Fluctuations in Adélie penguin prey size in the mid to late Holocene, northern Marguerite Bay, Antarctic Peninsula

We investigated temporal changes in Adélie penguin prey size in northern Marguerite Bay, Antarctic Peninsula, through excavations of three abandoned and one active colony at Lagoon (67°35'S, 68°16'W) and Ginger Islands (67°45'S, 68°41'W), respectively, in austral summer 1999/2000. Radiocarbon dates on penguin bones and eggshell fragments collected at each site indicate that Lagoon Island was first occupied after 6000 BP and Ginger Island near 2275 BP. Identifiable non-krill prey remains (otoliths and squid beaks) were recovered from ornithogenic soils at all sites, with Antarctic silverfish (Pleuragramma antarcticum) and squid (Psychroteuthis glacialis) being the most abundant species represented in the deposits. Estimated mean standard lengths and mantle lengths of these two prey taxa, based on regressions with otolith and beak measurements respectively, indicate that Adélie penguins primarily select these prey within a mean size range of 95-117 mm. Prey size also varied significantly across seven occupation periods from 6000 BP to the present, but did not correlate with climate change.     

Immunohistochemical demonstration of keratins in human ovarian neoplasms. A comparison of methods

A comparison of five immunohistochemical methods for the demonstration of keratins in human ovarian neoplasms using affinity-purified polyclonal rabbit antibody was made. The use of indirect immunofluorescence on frozen sections briefly fixed in acetone was found to be the most sensitive method and demonstrated keratin in all 14 primary and 1 metastatic ovarian epithelial neoplasms studied. Protein A-peroxidase, peroxidase--antiperoxidase (PAP), indirect peroxidase, or the avidin--biotinylated peroxidase complex (ABC) methods applied to formalin-fixed tissues were less sensitive and led to false negative results in 9 of 15, 1 of 15, 8 of 15, and 6 of 15 cases, respectively. A single case of dysgerminoma failed to reveal keratin by any method.     

Evolutionally guided enzyme design

A combination of "rational" and "irrational" strategies for the creation of enzymes with novel properties is proving to be a powerful concept in the field of enzyme engineering. Guided by principles of physical organic chemistry, rational design strategies are used to identify suitable target enzymes and to choose appropriate molecular biological methods for engineering purposes. In contrast, irrational (or random) strategies are centered around the biological paradigm of stochastic molecular evolution. As illustrated in this review, such a hybrid approach is particularly useful for the design of new modular enzymes. (c) 1996 John Wiley & Sons, Inc.     

Directed evolution of Aspergillus niger glucoamylase to increase thermostability

Using directed evolution and site‐directed mutagenesis, we have isolated a highly thermostable variant of Aspergillus niger glucoamylase (GA), designated CR2‐1 . CR2‐1 includes the previously described mutations Asn20Cys and Ala27Cys (forming a new disulfide bond), Ser30Pro, Thr62Ala, Ser119Pro, Gly137Ala, Thr290Ala, His391Tyr and Ser436Pro. In addition, CR2‐1 includes several new putative thermostable mutations, Val59Ala, Val88Ile, Ser211Pro, Asp293Ala, Thr390Ser, Tyr402Phe and Glu408Lys, identified by directed evolution. CR2‐1 GA has a catalytic efficiency (k_cat/K_m) at 35°C and a specific activity at 50°C similar to that of wild‐type GA. Irreversible inactivation tests indicated that CR2‐1 increases the free energy of thermoinactivation at 80°C by 10 kJ mol^?1 compared with that of wild‐type GA. Thus, CR2‐1 is more thermostable (by 5 kJ mol^?1 at 80°C) than the most thermostable A. niger GA variant previously described, THS8 . In addition, Val59Ala and Glu408Lys were shown to individually increase the thermostability in GA variants by 1 and 2 kJ mol^?1, respectively, at 80°C.     

Dissimilar plasmids isolated from Pseudomonas diminuta MG and a Flavobacterium sp. (ATCC 27551) contain identical opd genes.

The opd (organophosphate-degrading) gene derived from a 43-kilobase-pair plasmid (pSM55) of a Flavobacterium sp. (ATCC 27551) has a sequence identical to that of the plasmid-borne gene of Pseudomonas diminuta. Hybridization studies with DNA fragments obtained by restriction endonuclease digestion of plasmid DNAs demonstrated that the identical opd sequences were encoded on dissimilar plasmids from the two sources.     

Phosphate Starvation Inducible Metabolism in Lycopersicon esculentum: II. Characterization of the Phosphate Starvation Inducible-Excreted Acid Phosphatase

Three-day-old suspension cultured cells of Lycopersicon esculentum transferred to a Pi-depleted medium had 2.7 times the excreted acid phosphatase (Apase) activity of cells transferred to a Pi-sufficient medium. Cell growth during this time period was identical for the two treatments. Excreted Apase activity was resolved into two fractions on a Sephadex G-150 column. Most of the phosphate starvation inducible (psi) enhancement in activity was in the lower molecular weight fraction. These two fractions exhibited different substrate versus pH activity profiles. With a native polyacrylamide gel electrophoresis assay, the lower molecular weight fraction resolved into two bands of activity. Both column fractions resolved into the same single band of activity with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The apparent molecular weight of this enzyme was 57 kilodalton. These data indicate that L. esculentum has at least two isozymes of the psi-excreted Apase and that these isozymes may associate to form high molecular weight aggregates. Labeling studies using [³⁵S]methionine show that the psi response in tomato cells is complex and involves changes in the steady state levels of several excreted proteins.     

