Photon-counting CT using multi-material decomposition algorithm enables fat quantification in the presence of iron deposits

PURPOSE

A new generation of CT detectors were recently developed with the ability to measure individual photon's energy and thus provide spectral information. The aim of this work was to assess the performance of simultaneous fat and iron quantification using a clinical photon-counting CT (PCCT) and its comparison to dual-energy CT (DECT), MRS and MRI at 3 T.

METHODS

Two 3D printed cylindrical phantoms with 32 samples (n = 12 fat fractions between 0 % and 100 %, n = 20 with mixtures of fat and iron) were scanned with PCCT and DECT scanners for comparison. A three-material decomposition approach was used to estimate the volume fractions of fat (FF), iron and soft tissue. The same phantoms were examined by MRI (6-echo DIXON, a.k.a. Q-DIXON) and MRS (multi-echo STEAM, a.k.a. HISTO) at 3 T for comparison.

RESULTS

PCCT, DECT, MRI and MRS computed FFs showed correlation with reference fat fraction values in samples with no iron (r > 0.98). PCCT decomposition showed slightly weaker correlation with FFref in samples with added iron (r = 0.586) compared to MRI (r = 0.673) and MRS (r = 0.716) methods. On the other hand, it showed no systematic over- or underestimation. Surprisingly, DECT decomposition-derived FF showed strongest correlation (r = 0.758) in these samples, however systematic overestimation was observed. FF values computed by three-material PCCT decomposition, DECT decomposition, MRI and MRS were unaffected by iron concentration.

CONCLUSIONS

This in-vitro study shows for the first time that photon-counting computed tomography may be used for quantification of fat content in the presence of iron deposits.

The electron beam irradiation of collagen in the dry and gel states: The effect of the dose and water content from the primary to the quaternary levels

The aim of our study was to describe the impact of collagen in the gel and dry state to various doses of electron beam radiation (1, 10 and 25 kGy) which are using for food processing and sterilization. The changes in the chemical compositions (water, amino acids, lipids, glycosaminoglycans) were analyzed and the changes in the structure (triple-helix or β-sheet, the integrity of the collagen) were assessed. Subsequently, the impact of the applied doses on the mechanical properties, stability in the enzymatic environment, swelling and morphology were determined. The irradiated gels evinced enhanced degrees of cross-linking with only partial degradation. Nevertheless, an increase was observed in their stability manifested via a higher degree of resistance to the enzymatic environment, a reduction in swelling and, in terms of the mechanical behaviour, an approximation to the non-linear behavior of native tissues. In contrast, irradiation in the dry state exerted a somewhat negative impact on the observed properties and was manifested mainly via the scission of the collagen molecule and via a lower degree of stability in the aqueous and enzymatic environments. Neither the chemical composition nor the morphology was affected by irradiation.

The investigation of batch-to-batch variabilities in the composition of isolates from fish and mammalian species using different protocols

The aim of this study was to investigate batch-to-batch inconsistencies in the processing of pig and fish collagen isolates processed using two protocols that differed in terms of the acetic acid concentrations applied and the pre- and post-extraction steps, and which were previously tested in our laboratory with the intention of preserving the biological structures and functions of the collagen isolates for biomedical purposes. Both the major and minor components such as the amino acids, lipids, water, glycosaminoglycan and ash contents and elemental content, as well as the structure and morphology of the raw sources and the resulting batches of isolates were subsequently examined in detail applying standardized analytical methods including high perfomance liquid chromatography, ultraviolet-visible and infrared spectrometry, polyacrylamide gel electrophoresis, energy dispersive spectroscopy and scanning electron microscopy. All the fish isolates provided severalfold higher yields (8-45 wt%) than did the pig isolates (3-9 wt%). In addition, the variability of the fish isolate yields (the coefficient of variation for processing A: 16.4-32.9 % and B: 6.8-17.4 %) was significantly lower (p ≤ 0.05, n = 5) than that of the pig isolates (A: 27.7-69.8 %; B: 35.3-87.9 %). In general, the fish skin batches had significantly higher protein contents (˃60 wt%) and lower lipid contents (<10 wt%) than the pig skin batches (<55 wt% protein and up to 66 wt% lipid). In addition, the fish skin batches did not differ significantly in terms of their composition applying the same processing method, whereas the pig skin batches exhibited considerable variations in terms of their compositions, particularly regarding the protein and lipid contents. It can be stated that, concerning the fish isolates, processing B was, in most cases, slightly more efficient and reproducible than processing A. However, concerning the pig isolates, although processing A appeared to be more efficient than processing B in terms of the yield, it resulted in the production of isolates that contained a certain level of contaminants. The study provides a comprehensive discussion on the suitability of the processing protocol in terms of producing batches of reproducible quality according to the specific type of biomaterial processed from different animal species.

Properties of Bovine Collagen as Influenced by High-Pressure Processing

The physical properties and structure of collagen treated with high-pressure technologies have not yet been investigated in detail. The main goal of this work was to determine whether this modern gentle technology significantly changes the properties of collagen. High pressure in the range of 0-400 MPa was used, and the rheological, mechanical, thermal, and structural properties of collagen were measured. The rheological properties measured in the area of linear viscoelasticity do not statistically significantly change due to the influence of pressure or the duration of pressure exposure. In addition, the mechanical properties measured by compression between two plates are not statistically significantly influenced by pressure value or pressure hold time. The thermal properties T_on and ∆H measured by differential calorimetry depend on pressure value and pressure hold time. Results from amino acids and FTIR analyses show that exposure of collagenous gels to high pressure (400 MPa), regardless of applied time (5 and 10 min), caused only minor changes in the primary and secondary structure and preserved collagenous polymeric integrity. SEM analysis did not show changes in collagen fibril ordering orientation over longer distances after applying 400 MPa of pressure for 10 min.

