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Biomedical subjects

J A Scott

Publications and source records attributed to J A Scott.

At least 37 records · Page 2Linked to original sources

Does the activation of poly (ADP-ribose) synthetase mediate tissue injury in the sepsis induced by cecal ligation and puncture?

Poly (ADP-ribose) synthetase (PARS) is a DNA protective enzyme activated by single-strand breakage. It is suspected that exaggerated PARS activation related to biochemical stress by reactive oxygen and nitrogen species contributes to cellular injury in sepsis. The main hypothesis is that PARS activation leads to massive ATP and NAD consumption and consequent cellular energy depletion. The PARS inhibitor 3-amino-benzamide (3AB) is protective in rodents challenged with either endotoxin or intraperitoneal zymozan. The present experiment was designed to test the effect of 3AB in a more clinically relevant model of sepsis, namely polymicrobial sepsis induced by cecal ligature and puncture (CLP). Adult male Wistar rats were anesthetized, instrumented with catheters in the jugular vein and in the carotid artery, and then randomized into three groups: Sham (no laparotomy, n = 13), CLP (n = 15), and CLP/3AB (n = 18). All animals were allowed to recover and they received a continuous intravenous infusion of saline (20 mL/kg/h) and fentanyl (20 microg/kg/h). 3AB was administered to the CLP/3AB group as an intravenous bolus (10 mg/kg) followed by a continuous intravenous infusion (10 mg/kg/h). After 24 h, blood was drawn for the determination of biological indicators of organ injury. Rats were then anesthetized and biopsies of the liver were quickly frozen into liquid nitrogen for the subsequent determination of NAD and ATP levels. Further organ samples were collected for the assay of myeloperoxidase (MPO) to indicate tissue infiltration by leukocytes, and nitrotyrosine to indicate the level of biochemical stress by reactive nitrogen species. Twenty-four-hour mortality was 0/13 (Sham), 1/15 (CLP), and 5/18 (CLP/3AB; p = NS). In the surviving rats, CLP induced a clear elevation of liver enzymes, bilirubin, and pancreatic lipase, but not creatinine in the plasma, as well as a marked increase of MPO activity in liver, jejunum, and lung, but not kidney or heart. None of these variables was affected by treatment with 3AB. Furthermore, CLP did not cause depletion of NAD or ATP in the liver, nor any change in the nitrotyrosine content of any organ. These data argue against a general role of PARS activation in the pathogenesis of sepsis-induced tissue injury.

Adenosine Triphosphate↗

Increased L-arginine uptake and inducible nitric oxide synthase activity in aortas of rats with heart failure.

L-Arginine crosses the cell membrane primarily through the system y(+) transporter. The aim of this study was to investigate the role of L-arginine transport in nitric oxide (NO) production in aortas of rats with heart failure induced by myocardial infarction. Tumor necrosis factor-alpha levels in aortas of rats with heart failure were six times higher than in sham rats (P < 0.01). L-Arginine uptake was increased in aortas of rats with heart failure compared with sham rats (P < 0.01). Cationic amino acid transporter-2B and inducible (i) nitric oxide synthase (NOS) expression were increased in aortas of rats with heart failure compared with sham rats (P < 0.05). Aortic strips from rats with heart failure treated with L-arginine but not D-arginine increased NO production (P < 0.05). The effect of L-arginine on NO production was blocked by L-lysine, a basic amino acid that shares the same system y(+) transporter with L-arginine, and by the NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). Treatment with L-lysine and L-NAME in vivo decreased plasma nitrate and nitrite levels in rats with heart failure (P < 0.05). Our data demonstrate that NO production is dependent on iNOS activity and L-arginine uptake and suggest that L-arginine transport plays an important role in enhanced NO production in heart failure.

Animals↗

Noninvasive measurement of exhaled nitric oxide in a spontaneously breathing mouse.

