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R Shapiro

Publications and source records attributed to R Shapiro.

At least 19 recordsLinked to original sources
PubMed1997

Site-specific mutagenesis reveals differences in the structural bases for tight binding of RNase inhibitor to angiogenin and RNase A.

RNase inhibitor (RI) binds with extraordinary affinity (Ki approximately 10(-13)-10(-16) M) to diverse proteins in the pancreatic RNase superfamily. In the present study, the structural basis for the recognition of two RI ligands, human angiogenin (Ang) and bovine RNase A, has been investigated by site-specific mutagenesis of human RI and Ang. The RI residues examined were those that appear to form strong contacts with RNase A in the crystal structure of the porcine RI x RNase A complex [Kobe, B. & Deisenhofer, J. (1995) Nature (London) 374, 183-186] that would not be replicated in the Ang complex. Ala substitutions of five of these residues (Glu-287, Lys-320, Glu-401, Cys-408, and Arg-457) were found to have little or no effect on binding of RNase A. In contrast, replacements of Tyr-434, Asp-435, and Tyr-437 and deletion of the C-terminal residue Ser-460 substantially weakened affinity for RNase A: the losses of binding energy associated with the mutations were 5.9, 3.6, 2.6, and 3.5 kcal/mol, respectively. Thus these four residues, which are neighbors in the tertiary structure, appear to constitute a "hot spot" for the RNase A interaction. However, only one of them, Asp-435, was equally important for binding of Ang; the Ki increases produced by mutations of the others were 20- to 93-fold smaller for Ang than for RNase A. Consequently, Tyr-434 plays a significant but lesser role in the Ang complex, whereas Tyr-437 and Ser-460 make only minor contributions. Ala mutations of four Ang residues (His-8, Gln-12, Asn-68, and Glu-108) that correspond to RI contacts on RNase A produced no major changes in affinity for RI. These findings indicate that RI uses largely different interactions to achieve its extremely tight binding of RNase A and Ang.

Animals↗
PubMed1997

Tacrolimus rescue therapy for renal allograft rejection--five-year experience.

Over the 5 year period from 7/14/1989 until 5/24/1994, we have attempted graft salvage with tacrolimus conversion in a total of 169 patients (median age 33 years, range 2-75 years) with ongoing rejection on baseline CsA immunosuppression after failure of high dose corticosteroids and/or antilymphocyte preparations to reverse rejection. The indications for conversion to tacrolimus were ongoing, biopsy confirmed rejection in all patients. The median interval to tacrolimus conversion was 2 months (range 2 days to 55 months; mean 4.3+/-2.6 months) after transplantation. All patients had failed high dose corticosteroid therapy and 144 (85%) of the 169 patients had received at least one course of an antilymphocyte preparation plus high dose corticosteroid therapy prior to conversion. Twenty-eight patients (17%) were dialysis-dependent at the time of conversion owing to the severity of rejection. With a mean follow-up of 30.0+/-2.4 months (median 36.5 months, range 12-62 months), 125 of 169 patients (74%) have been successfully rescued and still have functioning grafts with a mean serum creatinine (SCR) of 2.3+/-1.1 mg/dl. Of the 144 patients previously treated with antilymphocyte preparations, 117 (81%) were salvaged. Of the 28 patients on dialysis at the time of conversion to tacrolimus, 13 (46%) continue to have functioning grafts (mean SCR 2.15+/-0.37 mg/dl) at a mean follow-up of 37.3+/-16.7 months. In the 125 patients salvaged, prednisone doses have been lowered from 28.0+/-9.0 mg/d (median 32, range 4-60 mg/d) preconversion to 8.5+/-4.1 mg/d (median 12 mg/d, range 2.5-20 mg/d) postconversion. Twenty-eight patients (22.4%) are currently receiving no steroids. This 5 year experience demonstrates that tacrolimus has sustained efficacy as a rescue agent for ongoing renal allograft rejection. Based on these data, we recommend that tacrolimus be used as an alternative to the conventional drugs used for antirejection therapy in renal transplantation.

Adolescent↗
PubMed1997

Word-stem completion priming for perceptually and conceptually encoded words in patients with Alzheimer's disease.