Correlation between age, location, orientation, loading velocity and delamination strength in the human aorta

Aortic dissection is a biomechanical phenomenon associated with a failure of internal cohesion, which manifests itself through the delamination of the aortic wall. The goal of this study is to deepen our knowledge of the delamination strength of the aorta. To achieve this, 661 peeling experiments were carried out with strips of the human aorta collected from 46 cadavers. The samples were ordered into groups with respect to (1) anatomical location, (2) orientation of the sample, and (3) extension rate used within the experiment. The obtained results are in accordance with the hypothesis that delamination resistance is not sensitive to the extension rates 0.1, 1, 10, and 50 mms^-1. We arrived at this conclusion for all positions along the aorta investigated in our study. These were the thoracic ascending (AAs), thoracic descending (ADs), and the abdominal aorta (AAb), simultaneously considering both the longitudinal (L) as well as the circumferential (C) orientations of the samples. On the other hand, our results showed that the delamination strength differs significantly with respect to the anatomical position and orientation of the sample. The medians of the delamination strength were as follows, 4.1 in AAs-L, 3.2 in AAs-C, 3.1 in ADs-L, 2.4 in ADs-C, AAb-L in 3.6, and 2.7 in AAb-C case (all values are in 0.01·Nmm^-1). This suggests that resistance to crack propagation should be an anisotropic property and that the aorta is inhomogeneous along its length from the point of view of delamination resistance. Finally, correlation analysis proved that the delamination strength of the human aorta significantly decreases with age.

Experimental surgery as part of the development of degradable biomaterials for cardiovascular surgery

Introduction: Cardiovascular diseases are responsible for significant morbidity and mortality in the population. Artificial vascular grafts are often essential for surgical procedures in radical or palliative treatment. Many new biodegradable materials are currently under development. Preclinical testing of each new material is imperative, both in vitro and in vivo, and therefore animal experiments are still a necessary part of the testing process before any clinical use. The aim of this paper is to present the options of using various experimental animal models in the field of cardiovascular surgery including their extrapolation to clinical medicine. Methods: The authors present their general experience in the field of experimental surgery. They discuss the selection process of an optimal experimental animal model to test foreign materials for cardiovascular surgery and of an optimal region for implantation. Results: The authors present rat, rabbit and porcine models as optimal experimental animals for material hemocompatibility and degradability testing. Intraperitoneal implantation in the rat is a simple and feasible procedure, as well as aortic banding in the rabbit or pig. The carotid arteries can also be used, as well. Porcine pulmonary artery banding is slightly more difficult with potential complications. The banded vessels, explanted after a defined time period, are suitable for further mechanical testing using biomechanical analyses, for example, the inflation-extension test. Conclusion: An in vivo experiment cannot be avoided in the last phases of preclinical research of new materials. However, we try to strictly observe the 3R concept – Replacement, Reduction and Refinement; in line with this concept, the potential of each animal should be used as much as possible to reduce the number of animals.

The relevance of adhesion G protein-coupled receptors in metabolic functions

G protein-coupled receptors (GPCRs) modulate a variety of physiological functions and have been proven to be outstanding drug targets. However, approximately one-third of all non-olfactory GPCRs are still orphans in respect to their signal transduction and physiological functions. Receptors of the class of Adhesion GPCRs (aGPCRs) are among these orphan receptors. They are characterized by unique features in their structure and tissue-specific expression, which yields them interesting candidates for deorphanization and testing as potential therapeutic targets. Capable of G-protein coupling and non-G protein-mediated function, aGPCRs may extend our repertoire of influencing physiological function. Besides their described significance in the immune and central nervous systems, growing evidence indicates a high importance of these receptors in metabolic tissue. RNAseq analyses revealed high expression of several aGPCRs in pancreatic islets, adipose tissue, liver, and intestine but also in neurons governing food intake. In this review, we focus on aGPCRs and their function in regulating metabolic pathways. Based on current knowledge, this receptor class represents high potential for future pharmacological approaches addressing obesity and other metabolic diseases.

Vancomycin-Loaded Collagen/Hydroxyapatite Layers Electrospun on 3D Printed Titanium Implants Prevent Bone Destruction Associated with S. epidermidis Infection and Enhance Osseointegration

The aim of the study was to develop an orthopedic implant coating in the form of vancomycin-loaded collagen/hydroxyapatite layers (COLHA+V) that combine the ability to prevent bone infection with the ability to promote enhanced osseointegration. The ability to prevent bone infection was investigated employing a rat model that simulated the clinically relevant implant-related introduction of bacterial contamination to the bone during a surgical procedure using a clinical isolate of Staphylococcus epidermidis. The ability to enhance osseointegration was investigated employing a model of a minipig with terminated growth. Six weeks following implantation, the infected rat femurs treated with the implants without vancomycin (COLHA+S. epidermidis) exhibited the obvious destruction of cortical bone as evinced via a cortical bone porosity of up to 20% greater than that of the infected rat femurs treated with the implants containing vancomycin (COLHA+V+S. epidermidis) (3%) and the non-infected rat femurs (COLHA+V) (2%). The alteration of the bone structure of the infected COLHA+S. epidermidis group was further demonstrated by a 3% decrease in the average Ca/P molar ratio of the bone mineral. Finally, the determination of the concentration of vancomycin released into the blood stream indicated a negligible systemic load. Six months following implantation in the pigs, the quantified ratio of new bone indicated an improvement in osseointegration, with a two-fold bone ingrowth on the COLHA (47%) and COLHA+V (52%) compared to the control implants without a COLHA layer (27%). Therefore, it can be concluded that COLHA+V layers are able to significantly prevent the destruction of bone structure related to bacterial infection with a minimal systemic load and, simultaneously, enhance the rate of osseointegration.