Nitric oxide (NO) has been detected in the exhaled gas of animals and humans. In previous work, investigators have used anesthetized, mechanically ventilated animals to obtain exhaled NO (E(NO)) measurements, which has unclear effects on the levels of E(NO) and does not allow for repeated analysis of E(NO). We sought to measure E(NO) from a single, spontaneously breathing mouse. The mouse was placed in a small Plexiglas chamber and allowed to acclimatize before exhaled gas was collected for E(NO) analysis. Under optimal operating conditions of flow and pressure, the mean concentration of exhaled NO (FE(NO)) of 25 mice was 10.1 +/- 1.0 ppb. The maximal variation of FE(NO) when repeatedly measured daily in individual animals was 2.1 ppb. Administration of L-NAME, a nonselective NOS inhibitor, reduced FE(NO) by 51 +/- 6% (p < 0.01). Intraperitoneally administered lipopolysaccharide induced acute lung injury and increased FE(NO) by 30 +/- 7% (p < 0.05). We have demonstrated that it is possible to noninvasively measure E(NO) from a single, spontaneously breathing mouse. This novel technique provides a stable, reproducible, and responsive measure of E(NO) in mice. This technique will be of use in determining cellular and isoform sources of E(NO), as well as the role of endogenous NO in lung disease.

Analysis of Variance↗

Psychosocial factors associated with the abandonment of breastfeeding prior to hospital discharge.

A prospective study of 556 women from Perth, Western Australia, and 503 women from the Darling Downs area, Queensland, Australia, was conducted to identify factors associated with the abandonment of breastfeeding prior to hospital discharge. In total, 88% of women initiated breastfeeding, but 5% discontinued breastfeeding while still in the hospital. Discontinuation of breastfeeding prior to discharge was associated with a number of psychosocial factors, namely, infant feeding method being chosen after becoming pregnant, a perception by the mother that the infant's father either preferred formula feeding or was ambivalent about how the infant was fed, and whether the mother's own mother had ever breastfed. Judicious questioning prenatally regarding a women's commitment to, social support for, and prior exposure to breastfeeding will help identify those women most at risk of abandoning breastfeeding prematurely. Such women should be targeted for additional support while in the hospital.

Adult↗

The fetal origins of disease hypothesis: public health implications for the Asia-Pacific region.

There has been rapid development in the Asia-Pacific region, leading to improvements in the food supply and nutrition. The high prevalence of low birth weight has been a problem in many countries and continues to be a problem in some parts of the region. In the past few years an epidemic of obesity and chronic disease has emerged. The fetal origins hypothesis links the high prevalence of low birth weight and recent increasing obesity to explain the emerging epidemic of chronic disease. One public health strategy to challenge this epidemic is the promotion of breastfeeding of all infants. Breastfeeding has been shown to protect against childhood obesity, and is "dose related", that is, the longer an infant is breastfed, the lower the risk of obesity.

Asia, Southeastern↗

Cytochrome P450 metabolites of arachidonic acid but not cyclooxygenase-2 metabolites contribute to the pulmonary vascular hyporeactivity in rats with acute Pseudomonas pneumonia.

We have previously demonstrated depressed vascular contractility in intralobar pulmonary artery (PA) rings isolated from rats with acute Pseudomonas pneumonia. Here we describe the role of arachidonic acid (AA) metabolites in the regulation of pulmonary vascular tone in inflammation. Pneumonia was induced by intratracheal injection of P. aeruginosa organisms. Rats were sacrificed 44 h later. EETs and 20-HETE were formed at significantly lower rates in pneumonia compared with control lung microsomes. Vasoactive effects of CYP metabolites (5,6-EET, 8,9-EET, 11,12-EET, 14,15-EET, and 20-HETE) on small PA rings from control or pneumonia rats were assessed in vitro. All four EETs and 20-HETE were more potent PA vasoconstrictors than KCl or phenylephrine (PE). However, this potency was attenuated in PA rings from pneumonia lungs compared with control. In contrast, pneumonia had no effect on COX activity [total pulmonary prostaglandin (PG), PGE(2), and 6-keto-PGF(1 alpha)]. In vitro vascular contractility to KCl, PE, or PGF(2 alpha) was assessed in small PA rings from control and pneumonia rats in the presence and absence of the COX-2 inhibitor NS-398 (10 microM). NS-398 did not reverse the attenuated contractile responses to KCl, PE, or PGF(2 alpha) in pneumonia rats. Nitrite/nitrate levels, inducible nitric-oxide synthase and heme oxygenase activities were all significantly elevated in pneumonia lungs. In conclusion, vasodilator PGs produced by COX-2 do not contribute to the depressed PA contractility in this model of pneumonia. Depressed pulmonary production and vasoconstrictor effects of CYP metabolites of AA (possibly due to increased NO and/or carbon monoxide) indicate a potential role for these vasoactive metabolites in this model of acute pneumonia.

