Biotransformation of 4-dimethylaminophenol in the isolated perfused rat liver and in the rat

Isolated rat livers were perfused with various concentrations of 4-dimethylaminophenol-[¹⁴C] (DMAP). During single pass perfusion with modified protein-free Krebs-Henseleit solution up to 70μM prehepatic 4-dimethylaminophenol (DMAP) were metabolized by the liver. The main route of biotransformation was conjugation. At steady state conditions glucuronide formation showed an apparent V_max of 8.5 μmoles × min^?1 × g protein^?1, and K_m of 562 μM, whereas sulfate formation had an apparent V_max of 1.2 and a K_m of 35. Thus, at low substrate concentration the sulfate conjugation outweighed glucuronidation whereas at high substrate concentration the ratio of conjugates was reversed. In contrast to DMAP-sulfate, some DMAP-glucuronide was stored by the liver and was released with a half life of about 15 min which showed positive correlation with the dose of DMAP during the washout period. Perfusion with human or rat erythrocytes demonstrated the other important path of biotransformation of DMAP within erythrocytes, namely thioether formation with glutathione and SH-groups of hemoglobin. The pattern of DMAP-conjugation was affected depending on the time of prehepatic exposure to erythrocytes, and the species of red cells. The results obtained from the isolated metabolic system resemble the hepatic part of the overall metabolism under in vivo conditions.     

Effects of 4-dimethylaminophenol,Co2EDTA,or NaNO2 on cerebral blood flow and sinus blood homeostasis of dogs in connection with acute cyanide poisoning

The effects of the cyanide antidotes DMAP, Co₂EDTA, and NaNO₂ on cerebral blood flow (CBF) and cerebral blood gases were investigated in connection with acute poisoning of dogs by cyanide. The substances were injected intravenously. Local CBF as measured with thermocouples in the cingulum increased by 100–200% after a non-lethal dose of KCN (1 mg/kg) and by 50% after injection of NaNO₂ (15 mg/kg), that oxidized some 20% of the total hemoglobin to ferrihemoglobin. Co₂EDTA (10 mg/kg) induced a decrease in local CBF of 30% and in brain temperature of 0.5°C. The temperature diminished also after poisoning by KCN, but it rose by 0.15°C after the administration of NaNO₂. Local CBF and sinus sagittalis blood flow increased by 60–160% for about 15 min, and the brain temperature decreased by 0.4–0.5°C when DMAP (3.25 mg/kg) or Co₂EDTA (15 mg/kg) was injected 1 min after poisoning by cyanide (4 mg/kg), a dose that always caused respiratory arrest. Immediately after injection of DMAP the brain temperature rose transiently by 0.1–0.2°C. Co₂EDTA did not exert such an effect. In the sinus sagittalis blood of artificially ventilated animals pCO₂ decreased rapidly by 10–20 mmHg after poisoning and approached the initial level after treatment with DMAP or Co₂EDTA. The highest value of pO₂ was about 80 mmHg and 50 mmHg after injection of DMAP and Co₂EDTA, respectively; thereafter pO₂ declined to 20 mmHg or 40 mmHg at 20 min. The lactate concentration increased by 60–70% without tendency to return to normal.     

The effect of prior treatment with 4-dimethylaminophenol (DMAP) on animals experimentally poisoned with hydrogen cyanide

Six dogs were given sufficient oral 4-dimethylaminophenol (DMAP) to produce a peak methaemoglobin level of 12–15%. Five out of the six dogs then survived an intravenous injection of approximately 2 LD₅₀'s of hydrogen cyanide given when the methaemoglobin had reached 8–10%. The sixth dog died after 44 min. When the same dose of hydrogen cyanide was given to dogs, not previously given DMAP, all three died within 11/2 min. It was concluded that prior treatment with oral DMAP provided a large measure of protection against cyanide poisoning. Comparison of cyanide levels in whole blood and plasma in the two groups of dogs lent support to the hypothesis that methaemoglobin complexed with cyanide in the erythrocytes causing the plasma cyanide to remain lower than it did in unprotected animals.     

