Anisotropic damage of soft tissues in supra-physiological deformations

Soft tissues may undergo mechanical damage under supra-physiological deformations caused by medical treatments such as balloon-angioplasty and stent deployment. This damage is exhibited as a softening in the mechanical behavior of tissues. In this work, alteration of the collagen network is treated as the origin of damage and loss of stiffness. Inspired by the hierarchical structure of the collagen network, the mechanical properties of collagenous tissues are connected to model parameters. Softening of esophageal and arterial tissues under directional cyclic loading is investigated to determine evolution of the associated material parameters through damage progress. An evolution law is proposed which predicts the mechanical behavior of tissues after excessive deformations. Various deformation measures are examined as the damage parameter to determine the most appropriate one for general 3D loading. It is observed that, if the Green-Lagrange strain in the direction of the fibers is used as the damage parameter, the proposed law well describes the evolution of the collagen network's stiffness. The results not only facilitate prediction of the deformation-induced damage under supra-physiological deformations but also are useful for surgeons in better planning of surgical procedures and stents design.

Rotavirus Infection Enhances Levels of Autoantibodies Against Islet Cell Antigens GAD65 and IA-2 in Children with Type 1 Diabetes

BACKGROUND

Some studies implicate rotavirus infection as a trigger for the development of type 1 diabetes mellitus (T1DM) in children, however findings are controversial.

OBJECTIVES

We investigated the link between rotavirus infection and autoantibodies against islet antigens and T1DM in children.

METHODS

Serum samples from 80 new-onset diabetic and 80 nondiabetic children were screened for anti-rotavirus IgG, anti-GAD65 and anti-IA-2 autoantibodies using ELISA kits.

RESULTS

Positivity percentages of anti-rotavirus IgG detection in diabetic and nondiabetic children were 51.3% and 35.0%, respectively (p = 0.03). The mean anti-GAD65 and anti-IA-2 antibody titers in anti-rotavirus IgG positive samples were statistically higher than that the anti-rotavirus IgG negative samples. A positive correlation was found between anti-rotavirus IgG and anti-GAD65 antibody levels (p = 0.004; r = 0.22).

CONCLUSIONS

Our findings support the hypothesis that rotovirus infection may induce T1DM in children.

Disease-Specific Assessment of Quality of Life after Decompression Surgery for Graves' Ophthalmopathy

Purpose

Graves' ophthalmopathy (GO) is an organ-specific autoimmune disease. Hydrophily of accumulated acidic mucopolysaccharides into bulbar adipose tissue leads to swelling of the eye muscles. Orbital surgical decompression is performed in severe cases of compressive optic neuropathy and severe corneal exposure or failure of steroid therapy. The study was designed to evaluate decompression surgery with respect to the clinical benefit and the patient's satisfaction by means of a disease-specific questionnaire.

METHODS

The 90-item study questionnaire was distributed to 105 patients with GO who underwent orbital decompression surgery at the authors' institution.

Results

A total of 88% of patients stated that decompression had helped them, 80% of the interviewees would undergo decompression again, 78% were content with their eye symptoms, and 71% were satisfied with the cosmetic result of decompression. Furthermore, analysis showed a clinically relevant increase in quality of life after surgery. The correlation between the clinical endpoint proptosis at last examination and the quality of life score proved to be significant (p=0.05).

CONCLUSIONS

The large majority of interviewees were satisfied with the result of the orbital decompression. These results confirmed that disfiguring proptosis is an important indication for decompression surgery.

Application of Human Acellular Breast Dermal Matrix (ABDM) in Implant-Based Breast Reconstruction: An Experimental Study

BACKGROUND

The use of acellular dermal matrices (ABDM) has become more common for breast reconstruction to improve postoperative outcomes. We evaluated the efficacy of breast reconstruction by the application of human ABDM in a sheep model.

