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At least 1,261 records · Page 70Linked to original sources
PubMed2005

Effect of long-distance road transport on thyroid and adrenal function and haematocrit values in Limousin cattle: influence of body weight decrease.

The purpose of this study was to evaluate the effect of long-distance road transport as a relevant stressor on total and free iodothyronines, cortisol levels and haematocrit values in 10 male Limousin cattle. Serum T3,T4,fT3,fT4 and cortisol concentrations were analysed by immunoenzymatic assays. Serum cortisol levels and haematocrit modifications were also evaluated on the basis of percentage body weight decrease. The results showed a general increase of total and free iodothyronines and cortisol levels after short-and long-distance road transport and a decrease 15 days after transport, as compared to basal values. Significant positive correlations between T3 and T4, between T3 and fT3, and between T4 and fT4 were found. These results suggest that transport stress induces an increase in the activity of thyroid and adrenal function in Limousin cattle that is evident after even a short-distance road transport and continues to increase after long-distance transport.

Adrenal Glands↗
PubMed1992

Influence of the distance between interrupted sutures and the tension of sutures on the healing of experimental colonic anastomoses.

Certain technical factors determine the success of the creation of intestinal anastomoses. The influence of the distance between interrupted sutures and the suture tension on wound healing was investigated in an experimental study using a specially designed suture model. The combination of a long suture distance (group A, 2.5 mm) and a short suture distance (group B, 1.5 mm) with three different suture tensions, i.e., (1) no tension; (2) moderate tension; and (3) high tension, resulted in six different techniques. Tension was created by means of a spring balance. The anastomoses were examined macroscopically, histologically by microangiography, and by bursting pressure. Apposition of the bowel wall between the interrupted sutures was inappropriate due to prolapse of the mucosa in 7.9% of the patients in group A but did not occur in groups B2 and B3. The leakage rate was 4.6% in group A and 1.3% in group B. Early healing of the mucosa was noted in group B2. Bursting pressure was significantly higher on day 2 and 4 in groups B2 and B3. The results demonstrate the influence of suture technique on the wound healing of intestinal anastomoses. The best healing pattern was achieved by a small distance between the sutures and a moderate suture tension.

Anastomosis, Surgical↗
PubMed1977

Detection and reading distances of retroreflective road signs during night driving.

The detectability and legibility of road signs of different reflective intensities were studied in night driving conditions. The results indicated that for obtaining optimal detectability and legibility distances, the reflective intensity of a new road sign should be in the range of 4 to 10 mcd/lux x cm(2). For signs in this range it was shown that doubling the area of a sign increased a detection distance of about 600 m by about 150-200 m. Opposing headlights on an oncoming car decreased detection distances of 500-900 m by about 100 m. Finally, it was found that standard signs, with a text 170 mm high, permitted reading from a distance of about 115 m.

Journal Article↗
PubMed1988

Principal component analysis of intercusp distances on the lower first molars of three human populations.

The distances between the five main cusps of lower first molars were measured on moiré photographs of casts obtained from Japanese, Dutch and Australian Aboriginal children. Principal component analysis of the intercusp distances, log transformed and standardized so that average tooth size was held constant, revealed three sources of shape variation in cusp topography. All populations were similar for scores on component 1 which was concerned with variations in the position of the hypoconulid. The Dutch had lowest scores on component 2 indicating small buccolingual distances compared with mesiodistal, whereas the Australian Aboriginals had the lowest mean score on component 3, expressing the distances between metaconid, entoconid and hypoconulid.

Asian People↗
PubMed1989

Quantitative analysis of single muscle fibre action potentials recorded at known distances.

In vivo records of single fibre action potentials (SFAPs) have always been obtained at unknown distance from the active muscle fibre. A new experimental method has been developed enabling the derivation of the recording distance in animal experiments. A single fibre is stimulated with an intracellular micropipette electrode. The same electrode is used thereafter for labelling with an auto-fluorescent dye, Lucifer Yellow. In this method there is no use of chemical fixation. The tissue structure is kept as well as possible. In cross-sections the fluorescent fibre is seen and its position is quantitized with respect to the tip of one or more recording wire electrodes. Morphometric data, such as the recording distance and the fibre cross-sectional area, are used for the interpretation of parameters of the SFAPs (peak-peak amplitude, time between the first positive and negative peaks). The present results show that within 300 microns recording distance is not as dominant for the SFAP shape as expected. The method offers also a direct check of the relation between the muscle fibre; diameter and the conduction velocity of the action potential. In the present small set of data there is no simple linear relationship.

