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Biomedical subjects

G M Davis

Publications and source records attributed to G M Davis.

At least 37 records · Page 2Linked to original sources
PubMed2000

Pulmonary outcome in extremely low birth weight infants.

OBJECTIVE: To determine whether infants with hyaline membrane disease (HMD) superimposed on immature lung disease (ILD) have more abnormal lung function and respiratory drive during the evolution of chronic neonatal lung disease (CNLD) in extremely low birth weight infants (ELBW; <1000 g). METHODS: We measured lung mechanics (respiratory frequency, tidal volume, minute ventilation, lung resistance, lung compliance, lung impedance, and work of breathing per minute) and respiratory drive (airway opening pressure 100 milliseconds after initiation of breath [P(0.1)] and maximal inspiratory pressure generated during airway occlusion) on 3 occasions before term in 24 ELBW infants. RESULTS: Ten infants with ILD (mean [95% CI] gestation: 24.3 weeks [23.1,25.4]; birth weight: 675 g [553,798]) were studied at 27, 31, and 35 weeks of postconceptional age and 14 infants with HMD superimposed on ILD (gestation: 25.1 weeks [24.4,25.9]; birth weight: 687 g [601,773]) were studied at 28, 32, and 35 weeks of postconceptional age. There were no statistically significant differences between the groups for respiratory frequency, tidal volume, minute ventilation, lung resistance, lung compliance, lung impedance, work of breathing per minute, P(0.1), and maximal inspiratory pressure generated during airway occlusion. With increasing age, both groups demonstrated increased respiratory drive as measured by P(0.1) without significant changes in respiratory frequency or CO(2). Work of breathing per minute increased in the HMD group with age and was higher in extubated subjects. A similar trend with age was demonstrated in ILD infants. Regardless of whether the initial lung disease was ILD alone or HMD + ILD, ELBW infants developed a mildly reduced lung compliance/kg (.8-1.1 mL/cm.H(2)O/kg) and high lung resistance (75-125 cm.H(2)O/L/second) pattern of CNLD, which changed little after 3 weeks of age. Survival to 6 months was 23/24 (96%). Oxygen dependency was 16/24 (67%) at 35 weeks, yet only 5/23 (22%) survivors required oxygen at discharge from the neonatal unit (43 weeks). CONCLUSIONS: The visco-elastic and flow-resistive properties of the lungs in ELBW infants with CNLD remain only mildly abnormal, suggesting a more favorable prognosis for lung function in later years than previously reported.

Chronic Disease↗
PubMed2000

Erhaia (Gastropoda: Rissooidea): phylogenetic relationships and the question of Paragonimus coevolution in Asia.

The human lung fluke Paragonimus is transmitted by gastropod taxa of two superfamilies: Ceritheoidea and Rissooidea. The question whether or not Paragonimus shows the same specificity of host-parasite coevolved relationship as the human blood fluke Schistosoma was inspired by the finding of two sympatric snail species as hosts for Paragonimus skrjabini in Fujian Province, China: Gammatricula and Erhaia. The former species can clearly be classified as Pomatiopsidae: Triculinae. The latter has previously been classified as Pomatiopsidae: Pomatiopsinae. However, this classification based on anatomical characteristics is uncertain. In order to obtain a robust phylogenetic hypothesis for Erhaia, we have studied three gene fragments from this taxon as well as from twelve related taxa. The data show that the species involved represent four families: Pomatiopsidae, Hydrobiidae, Cochliopidae (here raised to family status), and Amnicolidae. Erhaia fits securely into the Amnicolidae. This indicates that P. skrjabini has not coevolved with snail lineages. However, P. skrjabini has so far only been reported from rissooidean snails, whereas members of the Paragonimus westermani complex have only been found in ceritheoidean snails. The implication is that there is a host specificity on the superfamily level. However, Asian freshwater species of the Ceritheoidea and Rissooidea usually are not sympatric and often prefer different habitats. It is therefore possible that ecological niche partitioning plays the primary role for Paragonimus evolution.

