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排序方式: 共有480条查询结果,搜索用时 15 毫秒
1.
2.
Alveolar liquid pressures in newborn and adult rabbit lungs 总被引:1,自引:0,他引:1
To study the effects of lung maturation and inflation on alveolar liquid pressures, we isolated lungs from adult and newborn rabbit pups (1-11 days old). We used the micropuncture technique to measure alveolar liquid pressure at several transpulmonary pressures on lung deflation. Alveolar liquid pressure was greater than pleural pressure but less than airway pressure at all transpulmonary pressures. Alveolar liquid pressure decreased further below airway pressure with lung inflation. At high transpulmonary pressure, alveolar liquid pressure was less in newborn than in adult lungs. To study the effects of edema, we measured alveolar liquid pressures in newborn lungs with different wet-to-dry weight ratios. Alveolar liquid pressure increased with progressive edema. In addition, we compared alveolar liquid and perivenular interstitial pressures in perfused newborn lungs and found that they were similar. Thus alveolar liquid pressure can be used to estimate perivenular interstitial pressure. We conclude that the transvascular pressure gradient for fluid flux into the interstitium might increase with lung inflation and decrease with progressive edema. Furthermore, this gradient might be greater in newborn than adult lungs at high inflation pressures. 相似文献
3.
J. M. Addington-Hall L. D. MacDonald H. R. Anderson J. Chamberlain P. Freeling J. M. Bland J. Raftery 《BMJ (Clinical research ed.)》1992,305(6865):1317-1322
OBJECTIVES--To measure effects on terminally ill cancer patients and their families of coordinating the services available within the NHS and from local authorities and the voluntary sector. DESIGN--Randomised controlled trial. SETTING--Inner London health district. PATIENTS--Cancer patients were routinely notified from 1987 to 1990. 554 patients expected to survive less than one year entered the trial and were randomly allocated to a coordination or a control group. INTERVENTION--All patients received routinely available services. Coordination group patients received the assistance of two nurse coordinators, whose role was to ensure that patients received appropriate and well coordinated services, tailored to their individual needs and circumstances. MAIN OUTCOME MEASURES--Patients and carers were interviewed at home on entry to the trial and at intervals until death. Interviews after bereavement were also conducted. Outcome measures included the presence and severity of physical symptoms, psychiatric morbidity, use of and satisfaction with services, and carers'' problems. Results from the baseline interview, the interview closest to death, and the interview after bereavement were analysed. RESULTS--Few differences between groups were significant. Coordination group patients were less likely to suffer from vomiting, were more likely to report effective treatment for it, and less likely to be concerned about having an itchy skin. Their carers were more likely to report that in the last week of life the patient had had a cough and had had effective treatment for constipation, and they were less likely to rate the patient''s difficulty swallowing as severe or to report effective treatment for anxiety. Coordination group patients were more likely to have seen a chiropodist and their carers were more likely to contact a specialist nurse in a night time emergency. These carers were less likely to feel angry about the death of the patient. CONCLUSIONS--This coordinating service made little difference to patient or family outcomes, perhaps because the service did not have a budget with which it could obtain services or because the professional skills of the nurse-coordinators may have conflicted with the requirements of the coordinating role. 相似文献
4.
Adaptation to High-Intensity, Low-Wavelength Light among Surface Blooms of the Cyanobacterium Microcystis aeruginosa 总被引:2,自引:0,他引:2 下载免费PDF全文
Hans W. Paerl Patricia T. Bland N. Dean Bowles Mark E. Haibach 《Applied microbiology》1985,49(5):1046-1052
Natural populations of the nuisance bloom cyanobacterium Microcystis aeruginosa obtained from the eutrophic Neuse River, N.C., revealed optimal chlorophyll a-normalized photosynthetic rates and resistance to photoinhibition at surface photosynthetically active radiation (PAR) intensities. At saturating PAR levels these populations exhibited higher photosynthetic rates in quartz than in Pyrex vessels. Eucaryotic algal populations obtained from the same river failed to counteract photoinhibition. At saturating PAR levels, such populations generally yielded lower photosynthetic rates in quartz containers than they did in Pyrex containers. Cultivation of natural Microcystis populations under laboratory conditions led to physiologically distinct populations which had photoinhibitory characteristics similar to those of other cultured cyanobacterial and eucaryotic algae. Our findings indicate that (i) photosynthetic production among natural surface populations is best characterized and quantified in quartz rather than Pyrex incubation vessels; (ii) extrapolation of natural photoinhibitory trends from laboratory populations is highly subjective to culture and PAR histories and may yield contradictory results; and (iii) buoyant surface-dwelling populations, rather than exhibiting senescence, are poised at optimizing PAR utilization, thereby maintaining numerical dominance in eutrophic waters when physico-chemical conditions favor bloom formation. 相似文献
5.
M. M. Bland D. F. Matzinger C. S. Levings III 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,69(5-6):535-541
Summary Mitochondrial DNAs from Nicotiana tabacum, an amphiploid, and its putative progenitor species, N. sylvestris and N. tomentosiformis were compared in structure and organization. By using DNA transfer techniques and cloned fragments of known genes from maize and N. sylvestris as labeled probes, the positions of homologous sequences in restriction digests of the Nicotiana species were analyzed. Results indicate that the mitochondrial DNA of N. tabacum was inherited from N. sylvestris. Conservation in organization and sequence homology between mtDNAs of N. tabacum and the maternal progenitor, N. sylvestris, provide evidence that the mitochondrial genome in these species is evolutionarily stable. Approximately one-third of the probed restriction fragments of N. tomentosiformis mtDNA showed conservation of position with the other two species. Pattern variations indicate that extensive rearrangement of mtDNA has occurred in the evolution of these Nicotiana species. 相似文献
6.
