Cardioselective and cumulative oxidation of mitochondrial DNA following subchronic doxorubicin administration

We recently reported the preferential accumulation of 8-hydroxydeoxyguanosine (8OHdG) adducts in cardiac mitochondrial DNA (mtDNA) following acute intoxication of rats with doxorubicin (C.M. Palmeira et al., Biochim. Biophys. Acta, 1321 (1997) 101-106). The concentration of 8OHdG adducts decreased to control values within 2 weeks. Since conventional antineoplastic therapy entails repeated administration of small doses of doxorubicin, it was of interest to characterize the kinetics for the accumulation and repair of 8OHdG adducts in the various DNA fractions. Weekly injections of doxorubicin (2 mg/kg, i.p.) to adult male Sprague-Dawley rats caused a cumulative dose-dependent increase in the concentration of 8OHdG adducts in both mtDNA and nuclear DNA (nDNA) from heart and liver. Following six weekly injections, the concentration of 8OHdG in cardiac mtDNA was 50% higher than liver mtDNA and twice that of cardiac nDNA. In contrast to the rapid repair of 8OHdG observed during the first days following an acute intoxicating dose of doxorubicin, the concentration of 8OHdG adducts remained constant between 1 and 5 weeks following the last injection. This was true for all DNA fractions examined. The cardioselective accumulation and persistence of 8OHdG adducts to mtDNA is consistent with the implication of mitochondrial dysfunction in the cumulative and irreversible cardiotoxicity observed clinically in patients receiving doxorubicin cancer chemotherapy.     

Complete plastid genome sequences of Drimys, Liriodendron, and Piper : implications for the phylogenetic relationships of magnoliids

Background  

The magnoliids with four orders, 19 families, and 8,500 species represent one of the largest clades of early diverging angiosperms. Although several recent angiosperm phylogenetic analyses supported the monophyly of magnoliids and suggested relationships among the orders, the limited number of genes examined resulted in only weak support, and these issues remain controversial. Furthermore, considerable incongruence resulted in phylogenetic reconstructions supporting three different sets of relationships among magnoliids and the two large angiosperm clades, monocots and eudicots. We sequenced the plastid genomes of three magnoliids, Drimys (Canellales), Liriodendron (Magnoliales), and Piper (Piperales), and used these data in combination with 32 other angiosperm plastid genomes to assess phylogenetic relationships among magnoliids and to examine patterns of variation of GC content.     

Relationship between the structure of chromosomal protein HMG1 and its accumulation in the cell nucleus

When microinjected into the cytoplasm of cultured mammalian cells, non-histone chromosomal protein HMG1 migrates into the nucleus and binds to the chromatin. To define the features of the HMG1 molecule which are essential for this activity, fragments of HMG1 and chemically modified HMG1 molecules were injected into HeLa cells and the capacity of each of these probes to accumulate in the nucleus was measured by an autoradiographic technique. Fragments representing the C-terminal and central portions of HMG1 did not concentrate in the nucleus; a fragment which consisted of the N-terminal two-thirds of the molecule and which lacked the 41 consecutive aspartate and glutamate residues located near the C-terminal end of the molecule accumulated to about the same extent as intact HMG1. When the amino groups of HMG1 were chemically modified, there was a progressive loss in the ability of the protein to accumulate in the nucleus; derivatization of one-fourth of the total amino groups reduced the concentration of microinjected protein in the nucleus relative to that in the cytoplasm to one-half of the original value. In contrast, modification of one-fourth of the total carboxyl groups did not significantly affect the capacity of HMG1 to accumulate in the nucleus, although further modification resulted in decreased nuclear accumulation. Iodination of tyrosine residues was without effect and modification of the cysteine residues had only a modest effect on the ability of HMG1 to concentrate in the nucleus.     

Effect of uncomplicated pregnancy on body water content and distribution in baboons

Body water content and distribution were estimated before, during, or after 32 pregnancies in baboons. Water content of the various compartments (in liters) correlated with body weight in both nonpregnant and pregnant baboons, and with length of gestation in pregnant baboons. In proportion to body weight (in ml/kg), most water compartments did not change significantly with length of gestation. Mean plasma volume and blood volume were higher during pregnancy than before or after.     

Using Dung to Estimate Gorilla Density: Modeling Dung Production Rate

There is an urgent need for information on western gorilla population sizes and distribution to improve present and plan future conservation actions. Researchers traditionally have estimated gorilla densities on the basis of nest counts despite demonstrated variation in nest production and decay rates. The variation may lead to large biases in estimates of gorilla abundance. We investigated the use of an alternate index of gorilla abundance, via defecation data collected from habituated gorillas at Bai Hokou, Central African Republic. Our sample of 274/370 defecation events/dung piles produced a production rate of ca. 5 dung piles/d: comparable to previous estimates based on much smaller sample sizes. Heuristic models that failed to account for imperfect dung pile detection produced a lower defecation rate estimate than that of a maximum likelihood model that explicitly modeled detection probability. Generalized linear modeling (GLM) showed that dung pile production rate was strongly linked to rainfall, suggesting that failure to correct for seasonal variation in dung pile production rates could lead to substantial biases in gorilla abundance estimates. In our study, failing to distinguish between the number of defecation events and the number of dung piles produced would lead to a ca. 31% overestimate of true gorilla numbers. The use of dung as an index of gorilla abundance shows potential, but more fieldwork and modeling on seasonal variation in dung production rates is required.     

