PubMed Health⌕ Search

Biomedical subjects

T Hildebrand

Publications and source records attributed to T Hildebrand.

At least 19 recordsLinked to original sources
PubMed2003

Complete proteinogram of cerebrospinal fluid and its contribution to the diagnostics of inflammatory and autoimmune diseases of the central nervous system.

Complete evaluation of cerebrospinal fluid proteinogram represents a routine request of the clinician in the analysis of CSF in the Czech Republic. It comprises the measurement of concentrations of acute phase proteins (CRP, orosomucoid, haptoglobin, transferrin, prealbumin), immunoglobulins (IgG, IgA, IgM), compressive markers (albumin, fibrinogen), markers of CNS tissue destruction (apolipoproteins A-I, A-II, Apo B), complement components (C3, C4), alpha-1-microglobulin, beta-2-microglobulin, and proteinase inhibitors (alpha-1-antitrypsin, antithrombin III). Therefore, 19 CSF proteins of precisely verified clinical relevance are routine parameters for the assessment of the functional state of the blood-CSF barrier, presence of the intrathecal synthesis of immunoglobulins, inflammatory changes and verification of CNS tissue destruction. Evidence of these clinically relevant and independent parameters enabled the detection of the presence of autoimmune and neuroinfective diseases of CNS, even in clinical cases where the basic CSF parameters do not express relevant changes, or they are of a bordering or non-specific character. Clinically typical and the most significant abnormalities in the CSF proteinogram represent themselves a new access to a contemporary CSF analysis. Despite the fact that assessment of CSF proteins and their analysis is quite a difficult field in laboratory medicine, it is now routinely requested and routinely performed in the Czech Republic.

Autoimmune Diseases of the Nervous System↗
PubMed1999

Direct three-dimensional morphometric analysis of human cancellous bone: microstructural data from spine, femur, iliac crest, and calcaneus.

The appearance of cancellous bone architecture is different for various skeletal sites and various disease states. During aging and disease, plates are perforated and connecting rods are dissolved. There is a continuous shift from one structural type to the other. So traditional histomorphometric procedures, which are based on a fixed model type, will lead to questionable results. The introduction of three-dimensional (3D) measuring techniques in bone research makes it possible to capture the actual architecture of cancellous bone without assumptions of the structure type. This requires, however, new methods that make direct use of the 3D information. Within the framework of a BIOMED I project of the European Union, we analyzed a total of 260 human bone biopsies taken from five different skeletal sites (femoral head, vertebral bodies L2 and L4, iliac crest, and calcaneus) from 52 donors. The samples were measured three-dimensionally with a microcomputed tomography scanner and subsequently evaluated with both traditional indirect histomorphometric methods and newly developed direct ones. The results show significant differences between the methods and in their relation to the bone volume fraction. Based on the direct 3D analysis of human bone biopsies, it appears that samples with a lower bone mass are primarily characterized by a smaller plate-to-rod ratio, and to a lesser extent by thinner trabecular elements.

Adult↗
PubMed1998

Morphometric analysis of human bone biopsies: a quantitative structural comparison of histological sections and micro-computed tomography.

As a part of the European Union BIOMED I study "Assessment of Bone Quality in Osteoporosis," the trabecular structure of transiliac bone biopsies was assessed by conventional histomorphometry and by three-dimensional microcomputed tomography (microCT). Sixty-three cylindrical human transiliac bone specimens were obtained post mortem from 27 women and 36 men (age 23-92 years) and evaluated morphometrically in this study. For the conventional histomorphometric analysis, a pair of four undecalcified sections were prepared from two regions in the mediolateral plane of the bone cores. The sections were stained with the von Kossa technique to obtain high-contrast two-dimensional images. Prior to the histologic sectioning the samples were measured with a desktop microCT, providing a 14 microm nominal resolution. The morphometric parameters computed by both methods in two or three dimensions, respectively, were bone volume density (BV/TV), bone surface density (BS/TV), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp). Results showed highly significant (p < 0.0001) correlations between conventional histology and microCT for BV/TV (r = 0.93), BS/TV (r = 0.91), Tb.Th (r = 0.84), and Tb.Sp (r = 0.91). The mean percentage differences between histology and microCT ranged from 2.5% (BV/TV) to 6.1% (Tb.Th). The high correlations and the low differences in terms of absolute numbers between conventional histomorphometric and microtomographic analysis are very promising for the use of micro-tomographic imaging. MicroCT is a nondestructive, fast, and very precise procedure that allows the measurement of cancellous and compact bone in unprocessed biopsies or small bones, as well as a fully automatic determination of three-dimensional morphometric indices.

