Biomedical subjects

P Russ

Publications and source records attributed to P Russ.

11 recordsLinked to original sources

PubMed2000

Interactions of conformationally biased north and south 2'-fluoro-2', 3'-dideoxynucleoside 5'-triphosphates with the active site of HIV-1 reverse transcriptase.

Molecular dynamics simulations of a ternary complex of HIV-1 reverse transcriptase (RT), double-stranded DNA, and bound dideoxynucleoside-5'-triphosphate (RT-DNA-ddNTP), utilizing the ddNTPs ddATP, betaFddATP, and alphaFddATP, explain the experimentally observed order of potency of these 5'-triphosphates as inhibitors of RT: ddATP > betaFddATP > alphaFddATP. On the basis of RT's known preference to bind the incoming dNTP (or ddNTP) with a north conformation at the polymerase site, alphaFddATP, which in solution prefers almost exclusively a north conformation, was predicted to be the most potent inhibitor. However, Tyr115, which appears to function as a steric gate to preclude the binding of ribonucleoside 5'-triphosphates, prevents the effective binding of alphaFddATP in its preferred north conformation. The south-biased betaFddATP, while able to bind to RT without hindrance by Tyr115, has to pay a high energy penalty to be flipped to the active north conformation at the polymerase site. Finally, the more flexible and less conformationally biased ddATP is able to switch to a north conformation at the RT site with a smaller energy penalty than betaFddATP. These results highlight the opposite conformational preferences of HIV-1 RT for alphaFddATP and betaFddATP and help establish conformational guidelines for optimal binding at the polymerase site of this enzyme.

Anti-HIV Agents↗

PubMed2000

Kinetics and crystal structure of the wild-type and the engineered Y101F mutant of Herpes simplex virus type 1 thymidine kinase interacting with (North)-methanocarba-thymidine.

Kinetic and crystallographic analyses of wild-type Herpes simplex virus type 1 thymidine kinase (TK(HSV1)) and its Y101F-mutant [TK(HSV1)(Y101F)] acting on the potent antiviral drug 2'-exo-methanocarba-thymidine (MCT) have been performed. The kinetic study reveals a 12-fold K(M) increase for thymidine processed with Y101F as compared to the wild-type TK(HSV1). Furthermore, MCT is a substrate for both wild-type and mutant TK(HSV1). Its binding affinity for TK(HSV1) and TK(HSV1)(Y101F), expressed as K(i), is 11 microM and 51 microM, respectively, whereas the K(i) for human cytosolic thymidine kinase is as high as 1.6 mM, rendering TK(HSV1) a selectivity filter for antiviral activity. Moreover, TK(HSV1)(Y101F) shows a decrease in the quotient of the catalytic efficiency (k(cat)/K(M)) of dT over MCT corresponding to an increased specificity for MCT when compared to the wild-type enzyme. Crystal structures of wild-type and mutant TK(HSV1) in complex with MCT have been determined to resolutions of 1.7 and 2.4 A, respectively. The thymine moiety of MCT binds like the base of dT while the conformationally restricted bicyclo[3.1.0]hexane, mimicking the sugar moiety, assumes a 2'-exo envelope conformation that is flatter than the one observed for the free compound. The hydrogen bond pattern around the sugar-like moiety differs from that of thymidine, revealing the importance of the rigid conformation of MCT with respect to hydrogen bonds. These findings make MCT a lead compound in the design of resistance-repellent drugs for antiviral therapy, and mutant Y101F, in combination with MCT, opens new possibilities for gene therapy.

Amino Acid Substitution↗

PubMed2000

Synthesis, biological activity, and molecular modeling of ribose-modified deoxyadenosine bisphosphate analogues as P2Y(1) receptor ligands.

The structure-activity relationships of adenosine-3', 5'-bisphosphates as P2Y(1) receptor antagonists have been explored, revealing the potency-enhancing effects of the N(6)-methyl group and the ability to substitute the ribose moiety (Nandanan et al. J. Med. Chem. 1999, 42, 1625-1638). We have introduced constrained carbocyclic rings (to explore the role of sugar puckering), non-glycosyl bonds to the adenine moiety, and a phosphate group shift. The biological activity of each analogue at P2Y(1) receptors was characterized by measuring its capacity to stimulate phospholipase C in turkey erythrocyte membranes (agonist effect) and to inhibit its stimulation elicited by 30 nM 2-methylthioadenosine-5'-diphosphate (antagonist effect). Addition of the N(6)-methyl group in several cases converted pure agonists to antagonists. A carbocyclic N(6)-methyl-2'-deoxyadenosine bisphosphate analogue was a pure P2Y(1) receptor antagonist and equipotent to the ribose analogue (MRS 2179). In the series of ring-constrained methanocarba derivatives where a fused cyclopropane moiety constrained the pseudosugar ring of the nucleoside to either a Northern (N) or Southern (S) conformation, as defined in the pseudorotational cycle, the 6-NH(2) (N)-analogue was a pure agonist of EC(50) 155 nM and 86-fold more potent than the corresponding (S)-isomer. The 2-chloro-N(6)-methyl-(N)-methanocarba analogue was an antagonist of IC(50) 51.6 nM. Thus, the ribose ring (N)-conformation appeared to be favored in recognition at P2Y(1) receptors. A cyclobutyl analogue was an antagonist with IC(50) of 805 nM, while morpholine ring-containing analogues were nearly inactive. Anhydrohexitol ring-modified bisphosphate derivatives displayed micromolar potency as agonists (6-NH(2)) or antagonists (N(6)-methyl). A molecular model of the energy-minimized structures of the potent antagonists suggested that the two phosphate groups may occupy common regions. The (N)- and (S)-methanocarba agonist analogues were docked into the putative binding site of the previously reported P2Y(1) receptor model.

