PubMed Health⌕ Search

Biomedical subjects

J A Ryan

Publications and source records attributed to J A Ryan.

At least 19 recordsLinked to original sources
PubMed1992

Nature of the interaction of growth factors with suramin.

Suramin inhibits the binding of a variety of growth factors to their cell surface receptors. The direct interaction of suramin with acidic fibroblast growth factor has been detected by the enhancement of the drug's fluorescence in the presence of the protein with the maximum effect occurring at a molar ratio of suramin to aFGF of 2:1. This interaction stabilizes aFGF to thermal denaturation and partially protects a free thiol in its polyanion binding site from oxidation. The binding of suramin to aFGF also induces aggregation of the growth factor to at least a hexameric state as detected by static and dynamic light scattering as well as by gel filtration studies. Both CD and amide I' FTIR spectra of aFGF in the presence and absence of suramin suggest that the drug may also be causing a small conformational change in the growth factor. Suramin produces an even greater aggregation of bFGF and PDGF but not of EGF or IGF-1. Evidence for a suramin-induced conformational change in IGF-1 but not EGF is found by CD, however. It is concluded that suramin binds to many growth factors and that this induces microaggregation and, in some cases, conformational changes. In the case of aFGF, suramin interacts at or near its heparin binding site. The relationship between these phenomena and the anti-growth factor activity of suramin remains to be clearly elucidated.

3T3 Cells↗
PubMed1992

Structural implications of spectroscopic characterization of a putative zinc finger peptide from HIV-1 integrase.

The N-terminal domain of human immunodeficiency virus (HIV-1) integrase (IN) contains the sequence motif His-Xaa3-His-Xaa23-Cys-Xaa2-Cys, which is strongly conserved in all retroviral and retrotransposon IN proteins. This structural motif constitutes a putative zinc finger in which a metal ion may be coordinately bound by the His and Cys residues. A recombinant peptide, IN(1-55), composed of the N-terminal 55 amino acids of HIV-1 IN was expressed in Escherichia coli and purified. Utilizing a combination of techniques including UV-visible absorption, circular dichroism, Fourier transform infrared, and fluorescence spectroscopies, we have demonstrated that metal ions (Zn2+, Co2+, and Cd2+) are bound with equimolar stoichiometry by IN(1-55). The liganded peptide assumes a highly ordered structure with increased alpha-helical content and exhibits remarkable thermal stability. UV-visible difference spectra of the peptide-Co2+ complexes directly implicate thiols in metal coordination, and Co2+ d-d transitions in the visible range indicate that Co2+ is tetrahedrally coordinated. Mutant peptides containing conservative substitutions of one of the conserved His or either of the Cys residues displayed no significant Zn(2+)-induced conformational changes as monitored by CD and fluorescence spectra. We conclude that the N terminus of HIV-1 IN contains a metal-binding domain whose structure is stabilized by tetrahedral coordination of metal by histidines 12 and 16 and cysteines 40 and 43. A preliminary structural model for this zinc finger is presented.

Amino Acid Sequence↗
PubMed1991

Stabilization of the FK506 binding protein by ligand binding.

Although the rotamase activity of the FK506 binding protein is inhibited by ligand binding, it is hypothesized that the ligand/protein complex itself may be responsible for the immunosuppressive effects of FK506. We have therefore examined the structure of the FK506 binding protein in the presence of an analog of FK506 (FK520) by a combination of fluorescence, CD, FTIR and calorimetry. While only small changes in the overall structure of the protein may be induced by ligand, a large change in thermal stability of the binding protein is observed.

Anti-Bacterial Agents↗
PubMed1991

The structure of human acidic fibroblast growth factor and its interaction with heparin.

