Bounding fluid viscosity and translational diffusion in a fluid lipid bilayer

Fluorescence recovery after photobleaching was used to investigate the translational diffusion of a fluorescent derivative of a membrane-spanning lipid in L phase multibilayers of 1-palmitoyl-2-oleoylphosphatidylcholine prepared in water and in glycerol. The translational diffusion coefficient in hydrated bilayers (D _w) ranged between 2 and 5x10^–8 cm²/s and in glycerinated bilayers (D _g) the range was between 3 and 24×10^–10 cm²/s between 10° and 40°C. These results are discussed in terms of models for diffusion in membranes.     

Frost resistance of winter rape leaves as related to the changes in water potential and growth capability

Differential thermal analysis indicated that the frost resistance of winter rape leaves ( Brassica napus L. var. oleifera L. cv. Gòrczanski), collected from plants grown in the cold (5/2°C), relies mainly on their ability to supercool to −9 to −11°C, i.e. consists in freezing avoidance. Initiation of ice formation in the cold-acclimated leaves resulted in the death of more than 50% of the cells as determined with a conductivity method. The development of freezing tolerance appeared to be an attribute of the second stage of plant hardening and was induced by the exposure of plants to a slightly subzero temperature (−5°C) for 18 h. Such a treatment brought about a sudden and persistent water potential decrease in the leaves, despite the fact that they had reabsorbed water from the medium prior to water potential measurements. Water potential changes were associated with a higher growth capability of the leaves as checked by determinations of disk area increments. It is suggested that the increased frost tolerance of the cold-grown winter rape leaves, subjected to subfreezing temperature, is related to the decreased water potential of the tissue caused by changes in turgor and/or in osmotic pressures of the cells.     

Localization of mitochondria in plant cells by vital staining with rhodamine 123

The positively-charged fluorescent dye rhodamine 123 (r-123) specifically stains mitochondria in living plant protoplasts, suspensionculture cells, and root hairs. This dye functions as a vital stain and permits visualization of the localization, distribution and movement of the mitochondria. Dehydration of root hairs caused mitochondria to aggregate into clumps. Mitochondria were either homogenous or heterogeneous and were frequently seen to accumulate in the perinuclear regions of suspension-culture cells but not in those of protoplasts or root-hair cells. Dinitrophenol and high concentrations of ethyleneglycol-bis(-aminoethyl ether)-N,N,N,N-tetraacetic acid and KCl immediately eliminated fluorescence in r-123-stained mitochondria whereas ionomycin enhanced it. Treatment of seedlings with r-123 resulted in differential brightness of fluorescence in different tissues. Meristematic tissues, such as root and shoot tips, exhibited the brightest fluorescence. The cytotoxicity of r-123 in both germinating seedlings and suspension-culture cells was low. The specificity, sensitivity and low toxicity of r-123 should make it a useful tool in experiments designed to examine agents and conditions which affect the location, the physiological status or the viability of mitochondria.Abbreviations EGTA ethyleneglycol-bis-(-aminoethyl ether)N,N,N,N-tetraacetic acid - DAPI 46-diamidino-2-phenylindole - r-123 rhodamine 123     

Effect of photoperiod and temperature on the development of frost hardiness in three Alnus species

The influence of short day and low temperature on cold acclimation of A. crispa (Ait.) Pursh, A. glutinosa (L.) Gaertn. and A. rubra Bong, was investigated. Two clones of each species originating from in vitro propagation were exposed to three daylength/temperature treatments. Periodically plantlets were exposed to controlled freezing temperature in order to evaluate their level of frost hardiness.
Short day (SD) and cold temperature (CT) and long day (LD) and cold temperature (CT) were the most effective treatments for the development of frost hardiness in shoots and roots of the three species tested. Short day (SD) and warm temperature (WT) induced a significant increase in hardiness in shoots of all three species. However, this treatment did not trigger root hardening. A. crispa was found to be the hardiest species followed by A. glutinosa and A. rubra . Intraspecific variation was observed between the two A. glutinosa clones. A glutinosa clone AG8, a Russian provenance, showed a greater freezing resistance than A. glutinosa clone AG2, a German provenance.     

