Efficacy of postdeployment balloon dilatation for current generation stents as assessed by intravascular ultrasound

Adjunctive balloon dilatation strategy has been shown to improve optimal stent deployment. As improvements in current stent designs evolve, less adjunctive balloon dilatation may be needed. However, few data currently exist to support this practice. We evaluated 88 native coronary lesions treated with single stent implantation (Nir, Tristar or S670). Serial intravascular ultrasound was performed after successful stent deployment and again after adjunctive balloon dilatation. To investigate further the precise expansion characteristics of the stents, serial volumetric intravascular ultrasound analyses were performed in 40 patients with automated pullback. After adjunctive balloon dilatation, minimal stent area increased significantly, from 6.4 +/- 2.1 to 7.4 +/- 2.2 mm(2) (p <0.001). Volumetric analysis showed a corresponding increase in stent volume index (6.6 +/- 1.8 to 7.5 +/- 2.0 mm(3)/mm, p <0.001). In the analysis of cross sections at 0.5-mm axial intervals, the percentage of cross sections, where stent area was > or =80% of the average reference lumen area, increased from 51% to 78% (p <0.001). Similarly, the percentage of cross sections, where stent area was > or =90% of the average reference lumen area, increased from 29% to 56% (p <0.001) with postdilatation. Postdeployment high- pressure balloon dilatation improved minimal stent area and volumetric expansion throughout the stented segment.

Vascular brachytherapy: what have we learned from intravascular ultrasound?

With the advent of intravascular brachytherapy (IVBT), a striking reduction in the rate of restenosis has been observed. The use of intravascular ultrasound (IVUS) during IVBT trials has shown many aspects and relevant pathophysiologic mechanisms following this practical therapy. Specifically, IVUS quantitative assessments have demonstrated a drastic inhibition of both neointimal formation and negative remodeling to be the predominant vascular response to IVBT. Moreover, IVBT has shown promise for challenging high-risk restenosis cases, such as patients with diabetes mellitus and smaller caliber target vessels. However, unexpected radiation-induced complications have also been discovered, as more patients have been treated for a broad class of lesion subsets. Edge effect, induced by catheter-based radiation, was seen to be due to geographic miss of the radiation source, advocating a new concept known as "radiation edge". Furthermore, late thrombosis, which is known to be strongly associated with new stent implantation following IVBT, may be avoided with novel antiplatelet agents. Two additional complications, whose clinical significance remains unclear, are unhealed dissection and late stent malapposition featured by IVUS qualitative assessment. Unhealed dissection was observed in half of radiated dissections and late stent malapposition has been seen for all radiation sources in a small percentage of cases at 6-12 months follow-up. Radiation sources, dosimetry, and delivery methods continue to improve and should ultimately translate to more effective treatment for the patient with atherosclerotic coronary disease.

Preintervention arterial remodeling affects clinical outcome following stenting: an intravascular ultrasound study

OBJECTIVES

The study was done to elucidate the relationship between baseline arterial remodeling and clinical outcome following stenting.

BACKGROUND

The impact of preintervention arterial remodeling on subsequent vessel response and clinical outcome has been reported following nonstent coronary interventions. However, in stented segments, the impact of preintervention remodeling on clinical outcome has not been clarified.

METHODS

Preintervention remodeling was assessed in 108 native coronary lesions by using intravascular ultrasound (IVUS). Positive remodeling (PR) was defined as vessel area (VA) at the target lesion greater than that of average reference segments. Intermediate or negative remodeling (IR/NR) was defined as VA at the target lesion less than or equal to that of average reference segment. Remodeling index expressed as a continuous variable was defined as VA at the target lesion site divided by that of average reference segments.

RESULTS

Positive remodeling was present in 59 (55%) and IR/NR in 49 (45%) lesions. Although final minimal stent areas were similar (7.76 +/- 1.80 vs. 8.09 +/- 1.90 mm2, p = 0.36), target vessel revascularization (TVR) rate at nine-month follow-up was significantly higher in the PR group (22.0% vs. 4.1%, p = 0.01). By multivariate logistic regression analysis, higher remodeling index was the only independent predictor of TVR (p = 0.02).

