Search PubMed⌕ Search

Biomedical subjects

B S Grewal

Publications and source records attributed to B S Grewal.

13 recordsLinked to original sources
PubMed2000

Transdermal macromolecular delivery: real-time visualization of iontophoretic and chemically enhanced transport using two-photon excitation microscopy.

PURPOSE: To investigate the transdermal delivery of a model macromolecule by passive and iontophoretic means following pretreatment with C12-penetration enhancers and to visualise transport across human stratum corneum (SC) in real time. METHODS: Transport studies of dextran, labelled with fluorescent Cascade Blue (D-CB: M(R) = 3 kDa) across human stratum corneum, were conducted during passive and iontophoretic modes of delivery following pretreatment with either dodecyltrimethylammonium bromide (DTAB), sodium dodecyl sulphate (SDS) or Azone. Size-exclusion chromatography was used to assess maintenance of dextran structural integrity throughout experimental lifetime. Two-photon excitation microscopy was employed to visualise real-time dextran transport during current application. RESULTS: The positively charged C12-enhancer DTAB elevated passive D-CB steady-state flux (J(ss)) and was the only enhancer to do so above control during iontophoresis. The negatively charged SDS had the least effect during both stages. On-line macromolecular transport was visualised, indicating both inter- and intra-cellular pathways across SC during current application. No transport was visible across untreated SC during passive transport. CONCLUSIONS: Use of a positively charged enhancer may improve J(ss) of anionic macromolecular penetrants during passive and iontophoretic delivery. On-line visualisation of iontophoresis across SC was possible and can provide mechanistic insight into SC transport pathways.

Administration, Cutaneous↗
PubMed1992

Factors influencing left-ventricular stiffness.

The aim of the study was to investigate the relative contributions of geometrical and material factors to overall left-ventricular cavity stiffness. Left-ventricular cavity shapes were reconstructed using a computer and the variation of myocardial elastic modulus was calculated, by the finite element method, through the passive phase of diastole when rising volume coincided with rising pressure. Geometric data were obtained from biplane cineangiography, with micromanometer pressure measurements, for ten patients with left ventricular disease. Dimensional analysis was applied to the initial and derived data from which the influences of myocardial compliance, wall thickness-to-long dimension ratio, and aspect ratio (long-to-short axes) were determined. The ratio between the volume elasticity and the myocardial modulus of elasticity, the normalized stiffness ratio (NSR), is proposed as a useful index of left ventricular mechanical behaviour in diastole. The volume elasticity of the chamber is dependent not only upon the myocardium elastic modulus and the wall thickness ratio, but also on the shape of the chamber. Changes in the thickness/radius ratio of the ventricle have less effect upon its distention than those in the long dimension/radius ratio. The left ventricle becomes more spherical in shape through diastole and hence becomes stiffer by this geometric mechanism.

Cineangiography↗
PubMed1990

Relation between intraventricular pressure and volume in diastole.

The pressure-volume curves for 10 patients with various types of heart disease were studied throughout mid to late diastole when both pressure and volume were increasing. The results were used to test a currently held theory that the form of this relation is exponential. It was found that for the patients examined this hypothesis was not valid.

Adult↗
PubMed1986

Congenital choanal atresia in North African infants.

Eleven cases of congenital choanal atresia seen over a period of 2 years are described. Its incidence in the community was 1 in 3100 births. Twenty-seven per cent of cases were missed at birth, suggesting an even higher incidence. The anomaly was significantly commoner in infants of younger mothers with less than four children (P less than or equal to 0.05). Maternal polyhydramnios was present in three cases (P less than or equal to 0.0001). The sex incidence was equivocal and three infants were of low birthweight. The atresia was bilateral in the majority of the cases, and associated congenital anomalies were present in five of the 11 infants. Five underwent surgery with no complications.

Adult↗