Search PubMed⌕ Search

Biomedical subjects

G Bowes

Publications and source records attributed to G Bowes.

At least 91 records · Page 5Linked to original sources

Deaths from asthma in Victoria: a 12-month survey.

The circumstances surrounding the death of all patients who died from asthma in the State of Victoria over a 12-month period from May 1, 1986 were investigated. Data were collected using an interviewer-administered questionnaire as soon as practicable after registration of the death. In 168 cases asthma was considered to be the cause of death and adequate data were obtained in 163; 75 of these were male (74 over 60 years of age). Thirteen per cent had a history of trivial or mild asthma, 22% of moderate and 65% of severe asthma. Thirty-four per cent had not been limited at all or only by active sport, while 39% had had no previous hospital admission for asthma. In only 18% had there been a previous admission to an intensive care unit. Forty-seven per cent were taking inhaled beclomethasone or sodium cromoglycate regularly and 27% were taking corticosteroids by mouth regularly. Death occurred outside hospital in 150 of 163 subjects. In the final attack 58% had a sudden onset and collapsed within minutes, 20% were found dead and 27% had an acute progression of an established attack. Twenty-nine per cent of the deaths were assessed as preventable: preventable factors included inadequate assessment or therapy of prior asthma (35%), poor compliance with therapy (33%) and delay in seeking help (43%). As a significant number of subjects in this survey could not be classified as "high risk", it is important that clinicians ensure that all patients are aware of optimal maintenance management and have a clear individualized plan of what to do in the event of deteriorating asthma.

Adolescent↗

Pseudomonas aeruginosa empyema in an adult with cystic fibrosis.

Pseudomonas aeruginosa is frequently grown from the sputum of adults with cystic fibrosis-related bronchiectasis. A rare case of pseudomonal empyema is reported in this clinical setting. Early diagnosis permitted successful treatment with closed needle aspiration and intravenous antibiotics.

Adult↗

Degradation of 2-carboxyarabinitol 1-phosphate by a specific chloroplast phosphatase.

The catalytic degradation of 2-carboxyarabinitol 1-phosphate (CA 1-P), a naturally occurring inhibitor of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), was investigated by chromatographic and spectroscopic analyses of the reaction products. Carboxy-labeled [(14)C]CA 1-P was incubated with a partially purified tobacco (Nicotiana rustica) chloroplast protein that has been shown previously to catalyze metabolism of CA 1-P to a form incapable of inhibiting Rubisco (ME Salvucci, GP Holbrook, JC Anderson, and G Bowes [1988] FEBS Lett 231: 197-201). In the presence and absence of NADPH, ion-exchange chromatography showed a progressive conversion of [2'-(14)C]CA 1-P to a labeled compound which coeluted with authentic carboxyarabinitol. Parallel assays with unlabeled CA 1-P showed a concomitant decrease in the ability of reaction samples to inhibit Rubisco activity. In separate experiments, a 1:1 stoichiometry was found between the release of inorganic phosphate from [2'-(14)C]CA 1-P and accumulation of the (14)C-labeled product. Liberation of inorganic phosphate was not observed when the tobacco enzyme was incubated with ribulose-1,5-bisphosphate, fructose-1,6-bisphosphate, glucose-1-phosphate, glucose-6-phosphate, or 6-phosphogluconate. Proton nuclear magnetic resonance spectroscopy of the labeled CA 1-P reaction product established its identity as carboxyarabinitol. We therefore propose that light-stimulated degradation of CA 1-P is catalyzed in vivo by a specific phosphatase, 2-carboxyarabinitol 1-phosphatase. Carboxyarabinitol 1-phosphatase activity was detected in the absence of NADPH, but increased threefold when 2 millimolar NADPH was present. Thus, while not required for the reaction, NADPH may play an important role in the regulation of CA 1-P degradation.

Journal Article↗

Effect of sinoaortic denervation on arousal responses to hypotension in newborn lambs.