CONCLUSIONS

Lesions with PR before intervention appear to have a worse clinical outcome following IVUS-guided stenting. Intravascular ultrasound imaging before stenting may be helpful to stratify lesions at high risk for accelerated intimal proliferation.

Effects of cilostazol on late lumen loss and repeat revascularization after Palmaz-Schatz coronary stent implantation

BACKGROUND

Cilostazol is an antiplatelet agent that increases the intracellular concentration of cyclic adenosine monophosphate by inhibiting phosphodiesterase III; it has been shown to reduce neointimal hyperplasia in animal balloon injury models.

METHODS

One hundred thirty patients who underwent elective stenting (Palmaz-Schatz stent) were randomly assigned to cilostazol treatment 200 mg/d (n = 65) or to ticlopidine treatment 200 mg/d (n = 65). Angiographic follow-up was performed at 6 months, and clinical follow-up was continued up to 1 year.

RESULTS

One sudden death and one myocardial infarction resulting from subacute occlusion were observed in the ticlopidine group. Drug adverse effects were observed in 3 patients in the cilostazol group, as opposed to 6 patients in the ticlopidine group. In the intention-to-treat analysis, 56 patients (61 lesions) in the cilostazol group and 58 patients (58 lesions) in the ticlopidine group were assessed with quantitative coronary angiography. Late loss in the cilostazol group was smaller (0.58+/-0.52 mm vs. 1.09+/-0.65 mm, P<.0001) than in the ticlopidine group. The restenosis rate was lower in the cilostazol group than in the ticlopidine group (16% vs. 33%, P = .044). The target vessel revascularization rate at 1 year was 23% in the cilostazol group and 42% in the ticlopidine group (P =.03).

CONCLUSIONS

The results of this study suggest that cilostazol may be a safe medication that is effective in preventing restenosis after stent implantation.

[Gamma-interferon-induced cardiomyopathy during treatment of renal cell carcinoma: a case report]

A 78-year-old woman with renal cell carcinoma and pulmonary metastasis presented with reversible cardiomyopathy induced by gamma(gamma)-interferon. She was treated with gamma-interferon twice a week since November 1996. She presented with severe acute congestive heart failure and gamma-interferon was immediately discontinued in December 1997. Left ventricular fractional shortening was 38% before admission, 12% on admission, and improved to 31% by 40 days after discontinuation of interferon together with administration of diuretics and angiotensin converting enzyme inhibitor. We restarted the same gamma-interferon regimen because it was effective against renal cell carcinoma after 47 days. She has remained well with no significant changes of cardiac function or renal cell carcinoma for almost one year.

Retrospective analysis of cerebral complications after coronary artery bypass grafting in elderly patients

The present study retrospectively investigated cerebral complications of coronary artery bypass grafting in 205 consecutive patients aged 70 years or older, who underwent elective cardiopulmonary bypass from 1990 to 1997. Computed tomography of the brain and chest was done before surgery. Ten patients had so-called 'aortic no-touch surgery' and suffered no cerebral complications; the other 195 patients had conventional surgery. Adverse cerebral events occurred in 8.7%, including cerebral infarction (4.1%), diffuse encephalopathy (1.0%), convulsions (1.0%), transient disturbance of consciousness (1.0%), and severe loss of volition (1.5%). Multivariate analysis showed that only the detection of calcification of the ascending aorta was significantly associated with cerebral complications (p = 0.029). Total clamping tended to be superior to partial clamping for prevention of cerebrovascular accidents. The mortality rate was 7.3%. In-hospital death was related to age (p = 0.0062), cerebral complications (p = 0.0032), and a low left-ventricular function (p = 0.018). Therefore, chest computed tomography to assess the ascending aorta should be performed preoperatively. Modified techniques like aortic no-touch surgery or other therapies combined with coronary intervention may be needed in elderly patients with severe calcification of the ascending aorta.

