Outcomes of Mechanical Thrombectomy in the Early (<6-hour) and Extended (≥6-hour) Time Window Based Solely on Noncontrast CT and CT Angiography: A Propensity Score-Matched Cohort Study.

BACKGROUND AND PURPOSE: Current stroke care recommendations for patient selection for mechanical thrombectomy in the extended time window demand advanced imaging to determine the stroke core volume and hypoperfusion mismatch, which may not be available at every center. We aimed to determine outcomes in patients selected for mechanical thrombectomy solely on the basis of noncontrast CT and CTA in the early (<6-hour) and extended (≥6-hour) time windows. MATERIALS AND METHODS: Consecutive mechanical thrombectomies performed for acute large-vessel occlusion ischemic (ICA, M1, M2) stroke between February 2016 and August 2020 were retrospectively reviewed. Eligibility was based solely on demographics and noncontrast CT (ASPECTS) and CTA, due to the limited availability of perfusion imaging during the study period. Propensity score matching was performed to compare outcomes between time windows. RESULTS: Of 417 mechanical thrombectomies performed, 337 met the inclusion criteria, resulting in 205 (60.8%) and 132 (39.2%) patients in the 0- to 6- and 6- to 24-hour time windows, respectively. The ASPECTS was higher in the early time window (9; interquartile range = 8-10) than the extended time window (9; interquartile range = 7-10; P = .005). Propensity score matching yielded 112 well-matched pairs. Equal rates of TICI 2b/3 revascularization and symptomatic intracranial hemorrhage were observed. A favorable functional outcome (mRS 0-2) at 90 days was numerically more frequent in the early window (45.5% versus 33.9%, P = .091). Mortality was numerically more frequent in the early window (25.9% versus 17.0%, P = .096). CONCLUSIONS: Patients selected for mechanical thrombectomy in the extended time window solely on the basis of noncontrast CT and CTA still achieved decent rates of favorable 90-day functional outcomes, not statistically different from patients in the early time window.

A Method to Estimate Brain Volume from Head CT Images and Application to Detect Brain Atrophy in Alzheimer Disease.

BACKGROUND AND PURPOSE: Total brain volume and total intracranial volume are important measures for assessing whole-brain atrophy in Alzheimer disease, dementia, and other neurodegenerative diseases. Unlike MR imaging, which has a number of well-validated fully-automated methods, only a handful of methods segment CT images. Available methods either use enhanced CT, do not estimate both volumes, or require formal validation. Reliable computation of total brain volume and total intracranial volume from CT is needed because head CTs are more widely used than head MRIs in the clinical setting. We present an automated head CT segmentation method (CTseg) to estimate total brain volume and total intracranial volume. MATERIALS AND METHODS: CTseg adapts a widely used brain MR imaging segmentation method from the Statistical Parametric Mapping toolbox using a CT-based template for initial registration. CTseg was tested and validated using head CT images from a clinical archive. RESULTS: CTseg showed excellent agreement with 20 manually segmented head CTs. The intraclass correlation was 0.97 (P < .001) for total intracranial volume and 0.94 (P < .001) for total brain volume. When CTseg was applied to a cross-sectional Alzheimer disease dataset (58 with Alzheimer disease patients and 58 matched controls), CTseg detected a loss in percentage total brain volume (as a percentage of total intracranial volume) with age (P < .001) as well as a group difference between patients with Alzheimer disease and controls (P < .01). We observed similar results when total brain volume was modeled with total intracranial volume as a confounding variable. CONCLUSIONS: In current clinical practice, brain atrophy is assessed by inaccurate and subjective "eyeballing" of CT images. Manual segmentation of head CT images is prohibitively arduous and time-consuming. CTseg can potentially help clinicians to automatically measure total brain volume and detect and track atrophy in neurodegenerative diseases. In addition, CTseg can be applied to large clinical archives for a variety of research studies.

Multiple sclerosis: an important role for post-translational modifications of myelin basic protein in pathogenesis.