Silencing of the DNA methyltransferase 1 associated protein 1 (DMAP1) gene in the invasive ladybird Harmonia axyridis implies a role of the DNA methyltransferase 1‐DMAP1 complex in female fecundity

The invasive harlequin ladybird Harmonia axyridis is a textbook example of polymorphism and polyphenism as the temperature during egg development determines the frequency of melanic morphs and the number and size of black spots in nonmelanic morphs. Recent concepts in evolutionary biology suggest that epigenetic mechanisms can translate environmental stimuli into heritable phenotypic changes. To investigate whether epigenetic mechanisms influence the penetrance and expressivity of colour morphs in H. axyridis, we used RNA interference to silence key enzymes required for DNA methylation and histone modification. We found that neither of these epigenetic mechanisms affected the frequency of different morphs, but there was a significant impact on life‐history traits such as longevity and fecundity. Strikingly, we found that silencing the gene encoding for DNA methyltransferase 1 associated protein 1 (DMAP1) severely reduced female fecundity, which correlated with an abundance of degenerated ovaries in DMAP1‐knockdown female beetles. Finally, we observed significant differences in DMAP1 expression when we compared native and invasive H. axyridis populations with a biocontrol strain differing in egg‐laying capacity, suggesting that the DNA methyltransferase 1‐DMAP1 complex may influence the invasive performance of this ladybird.     

Novel 1p tumour suppressor Dnmt1-associated protein 1 regulates MYCN/ataxia telangiectasia mutated/p53 pathway

Neuroblastoma (NB) is a paediatric solid tumour which originates from sympathetic nervous tissues. Deletions in chromosome 1p are frequently found in unfavourable NBs and are correlated with v-myc avian myelocytomatosis viral oncogene neuroblastoma derived homolog (MYCN) amplification; however, it remains to be elucidated how the 1p loss contributes to MYCN-related oncogenic processes in NB. In this study, we identified the role of Dnmt1-associated protein 1 (DMAP1), coded on chromosome 1p34, in the processes.We studied the expression and function of DMAP1 in NB and found that low-level expression of DMAP1 related to poor prognosis, unfavourable histology and 1p Loss of heterozygosity (LOH) of primary NB samples. Intriguingly, DMAP1 induced ataxia telangiectasia mutated (ATM) phosphorylation and focus formation in the presence of a DNA damage reagent, doxorubicin. By DMAP1 expression in NB and fibroblasts, p53 was activated in an ATM-dependent manner and p53-downstream pro-apoptotic Bcl-2 family molecules were induced at the mRNA level, resulting in p53-induced apoptotic death. BAX and p21^Cip1/Waf1 promoter activity dependent on p53 was clearly up-regulated by DMAP1. Further, MYCN transduction in MYCN single-copy NB cells accelerated doxorubicin (Doxo)-induced apoptotic cell death; MYCN is implicated in DMAP1 protein stabilisation and ATM phosphorylation in these situations. DMAP1 knockdown attenuated MYCN-dependent ATM phosphorylation and NB cell apoptosis. Together, DMAP1 appears to be a new candidate for a 1p tumour suppressor and its reduction contributes to NB tumourigenesis via inhibition of MYCN-related ATM/p53 pathway activation.     

Preparation and characterization of hydroxyapatite nanoparticles carrying insulin and gallic acid for insulin oral delivery

Although nanoparticles carriers for oral delivery of insulin have been researched for many years, this method still fails to solve issues with toxicity, biocompatibility, and degradability in the organism. We therefore developed an innovative conjugation system to solve this problem. Nano hydroxyapatite (HAP) particles were used as the core, then polyethylene glycol (PEG) was wrapped onto the surface of hydroxyapatite, and, finally, insulin (INS) and gallic acid (GA) were conjugated with PEG. PEG functionalized HAP was increased the hydrophilicity of the nanoparticles, also protected them from degradation in the gastrointestinal (GI) tract. Most importantly, the in vivo absorption of nanoparticles in rat small intestines revealed that HAP-PEG-GA-INS was absorbed by the small intestine epithelium. The blood glucose of the type 1 diabetes (T1D) rats that were given intragastrically HAP-PEG-GA-INS showed an obvious downward trend. Overall, we synthesized a safe, non-toxic, and effective oral insulin delivery system.     