Animals↗

PubMed2000

Acute pancreatitis during immunosuppression with tacrolimus following an allogeneic umbilical cord blood transplantation.

Tacrolimus is increasingly used for graft-versus-host disease (GVHD) prophylaxis and therapy in the allogeneic stem cell transplant (allo-SCT) setting. Pancreatitis, previously described as a side-effect of cyclosporine, has not been reported in allo-SCT recipients receiving tacrolimus. We present here a case of acute pancreatitis in a 28-year-old patient with chronic myelogenous leukemia (CML) who received an unrelated umbilical cord blood transplant (UCBT) and tacrolimus for GVHD prophylaxis. On day +31 post-transplant, she developed severe acute pancreatitis with multiorgan failure, from which she recovered completely. Tacrolimus was the probable cause of pancreatitis in this patient.

Adult↗

PubMed1998

Percutaneous mesenteric venous thrombectomy and thrombolysis: successful treatment followed by liver transplantation.

Mesenteric vein thrombosis (MVT) is a rare cause of intestinal ischemia. Because of its nonspecific symptoms, diagnosis is often delayed. We describe a patient with liver cirrhosis who developed acute MVT while waiting for liver transplantation. Surgical intervention carried a high risk because of her underlying cirrhosis. Mesenteric venous thrombectomy and thrombolysis were performed with an AngioJet (Possis Medical, Minneapolis, MN) thrombectomy device and streptokinase infusion through transjugular route. The patient subsequently received an orthotopic liver transplant. We also present a review of the literature about the occurrence and treatment options for MVT.

Aged↗

PubMed1997

Postmenopausal estrogen therapy selectively stimulates hepatic enlargement in women with autosomal dominant polycystic kidney disease.

The goal of this study was to determine whether use of postmenopausal estrogen (Premarin, Wyeth-Ayerst, Philadelphia, PA) in women with autosomal dominant polycystic kidney disease (ADPKD) increases liver, hepatic cyst, or kidney volume. We also determined whether clinical symptoms correlated with the volume of either the liver or kidneys. Eight women off estrogen (control, C) and 11 others on estrogen (Premarin, E) were studied basally and after 1 year. The two groups were similar in age, weight, age at menarche, and gravida. Volumes of total liver, hepatic cysts, hepatic parenchyma, and total kidney were measured by a validated computed tomography (CT) technique. Estrogen treatment was associated with a selective increase in total liver volume (E vs. C: delta = 7% +/- 12% vs. -2% +/- 8%, P < .03) and no change in kidney volume (E vs. C: delta = 0% +/- 6% vs. -2% +/- 6%, P = NS). Symptoms were common, regardless of estrogen treatment (abdominal pain 60%, shortness of breath 40%, or both 35%). Patients with symptoms of abdominal pain and shortness of breath had significantly increased hepatic volumes (P < .03) but similar kidney volume compared with patients without symptoms. We conclude that estrogen treatment of postmenopausal ADPKD women is associated with selective liver enlargement and that abdominal symptoms in ADPKD patients may be because of extensive hepatic cystic disease.

Antipyrine↗

PubMed1996

Nucleosides with a twist. Can fixed forms of sugar ring pucker influence biological activity in nucleosides and oligonucleotides?

