Biomedical subjects

D J Stewart

Publications and source records attributed to D J Stewart.

At least 163 records · Page 9Linked to original sources

PubMed1993

Use of a gram- signal peptide for protein secretion by gram+ hosts: basic protease of Dichelobacter nodosus is produced and secreted by Bacillus subtilis.

The bprV gene, encoding the extracellular basic protease of the Gram- anaerobic bacterium Dichelobacter nodosus, was expressed and the protein secreted in Bacillus subtilis using the novel cloning/expression vector pNC3 [Wu et al., Gene 106 (1991) 103-107]. The pre- and pro-peptides were processed correctly in this heterologous system, and the 127-amino acid C-terminal extension region was also removed. The recombinant gene product was indistinguishable biochemically or immunochemically from the authentic protease and was able to form crystals upon dialysis, as was found for the authentic protease. This is the first example of the direct secretion of a Gram- extracellular enzyme in B. subtilis via its own signal peptide. The fact that this gene can be expressed and its product secreted in both Escherichia coli and B. subtilis provides a unique opportunity to study and compare the similarities and differences in protein secretion between Gram- and Gram+ organisms.

Amino Acid Sequence↗

PubMed1993

Expression of endothelin-1 in lungs of patients with cryptogenic fibrosing alveolitis.

The vasoconstrictor and mitogenic peptide endothelin-1 (ET-1) is believed to play a part in fibrosis and collagen production. We examined expression of ET-1 in lung tissue from 52 patients with interstitial lung fibrosis, of whom 45 had cryptogenic fibrosing alveolitis (CFA), 10 had CFA and concomitant pulmonary hypertension, and 7 had non-specific focal fibrosis. 17 normal unused donor lungs were studied as controls. Immunohistochemistry and in-situ hybridisation were done with polyclonal antisera to ET-1 and its precursor big ET-1, and complementary RNA probes for preproET-1. Normal lung tissue and that from patients with focal fibrosis expressed very little ET-1. By contrast, there was striking expression of ET-1 in lung tissue from patients with CFA. Immunostains for ET-1 and big ET-1 and expression of ET-1 mRNA were most prominent in airway epithelium and type II pneumocytes, particularly those lining areas of young granulation tissue. ET-1-like immunoreactivity and mRNA were also present in pulmonary vascular endothelial cells, particularly in specimens from patients with pulmonary hypertension. In all patients, there was a significant correlation between ET-1-like immunoreactivity and histological parameters of disease activity (r = 0.78, 95% CI 0.65-0.87, p < 0.001). These findings suggest a possible role for cell-specific expression of ET-1 in the pathogenesis of CFA and associated pulmonary hypertension.

Biomarkers↗

PubMed1993

Expression of endothelin-1 in the lungs of patients with pulmonary hypertension.

BACKGROUND: Pulmonary hypertension is characterized by an increase in vascular tone or an abnormal proliferation of muscle cells in the walls of small pulmonary arteries. Endothelin-1 is a potent endothelium-derived vasoconstrictor peptide with important mitogenic properties. It has therefore been suggested that endothelin-1 may contribute to increases in pulmonary arterial tone or smooth-muscle proliferation in patients with pulmonary hypertension. We studied the sites and magnitude of endothelin-1 production in the lungs of patients with various causes of pulmonary hypertension. METHODS: We studied the distribution of endothelin-1-like immunoreactivity (by immunocytochemical analysis) and endothelin-1 messenger RNA (by in situ hybridization) in lung specimens from 15 control subjects, 11 patients with plexogenic pulmonary arteriopathy (grades 4 through 6), and 17 patients with secondary pulmonary hypertension and pulmonary arteriopathy of grades 1 through 3. RESULTS: In the controls, endothelin-1-like immunoreactivity was rarely seen in vascular endothelial cells. In the patients with pulmonary hypertension, endothelin-1-like immunoreactivity was abundant, predominantly in endothelial cells of pulmonary arteries with medial thickening and intimal fibrosis. Likewise, endothelin-1 messenger RNA was increased in the patients with pulmonary hypertension and was expressed primarily at sites of endothelin-1-like immunoreactivity. There was a strong correlation between the intensity of endothelin-1-like immunoreactivity and pulmonary vascular resistance in the patients with plexogenic pulmonary arteriopathy, but not in those with secondary pulmonary hypertension. CONCLUSIONS: Pulmonary hypertension is associated with the increased expression of endothelin-1 in vascular endothelial cells, suggesting that the local production of endothelin-1 may contribute to the vascular abnormalities associated with this disorder.