Myelin basic protein (MBP) represents a candidate autoantigen in multiple sclerosis (MS). We isolated MBP from normal and MS human white matter and purified six components (charge isomers) to compare the post-translational modifications on each. The sites and extent of methylation, deimination, and phosphorylation were documented for all tryptic peptides by mass spectrometry. We found that mono and dimethylated arginine 107 was increased in MS samples; deimination of arginine occurred at a number of sites and was elevated in MS; phosphorylation was observed in 10 peptides in normal samples but was greatly reduced or absent in most peptides from MS samples. Data obtained with MBP isolated from fresh brain obtained from a spontaneously demyelinating mouse model supported the view that the changes observed in human brain were probably related to pathogenesis of demyelination, i.e. we found decreased phosphorylation and decreased amounts of glycogen synthesis kinase in brain homogenates using specific antibodies. This study represents the first to define post-translational modifications in demyelinating disease and suggest an important role in pathogenesis.

Effects of natural products and nutraceuticals on steroid hormone-regulated gene expression.

BACKGROUND: There is an increasing trend in the use of complementary and alternative therapies to treat or prevent hormonally dependent pathologies. Methods determined whether several of these natural products and nutraceuticals, commonly taken for hormone-related effects, possess steroid hormone activity. The agonist and antagonist estrogenic, androgenic, and progestational activities of 20 natural products and nutraceuticals were assessed using an in vitro tissue culture indicator system. Two steroid-regulated proteins (pS2 and prostate-specific antigen [PSA]) were quantified, using ELISA-type immunoassays, as markers of agonist and antagonist activity. RESULTS: Four of the products tested, two isoflavone preparations, Promensil and Estro-Logic, chamomile, and grapeseed extracts, were found to have weak estrogenic agonist activity, with the latter two also demonstrating weak progestational activity. Several of the products tested exhibited antagonistic (blocking) activity, including antiestrogenic activity by Prostate-Ease, wild yam root, and dong quai, and antiandrogenic activity by dong quai, Promensil, and rosehips. CONCLUSIONS: Several of these natural products demonstrate weak steroid hormone activity.

Studies of posttranslational modifications in spiny dogfish myelin basic protein.

The objective of this investigation was to determine whether nonmammalian myelin basic protein contained charge isomers resulting from extensive posttranslational modifications as seen in mammalian MBP. Four charge isomer components from dogfish MBP have been isolated. These forms arise by phosphorylation and deamidation modifications. Components C1, C2 and C3 have been characterized. We are currently characterizing component C8. Dogfish MBP is less cationic than mammalian MBP and has about 50% lower mobility on a basic pH gel electrophoresis relative to human and to bovine MBP. The mammalian component C1, which is unmodified, is modified in the dogfish by phosphorylation. The reduced electrophoretic mobility is largely attributable to the charge reduction resulting from phosphorylation in serine 72, 83, and 120 or 121 in C1, and C3. In component C2, two or three phosphate groups were distributed among residues 134, 138 and 139. It was found that dogfish amino acid residue 30 was a lysine residue and not a glutamate residue as reported in the literature.

Effect of a very-high-fiber vegetable, fruit, and nut diet on serum lipids and colonic function.

