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1.
The effect of inosine on the development of competence is dependent upon the time at which it is added to the competence medium. Competence is inhibited if inosine is added within 15 min after the development begins, but is stimulated if the addition is made at later times. Protein synthesis is stimulated by the addition of inosine, but the effect is quantitatively similar regardless of the time at which inosine is added. 相似文献
2.
Stephen R. Cohen 《Journal of neurochemistry》1980,35(4):1008-1012
Concentrative influx of γ-aminobutyric acid (GABA) and α-aminoisobutyric acid (AIB) into incubated mouse cerebrum slices is decreased when pyruvate is substituted for glucose. Influx of GABA from pyruvate medium is not increased by presence of glucose, 2-deoxy-d -glucose (2-DOG), or 3-O-methyl-d -glucose (3-O-MeG). Influx of AIB is restored to the rate from glucose medium if 2-DOG is present initially, but is not restored if 2-DOG is added with AIB. Influx is not restored if 3-O-MeG is present initially, but is restored if 3-O-MeG is added with AIB. Influx is restored if glucose is present initially or is added with AIB. 相似文献
3.
268例难治性下呼吸道感染的细菌学分析 总被引:5,自引:0,他引:5
通过本组268 例难治性呼吸道感染病人标本培养结果分析,阳性246 例占91.8 % ,有154 例检出厌氧菌,占57 % ,104 例检出需氧菌,占39 % ,混合感染133 例,占50 % 。试验结果证实,厌氧菌感染在难治性下呼吸道感染病例中占了很大比例,这一结果为难治性下呼吸道感染的治疗提供了有价值的参考数据。 相似文献
4.
Wang W 《Mathematical biosciences》2006,201(1-2):58-71
An epidemic model with a limited resource for treatment is proposed to understand the effect of the capacity for treatment. It is assumed that treatment rate is proportional to the number of infectives below the capacity and is a constant when the number of infectives is greater than the capacity. It is found that a backward bifurcation occurs if the capacity is small. It is also found that there exist bistable endemic equilibria if the capacity is low. 相似文献
5.
药敏药片经临床对金黄色葡萄球菌、大肠埃希氏菌、铜绿假单胞菌等235株考核.表明药片工艺研究先进,药片与培养基结合牢固,无断裂、崩解,不渗出颗粒,抑菌圈呈同心园扩散.边缘清楚。药物含量均匀,释放度好。药片抑菌差仅1~3mm;而纸片抑菌差为2~12mm。药片变黑系数CV为2.71~4.21;而纸片CV为3.82~14.36。表明纸片片间差大,药片精密度明显好于纸片。 相似文献
6.
沙冬青淀粉粒及其与叶绿体发育的关系 总被引:5,自引:0,他引:5
沙冬青叶绿体中的淀粉粒一般为1-3个,主要有4种类型。第1种外周部分电子密度较高,中央部分较低,但每个部分的电子密度十分均匀。它们近似椭圆形,附近的类囊体形态正常,结构清晰。第2种电子密度由外向内逐渐变低,多为椭圆形,附近的类囊体较清晰。第3种外周部分的电子密度很高,中央部分不均匀,形状多种多样,附近的类囊体有的不清晰。第4种电子密度很低,十分均匀,形状不规则,附近的类囊体已经解体或正在解体。分析表明,淀粉的形态变化明显与叶绿体发育有关。 相似文献
7.
Autogenous control of Escherichia coli threonyl-tRNA synthetase expression in vivo 总被引:16,自引:0,他引:16
M Springer J A Plumbridge J S Butler M Graffe J Dondon J F Mayaux G Fayat P Lestienne S Blanquet M Grunberg-Manago 《Journal of molecular biology》1985,185(1):93-104
The regulation of the expression of thrS, the structural gene for threonyl-tRNA synthetase, was studied using several thrS-lac fusions cloned in lambda and integrated as single copies at att lambda. It is first shown that the level of beta-galactosidase synthesized from a thrS-lac protein fusion is increased when the chromosomal copy of thrS is mutated. It is also shown that the level of beta-galactosidase synthesized from the same protein fusion is decreased if wild-type threonyl-tRNA synthetase is overproduced from a thrS-carrying plasmid. These results strongly indicate that threonyl-tRNA synthetase controls the expression of its own gene. Consistent with this hypothesis it is shown that some thrS mutants overproduce a modified form of threonyl-tRNA synthetase. When the thrS-lac protein fusion is replaced by several types of thrS-lac operon fusions no effect of the chromosomal thrS allele on beta-galactosidase synthesis is observed. It is also shown that beta-galactosidase synthesis from a promoter-proximal thrS-lac operon fusion is not repressed by threonyl-tRNA synthetase overproduction. The fact that regulation is seen with a thrS-lac protein fusion and not with operon fusions indicates that thrS expression is autoregulated at the translational level. This is confirmed by hybridization experiments which show that under conditions where beta-galactosidase synthesis from a thrS-lac protein fusion is derepressed three- to fivefold, lac messenger RNA is only slightly increased. 相似文献
8.
