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Biomedical subjects

J L Allen

Publications and source records attributed to J L Allen.

At least 19 recordsLinked to original sources
PubMed2001

Detection of feline calicivirus, feline herpesvirus 1 and Chlamydia psittaci mucosal swabs by multiplex RT-PCR/PCR.

A single tube, multiplex reverse transcription (RT)-polymerase chain reaction (PCR)/PCR assay was developed for detection of feline herpesvirus 1 (FHV1), Chlamydia psittaci and feline calicivirus (FCV) in cats with upper respiratory tract disease (URTD), incorporating a simple, rapid extraction procedure capable of extracting both DNA and RNA. The assay was found to be as sensitive in vitro as simplex assays that have previously been shown to be as sensitive as, or more sensitive than, culture for each pathogen in experimentally infected cats. Conjunctival alone or both conjunctival and oropharyngeal swabs were collected from cats in 104 households with URTD. FHV1 was detected in 18 (17.3%) and C. psittaci was detected in 12 (11.5%) households. The prevalence of C. psittaci was not significantly different to that determined using a duplex PCR assay for C. psittaci and FHV1. The prevalence of FCV was affected by sample storage temperature. Of samples stored at -70 degrees C, 0/31 were positive for FCV but FCV was detected in 10/73 (13.7%) samples stored at 4 degrees C (P=0.006). Of the samples stored at 4 degrees C, 3/19 (15.8%) conjunctival swabs were positive for FCV and 6/32 (18.8%) oropharyngeal/conjunctival swabs were positive for FCV (P=0.79). The potential utility of restriction endonuclease analysis of RT-PCR products resulting from amplification of the hypervariable region of the capsid protein gene of FCV in field samples, without prior cultivation, was also examined. The assay may have considerable importance for diagnosis and epidemiological surveys of feline upper respiratory tract pathogens.

Animals↗
PubMed2000

Laser pyrolysis fabrication of ferromagnetic gamma'-Fe4N and FeC nanoparticles.

Using the laser pyrolysis method, single phase gamma'-Fe4N nanoparticles were prepared by a two step method involving preparation of nanoscale iron oxide and a subsequent gas-solid nitridation reaction. Single phase Fe3C and Fe7C3 could be prepared by laser pyrolysis from Fe(CO)5 and 3C2H4 directly. Characterization techniques such as XRD, TEM and vibrating sample magnetometer were used to measure phase structure, particle size and magnetic properties of these nanoscale nitride and carbide particles.

Carbon Compounds, Inorganic↗
PubMed1999

Impaired cytokine signaling in mice lacking the IL-1 receptor-associated kinase.

Stimulation of the type 1 IL-1R (IL-1R1) and the IL-18R by their cognate ligands induces recruitment of the IL-1R-associated kinase (IRAK). Activation of IRAK leads in turn to nuclear translocation of NF-kappaB, which directs expression of innate and adaptive immune response genes. To study IRAK function in cytokine signaling, we generated cells and mice lacking the IRAK protein. IRAK-deficient fibroblasts show diminished activation of NF-kappaB when stimulated with IL-1. Immune effector cells without IRAK exhibit a defective IFN-gamma response to costimulation with IL-18. Furthermore, mice lacking the Irak gene demonstrate an attenuated response to injected IL-1. Deletion of Irak, however, does not affect the ability of mice to develop delayed-type hypersensitivity or clear infection with the intracellular parasite, Listeria monocytogenes. These results demonstrate that although IRAK participates in IL-1 and IL-18 signal transduction, residual cytokine responsiveness operates through an IRAK-independent pathway.

Animals↗
PubMed1999

Mechanisms of nocturnal oxyhemoglobin desaturation in children and adolescents with sickle cell disease.

