Plant cells on earth and in space

Two quite different types of plant cells are analysed with regard to transduction of the gravity stimulus: (i) Unicellular rhizoids and protonemata of characean green algae; these are tube-like, tip-growing cells which respond to the direction of gravity. (ii) Columella cells located in the center of the root cap of higher plants; these cells (statocytes) perceive gravity. The two cell types contain heavy particles or organelles (statoliths) which sediment in the field of gravity, thereby inducing the graviresponse. Both cell types were studied under microgravity conditions (10(-4) g) in sounding rockets or spacelabs. From video microscopy of living Chara cells and different experiments with both cell types it was concluded that the position of statoliths depends on the balance of two forces, i.e. the gravitational force and the counteracting force mediated by actin microfilaments. The actomyosin system may be the missing link between the gravity-dependent movement of statoliths and the gravity receptor(s); it may also function as an amplifier.     

The development of vestibular connections in rat embryos in microgravity

Existing experimental embryological data suggests that the vestibular system initially develops in a very rigid and genetically controlled manner. Nevertheless, gravity appears to be a critical factor in the normal development of the vestibular system that monitors position with respect to gravity (saccule and utricle). In fact several studies have shown that prenatal exposure to microgravity causes temporary deficits in gravity-dependent righting behaviors, and prolonged exposure to hypergravity from conception to weaning causes permanent deficits in gravity-dependent righting behaviors. Data on hypergravity and microgravity exposure suggest some changes in the otolith formation during development, in particular the size although these changes may actually vary with the species involved. In adults exposed to microgravity there is a change in the synaptic density in the optic sensory epithelia suggesting that some adaptation may occur there. However, effects have also been reported in the brainstem. Several studies have shown synaptic changes in the lateral vestibular nucleus and in the nodulus of the cerebellum after neonatal exposure to hypergravity. We report here that synaptogenesis in the medial vestibular nucleus is retarded in developing rat embryos that were exposed to microgravity from gestation days 9 to 19.     

Helium and sulfur hexafluoride bolus washin in short-term microgravity.

We performed single-breath washout (SBW) tests in which He and sulfur hexafluoride (SF6) were inspired throughout the vital capacity inspirations or were inhaled as discrete boluses at different points in the inspiration. Tests were performed in normal gravity (1 G) and in up to 27 s of microgravity (microG) during parabolic flight. The phase III slope of the SBW could be accurately reconstructed from individual bolus tests when allowance for airways closure was made. Bolus tests showed that most of the SBW phase III slope results from events during inspiration at lung volumes below closing capacity and near total lung capacity, as does the SF6-He phase III slope difference. Similarly, the difference between 1 G and microG in phase III slopes for both gases was entirely accounted for by gravity-dependent events at high and low lung volumes. Phase IV height was always larger for SF6 than for He, suggesting at least some airway closure in close proximity to airways that remain open at residual volume. These results help explain previous studies in microG, which show large changes in gas mixing in vital capacity maneuvers but only small effects in tidal volume breaths.     

Behavior of free-swimming cells under various accelerations

The different steps of the gravity signal-transduction chain on the cellular level are not identified. In our experiments performed up to now we mainly stressed our attention on the last step, the response of the cells. Swimming behavior is a suitable indicator for the physiological status of a Paramecium cell. Depending on membrane potential and/or concentrations of Ca++, cGMP and cAMP the beating direction and the beating velocity of the cilia are influenced in a characteristical way leading to a changed swimming activity of the cell. The behavior of Paramecium is influenced by various stimuli from their environment. Previous studies have demonstrated that under controlled conditions Paramecium shows a clear gravity-dependent behavior resulting in negative gravitaxis and gravikinesis (speed regulation in dependence of gravity). By changing the orienting stimulus (gravity) we expected changes of the swimming behavior. Additional experiments were performed using pawn mutant d4-500r. Due to defective Ca(2+)-channels the membrane of this mutant cannot depolarize. As a consequence d4-500r cannot perform phobic responses and swim backwards. Comparative experiments are also performed with the ciliate Loxodes striatus. In contrast to Paramecium this ciliate possesses statocyst-like organelles--the Müller Organelles.     

