Biomedical subjects

A E Hawley

Publications and source records attributed to A E Hawley.

6 recordsLinked to original sources

PubMed2003

Decrease in fibrin content of venous thrombi in selectin-deficient mice.

The purpose of this study was to quantify the fibrin content of thrombi produced in a mouse model of venous thrombosis and correlate this to thrombus mass. The role of P-selectin, E-selectin, and IL-10 on thrombus fibrin content was analyzed using knockout (KO) mice. Five groups of mice were evaluated: control (N = 10), P-selectin KO (N = 7), E-selectin KO (N = 5), combined E-/P-selectin KO (N = 12), and IL-10 KO (N = 10). Venous thrombosis was induced by ligation of the infrarenal IVC. Mice were sacrificed on postoperative days (POD) 2 and 6. Thrombus mass was calculated. Sections of IVC were stained with an antibody that cross reacts with mouse fibrin. The distribution of RGB color pixels was generated from digitized micrographs of the thrombus of each animal. The mean pixel value for each group was compiled and analyzed using 2-way ANOVA. Mean pixel value per group was correlated with the mean thrombus mass per group. Color analysis demonstrated significant decreases in the analyzed fibrin content on POD-2 between the control vs E-/P-selectin KO (P < 0.05) and control vs IL-10 KO (P < 0.05) groups. In addition, significantly less fibrin staining was noted on POD-6 between the control vs E-selectin KO (P = 0.03), control vs P-selectin KO (P = 0.01), and control vs E-/P-selectin KO (P < 0.01). There was a strong overall correlation between the mean pixel value for each group and the thrombus mass (R = 0.964; P < 0.01). This study demonstrates a difference in fibrin content of thrombi produced in animals deficient in E-selectin, P-selectin, and IL-10, supporting their importance in thrombus amplification, fibrin formation, and the mass of thrombus formed.

Animals↗

PubMed1998

The effect of lymphatic oedema on the uptake of colloids to the lymph nodes.

The majority of pathological conditions of the lymphatic system can result in some degree of lymphoedema, which in turn causes a reduced rate of lymph flow. In some cases, such as when nodes are invaded by tumour metastases, blockage of the lymphatic vessels may occur. In order to investigate the effect of such pathology on nanosphere uptake in regional lymph nodes, the fate of model polystyrene nanospheres, surface modified with block co-polymers of the poloxamine series, was determined following subcutaneous administration in a rat model with lymphoedema (induced by the administration of lambda-carrageenan). A drastic reduction of injection site drainage and lymph node uptake of nanospheres was observed in the inflammation model compared to control animals. The observations suggest that biodegradable nanospheres based on these will be suitable for the detection of oedema in the lymphatic system.

Animals↗

PubMed1997

Lymph node localisation of biodegradable nanospheres surface modified with poloxamer and poloxamine block co-polymers.

Studies were performed to develop a sub-100 nm biodegradable colloidal system for the efficient delivery of drugs and diagnostic agents to the lymphatic system. Nanospheres of poly(lactide-co-glycolide) were prepared by interfacial polymer deposition. The nanospheres were coated with block co-polymers in order to modify their surface characteristics. Radiolabelling of the nanospheres for in vivo tracing was achieved by the incorporation of the lipophilic complex 111In-oxine during nanosphere preparation. In vitro stability of the radiolabelled nanospheres was determined in rat serum at 37 degrees C. The lymphatic distribution of the nanospheres was determined after subcutaneous administration to the rat. Lymphatic uptake of all coated systems was enhanced compared to the uncoated nanospheres, and a maximal uptake of 17% of the administered dose in the regional lymph nodes was achieved. These observations suggest that the nanospheres are suitable for diagnostic and therapeutic applications in clinical and experimental medicine.

Animals↗

PubMed1997

Preparation of biodegradable, surface engineered PLGA nanospheres with enhanced lymphatic drainage and lymph node uptake.

PURPOSE: Nanospheres can be utilised for the targeting of drugs and diagnostic agents to the regional lymph nodes. The surface modification of model polystyrene, (PS), and poly(lactide-co-glycolide),(PLGA), nanospheres by poly(lactide)-poly(ethylene glycol), (PLA:PEG), copolymers has been assessed by in vitro characterisation and in vivo biodistribution studies following subcutaneous administration of the nanospheres to the rat. METHODS: Three PLA:PEG copolymers were investigated, with PEG chain lengths of 750, 2000 and 5000 Da. The PLA:PEG copolymers were either coated onto the surface of PS and PLGA nanospheres or used as a co-precipitate in the formation of PLGA-PLA:PEG nanospheres. Coating of the nanospheres was confirmed by an increase in their particle size and a corresponding decrease in the surface potential. The kinetics of injection site drainage and lymph node retention was determined over a 24 hour time course for naked, coated and co-precipitated nanosphere systems. RESULTS: Dependent on the surface characteristics, the distribution of the nanospheres can be significantly modified and the lymph node localisation dramatically enhanced by coating their surfaces with PLA:PEG copolymers or by producing co-precipitate nanospheres of PLGA and PLA:PEG. CONCLUSIONS: A fully biodegradable nanosphere system has been developed with excellent lymph node targeting characteristics.

Animals↗

PubMed1994

High-performance liquid chromatographic assay for 2'-deoxy-3'-thiacytidine in human serum.

A high-performance liquid chromatographic method for the determination of 2'-deoxy-3'-thiacytidine (3TC), a novel dideoxy-nucleoside analogue, in human serum is described. 3TC was extracted from serum samples using Bond Elut Certify solid-phase extraction cartridges prior to reversed-phase chromatography with UV detection. The method has been shown to be valid over the concentration range 10-5000 ng/ml using a 1-ml sample volume, both before and after heat treatment of the samples at 60 degrees C for 3 h. The method has been automated using a Zymark robot and used in the analysis of serum samples from HIV positive patients.

Antiviral Agents↗

PubMed1994

Surface engineered nanospheres with enhanced drainage into lymphatics and uptake by macrophages of the regional lymph nodes.

The concept of steric stabilization as used in colloid science is applied to carefully manipulate the drainage and lymphatic distribution of subcutaneously administered model polystyrene nanospheres. A wide range of synthetic polyoxyethylene (POE)/polyoxypropylene (POP) block co-polymers of poloxamine and poloxamer series have been used to produce sterically stabilized nanospheres. We have found a correlation between the length of the stabilizing POE chains of the block co-polymers and nanosphere drainage and passageway across tissue lymph interface in dermal lymphatic capillaries in the rat footpads; the longer the POE chains, the faster the particle drainage. Nanospheres conditioned with block co-polymers of POE chains of 5-15 ethylene oxide units are effectively opsonized in lymphatics; a process which dramatically enhances sequestration (up to 40% of the administered dose) by macrophages of the regional lymph nodes. If the dimensions of the stabilizing POE chains of the poloxamines and poloxamers exceed the range of the Van der Waals force of attraction, opsonization fails to occur and rapidly drained engineered vehicles escape clearance by macrophages of the regional nodes, reach the systemic circulation and remain in the blood for prolonged periods. These observations suggest that a lymphatic delivery composition based on polymer-coated particles will be advantageous for many applications in clinical and experimental medicine.

Animals↗