δ15N Values in Crassostrea virginica Shells Provides Early Direct Evidence for Nitrogen Loading to Chesapeake Bay.

Crassostrea virginica is one of the most common estuarine bivalves in the United States' east coast and is frequently found in archaeological sites and sub-fossil deposits. Although there have been several sclerochronological studies on stable carbon and oxygen isotopes in the shells of this species, less is known about δ15N values within their shells, which could be a useful paleoenvironmental proxy to assess estuarine nitrogen dynamics. Modern C. virginica samples were collected in Chesapeake Bay for comparison with archaeological shells from nearby sites ranging in age from ~100 to 3,200 years old. Left valves were sampled by milling the hinge area and the resulting powder was analyzed for %N and δ15N values. Comparison of δ15N values between C. virginica shells shows relatively constant values from ~1250 BC to ~1800 AD. After ~1800 AD, there are rapid increases in 15N enrichment in the shells, which continue to increase in value up to the modern shell values. The increase in δ15N values is evidence of early anthropogenic impact in Chesapeake Bay. These results corroborate the observation that coastal nitrogen pollution occurred earlier than the 19th century and support the use of oyster shell δ15N values as a useful environmental proxy.

Determination of moisture in rubber stoppers: effect of Karl Fischer oven temperatures.

Moisture released from rubber stoppers of pharmaceutical products may adversely affect product quality during storage. The objective of the current study was to identify an appropriate method to quantify free moisture in processed stoppers. The moisture content in stoppers is commonly determined by the Karl Fischer (KF) method. However, for the FM257/2 stoppers from Helvoet, our results suggest that the KF assay results are always lower than that from the gravimetric method and increase with the KF oven temperatures used. The systematic study presented in this manuscript shows that, although moisture results vary with respect to KF oven temperatures, reproducible results are obtained at fixed temperatures. Therefore, the observed variation can not be explained by the release of volatile chemicals from this rubber-affecting KF reagents. Furthermore, by extrapolating moisture results obtained with different thicknesses of rubber slabs to zero thickness, it was found that the diffusion barrier is also not a major source for the variation. It is hypothesized that the moisture in rubber stoppers can be free or bound. The KF method measures both free and bound moisture. As higher KF oven temperatures are used, more bound moisture is released and determined by the KF method. By deducting the bound moisture (measured by the KF method for samples dried at 100 degrees C for one week) from the sample moisture, the amount of free moisture (which is releasable) can be estimated. A KF oven temperature at 250 degrees C is recommended based on the accuracy and precision of the results. This method was validated by showing consistency with the gravimetric method for stoppers undergoing desorption at 25 degrees C and 0% relative humidity (equilibrated with P2O5). An example is also presented to show the application of this method.

Development of a dye ingress method to assess container-closure integrity: correlation to microbial ingress.

To demonstrate maintenance of parenteral product sterility, container-closure integrity over the shelf life of the product is critical. In the past, sterility testing has been used to ensure closure integrity. However, because of the limitations associated with sterility testing, there is a need for an improved method for evaluating container-closure integrity. This article describes the development of a physical test method (dye ingress) for the evaluation of container-closure integrity. FD&C Red No. 40 dye was used in dye ingress studies. The dye solution visual detection limit was similar to the spectophotometric detection limit. This limit was approximately 0.0025 microL of dye/mL, which corresponds to an absorbance of approximately 0.002 absorbance units at 506 nm. Breached vials with various sizes of microtubes were utilized to correlate the dye ingress method with a microbial ingress method. The inner diameter of the microtubes ranged from 2 to 75 microns. The dye ingress and microbial ingress methods had similar sensitivity to breached vials. One advantage of the dye method over microbial ingress is that it may be utilized with vials containing formulations that are cidal or static to microbes. Thus, the dye ingress method is considered an excellent test method for evaluating container-closure integrity.

The adsorption of insulinotropin to polymeric sterilizing filters.

The adsorption characteristics of insulinotropin, a 31-amino acid peptide, to several different sterilizing filters were investigated in the present report. The 0.2 micron filters used in the study were a Nylon-66 filter, a hydroxyl-modified polyamide (BioInert) filter, a polyvinylidene fluoride (PVDF) filter, and a polyhydroxy-propyl-acrylate-grafted polyvinylidene fluoride (GV) filter. The results indicate a rank ordering of adsorption (low to high) of GV, BioInert, Nylon-66, and PVDF. Based on these results, it is possible to predict the amount of solution which must be passed through the specific filter to saturate the binding sites per unit area.

