Hydraulic permeability of meniscus fibrocartilage measured via direct permeation: Effects of tissue anisotropy,water volume content,and compressive strain

Hydraulic permeability is an important material property of cartilaginous tissues, governing the rate of fluid flow, which is crucial to tissue biomechanics and cellular nutrition. The effects of strain, anisotropy, and region on the hydraulic permeability in meniscus tissue have not been fully elucidated. Using a one-dimensional direct permeation test, we measured the hydraulic permeability within statically compressed porcine meniscus specimens, prepared such that the explants were in either the axial or circumferential direction of either the central or horn (axial direction only) region of the medial and lateral menisci. A constant flow was applied and the pressure difference was measured using pressure transducers. Specimens were tested under 10–20% compressive strain. Permeability values were in the range of 1.53–1.87 × 10⁻¹⁵ m⁴/Ns, which is comparable to values found in the literature. Permeability was significantly anisotropic, being higher in the circumferential direction than in the axial direction. Additionally, there was a significant negative correlation between strain level and permeability for all groups. Lastly, no statistically significant difference was found between permeability coefficients from different regional locations. This study provides important information regarding structure-function relationships in meniscal tissues that helps to elucidate biomechanics and transport in the tissue, and can aid in the understanding of the tissue’s role in the function of the knee joint and onset of osteoarthritis.     

Influence of stem lacunar structure on gas transport: relation to the oxygen transport potential of submersed vascular plants

The influence of stem lacunar structure on the potential of diffusion and mass flow to meet estimated root O₂ demands was evaluated and compared in four submersed aquatic plant species. Internodal lacunae formed large continuous gas canals which were constricted at the nodes by thin, perforated diaphragms. Gas transport studies showed that nodes had little effect on diffusion, but significantly reduced mass flow. Measured diffusive resistances approximated those predicted by Fick's first law, ranged from 203 to 5107 × 10⁸ s m⁻⁴ and increased as lacunar area decreased in Potamogeton praelongus, two Myriophyllum species and Elodea canadensis. Our analysis suggested that diffusion could satisfy estimated root O₂ demands given the development of relatively steep O₂ gradients (0.15–0.35 mol O₂ mor⁻¹ per 0.5 m stem) between shoots and roots. Plants with high resistances (e.g. > 750 × 10⁸ s m⁻⁴) and long lacunar pathlengths may be unable, even during active photosynthesis, to support the O₂ demands of a large root system by diffusion alone. Measured nodal resistances to mass flow approximated those predicted by Hagen-Poiseuille law and ranged from 46 to 2029 × 10⁸ Pa s m⁻³. Our analysis suggested that these resistances were quite low and that relatively small pressure differentials (< 150 Pa per 0.5 m stem) could drive mass flow at rates which would support root O₂ demands. Possible mechanisms whereby plant architecture may serve to maintain these pressure differentials are proposed.     

Analysis of phenolic compounds in health care products by low‐pressure liquid‐chromatography with monolithic column and chemiluminescent detection

This paper presents a new application for monolithic columns with low‐pressure chromatographic separation using an flow injection analysis configuration with chemiluminescent detection for the determination of a mixture of phenolic compounds: phloroglucinol, 2,4‐dihydroxybenzoic acid, salicylic acid, methyl paraben and n‐propyl gallate. The procedure consists of the separation of these compounds on a reverse‐phase ultra‐short monolithic column with pH 3.0 acetate buffer and 5% acetonitrile as carrier phase. The detection is based on a chemiluminescence measurement coming from Ce(IV)–Rhodamine 6G chemistry with the incorporation of two different chemiluminescent chemical conditions in the chromatographic setup in order to enhance the sensitivity for the different phenolic compounds. All separation and detection variables were optimized to propose a determination method. The analysis is performed in 280?s, with the sampling frequency being some 13 h^?1. The calibration function is a double reciprocal function obtaining good results within two orders of magnitude. The limits of detection were 8.8 × 10 ^?8 m (phloroglucinol), 2.7 × 10 ^?8 m (2,4‐dihydroxybenzoic acid); 2.3 × 10 ^?8 m (salicylic acid); 5.2 × 10 ^?8 m (methyl paraben) and 4.1 × 10 ^?6 m (n‐propyl gallate), and the relative standard deviations at a medium level of the linear range were 4.4% (phloroglucinol), 2.8% (2,4‐dihydroxybenzoic acid), 5.2% (salicylic acid), 3.6% (methyl paraben) and 6.8% (n‐propyl gallate). The method was applied and validated satisfactorily for the determination of these compounds in healthcare products, comparing the results against an HPLC reference method. Copyright © 2009 John Wiley & Sons, Ltd.     

