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Biomedical subjects

D M Cooper

Publications and source records attributed to D M Cooper.

At least 55 records · Page 3Linked to original sources
PubMed2000

The effect of polymorphisms of the beta(2)-adrenergic receptor on the response to regular use of albuterol in asthma.

Inhaled beta-adrenergic agonists are the most commonly used medications for the treatment of asthma although there is evidence that regular use may produce adverse effects in some patients. Polymorphisms of the beta(2)-adrenergic receptor (beta(2)-AR) can affect regulation of the receptor. Smaller studies examining the effects of such polymorphisms on the response to beta-agonist therapy have produced inconsistent results. We examined whether polymorphisms at codon 16 (beta(2)-AR-16) and codon 27 (beta(2)-AR-27) of the beta(2)-AR might affect the response to regular versus as-needed use of albuterol by genotyping the 190 asthmatics who had participated in a trial examining the effects of regular versus as needed albuterol use. During the 16-wk treatment period there was a small decline in morning peak expiratory flow in patients homozygous for arginine at B(2)-AR-16 (Arg/Arg) who used albuterol regularly. This effect was magnified during a 4-wk run out period, during which all patients returned to using as-needed albuterol, so that by the end of the study Arg Arg patients who had regularly used albuterol had a morning peak expiratory flow 30. 5 +/- 12.1 L/min lower (p = 0.012) than Arg/Arg patients who had used albuterol on an as needed basis. There was no decline in peak flow with regular use of albuterol in patients who were homozygous for glycine at beta(2)-AR-16. Evening peak expiratory flow also declined in the Arg/Arg patients who used albuterol regularly but not in those who used albuterol on an as-needed basis. No significant differences in outcomes between regular and as-needed treatment were associated with polymorphisms at position 27 of the beta(2)-AR. No other differences in asthma outcomes that we investigated occurred in relation to these beta(2)-AR polymorphisms. Polymorphisms of the beta(2)-AR may influence airway responses to regular inhaled beta-agonist treatment.

Adolescent↗
PubMed2000

Muscle size and cardiorespiratory response to exercise in cystic fibrosis.

The mechanism responsible for diminished exercise performance in cystic fibrosis (CF) is not clear. We hypothesized that reduced muscle size, rather than an intrinsic muscle defect, was the primary factor in such diminished exercise performance. Twenty-two subjects with CF (14 females and eight males, aged 6.5 to 17.7 yr, with FEV(1) of 46% to 111% predicted) participated in a study of this hypothesis, and were compared with healthy children tested in the same laboratory. Muscle size was estimated from midthigh muscle cross-sectional area (CSA) obtained by magnetic resonance imaging, and fitness was determined by progressive cycle ergometer exercise testing with breath-by-breath measurements of gas exchange. Peak oxygen consumption (V O(2)) was reduced in CF subjects (956 +/- 81 [mean +/- SEM] ml/min, as compared with 1,473 +/- 54 ml/min in controls; p < 0.00001). Surprisingly, CF subjects had a lower peak V O(2) per CSA (mean for CF subjects 70 +/- 3% predicted, p < 0.0001) than did controls, whereas muscle CSA in CF subjects was not significantly smaller than in controls. The scaling parameters of peak V O(2) and muscle CSA did not differ significantly between healthy controls (0.80 +/- 0.16) and CF subjects (1.03 +/- 0.12). Indexes of aerobic function that are less effort-dependent than peak V O(2) were also lower in the CF subjects (e.g., the slope of V O(2) versus work rate [WR] (DeltaV O(2)/DeltaWR) was 68 +/- 2% predicted; p < 0.005). The study data did not support the initial hypothesis, and suggest a muscle-related abnormality in oxygen metabolism in patients with CF.

Adolescent↗
PubMed2000

Effect of exercise training on erythrocyte insulin-like growth factor-I receptor binding in adolescent males.

