Physiological and biomechanical differences between wheelchair-dependent and able-bodied subjects during wheelchair ergometry

The purpose of this study was to compare the physiological and biomechanical responses of wheelchair-dependent persons (WCD) to able-bodied persons (AB) during manual wheelchair ergometry. Five WCD and five AB performed a discontinuous wheelchair ergometer test starting at 12.8 W at 30 rev.min-1 (57 m.min-1) with increments of 7.0 W at 6-min intervals. Biomechanical data were collected 3.5 min into each stage followed by the collection of physiological data. After the fifth stage, peak oxygen consumption was determined by having the subject work against a resistance of 14.7-19.6 N at 30 rev.min-1. The WCD had significantly higher net mechanical efficiency at 26.7, 33.6 and 40.6 W in comparison to the AB. The WCD had significantly greater shoulder extension at the point of initial wheel contact as measured by the shoulder angle, while the AB had significantly greater shoulder range of motion at all work rates in comparison to the WCD. The results demonstrate that a significant physiological difference exists in the manner by which WCD and AB accomplish wheelchair ergometry. The biomechanical differences between AB and WCD were found to be a prominent factor contributing to the higher mechanical efficiency of WCD over AB. It was concluded that basic physiological and biomechanical differences exist between WCD and AB in manual wheelchair locomotion and that these differences are important considerations to the interpretation of data in wheelchair ergometry studies.     

消炎痛对大鼠肝线粒体微粒体^45Ca摄取及膜流动性的影响

我们曾报道消炎痛预处理在大鼠能引起明显的肝保护作用,为了进一步探讨消炎痛肝保护作用的机制,本工作观察了它对大鼠肝线粒体、微粒体钙调节作用及膜流动性的影响。结果表明,经消炎痛整体预处理的大鼠肝线粒体和微粒体的钙摄取及膜流动性均明显增加,但是,将消炎痛直接加入由正常大鼠分离的线粒体或微粒体中,则反而使膜的流动性降低。这些变化可能与消炎痛的肝保护作用有关。     

在原代培养的大鼠肝细胞观察消炎痛的细胞保护作用

我们曾观察到消炎痛预处理能明显减轻四氯化碳和半乳糖胺对大鼠的肝损伤作用,本工作采用原代培养的大鼠肝细胞进一步观察了这一现象。结果表明,经消炎痛整体处理后分离的大鼠肝细胞,在原代培养的条件下,对四氯化碳的损伤仍然具有明显的抵抗作用,表现为细胞内酶的漏出少于对照组。正常大鼠离体肝细胞在原代培养条件下用消炎痛处理,在相当大的剂量和相当长的时间范围内未出现明显的抗损伤作用。结果提示:消炎痛整体处理可使肝细胞本身获得抗损伤的能力,而这种抗损伤能力的产生可能有赖于肝细胞外其它因素的参与。     

Regional brain GABA metabolism and release during hepatic coma produced in rats chronically treated with carbon tetrachloride

Hepatic coma was induced in rats chronically treated with CCl₄, by means of a single injection of ammonium acetate. The activities of glutamate decarboxylase (GAD) and GABA transaminase (GABA-T), as well as the synaptosomal uptake and release of [³H]GABA, were measured in the following brain areas of the comatose rats: cortex, striatum, hypothalamus, hippocampus, midbrain and cerebellum. Hepatic coma was associated with a general decrease of GAD activity, whereas GABA-T activity was diminished only in the hypothalamus, striatum and midbrain. During hepatic coma, the K⁺-stimulated [³H]GABA release was notably diminished in the striatum and cerebellum, whereas a significant increase was observed in the hippocampus. [³H]GABA uptake increased in most regions after CCl₄ treatment, independently of the presence of coma. The results indicate that GABAergic transmission seems to be decreased in most cerebral regions during hepatic coma.     

Analysing partitioning of recently fixed and of reserve carbon in reproductive Phaseolus vulgaris L. plants

Abstract. Partitioning of recently-fixed carbon among plant organs and subsequent distribution of reserve carbon were studied by supplying whole shoots of bean plants ( Phaseolus vulgaris L.) with ¹⁴C-labelled CO₂ of constant specific radioactivity throughout a photoperiod. The gain of tracer carbon in each part revealed net accumulation of recently-fixed carbon from direct fixation, import or both. Growth rate coefficients describing the present pattern of plant growth were calculated from ratios of tracer carbon to total carbon present in plant organs and were used to project future plant form. The period 10–20 d after the start of flowering was marked by a major increase in partitioning of recently-fixed carbon to reproductive growth. Growth rates for the plant and its parts during this period were projected on the basis of growth rate coefficients and were found to be similar to rates measured by gravimetric growth analysis. Changes in tracer carbon recovered in individual organs after chase periods of various lengths revealed net decreases for leaves and stems. About 9% of the carbon distributed to fruits came from reserves even in the absence of obvious stress. Respiratory loss during the chase period was determined from the progressive drop in recovery of the original tracer carbon. The methods are being applied to measure current net accumulation rates in studies of sink organ physiology, and to compare partitioning of recently-fixed and of stored carbon in several plant species under defined growth conditions.     