Determination of glycosaminoglycans in biological matrices using a simple and sensitive reversed-phase HPLC method with fluorescent detection

This paper suggests a sensitive reversed-phase gradient HPLC method combined with fluorescence detection that has been developed, optimized and tested via the quantitative analysis of authentic biological material in an effort to determine and subsequently compare the total content of glycosaminoglycans (GAGs) in various collagen-based biomaterials intended for medical application. The proposed analytical method enabled the identification and separation of the GAGs present from the other components in the samples using commonly-available laboratory equipment; moreover, the very low detection limit of the method permits the determination of GAGs even for very small samples. This study describes the development of the method, including the isolation and processing of the collagen samples prior to HPLC analysis and the optimal parameters applied during the chromatographic analysis. The application of the method in laboratory practice is documented by means of several examples of the determination of GAGs employing both commercial standards and real collagen samples isolated from various animal tissues.

Vancomycin-releasing cross-linked collagen sponges as wound dressings

The study presents a novel vancomycin-releasing collagen wound dressing derived from Cyprinus carpio collagen type I cross-linked with carbodiimide which retarded the degradation rate and increased the stability of the sponge. Following lyophilization, the dressings were subjected to gamma sterilization. The structure was evaluated via scanning electron microscopy images, micro-computed tomography, and infrared spectrometry. The structural stability and vancomycin release properties were evaluated in phosphate buffered saline. Microbiological testing and a rat model of a wound infected with methicillin-resistant Staphylococcus aureus (MRSA) were then employed to test the efficacy of the treatment of the infected wound. Following an initial mass loss due to the release of vancomycin, the sponges remained stable. After 7 days of exposure in phosphate buffered saline (37°C), 60% of the material remained with a preserved collagen secondary structure together with a high degree of open porosity (over 80%). The analysis of the release of vancomycin revealed homogeneous distribution of the antibiotic both across and between the sponges. The release of vancomycin was retarded as proved by in vitro testing and further confirmed by the animal model from which measurable concentrations were observed in blood samples 24 hours after the subcutaneous implantation of the sponge, which was more than observed following intraperitoneal administration. The sponge was also highly effective in terms of reducing the number of colony-forming units in biopsies extracted from the infected wounds 4 days following the inoculation of the wounds with the MRSA solution. The presented sponges have ideal properties to serve as wound dressing for prevention of surgical site infection or treatment of already infected wounds.

The repertoire of Adhesion G protein-coupled receptors in adipocytes and their functional relevance

BACKGROUND

G protein-coupled receptors (GPCR) are well-characterized regulators of a plethora of physiological functions among them the modulation of adipogenesis and adipocyte function. The class of Adhesion GPCR (aGPCR) and their role in adipose tissue, however, is poorly studied. With respect to the demand for novel targets in obesity treatment, we present a comprehensive study on the expression and function of this enigmatic GPCR class during adipogenesis and in mature adipocytes.

METHODS

The expression of all aGPCR representatives was determined by reanalyzing RNA-Seq data and by performing qPCR in different mouse and human adipose tissues under low- and high-fat conditions. The impact of aGPCR expression on adipocyte differentiation and lipid accumulation was studied by siRNA-mediated knockdown of all expressed members of this receptor class. The biological characteristics and function of mature adipocytes lacking selected aGPCR were analyzed by mass spectrometry and biochemical methods (lipolysis, glucose uptake, adiponectin secretion).

RESULTS

More than ten aGPCR are significantly expressed in visceral and subcutaneous adipose tissues and several aGPCR are differentially regulated under high-caloric conditions in human and mouse. Receptor knockdown of six receptors resulted in an impaired adipogenesis indicating their expression is essential for proper adipogenesis. The altered lipid composition was studied in more detail for two representatives, ADGRG2/GPR64 and ADGRG6/GPR126. While GPR126 is mainly involved in adipocyte differentiation, GPR64 has an additional role in mature adipocytes by regulating metabolic processes.

CONCLUSIONS

Adhesion GPCR are significantly involved in qualitative and quantitative adipocyte lipid accumulation and can control lipolysis. Factors driving adipocyte formation and function are governed by signaling pathways induced by aGPCR yielding these receptors potential targets for treating obesity.

Evaluation of collagen/hydroxyapatite electrospun layers loaded with vancomycin, gentamicin and their combination: Comparison of release kinetics, antimicrobial activity and cytocompatibility

The aim of this study was to develop a biodegradable nanostructured electrospun layer based on collagen (COL), hydroxyapatite nanoparticles (HA), vancomycin hydrochloride (V), gentamicin sulphate (G) and their combination (VG) for the treatment of prosthetic joint infections and the prevention of infection during the joint replacement procedure. COL/HA layers containing different amounts of HA (0, 5 and 15 wt%) were tested for the in vitro release kinetics of antibiotics, antimicrobial activity against MRSA, gentamicin-resistant Staphylococcus epidermidis and Enterococcus faecalis isolates and cytocompatibility using SAOS-2 bone-like cells. The results revealed that the COL/HA layers released high concentrations of vancomycin and gentamicin for 21 days and performed effectively against the tested clinically-relevant bacterial isolates. The presence of HA in the collagen layers was found not to affect the release kinetics of the vancomycin from the layers loaded only with vancomycin or its combination with gentamicin. Conversely, the presence of HA slowed down the release of gentamicin from the COL/HA layers loaded with gentamicin and its combination with vancomycin. The combination of both antibiotics exerted a positive effect on the prolongation of the conversion of vancomycin into its degradation products. All the layers tested with different antibiotics exhibited potential antibacterial activity with respect to both the tested staphylococci isolates and enterococci. The complemental effect of vancomycin was determined against both gentamicin-resistant Staphylococcus epidermidis and Enterococcus faecalis in contrast to the application of gentamicin as a single agent. This combination was also found to be more effective against MRSA than is vancomycin as a single agent. Importantly, this combination of vancomycin and gentamicin in the COL/HA layers exhibited sufficient cytocompatibility to SAOS-2, which was independent of the HA content. Conversely, only gentamicin caused the death of SAOS-2 independently of HA content and only vancomycin stimulated SAOS-2 behaviour with an increased concentration of HA in the COL/HA layers. In conclusion, COL/HA layers with 15 wt% of HA impregnated with vancomycin or with a combination of vancomycin and gentamicin offer a promising treatment approach and the potential to prevent infection during the joint replacement procedures.