This study examined whether the frequently reported word-stem completion priming deficit of Alzheimer's disease (AD) patients could be characterized as either a semantic encoding deficit or a conceptual priming deficit. AD patients and normal elderly control subjects studied words in two conditions: (1) reading visually presented words aloud, which maximizes perceptual encoding of seen words, and (2) generating words aloud from definitions, which maximizes conceptual encoding of words not seen but retrieved on the basis of semantic context. Recognition accuracy was greater for words that were generated at study, and word-stem completion priming was greater for words that were read at study. For the AD patients, recognition accuracy was impaired and word-stem completion priming was intact for words encoded in both conditions. The findings are discussed in terms of discrepant results about word-stem completion priming in AD.

Aged↗
PubMed1997

Acquired von Willebrand disease in a patient with angiodysplasia resulting from immune-mediated clearance of von Willebrand factor.

A patient with a severe bleeding tendency due to acquired von Willebrand disease (VWD) is presented. Although no underlying disorder has emerged during 6 years of follow-up, an immune-mediated mechanism was responsible for acquired VWD in this patient as demonstrated by detection of von Willebrand factor (VWF)/anti-VWF complexes in the patient's plasma and their removal by protein A-sepharose beads and resumption of normal haemostasis with correction of VWF antigen, VWF activity and VWF multimeric pattern after treatment of the patient with high-dose gammaglobulin. Detection of anti-VWF antibodies in the patient's plasma had a significant impact on the choice of therapeutic intervention to control bleeding.

Angiodysplasia↗
PubMed1997

The effect of quadriceps femoris, hamstring, and placebo eccentric fatigue on knee and ankle dynamics during crossover cutting.

This study attempted to determine the effect of eccentric quadriceps femoris, hamstring, and placebo fatigue on stance limb dynamics during the plant-and-cut phase of a crossover cut. Twenty female college students (task trained) were tested. Hamstring fatigue resulted in decreased peak impact knee flexion moments (p < or = .01), increased internal tibial rotation at peak knee flexion (p < or = .05), and decreased peak ankle dorisflexion (p < or = .05). Quadriceps fatigue resulted in increased peak ankle dorsiflexion moments (p < .01), decreased peak posterior braking forces (p < or .01), decreased peak knee extension moments (p < or = .01), delayed peak knee flexion (p < or = .01), delayed peak propulsive forces (p < .01), and delayed subtalar peak inversion moments (p < or = .05). Fatigue of either muscle group produced earlier peak ankle plantar flexion moments (p < = .05) and decreased peak propulsive knee flexion moments (p < or = .05). Variables requiring further study (p < or = .1) provide discussion data. Soleus, gastrocnemius, tibialis anterior, and deep posterior compartment calf muscles serve as dynamic impact force attenuators, compensating for fatigued proximal muscles.

Adult↗
PubMed1996

Tacrolimus in pediatric renal transplantation.

Tacrolimus was used as the primary immunosuppressive agent in 69 pediatric renal transplantations between December 17, 1989, and June 30, 1995. Children undergoing concomitant or prior liver and/or intestinal transplantation were excluded from analysis. The mean recipient age was 10.3+/-5.0 years (range, 0.7-17.5 years). Seventeen (24.6%) children were undergoing retransplantation, and six (8.7%) had a panel reactive antibody level of 40% or higher. Thirty-nine (57%) cases were with cadaveric kidneys, and 30 (43%) were with living donors. The mean donor age was 28.0+/-14.7 years (range, 1.0-50.0 years), and the mean cold ischemia time for the cadaveric kidneys was 27.0+/-9.4 hr. The antigen match was 2.7+/-1.2, and the mismatch was 3.1+/-1.2. All patients received tacrolimus and steroids, without antibody induction, and 26% received azathioprine as well. The mean follow-up was 32+/-20 months. One- and 4-year actuarial patient survival rates were 100% and 95%. One- and 4-year actuarial graft survival rates were 99% and 85%. The mean serum creatinine level was 1.2+/-0.8 mg/dl, and the calculated creatinine clearance was 82+/-26 ml/min/1.73 m2. The mean tacrolimus dose was 0.22+/-0.14 mg/ kg/day, and the level was 9.5+/-4.8 ng/ml. The mean prednisone dose was 2.1+/-4.9 mg/day (0.07+/-0.17 mg/kg/day), and 73% of successfully transplanted children were off prednisone. Seventy-nine percent were not taking any antihypertensive medications. The mean serum cholesterol level was 158+/-54 mg/dl. The incidence of delayed graft function was 4.3%. The incidence of rejection was 49%, and the incidence of steroid-resistant rejection was 6%. The incidence of rejection decreased to 27% in the most recent 26 cases (January 1994 through June 1995). The incidence of new-onset diabetes was 10.1%; six of the seven affected children were able to be weaned off insulin. The incidence of cytomegalovirus disease was 13%, and that of posttransplant lymphoproliferative disorder was 10%; the incidence of posttransplant lymphoproliferative disorder in the last 40 transplants was 5% (two cases). All of the children who developed posttransplant lymphoproliferative disorder are alive and have functioning allografts. Based on this data, we believe that tacrolimus is a superior immunosuppressive agent in pediatric renal transplant patients, with excellent short- and medium-term patient and graft survival, an ability to withdraw steroids in the majority of patients, and, with more experience, a decreasing rate of rejection and viral complications.