Adult↗

PubMed1993

Regulation of the endothelin-1 transmembrane signaling pathway: the potential role of agonist-induced desensitization in the coronary artery of the rapid ventricular pacing-overdrive dog model of heart failure.

This study examined the potential role of ET-1 and the contribution of protein kinase C (PKC) in the desensitization of the ET-1 transmembrane signaling pathway in the left circumflex coronary artery (CCA) of a dog model of congestive heart failure (CHF). In the CCA of the rapid ventricular pacing-overdrive dog model of CHF, elevated plasma endothelin levels were associated with a decrease in the basal accumulation of inositol phosphates and ET-1 mediated activation of phosphatidylinositol (PI) turnover (P < 0.05). To assess whether elevated plasma ET-1 levels may have contributed to the diminished ET-1 responsiveness in the heart failure dogs, ET-1 generation of inositol phosphates was measured following a one hour pretreatment of normal coronary artery rings with 0.1 nM ET-1. As compared to non-treated rings, ET-1 pretreatment resulted in a 33% decrease of ET-1 (10 nM) production of inositol phosphates. To evaluate the role of PKC in this process, normal coronary rings pretreated for a period of one hour with the phorbol ester, phorbol 12-myristate 13-acetate (PMA, 1 microM), resulted in a similar attenuation (36%) of ET-1 production of inositol phosphates. In the presence of the protein kinase C inhibitor staurosporine, both the agonist and phorbol ester induced decreases in ET-1 mediated PI turnover were reversed. Staurosporine even potentiated (75%) ET-1 induced PI turnover despite ET-1 and PMA pretreatments. These results suggest that agonist-induced desensitization of ET-1 mediated PI turnover can occur and is at least one of the possible mechanisms contributing to the desensitization of the ET-1 transmembrane signaling pathway in the pacing-overdrive model of heart failure in the dog.

Alkaloids↗

PubMed1993

Human autopsy tissue distribution of the epipodophyllotoxins etoposide and teniposide.

Autopsy tissues were collected from ten patients who had received etoposide, 150-3480 mg, from 1 to 412 days antemortem and from five patients who had received teniposide, 234-1577 mg, from 3 to 52 days antemortem. Tissues were assayed for etoposide and teniposide using high-pressure liquid chromatography with electrochemical detection. Etoposide was detectable in tissues of three of four patients dying < 5 days after their last etoposide treatments to cumulative doses of 150-432 (median, 280) mg but was detectable in tissues of only one of six patients dying 7-412 (median, 37) days after their last etoposide treatment to a cumulative dose of 607-3600 (median, 1553) mg. The highest tissue concentrations were in the small bowel, prostate, thyroid, bladder, spleen, and testicle. Intermediate concentrations were found in the lymph node, skeletal muscle, adrenal gland, stomach, tumor, liver, lung, pancreas, and kidney, and the lowest concentrations were found in the heart, brain, diaphragm, vagina, and esophagus. Teniposide was detectable in one patient dying 3 days after a cumulative teniposide dose of 576 mg (spleen, prostate, heart > large bowel, liver, pancreas > thyroid, adrenal, stomach, small bowel, bladder, testicle, and skeletal muscle) but was not detectable in any tissue from four patients dying 5-52 (median, 8) days after their last treatment to a cumulative teniposide dose of 234-1577 (median, 520) mg. The very short tissue half-life contrasts with our previous observations for human autopsy tissue concentrations of mitoxantrone, doxorubicin, menogaril metabolites, diaziquone, and amsacrine. The short tissue half-life may help explain the schedule dependency of epipodophyllotoxin efficacy and may also help explain the lack of visceral toxicity of these compounds.