Oxyhemoglobin desaturation in patients with sickle cell disease has been proposed as a possible mechanism in the initiaton of vasco-occlusive pain crises. Nocturnal oxyhemoglobin desaturation (NOD) has been described with a prevalence of up to 40% in children and adolescents with sickle cell disease. The objective of this study was to evaluate the mechanisms of nocturnal oxyhemoglobin desaturation in sickle cell disease and determine the role of obstructive sleep apnea. We performed 16-channel polysomnograms and pulmonary function testing in 20 patients with sickle cell disease (ages 7-21 years) who had documented desaturation on home oximetry studies. The median saturation awake was 94% (quartile range, 88-95). Median saturation during REM sleep was 93.5% (88-95) and during non-REM sleep 93.5% (87.5-95). The median respiratory disturbance index was low (1.35 quartile range, 0.25-2.85). Twelve patients had no obstructive apnea recorded, while 3 patients had a total of 9 or 10 episodes during the entire study. The median snoring time was 5. 65% of total sleep time (quartile range, 1.35-22.65). There was no correlation between number of obstructive apneas and mean sleeping saturation (r = 0.012, p = 0.95). There was no correlation between pulmonary function data and prevalence of NOD. There was a strong, positive correlation between sleeping and awake saturation (r = 0.96, p < 0.001). We conclude that while nocturnal oxyhemoglobin desaturation may be common in children and adolescents with sickle cell disease, upper airway obstruction does not appear to play an important role in its genesis.

Adolescent↗
PubMed1999

Measurement of hemoglobin saturation by oxygen in children and adolescents with sickle cell disease.

Pulse oximetry is a noninvasive method of measuring oxyhemoglobin saturation. The validity of pulse oximetry in sickle cell disease (SCD) has been questioned. We evaluated pulse oximetry, arterial blood gas analysis, and co-oximetry in patients with SCD, and we assessed the effect of dyshemoglobin and altered blood-oxygen affinity on their accuracy. Sixteen patients with SCD aged 7-21 years had arterial and venous blood drawn and transcutaneous pulse oximetry performed. Oxyhemoglobin dissociation curves were plotted from the venous blood of 15 patients. Oxyhemoglobin saturation estimated by arterial blood gas analysis (SaO(2)) and measured by pulse oximetry (SpO(2)) were both higher than the saturation by co-oximetry (FO(2)Hb) (mean +/- SD = 96.3 +/- 1.6%, 94 +/- 3.1%, and 89.1 +/- 3.8%, respectively). There was a significant, positive correlation between SpO(2) and FO(2)Hb (r = 0.7, P = 0.002). The patients had elevated levels of methemoglobin (MetHb) and carboxyhemoglobin (COHb) (2.3 +/- 1.4% and 4.7 +/- 1.3%, respectively). The oxyhemoglobin dissociation curves were frequently shifted to the right with oxygen tensions elevated when hemoglobin was 50% saturated with oxygen (P(50)) (32.5 +/- 4.5 mm Hg). There was a strong correlation between the amounts of dyshemoglobin (MetHb + COHb) and the difference between SaO(2) and FO(2)Hb (r = 0.7, P = 0.002). There was no correlation between the difference between SaO(2) and FO(2)Hb and the P(50) (r = 0.27, P = 0.33) There was also a strong positive correlation between SaO(2)-SpO(2) and dyshemoglobin fraction (r = 0.77, P = 0.001). We conclude that pulse oximetry and arterial blood gas analysis overestimate oxygen saturation when compared to co-oximetry, but that SpO(2) is consistently closer than SaO(2) to FO(2)Hb. SpO(2) is partially affected by MetHb and COHb. The discrepancy between SaO(2) and FO(2)Hb is due to the presence of dyshemoglobin and a shifted oxyhemoglobin dissociation curve, but the effect from dyshemoglobin predominates.

Adolescent↗
PubMed1999

Localization of Mycobacterium leprae to endothelial cells of epineurial and perineurial blood vessels and lymphatics.

Infection of peripheral nerve by Mycobacterium leprae, the histopathological hallmark of leprosy, is a major factor in this disease, but the route and mechanisms by which bacilli localize to peripheral nerve are unknown. Experimentally infected armadillos have recently been recognized as a model of lepromatous neuritis; the major site of early accumulation of M. leprae is epineurial. To determine the epineurial cells involved, 1-cm segments of 44 nerves from armadillos were screened for acid-fast bacilli and thin sections were examined ultrastructurally. Of 596 blocks containing nerve, 36% contained acid-fast bacilli. Overall, M. leprae were found in endothelial cells in 40% of epineurial blood vessels and 75% of lymphatics, and in 25% of vessels intraneurally. Comparison of epineurial and endoneurial findings suggested that colonization of epineurial vessels preceded endoneurial infection. Such colonization of epineurial nutrient vessels may greatly increase the risk of endoneurial M. leprae bacteremia, and also enhance the risk of ischemia following even mild increases in inflammation or mechanical stress. These findings also raise the possibility that early, specific mechanisms in the localization of M. leprae to peripheral nerve may involve adhesion events between M. leprae (or M. leprae-parasitized macrophages) and the endothelial cells of the vasa nervorum.

