Development and validation of HPLC-DAD and LC-(ESI)/MS methods for the determination of sulfasalazine, mesalazine and hydrocortisone 21-acetate in tablets and rectal suppositories: In vitro and ex vivo permeability studies

Controlled-release tablets and rectal suppositories of sulfasalazine (SLF) and hydrocortisone 21-acetate (HA) were prepared as recommended dosage forms for the treatment of acute episodes of ulcerative colitis, in patients who do not respond to monotherapy. A High-Performance Liquid Chromatography (HPLC) Diode-array method with a gradient elution mobile phase was developed to evaluate the production quality of both formulations (assay and dissolution profiles in gastric and intestinal fluids). Method's validation was carried out providing good linearity (r ≥ 0.9995), precision (RSD < 1.53%), recovery (96.9% - 103.7%) and limits of detection (LOD_SLF = 12 ng/mL, LOD_HA = 15 ng/mL). Experimental design and Plackett-Burman methodology was constructed to study the robustness of the analysis. In all composite substrates, a freezing lipid precipitation approach was used as purification step. The method was optimized by applying Central Composite design mode. The in-vitro/ex-vivo permeability studies of both formulations were evaluated by a Liquid Chromatography-Electron Spray Ionization Mass Spectrometry (LC-ESI/MS) +/- mode. The analysis of sulfamethazine (internal standard, SLM, m/z 279), HA (m/z 449, [M + HCOO]^-), SLF (m/z 399) and its active metabolite mesalazine (MSL, m/z 154) was performed using a C₁₈ column and gradient elution. The validation of the method met the requirements of the International Council for Harmonization (ICH) (r ≥ 0.9997, RSD ≤ 4.62%, Recovery > 95%, LOD_SLF = 1.28 ng/mL, LOD_HA = 1.07 ng/mL, LOD_MSL = 3.16 ng/mL). Based on the results, important conclusions were drawn concerning the role of excipients and SLF metabolism.

The size, shape, density and ring of the dwarf planet Haumea from a stellar occultation

Haumea-one of the four known trans-Neptunian dwarf planets-is a very elongated and rapidly rotating body. In contrast to other dwarf planets, its size, shape, albedo and density are not well constrained. The Centaur Chariklo was the first body other than a giant planet known to have a ring system, and the Centaur Chiron was later found to possess something similar to Chariklo's rings. Here we report observations from multiple Earth-based observatories of Haumea passing in front of a distant star (a multi-chord stellar occultation). Secondary events observed around the main body of Haumea are consistent with the presence of a ring with an opacity of 0.5, width of 70 kilometres and radius of about 2,287 kilometres. The ring is coplanar with both Haumea's equator and the orbit of its satellite Hi'iaka. The radius of the ring places it close to the 3:1 mean-motion resonance with Haumea's spin period-that is, Haumea rotates three times on its axis in the time that a ring particle completes one revolution. The occultation by the main body provides an instantaneous elliptical projected shape with axes of about 1,704 kilometres and 1,138 kilometres. Combined with rotational light curves, the occultation constrains the three-dimensional orientation of Haumea and its triaxial shape, which is inconsistent with a homogeneous body in hydrostatic equilibrium. Haumea's largest axis is at least 2,322 kilometres, larger than previously thought, implying an upper limit for its density of 1,885 kilograms per cubic metre and a geometric albedo of 0.51, both smaller than previous estimates. In addition, this estimate of the density of Haumea is closer to that of Pluto than are previous estimates, in line with expectations. No global nitrogen- or methane-dominated atmosphere was detected.

Proteins from fish eggs that protect DNA from acid precipitation and inhibit DNA synthesis

We partially characterized proteins that inhibit DNA acid precipitation from various fish eggs (Sparus aurata, Dicentrarchus labrax, Mugil cephalus and Zeus faber). The active proteins were purified by acetone fractionation. The activity was found to be heat resistant. Of bivalent cations tested only Co(2+) and Cu(2+) exerted a profound promoting effect in the activity from all fish. The protein fraction from Sparus aurata inhibited DNA synthesis in PCR performed by different DNA polymerases. The possible role of DNA protective proteins in fish egg physiology is discussed.

Isolation and characterization of a protein from Mendole (Spicara maena) eggs that binds to DNA and inhibits its replication as well as its acid precipitation

Proteins that bind and protect nucleic acids from acid precipitation have been characterized from human and mouse plasma. In the present study, one protein from Mendole (Spicara maena) eggs was purified to homogeneity, by means of acetone fractionation and Sephadex G-100 gel filtration. The protein inhibited DNA replication, exerted by various DNA polymerases. Amino-acid sequence analysis in the amino terminus revealed a unique sequence. Its possible physiological role is discussed.