[Native aortic valve thrombus revealed by routine echocardiography: a case report]

A 75-year-old man presented with palpitations due to atrial flutter. Transthoracic echocardiography revealed a mobile aortic valve mass (17 mm in diameter) attached to the non-coronary cusp of the aortic valve. There was no evidence of hypercoagulative state. Computed tomography showed old cerebral infarction in the territory supplied by the right middle cerebral artery. The mass was surgically resected. The aortic valve was preserved because there were no organic changes in the valve. Histological examination demonstrated an organized thrombus. Only three cases of thrombus attached to the normal native aortic valve have been reported. Native aortic valve thrombus may be important in the differential diagnosis of aortic valve mass.

[Application of arbitrarily primed polymerase chain reaction analysis to epidemiological study of Salmonella enterica serovar enteritidis]

An arbitrarily primed polymerase chain reaction (AP-PCR) DNA profile was applied to epidemiological analysis of Salmonella enterica subsp. enterica serovar Enteritidis. A total 21 strains of S. Enteritidis isolated from 21 cases (10 cases of healthy persons, 7 cases of food poisoning outbreaks and 4 sporadic diarrhea cases), during the period between December 1991 and August 1996 in Wakayama City, were used. A total of 60 arbitrary primers (DNA oligomer (12) set, Wako) were screened with 4 S. Enteritidis strains of different cases. A-11, B-32, C-42 and C-45 primers were chosen. Plasmid DNA profiles, antimicrobial susceptibility patterns and phage types were also examined. The combination of these three methods resolved the collection into five groups (A to E). And type C strains were found in 17 cases (81%) out of 21 cases. However, according to AP-PCR DNA profile, all 21 strains were classified into six groups (I to VI), and 17 type C strains were classified into three groups (III, IV and V). Type IV was predominant in Wakayama City, and type C.IV was found in 15 cases (71%). In conclusion, we considered that AP-PCR DNA profile using appropriate primers was an effective epidemiological marker.

Onset of diabetes with high titer anti-GAD antibody after IFN therapy for chronic hepatitis

A case of hyperglycemia induced by the injection of interferon-alpha was experienced in our hospital. This patient showed a sustained high titer of anti-GAD antibody after the onset of diabetes, suggesting that the involvement of immunological disturbance by IFN induces the onset of the disease. However, the susceptibility and the response of the immune system differs from patient to patient, and only limited destruction of beta-cells in the islet of Langerhans and normalization of glucose tolerance by CSII was induced in this patient.

NMR studies of 1H resonances in the 10-18-ppm range for cytosolic aspartate aminotransferase

Continuing a previous investigation (Kintanar, A., Metzler, C. M., Metzler, D. E., and Scott, R. D. (1991) J. Biol. Chem. 266, 17222-17229), we have recorded 1H NMR spectra at 500 MHz in the 10-18-ppm range for the 93-kDa porcine cytosolic aspartate aminotransferase and for four specific mutant forms of the enzyme in which histidine 68 has been replaced by lysine or histidine 143, 189, or 193 has been replaced by glutamine. We have correlated resonances for apoenzyme, pyridoxamine and pyridoxal phosphate forms, and dicarboxylate complexes and have assigned imidazole NH resonances of active site histidines. The chemical shifts of several resonances undergo pH-dependent changes around the pKa of the Schiff base proton at the active site. Other resonances shift upon binding of dicarboxylates or other ligands. Phosphate or carboxylate ions, which can also occupy the site of the substrate's alpha-carboxylate, cause rapid exchange of the Schiff base proton. Although most resonances in the 10-18-ppm range disappear rapidly in D2O, a few are retained for months in the presence of the dicarboxylate inhibitor glutarate. We demonstrate that changes in chemical shifts and in exchange rates are sensitive indicators of electronic interactions of the enzyme with ligands and of conformational change. Nuclear Overhauser effects from NH protons have allowed us to identify resonances of CH protons of the imidazole rings of histidines 143, 189, and 193. Observed and predicted chemical shifts have been compared. We conclude that the net charge on this histidine cluster is zero but that some negative charge from the aspartate 222 carboxylate is donated inductively into the histidine 143 ring. Studies of the related enzyme from Escherichia coli are provided in an accompanying paper (Metzler, D. E., Metzler, C. M., Scott, R. D., Mollova, E. T., Kagamiyama, H., Yano, T., Kuramitsu, S., Hayashi, H., Hirotsu, K., and Miyahara, I. (1994) J. Biol. Chem. 269, 28027-28033). Our approach should be applicable to the study of active sites of a broad range of relatively large proteins.