The secondary and tertiary structure of recombinant human acidic fibroblast growth factor (aFGF) has been characterized by a variety of spectroscopic methods. Native aFGF consists of ca. 55% beta-sheet, 20% turn, 10% alpha-helix, and 15% disordered polypeptide as determined by laser Raman, circular dichroism, and Fourier transform infrared spectroscopy; the experimentally determined secondary structure content is in agreement with that calculated by the semi-empirical methods of Chou and Fasman (Chou, P. Y., and Fasman, G. C., 1974, Biochemistry 13, 222-244) and Garnier et al. (Garnier, J. O., et al., 1978, J. Mol. Biol. 120, 97-120). Using the Garnier et al. algorithm, the major secondary structure components of aFGF have been assigned to specific regions of the polypeptide chain. The fluorescence spectrum of native aFGF is unusual in that it is dominated by tyrosine fluorescence despite the presence of a tryptophan residue in the protein. However, tryptophan fluorescence is resolved upon excitation above 295 nm. The degree of tyrosine and tryptophan solvent exposure has been assessed by a combination of ultraviolet absorption, laser Raman, and fluorescence spectroscopy; the results suggest that seven of the eight tyrosine residues are solvent exposed while the single tryptophan is partially inaccessible to solvent in native aFGF, consistent with recent crystallographic data. Denaturation of aFGF by extremes of temperature or pH leads to spectroscopically distinct conformational states in which contributions of tyrosine and tryptophan to the fluorescence spectrum of the protein vary. The protein is unstable at physiological temperatures. Addition of heparin or other sulfated polysaccharides does not affect the spectroscopic characteristics of native aFGF. These polymers do, however, dramatically stabilize the native protein against thermal and acid denaturation as determined by differential scanning calorimetry, circular dichroism, and fluorescence spectroscopy. The interaction of aFGF with such polyanions may play a role in controlling the activity of this growth factor in vivo.

Algorithms↗
PubMed1991

Dioxin induces transforming growth factor-alpha in human keratinocytes.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a widespread environmental toxicant, is a tumor promoter that induces hyperplasia in epithelial cells. Exposure of cultured human keratinocytes to TCDD, resulted in a time-dependent dioxin-specific Ah receptor-mediated release of transforming growth factor-alpha (TGF-alpha) into the culture medium. Cultures exposed to TCDD showed a rate of TGF-alpha secretion into the medium of about 30 fmol/ml/day, as well as a 3- to 6-fold increase in TGF-alpha mRNA expression. Increased production of TGF-alpha in human keratinocytes exposed to TCDD demonstrates a modulation of autocrine regulation in those cells. These results suggest that induction of TGF-alpha could be an important part of the mechanism of dioxin-mediated toxicity and tumor promotion.

Blotting, Northern↗
PubMed1991

Role of surgery in multimodality therapy for gastrointestinal lymphoma.

Between 1973 and 1989, 49 patients with gastrointestinal lymphomas were treated at the Virginia Mason Medical Center, Seattle, Washington, and followed in the tumor registry. The purpose of this review was to determine the influence of treatment on long-term survival of these patients. The mean age was 63 years (range: 38 to 83 years). There were 33 men and 16 women. The primary tumor sites were gastric 33 (67%), small bowel 11 (22%), and colon 5 (10%). Common signs and/or symptoms at presentation were pain (n = 38), bleeding (n = 11), and weight loss (n = 14). The diagnostic sensitivities of contrast radiography, computed tomography, and endoscopic biopsy were 76%, 89%, and 79%, respectively. Forty-eight patients were treated, and one received supportive care only. Thirty-one patients had surgical resections, 33 patients had chemotherapy, and 16 patients had radiotherapy. Most (n = 30) had multimodality treatment. Statistically significant variables affecting survival rates in patients with gastric lymphomas were lower tumor stage, younger patient age, and surgical resection.

Adult↗
PubMed1991

Rapid verification of identity and content of drug formulations using mid-infrared spectroscopy.

A general method for the rapid verification of both identity and content of complete solid drug formulations has been devised. Infrared spectra for the samples were recorded using the diffuse reflectance technique, and specially written software was employed to identify the type of formulation and level of active ingredient. This software was devised to ensure reliable use when applied by those with minimal operator skills. Three differing drug tablet formulations containing simvastatin, enalapril maleate and lovastatin, as well as a capsule formulation containing finastride were studied. Adequate precision was obtained to reliably verify drug dosage levels. Near-infrared (NIR) and mid-infrared (MIR) spectrometers were evaluated for use with the method. The MIR instrument allowed sufficient resolution and spectral/structural selectivity to reliably verify correctness of either of two near derivative drugs necessarily present in the same clinical study. Drug tablet and capsule dosage levels tested ranged from 0.2 to 40 mg of drug. Approximately 1% (w/w) of the drug in the formulation was the minimum amount determined. Parameters affecting method ruggedness in routine use were optimized. Experimental addition of an extraneous material to a simvastatin formulation was easily detected and flagged by the routine test procedure. Subsequent data retrieval and searching against spectral libraries was used to demonstrate identification of the additive.

Anticholesteremic Agents↗
PubMed1991

Beta-carotene's effects on serum lipoproteins and immunologic indices in humans.