Animals↗
PubMed1998

Summary of the symposium establishing the safety of fat and macronutrient substitutes presented at the 33rd annual meeting of the Society of Toxicology, San Diego, California, March 13-17, 1994.

Macronutrient substitutes (MNS) are food ingredients designed to replace the organoleptic and/or functional properties of macronutrients such as fats or sugars in processed foods. Because they may be consumed in large quantities daily, traditional methods of safety evaluation are inappropriate. Conventional safety factors cannot be used in extrapolating animal data to humans due to the limitations of administering very large doses of MNS to animals. The proper evaluation of the safety of MNS involves appropriate studies in animals and humans including comparative biodispositional studies, genotoxicity and cytotoxicity studies, reproductive and developmental studies, mechanistic studies, digestive and fermentation studies, nutritional studies, and studies involving humans with special focus on gastrointestinal function. Guidelines for the proper conduct of human studies were presented and these include the use of competent investigators and IRB-approved protocols and the use of adequate numbers of healthy male and female volunteers. Postmarketing surveillance is the final step in the safety evaluation process for macronutrient substitutes. It was concluded that MNS should be evaluated on a case-by-case basis.

Animals↗
PubMed1998

Pulmonary function in hospitalized infants and toddlers with cystic fibrosis.

UNLABELLED: In older children with cystic fibrosis (CF), well-documented improvements in lung function occur during hospitalization for treatment of pulmonary exacerbations. OBJECTIVES: (1) To test the hypothesis that improvement in lung function occurs in infants and toddlers hospitalized because of CF pulmonary exacerbations. (2) To compare changes in lung function measured during forced expiratory flow and tidal breathing. STUDY DESIGN: Seventeen infants and toddlers with CF were evaluated at the beginning and end of hospitalization by the rapid thoracic compression technique to yield maximal flow at forced residual capacity. Tidal mechanics were measured by the esophageal balloon technique to yield lung conductance and compliance. RESULTS: Lung function improved during the course of hospitalization. The greatest change was observed in measurements of maximal flow at functional residual capacity (.VmaxFRC), increasing from 38.5% +/- 6% predicted (mean +/- SEM) to 59.8% +/- 6% at the end (p < 0.005). Lung conductance (GL) increased from 60% +/- 6% to 78% +/- 8% (p < 0.02); lung compliance (CL) increased from 66% +/- 5% to 75% +/- 5% (p < 0.03). The degree of improvement of .VmaxFRC, GL, and CL was related to baseline measurements; those with poorer pulmonary function at baseline had the greatest degree of improvement during hospitalization. CONCLUSION: Assessments of airflow obstruction from measurements of .VmaxFRC and GL do not necessarily demonstrate similar findings in a given infant with CF, perhaps because these two techniques measure different physiologic properties. Changes in .VmaxFRC may best reflect the predominant pathophysiology of lung disease in infants and toddlers with CF.

Anti-Bacterial Agents↗
PubMed1997

Airway hyperreactivity in children with sickle cell disease.