To examine whether hypotension reflexly initiates arousal from sleep and the mechanisms involved, we subjected sleeping lambs to hypotensive stimuli of 1-min duration, before and after sinoaortic denervation (SAD). In intact lambs, hypotension increased the probability of arousal from both quiet sleep (QS) and rapid-eye-movement (REM) sleep. Hypotension resulted in nonarousal in 42% (QS) and 47% (REM) of tests. Arousal time was significantly longer in REM (34.9 +/- 1.8 s, means +/- SE) than in QS (26.0 +/- 1.8 s). Arterial saturation of O2 (SO2) and PO2 measured at the point of arousal were unchanged from control values in those tests in which arousal occurred. In nonarousal tests, there was a significant fall in both SO2 (4.9 +/- 1.2%) and PO2 (21.6 +/- 4.2 mmHg). After SAD, hypotension did not increase the probability of arousal. Nonarousals significantly increased to 75% (QS and REM, P less than 0.02). We conclude that acute hypotension is a potent stimulus for arousal from sleep in newborn lambs. As the arousal response is abolished by SAD and is not correlated with arterial oxygenation, hypotensive arousal appears to be mediated via arterial baroreceptors.

Animals↗

Alternative methods of photosynthetic carbon assimilation in marine macroalgae.

Two green macroalgae, Codium decorticatum and Udotea flabellum, differ photosynthetically. Codium had high O(2)-sensitive, and Udotea low O(2)-insensitive, CO(2) compensation points; Codium showed a Warburg effect at seawater dissolved inorganic carbon levels and had photorespiratory CO(2) release, whereas Udotea did not. Seawater dissolved inorganic carbon levels did not saturate photosynthesis. For Codium, but not Udotea, the Warburg effect was increased by ethoxyzolamide, a carbonic anhydrase inhibitor, at high but not low pH. Isolated chloroplasts from both macroalgae showed a Warburg effect that was ethoxyzolamide-insensitive. In both macroalgae, chloroplastic and extrachloroplastic carbonic anhydrase activity was present. P-enolpyruvate carboxykinase (PEPCK) carboxylating activity in Udotea extracts was equivalent to that of ribulose bisphosphate carboxylase, and enzyme activities for C(4) acid metabolism and P-enolpyruvate regeneration were sufficient to operate a limited C(4)-like system. In Udotea, malate and aspartate were early-labeled photosynthetic products that turned over within 60 seconds. Photorespiratory compounds were much less labeled in Udotea. Low dark fixation rates ruled out Crassulacean acid metabolism. A limited C(4)-like system, based on PEPCK, is hypothesized to be the mechanism reducing photorespiration in Udotea. Codium showed no evidence of photosynthetic C(4) acid metabolism. Marine macroalgae, like terrestrial angiosperms, seem to have diverse photosynthetic modes.

Journal Article↗

Effects of CO(2) Concentration on Rubisco Activity, Amount, and Photosynthesis in Soybean Leaves.

Growth at an elevated CO(2) concentration resulted in an enhanced capacity for soybean (Glycine max L. Merr. cv Bragg) leaflet photosynthesis. Plants were grown from seed in outdoor controlled-environment chambers under natural solar irradiance. Photosynthetic rates, measured during the seed filling stage, were up to 150% greater with leaflets grown at 660 compared to 330 microliters of CO(2) per liter when measured across a range of intercellular CO(2) concentrations and irradiance. Soybean plants grown at elevated CO(2) concentrations had heavier pod weights per plant, 44% heavier with 660 compared to 330 microliters of CO(2) per liter grown plants, and also greater specific leaf weights. Ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) activity showed no response (mean activity of 96 micromoles of CO(2) per square meter per second expressed on a leaflet area basis) to short-term ( approximately 1 hour) exposures to a range of CO(2) concentrations (110-880 microliters per liter), nor was a response of activity (mean activity of 1.01 micromoles of CO(2) per minute per milligram of protein) to growth CO(2) concentration (160-990 microliters per liter) observed. The amount of rubisco protein was constant, as growth CO(2) concentration was varied, and averaged 55% of the total leaflet soluble protein. Although CO(2) is required for activation of rubisco, results indicated that within the range of CO(2) concentrations used (110-990 microliters per liter), rubisco activity in soybean leaflets, in the light, was not regulated by CO(2).