Chromatography, High Pressure Liquid↗

PubMed1993

Human autopsy-tissue distribution of menogaril and its metabolites.

Autopsy-tissues were obtained from eight patients who had last received menogaril (total cumulative dose, 175-1080 mg/m2) intravenously (one patient) or orally (seven patients) from 1 to 285 days prior to death. Tissue samples were assayed for menogaril and its metabolities by high-pressure liquid chromatography. Unchanged menogaril was found only in a single lung-tissue sample from a patient who had died < 24 h after receiving his last treatment. N-Demethylmenogaril was found in two lung-tissue samples and in single samples of the thyroid, lymph node, pancreas, cerebellum, and tumor. The major menogaril metabolite found in human autopsy-tissues was 7-deoxynogarol. The highest 7-deoxynogarol concentrations were found in the large bowel (median, 201 ng/g), liver (median, 183 ng/g), and lung (median, 177 ng/g). The heart ranked as the 9th of 18 organs in median 7-deoxynogarol concentration, after the large bowel, liver, lung, tumor, thyroid, skeletal muscle, adrenal gland, and kidney. The lowest concentrations were detected in brain tissue. Our results suggest that the low degree of cardiac toxicity and the possible pulmonary toxicity of menogaril may be related to relative tissue concentrations of menogaril metabolites. Tumor 7-deoxynogarol concentrations were comparable with those in normal tissues, except that concentrations in intracerebral tumors were higher than those in the normal brain. Tissue 7-deoxynogarol concentrations appeared to be directly related to the cumulative dose and inversely related to the time from the last treatment to death; the value obtained by dividing dose by time correlated (P < 0.05) with tissue 7-deoxynogarol concentrations.

Chromatography, High Pressure Liquid↗

PubMed1993

Phase II study of lonidamine plus radiotherapy in the treatment of brain metastases.

Twenty-nine patients received the cytotoxic radiosensitizing agent lonidamine before, during, and after cranial irradiation for brain metastases. One patient was ineligible (meningioma). In 28 eligible patients, median survival was 29 weeks (range, 2 to > 220 weeks). Nine patients (32%) survived > 1 year and 3 (11%) survived > 2 years. The major toxic effects of lonidamine were myalgias, nausea and vomiting, somnolence, and ototoxicity. There was no evidence that radiation skin toxicity or cerebral toxicity was increased by the addition of lonidamine. None of the patients experienced shrinkage of their extracerebral disease on lonidamine. Median survival duration in this study was at the upper limit of that reported in the literature for radiation alone, and the proportion of 2 year survivors was also higher than usual for radiation alone. Hence, further studies may be warranted.

Adult↗

PubMed1993

Phase II study of tiazofurin in gliomas in adults. A National Cancer Institute of Canada study.

The National Cancer Institute of Canada conducted a Phase II study of tiazofurin 1100 to 1375 mg/m2 IV daily x 5 days in adults with grade 2, 3, and 4 gliomas. No responses were seen. Five of sixteen evaluable patients had stable disease for 38 to 147 days (median, 75 days). Treatment was generally well tolerated, and hence the dose was escalated from 1100 mg/m2/day to 1375 mg/m2/day after the first twelve patients were entered. Treatment-induced hypertension requiring pharmacological intervention was seen in four patients. Gastrointestinal toxicity was generally mild. Treatment-related headache was seen in thirteen patients, and drowsiness or weakness was seen in seven patients. In summary, tiazofurin on this dose schedule does not have major activity against grade 2, 3, and 4 gliomas.

Adult↗

PubMed1993

Feasibility study of intraarterial vs intravenous cisplatin, BCNU, and teniposide combined with systemic cisplatin, teniposide, cytosine arabinoside, glycerol and mannitol in the treatment of primary and metastatic brain tumors.