Animals↗

Integration of multiple signals through cooperative regulation of the N-WASP-Arp2/3 complex.

The protein N-WASP [a homolog to the Wiskott-Aldrich syndrome protein (WASP)] regulates actin polymerization by stimulating the actin-nucleating activity of the actin-related protein 2/3 (Arp2/3) complex. N-WASP is tightly regulated by multiple signals: Only costimulation by Cdc42 and phosphatidylinositol (4,5)-bisphosphate (PIP2) yields potent polymerization. We found that regulation requires N-WASP's constitutively active output domain (VCA) and two regulatory domains: a Cdc42-binding domain and a previously undescribed PIP(2)-binding domain. In the absence of stimuli, the regulatory modules together hold the VCA-Arp2/3 complex in an inactive "closed" conformation. In this state, both the Cdc42- and PIP2-binding sites are masked. Binding of either input destabilizes the closed state and enhances binding of the other input. This cooperative activation mechanism shows how combinations of simple binding domains can be used to integrate and amplify coincident signals.

Actin Cytoskeleton↗

Aetiology, outcome, and risk factors for mortality among adults with acute pneumonia in Kenya.

BACKGROUND: Despite a substantial disease burden, there is little descriptive epidemiology of acute pneumonia in sub-Saharan Africa. We did this study to define the aetiology of acute pneumonia, to estimate mortality at convalescence, and to analyse mortality risk-factors. METHODS: We studied 281 Kenyan adults who presented to two public hospitals (one urban and one rural) with acute radiologically confirmed pneumonia during 1994-96. We did blood and lung-aspirate cultures, mycobacterial cultures, serotype-specific pneumococcal antigen detection, and serology for viral and atypical agents. FINDINGS: Aetiology was defined in 182 (65%) patients. Streptococcus pneumoniae was the most common causative agent, being found in 129 (46%) cases; Mycobacterium tuberculosis was found in 26 (9%). Of 255 patients followed up for at least 3 weeks, 25 (10%) died at a median age of 33 years. In multivariate analyses, risk or protective factors for mortality were age (odds ratio 1.51 per decade [95% CI 1.04-2.19]), unemployment (4.42 [1.21-16.1]), visiting a traditional healer (5.26 [1.67-16.5]), visiting a pharmacy (0.30 [0.10-0.91]), heart rate (1.64 per 10 beats [1.24-2.16]), and herpes labialis (15.4 [2.22-107]). HIV-1 seropositivity, found in 52%, was not associated with mortality. Death or failure to recover after 3 weeks was more common in patients with pneumococci of intermediate resistance to benzylpenicillin, which comprised 28% of pneumococcal isolates, than in those infected with susceptible pneumococci (5.60 [1.33-23.6]). INTERPRETATION: We suggest that tuberculosis is a sufficiently common cause of acute pneumonia in Kenyan adults to justify routine sputum culture, and that treatment with benzylpenicillin remains appropriate for clinical failure due to M. tuberculosis, intermediate-resistant pneumococci, and other bacterial pathogens. However, interventions restricted to hospital management will fail to decrease mortality associated with socioeconomic, educational, and behavioural factors.

Acute Disease↗

Influence of sex and age on duration and frequency of sleep apnea events.