Cell-cycle progression is altered in some colcemid-resistant mutants of fission yeast. The duration of particular stages of the cell cycle is different but total doubling time is unchanged from that of wild type. Cell-plate formation is prolonged relative to wild type but concomitant DNA synthesis is not affected. Separation of daughter cells is inhibited in some strains, giving rise to unusual cell morphologies. Control of cell division is altered in two ways: Critical size for division is increased. The probability of division a function of size is decreased. 相似文献
9.
Failure to Maintain Glycolysis in Anoxic Nerve Terminals 总被引:8,自引:6,他引:2
Synaptosomal glycolysis is stimulated eight- to 10-fold when the respiratory chain is inhibited by cyanide or by anoxia. However, the stimulation is transient and after 15 min declines toward the preanoxic rate. The decline is not seen when Ca2+ is absent or when the respiratory chain is inhibited by rotenone. The decline in glycolysis is reversible, is not due to substrate exhaustion, and is the cause, rather than the effect, of lowered synaptosomal ATP/ADP ratios. The failure to maintain glycolysis when the terminal oxidase of the respiratory chain is inhibited may have relevance to the sensitivity of the brain to anoxic damage. 相似文献
10.
本文根据我们严密设计的小集水区径流场连续6年的水文测定数据,进行了杉木人工林水量平衡和蒸散的研究。结果表明:集水区年平均降雨量1065.5mm, 在林冠作用面降雨量的分配中,林冠截留雨量264.6mm,截留率24.8%;穿透过林冠层的雨量799.82mm,树干径流量1.08mm,分别占降雨量的75.1%和0.1%。林内降水到达林地时,在枯枝落叶层这个作用面上净降水进行再分配,其中,地表径流量9.27mm,地下径流量203.00mm,总径流系数0.199。土壤蓄水量月变化较大,但年变化很小,占降雨量的1.2%。系统水量最大的输出是蒸散,每年以气态形式返回大气的水量866.03mm,占降雨量81.3%。在蒸散的水量中,林冠截留雨量的直接物理蒸发量为264.6mm,占总蒸散量的31.6%。 相似文献
11.
Ashcroft R 《Bioethics》1999,13(3-4):314-326
It is widely maintained that a clinical trial is ethical only if some form of equipoise between the treatments being compared obtains. To be in equipoise between two treatments A and B is to be cognitively indifferent between the statement 'A is strictly more effective than B' and its negation. It is natural to claim that equipoise regarding A and B is necessary for randomised assignment to treatments A and B to be beneficent and non-maleficent and is sufficient for such an assignment to be fair. Cashing this out precisely is difficult, and various forms of equipoise have been discussed which consider whose equipoise is relevant to the decision. This is to make judgement of equipoise something to be managed socially, while its prima facie significance is supposedly cognitive. Recent reconstructions of equipoise-like concepts in epistemology give clues about how to understand equipoise cognitively. In this paper I examine some of this work and discuss how successful it has been. I suggest that while this work is promising, it still has far to go, and that while equipoise remains the best theory we have of the cognitive justification for clinical trials, it is nonetheless incoherent. 相似文献
12.
两型豆花粉和叶表皮的扫描电镜观察 总被引:5,自引:1,他引:4
两型豆花粉和叶表皮在扫描电镜下的形态特征:花粉近球形至矩球形,三孔沟,外壁表面较粗糙,侧壁具疣状突起至块状突起,极面具粗网状纹饰,但两型豆祖山居群属于萌发沟不明显型,两型豆燕塞湖居群属于萌发沟明显型。叶表皮细胞不规则,排列紧密,叶脉表皮细胞长圆柱形,长轴与叶脉平行,角质膜薄,表皮毛均为单细胞非腺毛,气孔器仅分布在下表皮,属于平列型,偶见不规则型。表皮毛和气孔器在叶片上分布不均匀,两型豆祖山居群叶表皮毛和气孔器的平均密度大于两型豆燕塞湖居群叶表皮毛和气孔器的平均密度,自然生长的两型豆叶表皮毛和气孔器的平均密度大于遮光条件下的两型豆。 相似文献
13.