Permeability evaluation of 45S5 Bioglass®-based scaffolds for bone tissue engineering

Permeability is a key parameter for microstructural design of scaffolds, since it is related to their capability for waste removal and nutrients/oxygen supply. In this framework, Darcy's experiments were carried out in order to determine the relationship between the pressure drop gradient and the fluid flow velocity in Bioglass^®-based scaffolds to obtain the scaffold's permeability. Using deionised water as working fluid, the measured average permeability value on scaffolds of 90–95% porosity was 1.96×10^?9 m². This value lies in the published range of permeability values for trabecular bone.     

Optimum capillary number for oxygen delivery to tissue in man

The optimum number of total capillaries in the whole human body was estimated from the analysis of the efficiency for oxygen (O₂) transport in the vascular-tissue system. We used a tissue model composed of uniform spheres in which O₂ diffuses from the capillary located at the centre of each sphere towards the surrounding tissue consuming O₂ at a constant rate. The tissue mass supplied by a single capillary was estimated as the area of positive O₂ concentration under a given condition of capillary flow and O₂ consumption rate. Total tissue mass was determined as the function of the capillary numbern and the total blood flow. On the other hand, the energy cost required to maintain the vascular system withn terminals was assessed by using the minimum volume model (Kamiya and Togawa,Bull. math. Biophys. 34, 431–438, 1972). The efficiency of the entire vascular-tissue system was evaluated by calculating the ratio of total tissue mass/cost function. The result of the calculation using physiological data of cardiac output and O₂ consumption for an average human adult during a heavy exercise revealed the maximum efficiency occurring at the capillary number 3.7×10¹⁰ which coincided well with its normal range of physiological estimates (3.2×10¹⁰–4.2×10¹⁰). We concluded that the entire vascular-tissue system is constructed so as to attain the highest efficiency in O₂ transport at its maximum activity.     

Selective determination of human immunoglobulin G by flow‐injection chemiluminescence

A novel flow‐injection chemiluminescence method was developed for the selective determination of human immunoglobulin G (IgG) in the presence of thiomersal by changing the flow rates of peristaltic pump. The study was based on the independence and additivity of the CL signals of human IgG and thiomersal in the galangin–potassium permanganate–polyphosphoric acid system. In meantime, two equations relating to the concentrations of mixing solutions of human IgG and thiomersal vs the CL intensity were established and solved, on the basis of which the content of thiomersal included in samples was simultaneously determined too. The enhanced CL intensity was in proportion to concerntrations in the range 8.0 × 10^?7 to 8.0 × 10^?5 g/mL for human IgG and 1.0 × 10^?7 to 2.0 × 10^?6 g/mL for thiomersal with the detection limits of 5.0 × 10^?7 g/mL for human IgG and 6.0 × 10^?8 g/mL for thiomersal, respectively. The relative standard deviation for 1.0 × 10^?5 g/mL human IgG was 0.8% and for 2.0 × 10^?7 g/mL thiomersal it was 2.0% (n = 10). The proposed method was applied to determine three synthetic samples with recoveries of 91.5–109.5%. In addition, the possible chemiluminescence mechanisms are discussed as well. Copyright © 2010 John Wiley & Sons, Ltd.     