Changes in gravity rapidly alter the magnitude and direction of a cellular calcium current

In single-celled spores of the fern Ceratopteris richardii, gravity directs polarity of development and induces a directional, trans-cellular calcium (Ca²⁺) current. To clarify how gravity polarizes this electrophysiological process, we measured the kinetics of the cellular response to changes in the gravity vector, which we initially estimated using the self-referencing calcium microsensor. In order to generate more precise and detailed data, we developed a silicon microfabricated sensor array which facilitated a lab-on-a-chip approach to simultaneously measure calcium currents from multiple cells in real time. These experiments revealed that the direction of the gravity-dependent polar calcium current is reversed in less than 25 s when the cells are inverted, and that changes in the magnitude of the calcium current parallel rapidly changing g-forces during parabolic flight on the NASA C-9 aircraft. The data also revealed a hysteresis in the response of cells in the transition from 2g to micro-g in comparison to cells in the micro-g to 2-g transition, a result consistent with a role for mechanosensitive ion channels in the gravity response. The calcium current is suppressed by either nifedipine (calcium-channel blocker) or eosin yellow (plasma membrane calcium pump inhibitor). Nifedipine disrupts gravity-directed cell polarity, but not spore germination. These results indicate that gravity perception in single plant cells may be mediated by mechanosensitive calcium channels, an idea consistent with some previously proposed models of plant gravity perception.     

枫蓼肠胃康口服液HPLC指纹图谱研究

建立了一种整体定性鉴别和指标成分定量的HPLC指纹图谱方法,对由牛耳枫和辣蓼两味药材组成的枫蓼肠胃康口服液原料及成品进行了指纹图谱研究,并测定了指标成分芦丁、金丝桃苷和异鼠李素的含量。采用Waters ODS C18色谱柱(250 mm×4.6 mm I.D.5μm),用含甲醇和甲酸溶液作为流动相,进行梯度洗脱,并对原料和成品的相应色谱峰进行归属鉴别。结果显示芦丁、金丝桃苷和异鼠李素得到了满意的线性范围,相关系数均大于0.999。按照SFDA的要求,对原料和成品的色谱指纹图谱采用相关系数法和夹角余弦法两种数学方法计算它们的相似度,两种计算方法相似度均不小于0.852。表明建立的枫蓼肠胃康口服液的定性定量方法显著优于传统的质量控制方法。     

The biophysical limitations in physiological transport and exchange in plants grown in microgravity

This paper describes how changes in the physical behavior of fluids and gases in microgravity can limit the physiological transport and exchange in higher plants. These types of effects are termed indirect effects of microgravity because they are not due to gravity interacting with the mass of the plant body itself. The impact of limiting gravity-dependent transport phenomena has been analyzed by the use of mathematical modeling to simulate and compare biophysical transport in the 1g and spaceflight environments. These data clearly show that the microgravity environment induces significant limitations on basic physiological and biochemical processes within the aerial and rootzone portions of the plant. Furthermore, this mathematical model provides a solid foundation for explaining the physiological effects that have been noted in past spaceflight experiments.     

Characteristics of adaptation and maladaptation of human cardiovascular system under space flight conditions