Animals↗
PubMed2000

Gene sequencing for identification of Paragonimus eggs from a human case.

OBJECTIVE: To identify the etiologic agent from a paragonimiasis patient using molecular techniques. METHODS: The complete nuclear ribosomal DNA second internal transcribed spacer (ITS2) gene sequence of eggs in sputum from a paragonimiasis patient was obtained by directly auto-sequencing its PCR product. ITS2 genes from eggs of Paragonimus westermani and Pagumogonimus skrjabini (both from animal hosts) were also sequenced for comparison. In addition, morphological comparisons were made with the eggs of the two species. RESULTS: The ITS2 gene from the human case was 100% identical with the sequence from the eggs of P. westermani from an experimentally infected dog but only 92% identical with the sequence from the eggs of P. skrjabini. Morphologically, the eggs from the human case more resembled those from P. westermani infected dog. CONCLUSION: The patient was diagnosed to be suffered from paragonimiasis westermani by gene sequence analysis.

Animals↗
PubMed2000

[Allozyme-based genetic variation within an unstable "population" of Chinese Oncomelania hupensis (Gastropoda: Rissoacea: Pomatiopsidae)].

OBJECTIVE: To answer the following questions: 1. For Oncomelania snails collected two years apart from the same locality, has there been genetic divergence? 2. How much experimental error has there been in studying subsets of these populations? 3. As this is an unstable population, what has the net effect been on Hardy-Weinberg equilibrium (HWe)? METHODS: Allozymes were studied using horizontal starch gel electrophoresis. Data collected from numbers of experiments were compiled. Data from each collection were divided into two equal subsets based on chronology of the experiments. Thirty-four loci were studied using 72 to 180 snails per subset. RESULTS: The mean number of alleles per locus ranged from 1.5-1.9. With each consecutive subset, the % polymorphic loci dropped from 38.2 to 17.6. The mean heterozygosity was very low: 0.033 to 0.049 and not significantly different from Hardy-Weinberg expectations. Ten loci and 11 alleles exclusive to the first group were eliminated from the overall study reducing the number of polymorphic loci from 19 to 10. There were significant departures from HWe at five loci having a substantial number of individuals for each allele. Nei's and Wright's D were 0.003 +/- 0.001 and 0.054 +/- 0.006 respectively. CONCLUSION: 1. There were significant errors seen primarily in the results scored in the earliest experiments. 2. These earlier errors involving scoring difficult to resolve loci, and interpretation of rare alleles that were not found in later experiment had no significant effect on overall genetic distance. 3. The use of Wright's D for closely related populations is explained. Results with Nei's D indicated no significant difference among the four subunits; Wright's D yielded significant difference between the collections made two years apart, attributed to the annual flooding of the Yangtze River mixing snails from different localities. 4. Major polymorphic loci were not in Hwe as predicted using the unstable population model. 5. One must study 25 or more individuals to find relatively rare alleles and study population genetics.

Alleles↗
PubMed1999

Cardiovascular responses to an orthostatic challenge and electrical-stimulation-induced leg muscle contractions in individuals with paraplegia.