A novel gentamicin-releasing wound dressing prepared from freshwater fish Cyprinus carpio collagen cross-linked with carbodiimide

Our study presents a novel collagen wound dressing prepared from freshwater fish skin ( Cyprinus Carpio) collagen type I. Half of the sponges were cross-linked with carbodiimide. The cross-linked and non-cross-linked collagen sponges were subsequently impregnated with gentamicin and lyophilized thus allowing for the attainment of the appropriate gentamicin content without the removal thereof during the cross-linking stage. The structure was evaluated via micro-CT and infrared spectrometry and the structural stability and gentamicin release properties were evaluated in phosphate buffer solution. The sponges were further tested via a rat model of an infected wound with Pseudomonas aeruginosa inoculation and compared with a reference commercial product. The sponges thus prepared provided a degree of open porosity that was comparable to or higher than that of the reference commercial product. Spectrometry analysis revealed that the cross-linked collagen sponge and reference commercial product sponge preserved their secondary collagen structure after 168 h while early accelerated degradation was observed with respect to the non-cross-linked collagen sponge. Gentamicin was released rapidly from all the sponges. Compared to those animals with gentamicin-containing sponges or gentamicin administered intramuscularly, the animals with the cross-linked collagen sponge without gentamicin exhibited marked clinical and laboratory infection signs. Both the administration routes (intramuscular and via gentamicin-containing sponges) provided similar gentamicin plasma levels. The resulting highly homogeneous product which was characterized by excellent structural and clinical properties proved effective in terms of the treatment of a surgical wound infection in a rat model. We demonstrated that all the gentamicin was released from the sponge and was absorbed in the systemic circulation. This is the first time that Cyprinus Carpio collagen has been used in the preparation of wound dressings. Thus, gentamicin-containing sponges provide a promising tool for the treatment and prevention of surgical site infections.

Note on the use of different approaches to determine the pore sizes of tissue engineering scaffolds: what do we measure?

Background

Collagen-based scaffolds provide a promising option for the treatment of bone defects. One of the key parameters of such scaffolds consists of porosity, including pore size. However, to date, no agreement has been found with respect to the methodology for pore size evaluation. Since the determination of the exact pore size value is not possible, the comparison of the various methods applied is complicated. Hence, this study focuses on the comparison of two widely-used methods for the characterization of porosity—scanning electron microscopy (SEM) and micro-computed tomography (micro-CT).

Methods

7 types of collagen-based composite scaffold models were prepared by means of lyophilization and collagen cross-linking. Micro-CT analysis was performed in 3D and in 2D (pore size parameters were: major diameter, mean thickness, biggest inner circle diameter and area-equivalent circle diameter). Afterwards, pore sizes were analyzed in the same specimens by an image analysis of SEM microphotographs. The results were statistically evaluated. The comparison of the various approaches to the evaluation of pore size was based on coefficients of variance and the semi-quantitative assessment of selected qualities (e.g. the potential for direct 3D analysis, whole specimen analysis, non-destructivity).

Results

The pore size values differed significantly with respect to the parameters applied. Median values of pore size values were ranging from 20 to 490 µm. The SEM values were approximately 3 times higher than micro-CT 3D values for each specimen. The Mean thickness was the most advantageous micro-CT 2D approach. Coefficient of variance revealed no differences among pore size parameters (except major diameter). The semi-quantitative comparison approach presented pore size parameters in descending order with regard to the advantages thereof as follows: (1) micro-CT 3D, (2) mean thickness and SEM, (3) biggest inner circle diameter, major diameter and area equivalent circle diameter.

Conclusion

The results indicated that micro-CT 3D evaluation provides the most beneficial overall approach. Micro-CT 2D analysis (mean thickness) is advantageous in terms of its time efficacy. SEM is still considered as gold standard for its widespread use and high resolution. However, exact comparison of pore size analysis in scaffold materials remains a challenge.

Electronic supplementary material

The online version of this article (10.1186/s12938-018-0543-z) contains supplementary material, which is available to authorized users.

