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Biomedical subjects

D J Stewart

Publications and source records attributed to D J Stewart.

At least 109 records · Page 6Linked to original sources
PubMed1997

Cyclophosphamide and fluorouracil combined with mitoxantrone versus doxorubicin for breast cancer: superiority of doxorubicin.

PATIENTS AND METHODS: We conducted a randomized, multicenter study of intravenous cyclophosphamide 500 mg/m2 plus fluorouracil 500 mg/m2 combined with either mitoxantrone (Novantrone, Lederle Cyanamid Canada Ltd, Willowdale, Ontario) 10 mg/m2 (CNF) or doxorubicin (Adriamycin, Adria Laboratories of Canada Ltd, Mississauga, Ontario) 50 mg/m2 (CAF) every 3 weeks in advanced breast cancer. RESULTS: The response rate in 249 randomized patients was 36% with CNF (44 of 121) and 48% with CAF (62 of 128) (P = .054), with complete remissions in 10 patients (8.3%) on CNF and in 13 (10.2%) on CAF. If only fully assessable patients are considered, the response rate was 48% (44 of 91) with CNF and 60% (62 of 103) with CAF (P = .098). At time of analysis, all except 10 patients (one CNF and nine CAF) had died. The median survival time with CAF was longer than with CNF (15.2 v 10.9 months; P = .003), and time to progression was also longer with CAF (5.3 v 3.2 months; P < .03). Survival differences remained significant (P = .006) if patients who failed to meet all eligibility criteria were excluded. Favorable prognostic factors for survival in a Cox regression model included good performance status (P < .0001); less than two organ systems involved by tumor (P < .0001); no involvement of lung, liver, or brain (P < .003); involvement of bone or bone marrow (P < .009), prior surgery for breast cancer (P < .006); being premenopausal (P < .03); > or = 3 years from diagnosis until randomization on this study (P < .03); and treatment with CAF (P < .03). Alopecia > or = grade 3 was reported in 55% of patients with CAF and 12% of patients with CNF (P < .001), while other > or = grade 3 toxicities did not differ significantly. Priestman-Baum quality-of-life assessment was comparable on the two study arms. CONCLUSION: In patients with advanced breast cancer, CAF was associated with longer survival than was CNF, with an increase in alopecia, but not in other toxicities.

Adult↗
PubMed1997

Chemotherapy in stage IV (metastatic) non-small-cell lung cancer. Provincial Lung Disease Site Group.

GUIDELINE QUESTION: In patients with metastatic, stage IV non-small-cell lung cancer (NSCLC) does chemotherapy improve survival and quality of life? OBJECTIVE: To make recommendations about the role of chemotherapy in the treatment of metastatic (stage IV) NSCLC. OUTCOMES: Survival and quality of life are the primary endpoints of interest. Specifically, 1-year survival will be considered. PERSPECTIVE: Evidence was selected and reviewed by 3 medical oncologists and the project coordinator of the Ontario Cancer Treatment Practice Guidelines Initiative. Drafts of this document have been circulated and reviewed by the Provincial Lung Disease Site Group (Lung DSG). The Lung DSG comprises medical and radiation oncologists, pathologists, surgeons, epidemiologists, a psychologists and a medical sociologist. There was no consumer participation in the development of this guideline. QUALITY OF EVIDENCE: There were 3 meta-analyses available for review, but only 1 is discussed in detail. The largest and most comprehensive meta-analysis is based on 11 randomized controlled trials involving 1190 patients. The main comparisons were chemotherapy plus supportive care versus supportive care alone. The largest trial included in the meta-analysis involved randomization of 188 patients, and the smallest trial involved randomization of 32 patients. Only trials that had accrued patients between Jan. 1, 1965, and Dec. 31, 1991, were included in the analysis. BENEFITS: A survival benefit at 1 year was seen for the group of patients treated with chemotherapy (pooled hazard ratio 0.84; 95% confidence interval [CI], 0.74 to 0.95). Subgroup analyses suggested a benefit for patients receiving chemotherapy regimens containing cisplatin (pooled hazard ratio, 0.73; 95% CI, 0.63 to 0.85; relative risk reduction for death, 27%; absolute improvement in 1 year survival, 10%; 95% CI, 5% to 18%; gain in median survival 1.5 months; 95% CI, 1 to 2.5 months). No benefit for patients treated with chemotherapy was found beyond 1 year. None of the randomized trials successfully measured quality of life using QOL assessment instruments. No firm conclusions can be made about the potential benefits (as measured by quality of life) that chemotherapy has for patients with metastatic NSCLC, as there are no available data from randomized controlled trials. However, several trials have documented relief of cancer-related symptoms, such as pain, cough, hemoptysis or dyspnea in the majority (approximately 70%) of patients. HARMS: In a subgroup analysis of trials that used long-term alkylating agents other than cisplatin (an approach no longer used as therapy in NSCLC) as part of the chemotherapy regimen, the meta-analysis demonstrated a detrimental effect of chemotherapy on survival (pooled hazard ratio, 1.26; 95% CI, 0.96 to 1.66, p = 0.09). In general, myelosuppression, sepsis resulting in hospitalization, drug-specific toxicities and death are potential complications of chemotherapy.

