Technics of measuring the motive force of very small ameboid cells]

A technic have been perfected which measures directly the motive force of very small ameboid cells and indicates the tropism of the amoeba. By using this technic, the motive force of Entamoeba histolytica was measured. It varied between +/- 1.5 x 10-4 dyne. We have also shown chimiotactism in Entamoeba histolytica. The metabolic coumpound excreted by this cell induced negative tropism.     

Configurational statistics of the DNA duplex: Extended generator matrices to treat the rotations and translations of adjacent residues

The base-to-base virtual bond treatment of nucleic acids used in statistical mechanical calculations of polynucleotide chain properties has been refined by incorporating the six parameters that relate the positions and orientations of sequential rigid bodies. The scheme allows for the sequence-dependent bending, twisting, and displacement of base pairs as well as for asymmetry in the angular and translational fluctuations of individual residues. Expressions are developed for the generator matrices required for the computation, as a function of chain length, of various parameters measuring the overall mean extension and shape of the DNA. Quantities of interest include the end-to-end vector r , the square of the end-to-end distance r², the square radius of gyration s², the center-of-gravity vector g , the second moments of inertia S ^×2, and the higher moments of r and g . The matrix expressions introduced in the 1960s by Flory and co-workers for the determination of configuration-dependent polymer chain averages are decomposed into their translational and orientational contributions so that the methods can be extended to the rigid body analysis of chemical moieties. The new expressions permit, for the first time, examination of the effects of sequence-dependent translations, such as the lateral sliding of residues in A- and B-helices and the vertical opening of base pairs in drug–DNA complexes, on the average extension and shape of the long flexible double helix. The approach is illustrated in the following paper using conformational energy estimates of the base sequence-dependent flexibility of successive B-DNA base pairs. © 1994 John Wiley & Sons, Inc.     

Development of an optical 3-D position measuring system for simultaneous detection of 6 degrees of freedom]

A few years ago it became possible to carry out complicated surgical procedures in humans with the required precision by combining medical imaging (MRI, CT) with minimally invasive surgery. The confined space within these imaging systems and the resulting inaccuracies associated with the manual use of instruments increasingly make necessary the help of aids ranging from positioning systems to robotic devices, which themselves must be position controlled. A position sensor has been developed for a medical robotic system allowing the image-controlled insertion of injection needles and the simultaneous administration of different drugs. The 3D position coordinates are determined by a noncontact optical principle, which also enables simultaneous determination of all 6 basic degrees of freedom of the robotic system (3 translational, 3 rotational). On the basis of an area image sensor and the measurement of a geometrically defined structure in the path of the rays between sensor and light source, the position coordinates are calculated almost real time. Special emphasis was placed on designing the sensor system to cover a sufficiently large workspace to enable it to cover the entire intervention area. The sensor described herein determines the position coordinates in a volume of 10 x 10 x 10 cm at a resolution of up to 1 mm for translations and 1 degree for rotations.     

Mechanical effects on measuring displacement of the knee joint with the knee arthrometer KT1000 and KT2000]

The KT2000 knee ligament arthrometer manufactured by the MEDmetric Corporation is used in the field of orthopedics to establish quantitatively the size of the anterior and posterior draw phenomena of the knee joint. The basis for the measurement is the Lachman test in which a force is applied to the tibia relative to the femur. The resulting displacement is limited by the cruciate ligaments. The measurements obtained for a potentially injured knee are compared with those of the healthy knee and empirical threshold values, and serve as a basis for deciding whether to operate on patients with cruciate ligament insufficiency. The subject of the present study is a design shortcoming of the KT2000 that may falsify the measured results when the device is not correctly employed. A simple mechanical modification of the KT2000 can reduce this error. In the present study, the error is quantified and we show how the modification can keep it within tolerable limits.     