Journal Article↗

Acute myopathy in severe acute asthma treated with intravenously administered corticosteroids.

An association between the use of parenteral corticosteroids in acute asthma and the development of an acute myopathy was first reported in 1977. We report 2 further cases that contribute significantly to our knowledge of this rare complication of the treatment of acute asthma. These cases demonstrate that the acute myopathy is not just a complication of the use of parenteral hydrocortisone in patients requiring ventilatory support during an episode of acute asthma. The acute myopathy can occur with several parenteral corticosteroids, may be severe (with rhabdomyolysis and myoglobinuria), and may have protracted morbidity. Prospective follow-up allowed demonstration of histopathology, electrophysiology, and also the contribution of various pharmacologic agents. Careful analysis of the evidence strongly implicates corticosteroids as the causative agent.

Acute Disease↗

Drought Stress and Elevated CO(2) Effects on Soybean Ribulose Bisphosphate Carboxylase Activity and Canopy Photosynthetic Rates.

Soybean (Glycine max [L.] cv Bragg) was grown at 330 or 660 microliters CO(2) per liter in outdoor, controlled-environment chambers. When the plants were 50 days old, drought stress was imposed by gradually reducing irrigation each evening so that plants wilted earlier each succeeding day. On the ninth day, as the pots ran out of water CO(2) exchange rate (CER) decreased rapidly to near zero for the remainder of the day. Both CO(2)-enrichment and drought stress reduced the total (HCO(3) (-)/Mg(2+)-activated) extractable ribulose-1,5-bisphosphate carboxylase (RuBPCase) activity, as expressed on a chlorophyll basis. In addition, drought stress when canopy CER values and leaf water potentials were lowest, reduced the initial (nonactivated) RuBPCase activity by 50% compared to the corresponding unstressed treatments. This suggests that moderate to severe drought stress reduces the in vivo activation state of RuBPCase, as well as lowers the total activity. It is hypothesized that stromal acidification under drought stress causes the lowered initial RuBPCase activities. The K(m)(CO(2)) values of activated RuBPCase from stressed and unstressed plants were similar; 15.0 and 12.6 micromolar, respectively. RuBP levels were 10 to 30% lower in drought stressed as compared to unstressed treatments. However, RuBP levels increased from near zero at night to around 150 to 200 nanomoles per milligram chlorophyll during the day, even as water potentials and canopy CERs decreased. This suggests that the rapid decline in canopy CER cannot be attributed to drought stress induced limitations in the RuBP regeneration capability. Thus, in soybean leaves, a nonstomatal limitation of leaf photosynthesis under drought stress conditions appears due, in part, to a reduction of the in vivo activity of RuBPCase. Because initial RuBPCase activities were not reduced as much as canopy CER values, this enzymic effect does not explain entirely the response of soybean photosynthesis to drought stress.

Journal Article↗

The efficacy of nedocromil sodium (Tilade) in asthma.

Nedocromil sodium is a new antiasthmatic drug with properties similar to sodium cromoglycate. We examined the efficacy of nedocromil sodium compared to placebo in 71 asthmatic patients in a three-centre double-blind parallel group study over 12 weeks. During the study the patients' maintenance inhaled corticosteroids were progressively withdrawn. Nedocromil sodium had an advantage over placebo in the number of withdrawals related to uncontrolled asthma, 14 and 24 respectively (p = 0.03). Changes in symptom scores, peak flow rates and bronchodilator use favoured nedocromil sodium occasionally during the study. The unusual taste of the active drug was reported frequently. Nedocromil sodium is more efficacious than placebo in asthma maintenance, but does not replace inhaled corticosteroids.

Administration, Inhalation↗

Photosynthesis and Growth of Water Hyacinth under CO(2) Enrichment.