Carcinoma, Non-Small-Cell Lung↗
PubMed1996

Human pulmonary circulation is an important site for both clearance and production of endothelin-1.

BACKGROUND: Animal studies suggest a major role of the pulmonary circulation in the clearance of circulating endothelin-1 (ET-1). The contribution of the human pulmonary circulation to plasma ET-1 clearance, however, has never been quantified. The absence of an AV gradient in plasma ET-1 has previously been interpreted as evidence that the lungs do not have a role in modulating circulating ET-1 levels. This study was designed to quantify and discern between pulmonary ET-1 clearance and production in humans. METHODS AND RESULTS: We studied 13 subjects by combining the multiple indicator-dilution technique with the measurement of immunoreactive ET-1 (irET-1). All patients had normal left ventricular ejection fractions (61 +/- 7%, mean +/- SD) and baseline hemodynamics. Mean pulmonary ET-1 extraction was 47 +/- 7%. The ET-1 extracted does not return to circulation and can be characterized by a sequestration rate constant: Kseq = 0.048 +/- 0.019 s-1. There was no significant difference between irET-1 levels from the pulmonary artery and aorta (0.61 +/- 0.29 and 0.68 +/- 0.33 pg/mL, respectively; P = .22); the normal lung consequently produces an amount of ET-1 that is quantitatively similar to the amount that has been extracted. CONCLUSIONS: The human lung is an important site for both clearance and production of ET-1. There is a normal physiological balance of ET-1 across the pulmonary circulation, which explains the absence of difference in AV ET-1 levels despite a 47 +/- 7% clearance. Reduced pulmonary clearance or increased production of this peptide may contribute to the increase in circulating levels found in various cardiovascular conditions.

Aged↗
PubMed1996

Lambert-Eaton myasthenic syndrome presenting with severe respiratory failure.

Two cases of Lambert-Eaton myasthenic syndrome (LEMS) who presented with primary respiratory failure are reported. In each case, although not initially suspected clinically, the electrophysiological findings, which included reduced compound muscle action potential amplitudes, decrement to 3-Hz stimulation, and potentiation after 40-Hz stimulation, led to the diagnosis in the critical care unit. Electrophysiological studies of the respiratory system, including repetitive nerve stimulation of the phrenic nerve, were extremely valuable in management. As shown by these cases, the severe respiratory failure in LEMS is reversible with treatment. Thus, LEMS should be considered in cases of unexplained respiratory failure, other clinical features of the disorder sought, and the electrophysiological hallmarks looked for including studies of the respiratory system.

Action Potentials↗
PubMed1996

Cytotoxicity, accumulation, and efflux of cisplatin and its metabolites in human ovarian carcinoma cells.