目的:了解老年教师骨质疏松病的情况,用超声骨密度仪对813例老年教师做跟骨超声振幅衰减值研究。方法:超声测量是一种新技术,利用不同密度的物体衰减值不同及穿过不同密度物体声速不同等特性对跟骨进行成像,并计算最具说明性区域的一系列数据。参数中BUA值为最主要的参数,三根等距离曲线的形态和宽度能直观分析出年龄与骨量变化的关系。结果:本文男性平均BUA为63.87dB/MHz,得出回归公式:体重=189.1417 0.2062BUA-0.0224SOS。女性平均BUA为58.9dB/MHz,各年龄分组的BUA值与参考值很接近,统计学显示无意义。结论:调查发现男性和女性的骨质不同,男性BUA骨峰值比女性高。BUA值与其体重有密切关系。在60岁以后(或绝经1-5年后)年龄增长与BUA值无明显关系,说明随着年龄的增加骨量减少很小或不减少。利用这种关系,假如BUA值突然下降则提示近期发生骨质疏松。 相似文献
14.
A general three-stage discrete-time population model is studied. The inherent net reproductive number for this model is derived. Global stability of the origin is established provided that the inherent net reproductive number is less than one. If it is larger than one the existence of a unique positive fixed point is proved and the persistence of the system is established. Finally, for certain parameter ranges global stability of the positive fixed point is proved. 相似文献
15.
C Greuet 《Cytobiologie》1978,17(1):114-136
In this study, more details of the different parts of the "ocelloide" of Nematodinium are given. The "hyalosome" which has a radial symmetry is made of endoplasmic reticulum, except the mitochondrial layer. There is only one constrictor ring and only a beginning of the periocellar gallery. The basal sheet on which the crystalline lens lies is a local differentiation of the cortical layer which is observed on the ceiling of the ocellar camera. This camera is related to the intercingular sulcus. There is also an ocellar fiber. The "melanosome" which is made of a double membrane and of many couples of thylakoids is flattened dorso-ventrally. The structure of the retina is similar to that observed in the other Warnowiidae. The pigmented ring is rather well developed and is in continuity with the upper part of the retina. Owing to the simpler organization of its ocelloide, Nematodinium is situated before the genera Warnowia and Erythropsidinium in the evolutionary series. 相似文献
16.
短柄五加大,小孢子发生和雌,雄配子体发育的研究 总被引:6,自引:2,他引:4
短柄五加花药5枚,每个花药四个花粉囊。小孢子母细胞减数分裂时,胞质分裂为同时型,产生正四面体形的四分体。花药壁由表皮、药室内壁、中层和绒毡层四层细胞组成,其发育类型为双子叶型。腺质绒毡层,其细胞为二核。三细胞型花粉。子房5室,每室两个胚珠,上胚珠败育,下胚珠可育。下胚珠倒生,具单珠被,厚珠心。大孢子母细胞减数分裂形成线性排列的四个大孢子,雌配子体发育属蓼型。开花当天,花粉散开,雌配子体尚未成熟,处 相似文献
17.
《Journal of biological dynamics》2013,7(4):415-427
A general three-stage discrete-time population model is studied. The inherent net reproductive number for this model is derived. Global stability of the origin is established provided that the inherent net reproductive number is less than one. If it is larger than one the existence of a unique positive fixed point is proved and the persistence of the system is established. Finally, for certain parameter ranges global stability of the positive fixed point is proved. 相似文献
18.
An antidiuretic mechanism is proposed for Rhodnius prolixus, whose activity is manifested when the diuretic phase has terminated and is maintained until the insect has fed again. Presumably this mechanism acts at the level of the proximal rectal sphincter and is inhibited by ingestion, mechanical distension of the gut and central disinhibition by decapitation. It is suggested that the antidiuretic activity is maintained by the nervous system and is modified when there is distention of the gut or when the nervous signal is interrupted by decapitation. It is demonstrated that the excretion of urine in R. prolixus is not controlled exclusively by the diuretic hormone, but rather that factors not linked to the haemolymph maintain the insects in a diuretic or nondiuretic state. 相似文献
19.
Igor Karšaj Carlo Sansour Jurica Sorić 《Biomechanics and modeling in mechanobiology》2009,8(5):359-370
In this paper, a hyperelastic and thermodynamically consistent model for soft tissue is developed that is able to describe
the change of the initial orientation of the collagen fibres. Full numerical implementation is considered as well. The collagen
architecture is assumed to reorient driven by a specific thermodynamical force. The anisotropy is described by a strain energy
function, which is decomposed into a part related to the matrix and a part related to the fibres. The initial fibre orientation
is defined by a structural tensor, while the current orientation is described by a time-dependent structural tensor, which
results from the initial one by a rotational transformation. The rotation tensor is obtained via an integration process of
a rate tensor, which depends on an adequately defined thermodynamical force. The integration is achieved via an exponential
map algorithm, where it is shown that the rotation is necessarily a two-parametric one. Efficiency of the proposed formulation
is demonstrated using some numerical examples. 相似文献