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PubMed1988

Tendon transfer for median nerve palsy.

A large number of tendon transfers have been described that restore opposition to the thumb and provide thumb and finger flexion. To provide optimal results following tendon transfers, one needs to follow the principles of tendon transfer: normal tissue equilibrium, movable joints, and a scar-free bed. Once these are present, we must look to available tables to determine an appropriate tendon transfer, matching up the lost muscle mass, fiber length, and cross-sectional area and then pick out muscle-tendon units of similar size, strength, and potential excursion. For low median nerve palsy (Table 4), we have found from our experimental and clinical studies that the FDS of the long and ring fingers or the wrist extensors (ECR or ECRL) best approximate the force and motion required for full thumb opposition and strength. These transfers are preferred in median nerve palsy or combined median ulnar nerve palsy when both strength and motion are required. In circumstances where only thumb mobility is desired, the EIP is an ideal transfer. Also, the extensor digitorum quinti (EDQ) and ADQ have sufficient mean fiber length (muscle excursion) to provide full thumb opposition. The palmaris longus transfer (Camitz transfer) is an abduction rather than an opposition transfer and should be reserved for selected cases of long-term carpal tunnel syndrome. For high median nerve palsy (Table 5), transfers of the brachioradialis or ECRL to restore lost thumb flexion (FPL) and side-to-side transfer of the FDP of the index finger are generally sufficient. A separate transfer to restore independent flexion of the index finger could be performed by utilizing the pronator teres or extensor carpi radialis ulnaris tendon muscle units. As they combine a proper direction of action, pulley location, and tendon insertion, tendon transfers for median nerve palsy are usually quite successful. In considering any of these elective procedures, however, it is important to remember that tendon transfers are muscle balance operations. The effect of transfer on restoring function must be carefully studied to assess the loss of function that such a transfer may endure.

Hand↗

PubMed1977

[Metabolic disorders and current treatment of the surgical patient with pancreatitis].

Very frequently in acute and chronic pancreatitis, the surgical treatment is indispensable. The disease itself is accompanied by metabolic disturbances, protein deficiency, hepatic lesion, by diabetes and malabsorption syndrome. Following the laboratory parameters we were able to perform partial or total hyperalimentation, correction of acid-base dis-equilibrium and to obtain the positive nitrogen balance, and in this way keep the patients in optimal conditions pre- and postoperatively.

Acute Disease↗

PubMed1996

Tissue impedance as a function of temperature and time.

Tissue impedance dependence on temperature has been measured for six tissue types. The information was gathered using an automated laboratory under computer control. This information is needed to be able to input these values into a computer model that predicts temperature distribution produced by delivery of radio frequency energy. Due to the thermal dose of time and temperature, tissue properties change and no published data are available that document this. Since there are no theoretical predictions, empirical data were measured to supply this information. Using an aluminum cylindrical cavity of volume 1.69 cm3, muscle, liver, brain, and fat tissue impedance were measured at 500 kHz over a range of temperatures. All tests began at room temperature where baseline measurements were made. The cylinder was then placed in a constant temperature water bath at between 30 and 90 degrees C. The tests were run for a period of 10 to 30 minutes. Temperature homogeneity was carefully studied throughout the volume of the cylinder. It was found that thermal equilibrium occurred within four minutes. Special care was taken with the tissue sample in regard to optimize moisture and freshness, and minimize fat content. Grain orientation was also taken into consideration depending on the test. For all tissue types, resistivity decreased initially as the sample temperature equilibrated with the bath temperature. For temperatures less than 75 degrees C, resistivity values remained approximately constant over time.

Adipose Tissue↗

PubMed1977

Steady state kinetics and binding of eukaryotic cytochromes c with yeast cytochrome c peroxidase.

