Biomedical subjects

S A Little

Publications and source records attributed to S A Little.

At least 19 recordsLinked to original sources

PubMed2003

Teratogen-induced activation of caspase-6 and caspase-7 in early postimplantation mouse embryos.

BACKGROUND: Previous work has shown that teratogens such as hyperthermia (HS), 4-hydroperoxycyclophosphamide (4CP), and staurosporine (ST) induce cell death in day 9 mouse embryos by activating the mitochondrial apoptotic pathway. Key to the activation of this pathway is the activation of a caspase cascade involving the cleavage-induced activation of an initiator procaspase, caspase-9, and the downstream effector procaspase, caspase-3. For example, procaspase-3, an inactive proenzyme of 32 kDa is cleaved by activated caspase-9 to generate a large subunit of approximately 17 kDa and a small subunit of approximately 10 kDa. In turn, caspase-3 is known to target a variety of cellular proteins for proteolytic cleavage as part of the process by which dying cells are eliminated. Previous work has also shown that neuroepithelial cells are sensitive to teratogen-induced activation of this pathway and subsequent cell death whereas cells of the heart are resistant. Although caspase-3 is a key effector caspase activated by teratogens, two other effector caspases, caspase-6 and caspase-7, are known; however, their role in teratogen-induced cell death is unknown. METHODS: Because cleavage-induced generation of specific subunits is the most specific assay for activation of caspases, we have used antibodies that recognize the procaspase and one of its active subunits and a Western blot approach to assess the activation of caspase-6 and caspase-7 in day 9 mouse embryos (or heads, hearts and trunks isolated from whole embryos) exposed to HS, 4CP, and ST. To probe the relationship between teratogen-induced activation of caspase-9/caspase-3 and the activation of caspase-6/caspase-7, we used a mitochondrial-free embryo lysate with or without the addition of cytochrome c, recombinant active caspase-3, or recombinant active caspase-9. RESULTS: Western blot analyses show that these three teratogens, HS, 4CP, and ST, induce the activation of procaspase-6 (appearance of the 13 kDa subunit, p13) and caspase-7 (appearance of the 19 kDa subunit, p19) in day 9 mouse embryos. In vitro studies showed that both caspase-6 and caspase-7 could be activated by the addition of cytochrome c to a lysate prepared from untreated embryos. In addition, caspase-6 could be activated by the addition of either recombinant caspase-3 or caspase-9 to a lysate prepared from untreated embryos. In contrast, caspase-7 could be activated by addition of recombinant caspase-3 but only minimally by recombinant caspase-9. Like caspase-9/caspase-3, caspase-6 and caspase-7 were not activated in hearts isolated from embryos exposed to these three teratogens. CONCLUSIONS: HS, 4CP and ST induce the cleavage-dependent activation of caspase-6 and caspase-7 in day 9 mouse embryos. Results using DEVD-CHO, a caspase-3 inhibitor, suggest that teratogen-induced activation of caspase-6 is mediated by caspase-3. In addition, our data suggest that caspase-7 is activated primarily by caspase-3; however, we cannot rule out the possibility that this caspase is also activated by caspase-9. Finally, we also show that teratogen-induced activation of caspase-6 and caspase-7 are blocked in the heart, a tissue resistant to teratogen-induced cell death.

Animals↗

PubMed2002

Influence of cigarette smoking on inhaled corticosteroid treatment in mild asthma.

