In vitro and ex vivo platelet interactions with hydrophilic-hydrophobic poly(ethylene oxide)-polystyrene multiblock copolymers

Hydrophilic-hydrophobic multiblock copolymers synthesized from telechelic oligomers of poly(ethylene oxide) (PEO) and polystyrene (PS) have been used to study the influence of hydrophilic and hydrophobic balance on interfacial interactions of these surfaces with blood components. In vitro coagulation assays show no inherent ability of these amphiphilic surfaces to affect contact activation or coagulation factors. In vitro platelet adhesion and release reactions from rabbit platelet-rich plasma were shown to be greatest on Biomer and PS homopolymer surfaces and least on cross-linked PEO surfaces, with the PEO-PS block copolymers demonstrating intermediate responses. These same substrates were tested in a new low-flow, low-shear arterio-artery shunt system in rabbits. Whole blood occlusion times were not a direct function of hydrophilic content as both PEO and PS homopolymers and Biomer showed short occlusion times, while PEO-PS block copolymers prolonged occlusion times considerably, depending on composition. Overall, results suggest that PEO-PS block copolymers promote unique whole blood responses in contrast to homopolymer and Biomer controls which are more complex than direct correlations to bulk hydrophilic and hydrophobic contents.

Scanning and transmission electron microscopic evaluation of the U-100 total artificial heart blood contacting surface

Thrombus formation, cell adhesion, mineralization, and the adsorbed protein layer have been investigated on blood contacting surfaces of the Utah-100 total artificial heart (TAH). Retrieval analysis was performed on two calves (at 7 and 97 days) and a sheep (at 21 days). Six locations on each ventricle were systematically evaluated by scanning electron microscopy. Transmission electron microscopy was used to measure the thickness and distribution of proteins (albumin, IgG, and fibrinogen) on the surface. Gross thrombus was detected only on the left atrial cuff in the 97 day calf. SEM demonstrated fairly clear surface morphology, with minimal platelet adhesion and activation, and little thrombus formation. At 97 days, calcium deposits were detected along the diaphragm-housing junction. Protein layer thickness on the diaphragm increased with implant time; dominant proteins detected on the surface were fibrinogen and IgG, rather than albumin. Improvements in design and fabrication techniques have demonstrated decreased intradevice thrombosis with the U-100 TAH. However, systemic thromboembolism still remains a problem, and further improvements in the blood contacting surface of the U-100 TAH are necessary to achieve a thrombus free TAH.

In vivo protein adsorption onto polymers: a transmission electron microscopic study

This paper reports in vivo protein adsorption onto polymers, including Biomer, PEO grafted Biomer (B-PEO-4K), heparin immobilized Biomer with PEO spacers (B-PEO-4K-HEP), and HEMA-Styrene block copolymer (H-S). Vascular grafts (6 mm ID, 7 cm in length) were fabricated with Biomer, coated on their luminal surfaces with test polymers, and implanted into the abdominal aorta of dogs. After 3 weeks-1 month, the grafts were retrieved and processed for TEM and SEM. TEM measured the thickness of adsorbed protein layers stained with a OsO4 solution, and the distribution pattern of adsorbed proteins (albumin, IgG and fibrinogen) using the immunoperoxidase technique. Retrieved grafts of Biomer and B-PEO-4K showed mural thrombi along the graft length, while thrombus formation on B-PEO-4K-HEP and H-S grafts was limited to the anastomotic sites. SEM pictures of B-PEO-4-HEP and H-S surfaces demonstrated clear morphology, with minimal platelet adhesion and activation, and microthrombi. Biomer and B-PEO-4K demonstrated a thick proteinaceous layer (1000-2000 A), whereas B-PEO-4K-HEP and H-S showed what can be described as a monolayer protein thickness (200-300 A). B-PEO-4K-HEP and H-S showed a monolayer-like adsorbed protein pattern, with high concentrations of albumin and IgG, and less fibrinogen, while Biomer and B-PEO-4K showed multilayered patterns with relatively high concentrations of fibrinogen, and less albumin. These results suggest that the surface properties of polymer may control protein adsorption pattern, and the composition of adsorbed protein is essential to in vivo long-term blood compatibility.