1. The steady state kinetics for the oxidation of ferrocytochrome c by yeast cytochrome c peroxidase are biphasic under most conditions. The same biphasic kinetics were observed for yeast iso-1, yeast iso-2, horse, tuna, and cicada cytochromes c. On changing ionic strength, buffer anions, and pH, the apparent Km values for the initial phase (Km1) varied relatively little while the corresponding apparent maximal velocities varied over a much larger range. 2. The highest apparent Vmax1 for horse cytochrome c is attained at relatively low pH (congruent to 6.0) and low ionic strength (congruent to 0.05), while maximal activity for the yeast protein is at higher pH (congruent to 7.0) and higher ionic strength (congruent to 0.2), with some variations depending on the nature of the buffering ions. 3. Direct binding studies showed that cytochrome c binds to two sites on the peroxidase, under conditions that give biphasic kinetics. Under those ionic conditions that yield monophasic kinetics, binding occurred at only one site. At the optimal buffer concentrations for both yeast and horse cytochromes c, the KD1 and KD2 values approximate the Km1 and Km2 values. At ionic strengths below optimal, binding becomes too strong and above optimal, too weak. 4. Under ionic conditions that are optimal and give monophasic kinetics with horse cytochrome c but are suboptimal for the yeast protein, yeast cytochrome c strongly inhibits the reaction of horse cytochrome c with peroxidase, uncompetitively at one site and competitively at a second site. The appearance of the second site under monophasic conditions is interpreted as an allosteric effect of the inhibitor binding to the first site. 5. The simplest model accounting for these observations postulates two kinetically active sites on each molecule of peroxidase, a high affinity and a low affinity site, that may correspond to the free radical and the heme iron (IV) of the oxidized enzyme, respectively. Both oxidizing equivalents may be discharged at either site. Furthermore, the enzyme appears to exist as an equilibrium mixture of a high ionic strength form, EH and a low ionic strength form, EL, the former reacting optimally with yeast cytochrome c, and the latter with horse cytochrome c.

Animals↗

PubMedDate not supplied

Factors affecting multiresidue determination of priority herbicides when using solid-phase microextraction.

A solid-phase microextraction (SPME) procedure was developed for the determination of 10 selected organonitrogen herbicides (s-ethyl dibropylthiocarbamate [EPTC], molinate, propachlor, trifluralin, simazine, atrazine, propazine, terbuthylazine, alachlor, and prometryn) and was tested with various natural waters. Gas chromatography coupled with flame thermionic and mass spectrometric detection was used for quantitation. For this purpose, polydimethylsiloxane and polyacrylate fibers were used and the factors affecting the SPME process such as pH, ionic strength, methanol content, memory effect, stirring rate, and adsorption-time profile were investigated and optimized. By using spiked liquid chromatography water, optimal factors were determined to be 25% salt, <0.5% methanol, stirring rate of 960 rpm, pH 4, and an equilibrium time of 30 min. These conditions were used in further studies of the fibers and in analysis of natural water samples. The method was applied to spiked natural waters such as ground water, sea water, lake water, and river water at a concentration range of 0.5-10 microg/L. Limits of detection ranged from 5 to 90 ng/L, and precision ranged from 5 to 15% (as relative standard deviation), depending on the pesticide, fiber, and detector used. The recoveries of herbicides were 70.2-118.4%, and the average r2 values of the calibration curves were >0.99 for all analytes. The results demonstrate the suitability of the SPME method to determine these organonitrogen herbicides in various natural waters. River water samples originating from the Epirus region (Northwestern Greece) were analyzed to verify the performance of the optimized method by comparing the results obtained by SPME with those obtained by using conventional solid-phase extraction of the selected herbicides.

Calibration↗

PubMedDate not supplied

[The role of the oxygen-binding properties of the blood in maintaining pro-oxidant-antioxidant equilibrium in the body].

