Search PubMed⌕ Search

Biomedical subjects

M Green

Publications and source records attributed to M Green.

At least 325 records · Page 18Linked to original sources
PubMed1994

Respiratory muscle function in patients with asbestos-related pleural disease.

The effect of asbestos-related pleural disease (ARPD) on the generation of maximum respiratory pressure was investigated in 11 male patients with ARPD mean age 57 years, range 45-74, and mean duration of asbestos exposure of 9.9 years, range 5-16. There were three smokers, seven ex-smokers and one non-smoker. Breathlessness ranged from grade 1-3 on the MRC score. The extent of pleural disease was calculated using a score based on the ILO score for pleural disease. Full respiratory function tests, global respiratory muscle strength and diaphragmatic strength were assessed. Respiratory muscle strength, including diaphragm strength, was normal. Recoil pressure was high or at the upper limit of normal in four patients and correlated with chest radiograph score for pleural disease (r = 0.65, P < 0.02). There was no difference in either global respiratory muscle or diaphragmatic strength between patients with and without involvement of one or both costophrenic angles or between patients with mild or severe breathlessness. We conclude that respiratory muscle strength is not importantly reduced in ARPD, and it is unlikely that weakness contributes to breathlessness in these patients. By contrast reduced chest wall compliance is likely to be an important factor in breathlessness in some cases.

Aged↗
PubMed1994

Analysis of the structure and synthesis of GRP94, an abundant stress protein of the endoplasmic reticulum.

The synthesis and cotranslational modification of GRP94, an abundant, resident protein of the endoplasmic reticulum belonging to the hsp90 family of stress proteins, has been studied in transient expression studies in COS cells. A fraction of the expressed murine GRP94 was more highly glycosylated than normal, having a greater number of endoglycosidase H (Endo H)-sensitive oligosaccharide moieties than authentic GRP94. To understand better the basis for the appearance of the hyperglycosylated form and determine the acceptor sites that were used for this extra glycosylation, we have used in vitro mutagenesis techniques to construct a set of point mutants and deletion mutants of GRP94. Analysis of the expression of wild-type GRP94 and the mutant proteins has revealed that Asn-196 is the acceptor site used in normal glycosylation of GRP94 and that hyperglycosylation is dependent upon the level of expression of the GRP94 and is occurring at acceptor sites in the carboxy-terminal region of the protein. We have shown, in addition, that Cys-117 is involved in the formation of a disulfide-bonded homodimer of GRP94. Finally, analysis of deletions made from the amino terminus of the mature protein has demonstrated that these alterations change the pattern of usage of the remaining N-glycosylation sites in the mutants.

Amino Acid Sequence↗
PubMed1994

IS6770, an enterococcal insertion-like sequence useful for determining the clonal relationship of clinical enterococcal isolates.

Enterococci expressing resistance to antimicrobial agents are increasingly important nosocomial pathogens. Effective strategies to prevent or abort outbreaks of resistant enterococcal infection will rely on an accurate understanding of the mechanisms by which these organisms spread. A 1065-bp insertion-like sequence (IS6770) is present in varying copy numbers in > 90% of enterococcal strains thus far examined. Hybridization patterns resulting from hybridization of enterococcal genomic DNA with an internal IS6770 probe vary considerably between unrelated strains and correlate well with results of pulsed-field gel electrophoresis and field-inversion gel electrophoresis in identifying clonal relationships among enterococcal isolates. IS6770 analysis of several outbreaks of resistant enterococci has confirmed the spread of single resistant clones rather than the emergence of resistance within the resident flora. These results suggest that IS6770 hybridization will be a useful tool for tracing the epidemiology of nosocomial enterococcal infections.

Amino Acid Sequence↗
PubMed1994

Diagnosis, management, and implications of maternal depression for children and pediatricians.

The past decade has witnessed a marked increase in the quantity and quality of research relating to maternal depression and the children of depressed mothers. Such children are at heightened psychological risk of problems in adjustment and depression. The outcomes in this vulnerable group are determined by many influences in the child, the mother, and the family. There is a reciprocal relationship between psychological problems in the child and in the mother. Recently, the contextual and transactional aspects of maternal depression has been emphasized in the literature. Attention has to be given not only to the mother and her child but also to acute and chronic family stressors. In this not uncommon life event, the pediatrician has a key role in early identification and intervention, both preventive and therapeutic.