Detecting and measuring small numbers of viable Coxiella burnetii

Coxiella burnetii is an acidophilic, intracellular bacterium that causes the human disease Q fever. In some studies, it is important to distinguish between viable and nonviable C.?burnetii. We compared four methods for detecting and measuring viable C.?burnetii in biological samples as follows: growth in two different cell culture lines, infection of severe combined immunodeficient (SCID) mice (leading to death) and infection of SCID mice with detection of C.?burnetii in their spleen (after euthanasia at day 50 postinfection). Two isolates of C.?burnetii were used ('Henzerling' and 'Arandale'). Our in-house qPCR assay for C.?burnetii DNA was used as a control. SCID mouse inoculation was more sensitive than cell culture. The assay that detected C.?burnetii in SCID mouse spleens was slightly more sensitive than SCID mice deaths alone. Approximately one viable C.?burnetii cell could be detected by this method, making it suitable for determining the viability of C.?burnetii in a sample.     

Growth and development of extreme-thermophilic bacteria at 70 degrees]

Nine cultures of non-sporeforming gram-negative extreme-thermophilic bacterium Thermus flavus have been isolated from hot springs of Kamchatka. Their optimal growth temperature on a solid potato medium was 70 to 76 degrees C, and on a liquid medium (20 per cent potato broth containing 0.5 per cent peptone and 0.1 per cent yeast extract) 70 degrees C. The minimum time of generation of the bacterium, strain 71, growing on the liquid medium at 70 degrees C, was 52 minutes. Other extreme-thermophilic cultures differ from the strain 71 by a lower growth rate. The maximum biomass yield was 1.96 g per litre of the medium after 6 to 9 hours of growth. The extreme-thermophilic bacteria of Kamchatka are similar to those from the hot springs of Japan.     

A yardstick for measuring populations of small rodents

(1) Six-monthly trappings (summer and winter) were done between 1952 and 1969 of Wood mice (Apodemus sylvaticus) and Bank voles (Clethrionomys glareolus) in Wytham Woods, near Oxford. One hundred and fifty Longworth live traps were used on two 2-acre grids in oak-ash-sycamore woodland. (2) The traps were pre-baited for 48 hours and then set. The catch was examined on the evening of the same day and on the following morning. The total of animals caught during the 24 hours was used as an index to the actual numbers present. Animals retrapped in the morning (identified by a simple method of marking) were omitted from the total. (3) Between 1969 and 1972 the same procedure was used but trapping, evening and morning, was continued for 3-4more days until some 75–80% of the catch consisted of marked animals. (4) This enabled estimates to be made of the actual numbers of voles and mice present at each trapping and so to assess the proportion of the total present which was caught ring the first 24 hours. (5) These estimates were made by (Method la) a straight Lincoln Index, (Method lb) a Lincoln Index method as modified by Hayne (1949) and (Method 2) by Hayne's trap-out method. Over six trappings the estimates by these methods showed reasonable agreement. (6) Comparison of the index trapping (i.e. the numbers caught during the first 24 hours) with the estimates of the total numbers present showed that, on all occasions, more than half of the mice and voles present entered the traps during the first 24 hours. With Bank voles there was a tendency for about half of them to be trapped during this time during the winter and about three-quarters of them during the summer. (7) With Wood mice the figures are more variable but, again, never less than half were trapped during the first 24 hours and, on some occasions, nearly the whole of the population. (8) These results show that reasonably accurate estimates of the numbers of these rodents can be achieved within 3–4 days' trapping (estimates that can be cross-checked by different methods) by using a high density of traps (see (1) above). Furthermore, trapping for 24 hours only will always catch at least half of the population present and, on occasions, considerably more than half.     

Photodissociation of carboxyhemoglobin with different degrees of saturation]

The graphical method is suggested and treated for obtaining of the binding curves in photodissociation conditions. Some kinetic properties of photolisis of HbCO are discussed in connection with sharp increase of free gase concentration in solution.     

