The role of the cytoskeleton in volume regulation and beading transitions in PC12 neurites

We present investigations on volume regulation and beading shape transitions in PC12 neurites, conducted using a flow-chamber technique. By disrupting the cell cytoskeleton with specific drugs, we investigate the role of its individual components in the volume regulation response. We find that microtubule disruption increases both swelling rate and maximum volume attained, but does not affect the ability of the neurite to recover its initial volume. In addition, investigation of axonal beading—also known as pearling instability—provides additional clues on the mechanical state of the neurite. We conclude that volume recovery is driven by passive diffusion of osmolites, and propose that the initial swelling phase is mechanically slowed down by microtubules. Our experiments provide a framework to investigate the role of cytoskeletal mechanics in volume homeostasis.     

Is bigger always better? A critical appraisal of the use of volumetric analysis in the study of the hippocampus

A well-developed spatial memory is important for many animals, but appears especially important for scatter-hoarding species. Consequently, the scatter-hoarding system provides an excellent paradigm in which to study the integrative aspects of memory use within an ecological and evolutionary framework. One of the main tenets of this paradigm is that selection for enhanced spatial memory for cache locations should specialize the brain areas involved in memory. One such brain area is the hippocampus (Hp). Many studies have examined this adaptive specialization hypothesis, typically relating spatial memory to Hp volume. However, it is unclear how the volume of the Hp is related to its function for spatial memory. Thus, the goal of this article is to evaluate volume as a main measurement of the degree of morphological and physiological adaptation of the Hp as it relates to memory. We will briefly review the evidence for the specialization of memory in food-hoarding animals and discuss the philosophy behind volume as the main currency. We will then examine the problems associated with this approach, attempting to understand the advantages and limitations of using volume and discuss alternatives that might yield more specific hypotheses. Overall, there is strong evidence that the Hp is involved in the specialization of spatial memory in scatter-hoarding animals. However, volume may be only a coarse proxy for more relevant and subtle changes in the structure of the brain underlying changes in behaviour. To better understand the nature of this brain/memory relationship, we suggest focusing on more specific and relevant features of the Hp, such as the number or size of neurons, variation in connectivity depending on dendritic and axonal arborization and the number of synapses. These should generate more specific hypotheses derived from a solid theoretical background and should provide a better understanding of both neural mechanisms of memory and their evolution.     

Evaluation of the killing volume of gas bubbles in sparged animal cell culture bioreactors

The detrimental effect of direct gas sparging on insect cells was investigated in bubble columns with various gas flow rates and bubble sizes. The first-order cell death rate was shown to be directly proportional to the gas flow rate and inversely proportional to the bubble size. The specific killing volume of a bubble, killing volume per unit volume of bubble, was found to have a linear correlation with the specific interfacial area of a bubble. Based on these experimental results and the analysis of a bursting bubble at the liquid surface, it was concluded that the killing volume of a bubble is in the liquid layer surrounding the bubble before its rupture, and most important, in the liquid layer beneath the bubble cavity. Cell damage in the bubble film cap was relatively insignificant compared to that in the liquid layer underneath the bubble cavity, except for very large bubbles (i.e., bubble diameter over 5 mm).     

Electroplethysmographic determination of the regional relative engorgement of the lungs

On the strength of the theoretical research of a biophysical model of the lung structure and the following experimental checking of the results obtained a method of calculation of the regional relative blood volume in the lungs by the data of electroplethysmographic examination of the lungs and measurement of specific electrical conductivity of the blood is proposed. Calculation formulae for the determination of the regional relative blood volume in the lungs were derived their working ranges within the limits of application of the proposed calculation method in clinical and physiological examination of the lungs were established.     

Leaf structure and specific leaf mass: the alpine desert plants of the Eastern Pamirs, Tadjikistan

