Stratum Corneum Sampling to Assess Bioequivalence between Topical Acyclovir Products

PURPOSE

To examine the potential of stratum corneum (SC) sampling via tape-stripping in humans to assess bioequivalence of topical acyclovir drug products, and to explore the potential value of alternative metrics of local skin bioavailability calculable from SC sampling experiments.

METHODS

Three acyclovir creams were considered in two separate studies in which drug amounts in the SC after uptake and clearance periods were measured and used to assess bioequivalence. In each study, a "reference" formulation (evaluated twice) was compared to the "test" in 10 subjects. Each application site was replicated to achieve greater statistical power with fewer volunteers.

RESULTS

SC sampling revealed similarities and differences between products consistent with results from other surrogate bioequivalence measures, including dermal open-flow microperfusion experiments. Further analysis of the tape-stripping data permitted acyclovir flux into the viable skin to be deduced and drug concentration in that 'compartment' to be estimated.

CONCLUSIONS

Acyclovir quantities determined in the SC, following a single-time point uptake and clearance protocol, can be judiciously used both to objectively compare product performance in vivo and to assess delivery of the active into skin tissue below the barrier, thereby permitting local concentrations at or near to the site of action to be determined.

Topical bioavailability of diclofenac from locally-acting, dermatological formulations

Assessment of the bioavailability of topically applied drugs designed to act within or beneath the skin is a challenging objective. A number of different, but potentially complementary, techniques are under evaluation. The objective of this work was to evaluate in vitro skin penetration and stratum corneum tape-stripping in vivo as tools with which to measure topical diclofenac bioavailability from three approved and commercialized products (two gels and one solution). Drug uptake into, and its subsequent clearance from, the stratum corneum of human volunteers was used to estimate the input rate of diclofenac into the viable skin layers. This flux was compared to that measured across excised porcine skin in conventional diffusion cells. Both techniques clearly demonstrated (a) the superiority in terms of drug delivery from the solution, and (b) that the two gels performed similarly. There was qualitative and, importantly, quantitative agreement between the in vitro and in vivo measurements of drug flux into and beyond the viable skin. Evidence is therefore presented to support an in vivo - in vitro correlation between methods to assess topical drug bioavailability. The potential value of the stratum corneum tape-stripping technique to quantify drug delivery into (epi)dermal and subcutaneous tissue beneath the barrier is demonstrated.

3D hyperbranched heterostructures of Ag nanocrystals-decorated ZnO nanopillars: controlled growth and characterization of the optical properties

Mechanistic formation of 3D hierarchical structure of silver-decorated ZnO nanopillars grown on Zn foilviaa hydrothermal route.

Facile synthesis of a Ag/MoS2 nanocomposite photocatalyst for enhanced visible-light driven hydrogen gas evolution

Ag-decorated MoS₂ nanocomposite photocatalyst with enhanced visible-light driven hydrogen gas evolution performance.

Glycosylphosphatidylinositol-specific phospholipase D is expressed by macrophages in human atherosclerosis and colocalizes with oxidation epitopes

BACKGROUND

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) may play an important role in inflammation, because it can hydrolyze the GPI anchors of several inflammatory membrane proteins (eg, CD106, CD55, and CD59) and its hydrolytic products upregulate macrophage cytokine expression (eg, interleukin-1 and tumor necrosis factor-alpha). Because of its potential regulatory role in inflammatory reactions, we hypothesized that GPI-PLD might be expressed in atherosclerosis.

METHODS AND RESULTS

Immunohistochemistry using human GPI-PLD-specific rabbit polyclonal antiserum was performed on a total of 83 nonatherosclerotic and atherosclerotic human coronary arteries from 23 patients. Macrophages, smooth muscle cells, apoA-I, and oxidation epitopes also were identified immunohistochemically. Cell-associated GPI-PLD was detected in 95% of atherosclerotic segments, primarily on a subset of macrophages. Extracellular GPI-PLD was present in only 30% of atherosclerotic segments and localized to regions with extracellular apoA-I. In contrast, GPI-PLD was not detected in nonatherosclerotic segments. Expression of GPI-PLD mRNA by human macrophages was confirmed in vitro by reverse transcription/polymerase chain reaction. Further studies demonstrated that GPI-PLD-positive plaque macrophages contained oxidation epitopes, suggesting a link between oxidant stress and GPI-PLD expression. This possibility was supported by studies in which exposure of a macrophage cell line to H2O2 led to a 50+/-3% increase in steady-state GPI-PLD mRNA levels.

CONCLUSIONS

Collectively, these results suggest that oxidative processes may regulate GPI-PLD expression and suggest a role for GPI-PLD in inflammation and in the pathogenesis of atherosclerosis.

Pacemaker lead extraction in pacemaker endocarditis with lead vegetation: usefulness of transesophageal echocardiography

While pacemaker endocarditis is rare, it is a complication that mandates removal of the permanent pacemaker system, including the electrode lead. Many modes of lead removal have been used. The choice of method is determined largely by lead type and chronicity (i.e., risk of substantial adhesions, hence, lead tip mobility). Patient selection has been based on general preoperative risk assessment. It is proposed that the presence of lead vegetation be considered in the decision-making process. Vegetation can be diagnosed by preoperative echocardiography, especially with clinical suspicion of embolism. Transesophageal echocardiography appears to be particularly sensitive. If vegetation is detected, open heart surgery should be strongly considered for lead removal as opposed to dilator sheath counter traction. The latter method risks shearing off the vegetation, which may result in septic--even massive--pulmonary embolus.

