Effects of packaging and storage on the dissolution of model prednisone tablets.

The effects of packaging and storage in multiple-unit and unit-dose containers on dissolution rate of model prednisone tablets are reported. USP Prednisone Dissolution Calibrator Tablets were packaged in three multiple-unit and five unit-dose containers. Packaged tablets were stored for three to six months under three conditions: 40 degrees C and 85% relative humidity (R.H.), 37 degrees C and 75% R.H., and 22 degrees C and 75% R.H. Dissolution rate was measured at pre-determined intervals during storage. For each condition tested, two separate runs of six tablets each were performed. Tablets in the least moisture-permeable containers were least affected by storage. The conditions of high heat and humidity caused the greatest change in dissolution rate. When stored at 22 degrees C and 75% R.H., little change in dissolution rate occurred in any packaged tablets. It is concluded that packaging and storage conditions affect tablet dissolution characteristics markedly. The practice of labeling repackaged tablets with the expiration date of the original container is shown to be invalid.

Spirals and G-bands as a function of chromosome length.

The quantitative relationship between spirals and G-bands with regard to length has been investigated. Graphical analysis of sub-chromatid structure showed that the numbers of spirals and G-bands are directly proportional to chromosome length. Equations are derived which predict the number of G-bands or gyri appearing based on chromosome length. The width of chromatids was not found to increase proportionately in shorter chromatids. Calculations indicated that the major events occurring during chromosome contraction in metaphase are the shortening of the chromonemata, reduction in numbers of gyri and a slight reduction in unit gyrus length.

Effects of acetic acid-alcohol, trypsin, histone 1 and histone fragments on Giemsa staining patterns in chromosomes.

In an effort to minimize subjective bias, a classification scheme was devised to assess Giemsa staining patterns obtained with experiments involving acetic acid-alcohol and exogenously applied histone 1 and polypeptides. A single rinse of metaphase preparations with acetic acid-alcohol quantitatively reduced Giemsa dye binding. Acid-alcohol irreversibly changed the conformation of H1 and its ability to interfere with trypsin G-banding. Our results suggest that, in addition to protein extraction, acid-alcohol may alter the conformation of acid-insoluble components of metaphase chromosomes. The carboxy-terminal polypeptide (residues 73--212) from NBS cleavage of H1 was an effective inhibitor of Giemsa staining and trypsin G-banding. However, this polypeptide which is preferential for supercoiled DNA was much less efficient in inhibiting Giemsa staining of trypsinized metaphase chromosomes. The molecular consequences of these experiments are discussed.

Stimulus control of differential-reinforcement-of-low-rate responding.

Five pigeons were given single-stimulus training on an 8-sec differential-reinforcement-of-low-rate schedule followed by steady-state generalization training using 12 wavelength stimuli. Three birds had a high percentage of reinforced responses on the training schedule and flat generalization gradients of total responses. The birds with fewer reinforced responses had much steeper generalization gradients. Generalization gradients plotted as a function of both stimulus wavelength and interresponse time showed that for most birds, stimulus control was restricted to responses with long interresponse times. Responses with very short interresponse times were not under stimulus control and there was some evidence of inhibitory control of short interresponse times. Interresponse-times-per-opportunity functions, plotted as a function of stimulus wavelength, showed that stimulus wavelength controlled the temporal distribution of responses, rather than the overall rate of response. The data indicate that the differential-reinforcement-of-low-rate schedule generates several response categories that are controlled in different ways by wavelength and time-correlated stimuli, and that averaging responses regardless of interresponse-time length obscures this control.