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Biomedical subjects

J A Goldstein

Publications and source records attributed to J A Goldstein.

At least 19 recordsLinked to original sources
PubMed2006

Percutaneous vascular interventions in renal artery diseases.

Renal artery stenosis (RAS) is a progressive manifestation of atherosclerosis. It is associated with hypertension and progressive renal failure. Noninvasive testing includes renal artery duplex, computed tomographic angiography (CTA) and magnetic resonance angiography (MRA). Percutaneous transluminal renal angioplasty and stenting (PTRAS) is indicated for significant atherosclerotic RAS while percutaneous transluminal renal angioplasty (PTRA) is indicated for fibromuscular dysplasias (FMD) associated with the proper clinical indications. PTRAS is associated with a high technical success rate and an acceptable adverse event and restenosis rate. PTRAS appears to improve control of hypertension and renal preservation. All patients should be followed clinically and with periodic duplex ultrasonography. Restenosis is treated with repeat angioplasty and occasionally stenting. Current and future areas of investigation will involve distal protection and drug eluting stents.

Angioplasty, Balloon↗
PubMed2004

Effect of high-dose intravenous eletriptan on coronary artery diameter.

The goal of this study was to evaluate the coronary vasoconstrictive effects of high doses of eletriptan compared with a standard dose of sumatriptan. Patients with no clinically significant coronary artery disease were randomized to receive high-dose intravenous eletriptan (n = 24) vs a standard dose of sumatriptan (n = 18; 6 mg subcutaneously) vs placebo (n = 18). Serial angiograms were obtained. The primary non-inferiority analysis found equivalence between the mean maximum change in left anterior descending coronary artery diameter for eletriptan, -22%[95% confidence interval (CI) -26, -19], and sumatriptan, -19% (95% CI -22, -16). The change due to placebo was -16% (95% CI -20, -12). No individual cases of clinically significant vasoconstriction were observed. The results confirm that eletriptan has a broad cardiovascular safety margin, with plasma concentrations comparable to three to five times the Cmax of an oral 80-mg dose associated with modest vasoconstriction equivalent to standard therapeutic doses of sumatriptan.

Adult↗
PubMed2001

Ticlopidine as a selective mechanism-based inhibitor of human cytochrome P450 2C19.

Experiments using recombinant yeast-expressed human liver cytochromes P450 confirmed previous literature data indicating that ticlopidine is an inhibitor of CYP 2C19. The present studies demonstrated that ticlopidine is selective for CYP 2C19 within the CYP 2C subfamily. UV-visible studies on the interaction of a series of ticlopidine derivatives with CYP 2C19 showed that ticlopidine binds to the CYP 2C19 active site with a K(s) value of 2.8 +/- 1 microM. Derivatives that do not involve either the o-chlorophenyl substituent, the free tertiary amine function, or the thiophene ring of ticlopidine did not lead to such spectral interactions and failed to inhibit CYP 2C19. Ticlopidine is oxidized by CYP 2C19 with formation of two major metabolites, the keto tautomer of 2-hydroxyticlopidine (1) and the dimers of ticlopidine S-oxide (TSOD) (V(max) = 13 +/- 2 and 0.4 +/- 0.1 min(-1)). During this oxidation, CYP 2C19 was inactivated; the rate of its inactivation was time and ticlopidine concentration dependent. This process meets the chemical and kinetic criteria generally accepted for mechanism-based enzyme inactivation. It occurs in parralel with CYP 2C19-catalyzed oxidation of ticlopidine, is inhibited by an alternative well-known substrate of CYP 2C19, omeprazole, and correlates with the covalent binding of ticlopidine metabolite(s) to proteins. Moreover, CYP 2C19 inactivation is not inhibited by the presence of 5 mM glutathione, suggesting that it is due to an alkylation occurring inside the CYP 2C19 active site. The effects of ticlopidine on CYP 2C19 are very analogous with those previously described for the inactivation of CYP 2C9 by tienilic acid. This suggests that a similar electrophilic intermediate, possibly a thiophene S-oxide, is involved in the inactivation of CYP 2C19 and CYP 2C9 by ticlopidine and tienilic acid, respectively. The kinetic parameters calculated for ticlopidine-dependent inactivation of CYP 2C19, i.e., t(1/2max) = 3.4 min, k(inact) = 3.2 10(-3) s(-1), K(I) = 87 microM, k(inact)/K(I) = 37 L.mol(-1).s(-1), and r (partition ratio) = 26 (in relation with formation of 1 + TSOD), classify ticlopidine as an efficient mechanism-based inhibitor although somewhat less efficient than tienilic acid for CYP 2C9. Importantly, ticlopidine is the first selective mechanism-based inhibitor of human liver CYP 2C19 and should be a new interesting tool for studying the topology of the active site of CYP 2C19.

