Structure of the concanavalin A-methyl alpha-D-mannopyranoside complex at 6-A resolution.

The carbohydrate binding site of concanavalin A has been identified in crystals of the concanavalin A-methyl alpha-D-mannopyranoside complex and is 35 A from the iodophenol binding site (K. D. Hardman and C. F. Ainsworth (1973), Biochemistry 12,4442), which has been postulated to be adjacent to the carbohydrate-specific binding site (Edelman et al. (1972), Proc. Natl. Acad. Sci. U.S.A. 69, 2580). The crystals are orthorhombic in space group C222(1) and crystal denisty measurements indicate a protein mass of four monomers (molecular weight of 104 000) per asymmetric unit. However, the electron density map contains eight monomers/asymmetric unit, revealing lattice disorder. The electron density map with a nominal resolution of 6 A has been solved using three heavy-atom derivatives and the position and orientation of each monomer established. Atomic coordinates of the native protein which has previously been determined (K. D. Hardman (1973), Adv. Exp. Med. Biol. 40, 103) were transposed into this new space group and the gross conformations of the monomers, dimers, and tetramers were found to be very similar to the previous structure. However, some minor differences were apparent even at this resolution. After crystal growth, the methyl alpha-D-mannopyranoside was replaced by o-iodophenyl beta-D-glucopyranoside or methyl 2-iodoacetimido-2-deoxy-alpha-D-glucopyranoside in separate experiments, and difference electron density maps were calculated. The highest peaks for both iodinated sugar derivatives associated with each monomer agreed within a few angstroms of each other and were found near side chains Tyr-12 and -100 and Asp-16 and -208. This region is 10-14 A from the manganese, in good agreement with nuclear magnetic resonance (NMR) studies in solution (C. F. Brewer et al. (1973), Biochemistry 12, 4448) and with the site predicted from crosslinked 1222 crystal studies (K. D. Hardman (1973), Adv. Exp. Med. Biol. 40, 103).     

Cyclic nucleotide phosphodiesterase activities of pig coronary arteries.

Most (85% or more) of the cyclic nucleotide phosphodiesterase (3' :5' -cyclic-AMP 5'-nucleotidohydrolase, EC 3.1.4.17) activity of pig coronary arteries was found in the 40 000 times g supernatant fraction of homogenates of the intima plus media layer. Chromatography of the soluble fraction of this layer on DEAE-cellulose resolved two phosphodiesterase activities and a heat stable, non-dializable activator. Peak I activity had apparent Km values of 2-4 muM for cyclic GMP and 40-100 muM for cyclic AMP. Peak II activity was relatively specific for cyclic AMP and exhibited apparent negatively cooperative behavior. Peak I but not peak II activity could be stimulated 3-8-fold by the addition of the boiled activator fraction or a boiled crude supernatant fraction. Cyclic AMP hydrolysis by peak I or peak II was more rapid in the presence of Mn-2+ than Mg-2+, but the latter promoted hydrolysis of cyclic GMP by peak I more effectively than did Mn-2+ in the presence of activator. In the absence of added metals, ethylene bis(oxyethylenenitriol)tetra-acetic acid (EGTA) and EDTA both inhibited hydrolysis of cyclic AMP and cyclic GMP by phosphodiesterase activities in the supernatant fraction and in peak I, but EDTA produced more complete inhibition at lower concentrations than did EGTA. Imidazole (1 muM to 10 mM) had virtually no effect on the hydrolysis of cyclic AMP or cyclic GMP catalyzed by either of the two separated peaks or by total phosphodiesterase activities in crude supernatant or particulate fractions.     

Alterations in biosynthetic accumulation of collagen types I and III during growth and morphogenesis of embryonic mouse salivary glands.

We examined the biosynthetic patterns of interstitial collagens in mouse embryonic submandibular and sublingual glands cultured in vitro. Rudiments explanted on day 13 of gestation and cultured for 24, 48, and 72 h all synthesized collagen types I, III, and V. However, while the total incorporation of label into collagenous proteins did not change over the three-day culture period, the rate of accumulation of newly synthesized types I and III did change. At 24 h, the ratio of newly synthesized collagen types I:III was approximately 2, whereas at 72 h, the ratio was approximately 5. These data suggest that collagen types I and III may be important in initiation of branching in this organ, but that type I may become dominant in the later stages of development and in maintenance of the adult organ.     

