Mesenchymal/epithelial regulation of retinoic acid signaling in the olfactory placode.

We asked whether mesenchymal/epithelial (M/E) interactions regulate retinoic acid (RA) signaling in the olfactory placode and whether this regulation is similar to that at other sites of induction, including the limbs, branchial arches, and heart. RA is produced by the mesenchyme at all sites, and subsets of mesenchymal cells express the RA synthetic enzyme RALDH2, independent of M/E interactions. In the placode, RA-producing mesenchyme is further distinguished by its coincidence with a molecularly distinct population of neural crest-associated cells. At all sites, expression of additional RA signaling molecules (RARalpha, RARbeta, RXR, CRABP1) depends on M/E interactions. Of these molecules, RA regulates only RARbeta, and this regulation depends on M/E interaction. Expression of Fgf8, shh, and Bmp4, all of which are thought to influence RA signaling, is also regulated by M/E interactions independent of RA at all sites. Despite these common features, RALDH3 expression is distinct in the placode, as is regulation of RARbeta and RALDH2 by Fgf8. Thus, M/E interactions regulate expression of RA receptors and cofactors in the olfactory placode and other inductive sites. Some aspects of regulation in the placode are distinct, perhaps reflecting unique roles for additional local signals in neuronal differentiation in the developing olfactory pathway.

Speciation and preservation of inorganic arsenic in drinking water sources using EDTA with IC separation and ICP-MS detection.

The native distribution of As(III) and As(v) in drinking water supplies can influence the treatment removal strategy. The stability of As(III) and As(v) in iron-rich drinking waters can be affected by the formation of Fe precipitates (Fe oxides and/or hydroxides designated by "FeOOH"). These precipitates (ppts) can form during the transport of the sample to the laboratory for arsenic speciation analysis. The analysis of the ppt indicates considerable loss of the aqueous arsenic species (As(aq)) to the solid phase "FeOOH" ppt. Studies of laboratory reagent water containing both As(III) and Fe(III) indicate that the resulting "FeOOH" ppt contained a mixture of As(III) and As(v) with near quantitative removal of the As(aq) in 18 hr. The corresponding aqueous fraction after filtration through a 0.45 microm filter was composed primarily of As(v). The formation of "FeOOH" ppt and the loss of As(aq) to the ppt can be virtually eliminated by the use of EDTA, which sequesters the FeIII). Reagent water fortified with Fe(III), As(III) and EDTA produced less than a 1 ppb change in the As(III)aq concentration over 16 d. The EDTA treatment was also tested on three well waters with different native As(III )/As(v) ratios. The native distribution of As(III)/As(v) was stabilized over a period of 10 d with a worst case conversion of As(III) to As(v) of 2 ppb over a 30 d period. All well waters not treated with EDTA had dramatic losses (a factor of 2-5) of As(aq) in less than 1 d. These results indicated that EDTA preservation treatment can be used to preserve As(aq) in waters where the predominant species is the reduced form [As(III)] or in waters which the predominant species is the oxidized form [As(v)]. This preliminary investigation of EDTA to preserve As species in Fe-rich waters indicates stability can be achieved for greater than 14 d.

Extraction and detection of arsenicals in seaweed via accelerated solvent extraction with ion chromatographic separation and ICP-MS detection.

An accelerated solvent extraction (ASE) device was evaluated as a semi-automated means of extracting arsenicals from ribbon kelp. The effect of the experimentally controllable ASE parameters (pressure, temperature, static time, and solvent composition) on the extraction efficiencies of arsenicals from seaweed was investigated. The extraction efficiencies for ribbon kelp (approximately 72.6%) using the ASE were fairly independent (< 7%) of pressure, static time and particle size after 3 ASE extraction cycles. The optimum extraction conditions for the ribbon kelp were obtained by using a 3 mL ASE cell, 30/70 (w/w) MeOH/H2O, 500 psi (1 psi = 7 KPa), ambient temperature, 1 min heat step, 1 min static step, 90% vol. flush, and a 120 s purge. Using these conditions, two other seaweed products produced extraction efficiencies of 25.6% and 50.5%. The inorganic species present in the extract represented 62.5% and 27.8% of the extracted arsenic. The speciation results indicated that both seaweed products contained 4 different arsenosugars, DMA (dimethylarsinic acid), and As(V). One seaweed product also contained As(III). Both of these seaweed products contained an arsenosugar whose molecular weight was determined to be 408 and its structure was tentatively identified using ion chromatography-electrospray ionization-mass spectrometry/mass spectrometry (IC-ESI-MS/MS).

Using an admissions exam to predict student success in an ADN program.

Nursing faculty strive to admit students who are likely to successfully complete the nursing curriculum and pass NCLEX-RN. The high cost of academic preparation and the nursing shortage make this selection process even more critical. The authors discuss how one community college nursing program examined academic achievement measures to determine how well they predicted student success. Results provided faculty with useful data to improve the success and retention of nursing.

Ras1 signaling and transcriptional competence in the R7 cell of Drosophila.

