A New Material Concept for the Red Cell Membrane

The proposition is made that the red cell membrane is a two-dimensional, incompressible material and a general stress-strain law is developed for finite deformations. In the linear form, the character of such a material is analogous to a two-dimensional Mooney material (e.g., rubber), indicating that the molecular structure in the plane of the membrane would consist of long chains, randomly kinked and cross-linked in the natural state. The loose network could be provided by the protein component and the lipid phase could exist interstitially as a liquid bilayer, giving the membrane its two-dimensional incompressibility. The material provides the capability of large deformations exhibited by the discocyte and yet the rigidity associated with the osmotic spherocyte state. It is demonstrated that a membrane of this type can form a sphere at constant area. An illustrative example of the application to single cell discocyte-to-osmotic spherocyte transformations is presented.     

液氮喷雾治疗器的研制与临床应用

介绍了液氮雾化的原理,自行研制新型液氮喷雾治疗器经过,并用于临床治疗,冷冻治疗242例雀斑,疗效显著,经1年~3年追踪观察,治愈率为81.4%,有效率复发率为0.02%。结果显示新型液氮治疗器适用于治疗小的、表浅的和某些特殊部位的皮损,对色素性疾病有很好的疗效。     

Dictyostelium discoideum: a New Method for Cloning in Liquid Medium

Dictyostelium discoideum can be cloned in droplets of liquid medium by a method that permits observation of the complete life cycle. This alternative to solidified media provides advantages in clonal analysis.     

Cell Size Control: New Evidence for a General Mechanism

Continuously proliferating cells have to precisely double their size during each cycle to maintain constant volumes. Time and again, this fact raised questions on the existence of an active cell size control mechanism in eukaryotic cells, which would prevent delayed or premature cell division at inadequate mass. We addressed this open issue by recapitulating in animal cells several long-standing experiments which had identified such a mechanism in yeast. As a model, mainly chicken erythroblasts were used, whose proliferation can be driven either by a constitutively active oncogene (v-ErbB) or the physiological cytokines stem cell factor + erythropoietin. V-ErbB-driven cells proliferated faster than Epo/SCF-driven cells (doubling time 13 vs. 22 hours) and exhibited a 1.4-fold increased cell volume, due to a two-fold higher rate of global protein synthesis. Rapid and complete phenotypic reversion was achieved by exchanging the respective factors. To analyze the switch from one proliferation mode to the other in detail, we followed cell cycle progression of cells re-cultivated after synchronization by centrifugal elutriation. The results indicated that altered protein synthesis rates exclusively influenced G1 phase duration. Additional experiments with chicken erythroblasts and mammalian fibroblasts treated with low doses of aphidicolin (artificially prolonging S-phase) also pointed to the existence of a general size sensing mechanism in G1, ensuring cell size maintenance over many divisions, probably similar to the situation in yeast but certainly regulated at additional levels in higher eukaryotes.     

Hanging Magnetic Stirrer Which Minimizes Cell Disruption

A magnetic stirring bar enclosed in tubing forms a large paddle which produces good mixing at slow rotational speeds. It is suspended above the bottom of the vessel and cannot grind cells or become misaligned.     

A New Concept for DNA-Arrays

Abstract

We will insert a cleavage site in an oligodeoxynucleotide, which can be used for a selective and quantitative cleavage. For that reason we synthesized the four 5′-S-(4,4′-dimethoxytrityl)-mercapto-2′-deoxynucleotide-3′-O-(2-cyanoethoxydiisopropylamino)-phosphites ( 5a–d ). The cleavage of P-S and C-S bonds is described (Mag, M.; Lücking, S.; Engels, J.W. Synthesis and selective cleavage of an oligodeoxy-nucleotide containing a bridged internucleotide 5′-phosphorthioate linkage Nucleic Acids Res. 1991, 19 (7), 1437–1441; Marriott, J.H.; Mottahedeh, M.; Reese, C.B. 9-(4-methoxyphenyl)xanthen-9-thiol: A useful reagent for the preperation of thiols. Tetrahedron Lett. 1990, 31 (51), 7485–7488; Divakar, K.J.; Mottoh, A.; Reese, C.B.; Shanghvi, Y.S. Approaches to the synthesis of 2′ thio analogues of pyrimidine ribosides. J. Chem. Sc., Perkin Trans. 1 1990, 969–974). The oligodeoxynucleotides with an achiral bridged 5′-phosphorothioate linkage 5′-O-P-S-3′ are synthesized by the phosphoramidite procedure.     