Racemization and intramolecular nucleophilic substitution reactions of ibutilide.

The kinetics and mechanisms of the racemization and cyclization reactions of ibutilide are described. The cyclization reaction yields a bell-shaped rate-pH curve consistent with a change in rate-determining step. It is hypothesized that the hydroxyl group leaves to form a carbocation intermediate; this is followed by nucleophilic attack by the amine. This mechanism is supported by kinetic analysis, aniline trapping of carbocation intermediate, and observation of all four stereo-isomers of the resulting quaternary ammonium compound. Whereas racemization can also progress through the carbocation intermediate, a direct SN2 mechanism appears to be the major route for the racemization reaction.

Coexistence of Hydroid Eating Nudibranchs: Do Feeding Biology and Habitat Use Matter?

The feeding biologies and habitats of four nudibranchs in colonies of the hydroid Obelia geniculata were investigated to determine whether these factors contribute to the coexistence of the nudibranchs. The radulae and feeding behaviors showed species-specific traits. Dendronotus frondosus has a multi-seriate radula; when small (<5 mm), individuals are suctorial feeders, whereas larger nudibranchs (>5 mm), bite whole polyps. Doto coronata uses a flat, uniseriate radula to penetrate stolons. Eubranchus exiguus penetrates hydrothecae with a triseriate radula. Tergipes tergipes has a curved, uniseriate radula and rakes naked tissue. Each species of nudibranch occupied a distinct area within the hydroid colony, suggesting that the micro-habitats are dictated by feeding biology. D. frondosus occupies hydrocauli towards the center of the colony, D. coronata occurs along the edge of the colony on the kelp surface, E. exiguus is found on hydrocauli at the edge of the colony, and T. tergipes sits atop tall hydrocauli in the center of the colony. Separation in the hydroid food resource exists among these nudibranchs and equilibrial coexistence could have operated, but equilibrial conditions necessary for exclusion are unlikely to occur or persist significantly long. Thus, this assemblage of nudibranchs appears structured by non-equilibrial processes perhaps similar to populations of phytophagous insects.

Development of a preformulation lipophilicity screen utilizing a C-18-derivatized polystyrene-divinylbenzene high-performance liquid chromatographic (HPLC) column.

Alkane/water partition coefficients have been predicted from the retention times of solutes using a C-18-derivatized polystyrene-divinylbenzene HPLC column (Act-I). Several classes of compounds, with molecular weights from 78 to 379 and partition coefficients ranging over several orders of magnitude, were included in the present study. A high correlation coefficient (0.953) was obtained from log-log plots of alkane/water partition coefficients versus capacity factor. A poor correlation was observed for octanol/water partition coefficient, presumably due to the hydrogen-bonding capability of octanol. The alkane/water correlation suggests that the system is devoid of significant specific solute-stationary phase interactions which are known to impart anomalous retention behavior to traditional reverse phase columns. Deviations of calculated alkane/water partition coefficients (and Hansch II alkane coefficients) from observed values could not be explained in terms of solute (or substituent) polarizability, dipole moment, sigma para, or pKHB values, further suggesting that specific interactions between the stationary phase and the solute are not significant. A molecular weight dependence that was independent of lipophilicity was observed. Thermodynamic and extra-thermodynamic parameters of retention were obtained in order to investigate retention mechanisms for the Act-I column. The molecular weight dependence does not appear to be due to size exclusion or entropic expulsion of the solute from the stationary phase. Hansch II substituent coefficients calculated from retention times were found to be similar for benzene and steroid derivatives. Thus, the Act-I column may be utilized as a rapid lipophilicity screen for drug candidates of similar molecular weight.

Effects of long-term hydration leading to the development of polar channels in hairless mouse stratum corneum.

Dramatic increases in in vitro permeability coefficients have been observed following the long-term hydration (days) of hairless mouse skin. The effect is greatest for extremely polar or ionized solutes. Differential scanning calorimetry has been utilize in complementary studies in an attempt to assess if the altered permeability may be due to the irreversible alteration of lipid fluidity or keratin structure. The melting range of the lipid endotherms appears to be unaffected when stratum corneum is subjected to hydration conditions similar to those in the permeability experiments. Endotherms attributed to keratin appear to be altered by long-term hydration. However, no quantitative correlation was found between the keratin endotherm area and the permeabilities. The permeability data fit a model where the total permeability coefficient at a given time is the sum of the permeability coefficients associated with the lipid route and the polar route. Permeation increases with hydration time due primarily to alteration of the polar route. Based on molecular weight, no limitation of diffusion in the polar pathway was detected.