Adult↗
PubMed1998

Do quantitative ultrasound measurements reflect structure independently of density in human vertebral cancellous bone?

Ultrasonic measurements were made in three orthogonal directions on 70 vertebral bone cubes. Apparent density (rho) was determined, and microcomputed tomography was used to derive a range of microstructural parameters. Qualitatively different ultrasonic behavior was observed in the craniocaudal (CC) axis, in which two distinct waves propagated. In this direction, only attenuation correlated strongly with rho (r2 = 80%), whereas, in the anteroposterior (AP) and mediolateral (ML) axes, there were significant correlations between all ultrasonic parameters and rho (r2 = 57%-79%). Microstructural parameters were, in general, correlated with ultrasonic properties, but when adjusted for rho, few significant relationships remained and the additional variance explained by individual microstructural parameters was relatively small (< 25% for CC axis, < 3% for AP, 0% for ML). In stepwise regression analysis including rho and all of the microstructural parameters, rho remained the primary determinant of ultrasonic properties in the transverse axes: Combinations of structural parameters explained, at most, an additional of 6% of the variability in ultrasonic properties in the AP axis, but failed to contribute significantly in the ML axis. In the CC axis, structural parameters played a greater role, but the pattern of associations was complex and the predictive power of the models was generally much less than that for the transverse axes. These data indicate that the ability of ultrasound to reflect aspects of trabecular structure is strongly dependent on the direction in which ultrasonic measurements are made, and provide only qualified support for the hypothesis that ultrasound reflects cancellous bone structure independently of bone density.

Absorptiometry, Photon↗
PubMed1997

Ridge number density: a new parameter for in vivo bone structure analysis.

An advanced analysis of the mechanical properties of bone should include information about the microarchitecture of cancellous bone in addition to its density. It has recently been shown that high-resolution quantitative computed tomography and magnetic resonance imaging have the potential to assess such information in a noninvasive way in patients. Both techniques, however, lack sufficient spatial resolution to image the individual trabeculae with true precision. In this work, a new parameter, Ridge number density (RND), is introduced. RND is a measure for the trabecular number, which can be extracted directly from high-resolution three-dimensional (3D) images of patients. We applied the RND technique to a test group of nine healthy, postmenopausal women measured repetitively with a high-resolution 3D peripheral quantitative computed tomography (3D-pQCT) system with 165 x 165 x 165 microm3 voxel size. Simultaneously with the RND determination, the trabecular bone density (TBD) was also assessed in the same volume of interest. The examination site was the distal radius. The intersubject variability of the measured test group was 10.5% for RND and 26.3% for TBD. The root mean square error between first and second examinations (midterm reproducibility) was 1.6% and 1.1%, respectively. RND is determined independently from TBD and pertains to the structure of the cancellous bone. As such, it might add crucial information in cases where bone mass or bone density measurements alone give ambiguous results.

Bone Density↗
PubMed1997

The quality of trabecular bone evaluated with micro-computed tomography, FEA and mechanical testing.