Tissue pro-oxidant generation under standard conditions is equilibrated with the activity of intra- and extracellular antioxidants; thus some optimal level of pro-oxidant-antioxidant balance is created. Oxygen-dependent nature of lipid peroxidation processes implicates its complex multilevel regulatory system, where systemic mechanisms may dominate upon the intracellular ones. This suggests a necessity in the investigation of body oxygen transport not only in terms of the requirements of energetic metabolism in electron acceptor but also as a physiological mechanism for antioxidant defense and, in general, as the mechanism involved in a maintenance of pro-oxidant-antioxidant balance. The hemoglobin-oxygen affinity has a special place in a complex antioxidant system hierarchy, because it determines the condition of oxygen diffusion to tissues and ultimately the value of tissue pO2. The blood oxygen-binding properties under different hyperthermic states with or without a correction of hemoglobin-oxygen affinity and L-arginine-NO pathway were shown to be involved into a complex integration with elements of different functional systems and to play an important role in complex physiologic mechanisms for the maintenance of pro-oxidant-antioxidant balance. The oxyhemoglobin dissociation curve shift leftwards may have an adaptive effect under conditions of low oxygen utilization because of limitation of oxygen fraction spent on a free radical generation and the following initiation of lipid peroxidation processes.

Animals↗

PubMed2002

Multistage electrophoresis II: treatment of a kinetic separation as a pseudoequilibrium process.

An electrophoresis device is described which separates cells, particles, proteins and other separands by collecting samples having decreasing electrophoretic mobility in a train of inverted cavities while an electric field is applied between the inverted cavities and a sample cuvette containing a mixture of cells, particles, proteins or other separands. A circular plate is provided for the inverted cavities, and this circular plate is rotated to collect fractions. The system utilizes an innovative purification method that combines free electrophoresis and multistage extraction in an instrument capable of separating living cells, particles, and proteins in useful quantities at high concentrations. Most multistage processes are based on equilibrium separations, but electrophoresis is a kinetic separation; therefore, a pseudoequilibrium paradigm was developed for use in optimizing separation parameters including number of stages and electrophoresis time per stage. This paradigm allows the application of McCabe-Thiele type analysis, and it was calculated, for example, that two separands differing by 20% in electrophoretic mobility can be purified to 95% purity with acceptable yield in about seven stages. Laboratory experiments demonstrated a 95% purification in four stages of a separand originally present at 4% when electrophoretic mobilities differed by 80%.

Anions↗

PubMed1984

Comparison of equilibrium and disequilibrium assay conditions for ergocalciferol, cholecalciferol and their major metabolites.

The comparison of equilibrium and disequilibrium assay conditions for ergocalciferol, cholecalciferol and their major metabolites were investigated to evaluate: (1) optimization of sensitivity (2) crossreactivity of these compounds in their respective assays and (3) side chain steric requirements of the vitamin D molecule for optimum binding to the calciferol binding protein or bovine thymus receptor. Disequilibrium assay conditions improved assay sensitivity 30-fold for the calciferol assay and approx 3-fold for metabolites in the 25-hydroxycalciferol and 1,25-dihydroxycalciferol assays. Ergocalciferol compounds were uniformly less efficient in their association with the proteins tested than were their cholecalciferol counterparts, with one exception. In the calciferol assay, cholecalciferol had greater affinity for the the calciferol binding protein than did ergocalciferol. In the 25-hydroxycalciferol assay affinity for the calciferol binding protein was 25-hydroxycholecalciferol = 24,25-dihydroxycholecalciferol greater than 25-hydroxyergocalciferol greater than 25S,26-dihydroxycholecalciferol greater than 24,25-dihydroxyergocalciferol greater than 25,26-dihydroxyergocalciferol. In the assay for 1,25-dihydroxycalciferol, bovine thymus receptor recognized 1,25-dihydroxyergocalciferol and 1,25-dihydroxycholecalciferol equally. From the forthcoming data it appears that hydroxyl and/or methyl groups on the calciferol side chain alter the ability of these physiological compounds to associate with the calciferol binding protein.

Binding, Competitive↗

PubMed1979

Protein-protein interactions studied by counter-current distribution. I. Theoretical computations.

Many biological macromolecules are known to interact either with themselves, with other macromolecules or with small compounds. A simple equilibrium method for detecting and quantifying these interactions is to study the mutual influence of the molecules on their respective counter-current distribution in liquid-liquid biphasic systems. The theoretical counter-current distribution patterns for the components in an interacting system, A + B in equilibrium AB, have been calculated for two models in order to establish the boundary conditions and to optimize the experimental procedure. The patterns have been calculated for a range of association constants, partition coefficients and initial concentrations of the two reactants.