DCPA Causes Cell Plate Disruption in Wheat Roots

Light and electron microscopy were used to investigate the effectsof the herbicide DCPA (dimethyl tetrachloroterephalate) on wheatroot meristems. Three different sorts of disruption are found.In the epidermal cells, the walls are incomplete and/or curved,as well as being oriented in directions other than perpendicularto the long axis of the root. In developing cell plates, phragmoplastmicrotubule arrays are oriented in many directions in this layer,probably accounting for the wall abnormalities. In the calyptrogenand cortical layers, no walls or incomplete walls are formedbetween the nuclei, so that these cell layers are essentiallyone large cell with multiple nuclei. This effect has not beenobserved for any other herbicide. Prometaphase figures witha few microtubules and multipolar mitosis are the predominantabnormalities in the meristematic zone. Aberrant cell wallsare also found in this tissue layer. These data indicate thatDCPA is effective at disrupting phragmoplast micTotubule arraysand cell wall formation. Herbicide, mitosis, cell plate, cell wall     

三种微藻细胞破碎方法的比较

目的:获得最佳的微藻藻胆蛋白提取方法.方法:采用溶胀法、反复冻融法、低浓度氯化钙溶液提取法和玻璃珠处理法等四种方法分别对紫球藻、蔷薇藻和念珠藻三种藻细胞进行破碎,通过测定藻红蛋白的纯度和浓度对四种细胞破碎方法效果进行比较.结果:当细胞密度为1.00g/L时,采用反复冻融法处理紫球藻和蔷薇藻时能够获得最高的藻红蛋白纯度(OD545/OD280),分别为1.250和1.669,藻红蛋白的浓度分别为29.788,mg/L和36.026mg/L,细胞密度对藻红蛋白纯度影响较小;低浓度氯化钙溶液提取法能使念珠藻藻红蛋白的纯度(OD545/OD280)达到0.477.结论:紫球藻和蔷薇藻经反复冻融法破碎细胞,藻红蛋白纯度高,提取效果好;而对念珠藻藻红蛋白提纯采用低浓度氯化钙溶液提取法效果好.     

Liquid Nitrogen Preservation of Standard Inoculum: Gas-Phase Storage

Liquid nitrogen storage was the most satisfactory of several methods tested for supplying standard Streptomyces viridoflavus inoculum for laboratory and pilot plant experimentation. Shake-flask cultures were subdivided into sterile cotton-plugged ampoules and stored in the gas space of a liquid nitrogen refrigerator. There were no detectable changes in viability or in candidin-producing capacity over a 12-month test period. The procedure also proved satisfactory with all other organisms tested.     

Long-Term Preservation of Anaplasma marginale in a Liquid Nitrogen Repository

The infectivity of Anaplasma marginale was maintained in liquid nitrogen storage throughout a 4-yr test period.     

Calculation of Externally Applied Electric Field Intensity for Disruption of Cancer Cell Proliferation

It is already known that electrostatic, magnetostatic, extremely low-frequency electric fields, and pulsed electric field could be utilized in cancer treatment. The healing effect depends on frequency and amplitude of electric field. In the present work, a simple theoretical model is developed to estimate the intensity of electrostatic field that damages a living cell during division. By this model, it is shown that magnification of electric field in the bottleneck of dividing cell is enough to break chemical bounds between molecules by an avalanche process. Our model shows that the externally applied electric field of 4?V/cm intensity is able to hurt a cancer cell at the dividing stage.     

Microcontact Peeling as a New Method for Cell Micropatterning

Micropatterning is becoming a powerful tool for studying morphogenetic and differentiation processes of cells. Here we describe a new micropatterning technique, which we refer to as microcontact peeling. Polydimethylsiloxane (PDMS) substrates were treated with oxygen plasma, and the resulting hydrophilic layer of the surface was locally peeled off through direct contact with a peeling stamp made of aluminum, copper, or silicon. A hydrophobic layer of PDMS could be selectively exposed only at the places of the physical contact as revealed by water contact angle measurements and angle-resolved X-ray photoelectron spectroscopy, which thus enabled successful micropatterning of cells with micro-featured peeling stamps. This new micropatterning technique needs no procedure for directly adsorbing proteins to bare PDMS in contrast to conventional techniques using a microcontact printing stamp. Given the several unique characteristics, the present technique based on the peel-off of inorganic materials may become a useful option for performing cell micropatterning.