Most standard methods to predict bone quality are merely based on apparent density measurements. However, apparent density alone does neither explain all variation of the mechanical properties nor does it account for the structural anisotropy of trabecular bone. Thus, apparent density alone might not be sufficient to accurately predict the quality of bone. This study investigates if a new approach based on microstructural computer models can provide additional and relevant information on bone quality. 58 human trabecular bone samples from the femoral head were measured with a 3-D micro-Computed Tomography (micro-CT) system providing a voxel representation of the bone microarchitecture with a resolution of 28 microns. Based on such representations, the orthotropic stiffness matrices and the principal directions were computed for 5 mm cubes with microstructural Finite Element Analysis (FEA). For a subset of six samples the moduli were then validated with tri-axial mechanical compression tests. The results show that on average 15% of the variation of the elastic properties are not explained by bone volume fraction. Differences of elastic properties between samples with the same bone volume fraction range up to 53%. The variation of the degree of anisotropy is unrelated to that of the bone volume fraction. Finally, the direction-dependent stiffness of the trabecular bone differs by a factor of four, indicating that one single (isotropic) modulus as predicted from apparent density measurements might not be adequat. It is concluded that micro-CT-based FEA provides new and additional information about anisotropy and mechanical properties in a direct and non-destructive way, and thus will be important in the future for advanced failure risk prediction. An extension to patient examinations using high-resolution CT or MRI techniques is envisaged.

Biomechanical Phenomena↗
PubMed1996

In vivo reproducibility of three-dimensional structural properties of noninvasive bone biopsies using 3D-pQCT.

Trabecular bone architecture is one of the main factors influencing the mechanical behavior of cancellous bone. To assess the three-dimensional trabecular microstructure of intact bones, we introduced the concept of noninvasive bone biopsy, a method to assess and analyze cancellous bone based upon three-dimensional peripheral quantitative computed tomography in vivo (3D-pQCT). The aim of this work was to demonstrate the potential of noninvasive bone biopsies as a basis for structural and mechanical analysis of trabecular bone in the process of rapid bone loss. A group of six healthy young male volunteers was measured to provide data on the reproducibility of structural parameters. Baseline and 1-month follow-up measurements were performed to provide data on short-term precision of the procedure, and three of the controls were reanalyzed within 3-6 months to estimate long-term precision. Prior to structural evaluation, the baseline and follow-up measurements were repositioned three-dimensionally to ensure matching volumes of interest (VOI). Trabecular bone density (TBD) as well as structural indices were analyzed for all measurements. The VOIs were analyzed morphometrically by evaluating bone volume (BV/TV) and trabecular number (Tb.N) based on a direct three-dimensional approach. Trabecular thickness (Tb.Th) and trabecular separation (Tb.Sp) were derived from these two indices. The data of the measurements at 1 month to determine the short-term precision was in excellent agreement with the baseline measurements. The results showed that structural parameters can be reproduced in vivo with a coefficient of variation of less than 0.5%. With a typical spread of 4% for the structural indices within the group of healthy volunteers, an intraclass correlation of better than 0.98 was reached. We conclude that high-resolution 3D-pQCT has the potential to detect structural changes in trabecular bone during therapeutic and diagnostic trials.

Adult↗
PubMed1996

Resolution dependency of microstructural properties of cancellous bone based on three-dimensional mu-tomography.

Micro-computed tomography (microCT) is an emerging technique for the non-destructive assessment and analysis of the three-dimensional cancellous bone architecture. However, the procedures the procedures and applications used to quantify bone structures are not yet standardized. The aim of this study was to provide more insight in the resolution-dependency of microstructural properties of three-dimensional trabecular bone. Ten iliac crest bone biopsies were measured using a newly devised microCT system providing a nominal isotropic resolution of 14 microns. To study the resolution dependency the measured data were reconstructed on reduced image arrays with reduction factors ranging from 2 to 20. To assess the structural properties, morphometric parameters were computed based on a truly three-dimensional approach. The results showed a strong resolution dependency of the structural properties and that, if very precise results are needed, only the highest resolution will predict the correct values. Nevertheless, since the properties either decrease or increase monotonously up to a nominal resolution of about 175 microns, the values appear to be restorable using a suitable calibration procedure.

Bone Matrix↗
PubMed1995

[Neurohumoral activity in liver cirrhosis].

