaling and control processes including development, cell migration and division, blood vessel formation, wound repair, and tumor progression. Lipid phosphate phosphatases (LPPs) regulate the dephosphorylation of lipid phosphates, thus modulating their signals and producing new bioactive compounds both at the cell surface and in intracellular compartments. Knock-down of endogenous LPP2 in fibroblasts delayed cyclin A accumulation and entry into S-phase of the cell cycle. Conversely, overexpression of LPP2, but not a catalytically inactive mutant, caused premature S-phase entry, accompanied by premature cyclin A accumulation. At high passage, many LPP2 overexpressing cells arrested in G(2)/M and the rate of proliferation declined severely. This was accompanied by changes in proteins and lipids characteristic of senescence. Additionally, arrested LPP2 cells contained decreased lysophosphatidate concentrations and increased ceramide. These effects of LPP2 activity were not reproduced by overexpression or knock-down of LPP1 or LPP3. This work identifies a novel and specific role for LPP2 activity and bioactive lipids in regulating cell cycle progression.