We tested the effects of feeding a diet very high in fiber from fruit and vegetables. The levels fed were those, which had originally inspired the dietary fiber hypothesis related to colon cancer and heart disease prevention and also may have been eaten early in human evolution. Ten healthy volunteers each took 3 metabolic diets of 2 weeks duration. The diets were: high-vegetable, fruit, and nut (very-high-fiber, 55 g/1,000 kcal); starch-based containing cereals and legumes (early agricultural diet); or low-fat (contemporary therapeutic diet). All diets were intended to be weight-maintaining (mean intake, 2,577 kcal/d). Compared with the starch-based and low-fat diets, the high-fiber vegetable diet resulted in the largest reduction in low-density lipoprotein (LDL) cholesterol (33% +/- 4%, P <.001) and the greatest fecal bile acid output (1.13 +/- 0.30 g/d, P =.002), fecal bulk (906 +/- 130 g/d, P <.001), and fecal short-chain fatty acid outputs (78 +/- 13 mmol/d, P <.001). Nevertheless, due to the increase in fecal bulk, the actual concentrations of fecal bile acids were lowest on the vegetable diet (1.2 mg/g wet weight, P =.002). Maximum lipid reductions occurred within 1 week. Urinary mevalonic acid excretion increased (P =.036) on the high-vegetable diet reflecting large fecal steroid losses. We conclude that very high-vegetable fiber intakes reduce risk factors for cardiovascular disease and possibly colon cancer. Vegetable and fruit fibers therefore warrant further detailed investigation.

Steroid hormone activity of flavonoids and related compounds.

Soy isoflavones have been studied extensively for estrogenic and antiestrogenic properties. Other flavonoids, found in fruits, vegetables, tea and wine, have been much less tested for steroid hormone activity. We therefore assessed the estrogenic, androgenic and progestational activities of 72 flavonoids and structurally-related compounds. These compounds were tested on BT-474 human breast cancer cells at concentrations of 10(8)-10(-5) M, with estradiol (estrogen), norgestrel (progestin) and dihydrotestosterone (androgen) used as positive controls, and ethanol (solvent) as a negative control. pS2, an estrogen-regulated protein, and prostate-specific antigen (PSA), regulated by androgens and progestins, were quantified in tissue culture supernatants using ELISA-type immunofluorometric assays developed in-house. Of the 72 compounds tested, 18 showed estrogenic activity at 10(-5) M. Of this subset, seven also showed progestational activity at this concentration. The soy isoflavones, biochanin A and genistein, showed the most potent estrogenic activity, with a dose-response effect up to 10(-7) M. Of all other flavonoids, luteolin and naringenin displayed the strongest estrogenicity, while apigenin had a relatively strong progestational activity. Based on our data, we have formulated a set of structure/function relationships between the tested compounds. Flavonoids, therefore, exhibit significant steroid hormone activity, and may have an effect in the modification of cancer risk by diet, or in cancer therapeutics and prevention.

Is ICI 182,780 an antiprogestin in addition to being an antiestrogen?

The pure antiestrogen ICI 182,780 has been shown to have antiprogestin activity in reporter gene constructs. Cell lines, naturally devoid of progesterone receptors (PR) were transfected with either the A or B forms of the human PR and a luciferase construct driven by a progesterone-response element (PRE). Because this system is an artificial one, our purpose was to determine whether these observations could be made in a human breast cancer cell line, naturally containing PR. We further evaluated the dose-response of ICI 182,780 and RU-486 (mifepristone) on PR and estrogen receptors (ER) in the presence of either progesterone, norgestrel or estradiol. These effects were measured using immunoassays for prostate-specific antigen (PSA) and human glandular kallikrein (hK2) and pS2. We found that ICI 182,780 blocked progesterone-stimulated PSA and hK2 production 100% at 10(-5) M, which decreased significantly by 10-6 M. This inhibition did not occur when norgestrel was the progestin used. RU-486 showed 100% blockade for both progestins at all concentrations used. We concluded that the antiprogestin activity of ICI 182,780 exists for progesterone only. This weak antiprogestin activity may be unlikely to have significant clinical implications.

Effect of soy protein foods on low-density lipoprotein oxidation and ex vivo sex hormone receptor activity--a controlled crossover trial.

