Physical and biological properties of a novel siloxane adhesive for soft tissue applications.

The aim of this study was to investigate the adhesive properties of an in-house aminopropyltrimethoxysilane-methylenebisacrylamide (APTMS-MBA) siloxane system and compare them with a commercially available adhesive, n-butyl cyanoacrylate (nBCA). The ability of the material to perform as a soft tissue adhesive was established by measuring the physical (bond strength, curing time) and biological (cytotoxicity) properties of the adhesives on cartilage. Complementary physical techniques, X-ray photoelectron spectroscopy, Raman and infrared imaging, enabled the mode of action of the adhesive to the cartilage surface to be determined. Adhesion strength to cartilage was measured using a simple butt joint test after storage in phosphate-buffered saline solution at 37 degrees C for periods up to 1 month. The adhesives were also characterised using two in vitro biological techniques. A live/dead stain assay enabled a measure of the viability of chondrocytes attached to the two adhesives to be made. A water-soluble tetrazolium assay was carried out using two different cell types, human dermal fibroblasts and ovine meniscal chondrocytes, in order to measure material cytotoxicity as a function of both supernatant concentration and time. IR imaging of the surface of cartilage treated with APTMS-MBA siloxane adhesive indicated that the adhesive penetrated the tissue surface marginally compared to nBCA which showed a greater depth of penetration. The curing time and adhesion strength values for APTMS-MBA siloxane and nBCA adhesives were measured to be 60 s/0.23 MPa and 38 min/0.62 MPa, respectively. These materials were found to be significantly stronger than either commercially available fibrin (0.02 MPa) or gelatin resorcinol formaldehyde (GRF) adhesives (0.1 MPa) (P < 0.01). Cell culture experiments revealed that APTMS-MBA siloxane adhesive induced 2% cell death compared to 95% for the nBCA adhesive, which extended to a depth of approximately 100-150 microm into the cartilage surface. The WST-1 assay demonstrated that APTMS-MBA siloxane was significantly less cytotoxic than nBCA adhesive as an undiluted conditioned supernatant (P < 0.001). These results suggest that the APTMS-MBA siloxane may be a useful adhesive for medical applications.

Synthesis and properties of amphiphilic networks 3: preparation and characterization of block conetworks of poly(butyl methacrylate-block-(2,3 propandiol-1-methacrylate-stat-ethandiol dimethacrylate)).

Amphiphilic conetwork polymers were prepared and studied as substrates in the culture of dermal fibroblasts. Both block and random conetworks polymers were produced by radical polymerization of either low-molecular weight monomers or oligomeric macromonomers. The oligomeric macromonomers were prepared by methacrylation of biscarboxy oligo(butyl methacrylates) (OBMA). The latter were synthesized by ozononolysis of poly(butyl methacrylate-co-butadiene) materials. The hydrophilic component was derived from copolymerization with 2,3 propandiol-1-methacrylate and cross-linking was provided by inclusion of ethandiol dimethacrylate (EDMA). None of the synthesized materials showed indications of cytotoxicity to human dermal fibroblasts. All of the block conetworks were highly phase separated and possessed pores on the micron length scale. The equilibrium water contents of the latter could be controlled by addition of EDMA. Block conetworks that did not contain EDMA were highly swollen and had smoother surfaces than those that contained EDMA. The former were poor substrates for cell proliferation (as measured by monitoring DNA content) whilst the latter class gave increasing levels of DNA during culture; an indicator proliferation. The performance of these materials in cell culture was also dependent on the fraction of OBMA in the formulation. Increasing the fractions of BMA, either in the random terpolymer or block networks, system had the effect of increasing both cell proliferation and viability (as measured by the Alamar Blue assay).

A quantitative analysis of the intranasal delivery of topical nasal drugs to the middle meatus: spray versus drop administration.

The delivery of nasal drugs specifically to the middle meatus is of critical importance in the medical treatment of rhinosinusitis. In this respect, topical nasal drug administration by drops has generally been perceived to be superior to nasal sprays, although there is a lack of evidence to support this notion. This study aims to compare the intranasal delivery of nasal sprays and drops to the middle meatus in vivo, using a novel quantitative method. A surgical patty was placed in the middle meatus. Radio-labelled topical nasal drops and aqueous sprays were administered in a standardized fashion in normal volunteers (10 nasal cavities). The subsequent absorption of administered radio-labelled saline on the patty was measured using a gamma counter. A randomized prospective crossover design was used for the study. The mean percentage (range) of absorbed administered saline on the swab was 8.7 (0.3-39.5) and 9.7 (0.03-20.4) for the spray and drop administration techniques respectively (p = 0.8). Thus, there is wide variation in the delivery of topical nasal drugs and the perceived superiority of nasal drop administration, in terms of delivery to the middle meatus, may be incorrect.