The purpose of this study was to investigate the cardiovascular and haemodynamic responses that occur during moderate orthostatic challenge in people with paraplegia, and the effect of electrical stimulation (ES)-induced leg muscle contractions on their responses to orthostatic challenge. Eight males with complete spinal lesions between the 5th and 12th thoracic vertebrae (PARA) and eight able-bodied individuals (AB) volunteered for this study. Changes in heart rate (fc), stroke volume (SV), cardiac output (Qc), mean arterial pressure (MAP), total peripheral resistance (TPR), limb volumes and indices of neural modulation of fc, [parasympathetic (PNS) and sympathetic (SNS) nervous system indicators] were assessed during: (1) supine rest (REST), (2) REST with lower-body negative pressure at -30 torr (LBNP -30, where 1 torr = 133.32 N/m2), and (3) for PARA only, LBNP -30 with ES-induced leg muscle contractions (LBNP + ES). LBNP -30 elicited a decrease in SV (by 23% and 22%), Qc (by 15% and 18%) and the PNS indicator, but an increase in fc (by 10% and 9%), TPR (by 23% and 17%) and calf volume (by 1.51% and 4.04%) in both PARA and AB subjects, respectively. The SNS indicator was increased in the AB group only. Compared to LBNP -30, LBNP + ES increased SV (by 20%) and Qc (by 16%), and decreased TPR (by 12%) in the PARA group. MAP was unchanged from REST during all trials, for both groups. The orthostatic challenge induced by LBNP -30 elicited similar cardiovascular adaptations in PARA and AB subjects. ES-induced muscle contractions during LBNP -30 augmented the cardiovascular responses exhibited by the PARA group, probably via reactivation of the skeletal muscle pump and improved venous return.

Adult↗
PubMed1999

Postural control during stance in paraplegia: effects of medially linked versus unlinked knee-ankle-foot orthoses.

OBJECTIVE: To investigate the effect of medially linking knee-ankle-foot orthoses (KAFOs) on postural stability and sway during (1) quiet standing and (2) functional activities for persons with spinal cord injury (SCI). DESIGN: A randomized, mixed design, with the factors being activity (quiet standing and two function-mimicking tasks), SCI (present or not), and type of orthosis used in SCI group (linked or unlinked KAFO). PARTICIPANTS: Nine men with T5 to T12 paraplegia, 8 of whom had complete lesions and 1 with some sacral sparing (American Spinal Injury Association grade B) without proprioception, matched to 9 able-bodied men. MAIN OUTCOME MEASURES: Mean amplitude of sway and sway path in anteroposterior and mediolateral directions, derived from center of pressure measurements on a force platform. RESULTS: All men with SCI were able to stand unsupported and perform function-mimicking activities in medially linked KAFOs; however, when wearing unlinked KAFOs only 5 could maintain balance during quiet stance and 3 could maintain balance during activity. Significant differences were found between linked and unlinked KAFOs; side-to-side mean amplitude of sway was less and sway path was greater for SCI subjects when they wore the linked KAFOs. CONCLUSION: Medial linkage of bilateral KAFOs provides an effective strategy to improve stability and increase postural control for persons with SCI, facilitating performance of functional activities during standing without upper limb support.

Activities of Daily Living↗
PubMed1999

Cardiorespiratory responses to arm cranking and electrical stimulation leg cycling in people with paraplegia.

PURPOSE: The purpose of this study was to assess the cardiorespiratory responses during arm exercise with and without concurrent electrical stimulation-induced leg cycling in people with paraplegia. METHODS: On separate days, 10 subjects with spinal cord injuries (T5-T12) performed either arm cranking (ACE), or simultaneous arm cranking + electrical stimulation-induced leg cycling (ACE+ES-LCE) graded exercise tests. RESULTS: During submaximal, steady-state exercise, ACE+ES-LCE elicited significantly higher VO2, (by 0.25-0.28 L x min(-1)) stroke volume (by 13 mL), and VE(BTPS) (by 9.4 L x min(-1)) compared with ACE alone. In contrast, there were no significant differences of submaximal HR, cardiac output, or power output between the exercise modes. At maximal exercise, ACE+ES-LCE elicited significantly higher VO2 (by 0.23 L x min(-1)) compared with ACE alone, but there were no differences in power output, HR, or VE(BTPS). CONCLUSIONS: These results demonstrate that during submaximal or maximal exercise there was a greater metabolic stress elicited during ACE+ES-LCE compared with during ACE alone. The higher stroke volume observed during submaximal ACE+ES-LCE, in the absence of any difference in HR, implied a reduced venous pooling and higher cardiac volume loading during ACE+ES-LCE. These results suggest that training incorporating ACE+ES-LCE may be more effective in improving aerobic fitness in people with paraplegia than ACE alone.