The goal of this study was to analyze and generalize hemodynamic data collected over 20 years from 26 cosmonauts, who had flown from 8 to 438 days aboard orbital stations Salut-7 and Mir. This paper describes the results of ultrasonographic studies of the heart and arterial and venous peripheral vessels in different parts of human body as well as the study of venous capacity by occlusion aeroplethysmography. It was established that, at rest, the key hemodynamic parameters (the pumping function of the heart and blood supply of the brain) and integral parameters (blood pressure and heart rate) were best “protected” and remained stable throughout long exposure in microgravity. In the absence of gravitational stimulation, arterial resistance decreased in almost all vascular regions below the heart level; i.e., the antigravity distribution of the vascular tone was gradually lost as unneeded in microgravity. Venous hemodynamics was found to be most sensitive to microgravity: changes in it were expressed earlier and were more pronounced than in the arterial part of the vasculature. The changes included deceleration of venous return, a decrease in the vascular resistance in the lower body, and an increase in the leg’s venous network capacity. The functional test with the lower body’s negative pressure revealed a deterioration of gravity-dependent responses, which increased with an increase in the duration of the space flight. Cardiovascular deconditioning clearly manifested itself after the return to the Earth’s gravity as a decreased g-tolerance during reentry and orthostatic instability in the post-flight period. The results of this study confirmed the multifactorial genesis of orthostatic instability during space flights including blood redistribution, changes in the regulation of vascular tone of arterial and venous vessels in legs, and hypovolemia.     

The effects of hypergravity and substrate vibration on vestibular function in developing chickens

We used linear vestibular evoked potentials (VsEPs) to characterize peripheral and central vestibular function in birds following embryogenesis at 2G centrifugation or at elevated levels of vibration (+20dB re: background levels). Additionally, we characterized peripheral and central vestibular adaptation to 2G centrifugation in early post-hatch birds. Linear VsEP response peak latencies, amplitudes, thresholds and input/output functions were quantified and compared between experimental and control animals. Birds vibrated throughout embryogenesis and up to one-week post-hatch revealed no changes in linear VsEP response components compared to control siblings. Birds centrifuged at 2G throughout embryogenesis also evidenced no changes in the linear VsEP measured at hatch (P0). Significant changes were seen, however, for linear VsEPs of post-hatch birds placed at 2G for 7 days beginning on post-hatch day 5. Linear VsEPs for these animals displayed significant reductions in response amplitudes associated with peaks P2, N2 and P3, response peaks generated by central neural relays of gravity receptors. The earliest response components, generated by the peripheral vestibular nerve (i.e., P1, N1), were not significantly altered with the 7-day exposure to 2G. Thus, there was no evidence of generalized changes in peripheral gravity receptor excitability or in the rate of maturation in developing animals under increased levels of gravity or vibration. If gravity level plays a critical role in shaping peripheral vestibular ontogeny at magnitudes between 1 and 2G, then it may serve to stabilize function under changing G-fields or it may operate on physiological features that can not be resolved by the VsEP. In contrast, exposure to elevated gravity during post-hatch periods does alter central vestibular function thus providing direct evidence for central vestibular adaptation to the gravitational environment. The fact that central functional change was observed in hatchlings and not embryos, raises the possibility that the first 2-weeks post-hatch may be a critical period of "heightened developmental sensitivity" to hypergravity.     

Spontaneous beat-by-beat fluctuations of total peripheral and cerebrovascular resistance in response to tilt

Beat-by-beat estimates of total peripheral resistance (TPR) can be obtained from continuous measurements of cardiac output by using Doppler ultrasound and noninvasive mean arterial blood pressure (MAP). We employed transfer function analysis to study the heart rate (HR) and vascular response to spontaneous changes in blood pressure from the relationships of systolic blood pressure (SBP) to HR (SBP-->HR), MAP to total peripheral resistance (TPR) and cerebrovascular resistance index (CVRi) (MAP-->TPR and MAP-->CVRi), as well as stroke volume (SV) to TPR in nine healthy subjects in supine and 45 degrees head-up tilt positions. The gain of the SBP-->HR transfer function was reduced with tilt in both the low- (0.03-0.15 Hz) and high-frequency (0.15-0.35 Hz) regions. In contrast, MAP-->TPR transfer function gain was not affected by head-up tilt, but it did increase from low- to high-frequency regions. The phase relationships between MAP-->TPR were unaffected by head-up tilt, but, consistent with an autoregulatory system, changes in MAP were followed by directionally similar changes in TPR, just as observed for the MAP-->CVRi. The SV-->TPR had high coherence with a constant phase of 150-160 degrees. Together, these data that showed changes in MAP preceded changes in TPR, as well as a possible link between SV and TPR, are consistent with complex interactions between the vascular component of the arterial and cardiopulmonary baroreflexes and intrinsic properties such as the myogenic response of the resistance arteries.     