This study examines interrelationships between eight leaf attributes (specific leaf mass, area, dry mass, lamina thickness, mesophyll cell number per cm², mesophyll cell volume, chloroplast volume, and number of chloroplasts per mesophyll cell) in field-grown plants of 94 species from the Eastern Pamir Mountains, at elevations between 3800 and 4750 m. Unlike most other mountain areas, the Eastern Pamirs, Karakorum system, Tadjikistan provide localities where low temperatures and radiation combine with moisture stress at high altitudes. For all the attributes measured, significant differences were found between plants with different mesophyll types. Leaves with dorsiventral palisade structure (dorsal palisade, ventral spongy mesophyll cells) had thicker leaves with larger but fewer mesophyll cells, containing more and larger chloroplasts. These differences in mesophyll type are reflected in differences in the total surface of mesophyll cells per unit leaf area ( A _mes/ A ) or volume ( A _mes/ V ). Plants with isopalisade leaf structure (palisade cells under both dorsal and ventral surfaces) are more commonly xerophytes and their increased values of A _mes/ A and A _mes/ V decrease CO₂ mesophyll resistance, which is an important adaptation to drought. Path analysis shows the critical importance of mesophyll cell volume in leading to the covariance between the different leaf attributes and hence to specific leaf mass (SLM), even though mesophyll cell volume is not itself strongly correlated with SLM. This is because mesophyll cell volume increases SLM through its effects on leaf thickness and chloroplast number per cell, but decreases SLM through its negative effect on mesophyll cell density.     

The arterial pattern and fractal dimension of the dog kidney.

A method has been developed by which it is possible to measure the fractal dimension of the arterial tree of the kidney. The objective of this work is to determine a method which permits us to discriminate between the architectures of specific organs by reference to a unique number, namely the fractal dimension of the arterial tree of that organ. This method opens the possibility of a new taxonomy for normal organs and for the pathological injiries related to the vascular morphology of those organs. The method that we have devised uses as its input the volume which is taken up by the arterial tree of the kidney. In order to calculate this volume we first obtained a plastic cast (the arteries were filled with Araldite CY233 plastic resin after which the organic tissues were corroded); thereafter we constructed a theoretical arterial tree having the same volume as the renal one. From this simplified tree, we were able to calculate its fractal dimension. The complete process of constructing the theoretical arterial tree and the subsequent calculation of its fractal dimension was carried out automatically by way of a computer programme to which we have given the name fractal program.     

Hydration of the compact and extended forms of pFh fragments from IgG3 Kuc and Sur

It has been shown using scanning microcalorimetry and densitometry that partial specific heat and specific partial volume of two pFh fragments of IgG3 increase during the decay of its tertiary structure, the secondary structure, the double poly-L-proline helix, being unchanged. This effect may be explained by a high degree of hydration, which increases on globule decompactization due to increased accessibility of peptide groups of the helix to solvent.     

Application of Bifidobacterium strains to the breadmaking process

The possible use of bifidobacterial strains from different origin (adult and infant humans, and chicken) as novel starter cultures for breadmaking was evaluated. Fermentative parameters of doughs (pH, volume, total titrable acidity [TTA], lactic and acetic acids production and rheofermentative parameters) and technological parameters of breads (specific volume, bread shape and crumb hardness) were analyzed. Human bifidobacterial strains could replace Lactobacillus strains, commercialized for breadmaking, as they yielded breads with similar characteristics but with the advantage of having softer crumbs. Important differences between the behavior of chicken bifidobacterial strains and human bifidobacterial strains were found when comparing bread TTA, bread shape and bread volume. Breads made with chicken strains showed significantly lower (p < 0.05) specific bread volume than those made with human strains, while showing similar values of TTA. The effects observed when using bifidobacterial strains from different origin as novel starter cultures for breadmaking seemed to depend on the strain and its origin.     

Model of Red Blood Cell Rotation in the Flow toward a Cell Sizing Orifice: Application to Volume Distribution

The rotation of human red blood cells (RBC) as they flow in the shear field established by a Coulter type orifice is modeled. This model, based on hydrodynamics of ellipsoid rotation in laminar creeping flow, is used to calculate the probability of the cells entering the orifice with a specific orientation. The electrical resistance change produced by a cell passing through the orifice of an electronic cell volume detector is the product of an orientation-dependent shape factor and the cell volume. This paper presents a method to calculate the shape factor probability distribution which can be used to predict its effect on the cell volume distribution. Experimental results confirm the theoretical prediction that the right skewness of resistance change distributions is in part a result of the nonspherical shape of red cells.     

