A Two-Ocean Bouillabaisse: Science,Politics, and the Central American Sea-Level Canal Controversy

As the Panama Canal approached its fiftieth anniversary in the mid-1960s, U.S. officials concerned about the costs of modernization welcomed the technology of peaceful nuclear excavation to create a new waterway at sea level. Biologists seeking a share of the funds slated for radiological-safety studies called attention to another potential effect which they deemed of far greater ecological and evolutionary magnitude – marine species exchange, an obscure environmental issue that required the expertise of underresourced life scientists. An enterprising endeavor to support Smithsonian naturalists, especially marine biologists at the Smithsonian Tropical Research Institute in Panama, wound up sparking heated debates – between biologists and engineers about the oceans’ biological integrity and among scientists about whether the megaproject represented a research opportunity or environmental threat. A National Academy of Sciences panel chaired by Ernst Mayr failed to attract congressional funding for its 10-year baseline research program, but did create a stir in the scientific and mainstream press about the ecological threats that the sea-level canal might unleash upon the Atlantic and Pacific. This paper examines how the proposed megaproject sparked a scientific and political conversation about the risks of mixing the oceans at a time when many members of the scientific and engineering communities still viewed the seas as impervious to human-facilitated change.     

Controlling the aggregation of conjugates of streptavidin with smart block copolymers prepared via the RAFT copolymerization technique

Block copolymers containing stimuli-responsive segments provide important new opportunities for controlling the activity and aggregation properties of protein-polymer conjugates. We have prepared a RAFT block copolymer of a biotin-terminated poly(N-isopropylacrylamide) (PNIPAAm)-b-poly(acrylic acid) (PAA). The number-average molecular weight (M(n)) of the (PNIPAAm)-b-(PAA) copolymer was determined to be 17.4 kDa (M(w)/M(n) = 1.09). The PNIPAAm block had an M(n) of 9.5 kDa and the poly(acrylic acid) (PAA) block had an M(n) of 7.9 kDa. We conjugated this block copolymer to streptavidin (SA) via the terminal biotin on the PNIPAAm block. We found that the usual aggregation and phase separation of PNIPAAm-SA conjugates that follow the thermally induced collapse and dehydration of PNIPAAm (the lower critical solution temperature (LCST) of PNIPAAm is 32 degrees C in water) is prevented through the shielding action of the PAA block. In addition, we show that the cloud point and aggregation properties (as measured by loss in light transmission) of the [(PNIPAAm)-b-(PAA)]-SA conjugate also depended on pH. At pH 7.0 and at temperatures above the LCST, the block copolymer alone was found to form particles of ca. 60 nm in diameter, while the bioconjugate exhibited very little aggregation. At pH 5.5 and 20 degrees C, the copolymer alone was found to form large aggregates (ca. 218 nm), presumably driven by hydrogen bonding between the -COOH groups of PAA with other -COOH groups and also with the -CONH- groups of PNIPAAm. In comparison, the conjugate formed much smaller particles (ca. 27 nm) at these conditions. At pH 4.0, however, large particles were formed from the conjugate both above and below the LCST (ca. 700 and 540 nm, respectively). These results demonstrate that the aggregation properties of the block copolymer-SA conjugate are very different from those of the free block copolymer, and that the outer-oriented hydrophilic block of PAA shields the intermolecular aggregation of the block copolymer-SA bioconjugate at pH values where the -COOH groups of PAA are significantly ionized.     

Direct susceptibility testing on positive blood cultures using Autobac I

Direct susceptibility tests on 243 on positive blood cultures were performed using a rapid Autobac I procedure and the standard Autobac I procedure. After examining 1762 disc comparisons there was an overall agreement between the two techniques of 95%. A total of 1.5% very major, 1.4% major and 1.8% minor discrepancies occured.     

Progression of coronary and mesenteric vascular dysfunction in Zucker obese and Zucker diabetic fatty rats

We investigated the progression of vascular dysfunction associated with the metabolic syndrome with and without hyperglycemia in lean, Zucker obese, and Zucker diabetic fatty (ZDF) rats. Responses of aorta and small coronary and mesenteric arteries were measured to endothelium-dependent and -independent vasodilators. Indices of oxidative stress were increased in serum from ZDF rats throughout the study, whereas values were increased in Zucker obese rats later in the study [thiobarbituric acid reactive substances: 0.45 +/- 0.02, 0.59 +/- 0.03 (P < 0.05), and 0.58 +/- 0.03 (P < 0.05) mug/ml in serum from 28- to 40-wk-old lean, Zucker obese, and ZDF rats, respectively]. Acetylcholine (ACh)-induced relaxation was not altered in vessels from lean animals from 8-40 wk. ACh-induced relaxation was nearly abolished in coronary arteries from 28- to 36-wk-old Zucker obese rats and by 16-36 wk in ZDF rats and was attenuated in aorta and mesenteric vessels from ZDF rats [%relaxation to 10 muM ACh: 72.2 +/- 7.1, 17.9 +/- 5.9 (P < 0.05), and 23.0 +/- 4.5 (P < 0.05) in coronary vessels; and 67.9 +/- 9.2, 50.1 +/- 5.5, and 42.3 +/- 4.7 (P < 0.05) in mesenteric vessels from 28- to 40-wk-old lean, Zucker obese, and ZDF rats, respectively]. The attenuated ACh-induced relaxation was improved when vessels were incubated with tiron, suggesting superoxide as a mechanism of endothelial dysfunction. Sodium nitroprusside-induced relaxation was not altered in aorta or coronary arteries and was potentiated in mesenteric arteries from Zucker obese rats. Our data suggest that diabetes enhances the progression of vascular dysfunction. Increases in indices of oxidative stress precede the development of dysfunction and may serve as a marker of endothelial damage.     