Countercurrent Distribution↗

PubMed1997

Engineering the independent folding of the subtilisin BPN' prodomain: analysis of two-state folding versus protein stability.

In complex with subtilisin BPN', the 77 amino acid prodomain folds into a stable compact structure comprising a four-stranded antiparallel beta-sheet and two three-turn alpha-helices. When isolated from subtilisin, the prodomain is 97% unfolded even under optimal folding conditions. Traditionally, to study stable proteins, denaturing cosolvents or temperatures are used to shift the equilibrium from folded to unfolded. Here we manipulate the folding equilibrium of the unstable prodomain by introducing stabilizing mutations generated by design. By sequentially introducing three stabilizing mutations into the prodomain we are able to shift the equilibrium for independent folding from 97% unfolded to 65% folded. Spectroscopic and thermodynamic analysis of the folding reaction was carried out to assess the effect of stability on two-state behavior and the denatured state. The denatured states of single and combination mutants are not discernably different in spite of a range of DeltaGunfolding from -2.1 to 0.4 kcal/mol. Conclusions about the nature of the denatured state of the prodomain are based on CD spectral data and calorimetric data. Two state folding is observed for a combination mutant of marginal stability (DeltaG = 0). Evidence for its two-state folding is based on the observed additivity of individual mutations to the overall DeltaGunfolding and the conformity of DeltaGunfolding vs T to two-state assumptions as embodied in the Gibbs-Helmholz equation. We believe our success in stabilizing the two-state folding reaction of the prodomain originates from the selection of mutations with improved ability to fold subtilisin rather than selection for increase in secondary structure content. The fact that a small number of mutations can stabilize the independent folding of the prodomain implies that most of the folding information already exists in the wild-type amino acid sequence in spite of the fact that the unfolded state predominates.

Bacillus subtilis↗

PubMed1999

The cleavage step of ribonuclease P catalysis is determined by ribozyme-substrate interactions both distal and proximal to the cleavage site.

The cleavage step of bacterial RNase P catalysis involves concentration-independent processes after the formation of the ribozyme-substrate complex that result in the breaking of a phosphodiester bond. The 2'OH group at the cleavage site of a pre-tRNA substrate is an important determinant in the cleavage step. We determined here that in contrast to a tRNA substrate, the 2'OH at the cleavage site of two in vitro selected substrates has no effect, whereas a 2'OH located adjacent to the cleavage site has a similarly large effect on the cleavage step. This result indicates that a unique 2'OH in the vicinity of the cleavage site interacts with the ribozyme to achieve the maximal efficiency of the cleavage step. Individual modifications in a pre-tRNA substrate that disrupt ES interactions proximal to the cleavage site generally have little effect on the usage of this unique 2'OH. Ribozyme modifications that delete the interactions involving the T stem-loop of the tRNA have a large effect on the usage of this unique 2'OH and also alter the location of this 2'OH. We propose a new ES complex prior to the bond-breaking step in the reaction scheme to explain these results. This second ES complex is in fast equilibrium with the initial ES complex formed by bimolecular collision. The ribozyme interaction with this unique 2'OH shifts the equilibrium in favor of the second ES complex. The formation of the second ES complex may require optimal geometry of the two independently folding domains of this ribozyme to precisely position crucial functional groups and Mg2+ ions in the active site. Such a domain geometry is significantly favored by the RNase P protein. In the absence of the protein, spatial rearrangement of these domains in the ES complex may be necessary.

Bacillus subtilis↗

PubMed2002

Coordination of the neptunyl ion with carbonate ions and water: a theoretical study.

The results of a study on the ground-state of monocarbonate, bicarbonate, and tricarbonate complexes of neptunyl using multiconfigurational second-order perturbation theory (CASSCF/CASPT2) are presented. The equilibrium geometries of the complexes corresponding to neptunium in the formal oxidation state (V) have been fully optimized at the CASPT2 level of theory in the presence of an aqueous environment modeled by a reaction field Hamiltonian with a spherical cavity. Some water molecules have been explicitly included in the calculation. This study is consistent with the hypothesis that the monocarbonate complex has a pentacoordinated structure with three water molecules in the first coordination shell and that the bicarbonate complex has a hexacoordinated structure, with two water molecules in the first coordination shell. The typical bond distances are in good agreement with experimental results. The tricarbonate complex was studied with explicit counterions, which resulted in somewhat longer Np-carbonate bond distances than experiment indicates.