The sugar moiety of nucleosides in solution is known to exist in a rapid dynamic equilibrium between extreme Northern and Southern conformations as defined in the pseudorotational cycle. In the present work, we describe how the bicyclo[3.1.0]hexane template fixes the ring pucker of 2'-deoxy-methanocarba-nucleosides 1-5 and 12 to values corresponding to either one of these two extreme conformations that are typical of nucleosides. The syntheses of the fixed Northern conformers 1-5 were performed by Mitsunobu coupling of the heterocyclic bases with the chiral carbocyclic alcohol 6 [(1R,2S,4R,5S)-1-[(benzyloxy)methyl]-2-(tert-butyloxy)-4-hydrox ybicyclo[3.1.0]hexane], while the synthesis of the Southern conformer, (S)-methanocarba-T (12), was reported earlier. Carbocyclic thymidine (carba-T, 13) was used as a reference, flexible carbocyclic nucleoside. Antiviral evaluation of these compounds revealed a very potent antiherpetic activity associated with the Northern thymidine analogue 2, which was more powerful than the reference standard acyclovir against both HSV-1 and HSV-2. (N)-Methanocarba-T (2) was further evaluated as a component of a short oligodeoxynucleotide (ODN) phosphorothioate (5'-CTTCATTTTTTCTTC-3') where all thymidines were replaced by 2. The expected thermodynamic stability resulting from the preorganization of the pseudosugar rings into a Northern conformation, typical of A-DNA, was evident by the increase in Tm of the corresponding DNA/RNA heteroduplex. However, the rigid A-tract ODN caused loss of RNase H recruitment. A detailed conformational analysis of (N)-methanocarba-T (2) and (S)-methanocarba-T (12), as representative examples of conformationally rigid pseudorotational antipodes, revealed that in addition to their different forms of ring pucker, (S)-methanocarba-T appears to be a rather stiff molecule with fewer low-energy conformational states available compared to (N)-methanocarba-T. The syn/anti-energy barrier for these nucleoside analogues is 5-6 kcal/mol higher than for common nucleosides.

Acyclovir↗

PubMed1996

Cavernous lymphangioma presenting as a vaginal discharge in a six-year-old female: a case report.

STUDY OBJECTIVE: This case report is written to describe a new and unusual presentation of retroperitoneal cavernous lymphangioma. INTERVENTIONS: A large cystic abdominal mass was discovered during an examination under anesthesia to evaluate a vaginal discharge in a 6-year-old girl. The mass was diagnosed by computed tomography (CT) and removed via laparotomy with argon beam coagulation of smaller cystic lesions. RESULTS: Six months postoperatively, the patient had a negligible amount of vaginal discharge. CONCLUSIONS: Cavernous lymphangioma should be considered as a rare cause of vaginal discharge in young females.

Biopsy↗

PubMed1976

Synthesis, structure determination, spectral properties, and energy-linked spectral responses of the extrinsic probe oxonol V in membranes.

The direct synthesis of bis]3-phenyl-5-oxoisoxazol-4-yl]pentamethineoxonol, which is shown to be the fluorescent probe OX-V (formerly MC-V), is described. The emission lifetime (0.9 +/- 0.1 ns) and the spectral properties of this dye in a number of systems are presented as well as the relative polarizations associated with the transition moments of the observable electronic transitions. The structure of OX-V was determined using elemental analysis and infrared and 1H nuclear magnetic resonance (NMR) spectroscopy. The use of the contact shift reagent, Eu(fod)3-d27, greatly facilitated the interpretation of the NMR results. In aqueous media, the anionic form of OX-V is present virtually exclusively due to the low solubility of the neutral species; formation of the latter species occurs when ethanol or methanol solutions of OX-V are acidiied. Both neutral and anionic dye forms can be detected in chloroform-ethanol solvents. The fluorescence intensity from excitation of the neutral species is an order of magnitude weaker than that from excitation of the anionic form and may result from the formation of excited anions due to the loss of a proton by the neutral species in the excited state. Polarization results indicate that the visible absorption of the dye is due to a single electronic transition. OX-V has been employed as a probe primarily in beef heart submitochondrial particles, reconstituted ATPase vesicles,a nd pigeon heart mitochondria. The energy-linked spectral changes of the probe in these preparations are described and mechanisms proposed for the spectral effects.

Animals↗

PubMedDate not supplied

Conformationally restricted nucleosides. The reaction of adenosine deaminase with substrates built on a bicyclo[3.1.0]hexane template.

Adenosine deaminase (ADA) can discriminate between two distinct (North and South), conformationally rigid substrate conformers. (N)-methanocarba-2'dA (4) is deaminated 100 times faster than the antipodal (S)-methanocarba-2'dA (5), whereas a non-rigid analogue, aristeromycin (6), is deaminated at an intermediate rate. These results are in agreement with crystallographic data from ADA-ribonucleoside complexes showing the furanose ring of the bound purine in a C3'-endo (North) conformation. The data presented here suggests that 4 and 5 are useful probes to ascertain conformational preferences by purine metabolizing enzymes.

Adenosine Deaminase↗

PubMedDate not supplied

Detecting i.v. infiltrations using a Venoscope.

This research evaluates the Venoscope for its ability to detect infiltrations when present (sensitivity) and to detect the absence of infiltrations when not present (specificity), and compares these findings with those obtained via ultrasonography. Health adult volunteers were randomly assigned to receive or not receive an intentionally made 5-ml normal-saline infiltration. The Venoscope had a sensitivity of .92-.93 and a specificity of .89-1.0. Ultrasound had a sensitivity of .92-.93 and a specificity of .22-.25. The Venoscope, which is simple and easy to use, is a valid indicator of the presence and absence of i.v. infiltrations.

Adolescent↗