Water hyacinth (Eichhornia crassipes [Mart.] Solms) plants were grown in environmental chambers at ambient and enriched CO(2) levels (330 and 600 microliters CO(2) per liter). Daughter plants (ramets) produced in the enriched CO(2) gained 39% greater dry weight than those at ambient CO(2), but the original mother plants did not. The CO(2) enrichment increased the number of leaves per ramet and leaf area index, but did not significantly increase leaf size or the number of ramets formed. Flower production was increased 147%. The elevated CO(2) increased the net photosynthetic rate of the mother plants by 40%, but this was not maintained as the plants acclimated to the higher CO(2) level. After 14 days at the elevated CO(2), leaf resistance increased and transpiration decreased, especially from the adaxial leaf surface. After 4 weeks in elevated as compared to ambient CO(2), ribulose bisphosphate carboxylase activity was 40% less, soluble protein content 49% less, and chlorophyll content 26% less; whereas starch content was 40% greater. Although at a given CO(2) level the enriched CO(2) plants had only half the net photosynthetic rate of their counterparts grown at ambient CO(2), they showed similar internal CO(2) concentrations. This suggested that the decreased supply of CO(2) to the mesophyll, as a result of the increased stomatal resistance, was counterbalanced by a decreased utilization of CO(2). Photorespiration and dark respiration were lower, such that the CO(2) compensation point was not altered. The photosynthetic light and CO(2) saturation points were not greatly changed, nor was the O(2) inhibition of photosynthesis (measured at 330 microliters CO(2) per liter). It appears that with CO(2) enrichment the temporary increase in net photosynthesis produced larger ramets. After acclimation, the greater total ramet leaf area more than compensated for the lower net photosynthetic rate on a unit leaf area basis, and resulted in a sustained improvement in dry weight gain.

Journal Article↗

A 4-week Australian multicentre study of nedocromil sodium in asthmatic patients.

The use of nedocromil sodium 4 mg q.i.d. in asthmatics with mildly unstable asthma induced by a reduction of their inhaled beclomethasone dipropionate dose was investigated in a double-blind, parallel group, placebo-controlled study. Compared with placebo, nedocromil sodium improved night-time and daytime asthma score, night-time and daytime bronchodilator use, and evening PEFR at some stage during the 4-week treatment. It is concluded that nedocromil sodium exerts a beneficial effect in chronic asthma.

Adolescent↗

The circulation in sleep in newborn lambs.

Interaction of the cardiovascular, homeothermic and behavioural systems has particular significance in early life as this period of development sees high cardiac output, limited circulatory reserves, a particular vulnerability to thermal stress, and long periods of rapid eye movement (REM) sleep during which thermal regulation may be suspended. In unstressed lambs, significant cardiovascular differences exist between behavioural states of sleep and wakefulness, with the REM sleep-state being outstanding. In REM sleep there is wide cardiac output variation, a low heart rate, and a high stroke volume. High levels of cardiac output occurring in combination with poorer oxygenation and respiration in REM may represent a risk to the newborn, as cardiac performance is already high and reserves are low in comparison with the adult. Lambs respond to cool stress with increases of cardiac output and oxygen consumption in wakefulness and quiet sleep, but not in REM sleep. Suspension of thermoregulatory processes in REM sleep also points to this as the more vulnerable state for the newborn. Arousal responses from quiet sleep or REM sleep to wakefulness occur if lambs are subjected to acute reductions of blood pressure. There is a delay before arousal which is longer in REM sleep than in quiet sleep. Animals fail to arouse in approximately 40% of hypotensive tests in both states. This shared feature of the sleep-states (failure to arouse) may be more important than the state-related difference (longer delay before arousal in REM) in understanding a cardiovascular mechanism of Sudden Infant Death Syndrome.

Animals↗

State-related incidence of spontaneous breathing during high frequency ventilation.

Previous reports indicate that apnea is induced by high frequency ventilation (HFV) in anesthetized animals. We have studied conscious dogs ventilated with HFV during sleep and wakefulness to determine if this apnea is state related. Eucapnic apnea or very low breathing frequencies were observed during quiet wakefulness, quiet sleep and tonic REM sleep. However, spontaneous breathing at nearly normal rates was invariably seen during phasic REM sleep. We conclude that HFV as administered induces apnea or near apnea in conscious animals and that the inhibitory pathways causing this apnea are probably disabled during phasic REM sleep.