Cisplatin (CP) is one of the most useful antineoplastic drugs. When CP is dissolved in human plasma, different metabolites are formed. Using the OV 2008 human ovarian cancer cell line, we examined the relative cytotoxicities of CP and its metabolites (aquated CP [AP], monomethionine CP [MP], bismethionine CP [BP], and a mixture of CP metabolites in ultrafiltrated human plasma [UP]) in vitro. By clonogenic assay, cell survival (percent of mean +/- SE) of OV 2008 cells exposed for 1 hr to 6.7 microM of CP was 9.8 +/- 0.7 and for its equal platinum contents of AP, MP, BP, and UP solutions were 3.3 +/- 0.7, 9.8 +/- 0.9, 15.9 +/- 1.1, 76.8 +/- 2.1, and 13.1 +/- 0.7, respectively. AP was the most cytotoxic species, and BP was the least cytotoxic species. Cellular platinum uptake (ng/10(6) cells) after addition of 0.33, 1.6, and 2.5 mM of each species for 1 hr was measured and a strong correlation was found between cytotoxicity of each CP metabolite and its corresponding cellular platinum (Pt) uptake (r = 0.997). There was a strong correlation between cytotoxicity of the CP metabolites and their DNA binding. With fractionation of these cells into DNA, nucleoplasm and cytoplasm, the highest platinum content was found on DNA. The most important factor that seems to be responsible for the cytotoxicities of the different CP metabolites is the amount of their associated intracellular accumulation, and particularly the degree of their binding to DNA.

Carcinoma↗
PubMed1996

Active vs. passive resistance, dose-response relationships, high dose chemotherapy, and resistance modulation: a hypothesis.

With chemotherapy, the in vitro and clinical dose-response curve is steep in some situations, but is relatively flat in others, possibly due to the mechanism by which tumors are resistant to chemotherapy. For tumors with resistance due to factors that actively decrease chemotherapy efficacy (e.g., p-glycoprotein, glutathione, etc.), one would predict that high dose chemotherapy and therapy with some resistance modulating agents would increase therapeutic efficacy. Such "active" resistance would most likely generally arise from gene amplification or over expression, and would be characterized by a shoulder on the log response vs. dose curve, with eventual saturation of the protective mechanism. On the other hand, one would expect that high dose chemotherapy and most resistance modulating agents would be of little value for tumors with resistance due to defective apoptosis or due to a deficiency in or decreased drug affinity for a drug target, drug activating enzyme, drug active uptake system, or essential cofactor. Such "passive" resistance would most likely generally arise from gene down regulation, deletion, or mutation, and would probably be characterized by a relatively flat log response vs. dose curve, or by a curve in which a steep initial section is followed by a plateau, as target, etc., is saturated. (If response were plotted vs. log dose, then compared to the curve for a sensitive cell line, the curve for active resistance would be analogous to the pharmacodynamic curve seen with competitive antagonism [i.e., a sigmoid curve shifted to the right], and the curve for most types of passive resistance would be analogous to the pharmacodynamic curve seen with noncompetitive antagonism [i.e., a sigmoid curve with reduced maximal efficacy]. As such, one might also refer to active vs. passive resistance as competitive vs. noncompetitive resistance, respectively.) Many tumor types probably possess a combination of active and passive mechanisms of resistance. New in vivo strategies could be helpful in defining dose-response relationships, mechanisms of resistance, and targets for resistance modulation. Such in vivo studies would be conducted initially in animals, but might also be tested clinically if animal studies demonstrated them to be feasible and useful. These in vivo studies would be conducted by randomizing 5-25 subjects to one of 10-20 dose levels over a potentially useful therapeutic range. Nonlinear regression analysis would then be used to define the characteristics of a curve generated by plotting against dose the log percent tumor remaining after the first course of therapy. While this might offer insight into the nature of resistance mechanisms present initially, plotting further tumor shrinkage vs. dose-intensity vs. course number for each later treatment course (or plotting dose-intensity vs. time to tumor progression) might provide information on how tumors become increasingly resistant to drugs following treatment.