Journal Article↗

PubMed2001

An ab initio investigation of 2-amino-2-imidazoline: a key moiety in chemical and biochemical processes.

The 2-amino-2-imidazoline moiety is currently used not only in drugs, but also in insecticides, and fungicides. Ab initio calculations are performed to evaluate the molecular properties of the two tautomeric forms and the protonated form with extended basis sets ranging from 6-31G* to 6-311++G** at Hartree-Fock and density functional (BLYP and B3LYP) levels. Møller-Plesset perturbation is tested at the MP2/6-31G* level only. Optimized geometry structures, energies and thermochemical properties are generated. Basis set and correlation effects on geometries, tautomer equilibrium constant and protonation enthalpy are carefully analysed. Although observed for the isolated molecule, these results may be extrapolated to chemical and biochemical systems of interest.

Fungicides, Industrial↗

PubMed1982

Studies on the binding of a 32K rat epididymal protein to rat epididymal spermatozoa.

A glycoprotein of molecular weight 32K has been isolated and purified from the rat caudal epididymal fluid by gel filtration, ion-exchange and affinity chromatography. The highly purified protein was labeled with radioactive iodine and the binding of the 125I-labeled 32K rat epididymal protein (REP) to washed rat caudal epididymal sperm was studied under various conditions. Scatchard plots of the binding data revealed two binding kinetics. One bound with high affinity (KD = 2.6 X 10(-10) ) but low capacity. The other bound with lower affinity (KD = 2.2 X 10(-9)M) but high capacity. The rate of binding of the labeled protein to sperm was dependent on the temperature of the incubation medium. At the scrotal temperature of 33 degrees C, maximal binding was obtained after 40 min. However, at 22 degrees C equilibrium state was reached after 90 min and at 0 degrees C, the equilibrium rate was not reached even after 120 min of incubation. Binding showed dependence on extracellular pH (optimal pH at 4) and ionic strength of the incubation medium. High ionic strength was found to inhibit binding of the 125I-labeled 32K REP to rat caudal epididymal sperm. Specific binding was abolished by 100-fold molar excess unlabeled 32K REP or by native rat caudal epididymal fluid proteins, but not by albumin or ovalbumin. This indicates high specificity of binding. This study has provided direct evidence for the interaction of an epididymal protein with epididymal spermatozoa.

Animals↗

PubMed1977

The denaturation-renaturation of chicken-muscle triosephosphate isomerase in guanidinium chloride.

1. The process of denaturation of the chicken muscle dimeric enzyme triosephosphate isomerase on addition of guanidinium chloride has been studied at pH 7.6, the pH at which the recovery of activity is optimal (100%) on removal of denaturant. Determinations of the sedimentation coefficient, intrinsic viscosity, molecular weight (by sedimentation equilibrium studies) and the absorption coefficient at 280 nm in various concentrations of guanidinium chloride concurred in showing a single, sharp transition at about 0.7 M guanidinium chloride at a protein concentration 1-5 mg/ml from the native enzyme to the dissociated, unfolded chains of the monomer. Relative fluorescent intensity measurements revealed a single transition at about 0.4 M guanidinium chloride at enzyme concentrations of about 0.05 mg/ml. 2. The process of denaturation in different guanidinium chloride concentrations was first order with respect to enzyme and about sixth order with respect to denaturant. 3. The rate of attainment of equilibrium during the renaturation obeyed second-order/first-order reversible kinetics. It was concluded that the rate-determining step in renaturation at pH 7.6 must be the association of two subunits.

Animals↗

PubMed1996

Antibodies to bovine serum albumin in Brazilian children and young adults with IDDM.