Alkylation↗
PubMed2001

Lumbar sagittal alignment after fusion with a threaded interbody cage.

STUDY DESIGN: Records of 111 patients randomly selected from a population who received an interbody fusion cage during a clinical Investigation Device Exemption trial (BAK/L) yielded 126 operative levels and were retrospectively assessed. OBJECTIVES: This study examined lumbar spine sagittal alignment and clinical outcomes before and 2 years after fusion surgery. SUMMARY OF BACKGROUND DATA: Lumbar lordosis is important in spinal sagittal alignment and balance, especially the L4-S1 area. Perceived consensus is that anatomically correct lumbar lordosis is desired and that a loss of lumbar lordosis may lead to spine pathology. There is little information on lumbar lordosis after interbody fusion. METHODS: A random sample of 111 patients who received a cylindrical cage implant (total pool of 947 patients) yielded 126 operative lumbar segments. There were 52 posterior approaches and 59 anterior approaches, and all cages were placed in the L4-L5 or L5-S1 levels. Preoperative and 2-year follow-up lateral radiographs were measured for segmental lordosis. Cage position was measured relative to the posterior longitudinal ligament. Segmental lordotic change was correlated to clinical outcome at the 2-year follow-up. RESULTS: Preoperative lordosis was different as a function of surgical approach. There was a significant 2-year decrease in lordosis with the posterior approach group; however, all intervertebral angles were within typical ranges. Clinical outcomes were significantly improved 2 years postsurgery. There was no correlation between changes in lordosis and clinical outcomes. CONCLUSIONS: Interbody lumbar fusion with a threaded cylindrical cage does not appear to have any clinically relevant effects on segmental lordosis, which is maintained within anatomically normal levels. Clinical outcome measures show significant postsurgery improvement, and changes in lordotic angles are not predictive of clinical outcome.

Humans↗
PubMed2001

Cochlear gene delivery through an intact round window membrane in mouse.

Cochlear gene transfer studies in animal models have utilized mainly two delivery methods: direct injection through the round window membrane (RWM) or intracochlear infusion through a cochleostomy. However, the surgical trauma, inflammation, and hearing loss associated with these methods lead us to investigate a less invasive delivery method. Herein, we studied the feasibility of a vector transgene-soaked gelatin sponge, Gelfoam, for transgene delivery into the mouse cochlea through an intact RWM. The Gelfoam absorbed with liposomes and adenovirus, but not with adeno-associated virus (AAV), was successful in mediating transgene expression across an intact RWM in a variety of cochlear tissues. The Gelfoam technique proved to be an easy, atraumatic, and effective, but vector-dependent, method of delivering transgenes through an intact RWM. Compared with the more invasive gene delivery methods, this technique represents a safer and a more clinically viable route of cochlear gene delivery in humans.

Adenoviridae↗
PubMed2001

Identification of human CYP2C19 residues that confer S-mephenytoin 4'-hydroxylation activity to CYP2C9.

CYP2C19 is selective for the 4'-hydroxylation of S-mephenytoin while the highly similar CYP2C9 has little activity toward this substrate. To identify critical amino acids determining the specificity of human CYP2C19 for S-mephenytoin 4'-hydroxylation, we constructed chimeras by replacing portions of CYP2C9 containing various proposed substrate recognition sites (SRSs) with those of CYP2C19 and mutating individual residues by site-directed mutagenesis. Only a chimera containing regions encompassing SRSs 1--4 was active (30% of wild-type CYP2C19), indicating that multiple regions are necessary to confer specificity for S-mephenytoin. Mutagenesis studies identified six residues in three topological components of the proteins required to convert CYP2C9 to an S-mephenytoin 4'-hydroxylase (6% of the activity of wild-type CYP2C19). Of these, only the I99H difference located in SRS 1 between helices B and C reflects a change in a side chain that is predicted to be in the substrate-binding cavity formed above the heme prosthetic group. Two additional substitutions, S220P and P221T residing between helices F and G but not in close proximity to the substrate binding site together with five differences in the N-terminal portion of helix I conferred S-mephenytoin 4'-hydroxylation activity with a K(M) similar to that of CYP2C19 but a 3-fold lower K(cat). Three residues in helix I, S286N, V292A, and F295L, were essential for S-mephenytoin 4'-hydroxylation activity. On the basis of the structure of the closely related enzyme CYP2C5, these residues are unlikely to directly contact the substrate during catalysis but are positioned to influence the packing of substrate binding site residues and likely substrate access channels in the enzyme.