Exercise training leads to tissue anabolism by acting through the growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis, but the role of tissue IGF-I receptors in this process is not known. Erythrocyte IGF-I receptor binding is known to be affected by circulating levels of IGF-I. We hypothesized that training would lead to alterations in erythrocyte IGF-I binding. Thirty-eight adolescent males (mean age 16+/-0.7 yr) were randomized to a control (n=18) or endurance training intervention lasting 5 weeks. Erythrocyte IGF-I binding was measured by standard techniques. Quantity of receptor binding sites (R), binding affinity constant (Kaff), and nonspecific binding (NS) were calculated. Training led to increases (p<0.05) in 1) Kaff x R - an index of overall binding capacity (control, 7.3 +/-8.0%; trained, 60+/-21%); and 2) NS (control, 1.5+/-6.6%; trained 23.2+/-7.5%). Kaff, R, and R/erythrocyte increased in trained subjects, but not significantly so. These results suggest a training-associated upregulation of IGF-I binding. Finally, the unexpected increase in NS may reflect IGF binding protein activity, rather than changes in the erythrocyte IGF-I receptors themselves.

Adolescent↗
PubMed2000

The thin blue line: a review and discussion of aseptic technique and postprocedural infections in rodents.

A basic tenet of animal welfare philosophy is that pain and distress must be minimized whenever possible without interfering with the goals of the research. Aseptic technique during surgical procedures is essential to prevent pain and distress associated with post-procedural infections. However, many investigators have found that applying the aseptic techniques used for large animal and human surgery is not always practical when performing surgery on small rodents. Furthermore, the efficacy of some of these techniques for preventing post-procedural infections has been questioned. This review examines what is known about the development of postprocedural infections in animals and humans and the methods used to prevent them. Detection of postprocedural infections in rodents can be difficult unless objective measurements of physiologic indices are made. These measurements should be used experimentally to assess the relative benefits of various methods for preventing postprocedural infections. Measures of contamination, such as quantitative bacterial cultures, also can be used; however, they do not reliably predict infection rates. Much of the dogma about decontamination of skin and hair prior to surgery is not supported by valid experimental evidence. Hair removal may not be necessary. Alcohol may in fact be a better disinfectant than is often credited. Draping should be used when it contributes to the maintenance of the sterile field, but when it does not, modification of surgical technique may provide more protection from infection than the drape does. The contribution of surgical technique to the prevention of postprocedural infections is probably equal to that of aseptic technique. Further research needs to be done to assess various aseptic techniques for use in rodent surgery.

Animal Welfare↗
PubMed1999

Inhibition by calcium of mammalian adenylyl cyclases.

Ca(2+) regulates mammalian adenylyl cyclases in a type-specific manner. Stimulatory regulation is moderately well understood. By contrast, even the concentration range over which Ca(2+) inhibits adenylyl cyclases AC5 and AC6 is not unambiguously defined; even less so is the mechanism of inhibition. In the present study, we compared the regulation of Ca(2+)-stimulable and Ca(2+)-inhibitable adenylyl cyclases expressed in Sf9 cells with tissues that predominantly express these activities in the mouse brain. Soluble forms of AC5 containing either intact or truncated major cytosolic domains were also examined. All adenylyl cyclases, except AC2 and the soluble forms of AC5, displayed biphasic Ca(2+) responses, suggesting the presence of two Ca(2+) sites of high ( approximately 0.2 microM) and low affinity ( approximately 0.1 mM). With a high affinity, Ca(2+) (i) stimulated AC1 and cerebellar adenylyl cyclases, (ii) inhibited AC6 and striatal adenylyl cyclase, and (iii) was without effect on AC2. With a low affinity, Ca(2+) inhibited all adenylyl cyclases, including AC1, AC2, AC6, and both soluble forms of AC5. The mechanism of both high and low affinity inhibition was revealed to be competition for a stimulatory Mg(2+) site(s). A remarkable selectivity for Ca(2+) was displayed by the high affinity site, with a K(i) value of approximately 0.2 microM, in the face of a 5000-fold excess of Mg(2+). The present results show that high and low affinity inhibition by Ca(2+) can be clearly distinguished and that the inhibition occurs type-specifically in discrete adenylyl cyclases. Distinction between these sites is essential, or quite spurious inferences may be drawn on the nature or location of high affinity binding sites in the Ca(2+)-inhibitable adenylyl cyclases.