Comparison of ground sections, paraffin sections and micro-CT imaging of bone from the epiphysis of the porcine femur for morphometric evaluation

The aim of this study was to compare data on the volume fraction of bone and the thickness of the cortical compact bone acquired during microcomputed tomography (micro-CT) analysis with data acquired from identical samples using stereological analysis of either decalcified paraffin sections or ground sections. Additionally, we aimed to compare adjacent tissue samples taken from the major trochanter of the porcine femur to map the basic biological variability of trabecular bone. Fifteen pairs of adjacent tissue blocks were removed from the major trochanter of the proximal epiphyses of porcine femurs (female pigs aged 24-39 months, weight=59.16±8.15kg). In each sample, the volume of the cortical compact bone, the volume of the trabecular bone, and the thickness of the cortical compact bone was assessed using micro-CT. Afterwards, half of the samples were decalcified and processed using paraffin histological sections. Another half was processed into ground sections. The volume and thickness of bone was assessed in histological sections using stereological techniques. There were no significant differences in the bone volumes and thicknesses measured by micro-CT and the corresponding values quantified in decalcified sections. Similarly, there were no differences between the results from micro-CT and the analysis of the corresponding ground sections. Histomorphometric studies based on relatively low numbers of undecalcified ground sections or demineralized paraffin sections of bone yield data on bone volume and the thickness of cortical compact bone that is comparable with three-dimensional micro-CT examination. The pilot data on the variability of cortical compact bone and trabecular bone volumes in the porcine major trochanter provided in this study aim for planning experiments in the field of bone healing and implantology.

Generating standardized image data for testing and calibrating quantification of volumes, surfaces, lengths, and object counts in fibrous and porous materials using X-ray microtomography

Quantification of the structure and composition of biomaterials using micro-CT requires image segmentation due to the low contrast and overlapping radioopacity of biological materials. The amount of bias introduced by segmentation procedures is generally unknown. We aim to develop software that generates three-dimensional models of fibrous and porous structures with known volumes, surfaces, lengths, and object counts in fibrous materials and to provide a software tool that calibrates quantitative micro-CT assessments. Virtual image stacks were generated using the newly developed software TeIGen, enabling the simulation of micro-CT scans of unconnected tubes, connected tubes, and porosities. A realistic noise generator was incorporated. Forty image stacks were evaluated using micro-CT, and the error between the true known and estimated data was quantified. Starting with geometric primitives, the error of the numerical estimation of surfaces and volumes was eliminated, thereby enabling the quantification of volumes and surfaces of colliding objects. Analysis of the sensitivity of the thresholding upon parameters of generated testing image sets revealed the effects of decreasing resolution and increasing noise on the accuracy of the micro-CT quantification. The size of the error increased with decreasing resolution when the voxel size exceeded 1/10 of the typical object size, which simulated the effect of the smallest details that could still be reliably quantified. Open-source software for calibrating quantitative micro-CT assessments by producing and saving virtually generated image data sets with known morphometric data was made freely available to researchers involved in morphometry of three-dimensional fibrillar and porous structures in micro-CT scans.

Dry versus hydrated collagen scaffolds: are dry states representative of hydrated states?

Collagen composite scaffolds have been used for a number of studies in tissue engineering. The hydration of such highly porous and hydrophilic structures may influence mechanical behaviour and porosity due to swelling. The differences in physical properties following hydration would represent a significant limiting factor for the seeding, growth and differentiation of cells in vitro and the overall applicability of such hydrophilic materials in vivo. Scaffolds based on collagen matrix, poly(DL-lactide) nanofibers, calcium phosphate particles and sodium hyaluronate with 8 different material compositions were characterised in the dry and hydrated states using X-ray microcomputed tomography, compression tests, hydraulic permeability measurement, degradation tests and infrared spectrometry. Hydration, simulating the conditions of cell seeding and cultivation up to 48 h and 576 h, was found to exert a minor effect on the morphological parameters and permeability. Conversely, hydration had a major statistically significant effect on the mechanical behaviour of all the tested scaffolds. The elastic modulus and compressive strength of all the scaffolds decreased by ~95%. The quantitative results provided confirm the importance of analysing scaffolds in the hydrated rather than the dry state since the former more precisely simulates the real environment for which such materials are designed.

[Chest drain injury of the heart]

INTRODUCTION

Injury to the heart during chest drainage is a very rare but potentially fatal complication of the procedure.

CASE REPORT

A 56-year-old, polymorbid, poorly co-operative and extremely obese patient with chronic cardiac subcompensation and pleural effusion was admitted to a district hospital. A drain was inserted into the left pleural cavity in order to evacuate the pleural effusion. Fresh oxygenated blood was flowing out from the drain. The drain was clamped immediately. Echocardiography showed drain insertion into the left ventricle. A cardiac surgeon was contacted and indicated patient transfer to a cardiac surgery department followed by an emergency surgery. During the surgery performed through a left thoracotomy, a defect in the left ventricular wall was sutured. The patient was then stabilized, transferred back to the district hospital and, after achieving cardiopulmonary compensation, discharged home.

CONCLUSION

Injury to the heart in chest drainage is a very serious iatrogenic complication. If it is to be managed successfully, the site of the insertion of the drain tip needs to be correctly identified and the drain must not be extracted. A surgical department capable of adequately addressing this complication needs to be contacted promptly, as emergency surgery may be the only lifesaving possibility.Key words: chest drainage - complication - heart injury.

The Sustainable Release of Vancomycin and Its Degradation Products From Nanostructured Collagen/Hydroxyapatite Composite Layers

Infections of the musculoskeletal system present a serious problem with regard to the field of orthopedic and trauma medicine. The aim of the experiment described in this study was to develop a resorbable nanostructured composite layer with the controlled elution of antibiotics. The layer is composed of collagen, hydroxyapatite nanoparticles, and vancomycin hydrochloride (10 wt%). The stability of the collagen was enhanced by means of cross-linking. Four cross-linking agents were studied, namely an ethanol solution, a phosphate buffer solution of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide, genipin, and nordihydroguaiaretic acid. High performance liquid chromatography was used so as to characterize the in vitro release rates of the vancomycin and its crystalline degradation antibiotically inactive products over a 21-day period. The maximum concentration of the released active form of vancomycin (approximately 265 mg/L) exceeded the minimum inhibitory concentration up to an order of 17 times without triggering the burst releasing effect. At the end of the experiment, the minimum inhibitory concentration was exceeded by up to 6 times (approximately 100 mg/L). It was determined that the modification of collagen with hydroxyapatite nanoparticles does not negatively influence the sustainable release of vancomycin. The balance of vancomycin and its degradation products was observed after 14 days of incubation.