Action Potentials↗
PubMed1985

Calculation of protein conformations by proton-proton distance constraints. A new efficient algorithm.

We have developed a method to determine the three-dimensional structure of a protein molecule from such a set of distance constraints as can be determined by nuclear magnetic resonance studies. The currently popular methods for distance geometry based on the use of the metric matrix are applicable only to small systems. The method developed here is applicable to large molecules, such as proteins, with all atoms treated explicitly. This method works in the space of variable dihedral angles and determines a three-dimensional structure by minimization of a target function. We avoid difficulties hitherto inherent in this type of approach by two new devices: the use of variable target functions; and a method of rapid calculation of the gradient of the target functions. The method is applied to the determination of the structures of a small globular protein, bovine pancreatic trypsin inhibitor, from several artificial sets of distance constraints extracted from the X-ray crystal structure of this molecule. When a good set of constraints was available for both short- and long-range distances, the crystal structure was regenerated nearly exactly. When some ambiguities, such as those expected in experimental information, are allowed, the protein conformation can be determined up to a few local deformations. These ambiguities are mainly associated with the low resolving power of the short-range information.

Aprotinin↗
PubMed1986

Structure refinement of oligonucleotides by molecular dynamics with nuclear Overhauser effect interproton distance restraints: application to 5' d(C-G-T-A-C-G)2.

The solution structure of the self-complementary DNA hexamer 5' d(C-G-T-A-C-G)2 is refined by restrained molecular dynamics in which 192 interproton distances, determined from pre-steady-state nuclear Overhauser enhancement measurements, are incorporated into the total energy of the system in the form of effective potentials. First the method is tested by applying an idealized set of distance restraints taken from classical B-DNA to a simulation starting off from A-DNA and vice versa. It is shown that in both cases the expected transition between A- and B-DNA occurs. Second, a set of restrained molecular dynamics calculations is carried out starting from both A- and B-DNA with the experimental interproton distances for 5' d(C-G-T-A-C-G)2 as restraints. Convergence to the same B-type structure is achieved with the interproton distances equal to the measured values within experimental error. The root-mean-square atomic difference between the two average restrained dynamics structures (less than 1 A) is approximately the same as the root-mean-square fluctuations of the atoms.

DNA↗
PubMed1987

Protein structures in solution by nuclear magnetic resonance and distance geometry. The polypeptide fold of the basic pancreatic trypsin inhibitor determined using two different algorithms, DISGEO and DISMAN.

A set of conformational restraints derived from nuclear magnetic resonance (n.m.r.) measurements on solutions of the basic pancreatic trypsin inhibitor (BPTI) was used as input for distance geometry calculations with the programs DISGEO and DISMAN. Five structures obtained with each of these algorithms were systematically compared among themselves and with the crystal structure of BPTI. It is clear that the protein architecture observed in single crystals of BPTI is largely preserved in aqueous solution, with local structural differences mainly confined to the protein surface. The results confirm that protein conformations determined in solution by combined use of n.m.r. and distance geometry are a consequence of the experimental data and do not depend significantly on the algorithm used for the structure determination. The data obtained further provide an illustration that long intramolecular distances in proteins, which are comparable with the radius of gyration, are defined with high precision by relatively imprecise nuclear Overhauser enhancement measurements of a large number of much shorter distances.

Algorithms↗
PubMed1989

Determination of the complete three-dimensional structure of the trypsin inhibitor from squash seeds in aqueous solution by nuclear magnetic resonance and a combination of distance geometry and dynamical simulated annealing.