Simulating effects of environmental factors on biological control of Tetranychus urticae by Typhlodromus pyri in apple orchards

Successful biological control of mites is possible under various conditions, and identifying what are the requirements for robust control poses a challenge because interacting factors are involved. Process-based modeling can help to explore these interactions and identify under which conditions biological control is likely, and when not. Here, we present a process-based model for population interactions between the phytophagous mite, Tetranychus urticae, and its predator, Typhlodromus pyri, on apple trees. Temperature and leaf nitrogen concentration influence T. urticae rates of development and reproduction, while temperature and rate of ingestion of prey and pollen influence T. pyri rates of survival and reproduction. Predator and prey population dynamics are linked through a stage structured functional response model that accounts for spatial heterogeneity in population density throughout the trees. T. urticae biomass-days (BMD’s), which account for sizes of larvae, nymphs and adults, indicate level of mite-induced leaf damage. When BMD’s exceed 290 per leaf, there are economic losses. When BMD’s exceed 350 per leaf, T. urticae population growth is curbed and eventually the population decreases. Simulations were run to determine which conditions would lead to current year economic loss and increased risk of loss in the following year, i.e. where more T. urticae than T. pyri are present at the end of September. Risk was high with one or more of the following initial conditions: a high prey: predator ratio (10:1 or more); a low to intermediate (0.04–0.2 T. urticae per leaf) initial density; T. urticae with a higher initial proportion of adult females than T. pyri; and a delayed first detection of mites, whether in late July, or sometimes in late June, but not in early June. Warm summer weather, higher leaf nitrogen and T. urticae immigration into trees were also risk factors. Causes for these patterns based on biological characteristics of T. urticae and T. pyri are discussed, as are counter measures which can be taken to reduce risk.     

Omega-3 Eicosapentaenoic Acid Decreases CD133 Colon Cancer Stem-Like Cell Marker Expression While Increasing Sensitivity to Chemotherapy

Colorectal cancer is the third leading cause of cancer-related death in the western world. In vitro and in vivo experiments showed that omega-3 polyunsaturated fatty acids (n-3 PUFAs) can attenuate the proliferation of cancer cells, including colon cancer, and increase the efficacy of various anticancer drugs. However, these studies address the effects of n-3 PUFAs on the bulk of the tumor cells and not on the undifferentiated colon cancer stem-like cells (CSLCs) that are responsible for tumor formation and maintenance. CSLCs have also been linked to the acquisition of chemotherapy resistance and to tumor relapse. Colon CSLCs have been immunophenotyped using several antibodies against cellular markers including CD133, CD44, EpCAM, and ALDH. Anti-CD133 has been used to isolate a population of colon cancer cells that retains stem cells properties (CSLCs) from both established cell lines and primary cell cultures. We demonstrated that the n-3 PUFA, eicosapentaenoic acid (EPA), was actively incorporated into the membrane lipids of COLO 320 DM cells. 25 uM EPA decreased the cell number of the overall population of cancer cells, but not of the CD133 (+) CSLCs. Also, we observed that EPA induced down-regulation of CD133 expression and up-regulation of colonic epithelium differentiation markers, Cytokeratin 20 (CK20) and Mucin 2 (MUC2). Finally, we demonstrated that EPA increased the sensitivity of COLO 320 DM cells (total population) to both standard-of-care chemotherapies (5-Fluorouracil and oxaliplatin), whereas EPA increased the sensitivity of the CD133 (+) CSLCs to only 5-Fluorouracil.     

Direct evidence implicates feral cat predation as the primary cause of failure of a mammal reintroduction programme

As evidence mounts that the feral Cat (Felis catus) is a significant threat to endemic Australian biodiversity and impedes reintroduction attempts, uncertainty remains about the impact a residual population of cats following control will have on a mammal reintroduction programme. Also, behavioural interactions between cats and their prey continue to be an area of interest. Within the framework of an ecosystem restoration project, we tested the hypotheses that successful reintroductions of some medium‐sized mammals are possible in locations where feral cats are controlled (but not eradicated) in the absence of European Red Fox (Vulpes vulpes), and that hare‐wallabies that dispersed from their release area are more vulnerable to cat predation compared with those that remain at the release site. We used radiotelemetry to monitor the survivorship and dispersal of 16 Rufous Hare‐wallabies (Lagorchestes hirsutus spp.) and 18 Banded Hare‐wallabies (Lagostrophus fasciatus fasciatus) reintroduced to four sites within Shark Bay, Western Australia. Nearly all foxes were removed and feral cats were subject to ongoing control that kept their indices low relative to prerelease levels. All monitored hare‐wallabies were killed by cats within eight and 10 months following release. Significant predation by feral cats was not immediate: most kills occurred in clusters, with periods of several months where no mortalities occurred. Once a hare‐wallaby was killed, however, predation continued until each population was eliminated. Animals remaining near their release site survived longer than those that dispersed. The aetiology of predation events observed offers new insights into patterns of feral cat behaviour and mammal releases. We propose a hypothesis that these intense per capita predation events may reflect a targeted hunting behaviour in individual feral cats. Even where feral cats are controlled, the outcome from consistent predation events will result in reintroduction failures. Managers considering the reintroduction of medium‐sized mammals in the presence of feral cats should, irrespective of concurrent cat control, consider the low probability of success. We advocate alternative approaches to cat‐baiting alone for the recovery of cat‐vulnerable mammals such as hare‐wallabies.     