The effects of different cross-linking conditions on collagen-based nanocomposite scaffolds-an in vitro evaluation using mesenchymal stem cells

Nanocomposite scaffolds which aimed to imitate a bone extracellular matrix were prepared for bone surgery applications. The scaffolds consisted of polylactide electrospun nano/sub-micron fibres, a natural collagen matrix supplemented with sodium hyaluronate and natural calcium phosphate nano-particles (bioapatite). The mechanical properties of the scaffolds were improved by means of three different cross-linking agents: N-(3-dimethylamino propyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide in an ethanol solution (EDC/NHS/EtOH), EDC/NHS in a phosphate buffer saline solution (EDC/NHS/PBS) and genipin. The effect of the various cross-linking conditions on the pore size, structure and mechanical properties of the scaffolds were subsequently studied. In addition, the mass loss, the swelling ratio and the pH of the scaffolds were determined following their immersion in a cell culture medium. Furthermore, the metabolic activity of human mesenchymal stem cells (hMSCs) cultivated in scaffold infusions for 2 and 7 days was assessed. Finally, studies were conducted of cell adhesion, proliferation and penetration into the scaffolds. With regard to the structural stability of the tested scaffolds, it was determined that EDC/NHS/PBS and genipin formed the most effectively cross-linked materials. Moreover, it was discovered that the genipin cross-linked scaffold also provided the best conditions for hMSC cultivation. In addition, the infusions from all the scaffolds were found to be non-cytotoxic. Thus, the genipin and EDC/NHS/PBS cross-linked scaffolds can be considered to be promising biomaterials for further in vivo testing and bone surgery applications.

Support for the initial attachment, growth and differentiation of MG-63 cells: a comparison between nano-size hydroxyapatite and micro-size hydroxyapatite in composites

Hydroxyapatite (HA) is considered to be a bioactive material that favorably influences the adhesion, growth, and osteogenic differentiation of osteoblasts. To optimize the cell response on the hydroxyapatite composite, it is desirable to assess the optimum concentration and also the optimum particle size. The aim of our study was to prepare composite materials made of polydimethylsiloxane, polyamide, and nano-sized (N) or micro-sized (M) HA, with an HA content of 0%, 2%, 5%, 10%, 15%, 20%, 25% (v/v) (referred to as N0–N25 or M0–M25), and to evaluate them in vitro in cultures with human osteoblast-like MG-63 cells. For clinical applications, fast osseointegration of the implant into the bone is essential. We observed the greatest initial cell adhesion on composites M10 and N5. Nano-sized HA supported cell growth, especially during the first 3 days of culture. On composites with micro-size HA (2%–15%), MG-63 cells reached the highest densities on day 7. Samples M20 and M25, however, were toxic for MG-63 cells, although these composites supported the production of osteocalcin in these cells. On N2, a higher concentration of osteopontin was found in MG-63 cells. For biomedical applications, the concentration range of 5%–15% (v/v) nano-size or micro-size HA seems to be optimum.

Optimizing and evaluating the biocompatibility of fiber composites with calcium phosphate additives

Composite materials based on a polyamide fabric (aramid) and a polydymethylsiloxane (PDMS) matrix were designed for application in bone surgery. In order to increase the bioactivity, 2, 5, 10, 15, 20, and 25 vol.% of nano/micro hydroxyapatite (HA) and tricalcium phosphate (TCP) were added. We studied the effect of the additives on the biocompatibility of the composite. It appears that nano additives have a more favorable effect on mechanical properties than microparticles. 15 vol.% of nano hydroxyapatite additive is an optimum amount for final application of the composites as substitutes for bone tissue: in this case both the mechanical properties and the biological properties are optimized without distinct changes in the inner structure of the composite.

[Hemipelvectomy for a desmoidal tumor]

A case- review describing a desmoid in a young female. The tumor originated at the tendinuous attachment of the m. rectus abdominis on the pubic bone, which had had two relapses. During the third--so far the latest--procedure it required left-sided hemipelvectomy with resection of the rectum and a part of the vagina. The patient was instructed about the serious character of the disease, the requirement for the radical resection and about the requirement for a careful long-term follow-up of the patient after the procedure.

[Extragenital endometriosis as a subject of interest for the surgeon]

Endometriosis is a common gynaecological disorder, affecting 10-15% of the fertile female population. Most frequently, it affects internal genitalia, the main symptoms being pelvialgia and infertility. In 5% of the cases the disorder may also affect extragenital structures and present itself as endometriomas of the appendix, the small or the large intestine, the umbilicus, the inguinal canal, the residual scars after laparotomies or the diaphragm. They may also imitate a malignancy. The diagnostic key is the cyclic character of the pain or of the bleeding to the tract and the laparoscopic confirmation of the presence of the foci. When the diagnosis is known, a simple excision, extirpation or resection suffices. In case the malignancy cannot be excluded, a more extensive procedure is indicated. The authors present two case-reviews during a twelve-year period, in both cases the sigmoid was affected. In the first case, a radical resection of the rectosigmoid due to a suspected malignancy was performed, while in the second case, a simple excision of the endometrioma where the diagnosis was known was performed. The authors stress-out advantages of the interdisciplinary approach to the treatment of the complicated cases of endometriosis, so that the disorder would be solved in one surgical procedure.

