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Biomedical subjects

R C Rowe

Publications and source records attributed to R C Rowe.

At least 55 records · Page 3Linked to original sources
PubMed1985

The effect of temperature on the conductivity of gels and emulsions prepared from cetrimide and cetostearyl alcohol.

The conductivity of gels and emulsions containing cetrimide, cetostearyl alcohol, liquid paraffin and water has been studied over the temperature range +35 to -10 degrees C. All samples froze at temperatures below -5 degrees C and exhibited hysteresis on rewarming to room temperature with an initial increase in conductivity up to 15 degrees C followed by a decrease to 25 degrees C. The amount of hysteresis was dependent on the cetostearyl alcohol content and appeared to be related to changes in the microstructure of the liquid crystalline network.

Cetrimonium↗
PubMed1985

A photometric analysis of tablet movement in a side-vented perforated drum (Accela-Cota).

A novel particle tracing technique has been used to study the effect of the normal process variables i.e. drum speed, drum loading and the presence/absence of mixing elements (baffles) on the movement of tablets in a side-vented perforated drum (24 in diameter Accela-Cota). The technique involves measuring the duration of light emission from a single luminous tablet using a photomultiplier mounted to scan the same area as a spray gun, and has enabled the quantification of both the time that the tablet spends on the surface per pass (surface time) and the time that the tablet spends within the bulk of the tablet bed (circulation time) over run lengths equating to the normal tablet coating cycle. The technique also allows the study of the uniformity of tablet appearances by means of circulation profiles. It was found that, while both the surface and circulation times decreased with increasing drum speed and loading, there was irregularity of tablet appearance especially at low drum speeds and in the absence of baffles.

Photometry↗
PubMed1985

The characterization of wet powder masses suitable for extrusion/spheronization.

The characterization of the flow of wet powder masses has been achieved using a ram extruder. Force/displacement curves obtained when material is forced through dies of varying length were found to exhibit three stages: (1) compression (2) steady state flow and (3) forced flow. To provide high quality extrudate it was found preferable to ensure that the compression stage was as short as possible and that steady state flow predominated. To produce these conditions, an optimum composition, die length and ram speed were required. The implications of these findings in relation to the provision of suitable formulations and production conditions for the preparation of spherical granules are discussed.

Cellulose↗
PubMed1985

Gloss measurement on film coated tablets.

The gloss of film coated tablets has been assessed using a commercially available specular glossmeter modified to measure the specular reflectance of individual flat-faced, film-coated tablets. For all the pigmented film formulations studied, there was a decrease in gloss with increasing pigment concentration, the magnitude of the decrease being dependent on the pigment used. Film coatings prepared using an aqueous coating system had a much lower gloss reading than those prepared using an organic solvent coating system. Increasing the mean particle size of an inert filler particle resulted in a minimum gloss reading at intermediate particle sizes, while increasing the polymer concentration resulted in a significant decrease in gloss. In the latter case a power law equation was found to fit the data relating the percentage decrease in gloss with the percentage increase in roughness. The results are consistent with the known theories of specular reflectance and illustrate the potential of this rapid and simple technique in the optimization of film formulation and process variables during product development.

Particle Size↗
PubMed1985

An investigation of the structural changes occurring in a cetostearyl alcohol/cetrimide/water gel after prolonged low temperature (4 degrees C) storage.

Structural changes in a ternary gel prepared using the mixed emulsifier system of cetrimide and cetostearyl alcohol after prolonged low temperature (4 degrees C) storage have been studied using freeze-etch transmission electron microscopy and other techniques. The system changed from an opaque smooth gel of high viscosity, low conductivity and low free water, to a pearlescent milky lotion of low viscosity, high conductivity and high free water. Subsequent equilibration of the thinned system to room temperature (25 degrees C) over 48 h produced an opaque granular gel of similar consistency, but slightly higher conductivity and higher free water than the initial sample. Microscopical examination by both differential interference contrast and freeze-etch electron microscopy showed the system changed from one consisting of a liquid crystalline network localized around cetostearyl alcohol particles, to a system consisting of large waxy plates coexisting with some residual liquid crystalline network. A supportive mechanism for the thinning of the ternary gel at prolonged low temperature storage has been inferred by comparing data with that produced by other workers studying the fusion of phospholipid membranes considered to be morphologically similar to the liquid crystalline network observed in this ternary gel.

Cetrimonium↗
PubMed1985

Flow defects in wet powder mass extrusion.