Animals↗

Effect of supplemental nocturnal oxygen on gas exchange in patients with severe obstructive lung disease.

We studied the effect of supplemental nocturnal oxygen on blood gases in 15 patients with severe but stable chronic obstructive lung disease (ratio of forced expired volume in one second to forced vital capacity, 37.2 +/- 1.8 [mean +/- S.E.] per cent of predicted; arterial oxygen tension, 50.7 +/- 1.4 mm Hg; and arterial carbon dioxide tension [PCO2], 53.1 +/- 1.5 mm Hg). Sleep variables and measures of gas exchange were determined on two consecutive nights; on the first night the subjects breathed supplemental oxygen, and on the second they breathed room air. Transcutaneous PCO2 was measured with an infrared sensor, and arterial oxygen saturation with an ear oximeter. Breathing of supplemental oxygen sufficient to keep oxygen saturation at or above 90 per cent was associated with only small increases (less than 6 mm Hg) in PCO2 throughout sleep, as compared with values while subjects were breathing room air. The increase in PCO2 occurred early in the night and was not progressive. Only three patients, who were found to have obstructive sleep apnea in addition to obstructive lung disease, had larger increases in PCO2 during sleep and reported morning headaches. We conclude that nocturnal oxygen does not induce clinically important increases in PCO2 during sleep in patients with stable obstructive lung disease and therefore can safely be used to prevent the dangerous consequences of hypoxia.

Aged↗

Dark/Light modulation of ribulose bisphosphate carboxylase activity in plants from different photosynthetic categories.

Ribulose bisphosphate carboxylase/oxygenase (RuBPCase) from several plants had substantially greater activity in extracts from lightexposed leaves than dark leaves, even when the extracts were incubated in vitro with saturating HCO(3) (-) and Mg(2+) concentrations. This occurred in Glycine max, Lycopersicon esculentum, Nicotiana tabacum, Panicum bisulcatum, and P. hylaeicum (C(3)); P. maximum (C(4) phosphoenolpyruvate carboxykinase); P. milioides (C(3)/C(4)); and Bromelia pinguin and Ananas comosus (Crassulacean acid metabolism). Little or no difference between light and dark leaf extracts of RuBPCase was observed in Triticum aestivum (C(3)); P. miliaceum (C(4) NAD malic enzyme); Zea mays and Sorghum bicolor (C(4) NADP malic enzyme); Moricandia arvensis (C(3)/C(4)); and Hydrilla verticillata (submersed aquatic macrophyte). It is concluded that, in many plants, especially Crassulacean acid metabolism and C(3) species, a large fraction of ribulose-1,5-bisphosphate carboxylase/oxygenase in the dark is in an inactivatable state that cannot respond to CO(2) and Mg(2+) activation, but which can be converted to an activatable state upon exposure of the leaf to light.

Journal Article↗

An efferent pathway mediating reflex tracheal dilation in awake dogs.

Lung inflation is known to produce reflex relaxation of tracheal smooth muscle (TSM) and dilation of the upper airway, but the specific efferent pathway involved has not been established. Therefore we examined TSM tone in four trained awake dogs by measuring pressure changes in the water-filled cuff of an endotracheal tube that was inserted into the lower cervical trachea through a permanent tracheostomy. Under control conditions, sustained lung inflation with 1 liter of air produced apnea (Hering-Breuer inflation reflex) and a decrease in cuff pressure (Pcuff) of 37.4 +/- 12.0 (mean +/- SD) cmH2O. beta-Adrenergic blockade with propranolol had no effect on either the apneic or TSM responses to lung inflation. Efferent parasympathetic blockade with atropine sulfate (1.2-2.4 mg) abolished TSM tone, which was then restored to control levels by a continuous intravenous infusion of serotonin (14-28 micrograms X kg-1 X min-1). Under these conditions, lung inflation still induced reflex apnea but no longer relaxed TSM tone (mean decrease in Pcuff, 2.7 +/- 1.4 cmH2O, P less than 0.001). The findings indicate that reflex tracheal dilation in response to lung inflation is mediated by an efferent cholinergic (parasympathetic) pathway.

Adrenergic beta-Antagonists↗