[Visceral reduction in surgical treatment of "impossibly" large abdominal hernias]

The authors present a group of 6 patients treated in 1996-2000 with giant "impossible" hernia the contents of which "lost their rights in the abdominal cavity". The patients involved were old polymorbid people (mean age 75 years), 5 suffered from acute, one from chronic obstruction of the gut. After intensive preparation the authors implemented a hernioplasty, using an excessive surgical mesh, reduced the volume of the abdominal contents by the omentum in all subjects, by the right colon in two and by a 0.5-1 m segment of the ileum in 3 patients. Only one extremely polymorbid patient died because of multiorgan failure on the 17th day after surgery. In 5 patients artificial ventilation was necessary from 2 hours to 17 days. As to complications, diarrhoea was recorded in one patient and infection of the mesh in another one. The authors conclude that the majority of "impossible" incarcerated hernias can be resolved by visceroreduction and enlargement of the volume of the abdominal cavity by inserting an excessive surgical mesh into the enlarged hernial neck. In elective operations of such hernias for the preparation forced reduction of the weight can be used and the technique of enlargement of the abdominal volume by intermittent pneumoperitoneum. In this way a giant "impossible" hernia can be treated without threatening the patient's life by cardiopulmonary failure.

Sclerosing papillary carcinoma of the thyroid with tubular features

A case of papillary thyroid carcinoma (PTC) in a twenty-seven year old female is reported. The patient presented with complaints of a goiter and associated dysphagia. Histologically, the tumor was characterized by diffuse growth of branching tubules lined by a single layer of the tumor cells and surrounded by circularly arranged fibrous tissue of variable thickness. Focally, micropapillary projections of the epithelium budding into the lumen of tubules were visible. The cells showed features of PTC (overlapping ground glass nuclei, multiple grooves and pseudoinclusions). Nevertheless, no areas of "classical" PTC were identified. A striking feature was the presence of a severe lymphoplasmocytic infiltrate and the presence of plentiful S-100 protein positive dendritic/Langerhans cells. The tumor shares several features with diffuse sclerosing PTC, namely the age and sex of the patient, the infiltrative growth pattern and the presence of severe chronic thyroiditis that is associated with a large number of dendritic/Langerhans cells in the background. There are, however, several distinct differences - particularly the absence of massive squamous metaplasia, psammoma bodies, areas of classical PTC, and also lack of invasion of lymphatic vessels. We believe that this tumor represents an unusual example of diffuse sclerosing PTC with special tubular features.

[Primary carcinoma of the duodenum]

The authors describe the case of a 70-year-old man with primary adenocarcinoma of the fourth segment of the duodenum. Due to the infrequency of the condition there was diagnostic and therapeutic uncertainty. After the endoscopic and bioptic diagnosis three months elapsed before an incorrectly indicated derivation operation and only after another month the tumour was resected. The exhausted patient developed postoperative pancreatitis with subsequent multiorgan failure to which he succumbed. The disease should be suspected even if the symptomatology is poor. The patient suffered only from nausea and anaemia. From the diagnostic aspect endoscopic examination is most useful for the oral segment of the duodenum and double contrast examination for the aboral one. The method of treatment is duodenopancreatectomy for the upper part and segmental resection for the distal part of the duodenum.

[Reoperation of gastric banding in obesity]

From September 1988 till June 1997 the authors performed gastric banding for morbid obesity in 644 patients. In 14 (2.2%) reoperation was necessary: on account of stenosis of the stoma with excessive weight loss in 10, inadequate weight loss in four patients. Correction was performed by prolonging the circumference of the cuff in five and by re-banding of the stomach and creation of a stoma with a 12 mm diameter and a "small stomach" with a volume of 15 ml in nine patients. No death nor complications were recorded. The results with complete recovery of the condition were excellent in the group with excessive weight loss, more modest in the group with a small weight loss. The authors emphasize the necessity of comprehensive care of obese patients; an optimal bariatric operation must be followed by long-term follow-up of patients to achieve a change of lifestyle as regards dietary habits as well as regular physical activity.

[Allogenic vein transplantation in vascular surgery]

The authors evaluate retrospectively a group of 159 applications of venous transplants for arterial reconstruction in 54 patients and for preparation of a haemodialyzation approach in the remaining 105 patients. As allograft they used the stem of the saphena magna from patients with varices kept in saline with addition of an antibiotic at a temperature of 4 degrees C. Twelve-month patency rate was in vascular reconstructions 84%, in secondary arteriovenous fistulae 45.8%. Based on data in the literature and their own experience the authors draw attention of vascular surgeons to this cheap and available material and recommend its wider use as a second choice replacement.

[Gastric banding in the treatment of obesity]

Failure of conservative treatment of obesity stimulated the development of bariatric surgery. The authors performed in 1988-1995 GB in 248 obese patients with a mean overweight of 48.2 kg and with serious comorbidity. The mortality in the group was 1.6%, the morbidity 12.5%. Within 12 months after operation the overweight of the patients declined by 70%, within 24 months by 57%. In the majority of patients the comorbidity receded, the blood sugar level reached normal levels, dyspnoea and hypertension improved as well as the psychic state and social position. The attained results confirm that this treatment of morbid obesity is justified and the authors recommend its wider use. Perspectively laparoscopic gastric banding is associated with a reduced mortality and morbidity, however it is also associated with higher costs.

[Traumatic dissection of the duodenal wall in a child]

The authors present the case of a 6-year-old girl admitted to the department three days after a blunt abdominal injury. On surgical revision a dissecting haematoma of the wall of retroperitoneal duodenal sections was revealed. After its treatment and nutritive puncture jejunostomy the subsequent postoperative course was free from complications. This is an infrequent GIT injury in childhood which can be treated also by conservative methods.