A fully coupled fluid-structure interaction model of the secondary lymphatic valve

Abstract

The secondary lymphatic valve is a bi-leaflet structure frequent throughout collecting vessels that serves to prevent retrograde flow of lymph. Despite its vital function in lymph flow and apparent importance in disease development, the lymphatic valve and its associated fluid dynamics have been largely understudied. The goal of this work was to construct a physiologically relevant computational model of an idealized rat mesenteric lymphatic valve using fully coupled fluid-structure interactions to investigate the relationship between three-dimensional flow patterns and stress/deformation within the valve leaflets. The minimum valve resistance to flow, which has been shown to be an important parameter in effective lymphatic pumping, was computed as 268?g/mm⁴?s. Hysteretic behavior of the lymphatic valve was confirmed by comparing resistance values for a given transvalvular pressure drop during opening and closing. Furthermore, eddy structures were present within the sinus adjacent to the valve leaflets in what appear to be areas of vortical flow; the eddy structures were characterized by non-zero velocity values (up to ～4?mm/s) in response to an applied unsteady transvalvular pressure. These modeling capabilities present a useful platform for investigating the complex interplay between soft tissue motion and fluid dynamics of lymphatic valves and contribute to the breadth of knowledge regarding the importance of biomechanics in lymphatic system function.     

Errors Introduced in Radioligand Binding Studies Due to Displaceable,Cation Dependent, [3H]prazosin Binding to Glass-Fibre Filters and Glass Surfaces

Abstract

[³H]prazosin not only specifically and homogeneously labels α₁-adrenoceptors, but also binds to glass surfaces and non-linearly to the glass-fibre filters, commonly used in radioligand binding experiments. Binding to filters can be modulated by unlabeled α-adrenergic compounds and cations. If no correction is applied for displaceable filter binding, analysis of [³H]prazosin binding experiments leads to erroneous results. Analysis of [³H]prazosin saturation experiments on guinea-pig cerebral cortex membranes with correction for filter binding before the non-linear fit procedure indicated that [³H]prazosin labels a homogeneous population of α₁-adrenoceptors (R_tot: 8.33 fmol˙mg^?1 wet tissue) with a dissociation constant of 1.28×10^?10 M. However, analysis of the same data after correction for non-specific binding, (determined in parallel experiments by adding 10 μM phentolamine to the incubation medium) resulted in a best fit to a model in which [³H]prazosin labels two α₁-adrenoceptor subpopulations (R₁: 15.0 fmol˙mg^?1 and R₂: 14.6 fmol˙mg^?1 wet tissue) with dissociation constants of respectively 1.78×10^?10 and 5.63×10^?9 M. The discrepancy between the two methods of analysis is due to displacement of the radioligand from the filters by phentolamine.

Prazosin and oxymetazoline are also able to displace filter-bound [³H]prazosin. The extent to which displaceable filter binding distorts the proper results depends on the actual magnitude of the error and also on the method of analysis.     

Very high density of CHO cells in perfusion by ATF or TFF in WAVE bioreactor™. Part I. Effect of the cell density on the process

High cell density perfusion process of antibody producing CHO cells was developed in disposable WAVE Bioreactor? using external hollow fiber filter as cell separation device. Both “classical” tangential flow filtration (TFF) and alternating tangential flow system (ATF) equipment were used and compared. Consistency of both TFF‐ and ATF‐based cultures was shown at 20–35 × 10⁶ cells/mL density stabilized by cell bleeds. To minimize the nutrients deprivation and by‐product accumulation, a perfusion rate correlated to the cell density was applied. The cells were maintained by cell bleeds at density 0.9–1.3 × 10⁸ cells/mL in growing state and at high viability for more than 2 weeks. Finally, with the present settings, maximal cell densities of 2.14 × 10⁸ cells/mL, achieved for the first time in a wave‐induced bioreactor, and 1.32 × 10⁸ cells/mL were reached using TFF and ATF systems, respectively. Using TFF, the cell density was limited by the membrane capacity for the encountered high viscosity and by the pCO₂ level. Using ATF, the cell density was limited by the vacuum capacity failing to pull the highly viscous fluid. Thus, the TFF system allowed reaching higher cell densities. The TFF inlet pressure was highly correlated to the viscosity leading to the development of a model of this pressure, which is a useful tool for hollow fiber design of TFF and ATF. At very high cell density, the viscosity introduced physical limitations. This led us to recommend cell densities under 1.46 × 10⁸ cell/mL based on the analysis of the theoretical distance between the cells for the present cell line. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:754–767, 2013     

