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Biomedical subjects

J W Ryan

Publications and source records attributed to J W Ryan.

At least 73 records · Page 4Linked to original sources
PubMed1987

The effect of previous thoracic surgery on gallium uptake in the chest.

To determine the frequency, average duration, and characteristic patterns of persistent gallium uptake caused by thoracotomy, serial postsurgical scans of 51 patients were reviewed. In each of these cases a thoracotomy had been performed for resection of lung cancer, and there had been no evidence of recurrent tumor for at least 2 yr following surgery. Postoperative gallium activity due to non-neoplastic postoperative changes occurred in 15 patients. Five of six patients scanned within 3 mo of surgery and six of 21 scanned 3 to 6 mo following surgery showed persistent uptake at the operative site. All 13 patients who had subsequent scans demonstrated eventual clearing. Activity persisted more than 18 mo postoperatively in only one patient. Patterns of gallium accumulation included both focal chest wall uptake at the incision site and diffuse pleural activity.

Gallium Radioisotopes↗
PubMed1986

Synthetic inhibitors of carboxypeptidase N.

Further to explore the functions of carboxypeptidase N (CPN) in vivo, we undertook two studies to find CPN inhibitors of high potency and relatively long duration of action. In each study we examined for inhibition of hydrolysis of [3H]benzoyl-Ala-Arg using pure bovine serum CPN or human serum. In the first such study we synthesized a series of acyl amino acids and acyl di - and tripeptides containing arginine, lysine or both. All proved to be weak inhibitors (Ki = 10(-3) to 10(-4) M). N alpha-carbamoyl-Arg was the strongest: Ki = 3.5 X 10(-5) M. In the second study we prepared S-acyl (thio ester) derivatives of the highly potent CPN inhibitor 2-mercaptomethyl-3-guanidinoethylthiopropionic acid (2-MGP), as certain S-acyl groups markedly increase the duration of captopril, another mercapto-containing compound. Acetyl-, Boc-phenylalanyl-, phenylalanyl-, benzoyl-alanyl-, alanyl-, and Boc-alanyl-2-MGP retained the high potency of 2-MGP in vitro. Although Ala-2-MGP exerted maximum effects in vivo, like those of 2-MGP, the duration of action of Ala-2-MGP was slightly shorter than that of 2-MGP. These results indicate that the mercapto group of 2-MGP can be taken up in some forms of thioester linkage and still remain virtually the full potency of 2-MGP itself. Thus, it appears that a free mercapto function is not essential for the action of 2-MGP.

Amino Acids↗
PubMed1986

Carboxyalkyl peptide inhibitors of kininase II: chiral synthesis.

Heretofore, carboxyalkyl peptide inhibitors of kininase II (e.g. N-[1-carboxy-3-phenylpropyl]-Ala-Pro, "enalaprilic acid") have been synthesized by means that yield racemic product. Typically, the secondary amine bond is formed by reacting an amino acid or dipeptide with a 2-keto carboxylic acid ester or imide. The group providing the 2-keto function must be used in excess, and the desired S,S,S isomer must be obtained by resolution procedures. We have developed a procedure whereby enalaprilic acid, RAC-X-64 and related compounds are synthesized stereospecifically and in relatively high yields.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1986

Slow tight binding inhibitors of angiotensin converting enzyme.

We have found that apparent Ki values of some, but not all, carboxyalkyl-dipeptide inhibitors of angiotensin converting enzyme decrease as a function of incubation time. The most potent of the ACE inhibitors tested so far is RAC-X-65 (N-[1(S)-carboxy-3-carboxanilidiopropyl]-L-Ala-L-Pro). When RAC-X-65 is not preincubated with human serum ACE (2.4 X 10(-11) M), the apparent Ki value is 4.4 X 10(-10) M. Preincubation of RAC-X-65 with ACE for 15 min before addition of substrate yields an apparent Ki of 4.1 X 10(-11) M. a 90 min preincubation of the inhibitor with ACE yields an apparent Ki of 1.2 X 10(-11) M, i.e., the reaction of the inhibitor with enzyme is virtually stoichiometric. The enzyme:inhibitor complex is poorly separated by molecular sieve chromatography or by dilution. That such tightly bound complexes are formed in vivo is suggested by the following results: The intravenous ED50 (anesthetized rats) of RAC-X-65 is 9.43 nmol/kg, and the time for half recovery (t1/2) of responsiveness to i.v. angiotensin I, 120 ng/kg, following a cumulative dose of 240 nmol/kg of the inhibitor is 165 min. For comparison, the i.v. ED50 of captopril is 105 nmol/kg, and its t1/2 following a cumulative dose of 240 nmol/kg is 16 min. Implied is the possibility that slow tight binding inhibitors of ACE may be used in a 1 pill per day regimen for the treatment of hypertension.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1986

