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Biomedical subjects

J R Rubin

Publications and source records attributed to J R Rubin.

At least 19 recordsLinked to original sources
PubMed2005

Mercury levels and relationships in water, sediment, and fish tissue in the Willamette Basin, Oregon.

In Oregon's Willamette River Basin (the Basin), health advisories currently limit consumption of fish that have accumulated methylmercury (MeHg) to levels posing a significant human health risk. These advisories created the requirement for a mercury total maximum daily load for the Basin, which required a greater understanding of the behavior, distribution, and levels of mercury and MeHg in the Basin. In 2002, the Oregon Department of Environmental Quality initiated a study to measure (using ultraclean techniques) mercury and MeHg levels in water, sediment, and fish samples collected throughout the Basin. Results from the Middle Fork (nominal background) suggested that naturally occurring surface-water concentrations of mercury and MeHg would on an annual average basis be expected in the range of 0.5 to 1.0 and 0.04 to 0.06 ng L(-1), respectively. Concentrations in the Coast Fork (Cottage Grove), which were markedly higher, are likely the result of historical mining discharges. The possibility exists that wetlands alone could contribute the dissolved MeHg levels (approximately 0.04 ng L(-1)) observed in the Main Stem. Mercury levels in sediment were similar, and near background, in the Main Stem, Coast Fork (Row River), and Middle Fork but significantly increased in the Coast Fork (Cottage Grove). Fish tissue mercury levels were typically highest in piscivorous and lowest in invertivorous species but highest in the Coast Fork (Cottage Grove). In the Coast Fork and Cottage Grove Reservoir, discharges from historical mercury mining activities appear to have significantly impacted water, sediment, and fish tissue levels; however these impacts do not appear to extend into the Main Stem. Basinwide mercury data are at present too spottily distributed to determine whether significant mercury point sources exist along the Main Stem.

Animals↗
PubMed2001

Novel bicyclic lactam inhibitors of thrombin: potency and selectivity optimization through P1 residues.

Peptidomimetic inhibitors of thrombin lacking the important Ser195-carbonyl interaction have been prepared. The binding energy lost after the removal of the activated carbonyl was recaptured through a series of modifications of the P1 residues of the bicyclic lactam inhibitors. Selected substituted compounds displayed useful pharmacological profiles both in vitro and in vivo.

Animals↗
PubMed2001

Structure-based design of caspase-1 inhibitor containing a diphenyl ether sulfonamide.

A series of compounds was designed and prepared as inhibitors of interleukin-1beta converting enzyme (ICE), also known as caspase-1. These inhibitors, which employ a diphenyl ether sulfonamide, were designed to improve potency by forming favorable interactions between the diphenyl ether rings and the prime side hydrophobic region. An X-ray crystal structure of a representative member of the diphenyl ether sulfonamide series bound to the active site of caspase-1 was obtained.

Caspase 1↗
PubMed2000

Structural basis of the thrombin selectivity of a ligand that contains the constrained arginine mimic (2S)-2-amino-(3S)-3-(1-carbamimidoyl- piperidin-3-yl)-propanoic acid at P1.

We have studied the thrombin and trypsin complexed structures of a pair of peptidomimetic thrombin inhibitors, containing different P1 fragments. The first has arginine as its P1 fragment, and the second contains the constrained arginine mimic (2S)-2-amino-(3S)-3-(1-carbamimidoyl-piperidin-3-yl)-propano ic acid (SAPA), a fragment known to enhance thrombin/trypsin selectivity of inhibitors. On the basis of an analysis of the nonbonded interactions present in the structures of the trypsin and thrombin complexes of the two inhibitors, the calculated accessible surfaces of the enzymes and inhibitors in the four complexes, data on known structures of trypsin complexes of inhibitors, and factor Xa inhibitory potency of these compounds, we conclude that the ability of this arginine mimic to increase thrombin selectivity of an inhibitor is mediated by its differential interaction with the residue at position 192 (chymotrypsinogen numbering). Thrombin has a glutamic acid at residue 192, and trypsin has a glutamine. The analysis also suggests that this constrained arginine mimic, when present in an inhibitor, might enhance selectivity against other trypsin-like enzymes that have a glutamine at residue position 192.