Amino Acid Substitution↗
PubMed2001

Assessment of denaturing high-performance liquid chromatography (DHPLC) in screening for mutations in connexin 26 (GJB2).

Mutations in the gene GJB2 encoding connexin 26 (Cx26), a gap junction protein, have been shown to be responsible for a majority of recessive nonsyndromic hereditary hearing impairment in children. Over 60 different mutations in Cx26 have been reported. To obviate the need for direct sequencing of each specimen, a variety of screening techniques have been used to detect mutations in Cx26. However, each of these methods has significant shortcomings including expense, time consumption, and limited sensitivity. Denaturing high-performance liquid chromatography (DHPLC) has been recently introduced as a rapid and highly sensitive method of detecting sequence alterations. We have assessed the efficacy of DHPLC as a screening assay for detecting mutation in Cx26 coding region in 154 patients with hereditary hearing impairment. The GJB2 coding exon was amplified in one or two fragments, analyzed by DHPLC, and sequenced. Sequence analysis identified sequence variations in 34 patients concordant with abnormal DHPLC results. Three novel Cx26 mutations were identified: a single base pair substitution 511G>A, a 4 bp insertion 504insAACG, and a 3 bp deletion 358delAGG in three unrelated patients. In 120 patients with normal Cx26 sequence, DHPLC was normal. These results yield sensitivity and specificity of 100% for DHPLC-based detection of Cx26 mutations, and demonstrate that DHPLC is a highly sensitive and specific method of screening for sequence variations in Cx26 that is time and labor efficient. Further, our experience suggests that DHPLC screening alone followed by DNA sequencing only when DHPLC is abnormal may be adequate for identification of all sequence alterations in Cx26.

Chromatography, High Pressure Liquid↗
PubMed2001

Clinical relevance of genetic polymorphisms in the human CYP2C subfamily.

The human CYP2Cs are an important subfamily of P450 enzymes that metabolize approximately 20% of clinically used drugs. There are four members of the subfamily, CYP2C8, CYP2C9, CYP2C19, and CYP2C18. Of these CYP2C8, CYP2C9, and CYP2C19 are of clinical importance. The CYP2Cs also metabolize some endogenous compounds such as arachidonic acid. Each member of this subfamily has been found to be genetically polymorphic. The most well-known of these polymorphisms is in CYP2C19. Poor metabolizers (PMs) of CYP2C19 represent approximately 3-5% of Caucasians, a similar percentage of African-Americans and 12-100% of Asian groups. The polymorphism affects metabolism of the anticonvulsant agent mephenytoin, proton pump inhibitors such as omeprazole, the anxiolytic agent diazepam, certain antidepressants, and the antimalarial drug proguanil. Toxic effects can occur in PMs exposed to diazepam, and the efficacy of some proton pump inhibitors may be greater in PMs than EMs at low doses of these drugs. A number of mutant alleles exist that can be detected by genetic testing. CYP2C9 metabolizes a wide variety of drugs including the anticoagulant warfarin, antidiabetic agents such as tolbutamide, anticonvulsants such as phenytoin, and nonsteroidal anti-inflammatory drugs. The incidence of functional polymorphisms is much lower, estimated to be 1/250 in Caucasians and lower in Asians. However, the clinical consequences of these rarer polymorphisms can be severe. Severe and life-threatening bleeding episodes have been reported in CYP2C9 PMs exposed to warfarin. Phenytoin has been reported to cause severe toxicity in PMs. New polymorphisms have been discovered in CYP2C8, which metabolizes taxol (paclitaxel). Genetic testing is available for all of the known CYP2C variant alleles.

Alleles↗
PubMed2001

Detection of fungi in the nasal mucosa using polymerase chain reaction.