Adenosine deaminase activity in hepatomas of varying degrees of malignancy]

In highly malignant Gelshtein 22A hepatcma and ascites Ehrlich carcinoma adenosine deaminase activity was found to be reduced 3-fold as compared with that of the normal mouse liver. In less malignant hepatomas adenosine deaminase activity drops only by 20%. A certain reduction of adenosine deaminase activity was also noted in the liver to tumour-bearing mice.     

Effect of dihydroxyacetone on metabolic parameters and survival of resuspended erythrocytes after storage at 25 degrees and 4 degrees]

Erythrocyte concentrates from CPD blood were resuspended after separating the leukocyte-thrombocyte layer and stored at 4 degrees C and 25 degrees C. The solutions for resuspension differed in the content of substrate, pH, condition of sterilization and the resuspension volume used, 1 or 4 volumes of cell concentrate to 1 volume of resuspension solution. At 4 degrees C, there was no effect of DHA on the the 2.3 bisphosphoglycerate content (P2G content). The decreased activity of triokinase at low temperature, phosphate deficiency and a partial disintegration of DHA during the autoclave as well as the difference of the commercial DHA preparations are discussed as underlying causes. At 25 degrees C DHA delayed the P2G decrease during storage. The enhanced triokinase activity above 15 degrees C is principally considered to be the cause for it. High rates of haemolysis, rapid ATP decrease, survival rates of 56% after a storage of three weeks for erythrocyte resuspensions with DHA in used compositions render a clinical application impossible at present. It could be well suitable as a substrate for resynthesizing P2G. An addition of ascorbate + nicotinamid + adenin at a storage temperature of 4 degrees C had no influence on the P2G content. A resuspension solution on the basis of xylitol with additions of sorbitol, bicarbonate, inorganic phosphate, pyruvate, adenine and guanosine showed the best properties in the content of P2G and ATP, lactate formation and survival rate during a storage at 4 degrees C.     

Explicit distance geometry: identification of all the degrees of freedom in a large RNA molecule.

An alternative approach to distance geometry ("explicit" distance geometry) is being developed for problems, such as the modeling of RNA folding in the ribosome, where relatively few distances are known. The approach explicitly identifies minimal sets of additional distances that can be added to a distance matrix in order to calculate structures that are consistent with all the known information without distorting the original input data. These additional distances are bounded to the extent possible by the known distances. These explicitly added distances can be treated as degrees of freedom and used to explore the full range of alternative foldings consistent with the original input in an organized way. The present paper establishes that it is practical to explicitly determine such degrees of freedom for even very large RNAs. To demonstrate the feasibility of the approach tRNA was represented as a simple undirected graph containing all relevant information represented in the usual cloverleaf secondary structure and nine base-base tertiary interactions. Using a three atom representation for each residue a total of 206 degrees of freedom are explicitly identified. To accomplish this a graph theoretic approach was used in which a minimal covering cycle basis was determined.     

Fluorometric procedures for measuring triglyceride concentrations in small amounts of tissue and plasma

It has been previously shown that triglycerides can be specifically hydrolyzed by lipase from Rhizopus arrhizus in the presence of hog liver esterase and sodium dodecyl sulfate. The glycerol produced can then be measured by sequential reactions with glycerokinase, pyruvate kinase, and lactate dehydrogenase: glycerol and ATP are converted to glycerol-3-phosphate and ADP by glycerokinase; the ADP reacts with phosphoenolpyruvate and pyruvate kinase to yield pyruvate; the pyruvate is converted to lactate with lactate dehydrogenase, and the cofactor NAD+ is simultaneously reduced to NADH. This report describes procedures by which either the disappearance of NADH or the appearance of NAD+ was determined fluorometrically, with 10- to 100-fold greater sensitivity than by spectrophotometry. In addition, enzymatic cycling of NAD+ was used to increase the sensitivity of the assay over 1000-fold, and thereby provided accurate measurement of less than 1 ng of triglyceride. Results obtained from the three fluorometric methods were highly correlated with an automated periodate oxidation method using serum samples and lipid extracts of muscle tissue.     