Glycolysis and glucose oxidation during reperfusion of ischemic hearts from diabetic rats

Stimulationg of glucose oxidation by dichloroacetate (DCA) treatment is beneficial during recovery of ischemic hearts from non-diabetic rats. We therfore determined whether DCA treatment of diabetic rat hearts (in which glucose use is extremely low), increases recovery of function of hearts reperfused following ischemia. Isolated working hearts from 6 week streptozotocindiabetic rats were perfused with 11 mM [2-³H/U-¹⁴C]glucose, 1.2 mM palmitate, 20 μU/ml insulin, and subjected to 30 min of no flow ischemia followed by 60 min reperfusion. Heart function (expressed as the product of heart rate and peak systolic pressure), prior to ischemia, was depressed in diabetic hearts compared to controls (HR × PSP × 10^?3 was 18.2 ± 1 and 24.3 ± 1 beats/mm Hg/min in diabetic and control hearts respectively) but recover to pre-ischemic levels following ischemia, whereas recovery of control of control hearts was significantly decreased (17.8 ± 1 and 11.9 ± 3 beats/mm Hg/min in diabetic and control hearts respectively). This enhanced recovery of diabetic rat hearts occurred even though glucose oxidation during reperfusion was significantly reduced as compared to controls (39 ± 6 and 208 ± 42 nmol/min/g dry wt, in diabetic and control hearts respectively). Glycolytic rate (³G₂O production) during reperfusion were similar in diabetic and control hearts (1623 ± 359 and 2071 ± 288 nmol/min/g dry wt, respectively). If DCA (1 mM) was added at reperfusion, hearts from control animals exhibited a significant improvement in function (HR × PSP × 10^? recovered to 20 ± 4 beats/mm Hg/min) that was accompanied by a 4-fold increase in glucose oxidation (from 208 ± 42 to 753 ± 111 nmol/min/g dry wt). DCA was without effect on functional recovery of diabetic rat hearts during reperfusion but did significantly increase glucose oxidation from 39 ± 6 to 179 ± 44 nmol/min/g dry wt). These data suggests that, unlike control hearts, low glucose oxidation rates are not an important factor in reperfusion recovery of previouskly ischemic diabetic rat hearts.     

西部欠发达地区生态经济系统能值分析——以青海省海西蒙古族藏族自治州为例

青海省海西蒙古族藏族自治州（简称海西州）生态环境脆弱,快速发展的工业活动对当地生态环境造成严重破坏。海西州地处青藏高原东北部,是我国重要的生态安全屏障之一,在全国生态建设中处于特殊地位。能值分析法是一种基于热力学理论的环境核算方法。利用能值分析法对海西州生态经济系统运行现状进行评估;并应用能值指标评价海西州生态经济系统的可持续发展水平;通过对能值指标的时间序列分析揭示海西州生态经济系统的发展趋势,以期为海西州生态经济系统的可持续发展提供参考依据。研究结果表明,2016年支撑海西州生态经济系统运行的总能值投入量为6.69×10²⁴ sej,是2010年总能值投入量的1.94倍。在2010-2016年的7年内,不可更新资源的能值投入占当年总能值投入量的比例均超过90%,而可更新资源能值投入量与从系统外输入到海西州的能值量占比均较低。基于能值的指标分析显示：海西州的人均能值使用量、能值密度、能值货币比率、环境负载率分别从2010年的8.84×10¹⁸ sej/人、1.15×10¹³ sej/m²、3.05×10¹⁴ sej/US$、103.02增加到2016年的1.65×10¹⁹ sej/人、2.22×10¹³ sej/m²、9.12×10¹⁴ sej/US$、213.47;而相应的能值产出率、能值可持续发展指数则分别从2010年的2.66×10³和25.84降低到2016年的1.23×10³和5.74。研究结果表明虽然海西州经济得到发展、人民生活质量得到提高,而经济发展对当地不可再生资源依赖较大,给环境造成的压力不断增加。为从长远角度实现海西州的可持续发展,亟需转变经济发展方式,降低对不可更新能源的过度开发。此外,研究结果显示,海西州的能值交换率小于1,这说明研究时间范围内,海西州在对外贸易过程中处于不利地位,因此需增加单位产品的附加值以促进能值流的合理流动。     