BACKGROUND: Although inhaled corticosteroids have an established role in the treatment of asthma, studies have tended to concentrate on non-smokers and little is known about the possible effect of cigarette smoking on the efficacy of treatment with inhaled steroids in asthma. A study was undertaken to investigate the effect of active cigarette smoking on responses to treatment with inhaled corticosteroids in patients with mild asthma. METHODS: The effect of treatment with inhaled fluticasone propionate (1000 microg daily) or placebo for 3 weeks was studied in a double blind, prospective, randomised, placebo controlled study of 38 steroid naïve adult asthmatic patients (21 non-smokers). Efficacy was assessed using morning and evening peak expiratory flow (PEF) readings, spirometric parameters, bronchial hyperreactivity, and sputum eosinophil counts. Comparison was made between responses to treatment in non-smoking and smoking asthmatic patients. RESULTS: There was a significantly greater increase in mean morning PEF in non-smokers than in smokers following inhaled fluticasone (27 l/min v -5 l/min). Non-smokers had a statistically significant increase in mean morning PEF (27 l/min), mean forced expiratory volume in 1 second (0.17 l), and geometric mean PC20 (2.6 doubling doses), and a significant decrease in the proportion of sputum eosinophils (-1.75%) after fluticasone compared with placebo. No significant changes were observed in the smoking asthmatic patients for any of these parameters. CONCLUSIONS: Active cigarette smoking impairs the efficacy of short term inhaled corticosteroid treatment in mild asthma. This finding has important implications for the management of patients with mild asthma who smoke.

Administration, Inhalation↗

PubMed2002

High resolution computed tomographic assessment of airway wall thickness in chronic asthma: reproducibility and relationship with lung function and severity.

BACKGROUND: In some patients chronic asthma results in irreversible airflow obstruction. High resolution computed tomography (HRCT) has been advocated for assessing the structural changes in the asthmatic lung and permits investigation of the relationships between airway wall thickening and clinical parameters in this condition. METHODS: High resolution CT scanning was performed in 49 optimally controlled asthmatic patients and measurements of total airway and lumen diameter were made by two independent radiologists using electronic callipers. Wall area as % total airway cross sectional area (WA%) and wall thickness to airway diameter ratio (T/D) were calculated for all airways clearly visualised with a transverse diameter of more than 1.5 mm, with a mean value derived for each patient. Intra- and inter-observer variability was assessed for scope of agreement in a subgroup of patients. Measurements were related to optimum forced expiratory volume in 1 second (FEV1), forced mid expiratory flow, carbon monoxide gas transfer, two scores of asthma severity, airway inflammation as assessed with induced sputum, and exhaled nitric oxide. RESULTS: Neither observer produced a statistically significant difference between measurements performed on two occasions but there was a significant difference between observers (limits of agreement -2.6 to 6.8 for WA%, p<0.0001). However, mean WA% measured on two occasions differed by no more than 5.4% (limits of agreement -4.0 to 5.4; mean (SD) 0.7 (2.4)). Statistically significant positive associations were observed between both WA% and T/D ratio and asthma severity (r(S)=0.29 and 0.30, respectively, for ATS score), and an inverse association with gas transfer coefficient was observed (r(S)=-0.43 for WA% and r(S)=-0.41 for T/D). No association was identified with FEV1 or airway inflammation. CONCLUSIONS: The airway wall is thickened in more severe asthma and is associated with gas transfer coefficient. This thickening does not relate directly to irreversible airflow obstruction as measured with FEV1.

Airway Obstruction↗

PubMed2001

Co-localization of active caspase-3 and DNA fragmentation (TUNEL) in normal and hyperthermia-induced abnormal mouse development.

