Reproducibility of the Measurement of Bulk/Tapped Density of Pharmaceutical Powders Between Pharmaceutical Laboratories.

The bulk properties of a powder are dependent on the preparation, treatment, and storage of the sample, that is, how it was handled. The particles can be packed to have a range of bulk densities and, moreover, the slightest disturbance of the powder bed may result in a changed bulk density. Thus, the bulk density of a powder is often difficult to measure with good reproducibility and, in reporting the results, it is essential to specify how the determination was made.

Mechanical Properties and Tableting Behavior of Amorphous Solid Dispersions.

Amorphous solid dispersions (ASDs) consisting of acetaminophen (APAP) and copovidone were systematically studied to identify effects of drug loading and moisture content on mechanical properties, thermal properties, and tableting behavior. ASDs containing APAP at different levels were prepared by film casting and characterized by differential scanning calorimetry and nanoindentation. The glass transition temperature (T) continuously decreased with increasing amount of APAP, but the hardness of ASDs was increased at a low APAP content and reduced at high APAP content.

Psychrometric analysis of the environmental equivalency factor for aqueous tablet coating.

Process control of aqueous tablet coating depends on a number of thermodynamic and psychrometric variables. Since many of these variables are interdependent, the choice of parameters by which to control the process or designate a design space is not necessarily obvious. Several mass or heat conservation models for aqueous tablet coating can be found in the literature, varying in approach and proposed method for controlling the coating process.

The rho-guanine nucleotide exchange factor domain of obscurin regulates assembly of titin at the Z-disk through interactions with Ran binding protein 9.

Obscurin is an approximately 800-kDa protein composed of structural and signaling domains that organizes contractile structures in striated muscle. We have studied the Rho-GEF domain of obscurin to understand its roles in morphogenesis and signaling. We used adenoviral overexpression of this domain, together with ultrastructural and immunofluorescence methods, to examine its effect on maturing myofibrils.

Obscurin modulates the assembly and organization of sarcomeres and the sarcoplasmic reticulum.

Obscurin (approximately 800 kDa) in striated muscle closely surrounds sarcomeres at the level of the M-band and Z-disk where, we hypothesize, it participates in the assembly of the contractile apparatus and membrane systems required for Ca2+ homeostasis. In this study, we used small inhibitory RNA (siRNA) technology to reduce the levels of obscurin in primary cultures of skeletal myotubes to study its role in myofibrillogenesis and the organization of the sarcoplasmic reticulum (SR). siRNA-treated myotubes showed a specific and dramatic reduction in the approximately 800 kDa form of obscurin by reverse transcription-polymerase chain reaction, immunoblotting, and immunofluorescence.

De novo myofibrillogenesis in C2C12 cells: evidence for the independent assembly of M bands and Z disks.

We studied the distribution of the giant sarcomeric protein obscurin during de novo myofibrillogenesis in C(2)C(12) myotubes to learn when it is integrated into developing sarcomeres. Obscurin becomes organized first at the developing M band and later at the mature Z disk. Primordial M bands consisting of obscurin, myomesin, and M band epitopes of titin assemble before adult fast-twitch sarcomeric myosin is organized periodically and nearly concurrently with primitive Z disks, which are composed of alpha-actinin and Z disk epitopes of titin.

Obscurin regulates the organization of myosin into A bands.

Obscurin is a giant sarcomeric protein composed of adhesion modules and signaling domains. It surrounds myofibrils at the level of the Z disk and the M line. To study the role of obscurin during myofibrillogenesis, we used adenovirus-mediated gene delivery to overexpress part of its COOH terminus in primary cultures of postnatal day 1 (P1) skeletal myotubes.