Effect of radial artery harvesting on tissue perfusion and function of the hand.

This study was designed to measure the degree to which hand and forearm blood flow is reduced following harvesting of the radial artery in myocardial revascularization surgery and determine whether there is an effect on hand function. Twenty patients who had the radial artery used for myocardial revascularization underwent bilateral blood flow assessment of hands and forearms using Technetium-99m human serum albumin and clinical evaluation of hand function. Mean tissue perfusion in ml/100 ml/min +/- SD was as follows: donor hand 21.9 +/- 5.6, non-donor hand 25.5 +/- 6.1 (P = 0.00043), donor arm (hand and forearm) 17.5 +/- 3.7 and non-donor arm (hand and forearm) 21 +/- 5.1 (P = 0.000681). No clinical evidence of hand claudication was detected. This study suggests that removal of the radial artery reduces the tissue perfusion of the hand and forearm but does not affect hand function in the short term. The use of radial artery grafts in patients at risk of developing peripheral vascular disease should be carefully considered

Association of simian immunodeficiency virus Nef with the T-cell receptor (TCR) zeta chain leads to TCR down-modulation.

The Nef protein of simian immunodeficiency virus (SIV) is dispensable for replication in established T-cell lines but essential for high level virus replication in the adult host, though the mechanism by which Nef contributes to this has remained unclear. We demonstrate here that SIV Nef binds to the zeta chain of the T-cell receptor (TCR). SIV Nef proteins that interact with TCR zeta in a yeast two-hybrid system also reduce T-cell surface expression levels of TCR alphabeta, CD3 and CD4. These findings are the first demonstration that Nef can bind directly to a component of the TCR-CD3 complex and modulate its surface expression.

Expression of CYP71B7, a cytochrome P450 expressed sequence Tag from Arabidopsis thaliana.

The systematic sequencing of anonymous cDNA clones (expressed sequence tags or ESTs) from the plant Arabidopsis thaliana has identified a number of cDNAs with similarity to known cytochrome P450 sequences. The partial sequence of one of these cDNAs, 5G6, indicated that it was likely to encode a full-length cytochrome P450 monooxygenase (cyt P450) sequence. In this paper we describe the complete sequence of this clone, which has been designated CYP71B7 in accordance with the nomenclature for the cyt P450 gene superfamily. The cDNA was used to determine the pattern of expression of the corresponding gene in A. thaliana. Northern hybridization analysis indicated that maximal expression of CYP71B7 occurred in rosette leaves. Weaker hybridizing bands were also detected by Northern analysis of RNA from roots, leaves, flowers, and siliques. No expression could be detected in stem tissue. Southern analysis indicated that the CYP71B7 gene was likely to exist as a single copy in the genome of A. thaliana. CYP71B7 was expressed episomally in yeast, and microsomes prepared from transgenic yeast exhibited a carbon monoxide difference spectrum characteristic of cyt P450. Microsomes from yeast expressing CYP71B7 were assayed for enzymatic activity with synthetic model cyt P450 substrates. Microsomes from yeast cells expressing CYP71B7 or those from control cells exhibited no detectable NADPH-supported 7-ethoxycoumarin or 7-ethoxyresorufin deethylase activities. However, in the presence of cumene hydroperoxide, activity was observed with microsomes from cells expressing CYP71B7 with 7-ethoxycoumarin as substrate. Organic hydroperoxides are well known to support cyt P450 catalysis in the absence of electrons from NADPH. The yeast microsomes contained high levels of endogenous NADPH-ferricytochrome P450 reductase (CPR) activity. The data suggest that this A. thaliana cyt P450, although expressed in an active form, is incapable of accepting electrons from the endogenous yeast CPR protein.

Perfusion defects in vibration white finger: a clinical assessment using isotope limb blood flow.

Vibration white finger is a vasospastic disorder caused by long-term exposure to vibration tools. In an attempt to assess the extent of obliterative vessel disease in this disorder, hyperaemic hand blood flow was measured using technetium-labelled human albumin and a gamma camera. This method quantitates blood flow in ml/100 ml of tissue per min in addition to providing a perfusion image used to assess vessel disease. A perfusion score is then given to this image to reflect the extent of disease. The results of this study demonstrate that 78% of patients with vibration white finger had evidence of organic vessel disease. Moreover, patients with advanced disease tend to be bilaterally affected. The use of this simple method is advocated to aid in the diagnosis of vibration white finger; this may be particularly important for medicolegal purposes.

Radionuclide limb blood flow measurements to resolve diagnostic problems in vascular surgery.