The complete three-dimensional structure of the trypsin inhibitor from seeds of the squash Cucurbita maxima in aqueous solution was determined on the basis of 324 interproton distance constraints, 80 non-nuclear Overhauser effect distances, and 22 hydrogen-bonding constraints, supplemented by 27 phi backbone angle constraints derived from nuclear magnetic resonance measurements. The nuclear magnetic resonance input data were converted to the distance constraints in a semiquantitative manner after a sequence specific assignment of 1H spectra was obtained using two-dimensional nuclear magnetic resonance techniques. Stereospecific assignments were obtained for 17 of the 48 prochiral centers of the squash trypsin inhibitor using the floating chirality assignment introduced at the dynamical simulated annealing stage of the calculations. A total of 34 structures calculated by a hybrid distance geometry-dynamical simulated annealing method exhibit well-defined positions for both backbone and side-chain atoms. The average atomic root-mean-square difference between the individual structures and the minimized mean structure is 0.35(+/- 0.08) A for the backbone atoms and 0.89(+/- 0.17) A for all heavy atoms. The precision of the structure determination is discussed and correlated to the experimental input data.

Amino Acid Sequence↗
PubMed1989

Nuclear magnetic resonance studies of flexible opiate conformations at monoclonal antibody binding sites. Quantitative interproton distances obtained from comparing theoretical and experimental transferred nuclear Overhauser enhancement: correlation with antibody sequence.

A previous publication described the use of qualitative intramolecular 1H-transferred nuclear Overhauser effect measurements to determine the conformations of flexible ligands at monoclonal anti-opiate antibody binding sites. This paper concentrates on the quantitative interpretation of experiments of this type using the ligand nalorphine (N-allyl morphine) and a single anti-opiate monoclonal antibody. I compare the experimental unidimensional driven nuclear Overhauser effect buildup curves to theoretical curves derived with a knowledge of the fixed interproton distances in the ligand. The discussion covers the potential accuracies of derived distances and concentrates on two problem areas associated with determining structures from this type of experiment. The most serious one is the case where, because of particular multiproton spatial distributions, spin diffusion is so rapid that it cannot be determined experimentally and where numerical fits of theoretical calculations are misleading. The results show that, while intraligand spin diffusion complicates the interpretation for some proton pairs, with many others accuracies within about 0.3 A for interproton distances from 2 to 4 A are attainable. The results confirm the earlier report that the conformation of nalorphine in this antibody binding site differs from the major one present in solution or in the crystal. An important aspect of the work is that theoretical prediction of nuclear Overhauser effect time-dependence is an important practical tool for recognizing cases where interpretation of experiments will be difficult. Initial data on protein-to-ligand transferred nuclear Overhauser effect are presented, which show that at least one aromatic amino acid residue is closely involved in the binding of the ligand. The companion paper presents the primary sequences of the variable regions of the antibodies being used in our studies. In this paper, these and associated immunochemical studies are correlated with the nuclear magnetic resonance results. The combination of data presented in the two papers provides a basis for future work on protein-ligand interproton distances in the range 1 to 5 A using both transferred nuclear Overhauser effect (for rapidly exchanging ligands) and isotope-edited, indirectly detected nuclear Overhauser effect (for tightly bound ligands).

Antibodies, Monoclonal↗
PubMed1991

Fluorescence energy transfer distance measurements using site-directed single cysteine mutants. The membrane insertion of colicin A.