Antineoplastic Agents↗
PubMed1996

PROMACE-MOPP and intrathecal chemotherapy for CNS lymphomas.

UNLABELLED: We conducted a Phase II study of PROMACE-MOPP and intrathecal (IT) therapy followed by cranial radiation in 7 patients (4 male, 3 females) with diffuse large cell lymphomas (including one T cell) involving the central nervous system (CNS). Median age was 47 years (range, 25-78). Median performance status was 2 (range, 2 to 3). Two patients had positive CSF cytology. No patients had prior chemotherapy or radiotherapy. Treatment consisted of PROMACE (cyclophosphamide 650 mg/m2, etoposide 120 mg/m2 days 1 and 8, methotrexate (MTX) 1.5 g/m2 and folinic acid 50 mg/m2 (x 5) day 15, and prednisone 60 mg/m2 days 1-14) x 3-4 courses. MOPP consisted of mustargen 6 mg/m2 and vincristine 1.4 mg/m2 days 1 and 8, procarbazine 100 mg/m2 and prednisone 40 mg/m2 po days 1-14 x 3-4 courses. IT drugs were MTX 20 mg and hydrocortisone 20 mg day 1 and cytosine arabinoside 100 mg day 8, courses 2 to 6, or more frequently if CSF cytology was positive. Following MOPP, 4000 cGy whole brain radiation (XRT) and 2000 cGy boost was given. Response was evaluated before XRT. Two patients declined XRT, 3 declined MOPP and 2 declined IT drugs. Two patients had extracerebral disease and 5 were primary CNS lymphomas. Response after PROMACE was CR: 3 patients; PR 2: stable 1. One patient, with extracerebral disease, experienced PR in the abdomen and CR by CT scan in the brain, but had persistent positive CSF cytology. This patient died from pneumocystis pneumonia 10 weeks after her last CSF cytology and 17 weeks after her diagnosis. After PROMACE +/- MOPP 6 patients experienced CR's. Median (range) survival was 100 (17-334) weeks, with 1 patient lost to follow up at 32 weeks. Toxicity included febrile neutropenia; 6 patients; pneumocystis pneumonia: 1 (fatal); thrombocytopenia; 5; stomatitis: 3; diarrhea; 2; nausea; 3. CONCLUSION: This regimen is active in the treatment of CNS lymphomas, although toxicity is substantial.

Adult↗
PubMed1996

The integrity of cisplatin in aqueous and plasma ultrafiltrate media studied by 195Pt and 15N nuclear magnetic resonance.

195Pt and 15N nuclear magnetic resonance (NMR) was used to study the chemical equilibria of cisplatin in water and plasma ultrafiltrate (PUF). Cisplatin was found to be stable for at least 2, but no longer than 5 months in a reconstituted clinical formulation, as determined by 195Pt NMR. In aqueous solution, the cis-PtCl2(NH3)2 195Pt and 15N NMR signal intensities decreased with time and the formation of [PtCl(H2O)(NH3)2]+ at PH values of 3.0, 6.5, 7.5 and 9.5 was observed within 24 h of sample preparation. In addition, [Pt(H2O)2(NH3)2]++ was observed at pH 3.0, and [PtCl(OH)(NH3)2] and [Pt(OH)2(NH3)2] were observed at pHs 7.5 and 9.5. During incubation of PUF with cisplatin for 35 h, 15N NMR signals for at least eight cisplatin derivatives appeared at different times, whereas only four were observed by 195Pt NMR. With our NMR protocols, the detection limit for quantifiable cisplatin derivatives is estimated at 500 microM using 195Pt NMR and < or = 200 microM using 15N NMR. In addition to providing useful information about the chemical stability of cisplatin and derivatives formed in aqueous solution, these magnetic resonance techniques, particularly 15N NMR, can provide useful information about the metabolism of cisplatin in biological regimes.

Blood↗
PubMed1996

Paclitaxel plus hydroxyurea as second line therapy for non-small cell lung cancer.

