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Biomedical subjects

H Kohl

Publications and source records attributed to H Kohl.

At least 19 recordsLinked to original sources
PubMed2001

Quantitative analyses of the biomineralization of different hard tissues.

The primary crystallites of the different developing hard tissues have an apatite structure. However, they have crystal lattice distortions representing an intermediate state between amorphous and fully crystalline. We have applied energy-filtering transmission electron microscopy in the selected area electron diffraction mode to analyse different stages of crystal formation in dentine, bone, enamel and inorganic apatite mineral. We have obtained quantitative information on the degree of crystal lattice distortion using the paracrystal theory of Hosemann and Bagchi. We have found that the early formed crystallites of the hard tissues being analysed have a paracrystalline character comparable to biopolymers. However, with maturation, the lattice fluctuations of the crystallites of the hard tissues bone, enamel and dentine decrease to form a typical (para)crystalline character. Also the decrease of the organic proportion in the matrix corresponds to the decrease of the lattice fluctuation of the crystallites in the different hard tissues during maturation.

Animals↗
PubMed2001

Shoulder range of motion characteristics in collegiate baseball players.

BACKGROUND: To determine range of motion and capsular characteristics of dominant and nondominant shoulders in baseball players. Our hypothesis was that there is a significant difference between dominant and nondominant range of motion in collegiate baseball players with unoperated and without shoulder pain. METHODS DESIGN: prospective, range of motion measurements during regular season. SETTING: two collegiate baseball teams in Houston. PARTICIPANTS: 15 pitchers and 23 position players. MAIN OUTCOME MEASURES: shoulder range of motion was evaluated by goniometric technique in all baseball players. Horizontal adduction (cross body reach test) and active internal rotation (reach behind back) in standing position and external rotation and internal rotation in supine lying position were measured for each player. RESULTS: Average external rotation with the arm in 90 degrees of abduction was significantly greater and average internal rotation was less in the dominant shoulder than in the nondominant shoulders, both in pitchers and position players. There was no statistical difference in shoulder horizontal adduction. Both dominant and nondominant shoulders of pitchers had greater average range of motion in horizontal adduction and external rotation at 90 degrees of abduction and less average internal rotation than those of position players. Although there was a significant difference in active internal rotation as cm between dominant and nondominant shoulders both in both groups, no difference was found between pitchers and position players. CONCLUSIONS: Differences in the range of motion in the throwing shoulder of baseball players exist involved in overhead throwing motions and should be considered in rehabilitation of the upper extremity after injury and in the prevention of injury for pitchers and position players.

Adolescent↗
PubMed2000

Computation of contrasts in atomic resolution electron spectroscopic images of planar defects in crystalline specimens

The image obtained in a conventional transmission electron microscope contains contributions from elastically and from inelastically scattered electrons. The electron spectroscopic imaging mode of an energy-filtering transmission electron microscope allows us to separate these two different contributions by inserting an energy-selecting slit in the energy-dispersive plane of an imaging energy filter. Selecting a specific energy loss corresponding to the ionization of the inner shell of a particular element one can obtain information on the distribution of the element within the specimen. The contrast is then caused by inelastically scattered electrons. For crystalline specimens, however, the contrast will be influenced additionally by the elastic contrast. This elastic contrast arises from electron diffraction and increases with increasing crystal thickness. Therefore the intensity distribution in the image cannot directly be interpreted as an elemental map. For a reliable interpretation of contrast formation in elemental maps it is therefore necessary to compute theoretical energy-loss images for various crystal thicknesses and compare these images with the experimental images. As an example we discuss the influence of electron diffraction effects on energy-loss images of two crystals with planar defects. Linescans are computed for various thicknesses of these crystals. Our calculations are performed using first-order perturbation theory to describe the transitions between the Bloch-wave states of the incident electron. The computed linescans for various crystal thicknesses show clearly that the influence of the elastic contrast on an image increases when we investigate thicker specimens. Furthermore, the comparison between elastic and energy-loss images demonstrates the partial preservation of the elastic contrast as a function of thickness. We find that for specimens thicker than about one third of the extinction length (here approximately 80-100 A) it is impossible to interpret an energy-loss image directly as elemental map.