Adenosine Triphosphate↗
PubMed1999

Differential activation of adenylyl cyclases by spatial and procedural learning.

Adenylyl cyclases (ACs) are involved in a variety of advanced CNS functions, including some types of learning and memory. At least nine AC isoforms are expressed in the brain, which are divisible into three broad classes based on the ability of Ca(2+) to modulate their activity. This study examined the hypothesis that different learning tasks would differentially activate ACs in selected brain regions. The ability of forskolin or Ca(2+) to enhance AC activity in the hippocampus, parietal cortex, striatum, and cerebellum was examined after mice had been trained in either a spatial or procedural learning task using a Morris water maze. Sensitivity of ACs to forskolin was enhanced to a greater degree in most brain regions after procedural learning, but Ca(2+)-sensitive ACs in the hippocampus were more sensitive to spatial learning. Because nonspecific behavioral elements, such as stress or motor activity, were similar in both experimental tasks, these results provide the first evidence that acquisition of different kinds of learning is associated with selective changes in particular AC species in a mammalian brain and support the idea that different biochemical processing, involving particular isoforms of ACs, subserves different memory systems.

Adenylyl Cyclases↗
PubMed1999

Adenovirus-mediated expression of an olfactory cyclic nucleotide-gated channel regulates the endogenous Ca2+-inhibitable adenylyl cyclase in C6-2B glioma cells.

Previous studies have established that Ca2+-sensitive adenylyl cyclases, whether endogenously or heterologously expressed, are preferentially regulated by capacitative Ca2+ entry, compared with other means of elevating cytosolic Ca2+ (Chiono, M., Mahey, R., Tate, G., and Cooper, D. M. F. (1995) J. Biol. Chem. 270, 1149-1155; Fagan, K. A., Mahey, R., and Cooper, D. M. F. (1996) J. Biol. Chem. 271, 12438-12444; Fagan, K. A., Mons, N., and Cooper, D. M. F. (1998) J. Biol. Chem. 273, 9297-9305). These findings led to the suggestion that adenylyl cyclases and capacitative Ca2+ entry channels were localized in the same functional domain of the plasma membrane. In the present study, we have asked whether a heterologously expressed Ca2+-permeable channel could regulate the Ca2+-inhibitable adenylyl cyclase of C6-2B glioma cells. The cDNA coding for the rat olfactory cyclic nucleotide-gated channel was inserted into an adenovirus construct to achieve high levels of expression. Electrophysiological measurements confirmed the preservation of the properties of the expressed olfactory channel. Stimulation of the channel with cGMP analogs yielded a robust elevation in cytosolic Ca2+, which was associated with an inhibition of cAMP accumulation, comparable with that elicited by capacitative Ca2+ entry. These findings not only extend the means whereby Ca2+-sensitive adenylyl cyclases may be regulated, they also suggest that in tissues where they co-exist, cyclic nucleotide-gated channels and Ca2+-sensitive adenylyl cyclases may reciprocally modulate each other's activity.

Adenoviridae↗
PubMed1999

Calmodulin-binding sites on adenylyl cyclase type VIII.

Ca2+ stimulation of adenylyl cyclase type VIII (ACVIII) occurs through loosely bound calmodulin. However, where calmodulin binds in ACVIII and how the binding activates this cyclase have not yet been investigated. We have located two putative calmodulin-binding sites in ACVIII. One site is located at the N terminus as revealed by overlay assays; the other is located at the C terminus, as indicated by mutagenesis studies. Both of these calmodulin-binding sites were confirmed by synthetic peptide studies. The N-terminal site has the typical motif of a Ca2+-dependent calmodulin-binding domain, which is defined by a characteristic pattern of hydrophobic amino acids, basic and aromatic amino acids, and a tendency to form amphipathic alpha-helix structures. Functional, mutagenesis studies suggest that this binding makes a minor contribution to the Ca2+ stimulation of ACVIII activity, although it might be involved in calmodulin trapping by ACVIII. The primary structure of the C-terminal site resembles another calmodulin-binding motif, the so-called IQ motif, which is commonly Ca2+-independent. Mutagenesis and functional assays indicate that this latter site is a calcium-dependent calmodulin-binding site, which is largely responsible for the Ca2+ stimulation of ACVIII. Removal of this latter calmodulin-binding region from ACVIII results in a hyperactivated enzyme state and a loss of Ca2+ sensitivity. Thus, Ca2+/calmodulin regulation of ACVIII may be through a disinhibitory mechanism, as is the case for a number of other targets of Ca2+/calmodulin.