OBJECTIVES: Differences between men and women potentially provide insight into the regulation sleep apnea events. This study, therefore, examined how apnea frequency and duration varied according to age, sex, and sleep stage in a clinical population. DESIGN: NA SETTING: NA PATIENTS: Patients were 215 women and 215 men referred to a sleep disorders center with symptoms of obstructive sleep apnea and matched for BMI. Apnea events were compared across three age groups (18-39, 40-59, and 60-88 years) in stage 2 and in REM sleep. INTERVENTIONS: NA RESULTS: In stage 2 sleep, young and middle aged women were similar averaging 15 and 13 apnea events per hour respectively. Men had significantly more events averaging 27 and 30 events per hour for the corresponding age groups. The apnea frequency doubled from middle age to older women, and the sex difference narrowed between the older males and females to a non significant difference (26 events per hour for women versus 34 events per hour for men). Apnea duration was significantly longer in men than in women. Stage 2 apnea duration increased significantly with age for men (20.1, 21.5, 23.8 s) and women (16.7, 18.3, 20.6 s) across the three age groups. This also occurred in REM sleep in for men (22.8, 26.5, 29.8 s) and women (19.3, 22.4, 26.6 s). CONCLUSIONS: Duration did not demonstrate the marked "menopausal effect" that there was for apnea frequency. Female gender and younger age conferred benefit primarily by preventing airway collapse (reduced apnea frequency) with less of an effect on apnea duration, i.e., the ability to end the apnea. Compared to stage 2 sleep, REM sleep reduced the differences between men and women in apnea frequency. One explanation may be that differences in muscle tone of the upper airway account for the sex differences in apnea frequency.

Adolescent↗

Pulmonary microvascular changes during sepsis: evaluation using intravital videomicroscopy.

A variety of pulmonary microvascular changes occur during sepsis. These include abnormal vascular reactivity, leukocyte sequestration, and leakage of protein into the alveoli. Based on intravital videomicroscopy we have developed a method to directly assess in vivo the changes that occur in the pulmonary microcirculation in a rat model of sepsis. Male Sprague-Dawley rats were assigned to control or sepsis groups. Sepsis was induced by cecal ligation and perforation. Twenty four hours later, rats were anesthetized, mechanically ventilated, and their lung prepared for intravital videomicroscopy. A specially designed transparent thoracic window was inserted into the chest wall. The dependent surface of the lung was superfused with saline solution and visualized with an inverted microscope. Vascular contractility, to phenylephrine, (PE) and hypoxia of small (15-25 microm in diameter) and medium (40-50 microm) arterioles was examined. Leukocyte traffic in the pulmonary microcirculation was studied after in vivo labeling of leukocytes with Rhodamine and visualized with fluorescence microscopy. Leak of albumin into the alveolar space was measured with FITC-labeled albumin and fluorescence microscopy. Both small and medium sized pulmonary arterioles in septic animals exhibited attenuated vascular contractility to phenylephrine, but only medium-sized arterioles displayed hypocontractility to hypoxia. Further, in septic animals there was an increase in both the number of stationary leukocytes in the pulmonary microcirculation and an increase in alveolar capillary protein leak. We conclude: (1) direct visualization of the pulmonary microvascular pressor response to hypoxia and PE in the rat is possible using this technique, (2) similar to previous in vitro studies with larger vessels, pulmonary arterioles have an attenuated contractile response to PE and hypoxia in sepsis, and (3) there is an increase in both the number of stationary leukocytes and protein leak into the alveolus in the lungs of septic animals.

Animals↗

Effects of inhaled nitric oxide in a rat model of Pseudomonas aeruginosa pneumonia.

OBJECTIVE: Antimicrobial effects of nitric oxide (NO) have been demonstrated in vitro against a variety of infectious pathogens, yet in vivo evidence of a potential therapeutic role for exogenous NO as an antimicrobial agent is limited. Thus, we assessed the effects of inhaled NO on pulmonary infection, leukocyte infiltration, and NO synthase (NOS) activity in a rat model of Pseudomonas aeruginosa pneumonia. DESIGN: Controlled animal study. SETTING: Research laboratory of an academic institution. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: After intratracheal instillation of either P. aeruginosa or saline (sham), rats were randomly exposed to either 40 ppm of inhaled NO or room air (RA) for 24 hrs before they were killed. MEASUREMENTS AND MAIN RESULTS: Inhaled NO in pneumonia rats markedly reduced pulmonary bacterial load (0.02+/-0.01% vs. 0.99+/-0.59% of bacterial input in pneumonia with room air, p < .05) and pulmonary myeloperoxidase activity, a marker of leukocyte infiltration (21.7+/-3.8 vs. 55.0+/-8.1 units in pneumonia with room air, p < .05), but had no effect on systemic hemodynamics or gas exchange. Pneumonia was associated with enhanced pulmonary NOS activity (8.8+/-2.4 vs. 0.2+/-0.1 pmol citrulline/min/mg protein in sham, p < .01) and increased plasma levels of nitrites/nitrates (NOx-; 45+/-7 vs. 16+/-3 micromol/L in sham, p < .01). Inhaled NO therapy attenuated the pneumonia-induced increase in pulmonary calcium-independent NOS activity (p < .05) and markedly increased plasma NOx- levels. Exposure of P. aeruginosa in culture to 40 ppm of ambient NO confirmed a delayed antibacterial effect of NO in vitro. CONCLUSIONS: Inhaled NO has an important antibacterial effect both in vitro and in vivo against P. aeruginosa and is associated with reduced pulmonary leukocyte infiltration in vivo. These results in a rat model of P. aeruginosa pneumonia suggest that future studies should address the possible clinical effects of inhaled NO therapy in pneumonia.