Journal Article↗
PubMed2000

Methods for ELNES-quantification: characterization of the degree of inversion of Mg-Al-spinels

The energy loss near-edge structures in electron energy-loss spectra contain information about bonding characteristics, the electronic structure and coordinations of the excited atoms. We have calculated sets of reference spectra for the normal and for the inverse Mg-Al-spinel using a full multiple scattering approach. By a quantitative comparison of these reference spectra with experimental data ELNES-quantification becomes possible. We characterized the degree of inversion lambda by the analysis of the relative peak-intensities and the relative peak-positions within 35 eV beyond the edge onset. The results demonstrate that by using the provided methods ELNES-quantification will become possible when uncertainties in the experiment are reduced and a better fit of the simulations to the experiment is achieved.

Journal Article↗
PubMed1999

Relativistic calculations of intensity distributions in elemental maps using contrast transfer functions.

The interpretation of highly resolved elemental maps is not straightforward: one has to consider the quantum mechanical nature of the scattering process as well as the influence of the microscope. Existing calculations of the contrast in elemental maps are based on a non-relativistic approach, while in most of the currently installed electron microscopes, the electrons penetrate the specimen with relativistic energies >/= 200 keV. Therefore, we have recalculated the intensity distribution in elemental maps based on a fully relativistic theory. Using the concept of contrast transfer functions, the simulations account for lens aberrations as well as the defocus. Surprisingly, the results exhibit considerable deviations between the relativistic and non-relativistic calculations even in the region of low acceleration voltages such as 100 kV. These differences increase with increasing acceleration voltage and are strongly dependent on aperture and energy loss. Quantitative simulations and evaluations of highly resolved elemental maps should therefore make use of a fully relativistic theory.

Journal Article↗
PubMed1999

Quantitative electron spectroscopic diffraction analyses of the crystal formation in dentine.

Newly formed apatitic crystallites of different hard tissues consist, according to our investigations, of chains composed of nanometre-sized particles (islands, dots) arising at nucleating sites of the collagenous and noncollagenous matrix macromolecules. In dentine these islands coalesce rapidly in longitudinal direction to form needle-like crystallites which further coalesce to ribbon-like crystallites. We have concluded that the centre-to-centre distances between these islands represent the distances between the nucleating sites of the matrix macromolecules. We have applied energy-filtering transmission electron microscopy in the selected area electron diffraction mode at different stages of crystal formation in dentine and have obtained quantitative information of the degree of crystal disorder on the basis of the paracrystal theory. The fluctuation of the lattice plane distances in c-axis direction decreases, proceeding from the region near the dentine/predentine border to the dentine/enamel border.

Animals↗
PubMed1997

Quantitative electron-spectroscopic diffraction (ESD) and electron-spectroscopic imaging (ESI) analyses of dentine mineralisation in rat incisors.

Primary crystal formations in all hard tissues are, according to our investigations, Ca-phosphate chains composed of nanometer sized particles (dots) which develop along the matrix macromolecules. In circumpulpal dentine the centre-to-centre distances between the dots inside the chains reflect the distances between the crystal nucleating sites ("active sites") along the collagen matrix macromolecule. The centre-to-centre distances at the surface of the mineralised collagen fibrils probably reflect the distances between nucleating sites of noncollagenous proteins attached to collagen. These needle-like chains of dots coalesce in lateral directions to form ribbon-like crystallites. The morphological results are supported by correlated small area diffraction studies in the same regions of dentine. We have found that the first appearing Bragg-reflection has a lattice spacing value of 0.388 nm, which corresponds to the (111) apatite value. For the earliest crystal formations the intensity of the (002) reflection is higher than that of the (300)-reflection. A maximum of the net-signal-intensity ratio of the (002) to (300) Bragg-reflection appears at the mineralisation front. This peak repeats with decreasing height 3 to 5 times with a distance range of about 8-16 microm through the whole dentine zone, which corresponds to the distances of the incremental lines, called "von Ebner lines".