Functional roles of valine 37 and glycine 38 in the mobile loop of porcine cytosolic aspartate aminotransferase

The functional roles of Val37 and Gly38 in porcine cytosolic aspartate aminotransferase have been studied in the site-directed mutants V37A, G38A, and G38S where the size and hydrophobic character of these residues has been altered. Previous x-ray studies have shown that Val37 and Gly38, which are part of a flexible loop, interact directly with bound substrate. From x-ray and solution experiments we find that the V37A, G38A, and G38S mutations do not cause significant perturbations to the unliganded enzyme. Replacing Val37 with a less bulky alanine residue does not affect the maximal catalytic rate (kcat), but it does increase significantly the Michaelis constants for substrates in the overall transamination reaction between aspartate and 2-oxoglutarate. On the other hand, replacing Gly38 with alanine or serine results in striking decreases in kcat to 5 and 0.6%, respectively, of the value observed for the wild-type enzyme, as well as in considerable increases in Km values. Consequently, the catalytic competence, kcat/Km, decreases by 3 orders of magnitude for G38A and by 4 orders of magnitude for G38S. Single turnover reactions of G38A and G38S with four individual substrates (aspartate, glutamate, oxalacetate, and 2-oxoglutarate) are characterized by kinetic parameters that are largely consistent with those of the overall reaction. In addition, the mutations at position 38 impair more seriously the catalytic competence of the enzyme toward C5-substrates than toward C4-substrates. We conclude that Gly38 is probably required for proper function of the enzyme because it permits a high level of flexibility for the 36-39 peptide, which in turn allows the essential substrate-induced movement of the small domain.

Purification and characterization of cytochrome P450 from an isobutene-forming microorganism, Rhodotorula minuta

A cytochrome P450 was purified from microsomes of Rhodotorula minuta. The optical spectrum of the purified cytochrome was characteristic of a low-spin ferric heme protein. Isovalerate caused a type I spectral change in it. The amino-terminal sequence of the cytochrome was different from those of other known microsomal cytochrome P450s. These results indicate that the cytochrome, which is tentatively named P450rm, is a novel species of cytochrome P450.

Two reactions are simultaneously catalyzed by a single enzyme: the arginine-dependent simultaneous formation of two products, ethylene and succinate, from 2-oxoglutarate by an enzyme from Pseudomonas syringae

A single enzyme isolated from Pseudomonas syringae pv. phaseolicola PK2 simultaneously catalyzed two reactions, namely, the formation of ethylene and succinate from 2-oxoglutarate, at a molar ratio of 2:1. In the main reaction, 2-oxoglutarate was dioxygenated to produce one molecule of ethylene and three molecules of carbon dioxide. In the sub-reaction, both 2-oxoglutarate and L-arginine were mono-oxygenated to yield succinate plus carbon dioxide and L-hydroxyarginine, respectively, the latter being further transformed to guanidine and L-delta 1-pyrroline-5-carboxylate. We propose a dual-circuit mechanism for the entire reaction, in which the binding of L-arginine and 2-oxoglutarate in a Schiff-base structure generates a common intermediate for two reactions.