Validation of manometric microrespirometers for measuring oxygen consumption in small arthropods

Scientists have used numerous techniques to measure organismal metabolic rate, including assays of oxygen (O(2)) consumption and carbon dioxide (CO(2)) production. Relatively few studies have directly compared estimates of metabolic rate on the same groups of animals as determined by different assay methods. This study directly compared measures of the metabolic rate of three lines of Drosophila simulans as determined either from direct measures of CO(2) production using infrared gas analysis (IRGA), or from estimates of O(2) consumption based on manometeric techniques. Determinations of metabolic rate of the same cohorts of flies using these two methods produced results that often differed widely. Typically metabolic rate as determined by the manometric method was significantly greater than that determined by CO(2) output. These differences are difficult to explain by simple biotic or abiotic factor(s). Because of the idiosyncratic nature of these differences it is not possible to use a simple factor to convert from metabolic rate measurements done using manometric techniques to those expected from direct measures of CO(2) output or O(2) consumption. Although manometric devices are simple to construct and use, measurements of metabolic rate made with this method can vary significantly from measurements made by directly assaying CO(2) production or O(2) consumption.     

Suppression of intrachromosomal gene conversion in mammalian cells by small degrees of sequence divergence

Pairs of closely linked defective herpes simplex virus (HSV) thymidine kinase (tk) gene sequences exhibiting various nucleotide heterologies were introduced into the genome of mouse Ltk- cells. Recombination events were recovered by selecting for the correction of a 16-bp insertion mutation in one of the tk sequences. We had previously shown that when two tk sequences shared a region of 232 bp of homology, interruption of the homology by two single nucleotide heterologies placed 19 bp apart reduced recombination nearly 20-fold. We now report that either one of the nucleotide heterologies alone reduces recombination only about 2.5-fold, indicating that the original pair of single nucleotide heterologies acted synergistically to inhibit recombination. We tested a variety of pairs of single nucleotide heterologies and determined that they reduced recombination from 7- to 175-fold. Substrates potentially leading to G-G or C-C mispairs in presumptive heteroduplex DNA (hDNA) intermediates displayed a particularly low rate of recombination. Additional experiments suggested that increased sequence divergence causes a shortening of gene conversion tracts. Collectively, our results suggest that suppression of recombination between diverged sequences is mediated via processing of a mispaired hDNA intermediate.     

A method for measuring small retardations of structures in living cells

A new half shade method for measuring retardations in optically complicated structures is presented. By using a polarization microscope with an extinction of 10⁵, a retardation as small as a tenth of a mμ (in objects not larger than a micron in diameter) can be measured very rapidly by this method. Especially important is the fact that such measurements can easily be made without injury, directly upon the living cells.     

Reliability of an individually molded shank shell for measuring tibial transverse rotations during the stance phase of walking

Use of a shank shell has been shown to estimate tibial transverse rotations better than skin-mounted markers. However, the day-to-day reliability of the transverse tibial rotations using an individually molded shank shell has not been previously investigated. This study examined the between-tests and trials reliability of an individually molded shank shell for measuring peak tibial internal and external rotations, time of peak values, and tibia range of motion during 5 walking trials. The trial-to-trial reliability of tibial transverse rotations was measured in 14 healthy individuals while the test-retest reliability was measured in 10 persons on two occasions. Trial-to-trial reliability for peak transverse rotations, time of peak values, and tibia range of motion ranged from ICC (3,1) 0.59-0.95. The PCA between trials showed that 88-99 % of values were within 3 degrees of agreement. Test-retest reliability for peak rotations, tibia range of motion, and time of peak values ranged from ICC (3,1) 0.70-0.89 with SEM 1.6-2.21 degrees , 0.021 %, and 0.034 %, respectively. The PCA between tests showed that 70-100 % of values were within 3 degrees of agreement. The use of an individually molded shell and the close attachment of the shank shell to the individual's shank resulted in reliable test-retest and trial-to-trial data.