Sixteen patients with intracerebral tumors received intraarterial cisplatin, teniposide, and BCNU combined with intravenous cisplatin, teniposide, and cytosine arabinoside. Oral glycerol and intravenous mannitol were given along with the intravenous chemotherapy in an attempt to increase drug delivery to tumor by augmenting tumor blood flow. Thirteen additional patients were treated with the same regimen, but received all the chemotherapy intravenously. Of the 16 patients receiving intraarterial chemotherapy (median survival, 14 weeks), none responded, 5 (31%) were stable for > 8 weeks, 8 (50%) failed, and 3 (19%) were unevaluable due to early death. Of the 13 patients receiving all their treatment intravenously (median survival, 13 weeks), 3 (23%) responded, 1 (8%) was stable, 7 (54%) failed, and 2 (15%) were unevaluable due to early death. In the patients receiving intraarterial chemotherapy, toxicity included ipsilateral retinal toxicity (2 patients), ocular pain or headache (10), periorbital swelling and flushing (6), increased brain edema with focal neurological deficits and drowsiness (5), and catheter-related carotid artery thrombosis followed by fatal herniation (1). Myelosuppression was worse in patients who received all their treatment intravenously than in those receiving intraarterial chemotherapy (p < 0.05). Neutropenic sepsis developed in 4 patients on the intraarterial arm (1 fatal) and in 5 patients on the intravenous arm (2 fatal). Other toxic effects were similar whether or not patients received intraarterial treatment or only intravenous treatment. Overall, toxicity of this regimen was excessive, and response rates were lower than would have been expected with single agent therapy.

Adult↗

PubMed1993

Pentoxifylline decreases cyclosporine-induced renal endothelin release and vasoconstriction.

Cyclosporine (CSA) causes an acute vasoconstriction of renal artery and a significant increase in renal endothelin release. Pentoxifylline, a vasodilator, has been suggested to prevent CSA toxicity. To study the effect of pentoxifylline treatment on CSA-related vasoconstriction and endothelin release, a model of renal autoperfusion in the dog was used. Oral pentoxifylline at the dose of 400 mg three times daily for 3 days was given to 15 dogs. Pure powder CSA (10 mg) was injected into the isolated renal artery perfused at constant flow; changes in perfusion pressure reflected variations in vascular resistance. In the pentoxifylline-treated group (15 dogs), the infusion of CSA caused an average increase of 27 +/- 8 mm Hg in renal perfusion pressure, compared with 60 +/- 10 mm Hg in a control group of 8 untreated animals (p < or = 0.05). Plasma concentration of endothelin in the renal vein increased from an average of 1.2 +/- 0.2 pg/mL before to 2.4 +/- 0.5 pg/mL after CSA administration (p < or = 0.05) in the control group, whereas it did not change significantly in the pentoxifylline-treated group. Thus, oral pretreatment with pentoxifylline significantly decreased the renal vasoconstriction and endothelin release due to CSA administration.

Animals↗

PubMed1993

Active chemotherapy for metastatic stromal cell tumor of the testis.

Metastatic stromal cell tumors of the testis are largely refractory to chemotherapy. We report a case of a young man with widely metastatic testicular stromal cell tumor who achieved complete clinical remission following chemotherapy with etoposide, ifosfamide, cisplatin, and bleomycin.

Adolescent↗

PubMed1993

Doxorubicin plus metronidazole in the treatment of recurrent or metastatic squamous cell carcinoma of the head and neck.

Twenty-five patients were treated on a Phase II study of doxorubicin, 60-75 mg/m2 intravenously every 3 weeks, accompanied by metronidazole, 1500 mg/m2 orally 12 hours and immediately before the doxorubicin and 6 hours and 24 hours after the doxorubicin. Of 23 patients evaluable for response, 2 (9%) achieved complete remissions, 2 (9%) achieved partial remissions, and 4 (18%) were stable (one of whom achieved a minor response). One patient with an inoperable biopsy-proven 4 x 3 x 3 cm recurrence following radiation and surgery has had a complete remission that persists at 8 years. The second patient who achieved a complete remission subsequently underwent surgical resection of the involved area. No residual tumor was found, and he remains disease free after 8.5 years. Doxorubicin toxicity did not appear to be augmented significantly by metronidazole. Although the response rate seen in this study was low, the occurrence of two long-term complete remissions suggests that this combination should be studied further in other tumor types.