Cell-lineage patterns in the shoot apical meristem of the germinating maize embryo

A fate map for the shoot apical meristem of Zea mays L. at the time of germination was constructed by examining somatic sectors (clones) induced by -rays. The shoot apical meristem produced stem, leaves, and reproductive structures above leaf 6 after germination and the analysis here concerns their formation. On 160 adult plants which had produced 17 or 18 leaves, 277 anthocyanin-deficient sectors were scored for size and position. Sectors found on the ear shoot or in the tassel most often extended into the vegetative part of the plant. Sectors ranged from one to six internodes in length and some sectors of more than one internode were observed at all positions on the plant. Single-internode sectors predominated in the basal internodes (7,8,9) while longer sectors were common in the middle and upper internodes. The apparent number of cells which gave rise to a particular internode was variable and sectors were not restricted to the lineage unit: a leaf, the internode below it, and the axillary bud and prophyll at the base of the internode. These observations established two major features of meristem activity: 1) at the time of germination the developmental fate of any cell or group of cells was not fixed, and 2) at the time of germination cells at the same location in a meristem could produce greatly different amounts of tissue in the adult plant. Consequently, the developmental fate of specific cells in the germinating meristem could only be assigned in a general way.Abbreviations ACN apparent cell number - LI, LII, LI-LII sectors restricted to the epidermis, the subepidermis, or encompassing epidermis and subepidermis - PCN progenitor cell     

Damage to cultured lens epithelial cells of squirrels and rabbits by UV-A (99.9%) plus UV-B (0.1%) radiation and alpha tocopherol protection

The purpose of this research is to observe the near-UV radiation induced damage to cultured rabbit and squirrel lens epithelial cells as related to destruction and alterations of specific biochemical targets in the cells and to determine protective effects on the cells and targets that are provided by -tocopherol.Confluent monolayers of cultured rabbit and squirrel lens epithelial cells were exposed to black light (BL) lamps, which emit predominantly UV-A radiation. These cells received a mixture 3 J/cm² of UV-A and 4 mJ/cm² of UV-B per h. This mixture is termed near UV_A (ie:predominantly UV-A). Cells were exposed in Tyrode's or in MEM without or with -tocopherol added at 2.5–10 g/ml. Analyses of cell viability and survival, the physical state of cytoskeletal actin, and the activities of Na-K-ATPase and catalase were made.Exposure to near UV_A damaged these cells as measured by vital staining and colony forming ability. Pretreatment with -tocopherol decreased the magnitude of near UV_A cytotoxicity. Near UV_A exposure in MEM always produced more damage to the cells and biochemical targets than in Tyrode's. Cytoskeletal actin was degraded and the activities of Na-K-ATPase and catalase were markedly inhibited by UV-exposure. All of these targets were at least partially protected by -tocopherol in the medium. Without -tocopherol added to the media, the viability and survival of the cells did not recover even after 25 h of incubation. Cell viability was better protected from near UV_A by -tocopherol than was the ability to grow into colonies. This indicates that -tocopherol protects actin, catalase, and Na-K-ATPase from near UV_A damage.     

The Maryland mammoth allele reduces floral stimulus activity in stem piece explants of Nicotiana tabacum (Solanaceae)

The response of axillary buds to floral stimulus activity in stem pieces was examined in two near-isogenic cultivars of tobacco that differ in the recessive maryland mammoth (mm) allele, which confers short-day behavior. All axillary buds from day-neutral plants assayed on six-internode stem pieces made few nodes (less than 20) before flowering, while axillary buds from plants homozygous for mm assayed on six-internode stem pieces either did not flower in noninductive conditions or made many nodes before flowering in inductive conditions. About 80% of day-neutral axillary buds grafted onto day-neutral stem pieces did not respond to floral stimulus in stem pieces, indicating that the floral stimulus in stem pieces is ephemeral. In other graft combinations, the proportion of axillary buds that did respond to floral stimulus in stem pieces was substantially reduced from the 20% of day-neutral buds on day-neutral stem pieces that responded. These results indicate that the mm allele probably reduces both the amount of floral stimulus activity in stem pieces and the competence of axillary buds to respond.     

Role of stem cells during diabetic liver injury

Diabetes mellitus is one of the most severe endocrine metabolic disorders in the world that has serious medical consequences with substantial impacts on the quality of life. Type 2 diabetes is one of the main causes of diabetic liver diseases with the most common being non‐alcoholic fatty liver disease. Several factors that may explain the mechanisms related to pathological and functional changes of diabetic liver injury include: insulin resistance, oxidative stress and endoplasmic reticulum stress. The realization that these factors are important in hepatocyte damage and lack of donor livers has led to studies concentrating on the role of stem cells (SCs) in the prevention and treatment of liver injury. Possible avenues that the application of SCs may improve liver injury include but are not limited to: the ability to differentiate into pancreatic β‐cells (insulin producing cells), the contribution for hepatocyte regeneration, regulation of lipogenesis, glucogenesis and anti‐inflammatory actions. Once further studies are performed to explore the underlying protective mechanisms of SCs and the advantages and disadvantages of its application, there will be a greater understand of the mechanism and therapeutic potential. In this review, we summarize the findings regarding the role of SCs in diabetic liver diseases.