Antithrombogenic surfaces: characterization and bioactivity of surface immobilized PGE1-heparin conjugate

A covalently bonded conjugate of commercial grade heparin and prostaglandin E1 (PGE1) was synthesized to prevent both fibrin formation and platelet aggregation during thrombus formation. The PGE1-heparin conjugate was immobilized on an imidazole carbamate derivatized sepharose bead surface through hydrophilic spacer groups (diamino-terminated polyethylene oxides). One end of the spacer group was coupled to the derivatized surface through a urethane bond between the amine group of the spacer and the derivatized surface. The free amine group of the immobilized spacers was coupled to a carboxylic group of the PGE1-heparin conjugate through an amide bond. Bioactivity of the immobilized conjugate (heparin activity) was measured in terms of increased clotting times (thrombin time assay) and for the inactivation of Factor Xa. Bioactivity of the immobilized compound (PGE1 activity) was analyzed by platelet adhesion and platelet release reactions using C14-5-hydroxytryptamine (5-HT). The conjugate immobilized via the C2 spacer showed the highest incidence of platelet adhesion, 5-HT released and the lowest activity for coagulation factors. In contrast, the 1000 and 4000 immobilized systems showed a significant reduction in platelet activation, while having the greatest effect on coagulation factors. The results of these experiments imply that the immobilized conjugate is active in preventing both pathways of thrombus formation, and the efficacy is improved through the use of long-chain hydrophilic spacer groups.

A survey of externally recognizable genitourinary anomalies in Korean newborns. Korean Urological Association

To estimate the incidence of externally recognizable genitourinary anomalies and associated anomalies in the newborns in Korea, retrospective and prospective studies have been performed. Thirty eight of 48 urology training hospitals participated in this nationwide survey. In this study we have included minor defects or variations in the anomaly to evaluate the incidence of the recognizable genitourinary conditions in the newborns. The incidence of genitourinary anomaly in 1,000 newborn delivery in a year was 11.0 in the prospective study and this figure is about three times higher than the retrospective study and is considered to be close to the true incidence. The incidence of genitourinary anomaly in 1,000 male newborn was 20.4. Hydrocele, cryptorchidism and hypospadias were most commonly observed. The incidence of hydrocele in 1,000 male newborn was 9.89 and the incidence of cryptorchidism was 7.26 and the incidence of hypospadias was 2.13. The incidence of associated anomaly in 100 genitourinary anomaly was 7.9. Congenital heart diseases and anorectal anomalies were commonly associated anomalies. In the newborns with genitourinary anomalies, premature infants account larger portion than is usually reported in total delivery.

[The transformation of gamma-tocopherol to alpha-tocopherol in the animal organism; a generational study in rats]