Adult↗

PubMed1993

Cisplatin, cytosine arabinoside, and pentoxifylline in the treatment of squamous cell carcinoma of the head and neck.

Nine patients were entered on a Phase I-II study of cisplatin, cytosine arabinoside, and pentoxifylline in the treatment of advanced head and neck cancer. The treatment regimen consisted of cisplatin 100 mg/m2 intravenously on day 1 only, cytosine arabinoside 2,000 mg/m2 intravenously on days 1 and 2, and pentoxifylline 400 mg orally three times daily beginning 7 to 14 days before the chemotherapy. The pentoxifylline was continued between chemotherapy cycles. Chemotherapy courses were repeated at 3- to 4-week intervals. Partial remission were seen in two patients, two patients were stable, and five patients failed on treatment. Dose-limiting toxicity was granulocytopenia. Pentoxifylline itself caused some nausea and anorexia. Although the patient numbers were small, there was no indication that pentoxifylline increased the efficacy of this chemotherapy in head and neck cancer. It is possible that another dose schedule might have been more effective.

Adult↗

PubMed1993

Phase II multicenter study of epirubicin for hormone-resistant prostatic cancer with measurable soft tissue disease.

Twenty-six patients with prostatic cancer were treated with courses of epirubicin at 3-week intervals, starting at an initial intravenous dose of 75 mg/m2. All patients had progressive disease after orchiectomy and/or antiandrogen therapy and had measurable soft tissue lesions. There were three partial responders (response rate: 12%; 95% confidence limits: 4-29%). Major toxicity was myelosuppression, and there were two drug-related deaths. Epirubicin in this dose and schedule cannot be recommended for treatment of prostatic cancer.

Aged↗

PubMed1993

Cyclosporine-induced elevation in circulating endothelin-1 in patients with solid-organ transplants.

The long-term use of cyclosporine is associated with significant complications, including hypertension and renal failure. Recent data from animal experiments suggest that alterations in renal function induced by high-dose CsA may be mediated by endothelin-1 (ET-1), a potent endothelium-derived vasoconstrictor and mitogenic peptide. The aim of the present study was to determine the effect of oral CsA on circulating levels of ET-1 in patients receiving standard immunosuppressive therapy following solid-organ transplantation (13 renal, 7 heart, 1 heart-lung, 1 liver). Plasma levels of ET-1 were measured by radioimmunoassay over a 24-hr period beginning with the oral administration of a single daily dose of CsA in 18 patients (5.6 +/- 0.5 mg/kg), or similar immunosuppressive therapy without CsA in 4 patients. Blood levels of CsA (parent compound and metabolites) were measured in 10 of the patients by RIA. Predose levels of ET-1 were similar in the two groups (1.73 +/- 0.32 and 1.29 +/- 0.9 pg/ml, respectively). Patients not receiving CsA showed no change in plasma ET-1 over the 24-hr period. In contrast, in the CsA-treated group there was a significant increase in plasma ET-1, reaching a peak at 6 hr (2.45 +/- 0.56 pg/ml, P < 0.03) that followed the peak increase in CsA parent compound and preceded the peak increase in metabolites. No significant differences were found between peak and trough levels of ET-1 in patients with moderate renal dysfunction (creatinine (Cr) > or = 150 mumol/L) compared with those with near-normal renal function, or patients receiving renal compared with nonrenal grafts. However, patients with long-term grafts (> 60 days) showed an exaggerated response to CsA, with a fractional increase in plasma ET-1 of 3.67 +/- 0.52 (n = 8) compared with 2.16 +/- 0.28 (n = 10) for patients with more recent grafts (P < 0.05). Therefore, oral administration of CsA causes an increase in circulating ET-1 in patients with solid-organ transplants that might contribute to CsA-associated nephrotoxicity and hypertension, particularly during long-term immunosuppressive therapy.