Adult↗
PubMed1999

Delayed presentation of traumatic arterial vasospasm.

Traumatic arterial vasospasm with no surrounding anatomic damage is a rare finding. Delayed presentation of arterial vasospasm several days from the inciting event is also rare. However, when the diagnosis of arterial vasospasm is considered, evaluation and treatment must be initiated promptly to avoid prolonged ischemia to the extremity. We present an 11-year-old female who presented with a delayed presentation of arterial vasospasm, and also review the literature.

Angiography↗
PubMed1999

A molecular perspective on the genera Paragonimus Braun, Euparagonimus Chen and Pagumogonimus Chen.

The status of the genera Euparagonimus Chen, 1963 and Pagumogonimus Chen, 1963 relative to Paragonimus Braun, 1899 was investigated using DNA sequences from the mitochondrial cytochrome c oxidase subunit I (CO1) gene (partial) and the nuclear ribosomal DNA second internal transcribed spacer (ITS2). In the phylogenetic trees constructed, the genus Pagumogonimus is clearly not monophyletic and therefore not a natural taxon. Indeed, the type species of Pagumogonimus, P. skrjabini from China, is very closely related to Paragonimus miyazakii from Japan. The status of Euparagonimus is less obvious. Euparagonimus cenocopiosus lies distant from other lungflukes included in the analysis. It can be placed as sister to Paragonimus in some analyses and falls within the genus in others. A recently published morphological study placed E. cenocopiosus within the genus Paragonimus and probably this is where it should remain.

Animals↗
PubMed1999

[Studies on allozyme of Gammatricula].

AIM: To furnish molecular genetic evidences for taxonomy of Gammatricula. METHODS: A total of 24 enzymes of 6 populations of Gammatricula songi and 1 population of Gammatricula chinensis collected from Kaihua County and Chunan County of Zhejiang Province were studied using horizontal starch gel electrophoresis. RESULTS: 29 loci were found. The percentages of polymorphic loci of G. songi populations were 6.9%-13.8%. All loci of G. chinensis were monomorphic. The Nei's distance among G. songi populations did not exceed 0.12. The Nei's distance between G. songi and G. chinensis was 0.73. CONCLUSION: The allozyme variations of inter-G. songi are limited, but the allozyme variation between G. songi and G. chinensis is significant.

Alleles↗
PubMed1998

Energy expenditure during gait using the walkabout and isocentric reciprocal gait orthoses in persons with paraplegia.

OBJECTIVE: To compare the energy expenditure during walking using the Walkabout Orthosis (WO) and the Isocentric Reciprocal Gait Orthosis (IRGO) in persons with paraplegia. DESIGN: A randomized cross-over design. PATIENTS: Ten individuals with complete T9-12 paraplegia. INTERVENTIONS: Subjects were trained to walk using the WO and the IRGO with elbow crutches. MAIN OUTCOME MEASURES: Subjects' energy expenditures during walking using each orthosis over three different terrains--flat tile, flat carpet, and 4 degrees uphill ramp--were compared. Data collected included expired ventilation (L/min), heart rate (beats/ min), speed of walking (m/min), oxygen uptake (VO2; L/min and mL/kg/min), oxygen cost (O2 cost; mL/kg/m), and Physical Cost Index (PCI; beats/m). Subjects walked at a self-selected pace. RESULTS: Subjects walked significantly slower with the WO than with the IRGO, regardless of the surface (p < .05). The average speed of walking ranged from 5.2+/-1.3 for the WO on the tiled surface to 11.5+/-2.3m/min for the IRGO on the carpeted surface. Despite marked differences in self-selected walking speeds between the two orthoses, there were no differences in either heart rate or VO2 among orthoses or surfaces. However, the O2 cost of gait was significantly greater for the WO (range, 3.95 to 4.91mL/kg/m) compared with the IRGO (range, 1.6 to 1.8mL/kg/m). Likewise, the PCI was significantly greater using the WO (range, 8.4 to 10.3beats/m) than the IRGO (range, 4.3 to 7.0beats/m). CONCLUSIONS: This study shows that the metabolic demands of walking with the WO are greater than walking with the IRGO in individuals with T9-12 paraplegia.