The ion-channel-forming C-terminal fragment of colicin A binds to negatively charged lipid vesicles and provides an example of insertion of a soluble protein into a lipid bilayer. The soluble structure is known from X-ray crystallography and consists of a ten-helix bundle containing a hydrophobic helical hairpin. In this work fluorescence spectroscopy was used to study the membrane-bound structure. An extrinsic probe, N'-(iodoacetyl)-N'-(5-sulfol-naphthyl)ethylenediamine (IAEDANS) was attached to mutant proteins each of which bears a unique cysteine residue. Three mutants K39C (helix 2), T127C (between helices 6 and 7) and S16Crpt (helix 1, which bears a decapeptide repeat before the mutation) gave useful derivatives. In the soluble protein they showed emission wavelengths decreasing in the order K39C greater than T127C greater than S16Crpt and although all showed blue shifts on addition of dimyristoylphosphatidylglycerol (DMPG) this order was maintained in the membrane-bound state. These shifts were not indicative of deep membrane insertion. Polarization of IAEDANS revealed differences in mobility between mutants. The three tryptophan residues were used as a compound donor to IAEDANS in resonance energy transfer distance determinations. The values obtained for the soluble form were 1.2 A to 3.2 A longer than in the crystal structure. On addition of lipids the indicated distances increased: S16Crpt-I(AEDANS) 6.45 A (22%), K39C-I 5.45 A (18%) and T127C-I 2.4 A (14%). N-bromosuccinimide (NBS) completely abolishes the tryptophan emission from the thermolytic fragment. When lipids were added to a mixture containing ten NBS-treated channel-forming fragments to one IAEDANS labelled fragment the indicated distances increased rather more: S16Crpt-I 9.7 A (38%), K39C-I 8.1 A (36%) and T127C-I 2.5 A (16%). This showed that intermolecular transfer reduces the distance estimated in samples containing only labelled protein. The ensemble of results shows that the amphipathic helices of the C-terminal fragment open out on the surface of the lipid bilayer during the initial phase of membrane insertion.

Colicins↗
PubMed1977

Interocclusal distance: a comparison between American Caucasians and Negroes.

Cephalometric analyses were performed on groups of American Negro and Caucasian subjects to establish whether or not there were differences in interocclusal distance attributable to ethnic origin. Statistically significant differences were found between the mean interocclusal distances of the two treatment groups, supporting the hypothesis that American Negroes have an average interocclusal distance which is less than that of Caucasians. The findings of this study support the concept that fixing the interocclusal distance at 3 mm. for all complete and partial denture patients is not justified.

Adult↗
PubMed1978

Dentinal crazing and interpin distance.

All three types of self-threading plus cause dentinal crazing. The frequency and degree of damage done to the dentin varies significantly between the three types of pins and depends upon the differences in the diameters of the drill and the pin. When two or more pins are placed in dentin, the potential for dentinal damage increases. Minikin pins (0.019-inch diameter) caused the least damage, in terms of both degree and frequency. The optimum and safe interpin distance using Minikin pins suggested by this study is 3 mm. Minim and Regular pins (0.023- and 0.031-inch diameters, respectively) caused more injury than Minikin pins. The Regular pins showed more damaging effects on dentin than Minim pins, both in terms of degree and frequency. On the basis of this study, the minimum interpin distance using Minim or Regular pins should be 5 mm. These minimum interpin distances are applicable only in situations where the dentin is not dehydrated or embrittled due to endodontic treatment. In teeth that have been endodontically treated, it would be advisable to use only the smallest self-threading pins and possibly increase the interpin distance if two or more pins are to be used.

Dental Pins↗
PubMed1982

Interocclusal distance measurement comparing chin and tooth reference points.

In a group of nine dentate students with a mean age of 23.1 years, a comparison of their interocclusal distances was determined using tooth and chin reference points. This determination was made with two reference LEDs, one attached to a lower tooth and the other attached to a point on the chin. These two LEDs were registered simultaneously using the Selspot system and analyzed with the use of a computer. Three different methods were used to establish the interocclusal distance: a phonetic method, a relaxation method, and a swallowing method. Independent of the method selected, there was a greater interocclusal distance recorded by the tooth-attached reference LED. This study indicates that, in the clinical determination of interocclusal distance, where a chin reference is used the dentist should be aware of this difference--especially when lip activity is involved.

Adult↗
PubMed1990

Sex difference in intercondylar distance.

Intercondylar distances that had been determined by means of the Minigraph and Simulator instruments were statistically compared for 130 men and 130 women. The mean intercondylar distance for men was 108 mm (SD = 7.2, SE = 0.6) and for women, 102 mm (SD = 7.4, SE = 0.6). The difference was highly significant (p less than 0.0001). It was hypothesized that adjustable articulators that have a lower limit of 90 mm for the intercondylar distance adjustment will not be adjustable for 5% of women having a smaller intercondylar distance. An articulator with a lower limit of 96 mm will not be adjustable for 20% of women and 5% of men. An adjustment range of 80 to 130 mm is suggested that, on the basis of the data gathered from this study, would miss only one woman in 10,000 at the lower limit and one man in 10,000 at the upper limit.