Plant-derived estrogen analogs (phytoestrogens) may confer significant health advantages including cholesterol reduction, antioxidant activity, and possibly a reduced cancer risk. However, the concern has also been raised that phytoestrogens may be endocrine disrupters and major health hazards. We therefore assessed the effects of soy foods as a rich source of isoflavonoid phytoestrogens on LDL oxidation and sex hormone receptor activity. Thirty-one hyperlipidemic subjects underwent two 1-month low-fat metabolic diets in a randomized crossover study. The major differences between the test and control diets were an increase in soy protein foods (33 g/d soy protein) providing 86 mg isoflavones/2,000 kcal/d and a doubling of the soluble fiber intake. Fasting blood samples were obtained at the start and at weeks 2 and 4, with 24-hour urine collections at the end of each phase. Soy foods increased urinary isoflavone excretion on the test diet versus the control (3.8+/-0.7 v 0.0+/-0.0 mg/d, P < .001). The test diet decreased both oxidized LDL measured as conjugated dienes in the LDL fraction (56+/-3 v 63+/-3 micromol/L, P < .001) and the ratio of conjugated dienes to LDL cholesterol (15.0+/-1.0 v 15.7+/-0.9, P = .032), even in subjects already using vitamin E supplements (400 to 800 mg/d). No significant difference was detected in ex vivo sex hormone activity between urine samples from the test and control periods. In conclusion, consumption of high-isoflavone foods was associated with reduced levels of circulating oxidized LDL even in subjects taking vitamin E, with no evidence of increased urinary estrogenic activity. Soy consumption may reduce cardiovascular disease risk without increasing the risk for hormone-dependent cancers.

Development and evaluation of a competitive time-resolved immunofluorometric assay for the estrogen-regulated protein pS2.

We have developed a competitive assay to measure the estrogen-regulated protein pS2. A monoclonal pS2 antibody (mAb) and a biotinylated pS2 peptide are used, with time-resolved fluorometry as a detection technique. The assay has a detection limit of 16 ng/mL and is precise (within-run and day-to-day Cvs 3-12%). We used this assay to determine steroid hormone activity of six steroids in cell culture, both in terms of time course and dose response. pS2 concentrations in the tissue culture supernatant of the BT-474 breast carcinoma cell line were significantly higher when estradiol was the stimulating steroid. There was a significant time course and dose response observed for estradiol, but not for the other steroids. The availability of a sensitive, reliable, and convenient method for quantifying pS2 will allow for many research applications including the screening of natural and synthetic compounds for putative estrogenic activity.

On-line capillary electrophoresis/microelectrospray ionization-tandem mass spectrometry using an ion trap storage/time-of-flight mass spectrometer with SWIFT technology.

The development of a system capable of the speed required for on-line capillary electrophoresis-tandem mass spectrometry (CE-MS/MS) of tryptic digests is described. The ion trap storage/reflectron time-of-flight (IT/reTOF) mass spectrometer is used as a nonscanning detector for rapid CE separation, where the peptides are ionized on-line using electrospray ionization (ESI). The ESI produced ions are stored in the ion trap and dc pulse injected into the reTOF-MS at a rate sufficient to maintain the separation achieved by CE. Using methodology generated by software and hardware developed in our lab, we can produce SWIFT (Stored Waveform Inverse Fourier Transform) ion isolation and TICKLE activation/fragmentation voltage waveforms to generate MS/MS at a rate as high as 10 Hz so that the MS/MS spectra can be optimized on even a 1-2 s eluting peak. In CE separations performed on tryptic digests of dogfish myelin basic protein (MBP) where eluting peaks 4-8 s wide are observed, it is demonstrated that an acquisition rate of 4 Hz provides > 20 spectra/peak and is more than sufficient to provide optimized MS/MS spectra of each of the eluting peaks in the electropherogram. The detailed structural analysis of dogfish MBP including several posttranslational modifications using CE-MS and CE-MS/MS is demonstrated using this method with < 10 fmol of material consumed.

Mechanisms of bioprosthetic heart valve failure: fatigue causes collagen denaturation and glycosaminoglycan loss.