Alanine↗
PubMed2000

Systemic consequences of oxidative stress following aortic surgery correlate with the degree of antioxidant defenses.

The purpose of this study was to correlate the preoperative level of antioxidant defenses, measured by the plasma total antioxidant capacity (TAC), to the degree of postoperative systemic inflammatory response, measured by the severity of pulmonary injury following elective aortic surgery. Twenty-four patients had TAC measured preoperatively and 24 hr postoperatively. Chest radiography and arterial blood gases were obtained preoperatively and serially during the first 24 hr after surgery. Using objective radiologic criteria and blood gas analysis, the degree of pulmonary edema and pulmonary dysfunction were quantified. All patients showed evidence of pulmonary dysfunction in the first 24 hr following surgery. Fifteen of the 24 patients showed radiographic evidence of noncardiogenic pulmonary edema in the immediate postoperative period. In this group, the TAC was lower than in those without pulmonary edema immediately following surgery (p = 0.03). Preoperative TAC was associated with the degree of pulmonary edema in the postoperative period (r = -0.372, p = 0.067). These results suggest that preoperative antioxidant supplementation may favorably impact the severity of systemic inflammatory response following ischemia and reperfusion injury.

Aged↗
PubMed2000

What influences medical students' choice of surgical careers.

BACKGROUND: Recent emphasis in medical education has been to encourage students to pursue primary care careers. This could have a negative impact on applications to surgical residencies. METHODS: To determine what factors are most influential for a student to pursue a surgical career in spite of this environment, third- and fourth-year medical students were surveyed with a 40-item questionnaire. RESULTS: The response rate was 37% (76/205). Those students considering a career in surgery were more likely than their counterparts to be motivated by role models (P <.006), career opportunities (P <.006), and academic opportunities (P <.013) in surgery. They were less likely than their counterparts to be discouraged from surgery on the basis of lifestyle (P <.001), time commitment (P <.001), call schedules (P <.001), or residency length (P <.028). No differences regarding financial rewards, research opportunities, or intellectual challenges were seen between the groups. Neither race nor sex had a significant role in the selection of surgery as a career. CONCLUSIONS: The data suggests that students are more likely to be influenced to pursue surgical careers by offering early exposure to positive role models and career and academic opportunities in surgery. Knowledge of these influences on student career choices should help surgical educators attract and maintain student interest in surgical careers.

Career Choice↗
PubMed2000

Progress in the development of inhibitors of SH2 domains.

SH2 domains are discrete structural motifs common to a variety of critical intracellular signaling proteins. Inhibitors of specific SH2 domains have become important therapeutic targets in the treatment and/or prevention of restenosis, cancers (including small cell lung), cardiovascular disease, osteoporosis, apoptosis among others. Considering the social and economic impact of these diseases significant attention has been focused on the development of potent and selective inhibitors of specific SH2 domains. In particular, considerable research has been performed on Src, PI 3-kinase, Grb2 and more recently, Lck. In this review, we will focus on progress in the development of inhibitors for these specific SH2 domains and evaluate potential future targets.

Amino Acid Sequence↗
PubMed1999

Mechanism of triclosan inhibition of bacterial fatty acid synthesis.

Triclosan is a broad-spectrum antibacterial agent that inhibits bacterial fatty acid synthesis at the enoyl-acyl carrier protein reductase (FabI) step. Resistance to triclosan in Escherichia coli is acquired through a missense mutation in the fabI gene that leads to the expression of FabI[G93V]. The specific activity and substrate affinities of FabI[G93V] are similar to FabI. Two different binding assays establish that triclosan dramatically increases the affinity of FabI for NAD+. In contrast, triclosan does not increase the binding of NAD+ to FabI[G93V]. The x-ray crystal structure of the FabI-NAD+-triclosan complex confirms that hydrogen bonds and hydrophobic interactions between triclosan and both the protein and the NAD+ cofactor contribute to the formation of a stable ternary complex, with the drug binding at the enoyl substrate site. These data show that the formation of a noncovalent "bi-substrate" complex accounts for the effectiveness of triclosan as a FabI inhibitor and illustrates that mutations in the FabI active site that interfere with the formation of a stable FabI-NAD+-triclosan ternary complex acquire resistance to the drug.