Adult↗

PubMed1993

The effects of antigenic competition on the efficacy of multivalent footrot vaccines.

A multivalent footrot vaccine has been developed, containing pilus antigens produced in recombinant Pseudomonas aeruginosa and representing all nine serogroups of Dichelobacter (Bacteroides) nodosus commonly recognised in the field. The responses of sheep to the multivalent vaccine have been compared with those to monovalent vaccines representing only a single serogroup. Antigenic competition between serogroups occurred in sheep immunised with the multivalent formation, but high levels of protection were still achieved. The study showed that in multivalent footrot vaccines, antigenic competition is predominantly due to the presence of a family of immunologically-related pilus antigens rather than to interference by extraneous proteins.

Agglutination Tests↗

PubMed1993

Ontogeny of Big endothelin-1 effects in newborn piglet pulmonary vasculature.

Endothelin-1 (ET-1), a 21-amino acid peptide produced by endothelial cells, results from the cleavage of preproendothelin, generating Big ET-1, which is then cleaved by the ET-converting enzyme (ECE) to form ET-1. Big ET-1, like ET-1, is released by endothelial cells. Big ET-1 is equipotent to ET-1 in vivo, whereas its vasoactive effects are less in vitro. It has been suggested that the effects of Big ET-1 depend on its conversion to ET-1. ET-1 has potent vasoactive effects in the newborn pig pulmonary circulation, however, the effects of Big ET-1 remain unknown. Therefore, we studied the effects of Big ET-1 in isolated perfused lungs from 1- and 7-day-old piglets using the ECE inhibitor, phosphoramidon, and the ETA receptor antagonist, BQ-123Na. The rate of conversion of Big ET-1 to ET-1 was measured using radioimmunoassay. ET-1 (10(-13) to 10(-8) M) produced an initial vasodilation, followed by a dose-dependent potent vasoconstriction (P < 0.001), which was equal at both ages. Big ET-1 (10(-11) to 10(-8) M) also produced a dose-dependent vasoconstriction (P < 0.001). The constrictor effects of Big ET-1 and ET-1 were similar in the 1-day-old, whereas in the 7-day-old, the constrictor effect of Big ET-1 was less than that of ET-1 (P < 0.017).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1993

Endothelin-1 in acute lung injury and the adult respiratory distress syndrome.

Endothelial damage is a hallmark of acute lung injury. Endothelial mediators may increase pulmonary vascular tone and induce pulmonary arterial muscularization, thereby contributing to the pulmonary hypertension seen with acute lung injury. We measured plasma levels and net pulmonary clearance of endothelin-1, a potent endothelium-derived vasoconstrictor peptide and smooth muscle mitogen, in 26 patients with early acute lung injury, the adult respiratory distress syndrome, and pulmonary hypertension. Nineteen had another data collection at clinical improvement or worsening. Control subjects (n = 25) had no pulmonary hypertension or lung injury. Initial mixed venous and systemic arterial plasma endothelin-1 levels were elevated (4.6 +/- 0.6 SEM and 4.9 +/- 0.6 pg/ml, respectively) as compared with control subjects (0.9 +/- 0.1 and 0.6 +/- 0.1 pg/ml). The systemic arterial/venous endothelin-1 ratio was 1.1 +/- 0.1 (0.7 +/- 0.1 in control subjects), indicating a reduction in normal net pulmonary endothelin-1 clearance. With clinical improvement, as compared with clinical worsening, mean plasma endothelin-1 levels, arterial/venous ratio, and pulmonary arterial pressure fell significantly towards normal. Thus, patients with acute lung injury have marked early increases in circulating plasma endothelin-1 levels, associated with abnormal pulmonary endothelin-1 metabolism. These abnormalities reverse in patients who recover. Through its actions, endothelin-1 could contribute to the pulmonary hypertension seen in acute lung injury.

Blood Pressure↗