Animals↗
PubMed1992

The clinical significance of antisperm antibodies in infertile couples.

Sera from 150 women and 162 men with unexplained infertility were examined using a commercial enzyme-linked immunosorbent assay (ELISA) kit for antisperm antibodies. The results were compared to those of the Friberg agglutination test, the post-coital test, the sperm-cervical mucus contact (SCMC) test and the pregnancy rate. We also tested follicular fluids obtained from 38 women who underwent in-vitro fertilization (IVF). These data were compared with those obtained in serum, post-coital test data and with the later development of the oocyte in IVF. Antibodies in follicular fluid were found only in women with antibodies circulating in serum. The correlation coefficient between these was 0.88 (P < 0.001). There was no correlation between antisperm antibodies in serum found with the ELISA test, and with the agglutination test, the post-coital test or the SCMC test. Neither was there any correlation between antibodies in follicular fluid and the post-coital test, the pregnancy rate or successful IVF.

Agglutination Tests↗
PubMed1990

[Contribution to cervical pregnancy].

It is reported on a rare case of cervical pregnancy as a dangerous form of ectopic pregnancy. Etiology of this case is described only hypothetically like in literature. Clinical diagnosis always is difficult and was made seldom prior to operation. By ultrasonics cervical pregnancy diagnosis is possible if it is considered. On the other hand even that can mislead as cases from literature and our case show. For prognosis the same principles are applicable as with any other ectopic pregnancy--it must be finished definitely a certain number of pregnancies carried to term can be found in literature. Mortality has been reduced by the generally improved operation conditions. Primary hysterectomy has proven therapy of choice. Conserving uterus after ligature or embolisation of the internal iliac artery seems to be justified only in exceptional cases. In early pregnancy up to the 8th gestational week vacuum extraction or curettage can be tried.

Adult↗
PubMed1989

Wolf Piezolith 2200 versus the modified Dornier HM3. Efficacy and range of indications.

From February to September 1987, a prospective study was performed at two clinics to compare the Piezolith and the Dornier HM3+ lithotripters. Based on the same clinical indications for extracorporeal shock wave lithotripsy, 334 patients were treated with the Dornier HM3+ and 378 patients with the Piezolith. Whereas stone size was similar in both groups, more ureteral calculi were treated with the Dornier HM3+ (31.1 versus 23%). The rate of successful disintegration and total number of auxiliary measures were similar in both groups. However, the mean number of impulses (HM3+ 1,997 versus Piezolith 2,855) and number of secondary ESWL treatments (HM3+ 15.5% versus Piezolith 45%) differed significantly. According to the locating systems, the success of in situ treatment was similar for renal calculi; however, fewer ureteric stones could be treated in situ at the Piezolith (HM3+ upper ureter 70.6%, middle ureter 82%, distal ureter 71.4% versus Piezolith upper ureter 37.5%, middle ureter 0%, distal ureter 62.8%). The stone-free rate at discharge and after 3 months did not differ in both centers (HM3+ 75% versus Piezolith 72%).

Child↗
PubMed1989

Plasma insulin and glucagon levels and leg measurements of lame turkeys.