Effects of boundary layer conductance on substomatal pressures of carbon dioxide

Abstract. Gas exchange measurements were made on single leaves of three C₃ and one C₄ species at air speeds of 0.4 and 4.0 m s⁻¹ to determine if boundary layer conductance substantially affected the substomatal pressure of carbon dioxide. Boundary layer conductances to water vapour were 0.4 to 0.5 mol m⁻² s⁻¹ at the lower air speed, and 1.2 to 1.5 mol m⁻² s⁻¹ at the higher air speed. Substomatal carbon dioxide pressures were about 5 Pa lower at low boundary layer conductance in the C₃ species, and about 3 Pa lower in the C₄ species when measurements were made at high and moderate photosynthetic photon flux densities. No evidence of stomatal adjustment to altered boundary layer conductance was found. Photosynthetic rates at high photon flux densities were reduced by about 20% at the low air speed in the C₃ species. The commonly reported values of substomatal carbon dioxide pressure for C₃ and C₄ species were found to occur only when measurements were made at the higher air speed.     

The efficiency of water use in water stressed plants is increased due to ABA induced stomatal closure

Gas exchange and abscisic acid content of Digitalis lanata EHRH. have been examined at different levels of plant water stress. Net photosynthesis, transpiration and conductance of attached leaves declined rapidly at first, then more slowly following the withholding of irrigation. The intercellular partial pressure of CO₂ decreased slightly. The concentration of 2-cis(S)ABA increased about eight-fold in the leaves of non-irrigated plants as compared with well-watered controls. A close linear correlation was found between the ABA content of the leaves and their conductance on a leaf area basis. In contrast, the plot of net assimilation versus ABA concentration was curvilinear, leading to an increased efficiency of water use during stress. After rewatering, photosynthesis reached control values earlier than transpiration, leaf conductance and ABA content. From these data it is concluded that transpiration through the stomata is directly controlled by the ABA content, whereas net photosynthesis is influenced additionally by other factors.Possible reasons for the responses of photosynthesis and water use efficiency to different stress and ABA levels are discussed.Abbreviations A net CO₂ assimilation - ABA abscisic acid - C_i intercellular CO₂ concentration - g stomatal conductance - T transpiration - WUE water use efficiency     

Recycling of CO2 via Crassulacean acid metabolism in the rock outcrop succulent Sedum pulchellum Michx. (Crassulaceae)

Under well-watered conditions in the laboratory, Sedum pulchellum assimilated CO₂ only during the day, yet exhibited small nocturnal increases in tissue acid content followed by deacidification in the light (CAM-cycling). When drought-stressed, little CO₂ was fixed in the day and none at night, yet even greater acid fluctuations were observed (CAM-idling). Calculations indicate that water savings associated with CAM-cycling when water is available are small. Water saving is more likely to be significant during CAM-idling when water supply is limited and stomata are closed day and night. Thus, in this species, CAM-idling may be of greater benefit to the plant, relative to CAM-cycling, in surviving habitats prone to frequent drought stress.Abbreviations A CO₂ exchange rate - CAM Crassulacean acid metabolism - c_i shoot internal CO₂ concentration - g_c shoot conductance to CO₂ - PPFD photosynthetic photon flux density - WUE water-use efficiency Supported by National Science Foundation Grant No. DMB 8506093.     

Growth and activities of enzymes of primary metabolism in batch cultures of Catharanthus roseus cell suspension under different pCO2 conditions

In vitro enzyme activities of glycolysis, pentose-phosphate pathway and dark CO₂ fixation were assayed in batch cultures of heterotrophic Catharanthus roseus cells under various gassing rates and partial pressures of carbon dioxide. Detrimental effects of low pCO₂ culture conditions on the growth characteristics could be linked to marked changes in levels of enzymes of primary metabolism during growth. The enzyme levels observed during the early stages of growth were found to be more stable when a constant pCO₂ (20 mbar) was maintained and enabled exponential growth to be reached more rapidly.The importance of carbon dioxide as a conditioning factor of the culture medium is discussed.     

The efficiency of pitfall trapping for polyphagous predatory Carabidae

ABSTRACT.

• 1 The efficiency of pitfall trapping was investigated for seven carabid species, using time-lapse video recording equipment, in the laboratory.
• 2 The effects of differing substrates, trap designs and seasons of collection on the capture rates of the carabids was also investigated.
• 3 Capture rate differed significantly between the species studied. The differences in capture rates between the species were unrelated to beetle size, speed of movement and diurnal behaviour.
• 4 Few differences arose in the capture rates when type of substrate or trap or season of capture were changed.