The biosynthesis of alpha-tocopherol, the most effective vitamer among the vitamin E-group, is found only in higher plants and microorganisms. Due to the lack of the shikimate pathway, animals are not able to synthesize alpha-tocopherol. Also not found is a whole enteral synthesis; only the conversion of dimethyletocol to trimethyletocol seems to be possible. Using four generations of rats, we sought to determine: Is a transformation of gamma-tocopherol to alpha-tocopherol in the animal body possible? Are there any differences in the transformation rates in organs, tissues, or in the entire body along the generations? Does gut flora play any role in the conversion of gamma-tocopherol? Is it possible to increase the efficiency of the transformation by supplying additional CH3-groups? Wistar rats were fed a semisynthetic basal diet, supplemented with 78.8 mg DL-gamma-tocopherol/kg in the first three generations (F1-F3). In the fourth generation (F4), some of the animals were fed a vitamin E-free diet and gamma-tocopherol (approx. 1.5 mg on alternate days) was injected s.c. Two other groups of animals received the basal diet containing additional methionine (0.25%) or choline (0.45%), as well as gamma-tocopherol (as in F1-F3). alpha- and gamma-tocopherol were analyzed by HPTLC in the whole body and in serum, liver, heart, lung, gut, gonads, and feces. The ratio of alpha-/gamma-tocopherol (micrograms/micrograms) as transformation rate and vitamin E-biopotency (microgram alpha-tocopherol equivalents/g) were calculated. Growth and fertility were normal until the fourth generation; no abnormal developments could be recognized. alpha-tocopherol was found in the whole-body as well as in all tissues and organs. In the whole-body, vitamin E-biopotency decreased 25-70% in F2 and F3. On the other hand, the increase of the transformation rate of gamma- to alpha-tocopherol amounted to 23% (F2) and 168% (F3). Highest conversion rates were found in F2 and F3 for feces, followed by gonads and lungs; the lowest rates were found for serum and liver. Due to the s.c. injection of gamma-tocopherol, feces showed a four-times lower transformation rate in F4 than in F3. There was an increase in heart, gut, lung and serum for both transformation rate and vitamin E-biopotency. These parameters could be improved also by the additional supplements of methionine and choline. Both methyl-group-donators revealed nearly the same positive effect. The results show that the animal organism can adapt to gamma-tocopherol supply over generations.(ABSTRACT TRUNCATED AT 250 WORDS)

New findings in obsessive-compulsive disorder

During the past several years, impressive progress has been achieved in the field of obsessive-compulsive disorder (OCD). Improved diagnosis and treatment of this disorder has brought about renewed interest and optimism. Newer biological findings as well as drug treatment of obsessive-compulsive disorder are summarized here. A brief clinical description of obsessive-compulsive disorder is also included.

Synthesis and characterization of poly(dimethylsiloxane)-poly(ethylene oxide)-heparin CBABC type block copolymers

Heparin and poly(ethylene oxide) were coupled to a central anchoring block of poly(dimethylsiloxane) in order to investigate its blood compatible properties. Diamino telechelic poly(dimethylsiloxane) (PDMS-(NH2)2, Mw = 20,000) was first modified to isocyanate functionalities using toluene 2,4-diisocyanate. This modified PDMS was then coupled to diamino-telechelic poly(ethylene oxide) (PEO-(NH2)2, Mw = 2000, 4000, 6000) to create BAB type copolymers having terminal free amino groups. These amino groups were covalently coupled to heparin containing terminal aldehyde groups using sodium cyanoborohydride to yield a bioactive, CBABC type block copolymer. The physical characterization of these copolymers was performed with IR, NMR, sulphur elemental analysis, Wilhelmy plate contact angle, and differential scanning calorimetry (DSC). CBABC block copolymer surfaces demonstrated heparin bioactivity in in vitro evaluation, and improved nonthrombogenic properties during ex vivo A-A shunt experiments.

Flu-like symptoms associated with fluoxetine overdose: a case report

The serotonin reuptake inhibitor zimelidine may cause flu-like symptoms and Guillain-Barre syndrome. Guillain-Barre syndrome has not been reported with the use of the structurally related serotonin reuptake inhibitor fluoxetine. Flu-like symptoms are described in the manufacturer's literature on fluoxetine but are absent from published studies. We describe a patient who developed flu-like symptoms, urticaria and angioedema 2 days after fluoxetine overdose. There were no neurologic sequelae. This case confirms that fluoxetine may be associated with flu-like symptoms and suggests that, because these symptoms occurred after overdose, they may be dose related. The additional findings in this patient suggestive of allergy, an unusual feature of drug overdose, are discussed.

Surface modification for improved blood compatibility

Several surface modification techniques are currently being used to improve the biocompatibility of blood-contacting devices. These include the immobilization of bioactive materials to prevent thrombus generation and platelet activation, the incorporation of hydrophilic grafts onto practical hydrophobic surfaces (polyurethanes) to reduce protein adsorption, and the concept of microdomain-phase separated surfaces to regulate cellular and protein adhesion.