Adenylyl Cyclases↗
PubMed1999

Respiratory morbidity of hospitalized children with Trisomy 21.

OBJECTIVE: To review the respiratory morbidity in children with Trisomy 21 admitted to a teaching hospital. METHODOLOGY: A retrospective chart review of 232 admissions to John Hunter Children's Hospital during a 6.5-year period (1991-98). The primary outcome measures included: (i) primary reason for admission, (ii) concomitant respiratory pathology, (iii) admission to the Intensive Care Unit (ICU), (iv) length of stay and (v) costs of admission. RESULTS: Fifty-four per cent of admissions were primarily for respiratory tract pathology, dominated by pneumonia, bronchiolitis and croup. Admission to the ICU was required for 10% of admissions, most commonly for pneumonia (10/23). Congenital heart disease (CHD) was present in 33% of patients. The median length of stay and cost of admission for a child with Trisomy 21 (without CHD) with common respiratory conditions such as bronchiolitis, asthma or pneumonia was two to three times greater than in patients without Trisomy 21. CONCLUSION: Lower respiratory pathology is most common cause for acute hospital admission in children with Trisomy 21. The presence of CHD did not influence admission rates to hospital. However, patients with CHD had longer lengths of stay, appeared to have more severe illness, were more likely to require admission to an ICU and were more likely to require ventilatory support.

Adolescent↗
PubMed1999

Effect of growth hormone therapy in mitigating hypoxia-induced and food restriction-induced growth retardation in the newborn rat.

OBJECTIVE: Hypoxia may alter the neuroendocrine control of catabolic and anabolic states early in postnatal life by modulating the growth hormone-insulin-like growth factor-I (GH-IGF-I) system. We wondered: a) to what extent hypoxia effects on the GH-IGF-I axis differed from those of food deprivation alone; and b) whether administration of exogenous GH mitigates alterations of the GH-IGF-I axis caused by hypoxia or food restriction. DESIGN: Prospective laboratory investigation using nursing dams and suckling pups. Experimental groups included: a) room air control subjects; b) hypoxia-exposed subjects (FIO2, 0.12); or c) room air breathing subjects whose dam food intake was matched to that of hypoxic dams. Half of the pups in each group were administered rat GH (100 microg subcutaneously each day), and the remaining received vehicle alone. The intervention lasted 18 days. SETTING: Research laboratory in a university medical center. SUBJECTS: Twelve litters of 1-day-old Sprague-Dawley rat pups and nursing dams. INTERVENTIONS: Hypoxia exposure, food restriction, GH administration. MEASUREMENTS AND MAIN RESULTS: By the end of the study, body weights of the hypoxic and pair-fed pups were significantly lower than the weights of control animals (p < .001 for both groups), and weight gain correlated significantly with total dam food consumption (r2 = .85, p < .0001). GH administration increased weight gain only in hypoxic animals (p < .001) but it increased tail lengths significantly in both hypoxic and control pups (p < .001). Serum IGF-I levels in both hypoxic and pair-fed pups were significantly lower than in control animals. Serum IGF-binding protein-3 (IGFBP-3) was significantly lower in the hypoxic compared with the control animals. GH administration resulted in significant increases in serum levels of IGFBP-3 in both the control (p < .05) and the hypoxic (p < .01) pups compared with their vehicle-treated litter mates. CONCLUSIONS: Exogenous GH attenuates growth impairment associated with hypoxia but not with food restriction, and these effects may be mediated in part by IGFBP-3.

Animals↗
PubMed1999

Effect of exercise on cytokines and growth mediators in prepubertal children.