HYPOTHESIS: Fungi have been increasingly recognized as important pathogens in sinusitis. However, detection of fungus with conventional culture techniques is insensitive and unreliable. Polymerase chain reaction (PCR) is an exquisitely sensitive assay that can detect the DNA of 10 or less fungal elements. The aim of this study was to compare the sensitivity of conventional culture techniques using PCR analysis. METHODS: Nasal swabs and DNA samples were collected from the nasal cavities of control subjects and patients with chronic sinusitis. Fungal-specific PCR analysis and standard cultures were performed on every sample. chi2 analysis was used to test for statistical differences between groups. RESULTS: PCR analysis detected fungal DNA in 42% and 40% of control subjects and patients with chronic sinusitis while standard cultures were positive in 7% and 0%, respectively. There was no statistically significant difference in the prevalence of fungi in the normal volunteers and patients with chronic rhinosinusitis. CONCLUSION: PCR is significantly more sensitive than nasal swab cultures in detecting the presence of fungi in nasal mucosa. In addition, our study suggests that the presence of fungi alone is insufficient to implicate it as the pathogen in chronic sinusitis.

Chronic Disease↗
PubMed2001

Polymorphisms in human CYP2C8 decrease metabolism of the anticancer drug paclitaxel and arachidonic acid.

Cytochrome P450 (CYP) 2C8 is the principal enzyme responsible for the metabolism of the anti-cancer drug paclitaxel (Taxol). It is also the predominant P450 responsible for the metabolism of arachidonic acid to biologically active epoxyeicosatrienoic acids (EETs) in human liver and kidney. In this study, we describe two new CYP2C8 alleles containing coding changes: CYP2C8*2 has an Ile269Phe substitution in exon 5 and CYP2C8*3 includes both Arg139Lys and Lys399Arg amino acid substitutions in exons 3 and 8. CYP2C8*2 was found only in African-Americans, while CYP2C8*3 occurred primarily in Caucasians. Neither occurred in Asians. The frequency of the CYP2C8*2 allele was 0.18 in African-Americans, and that of CYP2C8*3 was 0.13 in Caucasians. CYP2C8*1 (wild-type), CYP2C8*2 and CYP2C8*3 cDNAs were expressed in Escherichia coli, and the ability of these enzymes to metabolize both paclitaxel and arachidonic acid was assessed. Recombinant CYP2C8*3 was defective in the metabolism of both substrates. The turnover number of CYP2C8*3 for paclitaxel was 15% of CYP2C8*1. CYP2C8*2 had a two-fold higher Km and two-fold lower intrinsic clearance for paclitaxel than CYP2C8*1. CYP2C8*3 was also markedly defective in the metabolism of arachidonic acid to 11,12- and 14,15-EET (turnover numbers 35-40% that of CYP2C8*1). Thus, CYP2C8*3 is defective in the metabolism of two important CYP2C8 substrates: the anticancer drug paclitaxel and the physiologically important compound arachidonic acid. This polymorphism has important clinical and physiological implications in individuals homozygous for this allele.

Alleles↗
PubMed2001

Identification of a null allele of CYP2C9 in an African-American exhibiting toxicity to phenytoin.

Cytochrome P450 (CYP) 2C9 is the principal enzyme responsible for the metabolism of numerous clinically important drugs. Two polymorphic alleles CYP2C9*2 and CYP2C9*3 have been documented which affect the metabolism and clinical toxicity of drugs such as phenytoin, warfarin, glipizide, and tolbutamide. The present study reports the first example of a null polymorphism in CYP2C9. This mutation dramatically affects the half-life and clinical toxicity of phenytoin. The study subject was a female African-American presented to the emergency department with phenytoin toxicity evidenced by mental confusion, slurred speech, memory loss and the inability to stand. She exhibited extremely poor clearance of phenytoin with an elimination half-life of approximately 13 days. Genotyping studies demonstrated that the patient did not possess any known variant CYP2C9 alleles. Phenytoin is metabolized to a minor extent by the polymorphic CYP2C19, but this individual did not possess any variant CYP2C19 alleles. Sequencing studies revealed that the individual was homozygous for a new CYP2C9 allele (CYP2C9*6) with the deletion of an adenine at base pair 818 of the cDNA. The clearance of phenytoin in this individual is estimated to be approximately 17% of that observed in normal patients. The frequency of this allele was 0.6% (95% confidence limits of 0.1 to 3.5%) in 79 African-Americans and 0% (95% confidence limits of 0 to 1.1%) in 172 Caucasians. The study also demonstrates the severe clinical consequences to patients with a null mutation in CYP2C9 after treatment with normal doses of phenytoin.