Estimation of fetal lung volume using enhanced 3-dimensional ultrasound: a new method and first result

OBJECTIVE

To measure fetal lung volume using a computer based, enhanced, 3-dimensional ultrasound imaging system.

DESIGN

An observational study.

SETTING

The Fetal Medicine Unit at Guys Hospital, London.

PARTICIPANTS

Twenty healthy women with a singleton pregnancy between 24 and 36 weeks of gestation were scanned on one occasion during pregnancy using an ultrasound based 3-dimensional imaging system. All delivered at term with weights above the 10th centile for gestation.

RESULTS

Total lung volume increased exponentially with gestational age. Right lung volume measured consistently greater than left lung volume.

CONCLUSIONS

The use of this new enhanced 3-dimensional imaging system allows for estimations of fetal lung volume. Preliminary data confirm that fetal lung volume, measured by a computerised 3-dimensional ultrasound imaging system increased exponentially with gestational age. The use of this system has obvious application in the further study of lung growth in utero and possible clinical application in disease states where fetal lung growth may be impaired.

Application of a new discreet form of Gauss' theorem for measuring volume

Volume measurements are useful in many branches of science and medicine. They are usually accomplished by acquiring a sequence of cross sectional images through the object using an appropriate scanning modality, for example x-ray computed tomography (CT), magnetic resonance (MR) or ultrasound (US). In the cases of CT and MR, a dividing cubes algorithm can be used to describe the surface as a triangle mesh. However, such algorithms are not suitable for US data, especially when the image sequence is multiplanar (as it usually is). This problem may be overcome by manually tracing regions of interest (ROIs) on the registered multiplanar images and connecting the points into a triangular mesh. In this paper we describe and evaluate a new discreet form of Gauss' theorem which enables the calculation of the volume of any enclosed surface described by a triangular mesh. The volume is calculated by summing the vector product of the centroid, area and normal of each surface triangle. The algorithm was tested on computer-generated objects, US-scanned balloons, livers and kidneys and CT-scanned clay rocks. The results, expressed as the mean percentage difference +/- one standard deviation were 1.2 +/- 2.3, 5.5 +/- 4.7, 3.0 +/- 3.2 and -1.2 +/- 3.2% for balloons, livers, kidneys and rocks respectively. The results compare favourably with other volume estimation methods such as planimetry and tetrahedral decomposition.

Quantitative measures of the palate using enhanced electropalatography

Electropalatography (EPG) is a useful tool for investigating tongue dynamics in experimental phonetic research and speech therapy. However, data provided by EPG are a two-dimensional representation in which all absolute positional information is lost. This paper presents an enhanced EPG (eEPG) system which uses digitised palate shape data to display the tongue-palate contact pattern in three dimensions. The palate shapes are obtained using a colour-encoded structured light three-dimensional digitisation system. The three-dimensional palate shape is displayed on a Silicon Graphics workstation as a surface made up of polygons represented by a quadrilateral mesh. EPG contact patterns are superimposed on to the three-dimensional palate shape by displaying the relevant polygons in a different colour. By using this system, differences in shape between individual palates, apparent on visual inspection of the actual palates, are also apparent in the image on screen. Further, methods have been devised for computing absolute distances along paths lying on the palate surface. Combining this with calibrated palate shape data allows accurate measurements to be made between contact locations on the palate. These have been validated with manual measurements. In addition, vocal tract areas in the oral cavity have been estimated by using the absolute measurements on the palate for a given contact pattern, and assuming a flat tongue profile in the uncontacted area.

Femoral neuropathy after renal transplantation

We report nine cases of neuropathy occurring after renal transplantation, seven of them femoral and two lateral femoral cutaneous. The average time of onset of symptoms is 2.2 days after surgery. Quadriceps weakness, hypoesthesia, and abnormal results of EMG and nerve conduction studies are common and occur on the same side as the operation. The symptoms usually resolve within weeks, but motor and sensory changes can persist. The lesion is thought to be secondary to compression caused by a hematoma at the operative site.

The syndrome of retroperitoneal hemorrhage and lumbar plexus neuropathy during anticoagulant therapy

A syndrome of retroperitoneal hemorrhage during anticoagulant therapy associated with nerve involvement in femoral nerve or lumbar plexus is described. Twenty-one cases were collected from the English-language literature, and five new cases were added for review and analysis. In these 26 cases spontaneous hemorrhage occurred under iliopsoas fascia in the retroperitoneal space. The clinical picture, involved nerves, laboratory findings of coagulation studies, anemia, and the outcome of these cases are summarized and discussed. Retroperitoneal space may contain a large quantity of internal hemorrhage. Irreversible damage of lumbar plexus or femoral nerve may result from entrapment of nerves in the hematoma. Laboratory coagulation studies may guide effective administration of anticoagulant therapy and minimize hemorrhagic complication, but they will not eliminate the risk of hemorrhage completely.