Molecular cloning in Escherichia coli, expression, and nucleotide sequence of the gene for the ethylene-forming enzyme of Pseudomonas syringae pv. phaseolicola PK2

The gene for the ethylene-forming enzyme of Pseudomonas syringae pv. phaseolicola PK2 was found to be encoded by an indigenous plasmid, designated pPSP1. The gene for the ethylene-forming enzyme was cloned and expressed in Escherichia coli JM109. Nucleotide sequence analysis of the clone revealed an open reading frame that encodes 350 amino acids (mol. wt. 39,444). In a comparison with other proteins, the homology score for the entire amino-acid sequence of the ethylene-forming enzyme of Pseudomonas syringae versus ethylene-forming enzymes from plants and 2-oxoglutarate-dependent dioxygenases was low. However, functionally significant regions are conserved.

Presequence binding factor-dependent and -independent import of proteins into mitochondria

A cytosolic protein factor(s) is involved in the import of precursor proteins into mitochondria. PBF (presequence binding factor) is a protein factor which binds to the precursor form (pOTC) of rat ornithine carbamoyltransferase (OTC) but not to the mature OTC, and is required for the mitochondrial import of pOTC. The precursors for aspartate aminotransferase and malate dehydrogenase as well as pOTC synthesized in a reticulocyte lysate were efficiently imported into the mitochondria. However, the precursors synthesized in the lysate depleted for PBF by treatment with pOTC-Sepharose were not imported. Readdition of the purified PBF to the depleted lysate fully restored the import. pOTC synthesized in the untreated lysate sedimented as a complex with a broad peak of around 9 S, whereas pOTC synthesized in the PBF-depleted lysate sedimented at an expected position of monomer (2.5 S). When the purified PBF was readded to the depleted lysate, pOTC sedimented as a complex of about 7 S. In contrast to most mitochondrial proteins, rat 3-oxoacyl-CoA thiolase is synthesized with no cleavable presequence and an NH2-terminal portion of the mature protein functions as a mitochondrial import signal. The thiolase synthesized in the PBF-depleted lysate could be efficiently imported into the mitochondria, and readdition of PBF had little effect on the import. The thiolase synthesized in the untreated, the PBF-depleted, or the PBF-readded lysate sedimented at an expected position of monomer (2.5 S). These observations provide support for the existence of PBF-dependent and -independent pathways of mitochondrial protein import.

[Vitamin B6 dependency syndrome]

Many enzymes that require pyridoxal 5'-phosphate (PLP), a coenzyme from a vitamin B6, are involved in amino acid metabolism. B6 dependency syndromes are defined as a group of metabolic disorders which are prevented or alleviated by non-physiologically large doses of vitamin B6, and, hence, they are tacitly accounted for by some structural alteration in a responsible B6-dependent enzyme such as a decrease on the affinity for PLP as compared to the normal. In this article, the mode of binding the coenzyme is exemplified by the case of aspartate aminotransferase, a typical B6-dependent enzyme whose three-dimensional structure is known, and, several B6 dependency syndromes are briefly reviewed. Among these syndromes, the molecular basis of only gyrate atrophy has recently been defined by the identification of a mutation in the relevant enzyme, ornithine aminotransferase.

[Molecular biological aspects of amino acid metabolizing enzymes]

This article briefly describes the molecular biological aspect of studies on some enzymes involved in amino acid metabolism. Aspartate aminotransferase is one most extensively studied enzyme. Together with its three dimensional structure, recent studies using site-directed mutagenesis have led to the understanding of its structure-function relationships. Successful cDNA cloning of other aminotransferase has enabled us to understand the degree of homology in amino acid sequence. cDNAs for several amino acid decarboxylases were also cloned. Genomic structures for the enzymes involved in urea cycle have been studied. These studies have provided a molecular basis for some hyperammonemias. Its is strongly anticipated that the understanding of other metabolic disorders may be promoted by further accumulation of molecular biological data on the relevant enzymes.