Quinone reduction via secondary B-branch electron transfer in mutant bacterial reaction centers

Symmetry-related branches of electron-transfer cofactors-initiating with a primary electron donor (P) and terminating in quinone acceptors (Q)-are common features of photosynthetic reaction centers (RC). Experimental observations show activity of only one of them-the A branch-in wild-type bacterial RCs. In a mutant RC, we now demonstrate that electron transfer can occur along the entire, normally inactive B-branch pathway to reduce the terminal acceptor Q(B) on the time scale of nanoseconds. The transmembrane charge-separated state P(+)Q(B)(-) is created in this manner in a Rhodobacter capsulatus RC containing the F(L181)Y-Y(M208)F-L(M212)H-W(M250)V mutations (YFHV). The W(M250)V mutation quantitatively blocks binding of Q(A), thereby eliminating Q(B) reduction via the normal A-branch pathway. Full occupancy of the Q(B) site by the native UQ(10) is ensured (without the necessity of reconstitution by exogenous quinone) by purification of RCs with the mild detergent, Deriphat 160-C. The lifetime of P(+)Q(B)(-) in the YFHV mutant RC is >6 s (at pH 8.0, 298 K). This charge-separated state is not formed upon addition of competitive inhibitors of Q(B) binding (terbutryn or stigmatellin). Furthermore, this lifetime is much longer than the value of approximately 1-1.5 s found when P(+)Q(B)(-) is produced in the wild-type RC by A-side activity alone. Collectively, these results demonstrate that P(+)Q(B)(-) is formed solely by activity of the B-branch carriers in the YFHV RC. In comparison, P(+)Q(B)(-) can form by either the A or B branches in the YFH RC, as indicated by the biexponential lifetimes of approximately 1 and approximately 6-10 s. These findings suggest that P(+)Q(B)(-) states formed via the two branches are distinct and that P(+)Q(B)(-) formed by the B side does not decay via the normal (indirect) pathway that utilizes the A-side cofactors when present. These differences may report on structural and energetic factors that further distinguish the functional asymmetry of the two cofactor branches.     

Persistent parvovirus B19 viremia with chronic arthralgia treated with ascorbic acid: a case report

Introduction

According to some studies, ascorbic acid possesses antiviral properties. These studies were mainly focused on the common cold, with very few focusing on other viral infections.

Case presentation

We report the case of a 54-year-old Caucasian woman with chronic arthralgia due to persistent parvovirus B19 viremia. High doses of ascorbic acid treatment were initiated due to the failure of conventional analgesic therapy. Clinical benefit was observed with a simultaneous loss of biological parvovirus B19 viremia.

Conclusions

This observation shows a potential benefit of the use of ascorbic acid against parvovirus B19 infections, even if this case is not sufficient to draw any definite conclusions.     

A hierarchical Bayesian network approach for linkage disequilibrium modeling and data-dimensionality reduction prior to genome-wide association studies

Background  

Discovering the genetic basis of common genetic diseases in the human genome represents a public health issue. However, the dimensionality of the genetic data (up to 1 million genetic markers) and its complexity make the statistical analysis a challenging task.     

Syk associates with clathrin and mediates phosphatidylinositol 3-kinase activation during human rhinovirus internalization

Human rhinovirus (HRV) causes the common cold. The most common acute infection in humans, HRV is a leading cause of exacerbations of asthma and chronic obstruction pulmonary disease because of its ability to exacerbate airway inflammation by altering epithelial cell biology upon binding to its receptor, ICAM-1. ICAM-1 regulates not only viral entry and replication but also signaling pathways that lead to inflammatory mediator production. We recently demonstrated the Syk tyrosine kinase to be an important mediator of HRV-ICAM-1 signaling: Syk regulates replication-independent p38 MAPK activation and IL-8 expression. In leukocytes, Syk regulates receptor-mediated internalization via PI3K. Although PI3K has been shown to regulate HRV-induced IL-8 expression and clathrin-mediated endocytosis of HRV, the role of airway epithelial Syk in this signaling pathway is not known. We postulated that Syk regulates PI3K activation and HRV endocytosis in the airway epithelium. Using confocal microscopy and immunoprecipitation, we demonstrated recruitment of the normally cytosolic Syk to the plasma membrane upon HRV16-ICAM-1 binding, along with Syk-clathrin coassociation. Subsequent incubation at 37 degrees C to permit internalization revealed redistribution of Syk to punctate structures resembling endosomes and colocalization with HRV16. Internalized HRV was not detected in cells overexpressing the kinase inactive Syk(K396R) mutant, indicating that kinase activity was necessary for endocytosis. HRV-induced PI3K activation was dependent on Syk; Syk knockdown by small interfering RNA significantly decreased phosphorylation of the PI3K substrate Akt. Together, these data reveal Syk to be an important mediator of HRV endocytosis and HRV-induced PI3K activation.