Protein recovery from cell debris using rotary and tangential crossflow microfiltration

Protein recovery from a bacterial lysate was accomplished using microfiltration membranes in a flat crossflow filter and in a cylindrical rotary filter. Severe membrane fouling yielded relatively low long-term permeate flux values of 10(-4)-10(-3) cm/s (where I cm/s = 3.6 x 10(4) L/m(2) - h). The permeate flux was found to be nearly independent of transmembrane pressure and to increase with increasing shear rate and decreasing solids concentration. The flux increased with shear to approximately the one-third power or greater for the flat filter and the one-half power or greater for the rotary filter; the stronger dependence for the rotary filter is thought to result from Taylor vortices enhancing the back transport of debris carried to the membrane surface by the permeate flow. The average protein transmission or sieving coefficient was measured at approximately 0.6, but considerable scatter in the transmission data was observed. The largest sieving coefficients were obtained for dilute suspensions at high shear rate. The rotary filter provided higher fluxes than did the flat filter for dilute suspensions, but not for concentrated suspensions. (c) 1995 John Wiley & Sons, Inc.     

On the Crucial Stages in the Origin of Animate Matter

Theories of the origin of life have proposed hypotheses to link inanimate to animate matter. The theory proposed here derived the crucial stages in the origin of animate matter directly from the basic properties of inanimate matter. It asked what were the general characteristics of the link, rather than what might have been its chemical details. Life and its origin are shown to be one continuous physicochemical process of replication, random variation, and natural selection. Since life exists here and now, animate properties must have been initiated in the past somewhere. According to the theory, life originated from an as yet unknown elementary autocatalyst which occurred spontaneously, then replicated autocatalytically. As it multiplied to macroscopic abundance, its replicas gradually exhausted their reactants. Random chemical drift initiated diversity among autocatalysts. Diversity led to competition. Competition and depletion of reactants slowed down the rates of net replication of the autocatalysts. Some reached negative rates and became extinct, while those which stayed positive ``survived.' Thus chemical natural selection appeared, the first step in the transition from inanimate to animate matter. It initiated the first animate property, fitness, i.e., the capacity to adapt to the environment and to survive. As the environment was depleted of reactants, it was enriched with sequels—namely, with decomposition products and all other products which accompany autocatalysis. The changing environment exerted a selective pressure on autocatalysts to replace dwindling reactants by accumulating sequels. Sequels that were incorporated into the autocatalytic process became internal components of complex autocatalytic systems. Primitive forms of metabolism and organization were thus initiated. They evolved further by the same mechanism to ever higher levels of complexity, such as homochirality (handedness) and membranal enclosure. Subsequent evolution by the same mechanism generated cellular metabolism, cell division, information carriers, and a genetic code. Theories of self-organization without natural selection are refuted. Received: 29 March 1996 / Accepted: 30 May 1996     

Alterations in the activity of phospholipases A2 in postmortem white matter from patients with multiple sclerosis

Activities toward arachidonyl-labelled phospholipase A₂ substrates were assayed in fractions of white matter and cerebral cortex from control subjects and in fractions of demyelinated plaque, normal-appearing white matter and cerebral cortex from subjects who died with multiple sclerosis. Membranous activity at pH 8.6 in the presence of Ca²⁺, characteristic of 14 kDa secretory phospholipase A₂, in either multiple sclerosis white matter or cortex did not differ from controls, whereas membranous activity at pH 4.5 in the absence of added Ca²⁺, characteristic of lysosomal enzymes was increased over controls in both plaque and normal-appearing white matter but not cerebral cortex. Activity in the cytosol fraction, at pH 8.6 in the presence of Ca²⁺ and glycerol characteristic of the cytosolic 85 kDa enzyme was decreased by greater than 50% in both white matter and cortex samples from multiple sclerosis subjects. Immuno-precipitation and-blotting confirmed that the deficient activity was largely attributable to the 85 kDa enzyme although the enzyme protein was not similarly reduced.Special issue dedicated to Dr. Leon S. Wolfe.     

Comparison of gravimetry and planimetry in determining dry matter budgets for three species of phytophagous lepidopteran larvae

Gravimetric and a combination areal-gravimetric methods for determining dry matter budgets for leaf eating Lepidoptera were compared. The gravimetric method is based on dry weight/live weight ratios of the leaves fed to the larvae. In the areal-gravimetric method, the quantity of food offered to the larvae is determined from the area of leaf tracings and the dry matter content per unit area of the leaves. The areal-gravimetric method permits the use of larger leaf sprays and an open, gauze enclosed rearing chamber. There were no consistent differences in budget factors (growth, ingestion or egestion), nor were there any differences in the observed variability of the data attributable to the method used. However, the expected variability based on instrument precision for the gravimetric method is less than for the areal-gravimetric method. Experimental factors inherent in the gravimetric method introduce variability to the measurements that are not present in the areal method. Thirty to 60% of the variability in budget factors was attributed to intrinsic properties of the larvae, even though the larvae were taken from the same egg masses.