Adaptation, Psychological↗
PubMed1994

A comparison of different modes of noninvasive ventilatory support: effects on ventilation and inspiratory muscle effort.

The aims of noninvasive ventilation include the correction of hypoventilation and unloading of inspiratory muscles. Volume cycled flow generators, bi-level positive airway pressure and continuous positive airway pressure techniques have all been used with face and nasal masks. We have compared these modes of ventilatory support, administered by a nasal mask in stable, awake outpatients with chronic obstructive pulmonary disease or neuromusculo-skeletal disease in respect of their effects on ventilation, inspiratory muscle effort and oxygen saturation. There were no clinically significant differences between the volume cycled flow generator and bi-level positive airway pressure methods; compared to spontaneous ventilation, oxygen saturation increased and inspiratory muscle effort decreased. Tidal volume increased and respiratory rate reduced, the largest changes occurring with bi-level positive airway pressure. Only the volume cycled flow generator increased minute ventilation significantly. Ventilation and inspiratory muscle effort were unaffected by continuous positive airway pressure but oxygen saturation was lower than during spontaneous ventilation. In awake, stable outpatients acclimatised to nasal ventilation there were no clinically significant differences between volume cycled flow generator and bi-level positive airway pressure techniques, but continuous positive airway pressure was less effective.

Aged↗
PubMed1994

Simple test of synergy between ampicillin and vancomycin for resistant strains of Enterococcus faecium.

The combination of ampicillin and vancomycin kills some but not all strains of ampicillin- and vancomycin-resistant Enterococcus faecium. We compared a simple test for synergy utilizing a commercially available microdilution susceptibility system with time-kill studies and determined acceptable breakpoints for this test for 20 strains of ampicillin- and vancomycin-resistant E. faecium. The combination of ampicillin and vancomycin was tested for synergy by time-kill, broth macrodilution, and broth microdilution procedures. Repeat testing of isolates by macro- and microdilution synergy methods yielded MICs that were within one twofold dilution of each other for both intra- and intertest comparisons. Synergy was always detected by time-kill studies when the MIC of ampicillin in the combination synergy screen was < or = 8 micrograms/ml in the presence of vancomycin. No synergy was detected when the MIC was > 16 micrograms/ml in the combination microdilution synergy screen. The determination of the synergy by the broth microdilution procedure appears to be simple, convenient, and accurate.

Ampicillin↗
PubMed1994

Birth weight and head circumference standards for English twins.

This study was undertaken to provide reliable up to date information on birth weights and occipitofrontal head circumference measurements in relation to gestational age for English newborn twins. Records from 36 maternity units in England, mainly from 1988-92, have provided data on birth weights for over 19,000 newborn twins with gestational ages ranging from 23 to 41 weeks, and on head circumference measurements for over 5300 twins ranging from 28 weeks to 40 weeks' gestation. Centile charts have been produced for boy and girl twins showing the distribution of these values against gestational age. The findings confirm the greater weights of boys compared with girls throughout, increasing from a mean of about 50 g at early stages to 100 g later, in a similar way to that reported for singletons. Twins were lighter than comparable singletons by about 100 g at 24 weeks, increasing progressively to 4-500 g at 38 weeks' gestation. In contrast, differences in occipitofrontal head circumferences between singletons and twins were only evident with gestations longer than 35 weeks--and from 37 weeks' gestation onwards the mean head circumference of singletons exceeded that of twins by about 5 mm. It is recommended that in evaluating the significance of the birth weight of a twin in relation to gestation, twin standards such as the ones presented here should be used rather than those relating to singletons.

Birth Weight↗
PubMed1994

Maximum relaxation rate of the diaphragm during weaning from mechanical ventilation.