We tested paclitaxel (Taxol) and low dose hydroxyurea as second line therapy in 30 patients with non-small cell lung cancer since both drugs are active against non-small cell lung cancer in other settings, and since hydroxyurea may reverse chemotherapy resistance by disrupting double minute chromosomes. Hydroxyurea 500 mg was given orally each Monday, Wednesday, Friday starting 1 week before paclitaxel, and continuing until removal from study. Paclitaxel 135 mg/m2 was given i.v. over > or = 1 h every 3 weeks with dexamethasone, diphenhydramine, and ranitidine. Patients could have paclitaxel doses escalated to 175 mg/m2 in course 2 and to 200 mg/m2 in course 3, where tolerated. Sixteen males and 14 females were treated. All patients had previously received a single cisplatin-based chemotherapy regimen and 23 had previously received radiotherapy. Twelve patients had adenocarcinomas, six had squamous cell carcinomas, and 12 had large cell carcinomas. Eight patients had Stage IIIb cancers and 22 had Stage IV. Paclitaxel doses were 135 mg/m2 in 56 courses, 175 mg/m2 in 24, and 200 mg/m2 in 15. Treatment was well tolerated. Median granulocyte nadirs were 2.5 (x 10(9)/l) for paclitaxel 135 mg/m2, 1.8 for 175 mg/m2, and 1.3 for 200 mg/m2. No patient developed febrile neutropenia, and none required a dose reduction. Two patients had reversible anaphylaxis. Other toxicities were quite tolerable. They included fatigue, myalgias, dizziness, paresthesias, diarrhea, alopecia, mucositis, flushing, headache, swollen red hands, and anxiety. One patient had a partial remission and 15 had stable disease (including six with minor responses). Median survival was 20 (95% CI, 12-34) weeks, with 19% of patients remaining alive at 1 year from initiation of treatment. This is a well-tolerated regimen with modest activity as second line chemotherapy for patients with non-small cell lung cancer previously treated with cisplatin regimens. Higher doses would be feasible and other strategies are now being explored.

Aged↗
PubMed1996

Comparison of gene probe and conventional methods for the differentiation of ovine footrot isolates of Dichelobacter nodosus.

In a collaborative study that involved four Australian veterinary diagnostic laboratories a gene probe test based on the recombinant plasmids pJIR318, pJIR314B, and pJIR313, which contain genomic vap or vrl regions, was compared with conventional tests used for the differential diagnosis of ovine footrot. A total of 771 clinical dichelobacter nodosus isolates were tested and designated as belonging to one of several gene probe categories. The results showed that 87% of the virulent isolates belonged to gene probe category 1, compared to only 6% of the benign isolates. It was concluded that there was good correlation between the gene probe test and the virulence designation of these isolates as well as the results of elastase, gelatin-gel and protease isoenzyme tests. Furthermore, the gene probe test was converted to a polymerase chain reaction (PCR)-based test. It is suggested that diagnostic laboratories consider carrying out both this PCR test and tests based on the extracellular proteases of D. nodosus.

Animals↗
PubMed1996

Manipulation of the helper T cell response to influence antigenic competition occurring with a multivalent vaccine.

The reduction in antibody observed following inoculation with multiple heterologous Dichelobacter nodosus pili antigens is thought to be due to competition between antigen-specific B cells for a limited amount of T cell help. We demonstrate here that this competition is not further influenced by the expansion of cross-reactive antibody secreting cells at the expense of serogroup specific antibody secreting cells. The T cell determinants of pili recognized by sheep and BALB/c mice have been defined using 15 residue peptides. These T cell determinants include cross-reactive determinants in the conserved amino terminal region of the antigen. Here we investigate the effect of expanding the pili-specific T cell population by priming with pili derived T cell determinants. It was not possible to increase the antibody elicited in response to the multivalent vaccine by priming mice with either a synthetic peptide spanning a T cell determinant or with reduced and alkylated or heterologous serogroups of pili 4 weeks before inoculation with the multivalent vaccine. A strategy designed to increase the T cell population by inoculating animals with pili covalently coupled to an extrinsic T cell determinant was pursued.