Progressive restrictive defect with increasing age, obstructive lung disease, and bronchodilator responsiveness have been reported in sickle cell disease (SCD). Because airway hyperreactivity (AHR) can be underestimated when assessed by bronchodilator responsiveness in patients with normal baseline lung function, the aim of this study was to investigate the prevalence of AHR in SCD by cold-air bronchial provocation testing, and to assess whether AHR can be present in symptom-free patients with SCD. Forty patients aged 6 to 19 years (mean, 10.7 years +/- 3.5 SD) performed pulmonary function tests. Eighteen were known to have a history of reactive airway disease (RAD group), and 22 had no known history of RAD (non-RAD group). A control group, aged 6 to 7 years (mean, 10.5 +/- 3.1 years), consisted of 10 siblings of the non-RAD SCD group. There were no significant differences in age and height among the groups. If the forced expiratory volume in 1 second (FEV1) was greater than 70%, cold air challenge (CACh) was performed; if the FEV1 was less than 70%, aerosolized bronchodilator therapy was given. A decrease in FEV1 of more than 10% after CACh or an increase in FEV1 of 12% or greater after bronchodilator inhalation was considered evidence of AHR. In the RAD group, the total lung capacity was 88.9% +/- 14.0% of race-corrected predicted values, the forced vital capacity was 91.2% +/- 12.6%, and FEV1 was 85.3% +/- 16.2%. The mean maximal percent fall in FEV1 after CACh (n = 13) was 18.5% +/- 9.6% and was greater than 10% in 11 of 13 patients. The mean increase in FEV1 after bronchodilator therapy (n = 5) was 11.5% +/- 8.3%, and it was greater than 12% in 4 of 5 patients. In the non-RAD group the baseline total lung capacity was 101.6% +/- 11.7%, forced vital capacity was 95.5% +/- 10.2%, and FEV1 was 93.3% +/- 13.2%. The mean maximal percent fall in FEV1 after CACh (n = 19) was 14.1% +/- 8.8% and was greater than 10% in 13 of 19 patients. The mean increase in FEV1 after bronchodilator therapy (n = 3) was 14.7% +/- 11.3%, and was 12% of greater in 1 of 3 patients. In the control group the baseline total lung capacity was 105.7% +/- 12.1%, forced vital capacity was 96.2% +/- 11.1%, and FEV1 was 92.9% +/- 10.3%. The mean maximal percent fall in FEV1 was 5.0% +/- 2.5%, and was greater than 10% in none of 10 patients. The prevalence of AHR in the control group, the RAD group, and the non-RAD group was zero, 83%, and 64%, respectively (p < 0.0001). The overall prevalence in the SCD group was 73%. We conclude that there is a high prevalence of AHR in children with SCD and that airway hyperreactivity may exist in patients with SCD even in the absence of the clinical symptoms of RAD. AHR may be a significant component of sickle cell lung disease.

Administration, Inhalation↗
PubMed1997

Monitoring outbreaks of methicillin-resistant Staphylococcus aureus: use of a commercial database and personal computer.

A commercial database and personal computer were used to record relevant information on outbreaks of hospital infection associated with methicillin-resistant Staphylococcus aureus (MRSA). The data were easily stored, amended and retrieved, and there was sufficient flexibility and capacity within the data fields to allow day-to-day monitoring of the outbreak.

Cross Infection↗
PubMed1996

A gradient of cactus protein degradation establishes dorsoventral polarity in the Drosophila embryo.

Dorsoventral polarity in the Drosophila embryo is established by a signaling pathway active on the ventral and ventrolateral surfaces of the embryo. Signal transduction via the protein kinase Pelle frees the Rel-related protein Dorsal from its cytoplasmic inhibitor Cactus, allowing Dorsal to translocate into ventral and ventrolateral nuclei and direct gene expression. Here, we show by immunochemical analyses that Pelle-mediated signaling induces the spatially graded degradation of Cactus. Using a tissue culture system which reconstitutes Pelle-dependent Cactus degradation, we show that a motif in Cactus resembling the sites of signal-dependent phosphorylation in the vertebrate homologs IkappaB-alpha and IkappaB-beta is essential for Pelle-induced Cactus degradation. Substitution of four serines within this motif with nonphosphorylatable alanine residues generated a mutant Cactus that still functions as a Dorsal inhibitor but is resistant to induced degradation. Injection of RNA encoding this altered form of Cactus has a dominant negative effect on establishment of dorsoventral polarity in the embryo. We conclude that dorsoventral signaling results in a Cactus concentration gradient and propose that signal-dependent phosphorylation directs the spatially regulated proteolysis of Cactus protein.

Amino Acid Sequence↗
PubMed1996

Chest wall compliance in infants and children with neuromuscular disease.

Respiratory muscle weakness is the primary cause of respiratory dysfunction in neuromuscular disease (NMD), but structural abnormalities of the chest wall also play a role. In adults with NMD, restrictive lung disease is in part caused by reduced chest wall compliance (C(W)), believed to reflect stiffening of connective tissue resulting from chronically reduced chest wall motion in the presence of respiratory muscle weakness. We hypothesized that chronic limitation of chest wall motion in young children with NMD leads to structural underdevelopment of the chest wall, and results in increased, rather than decreased, C(W). In 18 subjects with NMD, ranging from 3 mo to 3.8 yr of age, we compared C(W) with values obtained in children without NMD. A modification of the Mead-Whittenberger technique was used, with respiratory muscle relaxation provided by brief manual ventilation. Respiratory system compliance (Crs) and lung compliance (C(L)) were calculated from airway opening pressure, transpulmonary pressure, and tidal volume. C(W) was calculated as 1/C(W) = 1/Crs - 1/C(L) during manual ventilation. C(W)/kg was higher in subjects with NMD than in controls, at 5.2 +/- 2.8 (mean +/- SD) versus 2.4 +/- 0.8 ml/cm H2O (p < 0.001). In subjects who had normal lung compliance values during spontaneous breathing (C(Lspont)), C(W)/C(Lspont) was significantly greater in subjects with NMD (5.5 +/- 3.2) than in controls (1.9 +/- 1.0) (p < 0.001). By predisposing to rib cage deformation and reduced end-expiratory lung volume, abnormally high C(W) in infants and young children with NMD may contribute to respiratory dysfunction.