Two-tank suspended growth process for accelerating the detoxification kinetics of hydrocarbons requiring initial monooxygenation reactions

An experimental evaluation demonstrated that suspended growth systems operated in a two-tank accelerator/aerator configuration significantly increased the overall removal rates for phenol and 2,4-dichlorophenol (2,4-DCP), aromatic hydrocarbons that require initial monooxygenations. The accelerator tank is a small volume that receives the influent and recycled biomass. It has a high ratio of electrondonor (BOD) to electron acceptor (O₂). Biomass in the accelerator should be enriched in reduced nicotinamide adenine dinucleotide (NADH + H⁺) and have a very high specific growth rate, conditions that should accelerate the kinetics of monooxygenation reactions. For the more slowly degraded 2,4-DCP, the average percentage removal increased from 74% to 93%, even though the volume of the two-tank system was smaller than that of the one-tank system in most experiments. The average volumetric and biomass-specific removal rates increased by 50% and 100%, respectively, in the two-tank system, compared to a one-tank system. The greatest enhancement in 2,4-DCP removal occurred when the accelerator tank comprised approximately 20% of the system volume. Biomass in the accelerator tank was significantly enriched in NADH + H⁺ when its dissolved oxygen (DO) concentration was below 0.25 mg/L, a situation having a high ratio of donor to acceptor. The accelerator biomass had its highest NADH + H⁺ content for the experiments that had the highest rate of 2,4-DCP removal. Biomass in the accelerator also had a much higher specific growth rate than in the aerator or the system overall, and the specific growth rate in the accelerator was inverselycorrelated to the accelerator volume.     

Cell shrinkage triggers the activation of mitogen-activated protein kinases by hypertonicity in the rat kidney medullary thick ascending limb of the Henle's loop. Requirement of p38 kinase for the regulatory volume increase response

The kidney medulla is exposed to very high interstitial osmolarity leading to the activation of mitogen-activated protein kinases (MAPK). However, the respective roles of increased intracellular osmolality and of cell shrinkage in MAPK activation are not known. Similarly, the participation of MAPK in the regulatory volume increase (RVI) following cell shrinkage remains to be investigated. In the rat medullary thick ascending limb of Henle (MTAL), extracellular hypertonicity produced by addition of NaCl or sucrose increased the phosphorylation level of extracellular signal-regulated kinase (ERK) and p38 kinase and to a lesser extent c-Jun NH(2)-terminal kinase with sucrose only. Both hypertonic solutions decreased the MTAL cellular volume in a dose- and time-dependent manner. In contrast, hypertonic urea had no effect. The extent of MAPK activation was correlated with the extent of MTAL cellular volume decrease. Increasing intracellular osmolality without modifying cellular volume did not activate MAPK, whereas cell shrinkage without variation in osmolality activated both ERK and p38. In the presence of 600 mosmol/liter NaCl, the maximal cell shrinkage was observed after 10 min at 37 degrees C and the MTAL cellular volume was reduced to 70% of its initial value. Then, RVI occurred and the cellular volume progressively recovered to reach about 90% of its initial value after 30 min. SB203580, a specific inhibitor of p38, almost completely inhibited the cellular volume recovery, whereas inhibition of ERK did not alter RVI. In conclusion, in rat MTAL: 1) cell shrinkage, but not intracellular hyperosmolality, triggers the activation of both ERK and p38 kinase in response to extracellular hypertonicity; and 2) RVI is dependent on p38 kinase activation.     

Improving wood quality in the western gulf forest tree improvement program: the problem of multiple breeding objectives

Currently, both industrial and private landowners in the Western Gulf Forest Tree Improvement Program (WGFTIP) area are compensated for their timber primarily based on the weight or volume of green wood reaching the mill gate. This places an immediate economic focus on adaptability and volume growth. However, selection for volume growth alone could result in decreased wood quality over time. Wood quality characteristics including stem straightness, wood specific gravity, and microfibril angle have either neutral or slightly unfavorable genetic correlations with volume growth in the WGFTIP loblolly pine (Pinus taeda L.) program. Since most WGFTIP members also consider wood quality an important selection criterion, the WGFTIP must define the best possible set of selection criteria given that (1) no single set of breeding objectives can be considered optimal for multiple products and (2) improvement in wood quality has no readily recognized economic importance in the existing market. To meet this challenge, the WGFTIP has implemented different strategies for its mainline breeding and deployment populations. In the mainline population, consistent breeding and selection criteria are used across members, while in the various deployment populations, selections are tailored to meet the specific needs of each member. The WGFTIP is also developing an elite wood quality population (WQEPop) based on backward selection. For the WQEPop to be successful, the economic importance of improved wood quality must be recognized, and landowners must be compensated for growing higher quality timber, especially if this results in reduced volume production. Improved methodology for within-family selection and for wood quality trait measurement is also important.     