BACKGROUND: Previous work has shown that caspase-3 activation and DNA fragmentation, two hallmarks of apoptosis, are induced in day 9 mouse embryos exposed to hyperthermia (43 degrees C); however, the methods used to assess caspase-3 activation (Western blot) and DNA fragmentation (gel electrophoresis) did not allow these apoptotic events to be localized to specific cells within the embryo. METHODS: To co-localize active caspase-3 and DNA fragmentation to specific cells, we used paraffin sections of day 13 mouse limb buds, sections of control and hyperthermia-treated day 9 mouse embryos, and sequential immunohistochemical staining for caspase-3 and TUNEL staining for DNA fragmentation. We used a primary rabbit antibody specific for the active, p17 subunit of caspase-3 and a goat anti-rabbit secondary antibody conjugated to Alexa 594 fluorochrome (red fluorescence) to localize active caspase-3. To co-localize DNA fragmentation, we subsequently processed the same sections by the TUNEL method using fluorescein-labeled dUTP (green fluorescence). RESULTS: Using this dual labeling approach, we show that active caspase-3 (caspase-3 positive) and DNA fragmentation (TUNEL positive) occur in a sub-population of interdigital mesenchyme cells of day 13 mouse limb buds. Using the same approach, we detected a small number of caspase-3 positive and TUNEL-positive cells in the central nervous system and in the mesenchyme of the first branchial arch of untreated day 9 mouse embryos. The number of caspase-3 and TUNEL-positive cells are greatly increased 5 hr after a brief exposure to hyperthermia (43 degrees C, 13 min). Caspase-3 and TUNEL-positive cells were most abundant in the neuroepithelium of the developing central nervous system, mesenchyme of the first pharyngeal arch, and somitic mesoderm. In contrast, the heart, mesencephalic mesenchyme, and the visceral yolk sac contained few, if any, caspase-3 and TUNEL-positive cells. CONCLUSIONS: This is the first demonstration that activation of caspase-3 and DNA fragmentation co-localize in cells programmed to die in the interdigital mesenchyme of day 13 limb buds and in the neuroepithelium and branchial arch mesenchyme of day 9 mouse embryos. Similarly, our results represent the first co-localization of teratogen-induced activation of caspase-3 and DNA fragmentation in specific cells of early postimplantation mouse embryos, and confirm that cells of the developing central nervous system are acutely sensitive to the cell death-inducing potential of hyperthermia, whereas cells of the heart are resistant. Finally, we show for the first time that, like cells of the heart, cells of the mesencephalic mesenchyme and the visceral yolk sac are also resistant to hyperthermia-induced apoptosis.

Animals↗

PubMed2001

Hepatocellular carcinoma: current surgical management.

At present the only potentially curative treatment for hepatocellular carcinoma (HCC) is either partial hepatectomy or total hepatectomy with orthotopic liver transplantation (OLT). Underlying liver reserve and regenerative capacity are the most important determinants of the risk of postoperative hepatic failure after partial hepatectomy; thus, careful preoperative assessment of liver function is mandatory. In specialized centers perioperative mortality is less than 5%, although cirrhotic patients are at increased risk. Various neoadjuvant and adjuvant therapies are under investigation, but as yet there are no data that demonstrate benefit from adjuvant systemic chemotherapy. The use of OLT is limited by the difficulty of obtaining donor livers. Patients selected for transplantation and partial hepatectomy represent two distinct subgroups, but their survival after treatment is comparable. Despite the progress in the management of HCC by surgical resection, the fact remains that the majority of these patients will experience local recurrences. This has led to the development of a variety of novel new treatments that require further evaluation.

Carcinoma, Hepatocellular↗

PubMed2001

Smoking and airway inflammation in patients with mild asthma.

STUDY OBJECTIVES: Cigarette smoking is common in asthmatic patients, and we investigated the impact of cigarette smoking on airway inflammation in asthma. DESIGN: Single-center observational study of airway inflammation in asthmatic and healthy smokers and nonsmokers. SETTING: Asthma research unit in a university hospital. PATIENTS OR PARTICIPANTS: Sixty-seven asthmatic and 30 nonasthmatic subjects classified as smokers or nonsmokers. Asthmatics had chronic, stable asthma and were not receiving inhaled or oral steroids at the time of the study. INTERVENTIONS: We examined induced-sputum cell counts and levels of interleukin (IL)-8 and eosinophilic cationic protein (ECP). Bronchial hyperreactivity was assessed using methacholine challenge. MEASUREMENTS AND RESULTS: Asthmatic smokers had higher total sputum cell counts than nonsmoking asthmatics and both smoking and nonsmoking healthy subjects. Smoking was associated with sputum neutrophilia in both asthmatics and nonasthmatics (median, 47% and 41%, respectively) compared with nonsmokers (median, 23% and 22%, respectively), and sputum IL-8 was increased in smokers compared with nonsmokers, both in subjects with asthma (median, 945 pg/mL vs 660 pg/mL, respectively) and in healthy subjects (median, 1,310 pg/mL vs 561 pg/mL, respectively). Sputum eosinophils and ECP levels were higher in both nonsmoking and smoking asthmatics than in healthy nonsmokers. In smoking asthmatics, lung function (FEV(1) percent predicted) was negatively related to both sputum IL-8 (r = - 0.52) and sputum neutrophil proportion (r = - 0.38), and sputum IL-8 correlated positively with smoking pack-years (r = 0.57) and percent neutrophil count (r = 0.51). CONCLUSIONS: In addition to the eosinophilic airway inflammation observed in patients with asthma, smoking induces neutrophilic airway inflammation; a relationship is apparent between smoking history, airway inflammation, and lung function in smoking asthmatics.