Administration, Inhalation↗

Validation of immune-complex enzyme immunoassays for diagnosis of pneumococcal pneumonia among adults in Kenya.

The efficacy of pneumococcal vaccines in protecting against pneumococcal pneumonia can feasibly be measured only with a diagnostic technique that has a high specificity (0.98 to 1.00) and a sensitivity greatly exceeding that of blood cultures (>0.2 to 0.3). In this context immune-complex enzyme immunoassays (EIAs) offer a novel, convenient diagnostic method, and we have investigated three such assays with appropriate study populations in Kenya. Sera from 129 Kenyan adults with pneumococcal pneumonia and 97 ill controls from the same clinics, but without pneumococcal disease syndromes, were assayed with immune-complex EIAs for pneumolysin, C-polysaccharide, and mixed capsular polysaccharides (Pneumovax II). At an optical density (OD) threshold yielding a specificity of 0.95, the sensitivities (95% confidence intervals) of the assays were 0.22 (0.15 to 0.30), 0.26 (0.19 to 0.34), and 0.22 (0.15 to 0.29), respectively. For pneumolysin immune complexes, human immunodeficiency virus (HIV)-positive patients had a higher mean OD than HIV-negative patients (639 versus 321; P < 0.0001), but stratification by HIV infection status did not alter the performance of this test. Combining the results of all three EIAs did not enhance the diagnostic performances of the individual assays. In Kenyan adults the sensitivities of the immune-complex EIAs could exceed that of blood cultures only at levels of specificity that were insufficient for the performance of vaccine efficacy studies.

Adult↗

Nitric oxide produced via neuronal NOS may impair vasodilatation in septic rat skeletal muscle.

Impaired vascular responsiveness in sepsis may lead to maldistribution of blood flow in organs. We hypothesized that increased production of nitric oxide (NO) via inducible nitric oxide synthase (iNOS) mediates the impaired dilation to ACh in sepsis. Using a 24-h cecal ligation and perforation (CLP) model of sepsis, we measured changes in arteriolar diameter and in red blood cell velocity (V(RBC)) in a capillary fed by the arteriole, following application of ACh to terminal arterioles of rat hindlimb muscle. Sepsis attenuated both ACh-stimulated dilation and V(RBC) increase. In control rats, arteriolar pretreatment with the NO donors S-nitroso-N-acetylpenicillamine or sodium nitroprusside reduced diameter and V(RBC) responses to a level that mimicked sepsis. In septic rats, arteriolar pretreatment with the "selective" iNOS blockers aminoguanidine (AG) or S-methylisothiourea sulfate (SMT) restored the responses to the control level. The putative neuronal NOS (nNOS) inhibitor 7-nitroindazole also restored the response toward control. At 24-h post-CLP, muscles showed no reduction of endothelial NOS (eNOS), elevation of nNOS, and, surprisingly, no induction of iNOS protein; calcium-dependent constitutive NOS (eNOS+nNOS) enzyme activity was increased whereas calcium-independent iNOS activity was negligible. We conclude that 1) AG and SMT inhibit nNOS activity in septic skeletal muscle, 2) NO could impair vasodilative responses in control and septic rats, and 3) the source of increased endogenous NO in septic muscle is likely upregulated nNOS rather than iNOS. Thus agents released from the blood vessel milieu (e.g., NO produced by skeletal muscle nNOS) could affect vascular responsiveness.

Acetylcholine↗

Epiglottic hypoplasia associated with lacrimo-auriculo-dental-digital syndrome.