Radiolabelled substrates for angiotensin converting enzyme.

Six [3H]benzoyl-tripeptides were prepared and tested as substrates for angiotensin converting enzyme. Each was prepared first as its [4-iodo]-benzoyl-analog, and an atom of 3H per molecule was introduced by catalytic dehalogenation in 3H2-gas. Kinetic parameters were measured at 37 degrees C using as buffer 0.05 M Hepes, pH 8.0 containing 0.1 M NaCl and 0.6 M Na2SO4. When the substrates were used at concentrations far below their respective Km values, fractional rates of substrate utilization per unit time for constant enzyme concentration were direct function of respective second order rate constants (Kc/Km). Although absolute values of Kc/Km differed for human enzyme as opposed to rabbit enzyme, relative values of Kc/Km were virtually identical. Similarly, relative rates of substrates utilization during passage through lungs of anesthetized rats were similar to relative values of Kc/Km measured in vitro. Thus, there is now a range of ACE substrates usable, in vitro and in vivo, under conditions of first order enzyme kinetics, conditions under which values of V/Km and Ki can be measured directly.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1986

Aggregate anaphylaxis and carboxypeptidase N.

Bradykinin (BK) is widely believed to play a role in the pathogenesis of anaphylaxis. To help clarify any such roles, we examined for effects of inhibitors of kininase II (angiotensin converting enzyme, ACE) and "kininase I" (carboxypeptidase N, CPN), on the early course of egg albumin-induced aggregate anaphylaxis in anesthetized guinea pigs. In this model, pulmonary and systemic arterial blood pressure (BP) rise (unless pulmonary fibrillation occurs), lung wgt increases by approximately 60% and pulmonary microvessels are occluded by cell-rich thrombi, all within 5 min of i.v. antigen. The 30 min mortality rate is approximately 2%. ACE inhibitors (BPP9a, Captopril and MK 422; doses up to 140 mumol/kg) do not make anaphylaxis more nor less severe in terms discernible by changes in BP, lung wgt, EKG or intravascular coagulation. In marked contrast, an inhibitor of CPN (2-mercaptomethyl-3-guanidinoethylthiopropionic acid, 2-MGP; 8-16 mumol/kg) increases the 30 min mortality rate to 94% and lung wgt to 180% of control. The animals die in ventricular fibrillation. Given the enormous BK potentiating effects of BPP9a, Captopril and MK 422, it seems likely that little if any BK is formed in the early min of anaphylaxis. 2-MGP does not potentiate BP effects of BK but markedly potentiates effects of C3a anaphylatoxin. Thus, our data support the views that BK is neither a primary nor secondary mediator of aggregate anaphylaxis, and the adverse effects of 2-MGP are best explained in terms of preservation of anaphylatoxins and not in terms of preservation of kinins.

3-Mercaptopropionic Acid↗
PubMed1986

A rapid, simple synthesis and purification of abscisic Acid glucose ester.

A simple and rapid technique was developed to synthesize abscisic acid glucose ester. The free acid of abscisic acid (ABA) was combined with CsHCO(3) to form the Cs salt of ABA. The Cs salt of ABA was then combined with acetobromo-alpha-d-glucose tetraacetate, and the tetraacetate derivative of abscisic acid glucose ester was formed. Acetate groups were selectively removed from the glucose moiety with a crude enzyme preparation derived from Helianthus annuus seeds. Abscisic acid glucose ester was purified via silica gel column chromatography and identified by micro NMR.

Journal Article↗
PubMed1986

Postoperative recurrence of lung cancer: detection by whole-body gallium scintigraphy.