Heparin immobilization onto segmented polyurethane-urea surfaces--effect of hydrophilic spacers

Heparin was immobilized onto segmented polyurethane-urea surfaces (Biomer) using hydrophilic poly(ethylene oxide) spacers of different chain lengths. The use of the hydrophilic spacer, poly(ethylene oxide), reduces protein adsorption and subsequent platelet adhesion on the surface. In addition, the bioactivity of the immobilized heparin is enhanced by the incorporation of these spacers. Immobilized heparin bioactivity is shown to be a function of PEO spacer length. Use of hydrophilic PEO spacers demonstrates that immobilized heparin's bioactivity is consistently higher than that of the C6 alkyl spacer, but heparin-immobilized surfaces demonstrate no chain length effect on platelet adhesion, even though they show less platelet adhesion compared to Biomer controls. In the case of PEO-grafted surfaces, platelet adhesion is decreased compared to Biomer controls, and C6 alkyl spacer-grafted surfaces, and exhibits a minimum at PEO 1000. In ex vivo A-A shunt experiments under low flow and low shear conditions, all heparinized surfaces exhibit significant prolongation of occlusion times compared to Biomer controls, indicating an ability of immobilized heparin to inhibit thrombosis in whole blood.

Non-traumatic ischaemic myelopathy: a review of 25 cases

The causes of ischaemic myelopathy are described in 25 patients. Nine developed following surgical manipulation or traumatic laceration of the aorta, 1 following intercostal artery ligation, 3 following aortic aneurysm dissection, 2 following myocardial infarction and/or cardiac arrest, 7 in the absence of any specifically identifiable predisposing factors, and 3 in association with decompression sickness. The degree of clinical recovery was greater among those with incomplete spastic (as opposed to complete flaccid) paralysis and among those in whom sensory loss below the level of injury was incomplete. Despite the diversity of mechanisms that may lead to the development of spinal cord ischaemia, structural damage seems in most instances to affect either grey matter or white matter predominantly. Some of the possible reasons for these preferential sites of damage are discussed.

Heparin neutralization of antiplatelet effect of aspirin and dipyridamole

Heparin is used as an anticoagulant for treatment or prevention of thromboembolism. Heparin has been shown also to 1) stimulate platelet aggregation and platelet release reaction, 2) enhance thromboxane A2 production in platelets, and 3) neutralize prostacyclin, a potent inhibitor of platelet aggregation. In the light of these observations, the effect of heparin on two commonly used antiplatelet agents, aspirin and dipyridamole, was investigated. It was noted that heparin reversed the antiplatelet effect of both aspirin and dipyridamole although the effect was relatively more pronounced with aspirin. Presence of aspirin in blood in vitro as well as in vivo resulted in the inhibition of release reaction and the secondary wave of platelet aggregation. In the presence of heparin, platelets previously treated with aspirin showed nearly normal platelet aggregation as well as the release reaction. This reversal by heparin of the inhibitory effect of aspirin was dose dependent; the neutralization of inhibitory effect being more pronounced as the concentration of heparin was increased at a given concentration of aspirin. The neutralization of antiplatelet effect of aspirin was observed in vitro as well as in vivo and whether heparin was added before or after the addition of aspirin. These observations suggest the need for caution in the event heparin and antiplatelet agents are administered concurrently.

GH secretory dynamics and responsiveness to SMS 201-995 treatment in acromegaly

Recently, SMS 201-995, a long acting somatostatin analogue, has been used in successful therapy for inhibition of growth hormone (GH) levels in acromegaly. But, it was reported that inhibitory and clinical effects in the individual patient were different in many cases. Therefore, to find the predictive factor for patients with effective inhibition of GH, we investigated the paradoxical response to thyrotropin releasing hormone (TRH), growth hormone releasing hormone (GHRH) and diurnal variation of GH secretion between responders and non-responders to SMS 201-995. The results were as follows; Responders, patients with suppressive response to SMS 201-995, totalled 4 of 8 patients. The paradoxical response of GH to TRH was observed in 3 of 4 responders and 3 of 4 non-responders. The response of GH to GHRH was not noted in either of the groups. The diurnal variation of GH secretion showed in one of the responders and in 3 of the non-responders. These results suggested that the absence of diurnal variation of GH secretion was a characteristic feature of responders to SMS 201-995 and thus diurnal variation of GH secretion could be used as a predictive factor for SMS 201-995 therapy, and the pathogenetic mechanism of acromegaly might be dependent on the controlled regulation of GHRH and endogenous somatostatin.