Doses of beta-carotene for cancer-prevention trials have been chosen based on epidemiologic data. Mechanisms of the putative antineoplastic effects by beta-carotene are unknown but may involve modulation of the immune system. We measured plasma carotenoid concentrations and selected immunologic indices at baseline and at 2 and 4 wk in 50 healthy humans (5 groups of 10 each) ingesting 0, 15, 45, 180, or 300 mg beta-carotene/d for 1 mo in this randomized placebo-controlled, open-label, parallel study. Plasma beta-carotene concentrations were markedly increased by 2 wk and were correlated with dose. Beta-carotene concentrations plateaued between 2 and 4 wk except for the 300-mg group. Thus, we developed a dose-concentration curve to optimize beta-carotene-dose selection to achieve target plasma concentrations. We were unable to identify any effects of beta-carotene ingestion on the immunologic indices studied, but modest increases in high-density-lipoprotein cholesterol were observed in all beta-carotene-treated groups.

Adult↗
PubMed1991

Emergence of a virulent clone of Neisseria meningitidis serotype 2a that is associated with meningococcal group C disease in Canada.

Multilocus enzyme electrophoresis was used to characterize 378 isolates of Neisseria meningitidis serogroup C recovered during a period of an increase in group C meningococcal disease in Canada. Thirty-four enzyme electrophoretic types were found among the isolates, which were predominantly (96.0%) serotype 2a. One clone (ET 15), characterized by a rarely occurring allele for the enzyme fumarase, was responsible for a focal outbreak in Ontario followed by the spread of group C disease across the province. This clone, which occurred infrequently among strains isolated in 1986, accounted for over 65% of group C strains associated with meningococcal disease in Canada in 1990.

Bacterial Typing Techniques↗
PubMed1991

Biologic and immune modulating agents in the treatment of childhood brain tumors.

The data on the utility of biologic response modifiers are quite sketchy. Although no true home-runs have been hit, there is evidence that some patients will benefit from these immunologic agents. The majority of studies for central nervous system tumors have been done in adults with highly aggressive anaplastic gliomas. Many of these patients had extensive disease at the time of treatment and determination of benefit is difficult. Few pediatric trials have been attempted. The evidence for efficacy for most agents is lacking, although there are encouraging responses in children with isolated leptomeningeal spread to radiolabeled monoclonal antibodies and for patients with progressive intracranial mass lesions to one form of beta-interferon. Given the limited alternatives for many of these patients, and the neurotoxicity of other means of therapy, future studies are clearly indicated in children with malignant brain tumors. The lack of evidence of efficacy in adult glioblastoma trials cannot be used as direct evidence for the nonutility of these agents for childhood brain tumors. By and large, children tend to tolerate higher doses of biologic response modifiers than adults, again raising the hope of greater utility of these drugs for pediatric patients. From the information available, it seems unlikely that these immunomodulating agents, in themselves, will be effective in the treatment of the majority of patients with brain tumors. But in combination with aggressive surgery, radiation, and possibly chemotherapy, these agents may in time add to the armamentarium available for the treatment of childhood brain tumors.

Adjuvants, Immunologic↗
PubMed1991

Endoscopic transpapillary therapy for disrupted pancreatic duct and peripancreatic fluid collections.

Eighteen patients with active pancreatic ductal disruptions, including 14 with definable fluid collections, were treated with transpapillary pancreatic duct drains or stents. Twelve of these patients had undergone a previous percutaneous or surgical pancreatic drainage procedure or both, and 8 had long-term drainage tubes in chronic fistulous tracts. Transpapillary catheters could be placed across the ductal disruption or directly into the fluid collection in each case, and 16 of 18 patients had resolution of the disrupted pancreatic duct. Twelve of 14 fluid collections resolved. Complications were limited to mild exacerbation of pancreatitis symptoms in 2 patients and 2 patients who developed subsequent stent occlusion leading to recurrent pancreatitis (1 patient) or recurrent duct blowout with pseudocyst (1 patient). Nine patients had variably significant ductal changes attributable to pancreatic duct stents. At a median follow-up of 16 months, 7 patients ultimately required surgery for ongoing pancreatic pain or residual/recurrent fluid collection. The transpapillary treatment of ongoing pancreatic ductal disruption with or without fluid collection has the potential to obviate surgery in some patients, change an urgent surgical procedure into an elective one, or even assist the surgeon in the performance of intraoperative pancreatography. Further study of this technique appears warranted and must be placed into the perspective of current therapies.

Acute Disease↗
PubMed1990

Management of enterovesical fistulas.