Adolescent↗
PubMed1996

"Suboptimal" kidney donors: the experience with tacrolimus-based immunosuppression.

Female, pediatric, and older donors have been associated with inferior graft survival after renal transplantation. We analyzed these three subgroups in 397 patients receiving tacrolimus-based immunosuppression. There were no differences in recipient age, incidence of retransplantation, or percentage of sensitized patients. Female donors, compared with male donors, were associated with comparable 1- and 3-year patient survival rates (96% and 93% vs. 95% and 92%, respectively) and comparable 1- and 3-year graft survival rates (90% and 80% vs. 88% and 81%, respectively). Renal function was also similar. Recipients of pediatric en bloc kidneys, when compared with recipients of other cadaveric kidneys, also had comparable 1- and 3-year patient survival rates (94% and 94% vs. 95% and 91%, respectively) and comparable 1- and 3-year graft survival rates (84% and 84% vs. 89% and 79%, respectively). Renal function was better in recipients of en bloc kidneys, with a mean serum creatinine level of 1.4+/-1.8 mg/dl vs. 2.0+/-1.5 mg/dl (P=0.01). In contrast to the first two subgroups, donors over 60 years of age, when compared with donors under 60 years of age, were associated with worse 1- and 3-year patient survival rates (88% and 80% vs. 96% and 94%, respectively; P<0.03) and worse 1- and 3-year graft survival rates (74% and 62% vs. 91% and 83%, respectively; P<0.0001). Renal function was worse in the older donor group, with a serum creatinine level of 2.7+/-1.2 mg/ml vs. 1.9+/-1.5 mg/dl (P=0.01). We conclude that, under tacrolimus-based immunosuppression, kidneys from female or very young pediatric donors are not associated with adverse outcomes, whereas kidneys from donors over 60 years of age are associated with inferior outcomes.

Adult↗
PubMed1996

The effect of legislative requirements on the use of breast-conserving surgery.

BACKGROUND: We studied the effect of state legislation requiring the disclosure of options for the treatment of breast cancer on the use of breast-conserving surgery in clinical practice. METHODS: The National Cancer Institute's Surveillance, Epidemiology, and End Results registry provided data on women from 30 through 79 years of age who underwent breast-conserving surgery or mastectomy for local or regional breast cancer from 1983 through 1990. We examined the trend over time in use of breast-conserving surgery among patients in four sites (Connecticut, Iowa, Seattle, and Utah) where there were no state laws specifically requiring the disclosure of options for the treatment of breast cancer by physicians. For four additional sites (Detroit, Atlanta, New Mexico, and Hawaii) that had such legislation, we determined whether the rate of breast-conserving surgery after the legislation was different from the expected rate. RESULTS: An attorney rated the legislation as giving most direction to physicians in Michigan, followed by Hawaii, Georgia, and New Mexico. The rate of breast-conserving surgery was up to 8.7 percent higher than expected in Detroit for six months after the passage of the Michigan law (P<0.01). The rate was up to 13.2 percent higher than expected in Hawaii for 12 months after that state's law was passed (P<0.05) and up to 6.0 percent higher than expected in Atlanta for 3 months after the passage of the Georgia law (P<0.01). After these transient increases, the surgery rates reverted to the expected levels. No significant effect was detected in New Mexico, where only a resolution without legal force was passed. CONCLUSION: Legislation requiring physicians to disclose options for the treatment of breast cancer appeared to have only a slight and transient effect on the rate of use of breast-conserving surgery.

Adult↗
PubMed1996

Characterization of mouse angiogenin-related protein: implications for functional studies on angiogenin.