Separation of BSA through FAU-type zeolite ceramic composite membrane formed on tubular ceramic support: Optimization of process parameters by hybrid response surface methodology and biobjective genetic algorithm

In this study, Faujasite (FAU) zeolite was coated on low-cost tubular ceramic support as a separating layer through hydrothermal route. The mixture of silicate and aluminate solutions was used to create a zeolitic separation layer on the support. The prepared zeolite ceramic composite membrane was characterized using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), particle size distribution (PSD), field emission scanning electron microscopy (FESEM), and zeta potential measurements. The porosity of ceramic support (53%) was reduced by the deposition of FAU (43%) zeolite layer. The pore size and water permeability of the membrane were evaluated as 0.179?µm and 1.62?×?10^?7?m³/m²?s?kPa, respectively, which are lower than that of the support (pore size of 0.309?µm and water permeability of 5.93?×?10^?7?m³/m²?s?kPa). The permeate flux and rejection potential of the prepared membrane were evaluated by microfiltration of bovine serum albumin (BSA). To study the influences of three independent variables such as operating pressure (68.94–275.79?kPa), concentration of BSA (100–500?ppm), and solution pH (2–4) on permeate flux and percentage of rejection, the response surface methodology (RSM) was used. The predicted models for permeate flux and rejection were further subjected to biobjective genetic algorithm (GA). The hybrid RSM-GA approach resulted in a maximum permeate flux of 2.66?×?10^?5?m³/m²?s and BSA rejection of 88.02%, at which the optimum conditions were attained as 100?ppm BSA concentration, 2 pH solution, and 275.79?kPa applied pressure. In addition, the separation efficiency was compared with other membranes applied for BSA separation to know the potential of the fabricated FAU zeolite ceramic composite membrane.     

Biochemical properties of the 1 alpha, 25-dihydroxyvitamin D3 cytoplasmic receptors from human and chick parathyroid glands

Cytoplasmic receptors for 1α, 25-dihydroxyvitamin D₃ from human parathyroid adenoma tissue and rachitic chick parathyroid glands have been characterized with regard to a number of physical, chemical, and ligand binding properties. Both receptors are 3.6–3.7 S proteins with molecular weights of approximately 75,000 and Stoke's molecular radii of 36 Å. It was found that the receptors possess a cysteine residue in or near the 1α, 25-dihydroxyvitamin D₃ binding site which is critical for ligand binding activity. The receptors both have equilibrium dissociation constants for 1α, 25-dihydroxyvitamin D₃ in the range of 2 to 5 × 10^?10m at 4 °C and second-order association rate constants for their seco-steroid ligand of 1 × 10⁷, m^?1 min^?1 (0 °C). The dissociation rate constants were found to be 5.3 × 10^?4 min^?1 (4 °C) for the human receptor and 1.3 × 10^?5 min^?1 (4 °C) for the chick receptor. The great deal of similarity which exists between the cytoplasmic 1α, 25-dihydroxyvitamin D₃ receptors from avian and mammalian parathyroid glands suggests a homologous function for these molecules in the two tissues.     

S-adenosylmethionine pool size and turnover rate in sea urchin embryos determined from simultaneous measurements of amounts and specific activities.

A procedure is presented for the simultaneous measurement of the tissue pool size and specific activity of methyl-labeled S-adenosylmethionine (SAM). The method of Kopin and Baldessarini (1971) is used with the introduction of a reference amount of SAM, methyl-labeled with a second isotope to provide an isotope dilution by the tissue sample. The SAM pool sizes in two species of sea urchin embryo were approximately constant during development from blastula to gastrula, being 6.8 and 6.3 × 10^?14 moles/embryo at these respective stages for Strongylocentrotus purpuratus and 15.7 and 14.2 × 10^?14 moles/embryo for Lytechinus pictus. The rates of turnover of SAM in the gastrulae of these two species are at least 2.7 × 10^?15 and 5.2 × 10^?15 moles/min/embryo, respectively.     

