Surgical augmentation of skin blood flow and viability in a pig musculocutaneous flap model

A porcine rectus abdominis musculocutaneous (TRAM) flap model was designed and validated in nine pigs. This TRAM flap was based on the deep inferior epigastric (DIE) vessels with an 8 x 18 cm transverse skin paddle at the superior end of the rectus abdominis muscle. The model was subsequently used to test our hypothesis of surgical augmentation of flap viability by vascular territory expansion. Specifically, we observed that ligation of the superior epigastric (SE) vessels at 4, 7, 14, and 28 days (N = 6 to 8) prior to raising the TRAM flaps significantly increased (p less than 0.05) the length and area of the viable skin in the transverse skin paddles of the treatment flaps compared with the contralateral shammanipulated control flaps. This significant increase in skin viability was seen to be accompanied by a significant increase (p less than 0.05) in skin and muscle capillary blood flow in the treatment TRAM flaps compared with the controls (N = 9). The mechanism of vascular territory expansion is unclear. We postulate that hypoxia resulting from the ligation of the superior epigastric vessels prior to the flap surgery may play a role in the triggering of the deep inferior epigastric artery to take over some of the territory previously perfused by the superior epigastric artery. This would then increase the skin and muscle capillary blood flow in the transverse paddle when the TRAM flap was raised on the deep inferior epigastric vascular pedicle.     

Sequencing of peptides and proteins from the carboxy terminus.

A new chemical method for carboxy-terminal (C-terminal) protein sequencing has been developed. This approach has been successfully used to sequence 5 residues of standard proteins and 5 to 10 residues of synthetic peptides at low nanomole levels. The sequencing procedure consists of converting the C-terminal amino acid into a thiohydantoin (TH) derivative, followed by transformation of the TH into a good leaving group by alkylation. Next, the alkylated TH is cleaved mildly and efficiently with (N = C V S)- anion, which simultaneously forms a TH on the newly truncated protein or peptide. Thus, after the initial TH derivatization, there is no return to a free carboxyl group at the C-terminus. An additional benefit of this method is that the alkylating moiety can be chosen with a variety of properties allowing for variation in the detection method. This chemistry has been adapted to automated protein sequencers with a cycle time of about 1 h.     

Establishment of polychlorinated biphenyl-degrading enrichment culture with predominantly meta dechlorination.

Enrichment of polychlorinated biphenyl (PCB)-dechlorinating microorganisms from PCB-contaminated sediments from the Upper Hudson River, N.Y., was attempted. The enrichment strategy was to use pyruvate as the electron donor and dechlorination of Aroclor 1242 as the electron acceptor. The enrichment medium also contained non-PCB-contaminated Hudson River sediments, which were required for the PCB-dechlorinating activity. An enrichment culture (that had stable PCBT-dechlorinating activity over nine serial transfers during 1 year) was established under these conditions; however, the rate of dechlorination did not increase after the second serial transfer. Dechlorination occurred primarily from the meta positions of the biphenyl molecule. Hydrogen could be substituted for pyruvate as the electron donor with equal activity, but when acetate was used as the electron donor a delay in dechlorination was observed. Sulfate and bromethane sulfonate inhibited dechlorination activity. The pyruvate-Aroclor 1242 enrichment also dechlorinated Aroclors 1248, 1254, and 1260; the extent of chlorine removed was the greatest for Aroclor 1254. For comparison, nonautoclaved non-PCB-contaminated Hudson River sediments used in the assay also dechlorinated Aroclors, but only after 12 to 16 weeks of incubation. This suggests that PCB-dechlorinating organisms were also present in these sediments but in numbers lower than those in the enrichment culture.     

Substrate-specific differences in the rate of bile acid carrier reorientation: studies on human placental basal vesicles.

The initial rate of transport of the bile acid glycocholic acid (GCA) has been measured in influx and efflux across placental basal membrane vesicles, and the mechanism of inhibition of its transport by the analogue taurochenodeoxycholic acid (TCDCA) analysed kinetically. This analogue, although trans-stimulating GCA efflux, inhibits influx in a way which does not depend upon substrate concentration; moreover, its potency as an inhibitor is markedly influenced by whether it is placed on one or on both sides of the vesicles membrane. These findings can be accounted for by postulating that both GCA and TCDCA are translocated through the carrier, but that the rate of loaded carrier reorientation is higher than that of the free carrier only when loaded with TCDCA and not with GCA.     