This paper describes the application of radionuclide limb blood flow measurements in 60 patients presenting to the vascular surgeons with exercise-induced leg pain. All patients were considered to be diagnostic problems since either their symptoms were atypical for peripheral vascular disease, or they had normal peripheral pulses and/or a normal ankle/brachial pressure index. Thirty-one patients were ultimately shown to have peripheral vascular disease and underwent treatment. In all these cases the limb blood flow to one or both legs was below the normal range. Twenty-three patients were shown, by myelography, computed tomography or plain radiography, to have orthopaedic disease and in all cases their limb blood flow to both legs was within the normal range. In five patients, the limb blood flow was normal and the symptoms spontaneously resolved, no cause for the leg pain having been found (one patient refused angiography). Radionuclide limb blood flow is a simple and reliable diagnostic test which is superior to the assessment of peripheral pulses or their ankle to brachial pressure index in resolving diagnostic problems in vascular surgery.

Hepatic perfusion index: a multicentre trial.

The reproducibility and accuracy of the hepatic perfusion index (HPI) was examined by consideration of in vitro and in vivo factors. A phantom was used to simulate liver blood flow and data acquired on nine gamma cameras. Dynamic hepatic scintigraphy was undertaken on 28 patients at two centres and values obtained for the HPI. Results from the phantom study showed good agreement between the nine cameras and also with the HPI values predicted from the measured phantom flow rates. The results of the patient study indicated a high degree of conformity between observers (r = 0.95, S.E = 0.03) but poorer correlation between the HPI values from the two centres (r = 0.67, S.E. = 0.09). These results imply that centres wishing to use HPI clinically should establish their own range of normality.

Pulmonary artery versus left ventricular venting: a radioisotope study of left ventricular function.

Radionuclide measurements of ejection fraction were used to assess immediate and late postoperative ventricular function after the use of either a pulmonary artery vent (group A) or a left ventricular vent (group B) in 20 patients undergoing aortic valve replacement for pure aortic stenosis. Ten patients were included in each group and anesthetic techniques, patient management, and septal temperatures were similar in all cases. No significant difference was found between the preoperative and immediate or 6-week postoperative ejection fractions, either taken overall or between the two groups (p greater than 0.05; Student's t test). No correlation was found between cross-clamp time, bypass time, or the occurrence of ventricular fibrillation and the immediate postoperative ejection fraction (p greater than 0.05; Student's t test). There was no significant difference in the incidence of ventricular fibrillation after each type of vent had been used (chi 1(0) = 3.32; p greater than 0.05). We did not demonstrate any abnormalities in regional wall motion associated with apical insertion of a left ventricular vent, and conclude that pulmonary artery and left ventricular vents are equally satisfactory in terms of postoperative ventricular performance.

A simple method of identifying loosening or infection of hip prostheses in nuclear medicine.

Joint replacement is now established as a reliable orthopaedic procedure for the relief of many painful degenerative conditions of the hip. When successful it enhances hip movement and relieves pain with a concomitant improvement in function and well being for the patient. When unsuccessful the persistence of pain usually signifies loosening or infection. Loosening may result from mechanical failure or infection. Accurate distinction between septic and aseptic loosening is important for planning and executing surgical intervention. The experience of the Department of Nuclear Medicine in Coventry assessing pathology in painful hip prostheses was retrospectively reviewed in 47 patients. These patients were imaged from 1985 to 1987 and all had good clinical follow-up enabling the diagnosis of loosening, infection or normal to be made with confidence. All patients had three phase bone imaging and some had additional gallium imaging. The images were reviewed with particular emphasis on the pattern of uptake in the late bone image and congruence of abnormal uptake in the early bone image and gallium image. It is concluded that for the majority of patients simple three phase bone imaging will provide the required diagnostic information.

Diagnosis of coronary artery disease using thallium imaging: tomographic versus planar imaging.

Coronary artery disease was evaluated with tomographic and planar thallium imaging in 31 subjects who had undergone coronary angiography for assessment of chest pain syndrome. Coronary arteriography revealed significant coronary artery disease in 17; and 14 had normal coronary arteries. The sensitivity and specificity for planar imaging was 71% and 79%, and that for tomography, 94% and 79% respectively. The sensitivity and specificity figures for individual coronary artery lesion detection for planar imaging were 87/83 for LAD, 33/100 for LCX and 50/86 for RCA respectively, and for tomography the figures were 87/87 for LAD, 33/95 for LCX and 90/76 for RCA respectively. The use of coronary arteriography as a gold standard was considered by assessing its interobserver variability, which was 16%. The interobserver variability for thallium imaging was 8% and 3% respectively for tomographic and planar acquisitions.