Prevention of insulin self-association and surface adsorption

The self-association of insulin monomers into oligomers and macromolecular aggregates leads to complications in the administration of insulin, both in conventional administration and in the development of long-term insulin delivery systems. These problems are aggravated by the tendency of insulin to adsorb onto the surface of solution containers and infusion devices. Furthermore, with insulin infusion devices, shear rates can be generated which can accelerate the self-association and surface adsorption processes. The effects of urea on shear-induced insulin self-association and surface adsorption were investigated. It was found that the addition of a certain concentration range of urea to insulin solutions greatly reduces both insulin self-association and surface adsorption. Circular dichroic studies established that these concentrations of urea also preserve insulin conformation under high shear rates, where conformations are altered without urea. Higher urea concentrations lead to insulin denaturation and accelerated self-association.

Covalently bound conjugates of albumin and heparin: synthesis, fractionation and characterization

Covalently bound conjugates of human serum albumin and heparin were prepared as compounds which could improve the blood-compatibility of polymer surfaces either by preadsorption or by covalent coupling of the conjugates onto blood contacting surfaces. The conjugates (10-16 weight % of heparin) were obtained by a condensation reaction between albumin and heparin using 1-ethyl-3-(dimethylaminopropyl)-carbodiimide. Unreacted albumin and heparin were removed by diethyl-aminoethyl (DEAE)-cellulose and Cibacron Blue Sepharose chromatography respectively. The activity of the heparin component incorporated in the albumin-heparin conjugates (Ac) was compared with that of the heparin used for the synthesis of the conjugates (Anat) by thrombin time, inhibition of Factor Xa and the activated partial thromboplastin time (APTT) assays. The Ac/Anat ratio for the above assays was as follows: Thrombin time 1.25, Factor Xa inhibition 0.5. and APTT 0.5. Gel filtration chromatography showed broad-molecular weight distributions. The conjugates were fractionated using immobilized antithrombin III (ATIII). High ATIII and low ATIII affinity conjugate fractions showed the same behavior as ATIII fractionated heparin with respect to thrombin times and Factor Xa inhibition.

The antiplatelet activity of immobilized prostacyclin

Owing to the chemical instability of prostacyclin, the direct immobilization of this prostaglandin has not been successful. A new procedure is described for the preparation of immobilized prostacyclin based on the conversion of immobilized prostaglandin F2 alpha to immobilized prostaglandin I2-Materials thus prepared show dramatic antiplatelet effects with regard to platelet aggregation and platelet adhesion. Radioimmunoassays of plasmas used in in vitro platelet tests and of buffers used in prostacyclin leakage studies established that these effects are not due to the release of prostacyclin from the respective immobilization substrates.

Immobilized heparin: spacer arm effects on biological interactions

Heparin immobilized to polymer surfaces via different length diaminoalkane spacer arms was evaluated for anticoagulant activity and for platelet interactions. The anticoagulant activity of the immobilized heparin, as determined by APTT assays, was found to increase with increasing spacer arm length. Variations in spacer arm length produced no affect on platelet retention or PF 4 release for heparin immobilized materials. To investigate immobilized heparin-adsorbed plasma protein interactions, XPS analysis of heparinized surfaces, before and after plasma contact, was conducted. Immobilized heparin was not able to penetrate adsorbed plasma protein layers with any spacer arm length evaluated, indicating that immobilized heparin does not directly interact with platelets.

Free fatty acid-induced platelet aggregation: studies with solubilized and nonsolubilized fatty acids

The aggregation response of washed porcine platelets to the sodium salts of stearic, oleic, palmitic, and myristic acids was analyzed turbidometrically. The fatty acids were prepared as aqueous suspensions and as taurocholate- or albumin-solubilized systems. The final concentration of fatty acid in the platelet preparation varied between 70 and 600 microM. This range was within or below the normal physiological limits of 300-1200 microM. Platelet aggregation was observed with both the suspended and taurocholate-solubilized fatty acids. The extent of platelet aggregate formation increased with the fatty acid concentration and chain length. With the exception of stearate, the taurocholate-solubilized fatty acids were more active than the suspensions. Albumin-solubilized fatty acids were devoid of platelet aggregating activity. Particle-size analysis of the solubilized fatty acids indicated that fatty acid precipitation had occurred subsequent to the addition of taurocholate-solubilized fatty acids to the platelets. This precipitation did not occur with the albumin-solubilized systems, suggesting that the fatty acids must assume a particulate physical state to induce aggregation. Platelet aggregation induced by fatty acids was not inhibited by 80 nM epoprostenol, 75 microM alprostadil, or 150 microM indomethacin. This finding indicated that the fatty acid-induced platelet aggregation was independent of cyclic AMP-related calcium shift, cyclooxygenase-arachidonate, or granular nucleotide release mechanisms.