Protein Metabolism in Cultured Plant Tissues

Rates of protein synthesis in normal callus tissues (either tight or loose morphological form), in crown gall callus tissues and in cultured pith cells were measured for both the lower surface cells (those in contact with the original growth medium) and upper surface cells (those never in contact with the growth medium until labeling). Cells of both surfaces of loose and crown gall callus and the upper-surface cells of tight callus had similar rates of protein synthesis, 29–31 mg of protein synthesized × (g protein)⁻¹× h⁻¹. The lower surface cells of tight callus had a 35% lower rate of synthesis, 20 mg × g⁻¹× h⁻¹. Pulse-chase experiments suggested that rates of protein degradation for all tissues were the same, 21–23 mg protein × (g protein)⁻¹× h⁻¹. Thus, there probably was no accumulation of protein in the lower surface cells of tight callus tissue, but the other tissues had rates of accumulation equaling 10 mg × (g protein)⁻¹× h⁻¹. Autoradiography and electron-microscopic examination of cells in tight callus labeled with ³H-leucine show that: (a) the lower-surface cells were more degenerate than cells within the callus or on the upper surface; and (b) the first few cell layers nearest the medium were preferentially labeled. Pulse-chase experiments were also used to quantitate the nonprecursor pool (defined as that tritium in the soluble amino acid pool that does not equilibrate with protein during a pulse-chase experiment). The nonprecursor pool increased linearly with time at the same rate as incorporation of ³H-leucine into protein. Furthermore, the nonprecursor pool copurified with leucine and was probably either D- or L-leucine.     

Flow-induced modulation of the permeability of endothelial cells cultured on microcarrier beads

The maintenance of endothelial barrier function is important in the regulation of fluid and solute balance between the vascular space and the surrounding tissue. Since fluid flow across endothelial cells stimulates a wide variety of endothelial responses, the effect of shear stress on barrier function was investigated. Bovine pulmonary artery endothelial cells were cultured on permeable microcarrier beads, placed in a chromatography column, and perfused. Indicator-dilution techniques were used to estimate the permeability of the cell-covered beads to low molecular weight tracers (sodium fluorescein—NaFlsc; cyanocobalamin—B12) as a function of flow rate through the column. Permeability values for both tracers were significantly increased (9.3 ± 0.6 to 19.3 ± 1.7 for NaFlsc; 8.2 ± 0.5 to 20.4 ± 3.1 for B12; mean ± SEM, × 10⁻⁵ cm/s, P < .05) when the flow rate was increased from 0.9 ml/min to 3.2 ml/min (corresponding to average shear stresses of 4.7 and 16.8 dynes/cm²). The permeability increase occurred within minutes of the flow increase, and was reversed by decreasing the flow rate to 0.9 ml/min. In the presence of cytochalasin D, the flow-induced permeability increase was not reversible. Neither inhibition of nitric oxide synthase (with N^G-monomethyl-L -arginine) nor inhibition of cyclooxygenase (with indomethacin) was capable of blocking the flow-induced permeability increase. These results indicate that the rapid modulation of endothelial barrier by flow in vitro is probably not due to prostacyclin or nitric oxide. © 1996 Wiley-Liss, Inc.     

The activation of diazinon by ganglia of the cockroach Periplaneta americana L. and its action on nerve conduction and cholinesterase activity