The records of 51 patients diagnosed with enterovesical fistulas at Virginia Mason Medical Center from 1974 to 1988 were reviewed. Diverticulitis (41%), Crohn's disease (17%), and colorectal cancer (16%) were the major causes. In 50 of 51 patients, the diagnosis was made on the basis of the clinical history and the urine culture. Radiologic and endoscopic studies failed to identify the fistula in 20%, though all were confirmed at operation or autopsy. In four of eight patients with fistulas secondary to colorectal cancer, malignancy was not diagnosed preoperatively. Operation was performed in 84% of the patients. One-stage resection of the bowel was performed in 66% of patients with the intent of removing the fistula. The complication rate was 8% with no deaths. All multi-stage procedures were performed for fistulas complicated by abscess or bowel obstruction. There were two postoperative deaths in patients with metastatic cancer undergoing palliative diversion. All eight patients treated by diverting colostomy had persistent fistulas and urinary sepsis. All eight patients treated with antibiotics but without operation were free of complications of the fistula until death from other causes. Enterovesical fistula is a clinical diagnosis. Preoperative studies should be used to delineate the bowel disease and search for malignancy rather than to see the fistula, which is clinically apparent. One-stage resection of the involved bowel is the procedure of choice in the absence of abscess or bowel obstruction. When resection is not feasible, medical management with antibiotics is preferable to colostomy.

Adult↗
PubMed1990

Value of diagnostic upper endoscopy preceding percutaneous gastrostomy.

Percutaneous gastrostomies, placed endoscopically or radiographically, have supplanted their surgical counterparts in many institutions. Although there are few comparative data, a cost advantage is claimed for the radiographic method, as no endoscopy is required. We performed upper endoscopy on 201 patients prior to attempted percutaneous endoscopic gastrostomy (PEG). The medical records of these patients were reviewed. Data collected included endoscopic findings which precluded gastrostomy, necessitated conversion to jejunostomy, or led to changes in medical management. For a total of 73 patients (36%), findings at pregastrostomy endoscopy led to major changes in medical management, including 35 patients with severe reflux esophagitis, 29 patients with peptic ulcers, and two patients with gastric outlet obstruction. Appropriate treatment of such conditions may improve morbidity, mortality, and cost by reducing length of hospital stay. The authors recommend diagnostic upper endoscopy in patients undergoing percutaneous gastrostomy, regardless of placement method.

Digestive System Diseases↗
PubMed1990

Long-term survival in patients undergoing percutaneous endoscopic gastrostomy and jejunostomy.

Percutaneous endoscopic gastrostomy (PEG) used to supply enteral nutrition has supplanted surgically placed feeding tubes in many institutions. These tubes are currently placed in: 1) patients with reversible disease with potential for recovery (stroke, Guillain-Barré syndrome); 2) patients with incurable disease with potential for extended survival (head and neck cancer, amyotrophic lateral sclerosis); or 3) patients who are terminal or seriously debilitated (head trauma, systemic malignancies). Few data are currently available regarding long-term survival, survival difference between various patient populations, and incidence of recovery of oral intake with subsequent PEG tube removal. In this study, records of 191 patients in whom PEG tubes were placed were retrospectively reviewed and information collected regarding underlying diseases (malignant vs nonmalignant), survival, and incidence of subsequent tube removal. Of the patients, 68 (36%) had cancer, and 123 (64%) had benign disease (usually stroke or other neurologic disorder). Survival curve analysis demonstrated that one-third of patients were dead within 60 days of PEG placement, and half were dead in the first 6 months. Total deaths were 115 (60%) at a median time of 164 days. No mortality was directly related to acute or subsequent PEG tube complications. Feeding tubes were removed in 41 patients (21%), 10 with cancer (5%), and 31 without (16%, p less than 0.05). These data on limited patient survival and low incidence of recovery of oral intake suggest that facilitation of hospital discharge into a less expensive home care or step-down facility is the most likely goal to be realized after PEG placement. Further, these results raise questions regarding the appropriateness of PEG placement in patients with anticipated early mortality or low likelihood of hospital discharge.

Aged↗
PubMed1989

Liver resection without blood transfusion.

A personal series of 58 liver resections was reviewed to identify technical factors minimizing blood transfusions. We identified a concept of vascular isolation prior to parenchymal division (VIP) which used singularly or in combination the following methods of vascular control: parenchymal compression, Pringle maneuver, hepatic venous tourniquet, hilar division, hepatic vein division, and Heaney maneuver. VIP significantly decreased the need for transfusion; of 34 patients with VIP only 2 (6 percent) required transfusion, whereas of 24 patients without VIP, 18 (75 percent) required transfusion (p less than 0.001).

Adult↗