The records were reviewed of 111 consecutive patients who had lung cancer resected and who were followed with serial postoperative whole-body gallium scans. Scans were obtained preoperatively at intervals of 3-6 months for about 1 year after surgery and subsequently at yearly intervals. The period of follow-up varied from 1 1/2 to 8 years. Of 55 patients who developed tumor recurrence, a gallium scan was the first indicator of recurrence in 11 (20%) and was judged helpful in confirming or localizing a recurrence in another 14 patients (25%). False-positive rates were determined from 175 postoperative scans in the other 56 patients who did not suffer recurrence. Of these 175 scans, 15 (9%) demonstrated abnormalities that were sufficiently suspicious that an additional diagnostic procedure, other than chest radiography, was performed for clarification. However, in no case did the gallium scan result adversely affect the management of the patient. Our data demonstrate that routine postoperative whole-body gallium scanning can facilitate early detection of recurrence in some cases. Judicious use of gallium scanning in cases with clinically suspected recurrence can enable prompt localization, diagnosis, and treatment of recurrent tumor.

Bone Neoplasms↗
PubMed1986

Uptake of N-[1 (S)-carboxy-(4-OH-3-125I-phenyl)ethyl]-L-Ala-L-Pro, an inhibitor of angiotensin-converting enzyme by rabbit lungs in situ.

Single pass extraction of a new iodinated inhibitor of angiotensin-converting enzyme (ACE) was measured by means of indicator-dilution techniques applied to rabbit lungs, perfused in situ at 20 ml/min with Krebs bicarbonate solution containing 3% bovine serum albumin. A bolus containing the inhibitor, N-[1(S)-carboxy-(4-OH-3-125I-phenyl)ethyl]-L-Ala-L-Pro (CPAP), and an intravascular marker, [14C]dextran, was injected and extraction calculated at the peak of the resulting venous outflow-time curve. In 13 of 21 lungs used, a synthetic substrate for ACE, [3H]benzoyl-phenylalanyl-alanyl-proline (BPAP), was added to the bolus and appearance of its hydrolysis product, [3H]benzoyl-Phe, measured in effluent samples. When low amounts (0.15 nmol) of [125I]CPAP were injected, pulmonary extraction (E) of CPAP was 67 +/- 14% (X +/- S.D; n = 21) and metabolism (M) of BPAP was 56 +/- 9% (n = 13). Addition of unlabeled CPAP (3, 34 or 340 nmol) to the Addition of unlabeled CPAP (3, 34 or 340 nmol) to the injected bolus caused dose-dependent reduction of E(CPAP) and M(BPAP) that was no longer evident 10 min after the largest dose of CPAP. Coadministration of the ACE inhibitor, captopril (3, 6, 8 and 28 nmol), also caused dose-dependent, reversible depression of both E(CPAP) and M(BPAP). Accordingly, extraction of CPAP by perfused rabbit lung is saturable. Inasmuch as CPAP inhibits ACE activity (as reflected by BPAP metabolism) and CPAP uptake is inhibited by captopril (which also inhibits BPAP hydrolysis), it appears that a large portion of this saturable process probably reflects binding to vascular ACE.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1985

Esophageal emptying and acid neutralization in patients with symptoms of esophageal reflux.

Clearance of refluxed acid from the distal esophagus is due to bolus emptying and salivary neutralization of acid. We compared results of 24-hour pH monitoring with acid clearance tests (ACT) and radioisotope swallows (RIS) in 26 symptomatic patients to determine which of the components of acid clearance is better correlated with gastroesophageal acid reflux (GER). Seven of eight patients with GER had delayed esophageal emptying on RIS. Abnormal salivary clearance of acid was present in nine of 18 patients without GER, accounting for a high false-positive rate of ACT. Delayed esophageal bolus emptying, not deficient acid neutralization by saliva, is the predominant component of abnormal acid clearance in patients with GER. RIS is superior to ACT as part of the evaluation of reflux symptoms, and may prove to be a valuable screening test for this condition.

Esophagogastric Junction↗
PubMed1985

Dimethylthiourea consumption reflects H2O2 concentrations and severity of acute lung injury.

