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Biomedical subjects

K Marshall

Publications and source records attributed to K Marshall.

At least 91 records · Page 5Linked to original sources
PubMed1987

Multiple tamping effects on drug dissolution from capsules filled on a dosing-disk type automatic capsule filling machine.

The effects of number of tamps and tamping force on drug dissolution from capsules filled on an instrumented dosing-disk automatic capsule filling machine (Hofliger-Karg) were studied using hydrochlorothiazide as a model, low dose, poorly soluble drug. Generally, there was a trend toward slower dissolution rate with increasing numbers of tamps, the effect being most marked when insoluble dicalcium phosphate dihydrate was the filler. Higher compression forces improved drug release when anhydrous lactose was the filler, but adversely affected the dicalcium phosphate-based capsules. Inclusion of 4% croscarmellose sodium disintegrant tended to nullify the effects of number of tamps or tamping force with both fillers; however, the disintegrant also markedly enhanced drug dissolution from the dicalcium phosphate-based formulation. Hydrochlorothiazide dissolution from the latter formulation without disintegrant appeared to follow a "diffusion from insoluble matrix" model regardless of number of tamps or their intensity. Mercury intrusion pore size distribution data for some plugs suggested that for tamps of equal force (100 or 200 N), further powder consolidation after two tamps does not occur.

Capsules↗
PubMed1987

A study on the effect of a single dose of tamoxifen on uterine hyperaemia and growth in the rat.

1 The effect of a single subcutaneous dose of tamoxifen on the rat uterotrophic response was investigated. 2 The parameters examined were uterine blood flow (measured by the microsphere technique), uterine wet and dry weights and the concentrations of cytosolic and nuclear oestrogen receptors. 3 Tamoxifen or its metabolites proved to be capable of eliciting a uterotrophic response of 35-42 days duration. The changes seen in uterine blood flow and weight are discussed in relation to oestrogen receptor distribution.

Animals↗
PubMed1986

An investigation of some factors influencing plug formation and fill weight in a dosing disk-type automatic capsule-filling machine.

The progressive formation of plugs resulting from successive tamps in a dosing disk-type automatic capsule-filling machine was investigated for three fillers: anhydrous lactose, dicalcium phosphate, and microcrystalline cellulose. An evaluation of seven compaction parameters revealed that all tamping stations and all piston positions within a station, with the exception of station #1, contribute equally to plug formation. Model calculations suggesting that fill weight could be achieved in only three tamps were supported by direct experimental observation. The effective available fill volume was shown to be greater than the nominal volume of the dosing disk cavity. This was verified by using a modified scrape-off at station #5, which eliminated the powder head over the disk at that station. Here, increases in tamping force resulted in harder plugs, as measured with an improved plug mechanical strength tester, with fill weights remaining unchanged. However, plug segments did not increase in mechanical strength when additional segments were compressed over them using the same force. For one excipient (microcrystalline cellulose), the fill weights and the mechanical strengths of systems containing 0, 0.10, 0.25, and 0.50% magnesium stearate were measured. The 0.10% level was found to be optimum in that it resulted in maximum plug mechanical strengths and fill weights, regardless of the number of tamps used and/or their intensity.

Capsules↗
PubMed1986

The effect of mepyramine and ranitidine on the oestrogen and anti-oestrogen stimulated rat uterus.

The aims of this study were to elucidate further the role of histamine in the rat uterotrophic response and to investigate the differences between the oestrogen and the anti-oestrogen induced uterine responses. The parameters examined were uterine blood flow (measured by the microsphere technique), uterine wet and dry weights. 17 beta-Oestradiol and the anti-oestrogen, tamoxifen, were used to stimulate the ovariectomised rat uterus and the antihistamines mepyramine (H1) and ranitidine (H2) were employed to modify these responses. The uterine changes evoked by oestradiol proved to be more susceptible to modification by the antihistamines than the tamoxifen-stimulated responses. The results suggest that histamine is involved in the early uterine response to oestradiol but histamine does not appear to play a major role in the uterine response to tamoxifen.

Aminopyridines↗
PubMed1986

Ornithine decarboxylase inhibition and the uterotrophic response to oestrogen in rats.

Pretreatment of mature ovariectomized rats with DL-5 alpha-difluoromethylornithine (DFMO) inhibits the 6-h uterine blood flow response to oestradiol and also depresses the stimulatory effect of oestradiol on wet and dry uterine weight. Results from this study indicate that polyamine synthesis is implicated in the uterine response to oestrogen.

Animals↗
PubMed1985

Multiple-hospital survey of ejection-fraction variability using a cardiac phantom.

A dynamic cardiac phantom was used to provide identical input data at 11 different nuclear medicine laboratories throughout the Philadelphia area, and the variability in the resulting calculations of ejection fraction (EF) was assessed. The variability observed between different operators using the same computer system averaged 3 EF units, which was similar to that between different observers using different types of computers. In the range of low ejection fractions, however, there was a suggestion that EFs calculated with an MDS computer were slightly lower than those from a DEC computer.

Cardiac Output↗
PubMed1982

Relationship of site-specific cancer mortality rates to altitude.

Mortality rates for all malignant neoplasms (combined) and for 34 site-specific cancer categories for selected high and low altitude populations are compared using two related techniques: confidence interval overlap for strictly descriptive purposes and analysis of standardized mortality ratios using lower and upper 95% statistical significance factors for the ratio of an observed value of a poisson variable to its expectation. Techniques are employed to minimize confounding due to industrialization, urbanization or selected cultural characteristics. Cancer mortality data for U.S. counties averaged over the 20-year period, 1950--1969, were used. For most comparisons a deficit in cancer mortality in high altitude counties was observed. The largest differences between the low and high altitude groups were found for cancers of the tongue and mouth, esophagus, larynx, lung and melanoma. Some limitations of ecologic studies are discussed.

Altitude↗
PubMed1980

Extracellular beta-D-fructofuranosidase elaborated by Streptococcus salivarius strain 51: preparation, and mode of action on a levan and on homologues of inulobiose.

Streptococcus salivarius strain 51 produces an extracellular beta-D-fructofuranosidase when grown in a levan-containing medium. The enzyme hydrolyses levan, and inulo-biose, -tetraose, -pentaose, and -hexaose, but has negligible effects on inulin, inulotriose, and inuloheptaose. The branching in S. salivarius strain 51 levan is through a single (2 yields 1)-beta-D linkage.

Candida↗
PubMed1976

Structure of the levan elaborated by Streptococcus salivarius strain 51: an application of chemical-ionisation mass-spectrometry.

The polysaccharide elaborated by Streptococcus salivarius strain 51 contains beta-D-fructofuranose residues linked through positions 2 and 6, as well as 1, 2, and 6. The approximate numbers of terminal, non-reducing D-fructofuranose residues and those linked through positions 2 and 6, and through 1, 2, and 6 in the average repeating-unit are 1, 7, and 1, respectively. The branches through the beta-(2 leads to 1)-linkage contain up to at least four D-fructofuranose residues. Chemical-ionisation mass-spectrometry aids the assignment of structures to O-acetyl-O-methylalditols obtained in methylation analysis.

Chromatography, Gas↗