As insulin is a regulator of cartilage and bone growth, plasma levels of pancreatic hormones were determined in 41 lame male turkeys with long bone distortion and 42 control toms without leg deformities. Blood samples were collected 3.5 h following the removal of feed and then 1 h after the return of feed. The day following blood collection, toms, 119 days of age, were slaughtered to obtain leg measurements. Body weight, width, and length of the tarsometatarsus, presence of tibial dyschondroplasia (TD) lesions, pancreas weight, and plasma glucose did not differ between lame and control turkeys. A significantly greater proportion of growth plates of the tarsometatarsus was closed in the control as compared to the lame turkeys. Pancreas weight relative to BW was significantly greater for lame as compared to control turkeys. Plasma insulin was undetectable in both fasted lame and control turkeys. When feed was returned to the turkeys, plasma insulin concentrations were significantly lower in lame compared to control turkeys. The return of feed had no effect on plasma glucagon levels in controls, but concentrations were decreased significantly in lame birds. These data suggest that the regulation of plasma insulin and glucagon may be altered in lame turkeys perhaps contributing to the cause of long bone distortion.

Analysis of Variance↗
PubMed1988

Evaluation and optimization of the performance of elastic and inelastic scanning transmission electron microscope imaging by correlation analysis.

Scanning Transmission Electron Microscopes (STEM) offer specific characters, such as multidetector configuration, energy loss spectroscopy, external control of the probe raster, which make them quite suited to digital image acquisition and innovative data processing. Considering pixel intensities as random variables, one can apply cross-correlation techniques to pairs of duplicated images. Such methods are used to investigate imaging properties of the instrument, such as the point resolution and the signal to noise ratio, in its different working modes. Concerning the annular dark field, one shows that there exist optimum values for defocus and angle of illumination which minimize the probe size at a value of about 0.5 nm. The same techniques are also used to evaluate the characteristics of energy filtered images recorded in a specific energy window loss around an ionization edge: the degradation in edge resolution with respect to the accompanying ADF images is only of the order of 0.2 to 0.3 nm, which sets the delocalization parameter for an energy loss of 100 eV (i.e. for U-O4-5) well below 1 nm in agreement with theoretical predictions.

DNA↗
PubMed1985

In vitro studies of a new synthetic thrombin inhibitor.

(2R, 4R)4-methyl-1-[N alpha-(3-methyl-1,2,3,4-tetrahydro-8-quinoline- sulfonyl)-L-arginyl]-2-piperidine carboxylic acid monohydrate (MCI-9038) was found to be a potent synthetic inhibitor of thrombin. In concentrations as low as 1 microM, the thrombin time, prothrombin time, and partial thromboplastin time were more than doubled. The venom (Bothrops atrox) time was similarly prolonged. The drug also inhibited the thrombin-induced activation of factors VIII and XIII. While MCI-9038 in concentrations of 10(-4) M had no effect on platelet aggregation induced by collagen, ADP, epinephrine, and arachidonate, nanomolar concentrations inhibited thrombin-induced platelet aggregation and the release of platelet ADP. The drug also significantly inhibited the adhesion of thrombin-treated platelets to cultured bovine aortic endothelial cells. We conclude that MCI-9038 is an extremely potent inhibitor of the effects of thrombin on platelets and clotting factors.

Arginine↗
PubMed1983

Fibrinolytic activity after administration of diflunisal and aspirin. A double-blind, randomized, placebo-controlled clinical trial.

A double-blind, randomized, placebo-controlled clinical trial was conducted to determine whether fibrinolysis was increased by the chronic administration of aspirin or diflunisal. Healthy male and female volunteers were randomized to receive either aspirin (1,300 mg every 12 h; 10 subjects), diflunisal (1,000 mg initially, then 500 mg every 12 h; 10 subjects), or placebo (10 subjects) for 8 days. Fibrinolytic activity was examined with the clot lysis assay, using native whole blood, platelet-rich plasma, and platelet-poor plasma, and with the kaolin-activated euglobulin lysis test. In addition, measurements were made of fibrinogen, fibrin/fibrinogen degradation products, plasminogen, and the thrombin time. Clot lysis was greater in whole blood and platelet-rich plasma than in platelet-poor plasma, and increased lysis was observed in specimens obtained in the afternoon as compared to those obtained in the morning. Fibrinolytic activity in the afternoon samples was significantly enhanced by both aspirin and diflunisal at the start of the trial (p less than 0.05), but by the afternoon of day 8, only aspirin showed some enhancement. Fibrinolytic activity, as measured by the euglobulin lysis time, actually declined in all study groups during the course of drug administration. No significant changes were recorded in any of the other assayed hemostatic parameters. We conclude that aspirin and diflunisal exert a modest, nonsustained enhancing effect on fibrinolysis in normal subjects.