Even though dimethylthiourea (DMTU) effectively scavenges O2 metabolites in vitro, it is often unclear if scavenging of O2 metabolites is the mechanism by which DMTU decreases tissue injury in biological models. Since DMTU not only scavenges O2 metabolites but is also consumed in a dose-response manner following reaction with hydrogen peroxide (H2O2) in vitro, we wondered whether DMTU would also be consumed by O2 metabolites in biological systems and if DMTU consumption would then reflect O2 metabolite concentrations and O2 metabolite-mediated injury. Our results supported this possibility. We found that selected nonprotecting concentrations of DMTU were consumed in isolated rat lungs perfused with H2O2 and that the amounts of DMTU consumed reflected both the added amounts of H2O2 and the corresponding degrees of H2O2-induced acute edematous injury. DMTU consumption was relatively specific for reaction with H2O2 occurring in isolated lungs that were injured by H2O2 but not lungs injured by elastase, oleic acid, histamine, or a venous pressure challenge. Our results suggest that measurement of DMTU consumption may be useful for assessing the presence and toxicity of O2 metabolites and the specificity of the protective effects of DMTU in biological systems.

Animals↗
PubMed1985

The pulmonary endothelial surface.

The understanding of endothelial metabolic properties has increased dramatically in recent years. Endothelial cells (ECs) process hormones, drugs, and many blood-borne substances by means of enzymes and transport processes. In turn, some hormones, blood cells, and cellular products interact with ECs via specific receptors on the luminal surface. Functional complexity is exemplified by the metabolism of the adenine nucleotides. ATP, ADP, and AMP are metabolized by enzymes of the endothelial surface to release adenosine, which may be immediately taken up into endothelium and reincorporated intracellularly into nucleotides. Equally complex is the metabolism of the kinins and angiotensins by ECs. Bradykinin is inactivated whereas angiotensin I is converted to angiotensin II. Bradykinin not thus degraded can act on endothelial receptors and stimulate the release of prostacyclin (PGI2). Thus bradykinin can amplify the release of another vasodilator, PGI2, and can stimulate the release of a powerful antiaggregatory agent (PGI2). Many of these complex metabolic reactions occur at the endothelial surface, a structure that is itself complex. ECs possess endothelial projections and caveolae as well as a fuzzy coat, or glycocalyx. Functions of the endothelial glycocalyx are not well understood, but the glycocalyx can now be visualized: it may act as a molecular sieve and provide a substratum for the initiation and progression of immunologic reactions.

Adenosine Diphosphate↗
PubMed1985

Glucocorticoid modulation of prostacyclin production in cultured bovine pulmonary endothelial cells.

The present study has examined the ability of glucocorticoids to modify the production of prostacyclin by endothelial cells derived from bovine pulmonary arteries. Binding studies with [3H]dexamethasone indicated that these cells possessed high-affinity binding sites for glucocorticoids (Kd approximately 4 nM). The cells released prostacyclin, measured serologically as its hydrolysis product 6-keto-prostaglandin F1 alpha. The release was strongly stimulated by a 5-min incubation with 50 nM bradykinin, 2 microM calcium ionophore A23187 or 1 to 5 microM arachidonic acid. Dexamethasone, 1 to 20 nM, suppressed prostacyclin release in response to bradykinin and ionophore in a dose-dependent manner. The suppressive effects required 24 hr for full expression. Maximal inhibition of bradykinin-induced prostacyclin release was approximately 65% and that of ionophore-induced release was approximately 35%. Total inhibition was not observed. Hydrocortisone at 20 nM inhibited bradykinin-induced release of prostacyclin by approximately 45% but had no effect on ionophore-induced release. Neither glucocorticoid inhibited prostacyclin release in response to arachidonic acid. Triton X-100 extracts and conditioned media from cells treated with 20 nM dexamethasone failed to modify prostacyclin release when added to fresh endothelial cells. We conclude that dexamethasone, in concentrations likely to produce virtually complete binding site occupancy, inhibits agonist-induced release of prostacyclin from bovine pulmonary endothelial cells. Inhibition appears to occur at the level of intracellular arachidonic acid release. However, we have been unable to obtain definitive evidence for the production of a macromolecular phospholipase inhibitor by endothelial cells in response to these low concentrations of steroid.

Animals↗