[Tension-free surgery of femoral hernias using the Lichtenstein method]

Based on 12 operations, the author report on the advantages of "plug tension-free" plastic operations. The femoral canal is along its entire course sealed by a cylinder of rolled up polyester net. This operation reduces the postoperative discomfort and danger of the development of a relapse.

[Venous aneurysms]

Venous aneurysms are a rare condition. It is an independent nosological unit which differs from varicosities by the following signs: it is not sex- or age-linked, it is found also in children, it can affect any vein, it is found as a solitary lesion and is not associated with prolongation of the affected vein. The therapeutic approach is surgical extirpation. The most serious clinical manifestation can be pulmonary embolism. The author presents four of his own observations with localization on the external jugular vein, the v. cephalica antebrachii, the anterior tibial vein and v. dorsalis digiti manus.

[Video thoracoscopic splanchnicectomy in persistent epigastric pain]

For palliation of persisting pain caused by inoperable malignity in the epigastrium or chronic pancreatitis a number of surgical and non-surgical operations of the splanchnic nerves was elaborated. Abdominal and thoracic approaches are associated with technical difficulties and burden the patient; blocks by puncture are associated with risk. The optimal procedure appears to be videothoracoscopic left-sided splanchnicectomy, the authors performed this operation in nine patients (in seven on account of a malignant process, in two on account of chronic pancreatitis). In all immediate alleviation of pain occurred, in two later some pain reappeared. Based on the favourable experience, the authors recommend this minimal invasive procedure.

[The Lichtenstein "tension free" operation for inguinal hernia]

The authors present their experience with operations of 264 inguinal hernias in 238 subjects where Lichtenstein's technique was used. The principle of the operation is reconstruction of the posterior wall of the inguinal canal by means of a synthetic mesh-tension free. The attained results in this group (L) were compared with a control group of 68 operated patients (group C) where the classical McVaye technique was used. They did not find a difference in the time taken up by the operation or the time of hospitalization. The postoperative mortality was 0.4% in group L and 2.9% in group C, the morbidity was 15.5% and 42.6% resp. So far they did not record a case of relapsing hernia or rejection of the mesh. The operation is easy to perform, economically unpretentious, the postoperative pain is milder and the sensation of discomfort slighter than after the classical operation. With regard to the assembled experience, the authors recommend the new operation not only in inguinal but also other types of hernias where tension free repair is impossible. For reconstruction they use polyester mesh CHS 100 manufactured by the Hosiery Research Institute in Brno.

[Isolated rupture of the external iliac vein in indirect blunt injuries]

The authors described an in this country hitherto unpublished observation of an isolated rupture of the external iliac vein following the fall of a patient from a height on her left side. The rupture developed most probably as a result of narrowing of the external iliac vein which crosses the left internal iliac artery. A mechanism of acute expansion of the external iliac vein due to a blast wave of venous blood expelled by an impact on the thigh and recoiled from the impediment at the site of crossing with the internal iliac vein was probably involved. After severing of the compressing artery, thrombectomy and suture of the lesion, the patient recovered ad integrum.

[Aneurysms of the renal artery in childhood]

The authors describe the case-history of a nine-year-old boy engaged in sports, suffering from serious hypertension due to an aneurysm of the renal artery of the right kidney. Vascular reconstruction was performed. They boy died, however, suddenly 20 hours after operation and on necropsy serious hypoplasia of the adrenals was revealed.

[Do we amputate too much or too little? A retrospective analysis of the situation in the East Bohemian Region]

A retrospective analysis of 1146 amputations of the lower extremities in five departments of the East Bohemin a region revealed that the number of amputations in the thigh is higher and less frequently preceded by angiographic examination and reconstruction operations of the arteries as compared with distinguished departments abroad. The mortality after amputations was 12.5%. The results call for more intensive training of vascular surgeons and the establishment of vascular surgical departments where it would be possible by early reconstruction operations made in time to prevent amputations or at least shift the height of the amputation in the most distal direction possible.

[Subtotal colectomy in the treatment of obstructive tumors in the left half of the colon]

The authors give an account of 14 patients during a two-year period where on account of an occluding tumour of the left half of the colon they performed subtotal colectomy with ileodescendent--in 2, ileosigmoideal--in 10 and ileorectal anastomosis in two patients. After operation and by the time when the material was processed, none of the patients died. Based on data in the literature and the authors' own material, the authors discuss the advantages of subtotal colectomy, as compared with hitherto used multistage procedures. The advantages include in particular a lower operative mortality (0-14%), a higher five-year survival (46%) a markedly lower morbidity, time economy, a shorter period of hospitalization and in particular, the patients are spared colostomy, even temporary one. The authors recommend subtotal colectomy as the method of choice on account of ileus caused by tumourous occlusion of the left half of the colon.

[Pharyngo-gastric anastomosis in the treatment of cancer of the pharyngo-esophageal region]

The authors submit their own experience with pharyngogastric anastomosis in patients where on account of circumferential cancer of the oesophagus and hypopharynx laryngopharyngooesophagectomy had to be performed. For the anastomosis a tubular flap of the greater curvature of the stomach was used which was pulled through the posterior mediastinum and sutured with the mucosa and musculature of the residual pharynx and the preserved upper half of the epiglottis. The operation is pretentious and requires satisfactory cardiopulmonary function of the patient. A disadvantage of the operation is substantial loss of gastric function, compensated by the patients by a therapeutic diet and medicinal substitution of the gastric chemism. An obvious advantage of the operation is the radical character of the oncological procedure and rapid rehabilitation of swallowing which was restored in the authors' patients on the 8th to 14th day.