The phylogenetic relationships among Noturus catfishes (Siluriformes: Ictaluridae) as inferred from mitochondrial gene cytochrome b and nuclear recombination activating gene 2

Madtom catfishes of the genus Noturus are a well-known component of the North American ichthyofauna. Original nucleotide sequence data were collected from mitochondrial (cytochrome b) and nuclear (recombination activating gene 2) genes and used to estimate genetic variation and infer phylogenetic relationships among and within species of Noturus. Mitochondrial sequences were variable among species and several species were found to contain considerable genetic diversity. Relationships among members of the subgenus Rabida were resolved and in many cases well supported. Relationships among members of the subgenus Schilbeodes were poorly resolved. Previous phylogenetic hypotheses and the traditional classification (except the furiosus species group) were rejected in their explicit form according to the Kishino-Hasegawa and Shimodaira-Hasegawa tests of tree score difference.     

Primary hyperparathyroidism in an adult female olive baboon (Papio anubis)

During an annual physical examination, a middle-aged adult female olive baboon (Papio anubis) in the time-mated breeding colony at the Biologic Resources Laboratory at the University of Illinois at Chicago was found to have a high serum calcium value (> 12 mg/dl). To determine the cause of the hypercalcemia, additional diagnostic tests, including thoracic and abdominal radiographs and a parathyroid panel (parathyroid hormone (PTH), ionized calcium, and parathyroid hormone-related protein (PTH-rp) assays), were performed. The radiographs did not reveal lesions suggestive of neoplasia. A parathyroid panel was obtained twice. Both times the PTH (23.4 and 46.4 pmol/L, normal = 2.91 to 4.57 pmol/L) and ionized calcium (1.68 and 2.10 mmol/L, normal = 1.31 to 1.37 mmol/L) were increased above values for adult females with normal calcium concentration. A tentative diagnosis of primary hyperparathyroidism was made. After a gamma-radiation scan and magnetic resonance imaging of the neck were done, exploratory surgery was performed to identify and remove the affected gland. After gland removal, the baboon's serum calcium, PTH (1.6 pmol/L), and ionized calcium (1.59 mmol/L) values decreased. Results of histologic examination confirmed the diagnosis of benign solitary parathyroid adenoma.     

Paracrine action of transforming growth factor-alpha in rectal crypt epithelium of humans

Colon and rectal mucosal crypt epithelium is a rapidly renewing cell population, where cell proliferation is normally balanced by cell loss. This report concerns the putative paracrine action of transforming growth factor alpha(TGF-alpha) in this homeostatic process. Immunohistochemical staining for proliferating cell nuclear antigen (PCNA) and TGF-alpha was performed on biopsy specimens of rectal mucosa taken from consenting patients. The height of the proliferative compartment in mid-axially sectioned crypts in each individual was determined from the distribution of PCNA stained cells. The number of TGF-alpha stained cells that exhibited intense positive staining in a continuous column from the mouth down the side of the crypt was also scored in each individual patient. There was a significant positive correlation (P=0.05,n =22 patients) between the height of the proliferative compartment and the number of cells staining for TGF-alpha. Non-cellular TGF-alpha reactivity was also observed in the lamina propria adjacent to the TGF-alpha reactive epithelial cells, indicating secretion of TGF-alpha by these epithelial cells. These findings suggest that TGF-alpha is released from epithelial cells in the upper compartment of the crypt into the adjacent lamina propria and then diffuses to the epithelial cells in the lower part of the crypt, resulting in expansion of the proliferative compartment.