Adult↗

PubMed2001

Adding group psychotherapy to medication treatment in dysthymia: a randomized prospective pilot study.

Patients with dysthymia have been shown to respond to treatment with antidepressant medications, and to some degree to psychotherapy. Even patients successfully treated with medication often have residual symptoms and impaired psychosocial functioning. The authors describe a prospective randomized 36-week study of dysthymic patients, comparing continued treatment with antidepressant medication (fluoxetine) alone and medication with the addition of group therapy treatment. After an 8-week trial of fluoxetine, medication-responsive subjects were randomly assigned to receive either continued medication only or medication plus 16 sessions of manualized group psychotherapy. Results provide preliminary evidence that group therapy may provide additional benefit to medication-responding dysthymic patients, particularly in interpersonal and psychosocial functioning.

Activities of Daily Living↗

PubMed2000

Cytochrome c release from mitochondria of early postimplantation murine embryos exposed to 4-hydroperoxycyclophosphamide, heat shock, and staurosporine.

Cell death is an early and common event in the pathogenesis associated with the abnormal development induced by a variety of teratogens. Previously, we showed that the cell death induced in day 9 mouse embryos by three teratogens, hyperthermia (HS), 4-hydroperoxycyclophosphamide (4-CP), and sodium arsenite (As), is apoptotic in nature involving the activation of caspase-3, cleavage of poly(ADP-ribose) polymerase (PARP), and DNA fragmentation. We now show that HS, 4-CP, and staurosporine (ST) induce the release of cytochrome c from mitochondria with kinetics suggesting a causal relationship with the activation of caspase-3 and caspase-2. This causal relationship is supported by data showing that procaspase-3 and -2 can be activated in vitro by the addition of cytochrome c to a S-100 fraction prepared from control day 9 embryos. Together, these data support the notion that these three teratogens induce changes in embryonic mitochondria resulting in the release of cytochrome c and the subsequent activation of caspase-9, the upstream activator of caspase-3. Previously, we also showed that cells within the day 9 mouse embryo are differentially sensitive/resistant to the cell death-inducing potential of HS, 4-CP, and As. The most dramatic example of this differential sensitivity is the complete resistance of heart cells, characterized by the lack of caspase-3 activation, PARP cleavage, and DNA fragmentation. We now show that this block in the terminal phase of the apoptotic pathway in heart cells is associated with a lack of teratogen-induced release of cytochrome c. Together, our data indicate that mitochondria play a pivotal role in cell death during the early phases of teratogenesis.

Animals↗

PubMed2000

Non-invasive markers of airway inflammation as predictors of oral steroid responsiveness in asthma.