Adult↗
PubMed1983

The inactivation of hemostatic factors by hematin.

Prolonged clotting times and reduced levels of clotting factors have been reported in hematin-treated patients. This effect persists for up to 5 hr after hematin infusion, associated with plasma levels ranging from 0.01 to 0.04 mg/ml. Therefore we performed in vitro studies to investigate the effects of hematin on fibrinogen, thrombin, factor VIII:C, and plasmin. Hematin in a final concentration of 0.01 mg/ml inhibited the clotting of bovine fibrinogen (1.3 to 2.6 mg/ml) by bovine thrombin (0.12 U/ml) and inhibited the hydrolysis of a synthetic substrate by human thrombin. However, if the hematin was first mixed with albumin (25 mg/ml), fourfold higher concentrations were required to prolong the thrombin clotting time. Hematin, 0.035 mg/ml, reduced VIII:C activity from 0.88 to 0.40 U/ml as measured by two-stage assay. Hematin (0.05 mg/ml) also inhibited the activation of VIII:C by thrombin (0.04 U/ml): baseline activity, 0.84 U/ml; thrombin-activated, 2.94 U/ml; with hematin added, 1.33 U/ml. Hematin also inhibited clot lysis. The inclusion of hematin (0.03 mg/ml) in the diluting buffer reduced the lysis of whole blood clots from 86% +/- 5 to 23% +/- 5 (p less than 0.001, mean +/- S.D. of four determinations) and decreased the lysis of 125I-fibrin clots induced by plasmin (0.02 CTA U/ml) from 100% to 27%. In concentrations as low as 0.09 microgram/ml, hematin inhibited the hydrolysis of a synthetic substrate by plasmin. Hematin was mixed with fibrinogen, albumin, or thrombin, and the mixtures applied to Sephadex G-200 columns. Adherence of the hematin to Sephadex was prevented by either prerinsing the column with albumin or using borate buffer at pH 9.2. Hematin co-eluted with each protein applied to the column and, in the case of fibrinogen, altered its electrophoretic mobility and markedly prolonged the thrombin clotting time of the eluted fibrinogen. We conclude that hematin binds to a variety of hemostatic proteins, inhibiting their biologic activity.

Animals↗
PubMed1981

Effects of diflunisal on platelet function and fecal blood loss.

The effects of diflunisal, a nonacetylated difluorinated salicylate, on platelet function were compared with those of aspirin and placebo. In a randomized, double-blind trial, normal subjects were given diflunisal, 250, 500, or 1,000 mg twice daily; aspirin, 650 or 1,300 mg twice daily; or placebo for 8-day periods. Difunisal, 250 mg, had no effect on platelet function, whereas 500 mg induced minimal inhibition of colagen-induced release of platelet serotonin, and 1,000 mg inhibited platelet malondialdehyde production, moderately prolonged template bleeding times (P = NS), and increased fecal blood loss (P less than 0.05). In contrast, aspirin, 650 mg, markedly inhibited collagen-induced platelet aggregation and serotonin release, and 1,300 mg prolonged bleeding time (P less than 0.01) and increased fecal blood loss (P less than 0.01). The effects of aspirin lasted for up to 5 days, whereas changes induced by diflunisal had returned to baseline 24 hr after the drug was discontinued. We conclude that in doses in the same range as those of aspirin diflunisal inhibits platelet function less.

Adult↗