Angiogenin-related protein (Angrp), the putative product of a recently discovered mouse gene, shares 78% sequence identity with mouse angiogenin (Ang). In the present study, the relationship of Angrp to Ang has been investigated by producing both proteins in bacteria and comparing their functional properties. We find that mouse Ang is potently angiogenic, but Angrp is not, even when assayed at relatively high doses. A deficiency in catalytic capacity, which is essential for the biological activity of Ang, does not appear to underlie Angrp's lack of angiogenicity. In fact, Angrp has somewhat greater ribonucleolytic activity toward tRNA and dinucleotide substrates than does Ang. Instead, an inability to bind cellular receptors is implicated since Angrp does not inhibit Ang-induced angiogenesis. Poor conservation of the Ang receptor recognition sequence 58-69 in Angrp most likely contributes to this defect. However, other substitutions must also influence receptor binding since an Angrp quadruple mutant that is identical to Ang in this segment still lacks both angiogenic activity and the capacity to inhibit Ang. The functional differences between Ang and Angrp, together with evidence presented herein that Angrp is regulated differently than Ang, suggest that the roles of the two proteins in vivo may be quite distinct.

Animals↗
PubMed1996

A combined kinetic and modeling study of the catalytic center subsites of human angiogenin.

Kinetic analysis and molecular modeling have been used to map the ribonucleolytic center of angiogenin (Ang). Pyrimidine nucleotides were found to interact very weakly with Ang, consistent with the inaccessible B1 pyrimidine binding site revealed by x-ray crystallography. Ang also lacks an effective phosphate binding site on the 5' side of B1. Although the B2 site that preferentially binds purines on the 3' side of B1 is also weak, its associated phosphate subsites make substantial contributions: both 3',5'-ADP and 5'-ADP have Ki values 6-fold lower than for 5'-AMP, and adding a 3'-phosphate to the substrate CpA increases Kcat/Km by 9-fold. Thus Ang has a functional P2 site on the 3' side of B2 and a site for a second phosphate on the 5' side of B2. Modeling of an Ang-d(ApTpApA) complex suggested that Arg-5 forms part of the P2 site and that a 2'-phosphate might bind more tightly than a 3'-phosphate. Both predictions were confirmed kinetically. The subsite map obtained by this combined approach indicated that 5'-diphosphoadenosine 2'-phosphate might be a more potent inhibitor than any of the nucleotides tested thus far. Indeed, its Ki value of 150 microM is 50-fold lower than that for the best nucleotide previously reported and 400-fold lower than the Km for the best dinucleotide substrate. This compound may serve as a suitable starting point for the eventual design of tight-binding inhibitors of Ang as antiangiogenic agents for human therapy.

Adenosine Diphosphate↗
PubMed1996

The use of tacrolimus in renal transplantation.

Tacrolimus (FK 506) is a novel immunosuppressive agent that has been in clinical use for solid organ transplantation since 1989. Early clinical trials of tacrolimus in liver, heart, kidney, lung, and intestinal transplantation at the University of Pittsburgh have demonstrated it to be a safe and effective agent with several potential advantages over existing immunosuppressive drugs. More recently, phase I and II multicenter trials of tacrolimus for renal transplantation have been performed; however, data are not yet available from these trials. Our experience with this drug has demonstrated excellent 1- and 2-year actuarial graft survival rates of 89% and 83%, respectively, in adult renal transplantation and 1- and 3-year graft survival rates of 98% and 85%, respectively in pediatric renal transplantation. A major advantage of tacrolimus noted in these trials was the ability to discontinue steroid therapy in approximately 50% of the patients. Tacrolimus has also shown efficacy as a rescue agent for renal allograft rejection failing conventional therapy in 74% of cases. This paper expands on these observations and focuses on the experience we have gained with the use of tacrolimus at our institution over the last 6 years.

Graft Survival↗
PubMed1996

Cryoablation of unresectable malignant liver tumors.

BACKGROUND: Unresectable malignant liver tumors, particularly metastases of gastrointestinal origin, are rapidly lethal in a vast majority of patients, regardless of treatment. PATIENTS AND METHODS: We evaluated 58 patients by laparoscopy and/or laparotomy. Thirty-nine were treated with cryoablation of liver tumors using a liquid-nitrogen cryoprobe delivering a tumoricidal temperature of -196 degrees C with intraoperative ultrasound monitoring. Histologic evaluation showed that 25 patients had colorectal metastases, 3 had gastric tumors, 4 hepatocellular carcinomas, 6 carcinoids, and 1 gastrinoma. RESULTS: All patients who received complete cryoablation are alive with a mean follow-up of 14 months. Five whose treatment could not be completed died between 3 and 9 months postoperatively. Thirteen patients (28%) have recurrent disease and 20 (51%) have no evidence of disease. There were no operative mortalities. Postoperative transient elevation of liver function tests and thrombocytopenia were noted. All patients received postoperative chemotherapy. CONCLUSION: Cryoablation is an active and safe treatment for advanced liver malignancies.