Economic weights of production and functional traits for Merinolandschaf, Romney, Romanov and Sumavska sheep in the Czech Republic

Economic weights of production and functional traits were estimated for the dual-purpose sheep breeds Romney (RY), Merinolandschaf (ML), Romanov (RV) and Sumavska (SA). A bio-economic computer model simulating the profit function for production systems with one lambing per year was used for the calculations. First, marginal economic values were calculated which were defined as partial derivatives of the profit function with respect to the average level for each trait. Applying gene-flow methodology, absolute and relative economic weights for direct and maternal components of the traits were then estimated for pure-bred production systems and systems which included partial terminal cross-breeding. The following traits were evaluated: birth weight, daily gain till weaning and during rearing, mature weight, dressing percentage, fleece weight, conception rate of ewe lambs and ewes, litter size at lambing (total number of lambs born per ewe lambing), survival rate of lambs at birth and till weaning and productive lifetime of ewes. Standardized economic weights were calculated as the product of the economic weight and the genetic standard deviation of each trait or trait component. The total economic importance was defined as the sum of the absolute (not taking into account the sign) standardized economic weights over all traits and trait components, and relative economic weights were then computed as the standardized economic weights expressed as percentages of total economic importance. The direct components of survival rate at birth and till weaning, the direct component of daily gain till weaning and litter size had the highest relative economic weights (greater than 10%) in pure-bred systems in all four breeds. In ML and RV, the maternal component of lamb survival rate till weaning also had a relative economic weight exceeding 10%. In systems with partial terminal cross-breeding for all four breeds, relative economic weights of maternal traits and trait components were slightly larger than in pure-bred production systems, particularly for litter size. Based upon comparison of relative economic weights of traits among breeds, separate breeding goals for RY and RV are recommended, whereas a common breeding goal is deemed appropriate for ML and SA.     

A method for characterizing the biodiversity in bat pinnae as a basis for engineering analysis

A quantitative analysis of the interspecific variability between beamforming baffle shapes in the biosonar system of bats is presented. The data set analyzed consisted of 100 outer ear (pinna) shapes from at least 59 species. A vector-space representation suitable for principal component analysis (PCA) was constructed by virtue of a transform of the pinna surfaces into cylindrical coordinates. The central axis of the cylindrical transform was found by minimizing a potential function. The shapes were aligned by means of their respective axes and their center of gravity. The average pinna of the sample was a symmetrical, obliquely truncated horn. The first seven eigenvalues accounted already for two-thirds of the variability around the mean, which indicates that most of the biodiversity in the bat pinna can be understood in a more low-dimensional space. The first three principal components show that most of the variability of the bat pinna sample is in terms of opening angle, left-right asymmetry, and selective changes in width at the top or the bottom of the pinna. The beampattern effects of these individual components have been characterized. These insights could be used to design bioinspired beamforming devices from the diversity in biosonar.     

GEOTROPISM OF AGRIOLIMAX

On an inclined glass plate the slug Agriolimax orients and creeps upward or downward. The angle of orientation on the plane (θ) is proportional to the logarithm of the component of gravity in the creeping plane. The coefficient of variability of the measured values of (θ) decreases linearly as the logarithm at the gravity component in the creeping plane increases. The cosine of the angle of orientation decreases almost directly in proportion to the sine of the angle of inclination of the creeping plane to the horizontal, as previously found for young rats (Crozier and Pincus). But a more satisfactory formulation for the present case shows that the sine of the angle of orientation (θ) decreases in direct proportion to the increase of the reciprocal of the sine of the angle of inclination of the creeping plane. This formulation is derived from the theory that the geotropic orientation is limited by the threshold difference between the pull of the body mass on the mutually inclined longitudinal muscles at the anterior end of the slug.     

