Virtual musculo-skeletal model for the biomechanical analysis of the upper limb

In this paper, a musculo-skeletal model of the upper limb is presented. The limb is modelled as a three-dimensional 7 degrees-of-freedom system, linked to the shoulder, which has been considered as frame. The upper limb model is made up of four links corresponding to the most important body segments: the humerus, the ulna, the radius and the hand, considered as a single rigid body. Particular attention has been paid to the modelling of joints in order to mimic all the possible arm and forearm movements (including prono-supination). The model also includes 24 muscles. The mathematical model used to describe the muscles is that proposed by Zajac in 1989, modified by the authors. The kinematic analysis has been performed including an ergonomics index to take into account the posture and joint physical limits. Moreover an optimization criterion based on minimum activation pattern has been included in order to find muscular activation coefficients. The results of the proposed methodology concerning muscular activations have been compared to those coming from processed EMG signals, which have been acquired during experimental tests.     

Isolation and characterization of a new bacillary phytase

From cell lysates of a recombinant Escherichia coli strain, Bacillus ginsengihumi phytase has been isolated and studied for the first time. The enzyme has been purified to homogeneity, and its primary structure has been determined. It has been concluded that phytase belongs to the class of β-propeller phosphatases. The molecular weight of the protein is 41 kDa, and pI is 4.8. Some physicochemical properties of the enzyme have been investigated.     

Mass and energy balance analyses of a downdraft gasifier

An empirical stoichiometric equation has been developed for wood chip gasification in a commercial-scale moving bed downdraft gasifier. The equation is based on an analysis of experimental overall and elemental material balance data obtained with the gasifier. A thermodynamic analysis of the gasifier has also been performed, based on the resultant empirical stoichiometric equation. The first-law and second-law thermodynamic efficiencies of the gasifier have been evaluated for four different operating modes at three different output temperatures.The resultant empirical stoichiometry is in agreement with the means of the experimental data within one standard deviation. The highest first-law and second-law thermodynamic efficiencies have been obtained when all products are considered useable; they are 90% and 62%, respectively. The lowest first-law and second-law efficiencies have been obtained when cool dry gas is considered as the only useable product; they are 72% and 53%, respectively. The heat loss from the system to the surroundings has been estimated to be 10% of the energy input; this corresponds to a loss of 7% of the available energy input. The available energy dissipation in the system, due to the various irreversibilities of the gasification process, has been evaluated to be 31% of the available energy input. This dissipation is not recoverable and reflects the nature of the process.     

Characterization of non-linear behaviour of an animal membrane using electro-kinetic studies

Electro-kinetic studies of water, aqueous solutions of urea, thiourea, glucose, creatinine and urine solution across urinary bladder membranes of goat have been used to explain non-linear behaviour. It has been found that fluxes are non-linearly related with forces. The structure of the membrane is a decisive factor when the range of driving forces is not too high. Stability of the steady state has also been examined and has been found to remain quite stable even in non-linear regions. The results have been examined using the methodology of non-equilibrium thermodynamics.     

Atherogenesis: a dysimmune disease

The immuno-inflammatory response is central to the development of atherosclerosis. The important players of the adaptive immune system are all involved in this pathologic process. Several antigens have been identified these last years and they are mostly self-molecules that have been modified due to the complex microenvironment that is generated within the diseased artery. Pro-atherogenic autoreactive T cells have been characterized. The presence of auto-reactive natural antibodies has also been confirmed in the lesions. All these, together with the data showing that adoptive transfer of lymphocytes is able to modulate the disease, fulfill the criteria put forth by Witebsky and Rose to define a disease as being autoimmune. However, the complexity of the disease process extends to the immune system. Although T cells are known to be pro-atherogenic, B cells have been clearly shown to be athero-protective. The fine balance between the two extensions of the adaptive immune response is the key to a successful therapeutic approach towards atherosclerosis.     