Many of the anabolic effects of exercise are mediated through insulin-like growth factor-I (IGF-I), but in adolescents, brief exercise training leads to reductions, rather than the expected increase, in circulating IGF-I. Certain cytokines--interleukin-(IL) 1beta (IL-1beta), IL-6 (IL-6), and tumor necrosis factor-alpha--are increased by exercise in adults and are known to inhibit IGF-I. To test the hypothesis that these cytokines might play a role in the adaptation to exercise, we measured the acute effects of exercise on selected cytokines and growth factors in 17 healthy 8- to 11-y-old children (4 females). Designed to mimic patterns and intensity of exercise found in the real lives of American children, the exercise protocol consisted of a 1.5-h soccer practice (of which about 40 min constituted of vigorous exercise). Pre- and postexercise urine and saliva samples were obtained in all subjects and both blood and urine in nine subjects. The exercise led to significant increases in circulating tumor necrosis factor-alpha (18 +/- 7%, p < 0.05) and IL-6 (125 +/- 35%, p < 0.01) as well as a significant increase in the antiinflammatory cytokine IL-1 receptor antagonist (33 +/- 10%, p < 0.01). Urine levels of IL-6 were also substantially increased by exercise (440 +/- 137%, p < 0.0001). Circulating levels of IGF-I were reduced to a small but significant degree (-6.4 +/- 3.2%, p < 0.05), although IGF-binding protein-1 (known to inhibit IGF-I) was substantially increased (156 +/- 40%, p < 0.001). Cytokines are systemically increased after relatively brief exercise in healthy children. This increase may alter critical anabolic agents such as IGF-I and its binding proteins.

Adult↗
PubMed1999

Wound healing: new understandings.

Understanding wound healing has moved from the cellular to the molecular level. In the clinical arena, however, care is often based on evaluation of the external manifestations of the wound, whereas treatments emanate primarily from tradition. Advances in knowledge make it necessary to understand healing at multiple levels to provide sound treatments. This article expands several molecular explanations for altered healing and suggests treatments aimed at restoring chronic wounds to a milieu for repair.

Acute Disease↗
PubMed1998

Regulation of adenylyl cyclase by membrane potential.

Mammalian adenylyl cyclases possess 12 transmembrane-spanning domains and bear a superficial resemblance to certain classes of ion channels. Some evidence suggests that bacterial and sea urchin sperm adenylyl cyclases can be regulated by membrane depolarization. In the present study, we explored the effect of altering membrane potential on the adenylyl cyclase activity of cerebellar granule cells with acute potassium depolarization. A biphasic stimulatory and then inhibitory response is evoked by progressive increases in the extracellular [K]:[Na] ratio in the absence of extracellular Ca2+. This effect does not mimic the linear increase in membrane potential elicited under the same conditions. Instead it appears as though membrane depolarization opens L-type (nimodipine-sensitive) Ca2+ channels, allowing the entry of Na+, which directly stimulates adenylyl cyclase activity. Gramicidin, which generates pores that are permeable to monovalent cations, and concurrently eliminates the membrane potential, permits a similar stimulation by extracellularly applied Na+. Although the results indicate no direct sensitivity of cerebellar granule cell adenylyl cyclase to membrane potential, they do demonstrate that, as a result of membrane depolarization, the influx of Na+, as well as Ca2+, will elevate cAMP levels.

Adenylyl Cyclases↗
PubMed1998

Dependence of the Ca2+-inhibitable adenylyl cyclase of C6-2B glioma cells on capacitative Ca2+ entry.

The ability of adenylyl cyclases to be regulated by physiological transitions in Ca2+ provides a key point for integration of cytosolic Ca2+ concentration ([Ca2+]i) and cAMP signaling. Ca2+-sensitive adenylyl cyclases, whether endogenously or heterologously expressed, require Ca2+ entry for their regulation, rather than Ca2+ release from intracellular stores (Chiono, M., Mahey, R., Tate, G., and Cooper, D. M. F. (1995) J. Biol. Chem. 270, 1149-1155; Fagan, K., Mahey, R., and Cooper, D. M. F. (1996) J. Biol. Chem. 271, 12438-12444). The present study compared the regulation by capacitative Ca2+ entry versus ionophore-mediated Ca2+ entry of an endogenously expressed Ca2+-inhibitable adenylyl cyclase in C6-2B cells. Even in the face of a dramatic [Ca2+]i rise generated by ionophore, Ca2+ entry via capacitative Ca2+ entry channels was solely responsible for the regulation of the adenylyl cyclase. Selective efficacy of BAPTA over equal concentrations of EGTA in blunting the regulation of the cyclase by capacitative Ca2+ entry defined the intimacy between the adenylyl cyclase and the capacitative Ca2+ entry sites. This association could not be impaired by disruption of the cytoskeleton by a variety of strategies. These results not only establish an intimate spatial relationship between an endogenously expressed Ca2+-inhibitable adenylyl cyclase with capacitative Ca2+ entry sites but also provide a physiological role for capacitative Ca2+ entry other than store refilling.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗
PubMed1998