BACKGROUND: Sputum eosinophil counts and exhaled nitric oxide (NO) levels are increased in asthma and both measurements fall in response to corticosteroids. METHODS: Exhaled NO levels and sputum eosinophil counts were assessed as non-invasive markers of the response to an oral steroid in 37 patients (19 women) with stable chronic asthma (mean (SD) age 48.6 (12.2) years, asthma duration 25. 9 (17.3) years, and baseline forced expiratory volume in one second (FEV(1)) 76.3 (21.9)% predicted). Spirometric tests, with reversibility to a beta agonist (2.5 mg nebulised salbutamol), and induced sputum (using nebulised 3% saline) were performed at recruitment and following treatment with 30 mg prednisolone/day for 14 days. RESULTS: Baseline NO levels correlated with the percentage improvement in FEV(1) from baseline to the post-steroid, post-bronchodilator value (r(s) = 0.47, p = 0.003), with an NO level of >10 ppb at baseline having a positive predictive value of 83% for an improvement in FEV(1) of > or =15% (sensitivity 59%, specificity 90%). Sputum eosinophilia (> or =4%) had a positive predictive value of 68% (sensitivity 54%, specificity 76%) for an increase in FEV(1) of > or =15%. A combination of sputum eosinophilia and increased NO levels resulted in a positive predictive value of 72% and a negative predictive value of 79% (sensitivity 76%, specificity 75%). CONCLUSION: Exhaled NO levels and sputum eosinophilia may be useful in predicting the response to a trial of oral steroid in asthma.

Administration, Inhalation↗

PubMed1999

Predictors of nocturnal oxygen desaturation in patients with COPD.

The aim of this study was to identify factors which might predict nocturnal desaturation (defined as a fall of > 4% from awake baseline level for > or = 5 min) in normoxic or mildly hypoxic patients with stable COPD [arterial O2 saturation (SaO2) > or = 91%]. The study was prospective in nature, had full ethical approval and was performed in the Respiratory Department of a city teaching hospital. Thirty-three patients [mean (SD) age 67.2 (9) years] with stable COPD [mean (SD) FEV1 36.8 (11.0)% pred.] were recruited via the respiratory outpatient clinics and through the respiratory wards. The following parameters were measured: daytime arterial blood gases; spirometry; lung volumes (helium dilution); single breath CO transfer factor (TLCO and KCO); maximum inspiratory (IMP) and expiratory mouth pressures; pulse oximetry (SpO2) across a 6-min walk test, and SpO2 during sleep. Seventeen patients who experienced nocturnal desaturation had significantly lower mean PaO2 and SaO2, and higher PaCO2 values compared to non-desaturators. There was a positive correlation between mean nocturnal SpO2 and daytime PaO2, SaO2, and minimum exercise SpO2, and a negative correlation between mean nocturnal SpO2 and PaCO2, and FRC. Regression analysis revealed that daytime SaO2 was the only independent predictor of mean nocturnal saturation (accounting for 61% of the variability in the mean nocturnal SpO2). We observed nocturnal desaturation in all patients with a daytime SaO2 < or = 93% but in no patient with SaO2 > or = 95%. We conclude that daytime SaO2 can be used to predict nocturnal desaturation in normoxic or mildly hypoxic patients with stable COPD. Nocturnal desaturation is likely in patients with COPD where daytime SaO2 < or = 93%, and unlikely where daytime SaO2 > or = 95%.

Exercise↗

PubMed1999

Sputum cellular and cytokine responses to inhaled endothelin-1 in asthma.

BACKGROUND: Endothelin (ET)-1 is a 21-amino acid peptide which has potent bronchoconstrictor activity. Animal studies show elevation of ET-1 during experimental airway inflammation, and inhibition of inflammation by endothelin-antagonists, suggesting pro-inflammatory activity for ET-1. OBJECTIVE: We wanted to assess any acute influence that bronchoconstrictor doses of inhaled ET-1 might have on cells, tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, nitrite (NO2) and albumin in induced sputum in asthma. METHODS: Bronchial challenge was performed using nebulized ET-1 (nebulized dose range 0.96-15.36 nmol) and placebo in 10 adult asthmatic subjects in a randomized double-blind placebo-controlled cross-over study. Sputum induction was performed 30 min and 4 h after placebo or ET-1 bronchial challenge. RESULTS: All subjects experienced dose-dependent bronchoconstriction to inhaled ET-1 with a mean (range) PC15 forced expiratory volume in 1 s (FEV1) to ET-1 of 9.45 (1.2-21.7) nmol. Comparing ET-1 with placebo inhalation, there was no change in sputum differential cell counts, TNFalpha, IL-1beta, NO2 or albumin at 30 min or 4 h after inhalation, nor was there a difference in these parameters at 4 h compared with 30 min after ET-1 inhalation. There was no fall in FEV1 at 4 h after ET-1 inhalation, suggesting that ET-1 inhalation is not associated with a late bronchoconstrictor response. CONCLUSIONS: We conclude that inhaled ET-1 does not appear to stimulate an acute inflammatory response in asthma as assessed by differential cell count, TNFalpha, IL-1beta, NO2 and albumin concentrations in induced sputum.