Dose-dependent enhancement effects of azone on skin permeability.

In vitro permeability experiments have been combined with differential scanning calorimetry (DSC) studies in an attempt to address the dose-dependent influence of Azone on the permeability coefficients of solutes for hairless mouse stratum corneum. A spray technique was developed to deliver uniformly and quantitatively small amounts of Azone to the stratum corneum. Permeability data obtained for several model solutes of varying lipophilicity suggest lipid fluidization and polar route enhancement as the mechanisms of action for Azone. Alkanols and steroids, both of which are enhanced primarily by lipid fluidization, had different degrees of relative enhancement. This provides evidence that the stratum corneum barrier is heterogeneous, rather than a homogeneous slab barrier. Two effects of Azone on the stratum corneum were detected by DSC. A decrease in the area and a shift to lower temperatures were noted for the lipid endotherms with increasing doses of Azone. A lipid fluidizing effect would qualitatively account for the increases in the permeability coefficients noted for more lipophilic solutes. The stratum corneum keratin endotherm also appears to be altered in the presence of Azone. It is possible that alteration of the keratin structure could lead to the development of polar routes in the stratum corneum.

Innovation within the federal healthcare services: initiatives and promises.

Within the healthcare services industry, innovation is offered as a process for ameliorating issues, improving services, and getting the most out of scarce resources. Medical Services in the Army, Navy, Air Force, Veterans Administration, and the Public Health Service have formed a Federal Healthcare Innovation Network (FHIN) to optimize the use of this management tool. In this article, the concept of innovation in healthcare services management and delivery is reviewed, initiatives in innovation within the five federal healthcare services are discussed, and the promises innovation holds for improved healthcare delivery are addressed.

Carboxyl group catalysis of acyl transfer reactions in corticosteroid 17- and 21-monoesters.

Succinate esters, although frequently employed as water-soluble prodrugs of poorly soluble parent drugs, are not sufficiently stable to allow long-term storage in solution. Intramolecular catalysis of ester hydrolysis by the terminal succinate carboxyl group is a contributing factor to this instability. Methylprednisolone 21-succinate has recently been reported to undergo both hydrolysis and 21 in equilibrium 17 acyl migration in aqueous solutions. Intramolecular catalysis by the terminal carboxyl group is seen in both reactions, but the catalytic mechanisms are not well understood. While acyl migration can only be catalyzed via the carboxyl group acting as a general acid or general base, hydrolysis may undergo either nucleophilic or general acid-base catalysis. To gain further insight into the catalytic mechanism, hydrolysis of methylprednisolone 21-succinate was carried out in aniline buffers to trap any succinic anhydride (as the anilide) that would form if the catalysis were nucleophilic. The nucleophilic mechanism was shown to account for only 15-20% of the overall catalysis. Comparisons of the rates of the intramolecularly catalyzed reactions of methylprednisolone 21- and 17-succinate were made with the same reactions of methylprednisolone 21- and 17-acetate catalyzed intermolecularly by acetate ion. Interestingly, intramolecular catalysis appears to favor acyl migration over hydrolysis. Hence, the hydrolysis of methylprednisolone 21-succinate is faster in basic solutions (pH greater than 7.4), while acyl migration becomes the dominant reaction in the catalyzed region of the pH profile between pH 3.6 and 7.4. Arguments are presented to account for these differences in catalytic efficiency in terms of the transition-state structures for the two reactions.

Synthesis and evaluation of a series of 2'-O-acyl derivatives of 9-beta-D-arabinofuranosyladenine as antiherpes agents.

A series of four 9-(2-O-acyl-beta-D-arabinofuranosyl)adenines (5a-d) was synthesized by acylation of 9-[3,5-bis-O-(tert-butyldimethylsilyl)-beta-D-arabinofuranosyl]adenine (2), followed by removal of the tert-butyldimethylsilyl groups under conditions (HOAc, tetra-n-butylammonium fluoride) that prevented acyl migration. The four 2'-O-acyl derivatives 5a-d showed activity in vitro against herpes type 1 viruses [virus ratings = 1.5-2.6; MIC50 = 26-72 micrograms/mL (8.48-21.3 X 10(-5) M)]. The 2'-O-acetyl (5a) and 2'-O-valeryl (5d) derivatives were evaluated in a guinea pig model for genital herpes (herpes type 2); only 5a showed potent activity when given 6 or 24 h postinfection.