BACKGROUND: The maximum relaxation rate (MRR; percentage fall in pressure/10 ms) of oesophageal (POES) and transdiaphragmatic (PDI) pressure slows under conditions of loaded breathing, and has been measured previously in normal subjects. MRR has not been measured in intubated patients weaning from mechanical ventilation. METHODS: Five postoperative patients who were expected to wean and nine patients who had previously failed were studied. POES and PDI MRR, peak oesophageal pressure during spontaneous breathing, maximum oesophageal pressure, and the inspiratory duty cycle were measured at rest during mechanical ventilation, in the first two minutes of spontaneous breathing, and after reventilation in those patients who failed, or before extubation in those patients who succeeded. RESULTS: At rest POES MRR in intubated patients had a range of 5.6-11 and PDI MRR 6.9-10.0, with a coefficient of variation of 9.9% and 7.3% respectively. POES and PDI MRR were similar before and after extubation in five postoperative patients, and POES MRR was reflected by endotracheal MRR measured at the airway. In five patients who failed to wean POES and PDI MRR slowed by 47% and 44%, and fully recovered after 10 minutes reventilation. In four patients who were successfully weaned MRR was unchanged during spontaneous breathing. At the time when MRR decreased, the respiratory muscles were heavily loaded in relation to their strength. CONCLUSIONS: Weaning failure occurs when the applied load exceeds the capacity of the respiratory muscles, and this is associated with a slowing of respiratory muscle MRR.

Adult↗
PubMed1994

Inspiratory muscle relaxation rate assessed from sniff nasal pressure.

BACKGROUND: Slowing of the maximum relaxation rate (MRR) of inspiratory muscles measured from oesophageal pressure (POES) during sniffs has been used as an index of the onset and recovery of respiratory muscle fatigue. The purpose of this study was to measure MRR at the nose (PNASAL MRR), to investigate its relationship with POES MRR, and to establish whether PNASAL MRR slows with respiratory loading. METHODS: Five normal subjects were studied. Each performed sniffs before and after two minutes of maximal isocapnic ventilation (MIV). In a separate session the subjects performed submaximal sniffs. POES and PNASAL were recorded during sniffs and the MRR (% pressure fall/10 ms) for each sniff was determined. RESULTS: Before MIV mean POES MRR was 8.9 and PNASAL MRR was 9.3. The mean (SD) difference between PNASAL MRR and POES MRR during a maximal sniff was 0.48 (0.34) (n = 64) and during submaximal sniffs was 0.28 (0.46) (n = 526). The subjects showed a mean decrease in sniff POES MRR of 27.4% (range 22.5-36%) after MIV and a similar reduction in sniff PNASAL MRR of 28.5% (range 24.1-41.3%). Both returned to control values within 5-10 minutes. CONCLUSIONS: PNASAL MRR reflects POES MRR over a wide range of sniff pressures, PNASAL MRR of maximal sniffs reflects POES MRR in normal subjects at rest and following MIV, so measurement of PNASAL MRR may be a useful non-invasive method for measuring inspiratory muscle MRR, thereby providing an index of respiratory muscle fatigue.

Air Pressure↗
PubMed1994

Potentiation of diaphragmatic twitch after voluntary contraction in normal subjects.

BACKGROUND: Skeletal muscle twitch responses may be transiently increased by previous contractions, a phenomenon termed twitch potentiation. The aim of this study was to examine the extent and time course of diaphragmatic twitch potentiation and its relationship to both the magnitude and duration of the preceding voluntary diaphragmatic contraction. METHODS: Twitch transdiaphragmatic pressure (PDI) was measured in six normal subjects, before and after voluntary diaphragm contractions of 100%, 75%, 50%, and 25% of maximum PDI (PDImax) sustained for five and 10 seconds. RESULTS: Twitch PDI was significantly increased after 100%, 75%, and 50% contractions. Following maximal contractions sustained for 10 seconds the mean increase in twitch PDI was 52%. Following 50% contractions sustained for five seconds the mean increase in twitch height was 28%. In all runs twitch PDI returned to rested levels within 20 minutes. CONCLUSIONS: Twitch potentiation can be substantial, even following submaximal contractions, and must be taken into account when twitch pressure is used to assess diaphragm contractility.

Adult↗
PubMed1994

Development of morphine glucuronidation in premature neonates.

In premature neonates (25-34 weeks gestation) who were given morphine intravenously during the first 24 h of life, only morphine, and morphine-3-glucuronide (M3G) were detected in plasma obtained after a 2-hour loading infusion, but morphine-6-glucuronide (M6G) could also be quantified following 24 h of continuous infusion. M3G/morphine and M6G/morphine plasma concentration ratios increased significantly with increasing birth weight. However, the M6G/M3G plasma concentration ratio decreased with increasing birth weight (and gestational age), thus providing the first indication in vivo of the differential development of uridinediphosphate glucuronosyltransferases in humans.