Amino Acid Sequence↗
PubMed1996

A multicentre, double-blind study comparing placebo, ondansetron and ondansetron plus dexamethasone for the control of cisplatin-induced delayed emesis. Ondansetron Delayed Emesis Study Group.

BACKGROUND: The purpose of this study was to investigate the efficacy and safety of oral ondansetron, given alone or in combination with dexamethasone in the control of cisplatin-induced delayed emesis. PATIENTS AND METHODS: This was an international, multicentre, double-blind, randomised, placebo-controlled, parallel group study. A total of 640 chemotherapy-naïve patients received ondansetron 8 mg i.v. and dexamethasone 20 mg i.v. for the control of acute emesis prior to cisplatin (> or = 70 mg/m2) on day 1. Patients who were not rescued or withdrawn on day 1 were to be randomised 24 hours after the start of cisplatin administration to one of four groups; group I placebo oral (p.o.), twice daily (bd) on days 2-6 (n = 125); group II ondansetron (8 mg p.o. bd) on days 2/3 followed by placebo (p.o. bd) on days 4-6 (n = 199); group III ondansetron (8 mg p.o. bd) on days 2-6 (n = 214); group IV ondansetron (8 mg p.o. bd) plus dexamethasone (4 mg p.o. bd) on days 2-6 (n = 66). RESULTS: On day 1, 81% of patients had complete control of acute emesis, with 68% having no emesis and no nausea. Over days 2/3 and over days 2-6, significantly more patients receiving ondansetron plus dexamethasone (group IV) reported no emesis and no nausea (49% and 45%, respectively) compared to ondansetron alone (32% and 27%, respectively) or placebo (group I; 33% and 27%, respectively; P < 0.05 for all pairwise comparisons). There were no significant differences in the control of emesis over days 2/3, where 61% of patients had complete emetic control (0 emetic episodes) with ondansetron plus dexamethasone (group IV), 54% with ondansetron (groups II + III) and 49% with placebo (group I). In the distribution of nausea grades, ondansetron plus dexamethasone (group IV) was significantly superior to ondansetron (groups II + III); P = 0.037) and placebo (group I; P = 0.013) over days 2/3. Over days 2-6 there were no significant differences in the control of emesis, however a comparison of the distribution of nausea grades over days 2-6 showed ondansetron plus dexamethasone (group IV) to be significantly superior to ondansetron (group III; P = 0.043) and placebo (group I; P = 0.024). All treatments were well tolerated and no unexpected drug-related adverse events were reported. There were no differences in the overall incidence of adverse events between the active treatment groups or placebo. Constipation and headache, recognised side effects of 5-HT3 receptor antagonists, were the most commonly reported adverse events with the incidence of constipation with ondansetron alone (group III) being significantly greater than with over days 2-6 (14% vs. 6%; P = 0.030). CONCLUSION: In contrast to some previous investigations, in this study, ondansetron alone appears to have a minor role in the control of cisplatin-induced delayed emesis and nausea. In conclusion, the combination of oral ondansetron plus dexamethasone is superior to ondansetron and to placebo.

Adult↗
PubMed1996

The hypotensive effect of L-arginine is associated with increased expired nitric oxide in humans.

Endothelial metabolism of L-arginine to L-citrulline and the potent vasodilator, nitric oxide (NO), is important in the regulation of vascular tone and resting BP. L-arginine improves abnormal endothelium-dependent vasodilation in the setting of hypercholesterolemia and has a vasodilatory effect in normal vessels, effects presumed to be mediated through increased endogenous NO production, although this has not been established by direct measurement of NO. In a randomized, placebo-controlled, crossover trial, 10 healthy male subjects received a 30-min infusion of 0.5 g/kg L-arginine hydrochloride. Subjects underwent continuous monitoring of BP and heart rate (HR) as well as intermittent determination of mixed expired NO concentration and plasma L-arginine and L-citrulline levels. Infusion of L-arginine produced a significant fall in mean BP with a peak effect of -9.3 +/- 0.9% (p<0.005). The hemodynamic effects of L-arginine were associated with an increase in mixed expired NO concentration (FeNO) of 55 +/- 15% (p<0.005) from 15 +/- 2 to 21 +/- 3 parts per billion (ppb) and an increase in the rate of pulmonary NO excretion of 118 +/- 45% (p<0.005), as well as a rise in plasma L-citrulline from 25 +/- 4 to 46 +/- 5 micromol/l (p<0.005). There was a significant correlation between the hypotensive response to L-arginine and the increase in expired NO (r=-0.68, p<0.05). The hypotensive effect of L-arginine in humans appears to be mediated, at least in part, by NO synthase metabolism of L-arginine and increased endogenous NO production as indicated both by increased plasma L-citrulline and by increased expired NO.