Pharmacokinetics of ethynyloestradiol in women for different populations

The pharmacokinetics of a dose of 50 microgram ethynyloestradiol administered orally was studied in fourteen centres. Absorption was rapid and the highest serum concentrations of total ethynyloestradiol were found in most subjects at 1 h and by 24 h concentrations were less than 250 pg/ml. Calculation of the half-lives for absorption, distribution and elimination showed wide variations between subjects, the half-life of elimination varying from 2.5 h to more than 30 h. Bioavailability as measured by the area under the serum ethynyloestradiol concentration-time curve also showed more than a ten-fold variation. Intra-centre differences in the various parameters measured were as large as the inter-centre differences.

Comparison of various quantization methods of segmental ventricular wall motion in ischemic heart disease

Numerous methods of measuring regional myocardial wall motion are in use. A critical comparison is needed to assess the strengths, weaknesses, accuracy, and precision of these methods. This paper reports the evaluation of five methods using computer-assisted interactive graphics. Fifty cines were selected: 16 from normal subjects, and 34 from patients with proven cardiovascular diseases. Tracings were made of the opacified left ventricle in end systole and diastole and digitized. All fifty cines were analyzed by five methods using computer-implemented graphic techniques. The results included a display of the silhouettes, which were translated and rotated according to various methods. In addition, the percent contraction for eleven myocardial regions was tabulated and displayed. The sixteen cines from normal subjects were used to derive a range of "house" normal values for region contraction patterns with which the measurements from the 34 abnormal patients were compared. The five methods were evaluated by comparing results from the computer-aided analysis with the visual assessment of two experienced radiologists. One method was found, the results from which agreed with the radiologists' visual impression for every case. This computer-aided method was quantitative and reproducible. Consequently, it can give information which supplements the visual impression.

Progestin permeation through polymer membrane V: Progesterone release from monolithic hydrogel devices

Progesterone release from monolithic devices prepared from various copolymers of poly(hydroxyethyl methacrylate) and poly(methoxyethoxyethyl methacrylate) or poly(methoxyethyl methacrylate) was examined. In general, plots of the fraction of drug released versus (time)1/2 were linear during the early stages of drug release. This behavior is similar to that found for drugs released from hydrophobic polymers such as polydimethyl siloxane. However, for some release curves using the hydrogels, a breakpoint appeared during the early stages of drug release. These breakpoints were due to the effects of water absorption by these polymers. From analyses of permeability coefficients, it was demonstrated that release rates also were dependent on the initial drug load and the equilibrium water content of the polymer. These conclusions were verified from cross-membrane diffusion studies on films depleted of their initial drug load. In conjunction with this work, the aqueous solubility of progesterone was determined by several methods; an average value of 38 micrograms/ml at 23 degrees was obtained.

Cutaneous manifestation of carcinoma of urinary bladder: carcinoma erysipelatodes

Cutaneous metastases from carcinoma of the urinary bladder is an uncommon finding. We present a patient with carcinoma of the bladder whose first manifestation of disseminated disease was a nodular erythematous skin rash diagnosed as carcinoma erysipelatodes. The presentation, diagnosis, and hospital course is given.

Effect of temperature and an ion-exchange resin on cation diffusion through silicone polymer tubing

Permeation of cations through silicone rubber tubing was measured, and the effect of an ion-exchange resin on the cation diffusion was determined. Silicone rubber has been used as a biomedical polymer and shows a very low solubility to ionizable species. Correlations between the calculated diffusion coefficients, with and without the resin, depended on the charge and number of waters of hydration for each cation. These increases ranged from 1.11 for potassium to 3.06 for iron, multiplied by the diffusion coefficient as a result of the resin. Solubilities of each cation in the polymer were temperature dependent. Activation energies were calculated for each cation by measuring the increased permeation with increasing temperature, with and without the resin. Decreasing magnitudes of activation energies ranged from 0.91 for sodium to 0.57 for iron when the resin was present. Correlations were established between the measured activation energies and reported free energy change for the hydration of each cation.

Rate of metabolism of norethisterone in women from different populations

The rate of metabolism of orally administered norethisterone was compared in fourteen centres by measuring plasma levels of the steroid by radioimmunoassay at varying times after oral administration of a 1 mg dose. The inter-centre differences were of the same order as the intra-centre differences. Variations in metabolism appeared not to be due to variations in body size.

Progestin permeation through polymer membranes I: diffusion studies on plasma-soaked membranes

The potential of several commercially available polymeric materials for use in controlled-release drug delivery devices was investigated. Progesterone was used as a model hydrophobic drug. The progesterone permeation rates through polydimethylsiloxane, two polyether urethanes, a hydroxyethyl methacrylate, a polyether urethan--polydimethylsiloxane blend, and a cellulosic membrane were determined. The permeabilities were obtained on nonsoaked membranes and on membranes soaked in plasma for varying times. The purpose of the plasma soaks was to examine the effects of lipid absorption and degradative processes within the membrane on progesterone permeability. This study identified several polymers that show potential for use in controlled-release drug delivery devices. The plasma treatment studies showed that several polymers may not be acceptable. The plasma soak studies were interpreted in terms of the mechanisms of drug permeation through the membranes.