The receptor tyrosine kinase Sevenless determines R7 cell fate by activation of the Ras1 pathway in a subset of equivalent cells competent to respond in the Drosophila eye. We show that the prospero gene becomes transcriptionally activated at a low level in all Sevenless-competent cells prior to Sevenless signaling, and this requires the activities of Ras1 and two Ras1/MAP kinase-responsive ETS transcription factors. Restriction of high-level prospero expression to the R7 cell appears as a subsequent event, which requires Sevenless activation of the Ras1/MAP kinase pathway. We show that Phyllopod, a nuclear factor whose expression is induced by Sevenless, interacts with another nuclear factor, Sina, to form a complex, and that both factors are involved in upregulating transcription of the prospero gene in the eye. Ultimately, prospero expression is required for proper connectivity of R7 photoreceptor axons to their synaptic targets. Our results suggest that specific transcriptional responses are linked to the mode of activation of the Ras1/MAP kinase signal transduction pathway.

HMO strategies for managing workers' compensation claims.

Health maintenance organizations (HMOs) have become very active in managing workers' compensation medical expense benefits. A survey of 316 HMOs shows that this activity takes the form of various network models and a range of services--such as utilization review and case management--that may not be linked to a provider network. Of the HMOs surveyed, 78 reported that, by using managed care services and provider discounts, they were able to save from 20 percent to 30 percent on occupational health claim costs.

Colorimetric determination of macrolide antibiotics using ferric ion.

Macrolide antibiotics such as erythromycin, oleandomycin, spiromycin, and tylosin are found to react with Fe(3+) in the presence of an acetic acid-sulfuric acid mixture to form a colored product having a useful absorption band at 592 nm. Troleandomycin forms only a weakly colored product upon reaction. The molar absorptivity is about 2900 1 mol(-1) cm(-1) for erythromycin and the detection limit is 5 mug ml(-1). This colorimetric method permits the analysis of fermentation broths containing either erythromycin or tylosin without a separation step.

Linoleic and linolenic acids are selectively secreted in triacylglycerol by hepatocytes from neonatal rats.

To determine whether specific fatty acids are metabolized differently by neonatal liver, hepatocyte cultures from neonatal (age: 5, 11, and 21 days) and adult rats were incubated with radiolabeled 18:1, 18:2, or 18:3. At each age, the rate of oxidation was highest for 18:3 and lowest for 18:1. Conversely, esterification was highest for 18:1 and lowest for 18:3. Fatty acid esterification was of the order: day 5 > day 11 > adult > day 21. When incubations contained each of two of the above fatty acids, one radiolabeled and the other not, 18:1 inhibited oxidation of radiolabeled 18:2 by up to 45% in neonatal hepatocytes. In addition, added 18:1 increased glycerolipid accumulation from 18:2 and 18:3. Under these conditions, the relative proportion of triacylglycerol secreted in the medium, compared with that accumulated in the cells, was two- to fourfold higher for day 11 and 21 rat hepatocytes. The results suggest that a specific mechanism exists in the livers of neonatal rats to spare n-3 and n-6 fatty acids from oxidation and instead secrete them in triacylglycerol.

Presqualene metabolism in two species of Lagenidium.

The fate of precursors of the isoprenoid pathway was studied in the sterol auxotroph Lagenidium giganteum and in the positive control organism Lagenidium callinectes. Acetate derived from glucose and mevalonic acid was converted to sterols and fatty acids in L. callinectes. Lagenidium giganteum converted mevalonic acid to sterols and fatty acids, but glucose-derived acetate was not utilized for sterol synthesis. The results showed that the defect in the isoprenoid pathway of L. giganteum occurs at the level of the beta-hydroxy-beta-methylglutarylcoenzyme A reductase-synthase complex. Various aspects of this defect are discussed relative to metabolism of the organism.

Squalene metabolism in two species of Lagenidium.

Squalene metabolism of the sterol auxotroph Lagenidium giganteum was studied and compared with that of the positive control Lagenidium callinectes. Application of experimentally derived precautions ensured both the stability and the purity of squalene during incubations. Under these conditions mycelia of L. giganteum converted squalene to squalene oxide and to a sterol-like compound. Cell-free and microsomal preparations also converted squalene to the oxide, which was identified by thin layer chromatography with five different solvent systems, by co-chromatography with authentic oxide, and by conversion to the glycol. Supporting evidence for the production of squalene oxide was obtained by gas-liquid chromatography, high performance liquid chromatography, and autoradiography. The squalene oxide produced was identified by mass spectrometry.

A phase II study of Adriamycin in previously untreated squamous cell carcinoma of the head and neck.

Twenty patients with squamous cell carcinoma of the head and neck (SCC H/N) were treated with Adriamycin (doxorubicin) at a dosage of 60 mg/m2 at 3-week intervals. No patient had received surgery, radiation, or chemotherapy before treatment with Adriamycin. Responses were observed in 44% of 18 evaluable tumors. We conclude that Adriamycin is a highly active drug in SCC H/N when no prior treatment has been administered.

Growth of human squamous head and neck cancer in vitro.

This study was undertaken to define the cloning efficiency of squamous head and neck (H/N) cancer in soft agar. Twenty squamous cell carcinomas of H/N origin were mechanically dissociated and cultured in the human tumor clonogenic assay ( HTSCA ). No growth was observed. Nine ascites specimens from separate patients with ovarian cancer were cultured during the same time period, and six grew, all with more than 30 colonies per plate. Thirty-one additional H/N specimens were enzymatically dissociated and cultured in the HTSCA . Again, no growth was observed. Sixteen of these enzymatically dissociated specimens were simultaneously cultured in identical media without agar. Five specimens grew. We conclude that squamous carcinoma of H/N requires anchorage and fibroblast support for successful growth in culture. Suspension in semisolid media is less effective than liquid tissue culture systems for in vitro growth of this tumor type.