Chilling,oxidative stress and antioxidant responses inArabidopsis thaliana callus

Chilling ofArabidopsis thaliana (L.) Heynh. callus tissue to 4 °C led to conditions of oxidative stress, as indicated by increased levels of the products of peroxidative damage to cell membranes. Cellular H₂O₂ was also observed to increase initially upon chilling but by day 8 cellular levels had declined to below control levels. Although levels of catalase activity remained similar to those in unchilled tissue, activity of ascorbate peroxidase increased between days 4 and 8 of chilling to 4 °C. In callus held at 23 °C, levels of reduced glutathione remained static whereas they rose in callus held at 4 °C. Levels of oxidised glutathione were initially low but increased significantly by day 4 in the chilled callus. At 23 °C, however, levels of oxidised glutathione remained low. Between days 1 and 3 at 4 °C, levels of glutathione reductase activity increased but by day 8 glutathione reductase activity was similar to that in cells held at 23 °C. Exposure of callus to abscisic acid at 23 °C also led to increased activities of ascorbate peroxidase and glutathione reductase.Abbreviations ABA abscisic acid - GSH reduced glutathione - GSSG oxidised glutathione - TTC 2,35-triphenyltetrazolium chloride This work is supported by a grant from the Biotechnology and Biological Sciences Research Council.     

Mutagen sensitivity and suppression of position-effect variegation result from mutations in mus209, the Drosophila gene encoding PCNA.

The mus209B1 mutant of Drosophila melanogaster exhibits a complex pleiotropy of temperature-sensitive (ts) lethality, hypersensitivity to DNA-damaging agents such as ionizing radiation and methyl methanesulfonate, suppression of position-effect variegation (PEV), and female sterility. Our discovery that mus209 encodes proliferating cell nuclear antigen (PCNA), which is an indispensable component of the DNA replication apparatus, suggests that alterations to chromosome replication may underlie that pleiotropy. Nine lethal mutations, three of them ts, genetically define the Pcna locus. Temperature shift studies reveal that the vital function of PCNA is required throughout virtually all stages of fly development, and that maternally encoded PCNA is essential for embryogenesis. All three ts mutants strongly suppress PEV, which suggests a role for PCNA in chromatin assembly or modification.     

The ecological significance of nickel hyperaccumulation: a plant chemical defense

Nickel hyperaccumulating plants have more than 1000 mg Ni kg^–1 dry weight when grown on nickel-bearing soils. We hypothesized that Ni hyperaccumulation could serve as a chemical defense against herbivores In feeding experiments with potential insect herbivores and Ni hyperaccumulating plants, only those inseets fed leaves from plants grown on non-nickel-bearing soil survived or showed a weight gain. Among chemical parameters measured, only Ni content of plants was sufficient to explain this result. When subjected to herbivory by lepidopteran larvae, plants grown on Ni-amended soil showed greater survival and yield than plants on unamended soil. Ni hyperaccumulation may be an effective plant chemical defense against herbivores because of its high lethality, apparent low cost, and broad spectrum of toxicity.     

Assignment of the gene encoding the human thyrotropin-releasing hormone receptor to 8q23 by fluorescence in situ hybridization

A cDNA for human thyrotropin-releasing hormone (TRH) receptor has been isolated from a human pituitary cDNA library. By using this cDNA as a biotinylated probe, the gene encoding the TRH receptor has been localized to chromosome 8q23 by in situ hybridization.     

The spatial variability of soil resources following long-term disturbance

The spatial distributions of selected soil properties in two adjacent sites in southwest Michigan were examined to evaluate the potential effects of chronic disturbance on resource heterogeneity. One site was a cultivated field that had been cleared, plowed, and cropped annually for decades prior to sampling while the other, uncultivated field was cleared of original forest in 1960 after which it was mown annually but never plowed or cropped. We took replicate samples from a 330-point unaligned grid across the sites for soil pH, gravimetric moisture, inorganic phosphorus, total carbon, and net nitrification and nitrogen mineralization potentials. Soils in the cultivated site contained less than half as much carbon as in the uncultivated site, but had higher levels of inorganic phosphorus and moisture, and higher soil pH. Potential net nitrogen mineralization and nitrification rates did not differ between sites. Geostatistical analysis showed that almost all properties examined were strongly autocorelated within each site; structural variance as a proportion of sample variance ranged from 30–95% for all properties, and for any given property differed little between sites. The distance over which this dependence was expressed, however, was for all properties but pH substantially less in the uncultivated site (7–26 m) as compared to the tilled site (48–108m), especially for total C and net nitrification and N mineralization. These results suggest that the spatial pattern and scale of soil variability can differ markedly among edaphically identical sites and that these differences can be related to disturbance history.