Abnormal dynamic cardiorespiratory responses to exercise in pediatric patients after Fontan procedure.

OBJECTIVES: Novel protocols were used to focus on dynamic cardiorespiratory function during submaximal exercise and on the recovery from 1-min pulses of exercise in children who had undergone Fontan corrections for single-ventricle lesions. BACKGROUND: Particularly in children, maximal oxygen uptake (VO2max), which is commonly used to assess the functional capability of patients after the Fontan procedure, is highly effort dependent and not physiologic and leads to uncomfortable metabolic and cardiorespiratory stress. Alternative approaches include the measurement of dynamic responses during progressive exercise and recovery after short bursts of exercise. These strategies yield mechanistic insight into cardiorespiratory impairment and can be used to gauge limitations in daily life activity. METHODS: Sixteen patients (mean [+/-SD] age 12.2 +/- 2.4 years; 9 boys) and 10 age-matched control subjects (mean age 12.2 +/- 2.4 years; 6 boys) performed two separate cycle ergometer tests in which gas exchange was measured on a breath by breath basis: 1) Progressive exercise was used to determine the dynamic relation among VO2, carbon dioxide production (VCO2), ventilation (VE), heart rate (HR) and work rate (WR). 2) A 1-min constant WR test was used to determine the recovery time for gas exchange and HR. RESULTS: Peak VO2 and anaerobic threshold were reduced in patients who underwent the Fontan procedure compared with control subjects by 57% and 52%, respectively (p < 0.001). Dynamic relations during progressive exercise--deltaVO2/deltaHR and deltaVO2/deltaWR--were decreased (p < 0.001) and deltaVE/deltaVCO2 was increased (p < 0.005) in the Fontan group patients. Recovery times for HR and VO2 were prolonged in the Fontan group patients by 154% and 69%, respectively (p < 0.01). CONCLUSIONS: The results demonstrate that submaximal gas exchange responses to progressive exercise and recovery times after brief high intensity exercise are abnormal in patients after the Fontan procedure. These observations complement the findings of reduced VO2max observed here and by others. We speculate that the mechanisms for these responses are related to 1) a pervasive reduction in stroke volume for both low and high intensity exercise, 2) an abnormal linkage of ventilation to tissue carbon dioxide production, and 3) increased dependence on anaerobic metabolism in skeletal muscles. The prolonged recovery of HR and VO2 provides a possible mechanism for reduced physical activity.

Adolescent↗
PubMed1998

Atypical mycobacterial pulmonary disease and bronchial obstruction in HIV-negative children.

Atypical mycobacterial infection in HIV-negative children usually presents with cervical lymphadenopathy. We report on 10 children who are HIV-negative and who presented with pulmonary disease, in whom either culture-proven atypical mycobacterium infection (four), positive avian Mantoux test (five), or lack of response to human tuberculosis treatment (one) had been observed. One case was subsequently diagnosed as chronic granulomatous disease and illustrates that children with atypical mycobacterial pulmonary infection should have their immune status fully investigated. Bronchial obstruction was observed in eight cases, and of these, endobronchial disease was found in six children. The diagnosis of atypical mycobacterial disease is difficult, and a negative avian Mantoux test does not exclude the diagnosis. The availability of clarithromycin and rifabutin has offered new therapeutic options in treating atypical mycobacterial pulmonary infection, but management of these cases can be prolonged and difficult.

Bronchial Diseases↗