The authors assessed in 40 patients with cirrhosis of the liver and in 33 controls the plasma renin activity (PRA), aldosterone (PA), the atrial natriuretic factor (ANF) and the digoxin like activity (DLA) in plasma under basal conditions. In patients with cirrhosis of the liver they found significantly lower levels of PRA, PA and DLA, as compared with the control group, the ANF levels were not significantly altered. In the group with cirrhosis the highest neuroendocrine activity was recorded, in particular of PRA and PA in decompensated cirrhotics receiving diuretic treatment. Therefore it is useful to combine diuretics with preparations or measures which reduce the activity of the renin-angiotensin-aldosterone system and/or promote the activity of natriuretic substances. The authors found a negative correlation between PRA and SNa, PRA and UNaV, while ANF did not correlate with natriuresis. The main determinant of Na excretion in decompensated cirrhosis is the activity of the renin-angiotensin-aldosterone system. DLA plasma levels also correlated inversely with SNa values and Na excretion and thus also reflect the severity of fluid retention.

Adult↗
PubMed1995

[Treatment of cholecysto-choledocholithiasis in the present era of minimally invasive laparoscopic surgery].

The authors try to contribute to the solution of the problem of cholecystolithiasis associated with choledocholithiasis. Nowadays in the era when choledochilithiasis is treated by low-invasion methods the solution has a different character. The majority of gallstones is symptomatic, their verification and removal by the endoscopic route is not associated with major problems. Concrements not detected during the perioperative period and not detected by diagnostic methods may cause various postoperative difficulties. The authors' experience is based on 302 laparoscopic cholecystectomies performed in the course of 14 months. They made cholangiographic examinations in 54 of the operated patients. This number comprised 21 where the examination was made before the operation, 18 during the operation and in 5 it was made during the postoperative period. In 20 patients (37.03%) the cholangiographic finding was positive. Due to intensive collaboration with the endoscopic centre, when using the method of therapeutic splitting und per operative cholangiography in indicated cases, they were able to reduce the risk of missed concrements to 0.33%.

Adult↗
PubMed1994

Non-invasive bone biopsy: a new method to analyse and display the three-dimensional structure of trabecular bone.

Three-dimensional structure is one of the main factors influencing the mechanical behaviour of cancellous bone. To analyse the trabecular bone structure non-destructively we used a peripheral QCT system and applied a special thin-slice technique to create high-resolution volumetric data sets serving as a basis for something we would like to call non-invasive bone biopsy. In order to obtain binary data sets, the mineralized bone in the CT volume was separated from bone marrow and muscle tissue with the help of a sophisticated three-dimensional segmentation algorithm based on the analysis of directional derivatives, which are computed from a locally approximated fit function of the original CT volume. Binary volumes including either a solid representation of trabecular plates and rods or a topological representation of the cancellous bone architecture were acquired. Such volumes can be processed non-destructively and, even more important, repetitively. By using a surface reconstruction algorithm based on interpolating triangulation it was possible to visualize the three-dimensional surface of the trabecular bone structure. The results showed that surface representation and visualization in combination with a multiple thin-slice measuring technique are valuable tools in studying three-dimensional bone architecture. In the future, the non-invasive bone biopsies will be evaluated by means of three-dimensional mechanical analysis incorporating finite element modelling and direct morphological investigations of the cancellous bone architecture for a better prediction of bone strength as an index for fracture risk or osteoporosis.

Biopsy↗
PubMed1994

[The effect of water immersion on humoral and urinary parameters in healthy persons and in patients with liver cirrhosis].