Adult↗
PubMed1998

Randomized controlled trial of ipratropium bromide and frequent low doses of salbutamol in the management of mild and moderate acute pediatric asthma.

OBJECTIVES: To compare the effectiveness and safety of alternative nebulized drug protocols in children with mild or moderate asthma exacerbations. METHODS: We conducted a blinded, randomized, controlled trial with a 2 x 2 factorial design. Two interventions, nebulized salbutamol in frequent low doses (0.075 mg/kg every 30 minutes) and the addition of ipratropium bromide (250 micrograms), were compared with salbutamol in hourly high doses (0.15 mg/kg every 60 minutes) in children with mild or moderate acute asthma. The primary end point was the improvement in respiratory resistance. Secondary end points included oxygen saturation, corticosteroid use, patient disposition, and relapse status. RESULTS: A total of 298 participants aged 3 to 17 years were studied, and 15% were admitted to the hospital; 14% of the children had relapses. No increased bronchodilation was associated with frequent low doses versus hourly high doses of salbutamol (RR = 0.9 [95% confidence interval 0.7, 1.3]) or the addition of ipratropium bromide versus placebo (RR = 1.0 [0.8, 1.3]). No group differences were observed in secondary end points. Salbutamol in frequent low doses was associated with increased vomiting (RR = 2.5 [1.1, 6.0]). CONCLUSION: Our results do not support the use of frequent low doses of nebulized salbutamol or the addition of ipratropium bromide compared with hourly high doses of salbutamol in children with mild or moderate asthma.

Acute Disease↗
PubMed1998

Long-term pulmonary sequelae of severe bronchopulmonary dysplasia.

OBJECTIVE: To evaluate the long-term pulmonary sequelae of survivors of bronchopulmonary dysplasia (BPD) of sufficient severity to have required supplemental oxygen for at least 1 month after term. STUDY DESIGN: Fifteen patients with a mean age of 1.1 years were matched to preterm infants of similar gestational age and age at time of study. Pulmonary function testing included spirometry, plethysmographic lung volumes, carbon monoxide diffusion capacity, and in 9 of 15 subjects with BPD, measurement of lung static elastic recoil pressures. RESULTS: The subjects with BPD had a mean expiratory volume in 1 second (FEV1) of 64% +/- 21% predicted (4 had an FEV1 < 50% predicted) compared with 85% +/- 11% (P < .01) for the preterm children in the control group. Subjects with BPD had a significant degree of gas trapping with a residual volume to total lung capacity ratio of 37% +/- 13% compared with 25% +/- 4% for the control group (P < .01). An inverse relationship was seen between the FEV1 and the time on supplemental oxygen (r = -0.84, P < .0001), with 3 of the 4 children whose FEV1 was < 50% requiring oxygen for more than 900 days. Those with the greatest degree of airflow limitation and gas trapping had the greatest abnormalities in both shape and position of the pressure volume curves of the lung. CONCLUSION: Severe BPD may result in moderate to severe long-term abnormalities in pulmonary function tests.

Bronchopulmonary Dysplasia↗
PubMed1998

Sleep-disordered breathing in children with myelomeningocele.