Suppression mechanisms for thrombus formation on heparin-immobilized segmented polyurethane-ureas

Heparin-immobilized segmented polyurethane-ureas (Biomer, Ethicon Co., Somerville, NJ) containing long poly(ethylene oxide) spacers (Mn = 4,000) have shown excellent nonthrombogenic properties through enhanced heparin bioactivity in vitro. In this study, three different surfaces, Biomer (B), PEO-grafted Biomer (B-PEO) and heparin-immobilized Biomer with PEO spacers (B-PEO-Hep), were investigated, using a rabbit A-A shunt model. Occlusion times, at various flow rates (2.5, 5.0, 7.5, and 15.0 ml/min) were measured using surface modified tubings (1.5 mm ID, 30 cm length) inserted into rabbit carotid arteries. Platelet count, aggregability, and activated partial thromboplastin time (aPTT) were measured with whole blood to observe systemic effects in ex vivo experiments. For Biomer and B-PEO, occlusion times were prolonged with an increasing flow rate, while platelet count and aggregability decreased. B-PEO showed prominent prolongation of occlusion time at flow rates over 5.0 ml/min with decreased platelet count and aggregability, indicating surface-induced platelet activation and systemic thromboembolization possibly caused by the presence of PEO. In contrast, B-PEO-Hep surfaces showed the longest and relatively flow-rate-independent occlusion times without detectable platelet activation. We concluded that the improved ex vivo blood compatibility of B-PEO-Hep, compared with Biomer and B-PEO, is due to the prevention of fibrin net formation by immobilized heparin, resulting in a reduction in fibrin related platelet aggregation and subsequent thrombus formation.

Myelopathy after the intrathecal administration of hypertonic saline

The neuropathological effects of intrathecally administered hypertonic saline have not been described previously. We report a patient who, within a day of receiving 20 ml of hypertonic (7.5%) saline intrathecally, developed flaccid paraplegia and complete sensory loss below the umbilicus. Subsequently, there was some transitory return of motor and coarse sensory function. The patient died 16 months after the injection. At autopsy, there was peripherally accentuated loss of myelinated fibers within the spinal cord from T12 downward, as well as dense collagenous thickening of the dorsal leptomeninges from T9 to T11. The findings in this case, coupled with observations made by others, serve to emphasize the need for extreme caution whenever planning any form of intrathecal therapy.

Poly(dimethylsiloxane)-poly(ethylene oxide)-heparin block copolymers. I. Synthesis and characterization

Amphiphilic block copolymers containing poly(dimethylsiloxane), poly(ethylene oxide), and heparin (PDMS-PEO-Hep) have been prepared via a series of coupling reactions using functionalized prepolymers, diisocyanates, and derivatized heparins. All intermediate steps of the synthesis yield quantifiable products with reactive end-groups, while the final products demonstrate bioactive, covalently bound heparin moieties. Due to the solvent systems required, commercial sodium heparin was converted to its benzyltrimethyl ammonium salt to enhance its solubility. The same procedure was applied to heparin degraded by nitrous acid in order to covalently couple it in solutions with the semitelechelic copolymers. As might be expected, this derivatization reduces the apparent bioactivity of the heparin. However, preliminary findings suggest that the bioactivity can be restored by reforming the heparin sodium salt.

Axillo-subclavian deep venous thrombosis in quadriplegia: a case report

In a patient with traumatic neuropathy at C6, a delayed DVT was observed in the left axillary-subclavian veins with consequent neurological symptoms, loss of brachioradialis and wrist extensor functions. Anticoagulation therapy for 12 weeks did not correct the occlusion of the veins. It is stressed that anticoagulation treatment should be started as early as possible, preferably within a few days after development of the DVT.