Adult↗
PubMed1996

Delayed expansion of V delta 2+ and V delta 1+ gamma delta T cells after acute Plasmodium falciparum and Plasmodium vivax malaria.

T lymphocytes that express T-cell receptors encoded by the gamma and delta T-cell receptor genes (gamma delta T cells), and preferentially those expressing the V gamma 9 and V delta 2 gene segments, are activated by microbial and parasitic organisms in vitro and have been implicated in the pathogenesis of the fever and rigors during acute malaria. We have found, in a cohort of nine nonimmune patients who contracted malaria during travel to endemic areas (five with Plasmodium falciparum and four with P. vivax infections) that gamma delta T lymphocytes expanded to comprise 17.92% +/- 11% of the peripheral blood mononuclear cells (vs 3.08% +/- 2.4% gamma delta cells in normal control subjects). Although V delta 2+ cells predominated among the gamma delta subset, gamma delta lymphocytes expressing the V delta 1 gene segment also expanded significantly in some patients. Importantly, the gamma delta cells continued to expand for 2 months after the infection, and the mean level of gamma delta cells peaked during the second month after the acute clinical syndrome, when patients were free of symptoms. Thus although gamma delta T cells may contribute to the pathogenesis of the acute clinical syndrome, our findings suggest that gamma delta lymphocytes could also play a role in generating an immune response to plasmodia.

Acute Disease↗
PubMed1996

Adjuncts to mechanical ventilation.

Adjunctive ventilatory strategies have been developed to improve oxygenation and carbon dioxide (CO2) removal during mechanical ventilation of critically ill patients. These techniques allow clinicians to attain their clinical goals at lower levels of ventilatory support. In this article, the authors discuss extracorporeal CO2 removal, venovenous intravena caval oxygenator, and tracheal gas insufflation as adjuncts to CO2 removal and nitric oxide, surfactant replacement therapy, perfluorocarbon-associated gas exchange, and prone positioning as adjuncts to oxygenation.

Animals↗
PubMed1996

Solution properties and computational analysis of an oligodeoxynucleotide containing N-(deoxyguanosin-8-yl)-1-aminopyrene.

An oligodeoxyribonucleotide 5'-d(CTCATGAPATTCC), in which G(AP) denotes N-(guanin-8-yl)-1-aminopyrene, the C8-guanine adduct of reductively activated 1-nitropyrene, was synthesized and characterized by polyacrylamide gel electrophoresis, absorption and fluorescence spectroscopy, circular dichroism, and thermal melting studies. Polyacrylamide gel electrophoresis showed slower mobility of the adducted oligonucleotide in single-stranded form compared to its unmodified counterpart, as expected. In duplex form, however (with a deoxycytidine opposite the adduct), the adducted 11mer migrated faster than the parent duplex. Absorption and fluorescence studies indicated significant interaction of the aminopyrene residue with the DNA bases in the modified 11mer. The spectroscopic data also suggested the presence of one or more conformers in which the aminopyrene residue is quasi-intercalative, as well as one(s) in which the aminopyrene is externally bound. Thermodynamic parameters for the helix-to-coil transitions for the 11mer duplex were determined. The difference in free energy (delta delta G degree) between the unmodified and modified sequences was relatively small (approximately 1.2 kcal/mol). Circular dichroism spectra indicated the presence of essentially B-form DNA. The energy minimizations suggested that the most stable conformers shared a common feature: displacement of the modified guanine from the double helix. In the global minimum, the aminopyrene residue was inserted in the helix in the site of displaced guanine. In other low energy structures, the aminopyrene was also displaced towards the minor groove (in addition to guanine), or partly inserted and partly in the groove. More conventional structures were also encountered, with anti-guanine within the helix and aminopyrene in the major groove, or syn-guanine within the helix, and aminopyrene in the minor groove. Such structures were 12-20 kcal/mol less stable than the global minimum, however. The C8-guanine adduct of aminopyrene thus appears to perturb the B-DNA structure to a greater extent than do the adducts of less bulky amines such as aminofluorene and 4-aminobiphenyl.

Base Sequence↗