Birth Weight↗
PubMed1994

Portable measurement of maximum mouth pressures.

We have compared a small portable mouth pressure meter (MPM) to our laboratory standard (LS) pressure recording equipment in order to evaluate this new device. The mouth pressure meter measures and displays as a digital read-out peak pressure for inspiratory and expiratory efforts. It samples the signal at 16 Hz, and an integral microprocessor is programmed to determine and display the maximum pressure averaged over one second both during inspiratory and expiratory manoeuvres (PImax and PEmax, respectively). A fine bore catheter connecting the mouthpiece of the mouth pressure meter to a Validyne pressure transducer enabled simultaneous measurement of pressure, which was analysed by LabVIEW, running on a Macintosh Quadra 700 computer. We studied 13 normal subjects and 11 patients with respiratory disease. Each subject performed inspiratory and five expiratory efforts. The values displayed from the mouth pressure meter were manually recorded. The mouth pressure meter reliably and accurately measured peak pressure and maximal pressure both for inspiratory and expiratory efforts in normals and patients. The mean +/- SD difference when compared with the Validyne method was 0.19 +/- 0.12 and -0.04 +/- 0.12 kPa, for PImax and PEmax, respectively. This portable device should be useful to measure mouth pressures, not only in the routine lung function laboratory but also at the bedside and in the clinic.

Adult↗
PubMed1994

Comparison of cervical magnetic stimulation and bilateral percutaneous electrical stimulation of the phrenic nerves in normal subjects.

Cervical magnetic stimulation is a new technique for stimulating the phrenic nerves, and may offer an alternative to percutaneous electrical stimulation for assessing diaphragmatic strength in normal subjects and patients in whom electrical stimulation is technically difficult or poorly tolerated. We compared cervical magnetic stimulation with conventional supramaximal bilateral percutaneous electrical stimulation in nine normal subjects. We measured oesophageal pressure (Poes), gastric pressure (Pgas) and transdiaphragmatic pressure (Pdi). The maximal relaxation rate (MRR) was also measured. The mean magnetic twitch Pdi was 36.5 cmH2O (range 27-48 cmH2O), significantly larger than electrical twitch Pdi, mean 29.7 cmH2O (range 22-40 cmH2O). The difference in twitch Pdi was explained entirely by twitch Poes, and it is possible that the magnetic technique stimulates some of the nerves to the upper chest wall muscles as well as the phrenic nerves. We compared bilateral, rectified, integrated, diaphragm surface electromyographic (EMG) responses in three subjects and found results within 10% in each subject, indicating similar diaphragmatic activation. The within occasion coefficient of variation, i.e. same subject/same session, was 6.7% both for magnetic and electrical twitch Pdi. The between occasion coefficient of variation, i.e. same subject/different days, was 6.6% for magnetic stimulation and 8.8% for electrical. There was no difference between relaxation rates measured with either technique. We conclude that magnetic stimulation is a reproducible and acceptable technique for stimulating the phrenic nerves, and that it provides a potentially useful alternative to conventional electrical stimulation as a nonvolitional test of diaphragm strength.

Action Potentials↗
PubMed1994

Familiarity and pop-out in visual search.

In this paper, we report that when the low-level features of targets and distractors are held constant, visual search performance can be strongly influenced by familiarity. In the first condition, a [symbol: see text] was the target amid [symbol: see text]s as distractors, and vice versa. The response time increased steeply as a function of number of distractors (82 msec/item). When the same stimuli were rotated by 90 degrees (the second condition), however, they became familiar patterns--2 and 5--and gave rise to much shallower search functions (31 msec/item). In the third condition, when the search was for a familiar target, N (or Z), among unfamiliar distractors, [symbol: see text]s (or [symbol: see text]s), the slope was about 46 msec/item. In the last condition, when the search was for an unfamiliar target, [symbol: see text] (or [symbol: see text]), among familiar distractors, Ns (or Zs), parallel search functions were found with a slope of about 1.5 msec/item. These results show that familiarity speeds visual search and that it does so principally when the distractors, not the targets, are familiar.

Adolescent↗