We present a case of a young boy with clinical manifestations of lacrimo-auriculo-dental-digital syndrome (LADD) with the additional finding of a hypoplastic epiglottis that caused airway obstruction at birth. We also reviewed the 30 cases of LADD that have been reported since 1967. It is a rare syndrome that includes lacrimal system, aural, digital, and dental anomalies. Our patient has lacrimal duct obstruction, deficient tissue in the inferior portion of the ear pinnae, and a hypoplastic epiglottis with collapse of the supraglottic tissue. Many findings of LADD are recognizable at birth. The clinical spectrum has widened with more case reports. Our patient adds a life-threatening airway abnormality, a hypoplastic epiglottis, to the clinical spectrum of LADD.

Abnormalities, Multiple↗

How well can radiologists using neural network software diagnose pulmonary embolism?

OBJECTIVE: This study evaluated and optimized the performance of an automated artificial neural network image interpreter in the diagnosis of pulmonary embolism on ventilation-perfusion lung scans. The computer interpretations were compared with the interpretations of three experienced observers. MATERIALS AND METHODS: Digital data were obtained from 100 patients with normal findings on chest radiographs who were undergoing both radionuclide ventilation-perfusion scanning and pulmonary angiography. Interpretations of differently trained neural networks were compared with those of three experienced nuclear medicine practitioners unaware of the clinical diagnosis. RESULTS: Machines running neural networks performed similarly to experienced scan interpreters in the detection of pulmonary embolism. Both the human observers and the networks performed best in cases with large emboli. Neural network performance was best in the right lung, when the networks were trained using only cases with large emboli and when networks were trained independently in the right and left lungs. The best predictions resulted from a collaborative interpretation incorporating both the human and computer predictions. CONCLUSION: Computers running artificial neural networks using scan data obtained directly from the anterior and posterior ventilation and perfusion images, without human involvement, perform comparably with experienced observers in patients with normal findings on chest radiographs. Human observers can improve their interpretations by incorporating computer output to formulate diagnostic prediction. The method of training the networks is critical to optimizing performance.

Adult↗

Raloxifene: a selective estrogen receptor modulator.

Raloxifene is a selective estrogen receptor modulator that produces both estrogen-agonistic effects on bone and lipid metabolism and estrogen-antagonistic effects on uterine endometrium and breast tissue. Because of its tissue selectivity, raloxifene may have fewer side effects than are typically observed with estrogen therapy. The most common adverse effects of raloxifene are hot flushes and leg cramps. The drug is also associated with an increased risk of thromboembolic events. The beneficial estrogenic activities of raloxifene include a lowering of total and low-density lipoprotein cholesterol levels and an augmentation of bone mineral density. Raloxifene has been labeled by the U.S. Food and Drug Administration for the prevention of osteoporosis. However, its effects on fracture risk and its ability to protect against cardiovascular disease have yet to be determined. Studies are also being conducted to determine its impact on breast and endometrial cancer reduction.

Bone and Bones↗

The burden of pneumococcal disease among adults in developed and developing countries: what is and is not known.

The burden of pneumococcal disease among adults in developed countries is neither widely known nor appreciated. The incidence of pneumococcal pneumonia is uncertain because a precise diagnosis cannot be obtained for most patients. Population-based data on invasive pneumococcal disease (e.g., bacteraemia and meningitis) suggest an annual incidence in all developed countries of > or =15-20 cases per 100,000 persons of all ages and > or =50 cases per 100,000 elderly adults (> or =65 years). In developing countries there are no population-based data on the burden of pneumococcal disease among adults. Studies of high risk groups, hospital-based studies, vaccine efficacy trials, extrapolations from surveillance of "native populations" in developed countries, and demographic studies in developing regions all suggest a high burden of disease. The broad variation in these estimates, however, indicates that better studies are needed. Increased use of pneumococcal vaccines among adults in all countries will depend on better scientific and public understanding of the burden of pneumococcal disease. In developing countries, intensive community-based studies of the impact of pneumococcal disease, or, alternatively, a "vaccine probe" approach, in which a population is vaccinated and the reduction in pneumonia is compared with that in a control population, could give more accurate estimates of the burden of disease and of the potential effectiveness of pneumococcal vaccination among adults.

Adult↗