Enoyl-(Acyl-Carrier-Protein) Reductase (NADH)↗
PubMed1999

Awake aortic aneurysm repair in patients with severe pulmonary disease.

BACKGROUND: We report the use of retroperitoneal aortic aneurysm repair utilizing exclusive regional anesthesia (no intubation or inhalation anesthetic) in high pulmonary risk patients. METHODS: Six patients were retrospectively reviewed. Pulmonary disease was diagnosed by clinical history and pulmonary function tests. Patients received intravenous sedation and regional anesthesia. Retroperitoneal aortoiliac aneurysm repair was performed. RESULTS: All patients used inhaled steroids and albuterol. Three required theophylline and home oxygen. FEV1 = 23% +/- 5% predicted, FVC = 34% +/- 5% predicted, and PO2 = 62 +/- 2 mm Hg. Operative time was 247 +/- 25 minutes. Blood loss was 840 +/- 479 mL. Five of six patients (83%) tolerated awake aneurysm repair and had intensive care unit stays of 2.4 +/- 0.6 days, and postoperative hospital stays of 8.2 +/- 1.8 days. One patient was converted to general anesthesia and had a prolonged hospital stay. CONCLUSIONS: With thorough patient communication, awake retroperitoneal aortic aneurysm repair can be safely performed in select patients with severe pulmonary disease.

Administration, Inhalation↗
PubMed1999

An in vitro investigation into conformational aspects of gabapentin.

Conformational analysis of constrained cyclohexane systems was pioneered fifty years ago by Barton and Hassel. We now report an investigation based on a conformational analysis of a number of novel cyclohexane based Gabapentin analogues coupled with their in vitro evaluation at the Gabapentin binding site. These data are used to propose a possible binding conformation for Gabapentin.

Acetates↗
PubMed1999

Nonpeptidic HIV protease inhibitors possessing excellent antiviral activities and therapeutic indices. PD 178390: a lead HIV protease inhibitor.

With the insight generated by the availability of X-ray crystal structures of various 5,6-dihydropyran-2-ones bound to HIV PR, inhibitors possessing various alkyl groups at the 6-position of 5,6-dihydropyran-2-one ring were synthesized. The inhibitors possessing a 6-alkyl group exhibited superior antiviral activities when compared to 6-phenyl analogues. Antiviral efficacies were further improved upon introduction of a polar group (hydroxyl or amino) on the 4-position of the phenethyl moiety as well as the polar group (hydroxymethyl) on the 3-(tert-butyl-5-methyl-phenylthio) moiety. The polar substitution is also advantageous for decreasing toxicity, providing inhibitors with higher therapeutic indices. The best inhibitor among this series, (S)-6-[2-(4-aminophenyl)-ethyl]-(3-(2-tert-butyl-5-methyl-phenylsulfa nyl)-4-hydroxy-6-isopropyl-5,6-dihydro-pyran-2-one (34S), exhibited an EC50 of 200 nM with a therapeutic index of > 1000. More importantly, these non-peptidic inhibitors, 16S and 34S, appear to offer little cross-resistance to the currently marketed peptidomimetic PR inhibitors. The selected inhibitors tested in vitro against mutant HIV PR showed a very small increase in binding affinities relative to wild-type HIV PR. Cmax and absolute bioavailability of 34S were higher and half-life and time above EC95 were longer compared to 16S. Thus 34S, also known as PD 178390, which displays good antiviral efficacy, promising pharmacokinetic characteristics and favorable activity against mutant enzymes and CYP3A4, has been chosen for further preclinical evaluation.

Cell Line↗
PubMed1998

Potent bicyclic lactam inhibitors of thrombin: Part I: P3 modifications.

Peptidomimetic inhibitors of general structure 1 have been prepared. Optimization of the binding affinities of these compounds through variation of the P3 hydrophobic residue is described. Selected substituted bicylic lactams displayed interesting pharmacological profiles both in vitro and in vivo.

Animals↗