Adult↗

PubMed1999

Effect of infused angiotensin II on the bronchoconstrictor activity of inhaled endothelin-1 in asthma.

STUDY OBJECTIVES: Endothelin (ET)-1 is a potent bronchoconstrictor, and asthmatics demonstrate bronchial hyperresponsiveness to ET-1 given by inhalation. Angiotensin II (Ang II) is increased in plasma in acute severe asthma, causes bronchoconstriction in asthmatics, and potentiates contractions induced by ET-1 in bovine bronchial smooth muscle in vitro, and contractions induced by methacholine both in vitro and in vivo. We wished to examine any potentiation of the bronchoconstrictor activity of inhaled ET-1 by infused Ang II at subbronchoconstrictor doses. DESIGN: Double-blind randomized placebo-controlled study. SETTING: Asthma research unit in university hospital. PATIENTS: Eight asthmatic subjects with baseline FEV1 88% predicted, bronchial hyperreactivity (geometric mean, concentration of methacholine producing 20% fall, methacholine PC20 2.5 mg/mL), and mean age 37.1 years. INTERVENTIONS: We examined the effect of subbronchoconstrictor doses of infused Ang II (1 ng/kg/min and 2 ng/kg/min) or placebo on bronchoconstrictor responses to inhaled ET-1 (dose range, 0.96 to 15.36 nmol). MEASUREMENTS: Oxygen saturation, noninvasive BP, and spirometric measurements were made throughout the study visits. Blood was sampled for plasma Ang II levels at baseline and before and after ET-1 inhalation. RESULTS: Ang II infusion did not produce bronchoconstriction per se at either dose prior to ET-1 challenge. Bronchial challenge with inhaled ET-1 produced dose-dependent bronchoconstriction, but there was no difference in bronchial responsiveness to ET-1 comparing infusion of placebo with Ang II at 1 ng/kg/min or 2 ng/kg/min (geometric mean, concentration of ET-1 producing 15% fall, 5.34 nmol, 4.95 nmol, and 4.96 nmol, respectively) (analysis of variance, p > 0.05). There was an increase in systolic and diastolic BP at the higher dose of Ang II compared to placebo (mean 136/86 vs 117/75 mm Hg, respectively). Plasma Ang II was elevated following infusion of both doses of Ang II compared to placebo. CONCLUSIONS: In contrast to the potentiating effect on methacholine-induced bronchoconstriction, Ang II at subbronchoconstrictor doses does not potentiate ET-1-induced bronchoconstriction in asthma.

Adult↗

PubMed1999

Venlafaxine in the treatment of dysthymia: an open-label study.

BACKGROUND: Numerous studies have demonstrated the effectiveness of antidepressant medications in the treatment of dysthymia, or chronic mild depression. Venlafaxine blocks reuptake of both serotonin and norepinephrine and may produce a more complete antidepressant response than do single-mechanism selective serotonin reuptake inhibitors. The purpose of this open-label study was to provide preliminary data on the tolerability and effectiveness of venlafaxine for patients with dysthymia. METHOD: Twenty-two dysthymic subjects (DSM-III-R criteria) were enrolled in this 10-week, open-label trial, and 5 dropped out prior to their second visit. Seventeen subjects (77.3%) received more than 1 week of medication. RESULTS: Of these 17 subjects, 13 (76.5%) were treatment responders. Results of paired sample t tests were highly significant, indicating that, on average, there was significant improvement on all measures of symptomatology and functioning, with mean +/- SD scores on the Hamilton Rating Scale for Depression decreasing from 20.95 +/- 6.50 at baseline to 6.06 +/- 5.49 at week 10. The mean +/- SD final dose was 178.68 +/- 70.80 mg/day. Side effects were reported by 17 (85%) of the 20 subjects for whom tolerability was assessed (the most common were fatigue, dry mouth, and nausea); 5 (22.7%) of 22 patients discontinued treatment because of side effects, primarily nausea (N = 3). CONCLUSION: These findings suggest the benefit of venlafaxine in the treatment of chronic depression and the need for more rigorous studies.