Bioprosthetic heart valve (BPHV) degeneration, characterized by extracellular matrix deterioration, remodeling, and calcification, is an important clinical problem accounting for thousands of surgeries annually. Here we report for the first time, in a series of in vitro accelerated fatigue studies (5-500 million cycles) with glutaraldehyde fixed porcine aortic valve bioprostheses, that the mechanical function of cardiac valve cusps caused progressive damage to the molecular structure of type I collagen as assessed by Fourier transform IR spectroscopy (FTIR). The cyclic fatigue caused a progressive loss of helicity of the bioprosthetic cuspal collagen, which was evident from FTIR spectral changes in the amide I carbonyl stretching region. Furthermore, cardiac valve fatigue in these studies also led to loss of glycosaminoglycans (GAGs) from the cuspal extracellular matrix. The GAG levels in glutaraldehyde crosslinked porcine aortic valve cusps were 65.2 +/- 8.66 microg uronic acid/10 mg of dry weight for control and 7.91 +/- 1.1 microg uronic acid/10 mg of dry weight for 10-300 million cycled cusps. Together, these molecular changes contribute to a significant gradual decrease in cuspal bending strength as documented in a biomechanical bending assay measuring three point deformation. We conclude that fatigue-induced damage to type I collagen and loss of GAGs are major contributing factors to material degeneration in bioprosthetic cardiac valve deterioration.

Inhibition of aortic wall calcification in bioprosthetic heart valves by ethanol pretreatment: biochemical and biophysical mechanisms.

The effectiveness of ethanol pretreatment on preventing calcification of glutaraldehyde-fixed porcine aortic bioprosthetic heart valve (BPHV) cusps was previously demonstrated, and the mechanism of action of ethanol was attributed in part to both lipid removal and a specific collagen conformational change. In the present work, the effect of ethanol pretreatment on BPHV aortic wall calcification was investigated using both rat subdermal and sheep circulatory implants. Ethanol pretreatment significantly inhibited calcification of BPHV aortic wall, but with less than complete inhibition. The maximum inhibition of calcification of BPHV aortic wall was achieved using an 80% ethanol pretreatment; calcium levels were 71.80+/-8.45 microg/mg with 80% ethanol pretreatment compared to the control calcium level of 129.90+/-7.24 microg/mg (p = 0.001). Increasing the duration of ethanol exposure did not significantly improve the inhibitory effect of ethanol on aortic wall calcification. In the sheep circulatory implants, ethanol pretreatment partly prevented BPHV aortic wall calcification with a calcium level of 28.02+/-4.42 microg/mg compared to the control calcium level of 56.35+/-6.14 microg/mg (p = 0.004). Infrared spectroscopy (ATR-FTIR) studies of ethanol-pretreated BPHV aortic wall (vs. control) demonstrated a significant change in protein structure due to ethanol pretreatment. The water content of the aortic wall tissue and the spin-lattice relaxation times (T1) as assessed by proton nuclear magnetic resonance spectroscopy did not change significantly owing to ethanol pretreatment. The optimum condition of 80% ethanol pretreatment almost completely extracted both phospholipids and cholesterol from the aortic wall; despite this, significant calcification occurred. In conclusion, these results clearly demonstrate that ethanol pretreatment is significantly but only partially effective for inhibition of calcification of BPHV aortic wall and this effect may be due in part to lipid extraction and protein structure changes caused by ethanol. It is hypothesized that ethanol pretreatment may be of benefit for preventing bioprosthetic aortic wall calcification only in synergistic combination with another agent.

Epidemiology and mortality of burns in Tehran, Iran.

In order to assist with the prevention of burn injuries the epidemiology of burns in Tehran was investigated. In a retrospective study, 1239 files of patients who were living in Tehran and were injured between March 1994 and March 1995 were studied. Sixty-three per cent of patients were male and 37 per cent were female (age range, 1 month to 93 years). The highest incidence of burns was in the 16-25 age group (30/100000). Patients with below 40 per cent of burned surface constituted 52.5 per cent of injuries. The most common cause of burns was kerosene accidents. The most common cause of burns in children was boiling water. In terms of social class the highest rate of burns was observed among illiterate people (burn rate (BR) 39/100000). The mean length of hospitalization was 12 days. Of the 1239 cases, 737 patients died. The mortality rate was 51 per cent in males and 69 per cent in females. The mean body surface area burned was higher in females. The mortality rate was higher and the length of hospitalization was shorter in comparison with other studies in other countries.