Progestin permeation through polymer membranes II: diffusion studies on hydrogel membranes

The potential use of hydrogels in controlled-release drug delivery systems for contraceptive steroids was investigated. The permeabilities, diffusion coefficients, and partition coefficients for progesterone were determined for hydrogels made from hydroxyethyl methacrylate containing varying amounts of ethylene glycol dimethacrylate and tetraethylene glycol dimethacrylate. In addition, copolymers of hydroxyethyl methacrylate with methoxyethyl methacrylate and methoxyethoxyethyl methacrylate were investigated. The results were interpreted in terms of the mechanisms of permeation of progesterone through the hydrogels. This study showed that progesterone permeated these membranes primarily through loose pores in the hydrogel network except at high concentrations of the cross-linker, ethylene glycol dimethacrylate, where dissolution and diffusion of the progesterone in the polymer network was the dominant mechanism.

Crossed fused renal ectopia presenting with blunt trauma

A case is presented of crossed fused renal ectopia in a fifteen-year-old black male which was diagnosed because of blunt trauma. Workup and management are discussed and pertinent x-ray films shown. The literature is reviewed with respect to renal trauma associated with congenital anomalies of the kidney.

Role of protein and fatty acid adsorption on platelet adhesion and aggregation at the blood-polymer interface

Thrombus formation on a foreign surface is a complicated process, involving many factors. However, there is little doubt that a foreign surface adsorbs plasma proteins upon blood contact and that the nature of this adsorbed layer may determine the mechanism of platelet adhesion and aggregation. The adhesion and aggregation of platelets play an important role in the initial events of thrombus formation on a foreign surface. In this work, adsorption studies using human blood plasma were done on several polymer surfaces. Some drugs which prevent platelet adhesion were utilized to verify the proposed mechanism for platelet adhesion which includes glycosyl transferase reaction. Also, adsorption and release of fatty acid salts, including fatty acid-bonded albumin, were investigated at different polymer interfaces. It is postulated that adsorbed fatty acid salts are released from the surface upon contact with plasma to form a high local concentration of fatty acid, and that this fatty acid suspension would cause platelet aggregation at the interface.

Effect of phthalate plasticizer on blood compatibility of polyvinyl chloride

The amount of a phthalate plasticizer on the surface of a sheet of polyvinyl chloride used in the fabrication of blood storage bags was quantified using attenuated total reflectance spectroscopy, water contact angle measurement, and weight loss due to methanol extraction. Water wettability increased as the amount of surface phthalate extracted by methanol increased, which indicates that the accumulation of phthalate on the surface increases hydrophobicity. The extraction of phthalate by methanol consists of two steps: (a) methanol first dissolves surface phthalate, and (b) phthalate in the bulk then diffuses through the surface. The adsorption of plasma proteins was investigated to determine the initial events as blood contacts the surface. The composition of adsorbed proteins on the methanol-cleansed surface differs from that on the uncleansed polyvinyl chloride surface. Albumin adsorption onto phthalate-contaminated surfaces is less than on cleansed surfaces while adsorption of gamma-globulin and fibrinogen is greater on phthalate-contaminated surfaces. Protein adsorption can be related to surface thrombus formation. Increases in platelet numbers appeared on phthalate-contaminated surfaces as compared with methanol-treated surfaces. A phthalate may enhance platelet adhesion and aggregation when it exists on a polymer surface.

Alterations in energy metabolism and ultrastructure upon reperfusion of the ischemic myocardium after coronary occlusion

The effects on myocardial function, metabolism and ultrastructure of 60 minutes of reperfusion, instituted after 30, 60 and 90 minutes of occlusion of the left anterior descending coronary artery, were studied in 48 dogs. Twelve sham-operated dogs served as controls. Coronary occlusion for 60 or 90 minutes caused significant depression in the first derivative of left ventricular pressure (dP/dt) (P less than 0.05) that could not be reversed by reperfusion. Upon reperfusion, creatine phosphate stores in myocardium made ischemic for 30 and 60 minutes, but not for 90 minutes, returned toward control levels, but stores of adenosine triphosphate (ATP) and total nucleotides and the ATP/adenosine diphosphate ratio of myocardium subjected to 60 and 90 minutes of ischemia were further decreased. After 60 and 90 minutes of ischemia, swelling of the sarcoplasmic reticulum and mitochondrial damage (swelling, decreased matrix density and partial loss of cristae) were seen. Myofibrils were relaxed in all these groups. Reperfusion produced gross contraction of myofibrils and aggravated these changes in mitochondria and sarcoplasmic reticulum. In the hearts subjected to 90 minutes of ischemia these changes were gross. The levels of creatine phosphokinase, glutamic oxaloacetic transaminase and lactic dehydrogenase in the coronary sinus blood increased dramatically (P less than 0.05) upon reperfusion after 60 or 90 minutes of occlusion, indicating severe impairment of cell membranes. This secondary rise in serum enzyme activity during reperfusion should be taken into consideration when estimating the size of a myocardial infarct from enzyme changes alone. It appears that 60 and 90 minutes of ischemia cause severe myocardial damage that is not reversed by reperfusion maintained for 1 hour although longer periods of reperfusion may be beneficial.