OBJECTIVE: To evaluate the prevalence of IgG antibodies to bovine serum albumin (BSA) in a cohort of Brazilian children and young adults with IDDM. RESEARCH DESIGN AND METHODS: Sera from 81 subjects with < 1 year of IDDM (group 1), III subjects with > 1 year of IDDM (group 2), and 207 normoglycemic subjects were tested using an immunofluorimetric assay. A receiver-operating-characteristic curve was used to establish the threshold of anti-BSA antibody titers defining the positivity of the assay. RESULTS: The distribution of the fluorimetric index (FI) of anti-BSA antibodies did not have a gaussian profile. Rank sum of FI was significantly higher in patients than in control subjects (P < 0.0001). Average logFI values of both IDDM groups were significantly higher than that of the control group (P < 0.005 for both groups). There was a trend toward higher FI levels in group 1 than in group 2 (P = 0.06). A FI cutoff of 0.7 optimized the ratio of true-positive to false-positive of the assay, with the best equilibrium between sensitivity and specificity. The prevalence of anti-BSA antibodies was 52% in group 1, 47% in group 2, and 28% in the control group (P = 0.0001). An independent association between anti-BSA antibodies and IDDM, with an odds ratio of 3.03 (P < 0.0001), was observed in a logistic regression analysis. However anti-BSA antibodies explained only 5% of the variability of IDDM versus NIDDM. CONCLUSIONS: Our results confirm that the prevalence of anti-BSA antibodies is higher in IDDM subjects than in control subjects, even after 1 year of diabetes. However, a large overlap of antibody titers is observed in patients and control subjects, suggesting that anti-BSA antibodies are neither sensitive nor specific markers of IDDM.

Adolescent↗

PubMed1999

Adsorptive control of water in esterification with immobilized enzymes. Continuous operation in a periodic counter-current reactor.

A periodic counter-current adsorptive-reactor system is developed to carry out continuous esterifications in organic solvents with immobilized enzymes. The system comprises a number of fixed-beds distributed between a reaction-adsorption zone and a regeneration zone and operated in a "merry-go-round" sequence. Water formed in the reaction is adsorbed preventing the formation of a free-water phase and deactivation of the biocatalyst. The adsorbed water is, in turn, recovered by desorption in the regeneration zone. The concept is tested experimentally on a laboratory-scale using, as a model, the esterification of isoamyl alcohol and propionic acid in hexane catalyzed by an immobilized lipase. Pure isoamyl alcohol is used as a regenerant to remove excess water from the biocatalyst. In the periodic steady-state, improvements in ester productivity greater than 50% over that achievable with a conventional fixed-bed reactor are demonstrated experimentally with just two beds in a series arrangement. Use of a water-selective adsorbent in conjunction with the biocatalyst provides further improvements by reducing accumulation of water on the enzyme. A mathematical model is also developed to predict the thermodynamic activity of water along the reactor and describe the dynamic behavior of the system. The model, based on independently developed rate and equilibrium parameters, successfully predicts the experimental behavior and provides an effective tool for scale-up and optimization.

Adsorption↗

PubMed1975

Supramolecular forms of actin from amoebae of Dictyostelium discoideum.

Actin purified from amoebae of Dictyostelium discoideum polymerizes into filaments at 24 degrees upon addition of KCl, as judged by a change in optical density at 232 nm and by electron microscopy. The rate and extent of formation of this supramolecular assembly and the optimal KCl concentrations (0.1 M) for assembly are similar to those of striated muscle actin. The apparent equilibrium constant for the monomer-polymer transition is 1.3 muM for both Dictyostelium and muscle actin. Although assembly of highly purified Dictyostelium actin monomers into individual actin filaments resembles that of muscle actin, Dictyostelium actin but not muscle actin was observed to assemble into two-dimensional nets in 10 mM CaCl2. The Dictyostelium actin also forms filament bundles which are 0.1 mum in diameter and which assemble in the presence of 5 mM MgCl2. These bundles formed from partially purified Dictyostelium actin preparations but not from highly purified preparations, suggesting that their formation may depend on the presence of another component. These actin bundles reconstituted in vitro resemble the actin-containing bundles found in situ by microscopy in many non-muscle cells.

Actins↗