Prevention of calcification of glutaraldehyde-crosslinked porcine aortic cusps by ethanol preincubation: mechanistic studies of protein structure and water-biomaterial relationships.

Clinical usage of bioprosthetic heart valves (BPHVs) fabricated from glutaraldehyde-pretreated porcine aortic valves is restricted due to calcification-related failure. We previously reported a highly efficacious ethanol pretreatment of BPHVs for the prevention of cuspal calcification. The aim of the present study is to extend our understanding of the material changes brought about by ethanol and the relationship of these material effects to the ethanol pretreatment anticalcification mechanism. Glutaraldehyde-crosslinked porcine aortic valve cusps (control and ethanol-pretreated) were studied for the effects of ethanol on tissue water content and for spin-lattice relaxation times (T1) using solid state proton NMR. Cusp samples were studied for protein conformational changes due to ethanol by ATR-FTIR spectroscopy. The changes in cuspal tissue-cholesterol (in vitro) interactions also were studied. Cusp material stability was assessed in terms of residual glutaraldehyde content and collagenase degradation. Water content of the cusp samples was decreased significantly due to ethanol pretreatment. The cuspal collagen conformational changes (per infrared spectroscopy) brought about by ethanol pretreatment were persistent even after rat subdermal implantation of cusp samples for 7 days. In vitro cholesterol uptake by cusps was greatly reduced as a result of ethanol pretreatment. Ethanol pretreatment of cusps also resulted in increased resistance to collagenase digestion. Cuspal glutaraldehyde content was not changed by ethanol pretreatment. We conclude that ethanol pretreatment of bioprosthetic heart valve cusps causes multi-component effects on the tissue/material and macromolecular characteristics, which partly may explain the ethanol-pretreatment anticalcification mechanism.

Determination of the sites of posttranslational modifications in the charge isomers of bovine myelin basic protein by capillary electrophoresis-mass spectroscopy.

The posttranslational modifications in each of the 18.5 kDa bovine myelin basic protein charge isomers C-1 to C-6 have been determined by the use of capillary electrophoresis-mass spectroscopy. The pattern of modifications is viewed as being unique to each charge isomer and is thought to reflect a specific placement and function for each isomer in the myelin membrane. Several of the sites of posttranslational phosphorylation were found to differ from a number of the reported sites that were phosphorylated in vitro by various kinases. These differences suggest that an extremely cautious approach be taken in identifying in vivo posttranslationally modified amino acid residues from residues that have been modified in vitro by various kinases. We have identified the following posttranslationally phosphorylated and deamidated, modified sites in the bovine MBP components C1-C6. C1 has no modification; C2 represents a deamidation of Gln 146; in C3, Thr 97 and Ser 164 are phosphorylated; in C4, Ser 54, Thr 97, and Ser 160 are phosphorylated; in C5 Ser 7, Ser 54, Thr 97, and Ser 164 are phosphorylated; and in C6, Ser 7, Ser 54, Thr 97, Ser 160, and Ser 164 are phosphorylated.

Substitution of D-Trp32 in NPY destabilizes the binding transition state to the Y1 receptor site in SK-N-MC cell membranes.