Administration, Oral↗
PubMed2001

A novel automated injection system for angiography.

The present method of performing manual coronary angiography requires repetitive manipulation of a cumbersome stopcock-manifold system and contrast injection by hand syringe. This study reports a novel mechanical contrast injector with automated manifold that provides finger touch operator-controlled contrast injections. The ACIST Injection System components include a software-controlled syringe injector, a disposable automated manifold without stopcocks, a disposable hand controller, and a touch screen control panel. The ACIST system was evaluated in 50 patients undergoing diagnostic coronary angiography (n = 37) or coronary interventions (n = 13). In all cases, the system was easy to use and provided excellent quality images even with four catheters, as well as imaging during stent positioning with 6Fr guides. This mechanical injector facilitates precision operator-controlled angiographic injections, provides superb high quality coronary images even with very small lumen catheters, and expedites ventriculography during angiographic procedures.

Automation↗
PubMed2001

What information do parents of newborns with cleft lip, palate, or both want to know?

BACKGROUND: The unexpected birth of a baby with a cleft lip and palate (CL/P) is a shocking and traumatic experience, generating anxiety for parents as well as the attendant health care team. Parents frequently leave the hospital with many unanswered questions because health care professionals do not educate them adequately. OBJECTIVE: To determine what information these parents felt was "critical" for them during the immediate newborn period and to determine how the "informer" was perceived during these encounters. DESIGN: Retrospective, self-administered questionnaire. SUBJECTS AND METHODS: Biologic parents of children with isolated CL/P aged 6 years and younger were surveyed. The questionnaire asked parents whether they remembered discussing diagnosis, prognosis, management, home care, and psychosocial issues. Parents were also asked to rank how "critical" it would have been for the "informer" to have discussed certain issues with them during this first day. RESULTS: Parents gave the highest priority to feeding and learning to identify illness in their baby; 95% wanted to be shown all normal aspects of their baby's exam, and 87% wanted to be told that the CL/P was not their fault. Usage of proper terminology to describe abnormal findings and receiving assurance that their child was not in pain were also important. Unfortunately, many parents reported that the informers did not address these issues. CONCLUSIONS: Parents of newborns with CL/P want basic information in the immediate newborn period, especially regarding feeding and recognizing illness. These data suggest that informers are not adequately discussing these issues with parents.

Attitude to Health↗
PubMed2001

Metabolism of chlorpyrifos by human cytochrome P450 isoforms and human, mouse, and rat liver microsomes.

One of the factors determining the toxicity of chlorpyrifos (CPS), an organophosphorus (OP) insecticide, is its biotransformation. CPS can be activated by cytochrome P450 (CYP) through a desulfuration reaction to form chlorpyrifos-oxon (CPO), a potent anticholinesterase. CPS can also be detoxified by CYP through a dearylation reaction. Using pooled human liver microsomes (HLM), a K(m(app)) of 30.2 microM and V(max(app)) of 0.4 nmol/min/mg of protein was obtained for desulfuration, and a K(m(app)) of 14.2 microM and a V(max(app)) of 0.7 nmol/min/mg of protein was obtained for dearylation. These activities are lower than those obtained from rat liver microsomes. Gender differences in humans were also observed with female HLM possessing greater activity than male HLM. Use of human CYP isoforms expressed in human lymphoblastoma cells demonstrated that CYP1A2, 2B6, 2C9*1, 2C19, and 3A4 are involved in CPS metabolism. CYP2B6 has the highest desulfuration activity, whereas dearylation activity is highest for 2C19. CYP3A4 has high activity for both dearylation and desulfuration. The use of phenotyped individual HLM demonstrated that predictions of metabolic activation and/or detoxication could be made based on relative amounts of CYP2B6, 2C19, and 3A4 in the microsomes. Thus, individuals with high CYP2C19 but low 3A4 and 2B6 are more active in dearylation than in desulfuration. Similarly, individuals possessing high levels of CYP2B6 and 3A4 have the greatest potential to form the activation product. These differences between individuals suggest that differential sensitivities to CPS may exist in the human population.

Animals↗