Occurrence of a novel group of hemagglutinins extractable by Pronase treatment in marine algae

Nine species of marine algae have been assessed for the presence of novel hemagglutinins not extractable with buffer, unless the algal tissue was pretreated with Pronase. All species examined contained hemagglutinins, indicating the existence of a novel group of hemagglutinins which differed from those reported previously in marine algae.     

Involvement of sulfatide in activation of protein kinase C by tumor promoters

Sulfatide (cerebroside sulfate) activated protein kinase C to the same extent as phosphatidylserine did with the tumor promoters, 12-O-tetradecanoylphorbol-13-acetate (TPA), teleocidin and debromoaplysiatoxin. Sulfatide and phosphatidylserine both induced specific binding of [3H]TPA to protein kinase C, although the ratios of specific to non-specific [3H]TPA binding to protein kinase C with the two were not the same. It is concluded that sulfatide is involved in activation of protein kinase C by tumor promoters in a slightly different way from phosphatidylserine.     

Acetylation of Histone H2AX at Lys 5 by the TIP60 Histone Acetyltransferase Complex Is Essential for the Dynamic Binding of NBS1 to Damaged Chromatin

The association and dissociation of DNA damage response (DDR) factors with damaged chromatin occurs dynamically, which is crucial for the activation of DDR signaling in a spatiotemporal manner. We previously showed that the TIP60 histone acetyltransferase complex acetylates histone H2AX, to facilitate H2AX exchange at sites of DNA damage. However, it remained unclear how the acetylation of histone H2AX by TIP60 is related to the DDR signaling. We found that the acetylation but not the phosphorylation of H2AX is essential for the turnover of NBS1 on damaged chromatin. The loss of H2AX acetylation at Lys 5 by TIP60 in cells disturbed the accumulation of NBS1 at sites of DNA damage. Although the phosphorylation of H2AX is also reportedly required for the retention of NBS1 at damage sites, our data indicated that the acetylation-dependent NBS1 turnover by TIP60 on damaged chromatin restricts the dispersal of NBS1 foci from the sites of DNA damage. These findings indicate the importance of the acetylation-dependent dynamic binding of NBS1 to damaged chromatin, created by histone H2AX exchange, for the proper accumulation of NBS1 at DNA damage sites.     

Partial disassembly of peroxisomes

Rat liver peroxisomes were subjected to a variety of procedures intended to partially disassemble or damage them; the effects were analyzed by recentrifugation into sucrose gradients, enzyme analyses, electron microscopy, and SDS PAGE. Freezing and thawing or mild sonication released some matrix proteins and produced apparently intact peroxisomal "ghosts" with crystalloid cores and some fuzzy fibrillar content. Vigorous sonication broke open the peroxisomes but the membranes remained associated with cores and fibrillar and amorphous matrix material. The density of both ghosts and more severely damaged peroxisomes was approximately 1.23. Pyrophosphate (pH 9) treatment solubilized the fibrillar content, yielding ghosts that were empty except for cores. Some matrix proteins such as catalase and thiolase readily leak from peroxisomes. Other proteins were identified that remain in mechanically damaged peroxisomes but are neither core nor membrane proteins because they can be released by pyrophosphate treatment. These constitute a class of poorly soluble matrix proteins that appear to correspond to the fibrillar material observed morphologically. All of the peroxisomal beta-oxidation enzymes are located in the matrix, but they vary greatly in how easily they leak out. Palmitoyl coenzyme A synthetase is in the membrane, based on its co-distribution with the 22-kilodalton integral membrane polypeptide.     

Repair of ultraviolet radiation damage in xeroderma pigmentosum cells belonging to complementation group F

DNA-repair characteristics of xeroderma pigmentosum belonging to complementation group F were investigated. The cells exhibited an intermediate level of repair as measured in terms of (1) disappearance of T4 endonuclease-V-susceptible sites from DNA, (2) formation of ultraviolet-induced strand breaks in DNA, and (3) ultraviolet-induced unscheduled DNA synthesis during post-irradiation incubation. The impaired ability of XP3YO to perform unscheduled DNA synthesis was restored, to half the normal level, by the concomitant treatment with T4 endonuclease V and ultraviolet-inactivated Sendai virus. It is suggested that xeroderma pigmentosum cells of group F may be defective, at least in part, in the incision step of excision repair.     