奇异果甜蛋白及其基因工程

奇异果甜蛋白(thaumatin)是迄今为止最甜的物质之一,对其研究具有很重要的意义。奇异果甜蛋白的生化性质基本清楚,基因序列和氨基酸序列都已测定。它的甜味可能是由奇异果甜蛋白上特定基团和受体结合引起的。对奇异果甜蛋白的生理功能知之甚少。近二十年来,在奇异果甜蛋白的基因工程上取得了一定进展,但仍然存在许多困难。 Abstract:Thaumatin is one of the sweetest substances known to date,it is important to study the thaumatin.The biochemical properties of thaumatin have been clarified clearly.Thaumatin had been isolated and sequenced.The mechanism of the sweetness of thaumatin may be due to the combination of some special groups and the receptors.The exact function of thaumatin is still not clear.Although gene engineering of thaumatin has been carried out for 20 years,there are still some difficulties to be solved for using in the market.     

VALSA EUGENIAE IN RELATION TO THE SUDDEN-DEATH DISEASE OF THE CLOVE TREE (EUGENIA AROMATICA)

The sudden-death disease of the clove tree is invariably associated with the fungus Valsa eugeniae. The pathogenicity of this fungus has been investigated experimentally, and it has been shown that it is a primary parasite on mature clove trees, that saplings are resistant to it, and that seedlings are immune. It has been experimentally demonstrated that water-borne spores of the fungus can invade the absorbing and the fibrous roots of the clove tree. The slow-decline disease, which affects clove saplings only, is associated with a slow and progressive root-rot over a period of many years. Valsa is also invariably associated with this disease, which occurs only in areas which have been replanted after the previous stand has been killed by sudden death. It is thought that slow decline is the symptom-expression of Valsa attack on young trees when these still retain some measure of juvenile resistance to it.     

Molecular cloning and characterization of the purE operon of Escherichia coli

The purE operon of Escherichia coli has been cloned and localized to a 1.7-kb HpaI fragment. The operon has been further characterized by subcloning into the lac fusion vector, pMC1403, and by the construction of BAL 31-generated deletions. The purE regulation region has been identified by assay of beta-galactosidase produced by pur-lac fusion plasmids and by RNA polymerase binding to end-labelled restriction fragments. Two purE promoters have been identified; one strong that is regulated by purines, the other weaker which is not regulated. The latter may be internal to the purE1 structural gene.     

The organization of capsaicin-sensitive visceral afferent systems

It has become clear that a number of neuropeptides are found in sensory nerves, some of which have been identified in visceral afferents. The best studied peptide is substance P, which has been localized in a population of capsaicin-sensitive visceral afferents. It has been established that there are a varied proportion of substance P-containing afferents in different visceral structures. In general, the peripheral termination of these nerves is around blood vessels. The central terminations of visceral afferents are in laminae I and V in the dorsal horn of the spinal cord. Substance P has been localized in these laminae and appears to be capsaicin-sensitive and therefore of sensory origin. Recently, substance K, which is derived from the same gene as substance P, has been found in visceral structures. Calcitonin gene-related peptide has been found in certain viscera to be contained in capsaicin-sensitive nerves. The contribution that other peptides make to visceral afferent innervation is not known.     

A study of the auxins in cabbage using countercurrent distribution

The counter-current distribution technique has been applied to the study of the identity of the auxins present in fresh cabbage. The results indicate that the major fraction of the auxin activity is probably due to 3-indoleacetic acid, but this is not established conclusively. In addition to the material presumed to be 3-indoleacetic acid, two other biologically active fractions were obtained from cabbage. Whether these are other auxins or “precursors” of 3-indoleacetic acid has not been established. It has been demonstrated that the colorimetric test which has been used by other workers is not specific for 3-indoleacetic acid, and conclusions which have been based on the use of this test must be reconsidered.     

The gel matrix of gastric mucus is maintained by a complex interplay of transient and nontransient associations

The gel nature of mucus is fundamental to its physiological functions; however, the structure of the mucus gel matrix is unclear. Here, small and large deformation rheology has been used to investigate the physical nature of the gel matrix and the forces that maintain this matrix in pig gastric mucus. The gelation process in mucus has been shown to be comparable with that of other polymer gel systems. Nongelling portions of mucin have been identified within the gel network, and the importance of transient, relaxable interactions to the maintenance of the mucus gel matrix has been demonstrated. The structure of the mucus gel matrix is considered in relation to the functional properties of mucus gels.     