METHODS

The sheep in group I (GI) (N = 4) underwent the following procedures on the right side: (1) breast reconstruction using human ABDM after total mastectomy, (2) human ABDM under the skin, near the breast area and on the left side, (3) fat injection and human ABDM after partial mastectomy, and (4) replacement of ABDM in the abdominal wall far from the breast. Sheep in group II (GII) (N = 4) underwent the following procedures. On the right side: (1) breast reconstruction using ABDM after total mastectomy, (2) replacement of ABDM under the skin, near the breast area, and on the left side, (3) application of vicryl synthetic mesh after partial mastectomy and (4) replacement of mesh under the skin, near the breast area.

RESULTS

Histological evaluations of decellularized skin scaffolds demonstrated a collagen-based matrix with preserved ECM and complete nuclear removal. Histological evaluations of implanted ABDM demonstrated a viable matrix with fibroblast infiltration and revascularization in all follow-ups. The overall surgical complication rate was significantly lower in the ABDM implant under the skin and near the breast in both short- and long-term follow-ups.

CONCLUSION

The results of this study demonstrated that the application of novel prepared ABDMs has promising outcomes for breast reconstruction to provide total coverage without the need for breast expansion before implant placement.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors http://www.springer.com/00266.

A novel technique for simultaneous whole-body and multi-organ decellularization: umbilical artery catheterization as a perfusion-based method in a sheep foetus model

The aim of this study was to develop a method to generate multi-organ acellular matrices. Using a foetal sheep model have developed a method of systemic pulsatile perfusion via the umbilical artery which allows for simultaneous multi-organ decellularization. Twenty sheep foetuses were systemically perfused with Triton X-100 and sodium dodecyl sulphate. Following completion of the whole-body decellularization, multiple biopsy samples were taken from different parts of 21 organs to ascertain complete cell component removal in the preserved extracellular matrices. Both the natural and decellularized organs were subjected to several examinations. The samples were obtained from the skin, eye, ear, nose, throat, cardiovascular, respiratory, gastrointestinal, urinary, musculoskeletal, central nervous and peripheral nervous systems. The histological results depicted well-preserved extracellular matrix (ECM) integrity and intact vascular structures, without any evidence of residual cellular materials, in all decellularized bioscaffolds. Scanning electron microscope (SEM) and biochemical properties remained intact, similar to their age-matched native counterparts. Preservation of the collagen structure was evaluated by a hydroxyproline assay. Dense organs such as bone and muscle were also completely decellularized, with a preserved ECM structure. Thus, as shown in this study, several organs and different tissues were decellularized using a perfusion-based method, which has not been previously accomplished. Given the technical challenges that exist for the efficient generation of biological scaffolds, the current results may pave the way for obtaining a variety of decellularized scaffolds from a single donor. In this study, there have been unique responses to the single acellularization protocol in foetuses, which may reflect the homogeneity of tissues and organs in the developing foetal body.

Hybrid carbon fiber/carbon nanotube composites for structural damping applications

Carbon nanotubes (CNTs) were grown on the surface of carbon fibers utilizing a relatively low temperature synthesis technique; graphitic structures by design (GSD). To probe the effects of the synthesis protocols on the mechanical properties, other samples with surface grown CNTs were prepared using catalytic chemical vapor deposition (CCVD). The woven graphite fabrics were thermally shielded with a thin film of SiO2 and CNTs were grown on top of this film. Raman spectroscopy and electron microscopy revealed the grown species to be multi-walled carbon nanotubes (MWCNTs). The damping performance of the hybrid CNT-carbon fiber-reinforced epoxy composite was examined using dynamic mechanical analysis (DMA). Mechanical testing confirmed that the degradations in the strength and stiffness as a result of the GSD process are far less than those encountered through using the CCVD technique and yet are negligible compared to the reference samples. The DMA results indicated that, despite the minimal degradation in the storage modulus, the loss tangent (damping) for the hybrid composites utilizing GSD-grown MWCNTs improved by 56% compared to the reference samples (based on raw carbon fibers with no surface treatment or surface grown carbon nanotubes) over the frequency range 1-60 Hz. These results indicated that the energy dissipation in the GSD-grown MWCNTs composite can be primarily attributed to the frictional sliding at the nanotube/epoxy interface and to a lesser extent to the stiff thermal shielding SiO2 film on the fiber/matrix interface.