BACKGROUND: Although patients with myelomeningocele and the Chiari II malformation are known to have sleep apnea and respiratory control deficits, the prevalence, types, severities, and associations of sleep-disordered breathing (SDB) have not been adequately defined. METHODS: A cross-sectional study of our myelomeningocele clinic population was undertaken to correlate polysomnographic results with historical data and findings from magnetic resonance imaging of the Chiari malformation, pulmonary function results, and nocturnal pulse oximetry. RESULTS: A questionnaire survey of symptoms was available for 107 of 109 children (98% of the clinic population), and 83 patients agreed to undergo overnight polysomnography. Breathing during sleep was classified as normal in 31 cases (37%), mildly abnormal in 35 cases (42%), and moderately/severely abnormal in 17 cases (20%). Among the 17 patients with moderately/severely abnormal SDB, 12 patients had predominantly central apneas and 5 had predominantly obstructive apnea. Patients with a thoracic or thoracolumbar myelomeningocele, those who had previously had a posterior fossa decompression operation, those with more severe brain-stem malformations, and those with pulmonary function abnormalities were more likely to have moderately/severely abnormal SDB, relative risks (95% confidence intervals) 9.2 (2.9 to 29.3), 3.5 (1.3 to 8.9), 3.0 (0.9 to 10.5), and 11.6 (1.6 to 81.3), respectively. Failure of obstructive SDB to resolve after adenotonsillectomy in four patients suggested abnormal control of pharyngeal airway patency during sleep. Nocturnal pulse oximetry accurately predicted moderately/severely abnormal SDB with a sensitivity of 100% and a specificity of 67%. CONCLUSIONS: The pathogenesis of SDB in patients with myelomeningocele involves the functional level of the spinal lesions, congenital and acquired brainstem abnormalities, pulmonary function abnormalities, disorders of upper airway maintenance, and sleep state. Polysomnography and nocturnal pulse oximetry should be performed in high-risk patients to detect and classify SDB.

Arnold-Chiari Malformation↗
PubMed1998

Respiratory function in children during recovery from neuromuscular blockade.

Residual neuromuscular blockade is a major risk factor for respiratory insufficiency. We examined the relationship between neuromuscular and respiratory function in 18 ASA I or II children aged 2-4 years. Lung function was measured by pneumotachography and transpulmonary pressure, neuromuscular transmission by first twitch response ratio (T1:T1) and train-of-four ratio (TOFR), before and at specific points in recovery from vecuronium paralysis. The tidal volume was directly related to maximal inspiratory pressure at occlusion (PIOCC), P < 0.001, whereas the minute ventilation (VE) was related to the respiratory drive (P0.1), P < 0.001. The best predictors of minute ventilation were the P0.1 (r = 0.57), and the TOFR (r = 0.62). PIOCC and P0.1 correlated closely (r = 0.889, P = 0.002) but TOFR and T1:T1 did not correlate with either. Our results show that the occlusion pressure measurements, P0.1 and PIOCC, were good predictors of both VE.kg-1 and respiratory work.

Anesthesia Recovery Period↗
PubMed1998

Efficacy of sequential early systemic and inhaled corticosteroid therapy in the prevention of chronic lung disease of prematurity.

In order to assess the efficacy of a combination of systemic and nebulized corticosteroids in reducing the incidence and severity of chronic lung disease (CLD) in very low birthweight (VLBW) infants, 60 ventilator-dependent infants < or = 1500 g were randomly assigned to receive either steroids or placebo as of 7 d. The steroid group (n = 30, GA = 25.8 +/- 1.6 weeks, BW = 731 +/- 147 g) received systemic dexamethasone for 3 d, followed by nebulized budesonide for 18 d. Control infants (n = 30, GA = 25.9 +/- 1.8 weeks, BW = 796 +/- 199 g) received systemic and inhaled saline. Steroid-treated infants required less ventilatory support between 9 and 17 d (p < 0.01), and had greater lung compliance at 10 d (p = 0.01), but not subsequently. CLD incidence at 36 weeks was 45.5% vs 56.0% in controls, and fewer steroid-treated infants required dexamethasone rescue (23.3% vs 56.7%, p = 0.017). Survival to discharge was similar (73.3% vs 83.3%), as were the durations of mechanical ventilation, supplemental oxygen use, and hospitalization. Tracheal effluent elastase/albumin ratios and serum cortisol values did not differ between groups, and no adverse effects were noted. We conclude that early dexamethasone administration was associated with improved pulmonary function, which was not sustained with nebulized budesonide. However, the steroid regimen studied reduced the need for dexamethasone rescue in infants with CLD.

Administration, Inhalation↗