Cephalometry↗
PubMed1994

Effects of filtration, collimation, and target-receptor distance on artificial approximal enamel lesion detection with the use of RadioVisioGraphy.

RadioVisioGraphy is an imaging modality that uses a charge-coupled device electronic sensor. Dental charge-coupled device imaging can be used to detect dental caries; however, it was not known what effect beam collimation, added filtration, or variable target-receptor distance has on this task. The purpose of this investigation was to study these effects were imaged by conventional radiography and RadioVisioGraphy varying exposure time, target-receptor distance, collimation, and filtration. Printed RadioVisioGraphy images without enhancement and E-speed radiographs were evaluated by five viewers. The number of true-positives and false-positives were compared as were sensitivity, specificity, positive and negative predictive values, accuracy, and entrance level radiation exposure. Added filtration reduced the false-positives regardless of collimation or target-receptor distance. True-positives and false-positives were greater at a target-receptor distance of 8 inch at exposures < 0.10 seconds (F < 0.0151). E-speed radiographs had a greater specificity and positive predictive value than RadioVisioGraphy images without image enhancement; however, no significant differences were found between RadioVisioGraphy images and E-speed radiographs in true-positive or false-positive identifications without image enhancement.

Analysis of Variance↗
PubMed1990

Maximal diffusion-distance within skeletal muscle can be estimated from mitochondrial distributions.

Mitochondrial volume density (Vv [mit]) distributions were measured with a test pattern of concentric rings centered upon randomly chosen capillaries in oxidative skeletal muscle cells of two Antarctic fishes, Trematomus newnesi and Notothenia gibberifrons. Vv(mit) in both species was highest in the ring closest to the capillary, minimal further from the capillary (at a distance that was characteristic for each species), and rose in the annuli furthest from the capillary. Plots of Vv(mit) against total area between each ring and the central capillary fit the form of a second-order polynomial (r2 greater than 0.9). If PO2 or blood-borne metabolite concentration predicates the pattern of Vv(mit) distribution, minimal Vv(mit) is at the same position as the minimum in concentration or gaseous partial pressure of capillary-supplied commodities. This minimum is the boundary between cylinders of tissue being supplied by adjacent capillaries, and thus delineates the maximal diffusion-distance for capillary-supplied commodities. Maximal diffusion-distance (microns) for T. newnesi = 26.23 +/- 1.64; N. gibberifrons = 21.45 +/- 0.51. For O2, maximal diffusion-distance conventionally is referred to as Krogh's radius, R. With an easily obtained estimate of numerical capillary density, these R values can be used to calculate a capillary tortuosity constant (c[k,0]) and capillary length density (Jv[c,f]). c(k,0) values were also determined using an established method, and R and Jv(c,f) values calculated from these values did not significantly differ from values determined from mitochondrial distributions. Mitochondrial distribution analysis may more accurately reflect changes in capillary blood flow and heterogeneity of diffusion and solubility constants within muscle than currently existing techniques. Similar distributions of Vv(mit) reported for several species of vertebrates suggest wide applicability of the method.

Animals↗
PubMed1990

Long-distance movement and viral assembly of tobacco mosaic virus mutants.

Spreading of tobacco mosaic virus in infected plants is of two modes: cell-to-cell movement (to adjacent cells) and long-distance movement (to distant parts of the plant). Viral coat protein has been suggested to be involved in long-distance movement. To analyze the function of coat protein in the movement, we used mutants with modifications in the coat protein gene or in the assembly origin on the genomic RNA. A mutant which has the coding region for the C-terminal 5 amino acids of the protein deleted and mutants with 1 amino acid inserted after residue 101 or 152 of the protein retained both the abilities of long-distance movement and assembly into virus particles. Other mutants in the coat protein gene eliminated the two abilities. A mutant with modifications in the assembly origin displayed greatly reduced abilities of both the movement and assembly. These results suggest that both the coat protein with its ability to assemble into virus particles and the assembly origin are involved in long-distance movement, and that virus particles may play a pivotal role in the movement.

Amino Acid Sequence↗