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Résumé Les budgets en matière sèche consommée par des lépidoptères ont été comparés par les méthodes gravimétrique et planimétrique. La méthode gravimétrique est basée sur le rapport poids sec/poids frais de feuilles consommées par les chenilles. Avec la méthode planimétrique, la quantité d'aliment proposée aux chenilles est déterminée par les tracés de la surface des feuilles et le contenu de matière sèche par unité de surface des feuilles. La méthode de planimétrie permet l'utilisation de plus grands rameaux de feuilles et de cages d'élevage extérieures en gaze. Il n'y avait pas de différence appréciable dans les éléments du budget (croissance, ingestion et déjection), ni aucune différence dans la variabilité observée des données attribuable à la méthode utilisée. Cependant, la variabilité attendue d'après la précision des mesures avec la méthode gravimétrique est inférieure à celle de la méthode planimétrique. est inférieure à celle de la méthode planimétrique. Des éléments expérimentaux, inhérents à la méthode gravimétrique, introduisent une variabilité dans les mesures que l'on n'a pas avec la méthode planimétrique. 30–60% de la variabilité dans la consommation ont été attribués à des paramètres internes à la chenille, même quand elles provenaient toutes de la même ooplaque.

     

大鼠尾核头部对中缝大核神经元单位活动的影响及其可能途径

用玻璃微电极细胞外记录大鼠中缝大核(NRM)神经元的单位放电。共记录277个细胞,NRM 神经元自发放电频率大都在每秒0.5—20次之间,平均为6.41 Hz。其中221个神经元被电刺激尾所激活,35个被抑制,21个无明显变化。NRM 神经元对躯体刺激的反应类型与自发放电的特征有关,兴奋型神经元的自发放电频率较低((?)=4.96Hz),而抑制性神经元的自发放电频率较高((?)=15.03 Hz)。在24例兴奋型神经元中,刺激尾核头部能够激活大多数 NRM 神经元的自发放电和抑制其伤害感受性反应。导水管周围灰质微量注射纳洛酮(2.5ug/0.5μl,n=15)。能够明显阻断刺激尾核头部激活 NRM 神经元自发放电和抑制伤害感受性反应的效应。     

Effects of dynamic impacts on human bones

Flat bones of human skeleton were subjected to dynamic indentation with ball indenters. The impacted surface was studied under high magnification and also by using the technique of multiple beam interferometry. The impulse caused the pile up of material at a little distance from the edge of the indent. The diameter of indent is found to increase as fourth root of the energy of impact. Bone structure also has the tendency to minimize the damage caused by external forces. There was about 90% recovery in deformation in the depth of indents due to internal stresses created inside the bone by the impact.     

Effects of N-serve (2-chloro-6-(trichloromethyl)pyridine) formulations on nitrification and on loss of nitrate in sand culture experiments

Summary N-serve (2-chloro-6-(trichloromethyl)pyridine) was tested as an inhibitor of nitrification of ammonium or urea in sand cultures. Nitrification was reduced but not prevented by N-Serve present at between 5 and 20 ppm in solution or by weight of sand. In the presence of root debris and acetone, used in some experiments at 2–4 ml/l of nutrient to convey N-Serve, denitrification was stimulated under the same conditions and resulted in loss of a large proportion of nitrate, probably mainly as gaseous products and some nitrite. These losses were greater when N-serve was also present. There was also conversion of nitrate to an insoluble form in the sand. A smaller proportional loss of nitrate occurred in other treatments in the presence of root debris when N-Serve was added without acetone, either as the commercial formulation 24E or as a solid. Thus, using N-Serve to inhibit nitrification may encourage denitrifying organisms especially in the presence of carbon sources including root debris or acetone. Large decreases of nitrate reductase activity in plants produced by using N-Serve in the presence of ammonium or urea were caused as much by losses of nitrate in the presence of acetone as by prevention of nitrate formation. Other N-Serve treatments (solid or 24E) decreased enzyme induction by between 50 and 90 per cent as a result mainly of reduced nitrification.     

Organic matter influences phytotoxicity of cadmium to soybeans

Summary Soybeans (Glycine max L. var. Williams) were grown for six weeks in a greenhouse in quartz sand containing 0, 0.5, 1, 2, 4 or 8% (w/w) sterilized peat moss. The cation exchange capacities of the organic matter-sand (OM-S) mixtures ranged from 0.01 to 8.88 meq/100 g dry weight. Imposed on each OM-S mixture was a treatment of 0, 1.25, 2.5, 5.0, 10.0 or 20.0 ppm Cd applied as CdCl₂·21/2H₂O. Height growth was measured weekly and at harvest plants were separated into leaves, stems and roots for dry weight and tissue Cd determinations. For plants grown in sand alone, height growth and dry matter accumulation in all tissues were reduced and Cd content was increased. These effects were correlated with increasing Cd concentration in the rooting medium. Inhibitions in growth by Cd were reduced by addition of organic matter; the amount of alleviation was dependent on both the level of organic matter and the cadmium treatment. In the 0, 0.5 and 1% OM-S mixtures, Cd content in the various tissues was correlated with metal treatment. Tissue levels were markedly reduced for Cd treatments in the 2, 4 and 8% OM-S mixtures, although there was a positive correlation between tissue Cd and the 1.25 and 2.5 Cd treatments. The order of Cd accumulation in the tissues was roots stems>leaves.     

Species decline: A perspective on extinction,recovery, and propagation

This keynote address was presented at the Conference on the Conservation of Endangered Species in Zoological Parks and Aquariums on April 18, 1982 at the National Aquarium in Baltimore. It outlines 1) future trends in the world's environment, resources, and population; 2) factors affecting species decline; 3) reasons for preserving life forms; and 4) techniques, with emphasis on captive propagation, used to assist in species recovery.