Synthesis of WS2 nanostructures from the reaction of WO3 with CS2 and mechanical characterization of WS2 nanotube composites

Tungsten disulfide (WS(2)) nanometer sheets, spheres, fibers and tubes were generated by a synthetic pathway that avoids the use of H(2)S as the source of sulfur and employs instead CS(2) vapor, carried by an Ar or N(2)/H(2) stream in a heated tubular furnace, for the reaction with WO(3) precursor powders. The experiments were conducted at temperatures between 700 and 1000 °C, while the reaction times expanded between 30 min and 24 h. Characterization methods used to analyze the products of the synthesis include TEM, SEM, XRD and EDX. We found a strong correlation between precursor and product microstructure, although the temperature and reaction times play a critical role in the products' microstructural features as well. WS(2) inorganic fullerene (IF) nanospheres are generated in a wide window of conditions, while nanotubes and nanofibers are only produced at high temperatures or long reaction times. A proposed growth mechanism based on the CS(2) synthetic approach is presented. Nanoindentation and nano-impulse techniques were used to characterize the mechanical properties of polymer matrix-WS(2) nanotube composites, finding them superior to equivalent SWCNT composites. The improvements in toughness of nanocomposites based on WS(2) can be attributed to geometrical and morphological effects that assisted several toughening mechanisms such as crack pinning and the formation of an immobilized polymeric interphase around the nanotubes.

Mikrobielle Keratitis nach Laser-in-situ-Keratomileusis

Laser in situ keratomileusis (LASIK) is an effective option and currently one of the most commonly applied surgical techniques in the correction of refractive errors such as myopia, hyperopia, and astigmatism. In contrast to photorefractive keratectomy, it maintains the integrity of Bowman's membrane and the epithelium leading to faster visual rehabilitation as well as less pain and discomfort. Nevertheless, following LASIK the stroma is exposed to infectious organisms. Sight-threatening complications after LASIK are reported to be as rare as 1 in 1000 procedures. However, any infectious keratitis remains potentially devastating. Reports about infectious keratitis following LASIK have increasingly surfaced in recent years. We present a review of the literature on microbial keratitis and present our own cases and recommendations for possible prophylaxis and therapy.

Disease-specific assessment of quality of life after decompression surgery for Graves' ophthalmopathy

PURPOSE

Graves' ophthalmopathy (GO) is an organ-specific autoimmune disease. Hydrophily of accumulated acidic mucopolysaccharides into bulbar adipose tissue leads to swelling of the eye muscles. Orbital surgical decompression is performed in severe cases of compressive optic neuropathy and severe corneal exposure or failure of steroid therapy. The study was designed to evaluate decompression surgery with respect to the clinical benefit and the patient's satisfaction by means of a disease-specific questionnaire.

METHODS

The 90-item study questionnaire was distributed to 105 patients with GO who underwent orbital decompression surgery at the authors' institution.

RESULTS

A total of 88% of patients stated that decompression had helped them, 80% of the interviewees would undergo decompression again, 78% were content with their eye symptoms, and 71% were satisfied with the cosmetic result of decompression. Furthermore, analysis showed a clinically relevant increase in quality of life after surgery. The correlation between the clinical endpoint proptosis at last examination and the quality of life score proved to be significant (p=0.05).

CONCLUSIONS

The large majority of interviewees were satisfied with the result of the orbital decompression. These results confirmed that disfiguring proptosis is an important indication for decompression surgery.

Phake Intraokularlinsen

Phakic intraocular lenses (PIOLs), which are located closer to the eye's nodal points than the anterior corneal surface, can provide superior optical quality for higher corrections because of retention of normal prolate corneal asphericity and larger effective optical zones. Improvements in the material and design of phakic intraocular lenses and their insertion devices combined with advances in the understanding of the anatomical and physiological interactions of the PIOLs with intraocular structures, have increased safety and efficacy. Safety of these implants over the long term remains a concern, but in several situations PIOLs are the refractive correction of choice. The purpose of this review is to compare the different types of PIOLs regarding outcome and complications. Improvements in imaging technologies should improve the accuracy of ICL sizing and allow more precise prediction of effective lens position with more accurate power calculation. It is important to inform patients that phakic lens surgery only corrects the refractive aspect, and that the refractive error itself as well as the changes by surgery still has the potential for serious complications.