Adult↗
PubMed1995

A single amino-acid change between the antigenically different extracellular serine proteases V2 and B2 from Dichelobacter nodosus.

Dichelobacter nodosus (Dn), the causative organism of ovine footrot, secrets three distinct types of extracellular serine proteases which have been implicated in virulence. Southern analyses have shown that the proteases are encoded by three separate genes, and the genes encoding an acidic protease V5 and a basic protease have already been characterised from virulent Dn strain 198. The gene encoding the third protease type, as represented by acidic protease V2, was isolated from an EcoRI-BamHI library of strain 198 genomic DNA by probing with a polymerase chain reaction (PCR) fragment generated with oligodeoxyribonucleotides based on protease V2 amino acid (aa) sequences. A further clone from an RsaI library was isolated to complete the 5' region of the gene to yield an ORF of 1803 bp encoding a protein precursor of 601 aa. The acidic protease V2 gene, aprV2, shows the same precursor structure as the bprV and aprV5 genes with 72% and 69% similarity at the nucleotide (nt) level and with 73% and 69% similarity at the aa level, respectively. As monoclonal antibodies consistently distinguish the virulent (V) and benign (B) forms of this protease, the gene encoding the acidic protease B2 from benign Dn strain 305 was isolated using the PCR and characterized to investigate the molecular basis for this difference in antigenicity. A 2-bp substitution in a single codon was identified which appeared to be responsible for a change of epitope.

Amino Acid Sequence↗
PubMed1995

Short-term pulmonary vasodilation with L-arginine in pulmonary hypertension.

BACKGROUND: Endothelial dysfunction may contribute to the pathogenesis of pulmonary hypertension through impaired production of the endothelium-derived vasodilator nitric oxide (NO). L-Arginine, the substrate for NO synthase (NOS), has a vasodilatory effect in systemic vascular beds and can correct abnormal endothelium-dependent vasodilation. It has been suggested that these two effects of L-arginine are mediated through NOS metabolism and enhanced NO production. Therefore, we assessed the short-term pulmonary hemodynamic effects of exogenous L-arginine in patients with pulmonary hypertension of various origins. METHODS AND RESULTS: During continuous hemodynamic monitoring, 10 subjects with pulmonary hypertension (mean pulmonary artery pressure [PAP], 54 +/- 5 mm Hg [mean +/- SEM]) received a 30-minute control infusion of hypertonic saline followed by a 30-minute infusion of 500 mg/kg of L-arginine. The hemodynamic effects of L-arginine were compared with those of prostacyclin titrated to maximally tolerated doses. The hemodynamic response to L-arginine was also studied in 5 subjects with heart failure but without pulmonary hypertension (mean PAP, 20 +/- 2 mm Hg) and 5 healthy control subjects. In subjects with pulmonary hypertension, infusion of L-arginine reduced mean PAP by 15.8 +/- 3.6% (P < .005) and pulmonary vascular resistance (PVR) by 27.6 +/- 5.8% (P < .005) compared with decreases of 13.0 +/- 5.5% (P < .005) and 46.6 +/- 6.2% (P < .005), respectively, with prostacyclin. L-Arginine infusion also increased the mean plasma level of L-arginine from 59 +/- 6 mumol/L to 10,726 +/- 868 mumol/L (P < .005), which was associated with a significant increase in the plasma level of L-citrulline, the immediate product of NOS metabolism of L-arginine. Moreover, the peak plasma level of L-citrulline correlated significantly with the reductions in mean PAP (r = .71, P < .05) and PVR (r = .70, P < .05), consistent with vasodilation mediated by NOS metabolism of exogenous L-arginine and increased NO production. L-Arginine also had a modest hypotensive effect in healthy control subjects and reduced systemic vascular resistance in subjects with heart failure in the absence of pulmonary hypertension. However, only small reductions in absolute pulmonary vascular resistance were observed in this latter group in response to L-arginine that did not reach significance. CONCLUSIONS: An exaggerated short-term pulmonary vasodilatory response to L-arginine in patients with pulmonary hypertension suggests a relative impairment in pulmonary vascular endothelial NO production that may contribute to increased pulmonary vascular tone and thus be important in the pathophysiology of pulmonary hypertension.