Conformational fluctuation of native-like and molten-globule-like cytochrome c observed by time-resolved hole burning

Nanosecond to millisecond conformational fluctuations of Zn-substituted cytochrome c (ZnCytc) have been studied by the time-resolved transient hole-burning method. The investigation of low-temperature dynamics has been made on the ZnCytc solution sample in a water-glycerol mixture. The conformational fluctuations in the native-like and the molten-globule (MG)-like states have been compared for the aqueous solution samples at room temperature. ZnCytc in the MG-like state has been prepared by adding 200 mM NaClO4 to the protein solution with a pH of 2.1, and the formation of the MG-like state has been confirmed by both the far-UV CD and the visible absorption spectra. The hole spectrum of ZnCytc has been found to consist of two nearly degenerate components, that is, the Qx and Qy bands. The temporal change in the Qx component hole spectrum has been extracted by fitting the observed hole spectrum to the three-Gaussian form. The experimental results for ZnCytc dissolved in a water-glycerol mixture have revealed that the conformational fluctuation of ZnCytc is suppressed around 200 K, which is nearly the same temperature as the glass-like transition point of Zn-substituted myoglobin (ZnMb) and also as the glass-transition point of the solvent. This supports the idea of the solvent-induced glass-like transition of a protein. It has been also found that at physiological temperatures the time scale of the conformational fluctuation of ZnCytc lies around a few tens of nanoseconds, which is 2-3 orders of magnitude faster than that of ZnMb. The experimental results for the aqueous solution samples have shown that the difference between the native-like and the MG-like states is not conspicuous. However, they are indicative of the appearance of the slower conformational fluctuation in the MG-like state.     

Importance of scaling exponents and other parameters in growth mechanism: an analytical approach

The growth process of a living organism is studied with the help of a mathematical model where a part of the surplus power is assumed to be used for growth. In the present study, the basic mathematical framework of the growth process is based on a pioneering theory proposed by von Bertalanffy and his work is the main intellectual driving force behind the present analysis. Considering the existence of an optimum size for which the surplus power becomes maximum, it has been found that the scaling exponent for the intake rate must be smaller than the exponent for the metabolic cost. A relationship among the empirical constants in allometric scaling has also been established on the basis of the fact that an organism never ceases to generate surplus energy. The growth process is found to continue forever, although with a decreasing rate. Beyond the optimum point the percentage of shortfall in energy has been calculated and its dependence on scaling exponents has been determined. The dependence of optimum mass on the empirical constants has been shown graphically. The functional dependence of mass variation on time has been obtained by solving a differential equation based on the concept of surplus energy. The dependence of the growth process on scaling exponent and empirical constants has been shown graphically.     

1, 4-alpha-Glucan phosphorylase from Klebsiella pneumoniae purification, subunit structure and amino acid composition.

1. A 1,4-alpha-glucan phosphorylase from Klebsiella pneumoniae has been purified about 80-fold with an over-all yield greater than 35%. The purified enzyme has been shown to be homogeneous by gel electrophoresis at different pH-values, by isoelectric focusing, by dodecylsulfate electrophoresis and by ultracentrifugation. 2. The molecular weight of the native enzyme has been determined to be 180 000 by ultra-centrifugation studies, in good agreement with the value of 189 000 estimated by gel permeation chromatography. 3. The enzyme dissociates in the presence of 0.1% dodecylsulfate or 5 M guanidine hydrochloride into polypeptide chains. The molecular weight of these polypeptide chains has been found to be 88 000 by dodecylsulfate polyacrylamide gel electrophoresis and 99 000 by sedimentation equilibrium studies, indicating that the native enzyme is composed of two polypeptide chains. 4. The enzyme contains pyridoxalphosphate with a stoichiometry of two moles per 180 000 g protein, confirming that the 1,4-alpha-glucan phosphorylase from Klebsiella pneumoniae is a dimeric enzyme. 5. The amino acid composition of the enzyme has been determined, and its correspondence to that of 1,4-alpha-glucan phosphorylases from other sources is discussed. 6. The pI of the enzyme has been shown to be 5.3 and its pH-optimum to be about pH 5.9. The enzyme is stable in the range from pH 5.9 to 10.5.     