Antidepressive Agents, Second-Generation↗

PubMed1998

Teratogen-induced cell death in postimplantation mouse embryos: differential tissue sensitivity and hallmarks of apoptosis.

Teratogen-induced cell death is a common event in the pathogenesis associated with tissues destined to be malformed. Although the importance of this cell death is recognized, little information is available concerning the biochemistry of teratogen-induced cell death. We show that three teratogens, hyperthermia, cyclophosphamide and sodium arsenite induce an increase in cell death in day 9.0 mouse embryos with concurrent induction of DNA fragmentation, activation of caspase-3 and the cleavage of poly (ADP-ribose) polymerase (PARP). Teratogen-induced cell death is also selective, i. e., some cells within a tissue die while others survive. In addition, cells within some tissues die when exposed to teratogens while cells in other tissues are relatively resistant to teratogen-induced cell death. An example of the latter selectivity is seen in the cells of the developing heart, which are resistant to the cytotoxic potential of many teratogens. We show that the absence of cell death in the heart is accompanied by the complete lack of DNA fragmentation, activtion of caspase-3 and the cleavage of PARP.

Animals↗

PubMed1997

Contribution of chondroitin-dermatan sulfate-containing proteoglycans to the function of rat mesenteric arteries.

Proteoglycans are an important nonfibrous matrix component of the arterial wall. Direct evidence for their role in resistance-sized arteries is lacking, although they likely have an important role in coordinating and regulating vessel behavior, presumably via interactions of their glycosaminoglycan chains or core proteins with other matrix molecules and/or the smooth muscle cell surface. The purpose of this study was to determine whether the removal of specific glycosaminoglycan chains from proteoglycans in resistance-sized mesenteric arteries would change the mechanical properties of the arterial wall, thereby affecting their functional behavior. The major finding of the study was that 65% removal of chondroitin-dermatan sulfate-containing glycosaminoglycans from the arterial wall increased vascular wall stiffness and altered the myogenic behavior of the artery. The significant alterations in myogenic behavior associated with changes in passive mechanics following partial glycosaminoglycan chain removal support our hypothesis that chondroitin-dermatan sulfate-containing proteoglycans contribute significantly to the functional behavior of resistance arteries. We speculate that these alterations are the result of changes in stress transfer between collagen fibrils and/or stress transfer between cells and collagen fibrils under applied pressure.

Animals↗

PubMed1997

Endothelin-1-induced bronchoconstriction in asthma.

Endothelin-1 (ET-1) has been indirectly implicated in the pathophysiology of asthma, and it is a potent bronchoconstrictor both in vitro and by inhalation in animal models in vivo. We examined the effect of inhaled ET-1 on airway tone in comparison with methacholine in eight asthmatics and five healthy volunteers in a double-blind randomized fashion. After a screening methacholine challenge each asthmatic had two ET-1 (doubling dose range, 0.96 to 15.36 nmol) and one methacholine (doubling dose range, 0.33 to 21.0 mumol) challenge, and normal subjects had a single ET-1 challenge. Inhalations were delivered using a dosimeter, and lung function measurements were made using constant-volume body plethysmography, with end points being a 35% fall in specific airway conductance (SGaw) and a 15% fall in FEV1. Samples for plasma ET-1 were taken before and after the inhalations, and pulse, blood pressure and oxygen saturation were monitored throughout the inhalations. All the asthmatic subjects displayed rapid-onset (< 5 min) dose-dependent bronchoconstriction to ET-1 across the dose range used, with mean (range) ET-1 PC35SGaw values of 5.15 (1.4 to 13.9) nmol, and 4.3 (1.2 to 8.3) nmol for the two ET-1 inhalations, and 0.42 (0.2 to 0.7) mumol for methacholine. Albuterol completely and rapidly reversed ET-1-induced bronchoconstriction, and in two patients not given albuterol, bronchoconstriction lasted 60 to 90 min. No significant bronchoconstriction was observed in any of the healthy volunteers across the ET-1 dose range used (mean PC35SGaw > 15.36 nmol). Oxygen saturation did not alter in either group, and plasma ET-1 did not change after ET-1 inhalation. Noninvasive blood pressure measurements revealed a fall in systolic blood pressure in normal subjects, with no change in asthmatics. Endothelin-1 is a potent bronchoconstrictor in asthma, with a bronchoconstrictor potency around 100 times that of methacholine in asthma. Asthmatics exhibit bronchial hyperreactivity to ET-1, and inhaled ET-1 can safely be given to asthmatics and normal subjects in the nebulized dose range 0.96 to 15.36 nmol.