[Complications of foldable intraocular lenses requiring explantation. Results of the 2000 and 2001 survey in Germany]

PURPOSE

A survey was sent to all members of the German Society of Ophthalmic Surgeons to evaluate complications that required explantation of foldable intraocular lenses (IOLs).

METHODS

Data on preoperative visual acuity, foldable IOL design and material, and the reason for explantation were obtained and analysed. We received 185 surveys for 2000 and 2001.

RESULTS

In 2000 and 2001, the most common reasons for IOL explantation were: incorrect lens power (31%) and dislocation (19%) in three-piece acrylic IOLs, incorrect power (31%) and decentration (17%) in monofocal silicone IOLs, and opacification (46%) in hydrophilic IOLs. The most common reasons for the exchange of monofocal IOLs were lens opacification in 2000 and incorrect IOL power in 2001.

CONCLUSION

Besides the most frequent complications of decentration and incorrect power observed in rigid IOLs,new complications associated with foldable IOLs occurred (e.g., optic opacification and calcification). Accurate calculation of IOL power and further improvements in material and design are still necessary to minimize the rate of explantations.

[Striae in the flap after laser in situ keratomileusis. Etiology, diagnosis and treatment]

OBJECTIVE

Laser in situ keratomileusis (LASIK) has become the leading refractive option to correct myopia, hyperopia and astigmatism. In addition to the relative rapid visual recovery and the lack of postoperative pain, new flap-related complications are being added. The formation of striae can lead to a significant loss of corrected visual acuity if the central pupil zone is affected. Awareness of possible complications is important not only for the surgeon, but also for the ophthalmologist in practice for a rapid diagnosis and prompt management.

CLINICAL COURSE AND THERAPY

Striae have a variety of appearances and are caused by misalignment/displacement of the corneal flap after replacement or are results of a slippage effect of the flap over the stromal bed after LASIK. Symptomatic striae ideally are treated on the first or second day after surgery by refloating the flap, irrigation with balanced salt solution or hypotonic saline solution, stroking and stretching the surface with moist and dry sponges. In more severe cases scraping away the epithelium and antitorque or interrupted sutures can be performed to treat persistent striae.

CONCLUSION

Symptomatic deep striae should be diagnosed early and managed promptly within the first days. Any later intervention decreases the chance of successful elimination and visual outcome. Hints to prevent the development of striae formation are provided.

[Complications with foldable intraocular lenses with subsequent explantation in 1998 and 1999. Results of a questionnaire evaluation]

PURPOSE

A questionnaire was sent to all members of the German Society of Ophthalmic Surgeons to evaluate complications of foldable intraocular lenses (IOLs) that required explanation.

METHODS

Information on preoperative visual acuity, foldable IOL design and material as well as the reason for IOL explantation was obtained and analysed. We received 167 completed questionnaires for 1998 and 1999.

RESULTS

In 1998 and 1999 the most common reasons for IOL explantation were as follows: incorrect lens power for 56% of the 3-piece hydrophobic acrylic IOLs, 16% because of glare or other photic phenomena, 40% of the 1-piece hydrophilic acrylic IOLs were explanted because of incorrect lens power and 30% for IOL damage. For the 3-piece monofocal silicone IOLs, 41% were explanted because of incorrect IOL power and 32% because of IOL decentration. For the 1-piece Hydrogel IOL, 76% were explanted because of opacification of the optic and 14% because of incorrect lens power. Most multifocal IOLs were explanted because of photic phenomena.