Changes in the anatomical structure of the first two leaves of barley caused by the absence of nitrogen or phosphorus in the nutrient medium

The absence of nitrogen or phosphorus in the nutrient medium affected quantitative anatomical characteristics of the first two leaves of spring barley: nitrogen deficiency brought about changes in both the leaf size and characteristics of stomata, whereas the effect of phosphorus absence was insignificant. N deficiency had an opposite effect on certain characteristics connected with volume ratios of tissues than that of P. The most marked finding is the decrease in the leaf volume and specific volume, and in specific volumes of most tissues at N deficiency and their increase at P deficiency. On the other hand, the number of stomata per unit leaf or photosynthetic tissue volume increased as the result of N deficiency and decreased at P deficiency.     

Effect of Nutrient Concentration on the Growth of Escherichia coli

The relationship between specific growth rate of Escherichia coli and the concentration of limiting nutrient (glucose or phosphate or tryptophan) has been determined for populations in a steady state. At high concentrations the specific growth rate is independent of the concentration of nutrient, but at low concentrations the specific growth rate is a strong function of the nutrient concentration. Such a relationship was predicted by Monod; however, Monod's equation does not predict the relationship over the entire range of nutrient concentration. If parameters of the equation are estimated from the results obtained at low concentrations, then at high concentrations of nutrient, the specific growth rate is significantly higher than that predicted by Monod's equation. These results were interpreted on the basis that the rate of growth is controlled by at least two parallel reactions and that the affinities of the enzymes catalyzing these reactions are different. The relationship between specific growth rate and mean cell volume was also measured, and the results indicate that mean cell volume depends not only on the specific growth rate but also on the nature of the limiting nutrient. There are different mean cell volumes at the same specific growth rate established by different limiting nutrients. Therefore, the mean cell volume is not uniquely determined by the specific growth rate.     

Resources of regeneration in planarians

We studied the intensity of blastema growth in operated planarians at an early stage of regeneration as a function of the following factors: area of regenerate and its function and number of regeneration foci (volume of regeneration). There was no direct dependence between the intensity of regeneration and the size of regenerating fragment, as well as the volume of regeneration. Some specific features of the early stage of regeneration have been described, which suggest its determinate character. The behavior of neoblasts during formation of blastemas with different localization is discussed.     

Resources of regeneration in planarians

We studied the intensity of blastema growth in operated planarians at an early stage of regeneration as a function of the following factors: area of regenerate and its function and number of regeneration foci (volume of regeneration). There was no direct dependence between the intensity of regeneration and the size of regenerating fragment, as well as the volume of regeneration. Some specific features of the early stage of regeneration have been described, which suggest its determinate character. The behavior of neoblasts during formation of blastemas with different localization is discussed.     

Numerical analysis for determination of the presence of a tumor and estimation of its size and location in a tissue

This article deals with the numerical analysis to ascertain the presence of a tumor and to estimate its size and location in a tissue. Heat transfer in the tissue is modeled using the Pennes bioheat transfer equation, and is solved using the finite volume method. Consideration is given to 1-D brain and breast tissues. Temperature distributions in the tissues are specific to the tumor grades, its locations and sizes, and these are different than that of a normal tissue. With temperature distribution known a priori, estimations of the position and the size of a tumor are done using the inverse analysis. The proposed approach gives a correct estimation of the presence of a tumor and its location and size.     

Immobilization of lipases onto the SBA-15 mesoporous silica

Lipase is an important enzyme which can catalyse the hydrolysis of lipids and has several applications and industrial potentials. In addition, different types of lipases are used as efficient catalysts in the enantioselective esterification and/or hydrolysis reactions and produce products in high yields and enantio excess as well. However, immobilization of lipases on the surface of a heterogeneous substrate is necessary to improve its specific catalytic activities as it can be isolated from the reaction mixture easily. Mesoporous silica materials are the best option for this aim due to their high specific surface area, ordered structure, and large pore volume. Hence, in this article, the role of SBA-15 and the modified SBA-15 mesoporous materials as support for different lipases and their catalytic activities are reviewed.     

Paper Chromatographic Techniques for the Determination of Cephalothin and Desacetylcephalothin in Body Fluids

Paper chromatographic procedures may be used to detect cephalothin and its metabolite desacetylcephalothin in urine, plasma, synovial fluid, and cerebrospinal fluid. Protein-bound antibiotics are released from plasma, cerebrospinal fluid, and synovial fluid by dilution with an equal volume of dimethylformamide. Data are presented on the sample preparation, paper chromatographic system, and other specific techniques.