Cytochrome P450 2E1-derived reactive oxygen species mediate paracrine stimulation of collagen I protein synthesis by hepatic stellate cells.

To evaluate possible fibrogenic effects of CYP2E1-dependent generation of reactive oxygen species, a model was developed using co-cultures of HepG2 cells, which do (E47 cells) or do not (C34 cells) express cytochrome P450 2E1 (CYP2E1) with stellate cells. There was an increase in intra- and extracellular H(2)O(2), lipid peroxidation, and collagen type I protein in stellate cells co-cultured with E47 cells compared with stellate cells alone or co-cultured with C34 cells. The increase in collagen was prevented by antioxidants and a CYP2E1 inhibitor. CYP3A4 did not mimic the stimulatory effects found with CYP2E1. Collagen mRNA levels remained unchanged, and pulse-chase analysis indicated similar half-lives of collagen I protein between both co-cultures. However, collagen protein synthesis was increased in E47 co-culture. Hepatocytes from pyrazole-treated rats (with high levels of CYP2E1) induced collagen protein in primary stellate cells, and antioxidants and CYP2E1 inhibitors blocked this effect. These results suggest that increased translation of collagen mRNA by CYP2E1-derived reactive oxygen species is responsible for the increase in collagen protein produced by the E47 co-culture. These co-culture models may be useful for understanding the impact of CYP2E1-derived ROS on stellate cell function and activation.     

Crystal structure of a novel mid-gut procarboxypeptidase from the cotton pest Helicoverpa armigera.

The cotton bollworm Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) is one of the most serious insect pests in Australia, India and China. The larva causes substantial economical losses to legume, fibre, cereal oilseed and vegetable crops. This pest has proven to be difficult to control by conventional means, mainly due to the development of pesticide resistance. We present here the 2.5 A crystal structure from the novel procarboxypeptidase (PCPAHa) found in the gut extracts from H. armigera larvae, the first one reported for an insect. This metalloprotease is synthesized as a zymogen of 46.6 kDa which, upon in vitro activation with Lys-C endoproteinase, yields a pro-segment of 91 residues and an active carboxypeptidase moiety of 318 residues. Both regions show a three-dimensional structure quite similar to the corresponding structures in mammalian digestive carboxypeptidases, the most relevant structural differences being located in the loops between conserved secondary structure elements, including the primary activation site. This activation site contains the motif (Ala)(5)Lys at the C terminus of the helix connecting the pro- and the carboxypeptidase domains. A remarkable feature of PCPAHa is the occurrence of the same (Ala)(6)Lys near the C terminus of the active enzyme. The presence of Ser255 in PCPAHa instead of Ile and Asp found in the pancreatic A and B forms, respectively, enlarges the S1' specificity pocket and influences the substrate preferences of the enzyme. The C-terminal tail of the leech carboxypeptidase inhibitor has been modelled into the PCPAHa active site to explore the substrate preferences and the enzymatic mechanism of this enzyme.     

Immunologic and nonimmunologic responsiveness in ragweed-sensitized dogs

The relationship between airway responsiveness to inhaled antigen and histamine, immunologic release of lung histamine, immunologic responsiveness of skin, and specific immunoglobulin E (IgE) antibodies were examined in 11 inbred allergic dogs immunized with extracts of ragweed and grass and 5 nonimmunized control dogs from the same colony. Airway responsiveness to antigen and histamine was characterized by the doses that increased the airflow resistance of the total respiratory system to twice the control values (ED200). Highly significant correlations were found between airway responsiveness and cutaneous responsiveness to antigen and other immunologic characteristics (e.g., IgE and histamine released from lung by inhaled antigen) in all dogs. In ragweed-sensitized dogs, there was an inverse correlation between immunologic responsiveness (reflected by the cutaneous response to antigen and histamine released from lung by inhaled antigen) and nonimmunologic responsiveness of airways (histamine ED200: r = 0.73, P less than 0.05 and r = 0.75, P less than 0.01, respectively). Antigen ED200 was also correlated with histamine release from lung after antigen inhalation (r = 0.74; P less than 0.01). We conclude that airway reactions to inhaled antigen in allergic dogs are dependent not only on immunologic factors but also on the degree of nonimmunologic airway responsiveness to histamine and that these factors are correlated inversely.     