Postnatal development of renin-angiotensin system in rats

The changes occurring in several components of the rat renin-angiotensin system (RAS) were studied for the brief postnatal period, between the fourth and tenth week of life. The parameters were: plasma renin activity (PRA), plasma renin concentration (PRC), plasma renin substrate (PRS) and the plasma angiotensin II concentration (AII). A gradual decrease in PRA with age was noticed. Between the fourth and the eighth weeks of life, this was attributed to a corresponding decline in both PRC and PRS. However, between the eighth and tenth weeks, no changes in PRA could be detected, but PRC and PRS increased, perhaps as a consequence of the changes in renal function and the AII increase observed. In this second period, simultaneously with the RAS changes described, there was reduced sodium chloride excretion as the glomerular filtration rate (GFR) stabilized. The data presented suggest that this postnatal period is critical, in rats, for the maturation of the RAS component control mechanisms; they appear to be closely related to the development of the renal function.     

Effects of Pro1266Leu mutation on structure and function of glycoprotein Ib binding domain of von Willebrand factor

Glycoprotein Ibα (GpIbα) binding ability of A1 domain of von Willebrand factor (vWF) facilitates platelet adhesion that plays a crucial role in maintaining hemostasis and thrombosis at the site of vascular damage. There are both “loss as well as gain of function” mutations observed in this domain. Naturally occurring “gain of function” mutations leave self-activating impacts on the A1 domain which turns the normal binding to characteristic constitutive binding with GPIbα. These “gain of function” mutations are associated with the von Willebrand disease type 2B. In recent years, studies focused on understanding the mechanism and conformational patterns attached to these phenomena have been conducted, but the conformational pathways leading to such binding patterns are poorly understood as of now. To obtain a microscopic picture of such events for the better understanding of pathways, we used molecular dynamics (MD) simulations along with principal component analysis and normal mode analysis to study the effects of Pro1266Leu (Pro503Leu in structural context) mutation on the structure and function of A1 domain of vWF. MD simulations have provided atomic-level details of intermolecular motions as a function of time to understand the dynamic behavior of A1 domain of vWF. Comparative analysis of the trajectories obtained from MD simulations of both the wild type and Pro503Leu mutant suggesting appreciable conformational changes in the structure of mutant which might provide a basis for assuming the “gain of function” effects of these mutations on the A1 domain of vWF, resulting in the constitutive binding with GpIbα.     

Changes in the biochemical composition of Balanus balanoides (L.) under experimental conditions: The effect of a starch diet

A comparison has been made of the changes in biochemical composition of experimental and natural populations of Balanus balanoides (L.). The ‘bodies’ and the ovary were separately analysed. The lipid components have been investigated in some detail; lipid classes were separated and the component fatty acids of the major components (triglycerides + diglycerides and phospholipids) determined.Animals fed on brine shrimp increased in weight more than the natural population, that of the starved animals was less, and that of animals fed on starch only, even less. The starch-fed animals continued to produce faecal pellets and it is suggested that the greater energy expenditure in feeding (cirral) activity with little gain of useful metabolic substrate was responsible for this decrease in body weight. These differences extend to the component lipid classes. Even so, these starch-fed animals produced ovarian tissue as, indeed, did starved animals, presumably by transfer of body material; the low level or absence of nutrients did not interfere with the hormonal stimulation of reproduction.     

Characterization of the caryopsis of common wheat varieties and F2 generation hybrids by means of multivariate analysis

Summary Nineteen parameters of common wheat kernels were investigated by the multivariate procedure. A relationship between the DBC parameter and both specific gravity and kernel filling was found. In some populations an interdependence of the DBC parameter and the subaleurone endosperm thickness was found. In the analysis of principal components the DBC parameter was represented mostly by particular component. Significant dependences were found between the dimensions as well as the weight of the caryopsis and some dimensions of the crease and endosperm cavity. The dendrite constructed on the basis of the calculated Mahalanobis's generalized distances matrix represents the near affinity of reciprocal hybrids or pure lines originating from a single cultivar as well as hybrids and their parental forms.