Incorporation of thioamide linkages into a growing peptide under SPPS conditions improved by salt effects

Amino acid methyl dithioesters may be coupled in the presence of DMAP and salts to a growing peptide chain on a polymeric resin with high coupling yields and low racemization. © Munksgaard 1995.     

Octachloronaphthalene induction of hepatic microsomal aryl hydrocarbon hydroxylase activity in the immature male rat

Administration of octachloronaphthalene to immature male Wistar rats resulted in a dose-dependent increase in several enzymic, electrophoretic and spectral parameters associated with induction of the hepatic microsomal enzymes. Compared to corn-oil (control) treated animals octachloronaphthalene (150 μmol · kg^?1 induced hepatic cytochrome P-450 (1.5-fold), benzo [a]pyrene hydroxylase (18-fold) and 4-chlorobiphenyl hydroxylase (18-fold) enzyme activities. In addition to increases in the relative peak intensities of the reduced microsomal cytochrome P-450 : CO and ethylisocyanide (EIC) difference spectra the peak maxima were observed at 448.5 and 452.2/428.0 nm, respectively. The effects of administering octachloronaphthalene to the rat were similar to those observed after pretreatment with 3-methylcholanthrene (MC) and electrophoresis of the induced microsomal proteins showed that both compounds enhanced heme-staining peptides with comparable electrophoretic mobilities. Moreover coadministration of MC (3 × 10 βmol · kg^?1) and octachloronaphthalene (2 × 150 μmol · kg^?1) indicated that their inductive effects were not additive. It was concluded that octachloronaphthalene was an MC-type inducer of hepatic microsomal enzymes.     

Effects of mycophenolic acid–glucosamine conjugates on the base of kidney targeted drug delivery

Mycophenolic acid has played an important role in treating immunosuppression and autoimmune diseases. Nevertheless, the agent needs a high dosage in treatment, following some side effects. To tackle this problem, in this study, mycophenolic acid–glucosamine conjugate (MGC), modified by 2-glucosamine, was synthesized to achieve kidney targeting and improved drug efficacy with a lower dosage. ¹H NMR, ¹³C NMR and HRMS spectroscopy were used to verify the conjugate whose stability was good in vitro. The transport of MGC by human proximal renal tubular epithelial HK-2 cells was temperature-, time-, concentration-dependent and saturable, suggesting the involvement of carrier-mediated uptake. In addition, the cellular uptake of MGC dropped substantially with the inhibition of megalin receptor. The specific tissue distribution indicated the commendable renal-targeting capability of MGC. The concentration of MGC was improved in the kidney except for other tissues, about 6.76 times higher than that of MPA. Further, the bioavailability of MGC in plasma decreased as compared with mycophenolic acid. Moreover, therapeutic effect of MGC was enhanced significantly compared with MPA in the acute kidney injury model. All the findings suggested the potential of mycophenolic acid–glucosamine conjugate in kidney targeted drug delivery.     

DDC/DMAP催化合成老年性降脂药姜黄素烟酸单酯

目的探讨姜黄素和烟酸为起始原料合成具有降血脂等作用的姜黄素衍生物的工艺性能。方法通过二环己基碳化二亚胺(DCC)/二甲基吡啶(DMAP)混合催化剂缩合催化,考察实验温度、反应时间以及原料配比等条件对反应的影响。结果得到产率65.1%,含量99.5%的姜黄素烟酸单酯产物,并获得最佳反应条件:n(姜黄素)∶n(烟酸)=1∶1.2;反应温度为10℃等实验数据。结论产品通过核磁共振和质谱表征,结构确切,工艺路线稳定,有较好的治疗老年病应用前景。