Adult↗
PubMed1995

Differentiation of embryonal carcinoma cells to a neural or cardiomyocyte lineage is associated with selective expression of endothelin receptors.

Endothelins (ETs) were initially characterized as potent vasoactive peptides acting through at least two distinct receptors, ETA and ETB. Subsequently, their significant growth- and hypertrophy-promoting properties in cardiac and other cells were recognized. We investigated the expression of endothelin receptors during differentiation of a pluripotential embryonal carcinoma cell line (P19) to a cardiomyocyte or a neural lineage. These cells resemble those of the inner cell mass of the blastocyst, and their differentiation is believed to closely mimic critical events in early embryogenesis. Differentiation of P19 to a cardiomyocyte lineage, by aggregation and exposure to dimethyl sulfoxide resulted in induction of ETA receptors as demonstrated by radioligand binding studies, Northern blotting, and reporter gene analysis. Moreover, the P19 differentiated to a cardiac lineage responded to ET-1 with a 3-fold increase in the secretion of atrial natriuretic peptide. In contrast, differentiation to a neural lineage, by aggregation and exposure to retinoic acid, was associated with the induction of predominantly ETB. Therefore, selective differentiation of the P19 led to the differential expression of endothelin receptors in a pattern consistent with that observed in normal myocardial and neural tissue. The induction of endothelin receptors in a model system of early embryogenesis provides strong support for the critical role of this peptide/receptor family in differentiation and development. As well, this model system is well suited for the study of the mechanisms controlling endothelin receptor expression during differentiation.

Animals↗
PubMed1995

Evidence for a role of endothelin 1 and protein kinase C in nitroglycerin tolerance.

We sought to examine mechanisms responsible for increased vasoconstriction that occurs during development of nitroglycerin tolerance. Rabbits were treated for 3 days with nitroglycerin patches (0.4 mg/hr), and their aortic segments were studied in organ chambers. This treatment resulted in attenuated in vitro relaxations to nitroglycerin and increased contractile sensitivity to angiotensin II, serotonin, phenylephrine, KCl, and a direct activator of protein kinase C, the phorbol ester phorbol 12,13-dibutyrate. The protein kinase C antagonists calphostin C (100 nM) and staurosporine (10 nM) corrected the hypersensitivity to constrictors in tolerant vessels, yet had minimal effects on constrictions in control vessels. Paradoxically, constrictions caused by endothelin 1 were decreased in nitrate-tolerant vessels. Immunocytochemical analysis revealed intense endothelin 1-like and big endothelin 1-like immunoreactivity in the media of nitroglycerin-tolerant but not of control aortas. The enhanced vasoconstriction to angiotensin II, serotonin, KCl, and phenylephrine could be mimicked in normal vessels by addition of subthreshold concentrations of endothelin 1, and this effect was prevented by calphostin C. We propose that increased autocrine production of endothelin 1 in nitrate tolerance sensitizes vascular smooth muscle to a variety of vasoconstrictors through a protein kinase C-mediated mechanism.

Alkaloids↗