Interfacial transfer kinetics of NO2 into pulmonary epithelial lining fluid.

Previous studies, both in intact lungs and epithelial lining fluid (ELF) (J. Appl. Physiol. 68: 594-603, 1990 and J. Appl: Physiol. 69: 523-531, 1990), have suggested that the steady-state absorption of inhaled NO2 is mediated by chemical reaction(s) between NO2 and ELF solute reactants. To characterize the kinetics of NO2 absorption into aqueous biological substrates across a gas-liquid interface, we utilized a closed system of known geometry and initial gas phase [NO2] [([NO2]g)0] to expose ELF (as bronchoalveolar lavage; BAL) and a biochemical model system (glutathione, GSH). Assessments of NO2 reactive uptake, into both GSH and ELF, indicated first-order NO2 kinetics [([NO2]g)0 less than or equal to 10.5 ppm] with effective rate constants of (kNO2)GSH = 4.8 and (kNO2)BAL = 2.9 ml.min-1.cm-2 (stirred). Above 10.5 ppm (1 mM GSH), zero-order kinetics were observed. Both (kNO2)GSH and (kNO2)BAL showed aqueous reactant dependence. The reaction order with respect to GSH and BAL was 0.47 and 0.64, respectively. We found no effect of interfacial surface area or bulk phase volume on kNO2. In unstirred systems, significant interfacial resistance was observed and was related to reactant concentration. These results indicate that NO2 reactive uptake follows first-order kinetics with respect to NO2 ([NO2]g less than or equal to 10.5 ppm) and displays aqueous substrate dependence. Furthermore the site of reactive absorption appears to be limited to near the aqueous surface interface. Unstirred conditions confine interfacial mass transfer kinetics in a dose-dependent manner. These phenomenological coefficients may provide the basis for direct extrapolation to environmentally relevant exposure concentrations.     

Chemical Contamination of California Drinking Water

Drinking water contamination by toxic chemicals has become widely recognized as a public health concern since the discovery of 1,2-dibromo-3-chloropropane in California''s Central Valley in 1979. Increased monitoring since then has shown that other pesticides and industrial chemicals are present in drinking water. Contaminants of drinking water also include naturally occurring substances such as asbestos and even the by-products of water chlorination. Public water systems, commercially bottled and vended water and mineral water are regulated, and California is also taking measures to prevent water pollution by chemicals through various new laws and programs.     

The Changing Alaskan Experience—Health Care Services and Cultural Identity

Before Western contact, Alaskan Native populations were self-sufficient in their health practices. Slowly, the Native health care system was replaced by a Western one which was highly effective in treating infectious diseases. As infectious diseases were brought under control by the Indian Health Service, the emergent leading health problems were related to violence, attributed in part to cultural disintegration. New types of Native health providers and new Native-controlled institutions evolved to provide culturally appropriate health and mental health services and to promote a stronger cultural identity.     

Outer membrane proteins of gentamicin induced small colony variants of Pseudomonas aeruginosa

Small colony variants (SCVs) of Pseudomonas aeruginosa NCTC 6750 (WT) were repeatedly isolated in an in vitro kinetic model after exposure to gentamicin (GM). There were minor differences biochemically and in phage and serotyping between the wild type (WT) strain and SCVs. Changes in outer membrane protein profiles were found. SCVs were more resistant to polymixin and to a range of aminoglycosides (except kanamycin), but were more susceptible to a range of other antibiotics (hydrophilic and hydrophobic) with differing modes of action.     

The dilution rate affects the outer membrane protein and lipopolysaccharide composition of Haemophilus influenzae type b grown under iron limitation.

When Haemophilus influenzae type b was grown under iron limitation in continuous culture, the dilution rate affected the outer membrane protein and lipopolysaccharide composition. Investigations of the effect of the reduced availability of iron or other environmental parameters on these surface components should be controlled for growth rate.     

Physiological and molecular effects of brassinosteroids on Arabidopsis thaliana

We examined the effects of brassinosteroids on Arabidopsis thaliana (L.) Henyh. ecotype Columbia in order to develop a model system for studying gene regulation by plant steroids. Submicromolar concentrations of two brassinosteroids, brassinolide and 24-epibrassinolide, stimulated elongation of Arabidopsis peduncles and inhibited root elongation, respectively. Furthermore, brassinolide altered the abundance of specific in vitro translatable mRNAs from peduncles and whole plants of Arabidopsis. Root elongation in the auxin-insensitive Arabidopsis mutant axr1 was inhibited by 24-epibrassinolide but not by 2,4-D, indicating an independent mode of action for these growth regulators in this physiological response.Abbreviations BR brassinolide - EBR 24-epibrassinolide; 2.4-D,2,4-dichlorophenoxyacetic acid - KPSC 10 mM potassium phosphate, pH 6.0, 2% sucrose, 50 g/ml chloramphenicol - PAGE polyacrylamide gel electrophoresis     

Functional expression of a myo-inositol/H+ symporter from Leishmania donovani.

The vast majority of surface molecules in such kinetoplastid protozoa as members of the genus Leishmania contain inositol and are either glycosyl inositol phospholipids or glycoproteins that are tethered to the external surface of the plasma membrane by glycosylphosphatidylinositol anchors. We have shown that the biosynthetic precursor for these abundant glycolipids, myo-inositol, is translocated across the parasite plasma membrane by a specific transporter that is structurally related to mammalian facilitative glucose transporters. This myo-inositol transporter has been expressed and characterized in Xenopus laevis oocytes. Two-electrode voltage clamp experiments demonstrate that this protein is a sodium-independent electrogenic symporter that appears to utilize a proton gradient to concentrate myo-inositol within the cell. Immunolocalization experiments with a transporter-specific polyclonal antibody reveal the presence of this protein in the parasite plasma membrane.     

THE DIRECT MEASUREMENT OF THE AXOPLASMIC TRANSPORT OF INDIVIDUAL RNA SPECIES: TRANSFER BUT NOT RIBOSOMAL RNA IS TRANSPORTED

Analysis of chick retinal and tectal RNA revealed that in addition to the major cytoplasmic RNAs (rRNA and tRNA), a number of the small mol wt nuclear RNAs (snRNAs) can also be detected. Subfractionation data indicated that one of these molecules, DD′, is of at least 95% nuclear location within the retina. Thus, very little, if any, of the retinal DD′ is available for axoplasmic transport from the retina into the optic nerve and tectum. Following intraocular injection of [³H]uridine, considerable incorporation of isotope into DD′ was observed within the optic tectum after 4, 8 and 16 days. This result indicates the presence of considerable local (i.e. tectal) synthesis. The specific activities of 29S, 18S and 5S rRNA and 4s tRNA relative to that of DD′ were measured in the optic tectum 8 and 16 days after the intraocular introduction of [³H]uridine. The same measurements were also made in intracranially injected animals. While the 29S/DD′, 18S/DD′ and 5S/DD′ specific activity ratios obtained were independent of the injection route, the 4S/DD′ ratio obtained from intraocularly injected animals was significantly greater (at least 2-fold) than that obtained from intracranially injected animals. Similar analysis was also performed with the optic nerve complex at 16 days post-injection with identical results. These results demonstrate that tRNA, but not rRNA, is transported from the retina into the optic nerve and tectum in the 2-day-old chicken.