Adult↗

PubMed1996

Tunica media remodeling in mesenteric arteries of hypertensive rats.

BACKGROUND: The tunica media of the vascular wall is a composite material comprised of smooth muscle cells and fibrous and nonfibrous matrix proteins. METHODS: Using morphometric techniques, this study quantifies the cell and matrix composition of normotensive (Wistar-Kyoto) and spontaneously hypertensive rat mesenteric arteries. RESULTS: The data show that the superior mesenteric artery (SMA) and small mesenteric arteries are different in matrix composition, cell-to-matrix ratio, and cellular dense body content. Compared with normotensive arteries, hypertensive arteries have less basement membrane but more collagen and extracellular matrix ground substance. SMA from hypertensive rats has about 30% less elastin than does normotensive artery. In contrast, the elastin content of small arteries of both strains was about the same and was less than 4% of the matrix area. Except in hypertensive SMA, membrane dense bodies occupy 7-10% of the cell area and more than 10 times the area occupied by cytoplasmic dense bodies. In contrast, cells from hypertensive SMA have about half the membrane dense body area of the normotensive cells. A decreased proportion of dense bodies in the hypertensive SMA is consistent with the "partial detachment" of these cells from the matrix. CONCLUSIONS: These results are consistent with both cellular and matrix "remodeling" in diseased vessels in response to continuous, long-term elevated blood pressure.

Animals↗

PubMed1996

Induction of heat shock protein 27 in rat embryos exposed to hyperthermia.

Previously we reported that eight proteins were reproducibly induced in postimplantation rat embryos exposed to a brief heat shock (43 degrees C, 15 min). The major heat-inducible rat embryo protein has now been identified as heat shock protein 72 (Hsp 72). In addition, the induction of Hsp 72 is temporally correlated with induction of thermotolerance. One of the other rat embryo proteins previously shown to be induced by elevated temperature is a heat shock protein of approximately 27 kilodaltons (Hsp 27). In this report we show that this protein is recognized by an antibody directed against a conserved peptide sequence of Hsp 27. Unlike Hsp 72, Hsp 27 is constitutively expressed in the rat embryo in the absence of any thermal stress; however, the level of Hsp 27 is increased approximately 2-3-fold after thermal stress (43 degrees C, 10 min). Immunohistochemical analysis revealed that the constitutively expressed Hsp 27 is localized primarily to cells of the heart, cells that are uniquely resistant to the cytotoxic effects of hyperthermia. After thermal stress, Hsp 27 is expressed in all tissues of the embryo. Finally, our data show that Hsp 27 exists in the rat embryo as three major isoforms indicative of different phosphorylation states. Furthermore, most Hsp 27 in the heart is phosphorylated, whereas in the rest of the embryo, nonphosporylated Hsp 27 predominates. After thermal stress, levels of phosphorylated isoforms increase dramatically in nonheart tissues of the embryo. Together, these results suggest that Hsp 27 may play a role in the development of thermotolerance in the postimplantation mammalian embryo.

Animals↗