Case-Control Studies↗
PubMed1996

Respiratory function in children with neuromuscular disease.

Respiratory failure is the most common cause of death in children with neuromuscular disease (NMD). This article provides a conceptual framework for understanding failure of the respiratory pump in these children. Pump failure can be attributed to faulty control of respiration, to mechanical defects, and to respiratory muscle fatigue. In most patients with NMD, respiratory drive is intact. Mechanical defects can be due to either an abnormal pump or an excessive respiratory load on which the pump must operate. In patients with NMD, the weak respiratory muscles cannot generate normal respiratory pressures. Furthermore, inefficient chest wall motion leads to increased work for the respiratory system. Abnormalities of lung and chest wall compliance increase respiratory load. The combination of a weak, inefficient respiratory pump and an abnormally high elastic load can predispose these patients to respiratory muscle fatigue. Respiratory muscle rest with nocturnal assisted ventilation, therefore, provides a rational approach to the treatment of chronic respiratory failure in patients with NMD. Areas of future research that may prove useful in the care of children with respiratory failure due to NMD include: the development of better ways of assessing respiratory muscle fatigue; studies to increase understanding of the role of mechanical ventilation in improving chest wall and respiratory pump function; and studies delineating the role of respiratory muscle training in these patients.

Child↗
PubMed1995

Developmental changes in chest wall compliance in infancy and early childhood.

Development of chest wall stiffness between infancy and adulthood has important consequences for respiratory system function. To test the hypothesis that there is substantial stiffening of the chest wall in the first few years of life, we measured passive chest wall compliance (Cw) in 40 sedated humans 2 wk-3.5 yr old. Respiratory muscles were relaxed with manual ventilation applied during the Mead-Whittenberger technique. Respiratory system compliance (Crs) and lung compliance (Cl) were calculated from airway opening pressure, transpulmonary pressure, and tidal volume. Cw was calculated as 1/Cw = 1/Crs - 1/Cl during manual ventilation. Mean Cw per kilogram in infants < 1 yr old was significantly higher than that in children > 1 yr old (2.80 +/- 0.87 vs. 2.04 +/- 0.51 ml.cmH2O-1.kg-1; P = 0.002). There was an inverse linear relationship between age and mean Cw per kilogram (r = -0.495, slope -0.037; P < 0.001). In subjects with normal Cl during spontaneous breathing, Cw/spontaneous Cl was 2.86 +/- 1.06 in infants < 1 yr old and 1.33 +/- 0.36 in older children (P = 0.005). We conclude that in infancy the chest wall is nearly three times as compliant as the lung and that by the 2nd year of life chest wall stiffness increases to the point that the chest wall and lung are nearly equally compliant, as in adulthood. Stiffening of the chest wall may play a major role in developmental changes in respiratory system function such as the ability to passively maintain resting lung volume and improved ventilatory efficiency afforded by reduced rib cage distortion.

Aging↗
PubMed1994

A comparison of three semi-selective media for the isolation of methicillin-resistant Staphylococcus aureus.

During the 1980s the emergence of multiple antibiotic-resistant strains of Staphylococcus aureus posed new problems for infection control worldwide, many of which still remain. In investigations of outbreaks of infection, the laboratory has a key role in identifying infected or colonised patients and staff. The rapid isolation and accurate identification of the causative organisms are essential for the implementation of appropriate control measures. Speed and accuracy in identification, by colonial morphology, is often difficult to achieve in the presence of a mixed population of commensal bacteria. To this end, the sensitivity of three media for the isolation of methicillin-resistant S. aureus (MRSA) from simulated clinical specimens was compared. Initial colonial recognition of MRSA was enhanced on methicillin-milk agar when compared with that on other media.

Culture Media↗