Inhibition by gossypol of tumor promoter-induced arachidonic acid metabolism in rat peritoneal macrophages

Rat peritoneal macrophages were prelabeled with [3H]arachidonic acid. The release of radioactivity into the medium was increased by treatment with TPA-type tumor promoters, such as TPA, teleocidin and aplysiatoxin, and the non-TPA-type tumor promoter, thapsigargin. Gossypol, at concentrations of 3 and 10 microM, inhibited the release of radioactivity stimulated by both types of tumor promoter, although the mechanism of stimulation of arachidonic acid metabolism is different in the two types of tumor promoter. Stimulation of prostaglandin E2 production by these tumor promoters was also inhibited by treatment with gossypol. Calcium ionophore A23187-stimulated release of radioactivity and prostaglandin E2 production were also inhibited by gossypol treatment. The mechanism of inhibition by gossypol of prostaglandin E2 production is discussed.     

Enteric absorption and pharmacokinetics of oseltamivir in critically ill patients with pandemic (H1N1) influenza

Background

Whether the enteric absorption of the neuraminidase inhibitor oseltamivir is impaired in critically ill patients is unknown. We documented the pharmacokinetic profile of oseltamivir in patients admitted to intensive care units (ICUs) with suspected or confirmed pandemic (H1N1) influenza.

Methods

We included 41 patients 18 years of age and older with suspected or confirmed pandemic (H1N1) influenza who were admitted for ventilatory support to nine ICUs in three cities in Canada and Spain. Using tandem mass spectrometry, we assessed plasma levels of oseltamivir free base and its active metabolite carboxylate at baseline (before gastric administration of the drug) and at 2, 4, 6, 9 and 12 hours after the fourth or later dose.

Results

Among the 36 patients who did not require dialysis, the median concentration of oseltamivir free base was 10.4 (interquartile range [IQR] 4.8–14.9) μg/L; the median concentration of the carboxylate metabolite was 404 (IQR 257–900) μg/L. The volume of distribution of the carboxylate metabolite did not increase with increasing body weight (R² = 0.00, p = 0.87). The rate of elimination of oseltamivir carboxylate was modestly correlated with estimations of creatinine clearance (R² = 0.27, p < 0.001). Drug clearance in the five patients who required continuous renal replacement therapy was about one-sixth that in the 36 patients with relatively normal renal function.

Interpretation

Oseltamivir was well absorbed enterically in critically ill patients admitted to the ICU with suspected or confirmed pandemic (H1N1) influenza. The dosage of 75 mg twice daily achieved plasma levels that were comparable to those in ambulatory patients and were far in excess of concentrations required to maximally inhibit neuraminidase activity of the virus. Adjustment of the dosage in patients with renal dysfunction requiring continuous renal replacement therapy is appropriate; adjustment for obesity does not appear to be necessary.A substantial number of cases of pandemic (H1N1) influenza have involved young adults and adolescents without serious comorbidities who present with severe viral pneumonia complicated by acute respiratory distress syndrome, rhabdomyolysis, renal failure and, occasionally, shock.^1,2 Antiviral therapy in such critically ill patients typically requires oral or nasogastric administration of the neuraminidase inhibitor oseltamivir. Current guidelines from the World Health Organization for the pharmacologic management of progressive or severe pandemic (H1N1) influenza recommend the consideration of high-dose therapy (≥ 150 mg twice daily).^3,4 Critically ill patients exhibit defects in gastrointestinal absorption because of impaired gut perfusion, edema of the bowel wall and ileus as a consequence of critical illness and shock.⁵ Whether the enteric absorption of oseltamivir is impaired in such patients is unknown.We undertook this study to document the pharmacokinetic profile of oseltamivir administered orally or by nasogastric tube in patients admitted to intensive care units (ICUs) with respiratory failure due to suspected or confirmed pandemic (H1N1) influenza.