Group versus population level demographics: An analysis of comparability using long term data on wild white‐faced capuchin monkeys (Cebus capucinus imitator)

Primates have long been used as indicator species for assessing overall ecosystem health. However, area‐wide census methods are time consuming, costly, and not always feasible under many field conditions. Therefore, it is important to establish whether monitoring a subset of a population accurately reflects demographic changes occurring in the population at large. Over the past 35 years, we have conducted 15 area‐wide censuses in Sector Santa Rosa, Costa Rica. These efforts have revealed important trends in population growth patterns of capuchin monkeys following the protection and subsequent regeneration of native forests. During this same period, we have also intensively studied a subset of the capuchin groups. Comparing these two datasets, we investigate whether the population structures of the closely monitored groups are reliable indicators of area‐wide demographic patterns. We compare the overall group size and the individual age/sex class compositions of study groups and nonstudy groups (i.e., those contacted during area‐wide censuses only). Our study groups contained more individuals overall with a larger proportion of infants, and there were indications that the proportion of adult and subadult males was lower. These differences can be ascribed either to sampling errors or real differences attributable to human presence and/or better habitat quality for the study groups. No other sex/age classes differed, and major demographic changes were simultaneously evident in both study and nonstudy groups. This study suggests that the Santa Rosa capuchin population is similarly impacted by large‐scale ecological patterns observable within our study groups.     

Changes in the levels of pituitary and steroid hormones in ovine and human ovarian follicular fluid

Changes in the protein and steroid hormones of follicular fluid, aspirated from different follicles of sheep and human ovaries, have been measured and correlated with the size of the follicles. As the fluid contains a number of proteins, steroids have been measured directly and after ether extraction. The follicular fluid concentrations of progesterone and 17 beta-oestradiol measured directly in the fluid increased with the size of the follicles. The levels of free testosterone remained constant in all sizes of follicles, while those of bound hormone showed a 10- to 15-fold increase over the free testosterone concentrations in both the sheep and human follicular fluid. A decrease in the levels of bound testosterone in the fluid of large follicles (LFFL) coincided with the increase in bound 17 beta-oestradiol, suggesting the possible conversion of bound testosterone to oestrogen as the follicle attained maturity. The ratio of follicle-stimulating hormone (FSH) to luteinizing hormone (LH) varied in the fluid obtained from different size follicles, being 1:7 in small (SFFL), 1.3.5 in medium (MFFL) and 1:2.3 in large (LFFL) follicles of sheep ovaries. The LH content of follicular fluid of different size follicles appeared to be the same, with LFFL showing a minor increase over SFFL. In the human, the fluid from medium follicles contained very little LH compared to LFFL. These differences in the pattern of LH levels present in the fluid from different size follicles between human and sheep ovaries presumably reflect species variations in the entry of LH into the follicles.     

Effect of alkyl side chain variation on the electron-transfer activity of ubiquinone derivatives

The effect of the alkyl side chain of the ubiquinone molecule on the electron-transfer activity of ubiquinone in mitochondrial succinate-cytochrome c reductase is studied by using synthetic ubiquinone derivatives that possess the basic ubiquinone structure of 2,3-dimethoxy-5-methyl-1,4-benzoquinone with different alkyl side chains at the 6-position. The alkyl side chains vary in chain length, degree of saturation, and location of double bonds. When a ubiquinone derivative is used as an electron acceptor for succinate-ubiquinone reductase, an alkyl side chain of six carbons is needed to obtain the maximum activity. However, when it serves as an electron donor for ubiquinol-cytochrome c reductase or as a mediator in succinate-cytochrome c reductase, an alkyl side chain of 10 carbons gives maximal efficiency. Introduction of one or two isolated double bonds into the alkyl side chain of the ubiquinone molecule has little effect on electron-transfer activity. However, a conjugated double bond system in the alkyl side chain drastically reduces electron-transfer efficiency. The effect of the conjugated double bond system on the electron-transferring efficiency of ubiquinone depends on its location in the alkyl side chain. When location is far from the benzoquinone ring, the effect is minimal. These observations together with the results obtained from photoaffinity-labeling studies lead us to conclude that flexibility in the portion of the alkyl side chain immediately adjacent to the benzoquinone ring is required for the electron-transfer activity of ubiquinone.     

CDC17: an essential gene that prevents telomere elongation in yeast

The CDC17 gene product performs an essential stage-specific function during the Saccharomyces cerevisiae cell cycle. When cdc17-1 strains are grown at the maximum permissive temperature, recombination is induced preferentially in the genetic interval of the chromosome closest to the telomere. Telomeres are longer in cdc17 strains than in CDC17 strains at the permissive temperature because of addition of sequence near or in the poly (C1-3A) telomeric DNA and become even longer when cells are propagated at elevated temperatures. The mitotic recombination events require RAD52 function, but telomere growth does not. Long telomeres are maintained for many generations when crossed into a CDC17+ background, suggesting that telomere length is largely conserved during replication. The altered telomere length phenotype of cdc17 mutations is recessive and coreverts and cosegregates with the temperature-sensitive lethal phenotype.