Azotobacter vinelandii ferredoxin I: cloning, sequencing, and mutant analysis

The structure of Azotobacter vinelandii ferredoxin I (AvFdI) has been extensively characterized by a variety of techniques. Although its physiological function is unknown, it has long been implicated as being involved in electron donation to nitrogenase. Here we report that the AvFdI gene (fdxA) has been cloned from an EcoRI digest lambda library using a synthetic oligonucleotide probe and that its sequence has been determined. The amino acid sequence deduced from the DNA sequence is identical to the previously published protein sequence. Analysis of the promoter region indicates that AvFdI is not a nif specific gene product. A mutant of A. vinelandii has been constructed which is identical to the wild-type, at the DNA level, except that the fdxA gene has been interrupted by insertion of a kanamycin cartridge. This mutant, called LM100, does not synthesize AvFdI but does synthesize the Fe and MoFe proteins of nitrogenase and grows at wild-type rates under N2-fixing conditions. This demonstrates that AvFdI is not required for N2 fixation by A. vinelandii. There is a small acidic protein, which is present in wild-type A. vinelandii, whose level is dramatically increased in LM100. The nature of this protein is under further investigation.     

Structural-functional organization of R-plasmid pBS222 with a broad range of bacterial hosts

The broad host-range plasmid pBS222 is compatible with broad host-range plasmids of all known incompatibility groups and codes for tetracycline resistance. pBS222 is efficiently mobilized by Inc P-1 plasmid RP4 and is also capable of conjugal transfer with low efficiency to different gramnegative microorganisms. The size of the plasmid (17.2 Kb) has been determined and its physical map has been constructed. The plasmid harbours the unique sites for restriction endonucleases BglII, HindIII, HpaI, KpnI, SmaI and XbaI cleawage. The plasmid derivatives pBS352-pBS355 have been obtained that carry kan- and cam-determinants in addition to tet-gene. Plasmid pBS355 has been used to clone EcoRI-fragments of phage lambda DNA. The plasmid pBS222 regions essential for replication and maintenance have been localized by DNA hybridization analysis of its mini-derivatives pBS356 and 357. pBS222 is a convenient model for investigations of the plasmid replication and maintenance mechanisms in different bacterial hosts as well as for the construction of broad host-range vectors.     

Influence of polymerization of D-amino acid oxidase on the behavior of the enzyme immobilized on chitosan by covalent fixation

D-Amino-acid oxidase is a flavoprotein using FAD as cofactor. The enzyme has been immobilized in the presence of FAD on a non-porous matrix: chitosan. This support is covalently bound to the enzyme with glutaraldehyde as cross-linking reagent. It is characterized by a good mechanical resistance to mechanical stirring. The enzymatic assays have been performed in batch reactor with D-phenylglycine as substrate by a spectrophotometric method which is based on the variation of the absorbance at 252 or 280 nm. The behaviour of the biocatalysts has been studied during repeated assays of 1 h at 25 degrees C in the absence of exogenous FAD. The experimental results have been compared with those obtained with the soluble enzyme tested in the presence or in the absence of FAD. The dependence of D-amino-acid oxidase on FAD concentration has been studied. Immobilized enzyme on chitosan appears to be less sensitive to the association-dissociation equilibrium of FAD. This property and the capacity of the enzyme to polymerize spontaneously in solution according to the experimental conditions have been established. The fact that the enzyme can exist in various oligomeric forms is of major importance because its catalytic expression is dependent of this phenomenon. The polymerization is known to be responsible for a decrease of the maximal rate V of the enzyme. It has also been shown that in the same way this decrease was accompanied by an improvement of the affinity of enzyme for substrates. Furthermore, the value of the dissociation constant of the apoenzyme-FAD complex is significantly smaller as the degree of polymerization is high. The conclusion is that the dissociation of the cofactor can be avoided if the immobilization step is carried out at high concentration of enzyme which is favourable to its polymerization.     

Influence of secondary reactions on the synthetic efficiency of DHAP-aldolases

The effect of secondary reactions on DHAP-dependent aldolase stereoselective synthesis yields is reported. The fuculose-1-phosphate aldolase catalyzed synthesis between DHAP and Cbz-S-alaninal has been chosen as case study. It has been demonstrated that DHAP is not only chemically degraded in the reaction medium, but also enzymatically. The last reaction has been shown to take place when type II aldolases are used as biocatalysts. In order to minimize the effect of non-desired reactions, temperature reduction has been shown to be favorable, and operation at 4 degrees C has been chosen as appropriate. On the other hand, the fed-batch addition of DHAP also increased the synthesis yields and, combined with low temperature, led to almost quantitative conversion.