Differential effects of prostaglandin synthetase stimulators on inhibition of cyclooxygenase.

The different effects of prostaglandin synthetase stimulators on inhibition of the cyclooxygenase by structurally distinct classes of nonsteroidal antiinflammatory agents suggest that the enzyme is altered by interaction with these stimulators. Reversible stimulation of prostaglandin synthetase activity by phenols and some other compounds and the relative influence of these stimulators on inhibitors of the cyclooxygenase were determined quantitatively. Two distinct classes of inhibitors were established. The fenamates were relatively weak inhibitors alone but were much more potent in the presence of phenolic compounds. In contrast, ibuprofen, indomethacin, and flurbiprofen were more potent than the fenamates and were reduced in effectiveness by the stimulators, as expected on the basis of two opposing actions. The relative potency of the cyclooxygenase stimulators (phenol greater than norepinephrine greater than tryptophan greater than benzoquinone greater than anisole) paralleled their synergistic action on the fenamates and their antagonist action on the nonfenamates. This correlation suggests that an enzyme alteration which leads to cyclooxygenase stimulation may also result in increased sensitivity to fenamates and decreased sensitivity to the other inhibitors, possibly by altering their capacity to bind.     

Experimental Exposures of Boreal Toads (Bufo boreas) to a Pathogenic Chytrid Fungus (Batrachochytrium dendrobatidis)

One of the major causes of worldwide amphibian declines is a skin infection caused by a pathogenic chytrid fungus (Batrachochytrium dendrobatidis). This study documents the interactions between this pathogen and a susceptible amphibian host, the boreal toad (Bufo boreas). The amount of time following exposure until death is influenced by the dosage of infectious zoospores, duration of exposure, and body size of the toad. The significant relation between dosage and the number of days survived (dose-response curve) supports the hypothesis that the degree of infection must reach a particular threshold of about 10⁷–10⁸ zoosporangia before death results. Variation in air temperature between 12°C and 23°C had no significant effect on survival time. The infection can be transmitted from infected to healthy animals by contact with water containing zoospores; no physical contact between animals is required. These results are correlated with observations on the population biology of boreal toads in which mortalities associated with B. dendrobatidis have been identified.     

Addition of glucosamine and mannose to nascent immunoglobulin heavy chains.

We have investigated the process of protein glycosylation in an attempt to answer the question of whether glucosamine and mannose are added to nascent chains prior to chain completion or only to completed chains after release from the ribosome. The MPC 11 mouse plasmacytoma cell line used in these studies synthesizes a glycosylated gamma2b heavy chain which accounts for 12% of the total protein synthesis. Nascent chains were separated from completed chains by ion-exchange chromatography of solubilized ribosomes on QAE-Sephadex. Our results indicate that both glucosamine and mannose are incorporated into nascent heavy chains prior to chain completion and release from the ribosome. Gel analysis of specifically immunoprecipitated nascent chains indicates that the carbohydrate moiety can be added to the nascent heavy chains very soon after the presumptive asparaginyl glycosylation site (CH2 domain) is synthesized on the ribosome.     

Pregnancy-associated esterase in sera of baboons

Baboon serum samples were resolved by starch gel electrophoresis and polyacrylamide gradient gel electrophoresis and stained with naphthol substrates for esterase activity. An esterase that hydrolyzed alpha-naphthyl butyrate in preference to alpha-naphthyl acetate was found in very high activities in some individuals but not others. It migrated just cathodal of the albumin band in starch gels. In polyacrylamide gradient gels, it co-migrated with albumin and had an apparent molecular weight of approximately 65,000 daltons. Electrophoretic analysis by gel electrophoresis of random serum samples from male and female baboons indicated that this esterase was present only in the sera of pregnant baboons. Further investigation of serial samples collected from carefully monitored baboons confirmed that the amount of activity of this esterase was correlated with stage of pregnancy. Therefore, it was named pregnancy esterase (PE). PE was detectable by gel electrophoresis and chromogenic staining techniques as early as day 30 of pregnancy; its activity gradually increased with progressive pregnancy and reached maximum activity near full term (182 days). Soon after parturition, the activity of PE decreased rapidly and was not detected in maternal sera by day 14 postpartum. No evidence of PE was detected in sera of pregnant humans.     

Growth of aortic vascular smooth muscle cells in lowered oxygen tension

Summary Primary cultures of vascular smooth muscle cells, isolated from rat aorta, were grown under normoxic (20% O₂) and mildly hypoxic (5 % O₂) conditions. Cells from both conditions were compared for growth characteristics, morphology, protein synthesis, lysosomal enzyme activity, and oxygen consumption. In no case was a consistently significant difference observed. These observations indicate that these cells can adapt or are adapted to mildly hypoxic conditions. Moreover, these results may indicate that the culture of vascular smooth muscle cells in mild hypoxia represents a closer approximation of in vivo growth conditions for these cells.Supported by HL19242