The retention rate of the spin label 3-isothiocyanto methyl-2,2,5,5-tetramethyl-1-pyrrolidinyl oxyl spin label (proxyl) attached to the porcine N-acetyl-NPY peptide and the porcine N-acetyl-D-Trp32-NPY peptide at Lys4 was investigated using SK-N-MC neuroblastoma cell membranes containing the Y1 receptor. The release rate of the spin labeled peptides was monitored by electron spin resonance and the KD was determined by a direct radiolabeled NPY displacement binding assay. The analyses show that for the porcine [Ac-Tyr1N epsilon 4-proxyl]-NPY, the KD was 8 x 10(-10) M and koff was 2.7 x 10(-4) sec-1 yielding a value for kon of 3.3 x 10(5) sec-1 M-1. The [Ac-Tyr1, N epsilon 4-proxyl,-D-Trp32]-NPY antagonist ligand had a value of KD equal to 1.35 x 10(-7) M and koff was 1.7 x 10(-4) sec-1 leading to a value for kon of 1.2 x 10(3) sec-1 M-1. The difference in the kon rates of two orders of magnitude is interpreted as demonstrating the N-acetyl-N epsilon 4 proxyl-D-Trp32-NPY ligand binding transition state to be of higher energy then for the unmodified NPY amino acid sequence.

Prevention of bioprosthetic heart valve calcification by ethanol preincubation. Efficacy and mechanisms.

BACKGROUND: Calcification of the cusps of bioprosthetic heart valves fabricated from either glutaraldehyde cross-linked porcine aortic valves or bovine pericardium frequently causes the clinical failure of these devices. Our investigations studied ethanol pretreatment of glutaraldehyde cross-linked porcine aortic valves as a new approach to prevent cuspal calcification. The hypothesis governing this approach holds that ethanol pretreatment inhibits calcification resulting from protein structural alterations and lipid extraction. METHODS AND RESULTS: Results demonstrated complete inhibition of calcification of glutaraldehyde-pretreated porcine bioprosthetic aortic valve cusps by 80.0% ethanol in rat subdermal implants (60-day ethanol-pretreated calcium level, 1.87 +/- 0.29 micrograms/mg tissue compared with control calcium level, 236.00 +/- 6.10 micrograms/mg tissue) and in sheep mitral valve replacements (ethanol-pretreated calcium level, 5.22 +/- 2.94 micrograms/mg tissue; control calcium level, 32.50 +/- 11.50 micrograms/mg tissue). The mechanism of ethanol inhibition may be explained by several observations: ethanol pretreatment resulted in an irreversible alteration in the amide I band noted in the infrared spectra for both purified type I collagen and glutaraldehyde cross-linked porcine aortic leaflets. Ethanol pretreatment also resulted in nearly complete extraction of leaflet cholesterol and phospholipid. CONCLUSIONS: Ethanol pretreatment of glutaraldehyde cross-linked porcine aortic valve bioprostheses represents a highly efficacious and mechanistically based approach and may prevent calcific bioprosthetic heart valve failure.

Preparation and characterization of high-surface-area polymer substrates for microcalorimetry.

The preparation and characterization of high-surface-area polymeric substrates suitable for the microcalorimetry of protein adsorption are described. High-surface-area polystyrene, poly(styrene-co-butyl methacrylate) and poly(styrene-co-allyl alcohol) were prepared by adsorbing polymer from solution onto fumed silica. Verification of adsorption of polystyrene by silica was determined by noting peak shifts of the surface silanol group in the infrared. The amount of polymer adsorbed was determined from adsorption isotherms. The minimum thickness of polystyrene required to mask silicon oxide properties was found to be that thickness at which contact angles became constant, about 35 A. Polymer densities were measured. Water contact angles on each polymer surface indicate that poly(styrene-co-allyl alcohol) has the surface most wettable by water. Polymer-water interfacial energies were estimated from pendant drop results and a harmonic mean equation along with contact angles. Two methods were used to estimate the polar and dispersion components of the three polymers. Both methods predicted polystyrene to have the highest interfacial energy against water, and one method predicted poly(styrene-co-allyl alcohol) to have the lowest. A Wilhelmy plate study verified the change in interfacial properties as a function of contact time with water. A study of the heats of adsorption of lysozyme by each substrate using a modified Tien-Calvet microcalorimeter demonstrated the suitability of the substrates for microcalorimetry.