When sixth abdominal ganglia of the cockroach Periplaneta americana were irrigated continuously with diazinon solution in situ, its effects on nerve conduction and cholinesterase activity closely resembled those of diazoxon; spontaneous activity and after-discharge increased until conduction was blocked, which happened while some cholinesterase was still uninhibited. The symptoms were only slightly relieved by irrigating ganglia with saline. Though the LD50's of diazinon and diazoxon applied topically to adult male P. americana were similar (2.5 ± 0.33 and 4.5 ± 0.38 μig. per insect), diazoxon was about 300 times more active than diazinon against nerve function and cholinesterase activity in the sixth abdominal ganglion. This is probably because in the nerve preparations contact between the insecticide and the tissues surrounding the nerve cord, which in whole insects convert diazinon, a thionophosphate, into its phosphate analogue diazoxon, a more active anticholinesterase, was minimized. Indeed, taking into account the evidence of workers who previously compared in vitro the anticholinesterase activities of several thionophosphates with those of their phosphate analogues and found the phosphates much more active, the effect of diazinon on cholinesterase activity and nerve function in our experiments was unexpectedly great. By applying diazinon to nerve cords with SKF 525-A, a compound likely to prevent oxidation of diazinon to diazoxon, an attempt was therefore made to decide whether diazinon directly affected nerve conduction or whether the effect resulted either from its conversion to diazoxon within the nerve tissue or from impurities in the diazinon used. Results were inconclusive, for SKF 525-A (p-diethylaminoethyl diphenylpropylacetate hydrochloride) not only failed to prevent the inhibition of cholinesterase, but interfered with the action of both diazinon and diazoxon on nerve conduction, and itself affected nerve conduction when applied alone. The possibility that diazinon is itself a mild anticholinesterase was not excluded. SKF 525-A applied to sixth abdominal ganglia at 2 × 10^-4M blocked conduction from cereal nerves to giant fibres in 50–97 min. and at 4 × 10^-5M decreased the post-synaptic response; applied to giant fibres at 2 × 10^-4M it blocked conduction in 90–208 min. The effects of the larger concentration were not completely reversible. Although SKF 525-A has been widely used to study the metabolism of drugs, its direct effects on conduction in nerve axons seem not to have been noted previously.     

Effect of pressure on the sol-gel transition of carrageenans

The effects of pressure on the sol-gel transition of κ- and ι-carrageenans were studied in KCl solutions under high pressures up to 3000 kg/cm². The carrageenan gels were destabilized by pressure: the pressure depression of melting temperature, (dT/dP)_m, was ?5.7 × 10^?3 and ?4.0 × 10^?3 K cm²/kg independent of KCl concentration for κ- and ι-carrageenans, respectively. The enthalpy, entropy and volume changes accompanying the gel formation were calculated from the Eldridge-Ferry's plots and the Clausius-Clapeyron equation. The volume change per unit cross-link (two disaccharide residues) was estimated to be (2.5 ～ 4.9) and (1.7 ～ 3.4) ml/mol for κ- and ι-carrageenans, respectively. The compressibility of both carrageenan molecules appeared to be larger by (1.6 ～ 2.6) × 10^?12 (κ-form) and by (0.8 ～ 1.3) × 10^?12cm²/dyn (i-form) in gel state as compared with in sol state These increases in volume and compressibility on gelation were attributed to a reduction of water of hydration from the carrageenan molecules, which is mainly due to a replacement of the polymer-water hydrogen bond by the polymer-polymer hydrogen bond. These results seemed not inconsistent with the idea that a double helix structure of carrageenan gels may persist in solution as well as in the solid state.     

Adult Rat Mesenchymal Stem Cells Delay Denervated Muscle Atrophy

To evaluate the function of rat mesenchymal stem cells (rMSCs) on denervated gastrocnemius muscles and to address the role of ciliary neurotrophic factor (CNTF) in rMSCs, denervated Wistar rats were separately injected with culture media (sham control), CNTF protein, 2.5?×?10⁵ siCNTF-treated rMSCs, 2.5?×?10⁵ GFP-transfected rMSCs, or 2.5?×?10⁵ untreated rMSCs. Muscle function was assessed at different time points post-surgery. Tibial nerve and gastrocnemius muscle samples were taken at 4, 8, and 12?weeks for histochemistry, and neuromuscular junction repair was also examined by electron microscopy. Fluorescence immunocytochemistry on tissue sections confirmed neurotrophin expression in rMSCs but with little evidence of neuronal differentiation. The engraftment of rMSCs significantly preserved the function of denervated gastrocnemius muscle based both on evaluation of muscle function and direct examination of muscle tissue. Further, the density and depth of the junctional folds were visibly reduced 12?weeks after surgery and transplantation, especially in control group. Knockdown of CNTF expression in rMSCs failed to block muscle preservation, although administration of CNTF protein alone inhibited muscle atrophy, which indicating that delivery of rMSCs could preserve gastrocnemius muscle function following denervation and post-junctional mechanisms involved in the repairing capability of rMSCs.