Surface impairment, in the form of the flow defects roughness and sharkskinning, has been shown to occur with microcrystalline cellulose/lactose/water mixes on extrusion under varying process conditions. These defects result from the imbalance of stresses at the outer wall of the extrudate on leaving the die and can be avoided by changing the process conditions that are known to affect these stresses, e.g. the length of the die, the velocity of throughput and the moisture content of the formulation.

Humidity↗
PubMed1985

Reflectance measurements on gels and emulsions containing cetrimide and cetostearyl alcohol--a preliminary investigation.

Various light scattering properties-the reflectivity, contrast ratio and scattering index of a series of gels and emulsions containing cetrimide, cetostearyl alcohol, water and liquid paraffin have been examined using reflectance measurements made at 560 nm using a four-filter, tristimulus colorimeter. The scattering properties of both systems were dependent on the total interfacial surface area of either the dispersed unreacted cetostearyl alcohol and/or the dispersed droplets of liquid paraffin, and hence increased with increasing concentration of both ingredients. For the emulsion containing liquid paraffin, the scattering properties increased linearly with the concentration of liquid paraffin but with the ternary gel system the scattering properties were not directly related to cetostearyl alcohol concentration. This was confirmed by microscopy as due to the changes in the size of the dispersed unreacted cetostearyl alcohol. The results illustrate the potential of this simple, reproducible non-destructive technique in the study of the structure of such systems.

Cetrimonium↗
PubMed1984

Convergent flow analysis in the extrusion of wet powder masses.

The angle of convergent flow which occurs when a wet powder mass is extruded through a die has been assessed by the inclusion of dyes in the mass before extrusion. The angles obtained are dependent on the powder components and their proportion, the moisture level, and the ratio of the dead space to the area of open die. The method allows assessment of the type and ease of flow which occurs during extrusion.

Cellulose↗
PubMed1984

The opacity of tablet film coatings.

The opacity of tablet film coatings containing a variety of pigments and fillers has been assessed using a contrast ratio defined as the ratio of the measured reflectance of the incident light when the film is placed on a black substrate to the measured reflectance of the incident light when the film is placed on a white substrate. Films pigmented with calcium carbonate, calcium sulphate or talc had very low contrast ratios and only the inclusion of titanium dioxide imparted opacity. Films pigmented with the coloured lake pigments had contrast ratios dependent on both the parent dye and the dye concentration with the contrast ratios decreasing blue greater than red greater than orange greater than yellow. Films pigmented with the synthetic iron oxides all had very high contrast ratios. The results are consistent with the known theories of light scattering and absorption and illustrate the potential of this accurate, rapid and simple technique in the optimization of film formulations during product development.

Chemistry, Pharmaceutical↗
PubMed1983

The refractive indices of polymer film formers, pigments and additives used in tablet film coating: their significance and practical application.

The refractive indices of both the polymer film formers and additives are a fundamental factor in defining the appearance of the subsequent film coatings. The refractive indices of the polymer film formers are all in the region of 1.5 but those of pigments and additives vary between 1.5-3.2. Most pigments and additives are also anisotropic, i.e. they possess different refractive indices depending on their orientation. These observations have implications in the use of pigments and additives for the production of both opaque films with good hiding power and film-coated tablets with highlighted intagliations.

Chemistry, Pharmaceutical↗
PubMed1983

Correlation of Nb2 bioassay and radioimmunoassay values for human serum prolactin.

The availability of a sensitive and specific bioassay (BA) for PRL in human serum has made possible a comparative assessment of PRL bioactivity and immunoactivity in normal and abnormal serum specimens. Serum was studied from 20 normal subjects and 54 patients with a variety of disorders relating to PRL secretion. The correlation between the results of both assays was very close in all subjects. The mean BA/RIA ratio in normal subjects was 0.90, with a range from 0.67-1.33, and in patients with disordered PRL secretion the mean BA/RIA ratio was 0.94, with a range from 0.53-1.58. Similar results were obtained with PRL stimulatory testing using TRH, metoclopramide, and domperidone, and samples of culture medium from both PRL-secreting and non-PRL-secreting human pituitary tumor cultures. In one patient with a high proportion of "big, big" PRL and hyperprolactinaemia a BA/RIA ratio of 2.47 was found, a value well outside the normal range. However another patient with a similar history had a ratio of 0.82, in the range observed in normal subjects. These findings indicate that in a wide variety of clinical disorders the correlation between PRL bioactivity in the Nb2 system and immunoactivity in human serum samples is remarkably good under basal and stimulated conditions. One exception was found, but the nature of the underlying PRL abnormality in this patient remains to be investigated.

Adult↗