The authors subjected 10 healthy subjects and 13 patients inflicted by liver cirrhosis in the stage of vascular decompensation (ascites and/or oedemas) to water immersion (WI). The group of healthy subjects responded during WI by a significant increase of diuresis and sodium diuresis at its maximum in the third hour, which was accompanied by a decrease of plasma aldosterone (PA) and a decrease of atrial natriuretic factor (ANF) and digoxin-like activity (DLA). The decrease of plasma vasopressin (PAVP) was not statistically significant. In patients with liver cirrhosis a significant increase of diuresis and sodium diuresis took place, whilst the response was significant already in the first hour of WI. Only 3 non-respondents were among the ill patients. In the group of liver cirrhotics also a significant decrease of AVP, PA, and an increase of ANF and DLA were recorded, the response of humoral factors was not significant due to great variability. A long term administration of diuretics (Spirolakton+Furosemid) did not decrease the serum K in ill patients. Hence, WI by means of supervention of volume expansion evokes an increase of diuresis and natriuresis in both healthy and ill subjects, the latter with decompensated liver cirrhosis which is associated with a controversial reaction of sodium diuresis and sodium retention factors. It is possible to use it as a supplementary method in the therapy of oedemas due to liver cirrhosis besides diuretic therapy. (Tab. 2, Fig. 3, Ref. 22.)

Adult↗
PubMed1993

Type IV renal tubular acidosis associated with Alport's syndrome.

A case of hereditary nephritis with mild reduction of renal function associated with renal tubular acidosis type IV is described. The patient was admitted with life-threatening hyperkalaemia. To our knowledge, type IV renal tubular acidosis has not been reported previously in association with Alport's syndrome in an adult patient.

Acidosis, Renal Tubular↗
PubMed1993

[Sjögren's syndrome].

The authors present an account on Sjögren's syndrome--clinical manifestations, diagnosis, pathogenetic aspects and treatment. The diagnosis was based on three findings: keratoconjunctivitis sicca, stomatodynia--xerostomia and other immunological, diseases. The authors used different immunological examinations, bioptic examination of the oral mucosa and parotid glands. As to gastroenterological examinations, the gastric secretion is examined according to Lambling's method, the gastroduodenum is subjected to radiographic examination, endoscopy is performed as well as a bioptic examination of the gastroduedenal mucosa.

Female↗
PubMed1993

Spirometric alterations in patients with reduced renal function.

Spirometric parameters were measured in 49 patients with reduced renal function. The patients were divided according to their glomerular filtration rate (GFR) into two groups: (A) GFR < 0.2 ml s-1-end stage renal failure; (B) GFR > or = 0.2 ml s-1. FEV1 and FEF25-75 were significantly lower in the end-stage renal failure group of patients. 80% of the patients with GFR < 0.2 ml s-1 and 31% of the patients with GFR > or = 0.2 ml s-1 had spirometric evidence of small airways dysfunction. In multiple stepwise regression analysis with ventilatory parameters as dependent variables and renal function, total protein, urea, creatinine, sodium, and hemoglobin levels, proteinuria, diuresis, and history of left ventricular failure as independent variables only GFR and total protein correlated significantly with FEV1 and FEF25. In conclusion, our study demonstrates that impairment of spirometric function in patients with renal insufficiency is continual, with reduction of GFR, and thus small airways dysfunction may be expected not only in patients with end-stage renal failure, but also in those with moderate GFR reduction.

Adult↗
PubMed1993

[Diagnosis and therapy of esophageal diseases].

In reflux disease the authors emphasize the following diagnostic procedures: a satisfactory case-history, endoscopy, aimed biopsy, radiographic evidence of reflux, radionuclide reflux scintigraphy and pH-metry. As to subsidiary examinations, they recommend Bernstein's perfusion test. In 50% of the patients with non-coronary chest pain the complaints are caused by diseases of the oesophagus. The latter include achalasia, dysphagia, idiopathic diffuse spasm, hyperdynamic oesophagus and irritable oesophagus. In the treatment of reflux disease the stage of the disease is decisive. Treatment is prolonged and the doses of drugs are higher than in duodenal ulcers. The basis are H2 blockers. In severe forms treatment with omeprazole is indicated. Surgery is indicated only in severe mucosal complications. In achalasia of the oesophagus this is disruption of the sphincter by the method of pneumatic dilatation or surgical myotomy. Idiopathic diffuse spasm and other disorders of oesophageal motility respond in different ways to treatment with calcium autagonists and nitrate treatment.

Esophageal Diseases↗