Maintenance of the cellobiose utilization genes of Escherichia coli in a cryptic state 总被引:6,自引:1,他引:5
The genes for cellobiose utilization are normally cryptic in Escherichia
coli. The cellobiose system was used as a model to understand the process
by which silent genes are maintained in microbial populations. Previously
reported was (1) the isolation of a mutant strain that expresses the
cellobiose-utilization (Cel) genes and (2) that expression of those genes
allows utilization of three beta- glucoside sugars: cellobiose, arbutin,
and salicin. The Cel gene cluster has now been cloned from that mutant
strain. In the course of locating the Cel genes within the cloned DNA
segment, it was discovered that inactivation of the Cel-encoded hydrolase
rendered the host strain sensitive to all three beta-glucosides as potent
inhibitors. This sensitivity arises from the accumulation of the
phosphorylated beta- glucosides. Because even the fully active genes
conferred some degree of beta-glucoside sensitivity, the effects of
cellobiose on a series of five Cel+ mutants of independent origin were
investigated. Although each of those strains utilizes cellobiose as a sole
carbon and energy source, cellobiose also acts as a potent inhibitor that
reduces the growth rate on glycerol 2.5-16.5-fold. On the other hand,
wild-type strains that cannot utilize cellobiose are not inhibited. The
observation that the same compound can serve either as a nutrient or as an
inhibitor suggests that, under most conditions in which cellobiose will be
present together with other resources, there is a strong selective
advantage to having the cryptic (Cel0) allele. In those environments in
which cellobiose is the sole, or the best, resource, mutants that express
the genes (Cel+) will have a strong selective advantage. It is suggested
that temporal alternation between these two conditions is a major factor in
the maintenance of these genes in E. coli populations. This alternation of
environments and fitnesses was predicted by the model for cryptic-gene
maintenance that was previously published.
相似文献
7.
Lung overexpansion increases pulmonary microvascular protein permeability in young lambs 总被引:3,自引:0,他引:3
D P Carlton J J Cummings R G Scheerer F R Poulain R D Bland 《Journal of applied physiology》1990,69(2):577-583
To study the effects of inflation pressure and tidal volume (VT) on protein permeability in the neonatal pulmonary microcirculation, we measured lung vascular pressures, blood flow, lymph flow (QL), and concentrations of protein in lymph (L) and plasma (P) of 22 chronically catheterized lambs that received mechanical ventilation at various peak inflation pressures (PIP) and VT. Nine lambs were ventilated initially with a PIP of 19 +/- 1 cmH2O and a VT of 10 +/- 1 ml/kg for 2-4 h (base line), after which we overexpanded their lungs with a PIP of 58 +/- 3 cmH2O and a VT of 48 +/- 4 ml/kg for 4-8 h. QL increased from 2.1 +/- 0.4 to 13.9 +/- 5.0 ml/h. L/P did not change, but the ratio of albumin to globulin in lymph relative to the same ratio in plasma decreased, indicating altered protein sieving in the pulmonary microcirculation. Seven other lambs were mechanically ventilated for 2-4 h at a PIP of 34 +/- 1 cmH2O and a VT of 23 +/- 2 ml/kg (base line), after which their chest and abdomen were bound so that PIP increased to 54 +/- 1 cmH2O for 4-6 h without a change in VT. QL decreased on average from 2.8 +/- 0.6 to 1.9 +/- 0.3 ml/h (P = 0.08), and L/P was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
8.
Iturin A: A potential new fungicide for stored grains 总被引:6,自引:0,他引:6
The removal of many synthetic fungicides from the market has created a demand for new, environmentally safe fungicides. Iturin A, a cyclic lipopeptide produced byBacillus subtilis, has strong antifungal properties and low mammalian toxicity. To determine the efficacy of this compound as a potential fungicide on stored feed grains, lots of corn, peanuts and cottonseed were treated with varying concentrations of iturin A. The mycoflora of treated seed was assayed along with that of untreated seed and seed treated with fungicides used commercially for planting seed. Fungal species varied considerably in their sensitivity to iturin A. Significant reductions in total mycoflora occurred in most seed lots tested at iturin A concentrations of 50 to 100 ppm. 相似文献
9.
Some rumen ciliates have endosymbiotic methanogens 总被引:16,自引:0,他引:16
Bland J. Finlay Genoveva Esteban Ken J. Clarke Alan G. Williams T.Martin Embley Robert P. Hirt 《FEMS microbiology letters》1994,117(2):157-161
Abstract Most of the small ciliate protozoa, including Dasytricha ruminantium and Entodinium spp. living in the rumen of sheep, were found to have intracellular bacteria. These bacteria were not present in digestive vacuoles. They showed characteristic coenzyme F420 autofluorescence and they were detected with a rhodamine-labelled Archaea-specific oligonucleotide probe. The measured volume percent of autofluorescing bacteria (1%) was close to the total volume of intracellular bacteria estimated from TEM stereology. Thus it is likely that all of the bacteria living in the cytoplasm of these ciliates were endosymbiotic methanogens, using H2 evolved by the host ciliate to form methane. Intracellular methanogens appear to be much more numerous than those attached to the external cell surface of ciliates. 相似文献
10.
Hypoproteinemia slows lung liquid clearance in young lambs 总被引:1,自引:0,他引:1
Cummings J. J.; Carlton D. P.; Poulain F. R.; Raj J. U.; Bland R. D. 《Journal of applied physiology》1993,74(1):153-160