Role of Asp222 in the catalytic mechanism of Escherichia coli aspartate aminotransferase: the amino acid residue which enhances the function of the enzyme-bound coenzyme pyridoxal 5'-phosphate

Asp222 is an invariant residue in all known sequences of aspartate aminotransferases from a variety of sources and is located within a distance of strong ionic interaction with N(1) of the coenzyme, pyridoxal 5'-phosphate (PLP), or pyridoxamine 5'-phosphate (PMP). This residue of Escherichia coli aspartate aminotransferase was replaced by Ala, Asn, or Glu by site-directed mutagenesis. The PLP form of the mutant enzyme D222E showed pH-dependent spectral changes with a pKa value of 6.44 for the protonation of the internal aldimine bond, slightly lower than that (6.7) for the wild-type enzyme. In contrast, the internal aldimine bond in the D222A or D222N enzyme did not titrate over the pH range 5.3-9.5, and a 430-nm band attributed to the protonated aldimine persisted even at high pH. The binding affinity of the D222A and D222N enzymes for PMP decreased by 3 orders of magnitude as compared to that of the wild-type enzyme. Pre-steady-state half-transamination reactions of all the mutant enzymes with substrates exhibited anomalous progress curves comprising multiphasic exponential processes, which were accounted for by postulating several kinetically different enzyme species for both the PLP and PMP forms of each mutant enzyme. While the replacement of Asp222 by Glu yielded fairly active enzyme species, the replacement by Ala and Asn resulted in 8600- and 20,000-fold decreases, respectively, in the catalytic efficiency (kmax/Kd value for the most active species of each mutant enzyme) in the reactions of the PLP form with aspartate. In contrast, the catalytic efficiency of the PMP form of the D222A or D222N enzyme with 2-oxoglutarate was still retained at a level as high as 2-10% of that of the wild-type enzyme. The presteady-state reactions of these two mutant enzymes with [2-2H]aspartate revealed a deuterium isotope effect (kH/kD = 6.0) greater than that [kH/kD = 2.2; Kuramitsu, S., Hiromi, K., Hayashi, H., Morino, Y., & Kagamiyama, H. (1990) Biochemistry 29, 5469-5476] for the wild-type enzyme. These findings indicate that the presence of a negatively charged residue at position 222 is particularly critical for the withdrawal of the alpha-proton of the amino acid substrate and accelerates this rate-determining step by about 5 kcal.mol-1. Thus it is concluded that Asp222 serves as a protein ligand tethering the coenzyme in a productive mode within the active site and stabilizes the protonated N(1) of the coenzyme to strengthen the electron-withdrawing capacity of the coenzyme.

High density lipoprotein mediates selective reduction in cholesteryl esters from macrophage foam cells

To elucidate an anti-atherogenic nature of high density lipoprotein (HDL) at cellular level, its in vitro effect on macrophage foam cells was examined. Rat peritoneal macrophages were converted to foam cells by incubation with [3H]cholesterol-labeled acetylated LDL. HDL addition to these foam cells resulted in a reduction in cellular radioactive cholesteryl esters (CE) as well as its CE mass. The radioactive free cholesterol (FC) was similarly reduced with time, whereas its FC mass level was unaltered. Other lipoproteins such as very low density lipoprotein and low density lipoprotein also reduced the radioactive FC. However, their CE-reducing capacity was negligibly weak. These results suggest that (i) CE reduction is selective to HDL, (ii) FC transfer from plasma membrane to lipoprotein (cholesterol efflux) expressed by reduction in radioactive FC is not selective to HDL but occurs to other lipoproteins, (iii) the CE-reducing capacity of HDL became weaker when cellular binding of HDL was reduced by chemical modification with tetranitromethane or a chemical cross-linker, dithiobis-succinimidylpropionate, suggesting an importance of the specific binding in the HDL-mediated CE reduction. These in vitro results gave an experimental support to a definite role of HDL as an anti-atherogenic lipoprotein in vivo.