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1.
A K Curran J R Rodman P R Eastwood K S Henderson J A Dempsey C A Smith 《Journal of applied physiology》2000,88(5):1840-1852
Our study was concerned with the effect of brain hypoxia on cardiorespiratory control in the sleeping dog. Eleven unanesthetized dogs were studied; seven were prepared for vascular isolation and extracorporeal perfusion of the carotid body to assess the effects of systemic [and, therefore, central nervous system (CNS)] hypoxia (arterial PO(2) = 52, 45, and 38 Torr) in the presence of a normocapnic, normoxic, and normohydric carotid body during non-rapid eye movement sleep. A lack of ventilatory response to systemic boluses of sodium cyanide during carotid body perfusion demonstrated isolation of the perfused carotid body and lack of other significant peripheral chemosensitivity. Four additional dogs were carotid body denervated and exposed to whole body hypoxia for comparison. In the sleeping dog with an intact and perfused carotid body exposed to specific CNS hypoxia, we found the following. 1) CNS hypoxia for 5-25 min resulted in modest but significant hyperventilation and hypocapnia (minute ventilation increased 29 +/- 7% at arterial PO(2) = 38 Torr); carotid body-denervated dogs showed no ventilatory response to hypoxia. 2) The hyperventilation was caused by increased breathing frequency. 3) The hyperventilatory response developed rapidly (<30 s). 4) Most dogs maintained hyperventilation for up to 25 min of hypoxic exposure. 5) There were no significant changes in blood pressure or heart rate. We conclude that specific CNS hypoxia, in the presence of an intact carotid body maintained normoxic and normocapnic, does not depress and usually stimulates breathing during non-rapid eye movement sleep. The rapidity of the response suggests a chemoreflex meditated by hypoxia-sensitive respiratory-related neurons in the CNS. 相似文献
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The fusarium mycotoxin zearalenone was transformed in cell suspension cultures of Zea mays giving α- and β-zearalenol and the β-D-glu cos ides of zearalenone and α- and β-zearalenol. The structure of zearalenone-4-β-D-glucopyranoside was determined by liquid — chromatography-mass spectrometry and specific hydrolysis with β-glucosidase. α- and β-zearalenol and their glucosides were identified by co chromatography using tic and HPLC and glucosidase — treatment Up to 50% of the mycotoxin added was bound to a non extractable or “bound” residue fraction. After treating this residue by a sequential cell wall fractionation procedure, zearalenone was found to be bound mainly to starch, hemicellulose, and lignin fractions. 相似文献
5.
Gene transfer is a major factor in bacterial evolution 总被引:17,自引:3,他引:14
Lateral gene transfer in four strains of Salmonella enterica has been
assessed using genomic subtraction. Strain LT2 (subspecies I serovar
Typhimurium) chromosomal DNA was used as target and subtracted by three
subspecies I strains of serovars Typhimurium (S21), Muenchen (S71), Typhi
(M229), and a subspecies V strain (M321). Data from probing random cosmids
of LT2 DNA with preparations of the residual LT2 DNA after subtraction were
used to estimate the amounts of LT2 DNA not able to hybridize to strains
S21, S71, M229, and M321 to be in the range of 84-106, 191-355, 305-629,
and 778-1,286 kb, respectively. Several lines of evidence indicate that
most of this DNA is from genes not present in strain M321 and not from
genes that have diverged in sequence. The amounts correlate with the
divergence of the four strains as revealed by multilocus enzyme
electrophoresis and sequence variation of housekeeping genes. Sequence of
39 of the fragments from the M321 subtracted residual LT2 DNA revealed only
six inserts of known gene function with evidence of both gain and loss of
genes during the development of S. enterica clones. Sixteen of the 39
segments have 45% or lower G+C content, below the species average, but over
half are within the normal range for the species. We conclude that even
within a species, clones may differ by up to 20% of chromosomal DNA,
indicating a major role for lateral transfer, and that on the basis of G+C
content, a significant proportion of the DNA is from distantly related
species.
相似文献
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J. P. Kielty L. J. Allen-Williams N. Underwood E. A. Eastwood 《Journal of Insect Behavior》1996,9(2):237-250
The responses ofPterostichus melanarius Illiger,Harpalus rufipes DeGeer, andNebria brevicollis Fabricius (Coleoptera: Carabidae) to olfactory cues of prey and habitat were studied in a four-arm continuous-airflow olfactometer. The process was semiautomated using time-lapse image analysis by microcomputer. The primary constituent of the aphid alarm pheromone, (E)--farnesene (EBF), was synthesized and tested for a kairomonal role in prey detection by carabids. In addition, individual beetles were exposed to odors from live aphids, live collembolans, and a crude extract of wheat. All three beetle species showed evidence of olfaction.P. melanarius responded to all the odors except collembolans,H. rufipes responded to EBF and wheat, andN. brevicollis to collembolans. The use of a defence allomone as a prey-finding kairomone by certain carabid species has implications for pest management. Manipulation of predator chemical ecology by the inclusion of behavior-modifying compounds in a crop spray mix with reduced amounts of insecticide may allow for efficient aphid control with less environmental contamination. 相似文献
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The proximal accessory flexor (PAF) of the myochordotonal organ (MCO) in the meropodite of crayfish walking legs contains two populations of muscle fibers which are distinguishable by their diameters. The large accessory (LA) fibers are 40-80 micrometer in diam and are similar in ultrastructure to other slow crustacean fibers. The small accessory (SA) fibers are 1-12 micrometer in diam and have a unique myofilament distribution at normal body lengths. There is extensive double overlap of thin filaments at these lengths, and some of them form bundles that may extend the length of the sarcomere. In the middle of the sarcomeres, thick and thin filaments are totally segregated from each other. When the fibers are stretched to lengths beyond double overlap length, the myofilament patterns are conventional. The segregated pattern is reestablished when stretched fibers are allowed to shorten passively. The length-tension relationship of the SA fibers is described by a linear ascending branch, a plateau, and a linear descending branch. The ascending branch encompasses normal body lengths from slack length (Ls) with maximum double overlap to the length at which double overlap ceases (1.8 X Ls). The descending phase is comparable to that of other skeletal muscles. That is, tension decreases in proportion with the reduction in thick-thin filament interdigitation (2 X Ls to 3 X Ls). 相似文献
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A study of the diagnostic composition of the inpatient population of Ontario and Canadian psychiatric facilities has shown an important change in hospital-treated illness over the period 1941-71. Patients with nonpsychotic disorders accounted for 54% of all admissions to Ontario public mental hospitals in 1971, compared with only 8% in 1941. The trend was similar for both first admissions and proportion of readmissions, and was similar for psychiatric units of general hospitals. In contrast, the overall rate of first admission for psychotic disorders to inpatient facilities remained remarkably constant over time, as did the proportion of readmissions among all admissions. The findings dispel the notion that the increasing proportion of readmissions is due largely to a rapid turnover of former long-stay psychotic patients (the "revolving-door phenomenon"). The findings could not be attributed to a changing prevalence of types of psychiatric illness, increased availability of psychiatric inpatient facilities or comprehensive medical insurance. 相似文献