犬脑内动脉构筑的显微X线解剖学研究

犬脑11只,经生理盐水冲洗脑血管后,注入20％钡胶液,切成0.2～1.0厘米的厚片,用显微X线法研究犬脑内各级动脉的构筑,其结果:1.皮质动脉的管径平均为25.9±0.005微米,平均长度为888.0±0.241微米。其形态与发出部位有关,分别呈栅状和瓶刷状。2.髓质动脉的管径平均为49.9±0.007微米。呈直线或孤形向心走行。3.皮质下动脉的管径平均为38.7±0.009微米。呈新月形或蟹钳状分布。4.豆纹动脉和内囊动脉的平均管径为70.0±0.021微米。呈锐角、反血流方向发自母干,再呈“S”形上升。5.丘脑动脉的平均管径为63.7±0.019微米,主要从下方进丘脑,呈树枝状分支。     

The relationship of calcium and parathyroid hormone in their effect on heart cells

Parathyroid hormone (PTH), the plasma concentration of which is raised in uremia, has been suggested as one of the agents responsible for the myocardial changes commonly seen in uremia. The effect of intact [1–84] PTH on rat heart cells grown in tissue culture has been studied. Addition of the hormone to the media significantly stimulated beating rate. The stimulation was directly proportional to the amount of PTH in the medium. Excessively high concentration of PTH caused immediate cessation of the beating, which was reversed by the addition of calcium to the medium. The extent of stimulation by PTH was inversely proportional to the calcium concentrations in the medium. Isoproterenol and phenylephrine at excessively high concentrations in the medium did not mimic the PTH effect either alone or together with PTH. When beating ceased due to verapamil the effect was not reversed by the addition of calcium to the medium.Calcium added to the myocytes seen after beating ceased reversed the effect and the cells started to beat again. Cells kept for a longer period in the arrested state were not revived by the addition of calcium.     

Seasonal changes in the pigments, carbohydrates and growth of red spruce as affected by ozone

Two-year-old red spruce seedlings were exposed to various levels ot ozone, from 0.4 to 3 times ambient levels, in open-top chambers in Ithaca, NY, USA. Exposures, which varied with changes in day length, commenced on May 30, 1987 and continued until December 14, 1987. Seedling biomass, carbohydrate contents, pigment contents, and rate of electron transport were assessed twice monthly during the fumigation period. Orthogonal quadratic or cubic polynomials were used to model the response through time each variable measured. A one-way analysis of variance model was fitted to every regression coefficient in each polynomial model to test for ozone effects on seasonal physiological patterns. Ozone did not influence growth, foliar pigment content, foliar starch content, root carbohydrate content, or rate of electron transport. The seasonal change of needle raffinose content differed between exposed to low (0.4 ×, 1×) and high (2×, 3×) ozone levels. There was also a trend towards reduced total soluble sugar content foliage during late autumn in higher ozone treatments.     

细梗香草的挥发油成分

本文对报春花科植物细梗香草(Lysimachia capillipes Hemsl.)的挥发性成分,用气相色谱和气质联用方法进行了定性和定量研究。鉴定出酸性成分75个,中性成分74个。在中性成分中鉴定出六氢金合欢烯酰丙酮、苯乙醇及香叶基丙酮等;酸性成分主要为棕榈酸、亚油酸、亚麻酸及一些二酸。     

The effect of glucose-6-phosphate isomerase genotype onin vitro specific activity andin vivo flux inMytilus edulis

Four samples of the musselMytilus edulis were taken between 1984 and 1987 from Stony Brook, New York, and used to study the glucose-6-phosphate isomerase (GPI) polymorphism in this species.In vitro specific activity andin vivo flux measured in the same animals were found to be significantly correlated. A significant effect of GPI genotype on flux was observed in one of the samples; overall, significant evidence of effect of genotype on enzyme activity was also obtained. GPI activities of common genotypes tend to deviate less from the population mean than those of rare (frequency less than 5%) genotypes. This suggests the possibility that rare GPI genotypes are rare as a consequence of having biochemical properties that deviate from an optimum level and, therefore, having a lower fitness. In support of this hypothesis, we found in one of our samples that shell length is a concave function of GPI activity with an intermediate optimum activity level. The financial support provided to P.J.N.S. by the Luso-American Educational Commission (Fulbright Program), the Instituto Nacional de Investigacao Científica (Portugal), and the Faculdade de Ciências da Universidade de Lisboa during several stages of this research is gratefully acknowledged. Financial support from the Ministerio de Educatión y Ciencia (Spain) in the form of a postdoctoral Fulbright/MEC fellowship to M.S. is also gratefully acknowledged. Research was supported by National Science Foundation Grant BSR-8415060 to R.K.K. This is contribution No. 736 from the Program in Ecology and Evolution, State University of New York at Stony Brook. On leave from Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande C2, Lisboa, Portugal.