CONCLUSION

In addition to the most common complications such as decentration and incorrect IOL power observed in rigid IOLs, new complications associated with foldable IOLs occurred such as optic opacification, glare and photic phenomena. Some complications seemed to appear in particular IOL types (opacification: SC-60BOUV, MDR), while others were observed in all types of foldable lenses. Accurate calculation of the IOL power and further improvement of the IOL material and design seem to be necessary to minimise the rate of explantations.

[Toric intraocular lens to correct high astigmatism after penetrating keratoplasty in a pseudophakic eye - a case report]

BACKGROUND

After penetrating keratoplasty residual astigmatism can be treated with various options. Correction with spectacles or contact lenses, methods such as radial keratotomy, photorefractive keratectomy (PRK) or Laser-in-situ keratomileusis (LASIK) are limited only to mild and moderate astigmatism. In laser ablation a sufficient corneal thickness must be ensured. On the other hand surgical correction is performed on transplanted tissue which can increase the risk of allograft rejection. In pseudophakic eyes the implantation of an individually designed toric intraocular lens (IOL) according to keratometry and biometry with a cylindrical power up to 12 D provides an alternative method for correcting higher astigmatism. This individually designed IOL can be implanted additionally to the existing IOL.

CASE

A 66-year-old patient presented after penetrating keratoplasty and implantation of an IOL 4 years ago with a visual acuity of 20/160 and residual astigmatism of - 10 D x 151(o). After biometry an individually manufactured toric PMMA-IOL of + 12 D cylindrical and - 9.5 D spherical power was implanted via a sclerocorneal tunnel incision additionally to the existing IOL into the ciliary sulcus. Postoperatively a well centered and stable positioned IOL was found. One year after implantation of the toric IOL the position was still unchanged and the graft had remained clear. Spherical equivalent refraction was + 1,5 D - 3,0 D x 141(o), with an uncorrected visual acuity of 20/60.

CONCLUSION

Implantation of a toric intraocular lens in pseudophakic eyes allows the correction of high astigmatism after penetrating keratoplasty. The advantage of this method compared to the keratorefractive options lies in its minor manipulation on the allograft.

Rational use of biological response modifiers in hematological malignancies--a review of treatment with interferon, cytotoxic cells and antibodies

During the last decade the use of various biologic therapeutics/biological response modifiers in hematological malignancies has increased dramatically. Alpha-interferon (alpha-IFN) alone has clearly a substantial antitumoral effect in many hematological diseases. During the coming decade an improved effect will probably be seen by combination of alpha-IFN with cytostatics and other biologic therapeutics as well as by finding the optimal conditions when alpha-IFN should be used. Using unconjugated mouse monoclonal antibodies (MAb) only, an overall response rate of 38% was noted in patients with advanced disease. MAb therapy might be improved by using other Ig molecules, combination with cytokines and by finding an optimal dosage schedule. Only a few patients with hematological malignancies have been treated with IL-2/LAK cells. An overall response rate of 41% was seen in heavily pretreated patients. In all biologic therapeutics, an improved efficacy will be noted if patients with a low tumor burden and an intact immune system are treated. Immunization/vaccination with "tumor antigen" will probably contribute to an improved prognosis, especially in patients with minimal residual disease. There are several good candidates to be used as tumor antigens in hematological malignancies i.e. the idiotypic receptors on T and B cells. Biotherapy in hematological tumors has come to stay. However, due to the complexity of the effector system it will take a long time before an effective treatment concept is developed.

Endotoxaemia in septic shock: clinical and post mortem correlations

The Limulus amoebocyte lysate assay was used as one of a series of laboratory and clinical investigations on a group of 31 patients suffering from septic shock in order to assess the clinical significance of this assay for the detection of circulating endotoxin in clinical gram-negative sepsis. Four patients with cardiogenic shock served as controls. Endotoxin was detected in the bloodstream of all patients with septic shock during the 24 h following referral and was not detected in the control patients. Eventual clinical recovery was associated with the disappearance of endotoxin from the peripheral blood. Blood cultures were unhelpful as a prognostic indicator in these critically ill patients. A quantitative assay of endotoxin in blood may allow a more precise relationship with the clinical manifestations of major sepsis.